JPS59201947A - Air-fuel ratio controller for internal-combustion engine - Google Patents

Abstract

PURPOSE:To make an air-fuel ratio matchable to a theoretical air-fuel ratio automatically whereby controllable in a stable manner, by storing an integral action time constant prior to one period and a proportional constant in memory, while controlling each of these constants with correction in order. CONSTITUTION:On the basis of each output signal out of a suction pressure sensor 2, a water temperature sensor 3 and an engine speed sensor 4, every operation takes place at a central processing unit 9, and an optimum fuel feed quantity to secure a theoretical air-fuel ratio is calculated. Then, in time of judgment that a feedback control mode is in a state of being executed, an output signal of an O2 sensor 1 is inputted, then a differential portion with the theoretical air- fuel ratio is found, and a solenoid valve 13 is controlled so as to make a fuel feed quantity into feedback control. At this time, an integral action time constant and a proportional constant both are corrected in regular sequence so as to be approximated to the theoretical air-fuel ratio every control at each time. With this constitution, duty as a fuel control signal to an O2 signal is set down to a signal to be constricted along with the elapse of time, thus stable fuel feed control is made possible to be done.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to an air-fuel ratio control device for an internal combustion engine, and particularly to prevention of vibration of a controlled variable in feedback control.

Background Art In recent years, with the rapid development of electronic technology, various devices have been electronically controlled. For example, in automobiles, by controlling the amount of fuel supplied in accordance with load fluctuations, fuel efficiency is improved by always bringing the air-fuel ratio close to the ideal air-fuel ratio. In this case, the conventionally commonly used air-fuel ratio control system for internal combustion engines (
Haha, an oxygen concentration detection sensor (hereinafter referred to as 02 sensor) provided in the exhaust passage detects the oxygen concentration contained in the exhaust gas and outputs an oxygen degree signal. The floor concentration signals of and are compared with the oxygen concentration signal at the ideal air-fuel ratio as shown in Fig.
The signal is converted into the signal shown in . This conversion signal is then integrated into the "H" and "L" parts and converted into a fuel supply control signal, and the opening/closing ratio (duty) of the fuel supply solenoid valve is controlled according to this fuel supply control signal. is configured.

However, in the air-fuel ratio control device for an internal combustion engine using feedback control with the above configuration, since the integral time constant of the integral part X and the proportional time constant of the proportional part Y are always constant, the fuel supply amount is equal to The problem is that the air-fuel ratio only vibrates in the vicinity and cannot be converged to a constant value that is the ideal air-fuel ratio, resulting in a decrease in fuel efficiency and exhaust gas characteristics.

DISCLOSURE OF THE INVENTION Accordingly, an object of the present invention is to reduce the oscillation phenomenon of the control amount that occurs during air/fuel efficiency feedback control as time passes.
It is an object of the present invention to provide an air-fuel ratio control device d for an internal combustion engine that can automatically converge to an ideal air-fuel ratio and perform predetermined control.

In order to achieve such an object, the air-fuel ratio control device for an internal combustion engine according to the present invention stores an integral time constant and a proportional constant from one cycle before, and decreases the integral time constant and proportional constant for each control. By stirring, the air-fuel ratio is converged to the ideal air-fuel ratio.

Therefore, in the air-fuel ratio control device for an internal combustion engine with the above configuration, the oscillation phenomenon of the fuel control amount is prevented and the air-fuel ratio is automatically converged to the ideal air-fuel ratio, so that fuel efficiency is improved and exhaust gas characteristics are improved. It has an excellent effect of improving.

BEST MODE FOR CARRYING OUT THE INVENTION FIG. 2 is a circuit diagram showing an embodiment of an air-fuel ratio control device for an internal combustion engine according to the present invention. In the figure, 1 is a 02 sensor installed in a part of the exhaust passage, 2 is a 2t negative pressure sensor installed in the intake passage and detects intake negative pressure, and 3 is a temperature sensor, which is used to cool the internal combustion engine. Measuring water temperature. 4
is a rotation sensor that detects the rotation of the internal combustion engine. 5～
7 is an analog-to-digital conversion circuit, and 02
The analog outputs of sensor 1, negative pressure sensor 2, and water temperature sensor 3 are converted into digital signals and output. 8 is a rotational speed detection circuit which calculates the rotational speed from the frequency of the pulse signal supplied from the rotation sensor 4 and outputs it as a digital signal. 9 is a central processing unit, and the analog/digital converters 5 to 7
and output signals of the rotational speed detection circuit 8 are taken in from input ports Pl-P4, respectively. 10.11 is a read only memory (hereinafter referred to as ROM) and a random access memory (hereinafter referred to as ILAM),
It is connected to the input port P of the central processing unit 1%9 and the input/output port P6. In addition, ROM10 and 几A
, M11 are omitted.

Reference numeral 12 denotes a solenoid valve circuit connected to the output port P7 of 9 in the central processing unit, which drives the solenoid valve 13 that controls the fuel supply needle to the internal combustion engine according to instructions from the central processing unit 9. do. Hereinafter, the operation of the circuit according to the configuration described in "2" will be explained using the flowchart shown in FIG.

When the internal combustion engine is started without interruption, power is supplied to each of the sensors 1 to 4 and each circuit to start operation. and,
02 sensor 1 generates an output at a level corresponding to the degree of dispersion contained in the exhaust gas, and this output signal is converted into a digital value in the analog fist digital conversion circuit 5 and then sent to the central processing unit 9. It is supplied to input port Pl. In addition, the negative pressure sensor 2 detects and outputs intake negative pressure,
This output signal is converted into a digital value in the analog-to-digital conversion circuit 6 and then supplied to the input port P2 of the central processing unit. The water temperature sensor 3 still detects and outputs the temperature of the cooling water, and this output signal is converted into a digital value in the analog-to-digital conversion circuit 7 and then supplied to the input port Pa of the central processing unit 9. Further, the rotation sensor 4 detects, for example, the rotation of the crankshaft and generates a rotation pulse, and the rotation speed detection circuit 8 outputs a digital rotation speed signal based on the frequency of this rotation. input capo of the central processing unit 9)
Supplied to P4. The central processing unit 9 has a first input capo.
) P2, P3. Negative pressure signal supplied to P4.

By performing various calculations based on the water temperature signal and rotational speed signal, the optimum fuel supply amount to obtain the ideal fuel ratio is calculated, and the solenoid valve drive circuit is configured to supply the fuel amount according to this calculated value. 12 to drive the solenoid valve 13. In this case, the flow rate control by the solenoid valve 13 is performed by varying the opening/closing ratio and duty of the solenoid valve 13. Next, the central processing unit 9 determines whether a feedback control mode instruction is given in step Sl, and determines whether the feedback control mode is instructed or not.
Only if it is S, the process moves to step S2 and the analog
The oxygen concentration signal supplied from the digital converter 5 to the input port PrIk is captured. When the process of step S2 is completed, the process moves to step S3, and it is determined whether the 02 signal taken in in step S2 is larger than the reference value at the ideal air-fuel ratio. . If the determination result in step S3 is No, the process proceeds to step S4, where it is determined whether or not it is a proportional control portion. Here, the determination in step S4 is N.

If so, the process moves to step S5 since it is an integral control part. Then, in this step S5, the previous integration time constant is read out from the AMII and stored in the ROM.
Execute the process of extracting the constant σ' from 1O and subtracting it from the above integral time constant.

Then, the integral time constant modified here is used to execute the integral operation for the integral control section, and the modified integral time constant is stored in the RAM for use in the next control, and the process moves to step S6. Further, if the determination in step S4 is YES, the process moves to step S7, reads out the previous proportionality constant from RAMII, and stores it in R
Correct by subtracting the constant σ read from OM10. Then, the process of the proportional part is executed using this modified proportionality constant, and the modified proportionality constant is stored in the RAM again.
Then, the process proceeds to step S6.

On the other hand, if the determination in step S3 mentioned above is YES, the process moves to step S8, where it is determined whether or not it is a proportional control portion.

If the determination in step S8 is NO, the process moves to step S9, where the same process as step S5 is executed, and then the process moves to step S6. If the determination in step S8 is still YES, the process moves to step S+o, executes the same process as step S7, and then moves to step S6. Tsui!
, shi, Since the integral time constant σ' and the proportionality constant σ are corrected by j1 deviation j order i6 so as to approach the ideal air-fuel ratio for each control, for example, as shown in 4th part 1(a). The duty as a fuel control signal for the 02 information becomes a signal that converges over time as shown in FIG. 4(b), and reaches a stable signal showing a substantially constant value for a predetermined time period A.

As explained above, the nitrous fuel ratio control device for an internal combustion engine using the above-mentioned structure 7 performs 10 control to approach the ideal air fuel ratio by feeding back the signal from the 02 sensor during each fuel supply control. In each control, the proportional constant and the integral time constant υ are stopped at the lit order 1σ, so the control automatically adjusts to the ideal air-fuel ratio as time progresses. Since it is converged and made constant, the vibrations that occur in the conventional system are prevented and stable control can be performed. Furthermore, since the fuel supply control is carried out in parallel, fuel efficiency is improved and exhaust gas characteristics are also improved.

[Brief explanation of the drawing]

Figures 1 (a) and (b) show the air-fuel ratio of 1 for conventional internal combustion engines.
FIG. 2 is a circuit diagram showing an embodiment of the desired fuel-fuel ratio fIi control device 6 for an internal combustion engine according to the present invention, and FIG. 3 is a waveform diagram for explaining the operation of the iIll +nil device. Flowchie F, 61<
Figures (a) and (b) are waveform diagrams illustrating the operation of the circuit shown in the second figure. l...Oxygen sensor (02 Senzan, 2...Negative pressure sensor, 3...Temperature sensor, 4 Rotation sensor, 5~
8...Analog-digital transformation 1. ! :5.8・
...Rotation speed detection circuit, 9...Central processing lp4! device t
ji, 10...Read only memory (ROM)
%11... Jindam access memory (ltAM),
12...71. '48 valve drive circuit, 13... solenoid valve. 1) Shiribahito, Representative Director of New Japan'rMki Co., Ltd.
Yozo Sasaki

Claims (1)

[Claims] (1) The central processing unit calculates and controls the optimum fuel supply amount by processing various signals including at least the intake negative pressure signal and the rotational speed signal, and also indicates the oxygen concentration in the exhaust gas. By supplying the oxygen concentration signal to the central processing unit, in the air-fuel ratio control of the internal combustion engine that executes feedback control according to the difference from the ideal air-fuel ratio, the ideal air-fuel ratio is determined every time the fuel is controlled. By sequentially varying and controlling various constants so as to achieve the desired air-fuel ratio, the fuel supply amount is automatically converged to the ideal air-fuel ratio, making fuel control stable and highly efficient. Air-fuel ratio control device for internal combustion engines.