MEMS switch triggered by shock and/or acceleration

摘要

An acceleration-triggered or shock-triggered, smart, tunable MEMS switch that may function as both a classic accelerometer and an acceleration threshold detector. A parallel element MEMS device has a stationary and a movable element forming a capacitor. Varying acceleration moves the movable member with respect to the stationary member, thereby changing the capacitance of the device. The capacitance varying may be used, in cooperation with appropriate circuitry, to provide a signal representative of instantaneous acceleration. By applying a biasing voltage, the movable element may be positioned in a predetermined fashion such that acceleration of a predetermined magnitude causes the movable element to pull in (snap down). The movable and stationary elements may function as a switch such that when the predetermined acceleration or shock level occurs, electrodes close, a current flows between the elements so that an external device such as an air bag may be activated.

主权项

1. A micro-electro-mechanical shock sensing system (MEMS), comprising:
a resonant micro-electro-mechanical structure configured to have a free state and a pull in state, and having a first electrode configured to interact with an electric field; a second electrode spaced from the resonant micro-electro-mechanical structure in the free state, configured to generate the electric field, to apply an electrostatic force on the resonant micro-electro-mechanical structure in the free state, and to form a conductive path together with the first electrode in the pull in state, wherein the spacing of the resonant micro-electro-mechanical structure from the electrode is responsive to at least a mechanical acceleration along an axis; and an electrical bias generator configured to selectively apply a voltage potential between the first electrode and the second electrode to generate the electrostatic force, to detect formation of the conductive path upon contact of the first and second electrodes and to detect the mechanical acceleration along the axis based on a capacitance of the first and second electrodes, said resonant micro-electro-mechanical structure being selectively responsive to a shock pulse in the mechanical acceleration having a peak amplitude along the axis to transition from the free state to the pull in state wherein a steady state mechanical acceleration along the axis of the peak amplitude as the peak amplitude of the shock pulse does not cause the transition from the free state to the pull in state.