JP5685574B2 - Bicycle drive unit - Google Patents

Description

  The present invention relates to a drive unit for a battery-assisted bicycle that uses a motor output as auxiliary power.

  There is an invention described in Patent Document 1 as a battery-assisted bicycle that uses a motor output as auxiliary power. The battery-assisted bicycle according to Patent Document 1 transmits the pedaling force received by the pedal, combines the transmitted driving force and the driving force from the motor, and then transmits the combined driving force to the rear wheels. Rotate the wheel.

DE102010028667

  The drive unit of the bicycle of Patent Document 1 is provided in the power transmission path between the crankshaft 20, the rotation shaft of the motor and the crankshaft 30 and the sprocket 28, and is separated from the shaft 30 holding the gears 32 and 34. Since it is provided, the drive unit becomes large.

  In view of the above-described problems, an object of the present invention is to provide a bicycle drive unit for realizing weight reduction and compactness in a bicycle drive unit having a motor for assisting traveling.

  A bicycle drive unit for solving the above problems includes a crankshaft, a motor having a hole in which the crankshaft can be disposed, a power transmission shaft that is provided apart from the crankshaft and transmits rotation of the crankshaft. And an output unit for transmitting the rotation of the power transmission shaft and summing up the output of the motor.

  As a result, the crankshaft can be passed through the hole of the motor and the sensor portion can be disposed inside the hole of the motor, so that the weight reduction and compactness of the bicycle drive unit can be realized.

  Furthermore, in the bicycle drive unit, the power transmission shaft may be connected to the crankshaft on one side of the motor in the axial direction of the crankshaft and to the output unit on the other side of the motor. Thereby, a relatively heavy motor can be arranged near the center of the drive unit in the axial direction of the crankshaft.

  Further, the drive unit of the bicycle may include a first connection mechanism that connects the crankshaft and the power transmission shaft, and a second connection mechanism that connects the power transmission shaft and the output unit.

  Furthermore, in the bicycle drive unit, the rotation shaft of the crankshaft and the rotation shaft of the motor may be provided coaxially. Thereby, the internal mechanism of a motor can be simplified.

  Furthermore, a sprocket may be connected to the output unit. Thereby, the output from an output part can be transmitted to a rear hub.

  Furthermore, the rotational force of the motor may be transmitted to the output unit via the one-way clutch. Thereby, it can prevent that the rotational force of a crankshaft is transmitted to a motor.

  Furthermore, the drive unit of the bicycle may further include a reduction mechanism, and the rotational force of the motor may be transmitted to the output unit via the reduction mechanism. Thereby, since the output of a motor can be decelerated and transmitted to an output part, the power transmission part which operates a motor efficiently can be implement | achieved.

  Furthermore, the drive unit of the bicycle may further include a reduction mechanism, and the rotational force of the motor may be input to the reduction mechanism, and the output of the reduction mechanism may be transmitted to the output unit via the one-way clutch. Accordingly, it is possible to both prevent the rotational force of the crankshaft from being transmitted to the motor and efficiently operate the motor.

  Further, in the bicycle drive unit, the first coupling mechanism may include any one of a gear, a sprocket, and a pulley.

  Furthermore, in the bicycle drive unit, the second coupling mechanism may include any one of a gear, a sprocket, and a pulley.

  Further, in the bicycle drive unit, the rotation shaft of the output section may be provided coaxially with the rotation shaft of the crankshaft. Thereby, since the bearing of the rotating shaft of an output part and the rotating shaft of a crankshaft can be integrated, the further weight reduction and compactization of the drive unit of a bicycle are implement | achieved.

  Further, the output unit may include a first coupling unit coupled to the output unit of the transmission mechanism and a second coupling unit coupled to the motor. And it is good for a 1st coupling | bond part to have an external gear. The second coupling part may have an internal gear. Thereby, the drive unit can synthesize the rotational torque of the crankshaft and the rotational torque of the motor.

  ADVANTAGE OF THE INVENTION According to this invention, the drive unit which implement | achieves weight reduction and compactness in the drive unit of the bicycle which has a motor for assist driving | running | working is realizable.

The side view of the battery-assisted bicycle incorporating the drive unit according to the first embodiment of the present invention. Sectional drawing of the drive unit which concerns on the 1st Embodiment of this invention. Sectional drawing of the drive unit which concerns on the 2nd Embodiment of this invention. Sectional drawing of the drive unit which concerns on the 3rd Embodiment of this invention.

  FIG. 1 is a right side view showing an example of a battery-assisted bicycle incorporating the drive unit 1 according to the first embodiment of the present invention. This battery-assisted bicycle is provided with a hub that is capable of rotating pedal force acting on the pedal 100 around the axle 106 of the rear wheel via a path of the crank arm 101 → the drive unit 1 → the front sprocket 103 → the chain 104 → the rear sprocket 105. Communicate to the body. In this process, the battery-assisted bicycle synthesizes the motor output as auxiliary power and assists in running. In the battery-assisted bicycle, a force corresponding to the torque acting on the crankshaft 102 of the drive unit 1 is detected by a sensor unit described later. Then, when the detected value exceeds the set value, the battery-assisted bicycle starts the motor and generates torque corresponding to the pedaling force as auxiliary power. The drive unit 1 including an assisting motor is generally disposed in the vicinity of a connecting portion between the lower end portion of the seat tube of the frame and the rear end portion of the down tube of the frame. The battery for driving the motor is arranged along the rear carrier, down tube or seat tube.

  The present invention is characterized by having a drive unit in which a rotating shaft of a crankshaft and a rotating shaft of a motor are configured coaxially. Below, the structure and function of the drive unit 1 are demonstrated. Referring to FIG. 2, the drive unit 1 includes a motor 120 having a hole 120a in which the crankshaft 102 can be disposed, and a sensor unit in which at least a part is disposed between the motor 120 and the crankshaft 102 inside the hole 120a. 150.

  As shown in FIG. 2, the crankshaft 102 is inserted into the through hole 111 a of the casing 111. The crankshaft 102 is rotatably supported by the casing 111 via bearings 112 and 113. Crank arms 101 are detachably attached to both ends of the crankshaft 102 by bolts. The crank arm 101 is disposed outside the casing 111. One of the two crank arms 101 may be configured so as not to be detachable from the crankshaft 102.

  The motor (electric motor) 120 has a hole 120a in which the crankshaft 102 can be placed. The hole 120 a is provided at the center of rotation of the motor 120. The motor 120 is arranged such that its rotation axis is coaxial with the rotation axis of the crankshaft 102. The stator 121 of the motor 120 is formed in a cylindrical shape, wound with an exciting coil, arranged on a concentric circle of the crankshaft 102, and fixed to the motor case 125 by a mounting portion 122. The motor case 125 is fixed to the casing 111. A hole 120 a is formed inside the stator 121 in the radial direction. The rotor 123 is formed in a cylindrical shape and is rotatably supported by the motor case 125. The rotor 123 includes, for example, a magnet (not shown) having a plurality of magnetic poles in the circumferential direction and a magnet holding part (not shown) that holds the magnet. The motor of the present embodiment is an outer rotor type motor in which a stator 121 is provided so as to be surrounded by a rotor 123. The rotor 123 is rotatably supported around the crankshaft 102 by a first bearing 124a and a second bearing 124b that are arranged at intervals in the crankshaft direction. The first bearing 124 a and the second bearing 124 b are supported by the motor case 125. The motor 120 is driven by an inverter (not shown). The inverter is driven by a control unit (not shown), and the control unit controls the inverter according to the pedaling force and the speed of the bicycle.

  The sensor unit 150 detects a twist applied to the crankshaft 102. Since this twist is proportional to the pedaling force applied to the crankshaft 102, the user's pedaling force applied to the crankshaft 102 can be determined by detecting the twist. The sensor unit 150 includes a hollow member 151 having an insertion hole in which the crankshaft 102 can be disposed and a strain sensor 155. The hollow member 151 includes a first connection portion 151a, a second connection portion 151b, and an insertion hole 151c. The first connection portion 151a is connected to the crankshaft 102. The second connection portion 151b transmits a rotational force to a power transmission shaft described later. The crankshaft 102 can be disposed in the insertion hole 151c. The hollow member 151 is separated from the crankshaft 102 disposed inside except for the first connection portion 151a. In the first connection portion 151a, the hollow member 151 is inserted into a key or serration protruding from the crankshaft 102 and fixed by means such as screwing or press-fitting. The first connection portion 151a and the second connection portion 151b are provided apart from each other in the direction of the crankshaft 102. The strain sensor 155 is a magnetostrictive sensor and includes a magnetostrictive element 155a provided in the hollow member 151 and a detection coil 155b provided around the magnetostrictive element 155a. The detection coil 155b is fixed to the motor case 125 by a fixing member 156. Thereby, the detection coil 155b is supported by the casing 111 so as not to rotate.

  At least a part of the sensor unit 150 is disposed between the motor 120 and the crankshaft 102. In the present embodiment, the space between the motor 120 and the crankshaft 102 is a range W between both ends of the stator 121 in the direction in which the rotation shaft of the motor 120 extends, and a region between the crankshaft 102. It is preferable that at least a part or all of the strain sensor 155 in the sensor unit 150 is provided in a region between both ends of the stator 121 and the crankshaft 102 in the direction in which the rotation shaft of the motor 120 extends. . At least part or all of the strain sensor 155 is in a range W between both ends of the stator 121 in the direction in which the rotation axis of the motor 120 extends, and in a range in which the strain sensor 155 overlaps with the rotor 123 in the direction in which the rotation axis of the motor 120 extends. It may be provided in a region between the shaft 102.

  The speed reduction mechanism 127 transmits the rotation of the rotor 123 to the torque transmission member 130. The speed reduction mechanism 127 has one or more gears. The example of FIG. 2 shows a case where the speed reduction mechanism 127 has two planetary gear mechanisms. The first planetary gear mechanism includes a first sun gear portion 128a coupled to the rotor 123, a plurality of first planetary gears 128b, and a first carrier portion 128c that rotatably supports the plurality of first planetary gears 128b. And a first ring gear portion 128d fixed to the casing 111. The second planetary gear mechanism includes a second sun gear portion 129a coupled to the first carrier portion 128c, a plurality of second planetary gears 129b, and a second carrier that rotatably supports the plurality of second planetary gears 129b. Part 129c and a second ring gear part 129d fixed to casing 111. The output of the speed reduction mechanism 127 is transmitted to the output unit 131 (details will be described later) via the torque transmission member 130. The torque transmission member 130 is coupled to the second carrier portion 129d and is integrally formed here. The torque transmission member 130 is rotatably supported on the inner surface of the output part 131 (details will be described later) via a one-way clutch 132 and a rotation support part 133. Although the rotation support part 133 is comprised by the sliding bearing in this Embodiment, you may be comprised by the bearing. The rotation support portion 133 is disposed on the outer side in the radial direction than the one-way clutch 132 with respect to the crankshaft. The torque transmission member 130 supports a plurality of clutch claws of the one-way clutch 132.

  The output unit 131 transmits the rotational force of the motor 120 and the rotational force of the crankshaft 102 to the front sprocket 103. The output part 131 is provided on the end side of the crankshaft 102. The output portion 131 is formed in an annular shape, and includes a first annular portion 131a, a second annular portion 131b, and a third annular portion 131c. The first annular portion 131a extends along the crankshaft 102. The second annular portion 131b extends in the radial direction with respect to the crankshaft 102 from the end of the first annular portion 131a on the motor 120 side. The third annular portion 131c extends in a direction parallel to the crankshaft 102 from the end of the second annular portion 131b on the motor side. The inner peripheral part of the output part 131 is connected to the torque transmission member 130 via the one-way clutch 132. A clutch groove of the one-way clutch 132 is formed in the inner peripheral portions of the first annular portion 131a and the second annular portion 131b. The clutch groove is a second connecting portion and constitutes an internal gear. A rotation support portion 133 is provided on the inner peripheral portion of the third annular portion 131c. The rotation support part 133 supports the rotation of the torque transmission member 130. A fourth annular portion 131d extending inward in the circumferential direction is provided at the end of the first annular portion 131a opposite to the second annular portion 131b. A bearing 113 is provided on the inner periphery of the fourth annular portion 131d. A bearing 134 is provided on the outer peripheral portion of the first annular portion 131a. Thereby, the output part 131 is rotatably supported by the casing 111. The bearings 113 and 134 are formed by, for example, radial bearings, the inner ring body of the bearing 113 supports the crankshaft 102, and the outer ring body of the bearing 134 is supported by the casing 111. The end portion of the output portion 131 (the end portion of the fourth annular portion) protrudes from the opening 111b of the casing 111 to the outside. The output part 131 includes a sprocket connection part 131e on the outer peripheral part of the part protruding from the casing 111 of the fourth annular part 131d. The front sprocket 103 is detachably attached to the sprocket connecting portion 131d by, for example, a bolt. As a result, the front sprocket 103 can rotate integrally with the output unit 131.

  The rotational force related to the second connection portion 151 b of the sensor unit 150 is transmitted to the power transmission shaft 160 via the first gear 114 and the second gear 161. The rotation of the power transmission shaft 160 is transmitted to the output unit 131 via the third gear 142.

  The second connection portion 151 b of the sensor unit 150 is connected to the first gear 114. The first gear 114 is provided at the end opposite to the end of the crankshaft 102 where the output portion 131 is located. In connection with this, the 1st connection part 151a of the sensor part 150 is provided in the output part 131 side. The first connecting portion 151 a is connected to the crankshaft 102 in a region between the motor 120 and the crankshaft 102. The first gear 114 is fixed to the second connecting portion 151b and rotates integrally with the crankshaft 102. The first gear 114 may be detachably attached to the second connection portion 151b by, for example, serration. The hollow member 151 is separated from the crankshaft 102 disposed inside except for the first connection portion 151a. A first coupling mechanism is formed including the first gear 114 and the second gear 161.

  The second gear 161 is fixed to the power transmission shaft 160 so as not to rotate, and rotates together. The second gear 161 is provided at one end of the power transmission shaft 160. The second gear 161 meshes with the first gear 114.

  The power transmission shaft 160 is rotatably supported by the support shaft 170. The support shaft 170 is provided apart from the crankshaft 102. That is, the power transmission shaft 160 is provided apart from the crankshaft 102. The rotating shaft of the power transmission shaft 160 is parallel to the rotating shaft of the crankshaft 102. A restriction member 175 that restricts the movement of the power transmission shaft 160 in the axial direction of the support shaft 170 may be provided on at least one of the support shaft 170 and the power transmission shaft 160. In the present embodiment, power transmission shaft 160 and support shaft 170 form a sliding bearing.

  The support shaft 170 has a first male screw portion (not shown) at both ends for fixing to an insertion port 115 formed in the casing 111 with a nut 116. The first female screw portion 24 is formed with a rotation-preventing portion (not shown) formed in parallel that is prevented from rotating around the insertion port 115.

  The third gear 142 is fixed to the other end of the power transmission shaft 160 so as not to rotate.

  A fourth gear 171 is formed on the outer peripheral portion of the output portion 131. The fourth gear 171 is a first connecting portion and constitutes an external gear. The fourth gear 171 is formed on the outer periphery of the second annular portion 131b and the third annular portion 131c. In the present embodiment, the fourth gear 171 is formed integrally with the output unit 131. The fourth gear 171 is in mesh with the third gear 142. A second coupling mechanism is formed including the third gear 142 and the fourth gear 171.

  The first and second coupling mechanisms are provided on the opposite side of the output unit 131 and the front sprocket 103 with the motor 120 interposed therebetween. As a result, the power transmission shaft 160 is connected to one crankshaft of the motor 120 in the axial direction of the crankshaft, and is connected to the output unit 131 on the other side of the motor 120.

  Next, the operation of this drive unit will be described. Torque due to the pedaling force of the rider is as follows: crank arm 101 → crankshaft 102 → first connecting part 151a → second connecting part 151b → first gear 114 → second gear 161 → power transmission shaft 160 → third gear 142 → output part 131 Via the transmission mechanism. On the other hand, the output torque from the motor is transmitted from the speed reduction mechanism 127 → the torque transmission member 130 → the one-way clutch 132 → the output unit 131. The output unit 131 combines these two torques and transmits the combined torque to the front sprocket 103. Thereby, the assist by a motor is implement | achieved.

  In the drive unit of the present embodiment, the rotation shaft of the crankshaft and the rotation shaft of the motor are coaxial, and at least a part of the sensor unit is disposed in the hole of the motor where the crankshaft is disposed. Thereby, the drive unit which has the motor for assist driving | running | working can be comprised lightweight and compactly.

  Further, by adjusting in advance the gear ratio (number of teeth) of the first to fourth gears 114, 161, 142, 171, the ratio of the rotational speed of the output unit 131 to the rotational speed of the crankshaft 120 can be increased or decreased. it can. Thereby, the setting according to the user of the bicycle provided with the drive unit of the present invention can be performed.

  FIG. 3 is a cross-sectional view of a drive unit according to the second embodiment of the present invention. The drive unit according to the second embodiment differs from the drive unit according to the first embodiment mainly in the following points. The motor 120 is an inner rotor type motor in which a rotor 123 is surrounded by a stator 121. In the following description, details different from those of the first embodiment will be described. Note that FIG. 3 illustrates the case where the speed reduction mechanism 127 has one gear for convenience, but is merely an example. The function of the speed reduction mechanism 127 is the same as that of the first embodiment.

  The second connection portion 151 b of the sensor unit 150 is connected to the first gear 114. The first gear 114 is fixed to the second connecting portion 151b and rotates integrally with the crankshaft 102. The first gear 114 may be detachably attached to the second connection portion 151b by, for example, serration. The first connecting portion 151 a is connected to the crankshaft 102 in a region between the motor 120 and the crankshaft 102. The hollow member 151 is separated from the crankshaft 102 disposed inside except for the first connection portion 151a.

  The second gear 161 meshes with the first gear 114. In the present embodiment, second gear 161 is formed integrally with power transmission shaft 160. The third gear 142 is formed integrally with the power transmission shaft 160. In the present embodiment, the power transmission shaft 160, the second gear 161, and the third gear 142 are integrally formed, but at least one of the power transmission shaft 160, the second gear 161, and the third gear 142 is formed. One of them may be integrally formed. Also in the present embodiment, at least a part of the sensor unit 150 is disposed between the motor 120 and the crankshaft 102, and at least a part or all of the strain sensor 155 is the rotation shaft of the motor 120. It is provided in a region W between both ends of the stator 121 in the extending direction and a region between the crankshaft 102.

  Although the above embodiment illustrates the case where the strain sensor 155 is a magnetostrictive sensor, it may be a strain gauge or a semiconductor strain sensor. Further, although the case where the magnetostrictive element 155a is arranged in the hollow member 151 is illustrated, the magnetostrictive element 155a may be arranged directly on the crankshaft 102. In this case, the hollow member 151 is not provided, and the first gear 114 is directly fixed to the crankshaft 102.

  FIG. 4 is a sectional view of a drive unit according to the third embodiment of the present invention. The drive unit according to the third embodiment differs from the drive unit according to the first embodiment mainly in the following points. The motor 120 is an inner rotor type motor in which a rotor 123 is provided so as to be surrounded by a stator 121, and has different detection means (torque detection means) for detecting human driving force. In the following description, details different from those of the first embodiment will be described. Note that FIG. 4 illustrates the case where the speed reduction mechanism 127 has one gear for convenience, but is merely an example. The function of the speed reduction mechanism 127 is the same as that of the first embodiment. Further, the same reference numerals are given to the same components as those of the above-described embodiment.

  The motor (electric motor) 120 is arranged so that its rotating shaft is coaxial with the rotating shaft of the crankshaft 102. The stator 121 of the motor 120 is arranged on a concentric circle of the crankshaft 102 around which an exciting coil is wound, and is fixed to the casing 111 by a mounting portion 122. The rotor 123 is rotatably supported on the crankshaft 102. The rotor 123 includes, for example, a magnet (not shown) having a plurality of magnetic poles in the circumferential direction and a magnet holding part (not shown) that holds the magnet. The motor according to the present embodiment is an inner rotor type motor in which a rotor 123 is provided so as to be surrounded by a stator 121. The rotor 123 is rotatably supported on the crankshaft 102 by a first bearing 124a and a second bearing 124b that are arranged at intervals in the crankshaft direction. The motor 120 is driven by an inverter (not shown). The inverter is driven by a control unit (not shown), and the control unit controls the inverter according to the pedal effort and speed.

  The speed reduction mechanism 127 transmits the rotation of the rotor 123 to the torque transmission member 130 and transmits the rotation of the torque transmission member 130 to the rotor 123. The speed reduction mechanism 127 has a planetary gear mechanism 126. The planetary gear mechanism 126 includes a sun gear 126a, an internal gear 126b disposed on the outer peripheral side of the sun gear 126a, and a plurality of (for example, three) planetary gears 126c that mesh with the sun gear 126a and the internal gear 126b. have. The sun gear 126 a is fixed to the rotor 123. The internal gear 126 b is provided on the attachment portion 122. The plurality of planetary gears 126c are rotatably supported by the torque transmission member 130. The torque transmission member 130 is a so-called carrier. Each planetary gear 126c has first and second gear portions having different numbers of teeth. The number of teeth of the first gear part is larger than the number of teeth of the second gear part. The first gear portion meshes with the sun gear 126a, and the second gear portion meshes with the internal gear 126b. The torque transmission member 130 is rotatably supported on the inner surface of the output unit 131 via a one-way clutch 132 and a rotation support unit 133. Although the rotation support part 133 is comprised by the sliding bearing in this Embodiment, you may be comprised by the bearing. The rotation support portion 133 is disposed on the outer side in the radial direction than the one-way clutch 132 with respect to the crankshaft. In this planetary gear mechanism 126, the internal gear 126 b is fixed to the casing 111 so as not to rotate, so that the rotation of the sun gear 126 a to which the rotor 123 is connected is decelerated and transmitted to the torque transmission member 130.

  The first coupling mechanism includes a first gear 114 and a second gear 141, and couples the crankshaft 102 and the power transmission shaft 160. The first gear 114 is provided on one end side of the crankshaft 102. The first gear 114 is fixed to the crankshaft 102 and rotates integrally with the crankshaft 102. The first gear 114 may be detachably attached to the crankshaft 102 by, for example, serration. The second gear 141 meshes with the first gear 114 to transmit a driving force to the power transmission shaft 160.

  In the present embodiment, power transmission shaft 160 is rotatably supported on support shaft 170 by a bearing. The power transmission shaft 160 is provided with a sensor unit 180 for detecting a driving force applied to the power transmission shaft 160. The second coupling mechanism includes a third gear 142 and a fourth gear 171 and couples the power transmission shaft 160 and the output unit 131. The third gear 142 is fixed to the other end of the power transmission shaft 160 so as not to rotate, and meshes with a fourth gear 171 provided in the output unit 131. The sensor unit 180 detects torsion applied to the power transmission shaft 160. Since this twist is proportional to the user's pedaling force applied to the crankshaft 102, the user's pedaling force applied to the crankshaft 102 can be determined by detecting the twist of the power transmission shaft 160. The sensor unit 180 includes a strain sensor 155. The strain sensor is a magnetostrictive sensor, and in this embodiment, includes a magnetostrictive element provided on the power transmission shaft 160 and a detection coil provided around the magnetostrictive element. The sensor unit 180 has the same configuration as the sensor unit 150 described above. The detection coil is fixed to the motor case 125.

  In this embodiment, the strain sensor is a magnetostrictive sensor, but may be a strain gauge or a semiconductor strain sensor. In this case, a transmitter that transmits a signal from a strain sensor provided on the power transmission shaft 160 to the outside by wireless or the like and a receiver that receives a signal from the transmitter may be further provided. In the above embodiment, transmission of driving force (torque and rotation) from the crankshaft 102 to the power transmission shaft 160 and transmission of torque from the power transmission shaft 160 to the output unit 131 are performed via gears. However, transmission of these torques may be performed using sprockets and chains, or pulleys and belts.

In addition, the first coupling mechanism is configured by the first gear 114 and the second gear 141, and the second coupling mechanism is configured by the third gear 142 and the fourth gear 171. You may comprise using the above gearwheel.
If the motor 120 can be driven at a low speed, the speed reduction mechanism 127 may be omitted. In that case, the motor output is transmitted to the one-way clutch 132 as it is.

DESCRIPTION OF SYMBOLS 1 Drive unit 102 Crankshaft 103 Sprocket 111 Casing 120 Motor 121 Stator 123 Rotor 127 Deceleration mechanism 130 Torque transmission member 131 Power transmission part 132 One-way clutch 161 Power transmission shaft

Claims (10)

A crankshaft,
A motor having a hole in which the crankshaft can be disposed;
A power transmission shaft provided apart from the crankshaft , disposed outside the motor in a radial direction of the crankshaft , to which rotation of the crankshaft is transmitted;
An output part to which the rotation of the power transmission shaft is transmitted and the output of the motor is summed , the front sprocket being detachable ;
A casing for housing the motor and the power transmission shaft;
With
The power transmission shaft is connected to the crankshaft on one side of the motor in the axial direction of the crankshaft, and connected to the output portion on the other side of the motor ,
The rotating shaft of the output unit is provided coaxially with the rotating shaft of the crankshaft.
Bicycle drive unit.   2. The bicycle drive unit according to claim 1, comprising: a first connection mechanism that connects the crankshaft and the power transmission shaft; and a second connection mechanism that connects the power transmission shaft and the output unit.   The bicycle drive unit according to claim 1 or 2, wherein the rotation shaft of the crankshaft and the rotation shaft of the motor are provided coaxially.   The bicycle drive unit according to any one of claims 1 to 3, wherein a sprocket is connected to the output unit.   The bicycle drive unit according to any one of claims 1 to 4, wherein the output of the motor is transmitted to the output unit via a one-way clutch. A further reduction mechanism;
The bicycle drive unit according to any one of claims 1 to 5, wherein an output of the motor is transmitted to the output unit via the speed reduction mechanism. A further reduction mechanism;
The output of the motor is input to the speed reduction mechanism,
The bicycle drive unit according to any one of claims 1 to 5, wherein an output of the speed reduction mechanism is transmitted to the output section via a one-way clutch.   The bicycle drive unit according to claim 2, wherein the first connection mechanism includes any one of a gear, a sprocket, and a pulley, and the second connection mechanism includes any one of a gear, a sprocket, and a pulley. The output unit is
A first coupling portion coupled to the power transmission shaft;
The bicycle drive unit according to any one of claims 1 to 8 , further comprising a second coupling portion coupled to the motor. The bicycle drive unit according to claim 9 , wherein the first coupling portion has an external gear, and the second coupling portion has an internal gear.

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