Angular velocity sensor

• US 6,298,723 B1
• Filed: 02/15/2000
• Issued: 10/09/2001
• Est. Priority Date: 04/04/1995
• Status: Expired due to Term

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Tamura, Masami, Terada, Jiro, Konno, Masashi, Sugawara, Sumio, Atoji, Nobuhisa
• Primary Examiner(s): MOLLER, RICHARD ALAN
• Application Number:
  US09/503,727
• Time in Patent Office: 602 Days
• Field of Search: 73/504.16
• 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

The invention relates to an angular velocity sensor used in posture control of a moving element or navigation system, and is intended to realize higher sensitivity, lower offset, lower offset drift, lower translation acceleration sensitivity, and higher impact resistance in a small size and at low cost.

Being made of ceramic piezoelectric material or crystal material, the constitution comprises four parallel oscillating arms 12 to 15, or 112 to 115, and a support member 11, or 111 for supporting one end of the oscillating arms or both ends commonly, in which outer two oscillating arms 12, 15, or 112, 115 of a compound tuning fork 10, or 110 in a comb shape of which position of the inside root of two oscillating arms each on inside and outside to the support member 11, or 111 in the oscillating arm direction is matched or different are used in the driving side tuning for, while inner two oscillating arms 13, 14, or 113, 114 are used in the detecting side tuning fork so as to correspond between driving and detection.

Claims

1. An angular velocity sensor formed from crystal material having crystal axes, said crystal axes including an electrical axis, a mechanical axis, and an optical axis,

said angular velocity sensor comprising four parallel oscillating arms and a first and second support member for commonly holding the four parallel oscillating arms at both ends of each of the four parallel oscillating arms,

said angular velocity sensor configured such that a base of said annular velocity sensor extending along a width of said angular velocity sensor is positioned on said electrical axis, a direction along a length of said angular velocity sensor forms an angle θ

with said mechanical axis and a direction along a depth of said angular velocity sensor forms the same angle θ

with said optical axis,

two of said four oscillating arms defining a driving side tuning fork and the other two of said four oscillating arms defining a detecting side tuning fork,

wherein each of the two oscillating arms of the detecting side tuning fork being cut in a middle portion of a respective oscillating arm such that each of said two oscillating arms of said detecting side tuning fork comprises a first and a second oscillating arm, said first oscillating arm of each of said two oscillating arms of said detecting side tuning fork extending from said first support member and said second oscillating arm of each of said two oscillating arms of said detecting side tuning fork extending from said second support member,

each of said first and second oscillating arms of each of said two oscillating arms of said detecting side tuning fork being positioned either outside or inside of said two oscillating arms of said driving side tuning fork,

said angular velocity sensor further comprising driving electrodes positioned on face and back surfaces or side surfaces of the driving side tuning fork and detecting electrodes positioned on face and back surfaces or side surfaces of the detecting side tuning fork such that applying an alternating-current power to the driving electrodes in either or both oscillating arms of the driving side tuning fork generates and maintains a width direction flexural oscillation in mutually reverse phases on the driving side tuning fork,

wherein when an angular velocity vector rotating and acting on the entire angular velocity sensor is applied from outside, said angular velocity sensor detects an electric charge generated in the detecting electrodes by a thickness direction flexural oscillation in mutually reverse phases on the detecting side tuning fork induced from a driving force of a thickness direction component of Coriolis force acting in an oscillating portion in the width direction of the driving side tuning fork or detecting side tuning fork, thereby obtaining an electrical signal in proportion to an input angular velocity.

2. An angular velocity sensor of claim 1, wherein the angle θ

may be zero degrees.

3. An angular velocity sensor of claim 1, wherein said angular velocity sensor is configured so that resonance frequency of width direction flexural oscillation in mutually reverse phases of driving side tuning fork and the resonance frequency of width direction flexural oscillation in mutually reverse phases of detecting side tuning fork are nearly equal, and that the resonance frequency of thickness direction flexural oscillation in mutually reverse phases of detecting side tuning fork may be also nearly equal.

4. An angular velocity sensor of claim 1, wherein said angular velocity sensor is configured so that the resonance frequency of width direction flexural oscillation in mutually reverse phases of driving side tuning fork and resonance frequency of width direction flexural oscillation in mutually reverse phases of detecting side tuning fork may be nearly equal, and that the resonance frequency of thickness direction flexural oscillation in mutually reverse phases of detecting side tuning fork may be different.

5. An angular velocity sensor of claim 1, wherein said annular velocity sensor is configured so that the resonance frequency of width direction flexural oscillation in mutually reverse phases of driving side tuning fork and resonance frequency of thickness direction flexural oscillation in mutually reverse phases of detecting side tuning fork may be nearly equal, and that the resonance frequency of width direction flexural oscillation in mutually reverse phases of detecting side tuning fork may be different.

6. An angular velocity sensor of claim 1, wherein said angular velocity sensor is configured so that the resonance frequency of thickness direction flexural oscillation in mutually reverse phases of driving side tuning fork and resonance frequency of thickness direction flexural oscillation in mutually reverse phases of detecting side tuning fork may be nearly equal to each other.

7. An angular velocity sensor of claim 1, wherein the first and second support members either possess a connection region coupled to an external supporting member so as to be symmetrical on the basis of a center line for symmetry of the angular velocity sensor in a plane defined by the width and length of the angular velocity sensor, or possess a hole structure or a protrusion structure for a symmetrical connection with the external supporting member.

8. An angular velocity sensor of claim 1, further comprising an amplitude control circuit for applying an alternating-current electric signal on a driving electrode on one oscillating arm of the driving side tuning fork, and holding constant the effective value of the alternating-current electric signal on the basis of width direction flexural oscillation in mutually reverse phases of driving side tuning fork induced on a driving electrode on the other oscillating arm of said driving side tuning fork.

9. An angular velocity sensor of claim 8, wherein a timing signal for detecting and extracting an angular velocity signal on the basis of an electric charge generated in a detecting electrode of said detecting side tuning fork upon input of an angular velocity from among other disturbance signals, is generated by said alternating-current electric signal.

10. An angular velocity sensor formed from a crystal material, comprising:

six oscillating arms, wherein two of said oscillating arms form a driving side tuning fork and four of said oscillating arms form a detecting side tuning fork;

first and second support members for coupling to said six oscillating members, wherein said six oscillating members are positioned between said first and second support members;

driving electrodes for coupling to said driving side tuning fork and adapted to receive an AC power signal; and

detecting electrodes for coupling to said detecting side tuning fork and adapted to output a detecting signal corresponding to an input angular velocity.

11. The angular velocity sensor of claim 10, wherein the driving side tuning fork is positioned outside of said detecting side tuning fork.

12. The angular velocity sensor of claim 10, wherein the driving side tuning fork is positioned inside of said detecting side tuning fork.

13. The angular velocity sensor of claim 10, wherein the two oscillating arms of said driving side tuning fork extend from the first support member to the second support member, and two of said four oscillating arms of the detecting side tuning fork extend from the first support member such that each of said two oscillating arms define a free end, and the other two of said four oscillating arms of the detecting side tuning fork extend from the second support member such that each of said other two oscillating arms define a free end.

14. The angular velocity sensor of claim 13, wherein the free end of each of said two oscillating arms faces a respective free end of each of said other two oscillating arms.

15. The angular velocity sensor of claim 10, wherein said first and second support members each include a first and second hole, respectively, adapted to be coupled to an external support member.

16. The angular velocity sensor of claim 15, wherein said first and second holes are positioned on a center line of said angular velocity sensor.