Electric bicycle mid-drive motor with belt-driven transmission

Abstract

An electric motor-assisted vehicle transmission transfers the relatively high-speed, low-torque rotation of an electric motor's output shaft to the vehicle's drive wheels, which rotate a chain, rear hub, and rear wheel to propel a bicycle or other vehicle. The electric motor's output shaft is offset from the crankshaft, and multiple belts transfer power from the electric motor to the drive wheels, reducing rotational speed and increasing torque. In some embodiments, three belts and three wheels transfer power from the electric motor to the drive wheels. Various sensors and devices send input signals to a controller, which determines when and how the electric motor powers the transmission to assist the vehicle, reducing the user's effort if the vehicle is a bicycle ridden by a user.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 63 / 433,546, filed December 19, 2022, which is incorporated herein by reference in its entirety.

[0002] The present disclosure relates to a transmission, particularly for electric bicycles or e-bikes, that uses multiple belts to convert power from an electric motor into an output. [Background technology]

[0003] Electric bicycles and electric motor-assisted vehicles have become increasingly popular in recent years, and cities such as Denver, Colorado, have implemented programs to promote the widespread use of electric bicycles. Electric bicycles have an electric motor that selectively assists the user by providing additional power to the bicycle in certain situations, such as when climbing steep hills. Some electric bicycles have a pedal-assist mode, in which the electric motor powers the bicycle in conjunction with the user's pedaling. Some electric bicycles, like mopeds, have a motor that can propel the bicycle without rider assistance or pedaling. Some electric bicycles have sensors that detect increased user effort, such as when climbing a hill, and the electric motor provides additional power to the bicycle based on the sensor's detection. As a result, electric bicycles provide improved fitness to users because riders pedal at least part of the time instead of sitting and driving a car. Electric bicycles are also environmentally friendly because they do not produce gaseous emissions, especially compared to gasoline-powered vehicles. Furthermore, electric bicycles open the world of cycling to a wider range of potential users. This includes users who are not physically capable of riding a regular bicycle without an electric motor, riders who want to commute in business attire but want to ride without getting dirty or sweaty, and riders who need to carry additional luggage such as food delivery, groceries, work supplies, or children.

[0004] Various technologies, including transmissions, allow electric motors to be integrated into bicycles. Electric motors are most efficient when they rotate their output shaft at a relatively high speed and low torque. Conversely, when cycling, the tire and crankshaft that the user pedals rotate at a relatively low speed and high torque. Thus, a transmission connects the electric motor to the bicycle, converting high speed / low torque to low speed / high torque. Existing gear trains, such as planetary gearing, use one or more gears, including spur and helical gears, to transmit power from the electric motor.

[0005] Existing gear trains that use gears to transmit power, particularly for electric motors and / or electric bicycles, have several drawbacks. Because the gears are typically made of solid metal, existing gear trains add weight, and the gears require lubrication because at least two gears are in metal-to-metal contact. Gears, particularly spur gears, generate loud noises that are undesirable for bicycles. Furthermore, metal gears wear over time and require regular maintenance to prevent failure. As described herein, embodiments of the present disclosure provide a transmission that transmits power using multiple belts rather than metal gears. This transmission is therefore lightweight, quiet, requires no lubrication, and requires little or no maintenance. Summary of the Invention

[0006] Embodiments of the present disclosure relate to a transmission that transfers power from an electric motor to a drive wheel of a bicycle, where the drive wheel rotates at a slower speed and with more torque than the electric motor, reducing the effort required by the user. It should be understood that the present disclosure encompasses embodiments in which the transmission does not include components such as an electric motor and / or a controller. Furthermore, while a transmission typically does not include the crankshaft or drive wheel of a vehicle, and particularly, in some embodiments, a bicycle, in some embodiments, the transmission may include such components.

[0007] One aspect of various embodiments of the present disclosure is to provide a transmission for use in a bicycle or electric bicycle, in which an electric motor is offset from a crankshaft to maintain a compact width of the transmission. The transmission is disposed in a bottom bracket of a bicycle frame and is coupled to a crankshaft. Pedals are connected to crank arms, which are connected to the crankshaft, and a user pedals to propel the bicycle forward. Therefore, the transmission must accommodate pedaling motion. Furthermore, while a user is riding the bicycle, the transmission must maintain a certain clearance from the ground to avoid contact with the ground. In consideration of these constraints, the electric motor is offset from the crankshaft to maintain a compact width between a first end and a second end of the crankshaft. In some embodiments, the electric motor has a width and position within the transmission such that the electric motor is completely disposed between the first end and the second end of the crankshaft in the width direction. The distance between the ends of the crankshaft is similar to the Q factor of a bicycle, which is the distance between the outside of the pedal hole on the left crank arm and the outside of the pedal hole on the right crank arm. However, the shape of the crank arms can result in differences between the Q factor and the ends of the crankshaft. While the Q factor varies depending on the type of bicycle, a narrow Q factor is generally preferred for aerodynamic characteristics, handling, and a more natural pedaling operation. Therefore, the distance between the ends of the crankshaft is generally narrow, and the width of the electric motor is positioned between the ends of the crankshaft, allowing for a balance between the operation of the crankshaft and the shape elements of the transmission.

[0008] Another aspect of various embodiments of the present disclosure is to provide a transmission having multiple belts that transmit power from the electric motor to the drive wheels, such that the drive wheels rotate at a slower speed and with greater torque than the output shaft of the electric motor. Compared to traditional gears, belts are cleaner, quieter, and require less maintenance. Because the electric motor is offset from the crankshaft and the drive wheels are positioned around the crankshaft, an odd number of belts are wound between the output shaft of the electric motor and the drive wheels. Based on physical constraints and the desired overall gear ratio, in a preferred embodiment, the transmission includes three belts. However, in other embodiments, the transmission can include any number of belts.

[0009] A further aspect of an embodiment of the present disclosure is to provide a transmission with a controller and related elements that controls the transmission and reduces user effort, i.e., energy input required by the user. The electric motor selectively powers multiple belts and drive wheels, and the controller determines when and how much power the electric motor provides. A number of different input devices send one or more input signals to the controller. For example, a user can turn a throttle or input an assist level with a shift lever or button. Alternatively or additionally, a torque sensor that detects the amount of user force applied to the crankshaft can send an input signal to the controller. The controller determines subsequent actions based on these input signals. Subsequent actions include providing power to the electric motor from a battery. The controller can also provide constant amperage, converting amperage, or otherwise providing amperage to the electric motor, powering the multiple belts and drive wheels.

[0010] Another aspect of an embodiment of the present disclosure is to provide a transmission in which an electric motor cooperates with a bevel gear that contributes to the overall gear ratio of the transmission. In some embodiments, the electric motor is an axial flux motor, and its internal volume is determined by how the axial flux motor and its elements convert electrical power into physical motion. The bevel gear is located within this internal volume to keep the transmission compact and contribute to the overall gear ratio of the transmission.

[0011] The advantages of the belt-driven center drive transmission described in various embodiments herein are: (1) it is ideally suited for integration with axial flux motor designs; (2) it is most suitable for performance; (3) it can use existing bicycle gear train technology, improving transmission efficiency and / or torque; and (4) it can integrate pulleys and belts.

[0012] A first aspect of the present disclosure provides a transmission for an electric motor assisted vehicle, the transmission including a crankshaft rotatable about a crankshaft configured to drive a drive wheel to propel the vehicle, an electric motor having an output shaft rotatable about a motor axis offset from the crankshaft, a first wheel rotatable about the crankshaft, the first wheel having a driven portion and a driving portion, a second wheel rotatable about a drive axis offset from the crankshaft, the second wheel having a driven portion and a driving portion, a third wheel rotatable about the crankshaft, the third wheel having a driven portion. a first belt engaging the output shaft of the electric motor and engaging the driven portion of the first wheel, the first wheel configured to rotate slower and with greater torque than the output shaft of the electric motor; a second belt engaging the drive portion of the first wheel and engaging the driven portion of the second wheel, the second wheel configured to rotate slower and with greater torque than the first wheel; a third belt engaging the drive portion of the second wheel and engaging the driven portion of a third wheel, the third wheel configured to rotate slower and with greater torque than the second wheel, the third wheel configured to drive the drive wheels to propel the vehicle.

[0013] In the transmission of the first embodiment, optionally, the output shaft of the electric motor has a motor sprocket with which the first belt engages, the motor sprocket having 16 to 20 teeth, the driven portion of the first wheel having 58 to 66 teeth, and the first gear ratio being approximately 2.90:1 to 4.13:1.

[0014] The transmission of a first aspect includes one or more of the foregoing embodiments, and optionally, the first wheel driving portion has a number of teeth between 28 and 32, the second wheel driven portion has a number of teeth between 58 and 66, and the second gear ratio is between about 1.81:1 and 2.36:1.

[0015] The transmission of a first aspect includes any one or more of the preceding embodiments, and optionally, the second wheel driving portion has 20-24 teeth, the third wheel driven portion has 58-66 teeth, and the third gear ratio is approximately 2.42:1 to 3.30:1.

[0016] The transmission of a first aspect includes any one or more of the preceding embodiments, and optionally, the output shaft of the electric motor has a motor sprocket engaged by a first belt, the motor sprocket having 17 to 21 teeth, the driven portion of the first wheel having 115 to 125 teeth, and the first gear ratio is approximately 5.48:1 to 7.35:1.

[0017] The transmission of a first aspect includes one or more of the preceding embodiments, and optionally, the first wheel driving portion has 26 to 30 teeth, the second wheel driven portion has 68 to 72 teeth, and the second gear ratio is approximately 2.27:1 to 2.77:1.

[0018] The transmission of a first aspect includes one or more of the preceding embodiments, and optionally, the second wheel driving portion has 26 to 30 teeth, the third wheel driven portion has 68 to 72 teeth, and the third gear ratio is approximately 2.27:1 to 2.77:1.

[0019] The transmission of a first aspect includes one or more of the foregoing embodiments, and optionally, the first belt has a width of about 7-11 mm, the second belt has a width of about 6-10 mm, and the third belt has a width of about 16-20 mm.

[0020] The transmission of a first aspect includes one or more of the foregoing embodiments, and optionally, the first belt is approximately 9 mm wide, the second belt is approximately 8 mm wide, and the third belt is approximately 18 mm wide.

[0021] The transmission of a first aspect includes one or more of the foregoing embodiments, and optionally, the first belt is a 33mm PowerGrip® GT® belt, the second belt is a 5mm PolyChain® GT® Carbon belt, and the third belt is a 5mm PolyChain® GT® Carbon belt.

[0022] The transmission of a first aspect includes one or more of the foregoing embodiments, and optionally further includes a controller in communication with the electric motor, the controller configured to receive an input signal, and the controller configured to cause the electric motor to transmit power to the drive wheels.

[0023] The transmission of a first aspect includes one or more of the foregoing embodiments, and optionally, the crankshaft, motor shaft and wheel shaft are parallel to one another.

[0024] The transmission of a first aspect includes one or more of the foregoing embodiments, and optionally, the first wheel and the third wheel are disposed around the crankshaft, and the third wheel is disposed between the first wheel and the drive wheel.

[0025] A second aspect of the present disclosure provides an electric motor-assisted vehicle transmission, the transmission having a crankshaft rotatable about a crank axis, the crankshaft configured to power drive wheels of the vehicle to propel the vehicle, the transmission further comprising an electric motor having an output shaft rotatable about a motor axis offset from the crankshaft, a plurality of belts transmitting power from the electric motor output shaft to the vehicle drive wheels, the electric motor output shaft configured to rotate at a higher speed and with less torque than the drive wheels, and a controller in communication with the electric motor, the controller configured to receive an input signal, the controller configured to cause the electric motor to transmit power to the drive wheels only via the plurality of belts.

[0026] A second aspect of the transmission optionally includes a first wheel rotatable about a crankshaft, the first wheel having a driven portion and a driving portion, a second wheel rotatable about a drive shaft offset from the crankshaft, the second wheel having a driven portion and a driving portion, a third wheel rotatable about the crankshaft, the third wheel having a driven portion, a first belt of the plurality of belts engaging an output shaft of the electric motor and engaging the driven portion of the first wheel, the first wheel configured to rotate slower and with greater torque than the output shaft of the electric motor, a second belt of the plurality of belts engaging the driving portion of the first wheel and engaging the driven portion of the second wheel, the second wheel configured to rotate slower and with greater torque than the first wheel, a third belt of the plurality of belts engaging the driving portion of the second wheel and engaging the driven portion of the third wheel, the third wheel configured to rotate slower and with greater torque than the second wheel, and the third wheel configured to engage the drive wheel and transmit power to the drive wheel.

[0027] The transmission of a second aspect includes one or more of the preceding embodiments, and optionally includes the electric motor being an axial flux motor, the axial flux motor including a stator and a rotor rotatable relative to the stator, and a bevel gear configured to engage an output shaft of the axial flux motor and to engage the rotor so that the output shaft rotates at a slower speed and with greater torque than the rotor.

[0028] The transmission of a second aspect includes one or more of the foregoing embodiments, and optionally includes an input device in communication with the controller and configured to receive a user action, the input device configured to send an input signal to the controller, and the input device being one of a throttle, a shift lever, or a button.

[0029] The transmission of a second aspect includes one or more of the preceding embodiments, and optionally includes a torque sensor in communication with the crankshaft and configured to detect torque applied to the crankshaft, the torque sensor configured to send an input signal to the controller.

[0030] The transmission of a second aspect includes one or more of the foregoing embodiments, and optionally includes a battery in communication with a controller, the controller configured to cause the battery to transmit power to the electric motor.

[0031] The transmission of a second aspect includes one or more of the foregoing embodiments, and optionally, the controller is configured to cause the battery to transfer power at either a constant amperage or a variable amperage.

[0032] A third aspect of the present disclosure provides an electric motor-assisted vehicle transmission, the transmission having a crankshaft rotatable about a crank axis, the crankshaft configured to propel the vehicle, the transmission further comprising an electric motor having an output shaft rotatable about a motor axis offset from the crankshaft, the electric motor having a stator and a rotor rotatable relative to the stator, a bevel gear engaged with the rotor and engaged with the output shaft of the electric motor, the output shaft configured to rotate at a slower speed and with a greater torque than the rotor, a plurality of belts transmitting power from the output shaft of the electric motor to output wheels, the output shaft of the electric motor configured to rotate at a higher speed and with a lower torque than drive wheels, the electric motor configured to transmit power to the output wheels only via the plurality of belts.

[0033] A third aspect of the transmission optionally includes a first wheel rotatable about a crankshaft, the first wheel having a driven portion and a driving portion; a second wheel rotatable about a drive shaft offset from the crankshaft, the second wheel having a driven portion and a driving portion; a third wheel rotatable about the crankshaft, the third wheel having a driven portion, the third wheel being an output wheel; a first belt of the multiple belts engaging the output shaft of the electric motor and engaging the driven portion of the first wheel, the first wheel configured to rotate slower and with greater torque than the output shaft of the electric motor; a second belt of the multiple belts engaging the drive portion of the first wheel and engaging the driven portion of the second wheel, the second wheel configured to rotate slower and with greater torque than the first wheel; a third belt of the multiple belts engaging the drive portion of the second wheel and engaging the driven portion of the third wheel, the third wheel configured to rotate slower and with greater torque than the second wheel, and the third wheel configured to propel the vehicle.

[0034] The transmission of a third aspect includes any one or more of the preceding embodiments, and optionally, the electric motor is an axial flux motor, and the inner surfaces of the stator and rotor define an interior space in which the bevel gear is disposed.

[0035] The transmission of a third aspect includes any one or more of the preceding embodiments, and optionally, the crankshaft extends along the crank axis between first and second ends, and the axial flux motor has a widthwise dimension located within the first and second ends along the crank axis.

[0036] The transmission of a third aspect includes one or more of the preceding embodiments, and optionally, the bevel gear provides a gear ratio of about 2:1, and the bevel gear rotates about an axis perpendicular to the motor shaft.

[0037] The transmission of a third aspect includes one or more of the foregoing embodiments, and optionally further includes a controller in communication with the electric motor and a battery in communication with the controller, the controller configured to receive an input signal, and the controller configured to cause the battery to transmit power to the electric motor.

[0038] As used herein, the terms "at least one," "one or more," and "and / or" are open-ended expressions that function both conjunctively and disjunctively. For example, "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" mean A only, B only, C only, A and B, A and C, B and C, or A, B, and C.

[0039] Unless otherwise specified, all numbers expressing quantities, dimensions, conditions, and the like used in the specification and claims should be understood to be modified in all instances by the term "about."

[0040] As used herein, the term "a" or "an" refers to one or more of that entity. Thus, the terms "a" (or "an"), "one or more," and "at least one" are used interchangeably herein.

[0041] The use of "including," "comprising," or "having," and their derivatives herein, is meant to encompass the items listed thereafter, and equivalents thereof, as well as additional items. Thus, the words "including," "comprising," or "having," and their derivatives, are used interchangeably herein. The use of "engaging" and its derivatives herein is meant to encompass either a direct or indirect connection between elements.

[0042] These and other advantages are apparent from the disclosure of the invention contained herein. The above-described embodiments, objects, and configurations are not complete or exhaustive. The Summary of the Invention is not intended to, and should not be construed as, representing the entire scope of the invention. Furthermore, references herein to "the invention" or aspects thereof should be understood to refer to several embodiments of the invention and should not necessarily be construed as limiting all embodiments to the particular description. The invention is described at various levels in the Summary of the Invention, the accompanying drawings, and the Detailed Description, and the inclusion or non-inclusion of elements, parts, etc. in the Summary of the Invention is not intended to limit the scope of the invention. Additional aspects of the invention will be more readily apparent from the Detailed Description, particularly when taken in conjunction with the drawings.

[0043] It should be understood that any feature or aspect described herein may be claimed in combination with any other feature or aspect described herein, whether or not from the same embodiment.

[0044] One or more aspects described herein may be combined with one or more other aspects described herein. One or more features described herein may be combined with one or more other features described herein. One or more embodiments described herein may be combined with one or more other embodiments described herein. [Brief explanation of the drawings]

[0045] Those skilled in the art will appreciate that the following description is merely illustrative of the principles of the present invention, which may be applied in various ways to provide many different and alternative embodiments. This description is made for the purpose of illustrating the general principles of the present teachings and is not meant to limit the inventive concepts disclosed herein.

[0046] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate preferred embodiments of the invention and, together with the description, serve to explain the principles of the invention. [Figure 1] 1 is a side view showing a portion of a bicycle with a gearbox according to an embodiment of the present disclosure. [Figure 2A] FIG. 1 is a perspective view of a transmission without a housing, shown in accordance with one embodiment of the present disclosure. [Figure 2B] FIG. 2B is a plan view of the transmission of FIG. 2A according to one embodiment of the present disclosure. [Figure 3A] FIG. 2 is an exploded view of the transmission of FIG. 1 according to one embodiment of the present disclosure. [Figure 3B] FIG. 3B is a horizontal cross-sectional view of the axial flux motor taken along line BB of FIG. 3A according to one embodiment of the present disclosure. [Figure 4] FIG. 2 is a schematic diagram of a controller and other elements according to an embodiment of the present disclosure.

[0047] It should be understood that the drawings are not necessarily drawn to scale and may be resized in various ways. In some embodiments, details that are not necessary for an understanding of the invention or that make other details difficult to understand have been omitted. It should, of course, be understood that the invention is not necessarily limited to the particular embodiments disclosed herein. 2. Bicycles 4 crankshaft 6 pedals 8 driving wheels 10 Chain 12 rear hub 14 rear wheels 16 Transmission 18 Crankshaft 20 First end 22 Second end 24 Electric motor 26 Output shaft 28 Motor shaft 30 First Wheel 32 First Belt 34 Second Wheel 36 Wheel axle (second wheel) 38 Second Belt 40 Third Wheel 42 Third Belt 44 Controller 46a, 46b Housing 48 Motor sprocket 50 First wheel driven part 52 First wheel drive unit 54 First belt tensioner 56 Second wheel driven part 58 Second wheel drive unit 60 Second belt tensioner 62 Torque sensor 64 Third wheel driven part 66 Third wheel drive unit 68 Third belt tensioner 70 Stator 72 windings 74 rotor 76 internal volume 78 Bevel Gear 80 Bevel Axis 82 Input Device 84 Detailed Description of Battery Invention

[0048] While the following text is a detailed description of numerous different embodiments, it should be understood that the legal scope of that description is defined by the language of the claims at the end of this disclosure. The detailed description is to be construed as exemplary only and does not describe every possible embodiment of the transmission, as describing every possible embodiment would be impractical, if not impossible. Numerous alternative embodiments, using current technology or technology developed after the filing date of this patent application, are contemplated and are within the scope of the claims. Furthermore, combinations of features shown in the various figures may be used to create additional embodiments of the invention. Thus, the dimensions, aspects, and features of one embodiment of the transmission can be combined with the dimensions, aspects, and features of other embodiments of the transmission to create the claimed embodiments.

[0049] FIG. 1 is a side view of a portion of a bicycle 2 having a transmission 16 according to an embodiment of the present disclosure. A user can operate pedals 6 to rotate a crankshaft 4 and a drive wheel 8, which in this embodiment is a sprocket. Rotation of the drive wheel 8 rotates a chain 10 that engages a sprocket on a rear hub 12, which in turn drives a rear wheel 14 to propel the bicycle 2. It is understood that this transmission 16 can be used with bicycles having multiple sprockets on the crankshaft 4 and / or rear hub 12, as found on some bicycles. In a preferred embodiment, the transmission 16 includes an electric motor (not shown in this illustration), although the electric motor may be located in a different location than shown herein, including outside the housing. Additionally, embodiments of the present disclosure can be used with other vehicles, such as mopeds, golf carts, or other small electric vehicles, that can benefit from a transmission 16 between two different rotational speeds.

[0050] FIG. 2A shows the transmission 16 of FIG. 1 with the housing removed to reveal various elements within the transmission 16, and FIG. 2B is a top view of the transmission of FIG. 2A. The crankshaft 4 is rotatable about a crank axle 18, which extends between a first end 20 and a second end 22. The pedals rotate the crankshaft 4, driving the drive wheel 8 and propelling the bicycle. In turn, the electric motor 24 has an output shaft 26 that rotates about a motor axis 28, with the electric motor 24 located between the first end 20 and the second end 22. As described herein, in some embodiments, the electric motor 24 is an axial flux motor that conforms to the shape of the bicycle transmission 16. However, it will be understood that the present disclosure encompasses embodiments in which the electric motor 24 is another type of motor, such as a radial electric motor.

[0051] A first wheel 30 is disposed around the crankshaft 4 and is rotatable about the crankshaft 18. A first belt 32 connects the output shaft 26 of the electric motor 24 to the first wheel 30, with the first wheel 30 rotating at a slower speed and with greater torque than the output shaft 26. A second belt 38 extends from another portion of the first wheel 30 to a second wheel 34 that is rotatable about a wheel shaft 36 that is offset from the crankshaft 18. The shafts 18, 28, and 36 are parallel to one another, and in some embodiments, the motor shaft 28 and the wheel shaft 36 are coaxial. In other embodiments, the wheel shaft 36 is offset from the motor shaft 28. The second wheel 34 rotates at a slower speed and with greater torque than the first wheel 30.

[0052] A third belt 42 extends from another portion of the second wheel 34 to a third wheel 40 that is positioned around the crankshaft 4 and is rotatable about the crank axle 18. The third wheel 40 rotates at a slower speed and with greater torque than the second wheel 34. The third wheel 40 is further engaged with the drive wheel 8, and the third wheel 40 transfers power to the drive wheel 8 to propel the bicycle.

[0053] In some embodiments, the overall gear ratio of the transmission 16 from the electric motor 24 to the drive wheels 8 is approximately 40:1. In various embodiments, the overall gear ratio is between approximately 20:1 and 50:1. Due to the fact that the drive wheels 8 and crankshaft 4 are rotatable about the crank axis 18 and the output shaft 26 of the electric motor 24 is rotatable about another motor axis 28, the number of belts must be an odd number. Constrained by this feature of the transmission 16 and the overall gear ratio and geometry of the transmission 16, three belts 32, 38, 42 represent a preferred embodiment of the transmission 16. However, it will be understood that the present disclosure encompasses one, five, and any odd number of belts.

[0054] FIG. 3A shows an exploded view of the transmission 16. Two portions of the housing 46a, 46b combine to enclose many of the elements of the transmission 16, essentially excluding the electric motor 24 and the controller 44. However, it will be understood that the present disclosure encompasses other configurations of the housing and components, including embodiments in which the electric motor 24 and the controller 44 are housed within a housing, as well as housing-less embodiments in which the components of the transmission 16 are integrated into the vehicle itself. The term "transmission" includes only the housings 46a, 46b and elements disposed within the housings, such as the crankshaft 4, and does not include elements such as the drive wheels. In some embodiments, the transmission 16 includes the electric motor 24 and the controller 44, even though the electric motor 24 and the controller 44 are located substantially outside the housings 46a, 46b. As described herein, some embodiments of the transmission 16 have three belts 32, 38, 42 having different characteristics, such as width, thickness, and length.

[0055] In some embodiments, first belt 32 is approximately 7-11 mm wide, second belt 38 is approximately 7-11 mm wide, and third belt 42 is approximately 25-35 mm wide. In various embodiments, first belt 32 is approximately 9 mm wide, second belt 38 is approximately 9 mm wide, and third belt 42 is approximately 30 mm wide. Third belt 42 is wider than first belt 32 or second belt 38 to handle the greater transmission torque and higher tension at this location in transmission 16.

[0056] In various embodiments, first belt 32 has 78 teeth and a 390 mm pitch length, second belt 38 has 81 teeth and a 405 mm pitch length, and third belt 42 has 78 teeth and a 390 mm pitch length. Each belt 32, 38, 42 has alternating teeth and grooves, and the driving and driven sprockets have alternating teeth and grooves that mesh with each belt 32, 38, 42. In some embodiments, first belt 32 is a Polychain® GT® Carbon 5MGT belt, second belt 38 is a Polychain® GT® Carbon 5MGT belt, and third belt 42 is a Polychain® GT® Carbon 5MGT belt. These belts are made from multi-layer polyurethane, although it will be understood that the present disclosure encompasses embodiments with belts of different sizes and types.

[0057] A motor sprocket 48 is coupled to the output shaft 26 of the electric motor 24, and a first wheel 30 has a driven portion 50 and a driving portion 52. The driven portion 50 has a larger outer diameter than the driving portion 52. A first belt 32 couples the motor sprocket 48 to the driven portion 50 of the first wheel 30. In some embodiments, the motor sprocket 48 has 16-20 teeth, and the driven portion 50 of the first wheel 30 has 58-66 teeth, resulting in a first gear ratio between approximately 2.90:1 and 4.13:1. In various embodiments, the motor sprocket 48 has 18 teeth, and the driven portion 50 of the first wheel 30 has 62 teeth, resulting in a first gear ratio of approximately 3.4:1.

[0058] The second wheel 34 has a driven portion 56 and a drive portion 58, and the second wheel 34 is rotatable about a boss or hub connected to the housings 46a, 46b. The driven portion 56 has a larger outer diameter than the drive portion 58. A second belt 38 connects the drive portion 52 of the first wheel 30 to the driven portion 56 of the second wheel 34. In some embodiments, the drive portion 52 of the first wheel 30 has 28-32 teeth and the driven portion 56 of the second wheel 34 has 58-66 teeth, resulting in a second gear ratio between approximately 1.81:1 and 2.36:1. In various embodiments, the drive portion 52 of the first wheel 30 has 30 teeth and the driven portion 56 of the second wheel 34 has 62 teeth, resulting in a second gear ratio of approximately 2.1:1.

[0059] The third wheel 40 has a driven portion 64 and a drive portion 66. The driven portion 64 has an outer diameter that is larger than the outer diameter of the drive portion 66. A third belt 42 connects the drive portion 58 of the second wheel 34 to the driven portion 64 of the third wheel 40. In some embodiments, the drive portion 58 of the second wheel 34 has 20-24 teeth and the driven portion 64 of the third wheel 40 has 58-66 teeth, resulting in a third gear ratio between approximately 2.42:1 and 3.30:1. In various embodiments, the drive portion 58 of the second wheel 34 has 22 teeth and the driven portion 64 of the third wheel 40 has 62 teeth, resulting in a third gear ratio of approximately 2.8:1. As described above, the first, second, and third gear ratios, in combination with the optional bevel gear of the electric motor 24, provide an overall gear ratio.

[0060] Furthermore, in this embodiment, the gear ratios are similar to each other to keep the overall size and shape of the transmission compact and maintain the size of the driving wheel portion. Similar gear ratios result in similar sizes of the driven wheel portions. Because the largest driven portion determines the size and shape of the transmission, making the driven portion sizes the same optimizes the transmission for a more compact size and shape. Furthermore, if the driving wheel portion is too small, it may not function or may slip relative to the belt due to fewer teeth contacting the belt. Therefore, keeping the gear ratios similar to each other prevents the driving portion from becoming too small.

[0061] In the described embodiment, the first, second, and third gear ratios are approximately 3.4:1, 2.1:1, and 2.8:1, respectively. If the three individual gear ratios were evenly distributed to create an overall gear ratio of 20:1, each gear ratio would be approximately 2.7:1. Therefore, the first, second, and third gear ratios of this embodiment are within ±30% of the 2.7:1 gear ratio to maintain a compact transmission form factor. However, the present disclosure encompasses transmission embodiments with other configurations. For example, the overall gear ratios may be different (e.g., 30:1, 40:1, etc.) or the number of belts may be different (e.g., 4, 5, 6, etc.), but the gear ratios may be similar to each other to maintain a compact transmission size and prevent the drive unit from becoming too small.

[0062] As described herein, the third wheel 40 engages the drive wheel 8 to transfer power to the drive wheel 8 to propel the vehicle. Thus, in some embodiments, the outer surface of the drive portion 66 interfaces with and transfers power to the inner surface of the drive wheel 8. In various embodiments, the drive portion 66 of the third wheel 40 is the drive wheel 8 itself. Furthermore, the drive portion 66 may transfer power to an intermediate element, such as an additional belt, collar, or the like, which transfers power to the drive wheel 8. For example, the drive portion 66 may be a spline interface that couples to a chainring spider that is connected to or part of the drive wheel 8.

[0063] FIG. 3A also shows a first belt tensioner 54 for the first belt 32, a second belt tensioner 60 for the second belt 38, and a third belt tensioner 68 for the third belt 42, which provide the proper tension to the belts 32, 38, 42 during operation of the transmission 16.

[0064] Finally, FIG. 3A shows a torque sensor 62 that detects torque between the crankshaft 4 and the third wheel 40 that engages the drive wheel. In this sense, the torque sensor 62 detects the torque the user applies to the pedals and crankshaft 4 relative to the third wheel 40 and drive wheel. When driving, the user may apply little torque to the crankshaft 4 when coasting downhill, but may apply a large torque to the crankshaft 4 when pedaling uphill. This can be a signal to the transmission 16 that the electric motor 24 should assist the user's effort. As described herein, the torque sensor 62 can be in communication with the controller 44 and the electric motor 24 to assist the user.

[0065] FIG. 3B shows a cross section of the electric motor 24 taken along line BB in FIG. 3A. In this embodiment, the electric motor 24 is an axial-flux motor having a stator 70, powered windings 72, and a rotor 74 that rotates relative to the stator 70 when the windings 72 receive power. Rotation of the rotor 74 rotates a bevel gear 78 about a bevel axis 80 perpendicular to the motor shaft 28, which in turn rotates the output shaft 26 of the electric motor 24 about the motor shaft 28. Incorporating the bevel gear 78 can further increase the overall gear ratio of the transmission. In some embodiments, the bevel gear 78 increases the 2:1 gear ratio, thereby reducing the wheel and belt contribution to the overall gear ratio of the transmission and allowing the other elements of the transmission to be smaller and more compact. The bevel gear 78 can be positioned about the output shaft 26, at least in part, within an interior volume 76 defined by the interior surfaces of the other elements 70, 72, and 74 of the electric motor 24, which in this embodiment is an axial-flux motor 24. The axial flux motor 24 may have an internal volume 76 due to the arrangement of the axial flux motor's elements for converting electrical power to mechanical power. This internal volume 76 is utilized by a bevel gear 78 to keep the transmission compact and contribute to the transmission's overall gear ratio. It will be appreciated that bevel gears can provide gear ratios other than 2:1, and that gears other than bevel gears provide gear ratios. Additionally, in some embodiments, the output shaft 26 is directly coupled to the rotor 74 or engages the rotor 74 without intermediate gears.

[0066] The axial flux motor 24 can have several performance characteristics that make it suitable for use in the described transmission. For example, the output speed of the axial flux motor 24 is approximately 2400 rpm and the output torque is approximately 3 Nm. The power output of the axial flux motor 24 is approximately 753.6024 watts at a voltage of approximately 36 volts. The physical dimensions of the axial flux motor 24 are approximately 90 mm in diameter and approximately 31 mm in width. Other characteristics are summarized in Tables 1-5. The characteristics of the axial flux motor 24 described herein are for illustrative purposes only.

[0067] Table 1 summarizes the power ratings of an exemplary axial flux motor 24. [Table 1]

[0068] Table 2 summarizes the geometric parameters of an exemplary axial flux motor 24. [Table 2]

[0069] Table 3 summarizes the winding configuration of an exemplary axial flux motor 24. [Table 3]

[0070] Table 4 summarizes the material composition of an exemplary axial flux motor 24. [Table 4]

[0071] Table 5 summarizes the optimum operating conditions for an exemplary axial flux motor 24. [Table 5]

[0072] FIG. 4 is a schematic diagram of a controller 44 and related components. The controller 44 coordinates various components to power the electric motor 24, which transmits power through a transmission to a drive wheel to assist the user in riding the bicycle. As part of the coordination, the controller 44 can selectively enable a battery 84 to power the electric motor 24. In some embodiments, the battery 84 is part of or integral with the transmission. In other embodiments, the battery 84 is separate from the transmission. For example, the transmission is located in a lower bracket of the bicycle frame, and the battery 84 is located in a lower tube of the frame and operatively connected to the transmission controller. Whether the battery 84 is integral with or separate from the transmission, having a removable battery 84 is advantageous because it allows the user to take the battery 84 to another location, such as their home or office, for charging. Various embodiments of the transmission include a generator or other similar element to power the controller, charge the battery, and generate electricity for other functions.

[0073] One or more input devices 82 send one or more input signals to controller 44, and controller 44 can take further action based on the one or more input signals. A torque sensor that detects torque applied to a crankshaft against a drive wheel can serve as an input device 82 to controller 44. Raw information from the torque sensor is sent as an input signal to controller 44, and the torque sensor itself can detect information such as torque value, speed data, etc. and send it as an input signal to controller 44. As an example, controller 44 can determine whether the torque value exceeds a predetermined threshold, and then controller 44 can allow a predetermined amount of power to flow from battery 84 to electric motor 24 to assist the user by powering the drive wheel.

[0074] The user may operate another input device 82 in communication with the controller 44. The input device 82 may be, for example, an assist level selector, such as a shift lever or button, a throttle, or the like. The shift lever or button, typically found on a bicycle handlebar, allows the user to select an assist level, which is transmitted as an input signal to the controller. In an exemplary embodiment, the assist level ranges from 0 to 10, with 0 being no assist from the electric motor and 10 being maximum assist from the electric motor. Thus, when the assist level is selected as 10, the controller 44 allows a large current value to flow to the electric motor 24 when the electric motor 24 is assisting the user. When the assist level is 9, the controller 44 reduces the current value until the assist level reaches 0, at which point the controller 44 disables current flow to the electric motor 24, eliminating pedal assistance to the user.

[0075] The assist level selection on the button or shift lever can be a selection of a discrete level of power assist, such as a number from 0 to 10, but the selection can also be from a potentially infinite number of power assist levels. Input device 82 is a device where the user moves a lever, dial, paddle, etc., and a sensor detects the amount of physical movement and sends an input signal to controller 44. In this sense, a twist throttle can also provide input signals to controller 44 from a potentially infinite number of twist angles. The twist throttle allows the user to operate the transmission and bicycle regardless of whether the user is operating the pedals or crankshaft.

[0076] Yet another possible input device 82 is a rain sensor that detects humidity and sends an input signal to the controller 44. The controller 44 can determine when the humidity exceeds a predetermined threshold, corresponding to, for example, rain, and can take further action, such as limiting or preventing power from flowing from the battery 84 to the electric motor 24, to prevent the bicycle from overspeeding or damaging electrical components in rainy weather.

[0077] Yet another possible input device 82 is a bicycle speed sensor. As described herein, speed data can be obtained from a torque sensor. Speed ​​data can also be obtained from a cadence sensor, a global positioning system (GPS), an accelerometer, etc. Speed ​​data has many uses, such as limiting the speed of the bicycle, as various countries have laws and regulations regulating the speed of e-bikes. The user can also set a speed limit for the bicycle. The input devices 82 described herein are exemplary in nature and are not an exhaustive list of possible input devices 82.

[0078] When controller 44 receives one or more input signals, controller 44 can determine how to operate the transmission. In one example, a user operates input device 82 to select ten of ten assist levels, with input device 82 sending a first input signal to controller 44. Furthermore, input device 82, which is a torque sensor, sends a second input signal to controller 44, and input device 82, which is a humidity sensor, sends a third input signal to controller 44. Controller 44 assesses that the humidity reading is below a threshold level at which excessive humidity is dangerous, that the torque reading is near a threshold level at which the user requires assistance, and that assist level 10 is associated with a predetermined amperage. Therefore, based on these input signals, controller 44 allows power to flow from battery 84 to electric motor 24 at a predetermined amperage to assist the user, but does not allow power to flow so fast that the speed data from the speed sensor exceeds a predetermined threshold, either set by the manufacturer or by the user to comply with laws and regulations.

[0079] The controller 44 can also control the characteristics of the electric motor 24 as it powers the transmission to assist the user. The electric motor 24 can rotate with a particular force, speed, momentum, acceleration, etc. The controller 44 can control these characteristics by controlling the flow of power from the battery 84 to the electric motor 24. In some embodiments, the controller 44 sends output signals to the electric motor 24 to control these characteristics. Additionally, the controller 44 can provide a dynamic response to one or more inputs, changing the current value over time. In some embodiments, the controller 44 maintains the current value over time.

[0080] While various aspects of the present invention have been described in detail, it will be apparent to those skilled in the art that modifications and variations of these embodiments may occur. However, it is to be understood that such modifications and variations are within the spirit and scope of the present invention, as set forth in the following claims. Moreover, the invention described herein may be implemented in other embodiments and in various ways. It is to be understood that the phraseology and terminology used herein are for the purpose of description only and are to be regarded as limiting.

Claims

1. An electric motor-assisted vehicle transmission, a crankshaft rotatable about a crank axis, the crankshaft configured to drive a drive wheel to propel the vehicle; an electric motor having an output shaft rotatable around a motor axis offset from the crankshaft; a first wheel rotatable around the crankshaft, the first wheel having a driven portion and a driving portion; a second wheel rotatable about a drive shaft offset from the crankshaft, the second wheel having a driven portion and a drive portion; a third wheel rotatable around the crankshaft, the third wheel having a driven portion; a first belt engaged with the output shaft of the electric motor and the driven portion of the first wheel, the first wheel being configured to rotate at a slower speed and with a greater torque than the output shaft of the electric motor; a second belt engaging the drive portion of the first wheel and engaging the driven portion of the second wheel, the second wheel configured to rotate at a slower speed and with a greater torque than the first wheel; a third belt engaging the drive portion of the second wheel and engaging the driven portion of the third wheel, the third wheel configured to rotate at a slower speed and with a greater torque than the second wheel, the third wheel configured to drive the drive wheel to propel the vehicle; Transmission.

2. 2. The transmission of claim 1, wherein the output shaft of the electric motor has a motor sprocket with which the first belt engages, the motor sprocket having 16 to 20 teeth, the driven portion of the first wheel having 58 to 66 teeth, and a first gear ratio of approximately 2.90:1 to 4.13:

1.

3. 2. The transmission of claim 1, wherein the driving portion of the first wheel has 28 to 32 teeth and the driven portion of the second wheel has 58 to 66 teeth, and the second gear ratio is approximately 1.81:1 to 2.36:

1.

4. 2. The transmission of claim 1, wherein the driving portion of the second wheel has 20 to 24 teeth and the driven portion of the third wheel has 58 to 66 teeth, providing a third gear ratio of approximately 2.42:1 to 3.30:

1.

5. The transmission of claim 1 , further comprising a controller in communication with the electric motor, the controller configured to receive an input signal, the controller configured to cause the electric motor to transmit power to the drive wheels.

6. 2. The transmission of claim 1, wherein said crankshaft, said motor shaft and said wheel shaft are parallel to one another.

7. 2. The transmission of claim 1, wherein said first wheel and said third wheel are disposed around said crankshaft, and said third wheel is disposed between said first wheel and said drive wheel.

8. 1. An electric motor assisted vehicle transmission, the transmission having a crankshaft rotatable about a crank axis, the crankshaft configured to power drive wheels of the vehicle to propel the vehicle, the transmission further comprising: an electric motor having an output shaft rotatable around a motor axis offset from the crankshaft; a plurality of belts for transmitting power from the output shaft of the electric motor to the drive wheels of the vehicle, the output shaft of the electric motor being configured to rotate at a higher speed and with a smaller torque than the drive wheels; A controller in communication with the electric motor is configured to receive an input signal, and the controller is configured to cause the electric motor to transmit power to the drive wheels only through the plurality of belts.

9. a first wheel rotatable around the crankshaft, the first wheel having a driven portion and a driving portion; a second wheel rotatable about a drive shaft offset from the crankshaft, the second wheel having a driven portion and a drive portion; a third wheel rotatable around the crankshaft, the third wheel having a driven portion; a first belt of a plurality of belts that engages with the output shaft of the electric motor and the driven portion of the first wheel, the first wheel being configured to rotate at a slower speed and with a greater torque than the output shaft of the electric motor; a second belt of the plurality of belts engaging the driving portion of the first wheel and engaging the driven portion of the second wheel, the second wheel configured to rotate at a slower speed and with a greater torque than the first wheel; a third belt of the plurality of belts that engages the drive portion of the second wheel and engages the driven portion of the third wheel, the third wheel configured to rotate at a slower speed and with a greater torque than the second wheel, and the third wheel configured to engage with the drive wheel and transmit power to the drive wheel; The transmission of claim 8.

10. The electric motor is an axial flux motor, a stator and a rotor rotatable relative to the stator; a bevel gear engaged with the output shaft of the axial flux motor and engaged with the rotor so that the output shaft rotates at a slower speed and with a greater torque than the rotor; The transmission of claim 8.

11. an input device in communication with the controller and configured to receive a user action, the input device configured to transmit the input signal to the controller, and the input device being one of a throttle, a shift lever, or a button; The transmission of claim 8.

12. a torque sensor in communication with the crankshaft and configured to detect torque applied to the crankshaft, the torque sensor configured to transmit the input signal to the controller. The transmission of claim 8.

13. a battery in communication with the controller, the controller configured to cause the battery to transmit power to the electric motor The transmission of claim 8.

14. The controller is configured to cause the battery to deliver power at either a constant amperage or a variable amperage.

14. The transmission of claim 13.

15. 1. A transmission for an electric motor assisted vehicle, the transmission having a crankshaft rotatable about a crank axis, the crankshaft configured to propel the vehicle, the transmission further comprising: an electric motor having an output shaft rotatable around a motor axis offset from the crankshaft, the electric motor having a stator and a rotor rotatable relative to the stator; a bevel gear engaged with the rotor and with the output shaft of the electric motor so that the output shaft rotates at a slower speed and with a greater torque than the rotor; The electric motor is provided with a plurality of belts that transmit power from the output shaft of the electric motor to an output wheel, the output shaft of the electric motor is configured to rotate at a higher speed and with a smaller torque than the drive wheel, and the electric motor is configured to transmit power to the output wheel only via the plurality of belts.

16. a first wheel rotatable around the crankshaft, the first wheel having a driven portion and a driving portion; a second wheel rotatable about a drive shaft offset from the crankshaft, the second wheel having a driven portion and a drive portion; a third wheel rotatable about the crankshaft, the third wheel having a driven portion, the third wheel being the output wheel; a first belt of a plurality of belts that engages with the output shaft of the electric motor and the driven portion of the first wheel, the first wheel being configured to rotate at a slower speed and with a greater torque than the output shaft of the electric motor; a second belt of the plurality of belts engaging the driving portion of the first wheel and engaging the driven portion of the second wheel, the second wheel configured to rotate at a slower speed and with a greater torque than the first wheel; a third belt of the plurality of belts engaging the driving portion of the second wheel and engaging the driven portion of the third wheel, the third wheel configured to rotate at a slower speed and with a greater torque than the second wheel, the third wheel configured to propel the vehicle; 16. The transmission of claim 15.

17. 16. The transmission of claim 15, wherein the electric motor is an axial flux motor, and the inner surfaces of the stator and rotor define an interior space in which the bevel gear is disposed.

18. 18. The transmission of claim 17, wherein said crankshaft extends along said crank axis between first and second ends, and said axial flux motor has a width dimension located within said first and second ends along said crank axis.

19. 16. The transmission of claim 15, wherein said bevel gear provides a gear ratio of approximately 2:1, said bevel gear rotating about an axis perpendicular to said motor shaft.

20. a controller in communication with the electric motor; a battery in communication with the controller, the controller configured to receive an input signal, the controller configured to cause the battery to transmit power to the electric motor.

16. The transmission of claim 15.

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