Method and device for avoiding overload when driving electric bicycle

Abstract

The invention relates to a method for avoiding overload in a drive unit of an electric bicycle which is driven in combination by means of a manual pedaling crank (2) and an electric motor (6), in which a torque (MS) determined via the pedaling crank (2) corresponding to the driver's expectation is determined by a driving controller (11), a downstream motor controller (12) takes into account the torque for generating a motor assist energy by means of a motor control device (13) of the motor (6), said motor assist energy being generated by means of the motor control device (13) of the motor (6), said motor assist energy being generated if an overload situation is detected from a curve of at least one measured or estimated variable # imgabs0 #, said overload situation being detected from a curve of at least one measured or estimated variable # imgabs0 #. If the driver's desired torque (MS) is detected, the torque (MS) corresponding to the driver's desired torque is adjusted by a load torque controller (15) in order to generate a limited torque (MSlim), which is supplied as an adjusted setpoint to the motor controller (12) in order to prevent overload damage to the drive train components.

Description

Technical Field

[0001] The invention relates to a method and a device for avoiding overload in an electric bicycle, which is driven by means of at least one manual pedal crank and at least one electric motor as a combined drive unit, wherein a torque M which is determined by a traction controller and corresponds to a driver's desire via the pedal crank is determined by a traction controller. S A motor controller connected downstream takes this torque into account in order to generate motor assistance energy by the electric motor.

[0002] The application field of the present invention extends to the drive unit of an electric bicycle, in particular to an electric power-assisted bicycle. Here, the drive generated by the muscle force is supported by an electric motor for providing motor auxiliary energy via a manual pedal crank. Background Art

[0003] According to the known prior art, in drive units for electric bicycles, plastic gears are usually used in transmission stages with large transmission ratios. Although this is conducive to the desired lightweight construction and low-noise operation, components of this type are subject to the risk of tooth fracture as a consequence of overload. In order to keep the drive forces acting on the plastic tooth flanks below a critical limit, the motor torque is usually limited accordingly within the scope of dimensioning the drive unit.

[0004] DE 10 2019 113 348 B4 discloses a method for adjusting a power support device for an electric bicycle. The power support device comprises a control unit and an electric motor. The adjustment method comprises the step of receiving sensor data from a torque sensor via a control unit, wherein the sensor data indicates a torque input of a torque generated by a user. Next, it is checked whether the torque input of the rider is less than the required motor torque of the motor. Then, it is determined by the control unit whether the calibrated motor decay time (Motorabfallzeit) of the motor is less than the scaled third frequency time of the third frequency speed of the rider. If the torque input is less than the required motor torque and the calibrated motor decay time is less than the scaled third frequency time, a torque decay factor is determined based on the third frequency speed. Next, the adjusted, required motor torque is determined by applying the torque decay factor to the required motor torque. Next, the motor is controlled so as to output a modulated motor torque according to the adjusted, required motor torque.

[0005] In particular, small electric motors can only generate low torques at similar currents in the context of the applications that are of interest here. Therefore, the drive trains of so-called mid-range electric motors usually have a transmission with a large transmission ratio in order to provide a high torque in a small installation space. However, this results in the drive train being torsionally weak and, in the case of excitation, for example by rapid changes in the torque of the motor or by switching processes or by other periodic excitations of the motor and repeated effects in the transmission components, generating poorly damped oscillations. These oscillations can lead to a number of uncomfortable symptoms for the rider, such as vibrations and knocks, modulation of the noise of the motor or the transmission or even the interesting dynamic overloads here, which in extreme cases can lead to the mentioned tooth fractures. Summary of the invention

[0006] The object of the present invention is to protect a drive unit of an electric bicycle from critical overload situations by means of simple technical means and also to ensure damping of the drive train.

[0007] This object is achieved by a method according to the invention for avoiding overloading in a drive unit of an electric bicycle, a device for carrying out the method, and a drive unit for an electric bicycle.

[0008] The present invention relates to a method for avoiding overload in a drive unit of an electric bicycle, wherein the electric bicycle is driven in combination with a manual pedal crank and an electric motor, wherein a torque corresponding to a driver's desire and obtained via the pedal crank is determined by a travel controller, and a motor controller connected downstream takes this torque into account for generating motor auxiliary energy via a motor control device of the electric motor, wherein if the presence / imminent occurrence of an overload is detected from a variation curve of at least one measured or estimated variable, the torque corresponding to the driver's desire is adjusted by a load torque controller in order to generate a limited torque, which is provided to the motor controller as an adjusted setpoint value in order to prevent overload damage to drive train components.

[0009] The invention includes the following method teaching: before the torque corresponding to the driver's request is used as a setpoint value by the motor controller, the torque M corresponding to the driver's request is adjusted by the load torque controller. S , more precisely in such a way that if an overload situation is detected from the course of at least one characteristic measured or estimated variable, a limited torque M is generated. S_lim This limited torque is provided to the motor controller as an adjusted setpoint value in order to prevent overload damage to the drive train components.

[0010] In other words, the control method according to the invention uses a load torque control instead of a conventional control of the preferred air gap torque of the electric motor. For this purpose, the torque M determined by the driving controller or driving control and corresponding to the driver's request S Instead of being directly input as a setpoint value into the motor controller of the electric motor, the load torque control device according to the invention is first adjusted in such a way that the torque is limited in the overload situation. The overload situation is determined based on representative measured values ​​and estimated values, which are explained in detail below.

[0011] The advantage of the control method according to the invention is in particular that the load torque regulator can dynamically adjust the load peak share of the inertia force of the rotor of the electric motor. Load peaks that could otherwise lead to tooth fractures on the gears of the drive unit, which are preferably made of plastic, are thus prevented. In addition, the dynamics of the drive train are compensated by the load torque control device. By predetermining the adjusted load torque, what the rider feels on the auxiliary energy support device can be adjusted more comfortably and more quickly. In addition, the closed control loop of the load torque control device increases the damping of the drive train system, so that vibrations and impacts are reduced at the same time.

[0012] The advantages associated with the solution according to the invention can be explained in more detail with reference to the following exemplary driving situations:

[0013] In conventional drive units, it can happen that the rider kicks the pedal backwards with great force during idling without the driver and thus pulls the electric motor in the reverse rotation direction. In conventional transmissions of the drive unit, this can lead to tooth fracture. The load torque control device according to the invention avoids this type of overload situation.

[0014] In other driving situations, for example if the rear structure of a so-called full-suspension mountain bike pops out, or the rear wheel slips and then suddenly reattaches, or the chain shift mechanism switches to the next gear and the chain is unloaded for a short time and then suddenly becomes tensioned again as soon as it is in the next pinion, the chain drive arranged on the output side of the drive unit pulls the sprocket and thus the electric motor backwards. The solution according to the invention avoids the resulting overloading of the drive unit.

[0015] Furthermore, it can happen that the switching process excites the drive train into vibrations, which leads to unpleasant acoustic modulation of the drive noise. The load torque control device according to the invention damps vibrations of this type.

[0016] According to a measure further improving the invention, after the presence of an overload is detected, the motor controller switches from an initial vibration damping control strategy to a load torque reduction control strategy by correspondingly changing the controller characteristic. This means that during a usage period in which no overload is detected, the load torque controller detects vibrations occurring in the drive train in a basic operating mode in order to damp these vibrations by changing the torque.

[0017] Characteristic measured or estimated variables S for detecting the vibrations to be damped and the overload situations that occur are selected from the set of variables occurring in the drive train. W , the parameter group includes: the motor phase current and the rotor position angle of the electric motor, and the parameters that can be estimated therefrom, such as, in particular, the air gap torque, the load torque, the rotor speed, the rotor angular acceleration; the driver's torque or pedal force manually applied via the pedal crank, the driver's pedaling frequency; the bearing force in the rotary bearing device of the drive unit; the switching signal of the electronic chain switching device (elektronische Kettenschaltung); the acceleration rate and rotation rate of the drive unit or the continued drive system; the wheel speed of the electric bicycle; and the chain tension.

[0018] Preferably, the sprocket torque of the sprocket on the output side of the drive train is output via the driving controller as the torque M corresponding to the driver's request. S .

[0019] Likewise, preferably, the air gap torque of the motor is output as the limited torque M via the load torque regulator. S_lim The drive torque of the electric motor is adjusted as a function of the air gap torque in such a way that an overload situation is avoided.

[0020] According to a preferred embodiment of the invention, the load torque controller is supplied with sensor signals as measurement signals for drive train damping and / or for overload detection, which are signal-processed by the load torque controller in a manner derived from the above-mentioned measured or estimated variables of the drive unit.

[0021] The solution according to the invention is particularly suitable for drive units which are designed to be free of freewheeling in terms of the hand pedal crank, because in particular when pedaling backwards, overload peaks can occur, as described above.

[0022] Preferably, a drive unit suitable for implementing the present invention has a speed change transmission arranged between the intermediate electric motor and the driven shaft, and a sprocket arranged on the driven shaft, the sprocket being used to transmit drive energy to the rear wheels of the electric vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Further measures for improving the invention are described in more detail below together with the description of preferred embodiments of the invention according to the accompanying drawings. The accompanying drawings show:

[0024] Figure 1 shows a schematic side view of a drive unit for an electric bicycle,

[0025] Figure 2 A block diagram showing the driving control and motor control of an electric bicycle according to the prior art, and

[0026] Figure 3 A block diagram of the driving control and motor control of the electric bicycle according to the present invention is shown. DETAILED DESCRIPTION

[0027] according to Figure 1 The drive unit of the electric bicycle (not shown in further detail here) is essentially composed of a manual pedal crank 2, which is rotatably supported on a drive housing 1 and receives the driving energy of the rider. The crankshaft 3 of the pedal crank 2 is used to transmit the torque to the driven shaft 4 without idling, which is designed as a hollow shaft and through which the crankshaft 3 extends coaxially to a sprocket 5 on the driven side. The further transmission of the driving energy to the rear wheel (not shown in further detail here) of the electric bicycle is achieved via the sprocket 5 on the driven side.

[0028] In order to additionally load the motor auxiliary energy, an electric motor 6 is also installed in the drive housing 1. The motor pinion 7 of the electric motor 6 forms a spur gear stage for an integrated transmission device together with the gear 8, which is used for the reduction transmission ( The gear 8 is coupled to the output shaft 4 of the drive unit 1 via the motor idler assembly 9 .

[0029] The electromechanical drive unit 1 is controlled by an electronic control unit 10 , the function of which is described below:

[0030] Figure 2 A conventional control device according to the prior art is shown. On the input side, the driving controller 11 is supplied with the driver torque applied to the pedal crank and corresponding to the driver's desire and the associated driver pedaling frequency. From this, the driving controller 11 determines the corresponding torque M to be applied. S The downstream motor regulator 12 takes into account the torque M S , for generating motor auxiliary energy by means of the motor control device 13. In this case, the motor controller 12 takes into account the rotor position angle α and the phase current I of the motor winding in a known manner in order to predetermine the corresponding phase voltage UP , used to generate the desired motor torque M of the motor control unit 13 M The electric motor torque M generated by loading the drive system 14 of the electric bicycle M .

[0031] Different from the prior art described above, Figure 3 , wherein the differences from the prior art are described below, while the above description applies correspondingly to the components with the same names.

[0032] According to the invention, if the load pressure torque regulator 15 detects the presence of an overload from the curve of the supplied measured and estimated variables, the load torque regulator 15 connected downstream of the driving controller 11 adjusts the torque M corresponding to the driver's request. S In this embodiment, the sensor signal S AD As a characteristic measured or estimated variable, the sensor signal describes the current vibration behavior from the parameters of the motor control device 13 so as to be used by the load torque control device 15 for drive train damping. In addition, the sensor signal of the parameters of the motor control device 13 is used The sensor signal enables overload detection, for example, in combination with the rotor position angle, a steeply increasing motor phase current pulse can be realized, from which variables such as, in particular, the air gap torque can be estimated in a known manner. Thus, the load torque control device 15 generates a limited torque M by, for example, the aforementioned current pulse when an overload situation is detected. S_lim In the present case, this limited torque is in the form of an air-gap torque which is provided to the motor controller 12 as a set setpoint value in order to prevent overload damage to the drive train components.

[0033] The present invention is not limited to the preferred embodiment described above. On the contrary, variations of the preferred embodiment are conceivable, which are all included in the protection scope of the present invention. Thus, for example, it is also possible to obtain other representative measurements or estimated variables for executing the load moment reduction control strategy or vibration damping control strategy according to the present invention.

Claims

1. A method for avoiding overload in a drive unit of an electric bicycle, the electric bicycle being driven in combination by means of a manual pedal crank (2) and an electric motor (6), wherein: The torque (M) which is determined by the driving controller (11) via the pedal crank (2) and corresponds to the driver's desire S ), a motor controller (12) connected downstream takes the torque into account in order to generate motor auxiliary energy via a motor control device (13) of the motor (6), It is characterized in that if from at least one measured or estimated parameter If an overload condition is detected in the change curve of S ) in order to generate a limited torque (M S_lim ), the limited torque is provided to the motor regulator (12) as an adjusted setpoint value to prevent overload damage to the drive train components.

2. The method according to claim 1, It is characterized in that After the presence of an overload situation is detected, the motor controller (12) switches from an initial vibration damping control strategy to a load torque reduction control strategy by correspondingly changing the controller characteristic.

3. The method according to claim 1, It is characterized in that At least one measured or estimated variable which is characteristic at least for the overload situation is selected from the group of variables related to the load moment. The parameter group includes: the motor phase current and rotor position angle of the electric motor, and parameters that can be estimated therefrom, such as, in particular, the air gap torque, the load torque, the rotor speed, the rotor angular acceleration; the driver's torque or pedal force manually applied via the pedal crank, the driver's pedaling frequency; the supporting force in the rotating bearing device of the drive unit; the switching signal of the electronic chain switching device; the acceleration rate and rotation rate of the drive unit or the continued drive system; the wheel speed of the electric bicycle; and the chain tension.

4. The method according to claim 1, It is characterized in that The sprocket torque of the sprocket (5) on the output side of the drive train is outputted via the driving controller (11) as a torque (M) corresponding to the driver's request. S ).

5. The method according to claim 1, It is characterized in that The air gap torque of the electric motor (6) is outputted as a limited torque (M) via the load torque regulator (15). S_lim ), adjusting the driving torque of the electric motor (6) according to the air gap torque.

6. The method according to claim 1, It is characterized in that The load torque regulator (15) is supplied with a sensor signal for overload detection and for drive train damping, the sensor signal being used as a measured or estimated variable of the drive unit ( S AD ) is processed by the signal.

7. A device for preventing overload in a drive unit of an electric bicycle, the electric bicycle having a manual pedal crank (2) and an electric motor (6) as a combined drive, wherein: The driving controller (11) determines a torque (M) which is determined via the pedal crank (2) and corresponds to the driver's request. S ), a motor controller (12) connected downstream takes the torque into account in order to generate motor auxiliary energy via a motor control device (13) of the motor (6), is characterized in that if the load torque regulator is based on at least one measured or estimated variable ( S AD ) changes, the load torque regulator (15) adjusts the rated torque (M) corresponding to the driver's desired torque. S ) in order to generate a limited torque (M S_lim ), the motor regulator (12) processes the limited torque into an adjusted rated value to prevent overload damage to the drive train components.

8. The device according to claim 7, It is characterized in that The drive unit is designed to be free of free rotation with respect to the manual pedal crank (2).

9. The device according to claim 7, It is characterized in that The drive unit comprises a speed change transmission (7, 8) arranged between an electric motor (6) and a driven shaft (4), and a sprocket (5) arranged on the driven shaft (4). 10 . A drive unit for an electric bicycle, the drive unit comprising an electronic device according to claim 7 for regulating a drive torque.

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