Displacement sensor, displacement detecting device, and operation device

• US 10,446,738 B2
• Filed: 03/10/2017
• Issued: 10/15/2019
• Est. Priority Date: 04/08/2011
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: Ando, Masamichi, Kawamura, Hideki
• Primary Examiner(s): Martin, J. San
• Application Number:
  US15/455,655
• Publication Number:
  US 20170186939A1
• Time in Patent Office: 949 Days
• CPC Class Codes: G01B 7/16 for measuring the deformation in a solid, e.g. by resistance strain gauge
• CPC Class Codes: G01D 5/18 by varying effective impedance of discharge tubes or semiconductor devices
• CPC Class Codes: G01D 5/185 using piezoelectric sensors
• CPC Class Codes: G01L 1/16 using properties of piezoelectric devices
• CPC Class Codes: H10N 30/302 Sensors
• CPC Class Codes: H10N 30/304 Beam type
• CPC Class Codes: H10N 30/857 Macromolecular compositions

Abstract

A displacement sensor having a rectangular shaped elastic member. A piezoelectric element is attached to a first main face of the elastic member. The piezoelectric element has a rectangular-shaped piezoelectric sheet and electrodes on both main faces of the piezoelectric sheet. The piezoelectric sheet is made of poly-L-lactic acid and is at least uniaxially-stretched. The piezoelectric element is attached so that the uniaxial-stretching direction of the piezoelectric sheet is 45° relative to a long-side direction of the elastic member. When the elastic member is bent along the long-side direction, the piezoelectric sheet is stretched along the long-side direction, and the piezoelectric element generates voltage of predetermined level.

Claims

1. A displacement sensor comprising:

an elastic member;

a flat-film-shaped piezoelectric element, the piezoelectric element including a pair of opposed electrodes and a piezoelectric sheet therebetween;

a first insulating element arranged between a first main surface side of the piezoelectric element and the elastic member; and

a second insulating element arranged on a second main surface side of the piezoelectric element opposite to the first main surface side,

wherein the piezoelectric sheet contains polylactic acid and was stretched at least in a uniaxial direction thereof, and

wherein a Young'"'"'s modulus of the second insulating element is higher than at least that of the piezoelectric sheet.

2. The displacement sensor according to claim 1, wherein the first insulating element is an adhesive adhering a first main surface of the of the piezoelectric element to the elastic member.

3. The displacement sensor according to claim 1, wherein the second insulating element is a protection film covering the piezoelectric element.

4. The displacement sensor according to claim 1, wherein the elastic member and the piezoelectric element are arranged relative to each other such that a neutral face of a bending of the piezoelectric element is a center axis in a thickness direction of the elastic member.

5. The displacement sensor according to claim 1, wherein the piezoelectric sheet is a substantially rectangular-shaped flat film, and wherein a stretch axis of the uniaxial direction is oriented along at least a direction of about 45°

or a direction of about −

45°

with respect to a long-side direction of the substantially rectangular-shaped flat film.

6. The displacement sensor according to claim 1, wherein the piezoelectric sheet is a substantially rectangular-shaped flat film, and wherein a stretch axis of the uniaxial direction is oriented along at least a direction of about zero degree or a direction of about 90°

with respect to a long-side direction of the substantially rectangular-shaped flat film.

7. The displacement sensor according to claim 1, wherein the piezoelectric sheet is a substantially rectangular-shaped flat film, and wherein a stretch axis of the uniaxial direction is oriented along at least a direction of about 22.5°

or a direction of about 67.5°

with respect to a long-side direction of the substantially rectangular-shaped flat film.

8. The displacement sensor according to claim 1, wherein the flat-film-shaped piezoelectric element attached to the first main face of the elastic member is a first flat-film-shaped piezoelectric element, the displacement sensor further comprising:

a second flat-film-shaped piezoelectric element attached to a second main face opposed to the first main face of the elastic member, the second piezoelectric element including a pair of opposed electrodes with a piezoelectric sheet therebetween, and

the piezoelectric sheet of the second flat-film-shaped piezoelectric element contains polylactic acid and was stretched at least in a uniaxial direction thereof.

9. The displacement sensor according to claim 8, wherein the piezoelectric sheet of the first flat-film-shaped piezoelectric element is a substantially rectangular-shaped first flat film, and wherein a stretch axis of the uniaxial direction is oriented along at least a direction of about 45°

or a direction of about −

45°

with respect to a long-side direction of the substantially rectangular-shaped first flat film, and

the piezoelectric sheet of the second flat-film-shaped piezoelectric element is a substantially rectangular-shaped second flat film, and wherein a stretch axis of the uniaxial direction is oriented along at least a direction of about zero degree or a direction of about 90°

with respect to a long-side direction of the substantially rectangular-shaped second flat film.

10. The displacement sensor according to claim 8, wherein the piezoelectric sheet of the first flat-film-shaped piezoelectric element is a substantially rectangular-shaped first flat film, and wherein a stretch axis of the uniaxial direction is oriented along at least a direction of about 22.5°

or a direction of about 67.5°

with respect to a long-side direction of the substantially rectangular-shaped first flat film, and

the piezoelectric sheet of the second flat-film-shaped piezoelectric element is a substantially rectangular-shaped second flat film, and wherein a stretch axis of the uniaxial direction is oriented along at least a direction of about 22.5°

or a direction of about 67.5°

with respect to a long-side direction of the substantially rectangular-shaped second flat film.

11. The displacement sensor according to claim 8, wherein the elastic member has conductivity, and

an electrode on the elastic member side of the first flat-film-shaped piezoelectric element and an electrode on the elastic member side of the second flat-film-shaped piezoelectric element are shared by the elastic member having conductivity.

12. The displacement sensor according to claim 1, wherein the displacement sensor comprises a stacked plurality of the flat-film-shaped piezoelectric elements.

13. The displacement sensor according to claim 8, wherein the displacement sensor comprises a stacked plurality of at least one of the piezoelectric sheet of the first flat-film-shaped piezoelectric element or the piezoelectric sheet of the second flat-film-shaped piezoelectric element.

14. The displacement sensor according to claim 1, wherein the pair of electrodes and the elastic member are translucent.