JPH0882236A - Fuel injection control device for engine - Google Patents

Abstract

PURPOSE: To compensate the inflow delay of the air-fuel mixture of fuel vapor and air flowing into a suction system through a purge passage, and supply a proper injection quantity to an engine to suppress the fluctuation of the air fuel ratio. CONSTITUTION: In a second injection quantity correcting part 57, a fuel injection correcting quantity Tevap as a second fuel correcting quantity considering a suction delay is calculated from the latest fuel injection correcting quantity Tevap new calculated by a first injection quantity correcting part 66 and the previous fuel injection correcting quantity Tevap old, and it is outputted to a fuel injection control part 58 as a final correcting quantity. Thus, at a low rotation with large suction delay, the ratio of the previous fuel injection correcting quantity Tevap old which is the unsucked portion is increased, and at a high rotation with small suction delay, the ratio of the latest fuel injection correcting quantity Tevap new is increased, whereby a purge flow rate slightly larger than the actual one is calculated to prevent the injection quantity from being excessively reduced, and a proper injection quantity is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control device for an engine which prevents fluctuations in the air-fuel ratio when purging fuel vapor generated in a fuel tank.

[0002]

2. Description of the Related Art Generally, in vehicles such as automobiles, in order to prevent the vaporized gas of fuel generated in a fuel tank from being discharged to the atmosphere, the vaporized fuel gas is temporarily adsorbed on activated carbon in a canister or the like. A so-called evaporative purge system is provided for storing and sucking the evaporated fuel gas in the canister from the intake passage into the combustion chamber of the engine under set operating conditions.

In this evaporative purge system, for example, as disclosed in Japanese Patent Laid-Open No. 63-85249, the valve installed in the purge passage between the canister and the intake passage is controlled to control the purge flow rate. Therefore, when the purge is executed, the fuel injection amount is corrected and controlled by the output from the air-fuel ratio sensor provided in the exhaust system, and the deviation of the air-fuel ratio from the target air-fuel ratio is corrected.

In this case, in the follow-up feedback control in which the fuel injection amount is corrected based on the output from the air-fuel ratio sensor provided in the exhaust system for the change in the air-fuel ratio due to the execution of the purge, the fluctuation of the air-fuel ratio due to the purge is avoided. In particular, in an engine equipped with an exhaust gas purification system using a three-way catalyst, the exhaust gas purification rate deviates significantly from the stoichiometric air-fuel ratio.

Therefore, in Japanese Patent Laid-Open No. 5-321711, an oxygen concentration sensor is provided in the vaporized fuel discharge passage, and the fuel component density in the vaporized fuel calculated from the oxygen concentration in the vaporized fuel, the intake pressure, and the purge. Disclosed is a technique for calculating the weight of the fuel component in the evaporated fuel from the flow rate of the evaporated fuel calculated from the control valve opening degree, reducing the injected fuel amount by this fuel component weight, and preventing the air-fuel ratio at the time of purging from being disturbed. Has been done.

Further, Japanese Patent Laid-Open No. 5-33733 discloses that
A mass flow meter is installed in the purge passage, and the output value of this mass flow meter and the flow rate of the air-fuel mixture flowing through the purge passage calculated from engine operating parameters such as throttle opening, intake pressure, valve opening area ratio of the purge control valve, etc. There is disclosed a technique in which the actual fuel vapor flow rate is calculated based on, and the basic fuel amount supplied to the engine is corrected according to the actual fuel vapor flow rate.

[0007]

However, the above-mentioned prior art (Japanese Patent Laid-Open No. 5-321711, Japanese Patent Laid-Open No. 5-321711).
No. 33733 gazette) does not consider the delay of the fluid when the evaporated fuel is purged from the purge passage to the intake system, and therefore the opening degree of the purge control valve interposed in the purge passage is larger than it actually is. Therefore, the purge flow rate will have to be calculated, and the fuel injection amount will decrease so much that the air-fuel ratio may become lean.

Further, the ratio of the fuel vapor and the air flowing through the purge passage largely varies depending on the filling state of the canister, and when the canister is hardly filled with the fuel vapor, the intake passage is purged from the purge passage. Most of the air is only air. Therefore, the air-fuel ratio becomes lean depending on the filling state of the canister, unless the fuel amount of the evaporated fuel flowing into the intake system by purging is corrected.

The present invention has been made in view of the above circumstances, and an object thereof is to compensate for an inflow delay of a mixture of fuel vapor and air flowing into a suction system from a purge passage, and to open a valve opening degree of a purge control valve. Even if the purge flow rate changes due to changes, the appropriate fuel injection amount is supplied to the engine to suppress fluctuations in the air-fuel ratio, and for the mixture of fuel vapor and air flowing into the intake system from the purge passage, An object of the present invention is to provide a fuel injection control device for an engine, which corrects the fuel injection amount supplied to the engine by both the fuel vapor amount and the air amount and enables accurate air-fuel ratio control.

[0010]

A first aspect of the present invention is a fuel injection control device for an engine, which feedback-controls a fuel injection amount supplied to the engine based on an output signal from an air-fuel ratio sensor interposed in an exhaust system. A first fuel injection amount correction means for calculating a first fuel correction amount based on a flow rate of a mixture of fuel vapor and air in a purge passage that connects a canister that stores evaporated fuel and an intake system, Based on an engine operating state, a purge delay calculating means for calculating a coefficient related to an intake delay of the air-fuel mixture purged from the purge passage to the intake system, and a coefficient related to the intake delay calculated by the purge delay calculating means. The first fuel correction amount calculated by the first fuel injection amount correction means is re-corrected to calculate the second fuel correction amount, and the second fuel correction amount is supplied to the engine. It is characterized in that a second fuel injection amount correcting means for outputting as a final correction amount for the fuel injection amount.

A second invention is the first invention according to the first invention.
The fuel injection amount correction means determines the flow rate of the air-fuel mixture based on the ratio between the opening degree of the opening / closing means interposed in the purge passage and the throttle opening degree, and then determines the flow rate of the fuel vapor in the air-fuel mixture at this flow rate. Multiplying by a coefficient representing the ratio of the amount of air and the amount of air,
It is characterized in that the fuel correction amount is calculated.

[0012]

In the first aspect of the invention, the first fuel correction amount is calculated based on the flow rate of the mixture of the fuel vapor and the air in the purge passage that communicates the canister that stores the evaporated fuel with the intake system. A coefficient relating to the intake delay of the air-fuel mixture purged from the purge passage to the intake system is calculated based on the engine operating state. Then, the first fuel correction amount is re-corrected by the coefficient related to the intake delay to calculate the second fuel correction amount, and the second fuel correction amount is finally corrected with respect to the fuel injection amount supplied to the engine. Output as a quantity.

According to a second aspect of the present invention, in the first aspect, the flow rate of the air-fuel mixture is calculated based on the ratio between the opening degree of the opening / closing means interposed in the purge passage and the throttle opening degree. A first fuel correction amount is calculated by multiplying by a coefficient that represents the ratio of the amount of fuel vapor in the mixture to the amount of air.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a functional block diagram of a fuel injection control system, FIG. 2 is a configuration diagram of an engine control system, FIG. 3 is a circuit block diagram of an electronic control system, and FIG. 4 is an evaporation correction initial stage. 5 is a flowchart of the fuel injection amount setting subroutine, FIG. 6 is a flowchart of the evaporation correction subroutine, and FIG. 7 is an explanatory diagram showing the relationship between the purge delay coefficient and the engine speed.

In FIG. 2, reference numeral 1 is an engine,
An intake passage 3 communicates with each intake port 2a formed in the cylinder head 2 of the engine 1. A throttle valve 4 is provided in the intake passage 3, and an intake air temperature sensor 5 is exposed immediately upstream of the throttle valve 4. Further, the throttle valve 4 has a throttle opening sensor 6 for detecting the opening of the throttle valve 4.
Are connected in series, and the intake air temperature sensor 5 in the intake passage 3
An air flow meter 7 is interposed on the upstream side of the portion facing the air cleaner, and an air cleaner 8 is attached on the upstream side of the air flow meter 7.

An unillustrated spark plug whose tip is exposed to the combustion chamber is attached to each cylinder head 2 for each cylinder, and an injector 9 is exposed immediately upstream of each intake port 2a of each cylinder. . This injector 9
The fuel is communicated with the fuel tank 10 via a fuel pipe (not shown), and the fuel whose pressure is regulated to a prescribed pressure is injected into the intake port 2a.

A discharge passage 11 for discharging the evaporated fuel generated in the fuel tank 10 extends from the upper portion of the fuel tank 10 and communicates with an upper portion of a canister 12 having an adsorption portion made of activated carbon or the like. Has been done. The canister 12 is provided with a fresh air introduction port communicating with the atmosphere at the bottom thereof, and a purge passage 13 for introducing a mixture of the fresh air from the fresh air introduction port and the evaporated fuel gas stored in the adsorbing section.
Is extended from the top.

The purge passage 13 is communicated with the intake passage 3 at a portion located downstream when the throttle valve 4 is fully closed.
In order to control the flow rate (purge flow rate) of the air-fuel mixture of No. 3, a canister purge control valve (C
A PC valve) 14 is interposed.

In the present embodiment, the CPC valve 14 is an electromagnetic valve whose valve opening is proportionally controlled according to the duty ratio of a drive pulse signal output from an electronic control unit 30 which will be described later. When the ratio is 0%, that is, the drive pulse signal is OFF, it is fully closed, and when the duty ratio is 100%, that is, it is fully open when continuous energization is performed.

The CPC valve 14 may be constituted by a proportional control valve that proportionally changes the opening area according to the value of energizing current.

Further, in the purge passage 13, the C
A purge temperature sensor 15 for detecting the temperature of the air-fuel mixture of evaporated fuel gas and air is provided upstream of the PC valve 14, and a concentration sensor for detecting the concentration of the air-fuel mixture is provided downstream of the CPC valve 14. 16 are faced. As the concentration sensor 16, for example, an air-fuel ratio sensor that detects the oxygen concentration in the air-fuel mixture is used.

A water temperature sensor 19 is provided in a cooling water passage 18 formed in the cylinder block 1a of the engine body 1.
And an O2 sensor 21 is exposed in an exhaust passage 20 communicating with the exhaust port 2b of the cylinder head 2, and the catalytic converter 2 is provided downstream of the O2 sensor 21.
2 is installed.

On the other hand, reference numeral 30 is an electronic control unit (ECU).
The ECU 30 detects the intake air temperature sensor 5, the throttle opening sensor 6, the air flow meter 7, the purge temperature sensor 15, the concentration sensor 16, the water temperature sensor 19, the O2 sensor 21, and the crank angle. Sensors such as the crank angle sensor 23 are connected, and actuators such as the injector 9 and the CPC valve 14 are connected.

The ECU 30, as shown in FIG.
PU31, ROM32, RAM33, input port 34,
The output port 35 is composed of a microcomputer connected to each other via a bus line 36 and its peripheral circuits.

The O2 sensor 21 and the crank angle sensor 23 are connected to the input port 34 via waveform shaping circuits 37 and 38, respectively, and the intake air temperature sensor 5, the throttle opening sensor 6 and the air flow are connected. Meter 7, the purge temperature sensor 15, the concentration sensor 1
6. The water temperature sensor 19 is the A / D converter 3 respectively.
They are connected via 9, 40, 41, 42, 43, 44. Further, the injector 9 and the CPC valve 14 are connected to the output port 35 by the drive circuit 4 respectively.
5, 46 are connected.

The ROM 32 stores a control program and various fixed data for control, and the RAM 33 outputs the output signals of the sensors and switches after data processing and the CPU 31 calculates them. Stores processed data. In the CPU 31, according to the control program stored in the ROM 32,
Fuel injection control, ignition timing control, purge control, etc. are executed.

As shown in FIG. 1, the function of the fuel injection control system by the ECU 30 is that the air-fuel ratio detecting section 50, the operating state detecting section 51, the purge flow rate comparing section 52, the purge temperature comparing section 53, and the purge concentration detecting section 54. , A first fuel injection amount correction unit 55, a purge delay calculation unit 56, a second fuel injection amount correction unit 57, a fuel injection amount control unit 58, and a purge control unit 59.

In the air-fuel ratio detecting section 50, based on the signal from the O2 sensor 21, an air-fuel ratio feedback correction coefficient LAMB for correcting the fuel injection amount by the air-fuel ratio feedback.
DA is calculated and output to the fuel injection control unit 58.

The operating state detecting section 51 detects parameters such as the cooling water temperature TW, the throttle opening θ, the intake air amount Q, and the engine speed N based on the signals from the sensors.

In the purge flow rate comparing section 52, the opening area of the purge passage 13 (evaporative purge passage area Aevap) determined by the opening of the CPC valve 14 and the opening area of the intake passage 3 (throttle opening by the throttle opening θ). The opening area ratio with the opening area Ath) is calculated and output to the first fuel injection amount correction unit 55.

In this case, the evaporation purge passage area Aevap is determined by the duty ratio DU of the drive pulse signal of the CPC valve 14.
TY and throttle opening area Ath
Is determined by the throttle opening θ, specifically, the map having the duty ratio DUTY as the grid and the map having the throttle opening θ as the grid respectively correspond to the evaporation purge passage area Aevap and the throttle opening area Ath.
Is stored, each area value is obtained by referring to each map, and then the aperture area ratio Aevap / Ath is calculated.

In the purge temperature comparison unit 53, the pre-throttle air temperature Tth based on the signal from the intake air temperature sensor 5
(Absolute temperature) is compared with the evaporation temperature Tevap (absolute temperature) before passing through the CPC valve 14 based on the signal from the purge temperature sensor 15, and the ratio is compared with the evaporation temperature correction coefficient Ktemp.
Is output to the first fuel injection amount correction unit 55.

In the purge concentration detector 54, the purge passage 1
The evaporation concentration Φ is detected on the basis of the signal from the concentration sensor 16 corresponding to 3 and is output to the first fuel injection amount correction unit 55. In the present embodiment, this evaporation concentration Φ is a value indicating the oxygen concentration of the air-fuel mixture in the purge passage 13, and Φ> when the amount of fuel vapor in the air-fuel mixture is larger than the amount of air.
1 and Φ <1 when the amount of fuel vapor in the mixture is smaller than the amount of air.

The concentration sensor 16 is not provided in the purge passage 13, but the O2 sensor 21 provided in the exhaust passage 20 is used to indirectly obtain the evaporation concentration from the difference between the output values when the canister purge is executed and when it is not executed. You can

In the first fuel injection amount correction unit 55, the basic fuel injection amount Tp calculated by the fuel injection control unit 58 which will be described later.
The opening area ratio Aevap from the purge flow rate comparison unit 52
/ Ath to obtain the purge flow rate, and further the temperature is corrected by the evaporation temperature correction coefficient Ktemp from the purge temperature comparison section 53, and then the purge flow rate is adjusted by the evaporation concentration Φ from the purge concentration detection section 54 to obtain the fuel in the mixture. A fuel injection correction amount Te as the first fuel correction amount Te is obtained by multiplying a coefficient (1-Φ) representing the ratio of the amount of steam and the amount of air, as shown in the following equation (1).
Calculate vapnew.

Tevapnew = Tp × (Aevap / Ath) × Ktemp × (1-Φ) (1) That is, the basic fuel injection amount Tp is multiplied by the ratio of the opening area of the purge passage 13 to the throttle opening area. , It is possible to know the accurate purge flow rate considering the influence of engine speed and atmospheric pressure.
The accuracy can be further improved. Then, the purge flow rate is multiplied by a coefficient representing the ratio of the amount of fuel vapor in the air-fuel mixture flowing in the purge passage 13 to the amount of air, whereby not only the amount of fuel vapor flowing from the purge passage 13 into the intake passage 3 but also the amount of air. In consideration of the above, it is possible to always obtain an accurate fuel correction amount regardless of the filling state of the canister 12.

The purge delay calculating section 56 calculates the intake delay coefficient X of the evaporated fuel which depends on the volume of the purge passage 13 from the CPC valve 14 to the intake passage 3. This inhalation delay coefficient X is a value assuming that there is no inhalation delay, X =
The value becomes 1, and the higher the engine speed, the larger the value (the intake delay decreases). Therefore, specifically, FIG.
As shown in, the engine speed N increases and X = 1
The intake delay coefficient X approaching the value of is stored in a map having the engine speed N as a parameter, and the intake delay coefficient X is obtained by referring to this map.

In the second fuel injection amount correction unit 57, the latest fuel injection correction amount Tevapnew calculated by the first fuel injection amount correction unit 55 is obtained from the intake delay coefficient X calculated by the purge delay calculation unit 56. Previous fuel injection correction amount Tev
apold and the fuel injection correction amount Teva as the second fuel correction amount considering the intake delay according to the following equation (2).
The fuel injection control unit 58 calculates p as the final correction amount.
Output to.

Tevap = (1−X) × Tevapold + X × Tevapnew (2) That is, the latest fuel calculated by the first fuel injection amount correction unit 55 in consideration of the delay of the fluid passing through the CPC valve 14. The injection correction amount Tevapnew is not adopted as it is, and at the time of low rotation with a large intake delay, the ratio of the previous fuel injection correction amount Tevapold that is the uninhaled amount is increased,
When the intake delay is small and the engine speed is high, the CP is increased by increasing the ratio of the latest fuel injection correction amount Tevapnew.
Even when the valve opening of the C valve 14 changes, the purge flow rate is calculated to be larger than it actually is to prevent the fuel injection amount from becoming excessively small, and the fuel injection amount is made appropriate.

In the fuel injection amount control unit 58, for example, the basic fuel injection amount Tp (Tp = K ×) calculated from the intake air amount Q detected by the operating state detection unit 51 and the engine speed N.
Q / N: K ... Injector characteristic correction constant) is corrected by various correction coefficients corresponding to the engine state to calculate the normal fuel injection amount Te in the non-purge execution state. This normal fuel injection amount Te is obtained by changing the basic fuel injection amount Tp from the air-fuel ratio feedback correction coefficient LAMBDA based on the output from the O2 sensor 21, as shown in the following equation (3).
In addition to the air-fuel ratio correction, the corrections are made by the various correction factors COEF related to the cooling water temperature correction, the acceleration / deceleration correction, the full-open increase correction, the post-idle increase correction, etc. It is calculated by correcting with the voltage correction coefficient TB to be interpolated.

Te = Tp × LAMBDA × COEF + TB (3) Then, as shown in the following equation (4), the normal fuel injection amount Te is added to the fuel injection amount from the second fuel injection amount correction unit 57 by the evaporation purge. The final fuel injection amount Teout is determined by adding the correction amount Tevap.

Teout = Te + Tevap (4) In this case, when the canister 12 is filled with a large amount of fuel vapor, the coefficient (1-
Φ) becomes negative, the fuel injection correction amount Tevap becomes a negative value, the normal fuel injection amount Te is reduced, and the canister 1
In a situation where 2 is empty, the coefficient (1-Φ) becomes positive and the fuel injection correction amount Tevap becomes a positive value, and the normal fuel injection amount Te is increased to correct the fuel amount with respect to the air content, Prevents the air-fuel ratio from becoming lean by drawing in the air.

When the operating condition detected by the operating condition detector 51 satisfies the canister purge condition, the purge controller 59 sets the duty ratio DUTY of the drive pulse signal of the CPC valve 14 and outputs it to the CPC valve 14. The flow rate of the purge passage 13 is controlled. The duty ratio DUTY is set with reference to a map having a grid of the basic fuel injection amount Tp and the engine speed N in order to set the purge flow rate according to the operating state.

The process relating to the fuel injection control by the ECU 30 will be described below with reference to the flow charts of FIGS.

Ignition switch (not shown) is ON
When the system power is turned on, first, the evaporative initialization subroutine shown in FIG. 4 is executed, and step S101
Then, the fuel injection correction amount Tevapold is initialized to "0".

Next, the fuel injection amount setting subroutine shown in FIG. 5 is executed every predetermined time (eg every 10.24 msec).
The fuel injection amount is set according to the execution state of the canister purge.

In this routine for determining the fuel injection amount, step
In S201, the basic fuel injection amount Tp is calculated, and the correction factors such as the air-fuel ratio feedback correction coefficient LAMBDA, various increase correction coefficients COEF, and the voltage correction coefficient TB are calculated to calculate the normal fuel injection amount Te (Te = Tp × L
AMBDA x COEF + TB).

Next, in step S202, it is determined whether or not the current operating state satisfies the canister purge condition. When the canister purge condition is satisfied, that is, in the case where the canister purge is to be executed in an operating state except when the engine is warmed up and idle or decelerated, the process proceeds from step S202 to step S203, When the duty ratio DUTY of the drive pulse signal for the CPC valve 14 is set with reference to the map using the engine speed N and the basic fuel injection amount Tp as a grid, the pulse signal of this duty ratio DUTY is output to the CPC valve 14. The valve opening degree is controlled to a predetermined value, and the process proceeds to step S205.

On the other hand, when the canister purge condition is not satisfied and the canister purge is not executed in step S202, the process proceeds from step S202 to step S204, the duty ratio DUTY is set to "0", and the CPC valve 14 is fully closed. Then, the process proceeds to step S205.

In step S205, the evaporation correction subroutine shown in FIG. 6 is executed to calculate the fuel injection correction amount Tevap. In this subroutine, first, step S301
Then, the throttle opening θ based on the signal from the throttle opening sensor 6 is referred to, and in step S302, the throttle opening area A is referred to by referring to a map using the throttle opening θ as a grid.
Set th.

Next, in step S303, the evaporation purge passage area Aevap is obtained by referring to the duty ratio grid map, and in step S304, the evaporation temperature correction coefficient Ktemp.
Is calculated, the purge concentration Φ is detected in step S305, and the process proceeds to step S306.

When the canister purge condition is not satisfied and the duty ratio DUTY is "0" in step S204 of the fuel injection amount setting subroutine, the evaporation purge passage area Aevap is "0" in step S303. Therefore, the fuel injection correction amount Tevapnew becomes “0”.

In step S306, the intake delay coefficient X is determined by referring to the map using the current engine speed N as a parameter.
In step S307, the basic fuel injection amount Tp is corrected by the area ratio Aevap / Ath, the evaporation temperature correction coefficient Ktemp, and the purge concentration Φ, and a new fuel injection correction amount Tevapnew is obtained.
Is calculated (Tevapnew = Tp × Aevap / Ath × Kte
mp x (1-Φ)).

In the following step S308, the above step S307
The latest fuel injection correction amount Tevapnew calculated in step 1 and the fuel injection correction amount Tevap calculated during the previous routine execution
After calculating the current fuel injection correction amount Tevap from the old using the intake delay coefficient X (Tevap = (1-X)
XTevapold + XxTevapnew), step S309
Then, the fuel injection correction amount Tevap is set as the old fuel injection correction amount Tevapold at the time of executing the next routine in the RAM 3
Stored in a predetermined address of No. 3, and return to the fuel injection amount setting subroutine.

Then, when returning to the fuel injection amount setting subroutine, in step S206, the fuel injection correction amount Teva calculated by the evaporation correction subroutine is added to the normal fuel injection amount Te.
The final fuel injection amount Teout is added with p, and a drive pulse signal corresponding to this fuel injection amount Teout is output to the injector 9 to exit the routine.

As a result, when the canister purge is started and the CPC valve 14 is opened, the fuel correction amount gradually changes, and the fuel injection correction amount Tevapnew and the intake delay coefficient X calculated every time the evaporation correction subroutine is executed. When and are constant, the fuel injection correction amount Tevapnew gradually converges. Meanwhile, the canister purge is stopped and the CP
When the C valve 14 is closed, the fuel injection correction amount Te before the CPC valve 14 is closed by the intake delay coefficient X
nvapold gradually decreases and converges to "0".
Therefore, the fuel injection amount Teout is appropriately set in consideration of the inflow delay of the mixture of fuel vapor and air from the purge passage 13, and the filling state of the canister 12 and the opening degree of the CPC valve are constantly changed. Therefore, the optimum air-fuel ratio can be maintained.

[0057]

As described above, according to the first aspect of the invention, based on the flow rate of the mixture of fuel vapor and air in the purge passage that connects the canister for storing evaporated fuel and the intake system, The first fuel correction amount is calculated, and a coefficient related to the intake delay of the air-fuel mixture purged from the purge passage to the intake system is calculated based on the engine operating state. Then, the first fuel correction amount is re-corrected by the coefficient related to the intake delay to calculate the second fuel correction amount, and the second fuel correction amount is finally corrected with respect to the fuel injection amount supplied to the engine. Since it is output as a quantity, it compensates for the inflow delay of the mixture of fuel vapor and air that flows into the intake system from the purge passage, and it is appropriate for changes in the purge flow rate due to changes in the valve opening of the purge control valve. It is possible to suppress the fluctuation of the air-fuel ratio by supplying the fuel injection amount to the engine.

Further, according to the second aspect of the present invention, after the flow rate of the air-fuel mixture is obtained based on the ratio of the opening degree of the opening / closing means interposed in the purge passage and the throttle opening degree, the mixing rate is set to this flow rate. In order to calculate the first fuel correction amount by multiplying by the coefficient representing the ratio of the amount of fuel vapor in the air to the amount of air, the mixture of fuel vapor and air flowing from the purge passage into the intake system is mixed with the fuel. It is possible to correct the fuel injection amount supplied to the engine by both the amount of steam and the amount of air, and enable accurate air-fuel ratio control.

[Brief description of drawings]

FIG. 1 is a functional block diagram of a fuel injection control system.

FIG. 2 is a block diagram of an engine control system

FIG. 3 is a circuit block diagram of an electronic control system.

FIG. 4 is a flowchart of an evaporation correction initialization subroutine.

FIG. 5 is a flowchart of a fuel injection amount setting subroutine.

FIG. 6 is a flowchart of an evaporation correction subroutine.

FIG. 7 is an explanatory diagram showing a relationship between a purge delay coefficient and an engine speed.

[Explanation of symbols]

 12 canister 13 purge passage 14 canister purge control valve 55 first fuel injection amount correction unit 56 purge delay calculation unit 57 second fuel injection amount correction unit

Claims (2)

[Claims] 1. A fuel injection control device for an engine, which feedback-controls a fuel injection amount supplied to an engine based on an output signal from an air-fuel ratio sensor interposed in an exhaust system, wherein a canister for storing evaporated fuel and an intake system are provided. And a first fuel injection amount correction means (55) for calculating a first fuel correction amount based on the flow rate of a mixture of fuel vapor and air in a purge passage communicating with The purge delay calculating means (56) for calculating a coefficient related to the intake delay of the air-fuel mixture purged from the purge passage to the intake system, and the first coefficient based on the coefficient related to the intake delay calculated by the purge delay calculating means. The first fuel correction amount calculated by the fuel injection amount correction means is re-corrected to calculate the second fuel correction amount, and the second fuel correction amount is finally determined with respect to the fuel injection amount supplied to the engine. The fuel injection control device for an engine is characterized in that a second fuel injection amount correcting means for outputting (57) as a Do correction amount. 2. The first fuel injection amount correction means (55)
Is the flow rate of the air-fuel mixture based on the ratio of the opening degree of the opening / closing means interposed in the purge passage and the throttle opening degree, and the flow rate of the fuel vapor amount and the air amount in the air-fuel mixture is set to this flow rate. The fuel injection control device for the engine according to claim 1, wherein the first fuel correction amount is calculated by multiplying by a coefficient representing a ratio.