1. Technical Field
The present invention relates to a rolamite sensor for sensing deceleration of a vehicle, and particularly to a sensor for actuating a vehicle occupant restraint such as an air bag.
2. Description of the Prior Art
A known rolamite sensor has a movable member, preferably a roller, which moves along a guide surface in response to deceleration of a vehicle in which the sensor is mounted. The sensor has two independent electrical circuits. Each circuit uses an S-shaped band which at least partially encircles the roller. Each band is welded at one end to a tensioner fixed to a base. The tensioners protrude upwardly from the base above the guide surface for the roller. The tensioners take up a significant amount of space and require the sensor to have a relatively large enclosure.
Another known rolamite sensor has two S-shaped bands which at least partially encircle the roller, but only one electrical circuit. The roller is electrically conductive and has a permanent magnet core. An electromagnet is operative to repel the roller. When the roller is repelled by the electromagnet, the circuit should be completed. Thus, the electromagnet is operated to test the sensor. The electromagnet has a coil wound around a plastic bobbin on a multi-piece magnetic core. The electromagnet is disposed beyond one end of the path of movement of the roller, and takes up a substantial part of the overall volume of the sensor. The electromagnet is fixed to the plastic base of the sensor, and the sensor is much larger than if the electromagnet were omitted.