Drive unit for a vehicle that can be propelled at least partially by muscle power and vehicle with such a drive unit

Abstract

The invention relates to a drive unit for a vehicle (1) that can be propelled at least partially by muscle power, comprising a hub housing (2) configured to be rotationally fixed to a drive wheel (3) of the vehicle (1), a switchable planetary gear set (4) with three shafts arranged therein, and an electric machine (5) with a rotor (6) and a stator (7) effectively connected thereto, wherein the switchable planetary gear set (4) is arranged radially within the electric machine (5) and coaxially thereto, a coupling device (8) and an adjusting thread (9) which are effectively connected to the rotor (6) via a torsion spring (10), wherein the coupling device (8) in a closed switching position connects two of the three shafts of the switchable planetary gear set (4) to each other in a rotationally fixed manner, whereby the planetary gear set (4) rotates as a unit, wherein the coupling device (8) in an open switching position,which is initiated by an over-torque and rotation of the torsion spring (10), decouples the two rotationally fixed shafts of the switchable planetary gear set (4) from each other by means of an adjusting thread (9), so that the drive power of the electric machine (5) is introduced into the planetary gear set (4) only via one of these two shafts, wherein a third shaft of the switchable planetary gear set (4) is supported on a stationary element via a freewheel device (11).

Description

[0001] The invention relates to a drive unit for a vehicle that can be propelled at least partially by muscle power. Furthermore, the invention relates to a vehicle with such a drive unit. In particular, the vehicle is designed as a bicycle or e-bike and has at least two wheels.

[0002] For example, DE 10 2019 114 120 A1 discloses a drive unit for a vehicle, comprising at least a housing, at least one electric motor with a stator and a rotor, and at least one gearbox unit engaged with the rotor. The gearbox unit comprises a single-stage or two-stage planetary gearbox.

[0003] German patent DE 10 2014 107 382 A1 describes an electric wheel hub drive with an electric motor, freewheel, planetary gear set, and load-shiftable friction clutch. With the friction clutch open, the electric motor is driven via a rotationally connected freewheel to the sun gear of the planetary gear set, which has a stationary ring gear. This connection is then via the planet gears and planet carrier to the wheel hub, with a corresponding reduction ratio. With the friction clutch closed, the electric motor is driven directly by the wheel hub, and the planetary gear set rotates without force due to the decoupling of the freewheel.

[0004] The CN 2 15 956 210 U describes a wheel hub motor with switchable speed for a two-wheeled electric vehicle.

[0005] DE 11 2011 104 916 T5 describes a motor-driven hub with a gear arrangement and a bidirectional rotatable electric motor for driving the gear arrangement. There is a first operating mode, when the motor rotates in a first direction to provide at least one first drive gear in the forward direction, and a second operating mode, when the motor rotates in the second direction to provide at least one second drive gear in the forward direction. A motor controller switches the motor between the directions of rotation depending on a speed parameter.

[0006] US Patent 2011 / 0034283A1 describes a gearshift mechanism comprising a first and second planetary gear set, a power supply connection for driving the first and second sun gears to the output of a power source, a hub sleeve surrounding the planetary gear sets, and a first and second one-way clutch for transmitting the drive from the output of each planetary gear set to the hub sleeve. In one of the planetary gear sets, the carrier arm is fixed, and the ring gear is the output. In the other planetary gear set, the ring gear is fixed, and the carrier arm is the output.

[0007] US Patent 2019 / 0077485A1 describes a motor power transmission device in which the rotation of the electric motor acts on a sun gear of a planetary reduction gear, and the rotation of the sun gear is then converted into the rotation of a planet carrier. A torque limiting mechanism is interposed between this and the output shaft, so that even if excessive reverse torque is introduced into the output shaft, the transmission of the reverse torque to the reduction gear is blocked to protect the reduction gear.

[0008] DE 10 2012 216 132 A1 describes a wheel hub drive with a drive train including an electric drive motor and a gearbox for torque conversion with at least two gears.

[0009] DE 10 2014 206 985 A1 describes a clutch actuator for actuating a friction clutch with an electric actuator motor arranged around the axis of rotation with a rotor driven around the axis of rotation, an actuating element that converts a linear motion into an axial motion for the axial displacement of a lever element of the friction clutch depending on a rotary drive of the actuating motor, and a two-stage planetary gear that switches automatically between the actuating element and the actuating motor depending on a load of the clutch actuator, with a sun gear rotationally coupled to the rotor, a ring gear fixed to the housing by means of a freewheel, planet gears meshing between the sun gear and the ring gear and rotatably mounted on a planet carrier, and a switching clutch that connects the sun gear and planet carrier in a switchable manner.

[0010] DE 10 2023 210 396 B3 describes a hub drive for a vehicle with two planetary gear sets.

[0011] The object of the invention is to create an alternative drive unit for a vehicle that is at least partially powered by muscle power. In particular, the drive unit should have two selectable gears and be of a compact design. Specifically, the gears should be selectable automatically. This object is achieved by the subject matter of claim 1. Preferred embodiments are described in the dependent claims, the description, and the figures.

[0012] A drive unit according to the invention for a vehicle that can be propelled at least partially by muscle power comprises a hub housing configured to be rotationally fixed to a drive wheel of the vehicle, a switchable planetary gear set with three shafts arranged therein, and an electric machine with a rotor and a stator effectively connected thereto, wherein the switchable planetary gear set is arranged radially within the electric machine and coaxially thereto, a coupling device, and an adjusting thread which are effectively connected to the rotor via a torsion spring, wherein in a closed switching position the coupling device connects two of the three shafts of the switchable planetary gear set rotationally fixed to each other, whereby the planetary gear set rotates in the block, wherein in an open switching position, which is initiated by exceeding the torque and twisting the torsion spring,The two shafts of the switchable planetary gear set, which are non-rotatably connected to each other, are decoupled from each other by means of an adjusting thread, so that the drive power of the electric machine is only introduced into the planetary gear set via one of these two shafts, with a third shaft of the switchable planetary gear set being supported on a stationary element via a freewheel device.

[0013] The coupling device, together with the adjusting thread and the torsion spring, enables switching on the planetary gear set, wherein the coupling device is configured to couple and decouple two shafts, in particular a sun gear and a planet carrier, of the switchable planetary gear set, wherein the adjusting thread converts a rotation into an axial feed, wherein the torsion spring is pre-tensioned and configured as a torque sensor. In particular, the adjusting thread comprises a threaded rod and a threaded nut axially displaceable therefrom.

[0014] When the drive torque is below a certain threshold, the torsion spring remains in its original position, so the drive power of the electric machine is transmitted via the two rotationally fixed shafts of the switchable planetary gear set. This causes the planetary gear set to rotate in a single unit, resulting in a gear ratio of 1. This gear ratio enables a direct drive, which is particularly suitable for achieving high speeds.

[0015] When the drive torque reaches a threshold, the torsion spring yields and twists, with the adjusting thread converting this rotation into an axial feed, thereby opening the coupling device. The drive power of the electric machine is then introduced only via one of the previously rotationally fixed shafts of the planetary gear set, for example, via a sun gear. This changes the gear ratio, reducing the speed at an output shaft, particularly at a planet carrier, of the switchable planetary gear set, while simultaneously increasing the torque. This allows, for example, a gradient requiring higher drive torque to be overcome.

[0016] Thus, the drive unit has two automatically shiftable gears, making it possible to use a compact electric machine, so that both a drive speed necessary for high speeds and a drive torque required for steep inclines are provided.

[0017] As soon as the load on the drive wheel falls below a threshold value, the torsion spring twists back into its original shape, thereby twisting the adjusting thread and thus axially displacing the coupling device so that the two shafts of the switchable planetary gear set are again connected to each other in a rotationally fixed manner.

[0018] Regardless of the clutch's position, in both of the aforementioned situations, the third shaft, preferably a ring gear, of the planetary gear set is supported by the freewheel mechanism against the stationary element. Thus, the freewheel mechanism prevents the ring gear from rotating when the vehicle is moving forward with the electric drive. In particular, the stationary element is non-rotatably connected to a wheel axle of the drive wheel, which in turn is non-rotatably connected to a frame of the vehicle.

[0019] In particular, the rotor is arranged radially within the stator, with the switchable planetary gear set also arranged radially within the rotor. Thus, the stator, the rotor, and the switchable planetary gear set are radially nested and axially overlapping, resulting in a particularly compact axial design for the drive unit, which is designed as a wheel hub motor for a vehicle, especially a bicycle.

[0020] The switchable planetary gear set has a first shaft, a second shaft and a third shaft, wherein the first shaft of the switchable planetary gear set is preferably designed as a sun gear, wherein the second shaft of the switchable planetary gear set is preferably designed as a planet carrier with several planet gears arranged on it, wherein the third shaft of the switchable planetary gear set is preferably designed as a ring gear.

[0021] According to one embodiment, the coupling device comprises a permanent magnet and an armature plate that frictionally engages with it. Thus, the coupling device is designed as a permanent magnet coupling, wherein, in a closed switching position of the coupling device, the armature plate frictionally engages with the permanent magnet to connect two shafts of the planetary gear set, in particular the sun gear and the planet carrier, in a rotationally fixed manner. In an open switching position of the coupling device, the armature plate and the permanent magnet are axially spaced apart to decouple the two shafts of the planetary gear set that were previously rotationally fixed to each other.

[0022] According to one embodiment, the armature plate is connected to the rotor via the torsion spring and to the first shaft, in particular the sun gear, of the switchable planetary gear set via the adjusting thread. Furthermore, the permanent magnet is connected to the second shaft, in particular the planet carrier, of the switchable planetary gear set. When the coupling device is opened, the permanent magnet remains on the planet carrier, with the armature plate, on which the threaded nut and the torsion spring are arranged, being axially spaced from the permanent magnet, so that an air gap is formed between them.

[0023] According to one embodiment, the adjusting thread is designed to axially displace at least the clutch device and the switchable planetary gear set during a reverse movement of the vehicle, such that the freewheel device can rotate freely. This prevents the electric motor from being dragged along during a reverse movement of the vehicle. The axial displacement of the planetary gear set initiated by the adjusting thread causes the freewheel device to disengage, thereby eliminating torque support on the connected third shaft, in particular on the ring gear, of the planetary gear set.

[0024] Preferably, at least one return spring is arranged in the hub housing to return the switchable planetary gear set and the associated clutch device to the center. In particular, the return spring acts on an output shaft, especially on the planet carrier of the planetary gear set or on a shaft non-rotatably connected to it. The return spring can, for example, be designed as a compression spring and arranged on a stationary component. In particular, several return springs can be provided. For example, the freewheel device includes at least one return spring.

[0025] According to one embodiment, a constant gear ratio stage is arranged in the power flow between the hub housing and the switchable planetary gear set. For example, this gear ratio stage is designed as a planetary gear set and comprises a sun gear, a ring gear, and a planet carrier with several planet gears arranged on it, which mesh with the sun gear and the ring gear. For example, the sun gear of the downstream gear ratio stage is rotationally fixed to the planet carrier of the switchable planetary gear set. Furthermore, the planet carrier of the gear ratio stage is then fixed in a stationary position, with the ring gear of the gear ratio stage being rotationally fixed to the hub housing. The constant gear ratio stage allows for further torque adjustment, which enables the electric machine to be designed more compactly and with lower power consumption.Preferably, the constant transmission stage is arranged axially adjacent to the electric machine and the switchable planetary gear set. This saves radial installation space.

[0026] The invention also relates to a vehicle that can be propelled at least partially by muscle power, comprising at least two wheels and a drive unit according to the invention. In particular, the vehicle is designed as a bicycle or e-bike. For example, the vehicle can have three or more wheels, wherein either one or more wheels can be electrically driven.

[0027] According to one embodiment, the vehicle comprises a generator with a rotor and a stator, wherein the generator's rotor is non-rotatably connected to the vehicle's pedal crankshaft. Thus, the generator is designed as a pedal generator and converts the kinetic energy introduced by the rider via the pedals into electrical energy. The harder the rider pedals and the greater the generator's resistance, the greater the electrical power generated by the generator. The electric machine, designed as a wheel hub motor, generates drive power at the drive wheel according to the generator's electrical output. For example, the generator and the wheel hub motor are connected to each other, at least indirectly or directly. In particular, the vehicle can have several wheel hub motors, each driving a drive wheel.If a pedal generator is arranged on the crankshaft, a mechanical connection between the crankshaft and the drive wheel is unnecessary. If a mechanical connection, for example a traction drive, particularly a chain or belt drive, is arranged between the crankshaft and the drive wheel, a pedal generator on the crankshaft can be omitted. According to one embodiment, the vehicle includes an electrical energy storage device that is electrically connected to the generator and the wheel hub motor. The energy storage device serves, on the one hand, to store electrical energy, in particular to absorb the electrical energy from the generator, and on the other hand, to provide electrical energy, in particular to feed electrical energy into the wheel hub motor and drive the drive wheel.

[0028] Further measures improving the invention are described in more detail below, together with a description of preferred embodiments of the invention, with reference to the figures. Fig. 1 a highly simplified schematic representation of a vehicle according to the invention in a first embodiment, Fig. 2 a highly simplified schematic representation of a vehicle according to the invention in a second embodiment, Fig. 3 a highly simplified schematic representation of a drive unit according to the invention in a first embodiment and Fig. 4 a highly simplified schematic representation of a drive unit according to the invention in a second embodiment.

[0029] In Fig. Figure 1 shows a vehicle 1 according to the invention, which can be propelled at least partially by muscle power, comprising a rear wheel designed as a drive wheel 3, a front wheel 42 which is pivotably arranged on a frame 43 via a fork, and a drive unit according to the invention. The vehicle 1 is designed in this case as a bicycle, in particular as an e-bike.

[0030] A crankshaft 41 is connected to pedals 45 via crank arms 44, with a generator 40, designed as a pedal generator, being effectively connected to the crankshaft 41. The drive unit comprises an electric machine 5, designed as a wheel hub motor, and a switchable planetary gear set 4, which are jointly arranged in a hub housing 2 and effectively connected to the drive wheel 3 of the bicycle in order to generate drive power at the drive wheel 3 according to an electrical output of the generator 40. An electrical energy storage device 46 is arranged on the frame 43 of the bicycle and electrically connected to the generator 40 and the electric machine 5.

[0031] When the rider pedals, the generator 40 produces electrical power, which serves as a measure of the electrical energy from the energy storage device 46 fed into the electric machine 5 at the drive wheel 3. Specifically, the electrical drive power provided by the electric machine 5 at the drive wheel 3 is the product of the electrical power of the generator 40 and a factor selectable by the rider by choosing the driving mode. There is no mechanical connection, in particular no chain or belt drive, between the wheel hub, which rotatably mounts the drive wheel 5 on the frame 43, and the pedal crank shaft 41, so the drive wheel 3 can only be driven by the drive unit.

[0032] Fig. Figure 2 shows an alternative embodiment of a vehicle 1 according to the invention, comprising a rear wheel designed as a drive wheel 3, a front wheel 42, and a drive unit according to the invention. The vehicle 1 is as in the embodiment according to Fig. 1, to which reference is made, is also designed as a bicycle, in particular as an e-bike. The only difference between these two embodiments is that the generator on the pedal crank shaft 41 is omitted and the pedal crank shaft 41 has a mechanical connection via a traction drive 50 to the drive unit and thus also to the drive wheel 3. Therefore, the rider can propel the bicycle with muscle power when the energy storage 46 is depleted. This reduces manufacturing costs.

[0033] Fig. Figure 3 shows a highly simplified section of a first embodiment of the drive unit according to the invention, in particular the upper half as seen from the axis of rotation 47. A hub housing 2 of the drive unit is non-rotatably connected to a rim of the drive wheel 3 via spokes (not shown in detail). A switchable planetary gear set 4 and an electric machine 5 with a rotor 6 and a stator 7 are arranged in the hub housing 2. The planetary gear set 4 is arranged coaxially with the electric machine 5 and radially within the electric machine 5, wherein the rotor 6 is effectively connected to the hub housing 2 via the planetary gear set 4, and the stator 7 is non-rotatably connected to a wheel axle 19, which is non-rotatably connected to the frame of the bicycle, via a stationary element. A rotor position sensor 31 is arranged on a rotor shaft, which interacts with a circuit board 30. Electrical energy transmission also takes place via the circuit board 30.

[0034] The switchable planetary gear set 4 has three shafts: a first shaft, designed as a sun gear 14; a second shaft, designed as a planet carrier 15; and a third shaft, designed as a ring gear 16. The ring gear 16 of the planetary gear set 4 is supported on the stationary element via a freewheel device 11. A coupling device 8 with an adjusting thread 9 and a torsion spring 10 are arranged in the power flow between the electric machine 5 and the planetary gear set 4.

[0035] The coupling device 8 is designed as a permanent magnet coupling and comprises a permanent magnet 12 and an armature plate 13 that engages with it in a frictional manner. The armature plate 13 is connected to the rotor 6 via the torsion spring 10 and to the sun gear 14 of the planetary gear set 4 via the adjusting thread 9. The permanent magnet 12 is connected to the planet carrier 15 of the planetary gear set 4.

[0036] In a closed switching position, as shown here, the coupling device 8 connects the sun gear 14 and the planet carrier 15 to each other in a rotationally fixed manner via the adjusting thread 9, causing the planet gear set 4 to rotate in a block and provide a direct transmission. This allows the bicycle to reach a maximum speed.

[0037] As soon as the load on the drive wheel increases, for example when driving uphill, the torsion spring 10 twists, with the adjusting thread 9 converting this rotation into an axial feed and thereby opening the clutch device 8, thus separating the armature plate 13 from the permanent magnet 12. The drive power of the electric machine 5 is then introduced via the adjusting thread 9 into the sun gear 14 of the planetary gear set 4. The transmission is achieved via the planet gears 17, which are rotatably mounted on the planet carrier 15 and mesh with the ring gear 16 and the sun gear 14. The translated drive power is supplied to the drive wheel via the planet carrier 15, which serves as the output shaft and is rotationally fixed to the hub housing 2. The automatically changing transmission ratio allows the drive wheel to achieve maximum torque.

[0038] When the load on the drive wheel falls below a threshold value, the torsion spring 10 automatically returns to its original shape, thereby rotating the adjusting thread 9 and thus moving the armature plate 13 back towards the permanent magnet 12, so that the sun gear 14 and the planet carrier 15 are once again rotationally fixed to each other. Because the clutch device 8 is designed as a friction clutch, the shifting process is smooth, particularly comparable to engaging a clutch. This improves driving and shifting comfort for the driver. Furthermore, the friction of the adjusting thread 9 and the associated components creates a shifting hysteresis, so that there is no constant back-and-forth switching in the range of the shifting torque.

[0039] Fig. Figure 4 shows a second embodiment of the drive unit according to the invention. This drive unit is similar to the drive unit according to [reference to relevant article]. Fig. 3, which is referenced, is designed as a wheel hub drive. Only the differences between these two embodiments are explained below. Fig. In the power flow between the hub housing 2 and the switchable planetary gear set 4, a constant gear stage 20 is arranged. The gear stage 20 is designed as a planetary gear set and comprises a sun gear 21, a ring gear 23, and a planet carrier 22 with several planet gears 24 arranged on it, which mesh with the sun gear 21 and the ring gear 23. The sun gear 21 of the gear stage 20 is non-rotatably connected to the planet carrier 15 of the switchable planetary gear set 4. The planet carrier 22 of the gear stage 20 is fixed to the wheel axle 19, with the ring gear 23 of the gear stage 20 being non-rotatably connected to the hub housing 2. The gear stage 20 enables an increase in torque, which allows the electric machine 5 to be designed more compactly.In this case, the transmission stage 20 is arranged axially adjacent to the electric machine 5 and the switchable planetary gear set 4 in the hub housing 2, thereby saving radial installation space.

[0040] Furthermore, a return spring 18 is arranged between the stationary component and the sun gear 21 of the transmission stage 20 for returning the switchable planetary gear set 4 and the associated components, in particular the sun gear 21 of the transmission stage 20 and the clutch device 8. Thus, the return spring 18 acts via the sun gear 21 of the transmission stage 20 on the planet carrier 15 of the planetary gear set 4. The adjusting thread 9 is designed to axially displace the clutch device 8 and the planetary gear set 4, in particular the planet carrier 15 and the sun gear 21, which is non-rotatably connected to it, when the bicycle is moved backward. This axial displacement also acts on the ring gear 16 and, consequently, on the freewheel device 11, which disengages and can rotate freely. This function prevents the electric motor 5 from being dragged along when the bicycle is moved backward.As soon as the bicycle is moved in the direction of travel again, the return spring 19 presses via the sun gear 21 of the transmission stage 20 onto the planet carrier 15 of the planet gear set 4 in order to return the adjusting thread, the planet gear set 4 and thus also the freewheel device 11 to the starting position, so that the ring gear 16 of the planet gear set 4 is again indirectly supported on the wheel axle 19 when driven by the electric machine 5.

[0041] Furthermore, a wheel speed sensor 32 is arranged inside the hub housing 2, protected from dust and moisture. Otherwise, the embodiment corresponds to the following. Fig. 4 according to the exemplary embodiment Fig. 3. Reference symbol list 1 vehicle 2 hub shells 3 drive wheel 4 planetary gear set 5 electric machine 6 Rotor 7 Stator 8 Coupling device 9 adjusting threads 10 torsion spring 11 Freewheel device 12 permanent magnets 13 Anchor plate 14 Sun wheel 15 planetary carriers 16 Ring gear 17 planetary gear 18 Return spring 19 wheel axle 20 translation level 21 Sun wheel 22 planetary carriers 23 Ring gear 24 planetary gear 30 circuit boards 31 Rotor position sensors 32 Wheel speed sensors 40 Generator 41 Crankshaft 42 front wheel 43 frames 44 Crankset 45 pedals 46 Energy storage 47 Rotation axis 50 traction drive

Claims

[1] Drive unit for a vehicle (1) that can be propelled at least partially by muscle power, comprising a hub housing (2) configured to be rotationally fixed to a drive wheel (3) of the vehicle (1), a switchable planetary gear set (4) with three shafts arranged therein, and an electric machine (5) with a rotor (6) and a stator (7) effectively connected thereto, wherein the switchable planetary gear set (4) is arranged radially within the electric machine (5) and coaxially thereto, a coupling device (8) and an adjusting thread (9) which are effectively connected to the rotor (6) via a torsion spring (10), wherein the coupling device (8) in a closed switching position connects two of the three shafts of the switchable planetary gear set (4) to each other in a rotationally fixed manner, whereby the planetary gear set (4) rotates in a block, wherein the coupling device (8) in an open switching position,which is initiated by exceeding the torque and twisting the torsion spring (10), decouples the two rotationally fixed shafts of the switchable planetary gear set (4) from each other by means of an adjusting thread (9), so that the drive power of the electric machine (5) is introduced into the planetary gear set (4) only via one of these two shafts, wherein a third shaft of the switchable planetary gear set (4) is supported on a stationary element via a freewheel device (11). [2] Drive unit according to claim 1, characterized by , that the coupling device (8) has a permanent magnet (12) and an armature plate (13) that interacts with it in a frictional manner. [3] Drive unit according to claim 2, characterized by , that the anchor plate (13) is connected to the rotor (6) via the torsion spring (10) and is connected to the first shaft of the switchable planetary gear set (4) via the adjusting thread (9). [4] Drive unit according to claim 2 or 3, characterized by , that the permanent magnet (12) is connected to the second shaft of the switchable planetary gear set (4). [5] Drive unit according to one of the preceding claims, characterized by , that the first shaft of the switchable planetary gear set (4) is designed as a sun gear (14), wherein the second shaft of the switchable planetary gear set (4) is designed as a planet carrier (15), wherein the third shaft of the switchable planetary gear set (4) is designed as a ring gear (16). [6] Drive unit according to one of the preceding claims, characterized by , that the adjusting thread (9) is designed to axially displace at least the clutch device (8) and the switchable planetary gear set (4) during a reverse movement of the vehicle (1) so that the freewheel device (11) can rotate freely. [7] Drive unit according to claim 6, characterized by, that at least one return spring (18) is arranged in the hub housing (2) for resetting the switchable planetary gear set (4) and the associated clutch device (8). [8] Drive unit according to one of the preceding claims, characterized by , that a constant transmission stage (19) is arranged in the power flow between the hub housing (2) and the switchable planetary gear set (4). [9] Vehicle (1) which can be propelled at least partially by muscle power, comprising at least two wheels and a drive unit according to one of the preceding claims. [10] Vehicle (1) according to claim 9, characterized by a generator (40) with a rotor and a stator, wherein the rotor of the generator (40) is connected to a pedal crank shaft (41) of the vehicle (1) in a rotationally fixed manner.

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