ANGULAR VELOCITY SENSOR AND ELECTRONIC DEVICE

• US 20080105052A1
• Filed: 10/30/2007
• Published: 05/08/2008
• Est. Priority Date: 10/30/2006
• Status: Active Grant

• Current Assignee: Sony Semiconductor Solutions Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Takahashi, Kazuo, Honda, Junichi, Inaguma, Teruo
• Granted Patent: US 7,673,512 B2
• Time in Patent Office: Days
• US Class Current: 73/504.16
• 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

An angular velocity sensor includes a base portion, three arm portions that extend as one piece from the base portion to an approximately same direction, a piezoelectric film formed on one surface of each of the arm portions, drive electrodes for excitation formed on the piezoelectric films of at least two outer arm portions, and detection electrodes for angular velocity detection formed on the piezoelectric film of at least a center arm portion. Among the three arm portions, the two outer arm portions are excited in phase, and the center arm portion is excited in opposite phase with the two outer arm portions. The drive electrodes excite the arm portions in a first direction vertical to surfaces on which the piezoelectric films are formed. The detection electrodes detect a vibration in a second direction parallel to the surfaces on which the piezoelectric films of the arm portions are formed.

Claims

1. An angular velocity sensor, comprising:

a base portion;

three arm portions that extend as one piece from the base portion to an approximately same direction;

a piezoelectric film formed on one surface of each of the arm portions;

drive electrodes for excitation formed on the piezoelectric films of at least two arm portions that are positioned on outer sides, among the three arm portions; and

detection electrodes for angular velocity detection formed on the piezoelectric film of at least a centrally-positioned arm portion, among the three arm portions, wherein

among the three arm portions, the two arm portions that are positioned on outer sides are excited in phase, and the centrally-positioned arm portion is excited in opposite phase with the two arm portions that are positioned on outer sides,

the drive electrodes are excited the arm portions in a first direction vertical to surfaces on which the piezoelectric films are formed, and

the detection electrodes detect a vibration in a second direction parallel to the surfaces on which the piezoelectric films of the arm portions are formed.

2. The angular velocity sensor according to claim 1, wherein among the three arm portions, the centrally-positioned arm portion is provided with a vibration plummet.

3. The angular velocity sensor according to claim 1, wherein a formation width of the centrally-positioned arm portion, among the three arm portions, is formed to be larger than that of the two arm portions that are positioned on outer sides.

4. The angular velocity sensor according to claim 1, wherein the three arm portions have a same resonant frequency in the first direction, and among resonant frequencies of the three arm portions in the second direction, only the resonant frequency of the centrally-positioned arm portion is set near the resonant frequency in the first direction.

5. The angular velocity sensor according to claim 1, wherein on the piezoelectric film of the centrally-positioned arm portion, among the three arm portions, a reference electrode that detects a vibration characteristic of the arm portion is formed.

6. The angular velocity sensor according to claim 1, wherein the detection electrodes are formed in pair on the piezoelectric film of the centrally-positioned arm portion, among the three arm portions, symmetrically about an axis of the arm portion, the detection electrode on one side is formed continuously from the arm portion via the base portion to the outer arm portion on that side, and the detection electrode on the other side is formed continuously from the arm portion via the base portion to the outer arm portion on that side.

7. The angular velocity sensor according to claim 1, wherein the base portion is formed with a plurality of external connecting terminals for inputting and outputting a signal to each of the arm portions, and each of the external connecting terminals is formed on one surface of the base portion at a position of minimum vibration between the three arm portions.

8. The angular velocity sensor according to claim 7, wherein each of the external connecting terminals is formed in a position deviated from an extended line of an axis of each of the arm portions.

9. The angular velocity sensor according to claim 7, wherein the base portion is provided with a cushioning portion having a width smaller than the formation width of the base portion between a root region of each of the arm portions and a formation area of the external connecting terminals.

10. An angular velocity sensor, comprising:

a first arm portion that includes a first drive electrode and is excited in a first direction by piezoelectric drive;

a second arm portion including a second drive electrode, arranged to extend in a length direction of the first arm portion, and being excited in the first direction in phase with the first arm portion by piezoelectric drive;

a third arm portion including detection electrodes for detecting Coriolis force acted in a second direction perpendicular to the first direction and the length direction, arranged to extend in the length direction between the first arm portion and the second arm portion, and being excited in opposite phase with the first and the second arm portions by counteraction of excitation of the first and second arm portions, and

a base portion that supports the first, second, and third arm portions.

11. The angular velocity sensor according to claim 10, wherein the third arm portion includes a vibration plummet.

12. The angular velocity sensor according to claim 10, wherein the first and second arm portions are formed in the second direction by a first width, and the third arm portion is formed in the second direction by a second width, which is larger than the first width.

13. The angular velocity sensor according to claim 10, wherein the first, second, and third arm portions have a same resonant frequency in the first direction, and the third arm portion has, in the second direction, a resonant frequency different from the resonant frequency in the first direction.

14. The angular velocity sensor according to claim 10, wherein the third arm portion includes a reference electrode that detects a vibration characteristic of the third arm portion.

15. The angular velocity sensor according to claim 10, wherein:

the third arm portion includes, as the detection electrodes,

a first detection electrode, and

a second electrode disposed symmetrically to the first detection electrode about an axis of the first direction of the third arm portion;

the first arm portion includes a third detection electrode that detects Coriolis force acted on the first arm portion;

the second arm portion includes a fourth detection electrode that detects Coriolis force acted on the second arm portion; and

the base portion includes

a first relay electrode that connects the first detection electrode and the third detection electrode; and

a second relay electrode that connects the second detection electrode and the fourth detection electrode.

16. The angular velocity sensor according to claim 10, further comprising:

a plurality of external connecting terminals, each of which is disposed in a position on the base portion where vibrations transmitted from the first, second, and third arm portions are minimum, for external connection of the first drive electrode, the second drive electrode, and the detection electrodes.

17. The angular velocity sensor according to claim 16, wherein the plurality of external connecting terminals are disposed in positions deviated from respective extended lines of axes in the first direction of the first, second, and third arm portions.

18. The angular velocity sensor according to claim 10, wherein the base portion comprises:

a support portion that supports the first, second, and third arm portions;

a fixing portion, including external connecting terminals for external connection of the first drive electrode, the second drive electrode, and the detection electrodes, formed in the second direction by a first width; and

a connection portion, formed in the second direction by a second width smaller than the first width, for connecting the support portion and the fixing portion.

19. The angular velocity sensor according to claim 18, wherein a following relationship is satisfied:

0.25≦

(f0/fv)≦

1/√

{square root over (2)}

where

fv is a resonant frequency of a first vibration system in the first direction of the first and second arm portions, the vibration system including the first, second, and third arm portions, and the support portion, and

f0 is a resonant frequency of a second vibration system in the first direction, the vibration system including the first, second, and third arm portions, the support portion, and the connection portion.

20. The angular velocity sensor according to claim 10, wherein the first and the second arm portions are excited by a first resonant frequency, and the third arm portion includes a vibration system of a second resonant frequency lower by 1 kHz to 2 kHz than the first resonant frequency.

21. An angular velocity sensor, comprising:

a first arm portion that includes a first drive electrode and is excited in a first direction by piezoelectric drive;

a second arm portion including a second drive electrode, arranged to extend in a length direction of the first arm portion, and being excited in the first direction in phase with the first arm portion by piezoelectric drive;

a third arm portion including detection electrodes for detecting Coriolis force acted in a second direction perpendicular to the first direction and the length direction, arranged to extend in the length direction between the first arm portion and the second arm portion, and being excited by piezoelectric drive in opposite phase with the first and the second arm portions, and

a base portion that supports the first, second, and third arm portions.

22. The angular velocity sensor according to claim 21, wherein:

the third arm portion includes, as the detection electrodes,

a first detection electrode, and

a second electrode disposed symmetrically to the first detection electrode about an axis of the first direction of the third arm portion;

the first arm portion includes a third detection electrode that detects Coriolis force acted on the first arm portion;

the second arm portion includes a fourth detection electrode that detects Coriolis force acted on the second arm portion; and

the angular velocity sensor further includes

a controller that calculates a first sum signal of an output signal from the first detection electrode and an output signal from the third detection electrode, and a second sum signal of an output signal from the second detection electrode and an output signal from the fourth detection electrode, respectively, and that detects a differential signal of the first sum signal and the second sum signal as a angular velocity signal.

23. An electronic device, comprising:

a main body; and

an angular velocity sensor,

wherein the angular velocity sensor includes;

a first arm portion, including a first drive electrode, that is excited in a first direction by piezoelectric drive;

a second arm portion, including a second drive electrode, arranged to extend in a length direction of the first arm portion, and being excited by piezoelectric drive in the first direction in phase with the first arm portion;

a third arm portion, including detection electrodes that detect Coriolis force acted in a second direction perpendicular to the first direction and the length direction, arranged to extend in the length direction between the first arm portion and the second arm portion, and vibrating in opposite phase with vibrations of the first and second arm portions by counteraction of excitation of the first and second arm portions; and

a base portion that supports the first, second, and third arm portions, and

wherein the angular velocity sensor is disposed within the main body.

24. An electronic device, comprising:

a main body; and

an angular velocity sensor,

wherein the angular velocity sensor includes;

a first arm portion that includes a first drive electrode and is excited in a first direction by piezoelectric drive;

a second arm portion including a second drive electrode, arranged to extend in a length direction of the first arm portion, and being excited in the first direction in phase with the first arm portion by piezoelectric drive;

a third arm portion including detection electrodes for detecting Coriolis force acted in a second direction perpendicular to the first direction and the length direction, arranged to extend in the length direction between the first arm portion and the second arm portion, and being excited by piezoelectric drive in opposite phase with the first and the second arm portions, and

a base portion that supports the first, second, and third arm portions, and

wherein the angular velocity sensor is disposed within the main body.