Drive unit for a bicycle with a continuously variable transmission

Abstract

The invention relates to a drive device (2) for a bicycle (1), comprising a housing (3) in which a drive arrangement (6) is arranged with a crankshaft (4) adjustable in its stroke and having several individual cranks (5), a driven arrangement (7) with an output shaft (9) operatively connected to a driven gear (8), and a crank-drive CVT transmission (10) operatively connecting the crankshaft (4) and the output shaft (9), the latter with an adjusting device (11) for setting the eccentricity of eccentrics (12) of the crank-drive CVT transmission (10) operatively connected to the individual cranks (5). The invention further relates to a bicycle (1) with such a drive device (2).

Description

[0001] The invention relates to a drive device for a bicycle. Furthermore, the invention relates to a bicycle with such a drive device.

[0002] German patent DE 10 2008 064 514 A1 discloses a transmission unit for a muscle-powered vehicle, comprising an input shaft that can be connected to cranks on opposite sides for driving the vehicle, and a first sub-transmission with a countershaft. A plurality of drive gears are mounted on the input shaft. A corresponding plurality of driven gears of the first sub-transmission are mounted on the countershaft, the driven gears of the first sub-transmission being designed as loose gears that can be non-rotatably connected to the countershaft by means of shifting devices. The countershaft forms an input shaft of a second sub-transmission, on which a plurality of second drive gears are mounted. The second sub-transmission has an output shaft on which a corresponding plurality of second driven gears are mounted.The second drive gears of the second sub-transmission are designed as loose gears, which can be connected to the input shaft in a rotationally fixed manner by means of shifting devices. The output shaft of the second sub-transmission is designed as a hollow shaft, which is arranged coaxially to the input shaft.

[0003] WO 2017 / 137 893 A1 describes a transmission comprising at least two axle segments, a crank arm attached at one end to each axle segment, the space between the at least two crank arms forming a gap, a connecting rod, a connecting axle rotatably connected to one end of the connecting rod, the connecting axle being attached at both ends to the at least two crank arms, and an actuator that moves the attachment point between the connecting axle and the at least two crank arms up and down along their length. It is not described that a drive assembly, an output assembly, and the crank-driven CVT transmission are arranged in a single housing.

[0004] WO 2019 / 016335 A1 describes a continuously variable transmission system that offers improved torque transmission output or efficiency. It does not describe the fact that the crank-driven CVT transmission comprises multiple individual cranks.

[0005] The object of the present invention is to propose a drive device for a bicycle with a transmission that enables stepless transmission variation and has an improved mechanical efficiency. This object is achieved by the subject matter of claim 1. Preferred embodiments are described in the dependent claims.

[0006] According to a first aspect of the invention, a drive device for a bicycle comprises a housing in which a drive arrangement with a crankshaft adjustable in the crank stroke with several individual cranks, an output arrangement with an output shaft operatively connected to an output wheel, and a crank-CVT transmission operatively connecting the crankshaft and the output shaft with an adjusting device for adjusting an eccentricity of eccentrics of the crank-CVT transmission operatively connected to the individual cranks are arranged.

[0007] The housing is preferably separately sealed and designed to be mounted on a bicycle frame. Preferably, the housing is designed to be rigidly connected to a bicycle frame via bolted connections. Alternatively, the housing can be an integral part of the bicycle frame. The crank-driven CVT transmission, the drive assembly, and the output assembly are integrated into the housing, with the transmission input, in the form of a crankshaft adjustable in its stroke, comprising a plurality of individual cranks arranged axially one behind the other on a common axis of rotation, being rotatably mounted on the housing and optionally having its output routed to the outside.

[0008] The drive assembly forms the input to the crank-driven CVT transmission, transmitting drive power, i.e., rotational speed and / or torque, to the CVT transmission via the drive assembly. The drive assembly comprises an input shaft that is operatively connected to the eccentrics and the adjusting mechanism. The input shaft is formed by the crankshaft.

[0009] The output assembly forms the output of the crank-driven CVT transmission. Drive power, continuously converted by the crank-driven CVT transmission depending on the set eccentricity of the eccentric, is routed from the crank-driven CVT transmission via the output assembly to drive at least one wheel of the bicycle. The output assembly comprises at least the output shaft. The output gear may be part of the output assembly. The output assembly, in the form of the output shaft, is also sealed and exits the housing. It is operatively connected to the output gear, which transmits the converted drive power, in particular drive torque, for example via a traction drive, to the driven wheel of the bicycle, especially the rear wheel. The design of the output gear depends on the configuration of the power transmission to the driven wheel. For example, the output gear is a sprocket if the traction drive is a chain drive.

[0010] The crank stroke of each individual crank arm can be adjusted uniformly and from a minimum to a maximum eccentricity for all individual crank arms simultaneously via an eccentric adjustment mechanism. While the minimum eccentricity can theoretically be zero, in bicycle applications it preferably corresponds to a value that is practical for a starting gear ratio.

[0011] Preferably, at least one connecting rod-like linkage is connected to the respective eccentric of the crank-driven CVT transmission, the linkage transmitting a torque to the output shaft via a freewheel. When the respective linkage overtakes the output shaft in the drive direction, the freewheel locks, allowing a torque to be transmitted to the output shaft while the freewheel is free-running, i.e., not locked, when the output shaft overtakes the linkage in the drive direction.

[0012] The crank-driven CVT transmission ("CVT" stands for "Continuously Variable Transmission") comprises several freewheels arranged axially side by side, which together form a freewheel assembly. Accordingly, the crank-driven CVT transmission has several eccentrics, connecting elements, and freewheels arranged axially side by side. Each eccentric, connecting element, and freewheel form a crank-driven CVT module. Alternatively, one eccentric, two connecting elements, and two freewheels could form a crank-driven CVT module. Preferably, the crank-driven CVT transmission has between two and twelve, more preferably between three and eight, and most preferably between three and five crank-driven CVT modules. This reduces system-related rotational irregularity and improves the driving experience for the user.

[0013] In one embodiment, the adjusting device has an adjusting shaft that is operatively connected to the crankshaft and arranged concentrically to it. The adjusting shaft has external teeth that engage with internal teeth on the eccentrics. Each individual crank is designed to adjust the eccentricity of the eccentrics by changing the relative angle of the adjusting shaft to the crankshaft. The adjusting shaft and the crankshaft are nested within each other, and the adjusting shaft can be rotated relative to the crankshaft so that the eccentricity of all eccentrics can be adjusted uniformly by rotating the individual cranks. The adjusting shaft preferably passes axially through the crankshaft and is arranged concentrically to it.

[0014] The adjusting device is preferably manually or electromechanically actuated. Accordingly, the gear ratio adjustment can be electromechanical, for example, via an adjusting motor that rotates the adjusting shaft relative to the crankshaft. The adjusting motor can be directly connected to the adjusting shaft as an actuator or via a gear reduction stage. The gear reduction stage can reduce the output speed of the adjusting motor, since only about one revolution of the adjusting shaft is necessary for the entire gear ratio range. The gear reduction stage can be designed as a planetary gear stage. The adjusting motor can be an electric machine configured to transmit drive power to the adjusting shaft.The adjustment motor can be connected to a control unit via signal transmission, which converts an input command, for example entered manually by the user, into a control signal for controlling the adjustment device and transmits this control signal to the adjustment motor.

[0015] For manual operation of the adjustment device, a Bowden cable can be connected to the adjustment shaft to effect the change in the relative angle between the adjustment shaft and the crankshaft. Manual operation of the adjustment device or the adjustment shaft is advantageous for a bicycle powered solely by muscle power, without an additional motor. The Bowden cable can be operated by the user's finger via a suitable actuation mechanism on the bicycle's handlebars.

[0016] In one embodiment, the crankshaft is operatively connected to a first electric machine. Accordingly, the bicycle is driven, at least in part, by the first electric machine. The first electric machine is configured to transmit drive power to the crankshaft. The first electric machine can have a drive shaft that is rotationally fixed to the crankshaft, in particular as a single unit.

[0017] If the drive system is intended for a bicycle powered solely by muscle power, the crankshaft is preferably designed as a pedal crankshaft or the crankshaft is fixedly connected to the pedal crankshaft. Accordingly, drive power generated by muscle power can be transmitted directly to the crankshaft, i.e., without a gear reduction.

[0018] In this sense, an alternative embodiment of the invention provides that the crankshaft is non-rotatably connected to the pedal crankshaft of the bicycle. Accordingly, the crankshaft and the pedal crankshaft are arranged coaxially to each other. The bicycle pedals are arranged on the pedal crankshaft, so that drive power generated by muscle power is transmitted directly to the crankshaft.

[0019] Preferably, the crankshaft is arranged parallel to the output shaft. Similarly, the driven gear is arranged parallel to the pedal crankshaft, which is fixed to the bicycle pedals.

[0020] To match the speeds and torques of the pedal-driven crankshaft and the crankshaft driven by the first electric motor, a gear reduction stage is provided between the pedal-driven crankshaft and the crankshaft. In this sense, the pedal-driven crankshaft of the bicycle is arranged parallel to the crankshaft.

[0021] The transmission stage can be a spur gear, although other types of transmissions are also conceivable, such as traction gears, planetary gears, or combinations of different transmission types. This allows, firstly, the center distance between the pedal crank shaft and the crankshaft to be bridged. Secondly, a desired pre-reduction ratio can be achieved. The transmission stage can provide a fixed ratio between 1:5 and 1:100, preferably between 1:10 and 1:70, and most preferably between 1:20 and 1:40. In this sense, the pedal crank shaft is operatively connected to the crankshaft via a transmission stage. The transmission stage is preferably designed and configured such that one direction of rotation of the pedal crank shaft corresponds to one direction of rotation of the crankshaft. Furthermore, the transmission stage preferably provides a speed increase.

[0022] The term "interconnected" means that further components or elements, such as a shaft, a chain, a belt or gears, can be arranged between two components or elements.

[0023] Preferably, the crank arm is arranged coaxially with the output shaft. The output shaft can be designed as a hollow shaft, to which the driven gear is fixedly mounted. The crank arm preferably passes axially through the output shaft. This ensures the familiar visual appearance of the bicycle, in which the driven gear, particularly the chainring, is arranged coaxially with the crank arm.

[0024] According to a second aspect of the invention, a bicycle comprises a drive device according to the first aspect of the invention. The bicycle can be propelled solely by the muscle power of a user or cyclist. Alternatively, the bicycle can be an electric bicycle, pedelec, or e-bike, in which the propulsion of the bicycle can be assisted or performed by at least one electric motor. In this case, the electric motor assists the user's power output, generally according to the rider's wishes and a torque input from the user. Therefore, the term "bicycle" is not limited to a bicycle propelled exclusively by muscle power without a motor, but also includes bicycles with an additional drive system. In particular, the term "bicycle" also encompasses cargo bikes with more than two wheels, especially those with three or four wheels.

[0025] The aforementioned drive device can be arranged as a type of central drive in the area of ​​the crank axle. Preferably, the housing of the drive device is located between a seat tube and a down tube of the frame. The housing can be an integral part of the bicycle frame or bolted to the bicycle frame.

[0026] Further measures improving the invention are described in more detail below, together with a description of two exemplary embodiments of the invention, with reference to the figures, wherein identical or similar components are provided with the same reference numeral. The figures show... Fig. 1 a highly schematic representation of a bicycle according to the invention with a drive device according to a first embodiment, Fig. 2 a highly schematic top view of the drive device according to the invention Fig. 1, Fig. 3 a schematic longitudinal sectional view of the drive device according to the invention Fig. 1 and Fig. 2, Fig. 4 a first schematic top view of the drive device according to the invention in a second embodiment in a first operating state, and Fig. 5 a second schematic top view of the drive device according to the invention Fig. 4 in a second operating state.

[0027] Fig. Figure 1 shows a highly simplified version of a bicycle 1 according to the invention. The bicycle 1 has a frame 20 on which a steerable first wheel 21, designed as a front wheel, and a second wheel 22, designed as a drive wheel or rear wheel, are mounted. The first wheel 21 can be manually pivoted by the user via a handlebar 23, on which the user can support and hold themselves using handlebar grips while riding, the handlebar 23 being connected to the first wheel 21 via a fork 24.

[0028] A drive device 2 is integrated into a housing 3 between a seat tube 25, a down tube 26, and two frame segments 31 of the frame 20 that rotate and support the second wheel 22. The design and function of the drive device 2 are described in various embodiments according to the Fig. Sections 2 to 5 are described in more detail. The housing 3 can be screwed to the frame 20 and is sealed to the outside.

[0029] The first embodiment according to Fig. Figures 1 to 3 show an exemplary drive device 2 for a bicycle 1 that can be propelled solely by the muscle power of a user (not shown here). For example, the user sits on a saddle 27 while riding and applies drive power to the drive device 2 via pedals 28, which are connected to a crank axle 19 of the drive device 2 via crank arms. The output of the drive device 2 is a driven gear 8, which transmits the drive power via a chain 29 to a sprocket 30 on the second wheel 22 to drive this rear wheel. The driven gear 8, the chain 29, and the sprocket 30 thus form a drive mechanism for the rear wheel, with the driven gear 8 and the sprocket 30 each being designed as a chainring.

[0030] In the Fig. 2 and Fig. Figure 3 shows the construction of the drive device 2 in more detail. The housing 3 of the drive device 2 contains a drive assembly 6 with a crankshaft 4, adjustable in its stroke and arranged on a drive shaft 32, with several individual cranks 5; an output assembly 7 with an output shaft 9, operatively connected to the output gear 8 and arranged on an output shaft 33; and a crank-driven CVT transmission 10, which effectively connects the crankshaft 4 and the output shaft 9, with an adjusting device 11 for setting the eccentricity of eccentrics 12 of the crank-driven CVT transmission 10, which are operatively connected to the individual cranks 5.

[0031] The crank-CVT transmission 10, in the present case and only by way of example, has four crank-CVT modules 34 arranged side by side, each comprising an eccentric 12, a connecting rod-like connecting element 13 and a freewheel 14. Fig. Figure 3 shows one of the crank CVT modules 34 in a view, with the other three crank CVT modules 34 indicated behind it. The connecting element 13 is rotatably mounted on one side via a first bearing element 35 relative to the eccentric 12 and on the other side via a second bearing element 36 relative to a freewheel lever 37 of the freewheel 14. In other words, the connecting element 13 is pivotally mounted on the eccentric 12 and on the freewheel 14. A torque can be transmitted from the crankshaft 4 and the eccentric 12 to the output shaft 9 via the freewheel 14 with a gear ratio.

[0032] The freewheel 14 is designed here as a friction-fit ball freewheel, which is configured to allow a shaft, here the output shaft 9, to rotate freely in one direction while transmitting a torque in the opposite direction. Thus, torque is transmitted to the output shaft 9 only in one direction of rotation of the freewheel 14. Several freewheel bodies 40 are arranged between a star-shaped inner freewheel ring 38 and an outer freewheel ring 39, with a spring-loaded locking element 41 arranged circumferentially between each pair of freewheel bodies 40, which achieves a torque-transmitting locking effect in the corresponding direction of rotation. The inner freewheel ring 38 is rotationally fixed to the output shaft 9, and the outer freewheel ring 39 is rotationally fixed to the freewheel lever 37.

[0033] When the connecting element 13 overtakes the output shaft 9 in the drive direction, the freewheel 14 locks, so that a torque is transmitted to the output shaft 9, while the freewheel 14 is free-running, i.e., not locked, when the output shaft 9 overtakes the connecting element 13 in the drive direction. The freewheels 14 can together form a freewheel assembly.

[0034] The freewheel 14 can be designed to be switchable in order to reverse its direction of action. This allows the bicycle 1 to travel in reverse, which can be particularly beneficial for handling cargo bikes.

[0035] In this case, the crankshaft 4 is connected to the coaxially arranged pedal crankshaft 19 in a rotationally fixed manner, wherein the crankshaft 4 and the pedal crankshaft 19 are arranged axially parallel to the output shaft 9 and to the output gear 8.

[0036] The crankshaft 4 can be driven by muscle power via the pedal crankshaft 19, whereby a gear ratio dependent on a set eccentricity of the eccentrics 12 relative to the crankshaft 4 is realized by means of the crank-CVT transmission 10. The gear ratio is continuously adjustable by following Fig. 3 an adjusting shaft 15 of the adjusting device 11 is rotated, so that a relative angle change of the adjusting shaft 15 relative to the crankshaft 4 arranged concentrically to it occurs, which causes an adjustment of the eccentricity of the eccentrics 12 by a change in the stroke of the individual cranks 5.

[0037] The adjusting shaft 15 can be operated manually, for example via a manually operated Bowden cable or the like. Alternatively, the adjusting device 11 can be operated analogously to the second embodiment according to Fig. 4 and Fig. 5 are electromechanically actuated, as described below. The adjusting shaft 15 has an external toothing 16 which engages with an internal toothing 17 of the eccentrics 12. The individual stroke of the individual cranks 5 of the crankshaft 4 is adjustable between a minimum and a maximum eccentricity by means of the adjusting device 11. The minimum eccentricity is selected such that starting the bicycle 1 is easy.

[0038] The second embodiment according to Fig. 4 and Fig. Figure 5 shows an exemplary drive device 2 for a bicycle 1 that can be driven both by the user's muscle power and with the assistance of at least one first electric machine 18. The drive device 2 thus comprises a first electric machine 18 as a drive unit, which is arranged as a mid-drive motor in the area of ​​the pedal crank 19. The first electric machine 18 is designed to assist the drive of the bicycle 1. Therefore, the bicycle 1 is designed as an e-bike. The first electric machine 18 comprises a stator 47 and a rotor 48, wherein the rotor 48 is operatively connected to the crank 4, in this case in a rotationally fixed manner. Furthermore, a second electric machine 51 is provided, which forms the adjustment motor of the adjustment device 11. The second electric machine 51 comprises a stator 49 and a rotor 50, wherein the rotor 50 is operatively connected to the adjustment shaft 15, in this case in a rotationally fixed manner.The first and second electric machines 18, 51 are arranged axially adjacent to each other, with the adjusting shaft 15 projecting into the coaxially arranged crankshaft 4. The adjusting shaft 15 and the crankshaft 4 are both arranged on the drive shaft 32.

[0039] In this arrangement, the pedal crankshaft 19 is arranged axially parallel to the crankshaft 4 and the adjusting shaft 15. The pedal crankshaft 19 is arranged coaxially to the output shaft 9 and passes axially through the hollow output shaft 9, being rotatably mounted to it. Furthermore, the pedal crankshaft 19 is sealed on both sides as it exits the housing 3. The pedal crankshaft 19, together with the output shaft 9, is arranged on the output shaft 33, whereby the drive power generated by muscle power and introduced via the pedal crankshaft 19 is transmitted to the crankshaft 4 via a transmission stage 52. Thus, the pedal crankshaft 19 is operatively connected to the crankshaft 4 via a transmission stage 52, in particular to match the speeds and torques of the pedal crankshaft 19 driven by muscle power and the crankshaft 4 driven by the first electric motor 18.The transmission stage 52 comprises a first gear 42 on the pedal crank shaft 19, a second gear 43 on the crankshaft 4, and an intermediate shaft 44 with two adjacent and rotationally fixed gears 45, 46, wherein a third gear 45 of the intermediate shaft 44 engages with the first gear 42 and a fourth gear 46 of the intermediate shaft 44 engages with the second gear 43. A fixed gear ratio between 1:5 and 1:100 can be achieved using the transmission stage 52.

[0040] The first electric machine 18 is intended to generate drive power for propelling the bicycle 1. The second electric machine 51 is also intended to assist the propulsion force. By lagging or leading with respect to the first electric machine 18, the second electric machine 51 can be used to rotate the adjusting shaft 15 relative to the crankshaft 4, resulting in an identical stepless adjustment of the gear ratio in the crank CVT modules 34. In contrast to the first embodiment according to Fig. 1 to Fig. 3 The crank-CVT transmission 10 comprises three instead of four crank-CVT modules 34, which are arranged next to each other or one behind the other in the axial direction.

[0041] The Fig. 4 and Fig. Figure 5 shows two different operating states of the drive device 2, wherein according to Fig. 5. Due to a rotation of the crankshaft 4, an adjustment of the eccentricity of the eccentrics 12 has occurred. Thus, the Fig. 4 and Fig. 5 different relative angle positions between the adjusting shaft 15 and the crankshaft 4.

[0042] Furthermore, in particular with regard to the functionality and the stepless translation adjustment, reference is made to the above explanations of the first embodiment. Reference symbol list 1 bicycle 2 Drive device 3 cases 4 Crankshaft 5 single crank 6 Drive arrangement 7 Output arrangement 8 Output wheel 9 Output wave 10 Crankshaft CVT transmissions 11 Adjustment device 12 eccentrics 13 Connecting element 14 Free run 15 Adjustment shaft 16 External teeth 17 Internal teeth 18 First electric machine 19 Crankshaft 20 frames 21 First wheel 22 Second wheel 23 handlebars 24 Fork 25 seat tube 26 down tube 27 saddles 28 Pedal 29 chain 30 toothed ring 31 frame segment 32 Drive axle 33 Output axle 34 Crank CVT Module 35 First bearing element 36 Second bearing element 37 freewheel levers 38 Freewheel inner ring 39 Freewheel outer ring 40 freewheel bodies 41 Locking element 42 First gear 43 Second gear 44 Intermediate shaft 45 Third gear 46 Fourth gear 47 Stator of the first electric machine 48 Rotor of the first electric machine 49 Stator of the second electric machine 50 Rotor of the second electric machine 51 Second electric machine 52 translation level

Claims

[1] Drive device (2) for a bicycle (1), comprising a housing (3) in which a drive arrangement (6) with a crankshaft (4) adjustable in the crank stroke with several individual cranks (5), a driven arrangement (7) with an output shaft (9) operatively connected to an output wheel (8) and a crank CVT transmission (10) operatively connecting the crankshaft (4) and the output shaft (9) with an adjusting device (11) for adjusting an eccentricity of eccentrics (12) of the crank CVT transmission (10) operatively connected to the individual cranks (5). [2] Drive device (2) according to claim 1, characterized by , that at least one connecting rod-like connecting element (13) is connected to the respective eccentric (12) of the crank CVT transmission (10), wherein the connecting element (13) transmits a torque to the output shaft (9) via a freewheel (14). [3] Drive device (2) according to claim 1 or claim 2, characterized by, that the adjusting device (11) has an adjusting shaft (15) which is operatively connected to the crankshaft (4) and arranged concentrically to it, wherein the adjusting shaft (15) has an external toothing (16) which engages with an internal toothing (17) of the eccentrics (12), wherein the respective individual crank (5) is designed to effect an adjustment of the eccentricity of the eccentrics (12) by changing the relative angle of the adjusting shaft (15) relative to the crankshaft (4). [4] Drive device (2) according to one of the preceding claims, characterized by that the adjusting device (11) can be operated manually or electromechanically. [5] Drive device (2) according to one of the preceding claims, characterized by , that the crankshaft (4) is operatively connected to a first electric machine (18). [6] Drive device (2) according to any of the preceding claims, characterized by, that the crankshaft (4) is connected to a pedal crankshaft (19) in a rotationally fixed manner. [7] Drive device (2) according to any one of the preceding claims 1 to 5, characterized by , that a pedal crank shaft (19) is arranged parallel to the crank shaft (4). [8] Drive device (2) according to claim 7, characterized by , that the pedal crank shaft (19) is operatively connected to the crank shaft (4) via a transmission stage (52). [9] Drive device (2) according to claim 7 or claim 8, characterized by , that the pedal crank shaft (19) is arranged coaxially to the output shaft (9). [10] Bicycle (1) comprising a drive device (2) according to any of the preceding claims.

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