Torque transmission arrangement for a drive device

Abstract

The present invention relates to a torque transmission arrangement (5) for a drive device (1) of a muscle-powered vehicle. The arrangement (5) has a first torque transmission component (7) with a first circumferential toothing (13), a second torque transmission component (10) with a second circumferential toothing (17) and a sensor device (11) for measuring a load variable of one of the torque transmission components (7; 10). The first and second circumferential toothing (13, 17) mesh for torque transmission along a toothing circle (K). A play between the teeth (14) of the first circumferential toothing (13) and the teeth (18) of the second circumferential toothing (17) is designed such that contact points (16.1, 16.2, 16.3) are arranged equidistantly to one another along the toothing circle (K).

Description

[0001] Torque transmission arrangement for a drive device

[0002] Technical area

[0003] The present invention relates to a torque transmission arrangement for a drive device of a human-powered vehicle. Furthermore, the present invention relates to a drive device for a human-powered vehicle having such a torque transmission arrangement, and to a human-powered vehicle having such a drive device. Furthermore, the present invention relates to a method for manufacturing such a torque transmission arrangement.

[0004] State of the art

[0005] Human-powered vehicles with electrical assistance, such as e-bikes or pedelecs, can have a drive device with a crank mechanism for transmitting a rider's muscle power and an electric motor for providing an assist torque. Due to the limited installation space and to enable easy assembly and disassembly, components in a torque transmission path of the drive device can be detachably connected to one another via a gearing. To control the electric motor of the drive device, a torque in the drive device is often detected using a torque sensor. Torque sensors are known, for example, from DE 10 2019 203 322 A1, DE 20 2011 052 156 U1, and EP 3480 575 A1.The object of the present invention was to provide a torque transmission arrangement with two torque transmission components connected via a toothing, which enables a reliable and accurate measurement of a load variable in one of the torque transmission components.

[0006] Description of the invention

[0007] This object is achieved by the torque transmission arrangement claimed in claim 1 for a drive device of a human-powered vehicle. The human-powered vehicle can be a single-track vehicle, for example, a bicycle. The bicycle can be an e-bike or a pedelec. The drive device can have a crank device via which a driver of the vehicle can transmit muscle power to the drive device.

[0008] The crank mechanism can be mechanically connected to an output of the drive mechanism, for example via a gear mechanism. The gear mechanism can be designed as a planetary gear mechanism and have one or more planetary stages. The output can be designed as a chainring or in another way. In addition, the drive mechanism can have an electric machine, which can also be mechanically connected to the drive mechanism or, preferably, the output of the drive mechanism. If the electric machine is connected to the output of the drive mechanism, a torque applied by a driver to the crank mechanism, which can be transmitted via a gear mechanism, and a torque provided by the electric machine can be added together.

[0009] The output of the drive device can be mechanically connected to a drive wheel of the vehicle, for example, the rear wheel of a bicycle. The mechanical connection can be formed by means of an endless circulating element, such as a chain or a belt. Accordingly, torque can be transmitted via the drive device to the drive wheel to propel the vehicle.

[0010] The torque transmission arrangement can be arranged at any location in the drive device. In one embodiment, the torque transmission arrangement is provided in a torque transmission path between the crank device described above and the gear mechanism described above.

[0011] The torque transmission arrangement has a first torque transmission component with a first circumferential toothing and a second torque transmission component with a second circumferential toothing. The torque transmission components can be substantially rotationally symmetrical components that can be rotationally symmetrical to a central axis. In one embodiment, the central axes of the torque transmission components can coincide, so that the torque transmission components can be arranged coaxially to one another. Both the first and the second torque transmission component have circumferential toothing that can be arranged along the circumference, for example the entire circumference, of the respective torque transmission component. Likewise, the circumferential toothing can have interruptions along the circumference, such as enlarged tooth gaps.The gear teeth can each extend both in the direction of the central axis of the respective torque-transmitting component and perpendicular thereto, for example in the radial direction of the respective component. To transmit torque, the first and second circumferential gear teeth mesh along a gear circle. For example, each tooth of the first torque-transmitting component meshes with a tooth of the second torque-transmitting component in order to be able to transmit torque between the components. The first circumferential gear teeth and, alternatively or additionally, the second circumferential gear teeth can each be designed as crown gear teeth or in another way. The crown gear teeth have a certain flank backlash due to manufacturing tolerances and assembly requirements.

[0012] In addition, the torque transmission arrangement comprises a sensor device for measuring a load variable from one of the torque transmission components. The sensor device can have one or more sensors, which can be arranged at the same or different locations. By means of the sensor device, a load variable, for example a torque transmitted via the component, can be determined. The torque can be determined, for example, based on a shear stress detected by the sensor device. For this purpose, the sensor device can have a strain gauge. The sensor device can be arranged and designed such that, based on the load variable from one of the torque transmission components detected with it, a torque applied by the driver to the crank device can be detected or calculated.Based on the load value detected by the sensor device, the electrical machine of the drive device described above can be controlled.

[0013] The clearance between the teeth of the first and second circumferential toothing is designed such that the contact points at which the first circumferential toothing first comes into contact with the second circumferential toothing at the start of torque transmission are arranged equidistant from one another along the toothing circle. The contact points are therefore positions at which the two toothings first come into contact with one another at the start of torque transmission between the components. The contact points may only be present when the torque transmission arrangement is new and may be eliminated during operation due to wear or superficial plastic deformation caused by loading above the yield point of the toothing material. Likewise, additional contact points may be added during operation due to wear or superficial plastic deformation.In one embodiment, the contact points are arranged equidistant from one another along the gearing circle only in the new state. The torque transmission arrangement can have any number of contact points.

[0014] The play between the teeth of the peripheral gearing can be designed in such a way that contact points result that lead to a homogeneous, for example symmetrical, load pattern in one of the torque transmission components. The homogeneous load pattern can, for example, be present in the torque transmission component in which a load variable can be measured using the sensor device. This allows a reliable and precise measurement of the load variable using the sensor device. If, on the other hand, the contact points were not arranged equidistant from one another, an inhomogeneous load pattern would result, which would lead to inaccuracies in the detection of the load variable using the sensor device. The present invention therefore enables a reliable and precise determination of a load variable of a torque transmission component that is in meshing engagement with another torque transmission component.

[0015] In one embodiment, the play between the teeth of the first circumferential toothing and the teeth of the second circumferential toothing is set up such that, at the beginning of torque transmission, three contact points are formed that are arranged equidistant from one another along the toothing circle. In this embodiment, the contact points can have an angle of 120° to one another. In one embodiment, only three and no further contact points are formed. By providing three contact points, a torque transmission arrangement with the advantages described above can be provided in a particularly simple manner. In an alternative embodiment, however, the play between the teeth of the circumferential toothing can also be set up such that, at the beginning of torque transmission, four, five, six, seven or more contact points are formed that are arranged equidistant from one another along the toothing circle.The contact points can be arranged in such a way that, when connected, they form an equilateral polygon. This would also make it possible to create larger tooth gaps along the circumference if functionally or manufacturing-wise necessary, without compromising the homogeneity of the load pattern.

[0016] According to one embodiment, the second or preferably first torque transmission component has smaller gaps between two adjacent teeth of the first circumferential toothing at the positions of the contact points than at all other positions. A gap can be a distance, for example an angular distance, in the circumferential direction between the adjacent teeth. The distance can also be a minimum distance between the adjacent teeth. The adjacent teeth can be teeth that are arranged next to one another in the circumferential direction of the torque transmission component. Within the scope of this embodiment, the gaps between two adjacent teeth at the positions of the contact points of the first circumferential toothing can also be smaller than all the gaps between adjacent teeth of the second circumferential toothing of the second torque transmission component.The smaller gaps can be created by enlarging the adjacent teeth, for example, circumferentially. This allows the attachment points to be formed in a particularly simple manner.

[0017] In one embodiment, the sensor device is designed to measure a load variable of the first torque component. The first torque component can be the component which has the smaller gaps described above. In one embodiment, the sensor device is aligned with one of the contact points in the circumferential direction of the gearing circle. In other words, within the scope of this embodiment, the sensor device can be aligned with one of the smaller gaps between adjacent teeth in the circumferential direction. This leads to the advantage that the sensor device can be used to measure the load variable at a location at which it has a particularly high value, for example a maximum value, or a value representative of the particularly relevant sensor cases.The sensor device can be a sensor device designed to measure torque in one of the torque transmission components. For example, the sensor device comprises a strain gauge, as described above.

[0018] In one embodiment, the first torque transmission component is essentially designed as a pot with a circumferential surface and, for example, a base. The circumferential surface can be cylindrical and the base can be circular, for example. The second torque transmission component can essentially be designed as a disk. In one embodiment, the second torque transmission component is designed as a planetary carrier, which can carry one or more planetary gears that can mesh with a sun gear and a ring gear. The planetary carrier can be part of the above-described transmission of the drive device. A central axis of the pot can coincide with a central axis of the disk, so that the pot and the disk can be arranged coaxially to one another.The second torque-transmitting component, i.e., the disk, can essentially close off an interior space defined by the first torque-transmitting component, i.e., the cup. Components of a planetary stage, such as a sun gear, a ring gear, and planetary gears, can be arranged in the interior of the cup.

[0019] The first circumferential toothing can be formed along an end face of the lateral surface of the pot. The end face can be the side of the lateral surface that is arranged parallel to a base of the pot. The first circumferential toothing on the end face of the lateral surface can have teeth that are distributed along the end face and each extend in the direction of the central axis of the pot. The second circumferential toothing can, in this embodiment, be formed on a circumferential surface of the disk and thus have teeth that are distributed over the circumference of the disk. The individual teeth can each extend perpendicular to the central axis, for example in the radial direction of the disk. Accordingly, the directions of extension of the individual teeth of the first circumferential toothing and the individual teeth of the second circumferential toothing can be arranged essentially perpendicular to one another.The present embodiment leads to the advantage that a torque transmission arrangement as described above can be provided in a space-saving environment of a drive device of a vehicle, for example a bicycle.

[0020] Furthermore, the present invention relates to a drive device for a muscle-powered vehicle with an output that is operatively connectable to a drive wheel of the vehicle. The output can be a chain wheel of the drive device. The drive wheel can be a rear wheel of a bicycle. The output can be mechanically operatively connected to the drive wheel via an endless circulating element, as described above. The drive device further comprises a crank device for introducing muscle power into the drive device. The crank device can comprise one or more cranks with pedals mounted thereon, via which a driver of the vehicle can introduce muscle power into the drive device. Furthermore, the drive device can comprise a gear for translating and transmitting the introduced muscle power to the output.

[0021] Furthermore, the drive device can have an electric machine that is mechanically connected to the output, via which a torque can be provided to the drive or preferably the output to assist the driver. In addition, the drive device comprises a torque transmission arrangement according to one of the previously described embodiments, wherein the torque transmission arrangement can be arranged in the torque transmission path between the crank device and the transmission. The present invention further relates to a human-powered vehicle with such a drive device. With regard to the design and advantages of the individual components, reference is made to the above explanations in connection with the torque transmission arrangement. In addition, the present invention relates to a method for producing a torque transmission arrangement according to one of the previously described embodiments.The method comprises defining a maximum clearance between the teeth of the first circumferential toothing and the teeth of the second circumferential toothing at the positions of the contact points. In addition, the method comprises defining a minimum clearance between the teeth of the first circumferential toothing and the teeth of the second circumferential toothing at all other positions, i.e. at all positions where no contact points are formed. The maximum clearance at the positions of the contact points is smaller than the minimum clearance at all other positions. This ensures that the contact points are formed at the targeted positions despite manufacturing tolerances and necessary clearances for assembly of the torque transmission components and their circumferential toothing.With regard to the design and advantages of the individual features, reference is made to the above explanations in connection with the torque transmission arrangement.

[0022] Short description of the characters

[0023] Figure 1 schematically shows a drive device for a muscle-powered vehicle according to an embodiment of the present invention.

[0024] Figure 2 shows schematically a torque transmission arrangement of the drive device from Figure 1 in a sectional view.

[0025] Detailed description of embodiments

[0026] Figure 1 shows a drive device 1 for a muscle-powered vehicle according to one embodiment of the present invention. In the present embodiment, the muscle-powered vehicle is designed as a bicycle, more precisely as a pedelec. The drive device 1 comprises a crank device 2, via which a rider of the bicycle can apply muscle power. The crank device 2 comprises a shaft, at the ends of which cranks 3 are provided for introducing a torque into the drive device 1 via the rider of the bicycle. In addition, the drive device 1 comprises an output 4, which in the present embodiment is designed as a chainring. The output 4 can be mechanically operatively connected to a drive wheel, for example a rear wheel, of the bicycle via an endless circulating element, for example a chain or belt.A torque introduced by the driver via the crank device 2 can be transmitted to the output 4 of the drive device 1 via a torque transmission arrangement 5 and a gear 6. In addition, the drive device 1 comprises an electric machine 20, which is also mechanically connected to the output 4 via a spur gear reduction gear with lateral drive (not shown). Alternatively, in an embodiment not shown, the electric machine 20 can also be connected to the drive 2 via a reduction gear with lateral drive. The electric machine 20 can provide a torque to assist the driver. The torque introduced by the driver via the crank device 2 and transmitted via the gear 6, as well as the torque provided by the electric machine 20 and transmitted via the spur gear (not shown), are therefore available at the output 4.

[0027] In the present embodiment, the transmission 6 is designed as a planetary gear and has a first planetary stage 6.1 and further planetary stages 6.2. The crank mechanism 2 is mechanically operatively connected to the first planetary stage 6.1 of the transmission 6 via the torque transmission arrangement 5. The first planetary stage 6.1 is, in turn, mechanically operatively connected to the further planetary stages 6.2. The further planetary stages 6.2 are mechanically operatively connected to the output 4.

[0028] As can be seen in Figure 1, the torque transmission arrangement 5 of the present embodiment has a first torque transmission component 7, which is designed as a pot. The pot 7 comprises a bottom surface 8 and a shell surface 9, wherein its central axis is arranged coaxially with a shaft of the crank device 2 connecting the cranks 3. In addition, the torque transmission arrangement 5 comprises a second torque transmission component 10, whose central axis coincides with the central axis of the pot 7. The second torque transmission component 10 is designed as a disk, more precisely as a planet carrier of the first planetary stage 6.1. The planet carrier 10 carries several planetary gears (not shown), which mesh with a sun gear and a ring gear of the first planetary stage 6.1. In the present embodiment, the first planetary stage is 6.1 is essentially received in the pot 7 and is enclosed in the direction of its central axis on one side by the base 8 and on the other side by the planet carrier 10. As can be seen from Figure 1, the base 8 of the pot 7 is permanently connected in a rotationally fixed manner to the crank device 2 for torque transmission. The pot 7 is further detachably connected to the planet carrier 10 of the first planetary stage 6.1 for torque transmission. This detachable connection is in the form of a toothing, which is described below with reference to Figure 2. Due to the detachable connection, simple assembly and tolerance compensation of the drive device 1 is possible in that the pot 7, the first planetary stage 6.1 and the planet carrier 10 can be stacked one inside the other.

[0029] A sensor device 11 for measuring a load variable of the first torque transmission component 7 is mechanically connected to the first torque transmission component 7, more precisely to the base 8 of the pot 7. In the present embodiment, the sensor device 11 is a device for measuring a torque applied to the pot 7, for example a strain gauge. Accordingly, a torque applied to the pot base 8 and, via this, a torque on the crank device 2 can be detected via the sensor device 11. The drive device 1 comprises a control device 12, to which the sensor device 11 is electronically connected. The control device 12 is further electronically connected to the electric machine 20 in order to control the electric machine based on the torque detected by the sensor device 11.

[0030] Figure 2 shows a sectional view through the torque transmission arrangement 5 of the drive device 1 at the location where the outer surface 9 of the pot 7 is detachably connected to the planet carrier 10. The sectional view is a section arranged perpendicular to the center axes of the pot 7 and the planet carrier 10. As can be seen from Figures 1 and 2, the pot 7 has a first circumferential toothing 13 on its outer surface 9, which is arranged on an end face of the outer surface 9. The circumferential toothing 13 is arranged along the entire circumference of the outer surface 9, with the teeth of the circumferential toothing 13 each extending in the direction of the center axis of the pot 7. Alternatively, in an embodiment not shown, the circumferential toothing 13 can be equidistant and rotationally symmetrical with local interruptions and thus does not extend over the entire circumference.The first circumferential toothing 13 comprises a plurality of teeth 14, wherein a gap 15 is formed between each adjacent teeth 14. The gaps 15 between adjacent teeth 14 each have a substantially identical distance, in this case an identical angular distance. However, at three positions the adjacent teeth 14 have a smaller gap 16.1, 16.2 and 16.3 than the gap 15 between all other adjacent teeth 14. In the present embodiment, the distances between adjacent teeth 14 are reduced to form the smaller gaps 16.1, 16.2 and 16.3 by widening the teeth 14 adjacent to the smaller gaps 16.1, 16.2 and 16.3 in the circumferential direction U. The positions 16.1, 16.2 and 16.3, at which the distances between adjacent teeth 14 are smaller than at all other positions, are arranged equidistant from one another in the circumferential direction U.Accordingly, the positions with the smaller distances between adjacent teeth 14 are each offset by 120° from one another.

[0031] Figure 2 also shows the second torque transmission component 10, which in this case is designed as a planetary carrier. The planetary carrier 10 has a second circumferential toothing 17, which is arranged on a radial outer surface in the circumferential direction. The teeth 18 of the second circumferential toothing 17 are evenly distributed over the circumference of the planetary carrier 10 and each extend perpendicular to the center axis of the planetary carrier 10. In the present embodiment, the teeth 18 are arranged such that adjacent teeth 18 are each at essentially the same distance from one another. The gaps 19 between adjacent teeth 18 of the second circumferential toothing 17 are therefore essentially the same size. The teeth 18 of the second circumferential toothing 17 are each arranged in a gap 15, 16.1, 16.2 and 16.3 between the teeth 14 of the first circumferential toothing 13.Accordingly, the first circumferential toothing 13 meshes with the second circumferential toothing 17 along a toothing circle K extending in the circumferential direction U. In the present case, both the first circumferential toothing 13 and the second circumferential toothing 17 are designed as crown toothing. In the present embodiment, the sensor device 11 is aligned in the circumferential direction U with one of the smaller gaps 16.1, 16.2, and 16.3.

[0032] If a torque is now applied to the first torque transmission component 7, i.e. the pot, via the crank device 2, the teeth 14 of the first circumferential toothing 13 begin to move in the gaps 19 of the second circumferential toothing 17. Since the teeth 14 of the pot 7 have smaller gaps 16.1, 16.2 and 16.3 in some positions than in all other positions, contact initially occurs between the two circumferential toothings 13 and 17 at positions 16.1, 16.2 and 16.3. These positions therefore represent contact points 16.1, 16.2 and 16.3 at which initial contact occurs between the toothings 13 and 17. Along the gear circle K, these contact points 16.1, 16.2, and 16.3 are therefore arranged equidistant from one another. Due to this equidistant arrangement of the contact points 16.1, 16.2, and 16.3 results in a homogeneous and rotationally symmetrical contact pattern, i.e. a substantially rotationally symmetrical torque load, in the first torque transmission component 7. Due to the homogeneous and rotationally symmetrical contact pattern, precise and reliable torque detection is possible with the sensor device 11 arranged on the bottom 8 of the pot 7.

[0033] If, on the other hand, the contact points were not arranged equidistant from one another, local load peaks would occur in the contact pattern, which would result in inaccurate and distorted torque measurements with the sensor device 11. Due to the precise and reliable torque measurement with the sensor device 11, the control device 12 can then control the electric machine 20 with equally high reliability and accuracy. In the new state, the three contact points 16.1, 16.2 and 16.3 arranged equidistant from one another will lead to a homogeneous contact pattern in the cup 7. Due to the high surface pressure, however, after a short time wear or superficial plastic deformation due to loading above the yield point of the gear material will occur, until all the other teeth also contribute to the contact pattern. Due to the wear orHowever, in the case of superficial plastic deformation, the contact pattern will always develop in such a homogeneous manner that the shear stress in the base 8 of the pot 7 provides reproducible and representatively evaluable plausible values, regardless of the existing manufacturing tolerances of the driving toothing between the pot 7 and the planet carrier 10.

[0034] In order to produce the torque transmission arrangement 5 shown in Figures 1 and 2, in a method for producing the torque transmission arrangement 5, a maximum play is first defined between the teeth 14 of the first circumferential toothing 13 and the teeth 18 of the second circumferential toothing 17 at the positions of the contact points 16.1, 16.2 and 16.3. Subsequently, a minimum play is defined between the teeth 14 of the first circumferential toothing 13 and the teeth 18 of the second circumferential toothing 17 at all other positions. The maximum play at the positions of the contact points 16.1, 16.2 and 16.3 is determined to be a smaller value than the minimum play at all other positions. In this way, it can be ensured that a torque transmission arrangement 5 is produced in which, at the beginning of the torque transmission, the contact points 16.1, 16.2 and 16.3 are arranged equidistant from one another.

[0035] Reference symbol

[0036] 1 drive device

[0037] 2 Crank device

[0038] 3 crank

[0039] 4 downforce

[0040] 5 Torque transmission arrangement

[0041] 6 gearboxes

[0042] 6.1, 6.2 Planetary stage

[0043] 7 first torque transmission component

[0044] 8 Pot base

[0045] 9 Shell surface

[0046] 10 second torque transmission component

[0047] 11 Sensor device

[0048] 12 Control device

[0049] 13 first peripheral gearing

[0050] 14 teeth

[0051] 15 gap

[0052] 16.1 ,16.2,16.3 smaller gap, investment points

[0053] 17 second peripheral toothing

[0054] 18 teeth

[0055] 19 gap

[0056] 20 electric machine

[0057] U circumferential direction

[0058] K Gear circle

Claims

Patent claims 1. Torque transmission arrangement (5) for a drive device (1) of a muscle-powered vehicle, comprising a first torque transmission component (7) with a first circumferential toothing (13), a second torque transmission component (10) with a second circumferential toothing (17) and a sensor device (11) for measuring a load variable of one of the torque transmission components (7; 10), wherein the first and second circumferential toothings (13, 17) mesh with one another for torque transmission along a toothing circle (K), and a play between the teeth (14) of the first circumferential toothing (13) and the teeth (18) of the second circumferential toothing (17) is designed such that contact points (16.1, 16.2, 16.3), at which the first circumferential toothing (13) first comes into contact with the second circumferential toothing (17) at the start of the torque transmission, are arranged equidistant from one another along the toothing circle (K).

2. Torque transmission arrangement (5) according to claim 1, characterized in that the play between the teeth (14) of the first circumferential toothing (13) and the teeth (18) of the second circumferential toothing (19) is arranged such that at the beginning of the torque transmission three contact points (16.1, 16.2, 16.3) arranged equidistant from one another along the toothing circle (K) are formed.

3. Torque transmission arrangement (5) according to one of the preceding claims, characterized in that the first torque transmission component (7) has smaller gaps between two adjacent teeth (14) of the first circumferential toothing (13) at the positions of the contact points (16.1, 16.2, 16.3) than at all other positions and than all gaps (19) between adjacent teeth (18) of the second circumferential toothing (17) of the second torque transmission component (10).

4. Torque transmission arrangement (5) according to claim 3, characterized in that the sensor device (11) is designed to measure a load variable of the first torque transmission component (7).

5. Torque transmission arrangement (5) according to one of the preceding claims, characterized in that the sensor device (11) is aligned in the circumferential direction (U) of the gearing circle (K) to one of the contact points (16.1; 16.2; 16.3).

6. Torque transmission arrangement (5) according to one of the preceding claims, characterized in that the sensor device (11) for measuring torque is formed in one of the torque transmission components (7; 10).

7. Torque transmission arrangement (5) according to one of the preceding claims, characterized in that the first torque transmission component (7) is designed essentially as a pot with a jacket surface (9) and the second torque transmission component (10) is designed essentially as a disk, wherein a central axis of the pot (7) coincides with a central axis of the disk (10), the first circumferential toothing (13) is formed along an end face of the jacket surface (9) of the pot (7) and extends in the direction of the central axis and the second circumferential toothing (17) is formed on a circumferential surface of the disk (10) and extends perpendicular to the central axis.

8. Drive device (1) for a muscle-powered vehicle with an output (4) operatively connectable to a drive wheel of the vehicle, a crank device (2) for introducing muscle power into the drive device (1), a gear (6) for translating and transmitting the introduced muscle power to the output (4), an electrical machine (20) mechanically operatively connected to the output (4) and a torque transmission arrangement (5) according to one of the preceding claims, wherein the torque transmission arrangement (5) is arranged in the torque transmission path between the crank device (2) and the gear (6).

9. Muscle-powered vehicle with a drive device (1) according to claim 8.

10. A method for producing a torque transmission arrangement (5) according to one of claims 1 to 7, comprising defining a maximum play between the teeth (14) of the first peripheral toothing (13) and the teeth (18) of the second circumferential toothing (17) at the positions of the contact points (16.1, 16.2, 16.3) and defining a minimum play between the teeth (14) of the first circumferential toothing (13) and the teeth (18) of the second circumferential toothing (17) at all other positions, wherein the maximum play at the positions of the contact points (16.1, 16.2, 16.3) is smaller than the minimum play at all other positions.

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