DRIVE UNIT AND ELECTRIC BICYCLE

Abstract

Drive unit (20) that can be mounted on a bicycle frame (12) of an electric bicycle (10) to generate a driving force that is transferred to a wheel (14R) of the electric bicycle (10), the drive unit (20) comprising: a case (21); an electric motor (25) which is arranged in the housing (21); a pedal crank shaft (22) which extends through the housing (21) along a right / left direction of the electric bicycle (10) and is rotatably mounted through the housing (21); a tubular connecting shaft (231) through which the pedal crank shaft (22) extends and which transmits a pedal force from one end section (231L) to another end section (231R), wherein one end section (231L) is coupled to the pedal crank shaft (22); a one-way clutch (50) for transmitting the pedal force, which was transmitted to the other end section (231R) of the connecting shaft (231), to a drive sprocket (34); and a speed limiter (24) with a transmission drive shaft (241) that reduces the speed generated by the electric motor (25) in order to increase the output torque of the electric motor (25), the housing (21) comprises: a first housing (211) with a first opening (402) through which one end of the pedal crank shaft (22) is passed, and a recess (404) in which the electric motor (25) is housed; a second housing (212) with a second opening through which another end of the pedal crank shaft (22) passes, wherein the second housing (212) and the first housing (211) together form an outer surface of the housing (21); and an inner cover (213) which covers at least one section of the electric motor (25) housed in the recess (404) of the first housing (211), wherein the inner cover (213) has a third opening (440) through which an output shaft (2522) of the electric motor (25) is passed, wherein the inner cover (213) rotatably supports the transmission drive shaft (241) of the speed limiter (24), wherein an outer circumferential edge (462) of the inner cover (213) extends between the transmission drive shaft (241) and the pedal crank shaft (22); wherein the recess (404) of the first housing (211) comprises a wall (406) extending around a circumference of the electric motor (25), the wall (406) holding the inner cover (213), where: the inner cover (213) has a projection (213b) that serves as a striking pin, and the wall (406) or the first housing (211) has a recess (406b) for engagement with the projection (213b) of the inner cover (213), wherein the projection (213b) is configured to penetrate the recess (406b) of the wall (406) or the first housing (211) in order to achieve alignment between the inner cover (213) and the wall (406) or between the inner cover (213) and the first housing (211), or the inner cover (213) has a recess, the wall (406) or the first housing (211) has a projection that serves as a striking pin for engaging with the recess of the inner cover (213), wherein the projection of the wall (406) or of the first housing (211) is configured to penetrate into the recess of the inner cover (213) in order to achieve alignment between the inner cover (213) and the wall (406) or between the inner cover (213) and the first housing (211).

Description

BACKGROUND 1. Technical area:

[0001] The present invention relates to a drive unit for attachment to a bicycle frame of an electric bicycle. The present invention also relates to an electric bicycle having such a drive unit. 2. Description of the state of the art:

[0002] Bicycles are widely used as a common means of transportation, regardless of age or gender. In recent years, electric bicycles, which utilize the power of an electric motor to assist the rider's pedaling, have become increasingly popular. Bicycles with an electric assist motor are disclosed, for example, in JP 2014-196080 A (hereinafter "Patent Document 1") and DE 10 2018 120 095 A1.

[0003] An electric bicycle comprises a drive unit with an electric motor and the like. Common types of drive units include those housed in the rear wheel hub and those mounted at the bottom of the bicycle frame (near the bottom bracket). The latter type of drive unit has become more popular in recent years.

[0004] The electric bicycle disclosed in Patent Document 1 includes a drive unit mounted at the bottom of the bicycle frame. This drive unit includes a housing, an electric motor, a crankshaft, and the like.

[0005] The electric motor, housed in the housing, generates drive power that is used to assist the rider's pedaling. The crankshaft extends through the housing along the vehicle's left / right direction. The pedals are attached to the crankshaft via arms. Within the housing, the crankshaft is rotatably supported by a pair of bearings. The rotation of the crankshaft is transmitted to the rear wheel via a drive sprocket, a chain, a driven sprocket, and the like.

[0006] A conventional drive unit essentially consists of three external parts, in particular: a stator cover that covers the stator of an electric motor; a housing that houses the motor and to which the stator cover is mounted; and another housing that is mounted so that it faces the housing.

[0007] Each exterior component typically requires painting. Therefore, as the number of exterior components increases, so does the cost of quality control for the paint job.

[0008] During assembly, when the stator cover and one housing are attached together, a waterproof sealant must be applied. Furthermore, when one housing and the other housing are attached together, the sealant must be applied again. This requires inspections of the fastening and application of the sealant, increasing the costs associated with assembly.

[0009] Reducing the number of outer sections would solve the aforementioned problem. On the other hand, reducing the number of outer sections may compromise the rigidity of the outer section (and thus the rigidity of the inner section), which would have been achieved by attaching the outer sections at a relatively high number of locations. SUMMARY

[0010] The present invention provides a drive unit that maintains the rigidity of the inner portion while maintaining the number of two outer parts, and an electric bicycle having such a drive unit.

[0011] The present invention is defined in independent claims 1 and 2. Preferred embodiments are subject of the subclaims.

[0012] A drive unit according to an embodiment of the present invention is a drive unit that is attachable to a bicycle frame of an electric bicycle to generate a driving force that is transmitted to a wheel of the electric bicycle, the drive unit comprising: a housing; an electric motor disposed in the housing; a crankshaft that extends through the housing along a right / left direction of the electric bicycle and is rotatably supported by the housing; a tubular connecting shaft through which the crankshaft extends and that transmits a pedaling force from one end portion to another end portion, the one end portion being coupled to the crankshaft; a one-way clutch for transmitting the pedaling force transmitted to the other end portion of the connecting shaft to a drive sprocket;and a speed limiter with a geared rotary shaft for reducing the speed generated by the electric motor to increase an output torque of the electric motor, the housing comprising: a first housing having a first opening through which one end of the pedal crankshaft is passed, and a recess in which the electric motor is housed; a second housing having a second opening through which another end of the pedal crankshaft is passed, the second housing and the first housing together forming an outer side of the housing;and an inner cover covering at least one end portion of the electric motor housed in the recess of the first housing, the inner cover having a third opening through which an output shaft of the electric motor passes, the inner cover rotatably supporting the gear rotation shaft of the speed limiter, an outer peripheral edge of the inner cover extending between the gear rotation shaft and the pedal crankshaft; and the recess of the first housing has a wall extending around a periphery of the electric motor, the wall supporting the inner cover.

[0013] The inner cover is held by the recess wall, which is a highly rigid section, preventing misalignment of the inner cover. This prevents misalignment of the speed limiter's transmission rotating shaft, which is held by the inner cover.

[0014] According to one embodiment, the first housing has an inclined surface between the recess and the first opening, extending from the first opening to the wall. The first housing with the inclined surface corresponding to the wall can increase the rigidity of the wall.

[0015] According to one embodiment, the first housing includes a further recess with the first opening at a bottom; and the inclined surface is an end portion of the further recess. Since the wall of the recess accommodating the electric motor is connected to the further recess, the rigidity of the wall of the recess accommodating the electric motor can be increased.

[0016] According to one embodiment, when the inner cover is viewed in a direction parallel to the output shaft of the electric motor, the outer peripheral edge of the inner cover extends around the outer periphery of the electric motor. The inner cover does not extend beyond the pedal crankshaft and is small in size, thereby increasing the rigidity of the inner cover. Since the inner cover has high rigidity, misalignment of the speed limiter's transmission rotating shaft, which is held by the inner cover, can be suppressed.

[0017] According to one embodiment, the outer peripheral edge of the inner cover is attached to the wall at multiple locations. Since the inner cover is attached to the wall at a plurality of positions, bending of the inner cover can be suppressed.

[0018] According to one embodiment, the inner cover rotatably supports the output shaft of the electric motor. The inner cover holds the gear rotating shaft of the speed limiter and the output shaft of the electric motor. Since both the gear rotating shaft of the speed limiter and the output shaft of the electric motor are held by a single part, misalignments between the gear rotating shaft of the speed limiter and the output shaft of the electric motor can be suppressed.

[0019] According to one embodiment, the drive unit further comprises an alignment structure for determining the relative positioning between the inner cover and the first housing. By aligning the inner cover and the first housing, alignment can be achieved between the gear rotation shaft of the speed limiter and the pedal crankshaft, thereby realizing smooth power transmission.

[0020] According to one embodiment, the inner cover has a first guide for determining a position of the inner cover relative to the first housing, wherein the first housing has a second guide for engaging the first guide. By aligning the inner cover and the first housing through engagement of the first and second guides, a more precise alignment between the gear rotation shaft of the speed limiter and the pedal crankshaft can be achieved, thereby realizing a smooth power transmission.

[0021] By aligning the inner cover and the first housing according to the invention with the aid of the striker pin, a more precise alignment between the gear rotating shaft of the speed limiter and the pedal crankshaft can be achieved, thereby realizing a uniform power transmission.

[0022] According to one embodiment, the inner cover and the wall form a pin-and-tenon joint structure, in which the inner cover is secured in the wall. By aligning the inner cover and the first housing via the pin-and-tenon joint structure (fitting piece), alignment can be achieved between the gear rotating shaft of the speed limiter and the pedal crankshaft, thereby realizing a smooth power transmission.

[0023] According to one embodiment, the inner cover and the wall comprise a pin-and-tenon joint structure, in which the inner cover is rotatable relative to the wall; either the projection of the inner cover or the projection of the first housing or the wall, or the recesses of the inner cover and the wall are located at a position lying on a straight line orthogonal to a line segment connecting the pedal crankshaft and the transmission rotating shaft of the speed limiter, and located at the outer peripheral edge. This positioning, which is located at the outer peripheral edge and away from the transmission rotating shaft, can reduce associated misalignment of the transmission rotating shaft, even if an offset occurs during an alignment operation with the striker pin.

[0024] According to one embodiment, the inner cover and the wall comprise a pin-and-tenon joint structure, in which the inner cover is rotatable relative to the wall; either the projection of the inner cover or the projection of the first housing or the wall, or the recesses of the inner cover and the wall are located at a position located on the outer peripheral edge and at which an angle between a line segment connecting the pedal crankshaft and the transmission rotating shaft of the speed limiter and a tangent from the pedal crankshaft to the outer peripheral edge is closest to 90 degrees. By positioning this at a location located on the outer peripheral edge and away from the transmission rotating shaft, the associated misalignment of the transmission rotating shaft can be reduced, even if an offset occurs during an alignment operation with the striker pin.

[0025] According to one embodiment, the drive unit further comprises a circuit board on which a drive circuit for driving the electric motor is mounted, wherein the inner cover comprises a first surface and a second surface; the first surface is a surface facing the electric motor; the second surface is a surface opposite the first surface; and within the housing, the circuit board is arranged in a space located on the second surface side of the inner cover. The circuit board is arranged at a position different from the recess for accommodating the electric motor. This allows the recess to be small, thereby increasing the rigidity of the wall of the recess.

[0026] According to one embodiment, the inner cover is enclosed by the first housing and the second housing and is not exposed outside the drive unit. Since the inner cover is not exposed to the outside, the parts of the housing that require painting are reduced to two: the first housing and the second housing. Furthermore, the housing parts that require the application of a waterproof sealant are reduced to two: the first housing and the second housing. This allows production costs to be reduced.

[0027] According to one embodiment, the inner cover is enclosed by the first housing and the second housing. Since the inner cover is enclosed without being exposed to the outside, the parts of the housing that require painting are reduced to two: the first housing and the second housing. Furthermore, the housing parts that require a waterproof sealant are reduced to two: the first housing and the second housing. This allows production costs to be reduced.

[0028] An electric bicycle according to an embodiment of the present invention includes a drive unit according to the above. Since the gear rotating shaft of the speed limiter is supported by the inner cover, an electric bicycle can be realized in which misalignment of the gear rotating shaft is prevented.

[0029] According to one embodiment of the present invention, a drive unit includes an inner cover covering at least one end portion of the electric motor housed in the recess of the first housing, the inner cover having a third opening through which an output unit of the electric motor passes. The inner cover rotatably supports the gear rotating shaft of the speed limiter, with an outer peripheral edge of the inner cover extending between the gear rotating shaft and the pedal crankshaft. The recess of the first housing includes a wall extending around the circumference of the electric motor, the wall supporting the inner cover. The inner cover is supported by the wall of the recess (which is a highly rigid portion) of the first housing, whereby misalignment of the inner cover can be suppressed.This can prevent misalignment of the speed limiter's gear rotating shaft, which is held by the inner cover. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a right side view showing an electric bicycle 10 according to an embodiment of the present invention. Fig. 2 is a cross-sectional view showing the internal structure of a drive unit 20 included in an electric motor assist bicycle 10 according to an embodiment of the present invention. Fig. 3 is a perspective view of the inside of a first housing 211. Fig. 4 is a perspective view of the outside of the first housing 211. Fig. 5 is a cross-sectional view for describing the relationship between a recess 404 and another recess 408. Fig. 6 is a perspective view of the inside of the first housing 211 with an inner cover 213 mounted thereon. Fig. 7 is a plan view for describing the relative positioning between the inner cover 213, a pedal crank shaft 22, and a transmission shaft 241. Fig. 8 is a diagram showing a circuit board 48 provided in the first housing 211. Fig. 9 shows an alignment structure 500 in which the inner cover 213 is fitted into a wall 406. Fig. 10 is an enlarged view of the alignment structure 500. Fig. 11A is a diagram for describing a method of determining an alignment hole(s) using a striker(s). Fig. 11B is a diagram showing the positions of a first hole(s) R and / or Ra on an outer peripheral edge 462. Fig. 11C is a diagram for describing another position that can be assumed as the position of an alignment hole. Fig. 12 is a cross-sectional view showing a straight striker pin 502 inserted into a first hole 213a in the inner cover 213 and a second hole 406a in the wall 406. Fig. 13 is a diagram showing a first modification of an alignment structure using a striker pin. Fig. 14 is a diagram showing a second modification of an alignment structure using a striker pin. DETAILED DESCRIPTION

[0030] Drive systems according to embodiments of the present invention and electric bicycles having such drive systems are described below with reference to the drawings. In the description of the embodiments, like component elements are denoted by the same reference numerals, and redundant descriptions are omitted. In embodiments of the present invention, the terms "front," "rear," "right," "left," "top," and "bottom" respectively mean front, rear, right, left, top, and bottom from the perspective of a rider sitting on the saddle (seat) of the electric bicycle and facing the handlebars. [Bicycle with electric auxiliary motor or electric bicycle]

[0031] With reference to Fig. 1, an electric bicycle 10 according to an embodiment of the present invention is described. Fig. 1 is a right side view showing the schematic structure of the electric bicycle 10.

[0032] The electric bicycle 10 includes a bicycle frame 12, a front wheel 14F, a rear wheel 14R, a handlebar 16, and a saddle 18. The electric bicycle 10 further includes a drive unit 20 and a battery unit 26.

[0033] The bicycle frame 12 includes a head tube 121, a top tube 122, a down tube 123, a seat tube 124 and a bracket 125.

[0034] The head tube 121, which extends in the up / down direction, is arranged at the front of the bicycle frame 12. A stem 27 is rotatably inserted into the head tube 121. The handlebar 16 is attached to the upper end of the stem 27. The front fork 28 is attached to the lower end of the stem 27. The front wheel 14F is rotatably mounted at the lower end of the front fork 28. In other words, the front wheel 14F is supported by the bicycle frame 12 via the stem 27 and the front forks 28.

[0035] The top tube 122, which extends longitudinally, is located at the rear end of the head tube 121. The front end of the top tube 122 is connected to the head tube 121. The rear end of the top tube 122 is connected to the seat tube 124.

[0036] The down tube 123, which extends in the longitudinal direction, is arranged at the rear end of the head tube 121. The down tube 123 is arranged below the top tube 122. The front end of the down tube 123 is connected to the head tube 121. In the Fig. In the example shown in Figure 1, the front end portion of the down tube 123 is also connected to the front end portion of the top tube 122. The rear end of the down tube 123 is connected to the bracket 125.

[0037] The battery unit 26 is mounted on the down tube 123. The battery unit 26 supplies the drive unit 20 with electrical energy. The battery unit 26 contains a battery and a control unit. The battery is a rechargeable battery that can charge and discharge. The control circuit controls the charging and discharging of the battery and also monitors the battery's output current, remaining power, etc.

[0038] The seat tube 124, which extends in the up-down direction, is arranged at the rear of the top tube 122 and the down tube 123. The lower end of the seat tube 124 is connected to the bracket 125. In other words, the seat tube 124 extends upward from the bracket 125.

[0039] In the Fig. In the example shown in Figure 1, the seat tube 124 is bent at a central end portion along the up-down direction. As a result, a lower end portion of the seat tube 124 extends along the up-down direction, while an upper end portion of the seat tube 124 extends along a direction inclined with respect to the up-down direction.

[0040] A seat post 29 is inserted into the seat tube 124. The saddle 18 is mounted at the upper end of the seat post 29.

[0041] The bracket 125 is located at the lower end of the bicycle frame 12. The bracket 125 supports the drive unit 20. The drive unit 20, mounted on the bicycle frame 12, generates a driving force that is transmitted to a wheel (here, the rear wheel 14R). Details of the drive unit 20 will be described later.

[0042] The bicycle frame 12 further includes a swingarm 30, a pair of connecting arms 303, and a suspension 304. The swingarm 30 includes a pair of chainstays 301 and a pair of seat stays 302.

[0043] The pair of chainstays 301 each extends in the longitudinal direction. The pair of chainstays 301 are arranged side by side in the right / left direction. The rear wheel 14R is arranged between the pair of chainstays 301. The pair of chainstays 301 are arranged symmetrically on the left and right sides. For this reason, Fig. 1 only the right chainstay 301 is shown.

[0044] The front end portion of each chainstay 301 is mounted on the bracket 125. In other words, each chainstay 301 extends rearward from the bracket 125. Each chainstay 301 is arranged to pivot relative to the bracket 125 about an axis extending in the right / left direction.

[0045] At the rear end portion of each chain stay 301, a wheel axle 141 of the rear wheel 14R is arranged such that the wheel axle 141 itself is not rotatable. In other words, the pair of chainstays 301 together support the rear wheel 14R so that the rear wheel 14R can rotate about the wheel axle 141. That is, the rear wheel 14R is held to the bicycle frame 12. A plurality of driven sprockets 32 are mounted on the rear wheel 14R.

[0046] The pair of seat stays 302 each extend in the longitudinal direction. The pair of seat stays 302 are arranged side by side in the right / left direction. The rear wheel 14R is arranged between the pair of seat stays 302. The pair of seat stays 302 are arranged symmetrically on the left and right sides. For this reason, Fig. 1 only the right seat stay 302 is shown.

[0047] The rear end portion of the left seat stay 302 is connected to the rear end portion of the left chain stay 301. The rear end portion of the right seat stay 302 is connected to the rear end portion of the right chain stay 301.

[0048] The pair of connecting arms 303 each extends in the longitudinal direction. The pair of connecting arms 303 are arranged side by side in the right / left direction. The seat tube 124 is arranged between the pair of connecting arms 303. The pair of connecting arms 303 are arranged symmetrically on the left and right sides. For this reason, Fig. 1 only the right connecting arm 303 is shown.

[0049] Each link arm 303 is mounted on the seat tube 124. Each link arm 303 is arranged to be pivotable relative to the seat tube 124 about an axis extending in the right / left direction.

[0050] Viewed from a side surface of the vehicle, the front end of each connecting arm 303 is located in front of the seat tube 124. Viewed from a side surface of the vehicle, the rear end of each connecting arm 303 is located behind the seat tube 124.

[0051] The rear end portion of the left link arm 303 is mounted to the front end portion of the left seat stay 302. The left link arm 303 is arranged to pivot about an axis extending in the right / left direction with respect to the left seat stay 302.

[0052] The rear end portion of the right link arm 303 is mounted to the front end portion of the right seat stay 302. The right link arm 303 is arranged to be pivotable relative to the right seat stay 302 about an axis extending in the right / left direction.

[0053] The suspension 304 is arranged in front of the seat tube 124 and rear of the down tube 123. The upper end portion of the suspension 304 is mounted on the pair of link arms 303. The suspension 304 is arranged to be pivotable with respect to the pair of link arms 303 about an axis extending in the right / left direction. The lower end portion of the suspension 304 is mounted on the bracket 125. The suspension 304 is arranged to be pivotable with respect to the bracket 125 about an axis extending in the right / left direction. The position at which the bracket 125 is mounted on the suspension 304 is in front of the position at which the bracket 125 is mounted on the seat tube 124.

[0054] A drive sprocket 34 is mounted on the drive unit 20 via a support element 33. A chain 36 is wound around the drive sprocket 34 and the driven sprockets 32. [Drive unit].

[0055] With reference to Fig. 2 describes an exemplary configuration of the drive unit 20. Fig. 2 is a cross-sectional view showing the internal structure of the drive unit 20.

[0056] As in Fig. 2, the drive unit 20 comprises a housing 21, a pedal crankshaft 22, a rotating shaft (axle) 23, a speed limiter 24 and an electric motor 25.

[0057] First, the configuration of the housing 21 according to the present embodiment will be described.

[0058] The housing 21 is attached to the bracket 125 ( Fig. 1) by a plurality of elements. The housing 21 includes a first housing 211, a second housing 212, and an inner cover 213. The first housing 211, the second housing 212, and the cover 213 are each formed of a metal material (e.g., an aluminum alloy).

[0059] In the right / left direction, the second housing 212 overlaps the first housing 211 from the right. The first housing 211 is secured to the second housing 212 by a plurality of fasteners. This creates a gap 214 between the first housing 211 and the second housing 212.

[0060] In the right / left direction, the inner cover 213 is overlapped from the right to close the recess of the first housing 211 in which the electric motor 25 is housed. The inner cover 213 is attached to the first housing 211 by a plurality of elements. This creates a space 215 between the left end portion of the first housing 211 and the inner cover 213, which is covered by the first housing 211 and the inner cover 213. The electric motor 25 is housed in the space 215.

[0061] Next, the configuration of the pedal crankshaft 22 according to the present embodiment will be described.

[0062] The pedal crankshaft 22 extends through the housing 21 in the right / left direction of the vehicle. In other words, the central axis CL1 of the pedal crankshaft 22 extends along the right / left direction. Viewed in the axial direction (thrust direction) of the pedal crankshaft 22, the central axis CL1 defines the rotation axis RC1 of the pedal crankshaft 22. The pedal crankshaft 22 rotates around the central axis CL1 with respect to the housing 21.

[0063] The pedal crankshaft 22 is rotatably supported within the housing 21 by a pair of bearings 38L and 38R. One (38L) of the pair of bearings 38L and 38R is arranged on one side along the thrust direction (here, the left side) and is hereinafter referred to as the "first bearing." The other (38R) of the pair of bearings 38L and 38R, however, is arranged on the other side (here, the right side) along the thrust direction and is hereinafter referred to as the "second bearing."

[0064] The first bearing 38L is a roller bearing that includes an inner ring 381, an outer ring 382, ​​and a rolling element 383. The first bearing 38L is arranged so that it does not move along the axial direction with respect to the pedal crankshaft 22. In the Fig. In the example shown in Figure 2, the inner ring 381 of the first bearing 38L is press-fitted into the crankshaft 22. The outer ring 382 of the first bearing 38L is pressed in the left direction by an elastic member 70.

[0065] The second bearing 38R is a roller bearing including an inner ring 384, an outer ring 385, and a rolling element 386. The second bearing 38R rotatably supports the pedal crankshaft 22 via an outer member 52 of a one-way clutch 50 and one or more plain bearings 40, which will be described later.

[0066] The pedal crankshaft 22 extends 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 right and left crank arms (not shown) are mounted on the pedal crankshaft 22. Pedals (not shown) are mounted on the crank arms.

[0067] Next, the configurations of the electric motor 25 and the speed limiter 24 according to the present embodiment will be described.

[0068] The electric motor 25 is housed in and attached to the housing 21. The electric motor 25 generates a driving force that assists the propulsion of the electric bicycle 10. The electric motor 25 includes a stator 251 and a rotor 252.

[0069] The stator 251 includes a plurality of (e.g., fourteen) coils 2512 around which coils 2511 are wound. An iron core 2513 is inserted into each coil 2512. The stator 251 is arranged in the space 215. In this state, the stator 251 is fixed to the first housing 211.

[0070] A support member 253 is mounted on the stator 251. The support member 253 is made of a resin material. A plurality of bus bars 25B are embedded in the support member 253. Each bus bar 25B is connected to a corresponding coil 2511. By controlling the current supply to the bus bars 25B, a magnetic force is generated in the stator 251.

[0071] The rotor 252 is arranged in the stator 251. The central axis CL2 of the rotor 252 runs parallel to the central axis CL1 of the crankshaft 22. In other words, the rotor 252 is arranged parallel to the crankshaft 22. Viewed in the axial direction of the crankshaft 22, the central axis CL2 defines the rotational axis RC2 of the rotor 252.

[0072] The rotor 252 includes a rotor main body 2521 and an output shaft 2522. These are described below. The outer peripheral surface of the rotor main body 2521 is magnetized circumferentially alternately into N-poles and S-poles. In the present embodiment, there are seven N-poles and seven S-poles.

[0073] The output shaft 2522 extends through the rotor main body 2521. The output shaft 2522 is fixed to the rotor main body 2521. In other words, the output shaft 2522 rotates together with the rotor main body 2521.

[0074] The output shaft 2522 is supported by two bearings 42L and 42R so that it can rotate about the central axis CL2 relative to the housing 21. The bearing 42L is fixed to the first housing 211. The bearing 42R is arranged further to the right than the rotor main body 2521 and is fixed to the inner cover 213. The output shaft 2522 extends through the inner cover 213. In the present embodiment, the inner cover 213 and the bearing 42R together support the output shaft 2522 so that the output shaft 2522 is rotatable; however, such a configuration is not essential. For example, the bearing 42R may be provided in the second housing 212, and the output shaft 2522 may be rotatably supported by the bearing 42R and the second housing 212. An output gear 252A is formed in a portion of the output shaft 2522 located in the space 214. The output gear 252A is, for example, a helical gear.

[0075] The speed limiter 24 is housed in the housing 21. Specifically, the speed limiter 24 is arranged in the space 214. The speed limiter 24 includes a transmission shaft 241, a first transmission gear 242, and a second transmission gear 243. In the present embodiment, the transmission shaft 241 is referred to as the "transmission rotating shaft."

[0076] The transmission shaft 241 is arranged in the housing 21. The central axis CL3 of the transmission shaft 241 runs parallel to the central axis CL1 of the pedal crankshaft 22. In other words, the transmission shaft 241 runs parallel to the central axis CL1 of the pedal crankshaft 22. Viewed in the axial direction of the transmission shaft 241, i.e., in the axial direction of the pedal crankshaft 22, the central axis CL3 defines the rotational axis RC3 of the transmission shaft 241.

[0077] The transmission shaft 241 is supported by two bearings 44L and 44R so that it can rotate around the central axis CL3. The bearing 44L is attached to the inner cover 213. In other words, the inner cover 213 supports the rotating shaft 241. The bearing 44R is attached to the second housing 212.

[0078] The first transmission gear 242 is formed, for example, from a plastic material. The first transmission gear 242 is arranged on the transmission shaft 241. The first transmission gear 242 is arranged closer to the bearing 44L than to the bearing 44R in the axial direction of the transmission shaft 241. The first transmission gear 242 meshes with the output gear 252A. As a result, a driving force generated by the electric motor 25 is transmitted from the output gear 252A to the first transmission gear 242. A one-way clutch 244 is provided between the first transmission gear 242 and the transmission shaft 241. As a result, the rotational force of the output gear 252A in the forward rotation direction is transmitted to the transmission shaft 241 via the first transmission gear 242, while the rotational force of the output gear 252A in the reverse rotation direction is not transmitted to the transmission shaft 241.Furthermore, the one-way clutch 244 prevents the rotational force of the pedal crankshaft 22 generated by the rider's human power from being transmitted in the forward rotation direction to the electric motor 25. The first transmission gear 242 is larger in diameter than the output gear 252A and has more teeth than the output gear 252A. In other words, the speed of the first transmission gear 242 is slower than that of the output gear 252A.

[0079] The second transmission gear 243 is made of a metal material (e.g., iron). The second transmission gear 243 is arranged on the transmission shaft 241. The second transmission gear 243 is arranged at a different position than the first transmission gear 242 in the axial direction of the transmission shaft 241. In the present embodiment, the transmission shaft 241 and the second transmission gear 243 are monolithically formed. The second transmission gear 243 rotates together with the transmission shaft 241. It should be noted that the second transmission gear 243 may be fixed to the transmission shaft 241 via a spline connection (or press fit).

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

[0082] The left end (i.e., one end portion) 231 of the connecting shaft 231 is connected to the pedal crankshaft 22 via a gear coupling or the like. Consequently, the connecting shaft 231 rotates together with the crankshaft 22 regardless of whether the pedal crankshaft 22 rotates in the forward or reverse direction.

[0083] A torque detector 232 is provided around the connecting shaft 231. The torque detector 232 is held by the first housing 211.

[0084] The torque detector 232 detects a torque that occurs in the connecting shaft 231 when the rider pedals. The torque detector 232 is a magnetostrictive torque sensor. The torque detector 232 outputs a signal corresponding to the detected torque to a controller mounted on the circuit board 48. Using the torque signal detected by the torque detector 232, the controller knows the rider's pedaling status and thus controls the electric motor 25.

[0085] The torque detector 232 includes a mounting shaft 2321, a coil 2322, a detecting element 2323, and a shield 2324.

[0086] The fixing shaft 2321 is mounted on the outer peripheral surface of the connecting shaft 231 and can rotate relative to the connecting shaft 231. The coil 2322 is arranged on the outer peripheral surface of the fixing shaft 2321. A predetermined voltage is applied to the coil 2322. The detection element 2323 detects a voltage change of the coil 2322 caused by deformation of the connecting shaft 231. As a result, a torque occurring in the connecting shaft 231, that is, a torque occurring in the pedal crank shaft 22, which rotates together with the connecting shaft 231, is detected. The shield 2324 prevents deterioration of the detection accuracy of the detection element 2323. The shield 2324 does not rotate with the connecting shaft 231.

[0087] Next, the configuration of the one-way clutch 50 according to the present embodiment will be described.

[0088] The one-way clutch 50 is arranged on the right side of the torque detector 232 along the axial direction of the pedal crankshaft 22. 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.

[0089] The inner member 51 has a cylindrical shape. The right end (i.e., the other end portion) 231R of the connecting shaft 231 is inserted into the left end (i.e., one end portion) of the inner member 51. The inner member 51 is arranged coaxially with the connecting shaft 231. In this state, the right end 231R of the connecting shaft 231 is connected to the left end of the inner member 51 via a spline connection or the like. As a result, regardless of whether the connecting shaft 231 rotates in the forward or reverse direction, the inner member 51 rotates together with the connecting shaft 231. In other words, regardless of whether the pedal crankshaft 22 rotates in the forward or reverse direction, the inner member 51 rotates together with the pedal crankshaft 22. The connecting shaft 231 and the inner member 51 serve as a crankshaft input shaft that rotates together with the pedal crankshaft 22.

[0090] A ring magnet 46 is attached to the outer peripheral surface of the inner member 51. Viewed in the axial direction of the pedal crankshaft 22, the ring magnet 46 is located in a position that overlaps a portion of the circuit board 48.

[0091] The ring magnet 46 rotates together with the inner member 51. By using a detection element provided on the circuit board 48 to detect a change in the magnetic field caused by the rotation of the ring magnet 46, the rotation of the pedal crank shaft 22 can be detected.

[0092] The outer member 52 has a cylindrical shape. The pedal crankshaft 22 is inserted into the outer member 52. The plain bearing(s) is (are) arranged between the outer member 52 and the pedal crankshaft 22. As a result, the outer member 52 is arranged so that it can rotate coaxially with the pedal crankshaft 22.

[0093] A ratchet mechanism is formed as a one-way clutch mechanism between the outer member 52 and the inner member 51. As a result, a rotational force of the inner member 51 in the forward rotation direction is transmitted to the outer member 52, while the rotational force of the inner member 51 in the reverse rotation direction is not transmitted to the outer member 52. Furthermore, a rotational force of the outer member 52 in the forward rotation direction, which is generated by the rotation of the electric motor 25, is not transmitted to the inner member 51.

[0094] The outer member 52 is supported by the second bearing 38R so that it can rotate relative to the housing 21 about the center axis CL1 of the crankshaft 22. The outer ring 385 of the second bearing 38R is connected to the second housing 212 by a clearance fit, and the inner ring 384 thereof is press-fitted to the outer member 52 of the one-way clutch 50.

[0095] The outer member 52 extends through the second housing 212. The drive sprocket 34 ( Fig. 1) is connected via the support element 33 ( Fig. 1) is attached to a portion of the outer member 52 which is located outside (ie on the right side) of the housing 21.

[0096] The outer member 52 includes a gear 2333. The gear 2333 meshes with a second transmission gear 243 of the speed limiter 24. The gear 2333 has a larger diameter than the second transmission gear 243 and has more teeth than the second transmission gear 243. This means that the speed of the gear 2333 is slower than the speed of the second transmission gear 243.

[0097] The outer member 52 transmits a resultant force, which is a combination of a human force (pedal force) transmitted to the other end portion 231R of the connecting shaft 231 and an auxiliary drive force from the electric motor 25, to the drive sprocket 34. A resultant force output shaft 235 is realized by the outer member 52, which outputs a resultant force combining the human force input via the one-way clutch 50 and the auxiliary drive force input via the gear 2333. The resultant force output shaft 235 is included in the rotating shaft 23.

[0098] The following are based on Fig. 3 to Fig. 14, the first housing 211 and the second housing 212 as well as the inner cover 213 according to the present embodiment are described in more detail.

[0099] Fig. 3 is a perspective view of the inside of the first housing 211. The first housing 211 has a first opening 402 through which one end of the pedal crankshaft 22 is passed, and a recess 404. It should be noted that the second housing 212 also has an opening (second opening) through which another end of the pedal crankshaft 22 is passed. As shown in Fig. 2 (although a perspective view of the second housing 212 with the second opening has been omitted), the second housing 212 is attached to the first housing 211 as if it were a lid for the first housing 211; thus, the second housing 212 and the first housing 211 together form the outside of the housing 21.

[0100] In the first housing 211, the electric motor 25 is housed in the recess 404. Therefore, no cover is required to cover the stator of the electric motor 25.

[0101] The recess 404 is formed by a wall 406 that fits around the periphery of the electric motor 25 when the electric motor 25 is housed in the recess 404. In the example shown, a portion (i.e., substantially the front half) of the wall 406, corresponding to the "front" of the first housing 211, is formed monolithically with the first housing 211. The remaining part (i.e., substantially the rear half) of the wall 406, however, is provided as a structure within the first housing 211.

[0102] As will be described in detail later, the wall 406 serves as a portion of an alignment structure that determines the relative positioning between the inner cover 213 and the first housing 211. Assuming that the inner cover 213 has a substantially planar, circular shape, the alignment structure uniquely determines the position of the inner cover 213 along the longitudinal direction and the right-to-left direction within the first housing 211, while the inner cover 213 determines the position with respect to the rotation angle. The wall 406 can be used to determine the positions of the inner cover 213 in the longitudinal direction and in the right / left direction within the first housing 211. Although Fig. While Figure 3 shows that the wall 406 is provided around the entire circumference of the electric motor 25, the wall 406 need not extend around the entire circumference. For example, it may extend around approximately two-thirds of the entire circumference of the electric motor 25.

[0103] In addition to the recess 404, the first housing 211 also contains a further recess 408. The further recess 408 is located in an area substantially enclosed by the dashed line. If the first opening 402 is considered the bottom, the further recess 408 tapers toward the bottom. In other words, the further recess 408 would correspond to the inner surface of a circular truncated cone whose upper base is the first opening 402.

[0104] Fig. 4 is a perspective view of the outside of the first housing 211. Viewed from the outside, a convex portion 424 and another convex portion 428 appear in the first housing 211, which correspond to the recess 404 and the further recess 408, respectively.

[0105] Fig. 5 is a cross-sectional view for describing the relationship between the recess 404 and the further recess 408. Fig. 5 shows the inclined surfaces 408a and 408b, which are portions of the further recess 408. The area where the recess 404 and the inclined surface 408a meet defines the upper end of a portion of the wall 406. In other words, the wall 406 is formed as a ridge. Since the recess 404 and the further recess 408 define the back surface structure of the convex portion 424 and the further convex portion 428 (which form the outer side), sufficiently high rigidity can be ensured. Since the inner cover 213 is supported using the recess 404 and the further recess 408 as portions of the wall 406, the rigidity of the wall 406 can be increased, thereby firmly supporting the inner cover 213.

[0106] As in Fig. As shown in Fig. 5, the inner cover 213 is surrounded by the first casing 211 and the second casing 212 without being exposed to the outside of the power unit 20. In other words, the inner cover 213 is enclosed within the power unit 20. Since the inner cover 213 is enclosed without being exposed to the outside, the parts of the casing that need to be painted at all are reduced to two, that is, the first casing 211 and the second casing 212. Furthermore, the casing parts that need to be waterproofed at all are reduced to two, that is, the first casing 211 and the second casing 212. This can reduce the production cost.

[0107] Next, the inner cover 213 is described with reference to Fig. 6 described in detail.

[0108] Fig. 6 is a perspective view of the inside of the first housing 211 with the inner cover 213 mounted thereon. The electric motor 25 is housed in the recess 404 of the first housing 211. The inner cover 213 is mounted to cover at least a portion of the electric motor 25. The inner cover 213 has an opening 440 through which the output shaft 2522 of the electric motor 25 extends in the "right" direction. In this description, the opening 440 may be referred to as the "third opening."

[0109] The area of ​​the electric motor 25 covered by the inner cover 213 may be substantially the entire area of ​​the electric motor 25, except for the through hole through which the output shaft 2522 passes, the through hole through which the wiring of the electric motor 25 passes, and any other required gaps, for example.

[0110] Together with the bearing 44L mounted on the inner cover 213, the inner cover 213 supports one end of the transmission shaft (gear rotation shaft) 241. As previously described, the inner cover 213 is supported on the wall 406 of the recess 404, which is a highly rigid portion; therefore, misalignment of the inner cover 213 can be suppressed. This also suppresses misalignment of the transmission shaft 241 held by the inner cover 213. Fig. 6, the output gear 252A and the like provided in connection with the transmission shaft 241 are not shown.

[0111] The transmission shaft 241 receives a driving force generated by the electric motor 25 via the output gear 252A, the first transmission gear 242, and the one-way clutch 244. If the transmission shaft 241 is misaligned (offset), the engagement between the output gear 252A and the first transmission gear 242 may be impaired, so that the driving power may not be transmitted properly. In the present embodiment, the drive unit consists of only the two housing parts, that is, the first housing 211 and the second housing 212, unlike a conventional drive unit whose outer parts are composed of three or more parts. Moreover, the inner cover 213 is provided to support the transmission shaft 241 at a position of high rigidity to prevent deflection or the like, whereby misalignment (offset) of the transmission shaft 241 can be prevented.In addition, by providing a through hole in the inner cover 213 through which the output shaft 2522 of the electric motor 25 is passed, and by setting the position at which the transmission shaft 241 is to be held, the distance between the two shafts is set, whereby the inter-shaft accuracy can be improved.

[0112] In the present embodiment, one reason for providing the inner cover 213 is to support the transmission shaft 241 with high precision. Although the inner cover 213 also has the function of a "lid" covering the electric motor 25, this function is not essential. Accordingly, the function of the inner cover 213 of supporting the transmission shaft 241 can be separated from its function as a "lid" covering the electric motor 25, so that their respective functions can be realized by more than one element. For example, the function of the inner cover 213 of supporting the transmission shaft 241 can be realized by using a metal frame (supported by the high-rigidity wall 406) to fix the bearing 44L and holding the transmission shaft (gearbox rotating shaft) 241 at one end.In this case, the metal frame is included in the meaning of the "inner cover" as used in this description. Its function as a "cover" can be realized, for example, by adding a resin cover. A resin cover can be processed relatively easily, even in a complex shape. It can be molded to cover the other sections of the electric motor 25 while providing the required gaps.

[0113] In Fig. 6, a portion of the pedal crankshaft 22 is shown for descriptive purposes. This relates to the physical arrangement and configuration of the inner cover 213, as described below. With reference to Fig. 7 The arrangement and configuration are described below.

[0114] Fig. 7 is a plan view for describing the relative positioning between the inner cover 213, the pedal crankshaft 22, and the transmission shaft 241. A portion 460 of an outer peripheral edge 462 of the inner cover 213 extends between the pedal crankshaft 22, indicated by dashed lines, and the transmission shaft 241. As used herein, the “outer peripheral edge” refers only to the edge of the inner cover 213. The inner cover 213 can have any shape and is not limited to a circle.

[0115] As in Fig. 7, when the inner cover is viewed from a direction parallel to the output shaft 2522 of the electric motor 25, the outer peripheral edge 462 of the inner cover 213 extends around the circumference of the electric motor 25. The inner cover 213 does not extend to the pedal crankshaft 22 and is relatively small in size, which can increase the rigidity of the inner cover 213 itself.

[0116] The inner cover 213 is fixed to the first housing 211 at a plurality of locations F1 to F3. In the present embodiment, the positions F1 to F3 are all located on the wall 406. Since the inner cover 213 is fixed at the positions F1 to F3 using the wall 406 (which has high rigidity) between the pedal crankshaft 22 and the transmission shaft 241 and is further supported along the wall 406, the deflection of the inner cover 213 can be suppressed. Also, due to the high rigidity of the inner cover 213, misalignment of the transmission shaft 241 supported by the inner cover 213 is further suppressed.

[0117] Although positions F1 to F3 can be chosen arbitrarily, they are preferably located near, for example, the transmission shaft 241 and the output shaft 2522 of the electric motor 25. The closer to the transmission shaft 241 and the output shaft 2522 of the electric motor 25, the higher the rigidity near each shaft can be. Screws can be used for fastening, or mounting pins can be pressed in.

[0118] Before attaching the inner cover 213 to the wall 406, an alignment is performed to determine the relative positioning between the inner cover 213 and the first housing 211. This alignment will be described later.

[0119] In connection with the attachment of the inner cover, a configuration without the wall 406 provided between the recess 404 and the further recess 408 ( Fig. 3) is possible. An example of such a configuration may be when the inner cover 213 extends through the entire interior of the first housing 211, so that it is held, for example, only by the inner surface of the first housing 211. In such an example, however, the inner cover may sag, potentially causing misalignment of the transmission shaft 241. On the other hand, thickening the inner cover 213 to prevent sagging of the inner cover would increase both weight and cost. Therefore, the configuration according to the present embodiment is preferable.

[0120] Fig. 8 shows a circuit board 48 provided in the first housing 211. A drive circuit for driving the electric motor 25 is mounted on the circuit board 48. The circuit board 48 is provided on the "right" side of the inner cover 213. For clarity, the surface of the inner cover 213 facing the electric motor 25 is referred to as the "first surface" and the opposite surface as the "second surface." The circuit board 48 is arranged in a space within the first housing 211 that is located on the second surface side. Thus, the electric motor 25 and the circuit board 48 are not assembled together, and the circuit board 48 is arranged in a space different from the recess 404 in which the electric motor 25 is housed. This allows the volume of the recess 404 to be reduced, thereby increasing the rigidity of the wall 406 of the recess 404.In the present embodiment, the circuit board 48 and the inner cover 213 are provided between the electric motor 25 and the engagement position between the output shaft 2522 and the transmission shaft 241. This allows for the grease to be prevented from penetrating the recess 404 in which the electric motor 25 is disposed, even if grease (which may be injected to prevent wear at the engagement position between the output shaft 2522 of the electric motor 25 and the transmission shaft 241) spreads or drips. Since the geometric area in which the inner cover 213 covers the electric motor 25 is enlarged, the penetration of grease can be more effectively prevented.

[0121] The above description illustrates that the circuit board 48 is provided in the first housing 211. However, as long as the above-mentioned relative positioning can be maintained, the circuit board 48 can be provided in the second housing 212 instead of the first housing 211. In other words, as long as the above-mentioned relative positioning within the housing of the drive unit 20 can be maintained, the circuit board 48 can be arranged in either the first housing 211 or the second housing 212.

[0122] In order to protect the circuit on the circuit board 48, a cover made of resin, for example, can be provided on the “right” side of the circuit board 48.

[0123] Next, the alignment process performed when assembling the inner cover 213 onto the first housing 211 will be described.

[0124] The first housing 211 according to the present embodiment includes an alignment structure for achieving alignment. The "alignment structure" is a structure in which the inner cover 213 fits into the wall 406 or a structure in which a striker is used to perform alignment. In the present embodiment, alignment structures are provided at two locations. Specifically, a structure in which the inner cover 213 fits into the wall 406 (one location) and a structure in which a striker is used to achieve alignment (one location) may be provided; alternatively, structures in which a striker is used to achieve alignment may be provided at two locations.

[0125] Fig. 9 shows an alignment structure 500 in which the inner cover 213 is fitted into the wall 406. Fig. 10 is an enlarged view of the alignment structure 500. A first guide 510 protrudes to the "left" from the first surface (i.e., the "left" surface) of the inner cover 213 and fits into a second guide 211a on the wall 406. The first guide 510 and the second guide 211a are provided on the inner cover 213 and the wall 406, respectively, so that they are brought into contact when the inner cover 213 is properly inserted into the wall 406.

[0126] For ease of explanation, assume that the shape of the first guide 510 on the inner cover 213 is circular on the first surface, and that the second guide 211a on the wall 406 is also circular. Since the first guide 510 has a diameter of 100 mm, the second guide 211a has a diameter of approximately 100.1 mm. The first guide 510 and the second guide 211a fit together longitudinally substantially without any rattling. The alignment structure 500 as such may be referred to herein as a "tenon joint structure (fitting piece)."

[0127] Since the pin connection structure is formed by the first guide 510 of the inner cover 213 and the second guide 211a of the wall 406, the first guide 510 on the opposite inner cover 213 can also be omitted at any location where the wall 406 is not provided on the circumference of the electric motor 25.

[0128] Next, a structure that uses a firing pin to achieve alignment is described.

[0129] Fig. 11A is a diagram for describing a method for determining an alignment hole(s) using a striker(s). The following description illustrates an example in which a first hole and a second hole are formed in the inner cover 213 and the wall 406, respectively, and a striker extends through the first hole into the second hole to achieve alignment. Fig. 12 is a cross-sectional view showing a straight striker pin 502 inserted into a first hole 213a in the inner cover 213 and a second hole 406a in the wall 406. In one example, such a striker pin 502 may be used to fix the position of the inner cover 213 relative to the first housing 211, as described below.

[0130] In Fig. 11A, the position of the rotational center of the pedal crankshaft 22 is designated by "P" and the rotational center of the transmission shaft 241 by "Q". The same applies to Fig. 11B and Fig. 11C, which will be referred to later.

[0131] The inventors considered where to place the first hole R and found that the first hole R can be advantageously provided (i) on a straight line L2 orthogonal to a line segment L1 connecting the positions P and Q, and (ii) at a position on the outer peripheral edge 462 of the inner cover 213.

[0132] In order to arrange the pedal crankshaft 22 and the transmission shaft 241 with the necessary precision, it is necessary that a misalignment manifests between the position P and the position Q of the rotation centers of the respective shafts, so that alignment using the alignment holes is not possible. Otherwise, alignment using the alignment holes, which is possible, must be equivalent to there being no offset, or no more than a tolerable offset, between the position P and the position Q of the rotation centers of the respective rotating shafts. Now, at any position on the aforementioned straight line L2, a certain distance can be provided between the position P and the position Q.The farther the position on line L2 is chosen from the intersection point between line L1 and line L2, the more likely it is that a displacement will occur between position P and position Q, which is why i) a position on line L2 is assumed. To keep the distances between position P and position Q equal, a point on a line L2 passing through a midpoint on line segment L1 can be assumed.

[0133] On the other hand, the reason why ii) a position at the outer peripheral edge 462 is adopted is that alignment of the inner cover 213 relative to the first housing 211 can be achieved, or more specifically, that the inner cover 213 can support the transmission shaft 241 with high precision.

[0134] Alignment structures may be provided at two positions. However, in the case where the aforementioned tenon joint structure is also provided, an alignment structure using a striker pin should be provided at only one position.

[0135] According to the present embodiment, the inner cover 213 is substantially circular, and the aforementioned tenon joint structure is adopted for the inner cover 213 and the inner wall 406. This leaves the inner cover 213 with only one degree of freedom in the direction of rotation. Therefore, a position on the outer peripheral edge 462 farthest from the center position is selected for alignment. By using the tenon joint structure to achieve alignment between the inner cover 213 and the wall 406, and further by using the striker pin to achieve alignment with respect to the relative rotation angle between the inner cover 213 and the wall 406, the alignment of the transmission shaft 241 as held by the inner cover 213 can also be easily achieved.

[0136] As for the second hole, the second hole may be provided at a location on the wall 406 opposite to the position of the first hole when the inner cover 213 is fixed in the correct position.

[0137] Therefore, by performing alignment with a first hole provided at a location located on the outer peripheral edge 462 of the inner cover 213 and away from the transmission shaft 241 and the pedal crankshaft 22, it is possible to align the transmission shaft 241 and the pedal crankshaft 22 so that they can be placed in their respective expected positions. Since the inter-shaft distance between the transmission shaft 241 and the pedal crankshaft 22 can be maintained within an error limit as intended, smooth power transmission can be realized.

[0138] In Fig. 11A shows a position of the first hole R determined by the above method. Fig. 11A also shows an example of a first hole Ra located at a different position. This first hole Ra is located on a straight line L2a perpendicular to the line segment L1, at a position on the outer peripheral edge 462 of the inner cover 213.

[0139] In an example other than the above example, a position selected solely based on the above condition (ii) (ie, at the outer peripheral edge 462 of the inner cover 213) may be adopted as the position of the alignment hole. Fig. 11B shows the positions of the first hole(s) R and / or Ra located on the outer peripheral edge 462. A position selected solely based on condition (ii) includes any position that also satisfies condition (i) and is intended to allow a wider selection range of the first hole position.

[0140] The inventors also looked for other methods for positioning the first hole that would allow for more precise alignment. Fig. Figure 11C is a diagram describing another position that can be used as the position of an alignment hole. In Fig. 11C, a hole Rb is assumed to be the alignment hole. Specifically, the first hole Rb is located at a position located at the outer peripheral edge 462 and at which the angle θ between the aforementioned line segment PQ and the tangent L3 from the position P to the outer peripheral edge 462 is closest to 90 degrees. In the Fig. 11C, a tangent could also extend from position P to the outer peripheral edge 462, with a tangent point near the Fig. 11A and Fig. 11B. However, based on the above-mentioned condition regarding the angle, the position indicated by “Rb” is selected as the position of the first hole.

[0141] In the case where no pin connection structure is provided, alignment structures with a striker pin may be provided at two locations. In this case, the distance between the alignment structures at two locations should preferably be as long as possible. Alignment between the transmission shaft 241 and the pedal crankshaft 22 can be easily achieved even if alignment structures with a striker pin are provided at two locations, thereby achieving similar effects as described above.

[0142] Next, with reference to Fig. 13 and Fig. 14 modifications of alignment structures using a firing pin are described.

[0143] Fig. Fig. 13 shows a first modification of an alignment structure using a striker pin. The inner cover 213 includes a projection 213b. The projection 213b serves as a striker pin that penetrates into a hole or recess 406b in the wall 406, thereby achieving alignment between the inner cover 213 and the wall 406. The position at which the projection 213b is to be attached can be determined using the method described with reference to Fig. 9. With this modification, it is not necessary to form a through hole in the inner cover. It is also not necessary to form a through hole in the wall 406.

[0144] Fig. 13 shows that the inner cover 213 has the protrusion 213b, while the wall 406 or the first housing 211 has the recess 406b. However, it may also be that the inner cover 213 has the recess and the wall 406 or the first housing 211 includes the protrusion.

[0145] Fig. Figure 14 shows a second modification of an alignment structure using a striker pin. A recess 530 is provided in the inner cover 213. Since the striker pin 510 fits into the recess 530 and also into a recess 520 in the wall 406, alignment between the inner cover 213 and the wall 406 is achieved. With this modification, it is not necessary to provide through holes in the inner cover 213 and the wall 406.

[0146] The above-mentioned firing pin and projection 213b, which serves as a firing pin, may have any desired shape. The projection 213b may typically have a straight shape. However, one end of the projection 213b may be tapered. Fig. The firing pin 502 shown in Figure 12 may also be tapered.

[0147] Thus, an illustrative embodiment of the present invention has been described above. However, the present invention is not limited to the above-described embodiment. Although the above-described embodiment illustrates, for example, an electric bicycle with suspension, the present invention can also be suitably applied to an electric bicycle without suspension.

[0148] Although the above-described embodiment illustrates a drive unit of a type in which human power and auxiliary power of the electric motor 25 are merged at a part rotating coaxially with the pedal crankshaft 22 (merge-at-crank type), the present invention is not limited thereto. The present invention is also suitably applicable to drive units of a type in which human power and auxiliary power are merged by a chain (merge-at-chain type). In the case of the merge-at-chain type, the outer member 52 does not have a gear 2333 for receiving the auxiliary drive power from the electric motor 25.

[0149] Therefore, an illustrative embodiment of the present invention has been described above.

[0150] A drive unit according to an embodiment of the present invention is a drive unit 20 mountable on a bicycle frame 12 of an electric bicycle 10 to generate a driving force transmitted to a wheel 14R of the electric bicycle.The drive unit 20 includes: a housing 21; an electric motor 25 disposed in the housing 21; a crankshaft 22 extending through the housing 21 along a right / left direction of the electric bicycle 10 and rotatably supported by the housing 21; a tubular connecting shaft 231 through which the crankshaft 22 extends and which transmits pedaling force from one end portion 231L to another end portion 231R, the one end portion 231L being coupled to the crankshaft 22; a one-way clutch 50 for transmitting the pedaling force transmitted to the other end portion 231R of the connecting shaft 231 to a drive sprocket 34; and a speed limiter 24 having a gear rotating shaft 241 for reducing the speed generated by the electric motor 25 to increase an output torque of the electric motor 25.The housing 21 comprises: a first housing 211 with a first opening 402 through which one end of the pedal crankshaft 22 is passed, and a recess 404 in which the electric motor 25 is housed; a second housing 212 with a second opening through which another end of the pedal crankshaft 22 is passed, the second housing 212 and the first housing 211 together forming an outer side of the housing 21; and an inner cover 213 covering at least one end portion of the electric motor 25d housed in the recess 404 of the first housing 211, the inner cover 213 having a third opening 440 through which an output shaft 2522 of the electric motor 25 is passed. The inner cover 213 rotatably supports the gear rotating shaft 241 of the speed limiter 24, with a portion 460 of an outer peripheral edge 462 of the inner cover 213 extending between the gear rotating shaft 241 and the pedal crank shaft 22.The recess 404 of the first housing 211 includes a wall 406 extending around the periphery of the electric motor 25, which wall 406 supports the inner cover 213. The inner cover 213 is supported by the wall 406 of the recess 404, which is a highly rigid portion, thereby suppressing misalignment of the inner cover 213. This can suppress misalignment of the gear rotating shaft 241 of the speed limiter 24, which is supported by the inner cover 213.

[0151] In one embodiment, the first housing 211 may have an inclined surface 408a between the recess 404 and the first opening 402, extending from the first opening 402 to the wall 406. In the first housing 211 with the inclined surface 408a corresponding to the wall 406, the rigidity of the wall 406 may be increased.

[0152] In one embodiment, the first housing 211 includes a further recess 408 with the first opening 402 at a bottom. The inclined surface 408a may be a portion of the further recess 408. Because the wall 406 of the recess 404, which accommodates the electric motor 25, is connected to the further recess 408, the rigidity of the wall 406 of the recess 404, which accommodates the electric motor 25, can be increased.

[0153] In one embodiment, when the inner cover 213 is viewed in a direction parallel to the output shaft 2522 of the electric motor 25, the outer peripheral edge 462 of the inner cover 213 may extend around the circumference of the electric motor 25. The inner cover 213 does not extend beyond the pedal crankshaft 22 and is small in size, thereby increasing the rigidity of the inner cover 213. Because the inner cover 213 has high rigidity, misalignment of the gear rotating shaft 241 of the speed limiter 24, which is held by the inner cover 213, can be suppressed.

[0154] In one embodiment, the outer peripheral edge 462 of the inner cover 213 can be secured to the wall 406 at multiple locations. Because the inner cover 213 is secured to the wall 406 at multiple positions, deflection of the inner cover 213 can be suppressed.

[0155] In one embodiment, the inner cover 213 can rotatably support the rotating shaft 2522 of the electric motor 25. The inner cover 213 supports the gear rotating shaft 241 of the speed limiter 24 and the output shaft 2522 of the electric motor 25. Since both the gear rotating shaft 241 of the speed limiter 24 and the output shaft 2522 of the electric motor 25 are held by a single part, misalignments between the gear rotating shaft 241 of the speed limiter 24 and the output shaft 2522 of the electric motor 25 can be suppressed.

[0156] In one embodiment, the drive unit 20 may further include an alignment structure for determining the relative positioning between the inner cover 213 and the first housing 211. By aligning the inner cover 213 and the first housing 211, alignment between the gear rotating shaft 241 of the speed limiter 24 and the pedal crankshaft 22 can be achieved, thereby realizing a smooth power transmission.

[0157] In one embodiment, the inner cover 213 may include a protrusion 213b or a recess for determining a position of the inner cover 213 relative to the first housing 211, wherein the first housing 211 includes a recess 406b or a projection for engaging the protrusion 213b or the recess. By aligning the inner cover 213 and the first housing 211 through engagement of the protrusion and the recess, a more precise alignment between the gear rotating shaft 241 of the speed limiter 24 and the pedal crankshaft 22 can be achieved, thereby realizing a smooth power transmission.

[0158] In one embodiment, the inner cover 213 may have a first hole 213a and the first housing 211 may have a second hole 406a; and a striker pin 502 may extend through the first hole 213a into the second hole 406a. By aligning the inner cover 213 and the first housing 211 using the striker pin 502, a more precise alignment between the gear rotating shaft 241 of the speed limiter 24 and the pedal crankshaft 22 can be achieved, thereby realizing a smooth power transmission.

[0159] In one embodiment, the inner cover 213 and the wall 406 may include a pin-and-tenon joint structure 500, in which the inner cover 213 is fitted into the wall 406. By aligning the inner cover 213 and the first housing 211 via the pin-and-tenon joint structure (counterpart) 500, a connection between the gear rotating shaft 241 of the speed limiter 24 and the pedal crankshaft 22 can be achieved, thereby realizing a smooth power transmission.

[0160] In one embodiment, the inner cover 213 and the wall 406 have a pin-and-tenon joint structure 500 in which the inner cover 213 is rotatable relative to the wall 406. The inner cover 213 includes a first hole 213a, and the first housing 211 includes a second hole 406a. A firing pin 502 extends through the first hole 213a into the second hole 406a. The first hole 213a (first hole R) may be located at a location on a straight line L2 that is orthogonal to a line segment L1 connecting the pedal crankshaft 22 and the transmission rotating shaft 241 of the speed limiter 24, and that is located on the outer peripheral edge 462.By providing the first hole 213a (first hole R) at a position located on the outer peripheral edge 462 and away from the gear rotating shaft 241, the misalignment of the gear rotating shaft 241 connected thereto can be reduced even if an offset occurs during an alignment operation with the striker pin 502.

[0161] In one embodiment, the inner cover 213 and the wall 406 have a pin-and-tenon joint structure in which the inner cover 213 can rotate relative to the wall 406. The inner cover 213 includes a first hole 213a, and the first housing 211 includes a second hole 406a. A firing pin 502 extends through the first hole 213a into the second hole 406a. The first hole 213a (first hole Rb) can be located at a location located on the outer peripheral edge 462 and at which an angle θ between a line segment L1 connecting the pedal crankshaft 22 and the gear rotating shaft 241 of the speed limiter 24 and a tangent L3 from the pedal crankshaft 22 to the outer peripheral edge 462 is closest to 90 degrees.By providing the first hole 213a (first hole Rb) at a position located on the outer peripheral edge 462 and away from the gear rotating shaft 241, the misalignment of the gear rotating shaft 241 connected thereto can be reduced even if an offset occurs during an alignment operation with the striker pin 502.

[0162] In one embodiment, the drive unit 20 further includes a circuit board 48 on which a drive circuit for driving the electric motor 25 is mounted. The inner cover 213 includes a first surface and a second surface. The first surface is a surface facing the electric motor 25, and the second surface is a surface opposite the first surface. Within the housing 21, the circuit board 48 can be arranged in a space located on the second surface side of the inner cover 213. The circuit board 48 is arranged at a location different from the recess 404 for receiving the electric motor 25. This allows the recess 404 to be small, thereby increasing the rigidity of the wall 406 of the recess 404.

[0163] In one embodiment, the inner cover 213 may be enclosed by the first housing 211 and the second housing 212 without being exposed to the outside of the drive unit 20. Since the inner cover 213 is not exposed to the outside, the parts of the housing 21 that require painting are reduced to two, namely, the first housing 211 and the second housing 212. Furthermore, the parts of the housing 21 that require the application of a waterproof sealant are reduced to two, namely, the first housing 211 and the second housing 212. This can reduce production costs.

[0164] In one embodiment, the inner cover 213 may be enclosed by the first housing 211 and the second housing 212. Since the inner cover 213 is enclosed without being exposed to the outside, the parts of the housing 21 that require painting at all are reduced to two, namely, the first housing 211 and the second housing 212. Furthermore, the parts of the housing that require the application of a waterproof sealant are reduced to two, namely, the first housing 211 and the second housing 212. This can reduce production costs.

[0165] An electric bicycle according to an embodiment of the present invention includes a drive unit 20 according to any one of the aforementioned embodiments. Since the gear rotating shaft 241 of the speed limiter 24 is supported by the inner cover 213, an electric bicycle 10 can be realized in which displacement of the gear rotating shaft 241 is suppressed in the drive unit 20.

[0166] The present invention is particularly useful in the field of electric bicycles and drive units incorporated into electric bicycles. List of reference symbols 10 electric bikes 12 bicycle frames 14R wheel 20 drive unit 21 housings 22 Crankshaft 24 rev limiter 241 Gearbox rotating shaft 25 electric motor 2525 output shaft 34 Drive sprocket 48 circuit board 50 One-way clutch 211 first housing 212 second housing 213 inner cover 213a first hole 213b projection 231 tubular connecting shaft 231L one end section 231R another end section 402 first opening 404 recess 406 Wall 406a second hole 406b recess 408 further recess 408a inclined surface 440 third opening 462 outer peripheral edge 500 tenon joint structure 502 firing pin L1 line segment L2 Straight L3 tangent Θ angle

Claims

[1] Drive unit (20) mountable on a bicycle frame (12) of an electric bicycle (10) to generate a driving force transmitted to a wheel (14R) of the electric bicycle (10), the drive unit (20) comprising: a housing (21); an electric motor (25) arranged in the housing (21); a pedal crankshaft (22) extending through the housing (21) along a right / left direction of the electric bicycle (10) and rotatably supported by the housing (21); a tubular connecting shaft (231) through which the pedal crankshaft (22) extends and which transmits a pedal force from one end portion (231L) to another end portion (231R), wherein said one end portion (231L) is coupled to said pedal crankshaft (22); a one-way clutch (50) for transmitting the pedal force transmitted to the other end portion (231R) of the connecting shaft (231) to a drive sprocket (34); and a speed limiter (24) with a gear rotating shaft (241) with which the speed generated by the electric motor (25) is reduced in order to increase an output torque of the electric motor (25), wherein the housing (21) comprises: a first housing (211) having a first opening (402) through which one end of the pedal crankshaft (22) is passed, and a recess (404) in which the electric motor (25) is housed; a second housing (212) having a second opening through which another end of the pedal crankshaft (22) is passed, the second housing (212) and the first housing (211) together forming an outer side of the housing (21); and an inner cover (213) covering at least a portion of the electric motor (25) housed in the recess (404) of the first housing (211), the inner cover (213) having a third opening (440) through which an output shaft (2522) of the electric motor (25) is passed, wherein the inner cover (213) rotatably supports the gear rotating shaft (241) of the speed limiter (24), wherein an outer peripheral edge (462) of the inner cover (213) extends between the gear rotating shaft (241) and the pedal crankshaft (22); wherein the recess (404) of the first housing (211) comprises a wall (406) extending around a circumference of the electric motor (25), the wall (406) holding the inner cover (213), where: the inner cover (213) has a projection (213b) serving as a striker, and the wall (406) or the first housing (211) has a recess (406b) for engaging with the projection (213b) of the inner cover (213), wherein the projection (213b) is configured to penetrate into the recess (406b) of the wall (406) or the first housing (211) to thereby achieve alignment between the inner cover (213) and the wall (406) or between the inner cover (213) and the first housing (211), or the inner cover (213) has a recess, the wall (406) or the first housing (211) has a projection which serves as a striking pin for engagement with the recess of the inner cover (213), wherein the projection of the wall (406) or of the first housing (211) is configured to penetrate into the recess of the inner cover (213) to thereby achieve alignment between the inner cover (213) and the wall (406) or between the inner cover (213) and the first housing (211). [2] A drive unit (20) mountable on a bicycle frame (12) of an electric bicycle (10) to generate a driving force transmitted to a wheel (14R) of the electric bicycle (10), the drive unit (20) comprising: a housing (21); an electric motor (25) arranged in the housing (21); a pedal crankshaft (22) extending through the housing (21) along a right / left direction of the electric bicycle (10) and rotatably supported by the housing (21); a tubular connecting shaft (231) through which the pedal crankshaft (22) extends and which transmits a pedal force from one end portion (231L) to another end portion (231R), wherein said one end portion (231L) is coupled to said pedal crankshaft (22); a one-way clutch (50) for transmitting the pedal force transmitted to the other end portion (231R) of the connecting shaft (231) to a drive sprocket (34); and a speed limiter (24) with a gear rotating shaft (241) with which the speed generated by the electric motor (25) is reduced in order to increase an output torque of the electric motor (25), wherein the housing (21) comprises: a first housing (211) having a first opening (402) through which one end of the pedal crankshaft (22) is passed, and a recess (404) in which the electric motor (25) is housed; a second housing (212) having a second opening through which another end of the pedal crankshaft (22) is passed, the second housing (212) and the first housing (211) together forming an outer side of the housing (21); and an inner cover (213) covering at least a portion of the electric motor (25) housed in the recess (404) of the first housing (211), the inner cover (213) having a third opening (440) through which an output shaft (2522) of the electric motor (25) is passed, wherein the inner cover (213) rotatably supports the gear rotating shaft (241) of the speed limiter (24), wherein an outer peripheral edge (462) of the inner cover (213) extends between the gear rotating shaft (241) and the pedal crankshaft (22); wherein the recess (404) of the first housing (211) comprises a wall (406) extending around a circumference of the electric motor (25), the wall (406) holding the inner cover (213), wherein the inner cover (213) has a recess (530) and the wall (406) has a recess (520), wherein a striker pin (510) penetrates into the recess (530) of the inner cover (213) and into the recess (520) of the wall (406) and thus achieves alignment between the inner cover (213) and the wall (406). [3] Drive unit (20) according to claim 1 or 2, wherein the first housing (211) has an inclined surface (408a) between the recess (404) and the first opening (402) extending from the first opening (402) to the wall (406). [4] Drive unit (20) according to claim 3, wherein, the first housing (211) comprises a further recess (408) with the first opening (402) on a bottom side; and the inclined surface (408a) is a portion of the further recess (408). [5] The drive unit (20) according to any one of claims 1 to 4, wherein, when the inner cover (213) is viewed in a direction parallel to the output shaft (2522) of the electric motor (25), the outer peripheral edge (462) of the inner cover (213) extends around the circumference of the electric motor (25). [6] Drive unit (20) according to one of claims 1 to 5, wherein the inner cover (213) rotatably supports the output shaft (2522) of the electric motor (25). [7] The drive unit (20) according to any one of claims 1 to 6, further comprising an alignment structure for determining the relative positioning between the inner cover (213) and the first housing (211). [8] The drive unit (20) according to claim 7, wherein the inner cover (213) has a first guide (510) for determining a position of the inner cover (213) relative to the first housing (211), the first housing (211) having a second guide (211a) for engaging the first guide (211a) of the inner cover (213). [9] Drive unit (20) according to one of claims 7 or 8, wherein the inner cover (213) and the wall (406) have a tenon joint structure (500) as an alignment structure in which the inner cover (213) is rotatable relative to the wall (406); either the projection (213b) of the inner cover (213) or the projection of the first housing (211) or the wall (406), or the recesses of the inner cover (213) and the wall (406) is / are located at a position located on a straight line (L2) that is orthogonal to a line segment (L1) that connects the pedal crankshaft (22) and the gear rotating shaft (241) of the speed limiter (24), and that is located on the outer peripheral edge (462). [10] Drive unit (20) according to one of claims 7 or 8, wherein the inner cover (213) and the wall (406) have a tenon joint structure (500) as an alignment structure, in which the inner cover (213) is rotatable relative to the wall (406); either the projection of the inner cover (213) or the projection of the first housing (211) or the wall (406), or the recesses of the inner cover (213) and the wall (406) is / are located at a position which is located on the outer peripheral edge (462) and at which an angle (θ) between a line segment (L1) connecting the pedal crankshaft (22) and the gear rotating shaft (241) of the speed limiter (24) and a tangent (L3) from the pedal crankshaft (22) to the outer peripheral edge (462) is closest to 90 degrees. [11] Drive unit (20) according to one of claims 1 to 10, further comprising a circuit board (48) on which a drive circuit for driving the electric motor (25) is mounted, wherein, the inner cover (213) comprises a first and a second surface; the first surface is a surface facing the electric motor (25); the second surface is a surface opposite the first surface; and within the housing (21) the circuit board (48) is arranged in a space which is located on the side of the second surface of the inner cover (213). [12] Drive unit (20) according to one of claims 1 to 11, wherein the inner cover (213) is surrounded by the first housing (211) and the second housing (212) and is not exposed to the outside of the drive unit (20). [13] Drive unit (20) according to one of claims 1 to 12, wherein the inner cover (213) is enclosed by the first housing (211) and the second housing (212). [14] Electric bicycle (10) comprising the drive unit (20) according to one of claims 1 to 13.

Images