Method for operating a drive unit of an electric bicycle

Abstract

The invention relates to a method for operating a drive unit of an electric bicycle, comprising the steps of: detecting a pedal rotation of the electric bicycle, and operating the drive unit at least in one driving mode based on the pedal rotation such that exclusively a motor torque generated by the drive unit causes propulsion of the electric bicycle.

Description

Prior ArtThe present invention relates to a method for operating a drive unit of an electric bicycle, and to an electric bicycle.Electric bicycles with drive units are known which can generate an engine torque to assist the driver during pedaling. Usually, the engine torque is generated depending on a pedaling force of the driver. For this purpose, the pedaling force is often detected as a torque by means of a torque sensor. In particular in the case of drive units arranged in the region of the bottom bracket, however, a cost-intensive and complex construction is often necessary for integrating the torque sensor.Disclosure of the InventionThe method according to the invention having the features of claim 1 is distinguished in contrast in that reliable and comfortable operation of the electric bicycle can be made possible by means of a particularly simple and cost-effective construction. In particular, simple and cost-effective hardware can be used in this case. This is achieved according to the invention by a method for operating a drive unit of an electric bicycle, comprising the steps:detecting a pedal rotation of the electric bicycle; andoperating the drive unit at least in a driving mode based on the pedal rotation in such a way that only an engine torque generated by the drive unit causes the electric bicycle to be propelled.In particular, a movement and / or a position of the pedals of a crank drive of the electric bicycle is considered as the pedal rotation.The driving mode is defined in particular in that the electric bicycle is moving, preferably at a predetermined minimum speed, of 15 km / h, for example.In other words, a pedal rotation of the electric bicycle is detected or monitored in the method. At least temporarily during operation of the electric bicycle, namely within the driving mode, the drive unit is operated, preferably controlled, based on the detected pedal rotation. In this case, the pedal rotation, that is to say the pedaling by the driver of the electric bicycle, does not contribute any torque to the propulsion of the electric bicycle. In particular, the pedal actuation for the driver of the electric bicycle is thereby effected substantially without resistance.The method thereby offers the advantage that the controlled operation of the drive unit can be made possible in a particularly simple and cost-effective manner. The pedal rotation can be detected, for example, by means of a rotational speed sensor and / or a position sensor or the like. Thus, a torque sensor and associated complex and cost-intensive hardware can be dispensed with. In addition, a particularly high driving comfort can be provided for the driver of the electric bicycle, since an effective propulsion of the electric bicycle is effected without the driver having to use significant effort. For example, the driver thus essentially "enters empty" due to the special operation of the drive unit, wherein the pedaling movement causes the corresponding generation of the engine torque by the drive unit.The dependent claims include preferred developments of the invention.Preferably, a carcass, i.e. in particular a treading frequency, is detected as the pedal rotation. In other words, the rotational speed of the crank drive of the electric bicycle is detected, and the controlled operation of the drive unit is carried out as a function of this detected rotational speed. This makes it possible to provide precise regulation of the target variable during operation of the drive unit, which can be made possible in a particularly simple manner.Particularly preferably, the drive unit is operated in such a way that an engine speed is greater than the detected carcass. That is, the motor rotates faster than the driver steps. As a result, it can be achieved with a control that is simple to implement that the pedaling of the driver does not make any direct contribution to the propulsion of the electric bicycle, and the propulsion is effected solely by the engine torque of the drive unit. Thus, a particularly force-saving operation for the driver and thus a high level of user comfort can be provided.The drive unit is preferably operated in such a way that the engine speed is greater than the detected carcass by a predetermined factor, which is preferably at least two. That is, the engine speed is preferably controlled to twice the tread frequency. This makes it possible to ensure in a particularly simple and reliable manner that the electric bicycle is driven via the engine torque without the driver engaging the drive train, for example even in the event of speed fluctuations of the electric bicycle.The predetermined factor is preferably adapted, in particular reduced or increased, as a function of the detected wheel speed and / or as a function of a detected speed of the electric bicycle and / or as a function of a drive transmission ratio of a drive system of the electric bicycle. A momentary total transmission ratio of the drive system of the electric bicycle can be considered as the drive transmission ratio, for example. Preferably, the drive transmission ratio can comprise a momentary gear stage of a shifting system of the drive system. For example, the drive transmission ratio can be detected or calculated.The driving mode is preferably defined, in particular exclusively, within a Kadenz range of at least 20 U / min, preferably at least 40 U / min, to a maximum of 100 U / min, preferably a maximum of 60 and / min. That is, the controlled operation of the drive unit such that the propulsion is effected exclusively by the engine torque takes place within a certain stepping frequency window. As a result, a driving operation that is particularly comfortable for the driver of the electric bicycle can be provided. In addition, the operation of the drive unit can be carried out particularly easily and efficiently within the kadenz range. Alternatively or additionally preferably, the driving mode is defined, in particular exclusively, within a predetermined speed range of a driving speed of the electric bicycle. For example, the speed range can be defined starting from a predetermined minimum speed, of in particular at least 10 km / h, preferably at least 20 km / h. Further alternatively or additionally preferably, the driving mode can be defined, in particular exclusively, within a predetermined transmission ratio range, in particular a drive transmission ratio of a drive system of the electric bicycle. For example, the transmission range can comprise only predetermined gear stages of the drive system, preferably only the highest gear stage.Preferably, a pedal deflection relative to a predetermined normal position is detected as the pedal rotation. Preferably, a predetermined crank position is considered as the normal position. In particular, a relative angle of cranks to the normal position can be detected as the pedal deflection. This means that the controlled operation of the drive unit takes place as a function of the currently detected position of the cranks.Particularly preferably, the normal position corresponds to a vertical crank position. That is, in the normal position, the cranks are arranged in the vertical direction.In this case, the drive unit is preferably operated in such a way as to accelerate the electric bicycle when the cranks are deflected by 90° with respect to the normal position, that is to say are arranged in particular in the horizontal direction.More preferably, the drive unit is operated in such a way as to slow down the electric bicycle when the cranks are arranged in the normal position. The deceleration can preferably take place by targeted braking of the electric bicycle. The braking of the electric bicycle can particularly preferably be effected by a generator operation of the drive unit.Preferably, the drive unit is operated in such a way as to maintain a momentary speed of the electric bicycle when the cranks are arranged in a position between the normal position and the horizontal direction deflected by 90°.A pedal pendulum about at least one predetermined pedal angle is preferably detected as the pedal rotation. Pedal oscillation is considered to be, in particular, cyclically repeating oscillation about a specific crank position. The predetermined pedal angle is preferably at least 10°, particularly preferably at most 20°. This makes it possible to provide a further alternative mode of operation with which the driver can initiate a drive of the electric bicycle in a particularly comfortable and force-saving manner.Particularly preferably, the operation of the drive unit takes place at least in the driving mode exclusively on the basis of the detected pedal rotation. That is, no further parameters, such as sensor signals or the like, are used, based on which the drive unit is operated. This allows particularly simple and efficient operation of the drive unit.Preferably, the operation of the drive unit comprises a regulation of a target variable based on the detected pedal movement. In particular, the target variable comprises an engine speed and / or an engine power and / or an engine torque and / or a speed of the electric bicycle.Preferably, the target variable or alternatively a change over time in the target variable, i.e. for example a gradient of the target variable, is controlled in proportion to the detected pedal movement. Particularly preferably, the regulation of the target variable or the change over time of the target variable is effected in proportion to a frequency and / or an amplitude of the pedal movement. This makes it possible to provide a particularly precise control of the speed and a particularly simple and precise control for the driver.Further preferably, the target variable or alternatively a change over time in the target variable is controlled disproportionately to the pedal movement. Particularly preferably, the control of the target variable or the change over time of the target variable is carried out in this case disproportionately to a frequency and / or an amplitude of the pedal movement. That is to say that, for example, a progressive, for example exponential, relationship is used rather than a linear relationship between pedal movement and target variable. As a result, a larger usable speed range can be provided for the regulation of the operation of the drive unit, in particular in a predefined kadenz range.The method is particularly preferably carried out with a small drive transmission ratio of a drive system of the electric bicycle. A drive transmission ratio is considered to be, in particular, an overall transmission ratio of a drive train of the electric bicycle. Alternatively preferably, the drive ratio of the drive system is reduced in a controlled manner before the drive unit is operated in the driving mode. That is to say that before the operation of the drive unit in the driving mode is provided, the overall transmission ratio is reduced in a targeted manner, for example by means of an electronic circuit. This ensures that the driver can always continuously freely pedal and, by means of the pedal actuation, can initiate the propulsion of the electric bicycle by means of the drive unit.Furthermore, the invention leads to an electric bicycle comprising a drive unit, a sensor device which is configured to detect a pedal rotation, and a control unit. The control unit is configured to carry out the described method. The sensor device can preferably comprise a rotational speed sensor and / or an angle sensor.Brief Description of the DrawingsThe invention is described below with reference to an exemplary embodiment in conjunction with the figures. Functionally identical components are identified in the figures by the same reference numerals. The following shows: FIG. 1 is a simplified schematic view of an electric bicycle in which a method according to a preferred exemplary embodiment of the invention is carried out, FIG. 2 shows a greatly simplified schematic view of a sequence of the method according to the invention, and FIG. 3 is a simplified schematic view of a velocity diagram when implementing the method according to the invention.Preferred Embodiments of the InventionFIG. 1 shows a simplified schematic view of an electric bicycle 100 in which a method according to a preferred exemplary embodiment of the invention is carried out.The electric bicycle 100 has a crank drive with two cranks 104 opposite each other with respect to a pedal axle 30. Pedals 102 are arranged on the cranks 104, by means of which pedals a driver can generate a pedaling torque by means of muscle force.In addition, the crank drive comprises a pedal shaft 108 which defines the pedal axle and which is connected to the cranks 104 in a rotationally fixed manner. Via pedal bearings, the pedal shaft 108 is rotatably mounted in a drive unit 1 of the electric bicycle 100.Furthermore, the electric bicycle 100 comprises a rider freewheel, which is arranged in particular between a chain plate 107 and the crank drive with the cranks 104. The rider freewheel enables a forward rotation of the chain plate 107 independently of the pedal movement.The drive unit 1 is part of a drive arrangement which additionally comprises a control unit 50 and a sensor arrangement 2.The sensor arrangement 2 is configured to detect a pedal rotation. In detail, the sensor arrangement 2 is configured to detect a carcass, for example by detecting a rotational speed of the cranks 104.In order to support the pedaling torque with an additional motor torque, the electric bicycle 100 comprises the drive unit 1, which is configured to generate the motor torque, preferably by means of an electric motor, which is supplied with electric energy in particular by an electric energy store 109.The drive unit 1 is configured to provide the engine torque preferably via a transmission on the pedal shaft 108.The drive unit 1 is actuated by means of the control unit 50 in that the control unit 50 controls the provision of an electric current to the electric motor of the drive unit 1.The operation of the drive unit 1 is provided as a function of a manual actuation of the crank drive by the driver of the electric bicycle 100 in such a way as to generate a specific engine torque as a function of the pedal movement detected by means of the sensor arrangement 2.In this case, the operation of the drive unit 1 takes place by means of the method 10 according to the invention in such a way that, in a driving mode, exclusively the motor torque generated by the drive unit 1 brings about propulsion of the electric bicycle 100. That is, in the running mode, the drive unit 1 is operated such that the driver does not come into torque transmitting engagement with the drive train of the electric bicycle 100.The method 10 (cf. FIG. 2 ) comprises the steps of detecting 11 the pedal rotation of the electric bicycle 100 by means of the sensor arrangement 2, and operating 12 the drive unit 1 in the driving mode.Here, the operation 12 of the drive unit 1 takes place in such a way that, in the driving mode, the engine speed is greater than the instantaneous carcass of the pedaling movement of the driver by a predetermined factor, of two for example.That is, the engine speed is controlled as a function of the detected carcass, wherein the engine speed is always kept greater than the current carcass, so that the driver "enters the empty". In particular, the chain plate 107 thus rotates faster in the driving mode than the crank drive, which is made possible in particular by the free running of the driver.Alternatively or in addition to the described regulation of the engine speed, an engine output and / or an engine torque and / or a speed of the electric bicycle 100 can preferably also be regulated as a target variable as a function of the detected pedal rotation.Furthermore, as an alternative to the direct regulation of the target variable, a change over time in the target variable can be regulated as a function of the detected pedal movement.The target variable or the change over time in the target variable can be regulated in various ways depending on the detected pedal movement. Preferred embodiments are described below with reference to FIG. 3, wherein the speed of the electric bicycle 100 is used as a target variable by way of example.FIG. 3 shows a simplified schematic view of a speed diagram 30 when carrying out method 10 according to the present invention.In a first embodiment, a proportional control of the speed 31 takes place as a function of the carcass 32, characterized by the straight line 35; this makes it possible, for example, to influence the target variable by the driver in a particularly sensitive manner.In a second embodiment, the speed 31 is controlled in a disproportionate manner, for example exponentially, as a function of the carcass 32, characterized by the curve 36; as a result, a greater speed range 39 can be covered within a specific carcass range 43 in comparison with the proportional speed range 38 of the proportional control.The carcass region 43 can furthermore be regarded as a comfortable region for pedaling for the driver. This carcass region 43 preferably extends from a minimum carcass 41 of 40 U / min to a maximum carcass 42 of 70 U / min.For simple operation of the electric bicycle 100 that is comfortable for the driver, the method 10 is preferably carried out exclusively within the carcass region 43.An alternative operating mode of the drive unit 1 preferably takes place at lower speeds, in particular during starting. For example, a predefined motor torque can be set during starting for a particularly simple and cost-effective implementation. Alternatively preferably, a torque-regulated operation of the drive unit 1 can take place during starting.In further preferred embodiments, as an alternative or in addition to the kadenz-based control of the drive unit 1, further pedal movements can be used as a basis for the operation of the drive unit 1.In a first preferred further embodiment, a pedal deflection relative to a predetermined normal position is detected as the pedal rotation. A vertical contour position is defined as a normal position. In this case, when the cranks 104 are deflected by 90° with respect to the normal position, i.e. are arranged horizontally, the drive unit 1 is operated in such a way as to accelerate the electric bicycle 100. When the cranks 104 are arranged in the normal position, i.e. vertically, a targeted slowing down, in particular a braking of the electric bicycle 100, can be effected, preferably by a generator operation of the drive unit 1. Furthermore, in an intermediate position of the cranks 104 between the normal position and the horizontal direction deflected by 90°, a momentary speed of the electric bicycle 100 can be maintained by a corresponding targeted operation of the drive unit 1.In a second preferred further embodiment, a pedal pendulum about at least one predetermined pedal angle is detected as the pedal rotation. This means that a cyclical oscillation of the cranks 104, for example by a specific curved order, is detected. The predetermined pedal angle is preferably at least 10°. In this case, the controlled operation of the drive unit 1 can thus be initiated by the driver of the electric bicycle 100 when the latter moves the pedals back and forth cyclically by the predetermined pedal angle.

Claims

Method for operating a drive unit (1) of an electric bicycle (100), comprising the steps of: - detecting a pedal rotation of the electric bicycle (100), and - operating the drive unit (1) at least in one driving mode based on the pedal rotation in such a way that only an engine torque generated by the drive unit (1) causes propulsion of the electric bicycle (100).Method according to Claim 1, wherein a carcass is detected as the pedal rotation.Method according to claim 2, wherein operating the drive unit (1) such that an engine speed is greater than the detected carcass.Method according to claim 3, wherein the operation of the drive unit (1) is effected such that the engine speed is greater than the detected carcass by a predetermined factor, preferably at least two.Method according to Claim 4, wherein the predetermined factor is adapted as a function of the detected wheel speed and / or a detected speed of the electric bicycle (100) and / or a drive transmission ratio of a drive system (20) of the electric bicycle (100).Method according to one of the preceding claims, - wherein the driving mode is defined within a Kadenz range of at least 20 U / min, preferably at least 40 U / min, to a maximum of 100 U / min, preferably a maximum of 60 U / min, and / or - wherein the driving mode is defined within a predetermined speed range, and / or - wherein the driving mode is defined within a predetermined transmission range.Method according to one of the preceding claims, wherein a pedal deflection relative to a predetermined normal position is detected as the pedal rotation.Method according to claim 7, wherein the normal position corresponds to a vertical crank position.Method according to one of the preceding claims, wherein a pedal oscillation by at least one predetermined pedal angle is detected as the pedal rotation.Method according to one of the preceding claims, wherein the operation of the drive unit (1) takes place at least in the driving mode exclusively on the basis of the pedal rotation.Method according to one of the preceding claims, wherein the operation of the drive unit (1) comprises regulating a target variable based on the detected pedal movement, in particular wherein the target variable comprises an engine rotational speed and / or an engine power and / or an engine torque and / or a speed.Method according to Claim 11, wherein the target variable or a change over time in the target variable is controlled in proportion to the detected pedal movement (frequency / amplitude).Method according to Claim 11, wherein the target variable or a change over time in the target variable is controlled in a manner disproportionate to the pedal movement.Method according to one of the preceding claims, wherein the method is carried out with a low drive transmission ratio of a drive system (20) of the electric bicycle (100), or wherein a drive transmission ratio of the drive system (20) is reduced before the drive unit (1) is operated in the driving mode.Electric bicycle, comprising: - a drive unit (1), - a sensor device (2) which is configured to detect a pedal rotation, and - a control unit (50) which is configured to carry out the method according to one of the preceding claims.

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