Acceleration sensor

• US 6,796,181 B2
• Filed: 12/19/2002
• Issued: 09/28/2004
• Est. Priority Date: 02/18/2000
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited, Fujitsu Media Devices Limited (Fujitsu Limited)
• Original Assignee: Fujitsu Limited, Fujitsu Media Devices Limited (Fujitsu Limited)
• Inventors: Tanaka, Hiroshi, Ishikawa, Hiroshi, Ikata, Osamu
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US10/322,632
• Publication Number:
  US 20030106373A1
• Time in Patent Office: 649 Days
• Field of Search: 735/143.4, 735/141.6, 735/140.1, 310/311, 310/329, 310/333, 367/180
• US Class Current: 73/514.34
• CPC Class Codes: G01P 15/0922 of the bending or flexing mode type

Abstract

An acceleration sensor includes a piezoelectric single-plate having a weight part and a detection part. The piezoelectric single-plate is, for example, an X-cut plate of LiNbO₃.

Claims

1. An acceleration sensor comprising:

a piezoelectric single-plate having a weight part and a detection part;

a detection electrode provided on a first surface of the piezoelectric single-plate, an electric signal caused by inertia force exerted onto the weight part resulting from acceleration being output via the detection electrode; and

a ground electrode provided on a second surface of the piezoelectric single-plate opposite to the first surface;

wherein the detection electrode includes two electrode parts arranged side by side in a main axis direction in which the acceleration is applied to the acceleration sensor.

2. The acceleration sensor as claimed in claim 1, wherein the piezoelectric single-plate has a supporting position which does not include a center of gravity of the piezoelectric single-plate.

3. The acceleration sensor as claimed in claim 1, wherein the piezoelectric single-plate has a supporting position which includes a center of gravity of the piezoelectric single-plate.

4. The acceleration sensor as claimed in claim 1, wherein the piezoelectric single-plate has a supporting position with which the detection electrode overlaps.

5. The acceleration sensor as claimed in claim 1, wherein the piezoelectric single-plate is an X-cut plate of LiNbO3.

6. The acceleration sensor as claimed in claim 1, further comprising another ground electrode provided on the first surface of the piezoelectric single-plate.

7. The acceleration sensor as claimed in claim 1, wherein the ground electrode is thicker than the detection electrode.

8. The acceleration sensor as claimed in claim 1, wherein the detection electrode and the ground electrode have respective densities that are greater than a density of the piezoelectric single plate.

9. The acceleration sensor as claimed in claim 6, further comprising an electrically conductive resin that electrically connects the ground electrode and said another ground electrode.

10. The acceleration sensor as claimed in claim 6, further comprising an insulating resin provided in a groove that separates the detection electrode and said another ground electrode from each other.

11. The acceleration sensor as claimed in claim 1, further comprising:

a package to which the piezoelectric single-plate is attached;

an electrode terminal provided on the package; and

an electrically conductive adhesive agent which attaches the piezoelectric single-plate to the package and electrically connects the detection electrode and the electrode terminal.

12. The acceleration sensor as claimed in claim 1, further comprising:

a package to which the piezoelectric single-plate is attached;

an electrode terminal provided on the package; and

an anisotropic electrically conductive adhesive agent which attaches the piezoelectric single-plate to the package and electrically connects the detection electrode and the electrode terminal.

13. The acceleration sensor as claimed in claim 1, further comprising a flexible printed-circuit cable to which the detection electrode and the ground electrode are connected.

14. The acceleration sensor as claimed in claim 1, further comprising a wire connecting the detection electrode and the ground electrode to electrode terminals formed on a member by which the piezoelectric single-plate is supported.

15. The acceleration sensor as claimed in claim 1, further comprising:

a package which accommodates the piezoelectric single-plate;

and an electrically conductive resin which electrically connects the ground electrode to an electrode terminal provided on the package.

16. The acceleration sensor as claimed in claim 1, further comprising:

an electric circuit that processes an electric signal output from the piezoelectric single-plate; and

a package which accommodates the electric circuit and the piezoelectric single-plate.

17. The acceleration sensor as claimed in claim 16, wherein the package is provided with a guide base positioning and supporting the piezoelectric single-plate.

18. The acceleration sensor as claimed claim 16, wherein the electric circuit is located below the piezoelectric single-plate.