JPS60224051A - Air-fuel ratio detecting device - Google Patents

Abstract

PURPOSE:To heighten the accuracy of detection over a wide range by detecting a current value and air-fuel ratio supplied to make an output of the oxygen partial pressure ratio detecting section of an oxgen sensor coincides with a target value, and judging abnormality of the sensor from the result and result of detection of voltage between two poles of a controlling section. CONSTITUTION:An atmosphere introducing section 15 is formed by laminating the first solid electrolyte 14 on an atmosphere introducing plate 13, and a gas introducing section 18 is formed by laminating the second solid electrolyte 17 on the electrolyte 14 through a spacer plate 16. An anode 20 and cathode 21 of a sensor cell, and a cathode 22 and anode 23 of a pump cell are provided on both faces of electrolytes 14, 17 opposite to each other. Current IP is supplied from a pump current supply circuit 37 of an air-fuel ratio detecting circuit 33 to make potential VS between sensor cells 20, 21 a target voltage Va, and air fuel ratio detection output V1 from the current IP and current VP between pump cells 23, 22 are outputted to an abnormality judging circuit 34 to detect the abnormality of the sensor 11 due to adhesion of carbon particles. At the same time, an output Vi is made monotonous and continuous over whole range of air fuel ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio detection device for detecting the air-fuel ratio of an air-fuel mixture based on the oxygen concentration in exhaust gas resulting from combustion of the air-fuel mixture, and particularly relates to an air-fuel ratio detection device for detecting an air-fuel ratio of an air-fuel mixture based on the oxygen concentration in exhaust gas from combustion of the air-fuel mixture. The present invention relates to an air-fuel ratio detection device suitable for detecting the air-fuel ratio of an air-fuel mixture.

In general, in internal combustion engines, in order to control the air-fuel ratio of the intake air-fuel mixture to a target value with high precision, the air-fuel mixture is controlled by detecting the oxygen concentration in the exhaust gas, which has a correlation with the air-fuel ratio. The air-fuel ratio is detected and the fuel supply amount is feedback-controlled.

An example of an oxygen sensor conventionally used in such an air-fuel ratio detection device is the one described in Japanese Patent Application Laid-Open No. 76450/1983. and explain.

This oxygen sensor 1 applies the principle of a kind of concentration battery that generates an electromotive force according to the oxygen concentration, and has a reference electrode 3 mainly composed of platinum on both sides of an oxygen ion conductive solid electrolyte 2. and an oxygen electrode 4 made of an alloy of gold and platinum are formed facing each other, and the reference electrode B is covered with a porous protective layer (coating layer) 5 to restrict the inflow and diffusion of oxygen. It is coated with a porous protective layer (coating layer) 6.

In this oxygen sensor 1, when a predetermined magnitude of current Ts is supplied to the reference electrode B in a gas to be measured, for example, exhaust gas, oxygen ions 02- are produced in an amount corresponding to the magnitude of the current Is. Solid electrolyte 2 in the direction opposite to the current Is
Because it moves through.

A reference oxygen partial pressure Pa is generated at the reference electrode 6, and at this time, an oxygen partial pressure P due to the oxygen partial pressure possessed by the dregs to be measured is generated at the oxygen electrode 4.
b is occurring.

Thereby, between the reference electrode B and the oxygen electrode 4, E = RT/4 F-# based on the oxygen partial pressures Pa and Pb.
n (P a / P b) ... = ... ■ However, an electromotive force E expressed by the Nernst equation where R: gas constant, T: absolute temperature F: Faraday constant is generated, and this electromotive force E is It changes depending on the oxygen sensitivity of the dregs. 1. Yuj1 can be taken out to the outside as an oxygen jacket of 1°8ka Vs.

FIG. 2 shows the change in the output Vs for each injected current value. In this case, the exhaust gas from the internal combustion engine is used as the gas to be measured, and the oxygen concentration is determined by the air-fuel ratio (equivalent ratio λ, where λ = current total air-fuel ratio / stoichiometric air-fuel ratio) of the air-fuel mixture supplied to the internal combustion engine. The figure is converted to .

However, the output Vs of this oxygen sensor 1 is.

When the inflow current Is is fixed, the air-fuel ratio range in which the output Vs changes is small, so it is difficult to detect the air-fuel ratio over a wide range.

Therefore, the output Vs of this oxygen sensor 1 is set to the target voltage Va(
For example, if the oxygen sensor output Vs is set as approximately the middle value between the upper and lower limits of the oxygen sensor output Vs which changes suddenly at the switching air-fuel ratio, and the inflow current IS is supplied so that the oxygen sensor output Vs becomes this target value Va, then this inflow current Is The value of
As shown in FIG. 3, it changes continuously according to the current air-fuel ratio.

Therefore, by detecting the value of the current Is flowing into the oxygen sensor 1, the actual air-fuel ratio can be detected over a wide range.

However, in such an air-fuel ratio detection device,
As can be seen from FIG. 3, the value of the inflow current Is increases not only when shifting to the lean side with the stoichiometric air-fuel ratio (λ=1) as the minimum value, but also when shifting to the rich side.

This is because in the rich region, there is almost no oxygen in the exhaust gas, so carbon dioxide G O2 in the exhaust gas in the space surrounding the oxygen electrode 4 is converted into monooxygen carbon C○ and oxygen ions O''-. This is because the oxygen ions 0''- are polarized and move through the solid electrolyte 2 to the oxygen electrode 31.The more the exhaust gas moves to the rich side, the more oxygen ions move, and the flow rate of the injected current Is increases. value increases.

Therefore, near the stoichiometric air-fuel ratio, two values of air-fuel ratio exist for the same value of injected current Is, and simply based on the value of injected current Is, the air-fuel ratio can be calculated over a wide range from the rich region to the lean region. There is a problem that the fuel ratio (oxygen concentration) cannot be detected.

■Once this invention was made in view of the above points, it is possible to detect a wide range of air-fuel ratios from the rich region to the lean region with high precision, and also detect the occurrence of abnormalities that make the detection results inaccurate. The purpose is to make it possible.

SUPERVISION For this reason, the air-fuel ratio detection device according to the present invention has a waste introduction section in which exhaust gas from combustion of a mixture of air and fuel is introduced through a means for restricting gas diffusion, and an oxygen ion conductive an oxygen partial pressure ratio detection section that has electrodes that are exposed to the gas of the waste introduction section and the gas of a predetermined oxygen concentration that face each other with a solid electrolyte in between, and outputs a voltage according to the oxygen partial pressure ratio between both electrodes; and an oxygen partial pressure control section that has electrodes facing each other with a solid electrolyte in between and controls the oxygen partial pressure of the gas introduction section according to the amount of current supplied between the two electrodes, A current is supplied to the oxygen partial pressure control unit so that the output of the oxygen partial pressure ratio detection unit of the sensor matches a predetermined target value, and the supplied current value is detected as an output indicating the air-fuel ratio, and the oxygen sensor The voltage between both electrodes of the oxygen partial pressure control section is detected, and an abnormality in the oxygen sensor is determined based on the detection result and the current detection result.

Embodiments of the present invention will now be described with reference to FIG. 4 and subsequent figures of the accompanying drawings.

FIGS. 4 and 5 are a longitudinal sectional view and an exploded perspective view showing an example of an oxygen sensor used in the present invention.

This oxygen sensor 11 has an air introduction plate 13 with grooves 13a formed on a substrate 12 made of alumina, and a flat oxygen ion conductive first solid electrolyte 14 on this air introduction plate 13. The grooves 13a of the air introduction plate 13 and the first solid electrolyte 14 form an air introduction section 15 into which air, which is a gas having a predetermined oxygen concentration, is introduced.

Then, on the first solid electrolyte 14, a thickness L (L
=O, about 1 mm) spacer plates 16 are laminated, and a flat second solid electrolyte 17 is laminated on this spacer plate 16, and these first solid electrolyte 14 and spacer plate 1 are laminated.
6 and the second solid electrolyte 17 form a waste introduction portion 18 which is a wide gap that also serves as a means for restricting the diffusion of waste into which exhaust gas is introduced.

Then, air introduction portions 1 are provided on both sides of the first solid electrolyte 14.
A sensor anode 20, which is an electrode that is exposed to the atmosphere, which is scum of a predetermined oxygen concentration in No. The oxygen partial pressure ratio detecting section C and below (referred to as sensor cell SCJ) outputs a voltage according to the oxygen partial pressure ratio between the cathode 21, that is, the oxygen partial pressure ratio between the atmosphere introduction section 15 and the gas introduction section 18. ing.

Further, gas introduction portions 18 are provided on both sides of the second solid electrolyte 17.
A pump cathode 22 is an electrode exposed to the exhaust gas, and a pump anode 2 is an electrode directly exposed to the exhaust gas.
3 are provided facing each other, and an oxygen partial pressure control unit (hereinafter referred to as [
(referred to as pump cell PCJ).

A heater 25 for heating the first solid electrolyte 14 and the second solid electrolyte 17 is printed on the surface of the substrate 12 on the side of the air introduction plate 13 in order to maintain the activity of the first solid electrolyte 14 and the second solid electrolyte 17.

Moreover, the sensor anode 20. Lead wires 2Ei and 27 are connected to the sensor cathode 21, respectively, and the pump cathode 22. Lead wires 28 and 29 are connected to the pump anode 23, and leads 11A30.61 are connected to the heater 25, respectively.

Furthermore, the first. 1 as the second solid electrolyte 14.17
For example, ZrO2t' Hr02, Th02.

C20, MgO, Y2o2゜Y in oxides such as Bi2O3
Using a sintered body containing B203 etc. as a solid solution, each electrode 20-2
4 contains platinum or gold as a main component.

Furthermore, in this embodiment, the entire partition wall between the atmosphere introduction section 15 and the waste introduction section 18 is filled with the first solid electrolyte 14, and the entire partition wall between the waste introduction section 18 and the exhaust gas atmosphere is filled with the first solid electrolyte 14. Although it is formed of the second solid electrolyte 17, the electrode 2
Only the portions corresponding to 0 to 24 may be formed of solid electrolyte.

FIG. 6 is a circuit diagram showing an example of an air-fuel ratio detection circuit using this oxygen sensor.

This air-fuel ratio detection circuit includes a detection circuit 33 that detects the air-fuel ratio.
and an abnormality determination circuit 34 that determines whether the oxygen sensor 11 is abnormal.
It consists of

First, in the detection circuit 33, the differential amplifier 35 calculates the difference (V a - Vs)
is detected and the difference voltage ΔV is output.

The pump current supply circuit 37 supplies the pump current Ip of the magnitude and direction according to the differential voltage ΔV from the differential amplifier 35 to the pump cell PC of the oxygen sensor 11.
The voltage difference ΔV from 5 is controlled so that ΔV=0 (Vs=Va). Note that a specific example of this pump current supply circuit 67 will be described later.

In other words, the differential amplifier 35 and the pump current supply circuit 37 constitute a current supply means.

Then, the pump current Ip supplied from the pump current supply circuit 37 to the pump anode 23 is converted into a voltage by a resistor 38, and the voltage across this resistor 38 is detected by a differential amplifier 3 days, and the air-fuel ratio detection output Vi Output as .

In other words, the resistor 38 and the differential amplifier 39 constitute current detection means.

On the other hand, in the abnormality determination circuit 34, the amplifier 41 outputs a voltage vb obtained by amplifying the air-fuel ratio detection output Vi from the detection circuit 33 by a predetermined time, and the differential amplifier 42 outputs a voltage vb that is amplified by a predetermined times the air-fuel ratio detection output Vi from the detection circuit 33. Reference voltage (1) Which differential voltage V c (V b - Vl) is detected and output.

The differential amplifier 44 receives a differential voltage V from this differential amplifier 42.
c and the voltage Vp between the pump anode 23 and pump cathode 22 of the pump cell Pc of the oxygen sensor 11 (Vp-Vc) is detected and output.

The first comparator 45 compares the differential voltage Vd from the differential amplifier 44 with the reference voltage v2 from the power supply 46, and when Vd≧v2, outputs the output signal S1 to a high level (H).
Make it.

Further, the second comparator 46 compares the air-fuel ratio detection output Vi from the detection circuit 33 with the reference voltage ■3 (Vs=O), and when Vi<V3(7), that is, the air-fuel ratio detection output Vi When the output signal S2 is negative, the output signal S2 is set to high level (H).
”.

Then, when the output signal S1 from the first comparator 45 and the output signal S2 from the second comparator 46 are both at high level H'', the AND circuit 47 outputs a positive
An abnormal signal S3 of H'l is output.

An example of the pump current supply circuit 37 in this air-fuel ratio detection circuit is shown in FIG.

This pump current supply circuit 37 includes a negative coefficient integrating circuit 50 that integrates the differential voltage ΔV from the differential amplifier 35 and a V that converts the integral output Ve from the negative coefficient integrating circuit 50 into a current.
-I conversion circuit 51.

The negative coefficient integrating circuit 50 includes a resistor 52 . capacitor 53
and an operational amplifier 54, inputs the differential voltage ΔV from the differential amplifier 65, and outputs an integral output VeCVe=−KSΔVdt, which is a positive constant] by integrating the differential voltage ΔV.

Further, the V-I conversion circuit 51 includes an operational amplifier 55° and a resistor 5.
6 and a differential amplifier 57, which detects the voltage across the resistor 56 according to the integral output V'e from the negative coefficient integrating circuit 50 and the pump current I'p supplied to the pump anode 26. Depending on the output, the operational amplifier 55
, a pump current Ip of a magnitude and direction corresponding to the integral output Ve is supplied.

Next, the operation of this embodiment configured as described above will be explained.

First, the pump current supply circuit 37 of this air-fuel ratio detection circuit is connected to the sensor cathode 21 of the sensor cell Sc, as described above.
The potential Vs between the sensor anode 20 and the target voltage Va
A pump current Ip is supplied to the pump cell PC so that.

That is, when the oxygen concentration in the waste introduction section 18 is lower than the predetermined oxygen concentration, as shown by the arrow IR in FIG.
3, oxygen ions are transferred from the pump anode 23 to the pump cathode 22, and the oxygen concentration in the gas introduction section 18 is controlled to a predetermined oxygen concentration.

Further, when the oxygen concentration in the gas introduction section 18 is higher than a predetermined oxygen concentration, a pump current Ip flowing from the pump anode 26 of the pump cell PC toward the pump cathode is supplied, as shown by the arrow IL in FIG. , transfer oxygen ions from the pump cathode 22 to the pump anode 23,
The oxygen concentration in the waste introduction section 18 is controlled to a predetermined oxygen concentration.

In this case, the target voltage Va may be any value as long as it corresponds to the potential Vs generated at the sensor anode 20, but in order to accurately maintain the potential Vs at the target value, it is preferable to The potential v with respect to the change in oxygen concentration of
It is preferable to set the voltage value at a point where the slope of the change in s is the largest, that is, an intermediate value between the upper and lower limits of the voltage value at which the potential Vs suddenly changes in response to a change in oxygen concentration.

Therefore, the target voltage Va is set to, for example, Va = 500m
When set to V, the pump current supply circuit 37 sets the potential V between the sensor anode 20 and the sensor cathode 21.
A pump current Ip is supplied to the pump anode electrode 26 such that V s =500 mV.

Therefore, the oxygen partial pressure in the atmosphere introduction section 15 is PC.

When the oxygen partial pressure in the waste introduction part 18 is PB, the oxygen partial pressure ratio PB/PC is calculated from the above-mentioned Nernst equation ((Equation 11)) as P B / P when the temperature is 1000 K.
C= l O” and PC+0.206aLm, so PR'p
-0,206X10-1'atm.

Here, the oxygen partial pressure in the gas to be measured, for example, the exhaust gas, is P
Assuming A, the amount Q of 02 entering the waste introduction section 18, which is a gap that also serves as a means for restricting gas diffusion, is Q=D (PA-PB), where D is the diffusion coefficient, and PBBO2 Since there is -, D-PA in Q becomes.

An amount of 02 equivalent to the amount Q of 02 is moved through the second solid electrolyte 17 by the pump current Ip to maintain the oxygen concentration in the waste introduction section 18 at a predetermined oxygen concentration, so that IpsuQ Ip- ,・PA...(@). However, K is a constant.

In other words, the value of the pump current 1p is proportional to the oxygen partial pressure in the exhaust gas, which is the gas to be measured.

In this case, the air-fuel ratio (A/F) is lean (λ>1)
On the side, oxygen molecules are pumped into the exhaust gas from the waste introduction section 18.

The above equation q) is valid as is.

On the other hand, on the rich (λ<1) side of the air-fuel ratio, the amount of oxygen molecules in the exhaust gas is extremely small.

The oxygen partial pressure PA will be about 10-'' to 10-'' (equilibrium oxygen partial pressure).

At this time, there are many carbon dioxide molecules C02 in the exhaust gas.

Then, the oxygen partial pressure in this exhaust gas is 10-” to 10-
”, the oxygen partial pressure in the waste introduction section 18 is set to 0, 206
In order to maintain X 10-'', a pump current IP is supplied in the direction of moving oxygen molecules from the exhaust gas atmosphere to the waste introduction section 18, that is, from the pump anode 23 to the pump cathode 22.

Therefore, especially on the surface of the pump anode 23, a reaction of CO2+ 2 e −+ CO+ O− occurs,
The O''- moves within the second solid electrolyte 17 and enters the waste introduction section 18.

As a result, a reaction of 2 CO+ 02→2CO2 occurs, particularly on the surface of the pump cathode 22, and the 02 transferred by the pumping is consumed.

In other words, on the rich side, the 0 consumed by the above reaction
This means that the amount of 2 is measured by the pump current.

The above reaction is proportional to the amount of CO that diffuses within one day from the gas introduction section. That is, in the gas introduction section 18, CO is also consumed by the above reaction, and the 60% partial pressure becomes approximately zero, so that the CO entering the gas introduction section 18 is
The amount of O, Qco, is calculated as follows, where Pco is the 00 partial pressure in the exhaust gas and D' is the diffusion coefficient.

becomes.

Therefore, the amount of 02 necessary to maintain the oxygen partial pressure in the gas introduction part 18 at 0.206X10-'' on the rich side,
That is, the amount of 02 that is pumped out of the exhaust gas atmosphere by the pump current is proportional to the concentration of CO in the exhaust gas.

On the rich side, the concentration of CO (or CO+HC) has a good correlation with the air-fuel ratio, so the pump current Ip continuously changes with the air-fuel ratio even on the rich side.

Therefore, the air-fuel ratio detection output Vi output from the detection circuit 33 changes continuously with respect to the air-fuel ratio from the rich region (λ×1) to the lean region (λ>l), as shown in FIG. .

However, while detecting the air-fuel ratio in the rich range, the oxygen sensor 11
When carbon particles adhere to the surface of the pump cell PC,
Since the pump current IP leaks through the carbon on the surface, the amount of effective current that performs the pumping action to control the oxygen concentration in the waste introduction section 18 to a predetermined oxygen concentration decreases.

As a result, the value of the pump current Ip supplied from the detection circuit 33 to the pump cell PC in order to maintain the oxygen concentration in the gas introduction part 18 at a predetermined oxygen concentration, that is, the air-fuel ratio detection output Vi
The value increases in the negative direction as shown by the dotted line in FIG.

Therefore, in such a case, the air-fuel ratio detection output Vi
does not correspond accurately to the actual air-fuel ratio, so when the air-fuel ratio of the internal combustion engine is feedback-controlled using this air-fuel ratio detection output Vi, it becomes impossible to control the air-fuel ratio to an accurate air-fuel ratio.

Therefore, in this air-fuel ratio detection device, the abnormality determination circuit 34 detects that carbon particles have adhered to the oxygen sensor 11 and the air-fuel ratio detection result is no longer accurate.

Next, the operation of this abnormality determination circuit 34 will be explained.

First, the oxygen sensor 1 input to this abnormality determination circuit 34
The voltage VP between the pump anode 23 and the pump cathode 2-2 of the first pump cell PC will be described.

The equivalent circuit of the pump cell PC can be divided into a self-electromotive force EP and an internal resistance Rp, as shown in FIG.

Therefore, the potential Vp of the pump anode 23 with respect to the pump cathode 22 of the pump cell PC is.

Vp=Ep×Ip−Rp...■.

By the way, as mentioned above, this self-electromotive force Ep is calculated from the Nernst equation mentioned above, where PA is the oxygen partial pressure in the exhaust gas and PB is the oxygen partial pressure in the gas introduction part 18. EP=RT/4F-j2n It is expressed as (PA/pB)+++■.

When the target voltage Va is set to 500 mV, as described above, the oxygen partial pressure PB of the waste introduction section 18 is
It is maintained at approximately 10" a shim.

On the other hand, the oxygen partial pressure (equilibrium oxygen partial pressure) PA in the exhaust gas is
On the rich side, approximately 10
-"atm, and on the lean side it becomes about 10-'atm.

As a result, the self-electromotive force Ep changes as shown in FIG. 10 with respect to the air-fuel ratio (equivalence ratio λ), as can be seen from the above-mentioned equation (2).

On the other hand, if the temperature is constant, the internal resistance Rp is on the rich side,
They are substantially constant on both lean sides, and the pump current 1p has a value proportional to the air-fuel ratio from the rich side to the lean side, as described above. The characteristics change with respect to the equivalence ratio λ) in the same manner as the characteristics shown in FIG. 8 described above.

Therefore, the potential Vp between the pump cathode 22 and the pump anode 23 of the pump cell PC is +11 as described above.
From the formula, it is the sum of the self-electromotive force Ep and the voltage drop of the internal resistance RP due to the pump current Ip (I p - Rp), so the air-fuel ratio (equivalence ratio λ) is as shown in Figure 11. Changes to

Here, when considering the characteristics of the potential VP with the air-fuel ratio detection output Vi as a parameter from FIGS. 8 and 11, the characteristics are approximately linear in the rich and lean regions, as shown by the solid line in FIG. 12. .

However, as described above, if carbon particles adhere to the oxygen sensor 11 in the rich region and the pump current Ip leaks, the apparent pump current Ip increases as shown by the dotted line in FIG. (The characteristics in Figure 11 do not change).

As a result, the potential Vp has characteristics that are erroneous than the actual ones, as shown by the dotted line in FIG.

Therefore, the abnormality determination circuit 34 generates a characteristic corresponding to the solid line in FIG. 12 and compares it with the actual potential VP to determine whether the oxygen sensor 11 is abnormal.

That is, the abnormality determination circuit 34 uses the differential amplifier 42 to convert the air-fuel ratio detection output Vi from the detection circuit 33 into the amplifier 4.
The reference voltage (1) is subtracted from the voltage vb which has been amplified by a predetermined factor in (1).

As a result, the voltage Vc output from the differential amplifier 42
As shown by the dashed line in FIG. 12, on the negative side (rich range) of the air-fuel ratio detection output Vi, the potential VP has a characteristic that substantially matches the potential VP when the oxygen sensor 11 is normal.

Therefore, the difference voltage Vd (VP Vc) between the potential Vp from the pump cell PC of the oxygen sensor 11 and the voltage Vc output from the differential amplifier 42 is determined by the differential amplifier 44, and the first comparator 45 calculates the difference voltage. It is determined whether Vd is equal to or higher than the reference voltage 72, that is, whether or not the actual potential VP deviates from the normal potential VP by a predetermined value 72 or more.

At this time, if the amount of deviation of the potential VP from the oxygen sensor 11 is more than a predetermined value (Vd≧■2), for example, the value shown by the dotted line in FIG. When the air-fuel ratio detection output Vi cannot be obtained, the first comparator 45 sets the output signal S to "H".

On the other hand, in the rich air-fuel ratio range, the air-fuel ratio detection output Vi is negative, so the output signal S2 of the second comparator 46 is also H''.

Therefore, the output signal S3 from the AND circuit 47 is H''
Therefore, it is detected that the air-fuel ratio detection output Vi is not accurate, that is, an abnormality in the oxygen sensor 11 is detected.

As a result, when the air-fuel ratio of the internal combustion engine is feedback-controlled based on the air-fuel ratio detection output Vi, when the output signal S3 from the abnormality determination circuit 34 becomes H,
By discontinuing feedback control and shifting to oven control, it is possible to avoid erroneously controlling an abnormal air-fuel ratio.

In addition, in this example, the abnormality of the oxygen sensor 11 due to carbon (-1 adhesion) is determined only in the rich region, but for example, the influence of carbon adhesion may remain even in the down region after driving in the rich region. be.

In this case, the voltage Vc output from the differential amplifier 42
For example, as shown in FIG. 13, the air-fuel ratio detection output V
Interelectrode potential VP of pump cell PC with i as a parameter
What is necessary is to generate one with approximately the same characteristics as -.

By doing so, it is possible to determine the abnormality of the oxygen sensor 11 over the entire region from the rich region to the rich region.

FIG. 14 is a block diagram showing an example of an air-fuel ratio control device for an internal combustion engine using such an air-fuel ratio detection device.

This air-fuel ratio control device is an electronically controlled fuel injection device (EGI).
) controls the air-fuel ratio of the internal combustion engine that supplies fuel.

First, the basic injection amount calculation unit 61 in the fuel supply system using EGI calculates 1 based on the intake air flow rate Q and the engine rotation speed N.
The basic injection amount Tp of fuel per rotation is calculated.

The various increase correction units 62 adjust the engine coolant temperature Tw.

Various increase corrections (water temperature increase correction) are made to the basic injection amount Tp by the on/off signal of the throttle switch, etc.

Starting and after-start increase correction, after idling increase correction.

(mixture ratio increase correction, etc.) to obtain a corrected injection amount T1.

The fuel cut correction unit 63 multiplies the correction injection MTs by a fuel cut coefficient to produce a correction injection amount when a fuel cut condition is satisfied based on on/off of the throttle switch, engine speed, vehicle speed, etc. Set T2 to zero.

The air-fuel ratio correction section 64 includes an air-fuel ratio correction coefficient determination section 7, which will be described later.
The corrected injection amount T2 is multiplied by the air-fuel ratio correction coefficient α from 4 and output as the corrected injection amount T3.

The battery voltage correction unit 65 corrects the corrected injection amount T3 according to the battery voltage VB and outputs a health signal Ti having a pulse width corresponding to the fuel injection amount.

Thereby, the power transistor 66 or the injector 67 is driven to inject fuel for a time corresponding to the pulse width of the pulse signal Ti. 7. The fuel (for example, gasoline) injected by the injector 67 is mixed with intake air, and the mixture is supplied into the cylinders of the engine and combusted.

Next, parts related to the air-fuel ratio feedback control system will be explained.

First, as mentioned above, the air-fuel ratio detection device 71 consisting of the oxygen sensor (air-fuel ratio sensor) 11 installed in the engine exhaust pipe and the air-fuel ratio detection circuit 70 shown in FIG. The fuel ratio is continuously detected, and the air-fuel ratio detection port 70 detects the air-fuel ratio (A/
In addition to outputting a voltage signal (detection output) ■i indicating F), an output signal (abnormal signal) S is output when the oxygen sensor 11 is abnormal.
Outputs 3.

The target value determination unit 72 sets the control target air-fuel ratio to a target value TL as a value corresponding to the voltage signal VN from the air-fuel ratio detection circuit 70.
Determine.

The differential amplifier 73 calculates the deviation ΔVi (ΔV i
=V i −T L) is detected and output.

The air-fuel ratio correction coefficient determination unit 64 determines an air-fuel ratio correction coefficient α by integrating the deviation ΔVi detected by the differential amplifier 76 using a predetermined integral coefficient, and uses this air-fuel ratio correction coefficient α as an air-fuel ratio feedback. It is output to the correction section 64.

Thereby, as described above, the air-fuel ratio feedback correction section 64 multiplies the air-fuel ratio correction coefficient α by the corrected injection amount T2 corresponding to the predetermined fuel supply amount to correct the fuel supply amount, so that the air-fuel ratio becomes the target. Feedback control is applied to the air-fuel ratio.

At the same time, when the abnormality signal S3 is input from the air-fuel ratio detection device 71, the air-fuel ratio correction coefficient determination unit 74 fixes the air-fuel ratio correction coefficient α to a predetermined value.

As a result, this air-fuel ratio control device receives feedback (
Since the closed) control is stopped and the air-fuel ratio is controlled by oven control, the air-fuel ratio will not be controlled to an incorrect air-fuel ratio, and drivability will not be impaired.

FIG. 15 is a sectional view showing another example of the oxygen sensor used in the present invention.

This oxygen sensor 81 has a through hole 82. between the first solid electrolyte 14 and the second solid electrolyte 17. are stacked across a spacer plate 82 having perforations therebetween to form a waste introduction section 18, and a second solid electrolyte 17 is placed in this gas introduction section 18.
The exhaust sludge is introduced through small holes 83, which are formed in the pump cathode 22 and the pump anode 23, and are means for restricting the diffusion of scum. Note that the other configurations are the same as those in the previous embodiment.

Even when this oxygen sensor 81 is used, by using an air-fuel ratio detection circuit similar to that of the previous embodiment, the air-fuel ratio detection output VP as shown in FIG. 8 and the potential Vp as shown in FIG. can be obtained.

In the above embodiment, an oxygen sensor that uses the atmosphere as a scum with a predetermined oxygen concentration is described, but the present invention is not limited to this. For example, an oxygen sensor whose oxygen concentration has been adjusted to a predetermined value as a calibration scum may be used. You can.

Furthermore, the oxygen sensor is not one in which the means for restricting the diffusion of scum is formed as gaps or small holes as in the above embodiments, but other porous bodies or the like may be used.

Furthermore, the air-fuel ratio detection device according to the present invention can also be used to detect the air-fuel ratio of various internal combustion engines for vehicles, fixed plants, industries, or ships, or to detect the air-fuel ratio of combustion scum in blast furnaces, etc. can.

Effects As explained above, the air-fuel ratio detection device according to the present invention includes a gas introduction section into which exhaust gas from combustion of a mixture of air and fuel is introduced through a means for restricting diffusion of scum;
an oxygen partial pressure ratio detection unit that has electrodes that are exposed to the dregs of the gas introduction unit and gas of a predetermined oxygen concentration, facing each other with an oxygen ion conductive solid electrolyte in between, and outputs a voltage according to the oxygen partial pressure ratio between the two electrodes; and an oxygen partial pressure control section that has electrodes facing each other with an oxygen ion conductive solid electrolyte in between and controls the oxygen partial pressure of the gas introduction section according to the amount of current supplied between both electrodes. A current is supplied to the oxygen partial pressure control unit so that the output voltage of the oxygen partial pressure ratio detection unit of the oxygen sensor matches a preset target value, and the supplied current value is used to determine the air-fuel ratio. In addition to detecting the output of In addition to being able to continuously detect a wide range of air-fuel ratios up to This eliminates the risk of impairing drivability.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing an example of a conventional oxygen sensor, and FIG. 2 is a diagram showing the relationship between the sensor output and the air-fuel ratio. FIG. 3 is a diagram showing the relationship between the injected current and the air-fuel ratio; FIGS. 4 and 5 are a longitudinal sectional view and an exploded perspective view showing an example of an oxygen sensor according to an embodiment of the present invention; FIG. FIG. 6 is a circuit diagram showing an example of the air-fuel ratio detection circuit, FIG. 7 is a circuit diagram showing an example of the pump current supply circuit of FIG. 6, and FIG. 8 is a diagram showing the relationship between the air-fuel ratio detection output and the air-fuel ratio. Figure 9 is a circuit diagram showing the equivalent circuit of the pump cell of the oxygen sensor shown in Figure 4. Figure 10 is a diagram showing the relationship between the self-electromotive force of the bomb cell and the air-fuel ratio. , Fig. 11 is a diagram showing the relationship between the inter-electrode potential of the pump cell and the air-fuel ratio, and Fig. 12 is a diagram showing the inter-electrode potential of the pump cell and the differential amplifier of Fig. 6, similarly using the air-fuel ratio detection output as a parameter. 42 is a diagram showing the output voltage Vc of No. 42. Fig. 16 shows the sixth example using the air-fuel ratio detection output as a parameter.
FIG. 14 is a block diagram showing an example of an air-fuel ratio control device for an internal combustion engine using the air-fuel ratio detection device according to the present invention; FIG. The figure is a sectional view showing another example of the oxygen sensor used in the present invention. 11.81... Oxygen sensor 14... First solid electrolyte 15... Atmosphere introduction part 1
7... Second solid electrolyte 18... Scrap introduction part 20
... Sensor anode 21 ... Sensor cathode 22
... Pump cathode 23 ... Pump anode SC
...Sensor cell (oxygen partial pressure ratio detection section PC...Pump cell (oxygen partial pressure control section) filter 6...Detection circuit 34.
... Abnormality determination circuit 35 ... Differential amplifier 36 ... Power supply 67 ... Pump current supply circuit 6S ... Differential amplifier Applicant Nissan Motor Co., Ltd. Agent Patent attorney Takato Osawa, [F] k Figure 5 3 Figure 7 Figure 8 Figure 13 Width Satoru

Claims (1)

[Scope of Claims] 1 Opposed with an oxygen ion conductive solid electrolyte in between, a waste introduction part into which exhaust gas from combustion of a mixture of air and fuel is introduced via a means for restricting diffusion of waste. An oxygen partial pressure ratio detection part having an electrode exposed to the waste of the waste introduction part and gas of a predetermined oxygen concentration and outputting a voltage according to the oxygen partial pressure ratio between both electrodes, and an oxygen ion conductive solid electrolyte are sandwiched between the oxygen partial pressure ratio detection part and the oxygen ion conductive solid electrolyte. an oxygen sensor comprising an oxygen partial pressure control section that has opposing electrodes and controls the oxygen partial pressure of the waste introduction section according to the amount of current supplied between both electrodes; and an oxygen partial pressure ratio detection section of the oxygen sensor. current supply means for supplying a current to the oxygen partial pressure control unit so that the output voltage of the oxygen partial pressure controller matches a preset target value; and a current for detecting the current value supplied by the current supply means as an output indicating the air-fuel ratio. A detection means and an abnormality determination means for determining an abnormality of the oxygen sensor based on a detection result of a voltage between both electrodes of an oxygen partial pressure control section of the oxygen sensor and a detection result of the current detection means. Characteristic air-fuel ratio detection device.