ACCELEROMETER WITH OVER-TRAVEL STOP STRUCTURE

• US 20100223997A1
• Filed: 03/09/2009
• Published: 09/09/2010
• Est. Priority Date: 03/09/2009
• Status: Active Grant

• Current Assignee: North Star Innovations Inc. (Wi-LAN Inc.)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: Geisberger, Aaron A., Lin, Yizhen, McNeil, Andrew C.
• Granted Patent: US 8,186,220 B2
• Time in Patent Office: Days
• US Class Current: 73/514.320
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/0814 for translational movement of the mass, e.g. shuttle type

Abstract

An accelerometer (50, 100, 120, 130) includes a substrate (58) and a proof mass (54) spaced apart from a surface (56) of the substrate (58). Compliant members (62) are coupled to the proof mass (54) and enable the proof mass (54) to move parallel to the surface (56) of the substrate (58) in a sense direction (68). Proof mass anchors (60) interconnect the compliant members (62) with the surface (56). The accelerometer (50, 100, 120, 130) includes an over-travel stop structure (52, 102, 122, 132) having stop anchors (70, 72) coupled to the substrate (58). The stop anchors (70, 72) are coupled to the substrate (58) at positions (76) on the surface (56) residing at least partially within an anchor attach area (71) bounded in the sense direction (68) by locations (78) of the proof mass anchors (60) on the surface (56).

Claims

1. A transducer adapted to sense acceleration comprising:

a substrate;

a proof mass positioned in spaced apart relationship above a surface of said substrate;

at least one compliant member coupled to said proof mass, said at least one compliant member enabling said proof mass to move substantially parallel to said surface of said substrate in response to said acceleration in a sense direction;

at least one proof mass anchor interconnecting said at least one compliant member with said surface, said at least one proof mass anchor being positioned on said surface at a perimeter of an anchor attach area in said sense direction; and

an over-travel stop structure having a stop anchor coupled to said substrate at a position on said surface residing at least partially within said anchor attach area.

2. A transducer as claimed in claim 1 wherein said stop anchor is a first stop anchor, and said over-travel stop structure further comprises a second over-travel stop anchor coupled to said substrate at a second position on said surface residing at least partially within said anchor attach area.

3. A transducer as claimed in claim 1 wherein said at last one proof mass anchor is one of multiple proof mass anchors each of which is positioned on said surface at said perimeter of said anchor attach area in said sense direction, separate locations of said proof mass anchors on said substrate define a centerline of said anchor attach area between said proof mass anchors that is perpendicular to said sense direction, and said stop anchor is coupled to said substrate at said position along said centerline.

4. A transducer as claimed in claim 3 wherein:

said at least one compliant member further enables said proof mass to move substantially parallel to said surface of said substrate in response to said acceleration in a second sense direction, said second sense direction being perpendicular to said sense direction;

said separate locations of said proof mass anchors on said substrate define a second centerline of said anchor attach area between said proof mass anchors that is perpendicular to said second sense direction; and

said transducer further comprises a second over-travel stop structure having a second stop anchor coupled to said substrate at a second position on said surface along said second centerline.

5. A transducer as claimed in claim 1 wherein said stop anchor is coupled to said surface of said substrate external to a periphery of said proof mass.

6. A transducer as claimed in claim 1 wherein said over-travel stop structure comprises a stop frame encircling a periphery of said proof mass.

7. A transducer as claimed in claim 6 wherein said stop frame is suspended above said substrate via an attachment of said stop frame to said stop anchor.

8. A transducer as claimed in claim 6 further comprising compliant anchor members interconnected between said stop frame and said substrate.

9. A transducer as claimed in claim 6 wherein said stop frame exhibits an inner perimeter that is greater than an outer perimeter of said proof mass such that said stop frame is spaced apart from said outer perimeter of said proof mass under nominal movement of said proof mass, and said proof mass contacts a portion of said stop frame under overload movement of said proof mass.

10. A transducer as claimed in claim 1 wherein said over-travel stop structure includes extension members extending from a periphery of said proof mass, and a stop post coupled with said stop anchor and located between a pair of said extension members.

11. A transducer as claimed in claim 10 wherein:

said pair of extension members are separated from one another by a spacing; and

said stop post exhibits a width that is less than said spacing such that said stop post is spaced apart from each of said pair of said extension members under nominal movement of said proof mass, and one of said pair of said extension members contacts said stop post under overload movement of said proof mass.

12. A transducer adapted to sense acceleration comprising:

a substrate;

a proof mass positioned in spaced apart relationship above a surface of said substrate;

at least one compliant member coupled to said proof mass, said at least one compliant member enabling said proof mass to move substantially parallel to said surface of said substrate in response to said acceleration in a sense direction;

at least one proof mass anchor interconnecting said at least one compliant member with said surface, said at least one proof mass anchor being positioned on said surface at a perimeter of an anchor attach area in said sense direction; and

an over-travel stop structure including a first stop anchor, a second stop anchor, and a stop frame encircling a periphery of said proof mass, each of said first and second stop anchors being coupled to said substrate at a position on said surface residing at least partially within said anchor attach area, and said stop frame being attached to said first and second stop anchors.

13. A transducer as claimed in claim 12 wherein said stop frame is suspended above said substrate via an attachment of said stop frame to each of said first and second stop anchors.

14. A transducer as claimed in claim 12 further comprising compliant anchor members interconnected between said stop frame and said substrate.

15. A transducer as claimed in claim 12 wherein said at last one proof mass anchor is one of multiple proof mass anchors each of which is positioned on said surface at said perimeter of said anchor attach area in said sense direction, separate locations of said proof mass anchors on said substrate define a centerline of said anchor attach area between said proof mass anchors that is perpendicular to said sense direction, and each of said first and second stop anchors is coupled to said substrate at positions along said centerline.

16. A transducer adapted to sense acceleration comprising:

a substrate;

a proof mass positioned in spaced apart relationship above a surface of said substrate;

compliant members coupled to said proof mass, said compliant members enabling said proof mass to move substantially parallel to said surface of said substrate in response to said acceleration in a sense direction;

proof mass anchors interconnecting said compliant members with said surface, wherein separate locations of said proof mass anchors on said substrate define a perimeter of an anchor attach area in said sense direction; and

an over-travel stop structure having a first stop anchor and a second stop anchor, said first and second stop anchors being coupled to said substrate at positions on said surface of said substrate residing at least partially within said anchor attach area.

17. A transducer as claimed in claim 16 wherein said over-travel stop structure comprises a stop frame encircling a periphery of said proof mass, said stop frame is coupled to each of said first and second stop anchors, and said each of said first and second stop anchors is coupled to said substrate at said positions external to a periphery of said proof mass.

18. A transducer as claimed in claim 17 wherein said stop frame exhibits an inner perimeter that is greater than an outer perimeter of said proof mass such that said stop frame is spaced apart from said periphery of said proof mass under nominal movement of said proof mass, and said proof mass contacts a portion of said stop frame under overload movement of said proof mass.

19. A transducer as claimed in claim 16 wherein:

said proof mass includes extension members extending from a periphery of said proof mass; and

said over-travel stop structure includes;

a first stop post extending above said surface and coupled with said first stop anchor, said first stop post being located between a first pair of said extension members; and

a second stop post extending above said surface and coupled with said second stop anchor, said second stop post being located between a second pair of said extension members.

20. A transducer as claimed in claim 19 wherein:

said first pair of extension members are separated from one another by a spacing;

said second pair of extension members are separated from one another by said spacing; and

each of said first and second stop posts exhibits a width that is less than said spacing such that said each of said first and second stop posts is spaced apart from said extension members of corresponding ones of said first and second pairs of said extension members under nominal movement of said proof mass, and one of said extension members of said each of said first and second pairs of said extension members contacts said each of said first and second stop posts under overload movement of said proof mass.