JPH10252534A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent sensing of a large shock at fuel injection time, even by large taking hysteresis for preventing hunting of repeating fuel injection and fuel cut. SOLUTION: A fuel injection control device has sensors 15 to 22 or the like as an operating condition detection means, fuel injection valves 8A to 8D, and a CPU as a fuel injection amount arithmetic means, fuel cut control means, averaging means and a fuel reset means. The CPU is included in an ECU 23 calculating a fuel injection amount injected from the fuel injection valve. At a transfer from fuel cut condition by the fuel injection valve to a fuel injection reset condition, a fuel injection amount TAU injected from a fuel injection means is set a little lower than a fuel injection amount calculated in accordance with an operating condition by the CPU as the fuel injection amount arithmetic means, thereafter, while gradually increasing this little lowered set fuel injection amount (averaging value) TAUSM, in the end, by injection with a fuel injection amount calculated in accordance with an engine operating condition, a sudden torque change is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel injection control device for an internal combustion engine, and more particularly to a fuel injection control device for an internal combustion engine that appropriately controls the amount of fuel injected into the internal combustion engine in accordance with the operating state of the engine.

[0002]

2. Description of the Related Art In recent years, computerization of internal combustion engine control has been advanced, and the amount of fuel supplied to an internal combustion engine (hereinafter referred to as "engine" unless otherwise specified as an internal combustion engine) is determined based on the operating state of the engine. Calculated by microcomputer,
As a result, a fuel injection control device for an internal combustion engine in which the engine is driven in an optimum state has become widespread.

In particular, in an electronic fuel injection control device, a basic fuel injection amount T calculated according to an engine load (intake pipe pressure or intake air amount) and an engine speed.
By performing various corrections on P, the optimum fuel injection amount (TAU) according to the traveling situation is determined. The determination of the fuel injection amount (TAU) by the above correction is based on the results obtained by inputting signals from various sensors arranged in various parts of the vehicle including the engine to the microcomputer, and by the microcomputer performing comprehensive processing based on the signals. Things.

By the way, when the amount of air sucked into the cylinder during traveling at high speed and light load such as downhill traveling becomes small,
Proper compression may not be obtained.
Then, the combustion of the air-fuel mixture becomes unstable, and incomplete combustion or misfire easily occurs. As a result, incomplete combustion gas and unburned gas remaining in the combustion chamber of the cylinder are exhausted from the cylinder and reach the catalytic converter in the exhaust pipe. Excessive combustion raises the temperature of the catalyst, causing thermal degradation of the catalyst and lowering the catalyst performance.

Therefore, the engine speed (NE) is higher than a predetermined set speed and the fuel injection amount (TAU) is set to a predetermined first set value (T) (hereinafter referred to as a "fuel stop determination value (T)"). When the following condition continues for a predetermined time, the fuel injection by the fuel injection valve is stopped (hereinafter, the stop of the fuel injection is referred to as "fuel cut"). The amount is equal to a second set value (T + HYS) (hereinafter referred to as a “fuel restart determination value (T + HYS)”.
S) ". ) When the fuel injection is restarted, the generation of incompletely combusted gas and unburned gas is suppressed even at high rotation and light load, thereby preventing catalyst deterioration of the catalytic converter. A fuel injection control device is provided (for example, see Japanese Patent Application Laid-Open No. 5-321720).

The reason why the fuel is cut after a predetermined time has elapsed is that it takes a certain amount of time before the temperature of the catalyst is damaged by the heat. The fuel cut is not performed until the predetermined time, and the fuel cut is performed after the lapse of the fuel cut.

The engine speed is proportional to the emission of incompletely combusted gas or unburned gas, and the higher the engine speed, the shorter the time required to reach the temperature at which the catalyst is damaged. Control for changing the time according to the engine speed is also performed.

[0008]

However, in such a fuel injection control device, if the downhill running is continued for a long time while the opening of the throttle valve is kept constant, the fuel cut is performed. In this case, the effect of increasing the negative pressure in the cylinder due to the inertia of the exhaust gas disappears, and the intake pipe pressure increases.

When the basic fuel injection amount is determined from the intake pipe pressure and the engine speed, if the intake pipe pressure increases, the fuel injection quantity also increases, and may exceed the fuel restart determination value (T + HYS). Then, the fuel is not cut and the combustion is restarted. Since the intake pipe pressure decreases due to the restart of combustion, the fuel injection amount is again reduced to the fuel stop determination value (T).
The fuel cut is performed as follows.

[0010] Assuming that the running resistance is the same and continuing the downhill running for a long time at the same accelerator opening for a long time, the fuel cut (F / C) and the fuel injection return are frequently repeated. This causes a so-called hunting phenomenon.

In order to prevent this hunting phenomenon, a fuel stop determination value (T) and a fuel restart determination value (T + HYS)
And a width (difference), that is, a hysteresis (HYS). However, there is an operation region where the hunting phenomenon cannot be prevented unless the hysteresis (HYS) is set not only to provide the hysteresis but also to increase the hysteresis (HYS).

On the other hand, if the hysteresis is set large,
There is a risk that a large shock will occur when fuel injection returns. That is, the fuel restart determination value (T
When (+ HYS) is increased, the fuel injection amount at the time of returning to the fuel injection becomes large, so that the state in which the engine does not generate torque due to the fuel cut is changed to a state in which large torque is generated. That is, a large shock as shown in FIG. 7 occurs due to a sudden change in torque.

In FIG. 7, a line indicated by a reference symbol TAU indicates a fuel injection amount, a line indicated by a reference symbol G indicates a longitudinal acceleration acting on the vehicle, the magnitude of an acceleration shock felt by the driver, and a symbol T. The line indicated by indicates the fuel stop determination value, and the symbol t
The line indicated by indicates the elapsed time, the line indicated by the symbol T + HYS indicates the fuel restart determination value, and the line indicated by the symbol TA indicates the throttle opening. In the running state of the vehicle shown in FIG. This indicates that the degree is constant over time.

FIG. 7 shows that when the fuel injection amount TAU exceeds the fuel restart determination value (T + HYS) and fuel injection is restored, the acceleration shock G sharply increases, and a large shock is generated there.

The present invention has been made in view of the above points, and the hunting phenomenon in which the fuel cut by the fuel injection means and the fuel injection return are frequently repeated when the vehicle is running at a high speed and a light load on a long downhill running. It is an object of the present invention to reliably prevent the occurrence of fuel injection and to suppress a shock at the time of fuel injection return.

[0016]

In order to solve the above problems, a fuel injection control device for an internal combustion engine according to the present invention has the following configuration.

That is, operating state detecting means for detecting an engine operating state including the engine speed of the internal combustion engine, and fuel for calculating a fuel injection amount (TAU) corresponding to the engine operating state detected by the operating state detecting means. Injection amount calculation means (CP
U), fuel injection means for injecting fuel into the engine based on the fuel injection amount (TAU) calculated by the fuel injection amount calculation means, and an engine speed higher than a predetermined speed by the operating state detecting means. And stopping the fuel injection by the fuel injection means when the fuel injection amount by the fuel injection amount calculation means becomes equal to or less than a first set value (T);
Fuel cut control means for returning fuel injection by the fuel injection means when the fuel injection amount becomes equal to or greater than a second set value (T + HYS) larger than the first set value; When the fuel injection amount is stopped, the fuel injection amount (T
Means for smoothing AU) using a predetermined smoothing coefficient, and when returning fuel injection by the fuel cut control means, the fuel injection is performed with the fuel injection amount smoothed by the smoothing means. And a fuel return means for performing the following.

A hysteresis (HYS) provided for the first set value (T) and the second set value (T + HYS)
May be provided in accordance with the engine operating state, and a smoothing coefficient changing means for changing the smoothing coefficient in accordance with the hysteresis (HYS).

In the fuel injection control device for an internal combustion engine according to the present invention, when the fuel injection means shifts from the fuel cut state to the fuel injection return state, the fuel injection amount calculated by the fuel injection amount calculation means according to the engine operating state. The fuel is not suddenly injected at (TAU), but is injected at an amount (average value TAUSM) that is slowed down by the smoothing means. Therefore, the torque change gradually changes from a small torque to a large torque, so that the first set value (T) serving as a reference for stopping fuel injection and a reference for returning fuel injection are provided. The second set value (T +
Even if a hysteresis (HYS) sufficient to prevent the hunting phenomenon is provided between the driver and the HYS, it can be said that the driver does not feel a sudden change in torque, so that the riding comfort performance is improved.

A hysteresis (HYS) provided for the first set value (T) and the second set value (T + HYS)
And a smoothing coefficient changing means for changing the smoothing coefficient in accordance with the hysteresis (HYS), so that the ride comfort performance can be improved in a finer state. Can be enhanced.

[0021]

Embodiments of the present invention will be described below with reference to the accompanying drawings. <Description of Apparatus Configuration> First, FIG. 1 shows a schematic configuration of a gasoline engine A equipped with a fuel injection control device for an internal combustion engine according to the present invention.

The gasoline engine A is a four-cylinder four-stroke engine and has a cylinder block 1 having a cylinder (not shown) inside. Each cylinder has a combustion chamber (not shown), and the intake passage 2 and the exhaust passage 3 communicate with each other.

In the intake passage 2, an air cleaner 4, a slot valve 5, a surge tank 6, and an intake manifold 7 are arranged in this order from the upstream side to the cylinder block 1, through which outside air (not shown). And taken into the cylinder.

The throttle valve 5 is for adjusting the amount of intake air flowing through the intake passage 2, and is opened and closed in conjunction with the operation of an accelerator pedal (not shown). The surge tank 6 is for smoothing the pulsation of the intake air.

The intake manifold 7 has a fuel injection valve 8 as a fuel injection means for injecting and supplying fuel to each cylinder.
A, 8B, 8C and 8D are attached. The fuel injected from each of the fuel injection valves 8A to 8D and the intake passage 2
The mixture of the outside air and the outside air introduced into each of the combustion chambers (not shown).

In order to ignite the air-fuel mixture introduced into each combustion chamber, a spark plug 9A, 9
B, 9C and 9D are attached. Spark plug 9A ~
9D is driven based on the ignition signal distributed by the distributor 11.

The distributor 11 is an igniter 1
2 is distributed to the ignition plugs 9A to 9D in synchronization with the crank angle of the engine 1. Then, the air-fuel mixture introduced into the combustion chamber by the ignition of the ignition plugs 9A to 9D burns, and the driving force of the engine 1 is obtained. The combustion gas generated in the combustion chamber as described above is discharged to the outside through the exhaust passage 3.

The exhaust passage 3 is provided with an exhaust manifold 13 and a catalytic converter 14 in order from the engine 1 toward the downstream side.
Are arranged. The catalytic converter 14 is a device that purifies hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) in exhaust gas by the action of a catalyst.

In order to detect the operating state of the engine 1, an intake pressure sensor 15, an intake temperature sensor 16, a throttle sensor 17, an oxygen sensor 18, a water temperature sensor 19, a rotational speed sensor 20, a cylinder discriminating sensor 21, and a vehicle speed sensor 22 Are provided as operating state detecting means.

An intake pressure sensor 15 is provided in the surge tank 6 and detects an intake pipe pressure (absolute pressure) PM. The intake air temperature sensor 16 is provided in the air cleaner case, and detects the temperature of the air taken into the engine 1 (intake air temperature).

The throttle sensor 17 is provided in the vicinity of the throttle valve 5, and detects an opening of the throttle valve 5, that is, a throttle opening (TA), and an idle switch for detecting whether or not the throttle valve 5 is fully closed. Built-in.

The oxygen sensor 18 is provided between the exhaust manifold 13 and the catalytic converter 14, and detects the oxygen concentration in the exhaust gas, that is, the air-fuel ratio A / F in the exhaust passage 3.

The water temperature sensor 19 is attached to a water outlet housing or the like, and detects the temperature of the cooling water of the engine 1 (cooling water temperature). The rotation speed sensor 20 is a rotor (not shown) built in the distributor 11.
Engine speed as engine speed from engine speed (NE)
Is detected.

The cylinder discriminating sensor 21 similarly detects a change in the crank angle of the engine 1 at a predetermined rate according to the rotation of the rotor of the distributor 11. Vehicle speed sensor 22
Is provided on a transmission (not shown) that is drivingly connected to the engine 1 and detects a vehicle speed (SPD).

The fuel injection valves 8A to 8D and the igniter 12 are electrically connected to an electronic control unit (hereinafter simply referred to as "ECU") 23. The ECU 23 includes:
Intake pressure sensor 15, intake temperature sensor 16, throttle sensor 17, oxygen sensor 18, water temperature sensor 19, rotational speed sensor 20, cylinder discriminating sensor 21 as operating state detecting means
And a vehicle speed sensor 22 are connected to each other. The ECU 23 controls the fuel injection valves 8A to 8D and the igniter 12 based on the output signals from the sensors 15 to 22.

Next, the electrical configuration of the ECU 23 will be described with reference to the block diagram of FIG. The ECU 23 calculates a fuel injection amount (fuel injection time) calculating means, a fuel cut (F /
C) Central processing unit (hereinafter simply referred to as “CPU”) 24 as control means, smoothing means and fuel return means;
A read-only memory (hereinafter simply referred to as “ROM”) 25 in which a control program and initial data necessary for executing the arithmetic processing by the CPU 24 are stored in advance, and a random access memory (hereinafter simply referred to as “ROM”) for temporarily storing the arithmetic result of the CPU 24. 26, a backup RAM 27 backed up by a battery so as to retain various data even after the power is turned off, and the sensors 15, 16, 17, 18, 18, 19, 20, 21. , 2
2 is connected to the external input circuit 28 and the fuel injection valves 8A to 8A.
8D and an external output circuit 29 to which the igniter 12 is connected. These are connected to each other by a bus 31.

The CPU 24 reads output signals from the sensors 15 to 22 as input values via the external input circuit 28. Further, the CPU 24 controls the driving of the fuel injection valves 8A to 8D and the igniter 12 via the external output circuit 29 based on these input values.

The CPU 24 executes various arithmetic processes according to a preset control program. That is, the CPU 24 serving as the fuel injection amount calculating means includes the intake pressure sensor 1
The fuel injection amount (TAU) according to the engine operating state detected by the operating state detecting means such as 5 is calculated.

The CPU 24 also functions as fuel cut control means, smoothing means and fuel return means. These functions of the CPU 24 will be sequentially clarified in the description of the routine for controlling the fuel injection shown in FIG.

In this routine, a fuel cut execution flag F1, a fuel return execution flag F2, and a fuel return elapsed time measuring counter C for counting the elapsed time after fuel return are provided.

The fuel cut execution flag F1 is reset to "0" in an initial routine when the engine is started, and the fuel return execution flag F2 is set to "1" in the initial routine when the engine is started. Further, the fuel return elapsed time measurement counter C starts counting operation when the fuel return condition is satisfied. The elapsed time after fuel injection return is measured by the fuel return elapsed time measurement counter C.

In step 100 (hereinafter, referred to as "S100"; other step numbers are also indicated by SNo.), The fuel injection amount (T
AU) is calculated. The fuel injection amount TAU is calculated by the following equation (1).
Is required.

TAU = TP · FAF · α · β (1) where TP is calculated according to the intake pipe pressure and the engine speed (NE). The basic fuel injection amount and FAF are feedback correction coefficients for controlling the target air-fuel ratio based on the output signal of the oxygen sensor 18. Α and β are correction coefficients corresponding to intake air temperature, engine water temperature, acceleration / deceleration, and the like.

After obtaining the fuel injection amount TAU, the next S102
Move to In S102, the engine speed (NE) detected by the speed sensor 20 is equal to the predetermined speed a.
(In the present embodiment, 1800 rpm) or not is determined. If the rotation speed is equal to or more than the predetermined rotation speed a, a positive determination is made and S1 is performed.
04, otherwise the control shifts to after S120 described below.

In S104, the idle switch 5a
It is determined whether or not is in a fuel cut (F / C) in the ON state. If the idle switch 5a is not in the ON state and the fuel cut (F / C) is not being performed, a negative determination is made and the process proceeds to S106.
If / C) is affirmative, a positive determination is made and the control proceeds to S118 described later as indicated by the arrow in the code.

In S106, it is determined whether or not the vehicle speed (SPD) is equal to or higher than a predetermined speed b (3 km in this embodiment). If the speed is equal to or higher than the predetermined speed b, a positive determination is made and S108 is performed.
Otherwise, the control shifts to S120 described later.

In S108, it is determined whether or not the value of the fuel cut execution flag F1 is "1". If the value of the fuel cut execution flag F1 is "1", an affirmative determination is made and the process proceeds to S122. If the value of the fuel cut execution flag F1 is not "1", that is, if it is "0", a negative determination is made. Then, the process proceeds to the next S110. The process of S122 will be described later.

In S110, the fuel injection amount (TAU) calculated in S100 is the fuel stop determination value T (800 μsec in this embodiment. The unit of the fuel injection amount is “μ”.
sec ”is because the fuel injection amount is adjusted by the injection time of the fuel injection valve.) It is determined whether or not the following is true. If TAU ≦ T, a positive determination is made and S11 is performed.
Then, the control shifts to S2 after S120 described later. In addition, it can be determined whether or not the traveling state is a high-speed and low-load traveling state based on the determination contents of S102 to S110.

In step S112, it is determined whether or not a predetermined time has elapsed since the conditions in steps S102 to S110 are satisfied. Here, the predetermined time is a time required for the catalyst temperature to rise due to incomplete combustion or misfire in proportion to the engine speed, and to reach a temperature at which the catalyst is damaged by the heat at that time, For example,
This predetermined time is defined as engine speed (NE) ≧ 3000r
pm, the engine speed (N
E) When <3000 rpm, it is preferable to change according to the engine speed (NE), for example, to 20 seconds. If the predetermined time has elapsed, an affirmative determination is made and the process proceeds to S114.
The control is shifted after. In this embodiment, the predetermined time is set to about 5 seconds.

S102 to S112 are the fuel cut conditions. Next, in S114, the value of the fuel cut execution flag F1 is set to "1". That is, from S102
When S114 is reached via S112, it is determined that the fuel cut condition has been satisfied, and the fuel cut execution flag F1, which was "0" when the engine was started, is changed from "0" to "1". is there. Thereafter, the process proceeds to S116.

In S116, the fuel return execution flag F
Reset the value of 2 to "0". This is S102-S
Since the fuel cut condition is satisfied via 112, the value of the fuel return execution flag F2, which was "1" when the engine was started, is changed to "0".

In S118, the fuel return elapsed time measurement counter C is reset to "0". This is because the current state is not the fuel return state but the fuel cut state. S12
At 0, the fuel injection amount (TAU) is set to “0”. This is because the fuel is cut off. Therefore, fuel injection from the fuel injection valves 8A to 8D to the cylinder is not performed.

S102 to S112 and S1 to be described later
30 indicates that the engine speed (NE) of the operating state detecting means (15 to 22) is higher than the predetermined speed a and the CP
When the fuel injection amount (TAU) calculated by U24 becomes equal to or less than the fuel stop determination value (T), the fuel injection valves 8A to 8A
D, the fuel injection is stopped, and the fuel injection by the fuel injection valves 8A to 8D is restored when the fuel injection amount (TAU) becomes equal to or more than the fuel restart determination value (T + HYS) larger than the fuel stop determination value (T). This is an essential component for the CPU 24 to function as a fuel cut control unit to be performed.

After S120, the process proceeds to S148. S148
Will be described later. The process returns to S108. When the CPU 24 makes an affirmative determination in S108 and proceeds to S122,
From the map M1 shown in FIG.
Hysteresis (HYS) according to E) is obtained.
The process moves to S124. The map M1 is stored in the ROM 25. Although the map M1 is set according to the engine speed (NE), it may be corrected according to the vehicle speed (SPD) or the shift position (gear position) of the manual transmission. For example, if the vehicle speed (SPD) is high or the shift position is at a high speed, the correction is made so that the hysteresis (HYS) becomes small.

The engine speed (NE) and the vehicle speed (S
The shift position of the manual transmission is determined based on the ratio (NVR) because the ratio (NVR) to the shift position of the manual transmission is correlated with the shift position of the manual transmission.

Since the map M1 changes the hysteresis (HYS) according to the operating state, that is, the engine speed (NE), this is referred to as hysteresis changing means. S1
24, in this (current) routine, S100
Is compared with the fuel injection amount (TAU) calculated in S100 in the previous routine (this TAU is referred to as “TAUold”).
If TAU> TAUold, an affirmative determination is made and S126 is performed.
Otherwise, the control shifts to S128 described below.

In S126, the map M2 shown in FIG.
Thus, an averaging coefficient K corresponding to the hysteresis (HYS) calculated in S122 is obtained, and then the process proceeds to S128.
The map M2 is stored in the ROM 25 similarly to the map M1. This map M2 changes the smoothing coefficient K according to the hysteresis (HYS), and is referred to as a smoothing coefficient changing means.

In step S128, the averaged fuel injection amount (TAU) is calculated using the averaged coefficient K determined in step S126.
SM), and then proceeds to S130. The smoothed fuel injection amount (TAUSM) is called the smoothed value,
The average value (TAUSM) is obtained by the following equation (2).

TAUSMi = {(K−1) · TAUSM _i−1 + TAU} / K = TAUSM _i−1 + (TAU−TAUSM _i−1 ) / K (2) where TAUSMi is obtained this time. and the Yo and the moderation values are possible, the TAUSM _i-1, to be larger the specific gravity of smoothed value TAUSM _i-1 is when the value of the smoothing coefficient K is that the previous moderation value obtained is greater In addition, when the value of the smoothing coefficient K is small, a correction process (smoothing process) is performed so that the specific gravity of the fuel injection amount TAU becomes large.

In steps S122 to S128, when the fuel injection is stopped by the fuel cut control means, the fuel injection amount (TAU) calculated by the CPU 24 should not be smoothed using a predetermined smoothing coefficient K. It is an essential component for making the CPU 24 function as an additional means.

In step S130, the fuel injection amount (TAU) calculated in accordance with the operating state of the engine is calculated based on the hysteresis (H) determined in step S122 as the fuel stop determination value (T).
YS), that is, the fuel restart determination value (T + H
YS) or not. In other words, TAU ≧ T
If + HYS, the fuel injection return condition is satisfied, that is, an affirmative determination is made, and the routine proceeds to S132. If TAU ≧ T + HYS, the fuel injection return condition is not satisfied, that is, a negative determination is made, and the routine goes to S134.

At S132, the fuel return execution flag F
Set the value of 2 to "1". That is, it is determined that the fuel injection return condition is satisfied, and the fuel return execution flag F2 is changed from "0" to "1". After that,
The process moves to S136.

The process returns to S130. In S130,
When the determination is negative and the process proceeds to S134, it is determined whether the value of the fuel return execution flag F2 is "1".
If the value of the fuel return execution flag F2 is "1", a positive determination is made, and the control proceeds to S132, that is, the control returns to the fuel injection return side routine. If the value of the fuel return execution flag F2 is not "1", that is, if it is "0", a negative determination is made, and the control shifts to after S116, that is, to a fuel cut side routine.

In S136, the fuel return elapsed time measurement counter C is incremented by 1 on the assumption that the fuel injection return condition is satisfied, and then the flow shifts to S138. In S138, it is determined whether or not the count value of the fuel return elapsed time measurement counter C is larger than a predetermined constant value X (for example, 0.5 sec). C
If ≧ X, an affirmative determination is made and the process proceeds to S144. If C ≧ X, a negative determination is made and the process proceeds to S140.

In S140, it is determined whether or not the vehicle is running in an accelerated state. If the vehicle is in the accelerated state, the process proceeds to S144. If not, a negative determination is made and the process proceeds to S142. Return to S140.

In S140, a negative determination is made and S14
In the case of shifting to 2, the fuel injection amount (TAU) is switched to the smoothed value (TAUSM) in S142 to suppress the fuel injection amount at the time of fuel return, and then control is shifted to S148 after S120. Annealing value (TAUSM)
Injection timing is achieved. What is injection timing?
This is a timing suitable for the fuel injection valves 8A to 8D to inject fuel.

Note that the meaning of S140 is supplemented by injecting the fuel with the smoothed fuel injection amount (TAUSM) until the predetermined time has elapsed (see S138) after the fuel is returned (YES in S130). (See S142),
Although a shock due to a sudden change in torque is prevented, during this time (until the predetermined time in S138 elapses), it is detected that an operation state requiring torque such as acceleration has been detected (the throttle sensor 17 changes in the opening direction). if you did this)
Then, by switching from the smoothed fuel injection amount (TAUSM) to the injection of the fuel injection amount (TAU) calculated according to the operating state of the engine (see S142), deterioration of the acceleration performance is prevented.

The process returns to S138 or S138. S13
In step S8 or step S140, when the determination is affirmative and the process proceeds to step S144, the value of the fuel cut execution flag F1 is reset to "0". Thereafter, the process proceeds to step S146 to reduce the smoothed fuel injection amount (TAUSM) calculated in step S128. Clear (reset to 0). This is to prevent the previously calculated smooth fuel injection amount (TAUSM) from remaining at the next fuel return. Then, S14 after S120
The control is shifted to 8, and the injection timing at the smoothed value (TAUSM) is achieved.

When the fuel injection control is returned by the fuel cut control means (CPU 24), the above-mentioned steps S130 to S142 serve as fuel return means for performing fuel injection with the fuel injection amount smoothed by the smoothing means (CPU 24). Are essential components for the CPU 24 to function.

In S148, the fuel injection valves 8A to 8A
It is determined whether D is in the injection timing state.
If it is determined in S148 that the injection timing has been reached, the process proceeds to S150, in which fuel injection is performed, and this routine is terminated.
If it is determined at 48 that it is not the injection timing, the routine is terminated as it is.

In step S150, the fuel injection, which has been or has not been smoothed, is performed by the fuel injection valves 8A to 8D, and then this routine is terminated. In addition,
The fuel injections that have not been annealed are S102 and S1.
This refers to fuel injection when a negative determination is made in 06, S110, and S112.

If it is determined in step S138 that the predetermined time X has elapsed, or if it is determined that the predetermined time X has not elapsed, the process proceeds to step S1.
If acceleration is detected at 40, the average value (TAUS
The injection in M) is stopped, and the fuel injection amount (TAU) calculated in S100 is injected when it is determined in S148 that the injection timing is reached.

Of the above-described configuration, each of the sensors 15 to 22 and the like as operating state detecting means, the fuel injection valves 8A, 8B, 8C and 8D as fuel injection means, fuel injection amount calculating means, fuel cut control The fuel injection control device for an internal combustion engine according to the present invention includes the means, the smoothing means, and the CPU 24 as the fuel return means. <Operation and Effect of Embodiment> Next, the operation and effect of such a fuel injection control device for an internal combustion engine will be described.

In the fuel injection control device for the internal combustion engine, when the fuel injection valve 8A, 8B, 8C, 8D shifts from the fuel cut state to the fuel injection return state, the fuel injection calculated by the CPU 24 according to the operating state of the engine A. Amount (TA
The fuel is not sharply injected in U), but is slowed down by annealing, so that the torque gradually changes from a small torque to a large torque. Therefore, the fuel stop determination value (T) as the fuel stop determination value
And a fuel restart determination value (T + HY) as a fuel restart determination value.
Even if hysteresis (HYS) sufficient to prevent the hunting phenomenon is provided between the driver and S), the driver does not feel a sudden change in torque. Therefore, excellent ride comfort performance with less shock can be exhibited (see FIG. 6).

In FIG. 6, what is indicated by a dashed line is an average value (TAUSM). Annealing value (TAUSM)
Compared to FIG. 7 showing the effect of the prior art in which
It can be seen that there is no significant change in the acceleration shock G when the fuel injection is returned without performing the smoothing process. FIG.
In order to clarify the comparison with the graph, a graph (shown by a two-dot chain line) showing the conventional acceleration shock G is superimposed on the graph showing the acceleration shock G (shown by the solid line) in FIG.

A map M which is a hysteresis changing means for changing the hysteresis (HYS) according to the operating state.
1 and a map M2 which is a smoothing coefficient changing means for changing the smoothing coefficient in accordance with the hysteresis (HYS), so that a finer riding comfort can be obtained.

Since finer fuel injection can be performed in this way, the air-fuel ratio can be controlled to a more suitable state, and there is also an effect that emission can be reduced and fuel efficiency can be improved.

[0078]

As described above, according to the fuel injection control apparatus for an internal combustion engine of the present invention, when the fuel injection means shifts from the fuel cut state to the fuel injection return state,
The fuel is not suddenly injected with the fuel injection amount calculated by the fuel injection amount calculating means according to the engine operating state, but is injected with the smoothed fuel injection amount (smoothed value). Therefore, the torque change gradually changes from a small torque to a large torque. Therefore, even if hysteresis is provided between the minimum value of the fuel injection amount and the fuel injection amount that causes the return of the fuel injection to prevent the hunting phenomenon, the driver does not feel a sudden change in torque. The excellent effect that the excellent ride comfort performance with less is exhibited.

Further, since there are provided a hysteresis changing means for changing the hysteresis in accordance with the operation state and a smoothing coefficient changing means for changing the averaging coefficient in accordance with the hysteresis, a finer riding comfort can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic plan view of a multi-cylinder engine employing a fuel injection control device for an internal combustion engine according to the present invention.

FIG. 2 is a block diagram showing an electrical configuration of the ECU.

FIG. 3 is a hysteresis (HYS) -engine speed (NE) diagram.

FIG. 4... Annealing coefficient (K) −Hysteresis (HY)
S) Diagram

FIG. 5 is a flowchart illustrating a routine for calculating an average value (TAUSM).

FIG. 6 is a diagram showing the effect of the fuel injection control device for an internal combustion engine according to the present invention.

FIG. 7 is a diagram for explaining a problem of the related art.

[Explanation of symbols]

A: gasoline engine a: predetermined rotation speed (of engine rotation speed) F1: fuel cut execution flag F2: fuel return execution flag HYS: hysteresis K: smoothing coefficient M1: map (hysteresis changing means) M2: map (smoothing coefficient) NE: engine speed T: first set value T + HYS: second set value TAU: fuel injection amount TAUSM: smoothed fuel injection amount 1… cylinder block 2… intake passage 3… exhaust passage 4 ... air cleaner 5 ... slot valve 6 ... surge tank 7 ... intake manifold 5a ... idle switch 8A, 8B, 8C, 8D ... fuel injection valve (fuel injection means) 9A, 9B, 9C, 9D ... spark plug 11 ... distributor 12 ... igniter 13: Exhaust manifold 14: Catalytic converter 15: Intake pressure sensor (operating state detection 16) Intake air temperature sensor (operating state detecting means) 17 ... Throttle sensor (operating state detecting means) 18 ... Oxygen sensor (operating state detecting means) 19 ... Water temperature sensor (operating state detecting means) 20 ... Rotational speed sensor (operating) State detecting means) 21: cylinder discrimination sensor (operating state detecting means) 22: vehicle speed sensor (operating state detecting means) 23: electronic control unit (ECU) 24: CPU (fuel injection amount calculating means, fuel cut control means, smoothing) Means, fuel return means) 25 dedicated memory (ROM) 26 random access memory (RAM) 27 backup RAM 28 external input circuit 29 external output circuit 31 bus No sign fuel injection control device for internal combustion engine.

Claims (2)

[Claims] 1. An operating state detecting means for detecting an engine operating state including an engine speed of an internal combustion engine, and a fuel injection amount calculation for calculating a fuel injection amount according to the engine operating state detected by the operating state detecting means. A fuel injection means for injecting fuel into the engine based on the fuel injection amount calculated by the fuel injection amount calculation means; an engine speed higher than a predetermined speed by the operating state detection means; When the fuel injection amount by the injection amount calculation means becomes equal to or less than the first set value, the fuel injection by the fuel injection means is stopped, and the fuel injection amount is equal to or more than the second set value larger than the first set value. A fuel cut control means for returning the fuel injection by the fuel injection means when the fuel injection amount is changed; and A smoothing means for smoothing the fuel injection amount calculated by the means using a predetermined smoothing coefficient; and a fuel smoothed by the smoothing means when returning fuel injection by the fuel cut control means. A fuel injection control device for an internal combustion engine, comprising: fuel return means for performing fuel injection with an injection amount. 2. A hysteresis changing means for changing a hysteresis provided in the first set value and the second set value according to an engine operation state, and not changing the smoothing coefficient according to the hysteresis. The fuel injection control device for an internal combustion engine according to claim 1, further comprising a coefficient changing means.