DE102017218351A1 - Rotor hollow shaft with integrated pump element - Google Patents

Abstract

The invention relates to a rotor hollow shaft (12) for a rotor (10) of an electrical machine (64), comprising a cylinder-shaped laminated core carrier (16) which is closed on both sides by a first end flange (22) and a second end flange (24). 26), wherein in the first end flange (22) an inlet opening (30) is formed, and within the wave cavity (26) arranged pump element (14), which is fluidly connected to the inlet opening (30) and arranged and formed in that a cooling medium (32) can be sucked in via the inlet opening (30) and can be conveyed via an outlet opening (52) of the pump element (14) against an inner lateral surface (34) of the cylindrically shaped laminated core carrier (16).

Description

The invention relates to a hollow rotor shaft with an integrated pump element for cooling a rotor and / or stator of an electrical machine, in particular a drive device or an engine and / or generator. In addition, the invention relates to a rotor comprising the rotor hollow shaft equipped with at least one laminated core according to the invention. Furthermore, the invention relates to an electric machine with the rotor according to the invention. Furthermore, the invention relates to a method for cooling an electric machine, comprising the rotor according to the invention.

Drive devices, in particular hybrid drive devices, are used to drive motor vehicles, wherein hybrid drive devices typically include an internal combustion engine and an electric machine. The case acting as a motor and generator electric machine has a shaft with a rotor arranged on the shaft and a rotor surrounding fixedly arranged stator. The stator and the rotor are disposed within a housing of the electric machine.

In the electric machine, in particular in its stator and / or rotor, waste heat is generated, so that cooling of the electric machine is required. In order to cool the electric machine, it is customary to use a cooling medium in the form of air or optionally water for cooling the electric machine and to guide this cooling medium through at least one region of the machine. The disadvantage here is the limited cooling of the electric machine, since only certain areas are flowed through by the cooling medium.

Furthermore, from the DE 10 2014 107 845 A1 a rotor hollow shaft for a rotor of an electric machine, in which the rotor hollow shaft, a cooling liquid is supplied. Accordingly, it is provided that the hollow rotor shaft has a sealed on both sides of end flanges cylinder jacket surrounding a shaft cavity, wherein on the end flanges in each case a shaft journal is formed and wherein in one of the shaft journal an inlet is provided, via which a cooling liquid into the shaft cavity and the Inner surface of the cylinder jacket arrives. In the wave cavity, a distribution element is arranged, which receives the coolant entering via the inlet, leads via a rotationally symmetrical discharge surface in the direction of the inner surface of the cylinder jacket and discharges onto the inner surface via an orifice region. A disadvantage of this concept is that active cooling liquid must be supplied to the shaft cavity from the outside and that, due to the rotationally symmetrical discharge surface within the wave cavity, no uniform cooling of the wave cavity in the axial direction of the wave cavity can be achieved.

There is a regular need to optimize the cooling of electrical machines, on the one hand to achieve a uniform cooling within the rotor, whereby contact voltages of the rotor bearing can be reduced and, on the other hand, to reduce the space of the electric machine.

It is the object of the present invention to provide a rotor hollow shaft for an electric machine, with which a uniform cooling of a rotor and / or stator can be achieved and, by means of which the space of an electric machine can be reduced.

The object is solved by the subject matters of the independent claims. Advantageous embodiments of the invention are set forth in the dependent claims, the description and the drawings, wherein each feature, both individually and in combination, may constitute an aspect of the invention. In this case, all combinations as well as isolated combinations between the features of the hollow rotor shaft, the rotor, the electric machine and / or the method can be used together. Furthermore, it is also provided and possible to combine any one or more features of the hollow rotor shaft, the rotor, the electric machine and / or the method as desired.

According to the invention, a rotor hollow shaft is provided for a rotor of an electrical machine, comprising a cylindrical plate core carrier enclosed on both sides by a first end flange and a second end flange, which surrounds a shaft cavity, wherein an inlet opening is formed in the first end flange, and a pump element arranged inside the shaft cavity , which is fluidly connected to the inlet opening and is arranged and configured such that via the pump element, a cooling medium can be sucked in via the inlet opening and conveyed via an outlet opening of the pump element against an inner jacket surface of the cylinder-shaped laminated core carrier.

It is thus an aspect of the invention that the rotor hollow shaft has a cylindrical shaped laminated core, which is closed on both sides at the mutually axially spaced end portions each with an end flange, so that a wave cavity is formed by the cylindrically shaped laminated core. On the laminated core carrier is preferably in the longitudinal direction of the cylindrical Blechpaketträgers arranged at least one laminated core to form the rotor.

Within the first end flange, an inlet opening is formed, via which a cooling medium can be fed to the shaft cavity. The inlet opening is preferably formed in the axial direction of the rotor axis.

It is further provided that a pump element is arranged within the shaft cavity, which is fluidly connected to the inlet opening. The pump element is arranged and designed such that the pump element sucks in a cooling medium via the inlet opening and conveys via an outlet opening of the pump element against an inner circumferential surface of the cylinder-shaped laminated core carrier. In this way, the cooling medium is sucked into the shaft cavity via the pump element arranged within the shaft cavity, so that no pump device arranged outside the rotor is required for the active transport of the cooling medium into the shaft cavity. Thus, the space of the electric machine can be reduced by the formation of the hollow rotor shaft with the integrated pump element.

Via the outlet opening of the pump element, the cooling medium is conveyed to and / or against the inner circumferential surface and / or injected. In this way, the cooling medium can preferably be directed to locations within the laminated core, which heat up very quickly or where a warming accumulates. In this way, a uniform cooling of the rotor can be made possible via the pump element within the shaft cavity to reduce contact stresses of the rotor bearing due to an excessive temperature gradient between an inner bearing ring and an outer bearing.

The cooling medium may preferably be a cooling liquid. Preferably, the cooling medium is an oil, an oil foam, a spray oil and / or a transmission oil. Particularly preferably, the cooling medium is electrically non-conductive and / or an electrically non-conductive oil.

A preferred development of the invention is that the pump element is a self-priming pump element, in particular a centrifugal pump. The self-priming pump element is preferably coupled to the first end flange such that a negative pressure in the shaft cavity is generated by a rotation of the hollow rotor shaft via the pump element, so that the pump element sucks the cooling medium via the inlet opening. In this way, solely by the configuration and / or design of the self-priming pump element, the cooling medium can be sucked in via the inlet opening in a simple manner. Thus, no separate control of the pump element is required, whereby costs and / or the installation space of the rotor can be reduced.

In an advantageous development of the invention, it is provided that the pump element has a passage element which has a first end section and a second end section spaced apart in the axial direction from the first end section, the first end section is fluidically connected to the inlet opening, and the second end section is closed wherein between the first end portion and the second end portion at least one passage opening is formed, and on the passage member in the region of the passage opening a pump impeller is arranged. In this way, the formation of a centrifugal pump is indicated, which is arranged within the shaft cavity and connected to the first end flange and / or clamped in this. In principle, it may be sufficient for the passage element to have a passage opening. It is usually provided that the passage element has a plurality of passage openings, which are arranged spaced from each other in the circumferential direction. By means of a rotation of the rotor, the throughflow element connected to the first end flange and thus also the pump impeller arranged on the passage element are set in rotation, whereby the pump impeller generates a negative pressure and / or a suction effect and thus the cooling medium via the at least one passage opening arranged in the passage element and sucks the inlet opening.

In this connection, a preferred development of the invention provides that the pump impeller has at least two impeller disks arranged at a distance from each other and a plurality of impeller blades arranged between the impeller disks, the impeller disks being arranged in a rotationally fixed manner on the pass-through element. The impeller blades may have a rectilinear but also a slightly curved course in the circumferential direction. In general, the impeller blades are circumferentially spaced from each other at regular intervals.

In principle, it may be sufficient for the pump element to be connected exclusively to the first end flange. An advantageous development of the invention is that the second end portion of the pass-through element is guided to the second end flange and arranged in this and / or rotatably connected thereto. In this way, the rigidity of the passage element and the Position security of the arranged on the passage element pump impeller can be increased.

In this context, a preferred development of the invention resides in the fact that between the at least one passage opening and the second end section a wall element is arranged and / or formed within the passage element. The negative pressure which can be generated by the pump impeller can thus be concentrated in the passage element via the wall element in such a way that the cooling medium is sucked in via the inlet opening.

In principle, it can be provided that the pump element and / or the pump impeller is arranged at any point in the axial direction of the rotor within the shaft cavity. An advantageous development of the invention provides that the pump element and / or the pump impeller is arranged centrally in the shaft cavity in the axial direction of the shaft cavity. Usually, the heat accumulates on the laminated core carrier laminated core due to the magnetic field between the rotor and the stator and a rotation of the rotor relative to the stator in the middle of at least one laminated core, while in the edge regions, the heat flows faster or cooled more easily can be. The outlet opening of the pump element is aligned in the radial direction in the direction of the hotspot of the laminated cores, so that can be effectively cooled via the pump element of the laminated core and thus arranged on the laminated core carrier laminated core.

An advantageous development of the invention is that the first end flange on a side facing away from the shaft cavity has a first shaft journal and / or the second end flange on a side facing away from the shaft cavity a second shaft journal. The respective shaft journals are aligned in the axial direction of the shaft cavity and serve to support the rotor hollow shaft in a shaft bearing. In this context, a preferred embodiment of the invention provides that the inlet opening is guided by the first shaft journal.

In a preferred embodiment of the invention it is provided that the first end flange and / or the second end flange has at least one recess which is arranged and designed such that a running on the inner circumferential surface of the cylindrical laminated core carrier cooling medium can escape via the recess from the shaft cavity , In this way, the cooling medium can preferably be conveyed and / or sprayed against a winding of the stator surrounding the rotor and / or the hollow rotor shaft in order to at least partially cool the winding, in particular the winding heads, of the stator.

In this context, an advantageous development is that the at least one recess is arranged and / or formed on an outer peripheral surface of the first end flange and / or the second end flange. The recess is thus a recess which extends from the outer circumference in the radial direction inwards. Preferably, a plurality of circumferentially spaced-apart recesses are provided.

In principle, it may be sufficient for the at least one recess to be arranged and / or formed in the first end flange and / or the second end flange. An advantageous development of the invention provides that the cylinder-shaped laminated core has on a first end flange facing the first end portion and / or on a second end flange facing the second end portion at least one opening formed in the radial direction, so that on the inner circumferential surface of the cylindrical trained laminated core carrier extending cooling medium can escape via the opening of the shaft cavity. In this way, an alternative possibility is provided to convey the cooling medium from the shaft cavity via the opening in the direction of the windings of a rotor surrounding the stator. In this way, the windings of the stator can be efficiently cooled.

The invention also relates to a rotor, comprising the rotor hollow shaft according to the invention equipped with at least one laminated core.

Furthermore, the invention relates to an electric machine, in particular for a drive train of a motor vehicle, with the rotor according to the invention.

Furthermore, the invention relates to a use of the hollow rotor shaft according to the invention for cooling a stator and / or a rotor of an electric machine.

• - Ansaugen eines Kühlmediums über das innerhalb des Wellenhohlraums angeordnete Pumpenelement;
• - Beförderung des von dem Pumpenelement angesaugten Kühlmediums über die Austrittsöffnung des Pumpenelements an die innere Mantelfläche des Blechpaketträgers, wobei das Kühlmedium gegen die innere Mantelfläche des Blechpaketträgers prallt.

The invention also relates to a method for cooling an electric machine, comprising the rotor according to the invention, comprising the steps:

• - Suction of a cooling medium via the arranged within the shaft cavity pump element;
• - Carriage of the sucked by the pump element cooling medium on the Outlet opening of the pump element to the inner circumferential surface of the laminated core, wherein the cooling medium impinges against the inner circumferential surface of the laminated core carrier.

It is thus an essential aspect of the invention that the cooling medium is sucked in via the pump element arranged within the shaft cavity. In this way, no pump outside the rotor is required, which actively pumps the cooling medium into the shaft cavity. Thus, the space of the electric machine can be reduced.

The pump element conveys the sucked cooling medium via an outlet opening of the pump element and / or via the impeller blades of the pump impeller radially outward against the inner circumferential surface of the laminated core. The cooling medium bounces against the inner circumferential surface, whereby the laminated core carrier and a laminated core arranged on the laminated core carrier can be cooled by impingement cooling.

Finally, a preferred development of the invention that the conveyed against the inner circumferential surface cooling medium escapes via at least one arranged in the first end flange and / or the second end flange recess from the shaft cavity and is injected against winding heads of the rotor at least partially surrounding stator. In this way, the cooling medium can be removed from the shaft cavity such that it also cools the winding heads of the stator, whereby an efficient cooling of the stator can be effected.

Further features and advantages of the present invention will become apparent from the dependent claims and the following embodiments. The embodiments are not limiting, but rather to be understood as exemplary, they should enable the skilled person to carry out the invention. The Applicant reserves the right to make individual or several of the features disclosed in the exemplary embodiments the subject matter of patent claims or to include such features in existing claims. The embodiments are explained in more detail with reference to figures.

• 1 eine schematische Schnittdarstellung durch einen Rotor mit einer Rotorhohlwelle, die ein integriertes Pumpenelement aufweist,
• 2 eine schematische Schnittdarstellung durch den Rotor, wobei das Pumpenelement als Kreiselpumpe mit einem Pumpenlaufrad ausgebildet ist,
• 3a einen Längsschnitt durch das Pumpenlaufrad,
• 3b eine Ansicht des Pumpenlaufrads,
• 3c einen Querschnitt durch das Pumpenlaufrad,
• 4 einen Längsschnitt durch den Rotor,
• 5a eine Ansicht der Rotorhohlwelle,
• 5b eine Ansicht des Durchleitelements mit dem ersten Stirnflansch und dem zweiten Stirnflansch,
• 6 einen Längsschnitt durch eine elektrische Maschine.

In these show:

• 1 1 is a schematic sectional view through a rotor with a hollow rotor shaft, which has an integrated pump element,
• 2 3 is a schematic sectional view through the rotor, the pump element being designed as a centrifugal pump with a pump impeller,
• 3a a longitudinal section through the pump impeller,
• 3b a view of the pump impeller,
• 3c a cross section through the pump impeller,
• 4 a longitudinal section through the rotor,
• 5a a view of the hollow rotor shaft,
• 5b a view of the passage element with the first end flange and the second end flange,
• 6 a longitudinal section through an electric machine.

In 1 is a sectional view of a rotor 10 shown a rotor hollow shaft 12 with an integrated pump element 14 includes. The rotor hollow shaft 12 has a cylindrical shaped laminated core carrier 16 on, on both sides of each other in the axial direction spaced end portions 18 . 20 each with a front flange 22 . 24 is completed, so that by the cylinder-shaped laminated core 16 a wave cavity 26 is trained. On the laminated box carrier 16 is in the longitudinal direction of the cylinder-shaped laminated core carrier 16 at least one laminated core 28 arranged to the rotor 10 train.

Within the first end flange 22 is an inlet opening 30 formed over which a cooling medium 32 the wave cavity 26 can be fed.

Inside the wave cavity 26 is the pump element 14 arranged, wherein the pump element 14 with the inlet opening 30 fluidly connected. The pump element 14 is arranged and configured such that the pump element 14 the cooling medium 32 over the inlet opening 30 sucks and against an inner surface 34 the cylinder-shaped laminated core carrier 16 promoted.

In this way, over that within the wave cavity 26 arranged pump element 14 the cooling medium 32 into the wave cavity 26 sucked so that no outside of the rotor 10 arranged and / or formed pump means for actively conveying the cooling medium 32 into the wave cavity 26 is required. In this way, the space of a the rotor 10 having electric machine by the formation of the hollow rotor shaft 12 with the integrated pump element 14 be reduced.

That via the pump element 14 conveyed cooling medium 32 bounces against the inner surface 34 of the laminated core carrier 16 , wherein the cooling medium 32 essentially perpendicular to the inner lateral surface 34 meets and produces a so-called "wall-jet". This means that the fluid flow of the cooling medium 32 from the impact location in the radial direction and / or in a radial manner over the inner circumferential surface 34 to be led. Very high heat transfer rates can be achieved around the center of the impact location, which decrease with increasing radial distance from the center of the impact location.

In this way, the cooling medium 32 preferably on locations within the laminated core carrier 16 be directed, which heat up very quickly or where a warming accumulates. In this way, via the pump element 14 within the wave cavity 26 a uniform cooling of the rotor 10 be allowed to reduce contact stresses of the rotor bearing due to a large temperature gradient between an inner bearing ring and an outer bearing.

Due to the centrifugal force of the around the rotor axis 36 the rotor hollow shaft 12 rotating rotor 10 becomes the cooling medium 32 to the inner lateral surface 34 pressed and towards the end areas 18 . 20 of the laminated core carrier 16 guided. In the on the end areas 18 . 20 arranged first end flange 22 and the second end flange 24 are recesses on a peripheral surface of the respective end flanges 38 arranged. In this way, the cooling medium 32 about the recesses 38 from the wave cavity 26 emerge and preferably against windings of the rotor 10 surrounding stator (not shown) to cool them.

That from the wave cavity 26 about the recesses 38 escaping cooling medium 32 becomes a cooling circuit 40 fed to the pump element again 14 to be able to perform or so again on the pump element 14 is sucked.

In 2 is the off 1 known rotor 10 shown, wherein the pump element 14 is designed as a self-priming centrifugal pump. The pump element 14 has a passage element 42 on, that has a first end section 44 and one to the first end portion 44 spaced in the axial direction arranged second end portion 46 having. The first end section 44 is with the inlet opening 30 fluidly connected, so that the cooling medium 32 over the inlet opening 30 and the first end portion 44 in the passage 42 is insertable. The second end section 46 is closed. Between the first end section 44 and the second end portion 46 is at least one passage opening 48 is formed, and on the passage element 42 is in the area of the passage opening 48 a pump impeller 50 arranged.

In this way, the formation of a centrifugal pump is indicated, which is within the wave cavity 26 is arranged and with the first end flange 22 rotatably connected and / or clamped in this. In principle, it may be sufficient for the passage element 42 only one passage opening 48 having. It is usually provided that the passage element 42 a plurality of passage openings 48 has, which are arranged spaced from each other in the circumferential direction.

By a rotation of the rotor 10 this will be with the first end flange 22 rotatably connected passage element 42 and thus also on the passage element 42 arranged pump impeller 50 rotated, causing the pump impeller 50 generates a negative pressure and / or a suction effect and thus the cooling medium 32 over in the passage element 42 arranged passage opening 48 and the inlet opening 30 sucks. About the centrifugal force is the cooling medium 32 pressed against the outer edge of the pump impeller and escapes through the outlet opening 52 ,

In the 3a . 3b and 3c is designed as a centrifugal pump pump element 14 shown in detail. Below is on the 3a . 3b and 3c simultaneously referred to. The pump impeller 50 has two mutually spaced impeller disks 54 and a plurality of between the impeller disks 54 arranged impeller blades 56 on, with the impeller discs 54 rotationally fixed on the passage element 42 are arranged. The impeller shovels 56 have a slightly curved or arcuate course in the circumferential direction.

The outlet openings 52 of the pump element 14 are on the outer edge of the pump impeller 50 between the respective impeller blades 56 and the impeller disks 54 educated.

4 shows that off 2 known rotor 10 , Unlike the in 2 shown rotor 10 is in 4 the passage element 42 with the second end portion 46 to the second end flange 24 guided and stored in this or rotatably connected to this. In this way, the rigidity of the passage element 42 and the positional safety of the on the passage element 42 arranged pump impeller 50 increase.

Between the least one passage opening 48 and the second end portion 46 is a wall element 58 within the passage element 42 arranged. The through the pump impeller 50 producible negative pressure can thus on the wall element 58 such within the passage element 42 be concentrated that over the inlet opening 30 the cooling medium 32 is sucked.

The pump element 14 or the pump impeller 50 is in the axial direction of the shaft cavity 26 in the center of the wave cavity 26 arranged. Usually, the heat accumulates in the on the laminated core 16 arranged laminated core 28 in consequence of a rotation of the rotor 10 relative to the stator (not shown) in the middle of the laminated core, while in the edge regions of the laminated core 28 the heat can flow off faster or be cooled more easily. The pump impeller 50 or the outlet openings 52 the pump impeller 50 are in the present embodiment in the radial direction in the direction of the hotspot of the laminated core 28 aligned so that over the pump element 14 the laminated core carrier 16 and thus on the laminated core 16 arranged laminated core 28 can be effectively cooled.

The first end flange 22 points to a wave cavity 26 side facing away from a first shaft journal 60 and / or the second end flange 24 points to a wave cavity 26 side facing away from a second shaft journal 62 on. The first shaft journal 60 and the second shaft journal 62 are each in the axial direction of the shaft cavity 26 aligned and serve to support the rotor hollow shaft 12 in a shaft bearing. The inlet opening 30 is through the first shaft journal 60 guided.

In 5a is a view of the rotor hollow shaft 12 shown and the 5b illustrates a view of the passage element 42 with the end flanges 22 . 24 , Below is on the 5a and 5b simultaneously referred to. The first end flange 22 and the second end flange 24 each have on an outer peripheral surface a plurality of circumferentially spaced-apart arranged recess 38 on. The recesses 38 cause that at the end areas 18 . 20 of the laminated core carrier 16 between the inner lateral surface 34 and the end flanges 22 . 24 in the area of the recesses 38 a gap is formed, via which the to the inner circumferential surface 34 conveyed cooling medium 32 from the wave cavity 26 can escape. In this way, the cooling medium 32 preferably against a winding of the rotor 10 surrounding stator (not shown) and / or sprayed to at least partially cool the windings of the stator.

6 shows an electric machine 64 in a housing 66 a gearbox 68 and an electric motor 70 having, wherein the electric motor 70 the rotor 10 and one the rotor 10 at least partially surrounding stator 72 includes. The rotor 10 is about shaft bearings 74 attached to the first shaft journal 60 and the second shaft journal 62 attack, in the case 66 relative to the stator 72 around the rotor axis 36 rotatably mounted. The second shaft journal 62 is with a transmission input shaft 76 coupled, allowing a rotational movement of the rotor 10 on the gearbox 68 is transferable.

As a result of a rotation of the rotor 10 becomes the cooling medium 32 which in the present embodiment is a transmission oil, via which in the first shaft journal 60 and the first end flange 22 arranged inlet opening 30 from that in the wave cavity 26 arranged self-priming pump element 14 , which is designed as a centrifugal pump, sucked in and over the outlet opening 52 of the pump element 14 and / or over the impeller blades 56 the pump impeller 50 radially outward against the inner circumferential surface 34 of the laminated core carrier 16 promoted. The cooling medium 32 bounces against the inner surface 34 , causing the laminated core carrier 16 and on the laminated core 16 arranged laminated core 28 be cooled by an impingement cooling.

That on the inner surface 34 conveyed cooling medium 32 escapes from the wave cavity 26 over in the first end flange 22 and the second end flange 24 arranged recesses 38 , Due to the centrifugal force of the rotating rotor 10 becomes the cooling medium 32 such from the recesses 38 flung it out on the winding heads 78 of the stator 72 meets, whereby these are also cooled. Subsequently, the cooling medium 32 supplied to a circulation cooling circuit so that it can be used for re-cooling.

LIST OF REFERENCE NUMBERS

10

rotor

12

Rotor hollow shaft

14

pump element

16

Laminated core carrier

18

First end area

20

Second end area

22

First end flange

24

Two front flange

26

wave cavity

28

laminated core

30

inlet port

32

cooling medium

34

Inner jacket surface

36

axis

38

recess

40

Cooling circuit

42

Durchleitelement

44

First end section

46

Second end section

48

Port

50

pump impeller

52

outlet opening

54

wheel disc

56

Laufradschauffel

58

wall element

60

First shaft journal

62

Second shaft journal

64

Electric machine

66

casing

68

transmission

70

engine

72

stator

74

shaft bearing

76

Transmission input shaft

78

winding head

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The 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

• DE 102014107845 A1 [0004]

Claims (12)

A rotor hollow shaft (12) for a rotor (10) of an electric machine (64) - On both sides of a first end flange (22) and a second end flange (24) closed cylindrical formed Blechpaketträger (16) surrounding a shaft cavity (26), wherein in the first end flange (22) an inlet opening (30) is formed, and - A within the shaft cavity (26) arranged pump element (14) which is fluidly connected to the inlet opening (30) and arranged and designed such that on the pump element (14) a cooling medium (32) via the inlet opening (30) sucked and via an outlet opening (52) of the pump element (14) against an inner circumferential surface (34) of the cylindrically shaped laminated core (16) is conveyed. Rotor hollow shaft (12) after Claim 1 , characterized in that the pump element (14) is a self-priming pump element, in particular a centrifugal pump. Rotor hollow shaft (12) after Claim 1 or 2 characterized in that the pump member (14) comprises a passage member (42) having a first end portion (44) and a second end portion (46) spaced axially from the first end portion (44), the first end portion (46); 44) is fluidly connected to the inlet opening (30), and - the second end section (46) is closed, wherein - at least one passage opening (48) is formed between the first end section (44) and the second end section (46), and on the passage element (42) in the region of the passage opening (48) a pump impeller (50) is arranged. Rotor hollow shaft after Claim 3 , characterized in that the second end portion (46) of the passage element (42) to the second end flange (24) out and stored in this and / or rotatably connected thereto. Rotor hollow shaft after Claim 3 or 4 characterized in that the impeller (50) comprises at least two impeller disks (54) spaced apart from each other and a plurality of impeller blades (56) disposed between the impeller disks (54), the impeller disks (54) being non-rotatably mounted on the passage member (42) are. Rotor hollow shaft according to one of the preceding claims, characterized in that the first end flange (22) on a side facing away from the shaft cavity (26) a first shaft journal (60) and / or the second end flange (24) on a side facing away from the shaft cavity (26) a second shaft journal (62). Rotor hollow shaft after Claim 6 , characterized in that the inlet opening (30) is guided by the first shaft journal (60). Rotor hollow shaft according to one of the preceding claims, characterized in that the first end flange (22) and / or the second end flange (24) has at least one recess (38) which is arranged and formed such that a on the inner circumferential surface (34) of the cylindrical laminated core (16) extending cooling medium (32) via the recess (38) from the shaft cavity (26) can escape. Rotor hollow shaft according to one of the preceding claims, characterized in that the cylinder-shaped laminated core (16) on a first end flange (22) facing first end portion (18) and / or on a second end flange (24) facing the second end portion (20) at least has an opening formed in the radial direction, so that on the inner circumferential surface (34) of the cylindrically shaped laminated core (16) extending cooling medium (32) via the opening from the shaft cavity (26) can escape. Rotor (10), comprising a with at least one laminated core (28) equipped rotor hollow shaft (12) according to one of the preceding claims. Electric machine (64), in particular for a drive train of a motor vehicle, comprising a rotor (10) according to claim (10). A method of cooling an electric machine (64), comprising a rotor (10) Claim 10 comprising the steps of: - aspirating a cooling medium (32) over the pumping element (14) disposed within the wave cavity (26); - Transport of the sucked by the pump element (14) cooling medium (32) via the outlet opening (52) of the pump element (14) to the inner circumferential surface (34) of the laminated core (16), wherein the cooling medium (32) against the inner circumferential surface (34 ) of the laminated core (16) bounces.

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