Vibratory gyroscopes and method for manufacturing the same

• US 6,389,897 B1
• Filed: 02/15/2000
• Issued: 05/21/2002
• Est. Priority Date: 02/17/1999
• Status: Expired due to Term

• Current Assignee: NGK Insulators Limited
• Original Assignee: NGK Insulators Limited
• Inventors: Kikuchi, Takayuki, Tani, Makoto
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US09/504,181
• Time in Patent Office: 826 Days
• Field of Search: 735/041.2, 735/041.4, 735/041.5, 735/041.6, 310/326, 310/327, 310/370
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/5607 using vibrating tuning forks double-ended tuning forks using planar vibrating masses suspended at opposite ends G01C19/5719

Abstract

The invention reduces the noise from a vibrating gyroscope used for detecting a turning angular rate, when the vibrator is subjected to external vibration. The vibrator is made out of a piezoelectric material. The vibrator vibrates in a driving vibration mode electrically excited in the vibrator and in a detection vibration mode occurring in the vibrator due to Coriolis force when the vibrator is turned. The surface of the vibrator includes a region where the stress induced in the vibrator due to the detection vibration mode is in a range of a local maximum. The gyroscope further has a damper, for reducing vibration sensitivity to external vibrations applied externally on the vibrator. The damper is made of a polymer and is provided on at least the region where the stress induced in the vibrator due to the detection vibration mode is in a range of a local maximum.

Claims

1. A vibratory gyroscope for detecting a turning angular rate, wherein the gyroscope comprises a piezoelectric vibrator that vibrates in a driving vibration mode which is electrically excited in the vibrator and in a detection vibration mode which occurs in the vibrator due to Coriolis force when the vibrator is turned, and the surface of the vibrator includes a first region where stress induced in the vibrator due to the detection vibration mode is in a range of a local maximum, the gyroscope further comprising a damper for reducing vibration sensitivity to external vibrations applied externally on the vibrator, the damper being made of a polymer and being provided on said first region and only other regions of the vibrator where the amplitude of vibration is less than 0.1 of the maximum amplitude of vibration in the vibrator in the driving vibration mode.

2. A vibratory gyroscope as claimed in claim 1, wherein the vibrator comprises one or more driving parts for electrically exciting vibration in the driving vibration mode and one or more detecting parts for detecting vibration in the detection vibration mode, with the damper provided on the detecting part.

3. A vibratory gyroscope as claimed in claim 2, wherein the vibrator is composed of a piezoelectric single crystal, and the gyroscope comprises a driving electrode, for electrically exciting a vibration in the driving vibration mode, on the surface of each driving part and a detecting electrode, for detecting the vibration in the detection vibration mode, on the surface of each detecting part.

4. A vibratory gyroscope as claimed in claim 3, wherein the detecting part comprises its root, the detecting electrode comprises an edge portion near the root, and the damper covers at least the edge portion.

5. A vibratory gyroscope as claimed in claim 2, wherein the vibrator extends in a specified plane and the entire surface includes a pair of main faces extending substantially in parallel with the specified plane and one or more side faces are substantially perpendicular to the specified plane, the damper provided on at least one face selected from the main faces and side faces.

6. A vibratory gyroscope as claimed in claim 2, wherein the whole surface includes a second region where the stress induced in the vibrator due to the driving vibration mode is not higher than {fraction (1/10)} of a maximum value of the stress due to the driving vibration mode, with the damper provided on the second region.

7. A vibratory gyroscope as claimed in claim 1, wherein the vibrator extends in a specified plane and the entire surface includes a pair of main faces extending substantially in parallel with the specified plane and one or more side faces are substantially perpendicular to the specified plane, the damper provided on at least one face selected from the main faces and side faces.

8. A vibratory gyroscope as claimed in claim 7, wherein the damper is provided on at least one main face of the detecting part and covers a maximum curvature point on the main face, the point located on the center line of the main face where the curvature of the center line is maximum when the vibrator is deformed in the detection vibration mode.

9. A vibratory gyroscope as claimed in claim 7, wherein the damper is provided on at least one main face of the detecting part and covers a maximum stress point on the main face, the point located on the center line of the main face where the stress is maximum in the center line when the vibrator is deformed in the detection vibration mode.

10. A vibratory gyroscope as claimed in claim 7, wherein the vibrator is turned around a turning axis crossing through the specified plane, the vibrator comprises a plurality of vibration systems each extending in the specified plane, the vibration systems include a first vibration system, whose vibration comprises a radial vibration component vibrating in a diametrical direction with respect to the center of gravity of the vibrator in the specified plane, and a second vibration system, whose vibration comprises a circumferential vibration component vibrating circumferentially with respect to the center of gravity in the specified plane, one of the first vibration system and second vibration system comprises the driving part and the other comprises the detecting part.

11. A vibratory gyroscope as claimed in claim 7, wherein the whole surface includes a second region where the stress induced in the vibrator due to the driving vibration mode is not higher than {fraction (1/10)} of a maximum value of the stress due to the driving vibration mode, with the damper provided on the second region.

12. A vibratory gyroscope as claimed in claim 7, wherein the vibrator is composed of a piezoelectric single crystal, and the gyroscope comprises a driving electrode, for electrically exciting a vibration in the driving vibration mode, on the surface of each driving part and a detecting electrode, for detecting the vibration in the detection vibration mode, on the surface of each detecting part.

13. A vibratory gyroscope as claimed in claim 1, wherein the whole surface includes a second region where the stress induced in the vibrator due to the driving vibration mode is not higher than {fraction (1/10)} of a maximum value of the stress due to the driving vibration mode, with the damper provided on the second region.

14. A vibratory gyroscope as claimed in claim 1, wherein the polymer is an elastomer wherein a ratio of a maximum to a minimum of its dynamic viscoelasticity is not more than three times between −

40°

C. to +85°

C.

15. A vibratory gyroscope for detecting a turning angular rate, the gyroscope comprising a piezoelectric vibrator comprising one or more driving parts for electrically exciting vibration in a driving vibration mode in the vibrator, one or more detecting parts, provided separately from the driving parts, for detecting Coriolis vibration in a detection vibration mode which occurs in the vibrator due to Coriolis force when the vibrator is turned, and a damper for reducing vibration sensitivity to external vibrations applied externally on the vibrator, the damper being made of a polymer and being provided on the detecting part, but not on the driving part.

16. A vibratory gyroscope as claimed in claim 15, wherein the damper is provided on only other regions in which each amplitude of vibration of each point is not less than 0.1 of the maximum amplitude of vibration in the vibrator in the driving vibration mode.

17. A vibratory gyroscope as claimed in claim 15, wherein the vibrator extends in a specified plane and the vibrator has a surface including a pair of main faces extending substantially in parallel with the specified plane and one or more side faces substantially perpendicular to the specified plane, with the damper provided on at least one face selected from the main faces and side faces.

18. A vibratory gyroscope as claimed in claim 17, wherein the damper covers a maximum curvature point on the main face of the detecting part, the point located on the center line of the main face where the curvature of the center line is maximum when the vibrator is deformed in the detection vibration mode.

19. A vibratory gyroscope as claimed in claim 17, wherein the damper covers a maximum stress point on the main face of the detecting part, the point located on the center line of the main face where the stress is maximum in the center line when the vibrator is deformed in the detection vibration mode.

20. A vibratory gyroscope as claimed in claim 17, wherein the vibrator is turned around a turning axis crossing through the specified plane, the vibrator comprises a plurality of vibration systems each extending in the specified plane, the vibration systems include a first vibration system, whose vibration comprises a radial vibration component vibrating in a diametrical direction with respect to the center of gravity in the specified plane, and a second vibration system, whose vibration comprises a circumferential vibration component vibrating circumferentially with respect to the center of gravity in the specified plane, one of the first vibration system and second vibration system comprises the driving part and the other comprises the detecting part.

21. A vibratory gyroscope as claimed in claim 17, wherein the detecting part has a surface including a region where stress induced in the vibrator due to the driving vibration mode is not higher than {fraction (1/10)} of a maximum value of the stress due to the driving vibration mode, with the damper provided on the region.

22. A vibratory gyroscope as claimed in claim 17, wherein the vibrator is composed of a piezoelectric single crystal, and the gyroscope comprises a driving electrode, for electrically exciting the vibration in the driving vibration mode, on the surface of each driving part and a detecting electrode, for detecting the vibration in the detection vibration mode, on the surface of each detecting part.

23. A vibratory gyroscope as claimed in claim 17, wherein the polymer is an elastomer wherein a ratio of a maximum to a minimum of its dynamic viscoelasticity is not more than three times between −

40°

C. to +85°

C.

24. A vibratory gyroscope as claim 15, wherein the detecting part has a surface including a region where stress induced in the vibrator due to the driving vibration mode is not higher than {fraction (1/10)} of a maximum value of the stress due to the driving vibration mode, with the damper provided on the region.

25. A vibratory gyroscope as claimed in claim 15, wherein the vibrator is composed of a piezoelectric single crystal, and the gyroscope comprises a driving electrode, for electrically exciting the vibration in the driving vibration mode, on the surface of each driving part and a detecting electrode, for detecting the vibration in the detection vibration mode, on the surface of each detecting part.

26. A vibratory gyroscope as claimed in claim 25, wherein the detecting part comprises its root, the detecting electrode comprises one edge portion near the root and the damper covers at least the edge portion.

27. A vibratory gyroscope as claimed in claim 15, wherein the polymer is an elastomer wherein a ratio of a maximum to a minimum of its dynamic viscoelasticity is not more than three times between −

40°

C. to +85°

C.