Air bag firing circuit.

摘要

An air bag firing circuit comprises a firing path (52) including in series a safing sensor (54), a squib (56), and a crash sensor (58). Each sensor comprises normally-open switch means (94) operated by an inertial mass and shunted by a resistor (84). A battery (82) maintains a known voltage across the firing path while suitable control means (80) checks the integrity of the firing path by reading and comparing the voltages achieved at various points (86,88,90) thereabout. The control means further tests each sensor individually by sequentially operating suitable test means incorporated therein, such as means (92) for biasing the inertial mass of each sensor towards its switch means to operate same, while determining the effect of such testing on the voltages achieved about the firing path. Upon the detection of a sensor failure, the malfunctioning sensor is removed from the firing path as by operating low-resistance shunt means (98) therefor, or by operating means incorporated within the sensor for operating the switch means thereof without regard to acceleration, such as means (92) for biasing its inertial mass towards its switch means to close same, thereby ensuring continued protection of the vehicle passengers until the sensor is serviced or replaced. If the malfunctioning sensor is the high-threshold crash sensor (58), the control means operates means on the low-threshold safing sensor (54) to increase the threshold thereof upon removal of the crash sensor from the firing path, thereby providing continuing protection for vehicle passengers.