DRIVE UNIT FOR AN ELECTRIC BICYCLE WITH TWO ELASTIC DEFORMATION SIGNAL ENCODERS AND CONTROL METHOD

Description

[0001] The proposed solution concerns a drive unit for an electric bicycle and a control method for such a drive unit.

[0002] It is known to use at least one electric motor in combination with a transmission device, e.g., one with a planetary gear stage, on an electric bicycle, i.e., a so-called e-bike or pedelec, to provide motor assistance while riding the electric bicycle. Such a drive unit has, firstly, a drive shaft (typically also called a bottom bracket shaft) through which a drive torque generated by the rider of the electric bicycle can be applied, and to which pedals are provided for this purpose. In addition to the first drive torque applied to the drive shaft by muscle power, a second drive torque can be provided by external power, e.g., by means of an electric motor.The drive unit's transmission device couples at least one electric motor and the output shaft, so that a torque can be transmitted to a wheel, usually a rear wheel of the electric bicycle, via an output shaft of the drive unit which is to be coupled to a wheel of the electric bicycle, which is based on the first and second drive torque.

[0003] In such drive units, the input and output shafts are typically arranged coaxially. The output shaft is then often designed as a hollow shaft. However, this makes the output shaft comparatively heavy and the drive unit's construction relatively complex. Furthermore, the combined torque—that is, the total torque resulting from the sum of the muscle-powered and externally powered drive torques—cannot be easily measured by sensors, for example, due to differing force input at the left and right ends of the drive shaft where the pedals are located. This compromise is accepted, however, in exchange for a supposedly more compact drive unit design.

[0004] However, for drive units for electric bicycles, especially drive units for so-called mid-drive motors, there is still a need for improved or alternative drive units, for example drive units where weight or costs can be saved.

[0005] Against this background, the drive unit of claim 1 and the control method of claim 14 are proposed.

[0006] The invention is defined by independent claims 1 and 14, the preferred embodiments by dependent claims.

[0007] Document EP 3 012 181 A1 shows the preamble of claim 1.

[0008] A proposed drive unit for an electric bicycle includes at least the following: a drive element for providing torque to drive the electric bicycle, a drive shaft for muscle-powered generation of a first drive torque by a rider of the electric bicycle, an electric motor for externally powered generation of a second drive torque on a rotor shaft coupled to the electric motor, and a transmission device for transmitting the second drive torque to the drive element.

[0009] According to the proposed solution, the output element is rotationally fixed to the drive shaft. Furthermore, the drive unit comprises at least two spatially spaced signal transmitters on a drive assembly encompassing the output element and the drive shaft. During operation of the drive unit, these transmitters can generate two successive measurement signals, the time interval between which varies depending on the magnitude of the first and second drive torques.

[0010] The proposed solution is based on the fundamental idea of ​​providing two signal transmitters on a drive assembly of a drive unit for an electric bicycle, in which the output element and the drive shaft are rotationally fixed to each other, so that the first and second drive torques (and thus a so-called rider torque and a motor torque) are added on the output element, and providing at least two signal transmitters for generating measurement signals within such a drive assembly in such a way that the measurement signals generated by the signal transmitters correlate in their time interval with the magnitudes of the first and second drive torques, or rather, that conclusions can be drawn about the magnitudes of the first and second drive torques (absolute or relative to each other) from the differences in the time intervals between the measurement signals.The time interval between the measurement signals of at least two spatially separated signal transmitters thus varies depending on the magnitudes of the first and second drive torques. Consequently, depending on the absolute or relative magnitudes of the first and second drive torques, a different measurable time interval between successive measurement signals results.

[0011] With respect to a rotational axis around which the drive shaft and the output element, which is fixed to it (e.g., fixed to it or formed integrally with it), rotate, a change in the phase shift between the two measurement signals provided by the signal transmitters can be evaluated. This allows for electronic inferences about the current level of a (total) torque for driving the e-bike and / or the current level of the first drive torque / rider torque (absolute or relative). From this, a control variable can be determined to specify the level of assistance provided by the electric motor. For example, given a known second drive torque / motor torque, the evaluated phase shift between the measurement signals can be used to calculate the level of the first muscle-powered drive torque / rider torque.Based on this, a control parameter can then be determined to adjust the support performance of the electric motor - for example, depending on a user-set support level.

[0012] In one embodiment, the at least two signal transmitters are arranged such that a change in the time interval between the measurement signals generated by the transmitters is representative of elastic deformation in the drive assembly resulting from the generated first and second drive torques. The drive assembly with the signal transmitters provided thereon is therefore designed in such a way that elastic deformation in the components of the drive assembly is specifically permitted and evaluated when, during operation of the drive unit to propel the e-bike, first and second drive torques generated by muscle power and external power are applied. Depending on the magnitude of the first and second drive torques, the size of the elastic deformation, and thus the spatial distance between the two signal transmitters, varies.This variation in spatial distance, in turn, leads to a measurable and evaluable variation in the temporal interval with which the measurement signals generated by the signal transmitters are recorded.

[0013] According to the invention, it is provided that a first signal transmitter which has at least two signal transmitters at a first location a) on the drive shaft or b) on a region of the output element associated with the drive shaft and a second signal transmitter which has at least two signal transmitters at a second location a) on a region of the drive element associated with the transmission device or b) on a region of the output element associated with an output gear of the output element.

[0014] The first signal transmitter is therefore located on a section of the drive shaft or a section of the output element close to the drive shaft, while the second signal transmitter, spaced apart from it, is located further away from the drive shaft on the output element, specifically on a region of the output element where the second drive torque generated by the electric motor is applied or transmitted towards the output. The location of the second signal transmitter can, in principle, be situated radially further outwards, relative to the axis of rotation of the drive shaft, than the location of the first signal transmitter.

[0015] Depending on the (mounting) location of a signal transmitter, and especially in relation to the other signal transmitter, varying degrees of change in the time intervals between the signals can be observed. This is because different elastic deformations can occur within the drive assembly between the respective sections during operation of the drive unit. For example, depending on the position of the at least two signal transmitters within the drive assembly, phase shifts of (absolute) at least 2° to 4°, particularly in the range of 3° to 5°, can be observed or deliberately allowed through the design of the drive assembly and the setting of a specific torsional stiffness.

[0016] This includes phase shifts in the range of -5° to +5°. Negative phase shifts can occur, for example, during recuperation or when riding a e-bike in reverse. Particularly with e-bikes designed as cargo bikes, electrically assisted or powered reverse riding is not uncommon.

[0017] A driven gear of the output element can, in principle, be connected to a power transmission element for driving the e-bike with the (total) torque resulting from the first and second drive torques. This power transmission element is designed to transmit the torque to a rear wheel of the e-bike. Such a power transmission element can be, for example, a chain or a belt. A driven gear for a chain, for instance, has teeth that engage with the chain. The driven gear can therefore be, in particular, a driven gear or a driven belt pulley.

[0018] In one embodiment, the drive unit for generating the first and / or second measurement signal includes at least one Hall sensor. In such a case, a signal transmitter can therefore be a Hall sensor on the drive assembly or a magnetic element that interacts with at least one stationary Hall sensor of the drive assembly when the drive shaft and the output element rotate, in order to generate a measurement signal as the Hall sensor passes through. In principle, the proposed solution, based on relatively simple signal transmitters and the measurement signals generated by them, allows conclusions to be drawn about the magnitude of the drive torques, and in one embodiment, specifically about the magnitude of a first drive torque / driver torque applied by muscle power. The use of a torque sensor on the drive assembly is thus unnecessary, for example.This, in turn, allows for corresponding measurements at comparatively low costs and in a minimal installation space. These cost advantages can be further increased by using inexpensive and relatively small Hall sensors.

[0019] In one embodiment, the drive unit includes an electronic control unit configured to determine a control variable representative of the magnitude of the first drive torque using the first and second measurement signals, as well as a signal representative of the second drive torque. The signal representative of the second drive torque could, for example, be a measurement signal or motor signal from the electric motor, since the second drive torque is generated by the electric motor. Thus, if the second drive torque / motor torque is known, the magnitude of the first drive torque can be easily determined from the time interval between the first and second measurement signals. This allows for the determination of a control variable that can be used to control the electric motor and, consequently, to adjust the magnitude of the second drive torque to be generated.For example, the user of an e-bike should be provided with assistance to propel the bike, the level of which depends on the power they exert through muscle power. In this configuration, the electronic control unit is therefore set up to calculate a control variable representative of the initial drive torque. This control variable can be a value that requires further processing to control the electric motor, or it can be a control signal that can be used directly to control the electric motor.

[0020] For example, in this context, the electronic control unit is configured to use at least one stiffness value, representative of the torsional stiffness of the drive assembly, the drive shaft, and / or the output element, stored in a memory, to determine the control variable. In particular, a corresponding stiffness value can be stored in a memory of the control unit. The stored stiffness value is then consequently a stiffness constant that is representative of the respective torsional stiffness. Specifically, such a stiffness constant can be determined and stored after a calibration process for the drive unit.Given a known torsional stiffness of the drive assembly, or at least within it, a change in the phase shift between the measurement signals of at least two signal transmitters allows conclusions to be drawn about a deformation-induced change in the spatial distance between the second signal transmitters and thus about the magnitudes of the applied drive torques with which the deformation is associated.

[0021] In one embodiment, the output element comprises at least one spring element that provides elastic deformability to at least one section of the output element where one of the signal transmitters is located. The at least one spring element thus introduces a predetermined degree of elasticity into the output element, for example, to allow a specific degree of deformability in a section of the output element. The at least one spring element can elastically connect two sections of the output element. Alternatively, the at least one spring element can also be integrated into the material of the output element, in particular by injection molding.

[0022] Through the at least one section of the output element which is elastically deformable against a restoring force of the at least one spring element and on which one of the signal transmitters is provided, a spatial change in position relative to the other signal transmitter is thus deliberately permitted during operation of the drive unit, to such an extent that a spatial change in position is accompanied by a significant, measurable change in the temporal sequence of the measurement signals when the signal transmitters rotating with the drive assembly are guided past at least one stationary sensor part (such as a Hall sensor) of the drive unit.

[0023] To limit the deformation path, defined by the at least one spring element, for elastic deformation occurring during operation of the drive unit to a permissible level – also, for example, with regard to preventing plastic and thus irreversible deformation – the drive assembly can, in a further development, include a block mechanism. Such a block mechanism can, in particular, be integrated into the output element itself. The block mechanism limits the elastic deformability of the at least one section of the output element carrying the signal transmitter, defined by the at least one spring element, to a predefined maximum deformation path.In this way, it is ensured that a section of the output element, on which a signal transmitter is provided, can only deform up to its maximum deformation path during operation of the drive unit and for propelling the e-bike (when subjected to a restoring force applied by at least one spring element), and in particular relative to the other signal transmitter. For example, a maximum deformation angle with respect to the axis of rotation of the drive shaft can be predetermined by the block mechanism. Once the maximum deformation path has been exceeded, the block mechanism consequently prevents further deformation of the section and thus mechanically limits the deformability of the section carrying the signal transmitter.The deformability of one of the signal transmitter sections is set, for example, such that elastic deformation occurs in a specific operating range of the drive unit, in which a rider of the electric bicycle applies a force below a threshold value to pedals connected to the drive shaft, thereby generating a first drive torque on the drive shaft that is below a torque threshold value.

[0024] One such torque threshold is, for example, 30 Nm. This torque threshold is chosen to correspond to the operating range of a typical e-bike ride with an average speed of 5-25 km / h. Below this torque threshold, the drive unit exhibits greater elastic deformation, resulting in comparatively large changes in the time intervals between measurement signals that can be electronically evaluated. Within the range of a muscle-powered drive torque of 0 to 30 Nm, the drive unit has a comparatively low torsional stiffness, and the measurement system is relatively sensitive. This allows for finely graduated motor assistance, increasing the power output by a factor of 3 or 4, for example.Above the torque threshold, the maximum possible support power is provided by at least one motor. Therefore, further evaluation of the measurement signals is no longer strictly necessary.

[0025] When the rider of the e-bike applies a force to the pedals exceeding the torque threshold, an atypical riding condition or operating range is assumed, such as a sprint or test ride. In this case, the electric motor's assistance output may be limited to a maximum value, and the torques evaluated by the sensors do not necessarily require fine-tuning. Accordingly, the block mechanism may be active. From the maximum deformation path defined by the block mechanism onward, the e-bike is considered to be operating in a riding condition where the rider is pedaling with a force exceeding a threshold, thus activating the electric motor to provide a specific, fixed level of assistance.

[0026] The drive unit's transmission system can, in principle, comprise at least one gear wheel, in particular a gear tooth or a gear pulley, which is driven via the rotor shaft and is designed to transmit the second drive torque to the output element. The gear wheel can also be rotationally fixed to the output element. This includes, in particular, the possibility that the output element, with an integrated gear wheel and an integrated output wheel, is formed integrally with the drive shaft.

[0027] In the case of a gear unit, the transmission assembly therefore includes at least one further gear that meshes with the gear unit, which is fixedly connected to the output element, in order to transmit the second drive torque to the output element. In an embodiment with a belt drive (e.g., in the form of a pulley), the transmission assembly is designed with at least one belt element, for example, in the form of a V-belt or toothed belt, to transmit the second drive torque to the output element.

[0028] In principle, the gear wheel can, for example, be designed for a rotationally fixed connection with the output element directly on the output element itself. This consequently implies that a section forming the gear wheel is materially bonded to a support or web section of the drive element. Alternatively, the gear wheel formed on the output element can also be formed integrally with a support or web section of the output element. In particular, in one embodiment, the gear wheel can be formed integrally with an output wheel of the drive element, which is intended for transmitting the torque resulting from the first and second drive torques. In such an embodiment, the gear wheel and the output wheel are therefore components of one and the same part on the output element.This further reduces the complexity of the drive unit and also simplifies its assembly. The output gear can, for example, be designed as either a gear or a belt pulley.

[0029] In principle, the output element can include a driven wheel that is connected to a power transmission element of the drive unit to propel the electric bicycle. Such a power transmission element then establishes a connection to a rear wheel of the electric bicycle, so that a torque resulting from the first and second drive torques can be transmitted from the output element to the rear wheel of the electric bicycle via the rotating driven wheel to propel the electric bicycle.

[0030] In one embodiment, the output element is formed directly on the drive shaft itself. Here, for example, the output element is formed integrally with the drive shaft, so that the drive shaft and the output element are parts or sections of a single component. Alternatively, the output element can be fixed to the drive shaft in a rotationally fixed manner, so that the drive shaft and output element form a drive assembly of at least two parts, in which the separately manufactured output element is fixed directly to the drive shaft in a rotationally fixed manner. Both of the above-described variants offer the advantage that no output shaft needs to be provided that is mounted coaxially with the drive shaft, and in particular, no coaxially mounted hollow shaft is required.

[0031] The drive unit can generally comprise a housing in which the electric motor is mounted and the drive shaft is rotatably mounted. The output element can be rotatably mounted at an opening in the housing. This specifically includes the possibility that an output gear of the drive element is rotatably mounted at the housing opening.

[0032] The direct rotatable mounting of an output gear connected to a transmission element at the housing opening can also mean that the drive unit functions entirely without an output shaft. In this case, for example, the gear wheel can be formed integrally with the output gear, with a circular cylindrical section of the output gear then providing the rotatable mounting on the drive unit housing.

[0033] The proposed solution also concerns an electric bicycle with a variant of a proposed drive unit.

[0034] Another aspect of the proposed solution concerns a control method for controlling at least one electric motor of a drive unit for an electric bicycle. A drive unit of an electric motor to be controlled within the framework of the proposed control method comprises at least the following: a drive shaft for the muscle-powered generation of a first drive torque by a rider of the electric bicycle, an output element non-rotatably connected to the drive shaft for providing a torque to drive the electric bicycle, at least one electric motor for the externally powered generation of a second drive torque on a rotor shaft coupled to the electric motor, a transmission device for transmitting the second drive torque to the output element, and at least two spatially spaced signal transmitters on a drive assembly comprising the output element and the drive shaft, via which two temporally successive measurement signals can be generated during operation of the drive unit, the temporal interval between which varies depending on the magnitude of the first and second drive torques.

[0035] One proposed control method then uses a control variable determined from the first and second measurement signals to control at least one electric motor.

[0036] The control system includes a possible adjustment of the level of the second drive torque to be generated by the at least one electric motor.

[0037] Implementation variants of a proposed control method can be realized, in particular, by utilizing implementation variants of a proposed drive unit. The features and advantages explained above and below in connection with implementation variants of a proposed drive unit therefore also apply to corresponding implementation variants of a proposed control method, and vice versa.

[0038] In particular, within one implementation variant of a proposed control method, at least one (measurement or motor) signal representative of the second drive torque and / or at least one stiffness value representative of the torsional stiffness of the drive assembly, the drive shaft, and / or the drive element can be used to determine the control variable. The at least one stiffness value can be determined, for example, during a calibration of the drive unit (i.e., a calibration process performed with the drive unit) and stored in a memory.

[0039] The attached figures illustrate possible implementation variants of the proposed solution.

[0040] This shows: Figure 1 schematically shows a first embodiment of a proposed drive unit for an electric bicycle, in which a drive shaft is formed integrally with an output element that integrates a gear and a driven gear and on which two radially offset signal transmitters are provided for determining a first drive torque (rider torque) applied by muscle power; Figure 2 shows a further development of the embodiment of the Figure 1 , in which the signal transmitters on the output element are positioned differently from each other; Figure 3 shows a further development of the embodiment of Figure 2 , in which at least one spring element is provided on the output element to specify an elastic deformation during operation of the drive unit and, in conjunction with a block mechanism, to limit it to a predefined dimension; Figure 4 shows an electric bicycle with an embodiment of a proposed drive unit.

[0041] The Figure 4 Figure 1 shows an electric bicycle 1 with a frame 10 on which a front wheel 11 and a rear wheel 12 are rotatably mounted. The rear wheel 12 can be driven with electric assistance via a drive unit A. For this purpose, the drive unit A has at least one electric motor M. A drive torque generated by the electric motor M – possibly in addition to a drive torque applied by muscle power via a drive shaft / bottom bracket axle T – can be transmitted to the rear wheel 12 by means of a power transmission element, for example in the form of a chain or a belt. Thus, not only can a first drive torque be transmitted to the rear wheel 12, which is applied by a rider of the electric bicycle 1 via pedals connected to the bottom bracket axle T, but the rear wheel 12 can also be driven by a second drive torque generated by the electric motor M.

[0042] The drive power supplied by the electric motor M is specified by an electronic control unit SE of the drive unit A. This electronic control unit SE specifies, for example, the electric motor's drive power to be supplied, depending on the user-selected support levels, with which a rider of the electric bicycle 1 is assisted when pedaling. A corresponding support level is then specified, for example, by an actuation unit 2. This actuation unit 2, coupled to the control unit SE, is provided on the handlebars of the electric bicycle 1 shown in Figure 5 and is equipped with a display 20.

[0043] In contrast to designs previously used in practice, the drive unit A of the proposed solution provides a rotationally fixed coupling of an output element 4 connected to the power transmission element 13 with the bottom bracket shaft T.

[0044] In one version of the Figure 1 For this purpose, for example, the bottom bracket axle T is formed integrally with the output element 4. The output element 4 is housed within a casing G of the drive unit A, from which the bottom bracket axle T protrudes on both sides, so that a pedal can be connected to the bottom bracket axle T at the shaft ends E1 and E2 protruding from the casing G. The output element 4 also forms an output gear, for example in the form of a drive belt pulley or – as in the Figure 1The drive element 4 is shown in the form of an output gear 41, to which the power transmission element 13 is connected. Furthermore, a gear 40, as part of a single-stage transmission unit, meshes with a drive gear 30, which is rotationally fixed to a rotor shaft 3 of the electric motor M. Since the gear 40 is an integral part of the drive element 4, a (second) drive torque generated by the electric motor M can be introduced into the output element 4. This results in the addition of a first drive torque applied to the bottom bracket axle T by muscle power and the second drive torque applied by the electric motor at the output element 4, providing a total torque at the output gear 41. The output gear 41, on which the added drive torques are applied, is rotatably mounted in a housing opening O of the housing G.

[0045] On a web section 45 of the output element 4, which extends radially outwards with respect to the axis of rotation of the bottom bracket shaft T, two signal transmitters in the form of magnetic elements 52 and 50 for Hall sensors 62, 60 of the drive unit A are provided radially offset from each other. When the bottom bracket shaft T and thus the output element 4, which is non-rotatably connected to it, rotates, the magnetic elements 50 and 52 are moved past the Hall sensors 60 and 62 and thereby generate measurement signals that correlate with the rotational speed of the drive assembly defined by the bottom bracket shaft T and the output element 4 and thus represent angular signals.

[0046] One magnetic element 52 is located in the area of ​​the bottom bracket shaft T, while the other magnetic element 50 is positioned in the area of ​​the gear 40. Due to the corresponding positioning of the two magnetic elements 52 and 50, as well as a correspondingly designed torsional stiffness of the drive assembly, it can be observed that, with the bottom bracket shaft T and the output element 4 being formed as a single unit, an elastic deformation occurs at the web section 45, depending on the magnitude of the drive torques and, in particular, the relative magnitudes of the drive torques. This elastic deformation results in a change in the spatial position of the magnetic elements 52 and 50 relative to each other, which also affects the measurement signals acquired when the bottom bracket shaft T and the output element 4 are rotated. These signals are generated at the Hall sensors 62 and 60 via the magnetic elements 52 and 50.It can be observed that the time interval between the generated measurement signals varies depending on how high the first and second drive torques are in absolute or relative terms.

[0047] This allows, for example, the use of the fact that the torsional stiffness of the drive assembly is known, for instance, through design and / or as a result of a previously performed calibration process with the drive unit A, and that the second drive torque generated by the electric motor M on the rotor shaft 3 is also known during operation of the drive unit A. From the occurrence or change of a phase shift in the measurement and angular signals generated at the Hall sensors 62 and 60, the first drive torque applied by muscle power, i.e., the so-called rider torque, can be calculated. A control variable determined on the basis of this calculated drive torque can be provided to the electronic control unit SE to control the assistance power to be supplied by the electric motor M.In this case, measurement signals αGes and αBasis generated by the Hall sensors are transmitted to the electronic control unit SE, which uses an integrated electronic evaluation logic to infer the currently applied driver torque and from this in turn to the control variable for controlling the electric motor M.

[0048] Differential measurement using the time intervals between the measurement signals αtotal and αbase of the Hall sensors 62 and 60, to infer the driver torque, can be implemented relatively cost-effectively and with minimal installation space. Furthermore, the measurement is possible even without temperature-related fluctuations in engine influences. In addition, the radial spacing of the magnetic elements 52 and 50 provides a comparatively high measurement resolution and thus good precision.

[0049] In the version of the Figure 2is a radially more outwardly located magnetic element 51 in the area of ​​the output gear 41 and thus - in comparison to the magnetic element 52 of the Figure 1 closer to the bottom bracket axle T - positioned. Here, the rider torque is determined from a differential measurement of measurement and angle signals α rider and α base from Hall sensors 61 and 60. The corresponding measuring section then focuses more strongly on the influence of the applied rider torque. The smaller radial distance also results in less rotation of the magnet elements 52 and 51 than with the magnet elements 52 and 50 of the Figure 1 For example, in a typical configuration of the drive unit A as a mid-drive motor for the electric bicycle 1, a maximum deformation path in the form of a maximum angle of twist can be achieved in the design variant of the Figure 1 up to ±5° in the version variant of the Figure 2 up to ±3°.

[0050] During the further training of Figure 3The elasticity of the web section 45 is increased by a spring element 7 in the force flow of the first drive torque and, furthermore, limited to a maximum value by a block mechanism, thus providing mechanical anti-rotation protection. In this way, a predetermined elastic deformability of the output element 4 in the web section 45 is specifically defined via the spring element 7, and therefore a comparatively large displacement of the magnet element 51 associated with the output gear 41 (with respect to the axis of rotation of the bottom bracket shaft T) relative to the magnet element 52 associated with the bottom bracket shaft T. The block mechanism on the web section 45 ensures that the elastic deformability of the web section 45, defined by the at least one spring element 7, is limited to a predefined maximum deformation path.If a force applied by a rider of the electric bicycle 1, with which the rider pushes into pedals attached to the shaft ends E1 and E2, exceeds a threshold value and thus generates a first drive torque above a torque threshold value, the block mechanism ensures that the magnetic element 51 (or in an analogous further development based on the design variant of the . Figure 1 the magnetic element 50) cannot be displaced beyond a maximum angle of rotation relative to the magnetic element 52 assigned to the bottom bracket shaft T.

[0051] The elastic deformability specified by the spring element 7 (or further spring elements) then covers, for example, normal operation of the drive unit A, in which a rider of the electric bicycle 1 does not pedal excessively hard. During a sprint or a test ride, in which the rider pedals with a force exceeding a threshold value, no (measurable) change occurs between the time intervals of α rider and α base (α total and α base ) and the calculated control variable for the control of the electric motor is thus set to a constant, fixed value. Reference symbol list

[0052] 1 Electric bicycle 10 Frame 11 Front wheel 12 Rear wheel 13 Power transmission element 2 Actuating unit 20 Display 3 Rotor shaft 30 Drive gear 4 Output element 40 Gearbox gear 41 Output gear 45 Web section 50, 51, 52 Magnet element (signal transmitter) 60, 61, 62 Hall sensor 7 Spring element A Drive unit E1, E2 Shaft end G Housing M Electric motor O Housing opening SE Electronic control unit T Bottom bracket / drive shaft α Total, α Rider, α Base Measurement / Angle signal

Claims

1. A drive unit for an electric bicycle (1), having - an output element (4) for providing a torque for driving the electric bicycle (1), - a drive shaft (T) for muscle-powered generation of a first drive torque by a rider of the electric bicycle (1), - an electric motor (M) for non-muscle-powered generation of a second drive torque on a rotor shaft (3) coupled to the electric motor (M), and - a transmission device (30, 40) for transmitting the second drive torque to the output element (4), characterized in that the output element (4) is connected to the drive shaft (T) in a rotationally fixed manner and the drive unit (A) comprises at least two spatially spaced signal generators (50, 52; 50, 51) on a drive assembly comprising the output element (4) and the drive shaft (T), via which two temporally successive measurement signals (αBaSis, αGes; αBasis, αFahrer) during operation of the drive unit (A) can be generated, the time interval between which varies depending on how high the first and second drive torques are, wherein - a first signal generator (52) of the at least two signal generators (50, 52; 50, 51) is provided at a first position a) on the drive shaft (T) or b) on a region of the output element (4) associated with the drive shaft (T), and - a second signal generator (50, 51) of the at least two signal generators (50, 52; 50, 51) is provided at a second position on a region of the output element (4) assigned to the transmission device (30, 40).

2. The drive unit according to claim 1, characterized in that the at least two signal generators (50, 52; 50, 51) are arranged in such a way that a change in the time interval between the measurement signals (αBaSis, αGes; αBasis, αFahrer) generated by the signal generators (50, 52; 50, 51) is representative of an elastic deformation in the drive assembly as a result of the generated first and second drive torques 35.

3. The drive unit according to claim 1 or 2, characterized in that the second position, in relation to an axis of rotation of the drive shaft (T), is located radially further outwards than the first position.

4. The drive unit according to one of the preceding claims, characterized in that - the drive unit (A) comprises at least one Hall sensor (60, 61, 62) for generating the first and / or second measurement signal (αBaSis, αGes; αBasis, αFahrer) and / or - the drive unit (A) comprises an electronic control unit (SE) which is set up, using the first and second measurement signals (αBaSis, αGes; αBasis, αFahrer) and using a signal representative of the second drive torque, to determine a control variable representative of the level of the first drive torque, wherein the electronic control unit (SE) is optionally configured to use at least one stiffness value stored in a memory, which is representative of the torsional stiffness of the drive assembly, the drive shaft (T), and / or the output element (4), for determining the control variable.

5. The drive unit according to one of the preceding claims, characterized in that the output element (4) comprises at least one spring element (7) which predetermines an elastic deformability of the output element (4) in at least one portion (45) of the output element (4) on which one of the signal generators (60, 62; 61, 62) is provided, wherein, optionally, the drive assembly comprises a blocking mechanism which limits the elastic deformability of the at least one portion (45) of the output element (4), as predetermined by the at least one spring element (7), to a predefined maximum deformation path.

6. The drive unit according to one of the preceding claims, characterized in that the transmission device (30, 40) comprises at least one transmission gear (40) which can be driven via the rotor shaft (3) and is provided for transmitting the second drive torque to the output element (4).

7. The drive unit according to claim 6, characterized in that the transmission gear (40) is connected to the output element (4) in a rotationally fixed manner.

8. The drive unit according to claim 7, characterized in that the transmission gear (40) is formed on the output element (4).

9. The drive unit according to claim 8, characterized in that the transmission gear (40) on the output element (4) is integrally formed with an output wheel (41) of the output element (4), which is provided for transmitting the torque resulting from the first and second drive torques.

10. The drive unit according to one of the preceding claims, characterized in that a power transmission member (13) is provided for transmitting the torque resulting from the first and second drive torques, which is coupled to a rear wheel (12) of the electric bicycle (1), and the output element (4) comprises an output wheel (41) which is connected to the power transmission member (13) for driving the electric bicycle (1) with the torque resulting from the first and second drive torques.

11. The drive unit according to one of the preceding claims, characterized in that the drive unit (A) comprises a housing (G) in which the electric motor (M) is accommodated and the drive shaft is rotatably mounted, and the output element (4) is rotatably mounted on a housing opening (O) of the housing (G).

12. The drive unit according to claim 9 or 10 and claim 11, characterized in that the output wheel (41) is rotatably mounted on the housing opening (O).

13. An electric bicycle with a drive unit according to one of the preceding claims.

14. A method for controlling at least one electric motor (M) of a drive unit (A) for an electric bicycle (1), wherein the drive unit (A) comprises at least: - a drive shaft (T) for muscle-powered generation of a first drive torque by a rider of the electric bicycle (1), - an output element (4) connected to the drive shaft (T) in a rotationally fixed manner to provide torque for driving the electric bicycle (1), - the at least one electric motor (E) for non-muscle-powered generation of a second drive torque on a rotor shaft (3) coupled to the electric motor (E), - a transmission device (30, 40) for transmitting the second drive torque to the output element (4) and at least two spatially spaced signal generators (50, 52; 50, 51) on a drive assembly comprising the output element (4) and the drive shaft (T), via which two temporally successive measurement signals (αBaSis, αGes; αBasis, αFahrer) during operation of the drive unit (A) can be generated, the time interval between which varies depending on how high the first and second drive torques are, wherein - a first signal generator (52) of the at least two signal generators (50, 52; 50, 51) is provided at a first position a) on the drive shaft (T) or b) on a region of the output element (4) associated with the drive shaft (T), and - a second signal generator (50, 51) of the at least two signal generators (50, 52; 50, 51) is provided at a second location on a region of the output element (4) assigned to the transmission device (30, 40), and wherein a control variable determined from the first and second measurement signals (αBaSis, αGes; αBasis, αFahrer) is used to control the at least one electric motor (M).

15. The method according to claim 14, characterized in that at least one stiffness value representative of the second drive torque and / or at least one stiffness value representative of the torsional stiffness of the drive assembly, the drive shaft (T) and / or the drive element (4) is additionally used to determine the control variable, wherein, optionally, the at least one stiffness value is determined and stored during calibration of the drive unit.