Abstract:
A simplified mid-motor drive system includes all necessary electronics and allows for throttle-only operation of the motor. The mid-motor drive system includes an arrangement of uni-directional drive connections (i.e., sprag clutches) between the motor and the pedals which allows each to operate independently or in conjunction, and allows simple modifications to gear ratios of packaged drive systems in order to adapt to regulatory requirements of different worldwide territories.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims the priority of U.S. Provisional Patent Application Ser. No. 62/218,388 filed Sep. 14, 2015, which application is incorporated in its entirety herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to electric bicycles and in particular a mid-drive arrangement for electric bicycles. 
         [0003]    In the electric bike market, the “hub” or in-wheel motor has been the dominated configuration. Unfortunately, in in-wheel motor bicycles, there is no way to give a mechanical advantage to the motor using a conventional bicycle transmission. Additionally, when using an in-wheel motor configuration, the rider may input power through the pedals and into a conventional bicycle transmission however, because there is no direct connection between the wheel motor and transmission, it is possible for the rider to choose a gear ratio on the transmission which fails to transfer the rider&#39;s power input into the pedals as a useful addition to the bicycle&#39;s propulsion. As a result, there is an increasing movement away from an in-wheel motor and there is a need for better alternative motor configurations. 
         [0004]    Mid-motor drive systems have been developed to replace wheel motor based electric drives, but known mid-motor designs use a complicated set of gears to combine the power of the motor with the rider power input through the pedals and then transfers all that power to a conventional bicycle transmission. This design often makes it impossible to operate the motor without rotating the pedals via an independent throttle such throttle driven operation being desirable by many consumers. Thus, a need remains for an improved mid-motor drive system. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    The present invention addresses the above and other needs by providing a simplified mid-motor drive system which includes all necessary electronics and allows for throttle-only operation of the motor. The mid-motor drive system includes an arrangement of uni-directional drive connections (i.e., sprag clutches) between the motor and the pedals which allows each to operate independently or in conjunction, and allows simple modifications to gear ratios of packaged drive systems in order to adapt to regulatory requirements of different worldwide territories. 
         [0006]    In accordance with one aspect of the invention, there is provided a mid-drive system allowing for all the power from the motor, as well as all the power from the rider (input through the pedals) to be transferred into a conventional bicycle transmission thus providing a mechanical gearing advantage. 
         [0007]    In accordance with another aspect of the invention, there is provided a mid-drive system package that can easily be integrated into a bicycle frame, with all necessary control electronics, which greatly simplifies the initial manufacturing, wiring and maintenance on an electric bike. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0008]    The above and other aspects, features and advantages of the present invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings wherein: 
           [0009]      FIG. 1  shows a bicycle having a mid drive according to the present invention. 
           [0010]      FIG. 2  shows a first embodiment of a mid-motor drive system according to the present invention. 
           [0011]      FIG. 3A  shows a side view of a motor of the mid-motor drive system according to the present invention. 
           [0012]      FIG. 3B  shows a front view of the motor of the mid-motor drive system according to the present invention. 
           [0013]      FIG. 4  shows a second embodiment of a mid-motor drive system according to the present invention. 
           [0014]      FIG. 5  shows a third embodiment of a mid-motor drive system according to the present invention. 
           [0015]    Corresponding reference characters indicate corresponding components throughout the several views of the drawings. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    The following description is of the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing one or more preferred embodiments of the invention. The scope of the invention should be determined with reference to the claims. 
         [0017]    Where the term “generally” is associated with an element of the invention, it is intended to describe a feature&#39;s appearance to the human eye, and not a precise measurement. 
         [0018]    A bicycle  40  including a mid-motor drive system  10  according to the present invention is shown in  FIG. 1 . The mid-motor drive system  10  is connected to a bicycle frame  42  and drives a chain (or belt)  30  connected to a drive sprocket  32  driving a bicycle wheel  44 . A rider may power the bicycle  40  using pedals  18 , or using the mid-motor drive system  10 , or using the pedals and the mid-motor drive system  10 . 
         [0019]    A first embodiment of a mid-motor drive system  10   a  is shown in  FIG. 2 , a side view of a motor  14  and bottom bracket  38  of the mid-motor drive system  10  is shown in  FIG. 3A , and a front view of the motor  14  and bottom bracket  38  is shown in  FIG. 3B . The motor  14  is preferably a doughnut motor. The mid-motor drive system  10   a  includes a housing  12  containing the motor  14  preferably coaxial with a pedal shaft  16   a  but rotationally decoupled to the pedal shaft  16   a  by bearings  17 , and pedals  18  attached to the pedal shaft  16   a.    
         [0020]    A mid shaft  16   b  resides parallel with the pedal shaft  16   a . The mid shaft  16   b  is coupled by a chain (or belt)  20   a  connecting a fixed (no clutch) sprocket  15   a  attached to the pedal shaft  16   a , to a sprocket  23   a , and the sprocket  23   a  is connected to the mid shaft  16   b  through uni-directional bearings (or sprag clutches)  22   b . The uni-directional bearing  22   a  couples the chain  20   a  to the mid shaft  16   a  when the chain  20   a  is driven by the pedals  18  to drive the bicycle forward, and decouples the chain  20   a  from the mid shaft  16   b  whenever the mid shaft  16   b  is rotating faster than a rotation produced by the chain  20   a.    
         [0021]    The mid shaft  16   b  is coupled to the motor  14  by a fixed (no clutch) sprocket  15   b  attached to the motor and a chain (or belt)  20   b  through uni-directional bearings (or sprag clutches)  22   b . The uni-directional bearing  22   b  couples the chain  20   b  to the mid shaft  16   b  when the chain  20   b  is driven by the motor  14  to drive the bicycle forward, and decouple the chain  20   b  from the mid shaft  16   b  whenever the mid shaft  16   b  is rotating faster than a rotation produced by the chain  20   b.    
         [0022]    Those skilled in the art will recognize that the uni-directional bearings  22   a  and  22   b  may be replaced by uni-directional bearings connecting the sprocket  15   b  to the motor  14  and/or connecting the sprocket  15   a  to the pedal shaft  16   a , thereby providing the same functionality as the uni-directional bearings  22   a  and  22   b.    
         [0023]    A sleeve  24  resides over the pedal shaft  16   a  on bearings to rotate independently of the pedal shaft  16   a . The mid shaft  16   b  is further fixedly (i.e., fixed to always rotate together, not through a clutch) coupled to the sleeve  24  by a chain (or belt)  20   c  to drive the sleeve  24 . The sleeve  24  carries a sprocket  28  coupled to the drive sprocket  32  by a chain (or belt)  30 . The sprocket  32  may be a conventional bicycle drive sprocket rotationally fixed to a bicycle wheel, or may be coupled to a transmission  36 , for example a multi-speed derailleur, rotationally connected to a bicycle wheel. 
         [0024]    A controller  13  resides inside or outside the housing  12  and is electrically connected to batteries  11  which may reside inside or outside the housing  12 , and to the motor  14 . The controller  13  provide power from the batteries  11  to the motor  14  and the controller  13  may receive data signals from the motor  14 , the batteries  11  and/or a pedal torque sensor  27 . The pedal torque sensor  27  cooperated with the chain  20   b  to measure the mechanical power generated by the rider to provide a control signal to the controller  13  as an input to the motor control  13 . The pedal torque sensor  27  may measure the torque on the pedal shaft  16   a  by the rider by sensing tension on the chain  20   b  between the pedal shaft  16   a  and mid shaft  16   b , or by other means. The pedal torque measurements may be used as an input by the controller  13  in determining the amount of motor  14  assistance in the drive system  10 . Alternately, multiple options exist for measuring pedal torque achieve the same result, and a mid drive system using any form of pedal torque measurement is intended to come within the scope of the present invention. A suitable torque sensor is described in U.S. Pat. No. 8,965,610 issued to one of the present inventors. 
         [0025]    The rider may rotate the pedals  18 , as on a conventional bicycle, and the bicycle can be powered by the electric motor  14 . Gear ratio may be changed between the motor sprocket  15  and the mid shaft  16   b  and between the pedal shaft  16   a  and the mid shaft  16   b  and between the mid shaft  16   a  and the sleeve  24  by replacing sprockets  15   a ,  15   b ,  23   a ,  23   b ,  23   c , and or  26  depending on the specific vehicle application. The gear ratio between the motor  14  and mid shaft  16   b  may be easily adjusted depending on the speed range of the motor and the specific vehicle application. 
         [0026]    A second embodiment of a mid-motor drive system  10   b  is shown in  FIG. 4 . The mid-motor drive system  10   b  is functionally the same as the mid-motor drive system  10   a , but the third mid shaft sprocket  23   c  and the sleeve sprocket  26 , the chain  20   c , and the sleeve  24  are placed by moving the sprocket  28  to the mid shaft  16   b.    
         [0027]    A third embodiment of a mid-motor drive system  10   c  is shown in  FIG. 5 . The mid-motor drive system  10   c  is similar to the mid-motor drive system  10   a , but the motor  14   a  is preferably a conventional low speed motor. The motor  14   a  has low rotational resistance when not under power and therefore may be rotationally fixed to the mid shaft  16   b  without producing rotational drag. The mid shaft  16   b  is coupled by the chain (or belt)  20   a  connecting the fixed (no clutch) sprocket  15   a  attached to the pedal shaft  16   a , to the sprocket  23   a , and the sprocket  23   a  is connected to the mid shaft  16   b  through uni-directional bearings (or sprag clutches)  22   a . The mid shaft  16   b  is coupled to the sleeve  24  through the uni-directional bearings  22   c  so that the mid shaft  16   b  can drive the sleeve  24  through the chain  20   c , but the sleeve  24  cannot drive the mid shaft  16   b  through the chain  20   c.    
         [0028]    The conventional bicycle sprocket or multispeed derailleur allows for connection via belt or chain to a variety of conventional bicycle transmissions in the rear wheel including, but not limited to, a derailleur, an internal hub, CVT or a traditional in-wheel motor allowing for additional motor output at a different gear ratio. 
         [0029]    Advantageously, the motor and pedals can operate independently of each other without interfering with each other, which means that the drive can be operated as a throttle driven power source with no rider pedal input, a pedal-assist power source that registers rider pedal input and supplies proportional power assist, or as a conventional pedal bike without adding significant amount of drag on the total system. 
         [0030]    While the invention herein disclosed has been described by means of specific embodiments and applications thereof, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope of the invention set forth in the claims. I claim: