Electric machine with oil cooling

Abstract

The invention relates to an electric machine (1) comprising: a housing (2), a stator (3) with a stator core (5) and a winding (6), and a rotor (4) rotatably mounted about an axis of rotation (A), with a rotor shaft (7), a rotor core (8), and a first end ring (9) and a second end ring (12) at the axial ends of the rotor core (8), wherein the rotor shaft (7) has an axial bore (14) and a first and a second radial bore (15, 16) arranged axially offset from one another, wherein a supply element (19) supplies cooling fluid to the first and second radial bore (15, 16), wherein the rotor core (8) has several axial passages (27, 27') extending between the axial ends of the rotor core, wherein the first end ring (9) has first channels (28) to connect the first radial bores (15) of the rotor shaft (7) with first axial to connect passages (27) of the rotor core (8), and the second end ring (12) has second channels (29),to connect the second radial bores (16) of the rotor shaft (7) with second axial passages (27') of the rotor core (8).

Description

[0001] The present invention relates to an electric machine, in particular a permanent magnet synchronous motor (PMSM). An electric machine typically comprises a stator and a rotor arranged radially within the stator. The stator carries windings that are connected to an alternating current (AC) supply to generate a rotating magnetic field. The rotor may include permanent magnets to generate a constant magnetic field.

[0002] Document WO 2021 094 670 A1 discloses a liquid-cooled electric machine comprising a rotor with magnets and a stator with windings. The rotor includes lamination stacks, magnets arranged within the stacks, and front and rear flanges adjacent to the stacks. The machine is configured to ensure transverse circulation of the coolant within the lamination stack, with a coolant supply for cooling the front and rear flanges. The coolant circulates from one of the front and rear flanges through the lamination stack via a cooling channel to the other of the front and rear flanges before exiting the rotor through a drain channel bounded by the flange. The front and rear flanges each bear axially against the lamination stack at one end, and the drain channels are hollow on the side of the flange facing the lamination stack.

[0003] From WO 2009 147 798 A1, a motor is known which comprises a stator with a stator winding and a stator core, and a rotor rotatably mounted on the inside of the stator core. The rotor is provided with a rotor shaft, a cylindrical rotor spindle, and a rotor core mounted on the rotor spindle. A cooling chamber is formed between the outer circumferential surface of the rotor shaft and the inner circumferential surface of the rotor spindle. An oil supply channel for the cooling oil is provided inside the rotor shaft. A cooling oil drain opening of the oil supply channel is formed on an outer circumferential surface of the rotor shaft that faces the cooling chamber.

[0004] Document CN 209184335 U discloses a cooling structure for a motor rotor. The motor comprises a hollow shaft, a rotor, a left magnetic isolation plate, and a right magnetic isolation plate. The shaft has an open end with a first oil bore arranged radially on both sides and in the central section. The end faces of the left and right magnetic plates are each provided with a radial oil inlet groove, an annular oil groove, a radial oil drain groove, and four sets of connecting oil grooves evenly distributed in the inner ring of the annular oil groove.

[0005] Document CN 112421833 A discloses an oil-cooled rotor structure comprising a rotating shaft, a first rotor pressure plate, a second rotor pressure plate, a rotor core, a front bearing, and a rear bearing. The inner surface of the rotating shaft has a blind hole open towards the rear end cover of the electric drive. The first rotor pressure plate is provided with an oil collection groove and an oil passage. Cooling oil enters the hollow shaft from the electrically driven rear end cover, forming a first oil distribution channel and a second oil distribution channel.

[0006] Document WO 2018 181 244 A1, which corresponds to US 2020 / 0099265 A1, discloses an electric motor with a stator and a rotor. The rotor includes a shaft through which cooling oil can flow. A rotor yoke is mounted on the shaft, to which magnets are attached, and end plates abut the ends of the rotor yoke. The rotor yoke has a cooling oil channel on a radially inner side of the magnet, through which the cooling oil can flow in the axial direction. The rotor yoke experiences a compressive force in the axial direction via the first end plate. The rotor yoke and the first end plate form a sealing section that seals the cooling oil in a section in the radial direction between the cooling oil channel and the magnet.

[0007] The power output of an electric machine, especially a PMSM, is limited by the temperature in the stator windings and the rotor magnets. Electric machines with indirect cooling systems, such as a water jacket, or direct air cooling systems have limited heat dissipation capabilities.

[0008] The object of the present invention is to propose an electric machine with an effective cooling structure.

[0009] According to the invention, an electric machine is proposed comprising: a housing, a stator arranged in the housing, comprising a stator core and a winding, and a rotor rotatably mounted in the housing about an axis of rotation, wherein the rotor comprises a rotor shaft, a rotor core connected to the rotor shaft, a first end ring at a first axial end of the rotor core, and a second end ring at an opposite second axial end of the rotor core, wherein the rotor shaft has an axial bore and first radial bores and second radial bores extending therefrom, which are arranged axially offset from one another, wherein a feed element extends into the axial bore to supply cooling fluid to the first radial bores and the second radial bores, wherein the rotor core comprises several axial channels extending between the first axial end and the second axial end.wherein the first end ring comprises several first channels that fluidically connect the first radial bores of the rotor shaft with a first subset of the axial passages of the rotor core, and the second end ring comprises several second channels that fluidically connect the second radial bores of the rotor shaft with a second subset of the axial passages of the rotor core.

[0010] One advantage of the proposed electric machine is that the direct oil cooling system utilizes the centrifugal force generated by the rotor's rotation to transport fluid through the rotor and to the end windings. The cooling fluid, in particular an oil, is fed into the hollow rotor shaft via the feed element, thus enabling a low-pressure fluid supply. Within the shaft chamber, the fluid spreads centrifugally, creating a flow along the shaft's inner wall. The fluid exits the shaft through the first set of radial bores to the inlets of the channels in the first end ring and through the second set of radial bores to the inlets of the channels in the second end ring. At their outer radial ends, the channels are fluidically connected to a respective axial passage in the rotor core.In this way, cooling fluid can flow from the first end ring through the first set of axial passages to the second end of the rotor core, and conversely, cooling fluid can flow from the second end ring through the second set of axial passages to the first end of the rotor core. Thus, the cooling fluid flows through the rotor and absorbs a large amount of heat.

[0011] The first and / or second channels can be formed or integrated into the inner surfaces of the respective first or second end ring. In particular, the first channels can be formed in a first side surface of the first end ring that is in contact with the first end of the rotor core. The second channels can be formed in a second side surface of the second end ring that is in contact with the second end of the rotor core. The first and second end rings are axially supported against the rotor shaft and are rotationally fixed to it.

[0012] The rotor core is preferably clamped axially between the two end rings and connected to the rotor shaft in a rotationally fixed manner. The first end ring is aligned in a defined rotational position relative to the rotor core, in particular such that the outlets of the end ring channels are aligned with the axial passages of the rotor core. The same applies to the second end ring, which is also arranged in a defined rotational position relative to the rotor core. In this way, the channels of the first and second end rings are fluidically connected to the respective axial passages of the rotor. The first and second axial passages of the rotor core can each have two circumferentially adjacent channels, between which a radial rib is formed. This rib can stiffen the structure of the rotor core in the region of the axial passages.

[0013] In one embodiment, the first channels of the first end ring are configured such that they are axially covered by the first side face of the rotor core, in particular by web sections of the rotor core at the first axial end. Alternatively or additionally, the second channels of the second end ring are configured such that they are axially covered by the second side face of the rotor core, in particular by web sections of the rotor core at the second axial end.

[0014] The feed element can be in the form of a lance connected to a stationary element, such as the housing or another associated element, like a housing cover or shield. The lance can be static or rotating. In this context, "static" means that the feed element is not rotatable but fixed relative to the housing or associated element. Compared to a rotating lance, a static feed element has the advantage that the fluid flow inside is not affected by the rotational speed of the electric machine, thus allowing for better control of the fluid flow to the shaft.

[0015] The supply element can comprise one or more openings arranged within the axial bore, particularly axially between the plurality of first radial bores and the plurality of second radial bores. In this way, both the group of first radial bores and the group of second radial bores are supplied with cooling fluid during operation. The length of the supply element can be configured such that its axial end is located within a central axial section of the rotor core, particularly within a central third of the rotor core. The axial bore of the rotor shaft can have annular recesses in the region of the first radial bores and the second radial bores. This results in a particularly effective fluid supply to the first and second groups of radial channels.

[0016] The rotor core can comprise several magnetic cavities containing permanent magnets. The axial passages can be arranged circumferentially between adjacent magnets. The axial passages can be located on a radial outer surface of the rotor core, particularly such that they overlap a portion of the magnets radially. The rotor core can have several cavities distributed circumferentially, with web sections formed around the cavities or magnetic cavities (in a cross-sectional view). The cavities serve to reduce weight; they can have a larger cross-section than the axial passages. Preferably, the cavities are arranged radially inward relative to the axial passages located on a radial outer surface of the rotor core. Web sections are formed between the cavities and the axial passages.The magnets of the rotor core can be arranged in pairs, with each pair being arranged in a V-shape in axial view. The first channels, or at least a section thereof extending radially from the inside out, are preferably arranged between two circumferentially adjacent pairs of magnets. The axial passages can comprise two or more circumferentially adjacent channels, between which a radial bridge is formed. Alternatively, however, each axial passage can also comprise a single channel.

[0017] According to a first embodiment, the first and second end rings are configured such that the cooling fluid flows axially through the rotor core. That is, fluid entering the first end ring flows through the rotor core and exits at the second end ring, and conversely, fluid entering the second end ring flows through the rotor core and exits at the first end ring. In particular, the first end ring can have several circumferentially distributed first outlets that are fluidically connected to the group or set of axial passages that receive fluid from the channels of the opposite second end ring. Correspondingly, the second end ring can have several circumferentially distributed outlets that are fluidically connected to the group or set of axial passages that receive fluid from the channels of the first end ring.

[0018] Part of the cooling fluid flows through the rotor core towards the first end ring and exits there through the first outlets to cool the first end winding of the stator. Another part of the cooling fluid flows through the rotor core in the opposite axial direction to the second end ring and exits there through the second outlets to cool the second end winding of the stator. The first outlets can be arranged between two circumferentially adjacent first channels. The second outlets can be arranged between two circumferentially adjacent second channels.

[0019] At least one, preferably all, first and second outlets are arranged on a smaller radius than the radius of the respective axial passages of the rotor core. By arranging the outlets in a radially inner position, the axial passages can completely fill with fluid before exiting the end ring. This maximizes the contact area between the fluid and the outer cavities of the rotor, resulting in very good heat transfer and absorption by the fluid.

[0020] According to a second embodiment, the first and second end rings are configured such that the cooling fluid flows axially through the rotor core twice. That is, fluid entering the first end ring flows through the axial passages to the opposite second end ring, where it is recirculated and flows back through axial return channels to the first end ring, where the fluid exits to cool the first end windings. Conversely, fluid entering the second end ring flows through the axial passages to the opposite first end ring, where it is recirculated and flows back through axial return channels to the second end ring, where it exits to cool the second end windings. In particular, the first end ring includes several return channels that fluidically connect the second set of axial passages to the second set of cavities in the rotor core.The second set of cavities opens into outlet openings provided in the second end ring to cool the second stator windings. Accordingly, the second end ring includes several reversing channels that fluidically connect the first set of axial passages with the first set of cavities in the rotor core. The first set of cavities opens into outlet openings provided in the first end ring to cool the first stator windings.

[0021] Preferably, the axial passages are arranged in a radially outer position and the cavities in a radially inner position. To reach the inner cavities or the inner level due to centrifugal forces, the outer part of the oil circuit should preferably be completely filled with fluid. When the fluid reaches the inner level or plane, it flows back through the rotor via the inner cavities. When the fluid reaches the circuit outlet, it is expelled to the respective winding heads.

[0022] In both embodiments, the first channels between a channel inlet and a channel outlet can be configured such that, in the assembled state, they each enclose or bypass one of the rotor core cavities. The channels are designed to run around the opening of the rotor core cavity to prevent coolant from unintentionally escaping into the cavity. In particular, the first channels can divide into two branches, between which a bridge or land section is formed, with the two branches rejoining behind the bridge. The first channels are preferably configured such that the bridge formed between the two branches covers the opening of the rotor core cavity in the assembled state.In this design, the cooling fluid flows from the radially inner inlets through the two branches circumferentially around an adjacent cavity opening and, behind the junction, as a channel to the radially outer outlet. The channel outlets are arranged so that they each overlap one of the axial passages of the rotor core to establish a fluid connection with it.

[0023] The rotor core can comprise several stacks of lamellae or rotor lamination stacks, in particular three or more stacks of lamellae, for example six stacks of lamellae or lamination stacks.

[0024] According to one embodiment, the feed element can be fluidically connected to a fluid reservoir to receive cooling fluid. The reservoir can be positioned higher than the axial bore of the hollow shaft with respect to the direction of gravity. However, in a cooling system with a pump, the reservoir can also be positioned independently of the hollow shaft. The fluid can be conveyed to the fluid reservoir by rotating elements of the electric machine, for example, from an oil pan via gears of a transmission connected to the hollow shaft.

[0025] Preferred embodiments are described below with reference to the drawings. These show Fig. 1A an electric machine in a longitudinal section in a first embodiment; Fig. 1B the electric machine from Fig. 1A in a cross-sectional view along the section line 1B-1B; Fig. 1C the electric machine from Fig. 1A in a three-dimensional exploded view; Fig. 1D a first end ring of the electric machine Fig. 1A in an axial view; Fig. 1E the first end ring of the electric machine Fig. 1A in a cross-sectional view along the section line 1E-1E; Fig. 1F the rotor core of the electric machine Fig. 1A in an axial view, showing the channels and openings of the adjacent end ring; Fig. 2A an electric machine in a longitudinal section in a second embodiment; Fig. 2B the electric machine from Fig. 2A in a cross-sectional view along the section line 2B-2B; Fig. 2C the electric machine from Fig. 2A in a three-dimensional exploded view; Fig. 2D a first end ring of the electric machine Fig. 2A in an axial view; Fig. 2E the first end ring of the electric machine Fig. 2A in a cross-sectional view along the section line 2E-2E; and Fig. 2F the rotor core of the electric machine Fig. 2A in an axial view, showing the channels and openings of the adjacent end ring.

[0026] The Fig. Figures 1A to 1F, which are described together below, show an electric machine 2 according to a first embodiment of the invention.

[0027] The electric machine 1 comprises a housing 2, a stator 3 connected to the housing, and a coaxially arranged rotor 4, which is rotatably mounted in the housing 2 about an axis of rotation A4. The stator 3 comprises a stator core 5 and a winding 6, which may consist of several conductors. The electric machine 2 can be configured, in particular, as a permanent magnet synchronous machine (PMSM) for powering a motor vehicle. The windings 6 can be connected to an alternating current supply to generate a rotating magnetic field.

[0028] The rotor 4 comprises a rotor shaft 7, a rotor core 8 connected to the rotor shaft 7, a first end ring 9 at a first axial end 10 of the rotor core, and a second end ring 12 at the opposite second axial end 13 of the rotor core. The rotor shaft 7 comprises an axial bore 14, a set of first radial bores 15, and a set of second radial bores 16. The two sets of bores are arranged in two radial planes with an axial distance from each other. In the axial regions of the first and second radial bores 15, 16, the rotor shaft 7 may optionally have first and second annular recesses 17, 18. Cooling fluid flowing along the inner wall of the axial bore 14 is thus easily drawn by centrifugal forces to the openings of the first and second radial bores 15, 16, which are radially offset from the radius of the central section of the inner wall.

[0029] A supply element 19 is provided to supply the hollow shaft with cooling fluid. The supply element 19 extends into the axial bore 14, allowing the cooling fluid to flow along the axial bore to the first and second radial bores 15 and 16. According to the present embodiment, the supply element 19 is designed in the form of a lance connected to a section 20 of the housing 2. The supply element 19 extends through an axial opening 22 of the rotor shaft 7, and a sealing element 23 may optionally be arranged at the end of the shaft to prevent backflow of fluid from the shaft 14 at the opening side. The supply element 19 is statically fixed, i.e., it is rotationally fixed to the housing 2 by fasteners 24. However, it is understood that the supply element can also be rotatable.The feed element 14 can be fluidically connected via an inlet 25 to a fluid reservoir (not shown) to receive cooling fluid. The reservoir can be positioned higher than the axial bore 14, so that the fluid is passively guided into the rotor shaft 7 by gravity. However, it is also possible to actively feed fluid into the rotor shaft using a pump.

[0030] The feed element can have one or more openings 26 in the section located within the bore 14. The openings 26 are preferably arranged axially between the first set of radial bores 16 and the second set of radial bores 17. Cooling fluid flows from the feed element axially between the two sets of bores into the hollow shaft. At the inner wall, the incoming fluid divides into a first cooling flow, which flows to the first radial bores 16, and a second cooling flow, which flows to the second radial bores 17. The length of the feed element 19 is preferably designed such that its axial end lies within a central axial region of the rotor core 8.

[0031] The rotor core 8 comprises several axial passages 27, 27' or channels extending between the first axial end 10 and the second axial end 13. These multiple axial passages can include first axial passages 27, for example, for a fluid flow through the rotor core 8 in a first axial direction, and second axial passages 27', for example, for a fluid flow through the rotor core 8 in an opposite second axial direction. The rotor core 8 is preferably axially clamped or clamped between the first and second end rings 9, 12 and rotationally fixed to the rotor shaft 7. For this purpose, the rotor core 8 can have engagement or positioning elements 41 on an inner circumferential region, which engage with corresponding elements 21 of the rotor shaft 7. The first end ring 9 is axially supported against the rotor shaft 7, in particular against an axial stop 21 or a shoulder of the rotor shaft.The first end ring 9 is positioned at an angle relative to the shaft 7 such that the inlets 30 of the channels 28 align with the first radial bores 15 of the shaft 7, and the outlets 32 of the end ring channels align with the axial passages 27 of the rotor core 8. The same applies to the second end ring 12, which is arranged in a defined rotational position relative to the shaft 7 and the rotor core 8 to also establish a fluid connection between them. To position the first and second end rings 9, 12 at a defined angular position, the rings can optionally have one or more positioning elements 33, which interact positively with corresponding positioning elements 31 of the rotor shaft 7. The positioning elements 33 can be arranged on the inner circumferential surface of the respective end ring 9, 12. The second end ring 12 is positioned axially on the rotor shaft 7 and contacts the rotor core 8.A clamping ring 34 is provided to axially support the second end ring 12 and to act axially against the rotor core 8. The clamping ring 34 is axially supported and connected to the rotor shaft 7.

[0032] The two end rings 9 and 12 are preferably identical in design, so for the sake of simplicity only one of the rings is described in detail. It goes without saying that all details described for the first end ring 9 also apply to the second ring 12.

[0033] The first end ring 9, which is in the Fig. 1D and Fig. As shown in detail in Figure 1E, the first end ring 12 comprises several channels 28 for fluidically connecting the first radial bores 15 of the rotor shaft 7 to a respective set of axial passages 27 of the rotor core 8. Similarly, the second end ring 12 comprises several second channels 29 for fluidically connecting the second radial bores 16 of the rotor shaft to a corresponding second set of axial passages 27' of the rotor core. The channels 28, 29 are formed or machined into the inner surfaces of the respective first or second end ring 9, 12. In particular, the first channels 28 are formed in a first side surface of the first end ring 9 that is in contact with the first end of the rotor core 8. Similarly, the second channels 29 are formed in a side surface of the second end ring 12 that is in contact with the opposite end of the rotor core 8.

[0034] As especially in Fig. As can be seen in Figure 1F, the rotor core 8 can have several pockets 35, 35' or cavities containing permanent magnets 36, 36'. The axial passages 27, 27' are preferably arranged circumferentially between two circumferentially adjacent magnets 36. In the radial direction, the axial passages 27, 27' are preferably arranged in a radially outer region of the rotor core 8, in particular such that they radially overlap at least a portion of the radially outer pockets 35. In the circumferential direction, the axial passages 27, 27' are preferably arranged such that they at least partially overlap a radial outer end of the inner pockets 35' in the circumferential direction. Each of the axial passages 27, 27' can comprise two separate channels 11, 11' with a web 51 formed between them. This can be advantageous for the structure of the rotor core 8 in the regions of the axial passages 27, 27'.It is understood, however, that a single axial passage with one channel is also possible. The end ring channels 28 can have a T-shaped outer section. In particular, the circumferential extent of the outlets 32 of the end ring channels 28 can be such that both axial channels 11, 11' of a respective first axial passage 27 are covered and fluidically connected. Accordingly, the passage openings 48 of the end rings 9, 12 can also have a circumferential extent to be fluidically connected to both axial channels 11, 11' of a respective second axial channel 27'.

[0035] The rotor can comprise one or more groups of magnets or magnet pairs distributed around its circumference. In the present embodiment, the rotor 8 comprises a radially outer group of pockets 35 containing outer magnets 36 and a radially inner group v of pockets 35' containing inner magnets 36'. The outer and inner magnets 36, 36' are arranged in pairs, preferably in a V-shape. The inner pockets 35' and magnets 36' are each larger than the outer pockets 35 and the magnets 36 contained therein.

[0036] The rotor core 8 comprises several cavities 37 distributed around its circumference, arranged radially inside the axial passages 27. As shown in Fig. As shown in Figure 1F, the rotor core 8 comprises annular inner web sections 38, intermediate web sections 39 formed between the cavities 37 and the magnet pockets 35', and outer web sections 40 formed between the groups of magnet pockets. It is understood, however, that the rotor may have a different design, for example, with only one magnet group and a correspondingly reduced number of pockets and webs. The cavities 37 may have a larger cross-section than the axial passages 27 and are arranged radially inside them. The channels 28 of the first end ring 9 are designed such that they are axially covered by the first side surface of the rotor core 8. In particular, the channels 28 are designed such that the inlets 30 are arranged in the region of the inner web sections 38, then divide into two branches 42, 42', each enclosing a rotor cavity 37 and 42', respectively.The cooling fluid flows around the opening of the cavity 37 and converges radially on the outside to form an intermediate section 43, which is connected to one of the outlets 32. This allows the cooling fluid to flow around the opening of the cavity 37, preventing unwanted ingress into the cavity. A web section 50 is formed between the two branches 42, 42', with the two branches converging again behind the web section in the flow direction. The second end ring 12 and the second rotor end are preferably designed in the same manner.

[0037] The rotor core 8 comprises several stacks of lamellae 44 or lamella packs, wherein, in the present embodiment, six stacks of lamellae or lamella packs are provided, but this number is not limited. Each stack of lamellae together forms the pockets 35, 35' in which respective magnets 36, 36' are embedded or received. Each of the magnets extends over the axial length of the respective stack of lamellae 44. Axially adjacent stacks of lamellae 44 can be arranged with a small circumferential offset relative to each other. The magnets embedded in the rotor generate a constant magnetic field. Thus, in an activated state, the rotor 4 is rotated about the axis of rotation A4 to drive the rotor shaft 7 and a drive train rotatably connected to it.

[0038] Further details of the first embodiment are described with regard to the design of the cooling system and the respective cooling flow. In the Fig. In the embodiment shown in Figures 1A to 1F, the first and second end rings 9, 12 are configured such that the cooling fluid flows axially through the rotor core. Cooling fluid entering the first end ring 9 flows through the rotor core 6 and exits at the second end ring 12. Conversely, fluid entering the second end ring 12 flows through the rotor core 6 and exits at the first end ring 9. The flow of the cooling fluid is shown schematically by arrows F. The first end ring 9 can have several outlets 45 distributed around its circumference, which are fluidically connected to the group or set of axial passages 27' that receive fluid from the channels 29 of the opposite second end ring 12. Accordingly, the second end ring 12 comprises several outlets distributed around its circumference, which are in fluid communication with the axial passages 27 and receive fluid from the channels 28 of the first end ring 9. As shown in particular in Fig. As can be seen in Figure 1D, the first outlets 45 can be arranged between two circumferentially adjacent first channels 28. Similarly, the outlets of the second end ring 12 can be arranged between two circumferentially adjacent second channels 29.

[0039] Thus, a first portion of the cooling fluid flows through the rotor core 8 towards the first end ring 9 and exits there through the first outlets 45 to cool the first end winding 46 of the stator 3. A second portion of the cooling fluid flows through the rotor core 8 in the opposite axial direction to the second end ring 12 and exits there through the second outlets to cool the second end winding 47 of the stator.

[0040] The first end ring 9 shows, as in Fig. As can be seen in Figure 1E, through-holes 48 are provided, with the outlet opening 45 being arranged on a smaller radius than the inlet opening 49, which receives fluid from the axial passage 27' of the rotor core 8. Because the outlets 45 are located at a radially more inward position, the axial passages 27' can fill completely with fluid before exiting the end ring 9. The orientation of the through-holes 48 can be selected such that the cooling fluid exiting the outlet 45 cools the end winding 46 most effectively. In this case, the axis of the through-hole 48 forms an angle with an axis parallel to the axis A4, which lies between 20° and 60°, for example, 30°.

[0041] The Fig. Figures 2A to 2F show an electrical machine 2 according to the invention in a second embodiment. This largely corresponds to the embodiment according to the Fig. 1A to 1F, whose descriptions regarding commonalities are hereby referenced. Identical or corresponding details are indicated with the same reference numerals as in the Fig. labeled 1A to 1F.

[0042] According to the second embodiment, which is in the Fig. As shown in Figures 2A to 2F, the first and second end rings 9, 12 are configured such that the cooling fluid flows axially through the rotor core 6 twice. The fluid entering the first end ring 9 flows through the axial passages 27 to the opposite second end ring 12, where it is returned and flows back through axial return channels to the first end ring 9, where the fluid exits to cool the first end windings 46. Similarly, fluid entering the second end ring 12 flows through the axial passages 27' to the opposite first end ring 9, where it is returned and flows back through axial return channels to the second end ring 12, where it exits to cool the second end windings 47. The return channels are formed by the cavities 37, 37' of the rotor core 8.

[0043] As especially in Fig. As can be seen in Figure 2D, the first end ring 9, in addition to the channels 28 to be connected to the first set of axial passages 27, comprises a plurality of reversing channels 52 for fluidically connecting the second set of axial passages 27' to the second set of cavities 37' of the rotor core 8. The reversing channels 52 can have a T-shaped configuration, with a circumferentially extending outer section connected to the rotor passage 27' and a radially inwardly extending radially to the rotor cavity 37'. The second set of cavities 37' opens into respective outlets 53 provided in the second end ring 12 for cooling the second stator windings 47. Accordingly, the second end ring 12 comprises several reversing channels that fluidically connect the first set of axial passages 27 to the first set of cavities 37 of the rotor core 8.The first set of cavities 37 opens into the outlets 45, which are provided in the first end ring 9 to cool the first stator windings 46. As in . Fig. As can be seen in Figure 2F, the outlets 45 are each arranged in a region within the two branches of a channel 28, such that they overlap with a respective first cavity 37. The axial passages 27, 27' are arranged in a radially outer position, and the cavities 37, 37' are arranged in a radially inner position. When the fluid reaches the outlets 45, 53 of the circuit, it is expelled in the direction of the respective winding heads 46, 47. Reference sign 1 electric machine 2 cases 3 Stator 4 Rotor 5 Stator core 6 windings 7 Rotor shaft 8 rotor core 9 first end ring 10 first axial end 11, 11' Channel 12 second end ring 13 second axial end 14 axial bore 15 first radial bores 16 second radial bores 17 first ring-shaped recess 18 second ring-shaped recess 19 Feed element Section 20 21 attacks 22 axial opening 23 Locking element 24 Fasteners 25 Admission 26 Opening 27, 27' axial passage 28 channels 29 channels 30 channel inlets 31 Positioning element 32 channel outlets 33 Positioning element 34 clamping ring 35, 35' bag 36, 36' Magnet 37, 37' cavity 38 Bridge section 39 Bridge section 40 Bridge section 41 Positioning element 42, 42' branch 43 Intermediate section 44 stacks of slats 45 Outlet 46 Development 47 Development 48 Passage opening 49 Admission 50 Land section 51 Bridge 52 Reversing channel 53 Outlet A4 axle F River R radius QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] WO 2021 094 670 A1

[0002] WO 2009 147 798 A1

[0003] CN 209184335 U

[0004] CN 112421833 A

[0005] WO 2018 181 244 A1

[0006] US 2020 / 0099265 A1

[0006]

Claims

[1] Electric machine (1), comprising: a housing (2), a stator (3) arranged in the housing (2), comprising a stator core (5) and a winding (6), and a rotor (4) which is rotatably mounted in the housing (2) about an axis of rotation (A), wherein the rotor (4) comprises a rotor shaft (7), a rotor core (8) connected to the rotor shaft (7), a first end ring (9) at a first axial end of the rotor core (8) and a second end ring (12) at an opposite second axial end of the rotor core (8), wherein the rotor shaft (7) has an axial bore (14) and extending from it first radial bores (15) and second radial bores (16) which are arranged axially offset from each other, wherein a feed element (19) is provided to direct cooling fluid into the axial bore (14) to supply the first radial bores (15) and the second radial bores (16), wherein the rotor core (8) has several axial passages (27, 27') distributed around the circumference and extending between the first axial end and the second axial end, wherein the first end ring (9) comprises first channels (28) which connect the first radial bores (15) of the rotor shaft (7) with a first set of axial passages (27, 27') of the rotor core (8), and the second end ring (12) has second channels (29) which fluidically connect the second radial bores (16) of the rotor shaft (7) with a second set of axial passages (27, 27') of the rotor core (8). [2] Electric machine according to claim 1, characterized by , that the first channels (28) are formed in a first side surface of the first end ring (9) which is in contact with the rotor core (8) at the first end, and / or that the second channels (29) are formed in a second side surface of the second end ring (12), which is in contact with the rotor core (8) at the second end. [3] Electric machine according to claim 1 or 2, characterized by that the first channels (28) of the first end ring (9) in contact with the first side of the rotor core (8) are designed such that they are axially covered at the first axial end by the web sections (38, 39) of the rotor core (8), and / or that the second channels (29) of the second end ring (12) which is in contact with the second side of the rotor core (8) are designed such that they are axially covered at the second axial end by the web sections of the rotor core (8). [4] Electric machine according to any one of claims 1 to 3, characterized by, that the first channels (28) between a channel inlet (30) and a channel outlet (32) are designed such that, in the assembled state, they bypass a cavity (37) of the rotor core (8), wherein the channel outlets (32) are arranged such that they are each in fluid communication with one of the axial passages (27, 27') of the rotor core (8). [5] Electric machine according to claim 4, characterized by , that the first channels (28) divide into two branches (42, 42') between which a land section (50) is formed, wherein the branches (42, 42') converge again behind the land section (50), wherein the branches (42, 42') are in particular designed such that the land section (50) covers the cavity (37) of the rotor core (8) when assembled. [6] Electric machine according to any one of claims 1 to 5, characterized by, that the feed element (19) is designed such that it extends into the axial bore (14) of the rotor shaft (7), and in particular is designed in the form of a lance which is non-rotatably connected to the housing (2) or a part connected thereto, wherein the feed element (19) has at least one opening (26) within the axial bore (14) which is arranged axially between the first radial bores (15) and the second radial bores (16). [7] Electric machine according to any one of claims 1 to 6, characterized by , that the axial bore (14) of the rotor shaft has annular recesses (17, 18) in the area of ​​the first radial bores (15) and the second radial bores (16). [8] Electric machine according to any one of claims 1 to 7, characterized by , that the rotor core (8) has several pockets (35, 35') containing permanent magnets (36, 36'), wherein the axial passages (27, 27') are arranged circumferentially between circumferentially adjacent magnets (36, 36'), wherein the rotor core (8) has several cavities (37, 37') distributed circumferentially, wherein - in a cross-sectional view - web sections (38, 39, 40) are formed around the cavities (37, 37') and the pockets (35, 35'). [9] Electric machine according to claim 8, characterized by , that the magnets (36, 36') are arranged in pairs, each pair having in particular a V-shape, the first channels (28) being arranged between two circumferentially adjacent pairs of magnets (36, 36'). [10] Electric machine according to any one of claims 1 to 9, characterized by, that each of the axial passages 27, 27' has two circumferentially adjacent channels 11, 11', between which a radial web 51 is formed. [11] Electric machine according to any one of claims 1 to 10, characterized by , that the first end ring (9) has several first outlets (45) distributed around the circumference into which the second set of axial passages (27') opens to cool a first end winding (46) of the stator (3), wherein the first outlets (45) are arranged between two circumferentially adjacent first channels (28), and / or that the second end ring (12) comprises several second outlets (53) distributed around the circumference into which the first set of axial passages (27) opens to cool a second end winding (47) of the stator (3), wherein the second outlets (53) are arranged between two circumferentially adjacent second channels (29). ( Fig.1A - 1F) [12] Electric machine according to claim 11, characterized by , that at least one of the first outlets (45) and the second outlets (53) is arranged on a smaller radius (R45) than a radius (R27) of the axial passages (27, 27') of the rotor core (8). [13] Electric machine according to any one of claims 1 to 12, characterized by , that the first end ring (9) comprises several reversing channels (52) which fluidically connect the second set of axial passages (27') with a second set of cavities (37') of the rotor core (8), wherein the second end ring (12) comprises several outlets (53) into which the second set of cavities (37') opens. ( Fig. 2A - 2F) [14] Electric machine according to any one of claims 1 to 13, characterized by , that the rotor core (8) comprises several stacks of lamellae (44), in particular one or more stacks of lamellae. [15] Electric machine according to any one of claims 1 to 14, characterized by , that the hydraulic system includes a fluid reservoir, wherein the supply element (19) is hydraulically connected to the fluid reservoir and receives cooling fluid from it. [16] Electric machine according to claim 15, characterized by , that the fluid reservoir is located in a higher position with respect to the direction of gravity than the axial bore (14) of the rotor shaft (7).

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