US20140069231A1 - Bicycle drive unit - Google Patents
Bicycle drive unit Download PDFInfo
- Publication number
- US20140069231A1 US20140069231A1 US13/718,044 US201213718044A US2014069231A1 US 20140069231 A1 US20140069231 A1 US 20140069231A1 US 201213718044 A US201213718044 A US 201213718044A US 2014069231 A1 US2014069231 A1 US 2014069231A1
- Authority
- US
- United States
- Prior art keywords
- motor
- crank axle
- axle
- drive unit
- power transmission
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16H—GEARING
- F16H37/00—Combinations of mechanical gearings, not provided for in groups F16H1/00 - F16H35/00
- F16H37/02—Combinations of mechanical gearings, not provided for in groups F16H1/00 - F16H35/00 comprising essentially only toothed or friction gearings
- F16H37/06—Combinations of mechanical gearings, not provided for in groups F16H1/00 - F16H35/00 comprising essentially only toothed or friction gearings with a plurality of driving or driven shafts; with arrangements for dividing torque between two or more intermediate shafts
- F16H37/065—Combinations of mechanical gearings, not provided for in groups F16H1/00 - F16H35/00 comprising essentially only toothed or friction gearings with a plurality of driving or driven shafts; with arrangements for dividing torque between two or more intermediate shafts with a plurality of driving or driven shafts
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62M—RIDER PROPULSION OF WHEELED VEHICLES OR SLEDGES; POWERED PROPULSION OF SLEDGES OR SINGLE-TRACK CYCLES; TRANSMISSIONS SPECIALLY ADAPTED FOR SUCH VEHICLES
- B62M6/00—Rider propulsion of wheeled vehicles with additional source of power, e.g. combustion engine or electric motor
- B62M6/40—Rider propelled cycles with auxiliary electric motor
- B62M6/55—Rider propelled cycles with auxiliary electric motor power-driven at crank shafts parts
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62M—RIDER PROPULSION OF WHEELED VEHICLES OR SLEDGES; POWERED PROPULSION OF SLEDGES OR SINGLE-TRACK CYCLES; TRANSMISSIONS SPECIALLY ADAPTED FOR SUCH VEHICLES
- B62M11/00—Transmissions characterised by the use of interengaging toothed wheels or frictionally-engaging wheels
- B62M11/04—Transmissions characterised by the use of interengaging toothed wheels or frictionally-engaging wheels of changeable ratio
- B62M11/06—Transmissions characterised by the use of interengaging toothed wheels or frictionally-engaging wheels of changeable ratio with spur gear wheels
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62M—RIDER PROPULSION OF WHEELED VEHICLES OR SLEDGES; POWERED PROPULSION OF SLEDGES OR SINGLE-TRACK CYCLES; TRANSMISSIONS SPECIALLY ADAPTED FOR SUCH VEHICLES
- B62M11/00—Transmissions characterised by the use of interengaging toothed wheels or frictionally-engaging wheels
- B62M11/04—Transmissions characterised by the use of interengaging toothed wheels or frictionally-engaging wheels of changeable ratio
- B62M11/14—Transmissions characterised by the use of interengaging toothed wheels or frictionally-engaging wheels of changeable ratio with planetary gears
- B62M11/145—Transmissions characterised by the use of interengaging toothed wheels or frictionally-engaging wheels of changeable ratio with planetary gears built in, or adjacent to, the bottom bracket
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T74/00—Machine element or mechanism
- Y10T74/19—Gearing
- Y10T74/19023—Plural power paths to and/or from gearing
- Y10T74/19051—Single driven plural drives
- Y10T74/19056—Parallel
Definitions
- This invention generally relates to a drive unit for an electrically assisted bicycle that uses a motor output as an assisting power.
- German Patent Publication No. DE 10 2010 028 667 One example of an electrically assisted bicycle is disclosed in German Patent Publication No. DE 10 2010 028 667 in which the electrically assisted bicycle uses a motor output as an assisting power to drive the bicycle.
- a pedaling force which is inputted by the pedals, is transmitted through the transmission mechanism and the transmitted drive force is then combined with a drive force from the motor. The combined drive force is then transmitted to a rear wheel of the bicycle to rotate the rear wheel.
- the present invention was conceived in view of the problem described above.
- One object proposed by this disclosure is to provide a lighter, more compact drive unit for a bicycle which has a motor for assisted riding.
- the bicycle drive unit comprises a motor, a crank axle, a power transmission axle and an output part.
- the motor includes a crank axle receiving hole.
- the crank axle is rotatably disposed in the crank axle receiving hole of the motor.
- the power transmission axle is separate from the crank axle and arranged to transmit rotation of the crank axle.
- the output part is operatively coupled to the motor and the power transmission axle to combine a rotational output of the motor and a rotational output of the transmission mechanism together.
- the bicycle drive unit can be made lighter and more compact.
- the power transmission axle is coupled to the crank axle at a first end of the motor in an axial direction of the crank axle and coupled to the output part at a second end of the motor.
- the motor which has a relatively large weight can be arranged in the vicinity of the center of the drive unit in the axial direction of the crank axle.
- the bicycle drive unit prefferably be provided with a first coupling mechanism coupling the crank axle and the power transmission axle, and a second coupling mechanism coupling the power transmission axle and the output part.
- the motor in the bicycle drive unit, it is preferable for the motor to have a rotational axis that is coaxially aligned with the rotational axis of the crank axle.
- a sprocket it is preferable for a sprocket to be connected to the output part. In this manner, the output from the output part can be transmitted to a rear hub or the like.
- the bicycle drive unit prefferably has a one-way clutch to transmit the output of the motor to the output part. In this manner, the rotational force of the crank axle can be prevented from being transmitted to the motor.
- the bicycle drive unit prefferably has a reduction gear mechanism to transmit the output of the motor to the output part.
- a reduction gear mechanism to transmit the output of the motor to the output part.
- the bicycle drive unit prefferably has a reduction gear mechanism, the output of the motor being inputted to the reduction gear mechanism, and the output of the reduction gear mechanism being transmitted to the output part through a one-way clutch. In this manner, it is possible to realize prevention of the rotational power of the crank axle being transmitted to the motor as well as efficient operation of the motor.
- the first coupling mechanism prefferably includes one of a gear, a sprocket and a pulley, and.
- the second coupling mechanism includes one of a gear, a sprocket and a pulley.
- the output part it is preferable for the output part to have a rotational axis that is axially aligned with the rotational axis of the crank axle. In this manner, since the bearings of the rotational axis of the output part and the rotational axis of the crank axle can be integrated, the bicycle drive unit can be made even lighter and more compact.
- the output part it is preferable for the output part to have a first joining section which is joined to the power transmission axle and a second joining section which is joined to the motor.
- the first joining section it is preferable for the first joining section to have an externally toothed gear wheel.
- the second joining section it is preferable for the second joining section to have an internally toothed gear wheel.
- a bicycle drive unit which has a motor for assisted riding, can be realized that is lighter and more compact.
- FIG. 1 is a simplified side elevational view of an electrically assisted bicycle equipped with a drive unit according to a first embodiment
- FIG. 2 is a cross sectional view of a drive unit according to the first embodiment
- FIG. 3 is a cross sectional view of a drive unit according to a second embodiment.
- FIG. 4 is a cross sectional view of a drive unit according to a third embodiment.
- FIG. 1 is a simplified, right side elevational view of an electrically assisted bicycle having the drive unit 1 , as described below.
- the electrically assisted bicycle has a pair of pedals 100 .
- the pedals 100 are each rotatably mounted to a crank arm 101 .
- the crank arms 101 are fixed to an end so a crank axle 102 that is operatively connected to a front sprocket 103 via the drive unit 1 .
- the front sprocket 103 drives a chain 104 which in turn drives a rear sprocket 105 .
- the rear sprocket 105 is mounted to a wheel axle 106 of a rear wheel.
- a pedaling force acting on the pedals 100 is transmitted along the following path: the crank arms 101 ⁇ the drive unit 1 ⁇ a front sprocket 103 ⁇ a chain 104 ⁇ a rear sprocket 105 ⁇ a hub body which rotates about the wheel axle 106 of the rear wheel.
- the drive unit 1 includes an assistance motor 120 that supplements the pedaling force of the rider.
- the crank axle 102 and the output shaft of the motor 120 are coaxial. With this arrangement, the pedaling force is combined with the assisting force provided by a motor output of the motor 120 such that a combined output force is transmitted to the rear wheel.
- a torque detecting device or sensor unit detects a torque acting on the crank axle 102 as described later. Then, when the detected value exceeds a set value, the assistance motor 120 is started to generate an assisting torque (i.e., assisting power) corresponding to the amount by which the detected torque from the pedaling power is insufficient.
- the drive unit 1 which includes the assistance motor 120 is typically arranged in the vicinity of a frame joint portion where a bottom end portion of a seat tithe of the frame and a rearward end portion of the down tube of the frame join together.
- a battery is typically arranged on a rear carrier, the down tube, or the seat tube for providing electrical driving power to drive the motor 120 .
- the drive unit 1 is configured such that the rotational axis of the crank axle 102 and the rotational axis of the assistance motor 120 are coaxial.
- the assistance motor 120 which has a crank axle receiving hole 120 a in which the crank axle 102 is rotatably disposed.
- a sensor unit 150 is at least partially arranged between the motor 120 and the crank axle 102 inside the crank axle receiving hole 120 a.
- the crank axle 102 is inserted into a through hole 111 a of a casing 111 .
- the crank axle 102 is rotatably supported by the casing 111 so as to freely rotate through a pair of roller bearings 112 and 113 .
- the crank arms 101 are detachably mounted on opposite ends of the crank axle 102 using bolts.
- the crank arms 101 are arranged on the exterior of the casing 111 .
- One of the crank arms 101 among the two crank arms 101 can be configured so as to not be detachable from the crank axle 102 .
- the motor 120 is an electric motor that has the crank axle receiving hole 120 a in which the crank axle 102 is rotatably arranged.
- the crank axle receiving hole 120 a is provided in a rotation center section of the motor 120 .
- the motor 120 is arranged such that its rotational axis is the same axis as the rotational axis of the crank axle 102 . In other words, the rotational axis of the assistance motor 120 is coincident with the rotational axis of the crank axle 102 .
- the motor 120 basically includes a stator 121 , a mounting structure 122 and a rotor 123 .
- the stator 121 of the motor 120 is formed in a cylindrical shape.
- the stator 121 is arranged coaxially with the crank axle 102 .
- a field coil is wound onto the stator 121 .
- the stator 121 is fixed to a motor case 125 with the mounting structure 122 .
- the motor case 125 is fixed to the casing 111 .
- the crank axle receiving hole 120 a is formed at an inner side in the radial direction of the stator 121 .
- the rotor 123 is formed in a cylindrical shape.
- the rotor 123 is rotatably supported around the crank axle 102 by the motor case 125 so as to freely rotate.
- the rotor 123 has, for example, a plurality of magnets (not shown) having a plurality of magnetic poles.
- the magnetic poles of the rotor 123 are arranged along a circumferential direction with a magnet holding section (not shown) holding the magnets.
- the motor 120 is an outer rotor type motor in which an outer perimeter of the stator 121 is surrounded by the rotor 123 .
- the rotor 123 is rotatably supported on the crank axle 102 with a first bearing 124 a and a second bearing 124 b so as to freely rotate about the crank axle 102 .
- the first and second bearings 124 a and 124 b are arranged to be spaced apart in the crank axle direction of the crank axle 102 .
- 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 which is not shown in the drawings.
- the inverter is driven by a control section which is not shown in the drawings, and the controller controls the inverter according to the pedaling force and a detected speed of the bicycle using known technology.
- the sensor unit 150 detects a twisting force, which is applied to the crank axle 102 . Since this twisting is proportional to the pedaling force of the user which is applied to the crank axle 102 , the pedaling force of the user which is applied to the crank axle 102 can be understood by detecting the twisting.
- the sensor unit 150 includes a hollow member 151 and a strain sensor 155 .
- the hollow member 151 has an insertion hole into which the crank axle 102 can be arranged.
- the hollow member 151 is provided with a first connection section 151 a, a second connection section 151 b and an insertion hole 151 c.
- the first connection section 151 a is connected to the crank axle 102 .
- the second connection section 151 b transmits the rotational force to the power transmission axle to be described later.
- the crank axle 102 can be arranged in the insertion hole 151 c. Except for the first connection section 151 a, the hollow member 151 is separated from the crank axle 102 , which is arranged at an inner side. In the first connection section 151 a, the hollow member 151 is inserted with a key or a serration which protrudes from the crank axle 102 and is fixed by means of screwing, press fitting, or the like.
- the first connection section 151 a and the second connection section 151 b are provided to be separated in the direction of the crank axle 102 .
- the strain sensor 155 is preferably a magnetostrictive sensor that includes a magnetostrictive element 155 a and a detection coil 155 b.
- the magnetostrictive element 155 a is provided in the hollow member 151 .
- the detection coil 155 b is provided at the periphery of the magnetostrictive element 155 a.
- the detection coil 155 b is fixed to the motor case 125 by a fixing member 156 . In this manner, the detection coil 155 b is supported by the casing 111 so as not to be able to rotate.
- One part of the sensor unit 150 is at least partially arranged between the motor 120 and the crank axle 102 .
- a region between the crank arms 101 is between the motor 120 and the crank axle 102 in the embodiment with a range W between both ends of the stator 121 in the direction in which the rotational axis of the motor 120 extends.
- at least one part or all of the strain sensor 155 is preferably provided in the region along the crank axle 102 and between both ends of the stator 121 in the direction in which the rotational axis of the motor 120 extends.
- At least one part or all of the strain sensor 155 can be provided in a region along the crank axle 102 in the range W between both ends of the stator 121 in the direction in which the rotational axis of the motor 120 extends and in a range overlapping with the rotor 123 in the direction in which the rotational axis of the assistance motor 120 extends.
- a reduction gear mechanism 127 transmits rotation of the rotor 123 to a torque transmitting member 130 .
- the reduction gear mechanism 127 includes one or more gears.
- the example of FIG. 2 shows a case in which the gear reduction mechanism 127 has two planetary gear mechanisms.
- a first planetary gear mechanism includes a first sun gear 128 a, a plurality of first planetary gears 128 b, a first carrier 128 c and a first ring gear 128 d.
- the first sun gear 128 a is coupled to the rotor 123 .
- the first carrier 128 c supports the first planetary gears 128 b so as to be able to rotate.
- the first ring gear 128 d is fixed to the casing 111 .
- a second planetary gear mechanism includes a second sun gear 129 a, a plurality of second planetary gears 129 b , a second carrier 129 c and a second ring gear 129 d,
- the second sun gear 129 a is coupled to the first carrier 128 c.
- the second carrier 129 c supports the plurality of second planetary gears 129 b so as to be able to rotate.
- the second ring gear 129 d is fixed to the casing 111 .
- the output of the gear reduction mechanism 127 is transmitted to an output part 131 (described in detail later) through the torque transmitting member 130 .
- the torque transmitting member 130 is joined to the second carrier section 129 d so as to be formed as unitary body.
- the torque transmitting member 130 is supported so as to be able to rotate on an inside face (described in detail later) of the output part 131 through a one-way clutch 132 and a rotation supporting part 133 .
- the rotation supporting part 133 is configured as a sliding bearing in the embodiment, but can be configured by a ball bearing.
- the rotation supporting part 133 is arranged farther to an outer side than the one-way clutch 132 in a radial direction with relation to the crank axle 102 .
- the torque transmitting member 130 supports a plurality of clutch pawls of the one-way clutch 132 .
- the output part 131 transmits rotational force of the motor 120 and rotational force of the crank axle 102 to the front sprocket 103 .
- the output part 131 is provided on an end portion side of the crank axle 102 .
- the output part 131 is formed in an annular shape.
- the output part 131 has a first annular portion 131 a, a second annular portion 131 b and a third annular portion 131 c.
- the first annular portion 131 a extends along the crank axle 102 .
- the second annular portion 131 b extends in the radial direction with respect to the crank axle 102 from the end portion of the motor side of the first annular portion 131 a.
- the third annular portion 131 c extends in a direction parallel to the crank axle 102 from the end portion of the motor side of the second annular portion 131 b.
- An inner circumferential portion of the output part 131 is coupled to the torque transmitting member 130 through the one-way clutch 132 .
- a clutch groove of the one-way clutch 132 is formed in an inner circumferential portion of the first annular portion 131 a and the second annular portion 131 b .
- the clutch groove is a second coupling section and configures an internally toothed gear wheel.
- the rotation supporting part 133 is provided on an inner circumferential portion of the third annular portion 131 c. The rotation supporting part 133 supports the rotation of the torque transmitting member 130 .
- a fourth annular portion 131 d extends to an inner side in the circumferential direction.
- the fourth annular portion 131 d is provided at the end portion of the first annular portion 131 a, which is the opposite side to the second annular portion 131 b .
- a bearing 113 is provided on an inner circumferential portion of the fourth annular portion 131 d.
- the bearing 134 is provided on an outer circumferential portion of the first annular portion 131 a. In this manner, the output part 131 is supported by the casing 111 so as to be able to rotate.
- the bearings 113 and 134 are formed as, for example, radial bearings, such that the inner ring body of the bearing 113 supports the crank axle 102 , and the outer ring body of the bearing 134 is supported by the casing 111 .
- the end portion of the fourth annular portion 131 d of the output part 131 protrudes to the outside from an opening 111 b of the casing 111 .
- the output part 131 is provided with a sprocket connection section 131 e in the outer circumferential portion of the portion which protrudes from the casing 111 of the fourth annular portion 131 d.
- a front sprocket 103 is removably attached to the sprocket connection section 131 d with, for example, a bolt. In this manner, the front sprocket 103 is able to rotate integrally with the output part 131 .
- the rotational force according to the second connection section 151 b of the sensor unit 150 is transmitted to the power transmission axle 160 through a first gear wheel 114 and a second gear wheel 161 .
- the rotation of the power transmission axle 160 is transmitted to the output part 131 through a third gear wheel 142 .
- the second connection section 151 b of the sensor unit 150 is coupled to the first gear wheel 114 .
- the first gear wheel 114 is provided at the end portion of the output part 131 which is the opposite side to the end portion of the crank axle 102 .
- the first connection section 151 a of the sensor unit 150 is provided at the output part side of the output part 131 .
- the first connection section 151 a is coupled to the crank axle 102 in a region between the assistance motor 120 and the crank axle 102 .
- the first gear wheel 114 is fixed to the second connection section 151 b and rotates integrally with the crank axle 102 .
- the first gear wheel 114 can be detachably mounted on the second connection section 151 b using, for example, serrations. Except for the first connection section 151 a, the hollow member 151 is separated from the crank axle 102 which is arranged at an inner side.
- the first gear wheel 114 and the second gear wheel 161 form a first coupling mechanism
- the second gear wheel 161 is fixed to the power transmitting axle 160 so as to not be able to rotate and rotates integrally therewith.
- the second gear wheel 161 is provided on one end portion of the power transmitting axle 160 .
- the second gear wheel 161 meshes with the first gear wheel 114 .
- the power transmission axle 160 is supported by a supporting axle 170 to freely rotate.
- the supporting axle 170 is provided to be separated from the crank axle 102 .
- the power transmission axle 160 is provided to be separated from the crank axle 102 .
- the rotational axis of the power transmission axle 160 is parallel to the rotational axis of the crank axle 102 .
- At least one of the supporting axle 170 and the power transmission axle 160 can be provided with a regulating member 175 which regulates the movement of the power transmission axle 160 in the axial direction of the supporting axle 170 .
- the power transmission axle 160 and the supporting axle 170 form a sliding bearing.
- a supporting axle 170 has first female threaded portions (not shown), which are for fixing to an insertion opening 115 which is formed in the casing 111 using a nut 116 , at both end portions thereof.
- Rotation preventing sections (not shown) are formed parallel and prevent the rotation in the insertion opening 115 . These rotation preventing sections are respectively formed in the first female threaded portions 24 .
- a third gear wheel 142 is fixed to the other end portion of the power transmission axle 160 so as not to be able to rotate.
- a fourth gear 171 is formed at an outer circumference of the output part 131 .
- the fourth gear 171 is configured as an externally toothed gear wheel which constitutes a first coupling section.
- the fourth gear 171 is formed at the outer circumference of the second annular portion 131 b and the third annular portion 131 c.
- the fourth gear 171 is formed integrally with the output part 131 .
- the fourth gear 171 meshes with the third gear wheel 142 .
- the third gear wheel 142 and the fourth gear 171 form a second coupling mechanism.
- the first coupling mechanism e.g., the first gear wheel 114 and the second gear wheel 161
- the second coupling mechanism e.g., the third gear wheel 142 and the fourth gear 171
- the power transmission axle 160 is coupled to the crank axle at one end of the motor 120 in the axial direction of the crank axle and coupled to the output part 131 at the other end of the motor 120 .
- a torque which is due to the pedaling force of a rider is transmitted through the transmission mechanism from the crank 101 ⁇ the crank axle 102 ⁇ the first connection section 151 a ⁇ the second connection section 151 b ⁇ the first gear wheel 114 ⁇ the second gear wheel 161 ⁇ the power transmission axle 160 ⁇ the third gear wheel 142 ⁇ the output part 131 .
- output torque from the motor 120 is transmitted from the reduction gear mechanism 127 ⁇ the torque transmitting member 130 ⁇ the one-way clutch 132 ⁇ the output part 131 .
- the output part 131 combines the two torques and transmits the combined torque to the front sprocket 103 . In this way, assistance using the motor is realized.
- the rotation axis of the crank axle 102 and the rotation axis of the motor 120 are the same axis and at least a part of the sensor unit 150 is arranged in the hole 120 a of the motor 120 in which the crank axle 102 is arranged. In this manner, the drive unit 1 which has the motor 120 for assisted riding can be configured to be lightweight and compact.
- FIG. 3 is a cross sectional view of the drive unit according to a second embodiment.
- the drive unit 1 according to the second embodiment differs from the drive unit according to the first embodiment primarily in the following ways.
- the motor 120 is an inner rotor type motor in which the stator 121 is provided to surround the outer perimeter of the rotor 123 .
- FIG. 3 illustrates a case where the reduction gear mechanism 127 has one gear, but this is only for illustration.
- the functions of the reduction gear mechanism 127 are the same as those of the first embodiment.
- the second connection section 151 b of the sensor unit 150 is coupled to the first gear wheel 114 .
- the first gear wheel 114 is fixed to the second connection section 151 b and rotates integrally with the crank axle 102 .
- the first gear wheel 114 can be detachably mounted on the second connection section 151 b using, for example, serrations.
- the first connection section 151 a is coupled to the crank axle 102 in a region between the motor 120 and the crank axle 102 . Except for the first connection section 151 a, the hollow member 151 is separated from the crank axle 102 which is arranged at an inner side.
- the second gear wheel 161 meshes with the first gear wheel 114 .
- the second gear wheel 161 is formed integrally with the power transmission axle 160 .
- the third gear wheel 142 is formed integrally with the power transmission axle 160 .
- the power transmission axle 160 is integrally formed with the second gear wheel 161 and the third gear wheel 142 , but the power transmission axle 160 can be integrally formed with at least either one of the second gear wheel 161 and the third gear wheel 142 .
- one part of the sensor unit 150 is at least partially arranged between the motor 120 and the crank axle 102 , and at least one part or all of the strain sensor 155 is provided in a region along the crank axle 102 in the range W between both ends of the stator 121 in the direction in which the rotational axis of the motor 120 extends.
- the strain sensor 155 is a magnetostrictive sensor
- the strain sensor 155 can be a strain gauge or a semiconductor strain sensor.
- the magnetostrictive element 155 a is arranged in the hollow member 151 has been illustrated, but the magnetostrictive element 155 a can be directly arranged in the crank axle 102 .
- the first gear wheel 114 is directly fixed to the crank axle 102 without providing the hollow member 151 .
- FIG. 4 is a cross sectional view of the drive unit according to a third embodiment.
- the drive unit according to the third embodiment differs from the drive unit according to the first embodiment primarily in the following ways. There are differences in that the motor 120 is an inner rotor type motor in which the stator 121 is provided to surround the outer perimeter of the rotor 123 , and there is a detection means (torque detection means) for detecting human driving force.
- the motor 120 is an inner rotor type motor in which the stator 121 is provided to surround the outer perimeter of the rotor 123 , and there is a detection means (torque detection means) for detecting human driving force.
- FIG. 4 illustrates a case where the reduction gear mechanism 127 has one gear, but this is only for illustration.
- the functions of the reduction gear mechanism 127 are the same as those of the first embodiment.
- the same reference numerals are used where the configuration is the same as the embodiments described above.
- the motor (electric motor) 120 is arranged such that the rotational axis thereof is the same axis as the rotational axis of the crank axle 102 .
- the stator 121 is arranged coaxially with the crank axle 102 .
- a field coil is wound onto the stator 121 .
- the stator 121 is fixed to a motor case 125 with the mounting structure 122 .
- the rotor 123 is formed in a cylindrical shape.
- the rotor 123 is rotatably supported around the crank axle 102 by the motor case 125 so as to freely rotate.
- the rotor 123 has, for example, a plurality of magnets (not shown) having a plurality of magnetic poles.
- the magnetic poles of the rotor 123 are arranged along a circumferential direction with a magnet holding section (not shown) holding the magnets.
- the motor 120 is an inner rotor type motor in which the rotor 123 is provided to surround the outer perimeter of the stator 121 .
- the rotor 123 is rotatably supported on the crank axle 102 with a first bearing 124 a and a second bearing 124 b so as to freely rotate about the crank axle 102 .
- the first and second bearings 124 a and 124 b are arranged to be spaced apart in the crank axle direction of the crank axle 102 .
- 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 which is not shown in the drawings.
- the inverter is driven by a control section which is not shown in the drawings, and the controller controls the inverter according to the pedaling force and a detected speed of the bicycle using known technology.
- the reduction gear mechanism 127 transmits rotation of the rotor 123 to the torque transmitting member 130 and transmits rotation of the torque transmitting member 130 to the rotor 123 .
- the reduction gear mechanism 127 has a planetary gear mechanism 126 .
- the planetary gear mechanism 126 has a sun gear 126 a, an internally toothed gear 126 b and a plurality of (for example, three) planet gears 126 c .
- the sun gear 126 a is fixed to the rotor 123 .
- the internally toothed gear 126 b is provided on the mounting structure 122 .
- the internally toothed gear 126 b is arranged around the outside circumference of the sun gear 126 a.
- the planet gears 126 c are supported so as to be able to rotate by the torque transmitting member 130 .
- the planet gears 126 c mesh with the sun gear 126 a and the internally toothed gear 126 b .
- the torque transmitting member 130 is a so-called carrier.
- Each of the planet gears 126 c has a first gear section and a second gear section which have a different number of teeth. The number of teeth in the first gear section is greater than the number of teeth than the second gear section.
- the first gear section meshes with the sun gear 126 a, while the second gear section meshes with the internally toothed gear 126 b .
- the torque transmitting member 130 is supported by an inside face of the output part 131 so as to be able to rotate through the one-way clutch 132 and the rotation supporting part 133 .
- the rotation supporting part 133 is configured as a sliding bearing in the embodiment, but can be configured by a ball bearing.
- the rotation supporting part 133 is arranged farther to an outer side than the one-way clutch 132 in a radial direction with relation to the crank axle.
- this planetary gear mechanism 126 since the internally toothed gear 126 b is fixed so as not to be able to rotate with respect to the casing 111 , the speed of the rotation of the sun gear 126 a to which the rotor 123 is coupled is reduced and transmitted to the torque transmitting member 130 .
- the first coupling mechanism is provided with a first gear wheel 114 and a second gear wheel 141 and couples the crank axle 102 and the power transmission axle 160 .
- the first gear wheel 114 is provided on one end portion side of the crank axle 102 .
- the first gear wheel 114 is fixed to the crank axle 102 and rotates integrally with the crank axle 102 .
- the first gear wheel 114 can be detachably mounted to the crank axle 102 using, for example, serrations.
- the second gear 141 meshes with the first gear wheel 114 and transmits driving power to the power transmission axle 160 .
- the power transmission axle 160 is supported by a supporting axle 170 using a ball bearing on as to freely rotate.
- a sensor unit 180 for detecting the driving power imparted to the power transmission axle 160 is provided in the power transmission axle 160 .
- the second coupling mechanism is provided with a third gear wheel 142 and a fourth gear wheel 171 and couples the power transmission axle 160 and the output part 131 .
- the third gear wheel 142 is fixed to the other end portion of the power transmission axle 160 so as not to be able to rotate and meshes with the fourth gear wheel 171 which is provided in the output part 131 .
- the sensor unit 180 detects twisting force, which is applied to the power transmission axle 160 .
- the sensor unit 180 is configured by the strain sensor 155 .
- the strain sensor is a magnetostrictive sensor and, in the embodiment, is provided with a magnetostrictive element which is provided in the power transmission axle 160 and a detection coil which is provided at the periphery of 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 111 .
- the strain sensor 155 can be a strain gauge or a semiconductor strain sensor.
- a transmitter which transmits a signal from the strain sensor which is provided in the power transmission axle 160 to the outside wirelessly or the like and a receiver which receives the signal from the transmitter can be further provided.
- axle 160 and the transmission of the torque from the power transmission axle 160 to the output part 131 are performed using gears, but the transmission of the torque can be performed using a sprocket and a chain, or a pulley and a belt.
- first coupling mechanism is formed by the first gear wheel 114 and the second gear wheel 141 and the second coupling mechanism is formed by the third gear wheel 142 and the fourth gear wheel 171 , but each of the coupling mechanisms can be configured using three or more gear wheels.
- the reduction gear mechanism 127 can be omitted. In this case, the motor output is transmitted to the one-way clutch 132 as it is.
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Abstract
Description
- This application claims priority under 35 U.S.C. §119 to Taiwanese Patent Application No. 101137720, filed Oct. 12, 2012 and to German Patent Application No. 102012109743.7 filed Oct. 12, 2012. The entire disclosures of Applications are hereby incorporated herein by reference.
- This application is a continuation-in-part application of U.S. patent application Ser. No. 13/608,151, filed on Sep. 10, 2012. The entire disclosure of U.S. patent application Ser. No. 13/608,151 is hereby incorporated herein by reference.
- 1. Field of the invention
- This invention generally relates to a drive unit for an electrically assisted bicycle that uses a motor output as an assisting power.
- 2. Background Information
- One example of an electrically assisted bicycle is disclosed in German Patent Publication No. DE 10 2010 028 667 in which the electrically assisted bicycle uses a motor output as an assisting power to drive the bicycle. In the electrically assisted bicycle disclosed in this German Patent Publication, a pedaling force, which is inputted by the pedals, is transmitted through the transmission mechanism and the transmitted drive force is then combined with a drive force from the motor. The combined drive force is then transmitted to a rear wheel of the bicycle to rotate the rear wheel.
- It has been found that with the drive unit of the above mentioned German Patent Publication, the drive unit becomes large due to the power transmission paths from the crank axle and the axle of the motor to the sprocket 28 being separated.
- The present invention was conceived in view of the problem described above. One object proposed by this disclosure is to provide a lighter, more compact drive unit for a bicycle which has a motor for assisted riding.
- In view of the state of the known technology and to achieve the object described above, the bicycle drive unit is provided that comprises a motor, a crank axle, a power transmission axle and an output part. The motor includes a crank axle receiving hole. The crank axle is rotatably disposed in the crank axle receiving hole of the motor. The power transmission axle is separate from the crank axle and arranged to transmit rotation of the crank axle. The output part is operatively coupled to the motor and the power transmission axle to combine a rotational output of the motor and a rotational output of the transmission mechanism together.
- In this manner, since the crank axle can be inserted in the hole in the motor and a sensor unit can be arranged inside the hole in the motor, the bicycle drive unit can be made lighter and more compact.
- Furthermore, in the bicycle drive unit, it is preferable for the power transmission axle to be coupled to the crank axle at a first end of the motor in an axial direction of the crank axle and coupled to the output part at a second end of the motor. In this manner, the motor which has a relatively large weight can be arranged in the vicinity of the center of the drive unit in the axial direction of the crank axle.
- Furthermore, it is preferable for the bicycle drive unit to be provided with a first coupling mechanism coupling the crank axle and the power transmission axle, and a second coupling mechanism coupling the power transmission axle and the output part.
- Furthermore, in the bicycle drive unit, it is preferable for the motor to have a rotational axis that is coaxially aligned with the rotational axis of the crank axle.
- Furthermore, it is preferable for a sprocket to be connected to the output part. In this manner, the output from the output part can be transmitted to a rear hub or the like.
- Furthermore, it is preferable or the bicycle drive unit to further have a one-way clutch to transmit the output of the motor to the output part. In this manner, the rotational force of the crank axle can be prevented from being transmitted to the motor.
- Furthermore, it is preferable for the bicycle drive unit to further have a reduction gear mechanism to transmit the output of the motor to the output part. In this manner, since the speed of the motor output can be reduced and transmitted to the output part, it is possible to realize a power transmission section which allows the motor to be operated efficiently.
- Furthermore, it is preferable for the bicycle drive unit to further have a reduction gear mechanism, the output of the motor being inputted to the reduction gear mechanism, and the output of the reduction gear mechanism being transmitted to the output part through a one-way clutch. In this manner, it is possible to realize prevention of the rotational power of the crank axle being transmitted to the motor as well as efficient operation of the motor.
- Furthermore, in the bicycle drive unit, it is preferable for the first coupling mechanism to include one of a gear, a sprocket and a pulley, and.
- Furthermore, in the bicycle drive unit, it is preferable for the second coupling mechanism to include one of a gear, a sprocket and a pulley.
- Furthermore, in the bicycle drive unit, it is preferable for the output part to have a rotational axis that is axially aligned with the rotational axis of the crank axle. In this manner, since the bearings of the rotational axis of the output part and the rotational axis of the crank axle can be integrated, the bicycle drive unit can be made even lighter and more compact.
- Furthermore, it is preferable for the output part to have a first joining section which is joined to the power transmission axle and a second joining section which is joined to the motor. Here, it is preferable for the first joining section to have an externally toothed gear wheel. in addition, it is preferable for the second joining section to have an internally toothed gear wheel. In this manner, the drive unit can combine the rotary torque of the crank axle and the rotary torque of the motor.
- According to the bicycle drive unit of the present disclosure, a bicycle drive unit, which has a motor for assisted riding, can be realized that is lighter and more compact.
- Referring now to the attached drawings which form a part of this original disclosure:
-
FIG. 1 is a simplified side elevational view of an electrically assisted bicycle equipped with a drive unit according to a first embodiment; -
FIG. 2 is a cross sectional view of a drive unit according to the first embodiment; -
FIG. 3 is a cross sectional view of a drive unit according to a second embodiment; and -
FIG. 4 is a cross sectional view of a drive unit according to a third embodiment. - Selected embodiments will now be explained with reference to the drawings. It will be apparent to those skilled in the art from this disclosure that the following descriptions of the embodiments are provided for illustration only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
- Referring initially to
FIG. 1 , a bicycle drive unit 1 is illustrated in accordance with a first embodiment. In particular,FIG. 1 is a simplified, right side elevational view of an electrically assisted bicycle having the drive unit 1, as described below. The electrically assisted bicycle has a pair ofpedals 100. Thepedals 100 are each rotatably mounted to acrank arm 101. Thecrank arms 101 are fixed to an end so acrank axle 102 that is operatively connected to afront sprocket 103 via the drive unit 1. Thefront sprocket 103 drives achain 104 which in turn drives arear sprocket 105. Therear sprocket 105 is mounted to awheel axle 106 of a rear wheel. Thus, in this electrically assisted bicycle, a pedaling force acting on thepedals 100 is transmitted along the following path: thecrank arms 101→the drive unit 1→afront sprocket 103→achain 104→arear sprocket 105→a hub body which rotates about thewheel axle 106 of the rear wheel. - As explained below, the drive unit 1 includes an
assistance motor 120 that supplements the pedaling force of the rider. In the first embodiment, thecrank axle 102 and the output shaft of themotor 120 are coaxial. With this arrangement, the pedaling force is combined with the assisting force provided by a motor output of themotor 120 such that a combined output force is transmitted to the rear wheel. - Normally, a torque detecting device or sensor unit detects a torque acting on the
crank axle 102 as described later. Then, when the detected value exceeds a set value, theassistance motor 120 is started to generate an assisting torque (i.e., assisting power) corresponding to the amount by which the detected torque from the pedaling power is insufficient. The drive unit 1 which includes theassistance motor 120 is typically arranged in the vicinity of a frame joint portion where a bottom end portion of a seat tithe of the frame and a rearward end portion of the down tube of the frame join together. A battery is typically arranged on a rear carrier, the down tube, or the seat tube for providing electrical driving power to drive themotor 120. - In the first embodiment, the drive unit 1 is configured such that the rotational axis of the
crank axle 102 and the rotational axis of theassistance motor 120 are coaxial. The structure and function of the drive unit 1 will be explained below with reference toFIG. 2 . Referring toFIG. 2 , theassistance motor 120 which has a crankaxle receiving hole 120 a in which thecrank axle 102 is rotatably disposed. Asensor unit 150 is at least partially arranged between themotor 120 and thecrank axle 102 inside the crankaxle receiving hole 120 a. - As shown in
FIG. 2 , in this drive unit 1, thecrank axle 102 is inserted into a throughhole 111 a of acasing 111. Thecrank axle 102 is rotatably supported by thecasing 111 so as to freely rotate through a pair ofroller bearings arms 101 are detachably mounted on opposite ends of thecrank axle 102 using bolts. The crankarms 101 are arranged on the exterior of thecasing 111. One of thecrank arms 101 among the two crankarms 101 can be configured so as to not be detachable from thecrank axle 102. - The
motor 120 is an electric motor that has the crankaxle receiving hole 120 a in which thecrank axle 102 is rotatably arranged. The crankaxle receiving hole 120 a is provided in a rotation center section of themotor 120. Themotor 120 is arranged such that its rotational axis is the same axis as the rotational axis of thecrank axle 102. In other words, the rotational axis of theassistance motor 120 is coincident with the rotational axis of thecrank axle 102. - The
motor 120 basically includes astator 121, a mountingstructure 122 and arotor 123. Thestator 121 of themotor 120 is formed in a cylindrical shape. Thestator 121 is arranged coaxially with thecrank axle 102. A field coil is wound onto thestator 121. Thestator 121 is fixed to amotor case 125 with the mountingstructure 122. Themotor case 125 is fixed to thecasing 111. The crankaxle receiving hole 120 a is formed at an inner side in the radial direction of thestator 121. Therotor 123 is formed in a cylindrical shape. Therotor 123 is rotatably supported around thecrank axle 102 by themotor case 125 so as to freely rotate. Therotor 123 has, for example, a plurality of magnets (not shown) having a plurality of magnetic poles. The magnetic poles of therotor 123 are arranged along a circumferential direction with a magnet holding section (not shown) holding the magnets. In this embodiment, themotor 120 is an outer rotor type motor in which an outer perimeter of thestator 121 is surrounded by therotor 123. Therotor 123 is rotatably supported on thecrank axle 102 with afirst bearing 124 a and asecond bearing 124 b so as to freely rotate about thecrank axle 102. The first andsecond bearings crank axle 102. Thefirst bearing 124 a and thesecond bearing 124 b are supported by themotor case 125. Here, themotor 120 is driven by an inverter which is not shown in the drawings. The inverter is driven by a control section which is not shown in the drawings, and the controller controls the inverter according to the pedaling force and a detected speed of the bicycle using known technology. - The
sensor unit 150 detects a twisting force, which is applied to the crankaxle 102. Since this twisting is proportional to the pedaling force of the user which is applied to the crankaxle 102, the pedaling force of the user which is applied to the crankaxle 102 can be understood by detecting the twisting. Thesensor unit 150 includes ahollow member 151 and astrain sensor 155. Thehollow member 151 has an insertion hole into which thecrank axle 102 can be arranged. Thehollow member 151 is provided with afirst connection section 151 a, asecond connection section 151 b and aninsertion hole 151 c. Thefirst connection section 151 a is connected to the crankaxle 102. Thesecond connection section 151 b transmits the rotational force to the power transmission axle to be described later. Thecrank axle 102 can be arranged in theinsertion hole 151 c. Except for thefirst connection section 151 a, thehollow member 151 is separated from thecrank axle 102, which is arranged at an inner side. In thefirst connection section 151 a, thehollow member 151 is inserted with a key or a serration which protrudes from thecrank axle 102 and is fixed by means of screwing, press fitting, or the like. Thefirst connection section 151 a and thesecond connection section 151 b are provided to be separated in the direction of thecrank axle 102. Thestrain sensor 155 is preferably a magnetostrictive sensor that includes amagnetostrictive element 155 a and adetection coil 155 b. Themagnetostrictive element 155 a is provided in thehollow member 151. Thedetection coil 155 b is provided at the periphery of themagnetostrictive element 155 a. Thedetection coil 155 b is fixed to themotor case 125 by a fixing member 156. In this manner, thedetection coil 155 b is supported by thecasing 111 so as not to be able to rotate. - One part of the
sensor unit 150 is at least partially arranged between themotor 120 and thecrank axle 102. A region between thecrank arms 101 is between themotor 120 and thecrank axle 102 in the embodiment with a range W between both ends of thestator 121 in the direction in which the rotational axis of themotor 120 extends. In thesensor unit 150, at least one part or all of thestrain sensor 155 is preferably provided in the region along thecrank axle 102 and between both ends of thestator 121 in the direction in which the rotational axis of themotor 120 extends. At least one part or all of thestrain sensor 155 can be provided in a region along thecrank axle 102 in the range W between both ends of thestator 121 in the direction in which the rotational axis of themotor 120 extends and in a range overlapping with therotor 123 in the direction in which the rotational axis of theassistance motor 120 extends. - A
reduction gear mechanism 127 transmits rotation of therotor 123 to atorque transmitting member 130. Thereduction gear mechanism 127 includes one or more gears. The example ofFIG. 2 shows a case in which thegear reduction mechanism 127 has two planetary gear mechanisms. A first planetary gear mechanism includes afirst sun gear 128 a, a plurality of firstplanetary gears 128 b, afirst carrier 128 c and afirst ring gear 128 d. Thefirst sun gear 128 a is coupled to therotor 123. Thefirst carrier 128 c supports the firstplanetary gears 128 b so as to be able to rotate. Thefirst ring gear 128 d is fixed to thecasing 111. A second planetary gear mechanism includes asecond sun gear 129 a, a plurality of secondplanetary gears 129 b, a second carrier 129 c and asecond ring gear 129 d, Thesecond sun gear 129 a is coupled to thefirst carrier 128 c. The second carrier 129 c supports the plurality of secondplanetary gears 129 b so as to be able to rotate. Thesecond ring gear 129 d is fixed to thecasing 111. - The output of the
gear reduction mechanism 127 is transmitted to an output part 131 (described in detail later) through thetorque transmitting member 130. Thetorque transmitting member 130 is joined to thesecond carrier section 129 d so as to be formed as unitary body. Thetorque transmitting member 130 is supported so as to be able to rotate on an inside face (described in detail later) of theoutput part 131 through a one-way clutch 132 and arotation supporting part 133. Therotation supporting part 133 is configured as a sliding bearing in the embodiment, but can be configured by a ball bearing. Therotation supporting part 133 is arranged farther to an outer side than the one-way clutch 132 in a radial direction with relation to the crankaxle 102. Thetorque transmitting member 130 supports a plurality of clutch pawls of the one-way clutch 132. - The
output part 131 transmits rotational force of themotor 120 and rotational force of thecrank axle 102 to thefront sprocket 103. Theoutput part 131 is provided on an end portion side of thecrank axle 102. Theoutput part 131 is formed in an annular shape. Theoutput part 131 has a firstannular portion 131 a, a secondannular portion 131 b and a thirdannular portion 131 c. The firstannular portion 131 a extends along thecrank axle 102. The secondannular portion 131 b extends in the radial direction with respect to the crankaxle 102 from the end portion of the motor side of the firstannular portion 131 a. The thirdannular portion 131 c extends in a direction parallel to the crankaxle 102 from the end portion of the motor side of the secondannular portion 131 b. An inner circumferential portion of theoutput part 131 is coupled to thetorque transmitting member 130 through the one-way clutch 132. A clutch groove of the one-way clutch 132 is formed in an inner circumferential portion of the firstannular portion 131 a and the secondannular portion 131 b. The clutch groove is a second coupling section and configures an internally toothed gear wheel. Therotation supporting part 133 is provided on an inner circumferential portion of the thirdannular portion 131 c. Therotation supporting part 133 supports the rotation of thetorque transmitting member 130. A fourthannular portion 131 d extends to an inner side in the circumferential direction. The fourthannular portion 131 d is provided at the end portion of the firstannular portion 131 a, which is the opposite side to the secondannular portion 131 b. Abearing 113 is provided on an inner circumferential portion of the fourthannular portion 131 d. Thebearing 134 is provided on an outer circumferential portion of the firstannular portion 131 a. In this manner, theoutput part 131 is supported by thecasing 111 so as to be able to rotate. Thebearings bearing 113 supports thecrank axle 102, and the outer ring body of thebearing 134 is supported by thecasing 111. The end portion of the fourthannular portion 131 d of theoutput part 131 protrudes to the outside from anopening 111 b of thecasing 111. Theoutput part 131 is provided with asprocket connection section 131 e in the outer circumferential portion of the portion which protrudes from thecasing 111 of the fourthannular portion 131 d. Afront sprocket 103 is removably attached to thesprocket connection section 131 d with, for example, a bolt. In this manner, thefront sprocket 103 is able to rotate integrally with theoutput part 131. - The rotational force according to the
second connection section 151 b of thesensor unit 150 is transmitted to thepower transmission axle 160 through afirst gear wheel 114 and asecond gear wheel 161. In addition, the rotation of thepower transmission axle 160 is transmitted to theoutput part 131 through athird gear wheel 142. - The
second connection section 151 b of thesensor unit 150 is coupled to thefirst gear wheel 114. Thefirst gear wheel 114 is provided at the end portion of theoutput part 131 which is the opposite side to the end portion of thecrank axle 102. Along with this, thefirst connection section 151 a of thesensor unit 150 is provided at the output part side of theoutput part 131. Thefirst connection section 151 a is coupled to the crankaxle 102 in a region between theassistance motor 120 and thecrank axle 102. Thefirst gear wheel 114 is fixed to thesecond connection section 151 b and rotates integrally with thecrank axle 102. Thefirst gear wheel 114 can be detachably mounted on thesecond connection section 151 b using, for example, serrations. Except for thefirst connection section 151 a, thehollow member 151 is separated from thecrank axle 102 which is arranged at an inner side. Thus, thefirst gear wheel 114 and thesecond gear wheel 161 form a first coupling mechanism, - The
second gear wheel 161 is fixed to thepower transmitting axle 160 so as to not be able to rotate and rotates integrally therewith. Thesecond gear wheel 161 is provided on one end portion of thepower transmitting axle 160. Thesecond gear wheel 161 meshes with thefirst gear wheel 114. - The
power transmission axle 160 is supported by a supportingaxle 170 to freely rotate. The supportingaxle 170 is provided to be separated from thecrank axle 102. In other words, thepower transmission axle 160 is provided to be separated from thecrank axle 102. The rotational axis of thepower transmission axle 160 is parallel to the rotational axis of thecrank axle 102. At least one of the supportingaxle 170 and thepower transmission axle 160 can be provided with a regulatingmember 175 which regulates the movement of thepower transmission axle 160 in the axial direction of the supportingaxle 170. In the embodiment, thepower transmission axle 160 and the supportingaxle 170 form a sliding bearing. - A supporting
axle 170 has first female threaded portions (not shown), which are for fixing to aninsertion opening 115 which is formed in thecasing 111 using anut 116, at both end portions thereof. Rotation preventing sections (not shown) are formed parallel and prevent the rotation in theinsertion opening 115. These rotation preventing sections are respectively formed in the first female threaded portions 24. - A
third gear wheel 142 is fixed to the other end portion of thepower transmission axle 160 so as not to be able to rotate. Afourth gear 171 is formed at an outer circumference of theoutput part 131. Thefourth gear 171 is configured as an externally toothed gear wheel which constitutes a first coupling section. Thefourth gear 171 is formed at the outer circumference of the secondannular portion 131 b and the thirdannular portion 131 c. In the embodiment, thefourth gear 171 is formed integrally with theoutput part 131. Thefourth gear 171 meshes with thethird gear wheel 142. Thus, thethird gear wheel 142 and thefourth gear 171 form a second coupling mechanism. - The first coupling mechanism (e.g., the
first gear wheel 114 and the second gear wheel 161) and the second coupling mechanism (e.g., thethird gear wheel 142 and the fourth gear 171) are arranged on the opposite side of theoutput part 131 and thefront sprocket 103 to interpose themotor 120. In this manner, thepower transmission axle 160 is coupled to the crank axle at one end of themotor 120 in the axial direction of the crank axle and coupled to theoutput part 131 at the other end of themotor 120. - Next, the operation of the drive unit will be described. A torque which is due to the pedaling force of a rider is transmitted through the transmission mechanism from the
crank 101→thecrank axle 102→thefirst connection section 151 a→thesecond connection section 151 b→thefirst gear wheel 114→thesecond gear wheel 161→thepower transmission axle 160→thethird gear wheel 142→theoutput part 131. On the other hand, output torque from themotor 120 is transmitted from thereduction gear mechanism 127→thetorque transmitting member 130→the one-way clutch 132→theoutput part 131. Theoutput part 131 combines the two torques and transmits the combined torque to thefront sprocket 103. In this way, assistance using the motor is realized. - In the drive unit 1 of the first embodiment, the rotation axis of the
crank axle 102 and the rotation axis of themotor 120 are the same axis and at least a part of thesensor unit 150 is arranged in thehole 120 a of themotor 120 in which thecrank axle 102 is arranged. In this manner, the drive unit 1 which has themotor 120 for assisted riding can be configured to be lightweight and compact. - In addition, by adjusting the gear ratios (number of gears) of the first to
fourth gear wheels output part 131 with respect to the number of rotations of thecrank axle 102. In this manner, setting can be performed according to the user of the bicycle which is provided with the drive unit 1. -
FIG. 3 is a cross sectional view of the drive unit according to a second embodiment. The drive unit 1 according to the second embodiment differs from the drive unit according to the first embodiment primarily in the following ways. Themotor 120 is an inner rotor type motor in which thestator 121 is provided to surround the outer perimeter of therotor 123. In the following description, detailed description will be given of the content which is different to the first embodiment. Here, for convenience,FIG. 3 illustrates a case where thereduction gear mechanism 127 has one gear, but this is only for illustration. The functions of thereduction gear mechanism 127 are the same as those of the first embodiment. - The
second connection section 151 b of thesensor unit 150 is coupled to thefirst gear wheel 114. Thefirst gear wheel 114 is fixed to thesecond connection section 151 b and rotates integrally with thecrank axle 102. Thefirst gear wheel 114 can be detachably mounted on thesecond connection section 151 b using, for example, serrations. Thefirst connection section 151 a is coupled to the crankaxle 102 in a region between themotor 120 and thecrank axle 102. Except for thefirst connection section 151 a, thehollow member 151 is separated from thecrank axle 102 which is arranged at an inner side. - The
second gear wheel 161 meshes with thefirst gear wheel 114. In the second embodiment, thesecond gear wheel 161 is formed integrally with thepower transmission axle 160. In addition, thethird gear wheel 142 is formed integrally with thepower transmission axle 160. In the embodiment, thepower transmission axle 160 is integrally formed with thesecond gear wheel 161 and thethird gear wheel 142, but thepower transmission axle 160 can be integrally formed with at least either one of thesecond gear wheel 161 and thethird gear wheel 142. In the embodiment, one part of thesensor unit 150 is at least partially arranged between themotor 120 and thecrank axle 102, and at least one part or all of thestrain sensor 155 is provided in a region along thecrank axle 102 in the range W between both ends of thestator 121 in the direction in which the rotational axis of themotor 120 extends. - In the embodiment described above, a case where the
strain sensor 155 is a magnetostrictive sensor has been illustrated, but thestrain sensor 155 can be a strain gauge or a semiconductor strain sensor. In addition, a case where themagnetostrictive element 155 a is arranged in thehollow member 151 has been illustrated, but themagnetostrictive element 155 a can be directly arranged in thecrank axle 102. In this case, thefirst gear wheel 114 is directly fixed to the crankaxle 102 without providing thehollow member 151. -
FIG. 4 is a cross sectional view of the drive unit according to a third embodiment. The drive unit according to the third embodiment differs from the drive unit according to the first embodiment primarily in the following ways. There are differences in that themotor 120 is an inner rotor type motor in which thestator 121 is provided to surround the outer perimeter of therotor 123, and there is a detection means (torque detection means) for detecting human driving force. In the following description, detailed description will be given of the content which is different to the first embodiment. Here, for convenience,FIG. 4 illustrates a case where thereduction gear mechanism 127 has one gear, but this is only for illustration. The functions of thereduction gear mechanism 127 are the same as those of the first embodiment. In addition, the same reference numerals are used where the configuration is the same as the embodiments described above. - Similar to the first embodiment, the motor (electric motor) 120 is arranged such that the rotational axis thereof is the same axis as the rotational axis of the
crank axle 102. Thestator 121 is arranged coaxially with thecrank axle 102. A field coil is wound onto thestator 121. Thestator 121 is fixed to amotor case 125 with the mountingstructure 122. Therotor 123 is formed in a cylindrical shape. Therotor 123 is rotatably supported around thecrank axle 102 by themotor case 125 so as to freely rotate. Therotor 123 has, for example, a plurality of magnets (not shown) having a plurality of magnetic poles. The magnetic poles of therotor 123 are arranged along a circumferential direction with a magnet holding section (not shown) holding the magnets. In the second embodiment, themotor 120 is an inner rotor type motor in which therotor 123 is provided to surround the outer perimeter of thestator 121. Therotor 123 is rotatably supported on thecrank axle 102 with afirst bearing 124 a and asecond bearing 124 b so as to freely rotate about thecrank axle 102. The first andsecond bearings crank axle 102. Thefirst bearing 124 a and thesecond bearing 124 b are supported by themotor case 125. Here, themotor 120 is driven by an inverter which is not shown in the drawings. The inverter is driven by a control section which is not shown in the drawings, and the controller controls the inverter according to the pedaling force and a detected speed of the bicycle using known technology. - The
reduction gear mechanism 127 transmits rotation of therotor 123 to thetorque transmitting member 130 and transmits rotation of thetorque transmitting member 130 to therotor 123. Thereduction gear mechanism 127 has aplanetary gear mechanism 126. Theplanetary gear mechanism 126 has asun gear 126 a, an internallytoothed gear 126 b and a plurality of (for example, three) planet gears 126 c. Thesun gear 126 a is fixed to therotor 123. The internallytoothed gear 126 b is provided on the mountingstructure 122. The internallytoothed gear 126 b is arranged around the outside circumference of thesun gear 126 a. The planet gears 126 c are supported so as to be able to rotate by thetorque transmitting member 130. The planet gears 126 c mesh with thesun gear 126 a and the internallytoothed gear 126 b. Thetorque transmitting member 130 is a so-called carrier. Each of the planet gears 126 c has a first gear section and a second gear section which have a different number of teeth. The number of teeth in the first gear section is greater than the number of teeth than the second gear section. The first gear section meshes with thesun gear 126 a, while the second gear section meshes with the internallytoothed gear 126 b. Thetorque transmitting member 130 is supported by an inside face of theoutput part 131 so as to be able to rotate through the one-way clutch 132 and therotation supporting part 133. Therotation supporting part 133 is configured as a sliding bearing in the embodiment, but can be configured by a ball bearing. Therotation supporting part 133 is arranged farther to an outer side than the one-way clutch 132 in a radial direction with relation to the crank axle. In thisplanetary gear mechanism 126, since the internallytoothed gear 126 b is fixed so as not to be able to rotate with respect to thecasing 111, the speed of the rotation of thesun gear 126 a to which therotor 123 is coupled is reduced and transmitted to thetorque transmitting member 130. - The first coupling mechanism is provided with a
first gear wheel 114 and a second gear wheel 141 and couples thecrank axle 102 and thepower transmission axle 160. Thefirst gear wheel 114 is provided on one end portion side of thecrank axle 102. Thefirst gear wheel 114 is fixed to the crankaxle 102 and rotates integrally with thecrank axle 102. Thefirst gear wheel 114 can be detachably mounted to the crankaxle 102 using, for example, serrations. The second gear 141 meshes with thefirst gear wheel 114 and transmits driving power to thepower transmission axle 160. - In the embodiment, the
power transmission axle 160 is supported by a supportingaxle 170 using a ball bearing on as to freely rotate. Asensor unit 180 for detecting the driving power imparted to thepower transmission axle 160 is provided in thepower transmission axle 160. The second coupling mechanism is provided with athird gear wheel 142 and afourth gear wheel 171 and couples thepower transmission axle 160 and theoutput part 131. Thethird gear wheel 142 is fixed to the other end portion of thepower transmission axle 160 so as not to be able to rotate and meshes with thefourth gear wheel 171 which is provided in theoutput part 131. Thesensor unit 180 detects twisting force, which is applied to thepower transmission axle 160. Since this twisting is proportional to the pedaling force of the user which is applied to the crankaxle 102, the pedaling force of the user which is applied to the crankaxle 102 can be understood by detecting the twisting of thepower transmission axle 160. Thesensor unit 180 is configured by thestrain sensor 155. The strain sensor is a magnetostrictive sensor and, in the embodiment, is provided with a magnetostrictive element which is provided in thepower transmission axle 160 and a detection coil which is provided at the periphery of the magnetostrictive element. Thesensor unit 180 has the same configuration as thesensor unit 150 described above. The detection coil is fixed to themotor case 111. - the embodiment, a case where the strain sensor is a magnetostrictive sensor has been illustrated, but the
strain sensor 155 can be a strain gauge or a semiconductor strain sensor. In this case, a transmitter which transmits a signal from the strain sensor which is provided in thepower transmission axle 160 to the outside wirelessly or the like and a receiver which receives the signal from the transmitter can be further provided. In the embodiments described above, the transmission of the driving power (torque and rotation) from thecrank axle 102 to the power transmission.axle 160 and the transmission of the torque from thepower transmission axle 160 to theoutput part 131 are performed using gears, but the transmission of the torque can be performed using a sprocket and a chain, or a pulley and a belt. - In addition, the first coupling mechanism is formed by the
first gear wheel 114 and the second gear wheel 141 and the second coupling mechanism is formed by thethird gear wheel 142 and thefourth gear wheel 171, but each of the coupling mechanisms can be configured using three or more gear wheels. - In addition, if the
motor 120 can be driven at a low speed, thereduction gear mechanism 127 can be omitted. In this case, the motor output is transmitted to the one-way clutch 132 as it is. - While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. For example, the size, shape, location or orientation of the various components can be changed as needed and/or desired so long as they do not substantially their intended function, Components that are shown directly connected or contacting each other can have intermediate structures disposed between them unless specifically stated otherwise. The functions of one element can be performed by two, and vice versa unless specifically stated otherwise. The structures and functions of one embodiment can be adopted in another embodiment. it is not necessary for all advantages to be present in a particular embodiment at the same time. Every feature which is unique from the prior art, alone or in combination with other features, also should be considered a separate description of further inventions by the applicant, including the structural and/or functional concepts embodied by such feature(s). Thus, the foregoing descriptions of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
Claims (12)
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US13/718,044 US8651993B1 (en) | 2012-09-10 | 2012-12-18 | Bicycle drive unit |
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US13/608,151 US9017201B2 (en) | 2011-10-13 | 2012-09-10 | Bicycle drive unit |
TW101137720A | 2012-10-12 | ||
TW101137720 | 2012-10-12 | ||
DE102012109743 | 2012-10-12 | ||
DE102012109743.7A DE102012109743B4 (en) | 2011-10-13 | 2012-10-12 | Bicycle drive unit |
TW101137720A TW201341262A (en) | 2011-10-13 | 2012-10-12 | Bicycle drive unit |
DE102012109743.7 | 2012-10-12 | ||
US13/718,044 US8651993B1 (en) | 2012-09-10 | 2012-12-18 | Bicycle drive unit |
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US13/608,151 Continuation-In-Part US9017201B2 (en) | 2011-10-13 | 2012-09-10 | Bicycle drive unit |
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US8651993B1 US8651993B1 (en) | 2014-02-18 |
US20140069231A1 true US20140069231A1 (en) | 2014-03-13 |
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US13/718,044 Active US8651993B1 (en) | 2012-09-10 | 2012-12-18 | Bicycle drive unit |
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