JPS59136525A - Fuel injection controlling apparatus for internal-combustion engine - Google Patents

Abstract

PURPOSE:To enable to supply fuel at a rate required by an engine in a reliable manner, by keeping the driving period of a fuel injection valve longer than a prescribed value by lowering the fuel injection valve driving frequency when the calculated period for driving the fuel injection valve becomes lower than a prescribed value. CONSTITUTION:When a throttle valve 3 is almost completely closed in the state that the speed of rotation of an engine 1 is high, that is, at the time of deceleration of an automobile, the output of a pressure sensor 2 is lowered, so that the driving period of a fuel injection valve 5 calculated by an arithmetic circuit 7 is decreased to a small value lower than the operational range of the fuel injection valve 5. In this state, a time-period comparing circuit 21 judges whether the calculated value of the driving period is smaller than a prescribed value stored in a minimum-value memory circuit 20 or not. In case that the calculated value is smaller than the prescribed value, the frequency of the output signal of a rotation sensor 4 is divided to 1/2, and the frequency-divided signal is applied to an output circuit 8 as a trigger signal. Thus, the driving frequency of the fuel injection valve 5 is reduced to 1/2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection control device for an internal combustion engine.
In particular, the present invention relates to improvements in fuel injection characteristics when an intermittent pulse-driven fuel injection valve is used in the device.

Conventionally, a fuel injection device shown in FIG. 1 has been used as a fuel injection device for an internal combustion engine. In Fig. 1, 1 is an internal combustion engine;
2 is a pressure sensor that detects the pressure in the intake pipe 6; 3 is a throttle valve provided in the intake pipe 6; 4 is a rotation sensor that detects the 10-rotation position of the internal combustion engine; 5 is a sensor that supplies fuel into the intake pipe 6; 7 is a calculation circuit that calculates the drive pulse width of the fuel injection valve 5 based on the signals from the pressure sensor 2 and the rotation sensor 4; and 8 is an output circuit that drives the fuel injection valve 5.

In the above configuration, the output of the pressure sensor 2 and the rotation sensor 4
The output of the engine is determined by the opening degree of the throttle valve 3 which is manually operated and the rotational speed of the internal combustion engine 1, and based on these outputs, the calculation circuit 7 calculates the amount of fuel required for the engine. Second
In the figure, (a) shows the rotation signal pulse obtained from the rotation sensor 4, and the output circuit 8 synchronizes with the rotation signal pulse based on the output of the calculation circuit 7 and outputs the drive signal shown in FIG. 1 is driven in addition to the negative injection valve 5. TO and τ8
are the drive period and drive time width (valve opening time width) of the fuel injection valve 5. As shown in FIG. 3, the fuel injection valve 5 has a characteristic that the amount of fuel injected is proportional to the driving time width τa. By controlling the driving time width τa, the desired fuel injection amount can be obtained. can get. This drive time width τ3 is the intake pipe 6
The larger the internal combustion engine pressure, that is, the output of the pressure sensor 2, the greater the desired air-fuel ratio. Normally, the driving time width τa is approximately 1.5 m when the internal combustion engine 1 is in an idling state with the lightest load. The formula becomes However, when the throttle valve 3 is almost closed and the engine speed is high, that is, when the car is decelerating or traveling down a slope, the output of the pressure sensor 2 is small, and the amount of fuel required per unit time is idling. Also, the drive period To of the fuel injection valve 5
Since the drive time width τa becomes shorter, the calculated value of the drive time width τa in the calculation circuit 7 becomes a significantly smaller value.

However, as shown in FIG. 3, there is a limit to the responsiveness of the fuel injection valve 5, and for example, when the drive time width τa is 1 m5eC or less, there is a drawback that fuel is not stably injected.

The present invention has been made in order to eliminate the above-mentioned drawbacks of the conventional art, and it reduces the driving frequency of the fuel injector when the calculated value of the =V time value of the fuel injector becomes less than a predetermined value. It is an object of the present invention to provide a fuel injection control device for an internal combustion engine, which can secure the engine drive time width to a predetermined value or more and reliably supply the amount of fuel required by the engine.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 4 is a configuration diagram showing an embodiment of the present invention, in which 20 is a minimum value storage circuit that stores in advance the minimum driving time width of the fuel injection valve 5, and 21 is a minimum value storage circuit that stores the minimum driving time width of the fuel injection valve 5 obtained by the calculation circuit 7.
22 is a data conversion circuit that converts the driving time width given to the fuel injection valve 5 based on the comparison result of the time width comparing circuit 21; 23 is a frequency division switching circuit that switches the driving frequency of the output circuit 8 according to the comparison result of the time width comparison circuit 21.

In this embodiment, the pressure sensor 2 is configured as described above, and when the throttle valve 3 is close to fully closed when the engine speed is high, that is, when the vehicle is decelerating or traveling down a slope. Since the output becomes very small, the operating time width of the fuel injection valve 5 calculated by the calculation circuit 7 is a small value and often falls below the operating range of the fuel injection valve 5 shown in FIG.

However, at this time, the time width comparison circuit 21 compares whether the calculated value of the driving time width is less than or equal to a predetermined value stored in advance in the minimum value storage circuit 20, and if it is determined that it is less than the predetermined value, the frequency division switching circuit 23 frequency-divides the rotation signal of the internal combustion engine 1, that is, the output signal of the rotation sensor 4 shown in FIG. 5(a), into i, and applies the frequency-divided signal to the output circuit 8 as a signal. Therefore, the driving frequency of the fuel injection valve 5 becomes -. In addition, the driving time width τa at this time is doubled by the data conversion circuit 22 as shown in FIG. It is converted to become
The same value is obtained as the fuel injection amount per unit time.

In this way, when the driving time width of the fuel injection valve 5 is small and reaches an unstable region of τ in FIG. Since the injection amount is controlled to be Q22Ql, the drive time width τa of the fuel injection valve 5 increases to a value τ2, and the fuel injection valve 5 can be used in a stable operating range. When the required amount of fuel becomes smaller, the frequency dividing ratio is increased to reduce the driving frequency of the fuel injection valve 5, thereby increasing the driving time width and allowing use in a stable range. However, if the soft division ratio is increased, the air-fuel mixture becomes non-uniform, so it is necessary to keep it within a range where the fuel injection valve 5 can be used stably.

Note that if the calculated value of the drive time width is greater than or equal to the predetermined value, /' Control similar to conventional methods is performed.

In the above embodiment, the load state of the engine is detected by detecting the pressure inside the intake pipe 6, but it may also be detected by detecting the amount of intake air. Further, the control of the fuel injection valve 5 may also be realized by a program using a microcomputer.

As described above, in the present invention, when the driving time width of the fuel injector falls below a predetermined value, the driving frequency of the fuel injector is reduced and the driving time width is increased in response to this reduction. In addition, when supplying the required amount of fuel, the fuel injection valve can be used in a stable operating range, avoiding unstable operating ranges with a small driving time range, and meeting the engine's requirements. It is important to ensure that the amount of fuel is supplied.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the conventional device, Fig. 2 is an operating waveform diagram of the conventional device, Fig. 3 is a characteristic diagram of the fuel injection valve, Fig. 4 is a block diagram of the device of the present invention, and Fig. 5 is a diagram of the device of the present invention. FIG. DESCRIPTION OF SYMBOLS 1... Internal combustion engine, 2... Pressure sensor, 3... Throttle valve, 4... Rotation center, 5... Fuel injection valve, 6...
・Intake pipe, 7... Arithmetic circuit, 8... Output circuit, 20
- Minimum value storage circuit, 21... Time width comparison circuit, 2
2...Data conversion circuit, 23...Branch switching circuit. Note that the same reference numerals indicate the same or similar parts. Agent Makoto Kuzuno - Figure 1 ■ Figure 2 @ Figure 3 tmsec Figure 4 6 Figure 5

Claims (1)

[Claims] An internal combustion engine in which the driving time width of a fuel injector that is driven in synchronization with engine rotation is controlled based on the results of calculations using operating parameters such as the engine's intake air amount, intake pipe pressure, and rotational speed. In the fuel injection control device, the driving frequency of the fuel injector is reduced when the calculated driving time width becomes equal to or less than a predetermined value, and the driving time width is increased in response to the reduction in the driving frequency. A fuel injection control device for an internal combustion engine, characterized in that: