Eddy-current-damped microelectromechanical switch
| DWPI Title: Microelectromechanical apparatus, for sensing acceleration event in e.g. seat belt retraction, has shuttle whose movement is damped by eddy current produced in response to movement of shuttle relative to each magnet on substrate |
| Abstract: A microelectromechanical (MEM) device is disclosed that includes a shuttle suspended for movement above a substrate. A plurality of permanent magnets in the shuttle of the MEM device interact with a metal plate which forms the substrate or a metal portion thereof to provide an eddy-current damping of the shuttle, thereby making the shuttle responsive to changes in acceleration or velocity of the MEM device. Alternately, the permanent magnets can be located in the substrate, and the metal portion can form the shuttle. An electrical switch closure in the MEM device can occur in response to a predetermined acceleration-time event. The MEM device, which can be fabricated either by micromachining or LIGA, can be used for sensing an acceleration or deceleration event (e.g. in automotive applications such as airbag deployment or seat belt retraction). |
| Use: Microelectromechanical (MEM) apparatus, for sensing acceleration or deceleration event in automotive application such as airbag deployment or seat belt retraction. |
| Advantage: The apparatus utilizes eddy-current damping to integrate acceleration input over time, thus eliminating fluid leakage, and eliminating thermal expansion of fluid-damped environmental sensing device. The apparatus utilizes microelectromechanical (MEM) fabrication technologies, thus eliminating the need for precision machining and eliminating the need for piece-part assembly, and hence reducing the size and weight. |
| Novelty: The apparatus (10) has a substrate (12) for holding multiple rare-earth permanent magnets (18), where the magnet comprises samarium-cobalt permanent magnet. An electrically-conductive shuttle (14) is suspended above the substrate by multiple springs (16). The shuttle is movable along a path in the plane of the substrate in response to acceleration of the apparatus. An electrical switch is operable based on the movement of the shuttle. The movement of the shuttle is damped by eddy current produced in response to the movement of the shuttle relative to each permanent magnet on the substrate. |
| Filed: 9/17/2007 |
| Application Number: US2007901384A |
| Tech ID: SD 7282.1 |
| This invention was made with Government support under Contract No. DE-NA0003525 awarded by the United States Department of Energy/National Nuclear Security Administration. The Government has certain rights in the invention. |
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