Load cell attachment structure

Abstract

This load cell attachment structure includes a male screw which is formed on a load sensing part of the load cell, a nut which attaches the load cell to the attachment plate by engaging with the male screw, and a wave washer which is disposed between the attachment plate and the nut.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a load cell attachment structure.

Priority is claimed on Japanese Patent Application No. 2004-259502, filed Sep. 7, 2004, and on Japanese Patent Application No. 2004-259503, filed Sep. 7, 2004, the content of which is incorporated herein by reference.

2. Description of Related Art

In order to control operating and the like of an air bag system when a collision of a vehicle happens, a load cell which measures load acting on a seat is mounted on the vehicle. Then, it is determined whether an occupant is seated or not, and whether the occupant who is seated is an adult or a child, and the like.

For example, there is a system which includes stud bolts projecting above, which is disposed on the front and rear of sliders of bilateral seat rails, a plate member which is fixed on the stud bolts and a seat frame. One end of the plate member is fixed on a tip of the stud bolts which go through holes of the seat frame, and the other end of the plate member is fixed on the seat frame (refer to U.S. Pat. No. 6,161,891). In the reference, amount of deformation of the plate member is measured.

Also, as shown in FIG. 7, there is a system in which a male screw 102 is disposed on a load sensing part 101 of a load cell 100, the load cell 100 is attached to a slider 103 of a seal rail facing upward toward the load sensing part 101, and an attachment plate 104 of a seat frame is attached to the load cell 100 by engaging a nut 105 with the male screw 102. In this system, when the attachment plate 104 is attached to the load sensing part 101 by fastening the nut 105 to the male screw 102 tightly, if only the attachment plate 104 of the seat frame warps or inclines slightly due to a minor accident of the vehicle or the like, the load cell 100 measures slight loads are caused by the warp or the incline. As a result, the load cell 100 cannot measure loads accurately. Accordingly, as shown in FIG. 8, it is proposed that clearance which allows warp or the incline of the attachment plate 104 be formed between the nut 105 and the load sensing part 101 by disposing a collar 106 between the nut 105 and the load sensing part 101. However, in this system, a fastening force along the longitudinal direction of the male screw 102 acts on the load sensing part 101 through the collar 106. As a result, the load cell 100 senses undesired load. In other words, drift force along the axis is caused on the load cell 100.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a load cell attachment structure capable of preventing a load cell from sensing undesired loads which are caused by warp or a incline of the attachment plate, and as a result, load cell can measure loads accurately.

A load cell attachment structure of the present invention for attaching a load cell to an attachment plate includes: a first fastening part which is formed on a 11sensing part 3826 25 does not sense an undesired load which is caused by the warp or incline of the attachment plate 26 due to a minor collision of the vehicle or the fastening force. As a result, it is possible to measure loads exactly.

In addition, the fastening force which is introduced through the collar part 42 is dispersed on the load sensing part evenly by the washer part 41. Therefore, the load cell 25 does not sense an undesired load (in other words, “drift force along the axis”) which is caused by the fastening force, and dispersion of initial values of the load cell caused by difference in fastening torque can be reduced. As a result, it is possible to measure load exactly. That is, when the washer 40 is a collar only, in the total sensing range of the load sensor 25, the range defined by counting out the weight of the seat as well as drift from the fastening force becomes the range that can be used to sense the weight of the occupant. However, when the washer 40 is provided with the washer portion 41 and the collar portion 42, in the total sensing range of the load sensor 25, the range defined by counting out only the weight of the seat becomes the range that can be used to sense the weight of the occupant. Accordingly, the effective sensing range of the sensor becomes extremely wide.

Since the wave washer 47 is disposed between the attachment plate 26 and the nut 50, if the attachment plate 26 does not warp or incline, or if the attachment plate 26 warps, the wave washer 47 deforms corresponding to the warp or incline. Therefore, it is possible to reduce the backlash of the attachment plate 26 which is disposed between the washer 49 and the washer part 41.

Since the collar part 42 is formed as a single body with the washer part 41, it is possible to reduce the quantity of parts and time in assembly. Naturally, the collar part 42 and the washer part 41 can also be separate. Note that, if the load cell 25 can measure loads exactly without the dispersion of the fastening force over the load sensing part 38, as shown in FIG. 4, the washer 40 may include only the collar part 42 without the washer part 41.

The load cell attachment structure of this embodiment may include another elastic body instead of the wave washer 47. For example, as shown in FIG. 5, a plate-spring shape washer 52 may be disposed between the nut 50 and the washer 41. The washer 52 is composed of a flat plate part 53 with a ring shape and a tapered part 54 which is disposed on the outside edge of the flat plate part 53. The tapered part 54 inclines with respect to the flat plate part 53. The flat plate part 53 closely contacts the lower surface of the nut 50 and the upper end surface of the collar part 42, and an outside edge of the tapered part 54 closely contacts the attachment plate 26.

Further, as shown in FIG. 6, a plate-spring 62 which is sandwiched between washers 63, 64 may be disposed between the nut 50 and the washer 40. The plate-spring 62 is composed of a flat plate part 60 with a ring shape and a tapered part 61 which is disposed on the outside edge of the flat plate part 60. The tapered part 61 inclines with respect to the flat plate part 60. The washer 63 is disposed between the plate-spring 62 and the nut 50, and the washer 64 is disposed between the plate-spring 62 and the collar part 42. The external diameter of the washer 63 is less than the external diameter of the washer 64, and the external diameter of the plate-spring 62 is less than the external diameter of the washer 64. The washer 63 closely contacts the lower surface of the nut 50, and the washer 64 closely contacts the upper end surface of the collar part 42. Further, an outside edge of the taper plate part 61 closely contacts the attachment plate 26. A resinous cover 66 is disposed on an inside edge of the attachment hole 45 of the attachment plate 26. The cover 66 prevents the inside edge of the attachment hole 45 from contacting the washer 40.

In the above embodiment, the structure in which the load cell 25 is attached to the attachment plate 26 by the male screw 36 being disposed on the load sensing part 38 of the load cell 25, and the nut 50 being thread-engaged with the male screw 36, is explained. However, a structure in which the load cell 25 is attached to the attachment plate 26 by a female screw being disposed on the load sensing part 38 of the load cell 25, and a bolt being thread-engaged with the female screw, may be applied. In this structure, the bolt is inserted into the penetration hole 43, and the collar part 42 of the washer 40 is disposed between the washer part 41 and a top of the bolt. Also, the wave washer 47 is disposed between the attachment plate 26 and the top of the bolt.

While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit or scope of the present invention. Accordingly, the invention is not to be considered as being limited by the foregoing description, and is only limited by the scope of the appended claims.

Claims

1. A load cell attachment structure for attaching a load cell to an attachment plate, the load cell including a main body and a load sensing part, the load cell attachment structure comprising:

a first fastening part which is formed on a load sensing part the main body of the load cell;

a second fastening part which attaches the load cell to the attachment plate by engaging with the first fastening part;

an elastic body which is disposed between the attachment plate and the second fastening part; and

a washer part which entirely covers the load sensing part, and is disposed between the attachment plate and the load sensing part.

2. A load cell attachment structure according to claim 1, further comprising:

a collar part which is disposed between the washer part and the second fastening part, wherein

a length of the collar part along an axis thereof is longer than a thickness of the attachment plate.

3. A load cell attachment structure according to claim 2, wherein

the first fastening part comprises a male screw,

the second fastening part comprises a nut,

the elastic body is disposed between the attachment plate and the nut, and

the collar part is disposed between the washer part and the nut.

4. A load cell attachment structure according to claim 2, wherein the collar part is formed as a single body with the washer part.

5. A load cell attachment structure for attaching a load cell to an attachment plate, the load cell including a main body and a load sensing part, the load cell attachment structure comprising:

a first fastening part which is formed on a load sensing part the main body of the load cell;

a second fastening part which attaches the load cell to the attachment plate by engaging with the first fastening part;

a washer part which entirely covers the load sensing part, and is disposed between the load sensing part and the attachment plate; and

a collar part which is disposed between the washer part and the second fastening part, wherein

a length of the collar part along an axis thereof is longer than a thickness of the attachment plate.

6. A load cell attachment structure according to claim 5, wherein

the first fastening part comprises a male screw,

the second fastening part comprises a nut, and

the collar part is disposed between the washer part and the nut.

7. A load cell attachment structure according to claim 5, wherein the collar part is formed as a single body with the washer part.

8. A load cell attachment structure for attaching a load cell to an attachment plate, the load cell including a main body and a load sensing part, the load cell attachment structure comprising:

a male screw which is formed on a load sensing part the main body of the load cell and which is inserted into an attachment hole formed in the attachment plate;

a nut which attaches the load cell to the attachment plate by engaging with the male screw;

an elastic body which is disposed between the attachment plate and the nut fastened on the male screw; and

a washer having a washer part and a collar part and which is disposed between the load sensing part and the attachment plate, in which the washer part covers all of the load sensing part and contacts the load sensing part, and the collar part is disposed between the washer part and the nut, wherein

the male screw is inserted into the collar part,

the collar part is inserted into the attachment hole,

the length of the collar part along an axis thereof is longer than a thickness of the attachment plate to have a space between the nut and the attachment plate, and

the elastic body having a thickness greater than the space is disposed between the attachment plate and the nut, and the nut is engaged with the male screw until the nut contacts the collar part.

9. A load cell attachment structure for attaching a load cell to an attachment plate, the load cell including a main body and a load sensing part, the load cell attachment structure comprising:

a male screw which is formed on a load sensing part the main body of the load cell and which is inserted into an attachment hole formed in the attachment plate;

a nut which attaches the load cell to the attachment plate by engaging with the male screw;

a plate-spring which is composed of a flat plate part and a tapered part disposed on the outside edge of the flat plate part and which is disposed between the attachment plate and the nut fastened on the male screw to push the attachment plate to the load sensing part; and,

a washer having a washer part and a collar part and which is disposed between the load sensing part and the attachment plate, in which the washer part contacts the load sensing part, and the collar part is disposed between the washer part and the nut;

wherein the flat plate part of the plate spring is disposed between the collar part and the nut.

10. The load cell attachment structure according to claim 9, wherein an elastic cover is disposed on an edge of the attachment hole.

11. The load cell attachment structure according to claim 10, wherein a space is formed between the elastic cover and the collar part.

12. The load cell attachment structure of claim 10, wherein the elastic cover is disposed between the attachment plate and the washer part.

13. The load cell attachment structure according to claim 9, wherein a second washer is disposed between the flat plate part and the collar part.

14. The load cell attachment structure according to claim 13, wherein a third washer is disposed between the nut and the flat plate part, and an outer diameter of the third washer is larger than that of the second washer.

15. The load cell attachment structure according to claim 2, wherein the elastic body is arranged at a periphery of the collar part.

16. The load cell attachment structure according to claim 4, wherein the elastic body is arranged at a periphery of the collar part.

17. The load cell attachment structure according to claim 1, wherein the washer part contacts the load sensing part.

18. The load cell attachment structure according to claim 1, wherein an outer edge of the elastic body is farther than a periphery of the main body of the load cell from the first fastening part arranged at a center of the main body.

19. The load cell attachment structure according to claim 1, wherein the washer part is larger in diameter than the load sensing part.

20. The load cell attachment structure according to claim 1, wherein an outer edge of the elastic body is farther than a periphery of the main body of the load cell from the male screw arranged at the center of the main body.

21. The load cell attachment structure according to claim 7, wherein the load cell warps when load downwardly acts on the load sensing part, and thereby the load acting on the load sensing part is measured by the load cell.

22. The load cell attachment structure according to claim 7, further comprising an elastic body which is disposed between the washer part and the second fastening part.

23. The load cell attachment structure according to claim 22, wherein the elastic body includes an inclination part.

24. The load cell attachment structure according to claim 5, wherein the washer part contacts the load sensing part.

25. The load cell attachment structure according to claim 5, wherein the load cell warps when a load downwardly acts on the load sensing part, and thereby the load acting on the load sensing part is measured by the load cell.

26. The load cell attachment structure according to claim 5, further comprising an elastic body which is disposed between the washer part and the second fastening part.

27. The load cell attachment structure according to claim 26, wherein the elastic body includes an inclination part.

28. The load cell attachment structure according to claim 26, wherein a second washer is disposed between the collar part and a nut included in the second fastening part.

29. The load cell attachment structure according to claim 26, wherein the elastic body includes a bending part.

30. The load cell attachment structure according to claim 26, wherein an end of the elastic body close to the second fastening part contacts a second washer.

31. The load cell attachment structure according to claim 26, wherein the attachment plate includes an attachment hole to which the first fastening part is inserted, and

a cover is disposed between a hole portion and the collar part.

32. The load cell attachment structure according to claim 31, wherein the cover prevents the collar part from contacting an attachment hole of an attachment plate.

33. The load cell attachment structure according to claim 31, wherein the cover is an independent member from the elastic body.

34. The load cell attachment structure according to claim 31, wherein the cover comprises an insertion portion to be inserted to the attachment hole, and an extension part outwardly-extending in a radial direction from the insertion portion.

35. The load cell attachment structure according to claim 31, wherein the elastic body includes a bending part.

36. The load cell attachment structure according to claim 5, wherein a second washer is disposed between the collar part and a nut included in the second fastening part.

37. The load cell attachment structure according to claim 5, further comprising an elastic body which is disposed between the attachment plate and the second fastening part, wherein the elastic body includes a bending part.

38. The load cell attachment structure according to claim 5, wherein the washer part is larger in diameter than the load sensing part.

39. The load cell attachment structure according to claim 5, further comprising an elastic body which is disposed between the attachment plate and the second fastening part, wherein an end of the elastic body close to the second fastening part contacts a second washer.

40. The load cell attachment structure according to claim 5, further comprising an elastic body which is disposed between the attachment plate and the second fastening part, wherein the elastic body is arranged at a periphery of the collar part.

41. The load cell attachment structure according to claim 5, further comprising an elastic body which is disposed between the attachment plate and the second fastening part, wherein an outer edge of the elastic body is farther than a periphery of the main body of the load cell from the male screw arranged at the center of the main body.

42. The load cell attachment structure according to claim 5, wherein the attachment plate includes an attachment hole to which the first fastening part is inserted, and

a cover is disposed between a hole portion and the collar part.

43. The load cell attachment structure according to claim 42, wherein the cover prevents the collar part from contacting an attachment hole of an attachment plate.

44. The load cell attachment structure according to claim 8, wherein the washer part contacts the load sensing part.

45. The load cell attachment structure according to claim 8, wherein an outer edge of the elastic body is farther than a periphery of the main body of the load cell from the male screw arranged at a center of the main body.

46. The load cell attachment structure according to claim 8, wherein the elastic body is arranged at a periphery of the collar part.

47. The load cell attachment structure according to claim 8, wherein the washer part is larger in diameter than the load sensing part.

48. A load cell attachment structure for attaching a load cell to an attachment plate, the load cell including a main body and a load sensing part, the load cell attachment structure comprising:

a first fastening part which is formed on the main body of the load cell;

a second fastening part which attaches the load cell to the attachment plate by engaging with the first fastening part;

a washer part which entirely covers the load sensing part, and is disposed between the load sensing part and the attachment plate;

a collar part which is disposed between the washer part and the second fastening part; and

an elastic body which is disposed between the washer part and the second fastening part, wherein

the elastic body is arranged at a periphery of the collar part, and

a length of the collar part along an axis thereof is longer than a thickness of the attachment plate.

49. The load cell attachment structure according to claim 48, wherein the elastic body includes an inclination part.

50. The load cell attachment structure according to claim 48, wherein a second washer is disposed between the collar part and a nut included in the second fastening part.

51. The load cell attachment structure according to claim 48, wherein the elastic body includes a bending part.