JP2588919B2 - Acceleration correction method for electronically controlled fuel injection device of engine - Google Patents

Description

The present invention relates to an electronically controlled fuel injection device for an engine,
In particular, it relates to an acceleration correction method for improving responsiveness and smoothness during acceleration.

<< Prior Art >> As shown in FIG. 2, fuel is injected from an injector 3 provided in an intake passage 2 of each cylinder 1 in synchronization with an engine cycle. 2. Description of the Related Art Electronically controlled fuel injection devices that perform variable control in accordance with the number of revolutions and the like are widely used in general automobiles and the like. 2, 4 is an air cleaner, 5 is an air flow meter, 6 is a throttle valve, 7 is a surge tank, 8 is an engine speed sensor, and 9 is a control unit. Inlet passage 2 of each cylinder 1 from surge tank 7
The injector 3 is provided for each cylinder 1.

Since the configuration and control method of this type of electronically controlled fuel injection device are described in detail in many documents, a portion related to the present invention will be extracted and described below.

A command value of the synchronous injection amount is calculated every moment using the intake air amount and the rotation speed of the engine as main parameters, and the synchronous injection time (synonymous with the injection amount) from the injector is controlled according to the command value. Various correction factors such as idle correction, post-start correction, intake air temperature correction, and air-fuel ratio correction are added to this basic control, and the synchronous injection amount is finely adjusted.

There is a fuel supply method called asynchronous injection in which fuel is injected from an injector at a timing irrelevant to the engine cycle, in contrast to synchronous injection synchronized with the engine cycle. The acceleration correction described in detail below is performed by this asynchronous injection.

When the throttle valve is suddenly opened by the acceleration operation,
The intake air amount increases, and accordingly, the synchronous injection amount increases, and the engine output increases. However, due to the rapid opening of the throttle valve, the air between the air flow meter and the throttle valve is sucked into the combustion chamber, and the response delay of the fuel supplied in response to the output of the sensor (such as the air flow meter 5) for detecting the amount of revenue air is generated. Mainly, the increase in the synchronous injection amount immediately after the acceleration operation cannot keep up with the increase in the intake air amount, and the air-fuel ratio temporarily becomes lean, resulting in poor acceleration responsiveness of the engine.

Therefore, acceleration correction by asynchronous injection is performed. That is, if an acceleration operation state in which the throttle valve is rapidly opened is detected, an appropriate amount of fuel is immediately injected from the injector 3 at once, asynchronously with the engine cycle. This is the conventional acceleration correction method. As a result, sufficient fuel is supplied immediately after the throttle valve is opened, and the acceleration response of the engine is improved.

The state of the fuel injection control at the time of acceleration described above is organized and shown in the timing chart of FIG. When the throttle valve opening is at the minimum (idle state), time point t1
Assume that a rapid acceleration operation is performed by the accelerator pedal and the throttle valve opening sharply increases as shown in FIG.
It is assumed that an acceleration operation is detected at time t2, which is slightly later than time t1, based on the rapid increase of the throttle valve opening.

Since the throttle valve opening is greatly opened from the minimum value, the intake air flow rate near the air flow meter 5 rapidly increases as shown in FIG. However, the output of the air flow meter 5 has a waveform delayed with respect to the actual increase in the air filling amount as shown in FIG. The controller (microcomputer) calculates the command value of the synchronous injection amount using the output of the air flow meter 5 and the engine speed as main parameters. In the example of FIG. 1, before the time point t1, the fuel cut conditions (throttle valve opening is minimum and engine speed is equal to or more than a certain value) are complete, and the command value of the synchronous injection amount is zero.
Therefore, no fuel injection is performed. Air flow meter 5
As shown in (D), the controller calculates the command value of the non-zero synchronous injection amount after the time point t3 in response to the start of the increase in the output. Then, after time t3, (E)
Synchronous injection is performed sequentially from the injectors 3 of the four cylinders as shown in FIG.

Since the acceleration response is not good only by the fuel supply by the synchronous injection, the asynchronous injection shown in (G) is performed. When a sudden change in the signal of the idle switch attached to the accelerator pedal or the output of the throttle valve opening sensor is detected,
At time t2, which is slightly later than t1, it is detected that the acceleration operation has been performed, and immediately an appropriate amount of fuel is injected from the injector 3 of each cylinder. This is asynchronous injection.

<< Problems to be Solved by the Invention >> In the above-described conventional acceleration correction method, as shown in FIG. 1 (J), although the engine output increases responsively due to the asynchronous injection, the engine output is immediately after that for a short time. The output drops sharply and then recovers. This temporary drop in engine output is called a breathing phenomenon at the time of acceleration. When this occurs, acceleration becomes jerky, and a smooth feeling of acceleration cannot be obtained.

The cause of the above-mentioned breathing phenomenon is that the throttle valve is suddenly opened, and a little later, the downstream of the injector (intake port)
The positive pressure wave arrives at FIG. 1 (H) shows the change in the intake air flow rate downstream of the injector.
The peak at t4 is a positive pressure wave. When the positive pressure wave reaches the downstream of the injector, the surrounding fuel is sucked into the combustion chamber at a stretch on the positive pressure wave. Since the suction efficiency at this time is extremely high, the amount of fuel adhering to the wall of the intake passage around the injector becomes extremely small, and the amount of fuel wall adhesion immediately after the arrival of the positive pressure wave becomes almost zero as shown in (I). Would. Therefore, the amount of fuel sucked into the engine at the next timing is reduced by the small amount of wall adhesion, and a drop in engine output as shown in (J) occurs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide an acceleration correction method that improves responsiveness during acceleration and performs smooth acceleration without a breathing phenomenon. It is in.

<< Means for Solving the Problems >> Therefore, according to the present invention, as shown in FIG. 1 (K), if an acceleration operation state in which the throttle valve is rapidly opened is detected (time t2), it is asynchronous with the engine cycle. Immediately thereafter, an appropriate amount of fuel is simultaneously injected from the injector, and after a predetermined time ΔT required for the positive pressure wave of the intake air to reach the intake port, an appropriate amount of the fuel is asynchronously synchronized with the engine cycle at time t5. Injected fuel.

<< Operation >> The first asynchronous injection at the time point t2 accelerates the rise of the engine output in the same manner as the conventional method. Thereafter, as shown in FIG. 1 (H), a positive pressure wave peaking at time t4 arrives at the intake port, the fuel intake efficiency is temporarily increased, and the fuel remaining on the peripheral wall surface is also absorbed. Is done. Immediately after this, the second asynchronous injection is performed at time t5,
It compensates for the amount of fuel wall adhesion that tends to be almost zero. As a result, as shown in (L), the fuel wall adhesion amount recovers immediately, preventing the fuel intake amount from decreasing after time t5. As a result, as shown in (M), the engine output increases with good responsiveness and accelerates smoothly without a breathing phenomenon immediately after acceleration.

<< Embodiment >> The acceleration correction method according to the present invention can be implemented very simply by slightly changing the program of a controller incorporated in a general automobile. The point of change is that after performing the first asynchronous injection at the time t2 when it is detected that the acceleration operation has been performed (this is of course the same as the conventional one), at the time t5 after a predetermined period of time ΔT has passed, t2 The point is that the second asynchronous injection is performed. This can be realized by a well-known simple timer processing by a microcomputer.

The time ΔT is determined according to the time from when the throttle valve is widely opened to when the positive pressure wave reaches the intake port. This time is a value specific to the engine, and can be easily obtained experimentally. Also, it is determined experimentally how much the injection amounts of the first and second asynchronous injections should be. This asynchronous injection amount may be fixed to a certain value, or may be changed according to the operating condition of the engine.

In the example described with reference to the time chart of FIG. 1, the state before performing the acceleration operation is the state of fuel cut with the throttle valve fully closed in the deceleration operation range. In this case, the breathing phenomenon immediately after acceleration, which is a conventional problem, appears remarkably. Therefore, the effect of the present invention is particularly large in this case. However, the breathing phenomenon immediately after acceleration does not occur only when accelerating from the fuel cut state, but also occurs in other cases to a lesser degree. Therefore, it is better to perform the second asynchronous injection according to the present invention even when accelerating from a state where the fuel cut is not performed. However, in this case, the second asynchronous injection amount is made smaller than during the acceleration from the fuel cut state. In order to perform such control, a flag is stored as to whether the state before acceleration is the fuel cut state or not, and the flag is referred to when controlling the asynchronous injection after the acceleration operation is performed, and the flag is set. The asynchronous injection amount will be changed according to the state.

As in the conventional case, when the synchronous injection and the asynchronous injection overlap in terms of timing, the injection time is extended by the overlap.

FIG. 3 is a flowchart showing an operation example of the control unit 9 according to the present invention. The routine shown in this flowchart is executed at fixed time intervals sufficiently shorter than the engine cycle.

First, in step S1, it is determined whether or not the delay counter IDT is counting, that is, immediately after acceleration, and if it is not immediately after acceleration but IDT is 0, it is determined whether or not the vehicle has entered the acceleration state in step S2 by the acceleration flag IACC. Is determined based on the value of. The acceleration flag IACC takes a value of 1 when the opening speed of the throttle valve is equal to or higher than a set value. In this case, the first asynchronous fuel injection as in the prior art is performed in step S3, and then the delay counter in step S4. Is counted, and if it is determined in step S2 that the vehicle is not in the accelerated state, the routine ends.

If NO in step S1, the delay counter is counting, and if it is determined in step S5 that it is time to perform the injection of the second asynchronous fuel of the present invention, the injection is performed in step S6, and then the process proceeds to step S4. Otherwise, the process directly proceeds to step S4 to count the day counter.

Here, the delay set value B in step S5 is the time Δ
This is an integer slightly larger than the value obtained by dividing T by the execution cycle of this routine.

In steps S7 and S8, after the second asynchronous fuel is injected so that the plurality of first and second asynchronous fuels are not injected by one acceleration (IDT ≧ B), the flag IACC is reset. Waiting and resetting the delay counter IDT.

<< Effects of the Invention >> As described in detail above, in the acceleration correction method according to the present invention, the first asynchronous injection is performed immediately after detecting the acceleration operation state, and then the positive pressure wave of the intake air flows to the intake port. Since the second non-synchronous injection is performed after an appropriate time required to reach the vehicle, smooth and responsive acceleration without a breathing phenomenon immediately after acceleration can be realized.

[Brief description of the drawings]

FIG. 1 is a timing chart of fuel injection control showing a comparison between the conventional acceleration correction method and the acceleration correction method according to the present invention. FIG. 2 is a schematic configuration diagram of an intake system of an engine to which the present invention is applied. FIG. 3 is a flowchart showing the control of the embodiment to which the present invention is applied. t1 ... time when the acceleration operation is performed t2 ... time when the state of the acceleration operation is detected (time when the first asynchronous injection is performed) t3 ... time when the increase of the synchronous injection amount starts t4 ... the peak of the positive pressure wave At the time of reaching the intake port t5 …… Time of the second asynchronous injection

Claims (1)

(57) [Claims] An electronic control system for an engine for injecting fuel in synchronization with an engine cycle from an injector provided in an intake passage of each cylinder and variably controlling the synchronous injection amount according to an intake air amount and a rotation speed of the engine. In the fuel injection device, when an acceleration operation state in which the throttle valve is rapidly opened is detected, an appropriate amount of fuel is immediately injected from the injector asynchronously with the engine cycle, and then a positive pressure wave of the intake air reaches the intake port. An acceleration correction method characterized by injecting an appropriate amount of fuel from the injector asynchronously with a cycle of an engine after a lapse of a predetermined time required to perform the operation.