JPS6078340A - air fuel ratio detector - Google Patents

Abstract

PURPOSE:To enable measurement of an air-fuel ratio from a lean to rich region by providing a means for feeding oxygen to the vicinity of an electrode where the diffusion of oxygen is limited by a diffusion resistor. CONSTITUTION:Electrodes 41a and 41b are provided on both surfaces of a solid electrolyte 40 and a diffusion chamber 44 is further formed to cover the electrode 41a by a diffusion resistor 43 having an orifice 42. A solid electrolyte 46 having electrodes 45a, 45b aref provided to a part of the resistor 43. A means for biasing oxygen consisting of the electrode 46, the electrodes 45a, 45b and a power source 48 supplies always a specified amt. of oxygen to the inside of the chamber 44. Since the biasing means is provided in the above-mentioned way, oxygen exists near the electrode 41a in the rich region as well. The air-fuel ratio from the rich to lean region is thus measured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an air-fuel ratio detector, and particularly to an air-fuel ratio detector suitable for use in controlling the air-fuel ratio of an internal combustion engine.

[Background of the invention]

As a conventional air-fuel ratio detector, for example, JP-A-51-4
5587, in which platinum electrodes are provided on the outside and inside of a bag-tubular solid electrolyte, the inner electrode is exposed to the atmosphere, and the outer electrode is brought into contact with the exhaust gas of an internal combustion engine. The output of this detector changes stepwise at the stoichiometric air-fuel ratio (λ=1.0). In other words, in the rich region (λ < i,,o) which is richer than the stoichiometric air-fuel ratio, approximately 800
A high output of mV can be obtained, and in a region where the air-fuel ratio is leaner than the stoichiometric air-fuel ratio (λ>1.0), a low output of about 200 mV can be obtained. This air-fuel ratio detector has now become popular and has been widely used for air-fuel ratio control of internal combustion engines.

However, this detector can only distinguish between rich and lean relative to the stoichiometric air-fuel ratio, whereas in recent years, the necessity of lean burn control of internal combustion engines has been taken up from the viewpoint of energy saving. In order to perform this control, an air-fuel ratio detector whose output changes linearly in a lean region is required.

Various types of such air-fuel ratio detectors have been researched and developed, and one known example is one described in Japanese Patent Laid-Open No. 55-62349.

In this detector, platinum electrodes are provided on both sides of a solid electrolyte, one of the platinum electrodes is covered with a porous diffusion resistor, a current is passed between the two electrodes, and the electromotive force at that time is measured.

This electromotive force changes linearly in the lean region. By reversing the direction of current flow, the electromotive force can be made to vary linearly in the rich region. That is, this detector can measure both lean and rich regions by changing the direction of current flow.

However, in order to be able to measure from a lean to a rich region, a means for switching the direction of current flow with the stoichiometric air-fuel ratio as a boundary is required, which results in a complicated configuration.

[Purpose of the invention]

An object of the present invention is to provide an air-fuel ratio detector that has a simple configuration and is capable of measuring air-fuel ratios from a lean region to a rich region.

[Summary of the invention]

The present invention is provided with an oxygen bias means for sending oxygen to the vicinity of the electrode where the diffusion of oxygen is restricted by the diffusion resistor.

By providing this bias means, oxygen is present near the electrode even in the rich region. Therefore, since the characteristics obtained by shifting the characteristics of the lean region to the rich side are obtained, it is possible to measure from the rich region to the lean region.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of an automobile engine control system equipped with an air-fuel ratio detector according to the present invention. In FIG. 1, 1 is a throttle chamber, 2 is a hot wire intake air amount detector, 3 is an injection valve, 4 is a throttle actuator having a throttle angle sensor, 5 is a spark plug,
6 is a water temperature sensor, 7 is an air-fuel ratio detector according to the present invention, 8 is a crank angle sensor, 9 is an ignition coil, 10 is a microcomputer, 11 is a control circuit for the air-fuel ratio detector 7, 12 is a heater control circuit, 13 is the combustion chamber, and in this system, the air-fuel ratio is varied from the rich region (λ<1) to the rich region (λ
The air-fuel ratio is controlled by detecting the air-fuel ratio using the air-fuel ratio sensor 7 which is capable of detecting the air-fuel ratio in the wide range of (1). That is, when the air-fuel ratio to be controlled is determined by the microcomputer 10 based on the rotation speed, load, water temperature, etc., it is output to the injection valve 3 and the slot actuator 4, and closed-loop control is performed. The intake air amount is detected by an intake air amount detector 2. The air-fuel mixture formed in the throttle chamber 1 enters the combustion chamber 13 and enters the spark plug 5.
ignition, and then the exhaust gas flows into the exhaust pipe 14. At this time, the actual air-fuel ratio is detected by the air-fuel ratio detector 7, and its signal is input to the microcomputer 10 to perform closed-loop control. Note that the air-fuel ratio detector 7 must be heated to a high temperature due to the characteristics of the solid electrolyte used, so a heater drive circuit 12 is provided.

FIG. 2 is a detailed configuration diagram of the microcomputer 10 shown in FIG. 1. Analog input signals include the air amount signal AP from the hot-wire intake air amount detector 2, the water temperature signal TW from the water temperature sensor 6, the throttle opening signal θ from the throttle actuator 4, and the air amount signal from the air-fuel ratio detector 7. There are fuel ratio signals 02, etc., and these signals are sent to the multiplexer 30.
, each signal is selected in a time-division manner and sent to the AD converter 31, where it is converted into a digital signal. The information signal 15 input as an on-off signal is treated as a 1-bit digital signal. Furthermore, pulse train signals CRP and C from the crank angle sensor 8
PP is also input. 32 is ROM.

33 is a CPU, and the CPU 33 is a digital arithmetic processor Fl.
-Central processing unit data, ROM
32 is a storage element that stores a control program and fixed data. RAM 34 is a readable and writable storage element.

The I10 circuit 35 sends signals from the AD converter 31 and each sensor to the CPU 33, and sends the signals from the CPU 33 to the drive circuit 36 of the injection valve 3, the throttle actuator 4, the ignition coil 9, and the heater of the air-fuel ratio detector 7. Send control signal 118% to drive circuit 12 or control circuit 11
-Has a sending function.

The air-fuel ratio detector 7 detects the air-fuel ratio e IJ Sochi region (λ<1)
It can be detected over a wide range from 1 to 1 in the lean region (λ>1). The principle will be explained using FIG.

The solid electrolyte 40 has electrodes 41a and 41b provided on both sides thereof, and a diffusion chamber 44 is configured to cover the electrodes 41a'i by a diffusion resistor 43 having an orifice 42. Furthermore, a solid electrolyte 46 having electrodes 45a and 45b is provided in a part of the diffused resistor 43. The electrode 41 is connected to a measuring device 47, and the electrode 45 is connected to a power source 48.

Here, the oxygen bias means consisting of the solid electrolyte 46, the electrodes 45a, 45b, and the power supply 48 is the main part of the present invention, and first, the operation of the components other than this oxygen bias means will be explained.

There are two types of operation: one is to apply a constant current jlt from the measuring device 47 in the direction shown in FIG. Current may be measured.

The solid line in FIG. 4(a) shows the former example. In other words, 7, stoichiometric air-fuel ratio (at λ = 101, the electromotive force changes stepwise and the lean region (λ) is 1.0)
The starting force also changes. The point at which this electromotive force changes varies depending on the flowing current 111 + 112 and the like. In the $3 figure, orifice 42 restricts oxygen from diffusing into diffusion chamber 44 from the surroundings. Oxygen corresponding to the surrounding oxygen concentration then diffuses. On the other hand, since the current flows from the device 47 in the direction shown in the figure, the oxygen in the diffusion chamber 44 is reduced to oxygen ions at the interface between the electrode 41a and the electrolyte 40.

These oxygen ions conduct ionically through the electrolyte 40 and are oxidized to oxygen at the interface between the electrolyte 40 and the electrode 41b.

That is, due to the oxygen pumping action of the solid electrolyte, oxygen within the diffusion chamber 44 is pumped out. Here, the pumping capacity of the oxygen pump differs depending on the current value flowing into it. If the air-fuel ratio is extremely high and there is a lot of oxygen in the surrounding area, the amount of diffusion from the orifice 42 will be large compared to the pumping capacity. Therefore, since both the surrounding area and the inside of the diffusion chamber 44 are filled with oxygen, the partial pressure difference of oxygen between the two is zero, but since the difference is very small, the electromotive force is close to zero. On the other hand, if the pumping capacity of the pump is sufficiently large compared to the amount of diffusion, the amount of oxygen in the diffusion chamber is close to zero. Therefore, since there is a partial pressure difference in oxygen concentration between the surroundings and the diffusion chamber, an electromotive force is generated.

Note that in the rich region, there is almost no oxygen in or around the diffusion chamber 44, so no electromotive force is generated. Therefore, depending on the method of flowing current between the electrodes, the method shown in Fig. 4 (
The characteristics are as shown by the solid line in a). The air-fuel ratio at which the electromotive force decreases in the lean region is the current flowing into the
11 r ''12, that is, it depends on the pumping capacity.

In addition, in FIG. 3, from the measuring device 47, the electrode 41a
, 41b, the relationship between the limiting current 11 flowing in the direction of the arrow in FIG. 3 and the air-fuel ratio λ is as shown by the solid line in FIG. 4(b). That is, in the lean region (λ>1.0.), a current that increases as the air-fuel ratio increases is obtained. The amount of oxygen diffusing from the orifice 42 is proportional to the surrounding oxygen partial pressure. On the other hand, between the electrodes 41a and 41b sandwiching the solid electrolyte 40,
A voltage (1) sufficient to pump out the oxygen in the diffusion chamber 44 is applied. Therefore, this oxygen pump pumps out all the oxygen that diffuses into the diffusion chamber 44.
It operates so that the partial pressure of oxygen within 4 is maintained at zero. As a result, the oxygen diffused from the orifice 42 and the oxygen pumped by the oxygen pump are balanced, so that the ionic current flowing through the oxygen pump is proportional to the surrounding oxygen concentration. Also, the ion current flowing through the oxygen pump is limited by the oxygen diffusing from the orifice 42, and is therefore referred to as a limiting current. Also, the rich region (λ(1,
At 01, even though a constant voltage is applied between the electrodes 41a and 41b, there are no oxygen ions to be transported, so the current value shifts from the ion conduction region to the electron conduction region, and the current value increases.

In the example of the solid line in Fig. 4 (a) and (b), the lean region (λ) is 1.0) and the rich region (λ (1, (2 values are taken in 11). Therefore, from the rich region Measurements over the entire range are not possible.

In the air-fuel ratio control of an internal combustion engine, the air-fuel ratio range to be controlled is such that the rich region is approximately 0.7<λ<0.8, and the stoichiometric air-fuel ratio is λ=1.0 (±0 .05), and the lean region is approximately 1.2<λ<1.4. Therefore, it is sufficient for the air-fuel ratio detector to take only two values within the range of λ from 0.7 to 0.7 or more.

Oxygen bias means was provided to obtain such characteristics, and as shown in FIG. 3, the solid electrolyte 4
6, electrodes 45a, 45b, and a power source 48. A voltage 1 is applied from the power source 48 between the electrodes 45a and 45b, and a current 12 flows in the direction shown. This oxygen bias means always supplies a constant amount of oxygen into the diffusion chamber 44 from the surroundings. By doing this, even in the rich region (λ<i, o), since oxygen exists in the diffusion chamber 44, the oxygen partial pressure on the electrode 41a side is higher than the oxygen partial pressure on the electrode 41b side. The electromotive force is shown in Figure 3 (a)
is maintained at a high level as shown by the dotted line.

By biasing this constant oxygen amount, the decrease in electromotive force at λ=1.0 at 12=0 is translated to the rich region as shown by the arrow in FIG. 4(a). Also, for the same reason, the electromotive force decreases due to the balance between the amount of oxygen moving through the solid electrolyte 40 and the amount of oxygen diffusing through the orifice 42, as shown by arrow B in FIG. 4(a). Translated to the rich side.

That is, by controlling 12 to bias an appropriate amount of oxygen into the diffusion chamber 44, it becomes possible to detect rich regions as well.

Further, by biasing oxygen as described above, the limiting current characteristic can also be shifted in parallel as shown by arrow C in FIG. 4(b). As a result, even in the rich region of λ<1.0, λ greater than a predetermined λ (for example, λ-0,7)
Linear output (limit current value) as shown by the dotted line
can be obtained.

The amount of parallel movement can be controlled by the magnitude of the current 12.

In this way, the rich region can be detected without converting the supply current value, polarity, etc. as in the past, so even if the air-fuel ratio transiently enters the rich region during operation, the actual air-fuel ratio cannot be detected. All changes can be measured smoothly, and there is no need to worry about entering the electron conduction region, so there is no dead zone and controllability is greatly improved.

FIG. 5 shows a specific configuration of an air-fuel ratio detector according to an embodiment of the present invention to which the above principle is applied.

The solid electrolyte 49 has a cylindrical shape and has an electrode 5 in the hollow part.
0a and 50b are inserted. Further, a third electrode 51 is provided in a cylindrical shape in a part of the solid electrolyte 49, and is protected by a porous coating layer 52, and a membrane-shaped heater 53 is attached to the outer periphery of the third electrode 51. A constant current i1 is supplied to the electrode 50 by a constant current side circuit 11. In addition, a current 12
flow. Furthermore, a current i3 for heating the control circuit 12 and the solid electrolyte 49 to a predetermined temperature, for example 800C, is passed into the heater 53. The current I3 is controlled to keep the current at a predetermined temperature. Note that 11 is injected into the electrode 50a so as to have a negative potential with respect to the electrode 50b, and the electromotive force change Ve and air-fuel ratio at this time are measured.

The operating principle of the air-fuel ratio detector according to the present invention will be explained with reference to FIG. The solid electrolyte 49 is porous,
Oxygen can move within the solid electrolyte 49 through the pores by diffusion. Moreover, since this porous solid electrolyte 49 can also function as a diffusion resistor, the limiting current can be detected by diffusion control. trench, 50% for electrode 50b
When a is set to a negative potential, oxygen ions move as shown by the dotted line in the figure. The limiting current value is measured by the amount of movement and the amount of oxygen moving near the electrode 50a due to diffusion. However, if this continues, the oxygen partial pressure near the electrode 50a becomes small in the rich region of λ<1.0, and a binary problem as shown in FIG. 4 occurs. Therefore, electrode 51'f: 12
flows from the electrode 51 to the electrode 50a by ionic conduction.
Oxygen total bias near . By appropriately selecting 12, the air-fuel ratio can be detected even in the rich region of λ<1.0 as shown by the dotted line in FIG. Incidentally, since the coating material 52 has a Bausis shape with sufficient porosity, oxygen can easily move through diffusion. 7th
The reason why the characteristics do not change as sharply as in FIG. 4(a) in the figure is because the diffusion resistor (in this case, the solid electrolyte 49) is porous in the configuration shown in FIG.
This is due to variations in resistance due to differences in pore diameter depending on location.

However, since this characteristic also provides a one-to-one ratio of 2 with respect to λ, it can be used as a control signal better than the characteristic shown in FIG. 4(a). Note that the example shown in FIG. 5 may be modified to measure the limiting current.

FIG. 8 shows the air-fuel ratio detector of FIG. 5 configured into a probe shape. In FIG. 8(a), the electrode 50 is welded to a support 54, and the support 54 is inserted into an insulating globe 55. Further, the electrode 51 is connected to the column 56, and the heater 53 is connected to the electrode 50a and the column 57, and the heater 53 is connected to the column 56. '57 is inserted into glove 55. Sensor section 5 in FIG. 8(a)
The AA cross section of No. 8 is shown in FIG. 8(b). electrode 50'a,
The solid electrolyte 49, the electrode 51, and the coating layer 52 (heater 53) are arranged in concentric circles.

FIG. 9 shows the overall configuration of the air-fuel ratio detector 7. The glove 55 to which the sensor section 58 is attached is stored in the looper 59 and attached to the exhaust pipe 14. Each electrode and heater wire (50a, 50b,
51 and 531 are taken out by lead wires as shown in FIG.

Note that by forming the sensor portion 58 in a cylindrical shape, it is possible to avoid the influence of changes over time due to thermal stress.

FIG. 10 shows an air-fuel ratio detector composed of a thin plate-shaped solid electrolyte 60. As shown in FIG. 10(a), the solid electrolyte 60 includes an electrode 61a.

A heater 63 is further attached to the sensors 61b and 62, and constitutes a sensor section 64. The operation of the sensor will be explained with reference to FIG. 10(b). The electrode 61a is the electrode 61
A current 11 is caused to flow by the circuit 11a so as to have a negative (low) potential with respect to b. Therefore, oxygen ions are
It moves from 1a towards 61b. At this time, the electrode 61a
Since the porous solid electrolyte 60 in the vicinity of becomes a diffusion resistor, the electromotive force changes stepwise at a predetermined air-fuel ratio.

Also, in this case, even when λ<1.0, the circuits 11b to 12 are applied so that the electrode 62 has a negative (lower) potential with respect to the electrode 61a so that the air-fuel ratio can be detected, and a constant amount of oxygen is biased. . The heater 63 is heated by the heater circuit 12.

FIG. 11 shows the overall configuration of a sensor using a thin plate-like solid electrolyte 60. The sensor section 64 is
stored in an adapter 66 with a looper 65,
It is attached to the exhaust pipe 14.

FIG. 12 shows another embodiment of the thin plate type. The solid electrolyte 67a is for sensing the air-fuel ratio, and has electrodes 68a and 68b attached thereto. The solid electrolyte 67b is for biasing (bumping) oxygen, and is provided with electrodes 69a and 69b, as well as an orifice 70 serving as a diffusion resistor. This 2
By the solid electrolytes 67a, 67b and the intermediate plate 71,
A diffusion chamber 72 is provided which communicates with the outside only through an orifice 70. Furthermore, a solid electrolyte 67a.

A heater 73 is attached to 67b.

The operation of the above sensor will be explained with reference to FIG. 12(b).

Normally, the stain flow jt'! in the circuit 11a! i-solid electrolyte 6
7a to move oxygen ions in the direction of the arrow. When this movement amount and the movement amount of oxygen diffusing into the diffusion chamber 72 through the orifice 70 are balanced, the electromotive force changes stepwise at an air-fuel ratio corresponding to il. Furthermore, here as well, a constant amount of oxygen is biased using the solid electrolyte 6°7b so that the air-fuel ratio can be detected even when λ<1.0. At this time, if an error current fz't is caused to flow through the circuit 11b in the direction of the arrow shown, the oxygen amount corresponding to 12 will be biased.

In the various cell configurations shown above, always +1 and 1
2 is allowed to flow, and oxygen bias and air-fuel ratio detection are performed at the same time.

In addition, in another method, as shown in Figure 13 (a), 12
is applied in a pulsed manner to bias oxygen for a certain period of time (bumping). During this period when pumping is not performed, the air-fuel ratio is detected (sensing) by flowing 11 as shown in FIG. 13(b). Furthermore, instead of the method shown in FIG. 13(b), there is also a method of applying a voltage to the sensor in a pulsed manner as shown in FIG. 13(b) and reading the limit current value at that time to detect the air-fuel ratio. FIG. 13) shows the period of this pumping (solid line) and sensing (dotted line).

Next, a pair of ' polarizations 74a and 74 as shown in FIG.
A method of performing the above-described bombing and sensing of FIG. 13 in a time-divisional manner using multiple sensors will be described. As shown in FIG. 14(a), IP is supplied from the power source 11 so that oxygen moves inside the solid electrolyte 75 into the diffusion chamber 76. This is the pumping action, and even if λ<1.0, the inside of the diffusion chamber 76 will be -1 or AV output. Old Y
H/4'L/Iff End 14 As shown in Figure (b), oxygen is supplied to the diffusion chamber 76 by flowing in the opposite direction to is'elp.
It is then discharged and sensing is performed. The above operation is shown in FIG. FIG. 15(A) shows a state in which ip1&: is applied in a pulsed manner, and FIG. 15(B) shows a state in which 1B is applied. FIG. 15C shows the periods of ponbin y<solid line) and sensing (dotted line), and it can be seen that the control is performed in a time-division manner.

FIG. 16(a) shows that the concentration of 02 and Co in the exhaust gas is λ
This is an indication for Since the CO concentration increases in the region of λ<1.0, there is a possibility that the oxygen transferred to the diffusion chamber 76 for bombing will be consumed by the reaction. Therefore, in order to bias a constant oxygen amount over the entire range of λ, λ
<1,0, more oxygen must be biased. In the process shown in FIG. 16(b), the value of iP is set to λ<
Should the value be increased at 1.0, or should the time T(ip) for applying 12 (pulse width in FIG. 15(a)) be increased when λ<1.0, as shown in FIG. 16(C)? All of the above objectives can be achieved by this method.

The specific structure of the principle diagram shown in Fig. 14 is shown in Fig. 17 and 1.
It is shown in Figure 8. FIG. 17 shows a cylindrical sensor including a porous solid electrolyte 75 and an electrode 74a.

74b is marked with a number corresponding to that in FIG. 14, and a heater 77 is added. In (a> and (b) of Fig. 17, the positions of the electrode 74 and the heater 77 are different. In Fig. 18, the structure is of a thin plate type, and the solid electrolyte 75 is
and electrodes 74a, 74. b corresponds to the number in FIG. Furthermore, a heater 77 and a porous diffusion resistor 78 are added. Based on the above, the air-fuel ratio can be detected over a predetermined range of λ of 2 or more by using a sensor with a simple structure and time-divisionally controlling the injected current or time-divisionally controlling the injected current and applied voltage. A detector is obtained.

Next, the advantages of controlling the engine using the air-fuel ratio detector according to the present invention will be explained.

Figure 19 shows a map of the air-fuel ratio with respect to the load for controlling the air-fuel ratio (A/F) to change depending on the operating condition. controlled. Here, from the viewpoint of power and fuel economy, A/F' is set to be large at partial load (lean range) and small at full load (rich range). One of the features of the air-fuel ratio detector according to the present invention is that it can perform closed-loop control over such a wide range of air-fuel ratios.

Next, control of transient operating conditions using the air-fuel ratio detector of the present invention will be explained.

FIG. 20(a) shows the state change when the accelerator pedal is depressed. (A) is the throttle opening, which changes in a stepwise manner, and following this, the air amount shown in (B) also increases in a stepwise manner. However, as shown in (c), the actual amount of fuel entering the engine increases with a delay, resulting in a shortage of the amount of air indicated by the shaded area. In response to this change in load, if the target air-fuel ratio of map control in Figure 19 changes from high to low as shown in (2), then the diagonal line (E) will change due to the delay in the fuel amount shown in (C). This means that the air-fuel ratio will deviate from the target air-fuel ratio by an amount corresponding to the portion shown in . Also the second
Figure 0 (b) shows the state change when the load is reduced, and the meanings of the symbols correspond to those in (a). Here again, due to the delay in the fuel amount shown in e, a deviation in the air-fuel ratio (shaded area) as shown in (e) occurs. Furthermore, here,
There are cases where the air-fuel ratio suddenly jumps to λ<1.0 at point A, and even in such cases, the present invention always maintains the total λ
An air-fuel ratio detector that can detect the range can detect the trajectory of A/'F without delay.

Moreover, the changes in A/F shown in (e) in FIGS. 20(a) and (b) are all λ<1. Even if it occurs in the O range, it can be detected by the air-fuel ratio detector according to the present invention.

A/
A method for correcting the deviation of F based on the output of the air-fuel ratio detector according to the present invention will be described below.

As shown in Fig. 21, when the load condition changes from ■→■→■→■, the control target for the air-fuel ratio also changes correspondingly, but as explained in Fig. 20, the actual air-fuel ratio is a flaw in tracking, and as shown by the shaded area in FIG. 21, it deviates by ΔX. Here, this ΔXl, Δx2+ Δx3
and the amount of change in air amount Qa as a load ΔQall ΔQa
2. Transient correction of the air-fuel ratio is performed based on ΔQa3.

First, the fuel amount is corrected using the differential value dQ of the amount of change ΔQa in the air amount due to the change in the load with respect to the time t shown in FIG.
This is performed by multiplying a/dt by the correction coefficient by 'k, that is, the correction amount is as shown in equation (1).

Correction amount 2K・(dQa/dt)・---(1) Here, K is a map as shown in FIG. 22, with dQa/dti on the horizontal axis, and is stored in the computer 10. There is.

The transient correction method will be explained using the flowchart of FIG. 23. First, in step 80, the intake air amount QalO before acceleration/deceleration is read as a load. At the same time, the air-fuel ratio (A
/F) MAP, O is read from the map shown in FIG. 19 (step 82). Further, as data after acceleration/deceleration, the intake air amount Qa, 1'e is read (step 84), and the air-fuel ratio to be controlled for this load (A/F 1M p++'(r) is read (step 86).Step 80
．． Based on Qar O+ 'Qa+ 1 read in step 84, in step 88, d Q a / d t
y<calculate. For this dQa/dt, step 9
0, the correction coefficient 'r is read from the map shown in FIG. 22, and in step 92, K-dQa/dte is calculated. Based on this calculated value, in step 94, the following correction is applied: G=G+G' (2). After outputting this G, Δx', which is proportional to the amount of the shaded portion in FIG. 21, is detected and read based on the signal of the air-fuel ratio sensor (step 96). This Δ
Based on X, ' is added to Δx=' from the equation (3) (step 98). This is (2
) is the correction amount of the correction coefficient that will be corrected again if ΔX occurs for some reason even after correction is applied using the formula.
The correction coefficient is rewritten as follows (step 100). This newly determined K is then rewritten as the K at the position corresponding to dQa/dt. When the next transient is detected, d Q
Immediately add reading correction to Kk corresponding to a/dt. In this way, Δxf based on the sensor output is used to calculate the correction amount of the correction coefficient, the correction coefficient Kt is corrected, and the data is constantly rewritten.

This eliminates fluctuations in the air-fuel ratio during transient times.

FIG. 24(a) shows the fluctuation range of the CO concentration when the engine is fully opened, and the air-fuel ratio is in the rich region. Since this CO fluctuation at full throttle is disadvantageous for fuel economy, closed-loop control is performed using the air-fuel ratio detector according to the present invention that can measure (A/F') even in the rich region (see Fig. 24). b
), it is possible to suppress the CO swing width ΔCO.

Next, the advantages of using the above-described air-fuel ratio detector according to the present invention during startup and warm-up will be explained.

FIG. 25(a) is a diagram showing the relationship between time immediately after startup and mixture concentration using water temperature as a parameter.

Each of the O curves shows the relationship when the initial water temperature is Tl*T2. Immediately after starting, the air-fuel mixture is concentrated, and as time passes, it becomes thinner as the water temperature rises. That is, in the warm-up operation state, if an appropriate AZF is given depending on the cooling water temperature, the engine can be operated without waste. By the way, since the air-fuel ratio detector according to the present invention can detect even in a rich region, it enables rich mixture control immediately after starting. If the relationship between the water temperature Tw and AZF shown in FIG. 25(b) is stored in the computer 10, operation can be performed according to this function during warm-up.

FIG. 25(C) is a control block diagram at this time.

The signal from the water temperature sensor 6 is input to the computer 10, A/F'& is determined by the function showing the relationship shown in FIG. 25(b), and the signal is output to the engine system 110. The air-fuel ratio detector 7 is
AZF during warm-up can be optimally controlled by detecting the actual air-fuel ratio and comparing this output with the output indicating A/Fk from the computer 10 to perform closed-loop control.

As explained above, according to the embodiment of the present invention, the air-fuel ratio can be continuously detected even in the limp region where the excess air ratio λ is λ>1.0 or the rich region where λ<1.0. is possible,
This makes it possible to control all air-fuel ratios, and also enables accurate air-fuel ratio control during transient operation.Furthermore, closed-loop control reduces fluctuations in CO concentration during full-throttle operation, significantly reducing fuel consumption. Furthermore, it is effective in reducing fuel consumption by controlling the air-fuel ratio appropriately even during warm-up operation immediately after startup.

〔Effect of the invention〕

According to the present invention, the air-fuel ratio from the lean region to the rich region can be measured with a simple configuration.

[Brief explanation of drawings]

1 and 2 are overall system diagrams of one embodiment of the present invention, FIGS. 3 and 4 are operation explanatory diagrams of one embodiment of the present invention, and FIGS. FIG. 7 is a more specific operational explanatory diagram of an embodiment of the present invention, FIGS. 8 and 9 are overall diagrams of an embodiment of the present invention, and FIGS. 10 and 11 are , FIG. 12 is an explanatory diagram of another embodiment of the present invention, FIG. 13 is a time chart diagram of a modified example of the present invention, and FIG. 14 to 16 are operation explanatory diagrams of still other embodiments of the present invention, and FIGS. 17 and 18 are detailed configuration diagrams of still other embodiments of the present invention. 19 to 24 are explanatory diagrams of an engine control system using the present invention, and FIG. 25 is an explanatory diagram of another engine control system using the present invention. 40.46,49. ．． 60,67.75...Solid electrolyte, 41,45,50,51.61. (32,68°6
9.74... Electrode, 11... Power supply, 47... Measuring device, 48... Power supply, 42.70... Orifice,
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Claims (1)

[Claims] 1. A solid electrolyte, first and second electrodes provided on the solid electrolyte, and means for restricting the diffusion of oxygen in the measurement gas to the first electrode. , an air-fuel ratio detector for detecting an air-fuel ratio based on an electric signal obtained between the two electrodes, comprising means for delivering a predetermined amount of oxygen to the vicinity of the first electrode; Detector. 2. In the device described in claim 1, the feeding means includes a second solid electrolyte and a third solid electrolyte provided thereon. The fourth electrode is arranged near the first electrode, and is characterized in that all of the oxygen around the third electrostrictive electrode is supplied to the fourth electrode via the second solid electrolyte. Air-fuel ratio detector. 3. In the device described in claim 1, the feeding means transports oxygen around the third electrode from the third electrode provided on the solid electrolyte through the solid electrolyte. An air-fuel ratio detector characterized in that the air-fuel ratio is supplied near the first electrode. 4.% The air-fuel ratio detector according to claim 2 or 3, wherein the feeding means always feeds oxygen into the vicinity of the first electrode. 5. In the item described in claim 2 or 3, the oxygen supply by the supply means and the air-to-air ratio Q-output by the electric signal are performed alternately. Air-fuel ratio detector. 6. In the device described in claim 1, the feeding means is means for flowing a current from the first electrode to the second electrode, and the feeding means is a means for flowing a current from the first electrode to the second electrode, and the feeding means is a means for flowing a current from the first electrode to the second electrode, and the feeding means is a means for flowing a current from the first electrode to the second electrode. An air-fuel ratio detector characterized by alternately detecting signals. 7. The air-fuel ratio detector according to claim 1, wherein the amount of oxygen fed by the feeding means is varied according to the air-fuel ratio. 8.% Permissible scope of claim 1 In the device described in claim 1, the electric signal is a voltage generated between both electrodes when a current is passed so as to pump oxygen near the first electrode toward the second electrode. An air-fuel ratio detector characterized by being a signal. 9. The device according to claim 1, wherein the electric signal is a limiting current signal that flows when a voltage is applied to pump oxygen near the first electrode toward the second electrode. Air-fuel ratio detector.