Resonant element

• US 20010002551A1
• Filed: 11/30/2000
• Published: 06/07/2001
• Est. Priority Date: 12/03/1999
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: Ohwada, Kuniki, Kawai, Hiroshi
• Granted Patent: US 6,430,998 B2
• Time in Patent Office: Days
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01P 15/0802 Details

Abstract

A resonant element includes: a fixed substrate having a main surface in orthogonal X- and Z-directions; a planar vibrating body fixed via support beams so as to be vibratable in an X-direction, the planar vibrating body having a weight portion which is isolated from the fixed substrate; an exciter for vibrating the planar vibrating body in the X-direction, and means for adjusting the resonance frequency of said planar vibrating body by providing electrostatic forces to said planar vibrating body, and for correcting the tilt of said planar vibrating body with respect to the substrate plane direction of said fixed substrate, the tilt correcting means being provided at least opposing edge areas of said planar vibrating body with a gap therebetween in the X-direction, on the plane side and spaced from said planar vibrating body in a Y-direction orthogonal to the X- and Z-directions.

Claims

1. A resonant element comprising:

a fixed substrate having a main surface extending in orthogonal X- and Z-directions;

a planar vibrating body connected to the fixed substrate via support beams so as to be vibratable in the X-direction, the planar vibrating body having a resonance frequency and a weight portion which is isolated from the fixed substrate;

an exciter for vibrating the planar vibrating body in the X-direction, and

tilt correcting means providing electrostatic forces to said planar vibrating body to adjust the resonance frequency of said planar vibrating body and to correct the tilt of said planar vibrating body with respect to the main surface of said fixed substrate.

2. A resonant element as claimed in

claim 1

, wherein:

the tilt correcting means is provided at least at opposing edge areas of said planar vibrating body with a gap in the X-direction therebetween and is spaced from said planar vibrating body in a Y-direction orthogonal to said X- and Z-directions.

3. A resonant element as claimed in

claim 1

, wherein:

said planar vibrating body has a frame body disposed above and isolated from the fixed substrate and wherein the weight portion is connected to the inside of said frame body by connection beams.

4. A resonant element as claimed in

claim 1

, wherein:

the tilt correcting means comprises a first tilt correcting element and a second tilt correction element, the first tilt correcting element being provided at least at opposing edge areas of said weight portion with a gap in the X-direction therebetween and being spaced from said planar vibrating body in the Y-direction, and the second tilt correcting element is provided at positions opposed to said frame body and across said first vibrating body tilt correcting means via gaps in the X-direction.

5. A resonant element as claimed in any one of claims 1-4, wherein:

stress canceling means are provided for directly or indirectly applying to said support beams forces in a direction such as to counteract any tensile stresses within said support beams caused by electrostatic attractive forces given to said planar vibrating body by said vibrating body tilt correcting means.

6. A resonant element as claimed in

claim 5

, wherein:

said stress canceling means are provided so as to be opposed to said vibrating body tilt correcting means and so as to sandwich said vibrating body between said stress canceling means and said vibrating body tilt correcting means via gaps.

7. A resonant element as claimed in

claim 6

, wherein:

said stress canceling means are structured and arranged to cancel the tensile stresses within said support beams by providing electrostatic attractive forces to said vibrating body.

8. A resonant element as claimed in any one of claims 1 through 4, wherein:

a vertical movement side electrode is provided on at least one of a front surface and a rear surface of said weight portion, and a fixed opposing electrode is disposed on a side opposed to said vertical movement side electrode and spaced from said weight portion in the Y-direction, the set of said vertical movement side electrode and said fixed opposing electrode functioning as a detecting electrode for detecting a vibration amplitude of said weight portion in the Y-direction due to an angular velocity being applied to said vibrating body about the Z-direction, the vibration amplitude corresponding to variation in the angular velocity of the rotation around the Z-axis.

9. A resonant element as claimed in

claim 8

, wherein:

said stress canceling means are provided so as to be opposed to said vibrating body tilt correcting means and so as to sandwich said vibrating body between said stress canceling means and said vibrating body tilt correcting means via intervals.

10. A resonant element as claimed in

claim 9

, wherein:

said stress canceling means are structured and arranged to cancel the tensile stresses within said support beams by providing electrostatic attractive forces to said vibrating body.

11. A resonant element as claimed in

claim 8

, wherein:

said weight portion is formed of silicon or polysilicon, and serves as the movement side electrode.

12. A method for adjusting the vibration of a resonant element comprising the steps of:

providing a resonant element including a fixed substrate having a main surface extending in orthogonal X- and Z-directions, a planar vibrating body fixed via support beams so as to be vibratable in the X-direction, the planar vibrating body having a resonance frequency and a weight portion which is isolated from the fixed substrate;

an exciter for vibrating the planar vibrating body in the X-direction, and tilt correcting means providing electrostatic forces to said planar vibrating body to adjust the resonance frequency of said planar vibrating body and to correct the tilt of said planar vibrating body with respect to the main surface of said fixed substrate;

detecting a resonance frequency of said planar vibrating body;

adjusting said resonance frequency to a desired value using said tilt correcting means;

detecting tilt of said planar body with respect to the main surface of said fixed substrate; and

correcting the tilt of said planar body with respect to the main surface of said fixed substrate using said tilt correcting means.

13. A method for adjusting the vibration of a resonant element in an angular velocity sensor and then determining angular velocity, comprising:

providing a resonant element including a fixed substrate having a main surface in orthogonal X- and Z-directions, a planar vibrating body fixed via support beams so as to be vibratable in the X-direction, the planar vibrating body having a weight portion which is isolated from the fixed substrate, an exciter for vibrating the planar vibrating body in the X-direction, tilt correcting means for providing electrostatic forces to said planar vibrating body to adjust the resonance frequency of said planar vibrating body and to correct the tilt of said planar vibrating body with respect to the main surface of said fixed substrate, a vertical movement side electrode is on at least one of a front surface and a rear surface of said weight portion, and a fixed opposing electrode is disposed on a side opposed to said vertical movement side electrode and spaced from said weight portion in the Y-direction, the set of said vertical movement side electrode and said fixed opposing electrode functioning as a detecting electrode for detecting a vibration amplitude of said weight portion in the Y-direction due to an angular velocity being applied to said vibrating body about the Z-direction, the vibration amplitude corresponding to variation in the angular velocity of the rotation around the Z-axis;

detecting a resonance frequency of said planar vibrating body;

adjusting said resonance frequency to a desired value using said tilt correcting means;

detecting tilt of said planar body with respect to the main surface of said fixed substrate;

correcting the tilt of said planar body with respect to the main surface of said fixed substrate using said tilt correcting means;

applying an angular velocity to said resonant element about a Y-axis orthogonal to said X- and Z- directions to cause said resonant body to vibrate in the Z-direction due to a Coriolis force; and

detecting the vibrating amplitude of said weight portion in the Y-direction using said detecting electrode to determine the angular velocity of the rotation around the Z-axis.