Angular velocity sensor

• US 6,367,326 B1
• Filed: 04/12/2000
• Issued: 04/09/2002
• Est. Priority Date: 07/10/1996
• Status: Expired due to Fees

• Current Assignee: Wacoh Company
• Original Assignee: Wacoh Company
• Inventors: Okada, Kazuhiro
• Primary Examiner(s): Chapman, John E.
• Application Number:
  US09/547,799
• Time in Patent Office: 727 Days
• Field of Search: 735/041.2, 735/041.5, 735/041.6, 735/040.3, 735/040.4, 735/040.8, 735/10, 735/143.9
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/5712 the devices involving a micromechanical structure
• CPC Class Codes: G01P 3/16 by using centrifugal forces of solid masses governors G05D13/10

Abstract

A pivotal shaft (130) is provided along the Z-axis on a semiconductor substrate (100), whose upper surface extends along the XY-plane, to fit a rotor (200) consisting of dielectric material. The rotor is supported by the pivotal shaft so that it can be inclined and can be rotated. The peripheral portion of the rotor constitutes weight bodies (211, 212), and stators (111, 115) consisting of conductive material are disposed at the periphery thereof. When a.c. voltages of predetermined period are delivered to the stators, the rotor is rotated while floating in accordance with the principle of the induction motor. When angular velocity ωx about the X-axis is applied to the substrate 100, Corioli'"'"'s force Fcz in the Z-axis positive direction is applied to the weight body (211) passing through the X-axis with velocity component in the Y-axis positive direction so that it becomes away from-the substrate. Corioli'"'"'s force −Fcz in the Z-axis negative direction is applied to the weight body (212) passing through the X-axis with velocity component in the Y-axis negative direction so that it becomes close the substrate. Capacitance elements C1, C2 are formed by fixed electrodes (141AB, 142AB) on the substrate and movement electrodes (231, 232) on the rotor. Difference between electrostatic capacitance values of both the capacitance elements is obtained to detect magnitude of applied Corioli'"'"'s force. The magnitude of the detected Corioli'"'"'s force is outputted as a value of angular velocity ωx about the X-axis. Even under the environment where acceleration is applied, the acceleration component is canceled by obtaining difference.

Claims

1. An angular velocity sensor comprising:

a substrate having an upper surface in an XY plane of an XYZ three dimensional coordinate system;

a first weight body, a second weight body, a third weight body and a fourth weight body for carrying out rotational movement about a Z-axis of said coordinates system in a non-contact state with respect to the upper surface of the substrate, said Z-axis being perpendicular to said upper surface and constituting an axis of rotation for said weight bodies and said weight bodies being supported so that respective weight bodies can move independently;

energy supply means for delivering energy to the first weight body so that the first weight body carries out a reversal rotational movement to traverse the positive X-axis in the clockwise and counterclockwise directions alternately while maintaining a fixed distance with respect to the upper surface of the substrate when no external force is applied, for delivering energy to the second weight body so that the second weight body carries out a reversal rotational movement to traverse the negative X-axis in the clockwise and counterclockwise directions alternately while maintaining a fixed distance with respect to the upper surface of the substrate when no external force is applied, for delivering energy to the third weight body so that the third weight body carries out a reversal rotational movement to traverse the positive Y-axis in the clockwise and counterclockwise directions alternately while maintaining a fixed distance with respect to the upper surface of the substrate when no external force is applied, and for delivering energy to the fourth weight body so that the fourth weight body carries out a reversal rotational movement to traverse the negative Y-axis in the clockwise and counterclockwise directions alternately while maintaining a fixed distance with respect to the upper surface of the substrate when no external force is applied, the rotational direction of the reversal rotational movement of the first weight body and the rotational direction of the reversal rotational movement of the second weight body being the same, the rotational direction of the reversal rotational movement of the third weight body and the rotational direction of the reversal rotational movement of the fourth weight body being the same and a rotational direction of the reversal rotational movement of the first and the second weight bodies and a rotational direction of the reversal rotational movement of the third and the fourth weight bodies being opposite;

distance above positive X-axis measurement means for measuring a distance between the upper surface of the substrate and the first weight body when the first weight body passes above the positive X-axis; and

distance above negative X-axis measurement means for measuring a distance between the upper surface of the substrate and the second weight body when the second weight body passes above the negative X-axis;

distance above positive Y-axis measurement means for measuring a distance between the upper surface of the substrate and the third weight body when the third weight body passes above the positive Y-axis;

distance above negative Y-axis measurement means for measuring a distance between the upper surface of the substrate and the fourth weight body when the fourth weight body passes above the negative Y-axis;

first difference calculation means for obtaining a difference between a distance measured by the distance above positive X-axis measurement means and a distance measured by the distance above negative X-axis measurement means; and

second difference calculation means for obtaining a difference between a distance measured by the distance above positive Y-axis measurement means and a distance measured by the distance above negative Y-axis measurement means;

thereby to detect an angular velocity about the X-axis applied to the substrate on the basis of a difference obtained by the first difference calculation means and to detect an angular velocity about the Y-axis on the basis of a difference obtained by the second difference calculation means.

2. An angular velocity sensor as set forth in claim 1:

wherein the first weight body, the second weight body, the third weight body and the fourth weight body are coupled through an intermediate member so that when the first weight body is positioned above the positive X-axis, the second weight body is positioned above the negative X-axis, the third weight body is positioned above the positive Y-axis and the fourth weight body is positioned above the negative Y-axis.

3. An angular velocity sensor as set forth in claim 1:

wherein a supporting body made of material capable of producing torsion about the Z-axis is secured on the upper surface of the substrate to support the weight bodies.

4. An angular velocity sensor as set forth in claim 1:

wherein the plural weight bodies have the same mass and shape.

5. An angular velocity sensor as set forth in claim 1:

wherein at least a portion of the weight bodies is constituted with dielectric substance; and

wherein the energy supply means comprises a plurality of electrodes disposed along an orbit of the rotational movement of the weight bodies and a voltage supply circuit for supplying, to the plurality of electrodes, a.c. voltages of which phases are different from each other.

6. An angular velocity sensor as set forth in claim 1, wherein said weight bodies are so arranged that said first and second weight bodies move as a pair in one direction and said third and fourth weight bodies move as a second pair in the opposite direction whereby to reduce torsional vibrations.