Angular velocity sensor

• US 6,237,415 B1
• Filed: 02/15/2000
• Issued: 05/29/2001
• 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: Konno, Masashi, Sugawara, Sumio, Atoji, Nobuhisa, Tamura, Masami, Terada, Jiro
• Primary Examiner(s): MOLLER, RICHARD ALAN
• Application Number:
  US09/503,737
• Time in Patent Office: 469 Days
• Field of Search: 73/504.16, 73/504.12, 73/504.02
• 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 comprising four oscillating arms made of ceramic piezoelectric material or crystal material integrally formed with a common support member such that the transition between each of said oscillating arms and said common support member defines a respective root end for each oscillating arm, each of said oscillating arms and a portion of said common support member being polarized along a portion of a length of said angular velocity sensor in a thickness direction or width direction of said angular velocity sensor by an externally applied voltage thereby defining a polarized portion of said angular velocity sensor, wherein said angular velocity sensor is configured such that an outer set of two of said oscillating arms form a driving side tuning fork and an inner set of two of said oscillating arms form a detecting side tuning fork or the inner set of two of said oscillating arms form the driving side tuning fork and the outer set of two of said oscillating arms form the detecting side tuning fork, said angular velocity sensor further comprising driving electrodes divided in two sections along a longitudinal axis of said angular velocity sensor disposed on face and back surfaces of the driving side tuning fork and common support member, and detecting electrodes along said longitudinal axis of said angular velocity sensor disposed on face, back and side surfaces of the detecting side tuning fork and support member, wherein said angular velocity sensor is configured such that an alternating current signal applied to the driving electrodes of the driving side tuning fork generates flexural oscillations in mutually reverse phases in the width direction of said angular velocity sensor and said common support member is mechanically coupled to said detecting side tuning fork to induce flexural vibrations in mutually reverse phases, whereby an electric charge quantity is generated by flexural vibrations in mutually reverse phases in the thickness direction of said annular velocity sensor generated by the Coriolis force based on the rotation angular velocity about said longitudinal axis of said angular velocity sensor applied from outside, wherein said electric charge quantity is detected by the detecting electrodes of the detecting side tuning fork.

2. An angular velocity sensor of claim 1, wherein, for each of said oscillating arms of said driving side tuning fork, said polarized portion of said angular velocity sensor is defined as the sum of about 50% to 80% of a length of a respective oscillating arm of said driving side tuning fork extending from the root end of said respective oscillating arm in a first direction and about a length corresponding to the width of the respective oscillating arm extending from said root end of said respective oscillating arm in a second direction, and for each of said oscillating arms of said detecting side tuning fork, said polarized portion of said angular velocity sensor is defined as the sum of about 50% to 80% of a length of a respective oscillating arm of said detecting side tuning fork extending from the root end of the respective oscillating arm in a first direction and about a first length corresponding to the width of the driving side oscillating arm plus a second length extending from said root end of said respective oscillating arm in a second direction opposite to said first direction, said second length measured by the distance between said root end of an oscillating arm of said driving side tuning fork and said root end of said respective oscillating arm of said detecting side tuning fork.

3. An angular velocity sensor of claim 1, wherein the four oscillating arms and common support member are configured so as to be equal in the resonance frequency in X_D mode of driving side tuning fork and resonance frequency in X_S mode of detecting side tuning fork, and nearly equal in the resonance frequency in Z_S mode generated by Coriolis force.

4. An angular velocity sensor of claim 1, wherein the four oscillating arms and common support member are configured so as to be equal in the resonance frequency in X_D mode of driving side tuning fork and resonance frequency in X_S mode of detecting side tuning fork, and different in the resonance frequency in Z_S mode generated by Coriolis force.

5. An angular velocity sensor of claim 1, wherein the four oscillating arms and common support member are configured so that the resonance frequency in X_D mode of driving side tuning fork may be different from the resonance frequency in X_S mode of detecting side tuning fork, and nearly equal to the resonance frequency in Z_S mode generated by Coriolis force.

6. An angular velocity sensor of claim 1, wherein a notch or a tiny hole is provided in a lower part of the common support member for holding or mounting said angular velocity sensor, said notch or tiny hole positioned on a nodal line of oscillation in a length direction of the detecting side tuning fork.

7. An angular velocity sensor of claim 1, further comprising a constant AC current control circuit for applying an AC signal to one driving electrode of one oscillating arm of the driving side tuning fork, and holding constant the amplitude of said AC signal in X_D mode induced in a monitor electrode, said monitor electrode is a functional expression of the other driving electrode of the other oscillating arm of the driving side tuning fork.

8. An angular velocity sensor of claim 7, wherein a timing signal for detecting and extracting the AC signal induced in said monitor electrode by the rotational angular velocity about the the longitudinal axis of said angular velocity sensor applied from outside is generated from a zero cross signal of the AC signal induced on the monitor electrode.

9. An angular velocity sensor comprising:

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

a support member coupled to each of said at least four oscillating arms;

at least two driving electrodes coupled to said driving side tuning fork; and

at least two detecting electrodes coupled to said detecting side tuning fork,

wherein only a portion of said angular velocity sensor is polarized.

10. The angular velocity sensor of claim 9, wherein said at least two driving electrodes and said at least two detecting electrodes are coupled only to said portion of said angular velocity sensor.

11. The angular velocity sensor of claim 9, wherein said portion of said angular velocity sensor includes a portion of said support member and a portion of each of said at least four oscillating arms.

12. The angular velocity sensor of claim 9, wherein said angular velocity sensor is formed from a ceramic piezoelectric material.

13. The angular velocity sensor of claim 9, wherein said at least two driving electrodes and said at least two detecting electrodes are coupled to a portion of said support member.

14. The angular velocity sensor of claim 9, further comprising a controller, said controller configured to apply a drive voltage to said angular velocity sensor such that a oscillation level of said angular velocity sensor is kept constant.

15. The angular velocity sensor of claim 9, wherein said at least four oscillating arms comprise at least two outer oscillating arms and at least two inner oscillating arms.

16. The angular velocity sensor of claim 15, wherein said at least two outer oscillating arms comprise the driving side tuning fork and said at least two inner oscillating arms comprise the detecting side tuning fork, and further wherein said at least two outer oscillating arms have a larger volume than said at least two inner oscillating arms.

17. The angular velocity sensor of claim 15, wherein said at least two outer oscillating arms comprise the detecting side tuning fork and said at least two inner oscillating arms comprise the driving side tuning fork, and further wherein said at least two inner oscillating arms have a larger volume than said at least two outer oscillating arms.