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 is at least partially propelled by muscle power, comprising a first electric machine (2) which is effectively connected to a pedal crank shaft (4) via a transmission (3), wherein the first electric machine (2) is configured to be operated as an electric motor with electrical energy from an energy storage device (5) to assist a user while pedaling, and to be driven via the pedal crank shaft (4) and operated as a generator to produce electrical energy for operating a second electric machine (6) which is configured to be effectively connected to a drive wheel (8) of the vehicle (1). The invention further relates to a vehicle (1) that is at least partially propelled by muscle power, comprising at least two wheels and such a drive unit.

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 method for operating such a drive unit and a vehicle with such a drive unit. In particular, the vehicle is designed as an e-bike and has at least two wheels.

[0002] Vehicles powered at least partially by muscle, such as bicycles with an auxiliary drive, are known in the art as e-bikes or electric bicycles. An electric bicycle is a bicycle with an electric machine designed as a drive motor. An energy storage device interacting with the drive motor supplies the electrical energy required to operate the drive motor. Furthermore, bicycles are known that do not have a mechanical connection between the pedal crank and the drive wheel, but instead have another electric machine designed as a pedal generator to produce electrical energy, and the drive motor is operated according to the specifications of this machine.

[0003] The pedal generator used to receive electrical power and input from the rider has greater inertia and more friction than a conventional bicycle, which has a mechanical connection between the crank axle and the drive wheel. This makes pedaling feel less effortful and is perceived as uncomfortable by the user. In other words, without generating any propulsion for the bicycle itself, the user needs to exert considerable force and energy to set the pedal generator in motion.

[0004] For example, DE 10 2017 213 305 A1 discloses a vehicle that is at least partially muscle-powered, with a pedal crank arrangement comprising a pedal crank with a pedal axle and a transmission device arranged coaxially around the pedal axle with an axially adjacent generator, wherein the pedal crank is connected to the generator via the transmission device in order to convert mechanical energy generated by the pedal crank into electrical energy.

[0005] Publication DE 10 2022 133 999 A1 discloses a drive module for a vehicle that is at least partially powered by muscle power, a method for controlling the drive module, a computer program product and a control unit, while DE 10 2021 127 649 B3 discloses an electric drive system and a method for controlling an electric drive system for a vehicle that is powered by muscle power.

[0006] From publication DE 10 2021 115 271 A1, a further drive arrangement for a muscle-powered vehicle with temperature sensing is known, and DE 10 2017 219 398 A1 shows a hybrid drive for an electric bicycle with a pedal crank drive.

[0007] The object of the invention is to improve a drive unit for a vehicle that is at least partially powered by muscle power. In particular, the drive unit should offer a high level of user comfort. These objectives are achieved by the subject matter of the independent claims. Preferred embodiments are described in the dependent claims, the description, and the figures.

[0008] A drive unit according to the invention for a vehicle that can be propelled at least partially by muscle power comprises a first electric machine which is connected to a pedal crank shaft via a transmission, wherein the first electric machine is configured to be operated as an electric motor with electrical energy from an energy storage device in order to assist a user in pedaling, and to be driven via the pedal crank shaft and operated as a generator in order to generate electrical energy for the operation of a second electric machine which is configured to be connected to a drive wheel of the vehicle, wherein the first electric machine is operated as a motor in the range of a pedal crank angle of approximately 180° and approximately 360° or 0°.

[0009] The first electric machine is motor-driven within a crank angle range of approximately 180° and approximately 360° or 0° because the lever arm for applying force to the pedals is minimal in this vertical orientation of the crank arms, which are rigidly connected to the crank axle. This results in particularly noticeable frictional resistance for the user. Therefore, the first electric machine is designed both as a pedal generator, capable of receiving power from the user, and as an electric motor, capable of driving the crank axle in such a way as to reduce the user's effort while pedaling. This improves user comfort. In other words, the first electric machine only drives the crank axle when the user is pedaling and thus rotating the crank axle.For example, a control device with at least one sensor configured to detect an angle of rotation determines the rotational speed of the pedal crank and controls the two electric motors. Specifically, the sensor can detect an angle of rotation on the pedal crank, on a rotor shaft of the first electric motor, or on a transmission shaft. For example, the sensor is integrated into the first electric motor or the transmission, simplifying assembly. The second electric motor is configured as a drive motor to power the drive wheel and operates according to the drive power generated by the user.

[0010] Advantageously, the drive power that the first electric machine introduces into the crankshaft is dimensioned such that the crankshaft is not accelerated, but merely the friction and inertia of the system at the crankshaft are reduced. For example, when operating as an electric motor, the first electric machine generates at least a torque that corresponds to the static frictional torque of the first electric machine and the gearbox. Alternatively or additionally, when operating as an electric motor, the first electric machine generates at least a torque that corresponds to the rotational inertia of the first electric machine and the gearbox. For example, the static frictional torque of the first electric machine and the gearbox and / or the rotational inertia of the first electric machine and the gearbox are determined empirically or through individual test runs before assembly and stored on a data memory of the control unit.Preferably, the rotational inertia of the first electric machine and the gearbox is the product of the rotational speed of the pedal crank shaft and a factor greater than 0 and less than 1. Preferably, this factor is greater than 0 and less than 0.1. In particular, the factor depends essentially on the gear ratio and the efficiency of the gearbox arranged between the first electric machine and the pedal crank shaft.

[0011] According to one embodiment, the first electric machine is configured to operate at least partially, and in particular intermittently, as an electric motor and at least partially, and in particular intermittently, as a generator during a pedal revolution. One pedal revolution corresponds to one revolution of the crank arm. According to one embodiment, the first electric machine is operated several times as an electric motor and several times as a generator during a pedal revolution. In particular, the first electric machine is operated alternately as an electric motor and generator during a pedal revolution. When the first electric machine is in the range of a crank arm angle of approximately 180° and approximately 360°, respectively, the first electric machine operates in the range of approximately 180° and approximately 360°.Since the first electric machine is operated as a motor at 0° because the lever arm for applying a pedaling force to the pedals is minimal in this vertical orientation of the pedal cranks which are non-rotatably connected to the crank shaft, and frictional resistance is therefore particularly noticeable to the user, the first electric machine is accordingly operated as a generator in the range of a pedal crank angle of approximately 90° and approximately 270° because the lever arm for applying a pedaling force to the pedals is maximal in this horizontal orientation of the pedal cranks which are non-rotatably connected to the crank shaft and a drive torque from the user must be supported.

[0012] The invention also relates to a method for operating a drive unit according to the invention, wherein the first electric machine is operated as an electric motor with electrical energy from the energy storage device to assist the user while pedaling, and is driven via the crank shaft and operated as a generator to produce electrical energy for operating the second electric machine. The assistance provided to the user while pedaling is dimensioned such that the system resistance at the crank shaft is reduced. For example, the first electric machine, when operating as an electric motor, generates a torque that corresponds to the sum of the rotational inertia and the static frictional torque of the first electric machine and the transmission.

[0013] The following equation illustrates what has been said previously: Torque generated at the first electric motor = Rotational inertia of the first electric motor and the gearbox + Static frictional torque of the first electric motor and the gearbox. The rotational inertia of the first electric motor and the gearbox can be calculated by multiplying the rotational speed of the pedal crank shaft by a factor between 0 and 1.

[0014] Furthermore, in generator mode, the user's torque is supported at the crank axle. Both measures actively apply rotational resistance to the crank axle via the first electric motor to simulate a classic pedaling feel for the user. Additionally, the first electric motor receives commands for operating the second electric motor. Specifically, this is achieved using the at least one sensor integrated into the first electric motor to detect the angle of rotation.

[0015] 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 an e-bike. For example, the vehicle can have three or more wheels, wherein either one or more wheels can be electrically driven.

[0016] Further measures improving the invention are described in more detail below together with a description of a preferred embodiment of the invention with reference to the single figure, which shows a highly simplified schematic representation of a vehicle according to the invention with a drive unit according to the invention.

[0017] The vehicle 1 according to the invention is designed as an e-bike and can be propelled at least partially by muscle power. The vehicle 1 comprises a rear wheel designed as a drive wheel 8, a front wheel 7 which is pivotably arranged on a frame 11 via a fork, and a drive unit according to the invention with a first electric machine 2 and a second electric machine 6.

[0018] A crankshaft 4 is connected to pedals 13 via crank arms 12, with the first electric machine 2, configured as a pedal generator, being effectively connected to the crankshaft 4 via a gearbox 3. The second electric machine 6, designed as a wheel hub motor, is effectively connected to the drive wheel 8 of the vehicle 1 via a switchable planetary gearbox (not shown) in order to generate drive power at the drive wheel 8 according to the drive power generated by the user at the crankshaft 4. A control device 9 with a sensor 10 for detecting an angle of rotation is configured to determine the rotational speed of the crankshaft 4 and to control the two electric machines 2 and 6. An electrical energy storage device 5 is arranged on the frame 11 of the vehicle 1 and is electrically connected to the two electric machines 2 and 6 and the control device 9.

[0019] The first electric machine 2 is configured to operate as an electric motor using electrical energy from an energy storage device 5 to assist a user while pedaling, and to be driven via the pedal crank shaft 4 and operated as a generator to produce electrical energy for operating the second electric machine 6. Specifically, the first electric machine 2 is operated alternately as an electric motor and generator several times during a pedal revolution. When operating as an electric motor, the first electric machine 2 generates a torque equal to the sum of a static frictional torque and the rotational inertia of the first electric machine 2 and the transmission 3, where the rotational inertia of the first electric machine 2 and the transmission 3 is the product of the rotational speed of the pedal crank shaft 4 and a factor greater than 0 and less than 1, in particular less than 0.1.

[0020] When the energy storage device 5 is discharged, the two electric machines 2 and 7 can no longer be supplied with electrical energy. From this point on, the user must pedal harder to overcome the frictional torque and rotational inertia of the first electric machine 2 and the gearbox 3. The first electric machine 2 then generates only the electrical energy intended to operate the second electric machine 6. For example, the electrical energy generated by the first electric machine 2 in generator mode is sufficient to cover a distance of 300 meters within 10 minutes using only the user's pedaling. Reference symbol list 1 vehicle 2 first electric machine 3 gearboxes 4. Crankshaft 5 Energy storage 6 second electric machine 7 front wheel 8 drive wheel 9 Control device 10 Sensor 11 frames 12 Crankshaft 13 pedals

Claims

[1] Drive unit for a vehicle (1) that can be propelled at least partially by muscle power, comprising a first electric machine (2) which is connected via a transmission (3) to a pedal crank shaft (4) in a propulsive manner, wherein the first electric machine (2) is configured to be operated as an electric motor with electrical energy from an energy storage device (5) to assist a user in pedaling, and to be driven via the pedal crank shaft (4) and operated as a generator to produce electrical energy for the operation of a second electric machine (6) which is configured to be connected to a drive wheel (8) of the vehicle (1) in a propulsive manner, wherein the first electric machine is operated as a motor in the range of a pedal crank angle of approximately 180° and approximately 360° or 0°. [2] Drive unit according to claim 1, characterized by, that a control device (9) with at least one sensor (10) for detecting an angle of rotation is configured to determine the speed of the pedal crank shaft (4) and to control the two electric machines (2, 6). [3] Drive unit according to one of the preceding claims, characterized by , that the first electric machine (2) is configured to operate at least partly as an electric motor and at least partly as a generator during a pedal revolution. [4] Drive unit according to one of the preceding claims, characterized by , that the first electric machine (2) in operation as an electric motor generates at least a torque that corresponds to the static frictional torque of the first electric machine (2) and the gearbox (3). [5] Drive unit according to one of the preceding claims, characterized by, that the first electric machine (2) in operation as an electric motor generates at least a torque that corresponds to a rotational inertia of the first electric machine (2) and the gearbox (3). [6] Drive unit according to claim 5, characterized by , that the rotational inertia of the first electric machine (2) and the gearbox (3) corresponds to the product of the rotational speed of the pedal crank shaft (4) and a factor that is greater than 0 and less than 1. [7] Drive unit according to claim 6, characterized by , that the factor is greater than 0 and less than 0.

1. [8] Method for operating a drive unit according to one of the preceding claims, wherein the first electric machine (2) is operated as an electric motor with electrical energy from the energy storage device (5) to assist the user when pedaling, and is driven via the pedal crank shaft (4) and operated as a generator to produce electrical energy for the operation of the second electric machine (6). [9] Method according to claim 8, characterized by , that the first electric machine (2) generates a torque during operation as an electric motor which corresponds to the sum of a rotational inertia and a static frictional torque of the first electric machine (2) and the gearbox (3). [10] Vehicle (1) which can be propelled at least partially by muscle power, comprising at least two wheels and a drive unit according to any one of claims 1 to 7.

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