JP2003120379A - Fuel injection control device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure a stable fuel injection even if an injection quantity after fuel reduction as a command to a fuel injection valve is below an injection quantity by a minimum pulse width. SOLUTION: A fuel injection control device for an engine, which comprises a means 21 for computing an injection quantity per cycle capable of producing a target air-fuel ratio as a first injection quantity and the fuel injection valves 4 for supplying the first injection quantity of fuel to an engine in every cycle, comprises a means 21 for computing, as a second injection quantity, an injection quantity obtained when a quantity equivalent to a purge fuel flow rate is subtracted from the first injection quantity so as to produce the target air-fuel ratio even during an introduction of purge gas, and a means 21 for executing control of injecting an injection quantity of fuel for two cycles at a time in a cycle and cutting the fuel injection in the next cycle when the second injection quantity is below a minimum injection quantity of the fuel injection valves.

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, and more particularly to a fuel injection control device provided with an evaporated fuel processing device.

[0002]

2. Description of the Related Art A fuel vapor treatment system mainly comprises a canister, a purge passage and a purge control valve. The vapor (gas containing fuel vapor) generated in the fuel tank is guided to the canister, and only the fuel particles are temporarily adsorbed and retained by the activated carbon in the canister. When the purge control valve is opened during engine operation, the suction pressure (lower than atmospheric pressure) generated downstream of the throttle valve causes the fuel particles adsorbed on the activated carbon to separate from the activated carbon and mix with the outside air, generating so-called purge gas. It The purge gas is introduced into the intake passage through the purge passage and burned as a part of fuel. Since the purge gas introduced from the portion into the intake passage acts as a disturbance to the air-fuel ratio control targeting the theoretical air-fuel ratio, the fuel flow rate in the purge gas (hereinafter referred to as " A technique has been proposed in which the fuel injection amount from the fuel injection valve is subtracted by the amount of "purge fuel flow rate") (see Japanese Patent Laid-Open No. 10-311255).

[0003]

By the way, if the fuel injection valve is given a smaller fuel injection pulse width than this, stable fuel injection cannot be performed. (Hereinafter referred to as "minimum pulse width") Tmin, so that the fuel amount by Tmin is smaller than the minimum fuel injection amount when the evaporative fuel treatment apparatus is not operating (for example, fuel injection amount during idling). By selecting the injection valve, the fuel can be injected more stably than the fuel injection valve even when the minimum fuel injection amount is supplied when the evaporated fuel processing device is not operating.

On the other hand, while there is a demand for reducing the size of the canister for the purpose of improving the mountability on the vehicle and reducing the cost, when the canister is small, the vapor generated in the fuel tank cannot be adsorbed and is released to the atmosphere. Since there is a concern that it will be discharged (overflow condition), it is necessary to install a canister of a certain size and burn all the purge gas from the canister in the engine, so the purge fuel flow rate tends to increase. is there.

Therefore, in order to obtain the stoichiometric air-fuel ratio even when the purged fuel flow rate is increased, the amount of fuel reduction from the fuel injection valve becomes large, and at this time, the injection after fuel reduction commanded to the fuel injection valve is made. A situation occurs in which the amount is below the injection amount due to the minimum pulse width Tmin. In such a situation, the fuel injection from the fuel injection valve becomes unstable, and if the insufficiency of this fuel injection makes it impossible to supply the injection amount that gives the theoretical air-fuel ratio accurately from the fuel injection valve, the actual air-fuel ratio becomes The fuel composition deviates from the fuel ratio, the conversion efficiency of the three-way catalyst provided in the exhaust passage decreases, and the exhaust composition deteriorates.

However, a technique for coping with such a situation has not been disclosed.

Therefore, in the present invention, when a situation occurs in which the injection amount after the fuel reduction commanded to the fuel injection valve falls below the injection amount by the minimum pulse width, the injection amount of fuel for two cycles is injected at one time in the current cycle. However, by executing the control to stop the fuel injection in the next cycle, even if the injection amount after the fuel reduction commanded to the fuel injection valve may fall below the injection amount by the minimum pulse width, stable fuel injection can be performed. The purpose is to secure and eliminate the influence on the exhaust gas composition.

Further, in this case, paying attention to the behavior of the intake air flow rate in the cylinder at the fuel injection timing, the fuel in this cycle is carried out so that half of the injection amount for two cycles is carried over to the fuel supply to the cylinder in the next cycle. By setting each timing of the start and end of injection, the fuel of the injection amount for two cycles is injected at one time in this cycle, and even when the fuel injection is stopped in the next cycle, It is also intended to achieve the stoichiometric air-fuel ratio in the next cycle in which fuel injection is stopped.

[0009]

According to a first aspect of the present invention, a first injection amount (first pulse width TI1) is calculated as an injection amount per cycle at which a target air-fuel ratio (for example, a theoretical air-fuel ratio) is obtained. In a fuel injection control device for an engine, which includes an injection amount calculation means and a fuel injection valve that supplies the first injection amount of fuel to the engine in each cycle, fuel particles in a vapor generated in a fuel tank are transferred to a canister. An adsorbed fuel processing device that adsorbs the adsorbed fuel in the canister as a purge gas into the intake passage by the intake pressure during engine operation, and the target air-fuel ratio can be obtained even while the purge gas is being introduced. And a second injection amount calculation means for calculating an injection amount obtained by subtracting the purge fuel flow rate from the first injection amount as a second injection amount (second pulse width TI2). When the amount (second pulse width TI2) is less than the minimum injection amount (minimum pulse width Tmin) of the fuel injection valve, two cycles of injection amount (third pulse width TI3) of fuel are injected at one time in this cycle, And a purge control means for executing control (purge control 2) for stopping fuel injection in the next cycle.

In a second aspect of the invention, in the first aspect, the injection amount for the two cycles is a value obtained by doubling the second injection amount in the current cycle.

In the third aspect of the invention, in the second aspect of the invention, half of the injection amount for the two cycles is carried over to the fuel supply to the cylinder in the next cycle at each time of the start and end of the fuel injection in the present cycle. To be set.

In a fourth aspect of the invention, in the third aspect of the invention, an area equal to the intake amount from the intake bottom dead center until the intake valve is closed is centered on the intake bottom dead center on the waveform of the intake air flow rate in the cylinder. On the other side, the first crank angle that divides the area is defined as the injection center timing ITC, and each of the timing before and after the injection center timing ITC can complete the injection of half of the injection amount for the two cycles. And the injection end timing.

In a fifth aspect of the present invention, when the injection amount for the two cycles is less than the minimum injection amount of the fuel injection valve during execution of the purge time control means in the first or second aspect, 2
The injection amount for a cycle is expanded to a value obtained by doubling the minimum injection amount, the expanded injection amount of fuel for the two cycles is injected once in this cycle, and the fuel injection in the next cycle is stopped. Execute control.

In a sixth aspect of the invention, in the fifth aspect of the invention, the fuel injection timing in this cycle is set so that half of the injection amount for the two extended cycles is carried over to the fuel supply to the cylinder in the next cycle. To do.

In the seventh invention, in the sixth invention, an area equal to the area corresponding to the intake amount from the intake bottom dead center to the closing of the intake valve is centered on the intake bottom dead center on the waveform of the intake air flow rate in the cylinder. On the other side, the first crank angle that divides the area is defined as the injection center timing ITC, and the injection is performed before and after the injection center timing ITC where half of the injection amount for the two extended cycles can be completed. It is set as the start timing and the injection end timing.

In the eighth invention, the target air-fuel ratio can be obtained even in the state in which the injection amount for the two cycles in the sixth or seventh invention is expanded to a value obtained by doubling the minimum injection amount of the fuel injection valve. So that the purge fuel flow rate is reduced.

A ninth aspect of the present invention is a first injection amount calculation means for calculating an injection amount per cycle for obtaining a target air-fuel ratio (for example, a theoretical air-fuel ratio) as a first injection amount (first pulse width TI1), In a fuel injection control device for an engine including a fuel injection valve that directly supplies the first injection amount of fuel into a cylinder for each cycle, fuel particles in vapor generated in a fuel tank are adsorbed to a canister. At the same time, an evaporated fuel processing apparatus for introducing adsorbed fuel in the canister as purge gas into the intake passage by suction pressure during engine operation, and the first air-fuel ratio so that the target air-fuel ratio can be obtained even during introduction of the purge gas Second injection amount calculation means for calculating the injection amount obtained by subtracting the purge fuel flow rate from the injection amount as the second injection amount (second pulse width TI2), and this second injection amount is the fuel. When less than the minimum injection quantity of events (the minimum pulse width Tmin), the injection amount of the two cycles to set the second injection quantity in this cycle by the value twice, the 2
First purge control means for performing control to inject fuel in an injection amount for one cycle at a time in this cycle and to stop fuel injection in the next cycle, and from the intake bottom dead center on the waveform of the intake air flow rate in the cylinder. An area equal to the period until the intake valve is closed is the first crank angle that divides the area on the opposite side from the intake bottom dead center as the injection center timing ITC. From this injection center timing ITC, the above two cycles are performed. Fuel injection timing setting means for determining the respective timings before and after the injection of half of the injection amount can be completed as the injection start timing and the injection end timing, and the injection end timing during the operation of the first purge time control means. Is delayed from the intake valve closing timing, the injection amount for the above two cycles is shortened to a value obtained by doubling the value obtained by subtracting the injection center timing from the intake valve closing timing. The second purge time control means for performing a control for injecting the fuel of the injection amount for one cycle at a time in this cycle and for stopping the fuel injection in the next cycle, and the second purge time control means for the two cycles. And a purge fuel flow rate adjusting means for adjusting the purge fuel flow rate so that the target air-fuel ratio can be obtained even when the injection amount is shortened to a value obtained by doubling the value obtained by subtracting the injection center timing from the intake valve closing timing. .

In a tenth invention, the injection center timing ITC in any one of the fourth, seventh and ninth inventions is changed according to the engine operating condition.

In the eleventh aspect, in the tenth aspect, when the intake valve opening / closing timing is the same regardless of the engine rotation speed Ne, the injection center timing ITC is set so that the engine rotation speed Ne becomes higher. Change to the retard side.

In a twelfth aspect of the present invention, when the valve timing control device capable of variably adjusting the intake valve closing timing with the intake valve operating angle being constant is provided in the tenth aspect, the injection center timing ITC is set to the intake valve closing timing. The more the timing is advanced, the more retarded it is.

In a thirteenth aspect of the present invention, when the variable intake control device capable of switching the effective length of the intake port is provided in the tenth aspect of the invention, the injection center timing ITC is set to the inoperative state of the variable intake control device. Change with the state.

[0022]

According to the first and second aspects of the present invention, the injection amount of fuel for two cycles is injected at a time in this cycle, so that the margin for the minimum injection amount is doubled. In other words, the reduction amount of the injection amount from the fuel injection valve in the range where stable fuel injection can be performed is increased, so that the exhaust composition is not affected.

According to the third and fourth aspects of the present invention, when the fuel of the injection amount for two cycles is injected at one time in the current cycle and the fuel injection is stopped in the next cycle, the fuel injection is performed in this cycle and The air-fuel mixture having the target air-fuel ratio can be obtained in the next cycle in which the fuel injection is stopped.

According to the fifth aspect of the present invention, even if the injection amount for two cycles falls below the minimum injection amount of the fuel injection valve due to an increase in the purge fuel flow rate, the margin for the minimum injection amount is doubled. It becomes possible to increase the amount of reduction of the injection amount from the fuel injection valve in the range where stable fuel injection can be performed, so that the exhaust composition is not affected.

According to the sixth and seventh aspects of the present invention, the injection amount of fuel for two cycles, which is the value obtained by doubling the minimum injection amount of the fuel injection valve, is injected at one time in this cycle, and the next cycle is injected. Even when the fuel injection is stopped, the air-fuel mixture having the same air-fuel ratio is obtained in the current cycle in which the fuel injection is performed and the next cycle in which the fuel injection is stopped.

According to the eighth aspect of the present invention, since the injection amount for two cycles falls below the minimum injection amount of the fuel injection valve due to the increase of the purge fuel flow rate, the minimum injection amount of the fuel injection valve is doubled. Even when the fuel of the injection amount for two expanded cycles is injected at one time in this cycle and the fuel injection is stopped in the next cycle, the target empty space is set in both this cycle in which fuel injection is performed and the next cycle in which fuel injection is stopped. A fuel-air mixture is obtained.

According to the ninth aspect of the invention, for the cylinder direct injection fuel injection type engine, when the injection end timing is delayed from the intake valve closing timing during the operation of the first purge time control means, two cycles are required. The injection amount is shortened to a value obtained by doubling the value obtained by subtracting the injection center timing from the intake valve closing timing, and this shortened injection amount of fuel for two cycles is injected at one time in this cycle, and then in the next cycle. Even when the fuel injection is stopped, the air-fuel mixture having the target air-fuel ratio is obtained both in this cycle in which the fuel injection is performed and in the next cycle in which the fuel injection is stopped.

According to the tenth aspect of the invention, the optimum injection center timing can be obtained according to the operating conditions.

When the injection center timing is constant, the injection center timing (ITC) is adjusted to match the low rotation speed as shown in FIG.
However, according to the eleventh aspect of the present invention, the injection center timing is changed to the retard side as the rotation speed becomes higher.
The injection center timing can be optimally determined regardless of the engine rotation speed.

When a valve timing control device capable of variably adjusting the intake valve closing timing while keeping the intake valve operating angle constant is provided, when the intake valve closing timing is on the retard side as shown in FIG. If (ITC) is adapted, the injection center timing will not be optimal when the intake valve closing timing advances, but according to the twelfth aspect of the invention, the injection central timing is set so that the intake valve closing timing is advanced. Since it is changed to the retard side, the injection center timing can be optimally set regardless of the intake valve closing timing.

When the variable intake control device capable of switching the effective length of the intake port is provided, the injection center timing is set when the variable intake control device is in a non-operating state (when the variable intake control valve is closed) as shown in FIG. If the (ITC) is adapted, the injection center timing will not be optimal when the variable intake control device is in the operating state (when the variable intake control valve is open), but according to the thirteenth invention, the variable intake control device is not Since the injection center timing is changed between the operating state and the operating state, it is possible to optimally determine the injection center timing when the variable intake control device is in the non-operating state or the operating state.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, 1 is an engine body, 2 is an intake passage, 3 is an exhaust passage, and 4 is a fuel injection valve provided in an intake port of each cylinder.

The intake passage 2 includes an intake pipe 2A and an intake collector 2
B, an intake manifold 2C, and a so-called electronically controlled throttle device that opens and closes the throttle valve 8 by a DC motor 9 and the like is installed in the intake pipe 2A, and the actual throttle valve opening detected by the throttle sensor 22 is opened. The throttle valve 8 is driven so that the degree matches the target opening command value from the control unit 21. The flow rate of air taken into the engine is adjusted by the opening of the throttle valve 8 determined at this time.

The fuel from the fuel tank 11 is supplied to the common rail 1 by the fuel supply pump 12 through the fuel supply passage 13.
The fuel having a constant pressure is supplied to the fuel injection valve 4 of each cylinder.

The control unit 21 receives position signals and reference position signals for each unit crank angle from the crank angle sensors 23 and 24, intake air flow rate signals from the air flow meter 25, cooling water temperature signals from the water temperature sensor 26, and the like. Based on these signals, the control unit 21 inputs the fuel injection pulse width per cycle at which a target air-fuel ratio, for example, a stoichiometric air-fuel ratio is obtained, to the first fuel injection pulse width (hereinafter simply referred to as “first pulse width”). It is calculated as TI1 and fuel is injected from the fuel injection valve 4 at a predetermined timing according to the calculated value.

In this case, the value of the first pulse width TI1 becomes the minimum value at the time of idling, etc., but the minimum pulse width Tmin of the fuel injection valve 4 becomes smaller than this minimum value. We have selected.

On the other hand, the vapor accumulated in the upper portion of the fuel tank 11 is guided to the canister 16 through the passage 15, only the fuel particles are adsorbed by the activated carbon in the canister 16, and the remaining air is provided vertically below the canister 16. It is released to the outside from the atmosphere release port (not shown).

The canister 16 is connected to the intake collector 2B downstream of the throttle valve 8 via a purge passage 17, and the purge passage 17 is provided with a normally closed purge control valve 18 driven by an actuator (eg, step motor). When the purge control valve 18 is opened in response to a signal from the control unit 21 under a certain condition (for example, after the engine is warmed up and operating at the stoichiometric air-fuel ratio and in the low load range), it greatly develops downstream of the throttle valve 8. Fresh air is introduced into the canister 16 from the atmosphere opening port of the canister 16 by the suction pressure (lower than atmospheric pressure). The fresh air separates the fuel particles from the activated carbon to generate a purge gas mixed with the fresh air, and the purge gas is introduced into the intake collector 2B through the purge passage 17 and burned in the combustion chamber.

Thus, the canister 16, the purge passage 17, the purge control valve 18 and the like constitute an evaporated fuel processing apparatus.

When the flow rate of purge fuel is large, the air-fuel ratio leans toward the rich side of the stoichiometric air-fuel ratio by that amount.
The purge fuel flow rate QP1 is calculated so that the stoichiometric air-fuel ratio is obtained even during introduction into the fuel cell (hereinafter referred to as “purging”), and the fuel injection pulse width reduced by the purge fuel flow rate QP1 is used for the second fuel injection. A pulse width (hereinafter, simply referred to as "second pulse width") TI2 is calculated, and an injection amount according to the second pulse width TI2 is supplied from the fuel injection valve 4 (FIG. 2).
(See the upper row).

In this case, if the purge fuel flow rate QP1 is large, the second pulse width TI2 may be less than the minimum pulse width Tmin of the fuel injection valve 4, and at this time as well, the second pulse width TI2 is used. When the injection valve 4 is driven, the fuel injection from the fuel injection valve 4 becomes unstable, and the air-fuel ratio cannot be maintained near the stoichiometric air-fuel ratio. Therefore, in the control unit 21, the second pulse width TI2 is set to the fuel injection valve during purging. When the pulse width becomes less than the minimum pulse width Tmin of 4,
As shown in the lower part of FIG. 2, the fuel injection pulse width for two cycles is set to the third fuel injection pulse width (hereinafter simply referred to as “third pulse width”).
Say. ) Calculated as TI3, this third pulse width TI
The injection amount of 3 is injected once in this cycle, and the fuel injection in the next cycle is stopped. Then, the fuel injection is repeated once every two cycles.

On the other hand, if two cycles of fuel are injected at one time during the intake stroke, the injection period may become longer and the injection end timing may approach the intake bottom dead center. At this time, the relationship with the intake valve open period is considered. Need to be considered. This will be described with reference to FIG.

FIG. 3 is a waveform of the intake air flow rate (weight flow rate) in the cylinder with respect to the crank angle. When this value is positive, the intake air flows into the cylinder, and conversely when it is negative, from the cylinder to the intake collector. Intake flows out (backflow)
It means to do. The area surrounded by a horizontal line passing through zero indicates the amount of intake air. As shown in the drawing, the intake air first flows backward from the cylinder toward the intake collector at the portion A immediately after the intake valve is opened. This is because the pressure in the intake collector is lower than the pressure in the cylinder. Then, the intake air is sucked into the cylinder at the portions B and C where the internal pressure of the cylinder becomes lower than the internal pressure of the intake collector.

However, since the intake valve is generally opened even after the intake bottom dead center has passed, the intake air once sucked into the cylinder at section D is returned to the intake collector due to the rise of the piston. From this, on the waveform of the intake air flow rate in the cylinder, the area equal to the area of the D portion (the area of the C portion) corresponding to the intake amount from the intake bottom dead center to the closing of the intake valve is centered around the intake bottom dead center. If the first crank angle that divides the area of the C portion on the opposite side is θ2, it can be considered that the intake air corresponding to the area of the C portion is not sucked into the cylinder in this cycle.

Considering that fuel injection is performed under such a characteristic of the intake air flow rate in the cylinder, the fuel injected into the intake air of the C portion is returned to the intake collector of the D portion, which contributes to the combustion in this cycle. Instead, it will contribute to combustion in the next cycle. From this, the air-fuel ratio of the air-fuel mixture in this cycle is determined by the fuel amount injected up to θ2, and the air-fuel ratio of the air-fuel mixture in the next cycle is determined by the fuel amount injected after θ2.

Therefore, if the fuel injection timing is set as follows, it is possible to obtain the air-fuel mixture of the theoretical air-fuel ratio in this cycle and the next cycle. That is, <1> θ2 is the injection center timing and the injection start timing θ1 is the injection center timing θ.
It is set to be a timing earlier than half by 2 (TI2) of the third pulse width TI3 which is the fuel injection pulse width of 2 cycles.

<2> The injection end timing θ3 is a timing after the injection center timing θ2 by a half (TI2) of the third pulse width TI3 which is the fuel injection pulse width for two cycles.

When the respective timings θ1 and θ3 for starting and ending the fuel injection are set in this way, it is TI2 that the fuel is injected between the injection start timing θ1 and the injection center timing θ2 in this cycle.
The injection amount is due to, and all of this injection amount remains in the cylinder for combustion in the present cycle, so that a mixture of the stoichiometric air-fuel ratio is obtained in this cycle.

Further, it is the injection amount by TI2 that is injected between the injection center timing θ2 and the injection end timing θ3 in this cycle, and the fuel of this injection amount returns to the intake collector in this cycle and stays there. Since all the stagnant fuel is sucked into the cylinder and burned in the next cycle, the stoichiometric air-fuel ratio mixture can be obtained in the next cycle even though the fuel injection is stopped.

The contents of this control executed by the control unit 21 will be described with reference to the following flow chart.

FIG. 4 is for setting a control flag, which is executed for each cycle.

In step 1, the first pulse width TI1 for obtaining the theoretical air-fuel ratio (target air-fuel ratio) is calculated. This calculation method is publicly known, and the calculation may be performed as follows, for example.

(A) The intake air flow rate (weight flow rate) Gair [g / m] per unit time measured by the air flow meter 25.
in] is measured.

(B) Fuel flow rate (weight flow rate) GFU required to obtain a mixture of stoichiometric air-fuel ratio at this intake air flow rate
EL [g / min] is calculated by the following equation: GFUEL = K1 × Gair ... where K1: coefficient. Even if the stoichiometric air-fuel ratio is set as the target, the ratio of the air flow rate to the fuel flow rate actually differs slightly depending on gasoline, and is about 14.3 for general commercial gasoline, so the coefficient K1 of the equation is 1/1.
4.3th place.

(C) Using the fuel flow rate GFUEL and the engine rotation speed Ne [rev / min], the fuel flow rate gfuel [g / min] per injection is gfuel = (GFUEL / Ne) × (number of cylinders / 2. ) ... is calculated by the formula.

(D) Fuel flow rate gfu per injection
el and the flow rate characteristic coefficient Kinj [ms / (g
/ Min)] using the pulse width TI1 per injection
[Ms] is calculated by the following formula: TI1 = gfuel × Kinj. The pulse width per injection is the first pulse width.

In step 2, it is determined whether or not purging is in progress. Whether or not the operating conditions are such that purging is performed at the stoichiometric air-fuel ratio operation is predetermined.

If purging is in progress, the routine proceeds to step 3, where the purge fuel flow rate QP1 is calculated. This calculation method is publicly known, and the calculation may be performed as follows, for example.

(F) From the purge gas flow meter 27 provided in the purge passage 17, the purge gas flow rate (weight flow rate) Gp
Measure ur [g / min].

(G) Similarly, the air-fuel ratio sensor 28 provided in the purge passage 17 measures the air-fuel ratio AFpur of the purge gas.

(H) These measured purge gas flow rates G
Using the pur and the air-fuel ratio AFpur of the purge gas, the purge fuel flow rate (weight flow rate) QP1 [g / min] is calculated by the equation QP1 = Gpur / AFpur.

In step 4, the pulse width TIP1 corresponding to the purge fuel flow rate is calculated. This calculation method is publicly known, and the calculation may be performed as follows, for example.

(P) Using the purge fuel flow rate QP1, the purge fuel flow rate per injection gpur [g / min] is calculated by the following equation: gpur = (QP1 / Ne) / (number of cylinders / 2).

(Vi) The purged fuel flow rate gpur per injection and the flow rate characteristic coefficient Kinj [ms / of the fuel injection valve]
(G / min)], the pulse width TIP1 [ms] corresponding to the purge fuel flow rate per injection is calculated by the equation TIP1 = gpur × Kinj.

In step 5, the pulse width obtained by subtracting the purge fuel flow rate equivalent pulse width TIP1 from the first pulse width TI1 is calculated as the second pulse width TI2 (= TI1-TIP1). The injection amount by the second pulse width TI2 is the fuel amount for achieving the stoichiometric air-fuel ratio even during the purge.

In step 6, this second pulse width Ti2 is compared with the minimum pulse width Tmin of the fuel injection valve 4. Second
If the pulse width Ti2 is smaller than the minimum pulse width Tmin (operating condition 1), the control 2 flag during purge (initial setting to zero) = 1 is set in step 7. On the other hand, when the second pulse width Ti2 is equal to or larger than the minimum pulse width Tmin, the process proceeds to step 8 and the purge control 1 flag (initially set to zero) = 1
And On the other hand, if purging is not in progress, the process proceeds from step 2 to step 9 and the normal time control flag (initially set to zero) = 1
And

Here, the purge time control 2 flag = 1 indicates that the purge time control 2 process is executed, and the purge time control 1 flag = 1 indicates that the purge time control 1 process is executed. = 1 is an instruction to execute the fuel injection control at the normal time (that is, at the time of non-purging).

Further, the above-mentioned purge control 2 is a fuel injection control in which when the operating condition 1 is satisfied during purging, the injection amount for two cycles is injected once in this cycle and the fuel injection in the next cycle is stopped. That is. This purge control 2
Is done for each cylinder in a multi-cylinder engine. On the other hand, the purge control 1 is a fuel injection control (that is, a conventional control) that reduces the fuel injection amount by the amount of the purge fuel flow rate when the operating condition other than the operating condition 1 is reached during the purging. .
The operating condition 1 is that the second pulse width Ti2 is the minimum pulse width Tm.
This is the case when it is smaller than in.

In this way, one of the three control flags becomes 1 for each cycle. That is, it is determined which of the purge control 2, the purge control 1, and the normal control is to be performed for each cycle.

FIG. 5 is for executing the processing of the control 2 at the time of purging. The flow of FIG. 5 is executed for each cycle only when the purge control 2 flag = 1.

In step 11, the processing state in the previous cycle is checked from the above three control flags. If a process other than the purge time control 2 (that is, the purge time control 1 or the normal time control) is being performed in the previous cycle, it is the timing at which the process of the purge time control 2 is first performed in this cycle.
At this time, the process proceeds to step 12, and after the previous injection completion flag (initially set to zero) = 0, the process proceeds to step 13, and when the process of the purge time control 2 is performed in the previous cycle, the process skips step 12. Go to step 13.

The previous injection completion flag = 0 is set in the first cycle after the process of the control 2 at the time of purging is performed is the first cycle after the process is changed to the process of the control 2 at the time of purging, and the second cycle after the process is always matched. This is for fuel injection.

This is because the previous injection completion flag is set in steps 17 and 18 after shifting to the processing of the control 2 at the time of purging.
It is only done in. In this case, the purge fuel flow rate is decreased and the fuel amount injected from the fuel injection valve 4 is increased,
When the pulse width TI2 becomes equal to or larger than the minimum pulse width of the fuel injection valve 4, the control 2 at the time of purge shifts to the control 1 at the time of purge. Therefore, if the previous injection completed flag remains set to 1 at the time of the shift, it will be again. The purge fuel flow rate increases and the second
When the pulse width TI2 is less than the minimum pulse width of the fuel injection valve, fuel injection is not executed in the first cycle after the transition from the purge control 1 to the purge control 2. Similarly, if during the purging, the control at the time of purging 2 shifts to the control at the normal time, and the previous injection completed flag remains set to 1 at the time of shifting, the purging condition becomes again and the purging fuel flow rate becomes If the second pulse width TI2 is less than the minimum pulse width at most, the control from the normal time control to the purge time control 2
Fuel injection is not executed in the first cycle after the transition to.
For the purpose of avoiding the occurrence of such a problem, the previous injection completion flag = 0 is set in steps 11 and 12 so that the fuel injection is always executed in the first cycle after the transition to the purge control 2.

In step 13, twice the second pulse width TI2 (calculated in step 5 of FIG. 4) is calculated as the third pulse width TI3.

In step 14, a value obtained by subtracting the second pulse width TI2 from the injection center timing ITC (constant value) is set as the injection start timing IT.

Here, since the crank angle [° ATDC], which is designed behind the intake top dead center, is adopted for both the injection center timing ITC and the injection start timing IT, it is determined from the ITC to TI2.
Subtracting means that the value that is TI2 ahead of ITC (advance side) is IT (see FIG. 3). Further, it is simply shown as "IT = ITC-TI2", but strictly speaking, since the unit of the second pulse width TI2 is [ms], this cannot be subtracted from ITC [° ATDC] as it is. Actually, the engine speed Ne [re at that time is
v / min] is used to convert the second pulse width TI2 [ms] into a crank angle [°], and this crank angle is subtracted from the injection center timing ITC.

In step 15, the previous injection completion flag is checked. As described above, if it is the initial cycle in which the process of the control 2 at the time of purge is started, the previous injection completion flag is set to 0, so the routine proceeds to step 16, where the third pulse width T13 [ms]
And the injection start timing IT [° ATDC] are transferred to the injection register. As a result, in the initial cycle in which the processing of the control 2 at the time of purge is started, in FIG. 3, θ1 (= IT) is the injection start timing and θ3 (= ITC + TI2) is the injection end timing.
The injection amount for a cycle is injected in this cycle.

In step 17, the previous injection completion flag is set to 1 in order to suspend the fuel injection in the next cycle. Also in the next cycle, if the purge control 2 flag = 1, steps 11 and 1
3, 14, 15 and the previous injection completion flag = 1 in step 15, it has been determined that fuel injection will not be performed in the next cycle because the fuel injection for 2 cycles has already been executed in this cycle. The process proceeds to step 18 and the previous injection completion flag = 0 is set, and the process ends. That is, in the cycle in which the previous injection completion flag = 1, the fuel injection is stopped because the injection register is not set.

By setting the previous injection completed flag in this way, the previous injection completed flag = 0 in step 15 means that fuel injection is not being executed in the previous cycle, and the previous injection completed flag = 1 shows the previous injection completed flag = 0. This means that fuel injection was performed in a cycle.

Here, the operation of this embodiment will be described with reference to FIG.

In FIG. 8, (b) shows how the fuel injection pulse width is shared by the purge control 1, and the second pulse width TI2 which is a value obtained by subtracting the purge fuel flow rate equivalent pulse width TIP1 from the first pulse width TI1. It is shown that the fuel injection valve 4 may share the above. This is the same as that disclosed by the conventional device.

However, when the purge fuel flow rate is increased (c)
When the second pulse width TI2 becomes smaller than the minimum pulse width Tmin as described above, a situation occurs in which the fuel injection valve 4 cannot stably perform fuel injection even if the second pulse width TI2 is instructed to the fuel injection valve 4. .

When this situation occurs in this cycle, according to the first embodiment, it is judged that the operating condition is 1, and the purge control 2 (the injection amount for two cycles is injected once in this cycle and the next cycle is performed). Stop the fuel injection at
As shown in (d), the fuel injection valve 4 is opened with the third pulse width TI3 which is the fuel injection pulse width for two cycles.

At this time, in this cycle, as shown in (e), T
The fuel of the injection amount of TI2 of the first half of I3 flows into the cylinder (the fuel of the injection amount of TI2 of the latter half flows back to the intake collector and remains), and the remaining TI1-TI.
The amount of 2 is supplemented by the purge fuel flow rate by TiP1.

In the next cycle, the fuel injection is not performed, but as shown in (f), the injection amount of fuel due to the second half TI2 staying in the intake passage in this cycle flows into the cylinder, and the remaining TI1- TI2 is also TIP
It is compensated by the purge fuel flow rate according to 1.

As described above, in the first embodiment, when the second pulse width TI2, which is the pulse width per injection for which the theoretical air-fuel ratio is obtained even during the purge, is less than the minimum pulse width Tmin of the fuel injection valve, 2 Since the fuel of the injection amount according to the third pulse width TI3, which is the fuel injection pulse width for one cycle, is injected at once in this cycle and the fuel injection is stopped in the next cycle, the margin to the minimum pulse width Tmin is doubled. Become. In other words, the reduction margin of the injection pulse width from the fuel injection valve 4 in the range where stable fuel injection can be performed expands, so that it does not affect the exhaust gas composition.

Further, the third pulse width TI3, which is the fuel injection pulse width for two cycles, is set to a value obtained by doubling the second pulse width TI2 in the present cycle, and the intake air flow rate in the cylinder is intaken. An area equal to the area corresponding to the intake amount from the bottom dead center to the closing of the intake valve is divided into the first crank angle that divides the area on the opposite side from the intake bottom dead center as the injection center timing θ2, and the injection start timing θ1. Is the timing (TI2) half the fuel injection pulse width for two cycles before this injection center timing θ2, and the injection end timing θ3 is half the fuel injection pulse width for two cycles (TI2) than this injection center timing θ2. ), The fuel injection is performed even when the fuel of the injection amount for two cycles is injected at one time in this cycle and the fuel injection is stopped in the next cycle. In this cycle and the next cycle in which the fuel injection is stopped, the air-fuel mixture having the stoichiometric air-fuel ratio is obtained.

The flowchart of FIG. 6 is the second embodiment,
It replaces FIG. 5 of the first embodiment.

In the first embodiment, when the second pulse width TI2 is less than the minimum pulse width Tmin of the fuel injection valve 2, 2
Third pulse width TI, which is the fuel injection pulse width for one cycle
Control of injecting the fuel of the injection amount according to No. 3 at once in this cycle and stopping the fuel injection in the next cycle (Purging control 2)
Was performed, but the minimum pulse Tm
When it becomes less than in, it becomes difficult to achieve the stoichiometric air-fuel ratio only by driving the fuel injection valve 4.

Therefore, in the second embodiment, in this case, the third
Expand the pulse width TI3 to the minimum pulse width Tmin,
Purge control is performed to inject the fuel in the injection amount according to the expanded third pulse width TI3 at one time in this cycle, to stop the fuel injection in the next cycle, and to cancel the fuel amount corresponding to the expanded fuel injection pulse width. The stoichiometric air-fuel ratio is obtained by controlling the valve opening to the closing side and reducing the purge fuel flow rate.

The parts different from those in FIG. 5 will be mainly described below. The same step numbers are assigned to the same parts as in FIG.

When the previous injection completion flag = 0 at step 15, the injection amount of fuel for two cycles is injected once, so the routine proceeds to step 21, where the third pulse width TI3 and the minimum pulse width Tmin are compared. The third pulse width TI3, which is the fuel injection pulse width for two cycles, is the minimum pulse width Tm.
When it is equal to or greater than in, the process proceeds to steps 16 and 17 as in the first embodiment, and the third pulse width TI3 and the injection start timing IT that is half the third pulse width (TI2) before the injection center timing ITC are used. In this cycle, two cycles of fuel are injected.

The third pulse width Ti3 is the minimum pulse width Tmi.
When it is smaller than n (operating condition 2), the routine proceeds to step 22 and thereafter, and the process 3 of the control 3 at the time of purge is performed.

Here, the purge control 3 means that when the operating condition 2 is satisfied during the processing of the purge control 2, the third pulse width TI3 is expanded to the minimum pulse width Tmin of the fuel injection valve 4, and this expansion is performed. Using the third pulse width TI3 and the injection start timing IT which is a value obtained by subtracting half of the third pulse width TI3 from the injection center timing ITC, fuel injection for two cycles is performed in this cycle, and This is a control for reducing the purge fuel flow rate so that the theoretical air-fuel ratio can be obtained even if the fuel injection pulse width is expanded. Further, it is a case where the third pulse width TI3, which is the fuel injection pulse width for two cycles under the above operating condition 2, is smaller than the minimum pulse width Tmin.

Specifically, in step 22, the minimum pulse width T
Set min as the third pulse width TI3. At this time, the average air-fuel ratio of the two cycles of this cycle and the next cycle deviates from the stoichiometric air-fuel ratio to the rich side. Therefore, in order to reduce the purge fuel flow rate, the purge amount reduction flag (initially set to zero) = 1 in step 23. . The purge amount reduction flag is necessary for performing the amount reduction correction of the purge fuel flow rate (described later in FIG. 7).

In step 24, a value obtained by subtracting half of the third pulse width TI3 from the injection center timing ITC is calculated as the injection start timing IT. Again, like step 14,
It is shown as "IT = ITC-TI3 / 2", but strictly speaking, T
The unit of I3 is [ms].
It cannot be subtracted from C [° ATDC]. Actually, the engine rotation speed Ne [rev / min] at that time
Is used to convert TI 3/2 [ms] into a crank angle [°], and this crank angle is subtracted from the ITC.

This completes the calculation of the third pulse width TI3 [ms] and the injection start timing IT [° ATDC].
Similar to the case of TI3 ≧ Tmin, the processes of steps 16 and 17 are performed, and the process of this cycle ends.

The flow chart of FIG. 7 is for correcting the reduction of the purge fuel flow rate, and is performed at regular intervals.

In step 31, the purge amount reduction flag is checked. Only when the purge amount reduction flag = 1, the process proceeds to step 32. The purge amount reduction flag = 1 is set by the third pulse width T
Since I3 is less than the minimum pulse width Tmin, the third pulse width TI3 is expanded to the minimum pulse width Tmin (steps 23 and 24 in FIG. 6).

The third pulse width TI3 is set to the minimum pulse width Tmi
When expanded to n, as shown in FIGS. 8 (i) and 8 (j), the purge fuel flow rate must take charge of subtracting half of the third pulse width Ti3 from the first pulse width TI1.

Therefore, in step 32, the first pulse width T
A value obtained by subtracting half of the third pulse width Ti3 from I1 is calculated as the purge fuel flow rate equivalent pulse width TiP2, and the purge fuel flow rate QP2 [g / min] is calculated in step 33 from this purge fuel flow rate equivalent pulse width TiP2 [ms]. Calculate The processing of steps 32 and 33 is exactly the reverse of the processing of steps 3 and 4 of FIG.

In step 34, this purge fuel flow rate QP
The opening of the purge control valve 18 is feedback-controlled so as to obtain 2. For example, the actual purge fuel flow rate is calculated based on the purge gas flow meter 27 and the air-fuel ratio sensor 28, a feedback amount is calculated according to the difference between the actual purge fuel flow rate QP2 and the purge fuel flow rate QP2, and the basic amount is supplied to the purge control valve 18. Add to the degree. The basic opening degree is given in advance according to operating conditions.

When the purge is stopped, the purge amount reduction flag is reset to zero.

The operation of the second embodiment will also be described with reference to FIG. 8. The case of the second embodiment is shown after (g).

As the purge fuel flow rate increases,
As in (g) and (h), the third pulse width TI3, which is a fuel injection pulse for two cycles, may fall below the minimum pulse width Tmin. In the present cycle, according to the second embodiment, the purge control 3 causes the third control as shown in (i) and (j).
The pulse width TI3 is expanded to the minimum pulse Tmin,
Further, the purge fuel flow rate is reduced so that the purge fuel flow rate shares the amount of TI1-TI3 / 2 (in terms of the purge fuel flow rate equivalent pulse width, from TIP1 of (g) to T of (j)).
iP2).

At this time, in this cycle, as shown in (k), the fuel of the injection amount by the first half (TI3 / 2) of the third pulse width flows into the cylinder (the fuel of the injection amount by the latter half of the third pulse width is It flows backward and stays in the intake passage), and the remaining T
I1-TI3 / 2 is supplemented by the purge fuel flow rate by TIP2.

Although fuel injection is not performed in the next cycle, as in (l), the fuel of the injection amount by the latter half (TI3 / 2) of the third pulse width that stayed in the intake passage in this cycle is injected into the cylinder. Inflow and remaining TI1-TI3
The amount of / 2 is supplemented by the purge fuel flow rate by TIP2 as in this cycle.

As described above, in the second embodiment, when the third pulse width TI3, which is the fuel injection pulse width for two cycles, is less than the minimum pulse width Tmin during the processing of the purge control 2, the third pulse width TI3 is set. Minimum pulse width Tmin
The injection amount of fuel with the expanded third pulse width TI3 is injected once in this cycle, and the fuel injection is stopped in the next cycle.
Third pulse width TI, which is the fuel injection pulse width for one cycle
Even if 3 is less than the minimum pulse width Tmin of the fuel injection valve, the minimum pulse width Tmin is the same as in the first embodiment.
It is possible to double the margin margin to the exhaust gas, which increases the reduction margin of the injection pulse width from the fuel injection valve 4 in the range where stable fuel injection can be performed, which may affect the exhaust gas composition. Absent.

Further, on the waveform of the intake air flow rate in the cylinder, an area equal to the area corresponding to the intake amount from the intake bottom dead center until the intake valve is closed is divided at the opposite side with the intake bottom dead center as the center. The crank angle of the injection center timing θ2
Then, the injection start timing θ1 is a timing half the third pulse width TI3 before the injection center timing θ2, and the injection end timing θ3 is the third pulse width TI from the injection center timing θ2.
Since it is set as a timing after only half of 3, the purge fuel flow rate is reduced so as to cancel out the increased fuel amount from the fuel injection valve due to the expansion of the third pulse width.
Even when the third pulse width TI3 is expanded to the minimum pulse width Tmin, the air-fuel mixture having the stoichiometric air-fuel ratio can be obtained in the current cycle in which fuel injection is performed and the next cycle in which fuel injection is stopped.

Next, when the opening / closing timing of the intake valve is the same regardless of the engine speed, the intake valve closing timing can be variably adjusted with the operating angle of the intake valve being constant when the engine speed changes. If the variable intake control device is equipped with a variable valve control device and the variable intake control device is capable of switching the effective length of the intake port when the intake valve closing timing is changed, The change waveforms of the intake air flow rate in the cylinder when switched to are shown in FIGS. 9, 10 and 11.

In the case of FIG. 9, the higher the rotational speed, the smaller the area of the D portion due to the intake inertia effect, and the smaller the area of the C portion. Since the drawing shows the same intake flow rate, the area of the B portion is reduced by the reduction of the area of the D portion. Therefore, if the injection center timing ITC having a constant value is adapted to the low rotation speed, the injection center timing ITC is not optimal at the high rotation speed, but the injection center timing ITC is retarded as the rotation speed becomes higher. By changing to, it is possible to optimally determine the injection center timing regardless of the engine rotation speed (third embodiment).

In the above case, as the intake valve closing timing is advanced as shown in FIG. 10, the area of the D portion becomes smaller, and the area of the C portion also becomes smaller. Therefore, if the injection center timing ITC of a constant value is adapted when the intake valve closing timing is on the retard side, the injection center timing ITC is not optimal when the intake valve closing timing is on the advance side. By advancing the intake valve closing timing and changing the injection central timing ITC to the retard side, the injection central timing can be optimally determined regardless of the intake valve closing timing (fourth embodiment).

In the above case, when the variable intake control valve is opened as shown in FIG. 11 (operating state of the variable intake control device), the area of the D portion changes (both larger and smaller depending on the system), This changes the area of the C portion. Therefore, if the injection center timing ITC of a constant value is adapted when the variable intake control valve is in the closed operation state (the non-operation state of the variable intake control device), the injection center timing is adjusted when the variable intake control valve is opened. Although the ITC is not optimal, the injection center timing ITC is changed when the variable intake control valve is opened, so that the injection center timing is optimized regardless of whether the variable intake control valve is open or closed. Can be set to (5th Embodiment).

The engine operating range is divided into a high rotational speed range and a low rotational speed range for the purpose of improving intake efficiency by utilizing the intake inertia effect, and the intake pipe length is long in the low rotational speed range. On the other hand, the variable intake control valve is a valve for switching the intake pipe length so that the intake pipe length becomes short in the high rotation speed range.

FIGS. 12, 14, and 16 are flowcharts showing the control contents of the third, fourth, and fifth embodiments described above with reference to FIGS. 9 to 11, and replace the FIG. 5 of the first embodiment. .

While the injection center timing ITC is constant in the first embodiment, the injection center timing ITC is variable in these three embodiments. Below, the part different from FIG. 5 will be mainly described. The same step numbers are assigned to the same parts as in FIG.

Step 4 in FIG. 12 of the third embodiment.
The engine rotation speed Ne is read at 1 and 42, and a table having the contents of FIG. 13 is searched from this rotation speed Ne, and the intake valve closing timing IVC is read at steps 51 and 52 in FIG. 14 of the fourth embodiment. , The intake center timing ITC is calculated by searching the table having the contents shown in FIG. 15 from the intake valve closing timing IVC, and the value obtained by subtracting the second pulse width TI2 from the injection center timing ITC is injected in step 14. Set as start time IT. In addition, in the fourth embodiment, the intake valve closing timing I
Since VC is calculated according to operating conditions (engine speed and load) in the flow of intake valve closing timing control (not shown), its value may be used.

Here, the injection center timing ITC is as shown in FIG.
As the engine speed Ne becomes higher as shown in FIG.
Further, the value is on the retard side as the intake valve closing timing IVC advances. The characteristics of FIGS. 13 and 15 are obtained in advance by experiments.

In FIG. 16 of the fifth embodiment, the variable intake control valve is viewed in step 61. If the variable intake control valve is in the open operation, the routine proceeds to step 62, where the set value 1 is set as the injection center timing ITC, and when the variable intake control valve is in the closed operation state, the routine proceeds to step 63 and the set value 2 is injected. After setting as the central period ITC, the process of step 14 is executed. Here, as shown in FIG. 11, when the area of the D portion becomes small when the variable intake control valve is opened, the injection center timing ITC when the variable intake control valve is opened is retarded more than when the variable intake control valve is closed. Setting values 1 and 2 are set so as to change to the side.

The flowchart of FIG. 17 is a sixth embodiment and replaces FIG. 5 of the first embodiment.

The sixth embodiment is intended for an in-cylinder direct injection fuel injection type engine in which fuel is injected into a cylinder from a fuel injection valve which directly faces a combustion chamber. When the in-cylinder direct injection fuel injection engine is targeted, the injection end timing may be later than the intake valve closing timing IVC during the processing of the purge control 2 as shown in FIG. The fuel component injected into the cylinder after the closing timing IVC stays in the cylinder without flowing back to the intake collector, so that the air-fuel ratio in this cycle becomes richer than the theoretical air-fuel ratio.

In order to avoid such enrichment of the air-fuel ratio,
In the sixth embodiment, when the injection end timing lags the intake valve closing timing, the injection period (fuel injection pulse width for two cycles)
To the intake valve closing timing, and the fuel of the injection amount by the shortened fuel injection pulse width is injected at one time in this cycle,
The purge fuel flow rate is adjusted by controlling the opening of the purge control valve so that the theoretical air-fuel ratio can be obtained even if the fuel injection is stopped in the next cycle and the fuel injection pulse width is shortened in this way.

Below, parts different from those in FIG. 5 will be mainly described. The same step numbers are assigned to the same parts as in FIG.

In step 71 of FIG. 17, a value obtained by adding half of the third pulse width TI3 (TI2 calculated in FIG. 4) to the injection center timing ITC is the injection end timing ITE.
And the intake valve closing timing IVC (constant value) is compared in step 72. Again, as in step 14, "ITE = ITC + TI"
Strictly speaking, since the unit of TI2 is [ms], it cannot be directly added to ITC [° ATDC]. Actually, TI2 [ms] is converted into a crank angle [°] using the engine rotation speed Ne [rev / min] at that time, and this crank angle is added to ITC. Similar to ITC, IVC is the crank angle [° ATDC] measured rearward from the intake top dead center.

The fact that the injection end timing ITE [° ATDC] is larger than the intake valve closing timing IVC [° ATDC] means that the injection end timing ITE is behind the intake valve closing timing IVC. It is judged that the condition 3 is satisfied, and the process proceeds to the process of the purge control 4 after step 73.

Here, the purging control 4 is a value obtained by subtracting the third pulse width TI3 from the intake valve closing timing IVC to the injection center timing ITC when the operating condition 3 is satisfied during the processing of the purging control 2. It is shortened to a doubled value, and the shortened third pulse width TI3 and the injection start timing IT which is a value obtained by subtracting half of the third pulse width TI3 from the injection center timing ITC This is a control for performing the fuel injection for one cycle and stopping the fuel injection for the next cycle, and adjusting the purge fuel flow rate so that the theoretical air-fuel ratio can be obtained even if the fuel injection pulse width is shortened in this way. Further, the above-mentioned operating condition 3 is the injection end timing ITE
Is when the intake valve closing timing is later than 1VC.

Specifically, at step 73, the intake valve closing timing I
A value obtained by doubling the value obtained by subtracting the injection center timing ITC from VC is set as the third pulse width TI3 [ms].
Here, as in step 14, "TI3 = (IVC-I
TC) × 2 ”, but strictly speaking, since the unit of TI3 is [ms], the right side and the left side are not equal. Actually, the crank angle section [°] obtained by subtracting the injection center timing ITC [° ATDC] from the intake valve closing timing IVC [° ATDC] is the engine rotation speed Ne [re] at that time.
The time [ms] required for the crank angle section is obtained using v / min], and a value obtained by doubling this time is set as the third pulse width TI3 [ms].

The injection end timing ITE is the intake valve closing timing IVC.
When it is later, when the injection period is up to the intake valve closing timing IVC, it is considered that the average air-fuel ratio for the two cycles of this cycle and the next cycle deviates from the theoretical air-fuel ratio by the amount of shortening the injection period. In step 74, the purge adjustment flag (initially set to zero) = 1 is set in order to adjust the purge fuel flow rate. This purge adjustment flag is necessary to adjust the purge fuel flow rate (FIG. 18).
See below).

In step 75, a value obtained by subtracting half of the third pulse width TI3 from the injection center timing ITC is calculated as the injection start timing IT. Again, like step 14,
It is shown as "IT = ITC-TI3 / 2", but strictly speaking, T
The unit of I3 is [ms].
It cannot be subtracted from C [° ATDC]. Actually, the engine rotation speed Ne [rev / min] at that time
Is used to convert TI 3/2 [ms] into a crank angle [°], and this crank angle is subtracted from the ITC.

With this, since the calculation of the third pulse width TI3 [ms] and the injection start timing IT [° ATDC] is completed,
Similar to the first embodiment, the processes of steps 16 and 17 are performed and the process of this cycle ends.

The flow chart of FIG. 18 is for adjusting the purge fuel flow rate and corresponds to FIG. 7. As shown in the figure, the control contents are the same as those in FIG. 7 except that the flag names are different. Therefore, the same parts as those in FIG. The purge adjustment flag is also reset to zero when purging is stopped.

According to the sixth embodiment, when the operating condition 3 is satisfied during the processing of the control 2 during purging, the third pulse width TI
3 is shortened to a value obtained by doubling the value obtained by subtracting the injection center timing ITC from the intake valve closing timing IVC, and the shortened third pulse width TI3 and half of the third pulse width TI3 from the injection center timing ITC are reduced. Injection start timing I which is the subtracted value
Fuel injection for two cycles is performed in this cycle using T and T (see FIG. 19), fuel injection is stopped in the next cycle, and the target air-fuel ratio is obtained even if the fuel injection pulse width is shortened in this way. To control the purge control valve opening to adjust the purge fuel flow rate (Purge control 4)
Therefore, for the in-cylinder direct injection fuel injection type engine, when the injection end timing is delayed from the intake valve closing timing during the processing of the purge time control 2, the third pulse width TI
3 is shortened to a value obtained by doubling the value obtained by subtracting the injection center timing from the intake valve closing timing, and the shortened third pulse width T
I3 injection amount of fuel is injected at one time in this cycle,
Even when the control for stopping the fuel injection in the next cycle is executed, the air-fuel mixture having the target air-fuel ratio is obtained in both the current cycle in which the fuel injection is performed and the next cycle in which the fuel injection is stopped.

Although the third, fourth, and fifth embodiments have been described on the premise of the first embodiment, they may be premised on the second and sixth embodiments.

[Brief description of drawings]

FIG. 1 is a control system diagram of an embodiment.

FIG. 2 is a schematic diagram showing the contents of control 2 at the time of purging of the first embodiment in comparison with a conventional device.

FIG. 3 is a change waveform diagram of an in-cylinder intake flow rate for explaining the content of fuel injection timing control added to the purge control 2.

FIG. 4 is a flowchart for explaining setting of three control flags.

FIG. 5 is a flowchart for explaining processing of control 2 at the time of purging.

FIG. 6 is a flowchart for explaining a process of control 2 at the time of purging according to the second embodiment.

FIG. 7 is a flowchart for explaining reduction correction of the purged fuel flow rate according to the second embodiment.

FIG. 8 is a schematic diagram for explaining controls 1 to 3 during purging.

FIG. 9 is a change waveform diagram of the in-cylinder intake air flow rate for explaining the variable control of the injection timing according to the third embodiment.

FIG. 10 is a change waveform diagram of in-cylinder intake air flow rate for explaining variable control of injection timing according to the fourth embodiment.

FIG. 11 is a change waveform diagram of the intake air flow rate in the cylinder for explaining the variable control of the injection timing according to the fifth embodiment.

FIG. 12 is a flowchart for explaining a process of control 2 at the time of purging according to the third embodiment.

FIG. 13 is a characteristic diagram of injection center timing with respect to engine rotation speed.

FIG. 14 is a flowchart for explaining a process of a control 2 at the time of purging according to the fourth embodiment.

FIG. 15 is a characteristic diagram of injection center timing with respect to intake valve closing timing.

FIG. 16 is a flowchart for explaining a process of control 2 at the time of purging according to the fifth embodiment.

FIG. 17 is a flowchart for explaining a process of a control 2 at the time of purging according to the sixth embodiment.

FIG. 18 is a flowchart for explaining the adjustment of the purge fuel flow rate according to the sixth embodiment.

FIG. 19 is a change waveform diagram of the intake air flow rate in the cylinder for explaining the operation of the sixth embodiment.

[Explanation of symbols]

4 Fuel injection valve 16 canisters 18 Purge control valve 1 control unit

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 41/34 F02D 41/34 H 43/00 301 43/00 301H 301M F02M 25/08 301 F02M 25/08 301J 301U F term (reference) 3G031 AA02 AA24 AA28 AB05 AC01 AD07 BA07 BB04 DA32 DA36 EA09 FA03 FA06 FA07 HA01 HA02 HA04 3G044 AA07 BA08 CA12 DA02 EA03 EA12 EA23 EA32 EA23 EA32 BA12 BA23 BA12 BA23 BA12 BA23 BA12 BA12 BA23 BA23 BA09 BA09 BA09 BA09 BA09 BA09 BA09 BA09 BA23 FA20 FA33 FA38 FA39 3G092 AA11 AA19 BA04 BA05 BB01 BB10 BB12 CB05 DC03 EA02 EA04 EB08 EC01 FA15 HA01Z HA11Z HA13X HA13Z HB01Z HB10X HB10Z HE01Z HE02ZA02 MA01 MA14 MA12 MA01 MA14 MA01 MA14 MA21 MA01 MA21 MA01 MA21 LA01 MA21 MA01 LA21 MA01 MA21 LA21 MA01 MA21 LA21 MA01 MA21 LA21 MA11 MA21 MA21 MA01 LA21 MA11 MA21 MA21 MA01 MA21 MA21 MA14 MA21 MA14 MA11 MA21 MA14 MA11 MA11 PE01Z PE03Z PE04Z PE08Z PE10A PE10Z

Claims (13)

[Claims] 1. A first injection amount calculation means for calculating an injection amount per cycle for obtaining a target air-fuel ratio as a first injection amount, and a fuel for supplying the engine with this first injection amount of fuel for each cycle. In a fuel injection control device for an engine equipped with an injection valve, the fuel particles in the vapor generated in the fuel tank are adsorbed to the canister, and the adsorbed fuel component in this canister is turned into a purge gas by the suction pressure during engine operation. And a fuel vapor treatment device that is introduced into the intake passage, and an injection amount obtained by subtracting the purge fuel flow rate from the first injection amount as the second injection amount so that the target air-fuel ratio can be obtained even during the introduction of the purge gas. Second injection amount calculation means for calculating, and when the second injection amount is less than the minimum injection amount of the fuel injection valve, the injection amount of fuel for two cycles is injected at one time in this cycle The fuel injection control device for an engine, further comprising: a purge control unit that executes control for stopping fuel injection in the next cycle. 2. The fuel injection control device for an engine according to claim 1, wherein the injection amount for the two cycles is a value obtained by doubling the second injection amount in the present cycle. 3. The fuel injection start and end timings in this cycle are set such that half of the injection quantity for the two cycles is carried over to the fuel supply to the cylinder in the next cycle. The fuel injection control device for the engine according to claim 2. 4. An area equal to the area corresponding to the intake amount from the intake bottom dead center until the intake valve is closed on the waveform of the intake air flow rate in the cylinder is divided at the opposite side with the intake bottom dead center as the center. Is set as the injection center timing, and each timing before and after the injection center timing at which half of the injection amount for the two cycles can be completed is set as the injection start timing and the injection end timing. The fuel injection control device for the engine according to claim 3. 5. When the injection amount for the two cycles falls below the minimum injection amount of the fuel injection valve during execution of the purge control means, the injection amount for the two cycles is a value obtained by doubling the minimum injection amount. 3. The control for executing the control of injecting the fuel of the injection amount for the expanded two cycles at a time in the current cycle and stopping the fuel injection in the next cycle. Fuel injection control device of the engine. 6. The fuel injection timing in the present cycle is set so that half of the injection amount for the expanded two cycles is carried over to the fuel supply to the cylinder in the next cycle. The fuel injection control device for the engine according to. 7. An area equal to the area corresponding to the intake amount from the intake bottom dead center until the intake valve is closed on the waveform of the intake air flow rate in the cylinder is divided at the opposite side with respect to the intake bottom dead center. Is set as the injection center timing, and the respective timings before and after which the half of the injection amount for the two cycles expanded from the injection center timing can be finished are defined as the injection start timing and the injection end timing. The fuel injection control device for the engine according to claim 6. 8. The purge fuel flow rate is reduced so that the target air-fuel ratio can be obtained even when the injection amount for the two cycles is expanded to a value obtained by doubling the minimum injection amount of the fuel injection valve. The fuel injection control device for the engine according to claim 6 or 7. 9. A first injection amount calculation means for calculating an injection amount per cycle for obtaining a target air-fuel ratio as a first injection amount, and a fuel of this first injection amount is directly supplied into a cylinder for each cycle. In a fuel injection control device for an engine equipped with a fuel injection valve, the fuel particles in the vapor generated in the fuel tank are adsorbed by the canister, and the adsorbed fuel component in the canister is changed by the suction pressure during engine operation. Evaporative fuel treatment device that is used as purge gas and is introduced into the intake passage, and second injection amount that is obtained by subtracting the purge fuel flow rate from the first injection amount so that the target air-fuel ratio can be obtained during the introduction of the purge gas. A second injection amount calculation means for calculating the injection amount, and when the second injection amount is below the minimum injection amount of the fuel injection valve, the injection amount for two cycles is the second injection in this cycle A first purge control means for executing a control of setting the amount to be a value doubled, injecting the fuel of the injection amount for the two cycles at once in the current cycle, and stopping the fuel injection in the next cycle; On the waveform of the intake air flow rate in the cylinder, the area equivalent to the period from the intake bottom dead center to the closing of the intake valve is equal to the area corresponding to the intake bottom dead center, and the first crank angle that divides the area is the injection center. And a first fuel injection timing setting unit that determines the respective timings before and after the injection center timing when half of the injection amount for the two cycles can be completed as the injection start timing and the injection end timing. When the injection end timing lags the intake valve closing timing during the operation of the time control means, the injection amount for the two cycles is shortened to a value obtained by doubling the value obtained by subtracting the injection central timing from the intake valve closing timing. Then, the second purge time control means for performing the control of injecting the fuel of the reduced injection amount for two cycles at one time in the current cycle and stopping the fuel injection in the next cycle, and the second purge time control means. The purge fuel for adjusting the purge fuel flow rate so that the target air-fuel ratio can be obtained even when the injection amount for the two cycles is shortened to a value obtained by doubling the value obtained by subtracting the injection center timing from the intake valve A fuel injection control device for an engine, comprising: a flow rate adjusting means. 10. The fuel injection control device for an engine according to claim 4, wherein the injection center timing is changed according to an engine operating state. 11. When the opening and closing timings of the intake valve are the same regardless of the engine rotation speed, the injection center timing is changed to the retard side as the engine rotation speed becomes higher. Item 10. The fuel injection control device for the engine according to item 10. 12. A valve timing control device capable of variably adjusting the intake valve closing timing while keeping the operating angle of the intake valve constant, wherein the injection center timing is retarded as the intake valve closing timing is advanced. 11. The method according to claim 10, wherein
The fuel injection control device for the engine according to. 13. When a variable intake control device capable of switching the effective length of an intake port is provided, the injection center timing is changed depending on whether the variable intake control device is in a non-operating state or an operating state. The fuel injection control device for the engine according to claim 10.