Rotor for electric motor and motor vehicle having electric motor

Abstract

The invention relates to a rotor (3) for an electric motor (2), said rotor (3) comprising at least one rotor lamination (4) having a plurality of rotor slots (10). A respective rotor slot (10) has a radially outer wall (11) and two side walls (12) adjoining the radially outer wall (11). The short-circuiting bars (5) of the rotor (3) are arranged in the respective rotor slots (10) in such a way that free spaces (14) are formed between the radially outer end regions (13) and the radially outer walls (11) of the short-circuiting bars (5). Furthermore, the free space (14) extends in the radial direction through a partial section (15) of the respective side wall (12) and is arranged there at least partially between the side face (34) of the shorting bar (5) and the side wall (12).

Description

TECHNICAL FIELD

[0001] The invention relates to a rotor for an electric motor. Furthermore, the invention relates to a motor vehicle having an electric motor with such a rotor. BACKGROUND

[0002] Motor vehicles can have electric motors which are configured, for example, to drive the motor vehicle. The electric motor comprises a rotor and a stator and can be configured, for example, as an asynchronous machine. The rotor of the electric motor can be configured, for example, as a short-circuit rotor or as a cage rotor The rotor then comprises a group of rotor laminations which each have a plurality of rotor slots. Short-circuit bars of the rotor are guided through the rotor slots, wherein, at the axial end of the group, a short-circuit ring is arranged respectively, at which the short-circuit bars each end.

[0003] The efficiency of the electric motor depends, inter alia, on the design of the rotor slots and the short-circuit bars. It can therefore be meaningful, for example, to preset the rotor slots in the respective rotor lamination purposefully, so that an electric motor having a particularly high efficiency can be provided.

[0004] DE 10 2017 003 294 A1 shows a rotor for an electric motor, which has a plurality of rotor slots arranged along a circumferential line of the rotor, wherein a short-circuit bar is arranged in each rotor slot. The rotor slots have a rotor slot exit area at their radially outer end. At least one rotor slot has an at least locally outwardly tapering cross section radially inwards at the rotor slot exit area.

[0005] EP 2 728 718 A1 shows a cage rotor for an electric machine, with a group of rotor laminations having slots, short-circuit rings cast at axial ends of the group of rotor laminations and bars arranged in the slots. The bars are supported in the slots by deformable bearings.

[0006] JP 2015035870 A shows a rotor of an induction machine, which has a rotor core connected with a rotor shaft and having a plurality of openings extending around the rotor shaft in an axial direction. SUMMARY

[0007] It is the task of the invention to provide a solution with the aid of which an electric motor can be provided with a rotor which is optimized in terms of efficiency.

[0008] This task is solved by the subject matter as follows:

[0009] A rotor for an electric motor, wherein the rotor comprises at least one rotor lamination having a plurality of rotor slots, wherein a respective rotor slot has a radially outer wall and two side walls adjacent to the radially outer wall, and a short-circuit bar of the rotor is arranged in a respective rotor slot in such a way that a free space is configured between a radially outer end region of the short-circuit bar and the radially outer wall, wherein the free space extends in the radial direction over a partial section of the respective side wall and is arranged there at least partially between the side of the short-circuit bar and the side wall,

[0010] and

[0011] A motor vehicle having an electric motor with a stator and a rotor according to the invention.

[0012] A first aspect of the present invention relates to a rotor for an electric motor. The electric motor is in particular an asynchronous machine, which alternatively can be referred to as a three-phase asynchronous machine. The electric motor is for example arranged in a motor vehicle. It can be configured to drive the motor vehicle. The rotor according to the invention is configured as a short-circuit rotor or cage rotor. It alternatively can be referred to as a rotor. The rotor comprises at least a rotor lamination. The rotor lamination alternatively can be referred to as a lamination cut. In one preferred example, the rotor has a number of rotor laminations, which together form a rotor lamination set or lamination set of the rotor. The rotor lamination set typically comprises a short-circuit ring at each of the oppositely arranged ends.

[0013] The respective rotor lamination has a plurality of rotor slots. For example, each rotor slot is arranged around the center point of the rotor lamination in a symmetrical manner. The respective rotor slot is a hole in the rotor lamination, through which one of a plurality of short-circuit bars of the rotor is guided. The plurality of rotor laminations of the rotor lamination set are arranged on top of each other in such a way that the rotor slots of each rotor lamination are arranged on top of each other at least partially overlapping, so that the respective short-circuit bar is guided through the entire rotor lamination set up to the short-circuit ring.

[0014] The respective rotor slot has a radially outer wall and two side walls which adjoin the radially outer wall. "Radial" here is with respect to an axis of rotation of the rotor which runs through a center point of the respective rotor lamination perpendicular to the surface of the rotor lamination. Thus, with respect to this axis of rotation, the radially outer wall of the rotor slot is the wall of the rotor slot which is farthest from the axis of rotation compared to the other walls of the rotor slot. The rotor slot can furthermore have an axially inner wall which opposes the axially outer wall. The respective short-circuit bar of the rotor is arranged in the respective rotor slot such that a free space is configured between the radially outer end region of the short-circuit bar and the radially outer wall of the rotor slot. This free space can alternatively be referred to as a cavity or empty partial region of the rotor slot. Thus, the radially outer end region of the short-circuit bar is not directly adjoined by the radially outer wall of the rotor slot, but is separated or spaced apart therefrom by the free space. The rotor slot is surrounded by the rotor lamination, i.e. viewed in a plane perpendicular to the axis of rotation of the rotor, the rotor slot is completely surrounded by walls which do not have any gaps or openings at any location. Thus, the free space in the rotor slot is always spatially separated from the air gap between the rotor and the stator of the electric motor.

[0015] The free space extends in the radial direction over a partial section of the respective side wall. The free space does not extend over the entire respective side wall. Viewed in the radial direction, the partial section is smaller than the total length of the side wall. In the partial section, the free space is arranged at least partially between the side of the short-circuit bar and the side wall. Thus, the rotor slot is configured such that its cross section has a larger face than the cross section of the short-circuit bar arranged in the rotor slot, wherein this larger face adjoins the radially outer end region of the short-circuit bar and is laterally arranged therefrom. Thus, the partial region of the short-circuit bar is positioned such that it is laterally and thus perpendicular to the radial direction and surrounded by the free space in the radial direction. Thus, the short-circuit bar adjoins the side wall of the rotor slot only outside the partial section. That is, there is a further partial section of the respective side wall which is different from the previously described partial section, and only in the further partial section does the short-circuit bar arranged in the rotor slot touch the side wall of the rotor slot. It can furthermore be provided that the short-circuit bar contacts the rotor slot at the axially inner wall of the rotor slot, that is, there is no free space arranged there. Thus, in one preferred example, the free space is only at the axially outer end region of the short-circuit bar and thus spatially closer to the stator, and not at the radially inner end region of the short-circuit bar.

[0016] By the design of the rotor, that is to say by the free space in the respective rotor slot, an insulation region is formed in the rotor lamination. For example, the leakage flux in the rotor lamination is thereby reduced. For example, the free space results in at least a reduction, in particular a prevention, of a locally high current density in the radially outer end region of the short-circuit bar compared to the radially inner end region of the short-circuit bar, so that a uniform current density can be achieved in the radial direction on the cross section of the short-circuit bar. This ultimately results in an increase in efficiency or an increase in performance of the electric motor compared to an electric motor whose rotor has no free space or a differently designed free space. The electric motor is thus provided with an efficiency-optimized rotor.

[0017] One embodiment is designed such that, viewed in the radial direction, the partial section of the respective side wall has a length which depends on the height of the short-circuit bar in the radial direction. Alternatively, the height of the short-circuit bar in the radial direction can be referred to as the length of the cross section of the short-circuit bar, wherein the cross section is perpendicular to the axis of rotation of the rotor. The height of the short-circuit bar does not mean its length in the axial direction, which generally corresponds to the length of the rotor lamination pack. In one example, the length of the partial section of the respective side wall can be 0.1 to 1 times the height of the short-circuit bar in the radial direction. It is thereby clear that the free space has a length in the radial direction which depends on the dimensions of the cross section of the short-circuit bar, so that the sought-after increase in efficiency can be achieved.

[0018] Another embodiment provides that the rotor slot has two corners each at two ends which are opposite one another in the radial direction in the region of the partial section of the respective side wall. Thus, the rotor slot has a total of four corners. The distance in the radial direction between a respective two of the corners corresponds to the length of the partial section. In two of the corners, the radially outer wall adjoins the respective side wall. These two corners form the radially outer ends of the rotor slot. They can be referred to as the two first corners of the rotor slot. The connection between these two corners can run straight, for example, or follow the contour of the rotor lamination, that is to say, for example, be rounded. In the two other corners of the rotor slot, which can be referred to as the two second corners of the rotor slot, the respective side wall has a turn, by means of which a respective wall section of the rotor slot opposite the radially outer wall is formed. In one preferred example, the turn leads to an angle of substantially 90 degrees with respect to the side of the short-circuit bar. At the end of the respective wall section opposite the turn, the side wall has, for example, a further turn, from which the side wall follows the respective side of the short-circuit bar in the direction of the radially inner wall of the rotor slot. The partial section of the respective side wall in which the free space is arranged ends at this further turn. "Substantially" here includes deviations of up to 10 degrees, 5 degrees or especially 1 degree. The distance between the two turns corresponds to the width of the free space between the respective side of the short-circuit bar and the respective side wall in the partial section.

[0019] The respective corners are rounded, in particular. In the region of the respective corner, the wall of the rotor slot can have a respective radius, which is the same at all corners. Alternatively thereto, the two first corners have a different radius compared to the two second corners, or even each corner can have its own radius, which is different from the radius of the other corners. The respective radius can be, for example, 1 to 3 times the thickness of the rotor lamination in the axial direction.

[0020] The corners promote the fact that, in the region of the partial section, the rotor slot has an angular or square shape without the short-circuit bar arranged there, by means of which the largest possible free space can be formed. This leads to the fact that the shape of the side wall in the partial section can be manufactured relatively easily and thus with less outlay. The following partial region of the rotor slot is then in particular coupled to the angular or square partial region of the rotor slot, in which the walls of the rotor slot and the outer face of the short-circuit bar adjoin or lie against one another.

[0021] A further embodiment provides that the rotor slot has at least one holding device outside the partial segment at at least one of the side walls. Preferably, the rotor slot has at least one holding device outside the partial segment on each of the two side walls, i.e. in each of the side walls in a further partial segment. The at least one holding device is configured to at least reduce the movement of the short-circuit bar in the radial direction. In particular, it is configured to prevent movement in the radial direction. The holding device thus serves to hold the short-circuit bar in the rotor slot when the rotor is rotating about the axis of rotation and, for example, does not move into the free space. Thus, the short-circuit bar, despite the rotation of the rotor, cannot, for example, hit against the radially outer wall of the rotor slot, but is held in the position provided for it, thereby configuring the aforementioned free space. This leads to a particularly reliable behavior of the rotor in operation.

[0022] One additional embodiment provides that the holding device is configured as an indentation in the side wall. The indentation engages into a protrusion of the short-circuit bar. In particular, the indentation and the protrusion are shaped to fit into each other such that the side of the short-circuit bar in the region of the protrusion directly abuts at the side wall of the rotor slot in the region of the indentation. The indentation or the protrusion is, for example, semicircular or angular, in particular triangular, quadrangular or polygonal. The holding device can alternatively be referred to as a holding structure of the rotor conductor tooth side. Furthermore, in one preferred example, the short-circuit bar is brought into the rotor slot in the further partial segment so precisely in fit that no relative movement can take place between the short-circuit bar and the wall of the rotor slot transverse to the radial direction. This means that the short-circuit bar remains in its position in the rotor slot even in the case of high centrifugal forces, which can act on the respective short-circuit bar in the case of high rotor rotational speeds.

[0023] A further embodiment provides that the short-circuit bar is tapered between a radially outer end region and an oppositely disposed radially inner end region of the short-circuit bar. Thus, at the radially outer end region, the outer width of the short-circuit bar is greater than the inner width thereof at the radially inner end region. In particular, the inner width of the short-circuit bar at the radially inner end region is between 0.35 and 0.65 times the outer width of the short-circuit bar at the radially outer end region. For example, the outer width can be 2 to 7 millimeters long, in particular in the case of a thickness of the rotor lamination in the axial direction of 0.15 to 0.35 millimeters.

[0024] It is clear from the tapered shape of the cross section of the short-circuit bar that, viewed in the radial direction, the short-circuit bar can have a narrower end and a wider end, wherein the free space is at the wider end. This advantageously contributes to increasing the efficiency of the rotor.

[0025] In another embodiment, the short-circuit bar is rounded at the radially outer end region. In one preferred example, the rounded end region is configured semicircular. In this case, it has a radius which depends on the outer width. In particular, the radius is between 0.3 and 0.7 times the outer width. Thereby, the free space is additionally increased, since the short-circuit bar does not have a corner region at the radially outer end region.

[0026] Another embodiment provides that the height of the short-circuit bar in the radial direction depends on the rotor lamination radius of the rotor lamination. In particular, the height is between one half and one quarter of the rotor lamination radius, or the rotor lamination radius is 2 to 4 times the height of the short-circuit bar. Thus, the dimensioning of the rotor slot depends on the dimensioning of the rotor lamination and thus matches the rotor lamination.

[0027] Furthermore, an embodiment can provide that the height of the short-circuit bar in the radial direction depends on the outer width of the short-circuit bar at its radially outer end region. In particular, the height of the short-circuit bar in the radial direction can then be approximately 4.5 to 7 times the outer width of the short-circuit bar.

[0028] Furthermore, an embodiment provides that the distance between the radially outer wall of the rotor slot and the radially outer edge of the rotor lamination depends on the thickness of the rotor lamination in the axial direction. The distance between the radially outer wall of the rotor slot and the radially outer edge of the rotor lamination is a part of the rotor lamination and thus filled with material. The distance is the spacing present between the free space and the outer edge of the rotor lamination. In particular, the distance is 0.5 to 2.5 times the thickness of the rotor lamination.

[0029] In another embodiment, the rotor has a plurality of rotor laminations, in which the rotor slots are respectively so arranged one above the other that the respective free spaces are connected to one another and together form a volume space through which a cooling fluid of a cooling system can be moved in order to cool the rotor. For example, an electrically non-conductive oil can be guided as cooling fluid through the volume space and thus through the respective free spaces. To this end, the cooling system can have at least one pump which is configured to pump and thus move the cooling fluid through the free spaces in the respective rotor laminations. The free spaces can thus be used in the active cooling of the rotor without the need for additional cooling channels for the cooling fluid. This saves space in particular and reduces the number of components required in the electric motor.

[0030] For example, copper, aluminum or silver are suitable as materials for the short-circuit bars. The mounted rotor can be a flow-extruded short-circuit cage, or the individual short-circuit bars can be fastened by friction welding. Before the rotor is cast, the free spaces can be filled with plaster or ceramic, and the plaster or ceramic can be removed later, so that the free spaces remain in the corresponding rotor slots in the rotor laminations. In general, the short-circuit bars can be cast or manufactured separately and then placed and welded into the rotor slots. Furthermore, known manufacturing techniques for rotors can be employed.

[0031] A further aspect of the application relates to a motor vehicle having an electric motor. The electric motor has a rotor as described above. Furthermore, the electric motor has a stator. The stator is arranged around the rotor. The electric motor is here configured as an asynchronous machine having a short-circuit rotor or a cage rotor.

[0032] The motor vehicle can be designed as a car, in particular as a passenger car or a goods car, or as a passenger bus or a motorcycle.

[0033] The application also comprises a development of the motor vehicle according to the application, which has the features already described in connection with the development of the rotor according to the application. For this reason, the corresponding development is not described here again.

[0034] The application also comprises combinations of the features of the described embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0035] Embodiments of the application are described below. To this end:

[0036] Figure 1 A schematic view of a motor vehicle with an electric motor is shown,

[0037] Figure 2 A schematic view of a rotor of an electric motor is shown,

[0038] Figure 3 A schematic partial view of a rotor lamination with short-circuit bars with a rotor is shown,

[0039] Figure 4 A partial view of a short-circuit bar in a rotor lamination is shown, and

[0040] Figure 5 A schematic partial view of a combination of a rotor and a stator is shown.

[0041] The embodiments explained below are preferred embodiments of the application. In the embodiments, the components are respectively features of the application which are to be viewed independently of one another, which respectively improve the application independently of one another, and which are therefore also to be considered as constituent parts of the application, either individually or in a different combination from that shown. Furthermore, the embodiments can also be supplemented by the further features of the application which have already been described.

[0042] In the figures, functionally identical elements are provided with the same reference signs. DETAILED DESCRIPTION

[0043] Figure 1 A motor vehicle 1 is shown. The motor vehicle 1 has an electric motor 2. Here, the electric motor 2 is configured to drive the motor vehicle 1, that is to say, together with further components of the drive train of the motor vehicle 1, to move the motor vehicle 1.

[0044] Figure 2 A rotor 3 of the electric motor 2 is shown. The rotor 3 has at least one rotor sheet 4. In one preferred example, the rotor 3 has a plurality of rotor sheets 4. The plurality of rotor sheets 4 can be jointly referred to as a rotor sheet group of the rotor 3. The rotor 3 furthermore has a plurality of short-circuit bars 5 which lead through openings in one rotor sheet 4 or in a plurality of rotor sheets 4. The openings are referred to as rotor slots 10 (see reference sign 10 in Figure 3 At the end of the short-circuit bars 5, the short-circuit bars lead into a respective short-circuit plate 6. In one preferred example, the entire intermediate space between the two short-circuit plates 6 in the axial direction B is filled with rotor sheets 4 which are placed directly next to one another. Furthermore, a shaft 7 of the rotor 3 and a thickness 30 of the rotor sheets 4 in the axial direction B are drawn. The thickness 30 is, for example, 0.15 to 0.35 millimetres.

[0045] Figure 3 A partial view of a rotor sheet 4 is shown. The partial view furthermore shows a portion of a stator 8 of the electric motor 2, wherein the stator 8 is arranged around the rotor 3. Between the stator 8 and the rotor 3, and more precisely between the stator 8 and the radially outer edge of the rotor sheet 4, there is an air gap 9. For example, the air gap width 29 of the air gap 9 can be between 2 and 4 times the thickness 30.

[0046] The rotor sheet 4 has a plurality of rotor slots 10. Here, a partial view of one of the rotor slots 10 is drawn. The rotor slot 10 has a radially outer wall 11 and two side walls 12 which adjoin the radially outer wall 11. One of the short-circuit bars 5 of the rotor 3 is arranged in the rotor slot 10 in such a way that a free space 14 is configured between a radially outer end region 13 of the short-circuit bar 5 and the radially outer wall 11. The free space 14 is a continuous hole in the rotor sheet 4 which is not filled by the short-circuit bar 5. For example, there is air in the free space 14. Furthermore, the free space 14 extends in the radial direction A over a partial section 15 of the respective side wall 12. The free space 14 is there arranged at least partially between the side face 34 of the short-circuit bar 5 and the respective side wall 12.

[0047] The partial segment 15 of the respective side wall 12 can have a length 16, which depends on a height 17 of the short-circuit bar 5 in the radial direction A, when viewed in the radial direction A. The height 17 of the short-circuit bar 5 is depicted in Figure 4 In one preferred example, the length 16 is between 0.1 and 1 times the height 17.

[0048] It is clear from Figure 3 The rotor slot 10 has two corners 20 at two oppositely arranged end portions 18, 19 of the partial segment 15 of the side wall 12, respectively, in the region of the partial segment 15 of the side wall 12. At two of the corners 20 at the end portion 18, the radially outer wall 11 of the rotor slot 10 adjoins the respective side wall 12 of the rotor slot 10. These two corners 20 limit the radially outer edge of the rotor slot 10. The two corners 20 are oppositely arranged to the two other corners 20 at the end portion 19. At these two corners 20, the respective side wall 12 has a turn, thereby forming a respective wall segment 21 of the rotor slot 10, which is oppositely arranged to the radially outer wall 11. This wall segment 21 of the respective side wall 12 ends here in a further turn, which is here depicted as an end point 35 of the partial segment 15. From the respective end point 35, a further partial segment 15 of the respective side wall 12 begins, in which the short-circuit bar 5 can be precisely arranged in the rotor slot 10.

[0049] The respective corners 20 can be configured rounded. For example, the radius r1 of the corners 20 at the end portion 18 can be the same as the radius r2 of the corners 20 at the end portion 19. Alternatively, the radii r1, r2 can differ from one another. For example, the respective radii r1, r2 correspond to 1 to 3 times the thickness 30 of the rotor lamination 4.

[0050] The rotor slot 10 can have a holding device 22 outside the partial segment 15 at at least one of the side walls 12. Here, the rotor slot has oppositely arranged holding devices 22 at both side walls 12. The respective holding device 22 is configured to at least reduce, in particular prevent, a movement of the short-circuit bar 5 in the radial direction A. The respective holding device 22 is here configured as a recess of the side wall 12. A protrusion 23 of the short-circuit bar 5 engages into this recess. The recess or the protrusion 23 is here configured semicircular. Alternatively, it can be angular, in particular triangular, quadrangular or polygonal. A plurality of holding devices 22 can be arranged at at least one of the side walls 12.

[0051] In Figure 3Furthermore, an outer width 26 in the radially outer end region 13 of the short-circuit bar 5 is drawn. The outer width 26 corresponds to the distance between two end points 35. Furthermore, a radius 27 is drawn, which describes the surface of the short-circuit bar 5 at its radially outer end region 13. Thus, the radially outer end region 13 can be rounded, wherein the rounded end region 13 is in particular semicircular. In this case, it has a radius 27, which depends on the outer width 26. For example, the radius can be between 0.3 and 0.7 times the outer width 26.

[0052] Furthermore, a distance 28 between the radially outer wall 11 of the rotor slot 10 and the radially outer edge of the rotor lamination 4 is provided. The distance 28 can depend on the thickness 30 of the rotor lamination 4. In particular, the distance 28 can be between 0.5 and 2.5 times the thickness 30 of the rotor lamination 4.

[0053] Furthermore, a width 36 of the radially outer wall 11 is drawn. This width can correspond to the length 16 of the partial segment 15 or be different therefrom. For example, the width 36 can correspond to 1 to 1.5 times the outer width 26.

[0054] Figure 4 The short-circuit bar 5 is shown in detail. The height 17 of the short-circuit bar 5 and the outer width 26 of the short-circuit bar 5 are drawn. Furthermore, Figure 4 It is shown that the short-circuit bar 5 can be rounded at the radially outer end region 13. The short-circuit bar 5 can be configured tapering between the radially outer end region 13 and an oppositely arranged radially inner end region 24. Thus, the inner width 25 at the radially inner end region 24 is smaller than the outer width 26. In particular, the inner width 25 in the radially inner end region 24 can be between 0.35 and 0.65 times the outer width 26 at the radially outer end region 13. The height 17 can furthermore depend on the outer width 26, wherein it can for example be between 4.5 and 7 times the outer width 26. The design of the rotor slot 10 is not drawn in detail in Figure 4 .

[0055] Figure 5 The rotor lamination 4 as well as a quarter of the stator 8, which surrounds a part of the rotor 3, is shown. It is clear that the stator 8 can have a plurality of stator windings 32. Furthermore, a rotor lamination radius 33 of the rotor lamination 4 is drawn. The height 17 can depend on the rotor lamination radius 33, wherein the height is for example between one quarter and one half of the rotor lamination radius 33, that is to say, the rotor lamination radius 33 can be 2 to 4 times the height 17.

[0056] If the plurality of rotor laminations 4 are connected to form a rotor lamination group, at least some of the free spaces 14 jointly form a volume space through which a cooling fluid, for example, can be pumped or otherwise moved through so that active cooling of the rotor 3 can be achieved.

[0057] Overall, the example shows an efficiency-optimized weight-reduced asynchronous machine (i.e., electric motor 2) with a lamination cut (rotor lamination 4). Such an asynchronous machine (i.e., electric motor 2) generally has a lower efficiency than a permanent magnet excited synchronous machine (PMSM) due to the additional induction excitation of the rotor field. These disadvantages can be reduced by cleverly optimizing the rotor lamination cut and thus the rotor slots 10 in the rotor lamination 4, so that a significant efficiency increase in the asynchronous machine can be achieved. In particular, the asynchronous machine can be produced more simply and more expediently than other machine types in terms of production technology. In addition, the rotor lamination 4 is optimized for simplified production. The use of air cavities (which are described here by the free spaces 14) has so far been meaningful precisely in order to improve the efficiency of the asynchronous machine. The specific design of the rotor lamination 4, more precisely the design concept of the rotor slots 10 here and the mutual geometric proportions and dimensions are decisive for a significant efficiency or performance increase in the electric motor 2.

[0058] Furthermore, maximum leakage flux suppression and weight reduction should be considered. The short-circuit bars 5 (or rotor bars) are fixed in the rotor conductor tooth flanks (side walls 12) in the rotor laminations (rotor laminations 4) by an additional holding structure (which can be implemented by holding devices 22) and are fixed against the action of centrifugal forces. Thus, they are fixed in the side walls 12 of the rotor slots 10.

[0059] Fluids for cooling can be guided through the individual free spaces 14 in order to cool hot spots of the rotor 3 (short-circuit bars 5 near the air gap 9). Here, it is important that the specific geometric implementation of the rotor, that is to say the design and here in particular the characteristic design geometry (cavities, short-circuit bars 5, radii) of the rotor laminations 4 are in mutual dimensioning. By particularly large free spaces 14, the leakage flux in the rotor laminations 4 can also be further reduced. In addition, it enables a reduction in mass, inertia and weight.

[0060] List of reference signs

[0061] 1 motor vehicle

[0062] 2 electric motor

[0063] 3 rotor

[0064] 4 rotor lamination

[0065] 5 short-circuit bar

[0066] 6 short-circuit plate

[0067] 7 shaft

[0068] 8 stator

[0069] 9 air gap

[0070] 10 rotor slot

[0071] 11 radially outer wall

[0072] 12 side wall

[0073] 13 radially outer end region

[0074] 14 free space

[0075] 15 partial segment

[0076] 16 length

[0077] 17 height

[0078] 18 end

[0079] 19 end

[0080] 20 corner

[0081] 21 wall segment

[0082] 22 holding device

[0083] 23 protrusion

[0084] 24 radially inner end region

[0085] 25 inner width

[0086] 26 outer width

[0087] 27 radius

[0088] 28 distance

[0089] 29 air gap width

[0090] 30 thickness

[0091] 32 stator winding

[0092] 33 rotor lamination radius

[0093] 34 side face

[0094] 35 end point

[0095] 36 width of the radially outer wall

Claims

1. A rotor (3) for an electric motor (2), wherein, The rotor (3) includes at least one rotating lamination (4) having a plurality of rotor slots (10), wherein each rotor slot (10) has a radial outer wall (11) and two side walls (12) adjacent to the radial outer wall (11), and the short-circuit bar (5) of the rotor (3) is arranged in the corresponding rotor slot (10) such that a free space (14) is formed between the radial outer end region (13) of the short-circuit bar (5) and the radial outer wall (11). Its features are, The free space (14) extends radially through a portion (15) of the corresponding sidewall (12) and is arranged there at least partially between the side (34) of the short-circuit bar (5) and the sidewall (12).

2. The rotor (3) according to claim 1, characterized in that, Viewed in the radial direction, a portion (15) of the corresponding sidewall (12) has a length (16) that depends on the height (17) of the short-circuit bar (5) in the radial direction, wherein the length is particularly between 0.1 times and 1 times the height (17).

3. The rotor (3) according to any one of the preceding claims, characterized in that, The rotor slot (10) has two corners (20) at two radially opposite ends (18, 19) in a region of a portion (15) of the corresponding sidewall (12), wherein, in two of the corners (20), the radial outer wall (11) is adjacent to the corresponding sidewall (12), and in the other two corners (20), the corresponding sidewall (12) has a bend, thereby forming a corresponding wall section (21) of the rotor slot (10) opposite to the radial outer wall (11), wherein the corresponding corners (20) are particularly rounded.

4. The rotor (3) according to any one of the preceding claims, characterized in that, The rotor slot (10) has a retaining device (22) at least in one of the sidewalls (12) outside the partial section (15), which is configured to at least reduce, and in particular prevent, movement of the short-circuit bar (5) in the radial direction.

5. The rotor (3) according to claim 4, characterized in that, The retaining device (22) is configured as a recess in the sidewall (12), wherein the protrusion (23) of the short-circuit bar (5) engages in the recess.

6. The rotor (3) according to any one of the preceding claims, characterized in that, The short-circuit bar (5) is constructed taperingly between the radially outer end region (13) and the oppositely positioned radially inner end region (24), wherein, in particular, the inner width (25) of the short-circuit bar (5) at the radially inner end region (24) is between 0.35 times and 0.65 times the outer width (26) at the radially outer end region (13).

7. The rotor (3) according to any one of the preceding claims, characterized in that, The short-circuit bar (5) is rounded at the radially outer end region (13), wherein the rounded end region (13) is in particular semi-circular and has a radius (27) that depends on the outer width (26) at the radially outer end region (13), wherein the radius (27) is in particular between 0.3 and 0.7 times the outer width (26).

8. The rotor (3) according to any one of the preceding claims, characterized in that, The height (17) of the short-circuit bar (5) in the radial direction depends on the radius (33) of the rotating body stack (4) and / or the outer width (26) of the short-circuit bar (5) at its radially outer end region (13), wherein the height (17) is particularly between one-half and one-quarter of the radius (33) of the rotating body stack and / or between 4.5 times and 7 times the outer width (26).

9. The rotor (3) according to any one of the preceding claims, characterized in that, The rotor (3) has a plurality of rotating body laminations (4), and the rotor slots (10) of the rotating body laminations are at least partially stacked such that the plurality of free spaces (14) are interconnected and together form a volume space, in particular the cooling fluid of the cooling system can move through the volume space to cool the rotor (3).

10. A motor vehicle (1) having an electric motor (2), the electric motor having a stator (8) and a rotor (3) according to any one of the preceding claims.

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