Angular velocity sensor

• US 7,059,188 B2
• Filed: 05/23/2005
• Issued: 06/13/2006
• Est. Priority Date: 03/30/1993
• Status: Expired due to Fees

• Current Assignee: Wacoh Company
• Original Assignee: Kazuhiro Okada
• Inventors: Okada, Kazuhiro
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US11/135,078
• Publication Number:
  US 20050210981A1
• Time in Patent Office: 386 Days
• Field of Search: 7350412-50415, 735/040.2, 735/040.3, 735/040.4, 735/143.2, 735/143.4, 738/620.42, 738/620.43
• US Class Current: 73/504.02
• CPC Class Codes: G01C 19/56 Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces
• CPC Class Codes: G01P 15/0907 of the compression mode type
• CPC Class Codes: G01P 15/0922 of the bending or flexing mode type
• CPC Class Codes: G01P 15/11 by inductive pick-up
• CPC Class Codes: G01P 15/123 by piezo-resistive elements, e.g. semiconductor strain gauges
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 2015/084 the mass being suspended at more than one of its sides, e.g. membrane-type suspension, so as to permit multi-axis movement of the mass

Abstract

A flexible substrate (110) having flexibility and a fixed substrate (120) disposed so as to oppose it are supported at their peripheral portions by a sensor casing (140). An oscillator (130) is fixed on the lower surface of the flexible substrate. Five lower electrode layers (F1 to F5: F1 and F2 are disposed at front and back of F5) are formed on the upper surface of the flexible substrate. Five upper electrode layers (E1 to E5) are formed on the lower surface of the fixed substrate so as to oppose the lower electrodes. In the case of detecting an angular velocity ωx about the X-axis, an a.c. voltage is applied across a predetermined pair of opposite electrode layers (E5, F5) to allow the oscillator to undergo oscillation Uz in the Z-axis direction. Thus, a Coriolis force Fy proportional to the angular velocity ωx is applied to the oscillator in the Y-axis. By this Coriolis force Fy, the oscillator is caused to undergo displacement in the Y-axis direction. As a result, the distance between opposite electrode layers (E3, F3) arranged in the positive direction of the Y-axis becomes smaller, and the distance between opposite electrode layers (E4, F4) arranged in the negative direction of the Y-axis becomes greater. Thus, capacitance value C3 increases and capacitance value C4 decreases. By change of the capacitance value, it is possible to detect the magnitude of the Coriolis force Fy, and to determine angular velocity ωx. Similarly, it is possible to detect an angular velocity ωy about the Y-axis and an angular velocity ωz about the Z-axis.

Claims

1. An angular velocity sensor for detecting an angular velocity component comprising:

an oscillator made of a substrate with an enough thickness to obtain a mass sufficient to provide the sensor with a required sensitivity;

a sensor casing for accommodating the oscillator therewithin;

a flexible member for connecting the oscillator to the sensor casing so that the oscillator can be moved with respect to the sensor casing;

an electrical driving device for oscillating the oscillator using electrical energy, said electrical driving device including a first electrode provided on the oscillator, a second electrode provided on a fixed member fixed to the sensor casing and an excitation element applying a voltage between said first electrode and said second electrode; and

a capacitance element including a pair of electrodes, a distance between said pair of electrodes being changed based on a deviation of the oscillator caused by Coriolis force.

2. An angular velocity sensor according to claim 1, wherein the oscillator is made of a silicon substrate.