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 (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

The present invention relates to an electrically operable axle drive train which can be filled with a hydraulic fluid, wherein the axle drive train has an electric machine and a transmission arrangement which forms a structural unit with the electric machine, wherein the transmission arrangement comprises a wet-running planetary transmission which is arranged in a transmission space of the transmission arrangement, wherein a low sump which is hydraulically connected to the transmission space in the direction of gravity for storing the lubricant which escapes from the transmission space and a high sump which is hydraulically connected to the low sump and 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 fluid can be conveyed from the high sump through a hydraulic circuit.Electric motors are increasingly used for the drive in motor vehicles in order to create alternatives to internal combustion engines that require fossil fuels. In order to improve the suitability of electric drives for all days and in addition to be able to offer users the usual riding comfort, considerable efforts have already been made.A detailed illustration of an electric drive is given in an article of the journal ATZ 113. Vol. 05 / 2011, pages 360-365 of Erik Schneider, Frank Fickl, Bernd Cebulski and Jens Liebold, with the title: High-Integration and Flexible Electric Drive Unit for E-vehicles. In this article, a drive unit for an axle of a vehicle is described, which comprises an electric motor which is arranged concentrically and coaxially with a bevel gear differential. Drive units of this type are also referred to as E-axles or electrically operable axle drive train.From DE 10 2010 048 837 A1, such a drive device with at least one electric motor and at least one planetary differential drivable with a rotor of the electric motor is known, wherein the planetary differential has at least one planet carrier operatively connected to a rotor of the electric motor, first planetary gears and second planetary gears rotatably mounted on the planetary carrier, as well as 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 mesh with the second sun gear and with one of the first planetary gears. Furthermore, the sun gears are arranged coaxially with a rotation axis of the rotor.Publications DE 10 2023 101 280 B3 and DE 10 2022 113 288 A1 show an electrically operable axle drive train, which can be filled with a hydraulic fluid, having an electric machine and a transmission arrangement. The transmission arrangement comprises a wet-running planetary transmission which is arranged in a transmission chamber of the transmission arrangement, wherein a low sump hydraulically connected to the transmission chamber and a high sump hydraulically connected to the low sump are provided below the transmission chamber in the direction of gravity. The volume of the low sump is greater than that of the high sump, in which a hydraulic pump is arranged, by means of which the hydraulic fluid can be conveyed out of the high sump through a hydraulic circuit. The high sump has an overflow channel which is hydraulically connected to the transmission chamber, wherein at least one hydraulic orifice is arranged in the hydraulic path through the overflow channel, said orifice locally narrowing the flow cross section of the overflow channel.In the development of electric machines and gear units provided for E-axes, there is a continuing need to increase their power densities, so that the cooling necessary for this purpose, in particular of the electric machines and the gear units, is becoming increasingly important. Due to the necessary cooling capacities, hydraulic fluids, such as cooling oils, have become established in most concepts for transporting heat away from the thermally exposed regions of an electric machine and / or a transmission.The transmissions usually provided in the designated E-axles are generally lubricated with a transmission oil, wherein this is frequently also used as cooling oil for the electric machine. In order to reliably deliver the lubricant or cooling oil to the various lubricating or cooling points, it is known to form a corresponding hydraulic fluid circuit in the corresponding E-axes. It is therefore quite common to form within an E-axis an oil sump for storing the amount of oil necessary for lubrication and cooling, from which sump the above-mentioned hydraulic fluid circuit is fed with oil.The volume required for an oil sump is, however, limited by two essential factors: on the one hand, by the available installation space in the electric axle drive train and, on the other hand, by the maximum permissible fill level in the transmission for achieving the efficiency specifications, in particular by avoiding splashing losses of rotating toothing components.Furthermore, a development aim is also regularly to avoid or at least to reduce oil foaming in the fluid circuit.It is therefore the object of the invention to provide an electric axle drive train for a motor vehicle which, with the most compact structural dimensions possible, realizes a high efficiency as a result of low splashing losses in the transmission arrangement and low oil foaming and effective cooling of the electric machine.This object is achieved by an electrically operable axle drive train which can be filled with a hydraulic fluid, wherein the axle drive train has an electric machine and a transmission arrangement which forms a structural unit with the electric machine, wherein the transmission arrangement comprises a wet-running planetary transmission which is arranged in a transmission space of the transmission arrangement, wherein a low sump which is hydraulically connected to the transmission space in the direction of gravity for storing the lubricant which escapes from the transmission space and a high sump which is hydraulically connected to the low sump and the volume of which is greater than that of the low sump, wherein at least one hydraulic pump by means of which the hydraulic fluid can be conveyed from the high sump through a hydraulic circuit is arranged in the high sump, wherein the high sump has an overflow duct which is hydraulically connected to the transmission space, wherein at least one hydraulic orifice is arranged in the hydraulic path through the overflow channel, said orifice locally narrowing the flow cross section of the overflow channel. It is provided here that a plurality of hydraulic apertures is arranged in the hydraulic path through the overflow channel. This can achieve a further improvement in the defoaming performance within the overflow channel.It is also 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. As a result, defoaming of the hydraulic fluid can be carried out directly at the inlet and / or outlet of the overflow channel, which has proven to be particularly effective. It is highly preferred that a hydraulic orifice is located in each case both at the inlet and at the outlet of the hydraulic fluid, which has shown particularly good defoaming results.By arranging a hydraulic orifice in the overflow channel, foaming of the hydraulic fluid during operation of the axle drive train can be effectively reduced. It is thus furthermore possible to prevent foamed hydraulic fluid from being able to pass from the high sump into other regions of the axle drive train.With respect to the transmission, due to the different air content in the hydraulic fluid (foam), the invention results in more precise control possibilities of the hydraulic fluid volume from the shifted ratios of suction and pump volume, to optimally utilize the functionality of "Cooling & Lubrication", which in turn improves the service life and performance of the transmission arrangement and of the electric machine.The thermal instability due to the reduced heat capacity of the hydraulic fluid caused by foaming thereof can thus also be subjected to a more targeted temperature control by the axle drive train according to the invention. This allows for efficient regulation of the operating temperature of the electric machine and transmission, ultimately contributing to optimal power development of the final drive train.By more accurately monitoring the oil levels by a corresponding reduction in foaming of the hydraulic fluid, further optimized lubrication can also be achieved, which leads to minimal losses and reduced friction in the axle drive train.Furthermore, breaking the foam in the overflow channel can also contribute to improved venting, since the risk of entry into the venting channel of the axle drive train is reduced and its operating reliability can thereby be optimized.A hydraulic orifice is a device used in the spill passage to control or regulate the flow of hydraulic fluid. The main function of a hydraulic orifice is thus in particular to locally reduce or increase the liquid flow of hydraulic fluid in the overflow channel in order to control the pressure or the speed of the hydraulic fluid in the overflow channel. By a corresponding pressure and / or speed adaptation of the hydraulic fluid, the hydraulic orifice can contribute to defoaming foamed hydraulic fluid when it passes through the overflow channel. The hydraulic orifice in particular brings about a reduction in the flow cross section within the overflow channel. For this purpose, for example, ribs can extend from a wall of the overflow channel into the channel.The term low sump refers in particular to the region within the axle drive train which serves as a collecting and intake region for the hydraulic fluid. In this region, the hydraulic fluid is in particular collected and sucked in.In the context of this application, the term high sump refers in particular to a hydraulic fluid reservoir located in a position higher than the suction area of the low sump with respect to gravity.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 represent these volume flows, the hydraulic fluid present in the axle drive train and stored in the stubs must generally be pumped through the cooling circuit of the stator of the electric machine several times per minute. In order to avoid too strong foaming of the hydraulic fluid, it is preferable to limit the circulation of the hydraulic fluid in the axle drive train to at most 5 circulations / minute, preferably at most 3 circulations / minute. In this context, it is then further preferred that the amount of hydraulic fluid stored in the drive train is between 1-8.5 liters, preferably between 1.5-6.5 liters.By arranging the hydraulic pump in the high sump, a particularly short routing with correspondingly low drag losses can be realized.By dividing into two sumps separated from one another, it is also possible to function second, larger sumps as a settling chamber for the hydraulic fluid, in that sufficient time can be given to the hydraulic fluid for defoaming.The hydraulic fluid is a flowable, liquid medium, preferably an oil. In principle, it would also be conceivable for the hydraulic fluid to be based on a water base and in particular to be formed as an emulsion which preferably contains an oil.First, the individual elements of the claimed subject matter of the invention are explained in the sequence in which they are stated in the set of claims and particularly preferred embodiments of the subject matter of the invention are described below.An electrically operable axle drive train includes an electric machine and preferably a transmission assembly coupled to the electric machine. The transmission arrangement and the electric machine form a structural unit. This can be formed, for example, by means of a drive train housing in which the transmission arrangement and the electric machine are accommodated jointly.Alternatively, it would of course also be possible for the electric machine to have a motor housing and / or the transmission to have a transmission housing, wherein the structural unit can then be effected by fixing the transmission with respect to the electric machine. The transmission housing is a housing for receiving a transmission. The object is to guide shafts present over the bearings and to provide the wheels (possibly cam disks) with the degrees of freedom under all loads that they require without hindering them in the rotational and possibly path movement, as well as to absorb bearing forces and supporting torques. A transmission housing can be formed in one or more shells, that is to say in an unshared or divided manner. The housing should also be able in particular to damp noises and vibrations and also to absorb lubricant securely. The gear housing is preferably formed from a metallic material, in particular preferably from aluminum, grey cast iron or steel cast iron, in particular by means of a primary molding process such as casting or die casting.The motor housing encloses the electric machine. A motor housing can also accommodate the control and power electronics. The motor housing can furthermore also be a component of a cooling system for the electric machine and can be designed in such a way that cooling fluid can be supplied to the electric machine via the motor housing and / or the heat can be dissipated to the outside via the housing surfaces. In addition, the motor housing protects the electric machine and the optionally present electronics from external influences.A motor housing can be formed in particular from a metallic material. Advantageously, the motor housing may be formed from a metallic casting material, such as aluminum die casting, magnesium die casting, grey casting or steel casting.The electric machine serves for converting electrical energy into mechanical energy and / or vice versa, and it generally comprises a stationary part referred to as a stator, stator or armature, and a part referred to as a rotor or rotor and arranged movably, in particular rotatably, with respect to the stationary part.The electric machine of the axle drive train according to the invention is preferably designed as an axial flow machine. The magnetic flux in an electric axial flux machine (AFM) is directed in the air gap between stator and rotor axially to a direction of rotation of the rotor of the axial flux machine. There are different types of axial flow machines. One known type is a so-called I-arrangement, in which the rotor is arranged axially next to a stator or between two stators. Another known type is a so-called H-arrangement in which two rotors are arranged on opposite axial sides of a stator.In principle, it is also possible for a plurality of rotor-stator configurations to be arranged axially next to one another as an I-type and / or H-type. In this context, it would also be possible to arrange both one or more rotor-stator configurations of the I-type and one or more rotor-stator configurations of the H-type next to one another in the axial direction. In particular, it is also preferable for the rotor-stator configuration of the H-type and / or of the I-type to be each of substantially identical design, such that they can be joined together in a modular manner to form an overall configuration. Such rotor-stator configurations can be arranged in particular coaxially with respect to one another and can be connected to a common rotor shaft or to a plurality of rotor shafts.In particular, the electric machine is dimensioned such that vehicle speeds greater than 50 km / h, preferably greater than 80 km / h and in particular greater than 100 km / h can be achieved. Particularly preferably, the electric motor has a power greater than 30 kW, preferably greater than 50 kW and in particular greater than 70 kW. It is furthermore preferred that the electric machine provides rotational speeds greater than 5,000 U / min, particularly preferably greater than 10,000 U / min, very particularly preferably greater than 12,500 U / min.Motor vehicles in the sense of this application are land vehicles which are moved by machine power without being bound to railway tracks. A motor vehicle can be selected, for example, from the group of passenger cars (passenger cars), trucks (trucks), small-size trucks, light-weight trucks, bicycles, buses (COM) or tractors.The transmission arrangement 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. The transmission arrangement is preferably designed as a planetary transmission, very particularly preferably as a shiftable, in particular two-speed planetary transmission.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 technically expedient manner and can define further embodiments of the invention. In addition, the features specified in the claims are more precisely described and explained in the description, further preferred embodiments of the invention being presented.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 sump and a second distal end of the hydraulic path is connected to the transmission chamber.The advantage of this embodiment is that a V- or U-shaped hydraulic path enables the hydraulic fluid to be guided more easily and in a more controlled manner in the direction of the transmission chamber, since the return flow of liquids into the wrong region can be minimized by the shaping.Furthermore, the V- or U-shaped hydraulic path has the advantage that it can prevent or make more difficult an over-sloshing of the hydraulic fluid, for example, during cornering, i.e., in particular during a left- or right-hand turn. This also prevents sloshing during the assembly of the axle drive train, for example if the axle drive train has to be rotated clockwise or counter-clockwise during the assembly. In principle, a V- or U-shaped hydraulic path can also contribute to an increase in the fill level of hydraulic fluid in the high sump.In this case, the hydraulic apertures can be substantially identical. In particular, the apertures can also have an identical flow cross section. In principle, it is also possible for the hydraulic baffles to have flow cross sections that are different from one another, which can contribute to further optimization of the defoaming.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 particularly good, because almost complete defoaming of the hydraulic fluid in the overflow channel.Furthermore, the invention can also be further developed to the effect that the overflow channel is formed at least in sections integrally, in particular monolithically, with a transmission housing of the axle drive train. The integration of the overflow channel into the transmission housing results in an integral structure. This reduces the number of separate parts in the drive train and thus reduces the risk of leaks or failures at the joints. An overflow channel, which is in particular also configured monolithically with the transmission housing, can additionally more efficiently dissipate heat of the hydraulic fluid. The monolithic structure may also help improve the structural integrity of the gearbox housing, which may be particularly advantageous in harsh environments or at high stress.In a likewise preferred embodiment variant of the invention, it can also be provided that at least one of the hydraulic baffles, preferably a plurality of the hydraulic baffles, particularly preferably all the hydraulic baffles, is formed integrally, in particular monolithically, with the overflow channel. This makes it possible to eliminate the need to separately mount and connect various parts. This can reduce the assembly effort and reduce the production time.It may also be advantageous to further develop the invention to the effect that, on the one hand, the hydraulic fluid can be conveyed from the low sump into the high sump and, on the other hand, the hydraulic fluid can be conveyed from the high sump into the hydraulic circuit by means of the hydraulic pump. It can be achieved in this way that a corresponding pump can have only one pump motor, which is to be preferred for cost reasons.According to a further preferred embodiment of the subject matter of the invention, it can be provided that the hydraulic pump has a first channel for extracting the hydraulic fluid from the low sump into the high sump, and the hydraulic pump has a second channel for conveying the hydraulic fluid from the high sump into the hydraulic circuit, wherein the second channel is designed as a high-pressure channel, so that the hydraulic fluid can be conveyed safely and with high efficiency through the cooling circuit of the stator. Furthermore, two delivery tasks can be implemented in the drive train by means of a pump.Finally, the invention can also be advantageously embodied such that the first channel has a riser pipe, which is configured such that, during operation of the axle drive train, the hydraulic fluid opens into the high sump above a maximum fill level of hydraulic fluid in the direction of gravity, and the channel inlet of the overflow channel is arranged above the opening of the riser pipe in the direction of gravity. This means that the inlet of the overflow channel is located higher than the mouth of the riser pipe. This may help to safely drain excess hydraulic fluid when the level in the high sump becomes too high, which may prevent overfilling and possible damage to the system.According to a further preferred development of the invention, it can also be provided that the hydraulic pump with its first channel delivers a volume flow of hydraulic fluid which is between 4-8 l / min, preferably between 5-7 l / min, which has likewise proved to be advantageous for avoiding or reducing foaming of the hydraulic fluid in the high sump.In a likewise preferred embodiment variant of the invention, it can also be provided that the deep sump has / has a discharge screw on the bottom with a magnet and / or the high sump has / has a discharge screw on the bottom with a magnet, as a result of which a separation or immobilization of metallic particles from the hydraulic fluid can be effected.It can also be advantageous to further develop the invention to the effect that a heat exchanger is arranged in the second channel, by means of which heat exchanger the hydraulic fluid guided through the second channel is cooled before entering the stator, which improves the cooling capacity that can be provided for the stator.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 channel upstream of the pump arrangement in the conveying direction, as a result of which particles can likewise be separated out of the hydraulic fluid, which can likewise contribute to an increased service life as a result of reduced wear in the axle drive train.The invention can also be advantageously embodied to the effect that the transmission chamber and the high sump are connected to one another at the top in the direction of gravity. In the head region of the high sump, a venting device can also be provided, by means of which both the transmission chamber and the high sump can be vented. The advantage which results from this is in particular that a compact design of the axle drive train is supported.The invention will be explained in more detail below with reference to figures without limiting the general concept of the invention.It shows: FIG. 1 shows two embodiments of electric final drive trains in a motor vehicle in each case in a schematic illustration, FIG. 2 shows 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 open transmission housing, FIG. 4 shows a housing cover of a transmission housing with an overflow channel in a perspective cross-sectional illustration, FIG. 5 shows a transmission housing with an overflow channel in a perspective cross-sectional illustration.FIG. 1 shows two electrically operable final drive trains 1 which can be filled with a hydraulic fluid 2, wherein the final drive trains 1 each have an electric machine 3 and a transmission arrangement 4 which forms a structural unit with the electric machine 3. In the illustration b of FIG. 1, a dog is shown. Twin or dual drive is shown, in which the axle drive train 1 is formed from two electric machines 3 and two transmission arrangements 4, one electric machine each being connected to a transmission arrangement 4 assigned to it.The transmission arrangement 4 comprises a wet planetary transmission 5, which is arranged in a transmission chamber 6 of the transmission arrangement 4, wherein below the transmission chamber 6 in the direction of gravity a deep sump 7 hydraulically connected to the transmission chamber 6 is provided for storing the hydraulic fluid 2 exiting from the transmission chamber 6 and a high sump 8 hydraulically connected to the deep sump 7, the volume of which is greater than that of the deep sump 7.A hydraulic pump 9 is arranged in the high sump 8, by means of which the hydraulic fluid 2 can be conveyed out of the high sump 8 through a hydraulic circuit 10. 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 from the high sump 8 into the hydraulic circuit 10. This can be easily understood from FIG. 2.The hydraulic pump 9 has a pump motor, not designated in detail. In particular, a suction filter can also be provided before and / or within the second channel 20. The hydraulic pump 9 draws in 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 within the hydraulic circuit 10 in the direction of the stator of the electric machine 3 and subsequently through the transmission arrangement 4.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.FIG. 3 shows a realization of the hydraulic circuit diagram shown in FIG. 2 that is already known from the prior art. The arrangement of the hydraulic pump 9 in the high sump 8 with its riser pipe 22 and orifice 21 can be seen particularly well.As can be seen from FIGS. 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 at least one hydraulic orifice 13 is arranged in the hydraulic path 12 through the overflow channel 11 and locally narrows the flow cross section of the overflow channel 11. FIG. 4 shows the cover of the transmission housing 18, which is placed on the transmission housing 18 shown in FIG. 5, as a result of which the overflow channel 11 is then defined accordingly by the two housing components bearing against one another.The first channel 19 of the hydraulic pump 9 has a riser pipe 22 which is configured such that, during operation of the axle drive train 1, the hydraulic fluid 2 opens into the high sump 8 in the direction of gravity above a maximum fill level of hydraulic fluid 2, and the duct inlet 16 of the overflow duct 11 is arranged above the opening 21 of the riser pipe 22 in the direction of gravity.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 transmission chamber 6. In the hydraulic path 12 through the overflow channel 11, a plurality of hydraulic orifices 13 are arranged. A hydraulic orifice 13 is arranged in each case 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 baffles 13 are also formed monolithically with the overflow channel 11.If the hydraulic fluid 2 now foams in the high sump 8 during operation of the axle drive train 1 and correspondingly expands further in the direction of the overflow channel 11, the foam is broken through the overflow channel during passage at the hydraulic apertures 13 along the hydraulic path 12. The hydraulic fluid 2 originating from the collapsed foam is then conducted back into the high sump 8 in the front region of the overflow channel 11 (with respect to the flow direction of the hydraulic fluid 2), while the hydraulic fluid 2 resulting from the collapsed foam is conducted into the transmission chamber 6 in the rear region of the overflow channel 11.The vent opening 25 of the transmission housing 18 is located in the upper region in the direction of gravity and can be clearly seen in FIG. 5. This arrangement has been specifically chosen to ensure that hydraulic fluid 2 does not inadvertently pass into the vicinity of the vent 25. The overflow channel 11 has been designed in a V-shaped configuration which optimally protects the venting opening 25 from undesired penetration of hydraulic fluid 2. It should be noted that the venting opening 25 is situated above the channel outlet 17 of the overflow channel 11 in the direction of gravity, which represents an effective safety measure before an unintentional entry of hydraulic fluid 2 into the venting opening 25.The invention is not limited to the embodiments shown in the figures. The foregoing description is, therefore, not to be considered as limiting, but illustrative. The following claims should be understood to mean that a said feature is present in at least one embodiment of the invention. This does not exclude the presence of further features. If the patent claims and the above description define "first" and "second" features, this designation serves to distinguish two features of the same type without specifying a ranking.List of reference characters1 Axle drive train 2 Hydraulic fluid 3 Electric machine 4 Transmission arrangement 5 Planetary transmission 6 Transmission chamber 7 Low sump 8 High sump 9 Hydraulic pump 10 Hydraulic circuit 11 Overflow channel 12 Hydraulic path 13 Orifice 14 End 15 End 16 Channel inlet 17 Channel outlet 18 Transmission housing 19 Flood 20 Flood 21 Orifice 22 Riser pipe 23 Low sump path 24 High sump path 25 Venting opening

Claims

Electrically operable axle drive train (1) fillable with a hydraulic fluid (2), wherein the axle drive train (1) has an electric machine (3) and a transmission arrangement (4) forming a structural unit with the electric machine (3), wherein the transmission arrangement (4) comprises a wet-running planetary transmission (5) which is arranged in a transmission space (6) of the transmission arrangement (4), wherein a low sump (7) hydraulically connected to the transmission space (6) for storing the hydraulic fluid (2) emerging from the transmission space (6) in the direction of gravity below the transmission space (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), Hydraulic fluid (2) can be conveyed 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 transmission space (6), wherein at least one hydraulic orifice (13) which locally narrows the flow cross section of the overflow channel (11) is arranged in the hydraulic path (12) through the overflow channel (11), wherein a plurality of hydraulic orifices (13) is arranged in the hydraulic path (12) through the overflow channel (11), characterized in 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).Drive train (1) according to Claim 1, characterized in that the hydraulic path (12) of the overflow duct (11) has a substantially V-shaped 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 transmission space (6).Drive train (1) according to Claim 1, characterized in that at least one hydraulic orifice (13) is arranged in the region of the duct inlet (16) of the overflow duct (11) and / or at least one hydraulic orifice (13) is arranged in the region of the duct outlet (17) of the overflow duct (11).Drive train (1) according to one of the preceding claims, characterized in that the overflow channel (11) is formed at least in sections integrally, in particular monolithically, with a transmission housing (18) of the axle drive train (1)Drive train (1) according to one of the preceding claims, characterized in that at least one of the hydraulic baffles (13), preferably a plurality of the hydraulic baffles (13), particularly preferably all the hydraulic baffles (13), is formed integrally, in particular monolithically, with the overflow channel (11).Drive train (1) according to one of the preceding claims, characterized in that, on the one hand, the hydraulic fluid (2) can be conveyed from the low sump (7) into the high sump (8) by means of the hydraulic pump (9) and, on the other hand, the hydraulic fluid (2) can be conveyed from the high sump (8) into the hydraulic circuit (10).Drive train (1) according to Claim 6, characterized in that the hydraulic pump (9) has a first channel (19) for extracting the hydraulic fluid (2) from the low sump (7) into the high sump (8), and the hydraulic pump (9) has a second channel (20) for conveying the hydraulic fluid (2) from the high sump (8) into the hydraulic circuit (10), wherein the second channel (20) is designed as a high-pressure channel.Drive train (1) according to Claim 7, characterized in that the first channel (19) has a riser pipe (22), which is configured such that, during operation of the axle drive train (1), the hydraulic fluid (2) opens into the high sump (8) in the direction of gravity above a maximum fill level of hydraulic fluid (2), and the duct inlet (16) of the overflow duct (11) is arranged above the opening (21) of the riser pipe (22) in the direction of gravity.

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