Multi-axial angular velocity sensor

• US 6,282,956 B1
• Filed: 10/13/1999
• Issued: 09/04/2001
• Est. Priority Date: 12/29/1994
• Status: Expired due to Fees

• Current Assignee: Wacoh Company
• Original Assignee: Kazuhiro Okada
• Inventors: Okada, Kazuhiro
• Primary Examiner(s): MOLLER, RICHARD ALAN
• Application Number:
  US09/417,338
• Time in Patent Office: 692 Days
• Field of Search: 735/040.2, 735/040.3, 735/040.4, 735/041.2
• US Class Current: 73/504.12
• 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 ω x 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 about a Z-axis in an XYZ three-dimensional coordinate system, the sensor comprising:

an oscillator having mass;

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 with at least a degree of freedom along an XY-plane in the coordinate system;

excitation means for oscillating the oscillator linearly in the X-axis direction; and

displacement detecting means for detecting a displacement of the oscillator in a Y-axis direction so that an angular velocity component about the Z-axis can be obtained based on the detected displacement.

2. An angular velocity sensor according to claim 1:

wherein the excitation means comprises capacitance elements including a first electrode provided on a surface of the oscillator and a second electrode provided on a surface of a fixed member fixed to the sensor casing so that the oscillator is oscillated based on Coulomb force by applying an a.c. signal to the capacitance elements.

3. An angular velocity sensor according to claim 1:

wherein the excitation means comprises a piezoelectric element disposed between a surface of the oscillator and a surface of a fixed member fixed to the sensor casing so that the oscillator is oscillated by applying an a.c. signal to the piezoelectric element.

4. An angular velocity sensor according to claim 1:

wherein the excitation means comprises a piezoelectric element disposed on a surface of the flexible member so that the oscillator is oscillated by applying an a.c. signal to the piezoelectric element.

5. An angular velocity sensor according to claim 1:

wherein the oscillator is comprised of magnetic material; and

wherein the excitation means comprises a coil attached to the sensor casing so that the oscillator is oscillated based on magnetic force by applying an a.c. signal to the coil.

6. An angular velocity sensor according to claim 1:

wherein the displacement detecting means comprises capacitance elements including a first electrode provided on a surface of the oscillator and a second electrode provided on a surface of a fixed member fixed to the sensor casing so that a displacement of the oscillator is detected based on a capacitance value of the capacitance elements.

7. An angular velocity sensor according to claim 1:

wherein the displacement detecting means comprises a piezoelectric element disposed between a surface of the oscillator and a surface of a fixed member fixed to the sensor casing so that a displacement of the oscillator is detected based on a voltage produced in the piezoelectric element.

8. An angular velocity sensor according to claim 1:

wherein the displacement detecting means comprises a piezoelectric element disposed on a surface of the flexible member so that a displacement of the oscillator is detected based on a voltage produced in the piezoelectric element.

9. An angular velocity sensor according to claim 1:

wherein the oscillator is comprised of magnetic material; and

wherein the displacement detecting means comprises a coil attached to the sensor casing so that a displacement of the oscillator is detected based on an inductance of the coil.

10. An angular velocity sensor according to claim 1:

wherein the displacement detecting means comprises a piezo resistance element disposed on a surface of the flexible member so that a displacement of the oscillator is detected based on a resistance value of the piezo resistance element.