JP2918734B2 - Evaporative purge 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 evaporative purge control method for an evaporative emission purge system mainly applied to automobiles.

[0002]

As evaporative gas purge control method of a conventional this type, such as the air-fuel ratio control apparatus described in JP-A-63-186955, the feedback control of the air-fuel ratio based on a signal from the O ₂ sensor At the same time, there is known an engine that purges gasoline vapor (evaporation) from a fuel tank into an intake system when the engine is idling. In an apparatus for performing such 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 is opened and closed with a variable duty to remove gasoline vapor attached to the charcoal canister. Purging.

Further, an evaporation reduction correction coefficient for correcting the gasoline vapor amount to be reduced so that the purged gasoline vapor does not affect the learning of the A / F learning correction coefficient is set. In some cases, the air-fuel ratio is controlled to be maintained near the stoichiometric air-fuel ratio.

[0004]

By the way, in the configuration described above, when the opening of the duty VSV increases with time or the opening time increases, the gasoline vapor amount increases accordingly. In such a case, when the duty VSV is closed and the evaporative purge ends, the surge tank is filled with rich gasoline vapor. At this time, as shown in FIG. 5, since the evaporation reduction correction coefficient is returned to 1.0 at the same time as the end of the evaporation purge, the air-fuel ratio becomes rich until the gasoline vapor in the surge tank runs out, and HC and CO increase. .

[0005] An object of the present invention is to solve such a problem.

[0006]

In order to achieve the above object, the present invention takes the following measures. That is, the evaporation purge control method according to the present invention includes:
When idling operation, when purging gasoline vapor adsorbed in the charcoal canister into the intake system based on the purge duty ratio, a reduction correction for correcting the fuel amount corresponding to the purged amount of gasoline vapor Coefficient, and the reduction correction coefficient and at least the air-fuel ratio are filtered.
A / F feedback compensator for feedback control
An evaporative purge control method in which the air-fuel ratio is controlled by a number to perform purging, wherein it is detected that gasoline vapor purging is stopped, and the decrease correction coefficient is detected to be less than a basic value. A predetermined value is added to the weight loss correction coefficient at the point in time, and after the gasoline vapor purge is stopped, the weight loss correction coefficient is gradually corrected toward the basic value.

[0007]

With such a configuration, the A / F feedback correction coefficient differs from the A / F feedback correction coefficient after the gasoline vapor purge is stopped.
Since the fuel loss correction coefficient does not instantaneously become the basic value, that is, the fuel amount is controlled by the fuel loss correction coefficient for a while even if the purge is stopped, the gasoline vapor remaining in the intake system causes The air-fuel ratio does not suddenly become rich from that point.

Therefore, depending on the rich state, HC or CO
Is suppressed, and deterioration of emission is prevented.

[0009]

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 correction coefficient and the voltage signal h from the O ₂ sensor 21, the 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 idling operation is performed, the gasoline vapor adsorbed by the charcoal canister 23 is purged into the intake system 1 based on the purge duty ratio EPDUTY.
An evaporative reduction correction coefficient KPG for correcting the fuel amount corresponding to the purged amount of gasoline vapor is set, and the evaporative reduction correction coefficient KPG and at least the air-fuel ratio are fed.
A / F feedback correction coefficient F for back control
When the air-fuel ratio is controlled by the AF to perform purging, and when the purging of gasoline vapor is stopped, it is detected that the evaporation reduction correction coefficient KPG is less than the basic value, and a predetermined value is set as the evaporation reduction correction coefficient KPG at that time. The program is programmed to add the values and to gradually correct the evaporation reduction correction coefficient KPG toward the basic value after the gasoline vapor purge is stopped. In this embodiment, the calculation of the effective injection time TAU is performed by the following arithmetic expression.

TAU = TP * FAF * KPG * α (where α represents another correction coefficient) The outline of this evaporative purge control program is shown in FIGS.
It is as shown in.

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. In step 52, it is determined whether or not the evaporation reduction correction coefficient PKG is less than 1.0, which is the basic value. In step 53, the addition value KPGINC at the time of the evaporative reduction return is added to the evaporative reduction correction coefficient KPG, and the routine proceeds to step 54. In step 54, it is determined whether or not the evaporation reduction coefficient KPG calculated in step 53 is greater than 1.0.
In the following cases, the process proceeds to the learning routine GR. In step 55, the evaporative reduction correction coefficient KPG exceeding 1.0 is set to 1.0, and the routine proceeds to the learning routine GR.

The learning routine GR may perform learning of the A / F learning correction coefficient KG by a method widely known in the art. That is, for example, for each skip of the A / F feedback correction coefficient FAF, an arithmetic mean of the immediately preceding skip value and the immediately preceding skip value is obtained, and it is detected which learning zone the engine operating condition corresponds to, Each time the air-fuel ratio feedback correction coefficient FAF is skipped, the value of the A / F learning correction coefficient KG in the learning zone is updated according to the magnitude of the arithmetic mean, and the A / F learning correction coefficient KG updated by the learning is used as the fuel injection amount. This is done by reflecting the above. 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. Specifically, for example, a cooling water temperature as an engine temperature is measured by a water temperature signal e from the water temperature sensor 17, and the measured cooling water temperature is a predetermined temperature α, for example, 70 ° C.
It is determined whether the temperature is equal to or higher than the predetermined value. If it is determined that the cooling water temperature is equal to or higher than the predetermined temperature α, the transient air-fuel ratio correction coefficient FA
It is programmed to determine whether or not EW is zero. If it is zero, it is determined whether or not the operating condition is within the learning zone. If it is within the learning zone, learning is performed. These determinations determine whether or not the operating state of the engine at the time of idling satisfies a predetermined learning condition. The determination that the engine is not warming up from the cooling water temperature by the transient air-fuel ratio correction coefficient F
Since the AEW is zero, it is determined that the operation is not in the transient state, and that the operation condition is in the learning zone. When at least the above three conditions are not satisfied, the process proceeds to a subroutine without learning as a driving situation that cannot be learned.

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 being purged, the control proceeds from step 51 to step 61 because the opening of the duty VSV 26 is positive. If the average value FAFAV of the A / F feedback correction coefficient FAF is smaller than the evaporative reduction calculation value lower limit KPGLO, the control proceeds from step 62 to step 63, and
As shown in FIG. 4, the evaporation reduction correction coefficient KPG is reduced, and the air-fuel ratio A / F is controlled so as to be maintained near the stoichiometric air-fuel ratio. These steps 61, 62, 63, 71, 7
In 2, when the average value FAFAV of the air-fuel ratio feedback correction coefficient FAF exceeds the calculated upper limit KPGHI and the lower limit KPGLO, the evaporation reduction correction coefficient KEPMI is added or subtracted to obtain the evaporation reduction coefficient KP.
G is corrected by the range of the evaporation reduction correction value KEPMI, and the air-fuel ratio A / F is controlled so as to be maintained near the stoichiometric air-fuel ratio.

Next, when purging of gasoline vapor is stopped,
The control proceeds from step 51 to step 52. If the evaporation reduction correction coefficient KPG at that time is less than 1.0, step 53 to step 54 is executed. By the control up to this point, the evaporation reduction correction coefficient KPG gradually approaches 1.0 by the addition amount KPGINC at the time of the evaporation reduction return from that during the execution of the purge. Therefore, step 5
In step 4, it is determined whether or not the evaporation reduction correction coefficient KPG is greater than 1.0, and if it exceeds 1.0 at that time, the process proceeds to step 55 → the learning routine GR, and
If it is below, the process proceeds to the learning routine. As shown in FIG. 4, when the evaporation reduction correction coefficient KPG is different from 1.0 when the gasoline vapor purge is stopped, the control repeats steps 51 → 52 → 53 → 54 → the learning routine GR, and the evaporation reduction. When the correction coefficient KPG exceeds 1.0, the process proceeds to steps 53 → 54 → 55 → a learning routine GR.

As described above, the evaporative reduction correction coefficient KPG is made to gradually approach 1.0 after the purge is stopped.
Even if gasoline vapor remains, the residual amount is corrected by the evaporation reduction correction coefficient KPG, so that the air-fuel ratio does not become rich, and deterioration of emission is prevented. Under such circumstances, the A / F learning correction coefficient KG
Learning is performed, so that it is not affected by the purged gasoline vapor.

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 weight loss correction coefficient is 0, and when the correction coefficient is negative, various constants may be added to the weight loss correction coefficient at that time to correct it.

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.

[0022]

According to the present invention, as described in detail above, the reduction correction coefficient does not immediately become the basic value after the gasoline vapor purge is stopped, that is, the A / F is maintained for a while even after the purge is stopped. and controls so as to reduce the amount of fuel by another decreasing correction coefficient and the feedback correction coefficient, air-fuel
It is possible to control the air-fuel ratio by following the ratio fluctuation well.
In addition, the air-fuel ratio does not suddenly become rich due to the gasoline vapor remaining in the intake system from that point in time. Therefore, the phenomenon that HC and CO increase due to the rich state is suppressed, and deterioration of emission is prevented.

[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 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

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 43/00 301 F02D 43/00 301M F02M 25/08 301 F02M 25/08 301J

Claims (1)

(57) [Claims] In an idling operation, when purging gasoline vapor adsorbed in a charcoal canister to an intake system based on a purge duty ratio, a fuel amount is corrected in accordance with a purged amount of gasoline vapor. set the reduction correction coefficient for, reducer amount correction coefficient and at least
A / F feed for feedback control of air-fuel ratio
An evaporative purge control method in which an air-fuel ratio is controlled by a back correction coefficient to perform purging, wherein it is detected that gasoline vapor purging has been stopped, and it is detected that the weight reduction correction coefficient is less than a basic value. An evaporative purge control method, wherein a predetermined value is added to the weight loss correction coefficient at that time, and after the gasoline vapor purge is stopped, the weight loss correction coefficient is gradually corrected toward a basic value.