Capacitive acceleration sensor

• US 7,398,683 B2
• Filed: 02/10/2004
• Issued: 07/15/2008
• Est. Priority Date: 02/11/2003
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: VTI Technologies Oy (Murata Manufacturing Co Limited)
• Inventors: Lehtonen, Tuomo
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US10/774,691
• Publication Number:
  US 20040216523A1
• Time in Patent Office: 1,617 Days
• Field of Search: 735/143.2
• US Class Current: 73/514.32
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/18 in two or more dimensions

Abstract

The invention relates to measuring devices used in the measurement of acceleration and, more specifically, to capacitive acceleration sensors. The capacitive acceleration sensor according to the present invention contains a movable electrode (5) of the acceleration sensor supported at an axis of rotation (7). Several pairs of electrodes are utilized in the acceleration sensor according to the present invention. Advantages of symmetry are achieved with the acceleration sensor structure according to the present invention, and it enables reliable and efficient measuring of acceleration, in particular in small capacitive acceleration sensor designs.

Claims

1. A capacitive acceleration sensor, comprising:

a pair of electrodes comprising

a movable electrode that is responsive to acceleration,

at least one stationary plate portion, and

an axis of rotation,

wherein the movable electrode is supported by springs such that the movable electrode is rigidly supported at the axis of rotation and is free to rotate about the axis of rotation; and

said capacitive acceleration sensor further comprising at least three additional pairs of electrodes,

wherein the at least three additional pairs of electrodes are of similar structure to the pair of electrodes,

wherein the position of the pairs of electrodes are arranged symmetrically with respect to at least two additional pairs of electrodes;

wherein the at least three additional pairs of electrodes and the pair of electrodes are configured to together provide multi-axis acceleration sensing using capacitive principles, and

wherein negative direction vectors of at least four movable electrodes intersect at essentially one point.

2. The capacitive acceleration sensor of claim 1, wherein a shape of the pair of electrodes comprises at least one of triangle-like or drop-like pairs of electrodes.

3. The capacitive acceleration sensor of claim 1, wherein only four pairs of electrodes are used in the acceleration sensor.

4. The capacitive acceleration sensor of claim 3, wherein the sensor is configured to sense acceleration in two axes.

5. The capacitive acceleration sensor of claim 3, wherein the sensor is configured to sense acceleration in three axes.

6. The capacitive acceleration sensor of claim 3, wherein the only four pairs of electrodes are positioned to form four different axes of symmetry.

7. The capacitive acceleration sensor of claim 3, wherein the only four pairs of electrodes are configured such that a positive direction vector of the movable electrode of each pair of the only four pairs of electrodes is at an angle of 90°

, 180°

, and 270°

in relation to a positive direction vector of the other three movable electrodes.

8. The capacitive acceleration sensor of claim 1, wherein only eight pairs of electrodes are used in the acceleration sensor.

9. The capacitive acceleration sensor of claim 8, wherein the sensor is configured to sense acceleration in two axes.

10. The capacitive acceleration sensor of claim 8, wherein the sensor is configured to sense acceleration in three axes.

11. The capacitive acceleration sensor of claim 8, wherein the eight pairs of electrodes are positioned to form four different axes of symmetry.

12. The capacitive, acceleration sensor of claim 1, wherein different pairs of electrodes of the pair of electrodes and the at least three additional pairs of electrodes are configured to measure different ranges of acceleration.

13. The capacitive acceleration sensor of claim 1, wherein some pairs of electrodes of the pair of electrodes and the at least three additional pairs of electrodes of the acceleration sensor are redundant.