Electrical transmission or interconnection systems – Vehicle mounted systems – Automobile
Patent
1991-03-11
1993-04-20
Gaffin, Jeffrey A.
Electrical transmission or interconnection systems
Vehicle mounted systems
Automobile
280735, 340436, 180274, B60R 2116
Patent
active
052045471
DESCRIPTION:
BRIEF SUMMARY
STATE OF THE ART
The present invention relates to an air bag system for protection of the occupants of a motor vehicle, such as the kind described in document No. WO-A-88/01241.
With such systems, it is required that reliable activation of the air bags be ensured in the situation that there is a loss of battery power at a time when such activation is needed and also in the event of shunts or short circuits forming in the driver's and/or front-seat passengers' gas generators. The firing of rearseat passengers' igniters or squibs and the vehicle crash recorder (when fitted) must also be ensured.
It is an object of the present invention to develop a system in which reliability and safety are considerably enhanced, especially in case of loss of battery power.
The aforegoing object is achieved by adopting the features set forth in the appended claims. One advantage of the present invention is that there is only one single energy storage capacitor to be monitored and that there is sufficient energy provided to fire a plurality of igniters or squibs even after a loss of battery power.
DRAWING
The invention is described further, by way of example only, with reference to the accompanying drawing which is a circuit diagram of one embodiment of an air bag protection system in accordance with the invention for the occupants of motor vehicles.
DESCRIPTION OF THE EXEMPLARY EMBODIMENT
The drawing shows part of an air bag protection system wherein a number of firing circuits 1a, 1b, 1c are connected in parallel between a regulated battery voltage U.sub.BATT and the grounded side 2 of the vehicle battery. Each firing circuit includes a respective igniter 3a, 3b, 3c connected in series with a respective power transistor T.sub.1, T.sub.2, T.sub.3 and a low ohmic resistor R.sub.1, R.sub.2, R.sub.3. Connected in series with the three resistors R.sub.1, R.sub.2, R.sub.3 is a mechanical switch 6 of known type, which is sensitive to vehicle deceleration and which only closes when a predetermined retardation is experienced (such as would be incurred, for example, in a collision). Thus, in this embodiment, the single mechanical switch is common to all three firing circuits. The three igniters 3a, 3b, 3c are connected via a monitoring switch 7 (also referred to as power stage 7) and diodes D.sub.1 and D.sub.2 to the regulated battery voltage U.sub. BATT. The diodes D.sub.1 and D.sub.2 serve as protection against incorrect battery polarisation and the monitoring switch 7 enables the circuit to be selectively tested for correct operation.
Also connected to the battery voltage U.sub.BATT, at a point downstream of the diode D.sub.1 is a single energy storage capacitor E, preferably of the AL-ELCO type, having a large capacitance value, for example 10,000 uF. It will be noted that this single storage capacitor E is commonly connected via the high side monitoring transistor 7 to all three firing circuits 1a, 1b and 1c.
The occupant protection system is triggered when, in the event of an accident, a sensor (not shown) is activated and supplies a pulsed signal, for example of 10 ms duration, to turn on the power transistors T.sub.1, T.sub.2 and T.sub.3 via driver stages 8 (only one shown) and additionally the high side power stage 7. Provided that the externally acting mechanical retardation on the vehicle has been sufficient to close the arming switch 6, current from the single energy storage capacitor E can then pass through the igniters so as to inflate the associated air bags (not shown).
In order to limit the current passing through the igniters to an acceptable level, the voltages on the resistors R.sub.1, R.sub.2, R.sub.3 are applied to the negative inputs (-) of respective comparators 9 (only one shown) serving as firing current limiters. The positive inputs (+) of the comparators are provided with reference Voltages by passing a current through respective resistors R.sub.4 from a constant current source 10 supplied with a stabilized voltage U.sub.STAB. Upon the voltage at the negative input exceeding the reference voltage at
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patent: 4220871 (1980-09-01), Yasui et al.
patent: 4438424 (1984-03-01), Yasui
patent: 4883623 (1987-08-01), Sterler et al.
patent: 4933570 (1990-06-01), Swart et al.
patent: 5046149 (1991-09-01), Nuran
Crispin Norbert
Jeenicke Edmund
Mattes Bernhard
Schumacher Hartmut
Gaffin Jeffrey A.
Robert & Bosch GmbH
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