JPH0313419B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling fuel injection timing in an electronically controlled fuel injection device for an internal combustion engine.

Conventionally, for example, in a synchronous fuel injection multi-cylinder engine, fuel is injected into all cylinders simultaneously in accordance with the ignition timing of a specific cylinder. In such conventional devices, as shown in the first cylinder of the time chart in Figure 1, even after the piston has passed the bottom dead center and the intake stroke has ended, the cylinder filling efficiency is generally adjusted in consideration of the inertia of the air-fuel mixture. In order to increase the engine speed, the intake valve is kept open until it is, for example, about 50 degrees Celsius (crank angle) past bottom dead center. Therefore, if fuel is injected just before or after the intake valve is closed, the timing of the intake valve's closing may be slightly off, or due to changes in engine speed, the air-fuel mixture may pass through the intake valve during the next compression stroke. There was a problem that fuel was blown back into the intake system, worsening the distribution of fuel into the cylinders.

Therefore, in order to prevent such fuel blowback, it is necessary to accurately control the fuel injection timing.
As a conventional countermeasure in such a case, a method has been adopted in which the crank angle is accurately detected and the fuel injection timing is determined based on this, as described in, for example, Japanese Patent Laid-Open No. 57-2431. Therefore, there are problems in that an expensive crank angle sensor is required and high-speed processing capability is required.

The present invention has been developed in view of the above points, and prevents the deterioration of fuel distribution into cylinders due to air-fuel mixture blowback, suppresses the amount of harmful HC and CO components in exhaust gas, and improves fuel efficiency. The purpose of the present invention is to provide a fuel injection timing control method that achieves the following.

Another object of the present invention is to provide a simple method that does not require an expensive crank angle sensor or high-speed processing capability to achieve this purpose.

This purpose is to determine the basic injection time of fuel based on the engine load, then correct the basic injection time according to the engine operating condition to determine the final injection time, and then calculate the final injection time for each cylinder of a multi-cylinder engine. In a method for controlling fuel injection timing in a fuel injection system for an internal combustion engine with an all-cylinder simultaneous injection method in which fuel is injected simultaneously from all cylinders from fuel injection valves equipped with the fuel injection valve, the fuel injection start timing is set to immediately before the intake valve closing timing of the cylinder or Taking into account that the fuel injection period does not overlap immediately after, it is expressed as an optimal delay time from the ignition timing, and the delay time is stored in advance in memory as map data that corresponds to the engine operating state, and the ignition timing is This is achieved by a fuel injection timing control method characterized in that, after detecting , the fuel injection timing is started in all cylinders simultaneously after waiting for the elapse of a delay time based on the map data.

Embodiments of the present invention will be described below based on the drawings.

FIG. 2 is a block diagram of an electronic control circuit of a fuel injection system for simultaneous synchronous injection of all cylinders at every revolution to which the method of the present invention is applied. An intake air amount signal Q is inputted from the engine, and a correction signal C is inputted from various sensors 4 such as a water temperature sensor via an A/D converter 5. Furthermore, the engine rotation speed N is calculated from the ignition signal F. At the same time, a signal representing the basic injection time Tp is generated from an analog calculation circuit 6 that calculates the basic injection time Tp based on a value indicating the engine load obtained by dividing the intake air amount represented by the intake air amount signal Q by the engine rotation speed. , a signal representing the engine rotational speed N is input. Then, the microcomputer 1 uses various sensors 4 for the input basic injection time Tp.
The final injection time Ti is stored in the built-in memory after being corrected in accordance with the correction signal from the final injection time Ti.

The output side of the microcomputer 1 is equipped with a preset down counter, tires, etc. (not shown), and the output of the timer is connected to an injector 8 via a drive circuit 7 such as a transistor. The valve is driven open for the final injection time Ti to be output, and fuel injection is performed.

In addition, as shown in FIG. 3, the non-volatile memory in the microcomputer 1 stores data on the optimal delay time t from the ignition timing to the injection start timing.
For example, a delay time t ₁ is stored as map data corresponding to the operating state of the engine, such as intake air amount Q ₁ and engine speed N ₁ , and a control program as shown in the flowchart of FIG. 4 is also stored.

That is, since the ignition timing always changes within the range of 0° to 30°C BTDC depending on the values Q, N, etc. representing the engine load, the delay time t takes into account the ignition timing correction time in advance, For example, due to the delay in the injection start timing, from the bottom dead center of the intake stroke of any cylinder.
This value is set to within 60℃, which means that fuel injection will not occur before or after the intake valve is closed.

Note that the delay time t may be map data using the intake pipe pressure P, which represents the engine operating state, instead of the intake air amount Q, and in the case of a configuration in which the ignition timing changes depending on the cooling water temperature, the engine rotation It may also be three-dimensional map data of the number N, intake air amount Q or intake pipe pressure P, and a signal from a water temperature sensor.

The fuel injection device constructed in this manner operates as follows according to the flowchart in FIG.

First, when a starter switch (not shown) is turned on, the microcomputer 1 performs a predetermined initial process, and then the process of this routine starts at a predetermined timing such as an ignition signal, and as shown in step 20, ignition is started from each sensor, etc. Signal F, intake air amount Q,
Correction data such as engine speed N and water temperature are input, and the process moves to the next step.

In the next step 30, the delay time t on the map data in FIG. 3 is retrieved from the engine speed N and intake air amount Q input in the previous step.

In the next step 40, the basic injection time Tp calculated by the analog calculator 6 is read, and the next step is started.
Go to 50.

In step 50, the basic injection time Tp is corrected based on correction data such as water temperature, and the final injection time is determined.
Find Ti.

Then, in the next step 60, the digital value corresponding to the delay time t retrieved in the step 30 is set in the preset down counter, and the process proceeds to the next step 70.

In the next step 70, the final injection time Ti calculated in the step 50 is set in a timer, and the processing of this routine ends.

Through this processing, the digital value corresponding to the delay time t set in the counter is counted down by the reference clock signal of the microcomputer 1, etc., and when the counter content reaches "0", the timer is Final injection time set
The injector 8 is driven and opened only by Ti, and fuel is injected.

To further explain the above-mentioned operation along the time charts of FIGS. 2 and 5, the fuel that was conventionally injected near the bottom dead center at the end of the intake stroke of the third cylinder as shown in FIG. In this embodiment, when the intake air amount is Q ₁ and the engine speed is N ₁ , the delay time is set to t ₁ and the intake valves of the first to third cylinders are closed, as shown in the time chart of Fig. 5. The fuel is injected in the middle of the intake stroke of the fourth cylinder, and deterioration in the cylinder distribution of fuel due to blowback of the air-fuel mixture is suppressed.

As described in detail above, the method of the present invention determines the fuel injection start timing based on the map format data pre-stored in the memory of the microcomputer to determine the optimal delay time from the ignition timing to the injection start timing. This is a control method that allows fuel injection to always be performed at the optimal timing set in advance according to changes in engine operating conditions, eliminating the need to inject fuel just before or after the intake valve closes. This has the effect of preventing deterioration of fuel distribution into cylinders.

Furthermore, the only signals input to the microcomputer are the engine speed and intake air amount, which has the effect of achieving the objective without using any other special sensors, such as a crank angle sensor.

Furthermore, since the injection timing can be controlled, deterioration in emissions due to combustion fluctuations can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a time chart explaining the operation according to the conventional fuel injection timing control method, FIG. 2 is a block diagram of an electronic control circuit of an embodiment to which the method of the present invention is applied, and FIG. 3 is a schematic diagram of map data. FIG. 4 is a flowchart showing the control program, and FIG. 5 is a time chart explaining the operation of this embodiment. 1... Microcomputer, 2... Distributor, 3... Air flow meter, 4... Various sensors, 6... Analog calculation circuit, 8... Injector.

Claims (1)

[Scope of Claims] 1. After determining the basic injection time of fuel based on the engine load, the final injection time is determined by correcting the basic injection time according to the operating condition of the engine. In a method for controlling fuel injection timing in a fuel injection system for an internal combustion engine with an all-cylinder simultaneous injection method in which fuel is injected simultaneously from a fuel injection valve provided in each cylinder to all cylinders, the fuel injection start timing is set to the intake valve closing timing of each cylinder. The fuel injection period is expressed as an optimal delay time from the ignition timing, taking into account that the fuel injection period does not overlap immediately before or after the engine, and the delay time is stored in advance in the memory as map data that corresponds to the engine operating state. . A method for controlling fuel injection timing, characterized in that after detecting the ignition timing, fuel injection is started in all cylinders at once after waiting for a delay time based on the map data to elapse.