JPS6157936B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection control device for a vehicle-mounted internal combustion engine, and more particularly to a fuel injection control device that uses a hot-wire flow meter to detect the amount of intake air.

A fuel injection control device for a vehicle-mounted internal combustion engine requires various engine parameters in order to generate fuel injection pulses, and a hot wire flowmeter is one of the instruments for measuring the amount of intake air.

In a hot wire type flowmeter, since the heating wire portion is placed in the gas flow to be measured, substances such as dust mixed or contained in the gas flow adhere to the heating current.
For this reason, the measurement characteristics of the flowmeter may change over time, resulting in measurement errors. In order to prevent this, each time the flow rate or current meter side ends, an excessive current is passed through the heating wire to heat it to a temperature of around 1000°C, which is sufficiently higher than the constant temperature at the time of measurement. A method is adopted in which the substances adhering to the heating wire are removed by burning them off.

In recent years, in order to remove the burn-off described above, fuel injection control devices maintain power supply even after the ignition switch is turned off, generate a burn-off signal, and apply an excessive current to the heating current for a predetermined period of time to burn out the adhered substances. Cutting is done. However, since the fuel injection control device maintains power supply even when the ignition switch is turned off, current flows to the ignition system and continues to inject fuel.
There was a problem with the engine not stopping.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a control method for a fuel injection control device that solves the above problems.

A method for controlling a fuel injection control device according to the present invention includes:
It detects the OFF state of the ignition switch, and if the ignition switch is in the OFF state, fuel is cut off.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a part of a fuel injection control device to which the control method of the present invention is applied, which is constructed by a microcomputer, and an ignition switch. In this diagram, the power supply voltage V _B from the battery
is supplied to the fuel injection control device via ignition switch 1 and line 2, while also being supplied by line 3. In the fuel injection control device, line 2 is connected to a smoothing circuit formed by coil L and capacitor _C1 . This smoothed output is output via a hot wire flowmeter (not shown), a constant voltage circuit formed by a resistor R ₁ and a Zener diode ZD ₁ , and a control circuit (not shown) consisting of a microprocessor etc. that performs program calculation processing. connected to Also, line 3 is a transistor
It is connected to a switch circuit formed by Q _1-2 , resistors R _2-3 and diode D ₁ . This switch circuit supplies power to the control circuit when the ignition switch 1 is off, and stops the power supply according to a command from the control circuit. Transistor Q ₃ , resistor R ₄
~R ₇ , diode D ₂ , capacitor C ₂ and Zener diode ZD ₂ , the potential difference detection circuit detects the potential difference between lines 2 and 3 that occurs when ignition switch 1 is off, and detects the potential difference between lines 2 and 3 of the control circuit. Outputs the ignition switch off signal to 0LSI. A burnout signal generation circuit formed by transistors _Q4-5 , Zener diodes _ZD3 , and resistors _R8-11 generates a burnout signal for burning off and removing deposits on the heating wire in response to instructions from the control circuit.

When the ignition switch 1 is on, power is supplied from the line 2 to the control circuit and the hot wire flowmeter. At this time, a signal is generated at the output terminal _P2 of the I/0LSI, which turns on the transistor _Q2 via the resistor _R3 . Furthermore, current flows to the base of transistor _Q1 via resistor _R2 and diode _D1 , turning on transistor _Q1 . Next, when ignition switch 1 is off, transistor Q ₁
A potential difference is generated across the diode D ₂ connected in the forward direction from the collector to the smoothed output, and this potential difference flows to the base of the transistor Q ₃ via the resistor R ₄ and turns on the transistor Q ₃ . Therefore, when the ignition switch is off, the power supply voltage V _B is applied to line 3 through the resistor R ₅ through transistors Q ₁ and Q ₃ .
The voltage is made constant by the Zener diode ZD ₂ , and is further integrated by the resistors R ₆ and R ₇ and the capacitor C ₂ to become I/
Apply the ignition switch off signal to the input terminal A13 of 0LSI. Also, at this time, the power supply voltage V _B
is supplied to the hot wire flow meter and control circuit via the diode _D2 in the same way as when the ignition switch 1 is in the on state. Next, I/0LSI output terminal P ₁
When a burnout pulse appears, this burnout pulse is applied to the base of transistor _Q4 via resistor _R8 , turning transistor _Q4 on. Therefore, the transistor _Q5 is turned off, a voltage is applied from the constant voltage circuit to the Zener diode _ZD3 via the resistor _R11 , and the burnout signal generation circuit generates a burnout signal.

The fuel injection control device including the above configuration and operating input/output parts operates according to a program incorporated in the control circuit. This operation will be explained using the flow diagram in FIG. First, turn on the ignition switch 11 and control circuit I/0LSI.
1 outputs a switching signal to output terminal P _{2 of}
2. At this time, judgment 1 whether the engine has started or not
3, and when the engine is not started, turn off the switching signal of output terminal _P214 . If the engine has started, it will proceed to the next step, and the control circuit will detect that the engine has stopped (15), and if the ignition switch 1 is in the on state (16), it will determine that the engine has stalled and will send a switching signal to the output terminal _P2 of the I/0LSI. 17, and turns off the transistor _Q1 . Next, when the state 16 of the ignition switch 1 is off, the power supply voltage V _B is supplied to the fuel injection control device by the transistor Q ₁ . The control circuit immediately cuts off the fuel 18 to prevent the engine from running out of control due to the supply voltage going around. Thereafter, a timer is set 19, and after 5 seconds, for example, a 1 second burnout pulse is generated at the output terminal _P1 of the I/0LSI 20, and the substance attached to the heating wire is burnt off. Then I/0LSI
The switching signal generation of output terminal _P2 stops,
Since the transistor _Q1 is turned off, the supply of the power supply voltage _VB is stopped.

As described above, according to the control method of the fuel injection control device according to the present invention, since the fuel is cut off by detecting that the ignition switch is turned off, it is possible for the engine to continue operating while the ignition switch is turned off. It will no longer occur.

Although an embodiment has been shown in which the method for controlling a fuel injection control device according to the present invention is executed by a program of a control circuit, it is possible to implement the present invention by providing hardware that performs the operations described above. Needless to say.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a part of a fuel injection control device to which the control method of the present invention is applied, and FIG. 2 is an operation flow diagram showing the control method of the fuel injection control device according to the present invention. Explanation of the symbols of the main parts: 1...Ignition switch, 2, 3...Line.

Claims (1)

[Claims] 1 Fuel injection control for a vehicle internal combustion engine configured to maintain power supply even after the ignition switch is turned off and generate a burn-off signal to burn off and remove dust attached to a hot-wire flowmeter 1. A control method for an apparatus, characterized in that fuel is cut off when it is detected that the ignition switch is turned off.