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

Abstract

The proposed solution relates in particular to a drive unit (A) for an electric bicycle (1), comprising - an output element (4) for providing a torque for driving the electric bicycle (1), - a drive shaft (T) for generating a first drive torque by a driver of the electric bicycle (1) by means of muscle force, - an electric motor (E) for the generation by external force of a second drive torque at a rotor shaft (3) coupled to the electric motor (E), and - a transmission device (30, 40) for transmitting the second drive torque to the output element (4). In a proposed drive unit (A), the output element (4) is connected in a rotationally fixed manner to the drive shaft (T). Furthermore, the drive unit (A) has at least two signal transmitters (50, 52; 50, 51), which are spaced apart from one another spatially in relation to one another, on a drive assembly which comprises the output element (4) and the drive shaft (T), via which, during operation of the drive unit (A), two temporally successive measurement signals (αBasis, αGes; αBasis, αFahrer) can be generated, the time interval of which varies as a function of the levels of the first and second drive torques.

Description

[0001] Drive unit for an electric bicycle with two signal sensors taking elastic deformation into account and control method

[0002] Description

[0003] The proposed solution relates to a drive unit for an electric bicycle and a control method for such a drive unit.

[0004] It is known to use at least one electric motor in combination with a transmission device, e.g. having a planetary gear stage, on an electric bicycle, thus on a so-called e-bike or pedelec, in order to provide motor assistance when riding the electric bicycle. A corresponding drive unit has, on the one hand, a drive shaft (typically also referred to as a bottom bracket shaft), via which a drive torque generated by a rider of the electric bicycle can be introduced and on which pedals are provided for this purpose. In addition to a first drive torque introduced at the drive shaft by muscle power, a second drive torque can be provided by external power, e.g. with the help of an electric motor.The at least one electric motor and the output shaft are coupled to one another via the transmission device of the drive unit, 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 that is to be coupled to a wheel of the electric bicycle, which torque is based on the first and second drive torque. In such drive units, the drive shaft and the output shaft are usually arranged coaxially to one another. The output shaft is then designed, for example, as a hollow shaft. However, the output shaft is then comparatively heavy and the structure of the drive unit is comparatively complex. In addition, a combined, i.e.The total torque resulting from the sum of the drive torques applied by muscle power and external power cannot be easily detected by sensors, for example, due to different force inputs at the left and right ends of the drive shaft, where the pedals are located. However, this is accepted in favor of a supposedly more compact design of the drive unit.

[0005] However, when it comes to drive units for electric bicycles, especially drive units for so-called mid-engines, there is still a need for improved or alternative drive units, for example drive units where weight or costs can be saved.

[0006] Against this background, the drive unit of claim 1 and the control method of claim 18 are proposed.

[0007] A proposed drive unit for an electric bicycle comprises at least the following:

[0008] - an output element for providing torque to drive the electric bicycle,

[0009] - a drive shaft for muscle-powered generation of a first drive torque by a rider of the electric bicycle,

[0010] - an electric motor for the externally powered generation of a second drive torque on a rotor shaft coupled to the electric motor and

[0011] - a transmission device for transmitting the second drive torque to the output element.

[0012] According to the proposed solution, the output element is connected to the drive shaft in a rotationally fixed manner. Furthermore, the drive unit comprises at least two spatially spaced-apart signal transmitters on a drive assembly comprising the output element and the drive shaft. During operation of the drive unit, two sequential measurement signals can be generated via these transmitters. The time interval between these signals varies depending on the magnitude of the first and second drive torques.The proposed solution is therefore based on the basic 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 connected to one another in a rotationally fixed manner, so that the first and second drive torques (and thus a so-called driver torque and a motor torque) are added on the output element, and of 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 levels of the first and second drive torques or conclusions can be drawn about the levels of the first and second drive torques (absolute or relative to one another) from the differences in the time intervals between the measurement signals.The temporal interval between the measurement signals of the at least two spatially spaced signal generators thus varies depending on the magnitudes of the first and second drive torques. Depending on the absolute or relative magnitude of the first and second drive torques, a different measurable temporal interval between successive measurement signals results.

[0013] In relation to an axis of rotation around which the drive shaft and the output element connected thereto in a rotationally fixed manner, for example fixed thereto in a rotationally fixed manner or formed integrally therewith, rotate, a change in a phase shift between the two measurement signals provided by the signal generators can be evaluated. This can be used to electronically determine the current level of a (total) torque for driving the electric bicycle and / or the current level of the first drive torque / rider torque (absolute or relative) and, if necessary, to determine a control variable that specifies the assistance power to be provided by the electric motor. For example, the evaluated phase shift between the measurement signals can be used to calculate the level of the first muscle-operated drive torque / rider torque, given a known second drive torque / motor torque.On this basis, a control variable can then be determined to adjust the support power of the electric motor - for example, depending on a support level set by the user.

[0014] In one embodiment, the at least two signal generators are arranged such that a change in the time interval between the measurement signals generated by the signal generators is representative of an elastic deformation on the drive assembly as a result of the generated first and second drive torques. The drive assembly with the signal generators provided thereon is consequently designed such that an elastic deformation on the components of the drive assembly is specifically permitted and evaluated when, during operation of the drive unit for driving the electric bicycle, first and second drive torques generated by human power and external power are present. Depending on the magnitude of the first drive torque and the second drive torque, the magnitude of the elastic deformation and thus the spatial distance between the two signal generators varies.This variation in the spatial distance in turn leads to a measurable and analyzable variation in the temporal interval with which the measurement signals generated by the signal transmitters are recorded.

[0015] In principle, it can be provided that

[0016] - a first signal generator of the at least two signal generators is provided at a first location a) on the drive shaft or b) on a region of the output element associated with the drive shaft and

[0017] - a second signal generator of the at least two signal generators is provided 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.

[0018] The first signal generator is therefore provided here on a section of the drive shaft or a section of the output element close to the drive shaft, while the second signal generator, spaced apart from it, is provided further away from the drive shaft on the output element, thus in a region of the output element where the second drive torque generated by the electric motor is applied or transmitted in the direction of the output. The second location, where the second signal generator is provided, can generally be located radially further outward relative to a rotational axis of the drive shaft than the first location, where the first signal generator is provided.

[0019] Depending on the location (attachment) of a signal generator, particularly in relation to the other signal generator, varying degrees of change in the time intervals between the signals can be detected, since elastic deformations of varying magnitudes 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 generators 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 specifically permitted by designing the drive assembly and setting a certain torsional stiffness. This includes phase shifts in the range of -5° to +5°. Negative phase shifts can occur, for example, during recuperation or when reversing with the electric bicycle.Especially with an electric bike designed as a so-called cargo bike, an electric motor-assisted or powered reversing movement is not uncommon.

[0020] In principle, an output gear of the output element can be connected to a power transmission member for driving the electric bicycle with the (total) torque resulting from the first and second drive torques. This power transmission member is intended for transmitting the torque to a rear wheel of the electric bicycle. Such a power transmission member can be, for example, a chain or a belt. A driven gear for a chain then has, for example, teeth that mesh with the chain. The driven gear can therefore be, in particular, a driven gear or a driven belt pulley.

[0021] In one embodiment, the drive unit comprises at least one Hall sensor for generating the first and / or second measurement signal. In such a case, a signal generator can therefore be formed by a Hall sensor on the drive assembly or by a magnetic element that interacts with at least one stationary Hall sensor of the drive assembly upon rotation of the drive shaft and the output element in order to generate a measurement signal when passing the Hall sensor. In principle, the proposed solution allows the level of the drive torque to be determined based on comparatively simply constructed signal generators and the measurement signals generated thereby, in particular, in one embodiment, the level of a first drive torque / driver torque applied by muscle power. The use of a torque sensor on the drive assembly is therefore not necessary, for example.This then allows for corresponding measurements at comparatively low cost and in minimal space. These cost advantages can be further increased by using inexpensive and comparatively small Hall sensors.

[0022] In one embodiment, the drive unit comprises an electronic control unit configured to determine a control variable representative of the level of the first drive torque using the first and second measurement signals and a signal representative of the second drive torque. The signal representative of the second drive torque can be, for example, 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, it is particularly easy to determine the level of the first drive torque from a time interval between the first and second measurement signals, and thus a control variable that can be used to control the electric motor and thus potentially adjust the level of the second drive torque to be generated.For example, a user of an electric bicycle should be provided with a level of assistance to drive the electric bicycle that depends on the amount of muscle power applied. The electronic control unit in this embodiment is therefore configured to calculate a control variable representative of the level of the first drive torque. This control variable can be a value that requires further processing to control the electric motor or a control signal that can be used directly to control the electric motor.

[0023] For example, in this context, the electronic control unit is configured to use at least one stiffness value stored in a memory to determine the control variable, representative of the torsional stiffness of the drive assembly, the drive shaft, and / or the output element. 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 representative of the respective torsional stiffness. In particular, such a stiffness constant can have been determined and stored after performing a calibration process for the drive unit.If the torsional stiffness of or at least within the drive assembly is known, a change in a phase shift between the measurement signals of the at least two signal transmitters can be used to determine a deformation-related change in a spatial distance between the second signal transmitters and thus the levels of the applied drive torques with which the deformation is accompanied.

[0024] In one embodiment, the output element comprises at least one spring element that provides elastic deformability of the output element in at least one section of the output element where one of the signal transmitters is provided. The at least one spring element thus specifically introduces elasticity of a predefined magnitude 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 to one another. Alternatively, the at least one spring element can also be integrated, in particular injected, into the material of the output element.

[0025] A spatial change in position with respect to the other signal generator is thus specifically permitted during operation of the drive unit via 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 generators is provided, to such an extent that a spatial change in position is also accompanied by a significant, measurable change in the temporal sequence of the measurement signals when the signal generators rotating with the drive assembly are guided past at least one stationary sensor part (such as a Hall sensor) of the drive unit.

[0026] In order to achieve a deformation path, predetermined by the at least one spring element, for an elastic deformation occurring during operation of the drive unit to a value classified as permissible—also, for example, with a view to avoiding plastic and thus irreversible deformation—the drive assembly can, in a further development, comprise a block mechanism. Such a block mechanism can, in particular, be integrated into the output element itself. The block mechanism limits the elastic deformability, predetermined by the at least one spring element, of the at least one section of the output element carrying the signal transmitter to a predefined maximum deformation path.In this way, it is achieved that a section of the output element on which a signal generator is provided can only deform (with a restoring force applied by the at least one spring element acting thereon) up to the maximum deformation path and in particular relative to the other signal generator during operation of the drive unit and the first and second drive torque generated for driving the electric bicycle. For example, a maximum deformation angle with respect to the axis of rotation of the drive shaft can be predetermined via the block mechanism. Once the maximum deformation path has been bridged, the block mechanism blocks further deformation of the section and thus mechanically limits the deformability of the section carrying the one signal generator.The deformability of the section carrying one of the signal transmitters is set, for example, such that elastic deformation occurs in a specific operating range of the drive unit, in which an electric bicycle rider pedals the pedals connected to the drive shaft with a force below a threshold value, thereby generating a first drive torque on the drive shaft that is below a torque threshold. Such a torque threshold is, for example, 30 Nm. The torque threshold is selected, for example, such that the operating range corresponds to a typical normal ride of the electric bicycle at an average speed in the range of 5-25 km per hour.Below the torque threshold, the drive assembly is designed to have greater inherent elastic deformability, resulting in comparatively large electronically analyzable changes in the time intervals between the measurement signals. In the range of a muscle-powered drive torque of 0 to 30 Nm, the drive assembly has comparatively low torsional rigidity, and the provided measurement system is comparatively sensitive. This allows the motor to provide finely graded assistance, for example, increasing the muscle-powered power by a factor of 3 or 4. Above the torque threshold, the maximum possible assistance is provided by at least one motor. Further analysis of the measurement signals is therefore no longer essential here.

[0027] If the force with which the electric bicycle rider pedals exceeds the torque threshold, an atypical riding condition or operating range is assumed, for example a sprint or test ride. For this purpose, the assistance power of the electric motor can be regulated to a maximum value, and the torques evaluated via the signal sensors do not necessarily have to control a fine-tuned adjustment. Accordingly, the blocking mechanism can be active here. From the maximum deformation distance, which is specified via the blocking mechanism, it is assumed that the electric bicycle is in a riding condition in which the electric bicycle rider pedals with a force that exceeds a (force) threshold, and thus the electric motor must be controlled to provide a specific, fixed assistance power.

[0028] The transmission device of the drive unit can generally comprise at least one gear wheel, in particular a gear wheel or a transmission belt wheel, which is drivable via the rotor shaft and is provided for transmitting the second drive torque to the output element. The gear wheel can also be connected to the output element in a rotationally fixed manner. This includes, in particular, the possibility of the output element being formed integrally with the drive shaft, with a gear wheel and an output wheel integrated therein.

[0029] In the case of a transmission gear, the transmission device therefore has at least one further gear that meshes with the transmission gear connected to the output element in a rotationally fixed manner, in order to transmit the second drive torque to the output element. In a variant with a transmission belt wheel (e.g., in the form of a pulley), the transmission device is designed with at least one belt element, for example, in the form of a V-belt or toothed belt, in order to transmit the second drive torque to the output element.

[0030] In principle, the gear wheel can, for example, be formed on the output element itself for rotationally fixed connection to the output element. This consequently includes a section forming the gear wheel being integrally connected 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 gear of the drive element, which is provided for transmitting the torque resulting from the first and second drive torques. In such an embodiment, a gear wheel and an output gear are therefore components of one and the same component on the output element.This further reduces the complexity of the drive unit and also simplifies assembly. The output gear can also be designed, for example, as an output gear or a driven belt pulley.

[0031] In principle, the output element can comprise an output gear connected to a power transmission member of the drive unit to drive the electric bicycle. Such a power transmission member then establishes a coupling 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 output gear to drive the electric bicycle.

[0032] In one embodiment, the output element is formed on the drive shaft itself. Here, the output element is formed integrally with the drive shaft, for example, so that the drive shaft and the output element are parts or sections of a single component. Alternatively, the output element can be rotationally fixed to the drive shaft, so that the drive shaft and output element form an at least two-part drive assembly, in which the separately manufactured output element is rotationally fixed directly to the drive shaft. Both variants explained above offer the advantage that no output shaft needs to be mounted coaxially to the drive shaft, in particular no coaxially mounted hollow shaft.

[0033] The drive unit can generally comprise a housing in which the electric motor is accommodated and the drive shaft is rotatably mounted. The output element can be rotatably mounted at a housing opening. This includes, in particular, an output gear of the drive element being rotatably mounted at the housing opening.

[0034] The direct rotatable mounting of an output gear connected to a transmission element at the housing opening can also result in the drive unit being able to operate entirely without an output shaft. 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 housing of the drive unit.

[0035] The proposed solution further relates to an electric bicycle with a variant of a proposed drive unit.

[0036] A further aspect of the proposed solution relates to 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:

[0037] - a drive shaft for muscle-powered generation of a first drive torque by a rider of the electric bicycle,

[0038] - an output element connected to the drive shaft in a rotationally fixed manner to provide a torque to drive the electric bicycle,

[0039] - at least one electric motor for externally powered generation of a second drive torque on a rotor shaft coupled to the electric motor,

[0040] - a transmission device for transmitting the second drive torque to the output element and - at least two spatially spaced-apart signal transmitters on a drive assembly comprising the output element and the drive shaft, via which two temporally successive measuring signals can be generated during operation of the drive unit, the time interval between which varies depending on how high the first and second drive torques are.

[0041] A proposed control method then uses a control variable determined from the first and second measurement signals to control the at least one electric motor.

[0042] The control includes a possible adjustment of the level of the second drive torque to be generated by the at least one electric motor.

[0043] Embodiments of a proposed control method can be implemented, in particular, using embodiments of a proposed drive unit. The features and advantages explained above and below in connection with embodiments of a proposed drive unit therefore also apply to corresponding embodiments of a proposed control method, and vice versa.

[0044] In particular, within the scope of one embodiment of a proposed control method for determining the control variable, 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. 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.

[0045] The attached figures illustrate possible embodiments of the proposed solution.

[0046] Here we show:

[0047] Figure 1 schematically shows a first embodiment of a proposed

[0048] Drive unit for an electric bicycle, in which a drive shaft is formed integrally with an output element which integrates a transmission gear and an output gear and on which two signal transmitters radially offset from one another are provided for determining a first drive torque (driver torque) applied by muscle power;

[0049] Figure 2 shows a further development of the embodiment variant of Figure 1, in which the

[0050] Signal transmitters on the output element are positioned differently from each other;

[0051] Figure 3 shows a further development of the embodiment variant of Figure 2, in which at least one spring element is provided on the output element in order to predetermine an elastic deformation during operation of the drive unit and, in interaction with a block mechanism, to limit it to a predefined amount;

[0052] Figure 4 shows an electric bicycle with a variant of a proposed drive unit.

[0053] Figure 4 shows an example of 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 the assistance of an electric motor 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 can be transmitted to the rear wheel 12 with the aid of a power transmission element, for example in the form of a chain or a belt, possibly in addition to a drive torque applied by muscle power via a drive shaft / bottom bracket shaft T. In this way, not only a first drive torque can 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 shaft T. Rather, the rear wheel 12 can also be driven via a second drive torque generated by the electric motor M.

[0054] The drive power generated by the electric motor M is specified via an electronic control unit SE of the drive unit A. This electronic control unit SE specifies, for example, the drive power to be generated by the electric motor, which assists a rider of the electric bicycle 1 when pedaling, depending on user-selected assistance levels. A corresponding assistance level is then specified, for example, via an actuating unit 2. This actuating unit 2, coupled to the control unit SE, is provided on a handlebar of the electric bicycle 1 in the electric bicycle 1 of Figure 5 and is equipped with a display 20.

[0055] In contrast to designs commonly used in practice to date, the drive unit A of the proposed solution provides for a rotationally fixed coupling of an output element 4 connected to the power transmission member 13 to the bottom bracket shaft T.

[0056] In one embodiment variant of Figure 1, for example, it is provided that the bottom bracket shaft T is formed integrally with the output element 4. The output element 4 is accommodated within a housing G of the drive unit A, from which the bottom bracket shaft T protrudes on both sides, so that a pedal can be connected to the bottom bracket shaft T at each of the shaft ends E1, E2 protruding from the housing G. The output element 4 further forms an output wheel, for example in the form of a driven belt wheel or - as shown in Figure 1 - in the form of an output gear 41, to which the power transmission member 13 is connected. Furthermore, in the present case, a transmission gear 40, as part of a single-stage transmission device, meshes with a drive gear 30, which is connected in a rotationally fixed manner to a rotor shaft 3 of the electric motor M.Because the transmission 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 shaft T by muscle power and the second drive torque applied by an electric motor at the output element 4, and the provision of a resulting total torque at the output gear 41. The output gear 41, to which the added drive torques are applied, is rotatably mounted in a housing opening O of the housing G.

[0057] 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 spindle 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 one another. When the bottom bracket spindle T and thus the output element 4, which is connected to it in a rotationally fixed manner, rotate, the magnetic elements 50 and 52 are guided past the Hall sensors 60 and 62 and in doing so generate measurement signals that correlate with the rotational speed of the drive assembly defined by the bottom bracket spindle T and the output element 4 and thus represent angle signals. In this case, one magnetic element 52 is provided in the area of ​​the bottom bracket spindle T, while the other magnetic element 50 is positioned in the area of ​​the transmission gear 40.Through the appropriate positioning of the two magnetic elements 52 and 50 and a correspondingly designed torsional rigidity of the drive assembly, it can be observed that, with a one-piece design of the bottom bracket spindle T and the output element 4, an elastic deformation occurs on the web section 45 depending on the level of the drive torques and, in particular, the levels of the drive torques relative to one another. This elastic deformation results in a change in the spatial position of the magnetic elements 52 and 50 relative to one another, which also affects the measurement signals recorded upon rotation of the bottom bracket spindle T and the output element 4, which are generated via the magnetic elements 52 and 50 at the Hall sensors 62 and 60. It can thus be observed that a time interval between the generated measurement signals varies depending on how high the first and second drive torques are, either absolutely or relative to one another.

[0058] This can then, for example, take advantage of the fact that the torsional stiffness of the drive assembly is known, for example through design and / or as a result of a previously performed calibration process with the drive unit A, and moreover, during operation of the drive unit A, the second drive torque generated by the electric motor M on the rotor shaft 3 is also known. From the occurrence of or a change in a phase shift in the measurement or angle signals generated at the Hall sensors 62 and 60, the first drive torque applied by muscle power, hence the so-called driver torque, can be calculated. A control variable determined on the basis of this calculated drive torque can be made available to the electronic control unit SE in order to control the assistance power to be applied by the electric motor M.In the present case, the measurement signals «Ges» and «Basis» generated by the Hall sensors are transmitted to the electronic control unit SE, which uses an integrated electronic evaluation logic to determine the currently applied driver torque and, from this, the control variable for controlling the electric motor M.

[0059] The differential measurement using the time intervals between the measurement signals □Ges and Oßasis of Hall sensors 62 and 60 to determine the driver torque can be implemented comparatively cost-effectively and with minimal installation space. The measurement is also possible without temperature-related fluctuations due to engine influences. Furthermore, the radial spacing of the magnetic elements 52 and 50 provides a comparatively high measurement resolution and thus good precision.

[0060] In the embodiment of Figure 2, a magnetic element 51 located further radially outward is positioned in the area of ​​the output gear 41 and thus closer to the bottom bracket spindle T than the magnetic element 52 of Figure 1. Here, the rider torque is determined from a differential measurement of measurement or angle signals □rider and «base of 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 leads to a smaller twisting of the magnetic elements 52 and 51 than with the magnetic elements 52 and 50 of Figure 1. For example, with a typical design of the drive unit A as a mid-engine for the electric bicycle 1, a maximum deformation path in the form of a maximum twisting angle can be up to ±5° in the embodiment of Figure 1 and up to ±3° in the embodiment of Figure 2.

[0061] In the further development of Figure 3, the elasticity at the web section 45 is increased by a spring element 7 in the force flow of the first drive torque and, moreover, limited to a maximum value by a block mechanism and thus a mechanical anti-twist device. Thus, a predetermined elastic deformability of the output element 4 in the web section 45 is specifically predetermined via the spring element 7, and thus a comparatively large displaceability of the magnetic element 51 assigned to the output gear 41 (with respect to the axis of rotation of the bottom bracket spindle T) relative to the magnetic element 52 assigned to the bottom bracket spindle T. The block mechanism on the web section 45 ensures that the elastic deformability of the web section 45 predetermined via 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 pedals attached to the shaft ends E1 and E2, exceeds a threshold value and thus generates a first drive torque that is above a torque threshold value, the block mechanism ensures that the magnetic element 51 (or in an analogous further development based on the embodiment variant of 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.

[0062] The elastic deformability specified via spring element 7 (or other spring elements) then covers, for example, normal operation of drive unit A, in which a rider of electric bicycle 1 does not pedal excessively hard. During a sprint ride or a test ride, in which the pedals are pedaled with force exceeding a threshold value, no (measurable) change occurs between the time intervals between the apahrer and "base" (OGes and Qßasis), and the calculated control variable for controlling the electric motor is thus set to a constant, fixed value.

[0063] List of reference symbols

[0064] 1 electric bike

[0065] 10 frames

[0066] 11 Front wheel

[0067] 12 rear wheel

[0068] 13 Power transmission link

[0069] 2 operating unit

[0070] 20 displays

[0071] 3 Rotor shaft

[0072] 30 drive gear

[0073] 4 Output element

[0074] 40 Gear

[0075] 41 Output gear

[0076] 45 bridge section

[0077] 50, 51 , 52 Magnetic element (signal generator)

[0078] 60, 61 , 62 Hall sensor

[0079] 7 Spring element

[0080] A drive unit

[0081] E1, E2 shaft end

[0082] G Housing

[0083] M electric motor

[0084] O Housing opening

[0085] SE Electronic Control Unit

[0086] T bottom bracket / drive shaft

[0087] ClGes, ÖFahrer, □Basic measurement / angle signal

Claims

Claims 1. Drive unit for an electric bicycle (1), with - a driven element (4) to provide 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 (E) for the externally driven generation of a second drive torque on a rotor shaft (3) coupled to the electric motor (E) 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 rotationally fixed to the drive shaft (T) and the drive unit (A) comprises at least two spatially spaced signal transmitters (50, 52; 50, 51) on a drive assembly comprising the output element (4) and the drive shaft (T), via which, during operation of the drive unit (A), two temporally successive measurement signals (a Ba sis, a Ges ; a Ba sis, a Fa hrer) can be generated, the time interval between which varies depending on the magnitude of the first and second drive torques.

2. Drive unit according to claim 1, characterized in that the at least two signal transmitters (50, 52; 50, 51) are arranged such that a change in the time interval between the measurement signals (a) generated by the signal transmitters (50, 52; 50, 51) BaSiS , OGes; a BaSiS , a Fa h rer) is representative of elastic deformation on the drive assembly as a result of the generated first and second drive torques.

3. Drive unit according to claim 1 or 2, characterized in that - a first signal transmitter (52) of which at least two signal transmitters (50, 52; 50, 51) are 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 transmitter (50, 51) of the at least two signal transmitters (50, 52; 50, 51) at a second location a) on an area of ​​the output element (4) associated with the transmission device (30, 40) or b) on a The output wheel (41) of the output element (4) is provided in the area of ​​the output element (4).

4. Drive unit according to claim 3, characterized in that the second position, with respect to an axis of rotation of the drive shaft (T), is located radially further outwards than the first position.

5. Drive unit according to one of the preceding claims, characterized in that the drive unit (A) for generating the first and / or second measurement signal (OBasis, aces; ciBasis, apahrer) comprises at least one Hall sensor (60, 61, 62).

6. Drive unit according to one of the preceding claims, characterized in that the drive unit (A) comprises an electronic control unit (SE) which is configured to determine a control variable representative of the magnitude of the first drive torque using the first and second measurement signals (□Basis, aces; aBasis, apahrer) and using a signal representative of the second drive torque.

7. Drive unit according to claim 6, characterized in that the electronic control unit (SE) is configured to use at least one stiffness value, representative of the torsional stiffness of the drive assembly, the drive shaft (T) and / or the output element (4), stored in a memory for determining the control variable.

8. Drive unit according to one of the preceding claims, characterized in that the output element (4) comprises at least one spring element (7) which provides an elastic deformability of the output element (4) in at least one section (45) of the output element (4) on which one of the signal transmitters (60, 62; 61 , 62) is provided.

9. Drive unit according to claim 8, characterized in that the drive assembly comprises a block mechanism which limits the elastic deformability of the at least one section (45) of the output element (4) to a predefined maximum deformation path via the at least one spring element (7).

10. Drive unit according to one of the preceding claims, characterized in that the transmission device (30, 40) has at least one gear wheel (40) comprises which can be driven via the rotor shaft (3) and is intended to transmit the second drive torque to the output element (4).

11. Drive unit according to claim 10, characterized in that the gear wheel (40) is rotatably connected to the output element (4).

12. Drive unit according to claim 11, characterized in that the gear wheel (40) is formed on the output element (4).

13. Drive unit according to claim 12, characterized in that the gear wheel (40) is formed integrally with an output wheel (41) of the output element (4) which is provided for the transmission of the torque resulting from the first and second drive torques.

14. Drive unit according to one of the preceding claims, characterized in that a power transmission element (13) is provided for the transmission of 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 a driven wheel (41) which is connected to the power transmission element (13) for driving the electric bicycle (1) with the torque resulting from the first and second drive torques.

15. 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 received and the drive shaft is rotatably mounted, and the output element (4) is rotatably mounted on a housing opening (O) of the housing (G).

16. Drive unit according to claim 13 or 14 and claim 15, characterized in that the output wheel (41) is rotatably mounted on the housing opening (O).

17. Electric bicycle with a drive unit according to one of the preceding claims.

18. 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 the following: - a drive shaft (T) for muscle-powered generation of a first drive torque by a rider of the electric bicycle (1), - a drive element (4) rotatably connected to the drive shaft (T) to provide a torque for driving the electric bicycle (1), - at least one electric motor (E) for the externally driven generation of a second drive torque on a rotor shaft (3) coupled to the electric motor (E), - a gear unit (30, 40) for transmitting the second drive torque to the output element (4) and - at least two spatially separated signal transmitters (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 (OBasis, ClGes, Oßasis, Opahrer) can be generated during operation of the drive unit (A), the temporal interval of which varies depending on the magnitude of the first and second drive torques, and wherein a control variable determined from the first and second measurement signals (OBasis, OGes; ciBasis, Opahrer) is used to control the at least one electric motor (M).

19. Method according to claim 18, characterized in that for determining the control variable 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 used.

20. Method according to claim 19, characterized in that the at least one stiffness value is determined and stored during a calibration of the drive unit.