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US 5,177,331 AGranted
Impact detector
AssigneeDelco Electronics Corporation
InventorsDavid B. Rich, Dan W. Chilcott
Life of this patent
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AssigneeDelco Electronics Corporation
InventorsDavid B. Rich, Dan W. Chilcott
Estimating the term…
An impact detector includes a center chip of micromachined silicon, a top cap, and a back plate, with the center chip being sandwiched between the top cap and the back plate. The center chip is micromachined to provide a seismic mass, a perimeter ring, and a plurality of beams interconnecting the perimeter ring and the seismic mass. The center chip and back plate mount aligned switch contacts which close to each other when the seismic mass moves from its static or nondisplaced position to its operative or displaced position. An electrostatic attractive force is generated between the seismic mass and the back plate. This electrostatic attractive force is less than the tensile force applied to the seismic mass by the beams so that the seismic mass remains in its static or nondisplaced position unless the impact detector is subjected to an impulsive force of sufficient magnitude and duration such that the inertial reaction force of the seismic mass when coupled with the electrostatic attractive force is greater than the tensile force so that the seismic mass moves to the operative displaced position. In the operative displaced position, the electrostatic attractive force latches the switch contacts to each other until the electrostatic attractive force is reduced and the tensile force can then return the seismic mass to its static or nondisplaced position.
An impact detector for detecting impact of a moving object with an obstacle comprising, a seismic mass, means applying a tensile force to the seismic mass to locate the seismic mass in a static or nondisplaced position and resist movement of the seismic mass to an operative displaced position, first contact means carried by the seismic mass for movement therewith, contact support means located in spaced relationship to the first contact means, second contact means on the contact support means for closure to the first contact means upon displacement of the seismic mass to the operative displaced position, and means applying an electrostatic force between the seismic mass and the contact support means biasing the seismic mass toward the displaced position, the tensile force applied to the seismic mass being sufficient to resist movement of the seismic mass to the displaced position by the electrostatic force, the application of an impulsive force to the seismic mass coupled with the electrostatic force overcoming the resistance of the tensile force and moving the seismic mass to the displaced position wherein the electrostatic force latches the first contact means to the second contact means, and means for reducing the electrostatic force between the seismic mass and contact support means in the displaced position of the seismic mass to allow the tensile force to unlatch the first and second contact means and return the seismic mass to the static or nondisplaced position.
An impact detector for detecting impact of a moving object with an obstacle comprising, a support, a seismic mass, a plurality of beams interconnecting the support and the seismic mass applying a tensile force to the seismic mass to locate the seismic mass in a static or nondisplaced position and resist movement of the seismic mass to an operative displaced position, first contact means carried by the seismic mass for movement therewith, contact support means located in spaced relationship to the first contact means, second contact means on the contact support means for closure to the first contact means upon displacement of the seismic mass to the operative displaced position, and means applying an electrostatic force between the seismic mass and the contact support means biasing the seismic mass toward the displaced position, the tensile force applied to the seismic mass being sufficient to resist movement of the seismic mass to the displaced position by the electrostatic force, the application of an impulsive force to the seismic mass coupled with the electrostatic force overcoming the resistance of the tensile force and moving the seismic mass to the displaced position wherein the electrostatic force latches the first contact means to the second contact means, and means for reducing the electrostatic force between the seismic mass and contact support means in the displaced position of the seismic mass to allow the tensile force to unlatch the first and second contact means and return the seismic mass to the static or nondisplaced position.
An impact detector for detecting impact of a moving object with an obstacle comprising, a silicon wafer micromachined to provide a seismic mass, a permiter ring surrounding the seismic mass and means interconnecting the perimeter ring and seismic mass and applying a tensile force to the seismic mass to locate the seismic mass in a static or nondisplaced position and resist movement of the seismic mass to an operative displaced position, first contact means carried by the seismic mass for movement therewith, contact support means located in spaced relationship to the first contact means, second contact means on the contact support means for closure to the first contact means upon displacement of the seismic mass to the operative displaced position, and means applying an electrostatic force between the seismic mass and the contact support means biasing the seismic mass toward the displaced position, the tensile force applied to the seismic mass being sufficient to resist movement of the seismic mass to the displaced position by the electrostatic force, the application of an impulsive force to the seismic mass coupled with the electrostatic force overcoming the resistance of the tensile force and moving the seismic mass to the displaced position wherein the electrostatic force latches the first contact means to the second contact means, and means for reducing the electrostatic force between the seismic mass and contact support means in the displaced position of the seismic mass to allow the tensile force to unlatch the first and second contact means and return the seismic mass to the static or nondisplaced position.
An impact detector for detecting impact of a moving object with an obstacle comprising, a silicon wafer micromachined to provide a seismic mass, a perimeter ring surrounding the seismic mass and a plurality of beams interconnecting the perimeter ring and seismic mass and applying a tensile force to the seismic mass to locate the seismic mass in a static or nondisplaced position and resist movement of the seismic mass to an operative displaced position, first contact means carried by the seismic mass for movement therewith, contact support means located in spaced relationship to the first contact means, second contact means on the contact support means for closure to the first contact means upon displacement of the seismic mass to the operative displaced position, and means applying an electrostatic force between the seismic mass and the contact support means biasing the seismic mass toward the displaced position, the tensile force applied to the seismic mass being sufficient to resist movement of the seismic mass to the displaced position by the electrostatic force, the application of an impulsive force to the seismic mass coupled with the electrostatic force overcoming the resistance of the tensile force and moving the seismic mass to the displaced position wherein the electrostatic force latches the first contact means to the second contact means, and means for reducing the electrostatic force between the seismic mass and contact support means in the displaced position of the seismic mass to allow the tensile force to unlatch the first and second contact means and return the seismic mass to the static or nondisplaced position.
Dependencies are inferred from the claim text.
No related US applications are recorded in the indexed filing history.
With conversion into electric or magnetic values: by making use of contacts which are actuated by a movable inertial mass
Contacts: switches making use of microelectromechanical systems [MEMS]
Switches operated by change of a physical condition: switches operated by change of acceleration, e.g. by shock or vibration, inertia switch
Details: damping means to avoid unwanted response
Term ended 5 Jul 2011 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
This invention relates generally to impact detectors and more particularly to an impact detector for detecting impact of a moving object, such as a vehicle, with an obstacle.
Impact detectors for detecting impact of a moving object, such as a vehicle, with an obstacle, are known. Generally such detectors include a movable seismic mass which is located in a static or nondisplaced position by some type of motion resistant force, such as an elastic spring, a magnet, an inclined surface, or various combinations of such forces. The seismic mass closes switch contacts when the impact detector is subjected to an impulsive force of sufficient magnitude and duration which is applied to the seismic mass in a direction generally opposite the direction of movement of the seismic mass. The impulsive force must also be of sufficient magnitude and duration to overcome any damping force applied to the seismic mass during movement, such as by viscous dampers, electromagnetic dampers, or otherwise. The impact detector is mounted to the moving object, such as a vehicle, and the switch contacts are connected to circuitry which uses the impact detection information for various purposes, such as to actuate an inflatable occupant restraint system.
The impact detector of this invention is of this general type and includes: a movable seismic mass located in a static or nondisplaced position by a motion resistant force; viscous fluid damping; and, switch contacts which are closed when the seismic mass moves to its displaced position when the impact detector is subjected to an impulsive force of sufficient magnitude and duration and in the appropriate direction. Closure of the switch contacts can actuate a vehicle occupant protection device, such as an inflatable occupant restraint system.
These and other features of this invention will be apparent from the following specification and drawings wherein:
FIG. 1 is a sectional view of an impact detector according to this invention, and
FIG. 2 is a partial perspective view of an impact detector according to this invention.
Referring now to the drawings, an impact detector 10 according to this invention includes a center chip 12, a top cap 14, and a back plate 16. The center chip 12 is a silicon wafer which is micromachined to provide an elongated seismic mass 18 of truncated pyramidal shape, four parallel spaced planar beams 20, and a perimeter ring 22 of generally square shape, all formed from a solid piece of silicon by known chemical etching process. The truncated shape of the seismic mass results from the particular chemical etching process used, preferential etching along certain crystal planes. Seismic masses of other shapes, such as rectangular, may also be provided with different etching processes. The beams 20 are planar and are shown parallel to each other, although the beams may be non-parallel located with respect to each other if so desired. The perimeter ring 22 provides a stable support for the seismic mass 18 and the beams 20.
The top cap 14 is likewise formed of a single piece of silicon and includes a depending flange 24 which seats on and is secured to the upper surface of the perimeter ring 22.
The back plate 16 is also formed of a single piece of silicon and includes a recess 26 which opens upwardly toward the center chip 12. It will be noted that the back plate is flush with the center chip 12 along three sides thereof but has one side 28 which extends outwardly of the center chip. The back plate is suitably secured to the lower surface of the perimeter ring 22 and cooperates therewith and the top cap 14 to provide an enclosed air filled space 30 within which the seismic mass 18 moves.
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