Drive device for an electric bicycle and electric bicycle

Abstract

A drive arrangement (5) for an electric bicycle (1) has a motor unit and a drive (10) for driving the electric bicycle (1). The drive arrangement (5) also has a transmission stage (20), wherein the drive (10) is configured to drive the transmission stage (20), which is configured to drive the electric bicycle (1). The transmission stage (20) is coupled to the drive (10) on the one hand and is provided for transmitting torque for driving the electric bicycle (1) on the other hand. The transmission stage (20) is configured as a shaft transmission, and the drive (10) and the shaft transmission can be arranged coaxially with respect to an axis of rotation (8) of a pedal crank (4) of the electric bicycle (1).

Description

Technical Field

[0001] The present invention relates to a drive mechanism for an electric bicycle and an electric bicycle having said drive mechanism. Background Technology

[0002] Bicycles have become a cost-effective, easy-to-operate, and emission-free mode of transportation. They have also expanded into sports and fitness equipment, and various types have been developed specifically for different sports applications.

[0003] Enthusiasm for e-bikes (especially so-called "pedelecs") has been growing in recent years, despite their considerable weight and high price. Potential customers include not only older, less physically fit, or less athletic cyclists, but also younger, more active riders who may use them for work or to extend their range and / or increase their speed without overloading their bodies. Mountain bikers, in particular, are increasingly drawn to electric-assisted mountain bikes. A key aspect of e-bikes is the provision of a reliable auxiliary drive system that enables high power delivery. Summary of the Invention

[0004] The objective of this invention is to provide a reliable drive system for an electric bicycle, which achieves a particularly clear and space-saving structure.

[0005] According to one aspect, a drive unit for an electric bicycle is disclosed. The drive unit has a motor unit for driving the electric bicycle. The drive unit also has a driver and a transmission stage, wherein the driver is configured to drive the transmission stage, and the transmission stage is configured to drive the electric bicycle. The driver is coupled to the transmission stage, and the transmission stage is configured to output or provide torque on the output side for driving the electric bicycle. The transmission stage is configured as a shaft drive, and the driver and the shaft drive are arranged coaxially with or configured to be arranged coaxially with the pedal crank of the electric bicycle about the axis of rotation of the pedal crank.

[0006] The aforementioned drive unit enables a reliable drive scheme for electric bicycles, achieving a distinctive and space-saving structure. The drive unit is particularly suitable for mounting on the bottom tube or seatpost of an electric bicycle, achieving an advantageous balance between low noise generation, high efficiency, and small structural dimensions. This is further achieved by arranging the elements of the drive unit coaxially with the pedal crankshaft of the electric bicycle.

[0007] The shaft drive of the transmission stage realizes a backlash-free transmission for transmitting large torques and is also called a strain wave gear drive or a so-called "Harmonic Drive". This achieves a high transmission ratio, for example, 100:1, and its outstanding feature is also high rigidity. The harmonic drive also has a "Wave Generator" or wave generator, which constitutes the driving element of the shaft drive. In addition, for example, there is a deformable cylindrical steel sleeve, called a "Flexspline", which constitutes the output element of the harmonic drive and is predetermined to deform by rotating the wave generator. In addition, an external element is provided, also called a "Circular Spline", and the external element interacts with the Flexspline by means of teeth, such that, for example, one rotation of the wave generator causes relative movement of the two teeth of the Flexspline with respect to the rigid spline.

[0008] Instead of shaft drives, the transmission stage of the drive unit can include a cycloidal drive, which also enables backlash-free transmission of large torques. The cycloidal drive transmits torque tactilely via a cam disc.

[0009] When auxiliary drive is required, the transmission stage is coupled to, or can be coupled to, the pedal crank of the electric bicycle, particularly by means of an output shaft. The output shaft is specifically coupled to the gears or sprockets of the electric bicycle. The pedal crank is specifically coupled to, or can be coupled to, the pedals of the electric bicycle. The drive unit thus achieves space-saving and efficient drive, wherein pedal drive and auxiliary electric drive are combined and coupled by means of an output shaft, or can be coupled when needed.

[0010] According to a preferred embodiment of the drive device, the driver is configured as an electric motor of a motor unit and includes a stator and a rotor, which are respectively annularly constructed and arranged such that the stator surrounds the rotor and the rotor is coupled to the transmission stage. The drive for the transmission stage thus uses an annular motor, allowing for a particularly space-saving structure of the drive device. In other words, the electric motor of the motor unit constitutes a driver for a shaft drive. Furthermore, the motor unit also includes, for example, a housing and an interface for driving the electric motor.

[0011] According to another embodiment of the drive unit, the transmission stage includes: a wave generator; a cylindrical outer ring having internal teeth; and a resilient transmission element having external teeth configured to predeterminely match the internal teeth of the outer ring. The transmission stage also includes a radial coupling element. The wave generator is configured to predeterminely deform the transmission element. The outer ring acts as the drive element of the transmission stage, and the radial coupling element acts as the output element of the transmission stage. The transmission element is arranged between the outer ring and the radial coupling element and provides a predetermined transmission ratio for the second transmission stage.

[0012] The following embodiments specifically illustrate the structure of the transmission stage as a shaft drive, wherein, for example, the external teeth of the elastic transmission element have two fewer teeth than the internal teeth of the outer ring. The shaft drive also includes a radial coupling element that reliably transmits torque from the output of the transmission stage to the output shaft of the drive system. The radial coupling element is configured to couple with the pedal crank, either directly or by means of one or more transmission elements.

[0013] According to another embodiment of the drive unit, the stator rotation is fixedly coupled to the outer ring about the rotational axis of the pedal crank, and the rotor is anti-torsional coupled to the wave generator. The outer ring is force-fitted, form-fitted, and / or material-fitted to the stator and is constructed to be non-rotatable about the rotational axis. The wave generator is force-fitted, form-fitted, and / or material-fitted to the rotor and is constructed to be rotatable about the rotational axis. The outer ring and stator can also be constructed integrally. Correspondingly, the wave generator and rotor can also be constructed integrally. At least the drive unit is correspondingly constructed such that, during operation and about the rotational axis of the pedal crank, the rotor rotates relative to the stator.

[0014] According to another embodiment of the drive unit, the radial coupling element has a plurality of radial protrusions on its outer side about the rotational axis of the pedal crank. These radial protrusions are configured to mate with a plurality of recesses located on the end side of the transmission element facing the radial coupling element. The engagement of the protrusions and recesses allows the radial coupling element to be coupled to and decoupled from the transmission element along the rotational axis of the pedal crank.

[0015] The radial coupling element is thus movable along the rotation axis of the pedal crank. In a coupled state, the radial coupling element reliably transmits torque from the output of the second transmission stage to the output of the drive system or drive unit, or in a decoupled state, allows the pedal crank to rotate independently without being restricted by the decoupled first and second transmission stages. Decoupling the pedal crank from the drive unit can be advantageous, for example, when the drive unit requires maintenance, in order to restore trouble-free or low-resistance operation. In this case, it is not necessary to rotate the transmission stages together and apply corresponding additional force, and the electric bicycle equipped with the drive unit can thus be used as a regular bicycle. The drive unit therefore preferably has the aforementioned axial mobility of the radial coupling element. However, alternatively, an axially fixed radial coupling element can also be provided.

[0016] According to another embodiment of the drive unit, the radial protrusion of the radial connecting element is configured such that it protrudes from the end side of the transmission element about a predetermined state of coupling with the transmission element along the rotation axis of the pedal crank. In other words, the protrusion is constructed to be greater in depth or longer than the recess. This arrangement allows for more reliable coupling between the two components and reliable torque transmission from the transmission element to the radial connecting element. The coverage of the protrusion is particularly related to the applied force and can be, for example, a few millimeters. Alternatively, the protrusion of the radial connecting element and the end side of the transmission element can be configured such that a one-to-one coverage or contact surface overlap is achieved, thereby enabling mechanically reliable coupling.

[0017] According to another embodiment of the drive unit, the driver and transmission stage are arranged and configured such that the driver is coaxially surrounding the transmission stage and the transmission stage is coaxially surrounding the pedal crank with respect to the rotation axis of the pedal crank. This achieves a substantially rotationally symmetrical and particularly space-saving structure for the drive unit of an electric bicycle, and helps to keep the number of components to be assembled to a minimum and the total weight of the drive unit to a low level. The rotation axis of the electric motor or the driver of the motor unit is correspondingly aligned with the rotation axis of the pedal crank.

[0018] According to another aspect, an electric bicycle is disclosed, having a bicycle frame having a lower frame section extending to a pedal bearing having a pedal crank. The electric bicycle has a drive unit according to any of the foregoing embodiments, the drive unit being arranged in or on the frame section such that the drive unit and transmission stage are coaxially arranged with the pedal crank and are capable of transmitting torque via the transmission stage to drive the electric bicycle. The electric bicycle substantially achieves the aforementioned features, advantages, and functions.

[0019] For mounting on a frame section, the frame section may have a notch, allowing the drive device to be reliably received. According to one embodiment, the drive device is arranged, for example as a component, in a coupled state, particularly assembled onto the frame section.

[0020] The electric drive unit for an electric bicycle preferably uses an electric motor of a motor unit as a driver for a transmission stage, which is constructed as a shaft drive or a cycloidal drive. The drive unit also preferably includes a movable radial coupling element that transmits torque from the output of the transmission stage, also known as a "flexible wheel," to the output of the drive system, thereby facilitating a beneficial and reliable power transfer from the motor unit to the pedal crank or to the gears or sprockets of the electric bicycle.

[0021] The drive unit achieves a highly efficient mechanical system for assisting in cycling, while also keeping noise generation low and the structure compact. This is particularly advantageously achieved by arranging the drive motor and transmission stage coaxially around the pedal crank axis relative to the drive system's pedal crank axis.

[0022] The outer ring used in the shaft drive device, also called a "fixspline," is rotatably and fixedly mounted to the stator of the electric motor. The wave generator, or "wave generator," is torsionally mounted to the rotor of the electric motor. The fixspline thus functions as both the stator and the rotor, while the wave generator functions as both the rotor and the rotor.

[0023] To minimize the required structural space of the shaft drive in the axial direction along the rotation axis of the pedal crank, a radial coupling element is preferably positioned between the output of the shaft drive and the output of the entire system. The coupling element between the flexure of a harmonic drive and the output shaft of a conventional drive system typically dictates a relatively long extension rod on the flexure. This rod can be eliminated by means of the radial coupling element, thereby enabling a very compact axial structure of the drive unit.

[0024] In addition to improving the propulsion of electric bicycles, the drive unit also possesses advantageous acoustic characteristics that minimize unwanted noise generation. The fewer interface components present, the fewer acoustic factors influence noise generation within the overall system. The drive unit can be implemented with a small number of interacting parts.

[0025] Furthermore, the structural variations of the drive unit offer cost advantages, which are realized through the potential for component savings resulting from the functional integration of the electric motor and transmission stage, as well as the elimination of mechanical interfaces. In summary, the drive unit thus provides the following advantages compared to conventional drive solutions:

[0026] ● Cost savings achieved through component elimination and fewer interfaces

[0027] ●Integrated design achieved through a compact structure

[0028] ●High power density and small space requirements

[0029] ● Improved acoustic characteristics, because the small amount used for the drive device is sufficient and thus there are very few resonators. Attached Figure Description

[0030] In the following description, embodiments, advantages, and functions are illustrated with reference to the accompanying drawings. The drawings show:

[0031] Figure 1 A schematic diagram of an electric bicycle with a drive mechanism is shown.

[0032] Figure 2-6 A schematic perspective view showing an embodiment of a drive unit for an electric bicycle, and

[0033] Figure 7 A schematic diagram showing a cross-sectional view of the transmission stage of a drive unit for an electric bicycle.

[0034] Identical, similar, or functional elements are given the same reference numerals in the accompanying drawings. For the sake of simplicity, not all elements shown may be labeled with their respective reference numerals in all drawings if necessary. Detailed Implementation

[0035] Figure 1 An electric bicycle 1 with a bicycle frame 2 is schematically shown. The bicycle frame also has a lower frame section 3 that forms a bottom tube. The frame section 3 extends in the direction of the pedal bearing and includes a pedal crank 4 that is coupled or can be coupled to an electric drive unit 5 for the electric bicycle 1.

[0036] Figure 2-6 Embodiments of the drive device 5 or its components are shown schematically in different perspective views. Figure 7 The components of the drive unit 5 are shown in a schematic cross-sectional view.

[0037] The drive unit 5 includes a motor unit and an electric motor 10, which constitutes a driver. The drive unit 5 also has a transmission stage configured to drive the electric bicycle 1. The electric motor 10 constitutes a driver for driving the transmission stage. The electric motor 10 is thus coupled to the transmission stage, and the transmission stage is configured on the output side to output or provide torque to drive the electric bicycle 1. The transmission stage is configured as a shaft drive 20, and the electric motor 10 and the shaft drive 20 are arranged coaxially about the rotation axis 8 of the pedal crank 4. Furthermore, the electric motor 10 and the shaft drive 20 are jointly assembled in a housing 30.

[0038] The drive unit 5 is not directly coupled to the pedal crank 4, but rather coupled via the output shaft 25, or, when necessary, to the pedal crank (see [link to relevant documentation]). Figure 5 and 6The output shaft 25 is connected to the sprocket of the electric bicycle 1 via an adapter, also known as a "spider." The sprocket drives the rear wheel of the electric bicycle 1 via a chain. The shaft of the pedal crank 4 can be decoupled from the output shaft 25 via a freewheel to prevent linkage of the crank caused by the motor or drive unit 5.

[0039] The electric motor 10 and the shaft drive 20 are constructed and arranged substantially rotationally symmetrically such that the axis of rotation 8 of the pedal crank 4 corresponds to the axis of rotation of the electric motor 10 and the axis of rotation of the shaft drive 20. The shaft drive 20 is constructed and arranged such that it is coaxial about the axis of rotation 8 around the pedal crank 4. The electric motor 10 is constructed and arranged such that it is coaxial about the axis of rotation 8 around a section of the shaft drive 20.

[0040] The shaft drive device 20 includes a cylindrical outer ring 22, which has internal teeth 221 (see...). Figure 5 and 6 The shaft drive 20 also includes a flexible transmission element 21 having external teeth 213 configured to mate with the internal teeth 221 of an outer ring 22. The external teeth 213 of the transmission element 21 specifically include fewer teeth than the internal teeth 221 of the outer ring 22. The shaft drive 20 also includes a radial coupling element 23. The outer ring 22 serves as the drive element and can also be referred to as a "Fixspline". The radial coupling element 23 serves as the output element of the shaft drive 20. The transmission element 21 is arranged between the outer ring 22 and the radial coupling element 23 and can also be referred to as a "Flexspline". A predetermined torque transmission ratio is provided by the mating external teeth 213 and internal teeth 221. The shaft drive 20 also includes a wave generator 24, also referred to as a "Wave Generator", and is configured to deform the transmission element 21 in a predetermined manner. The shaft drive 20 thus achieves a so-called "Harmonic Drive".

[0041] The electric motor 10 has a stator 11 and a rotor 12, both of which are constructed in a ring shape. The electric motor 10 thus realizes a ring motor, the ring motor shaft of which drives a transmission device 20 during operation. About the axis of rotation 8, the stator 11 is coaxially positioned around the rotor 12, and the rotor 12 is coaxially positioned around the wave generator 24 of the shaft transmission device 20. About the axis of rotation 8, the stator 11 is rotatably coupled to the outer ring 22, and the rotor 12 is torsionally coupled to the wave generator 24. During operation, this causes the rotor 12 and the wave generator 24 to rotate about the axis of rotation 8 relative to the stator 11 and the outer ring 22.

[0042] The radial connecting element 23 has a plurality of radial protrusions 232 on its outer side about the rotation axis 8. These protrusions are configured to mate with a plurality of recesses 212 located on the end side 214 of the transmission element 21 facing the radial connecting element 23. Thus, the radial connecting element 23 can be coupled to the transmission element 21 along the rotation axis 8 by means of the radial protrusions 232 engaging with the recesses 212.

[0043] In other words, the transmission element 21 has a plurality of protrusions 211 that extend on the end side 214 toward the radial connecting element 23 and predeterminely define the recess 212. The protrusions 232 also define the boundary of the recess 231 on the outer side surrounding the radial connecting element 23. In the coupled state of the transmission element 21 and the radial connecting element 23, the protrusions 211 thus also engage with the recesses 231.

[0044] Preferably, the radial protrusions 232 and recesses 212 are configured to be distributed at equal intervals on the respective components. Alternatively, the protrusions 211, 232 and the recesses 232, 212 may also be distributed differently and / or constructed in different numbers.

[0045] The radial coupling element 23 enables a particularly short configuration of the shaft drive 20 and further decouples the drive unit 5 from the pedal crank 4 or the output shaft 25 by means that the radial coupling element 23 is movably constructed along the axis of rotation 8 and can be decoupled from the transmission element 21 (see [link to original text]). Figure 6 The electric bicycle 1 can thus be used as a regular bicycle when needed, without the components of the drive unit 5 needing to rotate together. This can be beneficial, for example, when the drive unit 5 is impaired or requires maintenance.

[0046] The radial coupling element 23 is further coupled to the pedal crank 4 by means of the output shaft 25. Alternatively, the radial coupling element 23 may also be coupled to the pedal crank 4 or the output shaft 25 directly or by means of one or more transmission elements.

[0047] The electric drive unit 5 for the electric bicycle 1 uses the electric motor 10 of the motor unit as a driver for the shaft transmission device 20. The movable radial connecting element 23 enables a short structure for the drive unit 5 and further provides torque transmission from the transmission element 21 to the output shaft 25 and the pedal crank 4. Thus, reliable power transmission from the motor unit to the pedal crank 4 of the electric bicycle 1 is achieved in a very compact structural space.

[0048] The drive unit 5 realizes a highly efficient mechanical system for assisting in cycling and further keeps noise generation to a minimum. This is particularly advantageously achieved by arranging the drive electric motor 10 and the shaft transmission device coaxially with respect to the rotation axis 8 around the pedal crank 4.

[0049] List of reference numerals

[0050] 1 bicycle

[0051] 2 bicycle frames

[0052] 3-frame section (bottom pipe)

[0053] 4 pedals and cranks

[0054] 5 drive units

[0055] 8. Rotation axis of pedal crank / motor unit / transmission stage

[0056] 10 drives

[0057] Stator of 11 drive units

[0058] 12 drive unit rotor

[0059] 20-axis drive unit / drive stage

[0060] 21. Flexible transmission elements

[0061] 211 Protrusions of transmission components

[0062] 212 Recessed portion of transmission element

[0063] 213 External gears of transmission components

[0064] 214 End side of transmission element

[0065] 22-column outer ring

[0066] 221 outer ring internal teeth

[0067] 23 Radial connection elements

[0068] 231 Recessed portion of radial connecting element

[0069] 232 Protrusion of radial connecting element

[0070] 24-wave generator

[0071] 25 pedal crank output shaft

[0072] 30. Housing.

Claims

1. Drive arrangement (5) for an electric bicycle (1), having - a motor unit for driving the electric bicycle (1), - a drive (10), and - a transmission stage (20) which is coupled to the drive (10) and is configured to drive the electric bicycle (1), wherein the transmission stage (20) is coupled to the drive on the one hand and is configured to output a torque for driving the electric bicycle (1) on the other hand, wherein the transmission stage (20) is configured as a shaft transmission and the drive (10) and the shaft transmission can be arranged coaxially with respect to an axis of rotation (8) of a pedal crank (4) of the electric bicycle (1), wherein the transmission stage (20) comprises - a wave generator (24), - a cylindrical outer ring (22) having inner toothing (221), - an elastic transmission element (21) having outer toothing (213) which is configured to match the inner toothing (221) of the outer ring (22) in a predetermined manner, and - a radial coupling element (23), wherein the wave generator (24) is configured to deform the transmission element (21) in a predetermined manner, the outer ring (22) is configured as a drive element of the transmission stage, and the radial coupling element (23) is configured as an output element of the transmission stage (20), wherein the transmission element (21) is arranged between the outer ring (22) and the radial coupling element (23) and provides a predetermined transmission ratio of the transmission stage (20). The drive (10) is configured as an electric motor of the motor unit and comprises a stator (11) and a rotor (12), which are respectively configured annularly and are arranged such that the stator (11) surrounds the rotor (12) and the rotor (12) is coupled to the transmission stage (20). With respect to the axis of rotation (8) of the pedal crank (4), the stator (11) is coupled rotationally fixedly to the outer ring (22), and the rotor (12) is coupled to the wave generator (24) in a torsionally rigid manner. The radial coupling element (23) is coupled to the pedal crank (4). The radial coupling element (23) has a plurality of radial protrusions (232) on the outside with respect to the axis of rotation (8) of the pedal crank (4), which are configured to match a plurality of recesses (212) configured on an end side (214) of the transmission element (21) facing the radial coupling element (23), so that the radial coupling element (23) can be coupled to and decoupled from the transmission element (21) along the axis of rotation (8) of the pedal crank (4). The radial protrusions (232) of the radial coupling element (23) protrude in a predetermined manner beyond the end side (214) of the transmission element (21) with respect to the state of being coupled to the transmission element (21) along the axis of rotation (8) of the pedal crank (4). ​ ​ - a transmission stage (20), wherein ​ ​ ​ ​ ​ ​ 2. The drive device (5) according to claim 1, wherein ​ 3. The drive device (5) according to claim 2, wherein ​ 4. The drive arrangement (5) according to any one of claims 1 to 3, wherein ​ 5. The drive arrangement (5) according to any one of claims 1 to 3, wherein ​ 6. The drive device (5) according to claim 5, wherein ​ 7. The drive arrangement (5) according to any one of claims 1 to 3, wherein With respect to the axis of rotation (8) of the pedal crank (4), the driver (10) and the transmission stage (20) are constructed and arranged such that the driver (10) is coaxially surrounding the transmission stage (20) and the transmission stage (20) is coaxially surrounding the pedal crank (4).

8. An electric bicycle (1), comprising: - A bicycle frame (2), the bicycle frame having a lower frame section (3) extending to a pedal bearing, the pedal bearing having a pedal crank (4), and - The drive device (5) according to any one of the preceding claims is coupled to the bicycle frame (2) to drive the electric bicycle (1), such that the driver (10) and the transmission stage (20) are arranged coaxially with the pedal crank (4).

9. Electric bicycle (1) according to claim 8, wherein, The drive unit (5) is arranged as a component on the frame segment (3) in a coupled state.

Images