JPH0713619B2 - Oxygen concentration detector - Google Patents

Description

TECHNICAL FIELD The present invention relates to an oxygen concentration detection device for detecting the oxygen concentration in a gas such as engine exhaust gas.

BACKGROUND ART An air-fuel ratio that detects the oxygen concentration in the exhaust gas and purifies the air-fuel ratio of the air-fuel mixture supplied to the engine by feedback control to the target air-fuel ratio according to the detection results for the purpose of purifying exhaust gas from internal combustion engines and improving fuel efficiency. There is a fuel ratio control device.

As an oxygen concentration detecting device used in such an air-fuel ratio control device, there is one which generates an output proportional to the oxygen concentration in the gas to be measured. For example, an electrode pair is provided on both main surfaces of a flat plate-shaped oxygen ion conductive solid electrolyte member, one electrode surface of the solid electrolyte member forms a part of a gas retention chamber, and the gas retention chamber is introduced with the gas to be measured. Japanese Patent Laid-Open No. 52-72286 discloses a limiting current type oxygen concentration detecting device which is communicated through a hole. In this oxygen concentration detection device, when the oxygen ion conductive solid electrolyte member and the electrode pair act as an oxygen pump element to supply a current between the electrodes so that the gap chamber side electrode becomes the negative electrode, the negative electrode surface side Oxygen gas in the gas in the gas retention chamber is ionized, moves inside the solid electrolyte member toward the positive electrode surface, and is released as oxygen gas from the positive electrode surface. The limiting current value that can flow between the electrodes at this time is almost constant regardless of the applied voltage and is proportional to the oxygen concentration in the gas to be measured. Therefore, if the limiting current value is detected, the oxygen concentration in the gas to be measured is measured. be able to. However, when controlling the air-fuel ratio using such an oxygen concentration detection device, an output proportional to the oxygen concentration can be obtained from the oxygen concentration in the exhaust gas only when the air-fuel ratio of the air-fuel mixture is leaner than the stoichiometric air-fuel ratio. Therefore, the air-fuel ratio control in which the target air-fuel ratio is set in the rich region was impossible. Further, as an oxygen concentration detection device that can obtain an output proportional to the oxygen concentration in the exhaust gas in the lean and rich regions of the air-fuel ratio, two flat plate-like oxygen ion conductive solid electrolyte members are provided with electrode pairs, and two electrode pairs are provided. Each one electrode surface of the solid electrolyte member forms a part of the gas retention chamber, and the gas retention chamber communicates with the gas to be measured through the introduction hole. The other electrode surface of one solid electrolyte member faces the atmosphere chamber. An apparatus adapted to do so is disclosed in Japanese Patent Laid-Open No. 192955/1984. In this oxygen concentration detecting device, one oxygen ion conductive solid electrolyte member and the electrode pair act as an oxygen concentration ratio detecting battery element, and the other oxygen ion conductive solid electrolyte material and the electrode pair act as an oxygen pump element. It is like this. When the generated voltage between the electrodes of the oxygen concentration ratio detection battery element is equal to or higher than the reference voltage, a current is supplied so that oxygen ions move in the oxygen pump element toward the gas retention chamber side electrode,
When the voltage generated between the electrodes of the oxygen concentration ratio detection battery element is equal to or lower than the reference voltage, a lean current is supplied by supplying a current in the oxygen pump element so that oxygen ions move to the side opposite to the gas retention chamber side toward the electrodes. The current value is proportional to the oxygen concentration in the air-fuel ratio in the rich region. However,
In such an oxygen concentration detection device, the oxygen concentration detection characteristics are different between the rich side and the lean side, and good oxygen concentration detection output with good linearity cannot be obtained in a wide region, so the oxygen concentration detection output on the rich side or the lean side is obtained. There is a problem that the air-fuel ratio control becomes complicated because it must be corrected.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an oxygen concentration detection device capable of obtaining an oxygen concentration detection output with good linearity over lean and rich regions of the air-fuel ratio.

The oxygen concentration detection device of the present invention comprises a base forming first and second gas retention chambers and a gas introduction chamber each having an oxygen ion conductive solid electrolyte wall, and inner and outer wall surfaces of the electrolyte wall of the first gas retention chamber. Two first electrode pairs which are provided so as to face each other with this sandwiched therebetween to form a first sensor, and which are provided so as to face each other with the sandwiched therebetween on the inner and outer wall surfaces of the electrolyte wall portion of the second gas retention chamber. The two second electrode pairs, which form a second sensor having a detection characteristic different from that of the first sensor, and a difference between the voltage generated between one of the two first electrode pairs and the first reference voltage. A current having a value corresponding to the voltage is supplied between the other electrode pair of the two first electrode pairs, and the difference voltage between the voltage generated between the one electrode pair of the two second electrode pairs and the second reference voltage is used. A current supply means for supplying a current of a corresponding value between the other electrode pair of the two second current pairs. Wherein the door, the second to the first gas residence chamber communicates with the outside air introduction chamber through the first gas diffusion limiting means
It is characterized in that the oxygen concentration detection value corresponding to the supply current value by the current supply means is obtained by communicating through the gas diffusion restriction means and communicating with the second gas retention chamber through the third gas diffusion restriction means.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 show an air-fuel ratio control device using an oxygen concentration detection device according to the present invention. In this device,
An oxygen ion conductive solid electrolyte member 1 having a substantially cubic shape is provided. First and second gas retention chambers 2 and 3 and a gas introduction chamber 4 are formed in the oxygen ion conductive solid electrolyte member 1. The gas introduction chamber 4 communicates with an introduction hole 5 for introducing the exhaust gas of the gas to be measured from outside the solid electrolyte member 1,
The introduction hole 5 is located in the exhaust pipe (not shown) of the internal combustion engine so that the exhaust gas can easily flow into the gas introduction chamber 4. Communication holes 6 and 7 are formed in each wall portion between the gas introduction chamber 4 and the first and second gas retention chambers 2 and 3. The diameter of the communication hole 6 is larger than the diameter of the communication hole 7. Exhaust gas is introduced into the first gas retention chamber 2 through the introduction hole 5, the gas introduction chamber 4, and the communication hole 6, and the exhaust gas is introduced into the second gas retention chamber 3 through the introduction hole. 5, the gas introduction chamber 4, and the communication hole 7 are introduced. The oxygen ion conductive solid electrolyte member 1 is formed with a reference gas chamber 8 for introducing outside air or the like so as to separate the walls from the first and second gas retention chambers 2 and 3. Electrode pairs 11a, 11b, 12a, 12b are formed on the wall between the first gas retention chamber 2 and the gas introduction chamber 4 and on the wall between the first gas retention chamber 2 and the reference gas chamber 8, respectively. Further, electrode pairs 13a, 13b, 14a, 14b are provided on the wall between the second gas retention chamber 3 and the gas introduction chamber 4 and on the wall between the second gas retention chamber 3 and the reference gas chamber 8, respectively. Has been formed.
The electrode pair 11a, 11b has a through hole communicating with the communication hole 6 at the center, and the electrode pair 13a, 13b also has a through hole communicating with the communication hole 7 at the center. Solid electrolyte member 1 and electrode pair 11a, 11
b serves as the first oxygen pump element 15, and the solid electrolyte member 1 and the electrode pairs 12a and 12b serve as the first battery element 16. In addition, the solid electrolyte member 1 and the electrode pairs 13a and 13b are used as the second battery element 17, and the solid electrolyte member 1 and the electrode pairs 14a and 14b are used.
Respectively function as the second battery elements 18. Further, heater elements 19 and 20 are provided on the outer wall surface of the gas introduction chamber 4 and the outer wall surface of the reference gas chamber 8 of the solid electrolyte member 1, respectively. The heater elements 19 and 20 are electrically connected in parallel to each other, and
Also, the second oxygen pump elements 15 and 17 and the first and second battery elements 16 and 18 are heated uniformly, and the heat retention in the solid electrolyte member 1 is improved. The oxygen ion conductive solid electrolyte member 1 is integrally formed from a plurality of pieces.
Further, it is not necessary to form all the wall portions of the first and second gas retention chambers from the oxygen ion conductive solid electrolyte, and it suffices that at least the portion where the electrode pair is provided be formed of the solid electrolyte.

ZrO ₂ (zirconium dioxide) is used as the oxygen ion conductive solid electrolyte member 1, and Pt (platinum) is used as the electrodes 11a to 14b.

First and second oxygen pump elements 15, 17 and first and second
A current supply circuit 21 is connected to the battery elements 16 and 18.
As shown in FIG. 2, the current supply circuit 21 includes a differential amplifier circuit 22,2.
3, current detection resistors 24, 25, reference voltage sources 26, 27 and switching circuit 28,
It consists of 29. The outer electrode 11a of the first oxygen pump element 15 is connected to the output end of the differential amplifier circuit 22 via the switch 28a of the switching circuit 28 and the current detection resistor 24, and the inner electrode 11b is connected to the switch 29a of the switching circuit 29. It is designed to be grounded. The outer electrode 12a of the first battery element 16 is a differential amplifier circuit 22.
The inner electrode 12b is connected to the inverting input end of the switch and is grounded via the switch 29b of the switching circuit 29.
Similarly, the outer electrode 13a of the second oxygen pump element 17 is connected to the switching circuit 2
Differential amplifier circuit via switch 28b of 8 and current detection resistor 25
The inner electrode 13b is connected to the output terminal of 23 and is grounded via the switch 29a of the switching circuit 29. The outer electrode 14a of the second battery element 18 is connected to the inverting input terminal of the differential amplifier circuit 23, and the inner electrode 14b is connected to the switch 2 of the switching circuit 29.
It is designed to be grounded via 9b. A reference voltage source 26 is connected to the non-inverting input terminal of the differential amplifier circuit 22, and a reference voltage source 27 is connected to the non-inverting input terminal of the differential amplifier circuit 23. The output voltage of the reference voltage sources 26, 27 is a voltage (for example, 0.4 V) corresponding to the stoichiometric air-fuel ratio. Both ends of the current detection resistor 24 form an output of the first sensor, and both ends of the current detection resistor 25 form an output of the second sensor. Current detection resistor 2
The voltage between both ends of 4,25 is supplied to the air-fuel ratio control circuit 32 via the A / D converter 31 of the differential input, and the pump current values I _P (1), I _P (2 ) Is read into the air-fuel ratio control circuit 32. The air-fuel ratio control circuit 32 is composed of a microcomputer. The air-fuel ratio control circuit 32 is connected to a plurality of operating parameter detection sensors (not shown) for detecting the engine speed, the absolute pressure in the intake pipe, the cooling water temperature, etc., and the solenoid valve 34 is connected via the drive circuit 33. It is connected. solenoid valve
34 is provided in an intake secondary air supply passage (not shown) communicating with the intake manifold downstream of the engine carburetor throttle valve. Further, the air-fuel ratio control circuit 32 controls the switch switching operation of the switching circuits 28, 29, and the drive circuit 30 drives the switching circuits 28, 29 in response to a command from the air-fuel ratio control circuit 32. In addition,
Positive and negative power supply voltages are supplied to the differential amplifier circuits 22 and 23.

On the other hand, a current is supplied to the heater elements 19 and 20 by the heater current supply circuit 3
When supplied from 5, the heater elements 19 and 20 generate heat to heat the oxygen pump elements 15 and 17 and the battery elements 16 and 18 to an appropriate temperature higher than the exhaust gas.

In such a configuration, the exhaust gas in the exhaust pipe is introduced into the introduction hole 5
Flow into the gas introduction chamber 4 to diffuse, further flow into the first gas retention chamber 2 via the communication hole 6 to diffuse, and flow into the second gas retention chamber 3 via the communication hole 7. Spread.

In the switching circuits 28 and 29, the switch 28a connects the electrode 11a to the current detection resistor 24 and the switch 28b connects the electrode 13 as shown in FIG.
The connection line of a is opened, switch 29a grounds electrode 11b and opens the connection line of electrode 13b, and switch 2a
When 9b is placed in the selected position to ground electrode 12b and open the connection line of electrode 14b, the first sensor is in the selected state.

In the selected state of the first sensor, first, when the air-fuel ratio of the engine-supplied air-fuel mixture is in the lean region, the output level of the differential amplifier circuit 22 becomes a positive level, and this positive-level voltage is the resistance.
24 and the first oxygen pump element 15 are supplied to the series circuit.
Therefore, the pump current flows between the electrodes 11a and 11b of the first oxygen pump element 15. This pump current flows from electrode 11a to electrode 11b.
The oxygen in the first gas retention chamber 2 flows toward the electrode 11
At b, it is ionized, moves inside the first oxygen pump element 15, is released as oxygen gas from the electrode 11a, and oxygen in the first gas retention chamber 2 is pumped out.

By pumping out oxygen in the first gas retention chamber 2, an oxygen concentration difference occurs between the exhaust gas in the first gas retention chamber 2 and the gas in the reference gas chamber 8. Due to this difference in oxygen concentration, a voltage Vs is generated between the electrodes 12a and 12b of the battery element 16. This voltage Vs is supplied to the inverting input terminal of the differential amplifier circuit 22. Differential amplifier circuit 22
Since the output voltage of is equal to the voltage difference between the voltage Vs and the output voltage Vr ₁ of the reference voltage source 26, the pump current value is proportional to the oxygen concentration in the exhaust gas.

When the air-fuel ratio is in the rich region, the voltage Vs exceeds the output voltage Vr ₁ of the reference voltage source 26. Therefore, the output level of the differential amplifier circuit 22 is inverted from the positive level to the negative level. Due to this negative level, the pump current flowing between the electrodes 11a and 11b of the first oxygen pump element 15 decreases and the current direction is reversed. That is, since the pump current flows from the electrode 11b to the electrode 11a, the external oxygen is ionized at the electrode 11a and moves in the first oxygen pump element 15 to move from the electrode 11b into the first gas retention chamber 2 as oxygen gas. It is released and oxygen is pumped into the first gas retention chamber 2. Accordingly, the pump current is pumped in and out by supplying the pump current so that the oxygen concentration in the first gas retention chamber 2 is always constant, so that the pump current value I _P and the output voltage of the differential amplifier circuit 22. Is proportional to the oxygen concentration in the exhaust gas in the lean and rich regions, respectively. A solid line a in FIG. 3 shows the pump current value I _P.

The pump current value I _P is e, the diffusion coefficient for the exhaust gas through the introduction hole 5 and the communication hole 6 is σ _O , the oxygen concentration in the exhaust gas is P _O exh, and the oxygen concentration in the first gas retention chamber 2 is P _O exh. _{If O} v, it can be expressed by the following equation.

I _P = 4eσ _O (P _O exh−P _O v) (1) where the diffusion coefficient σ _O is the area of the introduction hole 5 is A ₁ and the communication hole 6 is 6.
Where A _{2 is} the area, Boltzmann's constant is k, absolute temperature is T, the length of the introduction hole 5 is l ₁ , the length of the communicating hole 6 is l ₂ and the diffusion constant is D, the following equation can be expressed. it can.

σ _O = (A ₁ / l ₁ + A ₂ / l ₂ ) D / kT (2) Next, the switch 28a opens the connection line of the electrode 11a, and the switch 28b connects the electrode 13a to the current detection resistor 25. Switch 29a grounds electrode 13b and opens the connection line of electrode 11b, and switch 29b grounds electrode 14b and the electrode
Once in the selected position to open the 12b connection line, the second
The sensor is selected.

In the selected state of the second sensor, the pump current is the electrode of the second oxygen pump element 17 so that the oxygen concentration in the second gas retention chamber 3 is always constant by the same operation as the selected state of the first sensor described above. Oxygen is supplied to between 13a and 13b, and oxygen is pumped in or pumped out. Therefore, the pump current value I _P and the output voltage of the differential amplifier circuit 23 are different from the oxygen concentration in the exhaust gas in the lean and rich regions, respectively. It is proportional. In the pump current value I _{P in} the second sensor selected state, the diffusion coefficient σ _O in the above equation (1) is determined by the introduction hole 5 and the communication hole 7, and P _O v is the oxygen in the second gas retention chamber 3. It is represented by the concentration. It has been clarified that the magnitude of the pump current value I _P becomes smaller as the diffusion resistance inversely proportional to the magnitude of the diffusion coefficient σ _O becomes larger in the lean and rich regions of the air-fuel ratio as shown in FIG. Therefore, in the second sensor selection state, the diffusion resistance becomes larger than in the first sensor selection state, so that the pump current value I _P becomes as shown by the broken line b in FIG.
Becomes smaller in the lean and rich regions,
By adjusting the size and length of the communication hole 7, as shown in FIG. 3, the pump current value characteristic in the rich region in the second sensor selected state becomes I in the lean region in the first sensor selected state. It is linearly continuous at _P = 0. The output voltage characteristics of the differential amplifier circuits 22 and 23 are also 0.
It becomes linearly continuous at [V].

The air-fuel ratio control circuit 32 operates as follows to obtain the linearly continuous output characteristic. As shown in FIG. 5, the air-fuel ratio control circuit 32 first determines whether or not the flag Fs indicating the selection state of the first and second sensors is "1" (step 51). When Fs = 0, the first sensor is in the selected state, so the pump current value I _P (1) of the first sensor output from the A / D converter 31 is read to correspond to the pump current value I _P (1). It is determined whether the oxygen concentration detection output value L _O2 is greater than or equal to a reference value L ref0 corresponding to 0 [V] of the output voltage Vs ₁ of the differential amplifier circuit 22 (step 52). L _O2 ≧ Lref 0 (Vs ₁
≧ 0), the first sensor selection state is continued because it is in the lean region, and when L _O2 <Lref0 (Vs ₁ <0), it is in the rich region and therefore the second sensor selection command is issued to the drive circuit 30. If so (step 53), the flag Fs is set to "1" to indicate that the second sensor has been selected (step 54). On the other hand, in the case of Fs = 1, the pump current value of the second sensor output from the A / D converter 31 because the second sensor selection state I _P (2) and Loading the pumping current I _P (2)
It is determined whether or not the oxygen concentration detection output value L _O2 corresponding to is greater than or equal to the reference value L ref0 corresponding to 0 [V] of the output voltage Vs ₂ of the differential amplifier circuit 23 (step 55). L _O2 ≤ Lref0 (V
If s ₁ ≦ 0), the second sensor selection state is continued because it is in the rich region, and if L _O2 > Lref0 (Vs ₂ > 0), it is in the lean region and therefore the first sensor selection command is sent to the drive circuit 30. Occurs (step 56) and the flag Fs is set to "0" to indicate that the first sensor has been selected (step 57). The drive circuit 30 drives the switches 28a, 28b, 29a, 29b to the above-mentioned first sensor selection position in response to the first sensor selection command, and the driving state is such that the second sensor selection command is supplied from the air-fuel ratio control circuit 32. Maintained until Further, the switches 28a, 28b, 29a, 29b are driven to the above-mentioned second sensor selection position in response to the second sensor selection command, and the driving state is the first
It is maintained until the sensor selection command is supplied from the air-fuel ratio control circuit 32. When the first or second sensor is selected in this way, the air-fuel ratio control circuit 32 causes the oxygen concentration detection output value L _{O2 of} the first or second sensor output from the A / D converter 31 to correspond to the target air-fuel ratio. It is determined whether or not it is larger than the target value Lref (step 58). If L _O2 ≤Lref, the air-fuel ratio of the supply air-fuel mixture is rich, so a command to open the solenoid valve 34 is issued to the drive circuit 33 (step 59). If L _O2 > Lref, the supply air-fuel mixture is supplied. Since the air-fuel ratio of is lean, the drive circuit 33
To the solenoid valve 34 is generated (step 60). The drive circuit 33 operates the solenoid valve 34 in response to the valve opening drive command.
Is opened to supply secondary air into the engine intake manifold to make the air-fuel ratio lean, and the valve-opening drive of the solenoid valve 34 is stopped in response to the valve-opening stop command to enrich the air-fuel ratio. Let The air-fuel ratio of the supply air-fuel mixture is controlled to the target air-fuel ratio by repeatedly performing this operation every predetermined period. In steps 52 and 55, the reference value Lref0, that is, the discrimination reference voltage of the voltages Vs ₁ and Vs ₂ is set to 0 [V], but the discrimination reference voltage of the voltage Vs ₁ is set to have hysteresis. It may be set to be slightly smaller than 0 [V], and the determination reference voltage of the voltage Vs ₂ may be set to be slightly larger than 0 [V].

In the embodiment of the present invention described above, the introduction hole 5 and the communication holes 6 and 7 are used as the first to third gas diffusion limiting means, and different diffusion resistances are obtained by the communication holes 6 and 7, respectively. However, not limited to this, in order to obtain different diffusion resistances, the diameters of the communication holes 6 and 7 are made equal, and 2 in the first gas retention chamber 2 is used.
Two second electrodes between the two first electrode pairs and in the second gas retention chamber 3
It is possible to form gaps between the electrode pairs and make the gap widths different, and as shown in FIG. 6, alumina (Al ₂ O 3
The porous body 38, 39, 40 such as ₃ ) may be filled in the introduction hole 5 and the communication holes 6, 7 to form a porous diffusion layer.

Further, in the above-described embodiment of the present invention, the air-fuel ratio of the supply air-fuel mixture is controlled to the target air-fuel ratio by supplying the secondary air according to the output of the first or second sensor. However, the air-fuel ratio may be controlled by adjusting the fuel supply amount according to the output of the first or second sensor.

EFFECTS OF THE INVENTION As described above, in the oxygen concentration detecting device of the present invention, the gas to be measured such as exhaust gas flows in via the first gas diffusion limiting means, and the second or the second gas introducing chamber. The first and second gas retention chambers that communicate with each other through the three gas diffusion limiting means and have different diffusion resistances to the inflow gas are provided.
The first and second electrode pairs are provided so as to face each other on the inner and outer wall surfaces of the electrolyte wall portion of each of the second and second gas retention chambers so as to oppose each other, for example, by adjusting the diffusion resistance by each gas diffusion limiting means. First with different oxygen concentration detection characteristics
Since the second sensor is obtained, it is possible to obtain an oxygen concentration detection output characteristic with a good linearity proportional to the oxygen concentration in the gas to be measured in a wide lean and rich region. Therefore, it is not necessary to correct the oxygen concentration detection output, the air-fuel ratio control becomes easy, and the accuracy of the air-fuel ratio control can be improved.

[Brief description of drawings]

FIG. 1 (a) is a plan view showing an embodiment of the oxygen concentration detection device according to the present invention, and FIG. 1 (b) is Ib-Ib of FIG. 1 (a).
A sectional view of a portion, FIG. 2 is a circuit diagram showing a current supply circuit including an air-fuel ratio control device, FIG. 3 is a diagram showing output characteristics of the device of FIG. 1, and FIG. 4 is a diffusion resistance and a pump current value. 5 is a flow chart showing the operation of the air-fuel ratio control circuit, FIG. 6 (a) is a plan view showing another embodiment of the present invention,
FIG. 6 (b) is a sectional view of a VIb-VIb portion of FIG. 6 (a). Explanation of symbols of main parts 1 …… Oxygen ion conductive solid electrolyte member 2,3 …… Gas retention chamber 4 …… Gas introduction chamber 5 …… Introduction hole 6,7 …… Communication hole 8 …… Gas reference chamber 15, 17 …… Oxygen pump element 16,18 …… Battery element 19,20 …… Heater element 21 …… Current supply circuit

Claims (4)

[Claims] 1. A substrate forming first and second gas retention chambers and a gas introduction chamber each having an oxygen ion conductive solid electrolyte wall, and on the inner and outer wall surfaces of the electrolyte wall of the first gas retention chamber. Two first electrode pairs that are provided so as to face each other with this sandwiched therebetween to form a first sensor, and are provided so as to face each other on the inner and outer wall surfaces of the electrolyte wall portion of the second gas retention chamber with this sandwiched therebetween. Forming a second sensor having an oxygen concentration detection characteristic different from that of the first sensor 2
Two second electrode pairs, and a current having a value corresponding to a difference voltage between a voltage generated between one of the two first electrode pairs and the first reference voltage is applied to the other of the two first electrode pairs. A current having a value corresponding to a difference voltage between a voltage generated between one electrode pair of the two second electrode pairs and a second reference voltage is supplied to the other electrode pair of the two second electrode pairs. An electric current supply means for supplying between the pair of electrodes, the gas introducing chamber communicates with the outside through a first gas diffusion limiting means, and communicates with the first gas retention chamber through a second gas diffusion limiting means, and An oxygen concentration detection device, which communicates with the second gas retention chamber via a third gas diffusion limiting means, and obtains an oxygen concentration detection value according to a supply current value by the current supply means. 2. The second gas diffusion limiting means comprises a first communicating hole, and the third gas diffusion limiting means comprises a second communicating hole having a size different from that of the first communicating hole. The oxygen concentration detection device according to claim 1. 3. A gap width between two first electrode pairs in the first gas retention chamber and a gap width between two second electrode pairs in the second gas retention chamber are different from each other. 2. An oxygen concentration detector according to claim 1. 4. The current supply means selectively supplies a current to either one of the other first electrode pair and the other second electrode pair according to the oxygen concentration detection value to supply the current value. The oxygen concentration detection device according to claim 1, wherein the oxygen concentration detection value according to the above is output.