JPH0763080A - Air-fuel ratio controller of internal combustion engine - Google Patents

Abstract

PURPOSE:To actualize the extent of highly accurate air-fuel ratio control by eliminating any turbulence in an air-fuel ratio with variations in a stationary compensation factor. CONSTITUTION:Evaporated gas produced in a fuel tank 14 is adsorbed by a canister 16 and then it is discharged to an inlet pipe 2 of an internal combustion engine 1. An electronic control unit 24 calculates a fuel supply into the engine 1 on the basis of a driving state of the engine 1, while it performs feedback control and leaning control on the basis of a detecting signal out of an oxygen sensor 10, whereby the fuel supply is compensated by the air-fuel ratio compensation factor set at that time. In addition, the ECU 24 compensates the fuel supply in terms of decrement according to discharge of the evaporated gas, thereby controlling the extent of fuel injection by an injector 5. Further the ECU 24 adjusts a decrement compensating portion in making it proportionate to a stationary compensation factor contained with the air-fuel compensation factor at a time when the fuel supply is compensated for decrement according to the discharge of the evaporated gas.

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 system for an internal combustion engine, and more particularly, to a canister for temporarily adsorbing fuel evaporative gas (hereinafter referred to as "evaporation gas") generated in a fuel tank, The present invention relates to an air-fuel ratio control device for an internal combustion engine, which has a configuration of discharging (purging) into an intake passage.

[0002]

2. Description of the Related Art Conventionally, in this type of air-fuel ratio control device, in order to reduce the amount of air-fuel ratio deviation between the actual air-fuel ratio and the target air-fuel ratio by an air-fuel ratio sensor, a feedback correction coefficient and learning as an air-fuel ratio correction coefficient are performed. Value is required. And
With this air-fuel ratio correction coefficient (feedback correction coefficient and learning value), feedback control and learning control of the air-fuel ratio are executed. Also, the fuel supply amount of the internal combustion engine is reduced and corrected according to the amount of evaporative emission (purge amount), and the fuel injection amount of the injector is obtained (for example, JP-A-63-1).
86955, JP-A-2-130240).

That is, in such an air-fuel ratio control device, an evaporation purge correction coefficient is set so as to be proportional to the amount of evaporation gas discharged, and the product of the evaporation purge correction coefficient and the amount of fuel supplied to the internal combustion engine is used to supply the amount of fuel supplied by evaporation gas. Is estimated (this is the amount of weight loss correction). Then, the fuel injection amount by the injector is calculated by subtracting the fuel supply amount by the evaporative gas from the fuel supply amount by the internal combustion engine. The evaporation purge correction coefficient is 1 for the internal combustion engine.
The ratio of the fuel supply amount of evaporative gas to the fuel supply amount of one time is shown.

FIG. 8 shows how the coefficient relating to the fuel supply amount after the reduction correction is changed when the steady correction coefficient FCON including the air-fuel ratio correction coefficient largely changes as a reflection of the learning control. . In FIG. 8, the evaporation purge correction coefficient FPRG is shown by a one-dot chain line (“0.3” in the figure).
Is fixed), and a solid line shows a coefficient (a steady-state correction coefficient FCON including an air-fuel ratio correction coefficient minus an evaporation purge correction coefficient FPRG) related to the fuel supply amount after the reduction correction.

According to this figure, when the steady-state correction coefficient FCON is "1.0", the evaporation purge correction coefficient FPRG is "0.3" and "FCON-FPRG" is "0.7". This is because when the fuel supply amount by the evaporative gas is "0.3 / 1.0", that is, 30% of the total fuel supply amount, the fuel injection amount by the injector is "0.7" of the total fuel supply amount.
/1.0 ", that is, 70% is controlled.
When the steady correction coefficient FCON does not change (FC
The above ratio at ON = 1.0) is the control target of the fuel injection amount by the injector.

[0006]

However, in the above conventional air-fuel ratio control device, the steady state correction coefficient FCON is "1.
When it fluctuates with respect to "0", there is a problem that the fuel injection amount by the injector deviates from a desired control target value and the air-fuel ratio control is adversely affected.

For example, when the steady-state correction coefficient FCON becomes "0.8" in FIG. 8, the value of "FCON-FPRG" becomes "0.5", and the fuel injection amount by the injector is "0" of the total fuel supply amount. 0.5 / 0.8 ", or about 63%. In this case, the fuel injection amount by the injector is less than the control target of 70%,
The air-fuel ratio shifts to the lean side. Then, the feedback air-fuel ratio control is repeatedly executed in order to eliminate the deviation of the air-fuel ratio and stabilize the air-fuel ratio, and it takes time to stabilize the air-fuel ratio, and the air-fuel ratio is disturbed during the period until stabilization. It causes the deterioration of the emission.

Further, the steady correction coefficient FCON is "1.
When it becomes 4 ", the value of" FCON-FPRG "becomes" 1.1 ", and the fuel injection amount by the injector becomes" 1.1 / 1.4 "of the total fuel supply amount, that is, about 79%. Will be controlled. In this case, the fuel injection amount by the injector becomes larger than the control target of 70%, so that the air-fuel ratio shifts to the rich side, and the air-fuel ratio is also disturbed.

The present invention has been made by paying attention to the above problems, and its object is to eliminate the disturbance of the air-fuel ratio due to the fluctuation of the steady correction coefficient and realize a highly accurate air-fuel ratio control. An object of the present invention is to provide an air-fuel ratio control device for an internal combustion engine that can achieve the above.

[0010]

In order to achieve the above object, the air-fuel ratio control apparatus of the present invention, as shown in FIG.
A fuel evaporative emission mechanism M2 for adsorbing the fuel evaporative emission generated in the fuel tank to the canister and releasing the fuel evaporative emission adsorbed to the canister to the intake passage of the internal combustion engine M1, and the fuel to the internal combustion engine M1. The injector M3 for injection and supply, the air-fuel ratio sensor M4 for detecting the air-fuel ratio of the internal combustion engine M1, the operating state detecting means M5 for detecting the operating state of the internal combustion engine M1, and the operation of the internal combustion engine M1 by the operating state detecting means M5. Fuel supply amount calculation means M6 for calculating the fuel supply amount to be supplied to the internal combustion engine M1 based on the state, and feedback control and learning control based on the detection result by the air-fuel ratio sensor M4, and the fuel supply amount calculation means Air-fuel ratio for injecting the fuel amount corrected by the air-fuel ratio correction coefficient for the fuel supply amount by M6 from the injector M3 Control means M7 and injection fuel reducing means M8 for reducing and correcting the correction fuel amount by the air-fuel ratio control means M7 in accordance with the amount of fuel evaporation gas released by the fuel evaporation gas releasing mechanism M2. M8
The gist of the present invention is to perform the reduction correction in proportion to the steady correction coefficient including the air-fuel ratio correction coefficient by the air-fuel ratio control means M7.

Further, as described in claim 2, the internal combustion engine M1
Set the transient correction coefficient required only during the transient operation of
During the transient operation of the internal combustion engine M1, in addition to the fuel amount reduction correction by the injected fuel amount reducing means M8, the fuel amount increase correction according to the transient correction coefficient may be executed.

[0012]

According to the above construction, the fuel evaporative emission mechanism M2
Temporarily adsorbs the fuel evaporative gas generated in the fuel tank to the canister and then discharges it to the intake passage of the internal combustion engine M1. The fuel supply amount calculation means M6 is the operating state detection means M5.
Based on the operating state of the internal combustion engine M1
Calculate the fuel supply amount to be supplied to. The air-fuel ratio control means M7 performs feedback control and learning control based on the detection result of the air-fuel ratio sensor M4, and injects the fuel amount corrected by the air-fuel ratio correction coefficient with respect to the fuel supply amount calculated by the fuel supply amount calculation means M6. Eject from M3. Further, the injected fuel reducing means M8 reduces and corrects the corrected fuel amount by the air-fuel ratio control means M7 in accordance with the amount of the fuel evaporative gas released by the fuel evaporative gas releasing mechanism M2. in this case,
The injected fuel reducing means M8 carries out the reduction correction in proportion to the steady correction coefficient including the air-fuel ratio correction coefficient by the air-fuel ratio control means M7.

In short, when the steady-state correction coefficient is held at a constant value (for example, "1.0"), the amount of fuel amount reduction correction by the injected fuel amount reducing means M8 is reduced by the fuel evaporation gas release mechanism M2. It may be uniquely set according to the amount of released gas. However, when the steady-state correction coefficient including the air-fuel ratio correction coefficient fluctuates from a constant value due to changes over time or individual differences, the corrected fuel amount by the air-fuel ratio control means M7 fluctuates, depending on the amount of fuel evaporative emission. If the fuel amount is uniquely reduced and corrected, the injected fuel amount becomes too small or too large, and the air-fuel ratio shifts to the lean side or the rich side.

On the other hand, when the reduction correction amount is made proportional to the steady correction coefficient as in the configuration of the present invention, the correction fuel amount by the air-fuel ratio control means M7 is always desired regardless of the fluctuation of the steady correction coefficient. Controlled by quantity. As a result, the fuel injection amount by the injector M3 is suppressed from being too small or excessive, the air-fuel ratio becomes stable, and precise air-fuel ratio control is always realized.

Further, in claim 2, the transient correction coefficient required only during the transient operation of the internal combustion engine M1 is set, and during the transient operation of the internal combustion engine M1, the injected fuel reducing means M8 is provided.
In addition to the reduction correction of the fuel amount by, the increase correction of the fuel amount according to the transient correction coefficient is executed. That is, it is preferable that the increase correction by the transient operation is set according to the transient level, and is performed separately from other corrections (air-fuel ratio correction by the air-fuel ratio correction coefficient and decrease amount correction by the fuel evaporative gas). Therefore, according to the configuration of claim 2, even during the transient operation,
High-precision air-fuel ratio control will be implemented.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the air-fuel ratio control device of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram schematically showing the construction of an air-fuel ratio control system for an on-vehicle internal combustion engine in this embodiment. As shown in the figure, the internal combustion engine 1 includes an intake pipe (intake passage) 2
And an exhaust pipe 3 are connected to each other, and an air cleaner 4 is arranged at the most upstream part of the intake pipe 2. In the intake pipe 2, an electromagnetic injector 5 is arranged on the downstream side of the air cleaner 4, and a throttle valve 6 which is opened / closed in conjunction with a depression operation of an accelerator pedal (not shown) is arranged on the downstream side of the injector 5. There is. An intake air temperature sensor 7 for detecting the temperature of intake air is arranged in the intake pipe 2,
The surge tank 8 of the intake pipe 2 is provided with an intake pressure sensor 9 for detecting intake pressure. The intake air temperature sensor 7 outputs a voltage signal corresponding to the intake air temperature, and the intake pressure sensor 9 outputs a voltage signal corresponding to the intake pressure. Further, in the exhaust pipe 3, and O ₂ sensor 10 as an air-fuel ratio sensor is disposed, the O ₂ sensor 10 outputs a voltage signal corresponding to the oxygen concentration in the exhaust gas.

Further, in the internal combustion engine 1, an exhaust gas recirculation device (hereinafter referred to as EGR) 1 for taking out a part of the exhaust gas from the exhaust pipe 3 and appropriately recirculating it to the intake pipe 2.
1 is provided. As the configuration of the EGR 11, one end of the recirculation passage 12 is connected to the exhaust pipe 3 and the other end is connected to the intake pipe 2. An electromagnetic EGR valve 13 is arranged in the middle of the recirculation passage 12.

On the other hand, the fuel supply system is provided with a fuel evaporative emission system. Specifically, one end of a tank port passage 15 is connected to the fuel tank 14, and a canister 16 containing activated carbon as an adsorbent is connected to the other end of the tank port passage 15. The canister 16 has
A purge port passage 17 for connecting the canister 16 and the surge tank 8 of the intake pipe 2 is connected, and a purge solenoid valve (hereinafter referred to as a purge valve) 18 is arranged in the middle of the purge port passage 17. It is set up. The purge valve 18 is controlled to open and close at a duty ratio set by an electronic control unit (hereinafter referred to as ECU) 24, which will be described later. Therefore, the evaporation gas generated in the fuel tank 14 is fed to the canister 16 via the tank port passage 15 and then discharged to the surge tank 8 according to the opening degree of the purge valve 18. Also, canister 1
At 6, an atmosphere opening hole 19 for introducing fresh air is provided.

The sensor group 20 is composed of various sensors for detecting the operating state of the internal combustion engine 1, and more specifically, a rotation speed sensor 21 for detecting the engine speed, the internal combustion engine 1
A water temperature sensor 22 for detecting the temperature of the cooling water circulating therein, a power steering switch 23 for detecting the presence or absence of an operation of a power steering (not shown), and the like.

The ECU 24 includes a CPU, ROM, RAM,
This is a well-known microcomputer including an I / O port and the like, and the ECU 24 receives detection signals from the intake air temperature sensor 7, the intake pressure sensor 9, the O ₂ sensor 10, and the sensor group 20. Then, the ECU 24 detects the intake temperature, intake pressure, engine speed, etc. based on the detection signals of various sensors. Further, the ECU 24 determines the fuel supply amount to the internal combustion engine 1 (in this embodiment, it is referred to as the basic injection time τ _P ) based on each detection result, and the basic injection time τ
Fuel injection of the injector 5 is performed by the final injection time τ calculated based on _P.

Further, the ECU 24 inputs the voltage signal from the O ₂ sensor 10 and compares the voltage signal with the threshold value V _ref to judge the rich / lean of the air-fuel mixture as shown in FIG. Then, the ECU 24 changes (skips) the feedback correction coefficient FAF stepwise in order to increase or decrease the fuel supply amount when changing from rich to lean and when changing from lean to rich, and at the time of rich or lean, feedback correction is performed. The coefficient FAF is gradually increased or decreased.

Further, the ECU 24 uses the O ₂
When there is an air-fuel ratio deviation between the actual air-fuel ratio (actual air-fuel ratio) of the sensor 10 and the target air-fuel ratio, learning control is performed to reduce the air-fuel ratio deviation amount, and the engine operating state (intake pressure, engine Learning value FL according to the air-fuel ratio deviation amount for each rotation speed)
Memorize AF. In addition, in this embodiment, the ECU 24
Sets the steady correction coefficient FCON as a coefficient that is always applied when the internal combustion engine 1 is operating, and sets the transient correction coefficient FTRN as a coefficient that is applied only during a transient operation of the internal combustion engine 1. Here, the steady correction coefficient FCON is a coefficient including an EGR correction coefficient FEGR set according to the control amount of the EGR 11 in addition to the air-fuel ratio correction coefficient including the feedback correction coefficient FAF and the learning value FLAF. In the present embodiment, the intake pressure sensor 9 and the rotation speed sensor 21 constitute an operating state detecting means, and the ECU 2
4 constitutes a fuel supply amount calculation means, an air-fuel ratio control means, and an injected fuel reduction means.

Next, the operation of the air-fuel ratio control system of this embodiment will be described with reference to the flow charts of FIGS.
The routines shown in FIGS. 2 and 3 are for performing opening / closing control of the purge valve 18 according to the air-fuel ratio.
It is activated by 24 in a predetermined cycle (for example, 10 ms cycle).

When the routines shown in FIGS. 2 and 3 are activated, the ECU 24 first determines in step 101 whether or not the storage process of the learning value FLAF for each engine operating state has been completed. That is, the learning value FLAF corresponding to the air-fuel ratio deviation amount is stored in the nonvolatile memory by the storage process of the learning value FLAF. Then, if the storage processing of the learning value FLAF has not been completed, the ECU 24 proceeds to step 102 and executes the storage processing. If the storage processing of the learning value FLAF has been completed, the ECU 24 executes step 10
Then, the flow shifts to 3 and the purge mode for controlling the purge valve is started.

In step 104, the ECU 24 determines whether or not the average value FAFAV of the feedback correction coefficient FAF is smaller than a predetermined value (2% in this embodiment), so that the air-fuel ratio is stable. It is determined whether or not there is. If FAFAV ≦ 2%, the ECU 24 considers that the air-fuel ratio is stable and proceeds to step 105 to increase the purge rate R _PRG by 0.2%. Also FAFAV
If> 2%, the ECU 24 considers that the air-fuel ratio is unstable and proceeds to step 106 to set the purge rate R _PRG to 0.2.
% Decrease. Here, the purge rate R _PRG represents the ratio of the purge flow rate introduced into the intake pipe 2 through the purge valve 18 and the intake air amount of the intake pipe 2 drawn through the air cleaner 4. . The initial value of the purge rate R _PRG is “0”.

After that, the ECU 24 calculates the intake air amount GA by multiplying the predetermined coefficient K, the engine speed Ne and the intake pressure PM in step 107 (GA = K.Ne.P).
M). Further, the ECU 24 determines the intake air amount G in step 108.
The purge flow rate GP is calculated by multiplying A by the purge rate R _PRG (GP = GA · R _PRG ).

Further, the ECU 24 causes the duty ratio D (%) for driving the purge valve 18 in step 109.
To calculate. Specifically, the duty ratio D corresponding to the purge flow rate GP and the intake pressure PM at that time is calculated using the characteristic diagram of FIG. At this time, the duty ratio D increases as the value of the purge flow rate GP increases or the value of the intake pressure PM increases.
Is set to a large value. Then, the ECU 24 corrects the duty ratio D according to the battery voltage in step 110, and then drives the purge valve 18 in step 111.

After that, the ECU 24 executes step 1 of FIG.
12, the feedback correction coefficient FAF is calculated by calculating the change amount ΔFAF twice before and after the feedback correction coefficient FAF.
A change in AF behavior is detected. Then, in the subsequent step 113, the ECU 24 determines whether the air-fuel ratio is rich or lean based on the result of comparison between the change amount ΔFAF of the feedback correction coefficient FAF and “0”. At this time, ΔF
If AF <0, the ECU 24 determines that the air-fuel ratio is rich, and proceeds to step 114, where the evaporative gas concentration P
Increase the memory value of _DEN by 0.1%. Also, ΔFAF ≧ 0
If so, the ECU 24 determines that the air-fuel ratio is lean and proceeds to step 115 to decrease the stored value of the evaporative gas concentration P _DEN by 0.1%. The evaporative gas concentration P
The initial value of _DEN is "0".

Further, the ECU 24 executes the evaluation in step 116.
Pogas concentration P_DENAnd purge rate R_PRGMultiply by and evaporative
The purge correction coefficient FPRG is calculated (FPRG = P_DEN
・ R _PRG). That is, the evaporation purge correction coefficient FPRG is
Vapogas concentration P_DENAnd purge rate R_PRGSet to a value proportional to
Is determined. The evaporation purge correction coefficient FPRG is
Evaporative fuel for one fuel supply to the fuel engine
Used as a ratio of supply.

After that, the ECU 24 executes the fuel injection control routine shown in the flowchart of FIG. Further, the ECU 24 determines in step 118 that the evaporative gas concentration P _DEN has a predetermined concentration (in this embodiment, 0.
3%) or less. And P _DEN ≧
If 0.3%, the ECU 24 executes step 104 in FIG.
Then, if P _DEN <0.3%, the routine ends.

On the other hand, when the routine of FIG. 4 corresponding to step 117 of FIG. 3 is started, the ECU 24 first reads the intake pressure PM in step 201, and then reads the engine speed Ne in step 202. And EC
In step 203, the U24 calculates a basic injection time τ _P (a single fuel supply amount to the internal combustion engine 1) according to the intake pressure PM and the engine speed Ne by using an injection time two-dimensional map (not shown). Further, in step 204, the ECU 24 calculates an intake air temperature correction coefficient FTHA as a correction amount of the intake air amount based on the detection signal of the intake air temperature sensor 7.

Further, the ECU 24 executes the steps 205,
In 206, the constant correction coefficient FCON, which is always required when the internal combustion engine 1 is operating, and the transient correction coefficient FTRN, which is only required when the internal combustion engine 1 is in transient operation, are calculated separately. Specifically, the steady correction coefficient FCON is the feedback correction coefficient F
AF, learning value FLAF, EGR correction term FEGR are set (FCON = 1 + FAF + FLAF + FEG
R). At this time, if each of the terms FAF, FLAF, FEGR is "0", the steady correction coefficient FCON is set to "1". Also, the transient correction coefficient FTRN is the acceleration increase term FT
A, set from the power steering increase term FPS (FTRN =
FTA + FPS). The acceleration increasing term FTA and the power steering increasing term FPS are set in accordance with the degree of change of the intake pressure PM and the presence / absence of power steering operation.
The FPS is "0" except during the transition.

Next, in step 207, the ECU 24 reads the evaporation purge correction coefficient FPRG obtained in step 116 of FIG. Then, the ECU 24
In the following step 208, the post-correction injection time τ _e is calculated by reducing the basic injection time τ _P calculated in step 203 by the amount of the evaporative gas purge. That is, the corrected injection time τ _e is calculated by the following equation.

Τ _e = τ _P · FTHA · (FCON + FTRN) −τ _P · FTHA · FCON · FPRG (1) According to the above equation (1), the reduction amount of the basic injection time τ _P is “τ _P "FTHA / FCON / FPRG" is an amount proportional to the evaporation purge correction coefficient FPRG and also an amount proportional to the steady correction coefficient FCON. Therefore, even when the steady correction coefficient FCON greatly changes with respect to “1” due to the learning control, the change in the steady correction coefficient FCON is reflected in the amount reduction correction. Further, since the steady correction coefficient FCON and the transient correction coefficient FTRN are set separately, the increase correction during the transient operation is performed regardless of the evaporative gas purge correction.

After that, the ECU 24 calculates the invalid injection time τ _V depending on the battery voltage in step 209, and adds the corrected injection time τ _e and the invalid injection time τ _{V in} the following step 210 to add the final injection time. Calculate τ (τ = τ _e + τ _V ). Then, the injector 5 is driven at the final injection time τ and injects fuel.

Here, the fuel supply amount of the injector 5 with respect to the total fuel supply amount to the internal combustion engine 1 will be described. FIG. 7 shows how the coefficient relating to the fuel supply amount after the reduction correction is changed when the steady correction coefficient FCON largely changes as a reflection of the learning control. Note that, in FIG. 7, the evaporation purge correction coefficient FPRG is shown by a one-dot chain line (fixed to “0.3” in the figure), and the coefficient concerning the fuel supply amount after reduction correction (FCON-FCON · FPRG) is shown by a solid line. Further, for the sake of convenience, the transient correction coefficient FTRN = “0” is assumed in this description assuming a steady operation.

According to this figure, when the steady correction coefficient FCON does not change, that is, when FCON = “1.0” is constant, the value of “FCON−FCON · FPRG” is “0.
7 ”. As a result, the fuel supply amount by the evaporative gas is controlled to 30% of the total fuel supply amount, and the fuel injection amount by the injector 5 is controlled to 70% of the total fuel supply amount.
The above ratio when the CON does not change is the control target.

Next, the steady correction coefficient FCON is "1.0".
When it changes from, for example, the steady correction coefficient FCON is as shown in FIG.
When it becomes "0.8" of "FCON-FCON
-The value of "FPRG" is "0.56". At this time, the fuel injection amount by the injector 5 with respect to the total fuel supply amount is controlled to "0.56 / 0.8", that is, 70%. That is, it can be seen that the ratio (70%) in the case where there is no change even if the steady correction coefficient FCON changes is held. When the steady correction coefficient FCON becomes "1.4", "FC
The value of “ON-FCON · FPRG” becomes “0.98”, and at this time, the fuel injection amount by the injector 5 is controlled to “0.98 / 1.4”, that is, 70% with respect to the total fuel supply amount. In this way, the fuel injection amount by the injector 5 with respect to the total fuel supply amount is always controlled to a desired amount regardless of the fluctuation of the steady correction coefficient FCON, and the disturbance of the air-fuel ratio that occurs in the conventional air-fuel ratio control device is suppressed. Will be done.

As described above in detail, in the air-fuel ratio control system of the present embodiment, the evaporative gas generated in the fuel tank 14 is once adsorbed to the canister 16 and then discharged to the intake pipe 2 of the internal combustion engine 1. did. Further, in order to estimate the amount of evaporative emission, the evaporative gas purge rate R _PRG and the evaporative gas concentration P _DEN are calculated (steps 105 and 1 in FIG. 2).
06, and steps 114 and 115 in FIG. 3, both values R
_PRG, was calculated evaporative gas purge correction coefficient FPRG from P _DEN (step 116 in FIG. 3). A feedback correction coefficient F is a coefficient that is always applied when the internal combustion engine 1 is operating.
The steady correction coefficient FCON was calculated from the AF, the learning value FLAF, and the EGR correction term FEGR (step 20 in FIG. 4).
5). Then, as the air-fuel ratio control, the steady correction coefficient FCO
Fuel supply amount to the internal combustion engine 1 according to N (basic injection time τ
_P ) was corrected. Further, the fuel supply amount to the internal combustion engine 1 (basic injection time τ _P ) according to the evaporation purge correction coefficient FPRG
Is reduced, that is, when the fuel injection amount of the injector 5 is calculated, the amount of reduction correction is made proportional to the steady correction coefficient FCON (step 208 in FIG. 4).

In short, when the steady-state correction coefficient FCON including the air-fuel ratio correction coefficient is held at a constant value (FCON = “1.0”), the reduction correction amount of the fuel supply amount to the internal combustion engine 1 is evaporated. It may be uniquely set according to the release amount of. However, when the steady correction coefficient FCON fluctuates from a constant value due to changes over time or individual differences, the fuel amount corrected by the air-fuel ratio control fluctuates according to the steady correction coefficient FCON. Therefore, if the amount of fuel is uniquely reduced and corrected according to the amount of evaporative emission, the amount of fuel injected by the injector 5 becomes too small or too large, and the air-fuel ratio deviates to the lean side or the rich side.

On the other hand, as in the present embodiment, the reduction correction amount due to the amount of evaporative emission is changed to the steady correction coefficient FCON.
When calculated in proportion to
The fuel injection amount by the injector 5 is always controlled to a desired amount regardless of the fluctuation of As a result, the air-fuel ratio is stable, the precise air-fuel ratio control is always realized, and the deterioration of the emission is suppressed.

Further, in this embodiment, the transient correction coefficient FTRN required only during the transient operation of the internal combustion engine 1 is set, and during the transient operation of the internal combustion engine 1, the air-fuel ratio correction by the steady correction coefficient FCON and the reduction by the evaporation gas are performed. In addition to the correction, an increase correction of the fuel supply amount according to the transient correction coefficient FTRN is executed. That is, it is preferable that the increase correction by the transient operation is set according to the transient level and is performed separately from other corrections. For example, during acceleration, an acceleration increase term is required, but if the correction amount due to this acceleration increase term is used without distinction from the steady correction coefficient FCON, the correction by air-fuel ratio control may be overcorrected. Therefore, by distinguishing between the steady correction coefficient FCON and the transient correction coefficient FTRN as in the present embodiment, highly accurate air-fuel ratio control is performed even during transient operation.

The present invention is not limited to the above embodiment, but can be embodied in the following modes. In the above embodiment, the steady correction coefficient FCON is set to the feedback correction coefficient FAF, the learning value FLAF, and the EGR correction coefficient F.
It was set by the sum of EGR. However, only the feedback correction coefficient FAF and the learning value FLAF are used for the steady-state correction coefficient FC.
It is also possible to set ON or set the steady correction coefficient FCON by adding other correction terms related to steady operation.

[0045]

According to the present invention, the outstanding effect that the disturbance of the air-fuel ratio due to the fluctuation of the steady correction coefficient can be eliminated and the highly accurate air-fuel ratio control can be realized is exhibited.

[Brief description of drawings]

FIG. 1 is a configuration diagram schematically showing an air-fuel ratio control device for an on-vehicle internal combustion engine in an embodiment of the present invention.

FIG. 2 is a flowchart showing a purge valve control routine.

FIG. 3 is a flowchart showing a purge valve control routine following FIG.

FIG. 4 is a flowchart showing a fuel injection control routine which is a subroutine of FIGS.

FIG. 5 is a diagram showing a characteristic of a duty ratio with respect to a purge flow rate.

FIG. 6 is a waveform diagram for explaining sensor signal processing.

FIG. 7 is a diagram showing a change in coefficient value according to a change in steady correction coefficient in the present embodiment.

FIG. 8 is a diagram showing a change in coefficient value according to a change in an air-fuel ratio correction coefficient in the conventional technique.

FIG. 9 is a block diagram corresponding to a claim.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine, 2 ... Intake pipe as an intake passage, 5 ... Injector, 9 ... Intake pressure sensor as an operating state detection means, 10 ... O ₂ sensor as an air-fuel ratio sensor, 14 ... Fuel tank, 16 ... Fuel evaporation A canister as a gas release mechanism, 18 ... a purge valve as a fuel evaporative gas release mechanism,
21 ... Revolution speed sensor as operating state detecting means, 24 ...
An ECU as a fuel supply amount calculation means, an air-fuel ratio control means, and an injected fuel reduction means.

Claims (2)

[Claims] 1. A fuel evaporative emission mechanism for adsorbing fuel evaporative emission generated in a fuel tank to a canister and releasing the fuel evaporative emission adsorbed to the canister to an intake passage of the internal combustion engine, and an internal combustion engine. An injector for injecting and supplying fuel, an air-fuel ratio sensor for detecting an air-fuel ratio of the internal combustion engine, an operating state detecting means for detecting an operating state of the internal combustion engine, and an internal combustion engine based on the operating state of the internal combustion engine by the operating state detecting means. Fuel supply amount calculation means for calculating the fuel supply amount to be supplied to the engine, feedback control and learning control are performed based on the detection result by the air-fuel ratio sensor, and the fuel supply amount calculated by the fuel supply amount calculation means is empty. Air-fuel ratio control means for injecting the fuel amount corrected by using the fuel ratio correction coefficient from the injector, and fuel consumption by the fuel evaporative emission mechanism. Injection fuel reducing means for reducing and correcting the correction fuel amount by the air-fuel ratio control means according to the discharge amount of the material evaporative emission gas, and the injection fuel reducing means includes an air-fuel ratio correction coefficient by the air-fuel ratio control means. An air-fuel ratio control device for an internal combustion engine, which performs a reduction correction in proportion to a steady correction coefficient. 2. A transient correction coefficient, which is required only during transient operation of the internal combustion engine, is set, and during transient operation of the internal combustion engine, a transient correction coefficient is provided in addition to the reduction correction of the fuel amount by the injected fuel reducing means. The air-fuel ratio control device for an internal combustion engine according to claim 1, which executes an increase correction of the fuel amount according to the above.