JP3518792B2 - Exhaust gas sensor and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an exhaust gas sensor and a method for manufacturing the same.

[0002]

2. Description of the Related Art As a sensor for detecting a detected component such as hydrocarbon (hereinafter referred to as HC), CO, or nitrogen oxide (hereinafter referred to as NOx) contained in exhaust gas of automobiles, for example, a resistance is used. Type sensors are known.
In this method, an oxide semiconductor such as SnO ₂ is used as a detection element, and the content of the detected component in exhaust gas is detected based on the resistance change of the oxide semiconductor due to adsorption of the detected component. . Separately, a CO sensor having a structure in which Pt porous electrodes are formed on both surfaces of a zirconia element and one porous electrode is covered with an oxidation catalyst has also been proposed. When a gas containing CO and oxygen is brought into contact with the sensor, an oxidation reaction of CO occurs at the electrode not covered with the oxidation catalyst, and the electrode potential becomes a mixed potential affected by CO concentration. CO on the electrode side covered with an oxidation catalyst
Are completely oxidized to a potential that depends on the oxygen concentration in the gas. Then, if the potential difference between both electrodes is taken out as an output, the CO concentration in the gas can be known based on this.

[0003]

First, the former resistance type sensor has a characteristic that the output of the detection element made of an oxide semiconductor changes depending on the concentration of oxygen contained in the exhaust gas. Therefore, even if the pollutant concentration is the same, there is a problem that the detected output value varies depending on the oxygen concentration in the exhaust gas. Therefore, for example, Japanese Patent Laid-Open No. 5-1807
94, etc., oxygen is sent into the exhaust gas by a pump element using a solid electrolyte to increase its concentration, and the relative fluctuation of the oxygen concentration in the gas is reduced to improve detection accuracy. Proposals have been made. However, when the concentration of oxygen in the exhaust gas changes greatly, the effect of suppressing the relative concentration fluctuation due to the introduction of oxygen from the pump element becomes insufficient, and there is a drawback that satisfactory detection accuracy cannot be obtained. On the other hand, in the latter type of sensor using a mixed potential, the same problem occurs because the potential of the electrode covered with the oxidation catalyst changes according to the oxygen concentration in the gas.

It is a first object of the present invention to provide an exhaust gas sensor which can detect the concentration of a component to be detected with high accuracy and a manufacturing method thereof even if the oxygen concentration in the exhaust gas changes. . It is a second object of the present invention to provide an exhaust gas sensor and a method for manufacturing the same that can omit or simplify the assembly process of the sensor and improve the manufacturing efficiency of the sensor.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a sensor for detecting a component to be detected contained in exhaust gas, the main part of which is configured as follows. That is, the exhaust gas sensor is composed of an oxygen ion conductive solid electrolyte, an oxygen concentration battery element having electrodes formed on both surfaces thereof, and an electrode formed on both surfaces composed of an oxygen ion conductive solid electrolyte, and oxygen. Between the concentration cell element, so as to form a gap of a predetermined amount allowed to flow the exhaust gas from the atmosphere to be measured, while being arranged to face the oxygen concentration cell element,
An oxygen pump element that pumps oxygen into the gap or pumps oxygen from the gap in a direction in which the absolute value of the concentration battery electromotive force generated in the oxygen concentration battery element decreases; and an oxygen pump element and an oxygen concentration battery element. A heating element for heating at least one of them to a predetermined sensor operating temperature is provided, and the oxygen concentration cell element and the oxygen pump element are configured as an integrated fired body that is laminated together in a state in which a gap is formed. .

According to the structure of the above exhaust gas sensor, the oxygen concentration battery element and the oxygen pump element are constituted as an integrated fired body laminated on each other, so that the following effects can be achieved. Since the oxygen pump element and the oxygen pump element are integrated at the same time as firing, the assembly process after firing can be omitted or simplified, and the manufacturing efficiency of the sensor can be improved. For example, in the case of a structure in which the oxygen concentration battery element and the oxygen pump element are separately fired and then integrated by bonding or the like after the firing, it is difficult to make the gap formation amount constant due to deformation during firing of the element. Therefore, the output level may vary among the individual sensors. However,
In the configuration in which the above-mentioned firing is integrated, it is easy to control the amount of formation of the gap, and therefore such a problem is unlikely to occur. When the oxygen concentration battery element and the oxygen pump element are formed in a thin plate shape (for example, a thickness of 1 mm or less, specifically 0.2 to 0.4 mm) to make the sensor compact, they are laminated after firing. In a configuration in which the elements are integrated with each other, mechanical strength, for example, impact resistance may be insufficient, and the element may be easily cracked or cracked. However, by integrating them by firing, the elements reinforce each other and the mechanical strength can be improved.

The integrated structure as described above can be efficiently obtained, for example, by the following manufacturing method. First, an electrode pattern to be an electrode is formed by printing using an electrode material powder paste on both surfaces of a first ceramic powder molded body to be an oxygen concentration battery element, and a second ceramic to be an oxygen pump element is formed. Similarly, electrode patterns are printed on both surfaces of the powder compact. Next, the first and second ceramic powder compacts are formed so that the electrode patterns to be the first electrode and the second electrode face each other, and a gap is formed between the facing electrode patterns. Stack on top of each other. Then, the laminated body is fired to obtain an oxygen concentration battery element and an oxygen pump element which are integrated with each other.

The oxygen pump element and the oxygen concentration cell element are
It is composed of a solid electrolyte having oxygen ion conductivity. As such a solid electrolyte, Y ₂ O ₃ or Ca can be used.
ZrO ₂ in which O is solid-dissolved is a typical one, but a solid solution of ZrO ₂ with an oxide of another alkaline earth metal element or rare earth metal element may be used. Moreover, HfO ₂ may be contained in the base ZrO ₂ .

Further, the exhaust gas sensor of the present invention can be more specifically configured as follows. That is, the exhaust gas sensor is composed of an oxygen ion conductive solid electrolyte, and an oxygen concentration battery element in which electrodes having oxygen permeability are formed on both surfaces thereof, and an oxygen ion conductive solid electrolyte, and oxygen permeation of both surfaces is performed. And an oxygen pump element disposed opposite to the oxygen concentration battery element so that a predetermined amount of clearance is formed between the oxygen concentration battery element and the oxygen concentration battery element, which allows the exhaust gas to flow therethrough. ,
A heating element for heating at least one of the oxygen pump element and the oxygen concentration cell element to a predetermined sensor operating temperature is provided. The oxygen pump element has a function of pumping oxygen into the gap or pumping oxygen from the gap in a direction in which the absolute value of the concentration battery electromotive force generated in the oxygen concentration battery element decreases. On the other hand, exhaust gas containing a component to be detected and oxygen is introduced into the gap and a space (opposite space) on the opposite side of the oxygen concentration battery element.

The electrode on the gap side of the oxygen pump element is the first electrode, the electrode on the gap side of the oxygen concentration battery element is the second electrode,
With the electrode on the opposite space side of the oxygen concentration battery element as the third electrode, the components to be detected in the exhaust gas introduced into the gap and the opposite space are at least in one of the gap and the opposite space, the first to third parts. It is consumed by reacting at least one of the electrodes with oxygen in the exhaust gas as an oxidation catalyst, and there is a difference in the consumption amount of the detected component due to the reaction with oxygen between the gap and the opposite space, Catalytic activity for the reaction between the detected components of the first to third electrodes and oxygen
Sex is adjusted. Then, the concentration battery electromotive force of the oxygen concentration battery element, the current value flowing in the oxygen pump element when reaching the predetermined electromotive force target value E C, as the information that reflects the concentration of the detected component in the exhaust gas When taken out, the oxygen concentration battery element and the oxygen pump element are configured as an integrated fired body that is laminated on each other with a gap formed between the first electrode and the second electrode.

In the exhaust gas sensor constructed as described above, the exhaust gas containing the component to be detected and oxygen is introduced into the space opposite to the space with the oxygen concentration cell element interposed therebetween.
The activity of the first and second electrodes arranged on the side facing the gap as the oxidation catalyst of the third electrode arranged on the opposite space side is due to the oxidation of the component to be detected on the gap side and the opposite space side. The amounts of consumption are adjusted so that there is a difference, and oxygen is also consumed in large amounts on the side where the detected components are consumed in large amounts. As a result, a difference in oxygen concentration occurs on both sides of the oxygen concentration cell element, and concentration cell electromotive force is generated based on the difference. The oxygen pump element pumps oxygen into the gap when the gap side is on the low oxygen concentration side, and pumps oxygen out of the gap when the gap side is on the high oxygen concentration side,
The concentration battery electromotive force is controlled to reach the electromotive force target value EC.

The concentration battery electromotive force is the electromotive force target value E.
The current that flows through the oxygen pump element when it reaches C (hereinafter referred to as the pump current) is a value that almost reflects the concentration value of the detected component in the exhaust gas. The concentration can be detected. Further, the value of the pump current is hardly affected by the oxygen concentration in the exhaust gas unless the concentration of the detected component in the exhaust gas changes, and the value of the pump current for the change in the concentration of the detected component is The change is also almost linear. As a result, even if the oxygen concentration changes within a predetermined range, the concentration of the component to be detected in the exhaust gas can be accurately detected. In addition, since the oxygen concentration battery element and the oxygen pump element are configured as an integrated fired body that is laminated on each other, the above-mentioned effects (1) to (3) can also be achieved.

The size of the gap formed between the oxygen concentration cell element and the oxygen pump element is preferably set to, for example, 1 mm or less. If the size of the gap exceeds 1 mm, the effect of restricting the inflow of new exhaust gas due to the gap becomes small, and the detection accuracy of the sensor may deteriorate. Further, if the ratio of the area Sp of the first electrode to the area Ss of the second electrode is set to Sp / Ss of 1 or more, the oxygen concentration in the vicinity of the second electrode can be made constant, and thus the accuracy of the sensor output and The stability can be improved.

In the exhaust gas sensor having the above structure, the absolute value of the concentration cell electromotive force of the oxygen concentration cell element is 10%.
The current value flowing through the oxygen pump element when the electromotive force target value E C set to mV or less is reached can be taken out as information that reflects the concentration of the detected component in the exhaust gas.

On the other hand, when a test gas containing 1% by volume or more of oxygen and containing substantially no component that reacts with oxygen at the sensor operating temperature is introduced into the gap and the opposite space, the oxygen-concentrated battery element is produced. The absolute value of the offset electromotive force is EOS (unit: mV), and the electromotive force target value EC is set in the range of (EOS-5) mV or more and (EOS + 5) mV or less, and the oxygen concentration battery The current value flowing in the oxygen pump element when the absolute value of the concentration battery electromotive force of the element reaches the electromotive force target value EC can be taken out as information reflecting the concentration of the detected component in the exhaust gas.

For example, if oxygen is pumped into or out of the gap by the oxygen pump element so that the oxygen concentration becomes equal to each other between the gap side and the opposite space side with the oxygen concentration battery element sandwiched therebetween, Since the pump current directly corresponds to the difference in the consumption amount of the detected component in the two spaces, the concentration of the detected component can be detected more accurately, and the detection result can be analyzed. It will be easy. In this case, if the oxygen concentrations on both sides of the oxygen concentration cell element are equal, the concentration cell electromotive force is theoretically 0. Therefore, the oxygen pump element uses oxygen to the gap so that the concentration cell electromotive force is 0. It will be pumped in or pumped out. However, even if the oxygen concentrations on both sides of the oxygen concentration battery element become equal, the electromotive force of the oxygen concentration battery element usually does not become zero, and a constant offset electromotive force often remains.

The present inventors have found that for most of the commonly used oxygen ion conductive solid electrolytes, the absolute value of the offset electromotive force is within the range of 10 mV or less when the oxygen concentration battery element is formed of the solid electrolyte. In the first configuration of the exhaust gas sensor of the present invention, the electromotive force target value EC is set to 10 mV or less, and the absolute value of the concentration battery electromotive force is the electromotive force target value EC.
It has been found that the concentration of the component to be detected in the exhaust gas can be accurately detected by adopting the value of the current flowing through the oxygen pump element when it reaches the detection signal as the detection signal. When the oxygen concentration range of the measurement atmosphere is known, it is desirable to set the offset electromotive force at the maximum oxygen concentration within that range as the electromotive force target value.

On the other hand, as a result of earnest studies, the present inventors have found the following, and have completed the second constitution of the present invention. That is, the offset electromotive force of the oxygen concentration battery element is more likely to fluctuate as the oxygen concentration in the exhaust gas relating to detection becomes lower, and when the electromotive force target value EC is set on the basis of the offset electromotive force at a certain oxygen concentration or less, The sensor output is easily affected by the oxygen concentration in the exhaust gas. And in order to solve this, 1 oxygen
The absolute value of the offset electromotive force generated in the oxygen concentration cell element when the test gas containing at least volume% and containing substantially no component that reacts with oxygen at the sensor operating temperature is introduced into the gap and the opposite space is EOS ( Unit: mV),
Based on this, the electromotive force target value EC is (EOS-5.0)
It is effective to set within the range of mV or more (EOS + 5.0) mV or less. By setting the electromotive force target value E C within the above range, a more stable sensor output that is not affected by the oxygen concentration in the exhaust gas can be obtained.
In this case, it is desirable to set the electromotive force target value EC as a value as close to EOS as possible in order to improve the detection accuracy of the sensor. The oxygen concentration in the test gas for determining EOS is preferably 10% or more.
Alternatively, it is better to use the atmosphere. Further, by setting the electromotive force target value E C to 10 mV or less as in the first configuration, it is possible to obtain a more stable and highly accurate sensor output.

The exhaust gas sensor of the present invention may be arranged, for example, on the downstream side of an oxidation catalytic converter or a three-way catalytic converter of a gasoline engine to detect deterioration of the three-way catalyst in the converter.
In this case, the oxygen in the exhaust gas is introduced into the exhaust gas sensor in a state where a considerable part of the oxygen is consumed by the oxidation of CO or HC in the upstream catalyst.
In this case, the oxygen concentration in the exhaust gas for detection is approximately 5000 ppm or less,
It is desirable that the exhaust gas sensor be configured so that the detected component can be accurately detected in the region where the oxygen concentration is low as described above. For that purpose, for example, the oxygen concentration is 10
The sensor output corresponding to 0 ppm is Q100, 1000
When the sensor output corresponding to ppm is Q1000, the output change rate Δ (%) = {| Q100−Q1000 | / Q100} × 100 becomes ± 30% or less, more preferably ± 10% or less, and It is preferable to set the electric power target value EC.

As a reference technique, a sensor of a type in which electrodes having different oxidation catalyst activities are formed on both sides of an oxygen concentration battery element, and oxygen pump elements are arranged to face each other with a certain amount of gap formed on one side thereof. For example, Japanese Patent Laid-Open No.
There is an air-fuel ratio sensor disclosed in Japanese Patent Publication No. 1-95243. However, the sensor disclosed in the above-mentioned publication uses C in the air-fuel mixture.
This is for detecting the ratio between the concentration of the combustion component such as O or HC and the oxygen concentration as an air-fuel ratio, and detects the amount of the component to be detected in the exhaust gas regardless of the oxygen concentration in the exhaust gas. The sensor of the present invention is fundamentally different in its purpose, action and effect. And, as a natural consequence thereof, the exhaust gas sensor of the present invention is set so that the electromotive force target value E C for the oxygen concentration battery element is adapted to the purpose of use peculiar to the present invention different from the air-fuel ratio sensor of the above publication, Further, the oxygen pump element has a feature that is not disclosed at all in the technology of the above publication, that it operates so as to bring the electromotive force of the oxygen concentration battery element closer to the electromotive force target value EC.

Next, in the exhaust gas sensor, a heating element is laminated on the opposite side of the gap to at least one of the oxygen concentration battery element and the oxygen pump element, and the oxygen concentration battery element, the oxygen pump element, and The heating element and the heating element can be configured as an integral fired body that is laminated on each other. As a result, the sensor assembly process including the heating element can be simplified, the entire sensor can be made more compact, and the reinforcing effect of the integrated heating element further improves the mechanical strength of the entire sensor. be able to.

In the sensor having the above structure, in the above-mentioned method, a third ceramic powder compact is provided on the opposite side of the gap to at least one of the first and second ceramic powder compacts. By stacking and firing the stacked body to obtain an oxygen concentration battery element, an oxygen pump element and a heating element which are integrated with each other, it is possible to efficiently manufacture.

In the exhaust gas sensor of the present invention, the above-mentioned gap may be configured to communicate with the outer space at a communication portion formed at the side edge of the stack of the oxygen concentration battery element and the oxygen pump element, for example. This allows the exhaust gas to be smoothly introduced from the communication portion into the gap. In this case, the communicating portion can be formed of a porous ceramic body that allows the gas to flow between the gap and the outer space. This makes it difficult for dirt particles such as soot and oil droplets contained in the exhaust gas to enter the gap, and thus the first or second electrode facing the gap,
It is possible to prevent or suppress the deterioration due to the attachment of the dirt particles. In this case, as a method of forming the communicating portion by the porous ceramic body, the communicating portion pattern to be the communicating portion is formed between the first and second ceramic powder compacts in the above-described method by forming the porous ceramic powder. An example is a method in which a paste made of (for example, porous Al ₂ O ₃ powder) or a powder mixture that becomes a porous ceramic body after firing is sandwiched in a form formed by printing or the like, and this is integrally fired.

Next, in the gap, between the oxygen concentration battery element and the oxygen pump element, a column portion can be formed which defines the gap between the oxygen concentration cell element and the oxygen pump element without hindering gas from entering and leaving the gap. . For example, when the oxygen concentration battery element and the oxygen pump element are formed in a plate shape, the first and second ceramic powder molded bodies described above are kneaded with a ceramic powder and an organic binder and molded into a sheet shape, so-called. Ceramic green sheets are often used. In this case, the ceramic green sheets laminated with a gap formed are deformed during firing and hang down toward the gap side, and the amount of the finally formed gap fluctuates, or in extreme cases, the gap is crushed and the upper and lower electrodes are crushed. There may be problems such as contact with. Therefore, as described above, by forming the column portion that defines the gap between the oxygen concentration battery element and the oxygen pump element, it is possible to stably form a gap of a desired size. As a result, it is possible to prevent problems such as output variations among the individual sensors due to variations in the gap amount.

The pillars can be efficiently formed by the following method. That is, a pillar portion pattern to be a pillar portion is formed by using the ceramic powder in at least one of the first and second ceramic powder compacts in a region corresponding to the gap. Next, the first and second ceramic powder compacts are laminated with each other so that a gap is formed on the side where the strut pattern is formed. Then, by firing the laminate, between the oxygen concentration battery element and the oxygen pump element,
A pillar portion based on the pillar pattern is formed. The pillar pattern can be formed by arranging a ceramic powder compact (for example, a ceramic green sheet) or by pattern printing using a ceramic powder paste.

Specifically, the supporting columns are formed in a dispersed manner in a spot-like or staggered manner in the gap forming region, or in a direction intersecting the stacking direction of the oxygen concentration battery element and the oxygen pump element. It is possible to form the partition into a partition wall shape that partitions the gap into two or more spaces. In addition, as the material of the supporting column, even if it is made of the same ceramic material as the oxygen concentration battery element and the oxygen pump element (that is, oxygen ion conductive solid electrolyte ceramic), a different ceramic material (for example, Al ₂ O ₃ (including porous material))
However, it is particularly preferable to use a material that can be integrated with the oxygen concentration battery element and the oxygen pump element by firing.

Next, the oxygen concentration battery element and the oxygen pump element can be formed in a horizontally long plate shape and can be arranged to face each other. In this case, the first to third electrodes can be formed on one end side in the plate surface longitudinal direction of the oxygen concentration battery element and the oxygen pump element. Similarly, on the other end side in the longitudinal direction of the plate surface, between the oxygen concentration battery element and the oxygen pump element, a spacer portion having substantially the same thickness as the gap is inserted, and the spacer portion and the oxygen concentration element are inserted. The battery element and the oxygen pump element can be integrated with each other by firing.
By arranging the spacer portion between the oxygen concentration battery element and the oxygen pump element, a necessary gap can be easily formed, and by integrating the spacer portion, a plate-shaped oxygen concentration battery element and an oxygen pump element can be formed. It can be reinforced, and thus the mechanical strength of the sensor can be improved.

The exhaust gas sensor having such a structure can be efficiently manufactured by the following method. That is, in the above-mentioned method, the first and second ceramic powder compacts are respectively formed in the shape of a horizontally long plate and are arranged to face each other, and the electrode patterns are arranged on the plate surfaces of the first and second ceramic powder compacts. It is formed on one end side in the longitudinal direction. Further, a spacer compact to be a spacer portion is inserted between the first and second ceramic powder compacts on the other end side in the plate surface longitudinal direction. Then, by firing a laminate of the spacer compact and the first and second ceramic powder compacts,
The oxygen concentration battery element and the oxygen pump element are joined and integrated with each other via a spacer portion based on the spacer molded body.

In this case, the dimensional accuracy of the gap can be improved by forming the above-mentioned pillar portion in the gap. Further, between the oxygen concentration battery element and the oxygen pump element, an auxiliary spacer portion may be inserted at a position opposite to the spacer portion with respect to the gap in the longitudinal direction.
In this way, the gap forming portion between the oxygen concentration battery element and the oxygen pump element is supported on both sides in the longitudinal direction by the spacer portion and the auxiliary spacer portion, so that the mechanical strength of the sensor in the gap portion is significantly improved. Can be made. On the other hand, a reinforcing spacer is interposed between the oxygen concentration battery element and the oxygen pump element so as to extend along a part of the peripheral edge of the gap, for example, along side edges on both sides of the oxygen concentration battery element and the oxygen pump element in the plate width direction. The mechanical strength of the sensor in the gap portion can be similarly improved by the insertion and integration. In this configuration, the spacer portion, the column portion, the auxiliary spacer portion, or the reinforcing spacer portion can be made of the same ceramic material as the oxygen concentration battery element and the oxygen pump element. In this case, it is desirable to interpose an insulating layer between them and at least one of the oxygen concentration battery element and the oxygen pump element to prevent current leakage between the oxygen concentration battery element and the oxygen pump element.

On the other hand, as a simpler sensor structure, the following can be exemplified. That is, the oxygen concentration battery element and the oxygen pump element are similarly formed in the shape of a horizontally long plate and are arranged to face each other, and each electrode is arranged on one end side in the plate surface longitudinal direction of the oxygen concentration battery element and the oxygen pump element. On the other hand, between the oxygen concentration battery element and the oxygen pump element in the above-mentioned gap, a pillar portion that defines the gap between the oxygen-concentration battery element and the oxygen pump element is formed so as to prevent the gas from entering and leaving the gap. Further, the oxygen concentration battery element and the oxygen pump element are joined and integrated with each other through an insulating layer in the other region except the gap. According to this configuration, since the gap can be formed without using the spacer portion, the sensor can be made more compact, and the steps of manufacturing the spacer portion and stacking the spacer portions can be omitted. It can be done more efficiently.

The following is an example of the specific manufacturing method. In the method, the first and second ceramic powder compacts are each formed in a horizontally long plate shape and stacked on each other, and the electrode pattern is formed in the plate surface longitudinal direction of the first and second ceramic powder compacts. It is formed on one end side. Then, in a region scheduled in the gap between the first and second ceramic powder compacts, a pillar portion pattern to be a pillar portion is formed using the ceramic powder paste, and the pillar portion pattern is overlapped. In a position where it does not occur, an auxiliary support pattern is formed in a region that is also planned in the gap by a powder paste made of a material that burns or decomposes (or burns or decomposes and disappears) during firing. Further, an insulating layer pattern is formed between the first and second ceramic powder compacts in regions other than the region scheduled for the gap. Then, by firing the laminated body, a gap and a pillar portion based on the above pillar portion pattern are formed between the oxygen concentration battery element and the oxygen pump element, while the oxygen concentration in other areas except the gap is increased. The battery element and the oxygen pump element are bonded to each other via an insulating layer based on the insulating layer pattern. The pillar pattern or the auxiliary support pattern can be formed by printing.

The pillar pattern and the auxiliary support pattern are
When the first and second ceramic powder compacts are laminated by forming them complementarily by printing or the like as described above, the pillar pattern is crushed between the first and second ceramic powder compacts based on the reinforcing effect of the auxiliary support pattern. Is prevented or suppressed. Since the auxiliary support pattern is burnt or decomposed and disappears by firing, a certain amount of gap can be accurately and extremely easily formed between the oxygen concentration battery element and the oxygen pump element. Further, by forming the first and second ceramic powder compacts with, for example, ceramic green sheets, even if the insulating layer pattern is formed to be considerably thinner than the pillar pattern, the first and second ceramic powder compacts are formed. By slightly bending the body, the two can adhere to each other through the insulating layer pattern and can be integrated by firing without any trouble.

The insulating layer pattern can be formed by using a paste of insulating ceramic powder, for example, Al ₂ O ₃ powder. In this case, the pillar pattern is formed using a paste such as an insulating ceramic powder having a larger particle size than the insulating layer pattern, for example, Al ₂ O ₃ porous powder, so that the pattern is more crushed during lamination. Can be hardened. On the other hand, the auxiliary support pattern can be formed, for example, by using a paste mainly composed of carbon powder.

Next, in the above exhaust gas sensor, the gap between the oxygen pump element and the oxygen concentration cell element is made as small as possible (preferably 1 mm or less), and a new exhaust gas inflow regulation effect by the gap is provided. It is advantageous to improve the detection accuracy of the sensor. Conversely, if the size of the gap is too large, the reaction between HC and oxygen on the electrode having catalytic activity becomes unstable, the electromotive force of the oxygen concentration cell becomes small, and a sufficient sensor output can be obtained. It may disappear. This tendency becomes particularly remarkable when the fluctuation of the oxygen concentration in the exhaust gas to be measured is large or the water vapor concentration in the gas is high. When a gap forming member that forms a predetermined gap (another gap) between the oxygen concentration battery element and the third electrode is formed on the side where the third electrode is formed, the size of the gap is increased. Also for the same reason, it is desirable to make it as small as possible (desirably 1 mm or less).

However, if the gap amount between the elements is made too small, a slight deformation at the time of firing will produce a gap forming amount when the oxygen pump element, the oxygen concentration battery element or the gap forming member is produced by firing this time. Have a big impact,
There may be a problem that the output tends to vary among the individual sensors. Therefore, in order to solve this, it is effective to use the following sensor structure. That is, the electrode on the gap side of the oxygen pump element is the first electrode, the electrode on the gap side of the oxygen concentration battery element is the second electrode, and the electrode on the opposite space side of the oxygen concentration battery element is the third electrode. A measurement chamber is formed so as to contact at least one of the three electrodes, and a gas communication portion is formed so as to penetrate a wall portion of the measurement chamber from the measured atmosphere side to the measurement chamber side. And
The gas communication part is configured as a diffusion regulation flow part including at least one of a small hole, a slit, and a porous communication part made of porous ceramic or porous metal.

The third structure of the exhaust gas sensor of the present invention is composed of an oxygen ion conductive solid electrolyte, and is composed of an oxygen concentration battery element having electrodes formed on both surfaces thereof and an oxygen ion conductive solid electrolyte. And electrodes are formed on both sides of the oxygen-concentrated battery element, and the oxygen-concentrated battery element is disposed so as to face the oxygen-concentrated battery element so as to form a predetermined amount of clearance allowing the passage of exhaust gas. In a direction in which the absolute value of the concentration battery electromotive force generated in the concentration battery element decreases, an oxygen pump element that pumps oxygen into the gap or pumps oxygen from the gap, and at least one of the oxygen pump element and the oxygen concentration battery element. , A heating element for heating to a predetermined sensor operating temperature, an electrode on the gap side of the oxygen pump element is a first electrode, an electrode on the gap side of the oxygen concentration battery element is a second electrode, an acid. At least one of the second electrode and the third electrode, and the measurement chamber formed so as to be in contact with the second electrode and the electrode on the space side opposite to the concentration cell element as the third electrode A gas communication portion formed so as to penetrate from the side to the measurement chamber side, wherein the gas communication portion is at least one of a small hole, a slit, and a porous communication portion made of porous ceramic or porous metal. It is characterized as a diffusion control distribution department including

In this way, even when the size of the gap is increased to a certain extent or more, the exhaust gas flows into the measurement chamber while the diffusion is regulated from the diffusion regulation flow section, and after being introduced into the measurement chamber. Similarly, it is discharged into the atmosphere to be measured while the diffusion is regulated by the diffusion regulation distribution unit. Therefore, even if the exhaust gas once introduced stays in the measurement chamber for a long period of time and the composition of the exhaust gas (especially the amount of oxygen or water vapor) in the atmosphere to be detected changes during that time, the effect on the gas in the measurement chamber is not affected. Since the size is small, a stable and high sensor output can be obtained, which in turn can improve the sensor detection accuracy.

The set of the measurement chamber and the diffusion control and flow section may be formed either on the second electrode side or the third electrode side of the oxygen concentration battery element, but the oxygen pump element and the oxygen concentration battery element may be formed. It is more desirable for the sensor output to form the above group at least on the side where the catalytic activity is high, that is, on the side where the reaction between oxygen and HC becomes more active, among the gap and the opposite space. It is even better if the sets are formed on both sides.

Next, regarding the formation form of the measurement chamber and the diffusion regulation flow part, when forming it in the gap side between the oxygen concentration cell element and the oxygen pump element, a wall is formed so as to surround the periphery of the second electrode. It is possible to form a portion and form a space surrounded by the inner surface of the wall portion and the respective facing surfaces of the oxygen concentration cell element and the oxygen pump element as a measurement chamber. In addition, the diffusion control and flow portion is formed in a form that penetrates at least one of the wall portion and the oxygen concentration battery element from the measured atmosphere side to the measurement chamber side, and communicates the measured atmosphere and the measurement chamber with each other. It can be a slit or a small hole. In addition,
The above-mentioned porous ceramic body (or a porous metal body) which allows the gas to flow between the gap and the atmosphere to be measured can also function as the diffusion regulation and flow section.

When the slit is formed as the diffusion-regulating flow portion, for example, a wall portion forming body that constitutes at least a part of the wall portion is arranged between the oxygen concentration battery element and the oxygen pump element, and the wall portion is formed. The slit may be formed between the formed body and at least one of the oxygen concentration battery element and the oxygen pump element in a form along the plate surface of the oxygen concentration battery element or the oxygen pump element. This allows
Exhaust gas can be smoothly introduced into the measurement chamber through the slit without causing a spatial deviation.

Next, when the width (spacing) of the slit is d and the dimension of the measurement chamber in the direction in which the oxygen concentration cell element and the oxygen pump element face each other (hereinafter referred to as the height of the measurement chamber) is h, d / It is preferable to adjust h in the range of 1/100 to 1/4. If d / h exceeds 1/4, the effect of restricting the diffusion of exhaust gas in the slit becomes insufficient, and the sensor output may not be obtained sufficiently. If d / h is less than 1/100, the inflow rate of gas into the measurement chamber or the outflow rate of gas from the measurement chamber becomes too small, and the detection accuracy of the sensor may deteriorate. More preferably, d / h is set in the range of 1/20 to 1/8. The ratio S / V of the area of the inner surface of the slit to the space volume V in the slit is 4 to 10 for the same reason.
It is preferable to adjust it to 0, preferably 20 to 50.

On the other hand, the absolute value of the slit width d is 0.01
It is preferable to adjust in the range of 1.0 mm. d is 1.0m
If it exceeds m, the effect of regulating the diffusion of exhaust gas in the slit becomes insufficient, and the sensor output may not be sufficiently obtained. On the other hand, if d is less than 0.01 mm, the inflow speed of gas into the measurement chamber or the outflow speed of gas from the measurement chamber becomes too small, and the detection accuracy of the sensor may deteriorate. It should be noted that d is more preferably set in the range of 0.02 to 0.05 mm.

Although the slit may be formed in the middle of the wall forming body in the thickness direction (the stacking direction of the oxygen concentration battery element and the oxygen pump element), the wall forming body and the oxygen concentration battery element may be formed. The structure formed with at least one of the oxygen pump elements is more advantageous in manufacturing the sensor. That is, in the former case, a ceramic molded body to be a wall forming body (hereinafter referred to as a wall forming body) is provided with a gap to be a slit in advance, or the ceramic molded body is thickened. It is inevitable that the number of man-hours will be slightly increased, such as by forming it in two parts adjacent to each other in the vertical direction and firing it with a gap formed between them. On the other hand, in the latter case, a predetermined amount of gap is formed between the wall forming molded body and the ceramic molded body to be the oxygen concentration cell element or the oxygen pump element (hereinafter referred to as element forming molded body). The exhaust gas sensor having the above structure can be easily manufactured only by firing.

The slits are, for example, a layer formed of a material (for example, carbon paste) which is burned out by firing between the wall portion forming compact and the element forming compact in a region where the slit is to be formed. It can be formed by sandwiching and firing the laminate to burn off the layer. In this case, the width of the formed slit can be freely adjusted according to the thickness of the layer to be formed.

Next, the wall forming body can be integrated with at least one of the oxygen pump element and the oxygen concentration cell element by firing. By integrating these by firing, the mechanical strength of the sensor can be improved. When the slit is formed only between the wall forming body and one of the oxygen pump element and the oxygen concentration battery element, the wall forming body and the element forming body are formed on the side where the slit is not formed. On the other hand, on the slit forming side,
It is possible to form a slit by partially sandwiching the sheet with respect to the laminated surface, and to integrate the wall forming molded body and the element forming molded body in the laminated surface region where the sheet is not interposed. In this case, the oxygen pump element or the oxygen concentration cell element for forming the wall portion is integrated with each other on the slit forming side in the portion other than the slit forming region, so that the strength of the sensor can be further increased.

On the other hand, in the case where the diffusion regulation flow portion is formed by a small hole instead of the slit, the small hole can be formed in, for example, the wall portion forming body. In this case, in order to allow the exhaust gas to flow into the measurement chamber without any deviation, it is preferable to form a plurality of small holes at predetermined intervals in the plate surface direction of the plate-shaped oxygen pump element or the oxygen concentration battery element. Further, the small holes may be formed in a shape penetrating the oxygen concentration battery element in the thickness direction.
In this case, it is desirable to form a plurality of the small holes at predetermined intervals along the peripheral edges of the second electrode or the third electrode in order to form an inflow state of the exhaust gas without any deviation.

Next, the oxygen pump element and the oxygen concentration battery element can be formed in a laterally long plate shape, and the diffusion control and flow portion has slits or predetermined portions formed on both sides of the oxygen pump element and the oxygen concentration battery element in the plate surface width direction. It may be a plurality of small hole groups arranged at intervals. In this way, the exhaust gas flowing into the measuring chamber from one of the slits or small holes is discharged from the other, so that a smooth exhaust gas flow is formed in the measuring chamber, and the sensor output The responsiveness can be improved.

Next, in the above exhaust gas sensor, a measuring chamber may be formed on the side opposite to the side facing the gap between the oxygen concentration cell elements. That is, the above-mentioned gap forming member that forms another gap between the oxygen concentration battery element and the opposite side of the oxygen concentration battery element is arranged,
A wall portion is formed between the gap forming member and the oxygen concentration battery element so as to surround the periphery of the third electrode, and is surrounded by the inner surface of the wall portion and each facing surface of the gap forming member and the oxygen concentration battery element. The space is the measurement room.

Also in this case, the diffusion control and flow section can be formed in substantially the same manner as in the case where the measurement chamber is formed between the oxygen pump element and the oxygen concentration cell element. That is, the diffusion control and circulation portion is formed in such a manner that it penetrates at least one of the wall portion and the gap forming member from the measurement atmosphere side to the measurement chamber side, and the measurement atmosphere and the measurement chamber communicate with each other. It can be configured as a slit or a small hole.
In addition, between the gap forming member and the oxygen concentration battery element, a wall forming body that constitutes at least a part of the wall can be arranged, and at least one of the wall forming body, the gap forming member, and the oxygen concentration battery element. The slits can be formed between the gap forming members or the plate surface of the oxygen concentration battery element.

The wall forming body can be integrated with at least one of the gap forming member and the oxygen concentration battery element by firing. Further, the gap forming member and the oxygen concentration battery element can be formed in a laterally long plate shape, and the diffusion regulation and flow portion is a slit formed on both sides in the plate surface width direction of the gap forming member and the oxygen concentration battery element. You can

Next, the second and third electrodes formed on both sides of the oxygen concentration battery element are used to detect the detected component relative to the detected component.
And catalytic activity for the reaction of oxygen with oxygen can be configured to be different from each other. As a result, the difference in the consumption amount of the detected component between the gap and the opposite space becomes large, the sensor output level is increased, and the detection sensitivity of the detected component can be improved. In this case, the linearity of the sensor output with respect to the concentration of the detected component in the exhaust gas is enhanced by making the catalytic activity of the second electrode for the reaction between the detected component and oxygen larger than that of the third electrode. ,
In some cases, the detection accuracy of the detected component can be further improved. In this configuration, the oxygen pump element pumps oxygen into the gap so that the absolute value of the concentration cell electromotive force generated in the oxygen concentration cell element decreases. Here, for both the first electrode and the second electrode, the detected component
If the catalytic activity for the reaction of oxygen with oxygen is made larger than that of the third electrode, the difference in the consumption amount of the detected component between the gap and the opposite space becomes further large, and the detection sensitivity of the detected component can be increased. .

More specifically, the second electrode and the third electrode have a difference of 2 in the detected component conversion rate η defined as follows.
It is desirable to use a combination of 0% or more. That is, a sample in which a disk-shaped porous electrode having a diameter of 8 mm was formed on the disk of an oxygen ion conductive solid electrolyte having a diameter of 12 mm and a thickness of 1 mm by the same material and condition as the second electrode or the third electrode. , Placed in a tubular body having a gas inlet and outlet and heated to a sensor operating temperature, and in that state, the tubular body contains 300 ppm of oxygen, 350 ppm of a component to be detected, and 3% of water vapor. The test gas, the balance of which is argon, is supplied from the inlet at a flow rate of 100 ml /
The concentration of the component to be detected in the test gas after discharge when Cs (unit: pp
As m), the detected component conversion rate η (%) is determined by the following equation: η = {(350-Cs) / 350} × 100 (1).

That is, when the component to be detected contained in the test gas is oxidized and consumed by using the electrode as an oxidation catalyst, the concentration Cs of the component to be detected in the test gas after discharge is reduced, so that the component to be detected is The conversion rate η increases. The thus the eta, the detected formed with respect to the detection component of each electrode in the sensor
A parameter that represents the catalytic activity for the reaction of the minute with oxygen ,
As a result, it can be used as a parameter reflecting the consumption amount of the component to be detected in the gap or the opposite space. By setting the difference in the value of η between the second electrode and the third electrode to be 20% or more, the difference in consumption of the detected component between the gap and the opposite space becomes large, and the sensor The output level can be increased and the detection sensitivity of the detected component can be improved. For example, the second electrode is more sensitive than the third electrode.
In the case where the second electrode is configured to have a high catalytic activity for the reaction between oxygen and oxygen, it is preferable to configure the second electrode so that the detected component conversion rate η is 20% or more higher than that of the third electrode. . The difference in η is more preferably 30%
The above is preferable.

Here, the value of η of the electrode changes depending on the sensor operating temperature. It can be said that it is desirable to set the sensor operating temperature so that the difference in η is 20% or more, preferably 30% or more. In this case, if the sensor operating temperature is set so that the pump current value of the oxygen pump element when the applied voltage is constant is as high as possible,
The detection sensitivity of the component to be detected is further improved.

Next, the component to be detected is, for example, CO or H.
In the case of C, among the above-mentioned first to third electrodes, the one having a high catalytic activity for the reaction with oxygen is a metal (a simple substance or an alloy) containing Pt, Pd, or Rh as a main component, or Pt-. Pd-based alloy, Pt-Rh-based alloy, Rh-Pd
The alloy may be composed of a system alloy, a Pd-Ag system alloy or the like (hereinafter, these are referred to as a high activity metal group in the present specification). On the contrary, the one whose catalytic activity should be low is a metal (a simple substance or an alloy) mainly containing any of Au, Ni and Ag, or a Pt-Au alloy, Pt-Ni.
Alloys, Pt-Ag alloys, Ag-Pd alloys, Au-
It can be composed of a Pd-based alloy or the like (hereinafter, these are referred to as a low activity metal group in the present specification).
Any of the metals has a reversible catalytic function for the dissociation reaction of oxygen molecules for injecting oxygen into the solid electrolyte constituting the above-described device and the recombination reaction of oxygen for releasing oxygen from the solid electrolyte (hereinafter , The oxygen dissociation catalytic function) is high, but there is a large difference between the former group and the latter group in the catalytic activity for the reaction between the hydrocarbon-based component to be detected and oxygen. Then, for example, the first electrode and the second electrode are composed of those belonging to a high-activity metal group such as a metal mainly containing Pt, Pd or Rh, and the third electrode is any one of Au, Ni and Ag. If it is made of a metal that belongs to the low-activity metal group such as a metal mainly composed of, the difference in consumption of the detected component between the above-mentioned gap and the opposite space becomes large, and the sensor output level is increased to detect the detected component. The detection sensitivity of the component can be improved.
Regarding the catalytic activity for the reaction of the above-mentioned components to be detected with oxygen, the difference between Pt or Pd and Au is particularly remarkable, and the use of a metal mainly containing these as the electrode material enhances the above-mentioned effect. Can be said to be more desirable.

When the component to be detected is, for example, methane, the detection sensitivity and selectivity may be particularly improved by combining the electrodes made of the above materials. Above all, detected components
The electrode with the higher catalytic activity for the reaction of hydrogen and oxygen with Pt
Alternatively, when Pd is the main metal and the lower electrode is also the Au main metal, the selectivity for methane detection can be significantly improved.

It should be noted that for the reaction between the component to be detected and oxygen
In the case of forming an electrode having a small catalytic activity , at least a portion including a contact surface with exhaust gas can be formed of a material which is catalytically inactive with respect to a reaction between a component to be detected and oxygen. In this case, it goes without saying that the entire electrode can be made of the above-mentioned catalytically inactive material, but at the contact portion with the exhaust gas, only the surface layer portion may be made of the catalytically inactive material, for example, The electrode may be obtained by forming the main body with a catalytically active material and coating the surface with a catalytically inactive material. Examples of the catalyst-inactive material include Au, Ni and Ag described above.
A metal belonging to a low activity metal group such as a metal mainly containing any one of SnO ₂ , ZnO, In ₂ O ₃ ,
Oxides such as WO ₃ and Bi ₂ O ₃ can be exemplified.

Next, a gas holding member made of a metal mesh or a porous metal may be inserted in the gap formed between the oxygen pump element and the oxygen concentration cell element. By doing so, the gas holding member functions as a spacer for forming the gap, and the dimensional accuracy of the gap can be improved. When the gas holding member is made of mesh, it is desirable to use a mesh having a mesh formation density of 100 to 500 mesh.

On the side of the oxygen concentration battery element on which the third electrode is formed, a gap forming member for forming a predetermined gap between the oxygen concentration battery element and the oxygen concentration battery element can be arranged. By doing this, the absolute value of the aforementioned offset electromotive force becomes smaller,
In addition, the fluctuation may be reduced and the detection accuracy of the sensor may be improved. In this case, the gap forming member may be a plate-shaped heating element for heating the oxygen concentration battery element to the sensor operating temperature. In this case, the heating element also serves as the gap forming member, and the sensor can be made compact.

Using the exhaust gas sensor of the present invention as described above, the following exhaust gas sensor system (hereinafter also simply referred to as "sensor system") can be constructed. That is, the sensor system, the exhaust gas sensor, an electromotive force detection means for detecting the concentration battery electromotive force generated in the oxygen concentration battery element, in the direction in which the absolute value of the detected concentration battery electromotive force decreases, Pump element voltage adjusting means for adjusting the voltage applied to the oxygen pump element so that oxygen is pumped into or discharged from the gap between the oxygen pump element and the oxygen concentration cell element, and Output means for outputting the current value flowing through the oxygen pump element or information reflecting the current value when the absolute value of the battery electromotive force reaches the electromotive force target value EC as information reflecting the concentration of the detected component With.

In this case, heat generation control means for controlling heat generation of the heating element can be provided so that the temperature of the oxygen concentration battery element approaches a predetermined temperature target value. That is, in the sensor system, the operation of the oxygen pump element is controlled with reference to the concentration cell electromotive force generated in the oxygen concentration cell element, but since the concentration cell electromotive force changes depending on the element temperature, the same If the temperature of the oxygen concentration battery element changes even if the concentration of the component to be detected is the same, the concentration battery electromotive force, and consequently the value of the pump current serving as concentration detection information, fluctuates, leading to an increase in measurement error. However, by providing the heat generation control means as described above, the heat generation of the heating element is controlled so that the temperature of the oxygen concentration battery element approaches the predetermined temperature target value. The measurement error of the detection component can be reduced, and the measurement accuracy can be improved.

The heat generation control means heats the temperature of the oxygen concentration battery element based on the temperature detection means for detecting the temperature of the oxygen concentration battery element and the temperature detection result of the temperature detection means. An energization control unit that controls energization of the element can be provided. As a result, even if the temperature of the oxygen concentration battery element changes temporarily due to a sudden change in exhaust gas temperature, the pump current information is corrected based on the detected temperature information, It is possible to maintain good detection accuracy of the component. In this case, the temperature of the oxygen concentration battery element may be measured by using a separately provided temperature sensor such as a thermistor or a thermocouple, but since the value of the internal resistance of the concentration battery element changes depending on the temperature, If the temperature is measured by utilizing, there is no need to provide a temperature sensor, and there is an advantage that the configuration of the measurement system can be simplified.

In this case, the sensor system includes a detected component concentration information correction means for generating temperature-compensated detected component concentration information based on the temperature information detected by the temperature detection means and the pump current information. A correction measurement result output means for outputting the generated concentration information of the detected component as a correction measurement result can be provided.

Specifically, the detected component concentration information correction means gives the relationship between the temperature deviation from the temperature target value and the correction amount for the pump current information (pump current correction amount) -temperature deviation-pump current correction amount. A correction reference information storage unit that stores related information as correction reference information, and a pump current that determines a pump current correction amount corresponding to a difference between a temperature detected by the temperature detection unit and a temperature target value by referring to the correction reference information. It can be configured to include a correction amount determination unit and a correction calculation unit that performs a calculation for correcting the measured pump current information based on the determined pump current correction amount. According to this, since the pump current information can be corrected by converting the temperature deviation from the target temperature into the pump current correction amount, the correction processing algorithm can be simplified, and by extension, the correction output of the detected component concentration measurement result can be obtained. The responsiveness can be enhanced.

In this case, the detected component concentration information correction means can be provided with pump current information-detected component concentration information conversion means for converting the pump current information into detected component concentration information, and output the corrected measurement result. The means may output the converted detected component concentration information as temperature-compensated detected component concentration information. Further, the pump current information-detected component concentration information conversion means, specifically, a storage means for storing pump current value-detected component concentration relationship information indicating the relationship between the pump current value and the detected component concentration, and its storage means. With reference to the stored pump current value-detection component concentration relationship information, it is possible to configure as a detection component concentration calculation means for calculating the detection component concentration indicated by the corrected pump current information, The corrected measurement result output means can be configured to output the calculation result. On the other hand, the corrected pump current information may be directly output to the outside.

On the other hand, the detected component concentration information correction means stores pump current information-detected component concentration relation information indicating the relationship between the pump current value and the detected component concentration value for each temperature as correction reference information. Based on the correction reference information storage means, the temperature information detected by the temperature detection means, and the measured pump current information, by referring to the correction reference information, the detected component corresponding to the temperature and the pump current value is detected. It may be configured to include a correction density information generating unit that generates the density value as the temperature information of the detected component density information. According to this configuration, it is necessary to prepare pump current information for each temperature-detected component concentration relationship information, but the measured temperature and pump current can be calculated without calculating the pump current correction amount from the detected temperature. The corresponding detected component concentration can be directly determined, and the responsiveness in the detected component concentration output can be further enhanced.

Next, the temperature detecting means is an internal resistance measuring means for measuring the internal resistance of the oxygen concentration battery element, and temperature information for generating information on the temperature of the oxygen concentration battery element based on the measured internal resistance value. It can be configured to include a generation unit and a temperature information output unit that outputs the generated temperature information. As described above, according to this configuration, it is not necessary to separately provide a temperature sensor or the like, and there is an advantage that the device configuration can be simplified.

Specifically, the internal resistance measuring means includes an internal resistance detection current supplying means for supplying a constant internal resistance detection current to the oxygen concentration battery element, and an oxygen concentration battery when the internal resistance detection current is supplied. And a voltage information detecting means for detecting information (voltage information) reflecting the voltage applied to the element, and measuring the internal resistance value of the oxygen concentration battery element based on the detected voltage information. it can. According to this, the internal resistance of the oxygen concentration battery element can be easily measured from the applied voltage when a constant current is applied.

Here, when there is a difference in oxygen concentration on both sides of the oxygen concentration battery element, a concentration battery electromotive force is generated in the oxygen concentration battery element, and the concentration voltage electromotive force information is included in the detected voltage information. May not be included or may be superimposed to cause an error. In this case, in measuring the internal resistance of the oxygen concentration battery element, the voltage applied to the oxygen concentration battery element is increased by setting the internal resistance detection current larger than a certain value, and the influence of the concentration battery electromotive force is relatively increased. Reducing the size is effective for improving the accuracy of internal resistance measurement. On the other hand, in order to eliminate or reduce the influence of the electromotive force of the concentration cell that is superposed or included, the following method is also effective. That is, in the internal resistance measuring means, in a state in which the internal resistance detection current is not passed through the oxygen concentration battery element,
Concentration battery electromotive force measuring means for measuring the concentration battery electromotive force of the oxygen concentration battery element, and voltage information correction means for correcting the content of the detected voltage information based on the information of the measured concentration battery electromotive force. To provide. Specifically, the influence of the concentration battery electromotive force component can be effectively removed by subtracting the measurement result of the concentration battery electromotive force by the concentration battery electromotive force measuring means from the detection result of the voltage information.

Next, when an internal resistance measuring current is applied to the oxygen concentration battery element, oxygen is transported in the oxygen concentration battery element in the opposite direction of the current application (that is, serves as an oxygen pump), and both sides of the oxygen concentration battery element are transported. Changes in the oxygen concentration of. As a result, when returning to the measurement of the concentration of the detected component by the exhaust gas sensor, the change in the oxygen concentration may cause an error in the measurement accuracy of the concentration of the detected component. Further, when the internal resistance value of the oxygen concentration battery element is high, it becomes difficult for oxygen ions in the oxygen concentration battery element to move,
Polarization may occur when a current is applied. Therefore, the correction current energizing means applies an internal resistance detection current to the oxygen concentration battery element to measure its internal resistance, and then applies a correction current to the oxygen concentration battery element in a direction opposite to the internal resistance detection current. By doing so, since the oxygen is transported in the opposite direction by the energization, the changed oxygen concentration approaches the state before the internal resistance measurement, and the measurement accuracy of the concentration of the detected component after restoration is improved. At the same time, the polarization state of the oxygen concentration battery element can be eliminated. In this case, the magnitude of the correction current and the energization time are set so that approximately the same amount of oxygen that is considered to be transported when the internal resistance detection current is energized is transported backward by the energization of the correction current. For example, it is preferable that a current having substantially the same magnitude as the internal resistance detection current is supplied for approximately the same time as the internal resistance detection current.

Next, the concentration cell electromotive force of the oxygen concentration cell element is compared with a predetermined control reference value, and a pump current corresponding to the difference between the concentration cell electromotive force and the electromotive force target value EC is directed to the oxygen pump element. It is possible to provide a pump current control means for outputting the output. As a result, the concentration battery electromotive force is equal to the electromotive force target value E.
The pump current value will be controlled so that it approaches C. Here, the internal resistance measuring means includes a pump current interruption means for interrupting the pump current output to the oxygen pump element by the pump current control means at a predetermined timing, and the internal resistance detection current conducting means is a pump current interruption means. The internal resistance detection current may be applied to the oxygen concentration battery element while the output of the current is cut off. Thereby, the interference between the internal resistance detection current and the pump current is prevented, and the internal resistance of the oxygen concentration battery element can be accurately detected.

In this case, if the output of the pump current is interrupted for a long time, the concentration battery electromotive force deviates from the electromotive force target value E C and becomes unstable, and detection of the detected component in the exhaust gas of the present invention. The original purpose of the device may be impaired. Therefore, in the internal resistance measuring means, the pump current cutoff means periodically cuts off the pump current output by the pump current control means at predetermined time intervals, whereby the internal resistance measuring means causes the internal pumping current cutoff means to periodically cut the pump current. It can be configured to periodically measure the internal resistance of the oxygen concentration battery element corresponding to the interruption of the current output. As a result, the frequency of the internal resistance measurement can be increased without continuously interrupting the output of the pump current for a long time, which in turn makes it possible to perform temperature compensation for the concentration measurement result of the detected component with higher accuracy. In addition, it is possible to improve the accuracy of the temperature control of the heating element by the heating control means that uses the internal resistance value as the temperature information.

[0073]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below with reference to the examples shown in the drawings. FIG. 1 shows an exhaust gas sensor 1 as an embodiment of the present invention. That is, in the exhaust gas sensor 1, a first heater 2 (heating element), an oxygen pump element 3, an oxygen concentration battery element 4, and a second heater 5 (heating element) each formed in a horizontally long plate shape are laminated in this order. It is configured as The oxygen pump element 3 and the oxygen concentration battery element 4 are composed of a solid electrolyte having oxygen ion conductivity. As such a solid electrolyte, ZrO _{2 in} which Y ₂ O ₃ or CaO is solid-dissolved is typical, but a solid solution of ZrO ₂ with an oxide of an alkaline earth metal or a rare earth metal other than that is used. You may. Moreover, HfO ₂ may be contained in the base ZrO ₂ . In this embodiment, Y ₂
It is assumed that a ZrO ₂ solid electrolyte ceramic in which O ₃ or CaO is dissolved is used. On the other hand, the first and second heaters 2 and 5 are composed of known ceramic heaters.

The oxygen pump element 3 is formed in a horizontally long plate shape,
Porous electrodes 10 and 11 having the ability to dissociate oxygen molecules are formed on both surfaces near one end in the longitudinal direction. Further, in the oxygen concentration battery element 4 (which also functions as a temperature detecting means), similar porous electrodes 12 and 13 are formed on both surfaces of the oxygen pump element 3 at positions corresponding to the electrodes 10 and 11. There is. A plate-shaped spacer portion 200 made of the same solid electrolyte ceramic as that of the elements is provided between the oxygen pump element 3 and the oxygen concentration cell element 4 except for the portions where the electrodes 10 to 13 are formed. Both surfaces thereof are integrated with the oxygen pump element 3 and the oxygen concentration battery element 4 by firing, with the insulating layers 201 and 202 made of Al ₂ O ₃ or the like interposed therebetween. Thereby, the electrode 11 of the oxygen pump element 3 is
A gap 15 is formed between the electrode 12 and the electrode 12 of the oxygen concentration battery element 4. In the gap 15,
Between the oxygen concentration battery element 4 and the oxygen pump element 3, the spacer portion 20 is provided along the side edge portions on both sides in the plate width direction.
An elongated reinforcing spacer portion 203 integrated with 0 is inserted and integrated. Then, the gap 15 communicates with the outer space by using the opening portion 204 opened between both the reinforcing spacer portions 203 as a communication portion on the end faces of the oxygen concentration battery element 4 and the oxygen pump element 3, so that the exhaust gas is discharged. It is possible to go in and out.

On the other hand, the first heater 2 and the oxygen pump element 3
Spacers 6 and 8 (FIG. 2) made of glass, cement, or the like are interposed between the oxygen concentration cell element 4 and the second heater 5, respectively. Has a predetermined amount of gaps 14 and 16, respectively. The gap 15 corresponds to the gap between the oxygen pump element and the oxygen concentration cell element, and the gap 16 corresponds to the opposite space. The second heater 5 also serves as a gap forming member.

FIG. 2 is a drawing in which the spacer portion 200 and the auxiliary spacer portion 203 are omitted in order to show the internal structure of the exhaust gas sensor 1. From the porous electrodes 10 and 11 of the oxygen pump element 3, electrode lead portions 10a and 11a extending integrally along the longitudinal direction of the element 3 toward the mounting base end side of the exhaust gas sensor 1 are integrally formed. ,
A connection terminal 10 is connected to the oxygen pump element 3 at the base end side.
One ends of b and 11b are buried. And, for example,
The connection terminals 10b and 11b are, as shown in FIG.
Conducting part 1 formed by sintering metal paste
0f electrically connects to the ends of the electrode lead portions 10a and 11a. In addition, the oxygen concentration battery element 4
Similarly, for each of the porous electrodes 12, 13 of
a and 13a are integrally formed with connection terminals 12b and 13b, respectively.

FIG. 3A shows an example of the entire structure of the exhaust gas sensor 1, and FIG. 3B shows its internal structure. That is, the main part of the exhaust gas sensor 1 is a laminated body 31 including the first heater 2, the oxygen pump element 3, the oxygen concentration battery element 4 and the second heater 5 shown in FIGS. 1 and 2,
Ceramic stopper 30 having square through hole 30a
Are fitted to the laminated body 31 from the outside. One end side of the laminated body 31 is opened, and the inside end of the ceramic porcelain tube 32 having the bottom portion 32b in which the through hole 32a is formed is formed on the other end side. 31a is arranged so as to project from the through hole 32a, and glass G is filled between the porcelain bushing 32 and the laminated body 31. The ceramic stopper 30 also plays a role of defining the amount of protrusion of the laminated body 31 from the porcelain tube 32 by contacting the end surface thereof with the inner surface of the bottom portion 32b of the porcelain tube 32.

The outer side of the porcelain insulator 32 is provided with a metal outer cylinder 3
3 and the metal shell 34 integrated with the outer cylinder 33 by the caulking coupling portion 34a. Metal shell 34
A male screw portion 34b for attaching the sensor 1 to an attachment portion (not shown) such as an exhaust pipe is formed on the outer peripheral surface of the, and the above-mentioned laminated body 31 is detected in the opening portion 34c formed at the tip side thereof. The end 31a is projected. An annular protector mounting sleeve 34d is integrally formed on the periphery of the opening 34c of the metal shell 34. A large number of through holes 3 that cover the detection end portion 31a and allow exhaust gas to flow to the detection end portion 31a.
A cylindrical protector 35 having 5a is fitted to the protector mounting sleeve 34d from the outside and further joined and integrated by spot welding or the like. On the other hand, in the space formed between the metal shell 34 and the intermediate portion of the porcelain bush 32, the caulking metal fitting 3 for receiving the processing force at the time of caulking is provided on the side close to the caulking coupling portion 34a.
6 is arranged, and the remaining space is filled with the filler 80.

On the other hand, each element 2 to 5 constituting the laminated body 31
A lead wire 37 is joined to the connection terminal (Fig. 1 etc.) of the same by welding or the like, and the terminal side of the lead wire 37 and the outer tube 33.
Extends outward from the end of. The middle portion of the lead wire 37 is a seal member 38 made of an elastic material such as rubber.
The outer protective cylinder 39 made of metal is fitted on the outer side of the protective outer cylinder 39. Then, the protective outer tube 39
The edge side of the is integrated with the outer cylinder 33 by caulking.

The exhaust gas sensor 1 is attached to, for example, a mounting portion provided on the exhaust pipe so that the protector 35 side is located inside the exhaust pipe. As shown in FIG. 4, in this state, the oxygen pump element 3 has a porous electrode 1
Voltage is applied through the lead wire 37 (FIG. 3) so that one of 0 and 11 is positive and the other is negative. And
In a porous electrode having a positive polarity, oxygen molecules in exhaust gas in contact with the porous electrode are dissociated on the electrode, and the dissociated oxygen acts as a driving force by the dissociated oxygen in the form of an element 3 Sent in. The oxygen ions transported in the element 3 by the voltage application receive electrons on the porous electrode having a negative polarity, are further recombined with oxygen molecules, and are released into the atmosphere.

In the oxygen concentration battery element 4, no voltage is applied to the porous electrodes 12 and 13, and the oxygen molecules in the exhaust gas contacting the electrodes 12 and 13 are dissociated on the electrodes 12 and 13. And diffuse into the element 4 in the form of oxygen ions, respectively. When there is a difference in oxygen concentration between the electrodes 12 and 13 side, a concentration gradient of oxygen ions is generated in the element 4, and a concentration cell electromotive force corresponding to the concentration gradient is generated between the electrodes 12 and 13. Will occur. In the following, the oxygen pump element 3 and the oxygen concentration cell element 4 will be described.
With respect to the gap 15 formed between the first electrode and the gap 15, the porous electrode 10 of the oxygen pump element 3 that does not face the gap 15 is the outer electrode, and the porous electrode 11 that also faces the gap 15 is the first electrode and the gap 15. The facing porous electrode 12 of the oxygen concentration battery element 4 is referred to as a second electrode, and the porous electrode 13 not facing the gap 15 is referred to as a third electrode.

On the other hand, of the above porous electrodes 10 to 13,
At least some of them have a function of dissociating or recombining oxygen molecules as described above, and a binding reaction between a hydrocarbon-based component to be detected in the exhaust gas in contact with oxygen, that is, combustion of the component to be detected. It also functions as an oxidation catalyst that accelerates the reaction. In the exhaust gas sensor of the present invention, the first electrode 11 and the second electrode 12 among the above four electrodes 10 to 13 are used.
And the third electrode 13, the catalytic activity for the reaction between the detected component and oxygen with respect to the detected component (hereinafter,
Below, the oxidation catalyst activity) is adjusted so that there is a difference in the consumption amount of the detected component due to the reaction with oxygen on both sides of the oxygen concentration battery element 4 (that is, the gap 15 side and the gap 16 side).

Specifically, referring to FIG. 4, the first electrode 11
The second electrode 12 and the second electrode 12 are, for example, Pt porous electrodes having a high oxidation catalytic activity for hydrocarbons, and the third electrode 13 is an Au porous electrode having a low oxidation catalytic activity. The sizes of the gap 15 and the gap 16 are adjusted within the range of 1 mm or less. On the other hand, the first electrode 11
The area Sp of the second electrode 12 is equal to or larger than the area SS of the second electrode 12.

A method of integrally firing the oxygen pump element 3 and the oxygen concentration battery element 4 will be described below with reference to FIG. That is, the unfired assembly 310 for forming the integrally fired body forms the first portion 211 (corresponding to the first ceramic powder compact) for forming the oxygen pump element 3 and the oxygen concentration battery element 4. For the second part 2
12 (corresponding to a second ceramic powder compact) and a third portion 213 for forming the gap 15. First, the first portion 211 is formed by using a green body obtained by kneading ZrO ₂ powder with an organic binder,
It contains a ZrO ₂ green sheet 220 to be the body of the oxygen pump element 3. Insulation for insulating between the lead portions 10a, 11a and the oxygen pump element 3 in the regions on both surfaces of the ZrO ₂ green sheet 220 except the portions where the electrodes 10, 11 (FIG. 2 etc.) are planned to be formed. The coats (insulating layer patterns) 221 and 222 are formed by using Al ₂ O ₃ paste or the like. After forming the insulating coats 221 and 222, the electrodes 10 and 11 and the lead portion 10 are formed.
electrode patterns 223 and 2 for forming a and 11a
24 is printed by Pt paste or the like. Further, a protective overcoat 225 is formed of Al ₂ O ₃ paste or the like on the electrode pattern 223 on the side to be the outer electrode 10.

On the other hand, similarly, the second portion 212 is also the ZrO ₂ green sheet 2 to be the main body of the oxygen concentration battery element 4.
Insulating coats (insulating layer patterns) 231 and 232 are formed on both surfaces of 30. Here, an electrode pattern 233 for forming the electrode 12 and its lead portion 12a is formed on the side of the insulating coat 231, but the electrode 13 (third electrode) made of Au has a low melting point and is made of ZrO ₂ . Since it is impossible to integrally burn the lead part,
Only an electrode lead portion pattern 234 for forming 3a is formed, and a protective overcoat 235 is applied thereon with an Al ₂ O ₃ paste.

Next, the third portion 213 is the spacer portion 20.
A ZrO ₂ green sheet 240 in which a portion 200a to be 0 (spacer molded body) and a portion 203a to be the reinforcing spacer portion 203 are integrally formed is mainly configured, and the bonding coats 241 and 242 are formed on both surfaces thereof. And are formed by using Al ₂ O ₃ paste or the like. The pasting coats 241 and 242 together with the above-mentioned insulating coats 222 and 231 become insulating layers 201 and 202 by firing, respectively, and form the spacer portion 200 and the reinforcing spacer portion 203, the oxygen pump element 3, and the oxygen concentration cell element 4. Play a role of joining each other.

The first portion 211 and the third portion 213 are laminated on each other, and Pt- for forming the terminals 10b and 11b (FIG. 2) corresponding to the end portions of the lead portions 10a and 11a between them. One end side of each of the Rh alloy wires 243a and 243b is sandwiched. A through hole 220a is formed at a position corresponding to the end of the lead portion 10a of the ZrO ₂ green sheet 220.
When forming the pattern of 0a, the paste is filled therein, and as shown in FIG. 2B, the filled paste is sintered to become the conductive portion 10f and the terminal 10 is formed.
b (Pt-Rh alloy wire 243b) is electrically connected to the lead portion 10b. On the other hand, the pattern of the lead portion 11a and the Pt—Rh alloy wire 243a are sandwiched between the ZrO ₂ green sheets 220 and 240 and are in direct contact with each other.

The second portion 212 is also laminated from the side opposite to the first portion 211 with respect to the third portion 213, and terminals 12b and 13b (FIG. 2) are formed corresponding to the end portions of the lead portions 12a and 13a. Pt-Rh alloy wire 24 for
4a, 244b is sandwiched on one end side,
The green assembly 310 is completed. A through hole 230a is provided at a position corresponding to the end of the lead portion 13a of the ZrO ₂ green sheet 230, similarly to the through hole 220a of the first portion 211, and a conductive portion based on the paste filled therein is formed. Thus, the terminal 13b and the lead portion 13a are electrically connected. In addition, the pattern of the lead portion 12a and the Pt-Rh alloy wire 244 that becomes the terminal 12b.
The a is sandwiched between the ZrO ₂ green sheets 240 and 230 and is in direct contact therewith.

By firing the unfired assembly 310, the oxygen pump element 3 shown in FIGS.
And the oxygen concentration battery element 4 with the third electrode 13 not formed.
An integrated fired product of is obtained. Then, as shown in FIG. 5, a pattern 245 is paste-printed on a corresponding position of the oxygen concentration battery element 4 using Au powder paste, and the temperature is lower than the firing temperature of the ceramics (for example, 850 to 850).
The third electrode 13 is formed by baking at 1000 ° C. and performing the secondary metallization process, and the main part of the exhaust gas sensor is completed.

The outline of the operating principle of the exhaust gas sensor 1 is as follows. As shown in FIG. 4, the exhaust gas sensor 1 is attached to the exhaust pipe, and the gap 15 between the oxygen pump element 3 and the oxygen concentration battery element 4 and the gap 16 between the oxygen concentration battery element 4 and the heater 5 (opposite When exhaust gas containing a hydrocarbon-based component to be detected and oxygen is introduced into the space), the electrodes 11 and 12 located on the gap 15 side are both formed of Pt and the gap 16 side. Electrode 1 located at
Since 3 is composed of Au, the amount of consumption of the component to be detected in the exhaust gas due to oxidation is larger on the gap 15 side than on the gap 16 side. On the side where the amount of component to be detected is large, the amount of oxygen in the exhaust gas EG is also large. Therefore, the oxygen concentration in the gap 16 becomes higher than that in the gap 15, and the oxygen concentration battery element 4, a concentration cell electromotive force is generated with the gap 16 side being positive.

Then, when oxygen is pumped from the gap 14 side to the gap 15 side by the oxygen pump element 3 so that the absolute value of the concentration battery electromotive force becomes a constant value of, for example, 10 mV or less, the oxygen pump element 3 is removed. The flowing current (hereinafter, referred to as oxygen pump current or pump current) has a value that reflects the amount of oxygen consumed for the oxidation of the component to be detected. Further, when the concentration of the detected component in the exhaust gas EG increases, the amount of oxygen consumed by the oxidation increases, and as a result, the pump current also increases. Therefore, by measuring the pump current, the concentration of the component to be detected in the exhaust gas EG can be known.

Next, in the exhaust gas sensor 1,
As shown in FIG. 6, a column portion 210 is formed between the oxygen concentration battery element 4 and the oxygen pump element 3 in the gap 15 to define the gap of the gap 15 without hindering gas from entering and leaving the gap 15. can do. In the example shown in FIG. 6, the support column 210 is formed of a solid electrolyte ceramic of the same material as the oxygen pump element 3 and the oxygen concentration battery element 4 into a partition wall shape that divides the gap 15 into two parts at an intermediate position in the longitudinal direction. Has been done. An auxiliary spacer portion 215 is inserted and integrated on the side opposite to the spacer portion 200 with respect to the gap 15. The gap 15 is formed in each of the openings 2 formed on both sides of the support column 210 on both side surfaces in the width direction of the stack of the oxygen pump element 3 and the oxygen concentration cell element 4.
The exhaust gas can enter and exit by communicating with the outer space with 04 as a communication portion.

The column 210 can be integrally formed with the oxygen pump element 3 and the oxygen concentration battery element 4 by firing the unfired assembly 310 shown in FIG. The green assembly 310 of FIG. 7 is constructed exactly as shown in FIG. 5 except for the third portion 213. Then, in the third portion 213, the spacer molded body 200a for forming the spacer portion 200 and the auxiliary spacer portion 2 arranged on the opposite side to the space scheduled in the gap 15 are sandwiched therebetween.
Auxiliary spacer molding 215a for forming 15 and
Further, the pillar portion molded body 210a as the pillar portion pattern arranged between the two is formed of the ZrO ₂ green sheet 240.
Formed on both sides of the above-mentioned first portion 21
1 and the second portion 212 are laminated.

Then, by firing this, the column portion 210 based on the column portion molded body 210a is formed between the oxygen concentration battery element 4 and the oxygen pump element 3.
By inserting the pillar portion molded body 210a at the time of firing, it is possible to prevent the ZrO ₂ green sheets laminated with a gap formed therebetween from being deformed at the time of firing and hanging down to the gap side. 15 can be stably formed. In addition, in the example shown in FIG.
Is formed so as to cross the electrodes 11 and 12 in the width direction, but it may be formed at a position where it does not interfere with the electrodes 11 and 12 as shown in FIG. In the figure, a plurality of column portions 210 are arranged at predetermined intervals on both sides of the oxygen concentration battery element 4 and the oxygen pump element 3 in the width direction so as to extend along the longitudinal direction thereof. On the other hand, if the length of the gap 15 in the longitudinal direction between the oxygen concentration battery element 4 and the oxygen pump element 3 is not so large, the strut portion 210 may be omitted as shown in FIG. is there.

At least one of the first and second heaters 2 and 5 may be integrated with the oxygen concentration battery element 4 and the oxygen pump element 3 by firing. FIG. 10 shows an example of the oxygen pump element 3
On the other hand, the first heater 2 is laminated on the side opposite to the gap 15, and the oxygen pump element 3, the oxygen concentration cell element 4, and the first heater 2 are formed as an integral fired body laminated on each other. There is. The second heater 5 is omitted.
Here, a gap 14 is formed between the first heater 2 and the outer electrode 10, and in the area other than the gap 14, the first heater 2 and the oxygen pump element 3 are made of Al ₂ O ₃ or the like. It is joined via the configured insulating layer 2c.

The above sensor structure has a structure as shown in FIG.
Basically, in the unfired assembly shown in FIG. 7, the fourth portion (third ceramic powder compact) to be the first heater 2 from the side opposite to the third portion 213 with respect to the first portion 211. It is obtained by stacking 214 and firing the unbaked assembly 310 obtained as the laminate. Hereinafter, the difference from FIG. 7 will be described. First portion 21
1 to 7, the overcoat 225 of FIG. 7 is omitted, and the Pt—Rh alloy wire 2 serving as the terminals 2a and 2b (FIG. 10) for energizing the heater from the side closer to the electrode pattern 223 is formed.
57a, 257b, bonding coat 256 (using Al ₂ O ₃ paste, etc.), auxiliary support pattern 255 for gap formation
(With carbon paste, etc.), overcoat 254
(Al ₂ O ₃ paste etc.), heater pattern 253
(Using Pt paste or the like), insulating coat 252 (Al ₂
O ₃ by paste or the like), ZrO ₂ green sheet 251
(Becomes the heater body), and overcoat 250 (A
1 ₂ O ₃ paste or the like) is laminated in this order to form the fourth portion 214. In addition, the column part 210 is shown in FIG.
It is omitted as in the configuration of FIG. Here, the auxiliary support pattern 255 for forming a gap is selectively formed in a region corresponding to the outer electrode 10 with respect to the electrode pattern 223, disappears during firing, and becomes a ZrO ₂ green sheet 251, as shown in FIG. A gap 14 is formed between the heater body 2 and the oxygen pump element 3 which are based on each other.

Next, FIG. 12 shows an example of the structure of an exhaust gas sensor which does not use a spacer portion, as a simpler structure. That is, in the exhaust gas sensor 1, the oxygen pump element 3 and the oxygen concentration battery element 4 are respectively formed in a horizontally long plate shape and are arranged to face each other, and the electrodes 10 to 13 are arranged in the oxygen pump element 3 and the oxygen concentration battery, respectively. The element 4 is formed on one end side in the longitudinal direction of the plate surface. Then, in the gap 15, the oxygen pump element 3
While the column portion 210 is formed between the oxygen concentration cell element 4 and the oxygen concentration battery element 4, the oxygen pump element 3 and the oxygen concentration cell element 4 have a thickness smaller than the height of the column portion 210 in the region excluding the gap 15. They are joined and integrated with each other via the insulating layer 260. The first and second heaters 2 and 5
Although at least one is provided, this is omitted in FIG.

The gap 15 is opened to both side surfaces in the width direction of the laminated body of the oxygen pump element 3 and the oxygen concentration battery element 4, and a communication portion 261 through which exhaust gas can flow in and out is formed.
The terminals 10b, 11b, 13b of the electrodes 10 to 13 are
On the end face side in the longitudinal direction of the oxygen pump element 3 and the oxygen concentration battery element 4, the base end side is projected so as to be sandwiched therebetween. The connection form of the terminals 10b and 13b to the electrodes 10 and 13 is the same as that shown in FIG. Also, since the electrodes 11 and 12 are commonly grounded as described later, the terminal 11b is connected to both electrodes 1
1 and 12 are shared between the terminals 1 and 12, and the terminal 12 in the configuration of FIG.
b is omitted. In addition, the column part 210 is shown in FIG.
As shown in (c), a rectangular cross section is formed in a scattered or staggered shape, but it may be formed in a circular cross section as shown in (d) of the figure, or (e) in the figure. As shown in FIG. 5, the rectangular cross sections having different lengths may be mixed.

Regarding the manufacturing method of the above sensor structure, FIG.
Will be explained. Also in this case, basically, the green assembly 31 including the first portion 211 and the second portion 212 described above is basically used.
It is manufactured by firing 0. However, it has the following manufacturing method differences from the sensor structure shown in FIG. First, the third portion including the ZrO ₂ green sheet for forming the spacer portion is omitted, and instead, the ceramic powder is provided in the area scheduled to be the gap 15 on the respective facing surfaces of the first portion 211 and the second portion 212. Using a paste (for example, a porous Al ₂ O ₃ powder paste), the pillar 2
Column patterns 266a and 266b to be 10 are formed. In addition, the pillar pattern 266a and 2
The gap 1 is also provided at a position where it does not overlap with 66b.
Auxiliary support patterns 267a and 267b are formed in a region scheduled for No. 5 by a powder paste (for example, carbon paste) made of a material that burns or decomposes during firing. Further, a bonding coat 269 as an insulating layer pattern is formed in the area other than the area scheduled for the gap 15 as described above.
The support pattern 266a and 266b is formed of l ₂ O ₃ powder paste or the like with a thickness smaller than the total height of the support pattern 266a and 266b.

By firing the unfired assembly 310, as shown in FIG. 15, the auxiliary support pattern 26 is provided between the oxygen concentration battery element 4 and the oxygen pump element 3.
7a and 267b disappear, and the pillar patterns 266a and 266b are integrated by firing to form the pillar 210, and the pillar 210 forms the gap 15 in a size-defined manner. On the other hand, in regions other than the gap 15, the oxygen concentration battery element 4 and the oxygen pump element 3 are bonded to each other via the insulating layer 260 based on the bonding coat 269.

Here, as shown in FIG. 14, the support column patterns 266a and 266b and the auxiliary support pattern 267 are provided.
a and 267b are formed complementarily so as to almost completely fill the plane, and when the first portion 211 and the second portion 212 are laminated, based on the reinforcing effect of the auxiliary support patterns 267a and 267b, the pillar pattern 266a, It is prevented or suppressed that the 266b is crushed between the two. Also,
The main parts of the first part 211 and the second part 212 are Zr.
Since the O ₂ green sheets 220 and 230 are formed, as shown in an exaggerated manner in FIG. 15A, even if the laminating coat 269 is formed to be considerably thinner than the total thickness of 266a and 266b, the ZrO _By slightly bending the _two green sheets 220 and 230, the _two green sheets 220 and 230 can be adhered to each other through the laminating coat 269 and can be integrated by firing without any trouble.

FIG. 16 shows a modification of the sensor structure obtained by a manufacturing method similar to that shown in FIG. In this structure, the communicating portion of the gap 15 is not the open portion,
Porous Ceramic Body 270 Made of Porous Al ₂ O ₃ Fired Body
Is configured as. Moreover, the column part 210 is not formed.

A method of manufacturing the above structure will be described with reference to FIGS. 17A and 17B, focusing on differences from FIG. First, FIG.
In place of the pillar portions patterns 266a and 266b, the communicating portion pattern 2 for forming the porous ceramic body 270.
71a and 271b are formed of a porous Al ₂ O ₃ powder paste, and auxiliary support patterns 272a and 272b for forming a gap made of carbon paste are formed in the gap forming portion as in FIG. By firing this, the communicating portion patterns 271a and 271b are integrated to form the porous ceramic body 270, and the gap forming auxiliary support patterns 272a and 272b disappear to form the gap 15.

A sensor system using the above exhaust gas sensor will be described below. FIG. 18 is a block diagram showing an electrical configuration of an example of a sensor system using the exhaust gas sensor 1. That is, the sensor system 50
Is the exhaust gas sensor 1 and the microprocessor 51.
And the exhaust gas sensor 1 and the microprocessor 51
It is composed of a peripheral circuit 50a for connecting to. The CPU 53 of the microprocessor 51 is the ROM 5
5, the detected component concentration information correction means, energization control means, pump current correction amount determination means, correction calculation means, correction concentration information generation means, internal resistance measurement means, temperature information generation means, and light and shade It is the main body of the battery electromotive force measuring means and the voltage information correcting means.

In the oxygen concentration battery element 4 of the exhaust gas sensor 1, the second electrode 12 is grounded, while the third electrode 13 is a switch mechanism, for example, the switch Sw1 of the bipolar analog switch circuit 60 composed of a CMOS-IC or the like. Is connected to the negative terminal side of the operational amplifier 61 (pump current control means) for inverting amplification via. On the other hand, on the positive terminal side of the operational amplifier 61, a power supply circuit 65 for giving an electromotive force target value EC
Are connected. The power supply circuit 65 has an electromotive force target value E
It is configured so that the set value of C can be changed within a certain range.
For example, in the example shown in the drawing, three fixed resistors 66a to
66c and one variable resistor 66d on each side, a bridge circuit 66, and a power supply 67 connected thereto. The variable resistor 66d has a resistance range of Rmin to Rm.
As ax, the resistance values of the fixed resistors 66a to 66c are adjusted so that the bridge is balanced at a certain resistance value Re where Rmin <Re <Rmax and the output voltage to the terminal of the operational amplifier 61 becomes zero. By shifting the resistance value of the variable resistor 66d from Re to the Rmin or Rmax side, the electromotive force target value EC can be changed within a certain range on both positive and negative sides with 0V interposed therebetween.

Next, the operational amplifier 61 is provided with the peripheral resistor 6
A differential amplifier is configured with 1a to 61d, and its output side is connected to the outer electrode 10 of the oxygen pump element 3 via a resistor 62 for current detection. On the other hand, the first electrode 11 side of the oxygen pump element 3 is commonly grounded with the second electrode 12 of the oxygen concentration battery element 4. As a result, the operational amplifier 6
1 is the concentration cell electromotive force input Em of the oxygen concentration cell element 4
Then, the differential voltage Em−EC from the electromotive force target value EC is inverted and amplified and applied to the first electrode 11 side of the oxygen pump element 3. If the electric resistance values of the resistors 61a and 61b are R1 and R2, respectively, the voltage gain of the operational amplifier 61 is A1 = R1 / R2.

Here, as shown in FIG. 19, if Em> EC, then Em-EC> 0. Therefore, the output voltage -A1 (Em-EC) of the operational amplifier 61 becomes negative and the oxygen pump element 3
Is applied with a voltage so that the first electrode 11 side becomes negative,
A pump current Ip flows through the oxygen pump element 3 in a direction in which oxygen is drawn into the gap 15. This pump current Ip is taken out as a voltage signal in the form of a voltage difference between both ends of the current detection resistor 62 (resistance value R3) by the operational amplifier 64 that constitutes a differential amplifier together with the peripheral resistors 64a to 64d. As shown in FIG. 18, it is digitized by the dipolar A / D converter 70 and input to the microprocessor 51. Incidentally, 64a and 64b are gain adjusting resistors (resistance values R5 and R6, respectively) of the operational amplifier 64.

Next, as shown in FIG. 18, the analog switch circuit 60 is provided on the third electrode 13 side of the oxygen concentration battery element 4.
The constant current power supply circuits 73 and 74 having different current values IC and different polarities are connected to each other through Sw2 and Sw3. The voltage signal VS on the third electrode 13 side is
It is adapted to be digitally converted by a dipolar type A / D converter 71 and input to the microprocessor 51. In addition, each switch Sw of the analog switch circuit 60
1 to Sw3 are turned on / off in response to a control signal from the microprocessor 51.

The first and second heaters 2 and 5 of the exhaust gas sensor 1 are connected to the microprocessor 51 via, for example, a common heater energizing circuit 72. Figure 2
An example of the heater energizing circuit 72 is shown in 0 (a). The heater energizing circuit 72 includes a D / A converter 80 for converting a heater control value given from the microprocessor 51 into an analog signal, and a current amplification transistor 8 connected to the D / A converter 80.
2 and the heaters 2 and 5 are connected to the transistor 82. The transistor 82 operates in the active region and increases the energization current of the heaters 2 and 5 according to the applied heater control value.

On the other hand, FIG. 20B shows PWM (pulse wi
Heater energizing circuit 7 adopting dth modulation) control method
2 shows an example. The main part of this circuit 72 is the PWM control circuit 85, which
D / A that converts the heater control value given by
Converter 86, triangular wave (or sawtooth wave) generating circuit 87, D / A converter 86 and triangular wave generating circuit 8
Single power supply operational amplifier 8 to which the output from 7 is input respectively
And 8 are included. Single power supply operational amplifier 88
Operates as a comparator that outputs either zero or a predetermined voltage V that is not zero according to the magnitude relationship between the heater control value and the triangular wave input value (in this embodiment, + V when the triangular wave input value is large, heater control Zero shall be output when the value is large). Hereinafter, the operational amplifier 88 is referred to as a comparator 88.

Further, FIG. 20C shows a triangular wave generating circuit 8
7 shows an example, and the main part thereof is composed of an operational amplifier 89 functioning as a comparator, and an integrating circuit 100 composed of an operational amplifier 98, a resistor 97 and a capacitor 99. The operational amplifier 89 outputs maximum positive and negative voltages, respectively, depending on whether the voltage added value at points A and B in the figure is positive or negative. The output voltage of the operational amplifier 89 is a square wave whose positive and negative voltage with respect to 0V is a constant value VZD due to the diode groups 92 to 95 and the Zener diode 96, and this is a triangular wave with the maximum positive and negative amplitude with respect to 0V being VZD by the integrating circuit 100. Is converted to. The period λ of the triangular wave (FIG. 21) can be adjusted according to the resistance value of the resistor 97 and the capacitance of the capacitor 99 of the integrating circuit 100. The generated triangular wave is amplified to a predetermined amplitude by the operational amplifier 101, and the comparator 88 of FIG.
Is output to.

FIG. 21 is a diagram for explaining the operation of the PWM control circuit 85. At the input of the comparator 88, the output of the comparator 88 is + V while the heater control voltage value Vi is smaller than the triangular wave input Vt. Otherwise, it is 0. As a result, the comparator 8
No. 8 has a duty ratio of {(Vi + Vmax) / 2Vmax} × λ
(However, -Vmax≤Vi≤ + Vmax, where Vmax is the maximum amplitude of the triangular wave input), the PWM wave is output. This P
The transistor 82 in FIG. 20B is switched at high speed by the WM wave output, and the heaters 2 and 5 are intermittently energized at the above duty ratio. Then, by changing the duty ratio according to the heater control voltage value Vi, the heat generation of the heaters 2 and 5 is adjusted.

Next, the microprocessor 5 shown in FIG.
Reference numeral 1 denotes an I / O port 52 serving as an input / output interface with the peripheral circuit 50a, and a CPU 5 connected to the I / O port 52.
3, RAM 54, ROM 55, clock circuit 56 and the like. In the RAM 54, the CPU 53
And a measured value memory area 54b for storing data of various measured values fetched in the process described later or various counter values generated in the process of the control process described later. Also, ROM5
5, a control program 55a that controls the output value determination of the detected component of the sensor system 50 and its output control,
Correction reference information 55b used by the control program 55a
(The content will be described later) is stored. Also,
The CPU 53 realizes a timer function for time measurement used in the process described later by counting clock pulses of a constant cycle generated by the clock circuit 56.

The operation of the sensor system 50 will be described below with reference to the flow of processing viewed from the CPU 53 of the microprocessor 51. 30 to 32 show the flowcharts thereof. First, in S1 of FIG. 30, activation processing of the exhaust gas sensor 1 is performed. The purpose of the activation process is to start the energization of the heaters 2 and 5 to stabilize the oxygen pump element 3 and the oxygen concentration battery element 4 at a predetermined operating temperature. Then, the element temperature is detected by measuring the internal resistance of the oxygen concentration cell element 4, and the internal resistance value RVS is shown in FIG.
This is performed by utilizing the fact that the temperature dependence is constant as shown in FIG.

Details of the processing are shown in FIG. That is, in S101, the heater energizing circuit 72 is set to the desired set value Vh0 as the control value Vi. At this time, Sw1 to Sw3 of the analog switch circuit 60 are all turned off, and the operational amplifier 61 is also deactivated. In this state, S10
2 to the heater energizing circuit 72, the heater control voltage value Vi
The heater energization is started by outputting the initial setting value Vh0. Then, when a certain time t0 has elapsed from the start of energization in S103, the temperature control process is started. First S10
In step 4, Sw2 of the analog switch circuit 60 in FIG. 18 is turned on, and in step S105, the activation judgment counter value N is cleared.

Next, in S106, the value of the voltage VS on the third electrode 13 side of the oxygen concentration battery element 4 is set to the A / D converter 7.
1 (FIG. 18), and the internal resistance RVS of the oxygen concentration battery element 4 is calculated from the value of VS in S107.
That is, since Sw1 is off and the operational amplifier 61 is also inactive, the constant current power supply 73 (current Ic: current for detecting internal resistance) is actuated to the oxygen concentration battery element 4 as shown in FIG.
The energization path shown in 2 is formed. Since the second electrode 12 side of the oxygen concentration battery element 4 is grounded, the voltage VS on the third electrode 13 side is VS = IC × RVS with the internal resistance of the oxygen concentration battery element 4 as RVS. It is represented by (1). Here, VS has the meaning as voltage information applied to the oxygen concentration battery element 4, and the internal resistance value RVS
Can be obtained by RVS = VS / IC (2). Strictly speaking, the concentration battery electromotive force Em of the oxygen concentration battery element 4 is superposed on the voltage VS, but the current Ic is sufficiently large in this activation process, and the concentration battery electromotive force Em is The partial pressure applied to the element 4 is negligible as compared with the partial pressure applied to the element 4, and the correction is not performed. However, the correction may be performed by the method described below.

As described above, as shown in FIG.
The value of RVS has a constant relationship with the element temperature T of the oxygen concentration battery element 4, and this relationship is used as the correction reference information 55b for R
If stored in the OM 55 (FIG. 18), the element temperature T can be determined from the value of RVS. Further, the RVS value itself can be used as the temperature information. In the present embodiment, in order to make the explanation easy to understand, as shown in FIG. 24B, a map 301 indicating the values of various internal resistances RVS and the element temperatures T in association with each other is stored in the ROM 55. Therefore, the temperature T corresponding to RVS is obtained by the interpolation method with reference to this map 301 (S1).
07). The value of the calculated internal resistance RVS is shown in FIG.
Is stored in the measured value memory area 54b, and is overwritten and updated when a new internal resistance RVS is detected and calculated.

This determined element temperature T is the upper limit value Tma.
It is determined in S108 and S110 whether or not the temperature is within the set temperature range of x and the lower limit value Tmin. When the element temperature T is higher than the upper limit value Tmax, the heater control voltage value Vi is reduced by a constant value ΔVi to suppress the heat generation of the heaters 2 and 5, and conversely is lower than the lower limit value Tmin. The heater control voltage value Vi is increased by ΔVi to increase the heaters 2, 5
Of heat is promoted (S109, S111). Also, T
If min≤T≤Tmax, the current value of Vi is maintained and the activation determination counter value N is incremented (S112,
S113).

Then, the value of the activation judgment counter value N is
For example, until the set value NS is reached, the above S106 to S1
13 is repeated at a constant time interval ta (S114,
S115), if N reaches NS, it is considered that the element temperature T has been maintained substantially within the set temperature range, as shown in FIG.
, The switch 2 of the analog switch circuit 60 is turned off, S
After turning on w1, turning on the operational amplifier 61 and warming up for a predetermined time tw, the activation process ends (S116, S117).

Returning to FIG. 30, when the activation process S1 is completed, the process proceeds to S2, and the detection of the pump current Ip of the oxygen pump element 3 is started. In this state, the analog switch circuit 6
For 0, only Sw1 is turned on, so the energization path is as shown in FIG. The operation of the sensor 1 in this state will be described below.

That is, as the sensor 1 comes into contact with the exhaust gas, a hydrocarbon such as methane (hereinafter referred to as HC) as a component to be detected reacts with oxygen in the gap 15 to reduce the oxygen concentration. Then, a concentration battery electromotive force Em having a positive value on the third electrode 13 side is generated in the oxygen concentration battery element 4. Here, if the electromotive force target value EC input to the operational amplifier 61 is 0, for example, Em-EC> 0. Therefore, the output voltage -A1 (Em-EC) of the operational amplifier 61 becomes negative and the oxygen pump A voltage is applied to the element 3 so that the first electrode 11 side becomes negative, and a pump current Ip flows in the oxygen pump element 3 in a direction to pump oxygen into the gap 15. Then, oxygen is pumped into the gap 15 by the oxygen pump element 3 and the concentration cell electromotive force Em gradually decreases, so that the oxygen pump current Ip is controlled to decrease. As a result, finally, the concentration cell electromotive force Em is almost zero.
The oxygen pump current is controlled so that the concentration of the component to be detected can be known from the equilibrium value of the oxygen pump current Ip at that time. As described above, the signal of the pump current Ip is converted into a voltage signal by taking the difference between the voltages across the resistor 62 for current detection by the operational amplifier 64, and the A / D converter 7
It is digitized by 0 and input to the microprocessor 51. However, the electromotive force target value EC is not always set to 0 in practice. The reason will be described below.

First, the fact that the concentration cell electromotive force is 0 means that both sides of the oxygen concentration cell element 4 (ie,
This means that the oxygen concentrations in the gaps 15 and 16) are equal. This means that the pump current is
It also means that it directly corresponds to the difference in the consumption amount of the component to be detected in and, so that the concentration of the component to be detected can be accurately detected and the detection result can be easily analyzed. However, usually, even if the oxygen concentrations in the gaps 15 and 16 become equal, the electromotive force of the oxygen concentration battery element 4 does not actually become 0, and a constant offset electromotive force often remains. In this case, the electromotive force target value EC corresponding to the offset electromotive force is set in the range of 10 mV or less, and the oxygen pump element 3 flows when the absolute value of the concentration battery electromotive force reaches the electromotive force target value EC. By using the current value as the detection signal, the concentration of the component to be detected in the exhaust gas can be detected more accurately.

Further, the offset electromotive force of the oxygen concentration battery element 4 tends to fluctuate as the oxygen concentration in the exhaust gas relating to detection decreases, and the electromotive force target value EC is set on the basis of the offset electromotive force at a certain oxygen concentration or less. When is set, the sensor output is easily affected by the oxygen concentration in the exhaust gas. Therefore, when a test gas containing, for example, 1% by volume or more (preferably 10% by volume or more) of oxygen and substantially no component that reacts with oxygen at the sensor operating temperature is introduced into the gaps 15 and 16, respectively. It is effective to set the absolute value of the offset electromotive force to EOS (unit: mV), and set the electromotive force target value EC within the range of (EOS-5) mV or more and (EOS + 5) mV or less with reference to this.

The change / adjustment of the electromotive force target value EC can be performed by adjusting the variable resistor 66d of the power supply circuit 65 as described above. Note that the offset electromotive force of the oxygen concentration battery element 4 shows a stable value over a relatively long period in the same oxygen concentration battery element 4, although the offset concentration of each oxygen concentration battery element 4 is different from each other. I often continue. Therefore, the variable resistor 66d needs to be changed after the resistance value is once adjusted in accordance with the offset electromotive force peculiar to the oxygen concentration battery element 4 being used, for example, at the time of shipment of the device 50. It is possible that there is no sex. In this case, it is convenient to configure the variable resistor 66d with a semi-fixed resistor.

Now, returning to FIG. 30, when the value of the pump current Ip is detected, the concentration of the detected component corresponding to this pump current Ip is determined. However, the pump current Ip
Since the value of changes with the element temperature T, the correction is performed as follows. First, the value of the internal resistance value RVS of the oxygen concentration battery element 4 stored in the RAM 54 (FIG. 18) is read, and the corresponding temperature T is determined by the map 301 (FIG. 2).
4) and determine (FIG. 30: S3). Since the pump current correction amount ΔIp for each temperature with respect to the value of the pump current Ip can be experimentally determined in the form as shown in FIG. 25B, the value of each ΔIp and the element temperature can be determined. If a map 302 showing the values of T in association with each other is created based on this and stored in the ROM 55 (correction reference information storage means), each pump current correction amount ΔI is obtained.
p can be determined by an interpolation method with reference to this map 302 (temperature deviation-pump current correction amount relation information) (FIG. 3: S4). Note that, as shown in FIG.
The map 302a in which the internal resistance value RVS and the pump current correction amount ΔIp are directly associated is stored, and the internal resistance value RVS is stored.
The correction amount ΔIp may be directly determined from the value of.

Next, in S5, the pump current correction amount ΔI
The p is added to the actually measured pump current Ip to correct it, and the hydrocarbon concentration CHC as the concentration of the detected component corresponding to the corrected pump current Ip 'is determined. That is, the value of the hydrocarbon concentration CHC with respect to the value of the various pump currents Ip 'is a map 30 that gives the relationship between the pump current Ip' and the hydrocarbon concentration CHC as shown in FIG. 27, for example.
4 (stored in the ROM 55), it can be determined by the interpolation method. When the hydrocarbon concentration CHC is thus determined, it is output as a temperature-compensated concentration detection value in S6. After that, the process returns to S2 and the subsequent processes are repeated.

As shown in FIG. 29B, the pump current Ip and the hydrocarbon concentration CHC are set for each value of the element temperature T.
And a two-dimensional map 302b in which
(Pump current information-detected component concentration relationship information)
The value of the hydrocarbon concentration CHC corresponding to the detected value of the pump current Ip and the value of the element temperature T may be directly determined by two-dimensional interpolation. Alternatively, the value of the pump current Ip that has been temperature-compensated by the above method may be output as it is.

Next, after the element temperature T is set during the activation process, the control is continued in parallel with the hydrocarbon concentration detection process. The flow of the process is shown in FIG. Note that this processing routine is an interrupt processing routine for the routine of FIG. 30, and is periodically executed by the CPU 53 by time measurement based on a clock pulse (by the clock circuit 56 (FIG. 18)). The execution cycle may be set in the range of 0.3 to 1 ms, for example. If the execution cycle exceeds 1 ms, it may not be possible to secure sufficient temperature measurement, and thus the accuracy of concentration detection by the sensor. On the other hand, if it is less than 0.3 ms, the ratio of the temperature measurement processing to the processing time of the CPU 53 becomes too large, the operation stop time of the oxygen pump element becomes long, and the concentration detection accuracy may not be sufficiently secured. However, there is a possibility that the execution cycle can be set to be equal to or less than the above value by adopting, as the CPU 53, a CPU capable of high-speed processing such as a high clock frequency. Note that FIG.
And Sw of the analog switch circuit 60 in the processing
The operation timing charts 1 to Sw3 are shown in association with the detected voltage signal VS on the third electrode 13 side of the concentration cell element 4.

First, in S201, with Sw1 of the analog switch circuit 60 of FIG.
The voltage signal VS on the third electrode 13 side of the oxygen concentration battery element 4 is read and stored in the measured value memory area 54b of the RAM 54 as the detected value VS1. This voltage signal VS is
The value corresponds to the concentration battery electromotive force Em input to the operational amplifier 61. Next, in S202, Sw1 is turned off and Sw2 is turned on instead. Then, the energization path becomes the state shown in FIG. 22, and the oxygen concentration battery element 4 is energized with the constant current IC for detecting the internal resistance. And constant current IC
The voltage signal VS is read after a lapse of a fixed time t1 from the start of the energization of No. 2 and stored in the measured value memory area 54b of the RAM 54 as the detected value VS2 (S203, S20)
4). As described above, the voltage signal VS at this time reflects the internal resistance of the oxygen concentration battery element 4, but in the form in which the concentration battery electromotive force Em of the oxygen concentration battery element 4 is superimposed or included. Has become. Therefore, by taking the difference between VS2 and VS1, the influence of the concentration cell electromotive force Em component can be removed (S209).

The reason why VS is measured after a lapse of a fixed time t1 from the start of the energization of the constant current IC is as follows. That is, when a constant current IC is applied to the oxygen-concentrated battery element 4, oxygen is transported in the oxygen-concentrated battery element 4 in the direction opposite to the energization (that is, from the gap 16 side to the 15 side), and the oxygen-concentrated battery element 4 is discharged. A change occurs in the oxygen concentration on both sides. As a result, as shown in FIG. 23, the concentration battery electromotive force Em and thus the value of VS also change as the current IC continues to flow. Here, in order to ensure the accuracy of the internal resistance measurement, it is important that the change in VS inevitably caused by energization be almost constant. Since a constant current IC is used as a current for measuring internal resistance, if the energization time until VS measurement is controlled to be t1 at all times, the oxygen transport amount, that is, both sides of the oxygen concentration battery element 4 can be controlled. The change in the oxygen concentration is also almost constant, and the change in the concentration cell electromotive force Em and thus VS can be made substantially constant. If the switching speed of the analog switch circuit 60 is sufficiently fast and the current level is stabilized sufficiently after switching the energizing path, VS may be measured immediately after the start of energizing the constant current IC.

Next, when the constant current IC is applied, the oxygen concentration on both sides of the oxygen concentration battery element 4 changes. As another problem, when the exhaust gas sensor 1 returns to the measurement of the hydrocarbon concentration, the oxygen concentration is changed. The change in concentration may affect the measurement accuracy of the concentration of the detected component. Further, when the internal resistance value of the oxygen concentration battery element 4 is high, the oxygen ions in the oxygen concentration battery element 4 become difficult to move, and polarization may occur due to current application. In order to solve this problem, this embodiment adopts the following method. That is, in S205 to S208 of FIG. 32, after a constant time t2 has elapsed after the detection of VS, Sw2 is turned off to end the energization of the constant current IC, while by turning on Sw3, the polarity is reversed. The current source 74 (correction current energizing means) energizes the correction current IA having the same magnitude in the opposite direction to IC for a time t3 substantially equal to the total energization time t1 + t2 of IC, and then turns off Sw3. As a result, approximately the same amount of oxygen is transported in the oxygen concentration cell device 4 in the opposite direction to the above, and the oxygen pumped from the gap 16 side to the gap 15 side is pumped back as a result of the IC energization, so to speak, and the changed oxygen concentration is changed. Can approach the state before measuring the internal resistance. If it can be determined that the effect on the oxygen concentration change on both sides of the oxygen concentration battery element 4 is small, such as when the energization time of the current IC for measuring the internal resistance of the oxygen concentration battery element 4 can be shortened sufficiently, FIG. As shown, the constant current power supply 74 for generating the correction current IA can be omitted (correspondingly, the analog switch circuit 60 having a small number of switch channels may be used).

Returning to FIG. 32, when the supply of the correction current IA is completed, the difference ΔVS between VS2 and VS1 in S209 as described above.
Then, RVS is calculated by the above equation (2) by calculating ΔVS as VS. Hereinafter, the process from S210 to S215 for determining the element temperature T from RVS and determining the heater control voltage value Vi based on it is almost the same as the process from S107 to S112 of the sensor activation process of FIG. , Description is omitted. After that, at S216, time t4
After standing by for a while, Sw1 is turned on in S217, and the internal resistance measuring process is ended. Thereafter, the hydrocarbon concentration measurement processing routine shown in FIG. 30 is executed again. The measured value of the element temperature T is updated every time the internal resistance measurement processing is performed, and the updated information of the element temperature T is always used in the hydrocarbon concentration measurement processing routine of FIG. Further, the heater temperature is also periodically corrected based on the measured value of the element temperature T.

As a result, the heaters 2 and 5 accurately maintain the temperature of the oxygen concentration battery element 4 at the set value, and the accuracy of measurement of the carbide concentration in the exhaust gas is improved. In addition, FIG.
As shown in, even if the exhaust gas temperature changes abruptly when a vehicle engine or the like undergoes rapid acceleration / deceleration, even if the temperature T of the oxygen concentration battery element 4 changes correspondingly, the oxygen pump current By correcting the temperature change of Ip, it becomes possible to continue the relatively accurate measurement of the carbide concentration without waiting for the element temperature T to be restored.

The internal resistance measuring process may be executed as a subroutine of the hydrocarbon concentration measuring process routine instead of as an interrupt routine. FIG. 33 shows an example of a flowchart in this case. The hydrocarbon concentration determination / output processing of S1 to S6 is exactly the same as that of FIG. 30, except that S30 is different.
By adding steps 1 to S303, the measurement counter Nm is incremented each time it is completed. Then, when Nm reaches a certain count number Nq in S302, the same internal resistance measurement processing as that shown in FIG. 32 is executed as S304. After execution of the internal resistance measurement process, the process returns to S301, the measurement counter Nm returns to 1, and the same process is repeated. In this method, there is no difference in that the internal resistance measurement process is performed regularly, but the characteristic is that the hydrocarbon concentration measurement process is executed every time a certain number of times, not necessarily at a constant time interval. is there. In this way, the hydrocarbon concentration measurement process is not interrupted due to the internal resistance measurement process, and the frequency of occurrence of errors and the like is reduced.

As shown in FIG. 28, the internal resistance RVS
The map 305 storing the value of the control voltage value Vi to be given to the heater energizing circuit 72 is stored in association with various values of the above, and by referring to this map, the map 305 is stored according to the value of the internal resistance RVS (ie, the element temperature T). The control voltage value Vi may be determined regardless of the current voltage value.

Further, the constant current generating circuit is shown in FIG.
Instead of using two units of 3 and 74, one unit may be used by switching the polarity at any time by using a polarity switching circuit (not shown). Also, the microprocessor 5
It is also possible to use a circuit capable of generating a current according to the contents of the current and polarity instructed from the first side. An example thereof is shown in FIG. That is, in this configuration, the voltage / current conversion circuit 189 is used instead of the constant current generation circuits 73 and 74.
Is used.

In the circuit 189, the current instruction voltage Vi from the microprocessor 51 is input to the operational amplifier 191 via the D / A converter (dipolar type) 190, and the current is supplied to the output side of the operational amplifier 191. A detection resistor 195 is connected, and the voltage drop in the resistor 195 due to the output of the operational amplifier 191 is fed back via the voltage follower 192. As a result, the voltage drop in the resistor 195, that is, the current value IO, is maintained at a constant value according to the input voltage Vi regardless of the connected load. In the figure, the resistance values of the resistors 193 and 194 are Rf,
If Rk and the resistance value of the resistor 195 are RS, then I0 = (Vi × Rf) / (Rk × RS) (3) In this case, the current IC for measuring the internal resistance is generated by the predetermined current instruction voltage Vi, and the correction current is applied in the direction opposite to the current IC by giving the current instruction voltage Vi 'having the opposite polarity to the voltage Vi. It can also be generated as an electric current. Further, the current level to be generated and the energization time can be freely set by changing the current instruction voltage value and its output time from the microprocessor 51 side.

Hereinafter, various possible modifications of the exhaust gas sensor used in the apparatus of the present invention will be illustrated.

First, on the outer electrode side of the oxygen pump element 3,
The atmosphere may be introduced here by separating it from the exhaust gas atmosphere. In addition, the combination of the materials of the electrodes 10 to 13 of the oxygen pump element 3 and the oxygen concentration battery element 4 is such that, if there is a difference in the consumption amount due to the oxidation of the detected component on both sides of the oxygen concentration battery element 4, Various combinations other than the above-described combinations shown in FIG. Fig. 36
(B) is an example in which the outer electrode 10 of the oxygen pump element 3 is composed of an Au porous electrode having a low oxidation catalytic activity. Further, (c) and (e) are examples in which one of the first electrode 11 and the second electrode 12 facing the gap 15 is made of an Au porous electrode. Further, (d) is an example in which both the first electrode 11 and the second electrode 12 are made of Au porous electrodes having low oxidation catalytic activity, and the third electrode 13 is made of Pt porous electrode having high oxidation catalytic activity. Is. In this case, the consumption amount of the component to be detected becomes higher on the side of the gap 16 than on the side of the 15th side, and the oxygen pump element 3 operates so as to pump out oxygen from the gap 15. (F) is an example in which the first electrode 11 is replaced with a porous Au electrode in the configuration.

On the other hand, the electrode with low oxidation catalytic activity is shown in FIG.
As shown in (a), the body portion 10 of the porous electrode, which belongs to the high-activity metal group such as Pt, Rh, Pd, Ir, etc.
1 is formed, and a catalytically inactive material (for example, a metal belonging to a low activity metal group such as a metal mainly containing Au or Ag, or S
A final electrode may be formed by applying a coating 102 of oxides such as nO ₂ , ZnO, In ₂ O ₃ , WO ₃ , and Bi ₂ O ₃ .

In this case, the coating 102 is formed by, for example, as shown in FIG. 37 (b), a method in which a paste containing the above-mentioned catalytically inactive material particles is applied to the main body 101 and re-baked. Alternatively, as shown in FIG. 3C, it can be formed by a vapor phase film forming method such as vacuum deposition or sputtering. Incidentally, as shown in FIGS. 37 (b) to 37 (c), the main body portion 1 formed into a porous body
Since 01 has a large number of voids P formed intricately, the coating 102 may not necessarily be formed deep inside the void P, but the catalytic activity for the reaction between the component to be detected and oxygen is not always required. If it can be made sufficiently small, such an uncoated portion may be formed.

Further, as shown in FIG. 38, a gap 15 formed between the oxygen pump element 3 and the oxygen concentration battery element 4.
A gas holding member 160 made of a metal mesh or a porous metal (made of Pt, for example) can be inserted in the above. When the gas holding member 160 is made of a metal mesh, the mesh formation density is 100 to 500.
It is desirable to use a mesh.

Next, in the exhaust gas sensor 1 shown in FIG. 1 and the like, the gap 15 between the oxygen pump element 3 and the oxygen concentration battery element 4 is made as small as possible (desirably 1 mm or less). It is advantageous to improve the detection accuracy of the sensor 1 by increasing the new exhaust gas inflow restriction effect of the sensor 15. Conversely, the gap 1
If the size of 5 is too large, the reaction between HC and oxygen on the electrodes having catalytic activity (the second electrode 11 and the third electrode 12 in this embodiment) becomes unstable, and the electromotive force of the oxygen concentration battery becomes small. Therefore, the sensor output may not be sufficiently obtained. However, if the amount of the gap 15 between the elements 3 and 4 is made too small, when the oxygen pump element 3 and the oxygen concentration battery element 4 are manufactured by firing this time, a slight deformation during firing forms the gap 15. This may have a large effect on the quantity, and variations in output may easily occur among the individual sensors. Hereinafter, a sensor structure effective for solving this will be described (note that the same parts as those of the sensor structure already described are denoted by the same reference numerals and detailed description thereof will be omitted).

That is, the exhaust gas sensor 4 shown in FIG.
In 00, a spacer portion 401 as a wall portion forming body is inserted between the oxygen concentration battery element 4 and the oxygen pump element 3, and the spacer portion 401 has a thickness at a position corresponding to the electrodes 11 and 12. Window part 401 that penetrates this in the vertical direction
a is formed. The spacer portion 401 is the window portion 401.
The wall portion 401 surrounding the electrodes 11 and 12 by a.
b is formed. The space surrounded by the inner surface of the wall portion 401b and the facing surfaces of the oxygen concentration battery element 4 and the oxygen pump element 3 is a measurement chamber 403 (gap 15). Then, between the wall portion 401b and the oxygen pump element 3 at a position corresponding to the measurement chamber 403, the measurement chamber 40 is provided on both sides in the width direction of the oxygen pump element 3.
3 is formed with a slit 402 as a diffusion and flow restricting portion that communicates the outside 3 with the atmosphere to be detected.

As shown in FIG. 56 (c), the slit 4
02 is a wall portion 401 on both sides of the second electrode 12 in the width direction.
The portion of the oxygen pump element 3 on the side of the laminated surface with the oxygen pump element 3 is formed by cutting out with a constant thickness, and as shown in FIG. It extends in the longitudinal direction. Further, the width d is the measurement chamber 403.
Is set to be smaller than the height h of, and specifically d /
h is 1/100 to 1/4, more preferably 1/20 to 1
It is set in the range of / 8. The absolute value of the slit width d is 0.01 to 1.0 mm, more preferably 0.0.
It is set in the range of 2 to 0.05 mm. Furthermore, the ratio S / V of the area of the slit inner peripheral surface to the space volume V in the slit 402 is adjusted in the range of 4 to 100, preferably 20 to 50. The slit 402 may be formed between the wall portion 401b and the oxygen concentration battery element 4 in the same manner.

The spacer portion 401 (wall portion 401b) is formed on the oxygen concentration cell element 4 over almost the entire stacking surface thereof, and for the oxygen pump element 3 except for the area where the slit 402 is formed. Similarly, almost all of the laminated surfaces are integrated by firing. In addition, the first heater 2 and the second heater 5 are the spacers 6
And 8 are laminated on the oxygen pump element 3 and the oxygen concentration battery element 4, respectively.

An integral laminated body of the oxygen pump element 3, the spacer portion 401 and the oxygen concentration battery element 4 which is a main part of the exhaust gas sensor 400 is formed by the same method as shown in FIG. It can be manufactured by stacking and firing ceramic green sheets (molded bodies) to be 401 and 4. At this time, in a region where the slit 402 is to be formed between the green sheet (ceramic molded body) to be the oxygen pump element 3 and the green sheet to be the spacer part, a material (for example, carbon) that is burned down at the firing temperature is used. If a layer having a predetermined thickness formed of paste or the like is sandwiched, this layer is burnt off during firing, and the slit 402 can be easily formed.

According to the above sensor structure, the measurement chamber 403
Even when the height h of the exhaust gas (that is, the size of the gap 15) is increased to a certain extent or more, the exhaust gas flows into the measurement chamber 403 while the diffusion of the exhaust gas is restricted by the slit 402, and after being introduced into the measurement chamber 403, the same. It is discharged into the atmosphere to be measured while the diffusion is regulated through the slit 402.
Therefore, the residence time of the exhaust gas once introduced in the measurement chamber 403 becomes long, and even if the exhaust gas composition (especially the amount of oxygen or water vapor) in the atmosphere to be detected changes during that time, Since the influence is small, the sensor 400
Output is improved, which in turn can improve the detection accuracy of the sensor 400. Further, since the oxygen pump element 3 and the oxygen concentration battery element 4 are integrated with each other through the spacer portion 401, the mechanical strength of the sensor 400 is enhanced.

A measurement chamber having a similar structure can also be formed on the third electrode 13 side of the oxygen concentration battery element 4.
FIG. 57 shows an example thereof. That is, in the sensor 400 of the same figure, the gap forming ceramic plate 406 as the gap forming member is integrated via the spacer portion 404 similar to the side of the second electrode 12 having the window portion 404a. A measurement chamber 407 is formed by the inner surface of the wall portion 404b formed by the spacer portion 404 and the respective facing surfaces of the oxygen concentration battery element 4 and the gap forming ceramic plate 406. A slit 405 similar to that on the second electrode 12 side is formed between the wall portion 404b and the oxygen concentration battery element 4 at a position corresponding to the measurement chamber 407. The second heater 5 is laminated on the gap forming ceramic plate 406. With this configuration, a more stable and high output sensor can be realized.

Note that the diffusion restricting flow section may be constituted by a small hole instead of the slit. For example, in the example shown in FIG. 62, a small hole 410 penetrating the wall portion 401b in the plate surface direction of the oxygen pump element 3 and the oxygen concentration battery element 4.
Are formed along the circumferential direction of the first and second electrodes 11 and 12 at predetermined intervals. On the other hand, in the example shown in FIG. 63, the small holes 4 penetrating the oxygen concentration battery element 4 in the thickness direction.
A plurality of 10 are formed along the periphery of the third electrode 13 at predetermined intervals.

Next, in the structure shown in FIG. 58, the oxygen concentration battery element 4 is integrated with the spacer portion 401 by firing, while the oxygen pump element 3 is not integrated but separated. Show. In this case, the slit 402 is
It is formed between the plate surface of the oxygen pump element 3 and the facing surface of the wall portion 401b. In addition, the first heater 2, the oxygen pump element 3, the oxygen concentration cell element 4 and the second heater 5
Are laminated via the spacers 6 to 8 to form a laminated body 31, and a ceramic stopper 30 having a rectangular through hole 30a is fitted to the laminated body 31 from the outside. As shown in FIG. 58, the spacer 7 is inserted between the spacer portion 401 and the oxygen pump element 3 and plays a role of forming a slit 402 having a predetermined size therebetween.

Assembly of the exhaust gas sensor 400 is as follows.
For example, it can be performed as follows. That is,
As shown in FIG. 59A, the elements 2 to 5 are connected to the spacers 6 to
8 is laminated to form a laminated body 31, and a ceramic stopper 30 is fitted to this as shown in FIG. Subsequently, as shown in (c), a lead wire 37 made of, for example, stainless steel is joined to each connection terminal of the elements 2 to 5 by welding, and further, as shown in (d), the laminated body 31 is attached to the porcelain tube 3
After being inserted in 2, and the inside thereof is filled with glass powder, this is heated to 900 to 1000 ° C. in a predetermined furnace to melt the glass powder, and a glass seal is made between the porcelain tube 32 and the laminated body 31.

Then, as shown in FIG. 60 (a), the porcelain bushing 32 in which the laminated body 31 is integrated is arranged in the metallic shell 34, and the caulking metal fitting 36 is provided between the porcelain bushing 32 and the metallic shell 34. After inserting, the outer tube 33 is covered on the exposed portion of the porcelain bushing 32 from the metal shell 34, and then the metal shell 34 is attached to the outer tube 3.
By caulking while heating toward 3, the caulking coupling portion 34a is formed, and the metal shell 34 and the outer cylinder 33 are integrated. Subsequently, as shown in FIG. 2B, another lead wire group 37a in which the seal member 38 and the protective outer cylinder 39 are integrated is welded to the corresponding lead wire 37 (hereinafter, integrated. Both lead wires are again given the reference numeral 37). Then, the seal member 38 and the protective outer cylinder 39 are slid on the lead wire 37, the ends thereof are inserted into the outer cylinder 33, and the space between them is caulked, whereby the state shown in FIG. Further, when the protector 35 is attached to the metal shell 34 by welding, the assembly of the exhaust sensor 400 is completed, as shown in FIG.

In this case as well, as shown in FIG. 61, a structure in which the measurement chamber 407 is formed on the third electrode 13 side is also possible. That is, in the sensor 400 of the same drawing, the spacer portion 404 for forming the measurement chamber 407 is integrated on the third electrode 13 side of the oxygen concentration battery element 4, and the inner surface of the wall portion 404b by the spacer portion 404, A measurement chamber 407 is formed by the oxygen concentration battery element 4 and the facing surfaces of the second heater 5. A slit 405 similar to that on the second electrode 12 side is formed between the spacer portion 404 and the second heater 5. In this configuration, the second heater 5 serves as a gap forming member.

[0155]

Example The following experiment was conducted on the exhaust gas sensor. (Example 1) Experiment 1 A ceramic green sheet containing Y ₂ O ₃ powder and ZrO ₂ powder was punched into a disk shape, and Pd (52
%)-Ag (48% by weight) alloy powder or Au powder mixed with a predetermined amount of ZrO2 powder to form a circular electrode pattern with a paste (all having an average particle diameter of metal powder of 1.0 μm). A Pd porous plate having a diameter of 8 mm was formed on a disk of a solid electrolyte made of a ZrO ₂ sintered body having a diameter of 12 mm and a thickness of 1 mm and containing 5 mol% of Y ₂ O ₃ by firing at a temperature of 1470 ° C. A sample having a porous electrode or a porous Au electrode was prepared. Next, FIG. 39 (a)
As shown in, each sample 174 is placed in a tubular body 173 having a gas inlet 171 and a gas outlet 172, and
This was kept at various temperatures of 675 to 850 ° C. by an electric furnace 175. And in that state, 300 ppm oxygen,
Methane 350ppm as a component to be detected, and water vapor 3%
A test gas containing and containing argon as the balance was introduced from an inlet 171 at a flow rate of 100 ml / min, and was introduced into the outlet 1
The methane concentration Cs (unit: ppm) in the test gas after being discharged when it was discharged from 72 was measured, and η = {(350-Cs) / 350} × 100 (unit:
%) Was obtained at each temperature.
FIG. 40 (a) shows the measurement result of the methane conversion rate η for each temperature. That is, in the sample using the Au porous electrode, the conversion rate η shows a low value of about 10% or less, whereas in the sample using the Pd porous electrode, η increases as the temperature rises, and 700 ° C. The difference in η between both samples is about 20%, 7
It can be seen that it reaches 30 to 40% at 50 ° C or higher.

Experiment 2 Next, a disk-shaped Au porous electrode having a diameter of 8 mm was used as an outer electrode and a first electrode on both surfaces of a solid electrolyte plate of the same material and size as in Experiment 1, under the same conditions as in Experiment 1. To form an oxygen pump element. Further, a Pd porous electrode having a diameter of 8 mm is formed as a second electrode on one surface of the same solid electrolyte disk, and an Au porous electrode having a diameter of 3 mm is formed as a third electrode on the other surface, thereby forming an oxygen concentration battery element. Was produced. Then, both elements are arranged so that the first electrode and the second electrode face each other, and a Pt mesh or Au of 100 to 500 mesh is interposed therebetween.
A sensor was produced by sandwiching the mesh and stacking them.

Then, each element (that is, the oxygen pump element 3 and the oxygen concentration cell element 4) is connected to the circuit shown in FIG. 39 (b), and the Pd porous electrode is used by using the device shown in FIG. 39 (a). Η measured in Experiment 1 between the Au and Au porous electrodes
This was heated to 750 ° C., which is the temperature at which the difference between the two becomes maximum.

In the circuit 200 of FIG. 39 (b), the second electrode 1 of the oxygen concentration battery element 4 of the exhaust gas sensor 1 is used.
2 and the third electrode 13 are respectively connected to the negative terminal (ground terminal) and the positive terminal of the non-inverting amplifier 20 (pump element voltage adjusting means, electromotive force detecting means). As a result, the concentration battery electromotive force generated in the element 4 has an electric resistance value R50 of the resistor 22 connected to the ground side of the non-inverting amplifier 20 and an electric resistance value R51 of the resistor 21 also connected in the negative feedback connection. Is amplified with a gain R51 / R50.

On the other hand, the output side of the non-inverting amplifier 20 is connected to the first electrode 11 of the oxygen pump element 3, and the amplified concentration cell electromotive force is applied to the oxygen pump element 3. Here, since the oxygen concentration becomes higher on the side of the gap 16, a concentration cell electromotive force having a positive value on the third electrode 13 side is generated in the oxygen concentration cell element 4. Then, the concentration cell electromotive force is amplified by the non-inverting amplifier 20 without the polarity being inverted, and is applied to the first electrode 11 of the oxygen pump element 3. This allows
A pump current flows in the oxygen pump element 3 with the first electrode 11 side being positive, and oxygen in the gap 14 is pumped to the gap 15 side as indicated by an arrow in the figure. This pump current is taken out as a sensor output reflecting the methane concentration in the exhaust gas EG by the output voltage of the inverting amplifier 23 (output means). In this embodiment, the output of the inverting amplifier 23 is inverted in polarity by the inverting amplifier 24 (R4 = R5) having a gain of 1.

With the circuit connected as described above, 50-
Methane as a component to be detected having various concentrations of 700 ppm, oxygen of 300 ppm, water vapor of 3% by volume, and a balance of a test gas consisting of argon were passed at a flow rate of 100 ml / min to start the oxygen concentration cell element at equilibrium. While measuring the electric power EMF, the oxygen pump element was operated so that the electromotive force EMF became the electromotive force target value EC, and the pump current Ip was measured.

As a result, as shown in FIG. 41, the pump current Ip (indicated by "●" in the figure) increases almost linearly with respect to the methane concentration in the test gas, and the methane concentration is detected from the Ip. I knew I could do it. Further, as shown in FIG. 40 (b), when the methane concentration was fixed to 300 ppm and the sensor temperature was changed from 650 to 850 ° C., the measurement was performed, and the sensor output showed the largest difference in η. 75
The maximum value is shown in the vicinity of 0 ° C., and it was also found that operating the sensor at a temperature at which the difference in η is as large as possible is effective in improving the sensor sensitivity. For reference, the electromotive force of the oxygen concentration battery element when the oxygen pump element was not operated was measured for each methane concentration (indicated by “◯” in FIG. 41). As a result, it was found that the electromotive force sharply increased in the vicinity of the methane content (about 200 ppm), which is almost the stoichiometric air-fuel ratio with respect to the oxygen concentration in the test gas. This means that in the region of the above composition or higher, almost all the amount of methane is consumed by the oxidation on the second electrode side (that is, the gap side) made of Pd having a large oxidation catalytic activity for methane, and conversely the oxidation catalytic activity is low. This means that methane is not consumed so much on the third electrode side (that is, on the opposite space side) made of Au, so that a large oxygen concentration difference occurs on both sides of the oxygen concentration battery element. As the oxygen concentration cell device, both the second electrode and the third electrode were Au porous electrodes, and both were Pd.
When a porous electrode was prepared and the same experiment was conducted using this, as shown in FIG. 42, almost no electromotive force was generated in these samples regardless of the methane concentration.

Further, in the test gas, water vapor (7.5
%), Carbon dioxide (10.0%), nitric oxide (284p
pm) and carbon monoxide (300 ppm) were mixed as an interfering gas, the influence of the pump current Ip on the methane concentration dependence was also investigated. As shown in the results in FIG. 43, it can be seen that the dependence of Ip on the methane concentration is hardly affected by the interfering gas, and the selectivity for methane detection is good.

Next, the methane concentration in the test gas was adjusted to 350 p
FIG. 44 shows the result of performing the same experiment with the oxygen concentration fixed to pm and variously changed in the range of 100 to 800 ppm. That is, the pump current Ip shows a substantially constant value regardless of the oxygen concentration in the test gas, and it can be seen that the influence of the oxygen concentration in the test gas on Ip as the sensor output is small.

(Example 2) A disk-shaped Au porous electrode having a diameter of 8 mm was used as the outer electrode and the first electrode on both surfaces of a solid electrolyte plate having the same material and size as in Experiment 1 of Example 1. An oxygen pump element was manufactured by forming under the same conditions as described above. In addition, a Pd or Au porous electrode having a diameter of 8 mm (Au is a comparative example) is used as a second electrode on one surface of the same solid electrolyte disk, and a Au porous material having a diameter of 3 mm is used as a third electrode on the other surface. An electrode was formed to produce an oxygen concentration battery element. Then, a sensor was manufactured by stacking both elements with a Pt mesh or Au mesh of 100 to 500 mesh interposed therebetween so that the first electrode and the second electrode face each other.

Then, each element (that is, the oxygen pump element 3 and the oxygen concentration battery element 4) is connected to a circuit similar to that shown in FIG. 39 (b), and the apparatus shown in FIG. 39 (a) is used. 0.3 to 0.8 while heating to 850 to 900 ° C
Methane as a component to be detected in various concentrations of 0.
A test gas consisting of 5% by volume of oxygen, 5% by volume of water vapor, and the balance of argon was passed through the furnace at a flow rate of 100 ml / min to measure the electromotive force EMF of the oxygen concentration battery element at equilibrium, The oxygen pump element is operated so that the electromotive force EMF becomes the electromotive force target value EC, and the pump current Ip
Was measured. Further, it was found that the pump current Ip increased almost linearly with the methane concentration in the test gas as shown in FIG. 45, and the methane concentration could be detected from the Ip.

Further, the methane concentration in the test gas was 0.5%.
FIG. 46 shows the result of carrying out a similar experiment with the oxygen concentration fixed to 0.3% and variously changed in the range of 0.3 to 0.8% by volume.
That is, the pump current Ip shows a substantially constant value regardless of the oxygen concentration in the test gas, and I as the sensor output.
It can be seen that the effect of the oxygen concentration in the test gas on p is small.

Further, the oxygen concentration battery element is reversed from the above with respect to the oxygen pump element, that is, the Au porous electrode is the second electrode and the Pd porous electrode is the third electrode. FIG. 47 shows the results of a similar experiment performed using test gases with various changes in methane concentration. In this case, the oxygen concentration battery element is not inverted.
As compared with the result of No. 5, it can be seen that the rate of change (gradient) of Ip with respect to the methane concentration is large, and the sensitivity of the sensor is improved.

Example 3 In the exhaust gas sensor 1 shown in FIGS. 1 and 2, the outer electrode 10, the first electrode 11 and the second electrode 12 are Pt porous electrodes, and the third electrode 13 is A.
What was formed by u porous electrode was produced. However,
The solid electrolyte used in each of the elements 2 to 5 was the same as in the above-mentioned Examples 1 and 2, and its dimensions were 4 mm × 45 mm × 0.1 mm.
It was 4 mm. The height of the gap 14 is 0.06 mm, the height of the gap 15 is 0.15 mm, and the height of the gap 16 is 0.07 mm.
And The sensor 1 is supplied with oxygen at 50 to 250,000 pp.
m, steam 10%, carbon dioxide gas 10%, and the balance was kept in a test gas, and the elements 3 and 4 were heated by the heaters 2 and 5 so as to reach 800 ° C. The temperature of the heater at this time was 900 ° C. In that state, the electromotive force (offset electromotive force) EOS generated in the oxygen concentration battery element 4 when the oxygen pump element 3 was not energized was measured for each oxygen concentration. Results are shown in FIG. That is, the offset electromotive force EOS rapidly increases when the oxygen concentration is less than 10000 ppm (1% by volume), whereas it is approximately 1 to 1.5 mV (more than 100,000 ppm) (1.22 mV in the atmosphere). You can see that it has stabilized.

Next, the sensor 1 is attached to the exhaust pipe,
Set sensor operating temperature 800 ℃, electromotive force target value E C -5
The oxygen pump element 3 is operated at various values of ˜8.3 mV, where oxygen 100 to 1000 ppm and water vapor 10
%, Carbon dioxide gas 10%, methane 0 or 300 ppm, and balance test gas (temperature 300 ° C.) at a flow rate of 12 L / min, and the pump current Ip (sensor output) was measured. The results are shown in FIGS. 49 and 50 in the form of oxygen concentration dependence of the sensor output corresponding to each electromotive force target value EC. At any methane concentration, Ec = 1.22 mV (equivalent to EOS in the atmosphere), -1.8 mV, 0 mV, 3.7 m
Regarding V and 4.2 mV (within the range of EOS ± 5 mV), the oxygen concentration dependency of the sensor output is small, while Ec = out of the range of (EOS-5) mV or more and (EOS + 5) mV or less -5mV, 5.1mV and 8.3m
It can be seen that at V, the oxygen concentration dependency of the sensor output is large.

(Embodiment 4) The same exhaust gas sensor 1 as in Embodiment 3 is attached to the exhaust pipe, and oxygen is added at 1000 pp.
m, carbon dioxide gas 10%, methane 0 to 500 ppm, and the balance nitrogen was passed through the test gas at various flow rates of 4 to 20 L / min, and the pump current Ip (sensor output) was measured. The results are shown in FIG. 51 in the form of the methane concentration dependence of the sensor output corresponding to each flow velocity. That is, it can be seen that the sensor 1 of the present invention described above exhibits a linear output with respect to the methane concentration, and the influence of the gas flow velocity is small.

(Embodiment 5) The same exhaust gas sensor 1 as in Embodiment 3 is attached to the exhaust pipe, and oxygen 100 to 100 is attached here.
0ppm, carbon dioxide 10%, methane 0-500ppm,
The test gas consisting of the balance nitrogen was passed at a flow rate of 12 L / min, and the pump current Ip (sensor output) was measured. The results are shown in FIG. 52 in the form of methane concentration dependence of the sensor output corresponding to each oxygen concentration. That is, it can be seen that the sensor 1 of the present invention shows a linear output with respect to the methane concentration, and the influence of the oxygen concentration is small.

Example 6 In the exhaust gas sensor 400 shown in FIG. 56, the outer electrode 10, the first electrode 11 and the second electrode 12 are Pt porous electrodes, and the third electrode 13 is Au.
What was formed with the porous electrode was produced. However, the solid electrolytes used in the respective elements 2 to 5 are the same as those in Examples 1 and 2 above.
The same size is used, and the dimensions are 4mm × 45mm × 0.4
mm. In addition, the height of the gap 14 is 0.06 mm, the gap 1
5 (that is, the measurement chamber 403) has a height h of 0.4 mm, the slit 402 has a width d of 0.05 mm, and the gap 16 has a height of 0.
It was set to 07 mm. This exhaust gas sensor 400 is attached to the exhaust pipe, where oxygen 1000ppm, carbon dioxide gas 10%,
A test gas consisting of 0 to 500 ppm of methane, 0 or 10% of water vapor, and the balance of nitrogen was passed at a flow rate of 12 L / min to measure the pump current Ip (sensor output). The results are shown in FIG. 53 in the form of methane concentration dependence of the sensor output corresponding to each amount of water vapor. That is, the above-mentioned sensor 1 of the present invention shows a linear output with respect to the methane concentration,
It can be seen that the effect is small even when humidified.

(Embodiment 7) The same exhaust gas sensor 1 as in Embodiment 3 is attached to the exhaust pipe, and oxygen is added at 1000 pp.
m, carbon dioxide gas 10%, methane 0 to 500 ppm, water vapor 0 or 10%, the balance mainly consisting of nitrogen, and further nitric oxide (270 ppm), carbon monoxide (270 ppm), propylene (270 ppmC (ppmC is the carbon equivalent concentration The test gas containing any one of (1)) as a disturbing gas was circulated at a flow rate of 12 L / min to measure the pump current Ip (sensor output). The results are shown in FIG. 54 in the form of the methane concentration dependence of the sensor output for each interfering gas component. That is, it can be seen that the above-mentioned sensor 1 of the present invention exhibits a linear output with respect to the methane concentration, has a small influence of the interfering gas, and exhibits excellent selectivity with respect to methane.

Next, the following experiment was conducted to confirm the performance of the measuring apparatus of the present invention. (Embodiment 8) An exhaust gas sensor similar to that of Embodiment 3 was used and incorporated into a sensor system 50 shown in FIG. The offset electromotive force of the oxygen concentration battery element of the exhaust gas sensor is +1.2 mV, and the electromotive force target value E
C was set to +1.2 mV. Further, the temperature setting of the oxygen concentration battery element by the heaters 2 and 5 was set to 750 ° C. In this state, attach the sensor to the exhaust pipe and place oxygen 100p here.
A test gas composed of pm, carbon dioxide gas 10%, methane 300 ppm, and the balance nitrogen was heated at a temperature of 650 ° C to 8 with a predetermined heating device.
After heating to 30 ° C. and flowing at a flow rate of 12 L / min, the output of the exhaust gas sensor was measured in the form of pump current Ip. First,
When the temperature of the oxygen concentration battery element was monitored from the value of its internal electromotive force, the element temperature could be controlled within the range of 750 ± 20 ° C. even if the exhaust gas temperature changed. On the other hand, for comparison, when the voltage applied to the heaters 2 and 5 was kept constant and no particular control was performed, the temperature fluctuated to 750 ± 50 ° C. Further, FIG. 26 shows the output value of the pump current Ip. When temperature control is performed (indicated by "●" in the figure), the output value of Ip is almost constant regardless of exhaust gas temperature, but when temperature control is not performed (indicated by "○" in the figure). ) Indicates that Ip greatly varies depending on the exhaust gas temperature.

(Example 9) In order to investigate the mechanical strength of the exhaust gas sensor of Example 3, a solid electrolyte plate having the same dimensions (4 mm x 45 mm x 0.4 mm) as those used for each of the elements 2 to 5 was used as a unit. As a test piece that is integrally fired in the form of three laminated layers (corresponding to a sensor structure in which the first heater 2, the oxygen pump element 3, and the oxygen concentration battery element 4 are integrally fired) Three types of test pieces were prepared: a fired test piece (corresponding to a sensor structure in which the oxygen pump element 3 and the oxygen concentration cell element 4 were integrally fired), and one solid electrolyte plate alone. Bending these test pieces with a predetermined bending tester using the thickness direction of the solid electrolyte plate as the bending direction, the upper span was 10 mm, the lower span was 30 mm, and the crosshead speed was 4-point bending at 0.5 mm / min. A load was applied and the bending load when the fracture occurred was measured. The results are shown in FIG. 55 in the form of test piece thickness dependence of a four-point bending load (represented by the bending load when the test piece breaks). That is, as the number of test pieces increases, specifically, the bending load is improved almost in proportion to the square of the thickness of the test piece.

(Embodiment 10) In the exhaust gas sensor 400 shown in FIG. 56, the outer electrode 10, the first electrode 11 and the second electrode 12 are Pt porous electrodes, and the third electrode 13 is A.
What was formed by u porous electrode was produced. However,
The solid electrolyte used in each of the elements 2 to 5 was the same as in the above-mentioned Examples 1 and 2, and its dimensions were 4 mm × 45 mm × 0.1 mm.
It was 4 mm. Further, the height of the gap 14 is 0.06 mm, the height h of the gap 15 (that is, the measurement chamber 403) is 0.4 mm, the width d of the slit 402 is 0.1 mm, and the height of the gap 16 is 0.
It was set to 07 mm. For reference, the oxygen pump element 3 and the oxygen concentration cell element 4 are not integrated, but a width of 0.4 between the both ends is opened to the atmosphere to be measured through a separate spacer.
A sensor having a gap of mm was also prepared. These exhaust gas sensors were attached to the exhaust pipe and the following experiment was conducted.

First, without operating the oxygen pump element, oxygen 100 ppm, carbon dioxide gas 10%, methane 0 to 500 pp.
A test gas consisting of m, water vapor 0 or 10%, and the balance nitrogen was passed at a flow rate of 12 L / min, and the electromotive force of the oxygen concentration battery element 4 was measured for each methane concentration. The results are shown in Fig. 64. That is, in the sensor of the reference example (FIG. 64 (a)), the electromotive force in the case where the water vapor is not added is relatively large, but the electromotive force is decreased in the case where the water vapor is added. On the other hand, it can be seen that the sensor of the example (FIG. 64 (b)) is less affected by humidification. In addition, the oxygen pump element is activated, oxygen 100 ppm, carbon dioxide 10
%, Methane 0 to 500 ppm, water vapor 0 or 10%, balance nitrogen was passed through at a flow rate of 12 L / min to measure the sensor output for each methane concentration.
5 shows. That is, the sensor of the reference example (FIG. 65 (a))
In Fig. 2, the sensor output is relatively large when water vapor is not added, but it is understood that the output is reduced when water vapor is added. On the other hand, the sensor of the embodiment (see FIG.
It can be seen that the effect of humidification is small in (b)).

Next, in order to investigate the effect of oxygen concentration on the sensor output, the same experiment was conducted under the same conditions while fixing the water vapor concentration to 10% and setting the oxygen concentration to either 100 or 1000 ppm. . The result is shown in FIG.
Shown in. That is, in the sensor of the reference example (Fig. 66 (a)), the sensor output level changes depending on the oxygen concentration, whereas in the sensor of the embodiment (Fig. 66 (b)), the influence of the oxygen concentration change is small. I understand.

[Brief description of drawings]

FIG. 1 is a plan view, a side view, and a sectional view taken along line AA of a main part of an example of an exhaust gas sensor of the present invention.

FIG. 2 is an explanatory diagram showing the detailed structure thereof.

FIG. 3 is an explanatory view showing an example of the assembly structure.

FIG. 4 is an operation explanatory view of the sensor.

5 is an exploded perspective view showing a method of manufacturing the exhaust gas sensor of FIG.

6A and 6B are a plan view, a side view, an AA sectional view, and a BB sectional view showing a first modified example of the exhaust gas sensor of FIG.

7 is an exploded perspective view showing a method of manufacturing the exhaust gas sensor of FIG.

8A and 8B are a plan view, a side view, an AA cross-sectional view, and a BB cross-sectional view showing a second modification of the exhaust gas sensor of FIG.

FIG. 9 is a plan view, a side view, and an AA sectional view and a BB sectional view of the third modified example.

FIG. 10 is a plan view, a side view, and a cross-sectional view taken along the line AA of the fourth modification.

11 is an exploded perspective view showing a method of manufacturing the exhaust gas sensor of FIG.

FIG. 12 is a plan view showing a fifth modification of the exhaust gas sensor of FIG. 1, a side view, a BB cross-sectional view, and cross-sectional views showing some modifications of the column portion thereof.

13 is an exploded perspective view showing a method of manufacturing the exhaust gas sensor of FIG.

FIG. 14 is an explanatory view schematically showing the positional relationship between the column pattern and the auxiliary support pattern.

FIG. 15 is an explanatory view of the action of the auxiliary support pattern.

16 is a plan view, a side view, and a cross-sectional view taken along line AA showing a sixth modification of the exhaust gas sensor of FIG.

17 is an exploded perspective view showing a method of manufacturing the exhaust gas sensor of FIG.

FIG. 18 is a block diagram showing an electrical configuration of an example of a measuring apparatus of the present invention using the sensor.

FIG. 19 is a block diagram showing a circuit operating system in the hydrocarbon concentration measurement mode.

FIG. 20 is a block diagram showing some examples of heater energizing circuits.

FIG. 21 is an explanatory diagram of PWM control of a heater.

FIG. 22 is a block diagram showing a circuit operating system at the time of measuring the internal resistance of the oxygen concentration battery element.

FIG. 23 is an operation timing chart of each switch when measuring the internal resistance of the oxygen concentration battery element.

FIG. 24 is a graph showing an example of the relationship between the element temperature and the internal resistance of the oxygen concentration battery element, and a conceptual diagram of a map showing the relationship between the internal resistance of the oxygen concentration battery element and the element temperature.

FIG. 25 shows a profile showing an example of measurement of pump current change due to sudden acceleration or deceleration of an engine, a graph showing an example of the relationship between element temperature and corrected pump current value, and the relationship between element temperature and corrected pump current value. The conceptual diagram of the map shown.

FIG. 26 is a graph showing the measurement results of Example 8.

FIG. 27 is a conceptual diagram of a map showing the relationship between pump current value and HC concentration.

FIG. 28 is a conceptual diagram of a map showing the relationship between the internal resistance value of the oxygen concentration battery element and the heater control voltage.

FIG. 29 is a conceptual diagram of a map showing the relationship between the internal resistance value of the oxygen concentration battery element and the corrected pump current value, and a conceptual diagram of a two-dimensional map showing the relationship between the element temperature, the pump current value and the HC concentration.

30 is a flowchart showing the flow of control on the microprocessor side in the apparatus of FIG.

FIG. 31 is a flowchart showing details of the sensor activation process.

FIG. 32 is a flowchart showing the details of the internal resistance measuring process.

33 is a flowchart showing the flow of another control mode on the microprocessor side in the apparatus of FIG. 18.

FIG. 34 is a block diagram of the apparatus of FIG. 18 in which a power source for applying a correction current is omitted.

FIG. 35 is a block diagram showing an example in which a constant-current power supply for measuring internal resistance and for supplying a correction current is replaced with a voltage-current conversion circuit in the device of FIG. 18.

FIG. 36 is a schematic diagram showing some modifications of the electrode configuration of the exhaust gas sensor.

FIG. 37 is an explanatory diagram of a method of forming a catalytically inactive electrode by coating.

FIG. 38 is a schematic diagram showing an example in which a gas holding member is interposed between an oxygen pump element and an oxygen concentration battery element.

FIG. 39 is a schematic diagram showing the experimental apparatus used in Example 1.

FIG. 40 is a graph showing the temperature dependence of the conversion rate η of methane between the Pd porous electrode and the Au porous electrode in Example 1, and the graph showing the temperature dependence of the output of the exhaust gas sensor using these electrodes. .

FIG. 41 is a graph showing the methane concentration dependence of the output of the exhaust gas sensor of the first embodiment.

FIG. 42 is a graph showing the methane concentration dependence of the electromotive force of the oxygen concentration battery element for each combination of various electrodes.

FIG. 43 is a graph showing the influence of interfering gas on the output of the exhaust gas sensor of the first embodiment.

FIG. 44 is a graph showing the effect of oxygen concentration on the output of the exhaust gas sensor of the first example.

FIG. 45 is a graph showing the methane concentration dependence of the output of the exhaust gas sensor of the second embodiment.

FIG. 46 is a graph showing the effect of oxygen concentration on the output of the exhaust gas sensor of the second embodiment.

FIG. 47 is a graph showing the methane concentration dependence of the output in the exhaust gas sensor of the modified example of Example 2.

48 is a graph showing the oxygen concentration dependence of the offset electromotive force of the oxygen concentration battery element in the exhaust gas sensor of Example 3. FIG.

FIG. 49 is a graph showing the oxygen concentration dependency of the sensor output when the electromotive force target value is set to various values in the exhaust gas sensor of Example 3 (methane concentration 0 ppm).

FIG. 50 is a graph showing the oxygen concentration dependence of the sensor output when the electromotive force target value is set to various values in the exhaust gas sensor of Example 3 (methane concentration 300 ppm).

51 is a graph showing the experimental results of Example 4. FIG.

52 is a graph showing the experimental results of Example 5. FIG.

FIG. 53 is a graph showing the experimental results of Example 6;

54 is a graph showing the experimental results of Example 7. FIG.

55 is a graph showing the experimental results of Example 9. FIG.

FIG. 56 is a plan view, a side view, and an AA cross-sectional view showing an example of a sensor having a structure in which exhaust gas is introduced into a measurement chamber through a slit.

FIG. 57 is a plan view, a side view, and a sectional view taken along the line AA of the first modification.

FIG. 58 is a plan view, a side view, and a sectional view taken along the line AA of the second modification.

59 is a process explanatory view showing an example of an assembling method of the sensor of FIG. 58. FIG.

FIG. 60 is an explanatory view of the process continued from FIG. 59.

FIG. 61 is a plan view, a side view, and a sectional view taken along the line AA of the third modification of the sensor in FIG. 56.

FIG. 62 is a partial plan view showing an example of a sensor having a structure in which exhaust gas is introduced into a measurement chamber through a small hole, and a BB sectional view thereof.

FIG. 63 is a partial plan view and a bottom view showing the modified example.

FIG. 64 is a graph showing the experimental results of Example 10.

FIG. 65 is another graph.

FIG. 66 is also another graph.

[Explanation of reference numerals] 1,400 Exhaust gas sensor 2 First heater (heating element) 3 Oxygen pump element 4 Oxygen concentration battery element 5 Second heater (heating element, gap forming member) 11 First electrode 12 Second electrode 13 Third electrode 15 Gap 16 Gap (opposite space) 50 Sensor system 50a Peripheral circuit 51 Microprocessor 53 CPU (Detected component concentration information correction means, energization control means, pump current correction amount determination means, correction calculation means, correction concentration information generation Means, internal resistance measuring means, temperature information generating means, concentration battery electromotive force measuring means, voltage information correcting means) 55 ROM (correction reference information storage means) 55a correction reference information 61 operational amplifier (pump current control means) 74 constant current power supply ( Correction current energizing means) 200 Spacer parts 201, 202 Insulating layer 204 Opening part 210 Strut part 211 First part (First powder compact) 212 second portion (second powder compact) 213 third portion 240 ZrO ₂ green sheet (spacer moldings) 241,242 lamination coating (insulating pattern) 266a, 266b strut pattern 302 map (temperature deviation-pump current correction amount relation information) 302b map (pump current information-detection component concentration relation information) 401, 404 spacer portion (wall portion forming body) 401b, 404b wall portion 402, 405 slit (diffusion regulation) Flow section) 403,407 Measuring chamber 410 Small hole (Diffusion regulation flow section)

─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yumi Kuroki 14-18 Takatsuji-cho, Mizuho-ku, Nagoya-shi, Aichi Japan Special Ceramics Co., Ltd. (72) Inventor Masashi Kita 14-18 Takatsuji-cho, Mizuho-ku, Nagoya No. 14 Nippon Takara Ware Co., Ltd. (72) Inventor Takafumi Oshima No. 14-18 Takatsuji-cho, Mizuho-ku, Nagoya-shi, Aichi Japan (56) Reference JP-A-6-288979 (JP, A) Sho 62-190459 (JP, A) JP 9-311120 (JP, A) JP 5-180794 (JP, A) JP 60-210760 (JP, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) G01N 27/416 G01N 27/41 G01N 27/419

Claims (26)

(57) [Claims] 1. A gas sensor for detecting a component to be detected contained in exhaust gas, comprising an oxygen ion conductive solid electrolyte, and an oxygen concentration battery element having electrodes formed on both surfaces thereof, and oxygen. Electrodes are formed on both surfaces of the ion-conducting solid electrolyte, and a predetermined amount of clearance is formed between the oxygen-concentrated battery element and the exhaust gas from the atmosphere to be measured. An oxygen pump that is arranged to face the oxygen concentration battery element and pumps oxygen into the gap or pumps oxygen from the gap in a direction in which the absolute value of the concentration battery electromotive force generated in the oxygen concentration battery element decreases. An element, and a heating element for heating at least one of the oxygen pump element and the oxygen concentration cell element to a predetermined sensor operating temperature, the gap
And the space on the opposite side of the oxygen concentration battery element
(Hereinafter referred to as the opposite space),
Exhaust gas containing oxygen is introduced, and the oxygen
The electrode on the gap side of the pump element is the first electrode, and the oxygen concentration is
The electrode on the side of the gap of the light battery element is the second electrode, and the oxygen concentration is
The electrode on the opposite space side of the light battery element as the third electrode,
In the exhaust gas introduced into the gap and the opposite space
The detected component of at least the gap and the opposite of
At least one of the first to third electrodes in one of the spaces
Also uses one of them as an oxidation catalyst to react with oxygen in the exhaust gas.
It is consumed by responding to the
Of the component to be detected due to the reaction with oxygen between the opposite space
In order to make a difference in consumption, the electrodes of the first to third electrodes are covered.
The catalytic activity for the reaction between the detection component and oxygen is adjusted
The exhaust gas sensor is characterized in that the oxygen concentration battery element and the oxygen pump element are configured as an integrated fired body that is laminated with each other with the gap being formed. 2. A gas sensor for detecting a component to be detected contained in exhaust gas, comprising an oxygen ion-conducting solid electrolyte, and having oxygen permeable electrodes formed on both surfaces thereof. A battery element and electrodes formed of an oxygen ion conductive solid electrolyte and having oxygen permeability are formed on both sides, and a predetermined amount of clearance is formed between the oxygen concentration battery element and the oxygen concentration battery element to allow the flow of exhaust gas. As described above, while being arranged to face the oxygen concentration battery element, oxygen is pumped into the gap or oxygen is discharged from the gap in a direction in which the absolute value of the concentration battery electromotive force generated in the oxygen concentration battery element decreases. An oxygen pump element for pumping out, and a heating element for heating at least one of the oxygen pump element and the oxygen concentration battery element to a predetermined sensor operating temperature, and the gap Exhaust gas containing a component to be detected and oxygen is introduced into a space on the opposite side of the oxygen concentration battery element (hereinafter referred to as an opposite space), and the gap of the oxygen pump element is introduced. Side electrode is the first electrode, the electrode on the side of the gap of the oxygen concentration battery element is the second electrode, the electrode on the opposite space side of the oxygen concentration battery element is the third electrode, in the gap and the opposite space. The detected component in the introduced exhaust gas is at least in one of the gap and the opposite space, and the first to
It is consumed by reacting with oxygen in the exhaust gas by using at least one of the third electrodes as an oxidation catalyst, and the consumption amount of the component to be detected due to the reaction with oxygen between the gap and the opposite space is increased. In order to make a difference , the reaction of the detected components of the first to third electrodes with the oxygen is touched.
Medium activity is adjusted, the concentration battery electromotive force of the oxygen concentration battery element, the current value flowing in the oxygen pump element when reaching a predetermined electromotive force target value EC,
While taking out as information that reflects the concentration of the detected component in the exhaust gas, the oxygen concentration battery element and the oxygen pump element, the gap between the first electrode and the second electrode An exhaust gas sensor, which is configured as an integrated fired body that is laminated with each other in the generated state. 3. The value of current flowing through the oxygen pump element when the absolute value of the concentration battery electromotive force of the oxygen concentration battery element reaches an electromotive force target value EC set to 10 mV or less, The exhaust gas sensor according to claim 2, wherein the exhaust gas sensor is taken out as information that reflects the concentration of the component to be detected therein. 4. The oxygen-concentrated battery element when a test gas containing 1% by volume or more of oxygen and containing substantially no component that reacts with oxygen at the sensor operating temperature is introduced into the gap and the opposite space. Let EOS (unit: mV) be the absolute value of the offset electromotive force that occurs in the
The value of the current flowing through the oxygen pump element when the absolute value of the concentration battery electromotive force of the oxygen concentration battery element reaches the electromotive force target value EC, which is set within the range of V or less, The exhaust gas sensor according to claim 2, wherein the exhaust gas sensor is extracted as information that reflects the concentration of the component to be detected. 5. The heating element is laminated on the opposite side of the gap to at least one of the oxygen concentration cell element and the oxygen pump element, and the oxygen concentration cell element, the oxygen pump element, and the heating element. And 4 are configured as an integrated fired body laminated on each other.
The exhaust gas sensor according to any one of 1. 6. A column portion is formed between the oxygen concentration battery element and the oxygen pump element in the gap so as to define the gap between the oxygen concentration cell element and the oxygen pump element in a state where the gas does not enter and leave the gap. The exhaust gas sensor according to any one of claims 1 to 5. 7. The exhaust gas sensor according to claim 6, wherein the pillar portion is made of a ceramic material that can be integrated with the oxygen concentration battery element and the oxygen pump element by firing. 8. The oxygen concentration battery element and the oxygen pump element are respectively formed in a horizontally long plate shape and are arranged to face each other, and the first to third electrodes are plates of the oxygen concentration battery element and the oxygen pump element. While being formed on one end side in the longitudinal direction of the surface, on the other end side in the longitudinal direction of the plate, the space between the oxygen concentration battery element and the oxygen pump element is approximately the same thickness as the gap. The exhaust gas sensor according to any one of claims 1 to 7, wherein a spacer portion is inserted, and the spacer portion and the oxygen concentration battery element and the oxygen pump element are integrated with each other by firing. 9. The oxygen concentration battery element and the oxygen pump element are respectively formed in a laterally long plate shape and are arranged to face each other, and the electrodes are arranged in the plate surface longitudinal direction of the oxygen concentration battery element and the oxygen pump element. A pillar that is formed on one end side and that defines the gap between the oxygen concentration battery element and the oxygen pump element in the gap without hindering gas from entering and exiting the gap. 9. The exhaust gas sensor according to claim 1, wherein a portion is formed, and the oxygen concentration battery element and the oxygen pump element are bonded to each other in an area other than the gap via an insulating layer. . 10. An electrode on the gap side of the oxygen pump element is a first electrode, an electrode on the gap side of the oxygen concentration battery element is a second electrode, and an electrode on the opposite space side of the oxygen concentration battery element is a first electrode. As the three electrodes, for at least one of the second electrode and the third electrode, a measurement chamber formed so as to be in contact with the second electrode and the third electrode, and a wall portion of the measurement chamber penetrates from the measured atmosphere side to the measurement chamber side. And a gas communication part formed in such a manner that the gas communication part includes at least one of a small hole, a slit, and a porous communication part made of porous ceramic or porous metal. The exhaust gas sensor according to any one of claims 1 to 9, which is said to be. 11. A gas sensor for detecting a component to be detected contained in exhaust gas, comprising an oxygen ion conductive solid electrolyte, and an oxygen concentration battery element having electrodes formed on both surfaces thereof, and oxygen. The oxygen-concentrated battery element is composed of an ion-conducting solid electrolyte and has electrodes formed on both sides thereof, and a predetermined amount of a clearance is formed between the oxygen-concentrated battery element and the oxygen-concentrated battery element to allow the flow of exhaust gas. And an oxygen pump element that pumps oxygen into the gap or pumps oxygen out of the gap in a direction in which the absolute value of the concentration battery electromotive force generated in the oxygen concentration battery element decreases. A heating element for heating at least one of the element and the oxygen concentration battery element to a predetermined sensor operating temperature, the gap, and the oxygen concentration battery element
The space on the opposite side of the space (hereinafter referred to as the opposite space)
And exhaust gas containing the detected component and oxygen, respectively
Of the oxygen pump element on the gap side of the oxygen pump element.
The electrode is the first electrode, and the gap side of the oxygen concentration battery element
An electrode is the second electrode, and the opposite space of the oxygen concentration cell element is
Side electrode as a third electrode, the gap and the opposite space
The detected component in the exhaust gas introduced into the
In at least one of the gaps and the opposite space,
At least one of the first to third electrodes is used as an oxidation catalyst.
Consumed by reacting with oxygen in the exhaust gas
The oxygen between the gap and the opposite space.
There may be a difference in the consumption of the detected components due to the reaction.
The reaction between the detected components of the first to third electrodes and oxygen.
The catalytic activity for is adjusted, for at least one of the second electrode and the third electrode, a measurement chamber formed so as to be in contact with the second electrode and the third electrode, and a wall portion of the measurement chamber from the measured atmosphere side from the measured atmosphere side. It has a gas communication portion formed so as to penetrate to the measurement chamber side, the gas communication portion, a small hole, a slit,
An exhaust gas sensor, which is a diffusion regulation distribution part including at least one of a porous communication part made of a porous ceramic or a porous metal. 12. A wall portion is formed between the oxygen concentration battery element and the oxygen pump element so as to surround the second electrode, and the inner surface of the wall portion, the oxygen concentration battery element and the oxygen pump element. The exhaust gas sensor according to claim 10 or 11, wherein a space surrounded by each of the facing surfaces is the measurement chamber. 13. The diffusion control and flow section is formed in such a manner that it penetrates at least one of the wall section and the oxygen concentration cell element from the measured atmosphere side to the measurement chamber side, and these measured sections are formed. The exhaust gas sensor according to claim 12, wherein the exhaust gas sensor is a slit or a small hole that allows the atmosphere and the measurement chamber to communicate with each other. 14. A wall forming body forming at least a part of the wall is arranged between the oxygen concentration battery element and the oxygen pump element, and the wall forming body and the oxygen concentration battery element. 13. The exhaust gas sensor according to claim 12, wherein the slit is formed between at least one of the oxygen pumping element and the oxygen pumping element so as to extend along a plate surface of the oxygen concentration cell element or the oxygen pumping element. 15. The exhaust gas sensor according to claim 14, wherein the wall portion forming body is integrated with at least one of the oxygen pump element and the oxygen concentration battery element by firing. 16. The oxygen pump element and the oxygen concentration battery element are formed in a laterally long plate shape, and the diffusion restricting flow portion is a slit formed on both sides of the oxygen pump element and the oxygen concentration battery element in the plate surface width direction. The exhaust gas sensor according to any one of claims 13 to 15, wherein 17. A gap forming member is arranged on the opposite side of the oxygen-concentration battery element from the side facing the gap, facing the gap and forming another gap with the oxygen-concentration battery element. A wall portion is formed between the gap forming member and the oxygen concentration battery element so as to surround the periphery of the third electrode, and the inner surface of the wall portion and the gap forming member and the oxygen concentration battery element are formed. The exhaust gas sensor according to claim 10, wherein a space surrounded by the facing surface is the measurement chamber. 18. The diffusion regulation and flow portion is formed in a form penetrating at least one of the wall portion and the gap forming member from the measured atmosphere side to the measured chamber side, and the measured atmosphere The exhaust gas sensor according to claim 17, wherein the exhaust gas sensor is a slit or a small hole that connects the measurement chamber with the measurement chamber. 19. A wall portion forming body which constitutes at least a part of the wall portion is arranged between the gap forming member and the oxygen concentration cell element, and the wall portion forming body and the gap forming member and 18. The exhaust gas sensor according to claim 17, wherein the slit is formed between at least one of the oxygen concentration battery elements and the gap forming member or the plate surface of the oxygen concentration battery elements. 20. The exhaust gas sensor according to claim 19, wherein the wall forming body is integrated with at least one of the gap forming member and the oxygen concentration battery element by firing. 21. The gap forming member and the oxygen concentration battery element are formed in a laterally long plate shape, and the diffusion restricting flow portion is a slit formed on both sides of the gap forming member and the oxygen concentration battery element in the plate surface width direction. The exhaust gas sensor according to claim 19 or 20, which is present. 22. The method of manufacturing an exhaust gas sensor according to claim 1, wherein an electrode material powder paste is used on both surfaces of the first ceramic powder compact to be the oxygen concentration battery element. By printing an electrode pattern to be the electrode, on both sides of the second ceramic powder molded body to be the oxygen pump element, by using an electrode material powder paste to print the electrode pattern to be the electrode, By laminating the first and second ceramic powder compacts so that the corresponding electrode patterns face each other and a gap is formed between the opposing electrode patterns, and firing the laminate. A method for manufacturing an exhaust gas sensor, characterized in that the oxygen concentration battery element and the oxygen pump element integrated with each other are obtained. 23. A third ceramic powder compact, which is to serve as the heating element, is laminated on at least one of the first and second ceramic powder compacts on the side opposite to the gap, and a laminate thereof. The method for manufacturing an exhaust gas sensor according to claim 22, wherein the oxygen concentration battery element, the oxygen pump element, and the heating element integrated with each other are obtained by firing. 24. For at least one of the first and second ceramic powder compacts, a pillar portion pattern to be the pillar portion is formed by using ceramic powder in a region corresponding to the gap, and then, the pillar portion pattern is formed. The first and second ceramic powder compacts are laminated on each other so that the gap is formed on the side where the pillar pattern is formed, and the laminate is fired to obtain the oxygen-concentrated battery element. And the oxygen pump element, the pillar portion based on the pillar pattern is formed.
3. The method for manufacturing the exhaust gas sensor according to item 3. 25. The first and second ceramic powder compacts are each formed in a horizontally long plate shape and are arranged to face each other, and the electrode patterns are formed on the plate surfaces of the first and second ceramic powder compacts. A spacer molded body which is formed on one end side in the longitudinal direction and is to be the spacer section between the first and second ceramic powder molded bodies on the other end side in the plate surface longitudinal direction. Is inserted, and by firing a laminate of the spacer compact and the first and second ceramic powder compacts,
25. The method for manufacturing an exhaust gas sensor according to claim 22, wherein the oxygen concentration battery element and the oxygen pump element are bonded to each other via the spacer portion based on the spacer molded body. 26. The first and second ceramic powder compacts are each formed in a laterally long plate shape and are stacked on each other, and the electrode pattern is a plate surface of the first and second ceramic powder compacts. While being formed on one end side in the longitudinal direction, the pillar portion should be formed by using a ceramic powder paste in a region scheduled in the gap between the first and second ceramic powder compacts. A pillar pattern is formed, and an auxiliary support pattern is formed by a powder paste of a material that burns or decomposes during firing in a region that is also planned in the gap at a position where it does not overlap with the pillar pattern. Forming an insulating layer pattern between the first and second ceramic powder compacts in a region other than the region scheduled for Thereby, between the oxygen concentration battery element and the oxygen pump element, the pillar and the pillar portion based on the pillar pattern are formed, while the oxygen concentration battery element and the oxygen pump are formed in other areas except the gap. 26. The method for manufacturing an exhaust gas sensor according to claim 22, wherein the element and the element are bonded to each other via the insulating layer based on the insulating layer pattern.