Method for operating a drive assembly of an electric bicycle

Abstract

The present invention relates to a method for operating a drive assembly (1) of an electric bicycle (100), wherein the drive assembly has a motor (2), an output shaft (3), a transmission (4) between the motor and the output shaft, and at least one bottom bracket (5) which supports the output shaft, said method comprising the following steps: - ascertaining (10) a motor torque of the motor, - ascertaining (11) a bearing force on the at least one bottom bracket, in particular by means of a bearing force sensor (50), preferably - ascertaining (12) an output force of the drive assembly on the basis of the ascertained bearing force, and - ascertaining (13) a motor portion of the output force and / or of the bearing force on the basis of the motor torque and mechanical transmission properties of a motor torque transmission path from the motor to the output shaft and / or to the at least one bottom bracket.

Description

[0001] R.413761

[0002] - 1 -

[0003] Description

[0004] title

[0005] Method for operating a drive system of an electric bicycle

[0006] State of the art

[0007] The present invention relates to a method for operating a drive arrangement of an electric bicycle, a drive arrangement of an electric bicycle, and an electric bicycle.

[0008] Drive systems for electric bicycles are known to include a drive unit capable of generating motor torque to assist the rider's pedaling. Typically, the motor torque is generated in relation to the rider's muscle power. This requires measuring the current rider torque, for example, using appropriate sensors. Often, this necessitates a complex sensor design and / or the detectable forces and torques are influenced by numerous factors.

[0009] Disclosure of the invention

[0010] In contrast, the method according to the invention with the features of claim 1 is characterized in that it enables a particularly precise and cost-effective measurement of forces and moments occurring at a bottom bracket of an electric bicycle, based on which, for example, the actual instantaneous rider torque can be determined. This is achieved according to the invention by a method for operating a drive assembly of an electric bicycle, wherein the drive assembly comprises a motor, an output shaft, R.413761

[0011] - 2 - a gearbox between the motor and the output shaft, and at least one bottom bracket which supports the output shaft, comprising the steps:

[0012] Determining the engine torque of the engine,

[0013] Determining a bearing force at the at least one bottom bracket, in particular by means of a bearing force sensor, preferably determining an output force of the drive arrangement based on the determined bearing force, and

[0014] Determining the motor component of the output force based on the motor torque and mechanical transmission characteristics of a motor torque transmission path from the motor to the output shaft and / or to at least one bottom bracket.

[0015] Preferably, the drive arrangement is designed such that a rider of the electric bicycle can apply a pedaling torque which contributes to an output torque at the output shaft.

[0016] In particular, the output torque can correspond to the sum of the pedaling torque and the motor torque generated by the motor. The motor torque can be transmitted to the output shaft via the gearbox.

[0017] Preferably, the drive arrangement can additionally include a crankshaft, which is non-rotatably connected to the output shaft or coupled via a freewheel. Cranks, by means of which the rider can generate pedaling torque, can be connected to the crankshaft. Alternatively, and preferably in the case where no rider freewheel is provided, the output shaft can also be considered the crankshaft.

[0018] In particular, the bearing force at the bottom bracket is measured as a momentary force acting on the bottom bracket in a radial direction with respect to the output shaft. This measurement can be performed, for example, using one or more mechanical force sensors.

[0019] A driven force is defined in particular as a force acting, preferably directly or indirectly, on the output shaft, which produces a driven torque. In particular, the driven torque can be used to propel the electric bicycle. R.413761

[0020] - 3 -

[0021] Particularly preferably, the output force can be considered to be an output element, such as preferably a chainring, that can be connected to the output shaft in a rotationally fixed manner. For example, in this case, the output force corresponds to a chain force.

[0022] Mechanical transmission properties of the motor torque transmission path are considered to be, in particular, forces and / or torques that cause losses in the torque transmission between the motor and the output shaft. These mechanical transmission properties are, in particular, known beforehand, for example, based on a geometric and / or mechanical design of the motor torque transmission path. Alternatively or additionally, the mechanical transmission properties may be determined and stored based on a calibration of the drive arrangement.

[0023] The motor component is specifically defined as a force and / or a percentage of the output force.

[0024] In other words, the method determines the motor torque, particularly directly at the motor. Additionally, a bearing force at the bottom bracket is determined. Based on the determined bearing force, a driven force of the drive assembly can preferably be determined, for example, based on a mechanical transmission between the output shaft and a driven element of the output shaft. Using the determined bearing force at the bottom bracket and a mechanical transmission of the motor torque via the motor torque transmission path from the motor to the output shaft and / or to the bottom bracket, the motor component of the driven force is then determined.

[0025] This method offers the advantage that a particularly simple and cost-effective design enables the simple and precise measurement of the instantaneous forces at the bottom bracket and motor. The motor's contribution to the resulting output force and / or bearing force can be precisely determined. Alternatively, or preferably additionally, other operating parameters, such as the rider's contribution to the output force and / or bearing force, can be calculated simply and reliably. The rider's contribution to the output force and / or bearing force can then be used, for example, directly to determine the functions of the e-bike.

[0026] - 4 - operate. It is particularly advantageous to use the driver's input in an engine control unit to operate the engine.

[0027] The dependent claims contain preferred further developments of the invention.

[0028] Preferably, the method further comprises the step of determining the rider's contribution to the output force and / or the bearing force based on the determined bearing force and the determined motor contribution. The rider's contribution is specifically defined as the portion of the bearing force measured by the bearing force sensor that is generated by the rider's muscle power while pedaling the e-bike. In particular, the rider's contribution corresponds to the difference between the output force or bearing force and the motor contribution. This allows the method to determine the instantaneous manual actuation of the drive system in a simple and highly precise manner, and, based on this, to implement further operating modes of the drive system, such as preferably motor actuation dependent on the rider's contribution to the output force.

[0029] The output force is preferably determined at a driven element that can be connected to the output shaft in a rotationally fixed manner. Preferably, the driven element is a chainring. In particular, the chainring and the output shaft can be directly connected to each other in a rotationally fixed manner. The driven force is thus preferably determined as a chain force acting on the driven element. In particular, the determination of the driven force is based on the geometric relationships between the output shaft and the driven element.

[0030] Preferably, the motor contribution to the bearing force is determined based on the output force at the output element and based on the mechanical transmission properties of a motor torque transmission path from the motor to the output element. Alternatively or additionally preferably, the bearing forces caused by the motor are determined based on the motor torque and based on the mechanical transmission properties of a torque and force transmission path from the motor to the bottom bracket. In other words, the physical and geometric properties of the mechanical motor torque transmission path from the motor to the output element or the bottom bracket are taken into account when determining the motor contribution in this R.413761.

[0031] - 5 -

[0032] The force acting on the output element is determined. This allows, for example, the forces and moments acting on the output element to be directly determined and analyzed. Thus, the motor contribution and / or rider contribution of the output force and / or bearing force can be determined particularly easily, directly, and precisely in relation to the relevant forces on the e-bike's drive system.

[0033] Preferably, the mechanical transmission characteristics of the motor torque transmission path include gear forces. Gear forces are considered to be, in particular, axial, radial, and / or tangential forces that arise during torque transmission through the gear due to the meshing of the gear teeth. These gear forces can be determined based on a known geometry and design of the gear and additionally based on instantaneous operating parameters of the drive assembly. For example, the gear forces can be determined based on the calculated motor torque and / or at least one rotational speed of an element of the drive assembly. In particular, these gear forces can induce reaction forces in the bottom bracket.By taking the gear forces into account, the motor contribution and driver contribution of the output force and / or bearing force of the drive arrangement can be calculated with particular precision.

[0034] Preferably, the mechanical transmission characteristics of the motor torque transmission path include bearing friction and / or transmission losses. Transmission losses can be considered, in particular, friction losses of the transmission or the like. Bearing friction and / or transmission losses can, for example, be known and stored based on a known geometry and / or design of the transmission and bearings, or alternatively, preferably, calculated based on additional instantaneous operating parameters. For example, the bearing friction and / or transmission losses can be estimated based on instantaneous rotational speeds and / or temperatures and / or an operating time of the drive arrangement. By additionally considering the transmission losses and / or bearing friction, the motor contribution and the driver contribution of the output force and / or bearing force can be estimated with particular precision. R.413761

[0035] - 6 -

[0036] Preferably, the mechanical transmission characteristics of the motor torque transmission path include temperature and / or aging effects. In particular, temperature effects can be detected using a temperature sensor. Aging effects can be detected, for example, based on the operating time of the drive arrangement. For instance, losses in the transmission during torque transmission, especially those due to friction, can be determined based on the temperature and / or aging effects. This allows the effects of torque transmission via the motor torque transmission path to be considered with high precision and reliability across all operating ranges of the drive arrangement, enabling the motor and driver contributions to the output force and / or bearing force to be determined with high accuracy.

[0037] Preferably, the mechanical transmission characteristics of the motor torque transmission path further include: a gear ratio of the gearbox and / or output geometries of the output shaft and / or output element, and / or bearing geometries of the bottom bracket and / or bearing force sensor.

[0038] In particular, all of these quantities are known in advance and, for example, stored. This allows the influence of the motor torque transmission on the output forces to be determined effectively and precisely based on several known properties of the drive arrangement, and thus the motor and driver contributions to the output forces to be determined simply and reliably.

[0039] Preferably, the mechanical transmission characteristics of the motor torque transmission path are determined using at least one characteristic map. For example, a separate characteristic map can be provided for various parameters, such as temperature and / or aging effects and / or rotational speeds and / or instantaneous motor torque. Alternatively or additionally, several parameters can be combined in one characteristic map. In particular, a characteristic map is considered to be a predefined relationship between at least two different parameters. For example, the characteristic map can include a predefined relationship between bearing frictions and temperature effects. Particularly preferably, a characteristic map can be R.413761

[0040] - 7 - include a predefined relationship between bearing friction and aging effects. At least one characteristic map can be known in advance, for example, based on calibration and / or tests of comparable drive arrangements. This allows the properties of the motor torque transmission to be estimated and taken into account particularly easily and accurately.

[0041] The procedure preferably also includes the following steps:

[0042] Determining a total output torque at the output element, which can be connected to the output shaft in a rotationally fixed manner, based on the determined bearing force; determining a motor output torque at the output element based on the motor torque and mechanical transmission properties of a motor torque transmission path from the motor to the output element; and determining a driver output torque at the output element based on the determined total output torque and the motor output torque.

[0043] In other words, this involves estimating the motor and driver contributions at the torque level. This allows for the direct determination of the driver output torque and the motor output torque, enabling an alternative, simpler, and more efficient operation of the drive system.

[0044] Preferably, the method further comprises the step of actuating the motor to generate motor torque depending on the determined rider contribution to the output force and / or bearing force. Preferably, the motor can alternatively or additionally be actuated depending on the determined rider output torque. In other words, the motor is actuated in such a way as to generate motor torque depending on the degree of pedal actuation by the e-bike rider. This enables efficient and comfortable operation of the e-bike.

[0045] Preferably, the motor is actuated in such a way as to provide a target support torque at the output shaft depending on the determined driver contribution of the output force and / or bearing force. In other words, based on the determined driver contribution of the output force, the R.413761

[0046] - 8 -

[0047] The desired support torque to be provided at the output shaft is determined. The motor is then actuated in such a way as to provide this desired support torque at the output shaft. Preferably, the mechanical motor torque transmission path between the motor and the output shaft is taken into account for this actuation. This means, for example, that a correspondingly higher motor torque can be provided, in particular to compensate for bearing friction and / or transmission losses, etc. This ensures with particular reliability that the desired support torque is provided at the output shaft, thus enabling a particularly comfortable ferry operation for the driver.

[0048] Preferably, the motor torque is determined based on an actuation signal from the motor and / or based on at least one motor sensor. In particular, the actuation signal can be an actuation current with which the motor is actuated. The motor sensor can, for example, be configured to detect the motor temperature and / or the rotor angle of the motor. Particularly preferably, the motor torque can be calculated based on a mathematical model of the motor and the actuation signal and / or the motor sensor signal. For example, the motor torque can be calculated from phase currents, rotor angle, and magnet temperature using the mathematical model. This allows for a precise determination of the motor torque using a simple and cost-effective design.

[0049] Furthermore, the invention leads to a drive arrangement for an electric bicycle, comprising a motor, an output shaft, a gearbox between the motor and the output shaft, a bottom bracket which supports the output shaft, and a control unit. The control unit is configured to carry out the described method.

[0050] Furthermore, the invention relates to an electric bicycle comprising the described drive arrangement.

[0051] Brief description of the drawings R.413761

[0052] - 9 -

[0053] An embodiment of the invention is described in detail below with reference to the accompanying drawings. The drawing shows:

[0054] Figure 1 shows a simplified schematic view of an electric bicycle, in which a method for operating a drive arrangement of the electric bicycle is carried out according to a preferred embodiment of the invention.

[0055] Figure 2 shows a sectional view of the drive arrangement of the electric bicycle of Figure 1.

[0056] Figure 3 shows a simplified schematic view of a detail of the

[0057] Drive arrangement of Figure 2, and

[0058] Figure 4 shows a highly simplified schematic view of the method according to the invention.

[0059] Embodiments of the invention

[0060] Preferably, all identical components, elements and / or units in all figures are provided with the same reference numerals.

[0061] Figure 1 shows a simplified schematic view of an electric bicycle 100, in which a method 20 for operating a drive arrangement 1 of the electric bicycle 100 is carried out according to a preferred embodiment of the invention.

[0062] The drive arrangement 1 comprises a motor, which is in particular an electric motor. The motor 2 can be supplied with electrical energy by means of an electrical energy storage device 109 of the electric bicycle 100. In the illustrated embodiment, the drive unit 1 is arranged in the area of ​​a bottom bracket of the electric bicycle 100.

[0063] The motor torque generated by motor 2 provides motor assistance to the pedaling force generated by the rider of the electric bicycle 100. The rider's muscle power can be applied via a crank mechanism with cranks 104. R.413761

[0064] - 10 -

[0065] The drive arrangement 1 further comprises a control unit 30, which is configured to actuate the motor 2 in a controlled manner. For example, the control unit 30 can control an electrical actuation current to actuate the motor 2.

[0066] The control unit 30 is configured to carry out the method 20 according to the invention.

[0067] The drive assembly 1 comprises, in addition to the motor 2, an output shaft 3, a gearbox 4 between the motor 2 and the output shaft 3, and a bottom bracket 5. Furthermore, the drive assembly 1 includes a crankshaft 33. The crankshaft 33 is non-rotatably connected to the cranks 104.

[0068] The output shaft 3 is arranged coaxially to the crankshaft 33 and thus, in particular, coaxially to the pedal axle 108.

[0069] A rider freewheel 39 can be arranged between the crankshaft 33 and the output shaft 3, via which a pedaling torque generated by the rider using the cranks 104 can be transmitted to the output shaft 3, as indicated by the arrow.

[0070] The pedaling torque can be transmitted via the output shaft 3 to an output element 6 which is rotationally fixed to the output shaft 3 and which is designed in particular as a chainring.

[0071] The motor 2 can preferably be designed coaxially with the crankshaft 33.

[0072] A motor torque generated by the motor 2 can also be transmitted via the gearbox 4, and preferably via a motor freewheel 29, to the output shaft 3 and thus to the output element 6, as indicated by arrow B.

[0073] The bottom bracket 5 is, for example, fixedly held in a housing 15 of the drive assembly 1 by means of a bearing receptacle 55. The bottom bracket 5 supports the output shaft 3 rotatably relative to the housing 15. R.413761

[0074] - 11 -

[0075] The drive arrangement 1 comprises two bottom brackets 5, 5'. A bearing force is detected at the output-side bottom bracket 5, that is, at the bottom bracket 5 which is arranged on the side of the output element 6, by means of a bearing force sensor 50.

[0076] The bearing force sensor 50 can be arranged on the bearing housing 55 and, for example, configured to detect forces in the axial direction of the pedal axle 108 and additionally in the radial direction with respect to the pedal axle 108. The bearing force sensor 50 can detect a resulting force acting on the bottom bracket 5.

[0077] Method 20 determines the pedaling torque generated by the rider based on the measured bearing force and taking into account the generated engine torque, as described in detail below. A highly simplified schematic representation of Method 20 is shown in Figure 4.

[0078] In a first step, the motor torque of motor 2 is determined. This can be done based on the electrical actuation of motor 2 by means of an actuation signal and preferably also based on a sensor signal from at least one motor sensor. The generated motor torque is then calculated based on the actuation current, a mathematical model of motor 2, and preferably further sensor data, such as temperature and instantaneous rotor position.

[0079] At the same time, a bearing force is determined at the bottom bracket 5 using the bearing force sensor 50.

[0080] Based on the determined bearing force, a driven force of the drive assembly 1 at the driven element 6 is then determined. In particular, the driven force is determined as a chain force at the chainring. The determination of the driven force based on the bearing force is carried out using predefined mechanical and physical relationships between the bearing force and the driven force, such as predefined lever laws of the drive assembly 1. Specifically, the driven force thus corresponds to the total driven force of the drive assembly 1, which results from the motor torque and the pedaling torque combined. R.413761

[0081] - 12 -

[0082] Subsequently, a motor component of the determined output force is determined based on the motor torque determined in step 10 and the mechanical transmission properties of the motor torque transmission path from the motor 2 to the output shaft 3 and the output element 6.

[0083] Furthermore, a driver contribution of the determined downforce is calculated based on the determined engine contribution and the determined downforce.

[0084] Based on the determined rider contribution, motor 2 is then actuated to generate motor torque. Specifically, the motor torque is generated variably depending on the determined rider contribution in order to provide a target support torque at the output shaft 3, dependent on the determined rider contribution to the output force. That is, depending on the degree of actuation of the output shaft 3 by the rider's pedaling torque, a motor torque is generated, which may also depend on a predetermined support factor selectable by the rider, to provide motor assistance to the rider's pedaling force.

[0085] In method 20, the mechanical motor torque transmission path, via which the motor torque is transmitted from motor 2 to output shaft 3 and additionally to output element 6, is also taken into account to determine 13 the motor component. The mechanical transmission properties of the motor torque transmission path comprise several parameters and characteristics, which are described below.

[0086] In particular, when determining 13 the motor component of the output force, the gear forces 45 of the transmission 4 are considered as mechanical transmission properties of the motor torque transmission path. Such gear forces 45 are shown by way of example in Figure 3 between various exemplary gears of the transmission 4. These gear forces 45, which occur due to the motor torque transmission via the transmission 4, cause radial and, in particular, additional axial forces that act on the output shaft 3 and can thus be detected by the bearing force sensor 5 as part of the bearing force. R.413761

[0087] - 13 -

[0088] The gear forces 45 depend on the magnitude of the generated motor torque and the predefined geometric and design properties of the gearbox 4. This means that, knowing the exact design of the gearbox 4 and the known motor torque determined in step 10, the motor component of the bearing force at the bottom bracket 5 generated by the motor 2 can be calculated. Based on this, the motor component of the output force at the output element 6 can then also be calculated.

[0089] In addition, bearing friction and transmission losses are considered as mechanical transmission properties of the motor torque transmission path. In particular, these parameters can influence the calculation of the gear forces and / or be considered separately. The bearing friction and transmission losses may be known in advance, for example, based on a calibration of the drive arrangement 1 and / or based on an estimation using the design characteristics of the drive arrangement 1.

[0090] Furthermore, temperature and aging effects are considered as part of the mechanical transmission properties of the motor torque transmission path. These temperature and aging effects impact the gear forces 45, as well as bearing friction and transmission losses. Alternatively or additionally, the temperature and aging effects can also be considered separately.

[0091] Furthermore, the following mechanical transmission properties can be taken into account: the gear ratio of the gearbox 4, the output geometries of the output shaft 3 and output element 6, and the bearing geometries of the bottom bracket 5 and bearing force sensor 50.

[0092] In particular, variable parameters of the mechanical transmission properties can be determined and factored in using at least one characteristic map. For example, temperature- and age-dependent transmission losses and bearing frictions can each be considered in the form of a characteristic map. The characteristic map can be found in particular in R.413761.

[0093] - 14 - be known and stored in advance, for example based on the design of the drive arrangement 1.

[0094] Method 20 thus offers the advantage that the actual pedaling torque of the rider can be determined with particular reliability and precision by accurately calculating the motor and rider contributions to the output force. A simple and cost-effective design of the drive assembly 1 can be used, for example, without the need for complex torque sensors or similar components. By considering the mechanical properties of the torque transmission path from the motor 2 to the output element 6, the corresponding contributions of the output force can be determined with exceptional accuracy in every operating situation of the drive assembly 1.

[0095] Figure 4 also shows, indicated by dashed arrows, an alternative path of method 20, which can be executed alternatively or additionally to steps 12, 13, and 14. This alternative path uses a calculation of the motor and driver contributions at the torque level. In detail, a total output torque at the output element 6 is determined 15. Subsequently, a motor output torque at the output element 6 is determined 16, based on the motor torque determined in step 10 and the mechanical transmission characteristics of the motor torque transmission path from motor 2 to output element 6. Furthermore, a driver output torque at the output element 6 is determined 17, based on the determined total output torque and the determined motor output torque 6. The actuation 25 of motor 2 is then carried out based on the driver output torque determined in step 17.

Claims

R.413761 - 15 - Claims 1. Method for operating a drive arrangement (1) of an electric bicycle (100), wherein the drive arrangement (1) comprises a motor (2), an output shaft (3), a transmission (4) between the motor (2) and the output shaft (3), and at least one bottom bracket (5) which supports the output shaft (3), comprising the steps: - Determining (10) a motor torque of the motor (2), - Determining (11) a bearing force at at least one bottom bracket (5), in particular by means of a bearing force sensor (50), - preferably determining (12) an output force of the drive arrangement (1) based on the determined bearing force, and - Determining (13) a motor component of the output force and / or the bearing force based on the motor torque and mechanical transmission characteristics of a motor torque transmission path from the motor (2) to the output shaft (3) and / or to the at least one bottom bracket (5).

2. The method of claim 1, further comprising the step of: - Determining (14) a driver contribution of the driven force and / or the bearing force based on the determined bearing force and the determined engine contribution.

3. Method according to one of the preceding claims, wherein the output force is determined at an output element (6) which can be connected to the output shaft (3) in a rotationally fixed manner.

4. Method according to claim 3, wherein the determination (12) of the motor component of the bearing force is based on the output force at the output element (6) and on mechanical transmission properties of a motor torque transmission path from the motor (2) to the output element (6). R.413761 - 16 - 5. Method according to one of the preceding claims, wherein the mechanical transmission properties of the motor torque transmission path comprise gear forces (45) of the transmission (4).

6. Method according to any of the preceding claims, wherein the mechanical transmission characteristics of the motor torque transmission path include bearing frictions and / or transmission losses.

7. Method according to one of the preceding claims, wherein the mechanical transmission properties of the motor torque transmission path include temperature influences and / or aging influences.

8. Method according to any of the preceding claims, wherein the mechanical transmission characteristics of the motor torque transmission path further comprise: - a gear ratio of the gearbox (4), and / or - Output geometries of output shaft (3) and / or output element (6), and / or - Bearing geometries of bottom bracket (5) and / or bearing force sensor (50).

9. Method according to one of the preceding claims, wherein the mechanical transmission properties of the motor torque transmission path are determined by means of at least one characteristic map.

10. A method according to any of the preceding claims, further comprising the steps of: - Determining (15) a total output torque at the output element (6) which can be connected to the output shaft (3) in a rotationally fixed manner, based on the determined bearing force, - Determining (16) a motor output torque at the output element (6) based on the motor torque and mechanical transmission characteristics of a motor torque transmission path from the motor (2) to the output element (6), and R.413761 - 17 - - Determining (17) a driver output torque at the output element (6) based on the determined total output torque and the engine output torque.

11. Method according to any one of claims 2 to 10, further comprising the step: - Actuation (25) of the motor (2) to generate a motor torque depending on the determined driver contribution of the output force and / or bearing force.

12. Method according to claim 11, wherein the actuation (25) of the motor (2) is carried out in such a way as to provide a target support torque on the output shaft (2) depending on the determined driver contribution of the output force and / or bearing force.

13. Method according to one of the preceding claims, wherein the motor torque is determined based on an actuation signal of the motor (2) and / or based on at least one motor sensor.

14. Drive arrangement of an electric bicycle (100), comprising: - one motor (2), - an output shaft (3), - a gearbox (4) between motor (2) and output shaft (3), - a bottom bracket (5) which supports the output shaft (3), and - a control unit (30) which is configured to carry out the method (20) according to one of the preceding claims.

15. Electric bicycle comprising a drive arrangement (1) according to claim 14.

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