Drive unit for a bicycle, and bicycle comprising such a drive unit

Abstract

The invention relates to a drive unit (110) for a bicycle (100), comprising a housing (1) having a drive shaft (2) which protrudes axially from the housing (1) on both sides, and having an output shaft (20) which is drivingly connected at least to the drive shaft (2) via a transmission (21). In addition, the drive unit (110) comprises at least one first protective cap (3) which is designed to protect a respective seal (5, 6), wherein the first protective cap (3) is arranged externally axially in front of the first seal (5) in the region of a first end face of the housing (1) and is radially spaced apart from the drive shaft (2) in such a way that a circumferential air gap is formed between the first protective cap (3) and the drive shaft (2).

Description

[0001] ZF Friedrichshafen AG File 306559 Friedrichshafen 2024-12-16

[0002] Drive unit for a bicycle and bicycle with such a drive unit

[0003] The invention relates to a drive unit for a bicycle. Furthermore, the invention relates to a bicycle with such a drive unit. Bicycles are known in various configurations from the prior art. Traditionally, a bicycle has steering for changing the direction of travel and a drive train for providing propulsion. The steering is operated by a user via handlebars to change the direction of travel of the bicycle. The drive train is operated by the user, for example via pedals, to propel and thus move the bicycle.

[0004] Bicycles that are propelled solely by the rider's muscle power are common. Bicycles that can also be powered by an electric motor in addition to the rider's power are also known. These are known as electric bicycles, pedelecs, or e-bikes. The electric motor typically assists the rider's power output according to the rider's input and torque. The electric motor can be a mid-drive motor located near the crank arm or a wheel drive directly on the drive wheel.

[0005] For example, DE 10 2023 204 911 A1 discloses a drive unit for a muscle- and / or motor-powered e-bike, comprising a housing that includes a first housing half and a further housing half, wherein a stator of a motor is mounted in the first housing half. The drive unit further comprises a pedal shaft assembly, at least one first circuit board, a rotor shaft assembly with a rotor and a rotor shaft, at least one further housing component, and at least one gearbox configured to transmit torque generated by the motor to the pedal shaft assembly. All assemblies are arranged such that they can be installed from a single main assembly direction.

[0006] Dirty bicycles are often cleaned using a pressure washer. This poses a challenge for the seals on the drive unit housing, as per ZF Friedrichshafen AG file 306559 Friedrichshafen 2024-12-16

[0007] Sealing lips usually cannot withstand the strong pressure of the water jet from a high-pressure cleaner and are undermined.

[0008] The object of the present invention is to improve a drive unit for a bicycle. In particular, the seals are to be protected from being washed away by water. This object is achieved by the components with the features of the independent claims. Advantageous embodiments are the subject of the dependent claims, the following description, and the figures.

[0009] According to a first aspect, a drive unit for a bicycle is provided, comprising a housing with a drive shaft that projects axially from the housing on both sides, and an output shaft that is connected to the drive shaft via a transmission, and comprising at least one first protective cap designed to protect a respective seal, wherein the first protective cap is arranged axially in front of the first seal in the area of ​​a first end face of the housing and is radially spaced from the drive shaft in such a way that a continuous air gap is formed between the first protective cap and the drive shaft.

[0010] The drive unit can include a second protective cap designed to protect a specific seal. This second protective cap is positioned axially in front of the second seal on a second end face of the housing and radially spaced from the drive shaft such that a circumferential air gap is formed between the second protective cap and the drive shaft. Furthermore, the drive unit can have more than two protective caps, each designed to protect a specific seal. These seals also serve as seals for additional shafts protruding from the housing. These additional protective caps essentially have the same functionality as the first and second protective caps.

[0011] For example, the protective cap can be ring-shaped and made of a metal or polymer. The protective cap serves to protect the seal and is positioned externally in front of it, creating an air gap between the cap and the drive shaft. This air gap has a minimal radial dimension to prevent the cap from contacting the drive shaft during operation. The air gap should be as large as necessary and as small as possible to prevent the cap from rubbing against the drive shaft and to provide optimal protection against water ingress.

[0012] The drive shaft is designed as a crankshaft and is configured to transmit torque from the user. The drive shaft is effectively connected to the output shaft via a gearbox with at least one planetary gear set. For example, the output shaft protrudes from the housing on one side and is effectively connected to a drive wheel of the bicycle via a traction drive, in particular a chain or toothed belt drive. In contrast, the crankshaft protrudes from the housing on both sides and is connected to pedals at both ends via crank arms.

[0013] According to one embodiment, the drive unit further comprises an electric drive motor arranged in the housing and configured to be effectively connected to the output shaft. For example, the drive motor is effectively connected to the output shaft via a traction drive and / or a fixed gear ratio and is configured to introduce auxiliary drive power into the drive train to assist the user. Thus, the output shaft is configured to receive the combined torque of the user's torque and the torque of the drive motor and transmit it to the drive wheel via the bicycle's traction drive.

[0014] According to one embodiment, the first protective cap is arranged on a first housing component, wherein the first housing component is configured to enclose electronics. The electronics can, for example, be designed as power electronics. Preferably, the first housing component is designed as a housing cover and is arranged on a second housing component, wherein the first seal is designed as a ZF Friedrichshafen AG File 306559 Friedrichshafen 2024-12-16

[0015] The first seal is designed as a shaft seal and is arranged radially between the second housing component and the drive shaft. In particular, the first seal is fixed to the second housing component and its sealing lip rests against an outer circumferential surface of the drive shaft. Preferably, the first protective cap rests axially against the first seal. Thus, the first seal forms an axial stop for the first protective cap, which facilitates its installation.

[0016] According to one embodiment, the first protective cap has several circumferentially distributed centering elements on its outer circumferential surface for radially centering the first protective cap on an inner circumferential surface of the housing, in particular on an inner circumferential surface of the second housing component. For example, the centering elements are arranged uniformly in the circumferential direction and are designed as rib-shaped radial projections extending in the axial direction. Preferably, the projections have a rounded surface, in particular a geometry that is at least partially cylindrical. Alternatively, the centering elements form a polygon shape and bear radially against the inner circumferential surface of the housing. This simplifies the assembly of the first protective cap.

[0017] According to one embodiment, the first protective cap has several circumferentially distributed, ramp-shaped locking elements on a second outer circumferential surface for axially fixing the first protective cap in a radial groove provided for this purpose on the housing, in particular on an inner circumferential surface of the first housing component. In the area of ​​each locking element, an axial recess is arranged in the end face of the first protective cap to create radial flexibility. In particular, the respective recess is arranged radially within the respective locking element on the first protective cap. Preferably, the respective recess extends circumferentially as an elongated hole. For example, a respective centering element is arranged circumferentially between two recesses.The respective recess in the front face of the first protective cap serves as a structural weakening and enables a radial ZF Friedrichshafen AG File 306559 Friedrichshafen 2024-12-16.

[0018] Springing of the respective area where the respective locking element is located, thereby simplifying the installation of the first protective cap.

[0019] According to one embodiment, the second protective cap is arranged radially between the drive shaft and the output shaft, with the second seal being designed as a shaft seal ring. Thus, the second protective cap is located inside the output shaft. For example, the second protective cap rests radially against the output shaft and is axially fixed to the output shaft by a screw. The screw is preferably designed as a collar bolt, which is configured to axially secure a chain sprocket that is rotationally fixed to the output shaft. The collar bolt thus fixes the protective cap in the axial direction and prevents it from coming loose.

[0020] According to one embodiment, the second protective cap has several axially oriented projections for axial contact with the screw element, with each projection having a corresponding axial recess to create axial flexibility. In particular, each recess is arranged radially within the projections on the second protective cap. Preferably, each recess extends circumferentially as an elongated hole. The recess on the second protective cap acts as a structural weakener and allows axial deflection of the circumferential area where the projections are located, thereby enabling simple preloading of the second protective cap. This results in axial securing of the protective cap.

[0021] According to one embodiment, the second protective cap has several circumferentially distributed centering elements on an inner circumferential surface for radially centering the second protective cap on an outer circumferential surface of the output shaft. For example, the centering elements form a polygon shape and bear radially against an axial shoulder of the output shaft. Alternatively, several circumferentially distributed ribs or webs can be formed on the inner circumferential surface of the second protective cap as centering elements. This simplifies the assembly of the second protective cap. ZF Friedrichshafen AG File 306559 Friedrichshafen 2024-12-16

[0022] According to a second aspect, a bicycle with a drive unit according to the first aspect is provided. The above definitions, as well as descriptions of the technical effects, advantages, and advantageous embodiments of the drive unit according to the invention, also apply analogously to the bicycle according to the invention. The bicycle can be designed as a conventional bicycle without a drive motor or as an electric bicycle, pedelec, or e-bike with a drive motor. If a drive motor is present, the user's power output is assisted by the drive motor according to a set riding mode and a torque input from the user. The drive motor is arranged as a mid-drive motor in the area of ​​the crank axle and is effectively connected to a drive wheel of the bicycle via a traction drive.In particular, the term bicycle also includes cargo bikes with multiple wheels, especially with three or four wheels.

[0023] An advantageous embodiment of the invention, which is explained below, is illustrated in the drawings, wherein identical or similar elements are provided with the same reference numeral. The drawings show:

[0024] Fig. 1 shows a highly simplified schematic representation of a bicycle according to the invention with a drive unit according to the invention.

[0025] Fig. 2 shows a highly simplified schematic sectional view of the drive unit.

[0026] Fig. 3 shows a schematic representation of a first protective cap,

[0027] Fig. 4 shows a schematic perspective view of the first protective cap,

[0028] Fig. 5 shows a schematic representation of a second protective cap and

[0029] Fig. 6 is a schematic perspective view of the second protective cap. ZF Friedrichshafen AG File 306559 Friedrichshafen 2024-12-16

[0030] Figure 1 shows a highly simplified representation of a bicycle 100. The bicycle 100 has a frame 104 on which a front wheel 101, a rear wheel 102 (designed as a drive wheel), a saddle 106, and handlebars 103 are arranged. The handlebars 103 comprise a stem and handlebar grips. During riding, i.e., during operation of the bicycle 100, a user (not shown in detail) sits, for example, on the saddle 106 and supports themselves on the handlebar grips. In this case, the bicycle 100 is designed as an e-bike and has a drive motor designed as an electric machine, which is integrated into a drive unit 1 of the bicycle 100. This drive unit 1 is designed to propel the bicycle 100 at least with the muscle power of a user.The user applies torque and rotational speed, in particular drive power, to the drive train of the bicycle 100 via pedals 107, which are connected via crank arms to a crank arm shaft 2 of the drive unit 1. The drive power is transmitted to the drive wheel via a traction drive 108 of the bicycle 100. According to an alternative embodiment, the drive motor in the drive unit 110 can be omitted.

[0031] The drive unit is arranged as a mid-drive motor in the area of ​​the crank arm and can, at the user's discretion, introduce auxiliary power into the drivetrain of the bicycle 100 to assist the user while riding. To generate this auxiliary power, the drive unit draws electrical energy from an energy storage device (not shown), which may be located on the frame 104. The auxiliary power is dependent on the user's pedaling force and is divided into various adjustable levels, with the user selecting the desired level of assistance. The pedaling force can be detected by means provided for this purpose, in particular sensors on the crank arm. If the user exerts more force on the pedals 107, the drive unit increases the assistance proportionally to the force, or torque, that the user applies to the drivetrain.

[0032] A section of the drive unit 110 is shown in Fig. 2. The drive unit 110 comprises a housing 1 (only partially shown), the drive shaft 2, which projects axially from the housing 1 on both sides to be connected to pedal cranks, and an output shaft 20, which is effectively connected to the drive shaft 2 via a transmission 21. The output shaft 20 is effectively connected to the drive motor 22, for example via a traction drive (not shown). The drive unit 110 further comprises a first protective cap 3 and a second protective cap 4, which are annular and made of a metal or polymer and are designed to protect a respective seal 5, 6, designed as a shaft seal, on the drive shaft 2.

[0033] The first protective cap 3 is arranged axially in front of the first seal 5 on a first end face of the housing 1 and radially spaced from the drive shaft 2 such that a circumferential air gap is formed between the first protective cap 3 and the drive shaft 2, preventing the first protective cap 3 from contacting the drive shaft 2 while still providing sufficient protection against water being washed under the first seal 5 located behind it. Furthermore, the second protective cap 4 is arranged axially in front of the second seal 6 on a second end face of the housing 1 and radially spaced from the drive shaft 2 such that a circumferential air gap is formed between the second protective cap 4 and the drive shaft 2, preventing the second protective cap 4 from contacting the drive shaft 2 while still providing sufficient protection against water being washed under the second seal 6 located behind it.Therefore, the respective air gap is designed to be as large as necessary and as small as possible.

[0034] In this case, the housing 1 is designed in multiple parts and comprises several housing components. The first protective cap 3 is arranged on a first housing component 7, which is designed to enclose electronics 8. The electronics 8, which may, for example, be designed as power electronics, comprise, for example, a circuit board and are arranged between the first housing component 7 and a second housing component 9. In this case, the first housing component 7 is designed as a housing cover and is arranged on the second housing component 9. The first seal 5 is arranged radially between the second housing component 9 and the drive shaft 2. The first protective cap 3 rests axially against the first seal 5. Furthermore, a ball bearing 17 is arranged radially between the second housing component 9 and the drive shaft 2 for rotatable mounting.Furthermore, the drive shaft 2 is rotatably mounted relative to the output shaft 20 via a needle bearing 18. The drive shaft 2 and the output shaft 20 are arranged coaxially and rotate about a common axis of rotation 25. The output shaft 20 is rotatably mounted in the housing 1 via another ball bearing 19, with a seal 24, arranged radially between the housing 1 and the output shaft 20, sealing the ball bearing 19 and consequently the entire drive unit 10. To protect the seal 24, an additional protective cap can be arranged axially from the outside at this point on the housing 1 in front of the seal 24.

[0035] The first protective cap 3 has several circumferentially distributed and axially rib-shaped centering elements 10 on an outer circumferential surface for radially centering the first protective cap 3 on an inner circumferential surface of the second housing component 9. Furthermore, the first protective cap 3 has several circumferentially distributed, ramp-shaped locking elements 11 on a second outer circumferential surface for axially fixing the first protective cap 3 in a radial groove provided for this purpose on the first housing component 7. In the area of ​​each locking element 11, an axial recess 12 is formed on the first protective cap 3 to create radial flexibility. The respective recess 12 is formed radially within the respective locking element 11 as an opening in an end face of the first protective cap 3.This structural weakening allows the areas with locking element 11 to spring radially inward during the assembly of the first protective cap 3 in the housing 1, thus simplifying the assembly of the first protective cap 3. The ramp-shaped locking elements 11 enable the axial insertion of the first protective cap 3 into the housing 1 and radial snap-in, as well as axial fixation in the final position of the first protective cap 3 on the housing 1.

[0036] The second protective cap 4 is arranged radially between the drive shaft 2 and the output shaft 20 and rests axially against the second seal 6. Furthermore, the second protective cap 4 rests radially against the output shaft 20 and is axially secured by a screw 13 designed as a collar screw. The screw 13 is also designed to axially secure a rotationally fixed component. (ZF Friedrichshafen AG File 306559 Friedrichshafen 2024-12-16)

[0037] The output shaft 20 is connected to the chain sprocket 23. The second protective cap 4 has several axially oriented projections 15 for axial contact with the screw element 13, with each projection 15 having an axial recess 16 to provide axial flexibility. Furthermore, the second protective cap 4 has several circumferentially distributed centering elements 14 on an inner circumferential surface for radially centering the second protective cap 4 on an outer circumferential surface formed on an axial journal of the output shaft 20.

[0038] Figures 3 and 4 show the first protective cap 3. In both figures, the centering elements 10, which are evenly distributed circumferentially on the outer surface of the first protective cap 3, extend to the inner surface of the housing for radial centering of the first protective cap 3. In this case, the centering elements 10 extend axially in a web-like fashion over a cylindrical section of the first protective cap 3 and have a substantially semicircular cross-section. On the second outer surface, which is located radially further outward than the first outer surface, ramp-shaped locking elements 11 are formed for axially fixing the first protective cap 3 to the housing.In the area of ​​the respective locking element 11, the respective axial recess 12 is arranged on the first protective cap 3, thereby enabling radial compliance of the areas with locking element 11 during the assembly of the first protective cap 3 in the housing.

[0039] Figures 5 and 6 show the second protective cap 4. Both figures show that the centering elements 14 on the inner circumferential surface of the second protective cap 4 form a polygonal shape for radially centering the second protective cap 4 on the outer circumferential surface of the output shaft. Figure 5 shows the inner side of the second protective cap 4, which is axially fitted onto the output shaft, while Figure 6 shows the outer side of the second protective cap 4. Several axially extending projections 15 are formed on the outer side of the second protective cap 4 for axial contact with the screw, with each projection having a corresponding axial recess 16. This allows the circumferential area with the projections 15 to deflect axially when the screw presses against it axially.

[0040] ZF Friedrichshafen AG File 306559 Friedrichshafen 2024-12-16

[0041] Reference mark

[0042] 1 case

[0043] 2 Drive shaft

[0044] 3 first protective cap

[0045] 4 second protective cap

[0046] 5 first seal

[0047] 6 second seal

[0048] 7 first housing component

[0049] 8 Electronics

[0050] 9 second housing component

[0051] 10 hundredweight element on the first protective cap

[0052] 11. Safety element on the first protective cap

[0053] 12. Cutout on the first protective cap

[0054] 13 Screws

[0055] 14 hundredweight element on the second protective cap

[0056] 15. Raising on the second protective cap

[0057] 16. Recess on the second protective cap

[0058] 17 ball bearings

[0059] 18 needle bearings

[0060] 19 ball bearings

[0061] 20 Output shaft

[0062] 21 gearboxes

[0063] 22 Drive machine

[0064] 23 chain sprocket I

[0065] 24 Seal

[0066] 25 Rotation axis

[0067] 100 bicycles

[0068] 101 front wheel

[0069] 102 rear wheel

[0070] 103 bicycle handlebars

[0071] 104 frames

[0072] 106 Saddle ZF Friedrichshafen AG File 306559 Friedrichshafen 2024-12-16

[0073] 107 pedals

[0074] 108 Traction drive

[0075] 110 drive unit

Claims

ZF Friedrichshafen AG File 306559 Friedrichshafen 2024-12-16 Patent claims 1. Drive unit (110) for a bicycle (100) comprising a housing (1 ) with a drive shaft (2) which projects axially out of the housing (1 ) on both sides, and an output shaft (20) which is connected to the drive shaft (2) via a transmission (21 ) in a drive-effective manner, at least one first protective cap (3) which is provided to protect a respective seal (5, 6), wherein the first protective cap (3) is arranged axially in front of the first seal (5) from the outside in the area of ​​a first end face of the housing (1 ) and is radially spaced from the drive shaft (2) such that a circumferential air gap is formed between the first protective cap (3) and the drive shaft (2).

2. Drive unit (110) according to claim 1, wherein the drive unit (110) comprises a second protective cap (4) which is designed to protect a respective seal (5, 6), wherein the second protective cap (4) is arranged axially in front of the second seal (6) in the area of ​​a second end face of the housing (1) and is radially spaced from the drive shaft (2) such that a continuous air gap is formed between the second protective cap (4) and the drive shaft (2).

3. Drive unit (110) according to claim 1 or 2, wherein the respective protective cap (3, 4) is formed in an annular disc shape from a metal or a polymer.

4. Drive unit (110) according to one of the preceding claims, wherein the first protective cap (3) is arranged on a first housing component (7) which is designed to enclose an electronics (8).

5. Drive unit (110) according to claim 4, wherein the first housing component (7) is designed as a housing cover and is arranged on a second housing component (9), wherein the first seal (5) is designed as a shaft seal and is arranged radially between the second housing component (9) and the drive shaft (2).

6. Drive unit (110) according to one of the preceding claims, wherein the first protective cap (3) comes into axial contact with the first seal (5). ZF Friedrichshafen AG File 306559 Friedrichshafen 2024-12-16 7. Drive unit (110) according to one of the preceding claims, wherein the first protective cap (3) has several centner elements (10) distributed circumferentially on an outer circumferential surface for radially centering the first protective cap (3) on an inner circumferential surface of the housing (1).

8. Drive unit (110) according to one of the preceding claims, wherein the first protective cap (3) has several circumferentially distributed ramp-shaped locking elements (11) on a second outer circumferential surface for axially fixing the first protective cap (3) in a radial groove provided for this purpose on the housing (1), wherein in the area of ​​the respective locking element (11) a respective axial recess (12) is arranged on the first protective cap (3) to create radial flexibility.

9. Drive unit (110) according to one of the preceding claims, insofar as it refers back to claim 2, wherein the second protective cap (4) is arranged radially between the drive shaft (2) and the output shaft (20), wherein the second seal (6) is designed as a shaft seal.

10. Drive unit (110) according to one of the preceding claims, insofar as it refers back to claim 2, wherein the second protective cap (4) comes into radial contact with the output shaft (20) and is held axially by a screw means (13).

11. Drive unit (110) according to claim 10, wherein the second protective cap (4) has several axially formed projections (15) for axial contact with the screw means (13), wherein in the area of ​​the respective projection (15) a respective axial recess (16) is arranged on the second protective cap (4) to create axial flexibility.

12. Drive unit (110) according to one of the preceding claims, insofar as it refers back to claim 2, wherein the second protective cap (4) has several circumferentially distributed centering elements (14) on an inner circumferential surface for ZF Friedrichshafen AG File 306559 Friedrichshafen 2024-12-16 radial centering of the second protective cap (4) on an outer circumferential surface of the output shaft (20).

13. Drive unit (110) according to one of the preceding claims, further comprising an electric drive machine (22) which is arranged in the housing (1) and is configured to be connected to the output shaft (20) in a driving capacity.

14. Bicycle (100) with a drive unit (110) according to one of the preceding claims.

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