JPH11310102A - Vehicular occupant protective device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the degradation of a detonator by storing an electric current value as a reference value of a judgement of whether or not to continue the inflow of an electric current flowing in a detonator according to a diagnosis of a switch circuit, and a stopping supply of a diagnostic current when the magnitude of the diagnostic current flowing in the switch circuit exceeds the reference value. SOLUTION: A low level signal is supplied to a switching transistor 18 from the output terminal P2 of a control circuit 14' by an electric potential difference generated between terminals B, C of a detonator 7 corresponding to a resistance value of the detonator 7, and is supplied to a first storage capacitor 19 by turning on it, and then, the switching transistor 18 is turned off, and an electric current value by the voltage is stored as a reference value. When discharge voltage of a second storage capacitor 22 is larger than the reference value, a judgment is made that the magnitude of a diagnostic current flowing in a switching circuit 6 exceeds the reference value, and output is put on a low level, and a driving transistor 15 is turned off, and a switching circuit 6 is turned off.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle occupant protection device for protecting an occupant from an accident by inflating an airbag in the event of a collision of a vehicle or the like.

[0002]

2. Description of the Related Art The structure of a conventional vehicle occupant protection system of this type will be described with reference to FIG. 1 is a vehicle-mounted battery, 2 is the vehicle-mounted battery 1 via an ignition switch 3.
, The backup capacitor 4 is charged with the boosted output. Reference numeral 6 denotes a switch circuit, the input side of which is connected to the booster circuit 2 through a backflow preventing diode 5.
The output side is connected to a primer 7 and a mechanical acceleration switch 8.

The switch circuit 6 is turned on by receiving an ignition pulse from a control circuit 14 to be described later via a drive transistor 15. At the time of diagnosis of the switch circuit 6,
The control circuit 14 supplies a diagnostic pulse having a pulse width smaller than the ignition pulse.

Reference numeral 11 denotes a diagnostic current supply circuit, which includes a switching transistor 11a, a diode 11b, and a resistor 11c.
Are connected in series, and the switching transistor 1
When a low level signal is supplied to 1a from the output terminal P2 of the control circuit 14, a constant voltage for supplying a diagnostic current to the primer 7 is supplied. Reference numeral 12 denotes a constant current circuit, and the control circuit 14
During the supply of a low-level signal from the output terminal P2 to the switching transistor 11a of the diagnostic current supply circuit 11, the current supplied to the primer 7 is reduced to, for example, 50 mA.
It has the function of keeping the temperature constant. Reference numeral 13 denotes a potential difference detection circuit which detects a potential difference between both terminals of the primer 7.

A control circuit 14 is constituted by a microcomputer or the like, has a collision judging function and a failure diagnosing function, executes these programs alternately, and executes a program for the collision judging function. An acceleration signal from an acceleration sensor (not shown) is input from a terminal A to determine the magnitude of the collision accident. When it is determined that the airbag needs to be deployed, a deployment pulse is output from the output terminal P3 to the drive transistor 15. Supply. When executing the failure diagnosis program, the control circuit 14 supplies a low level signal to the diagnosis current supply circuit 11 and
The voltage is supplied to the constant current circuit 12 via the inverting transistor 30 to activate the constant current circuit 12, to receive the supply of the voltage of both terminals B and C of the primer 7, and further to generate the potential difference signal from the potential difference detection circuit 13. In response to this, a failure diagnosis of the primer 7 is performed, and when a failure is detected, a lamp or the like (not shown) is turned on to notify the user. The control circuit 14 includes a 5 V power supply (constant voltage power supply circuit) 16 supplied from the vehicle-mounted battery 1.
When the supply voltage from the power supply drops below a predetermined value, it detects this and supplies a low level signal to the switching transistor 17 to turn it on, and the power supply from the vehicle-mounted battery 1 to the 5V power supply 16 is switched to the backup capacitor 4.

Next, the operation of the above configuration will be described below separately for the time of failure diagnosis, the time of collision determination, and the time of turning off the ignition switch 3. (During fault diagnosis) When a low-level signal is supplied from the output terminal P2 of the control circuit 14 to the switching transistor 11a and the inverting transistor 30 of the diagnostic current supply circuit 11, a small constant current flows through the primer 7.
The potential difference generated at both ends B and C of the primer 7 is detected by the potential difference detection circuit 13 and supplied to the terminal P1 of the control circuit 14. Further, the control circuit 14 inputs the voltage generated at both terminals B and C. If the magnitudes of the potential difference and the voltage are smaller than the reference values, it is determined that the primer 7 is short-circuited, and a lamp or the like (not shown) is driven to give an alarm.

At the time of collision determination, an acceleration signal is supplied from a terminal A to the control circuit 14. When it is determined that a serious accident has occurred based on the acceleration, the switch circuit 6 is turned on via the drive transistor 15 to turn on the primer 7, The supply of the electric power charged in the backup capacitor 4 to the series circuit including the mechanical acceleration switch 8 is started.

[0008] (When the ignition switch 3 is turned off) It is controlled that the supply voltage from the vehicle-mounted battery 1 generated when the ignition switch 3 is turned off (or when a power supply line equivalent thereto is disconnected) falls below a predetermined value. When the circuit 14 detects, the control circuit 14 supplies a low level signal from the output P4 to the switching transistor 17 to turn on the switching transistor 17, and until the charging voltage of the backup capacitor 4 falls below a predetermined value, the backup capacitor 4
Supplies power to the 5V power supply 16 in place of the vehicle-mounted battery 1.

[0009]

However, in the above-described vehicle occupant protection device, if the switch circuit is to be diagnosed, the connection between the primer 7 and the mechanical acceleration switch 8 is indicated by a dotted line in FIG. Generally, a bypass capacitor is provided between the point and the ground. In this case, the boosted voltage from the booster circuit 2 is applied to the primer 7 each time a diagnosis is made, and the bypass capacitor 31 is fully charged. Continue to run until Therefore, in the initial stage of charging, the current value is large, which is not preferable for the primer 7 whose operation is regulated by the amount of current, and may lead to deterioration of the primer 7.

Accordingly, the present invention has been made in view of the above-mentioned problems, and it is intended to prevent a large current from flowing through a primer in a short time so as to prevent deterioration of the primer. Aim.

[0011]

An occupant protection device according to the present invention determines a collision based on an acceleration signal from an acceleration sensor, and when determined to be a collision, is inserted between a DC power supply and a primer. The switch circuit is turned on to supply an ignition current from the DC power supply to the primer, and when the ignition current is not supplied, a diagnostic current is supplied to the primer and the switch circuit to diagnose the failure of the primer and the switch circuit. The vehicle occupant protection device further comprises a control unit for performing the diagnosis, and a bypass capacitor is inserted between the low potential side terminal of the primer and the ground. The voltage generated between the terminals of the primer and the reference value for determining whether to continue the flow of the current flowing into the primer with the diagnosis of the switch circuit are stored and stored in the switch circuit. When the magnitude of the cross current exceeds the reference value, characterized by stopping the supply of the diagnosis current flowing through the switch circuit.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 shows an embodiment according to the present invention. The same or equivalent components as those described in the conventional example shown in FIG. 2 are denoted by the same reference numerals, and detailed description thereof will be omitted. Circuit 23, bypass capacitor 31, reset transistor 21,
The point where the number 24 is added will be described below. The control circuit (control means) 14 'also has a current limiting function in addition to the various functions shown in FIG. 2, so that the added function and the peripheral circuits associated therewith will be described below.

The current control circuit 23 includes a switching transistor 18, a first storage capacitor 19, and an operational amplifier 20.
An output terminal P5 of the control circuit 14 'for flowing a diagnostic current to the primer 7.
Supplies a low-level signal to the diagnostic current supply circuit 11 from the
To supply. Accordingly, the potential difference generated between the terminals B and C of the primer 7 corresponding to the resistance value of the primer 7 becomes the control circuit 14 '.
A low-level signal is supplied to the switching transistor 18 from the output terminal P2 of
When supplied to the storage capacitor 19 and then the switching transistor 18 is turned off, a current value based on the voltage is held (stored) as a reference value. As a result, the switching transistor 18 is not turned on in the subsequent diagnosis of the switch circuit 6, and the output of the potential difference detection circuit 13 thereafter is temporarily stored in the second storage capacitor 22. The operational amplifier 20 compares the voltage supplied from the potential difference detection circuit 13 and stored in the second storage capacitor 22 with the charging voltage stored in the first storage capacitor 19 to compare the voltage with the second storage capacitor. When the charging voltage of the capacitor 22 is higher, the output is set to the low level and the driving transistor 15 is turned off, so that the switch circuit 6 is turned off.

In the current control circuit 23, the first and second reset transistors 21 and 24 include a control circuit 14 '.
When turned on by a high level signal from the corresponding output terminal P3 ', P3 ", the charge stored in the first and second storage capacitors 19, 22 is discharged. The first reset transistor 21 is When the switch circuit 6 is diagnosed, it is temporarily turned on in synchronization with the rising edge of the pulse, and after discharging the second storage capacitor 22,
Again, the potential difference generated between the terminals of the primer 7 by the diagnostic current as this pulse is stored. The switching transistor 18 and the first and second reset transistors 21 and 24 are set so as not to be turned on in an overlapping manner.

That is, in the above configuration, the control circuit 1
A signal for diagnosis is supplied to the diagnostic current supply circuit 11 and the constant current circuit 12 from the output terminal P5 of 4 ', and at the same time, a low level signal is supplied to the switching transistor 18 from the output terminal P2. As a result, the potential difference between the terminals B and C of the primer 7 generated by the diagnostic current for the primer 7 flowing through the primer 7, that is, the voltage corresponding to the magnitude of the inherent resistance value (variable) of the primer 7 is first stored. Is charged in the switching capacitor 19 and the switching transistor 18
Is held off and stored by being turned off by a signal from the control circuit 14 '.

Next, in order for the control circuit 14 'to diagnose the operation of the switch circuit 6, the pulse width is smaller than the ignition pulse for driving the primer 7 from the output terminal P4, and the time width is insufficient for ignition. The drive transistor 15 is turned on from the output terminal P4 by using the pulse of (1). As a result, the electric power charged in the backup capacitor 4 is supplied in series to the primer 7 and the bypass capacitor 31, and the boosted power is directly applied to the primer 7 in the initial stage. The potential difference between the terminals B and C of the primer 7 is detected by the potential difference detecting circuit 13 and stored in the second storage capacitor 22 and compared by the operational amplifier 20, and it is determined that the current value is larger than the current value flowing at the time of diagnosis of the lightning gap 7. Then, the output of the switch circuit 6 decreases toward the low level, and the switch circuit 6 is gradually turned off. As a result, even in the diagnosis of the switch circuit 6, the current (constant current) at the time of diagnosis of the primer 7 does not flow through the primer 7, and the deterioration of the primer 7 can be prevented.

[0017]

As described above, according to the present invention, the diagnostic current of the switch circuit can be suppressed to the reference value by the diagnostic current of the switch circuit.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of an occupant protection device according to an embodiment 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 Booster circuit 6 Switch circuit 7 Detonator 11 Diagnostic current supply circuit 12 Constant current circuit 14, 14 'Control circuit (control means) 21, 24 Reset transistor 23 Current control circuit

Claims (1)

[Claims] A collision determination is performed based on an acceleration signal from an acceleration sensor. When a collision is determined, a switch circuit interposed between a DC power supply and a squib is turned on, and the squib is detected by the DC power supply. Control means for supplying a diagnostic current to the primer and the switch circuit when the ignition current is not supplied and performing a failure diagnosis of the primer and the switch circuit, and a low potential side of the primer. In a vehicle occupant protection device having a bypass capacitor interposed between a terminal and a ground, the control means includes: a voltage generated between terminals of the primer when a diagnostic current is supplied to the primer; Is stored as a reference value for determining whether or not to continue the flow of the current flowing into the detonator along with the diagnosis, and when the magnitude of the diagnostic current flowing through the switch circuit exceeds the reference value, Vehicle occupant protection apparatus, characterized by stopping the supply of the diagnosis current flowing through the switch circuit.