Electrically operable drive train

Abstract

The invention relates to an electrically operable drive train (1) of a motor vehicle (2), comprising an electric machine (4) coolable by means of a cooling fluid (3) and comprising a gearbox arrangement (5) coolable by means of the cooling fluid (3), the gearbox input (6) of the gearbox arrangement being torque-transmittingly coupled to a rotor (7) of the electric machine (4), wherein the drive train (1) has a cooling circuit (8) for guiding the cooling fluid (3), the cooling fluid (3) being guidable in its direction of flow initially along a gearbox cooling path (9) through the gearbox arrangement (5) by means of the cooling circuit, before it is guided along a motor cooling path (10) through the the electric machine (4), wherein the cooling circuit (8) has a heat exchanger (11) downstream of the outlet (15) of the cooling fluid out of the motor cooling path (10) and upstream of the inlet (16) of the cooling fluid into the gearbox cooling path (9) in the direction of flow of the cooling fluid (3), thermal energy being drawable from the cooling fluid (3) and transferrable to a coolant circuit (12) by means of the heat exchanger, wherein a hydraulic control element (13) is arranged downstream of the heat exchanger (11) and upstream of the inlet of the cooling fluid (3) into the gearbox cooling path (9) in the direction of flow of the cooling fluid (3), the cooling fluid (3) being distributable between the gearbox cooling path (9) and a bypass line (14) by means of the hydraulic control element, wherein the bypass line (14) and the gearbox cooling path (9) are combined again downstream of the output (17) of the gearbox cooling path out of the gearbox arrangement (5).

Description

[0001] Electrically operated drive train

[0002] The present invention relates to an electrically operable drive train of a motor vehicle comprising an electric machine which can be cooled by means of a cooling fluid and a transmission arrangement which can be cooled by means of the cooling fluid and whose transmission input is coupled to a rotor of the electric machine in a torque-transmitting manner, wherein the drive train has a cooling circuit for guiding the cooling fluid, by means of which cooling circuit the cooling fluid can be guided in its flow direction initially along a transmission cooling path through the transmission arrangement before it is guided along an engine cooling path through the electric machine, wherein the cooling circuit has a heat exchanger in the flow direction of the cooling fluid after it leaves the engine cooling path and before it enters the transmission cooling path, by means of which heat exchanger thermal energy can be extracted from the cooling fluid and transferred to a coolant circuit.

[0003] Electric motors are increasingly being used to power motor vehicles, creating alternatives to combustion engines that require fossil fuels. Considerable efforts have already been made to improve the everyday suitability of electric drives and also to provide users with the same level of driving comfort they are accustomed to.

[0004] A detailed description of an electric drive can be found in an article in the magazine ATZ 113th year, 05 / 2011, pages 360-365 by Erik Schneider, Frank Fickl, Bernd Cebulski and Jens Liebold with the title: Highly integrated and flexible electric drive unit for electric vehicles. This article describes a drive unit for one axle of a vehicle which comprises an electric motor which is arranged concentrically and coaxially to a bevel gear differential, with a switchable 2-speed planetary gear set arranged in the power train between the electric motor and bevel gear differential, which is also positioned coaxially to the electric motor or the bevel gear differential or spur gear differential. The drive unit is very compact and, thanks to the switchable 2-speed planetary gear set, allows a good compromise between climbing ability, acceleration and energy consumption.Such drive units are also referred to as electric axles or electrically operated drivetrains. In addition to purely electric drivetrains, hybrid drivetrains are also known. Such drivetrains in a hybrid vehicle typically comprise a combination of an internal combustion engine and an electric motor, enabling – for example, in urban areas – purely electric operation while maintaining sufficient range and availability, especially for long-distance journeys. Furthermore, in certain operating situations, it is possible to use both the internal combustion engine and the electric motor simultaneously.

[0005] In the development of electric motors intended for electric axles or hybrid modules, there is a continuing need to increase their power densities, making the necessary cooling of the electric motors increasingly important. Due to the necessary cooling performance, hydraulic fluids, such as cooling oils, have become the preferred solution in most concepts for dissipating heat from the thermally stressed areas of an electric motor.

[0006] At the same time, gear assemblies in electric axles or hybrid modules require sufficiently good lubrication to not only cool the thermally stressed components but also provide sufficient lubrication to minimize friction losses in the gear assembly. Planetary gears, for example, also as differential gears, are often used in gear assemblies in electric axles or hybrid modules.

[0007] The design of a planetary drive in a motor vehicle transmission comprises at least one planetary gear set in which planetary gears are rotatably mounted on a planetary gear pin, supported by roller or plain bearings, which is housed in a planetary carrier. For long-term operation and to achieve a long service life of the planetary gear, effective lubrication of the planetary gear bearings and the dissipation of frictional heat are crucial. An oil is supplied as a lubricant, particularly from the direction of a drive or output shaft arranged centrally in the planetary drive, preferably by centrifugal force via oil channels or bores of the planetary gear bearing. DE 10 2010 054 868 A1 discloses a planetary gear that can be used as a differential, preferably as an axle differential.To lubricate the planetary gear bearings, the planetary gear pin incorporates a stepped bore lubricating oil channel, from which the lubricating oil flows through radial bores to the planetary gear bearings. An oil collecting tray inserted into the inlet side of the lubricating oil channel ensures targeted lubricating oil application.

[0008] According to DE 10 2005 054 084 A1, the planetary gear carrier of a planetary transmission comprises an oil collecting ring forming a grooved profile, the opening of which is aligned with the planetary gear carrier's orbital axis. Several oil guide channels are provided on the grooved profile side of the oil collecting ring facing the planetary gear carrier, through which the oil is guided from the grooved profile to the planetary gear bearing.

[0009] Furthermore, DE 199 60 157 A1 discloses a lubricant supply system using centrifugal force to lubricate the planetary gear bearings. The oil is fed into a central bore in the planetary gear pin via an oil catcher and from there, via radial openings, to the planetary gear bearings.

[0010] Patent EP 178 5646 B1 shows a section of an automatic transmission for a motor vehicle, comprising a planetary gear with a planetary carrier. Planetary gears are rotatably mounted on planetary gear pins fixed in the planetary carrier. An oil collecting tray has a radial, disc-shaped section that merges radially outward into a groove, from which a nozzle extends that engages a receptacle of the planetary gear pin. The oil entering the planetary gear pin is directed via a transverse bore to the bearing location of the planetary gear on the respective planetary gear pin.

[0011] A development goal for such powertrains is often to increase their range, for example, by optimizing the overall efficiency of the powertrain in cold temperatures. There is also a continuing need to make the cooling and / or lubrication in an electrically operated axle drive train of a motor vehicle as efficient and cost-effective as possible.

[0012] This object is achieved by an electrically operable drive train of a motor vehicle comprising an electric machine which can be cooled by means of a cooling fluid and a transmission arrangement which can be cooled by means of the cooling fluid, the transmission input of which is coupled to a rotor of the electric machine in a torque-transmitting manner, wherein the drive train has a cooling circuit for guiding the cooling fluid, by means of which the cooling fluid can be guided in its flow direction first along a transmission cooling path through the transmission arrangement before it is guided along an engine cooling path through the electric machine, wherein the cooling circuit has a heat exchanger in the flow direction of the cooling fluid after it leaves the engine cooling path and before it enters the transmission cooling path, by means of which heat exchanger thermal energy can be extracted from the cooling fluid and transferred to a coolant circuit,wherein, in the flow direction of the cooling fluid, a hydraulic control element is arranged downstream of the heat exchanger and upstream of the cooling fluid entering the transmission cooling path, by means of which hydraulic control element the cooling fluid can be distributed between the transmission cooling path and a bypass line, wherein the bypass line and the transmission cooling path are rejoined after its exit from the transmission arrangement, wherein the cooling fluid from the bypass line then has less thermal energy than the cooling fluid from the transmission cooling path.

[0013] This has the advantage that a particularly simple and cost-effective design of a cooling circuit can be realized in a drive train, which is characterized, among other things, by the fact that only one hydraulic pump needs to be installed for all operating modes.

[0014] Furthermore, the hydraulic control element can be used to adjust the flow of cooling fluid, which is also used to cool the electric motor, for the transmission assembly as needed. The cooling fluid requirement of the transmission assembly is generally many times lower than the volume flow of cooling fluid required to transport heat from the electric motor to the coolant circuit. The cooling fluid flow not required in the transmission assembly is routed past the bypass line via a bypass line and then recombined with the cooling fluid from the transmission assembly. The cooling fluid is then fed to the electric motor for cooling, thus creating a closed cooling circuit.

[0015] To further optimize the efficiency of the drivetrain, the transmission assembly can preferably be operated with a dry sump. The amount of cooling fluid used can also be advantageously reduced to a technically necessary minimum in the fluid sump of the transmission assembly. The goal of these measures is to minimize churning losses and reduce the thermally circulating mass in the form of excess cooling fluid in the entire cooling circuit.

[0016] The transmission cooling path and / or the engine cooling path can be designed, for example, as an open or closed channel, as a pipe, hose and / or as a hydraulic flow path, spray path, splash path or the like.

[0017] First, the individual elements of the claimed subject matter of the invention are explained in the order in which they appear in the set of claims, and subsequently particularly preferred embodiments of the subject matter of the invention are described.

[0018] An electric drive train of a motor vehicle can comprise at least one electric machine and at least one transmission arrangement, wherein the electric machine and the transmission arrangement preferably each form a structural unit. In particular, it can be provided that an electric machine and a transmission arrangement are each arranged in a common drive train housing. Alternatively, it would of course also be possible for the electric machine to have a motor housing and the transmission to have a transmission housing, wherein the structural unit can then be effected by fixing the transmission arrangement relative to the electric machine. This structural unit is occasionally also referred to as an electric axle. The electric machine and the transmission arrangement can also be accommodated individually or jointly in a drive train housing. The drive train housing is provided at least to accommodate the electric machine and the transmission arrangement.The drivetrain housing is preferably formed from a metallic material, particularly preferably from aluminum, gray cast iron, or cast steel, in particular by means of a primary forming process such as casting or die casting. However, it would also be possible in principle to form the drivetrain housing from a plastic.

[0019] In the context of the invention, the electric machine can be designed as a radial or axial flux machine. To create a particularly compact axle drive train, axial flux machines are preferred. The electric machine is intended in particular for use within an electrically operated drive train of a motor vehicle.

[0020] The rotor is the rotating part of the electric machine. The rotor comprises, in particular, a rotor shaft and one or more rotor bodies formed from rotor cores, arranged in a rotationally fixed manner on the rotor shaft. The rotor shaft can be hollow, which not only reduces weight but also allows the supply of lubricant or coolant to the rotor body.

[0021] According to the invention, it is provided that the electric machine has a motor cooling path for dissipating or supplying heat from or to the electric machine, wherein the hydraulic control element distributes the cooling fluid between the transmission cooling path and the bypass line to influence the thermal energy content of the cooling fluid upon entry into the engine cooling circuit.

[0022] In particular, the electric machine is dimensioned such that vehicle speeds greater than 50 km / h, preferably greater than 80 km / h, and especially greater than 100 km / h can be achieved. The electric motor particularly preferably has an output greater than 30 kW, preferably greater than 50 kW, and especially greater than 70 kW. It is further preferred that the electric machine provides rotational speeds greater than 5,000 rpm, particularly preferably greater than 10,000 rpm, and most preferably greater than 12,500 rpm.

[0023] The transmission arrangement of the electric drive train can be coupled, in particular, to the electric machine, which is designed to generate a drive torque for the motor vehicle. The drive torque is particularly preferably a main drive torque, so that the motor vehicle is driven exclusively by the drive torque.

[0024] The gear arrangement may comprise a gear reduction stage and / or a gear transmission stage. Furthermore, the gear arrangement may comprise a gear transmission, in particular a spur gear transmission, a bevel gear transmission, and / or a crown gear transmission. Furthermore, the gear arrangement may comprise a planetary gear transmission. The gear arrangement may further comprise a fixed transmission ratio or be designed to be switchable in multiple stages.

[0025] The transmission arrangement may include a differential gear. A differential gear is a planetary gear with one input and two outputs. Its function is typically to drive two wheels of a motor vehicle so that they can turn at different speeds while cornering, but with the same propulsive force.

[0026] The drive train preferably has a control unit, in particular for electronically controlling and / or regulating one or more technical systems of the drive train. In particular, a control unit can be provided for controlling and / or regulating a hydraulic pump and / or one or more hydraulic control elements.

[0027] A control unit has, in particular, a wired or wireless signal input for receiving, in particular, electrical signals, such as sensor signals. Furthermore, a control unit preferably also has a wired or wireless signal output for transmitting, in particular, electrical signals, for example, to electrical actuators or electrical consumers of the drive train, in particular a hydraulic pump and / or a hydraulic switching element.

[0028] Control and / or regulation operations can be performed within the control unit. It is particularly preferred that the control unit comprises hardware configured to execute software. The control unit preferably comprises at least one electronic processor for executing program sequences defined in software. The control unit may further comprise one or more electronic memories in which the data contained in the signals transmitted to the control unit can be stored and read out again. Furthermore, the control unit may comprise one or more electronic memories in which data can be stored in a modifiable and / or unmodifiable manner.

[0029] A control unit can comprise a plurality of control units, which are arranged, in particular, spatially separated from one another in the motor vehicle. Control units are also referred to as Electronic Control Units (ECUs) or Electronic Control Modules (ECMs) and preferably have electronic microcontrollers for performing computing operations for processing data, particularly preferably using software. The control units can preferably be networked with one another, enabling wired and / or wireless data exchange between control units. In particular, it is also possible to network the control units with one another via bus systems present in the motor vehicle or in the drive train, such as the CAN bus or LIN bus.

[0030] Furthermore, the drive train can preferably also have a thermal management system that controls the volume flows of cooling fluid and refrigerant within a thermal management system of the motor vehicle by means of switching elements that hydraulically act on a corresponding fluid, such as valves, slides, pumps, and the like. For this purpose, the hydraulic control system can, for example, completely or partially throttle a volume flow and / or distribute it to the relevant heat sources and sinks in subcircuits of the thermal management system of a motor vehicle. For this purpose, the hydraulic switching elements are preferably controlled and switched by an electronic control unit.

[0031] A hydraulic switching element can be a hydraulic pump, a switching valve, a controllable throttle valve, and the like. Preferably, a hydraulic switching element is electrically controllable. Furthermore, a hydraulic switching element preferably has at least two different, switchable operating states in which the hydraulic switching element acts in different ways on the corresponding fluid in a circuit.

[0032] For example, it would also be possible for the hydraulic switching element arranged in the cooling circuit, the hydraulic pump and the heat exchanger to form part of a thermal management system.

[0033] According to an advantageous embodiment of the invention, it can be provided that the hydraulic control element comprises at least one switchable directional control valve and / or at least one thermocouple and / or at least one hydraulic orifice for controlling the hydraulic flow of the cooling fluid into the transmission cooling path and the bypass line.

[0034] A directional control valve can be particularly advantageous for different operating modes of the drive train, especially when these occur for a limited time. This means that different switching positions can be used for different operating modes. For example, the lubrication / cooling of the gear arrangement can be increased accordingly for operation under full load and then immediately reduced again. This means that the amount of cooling fluid for the gear arrangement can be constantly adjusted, always with the aim of operating the gear arrangement with optimum efficiency. The directional control valve could also be used as a variable throttle in order to be able to operate many different operating modes optimally. This can be achieved, for example, in a spool valve by using the control edge as a variable orifice.

[0035] A thermocouple could be used to further distribute the cooling fluid flow as needed. For example, an automatically operating thermocouple located directly at the distribution point could increase or decrease the oil flow to the transmission assembly in line with the oil temperature, which in turn would provide the transmission assembly with cooling capacity as needed.

[0036] A particularly simple, robust, and cost-effective solution is a partitioning system using orifices. These passively operating orifices define the partitioning between the gearbox assembly and the bypass line using adapted cross-sections. This ensures both the lubrication and cooling of the gearbox assembly as needed and, through the use of a bypass line, enables optimized heat harvesting.

[0037] According to a further preferred development of the invention, the cooling circuit can also be provided with precisely one hydraulic control element. This allows for a particularly simple and cost-effective design of the cooling system.

[0038] Furthermore, according to a likewise advantageous embodiment of the invention, it can be provided that the heat exchanger is arranged in the immediate structural proximity to the outlet of the cooling fluid from the engine cooling path in order to enable a loss-free transfer of the thermal energy stored in the cooling fluid between the engine cooling path and the heat exchanger, which can also contribute to improved efficiency and thus range optimization of the drive train.

[0039] According to another particularly preferred embodiment of the invention, a hydraulic sump can be provided at the bottom of the transmission assembly in the direction of gravity, so that the cooling fluid, which is guided at least partially through the transmission assembly by gravity, can be collected in the hydraulic sump. In this context, it is particularly preferred for the hydraulic sump to be designed as a dry sump in order to minimize splashing losses in the transmission assembly during its operation. Furthermore, the hydraulic sump can also serve as a reservoir or expansion tank for the cooling circuit.

[0040] Furthermore, the invention can also be further developed such that a hydraulic pump is arranged in the cooling circuit, by means of which the cooling fluid can be conveyed through the cooling circuit. In a likewise preferred embodiment of the invention, it can also be provided in this context that the hydraulic pump is arranged upstream of the engine cooling path in the direction of flow. It can also be advantageous to further develop the invention such that a hydraulic filter is arranged upstream of the hydraulic pump in the direction of flow and after the cooling fluid from the bypass line and the output from the transmission arrangement merge, which can contribute to filtering out, for example, wear particles from the transmission arrangement from the cooling circuit.

[0041] According to a further preferred embodiment of the subject matter of the invention, the cooling fluid can be a cooling oil. In principle, it would also be conceivable for the cooling fluid to be an aqueous emulsion, for example, a water-glycol mixture.

[0042] The invention will be explained in more detail below with reference to figures without limiting the general inventive concept.

[0043] It shows:

[0044] Figure 1 shows a motor vehicle with an electrically operated drive train in a schematic block diagram,

[0045] Figure 2 shows a block diagram of the electrically operated drive train.

[0046] Figure 1 shows an electrically operable drive train 1 of a motor vehicle 2 comprising an electric machine 4 and a transmission assembly 5 coupled to the electric machine 4. As can be seen from Figure 2, the electric machine 4, which can be cooled by a cooling fluid 3, and the transmission assembly 5, which can be cooled by the cooling fluid 3, form a structural unit. The transmission input 6 of the transmission assembly 5 is coupled to the rotor 7 of the electric machine 4 in a torque-transmitting manner.

[0047] The drive train 1 has a cooling circuit 8 for guiding the cooling fluid 3, by means of which the cooling fluid 3 can first be guided in its flow direction along a transmission cooling path 9 through the transmission arrangement 5 before it is guided along a motor cooling path 10 through the electric machine 4.

[0048] The cooling circuit 8 has a heat exchanger 11 in the flow direction of the cooling fluid 3 after its outlet 15 from the engine cooling path 10 and before its inlet 16 into the transmission cooling path 9. Thermal energy can be extracted from the cooling fluid 3 and transferred to a coolant circuit 12. The coolant circuit 12 can be used, for example, for air conditioning the vehicle interior or for thermal conditioning of the vehicle battery.

[0049] A hydraulic control element 13 is arranged in the flow direction of the cooling fluid 3 downstream of the heat exchanger 11 and upstream of the cooling fluid 3 entering the transmission cooling path 9. By means of this hydraulic control element, the cooling fluid 3 can be distributed between the transmission cooling path 9 and a bypass line 14. The bypass line 14 and the transmission cooling path 9 are rejoined after its outlet 17 from the transmission arrangement 5. There, the cooling fluid 3 from the bypass line 14 then has less thermal energy than the cooling fluid 3 from the transmission cooling path 9.

[0050] The hydraulic control element 13 can comprise at least one switchable directional control valve and / or at least one thermocouple and / or at least one hydraulic orifice for controlling the hydraulic flow of the cooling fluid 3 into the transmission cooling path 9 and the bypass line 14. Figure 2 clearly shows that the cooling circuit 8 has precisely one hydraulic control element 13.

[0051] The heat exchanger 11 is arranged in close structural proximity to the outlet 15 of the cooling fluid 3 from the engine cooling path 10 in order to enable a loss-free transfer of the thermal energy stored in the cooling fluid 3 between the engine cooling path 10 and the heat exchanger 11.

[0052] In the direction of gravity, a hydraulic sump 19 is formed on the bottom 18 of the gear arrangement 5, so that the cooling fluid 3, which is guided at least partially by gravity through the gear arrangement 5, can be collected in the hydraulic sump 19.

[0053] Furthermore, a hydraulic pump 20 is arranged in the cooling circuit 8, by means of which the cooling fluid 3 can be pumped through the cooling circuit 8. The hydraulic pump 20 is arranged upstream of the engine cooling path 10 in the flow direction. A hydraulic filter 21 is positioned upstream of the hydraulic pump 20 and after the cooling fluid 3 from the bypass line 14 and the output 17 from the transmission assembly 5 merge.

[0054] The invention is not limited to the embodiments illustrated in the figures. The above description is therefore not to be considered restrictive, but rather explanatory. The following claims are to be understood as meaning that a stated feature is present in at least one embodiment of the invention. This does not exclude the presence of further features. Where the claims and the above description define 'first' and 'second' features, this designation serves to distinguish between two similar features without establishing a priority. List of reference symbols

[0055] 1 drivetrain

[0056] 2 motor vehicles

[0057] 3 Cooling fluid

[0058] 4 electric machine

[0059] 5 Gear arrangement

[0060] 6 Gearbox input

[0061] 7 Rotor

[0062] 8 Cooling circuit

[0063] 9 Gearbox cooling path

[0064] 10 Engine cooling path

[0065] 11 heat exchangers

[0066] 12 Coolant circuit

[0067] 13 Control

[0068] 14 Bypass line

[0069] 15 Exit

[0070] 16 Entry

[0071] 17 Exit

[0072] 18 Floor

[0073] 19 Hydraulic sump

[0074] 20 Hydraulic pump

[0075] 21 hydraulic filters

Claims

Claims 1 . Electrically operable drive train (1) of a motor vehicle (2) comprising • an electrical machine (4) which can be cooled by means of a cooling fluid (3) and • a gear arrangement (5) which can be cooled by means of the cooling fluid (3), the gear input (6) of which is coupled to a rotor (7) of the electric machine (4) in a torque-transmitting manner, • wherein the drive train (1) has a cooling circuit (8) for guiding the cooling fluid (3), by means of which the cooling fluid (3) can first be guided along a transmission cooling path (9) through the transmission arrangement (5) in its flow direction, before it is guided along a motor cooling path (10) through the electric machine (4), • wherein the cooling circuit (8) has a heat exchanger (11) in the flow direction of the cooling fluid (3) after its exit (15) from the engine cooling path (10) and before its entry (16) into the transmission cooling path (9), by means of which heat exchanger thermal energy can be extracted from the cooling fluid (3) and transferred to a coolant circuit (12), characterized in that in the flow direction of the cooling fluid (3) after the heat exchanger (11) and before the entry of the cooling fluid (3) into the transmission cooling path (9) a hydraulic control element (13) is arranged, by means of which the cooling fluid (3) can be distributed between the transmission cooling path (9) and a bypass line (14), wherein the bypass line (14) and the transmission cooling path (9) are brought together again after its exit (17) from the transmission arrangement (5), wherein the cooling fluid (3) from the bypass line (14) then has less thermal energy there than the cooling fluid (3) from the transmission cooling path (9).

2. Drive train (1) according to claim 1, characterized in that the hydraulic control element (13) comprises at least one switchable directional control valve and / or at least one thermocouple and / or at least one hydraulic orifice for controlling the hydraulic flow of the cooling fluid (3) into the transmission cooling path (9) and the bypass line (14).

3. Drive train (1) according to claim 1 or 2, characterized in that the cooling circuit (8) has exactly one hydraulic control element (13).

4. Drive train (1) according to one of the preceding claims, characterized in that the heat exchanger (11) is arranged in the immediate structural proximity to the outlet (15) of the cooling fluid (3) from the engine cooling path (10) in order to enable a loss-free transfer of the thermal energy stored in the cooling fluid (3) between the engine cooling path (10) and the heat exchanger (11).

5. Drive train (1) according to one of the preceding claims, characterized in that a hydraulic sump (19) is arranged in the direction of gravity on the bottom (18) of the transmission arrangement (5), so that the cooling fluid (3) guided at least partially by gravity through the transmission arrangement (5) can be collected in the hydraulic sump (19).

6. Drive train (1) according to one of the preceding claims, characterized in that a hydraulic pump (20) is arranged in the cooling circuit (8), by means of which the cooling fluid (3) can be conveyed through the cooling circuit (8).

7. Drive train (1) according to claim 6, characterized in that the hydraulic pump (20) is arranged in the flow direction upstream of the engine cooling path (10).

8. Drive train (1) according to one of the preceding claims 6 to 7, characterized in that a hydraulic filter (21) is arranged upstream of the hydraulic pump (20) and downstream of the merging of the cooling fluid (3) from the bypass line (14) and the output (17) from the transmission arrangement (5).

9. Drive train (1) according to one of the preceding claims, characterized in that the cooling fluid (3) is a cooling oil.

10. Drive train (1) according to one of the preceding claims, characterized in that the gear arrangement (5) comprises a planetary gear.

Images