Sensor using piezoelectric elements

• US 5,780,749 A
• Filed: 03/17/1997
• Issued: 07/14/1998
• Est. Priority Date: 07/29/1993
• Status: Expired due to Term

• Current Assignee: Kazuhiro Okada
• Original Assignee: Kazuhiro Okada
• Inventors: Okada, Kazuhiro
• Primary Examiner(s): Dougherty, Elizabeth L.
• Application Number:
  US08/819,684
• Time in Patent Office: 484 Days
• Field of Search: 73/862.043, 73/862.042, 73/862.632, 73/DIG. 4
• US Class Current: 73/862.043
• CPC Class Codes: G01L 5/167 using piezoelectric means
• 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
• CPC Class Codes: Y10S 73/04 Piezoelectric

Abstract

The periphery of a disk having flexibility is fixed to a sensor casing, and a force applied to the central portion is detected. A doughnut disk-shaped piezoelectric element is positioned on the upper surface of the disk, and upper electrode layers indicated by patterns of D1 to D6 are formed on the upper surface of the piezoelectric element. Further, lower electrode layers similarly having pattern of D1 to D6 are formed on the lower surface of the piezoelectric element, and the lower surface of the lower electrode layer is fixed on the upper surface of the disk. Six detection elements D1 to D6 are formed each of which is constituted by a pair of upper and lower electrode layers and a portion of piezoelectric element put therebetween. Thus, force components exerted at an origin defined in the central portion of the disk in respective axes directions of X, Y, Z can be detected based on charges produced in detection elements D1, D2, detection elements D3, D4, and detection elements D5, D6, respectively.

Claims

1. A force sensor using piezoelectric elements comprising:

four detection elements composed of a piezoelectric element in a plate form, an upper electrode formed on an upper surface of said piezoelectric element and a lower electrode formed on a lower surface of said piezoelectric element;

a working body in which a force is produced on the basis of a physical action exerted from an external source;

supporting means for supporting said four detection elements on XY-plane of an XYZ three dimensional coordinate system having an X-axis, Y-axis and Z-axis so that a first detection element, a second detection element, a third detection element and a fourth detection element are respectively arranged in a negative region on the X-axis, in a positive region on the X-axis, in a negative region on the Y-axis and in a positive region on the Y-axis, respectively; and

connecting means for connecting said working body and said four detection elements so that an X-axis force component produced in said working body in the X-axis direction is transmitted to said first and second detection elements to cause a mechanical deformation therein and a Y-axis force component produced in said working body in the Y-axis direction is transmitted to said third and fourth detection elements to cause a mechanical deformation therein;

wherein the X-axis force component is detected on the basis of charges produced in the first detection element and the second detection element, and the Y-axis force component is detected on the basis of charges produced in the third detection element and the fourth detection element; and

wherein either a group of plural lower electrodes of a group of plural upper electrodes is constituted by a single electrode layer.

2. A force sensor using piezoelectric elements as set forth in claim 1

wherein predetermined polarization processing is implemented to piezoelectric elements of respective detection elements;

so that the first detection element and the second detection element have an opposite polarization characteristic each other and the third detection element and the fourth detection element have an opposite polarization characteristic each other.

3. A force sensor using piezoelectric elements as set forth in claim 1

wherein the working body has an enough weight to produce a force on the basis of an acceleration applied from an external source, thereby making it possible to detect acceleration.

4. A force sensor using piezoelectric elements as set forth in claim 1

wherein the connecting means locates the working body on the Z-axis.

5. A force sensor using piezoelectric elements as set forth in claim 1

wherein the working body has a shape of ring and the connecting means locates the working body around the Z-axis.