Method for operating a drive train for a work machine, drive train for a work machine and work machine

Abstract

Method for operating a drive train (1) for a working machine, wherein a first electric motor (2) drives a working drive (6) of the working machine via a first gear arrangement (4), wherein a second electric motor (3) drives a travel drive (7) of the working machine via a second gear arrangement (5) and wherein during a shifting operation of the second transmission arrangement (5) from a higher gear to a lower gear, the speed of the second electric motor (3) is increased, characterized in that during the switching process, a drive connection is established (22) between the first electric motor (2) and the travel drive (7) via a first clutch (8), so that the travel drive (7) is driven (24, 25, 27, 28) by the first electric motor (2) during the switching process.

Description

[0001] The present invention relates to a method for operating a drive train for a work machine according to the preamble of claim 1, a drive train for a work machine according to the preamble of claim 8 and a corresponding work machine.

[0002] Electrically powered work machines, such as wheel loaders, skid steer loaders, telescopic loaders, dump trucks and excavators, are known in the art. Such electrically powered work machines are either purely electrically powered, i.e. they are powered exclusively by an electric battery or accumulator. Or they are diesel-electric powered, which means that the required energy is provided by a diesel-powered generator, usually in conjunction with an electrical buffer storage device, such as an appropriately dimensioned capacitor. In all cases, the mechanical power required for the travel drive and the work drive is provided by one or more electric motors. Hybrid-electric work machines are also known, in which the required mechanical power is primarily provided by an internal combustion engine, usually a diesel engine.An additional electric motor typically takes on a so-called boost function.

[0003] Also known are powershift transmissions for off-highway vehicles, in which the speed of the drive unit and the speed of the gear to be engaged are synchronized during a gear shift. During an upshift, the speed of the drive unit is reduced accordingly, and during a downshift, it is increased accordingly.

[0004] In this context, DE 20 2014 000 738 U1 describes a wheel loader driven purely by an electric motor, which has a first electric motor for a travel drive and a second electric motor for a working drive.

[0005] EP 0 962 597 A2 discloses a battery-powered work machine that has two electric motors for the traction drive and another electric motor for the working drive. The two electric motors for the traction drive are integrated into the front axle, with each electric motor driving one wheel.

[0006] Furthermore, DE 10 2010 063 503 A1 discloses a multi-stage transmission for a work machine with a planetary design. The multi-stage transmission comprises a housing in which four planetary gear sets and several shafts are accommodated, as well as shifting elements formed by at least one brake and clutches, which, through their targeted actuation, can be used to achieve eight different gear ratios between an input and output shaft. The transmission of DE 10 2010 063 503 A1 enables power shifting.

[0007] DE 10 2013 204 672 A1 relates to a drive device for a tracked vehicle, wherein the drive device comprises an electric drive motor for providing driving power and an electric steering motor for providing steering power. Mechanical drive elements are provided for transmitting reactive power between a right drive side and a left drive side when cornering. An electric assist motor is also provided, which can optionally assist the drive motor or the steering motor.

[0008] DE 102 16 308 A1 discloses a wheel loader that performs operations by driving a hydraulic pump for driving a work machine and drive wheels of a vehicle by means of an engine. The wheel loader comprises a first electric motor capable of transmitting torque to the drive wheels, electricity storage means for transmitting electrical energy to and from the first electric motor, and a control device for controlling a generator operation of the first electric motor, which receives the torque transmission from the drive wheels and generates electrical power during deceleration of the vehicle, and stores the generated electrical energy in the electricity storage means.

[0009] DE 10 2012 204 717 A1 describes an electric motor drive device for a motor vehicle with a first electric machine, a second electric machine, and a transmission device with a planetary gear set, a spur gear transmission, and an output. The spur gear transmission has a first gear set with a first gear ratio, a second gear set with a second gear ratio, and a shifting device that can be shifted into a first shift position or a second shift position in order to further improve the drive device structurally and / or functionally.

[0010] CN 1 06 828 064 A1 relates to a dual-motor multi-mode drive system of an electric tractor and a control method therefor. The dual-motor multi-mode drive system includes an electromagnetic clutch, an A-motor, a B-motor, an A-shift motor, a PTO high / low gear shift motor, a differential lock shift motor, 1st and 2nd gear shift motors, 3rd and 4th gear shift motors, a B-shift motor, and a differential lock. The electric tractor is driven by the A-motor and the B-motor. After gear shifting, the two motors are meshed and driven via a transmission to provide power output and drive wheel power, respectively. Depending on the different positions of the control switch in the drive system, the drive system is in a different power drive mode.The power drive mode of the drive system is determined based on the work unit information provided by a complete controller.

[0011] DE 10 2010 063 503 A1 relates to a multi-stage planetary transmission, in particular a splitter transmission of a work machine, comprising a housing in which four planetary gear sets and several shafts are accommodated, and comprising shifting elements formed by at least one brake and clutches, the targeted actuation of which enables eight different gear ratios to be achieved between an input shaft and an output shaft. A third shaft is connected to a sun gear of a third planetary gear set and can be coupled by means of a first clutch to a fourth shaft, which is connected to a carrier of a second planetary gear set. A fifth shaft connects a ring gear of the second planetary gear set to a ring gear of the third planetary gear set and can be releasably coupled to the output shaft via a second clutch.Furthermore, a sixth shaft is coupled to a sun gear of the second planetary gear set and can be secured to the housing (1) by means of a first brake. The drive shaft is connected to a carrier of the third planetary gear set.

[0012] However, known electrically powered work machines have the disadvantage that speed synchronization of the gear ratios involved during a shift under load, particularly during a downshift, is more difficult than during an identical shift in a combustion-powered work machine. The reason for this lies, on the one hand, in the comparatively greater moment of inertia of an electric motor compared to a combustion engine, but above all in the significantly wider speed range of the electric motor, which can also result in comparatively higher differential speeds. This usually requires a correspondingly larger and more powerful dimensioning of the clutches in electrically powered work machines. However, such a comparatively larger and more powerful design of the clutch requires more space, increases weight, and increases manufacturing costs.Furthermore, comparatively larger clutches also have comparatively larger drag torques and friction losses.

[0013] It is an object of the invention to propose an improved method for operating a drive train for a work machine.

[0014] This object is achieved according to the invention by the method for operating a drive train for a work machine according to claim 1. Advantageous embodiments and further developments of the invention emerge from the dependent claims.

[0015] The invention relates to a method for operating a drive train for a work machine, wherein a first electric motor drives a work drive of the work machine via a first transmission arrangement, wherein a second electric motor drives a travel drive of the work machine via a second transmission arrangement, and wherein a speed increase of the second electric motor occurs during a shifting operation of the second transmission arrangement from a higher gear to a lower gear. The method according to the invention is characterized in that during the shifting operation, a drive connection is established between the first electric motor and the travel drive via a first clutch, so that the travel drive is driven by the first electric motor during the shifting operation.

[0016] When shifting from a higher gear to a lower gear, the first electric motor, which is assigned to the drivetrain, must increase its speed very quickly in order to establish the speed synchronization required for the shifting process between the clutch elements involved in the shifting process. According to the state of the art, this speed synchronization is achieved via corresponding friction work between the clutch elements involved in the shifting process. In particular, with electric motors, comparatively large speed differences occur, which disadvantageously have to be compensated for by particularly powerful and therefore heavy and expensive clutches. In addition, there is the work required to accelerate the speed of the second electric motor, which is correspondingly large due to the comparatively large mass moment of inertia and the comparatively large speed difference.

[0017] This is where the method according to the invention comes in: By advantageously enabling the traction drive to be driven by the first electric motor, which is actually assigned to the working drive, during the shifting process of the second transmission arrangement, the second electric motor can be separated from the traction drive in terms of drive, so that its entire available power can be used to increase its own speed as quickly as possible. Meanwhile, the necessary tractive force can be applied by the first electric motor, so that no interruption in tractive force occurs during the shifting process.

[0018] For the purposes of the invention, a shifting operation from a higher gear to a lower gear is understood to mean a shifting operation from a gear having a comparatively higher output speed and a comparatively lower output torque to a gear having a comparatively lower output speed and a comparatively higher output torque.

[0019] The increase in the speed of the second electric motor required for speed synchronization can preferably be achieved by briefly disconnecting the second electric motor from the drive during the gearshift process and increasing its speed accordingly during the disconnection from the drive. During the disconnection of the second electric motor, the drive is preferably driven by the first electric motor.

[0020] It is also conceivable and preferred to provide not only a single first or second electric motor, but also a plurality of first or second electric motors, which can be coupled to one another, for example, via a summing gear or can be detachably connected to the first or second gear arrangement via individual drive connections.

[0021] Preferably, at least the second transmission arrangement has a plurality of forward gears and at least one gear stage configured as a reverse gear. Particularly preferably, the number of forward gears corresponds to the number of reverse gears. The first transmission arrangement can also have more than one forward gear stage. Furthermore, one or more reverse gear stages of the first transmission arrangement are also conceivable. However, due to the ability of electric motors to change their direction of rotation, the provision of reverse gears is not always necessary.

[0022] According to a preferred embodiment of the invention, the gear shift is carried out under load. The term “under load” in the sense of the invention refers to a state of the drive train in which a torque is transmitted from the second electric motor, or during the gear shift also from the first electric motor, to the travel drive, so that the work machine, for example, accelerates or travels uphill at a constant speed. A gear shift under load is therefore a gear shift without an interruption in the tractive force. It is precisely during the gear shift that an interruption in the transmission of torque would occur without recourse to the method according to the invention, unless a disadvantageously large, expensive and heavy clutch is used in accordance with the prior art.In this respect, the advantages of the method according to the invention are also, and especially, evident during a shifting operation under load, since this is possible without interruption of the tractive force and with the presence of a comparatively small, inexpensive, and low-performance clutch. In effect, a drivetrain in which the method according to the invention is implemented thus achieves the same powershift capability without interruption of tractive force as a drivetrain equipped with a comparatively large, heavy, and expensive clutch.

[0023] According to a further preferred embodiment of the invention, the first electric motor drives the traction drive and the working drive simultaneously during the gearshift. This results in the advantage that the working drive is also not interrupted by the gearshift and remains continuously available. A drive connection is established between the first electric motor and the second transmission arrangement only via the first clutch, so that during the gearshift, the power required by the traction drive is provided by the first electric motor in addition to the power required by the working drive.

[0024] According to a further preferred embodiment of the invention, the available power of the first electric motor is used to synchronize the clutch halves of a clutch assigned to the lower gear. In this case, the clutch half assigned to the drive side of the drive train is synchronized, namely, accelerated. Accelerating the clutch half requires a significant amount of energy, which often cannot be provided by the second electric motor, which, after all, must accelerate its own speed.

[0025] Also connected to the clutch half is a series of additional gears or shafts that establish the drive connection from the first electric motor to the clutch half. This series of additional gears or shafts is preferably largely identical to the gears and shafts that establish the drive connection from the second electric motor to the clutch half after the gear shift. Thus, these gears and shafts are also advantageously brought to the required speed by the first electric motor.

[0026] According to a further preferred embodiment of the invention, the available power of the second electric motor is used to increase the speed of the second electric motor. Since the acceleration of the clutch half is performed by the first electric motor, the entire power available from the second electric motor can be used to adjust its own speed, which consequently leads to an overall faster shifting process, since all involved elements reach the required speeds more quickly.

[0027] As long as the second electric motor accelerates to the speed required to engage the lower gear, it is preferably decoupled from both the traction drive and the working drive. However, a small number of gears or shafts that are not detachable from the second electric motor may remain connected to the second electric motor and thus be driven or accelerated by it.

[0028] According to a further preferred embodiment of the invention, the first electric motor only drives the drive to the extent that a power difference between a power requirement of the drive and a power that can be provided by the second electric motor during the gearshift is bridged. This means that the mechanical power provided by the first electric motor during the gearshift is advantageously increased to exactly the extent that the drive does not experience any power restriction as a result of the gearshift, but also does not experience any unrequested power increase. This results in the advantage that the behavior of the drive is not influenced by the gearshift.The power requested by an operator of the work machine for the traction drive is therefore provided without restriction even during the gear shift. For this purpose, the power provided by the first electric motor is increased to the extent that the power provided by the second electric motor is reduced due to the gear shift. However, the total power provided to the traction drive remains unchanged.

[0029] According to a particularly preferred embodiment of the invention, the first electric motor only drives the travel drive to the extent that a power requirement of the working drive can be fully met during the gearshift process. This results in the advantage that it is always ensured that the working drive receives the required power requested by an operator of the work machine, even during the gearshift process, so that a sudden and, in particular, unexpected drop in power of the working drive can be avoided. A drop in power of the working drive that is unexpected for the operator could otherwise lead to a dangerous situation, for example if a lifting device of the work machine operated by the working drive no longer receives the power required to hold a lifted load.A short-term drop in power in the drive system, however, does not usually lead to a dangerous situation.

[0030] Fully meeting the power requirements of the auxiliary drive by the first electric motor is particularly important in situations where comparatively high power requirements are placed on both the traction drive and the auxiliary drive, which the first electric motor cannot provide in total. Therefore, if the total requested power exceeds the maximum power that can be provided by the first electric motor, the auxiliary drive requirement is fully met first. Any remaining power that can still be provided by the first electric motor is then made available to the traction drive during the gearshift process.

[0031] The invention further relates to a drive train for a work machine, comprising a first electric motor and a second electric motor as well as a first gear arrangement and a second gear arrangement, wherein the first electric motor and the first gear arrangement are assigned to a work drive of the work machine and wherein the second electric motor and the second gear arrangement are assigned to a travel drive of the work machine. The drive train according to the invention is characterized in that a drive connection can be established via a first clutch between the first electric motor and the travel drive. The drive train according to the invention thus advantageously comprises all the necessary devices and means to be able to carry out the method according to the invention. This in turn leads to the advantages already described in connection with the method according to the invention.

[0032] To ensure the most optimal execution of the method according to the invention by the drive train according to the invention, the first electric motor and the second electric motor are preferably coordinated with one another in terms of their available power and their torque / speed characteristic curve. This means that the maximum power that can be provided by the first electric motor advantageously lies in a range of 50% to 150% of the maximum power that can be provided by the second electric motor, in particular in a range of 80% to 120%. Furthermore, the torque / speed characteristic curve of the first electric motor advantageously lies in a range of 50% to 150% of the torque / speed characteristic curve of the second electric motor, in particular in a range of 80% to 120%.

[0033] It is particularly preferred that the first electric motor has a power that can be provided of less than 100% of the power that can be provided by the second electric motor, but has a higher dynamic, i.e. the ability to adjust the speed comparatively faster by accelerating or reducing the speed.

[0034] The drive train preferably further comprises a separate power electronics unit or a single, shared power electronics unit for controlling or regulating the speed or torque or the power to be provided by the first electric motor and the second electric motor. Likewise, the drive train preferably comprises an electronic control unit that controls or regulates the first electric motor and the second electric motor via their respective separate power electronics units or via the shared power electronics units.

[0035] According to a preferred embodiment of the invention, the first electric motor and the second electric motor are arranged in a common housing. This enables a space- and weight-saving arrangement of the first electric motor and the second electric motor within the drive train in a work machine. In addition, the common housing saves weight and costs compared to two individual housings. The first and the second electric motor can, for example, be installed axially one behind the other in a common housing, wherein the motor output shafts can, for example, point in opposite axial directions from the housing. However, an arrangement axially next to one another in a correspondingly designed housing is also possible and preferred, so that both motor output shafts can, for example, point in the same axial direction.

[0036] According to a further preferred embodiment of the invention, the second transmission arrangement is powershiftable across a plurality of gear ratios. This results in the advantage that the powershift capability provided by the method according to the invention is guaranteed not only for the shift from a very specific lower gear ratio to a very specific higher gear ratio, but for a multitude of gear ratios. This makes the drive train according to the invention more flexible. This requires a correspondingly adapted speed-torque behavior and a correspondingly designed performance, particularly of the first electric motor. Particularly preferably, the second transmission arrangement is powershiftable across all gear ratios. This leads to further increased flexibility of the drive train according to the invention.

[0037] Particularly preferably, the second transmission arrangement is shiftable via three second clutches or is powershiftable using the method according to the invention. In practical application, this has proven to be a good compromise between flexibility provided by a large number of powershiftable gears on the one hand, and the required space, weight, and manufacturing costs of the drive train on the other.

[0038] According to a further preferred embodiment of the invention, the working drive comprises at least one hydraulic pump whose hydraulic output can be adjusted via a pivot angle. Independently of this, the hydraulic output can of course also be adjusted via the speed of the at least one hydraulic pump and via the torque at the at least one hydraulic pump. However, since an additional degree of freedom for adjusting the hydraulic output is available via the pivot angle, this opens up the possibility of adjusting the speed or torque of the first electric motor during a gear shift largely according to the needs of the travel drive, because any influence of the changed speed or changed torque of the first electric motor on the at least one hydraulic pump can be compensated for by a corresponding adjustment of the pivot angle.

[0039] According to the invention, it is provided that the drive train is designed to carry out the method according to the invention.

[0040] It is preferably provided that the first electric motor or the second electric motor are further designed to recuperate kinetic energy during braking of the work machine. Due to the drive connection according to the invention, which can be established via the first clutch between the first electric motor and the second gear arrangement, kinetic energy can namely be advantageously recuperated from both the second and the first electric motor. For this purpose, the drive train advantageously further comprises an electrical energy store to which the electrical energy supplied by the recuperation operation can be fed. During recuperation operation, the first electric motor or the second electric motor operate as generators and convert mechanical, namely kinetic, energy into electrical energy. This electrical energy can later be taken from the electrical energy store if necessary in order to power the first electric motor or the second electric motor.to supply the second electric motor. Additionally, it can also be provided that the electrical energy storage device can be charged with external electrical energy via a charging cable or other suitable charging device, for example, an induction charging device. Using the first electric motor or the second electric motor for recuperation also reduces wear on a mechanical friction brake.

[0041] The invention further relates to a work machine comprising a drive train according to the invention. This also results in the advantages already described in connection with the drive train according to the invention for the work machine according to the invention.

[0042] According to a preferred embodiment of the invention, it is provided that the work machine is designed as a wheel loader.

[0043] Alternatively, the work machine can also be designed as a dumper, excavator, telehandler or tractor.

[0044] The invention is explained below by way of example with reference to embodiments shown in the figures.

[0045] They show: Fig. 1 shows, by way of example and schematically, a possible embodiment of a drive train according to the invention for a work machine, Fig. 2 shows, by way of example, another possible embodiment of a drive train 1 according to the invention for a working machine in the form of a wheel diagram in the form of a block diagram and Fig. 3 shows, by way of example and schematically, a possible embodiment of a method according to the invention for operating a drive train for a work machine in the form of a flow chart.

[0046] Identical objects, functional units, and comparable components are designated by the same reference symbols throughout the figures. These objects, functional units, and comparable components are identical in terms of their technical features, unless explicitly or implicitly stated otherwise in the description.

[0047] Fig. 1 shows, by way of example and schematically, a possible embodiment of a drive train 1 according to the invention for a Fig. 1 shows a work machine, not shown, in the form of a block diagram. The drive train 1 shown as an example comprises a first electric motor 2 and a second electric motor 3 as well as a first transmission arrangement 4 and a second transmission arrangement 5, 5'. The first electric motor 2 and the second electric motor 3 are arranged, for example, in a common housing 11. The second transmission arrangement 5, 5' consists, for example, of a drive-up gear stage 5 and a multi-stage, powershiftable transmission arrangement 5'. The first electric motor 2 and the first transmission arrangement 4 are assigned to a working drive 6 of the drive train 1, wherein the working drive 6 also includes, for example, an ePTO interface 12 (electric Power Take Off interface). The second electric motor 3 and the second transmission arrangement 5, on the other hand, are assigned to a travel drive 7 of the drive train 1, wherein the travel drive 7 also includes an output shaft 13.A first clutch 8 can also be used to establish a drive connection between the first electric motor 2 and the travel drive 7, the drive connection specifically running, for example, from the first electric motor 2 to a point between the gear ratio 5 and the powershift transmission arrangement 5'. This drive connection advantageously makes it possible to have the travel drive 7 driven by the first electric motor 2, which is actually assigned to the work drive 6, during a gear shift of the second transmission arrangement 5. This allows the second electric motor 3 to be drive-separated from the travel drive 7, and speed synchronization, in the sense of increasing the speed of the second electric motor 3, can be set or regulated without any loss of tractive power occurring in the travel drive 7. At the same time, the first electric motor can already synchronize or accelerate one clutch half and the gears and shafts connected to the clutch half.Accordingly, when carrying out the method according to the invention, it is not necessary to achieve the speed synchronization by friction work, so that corresponding clutches of the second transmission arrangement 5 can be designed to be comparatively smaller and more cost-effective than is usual in the prior art.

[0048] Fig. 2 shows an example of a further possible embodiment of a drive train 1 according to the invention for a Fig. 2 not shown working machine in the form of a wheel diagram. For example, the drive train 1 of the Fig. 2 a first electric motor 2 and a second electric motor 3, which are arranged in a common housing 9. Furthermore, the drive train 1 of the Fig. 2 a first gear arrangement 4 and a second gear arrangement 5, wherein the first electric motor 2 and the first gear arrangement 4 are assigned to a working drive 6 of the drive train 1. The second electric motor 3 and the second gear arrangement 5, in contrast, are assigned to a travel drive 7 of the drive train 1. A drive connection can be established between the first electric motor 2 and the second gear arrangement 5 via a first clutch 8, wherein the drive connection can be established, for example, from the first electric motor 2 to a shaft 14 of the second gear arrangement 5. Thus, when the first clutch 8 is engaged, the first electric motor 2 can drive the travel drive 7. The second gear arrangement 5 further comprises, for example, three second clutches 9, 9' and 9", in order to provide three shiftable gear stages of the second gear arrangement 5 by means of three different spur gear stages 10, 10', 10".

[0049] Fig.3 shows, by way of example and schematically, a possible embodiment of a method according to the invention for operating a drive train 1 for a work machine in the form of a flowchart. A first electric motor 2 of the drive train 1 drives a working drive 6 of the work machine via a first transmission arrangement 4, and a second electric motor 3 of the drive train 1 drives a travel drive 7 of the work machine via a second transmission arrangement 5. In method step 20, an operator of the work machine initiates a shifting operation from a higher gear to a lower gear of the second transmission arrangement 5. The shifting operation is initiated by actuating a corresponding shifting element of the work machine, for example, by a gear selector lever.In method step 21, a control unit checks whether the first electric motor 2, which is assigned to the working drive 6 of the work machine 1, still has sufficient power reserves in addition to driving the working drive 6 to support the gear shifting process. In the example, this is the case because the working drive 6 is not currently driven. In the following method step 22, a drive connection is therefore established between the first electric motor 2 and the travel drive 5, which occurs by closing a first clutch 8. In method step 23, the first clutch 8 is fully closed and both the first electric motor 2 and the second electric motor 3 transmit power to the travel drive 7, thus driving the travel drive 7. In method step 24, the second electric motor 3 reduces the power it transmits to the travel drive 7, while at the same time the first electric motor 2 increases the power it transmits to the travel drive 7.The increase in the transmitted power by the first electric motor 2 corresponds exactly to the reduction in the transmitted power by the second electric motor 3, so that a power difference between a power requirement of the drive 7 and a power that can be provided by the second electric motor 3 during the gear shift is bridged. In the subsequent method step 25, the second electric motor 3 reduces the power it transmits to the drive 7 to zero by opening a corresponding clutch. At the same time, the first electric motor 2 further increases the power it transmits to the drive 7. The drive 7 is now driven exclusively by the first electric motor 2. In step 26, the second electric motor 3 now begins speed synchronization in the sense of increasing the speed. The speed increase occurs, for example, by supplying maximum current to the second electric motor 3.As soon as the necessary speed increase has been completed and speed synchronization is achieved, clutch 9' of the second transmission arrangement 5, which is also involved in the gearshift process, closes. This re-establishes a drive connection between the second electric motor 3 and the drive 7. In method step 27, the first electric motor 2 reduces the power it transmits to the drive 7, while the second electric motor 3 increases the power it transmits to the drive 7 by the same amount. In this case, the reduction in the power transmitted by the first electric motor 2 corresponds exactly to the increase in the power transmitted by the second electric motor 3. The drive 7 thus receives a constant power supply. Finally, in method step 28, the first electric motor 2 no longer transmits any power to the drive 7. The drive 7 is again driven exclusively by the second electric motor 3.The first clutch 8 opens, thus interrupting the drive connection between the first electric motor 2 and the second transmission assembly 5 or the drive system 7. The gearshift is thus completed. Since power was transferred from the first electric motor 2 or the second electric motor 3 to the second transmission assembly 5 or the drive system 7 during the entire gearshift, the gearshift was performed under load. The drive train 1 is therefore capable of powershifting. Reference symbol 1 drivetrain 2 first electric motor 3 second electric motor 4 first gear arrangement 5 second gear arrangement 6 Working drive 7 Drive 8 first clutch 9, 9', 9" second coupling 10, 10', 10" spur gear stage 11 common housing 12 ePTO 13 Output shaft 14 Wave 20 Initiating the switching process 21 Checking the power reserves 22 Establishing the drive connection 23 Completely close the first clutch 24 Reducing the power of the second electric motor, increasing the power of the first electric motor 25 further reducing the power of the second electric motor, further increasing the power of the first electric motor 26 Speed ​​synchronization of the second electric motor 27 Reducing the power of the first electric motor, increasing the power of the second electric motor 28 further reducing the power of the second electric motor, further increasing the power of the first electric motor

Claims

[1] Method for operating a drive train (1) for a working machine, wherein a first electric motor (2) drives a working drive (6) of the working machine via a first gear arrangement (4), wherein a second electric motor (3) drives a travel drive (7) of the working machine via a second gear arrangement (5) and wherein during a shifting operation of the second transmission arrangement (5) from a higher gear to a lower gear, the speed of the second electric motor (3) is increased, characterized by that during the switching process, a drive connection is established (22) between the first electric motor (2) and the travel drive (7) via a first clutch (8), so that the travel drive (7) is driven (24, 25, 27, 28) by the first electric motor (2) during the switching process. [2] Method according to claim 1, characterized by that the switching operation is carried out under load. [3] Method according to at least one of claims 1 and 2, characterized by that the first electric motor (3) drives the travel drive (7) and the working drive (6) simultaneously during the switching process (24, 25, 27, 28). [4] Method according to at least one of claims 1 to 3, characterized by that a power available from the first electric motor (2) is used to synchronize clutch halves of a clutch (9, 9', 9") assigned to the lower gear stage. [5] Method according to at least one of claims 1 to 4, characterized by that a power available from the second electric motor (3) is used to increase a speed of the second electric motor (3). [6] Method according to at least one of claims 1 to 5, characterized bythat the first electric motor (2) drives the drive (7) only to the extent that a power difference between a power requirement of the drive (7) and a power that can be provided by the second electric motor (3) during the switching process is bridged (24, 25, 27, 28). [7] Method according to claim 6, characterized by that the first electric motor (2) drives the travel drive (7) only to the extent that a power requirement of the working drive (6) can be fully met during the switching process. [8] Drive train (1) for a working machine, comprising a first electric motor (2) and a second electric motor (3) and a first gear arrangement (4) and a second gear arrangement (5), wherein the first electric motor (2) and the first gear arrangement (4) are assigned to a working drive (6) of the working machine, wherein the second electric motor (3) and the second gear arrangement (5) are assigned to a travel drive (7) of the working machine and wherein a drive connection can be established between the first electric motor (2) and the drive (7) via a first clutch (8), characterized by that the drive train (1) is designed to carry out a method according to at least one of claims 1 to 7. [9] Drive train (1) according to claim 8, characterized by that the first electric motor (2) and the second electric motor (3) are arranged in a common housing (11). [10] Drive train (1) according to at least one of claims 8 and 9, characterized by that the second transmission arrangement (5) is powershiftable over a plurality of gear stages. [11] Drive train (1) according to at least one of claims 8 to 10, characterized bythat the working drive (6) comprises at least one hydraulic pump (12) whose hydraulic power can be adjusted via a pivoting angle. [12] Work machine comprising a drive train (1) according to at least one of claims 8 to 11.

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