JPH0316492B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fuel injection control device for an engine that performs fuel injection in accordance with the intake stroke of each cylinder.

(Prior Art) Conventionally, as an engine fuel injection control, for example, as seen in Japanese Patent Application Laid-Open No. 59-29733,
BACKGROUND ART A technique is known in which fuel is independently injected by outputting a fuel injection pulse to an injector disposed in each cylinder for each cylinder for a fuel injection time determined from the engine operating state in accordance with the intake stroke. This independent injection has excellent responsiveness to driving performance such as engine transient characteristics. For example, fuel is injected and supplied near the end of the intake stroke, and the fuel is unevenly distributed near the spark plug, resulting in stratification. It has features such as enabling lean combustion (see JP-A-58-85319).

The fuel injection time, that is, the fuel injection amount changes depending on the operating condition, and the injection timing needs to be changed accordingly. However, in the preceding example, the fuel injection end timing is set at a predetermined crank angle. ,
The fuel injection start timing is changed depending on the driving state, and as the amount of fuel is increased during acceleration, the fuel injection start timing is advanced.

Therefore, when the fuel injection timing is advanced during acceleration as described above, the injection timing (injection start timing in the previous example) is adjusted as the acceleration state ends or the degree of acceleration decreases and the injection amount decreases. Although it is necessary to delay the injection timing before acceleration, a sudden change in injection timing is accompanied by a large torque fluctuation, which may cause a torque shock to the engine's drivability.

In other words, in an engine in which fuel injection is performed while the intake valve is open in accordance with the intake stroke of each cylinder, and the injection timing is set in the latter half of the intake stroke to stratify the fuel as described above, When the operation shifts to acceleration, the amount of air increases responsively as the throttle opening increases, but there is a delay in fuel supply, and the air-fuel ratio tends to temporarily become lean at the beginning of acceleration. It is in. In particular, in the case of a lean-burn engine that is operated at a very lean air-fuel ratio in the steady-state operating region, the lean air-fuel ratio at the beginning of acceleration can cause the air-fuel ratio to become over-lean, causing a misfire. There is a possibility that this may occur. Therefore, in the early stages of acceleration as described above, it is necessary to instantaneously and rapidly advance the fuel injection timing to ensure good acceleration response. but,
When the acceleration state ends or the degree of acceleration decreases and the injection timing is delayed to recover,
If the injection timing is instantaneously delayed as in the case of acceleration transition, a large torque will occur due to a reduction in the fuel injection amount and a large fluctuation in the injection timing, which will have a negative impact on driving performance.

(Object of the Invention) In view of the above circumstances, the present invention injects fuel while the intake valve is open in accordance with the intake stroke of the cylinder, and also changes the fuel injection timing during acceleration, ensuring responsiveness during the initial stage of acceleration. However, it is an object of the present invention to provide a fuel injection control device for an engine which is designed to suppress shock upon return.

(Structure of the Invention) The fuel injection control device of the present invention obtains a fuel injection pulse according to the operating state of the engine, and sets a predetermined fuel injection pulse for each cylinder by an injection timing setting means for the intake stroke of each cylinder. When fuel injection is performed while the intake valve is open at the injection timing, when the acceleration detection means detects an accelerated driving state, the acceleration correction means instantaneously advances the injection timing, and at the same time The present invention is characterized in that when the detection means determines that the acceleration has ended, the injection timing is gradually delayed by the return control means.

FIG. 1 is an overall configuration diagram for clearly showing the configuration of the present invention.

Fuel is injected and supplied to the intake passage 2 of the engine 1 by an injector 3 arranged for each cylinder.The rotation of the engine 1 is detected by a rotation detection means 4, and the amount of intake air is detected. Detection is performed by means 5. The injection time calculating means 6 receives the signals from the rotation detecting means 4 and the intake air amount detecting means 5, and basically calculates the injection time based on the engine speed and the intake air amount.
Various corrections are made to determine the injection time corresponding to the fuel injection amount and output to the injection timing setting means 7.

The injection timing setting means 7 sets the injection time,
According to the engine rotational speed and a correction signal from the acceleration correction means 8 or return control means 9, which will be described later, the fuel injection timing, that is, the injection start time and the injection end time are set at a timing that matches the intake stroke of each cylinder, and the rotation is detected. Based on the signal from the means 4, a fuel injection pulse is output to the injector 3 of each cylinder at a predetermined time.

The acceleration correction means 8 receives a signal from the acceleration detection means 10 that detects the acceleration state of the engine, and sends an acceleration correction signal to the injection timing setting means 7 to instantly advance the injection timing (injection start timing) when acceleration is detected.
Output to. Further, the return control means 9 similarly receives a signal from the acceleration detection means 10, and performs return correction to gradually delay the injection timing advanced by the acceleration correction means 8 in accordance with the end of the acceleration state or a reduction in the degree of acceleration. A signal is output to the injection timing setting means 7.

(Effects of the Invention) According to the present invention, when acceleration is detected, the acceleration correction means instantly advances the injection timing,
In response to an increase in fuel injection amount, etc., fuel injection is performed with good responsiveness so as not to cause a fuel supply delay, and it is possible to avoid occurrence of an overlean air-fuel ratio, etc., and obtain good acceleration performance. Further, at the time of acceleration recovery, by gradually delaying the injection timing, which has been advanced by the acceleration correction means, by the return control means, it is possible to eliminate the occurrence of torque shock caused by sudden fluctuations in the injection timing. It is possible to obtain driving performance that is smooth and has a good feeling.

(Example) Examples of the present invention will be described below with reference to the drawings. FIG. 2 is an overall configuration diagram of an engine equipped with a fuel injection control device.

An injector 3 is disposed in an intake passage 2 that supplies intake air to a combustion chamber 12 of the engine 1, and fuel is supplied thereto. In this intake passage 2, an air cleaner 14, an intake air amount sensor 15 that measures the amount of intake air, and a throttle valve 16 that controls the amount of intake air are arranged in this order from the upstream side. On the other hand, a catalytic converter 18 is interposed in an exhaust passage 17 that discharges exhaust gas from the combustion chamber 12, and an air-fuel ratio sensor 19 is disposed in the exhaust passage 17 upstream of the catalytic converter 18.

The air-fuel ratio supplied to the combustion chamber 12 of the engine 1 is adjusted by the amount of fuel injected from the injector 3, and the fuel injection by the injector 3 is controlled by a control signal output from the controller 20. . The controller 20 includes an intake air amount signal from the intake air amount sensor 15 and a throttle opening sensor 2 that detects the opening of the throttle valve 16 in order to detect the operating state of the engine.
1, an engine rotation signal based on the ignition signal from the distributor 22 and the igniter 23, an intake air temperature signal from the intake air temperature sensor 24 disposed in the air cleaner 14, and a water temperature from the water temperature sensor 25 that detects the cooling water temperature. There are systems in which the signal and further the air-fuel ratio signal from the air-fuel ratio sensor 19 are input, and the fuel injection amount and fuel injection timing are controlled according to the operating state of the engine. Note that 26 is a battery.

The controller 20 has the functions of each of the means shown in FIG. Based on the above, the basic injection timing is calculated according to the intake stroke of each cylinder, and this basic injection timing is corrected to be earlier when acceleration is detected.
At the time of return, return correction is performed to gradually delay the return, the final injection timing is determined, and control is performed to output an injection pulse to the injector 3 at a predetermined time.

In the above control, the throttle opening detected by the throttle opening sensor 21 is used to detect the acceleration/deceleration state and calculate the target air-fuel ratio, and the intake air temperature detected by the intake air temperature sensor 24 is used to correct the intake air amount. The cooling water temperature measured by the sensor 25 is used to correct the injection amount according to the warm-up state, and the air-fuel ratio detected by the air-fuel ratio sensor 19 is used for feedback correction according to the difference from the target air-fuel ratio.

Fuel injection is performed at the injection timing set by the controller 20. For example, as shown in FIG. 3, the intake valve is at the top dead center TDC.
For the intake stroke, which opens from the front and closes after bottom dead center BDC, the fuel injection pulse P is output in the latter half of the intake stroke to perform fuel injection, thereby realizing fuel stratification. During non-acceleration, such as during steady operation, the injection pulse P reaches the bottom dead center as shown by the solid line.
Fuel injection is started at the basic injection timing θf before BDC, and during acceleration, the injection pulse P starts fuel injection earlier by the acceleration correction value θfa, as shown by the broken line.

The correction of the injection start timing during acceleration is the fourth
As shown in the figure, when not machining, the injection timing is at the basic injection timing θf, but when the state shifts to an acceleration state and acceleration is detected at point a, the injection timing is instantaneously advanced by the acceleration correction value θfa. This acceleration correction is made intermittently during accelerated driving. When the detection of the acceleration state is completed at point b, the injection timing is corrected to be gradually delayed so that the basic injection timing θf is reached after a predetermined period of time.

The operation of the controller 20 will be explained based on the flowchart shown in FIG. This flowchart only shows the routine for determining the fuel injection start timing.

After the start, the controller 20 moves to step S1.
Initialize the system at step S2, and set the engine speed Ne, intake air amount signal Tp, and throttle opening at step S2.
Load each of Ta, etc. Furthermore, step S3
Read the basic fuel injection time TpK calculated according to the intake air amount Tp.

Then, in step S4, the basic injection timing θf (injection start crank angle before bottom dead center) is calculated from a preset basic injection timing map for the engine speed Ne and the basic injection time TpK. The basic injection timing map is set such that the basic injection timing θf becomes earlier as the engine speed Ne becomes higher and as the basic injection time TpK becomes longer, that is, as the load becomes higher.

Next, in step S5, it is determined from the amount of change in the throttle opening degree Ta whether or not there is an acceleration operation state.
If YES, the flag F is set to 1 in step S6, and the injection timing correction value A is calculated in step S7.
The acceleration correction value A is set to a constant value.
After calculating the correction value A, in step S12, the above correction value A is set as the acceleration correction value θfa (crank angle), and in step S13, the basic injection timing θf and the acceleration correction value θfa are added to determine the final injection timing θo. Perform calculations. The final injection time θo during this acceleration is determined by the determination in step S5.
When the acceleration is detected as YES, the basic injection timing θf is immediately set earlier by the acceleration correction value θfa.

On the other hand, if the acceleration operation state shifts to the non-acceleration operation state, the determination in step S5 is NO.
Therefore, the process proceeds to step S8, where it is determined whether the correction value A is O or not. Immediately after the transition from the acceleration state, the above correction value A is not O, so if the determination is NO, the process proceeds to step S9, where this correction value A is subtracted by a predetermined value B for every 360° of crank angle. . Then, the final injection timing θo is calculated in steps S12 and 13, and the acceleration correction value θfa is gradually decreased in accordance with the predetermined value B, and the final injection timing θo is shifted to the retarded direction.

As mentioned above, when the correction value A decreases to O, the determination in step S8 becomes YES, and step S10
The flag F is reset to O in step S11, and the correction value A is set to O in step S11.
In this state, the final injection timing θo returns to the basic injection timing θf.

According to the above-described embodiment, the injection timing is advanced when acceleration is detected, and the injection timing is gradually restored when acceleration ends, thereby achieving good responsiveness and drivability.

Figure 6 shows a characteristic that delays the injection timing at the time of return, such that it is gradually delayed at the end of acceleration, but the return speed is increased midway through.
I try to keep it continuous.

In addition, Fig. 7 shows that with respect to increases and decreases in engine acceleration α, in the increasing state up to point c where the increase in acceleration α reaches its peak, the basic injection time θf is advanced by the acceleration correction value θfa, while at point c This example shows an example in which the injection timing is controlled to be gradually delayed even in the acceleration state when the acceleration α stops increasing after passing the peak of .

In the above embodiment, the correction value A during acceleration is set to a constant value regardless of the acceleration, but the correction value A may be changed depending on the magnitude of the acceleration. . That is, the acceleration may be detected and the correction value A may be set such that the greater the acceleration, the earlier the injection timing.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram for clearly showing the configuration of the present invention, FIG. 2 is an overall configuration diagram of an engine equipped with a fuel injection control device, and FIG. 3 is a characteristic diagram showing an example of fuel injection timing with respect to the intake stroke. Fig. 4 is a characteristic diagram showing the relationship between acceleration operation and fuel injection timing, Fig. 5 is a flowchart for explaining the operation of the controller, and Fig. 6 is a characteristic diagram showing the relationship between acceleration operation and fuel injection timing in another example. FIG. 7 is a characteristic diagram showing the relationship between acceleration operation and fuel injection timing in yet another example. DESCRIPTION OF SYMBOLS 1... Engine, 2... Intake passage, 3... Injector, 6... Injection time calculation means, 7... Injection timing setting means, 8... Acceleration correction means, 9...
...Return control means, 10... Acceleration detection means, 15...
...Intake air amount sensor, 20...Controller.

Claims (1)

[Claims] 1. Acceleration detection means for detecting an accelerating operating state in an engine fuel injection control device comprising injection timing setting means for setting fuel injection timing for each cylinder while the intake valve is open in accordance with the intake stroke of each cylinder. and an acceleration correction means for instantaneously advancing the injection timing during acceleration, and a return control means for gradually restoring the advanced injection timing when the acceleration detection means determines that the acceleration has ended. fuel injection control device.