Electric transmission drive unit and method for operating same

Abstract

The invention relates to an electric transmission drive unit (10) and to a method for producing same, in particular for a traction drive of a motor vehicle, comprising an electric motor (12), which has a rotor shaft (14) that drives a downstream gear transmission (20) with an output element (22) for translation, wherein the gear transmission (20) is disposed in a transmission housing (21) and comprises a plurality of gearwheels (24), wherein liquid cooling lubricant (30) in the transmission housing (21) can be conveyed from a cooling lubricant sump (32) via a lifting region (36) into a higher-placed cooling lubricant reservoir (34) by means of at least one gearwheel (25).

Description

[0001] Description

[0002] title

[0003] Electric gear drive unit and a method for operating such a unit

[0004] State of the art

[0005] The invention relates to an electric transmission drive unit and a method for operating such a unit according to the preamble of the independent claims.

[0006] EP 2 724 450 B1 discloses an electrical machine having a stator housing in which a stator with a wound lamination pack is arranged. To cool the electrical winding, the rotor shaft has a central cooling channel through which oil is conducted as a coolant. Spray openings are formed in the rotor shaft through which the coolant is sprayed onto the winding head of the electrical winding and then collects at the base of the motor housing. From there, the oil is pumped upwards into the rotor shaft by means of a separate oil pump. The disadvantage here is that the oil pump must be arranged as an additional component on the electric motor, and an electrical power supply for the oil pump must be provided. The invention aims to overcome these disadvantages.

[0007] Disclosure of the invention

[0008] The electric gear drive unit according to the invention and the method for producing such a unit with the features of the independent claims have the advantage that, by driving the coolant-lubricant transport system through the reduction gear of the drive unit, an additional electrically operated pump is dispensed with. The coolant-lubricant is not only distributed in an undefined manner within the gear housing by the rotating gear wheels, but is also lifted against gravity by a defined lifting range in order to specifically cool higher-lying components. By coupling the drive of the coolant transport system to the rotor shaft of the electric motor for the traction drive, the coolant flow rate is automatically adjusted to the increased cooling demand at higher speeds.To drive the coolant flow, the geometry of the gearbox housing and the geometry of a gearwheel mounted therein can be designed as a flow channel. Alternatively, a gear element of the reduction gear can drive a feed pump.

[0009] The measures listed in the subclaims result in advantageous refinements and improvements of the features specified in the independent claims. The cooling lubricant can be conveyed upwards particularly easily, directly through a gearwheel, whose teeth are constantly immersed in the coolant sump. The teeth of the gearwheel, in conjunction with the adjacent inner wall of the gear housing, transport the coolant to a higher level, where it can be specifically supplied to the components that require special cooling. The teeth are preferably designed as radially outer spur gears, which essentially act as a kind of impeller blade.

[0010] By designing the radial and / or axial gaps between the spur gear teeth and the corresponding inner wall of the gearbox housing, a flow channel can be created through which the coolant can be transported upwards against gravity in the lifting area. Adhesion and capillary forces act primarily in the flow channel, pulling the coolant upwards. By selecting the cross-section of this flow channel, the flow rate of coolant / lubricant can also be specified depending on the speed of the electric motor.

[0011] It is particularly advantageous if the raised coolant / lubricant is collected in a coolant / lubricant reservoir, from where it can be distributed to the components to be cooled. The coolant is picked up from the feed gear by means of a receiving ramp and directed into the coolant / lubricant reservoir. The receiving ramp is arranged in the upper area of ​​the feed gear, tangential to it at a very small radial distance. In this area, the radial gap between the spur gearing and the gearbox housing wall widens, so that the coolant is thrown radially outward onto the receiving ramp of the coolant / lubricant reservoir by centrifugal force.

[0012] Depending on the desired flow rate, the feed gear can be mounted directly on the output shaft or on an intermediate shaft of the reduction gear. Preferably, a gear with a particularly large diameter is mounted on the output shaft in the last reduction stage, allowing the coolant to be lifted by a particularly large amount at this last gear, allowing this high potential to reach all components to be cooled.

[0013] In an alternative design, the reduction gear drives a feed pump located in the cooling lubricant sump. The feed pump can be designed particularly simply as a cylindrical sleeve in which a rotating feed screw is arranged. The cooling lubricant can be drawn in at a first side, and a feed pressure can be built up at an axially opposite second side, by means of which the cooling lubricant can be conveyed upwards. The feed pressure is advantageously correlated with the speed of the electric motor.

[0014] It is particularly advantageous to install a riser pipe on the second side of the sleeve, through which the coolant is transported upwards against gravity over the lifting area. The riser pipe can be connected directly to the coolant / lubricant reservoir and / or routed directly to the components to be cooled. This ensures continuous, sufficient cooling of both the electric motor and the gear wheels.To seal between the sleeve and the conveyor screw, an elastic sealing lip can be arranged on its radially outer edge, which rests radially on the inside of the cylindrical sleeve. This can, on the one hand, increase the sealing effect between the conveyor screw and the sleeve, and on the other hand, the design of the sealing lip also creates a possibility for overpressure compensation, as the elastic sealing lip deforms when the pressure in the sleeve is too high, so that the coolant can flow back into the coolant-lubricant sump.

[0015] A pump gear, driven by the reduction gear, can be easily formed integrally on the screw conveyor shaft. Advantageously, the pump gear also has radially outer spur gearing that meshes with a gear of the gear train. The pump gear, together with the screw conveyor, can be manufactured particularly cost-effectively as a monolithic unit from plastic or metal.

[0016] It is particularly advantageous if radial openings - especially several - are formed along the axial direction of the rotor shaft, through which the coolant escapes in the radial direction. This allows the electric motor to be supplied with coolant in a targeted manner at its two winding heads. Likewise, several radial openings can be distributed around the circumference of the rotor shaft so that the winding head receives a uniform flow of coolant over its circumference. Centrifugal force propels the coolant upward from the rotor shaft, also against gravity, ensuring continuous cooling.

[0017] It is particularly advantageous to use a medium as the cooling lubricant that both lubricates the transmission components and cools the electric motor. A transmission oil with properties optimized for cooling is particularly suitable for this purpose. For cooling purposes, it is particularly important that the cooling lubricant be thinner than normal transmission oil. Preferably, the transmission drive unit also has an electronics housing in which electronics for controlling the electric motor are located. The purpose of this housing is to absorb, in particular, the heat generated by an inverter in the electronics housing. For this purpose, a cooling channel of a further cooling circuit is arranged between the transmission housing and the electronics housing. This cooling circuit is operated, for example, with cooling water as the second coolant.The second coolant first absorbs the heat from the electronics housing and is then directed through the cooling channel to the coolant / lubricant sump in the transmission housing, where it also absorbs heat. This allows the second coolant, which is required to cool the electronics housing, to also cool the coolant / lubricant in the transmission housing. This eliminates the need for an additional heat exchanger in the coolant / lubricant sump.

[0018] It is particularly advantageous if the cooling channel is designed as an integral part of the housing wall of the transmission drive unit. As a result, the cooling channel simultaneously represents a mechanical partition, for example between the electronics and the transmission, whereby no additional component is required for the second cooling circuit. In particular, the cooling channel can be arranged such that it absorbs heat from the electronics housing on one side and absorbs heat from the transmission housing - preferably from the cooling-lubricant sump - on a second, opposite side. In addition, a rib structure can optionally be formed within the cooling channel in order to increase the heat absorption of the second cooling liquid. The second cooling liquid preferably flows vertically downwards due to gravity, with the cooling channel extending in particular substantially over the entire vertical height of the entire transmission drive unit.

[0019] The cooling channel extends particularly advantageously on the underside of the electronics housing essentially over the entire surface of this underside.

[0020] This ensures strong and rapid heat absorption from the electronics into the second coolant. This large cross-section of the cooling channel can be designed as a type of double wall between the electronics housing and the gearbox housing. From this part of the cooling channel, which lies extensively against the electronics housing, it continues vertically downwards with a reduced cross-section. For example, the cooling channel here is tubular and extends downwards to the coolant / lubricant sump. The cooling channel can be particularly advantageously routed along an axial side wall of the gearbox housing - or in particular integrated into it. In the lower area of ​​the gearbox housing, the tubular cooling channel is routed approximately horizontally along the coolant / lubricant sump in order to extend the contact surface with it.The inlet for the cold second coolant is located in the upper area of ​​the electronics housing, while the outlet with the heated second coolant is located in the lower area of ​​the gearbox housing.

[0021] During operation of the liquid cooling system according to the invention, the rotation of the rotor shaft of the electric motor raises the cooling lubricant from the cooling lubricant sump into the elevated cooling lubricant reservoir by means of a gear element of the downstream gearbox, or transports it directly to elevated gear elements to be cooled. The cooling lubricant absorbs heat and flows back down into the cooling lubricant sump. This allows gear wheels and / or the electrical winding of the electric motor to be effectively cooled and, if necessary, lubricated. The cooling lubricant sump can be cooled by a second cooling liquid, with the second cooling liquid, in particular, first cooling the electronics housing arranged on the gearbox housing.

[0022] Liquid cooling is particularly advantageous for electric machines with a horizontal rotor shaft, such as a traction drive in a motor vehicle. Due to gravity, the cooling lubricant collects in the lower vertical area of ​​the gearbox housing in the cooling lubricant sump, so special care must be taken to ensure that the upper vertical area above the rotor shaft is also well supplied with coolant. The radial openings in the rotor shaft allow the cooling lubricant to be directed radially outward into the radial area of ​​the winding head. With this type of liquid cooling, high-performance electric machines can be adequately cooled even for continuous operation.As a coolant, for example, cooling oil can be used, which collects in the gear housing after wetting the winding head and can be lifted back up into the coolant-lubricant reservoir to create a first cooling circuit.

[0023] Description of the drawings

[0024] Further features of the invention will become apparent from the further details of the description and the drawings, as described in the following exemplary embodiments of the invention. They show:

[0025] Fig. 1 shows a first embodiment of an electric transmission drive unit according to the invention,

[0026] Fig. 2 is a detailed view of the embodiment according to Fig. 1 in section,

[0027] Fig. 3 is a further sectional view of a further embodiment,

[0028] Fig. 4 is a rear view of the embodiment according to Fig. 1,

[0029] Fig. 5 is a schematic view of another embodiment, and

[0030] Fig. 6 shows a further embodiment of a cooling-lubricant conveying device.

[0031] Fig. 1 shows a transmission drive unit 10, such as is used, for example, in an e-axle for the electric traction drive of a motor vehicle. An electric motor 12 has a rotor shaft 14 in the axial direction 8, which transmits a drive torque to a gear transmission 20 arranged in a transmission housing 21. The gear transmission 20 is designed here, for example, as a two-stage spur gear transmission, in which a gear wheel 24 mounted on an intermediate shaft 27 is driven by the rotor shaft 14. A further gear wheel 24 is arranged on the intermediate shaft 27 and meshes with a further gear wheel 24 mounted on an output shaft 23. An output element 22 is arranged on the output shaft 23, with which the available torque can then be transmitted, for example, to an axle of a motor vehicle.For the lubrication and cooling of the gear transmission 20, a cooling lubricant 30 is filled into the transmission housing 21, which collects in a cooling lubricant sump 32 in the lower area of ​​the transmission housing 21 due to gravity.

[0032] According to the invention, at least one of the gear wheels 25 transports coolant-lubricant 30 from the coolant-lubricant sump 32 via a lifting area 36 against the force of gravity into a coolant-lubricant reservoir 34. The at least one gear wheel 25 is arranged such that its radially outer spur toothing 26 has only a small radial gap 38 to an inner wall 39 of the gear housing 21 adjacent in the radial direction 7. As a result, the spur toothing 26 of the at least one gear wheel 25 acts as a type of paddle wheel, which lifts the coolant-lubricant 30 along the inner wall 39 of the gear housing 21 against the force of gravity in the vertical direction 6 upwards into the coolant-lubricant reservoir 34. For this purpose, a receiving ramp 40 is arranged in the upper region of the at least one gear wheel 25 tangentially to the spur gear toothing 26, which receives the cooling lubricant 30 from the spur gear toothing 26 and directs it into the cooling lubricant reservoir 34.In particular, the cooling lubricant 30 is conveyed upwards over a circumferential angle of more than 180° of the at least one gear wheel 25, so that the lifting area 36 approximately corresponds to the diameter of the at least one gear wheel 20. In this embodiment, the radial gap 38 to the inner wall 39 is so small over this circumferential angle that the cooling lubricant 30 is drawn upwards by adhesion forces and capillary forces with the rotation of the at least one gear wheel 25. From the cooling lubricant reservoir 34, the cooling lubricant 30 can be directed to the gear elements 24 to be cooled or to parts of the electric motor 12. In Fig. 1, the cooling lubricant reservoir 34 is directly connected to a cavity 15 in the rotor shaft 14. From this cavity 15, the cooling lubricant 30 can be guided through radial openings 16 in the rotor shaft 14 to an electrical winding 68 of the electric motor 12, as shown in Fig.3. An electronics housing 50 is arranged above the gear housing 21, which accommodates, for example, an inverter 52 for controlling the electric motor 12. In Fig. 1, the gear housing 21 has an axially open flange 18, which can be closed with a lateral gear housing cover 19.

[0033] Fig. 2 shows a section of at least one gear wheel 25. The spur gear teeth 26 are helical gear teeth, with the cooling lubricant 30 being able to be accommodated between the individual teeth. The radial gap 38 between the spur gear teeth 26 and the inner wall 39 of the gear housing 21 is adapted to the required flow rate of cooling lubricant 30 for the respective application, with increasing speed of the rotor shaft 14 also leading to more cooling lubricant 30 being conveyed into the cooling lubricant reservoir 34. The dimension of the radial gap 38 is, for example, 1-3 mm. Furthermore, an axial gap 37 is formed between the spur gear teeth 26 and the axial inner walls 39 of the gear housing 21, the dimensions of which are also designed to be so small that not too much cooling lubricant 30 can escape at the axial surfaces 35 of the spur gear teeth 26. In the embodiment according to Fig.2, the spur gearing 26 is designed as a separately manufactured gear rim 29, which here is screwed to the at least one gear wheel 25 by means of screws 28. This design creates a flow channel 42 between the spur gearing 26 and the inner wall 39 of the gear housing 21, in which flow channel the cooling lubricant 30 is drawn upwards with the rotation of the spur gearing 26. The desired flow rate of cooling lubricant 30 can then be specified by selecting the dimensions of the radial and axial gaps 38, 37. The at least one gear wheel 25 is arranged on the output shaft 23, which is designed, for example, as a hollow shaft. The lateral gear housing cover 19 is connected in a liquid-tight manner to the corresponding flange 18 by means of connecting screws 17. Fig. 3 shows a further section through the embodiment according to Fig. 1 along the rotor shaft 14 of the electric motor 12.The rotor shaft 14 is designed as a hollow shaft, so that the cavity 15 into which the cooling lubricant 30 is introduced is formed within the rotor shaft 14. A plurality of radial openings 16 are formed in the rotor shaft 14, through which the cooling lubricant 30 can be projected radially outward onto an electrical winding 68 of the electric motor 12. The electric motor 12 has a stator 60 arranged in a motor housing 62. The stator 60 has a yoke ring 64 from which stator teeth 66 extend radially inward. The electrical winding 68 is arranged on the stator teeth 66 and is controlled by electronics 51 arranged in the electronics housing 50 above the motor housing 62. The electrical winding 68 extends in the axial direction 8 beyond the yoke ring 64 and forms so-called winding heads 69 here.A rotor body (not shown) is attached to the rotor shaft 14, which, for example, accommodates permanent magnets that interact with the electrical winding 68. The rotor shaft 14 is mounted here by means of ball bearings 71, 72 in the bearing shields 70 of the motor housing 62. The radial openings 16 are formed in the axial region of the winding heads 69 in the rotor shaft 14, so that the cooling lubricant 30 wets the winding heads 69 during operation. The cooling lubricant 30 then flows downwards in the vertical direction 6 due to gravity into the cooling lubricant sump 32 of the gear housing 21. As shown in Fig.

[0034] 1 and 2, the cooling lubricant 30 is conveyed into the cooling lubricant reservoir 34 by means of at least one gear wheel 25. The axial end of the rotor shaft 14 protrudes from the motor housing 62 into the gear housing 21. A gear wheel 24 is attached to the rotor shaft, which meshes with another gear wheel 24 arranged on the intermediate shaft 27. The cooling lubricant reservoir 34 is connected directly to the cavity 15 of the hollow shaft-shaped rotor shaft 14 via an outflow nozzle 33. The outflow nozzle 33 is arranged in the lower region of the cooling lubricant reservoir 34, so that the cooling lubricant 30 flows from the cooling lubricant reservoir 34 into the hollow shaft 14 of the rotor by gravity. When the rotor shaft 14 rotates, the cooling lubricant 30 is then thrown outwards onto the electrical winding 68 through the radial openings 16 due to centrifugal force.The centrifugal force in particular creates a suction effect in the hollow shaft 14, which draws the oil into the hollow shaft 14.

[0035] Fig. 3 shows the two-stage gear transmission 20, in which a further gear wheel 24 is arranged on the intermediate shaft 27, which then drives the at least one gear wheel 25 on the output shaft 21. The transmission elements 24 are mounted in the transmission housing 21, with both the toothing and the bearings of the gear wheels 24 being continuously cooled and lubricated by the cooling lubricant 30 during operation. The electronics housing 50 is arranged above the transmission housing 21 and the motor housing 62 and, in particular, also accommodates an inverter 52 for the electric motor 12. A cooling channel 80, through which a second cooling fluid—for example, cooling water—flows, is formed between the electronics housing 50 on the one hand and the transmission housing 21 and the motor housing 62 on the other.The second cooling liquid 82 first flows along the underside 49 of the electronics housing 50 and is then guided downwards in the cooling channel 80 to the cooling-lubricant sump 34. In particular, an inlet 83 of the cooling channel 80 is arranged in the upper region of the transmission housing 21, whereas an outlet 84 of the cooling channel 80 is arranged in the lower region of the transmission housing 21. The second cooling liquid 82 flows around the underside 49 of the electronics housing 50 over a large area, thereby absorbing the heat generated in the electronics 51. The cooling channel 80 is then guided along an axial side wall 85 of the transmission housing 21 to the cooling-lubricant sump 34. The second cooling liquid 82 absorbs further heat from the cooling lubricant 30 when the cooling channel 80 is guided along the wall of the transmission housing 21 in the region of the cooling lubricant sump 32.Thus, the cooling lubricant 30 is cooled on the one hand via the transmission housing 21, and on the other hand by the cooling circuit of the second cooling liquid 82. The cooling channel 80 is preferably integrated into the housing wall of the transmission housing 21 and / or the motor housing 62 and / or the electronics housing 50 as a cooling pocket. The cooling channel 80 extends, in particular on the underside 49 of the electronics housing 50, essentially over its entire axial and tangential extent. From the electronics 51, the cooling channel 80 then extends tubularly downwards to the cooling lubricant sump 32, wherein the cooling channel.

[0036] 80 is preferably integrated into the axial side wall 85 of the gear housing 21

[0037] The course of the cooling channel 80 is illustrated in Fig. 4, which shows a rear view of the embodiment according to Fig. 1. The electronics housing 50, in which the inverter 52, for example, is arranged, is shown above the gear housing 21 and the motor housing 62. The cooling channel 80 extends approximately over the entire underside 49 of the electronics housing 50. From there, the cooling channel 80 runs approximately vertically downwards along the outside of the axial side wall 85 of the gear housing 21. The cooling channel 80 is, for example, integrated into the axial side wall 85 and here has, in particular, a tubular cross-section. In the lower region of the gear housing 21, the tubular cooling channel 80 is guided along the coolant-lubricant sump 34 - in particular, essentially horizontally. In this embodiment, no separate heat exchanger is provided, in which a cooling water circuit directly cools the coolant-lubricant 30.Advantageously, the entire cooling channel 80 can be integrated into the housing walls of the transmission housing 21 and / or the motor housing 62 and / or the electronics housing 50. In Fig. 4, the motor housing 62 extends in the axial direction 8 from the image plane beyond the axial side wall 85 of the transmission housing 21, so that the tubular part of the cooling channel 80 is preferably arranged in the axial region between the electric motor 12 and the gear transmission 20, as can also be seen in Fig. 3. The motor housing 62 can also be formed as an integral component of the transmission housing 21.

[0038] Fig. 5 schematically shows a further embodiment of a cooling channel 80, which is arranged between the electronics housing 50 and the cooling-lubricating sump 34. The second cooling liquid 82 initially only absorbs heat from the electronics housing 50 and only further along the cooling channel 80 does it then also absorb additional heat from the cooling-lubricating sump 34. In the illustration in Fig. 5, the cooling channel 80 is arranged such that the electronics housing 50 overlaps at least with the part of the transmission housing 21 in which the cooling-lubricating sump 34 is arranged. In particular, the underside 49 of the electronics housing 50 extends approximately in the vertical direction 6, so that in the lower region of the cooling channel 80, the electronics housing 50 rests on one side, and the wall of the transmission housing 21, which accommodates the cooling-lubricating sump 34, rests on the opposite side.As a result, at the inlet 83 of the second cooling liquid 82, the heat from the electronics housing 50 is primarily absorbed, wherein in the region of the outlet 84 of the cooling channel 80, where the second cooling liquid 82 is already heated to a certain degree, additional heat is also absorbed from the coolant-lubricant sump 34. Cooling fins 77 are formed within the cooling channel 80 in order to increase the surface area through which the second cooling liquid 82 can flow. The second cooling liquid 82 preferably flows from top to bottom in the direction of gravity. The cooling channel 80 can be designed directly as a partition wall integrated into the overall housing of the transmission drive unit 10 between the electronics housing 50 and the transmission housing 21, wherein the partition wall separates the electronics 50 from the hot transmission housing 21.

[0039] Fig. 6 shows a section of a further embodiment of a gear drive unit 10, in which the cooling lubricant 30 is pumped from the cooling lubricant sump 32 by means of a pump 90. The pump 90 is driven, for example, by the at least one gear wheel 25 of the gear transmission 20. The pump 90 has a cylindrical sleeve 92, within which a conveyor screw 93 is arranged. The conveyor screw 93 is connected via a worm shaft 94 to a pump gear 95, which is driven in particular by the at least one gear element 25 of the gear transmission 20. The sleeve 92 is arranged in the cooling lubricant sump 32, so that when the screw 93 rotates, the cooling lubricant 30 is pumped into the sleeve

[0040] 92 is sucked in. At a rear end 96 of the rear-closed sleeve

[0041] 93 has an opening 97 through which the cooling lubricant 30 can be forced into a riser 98, by means of which the cooling lubricant 30 can be directed to the components to be cooled, such as the electrical winding 68 or the gear wheels 24. In particular, the riser 98 leads to the cooling lubricant reservoir 34 in order to continuously fill it. From the cooling lubricant reservoir 34, the cooling lubricant 30 can be directed directly into the cavity 15 of the rotor shaft 14, for example, in accordance with the embodiment in Fig. 3. Optionally, an elastic sealing lip 99 can be formed on the radially outer edge of the conveyor screw 93, which allows the cooling lubricant 30 to flow back into the cooling lubricant sump 32 when excess pressure occurs in the sleeve 92.Due to the direct coupling of the pump gear 95 to the gear transmission 20, the flow rate of the cooling lubricant 30 is coupled to the speed of the electric motor 12, and thus to the cooling requirements of the electric motor 12 and the gear transmission 20. The pump gear 95 has an external toothing 91, which meshes, for example, with at least one gear wheel 25 and / or is driven via the rotor shaft 14 and / or the intermediate shaft 27 and / or the output shaft 23. The sleeve 92 and also the riser 98 can be integrated directly into the inner wall 39 of the gear housing 21. The worm shaft 94 is mounted at bearing points 100 within the gear housing 21. The desired flow rate of coolant-lubricant 30 can be adjusted via the geometry of the worm 93 and / or the coupling of the pump gear 95 to the gear transmission 20.

[0042] It should be noted that, with regard to the exemplary embodiments shown in the figures and in the description, a wide variety of combinations of the individual features are possible. For example, the specific contour and arrangement of the gear wheel 25 and the inner wall 39 of the gear housing 21 can be adapted accordingly to form the flow channel 42. Alternatively, the gear transmission 20 can also be varied, and the cooling lubricant 30 can be conveyed upwards in the vertical direction 6 not directly through the at least one gear wheel 25, but indirectly through the gear transmission 20. The shape and course of the cooling channel 80 can be adapted to the shape of the housing of the gear drive unit 10 and, in particular, can be fully or partially integrated into the housing walls.The electric machine 12 is preferably designed as an electronically commutated motor, wherein the electrical winding 68 can be designed as a plug-in winding or as a wound coil winding. The invention is particularly suitable for the rotary drive of components or as a traction drive in motor vehicles, but is not limited to this application.

Claims

Claims 1. Gearbox drive unit (10), in particular for a traction drive of a motor vehicle, with an electric motor (12) which has a rotor shaft (14) which drives a downstream gear transmission (20) with an output element (22) for reduction, wherein the gear transmission (20) is arranged in a transmission housing (21) and has a plurality of gear wheels (24), wherein by means of at least one gear wheel (25) liquid cooling lubricant (30) in the transmission housing (21) can be conveyed from a cooling lubricant sump (32) via a lifting area (36) into a higher cooling lubricant reservoir (34).

2. Gear drive unit (10) according to claim 1, characterized in that the at least one gear wheel (25) has a straight or oblique spur toothing (26) which dips into the cooling-lubricant sump (32) and acts as a paddle wheel for the cooling-lubricant (30).

3. Gear drive unit (10) according to one of the preceding claims, characterized in that the spur gearing (26) of the at least one gear wheel (25) is arranged in the lifting area (36) with a small gap (38, 37) to an inner wall (39) of the gear housing (21), in particular with respect to a radial direction (7) and / or an axial direction (8) of the gear wheel (25).

4. Gear drive unit (10) according to one of the preceding claims, characterized in that on the cooling lubricant reservoir (34) a receiving ramp (40) for the cooling lubricant (30) is arranged tangentially to the front Toothing (26) is arranged, and in particular in the region of the receiving ramp (40) the radial gap (38) is widened to the inner wall (39) of the gear housing (21).

5. Gear drive unit (10) according to one of the preceding claims, characterized in that the gear transmission (20) has an intermediate shaft (27) and an output shaft (23), and the at least one gear wheel (25) with the spur gearing (26) is arranged on the intermediate shaft (27) or on the output shaft (23).

6. Gear drive unit (10) according to one of the preceding claims, characterized in that the at least one gear wheel (25) drives a conveyor screw (93) as a function of the speed of the rotor shaft (14), which is arranged in a cylindrical sleeve (92), and the sleeve (92) is immersed - preferably completely - in the cooling lubricant sump (32) in order to suck in cooling lubricant (30) through an opening in the sleeve (92).

7. Gear drive unit (10) according to one of the preceding claims, characterized in that a riser (98) is connected to the cylindrical sleeve (92), through which riser the cooling lubricant (30) is conveyed into the cooling lubricant reservoir (34) - or in particular directly onto the elements to be cooled.

8. Gear drive unit (10) according to one of the preceding claims, characterized in that an elastic sealing lip (99) is formed on the radially outer edge of the conveyor screw (93), which rests against the inside of the sleeve (92) - in particular in order to enable a backflow of the cooling lubricant (30) due to the deformation of the elastic sealing lip (99) when an overpressure occurs in the sleeve (92).

9. Gear drive unit (10) according to one of the preceding claims, characterized in that the conveyor screw (93) is manufactured monolithically in one piece with an axially adjacent pump gear (95) which is driven via the at least one gear wheel (25) - wherein in particular the conveyor screw (93) with the pump gear (95) is made of plastic or steel.

10. Electric gear drive unit (10) according to one of the preceding claims, characterized in that the cooling lubricant (30) is conveyed into an axial cavity (15) within the rotor shaft (14), which has at least one radial passage (16) through which the electrical winding (68) of the electric motor (12) can be wetted with the cooling lubricant (30).

11. Electric gear drive unit (10) according to one of the preceding claims, characterized in that the rotor shaft (14) is arranged horizontally in the motor vehicle, and by means of the at least one radial passage (16) in the rotor shaft (14), the part of the electrical winding (68) which is arranged in the vertical direction (6) above the rotor shaft (14) can also be sufficiently wetted with cooling lubricant (30) by the centrifugal force.

12. Electric gear drive unit (10) according to one of the preceding claims, characterized in that the cooling lubricant (30) is designed simultaneously as a lubricant for the gear wheels (24) and as a coolant for the electric motor (12) - and is preferably a gear oil optimized for cooling.

13. Electric gear drive unit (10) according to one of the preceding claims, characterized in that an electronics housing (50) - in particular with an inverter (51) - is arranged on the gear housing (21), wherein a cooling channel (80) is formed between the gear housing (21) and the electronics housing (50), wherein a second cooling liquid (82) - preferably cooling water - can flow through the cooling channel (80), which can absorb heat from the electronics housing (50) in a first region and heat from the coolant-lubricant sump (32) of the gear housing (21) in a second region.

14. Electric transmission drive unit (10) according to one of the preceding claims, characterized in that the cooling channel (80) is arranged as an integral component of a transmission housing wall as a mechanical partition wall in such a way that in the flow path of the second cooling liquid (82) - in particular along the force of gravity - first heat from the electronics housing (50) and later also additional heat from the cooling lubricant sump (32) can be absorbed - wherein in particular a rib structure (77) is formed within the cooling channel (80).

15. Electric gear drive unit (10) according to one of the preceding claims, characterized in that the cooling channel (80) is formed over a large area along the electronics housing (50) and extends over a large part of a radial underside (49) of the electronics housing (50), and the cooling channel (80) then extends downwards on an axial side wall (85) of the gear housing (21) to the cooling-lubricating sump (32) - and in particular is guided along the axial side wall (85) of the gear housing (21) along the cooling-lubricating sump (32).

16. Method for operating an electric transmission drive unit (10), in particular according to one of the preceding claims, comprising the following steps: With the rotation of a rotor shaft (14) of an electric motor (12), cooling lubricant (30) is conveyed by means of at least one specific gear wheel (25) of a subsequent gear (20) arranged in a gear housing (21) from a cooling lubricant sump (32) into an elevated cooling lubricant reservoir (34) or directly to elevated gear elements to be cooled. Due to gravity, the cooling lubricant (30) flows downwards into the cooling lubricant sump (32) via the gear wheels to be cooled and / or via the electrical winding (68) of the electric motor (12) while absorbing heat. The cooling-lubricant sump (32) is optionally cooled by a circuit of a second cooling liquid (82), wherein in particular the second cooling liquid (82) also cools an electronics housing (50) which is flanged to the transmission housing (21).

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