JPH02271046A - Exhaust gas purifying device - Google Patents

Abstract

PURPOSE:To maintain a high exhaust gas purifying efficiency by performing feedback control based on the added signal for which an air-fuel ratio signal is proportionally amplified at a gain corresponding to an oscillating signal and the driving state around a signal level for which the air-fuel ratio signal is integrated as a center. CONSTITUTION:In an ECU7, a signal from an air-fuel ratio sensor 12 is compared in a standard signal forming circuit 21 and in a comparer 20, and the discriminated signal is proportionally amplified by a proportional amplifier 23 at a gain corresponding to an engine driving state from a CPU 70, and a rectangular wave oscillating signal is output by an oscillating signal generating circuit 24, around an output level of an integrator 22 as a center, its amplitude correspondent with a gain signal. Output signals of the circuits 23, 24 are added by an adder 25, and a fuel emission control signal is determined through a signal of each sensor by the CPU 70, injectors 8 being driven in order through a driver 74. Air-fuel ratio feedback control is thus possible sufficiently taking advantage of exhaust gas purifying ability as much as a catalyst converter of engine exhaust system can achieve, and high exhaust gas purifying effect in a wide air-fuel ratio range can be maintained thereby.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an engine purification device, and more specifically,
The present invention relates to an exhaust gas purification device that performs feedback control to a predetermined air-fuel ratio using an air-fuel ratio sensor provided in an engine exhaust system to maximize the purification function of a three-way catalytic converter provided in an exhaust passage.

[Conventional technology]

In order for the so-called three-way catalytic converter, which functions to remove the three harmful components contained in engine exhaust gas, to work effectively, the air-fuel ratio of the exhaust gas entering the three-way catalytic converter must be close to the stoichiometric air-fuel ratio. need to be kept. For this reason, regardless of whether the fuel supply mechanism is a carburetor type or a fuel injection type, an air-fuel ratio sensor (a so-called 0! sensor based on the action of an oxygen concentration cell) is used in the engine exhaust system to control the intake mixture of the engine. For example, Japanese Patent Application Laid-Open No. 52-4
An air-fuel ratio control method using a conventional air-fuel ratio sensor disclosed in Japanese Patent Publication No. 8738, Japanese Patent Publication No. 62-12379, etc. will be briefly explained with reference to FIG. 10 and FIG. 1). Figure 10(a), Figure 1) (al is the output signal of the O! sensor that generates an output voltage according to the 0□ concentration in the exhaust gas. In Figure 10), Figure 1.1 ) is shown in Figure 10 (a) above.
), 1) Compare the voltage signal in Fig. tar with the reference voltage signal of 0.5 V to obtain a waveform-shaped air-fuel ratio signal. (C), 1st) The air-fuel ratio is controlled proportionally and integrally (PI!#]1ll) as shown in Figure fcl.

The air-fuel ratio sensor detects 0.0% in exhaust gas. This is a device that detects the concentration, and it detects whether the air-fuel ratio during combustion in the engine combustion chamber is smaller than the stoichiometric air-fuel ratio (IL usually about 14.7) (hereinafter referred to as a rich state) or is significantly lean. )
This is to determine whether The amount of fuel supplied to the engine, that is, the air-fuel ratio λ, is controlled as follows according to this discrimination signal.

First, consider the case where the engine speed Ne is low. When the air-fuel ratio sensor output signal is reversed from the lean state to the rich state in Fig. 10 (bl, fcl, middle of Fig. 10), the feedback control amount signal (10 (C)) is delayed by the delay time to cause the lean side to skip by the skip amount B as a proportional amount. From then on, the integral constant (
When the air-fuel ratio signal (in Figure 10) changes from rich to lean, it immediately skips to the rich side by the skip amount B until it changes from lean to rich again. Integration is performed toward the rich side with slope C, and this is repeated in the following operations (see Figure 1).

fcl indicates the feedback control amount signal (Fig. 1) (C)) for the air-fuel ratio sensor output signal (Fig. 1)) when the engine speed Ne is high, and the control method is is the same as The delay time is to compensate for the difference in the detection response delay of the air-fuel ratio sensor output signal when the atmosphere around the detection part of the air-fuel ratio sensor changes from lean to rich or from solid to lean. In the drawings and FIG. 1), the illustrations are exaggerated for explanation purposes. With this control method, the average air-fuel ratio can be controlled to the stoichiometric air-fuel ratio, and the exhaust purification function of the three-way catalytic converter can be maximized.

[Problem to be solved by the invention]

However, as is clear from FIG. 10 and FIG. 1), the control period T and control amplitude A are small when the engine is on the high rotation and high load side, and both T and A are large when the engine is on the low rotation and low load side. This is due to various transmission delays between the time when the controlled air-fuel ratio actually reverses and the time when the air-fuel ratio sensor output reverses. This is because the transmission delay increases at low rotation speeds and low loads. If the transmission delay becomes even larger, as shown in FIG. 10 (fcl), even if the feedback control amount is skipped by B when the air-fuel ratio sensor is inverted, a phenomenon occurs in which the feedback control amount is not inverted and is only inverted after a while of integration. Therefore, the control n period T becomes thicker by the delay time from the reversal of the air-fuel ratio sensor to the reversal of the feedback control tit I, and accordingly, the control amplitude A also becomes larger.As a result, especially when the engine is idling, etc. Vibration (hunting) may cause discomfort to the driver, or when the feedback control amount changes from lean to rich or from rich to lean, as shown in Figure 10 (C) and Figure 1) [c]. Since the waveforms of the engine are different between low engine speed and high engine speed, the variation (difference) in the detection response delay of the air-fuel ratio sensor itself at the time of reversal is slightly shifted, and the predetermined detection response delay shown in Figure 10 is slightly different. There is a problem in that the delay time to be compensated cannot be adapted depending on the engine operating conditions, and the control air-fuel ratio deviates from the stoichiometric air-fuel ratio, deteriorating the exhaust purification characteristics of the three-way catalytic converter.

Furthermore, 0! Due to variations in sensor characteristics and changes over time,
Since it is difficult to always achieve the maximum purification characteristics that can be achieved for each three-way catalytic converter, there are issues such as having to use a three-way catalytic converter with an excessively large capacity with some margin. there were.

The present invention has been made to solve the above-mentioned problems, and aims to provide an exhaust gas purification device that can improve the exhaust gas purification efficiency of a catalytic converter and can also reduce the capacity of the catalytic converter. purpose.

[Means to solve the problem]

The exhaust gas purification device according to the present invention includes an air-fuel ratio sensor, a comparing means for comparing an output signal of the air-fuel ratio sensor with a reference signal and outputting a discrimination signal, and an integrating means for integrating the discrimination signal.
A means for detecting the operating state of the engine, a proportional processing means for proportionally processing the discrimination signal with a gain that is variably set according to the operating state, and a proportional processing means for proportionally processing the discrimination signal with a gain that is variably set according to the operating state. The apparatus includes signal generating means for generating a vibration signal, and means for feedback controlling the air-fuel ratio of the engine based on the addition result of the vibration signal and the proportional processing means.

An exhaust gas purification device according to another aspect of the present invention includes an air-fuel ratio sensor, a comparing means for comparing an output signal of the air-fuel ratio sensor with a reference signal and outputting a discrimination signal, and an integrating means for integrating the discrimination signal. A means for detecting the operating state of the engine; a signal generating means for changing the amplitude according to the operating state and generating a vibration signal centered on the output level of the integrating means; and feedback control of the air-fuel ratio of the engine based on the vibration signal. This means that there is a means to do so.

[For production]

The exhaust gas purification device according to the present invention uses, as an air-fuel ratio feedback control signal, a signal that oscillates around a signal level obtained by proportionally integrating a lean/rich discrimination signal.
The proportional amount of the proportional integral and the amplitude of vibration are changed according to the operating state of the engine.

The exhaust gas purification device according to another aspect of the present invention includes lean,
A signal that oscillates around a signal level obtained by integrating the rich determination signal is used as the air-fuel ratio feedback control signal, and the period of the oscillation is changed depending on the operating state of the engine.

〔Example〕

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

FIG. 1 is a diagram showing the entire system of an embodiment of the present invention, which is a typical fuel injection internal combustion engine using a microcomputer. The engine 1 is a well-known 4-cylinder 4-stroke spark ignition engine installed in a normal automobile, and combustion air is supplied to an air cleaner 2, an intake pipe 4, and a throttle valve 6.
Inhale through. Reference numeral 3 represents a known intake air amount sensor that detects this intake air amount.
It is also possible to employ the intake pipe pressure sensor I5 instead. As the intake air amount sensor 3, various types can be used, such as a potentiometer type, a heat wire type, a Karman vortex type, and an ultrasonic type. 5 is an intake temperature sensor, and 10 is an engine cooling water temperature sensor, of which a thermistor type is generally used. On the other hand, fuel is supplied from a fuel system (not shown) through electromagnetic fuel injection valves (hereinafter referred to as injectors) 8 provided corresponding to each cylinder. The injector 8 is of a constant injection pressure type, and the injection amount is proportional to the valve opening time. The exhaust gas after combustion is transferred to the exhaust manifold 1),
It is released into the atmosphere through the exhaust pipe 13, catalytic converter 14, etc. The air-fuel ratio sensor (0!
The sensor (also referred to as λ sensor) 12 detects the oxygen concentration in the exhaust gas, that is, the deviation of the actual air-fuel ratio from the stoichiometric air-fuel ratio, as a voltage. When the air-fuel ratio is higher than the stoichiometric ratio (lean), it produces an output of about o, hv. The catalytic converter 14 is filled with a three-way catalyst that simultaneously purifies three harmful exhaust gas components (NOx, Co, and 1)C. A signal from the primary terminal of the ignition coil is used as a rotation synchronization signal, and this signal is used to control the injection start timing and calculate the rotation speed. A control circuit (hereinafter referred to as ECU) 7 calculates the optimum fuel injection amount based on the signals from the sensors 3°15.5, 9.10.12 and the battery 16,
Controls the valve opening time of the injector 8.

Next, the internal structure of the ECU 7 will be explained in detail with reference to FIG. A microcomputer 70 is a main part of the ECU 7, and the inside thereof includes a known ROM, RAM, microprocessor, timer controller, etc., and has digital information input/output, calculation, and storage functions. The internal intake temperature sensor 5, engine coolant temperature sensor 10, and battery 1 of the above-mentioned sensors are connected to the microcomputer 70.
6 and the air-fuel ratio feedback control signal based on the output signal of the air-fuel ratio sensor 12 are manually inputted sequentially through the input interface 71 and the A/D converter 72, and the intake air amount sensor 3 is connected to the Karman vortex. If the output pulse signal is proportional to the air flow rate, the output pulse signal is inputted to the input port of the microcomputer 70 via the input interface 73 along with the output signal of the rotation sensor 9 and the input signal 17 of the key switch. ing. On the other hand, the output signal of the air-fuel ratio sensor 12 is input to the inverting input terminal of the comparator 20, and the output signal V1. of the reference signal forming circuit 21 is input to the non-inverting input terminal. ．． is input. The discrimination signal of the comparator 20 is input to an integrator 22 and a proportional amplifier circuit 23. The proportional amplification circuit 23 is configured to receive a signal from the microcomputer 70 according to the operating state of the engine 1 and variably set its gain, and proportionally amplify the discrimination signal from the comparator 20 using the gain. and output. 24 is a vibration signal generation circuit which generates a rectangular wave vibration signal centered around the output signal level of the integrator 22;
The amplitude of the vibration signal corresponds to the magnitude of the gain signal representing the gain Kp manually inputted from the proportional amplifier circuit 23. 25 is an adder which adds the output signal of the proportional amplifier circuit 23 and the output signal of the vibration signal generation circuit 24 and outputs the result to the interface 71. The result of this addition is
It is input to the microcomputer 70 via an interface 71 and an A/D converter 72. 74 is the output boat of the microcomputer 70 and the injector 8
This is the driver connected between the

Here, focusing on fuel injection control (air-fuel ratio control 'fJ), the microcomputer 70 outputs a fuel injection control signal calculated by the method described below via the driver 74,
The four injectors 8 are sequentially driven.

Next, a functional block diagram for such fuel injection control (injector drive time control) is shown in FIG. Basic driving time T.

The basic driving time determining means 30 determines the engine rotation speed per engine revolution from the intake air IIQ information from the intake air amount sensor 3 and the engine rotation speed Ne from the rotation sensor 9. Intake air amount Q/Ne
The information is obtained and the basic driving time T is determined based on this information. Next, a correction coefficient K is determined according to the engine coolant temperature determined by the engine coolant temperature sensor 10. , an intake air temperature correction unit 32 that sets a correction coefficient KAf according to the intake air temperature detected by the intake air temperature sensor 5, and a correction coefficient for acceleration increase according to the rate of change of Q/Ne. An acceleration increase correction means 33 for setting the voltage of the battery 16, and a dead time correction means 34 for setting the dead time (invalid time) T to correct the drive time according to the voltage of the battery 16 are provided in the program of the microcomputer 70. It is now working. Air fuel ratio sensor 1
As a result of the feedback operation based on the detection signal No. 2, the correction coefficient KAF is determined by the air-fuel ratio feedback correction means 35 with the same meaning as the above-mentioned respective correction coefficients.The operation will be explained using FIG.

FIG. 4 (81 shows the waveform of the input signal to the comparator 20. The solid line is the detection output of the air-fuel ratio sensor 12, and the dashed line is the output signal of the reference signal forming circuit 21 that determines the rich or lean judgment level. The reference signal Lay is the standard signal Lay.The comparator 20 compares the magnitude of these re-input signals.
The air-fuel ratio signal (fourth output), which is a lean determination signal, is input to the integrator 22 and the proportional amplification circuit 23. The proportional amplifier circuit 23 inputs a signal corresponding to the load condition of the engine 1 from the microcomputer 70, changes its gain as shown in FIG. do.

For example, the micro combiator 70 obtains the intake air amount Q/Ne information per engine revolution as explained in FIG. If the operating state is larger, it is determined that the operating state is other than that, and a signal corresponding to the result of this determination is output to the proportional amplification circuit 23. The proportional amplifier circuit 23 is shown in FIG.
As shown in C), the gain is set to a relatively small predetermined value in the no-load operating state, and is set to a relatively large predetermined value in other cases.

On the other hand, the integrator 22 integrates the air-fuel ratio signal (FIG. 4(b)) inputted from the comparator 20 as shown by the solid line fdl in FIG. 4, and outputs it to the vibration signal generation circuit 24. The vibration signal generation circuit 24 outputs a rectangular wave vibration signal with an amplitude corresponding to the gain of the proportional amplifier circuit 23 of 2, with the output signal of the integrator 22 as the center, in the waveform shown by the broken line in FIG. 4(d). do.

The amplitude of this vibration signal increases as the gain increases, and it has a period shorter than the inversion period at which the output signal of the comparator 20 is inverted, and in FIG. or 1M of lean) for approximately 2 to 3 cycles. The adder 25 adds the output signal of the proportional amplification circuit 23 (a signal obtained by proportionally amplifying the air-fuel ratio signal of the fourth output) and the output signal of the vibration signal generation circuit 24 (the signal indicated by the broken line in FIG. 4 [dl)]. Then, an air-fuel ratio feedback control signal having a waveform shown by the solid line in FIG. 4 is generated. This signal is a voltage signal corresponding to the air-fuel ratio correction coefficient KAF, and is input to the microcomputer 7G as a digital signal via the interface 71 and A/D converter 72.

Note that the change in gain is made to improve air-fuel ratio controllability (mainly responsiveness) when changing from, for example, a no-load operating state to other operating states.

Due to the above-described operation, the injector drive time T8.

can be calculated by the fuel injection time calculation means (program) according to the following formula as shown in FIG. 3, and this drive time T, 7. Then, the injector 8 is opened at a predetermined timing via the driver 74, in this case, in synchronization with the rotation of the engine 1, twice per revolution, and fuel is supplied to the engine 1.

Tiaj = Ta X K1)t X KAt X
AF + TD to KACX The above fuel injection control (air-fuel ratio control) is based on the air-fuel ratio correction coefficient K explained using Fig. 4.
Except for the feedback control circuit for generating a voltage signal equivalent to AF, already known techniques such as Japanese Patent Publication No. 62-1
The program is realized and operated by the method disclosed in Japanese Patent No. 2379, etc., and explanation of the program operation using flowcharts and the like will be omitted here.

FIG. 5 is an example of experimental results showing the effect of the above operation.

The three-way catalytic converter used as the catalytic converter 14 is a catalyst currently in practical use with a reduced capacity. Fig. 5 (al~(C) (Engine speed 200 Or, p, m, intake pipe negative pressure -335 mmHg,
As shown in Figure 13.81/s), the change in purification efficiency characteristics differs depending on the harmful components contained in the exhaust gas, such as IC, Co, and NOx, but in any case, the average air-fuel ratio A , /F is maintained near the stoichiometric air-fuel ratio, the purification efficiency is improved, and therefore, high purification efficiency is obtained over a wider range of average air-fuel ratios.

As mentioned above, the three-way catalytic converter alternately produces a slightly richer and slightly leaner mixture around the stoichiometric air-fuel ratio, which is better than the exhaust gas purification efficiency when a mixture with a uniform air-fuel ratio is supplied to the engine. Experimental results have shown that the purification efficiency is higher when the water is supplied using Furthermore, according to the results of measuring the purification efficiency characteristics by changing the amplitude and period of the vibration to various values and using a catalytic converter with a small catalyst capacity, it was found that the air-fuel ratio sensor can obtain a rich or lean reversal output response. It has been found that the purification efficiency is improved by supplying rich and lean exhaust gas to the catalyst at a stoichiometric air-fuel ratio at a shorter cycle of approximately 1) to 1/6 than the regular cycle.

Next, a second embodiment of the present invention will be described.

The overall system configuration is the same as in Figure 1, but the ECU
? The internal structure is different from the first embodiment, and FIG. 6 shows the structure. In FIG. 6, the same or equivalent parts as in the first embodiment are given the same reference numerals. 24A is a vibration signal generation circuit which receives the output signal of the integrator 22 and the frequency control signal Vtr*m sent from the microcomputer 70 via the D/A (digital/analog) converter 75, and generates the integrator. A rectangular wave vibration signal is generated centered around the output signal level of 22. This is a so-called voltage controlled oscillator configured such that the frequency of the vibration signal is variably set according to the level of the signal Vtr*s. The output signal of the vibration signal generation circuit 24A is input to the microcomputer 70 as an air-fuel ratio feedback control signal via an input interface 71 and an A/D converter 73.

Since the fuel injection control is the same as that explained using FIG. 3 in the first embodiment, the explanation thereof will be omitted.

Next, the operation for determining the air-fuel ratio correction coefficient KAF will be explained with reference to FIGS. 6 and 7. FIG. 7 fat is the human input signal waveform of the comparator 20, the solid line is the detection output of the air-fuel ratio sensor 12, and the dashed-dotted line is the reference signal of the reference signal forming circuit 21 that determines rich and lean judgment levels. .

The air-fuel ratio signal determined to be rich or lean by the comparator 20 (FIG. 7 [b)) is integrated by the integrator 22 as shown by the solid line +dl in FIG. A rectangular vibration signal centered around the output signal level is output as a waveform shown by the broken line in FIG. 7 (di).

FIG. 7 (cl is the D/A from the microcomputer 70.
An electric signal Vfr@Q for frequency word in input to the vibration signal generation circuit 24A via the converter 75, in this case, the engine rotation speed N obtained from the output of the rotation sensor 9.
A voltage proportional to e is being sent out. The vibration signal generation circuit 24A receives the frequency control electric signal Vfraq and performs change control to increase the frequency of the vibration signal in accordance with an increase in the engine rotation speed Ne. As can be understood by comparing the signal waveform of tel in Figure 7 with the signal waveform of the broken line in Figure 7 (di), the vibration frequency increases as the engine speed Ne increases. The signal exists for about 2 to 3 cycles as shown in FIG. 7 fdl within one rich or lean period of the signal of the 71st peak). As described above, the vibration signal generation rotation 24A is performed as shown in Fig. 7 (e).
) is generated. This signal is the air-fuel ratio correction coefficient K. The microcomputer 70 converts it into a digital signal via the interface 71 and A/D converter 72.
is input. Since the subsequent operations are the same as those in the first embodiment, their explanation will be omitted. In the case of this second embodiment as well, characteristics similar to those shown in FIG. 5 can be obtained.

In the second embodiment, the frequency control electrical signal Vrr*q
is made proportional to the engine rotational speed Ne, but may be made proportional to the intake air amount of the engine, and may be made to correspond to the output of the intake air amount sensor 3 or the intake pipe pressure sensor 15.

Further, the integral characteristic of the integrator 22 may be made different between the direction in which the air-fuel ratio of the air-fuel mixture supplied to the engine is enriched and the direction in which it is equalized.

Next, a third embodiment of the present invention will be described.

The overall system configuration is the same as in Figure 1, but the ECU
The structure inside T is different from the second embodiment, and FIG. 8 shows the structure. In FIG. 8, the same or equivalent parts as in FIG. 6 of the second embodiment are designated by the same reference numerals, and their explanation will be omitted. The third embodiment differs from the second embodiment in that a proportional amplifier circuit 23A with a constant gain and an adder 25 are added. The adder 25 adds the output signal of the proportional amplifier circuit 23A, which receives the output of the comparator 20, and the output signal of the vibration signal generation circuit 24A, and outputs the addition result as an air-fuel ratio feedback control signal to the interface interface 1, A/
The signal is input to the microcomputer 70 via a D converter 72.

Since the fuel injection control is the same as that explained using FIG. 3 in the first embodiment, the explanation thereof will be omitted.

Next, the operation for determining the air-fuel ratio correction coefficient KkF will be explained with reference to FIGS. 8 and 9. FIG. 9 (δ) shows the input signal waveform of the comparator 20, where the solid line is the detection output of the air-fuel ratio sensor 12, and the dashed-dotted line is the reference signal Vref of the reference signal forming circuit 21. FIG. 9 (bl is the waveform of the output signal of the comparator 20, FIG. 9 fcl is the vibration signal generation circuit 24A from the microcomputer 70 via the D/A converter 75.
This is the waveform of the frequency control electric signal Vtr*q that is input to the engine, and is proportional to the engine rotation speed Ne. Fig. 9 (The solid line dl is the waveform of the output signal of the integrator 22, and the broken line is the waveform of the output signal of the vibration signal generation circuit 24A. Fig. 9fa) -
Regarding the operation of obtaining the waveform signal up to Fig. 9fd), see the second section.
Since this is described in the embodiment, the explanation thereof will be omitted.

In addition, a proportional amplifier circuit 2 inputs the output signal of the comparator 20.
3A proportionally amplifies the input signal and outputs it to the adder 25.

The adder 25 adds the output signal of the proportional amplification circuit 23A and the output signal of the vibration signal generation circuit 24A (dashed line in FIG. 9 (di)) to obtain air-fuel ratio feedback of the waveform shown in FIG. 9 (solid line in al). A control signal is generated. This signal is a voltage signal corresponding to the air-fuel ratio correction coefficient KAF, and is input to the microcomputer 70 as a digital signal via an interface 71 and an A/D converter 72. Since this is the same as the first embodiment, its explanation will be omitted.

In the case of this third embodiment as well, characteristics similar to those shown in FIG. 5 can be obtained.

Also in the third embodiment, the frequency control electric signal V fr*
Instead of making Q proportional to the engine speed Ne, it may be made proportional to the intake air amount of the engine.

In each of the above embodiments, the feedback operations shown in FIGS. 4, 7, and 9 have been explained in an analog manner, but for example, the output signal of the comparator 20 or the air-fuel ratio sensor A/D conversion is performed in a time sufficiently shorter than the response time of the fuel ratio sensor 12, and in synchronization with the A/D conversion cycle,
If the subsequent operations are executed, it will become somewhat discrete, but
The operation completely similar to that shown in FIGS. 4, 7, and 9 can be realized, and the same effects as in the above embodiments can be achieved.

〔Effect of the invention〕

As described above, according to the present invention, a vibration signal centered on the signal level obtained by integrating the air-fuel ratio signal is generated, and the amplitude or frequency of this vibration signal is changed depending on the operating state of the engine. Since the air-fuel ratio of the engine is feedback-controlled based on this vibration signal and a signal obtained by adding a signal obtained by proportionally amplifying the air-fuel ratio signal with a gain according to the operating condition or the vibration signal, the air-fuel ratio of the engine is Air-fuel ratio feedback control is now possible to fully utilize the exhaust gas purification ability that the catalytic converter can achieve, making it possible to maintain high exhaust gas purification efficiency over a wider range of air-fuel ratios than before, while also reducing the catalyst capacity. be.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the entire system of an exhaust gas purification device according to an embodiment of the present invention, FIG. 2 is a block diagram of a control circuit system according to a first embodiment of the present invention, and FIG. 3 is a control diagram of a control circuit according to a first embodiment of the present invention. A functional block diagram explaining the operation of the circuit system, Fig. 4 is a signal waveform diagram showing the air-fuel ratio feedback control operation in the first embodiment, and Fig. 5 is an experiment showing the operation results of the conventional method and the embodiment of the present invention. A comparison diagram showing an example of data, FIG. 6 is a configuration diagram of the control circuit system according to the second embodiment, FIG. 7 is a signal waveform diagram showing the air-fuel ratio feedback control operation in the second embodiment, and FIG. 8 is a configuration diagram of the control circuit system according to the third embodiment, FIG. 9 is a signal waveform diagram showing the air-fuel ratio feedback control operation in the third embodiment, and FIG. 10 and FIG. 1) are the air-fuel ratio feedback of the conventional device. FIG. 3 is a signal waveform diagram showing a control iTJ operation. In the figure, I...engine, 3...intake air amount sensor, 4...
...Intake pipe, 6...Throttle valve, 7...ECU,
8... Injector, 9... Rotation sensor, 1)...
・Exhaust manifold, 12... Air-fuel ratio sensor, 13.
...Exhaust pipe, l4...Catalytic converter, 15...Intake pipe pressure sensor, 20...Comparator, 21...Reference signal formation circuit, 22...Integrator, 23.23A... Proportional amplifier circuit, 24° 24A... Vibration signal generation circuit, 2
5...Adder, 70...Micro combinator, 7
1... Interface, 72... A/D converter, 73... Interface, 74... Driver, 7
5...D/A converter.

Claims (2)

[Claims] (1) An air-fuel ratio sensor that is installed in an engine exhaust system that has a catalytic converter that removes harmful components of engine exhaust gas, and that detects an air-fuel ratio from the engine exhaust gas components, and an output signal of the air-fuel ratio sensor. Compare with the reference signal,
a comparing means for outputting a lean/rich discrimination signal; an integrating means having a predetermined integral characteristic for integrating the discrimination signal;
a detection means for detecting the operating state of the engine; a proportional processing means for variably setting a gain in response to a detection signal from the detection means; and proportional processing means for proportionally processing the discrimination signal using the gain; and an amplitude that changes in accordance with the gain. a signal generating means for generating a vibration signal having a period shorter than the inversion period of the discrimination signal centered on the output signal level of the integrating means; An exhaust gas purification device comprising means for feedback controlling an air-fuel ratio of the engine based on the addition result. (2) an air-fuel ratio sensor that is disposed in an engine exhaust system that has a catalytic converter that removes harmful components of engine exhaust gas, and that detects an air-fuel ratio from the engine exhaust gas components; and an output signal of the air-fuel ratio sensor. Compare with the reference signal,
a comparison means for outputting a lean/rich discrimination signal; an integrating means having a predetermined integral characteristic for integrating the discrimination signal; a detection means for detecting the operating state of the engine; and receiving a detection signal from the detection means; a signal generating means that generates a vibration signal having a period that is changed and controlled according to the operating state of the engine, centered around the output signal level of the integrating means; and feedback control of the air-fuel ratio of the engine based on the vibration signal. An exhaust gas purification device comprising means for.