Drive device, bicycle and method for operating same

Abstract

The invention relates to a drive device (18) for an electromotively driven bicycle (10), having an electromotive drive means (20), in particular an electric motor (26), and a transmission means (22), wherein a torque acting on a drive shaft (14) of the bicycle (10) can be transmitted by the transmission means (22) to an output shaft (16) of the bicycle (10), and wherein the torque can be at least partially generated by the drive means (20) and transmitted to the drive shaft (14). According to the invention, the drive means (20) and the transmission means (22) are located in a common housing (24).

Description

[0001] Drive device, bicycle and method for its operation

[0002] The invention relates to a drive device for a motor-driven bicycle according to the preamble of claim 1. The invention further relates to a motor-driven bicycle with such a drive device. In addition, the invention relates to a method for operating the drive device and / or the bicycle.

[0003] STATE OF THE ART

[0004] A drive device of the type mentioned above, intended for a motor-driven bicycle, is described in US Patent 2017 / 0291661 A1. It comprises a transmission unit designed as a fluid transmission, which provides a continuously variable transmission ratio, and a motor drive unit, the latter and the fluid transmission being arranged in a common housing in some embodiments. However, US Patent 2017 / 0291661 A1 is silent regarding the design and specific function of the fluid transmission.

[0005] Further drive devices in which a drive unit and a gearbox unit are arranged in a common housing are known from the publications DE 102018001 795 A1, DE 196 12 519 A1 and DE 102005009821 B3.

[0006] Drive devices of the type mentioned above, or corresponding electrically driven bicycles having such a drive device, are generally known from the prior art.

[0007] Such a bicycle is typically an e-bike, which uses an electric motor as a power assist. The electric motor generates torque that assists or completely propels the e-bike. The e-bike also has a transmission system that, depending on the operating conditions (for example, when riding uphill), translates the torque and the associated rotational speed of a shaft set in motion by the electric motor in a known manner to ensure optimal propulsion. A pedelec can be considered a subcategory of e-bikes. A pedelec is a type of electric bicycle with pedal assist. It is powered neither solely by muscle power nor solely by electric motor.

[0008] ASA-8791 WO

[0009] March 17, 2026: This is not solely mechanically powered, but a combination of both drive types. When the rider pedals, they are assisted by the built-in motor. When the rider stops pedaling, the motor also stops; these are referred to as bicycles with electric pedal assist.

[0010] The invention relates to an improvement of previously known e-bikes and pedelecs.

[0011] Currently, the vast majority of e-bikes and pedelecs feature a separate arrangement of the electric motor and the gearbox. Typically, a mid-drive motor powers a gearbox located at or connected to the rear wheel / axle. Alternatively, there are also vehicles with an integrated electric motor in the rear wheel hub and a separate gearbox behind it, which remains structurally separate from the electric motor and can be operated independently.

[0012] A disadvantage of this design is the relatively high space requirement and assembly effort, as certain mounting areas must be kept clear for the gearbox and electric motor, and their mechanical coupling is comparatively complex and therefore time-consuming. Furthermore, there is a considerable susceptibility to malfunctions / damage, especially in the case of the gearbox, which is usually unprotected or only covered by a plate on the bicycle.

[0013] In most cases, the transmission concepts used in this context employ a familiar chain or hub gear system to transmit torque and select a gear ratio. Alternatively, hub gears with defined gears or shaft-driven gearboxes are also available. More recent transmission concepts include continuously variable transmissions (CVTs) with a gearbox located at the rear wheel. These CVTs are typically mechanical transmissions in various designs, such as a belt-driven CVT (e.g., a Variomatic) with conical pulleys and a V-belt drive.

[0014] Well-known CVT transmissions, which are also used in mopeds and scooters, have several disadvantages. For example, the possible gear ratio range is rather narrow compared to derailleur gears, and the required installation space is comparatively large. Furthermore, there are efficiency disadvantages due to friction and heat losses. In addition, the transmissible drive torque is inherently lower than with derailleur gears.

[0015] ASA-8791WO

[0016] March 17, 2026. Shaft-driven transmissions, as commonly used in motorcycles, also have several disadvantages. Compared to derailleur systems, these transmissions require a significantly higher number of parts and a large amount of installation space. This results in high manufacturing and material costs. Shaft transmissions are comparatively heavy, and by design, shifting is not possible with stationary shafts. This means that on e-bikes, shifting is not possible when stationary or with the drive shaft not actively driven, such as when going downhill or without pedaling. Continuously variable shifting is not possible, and regular maintenance is required, particularly in the form of changing the lubricant necessary for operation.

[0017] Chain-driven gearboxes, as commonly found on bicycles, remain the dominant type of drivetrain for bicycles and e-bikes. These are characterized by relatively simple technology, low weight, and a wide gear range. Manufacturing costs are also relatively low. However, a disadvantage is the comparatively high wear of the components (especially chains and sprockets). Furthermore, they require significant maintenance and adjustment due to their rather sensitive mechanics, which can malfunction even with minor impacts. To date, chain-driven gearboxes are generally mounted on the rear wheel, with few exceptions, and are therefore positioned off-center from the motor.

[0018] The object of the invention is to provide an improved solution for drive devices and bicycles with regard to the disadvantages discussed above.

[0019] This problem is solved by a drive device, a bicycle, and a method according to the independent claims. Advantageous embodiments of the invention are the subject of the dependent claims, the description, and the drawings.

[0020] REVELATION OF THE INVENTION

[0021] The invention relates to a drive device for a bicycle that is at least partially driven by a motor, in particular an electric motor. The drive device comprises a motor drive unit and a transmission unit. The transmission unit enables the torque acting on a drive shaft of the bicycle to be transmitted to an output shaft of the bicycle. The drive unit allows the torque to be at least partially generated and transmitted to the drive shaft. In particular, the drive unit is designed as an electric motor, but it can also be designed, for example, as an internal combustion engine or similar. In the present invention, the term "transmission" in connection with torque refers to the conversion, scaling, and transmission of the torque.

[0022] ASA-8791WO

[0023] 17.03.2026 Torque, in particular a related rotational speed of the input and / or output shaft, in a selectable transmission ratio.

[0024] Furthermore, the transmission unit is designed as a hydraulically operated fluid transmission, enabling a continuously variable transmission ratio. The drive unit and the transmission unit are also arranged in a common housing. The transmission unit is thus integrated into the drive unit. In other words, the drive unit and the transmission unit are located in the same housing, so that the drive unit and the transmission unit are combined into a single (independently manageable) unit. The transmission unit and the drive unit are essentially directly coupled to each other.

[0025] According to the invention, the fluid transmission comprises a sealed fluid chamber filled with hydraulic fluid, wherein an actuator is arranged within the fluid chamber, dividing the total volume of the fluid chamber into a first partial volume and a second partial volume. The actuator thus divides the fluid chamber into an inlet chamber, or first partial volume, and an outlet chamber, or second partial volume. The actuator is arranged, preferably within the fluid chamber, to be displaceable, preferably longitudinally displaceable, such that the partial volumes can be continuously varied. It is provided that the aforementioned partial volumes are connected to each other (fluidically) by a compensating line, so that when the actuator is moved, the hydraulic fluid is equalized between the partial volumes.In the first sub-volume, at least one fluid actuator associated with the drive shaft is arranged, and in the second sub-volume, at least one further fluid actuator associated with the output shaft is arranged.

[0026] This allows the transmission ratio of the fluid transmission to be continuously adjusted. The compensating line ensures that the hydraulic fluid can flow from the first sub-volume into the second sub-volume and vice versa when displaced by the actuator. The total volume of hydraulic fluid in the divided fluid chamber remains constant, but the flow rate of hydraulic fluid to be delivered by each actuator varies depending on the size of the corresponding sub-volume, which is determined by the actuator's displacement.

[0027] Furthermore, it should be mentioned that combining the drive unit and fluid transmission into a single, integrated drive-transmission unit advantageously reduces the complexity of the entire drive system. The necessary interfaces for connecting the components, which are typically located at different positions on the bicycle, are also eliminated.

[0028] ASA-8791WO

[0029] March 17, 2026: The drive unit and fluid transmission are advantageously reduced in size. Typically, there is a mounting point for the drive unit around the bottom bracket area, as well as a suitable mount for a derailleur or internal gear hub on the rear triangle of the bicycle. Furthermore, bicycles with conventional derailleur gears are usually equipped with guides and clamps for shift cables. With the integrated design of the drive unit and transmission, only one mounting location is required for both components. The derailleur mount and related peripherals at the rear of the bicycle can also be eliminated. The optional integration of a freewheel function into the drive-transmission unit further simplifies and lightens the rear hub, as the freewheel mechanism can be omitted.The increased installation space at the rear wheel allows manufacturers of such bicycles to use wider, and therefore more durable and cost-effective, chains, or to utilize a belt drive as the interface to the rear wheel. Furthermore, this offers the additional advantage of reduced initial assembly and maintenance costs. Bicycle manufacturers typically source individual components from subcontractors. Delivering a single, manageable drive-gear unit reduces logistics and assembly effort, particularly because the integration of the drive system and fluid transmission into a single unit centralizes the bicycle's essential drive components. Advantageously, this also requires less installation space than conventional, decentralized gearbox and drive units.Furthermore, in the case of the drive-gearbox unit being installed as intended, the center of gravity of the bicycle shifts further towards the center of the vehicle, which contributes positively to the driving dynamics.

[0030] Fluid transmissions transfer energy by means of a flowing fluid, in particular an incompressible fluid, and are also known as hydraulic transmissions. In this process, an input mechanical power is converted into the specific energy of a mass flow and then back into a mechanical form at the output. Typically, a drive shaft sets an internal fluid in motion, which in turn drives an output shaft. Preferably, the fluid transmission is designed as a hydrostatic or hydrodynamic fluid transmission. In particular, the fluid transmission comprises at least one fluid actuator in the form of a hydraulic pump and / or a hydraulic motor, especially a positive displacement pump with an impeller or compressor wheel, or a gear pump / gear motor. Alternatively, the hydraulic pump or hydraulic motor can also be designed as a vane pump, axial, radial, or reciprocating pump.In particular, a fluidically closed circuit combination of two fluid actuators of the same design, or possibly of different designs, is conceivable, whereby stepless adjustability can be provided by changing the size of the fluid volumes or fluid chambers of the drive and / or driven actuator. A corresponding hydraulic fluid of the...

[0031] ASA-8791WO

[0032] March 17, 2026. Fluid transmissions can be liquid or gaseous. Advantageously, compared to conventional chain or hub gears for bicycles, fluid transmissions require significantly fewer components. The continuously variable transmission also advantageously allows shifting while stationary and can make gear ratio adjustments or shifts much faster than the other previously mentioned transmission types. The gear ratio change is preferably made by an actuator, particularly an electrically controlled one, which only has to overcome the frictional resistance within the hydraulic fluid. Chain rotations are therefore no longer necessary for a shifting process; the gear ratio change can occur at any time. Hydraulic fluid transmissions are advantageously much cheaper to manufacture than other transmission types, including continuously variable transmissions such as shaft transmissions.Due to the significantly smaller number of components, the fluid transmission is advantageously lighter than other transmissions, especially shaft transmissions. This makes riding easier and more comfortable for the user, particularly since active shifting is no longer necessary. The user benefits from a continuously variable transmission that always selects the correct gear and, for example, automatically downshifts when stationary, adjusts the gear ratio to the desired speed, or maintains a constant cadence across the entire speed range. Maintenance and robustness against misuse are increased compared to conventional derailleur systems. By integrating all relevant drive components (drive unit, transmission unit, freewheel, crank) within the drive-transmission unit, decentralized shifting components are eliminated.Particularly vulnerable derailleur systems with a rear-mounted derailleur are very sensitive to impacts, which can impair shifting performance. The option of using a belt drive reduces maintenance for the customer, as belts are less prone to wear than chains. Another advantage is that the integrated fluid transmission requires less maintenance over the typical lifespan of an e-bike compared to conventional derailleur systems. The hydraulic fluid transmission has very few components that are subject to mechanical contact or friction. These components can be designed to be sufficiently robust (e.g., the roller bearings). The remaining components are hydraulically mounted and therefore only experience fluid friction.

[0033] It is conceivable that the common housing is filled with hydraulic fluid from the fluid transmission, so that the drive unit, in particular an electric motor, is surrounded by the hydraulic fluid. This provides fluid cooling for the drive unit and simultaneously lubrication of all moving parts, thereby reducing sealing requirements, cooling problems, and minimizing the number of parts and component sizes.

[0034] ASA-8791WO

[0035] 17.03.2026Furthermore, it may be provided that the drive shaft and the output shaft are connected to each other, at least indirectly, through the aforementioned fluid chamber for the purpose of transmitting the torque.

[0036] In this case, adjusting the transmission ratio of the fluid transmission preferably comprises an initial adjustment during first commissioning, as well as subsequent adjustments during normal operation. Advantageously, the fluid transmission is designed with few components, making it more robust and less prone to failure. The achievable transmission range is advantageously much larger than that of other commonly used transmission types. The transmission ratio depends solely on the ratio of the chamber size / length of the input to the output side. Since the chamber size is limited only by the positioning tolerance of the actuator, transmission ranges exceeding 1000% are easily achievable.

[0037] It is conceivable to automatically adjust the transmission ratio, for example, based on an adjustable drive power, using the actuator. Thus, the actuator can independently adjust the appropriate transmission ratio via a self-regulating system – even without an active positioning device. In contrast, and according to a preferred embodiment, the actuator can be coupled to a positioning device for adjusting the transmission ratio, allowing the actuator to be moved. Preferably, the positioning device is electrically driven and / or the actuator can be moved automatically. Alternatively, manual adjustment is also possible, for example, using a manually adjustable slide as the positioning device.Advantageously, the use of the actuator for the shifting processes not only enables stepless automatic operation, but also allows the user to individually adjust the number and gear ratios of the individual gears.

[0038] According to a preferred further development, the actuating device can be operated automatically, allowing the gear ratio to be adjusted automatically. In particular, the actuating device can be controlled via an app. This advantageously makes switching or adjusting the gear ratios particularly convenient. Preferably, the gear ratio is automatically optimized or adjusted depending on the prevailing operating conditions. Furthermore, the user is offered a convenient, independent option, especially via the app's user interface, to select the number of gears and the desired gear ratios for each gear. The software translates the

[0039] ASA-8791WO

[0040] 17.03.2026 user-selected configuration in positioning positions of the actuator and thus in the necessary ratio of input chamber length to output chamber length.

[0041] Furthermore, the actuating device can be controlled via an app. The invention uses the term "app" as a common abbreviation for "application software." This app is preferably executable by a user on a mobile device, in particular a smartphone, smartwatch, or the like, and / or configured in such a way that it allows the user to adjust the transmission ratio of the fluid transmission via the aforementioned actuating device.

[0042] According to a preferred embodiment, the drive device may have at least one or more sensors configured to detect parameters relevant to the operation of the drive device, with the transmission ratio being optimally adjustable based on these parameters. In particular, said parameters include cadence, a user's heart rate, and / or operating efficiency. Preferably, the parameters include the user's power output and / or physiological values. Physiological values ​​are preferably the user's vital signs, such as blood pressure, heart rate (pulse), respiratory rate, body temperature, or blood oxygen saturation. A control unit, particularly one integrated into an app, for processing the sensor data and controlling the fluid transmission is also included.Its adjustment mechanism is preferably included. Advantageously, this allows the translation ratio to be individually adapted and optimized for the respective user.

[0043] According to a preferred embodiment, the fluid transmission can provide, or at least form, a cooling circuit for cooling the drive unit. In particular, a hydraulic fluid of the fluid transmission and / or a hydraulic line carrying the hydraulic fluid is at least partially thermally coupled to the drive unit. For example, components of the fluid transmission carrying the hydraulic fluid can be wound around the drive unit or the corresponding motor for heat dissipation, or at least be in sufficient contact / thermal coupling with it. The thermal coupling can be direct (hydraulic fluid in direct contact with the drive unit) or indirect (fluid line in contact with the drive unit). Advantageously, this provides an efficient and cost-effective method for cooling the drive unit.The maximum power output of electric motors used as drive devices is generally limited by the temperature of the corresponding copper windings. In the case of the present drive...

[0044] ASA-8791WO

[0045] March 17, 2026: The gearbox unit, due to its integration within the entire motor compartment, provides the necessary fluid for the hydraulic fluid transmission, thus enabling significantly improved thermal contact with the copper winding. This advantageously allows for an increase in maximum motor power while reducing the motor size for the same power output, resulting in further cost savings and reduced manufacturing effort.

[0046] According to a preferred further development, the drive device can be provided with an immobilizer function. Advantageously, this provides theft protection.

[0047] According to a preferred embodiment, the immobilizer function can be achieved by manually or automatically blocking the fluid transmission, particularly when the drive unit is switched off. For blocking, the actuator is arranged such that one of the two partial volumes of the fluid chamber is as small as possible and the other partial volume as large as possible. In this way, the fluid transmission can advantageously be "blocked" or "decoupled" from the drive unit, preventing the bicycle from being driven away and thus effectively preventing potential theft. When the bicycle is parked and the drive unit is switched off, the actuator reduces the length of either the inlet or outlet chamber to or close to zero. This results in a neutral position or a driving force that cannot be overcome by a person (transmission ratio towards infinity or zero), thus advantageously providing effective theft protection.

[0048] In a secondary aspect, the invention relates to a motor-driven, in particular electric, bicycle with a drive shaft, in particular a pedal axle, an output shaft, in particular a rear wheel axle, and a drive device according to the invention. The advantages already mentioned above arise in this respect.

[0049] According to a preferred embodiment, the drive device can be arranged, at least for the most part, in the area of ​​a center of gravity of the bicycle, in particular in the area of ​​a pedal bearing on a bicycle frame, or in the area of ​​a rear wheel hub of the bicycle. Advantageously, this improves the riding dynamics.

[0050] In a further, subordinate aspect, the invention relates to a method for operating the drive device and / or a bicycle, in particular the bicycle described above, according to the invention. It is provided that the transmission ratio can be adjusted by moving a longitudinally displaceable actuator within a closed fluid chamber, through which the

[0051] ASA-8791WO

[0052] March 17, 2026: The total volume of the fluid chamber is divided into two sub-volumes, and the relative volumes of these sub-volumes are adjusted accordingly. This results in the advantages already mentioned previously.

[0053] According to a preferred embodiment, the drive unit and the transmission unit can be essentially directly coupled by being arranged in a common housing and combined into a single, independently manageable unit. This results in the advantages already mentioned above.

[0054] According to a preferred embodiment, the transmission device can be hydraulically operated as a fluid transmission, with a continuously variable transmission ratio. In particular, a hydraulic fluid is conveyed, at least partially, by means of at least one fluid actuator, especially a pump impeller designed as an internal gear pump / motor within the fluid transmission. Advantageously, a hydraulic pump and a hydraulic motor can be connected in series in a closed hydraulic circuit with variable chamber volumes or hydraulic flows, and these pumps can be of the same or different designs, such as gear, vane, axial, radial, or reciprocating pumps / motors. The advantages already mentioned in this regard result, with the fluid actuator providing a cost-effective, mechanically robust, and efficient solution for conveying the hydraulic fluid.

[0055] According to a preferred further development, the actuator can be moved by an actuating device, particularly one driven by a motor. Specifically, the actuating device is operated automatically, and the gear ratio is adjusted automatically. This results in the advantages already mentioned above.

[0056] According to a preferred further development, the actuator can be controlled by an app. In particular, the gear ratio is individually set by a user, preferably via the app. This enables a customizable shift gradation, which can also be pre-configured as a profile, e.g., for mountainous, hilly, or flat terrain, or for gentle or challenging terrain. Preferably, additionally or alternatively, parameters relevant to the operation of the drive device, in particular speed, cadence, heart rate of a user, and / or operating efficiency or weather conditions (temperature, road wetness), and / or power output of a user, and / or physiological values ​​of a user, are recorded by at least one sensor, and the gear ratio is optimized based on these parameters. This results in the advantages already mentioned above.

[0057] ASA-8791WO

[0058] March 17, 2026. According to a preferred embodiment, the drive unit can be cooled at least partially by a hydraulic fluid of the fluid transmission, in particular wherein the drive unit, especially a copper winding of the drive unit, is directly or indirectly exposed to the hydraulic fluid at least in certain areas. The advantages mentioned above in this regard result.

[0059] According to a preferred embodiment, an immobilizer function can be provided by manually or automatically, in particular when the drive unit is switched off, causing a blockage of the transmission unit, whereby the actuator is arranged such that one of the two partial volumes is minimized and the other maximized, so that the transmission ratio is reduced to 0 or 00The position will be discontinued. The advantages already mentioned in advance will result.

[0060] DRAWINGS

[0061] Further advantages become apparent from the accompanying drawing description. The drawings illustrate exemplary embodiments of the invention. The drawing, the description, and the claims contain numerous features in combination. A person skilled in the art will expediently consider the features individually and combine them into meaningful further combinations.

[0062] They show:

[0063] Fig. 1 A highly simplified schematic representation of an electrically driven bicycle with an advantageous drive device,

[0064] Fig. 2 shows a schematic representation of the drive device.

[0065] Fig. 3 shows a simplified perspective view of a gear unit of the drive device, and

[0066] Fig. 4 shows a schematic representation of the operating principle of the transmission device.

[0067] In the figures, similar elements are numbered with the same reference symbols. The figures merely show examples and are not to be understood as limiting.

[0068] Figure 1 shows in a highly simplified schematic representation an advantageous bicycle 10, which in this case is designed as an electrically driven bicycle 10 or e-bike.

[0069] ASA-8791WO

[0070] March 17, 2026. The bicycle 10 comprises the components common to known bicycles, such as a frame, steering mechanism, front and rear wheels, etc., which are not shown in detail here for the sake of clarity. In order to set the bicycle 10 in motion during its intended operation, or to generate the torque necessary for propulsion, the bicycle 10 has, as further components, a pedal mount 12 or bicycle pedals, which are transmitted via a drive shaft 14 (here called the pedal axle) and an output shaft 16 (not shown, here called the rear wheel axle) to at least one of the wheels of the bicycle 10 (here called the rear wheel).

[0071] To assist the user in generating torque, i.e., to generate the torque at least partially, and in particular completely, the bicycle 10 further comprises an advantageous drive device 18, which, according to the present embodiment, is arranged in a central region of the bicycle 10. The drive device 18 comprises an electric motor drive unit 20 and a transmission unit 22. In the present embodiment, the drive unit 20 and the transmission unit 22 are advantageously arranged in a common housing 24.

[0072] The drive unit 20 is, in this case, an electric motor 26, but alternatively also an internal combustion engine or similar, by which the torque can be generated, at least partially, and transmitted to the drive shaft 14. The transmission unit 22, as will be explained in more detail later, is designed as a hydraulically operated fluid transmission 28. By means of the fluid transmission 28, the torque acting on the drive shaft 14 can be transmitted to the output shaft 16 and converted. This conversion includes, among other things, a transformation or scaling of the torque, in particular of the associated rotational speed of the drive shaft 14.

[0073] Figure 2 shows a highly simplified schematic representation of the drive device 18.

[0074] As previously discussed, all components of the drive device 18 are arranged together in the housing 24, so that the drive device 18, in particular its drive unit 20 and gearbox 22, is designed as a single, easily handled structural unit. The drive shaft 14 can be mechanically connected to the pedal receptacle 12, allowing a user to generate torque by operating the pedal receptacle 12 and thereby set the drive shaft 14 in rotation at a definable speed. Alternatively, a motorized drive without pedal assistance can also be provided. The drive unit 20 or the electric motor 26 is operatively connected to the drive shaft 14 via a spur gear 30 to provide the user with assistance when generating torque, if required.

[0075] ASA-8791WO

[0076] 17.03.2026 to support or even completely generate the torque. Thus, the torque acting on the drive shaft 14, or its speed, can be generated jointly by the electric motor 26 and the user operating the pedal 12.

[0077] As previously mentioned, the transmission device 22, or fluid transmission 28, enables the transmission of torque to the output shaft 16, which is rotatably mounted on ball bearings 32 and connected to the wheel of the bicycle 10 via an output pinion 33. The fluid transmission 28 is designed to convert the speed or torque of the drive shaft 14 to the output shaft 16 as required, i.e., to transform and / or scale it. The corresponding transmission ratio of the fluid transmission 28 is advantageously continuously adjustable, as will be discussed in more detail later.

[0078] The fluid transmission 28 comprises a closed transmission housing 34 arranged within the common housing 24, in which the individual components of the fluid transmission 28 are arranged. These components include at least one, in this case two, fluid actuators, at least two retaining rings 36 associated with the fluid actuators, at least one seal 38, and at least two limiting sleeves 40. Each fluid actuator is designed in two parts, with an outer and an inner fluid actuator configured as a hydraulic pump and as a hydraulic motor fluidically connected in series with it, and associated with a corresponding drive shaft 14 and the output shaft 16. Thus, the fluid transmission 28, as a fluid actuator, preferably as a positive displacement pump, for example as an internal gear pump with a compressor wheel or impeller, comprises an inner drive actuator 42 and an outer drive actuator 44, as well as an inner output actuator 46 and an outer output actuator 48.

[0079] The fluid transmission 28, enclosed within its housing 34, features a closed fluid chamber 50 filled with hydraulic fluid. This chamber connects the input shaft 14 and the output shaft 16 indirectly via fluid actuators 42-48 to transmit torque. To adjust the transmission ratio, the fluid transmission 28 includes an actuator 52, either located within or partially integrated into the fluid chamber 50. This actuator divides the fluid chamber 50 into two sub-chambers, or subdivides the total volume of the fluid chamber 50 into two volumes. The actuator 52 is movable within the fluid chamber 50 by an actuating unit 54 (in this case, an electrically adjustable actuating unit 54) such that the volumes of the sub-chambers can be continuously adjusted relative to each other. By changing the volumes of these sub-chambers, the transmission ratio can be continuously adjusted.

[0080] Figure 3 shows a perspective cross-sectional view of the fluid transmission 28.

[0081] ASA-8791WO

[0082] March 17, 2026. As previously discussed in detail with reference to Figure 2, the fluid chamber 50 formed inside the gearbox housing 34 is divided into two sub-volumes by the actuator 52. Each of these sub-volumes is assigned one of the two fluid actuators 42-48. In this case, the fluid gearbox 28 is connected to the drive shaft 14 on the left side in Figure 3, so that the inner drive actuator 42 and the outer drive actuator 44 are arranged in the left sub-volume. On the right side in Figure 3, the fluid gearbox 28 is connected to the output shaft 16. Accordingly, the inner output actuator 46 and the outer output actuator 48 are arranged in the right sub-volume. Both fluid actuators 42-48 are held in position by the retaining rings 36, and the sub-volumes are further closed off by the limiting sleeves 40.

[0083] The following section will discuss the operating principle of the fluid transmission 28 in more detail with reference to the three individual illustrations A, B, and C shown in Figure 4. Figure 4 shows a highly simplified schematic representation of the fluid transmission 28 in its three illustrations.

[0084] In each of the three individual diagrams A, B, and C, the previously mentioned partial volumes of fluid chamber 50 are schematically depicted. Thus, the three diagrams each show the first partial volume 56 and the second partial volume 58 of fluid chamber 50, with one of the two fluid actuators 42-48 arranged in each of the partial volumes 56 and 58, respectively. The partial volumes 56 and 58 are connected to each other by a compensating line 60, enabling the necessary equalization of the hydraulic fluid when the actuator 52 is moved. In other words, the compensating line 60 allows the hydraulic fluid to flow from the first partial volume 56 into the second partial volume 58 and vice versa when displaced by the actuator 52.Thus, the total volume of the hydraulic fluid in the subdivided fluid chamber 50 always remains constant, but the delivery volume of the hydraulic fluid to be delivered by the fluid actuators 42 - 48 varies depending on the size of the corresponding subvolume 56, 58 determined by the displacement of the actuator 52.

[0085] In illustration A of Figure 4, the transmission ratio is set to 1:2, meaning that the torque L1 acting on the drive shaft 14, or its rotational speed, is doubled when L2 is transmitted to the output shaft 16. Accordingly, the first partial volume 56 assigned to the drive shaft 14 is only half the size of the second partial volume 58 assigned to the output shaft 16. This results in the hydraulic fluid volume to be delivered by the fluid actuators arranged in the second partial volume 58—namely, the inner output actuator 46 and the outer output actuator 48—being twice as large as that delivered by the first partial volume 56.

[0086] ASA-8791WO

[0087] March 17, 2026. Partial volume 56 arranged by the fluid actuator, i.e., the inner drive actuator 42 and the outer drive actuator 44, determines the delivery volumes to be conveyed. This difference in the size of the partial volumes 56, 58, or the amount of hydraulic fluid to be conveyed by the respective fluid actuators 42-48, advantageously enables efficient torque conversion and a continuously adjustable transmission ratio.

[0088] In illustration B, the transmission ratio is 1:1, meaning that the torque or speed L1 is transmitted essentially unchanged as L2 from the input shaft 14 to the output shaft 16. Accordingly, the two partial volumes 56 and 58 are equal, so the respective hydraulic fluid delivery volume to be pumped by the corresponding fluid actuators 42–48 is also the same.

[0089] In illustration C of Figure 4, unlike illustration A, the transmission ratio is 2:1, meaning that the torque or speed L1 is halved when converted to L2 from the input shaft 14 to the output shaft 16. Accordingly, the first partial volume 56 is twice the size of the second partial volume 58. For further details, refer to the previous discussions.

[0090] Optionally, the fluid transmission 28 can provide, or at least partially form, a cooling circuit for cooling the electric motor 26. Due to the arrangement of the electric motor 26 and the fluid transmission 28 in the common housing 24, they are located relatively close to each other, so that the hydraulic fluid of the fluid transmission 28 can be thermally coupled to the electric motor 26 relatively easily in order to dissipate the heat generated by the electric motor 26 during operation. For example, the hydraulic fluid can flow around the electric motor 26, in particular around the compensating line 60 of the fluid chamber 50, which in this case surrounds the electric motor 26, at least partially.

[0091] Optionally, the actuating device 54 can be operated automatically for the automatic adjustment of the gear ratio, in particular using an app installed on an external device, such as a smartphone. In this case, a user can individually define the desired gear ratio, especially the number of different gears and their respective scaling, according to their needs. Based on this setting, the actuating device 54 can move the actuating actuator 52 accordingly to adjust the partial volumes 56, 58 of the fluid chamber 50.

[0092] ASA-8791WO

[0093] 17.03.2026Optionally, at least one sensor may be included for recording parameters relevant to the operation of the drive demand device 18, such as speed, cadence, user heart rate, weather conditions, and / or operating efficiency. In particular, the sensor may be designed to record a user's power output. The sensor is preferably also configured to record the user's physiological values. The transmission ratio of the fluid transmission 28 can be optimized based on these parameters.

[0094] Optionally, the drive device 18 can include an immobilizer function. This function is designed such that the fluid transmission 28 can be blocked manually or automatically, for example, when the electric motor 26 is switched off. To block the transmission, the actuator 52 is moved within the fluid chamber 50 such that one of the two partial volumes 56, 58 is essentially zero. This creates a gear ratio that is fundamentally insurmountable for a potential thief, so that the thief can no longer move the bicycle 10 under his own power.

[0095] ASA-8791WO

[0096] 17.03.2026 Reference list 10 Bicycle

[0097] 12 Pedal mount

[0098] 14 Drive shaft

[0099] 16 Output shaft

[0100] 18 Drive device

[0101] 0 Drive unit

[0102] 2 Gearbox unit

[0103] 4 cases

[0104] 26 Electric motor

[0105] 28 Fluid transmissions

[0106] 30 Spur gear

[0107] 32 ball bearings

[0108] 33 Output pinion

[0109] 34 Gearbox housing

[0110] 36 retaining rings

[0111] 38 Seal

[0112] 40 Limiting sleeve

[0113] 42 Internal drive actuator

[0114] 44 Outer drive actuator

[0115] 46 Internal output actuator

[0116] 48 Outer output actuator

[0117] 50 Fluid chamber

[0118] 52 Actuator

[0119] 54 Actuator

[0120] 56 First sub-volume

[0121] 58 Second sub-volume

[0122] 60 compensating line

[0123] ASA-8791 WO

[0124] March 17, 2026

Claims

Patent claims 1. Drive device (18) for a motor-driven bicycle (10), comprising a motor drive device (20), in particular an electric motor (26), and a transmission device (22) wherein the transmission device (22) can transmit a torque acting on a drive shaft (14) of the bicycle (10) to an output shaft (16) of the bicycle (10), (a) wherein the transmission device (22) is designed as a hydraulically operated fluid transmission (28) with a continuously variable transmission ratio, (b) wherein the drive unit (20) and the fluid transmission (28) are arranged in a common housing (24), characterized in that (c) the fluid transmission (28) has a closed fluid chamber (50) filled with hydraulic fluid, (d) in the fluid chamber (50) an actuator (52) is arranged which divides the total volume of the fluid chamber (50) into a first partial volume (56) and a second partial volume (58), wherein the actuator (52) is arranged to be displaceable such that the partial volumes (56, 58) are continuously variable and the transmission ratio is thereby continuously adjustable, (e) the partial volumes (56, 58) are connected to each other by a compensating line (60) so that when the actuator (52) is moved, the hydraulic fluid is equalized between the partial volumes (56, 58), (f) in the first partial volume (56) at least one fluid actuator (42, 44) associated with the drive shaft (14) and in the second partial volume (58) at least one extended fluid actuator (46, 48) associated with the output shaft (16) is arranged.

2. Drive device (18) according to claim 1, characterized in that the actuating actuator (52) is adjustable via an actuating device (54), in particular by an electric motor.

3. Drive device (18) according to claim 2, characterized in that the actuating device (54) can be operated automatically, so that the transmission ratio can be adjusted automatically. ASA-8791 WO 17.03.20264. Drive device (18) according to claim 2 or 3, characterized in that the actuating device (54) can be controlled by means of an app.

5. Drive device (18) according to one of claims 1 to 4, characterized in that at least one sensor or several sensors are provided, which is or are configured to detect operationally relevant parameters, in particular speed, cadence, heart rate and / or operational efficiency or weather conditions, and / or to detect a user's performance and / or to detect physiological values ​​of a user, wherein the transmission ratio is adjustable in an optimized manner based on the parameters.

6. Drive device (18) according to one of claims 1 to 5, characterized in that the compensating line (60) is designed such that the total volume of the hydraulic fluid in the fluid chamber (50) remains essentially constant when the actuator (52) is moved.

7. Drive device (18) according to one of claims 1 to 6, characterized in that the fluid transmission (28) provides or at least forms a cooling circuit for cooling the drive device (20), in particular wherein the hydraulic fluid of the fluid transmission (28) and / or a hydraulic line carrying the hydraulic fluid is thermally coupled to the drive device (20) at least in certain areas.

8. Drive device (18) according to one of claims 1 to 7, characterized in that the drive device (18) has an immobilizer function.

9. Drive device (18) according to claim 8, characterized in that the immobilizer function is formed by a blockage of the fluid transmission (28) that can be effected manually or automatically, in particular when the drive device (20) is switched off, wherein the actuator (52) is arranged for blockage such that one of the two partial volumes (56, 58) of the fluid chamber (50) is as small and the other partial volume (56, 58) is as large as possible.

10. Motor-driven, in particular electric motor-driven, bicycle (10) with a drive shaft (14), in particular pedal axle, an output shaft (16), in particular rear wheel axle, and a drive device (18) according to one of claims 1 to 9.

11. Bicycle (10) according to claim 10, characterized in that the drive device (18) is arranged at least largely in the area of ​​a center of gravity of the bicycle (10), in particular in the area of ​​a pedal bearing or in the area of ​​a rear wheel hub. ASA-8791WO 17.03.202612. Method for operating the drive device (18) according to one of claims 1 to 9, characterized in that the transmission ratio is adjusted by moving the actuator (52) to change the partial volumes (56, 58), wherein during moving a volume equalization of the hydraulic fluid between the partial volumes (56, 58) takes place via the equalization line (60).

13. Method according to claim 12, characterized in that the actuating device (54) is controlled by an app, in particular wherein the transmission ratio is individually set by a user, preferably by means of the app, and / or wherein parameters relevant for the operation of the drive device (18), in particular speed, cadence, heart rate of a user and / or operating efficiency or weather conditions, and / or for recording a user's performance and / or for recording physiological values ​​of a user, are set up, are recorded by at least one sensor and the transmission ratio is set in an optimized manner based on the parameters.

14. Method according to claim 12 or 13, characterized in that the drive device (20) is cooled at least partially by the hydraulic fluid of the fluid transmission (28), in particular wherein the drive device (20), in particular a copper winding of the drive device (20), is at least partially directly or indirectly surrounded by the hydraulic fluid.

15. Method according to one of claims 12 to 14, characterized in that an immobilizer function is provided by manually or automatically, in particular when the drive unit (20) is switched off, a blockage of the fluid transmission (28) is effected, in which the actuator (52) is arranged such that one of the two partial volumes (56, 58) is minimized and the other is maximized, so that the transmission ratio is set to 0 or °°. ASA-8791WO March 17, 2026

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