JP2001206190A - Occupant protective device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an erroneous ignition due to an earthing on the negative potential side of a detonator or a power short circuit on the positive potential side by providing a constant current circuit to both the negative potential and positive potential sides of the detonator. SOLUTION: This occupant protective device comprises a DC power, a detonator connected in series to the DC power, first and second switch circuits connected in series to each other so as to sandwich the detonator, an impact determining circuit operating the first and second switch circuits to turn on when the circuit determines based on an acceleration signal due to a collision transmitted from an acceleration sensor that a serious accident occurs, and a diagnosis circuit for diagnosing the detonator by feeding a diagnosing current to the detonator. First and second constant current circuits allowing to flow a same constant current are connected in series to each of the positive potential and negative potential sides of the detonator.

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.

[0002]

2. Description of the Related Art A conventional occupant protection system will be described with reference to FIG. In FIG. 3, reference numeral 1 denotes a vehicle-mounted battery, 2 denotes an ignition switch, 3 denotes a booster circuit supplied with a voltage from the battery 1 via a first backflow preventing diode 4 and outputs the voltage, and 6 denotes 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.

A constant current circuit 11 is connected in parallel to the mechanical acceleration switch 10. The constant current circuit 11a is activated by a clock pulse from a diagnostic means 15 of a microcomputer 13, which will be described later, and a current from the constant current source 11a. Resistor 11b, operational amplifier 11c, second resistor 11d, control transistor 11e that generates a reference voltage based on
An operational amplifier 11c controls the control transistor 11e so that the current flowing through the third 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 based on the supplied signal, the collision determining means 14 first outputs the first signal from the output terminal.
A trigger pulse is supplied to the switching transistor 7, and the first switching transistor 7 is turned on only for a predetermined time.

Reference numeral 15 denotes a diagnosis means, which is a
One of the functions provided in the microcomputer 13 is that the microcomputer 13 alternately operates with the collision judging means 14 after the ignition switch 2 is turned on, and outputs a clock pulse when the diagnostic means 15 is operating. 11
And a control signal synchronized with the clock pulse is supplied from another output terminal to a second switching transistor 16 for diagnosis described later. The diagnosing means 15 performs a failure diagnosis such as disconnection or short circuit of the primer 8 based on the magnitude of the voltage supplied from an operational amplifier 19 described later and the respective voltages of both terminals of the primer 8.

Reference numeral 16 denotes a second switching transistor for diagnosis, the emitter of which is connected to a constant voltage power supply line (+ V).
The base is the diagnostic means 15 of the microcomputer 13
The collector is connected to the connection point between the collector of the first switching transistor 7 and the squib 8 via a third backflow preventing diode 17 and a third resistor 18 in series. Reference numeral 19 denotes an operational amplifier to which a voltage generated at both ends of the primer 8 is input and a potential difference generated between both terminals of the primer 8 is supplied 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 (when the collision judging means 14 is operating), the microcomputer 13 sends the diagnostic means 15 and the collision judging means 14
Are alternately repeated, and when the collision judging means 14 is operating, the diagnosing means 15 is not operating, and the second switching transistor 16 for diagnosis and the constant current circuit 11 are off. As a result, the microcomputer 13
When the collision judging means 14 judges that a serious collision has occurred based on the acceleration signal from the acceleration sensor 12 supplied to the collision judging means 14, a low-level trigger pulse is output from the output terminal to the first switching transistor 7. Is supplied, so that the power charged in the backup capacitor 6 is reduced by the primer 8 and the second backflow prevention diode 9.
Flows to the mechanical acceleration switch 10 to deploy and drive an airbag (not shown).

(When the diagnostic means 15 is operating) As described above, the diagnostic means 15 and the collision judging means 14 alternately repeat the operation at intervals of a fixed time after the ignition switch 2 is turned on. When the diagnostic means 15 is operating, the collision determining means 14 does not operate, and the first switching transistor 7 is turned off. As a result, a clock pulse is supplied from the output control terminal of the diagnosis means 15 of the microcomputer 13 to the constant current circuit 11 and, simultaneously with that, a pulse control signal is simultaneously transmitted from the other output control terminal to the diagnostic output terminal. Output to the second switching transistor 16 and the second switching transistor 1
6. The control transistor 11e is turned on at the same time synchronously,
Repeat off.

As a result, the current detecting resistor 11f and the second
A small constant current for diagnosis (set to such a power as not to ignite the explosive by the primer) flows in a pulse shape into the primer 8 via the backflow preventing diode 9, and both ends of the primer 8 generated by the constant current are generated. Is detected by the operational amplifier 19 and supplied to the diagnosis 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, if the negative potential terminal A of the primer 8 is grounded at the time of diagnosis, for example, the second switching transistor 16 and the third backflow prevention diode are provided. There is a possibility that a large current exceeding the permissible current for diagnosing the primer may flow in series with the third resistor 17, the third resistor 18, and the primer 8, and the primer may be ignited.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems. A constant current circuit is connected to both the negative potential side and the positive potential side of a squib, and a ground fault or a positive potential on the negative potential side of the squib. To prevent erroneous ignition due to power short-circuit on the side.

[0012]

According to a first aspect of the present invention, there is provided a priming device connected in series to a power supply, first and second switch circuits connected in series across the priming device, and an acceleration associated with a collision from an acceleration sensor. A collision determination circuit that turns on the first and second switch circuits when it is determined that a serious accident has occurred based on the signal; and a diagnostic circuit that supplies a diagnostic current to the primer to diagnose the primer. In the occupant protection device provided, a first constant current circuit for supplying a constant current to the primer is connected to a positive potential side of the primer, and a constant current having the same magnitude as the constant current is supplied to a negative potential side of the primer. Second to inhale
A constant current circuit is connected in series, and the first and second constant current circuits are activated when the diagnostic circuit is activated.

According to a second aspect of the present invention, the first and second constant current circuits of the first aspect are connected to a common emitter follower circuit, and the emitter follower circuit is connected to the first and second constant current circuits. It is characterized in that the magnitude of the constant current is controlled.

According to a third aspect, in the second aspect, the magnitude of the constant current of the first constant current circuit is controlled by the collector current of the emitter follower circuit, and the magnitude of the constant current of the second constant current circuit is , Controlled by an emitter voltage of an emitter follower circuit.

[0015]

Next, an embodiment of the present invention will be described below. Embodiment 1 FIG. This embodiment will be described with reference to FIG. In FIG. 1, the same or equivalent components as those shown in FIG. 3 are denoted by the same reference numerals, detailed description thereof will be omitted, and only different components will be described. That is, a second constant current circuit (having a circuit configuration different from the constant current circuit 11 in FIG. 3, instead of the second switching transistor 16, the third backflow prevention diode 17 and the third resistor 18, and In the following description, only the point that the constant current circuit 11 is provided as a first constant current circuit and the constant current circuit 20 is referred to as a second constant current circuit) will be described below.

That is, the second constant current circuit 20 has substantially the same configuration as the first constant current circuit 11 in FIG.
In addition, the magnitude of the constant current flowing out and the magnitude of the constant current flowing in are set to be 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 second constant current circuit 20 is limited, that is, the magnitude of the small diagnostic current is limited. Therefore, the allowable current for the diagnosis of the primer 8 does not exceed the allowable current, so that if a collision accident occurs and the first switching transistor 7 is turned on and the mechanical acceleration switch 10 is turned on, the backup capacitor The electric power charged to 6 flows into the primer 8 to deploy the airbag.

Embodiment 2 FIG. This embodiment will be described with reference to FIG. In FIG. 2, the same or equivalent components as those shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted. Only different configurations will be described below.

That is, the microcomputer 13 comprises:
Diagnostic means 15 and collision determination means (same as that of FIG. 1) 14
The collision determining means 14 supplies a trigger pulse from the output terminal to the base of the first switching transistor 7 when it determines that a serious collision has occurred based on the supplied signal, and keeps the first switching transistor 7 constant. Turn on for hours.

The diagnostic means 15 supplies a low-level signal to the first and second regulating transistors 31g and 31h via a signal line L2 at the time of diagnosis, and also supplies a high-level signal (reference voltage) via a signal line L1. ) To the second
It is supplied to the control transistor 31b of the constant current circuit 31. The diagnostic means 15 inputs respective voltages of both terminals A and B of the primer 8 in the same manner as in the prior art,
The potential difference between the two terminals A and B is input via an operational amplifier (not shown in FIG. 2, but the same as that shown in FIG. 1) to diagnose a fault such as disconnection or short circuit of the primer 8. .

Reference numeral 30 denotes a first constant current circuit, which increases the current flowing through the emitter-follower-connected transistor 31b and the reference current setting resistor 31c constituting a part of a second constant current circuit 31, which will be described later, by, for example, 100 times. A current mirror circuit, which is used to convert the current into a constant current, and a backflow prevention diode 30b. When the diagnostic means 15 is in operation, the positive terminal A of the primer 6 is Current to the primer 6 via a constant current (constant current of the same size as a second constant current circuit 31 described later)
Pour in.

Reference numeral 31 denotes a second constant current circuit connected in parallel to the mechanical acceleration switch 10. The transistor 31b is connected to an emitter follower for generating a constant current reference voltage, a reference voltage resistor 31c, an operational amplifier 31d, a driving transistor 13e, It comprises a current detection resistor 31f, a first regulating transistor 31g, and a second regulating transistor 31h.

The emitter-follower-connected transistor 31b is obtained by impedance-converting a reference voltage in the signal line L1 and dividing a voltage lowered by the base-emitter voltage (VBE) of the transistor 31b by a reference resistor 31c. The current is used as a reference current for the first constant current circuit 30, and the voltage obtained thereby is used as a reference voltage for the second constant current circuit 31.

When the first regulating transistor 31g receives a high-level signal indicating that the diagnosis is not being performed from the diagnostic means 15, the first regulating transistor 31g is turned on, and the base of the transistor 31b constituting the emitter follower circuit is low. Similarly, when the second regulating transistor 31h receives a high-level signal indicating that diagnosis is not being performed from the diagnostic unit 15, the second regulating transistor 31h is turned on, and the base of the transistor 31b constituting the emitter follower circuit is turned on. At a low level to regulate the operation of the first and second constant current circuits 30, 31.

Next, the operation of the above configuration will be described. After the ignition switch 2 is turned on as described above (when the collision judging means 14 is operating), the microcomputer 13 sends the diagnostic means 15 and the collision judging means 14
Are alternately repeated, and when the collision judging means 14 is operating, the diagnosing means 15 is not operating, and a low level signal is supplied from the diagnosing means 15 to the emitter follower-connected transistor 31b via the signal line L1. And the first and second regulating transistors 31g, 31g of the second constant voltage circuit 30 through the signal line L2.
Since 31h is in the ON state, the first and second constant current circuits 30, 31 are inactive.

At this time, when the collision judging means 14 of the microcomputer 13 judges that a serious collision has occurred, a low-level trigger pulse is supplied to the switching transistor 7 from the output terminal.
The electric power charged in the backup capacitor 6 flows to the mechanical acceleration switch 10 through the squib 8, and an airbag (not shown) is deployed and driven.

(When the diagnostic means 14 is operating) As described above, after the ignition switch 2 is turned on, the diagnostic means 15 and the collision determining means 14 alternately repeat the operation at regular intervals. When the diagnostic means 15 is operating, the switching transistor 7 is turned off. Further, both the first and second regulating transistors 31g and 31h are turned off by the diagnostic means 15, and a high-level signal (reference voltage) is sent from the diagnostic means 15 to the emitter follower-connected transistor 31b via the signal line L1. Supplied to generate a reference voltage.

As a result, the voltage appearing on the emitter side of the emitter follower circuit 31b becomes a constant value obtained by subtracting the base-emitter voltage (VBE) from the signal line L1, and is obtained by dividing this voltage by the reference current setting resistor 31c. The obtained current flows as a collector current of the transistor 31b. Since the current also flows through the transistors 30a of the current mirror circuits 30a and 30c, the transistors 30a
, A constant current that is a mirror multiple of the constant current flowing through the transistor 30c flows. As a result, the first constant current circuit 30 performs a constant current operation. The voltage on the emitter side of the emitter-follower-connected transistor 31b is
The current detecting resistor 31 is applied as a reference voltage of d.
transistor 31 so as to be equal to the voltage generated at
control e. As a result, a constant current obtained by dividing the emitter voltage of the transistor 31b by the resistor 31f flows through the second constant current circuit 31. The voltage at both terminals A and B of the primer 8 generated by the constant current is supplied to the diagnostic means 15, and the potential difference between the terminals is detected by the operational amplifier from the diagnostic means 15.
Is diagnosed by being supplied to

[0028]

According to the first aspect of the present invention, even if any terminal of the squib is grounded or the power supply is short-circuited, the allowable current of the squib is not exceeded.

According to the second and third aspects of the present invention, the constant current value can be changed only by changing the output voltage of the microcomputer 13, so that it is possible to easily cope with primers having different specifications.

[0030]

[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 for describing Embodiment 2 of the present invention.

FIG. 3 is a circuit block diagram of a conventional occupant protection device.

[Description of Signs] 1 In-vehicle battery 2 Ignition switch 3 Boost circuit 4, 9 Backflow prevention diode 6 Backup capacitor 7 Switching transistor 8 Detonator 10 Mechanical acceleration switch 11, 20, 30, 31 Constant current circuit 12 Acceleration sensor 13 Microcomputer 14 Collision judgment means 15 Diagnosis means 19 Operational amplifier

Claims (3)

[Claims] 1. A judgment is made that a serious accident has occurred based on a primer connected to a DC power supply, first and second switch circuits connected to sandwich the primer, and an acceleration signal accompanying a collision from an acceleration sensor. An occupant protection device comprising: a collision judging circuit for turning on the first and second switch circuits when turning on; and a diagnostic circuit for supplying a diagnostic current to the primer to diagnose the primer. A first constant current circuit for flowing a constant current into the primer is connected to a potential side, and a second constant current circuit for drawing a constant current having the same magnitude as the constant current is connected in series to a negative potential side of the primer. When the diagnostic circuit is activated, the first and second
An occupant protection device characterized by operating a constant current circuit. 2. The first and second constant current circuits are connected to a common emitter follower circuit, and the emitter follower circuit controls the magnitude of the constant current of the first and second constant current circuits. The occupant protection device according to claim 1, wherein 3. The magnitude of the constant current of the first constant current circuit is controlled by the collector current of the emitter follower circuit, and the magnitude of the constant current of the second constant current circuit is controlled by the magnitude of the emitter follower circuit. 3. The occupant protection device according to claim 2, wherein the occupant protection device is controlled by an emitter voltage.