JPS62201352A - Oxygen concentration detector - Google Patents

Abstract

PURPOSE:To easily detect the change in an output characteristic by providing two sets of a 1st electrode pairs on the inside and outside wall surfaces of a 1st gas stagnating chamber communicating with the inside of an exhaust pipe via a 1st gas diffusion limiting means. CONSTITUTION:A base body forms the 1st and 2nd gas stagnating chambers 2, 3 and is so formed that the stagnating chamber 2 communicates with the inside of the exhaust pipe via the 1st gas diffusion limiting means and that the stagnating chamber 3 communicates with the inside of the exhaust pipe via the 2nd gas diffusion limiting means. Two pairs of the 1st electrode pairs 11a, 11b and 12a, 12b forming the 1st sensor are provided on the inside and outside wall surfaces in the electrolyte wall part of the stagnating chamber 2 so as to face each other with the wall part in-between. Two pairs of the 2nd electrode pairs 13a, 13b and 14a, 14b forming the 2nd sensor are similarly provided on the inside and outside wall surfaces in the electrolyte wall part of the stagnating chamber 3. Electric current is supplied to either of between one electrode pair of two pairs of the 1st electrode pairs and between one electrode pair of two pairs of the 2nd electrode pairs and the detected values of the oxygen concn. of the 1st and 2nd sensors corresponding to the supply current values are outputted. The abnormality of the 1st or 2nd sensor is detected according to the respective detected values of the oxygen concn.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an oxygen degree detection device for detecting the oxygen concentration in gas such as engine exhaust gas.

1 and ■ For the purpose of purifying the exhaust gas of internal combustion engines and improving fuel efficiency, the degree of oxygen in the exhaust gas is detected, and the air-fuel ratio of the mixture supplied to the engine is fed back to the target air-fuel ratio according to the result of this detection. There is an air-fuel ratio control device that controls the air-fuel ratio.

As an oxygen concentration detection device used in such an air-fuel ratio control device, there is one that generates an output proportional to the oxygen concentration in the gas to be measured. For example, an electrode pair may be provided on each of two flat oxygen ion conductive solid electrolyte members, and the metal electrode surface of one of the two solid electrolyte members may form a part of the gas retention chamber. JP-A-59-192955 discloses an apparatus in which the solid electrolyte member communicates with the gas to be measured through an inlet hole, and the other electrode surface of one solid electrolyte member faces an atmospheric chamber. In this oxygen concentration detection device, one oxygen ion conductive solid electrolyte member and electrode pair act as an oxygen concentration ratio detection battery element, and the other oxygen ion conductive solid electrolyte material and electrode pair act as an oxygen pump element. It looks like this. When the voltage generated between the electrodes of the oxygen concentration ratio detection battery element is equal to or higher than the voltage Q, a current is supplied so that oxygen ions move within the oxygen pump element toward the electrode on the gas retention chamber side, and the oxygen concentration ratio detection battery Is it based on the voltage generated between the electrodes of the element? By supplying current so that oxygen ions move within the oxygen pump element toward the electrode on the opposite side of the gas retention chamber when the voltage is below $, the current value changes to the oxygen concentration at air-fuel ratios in the lean and rich regions. The proportional characteristic is iffed.

When such an oxygen concentration detection device is installed in the exhaust pipe of an internal combustion engine to detect the oxygen concentration in the exhaust gas, it is difficult to detect oxides in the exhaust gas from entering the inlet hole after many years of use. It has been found that the output characteristics are adversely affected and the desired output characteristics gradually become impossible to achieve.

However, even if an abnormality occurs in which desired output characteristics cannot be obtained, it has conventionally been difficult to detect whether or not the output characteristics have changed after attaching an oxygen concentration detection device to an internal combustion engine or the like.

Therefore, 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 detection device of the present invention forms first and second gas retention chambers each having an oxygen ion conductive solid electrolyte wall, and the first gas retention chamber is connected to the exhaust gas of the internal combustion engine via the first gas diffusion restriction means. a base body which communicates with the inside of the pipe and whose second gas retention chamber communicates with the inside of the exhaust pipe via the second gas diffusion restriction means; The 11th ? two first electrode pairs forming a sensor, and two second electrodes disposed on the inner and outer wall surfaces of the electrolyte wall of the second gas retention chamber so as to face each other with the electrodes sandwiched therebetween, and forming a second sensor. vs.
-h between the two first electrode pairs and between the two second electrode pairs.
Current supply means for supplying a current between one electrode pair of the electrode pair and outputting the detected oxygen concentration values of the first and second sensors according to the supplied current value; 2 detection means for detecting an abnormality in the first or second sensor according to the detected value of the oxygen concentration.

L - Encircle the lid 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 trade,
An oxygen ion conductive solid electrolyte member 1 having a substantially cubic shape is provided. Inside the oxygen ion conductive solid electrolyte member 1, first and second gas retention chambers 2.3 are formed. The first gas retention chamber 2 communicates with an introduction hole 4 through which exhaust gas of the gas to be measured is introduced from outside the solid electrolyte member 1, and a second gas 81
) The retention chamber 3 communicates with an introduction hole 5 through which the exhaust gas of the gas to be measured is introduced from the outside of the solid electrolyte member 1. Introduction hole 4 is smaller than introduction hole 5, 3/? The inlet holes 4 and 5 are located in the exhaust pipe (not shown) of the internal combustion engine so that gas can easily flow into the first and second gas retention chambers 2 and 3. Further, the oxygen ion conductive solid electrolyte member 1 includes a reference gas chamber 6 into which outside air or the like is introduced, a first and a second gas retention chamber 2,
It is formed to separate 3 and a wall. An electrode image LL7 is formed within the wall of the first and second gas retention chambers 2.3 on the side opposite to the reference gas chamber 6. Gi electrode pairs 11a, 11b, 1 are provided on the wall between the first gas retention chamber 2 and the electrode protection hole 7 and between the first gas retention chamber 2 and the reference gas 1 small chamber 6.
2a and 12b are respectively formed, and on the wall between the second gas retention chamber 3 and the electrode protection hole 7 and between the second gas retention chamber 3 and the reference gas chamber 6, electrode pairs 13a, 13b, 14
a and 14b are each formed. The solid electrolyte member 1 and the electrode pair 11a, 11b serve as the first acid wood pump element 15, and the solid electrolyte '? 1 member 1 and the electrode pair 12a, 12b each act as a first battery element 16. In addition, the solid electrolyte member 1 and the electrode pair 13a, 13b serve as the second Pa elementary pump element 17, and the solid electrolyte member 1 and the electrode pair Ji/la
, 14b each act as the second battery element 18. Furthermore, heater elements 19 and 20 are provided on the outer wall surface of the electrode protection hole 7 of the solid electrolyte member 1 and the outer wall surface of the reference gas chamber 6, respectively. The heater elements r19.20 are electrically connected in parallel with each other, and the first and second oxygen pumps 15.1
7 and the first and second battery elements are heated evenly, and the heat retention within the solid electrolyte member 1 is improved. Note that the oxygen ion 1 conductive solid electrolyte member 1 is integrally formed from a plurality of pieces. Furthermore, it is not necessary that all the walls of the first and second gas retention chambers be made of the oxygen ion conductive solid electrolyte, and it is sufficient that at least only the portion where the electrode pair is provided is made of the solid electrolyte.

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

1st and 2nd oxygen pump elements? A current supply circuit 21 is connected to 15.17 and the first and second battery gates 16.18. As shown in FIG. 2, the current supply circuit 21 includes differential amplifier circuits 22, 23 . Current detection resistor 24.25. It consists of a reference voltage source 26.27 and a switching circuit 28.29. 1st
1'! ! The outer electrode 11a of the two-element pump element 15 is I,7
The switch 28a of the I switching circuit 28 is connected to the output terminal of the differential amplifier circuit 22 via the current detection resistor 24, and the inner electrode 1
1b is grounded via a switch 29a of the switching circuit 29. Outer electrode 1 of first battery element 16
2a is connected to the inverting input terminal of the differential amplifier circuit 22, and the inner electrode 12b is grounded via the switch 29b of the switching circuit 29.

Similarly, the outer electrode 13a of the second M-element pump element 17 is connected to the output terminal of the differential amplifier circuit 23 via the switch 28b of the switching circuit 28 and the current detection resistor 25, and the inner electrode 13a
13b is grounded via a switch 29a of the switching circuit 29. Outer mold K of second battery element 18
A14a is connected to the inverting input 13 of the differential amplifier circuit 23, and the inner electrode 14b is grounded via the switch 29b of the switching circuit 29. A reference voltage source 26 is connected to a non-inverting input terminal of the differential amplifier circuit 22, and a reference voltage source 27 is connected to a non-inverting input terminal of the differential amplifier circuit 23. The output voltage of the reference voltage source 26.27 is a voltage (for example, 0.4V) corresponding to the stoichiometric air-fuel ratio.

The distance between both ends of the current detection resistor 24 is the first t? The current detecting resistor 25 serves as the output of the second sensor. The voltage across the current detection resistor 24.25 is supplied to the air-fuel ratio control circuit 32 via the differential input A/D converter 31, and the pump lightning current value 1 flowing through the current detection resistor 24.25 is
p(1) and 1p(2) are read into the air-fuel ratio control circuit 32. The air-fuel ratio control circuit 32 consists of a microcomputer. The air-fuel ratio control circuit 32 is connected to a plurality of operating parameter detection sensors (U shown in the figure) that detect engine speed, intake pipe absolute pressure, cooling water temperature, etc. It is connected. Electric 1a
jf344 is provided in a secondary intake air supply passage (not shown) that communicates with the intake manifold downstream of the engine carburetor throttle valve. The air-fuel ratio control circuit 32 is the switching circuit 2
8. Controls the operation of two switches 9, and the drive circuit 30 switches between the switching circuits 28 and 9 in response to commands from the air-fuel ratio control circuit 32.
Drive 29. Note that a positive 0 power supply voltage is supplied to the differential amplifier circuits 22 and 23.

On the other hand, current is supplied to the heater elements 19, 20 from the heater current supply circuit 35, and the heater elements 19, 20 generate heat to heat the oxygen pump elements 15, 17 and the battery elements 16, 18 to an appropriate temperature higher than the exhaust gas. .

In such a configuration, the exhaust gas in the exhaust pipe passes through the introduction hole 4.
The gas flows into the first gas retention chamber 2 and diffuses therein, and also flows into the second gas n closed chamber 3 through the introduction hole 5 and diffuses therein.

In the switching circuits 28 and 29, switch 2 is connected as shown in FIG.
8a connects the electrode 11a to the current detection resistor 24, the switch 28b opens the connection line of the electrode 13a, the switch 29a grounds the electrode 11b and opens the connection line of the electrode 13b, and the switch 29b connects the voltage ff112b. When the selected position is set such that the electrode 14 is grounded and the connection line of the electrode 14 is opened, the first sensor becomes selected.

In the selection state of the first sensor, first, when the air-fuel ratio of the air-fuel mixture supplied to the engine is in the lean region, the differential amplifier circuit 22
The output level becomes a positive level, and this positive level voltage is supplied to the series circuit of the resistor 24 and the first oxygen pump element 15. Therefore, the electrode 11a of the first oxygen pump element 15,
A pump current flows between 11b and 11b. Since this pump current flows from the electrode 11a to the electrode 11b, oxygen in the first gas retention chamber 2 is ionized at the electrode 11b, moves within the first oxygen pump element 15, and is released from the electrode 11a as oxygen gas. , oxygen in the first gas B distillation chamber 2 is pumped out.

By pumping out the oxygen in the first gas retention chamber 2, there is a gap between the exhaust gas in the first gas retention chamber 2 and the gas in the reference gas chamber 6.
One prefecture concentration difference occurs. This oxygen concentration difference generates a voltage Vs between the electrodes 12a and 12b of the battery element 16. This voltage J) and Vsl are supplied to the inverting input terminal of the differential amplifier circuit 22. Since the output voltage of the differential amplifier circuit 22 is proportional to the difference voltage between the voltage Vs and the output voltage Vr+ 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 is the reference voltage source 2.
6 output voltage Vr+. Therefore, differential amplifier circuit 2
The output level of No. 2 is inverted from a positive level to a negative level. Due to this negative level, the electrode 11a of the first oxygen pump element 15
, 11b decreases, and the current direction is reversed. That is, the pump current flows from electrode 11b to electrode 1.
Since it flows in the direction 1a, external oxygen is ionized at the electrode 11'a and moves inside the first oxygen pump element 15 to the electrode 1.
1b is released into the first gas retention chamber 2 as oxygen gas, and the oxygen is pumped into the first gas retention chamber 2. Therefore,
Oxygen is pumped in and out by supplying a pump current so that the oxygen 1 degree in the first gas 8:1 retention chamber 2 is always constant, so the pump current value 1p and the X dynamic amplifier circuit 22 The output type B- is proportional to the oxygen concentration in the exhaust gas in the lean and rich regions, respectively. The broken line in FIG. 3 indicates the pump current value 1ρ.

In the pump current value IP, the electric charge is e, the diffusion coefficient for the exhaust gas by the introduction hole 4 is σ0, and the oxygen concentration in the exhaust gas is p□
exh, and if the oxygen concentration in the first gas retention chamber 2 is PoV, it can be expressed as in the following equation.

Ip = 4ecyo (Poexh-Pov) −(
1) Here, for the diffusion coefficient σ0, the area of the introduction hole 4 is A, the Boltzmann constant is k, the absolute temperature is T, the length of one entrance hole 4 is 9,
Letting the diffusion constant be D, it can be expressed as in the following equation.

σ o =D −A/kT 'J...
2) Next, switch 28a connects electrode 11a.
The switch 28b connects the electrode 13a to the current detection resistor 25, and the switch 29a connects the electrode 13a to the current detection resistor 25.
switch 29b grounds electrode 14b and opens the connection line of electrode 11b, and switch 29b grounds electrode 14b and opens the connection line of electrode 11b.
Selection to open connection line b (if left open, second
．． Sen υ becomes selected state.

In the selected state of the second sensor, the pump current is applied to 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 in the selected state of the first sensor described above. Since oxygen is supplied between fU13a and 13b and pumped out, the pump current is 1.
1tiIp and the output voltage of the differential amplifier circuit 23 are proportional to the oxygen concentration in the exhaust gas in the lean and rich regions, respectively.

The pump current value 1p in the second sensor selection state is expressed by assuming that the diffusion coefficient σ0 is due to the introduction hole 5 in the above equation (1), and PoV is the acid group concentration in the second gas retention chamber 3. . As shown in FIG. 4, it is clear that the magnitude of the pump current value 1p decreases as the diffusion resistance, which is inversely proportional to the magnitude of the diffusion coefficient σ0, increases in the lean and rich air-fuel ratio regions. Therefore, in the second Hin+1 selection state, the diffusion resistance is smaller than in the first sensor selection state, so as shown by the solid line a in FIG. 3, the magnitude of the pump current value 1p becomes large in the lean and rich regions. By adjusting the size and length of the introduction hole 5, as shown in FIG. It continues linearly at Ip=O. Also, differential amplifier circuit 22.23
The output voltage characteristic becomes linearly continuous at 0 [V].

Next, operation of the air-fuel ratio control circuit 32 according to the present invention will be explained. The air-fuel ratio control circuit 32 sequentially executes the air-fuel ratio detection and correction routine shown in FIG. 5 and the air-fuel ratio control routine shown in FIG. 6 in response to clock pulses. In the air-fuel ratio detection correction routine, the air-fuel ratio control circuit 321 first
It is determined whether the engine is in a predetermined operating state according to the F1 element 815F detection values of the plurality of operating parameter detection sensors (step 61). The predetermined operating state is an idle operating state.

It is a stable operating state such as a steady operating state. When it is determined that the operating state is the predetermined operating state, it is determined whether the air-fuel ratio is controlled to the target air-fuel ratio and the air-fuel ratio is stabilized (step 62).

When the air-fuel ratio is controlled to the target air-fuel ratio and the air-fuel ratio is stabilized, the first
Since the fluctuation in the oxygen concentration detection value of the sensor or the second sensor becomes smaller and falls within a predetermined range, the air-fuel ratio is stabilized when a predetermined period of time has elapsed since the oxygen concentration detection value fluctuation range of the selected sensor became less than or equal to the predetermined value. considered to be. When the air-fuel ratio is stable, the air-fuel ratio feedback (F/B) control according to the oxygen concentration detection value of the first or second sensor is stopped, and the execution of the air-fuel ratio control routine is stopped). A valve opening drive command and a valve opening drive stop command are generated to open the valve 34 at a predetermined duty ratio every predetermined period (step 63), and the flag FS representing the selection state of the first and second sensors is set to 111 II. It is determined whether there is one (step 64). In the case of Fs-0, the first sensor is selected, so the pump current value 1p(1) of the first sensor output from the A/D converter 31 is read and stored at the storage location Δ1 in the internal memory (not shown). (step 65). Then, a second sensor selection command is issued to the drive circuit 30, and the 21st sensor selection command is issued to the drive circuit 30. to the green selection state (step 66), and
Pump current of second sensor output from D converter 31]
Go j I p (2) is read and stored in storage location iHi A 2 of the internal memory (step 67). after that,
In step 68), a first sensor selection command is issued to the drive circuit 30 in order to bring the first sensor into the selected state again.
/Read the pump current value IP(1) of the first sensor output from the D converter 31 /v to the storage location A3 of the internal memory
(step 69). On the other hand, when Fs=1,
Since the second sensor is selected, the pump current value IP(2) of the second sensor output from the A/D converter 31 is read and stored in the storage location A1 of the internal memory (step 7
0). Then, a command to select the 7th sensor is issued to the drive circuit 30 to set the 1st sensor + J-m selection state (step 71), and the A/D conversion: pump current value Ip of the 1st sensor output from the 7th sensor 31 is output. (1) is read and stored at storage location 2 in the internal memory (step 72). After that, the second sensor is selected in order to enter the second sensor selection state again! A selection command is issued to the drive circuit 30 (step 73),
Step 74) reads the pump current value 1p(2) of the second sensor outputted from the D converter 31 and stores it in the storage location A3 of the internal memory. Next, in order to determine whether the fluctuation in the detected oxygen concentration value is small or not, the pump current value IP(1) or Ip(2) is read from the storage location A+, Δ3 in the internal memory and the pump current value 1p( Step 75 to calculate n absolute value Δlp of the difference between IP(1) and IP(2)
), it is determined whether the absolute value ΔIp is less than or equal to a predetermined value Δ[pr (step 76). If ΔIP≦ΔIpr,
The calculation formula of the correction coefficient @Kc o R+ (described later) is used to calculate the total () (step 77), ΔIp>ΔI p r
If 'Z, then the air-fuel ratio control (execution of the air-fuel ratio control routine) according to the detected value of the selected air-fuel ratio is restarted (step 78).

A correction coefficient KcoR+ for correcting the first detected oxygen concentration value LO2(1) is calculated from the following equation.

Kc on + -(1/C) ・lp (2) /
Ip (1)...(3) Here, C is R1/R2 and R+, R2 is the introduction hole 4°5
This is the diffusion resistance of each output characteristic change fiFi.

Note that since the diameter of the introduction hole 5 is larger than that of the introduction hole 4, oxides in the exhaust gas tend to adhere to the introduction hole 5. Therefore, only the change in the output characteristics of the first sensor is corrected and the output of the second sensor is adjusted. Complement 1 of characteristics is not performed.

Then, it is determined whether the calculated correction coefficient KCORI is greater than or equal to the predetermined value and less than or equal to the predetermined value (step 79), K
If +≦KcoR+≦2, restart the air-fuel ratio control according to the detected value of oxygen C1 of the selected sensor (J).Step 7
8) If , Kc ORl <K+, KCORI>K2, good air-fuel ratio feedback control cannot be expected even if the degree of change in output characteristics is greatly corrected, so a warning is issued to the driver by lighting a lamp, etc. (step 8
0).

Furthermore, as shown in FIG. 6, in the air-fuel ratio control routine, the air-fuel ratio control circuit 32 first determines which of the first and second sensors is to be selected (step 81). This is determined depending on the engine operating state or the air-fuel ratio control region.When it is determined that the first sensor 1 should be selected, a first sensor selection command is issued to the drive circuit 30. In step 82), O'' is set in the 7 lag Fs to indicate that the first sensor has been selected (step 83).On the other hand, when it is determined that the second sensor should be selected, the second sensor is selected. A selection command is issued to the drive circuit 30 (step 84), and '1'° is set to the flag Fs to indicate that the second sensor has been selected (step 85).

The drive circuit 30 switches the switch 2 in response to the selection command for the first run.
1t?8a, 28'b, 29a, 29b mentioned above? The drive state is Ill until the second sensor+1 selection command is supplied from the air-fuel ratio control circuit 32.
You will be charged ¥1. Further, in response to the second sensor selection command, the switches 28a, 28b, 29a, and 29b are activated as described above.
This driving state is maintained until the first sensor selection command is supplied from the air-fuel ratio control circuit 32.

Next, the pump current f output from the A/D converter 31
ffi I p (11 or Ip (2) is read (step 86), and it is determined whether the flag Fs is 0" (step 87). If l:s=o, in the first sensor υ selection state Therefore, read the pump current value 1p (11 multiplied by the correction coefficient KcoR1 in step 88), and calculate the corresponding oxygen concentration detection (1α and o2 (step 89))
. If Fs = 1, the second sensor is selected, and the corresponding detected oxygen concentration value LO2 is immediately obtained (step 89).
). Thereafter, it is determined whether the detected oxygen concentration value LO2 is a person based on the target value 1rer corresponding to the target air-fuel ratio.
Step 90). If LO2≦1rcf, the air-fuel ratio of the supplied air-fuel mixture is rich, so a command to open the solenoid valve 34 is issued to the drive circuit 33 (Step 91), LO
If 2>Lrer, supply a Aiki (7) Since the air-fuel ratio is lean, 11 of the solenoid valve 34 for the drive circuit 33
(2) A drive stop command is generated (step 92). The drive circuit 33 drives the solenoid valve 34 according to the valve opening drive command to supply secondary air into the engine intake manifold to make the air-fuel ratio lean, and operates the solenoid valve 34 in response to the valve opening drive stop command. 34 is stopped to enrich the air-fuel ratio. By repeating this operation at predetermined intervals, the air-fuel ratio of the supplied air-fuel mixture is ib controlled to the target air-fuel ratio.

In the embodiment of the present invention described above, the introduction holes 4 and 5 are used as the first and second gas diffusion restricting means.
The present invention is not limited to this, but by forming gaps between the two first electrode pairs in the first gas retention chamber 2 and the two second electrode pairs in the second gas retention chamber 3 and making the gap widths different. It is sufficient to obtain a diffusion resistance for each, or a porous material 38, 39 such as alumina (AQ203) may be filled into the introduction hole 4.5 to form a porous diffusion layer as shown in Fig. 7. .

Further, in the embodiments of the present invention described above, the first or second
J: To supply secondary air according to the output of t:
The air-fuel ratio of the supplied mixture is controlled to the target air-fuel ratio.
The present invention is not limited to this, and the air-fuel ratio may be controlled by adjusting the fuel supply m according to the output of the first or second sensor.

As described above, in the oxygen concentration detection device of the present invention, on the inner and outer wall surfaces of the electrolyte wall of the first gas retention chamber that communicates with the exhaust pipe through the first gas diffusion restriction means of the inlet hole. The first L? is provided with two pairs of first electrodes so as to face each other with this in between.
Similarly to the first sensor, the sensor faces the inner and outer walls of the electrolyte wall of the second gas retention chamber, which communicates with the exhaust pipe through a second gas diffusion restriction means such as an introduction hole. 2nd t?, which has two second electrode pairs. and is formed,
Due to the gas diffusion restriction means, each sensor has a different diffusion resistance, so even if oxides adhere, there will be a difference in the degree of change in the output characteristics of the first and second sensors. By comparing the oxygen concentration detection values of the sensors, it is possible to easily detect an abnormality in the first or second sensor.

[Brief explanation 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 a plan view showing an embodiment of the oxygen concentration detection device according to the present invention.
A cross-sectional view of part b, Figure 2 is a circuit diagram showing the current supply circuit including the air-fuel ratio control device, Figure 3 is a diagram showing the output characteristics of the device in Figure 1, and Figure 4 is the diffusion resistance and pump current value. FIGS. 5 and 6 are flowcharts showing the dynamics of the air-fuel ratio control circuit, and FIG. 7 is a plan view showing another embodiment of the present invention. Figure (b) shows ■b-■ in Figure 7(a).
It is a sectional view of part b. Explanation of symbols of main parts 1...Oxygen ion conductive solid electrolyte member 2.3
......Gas retention chamber 4.5...Introduction hole 6...Gas reference chamber 15.17...Acid pump element 16.18...
...Battery element 19.20...Heater element 21...Current supply circuit

Claims (3)

[Claims] (1) forming first and second gas retention chambers each having an oxygen ion conductive solid electrolyte wall, the first gas retention chamber communicating with the exhaust pipe of the internal combustion engine via a first gas diffusion restriction means; and the second gas retention chamber is opposed to the base body, which communicates with the inside of the exhaust pipe via a second gas diffusion restriction means, on the inner and outer wall surfaces of the electrolyte wall portion of the first gas retention chamber, with the base body interposed therebetween. two first electrode pairs disposed as above to form a first sensor, and a second sensor disposed oppositely on the inner and outer wall surfaces of the electrolyte wall portion of the second gas retention chamber with the electrodes interposed therebetween. two second electrode pairs to be formed;
A current is supplied between one of the two first electrode pairs and between one of the two second electrode pairs, and the oxygen concentration detection values of the first and second sensors are output in accordance with the supplied current value. and a detection means for detecting an abnormality in the first or second sensor according to the oxygen concentration detection value of the first sensor and the second oxygen concentration detection value. Concentration detection device. (2) When the current supply means supplies current between the one pair of first electrodes, the current supply means responds to the difference voltage between the voltage generated between the other pair of the two first electrode pairs and the first reference voltage. When a current with a value of 2. The oxygen concentration detection device according to claim 1, wherein a current having a value corresponding to a voltage difference from a reference voltage is supplied between said one second electrode pair. (3) The first gas diffusion limiting means includes a first introduction hole, and the second gas diffusion limiting means includes a second introduction hole having a different size from the first introduction hole. The oxygen concentration detection device according to scope 1.