Rotor of an electric machine with built-in magnets

Abstract

The present invention relates to a rotor (1) of an electric machine (10) with a rotor shaft (3) rotatable about a rotor axis (100) and a rotor body (2) arranged on the rotor shaft (3), which is in particular designed as a rotor lamination stack made of stacked laminations (4), wherein a shaft cooling channel (13) runs in the rotor shaft (3) and wherein at least one magnet pocket (5) for receiving a permanent magnet unit (6) is formed in the rotor body (2), wherein the permanent magnet unit (6) has an axial direction (200) oriented along the rotor axis (100) as well as a width direction (300) and a thickness direction (400), wherein the permanent magnet unit (6) is composed at least in certain regions along the width direction (300) and along the thickness direction (400) of at least two individual magnets (7a, 7b), which are in particular permanent magnets, characterized in that there is a separation between individual magnets (7a,7b) of the permanent magnet unit (6) at least one gap (9) is formed which extends along the axial direction (200) through the permanent magnet unit (6) and which is bounded both along the width direction (300) and along the thickness direction (400) by the individual magnets (7a, 7b) in order to form a magnetic cooling channel (8) extending in the axial direction (200), which is fluidically connected to the shaft cooling channel (13) and is designed for cooling the permanent magnet unit (6).

Description

State of the art The present invention relates to a rotor of an electric machine. The invention also relates to an electric machine with such a rotor. The rotor has integrated magnets. This means, in particular, that the magnets are composed of several individual magnets. Permanent magnet synchronous machines (PMMs) often use neodymium-based magnets alloyed with heavy rare earth elements, such as dysprosium and terbium. These heavy rare earth elements can be introduced via diffusion to improve their effectiveness and reduce wear. However, the amount of heavy rare earth elements required for diffusion increases with the thickness of the magnets. Furthermore, it is known that PWM losses in the magnet increase with its size. The prior art includes, on the one hand, segmented magnets, as described, for example, in DE 10 2010 002 786 A1. In this concept, several magnets per pole are attached separately to a rotor body. On the other hand, the prior art includes built-up magnets, as described, for example, in JP 2010 183791 A1. This document discloses a method for manufacturing divided permanent magnets that facilitates the formation of insulating layers between the individual permanent magnet pieces, even when the number of permanent magnet pieces is increased. Disclosure of the invention The rotor according to the invention allows a magnetic cooling channel to be formed in the magnets used, thereby enabling effective cooling of the magnets. The resulting lower magnet temperatures during rotor operation mean that less heavy rare earth elements are required to prevent demagnetization. For example, the magnets can be cooled using an oil or other cooling fluid. The rotor of an electric machine comprises a rotor shaft rotatable about a rotor axis and a rotor body arranged on the rotor shaft. The rotor body is typically designed as a lamination stack of stacked sheet metal lamellae. The electric machine in question is, for example, a permanent magnet synchronous machine. A shaft cooling channel is preferably formed in the rotor shaft. The shaft cooling channel preferably extends in the axial direction with respect to the rotor axis. At least one magnet pocket for receiving a permanent magnet unit is formed in the rotor body. The permanent magnet unit has an axial direction oriented along the rotor axis, as well as a width direction and a thickness direction. The permanent magnet unit is composed of at least two individual magnets, at least partially along its width and at least partially along its thickness. The individual magnets are, in particular, permanent magnets. The individual magnets are, in particular, manufactured separately from one another and assembled to form the permanent magnet unit. At least one gap is formed between the individual magnets of the permanent magnet unit. This gap extends axially through the permanent magnet unit with respect to the rotor axis. The gap is bounded by the individual magnets in both the width and thickness directions. This creates a magnetic cooling channel extending axially with respect to the rotor axis. This magnetic cooling channel is fluidically connected to the shaft cooling channel and serves to cool the permanent magnet unit. This enables direct cooling of the permanent magnets, effectively protecting them from high temperatures and minimizing the risk of demagnetization. The permanent magnet unit has the advantage of allowing segmentation instead of a single solid magnet. This segmentation enables a cooling slot, which would not be possible with solid magnets. The cooling system keeps the permanent magnet unit at a lower temperature than would be the case with a solid magnet. This allows for a reduction in heavy rare earth elements for the same demagnetizing load, resulting in a better CO2 balance and lower costs. Furthermore, segmentation along the thickness direction results in thinner individual magnets. This additionally and generally reduces the use of metals such as terbium or dysprosium. These metals diffuse into the magnets, which, at lower thicknesses, leads to material savings due to shorter diffusion times. Furthermore, segmentation also leads to a reduction in magnetic losses. The dependent claims describe preferred embodiments of the invention. Preferably, the permanent magnet unit comprises first and second individual magnets. The first individual magnets have a first cross-section, and the second individual magnets have a second cross-section. The second cross-section is preferably a partial cross-section of the first cross-section. The respective gap is formed between adjacent second individual magnets. Advantageously, the second individual magnets are arranged side by side along a direction selected from either the width direction or the thickness direction. The second individual magnets are, in particular, arranged between the first individual magnets in the other of the two directions. The second set of individual magnets is preferably arranged side by side in the width direction. The first set of individual magnets has the width of the permanent magnet unit in the width direction. The second set of individual magnets, arranged side by side in the width direction, together have, in particular, the width of the permanent magnet unit. This means that the width of the arrangement of the second set of individual magnets corresponds to the width of the permanent magnet unit. The width of the arrangement of the second set of individual magnets is, in particular, determined by the width dimension of the second set of individual magnets and by the width dimension of the gap between the second set of individual magnets. It is provided that the height of the first and second set of individual magnets is, in particular, the same. The height is, in particular, the dimension in the thickness direction. In a further preferred embodiment, the first individual magnets have the same thickness in the thickness direction as the permanent magnet unit. Furthermore, the second individual magnets, arranged side by side in the thickness direction, together have the same thickness as the permanent magnet unit. This means that the thickness of the arrangement of the second individual magnets corresponds to the thickness of the permanent magnet unit. The thickness of the arrangement of the second individual magnets is determined in particular by the dimension of the second individual magnets in the thickness direction and by the dimension of the gaps between the second individual magnets in the thickness direction. In particular, it is provided that the width dimension of the first and second individual magnets is the same in the width direction. Preferably, the gap between the individual magnets forming the gap is less than 1.0 mm, more preferably a maximum of 0.5 mm, and particularly preferably a maximum of 0.2 mm. Alternatively or additionally, the gap is at least 0.1 mm. These dimensions minimize any negative impact on the magnetic flux. Simultaneously, reliable cooling of the permanent magnets can be achieved by passing a cooling fluid through the gap. The permanent magnet unit is preferably clamped in the respective magnetic pocket, avoiding any gap. Avoiding a gap optimizes the magnetic flux. Alternatively or additionally, the permanent magnet unit is preferably glued into the magnetic pocket. This gluing is achieved particularly using a molding compound or resin. The permanent magnet unit preferably comprises several individual magnets along the axial direction of the rotor axis. The individual magnets are positioned identically, particularly with respect to their width and thickness. This makes it especially easy to implement a series of magnets in the axial direction. The individual magnets of the permanent magnet unit are preferably bonded together by a material-bonded connection. In particular, the individual magnets are glued together. This gives the permanent magnet unit high stability. Furthermore, the respective magnet cooling channel is reliably designed. Adjacent to one or both axial ends of the rotor body, an end disk is arranged. The end disk is, in particular, a plastic disk. Each magnetic cooling channel is fluid-connected to the rotor shaft's cooling channel via a flow connection in the end disk. This allows the magnetic cooling channels to be connected to the cooling channel, enabling the flow of cooling fluid from the cooling channel to cool the permanent magnets in the respective magnetic cooling channel. The end disk is, in particular, a balancing disk. Alternatively or additionally, a feed disk is arranged in the axial center of the rotor body. Each magnetic cooling channel is fluid-connected to the rotor shaft's cooling channel via a flow connection in the feed disk. This allows for a central supply of the cooling fluid. The cooling fluid is transported axially outwards through the magnetic cooling channels.From there, the cooling fluid can, for example, be sprayed onto the winding heads of a stator winding. The invention also relates to an electric machine. In particular, the electric machine is a permanent magnet synchronous machine. The electric machine has a rotor as described above and a stator. The stator comprises an electrical winding for driving the rotor. During operation of the electric machine, the permanent magnets of the rotor heat up. The heating of the permanent magnets can be counteracted by forming magnetic cooling channels in the permanent magnet units. This minimizes, in particular, the risk of demagnetization due to overheating. Brief description of the drawings Exemplary embodiments of the invention are described in detail below with reference to the accompanying drawings. In the drawing: Fig. 1 is a schematic view of an electric machine according to an exemplary embodiment of the invention; Fig. 2 is a schematic view of a rotor pole of a rotor of the electric machine according to the exemplary embodiment of the invention; Fig. 3 is a schematic view of a first alternative permanent magnet unit of the rotor of the electric machine according to the exemplary embodiment of the invention; Fig. 4 is a schematic view of a second alternative permanent magnet unit of the rotor of the electric machine according to the exemplary embodiment of the invention; Fig. 5 is a schematic view of a third alternative permanent magnet unit of the rotor of the electric machine according to the exemplary embodiment of the invention; and Fig.6 a schematic illustration of the manufacture of a permanent magnet unit of the rotor of the electric machine according to the embodiment of the invention. Embodiments of the invention Preferably, all identical components, elements and / or units in all figures are provided with the same reference numerals. Fig. 1 schematically shows an electric machine 10, which in the illustrated embodiment is a permanent magnet synchronous machine. The electric machine has a rotor 1 and a stator 11 with an electrical winding for driving the rotor 1. The rotor 1 has a rotor shaft 3 rotatable about a rotor axis 100. A shaft cooling channel 13 is located in the rotor shaft 3. The rotor 1 also has a rotor body 2, which is arranged on the rotor shaft 3. The rotor body 2 is specifically designed as a rotor lamination stack made of stacked laminations 4. The rotor body 2 has at least one magnetic pocket 5 for receiving a permanent magnet unit 6. In the illustrated embodiment, several magnetic pockets 5 are provided, each magnetic pocket 5 receiving a permanent magnet unit 6. The permanent magnet units 6 each form a magnetic cooling channel 8, which will be described later. The magnetic cooling channel 8 serves to directly cool the permanent magnet unit 6. An end disk 12 is arranged at each of the two axial ends 4a of the rotor body 4. Alternatively, it would also be possible to provide an end disk 12 at only one axial end 4a. The end disk 12 is, for example, a plastic disk, in particular a balancing disk. Each magnetic cooling channel 8 is fluid-connected to the shaft cooling channel 13 of the rotor shaft 3 via a flow connection 12a in the end disk 12. Thus, a cooling fluid can flow from the shaft cooling channel 13 into the magnetic cooling channels 8. The end disks 12 preferably also have a coolant outlet 12b, which is designed to remove the cooling fluid from the magnetic cooling channels 8. Alternatively, the cooling fluid can also be removed by splashing from the magnetic cooling channels 8. A further alternative could also be arranged centrally in the rotor body 4. Each magnetic cooling channel 8 is fluid-connected to the shaft cooling channel 13 via a flow connection in the feed disk.The cooling fluid is then transported axially outwards through the magnetic cooling channels 8. Fig. 2 schematically shows a rotor pole of rotor 1. The rotor pole has two magnet pockets 5 arranged in a V-shape. Thus, there are two permanent magnet units 6 per rotor pole. The permanent magnet units 6 are arranged symmetrically about a rotor pole center axis 500. The permanent magnet unit 6 has an axial direction 200, which is oriented along the rotor axis 100, as well as a width direction 300 and a thickness direction 400. To improve the magnetic flux, the permanent magnet unit 6 is clamped in the respective magnet pocket 5, avoiding a gap. Alternatively (shown with dashed lines), the magnet pockets 5 can also be larger than the permanent magnet units 6. In this case, the permanent magnet unit 6 is bonded into the respective magnet pocket 5, for example, using molding compound and / or resin.The permanent magnet unit 6 is composed, at least in part along the width direction 300 and along the thickness direction 400, of at least two individual magnets 7a, 7b. In the illustrated embodiment, the individual magnets are permanent magnets. A gap 9 is formed between two individual magnets 7a, 7b of the permanent magnet unit 6. The gap extends along the axial direction 200 through the permanent magnet unit 6 and is bounded by the individual magnets 7a, 7b along both the width direction 300 and the thickness direction 400. In this way, a magnetic cooling channel 8 extending in the axial direction 200 is formed. As previously described, this magnetic cooling channel 8 is fluidically connected to the wave cooling channel 13. The wave cooling channel 8 formed by the gap 9 is particularly advantageously in contact with all individual magnets 7a, 7b.Since the gap 9 runs in the axial direction through the permanent magnet unit 6, the wave cooling channel 8 formed by the gap 9 serves to cool the permanent magnet unit 6, in particular the individual magnets 7a, 7b. The effective cooling via the wave cooling channel 8 prevents overheating of the individual magnets 7a, 7b during operation of the electric machine 10. This reduces the risk of demagnetization of the individual magnets 7a, 7b, which is why a smaller proportion of rare earth materials, which counteract demagnetization, can be used. The individual magnets 7a, 7b of the permanent magnet unit 6 are bonded together, preferably by adhesive. In this way, the permanent magnet unit 6 can be handled as a single component and, in particular, inserted as a unit into the respective magnet pocket 5. This simplifies the assembly of the rotor 1, especially the fitting of magnets. Figures 3, 4, and 5 show different versions of the permanent magnet unit 6. In all versions, the permanent magnet unit 6 comprises first individual magnets 7a and second individual magnets 7b, wherein the first individual magnets 7a have a first cross-section and the second individual magnets 7b have a second cross-section different from the first. The second cross-section is a partial cross-section of the first. The respective gap 9 is formed between adjacent second individual magnets 7b. The basic arrangement is that the second individual magnets 7b are arranged either side by side along the width direction 300 or along the thickness direction 400, and in the other of the two directions between the first individual magnets 7a. Fig. 3 shows a first variant in which the second individual magnets 7b are arranged side by side along the width direction 300. Along the thickness direction 400, the second individual magnets 7b are arranged between the first individual magnets 7a. In the first variant according to Fig. 3, four individual magnets 7a, 7b are present, a total of two first individual magnets 7a and two second individual magnets 7b. The height of the first individual magnets 7a and second individual magnets 7b, measured along the thickness direction 400, is the same. The thickness D of the permanent magnet unit 6 is therefore formed by the three heights of the stacked first individual magnets 7a and second individual magnets 7b. The first individual magnets 7a have the width B of the permanent magnet unit 6 in the width direction 300. The second individual magnets 7b, located between the first individual magnets 7a, are arranged side by side in the lateral direction 300. A gap 9 is formed between the second individual magnets 7b in the lateral direction 300. The arrangement of the second individual magnets 7b with the intervening gap 9 has a total width B of the permanent magnet unit 6 in the lateral direction 300. Thus, a substantially cuboid-shaped permanent magnet unit 6 is formed. The depth T of the permanent magnet unit 6 in the axial direction 200 corresponds to the dimension of the rotor body 2 in the axial direction 200, so that the magnet pocket 5 is filled as much as possible with the permanent magnet unit 6 in the axial direction 200. Preferably, the permanent magnet unit 6 has several individual magnets 7a, 7b along the axial direction 200. The individual magnets 7a, 7b are positioned identically, particularly with respect to the lateral direction 300 and the thickness direction 400.This creates a series of magnets that extend axially through the magnetic pocket 5. Fig. 4 shows a second alternative of the permanent magnet unit 6, wherein the permanent magnet unit 6 is essentially constructed the same as in the first alternative as shown in Fig. 3. The only difference is that three instead of two wide individual magnets 7b are arranged side by side in the lateral direction 300. In this way, two gaps 9 are formed, the gaps 9 preferably being of equal size. The gaps 9 are each formed between two second individual magnets 7b spaced apart in the lateral direction 300. In this alternative, two cooling channels 8 are formed through the permanent magnet unit 6. Fig. 5 shows a third alternative of the permanent magnet unit 6. In this case, two second individual magnets 7b are arranged in the width direction 300 between two first individual magnets 7a. The second individual magnets 7b are arranged side by side in the thickness direction 400 and form a gap 9 in the thickness direction 400. The arrangement of the second individual magnets 7b with the gap 9 between them has a dimension in the thickness direction 400 that corresponds to the thickness D of the permanent magnet unit 6. The first individual magnets 7a have the thickness D of the permanent magnet unit 6 in the thickness direction 400. The width dimension of the first individual magnets 7a and second individual magnets 7b is, in particular, equal. Thus, the width B of the permanent magnet unit 6 is the sum of three width dimensions of the stacked first individual magnets 7a and second individual magnets 7b. In all alternatives, the distance S between the second individual magnets 7b to form the gap 9 is less than 1.0 mm, preferably a maximum of 0.5 mm, particularly preferably a maximum of 0.2 mm, and / or particularly at least 0.1 mm. The gap 9 is thus large enough to transport sufficient cooling fluid and small enough not to disturb the magnetic flux, or not to a significant extent. Fig. 6 schematically shows an exemplary manufacturing process for the permanent magnet unit 6 according to the first variant. For its manufacture, large but thin sintered plates 7c are used, which are stacked in the thickness direction 400 and have a gap 9 in the middle, for example with a spacer. These sintered plates 7c are bonded together. After bonding, the stacked sintered plates 7c are cut to size according to the required magnet width and length. Corresponding saw cuts 600 are provided for this purpose to produce the permanent magnet unit 6 of the desired dimensions. QUOTES INCLUDED IN THE DESCRIPTION This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature DE 10 2010 002 786 A1

[0003] JP 2010 183791 A1

[0003]

Claims

Rotor (1) of an electric machine (10), in particular a permanent magnet synchronous machine, with a rotor shaft (3) rotatable about a rotor axis (100) and a rotor body (2) arranged on the rotor shaft (3), which is in particular designed as a rotor lamination stack made of stacked laminations (4), wherein a shaft cooling channel (13) runs in the rotor shaft (3) and wherein at least one magnet pocket (5) for receiving a permanent magnet unit (6) is formed in the rotor body (2), wherein the permanent magnet unit (6) has an axial direction (200) oriented along the rotor axis (100) as well as a width direction (300) and a thickness direction (400), wherein the permanent magnet unit (6) is composed at least in certain areas along the width direction (300) and along the thickness direction (400) of at least two individual magnets (7a, 7b), which are in particular permanent magnets, characterized in that there is a separation between individual magnets (7a,7b) of the permanent magnet unit (6) at least one gap (9) is formed which extends along the axial direction (200) through the permanent magnet unit (6) and which is bounded both along the width direction (300) and along the thickness direction (400) by the individual magnets (7a, 7b) in order to form a magnetic cooling channel (8) extending in the axial direction (200), which is flow-connected to the shaft cooling channel (13) and is designed for cooling the permanent magnet unit (6). Rotor (1) according to claim 1, characterized in that the permanent magnet unit (6) comprises first individual magnets (7a) and second individual magnets (7b), wherein the first individual magnets (7a) have a first cross-section and the second individual magnets (7b) have a second cross-section, wherein the second cross-section is a partial cross-section of the first cross-section, and wherein the respective gap (9) is formed between adjacent second individual magnets (7b). Rotor (1) according to one of the preceding claims, characterized in that the second individual magnets (7b) are arranged side by side along one direction selected from the width direction (300) or thickness direction (400), wherein the second individual magnets (7b) are arranged between first individual magnets (7a) in the other of the two directions. Rotor (1) according to one of the preceding claims, characterized in that: • the second individual magnets (7b) are arranged side by side in the width direction (300), • the first individual magnets (7a) have the width (B) of the permanent magnet unit (6) in the width direction (300), and • the second individual magnets (7b) arranged side by side in the width direction (300), in particular with an intermediate gap (9), together have the width (B) of the permanent magnet unit (6), • the height of the first individual magnets (7a) and the second individual magnets (7b) is in particular the same. Rotor (1) according to one of claims 1 to 3, characterized in that: • the first individual magnets (7a) have the thickness (D) of the permanent magnet unit (6) in the thickness direction (400), and • the second individual magnets (7b) arranged next to each other in the thickness direction (400), in particular with an intermediate gap (9), together have the thickness (D) of the permanent magnet unit (6), • the width of the first individual magnets (7a) and second individual magnets (7b) is in particular the same. Rotor (1) according to one of the preceding claims, characterized in that a distance (S) between the individual magnets (7) to form the gap (9) is less than 1.0 mm, preferably a maximum of 0.5 mm, particularly preferably a maximum of 0.2 mm, and / or in particular at least 0.1 mm. Rotor (1) according to one of the preceding claims, characterized in that the permanent magnet unit (6) is clamped in the respective magnet pocket (5) avoiding a joining gap and / or is glued into the magnet pocket (5), in particular by means of a molding compound or a resin. Rotor (1) according to one of the preceding claims, characterized in that the permanent magnet unit (6) has several individual magnets (7a, 7b) positioned identically along the axial direction (200), in particular with respect to the width direction (300) and thickness direction (400). Rotor (1) according to one of the preceding claims, characterized in that the individual magnets (7a, 7b) of the permanent magnet unit (6) are materially bonded to one another, preferably glued. Rotor (1) according to one of the preceding claims, characterized in that an end disk (12), in particular a plastic disk, is arranged adjacent to an axial end (4a), in particular at both axial ends (4a), of the rotor body (4), wherein each magnetic cooling channel (8) is fluidly connected to the shaft cooling channel (13) of the rotor shaft (3) via a flow connection (12a) in the end disk and / or that a feed disk is arranged in an axial center of the rotor body (4), wherein each magnetic cooling channel (8) is fluidly connected to the shaft cooling channel (13) of the rotor shaft (3) via a flow connection in the feed disk. Electric machine (10), in particular permanent excitation synchronous machine, comprising a rotor (1) according to one of the preceding claims and a stator (11) with an electrical winding for driving the rotor (1).

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