Method for operating a drive unit for a muscle-powered vehicle in an Eco mode, drive unit, and vehicle

Abstract

The present invention relates to a method for operating a drive unit (1) for a muscle-powered vehicle in an Eco mode. The drive unit (1) comprises a pedal shaft (2) for receiving muscle power, a superimposed gear unit (6) designed as a planetary gear unit with an output (10), a driven gear (5), and an electric motor (12). The pedal shaft (2) and the electric motor (12) are mechanically connected to the superimposed gear unit (6), and the output (10) of the superimposed gear unit (6) is mechanically connected to the driven gear (5). The method includes acquiring (I) a signal to operate the drive unit (1) in an Eco mode, and limiting (IV) the power (P1) of the electric motor (12) of the drive unit (1) to a power limit (P1). LFurthermore, the invention relates to a drive device (1) with a control device (40) configured to perform such a method, and to a vehicle with such a drive device (1).

Description

[0001] The present invention relates to a method for operating a drive unit for a muscle-powered vehicle, in which a driving force for propelling the vehicle is generated, at least temporarily, by the muscle power of a driver of the vehicle. Furthermore, the present invention relates to a drive unit with a control unit configured to carry out such a method, and to a vehicle with such a drive unit.

[0002] German patent application DE 10 2017 219 607 A1 discloses a drive system for a pedelec with two electric motors and a superimposed transmission designed as a planetary gear set. DE 10 2017 219 602 A1, on the other hand, relates to a drive system for a pedelec with only a single electric motor and a superimposed transmission designed as a planetary gear set. Such pedelecs do not have mechanical gears, but rather an electric motor to adjust the appropriate pedaling cadence. Typically, the speed of the electric motor increases with the riding speed. The electric motor operates as a motor, and its power output increases with increasing riding speed.

[0003] DE 10 2017 111 876 A1 relates to a bicycle control device that controls a motor in different operating modes, wherein the support of the propulsion depends on the power input from the human and the limit values ​​of the output torque differ depending on the mode.

[0004] JP H07 - 323 880 A relates to an electrically assisted bicycle in which different support characteristics can be stored in a memory and selected via a selector switch in order to control the motor current depending on the driving speed and muscle power.

[0005] DE 10 2021 208 412 A1 relates to a drive system for an electric bicycle with an electric motor, a planetary gear and at least one freewheel, which enables a fixed or variable transmission between muscle power and wheel drive depending on the driving speed.

[0006] DE 10 2019 214 583 A1 relates to a bottom bracket drive for a bicycle in which an electric motor is coupled via a gearbox with a planetary stage and a freewheel in such a way that the crankshaft and the sun gear can be connected or disconnected depending on the operating condition.

[0007] Based on this, the object of the present invention is to provide an improved method for operating a drive unit for a muscle-powered vehicle, in which a driving force for propelling the vehicle is generated, at least temporarily, by the muscle power of a driver of the vehicle. This object is achieved by the subject matter with the features of the independent claims. Advantageous embodiments are described in the dependent claims.

[0008] The present invention relates to a method for operating a drive unit for a muscle-powered vehicle in an Eco mode. The muscle-powered vehicle can be a single-track vehicle, for example, a two-wheeler in the form of a pedelec or e-bike. Alternatively, the muscle-powered vehicle can be a multi-track vehicle, for example, a tricycle or a four-wheeled vehicle. The muscle-powered vehicle can also have a different configuration. The Eco mode of the drive unit can be a mode in which the drive unit consumes less energy than in a normal mode. In other words, the drive unit can be operated more energy-efficiently when the Eco mode is activated. The drive unit has a pedal shaft to which pedals can be attached to transmit muscle power from the rider to the pedal shaft.Furthermore, the drive unit comprises a driven wheel, which can be coupled to a wheel of the muscle-powered vehicle to transmit a driving force from the driven wheel to at least one wheel of the vehicle for propulsion. The driven wheel can be a sprocket, for example, a chainring. The driven wheel can be mechanically coupled to a wheel of the vehicle by means of a continuous recirculating element, for example, a chain. The drive unit can also have a housing in which some or all of the drive unit's components can be accommodated. The housing can be mounted on the vehicle in such a way that it is supported by the vehicle. The housing can be a stationary component that does not move during operation of the drive unit.

[0009] Furthermore, the drive unit comprises a superimposed gear set designed as a planetary gear set. The planetary gear set can be a negative planetary gear set. It can include a sun gear, a ring gear, and at least one planet gear held by a planet carrier, which meshes with both the ring gear and the sun gear. In one embodiment, the superimposed gear set can be a stepped planetary gear set. The drive unit also includes an electric machine, which can have a stator and a rotor. The stator can be fixed to a housing of the drive unit in a rotationally fixed manner. The electric machine can be electrically connected to and supplied with electrical energy by a battery (not shown).

[0010] The pedal shaft is mechanically connected to the superimposed transmission, for example, to the planet carrier of the superimposed transmission. In one embodiment, the mechanical connection between the pedal shaft and the superimposed transmission is provided by a freewheel in the torque transmission path from the pedal shaft to the superimposed transmission. In an alternative embodiment, the pedal shaft is permanently and rotationally fixed to the superimposed transmission. The superimposed transmission is also mechanically connected to the output gear. For example, the ring gear of the superimposed transmission is mechanically connected to the output gear, for example, permanently and rotationally fixed. Furthermore, the electric motor is mechanically connected to the superimposed transmission, for example, via a pre-reduction gear. The pre-reduction gear can have one or more planetary gear sets.The planet gear set(s) of the pre-reduction gear can each be designed as a negative planet gear set and have a sun gear, a ring gear and a planet carrier with a planet gear rotatably mounted on it, which meshes with both the respective sun gear and the respective ring gear.

[0011] The respective ring gears of the two planetary gear sets of the pre-reduction gearbox can be permanently fixed to a housing of the drive unit. The planet carrier of the first planetary gear set of the pre-reduction gearbox can be permanently fixed to a sun gear of the superimposed gearbox. The sun gear of the first planetary gear set of the pre-reduction gearbox can be permanently fixed to a planet carrier of the second planetary gear set of the pre-reduction gearbox. The sun gear of the second planetary gear set of the pre-reduction gearbox can be permanently fixed to a rotor of the electric machine. In one embodiment, the superimposed gearbox can be designed as a stepped planetary gear set and connected directly to the electric machine, thus eliminating the need for the pre-reduction gearbox.

[0012] The method of the present invention comprises acquiring a signal to operate the drive unit in an Eco mode. For this purpose, the signal can be input, for example, by a user of the muscle-powered vehicle, such as a cyclist, via a control unit. Alternatively or additionally, the signal to operate the drive unit in an Eco mode can be generated based on measured and / or state variables of the muscle-powered vehicle. In one embodiment, the signal can be generated depending on the state of charge of the battery of the muscle-powered vehicle. If the state of charge of the battery is, for example, below a certain threshold, a signal can be output indicating that the drive unit should be operated in Eco mode in order to conserve battery capacity and enable the longest possible operating time of the muscle-powered vehicle.

[0013] Furthermore, the method of the present invention comprises limiting the power output of the electric motor of the drive unit to a power limit. This power limit can be a predetermined value, which, for example, can be stored in a control unit of the drive unit. The power limit can be fixed or adjustable by a user, for example, during operation of the muscle-powered vehicle. Limiting the drive power of the electric motor ensures that its power is limited to the power limit when the drive unit is operated in Eco mode. The consequence of limiting the power output of the electric motor to the power limit according to the invention is that the total drive power from the rider and the electric motor does not increase further.Depending on the driving resistance, the driving speed may not be able to be increased further, which is acceptable in Eco mode. The electric motor, however, requires less electrical power, which increases the remaining operating time and the range of the muscle-powered vehicle. The range is also increased because the air resistance decreases due to the potentially lower driving speed. Thus, the present invention enables the operation of the drive system for a muscle-powered vehicle in an Eco mode, in which the driver receives minimal to moderate assistance. At the same time, good system efficiency is achieved, allowing for a long range.

[0014] If two elements are mechanically connected, they are coupled to each other directly or indirectly in such a way that a movement of one element in at least one direction causes a reaction of the other element. For example, a mechanical connection can be provided by a positive-locking or friction-locking connection. The mechanical connection can correspond to the meshing of corresponding gear teeth on the two elements. Further elements, such as one or more spur gear stages, can be provided between the elements. A permanently rotationally fixed connection between two elements, on the other hand, is understood to be a connection in which the two elements are rigidly coupled to each other in all intended states of the transmission. The elements can be individual components rigidly connected to each other or even as a single piece.

[0015] A freewheel can be provided between two mechanically connected components. This freewheel ensures that movement of one element only elicits a reaction from the other element in one direction of rotation, while movement in the opposite direction produces no reaction from the other element. The freewheel can have a first and a second element and be designed such that relative rotation between the freewheel elements is only permitted in a first direction, while relative rotation in the opposite direction is prevented. For this purpose, pawl elements, gears, or similar devices can be provided, which can optionally be pre-tensioned against each other to engage. The design of the freewheel is freely selectable, as long as the described function of the freewheel is fulfilled.

[0016] According to one embodiment, the method further includes determining the travel speed of the muscle-powered vehicle. This determination can be based, for example, on measuring the rotational speed of a component of the drive system, which is directly related to the travel speed of the muscle-powered vehicle. For this purpose, a measurement from a sensor integrated into the drive system can be used, which measures the corresponding rotational speed of the component. The travel speed is the speed at which the muscle-powered vehicle is moving. Furthermore, in this embodiment, the method includes comparing the determined travel speed with a limit speed. The limit speed can be fixed or adjustable, for example, by the driver of the muscle-powered vehicle.The limiting speed can be stored in a memory, for example, a non-volatile memory, or in a control unit of the drive system. In the present embodiment, the power output of the electric motor can be limited when the determined driving speed is greater than, for example, greater than or equal to, the limiting speed. This allows for conventional and comfort-optimized driving behavior for the user of the muscle-powered vehicle within a driving speed range up to the limiting speed. Simultaneously, at driving speeds above the limiting speed, energy-efficient driving can be enabled by limiting the power output of the electric motor.

[0017] The drive system can be designed for a maximum speed up to which it provides electric assistance to the muscle-powered vehicle. This maximum speed may be stipulated by legal regulations, for example. The maximum speed could be between 20 and 30 km / h, or, for instance, 25 km / h. The drive system can be designed to provide electric assistance to the driver of the muscle-powered vehicle only at speeds below this maximum speed. In one embodiment, the speed limit at which the power output of the electric motor is restricted is lower than the maximum speed. Thus, in this embodiment, the power output of the electric motor is limited at speeds below the maximum speed.This means that when operating the drive unit in Eco mode, energy can be saved even at driving speeds lower than the maximum driving speed in the present embodiment, thus increasing the range of the muscle-powered vehicle.

[0018] The drive unit includes an additional electric machine mechanically connected to the output of the superimposed transmission. While one electric machine may be arranged coaxially to the pedal shaft, the other electric machine may be arranged parallel to the pedal shaft at a distance. The additional electric machine may be mechanically connected to the superimposed transmission, for example, to the ring gear of the superimposed transmission, via a spur gear transmission. Furthermore, a reduction gear may be provided between the additional electric machine and the spur gear transmission, which may, for example, be designed as a planetary gear set. This may reduce the torque required for the additional electric machine. For example, the additional electric machine may have a stator that can be permanently and rotationally fixed to a housing of the drive unit.A rotor of the additional electric machine can be permanently and rotationally fixed to a sun gear of the pre-reduction unit, which is designed as a planetary gear set. A ring gear of the pre-reduction unit, which is designed as a planetary gear set, can be permanently and rotationally fixed to a housing of the drive unit. A planet gear of the pre-reduction unit, rotatably mounted on a planet carrier, can mesh with both the sun gear and the ring gear. A planet carrier of the pre-reduction unit, which is designed as a planetary gear set, can be mechanically coupled to the superimposed gear unit, for example, to the ring gear of the superimposed gear unit, by means of a spur gear drive.

[0019] The drive system is operated in such a way that the additional electric machine does not operate as a generator to avoid reactive power. For example, the drive system is operated in such a way that the additional electric machine does not operate as a generator at any driving speed, such as for all driving speeds below the maximum driving speed. In other words, the additional electric machine always operates only in such a way that it either delivers positive power or no power, but does not consume power at any operating point. The power limit of the first electric machine can be selected to enable this type of operation of the additional electric machine. By avoiding the generator-like and thus braking operation of the additional electric machine, the system efficiency can be increased.More precisely, by avoiding regenerative operation of the additional electric machine, reactive power in the drive system can be prevented, for example, electrical power flowing back from the additional electric machine to the electric machine. This allows the drive system to operate in an Eco mode with good system efficiency.

[0020] Such avoidance of generator operation of the additional electric machine can be achieved by controlling the additional electric machine in such a way that it neither consumes nor delivers power when the power of the electric machine is limited to a certain limit. For example, the electrical connection of the additional electric machine to a battery component of the drive unit can be disconnected. Such control of the additional electric machine can occur simultaneously or essentially simultaneously with the limitation of the electric machine's power to a certain limit.This has the advantage that the electric motor alone provides the maximum electrical assistance power available in Eco mode, thus optimally fulfilling its function of supporting the human pedaling torque. This is because the electric motor must generate torque and therefore also deliver power to achieve this function.

[0021] In one embodiment, the drive system is operated such that the power of the electric machine increases with increasing vehicle speed from a starting speed to the limiting speed. This increase can, for example, be linear, from a value of 0 at the starting speed to a value corresponding to the power limit at the limiting speed. Conversely, the power of the second electric machine can decrease with increasing vehicle speed from the starting speed to the limiting speed. For example, the power of the second electric machine can decrease linearly from a power level corresponding to the power limit at the starting speed to a power level of 0 at the limiting speed. The starting speed can be the speed at which the muscle-powered vehicle has begun moving.In other words, at speeds below the starting speed, the muscle-powered vehicle is still in the starting process.

[0022] In one embodiment, limiting the power of the electric motor to a specific power limit can include limiting the motor's rotational speed. This allows the motor's rotational speed to be limited despite increasing vehicle speed. As a result, the rider's pedaling cadence increases with speed. The present design therefore offers the advantage that it is generally understandable to the rider that the crank rotation speed increases with speed. If the rider were to maintain their pedaling torque, this could lead to increased power output from the rider of the muscle-powered vehicle at speeds exceeding the limit. However, it is a normal response for the rider to an increased pedaling cadence to reduce their pedaling force, thus also reducing the pedaling torque.Thus, the rider's power output may remain roughly constant despite an increased cadence. This means that the combined power output of the rider and electric motor does not increase further. Depending on the resistance, the riding speed may then be unable to be increased further, and the maximum speed of the drive system may not be reached. The latter is acceptable in Eco mode, however.

[0023] In an alternative embodiment, the power of the electric machine is limited not by its rotational speed, but by its torque. In other words, under this alternative embodiment, an increasing vehicle speed leads to an increasing rotational speed of the electric machine. However, to limit the power of the electric machine, the permissible torque decreases as the rotational speed of the electric machine increases. This results in less pedaling resistance for the rider, which implies that, at a constant crank speed, the rider's power output may decrease at speeds above the limiting speed. Consequently, the total power output of the rider and the electric machine would decrease.Depending on the resistance, the speed may not be able to be increased further, and the maximum speed may not be reached. However, this is acceptable in Eco mode. It may not be immediately clear to the rider why the pedaling resistance decreases as the speed increases, which is why this alternative design is not preferred.

[0024] In one embodiment, receiving a signal to operate the drive unit in Eco mode includes the activation of Eco mode by the driver of the muscle-powered vehicle via a control unit. The control unit can be a switch, for example, a mechanically operated switch, and / or an electronic control unit, for example, a touchpad. The control unit can be mounted on the muscle-powered vehicle in such a way that a user of the muscle-powered vehicle can operate it while the vehicle is in use. For example, the control unit can be mounted on the handlebars of the muscle-powered vehicle.

[0025] Furthermore, the present invention relates to a drive unit for a muscle-powered vehicle. The drive unit comprises a pedal shaft for receiving muscle power, a superimposed gear unit designed as a planetary gear set with one output, an output gear, an electric motor, and a control unit. The pedal shaft and the electric motor are mechanically connected to the superimposed gear set. The output of the superimposed gear set is mechanically connected to the output gear. The control unit is electronically connected to the electric motor and configured to execute the method according to one of the embodiments described above. For this purpose, the control unit can have one or more interfaces through which it is connected to the electric motor and, optionally, to a further electric motor.The one or more interfaces can be configured as input and / or output interfaces for controlling the electric machine. The control unit can be located within a housing of the drive unit and / or outside of a housing of the drive unit. The control unit can include one or more microprocessors, which can be configured, i.e., specifically programmed, to execute the method according to one of the embodiments described above. Regarding the design and advantages of the individual features of the drive unit, reference is made to the above explanations in connection with the method for operating the drive unit.

[0026] Furthermore, the present invention relates to a vehicle with at least two wheels and a drive unit according to the embodiment described above. The driven wheel of the drive unit is coupled to one of the wheels via a power transmission element for driving the vehicle. The vehicle can be a two-wheeler, for example a pedelec or e-bike, as described above. For an understanding of the individual features and their advantages, reference is made to the above descriptions in connection with the embodiments of the method for operating the drive unit. Fig. Figure 1 shows a drive device for a muscle-powered vehicle according to an embodiment of the present invention. Fig. Figure 2 shows a method for operating the drive unit for a muscle-powered vehicle. Fig. 1 according to an embodiment of the present invention. Fig. Figure 3 schematically shows the performance curve of the electrical machines of the drive system. Fig. 1 depending on the driving speed according to an embodiment of the present invention. Fig. Figure 4 schematically shows the power output of an electric machine of a drive device as a function of the driving speed according to a further embodiment of the present invention.

[0027] Fig. Figure 1 shows a drive unit 1 for a muscle-powered vehicle according to an embodiment of the present invention. The drive unit 1 comprises a pedal shaft 2 and a housing 3. Pedals 4 are permanently and rotationally fixed to the pedal shaft 2, via which a rider of the muscle-powered vehicle can transmit torque to the drive unit 1. The housing 3 of the drive unit 1 can be attached to a frame of the muscle-powered vehicle. In the present embodiment, the muscle-powered vehicle is a bicycle, for example, a pedelec. Furthermore, the drive unit 1 includes a driven gear 5, which can be designed as a chainring, to mechanically connect the drive unit 1 to a rear wheel of the bicycle, for example, via a chain or a belt.

[0028] The drive unit 1 according to the present embodiment further comprises a superimposed gear unit 6 designed as a planetary gear unit, which is arranged coaxially to the pedal shaft 2. The superimposed gear unit 6 includes a sun gear 7, a planet carrier 8 on which planet gears 9 are rotatably mounted, and a ring gear 10. In the present embodiment, the ring gear 10 forms an output of the superimposed gear unit 6. The pedal shaft 2 is mechanically operatively connected to the planet carrier 8 of the superimposed gear unit 6. In the present embodiment, the mechanical operative connection is effected via a freewheel 11. The output gear 5 is permanently and non-rotatably connected to the ring gear 10 of the superimposed gear unit 6. Furthermore, the drive unit 1 comprises a first electric machine 12 and a second or further electric machine 13. The first electric machine 12 comprises a stator 14 and a rotor 15.The second electric machine 13 also comprises a stator 16 and a rotor 17. The first electric machine 12 is arranged coaxially to the pedal shaft 2, while the second electric machine 13 is arranged parallel to the pedal shaft 2 at a distance. The stators 14 and 16 of the first 12 and second electric machines 13, respectively, are permanently fixed to the housing 3 to prevent rotation. The rotors 15 and 17 of the first 12 and second electric machines 13, respectively, are coaxial with the stators 14 and 16, respectively, and are rotatable within them.

[0029] The rotor 15 of the first electric machine 12 is mechanically connected to the sun gear 7 of the superimposed transmission 6 in the present embodiment via a pre-reduction gear 18. In the present embodiment, the pre-reduction gear 18 comprises a first planet gear set 19 and a second planet gear set 20. The planet gear sets 19 and 20 each have a sun gear 21 and 22, respectively, a planet carrier 23 and 24 with a planet gear 25 and 26 rotatably mounted thereon, respectively, and a ring gear 27 and 28, respectively. The ring gears 27 and 28 of the first 19 and second planet gear set 20 of the pre-reduction gear 18 are each permanently fixed to the housing 3 to prevent rotation. The planet carrier 23 of the first planet gear set 19 of the pre-reduction gear 18 is permanently connected to the sun gear 7 of the superimposed transmission 6 to prevent rotation.The sun gear 21 of the first planetary gear set 19 of the reduction gear 18 is permanently and rotationally fixed to the planet carrier 24 of the second planetary gear set 20 of the reduction gear 18. The sun gear 22 of the second planetary gear set 20 of the reduction gear 18 is permanently and rotationally fixed to the rotor 15 of the first electric machine 12.

[0030] The rotor 17 of the second electric machine 13 is mechanically connected to the ring gear 10 of the superimposed transmission 6 via a reduction gear 29 and a spur gear 30. In the present embodiment, the reduction gear 29 is designed as a planetary gear set comprising a sun gear 31, a planet carrier 32 with a planet gear 33 rotatably mounted thereon, and a ring gear 34. In the present embodiment, the ring gear 34 is permanently fixed to the housing 3 and the sun gear 31 is permanently connected to the rotor 17 of the second electric machine 13 in a rotationally fixed manner. The planet carrier 32 of the reduction gear 29 is mechanically connected to the ring gear 10 of the superimposed transmission 6, or the drive gear 5, via the spur gear 30.

[0031] Furthermore, the drive unit 1 includes a control unit 40 for controlling the first 12 and second electric machines 13, respectively. For this purpose, the electric machines 12 and 13 are each connected to the control unit 40 via a suitable interface. In the present embodiment, a control unit 41 is also connected to the control unit 40, through which the rider of the muscle-powered vehicle can input a command into the control unit 40. The control unit 41 can, for example, be a touchscreen display that can be attached to the bicycle. The touchscreen display can be mounted on the handlebars of the muscle-powered vehicle so that it is easily accessible to the rider. The control unit 40 includes a microprocessor configured to perform the following functions with reference to Fig. 2 described methods for operating the in Fig. 1 to execute the drive device shown 1.

[0032] In a first step (I), the driver uses the control unit 41 to input a command that the drive unit 1 should operate in an Eco mode to conserve the capacity of a battery (not shown). The control unit 41 then sends a signal to the control unit 40, which receives it. In a subsequent step (II), the control unit 40 determines the vehicle speed (v) of the human-powered vehicle and compares it in a subsequent step (III) with a limit speed (v2) stored in a memory location within the control unit 40, such as non-volatile memory.

[0033] Depending on the comparison in step III, the drive unit 1 will be configured according to the specifications in Fig. 3 schematically depicted behaviors were operated. Fig. Figure 3 shows the power output P1 of the first electric machine 12 as a function of the vehicle speed v. The power output P2 of the second electric machine 13 is also shown as a function of the vehicle speed v. The power outputs P1 and P2 are shown only between a starting speed v1 and a maximum vehicle speed v3, up to which the drive unit 1 is designed to provide electric assistance to the muscle-powered vehicle. In this embodiment, the maximum vehicle speed v3 corresponds to the maximum vehicle speed up to which electrically assisted driving is legally permitted. This could, for example, be a speed of 25 km / h. Vehicle speeds v below the starting speed v1 correspond to speeds during the acceleration phase.

[0034] If comparison step III shows that the driving speed v is less than the limiting speed v2 and greater than the starting speed v1, the control device 40 is configured to operate the first 12 and second electric machine 13 such that the power P1 of the first electric machine 12 increases linearly with increasing driving speed v from the starting speed v1 to the limiting speed v2. Conversely, the power P2 of the second electric machine 13 decreases linearly with increasing driving speed v in this speed range between the starting speed v1 and the limiting speed v2. The drive device 1 is designed such that the power P1 of the first electric machine 12 is zero at the starting speed v1 and the power P2 of the second electric machine 13 is zero at the limiting speed v2.Thus, from the starting speed v1, the power P2 of the second electric machine 13 can ensure support for the driver as long as the first electric machine 12 does not yet provide sufficient power due to the low rotational speed.

[0035] If, however, the comparison in step III shows that the driving speed v is greater than or equal to the limiting speed v2, then the control device 40 of the drive device 1 of the present invention is configured to reduce the power of the first electric machine 12 to a power limit P in a step IV. L to limit. As from Fig. As can be seen in section 3, this power limitation of the power of the first electrical machine 12 is limited to the power limit P. L for any speeds v greater than the limiting speed v2 and less than the maximum driving speed v3.

[0036] Simultaneously, the power of the first electric machine 12 is limited to the power limit P L In step IV, the second electric machine 13 is controlled via the control unit 40 in step V such that the second electric machine 13 neither absorbs nor supplies power. For this purpose, for example, an electrical connection between the second electric machine 13 and the battery (not shown) can be disconnected, so that the second electric machine 13 is operated neither in a motor nor in a generator mode. As a result, when the power of the first electric machine 12 is limited to a power limit P LIt was ensured that the second electric machine 13 was not operated in generator mode and thus did not produce reactive power. This allows an energy-efficient Eco mode to be provided for the drive unit 1, in which the driver receives moderate assistance while maintaining good system efficiency. The procedure then returns to step II.

[0037] In the present embodiment, the power P1 of the first electric machine 12 is limited by limiting the rotational speed of the first electric machine 12. This results in the rider's cadence increasing with increasing speed. It is generally understandable to the rider that the crank rotation speed increases with increasing speed v. Therefore, in an Eco mode, it is plausible that the rider must exert more power at higher speeds v. However, a normal reaction of the rider to an increased cadence is to reduce the pedaling force somewhat, thus also reducing the crank torque. Therefore, it is possible, for example, that the power P M The driver's speed remains approximately constant even at speeds v greater than the limiting speed v2, as in Fig. 3 shown.

[0038] Alternatively, in one embodiment, the power of the first electric machine 12 is limited to the power limit by limiting the torque of the first electric machine 12. As the vehicle speed v increases, the rotational speed of the first electric machine 12 also increases. The higher the rotational speed of the first electric machine 12 becomes, the lower the permissible torque of the first electric machine 12. This results in the pedaling resistance for the rider decreasing as the vehicle speed v increases. If the crank rotation speed remained constant, the human power output P would be M in the Fig. 3. Thus, contrary to what is shown, the power decreases from the limiting speed v2 towards the maximum driving speed v3. This would result in the total drive power from driver P being... M and decreases from the first electric machine 12. In contrast, the total drive power from driver P Mand the first electric machine 12 at driving speeds v greater than the limiting speed v2 and less than the maximum driving speed v3 in the in Fig. The design shown in section 3 remains constant and therefore does not increase further.

[0039] In both configurations, the driving speed v may not be able to be increased further at speeds above the limiting speed v2, depending on the driving resistance, so that the maximum driving speed v3 may not be reached. However, the latter is acceptable when the drive unit 1 is operating in an Eco mode.

[0040] In an alternative embodiment, the drive unit 1 features Fig. 1. No second electric machine 13 is used. This also eliminates the need for the pre-transformation 29 and the spur gear 30. Furthermore, the drive unit of this alternative configuration can be described in Fig. The drive device shown in Figure 1 corresponds to the method for operating such an alternative drive device. Fig. The method shown in point 2, wherein process step V for controlling the second electrical machine 13 is omitted. Accordingly, in this embodiment, the method returns to step II after step IV. Fig. 4 are the power P1 of the first electric machine 12, the power P M of humans as well as the performance limit P L This alternative configuration is shown as a function of the driving speed v. Regarding the power curve of the power P1 of the first electric machine 12, the power curve P M of man, the P L as well as the possibility of implementing the power limitation of the first electrical machine 12, reference is made to the explanations in connection with the embodiment according to Fig. 3 referred. Reference sign 1 Drive unit 2 Pedal shaft 3 cases 4 pedals 5 Output wheel 6 superimposed gear units 7, 21, 22, 31 Sun wheel 8, 23, 24, 32 Planetary carriers 9, 25, 26, 33 planetary gear 10, 27, 28, 34 Ring gear 11 Free run 12, 13 electric machine 14, 16 Stator 15, 17 Rotor 18 Pre-transmission gearboxes 19, 20 planetary gear set 29 Preliminary translation 30 Spur gear units 40 Control unit 41 Control unit I. Capture signal for operation in Eco mode II Determining driving speed III. Compare driving speed with maximum speed IV Limit performance to the performance limit V Control another electric machine P Performance v Driving speed v1 starting speed v2 limiting speed v3 maximum driving speed P1 Power electric machine P2 power further electric machine P M Human performance P L Performance limit

Claims

[1] Method for operating a drive unit (1) for a muscle-powered vehicle in an Eco mode, wherein the drive unit (1) comprises a pedal shaft (2) for receiving muscle force, a superimposed transmission (6) designed as a planetary gear set with an output, an output gear (5), and an electric machine (12), wherein the pedal shaft (2) and the electric machine (12) are mechanically connected to the superimposed transmission (6), and the output of the superimposed transmission (6) is mechanically connected to the output gear (5), comprising acquiring (I) a signal to operate the drive unit (1) in an Eco mode, and limiting (IV) a power (P1) of the electric machine (12) of the drive unit (1) to a power limit (P L ), characterized by, that the drive device (1) further comprises another electrical machine (13) mechanically connected to the output of the superimposed gear (6) and that the operation of the drive device (1) in Eco mode is such that the further electrical machine (13) does not operate as a generator in order to avoid reactive power. [2] Method according to claim 1, characterized by , that the procedure further comprises determining (II) a driving speed (v) of the muscle-powered vehicle and comparing (III) the determined driving speed (v) with a limiting speed (v2), wherein limiting (IV) the power of the electric machine (12) takes place when the determined driving speed (v) is greater than the limiting speed (v2). [3] Method according to claim 2, characterized by, that the limiting speed (v2) is less than a maximum driving speed (v3) up to which the drive device (1) is designed to provide electrical assistance to the muscle-powered vehicle. [4] Method according to claim 1, characterized by , that the procedure for limiting (IV) the power of the electrical machine (12) to a power limit (P L ) furthermore includes controlling (V) the further electrical machine (13) such that the further electrical machine (13) no longer absorbs or delivers power. [5] Method according to one of claims 2 or 3, characterized by, that the operation of the drive unit (1) in Eco mode is such that the power (P1) of the electric machine (12) increases with increasing driving speed (v) from a starting speed (v1) to the limiting speed (v2), while a power (P2) of the other electric machine (13) decreases with increasing driving speed (v) from the starting speed (v1) to the limiting speed (v2). [6] Method according to any one of the preceding claims, characterized by , that limiting (IV) the power (P1) of the electric machine (12) includes limiting a speed of the electric machine (12). [7] Method according to any one of the preceding claims, characterized by , that the acquisition (I) of a signal to operate the drive unit (1) in an Eco mode includes the setting of the Eco mode by a driver of the muscle-powered vehicle via a control unit (41). [8] Drive device (1) for a muscle-powered vehicle comprising a pedal shaft (2) for receiving muscle force, a superimposed transmission (6) designed as a planetary gear with an output, an output gear (5), an electric machine (12), a further electric machine (13) mechanically connected to the output of the superimposed transmission (6), and a control device (40), wherein the pedal shaft (2) and the electric machine (12) are mechanically connected to the superimposed transmission (6) and the output of the superimposed transmission (6) is mechanically connected to the output gear (5), wherein the control device (40) is connected to the electric motor (12) and is configured to carry out the method according to one of the preceding claims. [9] Vehicle with at least two wheels and a drive unit (1) according to claim 8, wherein the driven wheel (5) is coupled to one of the wheels via a power transmission element for driving the vehicle.

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