JPS62279265A - Self-diagnosing device for electromagnetic fuel injecting valve driving circuit system - Google Patents

Abstract

PURPOSE:To miniaturize a device, eliminate the need for using an integral circuit and enable a circuit to maintain an output signal at the time of detecting abnormality for a certain period of time, and enable secure detection even at the time of high speed rotation, by diagnosing plural fuel injection valve driving circuits with one self-diagnosing device. CONSTITUTION:Normally, the output of a monostable multivibrator 18 which is generated synchronized with the off action of transistors 12-1 to 12-4 continues for a very short time since it is stopped when back electromotive force is generated in solenoids 11-1 to 11-4. If the back electromotive force is not generated at the time of the off action of the transistors, the monostable multivibrator 18 is not reset and its output is continued for more than a certain period of time, enabling an abnormality to be detected. Also, the reset of the monostable multivibrator 18 is forbidden for a certain period of time, to maintain the output of the abnormality detecting signal for a defined period of time. Accordingly, the restriction of reading timing for a microcomputer can be relieved even at the time of high speed rotation, securely detecting abnormality, and the device can be miniaturized since plural circuit can be diagnosed with one self-diagnosing device.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a self-diagnosis device for an electromagnetic fuel injection valve drive circuit system.

(Prior art) In recent years, electronically controlled vehicles that use microcomputers (hereinafter referred to as microcomputers) to perform various controls have complex control systems, so in order to improve their safety and reliability, A self-diagnosis function is provided in various control systems, one of which is a drive circuit system for an electromagnetic fuel injection valve (see Japanese Patent Laid-Open No. 59-200024, etc.).

As a conventional self-diagnosis device for such an electromagnetic fuel injection valve drive circuit system, there is one that utilizes a back electromotive voltage generated in a solenoid of a fuel injection valve, and this is shown in FIG. 3 and will be explained.

In the figure, 1 is a solenoid of a fuel injection valve connected to a fuel injection valve, and 2 is a transistor to which an injection pulse T calculated by a microcomputer is applied via a drive circuit. 3 is a first comparator that determines the level of the back electromotive force generated in the solenoid 1 when the transistor 2 is turned off; the back electromotive voltage divided by the resistors R1 and R2 is input to the + side input;
Input the setting voltage ■ to the picture manual. Reference numeral 4 represents an integrating circuit that is composed of a resistor R2, a capacitor C, and a diode D, and integrates the output of the first comparator 3; 5 represents a second comparator for abnormality determination; Set voltage ■2 is applied manually to the + side input.

The operation of this conventional device will be explained with reference to the time chart of FIG.

When the transistor 2 is turned on by application of the injection pulse Ti, a current flows through the solenoid 1 and the fuel injection valve is opened.Thereafter, when the transistor 2 is turned off by the fall of the injection pulse T, the fuel injection valve is closed. At this time, a back electromotive force is generated in the solenoid 1. Therefore, the waveform voltage shown in FIG. 4 is applied to the + side input of the first comparator 3, and the output of the first comparator 3 is at the H'' level only during the period of the set voltage 71 or higher. The output is integrated by the integrating circuit 4, and the integrated output is applied to one side of the second comparator 5 and compared with the set voltage vz.

If the drive circuit system of the fuel injection valve is normal, the integral output of the integrating circuit 4 will never become lower than its set voltage 2, as shown by the solid line in FIG. 4, and the output of the second comparator 5 will be "L".
On the other hand, if an abnormality occurs and no back electromotive force is generated as shown by the broken line in Fig. 4, the integral output will continue to drop and become below the set voltage ■2, and the output of the second comparator 5 will decrease. becomes "H" level and is input to the input port of the microcomputer as an abnormality detection signal.

<Problems to be Solved by the Invention> However, in conventional multi-cylinder engines in which a fuel injection valve is provided for each cylinder, a self-diagnosis device as shown in Fig. 3 is provided for each injection valve. There were problems in that the diagnostic device unit was large and the cost was high.

Another problem was that it was difficult to design a circuit to reliably detect temporary pulse omissions during high engine speeds. That is, in order to detect temporary pulse omissions at high revolutions when the injection pulse interval becomes short, the time constant of the integrating circuit 4 may be reduced or the set voltage V2 of the second comparator 5 may be set high. If this is done, there is a risk that an abnormality detection signal will be output even though the engine is normal at low rotation speeds where the pulse interval is long.

Therefore, in order to satisfy both the prevention of such malfunctions at low speeds and the detection of temporary pulse omissions at high speeds, the time constant of the integrating circuit 4 and the set voltage of the second comparator 5 must be adjusted. ■It was very difficult to set up with 2. Furthermore, with regard to detection of pulse extraction at high rotation speeds, the detection signal output time is extremely short, so that reading operations in the microcomputer are subject to significant time constraints.

The present invention has been made in view of the above circumstances, and it diagnoses a plurality of fuel injection valve drive circuit systems with one self-diagnosis device, and also maintains this detection signal at a constant level when outputting an abnormality detection signal without using an integrating circuit. The purpose is to solve the conventional problems by creating a circuit configuration that allows time to continue.

Means for Solving the Problems> For this reason, in the present invention, a transistor is connected in series to each solenoid of each fuel injection valve provided for each cylinder, and each transistor is sequentially driven to drive the fuel injection valve to open. In the electromagnetic fuel injection valve drive circuit system, a first OR circuit that generates an output according to a back electromotive force when a back electromotive force is generated in any one of the solenoids due to the off operation of a transistor; a back electromotive voltage level determining means that issues a back electromotive voltage detection signal when the output level of the circuit is equal to or higher than a set value;
Each detection means detects the OFF operation of each transistor, a second OR circuit that outputs when any one of the detection means issues a detection signal, and an output that is triggered by the output of the second OR circuit. a monostable multivibrator that is reset by a back electromotive voltage detection signal of a back electromotive voltage level determination means and stops outputting; and an abnormality detection means that issues an abnormality detection signal when the output of the monostable multivibrator continues for a predetermined time or more; and means for stopping the output of the back electromotive voltage detection signal for a predetermined period of time when the abnormality detection signal is output.

In the above configuration, the output of the monostable multi-high break, which normally occurs in synchronization with the off-state of the transistor, is stopped when a back electromotive force higher than the set value is generated in the solenoid. The output of the multivibrator is extremely short-lived.

On the other hand, if a back electromotive force is not generated in the solenoid when the transistor is turned off, the monostable multivibrator will not be reset and its output will continue for a predetermined period of time or longer. This indicates that an abnormality has occurred. Then, when an abnormality is detected, the reset of the monostable multivibrator is prohibited for a predetermined period of time, and the abnormality detection signal output is held for a certain period of time, thereby greatly relaxing restrictions on the reading timing of the microcomputer. Furthermore, since a plurality of drive circuit systems are performed by one self-diagnosis device using an OR circuit, it is possible to reduce the size and cost of the self-diagnosis device unit.

<Example> Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 shows an embodiment in which the present invention is applied to a four-cylinder internal combustion engine.

In the figure, each of the solenoids 11-1 to 11-4 of the fuel injection valve provided for each cylinder has a transistor 12.
-1 to 12-4 are connected in series, and each transistor 12-1 to 12-4 receives an injection pulse T from a microcomputer,
It is driven on and off by injection pulses Tit to T1 sequentially outputted from the drive circuit 13 based on. Solenoids 11-1 to 11 of the transistors 12-1 to 12-4
The collector side connected to -4 is connected to the input side of a first OR circuit 14 consisting of a diode OR circuit. The first OR circuit 14 generates an output corresponding to the back electromotive force generated in each of the solenoids 11-1 to 11-4, and this output is connected to a voltage dividing resistor R5.

The voltage is divided by RI2 and input to the comparator 15. The comparator 15 compares the output level of the first OR circuit 14 with the set voltage 1, and outputs an "H" level output as a back electromotive voltage detection signal when the set voltage is 71 or more. It consists of

16-1 to 16-4 are the falling edges of each injection pulse Tit to Ti4 output from the drive circuit 13, that is, the transistor 1
2-1 to 12-4, each detection signal is sent to the second OR circuit 17.
Enter.

18 is triggered by the output of the second OR circuit 17 and outputs;
This is a monostable multivibrator that is reset by the back electromotive voltage detection signal (“H” level output) from the comparator 15 and stops outputting. 19 is monostable multivibrator 1
For example, the abnormality detection means is a low-pass filter that outputs an abnormality detection signal to the microcomputer when the output of No. 8 continues for a predetermined time or more.

The output side of the low-pass filter 19 is connected to the set voltage 1 input terminal side of the comparator 15, and while the low-pass filter 19 is outputting the abnormality detection signal,
The output value is superimposed on the normal set voltage 1, and the set voltage is set to v, which is higher than the value based on the maximum output value of the first OR circuit 14.
'(v,<v,''), the generation of the back electromotive voltage detection signal from the comparator 15 is stopped for a certain period of time.

Next, the operation will be explained with reference to the time chart shown in FIG. In addition, the output waveform of (al~(ml) in Fig. 2 is the first
This corresponds to each point indicated by a-m in the figure.

According to human power of the injection pulse T from the microcomputer, the injection pulse Tit to T shown in FIG.
i4 is applied. Then, transistors 12-1 to 1
2-4 are sequentially turned on, driving current flows through the solenoids 11-1 to 11-4 of the fuel injection valves of each cylinder, and the valves open.

Then, each injection pulse T8. Simultaneously with the falling of T and A, each transistor 12-1 to 12-4 is turned off, and at this time, each solenoid 1 is turned off as shown in FIG.
A back electromotive voltage is generated at 1-1 to 11-4.

When such back electromotive voltage is generated in one of the solenoids 11-1 to 11-4, for example, the solenoid 11-1, it is inputted to the comparator 15 via the first OR circuit 14 and compared with the set voltage (1). Under normal conditions, the back electromotive force is higher than the set voltage 71, and the output of the comparator 15 is at the "H" level, that is, the back electromotive force detection signal is output and is manually applied to the monostable multivibrator 18 (see Figure 2 (11). ，
01).

At this time, the monostable multivibrator 18 detects the fall of the injection pulse from the corresponding detection circuit 16-1 of the injection pulse fall detection circuits 16-1 to 16-4 before receiving the back electromotive voltage detection signal. The second OR circuit 17 is activated by the signal.
A trigger signal (FIG. 2(k)) is input through the circuit, and the output is generated by being triggered, and the output is stopped by being reset by the manual input of the back electromotive voltage detection signal. Therefore, under normal conditions, the output time of the monostable multivibrator 18 is extremely short as shown in FIG. 2 (1). In this case, the output of the monostable multivibrator 18 is canted by the low-pass filter 19 in the next stage, and the low-pass filter 19
There is no abnormality detection output from 9 (it is found to be normal).

On the other hand, for example, the solenoid 11-3 shown in Fig. 2(g)
If a pulse drop occurs and no back electromotive force is generated as shown by the broken line, the back electromotive voltage detection signal from the comparator 15 is not input to the monostable multivibrator 18 and is not reset, so the monostable multivibrator 18 The output is! ! Continued. When the output of the monostable multivibrator 18 continues for a predetermined time or more, an abnormality detection signal is output from the low-pass filter 19 and input to the microcomputer. At this time, the set voltage of the comparator 15 changes from ■1 to y% as shown in FIG. 2 (11) by the abnormality detection signal.
Therefore, for a certain period of time thereafter, even if a back electromotive voltage is input from another solenoid, the comparator 15 will not generate a back electromotive voltage detection signal, in other words, a reset signal for the monostable multivibrator 18.

Therefore, since the output of the monostable multivibrator 18 is held for a certain period of time, the abnormality detection signal from the low-pass filter 19 is also held for a certain period of time.

In this way, even if there is a temporary pulse dropout during high rotation, the microcontroller will have some leeway in the reading time, and the time constraints can be eased, and abnormalities can be detected reliably and reliability In addition, since multiple fuel injection valve drive circuit systems are tested with one self-diagnosis device,
This has the advantage that the self-diagnosis device unit can be made smaller and the cost can be reduced.

<Effects of the Invention> As described above, according to the present invention, a plurality of fuel injection valve drive circuit systems are diagnosed by one self-diagnosis device, so that the self-diagnosis device unit can be made smaller and lower in cost. can be achieved. Additionally, when an abnormality is detected, the result is stored and output for a certain period of time, which greatly alleviates the constraints on reading timing on the microcontroller side, and can reliably detect even temporary pulse omissions at high rotation speeds, improving reliability. .

Furthermore, there is an advantage that the circuit design is easier than that using a conventional integrating circuit.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is an output waveform time chart of the same embodiment, Fig. 3 is a block diagram showing a conventional example, and Fig. 4 is an output waveform time chart of the conventional example. Show chart. 11-1 to 11-4... Solenoid 12-1 to 1
2-4...Transistor 13...Drive circuit
14...First OR circuit 15...Comparator
16-1 to 16-4... Injection pulse falling detection circuit 17... Second OR circuit 18... Monostable multivibrator 19... Low pass filter

Claims (1)

[Claims] In an electromagnetic fuel injection valve drive circuit system, a transistor is connected in series with each solenoid of each fuel injection valve provided for each cylinder, and each transistor is sequentially driven based on an injection pulse to open the fuel injection valve. a first OR circuit that generates an output in accordance with the back electromotive force when a back electromotive force occurs in any one of the solenoids due to off-operation of the transistor; and an output level of the first OR circuit that is higher than a set value. a back electromotive voltage level determining means that issues a back electromotive voltage detection signal when 2-OR circuit and the second
A monostable multivibrator that is triggered by the output of the OR circuit and emits an output, and is reset and stops outputting by the back electromotive voltage detection signal of the back electromotive voltage level determination means, and the output of the monostable multivibrator continues for a predetermined time or more. An electromagnetic fuel injection valve drive circuit comprising: abnormality detection means for emitting an abnormality detection signal when the abnormality detection signal is output; and means for stopping the output of the back electromotive voltage detection signal for a predetermined period of time when the abnormality detection signal is output. System self-diagnosis device.