Rotor for an electrical machine and electrical machine

Abstract

Rotor for an electrical machine having an axis of rotation, a rotor core with a central rotor base body and at least two rotor segments which are distributed circumferentially around the rotor base body, wherein a plurality of permanent magnets are arranged between the rotor base body and the rotor segments, as well as electrical machine.

Description

[0001] The application relates to a rotor for an electrical machine having an axis of rotation, a rotor core with a central rotor base body and at least two rotor segments which are distributed in the circumferential direction around the rotor base body, wherein several permanent magnets are arranged between the rotor base body and the rotor segments, as well as to an electrical machine.

[0002] A rotor for an electric machine includes a plurality of permanent magnets and a rotor core defining pockets between a hub portion and a pole portion for receiving magnet pairs. Side webs of the rotor core extend between the outer surface and the radially outward ends of the magnet pockets. Center webs of the rotor core extend between adjacent openings for receiving the magnet pairs. Center and side webs provide structural integrity to the rotor and magnet retention. They are the result of hollowing out the rotor lamination to create pockets to house the magnets. The center web and side webs form the main path for electromagnetic flux leakage. In addition, the center web and side webs are subject to high mechanical stresses due to their small cross-sectional area.

[0003] US 11 152 825 B2 discloses a rotor for an electrical machine with magnet pairs and a web region therebetween. The laminations comprising the rotor form openings in the web region between the magnets of the individual pairs. A first projection extends from the pole region, and a second projection extends from the hub portion into the opening in the web region. A clip is mounted in the openings, and the remaining web region is filled with an adhesive material. The clip cooperates with the first projection, the second projection, and the adhesive material to create a structural connection between the hub portion and the pole region.

[0004] DE 10 2017 205 858 A1 discloses a rotor for a permanent magnet synchronous machine, wherein the rotor comprises a rotor body in which at least one recess extends substantially in the axial direction at least partially through the rotor body, and at least two permanent magnets, wherein the recess has at least two elongated first regions and at least one second region extending in the radial direction, which extends radially between the two first regions, wherein in each case a permanent magnet is accommodated in a first region and in the second region a connecting element is accommodated, which has at its respective ends a geometric widening corresponding to the contour of the second region of the recess.

[0005] GB 2 562 704 A discloses a rotor having one or more slots arranged between adjacent pairs of magnetic poles and one or more windings arranged in the one or more slots. A two-part support is located between the poles to hold the windings in place. The support consists of a base portion, preferably attached to the core with a fir-tree root-like connection, and a cover portion for attachment to the base portion to fix the windings to the core.

[0006] GB 2 546 298 A discloses a rotor assembly with a rotor carrier hub having a plurality of first fir-tree connecting members arranged around a circumference of the rotor carrier hub. The rotor assembly further has a plurality of rotor segments, each having a second connecting member. Each of the second connecting members is adapted to cooperate with at least one of the plurality of first connecting members to interconnect each of the rotor segments about the circumference of the rotor carrier hub. A plurality of securing members in the form of roll pins are each configured to be received between cooperating first and second connecting members and to form an interference fit therebetween to secure the rotor segments to the rotor carrier hub. The rotor segments and the support hub may be comprised of a plurality of laminations, the rotor hub being made of non-magnetic material.

[0007] One task is to reduce the electromagnetic leakage flux across the center web and side webs while maintaining the structural integrity of a rotor for an electrical machine having a rotor core and a plurality of permanent magnets housed in the rotor core.

[0008] The object is achieved by a rotor for an electrical machine according to claim 1. Further embodiments are the subject of the dependent claims.

[0009] The rotor for an electrical machine comprises an axis of rotation, a rotor core with a central rotor base body and at least two rotor segments distributed circumferentially around the rotor base body, a plurality of permanent magnets arranged between the rotor base body and the rotor segments, wherein the rotor base body and the rotor segments are separate, and wherein a plurality of non-magnetic members form connecting members between the rotor base body and the rotor segments.

[0010] Removing both the center web and the side webs of the rotor has the advantage of increasing the performance of an electric machine, allowing for higher torque and power, and allowing the motor to operate at higher speeds. To ensure the structural integrity of the rotor core, the center webs are replaced with non-magnetic links that form the connecting links. The rotor core is divided into the rotor base and the rotor segments. This means that the rotor core is not a single piece but is composed of several parts, and the rotor base and the rotor segments must be connected by non-magnetic links.

[0011] According to one embodiment, the non-magnetic members are positively connected to the rotor base body and the respective rotor segments. In particular, the non-magnetic members are connected to the rotor base body and / or to the respective rotor segments by dovetail joints. Furthermore, the non-magnetic members can be connected to the rotor base body and / or the respective rotor segments by a fir-tree joint. Fir-tree joints are known for providing multiple contact surfaces, through which large thermal and centrifugal stresses can be advantageously transmitted. They offer a larger contact area within the available space. A fir-tree joint consists of an arrangement of several pairs of opposing teeth or branches extending from a trunk; this arrangement is also referred to as a fir-tree root.The teeth or branches at the distal end of the trunk base have a smaller lateral extension than the teeth or branches closer to the trunk base. The colloquial term is derived from the shape of the tapered teeth or branches, which have the appearance of a Christmas tree. The Christmas tree connection is advantageous for establishing the connection between the rotor segments and the non-magnetic links, as this connection is located at the narrowest point between the two permanent magnets of a V-shaped magnet pair, where there is little space for a positive fit. A Christmas tree connecting link on the rotor segment has a small circumferential extension and thus fits into the tight space between the permanent magnets. The non-magnetic link accordingly includes a complementary recess to accommodate the small circumferential Christmas tree connecting link at its narrowest end.The connection between the non-metallic link and the rotor base body can advantageously be a simpler dovetail connection, as there is more space for this connection between the permanent magnets. The dovetail connection can be wider circumferentially, especially with the connecting piece on the non-metallic link and the complementary dovetail retaining recess on the rotor base body. Another advantage of the dovetail connection is its smaller radial expansion compared to the fir-tree connection. The non-metallic link extends less radially into the rotor base body, thereby minimizing its influence on the magnetic flux in the rotor base body.

[0012] The permanent magnets are arranged as magnet pairs between the rotor base body and one of the respective rotor segments, so that the respective non-magnetic members extend radially between the two permanent magnets, each of which forms one of the magnet pairs. The area between the two permanent magnets that form a magnet pair is also referred to as the central web area. Since the rotor base body is separated from the rotor segments, the central web areas do not contain any rotor core material. Instead, the non-magnetic members extend in the central web area. Furthermore, the areas between the radially outer ends of the two permanent magnets that form one of the magnet pairs are referred to as side web areas, and the side web areas also do not contain any rotor core material.The side web and center web areas form a space between the rotor body and the respective rotor segments, which is partially occupied by the permanent magnets and the non-magnetic element. The remainder of the space can be filled with air. Alternatively, the space can be at least partially filled with an epoxy or plastic filler.

[0013] According to a further embodiment, each rotor segment is wedge-shaped, with an axially extending outer surface of the rotor segment forming a portion of a circumferential surface of the rotor core. Two axially extending inner surfaces of the rotor segment abut the respective magnet pair, with the inner surfaces enclosing an obtuse angle, which is in particular between 100° and 140°. The rotor base body can have radially extending sections that form intermediate sections of the circumferential surface of the rotor core between each two adjacent rotor segments.

[0014] According to a further embodiment, the rotor base body and the rotor segments of the rotor core consist of a plurality of axially stacked laminations. The non-magnetic members can be extruded profiles that extend along an axial length of the rotor core or at least a portion of the axial length. The non-magnetic members can be made of aluminum, a metal matrix composite material, a non-magnetic metal, in particular non-magnetic steel, or carbon fiber. The permanent magnets can be bonded to the rotor base body and the rotor segments by an adhesive.

[0015] According to a further embodiment, the rotor base body comprises a frame structure with axially extending openings, with supports carrying the permanent magnets connected to a continuous hub ring extending in the circumferential direction. The number of rotor segments can be between six and ten.

[0016] Another aspect that also solves the above-mentioned problem concerns an electric machine. The electric machine consists of a rotor, as described above, and a stator, wherein the rotor is rotatable relative to the stator about the axis of rotation.

[0017] Embodiments of the rotor and the electric machine are explained with reference to the drawings, wherein Fig. 1 shows an embodiment of a rotor in a perspective view; Fig. 2 shows an enlarged section of Fig. 1; Fig. 3 shows the further enlarged detail in a plan view; Fig. 4 shows an enlarged detail of another embodiment of the rotor in a perspective view; Fig. 5 shows an embodiment of an electrical machine in a perspective exploded view; Fig. 6 shows the electric machine from Fig. 5 in a cross-sectional view; Fig. 7 shows an enlarged section of Fig. 6.

[0018] In Fig. 1 shows a rotor 1 for an electrical machine. The rotor 1 has a rotor shaft 18 and is rotatable about a rotational axis L. A rotor core 6 consists of a central rotor base body 2 and eight rotor segments 3 distributed around the circumference. The rotor base body 2 and the rotor segments 3 are separate components held together by non-magnetic members 4, which form connecting links between the rotor base body 2 and the rotor segments 3. Permanent magnets 5 are arranged between the rotor base body 2 and the rotor segments 3. The permanent magnets 5 are arranged in eight magnet pairs 7, each of which is located between the rotor base body 2 and one of the eight rotor segments 3. The rotor base body 2 and the rotor segments 3 of the rotor core 6 consist of a plurality of axially stacked lamellae 14. The non-magnetic members 4 are extruded profiles, e.g.made of aluminum, which extend along an axial length of the rotor core 6.

[0019] In Fig. 2 is an enlarged section of Fig. 1, which illustrates that the rotor base body 2 has radially extending sections 12 that form intermediate sections of the circumferential surface of the rotor core 6 between each two adjacent rotor segments 3. The rotor base body 2 further has a frame structure with axially extending openings 17, in which supports 15, which carry the permanent magnets 5, are connected to a circumferentially extending continuous hub ring 16.

[0020] In Fig. 3 shows the further enlarged detail in a plan view, with the axis of rotation L aligned orthogonal to the projection plane. The non-magnetic member 4 extends in a central web region, i.e. in the radial direction between the two magnets 5 that form one of the permanent magnet pairs 7. The material of the rotor core 6 was removed or omitted in the central web region to reduce the stray flux. A space between the magnets 5 is filled with the non-magnetic member 4 and an epoxy or plastic filler 9. The non-magnetic member 4 is positively connected to the rotor base body 2 and to the rotor segment 3. In particular, the non-magnetic member 4 is connected to the rotor base body 2 by a dovetail connection 22 and to the rotor segment 3 by a fir tree connection 23.A Christmas tree connecting link on the rotor segment 3 extends radially between the permanent magnets 5 and is locked to a corresponding Christmas tree connecting recess on the non-magnetic link 4.

[0021] In addition, the material of the rotor core 6 has been removed or omitted in the side web areas between the radially outer ends of the magnets and the outer surface 10 of the rotor core 6, which also advantageously reduces leakage flux. In the embodiment shown, the space between the rotor base body 2 and the rotor segment 3, which is not occupied by the permanent magnets 5 and the non-magnetic member 4, is filled with the filling compound 9 made of epoxy or plastic compounds. The permanent magnets 5 can be bonded to the rotor base body 2 and the rotor segments 3 by an adhesive in order to reduce radial deformation of the rotor segment 3 under centripetal force, particularly at its peripheral ends remote from the non-magnetic member 4. The rotor segment 3 is wedge-shaped and the axially extending outer surface 10 of the rotor segment 3 forms a portion of a circumferential surface of the rotor core 6.Two axially extending inner surfaces 11 of the rotor segment 3 bear against the magnet pair 7, wherein the inner surfaces 11 enclose an obtuse angle of approximately 120°.

[0022] A further embodiment of the rotor 1 is shown in Fig. 4, which shows an enlarged detail in a perspective view. Here, too, the material of the rotor core 6 was removed or omitted from the central web region and the side web regions to reduce leakage flux. In the embodiment shown, the space between the rotor base body 2 and the rotor segment 3, which is not occupied by the permanent magnets 5 and the non-magnetic member 4, is partially filled with the filler mass 9 made of epoxy or plastic compounds and partially with air 8. The epoxy or plastic filler mass 9 can contain reinforced plastics, hybrid reinforcements, and pre-impregnated materials for bonding and greater mechanical rigidity. It has been shown that a partial or complete filler mass 9 made of epoxy resin or plastic can reduce elastic deformation of the rotor segments 3 by up to 25%, particularly near the side web regions.The non-magnetic member 4 is connected to the rotor base body 2 by the dovetail connection 22 and to the rotor segment 3 by the fir tree connection 23.

[0023] In Fig. 5 shows an embodiment of an electrical machine in a perspective exploded view. Fig. 6 shows the electric machine from Fig. 5 in cross section and Fig. 7 shows an enlarged section of Fig. 6. In the cross-sectional views, the matching hatching of the magnets 5, the non-magnetic elements 4 and the filling compound 9 made of epoxy resin or plastic does not indicate identical materials. Fig. 5 to 7 are described together. The electrical machine comprises the rotor 1 and a stator 19, wherein the rotor 1 is rotatable relative to the stator 19 about the rotation axis L. The stator 19 comprises windings 20, which are arranged in Fig.5 are not shown and are received in slots 21 formed in the stator 19 in the axial direction. The rotor base body 2 and the rotor segments 3 are separate parts held together by the non-magnetic members 4, which form the connecting links between the rotor base body 2 and the rotor segments 3. The permanent magnets 5 are arranged between the rotor base body 2 and the rotor segments 3. The space not occupied by the permanent magnets 5 and the non-magnetic members 4 between the rotor base body 2 and the rotor segment 3, including the side web areas, is filled with the epoxy or plastic filler 9.

[0024] The rotational axis L defines the axial direction relative to rotor 1 and the electric machine. The radial and circumferential directions are defined relative to the rotational axis L. Reference symbol 1 rotor 2 rotor base bodies 3 rotor segments 4 Non-magnetic links 5 permanent magnets 6 Rotor core 7 pairs of magnets 8 Air 9 Filling compound 10 Outer surface 11 interior surfaces 12 radial sections 14 Stacked slats 15 carriers 16 Hub ring 17 openings 18 Rotor shaft 19 Stator 20 windings 21 slots 22 Dovetail joint 23 Christmas tree connection L Longitudinal axis QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 11 152 825 B2

[0003] DE 10 2017 205 858 A1

[0004] GB 2 562 704 A

[0005] GB 2 546 298 A

[0006]

Claims

[1] Rotor (1) for an electrical machine, comprising: a rotation axis (L), a rotor core (6) with a central rotor base body (2) and at least two rotor segments (3) distributed in the circumferential direction, a plurality of permanent magnets (5), wherein the permanent magnets are arranged between the rotor base body (2) and the rotor segments (3); wherein the rotor base body (2) and the rotor segments (3) are separate and wherein a plurality of non-magnetic members (4) form connecting members between the rotor base body (2) and the rotor segments (3). [2] Rotor according to claim 1, characterized by that the non-magnetic members (4) are positively connected to the rotor base body (2) and to the respective rotor segments (3). [3] Rotor according to one of the preceding claims, characterized bythat the non-magnetic members (4) are connected to the rotor base body (2) and / or to the respective rotor segments (3) by a dovetail connection (22) and / or by a fir tree connection (23). [4] Rotor according to claim 3, characterized by that the non-magnetic members (4) are connected to the rotor base body (2) via the dovetail connection (22), wherein the respective rotor segments (3) are connected to the non-magnetic members (4) via the fir tree connections (23). [5] Rotor according to one of the preceding claims, characterized by that the permanent magnets (5) are arranged in magnet pairs (7) between the rotor base body (2) and one of the respective rotor segments (3), wherein the respective non-magnetic members (4) extend in the radial direction between the respective two magnets (5) forming one of the permanent magnet pairs (7). [6] Rotor according to one of the preceding claims, characterized by that a space not occupied by the permanent magnets (5) between the rotor base body (2) and the respective rotor segments (3) is at least partially filled with air (8). [7] Rotor according to one of the preceding claims, characterized by that a space not occupied by the permanent magnets (5) between the rotor base body (2) and the respective rotor segments (3) is at least partially filled with an epoxy or plastic filling compound (9). [8] Rotor according to one of the preceding claims, characterized by that each rotor segment (3) is wedge-shaped, wherein an axially extending outer surface (10) of the rotor segment forms a portion of a circumferential surface of the rotor core. [9] Rotor according to claim 8, characterized bythat two axially extending inner surfaces (11) of the rotor segment (3) bear against the respective magnet pair (7), wherein the inner surfaces enclose an obtuse angle which is in particular between 100° and 140°. [10] Rotor according to one of the preceding claims 8 or 9, characterized by that the rotor base body (2) has radially extending sections (12) which form intermediate sections of the circumferential surface of the rotor core between each two adjacent rotor segments (3). [11] Rotor according to one of the preceding claims, characterized by that the rotor base body (2) and the rotor segments (3) of the rotor core are composed of a plurality of axially stacked lamellae (14). [12] Rotor according to one of the preceding claims, characterized by that the non-magnetic members (4) are extruded profiles extending along an axial length of the rotor core. [13] Rotor according to one of the preceding claims, characterized by that the non-magnetic members (4) are made of one of the following materials: aluminum, metal matrix composite, non-magnetic metal and carbon fiber. [14] Rotor according to one of the preceding claims, characterized by that the permanent magnets (5) are connected to the rotor base body (2) and to the rotor segments (3) by an adhesive. [15] Rotor according to one of the preceding claims, characterized by that the rotor base body (2) has a frame structure with axially extending openings (17), wherein supports (15) carrying the permanent magnets (5) are connected to a continuous hub ring (16) extending in the circumferential direction. [16] Rotor according to one of the preceding claims, characterized by that the number of rotor segments (3) is between six and twelve. [17] An electrical machine comprising a rotor (1) according to any one of the preceding claims and a stator (19), wherein the rotor is rotatable relative to the stator about the axis of rotation (L).

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