JPS6338535B2 - - Google Patents

Description

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

An electronically controlled fuel injection system for an internal combustion engine calculates a fuel injection pulse with a pulse width based on various engine parameters so that the engine always performs proper combustion, and uses the fuel injection pulse to drive an electromagnetic injection valve. It supplies fuel to the engine intermittently.

A conventional example of such an electronically controlled fuel injection device will be explained with reference to FIG.

In FIG. 1, reference numeral 1 denotes a waveform shaping circuit which shapes an ignition signal in a vibration waveform obtained from the primary side of an ignition coil (not shown) to generate a square wave rotation pulse. Waveform shaping circuit 1
A basic pulse generating circuit 2 is connected to the output end of the basic pulse generating circuit 2, and an output end of an air flow meter 3 provided in an intake pipe (not shown) is separately connected to the basic pulse generating circuit 2. An increase correction circuit 5 is connected to the output end of the basic pulse generation circuit 2 via a pulse width control circuit 4 that limits the maximum pulse width of the basic pulse. The increase correction circuit 5 is connected to various sensors such as a throttle opening sensor (not shown), a cooling water temperature sensor (not shown), etc., which detect the operating state of the engine so as to command correction of the pulse width of the basic pulse. has been done. A drive circuit 6 is connected to the output end of the increase correction circuit 5, and the drive circuit 6 drives an electromagnetic injection valve 7 provided for each cylinder.

In the electronically controlled fuel injection device with the above configuration,
A rotational pulse synchronized with the ignition of the engine, that is, the rotation of the crankshaft, is supplied from the output end of the waveform shaping circuit 1 to the basic pulse generation circuit 2. On the other hand, the air flow meter 3 generates a voltage according to the intake air amount of the engine. In response to the output voltage of the air flow meter 3 and the rotation pulse, the basic pulse generation circuit 2 generates a basic pulse corresponding to the basic injection amount. When the pulse width of the basic pulse is larger than the predetermined width, the pulse width limiting circuit 4 limits the pulse width of the basic pulse to the predetermined width. The pulse width of the basic pulse is corrected in the increase correction circuit 5 according to the output signals of various sensors, and becomes a fuel injection pulse. The drive circuit 6 drives the electromagnetic injection valve 7 in accordance with the pulse width of the fuel injection pulse thus generated, and fuel is supplied to the engine.

By the way, in an internal combustion engine, intake air is
As shown in the figure, the air passes through the air filter 8 in the direction of arrow Z and is supplied to the engine 12 via the flap 3a of the air flow meter 3 provided in the intake pipe 9, the throttle valve 10, and the surge tank chamber 11. The air flow meter 3 has a potentiometer (not shown) that is linked to the rotation of the flap 3a, and the flap 3a rotates according to the amount of intake air.
An output voltage corresponding to the rotation angle of the plug 3a is generated by the potentiometer. For example, if the throttle valve 10 is suddenly opened when the engine speed is low, the output voltage V _OUT of the air flow meter 3 changes as shown in FIG. In Fig. 3, time top is when the throttle valve is opened, period A is a delay in operation due to the inertia of flap 3, and period B is when flap 3a rotates extra due to the amount of air suddenly flowing in to fill surge tank chamber 11. The part where overshoot occurs, period C
is the part that has reached a steady state. Incidentally, the surge tank chamber 11 is formed to alleviate the pulsation of intake air caused by the cycle operation of the engine.

However, in the conventional electronically controlled fuel injection system, the pulse width limitation of the basic pulse by the pulse width limiting circuit 4 is set relatively large in consideration of the high load and high rotational engine operating conditions. Therefore, if the throttle valve 10 is suddenly opened when the engine speed is low as described above, the pulse width of the basic pulse will change during acceleration from a low number of times due to overshoot in period B in Fig. 3. Although the pulse width is large, it is not so large that the pulse width is limited by the pulse width limiting circuit 4, so there is a problem that the air-fuel ratio becomes overbalanced.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a control method for an electronically controlled fuel injection device that can prevent deterioration of the air-fuel ratio during acceleration of an engine from low rotation speeds.

A control method for an electronically controlled fuel injection device according to the present invention generates a basic pulse with a pulse width corresponding to a basic injection amount according to an intake air amount and an engine speed, and sets the pulse width of the basic pulse to a reference maximum pulse width or less. This control method generates fuel injection pulses by correcting the limited basic pulses according to various engine parameters, and injects fuel by the pulse width of the fuel injection pulses.The lower the engine speed, the higher the reference maximum. It is characterized by a small pulse width.

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

In FIG. 4, parts equivalent to those in FIG. There is. The rest of the configuration of the electronically controlled fuel injection system to which the control method of the present invention is applied is the same as that of the conventional example shown in FIG.

In the above configuration, the pulse width limiting circuit 4 sets the pulse width limit width of the basic pulse according to the generation of rotational pulses, that is, the engine rotational speed, and as shown in FIG. The maximum pulse width T _PMAX is also limited to be large.

As a result, when the throttle valve 10 is suddenly opened when the engine speed is low, an overshoot occurs in the output voltage waveform of the air flow meter 3 as shown in FIG. Even if the pulse width of the basic pulse generated at the end is large for acceleration from a low engine speed, the pulse width of the basic pulse is limited by the pulse width limiting circuit 4 to a pulse width corresponding to the engine speed. Let it happen.

As described above, according to the control method for an electronically controlled fuel injection device according to the present invention, the basic pulse is limited to the reference maximum pulse width or less, and the lower the engine speed, the smaller the reference maximum pulse width is set. Therefore, it is possible to prevent the air-fuel ratio from deteriorating when the engine accelerates from low rotation speeds, thereby improving driving performance, fuel efficiency, and exhaust gas purification.

In the electronically controlled fuel injection system to which the control method of the present invention described above is applied, the part surrounded by the broken line in FIG. 4 is replaced with a microcomputer to process the same operations as described above according to a program. It's also good. For example, the engine speed vs. maximum pulse width characteristic shown in Figure 5 is written in advance as a data table in the ROM, and the maximum pulse width corresponding to the detected engine speed is read from the data table, and the intake air amount and engine speed are When the basic pulse width set according to the number is larger than the read maximum pulse width, an operation is performed according to the program to make the basic pulse width equal to the maximum pulse width.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a conventional example of an electronically controlled fuel injection device, Fig. 2 is a schematic diagram showing an intake system of an internal combustion engine, Fig. 3 is an output voltage waveform diagram of an air flow meter, and Fig. 4 is a diagram of the present invention. A block diagram showing an electronically controlled fuel injection system to which the control method is applied, FIG. 5 is a maximum pulse width characteristic diagram of the basic pulse. Explanation of symbols of main parts, 1...Waveform shaping circuit, 2
...Basic pulse generation circuit, 3...Air flow meter,
4... Pulse width limiting circuit, 10... Throttle valve, 1
1...Surge tank room.

Claims (1)

[Claims] 1 Generate a basic pulse with a pulse width corresponding to the basic injection amount according to the intake air amount and engine speed of the internal combustion engine, limit the pulse width of the basic pulse to a reference maximum pulse width or less, and generate the limited basic pulse. A control method for an electronically controlled fuel injection device that generates a fuel injection pulse by correcting it according to various engine parameters, and injects fuel by the pulse width of the fuel injection pulse, wherein the lower the engine speed, the lower the reference value. A control method characterized by reducing the maximum pulse width.