Drive device for a bicycle

Abstract

The invention relates to a drive device (2) for a bicycle (1), comprising an electric motor (4), power electronics (6) connected thereto for signal transmission, wherein the power electronics (6) are arranged laterally to the electric motor (4) with respect to a forward direction of travel of the bicycle (1), a crank shaft (19), and at least two bearing elements (7a, 7b) for rotatably mounting the crank shaft (17) on a housing (3), wherein the electric motor (4) is arranged axially between the two bearing elements (7a, 7b), and wherein a force sensor (9) is provided on the bearing element (7a) facing the power electronics (6) in order to detect radial and tangential forces acting at least on the crank shaft (19). 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. The drive device comprises a crank axle for generating torque by muscle power and an electric motor for electric drive assistance. The invention further relates to a bicycle with such a drive device.

[0002] EP 0 983 934 B1 discloses a torque sensor for a lower support assembly of a bicycle, wherein the torque sensor has a lower support axle. The support assembly comprises an axle support element for supporting the axle for rotation about a support axis, wherein the axle support element has a first sensor mounting point. Furthermore, the lower support axle comprises a first pressure sensor for arrangement at the first sensor mounting point.

[0003] DE 10 2016 122 845 A1 describes a load cell for determining a radial force on a crankshaft. This includes a sleeve for receiving a bearing ring, a ring for mounting the load cell in a gearbox housing, axial support areas on the mounting ring for axially supporting the bearing ring, measuring areas for receiving radial forces on the receiving sleeve and connecting these to the mounting ring, wherein strain sensors are attached to at least two of the measuring areas.

[0004] DE 10 2010 003 050 A1 describes a bicycle with a crank mechanism, an electric motor and a drive shaft connected to these, which is supported by two bearings, one of which has a bearing force measurement.

[0005] DE 10 2009 014 247 A1 describes a drive system for a motor-assisted bicycle with a shaft driven by cranks and an electric motor arranged concentrically to it, which drives a planetary gear unit that, on the output side, drives a chainring connected to the shaft. The motor unit and gear unit are located in a housing connected to a sleeve within which the shaft rotates.

[0006] WO 2020 / 079 575 A1 describes the determination of a motor bearing for an electric motor. A first strain gauge element is located in the first section of a crankshaft mounting area, and a second strain gauge element is located in the opposite second section of the crankshaft mounting area. Evaluation electronics are connected to the two strain gauge elements and receive first and second signals from them. A first and second reference value for the first and second signals, respectively, is then determined, based on which the motor support is deactivated.

[0007] The object of the present invention is to propose a drive device for a bicycle comprising a pedal crank and an electric motor for electric drive assistance, wherein a torque acting on the pedal crank and a motor torque can be determined in a simple manner. This object is achieved by a drive device according to claim 1. Preferred embodiments are described in the dependent claims.

[0008] According to the invention, a drive device for a bicycle comprises an electric motor, power electronics connected to it for signal transmission (the power electronics being arranged laterally to the electric motor with respect to the forward direction of travel of the bicycle), a crankshaft, and at least two bearing elements for rotatably mounting the crankshaft to a housing (the electric motor being arranged axially between the two bearing elements), and a force sensor being provided on the bearing element facing the power electronics to detect radial and tangential forces acting at least on the crankshaft. This allows for easier communication between the force sensor and the power electronics. Furthermore, the available installation space can be utilized more efficiently.

[0009] Based on predefined geometric parameters such as the bearing spacing of the two crank arm bearing elements, the crank arm length, the pedal spacing, the module's installation orientation in the bicycle relative to the road surface and relative to the rider, or alternatively from calibration measurements, the input torque of the crank arm generated by muscle power can be derived with sufficient accuracy from the force sensor's measurement signals, particularly the recorded radial and tangential force components, and their progression over time. This information can then be used for further calculations. Therefore, the drive device proposed here allows for the simple determination of both acting torques—a first torque generated by muscle power and a second torque generated by the electric motor—with a single measurement.

[0010] The power electronics can incorporate evaluation software, which is configured to receive or optionally retrieve the measurement data from the force sensor, store it, and use it to calculate a power curve. Alternatively or additionally, the evaluation software can be located on a control unit that can be connected to the power electronics, the force sensor, and / or the electric machine via signal transmission.

[0011] The electric machine comprises a stationary stator, in particular a housing-mounted stator, and a rotatably mounted rotor. The electric machine can be designed as an internal or external rotor. The electric machine is configured to transmit drive power to a rotor shaft. The rotor is non-rotatably connected to the rotor shaft, in particular as a single unit. The rotor shaft can be directly or via an optional gear stage operatively connected to an output wheel if the drive device is designed as a central drive, for example, to drive at least one wheel of the bicycle via a traction drive. Alternatively, the rotor shaft can be operatively connected to the pedal crank shaft, in particular if the drive device is designed as a generator module for generating electrical energy for at least one separate drive module of the bicycle.

[0012] If a gear stage is provided, the rotor shaft serves as the gear input shaft.

[0013] In one embodiment, the electric motor is operatively connected to an output gear via a gear stage. The gear stage compensates for axial misalignment if the electric motor is arranged parallel to the crankshaft. If a concentric design is used, the gear stage can be arranged coaxially with both the electric motor and the crankshaft. The gear stage converts the drive power of the electric motor into a slower speed, while simultaneously increasing the torque.

[0014] The gear stage is preferably arranged on the side of the electric machine opposite the power electronics. This allows the force sensor to be positioned as close as possible to the power electronics and thus connected, at least for signal transmission, and optionally mechanically. The gear stage can be a planetary gear, a single- or multi-stage spur gear, a wave gear, or the like.

[0015] It is conceivable that at least one further electric machine is provided, which is operatively connected to the output wheel and, if applicable, to the optional gear stage. This further electric machine can be operatively connected to another gear stage, which in turn is coupled to the first gear stage of the first electric machine.

[0016] The output gear 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 specific 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.

[0017] The crankshaft passes axially through the housing of the drive unit and is rotatably mounted and sealed at its interfaces with the housing. The crankshaft can be solid or hollow. It can be a single piece or multi-piece. If multiple pieces are used, they are non-rotatably connected to each other. The crankshaft is operatively connected to the crank arms and pedals.

[0018] Preferably, the pedal crank shaft is arranged coaxially with the electric motor. This allows for a concentric, compact design of the drive device, as the drive-related components can be arranged around the pedal crank shaft.

[0019] The housing spatially defines the external boundaries of the drive unit. The housing can be constructed in one or more parts, with a base housing, for example, having mounting openings that can be closed by corresponding covers or housing segments. Preferably, the electric motor, the optional gear stage, the bearing elements, and the force sensor are arranged together within the housing. In this case, only the crank arm and the rotor shaft or the gearbox output shaft extend laterally from the housing to allow at least an indirect connection between the pedals or crank arms and the crank arm, or between the output gear and the gearbox output shaft. Accordingly, the output gear is located outside the housing. It is also conceivable that the output gear is located inside the housing, in which case the associated drive element can extend out of the housing.

[0020] In this context, "at least indirectly" means that two elements or components are effectively connected to each other via at least one further component located between them, or are directly and thus immediately connected to each other. Accordingly, further components or parts, in particular shafts or wheels, can be arranged between two shafts and / or wheels.

[0021] Preferably, the power electronics are mounted in a housing-mounted configuration. This means the power electronics are supported on the housing either separately or via the stator of the electric motor. Therefore, the power electronics are mounted to the bicycle frame. The power electronics enable a simple electrical and optionally mechanical connection of the force sensor, for example, to a circuit board of the power electronics. This connection can be implemented more easily, especially compared to conventional direct-measuring torque sensors on or attached to the rotating crank axle with signal processing. In this sense, the force sensor is at least electrically connected to a circuit board of the power electronics. In other words, the force sensor is contacted by the circuit board. Depending on the design of the drive system, the force sensor can also be mechanically connected to the circuit board.The force sensor or its housing can have corresponding pins for contacting the circuit board. The circuit board is preferably a printed circuit board (PCB).

[0022] The force sensor is designed to measure at least the forces exerted on a crank axle in both tangential and radial directions. The force sensor is capable of detecting and quantifying the force transmitted to the crank axle during the pedaling process of a bicycle. Tangential force measurement encompasses the measurement of forces acting along the longitudinal axis of the crank axle. These forces are generated by pedaling and are crucial for propulsion. The force sensor also detects forces acting perpendicular to the longitudinal axis of the crank axle. These forces can arise, for example, from lateral loads or irregularities in pedaling technique.

[0023] Preferably, the force sensor is an annular force sensor that is arranged at least partially around an outer ring of the bearing element facing the control electronics. Thus, the force sensor extends at least partially around the crank arm. Such a force sensor can also be understood as a torque measuring ring, enabling torque measurement at the crank arm during pedaling.

[0024] The force sensor is preferably arranged radially between the housing or a housing section of the housing on the one hand and an outer ring of the bearing element which is arranged on the axial side of the electric machine on which the power electronics are also provided on the other hand.

[0025] Using clipless pedals can offer an additional advantage, especially for sporty riders. The ability to "pull" on one pedal while "pushing" on the other allows for the generation of a consistent torque at the crank axle, which isn't directly detected by the force sensor. This could result in a very slight deviation of approximately 10% from the actual applied torque in a given measurement. However, this deviation is acceptable for most applications, particularly since this specific scenario is extremely rare on bicycles with at least partial electric assist.

[0026] According to a further aspect of the invention, a bicycle comprises a drive device according to the first aspect of the invention. The bicycle is, in particular, an electric bicycle, pedelec, or e-bike, typically with two wheels, wherein the bicycle can be driven purely by muscle power or assisted or performed by at least one electric motor. The electric motor assists the user's power output, generally according to the rider's wishes and a torque supplied by the user. In particular, the term "bicycle" also includes cargo bikes with more than two wheels, for example, with three or four wheels.

[0027] According to the invention, the aforementioned drive device is arranged as a generator module for generating electrical energy for at least one drive module of the bicycle. The drive device according to the invention is therefore advantageously suited for use as a generator module in a bicycle. The drive device can further comprise a drive module having at least one additional electric machine for rotating a wheel of the bicycle. The generator module has a generator that can be driven by the cyclist by pedaling force in drive mode, with the crankshaft being provided for transmitting the pedaling force from a pedal crank to the generator. The drive module can therefore be supplied with electrical energy by the generator in drive mode. The generator module can have an optional gear stage for converting the pedaling force, in particular into a higher speed (i < 1), to the generator.The electric machine of the drive device is therefore intended to generate electrical energy in order to supply the drive module with electrical energy.

[0028] Further measures improving the invention are described in more detail below, together with a description of a preferred embodiment 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 the invention in a preferred embodiment, Fig. 2 a highly schematic representation of the drive device according to the invention Fig. 1, and Fig. 3 a partial sectional view of the drive device according to the invention Fig. 1 and Fig. 2,

[0029] Fig. Figure 1 shows a bicycle 1 according to the invention in a highly simplified manner. 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.

[0030] 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 which receive and support the second wheel 22 in a rotating manner, the structure and function of the drive device 2 being illustrated by a simple example according to Fig. 2 in conjunction with Fig. 3 is described in more detail. The housing 3 can be screwed to the frame 20 and is sealed to the outside.

[0031] After Fig. The drive device 2 is provided for a bicycle 1 that can be propelled both by the user's muscle power and with the assistance of at least one electric motor 4. The user, seated on the saddle 27, can apply drive power to the drive device 2 by pedaling 28, which is connected to a crankshaft 19 of the drive device 2 via respective crank arms in a rotationally fixed manner. The electric motor 4 serves as a drive unit or as a (not included in the invention) mid-drive motor in the area of ​​the crankshaft 19 and is designed to provide drive assistance to the bicycle 1. Thus, the bicycle 1 is designed as an e-bike.

[0032] The output of the drive device 2 is formed by a driven wheel 8, which transmits the drive power via a Fig. The chain 29 shown in Figure 1 transmits power as a traction element to a sprocket 30 on the second wheel 22 to drive this rear wheel. The driven wheel 8, the chain 29, and the sprocket 30 thus form a traction drive for driving the rear wheel, with the driven wheel 8 and the sprocket 30 each being designed as a chainring.

[0033] In Fig. 2 in conjunction with Fig. Figure 3 shows the construction and operation of the drive device 2 in more detail. The housing 3 of the drive device 2, which is presented here only as an example, contains an electric machine 4, a gear stage 5 in the form of an exemplary wave gear, power electronics 6, and two freewheels 13 and 15. The electric machine 4 comprises a stator 17 and a rotor 18, the rotor 18 being non-rotatably connected to a rotor shaft 14. The rotor shaft 14 forms the input shaft of the gear stage 5.

[0034] The gear stage 5, or wave gear, comprises a wave generator 37, a rigid ring element 38 in the form of a ring gear with internal teeth 36, and a radially deformable, flexible ring element 12 with external teeth 39. The external teeth 39 of the flexible ring element 12 mesh with the internal teeth 36 of the rigid ring element 38 to transmit torque to two symmetrically opposed tooth engagement areas 32, of which only one is shown here, relative to the axis of rotation of the wave generator. The wave generator 37 has a non-circular bearing element 16, which projects axially into the flexible ring element 12. The bearing element 16 is not shown in detail here. The reference numeral 16 merely indicates the installation location of the bearing element 16 between the rotor shaft 14 and the flexible ring element 12.The bearing element 16 has an inner ring 34, an outer ring (not shown) and rolling elements arranged spatially between them (also not shown), wherein the inner ring 34 is non-rotatably connected to the rotor shaft 14.

[0035] In this case, the output shaft 40 serves as the gearbox output of gearbox stage 5, and is directly and non-rotatably connected to the aforementioned output wheel 8, wherein the output shaft 40 is non-rotatably connected on the one hand to the flexible ring element 12 and on the other hand to the pedal crank shaft 19 via the first freewheel 13.

[0036] The first freewheel 13 is arranged between the crank axle 19 on one side and the flexible ring element 12 and the output shaft 40 on the other side, and is designed to transmit a torque from the crank axle 19 to the output shaft 40 when the cyclist pedals 28 in such a way that the crank axle 19 rotates in a direction corresponding to the forward direction of travel. In the opposite direction of rotation of the crank axle 19, no torque is transmitted and the output shaft 40 can rotate relative to the crank axle 19.

[0037] The rigid ring element 38 is connected to the stator 18 via the second freewheel 15. The second freewheel 15 is thus effectively positioned between the rigid ring element 38 and the housing 3. The second freewheel 15 ensures that the rotatable components of the electric machine 4 and the gear stage 5 rotate without load when driving without electrical assistance. The freewheels 13 and 15 can, for example, be designed as clamping element freewheels.

[0038] The drive device 2 is concentrically designed, with the pedal crank shaft 19, which is rotatably mounted on a drive shaft 35, arranged coaxially to the electric motor 4 and to the gear stage 5. A compact design can be achieved if the gear stage 5 is arranged axially between the first freewheel 13 and the electric motor 4, and if the first freewheel 13 is arranged axially between the gear stage 5, in particular the flexible ring element 12, and the output shaft 40.

[0039] The electric machine 4 is connected to a power electronics unit 6 for controlling and regulating the drive assistance via signal transmission, the power electronics unit 6 being fixed to the housing or frame. The power electronics unit 6 is positioned laterally with respect to the forward direction of travel of the bicycle 1, according to Fig. The power electronics 6 are located on the left side of the electric machine 4, between the electric machine 4 and a left wall of the housing 3. The power electronics 6 comprise a substantially planar circuit board 11 in the form of a printed circuit board (PCB). The gear stage 5 is located on the side of the electric machine 4 opposite the power electronics 6.

[0040] The pedal crank shaft 19 is rotatably mounted on the housing 3 via a first bearing element 7a on the side facing the power electronics 6 and via a second bearing element 7b on the side facing the gear stage 5. The electric machine 4, i.e., the stator 17 and the rotor 18, is arranged axially between the two bearing elements 7a and 7b. A ring-shaped force sensor 9 is provided on the first bearing element 7a, i.e., the bearing element 7a facing the power electronics 6. This sensor is designed to detect radial and tangential forces, or forces in the radial and tangential directions, acting on the pedal crank shaft 19.

[0041] The force sensor 9 is after Fig. The inner ring 41 of the first bearing element 7a is arranged radially around an outer ring 10 and between the housing 3 and the outer ring 10. The inner ring 41 of the first bearing element 7a is non-rotatably connected to the pedal crank shaft 19.

[0042] The force sensor 9 is mechanically and electrically connected to the circuit board 11 of the power electronics 6. For this purpose, the force sensor 9 includes one or more pins 9a for contacting the circuit board 11. Reference symbol list 1 bicycle 2 Drive device 3 cases 4 Electric Machine 5 gear stage 6 Power Electronics 7a, 7b Bearing element 8 Output wheel 9 Force sensor 9a Pin 10 Outer ring 11 circuit board 12 Flexible ring element 13 First free run 14 Rotor shaft 15 Second free run 16 bearing element 17 Stator 18 Rotor 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 Tooth engagement area 34 Inner ring of the bearing element 35 Drive axle 36 Internal teeth 37 Wave generator 38 Rigid ring element 39 External gearing 40 Output shaft 41 inner ring

Claims

[1] Drive device (2) for a bicycle (1), comprising an electric machine (4), power electronics (6) connected thereto for signal transmission, wherein the power electronics (6) are arranged laterally to the side of the electric machine (4) with respect to a forward direction of travel of the bicycle (1), a pedal crank shaft (19) and at least two bearing elements (7a, 7b) for rotatably mounting the pedal crank shaft (17) on a housing (3), wherein the electric machine (4) is arranged axially between the two bearing elements (7a, 7b), and wherein a force sensor (9) is provided on the bearing element (7a) facing the power electronics (6) in order to detect radial and tangential forces acting at least on the pedal crank shaft (19). characterized by , that the drive device (2) is designed as a generator module for generating electrical energy for at least one drive module of a bicycle (1). [2] Drive device (2) according to claim 1, characterized by, that the power electronics (6) are arranged in a housing-fixed manner. [3] Drive device (2) according to claim 1 or claim 2, characterized by , that the pedal crank shaft (19) is arranged coaxially to the electric machine (4). [4] Drive device (2) according to one of the preceding claims, characterized by , that the force sensor (9) is a ring-shaped force sensor which is arranged at least partially around an outer ring (10) of the bearing element (7a) facing the line electronics (6). [5] Drive device (2) according to one of the preceding claims, characterized by , that the force sensor (9) is at least electrically connected to a circuit board (11) of the power electronics (6). [6] Drive device (2) according to any of the preceding claims, characterized by , that the electric machine (4) is operatively connected to an output wheel (8) via a gear stage (5). [7] Drive device (2) according to claim 6, characterized by , that the gear stage (5) is arranged on one side of the electric machine (4) opposite the power electronics (6). [8] Bicycle (1) comprising a drive device (2) according to any one of claims 1 to 7.

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