| 摘要 |
A crash sensing switch for automotive vehicles has a cylindrical piston that moves sealingly in a tube during a crash to bridge a pair of contacts. Viscous flow of air through ducts creates pressures that resist movement of the piston. A venting valve may be incorporated in the piston to increase contact dwell. Impedance of the ducts may be adjusted during manufacture by blocking one or more of the ducts. The clearance between the piston and the tube limits air flow between the piston and the walls of the tube and provides aerodynamic lubrication between the piston and the tube during cross axis vibrations. A piston ring may assist in preventing air flow between the piston and the walls of the tube. There may be compensation for changes of air viscosity with temperature. One way to compensate is to make the contacts of thermostat metal which bends with temperature to change the distance the piston must move to bridge the contacts. Another way is to provide a valve incorporating thermostat metal which opens or closes certain ducts to compensate for changes of air viscosity with temperature. Compensation for variation of air viscosity with temperature may be provided at higher temperatures but not at lower temperatures. An injection molded cap includes connector pins to form an integral connector and hermetically seal the interior from the environment. Contact height setters may be incorporated into the cap to assure the desired piston movement for switch closure. Calibration may be done at manufacture by adjusting the piston movement required for switch closure. The combination of these elements provides a crash sensing switch having superior performance and costing much less than known crash sensing switches.
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