Drive unit of an electric bicycle

Abstract

The invention relates to a drive unit of an electric bicycle, comprising a motor having a motor shaft, an output shaft, a transmission, a housing, and a rotor bearing, wherein the transmission is designed to transmit torque between the motor shaft and the output shaft, wherein the motor shaft is arranged coaxially to the output shaft, wherein the motor shaft is mounted by means of the rotor bearing, and wherein the rotor bearing is arranged at least partially within a stator of the motor in the axial direction.

Description

[0001] R.412906

[0002] - 1 -

[0003] Description

[0004] title

[0005] drive unit of an electric bicycle

[0006] State of the art

[0007] The present invention relates to a drive unit of an electric bicycle, and an electric bicycle.

[0008] Electric bicycle drive units are well-known and comprise a multitude of components, such as motors, gearboxes, bearings, circuit boards, and the like. These components are typically housed in a single casing. This often results in complex designs to best meet the various requirements of the drive unit, such as low weight, compact geometry, ease of assembly, and low cost.

[0009] Disclosure of the invention

[0010] In contrast, the drive unit according to the invention with the features of claim 1 is characterized by a particularly advantageous simple design, which has particularly compact dimensions. In particular, a particularly small axial dimension of the drive unit can be achieved. This is achieved according to the invention by a drive unit of an electric bicycle comprising a motor with a motor shaft, an output shaft, a gearbox, a housing, and a rotor bearing. The gearbox is configured for torque transmission between the motor shaft and the output shaft. The motor shaft is arranged coaxially with the crankshaft. In addition, the motor shaft is supported by means of the rotor bearing. The rotor bearing is arranged at least partially within a stator of the motor in the axial direction. R.412906

[0011] - 2 -

[0012] In particular, the stator is arranged radially outside a rotor of the motor, the rotor preferably being connected to the motor shaft in a rotationally fixed manner.

[0013] In other words, a drive unit is provided which is designed in a coaxial manner and has a rotor bearing by means of which the motor shaft of the motor is supported. The rotor bearing and stator are arranged to overlap at least partially in the axial direction.

[0014] Preferably, the transmission can be designed as a spur gear transmission with several gears, wherein the teeth of all gears are formed, in particular exclusively, on an outer circumference of the respective gear. In particular, the respective gears that mesh with each other are arranged to rotate about separate axes.

[0015] The drive unit thus offers the advantage of a particularly compact and lightweight design with few components. This design allows for a particularly compact drive unit geometry. In particular, space can be effectively saved in the axial direction. By arranging the rotor bearing and stator at least partially overlapping on the motor shaft, and especially within the motor shaft itself, more space can be provided for other components, enabling a particularly compact drive unit geometry in the axial direction. This allows for a particularly effective saving of space in the axial direction, resulting in a small axial dimension for the entire drive unit. Consequently, the cranks of the e-bike, which can be connected to the drive unit, can be positioned very close together along the axial direction.In particular, this allows for a low Q-factor. This enables especially comfortable and ergonomically advantageous geometries for the e-bike in the bottom bracket area.

[0016] The dependent claims describe preferred embodiments of the invention. R.412906

[0017] - 3 -

[0018] Preferably, the drive unit further comprises a bearing shield, wherein the motor shaft is supported in the bearing shield by means of the rotor bearing, and wherein the rotor bearing is arranged on a radially outer circumference of the motor shaft. The bearing shield is preferably attached to the housing. In particular, the bearing shield can be formed together with the housing as a single, integral component, or alternatively, preferably, it can be connected to the housing by means of a connection, preferably a material-fit and / or force-fit and / or positive-fit connection. Furthermore, the motor shaft is supported in the bearing shield by means of the rotor bearing. In particular, the bearing shield has a first bearing seat in which the rotor bearing is arranged. In other words, a drive unit is provided which is designed in a coaxial manner and has a bearing shield by means of which the motor shaft of the motor is supported.This means that the motor shaft is supported by the rotor bearing and the bearing shield. In particular, the motor shaft is not indirectly supported, at least not via the rotor bearing, for example, by another shaft such as the output shaft or a crankshaft. That is to say, preferably the rotor bearing is directly and mechanically immovably supported by the bearing shield against the housing of the drive unit.

[0019] This means the motor shaft is supported by the rotor bearing and the end shield. The rotor bearing is located on the radially outer circumference of the motor shaft. In other words, the motor shaft is positioned radially inside the rotor bearing, and, more importantly, the end shield is located radially outside the rotor bearing. Supporting the rotor bearing via the end shield allows for a simple, precise arrangement and a robust design. In particular, this enables advantageous, space-saving axial positioning of the rotor bearing, for example, partially within the motor. Furthermore, arranging the rotor bearing on the radially outer circumference of the motor shaft allows for a particularly advantageous arrangement of the rotor bearing to save axial installation space.

[0020] Preferably, the bearing shield includes an additional bearing seat for receiving an intermediate shaft bearing. This means that the bearing shield can hold another bearing, namely the intermediate shaft bearing, within and to the housing. This allows for a particularly simple and cost-effective design with few components and low weight for the drive system. R.412906

[0021] - 4 - unit provided. Preferably, the additional bearing seat is arranged at a radial distance from the first bearing seat of the rotor bearing. In particular, the additional bearing seat is designed as a recess in the bearing shield.

[0022] Preferably, the drive unit's transmission includes an intermediate shaft. The intermediate shaft is rotatably mounted in the bearing plate by means of an intermediate shaft bearing. Preferably, the transmission is configured to provide torque transmission from the motor shaft via the intermediate shaft to the output shaft. Preferably, the transmission comprises several meshing gears on the motor shaft, the intermediate shaft, and the output shaft. Preferably, the intermediate shaft is arranged parallel to the output shaft, and in particular, at a predetermined distance from the output shaft. This allows for an optimal gear ratio and drive unit geometry with a simple and advantageous design.

[0023] Preferably, the motor stator, rotor bearing, printed circuit board, rotor position sensor, and gearbox gear are arranged along an axial direction of the motor shaft, particularly in the order mentioned. The rotor position sensor can be, in particular, a component rotating with the motor shaft, i.e., with the motor rotor, by means of which the rotor position of the motor can be monitored, preferably by means of a rotor position sensor that can be arranged on the printed circuit board. It is particularly preferable that the rotor bearing and stator overlap at least partially in the axial direction. For example, the rotor bearing and printed circuit board can also overlap at least partially in the axial direction. This allows for a particularly space-saving design in the axial direction, in order to keep the installation space between the stator and gearbox to a minimum.

[0024] Preferably, the output shaft has an output interface configured for connection to an output element. For example, a chainring configured for connection to a transmission element, such as a bicycle chain, can be provided as the output element. The rotor bearing is arranged at one axial end of the motor shaft facing the output interface. In particular, the motor, preferably the rotor and stator, is arranged at one end of the drive unit facing away from the output interface. That is, the rotor bearing is located towards the inner area R.412906.

[0025] - 5 - of the drive unit. Preferably, the gearbox of the drive unit is arranged between the rotor bearing and the output interface. This allows for a simple, optimally space-saving arrangement and geometry of the drive unit components in order to keep the axial dimensions of the drive unit small.

[0026] The drive unit preferably further comprises a crankshaft arranged coaxially to the output shaft and located inside the motor shaft. In particular, the crankshaft is also arranged inside the output shaft. Preferably, the crankshaft can be connected to the cranks of the e-bike in a rotationally fixed manner. Preferably, the crankshaft and output shaft can be connected to each other in a rotationally fixed manner, particularly via a freewheel. The freewheel allows, for example, the rider to be disconnected from the drivetrain. Furthermore, the corresponding arrangement of the output shaft enables a particularly compact overall geometry of the drive unit.

[0027] Preferably, the motor shaft and / or a rotor of the motor is supported on the crankshaft by means of a second rotor bearing. Preferably, the second rotor bearing is located radially between the crankshaft and the motor shaft. In particular, the second rotor bearing is arranged at an axial end of the motor shaft or rotor facing away from the output interface. That is, the rotor of the motor and / or the motor shaft is supported directly on the crankshaft by means of the second rotor bearing. This allows for a simple and cost-effective design and assembly of the drive unit.

[0028] Preferably, the bearing shield is designed as a separate component from the housing. In particular, the bearing shield can be connected to the housing by an additional connection. For example, the connection can be a screw connection.

[0029] Preferably, the drive unit further comprises a carrier which is configured to hold components of the drive unit and preferably to guide lubricant within the housing. The carrier is particularly arranged within the housing. Lubricant guidance is specifically defined as the carrier providing certain lubricant reservoirs in which lubricant can be stored. In addition, the lubricant guidance enables the targeted placement of the lubricant, for example by means of appropriate R.412906.

[0030] - 6 - geometric design of the support, for areas of the drive unit requiring lubrication, in particular the gearbox. Preferably, the support is designed for fastening or fixing the components of the drive unit, such as circuit boards, electrical cables, or the like. This allows for a simple and easy-to-assemble design of the drive unit with few components.

[0031] Preferably, the bearing shield is arranged between the support and the housing. The bearing shield and the support are attached to the housing by means of a common fastening element. For example, the fastening element can comprise a screw connection. For example, the bearing shield can thus be clamped between the housing and the support.

[0032] This allows for a particularly simple design and assembly of the drive unit, as fewer components and fewer steps are required for fastening.

[0033] Preferably, the bearing shield is essentially sheet-metal in shape. In particular, the bearing shield is arranged orthogonally to an output axis of the output shaft. This means that the bearing shield extends essentially in a plane orthogonal to the output axis. This allows for a robust design with small axial dimensions of the drive unit.

[0034] Furthermore, the invention leads to an electric bicycle comprising the described drive unit.

[0035] Brief description of the drawings

[0036] Exemplary embodiments of the invention are described in detail below with reference to the accompanying drawings. The drawing shows:

[0037] Figure 1 shows a simplified schematic view of an electric bicycle with a drive unit according to a first embodiment of the invention.

[0038] Figure 2 shows a sectional view of the drive unit of Figure 1, R.412906

[0039] - 7 -

[0040] Figure 3 shows a perspective detail view of a bearing shield of the drive unit of Figure 1.

[0041] Figure 4 shows a perspective view of the drive unit of Figure 1.

[0042] Figure 5 shows a detailed sectional view of the drive unit of Figure 1, and

[0043] Figure 6 shows a sectional view of a drive unit according to a second

[0044] Exemplary embodiment of the invention.

[0045] Embodiments of the invention

[0046] Preferably, all identical components, elements and / or units in all figures are provided with the same reference numerals.

[0047] Figure 1 shows a simplified schematic view of an electric bicycle 100 with a drive unit 1 according to a first embodiment of the invention. Details of the drive unit 1 of the first embodiment are shown in Figures 2 to 5.

[0048] The drive unit 1 comprises a motor 2, which is in particular an electric motor. The motor 2 can be supplied with electrical energy by means of an electrical energy storage device 109 of the electric bicycle 100. The drive unit 1 is arranged in the area of ​​a bottom bracket of the electric bicycle 100. By means of motor torque generated by the motor 2, the pedaling force generated by the rider of the electric bicycle 100 can be motor-assisted. The rider's muscle force can be applied via a crank mechanism with cranks 104. The cranks 104 are rotationally fixed to a crankshaft 33.

[0049] The motor 2 comprises a motor shaft 22, at which the motor torque can be provided. The motor shaft 22 is arranged coaxially with an output shaft 3 of the drive unit 1. Motor shaft 22 and output shaft 3 are also arranged coaxially with the crankshaft 33. The shafts thus extend along a common crank axis 15. R.412906

[0050] - 8 -

[0051] Torque transmission from the crankshaft 33 to the output shaft 3 can be effected via a freewheel 30, and in particular a freewheel carrier 30a.

[0052] The motor torque 22 is transmitted to the output shaft 3 by means of a gearbox 4, and preferably a further freewheel 40.

[0053] The gearbox 4 comprises several gears 41, 42, 43, 44. In detail, the gearbox 4 comprises a first gear 41, which is non-rotatably connected to the motor shaft 22.

[0054] Furthermore, the transmission 4 comprises an intermediate shaft 45, on which a second gear 42 and a fourth gear 44 are arranged in a rotationally fixed manner. The intermediate shaft 45 is rotatably arranged about an intermediate shaft axis 45a that is parallel to the crank axis 15.

[0055] Furthermore, the gearbox 4 includes a third gear which can transmit the torque to the output shaft 3 via the second freewheel 40. In gearbox 4, the first gear 41 and the second gear 42 are meshed with each other. Additionally, the third gear 43 and the fourth gear 44 are meshed with each other.

[0056] The drive unit 1 further comprises a housing 5, within which all components of the drive unit 1 are arranged. The output shaft 3 and the crankshaft 33 protrude from the housing.

[0057] Outside the housing 5, the output shaft 3 has an output interface 35, at which the output shaft 3 and an output element 107, which is in particular a chainring, are connected to each other in a rotationally fixed manner.

[0058] The housing 5 has two housing parts 51, 52 which can be connected to each other to form a closed housing chamber 50 inside the housing 5. A seal 55 can be arranged between the two housing parts 51, 52 for a fluid-tight seal.

[0059] The motor 2 of the drive unit 1 comprises a stator 26, which is fixedly arranged on the first housing part 51. The motor 2 also comprises a rotor R.412906.

[0060] - 9 -

[0061] 27, which is arranged radially inside the stator 26. The motor shaft 22 is rotatably connected to the rotor 27.

[0062] The drive unit 1 further comprises a bearing shield 8, which is rotatably attached to the housing 4, and in which a rotor bearing 11 is mounted, which rotatably mounts the motor shaft 22 relative to the housing 5.

[0063] The rotor bearing 11 is arranged on a radially outer circumference of the motor shaft 22. The bearing shield 8 has a through-opening through which the motor shaft 22 extends. Adjacent to the through-opening, a first bearing seat 81 is formed in the bearing shield 8, in which the rotor bearing 11 is arranged (see Figure 3).

[0064] Furthermore, the bearing shield 8 is designed as an essentially flat sheet metal which extends in a plane orthogonal to the crank axis 15.

[0065] The bearing shield 8 provides direct, immovable mechanical support for the rotor bearing 11 on the housing 5. This enables a robust and precise arrangement of the rotor bearing 11 within the drive unit 1.

[0066] Furthermore, the special support provided by the bearing shield 8 from the radial outside allows for a particularly advantageous arrangement of the rotor bearing 11 in the motor 2. Specifically, the rotor bearing 11 can be positioned in a particularly space-saving manner, namely at least partially within the stator 26. This means that the rotor bearing 11 can be positioned (with reference to Figure 2) so far to the left that the stator 26 and rotor bearing 11 overlap axially, at least partially. This allows for a particularly small axial dimension for the drive unit 1. As a result, the cranks 104 can be arranged optimally close together, providing a particularly ergonomically advantageous geometry for the rider of the electric bicycle 100.

[0067] The bearing shield 8 further comprises an additional bearing seat 82, which is designed to receive an intermediate shaft bearing 12. The intermediate shaft 45 is rotatably mounted relative to the housing 5 by means of the intermediate shaft bearing 12; the additional bearing seat 82 can be designed as a cavity that is closed in the axial direction (see Figure 3). R.412906

[0068] - 10 -

[0069] The bearing shield 8 can be attached via several mounting areas 89. At each of these mounting areas 89, a screw connection can be made to the housing 5 and / or to a support 6 of the drive unit 1.

[0070] The carrier 6 is arranged inside the housing 5 and is designed to hold components of the drive unit 1 and to guide lubricant (see Figure 2).

[0071] Furthermore, the support 6 is designed to connect and stiffen the housing parts 51, 52. The support 6 includes through-openings, each containing a connecting sleeve 7. The connecting sleeves 7 extend axially between the two housing parts 51, 52. A screw 75 is screwed into each connecting sleeve 7 from outside the housing 5 to connect the housing parts 51, 52 to one another (see Figure 5).

[0072] As can be further seen in Figure 5, the bearing shield 8 and the support 6 are jointly attached to the housing 5 by means of the connecting element 75. In detail, the bearing shield 6 is arranged axially between the housing part 51 and the support 6 with the connecting element 7. This allows for a particularly simple and cost-effective design and assembly of the drive unit 1.

[0073] Furthermore, the drive unit 1 comprises at least one circuit board 9, which may, for example, include a control unit for the drive unit 1. The circuit board 9 extends essentially in a plane orthogonal to the crank axis 15 (see Figures 2, 4 and 5).

[0074] The circuit board 9 can also be fastened to the bearing shield 8 and the support 6 by means of the screw 75. In detail, the circuit board 9 can be arranged axially between the bearing shield 8 and the support 6 and, for example, be elastically supported relative to the support 6 by means of an elastic element 19. R.412906

[0075] - 11 -

[0076] For example, motor 2 and circuit board 9 can be connected to each other by means of lines 29 (Figure 5). The lines 19 can protrude through through-openings in the bearing shield 8.

[0077] A rotor position sensor 91 can be arranged at an axial end of the motor shaft 22 and axially between the circuit board 9 and the second gear 42 of the gearbox 4. This rotor position sensor is preferably designed as a flat sheet metal disk that is non-rotatably connected to the motor shaft 22. By means of a rotor position sensor on the circuit board 9, the position and / or rotation of the motor shaft 22 can be determined by detecting the position and / or rotation of the rotor position sensor 91.

[0078] Figure 6 shows a sectional view of a drive unit 1 according to a second embodiment of the invention. The second embodiment corresponds essentially to the first embodiment of Figures 1 to 5, with the difference being an alternative arrangement of the rotor bearing 11.

[0079] In the second embodiment shown in Figure 6, the rotor bearing 11 is arranged directly on an outer circumference of the crankshaft 33. Thus, the motor shaft 22 is supported by means of the rotor bearing 11, which is arranged radially partially inside the stator 26 of the motor 2. The rotor bearing 11 is also arranged axially partially inside the stator 26 of the motor 2 in order to enable the axially particularly compact design of the drive unit 1.

[0080] The drive unit 1 of the second embodiment therefore does not include a bearing shield for holding the rotor bearing 11. This allows for a simple and cost-effective design of the drive unit 1 with few components.

Claims

R.412906 - 12 - Claims 1. Drive unit of an electric bicycle (100), comprising: a motor (2) with a motor shaft (22), an output shaft (3), a gearbox (4), a housing (5), and a rotor bearing (11), wherein the gearbox (4) is configured for torque transmission between the motor shaft (22) and the output shaft (3), wherein the motor shaft (22) is arranged coaxially to the output shaft (3), wherein the motor shaft (22) is supported by means of the rotor bearing (11), and wherein the rotor bearing (11) is arranged at least partially within a stator (26) of the motor (2) in an axial direction.

2. Drive unit according to claim 1, further comprising a bearing shield (8), wherein the motor shaft (22) is supported in the bearing shield (8) by means of the rotor bearing (11), and wherein the rotor bearing (11) is arranged on a radially outer circumference of the motor shaft (22).

3. Drive unit according to claim 2, wherein the bearing shield (8) comprises a bearing seat (82) for receiving an intermediate shaft bearing (12).

4. Drive unit according to claim 3, wherein the transmission (4) comprises an intermediate shaft (45), and wherein the intermediate shaft (45) is supported in the bearing shield (8) by means of the intermediate shaft bearing (12).

5. Drive unit according to one of the preceding claims, wherein the stator (26) of the motor (2) and the rotor bearing (11) and a circuit board (9) and a rotor position sensor (91) and a gear (42) of the gearbox (4) are arranged along an axial direction of the motor shaft (22). R.412906 - 13 - 6. Drive unit according to one of the preceding claims, wherein the output shaft (3) has an output interface (35) which is configured for connection with an output element (107), and wherein the rotor bearing (11) is arranged at an axial end of the motor shaft (22) facing the output interface (35).

7. Drive unit according to one of the preceding claims, further comprising a crankshaft (33) which is arranged coaxially to the output shaft (3) and within the motor shaft (22).

8. Drive unit according to claim 7, wherein the motor shaft (22) and / or a rotor (27) of the motor (2) is mounted on the crankshaft (33) by means of a second rotor bearing (12).

9. Drive unit according to one of claims 2 to 8, wherein the bearing shield (8) is designed as a component separate from the housing (5).

10. Drive unit according to one of the preceding claims, further comprising a carrier (6) which is configured to hold components of the drive unit (1) and preferably to guide lubricant within the housing (4).

11. Drive unit according to claim 10, wherein the bearing shield (8) is arranged between the support (6) and the housing (4), and wherein the bearing shield (8) and the support (6) are attached to the housing (4) by means of a common fastening element (75).

12. Drive unit according to one of claims 2 to 11, wherein the bearing shield (8) is essentially sheet-metal shaped and is arranged orthogonally to an output axis (15) of the output shaft (3).

13. Electric bicycle comprising a drive unit (1) according to one of the preceding claims.

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