JPH05202816A - Method of learning and controlling air-fuel ratio - Google Patents

Abstract

PURPOSE:To prevent an idle leaning value from being learned deviating from a value corresponding to no gasoline vapor, caused by affection of gasoline vapor, by carrying out the learning of the idle learning value during idle operation when gasoline purge is not purged. CONSTITUTION:It is determined whether or not the operating condition of an engine 100 is in a condition such that an idle leaning value for the air-fuel ratio can be learned during idle operation (steps 51 to 53). When it is determined that the learning is possible (step 54), the idling time from the time when the temperature 17 of the engine exceeds a predetermined value after start of the engine, is counted by 16, and it is determined whether the idling time is longer than a set time or not (step 54). Only when it is determined that the idling time is shorter than a set time (step 55), the idle leaning value is learned in such a condition that no purge of gasoline vapor is carried out. Further, when the idling time exceeds the set time, the purge of gasoline vapor is carried out. Thereby it is possible to eliminate the affection of the purge of gasoline vapor from the idle learning value.

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 learning control method in an evaporative emission purge system mainly applied to automobiles.

[0002]

2. Description of the Related Art Conventionally, as an air-fuel ratio learning control method of this type, an air-fuel ratio is fed back based on a signal from an O ₂ sensor like an air-fuel ratio control device disclosed in Japanese Patent Laid-Open No. 63-186955. It is known to control and purge gasoline vapor (evaporative emission) from a fuel tank into an intake system when the engine is idling. Further, such a control device is configured to learn an idle learning value for air-fuel ratio control during idling so that the air-fuel ratio is always close to the stoichiometric air-fuel ratio.

[0003]

By the way, in the above-mentioned structure, the air-fuel ratio becomes rich due to the introduction of gasoline vapor during idling, and the idle learning value is learned based on the air-fuel ratio at that time. Therefore, the learned idle value is leaner than the actual value. However, as shown in FIG. 3, when the gasoline vapor is purged and cleaned during traveling and then becomes the idling state again, there is no gasoline vapor that can be used even if it is purged, so When the air-fuel ratio is controlled by the idle learning value learned at that time, the air-fuel ratio becomes lean and rough idle or stall may occur.

An object of the present invention is to eliminate such a problem.

[0005]

The present invention takes the following means in order to achieve such an object. That is, the air-fuel ratio learning control method according to the present invention detects whether the engine is in an idling state and determines whether the engine operating state is a state in which an idle learning value for air-fuel ratio control during idling can be learned. If it is determined that learning is possible, the idling time from the time when the engine temperature exceeds the set value after the engine is started is measured, and it is determined whether the measured idling time is shorter than the set time. However, only when it is determined that the idling time is shorter than the set time, the idle learning value is learned in a state in which the gasoline vapor is not purged, and when the idling time is equal to or longer than the set time, the idling time is learned. It is characterized by purging gasoline vapor even if it exists.

[0006]

With this structure, the learning of the idle learning value during idling is executed when the gasoline vapor is not being purged, so that learning in a rich state due to gasoline vapor can be performed. The idle learning value never goes to the lean side. Therefore, the idle learning value will not deviate from the value when there is no gasoline vapor and will not be learned due to the influence of gasoline vapor, and the occurrence of rough idle or stall will be prevented.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

An engine 100 schematically shown in FIG. 1 is for an automobile, and its intake system 1 is provided with a throttle valve 2 which opens and closes in response to an accelerator pedal (not shown), and a surge is provided downstream thereof. A tank 3 is provided.
Intake manifold 4 of intake system 1 communicating with surge tank 3
A fuel injection valve 5 is further provided in the vicinity of one end of the fuel injection valve 5, and the fuel injection valve 5 is controlled by the electronic control unit 6. Further, an O ₂ sensor 21 for measuring the oxygen concentration in the exhaust gas is attached to the exhaust system 20 at a position upstream of a three-way catalyst 22 arranged in a pipe line leading to a muffler (not shown). There is. This O ₂ sensor 21
Outputs a voltage signal h corresponding to the oxygen concentration.
A charcoal canister 23 adsorbs gasoline vapor accumulated in the fuel tank 24. Atmosphere is introduced from the lower part of the charcoal canister 23, and the duty VSV 26 provided in the pipe 25 communicating with the pipe between the charcoal canister 23 and the throttle valve 2 and the surge tank 3 is opened and closed. By controlling the opening and closing of the duty VSV 26 by the ratio, that is, the purge duty ratio described below, the purge amount of the gasoline vapor adsorbed by the charcoal canister 23 is controlled.

The electronic control unit 6 is mainly composed of a microcomputer system including a central processing unit 7, a storage unit 8, an input interface 9 and an output interface 11, and the input interface 9 has Is the intake pressure signal a from the intake pressure sensor 13 for detecting the pressure in the surge tank 3, the rotation speed signal b from the rotation speed sensor 14 for detecting the engine speed NE, and the vehicle speed. The vehicle speed signal c from the vehicle speed sensor 15, the LL signal d from the idle switch 16 for detecting the opening / closing state of the throttle valve 2, the water temperature signal e from the water temperature sensor 17 for detecting the cooling water temperature of the engine, and the above-mentioned O ₂ The voltage signal h or the like from the sensor 21 is input. On the other hand, from the output interface 11,
Fuel injection signal f for the fuel injection valve 5, ignition pulse g for the spark plug 18, duty VS.
Predetermined purge duty ratio EPDUTY for V26
The evaporation purge duty signal j which is turned on / off at is output respectively.

The electronic control unit 6 has an intake pressure signal a output from the intake pressure sensor 13 and a rotation speed signal b output from the rotation speed sensor 14 as main information, and various kinds of information are determined depending on engine conditions. Based on the correction coefficient and the voltage signal h from the O ₂ sensor 21, the A / F feedback correction coefficient F
The fuel injection valve opening time, that is, the injector final energization time T is determined by correcting the basic injection time TP by AF or the like, and the fuel injection valve 5 is controlled by the determined energization time T.
A program for feedback control for injecting fuel according to the engine load from the fuel injection valve 5 to the intake system 1 is built in. Further, in this program, the A / F learning correction coefficient is updated (learned) under a predetermined condition at idling based on the oxygen concentration in the exhaust gas, and the effective injection time is calculated based on the updated A / F learning correction coefficient. In addition to this, even when idling, the total time during which the LL signal d from the idle switch 16 is ON after the cooling water temperature exceeds the set value after the engine is started is calculated. If the time is equal to or longer than a predetermined time, the duty VSV25 is controlled to be opened / closed based on a predetermined purge duty ratio EPDUTY without learning the A / F learning correction coefficient at idling, and the program is programmed to purge the gasoline vapor. Is.

The outline of this air-fuel ratio learning control program is as shown in FIG.

In the learning control of the air-fuel ratio A / F, for example, every time the air-fuel ratio feedback correction coefficient FAF is skipped, the arithmetic average of the immediately preceding skip value and the immediately preceding skip value is obtained, and the learning condition of the engine is determined. It is detected whether it corresponds to a zone, and A / F of the learning zone is determined by the magnitude of the arithmetic mean each time the air-fuel ratio feedback correction coefficient FAF is skipped.
This is performed by updating the value of the F learning correction coefficient KG and reflecting the A / F learning correction coefficient KG updated by the learning in the fuel injection amount. The learning zone is defined by the engine speed NE and the intake pressure PM over almost the entire operating region of the engine.

In step 51, the cooling water temperature as the engine temperature is measured by the water temperature signal e from the water temperature sensor 17, and the measured cooling water temperature is a predetermined temperature α, for example, 7.
It is determined whether the temperature is 0 ° C. or higher, and the cooling water temperature is the predetermined temperature α.
If it is determined that the above, the process proceeds to step 52,
If less, go to step 61. In step 52,
It is determined whether or not the transient air-fuel ratio correction coefficient FAEW is zero. If it is zero, the process proceeds to step 53, and if it is not zero, the process proceeds to step 61. In step 53, it is determined whether or not the driving condition is in the learning zone. If it is in the learning zone, the process proceeds to step 54, and if not, the process proceeds to step 61.
The steps 51, 52 and 53 are
It is to determine whether or not the operating state of the engine during idling satisfies a predetermined learning condition. In this embodiment, the control is performed based on the cooling water temperature as the engine temperature and the control mode of the air-fuel ratio, and the control mode of the air-fuel ratio detects that the transient air-fuel ratio correction coefficient FAEW is zero, and the operation is in the transient state. It is determined that it is not. In step 54,
After the engine is started, that is, after the ignition switch is turned on, the cumulative time CLLONKG of the time when the LL signal d from the idle switch 16 is turned on after the cooling water temperature exceeds the set value γ is the predetermined time β (seconds) or less. It is determined whether or not, and if it is below, the process proceeds to step 55, and if it exceeds, the process proceeds to step 61. The predetermined temperature α and the set value γ do not need to match.
In step 55, since the learning condition at idling is satisfied, the learning of the A / F learning correction coefficient KG is executed. On the contrary, in step 61, even if it is detected that the LL signal d is on and idling, A /
The learning of the F learning correction coefficient KG is not performed, and the duty VSV25 is set based on the predetermined purge duty ratio EPDUTY.
Is controlled to open and close to purge the gasoline vapor adsorbed in the charcoal canister 23.

In the above-mentioned structure, the engine is started, the cooling water temperature is equal to or higher than the predetermined temperature α, and the air-fuel ratio feedback control is performed in the idling state instead of the transient state. Elapsed time after exceeding γ (cumulative time CLLONK
If G) is less than or equal to the predetermined time β, step 51 → step 52 → step 53 → step 54 → step 5
5, the control advances, and the learning of the A / F learning correction coefficient KG is executed. In this case, if the total of the previous idling time and the idling time this time is less than the predetermined time β, even if the normal running state after idling and then the idling again, the predetermined time is set at the time of idling this time. Until then, learning of the A / F learning correction coefficient KG is performed. On the other hand, if the cooling water temperature is lower than the predetermined temperature α, the transient air-fuel ratio correction coefficient FAEW is not zero even if the cooling water temperature is equal to or higher than the predetermined temperature α, or if the operating condition is not within the learning zone, the learning condition is satisfied. If not, the control is step 51 → step 61, step 51 → step 52 → step 61 or step 5
The sequence proceeds from 1 → step 52 → step 53 → step 61, and the charcoal canister 23 is purged without learning the A / F feedback correction coefficient KG.

As described above, when the idling is performed after the normal running in which the charcoal canister 23 is purged, even if the learning condition is satisfied, if the cumulative idling time is equal to or longer than the predetermined time β, A / F Feedback correction coefficient KG is not learned, so A / F
The feedback correction coefficient KG is not biased to the lean side and learned. Therefore, even when idling occurs when the gasoline vapor is swept from the charcoal canister 23, the air-fuel ratio does not become lean, and it is possible to prevent rough idle or stall.

The present invention is not limited to the embodiment described above. For example, although the cooling water temperature was measured as the learning condition in the above embodiment, it may be the temperature of the lubricating oil. In addition, the configuration of each unit is not limited to the illustrated example, and various modifications can be made without departing from the spirit of the present invention.

[0017]

As described in detail above, according to the present invention, the learning of the idle learning value for controlling the air-fuel ratio at the time of idling is executed when the gasoline vapor is not purged, and the idling is performed even at the time of idling. If the cumulative time is equal to or longer than the predetermined time, the gasoline vapor is purged, so there is no learning in the rich state due to gasoline vapor,
The idle learning value will not be on the lean side, so the idle learning value will be
It is possible to prevent the occurrence of rough idle and stall without learning by deviating from the value when there is no gasoline vapor.

[Brief description of drawings]

FIG. 1 is a schematic configuration explanatory view showing an embodiment of the present invention.

FIG. 2 is a flowchart showing a control procedure of the embodiment.

FIG. 3 is an operation explanatory view of a conventional example.

[Explanation of symbols]

 5 ... Fuel injection valve 7 ... Central processing unit 8 ... Storage device 9 ... Input interface 11 ... Output interface 23 ... Charcoal canister 25 ... Duty VSV β ... Predetermined time

Claims (1)

[Claims] 1. An idling state is detected, and it is determined whether or not an engine operating state is a state in which an idle learning value for air-fuel ratio control during idling can be learned.
When it is determined that the learning is possible, the idling time from the time when the engine temperature exceeds the set value after the engine is started is measured, and it is determined whether or not the measured idling time is shorter than the set time. Only when it is determined that the idling time is shorter than the set time, the idle learning value is learned without purging gasoline vapor, and when the idling time is equal to or longer than the set time, it is during idling. Also, an air-fuel ratio learning control method characterized by purging gasoline vapor.