Dynamic amount sensor

• US 7,886,597 B2
• Filed: 02/06/2007
• Issued: 02/15/2011
• Est. Priority Date: 02/14/2006
• Status: Active Grant

• Current Assignee: Seiko Instruments Incorporated (Seiko Group)
• Original Assignee: Seiko Instruments Incorporated (Seiko Group)
• Inventors: Egawa, Akira, Uchiyama, Takeshi, Yarita, Mitsuo
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US11/703,017
• Publication Number:
  US 20070240509A1
• Time in Patent Office: 1,470 Days
• Field of Search: 735/041.2, 735/143.2, 361/280
• 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 1/023 for acceleration measuring devices
• 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

A dynamic amount sensor has a detecting circuit that detects a change in an electrostatic capacitance of each of electrostatic capacitance elements comprised of a movable electrode and a fixed electrode. A switching circuit switches the detecting circuit to first and second connecting states that detect changes in the electrostatic capacitance of the electrostatic capacitance elements in accordance with a change in an attitude of the movable electrode in corresponding first and second detecting axes directions. In the first and second connecting states, the detecting circuit includes circuits formed by connecting the electrostatic capacitance elements in series which change electrostatic capacitances symmetrically along with inclination of the movable electrode in the corresponding first and second detecting axes directions. A carrier wave applying circuit applies carrier waves whose phases are inverted from each other by 180° to the electrostatic capacitance elements which are connected in series in the first and second connecting states of the detecting circuit.

Claims

1. A dynamic amount sensor comprising:

a frame having a hollow portion;

a plurality of flexible beams connected to the frame;

a mass supported on the frame by way of the flexible beams, a surface portion of the mass functioning as a movable electrode and changing an attitude thereof corresponding to an external force;

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

detecting means for detecting a change in an electrostatic capacitance of each of a plurality of electrostatic capacitance elements comprised of the movable electrode and a respective fixed electrode;

switching means for switching the detecting means to a first connecting state forming a first detecting circuit that detects a change in the electrostatic capacitance of the electrostatic capacitance elements in accordance with a change in an attitude of the surface portion of the mass in a first detecting axis direction, and for switching the detecting means to a second connecting state forming a second detecting circuit that detects a change in the electrostatic capacitance of the electrostatic capacitance elements in accordance with a change in an attitude of the surface portion of the mass in a second detecting axis direction; and

dynamic amount outputting means for outputting, in accordance with a detection result by the detecting means in the first and second connecting states, components of a dynamic amount acting on the surface portion of the mass in the first detecting axis direction and the second detecting axis direction;

wherein the first detecting circuit includes a circuit formed by connecting at least a first electrostatic capacitance element in series with at least a second electrostatic capacitance element, the first and second electrostatic capacitance elements changing electrostatic capacitances along with an inclination of the mass in the first detecting axis direction such that when the electrostatic capacitance of the first electrostatic capacitance element increases the electrostatic capacitance of the second electrostatic capacitance element decreases;

wherein the second detecting circuit includes a circuit formed by connecting at least a first electrostatic capacitance element in series with at least a second electrostatic capacitance element, the first and second electrostatic capacitance elements of the second detecting circuit changing electrostatic capacitances along with an inclination of the mass in the second detecting axis direction such that, for the second detecting circuit, when the electrostatic capacitance of the first electrostatic capacitance element increases the electrostatic capacitance of the second electrostatic capacitance element decreases; and

further comprising carrier wave applying means for applying carrier waves whose phases are inverted from each other by 180°

to the respective first and second electrostatic capacitance elements which are connected in series in the first detecting circuit and the second detecting circuit.

2. A dynamic amount sensor according to claim 1;

wherein the detecting means includes a third detecting circuit formed by connecting at least a first electrostatic capacitance element in series with at least a second electrostatic capacitance element, the first and second electrostatic capacitance elements of the third detecting circuit changing electrostatic capacitances along with a displacement of the mass in a third detecting axis direction thereof such that, for the third detecting circuit, when the electrostatic capacitance of the first electrostatic capacitance element increases the electrostatic capacitance of the second electrostatic capacitance element decreases; and

wherein the carrier wave applying means applies the carrier waves to the respective first and second electrostatic capacitance elements which are connected in series in the third detecting circuit.

3. A dynamic amount sensor according to claim 1;

wherein the dynamic amount outputting means separates detecting signals of the electrostatic capacitances of the respective first and second detecting circuits after a lapse of a predetermined time from a timing at which the switching means performs a switching operation.

4. A dynamic amount sensor according to claim 3;

wherein the predetermined time is set to a value which falls within a range of 3 through 4τ

from the timing of the switching operation by the switching means, where τ

is a time constant.

5. A dynamic amount sensor according to claim 1;

wherein the switching means switches the detecting means to a third connecting state forming a third detecting circuit that detects a change in the electrostatic capacitance of the electrostatic capacitance elements in accordance with a change in an attitude of the surface portion of the mass in a third detecting axis direction; and

wherein the dynamic amount outputting means outputs, in accordance with a detection result by the detecting means in the first, second, and third connecting states, components of a dynamic amount acting on the surface portion of the mass in the first detecting axis direction, the second detecting axis direction, and the third axis detecting direction.

6. A dynamic amount sensor according to claim 5;

wherein the third detecting circuit includes a circuit formed by connecting at least a first electrostatic capacitance element in series with at least a second electrostatic capacitance element, the first and second electrostatic capacitance elements of the third detecting circuit changing electrostatic capacitances along with a displacement of the mass in the third detecting axis direction; and

wherein the carrier wave applying means applies the carrier waves to the first and second electrostatic capacitance elements which are connected in series in the third detecting circuit.

10. A dynamic amount sensor according to claim 5;

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

wherein the switching means switches the detecting means at each constant period based on timing of a control clock signal; and

wherein in response to output signals from the amplifier circuit, the dynamic amount outputting means outputs the dynamic amount acting on the mass in the first, second and third detecting axes directions after separating the output detection signals from one another by performing time division processing in accordance with switching timing by the switching means.

11. A dynamic amount sensor according to claim 10;

wherein the third detecting circuit includes a circuit formed by connecting at least a first electrostatic capacitance element in series with at least a second electrostatic capacitance element, the first and second electrostatic capacitance elements of the third detecting circuit changing electrostatic capacitances along with a displacement of the mass in the third detecting axis direction; and

wherein the carrier wave applying means applies the carrier waves to the first and second electrostatic capacitance elements which are connected in series in the third detecting circuit.

12. A dynamic amount sensor according to claim 1;

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

wherein the switching means switches the detecting means at each constant period based on timing of a control clock signal; and

wherein in response to output signals from the amplifier circuit, the dynamic amount outputting means outputs the dynamic amount acting on the mass in the first and second detecting axes directions after separating the output detection signals from one another by performing time division processing in accordance with switching timing by the switching means.

13. A dynamic amount sensor according to claim 12;

further comprising a third detecting circuit including a circuit formed by connecting at least a first electrostatic capacitance element in series with at least a second electrostatic capacitance element, the first and second electrostatic capacitance elements of the third detecting circuit changing electrostatic capacitances along with an inclination of the mass in a third detecting axis direction such that, for the third detecting circuit, when the electrostatic capacitance of the first electrostatic capacitance element increases the electrostatic capacitance of the second electrostatic capacitance element decreases; and

wherein the carrier wave applying means applies the carrier waves to the first and second electrostatic capacitance elements which are connected in series in the third detecting circuit.

14. A dynamic amount sensor according to claim 12;

wherein the dynamic amount outputting means separates detecting signals of the electrostatic capacitances of the respective first and second detecting circuits after a lapse of a predetermined time from a timing at which the switching means performs a switching operation.

15. A dynamic amount sensor according to claim 14;

wherein the predetermined time is set to a value which falls within a range of 3 through 4τ

from the timing of the switching operation by the switching means, where τ

is a time constant.

7. A dynamic amount sensor according to 5;

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;

wherein the circuit of the first detection circuit includes first and second circuit portions connected in series, the first circuit portion being formed by connecting in parallel one of the electrostatic capacitance elements comprised of the movable electrode and a first of the four first electrodes positioned in a first quadrant on an x-y plane with one of the electrostatic capacitance elements comprised of the movable electrode and a second of the four first electrodes positioned in a second quadrant on the x-y plane, the second circuit portion being formed by connecting in parallel one of the electrostatic capacitance elements comprised of the movable electrode and a third of the four first electrodes positioned in a fourth quadrant on the x-y plane with one of the electrostatic capacitance elements comprised of the movable electrode and a fourth of the four first electrodes positioned in a third quadrant on the x-y plane;

wherein the circuit of the second detection circuit includes first and second circuit portions connected in series, the first circuit portion being formed by connecting in parallel the electrostatic capacitance element comprised of the movable electrode and the first of the four first electrodes positioned in the first quadrant on the x-y plane with the electrostatic capacitance element comprised of the movable electrode and the third of the four first electrodes positioned in the fourth quadrant on the x-y plane, the second circuit portion being formed by connecting in parallel the electrostatic capacitance element comprised of the movable electrode and the fourth of the four first electrodes positioned in the third quadrant on the x-y plane and the electrostatic capacitance element comprised of the movable electrode and the second of the four first electrodes positioned in the second quadrant on the x-y plane; and

wherein the switching means switches the first detection circuit and the second detection circuit by switching wire connecting states of the electrostatic capacitance elements.

8. A dynamic amount sensor according to 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;

wherein the circuit of the first detection circuit connects in parallel one of the electrostatic capacitance elements comprised of the movable electrode and a first of the four second electrodes positioned in the fourth quadrant on the x-y plane and one of the electrostatic capacitance elements comprised of the movable electrode and a second of the four second electrodes positioned in the third quadrant on the x-y plane with the electrostatic capacitance element comprised of the movable electrode and the first of the four first electrodes positioned in the first quadrant on the x-y plane, and connects in parallel one of the electrostatic capacitance elements comprised of the movable electrode and a third of the four second electrodes positioned in the first quadrant on the x-y plane and one of the electrostatic capacitance elements comprised of the movable electrode and a fourth of the four second electrodes positioned in the second quadrant on the x-y plane with the electrostatic capacitance element comprised of the movable electrode and the fourth of the first electrodes positioned in the third quadrant on the x-y plane; and

wherein the circuit of the second detection circuit connects in parallel the electrostatic capacitance element comprised of the movable electrode and the third of the four second electrodes positioned in the first quadrant on the x-y plane and the electrostatic capacitance element comprised of the movable electrode and the first of the four second electrodes positioned in the fourth quadrant on the x-y plane with the electrostatic capacitance element comprised of the movable electrode and the fourth of the four first electrodes positioned in the third quadrant on the x-y plane, and connects in parallel the electrostatic capacitance element comprised of the movable electrode and the second of the four second electrodes positioned in the third quadrant on the x-y plane and the electrostatic capacitance element comprised of the movable electrode and the fourth of the four second electrodes positioned in the second quadrant on the x-y plane with the electrostatic capacitance element comprised of the movable electrode and the first of the four first electrodes positioned in the first quadrant on the x-y plane.

9. A dynamic amount sensor according to 7;

wherein the fixed electrodes comprise a third electrode on a plane which face the first four electrodes in an opposed manner by way of the mass; and

wherein the third detecting circuit includes a circuit formed by connecting in series the electrostatic capacitance element comprised of the movable electrode and one of the four first electrodes and the electrostatic capacitance element comprised of the movable electrode and the third electrode.

16. A dynamic amount sensor comprising:

a frame having a hollow portion;

a plurality of flexible beams connected to the frame;

a mass supported on the frame by way of the flexible beams, a surface portion of the mass functioning as a movable electrode and changing an attitude thereof corresponding to an external force;

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

detecting means for detecting a change in an electrostatic capacitance of each of a plurality of electrostatic capacitance elements comprised of the movable electrode and a respective fixed electrode;

switching means for switching the detecting means to a first connecting state forming a first detecting circuit that detects a change in the electrostatic capacitance of the electrostatic capacitance elements in accordance with a change in an attitude of the surface portion of the mass in a first detecting axis direction, and for switching the detecting means to a second connecting state forming a second detecting circuit that detects a change in the electrostatic capacitance of the electrostatic capacitance elements in accordance with a change in an attitude of the surface portion of the mass in a second detecting axis direction; and

dynamic amount outputting means for outputting, in accordance with a detection result by the detecting means in the first and second connecting states, components of a dynamic amount acting on the surface portion of the mass in the first detecting axis direction and the second detecting axis direction;

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;

wherein the circuit of the first detection circuit includes first and second circuit portions connected in series, the first circuit portion being formed by connecting in parallel one of the electrostatic capacitance elements comprised of the movable electrode and a first of the four first electrodes positioned in a first quadrant on an x-y plane with one of the electrostatic capacitance elements comprised of the movable electrode and a second of the four first electrodes positioned in a second quadrant on the x-y plane, the second circuit portion being formed by connecting in parallel one of the electrostatic capacitance elements comprised of the movable electrode and a third of the four first electrodes positioned in a fourth quadrant on the x-y plane with one of the electrostatic capacitance elements comprised of the movable electrode and a fourth of the four first electrodes positioned in a third quadrant on the x-y plane;

wherein the circuit of the second detection circuit includes first and second circuit portions connected in series, the first circuit portion being formed by connecting in parallel the electrostatic capacitance element comprised of the movable electrode and the first of the four first electrodes positioned in the first quadrant on the x-y plane with the electrostatic capacitance element comprised of the movable electrode and the third of the four first electrodes positioned in the fourth quadrant on the x-y plane, the second circuit portion being formed by connecting in parallel the electrostatic capacitance element comprised of the movable electrode and the fourth of the four first electrodes positioned in the third quadrant on the x-y plane and the electrostatic capacitance element comprised of the movable electrode and the second of the four first electrodes positioned in the second quadrant on the x-y plane; and

wherein the switching means switches the first detection circuit and the second detection circuit by switching wire connecting states of the electrostatic capacitance elements.

17. A dynamic amount sensor according to 16;

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;

wherein the circuit of the first detection circuit connects in parallel one of the electrostatic capacitance elements comprised of the movable electrode and a first of the four second electrodes positioned in the fourth quadrant on the x-y plane and one of the electrostatic capacitance elements comprised of the movable electrode and a second of the four second electrodes positioned in the third quadrant on the x-y plane with the electrostatic capacitance element comprised of the movable electrode and the first of the four first electrodes positioned in the first quadrant on the x-y plane, and connects in parallel one of the electrostatic capacitance elements comprised of the movable electrode and a third of the four second electrodes positioned in the first quadrant on the x-y plane and one of the electrostatic capacitance elements comprised of the movable electrode and a fourth of the four second electrodes positioned in the second quadrant on the x-y plane with the electrostatic capacitance element comprised of the movable electrode and the fourth of the first electrodes positioned in the third quadrant on the x-y plane; and

wherein the circuit of the second detection circuit connects in parallel the electrostatic capacitance element comprised of the movable electrode and the third of the four second electrodes positioned in the first quadrant on the x-y plane and the electrostatic capacitance element comprised of the movable electrode and the first of the four second electrodes positioned in the fourth quadrant on the x-y plane with the electrostatic capacitance element comprised of the movable electrode and the fourth of the four first electrodes positioned in the third quadrant on the x-y plane, and connects in parallel the electrostatic capacitance element comprised of the movable electrode and the second of the four second electrodes positioned in the third quadrant on the x-y plane and the electrostatic capacitance element comprised of the movable electrode and the fourth of the four second electrodes positioned in the second quadrant on the x-y plane with the electrostatic capacitance element comprised of the movable electrode and the first of the four first electrodes positioned in the first quadrant on the x-y plane.

18. A dynamic amount sensor according to 16;

wherein the fixed electrodes comprise a third electrode on a plane which face the first four electrodes in an opposed manner by way of the mass; and

wherein the third detecting circuit includes a circuit formed by connecting in series the electrostatic capacitance element comprised of the movable electrode and one of the four first electrodes and the electrostatic capacitance element comprised of the movable electrode and the third electrode.