DE102020121724A1 - Electrical machine with internally cooled rotor shaft - Google Patents

Abstract

The invention relates to an electric machine (1) for a motor vehicle drive, having a stator (2) and a rotor (3) which is rotatably mounted relative to the stator (2), the rotor (3) having a rotor shaft (4) with a hollow shaft coolant distribution section (5) and wherein the coolant distribution section (5) has a radial inner wall (7) tapering conically towards an axial end (6), the coolant distribution section (5) being a cavity (8) of the rotor shaft (4) tube (10) which is accommodated and divided into a plurality of peripheral segments (9a, 9b).

Description

The invention relates to an electric machine for a motor vehicle drive, with a stator and a rotor which is mounted such that it can rotate relative to the stator, the rotor having a rotor shaft with a hollow coolant distribution section and the coolant distribution section having a radial inner wall which tapers conically towards an axial end.

Generic electrical machines with corresponding coolant distribution systems are already known from the prior art. Accordingly, disclosed, for example, the U.S. 2,330,121 A1 an electric machine with a shaft having a conical inner surface for circulating a fluid in use by means of corresponding guide vanes.

However, these known coolant distribution systems are relatively complex in terms of construction, so that the electric machine has a relatively high manufacturing outlay and assembly outlay.

It is therefore the object of the present invention to provide an electrical machine which generates a reliable flow of coolant, in particular when there is no external coolant pump, but which is significantly reduced in terms of manufacturing effort.

According to the invention, this is achieved in that the coolant distribution section is designed as a tube which is accommodated in a cavity of the rotor shaft and is divided into a plurality of circumferential segments.

A multi-part pipe designed in this way significantly reduces the manufacturing cost of the coolant distribution section. In a casting process for producing the tube, the peripheral segments are then produced individually as simply as possible, since the core or slide elements used up to now can be dispensed with.

Further advantageous embodiments are claimed with the dependent claims and explained in more detail below.

Accordingly, it is also advantageous if the pipe is designed in several parts, preferably in two parts. This results in a particularly suitable compromise between the number of components and the manufacturing effort. In this regard, it should also be pointed out that the tube can also be formed from more than two parts, for example three or four parts.

Furthermore, it is expedient if the tube is made of a plastic. This significantly reduces the manufacturing effort and the pipe can be efficiently mass-produced.

In addition, it is advantageous if a first peripheral segment is connected to the second peripheral segment via a plurality of retaining tabs which are pushed into depressions in a second peripheral segment in a non-positive and/or positive manner. A plurality of retaining tabs, which are spaced apart from one another, are preferably formed along the first peripheral segment and are pressed/pressed individually or in pairs into a (groove-like) indentation in the other second peripheral segment.

Accordingly, it is also advantageous if the second peripheral segment is connected to the first peripheral segment via a plurality of retaining tabs which are pushed into depressions in the first peripheral segment in a non-positive and/or positive manner. This ensures that the pipe can be assembled as simply as possible. This further increases the holding force between the circumferential segments.

For a centered and robust mounting of the tube, it is also expedient if the tube is supported axially with its first end on a shoulder of the rotor shaft.

If the rotor shaft is also provided with an (axial) opening protruding to the environment in its end region accommodating the first end of the tube, the cavity can be coupled to other regions of a coolant supply in the simplest possible manner.

Furthermore, it is advantageous if a second end of the tube has radial through-holes, via which a radial inner space of the tube is connected to a gap space formed radially between the hollow shaft and the tube. The gap space preferably continues to run in the opposite direction to the interior and also forms a coolant return. This results in a channel structure that is as simple as possible, but efficiently cools the rotor during operation.

Accordingly, it is also expedient if the rotor shaft is provided with radial outlet openings (bores) in its first end region, via which the coolant is in turn fed back to the corresponding coolant circuit.

Axially adjacent to the second end (of the tube), the rotor shaft is more preferably provided with a closure body that closes off the cavity. This locks the rotor shaft securely sealed at its second end region opposite the first end region.

If the two peripheral segments are designed as two half-shells that complement each other to form the tube, it is possible to implement the peripheral segments as identical parts and thus to further reduce the manufacturing effort.

In other words, according to the invention, a special internal shaft cooling of an E-axis is provided, which is equipped with a cone (conical inner wall of the tube) and using snap lugs/crushing ribs (retaining tabs) in connection with depressions.

The invention will now be explained in more detail below with reference to figures.

• 1 eine Längsschnittdarstellung einer erfindungsgemäßen elektrischen Maschine nach einem bevorzugten Ausführungsbeispiel, wobei eine im Betrieb erzeugte Kühlmittelströmung gut zu erkennen ist,
• 2 eine explodierte Darstellung eines in einer Rotorwelle der elektrischen Maschine nach 1 eingesetzten Rohrs zur Ausbildung eines Kühlmittelverteilungsabschnittes, wobei mehrere miteinander zusammenwirkende Haltelaschen und Vertiefungen an den Umfangssegmenten gut zu erkennen sind,
• 3 eine perspektivische Darstellung eines der beiden als Gleichteile ausgebildeten Umfangssegmente nach 2,
• 4 eine perspektivische Darstellung des Rohrs im zusammengebauten Zustand,
• 5 eine perspektivische Darstellung des in Querrichtung geschnittenen Rohres, wodurch eine Verbindung der beiden Umfangssegmente mittels einer Haltelasche und einer Vertiefung gut zu erkennen ist,
• 6 eine perspektivische Darstellung eines in der Rotorwelle im montierten Zustand fest aufgenommenen Endabschnittes des Rohres, sowie
• 7 eine schematische Darstellung eines Herstellvorgangs eines Umfangssegmentes.

Show it:

• 1 a longitudinal sectional view of an electrical machine according to the invention according to a preferred exemplary embodiment, with a coolant flow generated during operation being clearly visible,
• 2 an exploded representation of one in a rotor shaft of the electrical machine 1 tube used to form a coolant distribution section, with several interacting retaining tabs and indentations being clearly visible on the peripheral segments,
• 3 a perspective view of one of the two peripheral segments designed as identical parts 2 ,
• 4 a perspective view of the tube in the assembled state,
• 5 a perspective view of the tube cut in the transverse direction, whereby a connection of the two peripheral segments by means of a retaining tab and a recess can be clearly seen,
• 6 a perspective view of an end section of the tube that is firmly accommodated in the rotor shaft in the assembled state, and
• 7 a schematic representation of a manufacturing process of a peripheral segment.

The figures are only of a schematic nature and serve exclusively for understanding the invention. The same elements are provided with the same reference numbers.

A basic structure of an electric machine 1 according to the invention, as is preferably used in a drive train of a hybrid or purely electrically driven motor vehicle, is shown in 1 clearly visible. The electrical machine 1 is preferably used in an E-axis, ie a drive unit with a downstream gear arranged coaxially to an output axis. The electrical machine 1 typically has an essentially ring-shaped stator 2 accommodated in a housing and a rotor 3 rotatably mounted radially inside the stator 2 . During operation, the rotor 3 is used in the usual way to drive an input shaft of the transmission, which is not shown in detail for the sake of clarity.

In this embodiment, the rotor 3 has an integrated cooling device 23 . This cooling device 23 is connected to a coolant supply, for example a reservoir, which is not shown here for the sake of clarity. The cooling device 23 is used to automatically build up a coolant circuit when the rotor 3 is rotating in order to cool the rotor 3 .

The rotor 3 has a rotor shaft 4 on which a rotor body 24 is placed and fixed. The rotor body 24 preferably has a plurality of laminations, not shown here for the sake of clarity, which are stacked axially to form a laminated core and are firmly connected to one another and to the rotor shaft 4 . In addition, the rotor body 24 has, in the usual way, a plurality of magnet elements, likewise not shown for the sake of clarity, which interact with coils of the stator 2 in the usual way.

It can be seen that the rotor shaft 4 projects beyond this side by a specific length on each axial side of the rotor body 24 . Accordingly, the rotor shaft 4 has a first end area 14 which protrudes to a first axial side of the rotor body 24 and a second end area 22 which protrudes to a second axial side of the rotor body 24 .

The second end area 22 is rotatably supported directly via a bearing 25 relative to a housing.

The rotor shaft 4 is hollow throughout. The rotor shaft 4 consequently has a cavity 8 which is arranged radially inside the rotor body 24 and runs over the entire length of the rotor body 24 .

The hollow space 8 is sealed towards the second end area 22 with a sealing body 20 pressed directly into the rotor shaft 4 , here a sealing plug.

Toward the first end region 14 , the rotor shaft 4 is provided with an axial opening 15 which is further coupled to a coolant supply of the cooling device 23 . During operation, a coolant/cooling fluid consequently passes axially into the cavity 8 through the opening 15 .

A coolant distribution section 5 designed according to the invention is provided for distributing and conveying the coolant entering through the opening 15 into the cavity 8 during operation. This coolant distribution section 5 is designed as a pipe 10 separate from the rotor shaft 4 .

According to the invention, the tube 10 is realized in several parts. The tube 10 is also in connection with the 2 until 6 shown in detail. In this embodiment, the tube 10 is realized in two parts, but in this context it should also be pointed out that, according to further embodiments, the tube 10 can also be formed in more than two parts, for example three or four parts.

The tube 10 is made of a plastic. Thus, several peripheral segments 9a, 9b, here two in number, each made of a plastic.

It can also be seen that the peripheral segments 9a, 9b are realized as identical parts. The peripheral segments 9a, 9b thus each form a half-shell, with the two half-shells in the connected state according to 1 and 4 to complete the tube 10.

At a first axial end 6 of the tube 10, the tube 10 forms an annular collar 26 which bears directly axially against a shoulder 13 of the rotor shaft 4. This collar 26 is also centered relative to the rotor shaft 4 on the part of a radial support surface 27 of the rotor shaft 4 . Starting from the collar 26, a radial inner wall 7 of the tube 10, as formed by the inner sides of the two peripheral segments 9a, 9b, extends conically in the axial direction. Beginning at the first end 6 , the inner wall 7 of the tube 10 widens toward the second end 16 . Conversely, this means that the pipe 10 tapers conically starting from the second end 16 on the part of its inner wall 7 towards the first end 6 .

The conical extent of the inner wall 7 is continuous over almost the entire length of the pipe 10 . In particular, the tube 10 has this conical extension over the entire length of its section/area axially penetrating the rotor body 24 .

At the second end 16 a plurality of radial passage holes 17 distributed in the circumferential direction of the tube 10 are made in the tube 10 . As a result, an interior space 18 formed radially inside the tube 10 is connected to a gap space 19 implemented radially outside the tube 10 , namely radially between the tube 10 and the rotor shaft 4 .

A radially outer wall 28 of the tube 10 typically also preferably tapers and widens (in the opposite direction to the inner wall 7) from the second end 16 to the first end 6. The gap space 19 thus widens toward the first end region 14 of the rotor shaft 4 . In the first end region 14 protruding from the rotor body 24, a plurality of outlet openings 21 distributed in the circumferential direction are implemented in the form of radial bores in order to enable the coolant to be returned. This results in efficient cooling of the rotor 3 during operation.

With the 2 until 6 is also the closer attachment of the peripheral segments 9a, 9b shown together. In this exemplary embodiment, the respective peripheral segment 9a, 9b has a plurality of holding tabs 12 distributed in the longitudinal direction. The retaining tabs 12 are pressed into a recess 11 of the other peripheral segment 9a, 9b. It can be seen that axially between every two pairs of retaining tabs 12 there is an elongate recess 11 into which a pair of retaining tabs 12 of the other peripheral segment 9a, 9b is pressed. This results in a non-positive and positive connection of the two peripheral segments 9a, 9b in the assembled state.

with 7 Finally, reference is also made to the manufacturing advantage of the pipe 10 used according to the invention, from which it is easy to see that with a corresponding plastic injection molding process, the respective peripheral segment 9a, 9b can be manufactured without a core or slide element, but only by using two tool molds 29a, 29b.

In other words, according to the invention, the conical cylinder (tube 10) is cut in the axial direction and designed in several parts, for example in two parts. This has particular advantages in that a tool used to manufacture the cylinder no longer needs to have a slide that needs to be pulled out from the inside. This reduces tool costs and complexity. Furthermore, a previously necessary draft angle of 1.5° on the inner cylinder does not have to be maintained. As a result, the installation space on the inside diameter of the shaft can be made smaller. In addition, a geometry can be applied to the inner surface (not shown here for the sake of clarity).

reference list

1

electric machine

2

stator

3

rotor

4

rotor shaft

5

coolant distribution section

6

first end

7

inner wall

8th

cavity

9a

first circumferential segment

9b

second circumferential segment

10

pipe

11

deepening

12

retaining tab

13

unit volume

14

first end area

15

opening

16

second end

17

through hole

18

inner space

19

gap space

20

closure body

21

exit port

22

second end area

23

cooling device

24

rotor body

25

camp

26

Federation

27

support surface

28

outer wall

29a

first tool mold

29b

second tool mold

QUOTES INCLUDED IN DESCRIPTION

This list of the documents cited 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.

Patent Literature Cited

• US 2330121 A1 [0002]

Claims (10)

Electrical machine (1) for a motor vehicle drive, having a stator (2) and a rotor (3) which is rotatably mounted relative to the stator (2), the rotor (3) having a rotor shaft (4) with a hollow coolant distribution section (5) and wherein the coolant distribution section (5) has a radial inner wall (7) tapering conically towards an axial end (6), characterized in that the coolant distribution section (5) is accommodated as a cavity (8) in the rotor shaft (4). , In several peripheral segments (9a, 9b) divided tube (10) is formed. Electrical machine (1) according to claim 1 , characterized in that the tube (10) is formed in two or more parts. Electrical machine (1) according to claim 1 or 2 , characterized in that the tube (10) is made of a plastic. Electrical machine (1) according to one of Claims 1 until 3 , characterized in that a first peripheral segment (9a) is connected to the second peripheral segment (9b) via a plurality of retaining tabs (12) which are pushed into depressions (11) in a second peripheral segment (9b) in a non-positive and/or positive manner. Electrical machine (1) according to claim 4 , characterized in that the second peripheral segment (9b) is connected to the first peripheral segment (9a) via a plurality of retaining tabs (12) which are pushed into depressions (11) in the first peripheral segment (9a) in a non-positive and/or positive manner. Electrical machine (1) according to one of Claims 1 until 5 , characterized in that the tube (10) is supported axially with its first end (6) on a shoulder (13) of the rotor shaft (4). Electrical machine (1) according to claim 6 , characterized in that the rotor shaft (4) is provided in its end region (14) accommodating the first end (6) of the tube (10) with an opening (15) exiting towards the environment. Electrical machine (1) according to one of Claims 1 until 7 , characterized in that the tube (10) has a second end (16) radial through holes (17) via which a radial interior (18) of the tube (10) with a radial between the rotor shaft (4) and the tube ( 10) formed gap space (19) is connected. Electrical machine (1) according to one of Claims 1 until 8th , characterized in that the rotor shaft (4) is provided axially adjacent to the second end (16) of the tube (10) with a closure body (20) closing off the cavity (8). Electrical machine (1) according to one of Claims 1 until 9 , characterized in that the two peripheral segments (9a, 9b) are designed as two half-shells that complement each other to form the tube (10).

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