Oscillating micro-mechanical sensor of angular velocity

• US 7,325,451 B2
• Filed: 12/28/2005
• Issued: 02/05/2008
• Est. Priority Date: 12/31/2004
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: VTI Technologies Oy (Murata Manufacturing Co Limited)
• Inventors: Blomqvist, Anssi
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US11/318,435
• Publication Number:
  US 20060156813A1
• Time in Patent Office: 769 Days
• Field of Search: 735/041.4, 735/041.2, 735/040.2, 735/040.4, 735/041.5
• US Class Current: 73/504.04
• CPC Class Codes: G01C 19/5712 the devices involving a micromechanical structure

Abstract

The present invention relates to measuring devices used in measuring angular velocity and, more specifically, to oscillating micro-mechanical sensors of angular velocity. In the sensors of angular velocity according to the present invention, at least one pair of electrodes is provided in association with an edge of a seismic mass (1), (9), (10), (20), (30), (31), which pair of electrodes together with the surface of the mass (1), (9), (10), (20), (30), (31) form two capacitances such, that one of the capacitances of the pair of electrodes will increase and the other capacitance of the pair of electrodes will decrease as a function of the angle of rotation in the primary motion of the mass (1), (9), (10), (20), (30), (31). The structure of a sensor of angular velocity according to the present invention enables reliable and efficient measuring particularly in solutions for compact oscillating micro-mechanical sensors of angular velocity.

Claims

1. An oscillating, micro-mechanical sensor of angular velocity, said sensor comprising at least one seismic mass (1), (9), (10), (20), (30), (31), (45), (46) and associated movable electrode attached to a body of the sensor component at support areas such, that

in the sensor of angular velocity, a primary motion, which has to be generated, is an angular oscillation of the at least one seismic mass (1), (9), (10), (20), (30), (31), (45), (46) and the associated movable electrode about an axis perpendicular to the plane of the disk formed by the masses,

in addition to the primary motion, the seismic mass (1), (9), (10), (20), (30), (31), (45), (46) possesses a second degree of freedom in relation to a detection axis perpendicular to the primary motion, and that

in association with at least one edge of the seismic mass (1), (9), (10), (20), (30), (31), (45), (46), at least one pair of electrodes is provided, which the pair of electrodes together with the surface of the mass (1), (9), (10), (20), (30), (31), (45), (46) forms two capacitances such, that, as a function of an angle of rotation of the primary motion of the mass (1), (9), (10), (20), (30), (31), (45), (46), the capacitance of one pair of electrodes will increase and the capacitance of the other pair of electrodes will decrease.

2. Sensor of angular velocity according to claim 1, wherein the electrodes of the pair of electrodes are positioned equidistant on both sides of a detection axis.

3. Sensor of angular velocity according to claim 1, wherein a voltage of the same magnitude in relation to the potential of the mass (1), (9), (10), (20), (30), (31), (45), (46) is connected to both electrodes of the pair of electrodes.

4. Sensor of angular velocity according to claim 1, wherein the sensor further comprises:

a seismic mass and an associated movable electrode (1), which is attached to a body of a sensor component at an attachment spot (2),

bending springs (3)-(6) for the primary motion, connecting the attachment spot (2) to a surrounding stiff auxiliary structure and restricting the primary motion of the mass (1) essentially to an angular oscillation about the axis perpendicular to the plane of the disk, and

torsion springs (7), (8) for a detection motion, conveying the primary motion to the seismic mass (1) and simultaneously giving the mass (1) a second degree of freedom for the detection motion, which the detection motion is a rotary oscillation about a detection axis perpendicular to the axis of the primary motion.

5. Sensor of angular velocity according to claim 1, wherein the sensor further comprises:

two seismic masses (9), (10) and associated movable electrodes (9), (10), attached to a body of a sensor component at two attachment spots (11), (12),

bending springs (13), (14) for the primary motion connecting the attachment spots (11), (12) to surrounding stiff auxiliary structures or directly to the seismic masses (9), (10),

torsion springs (15)-(18) for the detection motion, and

a bending spring (19) connecting the seismic masses (9), (10) to each other, such that the resonators are connected in such a way, that both the primary motion of the masses (9), (10) and a detection motion are opposite phase motions of the two movable electrodes (9), (10).

6. Sensor of angular velocity according to claim 4, wherein the oscillation caused by an external angular velocity is detected capacitively by means of electrodes located above or underneath the seismic masses (1), (9), (10).

7. Sensor of angular velocity according to claim 6, wherein the electrodes located above or underneath the seismic masses are grown onto an inner surface of a wafer hermetically closing the sensor structure.

8. Sensor of angular velocity according to claim 1, wherein the sensor of angular velocity is a sensor of angular velocity measuring angular velocity in relation to two axes, the sensor comprising

a seismic mass and an associated movable electrode (20) attached to a body of the sensor component at an attachment spot (21),

bending springs (22)-(25) for the primary motion, connecting the attachment spot (21) to a surrounding stiff auxiliary structure and restricting the primary motion of the mass (20) essentially to an angular oscillation about the axis perpendicular to the plane of a disk,

torsion springs (26), (27) for a detection motion in a first direction conveying the primary motion to the seismic mass (20) and simultaneously giving the mass (20) a degree of freedom for the detection motion in the first direction, which the detection motion is a rotary oscillation essentially about a first detection axis perpendicular to the axis of the primary motion, and

torsion springs (28), (29) for a detection motion in a second direction conveying the primary motion to the seismic mass (20) and simultaneously giving the mass (20) a degree of freedom for the detection motion in the second direction, which the detection motion is a rotary oscillation essentially about a second detection axis perpendicular to the axis of the primary motion and to the first detection axis.

9. Sensor of angular velocity according to claim 1, wherein the sensor of angular velocity is a sensor of angular velocity measuring angular velocity in relation to two axes, the sensor comprising

two seismic masses and associated movable electrodes (30), (31) attached to a body of a sensor component at two attachment spots (32), (33),

bending springs (34), (35) for the primary motion connecting the attachment spots (32), (33) to surrounding stiff auxiliary structures,

torsion springs (36)-(39) for a detection motion in a first direction, conveying the primary motion to the seismic masses (30), (31) and simultaneously giving the masses (30), (31) a degree of freedom for the detection motion in the first direction,

torsion springs (40)-(43) for a detection motion in a second direction, conveying the primary motion to the seismic masses (30), (31) and simultaneously giving the masses mass (30), (31) a degree of freedom for the detection motion in the second direction, and

a bending spring (44) connecting the seismic masses (30), (31) to each other.

10. Sensor of angular velocity according to claim 4, wherein attachment spots (2), (11), (12), (21), (32), (33) are joined in an anodic manner to the wafer hermetically closing a sensor structure.

11. Sensor of angular velocity according to claim 4, wherein attachment spots (2), (11), (12), (21), (32), (33) are joined by means of a fusion joint to the wafer hermetically closing a sensor structure.