Electric machine with thermal coupling of the winding heads to a stator support structure by means of ceramic rings

Abstract

Electric machine, - wherein the electric machine has a rotor (3) and a stator stack (2), - wherein the rotor (3) is arranged on a rotor shaft (4) which is supported in bearings (5) so that the rotor (3) and the rotor shaft (4) are rotatable about an axis of rotation (6), - wherein the electric machine has a winding system which, viewed in the direction of the axis of rotation (6), extends from a first winding head (7) via a central section (8) to a second winding head (9), - wherein the central section (8) of the winding system is the section of the winding system which is arranged in the stator stack (2), - wherein the first winding head (7) is the section of the winding system which, viewed in the direction of the axis of rotation (6), extends beyond the stator stack (2) at one axial end, and the second winding head (9) is the section of the winding system which, viewed in the direction of the axis of rotation (6), extends beyond the stator stack (2) at the other axial end, - wherein the stator stack (2) is contacted on its side facing away from the rotor (3) by a support structure (10), - wherein the supporting structure (10) in the direction of the axis of rotation (6) covers not only the stator stack (2) but also the winding heads (7, 9), - wherein a heat conducting device (12, 12') made of a ceramic material is arranged in the area of ​​the winding heads (7, 9), - wherein the respective heat conducting device (12, 12') has at least one base ring (13) arranged between the respective winding head (7, 9) and the support structure (10), and - wherein the respective base ring (13) is under pressure against both the support structure (10) and the respective winding head (7, 9), characterized in that ceramic pieces (22 to 24) are inserted into the winding heads (7, 9).

Description

[0001] The present invention relates to an electric machine, - wherein the electric machine has a rotor and a stator assembly, - wherein the rotor is arranged on a rotor shaft which is supported in bearings, so that the rotor and the rotor shaft can be rotated about an axis of rotation, - wherein the electric machine has a winding system which, viewed in the direction of the axis of rotation, extends from a first winding head via a middle section to a second winding head, - wherein the central section of the winding system is the section of the winding system that is located in the stator stack, - wherein the first winding head is the section of the winding system which, viewed in the direction of the axis of rotation, extends beyond the stator stack at one axial end, and the second winding head is the section of the winding system which, viewed in the direction of the axis of rotation, extends beyond the stator stack at the other axial end, - wherein the stator stack is contacted by a support structure on its side facing away from the rotor, - whereby the supporting structure, viewed in the direction of the axis of rotation, covers not only the stator stack but also the winding heads, - wherein a heat conducting device made of a ceramic material is arranged in the area of ​​the winding heads, - wherein the respective heat conducting device has at least one base ring arranged between the respective winding head and the support structure, and - whereby the respective base ring is under pressure against both the supporting structure and the respective winding head.

[0002] Such an electrical machine is known, for example, from DE 10 2004 026 453 A1 or JP 2002 191 155 A.

[0003] From DE 10 2012 206 442 A1, an electric machine is known which has a rotor and a stator core. The rotor is arranged on a rotor shaft which is supported in bearings, so that the rotor and the rotor shaft are rotatable about an axis of rotation. The electric machine has a winding system which, viewed in the direction of the axis of rotation, extends from a first winding head through a central section to a second winding head. The central section of the winding system is the section of the winding system that is arranged in the stator core. The first winding head projects beyond the stator core at one axial end, viewed in the direction of the axis of rotation, and the second winding head projects beyond the stator core at the other axial end.The stator core is contacted on its side facing away from the rotor by a support structure, which, viewed in the direction of the axis of rotation, covers not only the stator core but also the winding heads. In DE 10 2012 206 442 A1, a receptacle for each winding head is arranged in the area of ​​the winding heads, into which the winding heads are pressed. The receptacles can be provided with a thin ceramic layer on their surfaces facing the winding heads.

[0004] From JP 2007 104 783 A, an electric machine is known that has a rotor and a stator core. The rotor is arranged on a rotor shaft, which is supported in bearings, so that the rotor and the rotor shaft are rotatable about an axis of rotation. The electric machine has a winding system that extends, viewed along the axis of rotation, from a first winding head through a central section to a second winding head. The central section of the winding system is the section of the winding system that is located in the stator core. The first winding head projects beyond the stator core at one axial end, viewed along the axis of rotation, and the second winding head projects beyond the stator core at the other axial end. Structures are arranged in the region of the winding heads that cover them.In the area of ​​each winding head, a heat-conducting device made of a metallic material is arranged, featuring a base ring located between the respective winding head and the support structure. The base ring is under pressure against both the support structure and the respective winding head. Each heat-conducting device also includes an additional ring located on the rotor-facing side of the winding heads, which is also under pressure against the respective winding head.

[0005] From DE 10 2004 023 475 A1, an electric machine is known which has a rotor and a support structure. The rotor is arranged on a rotor shaft which is supported in bearings, so that the rotor and the rotor shaft are rotatable about an axis of rotation. The electric machine has a winding system which, viewed in the direction of the axis of rotation, extends from a first winding head via a central section to a second winding head. The central section of the winding system is the section of the winding system that is arranged in the support structure. The first winding head projects beyond the support structure at one axial end of the stator stack, viewed in the direction of the axis of rotation, and the second winding head projects beyond the support structure at the other axial end of the support structure. The support structure is not a stator stack, as it is made of a non-magnetic material.The support structure is contacted on its side facing away from the rotor by another support structure, whereby this support structure, viewed in the direction of the axis of rotation, covers not only the first support structure but also the winding heads.

[0006] In electric machines, losses typically occur in both the stator and the rotor during operation. Stator losses generally consist of winding losses and remagnetization losses. Winding losses arise within the winding due to its ohmic resistance. Remagnetization losses result from the continuous remagnetization within the stator core. Remagnetization losses also occur in the rotor laminations. Depending on the machine type, eddy current losses in permanent magnets or current losses in a rotor cage or rotor winding may also occur.

[0007] In the stator winding, losses in the winding heads are a particular limiting factor, as their less efficient connection to the stator core means they are cooled less effectively than the central part of the winding, which is embedded within the core. Especially in highly utilized electric machines, such as those commonly used in electromobility, these losses must be dissipated and cooled away as efficiently and quickly as possible. Furthermore, electrical insulation between the different phases and layers of the winding must be ensured within the winding head.

[0008] In the prior art, the stator core, including the stator winding, is often cooled by means of water cooling. For this purpose, in a typical internal rotor motor, cooling channels are incorporated into a housing that radially surrounds the stator core. These channels are integrated into a cooling circuit. The winding is usually impregnated and / or dripped with resin. However, the impregnating resin has very low thermal conductivity. To improve the thermal connection of the winding ends, the winding ends are partially potted to improve heat dissipation to the housing and thus to the liquid cooling circuit. However, the potting materials used (usually resins) have a thermal conductivity of only a few W / mK. Therefore, even with this design, the winding ends represent the hotspots in the electric machine. Insulating paper is generally used to separate the phases and layers from each other.

[0009] The object of the present invention is to create possibilities by means of which improved cooling, in particular of the winding heads, can be achieved.

[0010] The problem is solved by an electric machine with the features of claim 1. Advantageous embodiments of the electric machine according to the invention are the subject of dependent claims 2 to 11.

[0011] According to the invention, an electric machine of the type mentioned above is designed by inserting ceramic pieces into the winding heads. This improves the heat transfer from the interior of the respective winding head to the respective heat conducting device.

[0012] Ceramic materials can exhibit relatively high thermal conductivity, with values ​​of up to 300 W / mK possible. This alone improves heat dissipation from the winding heads. Furthermore, the heat transfer is better the more tightly the heat-conducting elements are pressed against the respective winding head and the support structure. Because the base ring is under pressure against both the support structure and the winding head (i.e., clamped in the space between the winding head and the support structure), the heat transfer from the winding head to the heat-conducting element and from there to the support structure is further enhanced.

[0013] In a preferred embodiment of the electric machine, the base rings are divided into segments, each of which, viewed tangentially around the axis of rotation, covers only a portion of a full circle. This segmentation often makes it easier to insert the individual segments of the base rings into the space between the respective winding head and the support structure. The size of the segmentation can be determined as required. For example, the segments can cover 180°, 120°, 90°, 72°, 60°, or 45°. It is also possible to divide the machine into even more segments, resulting in an even smaller coverage angle per segment. Furthermore, all segments typically cover the same angle when viewed around the axis of rotation. However, in certain cases, it may be advantageous for the segments to cover a different angle.

[0014] In a further preferred embodiment, the heat-conducting devices each have an additional ring arranged on the side of the winding heads facing the rotor, which bears radially against the respective winding head under pressure. This design allows, in particular, the effective pressure on the base rings to be maximized. Furthermore, the area over which the respective heat-conducting device bears against the respective winding head can be increased.

[0015] Analogous to the base rings, in a preferred embodiment of the electric machine, the auxiliary rings are also divided into segments, each of which, viewed tangentially around the axis of rotation, covers only a portion of a full circle. This segmentation often makes it easier to insert the individual segments of the auxiliary rings into the space between the respective winding head and the rotor or rotor shaft. The size of the segmentation can be determined as required. The above explanations regarding the division of the base rings apply analogously.

[0016] In a further preferred embodiment, the heat-conducting devices each have an intermediate ring extending from the respective base ring towards the rotor, such that the base ring and the intermediate ring of the respective heat-conducting device have an L-shape, and the intermediate ring rests against the respective winding head when viewed in the direction of the axis of rotation. This design allows the area over which the respective heat-conducting device rests against the respective winding head to be increased.

[0017] If the additional rings are also present, the respective additional ring and the respective base ring can be connected to each other via the respective intermediate ring. This allows – at least in some configurations – the three individual rings of the respective heat-conducting device – the respective base ring, the respective additional ring, and the respective intermediate ring – to be mounted as a unit.

[0018] Analogous to the base rings and the additional rings, in a preferred embodiment of the electric machine the intermediate rings are also divided into segments, each of which, viewed tangentially around the axis of rotation, covers only a portion of a full circle. This segmentation often makes it easier to assemble the individual segments of the intermediate rings. The size of the segmentation can be determined as required. The above explanations regarding the division of the base rings and the additional rings apply analogously.

[0019] The segmentation of the individual rings of the respective heat-conducting device can, in principle, be selected independently of one another. However, the same segmentation is usually chosen. In particular, if the base rings, intermediate rings, and additional rings are all present, the individual segments will have a U-shape.

[0020] In a further preferred embodiment of the present invention, a portion of the ceramic pieces is mechanically connected to the respective heat conducting device. This allows the heat transfer from the respective winding head to be optimized not only to, but even into, the respective heat conducting device.

[0021] The ceramic material used for the heat-conducting elements can be selected as required. In particular, the ceramic material used for the heat-conducting elements can be a glass ceramic, an aluminum nitride, and / or an aluminum oxide.

[0022] Preferably, the winding heads, together with their respective heat-conducting devices, are encapsulated with a potting compound. This improves heat transfer within the winding heads and the thermal coupling of the winding heads to the heat-conducting devices.

[0023] Preferably, fluid channels containing a liquid coolant for the electric machine are arranged in the support structure or between the support structure and the stator assembly. This design improves heat dissipation from the housing.

[0024] The properties, features, and advantages of this invention described above, as well as the manner in which they are achieved, will become clearer and more readily understandable in connection with the following description of the exemplary embodiments, which are explained in more detail in conjunction with the drawings. These drawings show, in schematic representation: Fig. 1 a longitudinal section through an electric machine, Fig. 2 a section of the longitudinal section of Fig. 1, Fig. 3 a cross-section through the electric machine of Fig. 1 along a line III-III in Fig. 1, Fig. 4 a section of a longitudinal section through an electric machine, Fig. 5 a cross-section through the electric machine of Fig. 1 along a VV line in Fig. 4, Fig. 6 a section of a longitudinal section through an electric machine, Fig. 7 a cross-section through the electric machine of Fig. 5 along a line VII-VII in Fig. 6 and Fig. 8 a section of a longitudinal section through an electric machine.

[0025] According to Fig. Figure 1 comprises an electrical machine, generally designated by reference numeral 1, comprising a stator core 2 and a rotor 3. The rotor 3 is arranged on a rotor shaft 4, which in turn is supported in bearings 5. The rotor 3 and the rotor shaft 4 are thus rotatable about an axis of rotation 6. The stator core 2 surrounds the rotor 3 radially. The electrical machine 1 is therefore designed as an internal rotor motor. However, the electrical machine 1 could also be designed as an external rotor motor. In this case, the stator core 2 is arranged radially inside the rotor 3.

[0026] Insofar as the terms axial, radial, and tangential are used above and below, they always refer to the axis of rotation 6. Axial is a direction parallel to the axis of rotation 6. Radial is a direction orthogonal to the axis of rotation 6, either towards or away from it. Tangential is a direction that is orthogonal to both the axial and radial directions. Tangential thus means a direction that, with a constant axial position and at a constant radial distance from the axis of rotation 6, is circular around the axis of rotation 6.

[0027] The electric machine 1 has a winding system. The winding system consists of interconnected windings. It extends – see also Fig. 2 - in the axial direction from a first winding head 7 via a central section 8 to a second winding head 9. The central section 8 of the winding system is the section of the winding system that is located in the stator core 2. The first winding head 7 is the section of the winding system that, viewed in the axial direction, projects beyond the stator core 2 at one axial end. Similarly, the second winding head 9 is the section of the winding system that, viewed in the axial direction, projects beyond the stator core 2 at the other axial end.

[0028] Stator package 2 is configured according to the Fig. 1 and Fig. 2 is contacted on its side facing away from the rotor 3 by a support structure 10. In the case of an external rotor, the stator stack 2 is thus radially surrounded on the outside by the support structure 10. In the case of an internal rotor, the support structure 10 is arranged radially inside the stator stack 2. Viewed axially, the support structure 10 covers not only the stator stack 2 but also the winding ends 7, 9. Preferably, the electric machine 1 is further designed as a liquid-cooled electric machine. In this case, as shown in the illustration in Fig. Fluid channels 11 are arranged in the support structure 10, containing a liquid coolant for the electric machine 1. The liquid coolant can be, in particular, water. Alternatively, the fluid channels 11 can be arranged between the support structure 10 and the stator stack 2.

[0029] According to the Fig. 1, Fig. 2 to Fig. In the area of ​​the first winding head 7, a heat conducting device 12 is arranged. The heat conducting device 12 consists of a ceramic material. The ceramic material is selected to be electrically insulating, magnetically neutral, and to have high thermal conductivity. For example, the ceramic material can have a thermal conductivity between 20 and 300 W / mK (watts per meter and Kelvin). Examples of materials that meet these properties are glass ceramics, aluminum nitrides, and aluminum oxides. Mixtures of these materials are also possible.

[0030] Fig. Figure 2 shows a minimal design of the heat conducting device 12. According to Fig. 2 The heat conducting device 12 has a base ring 13. The base ring 13 is arranged between the first winding head 7 and the support structure 10. The base ring 13 is clamped between the support structure 10 and the first winding head 7. It is therefore under pressure against both the support structure 10 and the first winding head 7. The pressure is in Fig. 2 symbolized by arrows 14.

[0031] The base ring 13 is preferably arranged according to the illustration in Fig. The area is divided into 3 segments of 15. Each segment of 15 covers only a portion of a full circle in the tangential direction. The representation in Fig. Figure 3, in which segments 15 each cover an angle α of 45°, is purely exemplary. Other angles are also possible.

[0032] Fig. 4 shows in conjunction with Fig. 5 An advantageous embodiment of the electric machine 1. In this embodiment, the heat conducting device 12 has an additional ring 16 besides the base ring 13. In the case of an internal rotor, the additional ring 16 is arranged radially inside the first winding head 7. In the case of an external rotor, the additional ring 16 is arranged radially outside the first winding head 7. Generally speaking, the additional ring 16 is arranged on the side of the first winding head 7 facing the rotor 3; the additional ring 16 is in contact with the first winding head 7 under pressure. This is in Fig. 4 symbolized by arrows 17.

[0033] The additional ring 16 is preferably arranged according to the illustration in Fig. 5 is also subdivided into segments 18. Each segment 18 also covers only a portion of a full circle in the tangential direction. The representation in Fig. Figure 5, in which the segments 15 each cover an angle β of 45°, is purely exemplary. Other angles are also possible. As a rule, the angle β for the segments 18 of the additional ring 16 is identical to the angle α for the segments 15 of the base ring 13. However, this is not always mandatory.

[0034] The Fig. 6 and Fig. Figure 7 shows a further preferred embodiment of the electric machine 1. Within the framework of the embodiment according to the Fig. 6 and Fig. In addition to the base ring 13, the heat conducting device 12 has an intermediate ring 19. The intermediate ring 19 extends from the base ring 13 towards the rotor 3. The base ring 13 and the intermediate ring 19 thus have an L-shape. Viewed axially, the intermediate ring 19 rests against the first winding head 7. Preferably, the intermediate ring 19 rests against the first winding head 7 under pressure. This is in Fig. 6 is symbolized by arrows 20.

[0035] It is possible that the intermediate ring 19 corresponds to the representation in Fig. 7 is also subdivided into segments 21. In this case, the segments 21 also each cover only a portion of a full circle in the tangential direction. The representation in Fig. Figure 7, in which the segments 15 each cover an angle γ of 180°, is purely exemplary. Other angles are also possible. In particular, the angle γ for the segments 21 of the intermediate ring 19 can be different from the angle α for the segments 15 of the base ring 13. However, they can also be the same angle.

[0036] Fig. Figure 8 shows an advantageous embodiment which improves the design of the Fig. 4 and Fig. 5 on the one hand, and 6 and 7 on the other, are combined with each other. In the design according to Fig. In addition to the base ring 13, both the auxiliary ring 16 and the intermediate ring 19 are present. In this case, the auxiliary ring 16 and the base ring 13 are preferably connected to each other via the intermediate ring 19. It is possible that the intermediate ring 19 is undivided despite the subdivision of the base ring 13 and / or the auxiliary ring 16 into segments 15 and 18. Alternatively, as explained above, the intermediate ring 19 can also be subdivided into segments 21. It can be advantageous if the subdivision into segments 15, 18, and 21 is uniform for the base ring 13, the auxiliary ring 16, and the intermediate ring 19. In this case, the heat-conducting device 12 can be composed of several U-shaped pieces, each consisting of a segment 15 of the base ring 13, a segment 18 of the auxiliary ring 16, and a segment 21 of the intermediate ring 19.

[0037] Fig. 2, Fig. 4, Fig. 6 and Fig. Figure 8 also shows an essential embodiment of the electric machine 1 according to the invention. In particular, ceramic pieces 22 to 24 are inserted into the first winding head 7. The ceramic pieces 22 to 24 can be made of the same material as the heat conducting device 12. It is possible that the ceramic pieces 22 to 24 are inserted into the first winding head 7 independently of the heat conducting device 12. This alone has the advantage that rapid heat transfer to the heat conducting device 12 takes place within the first winding head 7. Preferably, as shown in the illustrations in the Fig. 2, Fig. 4, Fig. 6 and Fig. However, a portion of the ceramic pieces 22 to 24 are mechanically connected to the heat conducting device 12. This improves the heat transfer into the heat conducting device 12. Furthermore, the phases and layers of the winding system can also be insulated from each other by means of the ceramic pieces 22 to 24.

[0038] For optimal thermal coupling of the first winding head 7 to the heat conducting device 12, the first winding head 7 is preferably potted together with the heat conducting device 12 using a potting compound 25. Suitable potting compounds 25 are generally known to those skilled in the art.

[0039] The present invention has been explained above in connection with the first winding head 7. The design of the second winding head 9 is analogous. In particular, a heat conducting device 12' is also provided in the second winding head 9. The design of the heat conducting device 12' is completely analogous to the design of the heat conducting device 12. Furthermore, ceramic pieces are also inserted into the second winding head 9.

[0040] The present invention has many advantages. In particular, the heat-conducting devices 12, 12' enable a significantly improved thermal connection of the winding heads 7, 9 to the support structure 10. Temperature differences between the central section 8 of the winding system and the winding heads 7, 9 of the winding system can be avoided or at least reduced. The current-carrying capacity of the winding system as a whole, and thus the achievable continuous power of the electric machine 1, can be increased to the extent that the current-carrying capacity is limited by the possibility of heat dissipation from the winding heads 7, 9. Since the heat-conducting devices 12, 12' are electrically non-conductive, no eddy currents are generated in them, so that the electromagnetic behavior of the electric machine 1 is not affected by the heat-conducting devices 12, 12'.

[0041] Although the invention has been illustrated and described in detail by the preferred embodiment, the invention is not limited by the disclosed examples and other variations can be derived by the person skilled in the art without leaving the scope of protection of the invention.

Claims

[1] Electric machine, - wherein the electric machine has a rotor (3) and a stator stack (2), - wherein the rotor (3) is arranged on a rotor shaft (4) which is supported in bearings (5) so that the rotor (3) and the rotor shaft (4) are rotatable about an axis of rotation (6), - wherein the electric machine has a winding system which, viewed in the direction of the axis of rotation (6), extends from a first winding head (7) via a central section (8) to a second winding head (9), - wherein the central section (8) of the winding system is the section of the winding system which is arranged in the stator stack (2), - wherein the first winding head (7) is the section of the winding system which, viewed in the direction of the axis of rotation (6), extends beyond the stator stack (2) at one axial end, and the second winding head (9) is the section of the winding system which, viewed in the direction of the axis of rotation (6), extends beyond the stator stack (2) at the other axial end, - wherein the stator stack (2) is contacted on its side facing away from the rotor (3) by a support structure (10), - wherein the supporting structure (10) in the direction of the axis of rotation (6) covers not only the stator stack (2) but also the winding heads (7, 9), - wherein a heat conducting device (12, 12') made of a ceramic material is arranged in the area of ​​the winding heads (7, 9), - wherein the respective heat conducting device (12, 12') has at least one base ring (13) arranged between the respective winding head (7, 9) and the support structure (10), and - wherein the respective base ring (13) is under pressure both on the support structure (10) and on the respective winding head (7, 9), characterized by , that ceramic pieces (22 to 24) are inserted into the winding heads (7, 9). [2] Electric machine according to claim 1, characterized by , that the base rings (13) are divided into segments (15) which, viewed tangentially around the axis of rotation (6), each cover only a part of a full circle. [3] Electric machine according to claim 1 or 2, characterized by , that the heat conducting devices (12, 12') each have an additional ring (16) which is arranged on the side of the winding heads (7, 9) facing the rotor (3) and is radially pressurized against the respective winding head (7, 9). [4] Electric machine according to claim 3, characterized by , that the additional rings (16) are divided into segments (18) which, viewed tangentially around the axis of rotation (6), each cover only a part of a full circle. [5] Electric machine according to any one of the above claims, characterized by , that the heat conducting devices (12, 12') each have an intermediate ring (19) which extends from the respective base ring (13) towards the rotor (3), so that the base ring (13) and the intermediate ring (19) of the respective heat conducting device (12) have an L-shape, and the intermediate ring (19) is in contact with the respective winding head (7, 9) when viewed in the direction of the axis of rotation (6). [6] Electric machine according to claim 5 in combination with claim 3 or 4, characterized by , that the respective additional ring (16) and the respective base ring (13) are connected to each other via the respective intermediate ring (19). [7] Electric machine according to claim 5 or 6, characterized by , that the intermediate rings (19) are divided into segments (21) which, viewed tangentially around the axis of rotation (6), each cover only a part of a full circle. [8] Electric machine according to any one of the above claims, characterized by , that part of the ceramic pieces (22 to 24) is mechanically connected to the respective heat conducting device (12, 12'). [9] Electric machine according to any one of the above claims, characterized by , that the ceramic from which the heat conducting devices (12, 12') are made is a glass ceramic, an aluminium nitride and / or an aluminium oxide. [10] Electric machine according to any one of the above claims, characterized by , that the winding heads (7, 9) together with their respective heat conducting device (12, 12') are encased in a potting compound (25). [11] Electric machine according to any one of the above claims, characterized by, that fluid channels (11) are arranged in the support structure (10) or between the support structure (10) and the stator stack (3), in which a liquid coolant for the electric machine is located.

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