JP2001080453A - Occupant crash protection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the electric discharge by the grounding of the negative electrical potential side of a detonator by connecting first/second constant current circuits for streaming the same constant current in series to the positive electrical potential side and negative electrical potential side of the detonator respectively. SOLUTION: In a first switching transister 7, one end of a detonator 8 is connected to the collector and a diode for preventing a second reverse flow 9 and mechanical acceleration switch 10 are connected to the other end of the detonator 8 in series and earthed. When A point of the negative electrical potential side of the detonator 8 is grounded as shown by a broken line, as the bigness of the current streamed out from the constant current circuit 20 is kept to a constant, namely the bigness of a minute diagnosis current, the electric power held by a battery is not discharged in a moment. Therefore, even if any terminal of the detonator is grounded, as the electric power charged to the battery is not eliminated in a moment, the detonator can be operated surely.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an occupant protection device such as an airbag for protecting an occupant of a vehicle from a collision accident.

[0002]

2. Description of the Related Art A conventional occupant protection system will be described with reference to FIG. In FIG. 2, 1 is a vehicle battery, 2 is an ignition switch, 3 is a booster circuit supplied with a voltage from the battery 1 via a first backflow preventing diode 4 and outputs the voltage, and 6 is a backup capacitor. . Reference numeral 7 denotes a first switching transistor. One end of a primer 8 is connected to its collector. The other end of the primer 8 is connected in series with a second backflow prevention diode 9 and a mechanical acceleration switch 10 and is grounded. ing.

Reference numeral 11 denotes a constant current circuit connected in parallel to the mechanical acceleration switch 13. The constant current circuit 11a is activated by a clock pulse from a diagnosis means 15 of the microcomputer 13, which will be described later, and a current from the constant current source 11a. Resistor 11b, differential amplifier 11c, second resistor 11d, and control transistor 11e that generate a reference voltage based on
And a current detection resistor 11f, and the control transistor 11e is controlled so that a current value flowing through the current detection resistor 11f during diagnosis is constant.

An acceleration sensor 12 detects an acceleration generated in the front-rear direction of the vehicle at the time of a collision of the vehicle, and supplies a detection signal to a collision judging means 14 of the microcomputer 13. When the collision determining means 14 determines that a serious collision has occurred, the collision determining means 14 first outputs the first switching transistor 7 from the output terminal.
And turns on only for a certain period of time.

Numeral 15 is a diagnostic means which is one of the functions of the microcomputer 13 like the collision determining means 14. The diagnostic means 15 operates alternately with the collision determining means 14 after the ignition switch 2 is turned on to perform the diagnosis. When the means is operating, a clock pulse is supplied to the constant current circuit 11, and a control signal synchronized with the clock pulse is supplied to the diagnostic switching transistor 16 from another output terminal. The diagnosing means 15 performs a failure diagnosis such as disconnection or short circuit of the primer 11 based on the magnitude of the voltage supplied from the differential amplifier 41 described later.

Reference numeral 16 denotes a diagnostic switching transistor, the emitter of which is connected to the constant voltage power supply line (+ V), the base of which is connected to the output terminal of the diagnostic means 15 of the microcomputer 13, and the collector of which is a diode 17 for preventing backflow.
The third resistor 18 is connected in series to a connection point between the collector of the first switching transistor 9 and the primer 11. Reference numeral 19 denotes a differential amplifier which inputs a voltage generated between both ends of the primer 11 and supplies a potential difference generated between both terminals of the primer 11 to the diagnostic means 15.

Next, the operation of the above configuration will be described. After the ignition switch 2 is turned on as described above, the microcomputer 13 sets the diagnosis unit 15 and the collision judgment unit 1 (when the collision judgment unit 14 is operating).
4 is alternately repeated, and when the collision judging means 14 is operating, the diagnostic means 15 is not operating, and the diagnostic switching transistor 16 and the constant current circuit 11 are off. As a result, when an acceleration signal is supplied from the acceleration sensor 12 to the collision determination means 14 of the microcomputer 13, when the collision determination means 14 determines that a serious collision has occurred, the collision detection means 14 outputs a signal from the output terminal to the first switching transistor 7. A low-level trigger pulse is supplied, whereby the electric power charged in the backup capacitor 6 flows to the mechanical acceleration switch 10 via the primer 8 and the second backflow prevention diode 9, and an airbag (not shown) is deployed. .

When the ignition switch 2 is turned on (when the diagnostic means 15 is operating), the diagnostic means 15 and the collision determining means 14 of the microcomputer 13 alternately repeat the operation at a certain time interval thereafter. When the diagnostic means 15 is operating, the collision determining means 14 is not operating, and the first switching transistor 9 is turned off by the collision determining means 14. As a result, a clock pulse is supplied from the output terminal of the diagnosis means 15 of the microcomputer 13 to the constant current circuit 11, and a pulse control signal is output from another output terminal to the diagnosis switching transistor 16 in synchronization with the clock pulse. Then, the diagnostic switching transistor 16 and the control transistor 11e repeatedly turn on and off in synchronization.

As a result, a small constant current for diagnosis (set to such a power that the explosive is not ignited by the primer) is supplied to the primer 11 via the current detecting resistor 11f and the third backflow preventing diode 12. The potential difference between both ends of the primer 8 which flows in a pulsed form and is generated by the constant current is detected by the differential amplifier 19 and is supplied to the diagnostic means 15 of the microcomputer 13 for diagnosis. As a result, when it is determined that there is an abnormality, a lamp (not shown) is driven to light up.

[0010]

However, in the above occupant protection device, when the negative potential side terminal A of the primer 8 is grounded to the ground, for example, the first switching transistor 16, the backflow preventing diode 17, Third resistor 1
8, a large current may flow in series through the primer 8, and the electric power stored in the battery 1 may be discharged instantaneously.

The present invention has been made in view of the above problems, and has a constant current circuit on both the negative potential side and the positive potential side of a primer so as to prevent discharge due to ground fault on the negative potential side of the primer. The purpose is to do.

[0012]

The occupant protection apparatus according to the present invention comprises a DC power supply, a primer connected in series to the DC power supply, and first and second switch circuits connected in series across the primer. A collision judging circuit for turning on the first and second switch circuits when it is judged that a serious accident has occurred based on an acceleration signal accompanying a collision from an acceleration sensor; An occupant protection device having a diagnostic circuit for diagnosing a primer, wherein a first and a second constant current circuit for supplying the same constant current to each of a positive potential side and a negative potential side of the primer are connected in series. is there.

[0013]

Next, an embodiment of the present invention will be described below. Embodiment 1 FIG. A description will be given based on FIG. In FIG. 1, the same or equivalent components as those shown in FIG. 2 are denoted by the same reference numerals, and detailed description thereof will be omitted. Different configurations, that is, the first switching transistor 16 and the backflow prevention diode 17 Only the point that a constant current circuit 20 is provided instead of the third resistor 18 will be described below.

That is, a constant current circuit (first constant current circuit)
Reference numeral 20 is configured to be substantially the same as the constant current circuit 11 in FIG. 2, and is set so that the magnitude of the flowing constant current is also the same.

As a result, when the point A on the negative potential side of the primer 8 is grounded as shown by the broken line, the magnitude of the current flowing out of the constant current circuit 20 is constant, that is, the magnitude of the minute diagnostic current is reduced. Since the power is held, the power held by the battery 1 is not instantaneously discharged.

[0016]

As described above, according to the present invention, the power charged in the battery is not instantaneously lost even if any terminal of the primer is grounded, so that the primer is reliably operated. The effect of being able to do is exhibited.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram for describing Embodiment 1 of the present invention.

FIG. 2 is a circuit block diagram of a conventional occupant protection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 On-board battery 2 Ignition switch 3 Boost circuit 4, 9 Backflow prevention diode 6 Backup capacitor 7, 16 Switching transistor 8 Detonator 10 Mechanical acceleration switch 11, 20 Constant current circuit 12 Acceleration sensor 13 Microcomputer 15 Diagnosis means 14 Collision judgment means 19 Differential amplifier

Claims (1)

[Claims] 1. A DC power supply, a primer connected in series to the DC power supply, first and second switch circuits connected in series across the primer, and an acceleration signal accompanying a collision from an acceleration sensor. An occupant protection system comprising: a collision determination circuit that turns on the first and second switch circuits when it is determined that a serious accident has occurred; and a diagnostic circuit that supplies a diagnostic current to the primer to diagnose the primer. An occupant protection device, wherein a first and a second constant current circuit for supplying the same constant current are connected in series to each of a positive potential side and a negative potential side of the primer.