DYNAMIC ANALYSIS OF A MECHANICAL AIRBAG SYSTEM SENSOR

All-mechanical sensors for automotive airbag systems offer a compact and low cost yet highly reliable alternative to electrical sensors. In this paper, a non-linear dynamic model is presented that was used to improve the hammer-blow immunity of an all-mechanical ball-in-tube sensor without jeopardizing its endurance performance. Hammer-blows are impacts from within an automobile to the steering wheel or inflator shell that can occur during system installation or from aggressive driving. Sensor endurance is measured by the stability of calibration after being subjected to a sustained vibration environment. Numerical simulations of the model have elucidated the dynamics and mechanisms of operation of such sensors. Experimental hammer-blow tests and endurance tests, as well as simulations of these tests, have been performed. It is found that hammer-blow immunity can be improved without compromising endurance performance when a ball-seat spring is introduced with at least a 2·0 mm allowable deflection. Results which show the effect of varying the spring stiffness, allowable deflection, and pre-load are presented.