JP3158611B2 - Occupant protection device drive circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving circuit for an occupant protection device using an air bag or the like.

[0002]

2. Description of the Related Art Conventionally, in a driving circuit of an air bag, when there are a plurality of ignition devices (called squibs), ignition energy is distributed to each squib. A method using a timer and a dividing method using a resistor as disclosed in Japanese Utility Model Application Laid-Open No. 56-171361 have been proposed.

[0003]

However, when there are a plurality of squibs, if one of the squibs is short-circuited, a wasteful current flows through the squib, and in this case, the other squibs are ignited normally. To do
A large-capacity power supply and an auxiliary power supply (backup capacitor) were required.

In view of the above, the present invention has been made in view of the above-mentioned problems. In a drive circuit of an occupant protection device having a plurality of ignition devices, even if any one of the ignition devices is short-circuited, a power supply to the ignition device is provided. An object of the present invention is to prohibit the supply and guarantee the operation of another ignition device, and as a result, the large-capacity power supply and the auxiliary power supply (backup capacitor) described above are not required.

[0005]

SUMMARY OF THE INVENTION Therefore, the present invention comprises a plurality of igniters and a power supply means for commonly supplying power to the plurality of igniters for igniting them. In the drive circuit of the occupant protection device configured to operate the device , when a voltage generated in any one of the plurality of ignition devices is equal to or less than a predetermined value.
Short-circuit detection means for detecting a short-circuit state of the ignition device, and when the short-circuit detection means detects a short-circuit state of any one of the ignition devices, the power supply by the power supply means to the detected ignition device is prohibited. And a prohibition means for performing the above.

[0006]

In the above configuration, when any one of the plurality of ignition devices is short-circuited, the short-circuit state is detected by the short-circuit detecting means. The prohibition means prohibits the power supply from the power supply means from prohibiting the ignition device detected by the short-circuit detection means. Therefore, even if the power supply means commonly supplies power to a plurality of ignition devices in order to operate the occupant protection device, power is not supplied to the ignition device in the short-circuit state, Power is supplied to the other ignition devices.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to an embodiment shown in the drawings. FIG. 1 is a configuration diagram showing one embodiment. 1 is a G sensor for generating an electric signal according to the acceleration G applied to the vehicle, 2 is an arithmetic processing of the electric signal from the G sensor 1 to determine the collision state of the vehicle, and generates a high-level collision signal when the collision is determined. More specifically, an electric signal from the G sensor 1 is integrated, and when the integrated value exceeds a threshold level, a collision signal is generated. Reference numerals 3 and 4 denote AND circuits, which output a logical product signal of the signal from the operation unit 2 and the signal from the short detection circuit 5.

The short detection circuit 5 includes an operational amplifier 10
3 and 104, comparators 101 and 102, and the like. The resistors 106, 107, 109, and 110 are for creating reference voltages for the comparators 101 and 102. Since the comparators 101 and 102 are of the open collector type, the pull-up resistors 10
5, 108 are provided.

Reference numerals 10 and 11 denote squibs for deploying airbags for a driver seat and a passenger seat (not shown), respectively. Reference numerals 12 and 13 denote inverters for inverting the output level from the operation unit 2, and reference numerals 6 to 9 denote transistors provided on a power supply line to the squib. Reference numerals 16 to 19 denote diagnosis resistors for determining voltages on power supply lines (squib lines) of the squibs 10 and 11 when the transistors 6 to 9 are in an off state (normal state).

Reference numeral 14 denotes a backup capacitor serving as an auxiliary power supply, reference numeral 20 denotes a charging resistor, and reference numeral 21 denotes a discharging diode. Reference numeral 15 denotes a vehicle-mounted battery, 23 denotes an ignition switch, and 22 denotes a backflow prevention diode.

The short detection circuit 5 corresponds to short detection means, the squibs 10 and 11 correspond to a plurality of ignition devices, and the AND circuits 3 and 4 correspond to prohibition means.
In addition, the backup capacitor 14, the vehicle battery 15
Corresponds to the power supply means.

In the above configuration, when the ignition switch 23 is turned on, the circuits of the respective parts are activated.
Now, assuming that the vehicle is not in a collision state and a low-level electric signal is generated from the arithmetic unit 2, the outputs of the AND circuits 4 and 5 are at a low level, and the transistors 6 and 7 are off. The transistors 8 and 9 are also turned off via the inverters 12 and 13.

In this state, both ends of the squibs 10 and 11 become voltages divided by the resistors 18 and 19 and 16 and 17 respectively. A monitor current of about several mA to several tens mA flows through the squibs 10 and 11, and a voltage of several mV to several tens mV is generated at both ends of the squibs 10 and 11. This voltage is amplified by the operational amplifiers 103 and 104, and if the voltage is equal to or higher than a predetermined value, the squib 10,
11 is determined to be normal by the comparators 101 and 102. In this case, since the output sides of the comparators 101 and 102 are at a high level, the AND circuits 3 and 4 are not closed.

Therefore, in this state, when the vehicle collides and a high-level collision signal is output from the arithmetic unit,
The transistors 6 and 7 are turned on, and the transistors 8 and 9 are also turned on via the inverters 12 and 13 to supply ignition current to the squibs 10 and 11. As a result, an unillustrated airbag is deployed.

However, if any of the squibs is short-circuited, the short-circuit detecting circuit 5 detects the short-circuit and operates to inhibit the power supply to the squib. For example, if the squib 10 is short-circuited, the output of the operational amplifier 103 is close to 0 V, so that the output of the comparator 101 becomes low level. Therefore, the output of the AND circuit 4 becomes low level irrespective of the output from the arithmetic unit 2, and the transistor 6 is kept off.

In this state, even if the vehicle collides and the high-level signal is output from the arithmetic unit 2, the transistor 6 is kept off, so that no ignition current is supplied to the squib 10. On the other hand, squib 11 that is not short
, The transistors 7 and 9 are turned on in the same manner as described above, and the ignition current is supplied.

In the above case, if all the transistors 6 to 9 are turned on even if the squib 10 is short-circuited, most of the energy of the power supply is consumed on the squib 10 side. In extreme cases, the current flowing through the squib 11 may not reach the value required for ignition. However, the above-described operation of the short detection circuit 5 and the AND circuit 4 solves such a problem, and ensures that a squib that is not short-circuited is supplied with a sufficient ignition current.

Next, an embodiment using a microprocessor will be described. FIG. 2 is a partial configuration diagram showing the embodiment, in which a microprocessor (CPU) or the like is used in a part of the short detection circuit 5. Other configurations are shown in FIG.
Are the same as those shown in FIG.

In FIG. 2, each of the squibs 10, 11
Are amplified by the operational amplifiers 103 and 104, and A
/ D conversion is possible. The output is converted into a digital signal by the A / D converter 201 and is used as inputs a and b of the CPU 202.

The CPU 202 executes arithmetic processing according to the flowchart shown in FIG. 4, compares the inputs a and b with predetermined reference values I and J, respectively, and outputs a high-level output when the input exceeds the reference value. To do. It should be noted that the reference values I and J are the squibs 10 and 1 when the monitor current is supplied with a value smaller than the resistance value of the normal squib line.
It is determined by a value obtained by multiplying the voltage between both ends by the gain of the operational amplifiers 103 and 104.

In the above embodiment, the squibs 10 and 11 are provided for each of the driver's seat and the passenger's seat. However, the present invention is applied to a case where two squibs are used for one airbag. Is also good.

Furthermore, although the occupant protection device is described as being applied to an airbag, it may be applied to a preloader or the like.

[0023]

As described above, according to the present invention, even if any one of the plurality of ignition devices is short-circuited, the supply of power to the ignition device is prohibited. There is an excellent effect that it is possible to prevent unnecessary current from flowing to the ignition device, supply sufficient power to the other ignition device, and sufficiently guarantee the operation of the other ignition device. .

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention. .

FIG. 2 is a partial configuration diagram showing another embodiment of the present invention.

FIG. 3 is a flowchart showing the arithmetic processing of the microprocessor in FIG. 2;

[Explanation of symbols]

 3,4 AND circuit 5 Short detection circuit 10,11 Squib 14 Backup capacitor 15 Vehicle battery

Claims (1)

(57) [Claims] An occupant protection system comprising: a plurality of ignition devices; and power supply means for commonly supplying power to the plurality of ignition devices for igniting them, so as to operate an occupant protection device. In the driving circuit of the device, the ignition circuit is generated in any one of the plurality of ignition devices.
Short-circuit detecting means for detecting a short-circuit state of the ignition device when the voltage to be applied is equal to or less than a predetermined value; and the power supply to the ignition device detected when the short-circuit detection means detects a short-circuit state of any one of the ignition devices. And a prohibition means for prohibiting power supply by the means.