Drive unit for electrically assisted bicycle and electrically assisted bicycle

Abstract

The objective of this invention is to suppress electrolytic corrosion of the drive unit of an electric-assisted bicycle. This invention relates to a drive unit (20) for an electric-assisted bicycle (1), wherein the housing (21) and the shaft (30) are made of different metallic materials, and the outer periphery 63 of a dust seal (60) contacts the inner periphery (262) of the opening (261) of the housing (21) through which the shaft (30) passes. The outer end (265) of the inner periphery (262) of the opening (261) of the housing (21) in the rotation axis direction (D1) of the shaft (30) has a chamfered portion (266) that expands outward toward the opening (261). The dust seal (60) has a first lip (71) covering the chamfered portion (266). The dust seal (60) does not protrude outward beyond the outermost part (267) of the opening (261) in the rotation axis direction (D1).

Description

Technical Field

[0001] The present invention relates to a driving unit for an electric-assisted bicycle and the electric-assisted bicycle. Prior Art

[0002] Bicycles are widely used as a convenient means of transportation for men, women, young and old. In recent years, electric-assisted bicycles that use electric motors to assist the user's pedaling force have become increasingly popular (see, for example, Patent Document 1). The electric motor generates driving force by supplying electricity from a battery mounted on the vehicle. In an electric-assisted bicycle, the electric motor generates a driving force corresponding to the human power applied to the pedals by the user, which can reduce the burden on the user when driving on a slope or when carrying cargo. [Prior Technical Literature] [Patent Document]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2007-230411 Summary of the invention

[0004] [Problems that the invention aims to solve] The driving unit of the electric-assisted bicycle comprises a housing for accommodating the electric motor and a rotating shaft partially exposed outside the housing. For example, a crank arm is mounted on the rotating shaft.

[0005] When the housing and the shaft are made of different metal materials, if water accumulates between the opening of the housing and the shaft, it is easy to cause galvanic corrosion.

[0006] It is required to suppress the electrolytic corrosion of the drive unit of an electric-assisted bicycle. [Technical means to solve the problem]

[0007] This specification discloses a drive unit and an electric-assisted bicycle described in the following items.

[0008] [Project 1] A driving unit is a driving unit for an electric assisted bicycle and comprises: Electric motor; A housing that accommodates the electric motor; A rotating shaft rotatably supported by the housing and partially exposed to the outside of the housing; and An annular dust seal is disposed between the rotating shaft and the housing to prevent dust from entering the housing from the outside; and The housing and the shaft are made of different metal materials. The inner circumference of the dust seal is in slidable contact with the rotating shaft. The outer circumference of the dust seal is in contact with the inner circumference of the opening of the housing through which the shaft passes. The outer end of the inner circumference of the opening of the housing in the direction of the rotation axis of the shaft has a chamfered portion that expands in diameter toward the outside of the opening. The dust seal has a first lip covering the chamfered portion. The dust seal does not protrude outward in the direction of the rotation axis beyond the outermost portion of the opening in the direction of the rotation axis.

[0009] In the case where the housing and the shaft are made of different metal materials, if water accumulates between the opening of the housing and the shaft, electrolytic corrosion (electrical corrosion) is likely to occur. By applying a coating to the opening, electrolytic corrosion can be suppressed to a certain extent. However, in the case where a protrusion with a small thickness is provided at the opening, it is difficult for the coating to adhere to such a protrusion, and it is difficult for the coating to adhere well to the opening. According to an embodiment of the present invention, the dust seal has a first lip covering the chamfered portion of the opening. By covering the chamfered portion with the first lip, electrolytic corrosion can be suppressed even in the case where the coating is difficult to adhere well to the opening.

[0010] Furthermore, according to an embodiment of the present invention, the dust seal does not protrude outward in the rotation axis direction beyond the outermost portion of the opening in the rotation axis direction. This can reduce the width dimension of the drive unit.

[0011] A crank arm may be provided on the rotating shaft. When the dust seal protrudes outward beyond the opening of the housing, the dust seal may interfere with the crank arm. By preventing the dust seal from protruding outward beyond the opening, interference between the dust seal and the crank arm can be suppressed.

[0012] [Project 2] The driving unit as described in item 1, wherein the first lip of the dust seal has a shape extending toward the outside in the direction of the rotation axis and away from the rotation axis.

[0013] Thereby, the chamfered portion of the opening can be appropriately covered.

[0014] [Item 3] The drive unit as described in item 1 or 2, wherein a groove is provided on the inner peripheral portion of the opening along the circumferential direction of the opening, The outer peripheral portion of the dust seal has a second lip that is fitted into the groove.

[0015] The dust seal can be fixed to the housing by fitting the second lip of the dust seal into the groove of the opening.

[0016] [Item 4] A drive unit as described in item 3, wherein the opening has a protruding portion that becomes a wall portion on the outer side in the direction of the rotation axis of the groove, The chamfered portion is provided on the protruding portion.

[0017] Even when the paint is difficult to adhere well to the protruding portion, the first lip covers the chamfered portion, thereby suppressing the electrolytic corrosion.

[0018] [Item 5] A drive unit as described in item 3 or 4, wherein the second lip of the dust seal is embedded in the groove by snap-fit.

[0019] The dustproof seal can be fixed to the housing by buckle fitting, and dust and water can be more effectively prevented from entering the interior of the housing.

[0020] [Item 6] The driving unit as described in item 4, wherein the first lip and the second lip of the dust seal clamp the protrusion by elastic force.

[0021] Thereby, a gap is not easily generated between the first lip and the chamfered portion, and electrolytic corrosion can be more effectively suppressed. In addition, dust and water can be more effectively suppressed from entering the interior of the housing.

[0022] [Item 7] A drive unit as described in item 1 or 2, wherein the dust seal is pressed into the opening.

[0023] By pressing the dust seal into the opening, the dust seal can be fixed to the housing.

[0024] [Item 8] A drive unit as described in any one of items 1 to 7, wherein the inner peripheral portion of the dust seal has a sealing lip that contacts the rotating shaft in a slidable manner.

[0025] This can prevent oil from flowing out from the inside of the housing to the outside, and prevent water and dust from entering the inside of the housing from the outside.

[0026] [Item 9] The drive unit as described in item 8, wherein the inner peripheral portion of the dust seal further comprises a dust lip, the dust lip slidably contacts the rotating shaft and is arranged on the outer side than the sealing lip in the direction of the rotating shaft.

[0027] This can prevent dust from entering the interior from the outside of the housing.

[0028] [Item 10] A drive unit as described in any one of items 1 to 9, wherein the housing comprises a metal material having magnesium as a main component.

[0029] Thereby, the weight of the drive unit can be reduced.

[0030] [Item 11] A drive unit as described in any one of items 1 to 10, wherein the shaft comprises a metal material with iron as a main component.

[0031] Thereby, the rigidity and strength required for the rotating shaft can be achieved at a low cost.

[0032] [Item 12] An electric-assisted bicycle having a drive unit as described in any one of items 1 to 11.

[0033] This makes it possible to realize an electric-assisted bicycle equipped with a small-sized drive unit that has high durability against water. [Effects of the Invention]

[0034] In the case where the housing and the shaft of the drive unit are made of different metal materials, if water accumulates between the opening of the housing and the shaft, electrolytic corrosion (electrical corrosion) is likely to occur. By applying a coating to the opening, electrolytic corrosion can be suppressed to a certain extent. However, in the case where a protrusion with a small thickness is provided at the opening, it is difficult for the coating to adhere to such a protrusion, and it is difficult for the coating to adhere well to the opening. According to an embodiment of the present invention, the dust seal has a first lip covering the chamfered portion of the opening. By covering the chamfered portion with the first lip, electrolytic corrosion can be suppressed even in the case where the coating is difficult to adhere well to the opening.

[0035] Furthermore, according to an embodiment of the present invention, the dust seal does not protrude outward in the rotation axis direction beyond the outermost portion of the opening in the rotation axis direction. This can reduce the width dimension of the drive unit.

[0036] A crank arm may be provided on the rotating shaft. When the dust seal protrudes outward beyond the opening of the housing, the dust seal may interfere with the crank arm. By preventing the dust seal from protruding outward beyond the opening, interference between the dust seal and the crank arm can be suppressed. Simple diagram description

[0037] FIG. 1 is a right side view showing an electric assist bicycle 1 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing an example of the internal structure of the driving unit 20 according to the embodiment of the present invention. FIG. 3 is a cross-sectional view showing a portion of the housing 21 according to the embodiment of the present invention. FIG. 4 is a cross-sectional view showing the opening 261 of the housing 21 and the rotation shaft 30 passing through the opening 261 according to the embodiment of the present invention. FIG. 5 is a perspective view showing the dust seal 60 cut along a plane parallel to the rotation axis direction according to the embodiment of the present invention. FIG. 6 is a cross-sectional view showing an enlarged portion of the driving unit 20 according to the embodiment of the present invention. FIG. 7 is a cross-sectional view showing an enlarged portion of the driving unit 20 according to the embodiment of the present invention. FIG. 8 is a cross-sectional view showing the positional relationship between the opening 261 of the housing 21 and the dust seal 60 in the rotation axis direction D1 according to the embodiment of the present invention. FIG. 9 is a cross-sectional view showing a dust seal 60 fixed to the inner peripheral portion 262 of the opening 261 by press-fitting according to an embodiment of the present invention. Implementation

[0038] Hereinafter, the embodiments of the present invention will be described with reference to the drawings. In the description of the embodiments, the same reference symbols are marked for the same components, and their descriptions are omitted in the case of duplication. The symbols F, Re, L, R, U, and D marked in the drawings represent front, rear, left, right, top, and bottom, respectively. The front, rear, left, right, and top of an electric-assisted bicycle refer to the front, rear, left, right, and top of an electric-assisted bicycle based on the state in which the user sits on the seat (saddle) of the electric-assisted bicycle facing the handlebars. The following embodiments are illustrative, and the present invention is not limited to the following embodiments.

[0039] [Electric Assist Bicycle] FIG. 1 is a right side view showing an electric-assisted bicycle 1 according to the present embodiment.

[0040] The electric-assisted bicycle 1 has a body frame 2 extending in the front-rear direction. The body frame 2 includes a head tube 11, a down tube 12, an upper tube 14, a seat tube 16, a rear chain stay 18, a rear seat stay 19, and a bracket 26. The head tube 11 is arranged at the front end of the body frame 2. A handlebar steering column 13 is inserted into the head tube 11 in a rotatable manner. A handlebar 4 is fixed to the handlebar steering column 13. An instrument unit 5 for displaying various information related to the electric-assisted bicycle 1 is provided on the handlebar 4. A headlight 59 is provided in the front part of the handlebar 4.

[0041] A front fork 15 is fixed to the lower end of the handlebar steering column 13. The lower end of the front fork 15 supports the front wheel 6 as a steering wheel so that it can rotate.

[0042] The down tube 12 extends from the head tube 11 to the rear and obliquely downward. The seat tube 16 extends upward from the rear end of the down tube 12. The chain stay 18 extends from the lower end of the seat tube 16 to the rear. The bracket 26 connects the rear end of the down tube 12, the lower end of the seat tube 16, and the front end of the chain stay 18. The top tube 14 is provided in a manner that connects the head tube 11 and the upper part of the seat tube 16. The seat tube 17 is inserted into the seat tube 16, and the saddle 3 for the user to sit on is provided at the upper end of the seat tube 17.

[0043] The rear end of the rear chain fork 18 supports the rear wheel 7 as a driving wheel so that it can rotate. The rear seat fork 19 extends from the upper part of the seat tube 16 toward the rear oblique lower part. The lower end of the rear seat fork 19 is connected to the rear end of the rear chain fork 18. A speed changer 58 for changing the speed ratio is provided at the rear end of the rear chain fork 18. The speed changer can also be provided around the pedal crankshaft 22. A speed sensor 55 for detecting the rotation of the rear wheel 7 is provided at the rear part of the rear chain fork 18. The speed sensor 55 can also be provided at the lower part of the front fork 15 to detect the rotation of the front wheel 6.

[0044] The drive unit 20 is provided on a bracket 26 disposed near the center of the vehicle of the vehicle frame 2. An electric motor 25, an MCU (motor control unit), a speed reducer, etc. are accommodated in the housing of the drive unit 20. The pedal crankshaft 22 is supported by the drive unit 20 in a manner penetrating in the left-right direction. Crank arms 35 are provided at both ends of the pedal crankshaft 22. A pedal 37 is rotatably provided at the front end of the crank arm 35.

[0045] The down tube 12 is equipped with a battery unit 56 for supplying power to the drive unit 20 and the like. In the example shown in FIG. 1 , the battery unit 56 is installed inside the down tube 12. The down tube 12 may have a hollow shape. The down tube 12 may also have a U-shaped cross section at least in part and have a cover portion covering the U-shaped portion.

[0046] The battery unit 56 may be disposed on the outer surface of the down tube 12. The battery unit 56 may be mounted on the bracket 26 or the seat tube 16. The battery unit 56 may be detachable from the electric-assisted bicycle 1.

[0047] The battery unit 56 has a battery and a BMS (battery management system). The battery is a rechargeable battery that can be charged and discharged. The BMS controls the charging and discharging of the battery and monitors the output current and remaining amount of the battery.

[0048] The MCU of the drive unit 20 controls the operation of the electric motor 25 and controls the operation of each part of the electric assisted bicycle 1. The MCU has a semiconductor integrated circuit such as a processor and a motor drive circuit. The rotation of the pedal crankshaft 22 generated by the user stepping on the pedal 37 is transmitted to the rear wheel 7 via the drive sprocket 34 and the chain 53. The MCU controls the electric motor 25 in such a manner that a drive auxiliary output corresponding to the rotation output of the pedal crankshaft 22 generated by the user stepping on the pedal 37 is generated. The auxiliary force generated by the electric motor 25 is transmitted to the rear wheel 7 via the drive sprocket 34 and the chain 53. A belt, a shaft, etc. may be used instead of the chain 53.

[0049] [Driver unit] 2, an example of the structure of the drive unit 20 will be described. FIG2 is a cross-sectional view showing an example of the internal structure of the drive unit 20.

[0050] As shown in FIG. 2 , the drive unit 20 includes a housing 21 , a rotating shaft 30 , a transmission mechanism 40 , and an electric motor 25 .

[0051] First, the structure of the housing 21 of this embodiment will be described.

[0052] The housing 21 is fixed to the bracket 26 ( FIG. 1 ) by a plurality of fasteners. The housing 21 includes a first shell 211 , a second shell 212 , and a cover 213 . The housing 21 is formed of, for example, a metal material (magnesium alloy) having magnesium as a main component. By using a metal material having magnesium as a main component, the weight of the drive unit 20 can be reduced.

[0053] The first housing 211 overlaps the second housing 212 from the left side in the left-right direction. The first housing 211 and the second housing 212 are fixed by a plurality of fasteners. As a result, a space 214 is formed between the first housing 211 and the second housing 212.

[0054] The cover 213 overlaps the first housing 211 from the left side in the left-right direction. The cover 213 and the first housing 211 are fixed by a plurality of fasteners. As a result, a space 215 covered by the cover 213 is formed on the left side of the first housing 211. The electric motor 25 is accommodated in the space 215.

[0055] Next, the structure of the rotating shaft 30 of this embodiment will be described. The rotating shaft 30 includes the pedal crankshaft 22 and the rotating shaft 23.

[0056] The rotating shaft 30 is disposed so as to penetrate the housing 21 in the left-right direction of the vehicle, and is rotatably supported by the housing 21 .

[0057] FIG3 is a cross-sectional view showing a portion of the housing 21. An opening 261 is provided in the first shell 211 of the housing 21. An opening 281 is provided in the second shell 212. The opening 261 and the opening 281 each have a cylindrical shape. The rotating shaft 30 passes through the opening 261 and the opening 281, and a portion of the rotating shaft 30 is exposed to the outside of the housing 21.

[0058] The center axis CL4 of the pedal crankshaft 22 extends in the left-right direction. The center axis CL4 becomes the rotation center axis RC4 (fourth center axis) of the pedal crankshaft 22 when viewed from the axial direction (thrust direction) of the pedal crankshaft 22. The pedal crankshaft 22 rotates relative to the housing 21 around the center axis CL4. The rotation center axis RC4 becomes the rotation axis of the rotating shaft 30.

[0059] The rotating shaft 30 including the pedal crankshaft 22 passes through the housing 21 along the fourth center axis RC4, and is supported by the housing 21 so as to be rotatable around the fourth center axis RC4. The pedal crankshaft 22 is supported by a pair of bearings 38L and 38R in the housing 21 so as to be rotatable. The bearing 38L is arranged on the left side in the axial direction and fixed to the first housing 211. The bearing 38R is arranged on the right side in the axial direction and fixed to the second housing 212.

[0060] The pedal crankshaft 22 is disposed so as to penetrate the rotating shaft 23. The rotating shaft 23 is accommodated in the housing 21. The details of the rotating shaft 23 will be described below. A pair of left and right crank arms 35 (FIG. 1) are mounted on the pedal crankshaft 22. A pedal 37 (FIG. 1) is mounted on each of the crank arms 35.

[0061] The pedal crankshaft 22 includes, for example, a metal material with iron as a main component, such as carbon steel and alloy steel. By using a metal material with iron as a main component, the rigidity and strength required for the pedal crankshaft 22 can be achieved at a low cost.

[0062] Next, the structures of the electric motor 25 and the transmission mechanism 40 according to this embodiment will be described.

[0063] The electric motor 25 is accommodated in the housing 21 and fixed to the housing 21. The electric motor 25 generates a driving force for assisting the electric-assisted bicycle 1 in traveling. The electric motor 25 has a stator 251 and a rotor 252.

[0064] The stator 251 has a plurality of bobbins 2512 around which the coil 2511 is wound. An iron core 2513 is inserted into each bobbin 2512. The stator 251 is arranged in the space 215. In this state, the stator 251 is fixed to the first housing 211.

[0065] The rotor 252 is disposed inside the stator 251. The center axis CL1 of the rotor 252 is parallel to the center axis CL4 of the pedal crankshaft 22. That is, the rotor 252 is disposed parallel to the pedal crankshaft 22. The center axis CL1 becomes the rotation center axis RC1 (first center axis) of the rotor 252 when viewed from the axial direction of the pedal crankshaft 22.

[0066] The rotor 252 includes a rotor body 2521 and an output shaft 2522. On the outer circumferential surface of the rotor body 2521, N poles and S poles are magnetized alternately in the circumferential direction.

[0067] The output shaft 2522 is arranged to penetrate the rotor body 2521. The output shaft 2522 is fixed to the rotor body 2521. That is, the output shaft 2522 rotates together with the rotor body 2521.

[0068] The output shaft 2522 is supported by the housing 21 and can rotate around the first central axis RC1 inside the housing 21. The output shaft 2522 is supported by two bearings 42L and 42R and can rotate relative to the housing 21 around the central axis CL1. The bearing 42L is fixed to the cover 213. The bearing 42R is arranged on the right side of the rotor body 2521 and is fixed to the first housing 211. The output shaft 2522 is arranged to pass through the first housing 211. An output gear 252A is formed on the right part of the output shaft 2522. The output gear 252A is, for example, a helical gear.

[0069] The transmission mechanism 40 is accommodated in the housing 21. Specifically, the transmission mechanism 40 is arranged in the space 214. The transmission mechanism 40 has a speed reducer 24, an idler gear 41 and a rotating shaft 43. The transmission mechanism 40 transmits the torque of the electric motor 25 to the rotating shaft 23.

[0070] The speed reducer 24 is supported by the housing 21 and is rotatable, and increases the torque of the output gear 252A of the electric motor 25. The speed reducer 24 has a first transmission gear 241, a second transmission gear 242, and a transmission shaft 243. The center axis CL2 of the transmission shaft 243 is parallel to the center axis CL4 of the pedal crankshaft 22. That is, the transmission shaft 243 extends parallel to the center axis CL4 of the pedal crankshaft 22. The center axis CL2 becomes the rotation center axis RC2 (second center axis) of the transmission shaft 243 when viewed from the axial direction of the transmission shaft 243, that is, the axial direction of the pedal crankshaft 22. The speed reducer 24 is supported by the housing 21 inside the housing 21 and is rotatable around the second center axis RC2.

[0071] The first transmission gear 241 is arranged on the right part of the transmission shaft 243 in the axial direction. The left part of the transmission shaft 243 is supported by a bearing 44L so as to be rotatable. The first transmission gear 241 arranged on the right part of the transmission shaft 243 is supported by a bearing 44R so as to be rotatable. The transmission shaft 243 and the first transmission gear 241 are supported by two bearings 44L and 44R so as to be rotatable around the central axis CL2. The bearing 44L is fixed to the first housing 211. The bearing 44R is fixed to the second housing 212.

[0072] The first transmission gear 241 meshes with the output gear 252A of the electric motor 25. Thus, the driving force generated by the electric motor 25 is transmitted from the output gear 252A to the first transmission gear 241.

[0073] A one-way clutch 244 is disposed between the first transmission gear 241 and the transmission shaft 243. The one-way clutch 244 connects the transmission shaft 243 to the first transmission gear 241. The one-way clutch 244 restricts the rotation of the first transmission gear 241 relative to the transmission shaft 243 to one direction. The rotation force of the output gear 252A in the direction of rotating the rear wheel 7 ( FIG. 1 ) of the electric-assisted bicycle 1 forward is transmitted to the transmission shaft 243 via the first transmission gear 241, but the rotation force of the output gear 252A in the direction of rotating the rear wheel 7 backward is not transmitted to the transmission shaft 243. In addition, the one-way clutch 244 prevents the rotation force of the pedal crankshaft 22 in the forward rotation direction generated by the rider's human power from being transmitted to the electric motor 25.

[0074] The first transmission gear 241 has a larger diameter than the output gear 252A of the electric motor 25 and has more teeth than the output gear 252A. That is, the speed of the first transmission gear 241 is slower than that of the output gear 252A.

[0075] The second transmission gear 242 is formed of a metal material (e.g., iron). The second transmission gear 242 is disposed on the transmission shaft 243. The second transmission gear 242 is disposed at a position different from the first transmission gear 241 in the axial direction of the transmission shaft 243. The second transmission gear 242 has a smaller diameter than the first transmission gear 241 and has fewer teeth than the first transmission gear 241. In the present embodiment, the transmission shaft 243 and the second transmission gear 242 are formed integrally, but are not limited to this. The second transmission gear 242 can also be fixed to the transmission shaft 243 by serration connection (or press-fitting). The second transmission gear 242 rotates together with the transmission shaft 243. The transmission shaft 243 transmits the rotation of the first transmission gear 241 to the second transmission gear 242.

[0076] The idler gear 41 is formed of a metal material (e.g., iron). The idler gear 41 is disposed on the rotating shaft 43. The idler gear 41 is fixed to the rotating shaft 43 by, for example, a fastener, but is not limited thereto. The idler gear 41 may also be fixed to the rotating shaft 43 by serration coupling (or press-fitting). Furthermore, the idler gear 41 and the rotating shaft 43 may also be formed integrally. The idler gear 41 rotates together with the rotating shaft 43.

[0077] The center axis CL3 of the rotating shaft 43 is parallel to the center axis CL4 of the pedal crankshaft 22. That is, the rotating shaft 43 extends parallel to the center axis CL4 of the pedal crankshaft 22. The center axis CL3 becomes the rotation center axis RC3 (third center axis) of the rotating shaft 43 when viewed from the axial direction of the rotating shaft 43, that is, the axial direction of the pedal crankshaft 22. The idler gear 41 fixed to the rotating shaft 43 is supported by the housing 21 inside the housing 21 and can rotate around the third center axis RC3.

[0078] The rotating shaft 43 is supported by two bearings 46L and 46R so as to be rotatable about the central axis CL3. The bearings 46L and 46R are fixed to the first housing 211. The idler gear 41 is arranged closer to the bearing 46R than the bearing 46L in the axial direction of the rotating shaft 43. The idler gear 41 meshes with the second transmission gear 242 of the speed reducer 24. Thereby, the output torque of the electric motor 25 increased by the speed reducer 24 is transmitted to the idler gear 41.

[0079] Next, the structure around the pedal crankshaft 22 will be described.

[0080] The rotating shaft 23 is coaxially arranged with the pedal crankshaft 22 and can rotate together with the pedal crankshaft 22. The rotating shaft 23 includes a connecting shaft 231 and a one-way clutch 50.

[0081] The connecting shaft 231 has a cylindrical shape. The pedal crankshaft 22 is inserted into the connecting shaft 231. The connecting shaft 231 and the pedal crankshaft 22 are coaxially arranged.

[0082] The left end of the connecting shaft 231 is connected to the pedal crankshaft 22 by a sawtooth connection or the like. As a result, the connecting shaft 231 rotates together with the pedal crankshaft 22 regardless of whether the pedal crankshaft 22 rotates in the forward direction or the backward direction.

[0083] A torque detection device 232 is disposed around the connecting shaft 231. The torque detection device 232 is supported by the connecting shaft 231 and cannot rotate relative to the first housing 211. The torque detection device 232 detects the torque generated by the connecting shaft 231 when the driver steps on the pedal. The torque detection device 232 is, for example, a magnetostrictive torque sensor. The torque detection device 232 outputs a signal corresponding to the detected torque to the MCU mounted on the circuit substrate 110. The MCU refers to the torque detected by the torque detection device 232 to grasp the driver's pedaling state to control the electric motor 25. The external connector 130 is a connector for electrically connecting the drive unit 20 to an external device (such as a battery unit 56 and an instrument unit 5, etc.).

[0084] The one-way clutch 50 is arranged on the right side of the torque detection device 232 in the axial direction of the pedal crankshaft 22. The one-way clutch 50 is provided on the pedal crankshaft 22 via the connecting shaft 231. The one-way clutch 50 is arranged coaxially with the pedal crankshaft 22. The one-way clutch 50 includes an inner member 51 and an outer member 52.

[0085] The inner member 51 of the one-way clutch 50 has a cylindrical shape. The right portion of the connecting shaft 231 is inserted into the inner member 51. The inner member 51 is coaxially arranged with the connecting shaft 231. In this state, the right portion of the connecting shaft 231 is connected to the inner member 51 by a sawtooth connection or the like. As a result, the inner member 51 rotates together with the connecting shaft 231 regardless of whether the connecting shaft 231 rotates in the forward direction or the backward direction. That is, the inner member 51 rotates together with the pedal crankshaft 22 regardless of whether the pedal crankshaft 22 rotates in the forward direction or the backward direction. The connecting shaft 231 and the inner member 51 function as a crank rotation input shaft that rotates integrally with the pedal crankshaft 22.

[0086] The outer member 52 of the one-way clutch 50 has a cylindrical shape. The pedal crankshaft 22 is inserted into the outer member 52. A sliding bearing 49 is arranged between the outer member 52 and the pedal crankshaft 22. Thereby, the outer member 52 is arranged to be coaxially rotatable relative to the pedal crankshaft 22.

[0087] A ratchet mechanism as a one-way clutch mechanism is formed between the outer member 52 and the inner member 51. With this, the rotational force of the inner member 51 in the forward rotation direction is transmitted to the outer member 52, but the rotational force of the inner member 51 in the backward rotation direction is not transmitted to the outer member 52. In addition, the rotational force of the outer member 52 in the forward rotation direction generated by the rotation of the electric motor 25 is not transmitted to the inner member 51.

[0088] The outer member 52 is supported by the bearing 38R so as to be rotatable relative to the housing 21 about the central axis CL4 of the pedal crankshaft 22. The outer member 52 is disposed to penetrate the second housing 212. The driving sprocket 34 is mounted on the portion of the outer member 52 located outside (right side) of the housing 21.

[0089] The outer member 52 has a driven gear 233. The driven gear 233 is provided on the pedal crankshaft 22 via the one-way clutch 50 and the connecting shaft 231. The driven gear 233 meshes with the idler gear 41. The driven gear 233 has a larger diameter than the second transmission gear 242 and the idler gear 41, and has more teeth than the second transmission gear 242 and the idler gear 41. That is, the rotation speed of the driven gear 233 is slower than the rotation speed of each of the second transmission gear 242 and the idler gear 41. By meshing the idler gear 41 with each of the second transmission gear 242 and the driven gear 233, the output torque of the electric motor 25 increased by the speed reducer 24 can be transmitted to the driven gear 233 via the single idler gear 41.

[0090] The external member 52 transmits the combined force of the human power (pedal force) transmitted to the connecting shaft 231 and the auxiliary driving force of the electric motor 25 to the driving sprocket 34. The external member 52 realizes the combined force output shaft 235 that combines the human power input through the one-way clutch 50 and the auxiliary driving force input through the driven gear 233 and outputs the combined force output shaft 235. The combined force output shaft 235 rotates coaxially with the pedal crankshaft 22. The combined force output shaft 235 is included in the rotating shaft 23.

[0091] [Dust seal] Next, the dust seal of this embodiment will be described.

[0092] FIG. 4 is a cross-sectional view showing the opening 261 of the housing 21 and the rotation shaft 30 passing through the opening 261 .

[0093] The rotating shaft 30 is rotatably supported by the housing 21 via the bearing 38L. The outer ring of the bearing 38L is fixed to the housing 21. The bearing 38L is restrained from moving in the rotating axis direction of the rotating shaft 30 by the protrusion 273 of the housing 21 and the retaining rings 39 and 94.

[0094] An annular dust seal 60 is disposed between the opening 261 of the housing 21 and the rotating shaft 30. The dust seal 60 blocks the gap between the opening 261 and the rotating shaft 30, thereby preventing dust from entering the housing 21 from the outside.

[0095] In this embodiment, the rotating shaft 30 is provided with an adapter 92 for adjusting the shaft diameter of the pedal crankshaft 22. The adapter 92 is fixed to the pedal crankshaft 22 by, for example, press-fitting or serration coupling, so that the shaft diameter of a portion of the pedal crankshaft 22 becomes larger. The dust seal 60 is in contact with the adapter 92 of the rotating shaft 30 in a slidable manner. The dust seal 60 may also be in direct contact with the pedal crankshaft 22 of the rotating shaft 30.

[0096] FIG. 5 is a perspective view showing the dust seal 60 cut along a plane parallel to the rotation axis direction of the rotating shaft 30. FIG. 6 and FIG. 7 are cross-sectional views showing a part of the driving unit 20 in an enlarged manner, showing the area surrounded by the dotted line in FIG. 4 in an enlarged manner. FIG. 7 shows a state where the dust seal 60 is omitted. In order to explain the characteristic part of the present embodiment in an easy-to-understand manner, the bearing 38L is omitted in FIG. 6 and FIG. 7. In the example shown in FIG. 4, FIG. 6, and FIG. 7, the left side along the rotation axis direction D1 of the rotating shaft 30 becomes the outside of the housing 21, and the right side becomes the inside of the housing 21. With the opening 261 as a reference, the outside of the housing 21 along the rotation axis direction D1 is the outside of the opening 261.

[0097] As shown in FIG. 5 , the dust seal 60 includes a body 61 and a metal ring (reinforcement ring) 67. The body 61 is formed of an elastic body such as synthetic rubber. The metal ring 67 can improve the rigidity of the dust seal 60. A sealing lip 65 and a dust lip 66 are provided on the inner peripheral portion 62 of the dust seal 60. A first lip 71 and a second lip 72 are provided on the outer peripheral portion 63 of the dust seal 60.

[0098] As shown in FIG6 , the sealing lip 65 and the dust lip 66 provided on the inner circumference 62 of the dust seal 60 are in slidable contact with the adapter 92 of the rotating shaft 30. The dust lip 66 is arranged on the outer side of the sealing lip 65 in the rotation axis direction D1. The sealing lip 65 and the dust lip 66 prevent oil from flowing out from the inside of the housing 21 to the outside, and prevent water and dust from entering the inside of the housing 21 from the outside.

[0099] The first lip 71 and the second lip 72 provided on the outer circumference 63 of the dust seal 60 are in contact with the inner circumference 262 of the opening 261 of the housing 21 .

[0100] A groove 271 is provided in the inner circumference 262 of the opening 261 along the circumferential direction of the opening 261. The inner circumference 262 has a protrusion 272 that is an outer wall portion in the rotation axis direction D1 of the groove 271 and a protrusion 273 that is an inner wall portion. The protrusion 272 and the protrusion 273 have a shape extending from the inner circumference 262 generally toward the rotation shaft 30.

[0101] The second lip 72 of the dust seal 60 has a shape extending in a direction away from the rotating shaft 30, and is inserted into the groove 271 of the inner peripheral portion 262 of the opening 261. In this example, the second lip 72 is inserted into the groove 271 by snap-fitting. By inserting the second lip 72 into the groove 271, the dust seal 60 can be fixed to the housing 21. In addition, it is possible to prevent oil from flowing out from the inside of the housing 21 to the outside, and it is possible to prevent water and dust from entering the inside of the housing 21 from the outside.

[0102] The outer end 265 of the inner circumference 262 of the opening 261 in the rotation axis direction D1 has a chamfered portion 266 processed by C chamfering or R chamfering. The chamfered portion 266 has a shape that expands toward the outside of the opening 261. In this embodiment, the chamfered portion 266 is provided on the protruding portion 272.

[0103] The first lip 71 of the dust seal 60 has a shape that extends toward the outside in the rotation axis direction D1 and away from the rotation axis 30. As shown in FIG6, the first lip 71 covers the chamfered portion 266 of the opening 261. In this embodiment, the so-called "the first lip 71 covers the chamfered portion 266" may be a part of the first lip 71 covering the chamfered portion 266, or the first lip 71 covers the entire chamfered portion 266.

[0104] In the case where the housing 21 and the rotating shaft 30 are made of different metal materials, if water accumulates between the opening 261 of the housing 21 and the rotating shaft 30, electrolytic corrosion (electric corrosion) is likely to occur. By applying a coating to the opening 261, electrolytic corrosion can be suppressed to a certain extent. However, depending on the shape of the opening 261, there are cases where it is difficult for the coating to adhere well to the opening 261. For example, in the case where a protrusion 272 with a small thickness is provided in the opening 261, it is difficult for the coating to adhere to such a protrusion 272. According to the present embodiment, the dust seal 60 has a first lip 71 covering the chamfered portion 266 of the opening 261. By covering the chamfered portion 266 with the first lip 71, electrolytic corrosion can be suppressed even in the case where it is difficult for the coating to adhere well to the opening 261.

[0105] Furthermore, the first lip 71 and the second lip 72 of the dust seal 60 clamp the protrusion 272 by elastic force. Thus, a gap is not easily generated between the first lip 71 and the chamfered portion 266, and electrolytic corrosion can be more effectively suppressed. Furthermore, oil can be more effectively suppressed from flowing out from the inside of the housing 21 to the outside, and water and dust can be more effectively suppressed from entering the inside of the housing 21 from the outside.

[0106] Next, the positional relationship between the opening 261 of the housing 21 and the dust seal 60 in the rotation axis direction D1 will be described.

[0107] FIG8 is a cross-sectional view showing the positional relationship between the opening 261 of the housing 21 and the dust seal 60 in the rotation axis direction D1. In the example shown in FIG8, the left side along the rotation axis direction D1 is the outer side of the housing 21, and the right side is the inner side of the housing 21. The single-point chain line A1 shown in FIG8 represents the outermost position of the dust seal 60 in the rotation axis direction D1. The dotted line A2 shown in FIG8 represents the position of the outermost portion 267 of the opening 261 of the housing 21.

[0108] In this embodiment, the dust seal 60 does not protrude outward in the rotation axis direction D1 beyond the outermost portion 267 of the opening 261. Thus, the width dimension of the drive unit 20 can be reduced.

[0109] The crank arm 35 and other parts are mounted on the rotating shaft 30. When the dust seal 60 protrudes outward beyond the opening 261 of the housing 21, the dust seal 60 may interfere with the crank arm 35 and other parts. By preventing the dust seal 60 from protruding outward beyond the opening 261, the dust seal 60 can be prevented from interfering with the crank arm 35 and other parts.

[0110] The first lip 71 of the dust seal 60 covers the chamfered portion 266 within the range that the dust seal 60 does not protrude outward beyond the outermost portion 267 of the opening 261. As long as the dust seal 60 does not protrude outward beyond the outermost portion 267 of the opening 261, the first lip 71 can also cover the entire chamfered portion 266.

[0111] In the above example, the dust seal 60 is fixed to the inner circumference 262 of the opening 261 by snap-fitting, but the dust seal 60 may also be fixed to the inner circumference 262 by press-fitting.

[0112] Fig. 9 is a cross-sectional view showing the dust seal 60 fixed to the inner peripheral portion 262 of the opening 261 by press-fitting. In the example shown in Fig. 9, the groove 271 is not provided in the inner peripheral portion 262, and the dust seal 60 is fixed to the inner peripheral portion 262 by press-fitting.

[0113] The outer end portion 265 of the inner peripheral portion 262 in the rotation axis direction D1 has a chamfered portion 266. The first lip 71 of the dust seal 60 covers the chamfered portion 266 of the opening 261. This can suppress electric corrosion.

[0114] In the above embodiment, the drive unit 20 ( FIG. 2 ) includes four shafts, namely, the output shaft 2522, the transmission shaft 243, the rotation shaft 43, and the rotating shaft 30, but the number of shafts is not limited to 4. The present invention can also be applied to a drive unit including 5 or more shafts. For example, the present invention can also be applied to a drive unit in which a gear is arranged between the output gear 252A of the electric motor 25 and the first transmission gear 241 of the speed reducer 24, and torque is transmitted from the output gear 252A to the first transmission gear 241 via the gear.

[0115] In the above-mentioned embodiment, the driving unit 20 includes the idler gear 41 , but the present invention can also be applied to the driving unit 20 that does not include the idler gear 41 .

[0116] In the above embodiment, the entire electric motor 25 is accommodated in the housing 21, but the structure of the housing 21 is not limited thereto. Only a portion of the electric motor 25 may be accommodated in the housing 21. For example, an opening through which the electric motor 25 can pass may be provided in the left portion of the first housing 211, and a portion of the electric motor 25 may be installed through the opening so as to be located in the housing 21. In this case, the opening may be covered with a cover to achieve dustproof and waterproof properties.

[0117] The cover 213 (FIG. 2) may be a part of the housing 21 and may be included in the housing 21. The cover 213 has a shape that covers the side of the electric motor 25, and the electric motor 25 may also be supported by the cover 213. The form in which the electric motor 25 is supported by the cover 213 is also included in the form in which the electric motor 25 is supported by the housing 21.

[0118] In the above embodiment, a two-wheeled electric-assisted bicycle is exemplified as the electric-assisted bicycle 1, but the present invention is not limited thereto. For example, the electric-assisted bicycle 1 may also be a three-wheeled electric-assisted bicycle.

[0119] In the above embodiment, the driving wheel that transmits the manpower generated by the rider stepping on the pedals and the auxiliary force generated by the electric motor is the rear wheel, but the present invention is not limited to this. Depending on the form of the electric-assisted bicycle, the manpower and auxiliary force can also be transmitted to the front wheel, or to both the front wheel and the rear wheel. In addition, the present invention can also be applied to an electric-assisted bicycle with a hub motor installed on the front wheel.

[0120] The exemplary embodiments of the present invention have been described above. This specification discloses a drive unit and an electric-assisted bicycle described in the following items.

[0121] [Project 1] A driving unit 20 is a driving unit 20 for an electric-assisted bicycle 1 and comprises: Electric motor 25; Housing 21, which accommodates the electric motor 25; A rotating shaft 30, which is rotatably supported by the housing 21 and a portion of which is exposed outside the housing 21; and The annular dust seal 60 is disposed between the rotating shaft 30 and the housing 21 to prevent dust from entering the housing 21 from the outside; The housing 21 and the shaft 30 are made of different metal materials. The inner circumference 62 of the dust seal 60 is in contact with the rotating shaft 30 in a slidable manner. The outer circumference 63 of the dust seal 60 contacts the inner circumference 262 of the opening 261 of the housing 21 through which the shaft 30 passes. The outer end 265 of the inner circumference 262 of the opening 261 of the housing 21 in the rotation axis direction D1 of the rotating shaft 30 has a chamfered portion 266 that expands toward the outer side of the opening 261. The dust seal 60 has a first lip 71 covering the chamfered portion 266. The dust seal 60 does not protrude outward in the rotation axis direction D1 beyond the outermost portion 267 of the opening 261 in the rotation axis direction D1.

[0122] In the case where the housing 21 and the rotating shaft 30 are made of different metal materials, if water accumulates between the opening 261 of the housing 21 and the rotating shaft 30, electrolytic corrosion (electric corrosion) is likely to occur. By applying a coating to the opening 261, electrolytic corrosion can be suppressed to a certain extent. However, in the case where a protrusion 272 with a small thickness is provided at the opening 261, it is difficult for the coating to adhere to such a protrusion 272, and it is difficult for the coating to adhere well to the opening 261. According to an embodiment of the present invention, the dust seal 60 has a first lip 71 covering the chamfered portion 266 of the opening 261. By covering the chamfered portion 266 with the first lip 71, electrolytic corrosion can be suppressed even in the case where the coating is difficult to adhere well to the opening 261.

[0123] Furthermore, according to an embodiment of the present invention, the dust seal 60 does not protrude outward in the rotation axis direction D1 beyond the outermost portion 267 of the opening 261 in the rotation axis direction D1. Thus, the width dimension of the drive unit 20 can be reduced.

[0124] The crank arm 35 may be provided on the rotating shaft 30. When the dust seal 60 protrudes outward beyond the opening 261 of the housing 21, the dust seal 60 may interfere with the crank arm 35. By preventing the dust seal 60 from protruding outward beyond the opening 261, the dust seal 60 can be prevented from interfering with the crank arm 35.

[0125] [Project 2] In the driving unit 20 described in item 1, the first lip 71 of the dust seal 60 has a shape extending toward the outside in the rotation axis direction D1 and away from the rotation axis 30.

[0126] Thereby, the chamfered portion 266 of the opening 261 can be appropriately covered.

[0127] [Item 3] The driving unit 20 as described in item 1 or 2, wherein a groove 271 is provided in the inner circumference 262 of the opening 261 along the circumference of the opening 261, The outer peripheral portion 63 of the dust seal 60 has a second lip 72 that is fitted into the groove 271 .

[0128] By fitting the second lip 72 of the dust seal 60 into the groove 271 of the opening 261 , the dust seal 60 can be fixed to the housing 21 .

[0129] [Item 4] As described in the driving unit 20 of item 3, the opening 261 has a protrusion 272 which is a wall portion of the outer side of the groove 271 in the rotation axis direction D1. The chamfered portion 266 is disposed on the protruding portion 272 .

[0130] Even in the case where the paint is difficult to adhere well to the protrusion 272, the first lip 71 covers the chamfered portion 266, thereby suppressing the electrolytic corrosion.

[0131] [Item 5] In the drive unit 20 as described in item 3 or 4, the second lip 72 of the dust seal 60 is embedded in the groove 271 by snap-fitting.

[0132] By snap-fitting, the dust seal 60 can be fixed to the housing 21. In addition, dust and water can be more effectively prevented from entering the interior of the housing 21.

[0133] [Item 6] In the driving unit 20 described in item 4, the first lip 71 and the second lip 72 of the dust seal 60 clamp the protrusion 272 by elastic force.

[0134] Thereby, a gap is not easily generated between the first lip 71 and the chamfered portion 266, and electrolytic corrosion can be more effectively suppressed. In addition, dust and water can be more effectively suppressed from entering the interior of the housing 21.

[0135] [Item 7] The drive unit 20 as described in item 1 or 2, wherein the dust seal 60 is pressed into the opening portion 261.

[0136] By pressing the dust seal 60 into the opening 261, the dust seal 60 can be fixed to the housing 21.

[0137] [Item 8] In the drive unit 20 as described in any one of items 1 to 7, the inner circumference 62 of the dust seal 60 has a sealing lip 65 that contacts the rotating shaft 30 in a slidable manner.

[0138] This can prevent oil from flowing out from the inside of the housing 21 to the outside, and prevent water and dust from entering the inside of the housing 21 from the outside.

[0139] [Item 9] As described in the driving unit 20 of item 8, the inner circumference 62 of the dust seal 60 further has a dust lip 66, which is slidably in contact with the rotating shaft 30 and is arranged on the outer side of the sealing lip 65 in the rotation axis direction D1.

[0140] This can prevent dust from entering the interior of the housing 21 from the outside.

[0141] [Item 10] In the drive unit 20 as described in any one of items 1 to 9, the housing 21 comprises a metal material mainly composed of magnesium.

[0142] Thereby, the weight of the driving unit 20 can be reduced.

[0143] [Item 11] In the driving unit 20 as described in any one of items 1 to 10, the rotating shaft 30 comprises a metal material mainly composed of iron.

[0144] Thereby, the rigidity and strength required for the rotating shaft 30 can be achieved at a low cost.

[0145] [Item 12] An electric-assisted bicycle 1 comprises a drive unit 20 as described in any one of items 1 to 11.

[0146] Thereby, it is possible to realize the electric-assisted bicycle 1 equipped with the driving unit 20 which is highly durable against water and compact. [Industrial Applicability]

[0147] The present invention is particularly useful in the field of power-assisted bicycles.

[0148] 1: Electric Assisted Bicycle 2: Body frame 3: Saddle 4: Handle 5: Instrument unit 6:Front wheel 7: Rear wheel 11: Head tube 12: Down tube 13: Handlebar steering column 14: Top tube 15: Front fork 16: Seat tube 17: Seat tube 18: Chainstay 19: Seatstays 20:Driver unit 21: Shell 22: Pedal crankshaft 23: Rotation axis 24: Reducer 25: Electric Motor 26: Bracket 30: Rotating shaft 34: Drive sprocket 35: Crank arm 37: Pedal 38: Bearing 38L: Bearing 38R: Bearing 39: Buckle 40: Power transmission mechanism 41: Idle gear 42: Bearing 42L: Bearing 42R: Bearing 43: Rotation axis 44: Bearing 44L: Bearing 44R: Bearing 46: Bearing 46L: Bearing 46R: Bearing 49: Sliding bearing 50: One-way clutch 51: Internal components 52: External components 53:Chain 55:Speed sensor 56:Battery Cell 58: Speed changer 59: Headlight 60: Dust seal 61:Ontology 62: Inner periphery of dust seal 63: Outer periphery of dust seal 65: Sealing lip 66: Dust lip 67:Metal ring 71: Lip 1 72: Second Lip 92: Adapter 94: Buckle 110: Circuit board 130: External connector 211: Shell 212: Housing 213: Hood 214: Space 215: Space 231: Connecting shaft 232: Torque detection device 233: Driven gear 235: Heli output shaft 241: 1st transmission gear 242: 2nd transmission gear 243:Transmission shaft 244: One-way clutch 251: Stator 252: Rotor 252A: Output gear 261: Opening 262: Inner periphery 265: Outer end 266: Chamfer 267: outermost 271: Slot 272: Protrusion 273: Protrusion 281: Opening 2511: Coil 2512: bobbin 2513: Iron Heart 2521: Rotor body 2522: Output shaft A1: The outermost position of the dust seal A2: The outermost position of the opening CL1: Center axis CL2: Center axis CL3: Center axis CL4: Central axis D: Next D1: Rotation axis direction F: Front L:Left R:Right RC1: Rotation center axis RC2: Rotational axis RC3: Rotational axis RC4: Rotational axis Re:After U:Up

Claims

1. A drive unit for an electric-assisted bicycle, comprising: an electric motor; a housing housing the electric motor; a pivot rotatably supported on the housing and partially protruding from the outside of the housing; and an annular dust seal disposed between the pivot and the housing to prevent dust from entering the interior of the housing from the outside of the housing; the housing and the pivot being made of different metallic materials; the inner periphery of the dust seal slidably contacts the pivot; the outer periphery of the dust seal contacts the inner periphery of an opening in the housing through which the pivot penetrates; the outer end of the inner periphery of the opening in the rotational direction of the pivot has a chamfered portion that expands outward toward the outside of the opening; the dust seal has a first lip covering the chamfered portion; and the dust seal does not protrude outward beyond the outermost part of the opening in the rotational direction.

2. The drive unit of claim 1, wherein the first lip of the dust seal has a shape that extends outward toward the direction of the rotation axis and in a direction away from the rotation axis.

3. The drive unit of claim 1 or 2, wherein a groove is provided in the inner periphery of the opening along the circumferential direction of the opening, and the outer periphery of the dust seal has a second lip that is embedded in the groove.

4. The drive unit of claim 3, wherein the opening has a protrusion that forms the outer side of the wall in the direction of the rotation axis of the groove, and the chamfered portion is provided on the protrusion.

5. The drive unit as claimed in claim 3, wherein the second lip of the dust seal is inserted into the groove by means of a snap fastener.

6. The drive unit of claim 4, wherein the first lip and the second lip of the dust seal clamp the protrusion by means of elastic force.

7. The drive unit of claim 1 or 2, wherein the dust seal is pressed into the opening.

8. The drive unit of claim 1 or 2, wherein the inner periphery of the dust seal has a sealing lip that can slide and contact the shaft.

9. The drive unit of claim 8, wherein the inner periphery of the dust seal further has a dust lip that is slidably in contact with the rotating shaft and is disposed further outward than the sealing lip in the direction of the rotating shaft.

10. The drive unit of claim 1 or 2, wherein the housing comprises a metallic material with magnesium as the main component.

11. The drive unit of claim 10, wherein the aforementioned shaft comprises a metallic material with iron as its main component.

12. An electric-assisted bicycle having a drive unit as claimed in claim 1 or 2.

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