JPH03217635A - Air-fuel ratio control device of engine - Google Patents

Abstract

PURPOSE:To secure excellent fuel consumption and emission performance in an air-fuel ratio feedback control system by setting a delay time so as to eliminate discrepancy of the control air-fuel ratio after a lapse of a required delay time since the output of an air-fuel ratio sensor has crossed a criterion value. CONSTITUTION:After a required delay time elapsed since an output from an air-fuel ratio sensor C to an air-fuel ratio judging means D crosses a preset criterion value, a signal for judging variation of the air-fuel ratio is output to a feedback means F. The feedback means F calculates a feedback correction value so as to get a desired air-fuel ratio and outputs the calculated result to an air-fuel ratio adjusting means B. A response characteristic detecting means H detects a signal relating to the response characteristic of the air-fuel ratio sensor C on the basis of a reversing interval of the feedback correction signal, the variation speed of the output of the air-fuel sensor C, etc. A delay time setting means G which received this signal sets a delay time so as to eliminate the discrepancy of the control air-fuel ratio and outputs the delay time to the air-fuel ratio judging means D. Thus, it is possible to get excellent fuel consumption and emission performance.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an air-fuel ratio control device that performs feedback control of the air-fuel ratio of an air-fuel mixture supplied to an engine to a target value.

(Prior Art) Conventionally, for example, the air-fuel ratio sensor detects the air-fuel ratio of the air-fuel mixture supplied to the engine using an exhaust sensor, and performs feedback control of the air-fuel ratio so that the detected air-fuel ratio becomes a target value. For example, the reaction speed when the output crosses a predetermined judgment value corresponding to the stoichiometric air-fuel ratio is different when the air-fuel ratio is changing in the rich direction and when it is changing in the lean direction, and the subsequent air-fuel ratio If air-fuel ratio feedback control is performed based on this air-fuel ratio sensor output as is due to factors such as control response differences, the average state of air-fuel ratio control will deviate from the target value according to the above reaction speed difference, and the feedback control will be affected as a whole. For example, since it deviates from the target value to the rich side or lean side,
As seen in Publication No. 653, when the air-fuel ratio sensor output crosses the judgment value, the air-fuel ratio change detection signal is output after a predetermined delay period has passed depending on the direction, and the air-fuel ratio is changed by feedback control. Techniques for controlling so that the average state becomes a target value are known.

(Problem to be Solved by the Invention) However, when performing feedback control of the air-fuel ratio as described above, the air-fuel ratio sensor may be affected by individual differences due to manufacturing errors of the air-fuel ratio sensor or changes over time during use. The response characteristic changes from the reference state, and there is a problem in that the average value of air-fuel ratio fluctuations due to feedback control deviates from the target value.

In view of the above circumstances, the present invention provides an engine air-fuel ratio control device that corrects individual differences and changes over time in the response characteristics of air-fuel ratio sensors to improve convergence to a target air-fuel ratio. The purpose is to provide

(Means for Solving the Problems) In order to achieve the above object, the air-fuel ratio control device of the present invention, as shown in the basic configuration in FIG. The amount of fuel supplied from a fuel supply device A such as an injector is adjusted and controlled by a control signal such as a fuel injection pulse sent from an air-fuel ratio adjusting means B to the fuel supply device A.

Further, the engine E is provided with an air-fuel ratio sensor C, such as an 02 sensor, for detecting the air-fuel ratio of the air-fuel mixture, for example, in the exhaust passage. The output of the air-fuel ratio sensor C is output to the air-fuel ratio determining means D, and the air-fuel ratio determining means D is set by the delay period setting means G, which will be described later, after the air-fuel ratio sensor output crosses a preset determination value. When a predetermined delay period has elapsed, a signal for determining an air-fuel ratio change is output to the feed hack means F.

The feedback means F calculates a feedback correction value that increases or decreases the current control amount so that the air-fuel ratio detected based on the output of the air-fuel ratio determining means D becomes a preset target air-fuel ratio. This feedback correction value is sent to the air-fuel ratio adjusting means B.

On the other hand, the air-fuel ratio determining means D is provided with a delay period setting means G for setting a delay period. The delay period setting means G receives the output of the response characteristic detection means H, sets a delay period based on a signal related to the response characteristic of the air-fuel ratio sensor C, and outputs it to the air-fuel ratio determination means D.

The response characteristic detection means H detects a signal related to the response characteristic of the air-fuel ratio sensor C, such as the reversal interval of the feedback correction signal and the fluctuation speed of the air-fuel ratio sensor output. Upon receiving the signal, the delay period setting means G sets the delay period in a direction that absorbs the deviation in the control air-fuel ratio.

(Function) The engine air-fuel ratio control device described above basically sets the control amount by feedback control so that the detected air-fuel ratio becomes the target air-fuel ratio. In order to compensate for reaction speed differences, etc., the air-fuel ratio determination means determines the air-fuel ratio when a predetermined delay period set by the delay period setting means has elapsed after the air-fuel ratio sensor output crosses a preset judgment value. The feedback means outputs a change determination signal, and from this point on, the feedback means calculates a feedback correction value corresponding to the change in the air-fuel ratio sensor output and performs an inversion operation. Based on this signal, a delay period is set in the direction of absorbing the deviation in the controlled air-fuel ratio, and an appropriate delay period is set even if the response characteristics vary from the reference state due to individual differences in the air-fuel ratio sensor or changes over time. This setting reduces the deviation of the control air-fuel ratio from the target value, thereby achieving good fuel efficiency and emission performance.

(Example) Embodiments of the present invention will be described below along with the drawings.

FIG. 2 is an overall configuration diagram of a specific example.

A combustion chamber 2 is formed with a variable volume by a piston 4 that is slidably inserted into a cylinder 3 of an engine 1, and one end of an intake passage 5 that supplies intake air to this combustion chamber 2 is connected to an air cleaner 6.
The exhaust gas from the combustion chamber 2 is discharged through the exhaust passage 7. An injector 10 is arranged in the intake passage 5 on the downstream side of the throttle valve 8. Fuel is pumped from a fuel tank 25 to this injector lO by an oil pump 26, and the fuel pressure is adjusted by a fuel pressure regulator 27.

Further, evaporated fuel is adsorbed in the canister 28 , and the adsorbed fuel is released into the intake passage 5 by operating the purge valve 29 .

The air-fuel ratio of the air-fuel mixture supplied to the engine 1 is adjusted by the fuel injection amount from the injector 10, and a control signal (fuel injection pulse) is output to the injector 10 from a controller 15 having an internal CPU, etc. controlled by feedback. Further, the operation of the purge valve 29 is also performed by a control signal from the controller 15. The controller 15 receives an intake air amount signal from an air flow meter 16 which is installed in the intake passage 5 and detects the amount of intake air, and which is placed in the exhaust passage 7 and which detects the air-fuel ratio of the air-fuel mixture based on the oxygen concentration component in the exhaust gas. The air-fuel ratio signal from the air-fuel ratio sensor 17 to detect the engine speed, the engine rotation signal (crank angle signal) from the distributor 18 to detect the engine speed, the water temperature signal from the water temperature sensor 19 to detect the engine temperature from the cooling water temperature, and the throttle. A throttle opening signal from a throttle opening sensor 20 that detects the opening of the valve 8, an atmospheric pressure signal from an atmospheric pressure sensor 21, an intake temperature signal from an intake temperature sensor 22, and the like are input, respectively.

The fuel supply control by the controller 15 calculates the basic fuel injection amount based on the intake air amount and engine speed, performs various corrections such as warm-up increase correction according to the engine water temperature, and performs feedback. In the feedback region where the conditions are satisfied, feedback control is performed so that the detected air-fuel ratio becomes the target air-fuel ratio, and control is performed to adjust the reversal timing of the feedback control by setting a delay time. Further, in the learning region where the learning execution condition is satisfied, a signal related to the response characteristic of the air-fuel ratio sensor 17 is detected from the feedback correction value, and the delay period is learning-corrected based on this.

Next, feedback control of the air-fuel ratio by the controller 15 will be explained based on the flowcharts of FIGS. 3 and 4.

Before explaining the processing of each step, Fig. 5 shows the change characteristics of each value due to this routine.
A) When the output of the air-fuel ratio sensor 17 changes as shown in
02 is response delay T as shown in (B). R+ TOL changes, and this sensor output vO2 is, for example, the stoichiometric air-fuel ratio λ
At points a and C, which cross the judgment value Vs (slice level) corresponding to =1 and transition from lean to rich or from rich to lean, set the delay periods TLR and TRL in the delay counter in (C). At points b and d after the delay period, the sensor output v shown in (D)
The direction of increase/decrease in the feedback correction value CFB, which corrects the increase/decrease in the fuel supply amount in response to changes in O2, is reversed by the P value, and feedback control is performed to increase/decrease by the I value until the next reversal. Then, the inversion interval TI- in the decreasing direction or the inversion interval TI+ in the increasing direction of the feedback correction value CPH is determined, and this inversion interval TI
-, TI+ are signals including a response delay TOR+"Ol- in the response characteristics of the air-fuel ratio sensor 17, and are compared with a reference value and set a delay period TLR+ according to the difference.
This is to perform learning control on TRL.

In the main routine shown in FIG. 3, after control is started, the various signals mentioned above are inputted in step S1, and based on these, it is determined whether the feedback execution conditions are satisfied (S2).

The conditions for executing this feedback are that the engine water temperature is warmed up to a predetermined value or higher, no fuel increase correction has been performed after starting, and the air-fuel ratio sensor 17 is in an active state and its output is not stuck. If the determination in step S2 is YES and the feedback condition is satisfied, in step S3 feedback control is executed so that the detected air-fuel ratio becomes the target air-fuel ratio based on the calculation of the feedback correction value CFB, as shown in the subroutine of FIG. 4. .

That is, in the feedback correction value calculation subroutine of FIG. 4, the process waits for the sensor output vO2 to cross the determination value Vs and invert in step S2l. This judgment is Y
If the sensor output V02 is reversed in ES, it is determined in step S22 whether or not the previously detected air-fuel ratio was rich, and if this determination is YES and the detected air-fuel ratio is reversed from lean to rich, step S23 is performed. The learning value T described later in
A delay period TRL is set in a delay timer according to R and L. Then, in step S24, it is determined whether the delay period TRL has become O, and during the delay period (
If NO), the timer is subtracted in step 32B, and the feedback correction value CFB is set in step S27.
is gradually decreased by the I value. Further, when the determination in step S24 becomes YES and the delay period TRL ends, the process proceeds to step S25 and the feedback correction value CPB is
, and inverts the feedback correction value CFB in the increasing direction.

On the other hand, if the determination in step S22 is NO and the detected air-fuel ratio is reversed from rich to lean, step S28
The delay period TLR is set in the delay timer according to the learned value TLRL. Then, in step S29, it is determined whether the delay period TLR has become O. If the delay period TLR is in the delay period (No), the timer is subtracted in step S31, and the feedback correction value CFB is gradually adjusted in step S32. Increase by I value. Further, when the determination in step S29 is YES and the delay period TLR ends, the process proceeds to step S30, and the P value is subtracted from the feedback correction value CPB to create the feedback correction value CF.
Reverse B in the decreasing direction.

Following the execution of the feedback control as described above, the third
In step S4 in the figure, it is determined whether the operating region is in the learning region L or not. This learning area L is, as shown in Fig. 6,
In the map of load Ce (filling efficiency) and engine speed Ne, there is a region I where the temperature of the air-fuel ratio sensor 17 is approximately the same.
-III, and set the representative zones within these areas 1 to ■ as learning areas L (1 to 3), and based on the learning values TLRL and TRLL set for this learning area, the above areas 1 to ■ Delay period for each area TLR2TRL
This is to set.

If the determination in step S4 is YES and the object is in the learning area L, it is determined in step S5 whether or not learning execution conditions are satisfied. The learning execution conditions are a steady operating state in which the throttle opening is below a predetermined value and the engine water temperature, intake air temperature, and atmospheric pressure are within predetermined ranges.

If the determination in step S5 is YES and the learning execution conditions are met, in step S6 the purge valve 29 is turned OFF to stop the supply of evaporated fuel, and the process proceeds to step S7, where the feedback correction value CFB is increased and reversed at an increment reversal interval TI+.
L(i) and reduced inversion interval TI-L(i) are determined. This sample value T I ” L(i) , T
A guard process is performed in step S8 in which I-L(i) is compared with upper and lower limit values (upper and lower limit values that can occur in normal control),
In step S9, the sample count value i is incremented. When this count value i reaches a predetermined number of times N (Sl
O), delay period learning value TLRL (
n), T skin t(n) is learned and updated, and upon completion of learning, the purge valve 29 is turned ON (
(ready for operation).

Learning value TLt+L(n) in step Sll above,
T+u. The update of L(n) is the sample value TI+L(i)
, TI-L(i) N times average value and reference value TI”Lo,T
1/2 of the deviation from I-Lo is the previous learned value TLRL, (n
-1), TRL (n-1), and updates the sample value so that it approaches the reference value. The above-mentioned reference values TI"Lo, TI-Lo are set based on the values obtained by the air-fuel ratio sensor 17 having reference characteristics. The above-mentioned sample values TI"L(i), 71-L
(i) is the response delay T as shown in FIG. 5 above. R+ TOL and delay period TLR, TRL
It is a value that includes response delay T. , l, ToL becomes large, the inversion interval TI", TI- will also show a large value, and in that case, the delay period TLL" is set so that the inversion interval TI+TI-, that is, the sample value approaches the reference value.
This corrects the control air-fuel ratio by learning and correcting it to a small value.

Further, if the determination in step S4 or S5 is NO,
If it is not in the learning area L or the learning execution condition is not satisfied, the previous learning value TLRL (n-1) is set in step Sl3.
, T RL L (n-1) as the current learning value TtRL (
n), TbLL(n), and the counter is reset in step S14.

The reason why the learning regions 1 to 2 are set and learned as shown in FIG. This would actually reduce detection accuracy, so learning is performed in multiple temperature ranges to improve control accuracy.

According to the embodiment described above, in a steady operating state in which the feedback execution condition is satisfied, when the engine operating state is in the representative learning region L and the learning execution condition is satisfied, the response characteristic of the air-fuel ratio sensor 17 is changed. Measure the reversal interval of the feedback correction value CPH as a signal related to
Delay period T LR + T for fluctuations in response characteristics
By adjusting RL to reduce deviation of the control air-fuel ratio to the rich side or lean side, control accuracy in feedback control for converging the detected air-fuel ratio to the target air-fuel ratio can be improved. .

In the above embodiment, the signal related to the response characteristic of the air-fuel ratio sensor 17 is detected from the fluctuation characteristic of the feedback correction value CFB during steady operation, but this is detected from other signals. It's okay. For example, the output waveform of the air-fuel ratio sensor 17 is shown in FIG.
B) This output waveform is measured and the time from when the air-fuel ratio sensor output starts to change from a constant voltage state on the rich side or lean side until it crosses the judgment value Vs is measured. Even if the measured waveform of the air-fuel ratio sensor is compared with the reference waveform, the signal related to the response characteristic of the air-fuel ratio sensor is obtained and the delay period is corrected by comparing this signal with the reference time. It's good.

(Effects of the Invention) According to the present invention as described above, in the air-fuel ratio feedback control, the air-fuel ratio is determined when a predetermined delay period has elapsed after the air-fuel ratio sensor output crosses a preset determination value. detecting a signal related to the response characteristic of the air-fuel ratio sensor for outputting a determination signal of an air-fuel ratio change by the means;
By setting the delay period in the air-fuel ratio determination means in the direction of absorbing the deviation of the control air-fuel ratio based on this signal, the delay period can be set according to the state of the response characteristic of the air-fuel ratio sensor, and the air-fuel ratio Even if the response characteristics vary from the standard state due to individual differences in sensors or changes over time, it is possible to set an appropriate delay period, reducing the deviation of the control air-fuel ratio from the target value, resulting in good fuel efficiency and emissions. It is possible to ensure performance.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram to clearly show the configuration of the present invention, Fig. 2 is an overall configuration diagram of an engine air-fuel ratio control device showing a specific example of the invention, and Figs. 3 and 4 are processing of the controller. FIG. 5 is an explanatory diagram showing examples of changes in each value in feedback control. FIG. 6 is a characteristic diagram showing a learning area. E, 1... Engine, B... Air-fuel ratio adjustment means, C, 17... Air-fuel ratio sensor, D...
...Air-fuel ratio determination means, F...Feedback means, G...Delay period setting means, H...
. . . response characteristic detection means, 10 . . . injector, 15 . . . controller.

Claims (1)

[Claims] (1) Air-fuel ratio determining means that outputs a determination signal of an air-fuel ratio change when a predetermined delay period has elapsed after the air-fuel ratio sensor output crosses a preset determination value, and the output of the air-fuel ratio determining means In an engine air-fuel ratio control device, the engine air-fuel ratio control device includes feedback means for feedback-controlling the air-fuel ratio of the air-fuel mixture supplied to the engine to a target value using a feedback correction value calculated based on the feedback correction value calculated based on the feedback correction value calculated based on the response characteristic detection means for detecting;
An air-fuel ratio control device for an engine, comprising a delay period setting means for setting a delay period in a direction to absorb a deviation in the controlled air-fuel ratio based on a signal from the response characteristic detecting means, and outputting the delay period to the air-fuel ratio determining means. .