JPH07257314A - Diagnosing circuit for ignition device driving circuit - Google Patents

Abstract

PURPOSE:To distinguish and diagnose disconnection fault of a squib and short circuit fault of a mechanical acceleration switch by supplying the fine current to a resistance connected in parallel with a squib and a mechanical acceleration sensor, and diagnosing a fault on the basis of largeness of a voltage value generated in the terminal. CONSTITUTION:When a microcomputer 15 does not receive the acceleration signal with a collision from an acceleration sensor 14, the fine diagnosing current is always flowed from a booster circuit 4 to a resistor 10, a squib 11 and a resistor 17 in series, and the voltage generated at both ends of the squib 11 is supplied to a first and a second diagnosing circuits 18, 19, and the microcomputer 15 diagnoses the fault. For example, when a short circuit is generated between terminals of the squib 11, electric potential difference between the terminals becomes zero, and the first diagnosing circuit 18 detects it to supply the fault signal to the microcomputer 15. When the squib 11 is disconnected or a short circuit is generated between the terminals of a mechanical acceleration switch 12, electric potential in the grounding side of the squib 11 becomes zero, and the second diagnosing circuit 19 judges a fault to supply the fault signal to the microcomputer 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diagnostic circuit for an ignition device drive circuit such as an air bag system provided in an automobile.

[0002]

2. Description of the Related Art Conventionally, as an ignition device drive circuit having a diagnostic circuit of this type, for example, there is the one shown in FIG. 2, which will be described below. That is, in FIG. 2, 1 is a battery, 2 is an ignition switch, 3 is a backflow prevention diode, 4 is a step-up circuit (DC power supply) composed of a DC / DC converter, and its input terminal is a backflow prevention diode for the battery 1. 3 are connected. The output terminal of the booster circuit 4 is grounded via a resistor 6 and a backup capacitor 7 in series.
Reference numeral 5 is a backflow prevention diode, which is connected between the ignition switch 2 and the output terminal of the booster circuit 4,
Power is supplied to the backup capacitor 7 in parallel with the booster circuit 4.

A discharge diode 8 forms a rapid discharge path for the backup capacitor 7. Reference numeral 9 is a switching transistor (switch means), the emitter terminal of which is connected to the output terminal of the booster circuit 4, and the collector terminal of which is grounded through a squeeze (ignition device) 11 and a mechanical acceleration switch 12 in series. . The base terminal of the switching transistor 9 is
It is connected to a microcomputer 15, which will be described later, via the drive transistor 13.

Reference numeral 10 denotes a resistor connected between the emitter terminal and the collector terminal of the switching transistor 9 for supplying a minute diagnostic current to the squeeze 11. The diagnostic current at that time flows in series from the output terminal of the booster circuit 4 to the resistor 10, the squeeze 11, and the resistor 17 (which are connected in parallel to the mechanical acceleration switch 12).

Reference numeral 14 is an acceleration sensor for detecting the acceleration generated at the time of collision of the vehicle, and 15 is a microcomputer (judgment circuit), which calculates the scale of the collision based on the acceleration signal output from the acceleration sensor 14. When it is determined that a serious collision has occurred, the drive transistor 13
To a low level on the base terminal of the switching transistor 9. Further, when the microcomputer 15 receives a diagnostic signal indicating a failure from first and second diagnostic circuits 18 and 19 which will be described later, the microcomputer 15 turns on the alarm lamp 20 through a drive circuit (not shown).

Reference numeral 18 denotes a first diagnostic circuit, which is the squeeze 1
The voltage signal at both ends of 1 is input and the voltage difference between them is taken to diagnose the presence or absence of a short circuit in the squeeze 11, and the diagnosis result is supplied to the microcomputer 15.

A second diagnostic circuit 19 receives a voltage signal on the non-grounded side of the mechanical acceleration switch 12 and short-circuits the mechanical acceleration switch 12 based on the voltage signal, disconnects the squeeze 11, etc. Is diagnosed and the diagnostic result is supplied to the microcomputer 15.

Next, the operation of the above structure will be described.
Normally, the microcomputer 15 determines that the mechanical acceleration switch 12 is turned on when the vehicle has a collision accident, while the microcomputer 15 that receives the acceleration signal from the acceleration sensor 14 determines that the vehicle has caused a serious collision. Then, the microcomputer 15 creates a trigger signal having a predetermined time width, switches the output terminal from the low level state to the high level state, and turns on the switching transistor 9 only for the predetermined time.

As a result, a current is supplied in series from the booster circuit 4 and the backup capacitor 7 to the squeeze 11 and the acceleration switch 12, and the squib 11 ignites the explosive powder to inflate the airbag and protect the occupant.

Further, when the microcomputer 15 does not receive the acceleration signal from the acceleration sensor 14 due to the collision, a minute diagnostic current is constantly supplied from the booster circuit 4 to the resistor 1.
0, squib 11 and resistor 17 flow in series, and the diagnostic current generates predetermined voltages at both ends of the squeeze 11, that is, the non-ground side and the ground side, and the voltages are the first and second voltages. It is supplied to the diagnostic circuits 18 and 19 and the microcomputer 15 performs a failure diagnosis.

Therefore, for example, when the terminals of the squib 11 are short-circuited, the potential difference between the terminals of the squeeze 11 becomes zero, and the first diagnostic circuit 18 detects this and supplies a failure signal to the microcomputer 15.

When the squeeze 11 is disconnected or the terminals of the mechanical acceleration switch 12 are short-circuited, the ground side potential of the squeeze 11 becomes zero, that is, the ground potential, and the voltage is the second diagnosis. Since the voltage is supplied to the circuit 19, the second diagnostic circuit 19 (in a normal condition, the voltage corresponding to the resistance value of the resistor 12 is supplied) judges that it is a failure and supplies a signal indicating the failure to the microcomputer 15. To do.

The microcomputer 15 supplied with the signal indicating the failure turns on the alarm lamp 20 in a mode corresponding to the details of the failure.

[0014]

However, in the above-mentioned conventional ignition device drive circuit, the second diagnostic circuit 1 is used.
At 9, the voltage on the ground side of the squeeze 11 in the disconnection state of the squib 11 and the short-circuit state of the mechanical acceleration switch 12 is equal and has a zero potential, so that there is a problem that it is not possible to distinguish between them and perform failure diagnosis. there were.

Therefore, the present invention has been made in view of the above-mentioned problems, and provides a circuit capable of making a distinction between a disconnection failure of the squeeze 11 and a short-circuit failure of the mechanical acceleration switch. The purpose is to

[0016]

SUMMARY OF THE INVENTION An invention relating to a diagnostic circuit for an ignition device drive circuit is directed to a direct current power source for boosting and outputting an output voltage from a battery, and an explosive charge connected to an output side of the direct current power source. A squib that ignites, a mechanical acceleration switch connected in series to the squib, a switch means inserted between the DC power supply and the squeeze, and an acceleration signal is input, and a collision occurs based on the acceleration signal. Of the squeeze and the mechanical acceleration sensor, at least in each of the squeeze and the mechanical acceleration sensor. Resistors are connected in parallel, a minute current is supplied to each resistor, and based on the magnitude of the voltage value generated at each resistor terminal, the squeeze and mechanical Consisting includes a diagnostic circuit for performing failure diagnosis of the degree sensor.

[0017]

According to the present invention, the voltage value obtained by dividing the output voltage of the booster circuit into a predetermined value by the three resistors and the squeeze resistor in the normal state is supplied to the second diagnostic circuit.
Further, when the squeeze is broken, a predetermined voltage value divided by three resistors is supplied to the second diagnostic circuit, and when the mechanical acceleration switch is short-circuited, the voltage value of zero voltage becomes the second value.
It is supplied to the diagnostic circuit and outputs signals of those failure modes.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the structure will be described in detail with reference to FIG. In FIG. 1, the same or equivalent components as those of the conventional example shown in FIG. 2 are designated by the same reference numerals, detailed description thereof will be omitted, and only different portions will be described.

That is, the only difference is that the resistor 16 is connected in parallel to the squeeze 11 in FIG. In addition,
This resistance 16 is approximately 1 of the resistance value of the squeeze 11.
It is set to 500 times.

As a result, when the squeeze 11 is disconnected, the voltage value resistance-divided by the three resistors 10, 16 and 17 is supplied to the second diagnostic circuit 19 for failure diagnosis. Further, when the squeeze 11 is short-circuited, the same voltage is supplied to the first diagnosis circuit 18 to make a failure diagnosis. further,
When the mechanical acceleration switch 12 is short-circuited, the second diagnostic circuit 1
A ground voltage having a voltage value of zero is supplied to 9 for failure diagnosis.

Accordingly, the microcomputer 15
Is the alarm lamp 2 in the mode corresponding to the failure content based on the signal from each of the first and second diagnostic circuits 18 and 19.
Drive 0. The first and second diagnostic circuits 18,
It goes without saying that the function of 19 can be performed by the program of the microcomputer 15.

[0022]

As described above, according to the present invention,
Since the type of failure can be reliably diagnosed, the effect of improving the product quality is exhibited.

[Brief description of drawings]

FIG. 1 is a circuit explanatory view for explaining an embodiment of an ignition device drive circuit according to the present invention.

FIG. 2 is a circuit explanatory diagram for explaining a conventional example of the present invention.

[Explanation of symbols]

 1 Battery 4 Booster Circuit 7 Backup Capacitor 9 Switching Transistor 10, 16, 17 Resistor 11 Squeeze 12 Acceleration Switch 14 Accelerometer 15 Microcomputer 18, 19 Diagnostic Circuit

Claims (1)

[Claims] 1. A DC power supply for boosting and outputting an output voltage from a battery, a squeeze connected to the output side of the DC power supply for igniting explosives, and a mechanical acceleration switch connected in series with the squib. , A switch means inserted between the DC power supply and the squeeze, and an acceleration signal are input, the magnitude of the collision is judged based on the acceleration signal, and the switch means is turned on as necessary. In the ignition device drive circuit including a determination circuit that outputs a trigger signal for, at least the resistors are connected in parallel to each of the squeeze and the mechanical acceleration sensor, and a minute current is supplied to each resistor. A diagnostic circuit for diagnosing the failure of the squeeze and the mechanical acceleration sensor based on the magnitude of the voltage value generated at the terminal of each resistance. Ignition device drive circuit diagnostic circuit.