JPH01104935A - Air/fuel ratio controller for engine - Google Patents

Abstract

PURPOSE:To improve the responsiveness in the air/fuel ratio feedback control by setting the initial control quantity by reflecting the difference of the air/fuel ratio before the change of the operation state into the standard control quantity corresponding to the operation state, when the operation state changes. CONSTITUTION:Air/fuel ratio is varied by controlling a fuel feed device 3 arranged in an intake passage 2 by the control signal supplied from an air/fuel ratio adjusting means 4. An air-fuel ratio correcting means 7 which generates the feedback correction signal corresponding to the deviation between an aimed air-fuel ratio and the detected air-fuel ratio by an air/fuel ratio detecting means 6 is installed. Further, a setting means 8 which sets a standard control quantity according to the engine operation state is installed. The difference between the actual control quantity and the standard control quantity is detected by a difference detecting means 9, and when the operation state changes, the above- described difference before the change of the operation state is reflected into the control quantity after the change of the operation state by a reflexing means 10, while if the above-described difference is over a prescribed value, said reflection is suspended by a reflection suspending means 11.

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 of the air-fuel mixture being supplied to the engine is detected by an exhaust sensor, and the air-fuel ratio is adjusted by adjusting the air bleed of the carburetor so that the detected air-fuel ratio becomes the target value. An air-fuel ratio control device for an engine that performs feedback control for adjustment is known.

Further, in the air-fuel ratio control device as described above, when the air-fuel ratio detection signal does not change continuously for a predetermined period of time, the feedback control is stopped and the feedback signal to the air-fuel ratio adjusting means is fixed. For example, it is publicly known as seen in Japanese Patent Publication No. 54-25973.

(Problem to be Solved by the Invention) However, when performing feedback control of the air-fuel ratio as described above, if acceleration/deceleration is performed by repeatedly depressing the accelerator many times in a short period of time, The amount of fuel supplied tends to increase due to the supply of accelerating fuel by an accelerator pump, etc. and the main fuel dripping, etc., and the supplied air-fuel ratio becomes rich, and accordingly, the air-fuel ratio is adjusted to increase the amount of air bleed by feedback control. Control is performed to shift to the lean side.

At this time, if the operating state changes to idling, etc., the air-fuel ratio of the air-fuel mixture supplied to the engine suddenly becomes over-lean as the supply of increased fuel stops, causing the engine to stop or slow down. occurs.

That is, when accelerating fuel etc. is supplied and the air-fuel ratio of the air-fuel mixture is over-rich, when the operating condition changes from a state where the control amount of the air-fuel ratio adjustment means is large and the detected air-fuel ratio changes to the lean side, No matter what state the control variable is in, if it is a feedback condition, feedback is executed from the control variable. In particular, in idling operation, in order to improve its stability, rapid fluctuations in the control variable are avoided. The amount of change is set small to avoid this.

Therefore, it takes a long time to return from a large overrich control amount to a normal control amount in a steady state, and this feedback control response delay causes the air-fuel ratio of the mixture supplied to the engine to change at the beginning of a change in operating conditions. The engine suddenly becomes over-lean, the engine stops, etc., and it takes a long time to reach a stable operating state.

Regarding the above point, when the operating state changes from, for example, another operating zone to an idle zone, the control amount is fixed at a predetermined value to avoid the occurrence of a large deviation in the control amount due to a delay in feedback control. In this case, it is not possible to perform correction by feedback control for changes in the air-fuel ratio adjusting device such as a carburetor over time, or changes in the atmosphere such as intake air temperature or atmospheric pressure, resulting in the problem that the originally required air-fuel ratio cannot be obtained.

In view of the above circumstances, the present invention provides stable drivability by correcting aging of the air-fuel ratio adjustment device under normal operating conditions, and also prevents engine stoppage due to responsiveness of feedback control when operating conditions change. An object of the present invention is to provide an air-fuel ratio control device for an engine that prevents the occurrence of such problems.

(Means for Solving the Problems) In order to achieve the above object, the air-fuel ratio control device of the present invention includes an air-fuel ratio detecting means for detecting the air-fuel ratio of the air-fuel mixture, an air-fuel ratio adjusting means for changing the air-fuel ratio, an air-fuel ratio correcting means for controlling the air-fuel ratio adjusting means so that the air-fuel ratio falls within a preset range in response to the output of the air-fuel ratio detecting means; and a reference side of the air-fuel ratio adjusting means according to the operating state of the engine. ! a reference control amount setting means for setting the amount of il; a deviation detection means for detecting the deviation between the actual control amount and the reference control amount; and a reflection prohibition means that stops reflecting the deviation in the control amount after a change in the operating state when the deviation is equal to or greater than a predetermined value.

FIG. 1 is an overall configuration diagram for clearly showing the configuration of the present invention.

The air-fuel ratio of the air-fuel mixture supplied to the engine 1 is determined by adjusting the amount of fuel supplied from a fuel supply device 3 such as a carburetor disposed in the intake passage 2, and by adjusting the air-fuel ratio adjustment means such as an air bleed adjustment solenoid of this fuel supply device 3. The air-fuel ratio is controlled by adjusting it using a control signal such as a duty signal from No. 4.

Further, the engine 1 is provided with an air-fuel ratio detection means 6 for detecting the air-fuel ratio of the air-fuel mixture, such as a 02 sensor installed in the exhaust passage 5, and the air-fuel ratio detection signal from the air-fuel ratio detection means 6 is It is output to the correction means 7. The air-fuel ratio correction means 7 outputs a feedback correction signal to the air-fuel ratio adjustment means 4 according to the difference between the detected air-fuel ratio and the target air-fuel ratio so that the supplied air-fuel ratio becomes a target air-fuel ratio within a preset range. It is something to do.

On the other hand, a reference control amount setting means 8 is provided for setting a reference side @JIi1 such as a reference duty signal outputted from the air-fuel ratio adjustment means 4 to the fuel supply device 3 according to the operating state of the engine such as the idle zone, for example, This reference control amount is output to the air-fuel ratio adjusting means 4, and the air-fuel ratio correcting means 7
The control amount that is corrected by the feedback correction signal from and actually output to the fuel supply device 3 is calculated.

Furthermore, the deviation between the actual control amount output from the air-fuel ratio adjusting means 4 and the reference control amount set by the reference control amount setting means 8 according to the current operating state, that is, the correction amount for the reference control amount is determined. A deviation detecting means 9 is provided to detect the deviation, and its detection signal is output to the reflecting means 10. This reflecting means 10 transmits a correction signal corresponding to the deviation detected by the deviation detecting means 9 before the change in the operating state to the air-fuel ratio adjusting means 9 when the operating state changes, such as when moving from another operating zone to the idle zone. The above deviation is reflected in the control amount after the operating state changes, and it reflects the change in the reference control amount due to aging of the fuel supply device 3, the change in the reference control amount due to changes in intake air temperature or atmospheric pressure, etc. The responsiveness of feedback control is improved by correcting the amount of change from the beginning when the operating state changes.

Further, the detection signal of the deviation detecting means 9 is reflected by the reflection inhibiting means 1.
1, and this reflection is reflected by outputting a reflection prohibition signal to the reflecting means 10 when the deviation before the driving state change is larger than a predetermined value at the time of the driving state change as described above. The means 10 stops reflecting the deviation before the change in the control amount after the change when the operation changes, and the control amount by the air-fuel ratio adjusting means 4 at this time is equal to the reference control amount from the reference control amount setting means 8. is set as the initial control amount for feedback control.

(Function) In the engine air-fuel ratio control device as described above, the control amount is basically set using feedback correction control for the reference control amount under the operating condition so that the detected air-fuel ratio becomes the target air-fuel ratio. When the operating condition changes, the initial control amount is set by reflecting the deviation between the control amount before the change and the reference control amount in the reference control amount corresponding to the operating condition. The responsiveness of feedback control is improved by correcting changes in the standard control amount due to changes over time, changes in the standard control amount due to changes in intake air temperature or atmospheric pressure, etc. from the beginning when operating conditions change. .

In addition, for example, the supply air-fuel ratio is enriched by accelerating and decelerating by repeatedly pressing the accelerator repeatedly in a short period of time, and accordingly, the air-fuel ratio is shifted to the lean side by feedback control, which corresponds to the driving state. When the controlled variable has a larger deviation than the controlled variable, and the operating state changes to idling, etc., if the deviation before the operating state change is greater than a predetermined value, this deviation is used as the controlled variable after the change. By stopping the reflection and performing feedback control using the initial control amount after the change as the reference control amount for this operating state, it is possible to change the target value from the target value such as over lean air-fuel ratio that occurs during the response delay of feedback control. This prevents the engine from stopping due to large deviations in the engine speed, and achieves stable operating conditions as soon as possible.

(Example) The present invention will be described in detail below with reference to the drawings.

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

An air cleaner 15, a carburetor 16, and a throttle valve 17 are interposed in the intake passage 2 that supplies intake air to the engine 1 from the upstream side, and an air-fuel ratio sensor 18 (02 sensor), A catalyst device 19 is interposed in each case. The carburetor 16 also includes a fuel tank 2.
0 to the fuel supply passage 2 by the fuel pump 21.
2.

The structure of the carburetor 16 is shown in FIG.
2 is supplied to a float chamber 24, and a main fuel passage 27 is provided which opens from the float chamber 24 to a main nozzle 26 of the venturi portion 2a of the intake passage 2 via a main jet 25. A communicating main air bleed 28 is provided. Also,
A slow jet 2 branches off from the main fuel passage 27.
A slow fuel passage 32 opens to a slow port 30 and an idle port 31 near the throttle valve 17 via a
A slow air bleed 33 communicating with the slow fuel passage 32 is provided.

Furthermore, a main auxiliary air bleed 34 is connected to the main fuel passage 27, and a main duty solenoid valve 35 is installed in this main auxiliary air bleed 34. Further, a slow auxiliary air bleed 36 is also connected to the slow fuel passage 32, and a slow duty solenoid valve 37 is similarly installed in this slow auxiliary air bleed 36. Main and slow duty solenoid valve 35. In '37, a control signal (duty signal) is output from the control unit 38 to control the air-fuel ratio by adjusting the amount of bleed air.

Further, an acceleration pump 41 is provided that supplies acceleration fuel to an acceleration nozzle 40 provided in the venturi portion 2a of the carburetor 16, and this acceleration pump 41 is connected to the float chamber 24.
A pump chamber 45 in which ball valves 43 and 44 are disposed in the front and rear is formed in the middle of the acceleration fuel passage 42 that communicates with the fuel pump. A piston 46 provided in the pump chamber 45 is moved up and down by a rod 47 in conjunction with the throttle valve 17.
When the throttle valve 17 is opened, the piston 46 is pushed, which pushes the ball valve 44 on the outlet side and discharges the fuel in the pump chamber 45 from the acceleration nozzle 40. Furthermore, when the throttle valve 17 is closed, the piston 46 is pulled and fuel flows into the pump chamber 45 through the ball valve 43 on the inlet side.

As shown in FIG. 1, the control unit 38 outputs duty signals to the main and slow duty solenoid valves 35 and 37 of the carburetor 16 to control the air-fuel ratio by adjusting the amount of bleed air. An air-fuel ratio signal from the air-fuel ratio sensor 18 to detect, a negative pressure signal from the negative pressure sensor 50 to detect the intake pressure in the intake passage 2 downstream of the throttle valve 17, and an ignition signal to the distributor 51 to detect the engine speed. A signal from the ignition coil 52 to be output, and a water temperature sensor 5 that detects the cooling water temperature.
The water temperature signals from 3 are respectively input.

Next, the processing of the control unit 38 will be explained based on the flowchart of FIG. After starting, the operating state of the engine 1 is read in step S1 using the engine speed Ne and intake negative pressure Ce (boost value), and in step S2, the reference duty value D corresponding to the basic fuel is determined based on these signals.
Set base (base control amount). This reference duty value Dbase is, for example, 20% in the idle zone based on the map of engine speed Ne and intake negative pressure Ce (load).
%, and the feedback zone is set to 40%.

The duty value 10096 is a control amount that fully opens the duty solenoid valves 35 and 37 to achieve maximum lean.

Next, in step S3, the output R of the air-fuel ratio sensor 18 is read, and in step S4, the output R of the air-fuel ratio sensor 18 is "1".
This air-fuel ratio sensor 18 inverts its output at an air-fuel ratio near the stoichiometric air-fuel ratio, and a state in which it outputs a signal of "1" indicates that the detected air-fuel ratio is richer than the stoichiometric air-fuel ratio. This feedback control uses the stoichiometric air-fuel ratio as the target air-fuel ratio.

If the determination in step S4 is YES and the detected air-fuel ratio is richer than the target air-fuel ratio, in step S5 a predetermined 1x is added to the previous duty correction value DI'b to perform lean correction, If the determination in step S4 is No and the detected air-fuel ratio is leaner than the target air-fuel ratio, rich correction is performed by subtracting a predetermined value X from the previous duty correction value Df'b in step S6. This duty correction value Df
b is the reference duty value D ba as the reference control amount
The duty correction value DI'b is added to se to determine the duty value as the final control amount (step 511 described later), and the duty correction value DI'b is the deviation between the actual control amount and the reference control amount. ing.

In step S7, the absolute value of the duty correction value D['b, that is, the deviation between the actual control amount and the reference control amount set in step S5 or S6 above, is greater than the relatively large set value 1]'bo. This is to determine whether or not.

If the determination in step S7 is YES, in step S8, the change ff1DNe between the currently detected engine speed Ne and the previously detected engine speed Ne■, the currently detected intake negative pressure Ce and the previously detected intake negative pressure Cem is determined. amount of change DC
e is calculated, and in step S9 it is determined whether or not the driving state is changing so that the change QDNe or DCe is larger than the set value DNeo or DCco.

Then, when the determination in step S9 is YES and the operating state changes, the duty correction value Df is determined in step S10.
After setting 'b to 0, the final duty value is determined in step S11 using the basic duty value Dbase and the duty correction value DI'b. Based on this final duty value, in step S12, the main or slow duty solenoid valve 35 of the carburetor 16. A duty signal is output to 37 to execute air-fuel ratio control by adjusting the amount of bleed air. Furthermore, in step S13, memory values Ne11SCcI1 of the engine speed Ne and intake negative pressure Ce are updated.

Note that if the determination in step S9 is NO and the change in the operating state is small, the process directly proceeds to step S11 to perform duty correction value Df'b feedback correction control. Further, if the determination in step S7 is No, the duty correction value DI'b is greater than or equal to the set value Dfbo.

In the case below, even if the reference duty value D base set in step S2 changes when the operating condition changes, the process directly proceeds to step S-11 and the feedback control set in step S5 or S6 is performed. By correcting the reference duty value Dbase with the updated duty correction value Df'b, the duty correction value Dfb before the change in the driving condition is changed when the driving condition changes.
In other words, the deviation between the actual control amount and the reference control amount is reflected in the control amount after the operating state has changed.

However, if the determinations in steps S7 and S9 are YES, and the deviation is larger than the set value and the operating state changes, the duty correction value DI'b is set to 0 in step SIO, and the reflection of the deviation is stopped and the reference value is Duty value D b
This starts feedback control from ase.

FIG. 5 shows a time chart of air-fuel ratio control according to the above embodiment. This time chart shows changes in the air-fuel ratio at A and changes in the duty correction value Df'b at B for changes in the operating state such as repeating acceleration and deceleration from an idling state and then returning to an idling state. , C shows the change in the accelerator operation amount, and D shows the change in the engine speed. In a stable idle state, the duty correction value changes in a small range near O, the air-fuel ratio also changes in a small range near the stoichiometric air-fuel ratio, and a stable idle speed is obtained.

Then, when the accelerator is operated to accelerate or decelerate in a large range from point a, acceleration fuel is supplied by the operation of the acceleration pump 41 accompanying the acceleration operation, and the air-fuel ratio shifts to the rich side, and the duty correction value corresponds to this. becomes a large value as a lean correction, exceeding the set value Df'bo and reaching the upper limit of 100.
%.

When the accelerator is returned to the idle state at point b from this state, the supply of acceleration fuel is stopped and the air-fuel ratio suddenly shifts to the lean direction, but the duty correction value does not reflect the deviation up to that point and is shown in the broken line. As shown in FIG. This may cause the engine to stop. However, as shown by the solid line, if the reflection of the deviation is stopped at point b and the duty correction value is set to 0, the supply amount of bleed air will immediately decrease and the air-fuel ratio will not become over-lean.
A transition to a stable idling state occurs quickly. Moreover, it also prevents an overrich state from occurring when the operating state changes while the air-fuel ratio is shifting toward the lean side.

In addition, in the above embodiment, an example of air-fuel ratio control using a feedback carburetor equipped with an accelerator pump that operates in conjunction with a throttle valve is shown, but it is also applicable to air-fuel ratio control using a fuel injection type fuel supply device. It is. In addition, for detecting the air-fuel ratio, determining the operating state, etc., the well-known techniques of the above example can be appropriately adopted.

(Effects of the Invention) According to the present invention as described above, normally the control amount is set by feedback correction control for the reference control amount in the operating state so that the detected air-fuel ratio becomes the target air-fuel ratio, and the When the state changes, the initial control amount is set by reflecting the deviation before the change in the reference control amount corresponding to the operating state, thereby reducing the amount of change in the reference control amount due to aging of the fuel supply system. , the change in the reference control amount due to changes in intake air temperature or atmospheric pressure, etc. is corrected from the beginning when the operating state changes, improving the responsiveness of feedback control.
You can get stable operation.

In addition, when the operating state changes from a state where the correction value has increased due to repeated acceleration/deceleration, etc., if the deviation before the operating state change is larger than a predetermined value, the reflection of the deviation is stopped. Feedback control is performed using the subsequent initial control amount as the reference control amount for this operating state, and prevents engine stoppages due to large deviations from the target value such as over lean air-fuel ratio that occurs during feedback control response delays. As a result, stable operating conditions can be obtained quickly.

[Brief explanation of the drawing]

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 Fig. 3 is a structural example of a carburetor. 4 is a sectional view, FIG. 4 is a flowchart for explaining the processing of the control unit, and FIG. 5 is a timing chart of an example of air-fuel ratio control when operating conditions change. 1...Engine, 3...Group/Fuel supply device, 4
・Old... Air-fuel ratio adjustment means, 6... Air-fuel ratio detection means, 7... Air-fuel ratio correction means, 8... Reference control amount setting means, 9... ...deviation detection means, 10
...Reflection means, 11 Old...Reflection prohibition means, 1
6...Carburizer, 18...Air-fuel ratio sensor, 34.36...Auxiliary air bleed, 35°3
7...Duty solenoid valve, 38...
····Controller unit. Figure 1 2nd mouth

Claims (1)

[Claims] (1) an air-fuel ratio detection means for detecting the air-fuel ratio of the air-fuel mixture; an air-fuel ratio adjustment means for changing the air-fuel ratio; an air-fuel ratio correction means for controlling the air-fuel ratio adjustment means; a reference control amount setting means for setting a reference control amount of the air-fuel ratio adjustment means according to the operating state of the engine; and a deviation between the actual control amount and the reference control amount. a deviation detection means for detecting the deviation, a reflection means for reflecting the deviation before the change in the operating state on the control amount after the change in the operating state when the operating state changes, and a reflecting means for reflecting the deviation before the change in the operating state in the control amount after the change in the operating state when the deviation is a predetermined value or more; 1. An air-fuel ratio control device for an engine, comprising: a reflection inhibiting means for stopping reflection on a control amount.