WO2024155677A2

WO2024155677A2 - Infinitely variable internally geared hub transmission

Info

Publication number: WO2024155677A2
Application number: PCT/US2024/011786
Authority: WO
Inventors: Peter Ward; Anthony Mora; Joseph MOWAT
Original assignee: Gates Corporation
Priority date: 2023-01-17
Filing date: 2024-01-17
Publication date: 2024-07-25
Also published as: WO2024155677A3

Abstract

A continuously variable transmission for a vehicle, in particular a bicycle, assists a user under a variety of conditions. The transmission combines the reliability and efficiency of gears with the ability to continuously and infinitely vary the gear ratio of the transmission. The transmission can have a planetary gear set with planetary gears that receive an input torque via a carrier, a sun gear, and a ring gear that receives an output torque. An electric motor can be engaged with the sun gear to continuously vary the angular velocity of the sun gear and, thus, continuously vary the gear ratio of the transmission to increase or decrease the output torque at the ring gear. The ring gear can turn a rear wheel of a bicycle, and the transmission provides a potentially infinite number of gear ratios to suit a user.

Description

INFINITELY VARIABLE INTERNALLY GEARED HUB TRANSMISSION

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application Serial No. 63/439,441 filed January 17, 2023, which is incorporated herein in its entirety by reference.

FIELD OF THE INVENTION

The disclosure relates to a continuously variable transmission, in particular for a bicycle, that transmits power from a crankshaft to a rear hub using gears such that the gear ratio of the transmission is continuously variable through a potentially infinite number of gear ratios.

BACKGROUND OF THE INVENTION

Bicycles typically have a drive chain and sprockets to transmit power from a crankshaft at a bottom bracket of the bicycle to a rear wheel and tire at a rear hub of the bicycle, which propels the bicycle. Power is equal to torque times angular velocity, and thus, torque and angular velocity are inversely related for a given power. A gear ratio refers to the mechanical advantage provided by a transmission where the gear ratio is the output torque divided by the input torque, or the gear ratio is the input angular velocity divided by the output angular velocity. As discussed herein, the gear ratio can also be derived from the number of teeth in sprockets or gears of a transmission.

Some bicycles have a single gear ratio between a sprocket at the bottom bracket and a sprocket at the rear hub, and some bicycles have multiple possible gear ratios between multiple sprockets at the crankshaft and/or multiple sprockets at the rear hub. Bicycles with a single gear ratio are generally cheaper, simpler, and more reliable, but a single gear ratio can be optimized for only a narrow range of conditions. The single gear ratio can be a gear ratio where the sprocket at the rear hub has relatively more teeth, which provides increased torque for moving a bicycle from a rest position but will limit the ability of the user to achieve high speeds on the bicycle. Conversely, the single gear ratio can be a gear ratio where the sprocket at the rear hub has relatively fewer teeth, which allows for increased speed but will limit the ability of the user to initially propel the bicycle from a rest position.

Bicycles with multiple possible gear ratios typically have a derailleur that selectively moves the drive chain among sprockets at the bottom bracket and/or rear hub. Therefore, a user can start with a gear ratio to provide more torque and help propel the bicycle from a rest position, then the user can cause the derailleur to move the drive chain to another sprocket to establish a gear ratio. As a result, the user can further increase the speed of the bicycle, much like a conventional automobile cycling through gears as the automobile increases speed. However, even with multiple gear ratios, the user has only a few, finite number of gear ratios from which to select. These few gear ratios are optimized only for certain operating conditions that may not apply to a particular user.

Some bicycles have a continuously variable transmission that relies on specialized components to continuously vary the gear ratio of the transmission through a potentially infinite number of gear ratios to suit any operating condition for any user. While a “gear ratio” may imply the use of sprockets or gears, a “gear ratio” may also generally refer to the mechanical advantage of a transmission even if the specialized components are not sprockets or gears. The specialized components may be a sheave and belt system where a belt joins a set of driver sheaves to a set of driven sheaves, and the sheaves change positions to continuously change the gear ratio of the transmission. Alternatively, the specialized components may be a series of discs and rollers of a toroidal continuously variable transmission. The discs transmit power between a driver roller and a driven roller, and the discs can change positions against the rollers to continuously change the gear ratio of the transmission. While these transmissions are continuously variable, the specialized components are typically less efficient at transmitting power than chain and sprocket systems or geared systems, or the specialized components are less durable or reliable. Therefore, a tradeoff exists between the efficiency of a sprocket or geared transmission and the utility of a continuously variable transmission.

Another trend in bicycles is the increasing popularity of electric bicycles, or “e-bikes,” which is a further consideration for transmissions. Specifically, e-bikes introduce more components to a bicycle frame including an electric motor, a controller, a battery, and even a further transmission to interface the relatively high speed and low output torque of an electric motor with the relatively low speed and high torque requirements for propelling a bicycle. Moreover, some electric motors are positioned at the bottom bracket of the e-bike, which relegates transmission components to the rear hub. Sprocket or geared transmissions and continuously variable transmissions have been implemented at the rear hub of a bicycle, but these transmissions still have the aforementioned tradeoffs. SUMMARY OF THE INVENTION

Embodiments of the present disclosure relate to a novel transmission that combines the efficiency of a sprocket or geared transmission with the utility of a continuously variable transmission at a rear hub of a bicycle. The transmission of the present disclosure uses an outer planetary gear set to transmit power from a drive sprocket to the rear wheel and tire to propel the bicycle. In addition, the transmission uses an electric motor to continuously vary the speed of a sun gear of the outer planetary gear set to continuously vary the gear ratio of the transmission through a potentially infinite number of gear ratios. Thus, the transmission of the present disclosure can range among a potentially infinite number of gear ratios between the drive sprocket and the rear wheel and tire using gears. While embodiments of the present disclosure are described with respect to a bicycle, it will be appreciated that the present disclosure encompasses embodiments directed to other vehicles or any device that benefits from a continuously and infinitely variable change in a gear ratio using gears.

It is an aspect of embodiments of the present disclosure to provide a transmission that transmits power from a pedaling motion of a user to a rear wheel and tire with an efficient geared transmission. In some embodiments of the present disclosure, a user engages pedals to turn a crankshaft, which turns a drive chain and a drive sprocket at the rear hub. The present disclosure encompasses embodiments with only a single sprocket at the bottom bracket and a single drive sprocket at the rear hub, but it will be appreciated at the present disclosure also encompasses embodiments with multiple sprockets at the bottom bracket and/or rear hub. The drive sprocket turns a carrier of an outer planetary gear set, which turns outer planetary gears against a sun gear. This action turns a ring gear that is connected to a housing of the rear hub. Rotation of the housing turns the rear wheel and tire to propel the bicycle. In a first mode of operation, with a stationary sun gear, the transmission has a gear ratio as established by the configuration and number of teeth of the components of the outer planetary gear set.

It is a further aspect of embodiments of the present disclosure to provide a transmission that selectively rotates the sun gear to continuously vary the gear ratio of the transmission. In a second mode of operation, an electric motor rotates the sun gear to change the relative speed between the carrier and the sun gear. As a result, the outer planetary gears continue to drive the ring gear and housing but at a different gear ratio with an increased torque at the ring gear and housing. Since the electric motor can rotate the sun gear at any angular velocity within a range, the gear ratio is continuously and infinitely variable.

It is another aspect of embodiments of the present disclosure to provide a transmission with an inner planetary gear set that transmits power from an electric motor to the sun gear of the outer planetary gear set. The electric motor has an output that is relatively high speed and low torque whereas other components of the transmission rotate with relatively low speed and high torque. To bridge this difference, an output pinion on the output shaft of the electric motor is positioned within and engaged with a plurality of inner planetary gears, and each individual inner planetary gear is rotatable about a pin that extends into a stationary axle. In this sense, the “carrier” of the inner planetary gear set is the stationary axle. Then, the inner planetary gears are positioned within and engaged with teeth on an interior surface of the sun gear. Thus, the sun gear functions as both a sun gear for the outer planetary gear set and a ring gear for the inner planetary gear set. The inclusion of the inner planetary gear set results in the output at the sun gear being lower speed and higher torque compared to the input at the electric motor.

It is an aspect of embodiments of the present disclosure to provide a one-way clutch between the sun gear and a stationary axle of the transmission to limit rotation of the sun gear to only one direction. As described herein, in a first mode of operation, the sun gear is stationary and does not rotate relative to an axle, and in a second mode of operation, the sun gear rotates in one direction relative to the axle to continuously vary the gear ratio of the transmission. To accomplish this, a pawl system is utilized as a one-way clutch where a ratchet wheel is connected to an interior surface of the sun gear, and the ratchet wheel has teeth extending inwardly from an interior surface of the ratchet wheel. Biased pawls extend from an axle to engage the teeth of the ratchet wheel in such a manner that the sun gear can rotate only in one direction relative to the axle.

It is an aspect of embodiments of the present disclosure to provide a controller in communication with a battery and the electric motor to determine when and how the electric motor moves the sun gear to continuously vary the gear ratio of the transmission. The controller selectively allows the battery to transmit electric power to the electric motor based on one or more input signals from one or more input devices. An input device can be a device that detects an aspect or characteristic of the transmission such as the angular velocity of the carrier of the outer planetary gear set. An input device also can be a button or lever that a user engages to set a pedal assist level, an output torque, a cadence, etc. The one or more input devices transmit respective input signals to the controller, which then determines when and how to allow the battery to transmit electric power to the electric motor, if at all. “When” the controller allows the battery to transmit electric power to the electric motor can be a determination made by the controller based on, for instance, conditions or thresholds from the input signals or values derived from the input signals. “How” the controller allows the battery to transmit electric power to the electric motor can be the manner in which electric power is transmitted, for instance, with a constant or varying amperage. The controller can make a determination to transmit current at a constant or varying amperage also based on conditions or thresholds.

A first aspect of the present disclosure is to provide a continuously variable transmission for a vehicle, comprising a carrier configured to receive an input torque; a plurality of outer planetary gears rotatably engaged with the carrier; a sun gear positioned within and engaged with the plurality of outer planetary gears, wherein the sun gear is selectively rotatable; a ring gear positioned around and engaged with the plurality of outer planetary gears; wherein, in a first mode with the input torque, the sun gear is stationary, and the carrier and the plurality of outer planetary gears are configured to drive the ring gear with a first output torque; and wherein, in a second mode with the input torque, the sun gear rotates in a same direction as the carrier, and the carrier and the plurality of outer planetary gears are configured to drive the ring gear with a second output torque that is greater than the first output torque.

The continuously variable transmission of the first aspect may include, optionally, an electric motor engaged with the sun gear to selectively rotate the sun gear.

The continuously variable transmission of the first aspect may include one or more of the previous embodiments and, optionally, a plurality of inner planetary gears positioned within and engaged with the sun gear, wherein an output pinion of the electric motor is positioned within and engaged with the plurality of inner planetary gears to selectively transmit a motor torque from the electric motor to the sun gear to selectively rotate the sun gear.

The continuously variable transmission of the first aspect may include one or more of the previous embodiments and, optionally, a ratchet wheel connected to an interior surface of the sun gear; a drive axle positioned within the ratchet wheel; and a biased pawl positioned on the drive axle, wherein the biased pawl is configured to selectively engage the ratchet wheel such that the sun gear rotates in only one direction relative to the drive axle. The continuously variable transmission of the first aspect may include one or more of the previous embodiments and, optionally, a drive sprocket engaged with the carrier via a one-way clutch, wherein the drive sprocket transmits the input torque to the carrier as the drive sprocket rotates only in one direction relative to the carrier.

The continuously variable transmission of the first aspect may include one or more of the previous embodiments and, optionally, a housing in which the sun gear, the plurality of outer planetary gears, and the carrier are at least partially positioned, wherein the ring gear is connected to an interior surface of the housing such that the housing receives the first output torque and the second output torque.

The continuously variable transmission of the first aspect may include one or more of the previous embodiments and, optionally, that the housing is configured to receive at least one spoke of a wheel, and rotation of the housing turns the wheel.

A second aspect of the present disclosure is to provide a continuously variable transmission for a vehicle, comprising a ring gear configured to receive an output torque; a plurality of outer planetary gears positioned within and engaged with the ring gear, wherein the plurality of outer planetary gears is configured to receive a first input torque; a sun gear positioned within and engaged with the plurality of outer planetary gears; and an electric motor engaged with the sun gear to selectively rotate the sun gear with a second input torque, wherein the output torque is proportional to the first input torque and the second input torque, and the electric motor is configured to continuously vary the second input torque to continuously vary a gear ratio between the output torque and the first input torque.

The continuously variable transmission of the second aspect may include, optionally, a carrier joining the plurality of outer planetary gears, wherein the carrier is configured to receive the first input torque and transmit the first input torque to the plurality of outer planetary gears.

The continuously variable transmission of the second aspect may include one or more of the previous embodiments and, optionally, an axle, wherein the sun gear is engaged with the axle with a one-way clutch such that the sun gear rotates only in one direction relative to the axle.

The continuously variable transmission of the second aspect may include one or more of the previous embodiments and, optionally, a drive sprocket engaged with the carrier via a oneway clutch, wherein the drive sprocket transmits the first input torque to the carrier only as the drive sprocket rotates in one direction relative to the carrier. The continuously variable transmission of the second aspect may include one or more of the previous embodiments and, optionally, a controller in communication with the electric motor, wherein the controller is configured to receive an input signal, and the controller is configured to cause the electric motor to rotate the sun gear based on the input signal.

The continuously variable transmission of the second aspect may include one or more of the previous embodiments and, optionally, an input device in communication with the controller, wherein the input device is configured to transmit the input signal to the controller based on the input signal.

The continuously variable transmission of the second aspect may include one or more of the previous embodiments and, optionally, a battery in communication with the controller, wherein the controller is configured to cause the battery to transmit electric power to the electric motor.

A third aspect of the present disclosure is to provide a continuously variable transmission for a vehicle, comprising a first axle and a second axle configured to be secured to the vehicle, wherein the first axle has an aperture; an electric motor secured to the first axle and configured to receive electric power through the aperture of the first axle; and a planetary gear set having a ring gear, a plurality of outer planetary gears positioned within and engaged with the ring gear, and a sun gear positioned within and engaged with the plurality of outer planetary gears, wherein the sun gear is engaged with the second axle with a one-way clutch such that the sun gear rotates only in one direction relative to the second axle, and wherein the electric motor is configured to turn the sun gear in the one direction relative to second axle with varying angular velocities to vary a gear ratio between the ring gear and a carrier connected to the plurality of outer planetary gears.

The continuously variable transmission of the third aspect may include, optionally, a plurality of inner planetary gears rotatably connected to the second axle, wherein the plurality of inner planetary gears is positioned within and engaged with the sun gear, and an output pinion of the electric motor is positioned within and engaged with the plurality of inner planetary gears to turn the plurality of inner planetary gears and the sun gear.

The continuously variable transmission of the third aspect may include one or more of the previous embodiments and, optionally, that the output pinion is connected to an output shaft of the electric motor, and a bearing positioned in a bulkhead of a housing supports the output shaft of the electric motor.

The continuously variable transmission of the third aspect may include one or more of the previous embodiments and, optionally, that the plurality of outer planetary gears comprises four outer planetary gears, and the plurality of inner planetary gears comprises three inner planetary gears.

The continuously variable transmission of the third aspect may include one or more of the previous embodiments and, optionally, a housing that at least partially encloses the electric motor and the planetary gear set, wherein a first bearing is positioned between the housing and the first axle such that the housing can rotate about the first axle, and wherein a second bearing is positioned between the housing and the carrier such that the housing can rotate about the carrier.

The continuously variable transmission of the third aspect may include one or more of the previous embodiments and, optionally, a controller in communication with the electric motor, wherein the controller is configured to receive an input signal, and the controller is configured to cause the electric motor to rotate the sun gear based on the input signal.

The phrases "at least one", "one or more", and "and/or", as used herein, are open-ended expressions that are both conjunctive and disjunctive in operation. For example, each of the expressions "at least one of A, B and C", "at least one of A, B, or C", "one or more of A, B, and C", "one or more of A, B, or C" and "A, B, and/or C" means A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B and C together.

Unless otherwise indicated, all numbers expressing quantities, dimensions, conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about."

The term "a" or "an" entity, as used herein, refers to one or more of that entity. As such, the terms "a" (or "an"), "one or more" and "at least one" can be used interchangeably herein.

The use of "including," "comprising," or "having" and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Accordingly, the terms "including," "comprising," or "having" and variations thereof can be used interchangeably herein. The use of “engaged with” and variations thereof herein is meant to encompass any direct or indirect connections between components. It shall be understood that the term "means" as used herein shall be given its broadest possible interpretation in accordance with 35 U.S.C. § 112(f). Accordingly, a claim incorporating the term "means" shall cover all structures, materials, or acts set forth herein, and all of the equivalents thereof. Further, the structures, materials, or acts and the equivalents thereof shall include all those described in the summary of the invention, brief description of the drawings, detailed description, abstract, and claims themselves.

These and other advantages will be apparent from the disclosure of the invention(s) contained herein. The above-described embodiments, objectives, and configurations are neither complete nor exhaustive. The Summary of the Invention is neither intended nor should it be construed as being representative of the full extent and scope of the present disclosure. Moreover, references made herein to "the present invention", or aspects thereof should be understood to mean certain embodiments of the present invention/disclosure and should not necessarily be construed as limiting all embodiments to a particular description. The present invention is set forth in various levels of detail in the Summary of the Invention as well as in the attached drawings and the Detailed Description and no limitation as to the scope of the present invention is intended by either the inclusion or non-inclusion of elements, components, etc. in this Summary of the Invention. Additional aspects of the present invention will become more readily apparent from the Detailed Description, particularly when taken together with the drawings.

It is to be appreciated that any feature or aspect described herein can be claimed in combination with any other feature(s) or aspect(s) as described herein, regardless of whether the features or aspects come from the same described embodiment.

Any one or more aspects described herein can be combined with any other one or more aspects described herein. Any one or more features described herein can be combined with any other one or more features described herein. Any one or more embodiments described herein can be combined with any other one or more embodiments described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Those of skill in the art will recognize that the following description is merely illustrative of the principles of the disclosure, which may be applied in various ways to provide many different alternative embodiments. This description is made for illustrating the general principles of the teachings of this disclosure and is not meant to limit the inventive concepts disclosed herein.

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments and together with the general description of the invention given above and the detailed description of the drawings given below, serve to explain the principles of the invention.

Fig. 1 A is a perspective view of a bicycle frame and a rear hub in accordance with an embodiment of the present disclosure;

Fig. IB is a perspective view of the rear hub of Fig. 1 A in accordance with an embodiment of the present disclosure;

Fig. 2 is a cross-sectional, bottom plan view of the rear hub taken along line B-B in Fig. 1A in accordance with an embodiment of the present disclosure;

Fig. 3 is an exploded, perspective view of an electric motor and related components shown in Fig. 2 in accordance with an embodiment of the present disclosure;

Fig. 4 is an exploded, perspective view of an inner planetary gear and related components shown in Fig. 2 in accordance with an embodiment of the present disclosure;

Fig. 5 is an exploded, perspective view of an outer planetary gear and related components shown in Fig. 2 in accordance with an embodiment of the present disclosure;

Fig. 6 is a cross-sectional, bottom plan view of the rear hub taken along line B-B in Fig. 1 A in accordance with an embodiment of the present disclosure;

Fig. 7 is a cross-sectional, elevation view of inner and outer planetary gear sets and related components taken along line C-C in Fig. 6 in accordance with an embodiment of the present disclosure;

Fig. 8 is a cross-sectional, elevation view of a one-way clutch and related components taken along line D-D in Fig. 6 in accordance with an embodiment of the present disclosure; and

Fig. 9 is a schematic view of a controller and related components in accordance with an embodiment of the present disclosure.

It should be understood that the drawings are not necessarily to scale, and various dimensions may be altered. In certain instances, details that are not necessary for an understanding of the invention or that render other details difficult to perceive may have been omitted. It should be understood, of course, that the invention is not necessarily limited to the particular embodiments illustrated herein.

2 Bicycle Frame

4 Rear Hub

6 Brake Axle

8 Drive Axle

10 Drive Sprocket

12 Housing

14 Spoke Aperture

16 Brake Disc

17 Transmission

18a First Housing Portion

18b Second Housing Portion

20 Brake Fastener

22 Brake Bearing

24 Brake Bracket

26 Electric Motor

28 Mount

30 Mount Fastener

32 Brake Axle Aperture

34 Bulkhead

36 Output Bearing

38 Output Pinion

40 Inner Planetary Gear

42 Sun Gear

44 Ratchet Wheel

46 Retainer Ring

48 Outer Planetary Gear

50 Outer Planetary Bearing

52 Outer Planetary Pin

54 Washer 56 Ring Gear

58 Carrier

60 Drive Axle Bearing

62 Sun Gear Bearing

64 Carrier Bearing

66 Output Shaft

68 Nut

70 Inner Planetary Bearing

71 Output Pinion Teeth

72 Inner Planetary Pin

73 Inner Planetary Gear Teeth

74 Pawl

75 Pawl System

76 Pawl Spring

77 Sun Gear Teeth (Exterior Surface)

78 Retainer Ring

79 Outer Planetary Gear Teeth

80 One-Way Clutch

81 Ring Gear Teeth

82 First Input Torque

83 Sun Gear Teeth (Interior Surface)

84 Second Input Torque

85 Inner Planetary Gear Set

86 Output Torque

87 Outer Planetary Gear Set

88 Counterclockwise Side

90 Clockwise Side

92 Input Device

94 Controller

96 Battery DETAILED DESCRIPTION

Although the following text sets forth a detailed description of numerous different embodiments, it should be understood that the legal scope of the description is defined by the words of the claims set forth at the end of this disclosure. The Detailed Description is to be construed as exemplary only and does not describe every possible embodiment since describing every possible embodiment of the transmission would be impractical, if not impossible. Numerous alternative embodiments could be implemented, using either current technology or technology developed after the filing date of this patent, which would still fall within the scope of the claims. Additionally, any combination of features shown in the various figures can be used to create additional embodiments of the present disclosure. Thus, dimensions, aspects, and features of one embodiment of the transmission can be combined with dimensions, aspects, and features of another embodiment of the transmission to create the claimed embodiment.

Fig. 1 A shows a bicycle frame 2 with a rear hub 4, and Fig. IB shows another view of the rear hub 4 of the present disclosure. Like a typical bicycle, including an electric bicycle or e- bike, a user engages pedals to turn a crankshaft, which transmits power to the rear hub 4 via a drive chain. As the rear hub 4 turns, a wheel and tire connected to the rear hub 4 also turn to propel the bicycle.

As shown in Fig. IB, the rear hub 4 comprises a brake axle 6 and an opposing drive axle 8. These axles 6, 8 are secured to part of the bicycle frame 2 with a fastener such as a nut. A drive sprocket 10 receives power from the drive chain, and the drive sprocket 10 transmits power through a transmission to turn a housing 12 and propel the bicycle. The housing 12 encloses at least some of the components of the transmission, and the housing 12 has a plurality of spoke apertures 14 arrayed around a circumference of the housing 12. Spokes of a wheel extend through the spoke apertures 14 such that rotation of the housing 12 is transmitted to the wheel as well as a tire positioned on the wheel to propel the bicycle. Moreover, Fig. IB shows a brake disc 16 to which brake components can engage to stop the housing 12 from turning relative to the bicycle frame 2, and to stop the bicycle. Line B-B in also shown in Fig. 1A.

Fig. 2 shows a cross-sectional, bottom plan view of the rear hub 4 taken along line B-B in Fig. 1A. Specifically, Fig. 2 shows components of a transmission 17 that transmits power from the drive sprocket 10 to the housing 12. The term “transmission” can be used interchangeably with the term “rear hub” and can also refer to the components of the “rear hub” used for transmitting power. The housing 12 comprises a first portion 18a and a second portion 18b that are joined together. In some embodiments, the housing 12 is a single, continuous structure, and in other embodiments, the housing 12 comprises more than two portions joined together. At least one fastener 20 joins the brake disc 16 to the first portion 18a of the housing 12, and a brake bearing 22 allows the housing 12 to rotate relative to the brake axle 6. As noted herein, the brake axle 6 is joined to the bicycle frame 2, and the bicycle frame 2 may comprise a brake bracket 24 where brake components can be mounted to engage the brake disc 16.

The transmission 17 comprises an electric motor 26 that can selectively and infinitely vary the gear ratio of the transmission 17. The electric motor 26 is positioned within the housing 12 and is connected to a mount 28, which is secured to the brake axle 6 with a fastener 30. The brake axle 6 has an aperture 32 through which power can be delivered from an external source such as a battery, into the space within the housing 12, and to the electric motor 26. As the electric motor 26 is secured to the brake axle 6, many components of the electric motor 26 do not rotate relative to the bicycle frame 2. The electric motor 26 can be a DC motor, an AC motor, a servo motor, an axial flux motor, or any other motor that translates electric power to physical motion.

A bulkhead 34 traverses the space within the housing 12 to provide support to the housing 12 and to support an output shaft (66 in Fig. 3) of the electric motor 26. Specifically, an output bearing 36 is positioned between the bulkhead 34 and the output shaft of the electric motor 26 to allow the output shaft to rotate relative to the bulkhead 34. When the output shaft of the electric motor 26 rotates, the output shaft turns an output pinion 38, which drives a plurality of inner planetary gears 40 via gear teeth, which in turn drives a sun gear 42 also via gear teeth. In some embodiments, the inner planetary gears 40 rotate about bearings (70 in Fig. 4) and pins (72 in Fig. 4) in the drive axle 8, which does not rotate relative to the bicycle frame 2. Moreover, several components interact with the sun gear 42 to transmit power through the transmission 17 in a manner that allows the gear ratio to be continuously and infinitely variable. One end of the drive axle 8 is positioned within and engaged with the sun gear 42 via a pawl system (75 in Fig. 4) that serves as a one-way clutch. Specifically, a ratchet wheel 44 with asymmetrical gear teeth is connected to an interior surface of the sun gear 42. As described herein, the pawl system has biased pawls that engage teeth of the ratchet wheel 44 such that the sun gear 42 turns in only one direction relative to the drive axle 8. A retainer ring 46 retains components of the pawl system on the drive axle 8.

Next, a plurality of outer planetary gears 48 are positioned around and engaged with the sun gear 42 via gear teeth. Each outer planetary gear 48 is rotatable about a bearing 50 and pin 52 that extends into a carrier 58. A washer 54 is positioned about each pin 52 proximate to the carrier 58 to help distribute forces and retain components. A ring gear 56 is positioned around and engaged with the plurality of outer planetary gears 48 via gear teeth, and the ring gear 56 is connected to an interior surface of the housing 12 such that any power transmitted to the ring gear 56 is also transmitted to the housing 12 to propel the bicycle. The carrier 58 receives power from the drive sprocket 10 via a one-way clutch (80 in Fig. 6) or freewheel such that the drive sprocket 10 transmits power to the carrier 58 only when the drive sprocket 10 rotates in one direction relative to the carrier 58. The one-way clutch allows the drive chain, the sprocket at the bottom bracket, and the drive sprocket 10 to transmit power when the user pedals in the forward direction. However, the one-way clutch prevents transmission of power when a user pedals in the reverse direction, like some existing bicycles. It will be appreciated that the one-way clutch is optional, and in embodiments without the one-way clutch, a user may pedal in reverse to reverse the motion of the bicycle.

A drive axle bearing 60 is positioned between the carrier 58 and the drive axle 8 to allow the carrier 58 to rotate relative to the drive axle 8. A sun gear bearing 62 is positioned between the carrier 58 and the sun gear 42 to allow the carrier 58 to rotate relative to the sun gear 42. A carrier bearing 64 is positioned between the housing 12 and the carrier 58 to allow the housing 12 to rotate relative to the carrier 58 and, therefore, the drive axle 8.

Figs. 3-5 show exploded views of the various components in Fig. 2. Fig. 3 is an exploded, perspective view of the electric motor 26 and related components. Fasteners 20 secure the brake disc 16 to the first portion 18a of the housing, and a nut 68 secures the brake axle 6 to the frame of the bicycle or other vehicle. The brake bearing 22 allows the housing to rotate relative to the brake axle 6. The electric motor 26 is secured to the mount 28, which is secured to the brake axle 6 with a fastener 30. The electric motor 26 has an output shaft 66 that rotates when the electric motor 26 is supplied with electric power. The bulkhead 34 spans the housing and supports the output shaft 66 of the electric motor. An output bearing 36 allows the output shaft 66 to rotate relative to the bulkhead 34. Fig. 4 shows an exploded, perspective view of the inner planetary gears 40 and related components. As described herein, the output shaft of the electric motor turns an output pinion 38 affixed to the output shaft. The output pinion 38 has teeth 71 that turn against teeth 73 of the inner planetary gears 40 of the inner planetary gear set (85 in Fig. 7). The inner planetary gears 40 rotate about pins 72 and bearings 70 that extend into the drive axle 8. The drive axle 8 is secured to the bicycle and does not rotate relative to the bicycle frame (2 in Fig. 1). A drive axle bearing 60 allows a carrier of the outer planetary gear set (87 in Fig. 7) to rotate relative to the drive axle 8. Moreover, components of a pawl system 75 that limit rotation of the sun gear to only one direction. In this embodiment, three pawls 74 and respective pawl springs 76 are held in place in the drive axle 8 with a retainer ring 78. The pawls 74 engage a ratchet wheel in such a manner that the ratchet wheel and the sun gear can turn in only one direction relative to the drive axle 8. It will be appreciated that the present disclosure encompasses embodiments with other types of one-way clutches or pawl systems 75, a different number of pawls 74, a bias member other than pawl springs 76, springs 76 with linear or non-linear responses, etc.

Fig. 5 shows an exploded, perspective view of the outer planetary gears 48 and related components. The drive sprocket 10 selectively turns the carrier 58, and the carrier 58 drives the plurality of outer planetary gears 48, which are rotatably connected to the carrier 58 with respective bearings 50, pins 52, and washers 54. The exterior surface of the sun gear 42 has teeth 77 that turn against teeth 79 of the outer planetary gears 48, and a ratchet wheel 44 is secured to an interior surface of the sun gear 42 as described herein. In some embodiments, the sun gear 42 and the ratchet wheel 44 are a single structure. The teeth 79 of the outer planetary gears 48 turn against teeth 81 of the ring gear 56, and the ring gear 56 is secured to an interior surface of the second portion 18b of the housing. The sun gear bearing 62 allows the carrier 58 to rotate relative to the sun gear 42, and the carrier bearing 64 allows the housing to rotate relative to the carrier 58 and the drive axle.

Various gear ratios can be observed from the components shown in Figs. 3-5. Starting with the outer planetary gear set (87 in Fig. 7) and since the sun gear 42 is stationary in a first mode of operation, the gear ratio of the outer planetary gear set can be expressed as: gear rati o = — ^NRtns — ( 1 )

^& Nsun + NRing ^{V 7} where NRing is the number of teeth of the ring gear 56, and Nsun is the number of teeth on an exterior surface of the sun gear 42. In some embodiments, the ring gear 56 has between approximately 90 and 100 teeth, and the sun gear 42 has between approximately 38 and 45 teeth on an exterior surface. Accordingly, the gear ratio of the outer planetary gear set and the overall transmission in the first mode of operation with a stationary sun gear 42 is between approximately 1 :1.3 and 1 : 1.6. Thus, in a second mode of operation where the electric motor turns the sun gear 42 increase the output torque at the ring gear 56, the gear ratio or the mechanical advantage between the drive sprocket 10 and the ring gear 56 increases to a greater value such as 1 : 1 or 2: 1 or more, for example. In this second mode of operation, the gear ratio of the outer planetary gear set can be expressed as: gear ratio

For the inner planetary gear set (85 in Fig. 7), the inner planetary gears turn about a stationary axle and so the “carrier” is effectively stationary, and the gear ratio of the inner planetary gear set can be expressed as: gear ratio

where Nsi is the number of teeth on the interior surface of the sun gear 42, and NOP is the number of teeth of the output pinion 38. In some embodiments, the interior surface of the sun gear has between approximately 75 and 85 teeth, and the output pinion 38 has between approximately 10 and 15 teeth. Accordingly, the gear ratio of the inner planetary gear set is between approximately -8.5: 1 and -5: 1.

Figs. 6-8 show the operation of the components of the transmission 17 that allow the transmission 17 to transmit power efficiently with gear teeth and also to continuously and infinitely vary the gear ratio of the transmission 17. Fig. 6 is another cross-sectional, bottom plan view of the rear hub 4 and the transmission 17 that shows a first power input 82, a second power input 84, and a power output 86. The power output 86 at the ring gear 56 that turns the housing 12 and propels the bicycle is equal to the first power input 82 from the drive sprocket 10 plus the second power input 84 from the electric motor 26. This can be stated in the form of an equation as:

Po = Pi + P₂ (4) where Po is the output power, Pi is the first input power from the drive sprocket 10, and P2 is the second input power from the electric motor 26. Since power is torque times angular velocity. The above Equation 4 can be written as:

where T is torque, and co is angular velocity. These torques and angular velocities occur at particular components in the transmission 17. Specifically, the relevant component for power output is the ring gear 56 since the ring gear 56 turns the housing 12 and the rear wheel and tire, the relevant component for the first power input is the carrier 58 since a user powers the drive sprocket 10 and the carrier 58, and the relevant component for the second power input is the sun gear 42 since the electric motor 26 powers movement of the sun gear 42. Thus, the above Equation 5 can be written as:

where “Ring” is the ring gear 56, “Carrier” is the carrier 58, and “Sun” is the sun gear 42.

Rewriting the above Equation 6 in terms of output torque at the ring gear 56, which rotates the housing 12 and propels the bicycle or other vehicle, yields:

With this Equation 7 in terms of output torque at the ring gear 56, the transmission 17 generally has two modes of operation. In a first mode of operation, the electric motor 26 is not supplied with electric power and, thus, the output shaft of the electric motor 26 does not turn. As a result, the inner planetary gears 40 do not turn, and the sun gear 42 does not turn due to a one- way clutch discussed herein with respect to Fig. 8. With no power, no torque, and no angular velocity from the electric motor and the sun gear 42, the above Equation 7 reduces to:

Thus, the drive sprocket 10 turns the carrier 58, which drives the outer planetary gears 48 against the stationary sun gear 42. Then, the outer planetary gears 48 turn the ring gear 56 and the housing 12 with an output torque Tring according to above Equation 8. A gear ratio can be expressed as the angular velocity of the carrier 58 divided by the angular velocity of the ring gear 56. For a gear ratio of 0.77, as denoted by Equation 1, Equation 8 would yield:

This mode operation represents a lower torque and higher speed output at the ring gear 56 that is suitable for a vehicle that is in motion and a user that is intending to reach a high speed for the vehicle.

In a second mode of operation, the electric motor 26 is supplied with electric power and turns the output shaft to increase output torque Tring. This turns the inner planetary gears 40, which turns the sun gear 42. Now, with the sun gear 42 in motion and the carrier 58 turning the outer planetary gear 48, the outer planetary gears 48 are pushing off of a moving sun gear 42 rather than a stationary sun gear 42. According to Equation 7, the result is an increase in output torque Tring. With the electric motor 26 turning the output shaft, this represents a higher torque and lower speed output at the ring gear 56 that is suitable for a vehicle that is at rest or at a low speed. Since the electric motor 26 can continuously vary the angular velocity of the sun gear 42 from a rest to a high angular velocity, the relative speed between the carrier 58 and the sun gear 42 is continuously variable, and the gear ratio is continuously and infinitely variable to increase the output torque Tring. It will be appreciated that the one-way clutch 80 or freewheel is optional, and in embodiments without the one-way clutch 80, a user may pedal in reverse to reverse the motion of the bicycle.

With the above equations, operation of the transmission 17 can be expressed in terms of torque. For instance, in the first mode, the user supplies an input torque to the carrier 58, which causes a first output torque at the ring gear 56. Then, in a second mode with the electric motor 26 turning the sun gear 42, the user supplies the same input torque to the carrier 58, which causes a second output torque at the ring gear 56 that is greater than the first input torque due to the continuously and infinitely variable gear ratio of the transmission 17 between the ring gear 56 and the carrier 58. Similarly, the operation of the transmission 17 can be described in terms where the output torque at the ring gear 56 is proportional to a first input torque from the user at the carrier 58 and a second input torque from the electric motor 26 at the sun gear 42. Since, the electric motor 26 can continuously and infinite vary the second input torque, the gear ratio between the output torque and the first input torque is continuously and infinitely variable. Finally, Fig. 6 shows cut lines C-C and D-D.

Fig. 7 shows a cross-sectional, elevation view of components of the transmission 17 in Fig. 6 taken along line C-C. From this view, the motion of the components in the different modes of operation can be seen. In the first mode, the inner planetary gear set 85 does not rotate. Specifically, the electric motor does not receive electric power, the output shaft 66 does not rotate, the output pinion 38 connected to the output shaft 66 does not rotate, the inner planetary gears 40 engaged with the output pinion 38 do not rotate, and therefore the sun gear 42 does not rotate. When a user pedals to turn the drive chain and the drive sprocket, the outer planetary gear set 87 rotates. Specifically, the carrier 58 rotates in a counterclockwise direction to turn the outer planetary gears 48, which push off of the stationary sun gear 42. With the pawl system (75 in Fig. 8) serving as a one-way clutch, the sun gear 42 remains stationary rather than rotating in a clockwise direction. The outer planetary gears 48 rotate in a counterclockwise direction about their respective pins, which causes the ring gear 56 and housing 12 to rotate in a counterclockwise direction to propel the bicycle. The output torque at the ring gear 56 is according to Equation 8.

In a second mode, the electric motor receives electric power, and the output shaft 66 rotates in a clockwise direction. Thus, the output pinion 38 also turns in a clockwise direction, and the inner planetary gears 40 turn in a counterclockwise direction. Teeth (73 in Fig. 4) of the inner planetary gears 40 turn against teeth 83 on an interior surface of the sun gear 42, which causes the sun gear 42 to rotate in a counterclockwise direction, i.e., the direction allowed by the pawl system described in Fig. 8. As described above, the motion of the sun gear 42 causes the output torque Tring to increase. The electric motor can continuously vary the angular velocity of the output shaft 66 and, thus, continuously and infinitely vary the gear ratio to increase output torque Tring of the transmission 17.

It will be appreciated that the present disclosure encompasses embodiments of the transmission 17 where the electric motor can cause the output shaft 66 to rotate in either direction to either increase or even decrease the output torque Tring. A decrease in the output torque Tring would result in an increase in the output angular velocity (Oring which is more suitable for a bicycle or vehicle already in motion.

Moreover, it will be appreciated that the present disclosure encompasses embodiments of the transmission 17 in a first mode of operation where a stationary sun gear 42 represents a higher torque and lower speed output at the ring gear 56. With a reversal of the pawl system and direction of rotation of the output shaft of the electric motor, motion of the sun gear 42 caused by the electric motor continuously and infinitely varies the gear ratio to reduce the torque and increase the angular velocity output of the ring gear 56.

Fig. 8 shows a cross-sectional elevation view of a pawl system 75 that serves as a oneway clutch taken along line D-D in Fig. 6. The pawl system 75 limits rotation of the sun gear 42 to only one direction relative to the drive axle 8. As described herein, a ratchet wheel 44 can be described as part of the pawl system 75 and is connected to an interior surface of the sun gear 42. The ratchet wheel 44 has inwardly extending teeth on an interior surface of the ratchet wheel 44, and the teeth are asymmetrical with one side longer than the other. In the view depicted in Fig. 8, the counterclockwise side 88 of a tooth is longer than a clockwise side 90 of the same tooth, which causes the clockwise side 90 of the tooth to form a larger angle relative to the interior surface of the ratchet wheel 44 than the counterclockwise side 88.

Part of the pawl system 75 is positioned on an exterior surface of the drive axle 8 to engage the ratchet wheel 44. The pawl system 75 comprises at least one pawl 74 that is biased by a bias member 76 such as a spring. Specifically, the pawl 74 is biased outwardly into the teeth of the ratchet wheel 44 such that a distal end of the pawl interacts with the counterclockwise side 88 and the clockwise side 90 of the teeth of the ratchet wheel 44. In a first mode, forces attempt to turn the sun gear 42 in a clockwise direction. However, due to the asymmetric arrangement of the teeth, the distal end of the pawl 74 catches the clockwise side 90 of a tooth to prevent the sun gear 42 from rotating in a clockwise direction. In a second mode, forces turn the sun gear 42 in a counterclockwise direction. Now, the distal end of the pawl 74 drags along the exterior surface of a counterclockwise side 88 of an adjacent tooth, then another adjacent tooth, etc., which allows the sun gear 42 to rotation in a counterclockwise direction.

Fig. 9 shows a schematic view of a controller 94 and related components that dictate when and how the transmission changes the gear ratio of the transmission. The controller 94 is in communication with at least one input device 92 to receive input signals, and the controller 94 is in communication with a battery 96 and an electric motor 26 to dictate when and how the battery 96 supplies electric power to the electric motor 26. Communication is through wired connections as shown in Fig. 9 including a wire extending through an aperture (32 in Fig. 2) in the brake axle to supply electric power from the battery 96 to the electric motor 26, but it will be appreciated that the present disclosure encompasses other forms of transmitting signals and electric power such as wireless communication protocols and electromagnetic induction.

Input devices 92 can include sensors as well as buttons, dials, touchscreens, etc. for user inputs. For instance, one input device 92 is a sensor that detects the angular velocity of a component such as the carrier of the outer planetary gear set. The input device 92 transmits an input signal to the controller 94. Speed data of various components can also be derived from an input device 92 such as a torque sensor, a Hall sensor, or an accelerometer. In one scenario, the input device 92 transmits an input signal to the controller 94 indicating that the angular velocity of the carrier and, thus, the angular velocity of the drive sprocket. If the angular velocity is relatively slow and below a predetermined threshold, the controller 94 can determine that the user needs assistance, and the controller 94 allows the battery 96 to transmit electric power to the electric motor 26 to change the gear ratio and increase an output torque of the transmission at the ring bearing and housing.

The input device 92 can also include buttons, dials, touchscreen, etc. for receiving a user input. A user can engage the input device 92 to, for example, set a pedal assist level between 1- 10 where 1 represents a lower output torque and 10 represents a higher output torque to help the user with the initial propulsion of the bicycle. The input device 92 transmits an input signal to the controller 94. Then, the controller 94 can apply the information on the pedal assist level in a number of ways. Based on the pedal assist level, the controller 94 can change the aforementioned predetermined threshold for carrier and drive sprocket angular velocity. Therefore, a pedal assist level of 10 means the user desires more help and more output torque, and the controller 94 causes the transmission to change gear ratios and output a higher torque at a higher angular velocity threshold for the carrier and drive sprocket (meaning even a small reduction in angular velocity would cause the transmission to output a higher torque) compared to a pedal assist level 1, which means less help for the user, a different gear ratio, and less output torque. In another scenario, based on the pedal assist level, the controller 94 changes the amperage of the electric power transmitted from the battery 96 to the electric motor 26 rather than change the angular velocity thresholds of the carrier and drive sprocket. In some embodiments, the controller 94 both changes the amperage and the thresholds. Therefore, based on these conditions, the controller 94 determines “when” to allow electric power to be transmitted to the electric motor 26 and also “how” with, for example, constant or varying amperage.

With this operation of the controller 94 and related components, the controller 94 can function in many different modes. In one mode, the user manually selects the speed ratio between the ring gear and the carrier. This speed ratio can be expressed as:

where ORing is the angular velocity of the ring gear, and rocamer is the angular velocity of the carrier of the outer planetary gear set. In some embodiments, a user may select a speed ratio i between approximately 0.67 and 1.5. The angular velocity of the sun gear, rosun, can be expressed as:

where Nsun is the number of teeth of the sun gear, and NRing is the number of teeth of the ring gear. Each number of teeth is known to the controller 94, and an input device 92 detects the angular velocity of the carrier, ©carrier. This leaves the angular velocity of the sun gear, rosun, and the overall speed ratio i. Thus, the controller causes the battery 96 to supply electric power to the electric motor 26 to generate an angular velocity of the sun gear, rosun, that matches the user-set speed ratio i.

In another mode, the user manually selects a desired pedaling cadence, which governs the angular velocity of the carrier, rocamer. Thus, the controller 94 varies the speed ratio i and the angular velocity of the sun gear cosun such that a user naturally pedals at the desired cadence. If the cadence becomes too slow as detected by an input device 92, then the controller 94 lowers the speed ratio i until the target cadence is achieved. Conversely, if the cadence is too fast as detected by an input device 92, then the controller 94 increases the speed ratio i until the target cadence is achieved.

In yet another mode, the variables in Equation 11 are varied by the controller 94 to minimize the amount of electric power transmitted from the battery 96 to the electric motor 26, while still providing at least some gear and/or speed ratio variability to a user.

Further still, in some embodiments, one input device 92 is a sensor that detects a user sitting on a seat of bicycle. Based on a reading from the input device 92, the controller can cause the electric motor to change a gear ratio of the transmission or between a carrier and the ring gear.

While various embodiments of the present disclosure have been described in detail, it is apparent that modifications and alterations of those embodiments will occur to those skilled in the art. However, it is to be understood that such modifications and alterations are within the scope and spirit of the present disclosure, as set forth in the following claims. Further, the invention(s) described herein is capable of other embodiments and of being practiced or of being carried out in various ways. It is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

Claims

CLAIMS What is claimed is:

1. A continuously variable transmission for a vehicle, comprising: a carrier configured to receive an input torque; a plurality of outer planetary gears rotatably engaged with the carrier; a sun gear positioned within and engaged with the plurality of outer planetary gears, wherein the sun gear is selectively rotatable; a ring gear positioned around and engaged with the plurality of outer planetary gears; wherein, in a first mode with the input torque, the sun gear is stationary, and the carrier and the plurality of outer planetary gears are configured to drive the ring gear with a first output torque; and wherein, in a second mode with the input torque, the sun gear rotates in a same direction as the carrier, and the carrier and the plurality of outer planetary gears are configured to drive the ring gear with a second output torque that is greater than the first output torque.

2. The continuously variable transmission of Claim 1, further comprising: an electric motor engaged with the sun gear to selectively rotate the sun gear.

3. The continuously variable transmission of Claim 2, further comprising: a plurality of inner planetary gears positioned within and engaged with the sun gear, wherein an output pinion of the electric motor is positioned within and engaged with the plurality of inner planetary gears to selectively transmit a motor torque from the electric motor to the sun gear to selectively rotate the sun gear.

4. The continuously variable transmission of Claim 1, further comprising: a ratchet wheel connected to an interior surface of the sun gear; a drive axle positioned within the ratchet wheel; and a biased pawl positioned on the drive axle, wherein the biased pawl is configured to selectively engage the ratchet wheel such that the sun gear rotates in only one direction relative to the drive axle.

5. The continuously variable transmission of Claim 1, further comprising: a drive sprocket engaged with the carrier via a one-way clutch, wherein the drive sprocket transmits the input torque to the carrier as the drive sprocket rotates only in one direction relative to the carrier.

6. The continuously variable transmission of Claim 1, further comprising: a housing in which the sun gear, the plurality of outer planetary gears, and the carrier are at least partially positioned, wherein the ring gear is connected to an interior surface of the housing such that the housing receives the first output torque and the second output torque.

7. The continuously variable transmission of Claim 6, wherein the housing is configured to receive at least one spoke of a wheel, and rotation of the housing turns the wheel.

8. A continuously variable transmission for a vehicle, comprising: a ring gear configured to receive an output torque; a plurality of outer planetary gears positioned within and engaged with the ring gear, wherein the plurality of outer planetary gears is configured to receive a first input torque; a sun gear positioned within and engaged with the plurality of outer planetary gears; and an electric motor engaged with the sun gear to selectively rotate the sun gear with a second input torque, wherein the output torque is proportional to the first input torque and the second input torque, and the electric motor is configured to continuously vary the second input torque to continuously vary a gear ratio between the output torque and the first input torque.

9. The continuously variable transmission of Claim 8, further comprising: a carrier joining the plurality of outer planetary gears, wherein the carrier is configured to receive the first input torque and transmit the first input torque to the plurality of outer planetary gears.

10. The continuously variable transmission of Claim 9, further comprising: an axle, wherein the sun gear is engaged with the axle with a one-way clutch such that the sun gear rotates only in one direction relative to the axle.

11. The continuously variable transmission of Claim 9, further comprising: a drive sprocket engaged with the carrier via a one-way clutch, wherein the drive sprocket transmits the first input torque to the carrier only as the drive sprocket rotates in one direction relative to the carrier.

12. The continuously variable transmission of Claim 8, further comprising: a controller in communication with the electric motor, wherein the controller is configured to receive an input signal, and the controller is configured to cause the electric motor to rotate the sun gear based on the input signal.

13. The continuously variable transmission of Claim 12, further comprising: an input device in communication with the controller, wherein the input device is configured to transmit the input signal to the controller based on the input signal.

14. The continuously variable transmission of Claim 12, further comprising: a battery in communication with the controller, wherein the controller is configured to cause the battery to transmit electric power to the electric motor.

15. A continuously variable transmission for a vehicle, comprising: a first axle and a second axle configured to be secured to the vehicle, wherein the first axle has an aperture; an electric motor secured to the first axle and configured to receive electric power through the aperture of the first axle; and a planetary gear set having a ring gear, a plurality of outer planetary gears positioned within and engaged with the ring gear, and a sun gear positioned within and engaged with the plurality of outer planetary gears, wherein the sun gear is engaged with the second axle with a one-way clutch such that the sun gear rotates only in one direction relative to the second axle, and wherein the electric motor is configured to turn the sun gear in the one direction relative to second axle with varying angular velocities to vary a gear ratio between the ring gear and a carrier connected to the plurality of outer planetary gears.

16. The continuously variable transmission of Claim 15, further comprising: a plurality of inner planetary gears rotatably connected to the second axle, wherein the plurality of inner planetary gears is positioned within and engaged with the sun gear, and an output pinion of the electric motor is positioned within and engaged with the plurality of inner planetary gears to turn the plurality of inner planetary gears and the sun gear.

17. The continuously variable transmission of Claim 16, wherein the output pinion is connected to an output shaft of the electric motor, and a bearing positioned in a bulkhead of a housing supports the output shaft of the electric motor.

18. The continuously variable transmission of Claim 16, wherein the plurality of outer planetary gears comprises four outer planetary gears, and the plurality of inner planetary gears comprises three inner planetary gears.

19. The continuously variable transmission of Claim 15, further comprising: a housing that at least partially encloses the electric motor and the planetary gear set, wherein a first bearing is positioned between the housing and the first axle such that the housing can rotate about the first axle, and wherein a second bearing is positioned between the housing and the carrier such that the housing can rotate about the carrier.

20. The continuously variable transmission of Claim 15, further comprising: a controller in communication with the electric motor, wherein the controller is configured to receive an input signal, and the controller is configured to cause the electric motor to rotate the sun gear based on the input signal.