Accelerometer with integral bidirectional shock protection and controllable viscous damping
First Claim
1. A sensing device comprising:
- a supporting frame having an opening therein;
a mass disposed in the opening and movable along at least one axis;
a flexure coupled between the frame and the mass;
stop means integral to the supporting frame and the mass and mounted along the respective adjacent edges of the frame and the mass for restricting movement of the mass structure in at least one direction along the at least one axis; and
sensing means coupled to at least the flexure for detecting movement of the mass structure.
1 Assignment
0 Petitions
Accused Products
Abstract
A micromachined accelerometer includes integral bidirectional shock protection and controllable viscous damping. The accelerometer includes a frame in which a seismic mass is disposed and coupled to the frame by one or more cantilever beams. Upper and lower stops are provided around the periphery of the seismic mass and around the interior of the frame to limit the travel distance of the seismic mass. The accelerometer is fabricated, preferably from monocrystalline silicon, by defining an annular recess which extends into a first surface of a silicon substrate. Next, a layer is formed over the surface of the substrate but not in contact with the lower surface of the recessed region. An annular-shaped region of the substrate extending from the bottom surface of the substrate to the layer is then removed to define the seismic mass and frame. Finally, portions of the layer are removed to define the cantilever beams and integral bidirectional stops.
171 Citations
34 Claims
-
1. A sensing device comprising:
-
a supporting frame having an opening therein; a mass disposed in the opening and movable along at least one axis; a flexure coupled between the frame and the mass; stop means integral to the supporting frame and the mass and mounted along the respective adjacent edges of the frame and the mass for restricting movement of the mass structure in at least one direction along the at least one axis; and sensing means coupled to at least the flexure for detecting movement of the mass structure. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
-
-
15. An accelerometer comprising:
-
an annular supporting frame having an opening therethrough, the frame comprising a monocrystalline silicon substrate and an overlying epitaxial layer of monocrystalline silicon; a mass disposed in the opening and movable along an axis extending through the opening, the mass comprising a monocrystalline silicon substrate and an overlying epitaxial layer of monocrystalline silicon; a cantilever beam extending between the frame and the mass within the epitaxial layer to couple the mass to the frame; a plurality of stops within the epitaxial layer, each stop having a protrusion extending from one of the mass or the frame to the other of the mass or frame, each stop including a recess in the other of the mass or frame to define a travel distance between the recess and the protrusion; and sensing means disposed in the cantilever beam for detecting relative motion between the frame and the mass. - View Dependent Claims (16, 17)
-
- 18. A sensing device with a moving part and a non-moving part, the moving part being located in an opening in the non-moving part, the moving part being capable of a predefined range of motion along one axis, the axis being perpendicular to the non-moving part, and the non-moving part having overrange stops mounted thereon, the stops comprising protrusions on one of the moving or non-moving parts overlapping a recess on the other of the moving or non-moving part for preventing motion of the moving part beyond its predefined range.
-
20. A method of fabricating a sensing device comprising:
-
forming an annular recess extending into a first surface of a substrate, the recess defining a second surface; forming a layer over the first surface and over the recess, the layer not being in contact with the second surface; removing an annular-shaped region of the substrate extending from a bottom surface of the substrate to the recess to thereby define a mass; and removing a selected portion of the layer to define a cantilever beam extending across the recess and to define at least one stop over the recess for preventing movement of the mass beyond a fixed distance in a selected direction. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28)
-
-
29. A method of fabricating an accelerometer comprising:
-
etching a first annular recess extending into an upper surface of a first silicon substrate, and a second recess extending into a lower surface of the first silicon substrate; forming an epitaxial silicon layer over a surface of a second silicon substrate; attaching the epitaxial silicon layer to the upper surface of the first silicon substrate; removing the second silicon substrate; forming electronic circuit elements in the epitaxial layer; removing an annular-shaped region from the first substrate extending from the lower surface to the first annular recess to thereby define a mass and a frame; and removing a selected portion of the epitaxial layer to define at least one cantilever beam extending between the mass and the frame and to define a plurality of protrusions over the first recess for restricting movement of the mass with respect to the frame. - View Dependent Claims (30, 31)
-
-
32. A sensing device comprising:
-
a supporting frame having an opening therein; a mass disposed in the opening and movable along at least one axis; a flexure coupled between the frame and the mass; stop means integral to the supporting frame and the mass for restricting movement of the mass structure in the at least one direction along the at least one axis; and sensing means coupled to at least the flexure for detecting movement of the mass structure, the stop means further comprising an upper and lower stop means for restricting movement of the mass structure to between two positions along the at least one axis, the upper stop means further comprising a first recess in a surface of the mass and a first projection from the frame disposed to contact the mass when the mass is displaced upwardly from the frame. - View Dependent Claims (33)
-
-
34. A method of fabricating a sensing device comprising:
-
forming an annular recess extending into a first surface of a substrate, the recess defining a second surface; forming a layer over the first surface and over the recess, the layer not being in contact with the second surface; removing an annular-shaped region of the substrate extending from a bottom surface of the substrate to the recess to thereby define a mass; and removing a selected portion of the layer to define a cantilever beam extending across the recess and to define at least one stop over the recess for preventing movement of the mass beyond a fixed distance in a selected direction, the step of removing a selected portion of the layer further comprising removing a serpentine-shaped portion to define at least one pair of coplanar stops for preventing movement of the mass beyond a fixed distance in both of two directions.
-
Specification