WO2023156327A1

WO2023156327A1 - Drive device for an electric bicycle, and electric bicycle

Info

Publication number: WO2023156327A1
Application number: PCT/EP2023/053461
Authority: WO
Inventors: Julius Thorwart
Original assignee: Porsche Ebike Performance Gmbh
Priority date: 2022-02-16
Filing date: 2023-02-13
Publication date: 2023-08-24
Also published as: DE102022103627A1

Abstract

The invention relates to a drive device (5) for an electric bicycle (1) comprising a motor unit (13, 14) for driving the electric bicycle (1) and a hub axle (9, 10) that is coupled to the motor unit (13, 14). The drive device (5) also comprises a transmission (18, 19, 26) which is designed for driving the electric bicycle (1) and can be rotated about an axis of rotation (R), and which is coupled to the motor unit (13, 14) on one side and to the hub axle (9, 10) on the other side. The transmission (18, 19, 26) is designed to output a torque for driving the electric bicycle (1). The motor unit (13, 14) and the transmission (18, 19, 26) are arranged in a motor housing (6, 15), through which the hub axle (9, 10) extends. The hub axle (9, 10) has a first end section (91) and a second end section (92) in relation to the axis of rotation (R), which are designed to be coupled to a respective outer frame element (6, 7) of the electric bicycle (1) on opposite sides, wherein the second end section (92) is designed to be narrower than the first section (91).

Description

Driving device for an electric bicycle and electric bicycle

The invention relates to a drive device for an electric bicycle and an electric bicycle with such a drive device.

Bicycles are a cost-effective, easy-to-handle and emission-free means of transport. They have also been used as sports or fitness equipment, and types that are particularly suitable for different areas of use have emerged.

In recent years, enthusiasm for electric bicycles, especially so-called "pedelecs", has been growing, despite the high weight and price of bicycles. Potential customers are not only older, less fit cyclists or cyclists who are free from sporting ambitions, but also sporty, younger cyclists, be it for use on the way to work or because of the possibility of using them to extend the radius of action without overstraining one's own physique and/or to increase the cruising speed. Mountain bikers in particular seem to be showing increasing interest in electrically assisted mountain bikes. In the case of electric bicycles, it is important to provide a reliably supporting drive system that enables high power transmission.

It is an object on which the invention is based to create a reliable drive concept for electric bicycles that enables a clear structure and also contributes to high power transmission. According to one aspect, a drive device for an electric bicycle is disclosed. The drive device has a motor unit for driving the electric bicycle. The drive device further includes a hub axle coupled to the motor unit. The drive device also includes a transmission that is designed to drive the electric bicycle and can be rotated about an axis of rotation. The transmission is coupled to the motor unit on the one hand and to the hub axle on the other hand and is set up to output torque for driving the electric bicycle. The drive device also has a motor housing in which the motor unit and the transmission are arranged and through which the hub axle extends. In relation to the axis of rotation, the hub axle has a first end section and a second end section which are designed to be coupled on opposite sides to a respective outer frame element of the electric bicycle, the second end section being narrower than the first section.

By means of the drive device described, a reliable drive concept for electric bicycles can be implemented, which in particular enables an efficient and reliable rear wheel hub drive. Due to the tapering hub axle, which has a narrower and a wider free end, a structure of the drive device is provided which enables simplified assembly and also provides installation space for the other components or further components of the drive device in the area of the narrower second end section . The drive device described is particularly useful as an electric bicycle drive system a bicycle hub or a rear wheel of the electric bicycle.

According to a development of the drive device, the second end section has a diameter in relation to a radial direction transverse to the axis of rotation which is at least one millimeter smaller than a diameter of the first end section. For example, the first end portion is formed with a diameter of 12 mm and the second end portion is configured as an M10 section so that the hub axle tapers from 12 mm diameter to 10 mm diameter and the second end portion preferably includes a thread. Alternatively, other diameter values can also be provided, so that at least one end section is narrower than the other. Because the hub axle is tapered and has a narrower second end section, installation space can be provided that is suitable, for example, for a torque sensor.

Like the frame elements of the electric bicycle, the hub axle can be made of aluminum, so that the second end section and the second frame element have a respective thread, which engage in one another and are screwed together. Alternatively or additionally, a separate threaded element, for example as a steel insert, can be provided between the hub axle and the second frame element, which, together with the hub axle, enables the components of the drive device to be reliably connected and braced.

According to a development of the drive device, the first and second end sections each have a constant diameter in relation to a radial direction transverse to the axis of rotation. The two end sections can be designed, for example, as cylinders of different sizes that adjoin one another and gradually merge. Alternatively, one end section or both end sections can also have subsections with two or more different diameters, the second end section being narrower at its end facing outwards than the first end section at its opposite end facing outwards.

According to a further development of the drive device, the hub axle has a central section which is formed between the first end section and the second end section in relation to the axis of rotation. The middle section sets up a transition area between the two end sections, the middle section being designed in such a way that it tapers continuously, in sections or in steps towards the second end section. For example, the central portion may taper continuously, like a truncated cone, or have an intermediate region of constant diameter. Alternatively, the middle section may have one or more steps that are larger or smaller than the first and/or the second adjacent end section. In each case, however, at least one end of the second end section located axially on the outside is smaller or narrower than the first end section or than its associated end located axially on the outside. Accordingly, the end sections comprise the respective axial end area and extend from opposite sides to the central area, which introduces a change in the circumference of the respective end sections.

According to a preferred development of the drive device, the hub axle is designed in two parts and includes a A thru-axle and a sleeve-shaped drive axle through which the thru-axle extends. The plug-in axle and the drive axle are preferably designed in such a way that they each taper along the axis of rotation in the direction towards the second end section. Alternatively, only the hollow drive axle located further out can be tapered. The quick-release axle can also be sleeve-shaped or hollow. Alternatively, the quick-release axle is solid. The quick-release axle is in particular longer than the drive axle surrounding it, so that it protrudes from the drive axle on both sides. Thus, the quick-release axle can be coupled to the frame elements, in particular screwed, and the drive axle can be tightened in a predetermined manner. The drive axle serves in particular as a stabilizing holding element for the components of the drive device that surround it. In addition, the hub axle can also be designed in three parts, four parts or multiple parts and have elements that can be plugged into or coupled to one another.

According to a further development of the drive device, a predetermined free space is set up in relation to a radial direction transverse to the axis of rotation in the middle section between the plug-in axle and the drive axle. Such a free space can have a particularly beneficial effect on assembly of the drive device in which the quick-release axle is inserted into or through the drive axle. The free space between the quick-release axle and the drive axle can provide a certain amount of assembly play and can, for example, alleviate some of the specifications for tolerance accuracy in the manufacture of the individual components.

In relation to the drive axle, the transition area is between the larger first and the smaller second For example, the end section is designed to be as short as possible axially, so that the drive axis tapers relatively sharply or over a relatively short distance. A particularly long second end section and a relatively large amount of space for other components, such as sensors, bearings and gears, can thus be provided.

The quick-release axle is designed in particular to be able to absorb axial tension and to be able to compensate for any bending loads. It extends through the drive axle and can, for example, have the longest possible transition area between the larger diameter of the first end section and the smaller diameter of the second end section.

In this way, a notch effect can be kept low and a contribution can be made to useful stability with regard to bending.

Alternatively, a respective transition area of the thru-axle and/or the drive axle can also be configured differently, so that the two transition areas are realized very similarly, for example, and only a relatively small or even no cavity is formed between the thru-axle and the drive axle.

According to a further development, the drive device has a first and a second frame element which are arranged on opposite sides in relation to the axis of rotation outside the motor housing. The two frame elements are connected or coupled to a respective end section of the hub axle, so that one or both frame elements pre-tension the drive axle in cooperation with the quick-release axle. For example, the second end portion is screwed to the second frame member directly or by means of a threaded member and enables reliable and stably tightening and tensioning the drive axle against the opposing first frame member. An additional, separate threaded element, for example in the form of a sleeve-shaped steel insert, between the quick-release axle and the second frame element enables the components of the drive device to be connected and clamped in a particularly stable and reliable manner. The frame elements are arranged in particular outside of the motor housing and surround the hub axle at least in sections.

According to a further development, the drive device comprises a cassette body which is coupled to the motor housing and which surrounds the hub axle with respect to the axis of rotation and which is set up to transmit torque from a driver of the electric bicycle to the motor housing. The drive device also includes a sensor unit, which is coupled to the hub axle or the drive axle and/or is arranged adjacent to it in order to determine a torque of the driver. The sensor unit is arranged between the cassette body and the hub axle with respect to a radial direction transverse to the axis of rotation. The sensor unit is preferably arranged in the narrower second end section of the hub axle and the sensor unit and the second end section are designed to match one another. The sensor unit can be fitted onto the tapered area of the drive axle and surrounded by the drive axle by shaping it, so that an undesired twisting of the sensor unit is counteracted.

For example, a narrow installation space is available, so that the sensor unit is designed, for example, in the form of a plate and/or ring in order to be able to be arranged reliably and stably in the narrow installation space. Alternatively, the Sensor unit specify a certain shape, so that the second end portion of the hub axle is made particularly narrow and, for example, from a particularly stable material in order to accommodate or store the sensor unit and also provide a required stability of the drive device. The sensor unit can comprise a torque sensor and enable a power measurement that is linked to or processed with the operation of the electric motor in order to provide a reliable and efficient electric bicycle drive.

According to a development of the drive device, a length of the first end section and/or a length of the second end section along the axis of rotation are designed to be matched to an expansion of the motor unit, the transmission and/or the sensor unit. For example, the second end section is twice as long as the first in order to provide a correspondingly large amount of space for an elongate sensor unit.

According to a development of the drive device, the motor unit includes an electric motor with a rotor and a stator, the stator being arranged in the direct vicinity of a wall of the motor housing. The wall is directly adjacent to an outer area outside of the motor housing and as a result the electric motor is only shielded from the outer area by a wall of the drive device. Alternatively or additionally, the wall has an extension section that thermally conductively connects the wall to the outside area outside of the motor housing. The same also applies to a heat-generating motor unit which, for example, is based on a different drive and does not have an electric motor. A particularly efficient drive concept can be implemented for a rear wheel hub by means of the drive device described. Due to the fact that the heat can be dissipated directly by means of heat conduction, a design of the drive device is provided which can contribute to an increased continuous output of the electric motor. For example, the electric motor is shrunk directly into the motor housing and contacts the wall or has a heat-conducting intermediate element that connects the electric motor to the wall. In this way, the heat generated can be dissipated in a controlled manner by means of heat conduction through the material of the wall and, if necessary, the connecting intermediate element and released to the outside area or absorbed by the ambient air located in the outside area. A continuous material guide for heat conduction from the wall surrounding the electric motor to the outside outside of the motor housing can also be set up by means of a specifically introduced extension section.

The wall preferably has a cooling structure which comprises a plurality of ribs and/or other surface elevations which are arranged at a distance from one another on an outer side of the wall. By means of such surface structures, a surface enlargement of the outside of the wall and/or of the extension section is formed in a targeted manner, which surface faces the outside area. The drive device can thus be cooled even more efficiently by ambient air.

In particular, the stator forms a component of the

Electric motor, which in one operation a relatively large Heat component developed and is therefore preferably attached in the vicinity of a heat-dissipating wall. The rotor and/or the stator of the electric motor can be arranged on the wall of the motor housing or connected to it by means of an intermediate element, so that a material-guided heat conduction is set up through the wall to the outside area. Such a material-guided heat pipe is preferably designed in one piece. Alternatively, the wall and the further heat-conducting elements, which are connected to the wall in particular in an air-free manner, can form a coherent heat line without an air gap lying between them.

It is a finding of the present invention that in a conventional drive system for electric bicycles the available installation space is predetermined and relatively restricted, for example by a brake disc on one side and by a chain ring system on the other side. Within such an installation space, the interacting components are tightly installed in the axial and radial direction and, as a rule, are deliberately encapsulated in order to take up as little installation space as possible.

For example, a conventional drive system includes an electric motor with a rotor running on the outside and a stator on the inside, so that an external-rotor drive is implemented with respect to a rotational axis of the components. The stator is then, for example, fixedly mounted on an axle and arranged together with the rotor and permanent magnets in a rotor bell and a housing. As a rule, the stator forms a main heat source, which is accordingly very well encapsulated and installed very far away from the outer housing components. Alternatively, in a conventional drive system, the stator can be fixed in an enclosed bell, while the rotor rotates with permanent magnets inside. In such an internal rotor drive, the stator, as the main heat source, is arranged closer to the housing components on the outside, but is still installed in a heavily encapsulated manner.

The described relatively tightly packed conventional designs mean that heat dissipation, in particular from active parts of the drive system, to the housing parts around which the ambient air flows takes place only in a roundabout way, which often involves penetrating several different material walls and/or internal air gaps. Such reduced heat dissipation of the active parts can result in the power of the motor unit of the electric bicycle having to be reduced after a short time in order to avoid permanent damage to the drive system.

By means of the drive device described and the direct heat conduction to the outside made possible therein, heat from the electric motor can be dissipated promptly and in a targeted manner, and a significantly higher continuous output of the electric motor and the drive device can be achieved. This is achieved in particular by avoiding or at least significantly reducing heat-insulating air gaps and/or passages through several different material walls. The drive device thus provides heat dissipation, in particular on the basis of heat conduction through a material, and preferably includes no or at least only a relatively small proportion of heat dissipation or heat transfer in the form of thermal radiation. According to a development of the drive device, the motor housing includes a peripheral housing section which is rotatably coupled to the hub axle and in which the electric motor is arranged in direct proximity to the wall of the motor housing. When the drive device is in operation, the circumferential housing section rotates around the axis of rotation when the electric bicycle is being driven, which in particular also corresponds to an axis of symmetry or a longitudinal axis of the hub axle. The hub axle is stationary or rotationally fixed relative to the rotatable housing section and serves in particular to hold the components and to attach the drive device to the electric bicycle.

According to a further development, the drive device has a slip ring which is arranged inside the motor housing in relation to the axis of rotation. The slip ring comprises a first slip ring element and a second slip ring element which contact each other radially and/or axially with respect to the axis of rotation. A slip ring element is stationary coupled to the drive axle or the hub axle and therefore does not rotate about the axis of rotation. The other slip ring element is rotatably coupled to and rotates about the hub axle and the axis of rotation. The slip ring elements are coupled to the stator to provide power to the stator for torque generation during operation of the electric bicycle.

In this way, the stator can be supplied with energy, even if both components of the electric motor, the stator and the rotor, rotate about the axis of rotation. Alternatively, the stator may be rotationally or stationary to the hub axle or motor housing be coupled so that a direct wiring of the stator to the power supply can be set up. A slip ring can be saved with direct cabling.

According to a further development of the drive device, the motor housing is designed in two parts and, in addition to the circumferential housing section, includes a stator cover, which is coupled to one another so as to be rotatable with respect to the axis of rotation by means of a bearing. The housing section is rotatable and surrounds the stator cover, which is rotationally fixed or stationary coupled to the hub axle. The housing section has an axial opening through which the stator cover extends axially along the axis of rotation to the outside of the housing section. In this way, the stator cover with the stator or electric motor located therein can be shifted closer to the outside area and thus be better cooled. The electric motor is therefore not insulated and shielded from the outside area by a stator cover and a housing and any elements and/or air gaps arranged in between, but can transfer heat to the wall of the stator cover in a timely and efficient manner, which in turn transfers the heat to the Outside leads and gives off to the ambient air.

In addition, the drive device can include a brake disc for braking the electric bicycle as required, which is firmly coupled to the peripheral housing section. The brake disc then preferably has an axial or inner penetrating recess through which the stator cover extends axially along the axis of rotation. The stator cover can thus protrude through the housing section and through the brake disc to the outside area and reliable cooling of the electric motor allow, which usually forms the main heat source of the drive device. The stator cover and the electric motor are thus shifted axially and thereby also provide available installation space in the housing section, which can be used for further components of the drive device.

According to a further development of the drive device, the gearing is designed as a planetary gearing with a sun gear and at least one planetary gear and is arranged coaxially around the axis of rotation of the hub axle, so that the planetary gearing surrounds the hub axle. The planetary gear can be single-stage, two-stage or multi-stage. Furthermore, the planetary gear can include a ring gear.

Furthermore, the electric motor is preferably designed as a ring motor and is arranged coaxially around the hub axle in relation to the axis of rotation of the hub axle, so that the ring motor surrounds the hub axle. The hub axle can form a bearing seat for the planetary gear and/or the ring motor. In this way, one or both components can be arranged radially and in a particularly space-saving manner, in that they are coupled to the hub axle using ball bearings and/or roller bearings, for example.

With regard to the versions of the gear as a planetary gear and the motor unit as a ring motor, these components can be plugged or pushed onto the drive axle before the quick-release axle is passed through, so that an assembly can be provided and then coupled to the bicycle frame. Correspondingly, a method for producing the drive device can include providing and coupling the respective components include . For example, the electric motor is pushed onto the drive axle as a ring motor and then the planetary gear is also arranged axially adjacent to it. The subassembly can then be placed on the rear bicycle tire or on a rear dropout of the bicycle frame and the quick-release axle can be inserted through it and screwed to the frame elements. Alternatively, a different order of assembly can also be carried out, so that, for example, the quick-release axle is first inserted through the drive axle or the assembly and the drive device is thereby formed, which is then screwed to the frame elements by means of the end sections of the quick-release axle.

The described embodiments of the drive device each enable a reliable and efficient electric drive system for a rear wheel hub drive of an electric bicycle. In particular, by means of the tapered hub axle, which is preferably designed in two parts, the stiffness of the drive device can be increased and customer acceptance improved by using the quick-release axle, and installation space can also be made available for the sensor unit. In addition, a reliable heat dissipation by means of heat conduction and an enlarged axial installation space can be realized by targeted arrangement of the motor unit on a predetermined wall.

In another aspect, an electric bicycle is disclosed that includes a bicycle frame that extends to a bottom bracket and to a bicycle hub. The electric bicycle has a drive device according to one of the embodiments described above, which is arranged in or on the bicycle hub, so that a torque for driving the electric bicycle can be transmitted by means of the transmission. Essentially, the electric bicycle enables the aforementioned properties, advantages and functions.

For attachment to the bicycle hub and possibly to a frame section of the electric bicycle, this has a recess, for example, so that the drive device can be reliably accommodated.

According to one embodiment, the drive device is arranged, in particular mounted, or forms an assembly on the bicycle hub in the already coupled state, for example.

Embodiments, advantages and functions are explained in the following description using exemplary embodiments with the aid of the attached figures. In the figures show :

Figure 1 is a schematic view of a

Electric bicycle with a mounted drive device,

Figures 2-4 an exemplary embodiment of the drive device for the electric bicycle in different views,

Figures 5- 8 Another exemplary embodiment of the drive device for the electric bicycle in different views, and

FIGS. 9-11 another exemplary embodiment of the drive device for the electric bicycle in different views. Identical, similar or equivalent elements are provided with the same reference symbols in the figures. For reasons of clarity, not all of the elements shown are identified with the associated reference symbols in all of the figures.

FIG. 1 schematically shows an electric bicycle 1 with a bicycle frame 2 which extends in the direction of a bottom bracket 4 and in the direction of a rear bicycle hub 3 . The bicycle hub 3 is coupled to an electric drive device 5 for the electric bicycle 1 or can be coupled to one.

Terms such as "front," "rear," "top," "bottom," "right," "left," "outside," and "inside" refer to alignments or orientations of respective components, as defined in are illustrated in the figures and how they are arranged in an operational state of the electric bicycle 1 . The electric bicycle 1 usually has a front wheel and a rear wheel. An outer area designates an area outside of the electric bicycle 1 or outside of the drive device 5 . The drive device 5 can also be referred to as a rear wheel hub drive and is integrated into the rear bicycle hub 3 or arranged on it and transmits a provided driving force to the rear bicycle tire and thus to the road or the ground. The wheels of the electric bicycle 1 are set in motion directly by the drive device 5 so that a high level of efficiency can be achieved to support a rider of the electric bicycle 1 by means of the rear wheel hub drive.

As with reference to the following examples from and the

Figures 2- 11 is explained, allows the Drive device 5 a drive concept for electric bicycles, which has a clear structure and also contributes to a high power transmission.

FIGS. 2-4 schematically show an exemplary embodiment of the drive device 5 for the electric bicycle 1 in different views. The drive device 5 includes a motor unit with an electric motor for driving the electric bicycle 1 . The electric motor is designed as a ring motor with respect to an axis of rotation R and has a rotor 13 and a stator 14 which provide a drive torque in rotational interaction. With respect to the axis of rotation R, the rotor 13 is arranged radially on the inside and the stator 14 is arranged radially on the outside within a motor housing.

The drive device 5 also has a hub axle which is designed in two parts and comprises a plug-in axle 9 and a drive axle 10 which are coupled to the electric motor. The quick-release axle 9 and the drive axle 10 are sleeve-shaped and the quick-release axle 9 extends through the drive axle 10 so that the respective end sections 91 , 92 of the quick-release axle 9 protrude from the drive axle 10 .

The drive device 5 also includes a transmission, which is designed to drive the electric bicycle 1 and is mounted such that it can rotate about the axis of rotation R. The gearing is preferably designed as a planetary gearing 18 and is arranged axially adjacent to the electric motor in the motor housing. The planetary gear 18 comprises a sun gear and at least one planetary gear and can also be coupled to a ring gear 19 , a planetary carrier 21 and/or a freewheel 26 or have such components. The Planetary gear 18 is coupled to the electric motor on the one hand and to the hub axle on the other hand and is set up to output a torque for driving the electric bicycle 1 .

The drive device 5 also includes the motor housing, which includes a circumferential housing section 6 and possibly also a stator cover 15 (see FIGS. 5-11). According to FIGS. 2-4, the rotor 13 , the stator 14 and the planetary gear 18 are arranged in the housing section 6 . The hub axle with the quick-release axle 9 and the drive axle 10 extends through the housing section 6 . The electric motor and in particular the stator 14 are shielded from the outside area only by an adjacent wall 61 of the housing section 6 . An outer side 62 of the wall 61 thus borders at least in sections on the outer area and ambient air can flow directly around it. Heat generated by the electric motor during operation of the electric bicycle 1 can thus be dissipated to the outside area through the wall 61 by means of direct thermal conduction.

In the rear wheel hub drive, the stator 14 is shrunk directly into the peripheral housing section 6 . The direct connection of the stator 14 to the housing section 6 enables a particularly reliable and timely heat dissipation through heat conduction to the motor housing and thereby to the air flowing around in the outside area. The stator 14 is also supplied with a three-phase current by means of a slip ring 22 to generate a torque. The slip ring 22 comprises a first and a second slip ring element 23 , 24 which contact each other axially and/or radially with respect to the axis of rotation R. The power supply of the stator 14 is thus of the fixed drive axle 10 to the revolving housing section 6 and then to the stator 14 . In other exemplary embodiments, there is no need to install a slip ring 22 and direct wiring for the power supply to the stator 14 can be set up (see FIGS. 5-11). Power supply by means of the slip ring 22 is suitable if both the rotor 13 and the stator 14 are rotatable about the axis of rotation R, as shown in FIGS.

The rotor 13 is mounted on the stationary or rotationally fixed drive axle 10 by means of one or more bearings 25 and transmits a drive torque to the downstream planetary gear 18 . The planetary gear 18 converts speed and torque and the converted torque can be delivered to the revolving housing section 6 with a drive through the sun gear, either through the planet carrier 21 or through the ring gear 19 . Between the output, which is set up for example by the ring gear 19 and/or the planetary carrier 21, and the rotating housing section 6, the freewheel 26 can also be provided for decoupling a drive train when operating the electric bicycle 1 without support from the electric motor. According to an alternative configuration, the output can be set up by the sun gear.

The drive device 5 further comprises a brake disk 7 on one side and a cassette body 8 on the other side of the drive device 5 with respect to the axial arrangement of the components along the axis of rotation R . The brake disk 7 is used to brake the electric bicycle 1 and is firmly coupled to the surrounding housing section 6 , for example screwed. The cassette body 8 is as a pinion carrier by means of a second bearing 17 with the peripheral housing section 6 coupled. With respect to the axis of rotation R, the cassette body 8 surrounds the drive axle 10 and the through axle 9 and is set up to transmit a torque of a rider of the electric bicycle 1 to the motor housing. The drive torque of the driver is introduced through the cassette body 8 into the encircling housing section 6 . The cassette body 8 also contains or surrounds a sensor unit 20 of the drive device 5, which includes sensors for measuring the driver's torque.

The sensor unit 20 comprises a measuring sleeve which is coupled, for example screwed, to the cassette body 8 and into which the torque from the cassette body 8 is introduced at one end. At another end, the torque is transmitted to the housing section 6 via a freewheel. The sensor unit 20 also includes sensor electronics that enable the torque to be measured.

The sensor unit 20 is based, for example, on a magnetostrictive measuring principle. The measuring sleeve is made from steel, for example, and is designed to be permanently magnetic. Alternatively, it can also be ferromagnetic and can be electrically magnetized by a coil. The measuring sleeve is twisted by a torsional moment, so that the magnetic field in the measuring sleeve changes. Such a magnetic field change is proportional to the torque and can be detected with the help of coils in the sensor electronics.

The sensor unit 20 is arranged between the cassette body 8 and the drive axis 10 with respect to a radial direction transverse to the axis of rotation R. This can be made possible in particular to save space by the fact that the The hub axle with the through axle 9 and the drive axle 10 tapers in the direction of the second end section 92 . The cassette body 8 can also be decoupled from the surrounding housing section 6 by a freewheel. The freewheel is realized, for example, as a pawl freewheel or a toothed disk freewheel.

The quick-release axle 9 is set up to be coupled, in particular screwed, at opposite ends to outer frame elements 11 and 12 of the bicycle frame 2 of the electric bicycle 1 . On the drive side, between the two frame elements 11 and 12 , the fixed drive axle 10 is provided, on which both the rotating housing section 6 is mounted by means of a bearing 25 , as well as the rotor 13 and the cassette body 8 . The stationary drive axle 10 is designed in such a way that it provides the necessary rigidity to support the forces acting on it during operation.

The revolving housing section 6 is mounted on the drive axle 10 by means of two bearings 16 , 17 or 25 . These camps can also be referred to as main camps and beyond that other camps as other camps. In FIGS. 2-4, bearing 16 on the illustrated left-hand area of housing section 6 and bearing 25 on the illustrated right-hand area of housing section 6 can therefore be referred to as the main bearing. Technically, the bearings 16 , 17 and 25 are designed in particular to have the same effect and, essentially due to their installed position in the drive device 5 , experience position-dependent forces and/or serve position-dependent functions.

The fixed drive axle 10 is hollow, so that there is space inside for the quick-release axle 9, which can be inserted into the screwed into the second frame element 12 of the bicycle frame 2 by means of the narrower second end section 92 and thus braces the two frame elements 11 , 12 against the stationary drive axle 10 . The quick-release axle 9 is not designed with a uniform diameter, but tapers towards the right-hand side in order to provide installation space for the sensor unit 20 .

The drive device 5 can be used to provide efficient and directed heat dissipation and also a useful axle standard, which can have an advantageous effect on stiffness and customer acceptance by using the two-part hub axle with the plug-in axle 9 and the drive axle 10 .

FIGS. 5-8 schematically show another exemplary embodiment of the drive device 5 for the electric bicycle 1 in different views. According to this exemplary embodiment, the motor housing includes, in addition to the circumferential housing section 6 , a stator cover 15 which is coupled to one another by means of a first bearing 16 . In comparison to the previous exemplary embodiment, the diameter of the left or first bearing 16 is significantly larger. The first bearing 16 can also be referred to as the first main bearing and is arranged on the non-stationary or rotatable stator cover 15 . The circumferential housing section 6 is in turn arranged on the first main bearing 16 , so that the first main bearing 16 is arranged radially between the stator cover 15 and the housing section 6 . The bearing 17 forms a further, second main bearing and is arranged opposite one another between the housing section 6 and the cassette body 8 . Acting radial forces are absorbed by the main bearing 17, then through the cassette body 8, and then through the bearing

25 transferred to the fixed drive axle 10 .

Another bearing (not shown) is also provided between the measuring sleeve of the sensor unit 20 and the drive axle 10 . An acting radial force is accordingly transmitted to the housing section 6 , then to the bearing 17 , then to a freewheel body that may be present, then to the measuring sleeve of the sensor unit 20 screwed to the freewheel body, then to a roller bearing and then to the drive axle 10 . The additional bearing 25 according to FIGS. 5-8 serves as the freewheel body and essentially no radial forces are introduced by the driver at this position.

The stator cover 15 is in the shape of a bell and is located as far to the left as possible and extends through an inner or central recess 71 of the brake disc 7 . The left side of the drive device 5 shown in FIG. 5, on which the brake disc 7 is arranged, can also be referred to as the non-drive side. The right-hand side of the drive device 5 shown in FIG. 5, on which the cassette body 8 is arranged, can also be referred to as the drive side. The brake disk 7 is also fastened, in particular screwed, to the peripheral housing section 6 . The axial position of the brake disc 7 is unchanged compared to the previous exemplary embodiment, as are the braking flanks of the brake disc 7 . Due to the axial displacement of the electric motor and the stator cover 15

(For example, in comparison to the embodiment according to FIG. 2), axial installation space is available inside the drive device 5 for the other or further components of the drive device 5 . In particular, the axial outer side of the stator cover 15 is not surrounded by the surrounding housing section 6, so that heat dissipation is particularly efficient. The stator cover 15 is not installed tightly and is encapsulated inside the surrounding housing section 6 , but can emit the heat introduced from the stator 14 into the stator cover 15 by means of thermal conduction through the wall 151 directly to the air flowing around the outside area. Within the drive device 5, the heat is transferred from the stator 14 to the stator cover 15 predominantly by means of thermal conduction, but also by means of convection and thermal radiation. The heat is then emitted from the stator cover 15 to the ambient air by means of convection and radiation.

The heat dissipation can also be improved in that the stator cover 15 has a cooling structure 153 on the axial outside with a plurality of ribs which are spaced apart from one another and provide an enlarged surface around which the ambient air can flow (see FIG. 7).

FIG. 8 shows the drive device 5 according to FIG. 7, a possible arrangement and design of the left or first frame element 11 also being illustrated.

FIGS. 9-11 schematically show a further exemplary embodiment of the drive device 5 for the electric bicycle 1 in different views. According to this exemplary embodiment, the stator cover 15 comprises an extension section 152 which extends the wall 151 of the stator cover 15 and connects it to the outside. Also by means of such a guide from Stator cover 15 , which is surrounded by housing section 6 , can be set up for directed and timely heat dissipation by means of heat conduction.

The heat generated during operation of the stator 14 is transferred to the surrounding wall 151 of the stator cover 15 and guided through the material under the bearing 16 into the extension section 152 , from where the heat can be dissipated to the ambient air. Such a heat dissipation is significantly more efficient than a heat transfer which, for example, has to overcome the wall 151 of the stator cover 15, the wall 61 of the housing section 6 and in particular the air gap located between them. As previously described, the extension section 152 can have the additional cooling structure 153 on the outside. The extension section 152 can be configured in one piece with the wall 151 of the stator cover 15 or can be coupled to the wall 151 as a separate extension piece. In the design of the stator cover 15 with wall 151 and optionally provided extension section 152 , simple and time-saving assembly of the components is also taken into account in particular. The extension section 152 and the wall 151 are then preferably made of the same material.

The stator cover 15 or the wall 151 and the optionally provided extension section 152 are preferably made of aluminum or have aluminum. Compared to steel, for example, aluminum has a significantly higher thermal conductivity and also has weight advantages. Alternatively or additionally, one or more of the components described above could be made of magnesium or have magnesium, so that a low weight and reliable thermal conductivity of the drive device 5 can be achieved.

The hub axle has the through axle 9 and the drive axle 10 , each of which tapers in the direction of the second end section 92 , which enable simplified assembly and also provide installation space for the sensor unit 20 .

The wheel spindle 9 is illustrated in FIGS. 2-11 as having three sections, with the two opposite end sections 91 , 92 being connected to one another by a middle section 93 . The end sections 91 , 92 each have a substantially constant diameter in relation to a radial direction transverse to the axis of rotation R, the diameter of the second end section 92 being smaller than that of the first end section 91 . The middle section 93 establishes a transition area between the two end sections 91 , 92 , the middle section being formed so that it tapers continuously or stepwise towards the second end section 92 . The middle section 93 accordingly initiates a change in the circumference of the respective end sections 91 , 92 .

A length of the first end section 91 and/or a length of the second end section 92 along the axis of rotation R are configured in particular to match an expansion of the electric motor 13 , 14 , the planetary gear 18 and/or the sensor unit 20 . For example, the second end section 92 is twice as long as the first end section 91 in order to provide a correspondingly large amount of space for an elongate sensor unit 20 (see FIGS. 5-11). Alternatively, however, the first end section 91 can also be longer than the second end section 92, provided that the Permit or require components of the drive device 5 (see FIGS. 2-4). Alternatively, the first end section 91 and the second end section 92 can be designed with approximately the same length, provided that the components of the drive device 5 permit or require it.

For reasons of clarity, only the described sections 91, 92, 93 of the quick-release axle 9 are illustrated in FIGS. 2-11. However, the properties and features described can be transferred analogously to three sections of the drive axle 10, which are designed to follow one another and can follow an outer contour of the quick-release axle 9 or, as illustrated in Figures 2-11, a free space 94 between the quick-release axle 9 and the Set up drive axle 10 . Referring to the illustrated FIGS. 2-11, a middle section of the drive axle 10 thus begins further to the right than the middle section of the quick-release axle 9 . The free space 94 introduced between them can have a particularly beneficial effect on an assembly of the drive device 5 in which the quick-release axle 9 is inserted into the drive axle 10 and through the drive axle 10 . The free space 94 thus provides a certain amount of assembly play and can, for example, alleviate some of the specifications for tolerance accuracy in the production of the individual components of the drive device 5 .

A reliable drive concept for electric bicycles can be implemented by means of the drive device 5 described, which enables particularly efficient heat dissipation. In addition, an axially enlarged installation space can be set up and greater rigidity and improved customer acceptance of the drive device 5 can be achieved. The drive device 5 is particularly suitable for assembly or use in the hub of the rear wheel of the Suitable electric bicycle 1 and enables an advantageous drive system, in particular in terms of high ef fi ciency.

reference character list

1 electric bike

2 bike frames

3 bicycle hub

4 bottom bracket

5 drive device

6 housing

61 wall of the housing

62 outside of wall

7 brake disc

71 Recess of the brake disc

8 cassette body

9 thru axle

91 first end section of the quick-release axle

92 second end section of the thru axle

93 center section of the thru axle

94 free space

10 drive axle

11 outer frame member

12 outer frame member

13 rotors

14 stator

15 stator cover

151 wall of the stator cover

152 Extension section of the stator cover

153 Stator cover cooling structure

154 Outside of the stator cover

16 camps

17 camps

18 planetary gears

19 ring gear

20 sensor unit

21 planet carriers 22 loop fring

23 first slip ring element

24 second slip ring element

25 bearing 26 freewheel

R Axis of rotation of the electric motor / thru-axle

Claims

patent claims

1. Drive device (5) for an electric bicycle (1), having:

- A motor unit (13, 14) for driving the electric bicycle (1),

- a hub axle (9, 10) coupled to the motor unit (13, 14),

- A transmission (18, 19, 26) which is designed to drive the electric bicycle (1) and can be rotated about an axis of rotation (R) and which is connected on the one hand to the motor unit (13, 14) and on the other hand to the hub axle (9, 10) is coupled and is set up to deliver a torque for driving the electric bicycle (1), and

- a motor housing (6, 15) in which the motor unit (13, 14) and the transmission (18, 19, 26) are arranged and through which the hub axle (9, 10) extends, the hub axle (9, 10 ) in relation to the axis of rotation (R) has a first end section (91) and a second end section (92), which are designed to be coupled on opposite sides to a respective outer frame element (6, 7) of the electric bicycle (1), wherein the second end portion (92) is narrower than the first portion (91).

2. Drive device (5) according to claim 1, wherein the second end portion (92) has a diameter with respect to a radial direction transverse to the axis of rotation (R) which is at least one millimeter smaller than a diameter of the first end portion (91) .

3. Drive device (5) according to claim 2, wherein the first end portion (91) and the second end portion (92) in Reference to a radial direction transverse to the axis of rotation (R) each have a constant diameter.

4. Drive device (5) according to one of the preceding claims, in which the hub axle (9, 10) has a middle section (93) which, in relation to the axis of rotation (R), is between the first end section (91) and the second end section (92 ) and which establishes a transition region between the two end sections (91, 92), the middle section (93) being formed in such a way that it tapers continuously, in sections or in steps towards the second end section (92).

5. Drive device (5) according to one of the preceding claims, wherein the hub axle (9, 10) is formed in two parts and comprises a stub axle (9) and a sleeve-shaped drive axle (10) through which the stub axle (9) extends.

6. Drive device (5) according to claim 5, wherein the stub axle (9) and the drive axle (10) taper along the axis of rotation (R) towards the second end portion (92) of the hub axle, respectively.

7. Drive device (5) according to Claim 4 in conjunction with Claim 5 or 6, in which, with respect to a radial direction transverse to the axis of rotation (R), in the middle section (93) between the plug-in axle (9) and the drive axle (10) a predetermined free space (94) is set up.

8. Drive device (5) according to any one of claims 5-7, comprising: a first and a second frame element (11, 12) arranged on opposite sides with respect to the axis of rotation (R) outside the motor housing (6, 15) and connected to a respective end portion (91, 92) of the hub axle (9, 10) are coupled, so that the two frame elements (11, 12) brace the drive axle (10) in a predetermined manner in cooperation with the quick-release axle (9).

9. Drive device (5) according to claim 8, wherein the second end portion (92) is screwed directly or by means of a threaded member to the second frame member (12).

10. Drive device (5) according to one of the preceding claims, in which the motor unit comprises an electric motor with a rotor (13) and a stator (14) and the stator (14) in the direct vicinity of a wall (61, 151, 152) of the motor housing (6, 15), the wall (61, 151) directly adjoining an outer area outside of the motor housing (6, 15) and thereby the electric motor

(13, 14) is shielded from the outside area only by a wall of the drive device (5) and/or wherein the

Wall (61, 151) has an extension section (152) which thermally conductively connects the wall (61, 151) to the outside area.

11. Drive device (5) according to Claim 10, in which the wall (61, 151, 152) has a cooling structure (153) which comprises a plurality of ribs which are spaced apart from one another on an outer side (62, 154) of the wall (61 , 151, 152) are arranged.

12. Drive device (5) according to any one of the preceding

claims having: - a cassette body (8) which is coupled to the motor housing (6, 15) and which surrounds the hub axle (9, 10) with respect to the axis of rotation (R) and which is set up to transmit a torque of a rider of the electric bicycle (1st ) to be transmitted to the motor housing (6, 15), and

- a sensor unit (20), which is coupled to the hub axle (9, 10) to determine a torque of the driver and is transverse to the axis of rotation (R) in relation to a radial direction between the cassette body (8) and the hub axle (9, 10) is arranged.

13. Drive device (5) according to claim 12, wherein the sensor unit (20) is arranged in the narrower second end section (92) of the hub axle (9, 10) and the sensor unit (20) and the second end section (92) in coordination with one another are trained.

14. Drive device (5) according to one of the preceding claims, in which a length of the first end section (91) and / or a length of the second end section (92) along the axis of rotation (R) on an extension of the motor unit (13, 14), of the transmission (18, 19, 26) and/or the sensor unit (20) is designed to be coordinated.

15. Electric bicycle (1) comprising:

- a bicycle frame (2) extending to a bottom bracket (4) and to a bicycle hub (3), and

- A drive device (5) according to any one of the preceding claims, which is coupled to drive the electric bicycle (1) with the bicycle hub (3).