Electric bicycle drive unit having sealing member

Abstract

The present invention relates to a drive unit for an electric bicycle, comprising: an input shaft (1) that introduces a first input torque generated by the muscular force of a rider of the electric bicycle and has a holding portion (11) extending axially; an operating member (K) disposed on the holding portion (11) and separated by a shoulder portion (12); the shoulder portion (12) functions as a stopper for axially fixing the operating member (K) to the holding portion (11); an electric motor (E) that generates a second input torque when operated by an external force; an output shaft (2) that is operably connected to the electric motor (E) and receives the second input torque; the output shaft (2) that is configured as a hollow shaft; the input shaft (1) that is disposed coaxially with the output shaft (2) and at least a portion of the input shaft (1) that is disposed inside the output shaft (2), forming a cavity between the input shaft (1) and the inner surface of the output shaft (2); a seal member (4) that is disposed in the cavity and seals the cavity in the axial direction. The input shaft (1) has a support portion (14) against which the seal member (4) abuts. The stop member (3) is supported on the shoulder portion (12) and forms a stop surface (310) for the operating member (K). Furthermore, the stop member (3) is designed to reduce the gap (O) that allows access to the cavity, and the support portion (14) is configured so that the gap (O) is at least partially shielded by the stop member (3) when projected onto the input shaft (1).

Description

[Technical Field]

[0001] The proposed solution relates to a drive unit for an electric bicycle. [Background technology]

[0002] Electric bicycles, commonly referred to as e-bikes or pedelecs, are known to use at least one electric motor in combination with a transmission, for example with a planetary gear stage, to provide motor assistance when riding the electric bicycle via an output shaft connected to the wheels of the electric bicycle.

[0003] The electric motor provides a motor torque that amplifies and, if necessary, replaces the self-torque generated by human power at the drive shaft via the pedal crank. The electric motor and the output shaft are connected to each other via the drive unit's transmission, so that the motor torque is combined with the self-torque and transmitted as a total torque to the wheels via the output shaft.

[0004] The interface between the pedal crank and the drive shaft is often standardized in electric bicycles in accordance with the ISIS Drive standard. This standard requires that the drive shaft be provided with a shoulder with a diameter of at least 24 mm relative to the axis of rotation. The shoulder absorbs axial forces acting through the means that secure the pedal crank to the drive shaft (e.g., the biasing force of the screw acting on the pedal crank). To absorb these forces, a certain diameter difference is required between the top of the shoulder and the retaining part that has the teeth for the operating member in accordance with the standard. This diameter difference is usually related to the top of the teeth (the diameter of the tooth head in the ISIS standard). For this reason, the standard requires that the diameter of the drive shaft at the top be at least 24 mm.

[0005] In such drive units, the drive shaft and the output shaft are arranged coaxially with one another, and for this purpose the output shaft is configured as a hollow shaft, with a cavity usually provided between the drive shaft and the output shaft.

[0006] The drive unit is designed so that components inside the cavity (such as the freewheel and ball bearing assembly) are accessible from the outside through gaps. This creates the risk that water or dust can get in through the gaps and damage these components, resulting in the operation of the drive unit being impaired. The cavity is usually sealed against water and dust intrusion using a sealing member in the form of a radial shaft seal.

[0007] The seal member may include a seal body and at least one seal lip formed thereon, which contacts the output shaft. If a high-pressure water jet is directed at such a seal lip from an angle, the seal lip may invert and / or the water may turn around, causing water to penetrate past the seal member into the cavity. This is a known problem that can occur when cleaning drive units with high-pressure cleaners. Such drive units may become unusable after cleaning with a high-pressure cleaner because components located axially inside the seal member may be damaged by the intruding water.

[0008] Such drive units are required to be more robust and to optimize the required installation space. Summary of the Invention [Problem to be solved by the invention]

[0009] Based on this background, a drive unit as set forth in claim 1 is proposed as a first aspect of the present invention.

[0010] The drive unit includes a drive shaft for introducing a first drive torque generated by the rider's muscle power, and the drive shaft has an axially extending holding portion for locating an operating member, which is restricted by a shoulder portion that functions as a stopper for axially fixing the operating member to the holding portion.

[0011] The proposed drive unit further includes an electric motor that generates a second drive torque when actuated by an external force, and an output shaft operatively connected to the electric motor for receiving the second drive torque. The output shaft is configured as a hollow shaft, and the drive shaft is coaxially arranged with the output shaft and is at least partially inserted into the output shaft, thereby forming a cavity between the drive shaft and the inside of the output shaft.

[0012] The drive unit also includes a seal member disposed within the cavity to axially seal the cavity, and the drive shaft has a support portion against which the seal member abuts.

[0013] The drive unit also includes a stop member supported on the shoulder and providing a stop surface for the operating member, the stop member also being configured to reduce an access gap to the cavity, the degree of reduction referring to the degree to which at least a portion of the support is blocked by the stop member when the gap is projected onto the drive shaft within the cavity.

[0014] The following force flow may act on the drive shaft and the output shaft: A rider of an electric bicycle can apply a first drive torque to the drive shaft with his / her legs via an operating member, such as a pedal crank with pedals. The first drive torque is transmitted to the output shaft via an operable connection between the drive shaft and the output shaft. This connection may be via a coupling means, such as a freewheel. An electric motor is activated to generate a second drive torque, which is transmitted to the output shaft. The first drive torque and the second drive torque may be output as a total torque from the output shaft to the wheels of the electric bicycle. This output may be via an output member, such as a chain ring, disposed on the output shaft.

[0015] The drive shaft may include a retaining portion and protrude from the output shaft. An inner portion of the drive shaft may be defined by being supported inside the output shaft. Depending on the configuration of the operating member, a shoulder may be arranged on the inner portion. In principle, the shoulder may be arranged adjacent to the inner portion or only partially on the inner portion. In particular, the support and retaining portions for the operating member may be arranged on opposite axial sides of the shoulder.

[0016] A cavity between the drive shaft and the output shaft can form if the diameter of the drive shaft is less than 95%, especially less than 85%, of the inner diameter of the output shaft. If such a diameter difference exceeds 5%, especially more than 15%, a jacket-like cavity will form around the drive shaft.

[0017] The seal may be arranged on the output shaft (which is fixed in rotation) and abut against the drive shaft at a support (which is rotatable). Abutting against the support of the drive shaft, as opposed to abutting against the output shaft, has the advantage of minimising the contact area through which water can enter.

[0018] The seal member may be connected to the output shaft by a press fit. The installation space for the seal member may depend on the size of the cavity. The size of the cavity may be determined based on the height of the (splined) teeth formed on the outer periphery of the output shaft (or the depth of the corresponding grooves, or the height of the teeth on the output member) and the required wall thickness of the output shaft material (radially inside the gear train).

[0019] The stopper member may be configured to have increased robustness, particularly against cleaning with a high-pressure washer, which may be due to the stopper member designing a labyrinth-shaped gap for water to penetrate into the cavity, or an area of ​​the cavity adjacent to the gap.

[0020] By configuring the gap projection onto the drive shaft to be at least partially shielded by the stopper member, the possibility of the water jet from the high-pressure washer directly hitting the seal member, particularly at least one seal lip of the seal member, at full discharge water pressure (output pressure) (without being deflected) can be reduced. In particular, the contact area (axially adjacent to the stopper member) where the at least one seal lip and / or the seal member contacts the support can be shielded by the stopper member when the gap is projected onto the drive shaft. The at least one seal lip and the contact area are each located axially adjacent to the stopper member, which can be particularly important for water to flow around the seal member via the water jet. When the at least one seal lip and / or contact area is located in a position shadowed by the stopper member, the water jet must undergo at least one deflection at either the stopper member, another part of the seal member, the drive shaft, or the output shaft in order to reach the contact area and / or at least one seal lip. Deflecting the water jet can reduce the water pressure hitting the contact area and / or at least one seal lip.

[0021] The shadow of the support formed by the stop element can therefore be understood to mean that a (water jet) vector projected in any direction through the gap will not reach parts of the support, in particular the contact area. This shaded part of the support is protected, for example, from a direct water jet. In the directions excluded by the shielding, the water cannot continue to spread under high pressure along the support to the contact area, but must be deflected before it can reach the seal, so the possibility of water getting around the seal is already reduced.

[0022] In one embodiment, the stopper member blocks at least 55% of the gap or protrudes radially into the cavity at the top of the shoulder. In principle, it is desirable for the stopper member to block as much of the gap as possible, thereby increasing the likelihood that a water jet that may enter the cavity will be deflected by the stopper member. Therefore, the stopper member may block 60-80% of the gap, or even more than 80%. The stopper member may block the gap by partially filling it radially from the inside to the outside. In this case, the remaining gap may be smaller than if the stopper member were not blocking it.

[0023] The stopper element can have essentially any configuration as long as it is intended to reduce the gap. It may be advantageous for the stopper element to project radially into the cavity at the top of the shoulder. This allows the stopper element to be chamfered appropriately, so that a water jet directed at the stopper element is deflected outward from the cavity rather than toward the cavity. The top of the shoulder may correspond to a portion of the stopper element located on the support or intermediate portion side. It is not necessary for the stopper element to be formed so as to axially overlap the support or intermediate portion, although such a configuration may be more advantageous. In particular, the stopper element having a portion projecting into the cavity may be adjacent to a radial plane passing through the top of the shoulder.

[0024] Here, the apex of the shoulder can be understood as the apex in the cross section of the drive unit. The shoulder may be configured to essentially form an apex circle on the drive shaft.

[0025] In one embodiment, the stopper member protrudes axially into the cavity beyond the shoulder and / or has an outer surface that extends at least partially in the axial direction. This allows the gap and the adjacent cavity to be reduced in three dimensions. On the one hand, by forming the stopper member in, for example, a ring or sleeve shape, the gap and the adjacent cavity formed in the circumferential direction around the rotation axis can be reduced. On the other hand, the stopper member can additionally or alternatively reduce the gap and the adjacent cavity formed in the radial direction. Finally, the stopper member can additionally or alternatively reduce the cavity adjacent to the axial gap by a predetermined depth or more. By applying these together, the reduction in three dimensions can be achieved, which more effectively prevents water intrusion and allows the drive unit to be constructed more robustly.

[0026] By using a stopper member to reduce the gap, the gap may become smaller than the cavity formed behind it. Furthermore, by having a portion of the stopper member that protrudes axially from the gap into the cavity, the gap can appear to be extended in the axial direction. The stopper member may be configured to be long enough so that the projection of the gap onto the support is completely, rather than partially, covered by the stopper member. For example, it is desirable that the stopper member be shielded so that it is shaded from the shoulder to at least the contact area. This is because it reduces the possibility that the water jet will directly enter the cavity and hit the seal member with full discharge pressure.

[0027] A configuration in which at least a portion of the outer surface is formed to extend in the axial direction is advantageous in increasing the shadow area compared to a configuration in which the outer surface is inclined obliquely toward the cavity.

[0028] In one embodiment, the stopper element has a collar on the side of the holder for locating a tool. On the one hand, the collar allows for easy removal of the stopper element. On the other hand, the collar can limit the spatial angle at which the gap can be accessed (e.g. for a water jet).

[0029] When a drive unit is used on an electric bicycle in a predetermined operating condition, an installation space for the drive unit is provided on the electric bicycle in advance. The installation space for the drive unit generally affects the frame design of the electric bicycle, and an excessively large installation space may undesirably limit the comfort of riding the electric bicycle. This may be due to the installation space for the drive unit interfering with the chainstay of the frame. Therefore, it is desirable for the drive unit to be as compact as possible. In particular, to ensure installation space for the chainstay, a compact configuration that suppresses radial expansion is desirable.

[0030] The radial expansion of the installation space may be based on the diameter of the drive shaft. The drive shaft may have at least one step starting from the shoulder and extending beyond the support, which may be required for assembly and manufacturing reasons. This is because when an assembly of components on the drive shaft is placed beyond the shoulder and support, it is desirable for this assembly to have a larger diameter than the support. These components are, for example, freewheels and / or ball bearing assemblies. During assembly, these components are always installed before the seal member.

[0031] In one embodiment, the stop member has an outer diameter of at least 24 mm, although it is not excluded that the stop member may have an outer diameter of less than 24 mm in parts.

[0032] Therefore, even if the radial distance from the support part to the rotation axis of the drive shaft is less than 12 mm, it is possible to provide a drive unit formed in accordance with the ISIS Drive standard. In such a drive unit, the radial installation space of the support part can be kept small. For example, it is conceivable and possible for the support part to have a diameter of 23.0 to 24.0 mm, particularly 23.5 mm. This allows the radial installation space to be reduced by 0.5 mm compared to a configuration in which the support part is formed in accordance with the ISIS Drive standard.

[0033] In one embodiment, an intermediate portion is formed between the shoulder portion and the support portion, and the support portion is axially spaced apart from the shoulder portion via the intermediate portion. The intermediate portion can be inserted into the outer profile of the drive shaft, whereby the outer profile is formed to rise from the retaining portion via the shoulder with respect to the rotation axis and extend along the intermediate portion and the support portion parallel to the rotation axis. By providing the intermediate portion, the stop member can be supported by the intermediate portion in addition to the shoulder. For example, the stop member can form a forced fit, such as a press fit, with the drive shaft at the intermediate portion.

[0034] In one embodiment, the intermediate portion has a strip-shaped surface parallel to the axis of rotation, which allows for a secure press fit with the stop member.

[0035] In one embodiment, the shoulder is formed obliquely in the radial direction relative to the rotation axis. The shoulder may also be formed obliquely rising towards the support. The oblique shoulder configuration reduces notch stresses that arise along the drive shaft due to the axial force acting on the operating element by the fixing means. In principle, shoulders arranged parallel to the radial direction are also conceivable and possible.

[0036] A second aspect of the present invention relates to an electric bicycle equipped with the drive unit of the first aspect of the present invention. [Brief explanation of the drawings]

[0037] The accompanying drawings show examples of possible implementations of the proposed solution. [Figure 1A] FIG. 10 is a cross-sectional view of a drive unit with a stop member. [Figure 1B] FIG. 1B is an enlarged view of the cross-sectional portion of FIG. 1A. [Figure 2A] FIG. 10 is another view of an embodiment with a stop member. [Figure 2B] FIG. 2B is an enlarged view of the cross-sectional portion of FIG. 2A.

[0038] FIG. 1A shows a cross-sectional view of a drive unit of an electric bicycle. The drive unit includes a drive shaft 1 rotatable around a rotation axis D. A rider of the electric bicycle can apply a first drive torque to the drive shaft 1 by applying muscle force via a pedal crank-shaped operating member K. The operating member K is fitted to the drive shaft 1 and abuts against a stopper member 3 in the axial direction. The stopper member 3 thus functions as a stopper for the operating member K on the drive shaft 1. The operating member K is also fixed to the drive shaft 1 in the axial direction via a fixing means F. The operating member K is fixed between the fixing means F and the stopper member 3 in this way. The fixing means F applies an axial force to the operating member K, which is transmitted to the stopper member 3.

[0039] The drive unit has an output shaft 2 arranged coaxially with the drive shaft 1. This output shaft 2 is operatively connected to an electric motor E and absorbs a second drive torque generated by the electric motor E. An output member in the form of a carrier member T is arranged on the output shaft 2 and fixed to the output shaft 2 by a nut M. The output member can basically be fixed to the output shaft 2 by any fixing means. Examples of output members are belt blade carriers, belt blades or chain blades.

[0040] The carrier member T is arranged in a rotationally fixed manner on the connection portion 21 of the output shaft 2. For the rotationally fixed arrangement, the connection portion 21 has teeth with which the carrier member T engages. A first drive torque can be transmitted from the drive shaft 1 to the output shaft 2 via the operable connection, and the first and second drive torques are transmitted as a total torque to the wheels of the electric bicycle via the carrier member. The output shaft 2 is configured as a hollow shaft, inside which the drive shaft 1 is partially arranged.

[0041] The drive unit also has a housing G, in whose internal space an electric motor E is disposed, with a drive shaft 1 and an output shaft 2 protruding therefrom. The internal space of the housing G is sealed by an (external) seal (not shown) at the position of the output shaft 2 to protect the electric motor E.

[0042] A cavity is formed between the drive shaft 1 and the inside of the output shaft 2. The cavity occurs because the diameter of the drive shaft 1 is less than 85% of the inner diameter of the output shaft 2. The cavity is sealed by a (radially extending) seal 4, which forms an inner seal as opposed to an outer seal of the housing. Components located within the cavity, such as the freewheel, ball bearing assembly, and, if applicable, the electric motor E, are protected by the seal 4 from the ingress of water and dust which could lead to failure of the drive unit.

[0043] 1B is an enlarged view of the framed portion of FIG. 1A, and is a diagram for facilitating the explanation of the embodiment. The seal member 4 abuts against a support portion 14 of the drive shaft 1. The support portion 14 is formed as a part of the jacket-shaped outer surface of the drive shaft 1. This jacket-shaped outer surface preferably has a diameter of less than 24 mm, for example, 23.5 mm, relative to the rotating shaft. This ensures radial installation space for assembling other components on the axial back side of the seal member 4 (opposite the shoulder portion 12).

[0044] The seal member 4 has a seal body 40, which is fixed to the output shaft 2 by force fitting. The seal member 4 also has two seal lips 41, 42, which abut against the support part 14 at contact areas 141, 142. This allows the drive shaft 1 to be slidably supported on the seal lips 41, 42. Basically, the seal member 4 can be attached between the drive shaft 1 and the output shaft 2 in any manner.

[0045] The operating member K is fixed to the drive shaft 1 via a stop member 3 at a stop position formed by a shoulder 12 on the drive shaft 1. The operating member K is arranged on a holding part 11 of the drive shaft 1, which is limited in the axial direction by the shoulder 12. The shoulder 12 rises above the holding part 11 from a shoulder base 121 (located at the radial height of the holding part 11) to a top 122 of the shoulder 12. The top 122 is located at the same radial height as the support part 14.

[0046] The stopper member 3 has an outer diameter of 24 mm (or more) and therefore meets the ISIS Drive standard for the stop surface 310 of the operating member K.

[0047] The stopper member 3 has an inner contour that essentially follows the outer contours of the holding portion 11, the shoulder portion 12, and the intermediate portion 13 located between the shoulder portion 12 and the support portion 14, and abuts against this intermediate portion 13. The stopper member 3 has a stop portion 31 that is arranged on the holding portion 11 and supported by the shoulder portion 12. Axial force from the operating member K is received via the stop portion 31 through a stop surface 310 and transmitted to the drive shaft 1 via the shoulder portion 12. The stop surface 310 is arranged perpendicular to the rotation axis D. The stopper member 3 also has a protective portion 32, and is fixed to the intermediate portion 13 via this protective portion 32 by force fitting. The intermediate portion 13 has a strip-shaped outer surface parallel to the rotation axis D, which functions as an abutment for the stopper member 3.

[0048] The protective portion 32 protrudes axially into the cavity between the drive shaft 1 and the output shaft 2 and has an outer surface 320 extending in the axial direction. Due to the protective portion 32 protruding into the cavity and the outer surface 320 extending in the axial direction, the stopper member 3 reduces a large portion (85% or more, at least 95%) of the cavity area adjacent to the gap O, which is accessible from the outside. For example, when cleaning the drive unit with a high-pressure cleaner, a water jet S with discharge pressure directed toward the gap is likely to be deflected by the stopper member 3, resulting in minimal pressure acting on the sealing member 4 located axially rearward. At commonly used discharge pressures, the water jet S is unlikely to invert the sealing lips 41, 42 of the sealing member 4 or allow water to flow around. Due to the special configuration of the stopper member 3, water and dirt may continue to enter the cavity located axially rearward of the sealing member 4.

[0049] The stopper element 3 reduces the gap in the radial direction to less than 20%, particularly less than 5%, of its original size. Furthermore, the stopper element 3, together with the protective portion 32, fills at least 30% of the cavity up to the sealing element 4. Because the stopper element 3 reduces the gap, when the gap is projected onto the drive shaft 1 within the cavity, the support element 14 is partially covered by the stopper element 3. This (virtual) projection can be realized under certain conditions of use during (actual) cleaning with the water jet described above. Therefore, the shielding by the stopper element 3 protects at least a portion of the support element 14 from the water jet that directly enters the cavity and is not refracted. Complete protection from the direct water jet S (complete shielding of the projection of the gap O onto the support element 14) is desirable, but is not necessarily an absolute requirement. Even partial protection can reduce the probability that the direct water jet S will reach the sealing element 4.

[0050] To illustrate the advantages of the stopper member 3 configured in this manner, FIG. 1B shows a schematic representation of a water jet S refracted multiple times within the cavity. The water jet enters the cavity at the gap O between the stopper member 3 and the output shaft 2 due to the discharge pressure along a first direction. The water jet S first strikes the outer surface 320 of the protective portion 32, where it is first refracted. In the illustrated configuration of the stopper member 3, there is virtually no realistic and practical direction in which the water jet S can reach the gap without being refracted by the stopper member 3.

[0051] After the water jet S is first refracted at the outer surface 320, it spreads along the outer surface 320 in a second direction parallel to the rotation axis D. The water jet S then strikes the seal body 40 of the seal member 4, where it is refracted a second time. The water jet S then spreads in a third direction toward the support 14. The water jet S is refracted a third time at the support 14 and then spreads along a fourth direction toward the outer seal lip 41 of the seal lips 41, 42. By the time the water jet S reaches the seal lip 41, it has already been refracted three times, so the water pressure is significantly reduced compared to the discharge pressure impinging on the gap. Therefore, the outer seal lip 41 and even the inner seal lip 42 are less likely to invert or the water is less likely to flow around compared to when the water jet S directly contacts them under discharge pressure.

[0052] Figures 2A and 2B show another configuration of the drive unit. Unlike the embodiment of Figures 1A and 1B, the drive shaft 1 does not have an operating member K required to disassemble the drive unit.

[0053] 2B is an enlarged view of the framed portion of FIG. 2A, and shows a schematic representation of a tool W used to remove the stop member 3. The stop member 3 has a collar 33 on which the tool W is placed. Via the collar 33, the stop member 3 can be released from the forced engagement with the drive shaft 1. This release action is performed by a lever action, indicated by the arrow, with the abutment point on the output shaft 2 as the fulcrum. The collar 33 shown in FIG. 1B serves a similar purpose.

[0054] The outer diameter of the fastener member 3 is defined by a collar 33. Furthermore, the collar 33 is configured to at least partially shield the outer surface 320 of the fastener member 3. This configuration further reduces the possibility that a water jet from a high-pressure washer or other unwanted material will reach the seal member 4 directly without being deflected. [Explanation of symbols]

[0055] 1 drive shaft 11 Holding part 12 Shoulder 121 Shoulder base 122 Top 13 Middle section 14 Support part 141,142 contact area 2 output shafts 21 Connection 3 Fasteners 31 Stop section 310 Stop surface 32 Protection part 320 outer surface 33 Color 4 Sealing material 40 Seal body 41,42 Seal lip D rotation axis E Electric motor F Fixing means G Housing K operating member M nut O Gap S Water Jet T carrier material W tools

Claims

1. a drive shaft (1) for introducing a first drive torque generated by the muscle power of a rider of an electric bicycle, the drive shaft (1) having a holding portion (11) extending in the axial direction, an operating member (K) disposed in the holding portion (11), the operating member (K) being restricted by a shoulder portion (12), the shoulder portion (12) functioning as a stopper for fixing the operating member (K) to the holding portion (11) in the axial direction; an electric motor (E) that generates a second driving torque by being actuated by an external force; an output shaft (2) configured as a hollow shaft, operably connected to the electric motor (E) to receive the second drive torque, wherein the drive shaft (1) is coaxially disposed with the output shaft (2) and at least a portion of the output shaft (2) is disposed inside the output shaft (2) to form a cavity between the drive shaft (1) and the inside of the output shaft (2); a seal member (4) disposed in the cavity, sealing the cavity in the axial direction, and abutting against a support portion (14) of the drive shaft (1); a stop member (3) supported on said shoulder (12) and forming a stop surface (310) for said operating member (K); A drive unit for an electric bicycle comprising: The stop member (3) is formed to reduce a gap (O) allowing access to the cavity, and the degree of reduction is such that when the gap (O) is projected onto the drive shaft (1), at least a portion of the support portion (14) is shielded by the stop member (3).

2. 2. The drive unit according to claim 1, wherein the stop member (3) covers at least 55% of the gap and / or protrudes radially into the cavity at a portion of the shoulder (12) on the top (122) side.

3. 3. A drive unit according to claim 1 or 2, characterized in that the stop member (3) projects axially into the cavity beyond the shoulder (12) and / or has an outer surface (320) that extends at least partially axially.

4. 4. A drive unit according to claim 1, wherein the stopper member (3) has a collar (33) on the side of the holding part (11) for arranging a tool (W).

5. A drive unit according to any one of claims 1 to 4, characterized in that the stop member (3) has an outer diameter of 24 mm or more.

6. An intermediate portion (13) is formed between the shoulder portion (12) and the support portion (14), the support portion (14) is axially spaced from the shoulder portion (12) via the intermediate portion (13); 6. A drive unit according to any one of claims 1 to 5, characterized in that the stop element (3) is supported on the intermediate part (13) in addition to the shoulder part (12).

7. 7. A drive unit according to claim 6, characterized in that the intermediate part (13) has a strip-shaped outer surface parallel to the axis of rotation (D).

8. 8. A drive unit according to claim 1, wherein the shoulder (12) is formed radially obliquely relative to the axis of rotation (D).

9. An electric bicycle comprising a drive unit according to any one of claims 1 to 8.

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