JPH0746091B2 - 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 each of the two flat plate-shaped oxygen ion conductive solid electrolyte members, and one electrode surface of each of the two solid electrolyte members forms a part of the gas retention chamber to form the gas retention chamber. Japanese Patent Laid-Open No. 192955/1984 discloses a device in which the other electrode surface of one solid electrolyte member is in communication with the gas to be measured through an introduction hole and the other electrode surface faces the atmosphere chamber. 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 voltage generated between the electrodes of the oxygen concentration ratio detection battery element is higher than the reference voltage, a current is supplied so that oxygen ions move in the oxygen pump element toward the gas retention chamber electrode, and the electrodes of the oxygen concentration ratio detection battery element are supplied. When the generated voltage between the two is below the reference voltage, a current is supplied in the oxygen pump element so that the oxygen ions move toward the electrode on the side opposite to the gas retention chamber, and the current value in the lean-rich region air-fuel ratio is increased. Is obtained in proportion to the oxygen concentration.

In such an oxygen concentration detection device, when the oxygen concentration in the exhaust gas is detected by being provided in the exhaust pipe of an internal combustion engine, the oxide etc. in the exhaust gas adheres to the introduction hole due to long-term use and has a poor output characteristic. It has been found that there is a bad influence and desired output characteristics are not gradually obtained. However, even if an abnormality occurs in which desired output characteristics cannot be obtained, it has heretofore been difficult to detect whether or not the output characteristics have changed after attaching the oxygen concentration detection device to an internal combustion engine or the like.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an oxygen concentration detection device that can easily detect changes in output characteristics.

The oxygen concentration detecting device of the present invention is composed of an oxygen ion conductive solid electrolyte member, and is formed with the first and second gas retention chambers communicating with each other through the first gas diffusion limiting means. Is provided on the inner and outer wall surfaces of the electrolyte member surrounding the first gas retention chamber so as to be opposed to the base pair which is communicated with the gas to be measured through the second gas diffusion limiting means. Two first electrode pairs forming the first sensor, and two second electrodes forming the second sensor so as to face each other on the inner and outer wall surfaces of the electrolyte member surrounding the second gas retention chamber so as to sandwich them. And a current value 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 supplied between the other first electrode pair to supply the current value. Is output as the oxygen concentration detection value of the first sensor, and the two second A current having a value corresponding to the difference voltage between the voltage generated between the one electrode pair of the pole pair and the second reference voltage is supplied between the other second electrode pair, and the value corresponding to the supplied current value is set to the second value. It has a current supply means for outputting as a sensor oxygen concentration detection value and a detection means for detecting an abnormality of the first or second sensor according to the oxygen concentration detection value of the first sensor and the oxygen concentration detection value of the second sensor. It is characterized by that.

EXAMPLES Examples 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. In the oxygen ion conductive solid electrolyte member 1, first and second gas retention chambers 2 and 3 are formed. First
The gas retention chamber 2 communicates with an introduction hole 4 for introducing the exhaust gas of the gas to be measured from the outside of the solid electrolyte member 1. The introduction hole 4 is the first gas retention of the exhaust gas in the exhaust pipe (not shown) of the internal combustion engine. It is located so as to easily flow into the chamber 2. First
A communication hole 5 is formed in a wall portion between the gas retention chamber 2 and the second gas retention chamber 3, and exhaust gas is introduced into the second gas retention chamber 3 into the introduction hole 4, the first gas retention chamber 2, and the communication. It is adapted to be introduced through the hole 5. Further, the oxygen ion conductive solid electrolyte member 1 is formed with a reference gas chamber 6 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 protection holes 7 are formed in the walls of the first and second gas retention chambers 2 and 3 opposite to the reference gas chamber 6. First
Electrode pairs 11a and 11 are provided on the wall between the gas retention chamber 2 and the reference gas chamber 6 and on the wall between the first gas retention chamber 2 and the electrode protection hole 7.
b, 12a, 12b are respectively formed, and an electrode pair is provided on the wall between the second gas retention chamber 3 and the reference gas chamber 6 and on the wall between the second gas retention chamber 3 and the electrode protection hole 7. 13a, 13b, 14a and 14b are formed respectively. Solid electrolyte member 1 and electrode pair 11a, 11b
As the first oxygen pump element 15, and the solid electrolyte member 1 and the electrode pairs 12a and 12b as the first battery element 16.
Further, the solid electrolyte member 1 and the electrode pairs 13a, 13b serve as the second oxygen pump element 17, and the solid electrolyte member 1 and the electrode pairs 14a, 14b.
b acts as the second battery element 18, respectively. Further, the heater element 1 is provided on the outer wall surface of the reference gas chamber 6 and the outer wall surface of the electrode protection hole 7.
There are 9 and 20, respectively. The heater elements 19 and 20 are electrically connected in parallel to each other, and evenly heat the first and second oxygen pump elements 15 and 17 and the first and second battery elements, and at the same time, retain heat in the solid electrolyte member 1. We are trying to improve 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 at least only the portion where the electrode pair is provided may be formed from 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 is 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. The output of the first sensor is eliminated between both ends of the current detection resistor 24, and the output of the second sensor is provided between both ends of the current detection resistor 25. Current detection resistor
The voltage between both ends of 24, 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 this structure, the exhaust gas in the exhaust pipe is introduced into the introduction hole 4
Flows into the first gas retention chamber 2 and diffuses. The exhaust gas in the first gas retention chamber 2 flows into the second gas retention chamber 3 through the communication hole 5 and diffuses.

In the switching circuits 28 and 29, the switch 28a connects the electrode 11a to the resistor 24, the switch 28b opens the connection line of the electrode 13a, the switch 29a grounds the electrode 11b and the connection line of the electrode 13b as shown in FIG. The switch 29b and the electrode
The first sensor is in the selected state when it is brought to the selected position where the 12b is grounded and the connection line of the electrode 14b is opened.

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 range, the output level of the differential amplifier circuit 22 becomes a positive level, and this positive-level voltage is the current detection resistor 24 and the first level. It is supplied to the series circuit of the oxygen pump element 15. Therefore, the electrodes 11a, 11b of the first oxygen pump element 15
Pump current flows between them. This pump current flows from the electrode 11a to the electrode 11b, so that oxygen in the first gas retention chamber 2 is ionized at the electrode 11b and moves in the first oxygen pump element 15 to be released as oxygen gas from the electrode 11a. , First
Oxygen in the gas retention chamber 2 is pumped out.

By pumping out oxygen in the first gas retention chamber 2, a difference in oxygen concentration occurs between the exhaust gas in the first gas retention chamber 2 and the gas in the reference gas chamber 6. A voltage V _S is generated between the electrodes 12a and 12b of the battery element 16 due to this oxygen concentration difference. This voltage V _S is supplied to the inverting input terminal of the differential amplifier circuit 22. Since the output voltage of the differential amplifier circuit 22 is a voltage proportional to the difference voltage between the voltage V _S 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 V _S 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 the charge e, the diffusion coefficient of the introduction hole 4 to the exhaust gas is σ _O , and the oxygen concentration in the exhaust gas is P _O ex
When h is the oxygen concentration in the first gas retention chamber 2 and P _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 4, A is the Boltzmann constant, k is the absolute temperature, T is the introduction hole 4 When the flow rate is l and the diffusion constant is D, it can be expressed as the following equation.

σ _O = D · A / kTl (2) Next, the switch 28a opens the connection line of the electrode 11a, the switch 28b connects the electrode 13a to the current detection resistor 25, and the switch 29a grounds the electrode 13b. And open the connection line of electrode 11b, and switch 29b grounds electrode 14b and
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. The pump current value I _{P in} the second sensor selected state is defined by the diffusion coefficient σ _O in the above formula (1) by the introduction hole 4 and the communication hole 5, and P _O v is the oxygen in the second gas retention chamber 3. It is represented by the concentration. It is clear 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 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, and therefore the magnitude of the pump current value I _P becomes smaller in the lean and rich regions as indicated by the broken line b in FIG. by adjusting the size and length of 5 to the pump current value characteristic of the rich region in the second sensor selection state as shown in FIG. 3 is a pump current value characteristic of the lean region in the first sensor selection state I _P = It is continuous at 0. The output voltage characteristics of the differential amplifier circuits 22 and 23 are also 0.
It becomes linearly continuous at [V].

Next, the operation of the air-fuel ratio control circuit 32 according to the present invention will be described. The air-fuel ratio control circuit 32 sequentially executes the air-fuel ratio detection correction routine shown in FIG. 5 and the air-fuel ratio control routine shown in FIG. 6 in response to the clock pulse. In the air-fuel ratio detection correction routine, the air-fuel ratio control circuit 32 first determines whether or not the engine is in a predetermined operating state according to the output levels of the plurality of parameter detection sensors (step 61). The predetermined operating state is a stable operating state such as an idle operating state or a steady operating state. When it is determined that the operation state is the predetermined operation state, it is determined whether the air-fuel ratio is controlled to the target air-fuel ratio and the air-fuel ratio is stable (step 62). When the air-fuel ratio is controlled to the target air-fuel ratio and the air-fuel ratio becomes stable, the fluctuation of the oxygen concentration detection value of the first sensor or the second sensor becomes small and falls within the predetermined range, so the fluctuation range of the oxygen concentration detection value of the selected sensor is predetermined. It is considered that the air-fuel ratio has become stable when a predetermined time has elapsed after the value became less than or equal to the value. To stabilize the air-fuel ratio by stopping the air-fuel ratio feedback (F / B) control according to the oxygen concentration detection value of the first or second sensor (stopping the execution of the air-fuel ratio control routine) A valve opening drive command and a valve opening drive stop command are generated so as to open the solenoid valve 34 at a predetermined duty ratio at a predetermined cycle (step 63), and the flag Fs representing the selection state of the first and second sensors is set to " It is determined whether or not it is 1 "(step 64). 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 and the storage device A of the internal memory (not shown) is read. Store in ₁ (step 65). Then, the second sensor selection command is issued to the drive circuit 30, and the second
In the sensor selected state (step 66), the pump current value I _P (2) of the second sensor output from the A / D converter 31 is read and stored in the storage position A ₂ of the internal memory (step 6).
7). After that, a first sensor selection command is issued to the drive circuit 30 to bring it into the first sensor selected state again (step 68), and the pump current value I _P of the first sensor output from the A / D converter 31 is output. (1) is read and storage location A ₃ in the internal memory
(Step 69). On the other hand, when Fs = 1, the second
Since the sensor is in the selected state, the pump current value I _P (2) of the second sensor output from the A / D converter 31 is read and stored in the storage position A ₁ of the internal memory (step 70). Then, a first sensor selection command is issued to the drive circuit 30 to bring it into the first sensor selection state (step 71), and the pump current value I _P (1) of the first sensor output from the A / D converter 31. Is read and stored in the storage position A ₂ of the internal memory (step 7
2). After that, a second sensor selection command is issued to the drive circuit 30 to bring it into the second sensor selection state again (step 73), and the pump current value I _P of the second sensor output from the A / D converter 31 is output. Read (2) and store at internal memory A ₃
(Step 74). Next, in order to determine again whether or not the fluctuation of the oxygen concentration detection value is small, the pump current value I _P (1) or I _P (2) is calculated from the storage positions A ₁ and A ₃ of the internal memory.
Is read to calculate the absolute value ΔI _P of the difference between the pump current values I _P (1) or I _P (2) (step 75), and it is determined whether or not the absolute value ΔI _P is less than or equal to a predetermined value ΔI _P r. Yes (step 76).
If ΔI _P ≦ ΔI _P r, the correction factors K _COR1 and K _COR2 described later
Is calculated by the following calculation formula (step 77), and ΔI _P ＞
If ΔI _P r, the air-fuel ratio control (execution of the air-fuel ratio control routine) according to the oxygen concentration detection value of the selected sensor is restarted (step 78).

A correction coefficient K _COR1 for correcting the oxygen concentration detection value L _O2 (1) of the first sensor is calculated from the following equation, and K _COR1 = C / (I _P (1) / I _P (2) -1) ...... ( 3) A correction coefficient K _COR2 for correcting the oxygen concentration detection value L _O2 (2) of the second sensor is calculated from the following equation.

K _COR2 = (K _COR1 + C) / (1 + C) (4) where C is I _P (1) / I _P (2) -1 before the output characteristic change.
Is.

Then, it is determined whether the calculated correction coefficients K _COR1 and K _COR2 are greater than or equal to the predetermined value K _{1 and} less than or equal to the predetermined value K ₂ (step 79), and K ₁ ≤
If K _COR1 ≤ K ₂ or K ₁ ≤ K _COR2 ≤ K ₂ , restart the air-fuel ratio control according to the oxygen concentration detection value of the selected sensor (step 7
8), if K _COR1 <K ₁ , K _COR1 > K ₂ , and K _COR2 <K ₁ , K _COR2 > K ₂ , good air-fuel ratio feedback control cannot be expected even if the degree of change in output characteristics is largely corrected. A warning is issued to the driver by lighting such as (Step 8
0).

Further, as shown in FIG. 6, the air-fuel ratio control circuit 32 first determines whether to select either the first sensor or the second sensor in the air-fuel ratio control routine (step 81). This is determined according to the operating state of the engine or the control range of the air-fuel ratio. When it is determined that the first sensor should be selected, a first sensor selection command is issued to the drive circuit 30 (step 82), and "0" is set in the flag Fs to indicate that the first sensor is selected. Are set (step 83). on the other hand,
When it is determined that the second sensor should be selected, the second sensor
A sensor selection command is issued to the drive circuit 30 (step
84), "1" is set to the flag Fs to indicate that the second sensor has been selected (step 85). Drive circuit 30
Are switches 28a, 28b, 29a, 29 according to the first sensor selection command.
The b is driven to the above-mentioned first sensor selection position, and the driving state is maintained until the second sensor selection command is supplied from the air-fuel ratio control circuit 32. In addition, according to the second sensor selection command
28a, 28b, 29a, 29b are driven to the above-mentioned second sensor selection position, and the driving state is maintained until the first sensor selection command is supplied from the air-fuel ratio control circuit 32.

Next, the pump current value I output from the A / D converter 31
_P (1) or I _P (2) is read (step 86), and it is determined whether the flag Fs is "0" (step 87). Fs
If = 0, the pump current value I _P (1) read in is in the first sensor selection state and is multiplied by the correction coefficient K _COR1 (step 88) to obtain the corresponding oxygen concentration detection value L _O2 (step 89). . In the case of FS = 1, since the second sensor is selected, the read pump current value I _P (2) is multiplied by the correction coefficient K _COR2 (step 90) to obtain the corresponding oxygen concentration detection value L _O2 (step 89). ). Then, it is determined whether or not the oxygen concentration detection value L _O2 is larger than the target value Lref corresponding to the target air-fuel ratio (step 91). 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 92), and L _O2 > Lre
If f, the air-fuel ratio of the supply air-fuel mixture is lean, so a command to stop driving the solenoid valve 34 to open is issued to the drive circuit 33 (step 93). The drive circuit 33 drives the solenoid valve 34 to open in response to the valve opening drive command to supply secondary air into the engine intake manifold, thereby making the air-fuel ratio lean, and in response to the valve opening drive stop command, the solenoid valve 34. The valve opening drive of 34 is stopped to enrich the air-fuel ratio. 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 the embodiment of the present invention described above, the introduction hole 4 is used as the first gas diffusion limiting means and the communication hole 5 is used as the second gas diffusion limiting means, but the invention is not limited to this, and the first gas retention chamber is not limited to this. A gap may be formed between the two first electrode pairs in No. 2, and a porous body such as alumina (Al ₂ O ₃ ) is filled in the introduction hole 4 and the communication hole 5 as shown in FIG. A quality diffusion layer may be formed.

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, but the present invention is not limited to this. Alternatively, 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 first member is provided inside the base body made of the oxygen ion conductive solid electrolyte member.
And a second gas retention chamber are formed to communicate with each other via the first gas diffusion limiting means, and the first sensor communicates with the gas to be measured via the second gas diffusion limiting means. A second gas retention chamber in which two first electrode pairs are provided on the inner and outer wall surfaces of the wall portion so as to be opposed to each other with the first electrode pair interposed therebetween, and the second sensor communicates with the first gas retention chamber via the first gas diffusion limiting means. Of the electrolyte wall portion, the two second electrode pairs are provided so as to face each other with the electrolyte wall portion sandwiched therebetween, and a voltage generated between one electrode pair of the two first electrode pairs of the first sensor and a first reference voltage. A current having a value corresponding to the voltage difference between the two electrodes of the second sensor is supplied between the other pair of first electrodes, and a value corresponding to the supplied current value is output as the oxygen concentration detection value of the first sensor. A current having a value corresponding to the difference voltage between the voltage generated between the pair of electrodes and the second reference voltage It is made to be supplied between the second electrode pair of rectangular outputs a value corresponding to the current supplied as the oxygen concentration detection value of the second sensor. That is, since the first and second sensors that obtain an output proportional to the oxygen concentration in the gas to be measured are integrally formed and the output characteristics of the first and second sensors are different, the oxygen concentration detection value of the first sensor and the second sensor are different from each other. The abnormality of the first or second sensor can be easily detected by comparing the oxygen concentration detection values of the sensors.

[Brief description of drawings]

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

Front Page Continuation (72) Inventor Nobuyuki Ohno 1-4-1 Chuo, Wako-shi, Saitama, Ltd. Inside Honda R & D Co., Ltd. (56) Reference JP-A-61-283861 (JP, A)

Claims (1)

[Claims] 1. An oxygen ion conductive solid electrolyte member, wherein a first gas retention chamber and a second gas retention chamber communicate with each other through first gas diffusion limiting means, and the first gas retention chamber is the second. A base body, which is communicated with the gas to be measured through a gas diffusion limiting means, is provided on the inner and outer wall surfaces of the electrolyte member surrounding the first gas retention chamber so as to be opposed to each other with the same sandwiched therebetween. Two first electrode pairs forming a sensor, and two second electrodes forming a second sensor on the inner and outer wall surfaces of the electrolyte member surrounding the second gas retention chamber so as to face each other with the pair sandwiched therebetween. And a current having a value corresponding to a difference voltage between a voltage generated between one electrode pair of the two first electrode pairs and a first reference voltage between the other pair of the first electrodes A value corresponding to the value is used as the oxygen concentration detection value of the first sensor. And a current having a value corresponding to the difference voltage between the voltage generated between one of the two second electrode pairs and the second reference voltage is supplied between the other second electrode pair to supply the current. A current supply unit that outputs a value corresponding to the value as the oxygen concentration detection value of the second sensor, and the first or the second oxygen sensor according to the oxygen concentration detection value of the first sensor and the oxygen concentration detection value of the second sensor. An oxygen concentration detection device, comprising: a detection unit that detects an abnormality of the second sensor.