Air bag system for protection of the occupants of motor vehicles

• US 5,204,547 A
• Filed: 03/11/1991
• Issued: 04/20/1993
• Est. Priority Date: 09/14/1988
• Status: Expired due to Term

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Schumacher, Hartmut, Crispin, Norbert, Mattes, Bernhard, Jeenicke, Edmund
• Primary Examiner(s): Gaffin, Jeffrey A.
• Application Number:
  US07/663,842
• Time in Patent Office: 771 Days
• Field of Search: 180/274, 280/734, 280/735, 280/736, 340/436, 307/9.1, 307/10.1
• US Class Current: 307/10.1
• CPC Class Codes: B60R 21/017 including arrangements for providing electric power to safety arrangements or their actuating means, e.g. to pyrotechnic fuses or electro-mechanic valves

Abstract

An air bag system for protecting the occupants of a motor vehicle in the event of a collision has a plurality of firing circuits comprising air bag igniters (3a,3b,3c) in series with respective power transistors (T₁,T₂,T₃) which can be triggered in the event of an accident to inflate a corresponding plurality of air bags. A single energy storage capacitor (E) is connected to all of the firing circuits for supplying energy to activate the bag igniters over the upper common power stage (7) in the event that there is a loss of battery voltage when the system has been actuated. A comparator (9) monitors the voltage drops across respective resistors (R₁,R₂,R₃) in series with the power transistors (T₁,T₂, T₃) and reduces the current through these transistors in the event that an excessive current is detected. Steps are taken to ensure that the period of activation of the current supply to the igniters is limited.

Claims

1. A system for the protection of the occupants of a motor vehicle, particularly an air bag protection system, comprising:

a plurality of firing circuits coupled between a battery supply voltage and ground, each firing circuit including a bag igniter, each bag igniter being coupled in series with a respective triggerable power switch,

at least one retardation sensitive mechanical arming switch coupled to said power switches,

a single energy storage capacitor coupled to each of said firing circuits for supplying initiation energy to each circuit over an upper common power stage in the event of a loss of the battery supply voltage,

a plurality of resistors, each resistor being coupled in series with a respective power switch, and

a comparator for comparing the voltage across at least one of the resistors with a reference voltage and controlling the power switches based upon the comparison to limit the current flowing through the power switches, and hence through the bag igniters, from the energy storage capacitor.

2. A system according to claim 1, wherein the comparator limits the time duration for which the power switches are actuated.

3. A system according to claim 1, wherein the power switches are transistors.

4. A system for the protection of the occupants of a motor vehicle, particularly an air bag protection system, comprising:

a plurality of firing circuits coupled between a battery supply voltage and ground, each firing circuit including a bag igniter, each bag igniter being coupled in series with a respective triggerable power switch,

at least one retardation sensitive mechanical arming switch coupled to said power switches,

a single energy storage capacitor coupled to each of said firing circuits for supplying initiation energy to each circuit over an upper common power stage in the event of a loss of the battery supply voltage, and

means for limiting the current flowing through the individual triggerable power switches, and hence through the bag igniters, from the energy storage capacitor, wherein the means for limiting limits the time duration for which the power switches are actuated by using pulsed trigger signals for actuating said power switches.

5. An apparatus for actuating at least one safety device for protecting the occupants in a motor vehicle during a collision, comprising:

at least one firing circuit coupled to the safety device and to a voltage supply, the firing circuit being adapted to actuate the safety device in response to the passage of current therethrough, the firing circuit including an ignition device coupled in series with a transistor, the transistor being adapted to permit the passage of current through the ignition device to actuate the safety device;

a capacitor coupled to the firing circuit and to the voltage supply, the capacitor being adapted to supply voltage to the firing circuit upon disconnection of the voltage supply to, in turn, actuate the safety device;

means for determining the amount of current passing through the firing circuit from the capacitor; and

means for controlling the transistor as a function of the determined amount of current passing through the firing circuit from the capacitor to limit the current passing through the firing circuit from the capacitor to permit additional safety devices to be actuated by the capacitor.

6. An apparatus for actuating at least one safety device for protecting the occupants in a motor vehicle during a collision, comprising:

at least one firing circuit coupled to the safety device and to a voltage supply, the firing circuit being adapted to actuate the safety device in response to the passage of current therethrough, the firing circuit including an ignition device coupled in series with a transistor, the transistor being adapted to permit the passage of current through the ignition device to actuate the safety device;

a capacitor coupled to the firing circuit and to the voltage supply, the capacitor being adapted to supply voltage to the firing circuit upon disconnection of the voltage supply to, in turn, actuate the safety device;

a resistor coupled in series with the transistor; and

a comparator coupled to the resistor, the transistor and a reference voltage, the comparator being adapted to compare the voltage across the resistor to the reference voltage, and if the resistor voltage exceeds the reference voltage, to transmit a signal to the transistor to limit the level of current passing through the firing circuit from the capacitor to permit additional safety devices to be actuated by the capacitor.

7. An apparatus as defined in claim 6, further comprising:

an arming switch coupled between the resistor and ground, the arming switch being responsive to the acceleration of the motor vehicle to close in response to the acceleration exceeding a threshold level and, thus, permit current to pass through the firing circuit.

8. An apparatus for actuating a plurality of safety devices for protecting the occupants of a motor vehicle during a collision, comprising:

a plurality of firing circuits, each firing circuit being coupled to a respective safety device and to a voltage supply, each firing circuit including an ignition device coupled in series with a power switch, each power switch being adapted to permit the passage of current through the ignition device to actuate the respective safety device;

an electric storage device coupled to each firing circuit and to the voltage supply, the storage device being adapted to supply voltage to the firing circuits upon disconnection of the voltage supply to, in turn, actuate the safety devices;

means for determining the amount of current passing through at least one of the firing circuits from the electric storage device; and

a current limiting circuit coupled to each firing circuit and adapted to control at least one of the power switches as a function of the determined amount of current for limiting the current passing through the at least one of the firing circuits from the electric storage device to permit each firing circuit and, thus, safety device to be actuated by the electric storage device.

9. An apparatus for actuating a plurality of safety devices for protecting the occupants of a motor vehicle during a collision, comprising:

a plurality of firing circuits, each firing circuit being coupled to a respective safety device and to a voltage supply, each firing circuit including an ignition device coupled in series with a power switch, each power switch being adapted to permit the passage of current through the ignition device to actuate the respective safety device;

an electric storage device coupled to each firing circuit and to the voltage supply, the storage device being adapted to supply voltage to the firing circuits upon disconnection of the voltage supply to, in turn, actuate the safety devices; and

a current limiting circuit coupled to each firing circuit and adapted to limit the current passing through the firing circuits from the electric storage device to permit each firing circuit and, thus, safety device to be actuated by the electric storage device, wherein the current limiting circuit includes

a plurality of resistors, each resistor being coupled in series with a respective power switch; and

a plurality of comparators, each comparator being coupled to a respective resistor and power switch, and to a reference voltage, each comparator being adapted to compare the voltage across the respective resistor to the reference voltage, and if the resistor voltage exceeds the reference voltage, to transmit a signal to the respective power switch to correspondingly reduce the level of current passing therethrough.

10. An apparatus as defined in claim 9, wherein the electric storage device is a capacitor.