Electric motor

Abstract

The present invention relates to an electric motor (1), in particular a traction motor for driving a vehicle, having a rotor (3) with a stator (2) and a rotor shaft (7) mounted for rotation relative to the stator (2) about an axis of rotation (6). The rotor (3) is mounted on the rotor shaft (7) for common rotation and has a magnetic field generating device (9) for generating a rotor magnetic field at least while the electric motor (1) is in operation. The rotor shaft (7) includes a refrigerant distribution channel (10) coaxial with the axis of rotation (6) and has a refrigerant inlet (12) at an axial shaft end (11) opening into the refrigerant distribution channel (10). Improved cooling can be achieved if the rotor shaft (7) has a first radial outlet opening (17) opening into the refrigerant distribution passages (10) at the first axial device end (15) of the magnetic field generating device (9) such that the refrigerant (13) flows along the first device end (15) when the motor is running, and if the rotor shaft (7) has a second radial outlet opening (18) opening into the refrigerant distribution passages (10) at the second axial device end (16) of the magnetic field generating device (9) such that the refrigerant (13) flows along the second device end (16) when the motor is running.

Description

[Technical field]

[0001] The invention relates in particular to an electric motor which may be a drive motor or a traction motor for driving a vehicle. Preferably, it is a synchronous machine which may be permanently excited or may be externally excited. [Background technology]

[0002] Typically, an electric motor comprises a stator and a rotor rotatable about a rotation axis relative to the stator. During operation of such an electric motor, heat is generated. In the case of powerful electric motors, such as traction motors for example, a large amount of heat is generated in the process, which must be dissipated to avoid overheating of the electric and / or electronic components of the motor. Apart from this, the service life of a component can be substantially extended by cooling it. Therefore, there is a need to realize an efficient cooling method for such electric motors. Summary of the Invention

[0003] The present invention is directed to the problem of describing an improved, or at least different, method for cooling electric motors of the type mentioned above.

[0004] According to the invention, this problem is solved by the subject matter of the independent claims. Preferred embodiments are the subject matter of the dependent claims.

[0005] The invention is based on the general idea of ​​configuring a rotor shaft of a rotor in an electric motor with a stator, a rotor and a cavity such that the rotor shaft comprises a coolant distribution channel which can be supplied with a coolant via an axial coolant inlet during operation of the electric motor. This coolant can be gaseous or liquid. Furthermore, the rotor shaft carries a magnetic field generating device which generates a rotor magnetic field at least during operation of the electric motor. The magnetic field generating device has a first axial device end and a second axial device end. The rotor shaft then comprises at the first axial device end a number of first radial outlet openings which open into or lead to the coolant distribution channel. Separately from this, the rotor shaft comprises at the second axial device end a number of second radial outlet openings which open into or lead to the coolant distribution channel. During operation of the electric motor, the coolant can now exit the coolant distribution channel through the outlet openings and flow along the respective device end. Thus, an efficient cooling of the magnetic field generating device is achieved at the respective device end. Alternatively, the winding tips of the stator windings, which may also be acted upon by the coolant, are typically located at the machine ends.

[0006] The axis of rotation defines a longitudinal direction, i.e. the axial direction of the motor, which extends parallel to the axis of rotation, a radial direction extends perpendicular to the axis of rotation and a circumferential direction extends around the axis of rotation.

[0007] According to a preferred embodiment, the rotor may comprise, at the first device end, a first compensation ring arranged non-rotatably relative to the rotor shaft. The first compensation ring comprises an inflow chamber for each of the first radial outlet openings, which opens into the respective first radial outlet openings, i.e. each first outlet opening leads to a respective first inflow chamber. Furthermore, the rotor comprises, at the second device end, a second compensation ring arranged non-rotatably on the rotor shaft, which comprises a second inflow chamber for each of the second radial outlet openings, which opens into the respective second radial outlet openings, i.e. each second outlet opening leads to a respective second inflow chamber. Thus, during operation of the electric motor, the coolant passes through the outlet openings and enters the inflow chambers. Essentially, in turn, the magnetic field generating device comprises a plurality of first and second cooling channels extending in the axial direction and arranged alternately along the circumferential direction. On the inlet side, the first cooling channels each lead to the first inflow chambers. On the inlet side, the second cooling channels each lead to a second inflow chamber. The first compensation ring now additionally comprises a first outflow chamber between each of the two first inflow chambers in the radial direction, the second cooling channels each lead to a first outflow chamber at the outlet side, the first outflow chambers opening outward in the radial direction, so that the coolant can exit from the respective first outflow chamber there. The second compensation ring comprises a second outflow chamber between each of the two second inflow chambers in the circumferential direction, the first cooling channels each lead to a second outflow chamber at the outlet side, the second outflow chambers opening outward in the radial direction, so that the coolant can exit from the respective second outflow chamber there. During operation of the electric motor, the coolant thus flows from the coolant distribution channels through the radial outlet openings into the inflow chambers, and from the inflow chambers into the cooling channels, and then from the cooling channels into the outflow chambers, from where it then flows out of the rotor. Thus, an effective cooling of the magnetic field generating device is achieved.Alternatively, electronic components of the motor may be arranged on the first compensation ring and / or on the second compensation ring.For example, in a separately excited synchronous machine, the control device for generating the rotor magnetic field can be arranged on the rotor. These components arranged on the respective compensation rings can thus be effectively cooled.

[0008] It is further noted that in the magnetic field generating device, the coolant flows in the first cooling channel in a first axial direction, whereas in the second cooling channel in a second axial direction. A particular advantage with this device is that, during operation of the motor, centrifugal forces act on the first and second inlet chambers due to the rotation of the rotor, as a result of which the coolant is pumped in the desired flow direction. As a result, the motor according to the invention does not require a conveying device or only requires a relatively low-capacity or small-sized conveying device for pumping the coolant for the rotor cooling presented here, which therefore reduces the manufacturing costs and relaxes the installation space requirements.

[0009] According to a preferred further development, the inflow and outflow chambers extend in the circumferential direction and overlap in the respective compensation ring, such that the respective inflow chamber is radially adjacent to the respective outflow chamber on its outer side. Thus, in particular the outflow chambers can be dimensioned relatively large at the respective device end, such that they occupy a relatively large area. This improves the cooling of the respective device end. Apart from this, a relatively high dynamic pressure can thereby be achieved in the region of the inlet of the respective cooling channel, which delivers the coolant to the respective cooling channel, by suitable adaptation to the direction of rotation of the rotor during operation of the electric motor.

[0010] Another further development proposes that the inflow chambers are separated in each compensation ring from the respective outflow chambers by a first and a second separation wall, such that each first and second separation wall defines a respective inflow chamber radially inward and a respective outflow chamber radially outward, the respective separation walls thus forming a common limit for adjacent outflow and outflow chambers, which simplifies the construction of the respective compensation rings.

[0011] According to another further development, each outflow chamber has an outflow opening in each compensation ring, the first and second outflow openings being oriented to open radially and in a circumferential direction opposite to the direction of rotation of the rotor during operation of the electric motor, so that the coolant can preferably exit the respective outflow chamber substantially tangentially. Due to this orientation and positioning of the respective outflow openings, the coolant can also be uniformly delivered to this area by centrifugal forces due to the rotation of the coolant during operation of the electric motor.

[0012] In another further development, the first and second cooling channels can be arranged radially outwardly inside the magnetic field generating device, such that a relatively large radial distance between the cooling channels and the coolant distribution channels is achieved, which correspondingly increases the effective centrifugal force and improves the drive for the coolant.

[0013] It can now be provided that, essentially, inside the respective compensation ring, the cooling channels lead in each case on the outlet side to the region of the outflow opening of the respective outflow chamber. Additionally or alternatively, it can be provided that inside the respective compensation ring, the respective outflow chambers converge in the circumferential direction towards the respective outflow opening, i.e. the cross-sectional area through which the coolant can flow is reduced. These measures promote the flow of the coolant, which improves the efficiency of the cooling.

[0014] In another preferred embodiment, it can be provided that in each compensation ring, the respective inflow chamber diverges from the associated radial outlet opening in the direction of the respective cooling channel, i.e. the cross-sectional area through which the coolant can flow increases. On the one hand, this can facilitate the flow through the respective inflow chamber and on the other hand, in particular due to the dynamic pressure, an increased pressure can be realized on the inlet side of the respective cooling channel.

[0015] Then, certain embodiments are particularly preferred, in which the electric motor is configured as a separately excited electric motor, so that the magnetic field generating device comprises at least one rotor coil for generating the rotor magnetic field. The windings of the rotor coil are wound on a number of circumferentially distributed pole pieces, which are arranged non-rotatably relative to the rotor shaft. The first and second cooling channels can in turn extend in the circumferential direction between adjacent pole pieces inside the magnetic field generating device. Usually, longitudinal grooves are formed in the magnetic field generating device in the circumferential direction between the pole pieces to make it possible to realize the windings. The cooling channels can extend into these longitudinal grooves or be formed by these longitudinal grooves.

[0016] In another embodiment, the electric motor is also separately excited and comprises at least one rotor coil, the windings of which may comprise end windings at the machine end. By directing the coolant along the machine end via the outlet openings, these end windings are intensively cooled. When compensation rings are additionally provided, it may be substantially provided that the inlet chamber and / or the inlet chamber of the first compensation ring and / or the second compensation ring open towards the end windings. The respective chambers may be open along their entire extent. It is likewise conceivable that the wall of the respective compensation ring facing the respective machine end comprises at least one opening in the region of the respective chamber or comprises a plurality of openings by drilling. Thus, a direct action of the end windings by the coolant may also be realized here.

[0017] A separately excited motor may be separately excited in a conductive or inductive manner.

[0018] In an alternative embodiment, the electric motor may be configured as a permanently excited electric motor, so that the magnetic field generating device comprises a plurality of permanent magnets, i.e. for generating the rotor magnetic field. In this case, the magnetic field generating device, which holds the permanent magnets in its body, may comprise a plurality of axially extending flux separation gaps, so-called "flux barriers". These flux separation gaps are respectively arranged between two adjacent permanent magnets in the circumferential direction in order to reduce the magnetic flux passing through the body of the magnetic field generating device between the two permanent magnets. It may now be provided that the first and second cooling channels are essentially formed by these flux separation gaps or in the flux separation.

[0019] Further important features and advantages of the invention emerge from the dependent claims, the drawings and the associated drawing description with which the drawings are used.

[0020] It is to be understood that the features mentioned above or further described below can be used not only in the respective combinations mentioned, but also in other combinations or by themselves, without departing from the scope of the invention. For example, the elements mentioned above or further described below of a higher-level unit such as an individually designed installation, device or arrangement may form separate parts or elements of this unit or may be integrated within or part of this unit, even if shown differently in the drawings.

[0021] Preferred exemplary embodiments of the present invention are illustrated in the drawings and will be described in more detail in the following description, where like reference numbers refer to identical, similar, or functionally identical components. [Brief description of the drawings]

[0022] Each case is shown diagrammatically. [Figure 1] FIG. 1 is a highly simplified longitudinal section of an electric motor. [Diagram 2] FIG. 2 is a highly simplified cross-sectional view of the motor in the region of the first compensation ring according to the section line II of FIG. [Diagram 3] FIG. 3 is a highly simplified cross-sectional view of the motor in the region of the second compensation ring according to the section line III of FIG. [Figure 4] FIG. 4 is a highly simplified cross-sectional view of a rotor sector for a separately excited motor. [Diagram 5] FIG. 5 is a highly simplified cross-sectional view of a rotor sector for a permanently excited motor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] According to Fig. 1, the electric motor 1, which is preferably a drive motor, in particular a traction motor for driving a vehicle, comprises a stator 2 and a rotor 3. The stator 2 is fixed to a housing 4, only partially shown here, and comprises at least one stator coil 5 for generating a stator magnetic field. Relative to the stator 5, the rotor 3 is arranged rotatably about a rotation axis 6. For this purpose, the rotor 3 comprises a rotor shaft 7, which is rotatably mounted in the housing 4, for example by means of a bearing 8. Apart from this, the rotor 3 comprises a magnetic field generator 9, which is configured to generate a rotor magnetic field at least during operation of the electric motor 1.

[0024] The axis of rotation 6 defines a longitudinal or axial direction X, which is indicated by a double-headed arrow in Figure 1 and which extends parallel to the axis of rotation 6. A radial direction Y extends perpendicular to the axis of rotation 6 and is indicated by a double-headed arrow in Figure 1. A circumferential direction U extends around the axis of rotation 6 and is indicated by a double-headed arrow in Figures 2 and 3.

[0025] The rotor shaft 7 comprises here a coolant distribution channel 10 which runs coaxially to the rotation axis 6, in particular in the axial direction. At the axial shaft end 11, the rotor shaft 7 is provided with a coolant inlet 12 which opens into the coolant distribution channel 10. Through the coolant inlet 12, the electric motor 1 or the rotor 3 can be supplied with a liquid or gaseous coolant 13, here indicated by an arrow. An external conveying device 14, here indicated only symbolically, can be used here and can be configured as a pump or a blower. The conveying device 14 is arranged substantially outside the electric motor 1.

[0026] The magnetic field generator 9 has a first axial end 15, which in the embodiment of FIG. 1 is on the side with the coolant inlet 12. Apart from this, the magnetic field generator 9 has a second axial end 16, which is opposite to the first axial end 15. The rotor shaft 7 then has, in the region of the first axial end 15, a number of first radial outlet openings 17, which respectively open into the coolant distribution channels 10, only one of which is shown in the cross-sectional view of FIG. 1. For example, three such first radial outlet openings 17 can be arranged evenly distributed in the circumferential direction U according to FIG. 2. During operation of the electric motor 1, the coolant 13 can flow through these first outlet openings 17 along the first end 15. Apart from this, the rotor shaft 7 is provided in the region of the second device end 16 with a number of second radial outlet openings 18 which also open into the medium distribution channel 10. In the cross-sectional view of FIG. 1, only one of these two outlet openings 18 is shown. For example, three such second outlet openings 18 can be arranged in FIG. 3, evenly distributed in the circumferential direction U. During operation of the electric motor 1, the coolant can flow through these second outlet openings 18 along the second device end 16.

[0027] In some embodiments not shown here, the coolant 13 may exit radially from the first and second exit openings 17, 18 and may flow along the respective device ends 15, 16, cooling them in the process. The coolant 13 may also flow over and cool the windings 19 of the stator coil 5.

[0028] In the preferred embodiment shown here, the rotor 3 is provided on the rotor shaft 7 with a first compensation ring 20 in the region of the first device end 15 and a second compensation ring 21 in the region of the second device end 16, which are arranged non-rotatably relative to the rotor shaft 7. The first compensation ring 20 is provided with a first inlet chamber 22 for each of the first outlet openings 17, which first inlet chamber 22 opens into each of the first outlet openings 17. Similarly, the compensation ring 21 is provided with a second inlet chamber 23 for each of the second outlet openings 18, which second inlet chamber 23 opens into each of the second outlet openings 18.

[0029] The magnetic field generating device 9 comprises a plurality of first cooling channels 24 and a plurality of second cooling channels 25, each extending in the axial direction and arranged alternately along the circumferential direction U. In the cross-sectional view of FIG. 1, the first cooling channels 24 are shown at the bottom and the second cooling channels 25 at the top. Each of the first cooling channels 24 leads to a first inflow chamber 22 of the first compensation ring 20 on the inlet side. Each of the second cooling channels 25 leads to a second inflow chamber 23 of the second compensation ring 21 on the inlet side. The first compensation ring 20 additionally comprises a plurality of first outflow chambers 26, each of which is arranged in the circumferential direction U between two adjacent first inflow chambers 22. Apart from this, each of the second cooling channels 25 leads to such a first outflow chamber 26 on the outlet side. The second compensation ring 21 comprises a number of second outflow chambers 27, which are respectively arranged in the circumferential direction U between two adjacent second inflow chambers 23. Apart from this, each first cooling channel 24 leads at the outlet side to one such second outflow chamber 27. Thus, a below-described path through the rotor 3 is obtained for the coolant 13. According to the first coolant path 28, during operation of the electric motor 1, the coolant 13 flows from the coolant inlet 12 to the coolant distribution channel 10 and from there through the first outlet opening 17 to the first inflow chamber 22. From the first inflow chamber 22, the coolant 13 passes through the first cooling channel 24 and enters the second outflow chamber 27. There, the coolant 13 can thus leave the rotor 3 or from the second compensation ring 21 in the radial direction and act, for example, at the second device end 16 on the winding end 19 of the stator coil 5. According to the second coolant path 29, during operation of the electric motor 1, the coolant 13 flows from the coolant inlet 12 into the coolant distribution channel 10 and from there through the second outlet opening 18 into the second outlet chamber 23. From the second inlet chamber 23, the coolant 13 passes through the second cooling channel 25 and into the first outlet chamber 26. There, the coolant 13 can thus leave radially from the rotor 3 or from the first compensation ring 20 and act, for example, at the first device end 15 on the winding end 19 of the stator coil 5.

[0030] Since the rotor 3 rotates during operation of the electric motor 1, the coolant 13 contained therein therefore rotates with it. The coolant 13 is thus subjected to a centrifugal force. Due to the radial orientation of the inlet chambers 22, 23, this centrifugal force can propel the coolant 13 into the channels 28, 29. The external conveying device 14 can therefore be made with relatively small dimensions or even be omitted.

[0031] In the embodiment shown here, according to Fig. 2 and Fig. 3, three first cooling channels 24 and three second cooling channels 25 are provided, which are arranged alternately along the circumferential direction U. Thus, according to Fig. 2, three first inflow chambers 22 and three first outflow chambers 26 are formed in the first compensation ring 20, which are arranged alternately along the circumferential direction U. Analogously, according to Fig. 3, three second inflow chambers 23 and three second outflow chambers 27 are formed in the second compensation ring 21, which are arranged alternately along the circumferential direction U. According to Fig. 2, the first inflow chambers 22 and the first outflow chambers 26 extend in the circumferential direction U, respectively, in the first compensation ring 20, and the outflow chambers 22 and the outflow chambers 26 overlap in the circumferential direction U. This mutual overlapping thus occurs in such a way that, on its outer side, each first inflow chamber 22 is radially adjacent to the respective first outflow chamber 26, i.e. is arranged radially further inward. It is shown that each first inflow chamber 22 is separated from each first outflow chamber 26 by a first separation wall 30. Each first separation wall 30 defines the associated first inflow chamber 22 radially inward and the associated first outflow chamber 26 radially outward. Each first separation wall 30 starts from a first radial web 31 in the vicinity of the respective first outflow opening 17 and then runs radially outward in a circumferential direction U opposite to the rotor rotation direction 32, which is indicated by an arrow in FIG. 2 and which is realized during operation of the electric motor 1. According to FIG. 2, each first outflow chamber 26 comprises a first outflow opening 33, which opens radially and in a circumferential direction U opposite to the rotation direction 32.

[0032] According to FIG. 3, the second inflow chamber 23 and the second outflow chamber 27 each extend in the circumferential direction U in the second compensation ring 21, the second inflow chamber 23 and the second outflow chamber 27 overlapping each other in the circumferential direction U. This mutual overlap occurs in such a way that the respective second inflow chamber 23 is radially adjacent to the respective second outflow chamber 27 on the outside, i.e. is arranged radially more inward. It is shown that the respective second inflow chamber 23 is separated from the respective second outflow chamber 27 by a second separation wall 34. Each second separation wall 34 defines the associated second inflow chamber 23 radially inward and the associated second outflow chamber 27 radially outward. Each second separation wall 34 starts from a second radial web 35 in the vicinity of the respective second outflow opening 18 and then extends in the circumferential direction U against the direction of rotation 32 of the rotor, while being bent radially outward. This rotor rotation direction 32 is indicated by an arrow in Figure 3, which state is achieved during operation of the electric motor 1. According to Figure 3, each second outlet chamber 27 has a second outlet opening 36 which opens out radially and in a circumferential direction U opposite to the rotation direction 32.

[0033] In the embodiment of Fig. 1, the first cooling channel 24 and the second cooling channel 25 are arranged relatively far outward in the radial direction Y, i.e. at the magnetic field generating device 9. The first cooling channel 24 according to Fig. 2 can thus lead on the outlet side in each case into the region of the second outlet opening 33 of the respective second outlet chamber 26. Analogously to this, the second cooling channel 25 according to Fig. 3 can lead on the outlet side in each case in the region of the second outlet opening 36 of the respective second outlet chamber 27.

[0034] 2 and 3 it is furthermore evident that each first outflow chamber 26 converges in the circumferential direction U towards a respective first outflow opening 33. Similarly, each second outflow chamber 27 converges in the circumferential direction U towards a respective second outflow opening 36. Furthermore, it is provided here that each first inflow chamber 22 diverges from a first radial outlet opening 17 towards a respective first cooling channel 24. Apart from this, each second inflow chamber 23 diverges from a respective second radial outlet opening 18 towards a respective second cooling channel 25.

[0035] Preferably, the electric motor 1 is a synchronous machine configured as a separately excited electric motor 1. Thus, the magnetic field generator 9 comprises at least one rotor coil 37, shown in FIG. 4, which serves to generate a rotor magnetic field during operation of the electric motor 1. In FIG. 4, a winding 38 of the rotor coil 37 is additionally shown, which is wound around a pole piece 39. Each pole piece 39 is part of the magnetic field generator 9. The magnetic field generator 9 comprises a plurality of such pole pieces 39, which are aligned along a circumferential direction U and each carry a winding 38. It may be provided that the first cooling channel 24 and the second cooling channel 25 in turn extend in the circumferential direction U between adjacent pole pieces 39. It may be particularly provided that axial grooves 40 arranged in the circumferential direction U between adjacent pole pieces 39 form or accommodate these cooling channels 24, 25. In FIG. 4, two variants of the first cooling channel 24 and the second cooling channel 25 are shown, respectively, with dashed lines indicating the channels embedded in the body 42 of the magnetic field generating device 9.

[0036] The windings 38 have axial winding ends, illustrated in Fig. 1 and designated by 44. These winding ends 44 are respectively arranged in the region of the device ends 15, 16. It can in turn be provided that the first and second inlet chambers 22, 23 and / or the first and second outlet chambers 26, 27 open axially towards these windings 44, so that the coolant 13 directly impinges on and cools these windings 44.

[0037] However, the electric motor 1 can also be configured as a permanently excited electric motor 1. According to FIG. 5, the magnetic field generator 9 then comprises a plurality of permanent magnets 41, which serve to generate a rotor magnetic field. For this purpose, the permanent magnets 41 are arranged in a body 42 of the magnetic field generator 9, distributed in a circumferential direction U. To increase the power output, the magnetic field generator 9 can comprise a plurality of axially extending flux separation gaps 43, which are formed in the body 42. These flux separation gaps 43 are arranged in the circumferential direction between two adjacent permanent magnets 41 which they form a gap in the body 42, the flux separation gaps 43 blocking the magnetic flux passing through the body 42 at this location. The flux separation gaps 43 can form or house the first and second cooling channels 24, 25. In FIG. 5 two variants for the first cooling channel 24 and the second cooling channel 25, respectively, are reproduced, where dashed lines are used to indicate the channels embedded in the body 42 of the magnetic field generating device 9.

Claims

1. An electric motor (1), The electric motor has a stator (2), The electric motor has a rotor (3) with a rotor shaft (7), the rotor being rotatably mounted about a rotation axis (6) relative to the stator (2); the rotor (3) comprises a magnetic field generating device (9) fixed non-rotatably on the rotor shaft (7), the magnetic field generating device generating a rotor magnetic field at least during operation of the electric motor (1); the rotor shaft (7), coaxial with the axis of rotation (6), includes a refrigerant distribution channel (10) and has a refrigerant inlet (12) at an axial shaft end (11), the refrigerant inlet opening into the refrigerant distribution channel (10); the rotor shaft (7) at a first axial end (15) of the magnetic field generating device (9) is provided with a first radial outlet opening (17) opening into the coolant distribution channel (10), so that the coolant (13) flows along the first axial end (15) during operation of the electric motor (1); the rotor shaft (7) at a second axial end (16) of the magnetic field generating device (9) is provided with a second radial outlet opening (18) opening into the coolant distribution channel (10), so that the coolant (13) flows along the second axial end (16) during operation of the electric motor (1); Electric motor (1).

2. the rotor (3) comprises, at the first axial device end (15), a first compensation ring (20) fixed non-rotatably on the rotor shaft (7), the first compensation ring (20) comprising, for each of the first radial outlet openings (17), a first inlet chamber (22) opening into each of the first radial outlet openings (17); the rotor (3) at the second axial device end (16) is provided with a second compensation ring (21) fixed non-rotatably on the rotor shaft (7), the second compensation ring (21) being provided with, for each of the second radial outlet openings (18), a second inlet chamber (23) opening into each of the second radial outlet openings (18); The magnetic field generating device (9) includes a plurality of first cooling channels (24) and a plurality of second cooling channels (25) extending in an axial direction and arranged alternately along a circumferential direction (U), The first cooling passages (24) each open into the first inlet chamber (22) at an inlet side, The second cooling channels (25) each open at an inlet side into the second inlet chamber (23), The first compensation ring (20) has a first outflow chamber (26) between each of the two first inflow chambers (22) in the circumferential direction (U), the second cooling flow passages (25) communicate with the first outflow chambers (26) at the outlet side, and the first outflow chambers (26) open to the outside in the radial direction, the second compensation ring (21) is provided with a second outflow chamber (27) between each of the two second inflow chambers (23) in the circumferential direction (U), the first cooling flow passages (24) communicate with the second outflow chambers (27) at the outlet side, and the second outflow chambers (27) open to the outside in the radial direction; 2. Electric motor (1) according to claim 1.

3. the first inflow chambers (22) and the first outflow chambers (26) each extend in the circumferential direction (U) and overlap one another, such that each first inflow chamber (22) is radially outwardly adjacent to each first outflow chamber (26); the second inflow chambers (23) and the second outflow chambers (27) each extend in the circumferential direction (U) and overlap each other, so that each second inflow chamber (23) is radially outwardly adjacent to each second outflow chamber (27); 3. Electric motor (1) according to claim 2.

4. The first inlet chambers (22) are each separated from a respective one of the first outlet chambers (26) by a first separation wall (30), the first separation wall (30) defining, radially inwardly, each of the first inlet chambers (22) and, radially outwardly, each of the first outlet chambers (26); the second inlet chambers (23) are each separated from a respective second outlet chamber (27) by a second separation wall (34), the second separation wall (34) defining, radially inwardly, each of the second inlet chambers (23) and, radially outwardly, each of the second outlet chambers (27); An electric motor (1) according to claim 3.

5. the first cooling channel (24) and the second cooling channel (25) are disposed radially outwardly within the magnetic field generating device (9); 3. Electric motor (1) according to claim 2.

6. each of the first outflow chambers (26) comprises a first outflow opening (33) which opens radially and in the circumferential direction (U) opposite to the direction of rotation (32) of the rotor (2) during operation of the electric motor (1); each of the second outlet chambers (27) comprises a second outlet opening (36) which opens radially and in the circumferential direction (U) opposite to the direction of rotation (32) of the rotor (2) during operation of the electric motor (1); 3. Electric motor (1) according to claim 2.

7. the first cooling channels (24) on the outlet side each lead into the second outlet chamber (27) in the region of the second outlet opening (36), the second cooling channels (25) each lead on the outlet side into the region of the first outlet opening (33) of the first outlet chamber (26); An electric motor (1) according to claim 6.

8. each said first outflow chamber (26) converges in said circumferential direction (U) to a respective said first outflow opening (33); each said second outlet chamber (27) converges in said circumferential direction (U) to a respective said second outlet opening (36); An electric motor (1) according to claim 6.

9. Each of the first inlet chambers (22) diverges from the first radial outlet openings (17) into a respective one of the first cooling channels (24); Each of the second inlet chambers (23) diverges from the second radial outlet openings (18) into a respective one of the second cooling channels (25).

3. Electric motor (1) according to claim 2.

10. the electric motor (1) is energized from outside, the magnetic field generating device (9) comprises at least one rotor coil (37) for generating the rotor magnetic field, The windings (38) of the rotor coil (37) are wound around a plurality of pole pieces (39) distributed in the circumferential direction (U), The first cooling channel (24) and the second cooling channel (25) extend in the circumferential direction (U) between adjacent pole pieces (39).

3. Electric motor (1) according to claim 2.

11. the electric motor (1) is energized from outside, the magnetic field generating device (9) comprises at least one rotor coil (37) for generating the rotor magnetic field, the windings (38) of the rotor coil (37) have winding ends (44) at the first axial device end (15) and the second axial device end (16); the first inlet chamber (22) and the second inlet chamber (23), and / or the first outlet chamber (26) and the second outlet chamber (27) open towards the winding end (44); An electric motor (1) according to any one of claims 2 to 10.

12. the electric motor (1) is permanently excited, the magnetic field generating device (9) comprises a plurality of permanent magnets (41) which generate the rotor magnetic field, The magnetic field generating device (9) comprises a plurality of axially extending magnetic flux separation gaps (43), each of which is disposed between two adjacent permanent magnets (41) in the circumferential direction (U); the first cooling channel (24) and the second cooling channel (25) are defined by or extend into the flux separation gap (43); An electric motor (1) according to any one of claims 2 to 9.

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