Capacitive acceleration sensor

• US 6,938,485 B2
• Filed: 02/10/2004
• Issued: 09/06/2005
• Est. Priority Date: 03/05/2003
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: VTI Technologies Oy (Murata Manufacturing Co Limited)
• Inventors: Kuisma, Heikki, Lahdenperä, Juha, Mutikainen, Risto
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): BELLAMY, TAMIKO D
• Application Number:
  US10/774,688
• Publication Number:
  US 20040226374A1
• Time in Patent Office: 574 Days
• Field of Search: 735/143.2, 735/141.6, 735/142.1, 735/041.5, 735/041.2, 735/142.3, 735/143.6, 734/96, 361/280
• US Class Current: 73/514.32
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 3/0013 Structures dimensioned for mechanical prevention of stiction, e.g. spring with increased stiffness
• CPC Class Codes: B81C 1/0096 For avoiding stiction when the device is in use, i.e. after manufacture has been completed
• CPC Class Codes: B81C 2201/112 Depositing an anti-stiction or passivation coating, e.g. on the elastic or moving parts
• CPC Class Codes: G01P 15/08 with conversion into electric or magnetic values
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up

Abstract

The invention relates to measuring devices used for the measuring of acceleration, and specifically to capacitive acceleration sensors. The capacitive acceleration sensor according to the present invention comprises a pair of electrodes composed of a movable electrode (4) and a stationary electrode (5), and, related to the pair of electrodes, an isolator protrusion having a special coating. The invention provides an improved, more durable sensor structure, which withstands wear caused by overload situations better than earlier structures.

Claims

1. A capacitive acceleration sensor comprising at least one pair of electrodes, such that the pair of electrodes comprises a movable electrode responsive to the acceleration, at least one stationary electrode, and at least one isolator protrusion, wherein the isolator protrusion being coated with a diamond-like DLC coating, comprises a two-layer composite structure with a base layer that consists of oxide and the base layer is coated with a top layer of the diamond-like DLC coating.

2. The capacitive acceleration sensor of claim 1, wherein the diamond-like DLC coating of the top layer extends also onto the sides of the isolator protrusion.

3. The capacitive acceleration sensor of claim 2, wherein the diamond-like DLC coating of the top layer also extends beyond the edges of the isolator protrusion onto the area of the stationary electrode.

4. The capacitive acceleration sensor of claim 1, wherein the base layer is essentially thicker than the top layer.

5. The capacitive acceleration sensor of claim 1, wherein the pair of electrodes of the acceleration sensor comprises several isolator protrusions.

6. The capacitive acceleration sensor of claim 1, wherein the isolator protrusions are positioned on both sides of the movable electrode.

7. The capacitive acceleration sensor of claim 1, wherein the isolator protrusions are positioned on the stationary electrode.

8. The capacitive acceleration sensor of claim 1, wherein the isolator protrusions are positioned on the movable electrode.

9. The capacitive acceleration sensor of claim 1, wherein the diamond-like DLC coating of the isolator protrusion is grown by ion beam deposition.

10. The capacitive acceleration sensor of claim 1, wherein the diamond-like DLC coating of the isolator protrusion is grown by plasma enhanced chemical vapour deposition.

11. The capacitive acceleration sensor of claim 1, wherein the diamond-like DLC coating of the isolator protrusion is grown by arc discharge deposition.

12. A capacitive acceleration sensor comprising at least one pair of electrodes, such that the pair of electrodes comprises a movable electrode responsive to the acceleration, at least one stationary electrode, and at least one isolator protrusion, wherein the isolator protrusion being coated with a diamond-like DLC coating,

wherein the quality of the diamond-like DLC coating film of the isolator protrusion has been improved by increasing the proportion of bonds sp³/sp².

13. A capacitive acceleration sensor comprising at least one pair of electrodes, such that the pair of electrodes comprises a movable electrode responsive to the acceleration, at least one stationary electrode, and at least one isolator protrusion, wherein the isolator protrusion being coated with a diamond-like DLC coating,

wherein the quality of the diamond-like DLC coating film of the isolator protrusion has been improved by reducing the hydrogen content of the diamond-like DLC coating film.