Impact Sensor: Description and Operation
IMPACT SENSOR/INFLATORThe impact sensor/inflator assembly is mounted to the back of the airbag module. It seals the hole in the steering wheel side of the airbag cushion so that the gas produced in the inflator can be discharged directly into the cushion.
The impact sensor provides verification of the direction and severity of the impact. A spherical sensing mass housed in a cylinder will move forward and rotate a D-shaft when the vehicle is subjected to a frontal impact of sufficient severity. Airbag inflation is designed to occur at precisely calibrated vehicle deceleration force, and is not linked to vehicle road speed.
The D-shaft retains two spring loaded firing pins. When a firing pin is released by the D-shaft, it strikes and ignites a primer. The primer then reacts with the pelletized, solid generant contained in the inflator to produce the nitrogen gas that inflates the airbag cushion.