JP6435200B2 - Ion current measuring device - Google Patents

Description

  The present invention relates to an ionic current.

  The glow plug is a heater used as an auxiliary heat source for an internal combustion engine (for example, a diesel engine) using a compression ignition system. A function for measuring an ion current based on ions generated in the combustion chamber can be added to the glow plug. By measuring the current value of the ion current (hereinafter also referred to as “ion current value”), the combustion state of the fuel in the combustion chamber can be estimated. In order to realize the measurement of the ionic current value, a glow plug configuration in which a conductor different from the heating element is embedded in a ceramic base is known. In this configuration, by applying a voltage between the conductor and the ground potential (engine block), an ionic current flows through the conductor through the base (for example, Patent Document 1).

Japanese Patent No. 3605965

  In the case of the above prior art, since the substrate is made of ceramic, the electric resistance value of the substrate strongly depends on the temperature of the substrate. Therefore, the measured ionic current value strongly depends on the temperature of the substrate. For this reason, the detection accuracy of the ionic current value may deteriorate due to a change in the temperature of the substrate. Such a problem is not limited to a glow plug having a function of measuring an ion current, but is common to all ion current measuring apparatuses having a function of measuring an ion current value. In view of the above prior art, an object of the present invention is to reduce the influence on the detection accuracy of an ionic current value even if the temperature of a detection unit that detects the ionic current value changes.

  SUMMARY An advantage of some aspects of the invention is to solve the above-described problems, and the invention can be implemented as the following forms.

(1) According to one aspect of the present invention, the first and second conductors, and a ceramic base body embedded and held inside the first and second conductors in a state of being separated from each other, are provided. A detection unit attached in a state where the base body is exposed in a space where ions are generated by burning fuel; and a measurement unit that measures a current value flowing through the second conductor as an ion current based on the generated ions An ionic current measuring device is provided. The ion current measurement apparatus includes: an acquisition unit that acquires an electric resistance value of the base between the first conductor and the second conductor; and the acquisition unit that acquires the current value measured by the measurement unit. And a correction unit that performs correction based on the electrical resistance value acquired by the above. According to this aspect, since the ionic current value is corrected based on the electric resistance value of the substrate between the first conductor and the second conductor (hereinafter also referred to as “first substrate resistance value”), the second conductor Even if the electrical resistance value of the substrate between the space and the space (hereinafter referred to as “second substrate resistance value”) changes, the influence of the change on the detection accuracy of the ion current value can be reduced. This is because the first and second substrate resistance values have a strong correlation with each other. As a result, even if the temperature of the detection unit changes, the influence of the change on the detection accuracy of the ion current can be reduced.

(2) In the above embodiment, the first conductor may be a heating element that generates heat when energized. According to this embodiment, the detection unit can also function as a heater.

(3) According to another aspect of the present invention, the first and second conductors, and the ceramic base body embedded and held in the state where the first and second conductors are separated from each other, A detector that is attached in a state where the base body is exposed in a space where ions are generated when the fuel is burned; and a measurement that measures a value of a current flowing through the second conductor as an ion current based on the generated ions An ion current measuring device is provided in which the first conductor is a heating element that generates heat when energized. The ion current measuring apparatus includes: an acquisition unit that acquires an electric resistance value of the base body between the first conductor and the second conductor; and the electric resistance value acquired by the acquisition unit is a predetermined value A control unit that controls energization of the first conductor; and the measurement unit measures the current value under energization control by the control unit. According to this embodiment, even if the temperature around the detection unit changes, the energization to the first conductor is controlled so that the first base resistance value becomes a predetermined value. The fluctuation of the detection accuracy of the ion current value can be reduced.

(4) In the above aspect, the space may be a combustion chamber of an internal combustion engine; the detection unit may function as a glow plug by the heat generated by the first conductor. According to this embodiment, the detection unit can also function as a glow plug.

(5) In the above aspect, the acquisition unit is configured to generate the electric resistance based on a potential difference between the first conductor and the two conductors and a current value flowing between the first conductor and the two conductors. A value may be acquired. According to this aspect, the first base resistance value can be easily obtained.

  The present invention can be realized in various forms other than the above. For example, the detection unit may not be provided. Alternatively, it can be realized in the form of an ion current correction method, a detection unit control method, a computer program for realizing the method, a non-temporary storage medium storing the computer program, and the like.

The schematic block diagram of an ion current measuring apparatus. The fragmentary sectional view of a glow plug. Sectional drawing of the tip vicinity of a glow plug. The flowchart which shows an ion current measurement process. The graph which shows the time fluctuation of the measured current value. The graph which shows roughly the relationship between a 1st base | substrate resistance value and the highest surface temperature of a base | substrate. The flowchart which shows an ion current measurement process (embodiment 2).

  A first embodiment will be described. FIG. 1 shows a schematic configuration of an ion current measuring apparatus 100. The ion current measuring apparatus 100 is mounted on a diesel engine vehicle and measures an ion current value based on ions generated in the combustion chamber of the diesel engine. Furthermore, the ion current measuring apparatus 100 heats the combustion chamber. This heating is performed to assist the ignition of the fuel injected from the injector 459.

  The ion current measuring apparatus 100 includes a glow plug 1 and a control unit 50. The glow plug 1 is a ceramic glow plug. As shown in FIG. 1, the glow plug 1 is attached to the cylinder block 45 by screwing the male screw portion of the housing 4. Thereby, the tip of the glow plug 1 is mounted in a state where it is exposed to the combustion chamber of the cylinder block 45.

  The control unit 50 includes an ECU 52, a glow relay 53, a battery 54, and a glow relay 531. The glow relay 53 is disposed between the positive electrode of the battery 54 and the external lead wire 233 provided in the glow plug 1.

  The negative electrode of the battery 54 is connected to the cylinder block 45 via the glow relay 531. When the glow relay 53 is on, the negative electrode of the battery 54 is conducted to the cylinder block 45. Since the potential of the cylinder block 45 is the ground potential, when the glow relay 531 is on, the negative electrode of the battery 54 is grounded.

  The ECU 52 supplies power to the battery 54 via the external lead wire 233 provided in the glow plug 1 by turning on the glow relay 53 and the glow relay 531. The ECU 52 causes the glow plug 1 to generate heat by this power supply. The ECU 52 controls the heat generation of the glow plug 1 by controlling the ratio between the on time and the off time of the glow relay 53. The glow relay 531 is always turned on while heating is performed, and is turned off when heating is stopped.

  The control unit 50 further includes a DC power source 51, a relay 55, a resistor 521, and a potentiometer 522. The relay 55 is disposed between the resistor 521 and the external lead wire 333 provided in the glow plug 1. The relay 55 is for switching on / off of power feeding from the DC power source 51 to the glow plug 1.

  The negative electrode of the DC power source 51 is grounded by being connected to the cylinder block 45. The resistor 521 is disposed on the positive electrode side of the DC power supply 51. The potentiometer 522 measures a voltage value (voltage drop) that drops at the resistor 521. The ECU 52 uses these circuit configurations and measures the ion current value by using the glow plug 1 as a detection unit.

  FIG. 2 is a partial cross-sectional view of the glow plug 1. FIG. 3 is a cross-sectional view of the vicinity of the tip of the glow plug 1 and shows a state where the glow plug 1 is attached to the cylinder block 45. Hereinafter, a description will be given with reference to FIGS.

  As shown in FIG. 2, the glow plug 1 includes a housing 4, a heater 10, a terminal portion 23, a terminal portion 31, an internal lead wire 33, an internal lead wire 231, a connection terminal 232, and an external lead wire. 233, a connection terminal 332, an external lead wire 333, and a rubber bush 421. These members are assembled along the axis O of the glow plug 1. In the present specification, the heater 10 side of the glow plug 1 is referred to as “front end side”, and the opposite side is referred to as “rear end side”.

  As shown in FIG. 2, the housing 4 includes an outer cylinder 41, a protection cylinder 42, and a metal shell 47. The protective cylinder 42 is a substantially cylindrical member extending along the axis O, and has openings on the front end side and the rear end side. The opening on the front end side of the protective cylinder 42 is attached to the rear end of the metal shell 47. A rubber bushing 421 is inserted into the opening on the rear end side of the protective cylinder 42. The rubber bush 421 is a rubber cylindrical member. By inserting the rubber bush 421 into the protective cylinder 42, the tip side is sealed from the rubber bush 421. The outer cylinder 41 is disposed on the front end side of the protection cylinder 42. The metal shell 47 is provided with a male screw portion 43. The male screw portion 43 is used for mounting on the cylinder block 45 of the engine.

As shown in FIG. 3, the heater 10 is a substantially rod-shaped member having a hemispherical tip and extending along the axis O. The heater 10 is fixed in the housing 4 via an outer cylinder 41. The outer cylinder 41 is made of metal and is a ring-shaped member. The heater 10 includes an energization heating element 2, an electrode 3, a base 11, and a pair of lead wires 21 and 22. The energization heating element 2, the electrode 3, and the lead wires 21 and 22 are embedded and held in the base 11. The substrate 11 is made of a ceramic containing Si ₃ N ₄ (silicon nitride) as a main component.

  As shown in FIG. 2, the external lead wires 233 and 333 pass through the rubber bushing 421 and communicate with the inside of the glow plug 1. The external lead wire 233 is connected to the terminal portion 23 via the connection terminal 232 and the internal lead wire 231. The terminal portion 23 is disposed on the outer peripheral surface of the base body 11 with a gap between the terminal portion 23 and the inner peripheral surface of the housing 4. The terminal portion 23 is electrically connected to the housing 4 through the heater 10 as will be described later. As described above, the housing 4 is fixed to the cylinder block 45 so as to be electrically connected to the cylinder block 45 having the ground potential. The cylinder block 45 is connected to the negative electrode of the battery 54 as described above. Therefore, when the glow relays 53 and 531 are turned on, a closed circuit is formed.

  As shown in FIG. 3, the lead wire 21 is connected to the terminal portion 23. The lead wire 21 passes through the inside of the base 11 and is connected to one end of the energization heating element 2 having a U shape. The other end of the energization heating element 2 is connected to the outer cylinder 41 via the lead wire 22. Therefore, when the glow relays 53 and 531 are turned on, the voltage of the battery 54 is applied to the energization heating element 2, and a current flows through the energization heating element 2 embedded in the base 11. The energization heating element 2 is formed of a ceramic having a smaller electrical resistance value than that of the base 11, and the vicinity of the tip generates heat when energized.

  Next, a circuit for measuring the above-described ion current value will be described. As shown in FIG. 2, the external lead wire 333 is connected to the terminal portion 31 disposed at the rear end of the base body 11 via the connection terminal 332 and the internal lead wire 33. As shown in FIG. 3, one end of the electrode 3 is connected to the terminal portion 31, and extends along the axis O direction inside the base body 11. The other end of the electrode 3 is disposed near the tip of the energization heating element 2.

  The electrode 3 is made of a conductive ceramic, and is embedded in the base 11 while being isolated from the energization heating element 2. Therefore, when the relay 55 is turned on and the DC power supply 51 and the electrode 3 are brought into conduction, the potential of the electrode 3 becomes higher than the ground potential. When the potential of the electrode 3 increases, the potential of the substrate 11 also increases with respect to the ground potential. If the potential of the substrate 11 is high and ions are present in the combustion chamber, an ionic current is generated. This ion current flows through the space between the base 11 and the cylinder block 45. Since the negative electrode of the DC power supply 51 is connected to the cylinder block 45, a closed circuit is formed when an ionic current is generated.

  FIG. 4 is a flowchart showing ion current measurement processing. The ion current measurement process is repeatedly executed by the ECU 52.

First, the voltage drop 521 in the resistor ₅₂₁ is acquired using the potentiometer 522 (step S610). Since the drop voltage V ₅₂₁ fluctuates due to the influence of the ion current, in step S610, the value of the drop voltage V ₅₂₁ is acquired for at least one cycle of the engine.

Subsequently, the acquired voltage drop ₅₂₁ is divided by the resistance value of the resistor 521 to be converted into a current value I (step S620). FIG. 5 is a graph illustrating I (t) indicating the temporal variation of the current value I converted in step S620.

Next, the first substrate resistance value R ₁₁ is calculated (step S630). The first substrate resistance value R ₁₁ is the electrical resistance value of the substrate 11 between the energization heating element 2 and the electrode 3. The base 11 is made of ceramic and generally has an electric resistance value classified as an insulator. However, since the electric resistance value of the base 11 is naturally limited, a slight current flows through the base 11 when a high voltage is applied to the electrode 3. This current flows toward the conductor embedded in the base body 11 and the conductor in contact with the base body 11, and finally flows to the cylinder block 45 at the ground potential. The conductors arranged in the base 11 are the energization heating element 2, the lead wire 21, and the lead wire 22. The conductor in contact with the substrate 11 includes ions generated in the combustion chamber in addition to the terminal portion 23, the terminal portion 31, and the outer cylinder 41.

  Since the above ions are generated with the combustion of fuel in the combustion chamber, the ion current value fluctuates within the time of one cycle of the engine. On the other hand, the current through other paths hardly fluctuates in such a short time. Therefore, the current value converted in step S620 can be divided into an ionic current and a current through another path. Specifically, as shown in FIG. 5, the minimum value Imin in the time variation of the current value converted in step S620 is the amount of current through other paths, and the amount exceeding the minimum value Imin is the amount of ion current. is there. The amount exceeding the minimum value Imin is (I (t) -Imin), and this value is hereinafter referred to as a current value Iion (t).

  Most of the current through the other path flows from the vicinity of the tip of the electrode 3 to the vicinity of the tip of the energization heating element 2. This is because, as will be described later, the substrate 11 has a lower electrical resistance value as the temperature is higher. As described above, since the vicinity of the tip of the energization heating element 2 generates heat, the base 11 near the end of the energization heating element 2 has a higher temperature than other parts.

Therefore, in the calculation of the first substrate resistance value R ₁₁ , the current flowing outside the electrode 3 is ignored. Furthermore, the electrical resistance value of the energization heater 2 is smaller than the first base resistance R _11, ignored in the calculation of the first base resistance R _11. That is, the energization heating element 2 is handled as a conductor in this embodiment.

When the above is assumed, the first base resistance value R ₁₁ is calculated by the following equation (3). In the following formulas (1) to (3), V ₁₁ represents the potential difference between the energization heating element 2 and the electrode 3, and V ₀ represents the voltage of the DC power supply 51.

R ₁₁ = V ₁₁ / Imin… (1), V ₁₁ = V ₀ -V ₅₂₁ … (2)
Substituting equation (2) into equation (1) yields equation (3).
R ₁₁ = (V ₀ -V ₅₂₁ ) / Imin… (3)
In this embodiment, since V ₅₂₁ << V ₀ , Equation (3) can be transformed into the following Equation (4).
R ₁₁ = V ₀ / Imin… (4)

Subsequently, it is determined whether the first substrate resistance value R ₁₁ is equal to or less than a predetermined value (step S640). In order to explain the predetermined value, the relationship between the first substrate resistance value R ₁₁ and the maximum surface temperature of the substrate 11 will be described. The maximum surface temperature of the substrate 11 is the highest value among the surface temperatures of the substrate 11. The surface temperature of the base body 11 varies depending on the part, and usually the vicinity of the tip of the energization heating element 2 exhibits the maximum value.

FIG. 6 is a graph schematically showing the relationship between the first substrate resistance value R ₁₁ and the maximum surface temperature of the substrate 11. This graph is a semi-logarithmic graph showing the first substrate resistance value R ₁₁ as a logarithm. This relationship is acquired in advance by an experiment in which the first substrate resistance value R ₁₁ is actually measured while changing the maximum surface temperature of the substrate 11, and is stored in the ECU 52.

As shown in FIG. 6, as the made the higher maximum surface temperature of the substrate 11, the first base resistance R ₁₁ is greatly reduced. For example, as shown in FIG. 6, when the maximum surface temperature of the substrate 11 changes from 600 ° C. to 1200 ° C., the first substrate resistance value R ₁₁ becomes about 1/1000. Since the substrate 11 has such characteristics, the maximum surface temperature of the substrate 11 greatly affects the measurement of the ionic current value. This is because the substrate 11 acts as a resistance even in a closed circuit formed by the generation of an ionic current. Hereinafter, the resistance value of the base body 11 as the resistance in the closed circuit is referred to as a second base body resistance value R ₁₂ .

Relationship between the second base resistance R ₁₂ and the current value Iion (t) can be written as the following equation (5).
Iion (t) = V ₀ / (R ₁₂ + Rion (t))… (5)
The above Rion (t) means the ion resistance value Rion (t). The ion resistance value Rion (t) is an electric resistance value in the combustion chamber, and is a fluctuation value depending on the amount of ions generated in the combustion chamber.

On the other hand, the maximum surface temperature of the base 11 is a parameter controlled according to the operating condition of the engine. For example, in the present embodiment, 1200 ° C. is controlled as a target value when the engine is started. Thereafter, a temperature lower than 1200 ° C. is set as a target value, or heating is stopped. The second substrate resistance value R ₁₂ depends on the maximum surface temperature of the substrate 11 in the same manner as the first substrate resistance value R ₁₁ . Therefore, from equation (5), the current value Iion (t) depends on the maximum surface temperature of the substrate 11.

However, if the second substrate resistance value R ₁₂ << ion resistance value Rion (t), Expression (5) can be transformed into the following Expression (6).
Iion (t) = V ₀ / Rion (t)… (6)
That is, if the second substrate resistance value R ₁₂ << ion resistance value Rion (t), the current value Iion (t) hardly depends on the second substrate resistance value R ₁₂ , and eventually reaches the maximum surface temperature of the substrate 11. Little dependence.

  In the present embodiment, when the maximum surface temperature of the substrate 11 is 1200 ° C. or higher, Expression (6) is established even when the ion resistance value Rion (t) is minimum. “When the ion resistance value Rion (t) is minimum” means that the electrical resistance value in the combustion chamber becomes the minimum value in one cycle of the engine.

Therefore, in the present embodiment, if the maximum surface temperature is 1200 ° C. or higher, it is not necessary to correct the ion current value, and if the maximum surface temperature is less than 1200 ° C., it is necessary to correct the ion current value. The predetermined value of the first base resistance R ₁₁ at step S640, the resistance value in the first base resistance R ₁₁ (FIG. 6 in the case where the maximum surface temperature of 1200 ° C. A, hereinafter referred to as R ₁₁ @ 1200 ° C. ).

  Therefore, in step S640, it can be considered that it is determined whether the maximum surface temperature of the base 11 is 1200 ° C. or higher.

When the first substrate resistance value R ₁₁ is equal to or less than the predetermined value (step S640, YES), the current value Iion (t) is acquired as the ion current value (step S660).

On the other hand, when the first substrate resistance value R ₁₁ is larger than the predetermined value (step S640, NO), the current value Iion (t) is corrected (step S650), and the corrected current value is acquired as the ionic current value ( Step S660). When the current value after correction is expressed as Ic (t), this correction is described by the following equation (7).
Ic (t) = Iion (t) × {(R ₁₂ + Rion (t)) / (R ₁₂ @ 1200 ° C + Rion (t))}… (7)
The above R ₁₂ @ 1200 ° C. is the second substrate resistance value R ₁₂ corresponding to the case where the maximum surface temperature of the substrate 11 is 1200 ° C. Since R ₁₂ @ 1200 ° C. is a minute value compared to the minimum value of Rion (t), similarly to R ₁₁ @ 1200 ° C., equation (7) can be transformed into the following equation (8).
Ic (t) = Iion (t) × {(R ₁₂ + Rion (t)) / Rion (t)}… (8)

Furthermore, Formula (8) can be transformed into Formula (10) by substituting Formula (9). Equation (9) can be obtained by a modification of equation (5).
Rion (t) = (V ₀ / Iion (t))-R ₁₂ (9)
Ic (t) = Iion (t) / (1-Iion (t) × R ₁₂ / V ₀ ) ... (10)

In the present embodiment, the second substrate resistance value R ₁₂ is calculated by the equation (11).
R ₁₂ = R ₁₁ × R ₁₂ @ 1200 ° C / R ₁₁ @ 1200 ° C… (11)
The corrected current value Ic (t) is calculated by the equations (10) and (11). The value of R ₁₂ @ 1200 ° C./R ₁₁ @ 1200 ° C. is acquired in advance by experiments and stored in the ECU 52.

  After step S660, steps S670 to S690 for controlling heating in the combustion chamber are executed. First, a target temperature is determined (step S670). The target temperature is a target value for the maximum surface temperature of the substrate 11. The target temperature is determined based on an input value from the water temperature sensor 525, an input value from the rotation speed sensor 526, and other values related to the engine (for example, intake air temperature).

Subsequently, a target resistance value is determined (step S680). The target resistance value is the first substrate resistance value R ₁₁ corresponding to the target temperature determined in step S670. This determination is executed based on the relationship shown in FIG.

Finally, energization is controlled (step S690). Specifically, the ratio of the on time and the off time of the glow relay 53 is controlled so that the first base body resistance value R ₁₁ approaches the target resistance value. Thereafter, the ion current measurement process is finished.

According to the above embodiment, at least the following effects (a), (b), and (c) can be obtained.
(A) Even if the maximum surface temperature of the substrate 11 changes, the influence on the acquired value of the ionic current value can be reduced. The reason why this effect is brought about is considered to be mainly the following (a-1), (a-2), and (a-3).

(A-1) As described above, the second substrate resistance value R ₁₂ strongly depends on the maximum surface temperature of the substrate 11, similarly to the first substrate resistance value R ₁₁ . Therefore, the value of the ion current that actually flows depends strongly on the maximum surface temperature of the substrate 11. However, even if the maximum surface temperature of the substrate 11 changes, the measured ion current value is corrected in this embodiment, so that the influence can be offset.

(A-2) As shown in the above equation (11), by measuring the first substrate resistance value R ₁₁ , the fluctuation of the second substrate resistance value R ₁₂ can be estimated, and this estimation accuracy is high. The above effects can be obtained. This will be described in detail below.

Since the electrical resistance value of the substrate 11 is significantly reduced as the temperature increases, the electrical resistance value at the portion exhibiting the highest temperature in the substrate 11 between the energization heating element 2 and the electrode 3 is the first substrate resistance value. It becomes the dominant factor of R _11. Of the substrate 11 between the energization heating element 2 and the electrode 3, the portion exhibiting the highest temperature is near the tip of the energization heating element 2.

Similarly, of the base 11 between the surface of the electrode 3 and the substrate 11, the electric resistance value at the site exhibiting the highest temperature, becomes dominant factor of the second base resistance R _12. Of the substrate 11 between the electrode 3 and the surface of the substrate 11, the portion exhibiting the highest temperature is also near the tip of the energization heating element 2.

Since the two parts are close to each other in this way, the two maximum temperatures are close in value. As a result, the first base resistance value R ₁₁ and the second base resistance value R ₁₂ have a strong correlation with each other. Therefore, the first substrate resistance value R ₁₁ is excellent as a parameter for estimating the fluctuation of the second substrate resistance value R ₁₂ .

(A-3) The first substrate resistance value R ₁₁ and the second substrate resistance value R ₁₂ are parameters that strongly reflect the state of the local region as described above. It is hard to be affected by. Disturbance refers to engine coolant temperature, engine oil temperature, combustion chamber temperature, and the like.

(B) The acquisition of the first base resistance value R ₁₁ can be easily realized by the simple circuit described above.
(C) When the first substrate resistance value R ₁₁ is equal to or less than the predetermined value, the processing load is reduced because the correction of the ion current value is unnecessary.

  A second embodiment will be described. Since the second embodiment has the same hardware configuration as that of the first embodiment, the description thereof is omitted.

  FIG. 7 is a flowchart showing ion current measurement processing in the second embodiment. Since steps S610 to S630 are the same as those in the first embodiment, description thereof is omitted.

After the calculation of the first base body resistance value R ₁₁ (step S630), the ratio between the on time and the off time of the glow relay 53 is controlled so that the first base body resistance value R ₁₁ approaches the predetermined resistance value (step S700). . The predetermined resistance value is a predetermined fixed value. This fixed value will be described later.

Subsequently, it is determined whether or not the first base resistance value R ₁₁ is within a predetermined range (step S710). The predetermined range here is a range in which an error is added to the predetermined resistance value.

When the first substrate resistance value R ₁₁ is within the predetermined range (step S710, YES), the current value Iion (t) is acquired as the ion current value (step S720), and the ion current measurement process is ended.

On the other hand, if the first base resistance R ₁₁ is out of the predetermined range (step S710, NO), without acquiring the ion current value, completing the ion current measurement process.

  When this energization control is executed, the maximum surface temperature of the glow plug 1 is kept constant. Therefore, it is preferable to execute when the maximum surface temperature of the glow plug 1 is kept constant without any problem in engine operation. For example, a method that is executed only when the temperature is maintained at 1200 ° C. can be considered. In this case, the predetermined resistance value in step S700 is a resistance value corresponding to 1200 ° C.

Or the method of performing an ion current measurement process when heating is not requested | required can be considered. Even when the maximum surface temperature of the glow plug 1 is low and the ionic current value is affected by the second substrate resistance value R ₁₂ , the correction according to the method of the second embodiment can be avoided. Because, as described above, if the measurement is performed under the condition that the maximum surface temperature of the glow plug 1 is within a predetermined range, even if the ion current value is affected by the second substrate resistance value R ₁₂ , the effect is almost constant. This is because there is no problem in monitoring the behavior of the ionic current. In the case of this method, it is preferable that the maximum surface temperature is set so as not to hinder the operation of the engine. In this case, the predetermined resistance value in step S700 is a resistance value corresponding to the maximum surface temperature.

  Thus, the ion current measurement process of Embodiment 2 can accurately estimate the state of combustion in the combustion chamber without correcting the ion current value. As described above, as long as the technique for maintaining the maximum surface temperature of the glow plug 1 at 1200 ° C., the measurement of the ion current value itself can be performed with high accuracy as described in the first embodiment.

  The present invention is not limited to the embodiments, examples, and modifications of the present specification, and can be implemented with various configurations without departing from the spirit of the present invention. For example, the technical features in the embodiments, examples, and modifications corresponding to the technical features in the embodiments described in the summary section of the invention are to solve some or all of the above-described problems, or In order to achieve part or all of the effects described above, replacement or combination can be performed as appropriate. If the technical feature is not described as essential in this specification, it can be deleted as appropriate. For example, the following are exemplified.

  In the embodiment, it has been described that the glow plug 1 and the control unit 50 are included in the ion current measuring apparatus 100. However, the controller 50 may be regarded as an ion current measuring device, and the ion current measuring device 100 may be regarded as an ion current measuring system.

  The material of the substrate may be changed to another ceramic. For example, titanium diboride alone, a mixture of silicon nitride and titanium diboride, alumina, sialon, or the like may be used.

A circuit for obtaining the first substrate resistance value may be added. For example, a current may be measured by applying a voltage between a pair of external lead wires. If comprised in this way, since the voltage applied between an energization heat generating body and an electrode can be grasped | ascertained correctly, the measurement precision of a 1st base | substrate resistance value will improve.
The maximum surface temperature may be estimated from the relationship shown in FIG. 6 and the calculated first substrate resistance value.

  The subject of heating need not be a combustion chamber of a diesel engine. For example, you may use in order to detect the state of the ion in the ion implantation process in manufacture of a semiconductor. If heating is not necessary in such an application, the heat generated by the energization heating element may be used only for controlling the first and second substrate resistance values.

DESCRIPTION OF SYMBOLS 1 ... Glow plug 2 ... Current heating element 3 ... Electrode 4 ... Housing 10 ... Heater 11 ... Base | substrate 21 ... Lead wire 22 ... Lead wire 23 ... Terminal part 31 ... Terminal part 33 ... Internal lead wire 41 ... Outer cylinder 42 ... Protection cylinder DESCRIPTION OF SYMBOLS 43 ... Male thread part 45 ... Cylinder block 50 ... Control part 51 ... DC power supply 52 ... ECU
53 ... Glow relay 54 ... Battery 55 ... Relay 100 ... Ion current measuring device 231 ... Internal lead wire 232 ... Connection terminal 233 ... External lead wire 333 ... External lead wire 421 ... Rubber bushing 521 ... Resistance 522 ... Potentiometer 525 ... Water temperature sensor 526 ... Rotational speed sensor 531 ... Glow relay

Claims (7)

A space in which ions are generated when the fuel burns, the first and second conductors, and a ceramic base body embedded and held inside the first and second conductors separated from each other. A detection unit attached in a state where the base body is exposed,
A measurement unit for measuring a current value flowing through the second conductor as an ion current based on the generated ions;
An ionic current measuring device comprising:
An acquisition unit for acquiring an electric resistance value of the base body between the first conductor and the second conductor;
A correction unit that corrects the current value measured by the measurement unit based on the electrical resistance value acquired by the acquisition unit;
An ionic current measuring device comprising: The ion current measuring apparatus according to claim 1, wherein the first conductor is a heating element that generates heat when energized. A space in which ions are generated when the fuel burns, the first and second conductors, and a ceramic base body embedded and held inside the first and second conductors separated from each other. A detection unit attached in a state where the base body is exposed,
A measurement unit that measures a current value flowing through the second conductor as an ion current based on the generated ions, and
The first conductor is an ion current measuring device that is a heating element that generates heat when energized,
An acquisition unit for acquiring an electric resistance value of the base body between the first conductor and the second conductor;
A control unit that controls energization of the first conductor so that the electric resistance value acquired by the acquisition unit becomes a predetermined value;
The said measurement part measures the said electric current value under the electricity supply control by the said control part. The ion current measuring apparatus characterized by the above-mentioned. The space is a combustion chamber of an internal combustion engine;
The ion current measuring device according to claim 2, wherein the detection unit functions as a glow plug by heat generation of the first conductor. The acquisition unit, the potential difference between the first conductor and the pre-Symbol second conductor, and based on the current value flowing between the first conductor and the pre-Symbol second conductor, obtaining the electrical resistance The ion current measuring device according to any one of claims 1 to 4, wherein the ion current measuring device is characterized in that: A space in which ions are generated when the fuel burns, the first and second conductors, and a ceramic base body embedded and held inside the first and second conductors separated from each other. An ion current measuring device comprising a measuring unit that measures the value of the current flowing through the second conductor in the detection unit attached in a state where the base is exposed as an ion current based on the generated ions,
An acquisition unit for acquiring an electric resistance value of the base body between the first conductor and the second conductor;
A correction unit that corrects the current value measured by the measurement unit based on the electrical resistance value acquired by the acquisition unit;
An ionic current measuring device comprising: A conductor, a heating element that generates heat when energized, and a ceramic base that holds the conductor and the heating element in an embedded state in a state of being isolated from each other. An ion current measuring device comprising a measuring unit that measures a current value flowing through the conductor in a detection unit attached in a state where the base body is exposed in a generated space as an ion current based on the generated ions,
An acquisition unit for acquiring an electric resistance value of the base body between the conductor and the heating element;
A control unit that controls energization of the heating element so that the electrical resistance value acquired by the acquisition unit becomes a predetermined value;
The said measurement part measures the said electric current value under the electricity supply control by the said control part. The ion current measuring apparatus characterized by the above-mentioned.

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