Drive unit for electrically assisted bicycle and electrically assisted 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 electrically assisted bicycle and to an electrically assisted bicycle. [Background technology]

[0002] Bicycles are widely used by people of all ages and genders as an easily accessible means of transportation. In recent years, electrically assisted bicycles, which use an electric motor to assist the user's pedaling force, have become increasingly popular (see, for example, Patent Document 1). The electric motor generates driving force by receiving power from a battery installed in the vehicle. In electrically assisted bicycles, the electric motor generates driving force corresponding to the human force applied to the pedals by the user, thereby reducing the burden on the user when, for example, riding uphill or carrying luggage. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-230411 Summary of the Invention [Problem to be solved by the invention]

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

[0005] When the housing and the rotating shaft are made of different metal materials, there is a problem in that if water accumulates between the opening of the housing and the rotating shaft, galvanic corrosion is likely to occur.

[0006] There is a need to suppress electrolytic corrosion in the drive unit of an electrically assisted bicycle. [Means for solving the problem]

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

[0008] [Item 1] A drive unit for an electric assisted bicycle, An 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; an annular dust seal provided between the rotating shaft and the housing to prevent dust from entering the housing from the outside; Equipped with the housing and the rotating shaft comprise different metal materials; an inner circumferential portion of the dust seal slidably contacts the rotating shaft; an outer periphery of the dust seal contacts an inner periphery of an opening of the housing through which the rotary shaft passes; an outer end of the inner circumferential portion of the opening of the housing in the rotation axis direction of the rotary shaft has a chamfered portion whose diameter increases toward the outside of the opening; the dust seal has a first lip covering the chamfered portion; A drive unit, wherein 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] When the housing and the rotating shaft are made of different metals, accumulating water between the opening of the housing and the rotating shaft can easily cause galvanic corrosion. Galvanic corrosion can be suppressed to some extent by applying a coating to the opening. However, if the opening has a thin protrusion, the coating may not adhere well to the opening, making it difficult for the coating to adhere to such a protrusion. According to one 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 the coating does not adhere well to the opening.

[0010] Furthermore, according to one embodiment of the present invention, the dust seal does not extend beyond the outermost edge of the opening in the axial direction, thereby making it possible to reduce the width of the drive unit.

[0011] The rotating shaft may be provided with a crank arm. If the dust seal protrudes beyond the opening of the housing, the dust seal may interfere with the crank arm. By not protruding beyond the opening, the dust seal can be prevented from interfering with the crank arm.

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

[0013] This allows the chamfered portion of the opening to be covered appropriately.

[0014] [Item 3] a groove is provided in the inner periphery of the opening along a circumferential direction of the opening, 3. The drive unit according to item 1 or 2, wherein the outer periphery of the dust seal has a second lip that fits into the groove.

[0015] The second lip of the dust seal fits into the groove in the opening, thereby fixing the dust seal to the housing.

[0016] [Item 4] the opening has a protrusion that forms an outer wall of the groove in the rotation axis direction, Item 4. The drive unit according to item 3, wherein the chamfered portion is provided on the protrusion.

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

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

[0019] The snap fit allows the dust seal to be fixed to the housing, and also more effectively prevents dust and water from entering the interior of the housing.

[0020] [Item 6] 5. The drive unit according to item 4, wherein the first lip and the second lip of the dust seal sandwich the protrusion by elastic force.

[0021] This makes it difficult for a gap to form between the first lip and the chamfered portion, making it possible to more effectively suppress electrolytic corrosion and to more effectively prevent dust and water from entering the housing.

[0022] [Item 7] 3. The drive unit according to item 1 or 2, wherein the dust seal is press-fit into the opening.

[0023] The dust seal is press-fit into the opening, thereby fixing the dust seal to the housing.

[0024] [Item 8] 8. The drive unit according to any one of items 1 to 7, wherein the inner circumferential portion of the dust seal has a seal lip that is in slidable contact with the rotating shaft.

[0025] This makes it possible to prevent oil from leaking from the inside of the housing to the outside, and to prevent water and dust from entering from the outside of the housing to the inside.

[0026] [Item 9] Item 9. The drive unit according to item 8, wherein the inner peripheral portion of the dust seal further includes a dust lip that is in slidable contact with the rotating shaft and is positioned outward of the seal lip in the direction of the rotation axis.

[0027] This makes it possible to prevent dust from entering the housing from the outside to the inside.

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

[0029] This allows the weight of the drive unit to be reduced.

[0030] [Item 11] 11. The drive unit according to any one of items 1 to 10, wherein the rotating shaft comprises a metal material whose main component is iron.

[0031] This makes it possible to achieve the rigidity and strength required of the rotating shaft at low cost.

[0032] [Item 12] An electrically assisted bicycle equipped with a drive unit according to any one of items 1 to 11.

[0033] This makes it possible to realize an electrically assisted bicycle equipped with a small-sized drive unit that is highly durable against water. [Effects of the Invention]

[0034] When the housing and rotating shaft of a drive unit are made of different metals, accumulating water between the opening of the housing and the rotating shaft can easily cause galvanic corrosion. Galvanic corrosion can be suppressed to some extent by applying a coating to the opening. However, if the opening has a thin protrusion, the paint may not adhere well to the opening, making it difficult for the paint to adhere to such a protrusion. According to one embodiment of the present invention, the dust seal has a first lip that covers the chamfered portion of the opening. By having the first lip cover the chamfered portion, galvanic corrosion can be suppressed even when the paint does not adhere well to the opening.

[0035] Furthermore, according to one embodiment of the present invention, the dust seal does not extend beyond the outermost edge of the opening in the axial direction, thereby making it possible to reduce the width of the drive unit.

[0036] The rotating shaft may be provided with a crank arm. If the dust seal protrudes beyond the opening of the housing, the dust seal may interfere with the crank arm. By not protruding beyond the opening, the dust seal can be prevented from interfering with the crank arm. [Brief explanation of the drawings]

[0037] [Figure 1] 1 is a right side view showing an electrically assisted bicycle 1 according to an embodiment of the present invention. [Figure 2] 2 is a cross-sectional view showing an example of the internal structure of a drive unit 20 according to an embodiment of the present invention. FIG. [Figure 3] 2 is a cross-sectional view showing a part of a housing 21 according to an embodiment of the present invention. [Figure 4] 2 is a cross-sectional view showing an opening 261 of the housing 21 according to the embodiment of the present invention and a rotating shaft 30 passing through the opening 261. FIG. [Figure 5]1 is a perspective view showing a dust seal 60 according to an embodiment of the present invention, cut along a plane parallel to the rotation axis direction. [Figure 6] 2 is an enlarged cross-sectional view showing a part of the drive unit 20 according to the embodiment of the present invention. FIG. [Figure 7] 2 is an enlarged cross-sectional view showing a part of the drive unit 20 according to the embodiment of the present invention. FIG. [Figure 8] 2 is a cross-sectional view showing the positional relationship between an opening 261 of a housing 21 and a dust seal 60 in a rotation axis direction D1 according to the embodiment of the present invention. FIG. [Figure 9] 10 is a cross-sectional view showing a dust seal 60 fixed by press-fitting to an inner periphery 262 of an opening 261 according to an embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0038] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the embodiments, like components will be given like reference symbols, and duplicate descriptions will be omitted. The symbols F, Re, L, R, U, and D in the drawings represent front, rear, left, right, top, and bottom, respectively. In the case of an electrically assisted bicycle, the terms "front, rear, left, right, top, and bottom" refer to the front, rear, left, right, and top and bottom relative to the position in which the user is seated on the seat (saddle) of the electrically assisted bicycle, facing the handlebars. The following embodiments are examples, and the present invention is not limited to the following embodiments.

[0039] [Electric assisted bicycle] FIG. 1 is a right side view showing an electrically assisted bicycle 1 according to this embodiment.

[0040] The electrically assisted bicycle 1 has a body frame 2 that extends in the fore-and-aft 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 handle column 13 is rotatably inserted into the head pipe 11. A handle 4 is fixed to the handle column 13. The handle 4 is provided with a meter unit 5 that displays various information related to the electrically assisted bicycle 1. A headlamp 59 is provided in front of the handle 4.

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

[0042] The down tube 12 extends diagonally downward and rearward from the head pipe 11. The seat tube 16 extends upward from the rear end of the down tube 12. The chain stays 18 extend rearward from the lower end of the seat tube 16. A 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 stays 18. The top tube 14 is provided to connect the head pipe 11 and the upper part of 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 of the seat post 17.

[0043] The rear end of the chain stay 18 rotatably supports the rear wheel 7, which is a drive wheel. The seat stay 19 extends diagonally downward and rearward from the upper part of the seat tube 16. The lower end of the seat stay 19 is connected to the rear end of the chain stay 18. A derailleur 58 that changes the gear ratio is provided at the rear end of the chain stay 18. The derailleur may be provided around the pedal crankshaft 22. A speed sensor 55 that detects rotation of the rear wheel 7 is provided at the rear of the chain stay 18. The speed sensor 55 may be provided at the bottom of the front fork 15 to detect rotation of the front wheel 6.

[0044] A drive unit 20 is mounted on a bracket 26 located near the center of the vehicle body frame 2. The housing of the drive unit 20 accommodates an electric motor 25, an MCU (motor control unit), a reducer, etc. A pedal crankshaft 22 is supported by the drive unit 20 and passes through it in the left-right direction. Crank arms 35 are mounted on both ends of the pedal crankshaft 22. Pedals 37 are rotatably mounted on the tips of the crank arms 35.

[0045] A battery unit 56 that supplies power to the drive unit 20 and the like 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. At least a portion of the cross section of the down tube 12 may be U-shaped, and the down tube 12 may have a cover that covers 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 electrically assisted bicycle 1.

[0047] The battery unit 56 includes 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 capacity of the battery.

[0048] The MCU of the drive unit 20 controls the operation of the electric motor 25 and also controls the operation of each part of the electrically assisted bicycle 1. The MCU has a semiconductor integrated circuit such as a processor and a motor drive circuit. Rotation of the pedal crankshaft 22 generated when the user presses on the pedal 37 with their foot is transmitted to the rear wheel 7 via the drive sprocket 34 and chain 53. The MCU controls the electric motor 25 to generate an auxiliary drive output corresponding to the rotation output of the pedal crankshaft 22 generated when the user presses on the pedal 37 with their foot. The auxiliary force generated by the electric motor 25 is transmitted to the rear wheel 7 via the drive sprocket 34 and chain 53. A belt, a shaft, or the like may be used instead of the chain 53.

[0049] [Drive unit] An example of the configuration of the drive unit 20 will be described with reference to Fig. 2. 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 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 case 211, a second case 212, and a cover 213. The housing 21 is formed of, for example, a metal material containing magnesium as its main component (magnesium alloy). By using a metal material containing magnesium as its main component, the weight of the drive unit 20 can be reduced.

[0053] The first case 211 is placed on the second case 212 from the left side in the left-right direction. The first case 211 and the second case 212 are fixed together with 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 placed on the first case 211 from the left side in the left-right direction. The cover 213 and the first case 211 are fixed together with 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, a description will be given of the configuration of the rotating shaft 30 according to this embodiment. The rotating shaft 30 includes a pedal crankshaft 22 and a rotating shaft 23.

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

[0057] 3 is a cross-sectional view showing a portion 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 openings 261 and 281 each have a cylindrical shape. The rotating shaft 30 passes through the openings 261 and 281, and a portion of the rotating shaft 30 is exposed to the outside of the housing 21.

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

[0059] The rotating shaft 30 including the pedal crankshaft 22 passes through the housing 21 along a fourth central axis RC4 and is rotatably supported by the housing 21 about 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 located on the left side in the axial direction and is fixed to the first case 211. The bearing 38R is located on the right side in the axial direction and is fixed to the second case 212.

[0060] The pedal crankshaft 22 is disposed so as to pass through the rotating shaft 23. The rotating shaft 23 is housed 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. A pedal 37 (Fig. 1) is attached to each of the crank arms 35.

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

[0062] Next, the configurations 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 traveling of the electrically assisted bicycle 1. The electric motor 25 has a stator 251 and a rotor 252.

[0064] Stator 251 has a plurality of bobbins 2512 around which coils 2511 are wound. An iron core 2513 is inserted into each bobbin 2512. Stator 251 is disposed in space 215. In this state, stator 251 is fixed to 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. In other words, 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 central axis RC1 (first central axis) of the rotor 252.

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

[0067] The output shaft 2522 is disposed to pass through 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 so as to be rotatable around a first central axis RC1 inside the housing 21. The output shaft 2522 is rotatably supported by two bearings 42L and 42R relative to the housing 21 around a central axis CL1. The bearing 42L is fixed to the cover 213. The bearing 42R is disposed to the right of the rotor body 2521 and is fixed to the first case 211. The output shaft 2522 is disposed to pass through 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 helical gear.

[0069] The transmission mechanism 40 is accommodated in the housing 21. Specifically, the transmission mechanism 40 is disposed in the space 214. The transmission mechanism 40 has the reducer 24, an idle 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 reducer 24 is rotatably supported by the housing 21 and increases the torque of the output gear 252A of the electric motor 25. The reducer 24 has a first transmission gear 241, a second transmission gear 242, and a transmission shaft 243. A central axis CL2 of the transmission shaft 243 is parallel to a central axis CL4 of the pedal crankshaft 22. In other words, the transmission shaft 243 extends parallel to the central axis CL4 of the pedal crankshaft 22. The central axis CL2 is a rotation central axis RC2 (second central axis) of the transmission shaft 243 when viewed in the axial direction of the transmission shaft 243, i.e., when viewed from the axial direction of the pedal crankshaft 22. The reducer 24 is supported by the housing 21 inside the housing 21 so as to be rotatable about the second central axis RC2.

[0071] The first transmission gear 241 is disposed 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 a bearing 44L. The first transmission gear 241 disposed on the right portion of the transmission shaft 243 is rotatably supported by a bearing 44R. The transmission shaft 243 and the first transmission gear 241 are rotatably supported around the central axis line 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 an output gear 252A of the electric motor 25. As a result, the driving force generated by the electric motor 25 is transmitted to the first transmission gear 241 from the output gear 252A.

[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 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 that rotates the rear wheel 7 (FIG. 1) of the electrically assisted 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 that rotates the rear wheel 7 backward is not transmitted to the transmission shaft 243. The one-way clutch 244 also prevents the rotational force of the pedal crankshaft 22 in the forward rotation direction, which is generated by the rider's manual 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. In other words, the first transmission gear 241 is reduced in speed compared to the output gear 252A.

[0075] The second transmission gear 242 is made 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 different position 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 fewer teeth than the first transmission gear 241. In this embodiment, the transmission shaft 243 and the second transmission gear 242 are formed integrally, but this is not limiting. 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 idle gear 41 is made of a metal material (for example, iron). The idle gear 41 is disposed on the rotary shaft 43. The idle gear 41 is fixed to the rotary shaft 43 by, for example, but not limited to, a fastener. The idle gear 41 may be fixed to the rotary shaft 43 by serration coupling (or press fitting). Alternatively, the idle gear 41 and the rotary shaft 43 may be formed integrally. The idle gear 41 rotates together with the rotary shaft 43.

[0077] The central axis CL3 of the rotary shaft 43 is parallel to the central axis CL4 of the pedal crankshaft 22. That is, the rotary shaft 43 extends parallel to the central axis CL4 of the pedal crankshaft 22. The central axis CL3 becomes the rotation central axis RC3 (third central axis) of the rotary shaft 43 when viewed in the axial direction of the rotary shaft 43, that is, the axial direction of the pedal crankshaft 22. The idle gear 41 fixed to the rotary shaft 43 is supported by the housing 21 inside the housing 21 so as to be rotatable around the third central 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 case 211. The idle gear 41 is disposed closer to the bearing 46R than to the bearing 46L in the axial direction of the rotating shaft 43. The idle gear 41 meshes with the second transmission gear 242 of the reducer 24. As a result, the output torque of the electric motor 25, which has been increased by the reducer 24, is transmitted to the idle 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 and the pedal crankshaft 22 are disposed coaxially.

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

[0083] A torque detector 232 is disposed around the connecting shaft 231. The torque detector 232 is supported by the connecting shaft 231 and is unable to rotate relative to the first case 211. The torque detector 232 detects the torque generated in the connecting shaft 231 when the rider pedals. The torque detector 232 is, for example, a magnetostrictive torque sensor. The torque detector 232 outputs a signal corresponding to the detected torque to the MCU mounted on the circuit board 110. The MCU refers to the torque detected by the torque detector 232 to determine the pedaling state of the rider and control the electric motor 25. The external connection connector 130 is a connector for electrically connecting the drive unit 20 to an external device (for example, the battery unit 56 and the meter unit 5).

[0084] The one-way clutch 50 is disposed to the right 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 a connecting shaft 231. The one-way clutch 50 is disposed 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 disposed 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 a serration connection or the like. As a result, whether the connecting shaft 231 rotates forward or backward, the inner member 51 rotates together with the connecting shaft 231. In other words, whether the pedal crankshaft 22 rotates forward or backward, 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 plain bearing 49 is disposed between the outer member 52 and the pedal crankshaft 22. As a result, the outer member 52 is disposed so as to be rotatable coaxially with the pedal crankshaft 22.

[0087] A ratchet mechanism serving as a one-way clutch mechanism is formed between the outer member 52 and the inner member 51. As a result, 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 a bearing 38R so as to be rotatable relative to the housing 21 around the central axis CL4 of the pedal crankshaft 22. The outer member 52 is disposed to penetrate the second case 212. The drive sprocket 34 is attached to a portion of the outer member 52 located outside (on the right side) of the housing 21.

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

[0090] The outer member 52 transmits the resultant 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 outer member 52 realizes a resultant force output shaft 235 that combines and outputs the human power 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 this 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. Movement of the bearing 38L in the direction of the rotation axis of the rotating shaft 30 is restricted by a protrusion 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, and prevents dust from entering the housing 21 from the outside.

[0095] In this embodiment, the rotating shaft 30 is provided with an adapter 92 that adjusts 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 connection, and increases the shaft diameter of a portion 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 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 rotational axis direction of the rotating shaft 30. FIGS. 6 and 7 are enlarged cross-sectional views of a portion of the drive unit 20, showing an enlarged area surrounded by a dashed line in FIG. 4. FIG. 7 illustrates a state in which the dust seal 60 is omitted. To clearly explain the characteristics of this embodiment, the bearing 38L is not shown in FIGS. 6 and 7. In the example 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. With the opening 261 as the reference point, 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 (reinforcement ring) 67. The body 61 is formed of an elastomer such as synthetic rubber. The metal ring 67 increases the rigidity of the dust seal 60. An inner peripheral portion 62 of the dust seal 60 is provided with a seal lip 65 and a dust lip 66. An outer peripheral portion 63 of the dust seal 60 is provided with a first lip 71 and a second lip 72.

[0098] 6, the seal lip 65 and dust lip 66 provided on the inner circumferential portion 62 of the dust seal 60 are in slidable contact with the adapter 92 of the rotating shaft 30. The dust lip 66 is disposed further outward in the rotational axis direction D1 than the seal lip 65. The seal lip 65 and dust lip 66 prevent oil from leaking from the inside of the housing 21 to the outside, and prevent water and dust from entering from the outside of the housing 21 to the inside.

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

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

[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 a groove 271 on the inner periphery 262 of the opening 261. In this example, the second lip 72 fits into the groove 271 by snap fitting. By fitting 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 leaking from the inside to the outside of the housing 21, and to prevent water and dust from entering from the outside of the housing 21 to the inside.

[0102] An outer end 265 of the inner circumferential portion 262 of the opening 261 in the rotation axis direction D1 has a chamfered portion 266 that has been processed with C-chamfering or R-chamfering. The chamfered portion 266 has a shape that expands in diameter 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 outward in the rotational axis direction D1 and in a direction away from the rotating shaft 30. As shown in FIG. 6 , the first lip 71 covers the chamfered portion 266 of the opening 261. In this embodiment, "the first lip 71 covers the chamfered portion 266" may mean that the first lip 71 covers a portion 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, accumulating water between the opening 261 of the housing 21 and the rotating shaft 30 can easily cause galvanic corrosion. Galvanic corrosion can be suppressed to some extent by coating the opening 261. However, depending on the shape of the opening 261, it may be difficult to apply paint to the opening 261. For example, if the opening 261 has a thin protrusion 272, it is difficult to apply paint to such a protrusion 272. According to this embodiment, the dust seal 60 has a first lip 71 that covers the chamfered portion 266 of the opening 261. By having the first lip 71 cover the chamfered portion 266, it is possible to suppress galvanic corrosion even when it is difficult to apply paint to the opening 261.

[0105] Furthermore, the first lip 71 and second lip 72 of the dust seal 60 sandwich the protruding portion 272 by elastic force. This makes it less likely that a gap will form between the first lip 71 and the chamfered portion 266, making it possible to more effectively suppress electrolytic corrosion. This also makes it possible to more effectively suppress the outflow of oil from the inside of the housing 21 to the outside, and more effectively suppress the intrusion of water and dust from the outside of the housing 21 to the inside.

[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] 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. A dashed line A1 shown in Fig. 8 indicates the outermost position of the dust seal 60 in the rotational axis direction D1. A 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 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. This allows the size of the drive unit 20 in the width direction to be reduced.

[0109] Components such as the crank arm 35 are attached to the rotating shaft 30. If 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, etc. By not protruding beyond the opening 261, the dust seal 60 can be prevented from interfering with the crank arm 35, etc.

[0110] The first lip 71 of the dust seal 60 covers the chamfered portion 266 to the extent that the dust seal 60 does not protrude outward beyond the outermost portion 267 of the opening 261. If the dust seal 60 does not protrude outward 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 periphery 262 of the opening 261 by snap fitting, but the dust seal 60 may also be fixed to the inner periphery 262 by press fitting.

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

[0113] An outer end 265 of the inner circumferential 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 makes it possible to suppress electrolytic corrosion.

[0114] In the above-described embodiment, the drive unit 20 (FIG. 2) has four shafts: the output shaft 2522, the transmission shaft 243, the rotating shaft 43, and the rotating shaft 30. However, 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 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 is provided with the idle gear 41, but the present invention is also applicable to a drive unit 20 that does not have the idle 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 to this. Only a portion of the electric motor 25 may be housed in the housing 21. For example, the left portion of the first case 211 may have an opening through which the electric motor 25 can pass, and the electric motor 25 may be attached so that a portion of the electric motor 25 is positioned inside the housing 21 through the opening. In this case, the opening may be covered with a cover to protect against dust and water.

[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 may have a shape that covers the side of the electric motor 25, and the electric motor 25 may be supported by the cover 213. A form in which the electric motor 25 is supported by the cover 213 is also included in a form in which the electric motor 25 is supported by the housing 21.

[0118] In the above-described embodiment, a two-wheeled electrically assisted bicycle is used as the electrically assisted bicycle 1, but the present invention is not limited to this. For example, the electrically assisted bicycle 1 may be a three-wheeled electrically assisted bicycle.

[0119] In the above-described embodiment, the rear wheel is the drive wheel to which the rider's pedaling power and the assistive power generated by the electric motor are transmitted, but the present invention is not limited to this. Depending on the configuration of the electrically assisted bicycle, the human power and the assistive power may be transmitted to the front wheel, or to both the front and rear wheels. The present invention may also be applied to an electrically assisted bicycle in which a hub motor is provided on the front wheel.

[0120] The present specification discloses a drive unit and an electrically assisted bicycle as described in the following items.

[0121] [Item 1] A drive unit 20 for an electrically assisted bicycle 1, an electric motor 25; a housing 21 that accommodates an electric motor 25; a rotating shaft 30 rotatably supported by the housing 21 and partially exposed to the outside of the housing 21; an annular dust seal 60 provided between the rotating shaft 30 and the housing 21 to prevent dust from entering the inside of the housing 21 from the outside of the housing 21; Equipped with The housing 21 and the rotating shaft 30 are made of different metal materials, The inner periphery 62 of the dust seal 60 is in slidable contact with the rotating shaft 30, The outer periphery 63 of the dust seal 60 contacts the inner periphery 262 of the opening 261 of the housing 21 through which the rotating shaft 30 passes, an outer end portion 265 of an inner peripheral portion 262 of an opening 261 of the housing 21 in the rotation axis direction D1 of the rotating shaft 30 has a chamfered portion 266 whose diameter expands 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) has a dust seal (60) that does not protrude outward in the rotation axis direction (D1) beyond an outermost portion (267) of the opening (261) in the rotation axis direction (D1).

[0122] When the housing 21 and the rotating shaft 30 are made of different metal materials, accumulating water between the opening 261 of the housing 21 and the rotating shaft 30 can easily cause galvanic corrosion. Galvanic corrosion can be suppressed to some extent by coating the opening 261. However, if the opening 261 has a thin protrusion 272, the paint may not adhere well to the opening 261, for example, the paint may not adhere well to the protrusion 272. According to one 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 having the first lip 71 cover the chamfered portion 266, galvanic corrosion can be suppressed even when the paint does not 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. This allows the size of the drive unit 20 in the width direction to be reduced.

[0124] A crank arm 35 may be provided on the rotating shaft 30. If 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 not protruding the dust seal 60 outward beyond the opening 261, interference between the dust seal 60 and the crank arm 35 can be prevented.

[0125] [Item 2] Item 1: 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 rotation axis direction (D1).

[0126] This allows the chamfered portion 266 of the opening 261 to be covered appropriately.

[0127] [Item 3] A groove 271 is provided in the inner periphery 262 of the opening 261 along the circumferential direction of the opening 261, The drive unit (20) according to item 1 or 2, wherein the outer periphery (63) of the dust seal (60) has a second lip (72) that fits into the groove (271).

[0128] The second lip 72 of the dust seal 60 fits into the groove 271 of the opening 261 , thereby fixing the dust seal 60 to the housing 21 .

[0129] [Item 4] The opening 261 has a protrusion 272 that forms an outer wall of the groove 271 in the rotation axis direction D1, The drive unit (20) according to item 3, wherein the chamfered portion (266) is provided on the protrusion (272).

[0130] Even if it is difficult to apply paint well to the protruding portion 272, the first lip 71 covers the chamfered portion 266, thereby making it possible to suppress electrolytic corrosion.

[0131] [Item 5] 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] The dust seal 60 can be fixed to the housing 21 by snap fitting, and the intrusion of dust and water into the interior of the housing 21 can be more effectively prevented.

[0133] [Item 6] Item 5. 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 protrusion (272) by elastic force.

[0134] This makes it difficult for a gap to form between the first lip 71 and the chamfered portion 266, making it possible to more effectively suppress electrolytic corrosion. Also, it is possible to more effectively suppress the intrusion of dust and water into the interior of the housing 21.

[0135] [Item 7] 3. The drive unit (20) according to item 1 or 2, wherein the dust seal (60) is press-fit into the opening (261).

[0136] The dust seal 60 is press-fitted into the opening 261 , thereby fixing the dust seal 60 to the housing 21 .

[0137] [Item 8] 8. The drive unit (20) according to any one of items 1 to 7, wherein the inner periphery (62) of the dust seal (60) has a seal lip (65) that is in slidable contact with the rotating shaft (30).

[0138] This makes it possible to prevent oil from leaking from the inside of the housing 21 to the outside, and prevent water and dust from entering from the outside of the housing 21 to the inside.

[0139] [Item 9] The drive unit 20 described in item 8, wherein the inner peripheral portion 62 of the dust seal 60 is in slidable contact with the rotating shaft 30 and further has a dust lip 66 positioned outward of the seal lip 65 in the rotational axis direction D1.

[0140] This makes it possible to prevent dust from entering the housing 21 from the outside to the inside.

[0141] [Item 10] 10. The drive unit 20 according to any one of items 1 to 9, wherein the housing 21 includes a metal material whose main component is magnesium.

[0142] This allows the weight of the drive unit 20 to be reduced.

[0143] [Item 11] 11. The drive unit 20 according to any one of items 1 to 10, wherein the rotating shaft 30 comprises a metal material whose main component is iron.

[0144] This allows the rigidity and strength required for the rotary shaft 30 to be achieved at low cost.

[0145] [Item 12] An electrically assisted bicycle 1 equipped with a drive unit 20 according to any one of items 1 to 11.

[0146] This makes it possible to realize an electrically assisted bicycle 1 equipped with a drive unit 20 that is highly water-resistant and compact. [Industrial Applicability]

[0147] The present invention is particularly useful in the field of electrically assisted bicycles. [Explanation of symbols]

[0148] 1: Electrically assisted bicycle, 2: Body frame, 3: Saddle, 4: Handlebars, 5: Meter unit, 6: Front wheel, 7: Rear wheel, 11: Head pipe, 12: Down tube, 13: Handle 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 portion of dust seal, 63: Outer peripheral portion of 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 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 portion, 265: outer end, 266: chamfered portion, 267: outermost portion, 271: groove, 272: protrusion, 273: protrusion, 281: opening, A1: outermost position of dust seal, A2: outermost position of opening, D1: rotation axis direction

Claims

1. A drive unit for an electric assisted bicycle, An 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; an annular dust seal provided between the rotating shaft and the housing to prevent dust from entering the housing from the outside; Equipped with the housing and the rotating shaft comprise different metal materials; an inner circumferential portion of the dust seal slidably contacts the rotating shaft; an outer periphery of the dust seal contacts an inner periphery of an opening of the housing through which the rotary shaft passes; an outer end of the inner circumferential portion of the opening of the housing in the rotation axis direction of the rotary shaft has a chamfered portion whose diameter increases toward the outside of the opening; the dust seal has a first lip covering the chamfered portion; A drive unit, wherein 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.

2. The drive unit according to claim 1 , wherein the first lip of the dust seal has a shape that extends in a direction away from the rotary shaft while facing outward in the direction of the rotary shaft.

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

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

5. The drive unit of claim 3 , wherein the second lip of the dust seal fits into the groove by a snap fit.

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

7. 3. The drive unit according to claim 1, wherein the dust seal is press-fitted into the opening.

8. 3. The drive unit according to claim 1, wherein the inner circumferential portion of the dust seal has a seal lip that is in slidable contact with the rotating shaft.

9. 9. The drive unit according to claim 8, wherein the inner peripheral portion of the dust seal further includes a dust lip that is in slidable contact with the rotary shaft and is positioned outward of the seal lip in the direction of the rotary shaft.

10. 3. The drive unit according to claim 1, wherein the housing includes a metal material containing magnesium as a main component.

11. The drive unit according to claim 10 , wherein the rotating shaft comprises a metal material whose main component is iron.

12. An electrically assisted bicycle comprising the drive unit according to claim 1 or 2.

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