Shaft assembly

Abstract

The present invention relates to a shaft assembly (1) having an input shaft (2), an output shaft (3), a freewheel (5) and a transmission component (4). A connection (6) is formed between one of the shafts (2) and the transmission component (4). The freewheel (5) is arranged between the transmission component (4) and the other of the shafts (3). The shaft assembly (1) is designed to increase the torque-transmitting capability of the connection (6) between the shaft (2) and the transmission component (4) when a torque is applied to the freewheel (5) in a transmission direction (T). A torque can thus be reliably transmitted from the input shaft (2) via the transmission component (4) to the output shaft (3) in the transmission direction (T). The present invention also relates to a drive device having such a shaft assembly (1).

Description

[0001] Shaft arrangement

[0002] Technical area

[0003] The present invention relates to a shaft assembly having an input shaft, an output shaft, a freewheel, and a transmission component. Furthermore, the present invention relates to a drive assembly for a human-powered vehicle having such a shaft assembly.

[0004] State of the art

[0005] A key requirement for drive systems for electrically assisted bicycles is a design that is as compact as possible. Key functional elements in such a drive system are classic machine elements, such as shaft-hub connections, which can be realized using frictional connections. Freewheels are also key components in such drive systems. The objective of the present invention was to provide a shaft arrangement with a freewheel and a connection between two components that offers a compact installation space and high torque transmission capacity.

[0006] Description of the invention

[0007] This object is achieved by the claimed shaft arrangement having an input shaft, an output shaft, a freewheel, and a transmission component. At the input shaft, the torque to be transmitted by the shaft arrangement can be fed into the shaft arrangement. At the output shaft, the torque transmitted by the shaft arrangement can be output to a further component. The input shaft and / or the output shaft can each be designed as a hollow shaft. In an alternative embodiment, the input shaft and / or the output shaft is not designed as a hollow shaft, but as a solid shaft. The freewheel can be a component having two sections that can be rotated relative to one another. If the sections are moved in one direction relative to one another, the freewheel can lock in order to transmit torque from one of the sections to the other.If, however, the sections are moved in opposite directions relative to one another, the freewheel cannot be locked, meaning that no torque can be transmitted between the two sections. The freewheel can therefore be a one-way clutch. The freewheel can have any design, with one embodiment being designed as a force-locking or friction-locking freewheel. In addition, the shaft arrangement comprises a transmission component, which can be formed in one piece. In an alternative embodiment, the transmission component is formed from several pieces, which can be detachably or permanently connected to one another.

[0008] The shaft arrangement can be designed to be used in a drive device for a human-powered vehicle. The human-powered vehicle can be a single-track vehicle, for example a two-wheeler in the form of a pedelec or e-bike. The human-powered vehicle can alternatively be a multi-track vehicle, for example a tricycle or a vehicle with four wheels. The human-powered vehicle can also have a different design. The drive device for the human-powered vehicle can have a housing in which the shaft arrangement can be arranged. In addition to the shaft arrangement, a gear mechanism, for example a planetary gear mechanism, a pedal shaft and / or one or more electrical machines can be arranged in the housing. In addition, an output shaft can be arranged in the housing, which is mechanically connected, for example, to a chainring.The one or more electric motors can assist a rider in pedaling the pedal shaft, more specifically, in applying torque to the output shaft or chainring to propel the human-powered vehicle. The shaft assembly can be arranged in the torque transmission path between the pedal shaft and the output shaft.

[0009] A connection is formed between one of the shafts and the transmission component, i.e. between the input shaft and the transmission component or between the output shaft and the transmission component. The freewheel is arranged between the transmission component and the other of the shafts, i.e. the input shaft or the output shaft, which is not involved in the connection with the transmission component. The transmission component, the connection and the freewheel are therefore provided in the torque transmission path from the input shaft to the output shaft, and together can form a torque transmission chain. In one embodiment, no further components are arranged in the torque transmission path between the input shaft and the output shaft. In an alternative embodiment, further components are also provided in the torque transmission path between the input shaft and the output shaft.

[0010] The shaft arrangement of the invention is designed to increase the torque transmission capacity of the connection between the shaft and the transmission component when the freewheel is subjected to a torque in the above-described transmission direction. Thus, a torque can be reliably transmitted from the input shaft via the transmission component to the output shaft in the transmission direction. By increasing the torque transmission capacity of the connection between the shaft and the transmission component, a greater torque can be transmitted via the connection than would have been possible without the increase.

[0011] By increasing the torque transmission capacity of the connection, the shaft arrangement can be designed with thin-walled components and thus be particularly compact. This means that the connection between the shaft and the transmission component does not necessarily have to be designed for the torques occurring during normal operation. Instead, the connection can be designed with a torque transmission capacity that is lower than that required during normal operation. Nevertheless, the shaft arrangement can reliably transmit a torque occurring during normal operation, since the transmission capacity of the connection can be increased by the shaft arrangement itself.The present invention therefore leads to the advantage that a shaft arrangement with a freewheel and a connection between a shaft and a transmission component can be provided, which is particularly compact and yet can transmit relatively high torques between an input and an output shaft. In one embodiment, the input shaft, the transmission component and the output shaft are arranged coaxially to one another, for example coaxially to a coaxial axis of the shaft arrangement. Along the coaxial axis, the input shaft, the transmission component and / or the output shaft can have an overlap section in which two or all of these components can overlap. The input shaft, the transmission component and the output shaft can each be annular.The input shaft, the transmission component and / or the output shaft can be nested radially within one another, so that a power transmission path for transmitting a torque can run in the radial direction from the inside to the outside or from the outside to the inside.

[0012] In one embodiment, the connection between the shaft and the transmission component is a force-locking connection. The force-locking connection can be a shaft-hub connection. The force-locking connection between the shaft and the transmission component can be formed via a press fit, i.e., an interference fit between these components. In addition to the press fit, the connection can also have a material connection, which can be formed, for example, by gluing, soldering, and / or welding. If no torque is applied to the shaft arrangement, the force-locking connection can still exist. However, in this state, the force-locking connection cannot be designed to transmit all of the intended torques of the shaft arrangement.However, the torque transmission capacity of the force-locking connection can be increased by applying a torque to the freewheel in the transmission direction, as described above. In an alternative embodiment, the connection can alternatively or additionally have a form-locking connection.

[0013] In one embodiment, the freewheel has at least one clamping element which, when the freewheel is subjected to torque in the transmission direction, generates a clamping force to increase the torque transmission capacity of the connection. The freewheel can have a plurality of clamping elements which can, for example, be distributed equidistantly around the circumference of the freewheel. In addition, the freewheel can have a cage which can carry the clamping element(s). If the freewheel is subjected to torque in the transmission direction, the clamping element(s) can be clamped, for example via a force-locking connection, in order to be able to transmit torque via the freewheel. The clamping of the clamping element(s) can lead to the clamping force emanating from the freewheel.The clamping force can be a force acting in the radial direction of the shaft arrangement.

[0014] The clamping force can act on the transmission component, which can then be constricted, for example, if the freewheel is arranged radially outside the transmission component. If the freewheel is arranged radially inside the transmission component, the clamping force emanating from the freewheel can lead to an expansion of the transmission component. The deformation of the transmission component, i.e. the constriction or expansion, can be transferred to the connection formed between the transmission component and the shaft. If the connection is, for example, a force-locking connection, as explained above, this can be reinforced by the deformation of the transmission component. For example, the deformation can lead to an increase in the normal forces acting in the force-locking connection, which in turn is accompanied by an increase in the frictional forces of the force-locking connection.

[0015] In one embodiment, the shaft arrangement is designed such that the strength of the clamping force scales with the strength of the torque applied to the freewheel in the transmission direction. For example, the clamping force can scale linearly, exponentially, or in some other relationship with the torque applied to the freewheel. In other words, within the scope of this embodiment, with a larger torque to be transmitted, the clamping force is also increased, which in turn leads to an increase in the torque transmission capacity of the connection between the shaft and the transmission component. Within the scope of this embodiment, a load-dependent reinforcement of the connection between the transmission component and the shaft can therefore be provided.This allows for a shaft arrangement with a particularly compact design, as the self-reinforcing connection between the transmission component and the shaft enables the provision of a connection with a relatively low torque transmission capacity in the initial state. In other words, the wall thickness of the components can be selected to be significantly smaller than would be necessary for transmitting the torque through a static interference fit to absorb the necessary hoop stress. In addition, a much smaller overlap, i.e., an oversize, can be selected in the interference fit, which significantly simplifies the assembly of the components.

[0016] In one embodiment, the freewheel is designed as a clamping roller freewheel or a clamping body freewheel. Within the scope of this embodiment, however, the freewheel can also be designed in a different way, as long as it is designed as a force-locking or friction-locking freewheel. The clamping roller freewheel can have one or more clamping elements, which can be designed as clamping rollers. The clamping roller freewheel can have a rotating inner part which rotates together with the clamping rollers within an outer ring. When the freewheel rotates in the transmission direction, radial forces can arise which lead to the clamping rollers becoming wedged and a state of self-locking occurring. When rotating against the transmission direction, however, the clamping rollers are moved, for example, in the direction of a spring preload force, which releases the clamping.The roller type freewheel can be designed as a needle bearing freewheel or a sleeve type freewheel. The sprag type freewheel can be provided with one or more clamping elements in the form of non-circular sprags. When the freewheel is subjected to a torque in the transmission direction, the sprags can be rotated, thereby locking the freewheel. However, if the freewheel is subjected to a torque opposite to the transmission direction, this locking can be released. This design offers the advantage that the roller type freewheel and the sprag type freewheel have no free angle in the locking direction.

[0017] Within the scope of one embodiment, the shaft and the transmission component, between which the connection, for example the force-locking connection, is formed, are integrated into the shaft arrangement in such a way that they structurally support each other. The structural support can make the respective components more structurally resilient than they would be without the other component. Thus, the shaft arrangement can transmit a torque which the shaft and the transmission component would not be capable of individually. For example, the components each have wall thicknesses which individually do not meet the rigidity requirements of the freewheel. However, the sum of the wall thicknesses of the components can, within the scope of this embodiment, meet the radial rigidity requirements of the freewheel.In other words, the components in this embodiment would each deform unacceptably under normal load. However, the shaft arrangement is designed such that the components structurally complement each other in such a way that such unacceptable deformation does not occur under normal load on the shaft arrangement. As a result, the wall thickness of the individual components can be selected to be significantly smaller within the scope of the shaft arrangement in this embodiment.

[0018] In one embodiment, the input shaft is arranged within the transmission component in the radial direction of the shaft arrangement. The transmission component can in turn be arranged radially within the freewheel. The freewheel can in turn be arranged within the output shaft in the radial direction of the shaft arrangement. Accordingly, within the scope of this embodiment, in the torque transmission path from the radially inner input shaft to the radially outer output shaft, the connection is provided upstream of the transmission component and the transmission component is provided upstream of the freewheel. In an alternative embodiment, the arrangement of connection, transmission element and freewheel is reversed in the radial direction, so that the input shaft is first followed by the freewheel, which is arranged radially within the transmission element.Following the transmission element in the radially outward direction is the connection, which is arranged between the transmission element and the output shaft. In an alternative embodiment, the output shaft can be arranged radially inward and the input shaft radially outward.

[0019] Furthermore, the present invention relates to a drive assembly for a human-powered vehicle with a shaft assembly according to one of the previously described embodiments. The human-powered vehicle can be a two-wheeled vehicle, for example, a bicycle such as a pedelec or e-bike. For an understanding and the advantages of the individual features, reference is made to the above explanations in connection with the shaft assembly of the present invention.

[0020] Short description of the characters

[0021] Figure 1 shows a shaft arrangement according to an embodiment of the present invention.

[0022] Detailed description of embodiments

[0023] Figure 1 shows a shaft assembly 1 according to an embodiment of the present invention. The shaft assembly 1 of the present embodiment is designed to be used in a drive device of a bicycle, for example, a pedelec. The shaft assembly 1 has an input shaft 2 and an output shaft 3. In addition, the shaft assembly 1 has a transmission component.

[0024] 4 and a freewheel 5. The input shaft 2, the output shaft 3, the transmission component 4 and the freewheel 5 are designed coaxially to one another in the present embodiment. The input shaft 2 and the output shaft 3 are designed as a hollow shaft, wherein the input shaft 2 in the present embodiment is arranged radially inside the output shaft 3. In the direction of the coaxial axis K, the input shaft 2 and the output shaft 3 overlap in an overlap section U. In the radial direction R of the shaft arrangement 1, in the overlap section U between the input shaft 2 designed as a hollow shaft and the output shaft 3 designed as a hollow shaft, the transmission element 4 and the freewheel

[0025] 5 arranged.

[0026] As with the input shaft 2 and the output shaft 3, the transmission element 4 and the freewheel 5 are also annular elements which are arranged coaxially to the input shaft 2 and the output shaft 3. In the present embodiment, the transmission element 4 is a one-piece element which is connected to the radial outer surface of the input shaft 2 via a connection 6. Furthermore, the transmission element 4 is in contact with a radial inner surface of the freewheel 5. The freewheel 5 is therefore in contact with a radial outer surface of the transmission element 4 and furthermore with a radial inner surface of the output shaft 3. The connection 6 between the transmission element 4 and the input shaft 2 is a force-locking connection which in this case is designed as a force-locking shaft-hub connection.

[0027] The transmission element 4 has an annular, outward radial protrusion 4.1 at one end in the direction of the coaxial axis K. At the other end in the direction of the coaxial axis K, the transmission element 4 has an inward radial protrusion 4.2, also annular. The outward radial protrusion 4.1 of the transmission element 4 is in contact with an end face of the freewheel 5. Furthermore, the inward radial protrusion 4.2 of the transmission element 4 is in contact with an end face of the input shaft 2. The freewheel 5 has a cage 5.1 in which a plurality of clamping elements 5.2 are arranged, evenly distributed over the circumference of the freewheel 5. The cage 5.1 of the freewheel 5 is arranged in the radial direction R between the output shaft 3 and the transmission element 4. The transmission component 4 is in the direction of the coaxial axis K via its radial protrusions outwards 4.1 and inwards 4.2 is fixed between the output shaft 3 and the freewheel 5. In the radial direction R, the transmission component 4 is fixed between the input shaft 2 and the freewheel 5. In addition, the shaft arrangement 1 has an inner shaft 7 designed as a solid shaft, which is arranged coaxially to the coaxial axis K. The input shaft 2, designed as a hollow shaft, is arranged radially outside the inner shaft 7 and is adjustable in the circumferential direction relative to the inner shaft 7 via a bearing designed by means of rolling bearings 8.

[0028] The freewheel 5 is designed to transmit torque from the transmission component 4 to the output shaft 3 in a transmission direction T. In other words, the freewheel 5 locks when the transmission component 4 is moved in the direction of rotation T, and thereby transmits torque from the transmission component 4 to the output shaft 3. If, on the other hand, the transmission component 4 is moved in the direction opposite to the transmission direction T, the freewheel 5 is not locked and therefore no torque is transmitted from the transmission component 4 to the output shaft 3. In the present embodiment, the freewheel 5 is designed as a clamping roller or clamping body freewheel. The freewheel 5 has the clamping elements 5.2 described above. When the transmission component 4 moves in the transmission direction T, the clamping elements 5.2 are clamped to enable torque to be transmitted from the transmission component 4 to the output shaft 3.If, however, the transmission component 4 rotates opposite to the transmission direction T, this does not result in jamming of the clamping elements 5.2, so that in this case, no torque can be transmitted from the transmission component 4 to the output shaft 3. In the present embodiment, the freewheel 5 is designed such that jamming of the clamping elements 5.2 of the freewheel 5 leads to clamping forces in the radial direction R, which are transmitted from the freewheel 5 to the output shaft 3 and the transmission component 4. These radial forces are also known as parasitic radial forces, which emanate from frictionally engaged freewheels.

[0029] The shaft arrangement 1 is designed such that the radial forces generated by the freewheel 5 reinforce the frictional shaft-hub connection between the input shaft 2 and the transmission component 4. Such a reinforcement of the frictional connection 6 is accompanied by an increase in the torque transmission capacity of the frictional connection 6 between the input shaft 2 and the transmission component 4. More precisely, the clamping forces generated by the freewheel 5 in the locking direction T lead to a radial constriction of the transmission component 4, whereby the normal force in the radial direction R exerted by the transmission component 4 on the input shaft 2 and consequently also the frictional force in the circumferential direction is increased. The parasitic radial forces of the freewheel 5 are therefore used to further preload the press fit between the transmission component 4 and the input shaft 2.

[0030] The shaft arrangement 1 is designed such that the strength of the radial forces generated by the freewheel 5, i.e. the clamping forces in the radial direction R, scales with the strength of the torque applied to the freewheel 5 in the locking direction T. Consequently, the extent of the increase in the torque transmission capacity of the shaft-hub connection 6 also scales with the strength of the torque applied to the freewheel 5 in the locking direction T. The shaft arrangement 1 is designed such that the torque transmission capacity of the non-positive connection 6 is always increased by the clamping forces to at least such an extent that the torque to be transmitted via the shaft arrangement 1 from the input shaft 2 to the output shaft 3 can always be transmitted reliably.

[0031] The input shaft 2 and the transmission component 4 are structurally designed in such a way, for example in their wall thickness, that they individually do not meet the requirement of the freewheel 5 for structural rigidity during normal operation of the shaft arrangement 1. In other words, the components 2, 4 in this embodiment would each individually lead to inadmissible deformations under the intended load of the shaft arrangement 1. Together, however, they have a design, for example wall thicknesses, which fulfill the requirement regarding radial rigidity. In addition, the force-locking connection 6 between the input shaft 2 and the transmission component 4 has a significantly smaller overlap, i.e. a significantly smaller excess, than would be necessary for reliable transmission of the torques occurring during normal operation of the shaft arrangement 1.This allows for components 2 and 4 with thinner walls. The required torque transmission capacity and structural integrity of the components are therefore only achieved through the interaction of input shaft 2 and transmission component 4, as well as the radial clamping forces of the freewheel 5. As a result, a shaft arrangement 1 with a very thin-walled design and thus a compact size can be provided.

[0032] Reference symbol

[0033] 1 shaft arrangement

[0034] 2 input shaft

[0035] 3 Output shaft

[0036] 4 Transmission component

[0037] 4.1 , 4-2 radial protrusion transmission component

[0038] 5 Freewheel

[0039] 5.1 Free-range cage

[0040] 5.2 Freewheel clamping element

[0041] 6 force-locking connection

[0042] 7 inner shaft

[0043] 8 camps

[0044] K Coaxial axis

[0045] R Radial direction

[0046] U Overlap section

[0047] T Transmission direction

Claims

Patent claims 1. Shaft arrangement (1) with an input shaft (2), an output shaft (3), a freewheel (5) and a transmission component (4), wherein a connection (6) is formed between one of the shafts (2) and the transmission component (4) and the freewheel (5) is arranged between the transmission component (4) and the other of the shafts (3), wherein the shaft arrangement (1) is designed to increase the torque transmission capacity of the connection (6) between the shaft (2) and the transmission component (4) when the freewheel (5) is subjected to a torque in a transmission direction (T), in order to be able to reliably transmit a torque from the input shaft (2) via the transmission component (4) to the output shaft (3) in the transmission direction (T).

2. Shaft arrangement (1) according to claim 1, characterized in that the input shaft (2) and the output shaft (3) are designed as hollow shafts.

3. Shaft arrangement (1) according to claim 1 or 2, characterized in that the input shaft (2), the transmission component (4) and the output shaft (3) are arranged coaxially to one another.

4. Shaft arrangement (1) according to one of the preceding claims, characterized in that the connection is a force-locking connection (6).

5. Shaft arrangement (1) according to one of the preceding claims, characterized in that the freewheel (5) has at least one clamping element (5.2) which, when the freewheel (5) is subjected to the torque in the transmission direction (T), generates a clamping force to increase the torque transmission capacity of the connection (6).

6. Shaft arrangement (1) according to one of the preceding claims, characterized in that the shaft arrangement (1) is designed so that the strength of the clamping force corresponds to the strength of the force applied to the freewheel (5) in the transmission direction (T). Torque is scaled so that a safe torque transmission via the connection (6) from the shaft (2) to the transmission component (4) is guaranteed.

7. Shaft arrangement (1) according to one of the preceding claims, characterized in that the freewheel (5) is designed as a clamping roller freewheel or clamping body freewheel 8. Shaft arrangement (1) according to one of the preceding claims, characterized in that the shaft (2) and the transmission component (4), between which the connection (6) is formed, are integrated into the shaft arrangement (1) in such a way that they structurally support one another, so that torques can be transmitted via the shaft arrangement (1) for which the shaft (2) and the transmission component (4) are not individually capable.

9. Shaft arrangement (1) according to one of the preceding claims, characterized in that in the radial direction (R) of the shaft arrangement (1) the input shaft (2) is arranged within the transmission component (4), which is arranged in the radial direction (R) within the freewheel (5), which is arranged in the radial direction (R) within the output shaft (3).

10. Drive arrangement for a muscle-powered vehicle with a shaft arrangement (1) according to claim 9.

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