Rotor for an electric machine

Abstract

The invention relates to a rotor (1) for an electric machine (2), in particular for a permanently excited synchronous machine, - comprising a shaft (4) able to rotate about an axis of rotation (3), and a carrier (5) that is connected to the shaft (4) for conjoint rotation and has receptacles (6) oriented in the axial direction (24), - permanent magnets (7) being arranged in the receptacles (6). It is essential to the invention that provision is made for a non-magnetic, austenitic metal sleeve (8) that surrounds the carrier (5) and the permanent magnets (7).

Description

[0001] Rotor for an electric machine

[0002] The present invention relates to a rotor for an electric machine, in particular for a permanent magnet synchronous machine, according to the preamble of claim 1. The invention further relates to an electric machine with a housing in which such a rotor is mounted.

[0003] From WO 2021 / 225 902 A1, a generic rotor for an electric machine is known, comprising a shaft rotatable about an axis of rotation and a support fixed to the shaft with axially aligned receptacles, wherein permanent magnets are arranged in the receptacles. The rotor itself is encased in a sleeve wound from carbon fibers to fix both the support and the permanent magnets.

[0004] A disadvantage of the rotor known from the prior art is the comparatively complex manufacturing process of the fiber-wound sleeve, which, combined with the relatively high cost of carbon fibers, makes the production of such a sleeve expensive. Furthermore, such a plastic-fiber sleeve is also comparatively thick, which increases the distance between the rotor and a stator and thus reduces efficiency.

[0005] The present invention therefore addresses the problem of providing an improved or at least an alternative embodiment of a rotor of the generic type, which in particular overcomes the disadvantage known from the prior art. This problem is solved according to the invention by the subject matter of independent claim 1. Advantageous embodiments are the subject matter of the dependent claims.

[0006] The present invention is based on the general concept of transforming a previously known, comparatively complex, and therefore expensive sleeve made of carbon fibers embedded in plastic for enclosing a rotor into a comparatively thin and thus not only strong but also cost-effective metal sleeve. The rotor according to the invention for an electric machine, in particular for a permanent magnet synchronous machine, has a shaft rotatable about an axis of rotation and a support non-rotatably connected to the shaft with receptacles oriented primarily in the axial direction, i.e., parallel to the axis of rotation, in which permanent magnets are arranged. According to the invention, a non-magnetic, austenitic metal sleeve, often referred to simply as a metal sleeve in the following text, is provided, which surrounds and thereby encloses the support and the permanent magnets.This allows the gap between the rotor and stator of the electric machine to be kept extremely small, since the metal sleeve now provided according to the invention can be made significantly thinner in terms of its wall thickness than fiber-reinforced plastic sleeves known from the prior art. This allows the power output of an electric machine equipped with the rotor according to the invention to be increased. A further advantage of the non-magnetic, austenitic metal sleeve now used for the first time according to the invention is that, in addition, the magnetic field between the rotor and the stator is not affected or only marginally affected, which also contributes to increasing the power output of an electric machine equipped with the rotor according to the invention.In an advantageous embodiment of the rotor according to the invention, the support comprises laminated cores formed from individual layers of sheet metal and composed of a first segment with wedge-shaped recesses extending outwards, each with two flanks, and several second segments, each engaging in a corresponding recess and also extending outwards in a wedge shape, with two opposing flanks. The first and second segments are not connected to each other but are initially formed as separate components.Only when the rotor according to the invention is assembled are the permanent magnets arranged, in particular clamped, between one flank of a first sub-segment and the opposite flank of a second sub-segment. This assembly of first sub-segment, permanent magnets, and second sub-segments is then inserted into the non-magnetic, austenitic metal sleeve according to the invention. The non-magnetic, austenitic metal sleeve clamps the second sub-segments against the first sub-segment via the permanent magnets, thus ensuring a reliably fixed rotor. To fix the non-magnetic, austenitic metal sleeve, it can, for example, be heated and slid onto the conglomerate of first sub-segment, permanent magnets, and second sub-segments using a thermal joining process. After temperature equalization, i.e.,After the metal sleeve cools down, it contracts to such an extent that a reliable press fit is created.

[0007] In a further advantageous embodiment of the rotor according to the invention, an inner cooling channel is provided, which is bounded by the first sub-segment, two permanent magnets, and an associated second sub-segment. During operation, the inner cooling channel is supplied with cooling medium, thereby enabling cooling of the first sub-segment, the two permanent magnets adjacent to or engaging within the first cooling channel, and the associated second sub-segment of the carrier. Since several such second sub-segments are provided around the circumference of the rotor, for example, four, six, eight, or more, a particularly homogeneous, i.e., uniform, cooling of the rotor can be achieved by means of a corresponding number of inner cooling channels.

[0008] In a particularly preferred embodiment of the rotor according to the invention, an outer cooling channel is provided, which is bounded by the first sub-segment, an associated permanent magnet, an associated second sub-segment, and the non-magnetic, austenitic metal sleeve. Each permanent magnet thus engages with its radially inner end in an associated inner cooling channel and with its radially outer end in an associated outer cooling channel, and can thereby be effectively cooled. To form the inner and outer cooling channels, convex cooling channel walls can be provided in the first sub-segment and in the associated second sub-segments, respectively. These walls can be of varying depths depending on the cooling requirements.By limiting the outer cooling channels with the non-magnetic, austenitic metal sleeve, the sleeve itself can also be cooled by the cooling medium flowing through the respective outer cooling channel. This prevents the non-magnetic, austenitic metal sleeve from overheating to the point where, for example, a thermal connection is compromised. Heat transfer, i.e., in this case, cooling, to the stator can also occur via the cooled metal sleeve, thus enabling at least indirect cooling of the stator by means of the cooling medium flowing in the rotor.

[0009] In a particularly preferred embodiment of the rotor according to the invention, every second sub-segment is interconnected with two outer cooling channels and one inner cooling channel. This allows for particularly effective cooling of the outer sub-segments.

[0010] In a further advantageous embodiment of the rotor according to the invention, the non-magnetic, austenitic metal sleeve is made of stainless steel, in particular 1.4301, 1.4310, or 1.4404. 1.4301 steel is a commonly used chromium-nickel steel that, in addition to extremely good processing properties, also exhibits high corrosion resistance. 1.4310 steel also possesses very good weldability. 1.4404 steel is a stainless and austenitic, low-carbon chromium-nickel-molybdenum steel that is also resistant to intergranular corrosion in the welded state. By making the non-magnetic, austenitic metal sleeve from stainless steel, it can be designed not only to be comparatively thin and therefore lightweight, but also cost-effective and durable due to its high strength and corrosion resistance.

[0011] The non-magnetic, austenitic metal sleeve is expediently manufactured using a machining process. This machining process makes it particularly possible to achieve varying wall thicknesses in the axial direction, allowing the non-magnetic, austenitic metal sleeve to be thicker, for example, in the bearing areas, than in the areas of the second segment, the permanent magnets, and the first segment. This allows for the comparative consideration of individually occurring loads through appropriately adapted thicknesses, i.e., wall thicknesses of the non-magnetic, austenitic metal sleeve.

[0012] In a further advantageous embodiment of the rotor according to the invention, two bearing points are arranged on the outside of the non-magnetic, austenitic metal sleeve, wherein the radial wall thickness of the non-magnetic, austenitic metal sleeve is greater in the area of ​​these bearing points than in the area of ​​the support and the permanent magnets. This makes it possible to design the metal sleeve with varying wall thicknesses, i.e., with a greater wall thickness in the area of ​​the bearing points and a very thin wall thickness in the area of ​​the support and the permanent magnets, thereby allowing the metal sleeve to be optimally adapted to the loads occurring during operation.

[0013] The present invention is further based on the general concept of equipping an electric machine, in particular a permanent magnet synchronous machine, with a housing in which a rotor is mounted on rolling bearings as described in the preceding paragraphs. The electric machine also has a stator, which is arranged across an air gap relative to the rotor according to the invention. Thus, the advantages described with respect to the rotor according to the invention can also be transferred to the electric machine according to the invention. Specifically, these advantages lie in a cost-effective, high-quality, and durable design.

[0014] Further important features and advantages of the invention will become apparent from the dependent claims, the drawings and the associated description of the figures based on the drawings.

[0015] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the present invention. The components of a higher-level unit, such as a device, apparatus, or arrangement, mentioned above and those to be mentioned below, which are designated separately, can form separate parts or components of this unit or be integral areas or sections of this unit, even if this is depicted differently in the drawings.

[0016] Preferred embodiments of the invention are shown in the drawings and are explained in more detail in the following description, wherein identical reference numerals refer to identical or similar or functionally identical components.

[0017] They show, each schematically

[0018] Figure 1 shows a cross-sectional detail of a rotor according to the invention in the area of ​​two permanent magnets,

[0019] Figure 2 shows a sectional view through an electrical machine according to the invention, with a rotor according to the invention.

[0020] As shown in Figures 1 and 2, a rotor 1 according to the invention for an electric machine 2 (see Figure 2), which is in particular designed as a permanent magnet synchronous machine, has a shaft 4 rotatable about an axis of rotation 3 and a support 5 fixedly connected to the shaft 4 with receptacles 6 aligned in the axial direction 24. Permanent magnets 7 (see Figure 1) are arranged in these receptacles 6. According to the invention, a non-magnetic, austenitic metal sleeve 8 is provided, which surrounds the support 5 and the permanent magnets 7.

[0021] The non-magnetic, austenitic metal sleeve 8 is closed in the circumferential direction. The carrier 5 can have laminated cores, each layer of which is composed of a first sub-segment 9 with wedge-shaped outwardly widening recesses 10, each with two flanks 11, and several second sub-segments 12, each engaging in these recesses and also wedge-shaped outwardly widening, with two opposing flanks 13. A permanent magnet 7 is arranged, in particular clamped, between a corresponding flank 11 of the first sub-segment 9 and a corresponding opposing flank 13 of the second sub-segment 12.

[0022] Furthermore, an internal cooling channel 14 is provided, which is bounded by the first sub-segment 9, two permanent magnets 7 and an associated second sub-segment 12. Naturally, depending on the number of permanent magnets 7, a corresponding number of internal cooling channels 14 are also provided in the circumferential direction, through which a cooling medium 25 flows during operation and cools the rotor 1.

[0023] Furthermore, external cooling channels 15 are provided, two of which are shown in Figure 1, each external cooling channel 15 being bounded by the first sub-segment 9, an associated permanent magnet 7, an associated second sub-segment 12, and the metal sleeve 8. The rotor 1 and, in particular, the permanent magnets 7 can be optimally cooled by the internal cooling channels 14 and the external cooling channels 15, thereby enabling high performance of the electrical machine 2 according to the invention.

[0024] Every second sub-segment 12 is connected to circumferentially adjacent outer cooling channels 15 and an inner cooling channel 14. "Communicating" in this case means that the second sub-segment 12 borders one inner cooling channel 14 and two outer cooling channels 15. In the area of ​​the cooling channels 14, 15, the first sub-segment 9 and / or the second sub-segment 12 can have convex cooling channel walls 16, which, depending on the shape of the cooling channel walls 16, allows for further influence on individual and demand-based cooling.

[0025] As can be seen in particular from Figure 1, each permanent magnet 7 is communicatively connected to an outer cooling channel 15 and an inner cooling channel 14, i.e. each permanent magnet 7 protrudes into an associated inner cooling channel 14 and an outer cooling channel 15, thereby enabling optimal cooling of the temperature-sensitive permanent magnets 7.

[0026] The non-magnetic, austenitic metal sleeve 8 is made of stainless steel, in particular 1.4301, 1.4310 or 1.4404. This makes it possible to design the metal sleeve 8 not only to be corrosion-resistant but also to have optimal strength, thus enabling a small wall thickness. This helps to reduce the weight of the rotor 1 and therefore also of the electric machine 2, as well as to increase the power output of the electric machine 2, since the air gap 18 located between the rotor 1 and a stator 17 (see Figure 2) can be extremely small.

[0027] The non-magnetic, austenitic metal sleeve 8 can be manufactured, for example, as a deep-drawn part. Alternatively, manufacturing by machining is also conceivable, which in particular creates the possibility of forming the non-magnetic, austenitic metal sleeve 8 with different wall thicknesses in different areas. If one considers, for example, Figure 2, it can be seen that two bearing points 19 are arranged on the outside of the metal sleeve 8, which are connected to rolling bearings 20. In the area of ​​the bearing points 19, it is therefore conceivable to form the non-magnetic, austenitic metal sleeve 8 with a thicker wall, thereby providing the bearing points 19 with higher strength. In the area between the two bearing points 19, i.e.,In particular in the area of ​​the support 5, the non-magnetic, austenitic metal sleeve 8 can be designed with a smaller wall thickness, since in this area it does not perform a bearing function, but only has to prevent the rotor 1 from falling apart.

[0028] In Figure 2, the depicted metal sleeve 8 has a uniform wall thickness throughout, which is also feasible and allows for the cost-effective production of the non-magnetic, austenitic metal sleeve 8. Furthermore, by adapting the wall thickness of the metal sleeve 8 to the specific loads encountered, the overall weight of the metal sleeve 8, and consequently also of the rotor 1 or the electric machine 2, can be reduced. Additionally, resource consumption can be reduced with a non-magnetic, austenitic metal sleeve 8 whose wall thickness is individually adapted to the specific loads encountered.

[0029] Looking further at Figure 2, it can be seen that the stator 17 has windings with winding heads 21, with the metal sleeve 8 defining an internal space 22. The stator 17 is arranged in this space 22, here an annular space, and is itself fixed to a housing 23 of the electric machine 2. The cooling medium 25 flows within the metal sleeve 8 from one end of the rotor 1 to the other end of the rotor 1, i.e., in the axial direction 24, thereby cooling the rotor directly and the stator indirectly. This cooling enables the electric machine 2 to deliver a higher overall power output.

[0030] The non-magnetic, austenitic metal sleeve 8 allows for the creation of a rotor 1 that is not only durable but also cost-effective and resource-saving, as well as an electrical machine 2 that is also cost-effective, durable and resource-saving.

[0031] *****

Claims

Claims 1. Rotor (1) for an electric machine (2), in particular for a permanent magnet synchronous machine, - with a shaft (4) rotatable about an axis of rotation (3) and a support (5) connected to the shaft (4) with receptacles (6) aligned in the axial direction (24), - wherein permanent magnets (7) are arranged in the receptacles (6), characterized in that a non-magnetic, austenitic metal sleeve (8) is provided which surrounds the carrier (5) and the permanent magnets (7).

2. Rotor (1 ) according to claim 1 , characterized in that the support (5) has laminated cores which are composed of a first partial segment (9) with wedge-shaped outwardly expanding recesses (10) with two flanks (11 ) and several second partial segments (12) with two counter-flanks (13) which engage in these and also expand wedge-shaped outwards.

3. Rotor (1 ) according to claim 2, characterized in that a permanent magnet (7) is arranged, in particular clamped, between a flank (11 ) of the first sub-segment (9) and an associated counter-flank (13) of the outer sub-segment (12).

4. Rotor (1) according to claim 2 or 3, characterized in that, that an internal cooling channel (14) is provided, which is bounded by the first sub-segment (9), two permanent magnets (7) and an associated second sub-segment (12).

5. Rotor (1 ) according to one of claims 2 to 4, characterized in that an outer cooling channel (15) is provided, which is bounded by the first sub-segment (9), an associated permanent magnet (7), an associated second sub-segment (12) and the non-magnetic, austenitic metal sleeve (8).

6. Rotor (1) according to claim 5, characterized in that, - that every second sub-segment (12) is connected to two outer cooling channels (15) and one inner cooling channel (14), and / or - that each permanent magnet (7) is connected to an outer cooling channel (15) and an inner cooling channel (14) in a communicating manner.

7. Rotor (1 ) according to one of claims 1 to 6, characterized in that the non-magnetic, austenitic metal sleeve (8) is made of stainless steel, in particular of 1.4301 , 1.4310, or 1.4404.

8. Rotor (1 ) according to one of claims 1 to 7, characterized in that the non-magnetic, austenitic metal sleeve (8) is manufactured by machining or as a deep-drawn part.

9. Rotor (1 ) according to any one of claims 1 to 8, characterized in that two bearing points (19) are arranged on the outside of the non-magnetic, austenitic metal sleeve (8), wherein the radial wall thickness of the non-magnetic, austenitic metal sleeve (8) is greater in the area of ​​the bearing points (19) than in the area of ​​the support (5) and the permanent magnets (7).

10. Electric machine (2), in particular a permanent magnet synchronous machine, comprising a housing (23) in which a rotor (1) according to one of the preceding claims is mounted via rolling bearings (20), and a stator (17) which is spaced apart from the rotor (1) by an air gap (18). *****

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