Crash detection apparatus of air bag system

摘要

A crash detection apparatus of an air bag system comprises a detection unit for detecting acceleration caused therein by an automobile and outputting electric signals corresponding to the acceleration, a discrimination unit for discriminating, from the signals from the detection unit, a crash signal which is outputted on the basis of the acceleration caused by crash of the automobile, the crash signal being inputted into an inflator to inflate an air bag. The detection unit is a capacitance type semiconductor detector comprising a pair of fixed electrodes and a cantilevered movable electrode disposed between the fixed electrodes and fixed at an end thereof, and a servo control unit is electrically connected to the detection unit so as to form a negative feedback loop, of a detection signal. The servo control unit serves for applying electric energy temporarily to the detection unit to cause electrostatic force in the detection means for restricting movement of the movable electrode caused by acceleration at an initial position thereof. A diagnostic unit is provided for diagnosing the crash detection apparatus on whether or not the crash detection apparatus functions correctly, the diagnostic unit being electrically connected to the servo control unit to input a diagnostic signal to the negative feedback loop thereby to apply electrostatic force for diagnosis between the fixed electrode and the movable electrode.