JPS6143230A - Control method of fuel injection quantity in internal-combustion engine - Google Patents

Abstract

PURPOSE:To prevent an engine from generating its air-fuel ratio in a lean state, by asynchronously injecting fuel in quantity corresponding to the saturated adhering quantity in an intake pipe system when a throttle valve is opened from its idle position at naturally resetting time from a fuel cut. CONSTITUTION:An engine starts a fuel cut at time t1, and the engine, after it naturally resets the fuel cut at time t2, asynchronously injects fuel at time t3 before the time with injection not reaching a predetermined number of times gamma of injection when an idle signal LL is turned off. In this way, the wall surface of an intake pipe system is coated with sufficient fuel reaching its saturated adhering quantity. Thus air-fuel ratio can be prevented from becoming a lean state.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel injection amount control method for an internal combustion engine, and more particularly to a fuel injection amount control method at the time of return to engine cut.

[Conventional technology]

Conventionally, when the foot is removed from the accelerator pedal while a vehicle is running, that is, when the idle switch that detects the fully closed state of the throttle valve is turned on, it is determined that the vehicle is decelerating, and the vehicle speed SPD is set to α (for example, 1200rpm
) or above, the fuel supply is stopped (hereinafter referred to as "tununil cut") to allow the engine brake to function effectively and improve fuel efficiency. Then, the vehicle speed SrD is a sufficiently low value β (for example, 1000 rpm)
In order to ensure stable operation of the engine, when the temperature drops to below, the engine cut is restored.

By the way, normally, during steady running of a vehicle, the wall surface of the intake pipe system of each cylinder of the engine is supplied with 71. It is known that fuel adheres to the fuel and leaves it wet. This adhered fuel evaporates when it is cut into cylinders, and is then taken into each cylinder. Therefore, the air-fuel ratio of the air-fuel mixture supplied to each cylinder of the engine becomes lean until fuel equivalent to the saturated adhesion amount of the intake pipe system of each cylinder is supplied at the time of return to the engine cut, and engine operation becomes unstable (breathing). It becomes sticky, sluggish).

Therefore, in Japanese Patent Application No. 58-16753, it is proposed to supply a predetermined amount of fuel at the time of return to the unit cut. In other words, in a steady state, the basic fuel injection amount is determined by the engine load (intake pipe pressure or intake air amount per engine revolution) and engine speed, and is determined using various correction coefficients such as intake air temperature and engine cooling water temperature. Synchronous fuel injection is performed in which the fuel injection amount is determined by correcting the basic fuel injection amount, the fuel injection valve is opened at every predetermined crank angle, and the amount of fuel corresponding to the fuel injection valve is injected during the engine intake stroke. An example of application to an internal combustion engine is shown.

According to this, the mode of return from the fuel cut is divided into two modes: natural return and forced return, and the fuel injection amount is increased using different methods for each mode. Natural recovery occurs when the engine speed NB decreases to β and fuel injection is restarted. In this case, after the return, the injection time per synchronous injection is increased and the injection is performed a predetermined number of times, thereby pressurizing the fuel to be replenished in an amount corresponding to the saturated adhesion amount.

- 10,000, forced return occurs during the unit cut period, that is, when the synchronous injection is restarted by pressing one accelerator pedal before the vehicle speed SPD has been reduced to β. in this case,
Apart from the synchronous injection, the idle switch is turned on and the fuel injection is performed once for a predetermined time. The predetermined injection time at this time is the time required to inject the fuel corresponding to the saturated adhesion amount, and is determined depending on the capacity of the fuel engine and the target wall area of the intake pipe system. It is said to be about sec.

Furthermore, even during the above-mentioned natural recovery, there is a time delay after the idle switch is turned on until the intake pipe pressure or fc is increased to the fuel injection amount according to the engine load increase detection value of the intake air amount sensor. Therefore, in order to compensate for this control delay, a predetermined amount of fuel (injection time, for example, 1.5 msec) is injected asynchronously only once in a feedforward manner.

[Problem that the invention seeks to solve]

However, if the accelerator is pressed immediately after the natural return and the engine load is increased, the intake pipe system will be affected by the synchronous increase in injection amount corresponding to the saturated adhesion amount and the asynchronous injection amount due to the control delay compensation described above. There is a problem in that the fuel adhering to the wall of the cylinder does not reach saturation, and the air-fuel mixture taken into the cylinder becomes lean, causing the engine to stutter and sluggish.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fuel injection amount control method for an internal combustion engine that can prevent the engine from sluggishness or sluggishness even if the accelerator is depressed immediately after the natural return of the engine.

[Means for solving problems]

The present invention is characterized in that when the throttle valve is opened from the idle position after the twin cylinder cut due to synchronous injection has naturally returned and before the number of injections reaches a predetermined value, the fuel is saturated and adheres to the wall surface of the intake pipe system at an equal pressure. It is characterized by asynchronously injecting an amount of fuel corresponding to the amount of fuel.

[Effect]

In this way, based on the fact that the accelerator was pressed immediately after the natural return of the tsuyunil cut,
Since an amount of fuel corresponding to the saturated adhesion amount on the wall surface of the intake pipe system is supplied separately from the synchronous injection, the wall surface of the intake pipe system of each cylinder is quickly wetted with fuel. Therefore, since the fuel that is the sum of the engine load increase, the saturation deposition amount, and the control delay compensation described above is quickly supplied, it is possible to prevent the air-fuel ratio from becoming lean, thereby preventing the engine from becoming lean. This prevents shortness of breath and sluggishness.

〔Example〕

Hereinafter, the present invention will be explained based on t-Example.

Figure 1 shows a flowchart showing the control means of an embodiment of the present invention, Figure 2 shows an example of an internal combustion engine to which the invention can be applied, and Figure 3 shows a pressure control circuit. The block diagrams of each are shown below.

In FIG. 1, an air cleaner 2 is connected to a throttle body 6 via an inlet pipe 4. As shown in FIG. One fuel injection valve 8 is attached to the upstream side pressure of the throttle body 6, and a throttle valve is provided downstream of the fuel injection valve 8 to adjust the amount of air-fuel mixture sucked into the combustion chamber of the engine in conjunction with the accelerator pedal. 10 are arranged. An idle switch 12 is attached to the throttle valve 10, which is turned on when the throttle valve 10 is in the idle position and turned off when the throttle valve 10 is opened from the idle position. Furthermore, a pressure sensor 14 is attached downstream of the throttle valve 10 to detect the pressure in the intake pipe.

The throttle body 6 is connected to an intake manifold 16 having branch pipes connected to each cylinder of the engine, and the intake manifold 16 includes an intake air temperature sensor 18 that measures intake air from the temperature of the air-fuel mixture passing through the intake manifold. is installed. A riser portion 20 is provided at the upstream bottom portion 16a of the intake manifold 16. The riser portion 20 circulates the engine cooling water temperature and heats the air-fuel mixture.

Reference numeral 22 designates a well-known engine body, in which a combustion chamber 28 is formed by the bottom surface of a piston 24 and the inner wall of a cylinder 26, and the air-fuel mixture taken in through an intake valve 30 is ignited by a spark plug 32. It has become. A water jacket 34 is formed around the cylinder 26,
Engine cooling water is circulated through the water jacket 34 to cool the cylinder 26 and the like. An engine coolant temperature sensor 38 is attached to the cylinder block 36 and uses the temperature of the engine coolant in the water jacket 34.

An exhaust manifold 42 is connected to an exhaust port (not shown) of the cylinder head 40, and a sensor 44 for detecting the residual oxygen concentration in the exhaust gas is attached downstream of the exhaust manifold 42. Furthermore, the exhaust manifold 42 is connected to an exhaust pipe 48 via a catalytic converter 46 filled with a three-way catalyst.

Spark plug 32 is connected to control circuit 54 via distributor 50 and igniter 52 . A distributor 50KFi, an engine rotation angle sensor 56 each composed of a signal port fixed to the distributor shaft and a pickup fixed to the distributor housing, and a cylinder discrimination sensor 58 are attached. This cylinder discrimination sensor 58 is
In the case of a 6-cylinder engine, each revolution of the distributor shaft means two revolutions of the engine (720 degrees).
CA) at the reference position (for example, top dead center of a specific cylinder)
The engine rotation angle sensor 56 is busy outputting one pulse every 30 degrees CA, for example.

The control circuit 54 is a central processing unit (CPU) 60 equipped with one arithmetic and logic unit and registers as shown in FIG.
．． Read-only memory (R) that stores control programs, etc.
OM) 62, random access memory (RAM) 64,
Backup RAM (BU-RAM) 66, input/output hole)
+ Ilo) 6B, an analog-to-digital converter (ADC 170), and a bus 72 such as a data bus and a control bus that connects the controller.The 1106B includes a cylinder discrimination signal from the cylinder discrimination sensor 58. , an engine rotation speed signal from the engine rotation angle sensor 56, and an idle signal from the idle switch 12 (when LLJ is input, a fuel injection signal and an igniter for controlling the fuel injection valve 8 via a drive circuit (not shown) are input. The ADC 70 also receives an intake pipe pressure signal from the pressure sensor 14, an intake air temperature signal from the intake air temperature sensor 18, a water temperature signal from the water temperature sensor 38, and an O sensor. 44 air-fuel ratio signals are input, and these signals are sequentially converted into digital signals according to instructions from the CPU 60.

Next, a control procedure when the present invention is applied to the engine as described above will be explained along the flowchart K shown in FIG. 1, [F]). FIG. 1(A) shows a synchronous injection routine program, and FIG. 1(A) shows the procedure of an asynchronous injection routine program.

As shown in FIG. 1 (2), in the one-synchronous injection routine, it is determined in steps 100 to 107 whether or not a twin cylinder cut is being performed. That is, the idle signal L output from the idle switch in step 100
It is determined whether L is on or not, and if the determination is affirmative, the process moves to step 102, where it is determined whether the vehicle speed SPD is equal to or higher than a predetermined twin wheel cut starting rotation speed α (for example, 1200 rpm).

If an affirmative judgment is made here, it is a twin cut, so in step 103 the flag FC indicating that a twin cut is in progress is set above r I JK, and then the synchronous injection execution routine in step 106 is jumped to.
In step 112, a counter CFC for the number of synchronous injections is set.
Set the contents of ADD to γ and return to the main loop. In addition, γ is the time when the fuel that adheres to the wall surfaces of the intake pipe system due to synchronous injection, that is, the wall surfaces of the throttle body 6 and intake manifold 16 shown in FIG. 2, reaches the saturated adhesion state of This is the number of injections determined based on a sufficient amount of fuel supply. In the case of a negative judgment in step 102, it is judged in step 104 whether the flag FC is "1" or not, and in the case of an affirmative judgment, the process moves to step 105 and the vehicle speed SPD is set to 1000. If the judgment is negative, the process moves to step 112 since it is a twin cut as described above.

-10,000 If an affirmative determination is made in step 105, it means that the natural cut has returned, so in step 107 the flag FC is reset to "0" and the process proceeds to step 106. Note that if the determination of LL on in step 100 is negative, that is, if the accelerator is depressed,
Naturally, since the fuel injection is not cut, the process moves to step 106, where the fuel injection amount for each injection is determined according to a well-known synchronous injection execution routine, and the injection time T corresponding to the fuel injection amount is determined.
AU, open the single injection valve 8. Note that although it is temporarily stored in a memory such as the fuel injection time TAtlt register, it is set as a trap so that it is rewritten to 4Kr OJ to indicate completion of synchronous injection execution. After that, the process moves to step 108, and it is determined whether the contents of the CFCADD are "0" traps, and if the judgment is affirmative, the process returns to the main loop, and if the judgment is negative, the process moves to step 110, where the counter CFC is
Subtract "1" from the contents of ADD and return to the main loop.

The asynchronous injection routine program shown in FIG.
It is difficult to judge whether L has switched from on to off. That is, it is determined whether or not the accelerator pedal is depressed from an idle state.

If the determination is negative in step 200, the process returns to the main loop, and if the determination is affirmative, in step 202, the counter C is
It is difficult to judge whether the contents of FCADD are "0" or not.

That is, it is determined whether the number of synchronous injections executed by the above-mentioned synchronous injection routine after the accelerator is depressed has reached a predetermined value r. Step 2
If an affirmative determination is made in step 02, that is, if synchronous injection has been completed a predetermined number of times γ after the accelerator is depressed, the process moves to step 2086c. If the judgment is negative, step 20
4, the content of the counter CFCADD is reset to "0", and the process moves to step 206, where the fuel injection time TA is reset.
The contents of U are rewritten to T, and the process moves to step 208.

Note that T is determined to be the fuel injection time required for the fuel to adhere to the wall surface of the intake pipe system up to its saturated amount (for example, 6 m5ec). In step 208, the TAU stored in the welfare register or the like is rewritten to a value obtained by adding T, and the process proceeds to step 210. Note that T is the fuel injection time that compensates for the aforementioned control delay. In step 210, the fuel injection valve 8 is opened based on the fuel injection time TAU given in step 208 to perform asynchronous injection.

FIG. 4 shows the synchronous injection timing, idle signal LL, and
It shows the temporal changes in asynchronous injection.

As shown in the figure, consider the case where the engine cut starts at time t3, the engine self-recovers at 12 o'clock, and then the idle signal LL is turned off at time t1 before the predetermined number of injections γ is reached. and the control steps are steps 200, 202, 204, 2
06,208, fuel injection time TAU=T,
+T* asynchronous injection is executed in step 210. Here, T is, for example, 4.5 m sec,
If Tχ was set to 1.5 mSec,
A total of 6 m sec of asynchronous injection is carried out, so that the wall surface of the intake pipe system reaches its saturation adhesion amount with sufficient fuel and the control delay time can be compensated. On the other hand, in the synchronous injection execution subroutine 106 (not shown), a fuel injection time TAU corresponding to the increase in engine load is determined, and fuel supply corresponding to the increase in engine load is started.

As described above, according to this embodiment, even if the accelerator is depressed immediately after the natural return of the engine cut, the amount of fuel by synchronous injection corresponding to the increase in engine load and the amount of fuel adhering to the intake pipe system are saturated. Since fuel is supplied by asynchronous injection to compensate for control delay and control delay, it is possible to prevent the air-fuel ratio of the air-fuel mixture taken into the cylinder from becoming lean, thereby reducing engine sluggishness and sluggishness. It can be prevented.

In the above embodiment, an example in which the present invention is applied to the single-point injector type engine shown in FIG. 2 has been described, but the present invention is not limited to this. It is also possible to apply the present invention to an independent injection type engine that is equipped with an injection valve and injects fuel during the intake stroke of each cylinder. In this independent injection type engine, if the time during the fuel cut is particularly long, the fuel adhering to the inner wall of the intake manifold will evaporate, causing the same problem as above. In addition, in the above, we have described an engine in which the basic fuel injection amount is determined from the intake pipe pressure, engine speed, and K, but the basic fuel injection amount is not limited to this. It goes without saying that it is possible to apply this to an engine that determines the This has the effect of preventing the engine from becoming sluggish or sluggish.

[Brief explanation of drawings]

FIG. 1 (2), Q3) is a flowchart showing a control procedure of an embodiment of the present invention, FIG. 2 is a configuration diagram showing an example of an engine to which the present invention can be applied, and FIG. 3 is a control shown in FIG. The block diagram of the circuit and FIG. 4 are time charts for explaining the present invention in detail.

Claims (1)

[Claims] Synchronous fuel injection is performed in which fuel is injected at every predetermined crank angle based on the basic fuel injection amount determined by the engine load and engine speed, and when the throttle valve is in the idle position and the engine speed is above a predetermined value, the synchronized fuel injection is performed. In a fuel injection amount control method for an internal combustion engine in which fuel injection is stopped, after the engine speed drops below a predetermined value and the synchronous fuel injection is restarted, but before the number of fuel injections reaches the predetermined value, the throttle valve is 1. A fuel injection amount control method for an internal combustion engine, which comprises asynchronously injecting an amount of fuel corresponding to a saturated amount of fuel adhering to a wall surface of an intake pipe system when the engine is opened from an idle position.