Rotors and Electrical Machines

Abstract

The invention relates to a rotor (1) for an electric machine (2), comprising: a hollow shaft (3) with first cooling passages (4) for a coolant (5), a laminated core (7) arranged on the hollow shaft (3), and balance discs (8) arranged at the longitudinal ends of the laminated core (7), wherein a component (9) made of injection / cast molding material is arranged between the balance discs (8) and the laminated core (7), the component (9) having at least one second cooling passage (11) open in the axial direction (10) and connected in fluid communication with the first cooling passages (4) in the hollow shaft (3), the second cooling passage (11) being covered in the axial direction (10) by the balance disc (8).

Description

[Technical Field]

[0001] The invention relates to a rotor for an electric machine according to the preamble of claim 1, which rotor has a hollow shaft with a first cooling passage for a coolant. The invention also relates to an electric motor, in particular a traction motor, equipped with such a rotor.

[0002] German Patent Application No. DE 10 2015 014 535 A1 discloses a rotor for an electric machine of the type mentioned at the outset, which has a hollow shaft with a first cooling channel for a coolant, on whose axially longitudinal ends a laminated core is arranged, with balancing disks arranged to compensate for any imbalance that may occur.

[0003] From US Pat. No. 8,450,890 another rotor for an electric machine is known, which comprises a rotor shaft with a first cooling passage.

[0004] The increasing number of electric vehicles requires an increasing number of electric traction motors for driving these vehicles, and it is desirable for these electric motors to be optimized in terms of weight and structural space, on the one hand, and to have high performance, on the other. For this reason, it is known to actively cool these electric motors, for example by oil cooling. Without cooling, the rotor windings, particularly those carrying excitation currents, can heat up strongly during operation, which results in power losses for the electric motor. Furthermore, particularly dynamic operating conditions cause magnetic field changes that generate eddy currents in the rotor, which in turn requires magnets on the rotor of permanent magnet machines to maintain the function of active cooling as the situation demands.

[0005] However, a disadvantage of the rotors or electric motors known from the prior art is that the production of the cooling channels through which the coolant, usually oil, flows is not only technically complex and therefore expensive, but also often requires axial construction space that does not exist or can only be achieved by accepting lower power. Furthermore, in known rotors or electric motors, cooling of the winding head of the rotor winding, the PSM magnet (permanent magnet synchronous machine) or the stator winding head is either completely impossible or difficult to achieve.

[0006] The present invention therefore addresses the problem of providing an improved embodiment or at least one alternative embodiment of a rotor of the type mentioned at the outset, which is characterized by cooling passages that are particularly easy to manufacture and have a compact axial configuration.

[0007] The above problem is solved according to the invention by the subject matter of independent claim 1. Advantageous embodiments are the subject matter of the respective dependent claims.

[0008] The present invention is based on the general idea of ​​providing a rotor of an electric machine with multi-shell cooling passages, which eliminates the need for drilling or milling and significantly simplifies their manufacture. In this case, the first shell of the cooling passage is formed, for example, from an injection molding compound or a casting compound that covers the rotor winding (externally excited synchronous machine) or PSM magnets of the rotor. Using a correspondingly shaped injection molding tool, overmolding, or casting tool, a removable cooling passage can be molded in the material at low cost and with high precision. The longitudinal ends of the rotor winding or PSM magnets are injection molded using a plastic injection molding tool, which also provides, for example, electrical insulation. The second shell of the cooling passage is formed by an easily manufacturable balance disk, which is further formed by simply covering the cooling passage in a component manufactured from the injection molding compound or casting compound. This completely eliminates the need for complex drilling and / or milling. A rotor according to the present invention for an electric machine, such as a traction motor for an electric vehicle, has a hollow shaft with a first cooling passage for a coolant, such as oil. A laminated core with individual rotor plates is arranged on the hollow shaft, and a balance disk is arranged on the rotor shaft at at least one longitudinal end of the laminated core, thereby compensating for any imbalance that may occur. According to the present invention, a component made of injection molding material / cast molding compound is arranged between the balance disk and the laminated core. This component is initially axially open and thus easily removable, and has at least one second cooling passage connected to the first cooling passage in the hollow shaft, which is axially covered and closed by the balance disk. The injection molding material / cast molding compound component and the balance disk thus form two shells for the second cooling passage.A major advantage of this solution is that the at least one second cooling channel can be produced relatively easily and at the same time inexpensively using a corresponding negative mold of a plastic injection / overmolding / casting tool. Since the at least one second cooling channel is axially open in the component, this second cooling channel can be produced relatively easily and, if necessary, can also be reprocessed relatively easily. In this case, the second cooling channel, which is formed as a groove in the component, is closed axially by a balance disk, which allows for a relatively flexible, manufacturing-simple, and inexpensive design of the at least one second cooling channel.

[0009] It is of course clear here that the injection molding compound / cast molding compound can be made of plastic and thus have electrically insulating properties.

[0010] In an advantageous development of the rotor according to the invention, the component is conically shaped. Furthermore, the component can be annular, so that, in the assembled state, an annular intermediate space can be left free between the outer circumferential surface of the hollow shaft and the component. The conical design of the component allows different channel geometries of the at least one second cooling channel to be realized relatively easily. Here, the component can have an axial thickness that increases radially outward, so that the corresponding balance disk has an axial thickness that decreases radially outward in this region. Of course, non-conical configurations of the component are also possible, such as stepped configurations or configurations with a constant axial thickness radially outward. Components manufactured as cast or injection-molded components according to the invention allow for the production of second cooling channels with high geometric flexibility and low costs, since the second cooling channels only need to be milled once in a suitable injection-molding tool. This eliminates the need to individually form holes in the balance disks, for example forming second cooling passages, in each individual balance disk.

[0011] In another advantageous embodiment of the rotor according to the present invention, rotor windings with winding heads at their longitudinal ends are arranged in a laminated core. By appropriately arranging or configuring at least one second cooling channel in the component, direct cooling of these winding heads is easily possible, thereby improving the cooling of the rotor windings and thus the performance of the externally excited synchronous machine. In this case, the stator windings or stator winding heads of the externally excited synchronous machine can be cooled by the coolant discharged outward. Alternatively, PSM magnets can be arranged in a laminated core arranged on a hollow shaft, where the PSM magnets are embedded, particularly at their longitudinal ends, in the injection / cast molding compound of the component. The injection / cast molding compound of the component can hold or fix the PSM magnets. The stator windings or stator winding heads of a permanently excited synchronous machine can also be cooled by the coolant discharged outward.

[0012] In particularly preferred embodiments of the rotor according to the invention, at least one second cooling passage has a constant or variable cross section. Additionally or alternatively, the second cooling passage may be configured in a straight or curved manner. It is clear that this non-limiting list already provides a wide range of flexible possibilities for the geometry or cross-section of the passages in the rotor according to the invention, which in particular allows for individual influence on the different coolant flows.

[0013] Additionally or alternatively, the at least one second cooling passage can be configured to be closed or open radially outward, with a radially open configuration allowing for additional cooling of the surrounding components, while a radially closed configuration allows for improved cooling of the rotor windings or PSM magnets.

[0014] In another advantageous embodiment of the rotor according to the present invention, a balance disk and a component made of injection molding material / casting material are arranged at each of the two longitudinal ends of the laminated core, each of which has at least one second cooling passage axially open and connected to the first cooling passage in the hollow shaft, and which is axially covered by a corresponding balance disk. Providing at least one second cooling passage at each longitudinal end of the laminated core allows for improved cooling of the rotor, particularly the winding heads or longitudinal ends of the PSM magnets located on opposite sides of the rotor winding, and thus the PSM magnets themselves, thereby increasing the power output of an electric motor equipped with such a rotor. In this case, each second cooling passage can be directly connected to the first cooling passage arranged in the hollow shaft, or alternatively, a coolant, particularly cooling oil or transmission oil, can be supplied via a single second cooling passage or via a connecting passage connecting two second cooling passages. The connection between the first and second cooling passages or between the first and connecting passages is in this case usually effected via holes or longitudinal openings in the hollow shaft.

[0015] For this purpose, at least one connecting passage is arranged between at least two oppositely positioned second cooling passages or between two oppositely positioned intermediate chambers, via which the coolant can be supplied to the two oppositely positioned second cooling passages or from one second cooling passage / intermediate chamber on one longitudinal side to the oppositely positioned second cooling passage / intermediate chamber on the other longitudinal side.

[0016] In this case, the connecting passage can extend within the laminated core or between the laminated core and the hollow shaft. The connecting passage can also be directly connected to the first cooling passage in the hollow shaft through a radial passage. If the connecting passage is arranged within the laminated core, particularly effective cooling of the rotor winding or the magnets (PSM magnets) arranged within the laminated core is possible. For this purpose, the laminated core can be provided with corresponding longitudinal through-openings that form the connecting passage. If the connecting passage is arranged between the laminated core and the outer circumferential surface of the hollow shaft, the connecting passage can also be provided as a groove on the inner circumferential surface of the laminated core and can also extend longitudinally.

[0017] For this purpose, the balance disc is made of metal, in particular aluminum or stainless steel. Alternatively, the balance disc can be made of plastic and have a cutout for accommodating the balance weight. By making it out of aluminum or stainless steel, the balance disc can be made relatively thin in the axial direction due to its greater weight compared to plastic, which allows for a particularly compact structural shape in the axial direction.

[0018] In another advantageous embodiment of the solution according to the invention, the injection / casting compound is made from plastic, which not only allows for a relatively simple and at the same time weight-optimized production of the component, but also simultaneously provides electrical insulation, which separates the winding head of the rotor winding or the PSM magnet from the balance disk, especially if the balance disk is made from metal.

[0019] The invention is further based on the general idea of ​​providing an electric machine, in particular a traction motor, with a rotor as described in the previous paragraph, thereby transferring the advantages explained for the rotor to the electric machine, in particular the relatively compact design of the electric motor in the axial direction and a simple and cost-effective manufacturing method in terms of production technology.

[0020] In a preferred embodiment of the electric machine according to the present invention, the electric machine has stator windings, and the stator windings or their winding heads are cooled by the coolant flowing from the second cooling channel. In this case, the rotor has PSM magnets arranged in a laminated core. The electric machine is therefore a permanent magnet synchronous machine. However, alternatively, a rotor winding (exciter winding) may be provided, making the electric machine an externally excited synchronous machine.

[0021] Important further features and advantages of the invention emerge from the respective dependent claims, the drawings and the corresponding description taken in conjunction with the drawings.

[0022] It is clear that the features mentioned above and those which will be described below can be used not only in the respective combinations mentioned but also in other combinations or alone, without departing from the scope of the invention. Components of a higher-level unit, e.g. a device, assembly or apparatus, which are shown separately and which are mentioned above or further below, may form separate components or parts of that unit, even if shown separately in the respective figures, or may form integrated regions or sections of that unit.

[0023] Preferred embodiments of the present invention are illustrated in the drawings and explained in detail in the following description, where like reference numerals indicate identical or similar or functionally identical components. The figures each show, in outline, [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a cross-sectional view showing a rotor according to a first embodiment of the present invention. [Figure 2] 2 is a view similar to FIG. 1, but showing an embodiment having at least one connecting passageway. [Figure 3] 3 is a view similar to FIG. 2, but showing an embodiment having at least one connecting passage disposed between the laminated core and the outer peripheral surface of the hollow shaft. [Figure 4] 3 is a view similar to FIG. 2 but showing an embodiment with an alternative flow guide starting centrally within the hollow shaft between the laminated core ends. [Figure 5] FIG. 10 is a front view of a component having different second cooling passages and no balance disk. [Figure 6] FIG. 10 is a detailed view of a component with a constant linear second cooling passage. [Figure 7] 6 is a view similar to FIG. 5, but showing an embodiment in which the second cooling passage is further modified. [Figure 8] 10A-10C show another possible embodiment of a component with a collar. [Figure 9] 9 is a cross-sectional view of a rotor according to the invention comprising the components of FIG. 8; [Figure 10] FIG. 10 is a cross-sectional view similar to FIG. 9 but showing another cross section. [Figure 11] FIG. 11 is a cross-sectional view similar to FIG. 10 but showing an embodiment with coolant flow.

[0025] 1 to 4, a rotor 1 according to the invention for an electric machine 2, for example a traction motor for an electric vehicle (not shown), has a hollow shaft 3 which includes a first cooling passage 4 for a coolant 5. The coolant 5 can be, for example, cooling oil or transmission oil. A laminated core 7, which includes metal plates (not shown in detail), is arranged on the outer circumferential surface 6 of the hollow shaft 3. Two balance discs 8 are arranged on the longitudinal ends of the laminated core 7 to compensate for any imbalance of the rotor 1. Of course, a rotor 1 with only one balance disc 8 of this type is also possible. According to the invention, a component 9 (see also FIGS. 5 to 8 ) made of injection / casting material is arranged between the balance disc 8 and the laminated core 7. This component 9 has at least one second cooling channel 11 (see in particular FIGS. 5 to 7 ) that is open in the axial direction 10 and connected to the first cooling channel 4 in the hollow shaft 3, and which is covered in the axial direction 10 by the balance disc 8 to form a closed cooling channel. Via corresponding outlet openings 19, the coolant 5 can reach and cool the stator windings or stator winding heads 20′. The outlet openings 19 cause the coolant 5 to be discharged substantially radially and / or obliquely, or axially outward. The component 9 surrounds the winding heads 12 of the rotor windings 18 located at the longitudinal ends of the laminated core 7 and simultaneously electrically insulates these winding heads 12. In this case, each winding head 12 is used to deflect a winding wire, e.g., copper wire, and also to electrically connect a rotor winding 18, which will not be described in detail. The electric machine here is therefore an externally excited synchronous machine.

[0026] In general, the outlet openings 19 may be radially open (see openings 22 in Figures 1 to 7 and 11), but may also be axially open, as shown for example in Figures 8 to 11. The openings 22 may be oriented radially or obliquely relative to the axis of the rotor 1.

[0027] Alternatively, the PSM magnets 18' can be arranged on the hollow shaft 3 within the laminated core 7, with the PSM magnets 18' embedded at their longitudinal ends 12' in the injection molding / cast molding compound of the component 9. The injection molding / cast molding compound of the component 9 can hold or fix the PSM magnets 18'. In this case, the coolant 5 can reach the stator winding head 20' through corresponding outlet openings 19 to cool it. Thus, in this case, the electric machine is a permanent magnet synchronous machine. The PSM magnets 18' can also comprise a permanent magnet material containing rare earth metals, such as NdFeB, as known to those skilled in the art.

[0028] Thus, at least one rotor winding 18 (in the case of an externally excited synchronous machine) or permanent magnet 18' (in the case of a permanent magnet synchronous machine) is arranged as an excitation winding on the rotor 1. The stator is provided in each case with a number of stator windings with stator winding heads 20' supplied with alternating current in order to generate a rotating magnetic field.

[0029] The component 9 according to the present invention for injection molding or casting the winding head 12 or longitudinal end 12' of a PSM magnet 18' makes it possible for the first time to easily and yet with high quality produce the passage geometry of the at least one second cooling passage 11 using the plastic injection / casting / overmolding tool used to produce the component 9. The at least one second cooling passage 11 in the component 9 only needs to be formed in the form of a recess or groove, which is covered and thus closed off as a passage by the attachment of the balance disk 8. A major advantage of such a multi-shell second cooling passage 11 is that it allows for the relatively easy realization of almost any cooling passage geometry and almost any cross-section, which was not possible with conventional second cooling passages, which, for example, had to be drilled to extend into the balance disk 8. Furthermore, the component 9 according to the present invention eliminates the need to machine the respective balance disks 8 to realize the second cooling passage 11. This is because the balance disk 8 can be provided as a negative by the injection molding or casting tool used to manufacture the component 9. The manufacture of such a second cooling passage 11 therefore requires only one machining operation in the tool, which is significantly simpler and less costly than the separate machining of each balance disk 8 required to manufacture conventional cooling passages. In this case, the injection / cast molding material for the component 9 can be injection molded through the stacking core 7, so that the two end components 9 are connected to each other, i.e., integrally, via corresponding webs that extend through the stacking core 7 and form the component 9 by casting.

[0030] 1 to 4, it can be seen that the component 9 is conically shaped and has an axial thickness that increases radially outward. Likewise, a ramp 13 is arranged on the balance disc 8, which is formed complementary to the component 9. Of course, non-conical embodiments of the component 9 are also possible, for example, stepped or with a constant axial thickness radially outward.

[0031] The corresponding shape of the injection molding or casting tool can provide the second cooling passage 11 with a constant cross section and, for example, a linear extension, as shown in FIG. 6. According to FIG. 6, the second cooling passage 11 has a groove-like shape. Alternatively, the second cooling passage 11 can have a variable cross section, as shown in FIG. 7 and the corresponding second cooling passage 11 according to FIG. 5. The second cooling passage 11 according to FIG. 7 also has a curved extension. Similarly, the second cooling passage 11 can be configured to be closed radially outward, as indicated by reference numeral 11a in FIG. 5, or open radially outward, as indicated by reference numeral 11. In this case, a second cooling passage 11a closed radially outward has the advantage of better cooling one end face of the rotor and, via this end face, for example, the rotor winding head or the PSM magnet 18′.

[0032] 8 to 11, it can be seen that the component 9 has an at least partially surrounding collar 21. The collar 21 of the component 9 can here surround the balance disc 8, with the outlet openings 19 pointing axially. In this case, the second cooling passage 11 is formed in the area of ​​the collar 21 by the collar 21 and the outer circumferential surface of the balance disc 8 and has an axial section there. The coolant 5 can therefore flow out axially. Due to centrifugal force, the coolant collides there with an axial offset (see FIG. 11), thereby cooling other areas, such as the stator winding heads 20' protruding from the laminated core 7. In this case, the collar 21 has at least one opening 22 or does not completely surround the periphery but has a break through which part of the coolant 5 can flow out, for example, as in the component of FIG. 5, i.e., without axial offset as explained above, thereby providing a better distribution of the coolant 5 throughout the stator.

[0033] In particular, the second cooling channels 11 extending radially outward allow the coolant 5 to flow through the stator winding head 20', which may possibly only absorb a small amount of heat from the rotor 1, which also leads to heat losses (eddy current losses due to field asymmetries and field fluctuations, as well as winding losses during external excitation and possible commutation losses).An additional measure here is the passage 11a (see FIG. 5) which is not open radially outward and through which the coolant 5 flows in order to better cool the rotor 1.

[0034] It can already be seen from this non-limiting list or description that a wide variety of cross-sectional geometries and extensions are possible for the second cooling passage 11, and that each shape requires only a single operation of the injection molding tool or overmolding tool to manufacture.

[0035] Further observation of Figure 1 reveals that two through openings 14 are arranged in the hollow shaft 3, and that each second cooling passage 11 is connected to a first cooling passage 4 provided in the hollow shaft 3 via the through openings 14, and that the refrigerant 5 is supplied to each second cooling passage 11 via this first cooling passage 4.

[0036] In FIG. 2, only one through-opening 14 is provided, through which the coolant 5 is introduced directly into the second cooling channel 11 on the left. However, since the second cooling channel 11 is shown in cross-section, there would normally be several such through-openings 14 distributed around the entire circumference. In the illustrated embodiment, the component 9 is annular, which leaves a radially intervening space 15 between the component 9 and the outer surface 6 of the hollow shaft 3. The component 9 extends over the length of the rotor 1, where the injection molding compound / casting compound is injected through the receptacles (magnet pockets) of the rotor windings 18 or PSM magnets 18′, for example, so that it is injected to the left and flows out again on the right. 2 to 4 and 9, at least one connecting passage 16 through the laminated core 7 is arranged between two cooling passages 11 or between two intermediate chambers 15, so that the coolant 5 flowing from the first cooling passage 4 in the hollow shaft 3 into the intermediate chamber 15 via the through opening 14 is distributed between the second cooling passage 11 and the connecting passage 16. On the right side, the coolant 5 reaches the right-hand intermediate chamber 15 via the connecting passage 16 and from there further radially outward via the second cooling passage 11.

[0037] 3, such a connecting channel 16 is also provided, but in this case it is configured as a groove in the inner circumferential surface of the laminated core 7 and is on the other hand covered by the outer circumferential surface 6 of the hollow shaft 3. The connecting channel 16 here extends between the laminated core 7 and the outer circumferential surface 6 of the hollow shaft 3. In this case, the coolant 5 is fed directly into the connecting channel 16 via through-openings 14, for example holes, and from there in two axial directions 10 into the respective intermediate chambers 15 or into the respective second cooling channels 11. In this case, the intermediate chambers 15 form a component of each second cooling channel 11.

[0038] In the embodiment shown in Fig. 4, connecting channels 16 are likewise provided, but are arranged in the same radial height as the connecting channels 16 shown in Fig. 2. In this case, the coolant 5 is supplied into the connecting channels 16 via connecting channel sections 17 which are connected on the one hand to the first cooling channels 4 via the through openings 14 and on the other hand in fluid communication with the connecting channels 16. This allows for a particularly uniform supply of the coolant 5 to the two oppositely positioned second cooling channels 11, compared to, for example, the embodiment of the rotor 1 according to the invention shown in Fig. 2.

[0039] In this case, the first cooling passage 4 is directly connected to at least one second cooling passage 11 or corresponding intermediate chamber 15 in accordance with FIG. 2, and indirectly connects the left second cooling passage 11 or the left intermediate chamber 15 with at least one oppositely located second cooling passage 11, in this case the right cooling passage 11 or the right intermediate chamber 15, via a connecting passage 16, according to FIG.

[0040] According to the embodiment shown in Figures 3 and 4, the first cooling passage 4 is directly connected only to the connecting passage 16 and is indirectly connected to at least two second cooling passages 11 via the connecting passage 16.

[0041] In this case, common to all embodiments, the hollow shaft 3 is provided with at least one through-opening 14 for communication with the respective intermediate chamber 15 or second cooling channel 11 or channel section 17. The through-opening 14 can be embodied, for example, as a hole.

[0042] The balance disk 8 used can be made of metal, in particular aluminum or stainless steel, which, due to its weight, requires only a small structural height in the axial direction. In conjunction with the arrangement of the second cooling passages 11 between the balance disk 8 and the laminated core 7, a particularly compact structural shape of the rotor 1 in the axial direction 10 can be achieved. Different configurations or arrangements and numbers of the second cooling passages 11 also allow for particularly effective and individually controllable cooling of the rotor 1, in particular of the longitudinal ends 12' of the winding heads 12 or PSM magnets 18', which can increase the performance of an electric machine 2 equipped with such a rotor 1.

[0043] In this case, an axial gap remains between each balance disc 8 and the laminated core 7, forming an intermediate space 15, which advantageously prevents direct contact between the balance discs 8 and the laminated core 7. Since the components 9 are made from an injection / casting material, preferably plastic, it is also possible to make the balance discs 8 from metal, since the components 9 in this case would form an electrical insulator.

[0044] Regardless of the embodiment selected or described, the rotor 1 according to the invention makes it possible to achieve a particularly compact design in the axial direction 10 of the rotor 1, which likewise allows for particularly effective cooling, so that the resulting electric machine 2 is not only compact but also highly efficient.

Claims

1. The rotor (1) of the electrical machine (2), A hollow shaft (3) having a first cooling passage (4) for a refrigerant (5), The laminated core (7) is arranged on the hollow shaft (3), A balance disk (8) is positioned on the longitudinal end side of the laminated core (7) and In a rotor (1) equipped with, A component (9) made of injection molding material / cast molding material is disposed between the balance disc (8) and the laminated core (7), and the component (9) has at least one second cooling passage (11) that is open in the axial direction (10) and connected to the first cooling passage (4) in the hollow shaft (3), and the second cooling passage (11) is covered by the balance disc (8) in the axial direction (10) and forms a cooling passage that is at least partially closed. The component (9) is formed in a conical shape and has an axial thickness that increases radially outward, and an inclined portion (13) formed complementary to the component (9) is arranged on the balance disc (8). A rotor (1) characterized by the following features.

2. A rotor winding (18) with a winding head (12) at the longitudinal end is arranged within the laminated core (7), and the winding head (12) is embedded in the injection molding material / cast molding material of the component member (9), or A PSM magnet (18') is arranged within the laminated core (7), and the PSM magnet (18') is embedded in the injection molding material / cast molding material of the component member (9) at its longitudinal end (12'). The rotor according to claim 1.

3. The at least one second cooling passage (11) has a constant or variable cross-section. The rotor according to claim 1 or 2.

4. The at least one second cooling passage (11) is formed as a cooling passage (11a) that is closed radially outward, or as a cooling passage that is open radially outward, and / or The at least one second cooling passage (11) is formed in a straight or curved manner. The rotor according to claim 1 or 2.

5. A balance disc (8) and a component (9) made of injection molding material / casting material are arranged at each of the two longitudinal ends of the laminated core (7), and each component (9) has at least one second cooling passage (11) that is open in the axial direction (10) and connected to the first cooling passage (4) in the hollow shaft (3), and the second cooling passage (11) is covered by the corresponding balance disc (8) in the axial direction (10). The rotor according to claim 1 or 2.

6. An intermediate chamber (15) is positioned between the balance disk (8) and the laminated core (7). At least one connecting passage (16) is provided between the intermediate chambers (15) that are located opposite each other, or between at least two second cooling passages (11). The rotor according to claim 5.

7. The first cooling passage (4) is directly connected to at least one second cooling passage (11), and is indirectly connected to at least one opposing second cooling passage (11) via the connecting passage (16). The rotor according to claim 6.

8. The first cooling passage (4) is connected only to the connecting passage (16), and is further connected to at least two of the second cooling passages (11) via the connecting passage (16). The rotor according to claim 6.

9. The connecting passage (16) extends within the laminated core (7) or between the laminated core (7) and the hollow shaft (3). The rotor according to claim 6.

10. The balance disc (8) is formed from a metal, particularly aluminum or special steel. The rotor according to claim 1 or 2.

11. The injection molding material / cast molding material is formed from plastic. The rotor according to claim 1 or 2.

12. The aforementioned component (9) has a collar (21) that at least partially surrounds the outer circumference. The rotor according to claim 1 or 2.

13. An electric machine (2), particularly a traction motor, comprising a rotor (1) according to claim 1 or 2.

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