Pressing Force Sensor

• US 20150035411A1
• Filed: 10/16/2014
• Published: 02/05/2015
• Est. Priority Date: 04/17/2012
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: Kawamura, Hideki, Ando, Masamichi
• Granted Patent: US 10,024,739 B2
• Time in Patent Office: Days
• US Class Current: 310/330
• CPC Class Codes: B82Y 15/00 Nanotechnology for interacting, sensing or actuating, e.g. quantum dots as markers in protein assays or molecular motors
• CPC Class Codes: G01L 1/16 using properties of piezoelectric devices
• CPC Class Codes: H10N 30/302 Sensors
• CPC Class Codes: H10N 30/308 Membrane type
• CPC Class Codes: H10N 30/857 Macromolecular compositions
• CPC Class Codes: H10N 30/88 Mounts; Supports; Enclosures; Casings
• CPC Class Codes: H10N 30/883 Additional insulation means preventing electrical, physical or chemical damage, e.g. protective coatings
• CPC Class Codes: Y10S 977/742 Carbon nanotubes, CNTs
• CPC Class Codes: Y10S 977/762 Nanowire or quantum wire, i.e. axially elongated structure having two dimensions of 100 nm or less
• CPC Class Codes: Y10S 977/956 Of mechanical property

Abstract

A pressing force sensor that includes a flat membrane piezoelectric element and a support. The flat membrane piezoelectric element includes a piezoelectric sheet having a piezoelectric constant d14. A first electrode is formed on a first main surface of the piezoelectric sheet and a second electrode is formed on a second main surface thereof. Long directions of the first electrode and the second electrode and a uniaxial stretching direction of the piezoelectric sheet form an angle of 45°. An opening portion having an elliptical section is formed on the support. The flat membrane piezoelectric element abuts the opening portion of the support. The support and the flat membrane piezoelectric element are disposed such that the opening portion is included within an area of the second electrode.

Claims

1. A pressing force sensor comprising:

a piezoelectric sheet having a first main surface and a second main surface which are opposed to each other;

a first electrode on the first main surface;

a second electrode on the second main surface; and

a support abutting the second main surface side of the piezoelectric sheet,

wherein the support defines a space sized so as to allow deformation of at least a part of the second electrode, and

the piezoelectric sheet and the support are disposed such that distortion caused by an external force to the piezoelectric sheet over the space differs in two directions which are orthogonal to each other.

2. The pressing force sensor according to claim 1, wherein the space has different lengths in the two directions which are orthogonal to each other.

3. The pressing force sensor according to claim 1, wherein the piezoelectric sheet contains polylactic acid.

4. The pressing force sensor according to claim 3, wherein the piezoelectric sheet has been stretched in at least a uniaxial direction that is different from the two directions which are orthogonal to each other.

5. The pressing force sensor according to claim 4, wherein the uniaxial direction in which the piezoelectric sheet has been stretched forms an angle of approximately 45°

with respect to the two directions which are orthogonal to each other.

6. The pressing force sensor according to claim 1, wherein the piezoelectric sheet is fixed to only opposed ends in a long direction of the space of the support.

7. The pressing force sensor according to claim 1, wherein the space is a dent having a predetermined depth from a surface of the support.

8. The pressing force sensor according to claim 7, further comprising an elastic member disposed in the dent.

9. The pressing force sensor according to claim 7, further comprising a through hole extending from the dent and through the support.

10. The pressing force sensor according to claim 1, wherein the space is opened on an end side surface of the support.

11. The pressing force sensor according to claim 10, wherein a first width of the space at the end side surface of the support is smaller than a second width of the space proximal to a center of the support.

12. The pressing force sensor according to claim 10, wherein a first width of the space at the end side surface of the support is larger than a second width of the space proximal to a center of the support.

13. The pressing force sensor according to claim 1, wherein the pressing force sensor includes plural sets of the first electrodes, the second electrodes and the spaces.

14. The pressing force sensor according to claim 13, wherein the plural spaces are each opened on a respective end side surface of the support.

15. The pressing force sensor according to claim 1, further comprising a protective layer on the first main surface side of the piezoelectric sheet.

16. The pressing force sensor according to claim 15, wherein the protective layer is an insulating material having a lower Young'"'"'s modulus than the piezoelectric sheet.

17. The pressing force sensor according to claim 1, further comprising a push-in member adjacent the first main surface side of the piezoelectric sheet and configured to push at least a portion of the piezoelectric sheet opposed to the space.

18. The pressing force sensor according to claim 1, wherein materials of the first electrode and the second electrode are selected from the group consisting of an organic electrode containing ITO, ZnO and polythiophene as main components, an organic electrode containing polyaniline as a main component, a silver nanowire electrode and a carbon nanotube electrode.

19. The pressing force sensor according to claim 1, wherein a Young'"'"'s modulus of the support is higher than that of the piezoelectric sheet.