Strain sensor

• US 20030141867A1
• Filed: 01/29/2003
• Published: 07/31/2003
• Est. Priority Date: 01/29/2002
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Inoue, Tetsuo
• Granted Patent: US 6,960,911 B2
• Time in Patent Office: Days
• US Class Current: 324/209
• CPC Class Codes: G01L 1/125 by using magnetostrictive means magnetostrictive sensors H10N35/101
• CPC Class Codes: G01L 1/127 by using inductive means G01L1/122, G01L1/125 take precedence
• CPC Class Codes: G01L 9/16 by making use of variations in the magnetic properties of material resulting from the application of stress

Abstract

A strain sensor includes a sensor section having a magnetic material provided on one surface of a conductor, the magnetic material being formed integrally with the conductor and having a magnetic strain constant with an absolute value larger than 1×10⁻⁷, a fixing mechanism which fixes at least a part of the sensor section, an inductor disposed in a surface side of the sensor section which is opposite the surface on which the magnetic material is provided, the inductor being disposed opposite and away from the sensor section, and a detection unit which detects the amount of deformation of the sensor section caused by stress applied thereto on the basis of a change in inductance of the inductor.

Claims

1. A strain sensor comprising:

a sensor section having a conductor and a first magnetic material provided on one surface of the conductor, the magnetic material being formed integrally with the conductor and having a magnetic strain constant with an absolute value larger than 1×

10<sup>−

7</sup>;

a fixing mechanism which fixes at least a part of the sensor section;

an inductor disposed to face a surface of the sensor section which is opposite a surface on which the magnetic material is provided, the inductor being disposed away from the sensor section; and

a detection unit which detects an amount of deformation of the sensor section based on a change in inductance of the inductor.

2. A strain sensor according to claim 1, wherein the first magnetic material has a negative magnetic strain constant, and

wherein the fixing mechanism has a fixing portion which holds the sensor section so as to allow a central portion of the sensor section to be deformed in response to stress.

3. A strain sensor according to claim 1, wherein the first magnetic material has a positive magnetic strain constant.

4. A strain sensor according to claim 2, wherein the magnetic strain constant has a value of −

5×

10<sup>−

7</sup> or less.

5. A strain sensor according to claim 2, wherein the fixing mechanism fixes all periphery of the sensor section.

6. A strain sensor according to claim 3, wherein the magnetic strain constant has a value of 5×

10<sup>−

7</sup> or more.

7. A strain sensor according to claim 3, wherein the fixing mechanism fixes a part of the periphery of the sensor section.

8. A strain sensor according to claim 3, wherein the fixing mechanism has a member fixing the central portion of the sensor section.

9. A strain sensor according to claim 1, further comprising a second magnetic material disposed on a surface of the inductor which is opposite the surface on which the sensor section is disposed, the second magnetic material being disposed opposite and away from the sensor section.

10. A strain sensor according to claim 2, further comprising a second magnetic material disposed on a surface of the inductor which is opposite the surface on which the sensor section is disposed, the second magnetic material being disposed opposite and away from the sensor section.

11. A strain sensor according to claim 3, further comprising a second magnetic material disposed on a surface of the inductor which is opposite the surface on which the sensor section is disposed, the second magnetic material being disposed opposite and away from the sensor section.

12. A strain sensor according to claim 1, wherein the first magnetic material comprises a soft magnetic material.

13. A strain sensor according to claim 1, wherein the detection unit includes an oscillator which supplies an oscillation signal to the inductor, a phase detecting circuit to detect phase information on this oscillation signal, and an arithmetic circuit which converts the phase information detected by the phase detecting circuit into an output denoting an amount of deformation of the sensor section.

14. A strain sensor according to claim 2, wherein the detection unit includes an oscillator which supplies an oscillation signal to the inductor, a phase detecting circuit to detect phase information on this oscillation signal, and an arithmetic circuit which converts the phase information detected by the phase detecting circuit into an output denoting an amount of deformation of the sensor section.

15. A strain sensor according to claim 1, wherein the conductor comprises an elastically deformative material.

16. A strain sensor according to claim 1, wherein the conductor comprises a plastically deformative material.

17. A strain sensor according to claim 1, wherein the first magnetic material consists essentially of at least one material selected from a group consisting of permalloy, sendust, metal-based amorphous metal, heteroamorphous, and nanocrystal.

18. A strain sensor according to claim 1, wherein the inductor has a spiral shape.

19. A strain sensor according to claim 1, wherein the sensor section includes a glass substrate having a first surface on which the conductor is provided and a second surface on which the first magnetic material is provided.

20. A strain sensor according to claim 1, wherein the conductor has an electric resistance of 1×

10<sup>−

8</sup> [Q·

cm] or less.