JPH0720088A - Air-fuel ratio detector - Google Patents

Abstract

(57) [Abstract] [Purpose] By using an oxygen sensor in which an oxygen pump element and an oxygen concentration cell element are arranged opposite to each other, a signal corresponding to the air-fuel ratio can be obtained in the entire range of the air-fuel ratio. The air-fuel mixture can be feedback-controlled to a desired air-fuel ratio. [Structure] The oxygen concentration battery element 3 is provided in the exhaust manifold 3.
2 and the oxygen pump element 36 are arranged so as to face each other, and a theoretical air-fuel ratio detecting element 40 that outputs a theoretical air-fuel ratio signal capable of discriminating between a lean region and a rich region of the air-fuel ratio is provided. Then, by controlling the electromotive force of the battery element 32 or the pump current flowing through the pump element 36, the air-fuel ratio signal corresponding to the air-fuel ratio is detected in the lean region and the rich region of the air-fuel ratio,
Based on the theoretical air-fuel ratio signal, by inverting this air-fuel ratio signal when the air-fuel ratio is in the lean range or in the rich range, the actual air-fuel ratio signal corresponding to the air-fuel ratio in the entire range of the air-fuel ratio is obtained. Get it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio detecting device for detecting the air-fuel ratio of an air-fuel mixture supplied to a combustion device, and more particularly to an oxygen concentration cell device having porous electrodes on both sides of an oxygen ion conductive solid electrolyte. Also, the present invention relates to an air-fuel ratio detection device that includes a detection element section in which oxygen pump elements are opposed to each other with a gap interposed therebetween and that can detect the air-fuel ratio in the entire region from the rich region to the lean region of the air-fuel mixture.

[0002]

2. Description of the Related Art Conventionally, for example, in combustion equipment such as an internal combustion engine, in order to improve fuel efficiency and emission, the oxygen concentration in exhaust gas is detected and the air-fuel mixture burned in a combustion container is heated to near the stoichiometric air fuel. There is one that executes so-called feedback control, such as controlling to. And as an oxygen sensor used in this type of control device to detect the oxygen concentration in exhaust gas, for example, it is configured by depositing a porous electrode layer on an ion conductive solid electrolyte, and oxygen partial pressure of exhaust gas and oxygen of air Oxygen sensors that detect the combustion state near the stoichiometric air-fuel ratio due to the change in electromotive force caused by the difference with the partial pressure, such as oxygen sensors whose output voltage changes in a switching manner at the stoichiometric air-fuel ratio of the air-fuel mixture, are generally known. ing.

[0003]

By the way, in recent years, in addition to simply controlling the air-fuel ratio of the air-fuel mixture to near the stoichiometric air-fuel ratio,
By changing the target air-fuel ratio according to the operating state of the device and executing feedback control, it is considered that the fuel efficiency and emission are further improved and the drivability of the device is improved. Since the oxygen sensor described above can only detect the stoichiometric air-fuel ratio of the air-fuel mixture, it was not possible to control the air-fuel mixture to a desired air-fuel ratio.

On the other hand, in recent years, in order to realize the feedback control of the air-fuel ratio as described above, two plate-like oxygen ion conductive solid electrolytes having electrode layers provided on both front surfaces are parallel to each other with an interval therebetween. An oxygen concentration cell element in which a gap is provided on the front side to fix both the elements, one element is an oxygen pump element, and the other element is operated by an oxygen concentration difference between the ambient atmosphere and the gap. An oxygen sensor that has been proposed is proposed, and one configured to detect a signal corresponding to the air-fuel ratio at least in the lean region of the air-fuel mixture is considered,
In the case of this oxygen sensor, not only in the lean region of the air-fuel mixture, that is, when residual oxygen exists in the exhaust gas, but also in the rich region of the air-fuel mixture, that is, when there is no residual oxygen in the exhaust gas, CO and CO _{2 in the} exhaust gas , H ₂ O, etc., and a signal similar to the signal in the lean range is detected according to the air-fuel ratio in the rich range.

Therefore, the present invention uses an oxygen sensor in which the oxygen pump element and the oxygen concentration cell element are opposed to each other with a gap, and the detection signal is divided and combined into a rich region and a lean region to form a mixture gas. By providing an air-fuel ratio detection device capable of obtaining a signal corresponding to the air-fuel ratio in all regions from the rich region to the lean region, it is possible to perform feedback control of the air-fuel mixture supplied to the combustion equipment to a desired air-fuel ratio. The purpose is to do.

[0006]

As shown in the block diagram of FIG. 1, the structure of the present invention for attaining the above object has a structure in which porous electrodes are provided on both surfaces of an oxygen ion conductive solid electrolyte.
A theoretical element that detects the theoretical air-fuel ratio and outputs a theoretical air-fuel ratio signal capable of discriminating between a lean range and a rich range of the air-fuel ratio, and a detection element section M1 in which a plurality of elements are arranged to face each other with a gap. The fuel ratio detection means M2, one element of the detection element section M1 is an oxygen concentration battery element M3, and the other element is an oxygen pump element M.
4, an air-fuel ratio signal for controlling the electromotive force of the oxygen concentration cell device M3 or the pump current flowing through the oxygen pump device M4 to detect air-fuel ratio signals corresponding to the air-fuel ratio in the lean region and the rich region of the air-fuel ratio, respectively. The detection means M5 and the stoichiometric air-fuel ratio signal output from the stoichiometric air-fuel ratio detection means M2 are received, and when the air-fuel ratio is in the lean range or the rich range, it is detected by the air-fuel ratio signal detection means M5. The gist of an air-fuel ratio detecting device is characterized by including an actual air-fuel ratio signal detecting means M6 which inverts the air-fuel ratio signal and detects an actual air-fuel ratio signal corresponding to the air-fuel ratio in the entire region of the air-fuel ratio. .

[0007]

Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 2 is a schematic system diagram showing an internal combustion engine (engine) equipped with the air-fuel ratio detection apparatus of the present embodiment and its peripheral equipment. In the figure, 1 is an engine, 2 is a piston,
Reference numeral 3 is an exhaust manifold, 4 is an exhaust manifold 3, and an oxygen sensor used to detect the air-fuel ratio of the air-fuel mixture supplied to the engine 1 is provided for each cylinder, and 5 is provided for each cylinder to inject fuel. A fuel injection valve, 6 is an intake manifold, 7 is an intake manifold 6 provided in the intake manifold 6 and detects an intake air temperature, 8 is a water temperature sensor that detects a cooling water temperature of the engine 1, 9 is a throttle valve, and 10 is a throttle. A throttle opening sensor that detects the opening of the valve 9, 11 is an air flow meter that detects the amount of intake air, 12 is an air cleaner that purifies the intake air, 1
Reference numeral 3 denotes a rotation speed sensor for outputting a signal corresponding to the rotation of the engine 1 and detecting the engine rotation speed.

Reference numeral 20 represents an electronic control circuit composed of a microcomputer, which inputs / calculates the data output from each of the above-mentioned sensors in accordance with a control program, and the engine 1
A central processing unit (CPU) 21 that performs a process of controlling the fuel injection amount by driving the fuel injection valve 5 in accordance with the operating state of No. 1, and a control program executed by the CPU 21 and data such as a map are stored in advance. A read-on memory (ROM) 22, a random access memory (RAM) 23 for temporarily reading and writing data necessary for arithmetic processing, such as data output from the above sensors and input to the electronic control circuit 20. An input unit 24 including a waveform shaping circuit and an A / D converter corresponding to signals from the above-mentioned sensors, and a multiplexer selectively outputting the waveform-shaped digital signal to the CPU 21,
An output unit 25 that outputs a drive signal to the fuel injection valve 5 according to the fuel injection amount obtained by the arithmetic processing of the CPU 21;
The CPU 21, the ROM 22, and the RAM 23 are connected to each other, and the input unit 25 and the output unit 24 are connected to each other, and a bus line 26 to which each data is sent. The drive signal output from the electronic control circuit 20 is sent to the fuel injection valve 5, the fuel pressure adjusted by the fuel pressure adjusting valve 28, and the fuel pumped by the fuel pump 29 is supplied to the engine 1.

Next, the oxygen sensor 4, which is a main part of the present invention, will be described. In the oxygen sensor 4 of this embodiment, not only the oxygen concentration battery element M3 and the oxygen pump element M4 described above, but also a theory in which a metal oxide semiconductor is provided on the surface of an electrically insulating member corresponding to the theoretical air-fuel ratio detecting means M2. An air-fuel ratio detecting element is provided.

FIG. 3 is a cross-sectional view showing a state in which the oxygen sensor 4 is provided in the exhaust manifold 3, and is attached to an oxygen sensor attachment hole formed in the exhaust manifold 3 via an attachment member 31. . Reference numeral 32 represents an oxygen concentration battery element, and as shown in FIG. 4, for example, a plate-like ion conductive solid electrolyte 33 having a thickness of about 0.5 mm and made of stabilized or partially stabilized zirconia, thoria, ceria, or the like. About 20 on each side using thick film technology
Porous platinum electrode layers 34a and 34b having a thickness of μ and platinum electrodes 35a and 35b for extracting output are provided.
Further, 36 is constructed in the same manner as the oxygen concentration battery element 32,
This shows an oxygen pump element in which porous platinum electrode layers 38c and 38d and platinum electrodes 39c and 39d are provided on both sides of the ion conductive solid electrolyte 37.

Next, reference numeral 40 denotes the above theoretical air-fuel ratio detecting element, and as shown in FIG. 5, a thick film technique is used on the side surface of a flat electrically insulating member 41 made of alumina or the like and having a thickness of 0.7 mm. Heating resistor pattern 42 and electrode pattern 4
3a and 43b are formed, and electrodes 43 are formed on these pattern surfaces.
A 0.1 mm thick electrically insulating member 44 having an opening 44a provided so as to expose a and 43b is joined and sintered, and the electrode patterns 43a and 43b are further provided in the opening 44a.
Thickness of about 150μ made of titania, etc.
It is prepared by providing a metal oxide 45 of a certain degree.

The oxygen concentration battery element 32, the oxygen pump element 36, and the stoichiometric air-fuel ratio detecting element 40 have a gap between the oxygen concentration battery element 32 and the oxygen pump element 36 of 0.
A small gap of about 1 mm and a gap of about 0.1 mm between the oxygen pump 36 and the stoichiometric air-fuel ratio detecting element 40 are arranged opposite to each other using a heat-resistant and insulating spacer 47, and the mounting member 31 is provided. Through the exhaust manifold 3
Is attached to. As the spacer 47, a heat-resistant and insulating filling adhesive may be used.

Next, the pump current flowing through the oxygen pump element 36 is controlled in order to control the output voltage of the oxygen concentration battery element 32 to a constant value, and a signal corresponding to the air-fuel ratio of the air-fuel mixture supplied to the engine is extracted. An air-fuel ratio signal detection circuit corresponding to the air-fuel ratio signal detection means M5 will be described.

FIG. 6 shows a circuit diagram of this detection circuit, in which terminals a, b, c and d are respectively the platinum electrodes 3 of the oxygen battery element 32.
5a, 35b, a platinum electrode 39c of the oxygen pump element 36,
Connect to 39d. Then, the oxygen concentration in the exhaust gas or the CO and C in the exhaust gas output from the oxygen concentration battery element 32.
A voltage VS corresponding to O ₂ , H ₂ O, etc. is detected through a resistor R1 and an operational amplifier (hereinafter referred to as operational amplifier) OP1
The voltage Vs is amplified by the amplifying section 51 constructed around the above to obtain the voltage nVS amplified to a predetermined multiple n (for example, 5 times).

Next, the voltage nVS is input to the integrating circuit 52 mainly composed of the operational amplifier OP2, and the voltage determined by the Zener diode D1 is applied to the variable resistor VR1.
Predetermined voltage VO obtained by voltage division using
7 as a reference, and is extracted as the base voltage of the transistor TR1 in the pump current control circuit 53 including the next transistors TR1 and TR2, that is, the control voltage VB of the pump current. In addition, + B shown in the figure represents the battery voltage.

When the pump current flowing through the oxygen pump element 36 is controlled in this manner, the concentration of oxygen existing in the gap between the oxygen concentration cell element 32 and the oxygen pump element 36 is controlled, and the output of the oxygen concentration cell element 36 is controlled. The voltage is controlled to be constant. Therefore, by extracting the pump current of the oxygen pump element 36 as the air-fuel ratio signal V1 via the resistor R2, it is possible to detect a signal corresponding to the oxygen concentration in the exhaust gas or the concentration of CO, CO ₂ , H ₂ O or the like. As shown in FIG. 8, the air-fuel ratio signal V1 according to the air-fuel ratio of the air-fuel mixture can be detected in the lean region and the rich region of the air-fuel mixture, respectively. In FIG. 8, λ = 1 represents the stoichiometric air-fuel ratio.

Next, the metal oxide semiconductor 45 made of titania or the like in the stoichiometric air-fuel ratio detecting element 40 has a large resistance value when the mixture has a stoichiometric air-fuel ratio, that is, when the oxygen concentration in the exhaust gas becomes zero. As shown in FIG. 9, the resistance value changes, and the resistance value is large in the lean region and is small in the rich region. Further, as is clear from FIG. 5, the metal oxide semiconductor 45
One electrode pattern 43a of the electrode patterns 43a and 43b joined to is connected to the heating resistor pattern 42 which is the heater section.
When 0 is represented by an electric circuit, it becomes as shown in FIG.

Therefore, a signal that is detected by the stoichiometric air-fuel ratio detecting element 40 and indicates whether the air-fuel mixture is in the rich region or lean region with respect to the stoichiometric air-fuel ratio, that is, the resistance value of the metal oxide semiconductor 45. As the signal indicating the magnitude, the voltage supplied to the heating resistor pattern 42, which is the heater section, is divided, and a predetermined voltage is applied to the metal oxide semiconductor 45, for example, 1
It can be detected by supplying [V] and detecting the current value flowing at that time.

As the detection circuit for detecting the stoichiometric air-fuel ratio signal, for example, as shown in FIG. 11, the current flowing through the metal oxide semiconductor 45 is detected as a voltage signal by using the resistor R4, and the transistor TR3 is turned on / off. Can be detected by. That is, when the air-fuel ratio is in the rich region, the resistance value of the metal oxide semiconductor 45 decreases, so the voltage applied to the resistor R4 increases, the transistor TR3 is turned on, and the voltage on the collector side becomes zero. On the other hand, when the air-fuel ratio is in the lean range, the resistance value of the metal oxide semiconductor 45 increases, so that almost no voltage is applied to the resistor R4, the transistor TR3 is turned off, and the collector-side voltage is the battery voltage. Since the voltage is applied as it is, it is possible to detect the "H" level signal when the air-fuel ratio is in the lean range and the "L" level signal when the air-fuel ratio is in the rich range. Hereinafter, this signal is referred to as the theoretical air-fuel ratio signal Vrl.

The above-described air-fuel ratio signal detection circuit of FIG. 6 and the theoretical air-fuel ratio signal detection circuit of FIG. 11 are provided in the input section 25 of the electronic control circuit 20.
By the calculation processing of 21, the air-fuel ratio is read when detecting the air-fuel ratio of the air-fuel mixture supplied to the engine 1, and the air-fuel ratio is detected based on these two types of detection signals.

The air-fuel ratio detection process will be described below with reference to FIG.
It will be described with reference to the flowchart showing the control program shown in FIG. In the air-fuel ratio detection process, when the operating state of the engine 1 based on the output signals from the above-described sensors satisfies the feedback control condition, the fuel injection amount is calculated and the drive control of the fuel injection valve 5 is performed. It is executed as one of so-called main routines to be executed.

When this process is started, first step 1
01 is executed, and the air-fuel ratio signal V1 output from the air-fuel ratio signal detection circuit and the theoretical air-fuel ratio signal Vrl output from the theoretical air-fuel ratio signal detection circuit are read. Then, in the following step 102, it is judged whether or not the read theoretical air-fuel ratio signal Vrl is at the “L” level, that is, whether the air-fuel ratio of the air-fuel mixture is in the rich region, and Vrl =
If it is "L", the routine proceeds to step 103, where the air-fuel ratio signal V1 read at step 101 is subtracted from the set voltage V2 to obtain the actual air-fuel ratio signal V3 (= V2-V).
1) is calculated.

On the other hand, in step 102, Vrl =
If it is determined to be "H", the process proceeds to step 104, this time by adding the air-fuel ratio signal V1 read in step 101 and the set voltage V2 to obtain the actual air-fuel ratio signal V3. (= V1 + V2) is calculated.

When the actual air-fuel ratio signal V3 is obtained in step 103 or step 104 in this way, the routine proceeds to the following step 105, where a map or a predetermined map corresponding to the value of the actual air-fuel ratio signal V3 is used. The air-fuel ratio A / F of the air-fuel mixture is obtained from the arithmetic expression, and this air-fuel ratio detection processing is ended.

In the air-fuel ratio detection process, the air-fuel ratio signal V1 is adjusted according to the theoretical air-fuel ratio signal Vrl with reference to the set voltage V2, and the air-fuel ratio A / F is calculated based on the obtained actual air-fuel ratio signal V3. Is configured to detect
As shown in FIG. 13, this is obtained by inverting the air-fuel ratio signal V1 of FIG. 8 obtained by the air-fuel ratio signal detection circuit shown in FIG. 6 at the point of the theoretical air-fuel ratio (λ = 1), and making the value negative. It is corrected by the set voltage V2 so that it does not occur.

Therefore, step 103 or step 10
The actual air-fuel ratio signal V3 obtained at 4 has a value corresponding to the actual air-fuel ratio, and the actual air-fuel ratio A / F can be obtained using this actual air-fuel ratio signal V3 as a parameter.
Therefore, according to the air-fuel ratio detection device of this embodiment, the engine 1
The air-fuel ratio of the air-fuel mixture actually supplied can be detected, and the target air-fuel ratio is set according to the operating state of the engine 1, and the engine 1 is precisely controlled to improve fuel economy, emissions, etc. In this case, the air-fuel mixture can be controlled to a desired air-fuel ratio, and more precise feedback control can be realized.

In the present embodiment, the heater section for activating each element of the oxygen sensor 4 is provided in the stoichiometric air-fuel ratio detecting element 40, but in addition to this, for example, in the oxygen concentration battery element 32. Or oxygen pump element 36
It may be provided in any of the above, as long as each element can be heated.

Although the oxygen sensor 4 in which the stoichiometric air-fuel ratio detecting element 40 is integrated with the oxygen concentration cell element 32 and the oxygen pump element 36 is used, at least the oxygen concentration cell element 32 and the oxygen pump element 36 are separated by a gap. The stoichiometric air-fuel ratio detecting element 40 may be provided in another portion of the exhaust manifold 3.

Further, as the theoretical air-fuel ratio detecting means M5, either the rich region or the lean region of the air-fuel mixture can be detected,
Since it suffices to determine whether the air-fuel ratio is rich or lean, it is possible to use another type, for example, a battery type using a solid electrolyte, without using the stoichiometric air-fuel ratio detecting element 40. Well, oxygen concentration cell element 3
2 or the element resistance of the oxygen pump element 36 may be used for detection.

In the above embodiment, the actual air-fuel ratio signal detecting means M6 has been described by taking the air-fuel ratio detecting process performed by the electronic control circuit 20 as an example. The actual air-fuel ratio signal V3 can be obtained by using the actual air-fuel ratio signal detection circuit as shown in FIG.

As shown in the figure, the air-fuel ratio signal V1 output from the air-fuel ratio signal detection circuit shown in FIG. 6 is input to the + side input terminal of the operational amplifier OP3 via the resistor R3 and the zener diode D2. The predetermined voltage determined by is divided by the variable resistor VR2, and the set voltage V2 is input via the resistor R4. Also this operational amplifier OP
The + side input terminal of 3 is grounded via a resistor R5.
On the other hand, the-side input terminal of the operational amplifier OP3 is grounded via the resistor R6, and is connected to the output terminal via the resistor R7. Here, the relationship between the resistors R3 to R7 is R3 = R4 = 2.R5 = R6 = R7 / 3, and the air-fuel ratio signal V1 and the set voltage V2 are added to the output terminal of the operational amplifier OP3. Voltage (V1 +
V2) will be output.

Next, the voltage (V1 +) output from the operational amplifier OP3 is applied to the-side input terminal of the operational amplifier OP4.
V2) is input through the resistor R8, and the minus side input terminal is connected to the output terminal through the resistor R9. On the other hand, the predetermined voltage determined by the Zener diode D2 is also divided by the variable resistor VR3, and the set voltage V2 is input to the + side input terminal of the operational amplifier OP4 via the resistor R10.

SW1 shown in the figure is turned on by the theoretical air-fuel ratio signal Vrl output from the theoretical air-fuel ratio detection circuit.
Indicates an analog switch that is turned off, Vrl is "H"
ON when the level, that is, the mixture air-fuel ratio is in the lean range
In this state, the + input terminal of the operational amplifier OP4 is connected to the output terminal of the operational amplifier OP3, and when Vrl is at the “L” level and the air-fuel ratio is in the rich region, it is turned OFF and the + input of the operational amplifier OP4 is input. Terminal and operational amplifier OP
It is configured so that it is not connected to the output terminal of No. 3.

The resistors R8 to R10 have the same resistance value. Therefore, when the air-fuel ratio is in the lean range, this circuit functions as a mere buffer circuit, and the output terminal of the operational amplifier OP4 is (V1 The voltage of + V2) is output as it is, while when the air-fuel ratio is in the rich region, the voltage of (V2-V1) is output.

As described above, even when the signals output from the air-fuel ratio signal detection circuit and the stoichiometric air-fuel ratio signal detection circuit are processed by such a circuit configuration, when the air-fuel ratio is in the rich region. Output voltage to (V2-V1),
When the air-fuel ratio is in the lean range, set the output voltage to (V1 + V2
), And the actual air-fuel ratio signal V3 corresponding to the actual air-fuel ratio as shown in FIG. 13 can be obtained.

In the embodiment described above, the air-fuel ratio signal V1 is the theoretical air-fuel ratio (λ = 1) as the actual air-fuel ratio signal V3.
The air-fuel ratio signal V1 is inverted in the rich region from the rich region to the lean region, but the actual air-fuel ratio signal V1 is inverted in the lean region from the rich region to the lean region. The actual air-fuel ratio signal V3 may be configured to be small. If necessary, the air-fuel ratio signal V1 in the rich range may be cut and used as a lean sensor, or the air-fuel ratio signal V1 in the lean range may be cut. It is easy to use as a rich sensor.

In the above embodiment, the actual air-fuel ratio signal V3
Is configured to continuously change from the rich region of the air-fuel ratio to the lean region. For example, the variable resistance VR shown in FIG.
Set the voltage set by 2 and VR3 to different values,
As shown in FIG. 15, the actual air-fuel ratio signal may change stepwise at a point where the excess air ratio λ = 1 at which the air-fuel ratio becomes the stoichiometric air-fuel ratio. When the actual air-fuel ratio signal that changes stepwise at the point of λ = 1 is obtained in this way, it is likely that there is a detection delay in the air-fuel ratio signal detected by the air-fuel ratio signal detection circuit. Even at least, it is possible to accurately detect at least whether the air-fuel ratio is in the rich region or the lean region with respect to the stoichiometric air-fuel ratio, and the air-fuel ratio control near the stoichiometric air-fuel ratio can be executed with higher accuracy.

[0038]

As described above in detail, in the air-fuel ratio detection device of the present invention, two elements having porous electrodes on both surfaces of the oxygen ion conductive solid electrolyte are arranged opposite to each other with a gap therebetween. And a theoretical air-fuel ratio detecting means for detecting a stoichiometric air-fuel ratio and outputting a theoretical air-fuel ratio signal capable of discriminating between a lean region and a rich region of the air-fuel ratio. The element is an oxygen concentration cell element, the other element is an oxygen pump element, obtained by controlling the electromotive force of the oxygen concentration element or the pump current flowing through the oxygen pump element, respectively in the lean region and the rich region of the air-fuel ratio. The air-fuel ratio signal corresponding to the air-fuel ratio, based on the theoretical air-fuel ratio signal output from the theoretical air-fuel ratio detection means, by inverting the air-fuel ratio in the lean range or in the rich range, Fuel ratio In the entire region of the lean region from the local, the actual air-fuel ratio signal corresponding to the air-fuel ratio is configured to be detected.

Therefore, by using the air-fuel ratio detection device of the present invention, the air-fuel ratio of the air-fuel mixture supplied to the combustion equipment such as the internal combustion engine can be accurately detected, and the air-fuel ratio can be feedback-controlled to a desired air-fuel ratio. It becomes possible to realize more precise air-fuel ratio control.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is a schematic system diagram showing an engine equipped with the air-fuel ratio detection device of the embodiment and its peripheral equipment.

FIG. 3 is a cross-sectional view showing an oxygen sensor 4 attached to an exhaust manifold 3.

FIG. 4 is an explanatory diagram showing a structure of an oxygen concentration battery element 32.

5 is an explanatory diagram showing a structure of a stoichiometric air-fuel ratio detecting element 40. FIG.

FIG. 6 is a circuit diagram showing an air-fuel ratio signal detection circuit.

FIG. 7 is a voltage waveform diagram showing a control voltage VB output from the integrating circuit 52 and controlling the pump current.

FIG. 8 is an air-fuel ratio signal V detected by an air-fuel ratio detection circuit.
It is a diagram showing 1.

FIG. 9 is a diagram showing a change in resistance value of a metal oxide semiconductor 45 with respect to an air-fuel ratio.

FIG. 10 is a circuit diagram showing a theoretical air-fuel ratio detection element 40.

FIG. 11 is a circuit diagram showing a theoretical air-fuel ratio signal detection circuit.

FIG. 12 is a flowchart showing an air-fuel ratio detection process.

FIG. 13 is a diagram showing an actual air-fuel ratio signal V3.

FIG. 14 is a circuit diagram showing an actual air-fuel ratio signal detection circuit configured to detect an actual air-fuel ratio signal V3 by an electric circuit instead of the air-fuel ratio detection processing.

FIG. 15 is a diagram showing an actual air-fuel ratio signal that changes stepwise with the theoretical air-fuel ratio.

[Explanation of symbols]

M1 ... Detecting element section M2 ... Theoretical air-fuel ratio detecting means M3, 32 ... Oxygen concentration cell element M4, 36 ... Oxygen pump element M5 ... Air-fuel ratio signal detecting means M6 ... Actual air-fuel ratio signal detecting means 1 ... Engine 4 ... Oxygen sensor 20 ... Electronic control circuit 40 ... Theoretical air-fuel ratio detection element

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsumasa Yamada 14-18 Takatsuji-cho, Mizuho-ku, Nagoya, Aichi Nihon Special Ceramics Co., Ltd.

Claims (4)

[Claims] 1. A detection element section comprising two elements having porous electrodes on both sides of an oxygen ion conductive solid electrolyte, which are opposed to each other with a gap therebetween, and a theoretical air-fuel ratio is detected to detect an air-fuel ratio. The theoretical air-fuel ratio detecting means for outputting a theoretical air-fuel ratio signal capable of discriminating between the lean region and the rich region, one element of the detecting element part is an oxygen concentration battery element, and the other element is an oxygen pump element, and the oxygen Air-fuel ratio signal detection means for controlling the electromotive force of the concentration cell element or the pump current flowing through the oxygen pump element, and detecting the air-fuel ratio signal corresponding to the air-fuel ratio in the lean area and the rich area of the air-fuel ratio, respectively, the above, the theory Receiving the theoretical air-fuel ratio signal output from the air-fuel ratio detecting means, when the air-fuel ratio is in the lean range or the rich range, the air-fuel ratio signal detected by the air-fuel ratio signal detecting means is inverted, All areas And an actual air-fuel ratio detection signal for detecting an actual air-fuel ratio signal corresponding to the air-fuel ratio. 2. The air-fuel ratio detecting device according to claim 1, wherein the actual air-fuel ratio signal detecting means is configured to output an actual air-fuel ratio signal which changes stepwise in the stoichiometric air-fuel ratio. 3. The air-fuel ratio detection device according to claim 1, wherein the stoichiometric air-fuel ratio detection means is a stoichiometric air-fuel ratio detection element in which a metal oxide semiconductor is provided on the surface of the electrically insulating member. 4. The air-fuel ratio signal detecting means is configured to control the pump current of the oxygen pump element so as to keep the electromotive force of the oxygen concentration battery element constant, and to use the pump current as an air-fuel ratio signal. The air-fuel ratio detection device according to claim 3.