Electrical transmission or interconnection systems – Vehicle mounted systems – Automobile
Patent
1990-05-09
1992-07-28
Ro, Bentsu
Electrical transmission or interconnection systems
Vehicle mounted systems
Automobile
340436, 280735, B60R 2116
Patent
active
051343061
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to detonation circuits for detonating a vehicle air bag.
BACKGROUND OF THE INVENTION
In electronic restraining systems in vehicles, e.g. an inflatable air bag to restrain an occupant in the event of a crash, the system normally takes the form of one or more sensors which detect the deceleration of the vehicle and a control unit to monitor signals from each sensor and to supply an electrical signal to detonate electrically an inflation capsule to inflate the bag if the control unit determines that a crash condition has occurred. There is a requirement for the system to be able to trigger the safety function very rapidly in the event of a crash. However, it is also necessary that the restraining system should not be inadvertently actuated, for example in the event that a crash condition is incorrectly detected or if a short circuit occurs.
It is an object of the present invention to provide a detonation circuit for detonating an air bag which meets the above requirements and overcomes the aforementioned difficulties.
SUMMARY OF THE INVENTION
The detonation circuit according to the present invention has the additional advantages that faulty triggering of the detonation capsule is prevented in virtually all cases in which faults occur in the detonation circuit. The detonation circuit according to the present invention also enables the use of one energy reserve for a plurality of detonation circuits in as economical a way as possible. It also increases the security against false triggering, caused by a fault in the circuit affecting the triggering, such that an additional mechanical, acceleration-dependent switch need not be provided.
BRIEF DESCRIPTION OF THE DRAWINGS
By way of example only, a specific embodiment of the present invention will now be described, with reference to the accompanying drawings, in which:
FIG. 1 is a circuit diagram of an embodiment of air bag detonating apparatus in accordance with the present invention; and
FIGS. 2 and 3 are plots of voltage against time for a test switch transistor and firing transistor respectively of the embodiment of FIG. 1.
DETAILED DESCRIPTION
The circuit shown in FIG. 1 has as its object the electrical detonation of an air bag capsule 10 during a crash in which the vehicle to which the system is fitted is involved. The inflation capsule is connected to the secondary coil S of a step-down transformer 12 having a primary coil P and a secondary coil S. The primary coil P of the transformer 12 is connected in one direction to an energy reserve, indicated generally as 14, and to a command release detonation system 16, and in the other direction to a timed firing means 18.
The energy reserve comprises a capacitor 20 which is charged up to a working voltage of 50V from a vehicle battery voltage U.sub.B by means of a conventional DC/DC converter 22. Two decoupling diodes 24, 26 are connected from the battery voltage U.sub.B and from one side of the capacitor 20 (the other side being connected to earth E) to an output lead 28 of the energy reserve system F4. A test switch transistor 30 is also connected to the output lead 28.
The output of the command release detonation system 16 is connected to the base of the transistor 30. The command release detonation system is conventional, and comprises a first input 32 which conveys signals from a control unit CU.sub.1 when the control unit determines on the basis of information from a sensor (not shown) that a crash condition has occurred. A second input 34 leads from a monostable multivibrator (not shown) and both inputs are fed into an AND gate 36. Thus, when coincident signals are received by the AND gate 36 from the control unit and the monostable multivibrator, a "1" signal is output along lead 38 to the base of the transistor, and causes the transistor switch to close, i.e. to conduct. A high value resistor 40 bridges the emitter and the base of the transistor.
The collector of the transistor is connected to the primary coil P of the transformer 12. A stab
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Crispin Norbert
Mattes Bernhard
Schumacher Hartmut
Ro Bentsu
Robert & Bosch GmbH
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