Vehicle collision safety systems actuator - uses two glued oscillating, oppositely-polarised piezoceramic wafers mounted on circuit board, reacting to acceleration change

摘要

The accelerometer is used to release safety mechanisms in a vehicle during a head-on collision. A piezoelectric element (1) consisting of two oppositely polarised piezoceramic sections (4, 5) glued together is clamped directly on to a circuit board (3). The ceramic sections are connected to a charge amplifier which converts the high input impedance signal to a low impedance output which is proportional to the acceleration. In a collision the element oscillates flexurally to generate an electrical signal which releases the required safety procedures. The device is unsensitive to transverse accelerations since seat belts and air cushions are useless in a side collision. It is encapsulated to protect it from moisture. Frequency response is constant between 10 Hz and 1kHz which suffices for safety mechanism release.