Bicycle power transmission system

Abstract

To improve the riding comfort of bicycles equipped with a bicycle power transmission system. [Solution] The bicycle power transmission device comprises a first rotating body, a second rotating body, a friction member, and an elastic member. The second rotating body is arranged to rotate relative to the first rotating body. The friction member is arranged between the first rotating body and the second rotating body. The friction member is arranged to rotate relative to the first rotating body. The friction member is configured to rotate integrally with the second rotating body. The elastic member elastically connects the first rotating body and the second rotating body. The friction member has a base portion, a claw portion, and a projection portion. The base portion is annular. The claw portion extends from the base portion to a first axial side. The projection portion is arranged radially inward relative to the claw portion. The projection portion protrudes from the base portion to a first axial side. The second rotating body has an engagement hole and an engagement recess. The claw portion engages with the engagement hole. The projection portion engages with the engagement recess.

Description

Technical Field

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

Background Art

[0002] A power transmission device for a bicycle has a first rotating body and a second rotating body (for example, Patent Document 1). The first rotating body and the second rotating body are configured to be relatively rotatable. The first rotating body and the second rotating body are elastically connected by a coil spring.

[0003] When torque is input to the first rotating body, the first rotating body rotates relative to the second rotating body, and the coil spring is compressed. When the torque input to the first rotating body becomes small, the restoring force of the coil spring can compensate for the input torque.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The problem of the present invention is to improve the riding comfort of a bicycle equipped with a power transmission device for a bicycle.

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, a friction member, and an elastic member. The second rotating body is arranged to rotate relative to the first rotating body. The friction member is arranged between the first rotating body and the second rotating body. The friction member is arranged to rotate relative to the first rotating body. The friction member is configured to rotate integrally with the second rotating body. The elastic member elastically connects the first rotating body and the second rotating body. The friction member has a base portion, a claw portion, and a projection portion. The base portion is annular. The claw portion extends from the base portion to a first axial side. The projection portion is arranged radially inward relative to the claw portion. The projection portion protrudes from the base portion to a first axial side. The second rotating body has an engagement hole and an engagement recess. The claw portion engages with the engagement hole. The projection portion engages with the engagement recess.

[0007] With this configuration, the friction member slides against the first rotating body when the first and second rotating bodies rotate relative to each other due to the restoring force of the elastic member, thereby making the relative rotation between the first and second rotating bodies smoother. As a result, the riding comfort of a bicycle equipped with this bicycle power transmission device can be improved. Furthermore, the friction member has a claw portion that engages with an engagement hole in the second rotating body, and a projection positioned radially inward from the claw portion that engages with an engagement recess in the second rotating body. Therefore, the mounting of the friction member to the second rotating body can be made stable, and consequently, the friction torque generated between the first rotating body and the friction member can be made stable. As a result, the relative rotation between the first and second rotating bodies can be made even smoother, further improving the riding comfort of the bicycle.

[0008] The 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 friction member has a plurality of claw portions and a plurality of protrusions. Each claw portion and each protrusion are arranged alternately in the circumferential direction.

[0009] The bicycle power transmission device according to the third embodiment is configured as follows in the bicycle power transmission device according to the first or second embodiment: The protruding portion overlaps with the elastic member in a radial view.

[0010] A bicycle power transmission device according to the fourth embodiment is configured as follows in a bicycle power transmission device according to any of the first to third embodiments: The friction member has a plurality of claw portions and an outer wall portion. Each claw portion is spaced apart from each other in the circumferential direction. The outer wall portion protrudes from the base portion to the first axial side. The outer wall portion extends circumferentially between adjacent pairs of claw portions in the circumferential direction. The outer wall portion has an inner surface and a recess. The inner surface faces radially inward. The recess is formed on the inner surface. The recess is recessed radially outward.

[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 first to fourth embodiments: The friction member has a plurality of claw portions and an outer wall portion. Each claw portion is spaced apart from each other in the circumferential direction. The outer wall portion protrudes from the base portion to the first axial side. The outer wall portion extends circumferentially between adjacent pairs of claw portions in the circumferential direction. The outer wall portion is spaced apart from the claw portions in the circumferential direction.

[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 rotating body has a hub portion and a flange portion. The hub portion extends in the axial direction. The flange portion extends radially outward from the hub portion. 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 second plate is configured to rotate integrally with the first plate. A friction member is positioned between the flange portion and the first plate in the axial direction. The first plate has an engagement hole and an engagement recess.

[0013] The bicycle power transmission device according to the seventh embodiment further comprises a sprocket attached to the first plate in the bicycle power transmission device according to the sixth embodiment.

[0014] The bicycle power transmission device according to the eighth embodiment is configured as follows in the bicycle power transmission device according to any of the first to seventh embodiments: The friction member has a cylindrical portion. The cylindrical portion protrudes from the inner circumferential end of the base portion to the first axial side. The protruding portion is arranged radially outward of the cylindrical portion. The protruding portion is formed integrally with the cylindrical portion. [Effects of the Invention]

[0015] According to the present invention, the riding comfort of a bicycle can be improved. [Brief explanation of the drawing]

[0016] [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] Front view of the first plate. [Figure 5] Perspective view of the first friction member. [Figure 6] Front view of the first friction member. [Figure 7] Front view of the first friction member as it is attached to the first plate. [Figure 8] Side view of the stopper component. [Modes for carrying out the invention]

[0017] 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.

[0018] FIG. 1 is a cross-sectional view of the power transmission device 100. As shown in FIG. 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, a sprocket 6, a crank arm 7, a first friction member 8, a second friction member 9, a biasing member 13, a plurality of first nuts 11, and a plurality of second nuts 12. The power transmission device 100 is arranged to be rotatable about the rotation axis O.

[0019] 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).

[0020] FIG. 2 is a front view of the power transmission device 100 with some of the coil springs 4, the crank arm 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 rotation direction R (clockwise in FIG. 2).

[0021] <First Rotating Body> FIG. 3 is a front view of the first rotating body 2. As shown in FIG. 3, the first rotating body 2 has a plurality of accommodation holes 21. In the present embodiment, the first rotating body 2 has three accommodation holes 21. Each accommodation hole 21 penetrates in the axial direction. Each accommodation hole 21 is arranged at intervals in the circumferential direction. Each accommodation hole 21 is arranged at equal intervals.

[0022] 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.

[0023] As shown in Figures 1 to 3, the first rotating body 2 has a hub portion 22, an outer flange portion 23 (an example of a flange portion), 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.

[0024] The outer flange portion 23 extends radially outward from the hub portion 22. A housing hole 21 is formed in this outer flange portion 23. The housing hole 21 penetrates the outer flange portion 23 in the axial direction. The outer flange portion 23 is formed in the axial center of the hub portion 22.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] The first rotating body 2 can be made of, for example, iron, stainless steel, or carbon fiber reinforced plastic (CFRP).

[0029] <Second Rotating Body> 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 outer flange portion 23.

[0030] 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.

[0031] Figure 4 is a plan view of the first plate 31. As shown in Figure 4, the first plate 31 is disc-shaped and has an opening in the center. The hub portion 22 of the first rotating body 2 extends axially through this opening in the first plate 31.

[0032] 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.

[0033] 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.

[0034] The first plate 31 has a plurality of engagement holes 313 and a plurality of engagement recesses 314. The engagement holes 313 are through holes that penetrate the first plate 31 in the axial direction. The engagement holes 313 are rectangular in shape when viewed in the axial direction. Each engagement hole 313 is spaced apart in the circumferential direction. Each engagement hole 313 is located between a pair of adjacent first window portions 311 in the circumferential direction. In the radial direction, each engagement hole 313 and the first window portion 311 do not overlap.

[0035] The engaging recesses 314 are formed on the inner circumferential surface of the first plate 31. The engaging recesses 314 are recessed radially outward from the inner circumferential surface of the first plate 31. The engaging recesses 314 are semicircular in an axial view. Each engaging recess 314 is spaced apart in the circumferential direction. Each engaging recess 314 overlaps with the first window portion 311 in a radial view.

[0036] Each engagement hole 313 and each engagement recess 314 is arranged alternately in the circumferential direction. Each engagement recess 314 is positioned radially inward relative to each engagement hole 313.

[0037] As shown in Figure 1, 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] <First and second friction members> The first friction member 8 is positioned in the axial direction between the first rotating body 2 and the second rotating body 3. More specifically, the first friction member 8 is positioned in the axial direction between the outer flange portion 23 and the first plate 31. The first friction member 8 is positioned to be rotatable relative to the first rotating body 2. When the first friction member 8 and the first rotating body 2 rotate relative to each other, a friction torque is generated between the first friction member 8 and the first rotating body 2. The first friction member 8 rotates integrally with the second rotating body 3.

[0043] Figure 5 is a perspective view of the first friction member 8, Figure 6 is a front view of the first friction member 8 viewed from the first side in the axial direction, and Figure 7 is a front view of the first friction member 8 attached to the first plate 31. As shown in Figures 5 to 7, the first friction member 8 has a base portion 81, a plurality of claw portions 82, a plurality of protrusions 83, a plurality of outer wall portions 84, and a cylindrical portion 85.

[0044] The base portion 81 is annular in shape and extends in the circumferential direction. The base portion 81 is in contact with the outer flange portion 23 of the first rotating body 2. More specifically, the surface of the base portion 81 facing the second side in the axial direction is in contact with the outer flange portion 23 of the first rotating body 2. Therefore, when the first friction member 8 rotates relative to the first rotating body 2, a friction torque is generated between the base portion 81 and the outer flange portion 23.

[0045] Each claw portion 82 extends from the base portion 81 to the first axial side. Each claw portion 82 is configured to engage with the corresponding engagement hole 313. The claw portion 82 is rectangular in shape when viewed axially. The claw portion 82 penetrates the engagement hole 313 and extends beyond the first plate 31 to the first axial side of the first plate 31. The claw portion 82 has a retaining portion 821 at its tip. The retaining portion 821 protrudes radially outward. This retaining portion 821 interferes with the first plate 31, preventing the first friction member 8 from falling off the first plate 31 during assembly. The claw portions 82 are spaced apart from each other in the circumferential direction.

[0046] Each projection 83 protrudes from the base portion 81 in the first axial direction. Each projection 83 engages with the corresponding engagement recess 314. The circumferential gap between each projection 83 and the corresponding engagement recess 314 is smaller than the circumferential gap between each claw portion 82 and the corresponding engagement hole 313.

[0047] The projection 83 is semicircular in an axial view. The projection 83 is semi-cylindrical. The projection 83 is positioned radially inward relative to the claw portion 82. Each projection 83 is spaced apart from each other in the circumferential direction. Each projection 83 is arranged alternately with each claw portion 82 in the circumferential direction.

[0048] Each protrusion 83 overlaps with the corresponding coil spring 4 in a radial view. That is, each protrusion 83 is positioned radially inward of the corresponding coil spring 4.

[0049] The outer wall portion 84 protrudes from the base portion 81 in the first axial direction. The outer wall portion 84 is positioned between a pair of adjacent claw portions 82 in the circumferential direction. The outer wall portion 84 extends in the circumferential direction. The outer wall portion 84 is spaced apart from the claw portions 82 in the circumferential direction. The height of the outer wall portion 84 is lower than the height of the claw portions 82. Here, "height" of the claw portions 82 and the outer wall portion 84 refers to their respective axial dimensions. The tip surface of the outer wall portion 84 is in contact with the first plate 31.

[0050] The outer wall portion 84 has an inner surface 841 and a plurality of recesses 842. In this embodiment, each outer wall portion 84 has a pair of recesses 842. The inner surface 841 of the outer wall portion 84 faces radially inward. The recesses 842 are formed on the inner surface 841. The recesses 842 are recessed radially outward.

[0051] Each recess 842 is formed at the circumferential end of the outer wall portion 84. That is, each recess 842 is formed in the vicinity of the claw portion 82. The distance between each recess 842 and the claw portion 82 is shorter than the distance between each recess 842.

[0052] The cylindrical portion 85 protrudes axially from the inner circumferential end of the base portion 81 to the first side. The cylindrical portion 85 extends axially within the opening of the first plate 31. The outer circumferential surface of the cylindrical portion 85 is in contact with the inner circumferential surface of the first plate 31.

[0053] The projection 83 is located radially outward from the cylindrical portion 85. The projection 83 is integrally formed with the cylindrical portion 85. The height of the cylindrical portion 85 is the same as the height of the projection 83. Here, "height" of the projection 83 and the cylindrical portion 85 refers to their respective axial dimensions.

[0054] As shown in Figure 1, the second friction member 9 is positioned in the axial direction between the second plate 32 and the outer flange portion 23. The second friction member 9 rotates integrally with the second plate 32 and rotates relative to the outer flange portion 23. When the second friction member 9 and the outer flange portion 23 rotate relative to each other, a friction torque is generated between the second friction member 9 and the outer flange portion 23.

[0055] The second friction member 9 has a plurality of claw portions 91. Each claw portion 91 engages with the second plate 32, causing the second friction member 9 to rotate integrally with the second plate 32.

[0056] The first friction member 8 and the second friction member 9 can be made of, for example, a nylon resin, a nylon resin compounded with reinforcing fibers (such as aramid fibers or metal fibers), or iron.

[0057] <Biasing member> The biasing member 13 is positioned in the axial direction between the second friction member 9 and the second plate 32. The biasing member 13 biases the first friction member 8 and the outer flange portion 23 so that they press against each other. The biasing member 13 also biases the second friction member 9 and the outer flange portion 23 so that they press against each other. The biasing member 13 is, for example, a disc spring.

[0058] <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 11, and a second nut 12. 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.

[0059] 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.

[0060] <Stopper component> Figure 8 is a side view of the stopper member 5. As shown in Figures 1 and 8, the stopper member 5 works in cooperation with the first nut 11 and the second nut 12 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 11. 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] <First and second nuts> The first nut 11 is screwed onto the first threaded portion 52. The first nut 11 works in cooperation with the stopper portion 51 to clamp the sprocket 6 and the first plate 31. The first nut 11 is a flange nut.

[0074] The second nut 12 is screwed onto the second threaded portion 54. The second nut 12 works in cooperation with the stopper portion 51 to clamp the second plate 32. The second nut 12 is a flange nut.

[0075] <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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] <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.

[0080] 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.

[0081] [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.

[0082] (a) In the above embodiment, the sprocket 6 was attached to the first plate 31, but the sprocket 6 may be attached to the second plate 32. In this case, the crank arm 7 is attached to the first axial end of the hub portion 22.

[0083] (b) In the above embodiment, the biasing member 13 was positioned between the second friction member 9 and the second plate 32, but the biasing member 13 may be positioned between the first friction member 8 and the first plate 31.

[0084] (c) In the above embodiment, each projection 83 is arranged alternately with each claw portion 82 in the circumferential direction, but the configuration of the first friction member 8 is not limited thereto. For example, each projection 83 may overlap with the corresponding claw portion 82 in a radial view.

[0085] (d) In the above embodiment, the power transmission device 100 had a first friction member 8 and a second friction member 9, but the configuration of the power transmission device 100 is not limited thereto. For example, the power transmission device 100 may have only the first friction member 8 and not the second friction member 9. [Explanation of Symbols]

[0086] 2: First rotational body 22: Hub section 23: Outer flange section 3: Second rotational body 31: First Plate 313: Engagement hole 314: Engaging recess 32: Second Plate 4: Coil spring 6: Sprocket 8: First friction member 81: Base section 82: Nail area 83:Protrusion 84: Exterior wall 841: Inner surface 842: recess 85: Cylindrical section 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, A friction member is positioned between the first rotating body and the second rotating body, configured to be rotatable relative to the first rotating body and to rotate integrally with the second rotating body, An elastic member that elastically connects the first rotating body and the second rotating body, Equipped with, The friction member has an annular base portion, a claw portion extending from the base portion to a first axial direction, and a projection portion positioned radially inward from the claw portion and projecting from the base portion to a first axial direction. The second rotating body has an engagement hole into which the claw portion engages, and an engagement recess into which the protrusion portion engages. A power transmission device for bicycles.

2. The friction member has a plurality of claw portions and a plurality of protrusions, Each of the aforementioned claw portions and each of the aforementioned protrusions are arranged alternately in the circumferential direction. The bicycle power transmission device according to claim 1.

3. The aforementioned protrusion overlaps with the elastic member in a radial view. The bicycle power transmission device according to claim 1.

4. The friction member is A plurality of claw portions are arranged at intervals from each other in the circumferential direction, An outer wall portion that protrudes from the base portion in the first axial direction and extends circumferentially between a pair of adjacent claw portions in the circumferential direction, It has, The outer wall portion has an inner surface facing radially inward and a recess formed on the inner surface that is recessed radially outward. The bicycle power transmission device according to claim 1.

5. The friction member is A plurality of claw portions are arranged at intervals from each other in the circumferential direction, An outer wall portion that protrudes from the base portion in the first axial direction and extends circumferentially between a pair of adjacent claw portions in the circumferential direction, It has, The outer wall portion is arranged in the circumferential direction at a distance from the claw portion. The bicycle power transmission device according to claim 1.

6. 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 second rotating body is A first plate is 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 and is configured to rotate integrally with the first plate, It has, The friction member is positioned in the axial direction between the flange portion and the first plate. The first plate has the engagement hole and the engagement recess, The bicycle power transmission device according to claim 1.

7. The first plate further comprises a sprocket that is attached to the first plate, The bicycle power transmission device according to claim 6.

8. The friction member has a cylindrical portion that protrudes from the inner circumferential end of the base portion toward the first axial direction, The aforementioned protrusion is positioned radially outward from the cylindrical portion and is integrally formed with the cylindrical portion. The bicycle power transmission device according to claim 1.

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