Angular velocity sensor having one amplifying circuit for amplifying plural detection signals

• US 7,444,870 B2
• Filed: 01/19/2007
• Issued: 11/04/2008
• Est. Priority Date: 02/07/2006
• Status: Expired due to Fees

• Current Assignee: Seiko Instruments Incorporated (Seiko Group)
• Original Assignee: Seiko Instruments Incorporated (Seiko Group)
• Inventors: Egawa, Akira, Uchiyama, Takeshi, Yarita, Mitsuo
• Primary Examiner(s): Kwok; Helen C.
• Application Number:
  US11/655,576
• Publication Number:
  US 20070180909A1
• Time in Patent Office: 655 Days
• Field of Search: 735/040.2, 735/040.4, 735/041.2, 735/041.4, 735/041.5, 735/041.6
• 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 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 2015/0842 the mass being of clover leaf shape

Abstract

An angular velocity sensor amplifies a plurality of detection signals using one amplifying circuit and separates these detection signals after amplification. The angular velocity sensor detects displacements of a mass in the axial directions using x-, y- and z-axis detection circuits. A carrier wave whose phase is shifted 90° from that of a carrier wave of the z-axis detection circuit is applied to the x- and y-axis detection circuits and outputs of the axis detection circuits are collectively inputted to a current/voltage conversion circuit which outputs a combined signal to three synchronous detection circuits that separate the signal into x-, y- and z-axis detection signal components. In the synchronous detection circuits, by applying phase division processing to the combined signal, the z-axis detection signal component is separated from cross axis detection signal components and by applying time division processing to the signal components based on switching timing of the carrier wave, the x- and y-axis detection signal components are separated from each other.

Claims

1. An angular velocity sensor comprising:

a frame having a hollow portion;

a mass which is supported on the frame by way of resilient beams which are formed in an x-axis direction and a y-axis direction orthogonal to each other, has a thickness in a z-axis direction orthogonal to the x axis and the y axis respectively, wherein a surface portion of the mass functions as a movable electrode and changes a posture thereof corresponding to an external force;

a plurality of fixed electrodes which are arranged to face the mass in an opposed manner;

a first detection circuit which detects a change of electrostatic capacitance between the fixed electrodes and the movable electrode along with an inclination of the mass in the y-axis direction;

a second detection circuit which detects a change of electrostatic capacitance between the fixed electrodes and the movable electrode along with an inclination of the mass in the x-axis direction;

a third detection circuit which detects a change of electrostatic capacitance between the fixed electrodes and the movable electrode along with a displacement of the mass in the z-axis direction;

a phase shifting means which shifts a phase of a carrier wave which is applied to the third detection circuit by 90°

from a phase of a carrier wave which is applied to the first detection circuit and the second detection circuit;

a switching means which alternately performs the application of carrier wave to the first detection circuit and the second detection circuit based on timing of a control clock signal by switching the application for every fixed cycle;

an amplifying circuit to which output signals from the first detection circuit, the second detection circuit and the third detection circuit are inputted;

a first separation means which separates an angular velocity component signal which is constituted of a first detection signal indicative of the change of the electrostatic capacitance in the first detection circuit and a second detection signal indicative of the change of the electrostatic capacitance in the second detection circuit and a third detection signal indicative of the change of the electrostatic capacitance in the third detection circuit from each other by performing phase division processing based on the timing of the control clock signal in response to the output signals from the amplifying circuit;

a second separation means which separates the first detection signal and the second detection signal from each other by performing a time division processing based on switching timing of the carrier wave by the switching means in response to the angular velocity component signal;

an angular velocity output means which outputs an angular velocity acting about the x axis of the mass in response to the first detection signal and outputs an angular velocity acting about the y axis direction of the mass in response to the second detection signal; and

a driving means which oscillates the mass in the z-axis direction while performing a position control in response to the third detection signal.

2. An angular velocity sensor according to claim 1, wherein

the first detection circuit includes a circuit which is formed by connecting two electrostatic capacitance elements in series which change electrostatic capacitances symmetrically along with the inclination of the mass in the y-axis direction out of electrostatic capacitance elements which are constituted of the fixed electrodes and the movable electrode;

the second detection circuit includes a circuit which is formed by connecting two electrostatic capacitance elements in series which change electrostatic capacitances symmetrically along with the inclination of the mass in the x-axis direction out of electrostatic capacitance elements which are constituted of the fixed electrodes and the movable electrode;

the third detection circuit includes a circuit which is formed by connecting an electrostatic capacitance element which changes electrostatic capacitance along with the displacement of the mass in the z-axis direction and a specific electrostatic capacitance elements in series out of electrostatic capacitance elements which are constituted of the fixed electrodes and the movable electrode; and

the angular velocity sensor further includes a carrier wave applying means which applies carrier waves whose phases are inverted from each other by 1800 to the respective electrostatic capacitance elements which are connected in series in the first detection circuit, the second detection circuit and the third detection circuit.

3. An angular velocity sensor according to claim 1, wherein the second separation means, after a lapse of a predetermined time from the timing of switching of the carrier wave by the switching means, separates the first detection signal or the second detection signal.

4. An angular velocity sensor according to claim 2, wherein the second separation means, after a lapse of a predetermined time from the timing of switching of the carrier wave by the switching means, separates the first detection signal or the second detection signal.

5. An angular velocity sensor according to claim 1, wherein the fixed electrodes include four first electrodes which, using a center position of mass as a reference position, are arranged equidistantly around the reference position on the same plane,

the first detection circuit includes a circuit in which a circuit which is formed by connecting an electrostatic capacitance element which is constituted of the first electrode positioned in a first quadrant on an x-y plane out of four first electrodes and the movable electrode and an electrostatic capacitance element which is constituted of a first electrode positioned in a second quadrant on the x-y plane out of four first electrodes and the movable electrode in parallel, and a circuit which is formed by connecting an electrostatic capacitance element which is constituted of the first electrode positioned in a fourth quadrant on an x-y plane out of four first electrodes and the movable electrode and an electrostatic capacitance element which is constituted of a first electrode positioned in a third quadrant on the x-y plane out of four first electrodes and the movable electrode in parallel are connected in series, and

the second detection circuit includes a circuit in which a circuit which is formed by connecting the electrostatic capacitance element which is constituted of the first electrode positioned in the first quadrant on an x-y plane out of four first electrodes and the movable electrode and the electrostatic capacitance element which is constituted of the first electrode positioned in the fourth quadrant on the x-y plane out of four first electrodes and the movable electrode in parallel, and a circuit which is formed by connecting the electrostatic capacitance element which is constituted of the first electrode positioned in the third quadrant on the x-y plane out of four first electrodes and the movable electrode and the electrostatic capacitance element which is constituted of the first electrode positioned in the second quadrant on the x-y plane out of four first electrodes and the movable electrode in parallel are connected in series, and

the switching means switches wirings of the first detection circuit and the second detection circuit.

6. An angular velocity sensor according to claim 2, wherein the fixed electrodes include four first electrodes which, using a center position of mass as a reference position, are arranged equidistantly around the reference position on the same plane,

the first detection circuit includes a circuit in which a circuit which is formed by connecting an electrostatic capacitance element which is constituted of the first electrode positioned in a first quadrant on an x-y plane out of four first electrodes and the movable electrode and an electrostatic capacitance element which is constituted of a first electrode positioned in a second quadrant on the x-y plane out of four first electrodes and the movable electrode in parallel, and a circuit which is formed by connecting an electrostatic capacitance element which is constituted of the first electrode positioned in a fourth quadrant on an x-y plane out of four first electrodes and the movable electrode and an electrostatic capacitance element which is constituted of a first electrode positioned in a third quadrant on the x-y plane out of four first electrodes and the movable electrode in parallel are connected in series, and

the second detection circuit includes a circuit in which a circuit which is formed by connecting the electrostatic capacitance element which is constituted of the first electrode positioned in the first quadrant on an x-y plane out of four first electrodes and the movable electrode and the electrostatic capacitance element which is constituted of the first electrode positioned in the fourth quadrant on the x-y plane out of four first electrodes and the movable electrode in parallel, and a circuit which is formed by connecting the electrostatic capacitance element which is constituted of the first electrode positioned in the third quadrant on the x-y plane out of four first electrodes and the movable electrode and the electrostatic capacitance element which is constituted of the first electrode positioned in the second quadrant on the x-y plane out of four first electrodes and the movable electrode in parallel are connected in series, and

the switching means switches wirings of the first detection circuit and the second detection circuit.

7. An angular velocity sensor according to claim 3, wherein the fixed electrodes include four first electrodes which, using a center position of mass as a reference position, are arranged equidistantly around the reference position on the same plane,

the first detection circuit includes a circuit in which a circuit which is formed by connecting an electrostatic capacitance element which is constituted of the first electrode positioned in a first quadrant on an x-y plane out of four first electrodes and the movable electrode and an electrostatic capacitance element which is constituted of a first electrode positioned in a second quadrant on the x-y plane out of four first electrodes and the movable electrode in parallel, and a circuit which is formed by connecting an electrostatic capacitance element which is constituted of the first electrode positioned in a fourth quadrant on an x-y plane out of four first electrodes and the movable electrode and an electrostatic capacitance element which is constituted of a first electrode positioned in a third quadrant on the x-y plane out of four first electrodes and the movable electrode in parallel are connected in series, and

the second detection circuit includes a circuit in which a circuit which is formed by connecting the electrostatic capacitance element which is constituted of the first electrode positioned in the first quadrant on an x-y plane out of four first electrodes and the movable electrode and the electrostatic capacitance element which is constituted of the first electrode positioned in the fourth quadrant on the x-y plane out of four first electrodes and the movable electrode in parallel, and a circuit which is formed by connecting the electrostatic capacitance element which is constituted of the first electrode positioned in the third quadrant on the x-y plane out of four first electrodes and the movable electrode and the electrostatic capacitance element which is constituted of the first electrode positioned in the second quadrant on the x-y plane out of four first electrodes and the movable electrode in parallel are connected in series, and

the switching means switches wirings of the first detection circuit and the second detection circuit.

8. An angular velocity sensor according to claim 4, wherein the fixed electrodes include four first electrodes which, using a center position of mass as a reference position, are arranged equidistantly around the reference position on the same plane,

the first detection circuit includes a circuit in which a circuit which is formed by connecting an electrostatic capacitance element which is constituted of the first electrode positioned in a first quadrant on an x-y plane out of four first electrodes and the movable electrode and an electrostatic capacitance element which is constituted of a first electrode positioned in a second quadrant on the x-y plane out of four first electrodes and the movable electrode in parallel, and a circuit which is formed by connecting an electrostatic capacitance element which is constituted of the first electrode positioned in a fourth quadrant on an x-y plane out of four first electrodes and the movable electrode and an electrostatic capacitance element which is constituted of a first electrode positioned in a third quadrant on the x-y plane out of four first electrodes and the movable electrode in parallel are connected in series, and

the second detection circuit includes a circuit in which a circuit which is formed by connecting the electrostatic capacitance element which is constituted of the first electrode positioned in the first quadrant on an x-y plane out of four first electrodes and the movable electrode and the electrostatic capacitance element which is constituted of the first electrode positioned in the fourth quadrant on the x-y plane out of four first electrodes and the movable electrode in parallel, and a circuit which is formed by connecting the electrostatic capacitance element which is constituted of the first electrode positioned in the third quadrant on the x-y plane out of four first electrodes and the movable electrode and the electrostatic capacitance element which is constituted of the first electrode positioned in the second quadrant on the x-y plane out of four first electrodes and the movable electrode in parallel are connected in series, and

the switching means switches wirings of the first detection circuit and the second detection circuit.

9. An angular velocity sensor according to claim 5, wherein the fixed electrodes further include four second electrodes on a plane which face the four first electrodes in an opposed manner by way of the mass,

the first detection circuit includes a circuit which connects an electrostatic capacitance element which is constituted of the second electrode positioned in the fourth quadrant on an x-y plane out of four second electrodes and the movable electrode and an electrostatic capacitance element which is constituted of the second electrode positioned in the third quadrant on the x-y plane out of four second electrodes and the movable electrode with an electrostatic capacitance element which is constituted of the first electrode positioned in the first quadrant on the x-y plane out of four first electrodes and the movable electrode in parallel, and connects an electrostatic capacitance element which is constituted of the second electrode positioned in the first quadrant on an x-y plane out of four second electrodes and the movable electrode and an electrostatic capacitance element which is constituted of the second electrode positioned in the second quadrant on the x-y plane out of four second electrodes and the movable electrode with an electrostatic capacitance element which is constituted of the first electrode positioned in the third quadrant on the x-y plane out of four first electrodes and the movable electrode in parallel,

the second detection circuit includes a circuit which connects an electrostatic capacitance element which is constituted of the second electrode positioned in the first quadrant on the x-y plane out of four second electrodes and the movable electrode and an electrostatic capacitance element which is constituted of the second electrode positioned in the fourth quadrant on the x-y plane out of four second electrodes and the movable electrode with an electrostatic capacitance element which is constituted of the first electrode positioned in the third quadrant on the x-y plane out of four first electrodes and the movable electrode in parallel, and connects an electrostatic capacitance element which is constituted of the second electrode positioned in the third quadrant on the x-y plane out of four second electrodes and the movable electrode, and an electrostatic capacitance element which is constituted of the second electrode positioned in the second quadrant on the x-y plane out of four second electrodes and the movable electrode with an electrostatic capacitance element which is constituted of the first electrode positioned in the first quadrant on the x-y plane out of four first electrodes and the movable electrode in parallel.

10. An angular velocity sensor according to claim 6, wherein the fixed electrodes further include four second electrodes on a plane which face the four first electrodes in an opposed manner by way of the mass,

the first detection circuit includes a circuit which connects an electrostatic capacitance element which is constituted of the second electrode positioned in the fourth quadrant on an x-y plane out of four second electrodes and the movable electrode and an electrostatic capacitance element which is constituted of the second electrode positioned in the third quadrant on the x-y plane out of four second electrodes and the movable electrode with an electrostatic capacitance element which is constituted of the first electrode positioned in the first quadrant on the x-y plane out of four first electrodes and the movable electrode in parallel, and connects an electrostatic capacitance element which is constituted of the second electrode positioned in the first quadrant on an x-y plane out of four second electrodes and the movable electrode and an electrostatic capacitance element which is constituted of the second electrode positioned in the second quadrant on the x-y plane out of four second electrodes and the movable electrode with an electrostatic capacitance element which is constituted of the first electrode positioned in the third quadrant on the x-y plane out of four first electrodes and the movable electrode in parallel,

the second detection circuit includes a circuit which connects an electrostatic capacitance element which is constituted of the second electrode positioned in the first quadrant on the x-y plane out of four second electrodes and the movable electrode and an electrostatic capacitance element which is constituted of the second electrode positioned in the fourth quadrant on the x-y plane out of four second electrodes and the movable electrode with an electrostatic capacitance element which is constituted of the first electrode positioned in the third quadrant on the x-y plane out of four first electrodes and the movable electrode in parallel, and connects an electrostatic capacitance element which is constituted of the second electrode positioned in the third quadrant on the x-y plane out of four second electrodes and the movable electrode and an electrostatic capacitance element which is constituted of the second electrode positioned in the second quadrant on the x-y plane out of four second electrodes and the movable electrode with an electrostatic capacitance element which is constituted of the first electrode positioned in the first quadrant on the x-y plane out of four first electrodes and the movable electrode in parallel.

11. An angular velocity sensor according to claim 7, wherein the fixed electrodes further include four second electrodes on a plane which face the four first electrodes in an opposed manner by way of the mass,

the first detection circuit includes a circuit which connects an electrostatic capacitance element which is constituted of the second electrode positioned in the fourth quadrant on an x-y plane out of four second electrodes and the movable electrode and an electrostatic capacitance element which is constituted of the second electrode positioned in the third quadrant on the x-y plane out of four second electrodes and the movable electrode with an electrostatic capacitance element which is constituted of the first electrode positioned in the first quadrant on the x-y plane out of four first electrodes and the movable electrode in parallel, and connects an electrostatic capacitance element which is constituted of the second electrode positioned in the first quadrant on an x-y plane out of four second electrodes and the movable electrode and an electrostatic capacitance element which is constituted of the second electrode positioned in the second quadrant on the x-y plane out of four second electrodes and the movable electrode with an electrostatic capacitance element which is constituted of the first electrode positioned in the third quadrant on the x-y plane out of four first electrodes and the movable electrode in parallel,

the second detection circuit includes a circuit which connects an electrostatic capacitance element which is constituted of the second electrode positioned in the first quadrant on the x-y plane out of four second electrodes and the movable electrode and an electrostatic capacitance element which is constituted of the second electrode positioned in the fourth quadrant on the x-y plane out of four second electrodes and the movable electrode with an electrostatic capacitance element which is constituted of the first electrode positioned in the third quadrant on the x-y plane out of four first electrodes and the movable electrode in parallel, and connects an electrostatic capacitance element which is constituted of the second electrode positioned in the third quadrant on the x-y plane out of four second electrodes and the movable electrode and an electrostatic capacitance element which is constituted of the second electrode positioned in the second quadrant on the x-y plane out of four second electrodes and the movable electrode with an electrostatic capacitance element which is constituted of the first electrode positioned in the first quadrant on the x-y plane out of four first electrodes and the movable electrode in parallel.

12. An angular velocity sensor according to claim 8, wherein the fixed electrodes further include four second electrodes on a plane which face the four first electrodes in an opposed manner by way of the mass,

the first detection circuit includes a circuit which connects an electrostatic capacitance element which is constituted of the second electrode positioned in the fourth quadrant on an x-y plane out of four first electrodes and the movable electrode and an electrostatic capacitance element which is constituted of the second electrode positioned in the third quadrant on the x-y plane out of four second electrodes and the movable electrode with an electrostatic capacitance element which is constituted of the first electrode positioned in the first quadrant on the x-y plane out of four second electrodes and the movable electrode in parallel, and connects an electrostatic capacitance element which is constituted of the second electrode positioned in the first quadrant on an x-y plane out of four second electrodes and the movable electrode and an electrostatic capacitance element which is constituted of the second electrode positioned in the second quadrant on the x-y plane out of four second electrodes and the movable electrode with an electrostatic capacitance element which is constituted of the first electrode positioned in the third quadrant on the x-y plane out of four first electrodes and the movable electrode in parallel,

the second detection circuit includes a circuit which connects an electrostatic capacitance element which is constituted of the second electrode positioned in the first quadrant on the x-y plane out of four second electrodes and the movable electrode and an electrostatic capacitance element which is constituted of the second electrode positioned in the fourth quadrant on the x-y plane out of four second electrodes and the movable electrode with an electrostatic capacitance element which is constituted of the first electrode positioned in the third quadrant on the x-y plane out of four second electrodes and the movable electrode in parallel, and connects an electrostatic capacitance element which is constituted of the second electrode positioned in the third quadrant on the x-y plane out of four first electrodes and the movable electrode and an electrostatic capacitance element which is constituted of the second electrode positioned in the second quadrant on the x-y plane out of four second electrodes and the movable electrode with an electrostatic capacitance element which is constituted of the first electrode positioned in the first quadrant on the x-y plane out of four first electrodes and the movable electrode in parallel.

13. An angular velocity sensor according to claim 1, wherein the first separation means, after a lapse of a predetermined time from the timing at which the carrier waves are switched by the switching means, separates the third detection signal.

14. An angular velocity sensor according to claim 2, wherein the first separation means, after a lapse of a predetermined time from the timing at which the carrier waves are switched by the switching means, separates the third detection signal.

15. An angular velocity sensor according to claim 3, wherein the first separation means, after a lapse of a predetermined time from the timing at which the carrier waves are switched by the switching means, separates the third detection signal.

16. An angular velocity sensor according to claim 4, wherein the first separation means, after a lapse of a predetermined time from the timing at which the carrier waves are switched by the switching means, separates the third detection signal.

17. An angular velocity sensor according to claim 5, wherein the first separation means, after a lapse of a predetermined time from the timing at which the carrier waves are switched by the switching means, separates the third detection signal.

18. An angular velocity sensor according to claim 9, wherein the first separation means, after a lapse of a predetermined time from the timing at which the carrier waves are switched by the switching means, separates the third detection signal.

19. An angular velocity sensor according to claim 3, wherein the predetermined time is set to a value which falls within a range from 3 to 4τ

from the timing at which the carrier waves are switched by the switching means.

20. An angular velocity sensor according to claim 13, wherein the predetermined time is set to a value which falls within a range from 3 to 4τ

from the timing at which the carrier waves are switched by the switching means.