Displacement sensor, displacement detecting device, and operation device

Patent metadata

Field	Value
Publication number	US-10446738-B2
Application number	US-201715455655-A
Country	US
Kind code	B2
Filing date	Mar 10, 2017
Priority date	Apr 8, 2011
Publication date	Oct 15, 2019
Grant date	Oct 15, 2019

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.

First claim

The invention claimed is:

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.

Assignees

• Murata Manufacturing Co

Inventors

• Ando Masamichi
• Kawamura Hideki

Classifications

• G01D5/18

  by varying effective impedance of discharge tubes or semiconductor devices · CPC title

• G01B7/16 Primary

  for measuring the deformation in a solid, e.g. by resistance strain gauge · CPC title

• G01L1/16

  using properties of piezoelectric devices · CPC title

• H01L41/193

  Electricity · mapped topic

• H01L41/1132 Primary

  Electricity · mapped topic