Patent ID: 12195137

DETAILED DESCRIPTION

The power transmission unit for electric bicycles according to an exemplary embodiment shown inFIGS.1and2is a motor unit3including a motor53. The motor unit3is mounted on an electric bicycle1. The electric bicycle1is implemented as an electric assist bicycle. The motor unit3generates auxiliary driving force for the electric bicycle1.

As used herein, the “electric assist bicycle” refers to a bicycle designed to have the motor53generate auxiliary driving force for the electric bicycle1. The electric assist bicycles include not only electric assist bicycles as defined by applicable law but also other electric bicycles to be distinguished from electric assist bicycles by applicable law as well. Also, as used herein, the “auxiliary driving force” refers to additional force (i.e., assist force) to be applied to a wheel11of the electric bicycle1besides the force that the rider of the electric bicycle1applies by pumping pedals17(hereinafter referred to as “pedaling force”).

As used herein, the direction in which the electric bicycle1travels straight (forward) when the electric bicycle1is used in a normal way will be hereinafter referred to as a “forward direction” and the opposite direction thereof will be hereinafter referred to as a “backward direction.” Also, two directions including the forward direction and the backward direction will be hereinafter collectively referred to as “forward/backward directions” and two directions that are perpendicular to the forward/backward directions and aligned with a horizontal plane will be hereinafter referred to as “rightward/leftward directions.” Furthermore, one of the rightward/leftward directions which points to the left with respect to the forward direction will be hereinafter referred to as a “leftward direction” and the other of the rightward/leftward directions which points to the right with respect to the forward direction will be hereinafter referred to as a “rightward direction.”

The electric bicycle1according to this embodiment illustrated inFIG.1includes not only the motor unit3but also a plurality of wheels10,11, forks12, handlebars13, a frame2, a battery14, a saddle15, a pair of crank arms16, and a pair of pedals17.

The electric bicycle1according to this embodiment includes, as the plurality of wheels10,11, a front wheel10and a rear wheel11. The forks12include legs120and a steering column121. The legs120support the front wheel10rotatably. The steering column121extends upward from an upper end portion of the legs120.

The frame2according to this embodiment includes a head tube20, a top tube21, a down tube22, a seat tube23, seat stays24, chain stays25, and a bracket26.

To the head tube20, the steering column121is mounted to be rotatable with respect to the center axis of the head tube20. The handlebars13are mounted on an upper end portion of the steering column121. The rider may change the orientation of the front wheel10by turning the handlebars13to turn the steering column121around the center axis of the head tube20.

A front end portion of the top tube21is connected to the head tube20. A rear end portion of the top tube21is connected to the seat tube23. The saddle15includes a shaft150. The shaft150is mounted on an upper end portion of the seat tube23. The bracket26is connected to a lower end portion of the seat tube23. The down tube22is located under the top tube21. A front-end portion of the down tube22is connected to the head tube20. A rear end portion of the down tube22is connected to the bracket26. The battery14is attached removably to the down tube22. The battery14supplies power to the motor unit3.

To the rear end portion of the top tube21, respective front-end portions of the seat stays24are connected. The chain stays25are located under the seat stays24. Respective rear end portions of the seat stays24are connected to their corresponding rear end portions of the chain stays25. To the connection portion where the seat stays24and the chain stays25are connected together, the rear wheel11is mounted to be rotatable around a right/left axis. As used herein, “to be rotatable around the right/left axis” means being rotatable around a rotational axis that is parallel to the rightward/leftward directions. A rear sprocket18is fixed to the rear wheel11. Respective front-end portions of the chain stays25are connected to the bracket26.

The motor unit3is attached to the bracket26. The motor unit3according to this embodiment is designed to transmit power to only the rear wheel11, out of the front wheel10and the rear wheel11.

The motor unit3includes an input structure30. The input structure30is rotatable around the right/left axis. The pair of pedals17are coupled to the input structure30via the pair of crank arms16. Transmitting the pedaling force, applied to the pedals17, to the input structure30via the pair of crank arms16causes the input structure30to rotate.

The motor unit3according to this embodiment is a biaxial motor unit. As shown inFIG.2, the motor unit3includes two output structures, namely, a first output structure31and a second output structure32, as output structures for outputting the rotational power. Each of the first output structure31and the second output structure32is rotatable around the right/left axis. The first output structure31rotates by being supplied with the rotational power of the input structure30(i.e., the pedaling force). The second output structure32rotates to be powered by the motor53.

The motor unit3according to this embodiment further includes two drive sprockets, namely, a first drive sprocket51and a second drive sprocket52. The first drive sprocket51is fixed to the first output structure31. The first drive sprocket51rotates, along with the first output structure31, around the right/left axis. The second drive sprocket52is fixed to the second output structure32. The second drive sprocket52rotates, along with the second output structure32, around the right/left axis.

As shown inFIG.1, the electric bicycle1according to this embodiment further includes a power transmission medium19. The power transmission medium19transmits, to the rear sprocket18, the rotational power of the first drive sprocket51and the rotational power of the second drive sprocket52. In this embodiment, the power transmission medium19is implemented as an endless chain. The power transmission medium19is hung around the first drive sprocket51, the second drive sprocket52, and the rear sprocket18.

The rotational power of the first output structure31(seeFIG.2), which is rotated by the pedaling force applied to the input structure30, is transmitted to the rear wheel11via the first drive sprocket51, the power transmission medium19, and the rear sprocket18. Transmitting the rotational power of the first output structure31to the rear wheel11in this manner causes the rear wheel11to turn in the direction in which the electric bicycle1travels forward.

The rotational power of the second output structure32, which is rotated by running the motor53, is transmitted to the rear wheel11via the second drive sprocket52, the power transmission medium19, and the rear sprocket18in this order. That is to say, while the rider is pumping the pedals17and the motor53is running, the rotational power of the first output structure31and the rotational power of the second output structure32are transmitted to the rear wheel11via the power transmission medium19and the rear sprocket18. In that case, the resultant force, produced as the sum of the pedaling force applied to the input structure30and the auxiliary driving force of the motor53, causes the rear wheel11to turn in the direction in which the electric bicycle1travels forward.

As shown inFIG.2, the motor unit3according to this embodiment includes not only the motor53but also a case33, a speed reducer mechanism57, and a control board34as well. The case33forms the shell of the motor unit3. The case33is made of a metallic material such as aluminum or stainless steel.

The case33houses the input structure30, the first output structure31, the motor53, the speed reducer mechanism57, the second output structure32, and the control board34. Note that each of the input structure30, the first output structure31, and the second output structure32is housed only partially in the case33.

The case33according to this embodiment includes two members, namely, a first divided part331and a second divided part332. The first divided part331and the second divided part332are arranged side by side in the rightward/leftward direction. The first divided part331according to this embodiment is located on the left of the second divided part332.

The first divided part331is formed as a bottomed tubular member, which is open to the right (i.e., toward the second divided part332). The first divided part331has a first sidewall333and a first peripheral wall334, which protrudes to the right from a peripheral edge of the first sidewall333.

The second divided part332is formed in the shape of a bottomed cylinder, which is open to the left (i.e., toward the first divided part331). The second divided part332has a second sidewall335and a second peripheral wall336, which protrudes to the left from a peripheral edge of the second sidewall335.

The right end face of the first peripheral wall334constitutes a first joint surface337. The left end face of the second peripheral wall336constitutes a second joint surface338. With the first joint surface337and the second joint surface338joined together, the first divided part331and the second divided part332are fixed together with bolts38.

At the front-end portion of the case33, the input structure30and the first output structure31are located. The input structure30is caused to rotate by external force transmitted thereto. The input structure30according to this embodiment includes an input shaft35and a transmission mechanism40. The input shaft35is caused to rotate by the external force transmitted thereto. The input structure30rotates along with the input shaft35. The axial direction of the input shaft35according to this embodiment is parallel to the rightward/leftward direction. The input shaft35penetrates through the first sidewall333of the first divided part331and the second sidewall335of the second divided part332. That is to say, the input shaft35runs through the case33in the rightward/leftward direction.

As shown inFIG.3, the motor unit3according to this embodiment further includes a pair of bearings36,37. The pair of bearings36,37supports the input shaft35to allow the input shaft35to rotate around the right/left axis. Each of the pair of bearings36,37is implemented as a ball bearing. One bearing36, out of the pair of bearings36,37, is attached to the first divided part331and arranged inside the case33. The bearing36directly supports the input shaft35thereon.

The other bearing37, out of the pair of bearings36,37, is attached to the second divided part332and arranged inside the case33. The first output structure31according to this embodiment is provided on the outer periphery of the input shaft35and supports the input shaft35such that the input shaft35is rotatable around the right/left axis. Providing the first output structure31on the outer periphery of the input shaft35reduces a significant increase in the overall size of the motor unit3. The bearing37supports the first output structure31to allow the first output structure31to rotate around the right/left axis. That is to say, the bearing37supports the input shaft35via the first output structure31.

As shown inFIG.2, the pair of crank arms16are respectively fixed to the right and left end portions, protruding out of the case33, of the input shaft35. The pedaling force applied to the pedals17(seeFIG.1) causes the input shaft35to rotate along with the pair of crank arms16.

The transmission mechanism40transmits the rotational power of the input shaft35to the first output structure31, thereby rotating the first output structure31. The transmission mechanism40according to this embodiment includes a transmission member41and a one-way clutch46. The transmission member41has an overall shape of a cylinder that surrounds the input shaft35and is provided on the outer periphery of the input shaft35. The transmission member41and the first output structure31are arranged side by side in the rightward/leftward direction. The transmission member41is located on the left of the first output structure31. The transmission member41is coupled to the input shaft35and rotates along with the input shaft35around the right/left axis. The transmission member41rotates the first output structure31by transmitting the rotational power of the input shaft35to the first output structure31via the one-way clutch46.

As shown inFIG.3, the transmission member41according to this embodiment includes two members, namely, a first member411and a second member412. Each of the first member411and the second member412is formed in the shape of a cylinder, which is concentric with the input shaft35, and is provided on the outer periphery of the input shaft35.

Part of the first member411is located on the left of the first joint surface337and second joint surface338of the case33. Specifically, the first member411according to this embodiment is mostly located on the left of the first joint surface337and second joint surface338, and only its right end portion is located on the right of the first joint surface337and second joint surface338.

The first member411has a fitting portion42. The fitting portion42according to this embodiment is formed on an inner peripheral surface of a left end portion of the first member411. The input shaft35has a fitting portion43. The fitting portion43according to this embodiment is formed on the outer peripheral surface of a region, facing the fitting portion42, of the input shaft35. Each of the fitting portions42,43according to this embodiment is a spline and the fitting portion42is fitted into the fitting portion43, thus coupling the first member411to the input shaft35. That is to say, in this embodiment, the fitting portions42,43together form a coupling portion where the input shaft35and the transmission member41are coupled together. The first member411rotates along with the input shaft35.

A gap39is left between a portion, located on the right of the fitting portion42, of the first member411and the input shaft35. This allows, when the motor unit3is assembled, the input shaft35to be inserted easily into the first member411having the cylindrical shape.

The second member412is arranged beside the first member411in the rightward/leftward direction. The second member412is located between the first member411and the first output structure31. That is to say, the first member411, the second member412, and the first output structure31are arranged in this order along the rotational axis of the input shaft35. The second member412is located on the right of the first joint surface337and second joint surface338of the case33.

The second member412has a fitting portion44. The fitting portion44according to this embodiment is formed on an inner peripheral surface of a left end portion of the second member412. The first member411has a fitting portion45. The fitting portion45according to this embodiment is formed on the outer peripheral surface of a right end portion of the first member411. Each of the fitting portions44,45according to this embodiment is a spline and the fitting portion44is fitted into the fitting portion45, thus coupling the second member412to the first member411and allowing the second member412to rotate along with the first member411. The second member412is coupled to the input shaft35via the first member411.

The first output structure31is located, in the rightward/leftward direction, on the right of the first joint surface337and second joint surface338of the case33. The first output structure31is formed in the shape of a cylinder, which is concentric with the input shaft35, and is provided on the outer periphery of the input shaft35.

A left end portion of the first output structure31is provided on the outer periphery of a right end portion of the second member412. Between the left end portion of the first output structure31and the right end portion of the second member412, the one-way clutch46is located. The one-way clutch46may be implemented as, for example, a rachet one-way clutch. The one-way clutch46allows the rotational power to be transmitted from the second member412to the first output structure31only when the second member412rotates in one direction with respect to the first output structure31.

Specifically, if the rotational velocity of the second member412is higher than the rotational velocity of the first output structure31while the rear wheel11(seeFIG.1) is turning in the forward direction, the one-way clutch46allows the rotational power to be transmitted from the second member412to the first output structure31. That is to say, while the rear wheel11is turning in the forward direction, the one-way clutch46allows the rotational power to be transmitted only from the second member412to the first output structure31, not from the first output structure31to the second member412. This reduces, when the rider stops pumping the pedals17(seeFIG.1) while the motor53(seeFIG.2) is running, the chances of the input shaft35and the crank arms16, coupled to the input shaft35, continuing rotating by being powered by the motor53.

The right end portion of the first output structure31penetrates through the second sidewall335of the second divided part332. As shown inFIG.2, the first drive sprocket51is fixed onto the right end portion, protruding out of the case33, of the first output structure31. The pedaling force applied from the pedals17to the input shaft35via the crank arms16is transmitted to the first drive sprocket51via the first member411, the second member412, the one-way clutch46, and the first output structure31in this order. That is to say, in this embodiment, a human driving force transmission system for transmitting, to the first drive sprocket51, the pedaling force applied from the crank arms16to the motor unit3is formed by the input shaft35, the transmission mechanism40, and the first output structure31.

At the rear of the case33, the motor53, the speed reducer mechanism57, and the second output structure32are located. The motor53is housed in the first divided part331. The motor53includes a motor shaft54, a rotor55, and a stator56.

The axis of the motor shaft54is parallel to the rightward/leftward direction. The left and right end portions of the motor shaft54are respectively supported by a bearing47attached to the first divided part331and by a bearing48attached to the second divided part332to be rotatable around the right/left axis.

The motor shaft54penetrates through the rotor55in the rightward/leftward direction. The rotor55is fixed onto the motor shaft54and rotates, along with the motor shaft54, around the right/left axis. The stator56is provided on the outer periphery of the rotor55. The stator56rotates the rotor55.

The speed reducer mechanism57transmits the rotational power of the motor shaft54to the second output structure32to make the rotational velocity of the second output structure32lower than that of the motor shaft54. The speed reducer mechanism57according to this embodiment includes a gear58and a one-way clutch59. The gear58is rotatable around the right/left axis. On the outer peripheral surface of the gear58, provided is a tooth portion580with a plurality of teeth. In addition, on the outer peripheral surface of a portion, protruding to the right from the rotor55, of the motor shaft54, provided is a tooth portion540with a plurality of teeth. The tooth portion580and the tooth portion540mesh with each other. This allows the rotational power of the motor shaft54to be transmitted to the gear58, thus turning the gear58such that the gear58is interlocked with the motor shaft54. The number of teeth of the tooth portion580is larger than the number of teeth of the tooth portion540.

The second output structure32according to this embodiment is implemented as a shaft, of which the axis is parallel to the rightward/leftward direction. The motor unit3according to this embodiment further includes a pair of bearings60,61. The pair of bearings60,61supports the second output structure32to allow the second output structure32to rotate around the right/left axis. Each of the pair of bearings60,61is implemented as a ball bearing.

The pair of bearings60,61are located inside the case33. One of the pair of bearings60,61is attached to a bearing supporting portion3312, which forms part of the first divided part331. The other bearing61is attached to the second divided part332. The one bearing60may be attached to the first divided part331either directly or indirectly with another member interposed between them. The other bearing61may be attached to the second divided part332either directly or indirectly with another member interposed between them.

Optionally, the bearing supporting portion3312may be provided separately from the first divided part331. In that case, the bearing supporting portion3312is attached to the first divided part331. The bearing supporting portion3312is attached to the first divided part331by either fitting or fixing with a fixing member such as a screw. The bearing supporting portion3312may be made of the same metallic material as the first divided part331. Alternatively, the bearing supporting portion3312may be made of a different material from the first divided part331. For example, if the first divided part331is made of a metallic material, then the bearing supporting portion3312may be made of a resin. This reduces the weight of the bearing supporting portion3312, thus making the motor unit3more lightweight.

The first divided part331includes a motor case portion3313protruding to the left. The motor case portion3313covers the stator56and rotor55of the motor53. To the motor case portion3313, attached is a bearing47of the motor shaft54. The motor case portion3313is in contact with the stator56of the motor53. The heat generated by the stator56is dissipated into the outside air through the motor case portion3313. The motor case portion3313is formed integrally with the first divided part331. Optionally, the motor case portion3313may be provided separately from the first divided part331. In that case, the motor case portion3313is attached to the first divided part331with a fixing member such as a screw.

The motor case portion3313is open to the right (i.e., toward the second divided part332). The stator56of the motor53is arranged in the same space as the internal space of the case33which is formed by the first divided part331and the second divided part332.

The one-way clutch59is provided on the outer periphery of the second output structure32. On the outer periphery of the one-way clutch59, the gear58is provided. That is to say, the one-way clutch59is located between the second output structure32and the gear58. The one-way clutch59according to this embodiment is implemented as a rachet one-way clutch. The one-way clutch59allows the rotational power to be transmitted from the gear58to the second output structure32only when the gear58rotates in one direction with respect to the second output structure32.

Specifically, if the rotational velocity of the gear58is higher than the rotational velocity of the second output structure32while the rear wheel11(seeFIG.1) is turning in the forward direction, the one-way clutch59allows the rotational power to be transmitted from the gear58to the second output structure32. That is to say, while the rear wheel11is turning in the forward direction, the one-way clutch59allows the rotational power to be transmitted only from the gear58to the second output structure32, not from the second output structure32to the gear58. This reduces, when the motor53stops running and the rider pumps the pedals17(seeFIG.1), for example, the chances of the motor shaft54and the rotor55rotating, thus reducing the pedaling force to be applied to turn the rear wheel11, compared to a situation where the rotational power is transmitted from the second output structure32to the gear58.

The right end portion of the second output structure32penetrates through the second sidewall335of the second divided part332. The second drive sprocket52is fixed onto the right end portion, protruding out of the case33, of the second output structure32.

When the rotational power of the gear58is transmitted to the second output structure32via the one-way clutch59, the rotational power of the motor shaft54is transmitted to the second drive sprocket52via the gear58, the one-way clutch59, and the second output structure32in this order. This causes the second drive sprocket52to rotate, thus transmitting the auxiliary driving power of the motor53to the rear wheel11.

When viewed perpendicularly to the rightward/leftward direction, the control board34overlaps at least partially with the gear58. Optionally, the control board34may overlap entirely with the gear58when viewed perpendicularly to the rightward/leftward direction. Providing the control board34at such a position allows the control board34to be brought closer to the torque detection unit62along the axis of the input shaft35, thus enabling the torque detection unit62and the control board34to be interconnected with a shorter cable.

The control board34according to this embodiment is implemented as a printed wiring board. The thickness of the control board34is parallel to the rightward/leftward direction. The control board34has a board surface, which is one of the two surfaces along the thickness of the control board34. The control board34may be arranged such that the board surface of the control board34extends in a direction intersecting with the input shaft35. The control board34is located on the left of the first joint surface337and second joint surface338of the case33. The control board34overlaps with the first member411when viewed perpendicularly to the rightward/leftward direction.

The control board34includes a control unit for controlling the motor53. The control unit controls the operation of the respective elements by executing a program stored in a storage device such as a read-only memory (ROM). The battery14(seeFIG.1) is electrically connected to the control unit such that the control unit is powered by the battery14. The stator56is electrically connected to the control unit. The control board34according to this embodiment includes either a switching element such as a field-effect transistor (FET) or a microcomputer.

The motor unit3according to this embodiment further includes the torque detection unit62, the rotation detection unit63, and a motor rotation detection unit640. The torque detection unit62detects the torque (rotational power) of the input structure30. The rotation detection unit63detects the rotational state (such as a rotational position or the rotational velocity) of the input structure30. The motor rotation detection unit640detects the rotational state (such as a rotational position or the rotational velocity) of the motor53.

Each of the torque detection unit62, the rotation detection unit63, and the motor rotation detection unit640is electrically connected to the control unit. The control unit controls the motor53based the information detected by the torque detection unit62, the rotation detection unit63, and the motor rotation detection unit640. Specifically, on detecting, based on the torque of the first member411as detected by the torque detection unit62, that a torque has been generated in the input structure30, the control unit supplies power to the stator56, thereby running the motor53. In addition, based on the torque of the first member411detected by the torque detection unit62and the rotational position of the motor53detected by the motor rotation detection unit640while the motor53is running, the control unit controls the rotational velocity of the motor shaft54. Furthermore, on detecting, based on the information detected by the rotation detection unit63(such as the rotational position of a detection target90to be described later), that the input structure30is not rotating, the control unit stops supplying electric power to the stator56, thus stopping rotating the motor shaft54.

As shown inFIG.3, the torque detection unit62is provided on the outer periphery of the input structure30. The torque detection unit62according to this embodiment is located on the right of the coupling portion where the input shaft35and the transmission member41are coupled together (i.e., on the right of the fitting portions42,43). Also, the torque detection unit62is located on the left of the second member412and on the left of the first joint surface337and second joint surface338of the case33.

The torque detection unit62according to this embodiment is implemented as a magnetostrictive torque sensor, which includes a magnetostriction generating portion620, a coil621, and a coil housing622. The magnetostriction generating portion620is a member imparted with magnetic anisotropy and is formed on the outer peripheral surface of the first member411. The magnetostriction generating portion620may be formed spirally to define an angle of 45 degrees with respect to the rightward/leftward direction, for example. The coil621is arranged to be somewhat spaced from a region on the outer peripheral surface of the first member411where the magnetostriction generating portion620is provided. The coil housing622is provided to cover the coil621. The coil621and the coil housing622are supported by either the case33or a member attached to the case33, for example.

When the torque of the input shaft35is transmitted to the first member411, the magnetostriction generating portion620provided for the first member411is strained, thus producing a portion with increased permeability and a portion with decreased permeability. Thus, the torque of the first member411may be detected as a piece of information representing the torque of the input shaft35by measuring a difference in inductance of the coil621.

The weight of the rider could be applied as downward force from the pedals17to the input shaft35via the crank arms16. This force would constitute disturbance when the torque of the input shaft35is detected. Also, unlike the second member412, the first member411is not adjacent to the one-way clutch46, thus making the vibration caused by the one-way clutch46hardly transmissible to the first member411. Therefore, the torque of the input shaft35may be detected appropriately by detecting the torque of the first member411as is done in this embodiment.

The rotation detection unit63includes: a detection target630which rotates either along with, or while interlocking with, the input structure30; and a detection unit631for detecting a rotational state (such as a rotational position or rotational velocity) of the detection target630. As used herein, if something “rotates along with” something else, then it means that these two things rotate around the same rotational axis. Also, if something “rotates while interlocking with” something else, then it means that these two things rotate around two different rotational axes. The detection target630according to this embodiment rotates while interlocking with the input structure30.

The rotation detection unit63according to this embodiment includes a rotator632including the detection target630. The rotator632is rotatable around the right/left axis. The rotator632is arranged beside the input structure30in a direction perpendicular to the rightward/leftward direction. The rotational axis of the rotator632and the rotational axis of the input structure30are located at different positions in the direction perpendicular to the rightward/leftward direction.

The rotator632according to this embodiment includes a body633and the detection target630. The body633is a shaft extending parallel to the rightward/leftward direction. The case33includes a pair of supporting portions65,66for supporting the body633such that the body633is rotatable around the right/left axis. One supporting portion65, out of the pair of supporting portions65,66, is provided for the first divided part331, while the other supporting portion66is provided for the second divided part332.

The body633includes a bulge portion634. The bulge portion634is provided as an intermediate portion in the rightward/leftward direction of the body633. The bulge portion634is formed in the shape of a circular disk, which is larger than the rest of the body633when viewed in the rightward/leftward direction. The bulge portion634includes a tooth portion635. The tooth portion635has a plurality of teeth, which are provided on the outer peripheral surface of the bulge portion634.

The second member412includes a tooth portion413. The tooth portion413has a plurality of teeth, which are provided on the outer peripheral surface at a left end portion of the second member412. The tooth portion413rotates around the rotational axis, aligned with the rotational axis of the input shaft35, of the second member412. The tooth portion413meshes with the tooth portion635. This allows the body633(rotator632) to rotate while interlocking with the second member412. That is to say, a rotational member that rotates along with the input shaft35is constituted by the second member412, with which the rotator632rotates to interlock. Note that the rotational member to which the rotator632is coupled may be a member located closer to the input end than the one-way clutch46is in an input transmission system formed by the input shaft35, the transmission mechanism40, and the first output structure31. For example, the rotational member may be the first member411or may also be a part of the input shaft35.

The number of teeth of the tooth portion635is smaller than the number of teeth of the tooth portion413. This makes the rotational velocity of the rotator632higher than the rotational velocity of the second member412when the rotator632rotates while interlocking with the second member412.

The detection target630is attached on the outer peripheral surface of a left end portion of the body633. The detection target630rotates, along with the body633, around the right/left axis. The detection target630according to this embodiment may be implemented as either a member, in which a plurality of magnets are embedded such that the magnetic poles alternate along the circumference thereof, or a magnet, which is magnetized such that the magnetic poles alternate along the circumference thereof.

The detection target630is located on the left of the control board34and overlaps with the torque detection unit62when viewed perpendicularly to the rightward/leftward direction. The control board34overlaps with the torque detection unit62when viewed perpendicularly to the rightward/leftward direction. The detection target630is arranged at a position where the detection target630partially overlaps with the magnetostriction generating portion620and the coil621when viewed perpendicularly to the rightward/leftward direction. Note that the detection target630may overlap with at least one of the magnetostriction generating portion620or the coil621when viewed perpendicularly to the rightward/leftward direction.

Alternatively, the detection target630may also be arranged at a position where either at least a right end portion thereof or only the right end portion thereof overlaps with the magnetostriction generating portion620or the coil621when viewed perpendicularly to the rightward/leftward direction. This allows the detection target630and the control board34to be arranged closer to the first divided part331, thus allowing the space inside the case33to be made effective use of.

The detection unit631according to this embodiment is implemented as a hole integrated circuit (IC) for detecting the magnetic force of the magnets included in the detection target630. The detection unit631is mounted on the left surface, which is one of two surfaces along the thickness, of the control board34. The detection unit631is arranged beside the detection target630in the rightward/leftward direction and faces the detection target630. The detection unit631detects the rotational position of the detection target630by detecting a variation in magnetic field, which is involved with the rotation of the detection target630.

As shown inFIG.2, the motor unit3according to this embodiment further includes a motor detection unit64including a motor rotation detection unit640. The motor detection unit64further includes a rotator641in addition to the motor rotation detection unit640.

The rotator641is attached to the outer peripheral surface of the motor shaft54and rotates along with the motor shaft54around the right/left axis. The rotator641is located between the rotor55and the gear58. The rotator641is located on the left of the control board34and overlaps with the torque detection unit62when viewed perpendicularly to the rightward/leftward direction. The rotator641may be implemented as either a member, in which a plurality of magnets are embedded such that the magnetic poles alternate along the circumference thereof, or a magnet, which is magnetized such that the magnetic poles alternate along the circumference thereof.

The motor rotation detection unit640according to this embodiment is implemented as a hole integrated circuit (IC) for detecting the magnetic force of the magnets included in the rotator641. The motor rotation detection unit640is mounted on the left surface of the control board34. Alternatively, the motor rotation detection unit640may be mounted on the right surface of the control board34.

In this embodiment, the motor rotation detection unit640and the detection unit631of the rotation detection unit63are mounted on the same control board34. This eliminates the need to separately provide cables for connecting the motor rotation detection unit640and the rotation detection unit63to the control board34, thus reducing the number of members to be arranged in the case33and also reducing a significant increase in the overall size of the motor unit3. In addition, in this embodiment, the motor rotation detection unit640and the detection unit631of the rotation detection unit63are mounted on the same surface of the control board34. This facilitates mounting the detection unit631of the rotation detection unit63and the motor rotation detection unit640onto the control board34.

The motor rotation detection unit640is arranged beside the rotator641in the rightward/leftward direction and faces the rotator641. The motor rotation detection unit640detects the rotational position of the rotator641by detecting a variation in magnetic field, which is involved with the rotation of the rotator641.

When the motor unit3is assembled, for example, the members to be arranged in the case33are incorporated from the left (i.e., from the second joint surface338) into the second divided part332, and then the first joint surface337of the first divided part331and the second joint surface338of the second divided part332are joined together. In this embodiment, the detection target630of the rotation detection unit63overlaps with the torque detection unit62when viewed perpendicularly to the rightward/leftward direction (i.e., a direction aligned with the input shaft35) as shown inFIG.3. This allows the detection target630and the detection unit631for detecting a variation in magnetic field thereof to be arranged, as well as the torque detection unit62, on the left beside the first divided part331. This facilitates, when the motor unit3is assembled, incorporating the torque detection unit62, the detection target630, and the detection unit631into the second divided part332.

As shown inFIG.2, in this embodiment, the rotator641of the motor detection unit64also overlaps with the torque detection unit62when viewed perpendicularly to the rightward/leftward direction. In addition, in this embodiment, the detection target630of the rotation detection unit63and the rotator641of the motor detection unit64are located on the left of the first joint surface337and second joint surface338of the case33.

Furthermore, in this embodiment, the rotational axis of the rotator632and the rotational axis of the input structure30are located at mutually different positions in the direction perpendicular to the rightward/leftward direction. Thus, setting the rotational velocity of the rotator632at a value greater than the rotational velocity of the input structure30as is done in this embodiment allows the detection precision (resolution) of the rotation detection unit63to be improved with the number of magnetic poles provided for the detection target630reduced. Alternatively, the rotational velocity of the rotator632may be set a value less than the rotational velocity of the input structure30. In that case, the detection precision of the rotation detection unit63may be improved by increasing the diameter of the detection target630and the number of magnetic poles provided for the detection target630.

Also, the second member412constituting the rotational member according to this embodiment and the rotator632interlocking with the second member412rotate even when the one-way clutch46does not allow the rotational power to be transmitted from the first output structure31to the input shaft35. Thus, the rotational state of the input shaft35may be detected appropriately by having the detection unit631detect the rotational state of the rotator632that rotates while interlocking with the second member412.

As shown inFIG.3, a wall portion3311is provided as a partition between the detection target630and the coil621of the torque detection unit62. The wall portion3311reduces the chances of the magnetic force applied by the magnets in the detection target630affecting the coil621of the torque detection unit62. That is to say, this reduces the chances of the magnetic force of the magnets included in the detection target630causing a decline in the accuracy of a torque detection value obtained by the torque detection unit62. The wall portion3311may either form an integral part of the first divided part331or be provided separately from the first divided part331, whichever is appropriate. The wall portion3311is suitably made of a soft magnetic material such as iron. Using a soft magnetic material such as iron further reduces the chances of the magnetic force of the magnets included in the detection target630causing a decline in the accuracy of the torque detection value obtained by the torque detection unit62.

In this case, as measured in the forward/backward direction that is perpendicular to the rotational axis of the input shaft35, a distance L1from the rotator632(specifically, a point, closest to the motor rotation detection unit640, on the rotator632) to the motor rotation detection unit640is suitably equal to or less than a distance L2from a point642, most distant from the motor rotation detection unit640, on the input shaft35to the motor rotation detection unit640as shown inFIGS.4A and4B. In this case, the dimension as measured in the forward/backward direction of the control board34may be decreased by shortening the distance between the motor rotation detection unit640and the detection unit631corresponding to the rotator632. Note that the rotator632may be arranged behind the point642either entirely as shown inFIG.4Aor only partially as shown inFIG.4B, whichever is appropriate.

(Variations)

Next, variations of the exemplary embodiment described above will be enumerated one after another. In the following description of the first to fifth variations, any constituent element of each of these variations, having the same function as a counterpart of the first embodiment described above, will be designated by the same reference numeral as that counterpart's, and description thereof will be omitted herein.

(First Variation)

FIG.5illustrates a motor unit3A according to a first variation. The motor unit3A has the same configuration as the motor unit3(seeFIG.2) according to the exemplary embodiment described above except that the motor unit3A includes a second member412A instead of the second member412and a rotational member70. The second member412A has the same configuration as the second member412except that the second member412A does not have the tooth portion413according to the exemplary embodiment described above.

The rotational member70is formed in the shape of a circular ring, which is concentric with the second member412A. The rotational member70is provided on the outer periphery of a left end portion of the second member412A. The rotational member70is fixed to the second member412A and rotates, along with the second member412A, around the right/left axis. On the outer peripheral surface of the rotational member70, formed is a tooth portion71with a plurality of teeth.

The tooth portion71meshes with the tooth portion635of the rotator632. This allows the body633(i.e., the rotator632) to be coupled to the rotational member70and rotate while interlocking with the rotational member70. That is to say, in this variation, the rotational member70constitutes a rotating portion that rotates along with the input shaft35. The rotator632including the detection target630rotates while interlocking with the rotational member70. The number of teeth of the tooth portion635is smaller than the number of teeth of the tooth portion71.

(Second Variation)

FIG.6illustrates a motor unit3B according to a second variation. The motor unit3B has the same configuration as the motor unit3(seeFIG.2) according to the exemplary embodiment described above except that the motor unit3B includes a rotation detection unit63B instead of the rotation detection unit63and a second member412B instead of the second member412. The second member412B has the same configuration as the second member412except that the second member412B does not have the tooth portion413according to the exemplary embodiment described above.

The rotation detection unit63B according to this variation is an optical rotation detector. The rotation detection unit63B includes: a rotational member72that rotates along with the input structure30; and detection unit631B for detecting the rotational state (such as a rotational position or rotational velocity) of the rotational member72.

The rotational member72is formed in the shape of a circular ring, which is concentric with the second member412B. The rotational member72is provided on the outer periphery of a left end portion of the second member412B. The rotational member72is fixed to the second member412B and rotates, along with the second member412B, around the right/left axis. The rotational member72protrudes to the left from the second member412B and is provided on the outer periphery of the torque detection unit62.

The rotational member72includes a detection target630B. The detection target630B protrudes from a left end portion of the rotational member72toward the outer periphery. The detection target630B includes a light transmitting portion73. The light transmitting portion73has light transmitting property. The light transmitting portion73is provided at an end portion of the outer periphery of the detection target630B, for example, and may be configured as a plurality of cutouts or holes arranged along the circumference of the rotational member72. When viewed perpendicularly to the rightward/leftward direction, the detection target630B overlaps with the magnetostriction generating portion620and the coil621. Note that the detection target630B may overlap with at least one of the magnetostriction generating portion620or the coil621when viewed perpendicularly to the rightward/leftward direction.

The detection unit631B is implemented as an optical sensor. The detection unit631B is mounted on the left surface of the control board34and is located inside the case33. The detection unit631B overlaps with the torque detection unit62when viewed perpendicularly to the rightward/leftward direction. The detection unit631B includes a light-emitting unit74and a photodetector unit75. The light-emitting unit74and the photodetector unit75are arranged side by side in the rightward/leftward direction. Between the light-emitting unit74and the photodetector unit75, the detection target630B is provided. The detection unit631B detects the rotational position of the rotational member72by having the light-emitting unit74emit light toward the photodetector unit75and by having the photodetector unit75receive the light transmitted through the light transmitting portion73. Alternatively, the rotation detection unit63B may also be implemented as any other optical rotation sensor. Furthermore, the rotation detection unit63B does not have to be an optical rotation sensor.

The rotator632may be omitted from the motor unit3B according to this variation.

(Third Variation)

FIG.7illustrates a motor unit3C according to a third variation. The motor unit3C has the same configuration as the motor unit3(seeFIG.2) according to the exemplary embodiment described above except that the motor unit3C includes a rotation detection unit63C instead of the rotation detection unit63and a second member412C instead of the second member412. The second member412C has the same configuration as the second member412except that the second member412C does not have the tooth portion413according to the exemplary embodiment described above.

The rotation detection unit63C according to this variation is an optical rotation detector. The rotation detection unit63C includes: a rotational member76that rotates along with the input structure30; and detection unit631C for detecting the rotational state (such as a rotational position or rotational velocity) of the rotational member76. The rotational member76may have the same configuration as the rotational member72according to the second variation.

The detection unit631C may have the same configuration as the detection unit631B according to the second variation. Nevertheless, the detection unit631C is not mounted on the control board34but is fixed onto the case33(first divided part331) inside the case33. The detection unit631C is electrically connected to the control unit of the control board34.

The rotator632may be omitted from the motor unit3C according to this variation.

(Fourth Variation)

FIG.8illustrates a motor unit3D according to a fourth variation. The motor unit3D has the same configuration as the motor unit3(seeFIG.2) according to the exemplary embodiment described above except that the motor unit3D includes a rotation detection unit63D instead of the rotation detection unit63according to the exemplary embodiment and a second member412D instead of the second member412according to the exemplary embodiment. The second member412D has the same configuration as the second member412except that the second member412D does not have the tooth portion413according to the exemplary embodiment described above.

The rotation detection unit63D according to this variation is an optical rotation detector. The rotation detection unit63D includes: a rotational member77that rotates along with the input structure30; and detection unit631D for detecting the rotational state (such as a rotational position or rotational velocity) of the rotational member77.

The rotational member77is formed in the shape of a circular ring, which is concentric with the input shaft35. The rotational member77is provided on the outer periphery of the input shaft35and is provided on the left of the first member411and the torque detection unit62(i.e., opposite from the first output structure31). The rotational member77is fixed to the input shaft35and rotates, along with the input shaft35, around the right/left axis.

The rotational member77includes a detection target630D. The detection target630D protrudes from a left end portion of the rotational member77toward the outer periphery.

The detection target630D includes a light transmitting portion78. The light transmitting portion78has light transmitting property. The light transmitting portion78is provided at an end portion of the outer periphery of the detection target630D, for example, and may be configured as a plurality of cutouts or holes arranged along the circumference of the rotational member72.

The detection unit631D has the same configuration as the detection unit631B according to the second variation except that the detection unit631D is not mounted on the control board34but is fixed to the case33.

The detection target630D of the motor unit3D according to this variation is provided on the left of the coupling portion where the input shaft35and the transmission member41are coupled together (i.e., on the left of the fitting portions42,43), thus allowing an ample space to be left in an intermediate region in the rightward/leftward direction inside the case33. Thus, the control board34may be arranged in the intermediate region, a member of a large size (e.g., a tall member) such as an electrolytic capacitor may be arranged on the control board34, and a plurality of boards may be arranged, thus allowing the space inside the case33to be made effective use of. In addition, the detection target630D and the detection unit631for detecting the detection target630D, as well as the torque detection unit62, may also be arranged on the left beside the first divided part331. The rotator632may be omitted from the motor unit3D according to this variation. Optionally, the detection unit631D according to this variation, as well as the detection unit631B according to the second variation, may be mounted on the control board34.

(Fifth Variation)

FIG.9illustrates a motor unit3E according to a fifth variation. The motor unit3E according to this variation is a uniaxial motor unit that does not include the second output structure32(seeFIG.2) according to the exemplary embodiment. Note that the motor unit3E includes the same constituent elements as the motor unit3according to the exemplary embodiment. Thus, in the following description, any constituent element of the motor unit3E, having the same function as a counterpart of the motor unit3, will not be described all over again.

The motor unit3E includes an output structure31E instead of the first output structure31. In this variation, the motor53is provided in a front part of the case33and the input structure30and the output structure31E are provided in a rear end portion of the case33.

The output structure31E has the same configuration as the first output structure31except that the output structure31E includes a tooth portion84with a plurality of teeth. The tooth portion84is provided on the outer peripheral surface of a left end portion of the output structure31E and is located inside the case33.

The motor unit3E according to this variation includes a speed reducer mechanism57E instead of the speed reducer mechanism57according to the exemplary embodiment. The speed reducer mechanism57E is housed inside the case33. The speed reducer mechanism57E transmits the rotational power of the motor shaft54to the output structure31E to make the rotational velocity of the output structure31E lower than that of the motor shaft54. The speed reducer mechanism57E includes a transmission shaft80, a one-way clutch83, a first transmission gear81, and a second transmission gear82.

The transmission shaft80extends parallel to the rightward/leftward direction. The transmission shaft80is supported by either the case33or a bearing attached to the case33to be rotatable around the right/left axis. The one-way clutch83is provided on the outer periphery of the transmission shaft80and the first transmission gear81is provided on the outer periphery of the one-way clutch83. That is to say, the one-way clutch83is located between the transmission shaft80and the first transmission gear81.

The first transmission gear81is supported by the one-way clutch83to be rotatable around the right/left axis. The first transmission gear81includes a tooth portion810with a plurality of teeth. The tooth portion810is provided on the outer peripheral surface of the first transmission gear81. The tooth portion810meshes with the tooth portion540of the motor shaft54. This causes the first transmission gear81to rotate by the rotational power transmitted from the motor shaft54. The number of teeth of the tooth portion810is larger than the number of teeth of the tooth portion540.

The second transmission gear82is provided on the outer periphery of a region, located on the right of the one-way clutch83and the first transmission gear81, of the transmission shaft80. The second transmission gear82is fixed to the transmission shaft80and rotates, along with the transmission shaft80, around the right/left axis. The second transmission gear82includes a tooth portion820with a plurality of teeth. The tooth portion820is provided on the outer peripheral surface of the second transmission gear82.

The tooth portion820of the second transmission gear82meshes with the tooth portion84of the output structure31E, thus allowing the rotational power of the first transmission gear81to be transmitted to the output structure31E. The number of teeth of the tooth portion820of the second transmission gear82is smaller than the number of teeth of the tooth portion810of the first transmission gear81.

The one-way clutch83may be implemented as, for example, a rachet one-way clutch. The one-way clutch83allows the rotational power to be transmitted from the first transmission gear81to the transmission shaft80only when the first transmission gear81rotates in one direction with respect to the transmission shaft80.

Specifically, if the rotational velocity of the first transmission gear81is higher than the rotational velocity of the transmission shaft80while the rear wheel11(seeFIG.1) is turning in the forward direction, the one-way clutch83allows the rotational power to be transmitted from the first transmission gear81to the transmission shaft80. That is to say, while the rear wheel11is turning in the forward direction, the one-way clutch83allows the rotational power to be transmitted only from the first transmission gear81to the transmission shaft80, not from the transmission shaft80to the first transmission gear81. This reduces, when the motor53stops running and the rider pumps the pedals17(seeFIG.1), for example, the chances of the motor shaft54and the rotor55rotating, thus reducing the pedaling force to be applied to turn the rear wheel11, compared to a situation where the rotational power is transmitted from the transmission shaft80to the first transmission gear81.

When the rotational power of the first transmission gear81is transmitted to the transmission shaft80via the one-way clutch83, the rotational power of the motor shaft54is transmitted to the output structure31E via the first transmission gear81, the one-way clutch83, the transmission shaft80, and the second transmission gear82. Thus, while the rider is pumping the pedals17(seeFIG.1) and the motor53is running, the resultant force, produced as the sum of the rotational power of the second member412rotating with the pedaling force applied thereto and the rotational power of the second transmission gear82driven in rotation by the motor53, causes the output structure31E to rotate. This rotational power of the output structure31E allows the electric bicycle1to turn its wheels in the forward traveling direction.

The control board34overlaps with the first transmission gear81when viewed perpendicularly to the rightward/leftward direction. Note that the control board34may at least partially overlap with the first transmission gear81when viewed perpendicularly to the rightward/leftward direction. Providing the control board34at such a position allows the control board34to be brought closer to the torque detection unit62along the axis of the input shaft35, thus enabling the torque detection unit62and the control board34to be interconnected with a shorter cable. Furthermore, a cable extension portion of the torque detection unit62is suitably arranged on the right (closer to the second divided part332) along the axis of the input structure30. This allows the torque detection unit62and the control board34to be interconnected with an even shorter cable.

The motor unit3E according to this variation includes a rotation detection unit63E instead of the rotation detection unit63according to the first embodiment. As shown inFIG.10, the rotation detection unit63E includes: a rotator632E including a detection target630E; and a detection unit631E. The detection target630E, the rotator632E, and the detection unit631E may have the same configuration as the detection target630, the rotator632, and the detection unit631, respectively, according to the first embodiment except that the rotator632E is located behind the input structure30and that a right end portion of the rotator632E is supported by a supporting portion85attached to the case33to be rotatable around the right/left axis.

(Other Variations)

The motor units3,3A-3E and electric bicycles1according to the exemplary embodiment and its variations described above may have their design changed as appropriate.

For example, in the exemplary embodiment and the first, second, third and fifth variations described above, the detection target630,630B,630C,630E overlaps entirely with only a part of the torque detection unit62when viewed perpendicularly to the rightward/leftward direction. However, this is only an example of the present disclosure and should not be construed as limiting. Alternatively, only part of the detection target630,630B,630C,630E may overlap with part or all of the torque detection unit62. Optionally, the detection target630,630B,630C,630E may overlap either entirely, or only partially, with the magnetostriction generating portion620or coil621of the torque detection unit62when viewed perpendicularly to the rightward/leftward direction.

Also, the rotation detection unit63,63E does not have to be implemented as a rotation detector including magnets and a hole IC. Alternatively, the rotation detection unit63,63E may also be implemented as an optical rotation detector such as the rotation detection units63B-63D according to the second to fourth variations. Furthermore, the rotation detection units63B-63D do not have to be optical rotation detectors but may also include magnets and a hole IC as in the exemplary embodiment described above.

Furthermore, each of the detection unit631,631C and the motor rotation detection unit640does not have to be implemented as a hole IC but may also be a hole element or a magnetoresistance (MR) element, for example.

Optionally, the first member411may be located in its entirety on the left of the first joint surface337and the second joint surface338.

Furthermore, the rotator632,632E may also be arranged at such a position where when measured perpendicularly to the rotational axis of the input shaft35, the distance L1from the rotator632,632E to the motor rotation detection unit640is longer than the distance L2from a point, most distant from the motor rotation detection unit640, on the input shaft35to the motor rotation detection unit640.

Furthermore, the rotator641(seeFIG.2) has only to be a member that rotates along with, or interlocks with, the motor shaft54of the motor53. For example, the rotator641may also be a member that rotates while meshing with the motor shaft54or the rotor55.

Furthermore, the case33may also be made of a non-metallic material. The material for the case33is not limited to any particular material.

Furthermore, the fitting portions42,43do not have to be splines but may also be serrations, for example. Optionally, one of the fitting portions42,43may be an external thread and the other fitting portion42,43may be an internal thread. Likewise, the fitting portions44,45do not have to be splines but may also be serrations, for example. Optionally, one of the fitting portions44,45may be an external thread and the other fitting portion44,45may be an internal thread.

Furthermore, each of the one-way clutches46,59,83may be implemented as a roller-type one-way clutch or a sprag-type one-way clutch, for example.

Furthermore, each of the bearings36,37,60,61does not have to be a ball bearing but may also be a roller bearing, for example.

Furthermore, the torque detection unit62does not have to be a magnetostrictive torque sensor but may also be a torque sensor that uses a potentiometer, for example.

Optionally, the detection unit631,631E and the motor rotation detection unit640may be mounted on two different surfaces of the control board34. Alternatively, the detection unit631and the motor rotation detection unit640may be mounted on two different control boards.

Optionally, the power transmission unit for electric bicycles may also be a unit including no motor53. In that case, the auxiliary driving force for the electric bicycle1may be generated by, for example, either a motor provided in the vicinity of the power transmission unit for electric bicycles or a hub motor for driving the front wheel of the electric bicycle. In the latter case, in particular, when the motor is running, the rotational power of the rear wheel11of the electric bicycle1traveling is transmitted to either the first output structure31or the output structure31E via the power transmission medium19.

(Aspects)

As can be seen from the foregoing description of an exemplary embodiment and its variations, a power transmission unit for electric bicycles according to a first aspect has the following configuration. Specifically, the power transmission unit includes an input structure (30), an output structure (31,31E), a torque detection unit (62), a detection target (630,630B,630C,630E), and a detection unit (631,631B,631C,631E). The input structure (30) includes an input shaft (35). The input shaft (35) is caused to rotate by external force transmitted thereto. The input structure (30) rotates along with the input shaft (35). The output structure (31,31E) outputs rotational power by rotating along with the input structure (30). The torque detection unit (62) is provided on an outer periphery of the input structure (30). The detection target (630,630B,630C,630E) rotates either along with, or while interlocking with, the input structure (30). The detection unit (631,631B,631C,631E) detects a rotational state of the detection target (630,630B,630C,630E). At least part of the torque detection unit (62) and at least part of the detection target (630,630B,630C,630E) overlap with each other when viewed perpendicularly to a rotational axis of the input structure (30).

This aspect allows the torque detection unit (62), detection target (630,630B,630C,630E), and detection unit (631,631B,631C,631E) of the power transmission unit for electric bicycles to be arranged sufficiently close to each other along the rotational axis of the input structure (30). This simplifies the interconnection pattern of the torque detection unit (62) and the detection unit (631,631B,631C,631E), thus facilitating making effective use of the space inside the unit.

A power transmission unit for electric bicycles according to a second aspect may be implemented in combination with the first aspect. The second aspect has the following configuration. The input structure (30) includes a transmission member (41). The transmission member (41) is provided on an outer periphery of the input shaft (35) and arranged beside the output structure (31,31E) along an axis of the input shaft (35). The transmission member (41) is coupled to, and rotates along with, the input shaft (35). The transmission member (41) transmits rotational power of the input shaft (35) to the output structure (31,31E) to cause the output structure (31,31E) to rotate. The torque detection unit (62) is provided on an outer periphery of the transmission member (41).

This aspect allows the torque of the input shaft (35) to be detected accurately by detecting the torque of the transmission member (41) using the torque detection unit (62).

A power transmission unit for electric bicycles according to a third aspect has the following configuration. Specifically, the power transmission unit includes an input shaft (35), an output structure (31), a transmission member (41), a torque detection unit (62), a detection target (630D), and a detection unit (631D). The input shaft (35) is caused to rotate by external force transmitted thereto. The output structure (31) outputs rotational power. The transmission member (41) is provided on an outer periphery of the input shaft (35) and arranged beside the output structure (31) along an axis of the input shaft (35). The transmission member (41) is coupled to, and rotates along with, the input shaft (35). The transmission member (41) transmits rotational power of the input shaft (35) to the output structure (31) to cause the output structure (31) to rotate. The torque detection unit (62) is provided on an outer periphery of the transmission member (41). The detection target (630D) rotates while interlocking with the input shaft (35). The detection unit (631D) detects a rotational state of the detection target (630D). The detection target (630D) is located, along an axis of the input shaft (35), opposite from the output structure (31) with respect to a coupling portion where the input shaft (35) and the transmission member (41) are coupled together.

This aspect allows an ample space to be left in an intermediate region in the rightward/leftward direction inside the power transmission unit for electric bicycles. Thus, a control board (34) and other members may be arranged in the intermediate region in the rightward/leftward direction inside the unit, thus facilitating making effective use of the space inside the unit.

A power transmission unit for electric bicycles according to a fourth aspect may be implemented in combination with the second or third aspect. The fourth aspect has the following configuration. Specifically, the power transmission unit further includes a sprocket (51). The output structure (31,31E) is provided on the outer periphery of the input shaft (35). The sprocket (51) is mounted on the output structure (31,31E).

This aspect reduces an increase in the overall size of the power transmission unit for electric bicycles by arranging the output structure (31,31E) on the outer periphery of the input shaft (35).

A power transmission unit for electric bicycles according to a fifth aspect may be implemented in combination with any one of the second to fourth aspects. The fifth aspect has the following configuration. Specifically, the power transmission unit further includes a one-way clutch (46). The transmission member (41) includes a first member (411) and a second member (412,412A-412E). The first member (411) is provided on the outer periphery of the input shaft (35), coupled to the input shaft (35), and rotates along with the input shaft (35). The second member (412,412A-412E) is provided on the outer periphery of the input shaft (35), arranged beside the first member (411) along the axis of the input shaft (35), coupled to the first member (411), and rotates along with the first member (411). The one-way clutch (46) is located between the second member (412,412A-412E) and the output structure (31) and allows rotational power to be transmitted from the second member (412,412A-412E) to the output structure (31) only when the second member (412,412A-412E) rotates in one direction with respect to the output structure (31).

This aspect reduces the chances of the input shaft (35) continuing rotating by being powered by the motor (53) when the rider stops pumping pedals (17).

A power transmission unit for electric bicycles according to a sixth aspect may be implemented in combination with any one of the first to fifth aspects. The sixth aspect has the following configuration. The power transmission unit further includes a motor (53) and a control board (34). The control board (34) controls rotation of the motor (53).

This aspect allows the space inside the power transmission unit for electric bicycles, including the motor (53) and the control board (34), to be made effective use of.

A power transmission unit for electric bicycles according to a seventh aspect may be implemented in combination with the sixth aspect. The seventh aspect has the following configuration. Aboard surface of the control board (34) extends in a direction intersecting with a motor shaft (54) of the motor (53). The control board (34) overlaps with at least part of the torque detection unit (62) when viewed perpendicularly to a rotational axis of the input shaft (35).

This aspect allows the control board (34) to be arranged closer to the torque detection unit (62), thus enabling the torque detection unit (62) and the control board (34) to be interconnected with a shorter cable.

A power transmission unit for electric bicycles according to an eighth aspect may be implemented in combination with the sixth or seventh aspect. The eighth aspect has the following configuration. Specifically, the power transmission unit for electric bicycles further includes a motor rotation detection unit (640). The motor rotation detection unit (640) is mounted on the control board (34) and detects a rotational state of the motor (53). The detection unit (631,631B-631E) is mounted on the control board (34).

This aspect allows the detection unit (631,631B-631E) and the motor rotation detection unit (640) to be mounted on the same control board (34), thus reducing an increase in the overall size of the power transmission unit for electric bicycles.

A power transmission unit for electric bicycles according to a ninth aspect may be implemented in combination with the eighth aspect. The ninth aspect has the following configuration. Specifically, the detection unit (631,631B-631E) and the motor rotation detection unit (640) are mounted on the same surface of the control board (34).

This aspect allows the detection unit (631,631B-631E) and the motor rotation detection unit (640) to be mounted easily on the control board (34).

An electric bicycle (1) according to a tenth aspect has the following configuration. Specifically, the electric bicycle (1) includes a wheel (11) and the power transmission unit for electric bicycles according to any one of the first to ninth aspects. The power transmission unit outputs rotational power to the wheel (11).

This aspect provides an electric bicycle (1) including the power transmission unit for electric bicycles according to any one of the first to eighth aspects. While the foregoing has described what are considered to be the best mode and/or other examples, it is understood that various modifications may be made therein and that the subject matter disclosed herein may be implemented in various forms and examples, and that they may be applied in numerous applications, only some of which have been described herein. It is intended by the following claims to claim any and all modifications and variations that fall within the true scope of the present teachings.

REFERENCE SIGNS LIST

1Electric Bicycle11Wheel (Rear Wheel)3Power Transmission Unit for Electric Bicycles (Motor Unit)30Input Structure31Output Structure (First Output Structure)31E Output Structure34Control Board35Input Shaft41Transmission Member411First Member412,412A-412D Second Member46One-Way Clutch51Sprocket (First Drive Sprocket)53Motor62Torque Detection Unit630,630B-630E Detection Target631,631B-631E Detection Unit640Motor Rotation Detection Unit