JPH02130261A - Wire breakage diagnosing device for fuel injection valve driving circuit - Google Patents

Abstract

PURPOSE:To obtain the simplified software by installing a circuit for wave-form- shaping the reverse electromotive voltage of a solenoid by the OFF-operation of a transistor for driving the solenoid of a fuel injection valve and a circuit which is charged by the output supplied from the above-described circuit and is electrically discharged by an another clearing signal. CONSTITUTION:When a reverse electromotive force is generated in a solenoid 1 by the OFF-operation of a transistor 2 for driving the solenoid 1 of a fuel injection valve, the electromotive force is wave-form-shaped into the rectangular pulses by a wave-form shaping circuit 5, and the condenser C of a charge/discharge circuit 6 is charged by the output. When a standard signal REF is generated from a crank angle sensor 7, a judging means 9 judges the level of the terminal voltage of the condenser C, by using a microcomputer 8, and if the reverse electromotive voltage is generated normally, it is considered that the normal operation is executed, and a clearing means 10 outputs a clearing signal into the circuit 6, and the condenser C is electrically discharged. When wire breakage is generated in a fuel injection valve driving circuit, no reverse electromotive voltage is generated, and the terminal voltage of the condenser C does not increase, and kept at an L-level.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a disconnection diagnosing device for a fuel injection valve drive circuit.

<Prior Art> In an electronically controlled fuel injection system for an internal combustion engine, an electromagnetic fuel injection valve is provided in the engine intake system for each cylinder or for all cylinders in common, and the solenoid of this fuel injection valve is driven via a transistor. ing.

Referring to FIG. 6, the solenoid l of the fuel injection valve connected to the power source U is grounded via a transistor 2, and a drive pulse signal (Ti pulse ), when transistor 2 is turned on, solenoid 1 is energized, and fuel is injected by opening the fuel injection valve.When transistor 2 is turned off by the fall of the Ti pulse, solenoid 1 is de-energized. , fuel injection is stopped.

Here, when power is cut off, a back electromotive voltage is generated in the solenoid 1, so a break in the fuel injection valve drive circuit is diagnosed based on the presence or absence of this back electromotive voltage (Utility Model No. 62-1
(See Publication No. 52049, etc.).

That is, as shown in FIG. 6, the back electromotive voltage of the solenoid 1 is taken out via the diode 3, amplified by the amplifier circuit 4 including the transistor Tr, and passed through the waveform shaping circuit 5 including the Zener diode ZD. The back electromotive voltage is converted into a rectangular pulse (INJ-OK multiplied signal (see Fig. 7)).

Then, at the falling edge of the Ti pulse (Ti-END), an interrupt is generated by software, and the presence or absence of the INJ-OK multiplication signal is determined based on the back electromotive voltage.

<Problems to be Solved by the Invention> However, in such a conventional disconnection diagnosis device, there is a response delay in the circuit (Fig. 7a), so the Ti-
There is a restriction that the determination must be made after a certain delay time (Fig. 7b) after END, and therefore, the reference crank angle (180° in the case of a 4-cylinder engine) is determined from the crank angle sensor.
) and the reference signal interrupt processing (REF-JOB) that is executed in synchronization with the reference signal output for every unit crank angle (1 to 2 degrees) and the unit signal output from the crank angle sensor for every unit crank angle (1 to 2 degrees). Angular interrupt processing (ANGLE-
JOB), the T i -END interrupt is canceled. Therefore, the software configuration was complicated.

Also, at high speeds, background joff (BGJ)
) has a problem in that it can only be determined in the idle area due to reasons such as not rotating.

In view of these conventional problems, the present invention provides a disconnection diagnosing device for a fuel injection valve drive circuit that can simplify software and diagnose disconnections not only in the idling range but also in all ranges. The purpose is to

Means for Solving the Problems> For this reason, the present invention provides a waveform shaping circuit that shapes the waveform of a back electromotive voltage of a solenoid that occurs when a transistor for driving a solenoid of a fuel injection valve is turned off, and a a charging/discharging circuit that is charged by the output and discharged by receiving another clear signal, and determining means for determining the charging potential of the charging/discharging circuit at a predetermined timing and detecting a disconnection when the charging potential is equal to or less than a predetermined value; A clearing means for outputting a clear signal to the charging/discharging circuit after the determination by the determining means is provided to constitute a disconnection diagnosis device for a fuel injection valve drive circuit.

In the above configuration, when a back electromotive force is generated in the solenoid due to the off-operation of the transistor for driving the solenoid of the fuel injection valve, this waveform is shaped by the waveform shaping circuit, and the waveform shaping output is used to prevent charging. The discharge circuit is charged.

At a predetermined timing (for example, the timing at which a reference signal is generated from a crank angle sensor), the determining means first determines the charging potential of the charging/discharging circuit. If the back electromotive force is generated normally, the charging potential of the charging/discharging circuit is at H level, so in this case it can be considered normal.Next, the clearing means outputs a clear signal to the charging/discharging circuit to stop charging. Discharge the discharge circuit and prepare for the next judgment.

If there is a disconnection in the fuel injection valve drive circuit, no back electromotive voltage is generated and the charging potential does not rise, so when the determination means makes a determination at a predetermined timing, the charging potential of the charging/discharging circuit is at L level. If so, we diagnose it as a disconnection.

<Example> An embodiment of the present invention will be described below.

FIG. 1 shows the hardware configuration, and for the circuit in FIG. A charging/discharging circuit 6 including a transistor Trz for discharging C is additionally provided.

The crank angle sensor 7 outputs a reference signal REF to the microcomputer 8 at every reference crank angle (180 degrees in the case of a 4-cylinder engine), and also outputs a unit signal PO8 at every unit crank angle (1 to 2 degrees). .

The microcomputer 8 includes a determining means 9 and a clearing means 10 configured in software.

The determining means 9 determines the charging potential of the charging/discharging circuit 6 (the terminal voltage of the capacitor C) at a predetermined timing, in this example, when the reference signal REF from the crank angle sensor 8 is generated, and determines when the charging potential of the charging/discharging circuit 6 is below a predetermined value. Detects a disconnection.

The clearing means 10 outputs an H-level clearing signal to the base terminal of the transistor Trz of the charging/discharging circuit 6 after the determination by the determining means 9.

Next, the operation will be explained with reference to FIG. 2.

When the transistor 2 for driving the solenoid 1 of the fuel injection valve is turned off, a back electromotive force is generated in the solenoid 1, which is taken out via the diode 3, amplified by the amplifier circuit 4, and shaped into a rectangular shape by the waveform shaping circuit 5. The waveform is shaped into a pulse, and the capacitor C of the charge/discharge circuit 6 is charged by this waveform shaped output.

When the reference signal REF is generated from the crank angle sensor 7,
In the microcomputer 8, a predetermining means 9 determines the level of the terminal voltage of the capacitor C in the charging/discharging circuit 6. If the back electromotive force is generated normally, the terminal voltage of capacitor C is at H level, so this can be considered normal.

Next, the clear means 10 outputs an H level clear signal to the base terminal of the transistor Tr of the charging/discharging circuit 6, turning on the transistor Tr, discharging the capacitor C, and preparing for the next determination.

If there is a disconnection in the fuel injection valve drive circuit, no back electromotive force is generated and the terminal voltage of the capacitor C does not rise. At the time of determination, since the terminal voltage of capacitor C is at L level, a disconnection is diagnosed at this time.

Next, a specific example of the software configuration will be explained with reference to FIGS. 3 to 5.

Fig. 3 shows a routine called "external interrupt 1", in which an interrupt is generated by the offset signal 0FSET or unit signal PO3, and in step 1 (indicated by Sl in the figure, the same applies hereinafter), it is determined whether or not to start injection. However, when injection is to be started, an injection start interrupt process is performed in step 2. Next, in step 3, it is determined whether or not it is an angle interrupt based on the unit signal PO3, and if it is an angle interrupt, angle interrupt processing (ANOLE-JOB) is performed in step 4.

FIG. 4 shows a routine called "external interrupt 2", in which an interrupt is generated by the reference signal REF, and in step 11, the level of the INJ-OK multiplier signal input port, which is the terminal voltage of the capacitor C, is determined.

If this judgment is 1 level, proceed to step 12,
NC, clear the timer. After that, proceed to step 15.

Incidentally, the NG timer is incremented by a fixed time processing routine every 10m5 shown in FIG.

If the judgment in step 11 is L level, step 1
Proceeding to step 3, it is determined whether the measured value of the NG timer is greater than or equal to a predetermined value (for example, 5 seconds), and if it is greater than 5 seconds, it is assumed that a disconnection has been detected, and the process proceeds to step 14, where the NG flag is set. . After that, proceed to step 15.

If the time is less than 5 seconds, proceed directly to step 15.

In step 15, a clear signal is output.

After that, in step 16, reference signal interrupt processing (REF
-JOB).

In this embodiment, if the fuel injector is normal, a back electromotive force is always generated between the reference signal REF, so the determination is made when the reference signal REF is generated, but this determination can be made at any timing. It can be done with

<Effects of the Invention> As explained above, according to the present invention, by adding a few elements, the software can be significantly simplified, and the disconnection diagnosis can be performed not only in the idle area but also in all areas. can get.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is a signal waveform diagram of the same circuit, Figs. 3 to 5 are flow charts showing the software configuration, and Fig. 6 is a circuit showing a conventional example. 7 are signal waveform diagrams of the same circuit. 1... Solenoid of fuel injection valve 2... Transistor 3... Die... Waveform shaping circuit Angle sensor 9... Judgment means ode 4... Amplifying circuit 6... Charging/discharging circuit 7. ...Clear 8...Microcomputer IO...Clearing means patent applicant Japan Electronics Co., Ltd. Representative Patent attorney Fujio Sasashima No. 37 4th flash

Claims (1)

[Claims] A fuel injection valve drive circuit that drives a solenoid of a fuel injection valve via a transistor includes a waveform shaping circuit that shapes the waveform of a back electromotive force of the solenoid when the transistor turns off, and an output from this waveform shaping circuit. a charging/discharging circuit that is charged by the charging circuit and discharged by receiving another clear signal, and determining means that determines the charging potential of the charging/discharging circuit at a predetermined timing and detects a disconnection when the charging potential of the charging/discharging circuit is lower than a predetermined value; A disconnection diagnosing device for a fuel injection valve drive circuit, characterized in that a clearing means is provided for outputting a clear signal to the charging/discharging circuit after the determination by the determining means.