Abstract:
An electrically-driven bicycle comprises a bicycle frame. A bottom bracket shell is provided at a junction between a down tube and stays of the frame. An electric motor is connected to the bottom bracket shell, the electric motor having a hollow drive shaft with an output end projecting to a first side of the bottom bracket shell. A transmission connects the drive shaft to one of the a wheel and a drive train of the bicycle, to transmit a drive of the electric motor to the rear wheel. A crank set has an axle rotatably mounted within the hollow drive shaft for rotating independently from the drive shaft. Means are provided for transmitting pedaling actuation on the crank set to the rear wheel, the means being on the second side of the bottom bracket shell. An electrical drive system for bicycle is also provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority on U.S. Provisional Patent Application No. 61/314,773, incorporated herewith by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present disclosure relates to electrically driven bicycles and, more particularly, to a positioning of the various components of the electrical drive system on a bicycle, and to a configuration of electrical drive system. 
       BACKGROUND OF THE INVENTION 
       [0003]    It is commonly known to use electrical drive systems with bicycles. In such bicycles, the bicycles are not fully powered with the electrical drive system. Rather, the electrical drive system provides additional power to the pedaling performed by the user of the bicycle. Therefore, in conditions like hill climbing and headwind riding, additional power allows the rider to maintain relatively high speed while reducing the amount of additional pedaling power required. 
         [0004]    However, an important aspect of electrical drive system is where the various electrical components are positioned within the frame of the bicycle, as the frame of the bicycle has a relatively standard geometry, and how the electrical power is applied to the wheel. 
       SUMMARY OF THE APPLICATION 
       [0005]    It is therefore an aim of the present application to provide a novel bicycle frame and electrical drive assembly. 
         [0006]    Therefore, in accordance with a first embodiment, there is provided an electrically-driven bicycle comprising: a bicycle frame having a front frame portion to which a front wheel is rotatably mounted, and a rear frame portion to which a rear wheel is rotatably mounted, with a bottom bracket shell at a junction between a down tube of the front frame portion and stays of the rear frame portion; an electric motor connected to the bottom bracket shell, the electric motor having a hollow drive shaft with an output end projecting to a first side of the bottom bracket shell; a transmission connecting the output end of the drive shaft to at least one of the rear wheel and a drive train of the bicycle, to transmit a drive of the electric motor to the rear wheel; and the drive train comprising a crank set having an axle rotatably mounted within the hollow drive shaft for rotating independently from the drive shaft, and means for transmitting pedaling actuation on the crank set to the rear wheel, the means being on the second side of the bottom bracket shell. 
         [0007]    Further in accordance with the first embodiment, coils of the electric motor are accommodated in the bottom bracket shell. 
         [0008]    Still further in accordance with the first embodiment, the hollow drive shaft is rotatably mounted to the bottom bracket shell by bearings. 
         [0009]    Still further in accordance with the first embodiment, the transmission comprises a drive transmitting unit between the output end of the hollow drive shaft and a hub of the rear wheel, to directly transmit the drive of the electric motor to the rear wheel. 
         [0010]    Still further in accordance with the first embodiment, the transmission comprises a drive transmitting unit between the output end of the hollow drive shaft and a transfer axle rotatably mounted to the stays, to transmit a drive of the electric motor to the rear wheel through the transfer axle. 
         [0011]    Still further in accordance with the first embodiment, the transfer axle has a sprocket operatively engaged with a chain of the drive train. 
         [0012]    Still further in accordance with the first embodiment, the crank set has a ratchet system between cranks and a chain ring of the drive train. 
         [0013]    Still further in accordance with the first embodiment, the transfer axle is operatively connected to the rear wheel by a second drive transmitting unit, the transfer axle having at least one of gears, pulleys and sprockets at an input end and output end for altering a transmission ratio between the drive transmitting units. Still further in accordance with the first embodiment, the transmission comprises one of pulleys and at least one belt, and of sprockets and at least one chain. 
         [0014]    Still further in accordance with the first embodiment, the axle of the crank set is rotatably mounted inside the hollow drive shaft of the electric motor by bearings. 
         [0015]    Still further in accordance with the first embodiment, rotational axes of the hollow drive shaft and of the axle are coincident. 
         [0016]    In accordance with a second embodiment, there is provided an electrical drive system for bicycle comprising: a stator adapted to be fixedly received in a bottom bracket shell of a bicycle frame; a hollow drive shaft supporting a rotor and adapted to rotate as actuated by the cooperation of the rotor and the stator, the hollow drive shaft sized to have an output end projecting to a side of the bottom bracket shell away from a drive train of the bicycle; axle bearings in an inner cavity of the hollow drive shaft adapted to rollingly support an axle of a crank set such that the axle projects from both ends of the drive shaft; and a transmission adapted to connect the output end of the drive shaft to at least one of the rear wheel and a drive train of the bicycle, to transmit a drive of the electrical drive system to the bicycle. 
         [0017]    Further in accordance with the second embodiment, bottom bracket bearings are provided and the hollow drive shaft is adapted to be rotatably supporting to the bottom bracket shell by the bottom bracket bearings. Still further in accordance with the second embodiment, the transmission comprises a drive transmitting unit between the output end of the hollow drive shaft and a hub of the rear wheel, to directly transmit the drive of the electrical drive system to the rear wheel. 
         [0018]    Still further in accordance with the second embodiment, the transmission comprises a drive transmitting unit between the output end of the hollow drive shaft and a transfer axle adapted to be rotatably mounted to the stays, to transmit a drive of the electric motor to the rear wheel through the transfer axle. 
         [0019]    Still further in accordance with the second embodiment, the transfer axle has a sprocket adapted to be operatively engaged with a chain of the drive train. 
         [0020]    Still further in accordance with the second embodiment, the transfer axle is operatively connected to the rear wheel by a second drive transmitting unit, the transfer axle having at least one of gears, pulleys and sprockets at an input end and output end for altering a transmission ratio between the drive transmitting units. 
         [0021]    Still further in accordance with the second embodiment, the transmission comprises one of pulleys and at least one belt, and of sprockets and at least one chain. 
         [0022]    Still further in accordance with the second embodiment, rotational axes of the hollow drive shaft and of the axle bearings are coincident. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  is a left-side elevation view of a bicycle with an electrical drive system in accordance with an embodiment of the present disclosure, with a motor being behind the seat tube; 
           [0024]      FIG. 2  is a rear right side perspective view of the bicycle of  FIG. 1 , with fragmentation to show parts of the electrical drive system; 
           [0025]      FIG. 3  is a side elevation view of a bicycle with an electrical drive system in accordance with another embodiment of the present disclosure, with a motor being in a bottom bracket shell; 
           [0026]      FIG. 4  is an enlarged perspective view of a bottom bracket of the bicycle of  FIG. 3 ; 
           [0027]      FIG. 5  is a partly sectioned perspective view of the bottom bracket enclosing the motor of the bicycle of  FIG. 3 ; 
           [0028]      FIG. 6  is a sectional view of the bottom bracket enclosing the electric motor for the bicycle of  FIG. 3 ; 
           [0029]      FIG. 7  is a partly sectioned left perspective view of the bottom bracket enclosing a motor of a bicycle, with a transmission relating the motor to the drive train of the bicycle; 
           [0030]      FIG. 8  is a right perspective view of the bottom bracket enclosing the motor of the bicycle of  FIG. 7 ; 
           [0031]      FIG. 9  is a sectional view of the transmission of  FIG. 7 ; and 
           [0032]      FIG. 10  is a perspective view of a bottom bracket enclosing a motor of a bicycle, with a transmission relating the motor to the rear wheel of the bicycle. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0033]    Referring to the drawings, and more specifically to  FIGS. 1 and 2 , a bicycle having an electrical drive system in accordance with an embodiment of the present disclosure is generally shown at  10 . Among many other standard components not described for simplicity purposes, the bicycle  10  has a frame  12 , a drive train  13  and wheels  14 . 
         [0034]    The frame  12  is the main structural component of the bicycle  10 . 
         [0035]    The drive train  13  transmits pedaling power to the wheels  14 . 
         [0036]    The wheels  14  are the interface of the bicycle  10  with the road. The frame  12  may be any type of frame. For the present embodiment, a generally standard frame is described, but the electrical drive system may be used with any other type of frame. The frame  12  has a down tube  20  and a top tube  21 . The down tube  20  and the top tube  21  are interrelated at a front of the frame  12  by head tube  22 . The head tube  22  supports the fork by way of a headset that allows to control the trajectory of bicycle  10  from a handle bar. 
         [0037]    The down tube  20  and the top tube  21  diverge from one another toward the rear of the frame  12  and are interconnected by a seat tube  23 . A seat post supporting a seat is typically inserted in the seat tube  23  for the telescopic adjustment of the height of the seat. The down tube  20 , the top tube  21  and the seat tube  23  concurrently form a front triangle of the frame  12 . 
         [0038]    A rear wheel  14  is supported by the combination of a chain stays  24  and seat stays  25 . The seat tube  23 , chain stays  24  and seat stays  25  concurrently form the rear triangle of the frame  12 . The chain stays  24  have a support portion adjacent to the seat tube  23 . A bottom bracket shell  26  is positioned at the junction between the down tube  20  and the seat tube  23  and supports the crank set  30  (and a spindle thereof). The bottom bracket shell  26  is a tube oriented so as to have an own longitudinal axis normal to a plane of the frame  12 . 
         [0039]    Referring concurrently to  FIGS. 1 and 2 , the bottom bracket shell  26  encloses a bottom bracket rotatably supporting a crank set  30  to the frame  12 . The crank set  30  has cranks  31  interrelated by an axle/spindle  31 A of the bottom bracket, which axle/spindle  31 A is journaled by bearings. The cranks  31  support pedals of the bicycle  10 . On the right-hand side of the bicycle  10 , at least one chain ring  32  is secured to the crank set  30 . The chain ring  32  is connected to a cassette  33  of a plurality of cogs ( FIG. 2 ). The chain ring  32  and cassette  33  are interrelated by a chain. Alternatively, a belt-and-pulley drive could be used to transmit pedaling power to the rear wheel  14 , or other drives as well such as a shaft drive. 
         [0040]    Although not shown, a front derailleur and a rear derailleur may be used to change gear ratios by moving the chain between the chain rings  32  and cogs of the cassette  33 . The cassette  33  is typically supported to the rear wheel  14  by way of a free wheel, not visible as it is in the interior of the cassette  33 . The free wheel allows the rear wheel  14  to keep on turning while the crank set  30  is idle. The rear wheel  14  rotates about axle  40 . The axle  40  supports the cassette  33 . 
         [0041]    Still referring to  FIGS. 1 and 2 , the electrical drive system has a battery pack  50  that is supported by the frame at the junction between the down tube  20  and seat tube  23 . A motor  51  is supported by the support portion of the chain stay  24 , and is thus positioned in a gap between a periphery of the rear wheel  14  and the seat tube  23 , between the chain stay  24  and the seat stay  25 . 
         [0042]    A drive shaft of the motor  51  may be generally parallel to the axle  40  and supports a pulley (not shown), or chain ring/sprocket. The drive shaft projects toward the left-handle side of the frame  12 , while the pedal drive train is on the right-hand side of the frame  12 . 
         [0043]    The pulley is accommodated in a triangular shape cover from which protrudes rearwardly a belt  52  (or a chain, in accordance with the accessory used on the drive shaft). The belt  52  is peripherally mounted to an oversized pulley  53  mounted to the axle  40 . Although shown as oversized, the pulley  53  may be of any appropriate diameter. Accordingly, the bicycle  10  of  FIGS. 1 and 2  features a pulley and belt drive, although chain and sprocket configurations could be used as well. The pulley  53  mounted to the axle  40  may be in a fixed relation with the axle  40  and thus with the wheel  14 . However, a free wheel may be used as well to allow coasting in the absence of drive from the motor  51 . In an embodiment, the free wheel of the cassette  33  is used. The pulley and belt drive can be a multi-v drive, or any appropriate drive (e.g., synchronous belt, vee belt). 
         [0044]    As the pulley  53  is positioned on the other side of the wheel  14  when compared to the cassette  33 , the electrical drive system illustrated in  FIGS. 1 and 2  allows the combined drive from the rider of the bicycle and the electrical drive system. However, it is also considered to have the pulley  53  and cassette  33  on the same side as well. The pulley  53  may be connected to the wheel  14  by a free wheel, or without a free wheel. The presence of a free wheel advantageously removes the impact of the motor inertia when the motor is not assisting the pedaling. The pulley  53  may also be fixed in rotation to the wheel  14 , in the instance where the motor is used as an alternator to recharge the battery. It is pointed out that the free wheel of the electrical drive system may be located in the electrical drive system so as to use coasting to recharge the battery pack  50  via the use of the motor  51  as an alternator. 
         [0045]    Referring concurrently to  FIGS. 3 to 6 , a bicycle in accordance with another embodiment of the present disclosure is illustrated at  10 ′. The bicycle  10 ′ of  FIGS. 3 to 6  has numerous components similar to that of bicycle  10  of  FIGS. 1 and 2 , whereby like elements will bear like reference numerals. 
         [0046]    The significant difference between the bicycles  10  and  10 ′ is the positioning of the motor of the electrical drive system. The motor is located in an oversized bottom bracket shell  60 . The oversized bottom bracket shell  60  forms a casing  61  in which the motor  62  and bottom bracket are concealed. The motor  62  may be any type of electric motor, such as a brushless DC motor, with a stator  62 A being fixedly received in the bottom bracket shell  60 , while a rotor  62 B (e.g., permanent magnet rotor) is inside the stator  62 A. Accordingly, the motor  62  is actuated by the power source to cause a rotation of the rotor  62 B. 
         [0047]    A drive shaft of the motor  62  is the axle tube  63 , and is therefore hollow. The axle tube  63  is integral with the rotor  62 B, and is supported to the bottom bracket shell  60  by bearings  63 A. A longitudinal axis of the axle tube  63  is parallel to the rotational axis of the axle  40  of the bicycle  10 ′. A transmission is used to transmit the drive from the motor  62  to the rear wheel  14 . The transmission may feature a pulley  64  integral with the axle tube  63  on the left-hand side of the bicycle  10 ′ and therefore on the side opposite to the chain ring  32  and pedal drive train. However, the pulley  64  could also be on the right hand side of the bicycle  10 ′. 
         [0048]    By the configuration of the drive of the electrical drive system, rotation of the axle tube  63  is independent from that of the drive train of the bicycle. A drive transmitting unit such as belt  65  interrelates the pulley to the oversized pulley  53 . However, alternative solutions to the pulley and belt drive can be used such as a chain and sprockets, etc. 
         [0049]    Referring to  FIGS. 5 and 6 , an axle of the bottom bracket supporting the crank set  30  is illustrated at  70 . In the illustrated embodiment, the axle  70  is supported in the axle tube  63  by way of bearings  71 , with ends of the axle  70  projecting from opposed ends of the axle tube  63 . The axle  70  could also be separate from the axle tube  63 . It is observed that two of the bearings may be provided on the side of the pulley  64 , to strengthen the axle tube  63  thereat. Therefore, the bearings  71  allow a rotation of the axle  70  and of the crank set  30  independent from that of axle tube  63 . In the illustrated embodiment, the axes of rotation of the axle tube  63  and axle  70  of the crank set are coincident, as this configuration is space-efficient, but other eccentric configurations are possible. Other types of bottom brackets may be used as well. 
         [0050]    The operation of the electrical drive system of the bicycle  10 ′  FIGS. 3 to 6  is similar to that of the electrical drive system of bicycle  10  of  FIGS. 1 and 2 . 
         [0051]    Referring to  FIGS. 7-9 , there is illustrated an alternative drive configuration for the motor  62  of  FIGS. 3-6 . However, as several components are used commonly in the embodiments of  FIGS. 3-6  and  7 - 9 , like components will bear like reference numerals. 
         [0052]    The significant difference between the embodiments of  FIGS. 3-6  and of  FIGS. 7-9  is that the motor  62  does not drive the rear wheel directly in  FIGS. 7-9 , but rather uses the standard bicycle drive, namely chain  80  between the chain ring  32  and cassette  33  ( FIG. 2 ), by way of a transmission. According to an embodiment, the transmission has a transfer axle  81  that is rotatably mounted to the frame of the bicycle, for instance by way of bearings  82  in a support bracket  83  that is part of or adjacent to the chain stays  24 . The support bracket  83  may also be connected to the seat tube  23  ( FIG. 2 ), to the seat stays  25 . A pulley  84  (or sprocket, gear, etc) is secured to the transfer axle  81 , on the left side of the frame, with a belt  85  between the pulley  64  and the pulley  84  for the transmission of the drive from the motor  62  to the axle  81 . 
         [0053]    A sprocket  86  is secured to the other end of the axle  81 . The sprocket  86  is therefore meshed with the chain  80 , so as to transmit the drive of the motor  62  to the rear wheel  14  concurrently with the pedaling power. In an embodiment, the crank set  30  has some form of freewheel mechanism (i.e., ratchet), so as to allow the rider to coast while the motor  62  drives the rear wheel, and thus allow the temporary release of the cranks  31  from the chain ring  32 . Such type of crank set is referred to as a freewheeling crank set. 
         [0054]    The sprocket  86  may alternatively be a gear meshed with the chain ring  32 , etc. Also, there may be provided some play in the axial position of the sprocket  86  along the axle  81 , to allow shifting of the chain  80  between chain rings  32  in a multi-chain ring crank set. 
         [0055]    Referring to  FIG. 10 , the transfer axle  81  is illustrated as having an output wheel  90  (shown as a pulley, but alternatively a gear, sprocket, etc) related to the rear wheel  14  by way of a drive transmitting unit (shown as a belt, but alternatively gears, a chain, etc). The output wheel  90  is on the same side of the frame as the pulley  84 , but has a different diameter, thereby resulting in a mechanical advantage appropriate for the type of motor used relatively to the anticipated velocity range of the bicycle. Any appropriate gear ratios may be used with the transfer axle  81 . Moreover, the mechanical advantage may also be obtained y having the drive transmitting unit  91  on the same side as the drive train of the bicycle.