Bicycle power transmission system

Abstract

To improve the strength of the screw threads. [Solution] The bicycle power transmission device comprises a first rotating body, a second rotating body, an elastic member, a stopper member, and a first nut. The first rotating body has a stopper surface facing in the circumferential direction. 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 stopper member is attached to the second rotating body. The stopper member has a stopper portion and a first threaded portion. The stopper portion faces the stopper surface in the circumferential direction. The first threaded portion is integrally formed with the stopper portion and extends in the axial direction. The first nut is screwed onto the first threaded portion.

Description

Technical Field

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

Background Art

[0002] The power transmission device for a bicycle has a first rotating body and a second rotating body that are arranged to be relatively rotatable. The first rotating body and the second rotating body are elastically connected by an elastic member. The range of the torsional angle between the first rotating body and the second rotating body is regulated by a stopper member.

[0003] In the power transmission device for a bicycle disclosed in Patent Document 1, the maximum torsional angle between the first rotating body and the second rotating body can be changed by replacing the stopper member. This stopper member is attached by a bolt for fastening the second rotating body. This bolt extends so as to penetrate through the stopper member.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Due to reasons such as firmly fastening the second rotating body, there is a desire to improve the strength of the threaded portion of the bolt. Therefore, an object of the present invention is to improve the strength of the threaded portion.

Means for Solving the Problems

[0006] A bicycle power transmission device according to the first embodiment comprises a first rotating body, a second rotating body, an elastic member, a stopper member, and a first nut. The first rotating body has a stopper surface facing in the circumferential direction. 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 stopper member is attached to the second rotating body. The stopper member has a stopper portion and a first threaded portion. The stopper portion faces the stopper surface in the circumferential direction. The first threaded portion is integrally formed with the stopper portion and extends in the axial direction. The first nut is screwed onto the first threaded portion.

[0007] With this configuration, the threaded portion is integrally formed with the stopper portion, allowing the threaded portion to be thicker compared to conventional bolts where the threaded portion extends within a cylindrical stopper portion. As a result, the strength of the threaded portion can be improved.

[0008] 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 second rotating body has a first through hole. The stopper member has a first intermediate portion. The first intermediate portion is positioned between the stopper portion and the first threaded portion in the axial direction. The first intermediate portion has a smaller outer diameter than the stopper portion and a larger outer diameter than the first threaded portion. The first intermediate portion is positioned inside the first through hole.

[0009] A third embodiment of the bicycle power transmission device further comprises a sprocket in addition to the bicycle power transmission device of the second embodiment. The sprocket rotates integrally with the second rotating body. The sprocket has an engagement hole. The engagement hole overlaps with the first through hole in an axial view. The first intermediate portion is positioned within the engagement hole.

[0010] The bicycle power transmission device according to the fourth embodiment is configured as follows in the bicycle power transmission device according to the second or third embodiment: The stopper member has a constricted portion. The constricted portion is positioned between the first intermediate portion and the first threaded portion. This configuration allows for the relief of stress on the stopper member.

[0011] The fifth embodiment of the bicycle power transmission device is configured as follows in the bicycle power transmission device according to any of the second to fourth embodiments: The stopper member has a constricted portion. The constricted portion is positioned between the stopper portion and the first intermediate portion. This configuration makes it possible to relieve stress on the stopper member.

[0012] The bicycle power transmission device according to the sixth embodiment is configured as follows in the bicycle power transmission device according to any of the first to fifth embodiments: The first nut is a flange nut.

[0013] The bicycle power transmission device according to the seventh embodiment is configured as follows in the bicycle power transmission device according to any of the first to sixth embodiments: The stopper member has an engaging portion configured to engage with a tool.

[0014] The eighth embodiment of the bicycle power transmission device further comprises a second nut in addition to the bicycle power transmission device according to any of the first to seventh embodiments. The second rotating body has a first plate and a second plate. The first plate is positioned on a first axial side with respect to the first rotating body. The second plate is positioned on a second axial side with respect to the first rotating body. The stopper portion is positioned between the first plate and the second plate in the axial direction. The first threaded portion is positioned on a first axial side with respect to the first plate. The stopper member has a second threaded portion. The second threaded portion is positioned on a second axial side with respect to the second plate. The second threaded portion is integrally formed with the stopper portion. The second nut is screwed onto the second threaded portion.

[0015] The bicycle power transmission device according to the ninth embodiment is configured as follows in the bicycle power transmission device according to the eighth embodiment: The first plate has a first through hole. The second plate has a second through hole. The second through hole overlaps with the first through hole in an axial view. The stopper member has a first intermediate portion and a second intermediate portion. The first intermediate portion is positioned between the stopper portion and the first threaded portion in the axial direction. The second intermediate portion is positioned between the stopper portion and the second threaded portion in the axial direction. The first intermediate portion and the second intermediate portion have an outer diameter smaller than that of the stopper portion and an outer diameter larger than that of the first threaded portion. The first intermediate portion is positioned inside the first through hole. The second intermediate portion is positioned inside the second through hole. [Effects of the Invention]

[0016] According to the present invention, the strength of the screw portion can be improved. [Brief explanation of the drawing]

[0017] [Figure 1] Cross-sectional view of a power transmission device. [Figure 2] Front view of the power transmission device. [Figure 3] Side view of the stopper component. [Figure 4] Side view of a modified stopper member. [Modes for carrying out the invention]

[0018] 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.

[0019] 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 elastic members 4, a plurality of stopper members 5, 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 arranged to be rotatable about the rotation axis O.

[0020] The power transmission device 100 is mounted on a bicycle. The power transmission device 100 is mounted on, for example, a bicycle without an electric motor or the like, that is, a bicycle driven only by human power. Note that the power transmission device 100 may be mounted on a bicycle having an electric motor. In this case, for example, the bicycle may have an electric mode driven only by the electric motor and a human power mode driven only by human power. Note that the bicycle may have an assist mode driven by the electric motor and human power, or may not have an assist mode. The power transmission device 100 is configured to transmit the torque input to a pedal (not shown) attached to the tip of the crank arm 7 to a drive wheel (not shown).

[0021] Figure 2 is a front view of the power transmission device 100 with some of the elastic members 4, the crank arm 7, and the second plate 32 of the second rotating body 3 described later removed. As shown in Figure 2, the power transmission device 100 is configured to rotate in the rotation direction R (clockwise in Figure 2).

[0022] <First Rotating Body> As shown in Figures 1 and 2, the first rotating body 2 has a plurality of first accommodating portions 21. In this embodiment, the first rotating body 2 has three first accommodating portions 21. Each first accommodating portion 21 penetrates in the axial direction. The first accommodating portions 21 are arranged at intervals in the circumferential direction. The first accommodating portions 21 are arranged at equal intervals.

[0023] The first rotating body 2 is positioned 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.

[0024] The first rotating body 2 has a hub portion 22, an outer flange portion 23, and an inner flange portion 24. The hub portion 22 is cylindrical and extends in the axial direction. When the power transmission device 100 is mounted on a bicycle, a crankshaft (not shown) extends inside this hub portion 22.

[0025] The outer flange portion 23 extends radially outward from the hub portion 22. The first housing portion 21 is formed in this outer flange portion 23. The outer flange portion 23 is formed in the axial center of the hub portion 22.

[0026] The inner flange portion 24 extends radially inward from the hub portion 22. The inner flange portion 24 has spline holes 241 on its inner circumferential surface. The inner flange portion 24 is formed at the axial end of the hub portion 22. Specifically, the inner flange portion 24 is formed at the second axial end of the hub portion 22. The position where the inner flange portion 24 is located differs in the axial direction from the position where the outer flange portion 23 is located. That is, in a radial view, the inner flange portion 24 does not overlap with the outer flange portion 23.

[0027] 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 first housings 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.

[0028] 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.

[0029] The first rotating body 2 can be made of, for example, iron, stainless steel, or carbon fiber reinforced plastic (CFRP).

[0030] <Second Rotating Body> The second rotating body 3 is arranged to be rotatable in the rotational direction R. The second rotating body 3 is arranged to be rotatable relative to the first rotating body 2. The second rotating body 3 has a first plate 31 and a second plate 32.

[0031] 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 outer 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 outer flange portion 23. The second plate 32 is positioned on the second axial side with respect to the outer flange portion 23.

[0032] The first plate 31 and the second plate 32 are disc-shaped and have an opening in the center. The hub portion 22 of the first rotating body 2 extends axially through the openings of the first plate 31 and the second plate 32.

[0033] The first plate 31 has a plurality of second housing sections 311. Each second housing section 311 is spaced apart from each other in the circumferential direction. The second plate 32 has a plurality of third housing sections 321. Each third housing section 321 is spaced apart from each other in the circumferential direction.

[0034] The first plate 31 has a plurality of first through holes 312. Each first through hole 312 is spaced apart from each other in the circumferential direction. The second plate 32 has a plurality of second through holes 322. Each second through hole 322 is spaced apart from each other in the circumferential direction. Each second through hole 322 overlaps with the corresponding first through hole 312 in an axial view.

[0035] The first plate 31 and the second plate 32 can be made of, for example, iron, stainless steel, or carbon fiber reinforced plastic (CFRP).

[0036] <Elastic material> The elastic member 4 is housed in the first housing section 21, the second housing section 311, and the third housing section 321. The elastic member 4 is, for example, a coil spring. The elastic member 4 elastically connects the first rotating body 2 and the first plate 31 and the second plate 32 in the rotational direction. That is, torque from the first rotating body 2 is transmitted to the first plate 31 and the second plate 32 via the elastic member 4. The elastic member 4 also rotates together with the first rotating body 2, the first plate 31, and the second plate 32. When torque is transmitted, the elastic member 4 contracts, causing the first rotating body 2 and the second rotating body 3 to twist relative to each other. When the elastic member 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.

[0037] <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.

[0038] 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.

[0039] <Stopper component> Figure 3 is a side view of the stopper member 5. As shown in Figures 1 and 3, 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.

[0040] 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. More specifically, 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 also has first to fourth constricted portions 56 to 59. The stopper member 5 is solid and does not have a cavity inside. The stopper member 5 is made of metal, specifically steel. More specifically, the stopper member 5 is made of SWCH45K, S45C, or SCM435, etc.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] The first constricted portion 56 is positioned between the stopper portion 51 and the first intermediate portion 53. The first constricted portion 56 has a smaller outer diameter than the stopper portion 51 and the first intermediate portion 53.

[0053] The second constricted portion 57 is located between the first threaded portion 52 and the first intermediate portion 53. The second constricted portion 57 has a smaller outer diameter than the first threaded portion 52 and the first intermediate portion 53.

[0054] The third constricted portion 58 is located between the stopper portion 51 and the second intermediate portion 55. The third constricted portion 58 has a smaller outer diameter than the stopper portion 51 and the second intermediate portion 55.

[0055] The fourth constricted portion 59 is located between the second threaded portion 54 and the second intermediate portion 55. The fourth constricted portion 59 has a smaller outer diameter than the second threaded portion 54 and the second intermediate portion 55.

[0056] <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.

[0057] 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.

[0058] <crank arm> 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 inner flange portion 24 of the first rotating body 2. More specifically, the crank arm 7 is configured to spline-fit to the inner flange portion 24.

[0059] The crank arm 7 has an arm body portion 71 and a mounting portion 72. The arm body portion 71 extends radially. The mounting portion 72 extends axially from one of the ends of the arm body portion 71. A pedal (not shown) is attached to the other end of the arm body portion 71.

[0060] The tip portion 721 of the mounting portion 72 has a smaller outer diameter than the rest of the mounting portion 72. This tip portion 721 spline-fits to the inner flange portion 24. The tip portion 721 also penetrates the inner flange portion 24 in the axial direction. The tip portion 721 is then crimped and fixed to the inner flange portion 24. In detail, by crimping the tip portion 721, the tip portion 721 and the inner flange portion 24 become tightly fitted together. In addition, the outer diameter of the portion of the tip portion 721 that protrudes from the inner flange portion 24 in the first axial direction becomes larger due to the crimping process, and becomes larger than the inner diameter of the inner flange portion 24. As a result, the tip portion 721 cannot be removed from the inner flange portion 24, and it is possible to prevent the crank arm 7 and the first rotating body 2 from moving away from each other in the axial direction.

[0061] 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.

[0062] <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 elastic member 4. As a result, the second rotating body 3 rotates in the rotational direction R, and torque is transmitted to the drive wheels.

[0063] Here, when the elastic member 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.

[0064] The stopper member 5 is interchangeably attached to the first plate 31 and the second plate 32. Specifically, by unscrewing the first nut 8 and the second nut 9, the stopper member 5 can be removed from the first plate 31 and the second plate 32 and replaced with another stopper member 5. By replacing the stopper member 5, the maximum twist angle can be changed.

[0065] The stopper member 5 used in the power transmission device 100 can be selected from, for example, several types of stopper members 5 with different circumferential sizes. More specifically, the stopper member 5 can be selected from several types of stopper members 5 with different outer diameters. For example, the maximum twist angle can be reduced by replacing the stopper member 5 with a stopper member 5 having a larger outer diameter stopper portion 51. Conversely, the maximum twist angle can be increased by replacing the stopper member 5 with a stopper member 5 having a smaller outer diameter stopper portion 51. The power transmission device 100 is configured such that the maximum twist angle is reached before the elastic member 4 is fully compressed.

[0066] By screwing the removed first nut 8 and second nut 9 onto the first threaded portion 52 and second threaded portion 54, the stopper member 5 can be easily attached to the first plate 31 and second plate 32.

[0067] Preferably, the elastic member 4 has a spring constant such that the first rotating body 2 and the second rotating body 3 reach their maximum torsional angle when a torque of 100 N·m or less is applied to the first rotating body 2. Furthermore, it is preferable that the elastic member 4 has a spring constant such that the first rotating body 2 and the second rotating body 3 reach their maximum torsional angle when a torque of 20 N·m or more is applied to the first rotating body 2. The torque applied to the first rotating body 2 when this maximum torsional angle is reached is referred to as the maximum torque. While not particularly limited, for example, elastic members 4 with spring constants such that the maximum torque is approximately 90 N·m, 80 N·m, 70 N·m, 60 N·m, 50 N·m, 40 N·m, and 30 N·m are prepared. The system may be configured so that the user can appropriately select from these elastic members 4.

[0068] [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.

[0069] (a) In the above embodiment, the second rotating body 3 had a first plate 31 and a second plate 32, but the second rotating body 3 may have only the first plate 31. That is, the second rotating body 3 may not have the second plate 32. In this case, the stopper member 5 may not have the second screw portion 54 and the second intermediate portion 55.

[0070] (b) In the above embodiment, the stopper member 5 had a first intermediate portion 53, but the stopper member 5 does not have to have a first intermediate portion 53. That is, the first screw portion 52 may extend from the stopper portion 51 in the first axial direction. Also, the stopper member 5 does not have to have a second intermediate portion 55. That is, the second screw portion 54 may extend from the stopper portion 51 in the second axial direction.

[0071] (c) In the above embodiment, the sprocket 6 was made of a separate component from the first plate 31, but the sprocket 6 may be integrally made of the first plate 31 and a single component.

[0072] (d) As shown in Figure 4, the stopper member 5 may have an engaging portion 50. The engaging portion 50 is configured to be engageable with a tool. For example, the engaging portion 50 is composed of a pair of flat surfaces formed on the stopper portion 51. By engaging a wrench with this engaging portion 50, it is possible to prevent the stopper member 5 from rotating when removing the first nut 8 or the second nut 9. The engaging portion 50 may also be a hexagonal hole formed on the end face of the stopper member 5. [Explanation of Symbols]

[0073] 2: First rotational body 25: Stopper surface 3: Second rotational body 31: First Plate 312: First through hole 32: Second Plate 322: Second through hole 4: Elastic member 5: Stopper component 50: Engaging part 51: Stopper section 52: First threaded section 53: First Intermediate Section 54: Second threaded section 55: Second Middle Section 56: Waist area 57: Waist area 6: Sprocket 61: Engagement hole 8: First nut 9: Second nut 100: Bicycle power transmission device

Claims

1. A first rotating body having a stopper surface facing in the circumferential direction, 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 stopper member having a stopper portion facing the stopper surface in the circumferential direction, and a first screw portion integrally formed with the stopper portion and extending in the axial direction, which is attached to the second rotating body, A first nut that is screwed onto the first threaded portion, A power transmission device for bicycles, equipped with the following features.

2. The second rotating body has a first through hole, The stopper member has a first intermediate portion that is positioned between the stopper portion and the first screw portion in the axial direction. The first intermediate portion has a smaller outer diameter than the stopper portion and a larger outer diameter than the first screw portion. The first intermediate portion is positioned within the first through hole. The bicycle power transmission device according to claim 1.

3. The sprocket further comprises an engagement hole that overlaps with the first through hole in an axial view and rotates integrally with the second rotating body, The first intermediate portion is positioned within the engagement hole. The bicycle power transmission device according to claim 2.

4. The stopper member has a constricted portion positioned between the first intermediate portion and the first threaded portion. The bicycle power transmission device according to claim 2.

5. The stopper member has a constricted portion positioned between the stopper portion and the first intermediate portion. The bicycle power transmission device according to claim 2.

6. The first nut is a flange nut. The bicycle power transmission device according to claim 1.

7. The stopper member has an engaging portion configured to engage with a tool. The bicycle power transmission device according to claim 1.

8. Further equipped with a second nut, The second rotating body has a first plate positioned on the first axial side with respect to the first rotating body, and a second plate positioned on the second axial side with respect to the first rotating body. The stopper portion is positioned in the axial direction 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 stopper member has a second screw portion that is positioned on the second axial side with respect to the second plate and is integrally formed with the stopper portion. The second nut is screwed onto the second threaded portion. The bicycle power transmission device according to claim 1.

9. The first plate has a first through hole, The second plate has a second through hole that overlaps with the first through hole in an axial view, The stopper member has a first intermediate portion positioned in the axial direction between the stopper portion and the first screw portion, and a second intermediate portion positioned in the axial direction between the stopper portion and the second screw portion. The first intermediate portion and the second intermediate portion have a smaller outer diameter than the stopper portion and a larger outer diameter than the first screw portion. The first intermediate portion is positioned within the first through hole. The second intermediate portion is positioned within the second through hole. The bicycle power transmission device according to claim 8.

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