Angular velocity sensor

• US 6,076,401 A
• Filed: 03/02/1998
• Issued: 06/20/2000
• Est. Priority Date: 07/10/1996
• Status: Expired due to Term

• Current Assignee: Wacoh Company
• Original Assignee: Wacoh Company
• Inventors: Okada, Kazuhiro
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US09/029,471
• Time in Patent Office: 841 Days
• Field of Search: 73/504.12, 73/504.16, 73/504.15, 73/504.03, 73/504.04, 73/504.08, 73/514.39, 73/510
• 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 shaft (270) 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 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, Coriolis 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 moves away from the substrate. Coriolis 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 moves 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 and a second weight body which carry out rotational movement about a Z-axis of said coordinate 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;

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 direction and in the counterclockwise direction 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 second weight body so that the second weight body carries out a reversal rotational movement to traverse the negative X-axis in the clockwise direction and in the counterclockwise direction alternately while maintaining a fixed distance with respect to the upper surface of the substrate when no external force is applied;

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, wherein said distance above positive X-axis measurement means comprises a first fixed electrode and a second fixed electrode formed on the upper surface of the substrate disposed adjacent to each other in a vicinity of the positive X-axis, an electrically unitary first movement electrode formed on a lower surface of the first weight body which can be apposed to both the first fixed electrode and the second fixed electrode, and a first detection circuit for detecting an electrostatic capacitance value between said first fixed electrode and said second fixed electrode to obtain a distance between the upper surface of the substrate and the first weight body; 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, wherein said distance above negative X-axis measurement means comprises a third fixed electrode and a fourth fixed electrode formed on the upper surface of the substrate disposed adjacent to each other in a vicinity of the negative X-axis, an electrically unitary second movement electrode formed on a lower surface of the second weight body which can be opposed to both the third fixed electrode and the fourth fixed electrode, and a second detection circuit for detecting an electrostatic capacitance value between said third fixed electrode and said fourth fixed electrode to obtain a distance between the upper surface of the substrate and the second weight body;

thereby to detect an angular velocity about the X-axis applied to the substrate on the basis of 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.

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

wherein the energy supply means delivers energy to the first weight body and the second weight body so that a rotational direction of the reversal rotational movement of the first weight body and a rotational direction of the reversal rotational movement of the second weight body are the same;

and

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

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