Driving device for electric bicycle and electric bicycle

Abstract

In at least one embodiment, a drive device (1) for an electric bicycle (100) has a shaft (3) and a reversing transmission (2). The reversing transmission is configured to be coupled to the electric motor on one side and to the shaft on the other side such that torque can be transmitted from the electric motor to the shaft via the reversing transmission. The reversing transmission has a first transmission element (21) which can be rotated about a first axis (A1) and a second transmission element (22) which is coupled to the first transmission element. The second transmission element (22) is rotatable about a second axis (A2) running obliquely to the first axis. The drive device is configured for transmitting torque from the first transmission element to the shaft by coupling between the first transmission element and the shaft, and is further configured for rotating the shaft relative to the first transmission element in a first rotational direction. The first transmission element is also axially movable parallel to the first axis within a predetermined limit relative to the second transmission element, wherein the transmission elements remain coupled to each other within the predetermined limit.

Description

Technical Field

[0001] The invention relates to a drive device for an electric bicycle and an electric bicycle having the drive device. Background Art

[0002] Bicycles provide an inexpensive, easy-to-use and emission-free means of transport. Bicycles have also become popular as sports and fitness equipment, and types have been developed that are particularly suitable for different sports applications.

[0003] In recent years, despite the high weight and price for bicycles, there has been a growing interest in electric bicycles, especially so-called "pedelecs." In electric bicycles, it is important to provide a reliably supported drive system that allows a high power transmission. Summary of the invention

[0004] The object to be achieved is to provide a reliable drive device for an electric bicycle, in particular a drive device of simple construction, in which the forces generated are optimally supported. A further object is to provide an electric bicycle having such a drive device.

[0005] This object is achieved in particular by the subject matter of claims 1 and 15. Advantageous embodiments and developments are the subject matter of the remaining dependent claims and also emerge from the following description and the drawings.

[0006] First, a drive device for an electric bicycle is proposed.

[0007] In at least one embodiment, a drive device for an electric bicycle has a shaft and a reversing transmission. The reversing transmission is configured to be coupled to the motor on the one hand and to the shaft on the other hand, so that torque can be transmitted from the motor to the shaft via the reversing transmission. The reversing transmission has a first transmission element rotatable around a first axis and a second transmission element coupled to the first transmission element. The second transmission element can rotate around a second axis extending obliquely to the first axis. The drive device is configured to transmit torque from the first transmission element to the shaft through a coupling between the first transmission element and the shaft, and is also configured to rotate the shaft relative to the first transmission element in a first rotational direction. In addition, the first transmission element can be axially movable relative to the second transmission element within predetermined limits parallel to the first axis, wherein the transmission elements remain coupled to each other within the predetermined limits.

[0008] The present invention is based on the knowledge that, in particular, a reliable coupling between the first transmission element and the shaft should be ensured when the shaft is driven by an electric motor. On the other hand, if the shaft is not driven by an electric motor, the shaft rotates at least in one direction of rotation independently of the electric motor. In order to avoid the expensive axial positioning of the first transmission element, the first transmission element is arranged axially movable in the present invention, wherein the axial movement is released only within predetermined limits. As a result, the first transmission element is optimally positioned on the one hand and optimally supports the generated forces on the other hand. Advantageously, the shaft can be rotated relative to the first transmission element in a first direction of rotation so as to be decoupled from all transmission stages and the electric motor with respect to the first direction of rotation. As a result, for example, when the support of the electric motor is omitted, the pedaling resistance is small.

[0009] The shaft of the drive device is mounted, for example, so that it can rotate about an axis parallel to the first axis, in particular so that it can rotate about the first axis.

[0010] A reversing transmission, also referred to as an angular transmission, is configured in particular for coupling to an electric motor on the drive side and to a shaft on the driven side. For example, the second transmission element is configured for (direct) coupling to the electric motor. The reversing transmission can be a non-ratio reversing transmission, that is to say the output speed of the reversing transmission is equal to the input speed (ratio=1). Alternatively, the reversing transmission can have a transmission ratio of at least a factor of 1.5 or 2, for example a factor of 5, so that the output speed is not equal to the input speed.

[0011] The first and second transmission elements of the reversing transmission are coupled to one another, in particular such that a torque can be transmitted from the second transmission element to the first transmission element and / or vice versa. For example, the coupling is such that any rotation of the second transmission element about the second axis causes a rotation of the first transmission element about the first axis and / or vice versa. The transmission elements are in particular directly coupled to one another. The coupling between the first transmission element and the second transmission element is realized, for example, by a meshing engagement point between the first transmission element and the second transmission element. For example, the first transmission element and the second transmission element are directly engaged with one another.

[0012] A coupled joint is understood here and hereinafter to be a region in which forces or torques are transmitted between two elements, such as transmission elements. The region comprises in particular a contact point before two parts that are movable relative to one another and / or an intermediate region between parts that are movable relative to one another.

[0013] The second axis extends obliquely to the first axis, the second transmission element can rotate around the second axis, and the first transmission element can rotate around the first axis. For example, the second axis intersects the first axis at a point or extends obliquely relative to the first axis. The first axis and the second axis can extend perpendicularly to each other or extend at an angle of less than 90° to each other. For example, the angle between the first axis and the second axis is at least 30° or at least 45°.

[0014] The drive device is configured to transfer torque from the first transmission element to the shaft via a coupling between the first transmission element and the shaft. For example, a torque that assists the rotation of the shaft in a first rotational direction can be transferred from the first transmission element to the shaft. In other words, at least in a first operating state of the drive device, a coupling is formed between the first transmission element and the shaft, through which a torque can be transferred from the transmission element to the shaft or is transferred to the shaft. In the first operating state, the rotation of the shaft in the first rotational direction is then assisted or caused, for example, by the rotation of the first transmission element. For example, in the first operating state, the shaft and the first transmission element rotate together around the first axis without rotating relative to each other, that is, at the same rotational speed or angular velocity.

[0015] The drive device is further configured to rotate the shaft in a first rotational direction and relative to the second transmission element. In particular, the drive device is configured such that the shaft can be rotated at least in the first rotational direction independently of the first transmission element. For example, the shaft can be rotated in the first rotational direction without the first transmission element rotating. In other words, the drive device can be operated in a second operating state in which the shaft is rotated in the first rotational direction relative to the first transmission element. In the second operating state, the shaft is rotated, for example, by more than 360°, independently of the first transmission element.

[0016] The coupling between the first transmission element and the shaft is such that, in particular, a rotation of the first transmission element relative to the shaft in the first rotational direction is blocked, while a rotation of the shaft relative to the first transmission element in the first rotational direction is released.

[0017] The drive device is configured, for example, to switch back and forth between a first operating state and a second operating state or to be switched back and forth. The switch from the first operating state to the second operating state and / or the reverse switch is, for example, performed automatically. For example, when the rotation speed of the first transmission element in the first rotational direction is less than the rotation speed of the shaft in the first rotational direction, the switch from the first operating state to the second operating state is automatic. In addition, when the first transmission element rotates faster than the shaft in the first rotational direction, the switch from the second operating state to the first operating state can be automatic.

[0018] Here and hereinafter, the rotation of an element means a rotation about an axis about which the corresponding element can rotate. That is, for a first transmission element and / or shaft, a rotation about a first axis is meant. For a second transmission element, a rotation means a rotation about a second axis. The first direction of rotation is, for example, a clockwise or counterclockwise rotation. If not otherwise specified, here and hereinafter, a rotation also means a rotation relative to the housing of the drive device.

[0019] The first transmission element can also be axially movable relative to the second transmission element. Alternatively or additionally, the first transmission element can be axially movable relative to the shaft. Herein and hereinafter, if not otherwise specified, the direction parallel to the first axis is referred to as the axial direction. Correspondingly, the term axial is the first axis. In addition, here and hereinafter, if not otherwise specified, the azimuth direction represents the azimuth direction about the first axis, i.e. along the circumferential line around the first axis. If not otherwise specified, here and hereinafter, the radial direction represents the radial direction about the first axis, i.e. the direction perpendicular to the first axis and perpendicular to the azimuth direction. The terms azimuth and radial should be understood accordingly.

[0020] The first transmission element can be moved relative to the second transmission element and / or relative to the shaft within preset limits. That is, the first transmission element can be moved relative to the second transmission element and / or relative to the shaft in a defined area or within a defined distance range, for example at least 0.01 mm or at least 0.1 mm. In particular, an axial movement of the first transmission element beyond the limits is prevented. The circumferential side play between the first transmission element and the second transmission element is, for example, at least 0.01 mm and a maximum of 0.1 mm.

[0021] The first transmission element and the second transmission element remain coupled to one another within predefined limits. That is, the axial movement of the first transmission element relative to the second transmission element and / or relative to the shaft is limited so that the coupling is maintained even in the event of a maximum axial displacement / movement of the first transmission element. For example, the meshing engagement point always remains within predefined limits during the axial movement.

[0022] According to at least one embodiment, the axial movement of the first transmission element relative to the second transmission element in a first axial direction is limited by the second transmission element. Alternatively or additionally, the axial movement of the first transmission element relative to the second transmission element in an opposite second axial direction is limited by a limiting device.

[0023] The limitation in the first axial direction can be realized, for example, by the first transmission element stopping on the second transmission element. Alternatively, a damping element, such as a spring, can limit the movement of the first transmission element in the first axial direction. The limiting means can be a stop surface, against which the first transmission element stops when moving in the second axial direction. Alternatively, the limiting means can be a damping element, such as a spring, which limits the movement of the first transmission element in the second axial direction.

[0024] According to at least one embodiment, the limiting mechanism is axially fixed relative to the shaft and / or axially relative to the second transmission element. That is, at least a part of the limiting mechanism is arranged immovably in the axial direction relative to the shaft and / or the second transmission element. In addition, the limiting mechanism can be fixed in azimuth and / or radial direction.

[0025] According to at least one embodiment, the drive device is configured such that when the torque is transmitted from the second transmission element to the first transmission element, an axial force acts on the first transmission element. The axial force is directed via a limiting mechanism, for example to the shaft or to an element of the drive device that is axially fixed relative to the shaft. For example, the axial force is then absorbed by the shaft or the element, in particular completely absorbed.

[0026] The axial force acts in particular in a second axial direction, for example in a direction away from the first transmission element. The axial force can be derived by the limiting mechanism so that the axial force no longer generates an axial movement of the first transmission element relative to the second transmission element. For example, the first transmission element abuts against the limiting mechanism and the axial force presses the first transmission element against the limiting mechanism. Since the limiting mechanism derives the axial force and preferably derives it to the shaft or the element, the coupling for torque transmission between the first transmission element and the shaft is axially unloaded. This is advantageous because a plurality of couplings for torque transmission are not configured to absorb large axial forces.

[0027] According to at least one embodiment, the drive device has at least one bearing. By means of the bearing, the first transmission element is supported relative to the shaft in a manner that can rotate around the first axis. The bearing can be a rolling bearing, in particular a roller bearing or a ball bearing. The bearing can be an element independent of the shaft and the first transmission element, which element is arranged between the shaft and the first transmission element, for example radially between the first transmission element and the shaft. Alternatively, the shaft and / or the limiting mechanism and / or the first transmission element can be part of the bearing. For example, the shaft forms an inner ring of the bearing and / or the first transmission element forms an outer ring of the bearing or vice versa.

[0028] According to at least one embodiment, the coupling joint between the first transmission element and the shaft is arranged axially between two bearings. Each of these bearings can be designed like the above-mentioned bearings.

[0029] The coupling between the first transmission element and the shaft can be realized by a mechanical joint, at which the two elements touch each other for torque transmission (for example in the area of ​​the contact point). The coupled joint can then be a meshing contact point. Alternatively, the coupling can also be an electromagnetic coupling, in which the torque is transmitted, for example, by magnetic forces, in particular without direct contact.

[0030] The coupling between the first transmission element and the shaft can be carried out, for example, via a clutch of the drive device. In particular, the clutch can be arranged axially between two bearings. The clutch can also be formed as a unit with one or more bearings. The clutch can be an element independent of the first transmission element and the shaft. Alternatively, the first transmission element and / or the shaft can be part of the clutch.

[0031] In the present application, the term “coupling” refers to a coupled state, and the term “clutch” refers to a specific mechanism for forming the coupling.

[0032] According to at least one embodiment, the coupling between the first transmission element and the shaft is a one-way coupling, also referred to as an overrunning coupling. Correspondingly, the clutch can be a one-way clutch or an overrunning clutch. The one-way clutch is, for example, a sprag one-way clutch or a roller one-way clutch.

[0033] According to at least one embodiment, the reversing transmission is a bevel gear transmission. The first transmission element is then, for example, a crown gear and the second transmission element is a bevel pinion.

[0034] According to at least one embodiment, the reversing transmission has a transmission ratio of at least 2 or at least 4. Alternatively or additionally, the transmission ratio is a maximum of 8 or a maximum of 6. For example, the transmission ratio is at least 5 and a maximum of 6.

[0035] The bearing arrangement of the reversing transmission and the first transmission element is in particular selected such that the radial force F_R transmitted from the second transmission element to the first transmission element generates a friction force F_RE for the axial displacement of the first transmission element relative to the second transmission element, which is smaller than the axial force F_A transmitted from the second transmission element to the first transmission element. Therefore, it applies that: F_RE<FA. As a result, when the second transmission element rotates, the first transmission element is axially displaced and, for example, pressed against the limiting means.

[0036] According to at least one embodiment, the coupling joint between the crown gear and the bevel pinion is inclined at an inclination angle with respect to the first axis. The inclination angle is also referred to as the cone angle. The inclination angle is, for example, at least 45° or at least 60°. The angle of the joint with respect to the first axis corresponds in particular to the angle of the side surface of the bevel pinion with respect to the first axis. In particular, the forces generated enclose an angle of at least 45° or at least 60° with the first axis, for example.

[0037] An angle of inclination of at least 45° is advantageous in this respect, since the radial force component transmitted to the first transmission element is relatively small, so that the forces acting radially on the bearing or the clutch can be kept low. The axial forces are dissipated via the limiting means.

[0038] According to at least one embodiment, the shaft is a sprocket shaft, ie a shaft on which a sprocket is or can be fitted. The shaft is in particular a hollow shaft.

[0039] According to at least one embodiment, the limiting means is a stop surface. For example, the stop surface is axially fixed relative to the second transmission element and / or relative to the shaft. The stop surface can be a surface of the shaft or of an element axially fixed relative to the shaft. For example, the stop surface is axially, radially and azimuthally fixed relative to the shaft, i.e., in particular, immovable relative to the shaft.

[0040] According to at least one embodiment, a further stop surface is associated with the first transmission element. The further stop surface is, for example, axially and / or radially and / or azimuthally fixed relative to the first transmission element, i.e., in particular, arranged immovably relative to the first transmission element. For example, the further stop surface is a surface of the first transmission element.

[0041] According to at least one embodiment, the stop faces are opposite in the axial direction. The stop faces overlap each other, for example, radially and azimuthally, that is, the stop faces overlap in the radial direction and in the azimuth direction. In addition, the stop faces preferably face each other.

[0042] Two elements overlap in a direction, which means that the coordinates of the two elements have overlapping value ranges for the direction. In other words, the elements are then oriented relative to each other in the direction.

[0043] According to at least one embodiment, the stop surfaces are configured to stop each other in order to limit the axial movement of the first transmission element. That is, the axial movement of the first transmission element in the second axial direction relative to the second transmission element is limited by the further stop surface stopping against the stop surface. During the stop, the stop surface and the further stop surface are in direct contact with each other.

[0044] According to at least one embodiment, the stop surface is axially positioned between the second transmission element and the coupling engagement point between the first transmission element and the shaft. Therefore, in particular, the stop surface is axially positioned between the second transmission element and the clutch.

[0045] According to at least one embodiment, the region in which the stop faces abut against each other is radially offset relative to the first axis relative to the engagement point of the coupling between the first transmission element and the shaft or relative to the clutch. For example, the engagement point of the coupling and the region in which the stop faces abut against each other do not radially overlap each other. However, the region and the engagement point can overlap each other in azimuth. The region is offset radially inwardly relative to the engagement point or relative to the clutch, for example.

[0046] According to at least one embodiment, the stop surface is metallic, for example made of aluminum or stainless steel.

[0047] According to at least one embodiment, a lubricant is applied to the stop surfaces, and the lubricant facilitates relative rotation between the stop surfaces about the first axis.

[0048] According to at least one embodiment, the first transmission element radially surrounds the shaft partially or completely.

[0049] According to at least one embodiment, the coupling engagement point between the first transmission element and the shaft is arranged between the shaft and the first transmission element in the radial direction. In the axial direction, the engagement point can be arranged overlapping the first transmission element and the shaft. For example, the clutch is arranged radially between the first transmission element and the shaft and axially overlapping the shaft and the first transmission element.

[0050] Next, an electric bicycle is proposed. The electric bicycle is, for example, a so-called electric assist bicycle.

[0051] In at least one embodiment, the electric bicycle comprises a drive device according to one of the embodiments described herein. The electric bicycle also comprises an electric motor, wherein the electric motor is coupled to a reversing transmission such that the torque of the electric motor is transmitted to the first transmission element via the second transmission element. The electric bicycle can also have control electronics for controlling the electric motor.

[0052] The drive device described here and the electric bicycle described here will be explained in detail below based on exemplary embodiments with reference to the drawings. The same reference numerals indicate the same elements in the various drawings. If the elements or components in the different drawings are identical in terms of their function, their description is not repeated for each subsequent drawing. For reasons of clarity, elements may not be provided with corresponding reference numerals in all figures. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The accompanying drawings show:

[0054] Figure 1 An embodiment of an electric bicycle is shown;

[0055] Figure 2A cross-sectional view showing one embodiment of a drive device;

[0056] Figure 3 Show Figure 2 An enlarged detail of an embodiment of; and

[0057] Figure 4 and Figure 5 Shown in different operating states Figure 2 An embodiment of a drive device. DETAILED DESCRIPTION

[0058] Figure 1 Schematically, an electric bicycle 100 is shown with a bicycle frame 50, which also has a lower frame section 60, which forms a downtube. The frame section 60 extends in the direction of a pedal bearing, which comprises a pedal crank 40, which is coupled or can be coupled to a drive device 1 for the electric bicycle 100. The drive device 1 is coupled or can be coupled to an electric motor. The electric motor is arranged in the downtube of the frame 50, for example. Alternatively, the electric motor can also be arranged in the seat support tube.

[0059] exist Figure 2 A cross-sectional view of an embodiment of the drive device 1 is shown in FIG. Figure 1 Drive device 1 in. Figure 3 Shown enlarged Figure 2 Part of.

[0060] The drive device 1 comprises a housing 4. A reversing transmission 2 is arranged in the housing 4. The reversing transmission 2 comprises a first transmission element 21 and a second transmission element 22. Here, the reversing transmission 2 is a bevel gear transmission. The first transmission element 21 is a ring gear and the second transmission element 22 is a small bevel gear.

[0061] exist Figure 2 Axes A1 and A2 are also marked in FIG. The disk gear 21 (relative to the housing 4) is supported in a manner that allows rotation about the first axis A1, and the small bevel gear 22 (relative to the housing 4) is supported in a manner that allows rotation about the second axis A2. Axes A1 and A2 are perpendicular to each other. Figure 2 The radial direction R and the azimuthal direction C with respect to the first axis A1 are also indicated. The radial direction R is a direction perpendicular to the first axis A1 and the azimuthal direction C is a direction around the axis A1. Figure 2 In the illustration, the azimuth direction C points into the plane of the paper.

[0062] The crown gear 21 surrounds the shaft 3 of the drive device 1 in the radial direction R. The shaft 3 is also supported rotatably about the axis A1. The shaft 3 is a hollow shaft. The shaft 3 is guided out of the housing 4 and can be connected to a sprocket.

[0063] Figure 2 The drive device 1 is configured so that the bevel pinion 22 can be coupled to an electric motor for an electric bicycle. The direction of rotation of the rotor of the electric motor can extend parallel to the axis A2 and / or parallel to the longitudinal axis of the lower tube.

[0064] The bevel pinion 22 is driven by the energy provided by the motor, that is, rotated around the second axis A2. The bevel pinion 22 is coupled to the ring gear 21 via the engagement portion 212. The engagement portion 212 is a meshing engagement portion. Through the coupling via the engagement portion 212, the rotation of the bevel pinion 22 causes the ring gear 21 to rotate around the first axis A1.

[0065] A clutch 230 is provided between the disc gear 21 and the shaft 3 (see Figure 3 ). The clutch 230 is, for example, a one-way clutch. However, another mechanical clutch or an eddy current clutch can also be used.

[0066] The one-way clutch enables the shaft 3 to rotate relative to the disk gear 21 in a first rotational direction, for example clockwise or counterclockwise. On the contrary, the disk gear 21 cannot rotate relative to the shaft 3 in the first rotational direction. At most, the disk gear 21 can rotate together with the shaft, i.e., as fast as the shaft 3, in the first rotational direction. Here, by means of the coupling between the disk gear 21 and the shaft 3, a torque assisting the rotation is transmitted from the disk gear 21 to the shaft in a manner provided by the clutch 230. This is combined with Figure 4 and Figure 5 Elaborate in detail.

[0067] exist Figure 4 1 shows the drive device 1 in a first operating state, in which all the illustrated elements rotate except for the black element 41. The element 41 is a housing element of the housing 4. The rest of the housing is omitted for reasons of clarity.

[0068] In the first operating state, the small bevel gear 22 rotates around the second axis A2. The torque is transmitted to the disc gear 21 at the engagement portion 212, thereby forcing the disc gear to rotate around the first axis A1 in the first rotation direction. The torque is transmitted from the disc gear 21 to the shaft 3 through the one-way clutch 230, so that the shaft 3 rotates around the first axis A1 in the rotation direction at the same rotation speed as the disc gear 21. Therefore, the first operating state is particularly the following state, in which the electric motor transmits auxiliary torque to the shaft 3. For example, when the electric bicycle is running at a preset maximum speed of less than 25 km / h and the rider is pedaling, the first operating state is set. These two prerequisites are detected, for example, by means of sensors of the electric bicycle.

[0069] exist Figure 5 , the drive device 1 is shown in the second operating state. The black elements are again those elements that do not rotate. Thus, here only the shaft 3 rotates about the first axis A1, more precisely in the first direction of rotation. The small bevel gear 22 and the ring gear 21 do not rotate. That is, the shaft 3 rotates in the first direction of rotation relative to the ring gear 21, which is made possible by the one-way clutch 230 between the ring gear 21 and the shaft 3. The second operating state corresponds, for example, to an operating state in which the electric motor is switched off or the electric bicycle exceeds a preset maximum speed.

[0070] In order to facilitate the rotation of the shaft 3 relative to the crown gear 21 in the second operating state, to define a specific height for the freewheel, to absorb radial forces and to maintain the position of the crown gear 21, the drive device 1 comprises two bearings 231, 232 (see Figure 3 The one-way clutch 230 is axially disposed between two bearings 231 and 232 in a direction parallel to the first axis A1. The bearings 231 and 232 are rolling bearings, such as ball bearings.

[0071] exist Figures 2 to 5 In the drive device 1 of the embodiment shown in , the ring gear 21 is arranged axially movably relative to the shaft 3 and relative to the bevel pinion 22, more precisely, it is arranged axially movably within preset limits. On the one hand, the axial movement of the ring gear 21 is limited in a first axial direction, that is, towards the bevel pinion 22, by a stop at the bevel pinion 22. In the opposite second axial direction, the movement of the ring gear 21 is limited by a stop at a limiting means 30 in the form of a stop surface 30. The stop surface 30 is part of an element 32, which is axially fixed to the shaft 3. However, the stop surface 30 can also be part of the shaft 3, that is, it can be formed integrally or in one piece with the shaft 3.

[0072] The crown gear 21 has a further stop surface 210 which faces the stop surface 30 and radially and azimuthally overlaps the stop surface 30. The stop surfaces 30 and 210 are formed, for example, from metal and are covered with a lubricant.

[0073] When Figure 3When observing the force diagram in FIG. 2 , one advantage of limiting the axial movement of the crown gear 21 by means of the stop surface 30 becomes clear. When the crown gear 21 is driven by the bevel pinion 22, a force F is transmitted to the crown gear 21 at the engagement point 212. The force F is divided into a radial component F_R and an axial component F_A. Therefore, when driven, the crown gear 21 is pressed against the stop surface 30 in the axial direction by means of its further stop surface 210. The axial force F_A is hereby directed to the shaft 3 via the stop surface 30. In particular, the axial force F_A is greater than the friction force F_RE caused by the radial force F_R, which acts to prevent the crown gear 21 from moving along the axis A1.

[0074] Without the stop surface 30, the axially acting force F_A would be directed to the bearings 231, 232 and / or the freewheel 230. However, these elements are usually not configured to absorb large axial forces and may be damaged by such axial forces. In this regard, the service life of the drive device 1 is increased by limiting the freedom of movement of the stop surface 30 or the crown gear 21 in the axial direction.

[0075] The axial mobility of the crown gear 21 is also advantageous in the second operating state, in which the shaft 3 rotates relative to the crown gear 21. In this operating state, for example, the bevel pinion 22 is not driven, so that there is no axial force F_A pressing the crown gear 21 against the stop surface 30. The crown gear 21 can be moved away from the stop surface 30 at least a certain distance.

[0076] As a result, the two stop surfaces 30 , 210 can slide past each other proportionally and frictionlessly. This can be further improved by a lubricant provided on the stop surfaces 30 , 210 or between them.

[0077] It is clear from the above description that the axial displaceability of the crown gear 21 relative to the bevel pinion 22 or to the shaft 3 is advantageous compared to the axial fixing of the crown gear 21. Furthermore, the axial fixing of the crown gear 21 is very complex and is advantageously avoided here.

[0078] So outside Figure 3 It is found that the bevel gear transmission 2 of the present drive device 1 is designed such that the joint 212 between the bevel pinion 22 and the crown gear 21 is inclined with respect to the axis A1 and more precisely such that the angle of inclination α between the joint 212 and the axis A1 is at least 45°.

[0079] Considering the possible tilting between the crown gear 21 and the bevel pinion 22, it is advantageous to arrange the stop surface 30, 210 axially between the freewheel 230 or the bearings 231, 232 and the bevel pinion 22. The use of the second bearing 232 additionally reduces the risk of tilting between the bevel pinion 22 and the crown gear 21.

[0080] The present invention is not limited to the description based on the exemplary embodiments. Rather, the present invention includes any novel features and any combination of features, which in particular includes any combination of features in the claims, even if these features or these combinations themselves are not described in detail in the claims or exemplary embodiments.

[0081] Reference numerals list

[0082] 1. Drive equipment

[0083] 2 reversing transmission

[0084] 3 Axis

[0085] 4 Housing

[0086] 21 First transmission element

[0087] 22 Second transmission element

[0088] 30 Limiting Agency

[0089] 32 Components

[0090] 40 Pedal crank

[0091] 41 Shell components

[0092] 50 Bicycle Frame

[0093] 60 Frame Sections

[0094] 100 Electric Bicycles

[0095] 210 Additional stop surface

[0096] 212 Joint

[0097] 230 Clutch

[0098] 231 Bearing

[0099] 232 Bearings

[0100] A1 First axis

[0101] A2 Second axis

[0102] R Radial direction

[0103] C Azimuth direction

[0104] F-Force

[0105] F_R Radial component of the force

[0106] F_A Axial component of the force

[0107] F_RE Friction force

[0108] α Tilt angle

Claims

1. A drive device (1) for an electric bicycle (100), the drive device comprising: - shaft (3), a reversing transmission (2) for coupling to the electric motor on the one hand and to the shaft (3) on the other hand, so that a torque can be transmitted from the electric motor via the reversing transmission (2) to the shaft (3), wherein The reversing transmission (20) comprises a first transmission element (21) rotatable about a first axis (A1) and a second transmission element (22) coupled to the first transmission element, the second transmission element being rotatable about a second axis (A2) extending obliquely to the first axis (A1), The drive device (1) is configured to: - transmitting torque from the first transmission element (21) to the shaft (3) via a coupling between the first transmission element (21) and the shaft (3), - rotating the shaft (3) relative to the first transmission element (21) in a first rotational direction, The first transmission element (21) is axially movable relative to the second transmission element (22) parallel to the first axis (A1) within predetermined limits, wherein the transmission elements (21, 22) remain coupled to each other within the predetermined limits.

2. The drive device (1) according to claim 1, wherein - an axial movement of the first transmission element (21) in a first axial direction is limited by the second transmission element (22), and an axial movement of the first transmission element in an opposite second axial direction is limited by a limiting device (30), The limiting device (30) is axially fixed relative to the shaft (30) and / or relative to the second transmission element (22).

3. The drive device (1) according to claim 2, wherein - The drive device (1) is configured so that when the torque is transmitted from the second transmission element (22) to the first transmission element (21), an axial force acts on the first transmission element (21) and the axial force is directed via the limiting mechanism (30) to the shaft (3) or to an element axially fixed relative to the shaft (3).

4. The drive device (1) according to any one of the preceding claims, further comprising: at least one bearing (231, 232), by means of which the first transmission element (21) is supported relative to the shaft (3) in a manner rotatable about the first axis (A1).

5. The drive device (1) according to claim 4, wherein The coupling joint between the first transmission element (21) and the shaft (3) is arranged axially between two bearings (231, 232).

6. The drive device (1) according to any one of the preceding claims, wherein The coupling between the first transmission element (21) and the shaft (3) is a one-way coupling.

7. The drive device (1) according to any one of the preceding claims, wherein The reversing transmission (2) is a bevel gear transmission, wherein the first transmission element (21) is a ring gear and the second transmission element (22) is a bevel pinion.

8. The drive device (1) according to any one of the preceding claims, wherein The reversing transmission (2) has a transmission ratio of at least 4 and at most 6.

9. The drive device (1) according to any one of the preceding claims, wherein - The shaft (3) is a sprocket shaft.

10. A drive device (1) according to claim 2 or any one of claims 3 to 9 in dependence upon claim 2, wherein - the limiting means (30) is a stop surface (30), a further stop surface (210) is associated with the first transmission element (21) and is axially fixed relative to the first transmission element, The stop surfaces (30, 210) are arranged opposite each other in the axial direction, overlap each other radially and azimuthally and face each other, The stop surfaces (31, 210) are configured to stop each other in order to limit the axial movement of the first transmission element (21).

11. The driving device according to claim 10, wherein The stop surface (30, 210) is positioned axially between the second transmission element (22) and a coupling joint between the first transmission element (21) and the shaft (3).

12. A drive device according to claim 10 or 11, wherein The region in which the stop surfaces (30, 210) stop against one another is offset radially relative to the joint of the coupling between the first transmission element (21) and the shaft (3).

13. A drive device according to any one of claims 10 to 12, wherein - the stop surface (30, 210) is metallic, - A lubricant is applied to the stop surface (30, 210).

14. A drive device according to any one of the preceding claims, wherein - the first transmission element (21) at least partially radially surrounds the shaft (3), The coupling joint between the first transmission element (21) and the shaft (3) is arranged between the shaft (3) and the first transmission element (21) in the radial direction and overlaps with the first transmission element (21) and the shaft (3) in the axial direction.

15. An electric bicycle (100), comprising: - A drive device (1) according to any one of the preceding claims, - an electric motor, wherein The electric motor is coupled to the reversing transmission (2) such that the torque of the electric motor is transmitted to the first transmission element (21) via the second transmission element (22).

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