Method for controlling a drive device during a load shift

Abstract

The invention relates to a method for controlling a drive device having an electric machine (2), an output (3), and a transmission (1) for transmitting a torque from the electric machine (2) to the output (3). The transmission (1) has a first clutch (11) and a second clutch (12) and is designed to provide a first gear with the first clutch (11) and a second gear with the second clutch (12) for torque transmission. The method is adapted to transfer the first clutch (11) into an open state, transfer the second clutch (12) into a closed state, and change a control mode of the electric machine (2) from a standard mode to a synchronization mode for a power shift from the first gear to the second gear. The invention also relates to a drive device and a work machine having the drive device.

Description

Technical area

[0001] The present invention relates to a method for controlling a drive device. Furthermore, the invention relates to a drive device and a work machine having the drive device. State of the art

[0002] In work machines, for example, wheel loaders, their drive system serves to provide propulsion. For this purpose, work machines are conventionally equipped with an internal combustion engine that drives one input side of a transmission, with the transmission transmitting torque as driving force to an output.

[0003] DE 11 2018 000 362 T5 discloses a vehicle drive device that enables a large torque to be quickly transmitted to the wheels, even when starting an internal combustion engine and downshifting an automatic transmission are performed in the state where the internal combustion engine is stopped and the torque of a rotating electric machine is transmitted to the wheels. An engagement device is engaged, and the engine speed is increased to a startable speed. After the engine speed is increased to the startable speed, the engine is ignited, and the engagement device is then disengaged. After the engine is ignited, the engine speed is increased to a post-downshift synchronous speed by the engine torque, and the engagement device is disengaged.The speed of the rotary electric machine is then increased to the post-downshift synchronous speed, and the automatic transmission is downshifted. The engagement device is engaged after the downshift is completed.

[0004] EP 2 226 230 B1 discloses a control method for shifting a gear in an automatic manual transmission to change from a current gear to a next gear. The automatic manual transmission comprises a transmission provided with at least one primary shaft and at least one secondary shaft connected to drive wheels, and at least one clutch arranged between the primary shaft of the transmission and a drive shaft of an engine.The control method comprises the following steps: determining a target torque that must be transmitted via the clutch when the clutch is at least partially closed, determining a target rotational speed of the drive shaft of the engine when the clutch is at least partially closed, and determining a target engine torque of the engine according to the target torque that must be transmitted through the clutch and according to the rotational speed target of the drive shaft of the engine.

[0005] DE 101 38 998 A1 relates to a device and a method for controlling a gearshift sequence in a powershift transmission in a motor vehicle. To ensure smooth operation of the powershift transmission, DE 101 38 998 A1 provides that the device can be used to adjust a speed of the transmission input shaft and a torque at the transmission output shaft. To this end, DE 101 38 998 A1 proposes that, in a first phase, the torque at the transmission output shaft is set to a first torque target value, and, in a second phase, the speed of the transmission input shaft is set to a speed target value and, simultaneously, the torque of the transmission output shaft is set to a second torque target value.

[0006] In order not to interrupt the supply of drive power during gear changes, a combustion engine can be subjected to a powershift, in which the gear change takes place without any interruption in the drive power. During a powershift, a change is made from one current gear to another by disengaging a clutch and, for example, simultaneously engaging another clutch. The combustion engine is synchronized with the output via the additional clutch, as the changed gear results in a different gear ratio in the drive device between the combustion engine and the output. The combustion engine is braked to a new lower speed when shifting up, for example, and accelerated to a new higher speed when shifting down. This avoids a functional interruption in the drive power.

[0007] If an electric motor is used as a traction motor to provide propulsion instead of the combustion engine, the load on the respective clutches may be greater due to the higher inertia of the electric motor. For example, the clutch load, such as heat input into the clutches, may be increased, and clutch wear may be excessive. Furthermore, depending on the system design, the speed jumps between gears may be larger, as electric motors have a wider usable speed range. This type of manual transmission design also leads to increased clutch load. Description of the invention

[0008] A first aspect of the invention relates to a method for controlling a drive device. The drive device can be configured as a drive device of a vehicle, such as a work machine. The work machine can be configured, for example, as an agricultural machine or construction machine. A drive device can be configured to provide driving power for the vehicle. In addition, the drive device can also be configured to provide working power, for example, for working hydraulics.

[0009] The drive device comprises an electric motor, an output, and a transmission for transmitting torque from the electric motor to the output. The torque transmission can propel the vehicle. The electric motor can be designed, for example, as an asynchronous motor or synchronous motor. The electric motor can also be designed for recuperation. The drive device can have an energy storage device, such as a battery, for supplying energy to the electric motor. The drive device can have a motor controller for the electric motor, which can be designed, for example, as an inverter. The output can be designed, for example, as a driven axle, wheels, or a track.

[0010] The transmission has a first clutch and a second clutch and is designed to provide a first gear with the first clutch and a second gear with the second clutch for torque transmission. The transmission can be designed as a manual transmission, for example. The transmission can have spur gear sets and planetary gear sets, for torque transmission. The first gear can provide a different gear ratio between the electric motor and the output than the second gear. The transmission can be a multi-speed transmission with at least two gears. The first clutch and the second clutch can each be designed, for example, as a frictional clutch, such as a dry or wet multi-plate clutch. The first clutch and the second clutch can, for example, be designed as hydraulically actuated clutches which have a clutch pressure as a control variable.The possible torque transmission in a clutch may depend on the clutch pressure required to actuate it before, for example, excessive slippage occurs. The first clutch and / or the second clutch may also be designed as electrically or electromagnetically actuated clutches, which use a current as a control variable to adjust the transmittable torque.

[0011] The method of the first aspect is adapted to transfer the first clutch into an open state and the second clutch into a closed state for a powershift from the first gear to the second gear. The open state is a state in which no torque is transmitted between the input and output of the respective clutch. The closed state is a state in which there is complete frictional connection between the input and output of the second clutch and the entire applied torque can be transmitted. When a clutch is actuated, it can be adjusted from the open state to the closed state. In a slipping phase between the open state and the closed state, a clutch can already transmit torque, but not to the full extent.For example, for the powershift, the clutch pressure on the second clutch is increased, while the clutch pressure on the first clutch is reduced. The first gear is a starting gear, which is engaged before the powershift. The second gear is a target gear, which is engaged after the powershift. Both the starting gear and the target gear can be any gear of the transmission. Just as an example, the first gear can correspond to 1st gear of the transmission and the second gear to 2nd gear. The method is equally suitable for upshifts between non-adjacent gears, e.g. from 1st to 4th gear, and for downshifts with and without skipping gears, e.g. from 3rd to 2nd gear, from 5th to 1st gear, etc.Limitations on skipping gear steps can, however, arise from overloading the clutches, transmission components, or even the performance of the electric motor. The first clutch and the second clutch can also be any clutches assigned to the two gear steps during powershift operation. The first clutch can be a clutch that must be opened to change from the starting gear step, and the second clutch can be a clutch that must be closed to change to the target gear step. Depending on the gear step, the first clutch and the second clutch can therefore be different clutches in the transmission. For example, the transmission can have an assigned clutch for each gear step, which must be closed to engage that gear step.As a result of the powershift, the current speed of the electric motor changes from a starting speed to a target speed while the output speed remains constant. The target speed is lower than the starting speed for upshifts and higher than the starting speed for downshifts, provided the vehicle speed remains essentially constant during the shift.

[0012] The method of the first aspect is adapted to change a control mode of the electric machine from a standard mode to a synchronization mode for the load shift. The standard mode can, for example, be a mode for continuous operation of the electric machine before shifting and, alternatively or additionally, a mode for operating a permanently engaged gear. The synchronization mode can serve to control the electric machine in a suitable manner to support the transition of the current speed of the electric machine from the starting speed to the target speed and thus the load shift. For example, the engine control can use a different engine characteristic curve for engine control in the synchronization mode than in the standard mode.For example, in synchronization mode, the electric motor accelerates during upshifts and decelerates during downshifts in order to actively support synchronization with the output. The method is adapted, for example, to carry out a powershift in traction mode as well as a powershift in overrun mode. Traction mode can be an operating case in which the electric motor predominantly introduces power into the transmission. Traction mode occurs, for example, when the vehicle is accelerating or its speed is being maintained against driving resistance, for example against air resistance or gravity when driving uphill. Overrun mode can be an operating case in which the output predominantly introduces power into the transmission. Overrun mode occurs, for example, when the vehicle is rolling downhill.The electric motor can also recuperate to reduce its speed. This allows for particularly low energy consumption during powershifts. This supports the required frictional power of the second clutch and reduces clutch load. Active synchronization support from the electric motor during powershifts can reduce clutch slippage and the associated heat input into the clutches, thus relieving the load on the clutches while maintaining the same target slip time and improving their durability compared to synchronization solely by the clutches. Furthermore, the target slip time during powershifts can be shortened thanks to the synchronization mode without exceeding the permissible heat input into the clutches.

[0013] The method may comprise a step of performing the powershift from the first gear to the second gear. Performing the powershift may comprise disengaging the first clutch. Performing the powershift may comprise engaging the second clutch, wherein this engaging may at least partially overlap with the disengaging of the first clutch. For example, the second clutch may transmit a portion of the torque during the powershift that can no longer be transmitted by the first clutch because, for example, its clutch pressure is already too low. Performing the powershift may comprise a step of changing the control mode of the electric machine from the standard mode to the synchronization mode, for example at the start of the powershift and alternatively or additionally depending on an actuation of the second clutch.

[0014] The method for controlling the drive device can be divided into several phases. Likewise, the powershift can be divided into several phases. Before the powershift, there is a first phase during which the first clutch is closed, so that the electric motor and an output side of the first clutch have the same speed, and the second clutch is open, so that an output side of the second clutch has no connection to the electric motor. Thus, in the first phase, the transmission transmits the torque using the first gear. The electric motor is controlled using the standard mode. In the first phase, the acceleration or deceleration of the output therefore takes place via the electric motor and optionally a braking system. In the first phase, a request for a gear change and the powershift can already be made.For example, the second clutch can be pre-filled in the first phase, whereby the pre-filled second clutch then, for example, does not yet transmit any torque. The clutch pressure of the first clutch can already be reduced, but the entire torque can still be transmitted by the first clutch and is, for example, transmitted.

[0015] The actual shift of the load-transmitting clutch occurs in a second phase, during which the first clutch is shifted into an open state and the second clutch is shifted into a closed state. This second phase can also be referred to as an overlap phase, during which, for example, the clutch pressure of the second clutch is increased and the clutch pressure of the first clutch is reduced, so that the first clutch and the second clutch transmit the torque simultaneously and proportionally. The speed and torque of the output remain essentially constant during the power shift, thus avoiding a functional interruption of the drive force.

[0016] In addition, the electric machine is controlled with the synchronization mode as the operating mode during the second phase.

[0017] The second phase can be followed by a third phase during which the first clutch is disengaged and the second clutch is engaged, so that the electric motor and the output side of the second clutch have the same speed. The second gear is thus engaged and the powershift is complete. In the third phase, for example, the entire torque is transmitted by the second clutch alone. The second clutch may not yet be actuated with maximum clutch pressure. For example, the second clutch is actuated further in the third phase, e.g. by increasing the pressure, in order to fully engage the second clutch and to be able to safely transmit even higher torque.

[0018] In a further embodiment of the method, after the load shift has been completed, the control mode for the electric motor can be switched back to standard mode. Thus, in the third phase, the electric motor can be operated in standard mode again, so that a starting state for a new load shift prevails and the new load shift can be carried out without delay. Furthermore, the electric motor can then be controlled again, for example, using the usual motor characteristic curve for driving operation, which can be particularly energy-efficient.

[0019] In a further embodiment of the method, the control mode can be switched from synchronization mode to standard mode at a time when the second clutch is already transmitting the entire torque from the electric machine. For example, the control mode can be switched from synchronization mode to standard mode when the second clutch is just actuated sufficiently to transmit the entire torque currently provided by the electric machine. After the control mode has switched back to standard mode, a control variable of the second clutch can be increased to a locking amount to increase the torque transmission capacity. Optionally, a rate of change of the control variable of the second clutch can be increased so that the locking amount is reached more quickly. This allows the second clutch to be actuated particularly quickly with a maximum clutch pressure.

[0020] In a further embodiment of the method, the control mode can change from standard mode to synchronization mode at a time when the first clutch is still transmitting the entire torque from the electric machine. For example, the change can occur at a predetermined time interval at a time when the first clutch is no longer transmitting the entire torque for the first time. This time interval can be fixed or, for example, specified as a function of a drive device state, such as a current speed or a current torque of the electric machine. In principle, the electric machine can lag behind control specifications because the electric machine can only implement any control specifications with a time offset due to mass inertia, switching times, control times and other delays.In order to compensate for this time offset and to enable immediate control of the electric machine when entering a slipping phase of the clutches with the synchronization mode, for example to change the speed of the electric machine, the change of the control mode from the standard mode to the synchronization mode can be brought forward compared to the transition from the first phase to the second phase.

[0021] In a further embodiment of the method, the standard mode can be torque control of the electric machine and the synchronization mode can be speed control of the electric machine. With torque control, for example, the electric machine can be specified to generate torque depending on a vehicle state and, alternatively or additionally, a driving requirement. With speed control, for example, the electric machine can be specified to generate a speed depending on a vehicle state and, alternatively or additionally, a driving requirement. Torque control is particularly suitable as a standard mode. This means, for example, that respective power requirements can be implemented particularly easily and precisely. In addition, it can be used to accelerate or decelerate the output or the drive in the first phase and, alternatively or additionally, in the third phase.The driven machine can be easily controlled by specifying the appropriate torque on the electric motor. Speed ​​control is particularly suitable as a synchronization mode because it enables a simple and efficient transition from the starting speed to the target speed. For example, speed control can be used to reliably prevent excessive differential speed and, alternatively or additionally, excessive synchronization work in the clutches.

[0022] In a further embodiment of the method, the current speed of the electric motor can be converted from a starting speed to a target speed during a power shift from the first gear to the second gear using a predefined curve. This minimizes the synchronization effort of the clutches and, alternatively or additionally, optimizes the shift time. The predefined curve allows for a very flexible adjustment of clutch load, shift comfort, and shift time.

[0023] In a further embodiment of the method, a rate of change of the current speed can be constant at least in a partial range. For example, the rate of change of the current speed can always be constant during the transition from the starting speed to the target speed. For example, the predetermined curve can be partially linear, at least in certain areas, to effect a uniform increase or decrease in the clutch load. However, the rate of change of the speed can also be variable.

[0024] In a further embodiment of the method, the rate of change of the current speed can decrease at least in a partial range before reaching the target speed. This can provide a smooth transition of the second clutch between the slipping phase and the engaged state. This can improve shifting comfort and reduce clutch load.

[0025] In a further embodiment of the method, the rate of change of the current speed can increase at least in a partial range after leaving the starting speed. For example, the electric motor can initially brake or accelerate at a high rate of change in order to quickly reduce a differential speed in the second clutch in a mid-range of the powershift. This allows the shift time and, alternatively or additionally, the clutch load to be low.

[0026] In a further embodiment of the method, the standard mode can be torque control of the electric machine and the synchronization mode can be synchronization torque control of the electric machine. With synchronization torque control, the electric machine can generate a motor torque in order to change a current speed of the electric machine from a starting speed to a target speed. With speed control in synchronization mode, a load can be disregarded when programming a motor control. With torque control in synchronization mode, on the other hand, implementation of the control can be particularly simple and a reaction time of the electric machine can be particularly short. If the target speed during load switching is lower than the starting speed, the electric machine can generate a braking torque until the current speed of the electric machine reaches the value of the target speed.If the target speed during load switching is greater than the starting speed, the electric motor can generate an acceleration torque until the current speed of the electric motor reaches the target speed. Optionally, the braking torque or acceleration torque can be selected to be greater than the corresponding rated torques for a continuous load, since load switching only requires brief load peaks from the electric motor. This allows for particularly fast load switching.

[0027] According to the invention, a control variable of the first clutch is changed before the control mode changes from the standard mode to the synchronization mode for transferring the first clutch to the open state in order to coordinate an actual start of the transfer of the first clutch to the open state and the change of the control mode from the standard mode to the synchronization mode. Thus, the control variable, for example the clutch pressure, can already be reduced while the electric machine is still operating in the standard mode, so that the first clutch starts to slip and the switch to the synchronization mode occur simultaneously or with a desired time offset. For example, the control variable can be changed such that the first clutch can just about transmit a torque generated by the electric machine without slip or with a permissible slip.Optionally, the control variable of the first clutch can be maintained with a residual value during operation in synchronization mode. The first clutch can therefore remain slightly actuated, for example, by being pressed. For example, after the end of the power shift and return to the standard mode for controlling the electric motor, the first clutch can be completely deactuated, for example, by completely depressurizing.

[0028] In a further embodiment of the method, the second clutch can be pre-filled before the control mode changes from standard mode to synchronization mode. For example, a cylinder of a hydraulic actuator can already be filled with hydraulic oil. For example, a friction element of the second clutch can already be brought into engagement. This can reduce the reaction time when adjusting the second clutch for powershifting. Furthermore, the second clutch can be controlled more precisely. This can also facilitate timing of the control mode change.

[0029] A second aspect of the invention relates to a drive device. The drive device can, for example, be designed to carry out the method according to the first aspect. Respective advantages and further features can be found in the description of the first aspect, with embodiments of the first aspect also forming embodiments of the second aspect, and vice versa.

[0030] The drive device comprises an electric motor, an output, and a transmission for transmitting torque from the electric motor to the output. The transmission has a first clutch and a second clutch and is configured to provide a first gear stage with the first clutch and a second gear stage with the second clutch for torque transmission. For example, the associated clutch is engaged to provide the respective gear stage. The drive device comprises a control device. The control device may, for example, comprise a clutch control unit and an inverter.The control device is configured to transfer the first clutch to an open state for a power shift from the first gear to the second gear, to transfer the second clutch to an engaged state, and to change a control mode of the electric motor from a standard mode to a synchronization mode. The control device can be configured to perform at least one speed control or one torque control.

[0031] A third aspect relates to a work machine with a drive device. The work machine and, alternatively or additionally, its drive device can be designed, for example, to be operated using the method according to the first aspect. The work machine can have a drive device according to the second aspect. Respective advantages and further features can be found in the description of the first and second aspects, respectively, wherein embodiments of the first and second aspects also form embodiments of the third aspect, and vice versa.

[0032] The work machine has a drive device which has an electric machine, an output and a transmission for transmitting a torque from the electric machine to the output, wherein the transmission has a first clutch and a second clutch and is designed to provide a first gear stage with the first clutch and a second gear stage with the second clutch for the torque transmission. The drive device has a control device which is designed to transfer the first clutch into an open state for a power shift from the first gear stage to the second gear stage, to transfer the second clutch into a closed state and to change a control mode of the electric machine from a standard mode to a synchronization mode. The drive device is designed to drive the work machine for driving.For example, a drive torque is generated by the electric motor and transferred to the output via the transmission, translating the currently selected gear. The work machine can have an energy source designed to supply the electric motor with electrical energy. The work machine can have a working device that can also be driven by the drive device. Short description of the characters Fig. 1 is a schematic representation of a drive device of a work machine. Fig. 2 is a diagram showing a time course of various speeds and control variables for the control of the drive device according to Fig. 1 illustrates a load switching situation. Fig. 3 is a diagram showing a modified control of a drive motor of the drive device according to Fig. 1 illustrates the load switching. Detailed description of embodiments

[0033] Fig. 1 shows a schematic representation of a drive device according to one embodiment. The drive device has a transmission 1, an electric machine 2, and an output 3. The transmission 1 is a multi-speed transmission and has a first clutch 11 and a second clutch 12. The first clutch 11 is connected to a first transmission element 13. When the first clutch 11 is engaged and the second clutch 12 is disengaged, torque is transmitted from the electric machine 2 via the first clutch 11 and the first transmission element 13 to the output 3 with a first transmission ratio, i.e., a first gear stage. In the example shown, the first transmission element 13 is designed as a gear stage. The second clutch 12 is connected to a second transmission element 14.When the second clutch 12 is engaged and the first clutch 11 is disengaged, torque is transmitted from the electric motor 2 via the second clutch 12 and the second transmission element 14 to the output 3 with a second transmission ratio, i.e. a second gear stage. In the example shown, the second transmission element 14 is also designed as a gear stage, although the tooth diameters are different from those of the first transmission element 13. In other embodiments, at least one of the two transmission elements 13, 14 is designed as a planetary gear set. In the example shown, the first clutch 11 and the second clutch 12 are each designed as hydraulically actuated clutches. The first clutch 11 is controlled with a first clutch pressure K1 and the second clutch 12 with a second clutch pressure K2 as respective control variables. A position and a contact pressure are proportional to the control variable.At a high clutch pressure K1, K2, the two clutches 11, 12 are closed. The drive device further comprises a control device (not shown) that is adapted to selectively control the electric motor 2 and the actuation of the two clutches 11, 12.

[0034] Fig. Figure 2 is a diagram illustrating a time course of various speeds and control variables according to the embodiment. The abscissa 50 represents a time during a power shift from the first gear to the second gear, the left ordinate 52 represents speeds, and the right ordinate 54 represents clutch pressures. Fig. 2, a characteristic curve K1 illustrates the clutch pressure of the first clutch 11 and a characteristic curve K2 illustrates the clutch pressure of the second clutch 12. Furthermore, a characteristic curve n_EM illustrates a speed of the electric machine 2. A characteristic curve Δn_12 illustrates a difference in speed between an input and an output of the second clutch 12 and a characteristic curve Δn_11 illustrates a difference in speed between an input and an output of the first clutch 11.

[0035] During the illustrated power shift from the first gear to the second gear, the current speed n_EM of the electric machine 2 is transferred from a high starting speed n_EM_1 to a low target speed n_EM_2 at a constant output speed, since the second gear has a higher gear ratio than the first gear. In the example of Fig. 2 the power shift takes place from a lower gear to a higher gear (upshift), so that the starting speed n_EM_1 is greater than the target speed n_EM_2.

[0036] The load switching can be divided into a first phase P1, a second phase P2 and a third phase P3. The first phase P1 corresponds to the time in which the current speed n_EM of the electric machine 2 corresponds to the starting speed n_EM_1. Similarly, the third phase P3 corresponds to the time in which the current speed n_EM of the electric machine 2 corresponds to the target speed n_EM_2. In contrast, the second phase P2 corresponds to the time in which the current speed n_EM of the electric machine 2 is transferred from the starting speed n_EM_1 to the target speed n_EM_2. The phases P1, P2 and P3 are in Fig. 2 separated by vertical dashed lines.

[0037] Before the start of the power shift in the first phase P1, the first clutch 11 is fully closed and its clutch pressure K1 assumes a maximum value, so that the torque of the electric machine 2 is transmitted completely via the first clutch 11 and the first transmission element 13. A differential speed Δn_11 in the first clutch 11 is zero. Meanwhile, the second clutch 12 is fully open, so that the second clutch 12 and the second transmission element 14 do not transmit any torque. There may be a difference between an input speed of the respective clutches 11, 12 and the speed of the electric machine 2 due to further gear ratios between the electric machine 2 and the respective clutches 11, 12.

[0038] At the beginning of the powershift, but before the transition from the first phase P1 to the second phase P2, the second clutch 12 is pre-filled with a preliminary amount K2' of the clutch pressure K2. This eliminates any air gap in the second clutch 12. After the pre-filling of the second clutch 12, its clutch pressure K2 is maintained at the preliminary amount K2' or below and then further increased for the actual actuation of the second clutch 12. Also before the transition from the first phase P1 to the second phase P2, the clutch pressure K1 of the first clutch 11 is reduced.

[0039] The transition from the first phase P1 to the second phase P2 occurs as soon as the first clutch 11 can no longer fully transmit the torque of the electric motor 2 and part of the torque is supported by the second clutch 12. As soon as the first clutch 11 slips due to the decreased clutch pressure K1, the differential speed Δn_11 increases. As soon as the second clutch 12 begins to engage, the differential speed Δn_12 decreases. In the example shown, the slipping of the first clutch 11 and the engagement of the second clutch 12 begin at approximately the same time.

[0040] In the example shown, shortly before the transition from the first phase P1 to the second phase P2, the control mode of the electric machine 2 is changed from a standard mode to a synchronization mode. The standard mode is a torque control of the electric machine 2. The synchronization mode is Fig. 2, a speed control of the electric machine 2. The change already takes place before the transition to the second phase P2 in order to take delays in the regulation and control of the electric machine 2 into account. The control device then controls the electric machine 2 in the second phase P2 such that the current speed n_EM of the electric machine 2 is transferred in a speed-controlled linear manner from the starting speed n_EM_1 to the target speed n_EM_2. The target speed n_EM_2 is reached when the second clutch 12 completely transmits the torque. The speed of the electric machine 2 is synchronized with the target speed n_EM_2 purely by the speed control according to the synchronization mode. In another embodiment, the second clutch 12 contributes to this synchronization through friction work, wherein the electric machine 2 actively reduces its speed due to its speed control.In yet another embodiment, recuperation occurs. It should be noted here that the linear decrease in the current speed n_EM, and in particular the transitions to the starting speed n_EM_1 and the target speed n_EM_2, are only shown in an idealized manner; in the real case, the corresponding curves in the diagram will be rounded and smooth, rather than sharply bending.

[0041] In the first phase, the clutch pressure K1 of the first clutch 11 is reduced, so that at the start of the second phase P2, it can no longer fully transmit the torque of the electric motor 2. The clutch pressure K2 in the first clutch 11 is reduced rapidly in the second phase P2 shortly after its start, so that little or no torque is transmitted by the first clutch 11. In the example shown, when upshifting, the clutch pressure K1 of the first clutch 11 is maintained at a residual value K1' during the second phase P2. The clutch pressure K2 of the second clutch 12 continues to build up, so that it slips successively less and transmits more torque. As a result, the current speed n_EM is transferred to the target speed n_EM_2 during the second phase P2. Since the decreasing slipping of the second clutch 12 is superimposed on the aforementioned speed control, the electric motor 2 thus relieves the load on the second clutch 12.

[0042] The transition from the second phase P2 to the third phase P3 occurs as soon as the second clutch 12 can fully transmit the current torque of the electric machine 2 and is synchronized, whereby the differential speed Δn_12 in the second clutch 12 is zero. In the third phase P3, the clutch pressure K2 of the second clutch 12 is then further increased to a locking amount K2" with a steep gradient. This increase in the clutch pressure K2 of the second clutch 12 does not cause any synchronization work or frictional loading of the second clutch 12 and can therefore occur quickly. As a result, the second clutch 12 can then also reliably transmit higher torques. In addition, at the start of the third phase P3, the control mode changes back to standard mode, and the electric machine 2 continues to operate with torque control. The load shift is then completed.

[0043] Fig. Figure 3 is a diagram illustrating a modified control for load switching. Fig. 2, the current speed n_EM of the electric machine 2 is reduced linearly in the second phase P2, and the change from the constant starting speed n_EM_1 to the linearly decreasing current speed n_EM as well as from the linearly decreasing current speed n_EM to the target speed n_EM_2 occurs with an almost discrete jump in the rate of change. In the modified control of Fig. 3, the current speed n_EM of the electric machine 2 continues to decrease strictly monotonically. The speed of the electric machine 2 follows an S-shaped curve in the second phase P2. More precisely, the rate of change of the current speed n_EM increases after leaving the starting speed n_EM_1 and decreases again before reaching the target speed n_EM_2. If the course of the current speed n_EM over time is viewed as a mathematical function, then Fig. 2 the idealized kinked transition to the constant starting speed n_EM_1 and target speed n_EM_2 of a discontinuity in the first derivative of the function, which would result in a sudden jump in the angular acceleration of the electric machine 2. In contrast, the kink-free and S-shaped course of Fig. 3 a continuous derivative of the function and thus a gentle angular acceleration of the electric machine 2. This improves the switching comfort and reduces the load on the drive device in the modified embodiment. Reference symbol 1 gearbox 2 electric machine 3 Downforce 11 first clutch 12 second clutch 13 first gear element 14 second gear element 50 Abscissa: Time during a load shift 52 left ordinate in Fig. 2 and Fig. 3: Speed, differential speeds 54 right ordinate in Fig. 2: Clutch pressures Δn_11 Differential speed of the first clutch Δn_12 Differential speed of the second clutch n_EM current speed n_EM_1 Starting speed n_EM_2 Target speed K1 Control variable of the first clutch (clutch pressure) K1' Remaining amount K2 Control variable of the second clutch (clutch pressure) K2' provisional amount K2" locking amount P1 first phase P2 second phase P3 third phase

Claims

[1] Method for controlling a drive device which has an electric machine (2), an output (3) and a transmission (1) for transmitting a torque from the electric machine (2) to the output (3), wherein the transmission (1) has a first clutch (11) and a second clutch (12) and is designed to provide a first gear stage with the first clutch (11) and a second gear stage with the second clutch (12) for the torque transmission, wherein the method is adapted to transfer the first clutch (11) into an open state, to transfer the second clutch (12) into a closed state and to change a control mode of the electric machine (2) from a standard mode to a synchronization mode for a power shift from the first gear stage to the second gear stage, characterized bythat a control variable (K1) of the first clutch (11) is changed before the change of the control mode from the standard mode to the synchronization mode for transferring the first clutch (11) to the open state in order to coordinate an actual start of the transfer of the first clutch (11) to the open state and the change of the control mode from the standard mode to the synchronization mode. [2] Method according to claim 1, characterized by that after the load switching has taken place, the control mode for the electric machine (2) is changed back to the standard mode. [3] Method according to claim 2, characterized by that the change of the control mode from the synchronization mode to the standard mode is carried out at a time when the second clutch (12) is already transmitting the entire torque from the electric machine (2). [4] Method according to one of the preceding claims, characterized bythat the change of the control mode from the standard mode to the synchronization mode is carried out at a time when the first clutch (11) still transmits the entire torque from the electric machine (2). [5] Method according to claim 1 or 2, characterized by that the standard mode is a torque control of the electric machine (2) and the synchronization mode is a speed control of the electric machine (2). [6] Method according to claim 5, characterized by that a current speed (n_EM) of the electric machine (2) is transferred from a starting speed (n_EM_1) to a target speed (n_EM_2) during the load shift from the first gear stage to the second gear stage with a predetermined curve, wherein a rate of change of the current speed (n_EM) is constant at least in a partial range. [7] Method according to claim 5 or 6, characterized bythat a current speed (n_EM) of the electric machine (2) is transferred from a starting speed (n_EM_1) to a target speed (n_EM_2) during the load shift from the first gear to the second gear with a predetermined curve, wherein the rate of change of the current speed (n_EM) decreases at least in a partial range before reaching the target speed (n_EM_2). [8] Method according to one of claims 5 to 7, characterized by that a current speed (n_EM) of the electric machine (2) is transferred from a starting speed (n_EM_1) to a target speed (n_EM_2) during the load shift from the first gear stage to the second gear stage with a predetermined profile, wherein the rate of change of the current speed (n_EM) increases at least in a partial range after leaving the starting speed (n_EM_1). [9] Method according to claim 1 or 2, characterized byin that the standard mode is a torque control of the electric machine (2) and wherein the synchronization mode is a synchronization torque control of the electric machine (2), wherein during the synchronization torque control the electric machine (2) generates a motor torque in order to change a current speed (n_EM) of the electric machine (2) from a starting speed (n_EM_1) to a target speed (n_EM_2). [10] Method according to one of the preceding claims, characterized by that the second clutch (12) is pre-filled before the control mode changes from the standard mode to the synchronization mode. [11] Drive device comprising an electric machine (2), an output (3) and a transmission (1) for transmitting a torque from the electric machine (2) to the output (3), wherein the transmission (1) comprises a first clutch (11) and a second clutch (12) and is designed to provide a first gear stage with the first clutch (11) and a second gear stage with the second clutch (12) for the torque transmission, wherein the drive device comprises a control device which is designed to transfer the first clutch (11) into an open state for a power shift from the first gear stage to the second gear stage, to transfer the second clutch (12) into a closed state and to change a control mode of the electric machine (2) from a standard mode to a synchronization mode, characterized byin that the control device is further designed to change a control variable (K1) of the first clutch (11) before the change of the control mode from the standard mode to the synchronization mode for transferring the first clutch (11) into the open state, in order to coordinate an actual start of the transfer of the first clutch (11) into the open state and the change of the control mode from the standard mode to the synchronization mode. [12] Work machine, wherein the work machine has a drive device which has an electric machine (2), an output (3) and a transmission (1) for transmitting a torque from the electric machine (2) to the output (3), wherein the transmission (1) has a first clutch (11) and a second clutch (12) and is designed to provide a first gear stage with the first clutch (11) and a second gear stage with the second clutch (12) for the torque transmission, wherein the drive device has a control device which is designed to transfer the first clutch (11) into an open state for a power shift from the first gear stage to the second gear stage, to transfer the second clutch (12) into a closed state and to change a control mode of the electric machine (2) from a standard mode to a synchronization mode, and wherein the drive device is designed toto drive the work machine for driving, characterized by in that the control device is further designed to change a control variable (K1) of the first clutch (11) before the change of the control mode from the standard mode to the synchronization mode for transferring the first clutch (11) into the open state, in order to coordinate an actual start of the transfer of the first clutch (11) into the open state and the change of the control mode from the standard mode to the synchronization mode.

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