Strain element, torque sensor, and rotary apparatus

Abstract

To provide for example a strain element having excellent workability, and a torque sensor having it and a rotary apparatus.SOLUTION: Provided are for example a strain element (1) comprising a first section (111) extending in a radial direction, a second section (120) extending in a circumferential direction from the end of the first section (111), and a connection section (13) for connecting the first section (111) and the second section (120), a torque sensor (10) comprising the strain element (1), and a rotary apparatus (100) comprising the torque sensor (10).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a strain element, a torque sensor, and a rotating device. [Background technology]

[0002] A known detection device is one in which a strain sensor is attached to a deformable member. For example, Patent Document 1 discloses an input device that includes a rectangular substrate with fixing parts at the four corners and four strain sensors arranged on the substrate near the fixing parts, the strain sensors having a strip-like and arc-like shape, and electrodes provided along both sides of the strain sensors in the width direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-265518 Summary of the Invention [Problem to be solved by the invention]

[0004] When a detection device combining a strain element and a strain sensor is applied to a torque sensor of a rotating device, etc., the shape of the strain element becomes complex, and its manufacture may require complicated processing steps. An example of an object of the present invention is to provide a strain element that is easy to process, and a torque sensor and a rotating device that include the same. [Means for solving the problem]

[0005] The strain element of the present invention includes, for example, a first portion extending radially, a second portion extending circumferentially from an end of the first portion, and a connecting portion connecting the first portion and the second portion. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a perspective view showing a torque sensor according to an embodiment that is an example of the present invention; [Figure 2] FIG. 10 is another perspective view showing the torque sensor according to the embodiment that is an example of the present invention. [Figure 3] 1 is a plan view showing a torque sensor according to an embodiment that is an example of the present invention. FIG. [Figure 4] 1 is a cross-sectional view schematically showing a part of a rotating device according to an embodiment that is an example of the present invention. [Figure 5] 1 is a schematic diagram of a rotating device according to an embodiment that is an example of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0007] In describing the embodiments of the present invention, for convenience of explanation, the direction of arrow a along axis X (the central axis of the shaft S) is defined as one side in the axial direction. The direction of arrow b along axis X is defined as the other side in the axial direction. Here, the direction of arrow ab is referred to as the axial direction. Furthermore, the direction of arrow cd perpendicular to axis X is referred to as the radial direction, the direction of arrow c away from axis X is referred to as the outer side or one side in the radial direction, and the direction of arrow d approaching axis X is referred to as the inner side or other side in the radial direction. Furthermore, the direction of rotation around axis X is referred to as the circumferential direction. However, when referring to "extending in the circumferential direction," it may mean extending in a direction along or approximately along a straight line tangent to a circle centered on axis X, as viewed from the axial direction.

[0008] An embodiment of the present invention will now be described with reference to the drawings. Fig. 1 is a perspective view showing a torque sensor 10 in which a strain sensor 2 is attached to a strain element 1 according to this embodiment. Fig. 2 is another perspective view showing the torque sensor 10. Fig. 3 is a plan view showing the torque sensor 10.

[0009] As shown in FIG. 1 , the flexure body 1 includes an inner peripheral portion 11 and an outer peripheral portion 12. The inner peripheral portion 11 includes a retaining portion 110 and a first portion group (first portion 111, first portion 111, ...) consisting of a plurality of portions extending radially from the retaining portion 110. The outer peripheral portion 12 includes a second portion group (second portion 120, second portion 120, ...) consisting of a plurality of portions extending circumferentially from each end of the first portion 111. One first portion 111 belonging to the first portion group and one second portion 120 extending circumferentially from the end of the first portion 111 are connected by a connecting portion 13. In this embodiment, the flexure body 1 includes the same number of connecting portions 13 and second portions 120 as the number of first portions 111 included in the flexure body 1 (four in this embodiment).

[0010] The holding portion 110 is a cylindrical portion extending in the axial direction. The holding portion 110 has a cylindrical inner peripheral surface 110i around the axis X. The holding portion 110 is a portion that supports the shaft S via a bearing 3, which will be described later. In FIG. 1, the outer shape of the holding portion 110 (the shape formed by the outer contour line in the radial direction) is annular (approximately hexagonal) when viewed from the axial direction, but the outer shape of the holding portion 110 is not limited to being approximately hexagonal, and may be any shape, such as circular, approximately circular, elliptical, rectangular, polygonal, or a shape including complex irregularities.

[0011] An annular support part (flange) 112 that protrudes radially inward (in the direction of arrow d) is provided at the end of the other axial side (in the direction of arrow b) of the holding part 110. The support part 112 is a part that supports the bearing 3 (described later) from the other axial side (in the direction of arrow b) and limits movement of the bearing 3 to the other axial side (in the direction of arrow b).

[0012] 1, an end face 110a on one side in the axial direction of the holding portion 110 (in the direction of arrow a) shares a plane with an end face 111a on one side of the first portion 111, an end face 120a on one side of the second portion 120, and an end face 13a on one side of the connecting portion 13. As shown in FIG. 2, an end face 110b on the other side in the axial direction of the holding portion 110 (and an end face 112b on the other side of the support portion 112) shares a plane with an inner portion 111b1 of the end face 111b on the other side in the axial direction of the first portion 111. 2, the end face 110b on the other side (in the direction of arrow b) of the holding portion 110 (and the end face 112b on the other side of the support portion 112) is slightly to one side (in the direction of arrow a) of the outer portion 111b2 of the end face 111b on the other side of the first portion 111, the end face 120b on the other side of the second portion 120, and the end face 13b on the other side of the connecting portion 13. Therefore, the dimension of the holding portion 110 in the axial direction is slightly smaller than the dimensions of the first portion 111, the second portion 120, and the connecting portion 13. However, end face 110b of retaining portion 110 on the other axial side (direction of arrow b) (and end face 112b on the other side of support portion 112) may share a plane with the entire end face 111b on the other axial side of first portion 111, end face 120b on the other axial side of second portion 120, and end face 13b on the other axial side of connecting portion 13. That is, the dimensions of retaining portion 110 in the axial direction may be the same as the dimensions of first portion 111, second portion 120, and connecting portion 13. Furthermore, recesses (grooves) may be formed between retaining portion 110 and first portion 111, second portion 120, and connecting portion 13 in the radial direction, and the recesses may extend circumferentially.

[0013] As shown in Fig. 3, four first portions 111 protrude radially outward from the radially outer side (arrow c direction) of the holding portion 110. However, the number of first portions 111 in the flexure element 1 is not limited to four, and may be one, two, three, five or more. In this embodiment, each first portion 111 has a substantially right-angled triangular shape that becomes thinner toward the radially outer side (arrow c direction) when viewed from the axial direction. However, the shape of each first portion 111 when viewed from the axial direction may be any other shape, such as a rectangle.

[0014] Among the surfaces of the first portion 111 extending in the axial direction, a surface facing away from the direction in which the second portion 120 extends (a surface including the hypotenuse of the approximately right-angled triangle in FIG. 3) will hereinafter be simply referred to as a "surface 111f." In this embodiment, the faces 111f of two adjacent first portions 111 face in opposite directions in the circumferential direction. For example, when viewed from one side in the axial direction, the face 111f of one of the two adjacent first portions 111 faces in the clockwise direction, and the face 111f of the other first portion faces in the counterclockwise direction. However, in the circumferential direction, the faces 111f of all first portions 111 may face in the same direction, or the facing direction of the faces 111f of the first portions 111 may be alternated every few first portions 111, or the facing direction of the faces 111f of the first portions 111 may be alternated randomly.

[0015] The first portion 111 has an end face 111a (FIG. 1) on one side (arrow a direction) in the axial direction and an end face 111b (FIG. 2) on the other side (arrow b direction). The end face 111b on the other side in the axial direction of the first portion 111 has a portion 111b1 on the inner side (arrow d direction) and a portion 111b2 on the outer side (arrow c direction) in the radial direction. The inner portion 111b1 of the end face 111b is located on one side in the axial direction (arrow a direction) of the outer portion 111b2 of the end face 111b. In other words, the outer portion 111b2 of the end face 111b of the first portion 111 protrudes toward the other side in the axial direction (arrow b direction) beyond the inner portion 111b1 of the end face 111b. The inner portion 111b1 of the end face 111b of the first portion 111 shares a plane with the end face 110b on the other side in the axial direction (arrow b direction) of the holding portion 110. An outer portion 111b2 of the end face 111b of the first portion 111 shares a plane with the other end face 120b of the second portion 120 and the other end face 13b of the connecting portion 13. A step is provided at the boundary between the inner portion 111b1 and the outer portion 111b2 of the end face 111b of the first portion 111.

[0016] The second portion 120 is connected to the outer end (in the direction of arrow c) of each first portion 111 in the radial direction via a connecting portion 13. Each second portion extends in the circumferential direction from the outer end of the corresponding first portion 111 in the radial direction. The second portion 120 is a portion that can be used, for example, to attach the strain element 1 to an external device 4, which will be described later. As shown in FIG. 3, each second portion 120 has a substantially rectangular shape when viewed in the axial direction.

[0017] In this embodiment, the flexure body 1 has four second portions 120. However, the number of second portions 120 in the flexure body 1 is not limited to four, and may be one, two, three, five or more. In this embodiment, one second portion 120 is connected to one first portion 111. In this embodiment, four second portions 120 are arranged at positions that are approximately four-fold symmetric about the axis X. That is, the four second portions 120 are arranged at approximately equal intervals (approximately every 90°) in the circumferential direction. However, the multiple second portions 120 do not have to be arranged at approximately equal intervals in the circumferential direction. For example, a second second portion 120 may be arranged at an interval of n° from a first second portion 120, a third second portion 120 may be arranged at an interval of (180-n)° from there, and a fourth second portion 120 may be arranged at an interval of n° from there.

[0018] In this embodiment, the extension directions of two adjacent second portions 120 are opposite to each other in the circumferential direction. For example, when viewed from one side in the axial direction, one of the two adjacent second portions 120 extends in a clockwise direction and the other extends in a counterclockwise direction. However, all of the second portions 120 belonging to the second portion group may extend in the same direction in the circumferential direction, or the extension direction of the second portions 120 may be switched every few second portions 120, or the extension direction of the second portions 120 may be switched randomly. Since all four second portions 120 have the same configuration except for the direction in which they extend, only one second portion 120 will be described in detail below, and detailed descriptions of the other second portions 120 will be omitted.

[0019] As shown in Fig. 3, a hole 121 extending in the axial direction is formed near the center of the second portion 120. The hole 121 has a circular or approximately circular cross section. As will be described later, the second portion 120 is fixed to the external device 4 by a fastening member B such as a bolt that is inserted axially through the hole 121 (Fig. 4). In this way, the entire strain generating body 1 is fixed to the external device 4.

[0020] The second portion 120 has a first surface 122 and a second surface 123 that each extend in the axial direction. The first surface 122 of the second portion 120 extends parallel or approximately parallel to the surface 111f of the first portion 111 and faces in the opposite direction to the surface 111f of the first portion 111. The second surface 123 of the second portion 120 extends in a direction intersecting with the first surface 122 and faces outward in the radial direction (the direction of arrow c). In this embodiment, the second surface 123 of the second portion 120 is perpendicular or approximately perpendicular to the first surface 122.

[0021] The connecting portion 13 extends circumferentially from the radially outer end (in the direction of arrow c) of the first portion 111 and continues to the second portion 120. The connecting portion 13 has a surface 13c. The surface 13c extends in the axial and circumferential directions and faces radially outward (in the direction of arrow c). The surface 13c of the connecting portion 13 shares a plane with the second surface 123 of the second portion 120. As will be described later, the surface 13c of the connecting portion 13 is a deformable surface, and is the surface on which the strain sensor 2 is attached.

[0022] As shown in FIG. 3, a slit 14 is formed between the first portion 111 and the corresponding second portion 120. The slit 14 penetrates the strain body 1 in the axial direction. The slit 14 has a radially extending portion 141 and a circumferentially extending portion 142. The radially extending portion 141 and the circumferentially extending portion 142 extend in different directions, so the slit 14 has a curved shape. The angle formed between the radially extending portion 141 and the circumferentially extending portion 142 (angle θ shown in FIG. 3) is, for example, within a range of 80° to 180°. The angle θ may be within a range of 85° to 160°, 90° to 140°, or 95° to 135°. The first portion 111 and the second portion 120 face each other via the radially extending portion 141 of the slit 14. That is, in the circumferential direction, the first portion 111 and the second portion 120 face each other at a predetermined distance (the width of the portion 141 extending in the radial direction of the slit 14). Also, the holding portion 110 and the second portion 120 face each other via the portion 142 extending in the circumferential direction of the slit 14. That is, in the radial direction, the holding portion 110 and the second portion 120 face each other at a predetermined distance (the width of the portion 142 extending in the circumferential direction of the slit 14).

[0023] The slit 14 includes a space 143 surrounded by the first portion 111, the second portion 120, and the connecting portion 13. In this embodiment, the space 143 is a hole having a circular or approximately circular cross section (cross section perpendicular to the axial direction). The space 143 extends in the axial direction and penetrates the strain generating element 1 in the axial direction. In the slit 14, the radially extending portion 141, the circumferentially extending portion 142, and the space 143 are in communication with each other. The space 143 is connected to the radially outer end (direction of arrow c) of the radially extending portion 141 of the slit 14. The width of the space 143 (the dimension in the direction perpendicular to the extension direction of the slit 14 in FIG. 3 ) is wider than the radially extending portion 141 of the slit 14.

[0024] The retaining portion 110 and the second portion 120 are spaced apart by a predetermined distance in the radial direction, and the thickness (diametric dimension) of the connecting portion 13 is thinner than other portions of the strain generating body 1, so that when a radial force is applied to the retaining portion 110, the retaining portion 110 can be displaced mainly in the radial direction relative to the second portion 120. At that time, of the surfaces of the connecting portion 13, surface 13c in particular is easily deformed with strain.

[0025] Each connecting portion 13 has a surface 13c, so that the flexure element 1 has a plurality of surfaces 13c (four in this embodiment) as a whole. The surfaces 13c are arranged in the circumferential direction (FIG. 3).

[0026] The torque sensor 10 has a strain sensor 2 attached to a strain element 1. The strain sensor 2 is attached to each of the surfaces 13c of the connecting portion 13. By attaching a strain sensor 2 to each of the multiple surfaces 13c, the torque sensor 10 has multiple (four in this embodiment) strain sensors 2 attached to it. However, the strain sensors 2 may be attached to some of the multiple surfaces 13c. In this embodiment, the multiple strain sensors 2 are all attached to surfaces facing different directions. That is, the multiple surfaces 13c to which the strain sensors 2 are attached face in different directions (in this embodiment, directions that differ by 90°). The strain sensors 2 are attached so as to be able to detect strain on the surfaces 13c. The strain sensors 2 are attached to the surfaces 13c so that the orientation of the grid (typically the longitudinal direction of the strain sensors 2) is aligned in a predetermined direction. If the strain sensor 2 is a strain gauge, the strain on the surface 13c is detected as a change in resistance value. The strain sensor 2 may be any sensor such as a resistance element or a piezoelectric element.

[0027] As described above, in this embodiment, the strain sensor 2 is attached to the surface 13c of the connecting portion 13. However, the strain sensor 2 may be attached to one or more surfaces selected from the group consisting of, for example, the surface 111f of the first portion 111, the end face 111a on one side in the axial direction of the first portion 111, the end face 111b on the other side in the axial direction of the first portion 111, another surface of the connecting portion 13, the first surface 122 of the second portion 120, the second surface 123 of the second portion 120, the end face 120a on one side in the axial direction of the second portion 120, and the end face 120b on the other side in the axial direction of the second portion 120.

[0028] Typically, the strain sensors 2 are attached to the strain element 1 so that the grid orientation is perpendicular to the axial direction (circumferential direction). However, the grid orientation of the strain sensors 2 may be axial or radial, or may be oblique to the circumferential, radial, or axial direction, depending on the situation. Furthermore, among the multiple strain sensors 2, the grid orientation of two opposing strain sensors 2 may be axial, and the grid orientation of two other opposing strain sensors 2 may be circumferential. Furthermore, the grid orientation of two opposing strain sensors 2 may be oblique (first direction), and the grid orientation of two other opposing strain sensors 2 may be oblique (second direction) different from the first direction.

[0029] Next, a rotating device 100 including the torque sensor 10 will be described with reference to Figs. 4 and 5. The rotating device 100 is an example of a rotating device of the present invention. Fig. 4 is a cross-sectional view (a cross-sectional view taken along an axis X that is the central axis of the shaft S) that schematically shows a portion of the rotating device 100. Fig. 5 is a schematic diagram of the rotating device 100.

[0030] 4, the rotating device 100 includes a torque sensor 10, a bearing 3 attached to an inner peripheral portion 11 of a flexure body 1 of the torque sensor 10, and an external device 4 attached to a second portion 120 of the flexure body 1 of the torque sensor 10. In this embodiment, the bearing 3 is a ball bearing having an inner ring 31, rolling elements 32, and an outer ring 33. Note that the bearing 3 is not limited to a ball bearing, and may be various other bearings, such as a sleeve bearing.

[0031] In the radial direction, the bearing 3 is disposed inside (in the direction of arrow d) the holding portion 110 of the flexure body 1. The bearing 3 is held by the holding portion 110 of the flexure body 1. The inner ring 31 of the bearing 3 is press-fitted onto the outer peripheral surface (the outer surface in the radial direction) of the shaft S, or is bonded to the outer peripheral surface of the shaft S with a bonding material such as resin. In this way, the inner ring 31 of the bearing 3 is fixed to the shaft S. The outer ring 33 of the bearing 3 is press-fitted into the inner peripheral surface 110i of the holding portion 110 of the flexure body 1. The outer ring 33 of the bearing 3 may be bonded to the inner peripheral surface 110i of the holding portion 110 of the flexure body 1 with a bonding material such as resin. The bearing 3 supports the shaft S rotatably relative to the flexure body 1.

[0032] The shaft S is a cylindrical or approximately cylindrical member extending in the axial direction. The shaft S is supported by the strain body 1 via a bearing 3. In the axial direction, the other end of the shaft S (in the direction of arrow b) protrudes from a hole 41 in the external device 4. In this embodiment, when the shaft S receives a radial external force (or a radial component of the external force), the bearing 3 is displaced and the strain body 1 is deformed.

[0033] In this embodiment, a surface on one axial side (arrow a direction) of the support portion 112 of the strain element 1 contacts an end face on the other axial side (arrow b direction) of the outer ring 33 of the bearing 3. As a result, the support portion 112 supports the bearing 3 while restricting its movement toward the other axial side (arrow b direction).

[0034] In the external device 4, an attachment hole 42 recessed in the axial direction is formed at a position corresponding to the hole 121 of the second portion 120 of the flexure body 1. A fastening member B such as a bolt is inserted through or screwed into the hole 121 of the flexure body 1 and the attachment hole 42 of the external device 4, thereby fixing the flexure body 1 to the external device 4. However, the flexure body 1 may also be fixed to the external device 4 by any other means. For example, the flexure body 1 may be fixed to the external device 4 by bonding the second portion 120 to the external device 4. In that case, the hole 121 may not be formed in the second portion 120 of the flexure body 1.

[0035] FIG. 5 is a schematic diagram of a rotating device 100 that is an electrically assisted bicycle and an external device 4 that is its drive unit. As shown in FIG. 5, the torque sensor 10 is housed inside a housing 43 of the drive unit. However, the torque sensor 10 may also be attached to the outside of the housing 43 of the drive unit. Both ends of the shaft S protrude outside the housing 43. A first crank arm A1 and a second crank arm A2 are connected to the respective ends of the shaft S. A first pedal P1 is connected to the first crank arm A1, and a second pedal P2 is connected to the second crank arm A2.

[0036] When one of the pedals of the electrically assisted bicycle (the first pedal P1 or the second pedal P2) is stepped on, a force acts on the end of the shaft S closest to the pedal that is stepped on, tilting it downward in FIG. 5 , causing the bearing 3 to move radially, pressing a portion of the flexure element 1 radially outward and pulling another portion of the flexure element 1 radially inward. This causes stress to concentrate in a portion of the flexure element 1 near the slit 14 (e.g., the surface 13c of the connecting portion 13), resulting in deformation accompanied by strain. The strain is detected by the strain sensor 2. The torque sensor 10 can obtain the torque acting on the shaft from the strain detected by the strain sensor 2. The strain sensor 2 is connected to a circuit board (not shown), for example, located inside or outside the housing 43 of the external device 4, and a signal corresponding to the strain detected by the strain sensor 2 is input to the circuit board.

[0037] The presence of multiple strain sensors 2 makes it possible to detect strain in the strain element 1 in response to tilt in all directions of the shaft S. In particular, in the torque sensor 10 of this embodiment, the four second portions 120 are arranged at predetermined intervals around the axis X, making it possible to more accurately detect strain in all directions.

[0038] The flexure element 1 is configured to include a first portion 111 extending radially and a second portion 120 extending circumferentially from the end of the first portion 111, and can be easily designed into a simple shape with excellent workability. Furthermore, the flexure element 1 can be formed so that the slits 14 extend in the axial direction. In this case, there is no need to frequently change the direction in which the workpiece (material to be cut) is fixed during processing, and the flexure element 1 has even better workability.

[0039] The torque sensor 10 has a simple configuration including the strain element 1 and the strain sensor 2, which allows the entire device to be miniaturized. In addition, since no processing such as attaching a magnetostrictive material to the shaft S is required, manufacturing is easy.

[0040] Although the strain element, torque sensor, and rotating device of the present invention have been described above using preferred embodiments, the strain element, torque sensor, and rotating device of the present invention are not limited to the configurations of the above-mentioned embodiments. For example, the strain element 1 and torque sensor 10 according to the above-mentioned embodiments are used in an electrically assisted bicycle as the rotating device 100, but the strain element and torque sensor of the present invention are not limited to those used in electrically assisted bicycles. In other words, the rotating device of the present invention is not limited to electrically assisted bicycles.

[0041] In addition, a person skilled in the art can appropriately modify the torque sensor of the present invention and change the shapes, dimensions, and combinations of various components in accordance with conventionally known knowledge. As long as the components of the present invention are still included even after such modifications, they are of course included in the scope of the present invention. [Explanation of symbols]

[0042] 1...strain element, 10...torque sensor, 100...rotating device, 11...inner peripheral portion, 111...first portion, 12...outer peripheral portion, 120...second portion, 13...connecting portion, 14...slit, 141...portion extending radially of slit, 142...portion extending circumferentially of slit, 143...space, 2...strain sensor, 3...bearing, 4...external device.

Claims

1. a radially extending first portion; a second portion extending circumferentially from an end of the first portion; a connecting portion connecting the first portion and the second portion; A strain-generating body comprising:

2. The flexure element according to claim 1 , wherein the connecting portion extends in a circumferential direction.

3. The flexure element according to claim 1 or 2, wherein a slit is formed between the first portion and the second portion.

4. The flexure element according to claim 3 , wherein the slit has a portion extending in a radial direction and a portion extending in a circumferential direction.

5. a space surrounded by the first portion, the second portion, and the connecting portion is formed, The flexure element according to claim 4 , wherein the space is a part of the slit.

6. having an inner periphery and an outer periphery; the inner circumferential portion includes a first portion group configured by a plurality of portions extending in a radial direction, the first portion group including the first portion; The flexure element according to claim 1 , wherein the outer peripheral portion includes a second portion group configured by a plurality of portions extending in a circumferential direction, and the second portion group includes the second portion.

7. The strain element according to claim 6, a strain sensor attached to the strain generating body; A torque sensor comprising:

8. The torque sensor according to claim 7; a bearing attached to the inner peripheral portion of the strain generating body; an external device attached to the second portion of the strain generating body; A rotating device comprising:

Images