Drive unit for an electric bicycle

Abstract

Drive device (50) for an electric bicycle (100) comprising: - a planetary gear transmission (10) with three elements (12, 14, 16) all of which are rotatably mounted about the same axis of rotation (A); - a pedal shaft (2) coupled to a first (12) of the three elements to supply torque to the planetary gear transmission (10); - a motor (4) coupled to a second (14) of the three elements to supply torque to the planetary gear transmission (10); - an output element (6) coupled to a third (16) of the three elements to deliver torque from the planetary gear transmission (10), wherein: - the drive device (50) comprises only a single motor coupled to the output element (6) in such a way that torque can be transmitted from this motor to the output element (6), this motor being the motor (4) coupled to the second element (14); - the The planetary gear set (10) is a planetary gear set, - the first element (12) is a planet carrier,- the second element (14) is a sun wheel, and - the third element (16) is another sun wheel.

Description

[0001] A drive device for an electric bicycle is described. Furthermore, a method for operating a drive device for an electric bicycle, as well as an electric bicycle itself, is described.

[0002] Bicycles offer a cost-effective, easy-to-use, and emission-free means of transportation. They have also become widespread as sports and fitness equipment, and certain types have proven particularly suitable for various sporting applications.

[0003] In recent years, enthusiasm for electric bicycles (especially so-called "pedelecs") has grown, despite their relatively high weight and price compared to other bicycles. A key requirement for electric bicycles is providing a reliable and supportive drive system.

[0004] One task to be solved is to specify a drive device for an electric bicycle in which power transmission, gear function, and shifting function are implemented in a simple and compact design. Further tasks to be solved include specifying a method for operating such a drive device and an electric bicycle equipped with such a drive device.

[0005] First, the drive system for an electric bicycle is specified.

[0006] According to one embodiment, the drive device for an electric bicycle comprises a three-element planetary gear system, wherein all three elements are mounted to rotate about the same axis of rotation. Furthermore, the drive device includes a pedal shaft coupled to a first of the three elements to supply torque to the planetary gear system. The drive device includes a motor coupled to a second of the three elements to supply torque to the planetary gear system. Additionally, the drive device includes an output element coupled to a third of the three elements to transmit torque from the planetary gear system. The drive device has only a single motor, which is coupled to the output element in such a way that torque can be transmitted from this motor to the output element, with this motor being the one coupled to the second element.

[0007] The present invention is based, among other things, on the finding that stepless shifting and motor assistance during the operation of an electric bicycle can be achieved in a simple and cost-effective manner by means of a single motor coupled to a planetary gear system. The motor can then be used to predetermine both the gear ratio and the assisting torque.

[0008] The planetary gear system can have one or more stages. In addition to the first, second, and third elements, the planetary gear system can have further elements. For example, the first and second elements may be elements of the same planetary gear stage. The third element may also be an element of the same planetary gear stage as the first and second elements, or it may be an element of a different planetary gear stage.

[0009] The first, second, and third elements of the planetary gear system all rotate around the same axis of rotation during operation. This axis of rotation can coincide with the axis of rotation of the pedal shaft and / or the axis of rotation of the motor and / or the axis of rotation of the output element. The rotation occurs, for example, relative to a housing element of the drive unit.

[0010] The fact that the pedal shaft is coupled to the first element of the planetary gear system means that the pedal shaft is coupled to the first element before other elements of the planetary gear system, particularly before the second and third elements. The coupling of the pedal shaft to the first element can be direct or indirect. "Direct" means that the pedal shaft is directly connected to the first element. "Indirect" means that the pedal shaft is coupled to the first element via intermediate elements. For example, the pedal shaft might be coupled to the first element via an intermediate gear stage and / or a chain and / or a belt. The intermediate gear stage could be, for example, a bevel gear stage or a spur gear stage.

[0011] The pedal shaft and the first element can be rotationally fixed to each other, so that rotation of the pedal shaft, regardless of the direction of rotation, always results in rotation of the first element, and vice versa. Alternatively, the pedal shaft can be coupled to the first element via a freewheel, so that the pedal shaft and the first element can rotate relative to each other in one direction, but can only rotate together in the other direction.

[0012] All previously disclosed features for the coupling between the pedal shaft and the first element of the planetary gear system also apply accordingly to the coupling between the motor and the second element, or to the coupling between the output element and the third element.

[0013] The pedal axle is coupled, or can be coupled, to crank arms to allow manual propulsion by the rider of the e-bike. The motor is typically an electric motor. The electric motor can be an internal rotor or an external rotor motor. The motor can be flanged to the pedal axle. The output element is, for example, a chainring or a chainring spider. Alternatively, the output element can also be a rotating hub shell.

[0014] The drive unit can be located within or form part of the crankset. For example, the drive unit could be a mid-drive motor. Alternatively, it could be a hub drive, where the motor is located within the hub. The pedal shaft could then extend through one wheel, such as the rear wheel, of the e-bike, similar to a unicycle. Alternatively, the pedal shaft could be connected to the crankset via a belt or chain.

[0015] The drive device has only one motor capable of transmitting torque to the output element. Any other motor in the drive device cannot be used to exert torque on the output element.

[0016] According to another embodiment, the motor is a brushed motor, in particular a so-called brushed DC motor. The brushed motor can have permanent magnets, which are arranged, for example, in the stator. Alternatively, the motor can also be a brushless motor, in particular a so-called brushless DC motor (BLDC). The brushless motor can also have permanent magnets. These are arranged, for example, in the rotor.

[0017] A brushed motor offers several advantages, including high starting torque. It can also be used as a generator, for example, when riding an e-bike downhill or during braking. Electronic control of a brushed motor is relatively simple and therefore inexpensive. A brushless motor, on the other hand, usually offers higher speeds and requires less maintenance.

[0018] According to another embodiment, the motor speed is continuously adjustable. For example, the drive device further includes a PWM generator with which the motor is controlled. The speed can be continuously set by adjusting the PWM signal. The PWM generator can be part of a control device for the drive device.

[0019] According to another embodiment, the first element is a support on which a planetary gear is rotatably mounted. During operation, the support rotates about its axis of rotation. The planetary gear rotates around the support's axis of rotation. One axis of rotation of the planetary gear is, for example, parallel to the axis of rotation of the support, but offset from it.

[0020] According to another embodiment, the second element is a gear that meshes with the planetary gear. The gear can be a spur gear, a bevel gear, or a crown gear.

[0021] According to another embodiment, the third element is a further gear that meshes with the planetary gear. Alternatively, the further gear can also mesh with another planetary gear that is likewise rotatably mounted on the carrier and is non-rotatably connected to the planetary gear. The two non-rotatably connected planetary gears can then only rotate together about the same axis of rotation. The two non-rotatably connected planetary gears can be arranged on opposite sides of the carrier. The further gear can be a spur gear, a bevel gear, or a crown gear.

[0022] Several planetary gears can be rotatably mounted on the support. These planetary gears are arranged, for example, azimuthally offset from one another on the support. For instance, three or more planetary gears are rotatably mounted on one side of the support. Each of these planetary gears can be non-rotatably connected to another planetary gear on the opposite side of the support. Each planetary gear is, for example, in toothed mesh with the second or third element.

[0023] That the first element is the support, the second element a gear, and the third element a gear is one embodiment. However, it is equally conceivable that the second element or the third element is a support to which at least one planetary gear is rotatably mounted, and the remaining two elements are gears that mesh with the at least one planetary gear.

[0024] According to another embodiment, the epicyclic gear unit is a planetary gear unit. In this case, the epicyclic gear unit(s) are planet gears. For example, it is a planetary gear unit with one or two planetary gear stages. The first element is, for example, a planet carrier, the second element a sun gear, and the third element a ring gear. However, other configurations are also conceivable. The three elements are, for example, assigned to the same planetary gear stage. Alternatively, if the planetary gear unit has two or more planetary gear stages, the third element can also be another sun gear that is assigned to a different planetary gear stage than the first and second elements.

[0025] According to another embodiment, the planetary gear set is a bevel gear differential set. The first element is then, for example, a planetary gear carrier, the second element a bevel gear, and the third element another bevel gear. However, a different configuration is also conceivable here. In this case, the planetary gear(s) are planetary bevel gears that mesh with the bevel gear and the other bevel gear.

[0026] According to another embodiment, the planetary gear set is a crown gear differential set. The first element is then, for example, a planetary gear carrier, the second element a crown gear, and the third element another crown gear. However, a different configuration is also conceivable here. In this case, the planetary gears are spur gears that mesh with the crown gear and the other crown gear.

[0027] According to a further embodiment, the drive device also includes a control device that is connected to the motor via a signal connection. The control device is designed to determine, and in particular automatically determine, control information for the motor based on operating information representative of the operation of the e-bike.

[0028] The operating information includes, for example, measured variables or is determined based on the dependencies of measured variables. In particular, the drive device comprises one or more sensors for determining the operating information. The control information can be control signals or setpoints for controlling the motor.

[0029] According to a further embodiment, the operating information is representative of a torque exerted on the pedal shaft by the rider of the e-bike and / or representative of a rotational speed at which the rider rotates the pedal shaft. In particular, the drive device includes a torque sensor and / or a cadence sensor for detecting the torque or rotational speed. The operating information is then determined based on the measurements of the torque sensor and / or cadence sensor.

[0030] According to another embodiment, the operating information is representative of a manual control element operated by the rider of the electric bicycle. For this purpose, the electric bicycle or the drive device includes, for example, a manually operated control element. The control element is, for example, a throttle lever or a twist grip, with which the rider specifies the torque or speed to be applied by the motor. The rider's action on the control element is converted, for example, by means of a PWM generator into a PM signal for operating the motor. The control element can be located on the handlebars of the electric bicycle.

[0031] Next, the method for operating the drive device is described. This method can be used, in particular, to operate the drive device described herein. Therefore, all features disclosed for the drive device are also disclosed for the method, and vice versa.

[0032] According to one embodiment, the method comprises providing operating information and determining control information based on that operating information. The operating information is representative of the operation of the e-bike, for example, representative of the actual and / or desired operation. The control information is configured for controlling the motor. The method is, in particular, a computer-implemented method. The control information is, for example, a setpoint in a control loop or an electrical signal, such as the aforementioned PWM signal.

[0033] Next, the electric bicycle is described. The electric bicycle includes a drive system as described here.

[0034] The following sections provide a more detailed explanation of a drive device, a method, and an electric bicycle described herein, with reference to the drawings and an exemplary embodiment. Identical reference numerals denote identical elements in the individual figures. Where elements or components function identically in different figures, their description is not repeated for each subsequent figure. For the sake of clarity, elements may not be labeled with corresponding reference numerals in all illustrations.

[0035] They show: Fig. 1 an embodiment of the electric bicycle, Fig. 2 to 9 different embodiments of the drive device, Fig. 10 an embodiment of the method, Fig. 11 an embodiment of a circuit in a drive device.

[0036] Fig. Figure 1 schematically shows an electric bicycle 100 with a bicycle frame 110, which has a lower frame section 120. This forms a down tube. The lower frame section 120 extends towards the bottom bracket of the electric bicycle 100. The bottom bracket has a pedal axle 2, which is part of a drive unit 50 installed in the bicycle. A control element 130 is located on the handlebars of the electric bicycle 100. The control element 130 can be a throttle lever or a twist grip.

[0037] Fig. Figure 2 shows a first embodiment of the drive device 50. This is, for example, the drive device 50 of the Fig. 1. The drive device 50 comprises a housing 7 in which an electric motor 4 is arranged. The electric motor 4 has a stator 40 and a rotor 42. In this case, the electric motor 4 is an internal rotor motor. The electric motor 4 is, for example, a brushed DC motor with permanent magnets. During operation, the rotor 42 rotates about an axis of rotation A. This axis of rotation A simultaneously forms the axis of rotation of the pedal shaft 2, which can be manually set in motion by a bicycle rider by pedaling.

[0038] The housing 7 also contains a planetary gear set 10. In this case, the planetary gear set 10 is a planetary gear set with a sun gear 14, a planet carrier 12, and a ring gear 16, all of which are also mounted to rotate about the axis of rotation A. Several planet gears 18 are mounted to rotate on the planet carrier 12. The planet gears 18 mesh with the ring gear 16 and the sun gear 14.

[0039] The sun gear 14 is non-rotatably connected to the rotor 42 of the electric motor 4, so that torque can be transmitted from the electric motor 4 to the sun gear 14. The pedal shaft 2 is non-rotatably connected to the planet carrier 12, so that the torque exerted on the pedal shaft 2 by a cyclist is transmitted to the sun gear 14. The ring gear 16 is non-rotatably connected to an output element 6. The output element 6 comprises a chainring 62 which is coupled to a hollow shaft 60 of the output element 6. The hollow shaft 60 extends around the pedal shaft 2.

[0040] The drive device 50 further comprises a control device 8, which is arranged in the housing 7. The control device 8 is connected, for example, to the control element 130 of the electric bicycle 100 via a signal connection. When the control element 130 is actuated, operating information is generated that is representative of the actuation, for example, the position to which the twist grip 130 is turned. Depending on the operating information, the control device 8 determines control information for the control of the motor 4. For example, the speed of the motor 4 can be increased by turning the twist grip more forcefully.

[0041] During operation of the drive device 50, a torque exerted by the rider on the pedal shaft 2 can be transmitted to the output element 6 via the planetary gear 10. This serves to propel the electric bicycle. By activating the electric motor 4, an additional assisting torque can be transmitted from the electric motor 4 to the output element 6 via the planetary gear 10. At the same time, the gear ratio between the pedal shaft 2 and the output element 6 is changed. This will be explained in more detail using an example: For example, it is assumed that the gear ratio from the chainring to the rear wheel is 1:1. The diameter factor of the sun gear, planetary gear, and ring gear is assumed to be 2:1:4. If the sun gear is driven by the electric motor at 2 revolutions per second (rpm) and the planetary gear carrier is stationary, the ring gear rotates at 1 revolution per second (rpm), which corresponds, for example, to a speed of 3.6 km / h. If, on the other hand, the planetary gear carrier rotates at 1 revolution per second (rpm) and the sun gear is stationary, the ring gear rotates at 1.5 revolutions per second (rpm), and the bicycle then has a speed of 5.4 km / h. If both the sun gear and the planetary gear carrier rotate at 1 revolution per second (rpm), the ring gear rotates at 2.5 revolutions per second (rpm), which would correspond to a speed of 9 km / h. If the sun gear and planetary gear carrier each rotate at 3 revolutions per second (rpm), this corresponds to 7.5 revolutions per second (rpm) for the ring gear and a bicycle speed of 27 km / h (50 mph).

[0042] The electric motor 4 is not only useful for propelling the electric bicycle. If the bicycle's wheel, driven via chainring 62, is coupled to chainring 62 without a freewheel, as in Fig. As shown in Figure 2, the electric motor 4 can also be used for braking. The wheel drives the output element 6. Depending on the position of the twist grip, the electric motor 4 can then brake more or less strongly. The braking effect can be further increased, for example, by the rider pedaling backwards.

[0043] The electric motor 4 can also be used as a generator. Switching from motor to generator operation occurs automatically the moment the opposing current (braking power) exceeds the current (motor power). This switchover can occur across a wide speed range, even down to the point where the electric motor comes to a complete stop. The electric motor can be magnetically locked by bridging the motor terminals. This function can be activated, for example, by turning the twist grip to the zero position. The bicycle then moves solely by pedaling.

[0044] Overall, both acceleration and braking can be selected via the twist grip and by pedaling, either together or separately. In particular, the following driving modes are available with the 50 drive unit according to... Fig. 2 possible: 1. The rider propels the bicycle exclusively by operating the twist grip via the electric motor, that is, without pedaling. 2. The rider propels the bicycle exclusively by pedaling, that is, without the aid of the electric motor. 3. The rider propels the bicycle forward by pedaling and motor assistance. 4. When going downhill, the rider reduces pedaling and twists the throttle grip back until they are traveling downhill at the desired speed. During this process, the electric motor (4) can act as a generator to charge the e-bike's battery. 5. To brake, for example while going downhill, the rider turns the twist grip even further back. 6. The driver can achieve even stronger braking by pedaling backwards.

[0045] A possible wiring configuration within the drive device 50 of the Fig. 2 is in Fig. Figure 11 shows the control device 8, which includes a PWM generator 80 and an electrical switch 81, for example in the form of a MOSFET or IGBT. The power supply to the electric motor 4 is provided by a battery 9.

[0046] Fig. Figure 3 shows a second embodiment of the drive device 50. Unlike in the Fig. 2. Here, the electric motor 4 is not controlled by the actuation of a control element, but rather by operating information representative of the rotational speed at which the driver turns the pedal shaft 2. Alternatively or additionally, the operating information is representative of the torque exerted by the driver on the pedal shaft 2. Depending on this operating information, the control device 8 automatically determines control information, and the electric motor 4 is operated accordingly. For example, this can enable automatic gear shifting and automatic torque support. The operating information is determined based on measured values ​​acquired by a sensor 80, such as a cadence sensor or torque sensor.

[0047] In the case of the electric motor 4 of the Fig. 3. For example, this is a brushless DC motor, for instance with permanent magnets. Unlike in the Fig. 2 is in the Fig. 3. The planet carrier 12 is not rotationally fixed to the pedal shaft 2, but rather via a freewheel 22. This means that when the pedal shaft 2 is pedaled backwards, the planet carrier 12 is not engaged. Therefore, braking by pedaling backwards is not possible. The electric motor 4 also cannot be used as a generator.

[0048] Fig. Figure 4 shows a third embodiment of the drive device 50. Here, the electric motor 4 is an external rotor motor. The rotor 42 is coupled to the ring gear 14 of the planetary drive 10, the pedal shaft 2 to the planet carrier 12, and the sun gear 16 to the output element 6.

[0049] In the fourth embodiment of the drive device 50 according to Fig. In section 5, the planetary gear set 10 is a bevel gear differential set. The pedal shaft 2 is again non-rotatably connected to the planetary carrier 12. Planetary bevel gears 18 are provided on the planetary carrier 12, which mesh with a first bevel gear 14 and a second bevel gear 16. The first bevel gear 14 is non-rotatably connected to the rotor 42 of the electric motor 4, and the second bevel gear 16 is non-rotatably connected to the output element 6. The bevel gear differential set is particularly space-saving.

[0050] In the exemplary embodiment of the drive device 50 of the Fig. In the case of the planetary gear set 10, the differential gear set is a crown gear set. Accordingly, the planetary gears 18 are spur gears and the gears 14, 16, which are coupled to the rotor 42 and the drive 6, are crown gears.

[0051] In the exemplary embodiment of the Fig. In section 7, the electric motor 4 is again an external rotor. However, the rotor 42 is, for example, like in the... Fig. 3 coupled to the sun gear 14, the pedal shaft 2 to the planet carrier 12 and the output element 6 to the ring gear 16.

[0052] The exemplary embodiment of the Fig. Figure 8 shows a drive device 50, which can be installed, for example, in the rear wheel hub of an electric bicycle. Instead of a chainring, the output element 6 is a hub housing to which, for example, the spokes of the rear wheel are attached. Here, the pedal shaft 2 runs through the wheel, similar to a unicycle. Alternatively, the pedal shaft 2 could also be coupled to the planet carrier 12 via a chain or belt. In that case, the pedal shaft 2 would not need to run through the wheel.

[0053] In the exemplary embodiment of the Fig. The planetary gear set 10 is a two-stage planetary gear set. It has two sets of planet gears 18 and 18A, which are rotatably mounted on the planet carrier 12. The first set of planet gears 18 meshes with the sun gear 14, which is non-rotatably connected to the rotor 42 of the electric motor 4. The other set of planet carriers 18A meshes with another sun gear 16, which is non-rotatably connected to the output element 6. The planet gears 18 and 18A are arranged on both sides of the planet carrier 12. Opposing planet gears 18 and 18A are non-rotatably connected to each other.

[0054] Fig. Figure 10 shows an embodiment of the method for operating a drive device, for example any of the drive devices of the Fig.2 to 9. In this process, operating information BI is first provided or determined that is representative of the operation of the e-bike. The operating information BI can be representative, for example, of the actuation of the twist grip and / or of the torque exerted by the rider on the pedal shaft and / or of the rotational speed at which the rider pedals. Based on the operating information BI, control information SI is then determined, which is used to control the motor. Reference symbol list: 2 pedal shaft 4 engine 6 Output element 7 cases 8 Control device 9 Battery 10 planetary gear sets 12 first element 14 second element 16 third element 18 planetary gear 18A planetary gear 22 Freewheel 40 Stator 42 Rotor 50 Drive device 60 Hollow shaft 62 chainring 80 PWM generator 81 electrical switch 82 Sensor 100 electric bicycles 110 bicycle frames 120 down tube 130 Control element A axis of rotation BI Business Information SI Tax Information

Claims

[1] comprising a drive device (50) for an electric bicycle (100) - a planetary gear system (10) with three elements (12, 14, 16) which are all mounted to rotate about the same axis of rotation (A), - a pedal shaft (2) coupled to a first (12) of the three elements to feed torque into the planetary gear transmission (10), - a motor (4) coupled to a second (14) of the three elements to feed torque into the planetary gear unit (10), - an output element (6) coupled to a third (16) of the three elements to deliver torque from the planetary gear set (10), wherein - the drive device (50) has only a single motor which is coupled to the output element (6) in such a way that torque can be transferred from this motor to the output element (6), wherein this motor is the motor (4) coupled to the second element (14). [2] Drive device (50) according to claim 1, wherein - the motor (4) is a brushed DC motor with permanent magnets or a brushless motor with permanent magnets. [3] Drive device (50) according to claim 1 or 2, wherein - the speed of the motor (4) is continuously adjustable. [4] Drive device (50) according to one of the preceding claims, wherein - the first element (12) is a support on which a rotary wheel (18) is rotatably mounted, - the second element (14) is a gear that is in engagement with the planetary gear (18), - the third element (16) is another gear which is in engagement with the planetary gear (18) or in engagement with a further planetary gear (18A) mounted on the carrier (12) and non-rotatably connected to the planetary gear (18). [5] Drive device (50) according to claim 4, wherein - the epicyclic gear (10) is a planetary gear, - the first element (12) is a planetary carrier, - the second element (14) is a sun wheel, - the third element (16) is a hollow gear or another sun gear. [6] Drive device (50) according to claim 4, wherein - the planetary gear set (10) is a bevel gear differential set, - the first element (12) is a planetary gear carrier, - the second element (14) is a bevel gear, - the third element (16) is another bevel gear. [7] Drive device (50) according to claim 4, wherein - the planetary gear set (10) is a crown gear differential set, - the first element (12) is a planetary gear carrier, - the second element (14) is a crown wheel, - the third element (16) is another crown wheel. [8] Drive device according to one of the preceding claims, further comprising - a control device (8) which is connected to the motor (4) via a signal connection, wherein the control device (8) is configured to - to determine control information (SI) for the control of the motor (4) depending on operating information (BI) that is representative of the operation of the electric bicycle. [9] Drive device (50) according to claim 8, wherein - the operating information (BI) is representative of a torque exerted on the pedal shaft (2) by a rider of the electric bicycle (100) and / or is representative of a rotational speed at which the rider rotates the pedal shaft (2). [10] Drive device (50) according to claim 8 or 9, wherein - the operating information (BI) is representative of a manual operation of a control element (130) by a rider of the electric bicycle (100).

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