Drive unit for electric bicycle and electric bicycle

Abstract

To suppress electrolytic corrosion of a drive unit for an electric bicycle.SOLUTION: In a drive unit (20) for an electric bicycle (1), a housing (21) and a rotating shaft (30) are made of different metallic materials, and an outer peripheral part (63) of a dust seal (60) is in contact with an inner peripheral part (262) of an opening (261) of the housing (21) through which a rotating shaft (30) penetrates. An outer end (265) of the inner peripheral part (262) of the opening (261) of the housing (21) in a rotation axis direction (D1) of the rotating shaft (30) has a chamfered portion (266) that increases in diameter toward the outside of the opening (261). The dust seal (60) has a first lip (71) that covers the chamfered portion (266). The dust seal (60) does not protrude to an outer side in the rotation axis direction (D1) beyond the outermost part (267) of the opening (261) in the rotation axis direction (D1).SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a drive unit for an electric assist bicycle and an electric assist bicycle.

Background Art

[0002] Bicycles are widely popular among people of all ages and genders as a convenient means of transportation. In recent years, the popularity of electric assist bicycles that assist the user's pedaling force with an electric motor has been increasing (see, for example, Patent Document 1). The electric motor generates a driving force by being supplied with electric power from a battery mounted on the vehicle. In an electric assist bicycle, a driving force corresponding to the human power applied by the user to the pedals is generated in the electric motor, and for example, the burden on the user when traveling on a slope or carrying luggage can be reduced.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The drive unit of an electric assist bicycle includes a housing that houses an electric motor and a rotating shaft that partially protrudes outside the housing. A crank arm, for example, is attached to the rotating shaft.

[0005] When the housing and the rotating shaft contain different metal materials, there is a problem that when water accumulates between the opening of the housing and the rotating shaft, electrolytic corrosion (galvanic corrosion) is likely to occur.

[0006] It is required to suppress electrolytic corrosion of the drive unit of an electric assist bicycle.

Means for Solving the Problems

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

[0008] [Item 1] A drive unit for an electric assist bicycle, an electric motor, a housing that houses the electric motor, a rotating shaft that is rotatably supported by the housing and partially exposed outside the housing, an annular dust seal provided between the rotating shaft and the housing to suppress the intrusion of dust from outside the housing into the housing, comprising, the housing and the rotating shaft include different metal materials from each other, the inner peripheral portion of the dust seal is in slidable contact with the rotating shaft, the outer peripheral portion of the dust seal is in contact with the inner peripheral portion of the opening of the housing through which the rotating shaft passes, the outer end portion of the inner peripheral portion of the opening of the housing in the axial direction of the rotation axis of the rotating shaft has a chamfered portion that expands in diameter toward the outside of the opening, the dust seal has a first lip that covers the chamfered portion, a drive unit in which the dust seal does not protrude outward in the axial direction of the rotation axis more than the outermost portion of the opening in the axial direction of the rotation axis.

[0009] When the housing and the rotating shaft are made of different metal materials, if water accumulates between the opening of the housing and the rotating shaft, galvanic corrosion is likely to occur. Galvanic corrosion can be suppressed to some extent by painting the opening. However, when a small protrusion is provided at the opening, it may be difficult to apply paint well to such a protrusion, for example. According to an embodiment of the present invention, the dust seal has a first lip that covers the chamfered portion of the opening. By covering the chamfered portion with the first lip, galvanic corrosion can be suppressed even when it is difficult to apply paint well to the opening.

[0010] Also, according to an embodiment of the present invention, the dust seal does not protrude outward in the axial direction of the rotating shaft beyond the outermost part in the axial direction of the opening. Thereby, the size in the width direction of the drive unit can be reduced.

[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 the dust seal not protruding outward beyond the opening, interference between the dust seal and the crank arm can be suppressed.

[0012] [Item 2] The drive unit according to item 1, wherein the first lip of the dust seal has a shape extending in a direction away from the rotating shaft while facing outward in the axial direction of the rotating shaft.

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

[0014] [Item 3] A groove is provided along the circumferential direction of the opening in the inner peripheral portion of the opening. The drive unit according to item 1 or 2, wherein the outer peripheral portion of the dust seal has a second lip that fits 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] The opening has a protrusion that serves as an outer wall portion of the groove in the axial direction of the rotation axis, The chamfered portion is provided on the protrusion, and the drive unit according to item 3.

[0017] Even when it is difficult for the coating to adhere well to the protrusion, the first lip covers the chamfered portion, thereby suppressing electrolytic corrosion.

[0018] [Item 5] The second lip of the dust seal fits into the groove by snap fit, and the drive unit according to item 3 or 4.

[0019] The dust seal can be fixed to the housing by snap fit. Further, the intrusion of dust and water into the interior of the housing can be more effectively suppressed.

[0020] [Item 6] The first lip and the second lip of the dust seal sandwich the protrusion by elastic force, and the drive unit according to item 4.

[0021] This makes it difficult for a gap to form between the first lip and the chamfered portion, thereby more effectively suppressing electrolytic corrosion. Further, the intrusion of dust and water into the interior of the housing can be more effectively suppressed.

[0022] [Item 7] The dust seal is press-fitted into the opening, and the drive unit according to item 1 or 2.

[0023] The dust seal can be fixed to the housing by press-fitting the dust seal into the opening.

[0024] [Item 8] The drive unit according to any one of items 1 to 7, wherein the inner peripheral portion of the dust seal has a seal lip that slidably contacts the rotating shaft.

[0025] Thereby, it is possible to suppress the outflow of oil from the inside of the housing to the outside and the intrusion of water and dust from the outside of the housing to the inside.

[0026] [Item 9] The drive unit according to item 8, wherein the inner peripheral portion of the dust seal slidably contacts the rotating shaft and further has a dust lip disposed outside the seal lip in the axial direction of the rotating shaft.

[0027] Thereby, it is possible to suppress the intrusion of dust from the outside of the housing to the inside.

[0028] [Item 10] The drive unit according to any one of items 1 to 9, wherein the housing contains a metal material mainly composed of magnesium.

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

[0030] [Item 11] The drive unit according to any one of items 1 to 10, wherein the rotating shaft contains a metal material mainly composed of iron.

[0031] Thereby, the required rigidity and strength of the rotating shaft can be realized at low cost.

[0032] [Item 12] An electric assist bicycle equipped with the drive unit according to any one of items 1 to 11.

[0033] Thereby, it is possible to realize an electric assist bicycle equipped with a drive unit that has high durability against water and is small in size. [Advantages of the Invention]

[0034] When the housing of the drive unit and the rotating shaft include different metal materials from each other, if water accumulates between the opening of the housing and the rotating shaft, electrolytic corrosion (galvanic corrosion) is likely to occur. Electrolytic corrosion can be suppressed to some extent by applying paint to the opening. However, when a protruding portion with a small thickness is provided at the opening, there may be cases where it is difficult for the paint to adhere well to such a protruding portion, that is, it is difficult for the paint to adhere well to the opening. According to an embodiment of the present invention, the dust seal has a first lip that covers the chamfered portion of the opening. By the first lip covering the chamfered portion, electrolytic corrosion can be suppressed even when it is difficult for the paint to adhere well to the opening.

[0035] Also, according to an embodiment of the present invention, the dust seal does not protrude outward in the rotational axis direction beyond the outermost part of the opening in the rotational axis direction. Thereby, the size in the width direction of the drive unit can be reduced.

[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 the dust seal not protruding outward beyond the opening, interference between the dust seal and the crank arm can be suppressed.

Brief Description of the Drawings

[0037]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0038] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the embodiments, the same reference numerals are given to the same components, and the description thereof will be omitted when there is duplication. The reference signs F, Re, L, R, U, D attached to the drawings represent front, rear, left, right, up, and down, respectively. In the electric assist bicycle, front and rear, left and right, up and down mean front and rear, left and right, up and down based on the state where the user is seated on the seat (saddle) of the electric assist bicycle facing the handlebar. The following embodiments are examples, 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 assist bicycle 1 according to the present embodiment.

[0040] The electric assist bicycle 1 has a body frame 2 extending in the front-rear direction. The body frame 2 includes a head pipe 11, a down tube 12, a top tube 14, a seat tube 16, a chain stay 18, a seat stay 19, and a bracket 26. The head pipe 11 is disposed at the front end of the body frame 2. A handlebar column 13 is rotatably inserted into the head pipe 11. A handlebar 4 is fixed to the handlebar column 13. A meter unit 5 for displaying various information regarding the electric assist bicycle 1 is provided on the handlebar 4. A headlamp 59 is provided at the front portion of the handlebar 4.

[0041] A front fork 15 is fixed to the lower end portion of the handlebar column 13. The lower end portion of the front fork 15 rotatably supports a front wheel 6 which is a steering wheel.

[0042] The down tube 12 extends obliquely downward rearward from the head pipe 11. The seat tube 16 extends upward from the rear end portion of the down tube 12. The chain stay 18 extends rearward from the lower end portion of the seat tube 16. The bracket 26 connects the rear end portion of the down tube 12, the lower end portion of the seat tube 16, and the front end portion of the chain stay 18. The top tube 14 is provided so as to connect the upper portions of the head pipe 11 and the seat tube 16. A seat post 17 is inserted into the seat tube 16, and a saddle 3 on which a user sits is provided at the upper end portion of the seat post 17.

[0043] The rear end portion of the chain stay 18 rotatably supports a rear wheel 7 which is a drive wheel. The seat stay 19 extends obliquely downward rearward from the upper portion of the seat tube 16. The lower end portion of the seat stay 19 is connected to the rear end portion of the chain stay 18. A transmission 58 for changing the gear ratio is provided at the rear end portion of the chain stay 18. The transmission may be provided around a pedal crankshaft 22. A speed sensor 55 for detecting the rotation of the rear wheel 7 is provided at the rear portion of the chain stay 18. The speed sensor 55 may be provided at the lower portion of the front fork 15 to detect the rotation of the front wheel 6.

[0044] A drive unit 20 is provided on a bracket 26 disposed near the vehicle center portion of the vehicle body frame 2. Inside the housing of the drive unit 20, an electric motor 25, an MCU (motor control unit), a speed reducer, etc. are accommodated. The pedal crankshaft 22 is supported by penetrating the drive unit 20 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 tip of the crank arm 35.

[0045] A battery unit 56 for supplying power to the drive unit 20 etc. is mounted on the down - tube 12. In the example shown in FIG. 1, the battery unit 56 is attached inside the down - tube 12. The down - tube 12 may have a hollow shape. The down - tube 12 may have at least a part of its cross - section in a U - shape and may have a cover 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 assist bicycle 1.

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

[0048] The MCU of the drive unit 20 controls the operation of the electric motor 25 and also controls the operations of each part of the electric assist 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 when the user steps on the pedal 37 with the foot is transmitted to the rear wheel 7 via the drive sprocket 34 and the chain 53. The MCU controls the electric motor 25 so as to generate a drive assist output corresponding to the rotational output of the pedal crankshaft 22 generated when the user steps on the pedal 37 with the foot. The assist 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, or the like may be used instead of the chain 53.

[0049] [Drive Unit] With reference to FIG. 2, a configuration example of the drive unit 20 will be described. FIG. 2 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 configuration of the housing 21 according to the present 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 case 211, a second case 212, and a cover 213. The housing 21 is formed of, for example, a metal material (magnesium alloy) mainly composed of magnesium. By using a metal material mainly composed of magnesium, the weight of the drive unit 20 can be reduced.

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

[0054] The cover 213 is superposed on the first case 211 from the left side in the left - right direction. The cover 213 and the first case 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 case 211. The electric motor 25 is housed in this space 215.

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

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

[0057] FIG. 3 is a cross - sectional view showing a part of the housing 21. An opening 261 is provided in the first case 211 of the housing 21. An opening 281 is provided in the second case 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 part of the rotating shaft 30 is exposed outside the housing 21.

[0058] The central axis CL4 of the pedal crankshaft 22 extends in the left - right direction. The central axis CL4 becomes the rotation center axis RC4 (the fourth central axis) of the pedal crankshaft 22 when viewed from the axial direction (thrust direction) of the pedal crankshaft 22. The pedal crankshaft 22 rotates with respect to the housing 21 around the central 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 penetrates the housing 21 along the fourth central axis RC4 and is rotatably supported by the housing 21 around the fourth central axis RC4. The pedal crankshaft 22 is rotatably supported within the housing 21 by a pair of bearings 38L and 38R. The bearing 38L is arranged on the left side in the axial direction and is fixed to the first case 211. The bearing 38R is arranged on the right side in the axial direction and is fixed to the second case 212.

[0060] The pedal crankshaft 22 is arranged to penetrate the rotating shaft 23. The rotating shaft 23 is accommodated in the housing 21. Details of the rotating shaft 23 will be described later. A pair of left and right crank arms 35 (FIG. 1) are attached to the pedal crankshaft 22. Pedals 37 (FIG. 1) are attached to each of the crank arms 35.

[0061] The pedal crankshaft 22 includes a metal material mainly composed of iron such as carbon steel and alloy steel. By using a metal material mainly composed of iron, the required rigidity and strength of the pedal crankshaft 22 can be realized at low cost.

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

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

[0064] The stator 251 has a plurality of bobbins 2512 around which coils 2511 are wound. Iron cores 2513 are inserted into the respective bobbins 2512. The stator 251 is arranged in the space 215. In this state, the stator 251 is fixed to the first case 211.

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

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

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

[0068] The output shaft 2522 is supported by the housing 21 so as to be rotatable around the first central axis RC1 inside the housing 21. The output shaft 2522 is rotatably supported with respect to the housing 21 around the central axis CL1 by two bearings 42L and 42R. The bearing 42L is fixed to the cover 213. The bearing 42R is disposed on the right side of the rotor main body 2521 and fixed to the first case 211. The output shaft 2522 is disposed to penetrate the first case 211. An output gear 252A is formed on the right portion of the output shaft 2522. The output gear 252A is, for example, a spur gear.

[0069] The transmission mechanism 40 is housed in the housing 21. Specifically, the transmission mechanism 40 is disposed 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 rotatably supported by the housing 21 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 central axis CL2 of the transmission shaft 243 is parallel to the central axis CL4 of the pedal crankshaft 22. That is, the transmission shaft 243 extends parallel to the central axis CL4 of the pedal crankshaft 22. The central axis CL2 serves as the rotation center axis RC2 (second central 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 rotatably supported by the housing 21 around the second central axis RC2 inside the housing 21.

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

[0072] The first transmission gear 241 meshes with the output gear 252A of the electric motor 25. Thereby, 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 couples the transmission shaft 243 and 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 in one direction. The rotational force of the output gear 252A in the direction of rotating the rear wheel 7 (FIG. 1) of the electric assist bicycle 1 forward is transmitted to the transmission shaft 243 via the first transmission gear 241, but the rotational force of the output gear 252A in the direction of rotating the rear wheel 7 backward is not transmitted to the transmission shaft 243. Further, the one-way clutch 244 prevents the rotational force in the forward rotation direction of the pedal crankshaft 22 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 and more teeth than the output gear 252A of the electric motor 25. That is, the first transmission gear 241 is decelerated more than the output gear 252A.

[0075] The second transmission gear 242 is formed of a metal material (for example, 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 that of the first transmission gear 241 in the axial direction of the transmission shaft 243. The second transmission gear 242 has a smaller diameter and fewer teeth than the first transmission gear 241. In the present embodiment, the transmission shaft 243 and the second transmission gear 242 are integrally formed, but the present invention is not limited thereto. The second transmission gear 242 may be fixed to the transmission shaft 243 by serration coupling (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 metallic 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 be fixed to the rotating shaft 43 by serration coupling (or press-fitting). Further, the idler gear 41 and the rotating shaft 43 may be integrally formed. The idler gear 41 rotates together with the rotating shaft 43.

[0077] The central axis CL3 of the rotating shaft 43 is parallel to the central axis CL4 of the pedal crankshaft 22. That is, the rotating shaft 43 extends parallel to the central axis CL4 of the pedal crankshaft 22. The central axis CL3 serves as the rotation center axis RC3 (third central 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 rotatably supported by the housing 21 around the third central axis RC3 inside the housing 21.

[0078] The rotating shaft 43 is rotatably supported around the central axis CL3 by two bearings 46L and 46R. The bearings 46L and 46R are fixed to the first case 211. The idler gear 41 is disposed 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 configuration around the pedal crankshaft 22 will be described.

[0080] The rotating shaft 23 is disposed coaxially with the pedal crankshaft 22 and is rotatable 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 is disposed coaxially with the pedal crankshaft 22.

[0082] The left end of the connecting shaft 231 is connected to the pedal crankshaft 22 by means of serration connection or the like. As a result, no matter whether the pedal crankshaft 22 rotates in the forward rotation direction or the reverse rotation direction, the connecting shaft 231 rotates together with the pedal crankshaft 22.

[0083] A torque detection device 232 is arranged around the connecting shaft 231. The torque detection device 232 is supported by the connecting shaft 231 and is non-rotatable with respect to the first case 211. The torque detection device 232 detects the torque generated on the connecting shaft 231 when the driver pedals 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 board 110. The MCU grasps the pedaling state by the driver with reference to the torque detected by the torque detection device 232 and controls the electric motor 25. The external connection connector 130 is a connector for electrically connecting the drive unit 20 and an external device (for example, the battery unit 56 and the meter 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 arranged coaxially with the connecting shaft 231. In this state, the right portion of the connecting shaft 231 is connected to the inner member 51 by means of serration coupling or the like. As a result, no matter whether the connecting shaft 231 rotates in the forward rotation direction or the reverse rotation direction, the inner member 51 rotates together with the connecting shaft 231. That is, no matter whether the pedal crankshaft 22 rotates in the forward rotation direction or the reverse rotation direction, the inner member 51 rotates together with the pedal crankshaft 22. 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 coaxially and rotatably with respect 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. Thereby, 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 reverse rotation direction is not transmitted to the outer member 52. Further, 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 rotatably supported with respect to the housing 21 around the central axis CL4 of the pedal crankshaft 22 by a bearing 38R. The outer member 52 is arranged to penetrate the second case 212. A drive sprocket 34 is attached to a 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 a one-way clutch 50 and a connecting shaft 231. The driven gear 233 meshes with an idler gear 41. The driven gear 233 has a larger diameter and more teeth than the second transmission gear 242 and the idler gear 41. That is, the rotational speed of the driven gear 233 is slower than the respective rotational speeds of the second transmission gear 242 and the idler gear 41. By the idler gear 41 meshing 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 a single idler gear 41.

[0090] The outer member 52 transmits the resultant force of the manual force (pedal stepping force) transmitted to the connecting shaft 231 and the auxiliary driving force of the electric motor 25 to the drive sprocket 34. The outer member 52 realizes a resultant force output shaft 235 that synthesizes and outputs the manual force input via the one-way clutch 50 and the auxiliary driving force input via the driven gear 233. The resultant force output shaft 235 rotates coaxially with the pedal crankshaft 22. The resultant force output shaft 235 is included in the rotating shaft 23.

[0091] [Dust seal] Next, the dust seal according to the present embodiment will be described.

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

[0093] The rotating shaft 30 is rotatably supported by the housing 21 via a bearing 38L. The outer ring of the bearing 38L is fixed to the housing 21. The bearing 38L is restricted from moving in the rotational axis direction of the rotating shaft 30 by the protruding portion 273 of the housing 21 and snap 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 closes the gap between the opening 261 and the rotating shaft 30, suppressing the intrusion of dust from the outside of the housing 21 into the inside of the housing 21.

[0095] In the present embodiment, the rotating shaft 30 includes an adapter 92 that adjusts the shaft diameter of the pedal crankshaft 22. The adapter 92 is fixed to the pedal crankshaft 22, for example, by press fitting or serration coupling, increasing the shaft diameter of a part of the pedal crankshaft 22. The dust seal 60 is in slidable contact with the adapter 92 of the rotating shaft 30. The dust seal 60 may 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 rotational axis direction of the rotating shaft 30. FIGS. 6 and 7 are cross-sectional views showing a part of the drive unit 20 enlarged, showing the region surrounded by the broken line in FIG. 4 enlarged. FIG. 7 shows a state in which the dust seal 60 is omitted. To clearly explain the characteristic parts of the present embodiment, in FIGS. 6 and 7, the illustration of the bearing 38L is omitted. In the examples shown in FIGS. 4, 6, and 7, the left side along the rotational axis direction D1 of the rotating shaft 30 is the outside of the housing 21, and the right side is the inside of the housing 21. Based on the opening 261, the outside of the housing 21 along the rotational 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 (reinforcing ring) 67. The body 61 is formed of an elastomer such as synthetic rubber, for example. The metal ring 67 increases the rigidity of the dust seal 60. A seal 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 FIG. 6, the seal lip 65 and the dust lip 66 provided on the inner peripheral portion 62 of the dust seal 60 are slidably in contact with the adapter 92 of the rotating shaft 30. The dust lip 66 is disposed outside the seal lip 65 in the axial direction D1 of the rotation axis. The seal lip 65 and the dust lip 66 suppress the outflow of oil from the inside to the outside of the housing 21 and also suppress the intrusion of water and dust from the outside to the inside of the housing 21.

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

[0100] A groove 271 is provided along the circumferential direction of the opening 261 in the inner peripheral portion 262 of the opening 261. The inner peripheral portion 262 has a protruding portion 272 that serves as an outer wall portion in the axial direction D1 of the groove 271 and a protruding portion 273 that serves as an inner wall portion. The protruding portion 272 and the protruding portion 273 have a shape that extends generally toward the rotating shaft 30 from the inner peripheral portion 262.

[0101] The second lip 72 of the dust seal 60 has a shape that extends in a direction away from the rotating shaft 30 and fits into the groove 271 in the inner peripheral portion 262 of the opening 261. In this example, the second lip 72 is fitted into the groove 271 by snap fit. By fitting the second lip 72 into the groove 271, the dust seal 60 can be fixed to the housing 21. Also, the outflow of oil from the inside to the outside of the housing 21 can be suppressed, and the intrusion of water and dust from the outside to the inside of the housing 21 can be suppressed.

[0102] The outer end portion 265 in the axial direction D1 of the inner peripheral portion 262 of the opening 261 has a chamfered portion 266 that is chamfered with a C-chamfer or an R-chamfer. The chamfered portion 266 has a shape that expands in diameter toward the outside of the opening 261. In the present 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 away from the rotating shaft 30 while facing outward in the axial direction D1 of the rotating shaft. As shown in FIG. 6, the first lip 71 covers the chamfered portion 266 of the opening 261. In the present embodiment, "the first lip 71 covers the chamfered portion 266" may mean that the first lip 71 covers a part of the chamfered portion 266 or that the first lip 71 covers the entire chamfered portion 266.

[0104] When 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 (galvanic corrosion) is likely to occur. Electrolytic corrosion can be suppressed to some extent by applying paint to the opening 261. However, depending on the shape of the opening 261, it may be difficult for the paint to adhere well to the opening 261. For example, when a protruding portion 272 having a small thickness is provided in the opening 261, it is difficult for the paint to adhere to such a protruding portion 272. According to the present embodiment, the dust seal 60 has the first lip 71 that covers the chamfered portion 266 of the opening 261. By the first lip 71 covering the chamfered portion 266, electrolytic corrosion can be suppressed even when it is difficult for the paint to adhere well to the opening 261.

[0105] Further, the first lip 71 and the second lip 72 of the dust seal 60 sandwich the protruding portion 272 by an elastic force. Thereby, it is difficult for a gap to be formed between the first lip 71 and the chamfered portion 266, and electrolytic corrosion can be more effectively suppressed. Also, the outflow of oil from the inside of the housing 21 to the outside can be more effectively suppressed, and the intrusion of water and dust from the outside of the housing 21 to the inside can be more effectively suppressed.

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

[0107] 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 rotational axis direction D1. In the example shown in FIG. 8, the left side along the rotational axis direction D1 is the outside of the housing 21, and the right side is the inside of the housing 21. The dashed-dotted line A1 shown in FIG. 8 indicates the outermost position of the dust seal 60 in the rotational axis direction D1. The dashed line A2 shown in FIG. 8 indicates the position of the outermost portion 267 of the opening 261 of the housing 21.

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

[0109] Parts such as the crank arm 35 are attached to the rotating shaft 30. When the dust seal 60 protrudes outside the opening 261 of the housing 21, the dust seal 60 may interfere with the crank arm 35 or the like. Since the dust seal 60 does not protrude outside the opening 261, interference between the dust seal 60 and the crank arm 35 or the like can be suppressed.

[0110] Within a range where the dust seal 60 does not protrude outside beyond the outermost portion 267 of the opening 261, the first lip 71 of the dust seal 60 covers the chamfered portion 266. If the dust seal 60 does not protrude outside beyond the outermost portion 267 of the opening 261, the first lip 71 may cover the entire chamfered portion 266.

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

[0112] 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. In the example shown in FIG. 9, a 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 rotational 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. Thereby, electric erosion can be suppressed.

[0114] In the above-described embodiment, the drive unit 20 (FIG. 2) includes four shafts, namely, the output shaft 2522, the transmission shaft 243, the rotational shaft 43, and the rotational shaft 30, but the number of shafts is not limited to four. The present invention is also applicable to a drive unit having five or more shafts. For example, the present invention is also applicable to a drive unit in which a gear is disposed 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-described embodiment, the drive unit 20 includes the idler gear 41, but the present invention is also applicable to a drive unit 20 that does not include the idler gear 41.

[0116] In the above-described embodiment, the entire electric motor 25 is housed in the housing 21, but the structure of the housing 21 is not limited thereto. Only a part of the electric motor 25 may be housed 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 case 211, and a part of the electric motor 25 may be attached so as to be located within the housing 21 through the opening. Further, in that case, the opening may be covered with a cover for dust prevention and waterproofing.

[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 surface of the electric motor 25, and the electric motor 25 may 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-described embodiments, a two-wheeled electric assist bicycle has been exemplified as the electric assist bicycle 1, but the present invention is not limited thereto. For example, the electric assist bicycle 1 may be a three-wheeled electric assist bicycle.

[0119] In the above-described embodiments, the drive wheel to which the human power generated by the rider pedaling and the assisting force generated by the electric motor are transmitted was the rear wheel, but the present invention is not limited thereto. Depending on the form of the electric assist bicycle, those human power and assisting force may be transmitted to the front wheel, or may be transmitted to both the front wheel and the rear wheel. Further, the present invention may be applied to an electric assist bicycle provided with a hub motor on the front wheel.

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

[0121] [Item 1] A drive unit 20 for an electric assist bicycle 1, an electric motor 25, a housing 21 that houses the electric motor 25, a rotary shaft 30 that is rotatably supported by the housing 21 and partially exposed outside the housing 21, an annular dust seal 60 provided between the rotary shaft 30 and the housing 21 to suppress the intrusion of dust from outside the housing 21 into the housing 21, comprising, the housing 21 and the rotary shaft 30 include different metal materials from each other, the inner peripheral portion 62 of the dust seal 60 is in slidable contact with the rotary shaft 30, the outer peripheral portion 63 of the dust seal 60 is in contact with the inner peripheral portion 262 of the opening 261 of the housing 21 through which the rotary shaft 30 passes, the outer end portion 265 of the inner peripheral portion 262 of the opening 261 of the housing 21 in the rotational axis direction D1 of the rotary shaft 30 has a chamfered portion 266 that expands in diameter toward the outside of the opening 261, the dust seal 60 has a first lip 71 that covers the chamfered portion 266, The drive unit 20 in which the dust seal 60 does not protrude outward in the rotational axis direction D1 beyond the outermost portion 267 in the rotational axis direction D1 of the opening 261.

[0122] When the housing 21 and the rotating shaft 30 include different metal materials, if water accumulates between the opening 261 of the housing 21 and the rotating shaft 30, electrolytic corrosion (galvanic corrosion) is likely to occur. Electrolytic corrosion can be suppressed to some extent by applying paint to the opening 261. However, when a protruding portion 272 having a small thickness is provided in the opening 261, painting may not adhere well to such a protruding portion 272, and there may be cases where painting does not adhere well to the opening 261. According to an embodiment of the present invention, the dust seal 60 has a first lip 71 that covers the chamfered portion 266 of the opening 261. By the first lip 71 covering the chamfered portion 266, electrolytic corrosion can be suppressed even when painting does not adhere well to the opening 261.

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

[0124] A 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. Since the dust seal 60 does not protrude outward beyond the opening 261, interference between the dust seal 60 and the crank arm 35 can be suppressed.

[0125] [Item 2] The drive unit 20 according to Item 1, wherein the first lip 71 of the dust seal 60 has a shape that extends in a direction away from the rotating shaft 30 while facing outward in the rotational axis direction D1.

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

[0127] [Item 3] A groove 271 is provided along the circumferential direction of the opening 261 in the inner peripheral portion 262 of the opening 261, The drive unit 20 according to item 1 or 2, wherein the outer peripheral portion 63 of the dust seal 60 has a second lip 72 that fits 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] The opening 261 has a protruding portion 272 that serves as an outer wall portion in the rotational axis direction D1 of the groove 271, The drive unit 20 according to item 3, wherein the chamfered portion 266 is provided on the protruding portion 272.

[0130] Even when it is difficult for the paint to adhere well to the protruding portion 272, electric corrosion can be suppressed by the first lip 71 covering the chamfered portion 266.

[0131] [Item 5] The drive unit 20 according to item 3 or 4, wherein the second lip 72 of the dust seal 60 fits into the groove 271 by a snap fit.

[0132] By means of the snap fit, the dust seal 60 can be fixed to the housing 21. Also, the intrusion of dust and water into the interior of the housing 21 can be more effectively suppressed.

[0133] [Item 6] The drive unit 20 according to item 4, wherein the first lip 71 and the second lip 72 of the dust seal 60 sandwich the protruding portion 272 by elastic force.

[0134] This makes it difficult to form a gap between the first lip 71 and the chamfered portion 266, and thus electric corrosion can be more effectively suppressed. Further, the intrusion of dust and water into the interior of the housing 21 can be more effectively suppressed.

[0135] [Item 7] The dust seal 60 is press-fitted into the opening 261, and the drive unit 20 described in Item 1 or 2.

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

[0137] [Item 8] The inner peripheral portion 62 of the dust seal 60 has a seal lip 65 that slidably contacts the rotating shaft 30, and the drive unit 20 described in any one of Items 1 to 7.

[0138] This can suppress the outflow of oil from the interior of the housing 21 to the exterior, and the intrusion of water and dust from the exterior of the housing 21 to the interior.

[0139] [Item 9] The inner peripheral portion 62 of the dust seal 60 slidably contacts the rotating shaft 30, and further has a dust lip 66 disposed outside the seal lip 65 in the rotational axis direction D1, and the drive unit 20 described in Item 8.

[0140] This can suppress the intrusion of dust from the exterior of the housing 21 to the interior.

[0141] [Item 10] The housing 21 contains a metal material mainly composed of magnesium, and the drive unit 20 described in any one of Items 1 to 9.

[0142] This can reduce the weight of the drive unit 20.

[0143] [Item 11] The rotating shaft 30 is the drive unit 20 according to any one of items 1 to 10, including a metal material mainly composed of iron.

[0144] Thereby, the required rigidity and strength of the rotating shaft 30 can be realized at low cost.

[0145] [Item 12] An electric assist bicycle 1 including the drive unit 20 according to any one of items 1 to 11.

[0146] Thereby, an electric assist bicycle 1 equipped with a drive unit 20 having high durability against water and being small in size can be realized.

Industrial Applicability

[0147] The present invention is particularly useful in the field of electric assist bicycles.

Explanation of Signs

[0148] 1: Electric-assisted bicycle, 2: Body frame, 3: Saddle, 4: Handlebar, 5: Meter unit, 6: Front wheel, 7: Rear wheel, 11: Head pipe, 12: Down tube, 13: Handlebar column, 14: Top tube, 15: Front fork, 16: Seat tube, 17: Seat post, 18: Chain stay, 19: Seat stay, 20: Drive unit, 21: Housing, 22: Pedal crankshaft, 24: Reducer, 25: Electric motor, 26: Bracket, 30: Rotating shaft, 34: Drive sprocket, 35: Crank arm, 37: Pedal, 38: Bearing, 39: Snap ring, 40: Power transmission mechanism, 41: Idle gear, 42: Bearing, 43: Rotating shaft, 44: Bearing, 46: Bearing, 50: One-way clutch, 51: Inner member, 52: Outer member, 53: Chain, 55: Speed sensor, 56: Battery unit, 58: Transmission, 59: Headlamp, 60: Dust seal, 61: Body, 62: Inner peripheral part of the dust seal, 63: Outer peripheral part of the dust seal, 65: Seal lip, 66: Dust lip, 67: Metal ring, 71: First lip, 72: Second lip, 92: Adapter, 94: Snap ring, 110: Circuit board, 130: External connection connector, 211: Housing, 212: Housing, 233: Driven gear, 235: Resultant force output shaft, 241: First transmission gear, 242: Second transmission gear, 243: Transmission shaft, 252A: Output gear, 2522: Output shaft, 261: Opening, 262: Inner peripheral part, 265: Outer end part, 266: Chamfered part, 267: Outermost part, 271: Groove, 272: Protrusion, 273: Protrusion, 281: Opening, A1: Position of the outermost part of the dust seal, A2: Position of the outermost part of the opening, D1: Rotating shaft direction

Claims

Claim 1 A drive unit for an electric assist bicycle, comprising: an electric motor; a housing that houses the electric motor; a rotating shaft that is rotatably supported by the housing and partially exposed outside the housing; an annular dust seal provided between the rotating shaft and the housing to suppress the intrusion of dust from outside the housing into the housing; wherein the housing and the rotating shaft are made of different metal materials; an inner peripheral portion of the dust seal is in slidable contact with the rotating shaft; an outer peripheral portion of the dust seal is in contact with an inner peripheral portion of an opening in the housing through which the rotating shaft passes; an outer end portion of the inner peripheral portion of the opening in the housing in the axial direction of the rotating shaft has a chamfered portion that expands in diameter toward the outside of the opening; the dust seal has a first lip that covers the chamfered portion; the dust seal does not protrude outward in the axial direction of the rotating shaft beyond the outermost portion of the opening in the axial direction of the rotating shaft. A drive unit. Claim 2 The drive unit according to claim 1, wherein the first lip of the dust seal has a shape that extends away from the rotating shaft while facing outward in the axial direction of the rotating shaft. Claim 3 A groove is provided along the circumferential direction of the opening in the inner peripheral portion of the opening; The drive unit according to claim 1 or 2, wherein the outer peripheral portion of the dust seal has a second lip that fits into the groove. Claim 4 The opening has a protruding portion that serves as an outer wall portion of the groove in the axial direction of the groove; The drive unit according to claim 3, wherein the chamfered portion is provided on the protruding portion. Claim 5 The drive unit according to claim 3, wherein the second lip of the dust seal fits into the groove by snap fit. Claim 6 The drive unit according to claim 4, wherein the first lip and the second lip of the dust seal sandwich the protruding portion by elastic force. Claim 7 The drive unit according to claim 1 or 2, wherein the dust seal is press-fitted into the opening. Claim 8 The drive unit according to claim 1 or 2, wherein the inner peripheral portion of the dust seal has a seal lip that is in slidable contact with the rotating shaft. Claim 9 The drive unit according to claim 8, wherein the inner peripheral portion of the dust seal slidably contacts the rotary shaft and further has a dust lip disposed outside the seal lip in the axial direction of the rotary shaft.

10. The drive unit according to claim 1 or 2, wherein the housing contains a metal material mainly composed of magnesium.

11. The drive unit according to claim 10, wherein the rotary shaft contains a metal material mainly composed of iron.

12. An electric assist bicycle including the drive unit according to claim 1 or 2.

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