Drive system for electric bicycle with state detection of freewheel during switching process, and operating method

Abstract

The proposed solution relates in particular to a drive system for an electric bicycle (1), comprising:-a drive train (A) having at least one electric drive motor (M) for applying a driving force to drive a wheel (12) of the electric bicycle (1); -a switching device (15) for changing the transmission ratio between the drive train (A) and the wheel (12) to be driven, and-an electronic control unit (SE) for controlling the at least one drive motor (M) and the switching device (15). According to the invention, a free wheel (14) is arranged on the wheel (12) to be driven, which free wheel transmits the driving force generated by the at least one drive motor (M) to the wheel (12) in a transmission state, and the drive train (A) is decoupled from the wheel (12) in a decoupled state of the free wheel (14). The electronic control unit (SE) is configured to interrupt the switching process in the presence of an interruption criterion indicating a transmission state of the freewheel (15) and to evaluate a profile of a rotational speed of the at least one drive motor (M) and / or a profile of a motor current in order to detect the presence of the interruption criterion.

Description

Technical Field

[0001] The proposed solution relates in particular to a drive system for an electric bicycle. Background Art

[0002] It is known that at least one electric motor is used in combination with a transmission, for example with a planetary gear stage, on an electric bicycle (i.e. on a so-called electric bicycle (E-bike) or electric assisted pedal bicycle (Pedelec)) in order to provide motor support when riding the electric bicycle. The corresponding drive system has a drive shaft (which is typically also called a middle shaft) on the one hand, via which the drive torque generated by the rider of the electric bicycle can be introduced, and pedals are arranged on the drive shaft for this purpose. In addition to the first drive torque introduced on the drive shaft by muscle force, a second drive torque can also be provided by external force (such as by means of an electric drive motor). At least one drive motor and a driven shaft are coupled to each other via a transmission, so that the torque attributed to the first and second drive torques can be transmitted to the wheel, usually to the rear wheel of the electric bicycle, via the driven shaft to be coupled to the wheel of the electric bicycle.

[0003] The transmission ratio between a drive train with at least one electric drive motor and a wheel to be driven can be changed via an electronically controllable switching device (which is known, for example, from DE 10 2020 001 016 A1). The basic difficulty here is that, on the one hand, the automated switching process for changing the transmission ratio should only be performed when the driving force is applied via pedaling motion without muscle force. On the other hand, the switching process should be performed by a short forward movement of a power transmission link (typically a chain) that connects the drive train to the wheel to be driven in a manner controlled by an electric motor drive. For this purpose, the drive motor runs at a limited motor speed, and the wheel is not driven by the drive motor. Therefore, a free wheel (Freilauf) is provided on the wheel to be driven, and during the switching process, the free wheel should not be in a transmission state, in which the driving force generated by at least one drive motor is transmitted to the wheel to be driven. On the contrary, the free wheel should remain in a disconnected state, in which the drive train is disconnected from the wheel, so that the driving force generated by the motor drive is not transmitted to the wheel. During the switching process, the freewheel should therefore remain disengaged and thus in a decoupled state, for example by keeping the freewheel disengaged from the motor's perspective in such a way that the resulting speed of the pinion driven by the power transmission element is lower than the speed of the rear wheels.

[0004] During the switching process, it is relatively complex to detect the state of the freewheel directly by means of sensors. In principle, it is also conceivable to carry out a simple regulation of the motor speed and the rear wheel pinion speed, in which a limited motor speed is predetermined, which is significantly reduced, for example by 50%, compared to the speed calculated from the rear wheel speed and the switching ratio. However, if an error occurs when measuring the rear wheel speed by means of the speed sensor, or if the adopted switching ratio is incorrect, then in such an error case, a motor speed that is too high for the switching process may occur. Alternatively, it is also conceivable to provide an additional speed sensor for the wheel to be driven in order to ensure that no wheel acceleration occurs during the switching process (even in the event of an error). However, this additional speed sensor, which may need to be provided in addition to the speed sensor that is provided anyway for determining the transmission ratio, entails considerable additional costs. Summary of the invention

[0005] Against this background, the object of the proposed solution is to provide a drive system with the possibility of electronically controlled change of the transmission ratio, in which the switching process for changing the transmission ratio can be carried out and monitored in a simple manner.

[0006] To this end, a drive system for an electric bicycle is proposed, wherein, for changing the transmission ratio, an electronic control unit of the drive system is configured to perform a switching process, wherein the rotational speed of at least one drive motor is predetermined, in particular adjusted, via the electronic control unit, and the at least one drive motor can be operated with a variable motor current via the electronic control unit. The electronic control unit is also configured to interrupt the switching process if an interruption criterion exists, indicating that the freewheel is in the transmission state, and to evaluate the profile of the rotational speed of the at least one drive motor and / or the profile of the motor current in order to detect the presence of the interruption criterion.

[0007] The basic idea of ​​the proposed solution is therefore to interrupt an electronically controlled switching process, which must be carried out when the electric bicycle is rolling without pedaling movement in order to change the transmission ratio between the drive train and the drivable wheel, if the freewheel of the wheel is in the closed state or is closed, and thus the drive force of the drive motor is transmitted to the wheel, which in turn leads to an undesired acceleration of the wheel. In this case, the state of the freewheel is detected indirectly, more precisely via the change curve of the (motor) speed of at least one drive motor and / or the change curve of the motor current, and therefore no additional sensor device is required for this purpose. Therefore, in the proposed solution, after the switching process is triggered, the state of the freewheel is inferred based on the (time) change curve of the speed of at least one drive motor and / or the (time) change curve of the motor current, depending on whether the switching process triggered by this state is either executed or terminated or interrupted.

[0008] Here, in principle, the switching process can be automatically triggered in a manner known per se. For example, in a corresponding embodiment variant, the triggering and thus the start of the switching process depends on the fact that there is currently no driving force generated by muscle force operation, and therefore the pedals of the electric bicycle mounted on the middle shaft rod in a relatively rotationally fixed manner are not rotating. Then, the target speed of the drive motor predetermined for executing the switching process is calculated and predetermined by the electronic control unit based on the driving speed (for example, determined via the sensor signal of the speed sensor arranged on the wheel to be driven) and based on the transmission ratio between the currently adjusted drive system and the wheel to be driven. Therefore, the electronic control unit can be configured in particular to determine the target speed (to which at least one drive motor is to be accelerated during the switching process) based on the sensor signal representing the current driving speed of the electric bicycle and the current (i.e., before the start of the switching process) adjusted transmission ratio. After the switching process is started, the drive motor should only put the power transmission link of the drive system into motion when the free wheel is disconnected, so as to change at least one gear in an electronically controlled manner via the switching device, for example, by operating the derailer of the switching device. When the free wheel is closed, the switching process should be automatically interrupted.

[0009] In one embodiment variant, the electronic control unit is configured to detect the presence of an interruption criterion (and thus the possibility that the freewheel is in a closed state) based on the variation curve of the rotational speed of at least one drive motor and / or the variation curve of the motor current. This includes, in particular, detecting the presence of an interruption criterion based entirely on one or more of the mentioned variation curves. For example, the electronic control unit is configured to detect the presence of an interruption criterion based solely on the variation curve of the motor current or in combination with the variation curve of the rotational speed of at least one drive motor. It is thus recognized that the state of the freewheel on the driven wheel can be inferred solely from the variation curve of the motor current or in combination with the variation curve of the detected (motor) rotational speed. Therefore, it is possible to infer whether the freewheel is in an open or closed state based on the detected variation curve via an evaluation logic implemented, for example, by software in the control electronics, without requiring an additional sensor device on the freewheel itself for this purpose.

[0010] For example, it is provided that for the disconnected state of the freewheel during the switching process and thus for the open state of the freewheel, at least one reference speed profile for the time development of the speed and / or at least one reference current value profile for the time development of the motor current of at least one drive motor is stored in the memory of the electronic control unit. The electronic control unit can then be configured to detect the presence of an interruption criterion when a detected deviation of one or more of the measured values ​​from the reference speed profile and / or the reference current value profile exceeds a tolerance threshold. Thus, if the freewheel is in the open state and remains in the open state during the switching process and is therefore in the disconnected state, a characteristic reference speed profile and / or a characteristic reference current value profile will result. If a deviation from one or more of these stored profiles is detected during the switching process, it can be inferred that the freewheel is not (any longer) in the open state but in the closed state.

[0011] In order to detect whether an interruption criterion exists and thus whether the freewheel is possibly in a transmission state or has already changed into such a transmission state, the electronic control unit can be configured, for example, to check during the switching process:

[0012] - Is the speed increased until the predetermined target speed is reached while the motor current is increased to the maximum current value, and is the motor current decreased after the target speed is reached and maintained (the first check scenario), or

[0013] - Whether the speed is increased to the target speed when the motor current is increased to the target current value, and the target speed is maintained constant when the target current value is maintained below the maximum current value (second check scenario).

[0014] The first-mentioned check corresponds to a first check scenario, in which the electronic control unit checks whether the motor speed and the motor current develop as set during the acceleration phase of the drive motor for the switching process and in the subsequent switching phase, and it can therefore be assumed that the freewheel is in the disengaged state. Thus, the increase and the final decrease in the motor current below the predetermined maximum current value, while at the same time the speed of the drive motor is accelerated to the desired target speed and maintained, will lead to the conclusion that the freewheel is and remains disengaged. If the target speed is maintained, the switching phase, during which the transmission ratio is changed via the switching device, can then be ended.

[0015] In the above-mentioned check for the presence of an interruption criterion according to the second check scenario, it is assumed that during the acceleration phase, the speed initially increases to the target speed, while the motor current does not reach the maximum current value, but only increases to a target current value below the maximum current value. Then, with the freewheel disconnected, the target speed of the drive motor is maintained, while the motor current remains unchanged at the target current value. If a corresponding profile of the motor current and the speed of at least one drive motor is detected, it can be inferred that the freewheel is disconnected and the switching process is terminated without interruption.

[0016] In principle, the above-mentioned maximum current value can be a limit value for the motor current stored in the electronic control unit, which limit value can be predetermined by the control implemented using the control unit as the maximum value of the motor current for accelerating the at least one drive motor to the target speed. Thus, the maximum current value can be a basic (unterlagert) current target value, which is limited to a relatively small value that is sufficient to fully accelerate the drive motor in no-load operation. Therefore, when accelerating the drive motor, the control (possibly) requires that the maximum current be limited to a maximum current corresponding to the maximum current value.

[0017] By having the electronic control unit check in a corresponding embodiment whether the motor current and / or the speed of at least one drive motor develops as predefined during the switching process, it can be concluded that the freewheel is closed and therefore that an interruption criterion exists based on deviations from the corresponding reference profile. Thus, for example, closing the freewheel after reaching the target speed and the motor current has dropped will lead to an increase in the motor current again in the direction of the maximum current value. After the acceleration phase is over, a temporary drop in the speed profile can be observed again due to the closing of the freewheel. The evaluation logic of the electronic control unit is therefore set up here to detect whether a change from the decoupling state to the transmission state has occurred at the freewheel of the driven wheel, and therefore an undesired transmission of the drive torque from the drive motor to the wheel to be driven has occurred during the switching process.

[0018] Alternatively or additionally, in order to detect whether an interruption criterion exists (i.e., to detect the presence of an interruption criterion), the electronic control unit can check during the switching process whether the rotational speed of at least one drive motor reaches a predetermined target rotational speed within a predefined check time period. This includes checking whether a preset acceleration of the drive motor is achieved and / or whether the rotational speed of at least one drive motor (e.g., a rotor of the drive motor) cannot be further increased to the target rotational speed. If this is the case and can be detected electronically based on the change curve of the motor rotational speed, it can be assumed that the freewheel is in the closed state and, accordingly, the driving force generated by the drive motor is transmitted to the wheel to be driven. Therefore, the interruption criterion is met and the switching process is interrupted.

[0019] In principle, interrupting the switching process by the electronic control unit can include reducing the speed of at least one drive motor to an interruption value. Alternatively, when interrupting the switching process, at least one drive motor can be controlled to change to a fault state or can be deactivated and thus switched off.

[0020] The proposed solution also includes an electric bicycle having an embodiment variant of the proposed drive system.

[0021] The proposed solution also includes a method for operating a drive system on an electric bicycle. The drive system for an electric bicycle comprises a drive train with at least one electric drive motor for applying a driving force to drive a wheel of the electric bicycle, and an (electronically controllable) switching device for changing the transmission ratio between the drive train and the wheel to be driven. A freewheel is arranged on the wheel to be driven, which in a transmission state transmits the driving force generated by the at least one drive motor to the wheel, and in a decoupling state of the freewheel, the drive train is decoupled from the wheel. In order to change the transmission ratio, a switching process is performed, in which the rotation speed of the at least one drive motor is predetermined in an electronically controlled manner and the at least one drive motor is operated with a variable motor current. The switching process is interrupted when an interruption criterion is present, indicating that the freewheel is in the transmission state, wherein the change profile of the rotation speed of the at least one drive motor and / or the change profile of the motor current is evaluated in order to detect the presence of the interruption criterion.

[0022] The proposed operating method can be implemented in particular by means of the proposed drive system embodiment variant. Therefore, the features and advantages of the proposed drive system embodiment variant explained above and below also apply to the proposed operating method embodiment variant, and vice versa. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The figures illustrate by way of example possible embodiments of the presented solution.

[0024] in:

[0025] Figure 1 An electric bicycle is shown which has an embodiment variant of the proposed drive system;

[0026] Figure 2 Shown in use Figure 1 A reference value variation curve of the motor current during a switching process performed by the drive system in an electronically controlled manner;

[0027] Figure 3 shows further reference curves of the motor current and the motor speed during the switching process;

[0028] Figure 4 The flowchart diagram shows a variant implementation of the proposed operating method. DETAILED DESCRIPTION

[0029] Figure 1 An electric bicycle 1 is shown by way of example, which has a frame 10 on which a front wheel 11 and a rear wheel 12 are rotatably supported. The rear wheel 12 can be driven via a drive system having a drive train A in a manner supported by an electric motor. To this end, the drive train A has at least one electric drive motor in the form of an electric motor M. Here, the drive torque generated by the electric motor M can also be transmitted to the rear wheel 12 by means of a power transmission link (for example, in the form of a chain or belt) (in addition to the drive torque applied by muscle force via the drive shaft / middle shaft rod T, if necessary). In this way, not only the first drive torque applied by the rider of the electric bicycle 1 via the pedals connected to the middle shaft rod T can be transmitted to the rear wheel 12. More precisely, the rear wheel 12 can also be driven via the second drive torque generated by the electric motor M.

[0030] The driving power applied by the electric motor M is hereby predetermined via the electronic control unit SE of the drive unit A. The electronic control unit SE can, for example, determine the driving power to be applied by the electric motor drive to support the rider of the electric bicycle 1 when pedaling, depending on the support level selected by the user. The corresponding support level is then predetermined, for example, via the operating unit 2. Figure 1 In the electric bicycle 1 , the operating unit 2 coupled to the control unit SE is arranged on the handlebar of the electric bicycle 1 and is equipped with a display screen 20 .

[0031] In order to adjust the transmission ratio and thus the ratio of the (motor) rotation speed of the electric motor M to the rotation speed of the rear wheel 12 to be driven when necessary, the electric bicycle 1 also has a switching device 14. The switching device 14 can be controlled by the electronic control unit SE, so that it is possible to switch between different sprockets of the chain 13, for example, by means of a derailer of the switching device 14 on the hub of the rear wheel 12. During the switching process for changing the transmission ratio triggered by the electronic control unit SE, the chain 13 moves forward briefly, for which the electric motor M runs at a defined target speed. At this time, the free wheel 15 located in the area of ​​the hub of the rear wheel 12 must be in a disconnected state, so that the driving force generated by the electric motor M is not transmitted to the rear wheel 12. Therefore, even when there is no pedal movement on the middle axle rod T, the electric bicycle 1 in the forward movement should also implement an automated switching process. Accordingly, the electric bicycle 1 will not accelerate due to the switching process.

[0032] The proposed solution now allows a plausibility check and thus monitoring of the switching process without the need for additional sensors. Thus, the electronic control unit SE is coupled to the speed sensor 21 of the rear wheel 12 in order to infer, based on the wheel speed measured by the speed sensor 21 and based on the transmission ratio between the rotational speed of the electric motor M currently set and the rotational speed of the rear wheel 12, that a change in the transmission ratio and the target rotational speed of the electric motor M set for this purpose is required during the execution of the switching process, and automatically trigger such a switching process. However, the switching process itself is monitored without the need to learn additional sensor signals, in particular without the need to learn additional speed sensors, in such a way that during the switching process, only the temporal development of the motor current I of the electric motor M and the temporal development of its rotational speed n are monitored via the electronic control unit SE.

[0033] In the present case, for this purpose, regulation is performed via the electronic control unit SE for executing the switching process, during which the electric motor M is regulated to a constant target speed n by means of the electronic control unit. 目标 In addition, the current target value of the motor current as the basis is limited to a relatively small value as the current value maximum amount I 最大 (For example, limited to 2A). This current value is sufficient to fully accelerate the electric motor M when the free wheel 15 is in the disconnected state. Therefore, when the electric motor M is accelerating, the regulator of the electronic control unit SE can require that the motor current Imax be limited to the maximum current value Imax. 最大 (Of course, a current lower than the maximum current may also be required during acceleration.) If the freewheel 15 is in the closed state during the switching process, the motor current I will therefore be adjusted to a current value lower than the maximum current value I 最大 The current value level, and make the electric motor M reach the predetermined target speed n目标 .

[0034] This aspect combines Figure 2 Here, the motor current I is plotted against the time t. During the switching process, the motor current I increases to a maximum current value I in a first acceleration phase until the time t1. 最大 If the electric motor M then rotates at the target speed n 目标 The motor current I then characteristically decreases again from time t2 and remains at a current value clearly at the maximum value I 最大 Then, the switching process ends at time point t3.

[0035] Therefore, during the switching process, if the freewheel 15 is in the disconnected state and is therefore in the decoupled state, the motor current I required by the regulator of the electronic control unit SE must be maintained at the maximum current value I 最大 In contrast, if the free wheel 15 is in the closed state, then when the target speed n is reached, 目标 After that, the required motor current I will move towards the maximum current value I 最大 . Thus, even after or before time t1, with the freewheel 15 in the closed state, a brief drop in the speed n can be seen. Typically, the drop in the speed n occurs before this, since a drop in the speed b during the control process leads to an increase in the required current. If the freewheel 15 is already in the acceleration phase, i.e. closed before time t1, a brief overshoot of the speed n of the electric motor M can be observed.

[0036] Based on the time profile of the motor current I of the electric motor M, possibly in combination with the time profile of the rotational speed n of the electric motor M, it can therefore be concluded whether the freewheel 15 is open or closed, taking into account the control implemented in the electronic control unit.

[0037] Since when the freewheel 15 is closed, the electric motor M still introduces driving force to the rear wheel 12, although this situation should be excluded during the switching period, the switching process is interrupted in an electronically controlled manner when the freewheel 15 is detected to be closed. Therefore, if a deviation from the stored reference value curve for the motor current and / or the motor speed is detected that exceeds the tolerance threshold for measuring accuracy, it indicates that the freewheel 15 is in the closed state, and an interruption criterion exists. The electronic control unit SE will interrupt the switching process in response to this interruption criterion and significantly reduce the speed of the electric motor M or even switch off the electric motor M. In addition, via the interruption criterion, it can also be signaled that the speed measurement of the electric bicycle 1 is incorrect or the switching ratio used is incorrect, so that the drive system can enter a fault state.

[0038] Figure 3 The representative change curve of the motor current I and the speed n of the electric motor M during the switching process is described in FIG. 1 , and the electronic control unit SE can also consider using the change curve to check whether the switching process is carried out normally. Here, the speed n reaches the predetermined motor speed n at time t2. 目标 , but the motor current I does not increase to the limit value or the maximum current value I 最大 On the contrary, the motor current I only increases to a value below the maximum current value I 最大 The target current value I 目标 The required motor current I will then remain constant at this value, while the speed n will remain at the target speed n 目标 If the switching process is completed, the motor current I and the speed n both decrease (see Figure 3 Based on the detected curves of the motor current I and the (motor) speed n of the electric motor M, it can be indirectly inferred that the freewheel 15 is in the closed state, which in turn necessarily leads to the interruption of the switching process.

[0039] During the acceleration period of the electric motor M or after the acceleration phase, if the freewheel 15 is in the closed state, the same Figure 3 This includes, for example, the failure of the speed n to increase to the target speed n 目标 , or the target speed n cannot be reached at all within the specified inspection time period 目标 .

[0040] In an exemplary embodiment variant, in the case of the electric bicycle 1, when the pedals are at rest, a switching pulse for the electronically controllable switching device 14 is calculated, for example, by the electronic control unit SE based on the current switching ratio and the wheel speed measured via the speed sensor 21. Then, within a defined switching time (for example within 0.5 to 1.5 seconds), the maximum current value I is used to determine the switching pulse. 最大 (e.g. 1A to 3A) is the target speed n calculated and thus predetermined. 目标The switching pulse is realized via a speed regulator implemented in the electronic control unit SE. The speed of the electric motor M should be constantly predetermined during the switching time. The speed of the electric motor M can be designed, for example, so that the speed obtained at the rear wheel pinion based on the speed of the electric motor M is equivalent to 50% of the speed of the rear wheel. The freewheel is thus safely disconnected. During the switching time and when the pedals are at rest, it is not allowed to actively drive the rear wheel 12 by the electric motor M. With the proposed drive system, it is now possible to detect that the freewheel 14 on the rear wheel 12 is in a disconnected state during the switching process and remains in a disconnected state, and therefore no driving of the rear wheel 12 due to the operation of the electric motor M occurs during the switching process.

[0041] As described above, in this case, in a first step during the acceleration phase, the speed n can be monitored via the current value maximum I 最大 Predetermined minimum acceleration to target speed n 目标 If the acceleration is below the permissible acceleration, it is inferred that the freewheel 15 is closed and the switching process is interrupted. If the target speed n is not reached within a defined check period, 目标 , the freewheel 15 is considered to be closed and the switching process must therefore be interrupted.

[0042] On the other hand, if the speed regulator is optimally adjusted, current values ​​below the maximum permissible value I 最大 The motor current I, and then reaches the target speed n 目标 If the motor current I reaches the target speed n 目标 If the speed n continues to increase, in particular while it is decreasing or remaining constant, it is inferred that the freewheel 15 is closed and the switching process must be interrupted.

[0043] Similarly, when the motor current I reaches the target speed n during the switching phase (from time t1 to time t3), 目标 Then, the current value reaches the maximum value I 最大 When the free wheel 15 is lifted in the direction of , it is inferred that the free wheel 15 is closed.

[0044] Figure 4 The flowchart diagram also illustrates the above-mentioned individual steps of the corresponding operating method for the drive system. Thus, the switching process is first automatically started and thus triggered in an electronically controlled manner (step 401). In response to this, the motor speed n is adjusted toward the target speed value n calculated for the switching process via the regulation of the electronic control unit SE. 目标direction (step 402). In order to monitor the state of the freewheel 15 and exclude the transmission of driving force to the rear wheel 12 via the actuation of the electric motor M, the speed change curve and the motor current change curve of the electric motor M are monitored (step 403). Based on the saved reference change curve, the presence of an interruption criterion is checked, which indicates that the freewheel 15 is in the closed state (step 404). If the presence of the interruption criterion is not detected during the switching process and the freewheel 15 therefore remains in the open state, the switching process is completed as specified (step 405). In contrast, if the presence of the interruption criterion is detected, the switching process is interrupted by electronic control (step 406). The corresponding interruption then causes the speed of the electric motor M to be significantly reduced to the interruption value, or reduced until the electric motor M is turned off (step 407).

[0045] The proposed solution provides a possibility to detect, independently of the speed sensor, that the freewheel 15 is not closed and therefore the switching process must be interrupted, which helps to increase the safety and reliability of the drive system, in particular when carrying out the switching process, without incurring additional costs for expanding the sensor components.

[0046] Reference numerals list

[0047] 1. Electric bike

[0048] 10 Frame

[0049] 11 front wheels

[0050] 12 rear wheels

[0051] 13 Power transmission link

[0052] 14 Switching device

[0053] 15 Freewheel

[0054] 2 control unit

[0055] 20 Display

[0056] 21 Speed ​​sensor

[0057] A drive system

[0058] M Electric Motor

[0059] SE Electronic Control Unit

[0060] T middle shaft / drive shaft

Claims

1. A drive system for an electric bicycle (1), the drive system comprising - a drive train (A) having at least one electric drive motor (M) for applying a driving force to drive a wheel (12) of the electric bicycle (1), - a switching device (15) for changing the transmission ratio between the drive train (A) and the wheels (12) to be driven, and - an electronic control unit (SE) for controlling the at least one drive motor (M) and the switching device (15), in, A free wheel (14) is provided on the wheel (12) to be driven, wherein the free wheel transmits the driving force generated by the at least one drive motor (M) to the wheel (12) in a transmission state, and in a disconnected state of the free wheel (14), the drive system (A) is disconnected from the wheel (12), and wherein, in order to change the transmission ratio, the electronic control unit (SE) is configured to carry out a switching process, wherein the rotational speed (n) of the at least one drive motor (M) is predetermined via the electronic control unit (SE) and the at least one drive motor (M) can be operated with a variable motor current (I) via the electronic control unit (SE), It is characterized in that The electronic control unit (SE) is configured to interrupt the switching process if an interruption criterion is present, which indicates a transmission state of the freewheel (15), and to evaluate the profile of the rotational speed (n) and / or the profile of the motor current (I) of the at least one drive motor (M) in order to detect the presence of the interruption criterion.

2. The drive system according to claim 1, characterized in that: The electronic control unit (SE) is configured to detect the presence of the interruption criterion based on a profile of a rotational speed (n) and / or a profile of a motor current (I) of the at least one drive motor (M).

3. The drive system according to claim 2, characterized in that: The electronic control unit (SE) is configured to detect the presence of the interruption criterion based solely on the profile of the motor current (I) or in combination with the profile of the rotational speed (n) of the at least one drive motor (M).

4. The drive system according to any one of claims 1 to 3, characterized in that: For the decoupled state of the freewheel (15) during the switching process, at least one reference speed variation curve for the time development of the speed (n) and / or at least one reference current value variation curve for the time development of the motor current (I) of the at least one drive motor (M) is stored in a memory of the electronic control unit (SE), and the electronic control unit (SE) is configured to detect the presence of the interruption criterion when a deviation of one or more acquired measured values ​​from the reference speed variation curve and / or the reference current value variation curve exceeds a tolerance threshold.

5. The drive system according to claim 4, characterized in that: In order to detect whether the interruption criterion exists, the electronic control unit (SE) is configured to check during the switching process: - Is the current increased to the maximum value (I 最大 ) of the motor current (I), the speed (n) is increased until it reaches a predetermined target speed (n 目标 ), and whether the target speed (n 目标 ), the motor current (I) decreases, or - Is the current level increased to the target value (I 目标 ) of the motor current (I), the rotation speed (n) is increased to the target rotation speed (n 目标 ), and whether the target current value (I 目标 ) maintains a current value below the maximum amount (I 最大 ), the target speed (n 目标 ) remain unchanged.

6. The drive system according to claim 5, characterized in that: The maximum current value (I 最大 ) is a limit value for the motor current (I) stored in the electronic control unit (SE), which limit value can be predetermined by a regulation using the control unit (SE) as a maximum value for the motor current (I) for accelerating the at least one drive motor (M) to the target speed (n 目标 ).

7. A drive system according to any one of the preceding claims, characterised in that In order to detect whether an interruption criterion exists, the electronic control unit (SE) is configured to check during the switching process whether the rotational speed (n) of the at least one drive motor (M) reaches a predetermined target rotational speed (n) within a predefined check time period. 目标 ).

8. A drive system according to any one of the preceding claims, characterised in that The electronic control unit (SE) is configured to reduce the rotational speed (n) of the at least one drive motor (M) to an interruption value when the switching process is interrupted, or to control the at least one drive motor (M) to change to a fault state or to deactivate the at least one drive motor.

9. Drive system according to any one of the preceding claims, characterized in that The electronic control unit (SE) is configured to determine a target speed (n) to which the at least one drive motor (M) is to be accelerated during the switching process based on a sensor signal representing the current travel speed of the electric bicycle (1) and a currently set transmission ratio. 目标 ).

10. An electric bicycle having a drive system according to any one of the preceding claims.

11. A method for operating a drive system on an electric bicycle (1), wherein: The drive system comprises: - a drive train (A) having at least one electric drive motor (M) for applying a driving force to drive the wheels (12) of the electric bicycle (1), and - a switching device (15) for changing the transmission ratio between the drive train (A) and the wheels (12) to be driven, A free wheel (14) is provided on the wheel (12) to be driven, and in a transmission state, the free wheel transmits the driving force generated by the at least one driving motor (M) to the wheel (12), and in a disconnected state of the free wheel (14), the drive system (A) is disconnected from the wheel (12), and wherein a switching process is performed in order to change the transmission ratio, in which the speed (n) of the at least one drive motor (M) is predetermined in an electronically controlled manner and the at least one drive motor (M) is operated with a variable motor current (I), It is characterized in that The switching process is interrupted when an interruption criterion is present, which indicates that the freewheel (15) is in the transmission state, wherein the profile of the rotational speed (n) and / or the profile of the motor current (I) of the at least one drive motor (M) is evaluated in order to detect the presence of the interruption criterion.

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