Method for controlling a drive unit for a vehicle that can be operated at least temporarily by muscle power

Abstract

A method is provided for controlling a drive unit for a vehicle that can be operated at least temporarily by muscle power, wherein a first electric motor (70) can be operated with energy from an energy store in order to support a mechanical drive by means of an adjustable power, a first rotor (71) of the first electric motor (70) and an input element (4) of the mechanical drive are mechanically operatively connected to an output element (5) via a superimposing transmission in order to drive the vehicle, the direction of rotation of the input element (4) when driving the vehicle is formed by the direction of rotation of the drive, and at least one rotational speed sensor is designed to detect a rotational movement of at least one of the group consisting of the input element (4), the output element (5) and the first rotor (71). The method has the steps of determining (I) the rotational speed and direction of rotation of the input element (4) by means of the at least one rotational speed sensor; and switching off (II) the first electric motor (70) when a switch-off condition is reached. The switch-off condition is reached at least when the rotational speed of the input element (4) reaches or falls below a limit value and the direction of rotation of the input element (4) is opposite the direction of rotation of the drive at a rotational speed not equal to 0.

Description

[0001] Method for controlling a drive unit for a vehicle that can be operated at least temporarily with muscle power

[0002] The present invention relates to a method for controlling a drive unit for a vehicle that can be operated at least temporarily with muscle power, a control device for carrying out a method, a drive unit for a vehicle and a vehicle.

[0003] Methods for controlling a drive unit for an e-bike are known. The e-bike can have both an electric and a mechanical drive. The level of assistance provided by the electric drive to support the mechanical drive can be comparable to or higher than the mechanical power. If the assistance is provided unexpectedly, for example, there is a risk of injury to the rider or damage to the vehicle.

[0004] It is an object of the present invention to provide a method for controlling a drive unit for a vehicle that can be operated at least temporarily using muscle power, with which the vehicle can be operated safely.

[0005] The problem is solved by the subject matter having the features of the independent patent claims. Advantageous further developments are the subject of the dependent claims.

[0006] In a first aspect, a method for controlling a drive unit for a vehicle that can be operated at least temporarily using muscle power is provided. A first electric motor can be operated with energy from an energy storage device to assist a mechanical drive with an adjustable power output. The adjustable power, for example an assistance power, can be adjustable, for example, depending on a cadence and the pedaling torque of the rider. The first electric motor can be formed by a synchronous machine, for example a permanent magnet synchronous machine, or an asynchronous machine. The energy storage device can have a rechargeable battery. A first rotor of the first electric motor and an input element of the mechanical drive are mechanically operatively connected to an output element via a superposition gear to drive the vehicle.

[0007] The drive unit can therefore provide an eCVT system. The input element can have an input shaft, for example a pedal crankshaft. The input element can have pedals. The input element can be configured to input a mechanical drive force. The mechanical drive force can be generated by a rider's pedaling force. The input element can be generated by a gear set element, for example a first planet carrier of the superposition gearing. The output element can be generated by a sprocket, a pulley, or a gear. At least one of the input element and the output element can be rotationally connected to a gear set element of the superposition gearing. The input shaft can be rotationally connected to a gear set element of the superposition gearing via a first freewheel in a drive direction of rotation.

[0008] If two elements are mechanically operatively connected, they are directly or indirectly coupled to one another in such a way that a movement of one element causes a reaction in the other element. For example, a mechanical operative connection can be provided by a positive or frictional connection. The mechanical operative connection can correspond to the meshing of corresponding toothings of the two elements. Additional elements, such as one or more spur gear stages, can be provided between the elements. A permanently rotationally fixed connection between two elements, on the other hand, is understood to be a connection in which the two elements are rigidly coupled to one another in all intended states of the transmission. The elements can be present as individual components connected in a rotationally fixed manner or as a single piece.A switching element, such as a clutch or brake, can selectively establish or break a rotationally fixed connection between two elements. A switching element can also be designed, similar to a freewheel, to establish a rotationally fixed connection in only one direction of rotation.

[0009] The direction of rotation of the input element when driving the vehicle is defined as the drive direction of rotation. The drive direction of rotation of the input element can be a direction of rotation for which the vehicle can be moved in one direction of travel. If the direction of rotation of the input element is opposite to the drive direction of rotation, the rotational speed of the input element can mathematically have a negative sign and form a negative rotational speed.

[0010] At least one speed sensor is configured to detect a rotational movement of at least one of the input element, the output element, and the first rotor. The speed sensor can be configured to directly determine the speed and the direction of rotation of the input element. The speed sensor, for example a first speed sensor, can be configured to indirectly determine the speed and the direction of rotation of the input element, for example by detecting the speed of at least one of the first rotor and the output element. The drive unit can have a speed sensor, for example a second speed sensor, for detecting a rotor speed nEMs of the first rotor. The drive unit can have a speed sensor, for example a third speed sensor, for detecting an output speed n2 of the output element. The drive unit can, for example, have two or more speed sensors.

[0011] The method comprises determining a rotational speed and a direction of rotation of the input element via the at least one rotational speed sensor. The method can comprise determining at least one of the rotational speed and the direction of rotation of the input element via the at least one rotational speed sensor. The method can comprise one of a direct determination and an indirect determination of at least one of the rotational speed and the direction of rotation of the input element. The method comprises switching off the first electric motor when a switch-off condition is reached, which is reached at least when the determined rotational speed of the input element reaches or falls below a limit value and the determined direction of rotation of the input element is opposite to the drive direction of rotation.

[0012] The method can include checking whether the switch-off condition has been reached. The check can include comparing the speed nl or n1b of the input element, for example the input shaft, with the limit value. The limit value can be set by a user via a user interface. The limit value can have the unit rpm. The limit value can be formed by the value 0. The limit value can be formed by a value greater than 0, for example a positive value. The limit value can be formed by a value less than 0, for example a negative value. A value less than 0 can be associated with a speed of the input element opposite to the drive direction of rotation. The switch-off condition can then be met when the negative speed falls below the negative limit value or when the absolute value of the negative speed exceeds the absolute value of the negative limit value.

[0013] The limit value can cover a range of values. The value range can include the value 0. The limit value can be set so that it only covers a slight rotational movement of the input element against or in the drive direction of rotation or a combination thereof. A slight rotational movement of the input element against or in the drive direction of rotation can occur if the rotational movement is so small that it is barely perceptible to a user with the naked eye. A slight rotational movement of the input element against or in the drive direction of rotation can occur if the rotational movement is not disturbing to the user. The switch-off condition can be reached via the limit value if the speed of the input element is not equal to 0, but almost 0, regardless of the direction of rotation of the input element.Thus, the shutdown condition can be met when a rotational movement of the input element occurs that does not correspond to a rotational movement of the input element for mechanically driving the vehicle. A rotational movement of the input element for mechanically driving the vehicle can, for example, be provided by the usual cadences of a driver of the vehicle.

[0014] The limit value may be undershot if the speed of the input element in the direction of drive rotation is smaller than the limit value. For example, the limit value may be undershot if a signed speed of the input element is smaller than the limit value.

[0015] This method can reduce the probability that the pedals will be accidentally driven backward, for example, in the opposite direction of rotation, due to a functional or software error. The method thus provides a safety function.

[0016] The superposition gearing can comprise a planetary gearing. A planetary gearing can comprise at least one planetary gear set. A planetary gear set can be configured as a positive planetary gear set or a negative planetary gear set. A planetary gear set can comprise at least one planetary gear. The planetary gear can be configured as a stepped planetary gear.

[0017] The vehicle may have a control device. The control device may have an input interface and an output interface. The input interface may be configured to input signals into the control device. The input interface may be configured to input signals from at least one of the speed sensors. The control device may have a computing unit, a data memory, and a working memory. The control device may be configured to process the signals from the input interface. The control device may be configured to generate signals for the output interface. The output interface may be configured to output signals from the control device. For example, the output interface may be configured to control the first electric motor.The output interface may, for example, be configured to output at least one of a voltage value and a current value.

[0018] The vehicle may have a drive wheel. The drive wheel may be mechanically operatively connected to the output element. The drive wheel may be mechanically operatively connected to the output element via an output gear, for example a chain drive or a belt drive. The drive wheel may have a wheel hub. The drive wheel may, for example, be mounted on the stationary component via the wheel hub. The drive wheel may, for example, be non-rotatably connected to the output element of the output gear via the wheel hub by means of a second freewheel, at least in one direction of rotation, for example counter to the drive direction of rotation. The drive wheel may be formed by a rear wheel. In one embodiment of the method, the at least one speed sensor may be formed by a first speed sensor that is configured to detect the speed and the direction of rotation of the input element.Determining the speed and direction of rotation of the input element may include directly detecting the speed and direction of rotation via the speed sensor.

[0019] The direct detection of the speed and direction of rotation of the input element can be associated with a direct determination of the speed and direction of rotation of the input element. The direct detection of the speed and direction of rotation of the input element can lead to a directly determined speed n1 of the input element, for example, the input shaft. The shutdown condition can be met when the speed of the input element is 0. The shutdown condition can be met when the speed of the input element is less than 0, i.e., when the input element rotates opposite to the drive direction of rotation.

[0020] In one embodiment of the method, the superposition gear can be formed by a first planetary gear set. The at least one speed sensor can be formed by a second speed sensor, which is configured to detect the rotor speed of the first rotor, and by a third speed sensor, which is configured to detect the output speed of the output element. The first rotor can have the speed nEMs. The output element can have the speed n2. The drive unit can have the second speed sensor and the third speed sensor without having the first speed sensor. Determining the speed and the direction of rotation of the input element can comprise an indirect determination via the rotor speed of the first rotor and the output speed of the output element.

[0021] The indirect determination of the speed and direction of rotation of the input element can lead to an indirectly determined speed n1b of the input element, for example the input shaft. The indirect determination can comprise applying the Willis equation, i.e. the speed equation, to the first planetary set of the superposition gearing. The first planetary gear set can have a first gear set element, a second gear set element, and a third gear set element. The first gear set element can be formed by a first sun gear, the second gear set element by a first planet carrier, and the third gear set element by a first ring gear. The first sun gear can mesh with the first planet gear. The first planet gear can mesh with the first ring gear. The first planet gear can be rotatably mounted on the first planet carrier via a first planetary pin.The first planetary gear set may have a stationary gear ratio iO, for example from the first sun gear to the first planet carrier.

[0022] The input shaft can be mechanically operatively connected to the first planet carrier, for example, rotationally connected, or connected in a rotationally fixed manner via the first freewheel in the drive direction of rotation. The first rotor can be mechanically operatively connected to the first sun gear. The first rotor can be mechanically operatively connected to the first sun gear via a pre-stage gearing. The pre-stage gearing can have a second planetary gear set with a second sun gear. The pre-stage gearing can have a gear ratio iVorEMs, for example, from the second sun gear to the first sun gear of the first planetary gear set. The first rotor can be rotationally fixedly connected to the second sun gear. The output element can be mechanically operatively connected, for example, rotationally connected, to the first ring gear. As a result, the output element can be rotationally connected to a gear set element, for example, the third gear set element, of the superposition gearing.

[0023] The speed equation that can apply to the first planetary gear set is nWeb = (nSun - KFnRing Gear) / (1 - 0). Here, nWeb can be formed by the speed of the first planet carrier. If the input element is connected to the first planet carrier, nWeb=n1 or nWeb=n1b can apply. Here, nSun can be formed by the speed of the first sun gear. nRing Gear can be formed by the speed of the first ring gear. nSun can be formed by nEMs / iPreEMs. If the first ring gear is connected to the output element, nRing Gear=n2 can apply. Then the method can be designed so that the speed of the input element n1b is determined using the equation that n1b = ((nEMs / iPreEMs) - i0*n2) / (1 - i0).If the first freewheel is provided between the input shaft and the first planet carrier and, for example, connects the input element to the first planet carrier in a rotationally fixed manner in the drive direction of rotation, the speed of the first planet carrier can be determined instead of the speed of the input element using the equation that nWeb = ((nEMs / iVorEMs) - i0*n2) / (1-iO). The first freewheel can be set up in such a way that it allows the input element to rotate faster against the drive direction of rotation than the first planet carrier, but not slower. For this reason, to provide the safety function, nWeb can be determined instead of n1 or n1b. Then, for the safety function, nWeb can be compared with the limit value instead of n1 or n1b. The safety function therefore basically remains the same.The first freewheel can be used to prevent the inertial masses of the electric motors from exerting a disruptive torque reaction on the input element in the event of a sudden interruption in pedaling, for example an unwanted further rotation of the input element in the drive direction of rotation.

[0024] Using the calculated speed nSteg for the safety function has the advantage over directly determining the speed of the input element in that the first electric motor is not switched off if the user moves the input element, for example, the pedal, in the opposite direction of the drive rotation. The method can be designed so that the switch-off condition only occurs when the speed nSteg reaches or falls below the limit value.

[0025] When the input shaft rotates counter to the drive direction of rotation, the first freewheel can release the rotationally fixed connection between the input shaft and the first planetary carrier. The first planetary carrier then no longer rotates counter to the drive direction of rotation. The first freewheel can be provided on one of the first rotor, for example, connected between the first rotor and the second sun gear, or on the first sun gear, for example, connected between the first sun gear and the second planetary carrier.

[0026] In one embodiment of the method, the superposition gearing can be formed by a first planetary gear set. A second rotor of a second electric motor can be mechanically operatively connected to the output element via the superposition gearing for driving the vehicle. The second electric motor can be formed by a synchronous machine, for example a permanent magnet synchronous machine, or an asynchronous machine. The at least one speed sensor can be formed by the second speed sensor, which is configured to detect the rotor speed of the first rotor, and by a fourth speed sensor, which is configured to detect the rotor speed of the second rotor. The drive unit can have the second speed sensor and the fourth speed sensor without having the first speed sensor and the third speed sensor.Determining the rotational speed and the direction of rotation of the input element may comprise an indirect determination via the rotor speed of the first rotor and the rotor speed of the second rotor.

[0027] The method can be designed such that the second electric motor can be switched off at the same time or substantially at the same time as the first electric motor.

[0028] The second rotor can be mechanically connected, for example via a transmission, to a third gear set element, for example the first ring gear, of the superposition gear. The second rotor can have the speed nEMo. The transmission can have the gear ratio iVorEMo. As previously described, the third gear set element can be connected in a rotationally fixed manner to the output element. The speed of the output element n2 can then be determined from nEMo, where n2 = nEMo / iVorEMo. The speed of the first planet carrier can then be determined using the equation nSteg = ((nEMs / iVorEMs) - iO*(nEMo / iVorEMo)) / (1 - iO). The speed of the first planet carrier can thus be determined from the speeds of the two electric motors.

[0029] The second rotor can be mechanically connected, for example, via the transmission gear, to the second planetary gear set element, for example, the first planet carrier. The second rotor can have a rotational speed of nEMi. The transmission gear can have a gear ratio of iVorEMi. Then, nSteg can be determined from nEMi using the equation nSteg = nEMi / IVorEMi.

[0030] In one embodiment of the method, the switch-off condition can be reached if at least one of the directly determined speed of the input element and the indirectly determined speed of the input element reaches or falls below the limit value.

[0031] The switch-off condition can be met when one of the directly determined speed of the input element or the first planet carrier and the indirectly determined speed of the input element or the first planet carrier reaches or falls below the limit value. The switch-off condition can be met when the smaller of the directly determined speed of the input element or the first planet carrier and the indirectly determined speed of the input element or the first planet carrier reaches or falls below the limit value. The limit value for the directly determined speed of the input element or the first planet carrier and the indirectly determined speed of the input element or the first planet carrier can be different. In this respect, a direct limit value and an indirect limit value can exist.The shutdown condition can be reached when either the directly determined speed reaches or falls below the direct limit, or the indirectly determined speed reaches or falls below the indirect limit, or a combination thereof.

[0032] In one embodiment of the method, the switching off of the first electric motor may comprise at least one of controlling a rotor torque of the first rotor to a switch-off value, an active short circuit of the first electric motor, and switching an inverter lock.

[0033] The cut-off value can essentially comprise a value of 0, for example, at least one of a current and a voltage, for which the first rotor exhibits no or only a slight rotational movement, which, for example, leads to a rotational movement of the input element in the drive rotation direction. A slight rotational movement of the first rotor can occur if the rotational movement is so small that it is barely perceptible to a user with the naked eye. A slight rotational movement of the first rotor can occur if the rotational movement is not disturbing to the user.

[0034] The first electric motor can be operated with alternating current. The first electric motor can have three phases, for example, electrical conductors. For the active short circuit, the three phases of the first electric motor can be short-circuited. This ensures that the first electric motor cannot drive the input element if, for example, the vehicle is stationary, the drive wheel is prevented from rotating by a surface, and the output element is stationary. An active short circuit is particularly useful for the first electric motor designed as a permanent magnet synchronous machine (PSM).

[0035] The vehicle may have one or more inverters for operating the first electric motor. Each of the inverters may have one or more inverter switching units. The inverter switching units may be openable to lock the inverter. The supply of electrical power to the first electric motor may then be interrupted.

[0036] Shutting down the second electric motor may include at least one of controlling a rotor torque of the second rotor to a shutdown value, actively short-circuiting the second electric motor, and switching an inverter lock. Shutting down the second electric motor may be performed in the same manner as for the first electric motor.

[0037] In a second aspect, a control device is provided that is configured to execute a method according to one of the preceding embodiments. The control device can have at least one input interface for inputting signals into the control device and an output interface for outputting signals for controlling the drive unit.

[0038] The control device can have a user interface for inputting information, for example a limit value, for example for the speed of the input element, for determining the shutdown condition, into the control device. The control device can have an input interface and an output interface. The input interface can be configured to input signals into the control device. The input interface can be configured to input signals from at least one of the speed sensors. The control device can have a computing unit, a data memory, and a working memory. The control device can be configured to process the signals from the input interface. The control device can be configured to generate signals for the output interface. The output interface can be configured to output signals from the control device.For example, the output interface can be configured to control at least one of the first electric motor and the second electric motor. The output interface can be configured to output at least one operating parameter, for example a voltage value or a current value, of at least one of the first electric motor and the second electric motor.

[0039] In a third aspect, a drive unit is provided for a vehicle that can be operated at least temporarily using muscle power. A first electric motor can be operated with energy from an energy storage device to support a mechanical drive via a control device according to one of the embodiments of the second aspect with an adjustable power. A first rotor of the first electric motor and an input element of the mechanical drive are mechanically operatively connected to an output element via a superposition gear to drive the vehicle. At least one speed sensor is configured to detect a rotational movement of at least one of the input element, the output element, and the rotor.

[0040] Detecting the rotational movement may include detecting at least one of a rotational speed and a rotational direction. For example, a first rotational speed sensor may be provided. For example, a first rotational speed sensor may be provided that is configured to detect the rotational speed and the rotational direction of the input element. For example, a second rotational speed sensor may be provided that is configured to detect the rotor rotational speed of the first rotor. For example, a third rotational speed sensor may be provided that is configured to detect the output rotational speed of the output element.

[0041] In one embodiment of the drive unit, the superposition gearing can have a first planetary gear set with a first gear set element, a second gear set element, and a third gear set element. The input element can be mechanically connected to the second gear set element for inputting a drive force to the first planetary gear set. The first rotor can be mechanically connected to the first gear set element for inputting a drive force to the first planetary gear set. The output element can be mechanically connected to the third gear set element for outputting a drive force from the first planetary gear set.

[0042] The first electric motor can be configured to adjust a speed of the input element, for example, a user's pedaling frequency. This allows the drive unit to provide an electric continuously variable transmission, for example, an eCVT system. The first electric motor can be configured to adjust a gear ratio (iCVT). The first rotor can be arranged coaxially with the input element.

[0043] The first planetary gear set may include a first sun gear, a first planet carrier, a first planet pin, a first planet gear, and a first ring gear. The first sun gear may be arranged coaxially with the input element. The first sun gear may be arranged coaxially with the first rotor. The first sun gear may mesh with the first planet gear. The first planet gear may mesh with the first ring gear. The first planet gear may be rotatably mounted on the first planet pin, for example via a plain bearing, a needle bearing, or a roller bearing. The first planet gear may be formed by a stepped planet gear. The first planet pin may be attached to the first planet carrier.

[0044] The first planetary gear set can be formed by a positive planetary gear set or a negative planetary gear set. The first gear set element can be formed by the first sun gear. The second gear set element can be formed by the first planet carrier. The third gear set element can be formed by the first ring gear.

[0045] The input element can be connected to the second gear set element in a rotationally fixed manner. The input element can be connected to the second gear set element in a rotationally fixed manner in one direction via a first freewheel. The first freewheel can be configured such that the input element is connected to the second gear set element in a rotationally fixed manner in the drive direction and is connected to the second gear set element in a rotationally fixed manner counter to the drive direction.

[0046] The first rotor can be mechanically connected to the first gear set element via a pre-stage gearing. The pre-stage gearing can have a second planetary gear set. The second planetary gear set can be formed by a plus planetary gear set or a minus planetary gear set. The second planetary gear set can have a second sun gear, a second planet carrier, a second planet pin, a second planet gear, and a second ring gear. The first rotor can be connected in a rotationally fixed manner to the second sun gear. The second sun gear can mesh with the second planet gear. The second planet gear can mesh with the second ring gear.

[0047] The second planetary gear can be rotatably mounted on the second planetary pinion via a bearing, such as a needle bearing, a plain bearing, or a ball bearing. The second planetary gear can be formed by a stepped planetary gear. The second planetary pinion can be connected to the second planetary carrier.

[0048] The first rotor, the first planetary gear set, the second planetary gear set, the input member, and the output member may be arranged coaxially. The first planetary gear set and the second planetary gear set may be arranged in an axial direction between the first electric motor and the output member. The input member may be aligned in the axial direction. The input member may extend in the axial direction through at least one of the first rotor, the first planetary gear set, the second planetary gear set, and the output member.

[0049] The drive unit may comprise a stationary component, for example, a bicycle frame. The second ring gear may be fixed to the stationary component. The second planet carrier may be rotationally connected to the first gear set element of the first planetary gear set.

[0050] In one embodiment of the drive unit, a second rotor of a second electric motor can be operatively connected to the third gear set element for inputting a drive force into the superposition gear. The second electric motor can be configured to set a desired torque, a desired assist power, or a desired power difference for the mechanical drive. The second electric motor can be arranged axially parallel to the input element.

[0051] The second rotor can be mechanically connected to the second gear set element or the third gear set element via a transmission. The transmission can have a third planetary gear set. The third planetary gear set can have a third sun gear, a third planet carrier, a third planet pin, a third planet gear, and a third ring gear. The second rotor can be connected to the third sun gear in a rotationally fixed manner. The third sun gear can mesh with the third planet gear. The third planet gear can mesh with the third ring gear. The third planet gear can be rotatably mounted on the third planet pin via a bearing, for example a plain bearing, a needle bearing, or a ball bearing. The third planet gear can be formed by a stepped planet gear. The third planet pin can be attached to the third planet carrier.The third planetary carrier can be mechanically connected, for example, via a further transmission, to the third gear set element, for example the first ring gear, or to the second gear set element, for example the first planetary carrier, of the first planetary gear set. The third ring gear of the third planetary gear set can be fixed to the stationary component. The transmission can have an intermediate gear, for example a belt transmission, with an input element and an output element. The output element of the intermediate gear can be rotationally connected to the second or third gear set element, for example the first planetary carrier or the first ring gear.

[0052] In a fourth aspect, a vehicle is provided with at least one drive wheel and a drive unit according to one of the embodiments of the third aspect. The vehicle can be temporarily operated using muscle power. The vehicle can be formed by a bicycle, an e-bike, or a pedelec. The drive wheel is mechanically operatively connected to the drive unit such that the drive unit can propel the vehicle. The drive wheel can be mechanically operatively connected to the output element. The drive wheel can be mechanically operatively connected to the output element via an output gear, for example a chain drive or a belt drive. The drive wheel can have a wheel hub. The drive wheel can be mounted on the stationary component, for example via the wheel hub.An output element of the output gear can be connected to the drive wheel, for example via the wheel hub by means of a second freewheel, at least in one direction of rotation, for example the drive direction of rotation.

[0053] Figure 1 shows a flow diagram of an embodiment of a method for controlling a drive unit of a vehicle that can be operated at least temporarily with muscle power.

[0054] Figure 2 shows a flowchart of an embodiment of the method for controlling the drive unit.

[0055] Figure 3 shows a sectional view of a schematic diagram of an embodiment of the drive unit.

[0056] Figure 4 shows a sectional view of a schematic diagram of another embodiment of the drive unit

[0057] Figure 5 shows a sectional view of a schematic diagram of another embodiment of the drive unit.

[0058] Figure 6 shows a sectional view of a schematic diagram of another embodiment of the drive unit.

[0059] Figure 1 shows a flowchart of an embodiment of a method for controlling a drive unit of a vehicle, in this case an e-bike, which can be operated at least temporarily using muscle power. The drive unit has an input element 4, in this case a crankshaft of a mechanical drive with pedals, an output element 5, in this case a sprocket, a first electric motor 70 with a first rotor 71 and a first stator 72, an energy storage device, in this case a rechargeable battery, a superposition gear, and at least one speed sensor. The drive unit and its components are described in more detail with reference to Figures 3 to 6.

[0060] The first electric motor 70 can be operated with energy from an energy storage device to support the mechanical drive with an adjustable support power. The first rotor 71 of the first electric motor 70 and the input element 4 of the mechanical drive are mechanically operatively connected to the output element 5 via the superposition gear to drive the vehicle. A direction of rotation of the input element 4 is formed by a drive direction of rotation when driving the vehicle. The speed sensor is configured to detect a rotational movement of at least one of the input element 4, the output element 5, and the first rotor 71.

[0061] The method comprises, in a first step, determining a speed and a direction of rotation of the input element 4 via the at least one speed sensor. In a second step, the method comprises switching off the first electric motor 70 when a switch-off condition is reached. The switch-off condition is met at least when the speed of the input element 4 reaches or falls below a limit value and the direction of rotation of the input element 4 is opposite to the drive direction of rotation at a speed not equal to 0. The method then starts again with the first step. This can prevent the first electric motor 70 from exerting a force opposite to the drive direction of rotation on the input element 4 via the transmission gear when the driver is not applying any force to the pedals to drive the vehicle. This leads to a high level of operational reliability of the drive unit.

[0062] Further details of the process and the drive unit are described below.

[0063] The speed and direction of rotation of the input element 4 can be determined using various methods. In one embodiment, the speed sensor is configured to distinguish the direction of rotation of the input element 4. The speed and direction of rotation of the input element 4 can be determined directly. The speed sensor is connected between the input element 4 and the stationary component 9.

[0064] In one embodiment, the drive unit has a speed sensor for determining the rotor speed of the first rotor 71 and another speed sensor for determining the output speed of the output element 5. If the transmission has a first planetary gear set 10, as described with reference to Figures 3 to 6, the speed of the input element 4 can be determined indirectly via the speed equation at the first planetary gear set 10.

[0065] Figure 2 shows a flowchart of at least one of the preceding embodiments of the method for controlling the drive unit. The present embodiment has all features of at least one of the preceding embodiments. As previously described, the method begins with the first step, determining the speed and direction of rotation of the input element 4 via the at least one speed sensor. If the speed of the input element 4 falls below a limit value, then in the present embodiment the switch-off condition is reached. In the present case, the speed of the input element 4 is directed backward, i.e., is directed opposite to the drive direction of rotation and has a negative sign, and falls below a negative limit value. In other words, the absolute value of the speed of the input element 4 exceeds the absolute value of the negative limit value. The first electric motor 70 is then switched off.The method then begins again with the first step. Otherwise, the first electric motor 70 is operated in normal operation to support the mechanical drive with an assist power. The method then begins again with the first step.

[0066] In an alternative embodiment, the shutdown condition is reached when the rotational speed of input element 4 is 0. In this case, the rider does not move the pedal crankshaft. In an alternative embodiment, the shutdown condition is reached when the rotational speed of input element 4, either in the drive mechanism or opposite to the drive rotation direction, is less than a limit value. In this case, the rider barely moves the pedal crankshaft.

[0067] Figure 3 shows a sectional view of a schematic diagram of an embodiment of the drive unit. The drive unit can be controlled using a method according to one of the preceding embodiments. The drive unit has all the features of at least one of the preceding embodiments. The superposition gear is formed by the first planetary gear set 10. The drive unit further has a pre-stage gear formed by a second planetary gear set 20, a rear wheel as the drive wheel, which is operatively connected to the output element 5 via an output gear, in this case a chain drive, to drive the vehicle, and a stationary component 9, which in this case is formed by a bicycle frame.

[0068] The first rotor 71, the first planetary gear set 10, the second planetary gear set 20, the input member 4, and the output member 5 are arranged coaxially. The first planetary gear set 10 and the second planetary gear set 20 are arranged in an axial direction between the first electric motor 70 and the output member 5. The input member 4 extends in the axial direction through the first rotor 71, the first planetary gear set 10, the second planetary gear set 20, and the output member 5.

[0069] The first planetary gear set 10 has a first sun gear, a first planet carrier, a number of first planet pinions, a number of first planet gears, and a first ring gear. The first sun gear meshes with the first planet gears. Each of the first planet gears is rotatably supported on one of the first planet pinions. The first planet pinions are attached to the first planet carrier. The first planet gears mesh with the first ring gear. The second planetary gear set 20 has a second sun gear, a second planet carrier, a number of second planet pinions, a number of second planet gears, and a second ring gear. The second sun gear meshes with the second planet gears. Each of the second planet gears is rotatably supported on one of the second planet pinions. The second planet pinions are attached to the second planet carrier. The second planet gears mesh with the second ring gear.The input element 4 is connected to the first planetary carrier via a first freewheel 41, in a rotationally fixed manner in the drive direction of rotation. The input element 4 is rotatable relative to the first planetary carrier via the first freewheel 41, counter to the drive direction of rotation. The first ring gear is connected to the output element 5, in a rotationally fixed manner. As a result, the input element 4 is mechanically operatively connected to the output element 5 for driving the vehicle.

[0070] The first stator 72 is fixed to the stationary component 9. The first rotor 71 is connected in a rotationally fixed manner to the second sun gear. The second ring gear is fixed to the stationary component 9. The second planet carrier is connected in a rotationally fixed manner to the first sun gear. As a result, the first rotor 71 is mechanically connected to the output element 5 for driving the vehicle.

[0071] An output element, in this case an output sprocket, of the output gear is connected to the drive wheel in a rotationally fixed manner in the drive direction via a second freewheel 42. The drive wheel is rotatably mounted on the stationary component 9 via a bearing unit. The drive wheel is thus configured to drive the vehicle.

[0072] In an alternative embodiment, the first freewheel 41 is connected between the second planet carrier and the first sun gear such that the second planet carrier is connected to the first sun gear in a first preferred direction of rotation in a rotationally fixed manner. The second planet carrier is rotatable relative to the first sun gear in the opposite direction to the first preferred direction of rotation. In an alternative embodiment, the first freewheel 41 is connected between the first rotor 71 and the second sun gear such that the first rotor 71 is connected to the second sun gear in a second preferred direction of rotation. The first rotor 71 is rotatable relative to the second sun gear in the opposite direction to the second preferred direction of rotation. The first and second preferred directions of rotation are directions of rotation for which the vehicle can be moved in one direction of travel.

[0073] Figure 4 shows a sectional view of a schematic diagram of another embodiment of the drive unit. The present embodiment differs from the embodiments described with reference to Figure 3 in that the first freewheel 41 is not provided. The input element 4 is rotationally connected to the first planet carrier.

[0074] Figure 5 shows a sectional view of a schematic diagram of another embodiment of the drive unit. The present embodiment has all the features of one of the previous embodiments. In this case, the drive unit has a second electric motor 80 with a second rotor 81 and a second stator 82. The second stator 82 is fixed to the stationary component 9. The second rotor 81 is arranged axially parallel to the first rotor 71. The second rotor 81 is arranged in the same plane as the first rotor 71 in the axial direction. The second rotor 81 is operatively connected mechanically to the first ring gear via a transmission gear.

[0075] The transmission includes a third planetary gear set with a third sun gear, a third planet carrier, a number of third planet pinions, a number of third planet gears, and a third ring gear. The third sun gear meshes with the third planet gears. Each of the third planet gears is rotatably mounted on one of the third planet pinions. The third planet pinions are attached to the third planet carrier. The transmission further includes an intermediate gear, for example, a belt drive, with an input element and an output element.

[0076] The second rotor 81 is rotationally fixed to the third sun gear. The third ring gear is fixed to the stationary component 9. The third planet carrier is rotationally fixed to the input element of the intermediate gear. The output element of the intermediate gear is rotationally fixed to the first ring gear.

[0077] Figure 6 shows a sectional view of a schematic diagram of another embodiment of the drive unit. The present embodiment differs from the previous embodiment in that the output element of the intermediate gear is non-rotatably connected to the first planet carrier instead of the first ring gear. Reference numeral

[0078] 4 Input element

[0079] 5 Output element

[0080] 9 Stationary component

[0081] 10 First planetary gear set

[0082] 20 Second planetary gear set

[0083] 41 First freewheel

[0084] 42 Second freewheel

[0085] 70 First electric motor

[0086] 71 First rotor

[0087] 72 First stator

[0088] 80 Second electric motor

[0089] 81 Second rotor

[0090] 82 Second stator

[0091] I Determining a speed and a direction of rotation of the input element

[0092] II Switching off the first electric motor

Claims

Patent claims 1. A method for controlling a drive unit for a vehicle that can be driven at least temporarily by muscle power, wherein a first electric motor (70) is operable with energy from an energy storage device to support a mechanical drive with an adjustable power, a first rotor (71) of the first electric motor (70) and an input element (4) of the mechanical drive for driving the vehicle are mechanically operatively connected to an output element (5) via a superposition gear, a direction of rotation of the input element (4) when driving the vehicle is defined as a drive direction of rotation, at least one speed sensor is set up to detect a rotational movement of at least one of the input element (4), the output element (5) and the first rotor (71), the method comprises: - Determining (I) a rotational speed and a direction of rotation of the input element (4) via the at least one rotational speed sensor, and - Switching off (II) the first electric motor (70) when a switch-off condition is reached, which is reached at least when the determined speed of the input element (4) reaches or falls below a limit value and the determined direction of rotation of the input element (4) is opposite to the drive direction of rotation.

2. Method according to claim 1, characterized in that the at least one speed sensor is formed by a first speed sensor which is set up to detect the speed and the direction of rotation of the input element (4), and the determination (I) of the speed and the direction of rotation of the input element (4) comprises a direct detection of the speed and the direction of rotation via the speed sensor.

3. Method according to one of the preceding claims, characterized in that the superposition gear is formed by a first planetary gear set (10), the at least one speed sensor is formed by a second speed sensor, which is set up to detect the rotor speed of the first rotor (71), and by a third speed sensor, which is set up to detect the output speed of the output element (5), and the determination (I) of the speed and the direction of rotation of the input element (4) comprises an indirect determination via the rotor speed of the first rotor (71) and the output speed of the output element (5).

4. The method according to one of claims 1 or 2, characterized in that the superposition gear is formed by a first planetary gear set (10), a second rotor (81) of a second electric motor (80) is mechanically operatively connected to the output element (5) via the superposition gear for driving the vehicle, the at least one speed sensor is formed by a second speed sensor which is set up to detect the rotor speed of the first rotor (71), and by a fourth speed sensor which is set up to detect the rotor speed of the second rotor (81), and the determination (I) of the speed and the direction of rotation of the input element (4) comprises an indirect determination via the rotor speed of the first rotor (71) and the rotor speed of the second rotor (81).

5. Method according to claim 2 and 3 or 2 and 4, characterized in that the switch-off condition is reached when at least one of the directly determined speed of the input element (4) and the indirectly determined speed of the input element (4) reaches or falls below the limit value.

6. Method according to one of the preceding claims, characterized in that the switching off (II) of the first electric motor (70) comprises at least one of controlling a rotor torque of the first rotor (71) to a switch-off value, an active short circuit of the first electric motor (70) and switching an inverter lock.

7. Control device which is configured to carry out a method according to one of the preceding claims, wherein the control device has at least one input interface for inputting signals into the control device and an output interface for outputting signals for controlling a drive unit.

8. Drive unit for a vehicle that can be operated at least temporarily with muscle power, wherein a first electric motor (70) can be operated with energy from an energy store to support a mechanical drive via a control device according to claim 7 with an adjustable power, a first rotor (71) of the first electric motor (70) and an input element (4) of the mechanical drive for driving the vehicle are mechanically operatively connected to an output element (5) via a superposition gear, and at least one speed sensor is set up to detect a rotational movement of at least one of the input element (4), the output element (5) and the first rotor (71).

9. Drive unit according to claim 8, characterized in that the superposition gear has a first planetary gear set (10) with a first gear set element, a second gear set element and a third gear set element, the input element (4) is mechanically operatively connected to the second gear set element for inputting a drive force into the first planetary gear set (10), the first rotor (71) is mechanically operatively connected to the first gear set element for inputting a drive force into the first planetary gear set (10), and the output element (5) is mechanically operatively connected to the third gear set element for outputting a drive force from the first planetary gear set (10).

10. Drive unit according to claim 8 or 9, characterized in that a second rotor (81) of a second electric motor (80) is mechanically operatively connected to the third gear set element for inputting a drive force into the superposition gear.

11. A vehicle having at least one drive wheel and a drive unit according to one of claims 8 to 10, wherein the vehicle is temporarily operable by muscle power, and the drive wheel is mechanically connected to the drive unit such that the drive unit can move the vehicle.

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