Angular velocity sensor

• US 20030066350A1
• Filed: 04/22/2002
• Published: 04/10/2003
• Est. Priority Date: 10/09/2001
• Status: Active Grant

• Current Assignee: Fujitsu Limited, Fujitsu Media Devices Limited (Fujitsu Limited)
• Original Assignee: Fujitsu Limited
• Inventors: Ishikawa, Hiroshi, Warashina, Suguru, Machida, Atsushi, Satoh, Yoshio, Miyashita, Tsutomu
• Granted Patent: US 7,188,525 B2
• Time in Patent Office: Days
• US Class Current: 73/504.15
• CPC Class Codes: G01C 19/5607 using vibrating tuning forks double-ended tuning forks using planar vibrating masses suspended at opposite ends G01C19/5719
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details

Abstract

An angular velocity sensor is provided that includes a frame, an oscillator and torsion bars that connect the oscillator to the frame. The frame, the oscillator and the torsion bar are formed integral with each other by etching a material substrate in the thickness direction of the substrate. The oscillator, configured in the form of an H, includes a support, two first arms and two second arms. These arms extend from the support in an arm-extending direction perpendicular to the thickness direction of the substrate. The oscillator includes a mounting surface that is provided with a piezoelectric driver for generating in-plane oscillation of the oscillator, and with a piezoelectric detector for detecting out-of-plane oscillation of the oscillator.

Claims

1. An angular velocity sensor comprising:

a frame;

an oscillator; and

a first torsion bar that connects the oscillator to the frame;

wherein the frame, the oscillator and the torsion bar are formed integral with each other by etching a material substrate in a thickness direction of the substrate;

wherein the oscillator has an H-like form made up of a support, a pair of first arms and a pair of second arms, the first arms extending from the support in an arm-extending direction perpendicular to the thickness direction of the substrate, the second arms extending from the support oppositely to the first arms; and

wherein the oscillator includes a mounting surface that is provided with a piezoelectric driver for generating in-plane oscillation of the oscillator, and with a piezoelectric detector for detecting out-of-plane oscillation of the oscillator.

2. The sensor according to claim 1, wherein the oscillator is symmetrical with respect to each of two imaginary planes which are parallel to the arm-extending direction and perpendicular to each other.

3. The sensor according to claim 1, wherein the piezoelectric driver is provided on the first arms, the piezoelectric detector being provided on the second arms.

4. The sensor according to claim 1, wherein the piezoelectric driver is provided at a crotch defined by the paired first arms and the support.

5. The sensor according to claim 1, wherein the piezoelectric driver comprises a plurality of driving piezoelectric elements disposed symmetrically with respect to an imaginary line extending in the arm-extending direction.

6. The sensor according to claim 1, wherein at least one of the piezoelectric driver and the piezoelectric detector includes a piezoelectric film and a pair of electrodes sandwiching the piezoelectric film, the piezoelectric film being formed by one of vapor deposition, spattering and printing.

7. The sensor according to claim 1, wherein at least one of the piezoelectric driver and the piezoelectric detector includes a piezoelectric member and a pair of electrodes sandwiching the piezoelectric member, the piezoelectric member being formed by mechanical processing.

8. The sensor according to claim 1, wherein the substrate is a low-resistance substrate, at least one of the piezoelectric driver and the piezoelectric detector being provided on the oscillator via an insulating film.

9. The sensor according to claim 1, wherein the substrate is a high-resistance substrate, at least one of the piezoelectric driver and the piezoelectric detector being provided directly on the oscillator without an insulator.

10. The sensor according to claim 1, wherein the arm-extending direction is parallel to the frame, the paired first arms being spaced from each other by a first distance, the paired second arms being spaced from each other by a second distance, the first arms being spaced from the frame by a third distance, the second arms being spaced from the frame by a fourth distance, the first, second, third and fourth distances being equal to each other.

11. The sensor according to claim 1, further comprising a wiring pattern extending on the frame and the torsion bar to connect to at least one of the piezoelectric driver and the piezoelectric detector.

12. The sensor according to claim 1, wherein the substrate is provided with a driving circuit electrically connected to the piezoelectric driver, and with a detecting circuit electrically connected to the piezoelectric detector.

13. The sensor according to claim 1, wherein each of the first arms and the second arms has a tip formed with a thick region.

14. The sensor according to claim 1, wherein each of the first arms and the second arms has a tip provided with a weight.

15. The sensor according to claim 1, wherein the first and the second arms are shorter than the support in the arm-extending direction.

16. The sensor according to claim 1, wherein the torsion bar connects the support of the oscillator and the frame to each other.

17. The sensor according to claim 1, wherein the torsion bar has a thickness no greater than a thickness of the substrate.

18. The sensor according to claim 1, wherein the torsion bar has a cross section perpendicular to a longitudinal direction of the torsion bar, the cross section being symmetrical with respect to two lines perpendicular to each other.

19. The sensor according to claim 1, further comprising a second torsion bar that connects the oscillator to the frame, wherein the first and the second torsion bars in combination have a center of gravity that coincides with a center of gravity of the oscillator.

20. A method of making an angular velocity sensor that includes an H-like oscillator provided with a pair of first parallel arms and a pair of second parallel arms, the sensor also including a frame that supports the oscillator via a torsion bar, the method comprising the steps of:

forming a resist pattern on a material substrate; and

etching the substrate via the resist pattern;

wherein the resist pattern includes a primary resist and an etching control resist, the primary resist being formed with an opening in which the etching control resist is disposed; and

wherein the etching control resist is spaced from the primary resist by a constant distance.

21. The method according to claim 20, wherein the primary resist masks a substrate portion corresponding to the frame, the oscillator and the torsion bar, the etching control resist masking another substrate portion between the frame and the oscillator.

22. The method according to claim 20, wherein said constant distance is equal to a distance by which the first arms are spaced from each other.

23. The method according to claim 20, wherein the resist pattern includes a connecting portion that connects the etching control resist to the primary resist.