DE102023109412A1 - rotor and electric machine - Google Patents

Abstract

The invention relates to a rotor (1) of an electrical machine (2), in particular for a drive train (3) of a motor vehicle (4), comprising a rotor body (5) formed from a plurality of rotor laminations (22), wherein the rotor body (5) further comprises a plurality of cooling channels (9) extending axially through the rotor body (5) through which a cooling fluid (10) can flow, wherein the cooling channels (9) have a front-side outlet opening (11) in the rotor body (5), from which the cooling fluid (10) is released from the cooling channels (9) into the rotor environment during operation of the rotor (1), wherein a sealing channel (25) filled with a plastic (24) extends radially above the cooling channels (9) over their axial extent, which sealing channel is radially spaced from the cooling channel (9).

Description

The present invention relates to a rotor of an electric machine, in particular for a drive train of a motor vehicle, comprising a rotor body formed from a plurality of rotor laminations, wherein the rotor body further comprises a plurality of cooling channels extending axially through the rotor body, through which a cooling fluid can flow, wherein the cooling channels have a front-side outlet opening in the rotor body, from which the cooling fluid is released from the cooling channels into the rotor environment during operation of the rotor. The invention further relates to an electric machine.

Electric motors are increasingly being used to power motor vehicles in order to create alternatives to combustion engines that require fossil fuels. Considerable efforts have already been made to improve the everyday suitability of electric drives and to offer users the driving comfort they are used to.

A detailed description of an electric drive can be found in an article in the magazine ATZ, 113th year, 05/2011, pages 360-365 by Erik Schneider, Frank Fickl, Bernd Cebulski and Jens Liebold with the title: Highly integrated and flexible electric drive unit for electric vehicles. Such drive units are also referred to as e-axles or electrically operated drive trains.

In addition to purely electrically operated drive trains, hybrid drive trains are also known. Such drive trains in a hybrid vehicle usually comprise a combination of an internal combustion engine and an electric motor, and enable - for example in urban areas - purely electric operation while at the same time providing sufficient range and availability, especially for cross-country journeys. In certain operating situations, it is also possible to drive the vehicle simultaneously using the internal combustion engine and the electric motor.

When developing the electrical machines intended for e-axles and hybrid modules, there is a continuing need to increase their power density, so that the cooling of the electrical machines required for this is becoming increasingly important. Due to the necessary cooling performance, hydraulic fluids such as cooling oils have become established in most concepts for removing heat from the thermally stressed areas of an electrical machine.

For the stators of electrical machines, for example, jacket cooling and winding head cooling are known from the state of the art for the implementation of cooling of electrical machines using hydraulic fluids. While jacket cooling transfers the heat generated on the outer surface of the rotor core into a cooling circuit, with winding head cooling the heat transfer takes place directly on the conductors outside the rotor core in the area of the winding heads into the fluid.

Further improvements are provided by separately designed cooling channels, which are integrated into the laminated core of the stator (see e.g. EP3157138 A1 ) as well as in the slot in addition to the conductors (see e.g. Markus Schiefer: Indirect winding cooling of highly utilized permanent magnet synchronous machines with tooth coil winding, dissertation, Karlsruhe Institute of Technology (KIT), 2017).

Concepts are also known in which hydraulic fluid flows directly around the windings in order to increase the power density. Improved cooling with direct contact between hydraulic fluid and conductor in the slot is already known in principle from the state of the art. For example, DE 102015013018 A1 a solution for electrical machines with single-tooth windings, where the fluid flows directly around the windings wound around the teeth.

In addition to cooling the stators, it is also generally known to cool the rotors of electrical machines. In this case, an undesirable leak between the rotor laminations can lead to drag torques in the air gap between the rotor and stator and uncontrolled loss of coolant, which is often undesirable.

The object of the invention is to realize a rotor which can provide good sealing, high cooling performance and at the same time low manufacturing costs. It is also the object of the invention to realize an improved electrical machine.

This object is achieved by a rotor of an electric machine, in particular for a drive train of a motor vehicle, comprising a rotor body formed from a plurality of rotor sheets, wherein the rotor body further comprises a plurality of cooling channels extending axially through the rotor body, through which a cooling fluid can flow, wherein the cooling channels have a front-side outlet opening in the rotor body, from which the cooling fluid flows from the cooling channels into the rotor environment during operation of the rotor. A sealing channel filled with a plastic extends radially above the cooling channels over their axial extent and is spaced radially from the cooling channel.

This has the advantage that the uncontrolled loss of cooling fluid can be significantly reduced or even completely avoided through the sealing channels. This also avoids the unwanted drag torques that can otherwise be generated by an uncontrolled cooling fluid leaking out in the air gap between the rotor and stator. The plastic can be introduced into the sealing channel using transfer molding, for example. The sealing channels fill any gaps between the rotor plates and increase the tightness in the radial direction.

The sealing channels running axially through the rotor are preferably created by a corresponding punching pattern in the sheet metal design, for example by round or square openings, which then create the axial sealing channels by stacking the corresponding rotor sheets on top of each other, which are then filled with the plastic, for example during transfer molding, and radially act as a kind of "oil-tight bar" to ensure that the cooling channels located on an inner pitch circle have less radial leakage in the direction of the air gap.

According to an advantageous further development of the invention, the sealing channels can radially enclose the cooling channels assigned to them on one side or on both sides, at least in sections, so that the radial oil level is lower than the sealing layer due to the centrifugal oil pressure.

The number of cooling channels is preferably identical to the number of sealing channels.

First, the individual elements of the claimed subject matter of the invention are explained in the order of their relevance or their mention in the set of claims, and particularly preferred embodiments of the subject matter of the invention are described below.

A rotor is the rotating part of an electrical machine. The rotor comprises in particular a rotor shaft. The rotor shaft can be hollow, which on the one hand results in a weight saving and on the other hand allows the supply of lubricant or coolant to the rotor body. The hollow shaft of the contactless energy transmission device is preferably a rotor shaft of a rotor of an electrical machine that is hollow at least in sections.

In the sense of the invention, a rotor body is understood to mean the rotor without a rotor shaft. The rotor body is therefore composed in particular of a rotor laminated core and the permanent magnets introduced into the pockets of the rotor laminated core or fixed circumferentially to the rotor laminated core, as well as any axial cover parts that may be present for closing the pockets.

The rotor preferably has a plurality of rotor bodies. The rotor bodies are particularly preferably formed from essentially the same parts, in particular essentially identical. It is most preferred that the rotor bodies are formed from identical, in particular essentially identical rotor laminations. The rotor bodies are therefore particularly preferably formed from a rotor lamination stack, which is composed of a plurality of laminated individual laminations or rotor laminations, usually made from electrical steel, which are layered and packaged one above the other to form a stack, the so-called rotor lamination stack. The individual laminations can remain held together in the rotor lamination stack by gluing, welding or screwing. A rotor lamination stack can in particular also have permanent magnets introduced into the pockets of the rotor lamination stack or fixed to the circumference of the rotor lamination stack. It is possible for the rotor lamination stacks to be interlocked with one another, i.e. arranged at an angle to one another. This interlocking can be linear or V-shaped in order to avoid or at least reduce axial forces. The cooling channels are then preferably designed in such a way that no radial undercut is formed and that cooling fluid can flow out axially.

The term rotor magnet refers to the permanent magnets that are to be inserted into the pockets of the rotor laminated core. Permanent magnets can preferably be inserted into the pockets of the rotor laminated core. In this case, a single larger rotor magnet designed as a bar magnet or several smaller rotor magnets designed as permanent magnet elements can be provided per pocket.

A rotor laminated core can in particular form a rotor body. A rotor laminated core is understood to be a plurality of laminated individual sheets or rotor sheets, usually made of electrical steel, which are layered and packaged one on top of the other to form a stack, the so-called rotor laminated core. The individual sheets can then remain held together in the laminated core by gluing, welding or screwing. A rotor laminated core can in particular also contain inserts or which have magnetic elements fixed circumferentially to the rotor laminated core and, if present, axial cover parts for closing the pockets and the like.

The electrical machine can be designed in particular as a rotary machine. The rotary machine can be configured in particular as a radial flux machine. A radial flux machine is characterized by the fact that the magnetic field lines in the air gap formed between the rotor and stator extend in a radial direction. The gap between the rotor and the stator is referred to as the air gap. In a radial flux machine, this is a gap that is circular in cross-section and has a radial width that corresponds to the distance between the rotor body and the rotor body.

The electric machine is intended in particular for use within a drive train of a hybrid or fully electric motor vehicle. In particular, the electric machine is dimensioned such that vehicle speeds of greater than 50 km/h, preferably greater than 80 km/h and in particular greater than 100 km/h can be achieved. The electric motor particularly preferably has an output of greater than 50 kW, preferably greater than 80 kW and in particular greater than 150 kW. It is further preferred that the electric machine provides speeds of greater than 8,000 rpm, particularly preferably greater than 12,000 rpm, very particularly preferably greater than 15,000 rpm.

For the purposes of this application, motor vehicles are considered to be land vehicles that are moved by mechanical power without being tied to railway tracks. A motor vehicle can, for example, be selected from the group of passenger cars (PKW), lorries (LKW), mopeds, light motor vehicles, motorcycles, buses (KOM) or tractors.

According to an advantageous embodiment of the invention, it can be provided that the cooling channels are arranged on a circular path in the cross section of the rotor body. The advantage of this embodiment is that a particularly uniform cooling performance can be achieved. It is particularly preferred that the diameter of the circular path is selected such that the cooling channels run radially below the rotor magnets. It is also preferred that the center of the circular path runs coaxially to the axis of rotation of the rotor.

According to an advantageous embodiment of the invention, it can be provided that the fluid guide element is arranged radially above the outlet opening assigned to it. According to a further preferred development of the invention, it can also be provided that the fluid guide element is positioned radially aligned with the outlet opening assigned to it, whereby a particularly short fluid path can be realized between the outlet opening and the fluid guide element, which contributes to a particularly good and controlled fluid line.

Furthermore, according to a likewise advantageous embodiment of the invention, it can be provided that a fluid guide element is assigned to all outlet openings on a first end face of the rotor body and/or a fluid guide element is assigned to all outlet openings on a second end face of the rotor body, which contributes to a particularly good cooling effect.

According to another particularly preferred embodiment of the invention, it can be provided that two magnetic pockets adjacent in the circumferential direction in the cross-section of the rotor body each have a V-shaped arrangement with a tip pointing radially inwards. Furthermore, the invention can also be further developed in such a way that the outlet openings in the cross-section of the rotor body are positioned between two V-shaped arrangements of the magnetic pockets. Placing the cooling channel between the poles has the advantage that the space there has the least negative influence on the electrical machine from a strength and electromagnetic point of view.

In a likewise preferred embodiment variant of the invention, it can also be provided that the plastic bodies of two V-shaped arrangements adjacent in the circumferential direction emerge axially from the magnet pockets on the first end face of the rotor body and form a substantially W-shaped contour in cross section, wherein the fluid guide element is formed on the radially outward-pointing tip of the W-shaped contour. This ensures that the function of the electrical machine is not negatively affected. Bringing the oil closer to the magnets is also desirable because this is where the thermal hotspot is located and this can further improve cooling.

It may also be advantageous to further develop the invention in such a way that the fluid guide element is designed as a ramp which has a ramp surface inclined axially away from the rotor body and radially outwards, whereby particularly effective cooling can be achieved.

According to a further preferred embodiment of the subject matter of the invention, it can be provided that in the case of a plurality of Fluid guide elements formed on a first end face, the ramp surfaces of which are designed differently from one another. This ensures that, depending on the rotational speed of the rotor, sufficient cooling of the winding head can always be ensured.

According to an advantageous embodiment of the invention, it can be provided that a plurality of magnetic pockets extending axially through the rotor body, in each of which at least one rotor magnet is accommodated, and the rotor magnets are each fixed by means of a plastic body running in the magnetic pockets. According to a further preferred development of the invention, it can also be provided that the plastic of the sealing channel is identical to the plastic of the plastic body, whereby the sealing channel and the magnet fixation can take place in a transfer molding process, which is particularly advantageous in terms of production and cost.

Furthermore, according to a likewise advantageous embodiment of the invention, it can be provided that one of the sealing channels is aligned in the radial direction with the corresponding cooling channel, which has proven to be particularly advantageous with regard to the desired radial tightness.

According to a further particularly preferred embodiment of the invention, it can be provided that the cross-sectional contour of the cooling channels and/or the cross-sectional contour of the sealing channels are/is substantially identical, which can contribute to a uniform cooling performance over the circumference as well as to a uniform tightness of the cooling channels in the radial direction.

Furthermore, the invention can also be further developed in such a way that the sealing channels each have a circumferential extension which corresponds to at least 90% of the circumferential extension of a corresponding cooling channel, which has also proven to be advantageous for providing good radial tightness.

In a likewise preferred embodiment variant of the invention, it can also be provided that at least one of the plastic bodies with a fluid guide element protrudes axially from the rotor body and interacts with one of the outlet openings in such a way that cooling fluid emerging from the outlet opening during operation of the rotor is subjected to an axial force component by the fluid guide element of the plastic body, wherein the fluid guide element is arranged radially above the outlet opening assigned to it. This achieves the advantage that the fluid guide element can be formed integrally with the plastic body, for example during transfer molding or an injection molding process for fixing the stator magnets, whereby the fluid guide element can be manufactured particularly cost-effectively. As a material, plastic has the further advantage that it offers many geometric degrees of freedom with regard to its shape.

It may also be advantageous to further develop the invention in such a way that at least one of the plastic bodies and/or at least one of the fluid guide elements is connected to the plastic of the sealing channel.

According to a further preferred embodiment of the subject matter of the invention, it can be provided that the rotor has a plurality of rotor bodies which are arranged interlocked with one another, which can reduce the so-called torque rippling of the rotor.

The object of the invention is further achieved by an electrical machine comprising a hollow cylindrical stator and a rotor rotatably arranged in the stator, wherein a stator winding is accommodated in the stator, which emerges axially from the two end faces of the stator to form a winding head, wherein the rotor is designed according to one of the preceding claims and the fluid guide element is configured such that cooling fluid is guided to one of the winding heads during operation of the electrical machine.

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

• 1 ein Kraftfahrzeug mit einem elektrischen Antriebsstrang in einer schematischen Blockschaltdarstellung,
• 2 eine elektrische Maschine in einer schematischen Axialschnittdarstellung,
• 3 eine elektrische Maschine in einer Axialschnittansicht,
• 4 einen Rotor in einer ersten perspektivischen Axialschnittansicht,
• 5 einen Rotor in einer zweiten perspektivischen Axialschnittansicht,
• 6 einen Rotor in einer perspektivischen Axialschnittdarstellung,
• 7 eine erste Ausführungsform eines Rotorblechs in einer Frontalansicht,
• 8 eine zweite Ausführungsform eines Rotorblechs in einer Frontalansicht.

It shows:

• 1 a motor vehicle with an electric drive train in a schematic block diagram,
• 2 an electrical machine in a schematic axial section,
• 3 an electrical machine in an axial section view,
• 4 a rotor in a first perspective axial sectional view,
• 5 a rotor in a second perspective axial sectional view,
• 6 a rotor in a perspective axial section view,
• 7 a first embodiment of a rotor sheet in a front view,
• 8 a second embodiment of a rotor sheet in a front view.

The invention is explained using an electric machine 2 for a drive train 3 of a motor vehicle 4, as is also shown by way of example in the 1 is outlined.

The electric machine 2 is in the 2 shown in an axial sectional view. The electric machine 2 comprises a hollow cylindrical stator 19 and a rotor 1 rotatably arranged in the stator 19, wherein a stator winding 20 is accommodated in the stator 19, which emerges axially from the two end faces of the stator 19, forming a winding head 21. The rotor body 5 of the rotor 1, formed from a plurality of packaged rotor laminations 22, is connected in a rotationally fixed manner to the rotor shaft 23 and has a fluid guide element 12 which is configured such that cooling fluid 10 is guided to one of the winding heads 21 during operation of the electric machine 2. This is shown by the 2-5 explained in more detail.

In the exemplary embodiment shown, the rotor 1 of the electric machine 2 has two rotor bodies 5 which are arranged interlocked with one another. Each of the rotor bodies 5 has a plurality of magnetic pockets 6 which extend axially through the rotor body 5 and in which at least one rotor magnet 7 is accommodated. The rotor magnets 7 are each fixed by means of a plastic body 8 running in the magnetic pockets 6, wherein the rotor body 5 also has a plurality of cooling channels 9 which extend axially through the rotor body 5 and through which a cooling fluid 10 can flow. The cooling channels 9 each have an outlet opening 11 on the front side in the rotor body 5, from which the cooling fluid 10 is released from the cooling channels 9 into the rotor environment when the rotor 1 is in operation.

One of the plastic bodies 8 projects axially out of the rotor body 5 with a fluid guide element 12 and interacts with one of the outlet openings 11 in such a way that, during operation of the rotor 1, cooling fluid 10 emerging from the outlet opening 11 is subjected to an axial force component by the fluid guide element 12 of the plastic body 8.

The fluid guide element 12 is arranged radially above the outlet opening 11 assigned to it and the fluid guide element 12 is positioned radially aligned with the outlet opening 11 assigned to it.

A fluid guide element 12 is assigned to all outlet openings 11 on a first end face 13 of the rotor body 5, and a fluid guide element 12 is assigned to all outlet openings 11 on a second end face 14 of the rotor body 5.

Each two magnetic pockets 6 adjacent in the circumferential direction have a V-shaped arrangement 15 with a tip pointing radially inwards in the cross section of the rotor body 5. The outlet openings 11 are positioned in the cross section of the rotor body 5 between two V-shaped arrangements 15 of the magnetic pockets 6.

What the 4 It can also be seen that the plastic bodies 8 of two V-shaped arrangements 15 adjacent in the circumferential direction emerge axially from the magnet pockets 6 on the first end face 13 of the rotor body 5 and form a substantially W-shaped contour in cross-section, wherein the fluid guide element 12 is formed on the radially outward-pointing tip 16 of the W-shaped contour. The fluid guide element 12 is designed as a ramp 17 which has a ramp surface 18 inclined axially away from the rotor body 5 and radially outward. In a plurality of fluid guide elements 12 formed on a first end face 13, their ramp surfaces 18 are designed differently from one another.

The 3 and the 6 show clearly that a sealing channel 25 filled with a plastic 24 extends radially above the cooling channels 9 over their axial extent and is radially spaced from the cooling channel 9.

The plastic 24 of the sealing channel 25 is identical to the plastic of the plastic body 8, since it was introduced into the rotor 1 in a common transfer molding process. It can be seen from the 7 good that one of the sealing channels 25 is aligned in the radial direction with the corresponding cooling channel 9. The cross-sectional contour of the cooling channels 9 is identical in each case, just as the cross-sectional contour of the sealing channels 25 is essentially identical.

The sealing channels 25 each have a circumferential extension 26 which corresponds to at least 90% of the circumferential extension 27 of a corresponding cooling channel 9.

8 shows a further embodiment of a rotor sheet 22, in which the sealing channels 25 are longer on the circumference and extend radially further inwards than the respectively assigned sealing channel 25. The sealing channels 25 thus enclose the cooling channels 9 assigned to them radially on both sides at least in sections, so that the radial oil level is lower than the sealing layer due to the centrifugal oil pressure.

The invention is not limited to the embodiments shown in the figures. The The above description is therefore not to be regarded as restrictive, but as explanatory. The following patent claims are to be understood in such a way that a named 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 between two similar features without establishing a ranking.

list of reference symbols

1

rotor

2

electric machine

3

drivetrain

4

motor vehicle

5

rotor body

6

magnetic pockets

7

rotor magnet

8

plastic body

9

cooling channels

10

cooling fluid

11

outlet opening

12

fluid guide element

13

front side

14

front side

15

arrangement

16

Great

17

ramp

18

ramp area

19

stator

20

stator winding

21

winding head

22

rotor blades

23

rotor

24

plastic

25

sealing channel

26

extension

27

extension

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was 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

• EP 3157138 A1 [0007]
• DE 102015013018 A1 [0008]

Claims (10)

Rotor (1) of an electrical machine (2), in particular for a drive train (3) of a motor vehicle (4), comprising a rotor body (5) formed from a plurality of rotor sheets (22), wherein the rotor body (5) further has a plurality of cooling channels (9) extending axially through the rotor body (5) and through which a cooling fluid (10) can flow, wherein the cooling channels (9) have a front-side outlet opening (11) in the rotor body (5), from which the cooling fluid (10) is released from the cooling channels (9) into the rotor environment during operation of the rotor (1), characterized in that a sealing channel (25) filled with a plastic (24) extends radially above the cooling channels (9) over their axial extent, which sealing channel is radially spaced from the cooling channel (9). Rotor (1) after claim 1 , characterized in that with a plurality of magnetic pockets (6) extending axially through the rotor body (5), in each of which at least one rotor magnet (7) is accommodated, and the rotor magnets (7) are each fixed by means of a plastic body (8) running in the magnetic pockets (6) Rotor (1) after claim 2 , characterized in that the plastic (24) of the sealing channel (25) is identical to the plastic of the plastic body (8) Rotor (1) according to one of the preceding claims, characterized in that one of the sealing channels (25) is aligned in the radial direction with the corresponding cooling channel (9). Rotor (1) according to one of the preceding claims, characterized in that the cross-sectional contour of the cooling channels (9) and/or the cross-sectional contour of the sealing channels (25) are/is substantially identical. Rotor (1) according to one of the preceding claims, characterized in that the sealing channels (25) each have a circumferential extension (26) which corresponds to at least 90% of the circumferential extension (27) of a corresponding cooling channel (9). Rotor (1) according to one of the preceding claims, characterized in that at least one of the plastic bodies (8) with a fluid guide element (12) projects axially from the rotor body (5) and cooperates with one of the outlet openings (11) in such a way that, during operation of the rotor (1), cooling fluid (10) emerging from the outlet opening (11) is subjected to an axial force component by the fluid guide element (12) of the plastic body (8), wherein the fluid guide element (12) is arranged radially above the outlet opening (11) assigned to it. Rotor (1) according to one of the previous Claims 2 - 7 , characterized in that at least one of the plastic bodies (8) and/or at least one of the fluid guide elements (12) is connected to the plastic (24) of the sealing channel (25). Rotor (1) according to one of the preceding claims, characterized in that the rotor (1) has a plurality of rotor bodies (5) which are arranged interleaved with respect to one another. Electrical machine (2) comprising a hollow cylindrical stator (19) and a rotor (1) rotatably arranged in the stator (19), wherein a stator winding (20) is accommodated in the stator (19), which emerges axially from the two end faces of the stator (19) to form a winding head (21), characterized in that the rotor (1) is designed according to one of the preceding claims and the fluid guide element (12) is configured such that during operation of the electrical machine (2) cooling fluid (10) is guided to one of the winding heads (21).

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