Electric machine with oil cooling

Abstract

The invention relates to an electric machine (1) comprising: a housing (2); a stator (3) having a stator core (5) and a winding (6); and a rotor (4) rotatably supported about an axis of rotation (A), having a rotor shaft (7), a rotor core (8), and a first end ring (9) and a second end ring (12) at an axial end of the rotor core (8), in which the rotor shaft (7) comprises 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 a cooling fluid to the first and second radial bores (15, 16), where the rotor core (8) comprises a plurality of axial passages (27, 27 ') extending between the axial ends of the rotor core, where the first end ring (9) comprises a first channel (28) to connect the first radial bore (15) of the rotor shaft (7) with the first axial passage (27) of the rotor core (8), and where the first end ring (9) comprises a second channel (28) to connect the second radial bore (15) of the rotor shaft (7) with the second axial passage (27') of the rotor core (8). And the second end ring (12) comprises a second channel (29) to connect a second radial bore (16) of the rotor shaft (7) with a second axial passage (27 ') of the rotor core (8).

Description

Technical Field

[0001] The present invention relates to an electric machine, in particular a permanent magnet synchronous machine (PMSM). The electric machine typically comprises a stator and a rotor arranged radially inside the stator. The stator carries windings connected to an alternating current (AC) power source to generate a rotating magnetic field. The rotor may include permanent magnets to create a constant magnetic field. Background Art

[0002] From document WO 2021094670 A1, an electric machine with liquid cooling is known, comprising a rotor with magnets and a wound stator. The rotor comprises a stack of rotor laminations, a magnet housed in the lamination stack, and front and rear flanges adjacent to the laminations. The machine is configured to ensure cross-circulation of cooling liquid within the lamination stack using a liquid supply for cooling the front and rear flanges. The liquid circulates from the flange through the lamination stack, via the cooling channel, toward the other of the front and rear flanges before leaving the rotor through an evacuation channel defined by one of the front and rear flanges. Both the front and rear flanges are axially against the lamination stack at one end, and an evacuation channel is hollowly formed on the face of the flange facing the lamination stack.

[0003] From document WO 2009147798 A1, a motor is known, comprising a stator having a stator coil and a stator core and a rotor rotatably located on the inner peripheral side of the stator core. The rotor is provided with a rotor shaft, a cylindrical rotor starter and a rotor core mounted on the rotor starter. A cooling space is formed between the outer peripheral surface of the rotor shaft and the inner peripheral surface of the rotor starter. An oil supply passage for cooling oil is provided inside the rotor rotating shaft. A cooling oil discharge port of the oil supply passage is formed on the outer peripheral surface of the rotor rotating shaft facing the cooling space.

[0004] From document CN 209184335 U, a cooling structure for a rotor of a motor is known. 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, wherein the first oil holes are arranged on all sides and a middle portion in a radial direction, respectively. The left and right magnetic plate end faces are respectively provided with four sets of radial oil inlet grooves, annular oil grooves, radial oil discharge grooves, and connected oil grooves uniformly distributed in the inner ring of the annular oil groove.

[0005] From document CN 112421833 A, an oil-cooled rotor structure is known, 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 interior of the rotating shaft has a blind hole opening toward the rear end cover of the electric drive. The first rotor pressure plate is provided with an oil collecting groove and an oil through hole. The cooling oil enters the hollow shaft from the rear end cover of the electric drive to form a first oil distribution channel and a second oil distribution channel.

[0006] From the document WO 2018181244 A1 corresponding to US2020 / 0099265 A1, an electric motor having a stator and a rotor is known. The rotor includes: a shaft that allows cooling oil to flow therein. The rotor yoke is mounted on the shaft, wherein the magnet is fitted to the rotor yoke and the end plate is close to the end of the rotor yoke. The rotor yoke has a cooling oil passage formed on the radial inner side of the magnet, and allows the cooling oil to flow in the axial direction. The rotor yoke receives a pressing force in the axial direction via the first end plate. The rotor yoke and the first end plate form a sealing portion for sealing the cooling oil in a section located between the cooling oil passage and the magnet in the radial direction.

[0007] The performance of electric machines, in particular PMSMs, is limited by the temperature in the windings of the stator and the magnets of the rotor. Electric machines with indirect cooling systems, such as housing water jackets, or direct air cooling systems have limited heat evacuation capabilities. Summary of the invention

[0008] The object of the present invention is to provide a motor with an effective cooling structure.

[0009] According to the present invention, an electric machine is proposed, comprising: a housing; a stator, which is arranged in the housing and comprises a stator core and a winding; and a rotor, which is rotatably supported in the housing around a rotation axis, 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 comprises an axial bore and first and second radial bores extending therefrom and arranged axially offset from each other, wherein a supply element extends into the axial bore to supply a cooling fluid to the first and second radial bores, wherein the rotor core comprises a plurality of axial passages extending between the first and second axial ends, wherein the first end ring comprises a plurality of first channels, the plurality of first channels fluidly connecting 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 a plurality of second channels, the plurality of second channels fluidly connecting the second radial bores of the rotor shaft with a second subset of the axial passages of the rotor core.

[0010] The advantage of the proposed motor is that the direct oil cooling system uses the centrifugal force caused by the rotation of the rotor to push the fluid through the rotor and to the end windings. The cooling fluid (in particular, oil) is placed inside the hollow rotor shaft by a supply element, thereby allowing low-pressure fluid input. Inside the shaft chamber, the fluid is centrifugally distributed and creates a flow along the inner wall of the shaft. The fluid leaves the shaft through a first set of radial drillings to the inlet of the channel of the first end ring, and through a second set of radial drillings to the inlet of the channel of the second end ring. At their outer radial ends, the channels are connected to the corresponding axial passage fluids of the rotor core. In this way, the 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 vice versa, the cooling fluid can flow from the second end ring through the second set of axial passages to the first end of the rotor core. Therefore, the cooling fluid passes through the rotor, thereby absorbing a large amount of heat.

[0011] The first and / or second channel may be formed or engraved on the inner face of the respective first or second end ring. In particular, the first channel may be formed in a first side of the first end ring in contact with the first end of the rotor core. The second channel may be formed in a second side of the second end ring 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 connected to it in a rotationally fixed manner.

[0012] The rotor core is preferably axially clamped between 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 so that the outlet of the end ring channel is aligned with the axial passage of the rotor core. The same applies to the second end ring also being arranged in a defined rotational position relative to the rotor core. In this way, the channel fluids of the first and second end rings are connected to the corresponding axial passages of the rotor. The first and second axial passages of the rotor core can both include two circumferentially adjacent channels between which a radial web is formed. This can stiffen the structure of the rotor core in the region of the axial passage.

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

[0014] The feed element may be configured in the form of a lance connected to a stationary member, such as the housing or any other member connected thereto, such as a housing cover or hood. The lance may be configured as a stationary or rotating lance. The term stationary in this regard is intended to include that the feed element is not rotatable, but rather is held in a fixed manner relative to the housing or member connected thereto. Compared to a rotating lance, a stationary feed element has the advantage that the fluid flow inside is not affected by the rotational speed of the motor, thereby allowing a higher control of the fluid flow towards the shaft.

[0015] The supply element may comprise one or more openings arranged inside the axial borehole, in particular, axially arranged between the plurality of first radial boreholes and the plurality of second radial boreholes. In this way, cooling fluid is supplied to both the set of first radial boreholes and the set of second radial boreholes during operation. The length of the supply element may be configured such that the axial end of the supply element is located within a middle axial portion of the rotor core, in particular, within a middle third of the rotor core. The axial borehole of the rotor shaft may comprise an annular recess in the region of the first radial borehole and the second radial borehole. This results in a particularly efficient fluid supply to the first and second sets of radial tubes.

[0016] The rotor core may include a plurality of magnet cavities having permanent magnets received therein. The axial passage may be arranged between the respective adjacent magnets in the circumferential direction. The axial passage may be arranged at the radially outer region of the rotor core, in particular so as to overlap with a portion of the magnet in the radial direction. The rotor core may include a plurality of circumferentially distributed hollow cavities, wherein - in a cross-sectional view - a web portion is formed around the hollow cavity and the magnet cavity, respectively. The hollow cavities serve to reduce weight; they may have a larger cross-section than the axial passage. Preferably, the hollow cavities are arranged radially inwardly relative to the axial passage arranged at the radially outer region of the rotor core. A web portion is formed between the hollow cavity and the axial passage. The magnets of the rotor core may be arranged in pairs, wherein each pair may be arranged in a V-shape in an axial view. The first channel or at least a portion thereof extending from the radially inner portion to the outer portion is preferably arranged between two circumferentially adjacent pairs of magnets. The axial passage may include two or more circumferentially adjacent channels between which a radial web is formed. However, alternatively, each axial passage may also include a single channel.

[0017] According to a first embodiment, the first and second end rings are configured so that the cooling fluid passes axially through the rotor core once. That is, the fluid entering the first end ring flows through the rotor core and leaves at the second end ring, and vice versa, the fluid entering the second end ring flows through the rotor core and leaves at the first end ring. In particular, the first end ring may include: a plurality of first outlets distributed on the circumference, which are fluidically connected to a collection of axial passages that receive fluid from the channels of the opposite second end ring. Correspondingly, the second end ring may include: a plurality of outlets distributed on the circumference, which are fluidically connected to a collection of axial passages that receive fluid from the channels of the first end ring.

[0018] A portion of the cooling fluid flows through the rotor core toward the first end ring and exits there through the first outlet to cool the first end winding of the stator. Another portion of the cooling fluid flows through the rotor core in another axial direction toward the second end ring and exits there through the second outlet to cool the second end winding of the stator. The first outlet may be arranged between two circumferentially adjacent first channels. The second outlet may be arranged between two circumferentially adjacent second channels.

[0019] At least one, preferably both, of the first and second outlets are arranged on a radius smaller than the radius of the corresponding axial passage of the rotor core. Providing the outlets in a more radially inner position allows the axial passage to be completely filled with fluid before the fluid leaves the end ring. In this way, the contact surface between the fluid and the rotor outer cavity is maximized, resulting in very good heat transfer and absorption to the fluid.

[0020] According to a second embodiment, the first and second end rings are configured so that the cooling fluid passes axially through the rotor core twice. That is, the fluid entering the first end ring flows through the axial passage to the opposite second end ring, where it is returned and flows back through the axial return passage to the first end ring, where the fluid leaves to cool the first end winding. Vice versa, the fluid entering the second end ring flows through the axial passage to the opposite first end ring, where it is returned and flows back through the axial return passage to the second end ring, where it leaves to cool the second end winding. In particular, the first end ring includes: a plurality of reverse channels, connecting the second set of axial passages with the second set of cavities of the rotor core. The second set of cavities opens into an outlet provided in the second end ring to cool the second stator end winding. Correspondingly, the second end ring includes: a plurality of reverse channels, connecting the first set of axial passages with the first set of cavities of the rotor core. The first set of cavities opens into an outlet provided in the first end ring to cool the first stator end winding.

[0021] Preferably, the axial passage is arranged in a more radially outer position and the cavity is arranged in a more radially inner position. In order to reach the inner cavity or inner level due to centrifugal force, the outer part of the oil circuit should preferably be completely filled with fluid. When the fluid reaches the inner level, it passes back through the rotor through the inner cavity. When the fluid reaches the outlet of the circuit, it is discharged towards the corresponding winding head.

[0022] In both embodiments, a first channel can be formed between a channel inlet and a channel outlet so as to enclose a corresponding one of the cavities of the rotor core under installation conditions. The channel is formed so as to flow around the mouth of the rotor core cavity to avoid the cooling fluid from undesirably leaving the cavity. In particular, the first channel can be split into two branches, between which a land section is formed, wherein the two branches reunite behind the land section. The first channel is preferably formed so that the land section formed between the two branches covers the opening of the rotor core cavity under installation conditions. With this design, the cooling fluid can flow from the radially inner inlet, pass through the two branches circumferentially around the adjacent cavity opening, and after reunion, flow as a channel to the radially outer outlet. The channel outlet is arranged to overlap with a corresponding one of the axial passages of the rotor core to establish a fluid connection therewith.

[0023] The rotor core may comprise a plurality of lamination stacks, in particular three or more lamination stacks, for example six lamination stacks.

[0024] According to an embodiment, the supply element may be fluidically connected to a fluid reservoir to receive cooling fluid therefrom. The reservoir may be located in a position higher than the axial bore of the hollow shaft relative to the direction of gravity. However, in a cooling system comprising a pump, the reservoir may also be arranged independently relative to the hollow shaft. The fluid may be conveyed to the fluid reservoir by a rotating element of the motor, for example, by a gear of a gearbox connected to the hollow shaft from a sump. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The preferred embodiments are described below with reference to the accompanying drawings. Figure 1A The motor is shown in longitudinal section in a first embodiment; Figure 1B In the cross-sectional view according to the section line 1B-1B, Figure 1A Motor; Figure 1C The 3D exploded view shows Figure 1A Motor; Figure 1D The axial view shows Figure 1A A first end ring of the motor; Figure 1EIn the cross-sectional view according to the section line 1E-1E, Figure 1A A first end ring of the motor; Figure 1F The axial view is shown with the channels and openings adjacent to the end rings drawn in. Figure 1A The rotor core of the motor; Figure 2A The motor is shown in longitudinal section in a second embodiment; Figure 2B In the cross-sectional view according to the section line 2B-2B, Figure 2A Motor; Figure 2C The 3D exploded view shows Figure 2A Motor; Figure 2D The axial view shows Figure 2A A first end ring of the motor; Figure 2E In the cross-sectional view according to the section line 2E-2E, it is shown Figure 2A A first end ring of the motor; and Figure 2F The axial view is shown with the channels and openings adjacent to the end rings drawn in. Figure 2A The rotor core of the motor. DETAILED DESCRIPTION

[0026] The following will describe Figures 1A to 1F An electric machine 2 according to a first embodiment of the invention is shown.

[0027] The electric machine 1 comprises: a housing 2; a stator 3 connected to the housing; and a rotor 4 arranged coaxially therewith and supported rotatably in the housing 2 around a rotation axis A4. The stator 3 comprises a stator core 5 and a winding 6 which may be composed of a plurality of conductors. The electric machine 2 may be configured to drive a motor vehicle, in particular in the form of a permanent magnet synchronous motor (PMSM). The winding 6 may be connected to an AC power source 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 an opposite second axial end 13 of the rotor core. The rotor shaft 7 comprises an axial bore 14, a set 15 of first radial bores and a set 16 of second radial bores. The two sets of bores are in particular arranged in two radial planes at an axial distance from each other. In the axial region of the first and second radial bores 15, 16, the rotor shaft 7 may optionally have a first and a second annular recess 17, 18. The cooling fluid flowing along the inner wall of the axial bore 14 by centrifugal force thus very easily reaches the openings of the first and second radial bores 15, 16, which are radially obstructed compared to the radius of the central part of the inner wall.

[0029] A supply element 19 is provided to feed the hollow shaft with cooling fluid. The supply element 19 extends into the axial bore 14 so that the cooling fluid can flow along the axial bore to the first and second radial bores 15, 16. According to the present embodiment, the supply element 19 is configured in the form of a lance connected to a portion 20 of the housing 2. The supply element 19 extends through an axial opening 22 of the rotor shaft 7, wherein optionally, a closing element 23 can be arranged at the end of the shaft to avoid the fluid from flowing back outward from the shaft 14 at the opening side. The supply element 19 is stationary, i.e., it is non-rotatably fixed to the housing 2 by a fixing device 24. However, it should be understood that the supply element can also be configured to be rotatable. The supply element 14 can be fluidically connected to a fluid reservoir (not shown) via an inlet 25 to receive cooling fluid from it. The reservoir can be located in a position higher than the axial bore 14 so that the fluid is passively conveyed by gravity into the rotor shaft 7. However, it is also possible to actively supply the fluid into the rotor shaft by a pump.

[0030] At the portion arranged inside the boreholes 14, the supply element may have one or more openings 26. The openings 26 are preferably arranged axially between the first set 16 of radial boreholes and the second set 17 of radial boreholes. The cooling fluid flow emerges from the supply element into the hollow shaft axially between the two sets of boreholes. At the inner wall, the incoming fluid is divided into a first cooling flow flowing toward the first radial boreholes 16 and a second cooling flow flowing toward the second radial boreholes 17. The length of the supply element 19 is preferably configured so that its axial end is located in the middle axial region of the rotor core 8.

[0031] The rotor core 8 comprises a plurality of axial passages 27, 27' extending between the first axial end 10 and the second axial end 13. The plurality of axial passages may comprise: a first axial passage 27, for example for a fluid flow through the rotor core 8 in a first axial direction; and a second axial passage 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 between the first and second end rings 9, 12 and connected to the rotor shaft 7 in a rotationally fixed manner. For this, the rotor core 8 may have: a positioning element 41, arranged at the inner circumferential end of the counterpart element 21 engaging the rotor shaft 7. The first end ring 9 is axially supported against the rotor shaft 7, in particular, an axial stop 21 or shoulder of the rotor shaft. The first end ring 9 is angularly positioned relative to the shaft 7 so that the inlet 30 of the passage 28 is aligned with the first radial bore 15 of the shaft 7, and the outlet 32 ​​of the end ring passage is aligned with the axial passage 27 of the rotor core 8. The same applies to the second end ring 12 also being arranged in a defined rotational position relative to the shaft 7 and the rotor core 8 to establish a fluid connection therebetween. In order to position the first and second end rings 9, 12 in a defined angular position, the rings may optionally include one or more positioning elements 33 that actively interact with counterpart elements 31 of the rotor shaft 7. The positioning elements 33 may be arranged at the inner circumferential faces of the respective end rings 9, 12. The second end ring 12 is axially positioned on the rotor shaft 7 and contacts the rotor core 8. A clamping ring 34 is provided to axially support and axially press the second end ring 12 against the rotor core 8. The clamping ring 34 is axially supported connected to the rotor shaft 7.

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

[0033] Figure 1D and 1E The first end ring 9 shown in detail in the figure includes a plurality of channels 28 to fluidically connect the first radial bores 15 of the rotor shaft 7 with a corresponding set of axial passages 27 of the rotor core 8. Correspondingly, the second end ring 12 includes a plurality of second channels 29 to fluidically connect the second radial bores 16 of the rotor shaft with a corresponding second set of axial passages 27' of the rotor core. The channels 28, 29 are formed or engraved on the inner face of the respective first or second end ring 9, 12. More particularly, the first channel 28 is formed in a first side of the first end ring 9 in contact with a first end of the rotor core 8. Correspondingly, the second channel 29 is formed in a side of the second end ring 12 in contact with an opposite end of the rotor core 8.

[0034] As in particular Figure 1FAs can be seen in the figure, the rotor core 8 may include a plurality of grooves 35, 35' or cavities having permanent magnets 36, 36' received therein. The axial passages 27, 27' are preferably arranged between two circumferentially adjacent magnets 36 in the circumferential direction. In the radial direction, the axial passages 27, 27' are preferably arranged in the radially outer region of the rotor core 8, in particular so as to radially overlap at least part of the radially outer groove 35. In the circumferential direction, the axial passages 27, 27' are preferably arranged so as to circumferentially overlap at least partly with the radial outer end of the inner groove 35'. Each of the axial passages 27, 27' may include two separation channels 11, 11', with a web 51 formed therebetween. This may be advantageous for the structure of the rotor core 8 in the region of the axial passages 27, 27'. However, it should be understood that a single axial passage with one channel is also possible. The end ring channel 28 may have a T-shaped outer portion. In particular, the circumferential extension of the outlet 32 ​​of the end ring channel 28 can be such that all two axial channels 11, 11' of the corresponding first axial passage 27 are covered and fluidically connected. Correspondingly, the through opening 48 of the end ring 9, 12 can also have a circumferential extension to be fluidically connected to all two axial channels 11, 11' of the corresponding second axial passage 27'.

[0035] The rotor may include one or more groups of circumferentially distributed magnets or magnet pairs. In this embodiment, the rotor 8 includes: a radially outer group 35 of grooves, with outer magnets 36 received therein; and a radially inner group 35' of grooves, with inner magnets 36' received therein. The outer and inner magnets 36, 36' are arranged in pairs, and the pairs are preferably arranged in a V-formation. The inner grooves 35' and magnets 36' are larger than the outer grooves 35 and the magnets 36 received therein, respectively.

[0036] The rotor core 8 includes a plurality of circumferentially distributed cavities 37 arranged radially inward from the axial passage 27. Figure 1FAs can be seen in the figure, the rotor core 8 comprises an annular inner web portion 38, an intermediate web portion 39 formed between the cavity 37 and the magnet groove 35', and an outer web portion 40 formed between the groups of magnet grooves. However, it should be understood that the rotor can have a different design, for example, only one group of magnets and a correspondingly reduced number of grooves and webs. The cavity 37 can have a larger cross-section than the axial passage 27 and is arranged at a certain distance radially inward from it. The channels 28 of the first end ring 9 are formed so that they are axially covered by the first side of the rotor core 8. More specifically, the channels 28 are formed so that the inlet 30 is arranged in the region of the inner web portion 38, and then they are split into two branches 42, 42', which surround the corresponding rotor cavity 37 and merge again radially on the outside into an intermediate portion 43 connected to a corresponding one of the outlets 32. The cooling fluid can thus flow around the opening of the cavity 37, and undesirable drainage into the cavity is avoided. Between the two branches 42, 42' a covering section 50 is formed, wherein the two branches merge again in the flow direction behind the covering section. The second end ring 12 and the second rotor end are preferably configured in the same way.

[0037] The rotor core 8 includes a plurality of lamination stacks 44, of which six lamination stacks are provided in the present embodiment, but not limited thereto. Each lamination stack forms together a groove 35, 35' in which a corresponding magnet 36, 36' is embedded. Each of the magnets extends over the axial length of the corresponding lamination stack 44. Axially adjacent lamination stacks 44 may be arranged with a small circumferential offset relative to each other. The magnets embedded in the rotor create a constant magnetic field. Therefore, under activation conditions, the rotor 4 rotates about the axis of rotation A4 to drive the rotor shaft 7 and the transmission line rotatably connected to it.

[0038] Further details of the first embodiment are described with regard to the design of the cooling system and the corresponding cooling flows. Figures 1A to 1F In the embodiment shown in , the first and second end rings 9, 12 are configured so that the cooling fluid flows axially through the rotor core once. The cooling fluid entering the first end ring 9 flows through the rotor core 6 and exits at the second end ring 12. Correspondingly, the 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 schematically drawn using arrows F. The first end ring 9 may include: a plurality of outlets 45 distributed on the circumference, which are fluidically connected to a set of axial passages 27' that receive fluid from the channels 29 of the opposite second end ring 12. Correspondingly, the second end ring 12 includes: a plurality of outlets distributed on the circumference, which are fluidically connected to a set of axial passages 27 that receive fluid from the channels 28 of the first end ring 9. As particularly shown in Figure 1DAs can be seen in FIG. 1 , the first outlet 45 can be arranged between two circumferentially adjacent first channels 28 . Correspondingly, the outlet of the second end ring 12 can be arranged between two circumferentially adjacent second channels 29 .

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

[0040] As in Figure 1E As can be seen in Figure 1 , the first end ring 9 has a through opening 48, wherein the outlet 45 is arranged on a smaller radius than the inlet 49 receiving the fluid from the axial passage 27' of the rotor core 8. Providing the outlet 45 in a more radially inner position allows the axial passage 27' to be completely filled with fluid before the fluid leaves the end ring 9. The orientation of the through opening 48 can be selected as required so that the cooling fluid leaving the outlet 45 cools the end winding 46 most effectively. In the present case, the axis of the through opening 48 encloses an angle of between 20° and 60° (for example, 30°) with a line parallel to the axis A4.

[0041] Figures 2A to 2F In a second exemplary embodiment, an electric machine 2 according to the invention is shown. This corresponds largely to the exemplary embodiment according to Figures 1A to 1F Embodiments of the present invention are described with reference to the similarities. The same and / or corresponding details are provided with reference to Figures 1A to 1F The same reference numerals are used in the drawings.

[0042] according to Figures 2A to 2F In the second embodiment shown in FIG. 1 , the first and second end rings 9, 12 are configured so that the cooling fluid passes axially through the rotor core 6 twice. The fluid entering the first end ring 9 flows through the axial passage 27 to the opposite second end ring 12, where it is returned and flows back through the axial return passage to the first end ring 9, where the fluid exits to cool the first end winding 46. Correspondingly, the fluid entering the second end ring 12 flows through the axial passage 27' to the opposite first end ring 9, where it is returned and flows back through the axial return passage to the second end ring 12, where it exits to cool the second end winding 47. The return passage is formed by the cavities 37, 37' of the rotor core 8.

[0043] As in particular Figure 2DAs can be seen in the figure, in addition to the channels 28 to be connected to the first set 27 of axial passages, the first end ring 9 also includes a plurality of reverse channels 52 to fluidically connect the second set 27' of axial passages with the second set 37' of cavities of the rotor core 8. The reverse channels 52 may have: a T-shaped design, having a circumferentially extending outer portion connected to the rotor passage 27' and a radial portion extending radially inwardly to the rotor cavity 37'. The second set 37' of cavities opens into a corresponding outlet 53 provided in the second end ring 12 to cool the second stator end winding 47. Accordingly, the second end ring 12 includes: a plurality of reverse channels to fluidly connect the first set 27 of axial passages with the first set 37 of cavities of the rotor core 8. The first set 37 of cavities opens into an outlet 45 provided in the first end ring 9 to cool the first stator end winding 46. As shown in Figure 2F As can be seen in the figure, the outlets 45 are each arranged in a region within the two branches of the channel 28 so as to overlap with the respective first cavities 37. The axial passages 27, 27' are arranged in a more radially outer position and the cavities 37, 37' are arranged in a more radially inner position. When the fluid reaches the outlet 45, 53 of the circuit, it is discharged towards the respective winding heads 46, 47.

[0044] Reference numerals 1 Motor 2 Housing 3. Stator 4 Rotor 5. Stator core 6 Winding 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 drilling 15 First radial drilling 16 Second radial drilling 17 First annular depression 18 Second annular depression 19 Supply components 20 parts 21 Stopper 22 Axial opening 23 Closing element 24 Fixtures 25 Import 26 Opening 27, 27' axial passage 28 channels 29 channels 30-channel inlet 31 Positioning elements 32 channel exit 33 Positioning elements 34 Clamping ring 35, 35' groove 36, 36' magnet 37, 37' cavity 38 belly plate 39 belly plate 40 belly plate 41 Positioning elements 42, 42' branch 43 middle part 44 stacking 45 Exit 46 End winding 47 End winding 48 penetration opening 49 Import 50 Covered part 51 belly plate 52 Back Channel 53 Exit A4 axis F Flow R Radius

Claims

1. Motor (2), comprising: Housing (2); A stator (3) arranged in the housing (2) and comprising a stator core (5) and a winding (6); as well as A rotor (4) supported in the housing (2) rotatably 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) comprises an axial bore (14) and first radial bores (15) and second radial bores (16) extending therefrom and arranged axially offset from each other, wherein a supply element (19) is provided to direct a 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) comprises a plurality of axial passages (27, 27') distributed on the circumference and extending between the first axial end and the second axial end, The first end ring (9) includes a first channel (28) which fluidically connects a first radial bore (15) of the rotor shaft (7) with a first set (27, 27') of axial passages of the rotor core (8), and the second end ring (12) includes a second channel (29) which fluidically connects a second radial bore (16) of the rotor shaft (7) with a second subset (27, 27') of axial passages of the rotor core (8).

2. The motor according to claim 1, Features The first channel (28) is formed in a first side surface of the first end ring (9) in contact with the rotor core (8) at a first end, and / or The second passage (29) is formed in a second side surface of the second end ring (12) in contact with the rotor core (8) at a second end.

3. The electric machine according to claim 1 or 2, Features The first channels (28) of the first end ring (9) contacting the first side of the rotor core (8) are formed so that they are axially covered by the web portions (38, 39) of the rotor core (8) at the first axial end, and / or the second channels (29) of the second end ring (12) contacting the second side of the rotor core (8) are formed so that they are axially covered by the web portions (38, 39) of the rotor core (8) at the second axial end.

4. The electric machine according to any one of claims 1 to 3, Features The first channel (28) is formed between a channel inlet (30) and a channel outlet (32) so as to surround a cavity (37) of the rotor core (8) in an installed condition, wherein the channel outlet (32) is arranged so as to be fluidically connected to a respective one of the axial passages (27, 27') of the rotor core (8).

5. The motor according to claim 4, Features The first channel (28) is divided into two branches (42, 42') between which a covering portion (50) is formed, wherein the branches (42, 42') rejoin behind the covering portion (50), wherein the branches (42, 42') are formed in particular such that the covering portion (50) covers a cavity (37) of the rotor core (8) in the assembled state.

6. The electric machine according to any one of claims 1 to 5, Features The feed element (19) is configured to extend into an axial bore (14) of the rotor shaft (7) and is in particular configured in the form of a lance connected to the housing (2) or a part thereof, wherein the feed element (19) comprises at least one opening (26) inside the axial bore (14) which is arranged axially between the first radial bore (15) and the second radial bore (16).

7. The electric machine according to any one of claims 1 to 6, Features The axial bore (14) of the rotor shaft comprises annular recesses (17, 18) in the region of the first radial bore (15) and the second radial bore (16).

8. The electric machine according to any one of claims 1 to 7, Features The rotor core (8) comprises a plurality of grooves (35, 35') having permanent magnets (36, 36') received therein, wherein the axial passages (27, 27') are arranged between circumferentially adjacent magnets (36, 36') in the circumferential direction, The rotor core (8) comprises a plurality of circumferentially distributed cavities (37, 37'), wherein - in a cross-sectional view - web portions (38, 39, 40) are formed around the cavities (37, 37') and the grooves (35, 35').

9. The electric machine according to claim 8, Features The magnets (36, 36') are arranged in pairs, each pair in particular having a V-shape, wherein the first channel (28) is respectively arranged between two circumferentially adjacent pairs (36, 36') of magnets.

10. The electric machine according to any one of claims 1 to 9, Features Each of said axial passages 27 , 27 ′ comprises two circumferentially adjacent channels 11 , 11 ′ forming a radial web 51 therebetween.

11. The electric machine according to any one of claims 1 to 10, Features The first end ring (9) comprises: a plurality of first outlets (45) distributed on the circumference, the second set (27') of axial passages opening into the plurality of first outlets (45) for cooling the first end winding (46) of the stator (3), wherein the first outlets (45) are arranged between two circumferentially adjacent first channels (28), and / or the second end ring (12) comprises: a plurality of second outlets (53) distributed on the circumference, the first subset (27) of the axial passages opening into the plurality of second outlets (53) for cooling the second end winding (47) of the stator (3), wherein the second outlets (53) are arranged between two circumferentially adjacent second channels (29).

12. The electric machine according to claim 11, Features At least one of the first outlet (45) and the second outlet (53) is arranged on a radius (R45) smaller than a radius (R27) of an axial passage (27, 27') of the rotor core (8).

13. The electric machine according to any one of claims 1 to 12, Features The first end ring (9) includes a plurality of reverse channels (52) fluidly connecting a second subset (27') of axial passages with a second subset (37') of hollow cavities of the rotor core (8), wherein the second end ring (12) includes a plurality of outlets (53) into which the second subset (37') of hollow cavities opens.

14. The electric machine according to any one of claims 1 to 13, Features The rotor core (8) comprises a plurality of lamination stacks (44), in particular one or more lamination stacks.

15. The electric machine according to any one of claims 1 to 14, Features The hydraulic system comprises a fluid reservoir, wherein the supply element (19) is hydraulically connected to the fluid reservoir and receives cooling fluid therefrom.

16. The electric machine according to claim 15, Features The fluid reservoir is located at a higher position relative to the direction of gravity than the axial bore (14) of the rotor shaft (7).

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