JPH04339148A - Control device for air-fuel ratio of engine - Google Patents

Abstract

PURPOSE:To improve responsibility to the slippage of a air-fuel ratio by determining whether learning value having learned before leaving a learning domain is used as it is or new learning value is established basing on the length of a time for which the control domain of the air-fuel ratio stays in a domain except the learning domain after leaving the learning domain. CONSTITUTION:A previously established learning domain is kept as a map, and learning value is computed on the slippage of the air-fuel ratio of an air-fuel mixture detected by an airflow sensor 20a and O2 sensor 26, and time having elasped after escaping after the learning domain until shifting to it again is measured. When the measured time is judged to be shorter than previously established time, a fixed air-fuel ratio control is executed using the learning value obtained by the previous judgement, and on the other hand, the longer a term having elasped after escaping from the learning domain until entering the learning domain again becomes, the more the frequency of the use of the learning value obtained by the previous computation is reduced. Finally the width of injection pulse is computed on the above learning value for giving a control signal to an injector 11, and the fuel conforming to the above value is jetted.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio control device for an engine, and more particularly to an air-fuel ratio control device for an engine that performs learning control of an air-fuel ratio.

0002

[Prior Art] Conventionally, the air-fuel ratio of an engine is controlled by learning control, but the change in environmental conditions when the engine is restarted after a long period of time after the engine has been stopped, or when the air flow meter In order to prevent the air-fuel ratio from shifting due to age-related deterioration of the fuel system such as the engine and injector, where different amounts of fuel are injected for the same injection signal, the air-fuel ratio feedback correction coefficient is calculated based on the air-fuel ratio discrepancy. The learned value of the air-fuel ratio is set by calculating and averaging the values. This learned value is weighted and used each time the engine is started.

Further, feedback is temporarily stopped within the feedback region, and steady lean control is performed in which the air-fuel ratio is made lean by a predetermined amount based on the calculated learning value.

0004

[Problem to be Solved by the Invention] However, in the above-mentioned conventional engine air-fuel ratio control device, when the engine is restarted immediately after stopping, if the learning value is weighted every time the engine is started, there is no deviation in the air-fuel ratio. Nevertheless, learning control is executed, and the air-fuel ratio deviates because the learned value is not used during the learning time. Further, as described above, when lean control is performed using the learned value as a reference, there is a problem in that the execution of lean control is delayed, so the opportunity to perform lean control itself is reduced.

[0005]Furthermore, if the frequency of learning control to detect deviations in the basic injection amount is low, there is a problem that temporary deviations in the basic injection amount cannot be followed, which weakens the effectiveness of lean control and causes deterioration of driving performance. .

[0006]

[Means for Solving the Problems] The present invention has been made for the purpose of solving the above-mentioned problems, and has the following configuration as a means for solving the above-mentioned problems. That is, in a preset learning area, a calculation means for calculating a learned value based on a deviation in the air-fuel ratio of the air-fuel mixture, a storage means for storing the learning value calculated by the calculation means, and a storage means for storing the learning value in the storage means. an air-fuel ratio control device for an engine, comprising: updating means for updating a learned value that has been learned; a comparison means for comparing the time measured by the measuring means with a preset time; and when the comparing means determines that the time measured by the measuring means is shorter than the preset time, the updating means performs a learning process. and control means for prohibiting update of the value and performing predetermined air-fuel ratio control using the learned value in the storage means obtained in the previous determination.

[0007] Preferably, the air-fuel ratio control device for the engine includes a hot wire air flow sensor, and when the stay time in the high load region within the set period is short, the control means uses the previous learned value calculated by the calculation means. use. Preferably, the control means decreases the degree of use of the previous learning value by the calculation means, the longer the period from exiting the learning area to re-entering the learning area.

[0008]

[Operation] In the above configuration, the time from escaping the air-fuel ratio learning control area to re-entry is measured, and based on the result, the previous learning value is used as is, or learning is re-executed. It functions to determine the

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 is a diagram showing the overall configuration of an engine air-fuel ratio control device (hereinafter referred to as the device) according to an embodiment of the present invention. In the figure, a piston 2 is sliding in a combustion chamber 3 of an engine body 1, and an intake port 4 and an exhaust port 6 are supported in the combustion chamber 3. Further, an intake valve 7 is provided between the intake port 4 and the combustion chamber 3, and an exhaust valve 8 is provided between the exhaust port 6 and the combustion chamber 3.

A throttle valve 9 for controlling the amount of intake air is provided upstream of the intake port 4, and a surge tank 10 serving as an intake expansion chamber is provided downstream of the throttle valve 9. Further downstream, there is an injector 11 that injects and supplies fuel.
is provided. The amount of intake air into the intake port 4 is detected by the air flow sensor 20a in the air flow meter 20, and the temperature of the intake air is detected by the intake air temperature sensor 21.
Engine water temperature is detected by a water temperature sensor 5. The air flow sensor 20a is a sensor composed of a hot wire, and the wire is cooled at a higher rate as the amount of air flowing through the air flow meter 20 increases, and the wire is designed to keep the temperature constant. The amount of intake air is detected by the current value.

The throttle opening sensor 22 includes an idle switch (not shown) and detects the opening of the throttle valve 9. Further, the distributor 15 is provided with a rotational speed sensor 25 for detecting the engine rotational speed, and the exhaust port 6 is provided with an O2 sensor 26. Evaporated fuel from the fuel tank 18 due to temperature rise is adsorbed by the canister 17, and the evaporated gas is absorbed into the intake port 4 after being turned on and off by a purge control valve 16 controlled by an engine control unit (ECU) 30. Ru.

[0012] The engine control unit (ECU) 30 is
In addition to receiving outputs from the above-mentioned sensors, it also sends an ignition time control signal to the distributor 15 and a control signal to the injector 11 to adjust the fuel injection amount. Next, air-fuel ratio control in the apparatus of this embodiment will be explained in detail. FIG. 2 is a flowchart showing the air-fuel ratio control procedure in the apparatus of this embodiment. In the figure, in step S1, the engine control unit (ECU) 30 outputs various signals such as vehicle speed V based on the output from the rotation speed sensor 25, throttle opening TVO detected by the throttle opening sensor 22, and Air flow sensor 2
Read the intake air amount detected at 0a. Step S2
Now, the basic injection pulse width TP corresponding to the basic fuel injection amount determined by the engine speed and the intake air amount is calculated.

[0013] In step S3, the engine control unit (E
The CU 30 refers to the map shown in FIG. 3 to determine whether or not the air-fuel ratio control region is in the feedback region. As is clear from FIG. 3, this air-fuel ratio control region is divided into a feedback region and a high-load region, which are determined by the engine speed and engine load. (shaded area in FIG. 3). This lean region corresponds to a case where the engine speed is medium rotation and the engine load is medium load, and is a region used during steady running. Further, in a high load region, fuel increase correction is performed.

If the determination result in step S3 is YES, then in step S4, a counter 2, which is a counter for measuring the time during which the air-fuel ratio control stays in the high load region, is reset. In the following step S5, it is determined whether the control region is in the lean region or not. If the determination result in step S5 is YES, a counter 1 is set in step S6 for measuring the time when lean control of the air-fuel ratio shifts from execution to non-execution. Then, in step S7, it is determined whether a learning flag FLRN, which will be described later, is 0 or not. As a result of this determination, if the learning flag FLRN is 0, it is determined that the learning control described later has not been completed, and it is determined in step S8 whether the learning condition is met.

The learning conditions include whether the engine is in a steady operating state with small changes in throttle opening, whether the feedback correction coefficient CFB (described later) is within a predetermined range, and whether the fuel supply is increased after starting or during deceleration. It is determined whether this corresponds to a non-increase state, which is not an increase state. The reason for making these judgments is that a sudden change in the throttle opening may cause a deviation in the air-fuel ratio, and if there is a large fluctuation in the feedback correction coefficient CFB, the engine may be in an abnormal state. , when increasing the amount of fuel, learning the amount of increase leads to erroneous learning, and in the end,
This is because true learning cannot be performed even if learning control is executed in these states.

If the determination result in step S8 is YES, and the learning condition is satisfied, it is determined in step S9 whether or not this condition is satisfied for the first time. Then, if the determination in step S9 is YES, in step S10,
A timer T is set for executing purge cut, which will be described later. In the following step S11, it is determined whether or not the value of the timer T is 0. If not, in step S12, the purge control valve 16 is turned on and a purge cut is executed.

In the next step S13, feedback control of the air-fuel ratio is performed, and a feedback correction coefficient CFB, which is a coefficient for adjusting the air-fuel ratio to a target value, is calculated based on the value detected by the O2 sensor 26. In the following step S14, samples of the feedback correction coefficient CFB obtained in step S13 are accumulated in order to obtain a learning value in learning control. Then, in step S15, the timer T is decremented by 1 and the process moves to the next step.

When it is determined in step S11 that the timer T is 0, the air-fuel ratio feedback control is stopped in step S16, and in the next step S17, the average value CLRN of the feedback correction coefficient CFB accumulated in step S14 is calculated. calculate. Then, in step S18, the learning flag FLRN indicating the execution state of the learning control is set to 1 to end the learning control.

The purge cut in step S12 is as follows:
Learning control of the air-fuel ratio is originally intended to correct changes in the fuel system over time, and if the purge is turned on, the air-fuel ratio will be distorted, so if you perform the learning control with the purge turned on,
This is because it does not allow learning of air-fuel ratio deviations caused by deterioration of the injector or air flow meter. In other words, learning control determines the learned value of how far the air-fuel ratio, which is the basis for executing lean control of the air-fuel ratio, deviates, and then calculates the reference value of how much the air-fuel ratio should be corrected to the lean side. It is something that creates Note that the deterioration of the air flow meter refers to, for example, a decrease in sensitivity due to dust etc. adhering to the hot wire.

On the other hand, if the determination in step S7 is NO, it is assumed that learning control has been completed, and in step S20,
The lean coefficient CLEA is set so that the air-fuel ratio is on the lean side by a predetermined value based on the average value CLRN obtained in step S17.
Calculate N. Further, if the determination in step S5 or step S8 is NO, it is assumed that the air-fuel ratio control is not in the lean region or the learning condition is not satisfied, and the process proceeds to step S21, where it is determined whether the counter 1 is 0 or not. do. If this determination result is YES, it means that the count of counter 1 has finished and a predetermined time has passed since the lean control of the air-fuel ratio was shifted from execution to non-execution.
If the learning flag FLRN is set to 0 and the learning conditions are met, learning control can be executed again.

However, if the determination in step S21 is NO, it is assumed that a predetermined time has been counted since lean control transitioned from execution to non-execution, and counter 1 is decremented by 1 in step S23. Next step S2
In step 4, since the air-fuel ratio control at this time is in the feedback region, feedback control is performed. If the determination result in step S3 is NO and the air-fuel ratio control is in the high load region, it is determined in step S31 whether the value of counter 1 is 0 or not. If the determination result is NO, counter 1
is in the process of counting a predetermined time, and the process proceeds to step S32.
If the determination result is YES, the learning flag FLRN is decremented in step S33.
Set to 0.

In step S34, the above-mentioned counter 2 is incremented to update the stay time in the high load area. Then, in step S35, the coefficient CE for high load increase is
Calculate R. Note that the value of counter 1 and the value of counter 2 have the relationship shown in FIG. 4, and as counter 2 counts up and increases its value, the value of counter 1 decreases. Furthermore, in addition to counting the residence time in the high load region by the counter 2, the counter 1 also counts the elapsed time after the lean control transitions from execution to non-execution in the feedback region as air-fuel ratio control. In other words, even if the hot wire is exposed for a long time to an area where the amount of intake air is small, the rate at which the hot wire is contaminated with dust is small, and it can be determined that its characteristics are less affected by misalignment.

In step S40, other corrections such as acceleration increase are performed, and in subsequent step S41, the following equation (
1) Calculate the final pulse width T. T=TP×(1+CFB+CLEAN+CER+
CLRN+C)+TV...(1) Here, TV is the invalid injection time and C is a constant. Step S
In step S42, the injector 11 is controlled and the process proceeds to step S41.
Fuel injection is performed according to the pulse width T determined in .

As explained above, according to this embodiment,
The time that the air-fuel ratio control region stays in a region other than the lean region from the lean region as the learning region is counted, and the time when the air-fuel ratio control region stays in a region other than the lean region is counted and the time is determined when the air-fuel ratio control region exits the learning region, such as when it exits the steady lean control region due to temporary acceleration or deceleration. If the time it takes to return to the learning area again is shorter than the predetermined time, the learning value learned before leaving the learning area can be used as is, reducing the time until lean control is resumed and improving responsiveness to air-fuel ratio deviations. It has the effect of improving the

Furthermore, if the time it takes to return to the learning area is longer than a predetermined time, a new learning value is calculated when returning to the learning area, so that changes in environmental conditions and engine This has the effect of suppressing the influence of deviations in the air-fuel ratio caused by deterioration of the fuel system, etc., and improving the accuracy of the learned value.

[0026]

[Effects of the Invention] As explained above, according to the present invention,
The time taken to escape from the air-fuel ratio learning control area and re-enter is measured, and if that time is short, the previous learning value is used to quickly control the air-fuel ratio to the required air-fuel ratio and escape from the learning control area. Then, if the time until re-entry is longer than a predetermined time, the learned value is calculated again, so that even if there is a deviation in the basic air-fuel ratio during the period until re-entry, the influence of that deviation can be prevented. There is an effect that it can be done.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the overall configuration of an engine air-fuel ratio control device according to an embodiment of the present invention;

FIG. 2 is a flowchart showing the air-fuel ratio control procedure in the device of the embodiment;

[Fig. 3] Map showing the air-fuel ratio control area,

FIG. 4 is a diagram showing the relationship between the value of counter 1 and the value of counter 2.

[Explanation of symbols]

1 Engine body 2 Piston 3 Combustion chamber 4 Intake port 5 Water temperature sensor 6 Exhaust port 7 Intake valve 8 Exhaust valve 9 Throttle valve 10 Surge tank 11 Injector 12 Bypass passage 13 Bypass valve 15 Distributor 16 Purge control valve 17 Canister 18 Fuel tank 20 Air flow meter 20a Air flow sensor 21 Intake temperature sensor 22 Throttle opening sensor 25 Rotation speed sensor 26 O2 sensor

Claims (3)

[Claims] 1. Calculating means for calculating a learned value based on a deviation in the air-fuel ratio of the air-fuel mixture in a preset learning area; storage means for storing the learned value calculated by the calculating means; An air-fuel ratio control device for an engine, comprising: updating means for updating a learned value stored in the means; measuring means for measuring the time from exiting the learning area to transitioning to the learning area again; a comparing means for comparing the time measured by the measuring means with a preset time; and when the comparing means determines that the time measured by the measuring means is shorter than the preset time, the updating means and control means for prohibiting update of the learned value for the above determination, and performing predetermined air-fuel ratio control using the learned value in the storage means obtained in the previous determination. air-fuel ratio control device. 2. A hot wire airflow sensor is provided, and the control means uses the previous learned value calculated by the calculation means when the stay time in the high load area is short within the set period. An air-fuel ratio control device for an engine according to claim 1. 3. The control means is configured to reduce the degree of use of the previous learning value by the calculation means as the period from exiting the learning area to re-entering the learning area becomes longer. The air-fuel ratio control device for an engine according to item 1.