Force sensor

• US 6,523,423 B1
• Filed: 12/13/1999
• Issued: 02/25/2003
• Est. Priority Date: 12/25/1998
• Status: Expired due to Fees

• Current Assignee: NGK Insulators Limited
• Original Assignee: NGK Insulators Limited
• Inventors: Namerikawa, Masahiko, Shibata, Kazuyoshi
• Primary Examiner(s): Noori, Max
• Assistant Examiner(s): Martir, Lilybett
• Application Number:
  US09/460,019
• Time in Patent Office: 1,170 Days
• Field of Search: 738/620.4, 735/143.4, 738/627, 737/06, 345/365.4
• US Class Current: 73/862.391
• CPC Class Codes: G01L 1/16 using properties of piezoelectric devices
• CPC Class Codes: G01L 5/167 using piezoelectric means

Abstract

A force sensor includes: a supporting base having a hollow portion, a flexible plate having at least one detecting element and extending across over the hollow portion, and an operating member suspended over the hollow portion by the flexible plate. Inclined strength is given to the flexible plate so that it becomes stronger from an arbitrary position between the outer periphery of the operating member and the inner periphery of the supporting base toward the outer periphery of the operating member and/or toward the inner periphery of the supporting base. Another force sensor includes: a supporting base having a hollow portion, a flexible plate having at least one detecting element and extending across over the hollow portion, and an operating member suspended over the hollow portion by the flexible plate. A boundary between the flexible plate and the operating member and/or a boundary between the flexible plate and the supporting base have (has) a curvature.

Claims

1. A force sensor comprising:

a supporting base having an outer periphery, an inner periphery, and a hollow portion;

a flexible plate having at least one detecting element and extending across the hollow portion; and

an operating member having an outer periphery, an inner periphery, and suspended over the hollow portion by the flexible plate, the thickness of the flexible plate increasing from a position of which mechanical strength is lowest in the flexible plate between the outer periphery of the operating member and the inner periphery of the supporting base toward at least one of the outer periphery of the operating member and the inner periphery of the supporting base.

2. A force sensor according to claim 1, wherein the thickness of the flexible plate from said position of lowest mechanical strength toward the outer periphery of the operating member increases at a different rate than that of the flexible plate from said position of lowest mechanical strength toward the inner periphery of the supporting base.

3. A force sensor according to claim 1, wherein at least one of a boundary between the flexible plate and the operating member and a boundary between the flexible plate and the supporting base has curvature.

4. A force sensor according to claim 3, wherein the curvature of the boundary between the flexible plate and the operating member is different from that of the boundary between the flexible plate and the supporting base.

5. A force sensor according to claim 1, wherein the thickness of the flexible plate increases in tiers.

6. A force sensor according to claim 5, wherein the force sensor is produced using a green sheet lamination technique.

7. A force sensor according to claim 1, wherein said detecting element is a piezoelectric element.

8. A force sensor according to claim 1, wherein said operating member, said supporting base, and said flexible plate are unitarily formed, and at least one of them has a different chemical composition the others.

9. A force sensor according to claim 1, wherein only the flexible plate comprises a zirconia ceramic containing at least one of 0.1-0.6% by weight of titanium in terns of TiO₂ and 0.005-0.1% by weight of magnesium in terms of MgO.

10. A force sensor according to claim 9, wherein only the flexible plate comprises a zirconia ceramic containing at least one of 0.2-0.5% by weight of titanium in terms of TiO₂ and 0.01-0.05% by weight of magnesium in terms of MgO.

11. A force sensor according to claim 1, wherein a hardness of a part of the detecting element formed on a part of or an entire surface of the flexible plate is made higher in comparison with that of the other part by a hardening material.

12. A force sensor according to claim 1, wherein the force sensor is used as an acceleration sensor with using the operating member as a weight.

13. A force sensor comprising:

a supporting base having an outer periphery, an inner periphery, and a hollow portion;

a flexible plate having at least one detecting element and extending across the hollow portion; and

an operating member having an outer periphery, an inner periphery, and suspended over the hollow portion by the flexible plate, the composition of the flexible plate changing from a position of which mechanical strength is lowest in the flexible plate between the outer periphery of the operating member and the inner periphery of the supporting base toward at least one of the outer periphery of the operating member and the inner periphery of the supporting base.

14. A force sensor according to claim 13, wherein the composition of the flexible plate from said position of lowest mechanical strength toward the outer periphery of the operating member is different from that of the flexible plate from said position of lowest mechanical strength toward the inner periphery of the supporting base.

15. A force sensor according to claim 13, wherein said detecting element is a piezoelectric element.

16. A force sensor according to claim 13, wherein said operating member, said supporting base, and said flexible plate are unitarily formed, and at least one of them has a different chemical composition from the others.

17. A force sensor according to claim 13, wherein only the flexible plate comprises a zirconia ceramic containing at least one of 0.1-0.6% by weight of titanium in terms of TiO₂ and 0.005-0.1% by weight of magnesium in terms of MgO.

18. A force sensor according to claim 13, wherein a hardness of a part of the detecting element formed on a part of or an entire surface of the flexible plate is made higher in comparison with that of the other part by a hardening material.

19. A force sensor according to claim 13, wherein the force sensor is used as an acceleration sensor with using the operating member as a weight.

20. A force sensor comprising:

a supporting base having a hollow portion,

a flexible plate having at least one detecting element and extending across the hollow portion, and

an operating member suspended over the hollow portion by the flexible plate;

wherein at least one of a boundary between the flexible plate and the operating member and a boundary between the flexible plate and the supporting base has curvature, wherein the curvature of the boundary between the flexible plate and the operating member is different from that of the boundary between the flexible plate and the supporting base.

21. A force sensor according to claim 20, wherein only the flexible plate comprises a zirconia ceramic containing at least one of 0.2-0.5% by weight of titanium in terms of TiO₂ and 0.01-0.05% by weight of magnesium in terms of MgO.

22. A force sensor according to claim 20, wherein said operating member, said supporting base, and said flexible plate are unitarily formed, and at least one of them has a different chemical composition from the others.

23. A force sensor according to claim 20, wherein only the flexible plate comprises a zirconia ceramic containing at least one of 0.1-0.6% by weight of titanium in terms of TiO₂ and 0.005-0.1% by weight of magnesium in terms of MgO.

24. A force sensor according to claim 20, wherein said detecting element is a piezoelectric element.

25. A force sensor according to claim 23, wherein a part of the detecting element includes a hardening material that makes the hardness of said part higher than that of a remaining portion of the detecting element.

26. A force sensor according to claim 20, wherein the force sensor is used as an acceleration sensor with the operating member acting as a weight.

27. A force sensor comprising:

a supporting base having a hollow portion,

a flexible plate having at least one detecting element and extending across the hollow portion, and

an operating member suspended over the hollow portion by the flexible plate;

wherein at least one of a boundary between the flexible plate and the operating member and a boundary between the flexible plate and the supporting base has curvature, and said boundary is formed in tiers.

28. A force sensor according to claim 27, wherein said detecting element is a piezoelectric element.

30. A force sensor according to claim 27, wherein only the flexible plate comprises a zirconia ceramic containing at least one of 0.1-0.6% by weight of titanium in terms of TiO₂ and 0.005-0.1% by weight of magnesium in terms of MgO.

31. A force sensor according to claim 30, wherein only the flexible plate comprises a zirconia ceramic containing at least one of 0.2-0.5% by weight of titanium in terms of TiO₂ and 0.01-0.05% by weight of magnesium in terms of MgO.

32. A force sensor according to claim 27, wherein a part of the detecting element includes a hardening material that makes the hardness of said part higher than that of a remaining portion of the detecting element.

33. A force sensor according to claim 27, wherein the force sensor is used as an acceleration sensor with the operating member acting as a weight.

29. A force sensor according to clam 27, wherein said operating member, said supporting base, and said flexible plate are unitarily formed, and at least one of them has a different chemical composition from the others.