Electrically operated axle drive train that can be filled with hydraulic fluid

Abstract

The invention relates to an electrically operated axle drive train (1) that can be filled with a hydraulic fluid (2), wherein the axle drive train (1) comprises an electric machine (3) and a transmission assembly (4) forming a structural unit with the electric machine (3), wherein the transmission assembly (4) comprises a wet-running planetary gear (5) arranged in a transmission chamber (6) of the transmission assembly (4), wherein, in the direction of gravity, below the transmission chamber (6) there is a low sump (7) hydraulically connected to the transmission chamber (6) for storing the lubricant (2) exiting the transmission chamber (6) and a high sump (8) hydraulically connected to the low sump (7) whose volume is larger than that of the low sump (7), wherein at least one hydraulic pump (9) is arranged in the high sump (8) by means of which the hydraulic fluid (2) can be pumped from the high sump (8) through a hydraulic circuit (10).wherein the high sump (8) has an overflow channel (11) which is hydraulically connected to the gearbox chamber (6), wherein at least one hydraulic orifice (13) is arranged in the hydraulic path (12) through the overflow channel (11) which locally narrows the flow cross-section of the overflow channel (11).

Description

[0001] The present invention relates to an axle drive train that can be electrically operated and filled with a hydraulic fluid, wherein the axle drive train has an electric machine and a gear arrangement that forms a structural unit with the electric machine, wherein the gear arrangement comprises a wet-running planetary gear that is arranged in a gear chamber of the gear arrangement, wherein in the direction of gravity below the gear chamber there is a low sump that is hydraulically connected to the gear chamber for storing the lubricant emerging from the gear chamber and a high sump that is hydraulically connected to the low sump, the volume of which is greater than that of the low sump, wherein at least one hydraulic pump is arranged in the high sump, by means of which hydraulic pump the hydraulic fluid can be conveyed from the high sump through a hydraulic circuit.

[0002] 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.

[0003] A detailed description of an electric drive can be found in an article in the magazine ATZ, Volume 113, May 2011, pages 360-365, by Erik Schneider, Frank Fickl, Bernd Cebulski, and Jens Liebold, titled "Highly Integrated and Flexible Electric Drive Unit for E-Vehicles." This article describes a drive unit for a vehicle axle that includes an electric motor arranged concentrically and coaxially with a bevel gear differential. Such drive units are also referred to as e-axles or electrically operated axle drive trains.

[0004] DE 10 2010 048 837 A1 discloses such a drive device comprising at least one electric motor and at least one planetary differential drivable by a rotor of the electric motor. The planetary differential comprises at least one planetary carrier operatively connected to a rotor of the electric motor, first planetary gears and second planetary gears rotatably mounted on the planetary carrier, and a first sun gear and a second sun gear, each of which is operatively connected to an output shaft of the planetary differential. The first planetary gears mesh with the first sun gear, and each of the second planetary gears meshes with the second sun gear and with one of the first planetary gears. Furthermore, the sun gears are arranged coaxially with a rotational axis of the rotor.

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

[0006] The gears typically provided in the aforementioned electric axles are generally lubricated with gear oil, which is often also used as cooling oil for the electric motor. To reliably deliver the lubricant or cooling oil to the various lubrication or cooling points, it is common practice to create a corresponding hydraulic fluid circuit in the corresponding electric axles. Therefore, it is quite common to create an oil sump within an electric axle to store the amount of oil required for lubrication and cooling, from which the aforementioned hydraulic fluid circuit is supplied with oil.

[0007] However, the volume required for an oil sump is limited by two key factors: firstly, by the available installation space in the electric axle drive train and, secondly, by the maximum permissible fill level in the transmission to achieve the efficiency specifications, in particular by avoiding splashing losses of rotating gear components.

[0008] Furthermore, a development goal is regularly to avoid or at least reduce oil foaming in the fluid circuit.

[0009] It is therefore the object of the invention to provide an electric axle drive train for a motor vehicle which, with the most compact dimensions possible, achieves high efficiency through low splash losses in the transmission arrangement and low oil foaming as well as effective cooling of the electric machine.

[0010] This object is achieved by an electrically operated axle drive train that can be filled with a hydraulic fluid, wherein the axle drive train has an electric machine and a transmission arrangement that forms a structural unit with the electric machine, wherein the transmission arrangement comprises a wet-running planetary gear that is arranged in a transmission chamber of the transmission arrangement, wherein in the direction of gravity below the transmission chamber there is a low sump that is hydraulically connected to the transmission chamber for storing the lubricant emerging from the transmission chamber and a high sump that is hydraulically connected to the low sump, the volume of which is greater than that of the low sump, wherein at least one hydraulic pump is arranged in the high sump, by means of which the hydraulic fluid can be conveyed from the high sump through a hydraulic circuit, wherein the high sump has an overflow channel that is hydraulically connected to the transmission chamber,wherein at least one hydraulic orifice is arranged in the hydraulic path through the overflow channel, which locally narrows the flow cross-section of the overflow channel.,

[0011] By placing a hydraulic orifice in the overflow channel, foaming of the hydraulic fluid during axle drive train operation can be effectively reduced. Furthermore, foamed hydraulic fluid from the high sump can be prevented from entering other areas of the axle drive train.

[0012] With regard to the transmission, the shifted ratios of suction and pump volume due to the different air content in the hydraulic fluid (foam) result in more precise control options for the hydraulic fluid volume, making optimal use of the "Cooling & Lubrication" functionality, which in turn improves the service life and performance of the transmission assembly and the electric machine.

[0013] The thermal instability caused by the reduced heat capacity of the hydraulic fluid, which is caused by its foaming, can thus also be subjected to more targeted temperature control by the axle drive train according to the invention. This enables efficient regulation of the operating temperature of the electric motor and transmission, which ultimately contributes to optimal power delivery of the axle drive train.

[0014] By more precisely monitoring the oil levels and reducing the foaming of the hydraulic fluid, further optimized lubrication can be achieved, resulting in minimal losses and reduced friction in the axle drive train.

[0015] Furthermore, breaking the foam in the overflow channel can also contribute to improved ventilation, as the risk of entry into the ventilation channel of the axle drive train can be reduced and its operational reliability can thus be optimized.

[0016] A hydraulic orifice is a device used in the overflow channel to control or regulate the flow of hydraulic fluid. The main function of a hydraulic orifice is therefore to locally reduce or increase the flow of hydraulic fluid in the overflow channel in order to control the pressure or velocity of the hydraulic fluid in the overflow channel. By appropriately adjusting the pressure and / or velocity of the hydraulic fluid, the hydraulic orifice can help to defoam foamed hydraulic fluid as it passes through the overflow channel. In particular, the hydraulic orifice reduces the flow cross-section within the overflow channel. For this purpose, ribs can extend from a wall of the overflow channel into the channel, for example.

[0017] The term "deep sump" refers specifically to the area within the axle driveline that serves as the collection and intake area for the hydraulic fluid. This is where the hydraulic fluid is collected and drawn in.

[0018] In the context of this application, the term high sump refers in particular to a hydraulic fluid reservoir located in a position higher with respect to gravity than the intake area of ​​the low sump.

[0019] The hydraulic pump is preferably designed such that a volume flow of hydraulic fluid for cooling the stator of the electric machine of 5-25 l / min, most preferably 5-20 l / min, can be provided. To achieve these volume flows, the hydraulic fluid present in the axle drive train and stored in the sumps must generally be pumped through the cooling circuit of the stator of the electric machine several times per minute. To prevent excessive foaming of the hydraulic fluid, it is preferable to limit the circulation of the hydraulic fluid in the axle drive train to a maximum of 5 circulations / minute, preferably a maximum of 3 circulations / minute. In this context, it is then further preferred that the quantity of hydraulic fluid stored in the drive train is between 1-8.5 liters, preferably between 1.5-6.5 liters.

[0020] By arranging the hydraulic pump in the high sump, a particularly short routing with correspondingly low drag losses can be achieved.

[0021] By dividing the system into two separate sumps, it is also possible for the second, larger sump to function as a settling chamber for the hydraulic fluid, giving the hydraulic fluid sufficient time to defoam.

[0022] The hydraulic fluid is a flowable, liquid medium, preferably an oil. In principle, it would also be conceivable for the hydraulic fluid to be water-based and, in particular, to be in the form of an emulsion, preferably containing an oil.

[0023] 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.

[0024] An electrically operable axle drive train comprises an electric machine and preferably a transmission assembly coupled to the electric machine. The transmission assembly and the electric machine form a structural unit. This can be formed, for example, by a drive train housing in which the transmission assembly and the electric machine are jointly accommodated.

[0025] Alternatively, it would of course also be possible for the electric machine to have a motor housing and / or the gearbox to have a gearbox housing, in which case the structural unit is achieved by fixing the gearbox relative to the electric machine. The gearbox housing is a housing for accommodating a gearbox. Its job is to guide existing shafts via the bearings and to grant the wheels (and possibly cams) the degrees of freedom they require under all loads without hindering their rotational and possibly path-related movement, as well as to absorb bearing forces and support moments. A gearbox housing can be single- or multi-shell, i.e., undivided or split. In particular, the housing should also dampen noise and vibrations and be able to safely accommodate lubricant.The gear 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.

[0026] The motor housing encloses the electric machine. A motor housing can also accommodate the control and power electronics. The motor housing can also be part of a cooling system for the electric machine and be designed in such a way that cooling fluid can be supplied to the electric machine via the motor housing and / or heat can be dissipated to the outside via the housing surfaces. Furthermore, the motor housing protects the electric machine and any electronics from external influences.

[0027] A motor housing can, in particular, be formed from a metallic material. Advantageously, the motor housing can be formed from a metallic cast material, such as die-cast aluminum, die-cast magnesium, gray cast iron, or cast steel.

[0028] The electrical machine is used to convert electrical energy into mechanical energy and / or vice versa, and it generally comprises a stationary part known as a stator, stand or armature and a part known as a rotor or runner which is movable, in particular rotatable, relative to the stationary part.

[0029] The electric machine of the axle drive train according to the invention is preferably designed as an axial flux machine. The magnetic flux in an electric axial flux machine (AFM) is directed axially in the air gap between the stator and rotor relative to the rotational direction of the rotor of the axial flux machine. There are different types of axial flux machines. One common type is a so-called I-arrangement, in which the rotor is arranged axially next to a stator or between two stators. Another common type is a so-called H-arrangement, in which two rotors are arranged on opposite axial sides of a stator.

[0030] In principle, it is also possible for a plurality of I-type and / or H-type rotor-stator configurations to be arranged axially next to one another. In this context, it would also be possible to arrange one or more I-type rotor-stator configurations and one or more H-type rotor-stator configurations next to one another in the axial direction. In particular, it is also preferable for the H-type and / or I-type rotor-stator configurations to be essentially identical in design, so that they can be combined in a modular manner to form an overall configuration. Such rotor-stator configurations can, in particular, be arranged coaxially to one another and connected to a common rotor shaft or to multiple rotor shafts.

[0031] 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 speeds greater than 5,000 rpm, particularly preferably greater than 10,000 rpm, and most preferably greater than 12,500 rpm.

[0032] For the purposes of this application, motor vehicles are defined as land vehicles that are propelled by mechanical power without being tied to railway tracks. A motor vehicle can, for example, be selected from the group of passenger cars (PCs), trucks (HGVs), mopeds, light motor vehicles, motorcycles, buses (KOMs), or tractors.

[0033] The transmission arrangement can be coupled, in particular, to the electric motor, 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. The transmission arrangement is preferably designed as a planetary gear, most preferably as a switchable, in particular two-speed planetary gear.

[0034] Advantageous embodiments of the invention are specified in the dependent claims. The features listed individually in the dependent claims can be combined with one another in a technologically expedient manner and can define further embodiments of the invention. Furthermore, the features specified in the claims are further specified and explained in the description, where further preferred embodiments of the invention are presented.

[0035] According to an advantageous embodiment of the invention, it can be provided that the hydraulic path of the overflow channel has a substantially V- or U-shaped course, wherein a first distal end of the hydraulic path is connected to the high sump and a second distal end of the hydraulic path is connected to the gear chamber.

[0036] The advantage of this design is that a V- or U-shaped hydraulic path allows the hydraulic fluid to be guided more easily and in a more controlled manner towards the gear chamber, since the shape minimizes the backflow of fluids into the wrong area.

[0037] Furthermore, the V- or U-shaped hydraulic path has the advantage of preventing or hindering hydraulic fluid spillage, for example, when cornering, especially when turning left or right. This can also prevent spillage during axle drive assembly, for example, if the axle drive must be rotated clockwise or counterclockwise during assembly. In principle, a V- or U-shaped hydraulic path can also contribute to increasing the hydraulic fluid level in the high sump.

[0038] According to a further preferred development of the invention, a plurality of hydraulic orifices can also be arranged in the hydraulic path through the overflow channel. This can further improve the defoaming performance within the overflow channel.

[0039] The hydraulic orifices can be essentially identical in design. In particular, the orifices can also have identical flow cross-sections. It is also possible for the hydraulic orifices to have different flow cross-sections, which can contribute to further optimization of defoaming.

[0040] Furthermore, according to a likewise advantageous embodiment of the invention, it can be provided that at least one hydraulic orifice is arranged in the region of the channel inlet of the overflow channel and / or at least one hydraulic orifice is arranged in the region of the channel outlet of the overflow channel. This allows, on the one hand, defoaming of the hydraulic fluid directly at the inlet and / or outlet of the overflow channel, which has proven particularly effective. It is highly preferred that a hydraulic orifice is located at both the inlet and outlet of the hydraulic fluid, which has shown particularly good defoaming results.

[0041] According to a further particularly preferred embodiment of the invention, it can be provided that at least one hydraulic orifice is arranged in the hydraulic path of the overflow channel between its channel inlet and its channel outlet, which leads to a particularly good, because almost complete, defoaming of the hydraulic fluid in the overflow channel.

[0042] Furthermore, the invention can also be further developed such that the overflow channel is formed, at least in sections, in one piece, in particular monolithically, with a transmission housing of the axle drive train. Integrating the overflow channel into the transmission housing creates a one-piece structure. This reduces the number of separate parts in the drive train and thus lowers the risk of leaks or failure at the connection points. An overflow channel that is also designed, in particular, monolithically with the transmission housing can also dissipate heat from the hydraulic fluid more efficiently. The monolithic structure can also contribute to improving the structural integrity of the transmission housing, which can be particularly advantageous in demanding environments or under high stress conditions.

[0043] In a likewise preferred embodiment of the invention, it can also be provided that at least one of the hydraulic orifices, preferably a plurality of the hydraulic orifices, particularly preferably all hydraulic orifices, is formed integrally, in particular monolithically, with the overflow channel. This can eliminate the need to assemble and connect various parts separately. This can reduce assembly effort and shorten production time.

[0044] It may also be advantageous to further develop the invention such that the hydraulic pump can be used to pump the hydraulic fluid from the low sump to the high sump, and also to pump the hydraulic fluid from the high sump to the hydraulic circuit. This makes it possible for a corresponding pump to have only one pump motor, which is preferable for cost reasons.

[0045] According to a further preferred embodiment of the subject matter of the invention, the hydraulic pump can have a first flow channel for sucking the hydraulic fluid from the low sump into the high sump, and the hydraulic pump can have a second flow channel for conveying the hydraulic fluid from the high sump into the hydraulic circuit. The second flow channel is designed as a high-pressure flow channel so that the hydraulic fluid can be conveyed safely and with high efficiency through the stator's cooling circuit. Furthermore, two conveying tasks in the drive train can be realized using one pump.

[0046] Finally, the invention can also be advantageously implemented such that the first flow channel comprises a riser pipe configured such that, during operation of the axle drive train, the hydraulic fluid flows into the high sump in the direction of gravity above a maximum hydraulic fluid fill level, and the channel inlet of the overflow channel is arranged above the outlet of the riser pipe in the direction of gravity. This means that the inlet of the overflow channel is higher than the outlet of the riser pipe. This can help to safely drain excess hydraulic fluid if the fill level in the high sump becomes too high, preventing overfilling and potential damage to the system.

[0047] According to a further preferred development of the invention, it can also be provided that the hydraulic pump, with its first flood, delivers a volume flow of hydraulic fluid which is between 4-8 l / min, preferably between 5-7 l / min, which has also proven to be advantageous for avoiding or reducing the foaming of the hydraulic fluid in the high sump.

[0048] In a likewise preferred embodiment variant of the invention, it can also be provided that the deep sump has / has a bottom-side drain plug with a magnet and / or the high sump has / has a bottom-side drain plug with a magnet, whereby a separation or immobilization of metallic particles from the hydraulic fluid can be effected.

[0049] It may also be advantageous to further develop the invention in such a way that a heat exchanger is arranged in the second flow, by means of which the hydraulic fluid guided through the second flow is cooled before entering the stator, which improves the cooling capacity that can be provided for the stator.

[0050] According to a further preferred embodiment of the subject matter of the invention, it can be provided that a suction filter is arranged in the first flow in the conveying direction upstream of the pump arrangement, whereby particles can also be separated from the hydraulic fluid, which can also contribute to an increased service life through reduced wear in the axle drive train.

[0051] The invention can also be advantageously implemented such that the transmission compartment and the high sump are connected to each other at the head end in the direction of gravity. Furthermore, a vent can be provided in the head area of ​​the high sump, by means of which both the transmission compartment and the high sump can be vented. The advantage resulting from this is, in particular, that a compact design of the axle drive train is supported.

[0052] The invention will be explained in more detail below with reference to figures without limiting the general inventive concept.

[0053] It shows: Fig. 1 shows two embodiments of electric axle drive trains in a motor vehicle in a schematic representation, Fig. 2 a hydraulic block diagram of an axle drive train, Fig. 3 shows a perspective view of an axle drive train known from the prior art with an opened gearbox housing, Fig. 4 a housing cover of a gearbox housing with an overflow channel in a perspective cross-sectional view, Fig. 5 a gearbox housing with an overflow channel in a perspective cross-sectional view.

[0054] The Fig. 1 shows two axle drive trains 1 that can be electrically operated and filled with a hydraulic fluid 2, wherein the axle drive trains 1 each have an electric machine 3 and a transmission arrangement 4 that forms a structural unit with the electric machine 3. In the figure b of the Fig. 1 shows a so-called twin or dial drive, in which the axle drive train 1 is formed from two electric machines 3 and two transmission arrangements 4, wherein each electric machine is connected to a transmission arrangement 4 assigned to it.

[0055] The gear arrangement 4 comprises a wet-running planetary gear 5 which is arranged in a gear chamber 6 of the gear arrangement 4, wherein a low sump 7 which is hydraulically connected to the gear chamber 6 for storing the hydraulic fluid 2 emerging from the gear chamber 6 and a high sump 8 which is hydraulically connected to the low sump 7 and whose volume is greater than that of the low sump 7 are provided below the gear chamber 6 in the direction of gravity.

[0056] A hydraulic pump 9 is arranged in the high sump 8, by means of which the hydraulic fluid 2 can be conveyed from the high sump 8 through a hydraulic circuit 10. By means of the hydraulic pump 9, the hydraulic fluid 2 can be conveyed from the low sump 7 into the high sump 8 and, on the other hand, the hydraulic fluid 2 from the high sump 8 into the hydraulic circuit 10. For this purpose, the hydraulic pump 9 has a first flow 19 for sucking the hydraulic fluid 2 from the low sump 7 into the high sump 8 and a second flow 20 for conveying the hydraulic fluid 2 from the high sump 8 into the hydraulic circuit 10, wherein the second flow 20 is designed as a high-pressure flow. This can be clearly seen from the Fig. 2 can be understood.

[0057] The hydraulic pump 9 has a pump motor (not specified in more detail). In particular, a suction filter can also be provided upstream of and / or within the second flow channel 20. The hydraulic pump 9 draws the hydraulic fluid 2 from the high sump 8 via this suction filter and transports the filtered hydraulic fluid 2 via the high-pressure flow channel within the hydraulic circuit 10 toward the stator of the electric machine 3 and subsequently through the gear assembly 4. A suction filter can also be arranged upstream of the first flow channel 19 in the conveying direction, upstream of the hydraulic pump 9, to prevent particles and contaminants from entering the hydraulic pump 9.

[0058] The hydraulic circuit 10 comprises a low sump path 23 which hydraulically connects the transmission arrangement 4 to the low sump 7 and a high sump path 24 which hydraulically couples the high sump 8 to the transmission arrangement 4.

[0059] The Fig. 3 shows a prior art implementation of the Fig. 2. The arrangement of the hydraulic pump 9 in the high sump 8 with its riser pipe 22 and outlet 21 is particularly clearly visible.

[0060] As can be seen from the Fig. 4-5, the high sump 8 of an axle drive train 1 according to the invention now has - unlike in the embodiment of Fig. 3 - an overflow channel 11 which is hydraulically connected to the transmission chamber 6, wherein in the hydraulic path 12 through the overflow channel 11 at least one hydraulic orifice 13 is arranged, which locally narrows the flow cross-section of the overflow channel 11. In the Fig. 4 shows the cover of the gear housing 18, which is mounted on the Fig. 5 shown gear housing 18 is placed on top, whereby the overflow channel 11 is then defined accordingly by the two housing components being placed against one another.

[0061] The first flow 19 of the hydraulic pump 9 has a riser pipe 22 which is configured such that the hydraulic fluid 2 flows into the high sump 8 in the direction of gravity above a maximum fill level of hydraulic fluid 2 during operation of the axle drive train 1, and the channel inlet 16 of the overflow channel 11 is arranged above the mouth 21 of the riser pipe 22 in the direction of gravity.

[0062] The hydraulic path 12 of the overflow channel 11 has a substantially V- or U-shaped course, with a first distal end 14 of the hydraulic path 12 being connected to the high sump 8 and a second distal end 15 of the hydraulic path 12 being connected to the transmission chamber 6. A plurality of hydraulic orifices 13 are arranged in the hydraulic path 12 through the overflow channel 11. A hydraulic orifice 13 is arranged in the region of the channel inlet 16 and the channel outlet 17 of the overflow channel 11. Furthermore, a further hydraulic orifice 13 is positioned in the hydraulic path 12 of the overflow channel 11 between its channel inlet 16 and its channel outlet 17. The overflow channel 11 is formed monolithically with a transmission housing 18 of the axle drive train 1. Analogously, the hydraulic orifices 13 are also formed monolithically with the overflow channel 11.

[0063] If, during operation of the axle drive train 1, the hydraulic fluid 2 in the high sump 8 foams and expands accordingly further toward the overflow channel 11, the foam is broken up as it passes through the overflow channel at the hydraulic orifices 13 along the hydraulic path 12. The hydraulic fluid 2 resulting from the collapsed foam is then channeled back into the high sump 8 in the front area of ​​the overflow channel 11 (relative to the flow direction of the hydraulic fluid 2), while the hydraulic fluid 2 resulting from the collapsed foam is channeled into the transmission chamber 6 in the rear area of ​​the overflow channel 11.

[0064] The vent opening 25 of the gear housing 18 is located in the upper area in the direction of gravity and is in Fig.5. This arrangement was specifically chosen to ensure that hydraulic fluid 2 does not inadvertently enter the vicinity of the vent opening 25. The overflow channel 11 was designed in a V-shaped configuration, which optimally protects the vent opening 25 from unwanted ingress of hydraulic fluid 2. It should be noted that the vent opening 25 is located above the channel outlet 17 of the overflow channel 11 in the direction of gravity, which represents an effective safety measure against the inadvertent entry of hydraulic fluid 2 into the vent opening 25.

[0065] 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 in such a way 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 1 axle drive train 2 Hydraulic fluid 3 electric machine 4 Gear arrangement 5 planetary gears 6 Gearbox compartment 7 Deep swamp 8 High swamp 9 Hydraulic pump 10 Hydraulic circuit 11 Overflow channel 12 Hydraulic path 13 aperture 14 End 15 End 16 channel input 17 Channel output 18 Gearbox housing 19 Flood 20 Flood 21 Mouth 22 Riser pipe 23 Deep Swamp Trail 24 High Swamp Trail 25 Ventilation opening QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2010 048 837 A1

[0004] Cited non-patent literature

[0000] ATZ magazine, 113th year, 05 / 2011, pages 360-365 by Erik Schneider, Frank Fickl, Bernd Cebulski and

[0003]

Claims

[1] An axle drive train (1) which can be electrically operated and filled with a hydraulic fluid (2), wherein the axle drive train (1) has an electric machine (3) and a gear arrangement (4) forming a structural unit with the electric machine (3), wherein the gear arrangement (4) comprises a wet-running planetary gear (5) which is arranged in a gear chamber (6) of the gear arrangement (4), wherein, in the direction of gravity below the gear chamber (6), there is a low sump (7) hydraulically connected to the gear chamber (6) for storing the hydraulic fluid (2) emerging from the gear chamber (6), and a high sump (8) hydraulically connected to the low sump (7), the volume of which is greater than that of the low sump (7), wherein at least one hydraulic pump (9) is arranged in the high sump (8), by means of which the hydraulic fluid (2) is pumped from the high sump (8) through a hydraulic circuit (10). is eligible, characterized byin that the high sump (8) has an overflow channel (11) which is hydraulically connected to the gear chamber (6), wherein in the hydraulic path (12) through the overflow channel (11) at least one hydraulic orifice (13) is arranged, which locally narrows the flow cross-section of the overflow channel (11). [2] Drive train (1) according to claim 1, characterized by in that the hydraulic path (12) of the overflow channel (11) has a substantially V- or U-shaped course, wherein a first distal end (14) of the hydraulic path (12) is connected to the high sump (8) and a second distal end (15) of the hydraulic path (12) is connected to the gear chamber (6). [3] Drive train (1) according to claim 1 or 2, characterized by that a plurality of hydraulic orifices (13) are arranged in the hydraulic path (12) through the overflow channel (11). [4] Drive train (1) according to claim 3, characterized bythat at least one hydraulic orifice plate (13) is arranged in the region of the channel inlet (16) of the overflow channel (11) and / or at least one hydraulic orifice plate (13) is arranged in the region of the channel outlet (17) of the overflow channel (11). [5] Drive train (1) according to claim 3 or 4, characterized by that at least one hydraulic orifice (13) is arranged in the hydraulic path (12) of the overflow channel (11) between its channel inlet (16) and its channel outlet (17). [6] Drive train (1) according to one of the preceding claims, characterized by that the overflow channel (11) is formed at least in sections in one piece, in particular monolithically, with a transmission housing (18) of the axle drive train (1) [7] Drive train (1) according to one of the preceding claims, characterized bythat at least one of the hydraulic orifices (13), preferably a plurality of the hydraulic orifices (13), particularly preferably all hydraulic orifices (13) are formed integrally, in particular monolithically, with the overflow channel (11). [8] Drive train (1) according to one of the preceding claims, characterized by that by means of the hydraulic pump (9) on the one hand the hydraulic fluid (2) can be conveyed from the low sump (7) into the high sump (8) and on the other hand the hydraulic fluid (2) can be conveyed from the high sump (8) into the hydraulic circuit (10). [9] Drive train (1) according to claim 8, characterized by that the hydraulic pump (9) has a first flow (19) for sucking the hydraulic fluid (2) from the low sump (7) into the high sump (8), and the hydraulic pump (9) has a second flow (20) for conveying the hydraulic fluid (2) from the high sump (8) into the hydraulic circuit (10), wherein the second flow (20) is designed as a high-pressure flow. [10] Drive train (1) according to claim 9, characterized by in that the first flow (19) has a riser pipe (22) which is configured such that the hydraulic fluid (2) flows into the high sump (8) in the direction of gravity above a maximum fill level of hydraulic fluid (2) during operation of the axle drive train (1), and the channel inlet (16) of the overflow channel (11) is arranged above the mouth (21) of the riser pipe (22) in the direction of gravity.

Images