JP6179704B2 - Electric hub device and electric bicycle - Google Patents

Description

  The present invention relates to an electric hub device and an electric bicycle including the electric hub device.

  As a conventional electric hub device provided at the center of a wheel of an electric bicycle, for example, as shown in FIG. 8, a pair of left and right hub shafts fixedly disposed with respect to a frame 100 such as a chain stay of the electric bicycle. 101, 102, a hub body 103 rotatable with respect to the hub shafts 101, 102, and a motor 104 disposed inside the hub body 103 and rotating the hub body 103 (for example, Patent Document 1). 8, 105 is a spoke, 106 is a rotating shaft of the motor 104, 108 is a rotor of the motor 104, 109 is a stator of the motor 104, and the rotating shaft 106 is disposed between the left and right hub shafts 101 and 102. Yes. Reference numeral 110 denotes a chain for transmitting a pedaling force (manpower driving force) from the pedal, and 111 denotes a free wheel of the exterior transmission.

  The rotor 108 and the rotating shaft 106 of the motor 104 are interlocked with the hub body 103 via a speed reduction mechanism 107 including a planetary gear mechanism provided in the hub body 103. The hub body 103 includes a substantially cylindrical body member 121 that is open on one side, a disk-shaped cover member 122 that closes the opening side of the body member 121, a through-hole 123 formed in the center of the cover member 122, and A boss portion 124 and a cylindrical attachment member 125 inserted into the through hole 114 and externally fitted to the hub shaft 102 so as to be rotatable are provided.

  The free wheel 111 is rotatably fitted to the hub shaft 102 on the outer side of the hub body 103. The free wheel 111 includes a cylindrical outer body 113 having a plurality of sprockets 112 meshing with the chain 110, a cylindrical inner body 114 provided inside the outer body 113, an outer body 113 and an inner body 114, And a one-way clutch 115 that transmits the rotational driving force from the sprocket 112 only to the hub body 103. In addition, a large-diameter portion 126 is formed on one side of the inner body 114, and a sawtooth-like uneven portion is provided on the inner peripheral portion of the large-diameter portion 126 and the outer periphery of the boss portion 124 of the cover member 122. Serration portions 127 and 128 meshing with each other are formed and engaged. The serrated portions 127 and 128 have the same cross-sectional shape with respect to the axial direction of the hub shaft 102 (that is, the diameter is constant).

  When the user runs the electric bicycle, a pedaling force (human driving force) acting on the pedal is transmitted to the free wheel 111 via the chain 110, and the rotation of the free wheel 111 is transmitted from the outer body 113 to the one-way clutch. It is transmitted to the inner body 114 via 115. Further, the rotation of the inner body 114 is transmitted to the cover member 122 via the serration portions 127 and 128, whereby the inner body 114, the mounting member 125, the cover member 122, and the trunk member 121 are integrally rotated. The hub body 103 rotates around the axis. Further, the motor 104 is rotated in accordance with the pedaling force acting on the pedal, and the hub body 103 is rotated in a state where the rotational force of the motor 104 is added to the pedaling force (human power driving force) as an auxiliary driving force.

  As a structure for transmitting the driving force transmitted to the sprocket 112 meshing with the chain 110 such as the free wheel 111 to the hub body 103, instead of using the serrations 127 and 128, a cover member for the inner body 114 and the hub body 103. A structure in which the screw 122 is coupled with a screw is already widely implemented. However, when coupled with screws, the rotational driving force is transmitted while acting on the male screw portion in a direction perpendicular to the axial center thereof, so the male screw portion may be cut, and a large rotational driving force is generated. As a transmission mechanism, the reliability is lower than when the serration units 127 and 128 are used.

JP2012-121337

  By the way, the hub body 103 is often formed of a light alloy material such as aluminum for weight reduction or the like, and is more than a component that transmits the driving force from the chain 110 side such as the inner body 114 to the hub body 103. The strength is often low.

  Therefore, for example, even when the inner body 114 and the cover member 122 of the hub body 103 are coupled using serrations 127 and 128 as shown in FIG. When force is applied, the serration portion 128 of the cover member 122 may be broken due to insufficient strength. In order to prevent such problems, it is conceivable to use serrations 127 and 128 that are long in the axial direction. However, since the hub body 103 is disposed between the left and right frames 100 and has a limited width dimension, the hub body 103 incorporates many components such as the motor 104 and the speed reduction mechanism 107. Therefore, it is difficult to greatly increase the width of the electric hub device in order to make the serrations 127 and 128 significantly longer in the axial direction.

  The present invention solves the above-described problems, and provides an electric hub device capable of satisfactorily transmitting a manpower driving force to a hub body without significantly increasing the length of the serration portion in the axial direction. It is intended.

In order to solve the above-described problems, an electric hub device according to the present invention includes a manpower driving force transmission wheel body to which manpower driving force is transmitted, a hub shaft fixed to the frame, and a rotation with respect to the hub shaft. An electric hub device having a free hub body and a motor disposed on the hub body and rotating the hub body, wherein the human power driving force from the human power driving force transmission wheel is transmitted to the hub body. The serration joint is provided, and the serration joint is integrally formed with an input serration portion that receives a manpower driving force from the driving force transmission wheel body side and an output serration portion that transmits the manpower driving force to the hub body, and the output the diameter of the serrated portion is formed larger than the diameter of the input serration portion, serrated portion having a shape corresponding to the output serration portion to the hub body is formed, the output serration The manpower driving force per unit area acting on the serration part of the hub body from the central part is made smaller than the manpower driving force per unit area acting on the input serration part, so that manpower driving from the manpower driving force transmission wheel The force is transmitted to the hub body through the serration joint .

  With this configuration, when the human driving force transmitted from the human driving force transmission wheel body is transmitted to the hub body via the serration joint, the human driving force per unit area acting on the serration portion of the hub body from the output serration portion is reduced. Therefore, it can be made smaller than the manpower driving force per unit area acting on the input serration unit. As a result, even if the serration joint is not elongated in the axial direction, the serration portion of the hub body can receive the human driving force well, and the serration portion of the hub body is destroyed due to insufficient strength. It can prevent well.

  Further, the invention is characterized in that the serration portion of the hub body is formed in a recess formed in the hub body. With this configuration, the width of the hub body can be reduced as compared with the case where a serration portion is formed in a boss portion or the like that protrudes from the hub body.

  Further, the present invention is characterized in that a free wheel of an exterior transmission is provided, and the manpower driving force transmission wheel is provided on the free wheel. With this configuration, it is possible to satisfactorily cope with the case where the width of the hub body cannot be increased by providing the freewheel of the exterior transmission.

  Further, in the present invention, the diameter of the output serration portion of the serration joint is formed to be equal to or larger than the diameter of the cylindrical body to which the manpower driving force transmission wheel body of the freewheel is attached. It is characterized by being. With this configuration, compared to the case where the diameter of the output serration portion of the serration joint is smaller than the diameter of the cylindrical body, the human power driving force per unit area acting on the serration portion of the hub body Can be reduced. Thereby, the serration part of the hub body can be further prevented from being broken due to insufficient strength.

  According to the present invention, the serration joint that transmits the manpower driving force from the manpower driving force transmission wheel body to the hub body, the input serration portion that receives the manpower driving force, and the output serration portion that transmits the manpower driving force to the hub body. , And the diameter of the output serration portion is larger than the diameter of the input serration portion, so that the human power driving force per unit area acting on the serration portion of the hub body is input from the output serration portion. It can be made smaller than the human driving force per unit area acting on the serration portion. Thus, even if the serration joint is not elongated in the axial direction, the serration portion of the hub body can receive a human driving force well, and the hub body is made of an aluminum material having a relatively low strength. Even in this case, the serration portion of the hub body can be prevented from being broken due to insufficient strength, and the reliability is improved. Moreover, since it is not necessary to lengthen the serration joint in the axial direction, a compact state can be maintained as the electric hub device.

  Further, by forming the serration portion of the hub body in a recess formed in the hub body, compared to the case where the serration portion is formed in a boss portion or the like protruding from the hub body, the hub body The width can be reduced, and a more compact state can be maintained as the electric hub device.

  Further, even when the width of the hub body cannot be increased due to the provision of a free wheel of the exterior transmission, it is possible to cope with the problem without causing a problem by adopting the above configuration. . In addition, by forming the diameter of the output serration portion of the serration joint equal to or larger than the diameter of the cylindrical body to which the freewheeling manpower driving force transmission wheel is attached, the hub It is possible to better prevent the serration portion of the body from being destroyed due to insufficient strength.

Overall side view of an electric bicycle according to an embodiment of the present invention Side view of the electric hub device of the electric bicycle and the vicinity thereof Sectional view of the electric hub device Partial enlarged sectional view of the electric hub device Partial enlarged sectional view of the electric hub device Exploded perspective view of the electric hub device Exploded perspective view of the electric hub device Sectional view of a conventional electric hub device

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In FIG. 1, 1 is an electric bicycle. The electric bicycle 1 has a frame 2, a front wheel 3 and a rear wheel 4 provided on the frame 2, a pedal 5 on which a manpower driving force (stepping force of a user) is loaded, and a manpower driving force transmitted to the rear wheel 4 side. A chain 6 as a driving force transmission cable body, a crank gear 7 for transmitting a manpower driving force to the chain 6, a handle 8, an exterior transmission 18, a saddle 9, a battery 13, and a human force acting on the pedal 5. A detection device 31 for detecting a driving force, a control unit 14 and the like are provided. The frame 2 includes a chain stay 10, a back hawk 11, and the like, and a rear end 12 of a bifurcated shape is provided at the rear end of the chain stay 10 as shown in FIG. 2. As shown in FIG. 1, the exterior transmission 18 includes a rear derailleur 41 and a multistage freewheel 19. The rear wheel 4 includes an electric hub device 20 disposed at the center thereof, a plurality of spokes 15 extending radially from the electric hub device 20 in the radial direction of the rear wheel 4, and an outer peripheral end of the spoke 15. And a tire 17 attached to the outer peripheral side of the rim 16.

  As shown in FIGS. 2, 3, and the like, the electric hub device 20 includes a pair of left and right fixing hub shafts 21 and 22 fixed to the rear end 12 and the hub shafts 21 and 22. A rotatable hub body 23 and a motor 24 disposed inside the hub body 23 and rotating the hub body 23 are provided.

  As shown in FIGS. 3 to 5, the motor 24 is provided so as to be rotatable on the inner peripheral side of the motor housing 32, the stator 33 fixed inside the motor housing 32 and covered with resin, and the stator 33. The rotor 34 and a rotating shaft 35 inserted through the center of the rotor 34 are provided, and a brushless motor is provided. The motor 24 generates an auxiliary driving force according to the pedaling force detected by the detection device 31 by the control unit 14. Note that the control unit 14 may be configured to be switched to a regenerative operation in which electric power is generated by the rotational force from the rear wheel 4 and the battery 13 is charged.

  The rotating shaft 35 of the motor 24 is located between the hub shafts 21 and 22, and these shafts 21, 22 and 35 are disposed on the same axis 25. The motor housing 32 includes a housing body 36 on one side (left side in FIG. 3) and a housing body 37 on the other side (right side in FIG. 3) divided in the direction of the axis 25 of the rotation shaft 35. The stator 33 is sandwiched between both housing bodies 36 and 37, and the both housing bodies 36 and 37 are connected by a plurality of screws 38. The rotating shaft 35 and the rotor 34 are rotatably supported by bearings 39 and 40 disposed near the center of the housing bodies 36 and 37.

  The hub body 23 includes a substantially cylindrical body member 27 having an opening 26 on one end side (left side in FIG. 3) in the direction of the axis 25 of the hub shafts 21 and 22, and the other end portion of the body member 27 (FIG. 3). A disc-shaped cover member 28 that closes the right side), a through hole 29 formed in the center of the cover member 28, and inserted into the through hole 29 and screwed into the cover member 28 to be coupled. A cylindrical mounting member 30 that is externally fitted in a rotatable manner with respect to the hub shaft 22 is provided. The body member 27 and the cover member 28 are made of, for example, an aluminum alloy.

  One end portion (left end portion in FIG. 3) of the body member 27 of the hub body 23 is rotatably supported by one housing body 36 via a bearing 41. Also, as shown in FIGS. 3 and 4, one hub shaft 21 extends radially outwardly at the end of the portion protruding into the motor 24 (in this embodiment, it expands in a hexagonal shape). (Ii) An engaging portion 21a is formed. The engaging portion 21 a is engaged with and engaged with a hexagonal hole-shaped engaging hole 36 a formed in the housing body 36. Thereby, the one housing body 36 and the one hub shaft 21 are assembled in a state where they are regulated so as not to rotate around the shaft center 25.

  As shown in FIGS. 3 and 5, the other hub shaft 22 is inserted into the mounting member 30 and protrudes from the outside to the inside of the hub body 23. The other hub shaft 22 is formed with an engaging portion 22a at an end portion projecting into the motor 24 so as to expand outward in the radial direction (in this embodiment, expand in a hexagonal shape). The engaging portion 22 a is engaged with and engaged with a hexagonal hole-shaped engaging hole 50 a formed in the support frame 50 attached to the other housing body 37 via a screw 52. As a result, the support frame 50 and the other hub shaft 22 are assembled in a state where they are regulated so as not to rotate around the axis 25.

  As shown in FIGS. 3 and 5, the rotation shaft 35 of the motor 24 and the hub body 23 are linked via a speed reduction mechanism 45 provided adjacent to the motor 24 in the hub body 23. The speed reduction mechanism 45 includes a sun gear 46 formed at the end of the rotary shaft 35, an annular internal gear 47 (an example of an annular gear) attached to the inside of the cover member 28 via a connecting member 51, and And a plurality of rotatable planetary gears 48 meshing with the sun gear 46 and the internal gear 47. One end of the planetary gear 48 is supported by the other housing body 37 of the motor 24, and the other end of the planetary gear 48 is supported by a support frame 50 attached to the other housing body 37.

  Each planetary gear 48 includes a large gear portion 48a and a small-diameter gear portion 48b that are integrally formed with each other, and a support shaft portion 48c that rotatably supports the large gear portion 48a and the small gear portion 48b. Yes. Then, the sun gear 46 meshes with the large gear portion 48a of the planetary gear 48, and the internal gear 47 meshes with the small gear portion 48b of the planetary gear 48, whereby the rotation of the rotating shaft 35 of the motor 24 is reduced, that is, It is configured to increase the torque and transmit the auxiliary driving force to the hub body 23 to interlock the hub body 23. In addition, a thrust bearing 54 capable of receiving a force from the support frame 50 in the direction along the axis 25 is disposed between the cover member 28 and the support frame 50.

  As described above, the exterior transmission 18 is attached to the rear wheel 4, and the exterior transmission 18 includes the rear derailleur 41 (see FIG. 1) and the multistage freewheel 19. As shown in FIGS. 3 and 5, the free wheel 19 is rotatably fitted on the other hub shaft 22 on the outer side of the hub body 23. The free wheel 19 includes a plurality of sprockets 60 serving as a manpower driving force transmission wheel that selectively meshes with the chain 6 to transmit the manpower driving force from the chain 6, and a cylindrical outer member including these sprockets 60. A body 61, a cylindrical inner body 62 rotatably provided inside the outer body 61 via a bearing, and provided between the outer body 61 and the inner body 62 and from the sprocket 60 to the hub body 23 only. And a one-way clutch 63 that transmits the rotational driving force. The inner body 62 and the attachment member 30 are engaged with each other in the circumferential direction (rotation direction). The inner body 62 and the outer body 61 are made of a metal having sufficient rigidity such as chromium molybdenum steel.

  Further, as shown in FIGS. 5 to 7, a pair of serrations 53 a and 53 b each having a plurality of rough sawtooth portions are provided between the cover member 28 and the inner body 62. A serration joint 53 is provided to transmit the human driving force to the hub body 23. The serration joint 53 is made of an alloy having sufficient strength, and an input serration portion 53b that receives a human driving force from the inner body 62 and an output serration portion 53a that transmits the human driving force to the hub body 23 are integrally formed. Has been. And the diameter of the output serration part 53a is formed larger than the diameter of the input serration part 53b. In this embodiment, the diameter of the output serration portion 53a is formed larger than the diameter of the outer body 61 (the diameter of the mounting portion of the sprocket 60) as a cylindrical body to which the sprocket 60 of the freewheel 19 is mounted. However, the diameter of the output serration portion 53a may be equal to the diameter of the outer body 61 (the diameter of the attachment portion of the sprocket 60).

  The serration joint 53 is fitted into a serration portion 62 b formed on the inner periphery of a large diameter portion 62 a formed with an input serration portion 53 b at one end of the inner body 62. An output serration portion 53 a is formed near the center of the cover member 28 and is fitted into a serration portion 28 b formed in a recess 28 a that is recessed from the side surface to the inside of the motor 24. The force from the inner body 62 is transmitted to the cover member 28 satisfactorily.

  In addition, a bearing body 64 that rotatably supports the outer body 61 is provided inside the outer body 61. Reference numeral 65 denotes a lock nut for locking the ball press provided on the bearing body 64.

  An inner peripheral side end portion of each spoke 21 of the rear wheel 4 is connected to the outer peripheral portion of the hub body 23. Both hub shafts 21, 22 are inserted into grooves 12 a formed in the rear ends 12 of both chain stays 10, respectively. By screwing the nuts 66 to the hub shafts 21 and 22, the rear wheel 4 is attached between the chain stays 10 together with the electric hub device 20.

  As shown in FIG. 5, the other hub shaft 22 is restricted from rotating around the shaft center 25 between the rear stay 12 of the chain stay 10 on the side where the free wheel 19 is provided and the nut 66. A metal anti-rotation member 67 is provided. In the rotation preventing member 67, a protrusion 67 a as an integrally formed engaging portion is fitted in the groove 12 a of the rear pawl 12, and the rotation preventing member 67 extends in the direction of the axis 25 with respect to the rear pawl 12. It is engaged so as not to rotate as a center.

  In addition, as shown in FIG. 4, a detent member 70 is also provided in contact with the rear end 12 of the chain stay 10 on the side where the free wheel 19 is not provided. The anti-rotation member 70 is also formed with a protrusion 70a as an engaging portion that is engaged with and engaged with a groove 12a as an engaged portion formed in the rear pawl 12. The protrusion 70 a is fitted into the groove 12 a of the rear pawl 12, and the anti-rotation member 70 is engaged with the rear pawl 12 so as not to rotate around the direction of the axis 25. Further, the rotation preventing member 70 is fixed by a screw 72 in a state of being in direct contact with the housing body 36.

  In the above configuration, when the user runs the electric bicycle 1, the human driving force (stepping force) acting on the pedal 7 is detected by the detection device 31 and transmitted to the free wheel 19 via the chain 6. The wheel 19 rotates. The rotation of the free wheel 19 is transmitted from the outer body 61 to the inner body 62 via the one-way clutch 63 and further to the cover member 28 via the serration joint 53. As a result, the inner body 62, the attachment member 30, the cover member 28, and the body member 27 rotate integrally, and the hub body 23 rotates around the axis 25.

  Further, the control unit 14 controls driving of the motor 24 according to the human power driving force detected by the detection device 31. At this time, the rotating shaft 35 rotates together with the rotor 34, whereby the hub body 23 is decelerated about the axis 25 via the speed reducing mechanism 45 and rotates. As a result, the rear wheel 4 is rotationally driven by combining the manual driving force acting on the pedal 7 and the auxiliary driving force of the motor 24 output in accordance with the manual driving force.

  Further, in the case of having a regenerative function, the control unit 14 causes the motor 24 or the like to perform a regenerative operation when detecting a braking operation or downhill traveling. That is, the hub body 23 rotates with the rotation of the rear wheel 4, and the rotating shaft 35 and the rotor 34 of the motor 24 also rotate in conjunction with each other via the speed reduction mechanism 45. 13 to charge the battery 13 or the like.

  Here, in the above configuration, the serration joint 53 that transmits the manpower driving force from the sprocket 60 of the free wheel 19 to the hub body 23, the input serration portion 53 b that receives the manpower driving force, and the manpower driving force to the hub body 23. The output serration portion 53a to be transmitted is integrally formed, and the diameter of the output serration portion 53a is formed larger than the diameter of the input serration portion 53b. As a result, the manpower driving force per unit area that acts on the serration portion 28b of the hub body 23 (cover member 28) from the output serration portion 53a of the serration joint 53 per unit area that acts on the input serration portion 53b of the serration joint 53. It can be smaller than the human driving force.

  Therefore, even if the serration joint 53 is not elongated in the direction of the axis 25, the human body driving force can be satisfactorily received by the serration portion 28b of the hub body 23 (cover member 28), and the hub body can be reduced in weight. 23, even when an aluminum material having a strength lower than that of the serration joint 53 is used, the serration portion 28b of the hub body 23 (cover member 28) can be prevented from being broken due to insufficient strength, and reliability is improved. Moreover, since it is not necessary to lengthen the serration joint 53 in the direction of the axis 25, the electric hub device 20 can maintain a compact state in the width direction.

  Further, since the serration portion 28b of the hub body 23 (cover member 28) is formed in the concave portion 28a formed in the cover member 28, the serration portion is formed in a boss portion or the like that protrudes laterally from the cover member 28. Compared to the case, the width of the hub body 23 can be reduced. Therefore, a more compact state can be maintained as the electric hub device 20.

  In this embodiment, since the free wheel 19 of the exterior transmission 18 is provided in the electric hub device 20, it is important to reduce the width of the hub body 23 (to make it compact). The configuration is particularly effective.

  Further, in the above configuration, the diameter of the output serration portion 53a of the serration joint 53 is larger than or equal to the diameter of the outer body 61 (the diameter of the mounting portion of the sprocket 60). Therefore, compared to the case where the diameter of the output serration portion 53a of the serration joint 53 is smaller than the diameter of the outer body 61, the per unit area acting on the serration portion 28b of the hub body 23 (cover member 28). The human driving force can be reduced. As a result, the serration portion 28b of the hub body 23 (the cover member 28) can be further prevented from being broken due to insufficient strength, and as a result, the reliability of the electric hub device 20 and thus the electric bicycle 1 can be further improved. be able to.

  In the above embodiment, the case where the exterior transmission 18 is provided has been described. However, the present invention is not limited to this, and for the case where the exterior transmission 18 is not provided, as described above, The configuration related to the serration joint 53 can be similarly applied. Moreover, although the case of the electric bicycle 1 which can also perform regenerative operation | movement was described in the said embodiment, Of course, it can apply also to the electric bicycle which does not perform regenerative operation | movement. In the above embodiment, the case where the human driving force is transmitted to the sprocket 60 as the human driving force transmission wheel by the chain as the driving force transmission rope has been described. However, the present invention is not limited to this. For example, a toothed belt may be used as the driving force transmission cable body, and a gear as a human power driving force transmission wheel body meshing with the toothed belt may be used.

  The present invention is particularly suitable for an electric bicycle provided with an electric hub device. However, the present invention can also be applied to an electric vehicle other than the electric bicycle, such as an electric wheelchair, an electric motorcycle, an electric vehicle, and the like.

1 Electric bicycle 2 Frame 3 Front wheel
4 Rear wheels
5 Pedal 6 Chain 10 Chain stay 11 Back fork 12 Rear 13 Battery 14 Control unit 19 Free wheel 20 Electric hub device 21, 22 Hub shaft 23 Hub body 24 Motor 25 Shaft 27 Body member 28 Cover member 28a Concave portion 28b Serration portion DESCRIPTION OF SYMBOLS 31 Detection apparatus 32 Motor housing 33 Stator 34 Rotor 35 Rotating shaft 45 Deceleration mechanism 53 Serration joint 53a Output serration part 53b Input serration part 60 Sprocket 61 Outer body 62 Inner body 62b Serration part 63 One-way clutch

Claims (5)

A manpower driving force transmission wheel body to which manpower driving force is transmitted, a hub shaft fixed to the frame, a hub body rotatable with respect to the hub shaft, and a hub body disposed on the hub body. An electric hub device having a motor to be rotated,
A serration joint is provided for transmitting the manpower driving force from the manpower driving force transmission wheel body to the hub body,
The serration joint is integrally formed with an input serration portion that receives a manpower driving force from the driving force transmission wheel body side and an output serration portion that transmits the manpower driving force to the hub body,
The diameter of the output serration part is formed larger than the diameter of the input serration part,
A serration portion having a shape corresponding to the output serration portion is formed on the hub body, and a human-power driving force per unit area acting on the serration portion of the hub body from the output serration portion per unit area acting on the input serration portion. An electric hub device characterized in that the human power driving force from the human power driving force transmission wheel body is transmitted to the hub body via a serration joint .   2. The electric hub device according to claim 1, wherein the serration portion of the hub body is formed in a recess formed in the hub body.   3. The electric hub device according to claim 1, wherein a free wheel of an exterior transmission is provided, and the manpower driving force transmission wheel is provided on the free wheel. 4.   The diameter of the output serration portion of the serration joint is formed to be equal to or larger than the diameter of the cylindrical body to which the manpower driving force transmission wheel body of the freewheel is attached. The electric hub device according to claim 3.   An electric bicycle comprising the electric hub device according to any one of claims 1 to 4.

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