Abstract:
An apparatus and method for an electric bike retrofit for a disc brakes vehicle include an electric motor coupled with a rotor brake. The apparatus and method provide advantages in that the drive gear for the electric motor may be integrated with the brake rotor decreasing weight and minimizing necessary parts. The electric motor may mount to the existing brake caliper mounts and drive the brake rotor without the use of a chain, belt, or the like. Multiple gear ratios may be incorporated into the brake rotor allowing for shifting and increased efficiency of the electric drive system.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates in general to the field of electrical assist of traditionally human powered vehicles, e.g., bicycles, scooters, etc. More particularly, the present invention relates to bicycles equipped with a braking system that utilizes brake rotors and calipers. Specifically, the present invention relates to retrofitting electric assist to pedal-powered bicycles that use brake rotors and calipers. 
     2. Discussion of the Related Art 
     Riding bicycles is a popular pastime for physical exercise as well as a means of transportation. In an effort to promote the utilitarian benefits of bicycle riding, electric bicycles have become popular in recent times. Electric bicycles allow individuals to use the same bicycle to get physical exercise as well as a means of transportation while avoiding exhaustion. This may be done by allowing the operator to pedal as the sole means of propulsion, use an electric drive as the sole means of propulsion, or use the electric drive to assist the pedaling efforts of the operator. Electric bicycles supplement the riders pedaling motion to minimize fatigue, increase the distance the operator can travel, and provide a more relaxing means of transportation. 
     One drawback to electric bicycles is that they are considerably expensive. When the bicycle is designed from the ground up to incorporate electronic controls, an electric, motor, a battery pack, and the necessary hardware, it imposes a significant financial burden that many consumers are not willing to absorb. As a result, retrofitting existing bicycles with electric drives has become popular. 
     When retrofitting a bicycle with an electric drive, there are a number of possible locations to mount the electric equipment on the bicycle. One problem is that there is limited space available on a bicycle frame to accommodate the electric drive equipment. It is therefore desirable to minimize the components needed as well as minimize the required space needed for the electric drive. It is also desirable to improve existing electric bicycle retrofit packages by utilizing existing components of the pedal drive. 
     Another drawback to existing electric drive retrofits is that they utilize their own components to transfer the assisted power from the electric motor to the bicycle. For example, one popular retrofit uses a completely new rear wheel with an electric motor incorporated into the central hub of the wheel. This solution is typically very expensive and wheel damage is harder to repair as it is not a common “off the shelf” item. Other common electric retrofits add an electric motor to the bicycle frame and transfer power with a series of belts and/or chains. The added gear may be added directly to the crank or to the gears on the rear wheel. An added chain or belt is then used, providing additional weight, complexity, and maintenance to the bicycle. 
     What is therefore needed is an electric bicycle retrofit that utilizes existing components of the bicycle. What is also needed is a way to transfer the electric assist power to the bicycle without additional chains or gears. What is also needed is an improved electric retrofit that utilizes less space on the bicycle frame. 
     SUMMARY AND OBJECTS OF THE INVENTION 
     A pedal-powered bicycle frame may be retrofitted with an electric assist that attaches to the frame of the bicycle. More specifically, the electric assist may attach to the brake system of the bicycle. The brake system may include a device for attaching the brake system to the frame, a brake rotor with rotor gear teeth rotatably attached to the flame, and a brake caliper configured to selectively engage the rotor. In order to provide rotational force to the wheels of the bicycle, an electric motor may be attached to the device and also configured to engage the brake rotor gear teeth thus providing rotational force to the brake rotor and propelling the bicycle. 
     The electric retrofit assembly, including the electric motor and brake rotor, may be configured to retrofit onto the bicycle frame without modification of the brake caliper, frame, or the wheels attached to the frame. 
     In one embodiment, the brake rotor gear teeth may extend from the outer circumference of the brake rotor and selectively engage and disengage with a motor gear attached to the electric motor. In another embodiment, the brake rotor gear teeth may be between the outer circumference and a center point of the brake rotor. In this embodiment, each gear tooth consists of a hole in the side of the brake rotor. A plurality of holes, or gear teeth, may form multiple circumferential rings in the face of the brake rotor, each circumferential ring having a distinct diameter which produces a distinct gear ratio for each circumferential ring. 
     In the embodiment where the brake rotor includes circumferential rings, a shifting device may be configured to selectively engage and disengage the motor gear with each one of the circumferential rings while the bicycle is in motion and the brake rotor is turning. The motor gear may include an angle gear configured to engage the plurality of circumferential rings at a 90-degree angle to a face of the brake rotor. 
     In any embodiment, the electric motor may also provide braking by utilizing electrical regenerative braking, wherein the motor converts kinetic energy into electrical energy. Also in any embodiment, the electric motor may attach to the attachment device of the brake caliper, or may attach to the rear dropout, or axle, portion of the rear wheel of the bicycle. Regardless of the attachment point, the bicycle frame, wheels, and brake caliper do not require modification. 
     These and other aspects and objects of the present invention will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following description, while indicating preferred embodiments of the present invention, is given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A clear conception of the advantages and features constituting the present invention, and of the construction and operation of typical mechanisms provided with the present invention, will become more readily apparent by referring to the exemplary, and therefore non-limiting, embodiments illustrated in the drawings accompanying and forming a part of this specification, wherein like reference numerals designate the same elements in the several views, and in which: 
         FIG. 1  illustrates a side view of an electric motor and brake rotor drive gear attached to a bicycle frame according to one embodiment of the invention; 
         FIG. 1A  illustrates a side view of an electric motor and brake rotor drive gear attached to the front fork of a bicycle frame according to another embodiment of the invention; 
         FIG. 2  illustrates a side view of an electric motor and brake rotor drive gear attached to a frame of a bicycle according to another embodiment of the invention; and 
         FIG. 3  illustrates a side view of an electric motor and brake rotor drive gear attached to a frame of a bicycle according to yet another embodiment of the invention; 
     
    
    
     In describing the preferred embodiment of the invention which is illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, it is not intended that the invention be limited to the specific terms so selected and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. For example, the words “connected”, “attached”, or terms similar thereto are often used. They are not limited to direct connection but include connection through other elements where such connection is recognized as being equivalent by those skilled in the art. 
     DETAILED DESCRIPTION OF EMBODIMENTS 
     The present invention and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments described in detail in the following description. While the invention is directed toward use with bicycles, it is not limited to just traditional bicycles. The term “bicycle” is used to include any multi-wheeled form of transportation which may or may not include a seat. For example, scooters that support a rider in an upright, standing position are also included in the term “bicycle”. The “bicycle” may be chain driven, belt driven, pulley driven, gear driven, or any other form of rotational motion delivery. 
     An electric drive  8  retrofit is shown in  FIG. 1  attached to a frame  10  of a bicycle. Bicycle frames  10  commonly include a seat stay tube  12  and a chain stay tube  14  that converge at a rear wheel dropout  16 . The electric drive may also attach to any other bicycle regardless of the frame design. While it is preferred that the electric drive  8  be utilized on a frame  10  equipped with disc brakes, the electric drive  8  may be used on any wheeled vehicle. The electric drive  8  may also be used as a braking device through regenerative braking, where the kinetic energy of the rotating rotor  22  is converted into potential energy, or electricity, for storage in a battery pack on board the frame  10 . 
     The electric drive  8  consists of an electric motor  26  that powers a motor gear  32 . The motor gear  32  includes a plurality of motor gear teeth  34  that extend from the outer diameter of the motor gear  32  forming a spur gear. While a spur gear is shown, any other type of gear may be used such as internal ring gears, helical gears, face gears, worm gears, or the like. 
     In order to provide the frame  10  with forward momentum, the gear teeth  34  mesh with a mating gear incorporated in the brake rotor  22 . The brake rotor  22  may include rotor vents  38  which serve to cool the rotor  22  as well as lighten it. The brake rotor  22  may also be solid without vents  38 . Preferably, the rotor  22  mounts to the frame  10  about the rear wheel dropout  16  without any kind of modification to the rear wheel dropout  16 , the center axle  40 , the caliper  20 , bicycle drive chain  36 , or any other component of the bicycle. The electric drive  8  may also be attached to the frame  10  on the front fork  11  or front wheel portion of the bicycle in any of the mentioned embodiments. For example,  FIG. 1A  shows the electric drive  8  attached to the front fork  11  using a motor bracket  52 , similar to  FIG. 1 . Any of the embodiments shown in  FIGS. 2 and 3  may also be similarly located on the front fork  11 . All other components of the electric drive  8  remain the same, but locating the electric drive  8  on the front fork  11  improves bicycle performance when a suspension  13  is used. In bicycles with a suspension  13 , such as a shock absorber and/or spring, in the front portion, the un-sprung weight of the bicycle is reduced. Contrary to the rear wheel portion of the bicycle, the rear wheel dropout  16  is not commonly sprung when a suspension is used. However, the front fork  11  portion where the brake rotor  22  is located is often sprung with a suspension  13 . By locating the electric drive  8  on the front fork  11 , the un-sprung weight is reduced and the performance of the suspension  13  is increased. 
     By utilizing the rotor  22  as the drive gear for the electric drive  8 , the typical necessity of adding an additional gear, chain, belt, pulley, or any other device for an electrical, assist retrofit is eliminated. Also, the bicycle chain drive  36  and related gears are not tampered with. 
     In previous electric bicycle retrofits installation required a bicycle expert to disassemble the rear wheel and chain drive  36  from the frame  10 . By using the brake rotor  22  as the drive gear for the electric motor  26 , installation is simplified. The caliper  20  and brake line  18  may also remain in their original location. As a result, the electric drive  8  reduces the weight, cost, complexity, and installation difficulty of known electric drives. 
     For bicycles originally equipped with brake rotors, the rotor  22  may be furnished as a direct retrofit and not require any adjustment to the caliper  20 . For bicycles that do not have brake rotors, a conventional “disc brake” retrofit kit may be used that implements the rotor  22  with rotor gear teeth  28 . Additionally, the motor  26  may include a mounting attachment such as the motor mount eyes  30  or any other suitable fastening means. The motor  26  may either attach directly to the frame  10  by affixing to the caliper mount eyes  24  or with a motor bracket  52  to give the motor  26  the proper offset and clearance, thus allowing the motor gear  32  to mesh with the rotor  22 . On bicycles that use threaded bosses for caliper attachment, a similar motor bracket  52  may be used or the motor  26  may be designed with a housing allowing attachment without a motor bracket  52 . 
     While  FIG. 1  shows the caliper  20  attached to the seat stay tube  12  of the frame  10 , the caliper  20  may also attach to the chain stay tube  14  with or without a motor bracket  52 . According to  FIG. 2 , the electric motor  26  may also attached to the rear wheel dropout  16  with a fastener attached to the center axle  40  or other existing fastener. 
     When mounting the motor  26  to the rear wheel dropout  16 , a different type of gear on the motor  26  may be used. As shown in  FIG. 2 , the same rotor  22  may be used with rotor teeth  28  on the outer circumference of the rotor  22 . The motor  26  may include an angle gear  44  that meshes with the rotor gear teeth  28  at approximately a 90-degree angle. The angle gear  44  may extend from the motor  26  with a shaft  42  to provide optimal clearance or may be directly attached to the motor  26  without an extended shaft  42 . In this embodiment, the caliper  20  and caliper mount eyes are not used to retain the motor  26 . As a result, the motor bracket  52  shown in  FIG. 1  may be eliminated. 
     Transitioning now to  FIG. 3 , an alternative embodiment is shown wherein an alternative rotor  23  is used that does not include teeth on the outer circumference of the rotor  23 . The rotor  23  instead has a series of gear teeth circumferences  47  formed with concentric rings of holes  46  formed in the face of the rotor  23 . Each gear teeth circumference  47  forms an independent gear in the rotor  23 . The holes  46  allow for teeth on the angle gear  44  to insert into the holes  46 . As the motor  26  rotates the angle gear  44 , the rotor may be rotated thus providing forward momentum to the frame  10  of the bicycle. 
     The plurality of gear teeth circumferences forms a first gear teeth circumference  48 , a second gear teeth circumference  50 , and a third gear circumference  54 . Each gear circumference has a unique circumference, which means each gear teeth circumference  47  also has a different amount of holes  46 . As a result, the larger the gear teeth circumference, the taller the gear ratio. Similarly, the smaller the gear teeth circumference, the shorter the ratio. 
     The motor  26  may include a movable angle gear  44  which may move along the face of the rotor  23  along the shaft  42  or with any other suitable positioning device. In this configuration, multiple gear ratios may be attained allowing an operator to shift the angle gear  44  along a path and mesh with each gear teeth circumference  47  while the bicycle is in motion. As a result, the electric power stored onboard the frame  10  (not shown), may be conserved and utilized more efficiently by shifting the angle gear to a desired gear ratio for different inclines, terrains, or level of electrical assistance. The shifting may be used in combination with electronic controls (not shown) that can automate the shifting resulting in an automatic transmission, or the user may be able to selectively engage each gear teeth circumference  47 . Shifting may also be accomplished with mechanical means such as cables, linkages, or the like. The motor  26  may also mount to the rear wheel dropout  16  as shown in  FIG. 2  and utilize the rotor  23  with holes  46  and a shifting mechanism. 
     While the motor gear  32  is shown as a traditional spur gear that transfers rotational force from the motor  26  to the brake rotor  22 , the motor gear  32  may also perform the function of the caliper  20 . In such an embodiment, the motor gear  32  would include a split perpendicular to the gear teeth  32  dividing the motor gear  32  in half. A small spacing may be included between each motor gear  32  half with the rotor gear teeth  22  and a portion of the rotor  22  between the motor gear  32  halves. As the motor gear  32  is turned by the motor  26 , a portion of the motor gear  32  may engage the rotor gear teeth  28  to drive the brake rotor  22 . For example, the central axis of the motor gear  32  may include motor gear teeth  34 . When the operator engages the brakes via brake line  18  or other engagement means, each half of the motor gear  32  may “pinch” or clamp onto the rotor  22  which brings the rotation of the rotor  22  to a stop. 
     In a slightly different embodiment, the motor gear  32  is not split in half as mentioned above but may have a frictional device on each side of the motor gear  32  which acts just like pistons in a caliper slow the rotor&#39;s rotation. 
     In yet another embodiment, the motor gear  32  may be eliminated and replaced with drive wheels that engage each face of the rotor  22  with a frictional material exerting a clamping force of the rotor  22 . Each wheel may be rotated by the motor  26  to deliver rotational force. As a result, the brake rotor gear teeth  28  and caliper  20  may be eliminated. In order to provide braking, the motor  26  may be switched to a generator and provide regenerative braking power. The rotational force of the rotor  22  may be converted into electrical energy by the motor  26  which may then be stored in a storage device such as a battery. Also, the wheel may simply “lock-up” or provide added friction to the face of the rotor  22  in order to slow the rotation of the rotor  22 . 
     Although the best mode contemplated by the inventors of carrying out the present invention is disclosed above, practice of the present invention is not limited thereto. It will be manifest that various additions, modifications, and rearrangements of the features of the present invention may be made without deviating from the spirit and scope of the underlying inventive concept. It is intended that the appended claims cover all such additions, modifications, and rearrangements. Expedient embodiments of the present invention are differentiated by the appended claims.