Sensor using capacitance element

• US 6,378,381 B1
• Filed: 02/11/2000
• Issued: 04/30/2002
• Est. Priority Date: 03/01/1999
• Status: Expired due to Term

• Current Assignee: Wacoh Company
• Original Assignee: Wacoh Company
• Inventors: Itano, Hiromichi, Taniguchi, Nobumitsu, Okada, Kazuhiro
• Primary Examiner(s): Fuller, Benjamin R.
• Assistant Examiner(s): DAVIS, OCTAVIA L
• Application Number:
  US09/502,505
• Time in Patent Office: 809 Days
• Field of Search: 735/041.1, 738/620.43, 735/040.2, 737/80, 735/143.2
• US Class Current: 73/862.043
• CPC Class Codes: G01D 5/24 by varying capacitance
• CPC Class Codes: G01D 5/2417 by varying separation
• 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 2015/084 the mass being suspended at more than one of its sides, e.g. membrane-type suspension, so as to permit multi-axis movement of the mass

Abstract

A bottom fixed layer 110, displacement layer 125, and top fixed layer 130 are fixed in a layered structure by way of intervening pedestals 145, 155, which serve as spacers between the layers. The bottom and top fixed layers 110, 130 are rigid dielectric substrates. The displacement layer 125 is a flexible conductive substrate. On the top of the bottom fixed layer 110 are formed an electrode E11 on the right, electrode E12 on the left, and a washer-shaped electrode E15 in the middle. On the bottom of the top fixed layer 130 are formed an electrode E21 on the right, electrode E22 on the left, and a washer-shaped electrode E25 in the middle. These electrodes and the displacement layer 125 together form capacitance elements C11 to C25. When acceleration acts on the working body 160, the displacement layer 125 is displaced and a change in capacitance occurs in various capacitance elements. The X-axis acceleration component can then be calculated as (C11+C22) -(C12+C21), and the Z-axis acceleration component can be calculated as C25-C15.

Claims

1. A capacitance sensor using a capacitance element for detecting force or acceleration in a specific axis direction in an XYZ three-dimensional coordinate system having an X-axis, a Y-axis and a Z-axis, comprising:

a bottom fixed layer and a top fixed layer fixed with a gap therebetween and with surfaces thereof parallel to an XY plane and intersected by the Z-axis;

a displacement layer disposed between said bottom fixed layer and said top fixed layer so as to maintain a reference state substantially parallel to the XY plane under conditions in which a force or an acceleration is not at work, and to displace from said reference state when a force or an acceleration is at work;

a working body connected to a part of said displacement layer for causing displacement of the displacement layer based on an action of force or acceleration;

a positive X-axis bottom electrode formed on a top surface of the bottom fixed layer at a position corresponding to a positive region of the X-axis;

a negative X-axis bottom electrode formed on a top surface of the bottom fixed layer at a position corresponding to a negative region of the X-axis;

a positive X-axis top electrode formed on a bottom surface of the top fixed layer at a position corresponding to the positive region of the X-axis;

a negative X-axis top electrode formed on a bottom surface of the top fixed layer at a position corresponding to the negative region of the X-axis;

a displacement electrode formed on a bottom surface of the displacement layer at a position corresponding to the positive X-axis bottom electrode;

a displacement electrode formed on a bottom surface of the displacement layer at a position corresponding to the negative X-axis bottom electrode;

a displacement electrode formed on a top surface of the displacement layer at a position corresponding to the positive X-axis top electrode; and

a displacement electrode formed on a top surface of the displacement layer at a position corresponding to the negative X-axis top electrode;

where a positive X-axis bottom capacitance element is formed by the positive X-axis bottom electrode and an opposing displacement electrode;

a negative X-axis bottom capacitance element is formed by the negative X-axis bottom electrode and an opposing displacement electrode;

a positive X-axis top capacitance element is formed by the positive X-axis top electrode and an opposing displacement electrode;

a negative X-axis top capacitance element is formed by the negative X-axis top electrode and an opposing displacement electrode; and

a detection means having a function for detecting a force or an acceleration acting in an X-axis direction based on a difference between,

a sum of a capacitance of the positive X-axis bottom capacitance element and a capacitance of the negative X-axis top capacitance element, and

a sum of a capacitance of the negative X-axis bottom capacitance element and a capacitance of the positive X-axis top capacitance element.

2. A capacitance sensor as described in claim 1, wherein the bottom electrodes and the top electrodes are symmetrical to the XZ plane.

3. A capacitance sensor as described in claim 2, where the capacitance elements are all electrode pairs having the same shape, same size, and same electrode gap.

4. A capacitance sensor as described in claim 1, further comprising:

a bottom origin-surrounding electrode formed around a point of origin on a top surface of the bottom fixed layer;

a top origin-surrounding electrode formed around a point of origin on a bottom surface of the top fixed layer;

a displacement electrode formed on a bottom surface of the displacement layer at a position opposing the bottom origin-surrounding electrode; and

a displacement electrode formed on a top surface of the displacement layer at a position opposing the top origin surrounding electrode;

where a bottom origin-surrounding capacitance element is formed by the bottom origin-surrounding electrode and an opposing displacement electrode, and

a top origin-surrounding capacitance element is formed by the top-origin-surrounding electrode and an opposing displacement electrode; and

the detection means has a further function for detecting force or acceleration acting in the Z-axis direction based on a difference between a capacitance of the bottom origin-surrounding capacitance element and a capacitance of the top origin-surrounding capacitance element.

5. A capacitance sensor as described in claim 4, wherein the bottom origin-surrounding electrode and the top origin-surrounding electrode are rotationally symmetrical to the Z-axis.

6. A capacitance sensor as described in claim 5, wherein the elements surround an origin of the coordinate system and are arranged in electrode pairs having the same shape, size, and electrode gap.

7. A capacitance sensor as described in claim 1, further comprising:

a positive Y-axis bottom electrode formed on a top surface of the bottom fixed layer at a position corresponding to a positive region of the Y-axis;

a negative Y-axis bottom electrode formed on a top surface of the bottom fixed layer at a position corresponding to a negative region of the V-axis;

a positive Y-axis top electrode formed on a bottom surface of the top fixed layer at a position corresponding to the positive region of the Y-axis;

a negative Y-axis top electrode formed on a bottom surface of the top fixed layer at a position corresponding to the negative region of the Y-axis;

a displacement electrode formed on a bottom surface of the displacement layer at a position corresponding to the positive Y-axis bottom electrode;

a displacement electrode formed on a bottom surface of the displacement layer at a position corresponding to the negative Y-axis bottom electrode;

a displacement electrode formed on a top surface of the displacement layer at a position corresponding to the positive Y-axis top electrode; and

a displacement electrode formed on a top surface of the displacement layer at a position corresponding to the negative Y-axis top electrode;

where a positive Y-axis bottom capacitance element is formed by the positive Y-axis bottom electrode and an opposing displacement electrode;

a negative Y-axis bottom capacitance element is formed by the negative Y-axis bottom electrode and an opposing displacement electrode;

a positive Y-axis top capacitance element is formed by the positive Y-axis top electrode and an opposing displacement electrode; and

a negative Y-axis top capacitance element is formed by the negative Y-axis top electrode and an opposing displacement electrode; and

the detection means has a further function for detecting a force or an acceleration acting in a Y-axis direction based on a difference between,

a sum of a capacitance of the positive Y-axis bottom capacitance element and a capacitance of the negative Y-axis top capacitance element, and

a sum of a capacitance of the negative Y-axis bottom capacitance element and a capacitance of the positive Y-axis top capacitance element.

8. A capacitance sensor as described in claim 7, wherein the bottom electrodes and the top electrodes are symmetrical to the XZ plane or the YZ plane.

9. A capacitance sensor as described in claim 8, where the capacitance elements are all electrode pairs having the same shape, same size, and same electrode gap.

10. A capacitance sensor as described in claim 7, further comprising:

a bottom origin-surrounding electrode formed around a point of origin on a top surface of the bottom fixed layer;

a top origin-surrounding electrode formed around a point of origin on a bottom surface of the top fixed layer;

a displacement electrode formed on a bottom surface of the displacement layer at a position opposing the bottom origin-surrounding electrode; and

a displacement electrode formed on a top surface of the displacement layer at a position opposing the top origin-surrounding electrode;

where a bottom origin-surrounding capacitance element is formed by the bottom origin-surrounding electrode and an opposing displacement electrode, and

a top origin-surrounding capacitance element is formed by the top origin-surrounding electrode and an opposing displacement electrode; and

the detection means has a further function for detecting force or acceleration acting in the Z-axis direction based on a difference between a capacitance of the bottom origin-surrounding capacitance element and a capacitance of the top origin-surrounding capacitance element.

11. A capacitance sensor as described in claim 10, wherein the bottom origin-surrounding electrode and the top origin-surrounding electrode are rotationally symmetrical to the Z-axis.

12. A capacitance sensor as described in claim 11, wherein the elements surround an origin of the coordinate system and are arranged as electrode pairs having the same shape, size, and electrode gap.

13. A capacitance sensor as described in claim 1, wherein a first part of the displacement layer is affixed to the bottom fixed layer and top fixed layer,

a second part of the displacement layer is connected to the working body,

a third part of the displacement layer located between the first part and second part is made of a flexible material such that displacement of the displacement layer occurs with deflection of the third part.

14. A capacitance sensor as described in claim 1, wherein a plurality of displacement electrodes formed on the displacement layer are comprised of a single physical common electrode.

15. A capacitance sensor as described in claim 14, wherein a flexible, conductive substrate is used as the displacement layer, and as the single common electrode.

16. A capacitance sensor as described in claim 14, wherein non-common electrodes of each capacitance element pair, for which a sum of capacitance values is obtained, are electrically connected to each other at a connection node, and a capacitance between said connection node and the common electrode is used as said sum.

17. A capacitance sensor as described in claim 16, wherein a through-hole is formed in the bottom fixed layer and the top fixed layer at each electrode connecting position, and a pair of electrodes are connected using a wiring layer by way of said through-hole.

18. A capacitance sensor as described in claim 1, wherein a perimeter of the bottom fixed layer and a perimeter of the top fixed layer are fastened by a pedestal, a perimeter of the displacement layer is fastened by said pedestal, the working body is connected to a top center part of the displacement layer, and a through-hole for passing through the working body is formed in a center part of the top fixed layer.