JP2889418B2 - Air-fuel ratio learning control method - Google Patents

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 an automobile.

[0002]

The air-fuel ratio learning control method of a conventional this type, such as the air-fuel ratio control apparatus described in JP-A-63-186955, the feedback air-fuel ratio based on a signal from the O ₂ sensor It is known to control and purge gasoline vapor (evaporation) from a fuel tank into an intake system when the engine is idling. In such an apparatus for performing an evaporative purge,
For example, a duty VSV is provided in a passage communicating the charcoal canister and the intake system, and the duty VSV
V is opened and closed at a variable duty to purge gasoline vapor attached to the charcoal canister.

[0003]

In the above-described structure, if the purged gasoline vapor does not affect the learning of the A / F learning correction coefficient, which is the idle learning value, the learning is performed during the purge. Need to be banned. However, as shown in FIG.
If the learning is performed while the purge is not being performed and the learning during the purge is prohibited, the A / F feedback correction coefficient FAF causes the A / F feedback correction coefficient FAF to bring the air-fuel ratio close to the stoichiometric air-fuel ratio by the feedback control while the purge is not performed. Since the value is corrected to a value that can be maintained, the value is fixed at the time when the purge is started. Then, the air-fuel ratio, which is to be enriched by the amount of gasoline vapor due to the purge, is represented by A /
Since the control is performed to the lean side by the F feedback correction coefficient FAF, the A / F feedback correction coefficient F
AF was fixed to its lower limit, and the air-fuel ratio became rich and HC and CO increased.

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

[0005]

In order to achieve the above object, the present invention takes the following measures. That is, in the air-fuel ratio learning control method according to the present invention, when the gasoline vapor adsorbed in the charcoal canister is purged to the intake system based on the purge duty ratio in the idling operation, the idle for the air-fuel ratio control is controlled. The learning of the learning value is prohibited, a reduction correction coefficient for correcting the fuel amount corresponding to the purged amount of gasoline vapor is set, and the A / F feedback correction coefficient becomes a basic value by the reduction correction coefficient. It is characterized by the following.

[0006]

With such a configuration, the learning of the idle learning value is not performed during the execution of the purge of the gasoline vapor, but the A / F feedback correction coefficient becomes the basic value by the set reduction correction coefficient. To be corrected. Therefore, the air-fuel ratio is always maintained near the stoichiometric air-fuel ratio by the feedback control, and the deterioration of the emission is prevented.

[0007]

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). 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 near one end of the fuel injection valve 5, and the fuel injection valve 5 is controlled by an electronic control device 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 provided in a pipe leading to a muffler (not shown). I have. This O ₂ sensor 21
Outputs a voltage signal h corresponding to the oxygen concentration.
Reference numeral 23 denotes a charcoal canister that adsorbs gasoline vapor remaining in the fuel tank 24. The atmosphere is introduced from the lower part of the charcoal canister 23, and opens and closes a duty VSV 26 provided in the charcoal canister 23 and a pipe 25 communicating with a pipe line between the throttle valve 2 and the surge tank 3. The duty VSV 26 is controlled to open and close by the ratio, that is, the purge duty ratio described below, so that 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 device 8, an input interface 9, and an output interface 11, and the input interface 9 Are the intake pressure signal a from the intake pressure sensor 13 for detecting the pressure in the surge tank 3, the rotational speed signal b from the rotational speed sensor 14 for detecting the engine rotational 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 open / close 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, the O The voltage signal h and the like from the _two sensors 21 are input. On the other hand, from the output interface 11,
The fuel injection signal f for the fuel injection valve 5, the ignition pulse g for the spark plug 18, and the duty VS
A predetermined purge duty ratio EPDUTY for V26
, An evaporative duty signal j which is turned on and off is output.

The electronic control unit 6 uses the intake pressure signal a output from the intake pressure sensor 13 and the rotational speed signal b output from the rotational speed sensor 14 as main information, and various kinds of information determined according to the engine conditions. based on the voltage signal h from the correction coefficient and the _{O 2} sensor 21, a / F feedback correction coefficient F
The basic injection time TP is corrected by AF or an A / F learning correction coefficient KG learned under predetermined operating conditions to determine the fuel injection valve opening time, that is, the injector final energization time T,
A program for feedback control for controlling the fuel injection valve 5 based on the determined energization time T and injecting fuel corresponding to the engine load from the fuel injection valve 5 to the intake system 1 is incorporated. In this program, when the gasoline vapor adsorbed in the charcoal canister 23 is purged to the intake system 1 based on the purge duty ratio EPDUTY in the idling operation, the learning of the idle learning value for the air-fuel ratio control is further performed. Is set, a reduction correction coefficient for correcting the fuel amount is set in accordance with the purged amount of gasoline vapor, and the A / F feedback correction coefficient FAF is corrected based on the reduction correction coefficient so as to be a basic value. Is programmed as In addition,
In this embodiment, the effective injection time TAU is calculated using the following arithmetic expression.

TAU = TP * FAF * KPG * α (where α represents another correction coefficient) The outline of the air-fuel ratio learning control program is as shown in FIGS. 2 and 3.

In step 51, it is determined whether or not the purge duty ratio EPDUTY is zero, in other words, whether or not the duty VSV 26 is closed (opening degree = 0). The process proceeds to step 61 if not.

Step 52 and steps 53, 54, 55 and 56 which will be described in detail below include a so-called learning routine GR.
It is a step which comprises. In the learning in this embodiment, for example, for each skip of the A / F feedback correction coefficient FAF, an arithmetic average of the immediately preceding skip value and the present immediately preceding skip value is obtained, and the learning condition of the engine corresponds to which learning zone. And updates the value of the A / F learning correction coefficient KG in the learning zone according to the magnitude of the arithmetic mean every time the air-fuel ratio feedback correction coefficient FAF is skipped.
This is performed by 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 substantially the entire operating range of the engine. When such learning is performed, it is detected whether or not the vehicle is in an operating condition that satisfies the learning condition. In such a learning routine GR, the cooling water temperature as the engine temperature is measured by the water temperature signal e from the water temperature sensor 17,
In step 52, it is determined whether the measured cooling water temperature is equal to or higher than a predetermined temperature α, for example, 70 ° C., and if it is determined that the cooling water temperature is equal to or higher than the predetermined temperature α, step 53
The process proceeds to step 56 if not. In step 53, it is determined whether the transient air-fuel ratio correction coefficient FAEW is zero. If it is zero, the process proceeds to step 54, and if it is not zero, the process proceeds to step 56. Step 54
Then, it is determined whether or not the driving condition is within the learning zone. If the driving condition is within the learning zone, the process proceeds to step 55; Each determination here is for determining whether or not the operating state of the engine at the time of idling satisfies a predetermined learning condition.It is determined that the engine is not warming up from the cooling water temperature when the transient air-fuel ratio correction coefficient FAEW is zero. Therefore, it is determined that the operation is not in the transient state and that the operation condition is in the learning zone.

In FIG. 3, at step 61, the A / F
It is determined whether or not the average value FAFAV of the feedback correction coefficient FAF is smaller than the lower limit value KPGLO of the calculated evaporative reduction amount. If smaller, the process proceeds to step 62; otherwise, the process proceeds to step 71. In step 62, the evaporation reduction correction value KEPMI is subtracted from the evaporation reduction correction coefficient KPG, and the routine proceeds to step 63. In step 63, if the calculated evaporation reduction coefficient KPG is within the set evaporation reduction value upper limit KPGHI and lower limit KPGLO, the evaporation reduction correction is performed by the evaporation reduction correction coefficient KPG, and the evaporation reduction calculation value upper limit KPGHI or lower limit KPGHI is calculated. KP
If it exceeds GLO, the upper limit of the evaporative weight loss calculation value K
Evaporative reduction correction is performed by PGHI or lower limit KPGLO. In step 71, the average value FAFAV of the A / F feedback correction coefficient FAF is set to the upper limit K
It is determined whether the value is greater than PGHI. If the value is greater than PGHI, the process proceeds to step 72; otherwise, the process proceeds to step 63.
In step 72, the evaporation reduction correction value KEPMI is added to the evaporation reduction correction coefficient KPG, and the routine proceeds to step 63. The idling is detected by the idle switch 1
It is sufficient to judge that the LL signal d from 6 is ON.

In the above configuration, when the gasoline vapor is not purged, the control proceeds from step 51 to step 52, and if the conditions necessary for executing the learning are satisfied, the control proceeds from step 52 to 53 to 54 to 55. And control proceeds, and A
Learning of the / F learning correction coefficient KG is executed.

Next, when gasoline vapor is being purged,
Since the opening of the duty VSV 26 is positive, the control proceeds from step 51 to step 61. And A / F
If the average value FAFAV of the feedback correction coefficient FAF is smaller than the lower limit value KPGLO of the calculated evaporative reduction amount, the control proceeds from step 62 to step 63, and the evaporative reduction correction coefficient KPG is reduced as shown in FIG. F
The air-fuel ratio A / F is controlled to be maintained near the stoichiometric air-fuel ratio by correcting the feedback correction coefficient FAF to be the basic value of 1.0. Conversely, if the average value FAFAV of the A / F feedback correction coefficient FAF is larger than the upper limit KPGHI of the evaporative loss calculation value, step 51 →
The control proceeds in the order of 61 → 71 → 72 → 63. Thus, in these steps 61, 62, 63, 71 and 72, the average value FAFAV of the air-fuel ratio feedback correction coefficient FAF
Is the upper limit KPGHI and the lower limit KPGLO
If the value exceeds the evaporative weight loss correction value KEPMI
Is added or subtracted to correct the evaporation reduction coefficient KPG within the range of the evaporation reduction correction value KEPMI, and the average value FAFAV
Is between the upper limit value KPGHI and the lower limit value KPGLO, the evaporative reduction correction coefficient PKG is not changed by adding the evaporative decrease correction value KEPMI to the current state (FIG. 5). The A / F feedback correction coefficient FAF is corrected by the coefficient KPG to control the air-fuel ratio A / F to be maintained near the stoichiometric air-fuel ratio.

As described above, during the purge, the A / F
If the average value FAFAV of the feedback correction coefficient FAF does not satisfy the predetermined condition, the evaporative reduction correction coefficient KP
G is increased or decreased by a predetermined correction value range and the A / F feedback correction coefficient FAF is corrected so as to be always 1.0, so that the air-fuel ratio that is feedback-controlled is maintained near the stoichiometric air-fuel ratio. An increase in HC and CO can be suppressed.

The present invention is not limited to the embodiment described above. For example, in the above embodiment, the calculation of the effective injection time is performed by multiplying each correction coefficient. However, the effective injection time may be calculated by adding each correction coefficient. In this case, the basic value of the A / F feedback correction coefficient becomes 0, and the correction using the reduction correction coefficient may be performed so that the correction coefficient FAF becomes 0.

In addition, the configuration of each section is not limited to the illustrated example, and various modifications can be made without departing from the spirit of the present invention.

[0020]

According to the present invention, as described in detail above, the learning of the idle learning value is not performed during the purging of gasoline vapor, but the A / F feedback correction coefficient is basically determined by the set reduction correction coefficient. Since the air-fuel ratio is corrected so as to be a value, the air-fuel ratio is always maintained near the stoichiometric air-fuel ratio by feedback control, and it is possible to suppress an increase in HC and CO due to a rich state and prevent deterioration of emission.

[Brief description of the drawings]

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

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

FIG. 3 is a flowchart showing a control procedure of the embodiment.

FIG. 4 is an operation explanatory view of the embodiment.

FIG. 5 is an operation explanatory view of the embodiment.

FIG. 6 is an operation explanatory view of a conventional example.

[Explanation of symbols]

 Reference Signs List 5 fuel injection valve 7 central processing unit 8 storage device 9 input interface 11 output interface 23 charcoal canister 25 duty VSV KPG evaporation reduction coefficient

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F02M 25/08 F02D 41/14 F02D 45/00

Claims (1)

(57) [Claims] When the gasoline vapor adsorbed in a charcoal canister is purged to an intake system based on a purge duty ratio during idling operation, learning of an idle learning value for air-fuel ratio control is prohibited. A reduction correction coefficient for correcting the fuel amount is set in accordance with the purged amount of the gasoline vapor, and the A / F feedback correction coefficient is corrected by the reduction correction coefficient so as to be a basic value. Air-fuel ratio learning control method.