JPH079203B2 - On-board equipment self-diagnosis device - Google Patents

Description

The present invention relates to a self-diagnosis device for diagnosing whether or not there is an abnormality in an electric load such as a fuel injection valve mounted on a vehicle.

<Prior Art> A conventional example of this type of self-diagnosis apparatus is shown in FIG.

That is, the power transistor 2 built in the control unit is connected in series to the solenoid of the fuel injection valve 1. The power transistor 2 is turned on / off by the control device 3 via the current limiting resistor 2a so that the solenoid of the fuel injection valve 1 is energized from the battery 4.

Further, first and second voltage dividing resistors 5 and 6 are connected in parallel to the power transistor 2, and a voltage between the voltage dividing resistors 5 and 6 is applied to an input port of the control device 3.

Then, the control device 3 diagnoses whether or not there is an abnormality in the fuel injection valve 1 according to the voltage between the voltage dividing resistors 5 and 6. For example, when the voltage is held at a low level even when the power transistor 2 is turned on / off, the fuel injection valve 1
The solenoid of the fuel injection valve 1 is diagnosed as being disconnected, and the solenoid of the fuel injection valve 1 is diagnosed as short-circuited when the voltage is held at the high level even when the power transistor 2 is turned on and off. ing.

Further, the power transistor 2 includes a time constant resistor 7
And the capacitor 8 are connected in parallel, and these circuits 7 and 8 form a surge absorbing circuit of the fuel injection valve 1.

Incidentally, 9 is a power supply circuit for applying a constant voltage V _CC to the control device 3, 1
0 is a Zener diode for absorbing a large voltage, and 11 is an ignition switch.

<Problems to be Solved by the Invention> However, in such a conventional self-diagnosis apparatus, when the ignition switch 11 is turned off, in other words, when the power transistor 2 is turned off, the battery 4 is connected via the solenoid of the fuel injection valve 1 through the solenoid. Since a leak current flows through the first and second voltage dividing resistors 5 and 6 and the input port, there is a problem that the battery 4 is deteriorated or goes up.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a self-diagnosis device capable of self-diagnosing whether or not there is an abnormality in an electric load while preventing a leak current.

<Means for Solving the Problems> Therefore, according to the present invention, as shown in FIG. 1, the battery A power source, the electric load B, and the switching means C are connected in series, and the switching means C is turned on. A charging / discharging circuit D connected in parallel to the switching means C, a diode E having a cathode terminal connected to the charging / discharging circuit D, and an anode terminal of the diode E, in which the electric load B is energized. Current limiting resistor F
A voltage supply circuit G for applying a voltage via a voltage detector, a voltage detector H for detecting an anode terminal voltage of the diode E after a lapse of a predetermined time from the time when the switching means C is turned off, and a detected anode terminal voltage. And a judging means I for judging whether or not there is an abnormality in the electric load B based on the above.

<Operation> In this way, the state of the charging pressure of the charge / discharge circuit is detected from the cathode terminal voltage of the diode to determine whether or not there is an abnormality in the electrical load, and the diode prevents leakage current when the switch means is off. I chose

<Example> An example of the present invention will be described below with reference to FIGS. 2 to 4. The same elements as those in the conventional example are designated by the same reference numerals as those in FIG. 5, and the description thereof will be omitted.

In FIG. 2, the cathode terminal of the first diode 21 is connected to the collector terminal side of the power transistor 2 as the switching means, and the anode terminal of the second diode 22 is connected to the anode terminal of the first diode 21. There is. At the anode terminals of the first and second diodes 21 and 22, a constant voltage V _CC is supplied from a power supply circuit 9 as a voltage supply circuit.
Is applied via the current limiting resistor 23. The power supply circuit 9 has a constant voltage when the ignition switch 11 is turned on.
It is designed to output V _CC .

The cathode terminal of the second diode 22 is grounded via the resistor 24 and is connected to the input port of the controller 25. The control device 25 operates according to the flowchart shown in FIG. 3, and determines whether or not the solenoid of the fuel injection valve 1 is abnormal based on the voltage of the cathode terminal of the second diode 22, in other words, the voltage of the anode terminal of the first diode 21. It is supposed to diagnose.

Here, the control device 25 constitutes a voltage detection means and a determination means. Further, the time constant resistor 7 and the capacitor 8 forming the surge absorbing circuit form a charge / discharge circuit.

Next, the operation will be described with reference to the signal waveform diagram of FIG. 4 and the flowchart of FIG. The routine shown in the flowchart of FIG. 3 is designed to start the operation when the power transistor 2 is switched from on to off.

First, from the control device 25 to the power transistor 2, as shown in FIG.
When the pulse signal shown in is output, the power transistor 2
Is turned on and the collector voltage of the power transistor 2 becomes the fourth
It switches to the L level as shown in FIG. At this time, the constant voltage V _CC is applied from the power supply circuit 9 to the first and second diodes 21 and 22 through the current limiting resistor 23.
Since the cathode terminal of 21 is connected to the collector terminal of the power transistor 2, the anode terminal voltage of the first diode 21 and the cathode terminal voltage of the second diode 22 are
It changes at the same voltage level as the collector terminal voltage of the power transistor 2. As a result, the cathode terminal voltage of the second diode 22 is switched to the L level as shown in FIG. 4c.

When the power transistor 2 is turned on, the capacitor 8
Is discharged through the time constant resistor 7 and the power transistor 2.

In such a state, the control device 25 switches the power transistor 2 from on to off and starts execution of the routine shown in the flowchart of FIG.

That is, in S1, a predetermined time T _d (for example, 50 μsec) from the time when the power transistor 2 is switched from on to off
After delaying, the cathode terminal voltage of the second diode 22 is read at S2.

In S3, it is determined whether or not the read cathode terminal voltage is lower than the reference voltage. If YES, the process proceeds to S4, and if NO, S5.
Proceed to.

In S4, it is determined to be abnormal because the solenoid of the fuel injection valve 1 is broken.

On the other hand, in S5, it is determined that the solenoid of the fuel injection valve 1 is normal.

By the way, when the power transistor 2 is switched from on to off, a large voltage from the battery 4 is applied to the capacitor 8 via the solenoid of the fuel injection valve 1 when the solenoid of the fuel injection valve 1 is normal. This allows the condenser 8
The charging voltage of the power transistor rises instantly, so the power transistor 2
The collector voltage of the signal also rises sharply to H level as shown by the solid line in FIG. 4b. Therefore, the anode terminal voltage of the first diode 21 also rapidly rises to the constant voltage V _CC ,
The cathode terminal voltage of the second diode 22 is also instantly switched to the H level as shown by the solid line in FIG. 4c. Therefore, since the cathode terminal voltage exceeds the reference voltage after the elapse of the predetermined time _Td from the time when the power transistor 2 is switched from ON to OFF, the fuel injection valve 1 can be determined to be normal.

On the other hand, when the solenoid of the fuel injection valve 1 is disconnected, the constant voltage is applied to the capacitor 8 via the first diode 21.
Since only V _CC is applied, the charging voltage of the capacitor 8 rises relatively gently, so that the collector voltage of the power transistor 2 also gently rises as shown by the chain line in FIG. 4b. Accordingly, the anode terminal voltage of the first diode 21 rises gently, because this association with the cathode terminal voltage of the second diode also rises gently as FIG. 4 c in a broken line shows, after the predetermined time T _d elapses Since the cathode terminal voltage is maintained below the reference voltage, it can be determined that the solenoid of the fuel injection valve 1 is broken. Note that it may be determined that the solenoid of the fuel injection valve 1 is short-circuited when the cathode terminal voltage of the second diode 22 rises more rapidly than in the normal state.

In this way, it is possible to determine whether or not there is an abnormality in the solenoid of the fuel injection valve 1, and when the power transistor 2 is off, in other words, when the ignition switch 11 is off, control is performed from the battery 4 via the solenoid of the fuel injection valve 1. Leakage current can be prevented from flowing through the input port of the device 25 and the resistor 24 by the first diode 21, and thus the deterioration or rise of the battery 4 can be prevented.

<Effects of the Invention> As described above, the present invention connects the charging / discharging circuit in parallel to the switching means for operating the electric load, applies the voltage to the charging / discharging circuit through the diode and the current limiting resistor, and switches the switching means. Since the presence or absence of an abnormality in the electrical load is determined based on the voltage at the anode terminal of the diode after a lapse of a certain time from when the It is possible to prevent the deterioration of the battery or the exhaustion of the battery.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to the claims of the present invention, FIG. 2 is a circuit diagram showing an embodiment of the present invention, FIG.
FIG. 4 is a signal waveform diagram of each part of FIG. 2, and FIG. 5 is a circuit diagram showing a conventional example of a self-diagnosis device. 1 ... Fuel injection valve, 2 ... Power transistor, 4 ...
Battery, 7 ... Time constant resistor, 8 ... Capacitor, 9
...... Power supply circuit, 21 ...... First diode, 22 ...... Second diode, 23 ...... Current limiting resistor, 25 ...... Control device

Claims (1)

[Claims] 1. A vehicle-mounted device in which a battery power source, an electric load, and a switching means are connected in series, and the electric load is energized by turning on the switching means, which are connected in parallel to the switching means. A charging / discharging circuit, a diode whose cathode terminal is connected to the charging / discharging circuit, a voltage supply circuit for applying a voltage to the anode terminal of the diode via a current limiting resistor, and from the time when the switching means is turned off. A vehicle comprising: a voltage detection unit that detects an anode terminal voltage of the diode after a predetermined time has elapsed, and a determination unit that determines whether or not there is an abnormality in the electric load based on the detected anode terminal voltage. Self-diagnosis device for onboard equipment.