Bicycle power transmission system

Abstract

To perform crimping operations reliably. [Solution] The crank arm rotates integrally with the first rotating body. The first rotating body has a hub portion and a flange portion. The hub portion extends axially. The flange portion extends radially outward from the hub portion. The crank arm has a mounting portion and an arm body portion. The mounting portion is attached to the hub portion. The arm body portion extends radially outward from the mounting portion. The mounting portion has a mounting body portion and a tip portion. The mounting body portion abuts the hub portion in the axial direction. The tip portion extends axially from the mounting body portion. The tip portion has an outer diameter smaller than the outer diameter of the mounting body portion. The tip portion is crimped to the hub portion. The mounting body portion has an outer diameter larger than the outer diameter of the hub portion.

Description

Technical Field

[0001] The present invention relates to a power transmission device for a bicycle.

Background Art

[0002] Patent Document 1 discloses a power transmission device for a bicycle. The power transmission device for a bicycle has a first rotating body and a second rotating body. The first rotating body and the second rotating body are elastically connected by a coil spring. The crank arm is attached to the hub portion of the first rotating body.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The crank arm is attached to the hub portion of the first rotating body by caulking. The problem of the present invention is to provide a power transmission device for a bicycle capable of performing caulking stably.

Means for Solving the Problems

[0005] A bicycle power transmission device according to the first embodiment comprises a first rotating body, a second rotating body, an elastic member, and a crank arm. The second rotating body is arranged to be rotatable relative to the first rotating body. The elastic member elastically connects the first rotating body and the second rotating body. The crank arm rotates integrally with the first rotating body. The first rotating body has a hub portion and a flange portion. The hub portion extends axially. The flange portion extends radially outward from the hub portion. The crank arm has a mounting portion and an arm body portion. The mounting portion is attached to the hub portion. The arm body portion extends radially outward from the mounting portion. The mounting portion has a mounting body portion and a tip portion. The mounting body portion abuts the hub portion in the axial direction. The tip portion extends axially from the mounting body portion. The tip portion has an outer diameter smaller than the outer diameter of the mounting body portion. The tip portion is crimped to the hub portion. The mounting body has an outer diameter larger than the outer diameter of the hub.

[0006] With this configuration, since the outer diameter of the mounting body is larger than the outer diameter of the hub, the mounting body acts as a base when crimping the tip of the mounting part to the hub, allowing for stable crimping to be performed.

[0007] A bicycle power transmission device according to the second embodiment is configured as follows in the bicycle power transmission device according to the first embodiment: The hub portion has a hub body portion and a small diameter portion. The hub body portion extends in the axial direction. The hub body portion is cylindrical. The small diameter portion is cylindrical. The small diameter portion has an inner diameter smaller than the inner diameter of the hub body portion. The tip of the mounting portion is crimped to the small diameter portion.

[0008] A bicycle power transmission device according to the third embodiment is configured as follows in the bicycle power transmission device according to the second embodiment: The hub portion has a plurality of protrusions and a plurality of relief portions. Each protrusion extends axially on the inner circumferential surface of the small diameter portion. Each relief portion is formed at at least one axial end of each protrusion.

[0009] A bicycle power transmission device according to the fourth embodiment further comprises a fastening member in addition to the bicycle power transmission device according to any of the first to third embodiments. The second rotating body has a first plate and a second plate. The first plate is positioned on the first axial side with respect to the flange portion. The second plate is positioned on the second axial side with respect to the flange portion. The fastening member removably fastens the first plate and the second plate. The arm body is positioned so as not to overlap with the fastening member in an axial view.

[0010] The bicycle power transmission device according to the fifth embodiment is configured as follows in the bicycle power transmission device according to the fourth embodiment: The fastening member has a stopper portion, a first threaded portion, and a second threaded portion. The stopper portion is positioned between the first plate and the second plate. The first threaded portion is positioned on the first axial side with respect to the first plate. The second threaded portion is positioned on the second axial side with respect to the second plate. [Effects of the Invention]

[0011] According to the present invention, crimping can be performed stably. [Brief explanation of the drawing]

[0012] [Figure 1] Cross-sectional view of a bicycle power transmission system. [Figure 2] Front view of a bicycle power transmission system. [Figure 3] Front view of the first rotating body. [Figure 4] Figure 3 shows a cross-sectional view along line IV-IV. [Figure 5] Side view of the stopper component. [Figure 6] Enlarged cross-sectional view of the first rotating body and crank arm before crimping. [Figure 7] Enlarged cross-sectional view of the first rotating body and crank arm after crimping. [Modes for carrying out the invention]

[0013] The following description of the bicycle power transmission device 100 (hereinafter also simply referred to as the power transmission device 100) according to this embodiment will be made with reference to the drawings. In the following description, the axial direction refers to the direction in which the rotation axis O of the power transmission device 100 extends. The circumferential direction refers to the circumferential direction of a circle centered on the rotation axis O, and the radial direction refers to the radial direction of a circle centered on the rotation axis O. The first axial side refers to the left side of Figure 1, and the second axial side refers to the right side of Figure 1. The rotation direction R refers to the direction in which the power transmission device 100 rotates when the bicycle on which the power transmission device 100 is mounted is in motion. The rotation direction R is the clockwise direction in Figure 2.

[0014] Figure 1 is a cross-sectional view of the power transmission device 100. As shown in Figure 1, the power transmission device 100 includes a first rotating body 2, a second rotating body 3, a plurality of coil springs 4 (an example of an elastic member), a plurality of stopper members 5 (an example of a fastening member), a sprocket 6, a crank arm 7, a plurality of first nuts 8, and a plurality of second nuts 9. The power transmission device 100 is rotatably arranged around the rotation axis O.

[0015] The power transmission device 100 is mounted on a bicycle. The power transmission device 100 is mounted on a bicycle that does not have an electric motor, for example, that is, a bicycle that is driven only by human power. However, the power transmission device 100 may also be mounted on a bicycle that has an electric motor. In this case, for example, the bicycle may have an electric mode driven only by the electric motor and a human-powered mode driven only by human power. The bicycle may also have an assist mode driven by both the electric motor and human power, or it may not have an assist mode. The power transmission device 100 is configured to transmit torque input to a pedal (not shown) attached to the tip of the crank arm 7 to a drive wheel (not shown).

[0016] FIG. 2 is a front view of the power transmission device 100 with some coil springs 4, crank arms 7, and the second plate 32 of the second rotating body 3 described later removed. As shown in FIG. 2, the power transmission device 100 is configured to rotate in the rotational direction R (clockwise in FIG. 2).

[0017] <The first rotating body> FIG. 3 is a front view of the first rotating body 2, and FIG. 4 is a cross-sectional view taken along the line IV-IV of FIG. 3. As shown in FIGS. 3 and 4, the first rotating body 2 has a plurality of accommodating holes 21. In this embodiment, the first rotating body 2 has three accommodating holes 21. Each accommodating hole 21 penetrates in the axial direction. Each accommodating hole 21 is arranged at intervals in the circumferential direction. Each accommodating hole 21 is arranged at equal intervals.

[0018] The first rotating body 2 has a plurality of abutting surfaces 27. The abutting surface 27 is a surface that abuts against the coil spring 4. Specifically, the abutting surface 27 is a surface that abuts against the end surface of the coil spring 4 among the surfaces that define the accommodating hole 21. That is, the first rotating body 2 has a pair of abutting surfaces 27 for each accommodating hole 21. The pair of abutting surfaces 27 face in the circumferential direction and are opposed to each other.

[0019] The first rotating body 2 is arranged to be rotatable in the rotational direction R. Torque is input to the first rotating body 2 from the crank arm 7. The first rotating body 2 is configured to rotate integrally with the crank arm 7. The first rotating body 2 has a hub portion 22 and a flange portion 23.

[0020] The hub portion 22 is cylindrical and extends in the axial direction. In a state where the power transmission device 100 is mounted on a bicycle, a crankshaft (not shown) extends through the hub portion 22.

[0021] The hub portion 22 has a hub body portion 221 and a small-diameter portion 222. The hub body portion 221 is cylindrical and extends in the axial direction. The small-diameter portion 222 is located at the end of the hub portion 22. More specifically, the small-diameter portion 222 is located at the second axial end of the hub portion 22. The small-diameter portion 222 is cylindrical and extends in the axial direction. The small-diameter portion 222 has an inner diameter smaller than the inner diameter of the hub body portion 221.

[0022] The flange portion 23 extends radially outward from the hub portion 22. A housing hole 21 is formed in this flange portion 23. The housing hole 21 penetrates the flange portion 23 in the axial direction. The flange portion 23 is formed in the axial center of the hub portion 22. The position where the flange portion 23 is located differs in the axial direction from the position where the small diameter portion 222 is located. That is, in a radial view, the small diameter portion 222 does not overlap with the flange portion 23.

[0023] The flange portion 23 is inclined in the axial direction. More specifically, the flange portion 23 is inclined towards the second side in the axial direction. The flange portion 23 is inclined so that it approaches the second plate 32 as it moves radially outward. The flange portion 23 is inclined so that it moves away from the first plate 31 to which the sprocket 6 is attached. The flange portion 23 is also inclined toward the crank arm 7.

[0024] The flange portion 23 has a flange body portion 231 and an inclined portion 232. The flange body portion 231 extends radially outward from the hub portion 22. The flange body portion 231 is not inclined in the axial direction. That is, the flange body portion 231 extends substantially parallel to the plane perpendicular to the axis of rotation O. The flange body portion 231 is annular in shape and extends in the circumferential direction.

[0025] The inclined portion 232 extends radially outward from the outer peripheral end of the flange body portion 231. The inclined portion 232 is inclined in the axial direction. More specifically, the inclined portion 232 is inclined to the second axial side. Thus, in the flange portion 23, the flange body portion 231 is not inclined, but the inclined portion 232 is inclined in the axial direction. The inclined portion 232 corresponds to the outer peripheral portion of the flange portion 23. The inclined portion 232 is an annular shape extending in the circumferential direction. The inclination angle α of the inclined portion 232 is not particularly limited, but can be, for example, about 1 to 5°. The inclination angle α is the angle made between the plane perpendicular to the axis of rotation O and the inclined portion 232.

[0026] Line L in Figure 4 indicates the boundary between the flange body portion 231 and the inclined portion 232. The housing hole 21 is formed across the flange body portion 231 and the inclined portion 232. Therefore, the contact surface 27 extends across the flange body portion 231 and the inclined portion 232. The end face of the coil spring 4 is in contact with the flange body portion 231 and the inclined portion 232.

[0027] The hub portion 22 has a plurality of protrusions 24 and a plurality of relief portions 28. Each protrusion 24 is formed on the inner circumferential surface of the small diameter portion 222 of the hub portion 22. That is, the small diameter portion 222 has each protrusion 24. Each protrusion 24 extends in the axial direction. Each protrusion 24 is arranged in the circumferential direction. Each protrusion 24 constitutes a spline hole 241 within the hub portion 22.

[0028] Each relief portion 28 is formed at the second axial end of the corresponding protrusion 24. The relief portion 28 is formed by cutting the second axial end of each protrusion 24. The relief portion 28 is configured to accommodate burrs generated when forming each protrusion 24. In other words, the relief portion 28 is configured as a burr-receiving space. Because the relief portion 28 accommodates burrs generated when forming each protrusion 24, it is possible to suppress the generation of burrs on the second axial side from the hub portion 22.

[0029] The first rotating body 2 has a plurality of stopper surfaces 25. More specifically, the first rotating body 2 has a plurality of notches 26. Each notch 26 is spaced apart in the circumferential direction. The notches 26 are located between a pair of housing holes 21 in the circumferential direction. Each notch 26 opens radially outward. Of the inner wall surfaces defining the notches 26, the surface facing the rotation direction R becomes the stopper surface 25.

[0030] The stopper surface 25 is oriented in the circumferential direction. More specifically, the stopper surface 25 is oriented in the rotational direction R. The stopper surface 25 is positioned opposite the stopper portion 51 in the circumferential direction, with a gap between them.

[0031] The first rotating body 2 can be made of, for example, iron, stainless steel, or carbon fiber reinforced plastic (CFRP).

[0032] <Second Rotating Body> As shown in Figure 1, the second rotating body 3 is rotatable in the rotational direction R. The second rotating body 3 is rotatable relative to the first rotating body 2. The second rotating body 3 has a first plate 31 and a second plate 32. The first plate 31 and the second plate 32 are configured to rotate integrally with each other. The first plate 31 and the second plate 32 are rotatable relative to the flange portion 23.

[0033] The first plate 31 and the second plate 32 are spaced apart from each other in the axial direction. The first rotating body 2 is positioned between the first plate 31 and the second plate 32. That is, the first plate 31 and the second plate 32 are positioned to sandwich the first rotating body 2 in the axial direction. In detail, the flange portion 23 of the first rotating body 2 is positioned between the first plate 31 and the second plate 32 in the axial direction. The first plate 31 is positioned on the first axial side with respect to the flange portion 23. The second plate 32 is positioned on the second axial side with respect to the flange portion 23.

[0034] The first plate 31 is disc-shaped and has an opening in its center. The hub portion 22 of the first rotating body 2 extends axially through this opening in the first plate 31.

[0035] The first plate 31 has a plurality of first window portions 311. In this embodiment, the first plate 31 has three first window portions 311. The first window portions 311 penetrate the first plate 31 in the axial direction. Each first window portion 311 is spaced apart from the others in the circumferential direction.

[0036] The first plate 31 has a plurality of first through holes 312. Each first through hole 312 is spaced apart from the others in the circumferential direction. In the circumferential direction, each first window portion 311 and each first through hole 312 are arranged alternately.

[0037] The second plate 32 is disc-shaped and has an opening in its center. The hub portion 22 of the first rotating body 2 extends axially through this opening in the second plate 32. The second plate 32 is configured to rotate integrally with the first plate 31. In detail, the first plate 31 and the second plate 32 are fastened to each other by a plurality of stopper members 5.

[0038] The second plate 32 has a plurality of second window portions 321. In this embodiment, the second plate 32 has three second window portions 321. The second window portions 321 penetrate the second plate 32 in the axial direction. Each second window portion 321 is spaced apart from each other in the circumferential direction. Each second window portion 321 overlaps with the corresponding first window portion 311 in an axial view.

[0039] The second plate 32 has a plurality of second through holes 322. Each second through hole 322 is spaced apart from the others in the circumferential direction. In the circumferential direction, each second window portion 321 and each second through hole 322 are arranged alternately. Each second through hole 322 overlaps with the corresponding first through hole 312 in an axial view.

[0040] The first plate 31 and the second plate 32 can be made of, for example, iron, stainless steel, or carbon fiber reinforced plastic (CFRP).

[0041] <Coil spring> The coil spring 4 is housed within the housing hole 21, the first window 311, and the second window 321. The coil spring 4 elastically connects the first rotating body 2 and the first plate 31 and the second plate 32 in the rotational direction R. That is, torque from the first rotating body 2 is transmitted to the first plate 31 and the second plate 32 via the coil spring 4. The coil spring 4 also rotates together with the first rotating body 2, the first plate 31, and the second plate 32. When torque is transmitted, the coil spring 4 contracts, causing the first rotating body 2 and the second rotating body 3 to twist relative to each other. When the coil spring 4 is not contracted, the first rotating body 2 and the second rotating body 3 do not twist, and the twist angle is 0 degrees.

[0042] <Sprocket> The sprocket 6 is attached to the first plate 31. The sprocket 6 is attached to the first plate 31 by a stopper member 5, a first nut 8, and a second nut 9. The sprocket 6 rotates integrally with the first plate 31 and the second plate 32. The sprocket 6 has multiple teeth on its outer circumference. A chain (not shown) is attached to the sprocket 6, and torque is transmitted from the sprocket 6 to the drive wheel (not shown) via the chain or the like.

[0043] The sprocket 6 has a plurality of engagement holes 61. Each engagement hole 61 is spaced apart from each other in the circumferential direction. Each engagement hole 61 overlaps with the corresponding first through holes 312 and second through holes 322 in an axial view.

[0044] <Stopper component> Figure 5 is a side view of the stopper member 5. As shown in Figures 1 and 5, the stopper member 5 works in cooperation with the first nut 8 and the second nut 9 to removably fasten the first plate 31 and the second plate 32. The sprocket 6 is fastened to the first plate 31 by the stopper member 5 and the first nut 8. The stopper member 5 is attached to the second rotating body 3. The stopper member 5 is configured to rotate integrally with the second rotating body 3.

[0045] The stopper member 5 has a stopper portion 51, a first threaded portion 52, a first intermediate portion 53, a second threaded portion 54, and a second intermediate portion 55. The stopper portion 51, the first threaded portion 52, the first intermediate portion 53, the second threaded portion 54, and the second intermediate portion 55 are integrally formed from each other. In detail, the stopper portion 51, the first threaded portion 52, the first intermediate portion 53, the second threaded portion 54, and the second intermediate portion 55 are integrally formed from a single member. The stopper member 5 is solid and does not have a cavity inside.

[0046] The stopper portion 51 is cylindrical. The stopper portion 51 extends in the axial direction. The stopper portion 51 faces the stopper surface 25 in the circumferential direction. The stopper portion 51 is positioned between the first plate 31 and the second plate 32 in the axial direction. The stopper portion 51 is sandwiched between the first plate 31 and the second plate 32. The stopper portion 51 is positioned within the notch 26 of the first rotating body 2.

[0047] The first threaded portion 52 is integrally formed with the stopper portion 51. The first threaded portion 52 extends in the axial direction. Threads are formed on the outer circumferential surface of the first threaded portion 52. The outer diameter of the first threaded portion 52 is smaller than that of the stopper portion 51.

[0048] The first threaded portion 52 is positioned on the first axial side relative to the stopper portion 51. The first threaded portion 52 is positioned on the first axial side relative to the first plate 31. Furthermore, the first threaded portion 52 is positioned on the first axial side relative to the sprocket 6.

[0049] The first intermediate portion 53 is positioned axially between the stopper portion 51 and the first threaded portion 52. Specifically, the first intermediate portion 53 extends from the stopper portion 51 toward the first axial direction. The first threaded portion 52 extends from the first intermediate portion 53 toward the first axial direction.

[0050] The first intermediate section 53 is cylindrical. The first intermediate section 53 extends in the axial direction. The length of the first intermediate section 53 is less than the sum of the thickness of the first plate 31 and the thickness of the sprocket 6. Also, the length of the first intermediate section 53 is greater than the thickness of the first plate 31. Note that the length of each part of the stopper member 5 refers to the axial dimension.

[0051] The first intermediate portion 53 has a smaller outer diameter than the stopper portion 51 and a larger outer diameter than the first threaded portion 52. The first intermediate portion 53 is positioned within the first through hole 312 and the engagement hole 61. The first intermediate portion 53 does not protrude axially in the first direction from within the first through hole 312 and the engagement hole 61.

[0052] The second threaded portion 54 is integrally formed with the stopper portion 51. The second threaded portion 54 extends in the axial direction. Threads are formed on the outer surface of the second threaded portion 54. The second threaded portion 54 has a smaller outer diameter than the stopper portion 51. The second threaded portion 54 has approximately the same outer diameter as the first threaded portion 52.

[0053] The second screw portion 54 is positioned on the second axial side relative to the stopper portion 51. The second screw portion 54 is positioned on the second axial side relative to the second plate 32.

[0054] The second intermediate portion 55 is positioned in the axial direction between the stopper portion 51 and the second threaded portion 54. Specifically, the second intermediate portion 55 extends from the stopper portion 51 to the second axial direction. The second threaded portion 54 extends from the second intermediate portion 55 to the second axial direction.

[0055] The second intermediate section 55 is cylindrical. The second intermediate section 55 extends in the axial direction. The length of the second intermediate section 55 is shorter than the length of the first intermediate section 53. The length of the second intermediate section 55 is less than the thickness of the second plate 32.

[0056] The second intermediate portion 55 has a smaller outer diameter than the stopper portion 51 and a larger outer diameter than the second threaded portion 54. The second intermediate portion 55 has approximately the same outer diameter as the first intermediate portion 53. The second intermediate portion 55 is located within the second through hole 322. The second intermediate portion 55 does not protrude from within the second through hole 322 toward the second axial direction.

[0057] <First and second nuts> The first nut 8 is screwed onto the first threaded portion 52. The first nut 8 works in cooperation with the stopper portion 51 to clamp the sprocket 6 and the first plate 31. The first nut 8 is a flange nut.

[0058] The second nut 9 is screwed onto the second threaded portion 54. The second nut 9 works in cooperation with the stopper portion 51 to clamp the second plate 32. The second nut 9 is a flange nut.

[0059] <crank arm> As shown in Figure 1, the crank arm 7 is configured to rotate integrally with the first rotating body 2. That is, the crank arm 7 is rotatably positioned around the rotation axis O. The crank arm 7 is attached to the second axial end of the hub portion 22 of the first rotating body 2. In detail, the crank arm 7 is configured to spline-fit into spline holes 241 formed by a plurality of protrusions 24 on the inner circumferential surface of the hub portion 22.

[0060] The crank arm 7 has an arm body portion 71 and a mounting portion 72. The arm body portion 71 extends radially outward from the mounting portion 72. The arm body portion 71 is positioned so as not to overlap with the stopper member 5 in an axial view (see Figure 2). The arm body portion 71 is positioned so as to overlap with the coil spring 4 in an axial view.

[0061] The mounting portion 72 is connected to one end of the arm body portion 71. The mounting portion 72 extends in the axial direction. A pedal (not shown) is attached to the other end of the arm body portion 71. The mounting portion 72 is attached to the hub portion 22. The mounting portion 72 has a mounting body portion 723, a tip portion 721, and a mounting hole 722.

[0062] Figure 6 is an enlarged cross-sectional view of the crank arm 7 and the first rotating body 2, showing the mounting portion between the crank arm 7 and the first rotating body 2. Note that in Figure 6, parts other than the crank arm 7 and the first rotating body 2 are omitted from the description. As shown in Figure 6, the mounting body portion 723 is in contact with the hub portion 22 in the axial direction. The mounting body portion 723 is cylindrical. The mounting body portion 723 extends in the axial direction. The mounting body portion 723 has a first end face 724 facing the first side in the axial direction. The hub portion 22 has a second end face 223 facing the second side in the axial direction. The first end face 724 of the mounting body portion 723 is in contact with the second end face 223 of the hub portion 22.

[0063] The mounting body portion 723 has an outer diameter larger than the outer diameter of the hub portion 22. More specifically, the outer diameter of the first end face 724 of the mounting body portion 723 is larger than the outer diameter of the second end face 223 of the hub portion 22. Therefore, the entire second end face 223 of the hub portion 22 is in contact with the first end face 724 of the mounting body portion 723.

[0064] The tip portion 721 extends from the mounting body portion 723 to the first axial direction. More specifically, the tip portion 721 extends from the first end face 724 of the mounting body portion 723 to the first axial direction. The tip portion 721 has a smaller outer diameter than the mounting body portion 723. The tip portion 721 extends within the hub portion 22. This tip portion 721 spline-fits into the spline hole 241 formed by the multiple protrusions 24.

[0065] The tip portion 721 penetrates the spline hole 241 in the axial direction. The tip portion 721 is then crimped to the hub portion 22. More specifically, the tip portion 721 is crimped to the small diameter portion 222. More specifically, the tip portion 721 is crimped to each of the protrusions 24 formed on the small diameter portion 222.

[0066] By crimping the tip portion 721 onto each protrusion 24, the tip portion 721 and each protrusion 24 become tightly fitted together, as shown in Figure 7. In addition, the outer diameter of the portion of the tip portion 721 that protrudes from each protrusion 24 toward the first axial direction becomes larger due to the crimping process, and becomes larger than the inner diameter of the spline hole 241. As a result, the tip portion 721 cannot be removed from the spline hole 241, and the crank arm 7 and the first rotating body 2 are prevented from moving away from each other in the axial direction.

[0067] The mounting portion 72 has a mounting hole 722. This mounting hole 722 is rectangular in shape when viewed in the axial direction. A crankshaft (not shown) is fitted into this mounting hole 722, and the crank arm 7 rotates integrally with the crankshaft.

[0068] <Operation> The operation of the power transmission device 100 configured as described above will now be explained. First, when torque is input to the first rotating body 2 via the crank arm 7 by the user pedaling, the first rotating body 2 rotates in the rotational direction R. Then, torque is transmitted from the first rotating body 2 to the second rotating body 3 via the coil spring 4. As a result, the second rotating body 3 rotates in the rotational direction R, and torque is transmitted to the drive wheels.

[0069] Here, when the coil spring 4 is compressed and the torsional angle between the first rotating body 2 and the second rotating body 3 reaches a predetermined angle, the stopper surface 25 comes into contact with the stopper portion 51. By the stopper portion 51 coming into contact with the stopper surface 25 in this way, the first rotating body 2 is prevented from rotating further relative to the second rotating body 3. That is, the first rotating body 2 rotates relative to the second rotating body 3 until the stopper member 5 comes into contact with the stopper surface 25. After the stopper portion 51 comes into contact with the stopper surface 25, the first rotating body 2 rotates integrally with the second rotating body 3. The torsional angle between the first rotating body 2 and the second rotating body 3 when the stopper surface 25 comes into contact with the stopper portion 51 is called the maximum torsional angle. Note that when no torque is input to the power transmission device 100, the torsional angle between the first rotating body 2 and the second rotating body 3 is 0 degrees.

[0070] [Differentiation] Although embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications are possible without departing from the spirit of the invention. Furthermore, the following modifications can basically be applied simultaneously.

[0071] (a) In the above embodiment, the crank arm 7 is attached to the first rotating body 2 such that the arm body portion 71 does not overlap with the stopper member 5 in an axial view, but the configuration of the power transmission device 100 is not limited to this. For example, the arm body portion 71 may overlap with the stopper member 5 in an axial view.

[0072] (b) In the above embodiment, the relief portion 28 was formed at the second axial end of the protrusion 24, but the relief portion 28 may also be formed at the first axial end of the protrusion 24, or at both the first and second axial ends of the protrusion 24.

[0073] (c) In the above embodiment, the flange portion 23 is inclined in the axial direction, but the flange portion 23 does not have to be inclined in the axial direction. That is, the flange portion 23 may extend along a plane perpendicular to the axis of rotation O. [Explanation of Symbols]

[0074] 2: First rotational body 22: Hub section 221: Hub body 222: Small diameter part 23: Flange section 24: Convex part 28: Escape Department 3: Second rotational body 31: First Plate 32: Second Plate 5: Stopper component 51: Stopper section 52: First threaded section 54: Second threaded section 7: Crank arm 71: Arm body 72: Mounting part 721:Tip 723: Mounting body 100: Bicycle power transmission device

Claims

1. The first rotating body and, A second rotating body is arranged to be rotatable relative to the first rotating body, An elastic member that elastically connects the first rotating body and the second rotating body, A crank arm that rotates integrally with the first rotating body, Equipped with, The first rotating body has a hub portion extending in the axial direction and a flange portion extending radially outward from the hub portion. The crank arm has a mounting portion that is attached to the hub portion and an arm body portion that extends radially outward from the mounting portion, The aforementioned mounting portion is A mounting body portion that contacts the hub portion in the axial direction, The mounting body extends axially from the aforementioned mounting body, has an outer diameter smaller than the outer diameter of the mounting body, and has a tip portion that is crimped to the hub portion, It has, The mounting body has an outer diameter larger than the outer diameter of the hub portion. A power transmission device for bicycles.

2. The hub portion comprises a cylindrical hub body portion extending in the axial direction and a cylindrical small-diameter portion having an inner diameter smaller than the inner diameter of the hub body portion. The tip of the mounting portion is crimped to the small diameter portion. The bicycle power transmission device according to claim 1.

3. The hub portion is Multiple protrusions extending in the axial direction on the inner circumferential surface of the small diameter portion, A plurality of relief portions are formed at at least one end of each of the aforementioned protrusions in the axial direction, Having, The power transmission device for a bicycle according to claim 2.

4. Further comprising fastening members, The second rotating body is A first plate positioned on the first axial side with respect to the flange portion, A second plate is positioned on the second axial side with respect to the flange portion, It has, The fastening member removably fastens the first plate and the second plate, The arm body is positioned so as not to overlap with the fastening member in an axial view. The bicycle power transmission device according to claim 1.

5. The fastening member is A stopper portion is disposed between the first plate and the second plate, A first threaded portion is positioned on the first axial side of the first plate, A second threaded portion is positioned on the second axial side of the second plate, Having, The bicycle power transmission device according to claim 4.

Images