Drive unit for a vehicle

Abstract

The invention relates to a drive unit for a vehicle comprising an electric motor (3, 4) for at least periodically driving the vehicle by supplying electrical power to the electric motor (3, 4), a pedal crankshaft (2) for receiving muscular force to at least periodically drive the vehicle via muscular force, and an output element (14) via which a drive force for driving the vehicle can be output by the drive unit. A transmission with a predetermined transmission ratio is provided, which is coupled to an output element (5) of the electric motor (3, 4) on the input side and which can be coupled to the output element (14) of the drive unit via a transmission output element (9) on the output side. In addition, a pedal crankshaft output element (12) coupled to the pedal crankshaft (2) is provided, which can be coupled to the output element (14) of the drive unit. The drive unit has a torque-limiting assembly (20) which is designed for limiting a torque acting on a rotor (3) of the electric motor. When the torque-limiting assembly (20) exceeds a predefined maximum torque, a support element (8) is allowed to rotate relative to a stationary element of the drive unit. At least one of the axially and radially outward-facing surface portions (81; 82; 83; 84) of the support element (8) has an outwardly curved contour.

Description

[0001] Drive device for a vehicle

[0002] The present invention relates to a drive device for a vehicle that is driven at least temporarily by an electric motor and at least temporarily by muscle power. In particular, the invention relates to a drive device for a vehicle in which the drive power of an electric motor and the drive power generated by muscle power can be combined and used to drive the vehicle. In particular, the invention relates to a drive device in which concentricity deviations of elements within the drive device have a reduced impact on the operation and durability of the drive device.

[0003] The prior art according to DE 10 2015 100676 B3 describes a drive system for a bicycle or pedelec. This drive system uses an electric motor to generate propulsion power for the vehicle. The electric motor is coupled to an output element of the drive system via a shaft gear.

[0004] In the prior art according to EP 2 976 551 B1, a pin-ring gear is described, which represents a design of a shaft gear with which a predetermined transmission ratio can be provided for transmitting a driving force.

[0005] A drive device for a vehicle comprises the following: an electric motor for at least temporarily driving the vehicle by supplying electrical power to the electric motor, a pedal crankshaft for absorbing muscle power for at least temporarily driving the vehicle by muscle power, and an output element via which drive power for driving the vehicle can be output from the drive device; a transmission with a predetermined gear ratio, which is coupled on the input side to an output element of the electric motor and which can be coupled on the output side via a transmission output element to the output element of the drive device; a pedal crankshaft output element coupled to the pedal crankshaft, which can be coupled to the output element of the drive device;wherein the drive device has a torque limiting assembly which is configured to limit a torque acting in the power transmission path between the electric motor and the output element, wherein, when a predetermined maximum torque is exceeded, the torque limiting assembly permits rotation of a torque support component relative to a stationary element of the drive device, so that the torque acting on the rotor of the electric motor is limited to a permissible torque, wherein at least one of axially and radially outwardly facing surface sections of the torque support component is configured with an outwardly curved contour;

[0006] The drive device can be permanently mounted on the vehicle. The drive device can be designed as an assembly and mountable on the vehicle in such a way that a compact design is enabled. The vehicle can be intended for the transport of persons. Additionally, the vehicle can be intended for the transport of goods. The vehicle can be designed as a single-track vehicle. Alternatively, the vehicle can be designed as a multi-track vehicle. The vehicle can be designed as an e-bike or pedelec, in which both muscle power and the drive power of an electric drive can be used to drive the vehicle. An electrical energy storage device can be provided with which the electric motor of the drive device can be operated. Furthermore, a control device can be provided with which the operation of the electric motor can be controlled.The vehicle may have pedals mounted on the crank arm to enable the introduction of muscle power.

[0007] According to one embodiment, the torque support component can be coupled to a housing of the drive device for supporting a reaction torque, wherein the torque limiting assembly can be provided in the force transmission path between the torque support component and the housing in order to limit the support torque to a predetermined maximum support torque.

[0008] According to one embodiment, if the predetermined maximum support torque is exceeded by the torque limiting assembly, a rotation of the torque support component of the transmission relative to a stationary element can be permitted, so that the torque acting on the rotor of the electric motor due to the reaction torque can be limited to a permissible torque.

[0009] The torque acting on the rotor of the electric motor can result from the drive of the electric motor and the transfer function of the gearbox. In this case, the torque acting on the rotor of the electric motor corresponds to the existing drive torque of the electric motor. The torque acting on the rotor of the electric motor can additionally or alternatively result from an effect on the gearbox. In particular, if an effect occurs on the output side of the gearbox, this is at least partially transmitted to the rotor of the electric motor via the gearbox. Additionally or alternatively, torque pulses acting on the output side of the gearbox can be transmitted to the rotor of the electric motor via the gearbox.

[0010] Furthermore, the torque acting on the rotor of the electric motor can result from the dynamic operating mode of the drive device. In particular, the torque acting on the rotor of the electric motor can result from dynamic operating modes in conjunction with the inertia of the moving elements involved. Thus, the torque acting on the rotor of the electric motor can be subject to significant fluctuations if there are significant speed changes at the electric motor or if speed fluctuations are induced on the output side of the transmission.

[0011] According to one embodiment, the torque limiting assembly may comprise a friction clutch arrangement which may be preloaded by a preloading element such that, when a predetermined maximum torque applied to the torque limiting assembly is exceeded, slippage may be induced in the friction clutch arrangement, so that the torque limiting assembly may permit relative movement between the torque support component and the stationary element.

[0012] The friction clutch assembly can be formed from one or more friction clutch discs. Alternatively, the friction clutch assembly can be formed from one or more conical elements. The friction clutch assembly can be arranged axially symmetrically to an axis of symmetry of the drive device.

[0013] According to one embodiment, the torque support component can be rotationally symmetrical and have at least one radially outward-facing surface section on an outer circumference, which engages with an inner circumference of the stationary element via the outwardly curved contour. The outwardly curved contour of at least one of the radially outward-facing surface sections can be curved radially outwards. Furthermore, the outwardly curved contour of at least one of the axially outward-facing surface sections can be curved axially outwards. The curved contour can be rotationally symmetrical with respect to an axis of symmetry of the torque support component. The curved contour of at least one of the radially outward-facing surface sections can be provided to extend completely around the torque support component.The curved contour of at least one of the radially outward-facing surface sections can have a diameter that varies along the axial direction of the torque support component, with a maximum diameter in the axially central region of the curved contour. The curved contour of at least one of the radially outward-facing surface sections can be rotationally symmetrical with respect to an axis of symmetry of the

[0014] Torque support component. The curved contour of at least one of the radially outward-facing surface sections can be provided completely circumferentially around the torque support component. The curved contour of at least one of the radially outward-facing surface sections can be provided at a corresponding end section of the torque support component. The curved contour of at least one of the radially outward-facing surface sections can be a circular elevation of the surface section, which has an extension varying in the radial direction of the torque support component with a maximum axial extension in the radially central region of the curved contour.

[0015] According to one embodiment, the torque support component can be rotationally symmetrical and at least one radially outwardly facing surface section can be provided on the torque support component, which can engage with a radially inwardly facing surface of a holder of the prestressing element of the torque limiting assembly.

[0016] According to one embodiment, the torque support component can have two radially outwardly facing surface sections on an outer circumference, which can be axially spaced from one another.

[0017] According to one embodiment, the torque support component can extend axially and have at least one axially outwardly facing surface section which can engage with a radial section of the stationary element via the outwardly curved contour.

[0018] According to one embodiment, the torque support component can extend axially and have at least one axially outwardly facing surface portion which can engage with a radial portion of a holder of the prestressing element of the torque limiting assembly via the outwardly curved contour.

[0019] According to one embodiment, two axially outwardly facing surface sections can be provided on the torque support component, which can be provided on the axial end sections of the torque support component.

[0020] According to one embodiment, the outwardly curved contour of at least one of the surface sections can be formed with a predetermined radius of curvature. The predetermined radius of curvature for the curved contour of the radially outwardly facing surface section is a radius of the contour when viewed in a longitudinal section of the torque support component along the axial direction on the outer circumference of the torque support component.The predetermined radius of curvature is for the curved contour of the axially outwardly facing surface section a radius of the contour when viewing a longitudinal section of the torque support component along the axial direction at the axial end section of the torque support component. According to one embodiment, the radii of curvature of the outwardly curved contour can be designed for each surface section with a predetermined radius of curvature, wherein different radii of curvature can be provided at least for the radially outwardly facing surface sections.

[0021] According to one embodiment, the predetermined curvature radius can be designed such that a concentricity deviation between the torque support component and the stationary element can be compensated. According to the present concept, the surface sections with the predetermined curvature radius are not in full contact with a surface into which the surface section engages, thus allowing a certain degree of freedom of movement and preventing tilting of the torque support component. For this purpose, the curvature radii for predetermined dimensions of the drive device can be designed such that tilting of the torque support component can be reduced or prevented. This measure can reliably enable the torque limitation function.

[0022] According to one embodiment, the stationary element can be designed as a housing of the drive device and the torque support component can have an outer ring of the transmission, with which a reaction torque of the transmission can be introduced into the housing.

[0023] According to one embodiment, the transmission can be designed as a shaft transmission with a housing serving as a stationary element, which can have an inner bushing provided with external teeth and coupled to a transmission output element, an outer ring provided with internal teeth, which can be a torque support component of the transmission, and a bushing bearing drivable by the electric motor via an input side of the transmission for circumferentially deforming the inner bushing, wherein the external teeth of the inner bushing can have a smaller number of teeth than the internal teeth of the outer ring, and the circumferential deformation of the inner bushing can cause rotation of the inner bushing relative to the outer ring. According to one embodiment, the output element can be coupled to an output gear that drives at least one driven wheel of the vehicle via a traction means.In this case, a gear change mechanism can be provided between the output gear and the at least one driven wheel of the vehicle, which gear change mechanism is designed to change the gear ratio between the output gear and the at least one driven wheel in stages.

[0024] The traction means may be a chain that is guided over an arrangement of pinions or chainrings. If the traction means is designed as a chain, the gear change mechanism may be formed by a derailleur. The gear change mechanism designed as a derailleur may be provided with adjusting devices that guide the traction means designed as a chain to gears with different numbers of teeth. In particular, the

[0025] The derailleur system on the driven wheel can have a plurality of pinions with different numbers of teeth. Additionally or alternatively, the chain system on the pedal crank can have a plurality of chainrings with different numbers of teeth. By routing the chain to a predetermined combination of pinions or chainrings, the gear ratio between the output gear of the drive system and the driven wheel of the vehicle can be discretely adjusted.

[0026] The gearshift mechanism can alternatively be designed as a hub gear on the driven wheel of the vehicle. In this case, a gear transmission arrangement can be provided in the region of a hub of the driven wheel of the vehicle, with which the transmission ratio between the driven wheel and a drive element connected to the hub gear is discretely variable. In this case, the traction means can be a chain. Alternatively, the traction means can be a belt, including a toothed belt.

[0027] According to one embodiment, a freewheel can be provided in the power transmission path between the transmission output element and the output element. The freewheel between the transmission output element and the output element can be configured such that power can be transmitted from the transmission output element to the output element for driving the vehicle in the forward direction.

[0028] According to a further embodiment, a freewheel can be provided in the power transmission path between the pedal crankshaft output element and the output element. The freewheel between the pedal crankshaft output element and the output element can be designed such that power can be transmitted from the pedal crankshaft output element to the output element for driving the vehicle in the forward direction.

[0029] The vehicle of the aforementioned embodiments can be configured as an e-bike or pedelec. In particular, the vehicle can be configured as a single-track vehicle with a front wheel and a rear wheel. The driven wheel of the vehicle can be the rear wheel. The drive device can be mounted on a frame of the vehicle. The vehicle can further comprise an electrical energy storage device, which can be provided for supplying electrical energy to the drive device. The vehicle can further comprise an operating element with which the driver can operate the gear change mechanism.

[0030] Figure 1 shows a schematic representation of an embodiment of the drive device in a detailed view; and

[0031] Figure 2 shows a schematic representation of the embodiment of the drive device in an overall view.

[0032] In the following, embodiments are described with reference to the drawings.

[0033] Figure 1 is a detailed view of the embodiment shown in Figure 2. First, the basic structure of the drive device is explained with reference to Figure 2. Figure 2 shows a schematic representation of an embodiment of the drive device for a vehicle. In the view shown in Figure 2, the drive device is shown in section along an axis of symmetry. The drive device of Figure 2 has a housing 1, which forms an outer periphery of the drive device. Fastening means designed for fastening the drive device to a vehicle are provided on the housing 1.

[0034] Located within the housing 1 is a crankshaft 2, which extends axially through the housing 1 and protrudes from the housing 1 at both axial ends. The crankshaft 2 is rotatably mounted within the housing 1. Cranks (not shown in Figure 1) are mounted on the crankshaft 2 and are designed to transmit muscle power to the crankshaft 2.

[0035] The pedal crank shaft 2 has a pedal crankshaft output element 12, which in the present embodiment is provided as a radial projection on the pedal crankshaft 2. A first freewheel 13 is provided on the outer circumference of the pedal crank shaft output element 12, with which the pedal crankshaft output element 12 can be coupled to an output element 14 of the drive device. In the present embodiment, the output element 14 is designed as a sleeve-shaped element, on the inner circumference of which the first freewheel 13 is provided.

[0036] The output element 14 is rotatably mounted within the housing 1 and protrudes axially from the housing, as shown in Figure 2. A driven gear 15 designed as a toothed wheel is provided on the output element 14. Rotation of the output element 14 thus causes rotation of the driven gear 15, which is fixedly connected to the output element 14.

[0037] When the pedal crank shaft 2 rotates in a first direction, which is associated with a forward direction of the vehicle, the first freewheel 13 transmits the rotation of the pedal crankshaft output element 12 to the output element 14. Thus, in this case, the output gear 15 rotates due to the rotation of the pedal crank shaft 2 in the direction associated with the forward travel of the vehicle. When the pedal crank shaft 2 rotates in the opposite direction relative to the output element 14, the first freewheel 13 opens and the rotation of the pedal crank shaft 2 is not transmitted to the output gear 15. On the left side in Figure 2, an electric motor is provided in a corresponding cavity of the housing 1. The electric motor has a stator 4, which is mounted stationary to the housing 1. Furthermore, the electric motor has a rotor 3 which is arranged radially outside the stator 4 and which is rotatably supported on the housing 1 via a corresponding bearing.The motor, with the internal stator 4 and the external rotor 3, is thus designed as an external rotor. A control device is provided in the area located to the left of the electric motor in Figure 2. This control device serves to supply current to the stator 4 of the electric motor from an external energy source. When current is supplied to the stator 4, the winding of the stator 4 is energized, causing the rotor 3 of the electric motor to rotate. This rotation of the rotor 3 of the electric motor is transmitted to an output element 5 of the electric motor.

[0038] A gearbox is provided on the right-hand side of the electric motor in Figure 2. In the present embodiment, the gearbox shown in Figure 2 is designed as a shaft gearbox. The shaft gearbox has an inner bushing 7, on the outside of which a toothing is provided. The inner bushing 7 is designed as a sleeve that is flexible in the circumferential direction. An outer ring 8 is arranged outside the inner bushing 7, which in the present embodiment serves as a torque support component. The outer ring 8 has an internal toothing that can selectively engage with the external toothing of the inner bushing 7. In the present embodiment, a bushing bearing 6 is provided within the inner bushing 7. The bushing bearing 6 has an outer ring that deviates from a circular shape. In particular, the outer ring of the bushing bearing 6 is elliptical. The inner ring of the bushing bearing 6 is coupled to the output element 5 of the electric motor.

[0039] When the rotor 3 of the electric motor rotates, the bushing bearing 6 is set in rotation. Due to the non-circular shape of the outer ring 8 of the bushing bearing 6 and its contact with an inner circumference of the inner bushing 7, the inner bushing 7 is deformed circumferentially. As a design typical of a shaft gear, the inner bushing 7 has a number of teeth that is fewer than the number of teeth of the internal toothing of the outer ring 8. Thus, when the outer ring 8 is stationary and when the bushing bearing 6 rotates, the inner bushing 7 is set in rotation. The direction of rotation of the inner bushing 7 is opposite to the direction of rotation of the rotor 3 of the electric motor.

[0040] Due to the special design of the shaft gear, high gear ratios of 1:50 or more can be achieved in compact designs. In this application, an electric motor can be used that has a compact design due to its relatively high rated speeds. In particular, electric motors with a rated speed of 5,000 rpm or higher can be used. The reduced speed due to the gear ratio of the gear is transmitted to a support element 10 of the shaft gear, which is rotatably supported on the housing 1 via bearings.

[0041] A transmission output element 9 is coupled to a support element 10 provided on the outer ring 8 of the shaft gear. The rotation of the support element 10 is transmitted to the transmission output element 9, which is located radially outside the support element 10 of the shaft gear. A reaction torque is exerted on the outer ring 8 as a torque support component, which is transmitted to the housing 1 as a stationary element.

[0042] A second freewheel 11 is provided on the radially outer circumference of the transmission output element 9. The second freewheel 11 lies between the radial outer circumferential surface of the transmission output element 9 and the radial inner circumferential surface of the output element 14 of the drive device. The second freewheel 11 is configured to transmit a rotation of the transmission output element 9 associated with forward travel of the vehicle to the output element 14. A rotation of the transmission output element 9 relative to the output element 14 in a direction of rotation opposite to the direction of rotation associated with forward travel is not transmitted to the output element 14.

[0043] Thus, the rotations of the pedal crankshaft 2 and the transmission output element 9 are combined at the output element 14. In this way, the drive device is designed with a function for combining the muscle power introduced into the pedal crankshaft 2 and the drive force output by the rotor 3 of the electric motor.

[0044] In the present embodiment, the output gear 15 is designed as a chainring of a bicycle drive. The output gear 15, designed as a chainring, carries a chain (not shown) as a traction mechanism, which is provided with a sprocket set (also not shown) on a hub of a rear wheel of the bicycle. In one embodiment, the vehicle has a chain drive system that can guide the chain to sprockets with different numbers of teeth via a derailleur. In the present embodiment, the derailleur is operated by the rider via a control element.

[0045] During operation of the vehicle, the rider can apply muscle power to the drive system via the pedal crankshaft 2, which is then transmitted to the output element 14 via the first freewheel 13. Simultaneously, or at least temporarily, the drive power of the electric motor can also be transmitted to the output element 14 via the transmission shown in Figure 1 and the second freewheel 11. If, in such an operating state, the rider operates the control element to change the position of the chain in order to change the gear ratio between the output gear 15, which is designed as a chainring, and the rear wheel, dynamic speed changes occur and, due to the inertia of the mass-bearing elements, shocks are regularly caused. Furthermore, during operation of the vehicle, for example, when braking or driving on very uneven ground, strong vibrations and shocks arise in the drive train between the output gear 15 and the rear wheel of the vehicle.

[0046] To take these relationships into account, the drive device has a torque limiting assembly 20 shown in Figure 2. In the embodiment of Figure 2, a torque limiting assembly 20 is provided radially outside of the outer ring 8 and radially inside the housing 1. This torque limiting assembly has a friction clutch arrangement 21, a preloading element 22a and a holder 26. In the embodiment of Figure 2, the outer ring 8 is held stationary on the housing 1 via the torque limiting assembly 20 and thus fulfills the function of a torque support component for absorbing the reaction torque during operation of the drive device. The torque limiting assembly 20 has the spring 22, which is housed in the holder 26. The spring 22 according to the present embodiment has a plurality of spring elements. In particular, the spring 22 is formed from a plurality of helical compression springs distributed around the circumference of the spring 22.In an alternative embodiment, a spring 22 made of a single helical compression spring, disc spring, or the like is also conceivable. The holder 26 is mounted on the inner circumference of the housing 1. On the other side, relative to the axial direction, the friction clutch assembly 21 is provided on the outer circumference of the outer ring 8. This assembly consists of several friction clutch elements arranged concentrically around the outer circumference of the outer ring 8.

[0047] The friction clutch elements comprise stationary friction clutch elements that are non-rotatably mounted on the housing 1, and movable friction clutch elements that are fastened to the outer circumference of the outer ring 8. The stationary and movable friction clutch elements are alternately stacked on top of one another. Due to the spring force of the preload element 22, the stationary and movable friction clutch elements of the friction clutch assembly 21 are pressed together, so that up to a certain torque, the outer ring 8 remains stationary relative to the housing 1. If the maximum design torque is exceeded, slippage is generated at the friction clutch assembly 21, so that the stationary and movable friction clutch elements of the friction clutch assembly 21 can rotate relative to one another, and thus the outer ring 8 can rotate relative to the housing 1.

[0048] This ensures that, when a maximum support torque is exceeded, the outer ring 8 can rotate relative to the housing 1. This function ensures that the maximum torque acting on the rotor 3 of the electric motor can be limited.

[0049] Therefore, if the support torque acting on the outer ring 8 exceeds a maximum torque, the torque acting in the power transmission path of the drive device can be limited. In particular, the elements of the drive device's transmission can be protected from overload, thus improving operational reliability. For this purpose, the torque limiting assembly 20, and in particular the spring force of the preload element 22, is designed according to the specifications for protecting the elements used for power transmission in the drive device.

[0050] Figure 1 illustrates the concept of one embodiment of the torque support component. In Figure 1, the torque support component is the outer ring 8. It should be noted that in alternative embodiments, the torque support component is a separate element connected to the outer ring 8.

[0051] As shown in Figure 1, the outer ring 8 has an axial extension and is rotationally symmetrical. On the axial side of the outer ring 8, which is located in the region of the holder 26 of the prestressing element 22, a radially outward-facing surface section 81 has an outwardly curved contour. The curved contour is rotationally symmetrical and runs around the outer circumference of the outer ring 8. As shown in Figure 1, the outwardly curved contour has a radius of curvature R1, which is related to the contour when viewed in an axial longitudinal section of the outer ring. Furthermore, on the axial side of the outer ring 8, which is supported on a radially inwardly projecting section of the housing 1, a radially outward-facing surface section 82 has an outwardly curved contour. The curved contour is also rotationally symmetrical and also runs around the outer circumference of the outer ring 8.As shown in Figure 1, the outwardly curved contour has a radius of curvature R2, which is related to the contour when viewed in an axial longitudinal section of the outer ring. The radii of curvature R1 and R2 are different from each other. In particular, the radius of curvature R2 is smaller than the radius of curvature R1.

[0052] Additionally, surface sections 83 and 84 are provided at the axially opposite end regions of the outer ring 8, which are axially supported on the housing 1 and the holder 26 of the preloading element 22, respectively. These surface sections 83 and 84 also have contours curved outwardly, namely in the axial direction. The curved contours on the axially outward-facing surface sections 83 and 84 each have a radius of curvature R3 and R4, respectively.

[0053] The curved contours on the corresponding surface sections each form circumferential elevations from the surfaces. The outer ring 8 engages with the surface sections 81, 82, 83, 84 in the respective opposite surfaces and is supported accordingly.

[0054] Due to the surface sections provided with the curved contours as contact areas for mounting the outer ring 8, an improved degree of freedom is enabled in the event of possible manufacturing deviations of the elements of the drive device, so that tilting of the outer ring 8 is less likely, in particular if rotation of the outer ring 8 is to occur due to exceeding the maximum permissible torque on the torque limiting assembly 20. With the present embodiment, it can thus be ensured that excessive torque fluctuations, shocks and the transmission of strong torques due to the inertia of the overall system are only limited up to a maximum

[0055] The design value can be transferred to the rotor 3 of the electric motor. This improves the function and durability of the electric motor. At the same time, by designing the outer ring 8 as a torque support component, functional reliability can be improved when the permissible torque in the drive system is exceeded.

[0056] In the present embodiments, the drive device is applied to a bicycle configured as an e-bike or pedelec. In alternative embodiments, the drive device is applied to a multi-track vehicle, in particular to a vehicle with three or four wheels. Reference numerals

[0057] 1 housing

[0058] crankshaft

[0059] Rotor electric motor

[0060] Stator electric motor

[0061] 5 Output element electric motor

[0062] 6 bush bearings shaft gear

[0063] 7 Inner bushing shaft gear

[0064] 8 Outer ring (torque support component)

[0065] 9 Gearbox output element

[0066] 10 Support element shaft gear

[0067] 11 second freewheel

[0068] 12 T crankshaft output element

[0069] 13 first freewheel

[0070] 14 Output element

[0071] 15 Output gear

[0072] 20 Torque limiting assembly

[0073] 21 Friction clutch arrangement

[0074] 22 Preload element

[0075] 26 holders

[0076] 81 area section

[0077] 82 area section

[0078] 83 area section

[0079] 84 area section

[0080] R1-R4 radius of curvature

Claims

Patent claims 1 . Drive device for a vehicle, with - an electric motor (3, 4) for at least temporarily driving the vehicle by supplying electrical power to the electric motor (3, 4), a pedal crankshaft (2) for absorbing muscle power for at least temporarily driving the vehicle by muscle power and an output element (14) via which drive power for driving the vehicle can be output from the drive device; - a transmission with a predetermined transmission ratio, which is coupled on the input side to an output element (5) of the electric motor (3, 4) and which can be coupled on the output side via a transmission output element (9) to the output element (14) of the drive device; - a pedal crankshaft output element (12) coupled to the pedal crankshaft (2) and which can be coupled to the output element (14) of the drive device; wherein the drive device has a torque limiting assembly (20) which is designed to limit a torque acting in the power transmission path between the electric motor (3, 4) and the output element (14), wherein when a predetermined maximum torque is exceeded by the torque limiting assembly (20), a rotation of a torque support component relative to a stationary element of the drive device is permitted, so that the torque acting on the rotor (3) of the The torque acting on the electric motor (3, 4) is limited to a permissible torque, wherein at least one of the axially and radially outwardly facing surface sections (81; 82; 83; 84) of the torque support component is designed with an outwardly curved contour.

2. Drive device according to claim 1, characterized in that the torque support component is coupled to a housing (1) of the drive device for supporting a reaction torque, wherein the torque limiting assembly (20) is provided in the force transmission path between the torque support component and the housing (1) in order to limit the support torque to a predetermined maximum support torque.

3. Drive device according to claim 2, characterized in that when the predetermined maximum support torque is exceeded by the torque limiting assembly (20), a rotation of the torque support component of the transmission (3, 4) relative to a stationary element is permitted, so that the torque acting on the rotor (3) of the electric motor (3, 4) due to the reaction torque is limited to a permissible torque.

4. Drive device according to one of the preceding claims, characterized in that the torque limiting assembly (20) has a friction clutch arrangement (21) which is prestressed by a prestressing element (22) such that when a predetermined maximum torque applied to the torque limiting assembly (20) is exceeded, a slip in the friction clutch arrangement (21) is brought about, so that a relative movement between the torque support component and the stationary element is permitted by the torque limiting assembly (20).

5. Drive device according to one of the preceding claims, characterized in that the torque support component is rotationally symmetrical and has on an outer circumference at least one radially outwardly facing surface section (81, 82) which engages with an inner circumference of the stationary element via the outwardly curved contour.

6. Drive device according to one of the preceding claims, characterized in that the torque support component is rotationally symmetrical and at least one radially outwardly facing surface section (81) is provided on the torque support component, which engages with a radially inwardly facing surface of a holder (26) of the pretensioning element (22) of the torque limiting assembly (20).

7. Drive device according to claim 5 or 6, characterized in that the torque support component has on an outer circumference two radially outwardly facing surface sections (81, 82) which are axially spaced from one another.

8. Drive device according to one of the preceding claims, characterized in that the torque support component extends axially and has at least one axially outwardly facing surface section (83) which engages with a radial section of the stationary element via the outwardly curved contour.

9. Drive device according to one of the preceding claims, characterized in that the torque support component extends axially and has at least one axially outwardly facing surface section (84) which engages via the outwardly curved contour with a radial section of a holder (26) of the pretensioning element (22) of the torque limiting assembly (20).

10. Drive device according to claim 8 or 9, characterized in that on the torque support component two axially outwardly pointing Surface sections (83, 84) are provided which are provided at the axial end sections of the torque support component.

11. Drive device according to one of claims 5 to 10, characterized in that the outwardly curved contour of at least one of the surface sections (81, 82, 83, 84) is formed with a predetermined radius of curvature (R1, R2, R3, R4).

12. Drive device according to one of the claims Claim 11, characterized in that the radii of curvature of the outwardly curved contour are designed for each surface section with a predetermined radius of curvature, wherein different radii of curvature are provided at least for the radially outwardly facing surface sections (81, 82).

13. Drive device according to claim 11 or 12, characterized in that the predetermined radius of curvature is designed such that a concentricity deviation between the torque support component and the stationary element can be compensated.

14. Drive device according to one of the preceding claims, characterized in that the stationary element is designed as a housing (1) of the drive device and the torque support component has an outer ring (8) of the transmission, with which a reaction torque of the transmission can be introduced into the housing.

15. Drive device according to one of the preceding claims, characterized in that the transmission is designed as a shaft transmission with a housing (1) serving as a stationary element, which has an inner bushing (7) provided with external teeth and coupled to a transmission output element (9), an outer ring (8) provided with internal teeth, which is a torque support component of the transmission, and a bushing bearing (6) drivable by the electric motor (3, 4) via an input side of the transmission for the circumferential deformation of the inner bushing (7), wherein the external teeth of the inner bushing (7) have a smaller number of teeth than the internal teeth of the outer ring (8) and the circumferential deformation of the inner bushing (7) causes a rotation of the inner bushing (7) relative to the outer ring (8).

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