Strain-inducing body, torque sensor, and bicycle

Abstract

To provide a torque sensor which is small and can be manufactured easily.SOLUTION: A strain-inducing body 100 includes: a first cylindrical part 110 having a portion which is displaceable in a first direction X in a radial direction; and a second cylindrical part 120 having a portion which is displaceable in a second direction Y in the radial direction. The first direction X is different from the second direction Y. A torque sensor 10 includes the strain-inducing body 100 and a rod. The strain-inducing body 100 is fixed directly or through a bearing 101 to the rod. A bicycle 1 includes the torque sensor 10. The rod is a crank shaft 11 and a pedal 8 is rotatably attached to the crank shaft 11.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] 2. Description of the Related Art Magnetostrictive torque sensors are known as torque sensors for detecting the torque of a rotating body (for example, the crankshaft of an electrically assisted bicycle) (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-094416 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, torque sensors such as those described in Patent Document 1 require attaching a magnetic layer to the shaft and arranging a detection coil around the shaft, which tends to increase the size of the device and make it difficult to manufacture.

[0005] Therefore, an example of an object of the present invention is to provide a small, easy-to-manufacture torque sensor, or to provide a strain element that can constitute such a torque sensor, or to provide a bicycle equipped with such a torque sensor. [Means for solving the problem]

[0006] The strain body according to the present invention comprises a first cylindrical portion having a portion that is displaceable in a first direction in the radial direction, and a second cylindrical portion having a portion that is displaceable in a second direction in the radial direction, the first direction being different from the second direction.

[0007] The first cylindrical portion and the second cylindrical portion may be aligned in the axial direction.

[0008] Also, a first slit may be formed in the first cylindrical portion, and a second slit may be formed in the second cylindrical portion, with the first slit and the second slit being aligned in the axial direction.

[0009] In addition, in a radial direction, an outer shape of the first cylindrical portion may be smaller than an outer shape of the second cylindrical portion.

[0010] In addition, in the axial direction, a rib may be provided on the surface of the second tubular portion on the side of the first tubular portion, and in the circumferential direction, the position of the rib may overlap with the position of the slit of the second tubular portion or the position of the portion that can be displaced in the second direction.

[0011] A torque sensor according to the present invention includes the above-mentioned strain element and a rod, and the strain element is fixed to the rod directly or via another member.

[0012] The other member may be a bearing.

[0013] A bicycle according to the present invention includes the torque sensor described above, the rod being a crankshaft, and a pedal being rotatably attached to the crankshaft. [Brief description of the drawings]

[0014] [Figure 1] 1 is a side view showing an electric-assisted bicycle equipped with a torque sensor according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a perspective view showing a torque sensor according to an embodiment of the present invention. [Diagram 3] 3 is a schematic cross-sectional view of a portion of the torque sensor shown in FIG. 2 and a cross-sectional view of the vicinity of the torque sensor; FIG. [Figure 4] FIG. 3 is a perspective view showing a strain body provided in the torque sensor shown in FIG. 2. [Diagram 5] FIG. 5 is a front view of the strain body shown in FIG. [Figure 6]6 is a cross-sectional view taken along line VI-VI shown in FIG. 4. [Figure 7] FIG. 7 is a cross-sectional view taken along line VII-VII shown in FIG. [Figure 8] FIG. 13 is a side view showing a strain body according to a modified example of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Below, embodiments for implementing the strain body, torque sensor, and bicycle according to the present invention are illustrated with reference to the accompanying drawings. The embodiments illustrated below are intended to facilitate understanding of the present invention, and are not intended to limit the present invention. The present invention can be modified or improved from the following embodiments without departing from the spirit of the present invention. In addition, in the above-mentioned attached drawings, the dimensions of each component may be exaggerated or reduced, and hatching may be omitted, in order to facilitate understanding.

[0016] Fig. 1 is a side view of a bicycle equipped with a torque sensor, showing an example of a use of the torque sensor in this embodiment, which will be described later. As shown in Fig. 1, bicycle 1 includes a bicycle body 2 and a drive unit 9. In this embodiment, bicycle 1 is a so-called electrically assisted bicycle.

[0017] The bicycle body 2 includes a frame 3, a handlebar 4, a front wheel 5, a rear wheel 6, and a pair of pedals 8, 8, etc. The frame 3 connects the handlebar 4, the front wheel 5, the rear wheel 6, etc., and forms the skeleton of the bicycle 1, supporting the rider of the bicycle 1. When the bicycle 1 is traveling, if the direction perpendicular to the straight-ahead direction SD of the bicycle 1 (the direction in which the front wheel 5 and the rear wheel 6 are roughly aligned with the frame 3) and the vertical direction is defined as the width direction of the bicycle 1, the pair of pedals 8, 8 are provided on one side (the front side of the paper in FIG. 1) and the other side (the back side of the paper in FIG. 1) of the bicycle 1 in the width direction.

[0018] In the following description, the side of the front wheel 5 in the straight-ahead direction SD will be referred to as "front," and the side of the rear wheel 6 in the straight-ahead direction SD will be referred to as "rear." In Fig. 1, pedal 8A on one side (the front side of the page) of the pair of pedals 8, 8 in the width direction is shown, and the pedal 8 on the other side is omitted. The width direction of the bicycle 1 is the left-right direction when the bicycle 1 is traveling in the straight-ahead direction SD, and for example, the front side of the page in Fig. 1 corresponds to the left side, and the back side of the page corresponds to the right side.

[0019] The drive unit 9 is located approximately in the center of the bicycle 1 and includes a battery BA. The drive unit 9 detects the force (torque) applied by the rider of the bicycle 1 to the pair of pedals 8, 8, and draws power from the battery BA in accordance with the detected force (torque) to reduce the force applied by the rider to the pedals 8, 8. In addition to the battery BA, the drive unit 9 includes a motor (not shown) that is driven by power from the battery BA, a control unit (not shown) that controls the operation of the motor, a torque sensor 10, and a housing 12. The housing 12 is fixed to, for example, the frame 3 of the bicycle body 2, forms the outer shell of the drive unit 9, and houses the motor, the control unit, the torque sensor 10, and the like inside. When the rider pedals the pedals 8, 8, the torque sensor 10 detects the force (torque) applied. The control unit controls the power supplied from the battery BA to the motor based on the torque detected by the torque sensor 10 and typically the speed of the bicycle 1. The motor operates in accordance with the power and provides the rider with an assist force in accordance with the rider's pedaling.

[0020] FIG. 2 is a perspective view showing the torque sensor 10, and FIG. 3 is a schematic diagram showing a cross section of a portion of the torque sensor 10 and a cross section near the torque sensor 10. As shown in FIGS. 2 and 3, the torque sensor 10 includes a crankshaft 11 (rod). When the crankshaft 11 is attached to the bicycle 1, it extends in the width direction (left-right direction) of the bicycle 1 (see FIG. 1). Therefore, the axial direction Z of the crankshaft 11 when the crankshaft 11 is attached to the bicycle 1 corresponds to the width direction (left-right direction) of the bicycle 1. Hereinafter, the axial direction Z of the crankshaft 11 will be simply referred to as the "axial direction Z". In the axial direction Z, the crankshaft 11 has an end 11a on one side and an end 11b on the other side. In this embodiment, the end 11a on one side of the crankshaft 11 is on the left side when the bicycle 1 is traveling in the straight direction SD, and the end 11b on the other side is on the right side when the bicycle 1 is traveling in the straight direction SD. As shown in FIG. 1, pedals 8 are attached to one end 11a and the other end 11b of the crankshaft 11 so as to be rotatable about the crankshaft 11.

[0021] As shown in Fig. 2 and Fig. 3, in this embodiment, a flexure body 100 is attached near one end 11a of the crankshaft 11. That is, the torque sensor 10 includes the crankshaft 11 (rod) and the flexure body 100. The flexure body 100 is a cylindrical member whose central axis is the central axis CA of the crankshaft 11. The flexure body 100 deforms when subjected to stress, and in this embodiment, it is elastically deformed. However, it is also possible to configure the flexure body 100 to undergo plastic deformation. The material from which the flexure body 100 is formed is not particularly limited, and may be, for example, stainless steel (SUS).

[0022] In this embodiment, an example will be described in which the flexure body 100 is attached near the end 11a on one side of the crankshaft 11. However, the flexure body 100 may be attached near the end 11b on the other side of the crankshaft 11, or may be attached both near the end 11a on one side and near the end 11b on the other side.

[0023] FIG. 4 is a perspective view showing the flexure body 100. As shown in FIG. 2 to FIG. 4, the flexure body 100 includes a first tubular portion 110 and a second tubular portion 120. The first tubular portion 110 and the second tubular portion 120 are formed in a tubular shape (cylindrical shape in this embodiment) concentric with the central axis CA of the crankshaft 11, and are arranged in the axial direction Z. Specifically, in the flexure body 100, the first tubular portion 110 is located on the side closer to one end 11a of the crankshaft 11, and the second tubular portion 120 is located on the side closer to the other end 11b (the side farther from the one end 11a). Here, in the radial direction of the flexure body 100 (the direction perpendicular to the axial direction Z), the outer shape (e.g., outer diameter) of the first tubular portion 110 is smaller than the outer shape (e.g., outer diameter) of the second tubular portion 120.

[0024] In this embodiment, as shown in Fig. 3, a predetermined through hole 12h is formed in the housing 12 of the drive unit 9. The strain body 100 is attached to the housing 12 by fitting the first cylindrical portion 110 into the through hole 12h. The first cylindrical portion 110 may be, for example, press-fitted into the through hole 12h or screwed into the through hole 12h. On the side of one end 11a in the axial direction Z, the torque sensor 10 is accommodated inside the housing 12, except for one end 11a of the crankshaft 11 and a portion in the vicinity thereof, and a portion of the first cylindrical portion 110 on the side of the one end 11a with respect to the housing 12.

[0025] 2 to 4, the second tubular portion 120 includes a tubular (cylindrical in this embodiment) sidewall 122 and an annular portion 121 that is annular (circular in this embodiment) when viewed from the axial direction Z. In the axial direction Z, the annular portion 121 is connected to an end of the sidewall 122 on the first tubular portion 110 side, and extends radially inward (toward the central axis CA) from the sidewall 122.

[0026] FIG. 5 is a front view of the flexure body 100, and is a view of the flexure body 100 seen from the first tube portion 110 side. FIG. 6 is a cross-sectional view taken along the line VI-VI shown in FIG. 4. As shown in FIGS. 4 to 6, in the second tube portion 120, the surface 121a of the annular portion 121 on the first tube portion 110 side is provided with two ribs 130, 130 that protrude toward the first tube portion 110 side in the axial direction Z. The two ribs 130, 130 are spaced apart from each other in a second direction Y, which is one of the radial directions. The second direction Y corresponds to the vertical direction when the torque sensor 10 is attached to the bicycle 1. The two ribs 130, 130 include a rib 130c on one side c (e.g., the upper side in the vertical direction) in the second direction Y and a rib 130d on the other side d (e.g., the lower side in the vertical direction) in the second direction Y. That is, the rib 130c and the rib 130d are provided on the surface 121a of the annular portion 121 at an interval of 180° in the circumferential direction.

[0027] In this embodiment, the ribs 130c and 130d have the same configuration except for their positions. Therefore, hereinafter, the ribs 130c and 130d may be simply referred to as ribs 130, and the configurations of the ribs 130c and 130d may be described without distinguishing between the ribs 130c and 130d.

[0028] As shown in FIG. 5, the rib 130 extends from the inner edge of the annular portion 121 (the outer peripheral surface of the first cylindrical portion 110) toward the outside in the radial direction. In this embodiment, the radial length of the rib 130 is slightly shorter than half the radial length of the annular portion 121. However, the radial length of the rib 130 is not particularly limited as long as a part of the rib 130 protrudes from the side wall 111 of the first cylindrical portion 110 when viewed from the first cylindrical portion 110 side in the axial direction Z. In addition, in this embodiment, the circumferential length of the rib 130 is about 1 / 8 arc (45° arc) centered on the central axis CA. However, the circumferential length of the rib 130 is not limited to this.

[0029] As shown in FIG. 6, the rib 130 includes a first portion 131 that overlaps and connects to the side wall 111 of the first cylindrical portion 110 in the axial direction Z, and a second portion 132 that is located radially outward from the first portion 131. The second portion 132 is connected to the first portion 131 and is located radially outward from the side wall 111 of the first cylindrical portion 110. That is, the second portion 132 is a portion that protrudes from the side wall 111 when viewed from the first cylindrical portion 110 side in the axial direction Z. Here, the first portion 131 of the rib 130 is a portion of the rib 130 that connects to the side wall 111 of the first cylindrical portion 110, and therefore can also be considered as a part of the side wall 111 of the first cylindrical portion 110. The first cylindrical portion 110 and the second cylindrical portion 120 are connected to each other via the first portion 131 of the rib 130. In other words, the first cylindrical portion 110 is connected to the annular portion 121 of the second cylindrical portion 120 at the first portion 131 of the first cylindrical portion 110 .

[0030] As long as the rib 130c and the rib 130d are spaced apart from each other in the second direction Y, the dimensions and shapes of the rib 130c and the rib 130d may be different from each other.

[0031] 3, in this embodiment, the inner surface of the housing 12 contacts the surface of the second portion 132 of the rib 130 on the side of the first cylindrical portion 110. This brings the housing 12 and the annular portion 121 of the second cylindrical portion 120 close to each other in the axial direction Z, preventing the housing 12 from contacting the annular portion 121 of the second cylindrical portion 120. This configuration prevents the housing 12 from hindering deformation of the annular portion 121.

[0032] 7 is a cross-sectional view taken along line VII-VII in FIG. 4. As described above, the first tube portion 110 is connected to the annular portion 121 of the second tube portion 120 via the first portion 131 of the rib 130, and thus, as shown in FIG. 7, the first slits 110S are formed on one side and the other side of the first portion 131 of the rib 130 (i.e., the first portion 131 of the first tube portion 110). The two first slits 110S, 110S are separated from each other via the first portion 131 in the first direction X, which is one of the radial directions. The first direction X corresponds to the straight direction SD (see FIG. 1) when the torque sensor 10 is attached to the bicycle 1. In other words, the first direction X and the second direction Y are different (intersect) directions, and in this embodiment, they are directions that intersect each other at 90°.

[0033] The two first slits 110S, 110S include a first slit 110S1 on one side a (e.g., the front side) in the first direction X and a first slit 110S2 on the other side b (e.g., the rear side) in the first direction X. That is, when the first portion 131 is regarded as a part of the side wall 111 of the first cylindrical portion 110, the first slit 110S1 and the first slit 110S2 are formed in the first cylindrical portion 110. Moreover, the first slit 110S1 and the first slit 110S2 are provided in the side wall 111 of the first cylindrical portion 110 at an interval of 180° in the circumferential direction.

[0034] In this embodiment, the first slit 110S1 and the first slit 110S2 have the same dimensions and shapes except for their positions. Therefore, hereinafter, the first slit 110S1 and the first slit 110S2 may be simply referred to as the first slit 110S, and the configurations of the first slit 110S1 and the first slit 110S2 may be described without distinguishing between them.

[0035] In this embodiment, the first cylindrical portion 110 and the second cylindrical portion 120 are connected at the first portion 131 of the rib 130 as described above, and are separated in the axial direction Z at other portions. In this embodiment, the space formed by the first cylindrical portion 110 and the second cylindrical portion 120 being separated in the axial direction Z is the two first slits 110S. That is, in this embodiment, the length in the circumferential direction of the first slits 110S is equal to the shortest distance in the circumferential direction from the first portion 131 of the rib 130c to the first portion 131 of the rib 130d (see FIG. 5). In this manner, the first slits 110S1 and the first slits 110S2 are separated from each other in the circumferential direction via the first portion 131 of the rib 130c and the first portion 131 of the rib 130d. The first slits 110S are formed in a portion where there is no rib 130 in the circumferential direction (extending in the circumferential direction and being flat). The length of the first slit 110S in the circumferential direction is not particularly limited, but in this embodiment, it is longer than the length of each of the ribs 130c and 130d in the circumferential direction. The length of the first slit 110S in the circumferential direction is not particularly limited, but may be, for example, about a 3 / 8 arc (a 135° arc) centered on the central axis CA (see FIG. 5).

[0036] As long as the first slits 110S1 and 110S2 are separated from each other in the first direction X, the dimensions and shapes of the first slits 110S1 and 110S2 may be different from each other.

[0037] As shown in Fig. 4 and Fig. 6, two second slits 120S, 120S are formed in the side wall 122 of the second cylindrical portion 120. The two second slits 120S, 120S are separated from each other in the second direction Y. The two second slits 120S, 120S include a second slit 120S1 on one side c (e.g., the vertical upper side) in the second direction Y and a second slit 120S2 on the other side d (e.g., the vertical lower side) in the second direction Y. That is, the second slits 120S1 and the second slits 120S2 are separated from each other in the circumferential direction on the side wall 122 of the second cylindrical portion 120 and are provided at an interval of 180°.

[0038] In this embodiment, the second slits 120S1 and 120S2 have the same dimensions and shapes except for their positions. Therefore, hereinafter, the first slits 110S1 and 110S2 may be simply referred to as the first slits 110S, and the configurations of the first slits 110S1 and 110S2 may be described without distinguishing between the second slits 120S1 and 120S2.

[0039] As shown in FIG. 4 and FIG. 7, the length of the second slit 120S in the circumferential direction is about 2 / 5 arc (144° arc) centered on the central axis CA in this embodiment. However, the length of the second slit 120S in the circumferential direction is not particularly limited as long as the two second slits 120S, 120S are separated in the second direction Y. As shown in FIG. 6 and FIG. 7, the second slit 120S is aligned with the first slit 110S in the axial direction. In addition, the second slit 120S (position or area) overlaps with the first slit 110S (position or area) in the circumferential direction. In this embodiment, a part of the second slit 120S (position or area) overlaps with a part of the first slit 110S (position or area) in the circumferential direction. In this manner, in this embodiment, a part of the second slit 120S and a part of the first slit 110S overlap in the circumferential direction, so that the circumferential lengths of both the second slit 120S and the first slit 110S are expanded. Also, as shown in Fig. 4, in this embodiment, the second slit 120S and the rib 130 overlap in the axial direction, the second slit 120S (position or region) and the rib 130 (position or region) overlap in the circumferential direction, and the second slit 120S and the rib 130 are aligned in the second direction Y.

[0040] As long as the second slits 120S1 and the second slits 120S2 are separated from each other in the second direction Y, the dimensions and shapes of the second slits 120S1 and 120S2 may be different from each other.

[0041] In this embodiment, the first cylindrical portion 110, the second cylindrical portion 120, and the ribs 130, 130 are integrally molded to form the strain body 100. In addition, in Fig. 6 and Fig. 7, the boundary between the integrally molded first cylindrical portion 110 (rib 130) and second cylindrical portion 120 is shown by a dashed line for convenience.

[0042] As shown in FIG. 5, one or more strain sensors 140 are attached to the annular portion 121 of the second cylindrical portion 120. In this embodiment, the strain sensor 140 is a strain gauge. However, the strain sensor 140 does not have to be a strain gauge, and may be various sensors such as a piezoelectric element. In this embodiment, four strain sensors 140 are attached to a surface 121a of the annular portion 121 on the first cylindrical portion 110 side. The strain sensor 140 may be attached to a surface 121b (see FIG. 6) on the opposite side of the annular portion 121 from the first cylindrical portion 110 side. In this embodiment, the four strain sensors 140 are attached at intervals of approximately 90° on the same circle centered on the central axis CA (i.e., at positions with four-fold rotational symmetry). Two of the four strain sensors 140 are attached to rib 130c at positions symmetrical to each other in the circumferential direction, and the other two are attached to rib 130d at positions symmetrical to each other in the circumferential direction. Each of the four strain sensors 140 is located away from the rib 130.

[0043] Each of the strain sensors 140, which are strain gauges, detects the strain of the annular portion 121 based on a change in resistance value. That is, the multiple (four in this embodiment) strain sensors 140 are attached so as to be able to detect the strain of the annular portion 121, and are attached (attached) to the surface 121a of the annular portion 121 so that the grid direction of each strain sensor 140 (typically, the longitudinal direction of the strain gauge) is in the radial direction.

[0044] As shown in FIG. 3, a bearing 101 is accommodated as another member in an internal space 120IR of the second cylindrical portion 120 surrounded by a side wall 122 of the second cylindrical portion 120. The bearing 101 is, for example, a ball bearing. The bearing 101 is attached to the strain body 100 by fixing (for example, press-fitting or bonding) an outer peripheral surface of the bearing 101 to the side wall 122 of the second cylindrical portion 120. A crankshaft 11 as a rod is fitted in a through hole 101h of the bearing 101 formed by an inner peripheral surface of the bearing 101. For example, the crankshaft 11 may be press-fitted or bonded into the through hole 101h. The crankshaft 11 passes through the through hole 101h and the space inside the side wall 111 of the first cylindrical portion 110 in the axial direction Z. Thus, in this embodiment, the flexure body 100 is fixed to the crankshaft 11 (rod) via the bearing 101 (another member), whereby the crankshaft 11 is rotatably supported by the flexure body 100 and the housing 12. Although not shown, a bearing is also provided near the other end 11b of the crankshaft 11. Therefore, the crankshaft 11 is rotatably supported with respect to the housing 12 on both sides in the axial direction Z by the bearing 101 and the bearing provided near the other end 11b.

[0045] As shown in Figures 1 and 3, when the rider of the bicycle 1, for example, depresses (pushes vertically downward) one of the pair of pedals 8, 8 (for example, pedal 8A on one side in the width direction), the crankshaft 11 is pushed vertically downward and moves slightly vertically downward. Therefore, the bearing 101 is pushed vertically downward (to the other side d in the second direction Y) by the crankshaft 11 pushed vertically downward. In this way, a force pushing vertically downward (to the other side d in the second direction Y) is applied from the bearing 101 to the side wall 122 of the second tubular portion 120 of the strain body 100. Here, since the side wall 122 of the second cylindrical portion 120 has the second slits 120S formed on each of the one side c and the other side d in the second direction Y (see FIG. 6), the side wall 122 of the second cylindrical portion 120 is more likely to elastically deform in the portions where the second slits 120S are formed (the portion on the one side c and the other side d in the second direction Y). The second cylindrical portion 120 elastically deforms downward in the vertical direction (the other side d in the second direction Y) due to the force pressing downward in the vertical direction from the bearing 101.

[0046] As described above, the crankshaft 11 is pushed vertically downward and moves slightly vertically downward, whereby the crankshaft 11 comes into contact with the side wall 111 of the first cylindrical portion 110 of the strain body 100, and thus a force is applied to the side wall 111 of the first cylindrical portion 110 to push the side wall 111 vertically downward (toward the other side d in the second direction Y). Here, since the first slits 110S are formed in the side wall 111 of the first cylindrical portion 110 on each of the one side a and the other side b in the first direction X (see FIG. 7), the side wall 111 of the first cylindrical portion 110 is more likely to elastically deform in the portions where the first slits 110S are formed (the portion on the one side a and the other side b in the first direction X). Therefore, when a force is applied to the side wall 111 of the first cylindrical portion 110 in the vertical downward direction (toward the other side d in the second direction Y), the side wall 111 elastically deforms in the first direction X to a greater extent than the elastic deformation in the second direction Y. Thus, the side wall 111 elastically deforms in one direction (the first direction X) when viewed macroscopically.

[0047] Thus, the first cylindrical portion 110 has a portion that is displaceable in the first direction X (a portion on one side a and a portion on the other side b of the side wall 111) in the radial direction. The second cylindrical portion 120 has a portion that is displaceable in the second direction Y (a portion on one side c and a portion on the other side d of the side wall 122) in the radial direction.

[0048] Then, the elastic deformation of the side wall 122 of the second cylindrical portion 120 in the second direction Y is transmitted to the annular portion 121 of the second cylindrical portion 120, and the elastic deformation of the side wall 111 of the first cylindrical portion 110 in the first direction X is transmitted to the annular portion 121 via the rib 130. As a result, a first elastic deformation is caused in the annular portion 121 based on the elastic deformation of the side wall 122 in the second direction Y caused by the force pressing the pedal 8 downward in the vertical direction and the elastic deformation of the side wall 111 in the first direction X caused by the force pressing the pedal 8 downward in the vertical direction, and a first strain caused by this first elastic deformation is generated.

[0049] Next, consider a case where the rider of the bicycle 1 presses one of the pair of pedals 8, 8 (e.g., pedal 8A on one side in the width direction) in, for example, the straight-line direction SD (see FIG. 1). As described above, the straight-line direction SD corresponds to one side a in the first direction X. When the rider presses the pedal 8 forward, the crankshaft 11 is pushed forward (to the one side a in the first direction X) and moves forward slightly. Therefore, the bearing 101 is pushed forward (to the one side a in the first direction X) by the crankshaft 11 pushed forward. In this way, a force pushing forward (to the one side a in the first direction X) is applied from the bearing 101 to the side wall 122 of the second tubular portion 120 of the strain body 100 (to the one side a in the first direction X). Here, since the second slits 120S are formed in the side wall 122 of the second tube portion 120 on each of the one side c and the other side d in the second direction Y (see FIG. 6), the side wall 122 of the second tube portion 120 is more likely to elastically deform in the portions where the second slits 120S are formed (the portion on the one side c and the portion on the other side d in the second direction Y). Therefore, when a force pressing forward (the one side a in the first direction X) is applied to the side wall 122 of the second tube portion 120, the side wall 122 elastically deforms in the second direction Y to a greater extent than the elastic deformation in the first direction X. Thus, the side wall 122 elastically deforms in one direction (the second direction Y) when viewed macroscopically.

[0050] In addition, the crankshaft 11 is pushed forward and moves slightly forward, so that the crankshaft 11 comes into contact with the side wall 111 of the first cylindrical portion 110 of the strain body 100. As a result, a force is applied to the side wall 111 of the first cylindrical portion 110, which pushes the side wall 111 forward (toward one side a in the first direction X). Here, the first slits 110S are formed in the side wall 111 of the first cylindrical portion 110 on each of the one side a and the other side b in the first direction X (see FIG. 7), so that the side wall 111 of the first cylindrical portion 110 is more likely to elastically deform in the portions where the first slits 110S are formed (the portion on the one side a and the portion on the other side b in the first direction X). The first cylindrical portion 110 is elastically deformed forward (toward one side a in the first direction X) by the force pushing forward from the bearing 101.

[0051] Then, the elastic deformation of the side wall 122 of the second cylindrical portion 120 in the second direction Y is transmitted to the annular portion 121 of the second cylindrical portion 120, and the elastic deformation of the side wall 111 of the first cylindrical portion 110 in the first direction X is transmitted to the annular portion 121 via the rib 130. As a result, a second elastic deformation is caused in the annular portion 121 based on the elastic deformation of the side wall 122 in the second direction Y caused by the force of the pedal 8 being pushed forward and the elastic deformation of the side wall 111 in the first direction X caused by the force of the pedal 8 being pushed forward, and a second strain caused by this second elastic deformation is generated.

[0052] For example, when the pedal 8 is pushed forward and upward (for example, at an angle of 45°), the side wall 111 of the first tubular portion 110 elastically deforms in one direction (first direction X) when viewed macroscopically, and the side wall 122 of the second tubular portion 120 elastically deforms in one direction (second direction Y) when viewed macroscopically. Then, a third strain is generated in the annular portion 121 due to a third elastic deformation corresponding to the force pushing the pedal 8 forward and upward. In this way, a strain is generated in the annular portion 121 based on the elastic deformation due to each of the forces pushing the pedal 8 in a predetermined direction.

[0053] As shown in FIG. 5, one or more strain sensors 140 are attached to the surface 121a of the annular portion 121, and the strain of the annular portion 121 is detected by the strain sensor 140. As a result, when the pedal 8 is depressed in each direction, the torque sensor 10 can detect the strain corresponding to each of these directions. In particular, in this embodiment, the strain sensors 140 are attached to a plurality of positions (positions that are symmetrical in four rotations in this embodiment) on the surface 121a of the annular portion 121, and therefore the strain generated in the annular portion 121 can be detected more accurately based on the data of the strain of the annular portion 121 detected by each strain sensor 140. Then, the torque sensor 10 detects torque based on the detected strain, and an assist force according to the detected torque, etc. is supplied from the battery BA to the motor by, for example, the above-mentioned control unit.

[0054] The torque sensor 10 of this embodiment does not use a magnetostrictive sensor, but has a simple configuration in which the strain sensor 140 is provided on the strain body 100, and therefore there is no need to arrange a detection coil, etc., which is required when using a magnetostrictive sensor, around the crankshaft (rod), which is a rotating body. Therefore, the torque sensor 10 can be made smaller and the number of parts reduced. Furthermore, the torque sensor 10 does not require processing such as attaching a magnetic layer to the rotating body, and is therefore easy to manufacture. And, the strain body 100 of this embodiment can provide a torque sensor that is small, has a small number of parts, and is easy to manufacture.

[0055] Moreover, the flexure body 100 of this embodiment has a simple structure in which the first tubular portion 110 and the second tubular portion 120 are arranged side by side. Therefore, this flexure body 100 can achieve further miniaturization, a reduction in the number of parts, and ease of manufacture.

[0056] Furthermore, since bicycle 1 according to the present embodiment is equipped with a torque sensor that has a small number of parts and is easy to manufacture, it is possible to configure a bicycle (for example, an electrically assisted bicycle) with reduced manufacturing costs.

[0057] Although the present invention has been described above by taking the above embodiment as an example, the present invention is not limited to this.

[0058] For example, in the above embodiment, the first tubular portion 110 and the second tubular portion 120 are connected by the first portion 131 of the rib 130, and the first slits 110S, 110S are formed between the first portions 131, 131 in the circumferential direction. However, a flexure body as shown in the modified example in FIG. 8 may be formed. FIG. 8 is a side view (viewed from the first direction X) showing a flexure body 100A according to a modified example of the flexure body 100. As shown in FIG. 8, in the flexure body 100A, the bottom surface of the side wall 111 of the first tubular portion 110 (the surface of the first tubular portion 110 on the second tubular portion 120 side in the axial direction Z) is directly connected to the annular portion 121 of the second tubular portion 120. That is, in the flexure body 100A, the first tubular portion 110 and the second tubular portion 120 are not separated from each other in the axial direction Z. In the flexure body 100A, the first slits 110S, 110S are formed in the axial direction Z between the bottom surface (the surface of the first tubular portion 110 on the second tubular portion 120 side in the axial direction Z) and the top surface (the surface of the first tubular portion 110 on the opposite side to the second tubular portion 120 side in the axial direction Z) of the first tubular portion 110. As shown in FIG. 8, it is preferable to provide the rib 130 in the circumferential direction of the flexure body 100A at a location where the first slit 110S is not present. By providing the rib 130 at a location where the first slit 110S is not present in the circumferential direction, the deformation of the side wall 111 in the first direction X is prevented from being hindered by the rib 130, and the side wall 111 becomes more likely to elastically deform in the first direction X.

[0059] In the above embodiment, the example in which the flexure body 100 is attached near the end 11a on one side of the crankshaft 11 has been described. However, as described above, the flexure body 100 may also be attached near the end 11b on the other side. When the flexure body 100 is also attached near the end 11b on the other side, the flexure body 100 may include a first cylindrical portion 110 having a small outer shape located closer to the end 11b on the other side and a second cylindrical portion 120 having a large outer shape located farther from the end 11b on the other side, and the bearing 101 may be provided in the second cylindrical portion 120. In this way, the crankshaft 11 is rotatably supported on both sides in the axial direction Z by the bearing 101 provided in the second cylindrical portion 120 of the flexure body 100 near the end 11a on one side and the bearing 101 provided in the second cylindrical portion 120 of the flexure body 100 near the end 11b on the other side.

[0060] In the above embodiment, an example has been described in which the flexure body 100 is fixed to the crankshaft 11 (rod) via the bearing 101 (another member). However, as long as the crankshaft 11 is supported so as to be rotatable (rotatable) relative to the flexure body 100, the crankshaft 11 may be directly attached and fixed to the flexure body 100.

[0061] In the above embodiment, the first slits 110S are formed in the portion on one side a and the portion on the other side b in the first direction X in the side wall 111 of the first cylindrical portion 110, thereby making these portions displaceable in the first direction X in the first cylindrical portion 110. However, the portion displaceable in the first direction X in the first cylindrical portion 110 does not have to be formed by a slit, and for example, the portion on the one side a and the portion on the other side b in the first direction X may be made displaceable by forming them from a material that is more easily elastically deformed than other portions of the side wall 111.

[0062] In the above embodiment, the second slits 120S are formed in the portion on one side c and the portion on the other side d in the second direction Y in the side wall 122 of the second cylindrical portion 120, thereby making these portions displaceable in the second direction Y in the second cylindrical portion 120. However, the portion displaceable in the second direction Y in the second cylindrical portion 120 does not have to be formed by a slit, and for example, the portion on the one side c and the portion on the other side d in the second direction Y may be made displaceable by forming them from a material that is more easily elastically deformed than other portions of the side wall 122.

[0063] Furthermore, in the above embodiment, an example has been described in which the torque sensor 10 is used in a bicycle (electrically assisted bicycle). However, the torque sensor 10 may be applied to devices other than bicycles by applying the strain body 100 to a rotating body (rod) other than the crankshaft 11.

[0064] In addition, a person skilled in the art can appropriately modify the strain element, torque sensor, and bicycle of the present invention in accordance with conventionally known knowledge. As long as the configuration of the present invention is still provided even after such modifications, the modifications will of course be included in the scope of the present invention. [Explanation of symbols]

[0065] 1...bicycle, 8, 8A...pedal, 10...torque sensor, 11...crankshaft, 100...flexible body, 101...bearing, 110...first cylindrical portion, 110S...first slit, 120...second cylindrical portion, 120S...second slit, 130...rib, X...first direction, Y...second direction, Z...axial direction

Claims

1. a first cylindrical portion having a portion that is displaceable in a first direction in a radial direction; a second cylindrical portion having a portion that is displaceable in a second direction in the radial direction; Equipped with The first direction and the second direction are different from each other.

2. The flexure body according to claim 1 , wherein the first cylindrical portion and the second cylindrical portion are aligned in the axial direction.

3. A first slit is formed in the first cylindrical portion, A second slit is formed in the second cylindrical portion, The flexure body according to claim 1 or 2, wherein the first slits and the second slits are aligned in the axial direction.

4. The flexure body according to claim 1 , wherein an outer shape of the first cylindrical portion is smaller than an outer shape of the second cylindrical portion in a radial direction.

5. A rib is provided on a surface of the second cylindrical portion on the first cylindrical portion side in the axial direction, 5. The strain generating body according to claim 3, wherein a position of the rib overlaps, in a circumferential direction, a position of the second slit of the second cylindrical portion or a position of a portion displaceable in the second direction.

6. A device comprising the strain body according to any one of claims 1 to 5 and a rod, The torque sensor, wherein the strain element is fixed to the rod directly or via another member.

7. The torque sensor according to claim 6 , wherein the other member is a bearing.

8. A torque sensor according to claim 6 or 7 is provided, the rod is a crankshaft; A bicycle having pedals rotatably attached to the crankshaft.

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