Rolamite sensor

摘要

A rolamite sensor for use in sensing deceleration of a vehicle includes two separate electrical circuits for actuating two occupant restraints such as air bags. The sensor has a molded plastic base mounted on a metal chassis and a metal cover welded to the chassis to sealingly enclose the base. One surface of the base acts as a guide surface for a roller. A pair of thin metal bands are wrapped around the roller. Each band is fixed at one end to the base and at the other end to a J-shaped tensioner underneath the base. The roller is rollable on the guide surface under an applied force to cause the band to engage firing contacts to complete the electrical circuits. An optical electromagnet may be fixed to the chassis without increasing the overall size of the sensor. The electromagnet is selectively operable to attract the roller to test the sensor by completing the electrical circuits. The electromagnet includes a ferromagnetic core and a coil wound directly on the core. The roller has a ferromagnetic insert formed in a dumb-bell shape, that is, having a larger cross-section at its ends than in the middle to increase the attractive force of the electromagnet without significantly increasing weight and thus inertia of the roller. The chassis and the cover may be made of a ferromagnetic material to shield the sensor from external magnetic fields.