Rotor for electric machine

Abstract

The present application relates to a rotor for an electric machine, the rotor comprising a core rotatable about an axis of rotation and a plurality of magnets housed in the core, the core comprising an outer portion distributed circumferentially about the axis of rotation at a reduced radial distance, a first groove, an intermediate portion, a second groove and a hub portion. The rotor for the electric machine further includes a plurality of magnets received in pairs in the first and second grooves, where a central groove region of the first and second grooves extends between the magnets, and a non-magnetic bonding material is disposed in the central groove region.

Description

[0001] The present application relates to a rotor for an electric machine, the rotor including a core rotatable about a rotation axis and a plurality of magnets accommodated in the core.

[0002] A rotor for an electric machine includes a plurality of magnets and a rotor core, the rotor core defining a pocket for accommodating a magnet pair between a hub portion and an outer portion. The transverse bridge of the rotor core extends between the radial outer surface and the radial outer end of the magnet pocket. The central bridge of the rotor core extends between adjacent magnet openings for accommodating the magnet pair. The central bridge and the transverse bridge provide structural integrity for the rotor and magnet retention. However, the central bridge and the transverse bridge also form a major electromagnetic flux leakage path. In addition, the central bridge and the transverse bridge are subject to high mechanical stress due to their reduced cross-sectional area.

[0003] US11152825 B2 discloses a rotor for an electric machine, comprising a magnet pair with a bridge region between the magnet pairs. The laminations comprising the rotor define openings in the bridge region between each pair of magnets. A first protrusion extends from a pole portion, and a second protrusion extends from a hub portion into the opening of the bridge region. A clip is installed in the opening, and a bonding material fills the remaining portion of the bridge region. The clip cooperates with the first protrusion, the second protrusion, and the bonding material to provide a structural connection between the hub portion and the pole portion.

[0004] US 8896175 B2 discloses a rotor for an electric machine, the rotor being excited by magnetic poles formed by one or more embedded permanent magnets, the rotor comprising a magnet, and one or more embedded permanent magnets associated with the magnet defining a first magnetic pole and a second magnetic pole of alternating magnetic polarity along a rotor direction. For at least one of the one or more embedded permanent magnets, a rotor segment is arranged between the one or more embedded permanent magnets and a first surface of the magnet. At least one retainer element connects the rotor segment to a portion of the magnet.

[0005] US 9024499 B2 discloses a rotating electric machine rotor equipped with a rotor core and a pair of permanent magnets arranged in a V-shape open toward the outer periphery of the rotor core. The pair of permanent magnets are separated in the inner periphery direction of the rotor core, and the rotor core includes gaps formed between the separated permanent magnets.

[0006] EP 2645548 A2 discloses a synchronous electric machine having a rotor with a substantially cylindrical core with axially extending slots, a plurality of permanent magnets being arranged to define sets of alternating magnetic poles in a circumferential direction, the permanent magnets being located in corresponding ones of the slots, and a thermally conductive material being adjacent to the permanent magnets and the core for transferring heat of the permanent magnets.

[0007] One object is to reduce electromagnetic flux leakage via a central bridge and transverse bridges while maintaining the structural integrity of a rotor of an electric machine having a core and a plurality of permanent magnets housed in the core.

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

[0009] A rotor for an electric motor includes a core rotatable about an axis of rotation, the core including an outer portion, a first groove, an intermediate portion, a second groove, and a hub portion circumferentially distributed around the axis of rotation at a decreasing radial distance. The rotor for the electric motor further includes a plurality of magnets received in pairs in the first groove and the second groove, wherein a central groove region of the first groove and the second groove extends between the magnets, and a non-magnetic bonding material is disposed in the central groove region. A first reinforcement member is disposed in the first groove and embedded in the bonding material to provide a structural connection between the outer portion and the intermediate portion, and a second reinforcement member is disposed in the second groove and embedded in the bonding material to provide a structural connection between the intermediate portion and the hub portion.

[0010] Removing the center bridge of the rotor reduces flux leakage, advantageously improving the performance of the motor, allowing for higher torque and power, and the ability to drive the motor at higher speeds. The first and second grooves having magnets at different radial positions provide a double barrier against flux leakage, further improving performance. To provide structural integrity to the core, the center groove area of ​​both the first and second grooves is filled with a non-magnetic bonding material, in which the first and second reinforcement members are disposed.

[0011] The core may be assembled from individual electrical steel laminations. The hub portion is the central portion of the core. The second groove may be an opening extending through the core in the axial direction. If not stated otherwise, the terms axial, radial and circumferential are used relative to the axis of rotation. The second grooves are arranged circumferentially around the axis of rotation, usually evenly distributed. For example, four, six or eight or any generally even number of second grooves may be provided. The second grooves are arranged radially outside the hub portion. The circumferentially extending middle portion of the core is arranged radially outside the second grooves. The first grooves may be an opening extending through the core in the axial direction. The first grooves are arranged circumferentially around the axis of rotation, usually evenly distributed. For example, the number of first grooves is the same as the number of second grooves, and each first groove is assigned to a second groove. The central groove areas of the assigned first and second grooves may be arranged in a straight line in the radial direction. The central groove areas of the first and second grooves extending between the magnets are gaps filled with bonding material connecting two adjacent groove areas containing magnets, i.e. there is no central steel bridge connecting the hub portion to the middle portion or connecting the middle portion to the outer portion. The outer portion of the core surrounds the first groove radially outside the first groove. The radially outer surface of the core is part of the outer part. Two magnets can be accommodated in each of the first and second grooves, the two magnets forming a pair. The central groove area is located between the two magnets, which can be inserted into the first and second grooves in a form-fitting manner in the circumferential and radial directions. In the axial direction, the core can be closed by a cap, which also ensures that the magnets will be able to extend axially through the core.

[0012] According to one embodiment, at least one of the first reinforcement and the second reinforcement may be provided as fibers (e.g., glass or carbon fibers) added to the non-magnetic bonding material. The fibers may be arranged to extend primarily in the radial direction. Alternatively or additionally, at least one of the first reinforcement and the second reinforcement may be provided as non-magnetic particles (e.g., aluminum particles) added to the non-magnetic bonding material.

[0013] According to a further embodiment, at least one of the first reinforcement and the second reinforcement may include a clip profile arranged in the central groove area. The clip profile may be an extruded profile of a non-magnetic material such as plastic or aluminum. The clip profile extends axially in the central groove area that runs through the core. The clip profile may include a web extending in a radial direction across the central groove area and at least one hook portion arranged at at least one lateral end of the web. The hook portion may advantageously interact with a protrusion of the core extending into the central groove area to provide a shape fit with one of the outer portion, the middle portion, and the hub portion. The central groove area may be formed to provide an undercut in a radial direction for at least one of the first reinforcement and the second reinforcement.

[0014] According to another embodiment, the transverse groove area extends at the lateral end of at least one of the first groove and the second groove, and the non-magnetic bonding material is arranged in the transverse groove area. The transverse groove area of ​​the first groove can extend to the radial outer surface of the core so that the first groove is open to the air gap between the rotor and the stator, and the rotor is assembled inside the air gap. Removing the conductive core material from the transverse groove area advantageously further reduces the magnetic flux leakage. The transverse reinforcement can be arranged in the transverse groove area of ​​the first groove, embedded in the bonding material, to provide a structural connection across the transverse groove area of ​​the first groove in the circumferential direction. The transverse groove area may include one or more of fibers added to the non-magnetic bonding material, non-magnetic particles added to the non-magnetic bonding material, and a clip profile arranged in the transverse groove area of ​​the first groove. The web of the clip profile of the transverse reinforcement extends in the circumferential direction and may have a hook portion.

[0015] According to further embodiments, the opening extending axially through the core can be arranged in the radial direction between the transverse groove area of ​​the second groove and the radial outer surface of the core. The opening is usually not open towards the air gap. In any case, the opening advantageously forms a barrier to reduce magnetic flux leakage.

[0016] According to another embodiment, the magnets disposed in the second groove may have a larger cross-sectional area than the magnets disposed in the first groove. The magnets accommodated in pairs in the first groove and the magnets accommodated in pairs in the second groove may each be arranged to form a herringbone when viewed in cross section, generally pointing toward the axis of rotation. The first angle enclosed by the herringbone formed by the magnets disposed in the first groove may be greater than the second angle enclosed by the herringbone formed by the magnets disposed in the second groove.

[0017] An electric machine that also achieves the above object includes a rotor and a stator as described above, the rotor being rotatable relative to the stator about a rotation axis.

[0018] The embodiments will be described with reference to the accompanying drawings, in which

[0019] Figure 1 An embodiment of an electric machine having a rotor is shown in a schematic illustration;

[0020] Figure 2 Shown in perspective Figure 1 The rotor;

[0021] Figure 3 Shows Figure 1 Enlarged detail of the rotor;

[0022] Figure 4 shows an enlarged detail of a further embodiment of a rotor;

[0023] Figure 5An enlarged detail of a further embodiment of a rotor is shown.

[0024] exist Figure 1 , an electric machine is shown in a schematic cross-sectional view. The electric machine comprises a rotor 20 and a stator 21, the rotor 20 being rotatable relative to the stator 21 about a rotation axis A. The stator 21 comprises a winding 22, which passes through slots 23 in the stator 21 in an axial direction.

[0025] exist Figure 2 In the perspective view, Figure 1 The rotor 20. Figure 1 and Figure 2 The rotor 20 is described. The rotor 20 of the electric machine comprises a core 2 rotatable about an axis of rotation A. An outer portion 5, a first groove 8, a middle portion 6, a second groove 9 and a hub portion 4 are arranged circumferentially distributed around the axis of rotation A with decreasing radial distances. The core can be assembled from individual electrical steel laminations. The hub portion 4 forms the central portion of the core 2, which is attached to a shaft (not depicted). The second grooves 9 are arranged circumferentially and evenly distributed around the axis of rotation A. The second grooves 9 are arranged radially outside the hub portion 4. The circumferentially extending middle portion 6 of the core 2 is arranged radially outside the second grooves 9. The first grooves 8 are arranged circumferentially and evenly distributed around the axis of rotation A. The outer portion 5 of the core 2 surrounds the first grooves 8 radially outside the first grooves 8. The radial outer surface 18 of the core is part of the outer portion 5. The magnets 3 are accommodated in pairs in the first grooves 8 and the second grooves 9. Each pair of two grooves arranged in radially adjacent first grooves 8 and second grooves 9 establishes the magnetic poles of the rotor 20. The number of magnetic poles can be any even number, in particular between six and twelve. In the depicted embodiment, the rotor 20 comprises eight magnetic poles. The central groove area 7 of the first groove 8 and the second groove 9 extends between the corresponding magnets 3, and the central groove area 7 is filled with a non-magnetic bonding material. The central groove areas 7 of each two first grooves 8 and the second groove 9 are arranged along a straight line in the radial direction. The magnets 3 are inserted into the first grooves 8 and the second grooves 9 in a form-fitting manner in the circumferential and radial directions. As part of the first grooves 8 and the second grooves 9, the central groove area 7 extends axially through the core 2.

[0026] The first reinforcement 10 is arranged in the first groove 8 and embedded in the bonding material to provide a structural connection between the outer part 5 and the middle part 6. The first reinforcement 10 includes a clip profile 1, which is arranged in the central groove area 7. The first reinforcement 10 may further include fibers and / or non-magnetic particles (not depicted) added to the non-magnetic bonding material. The second reinforcement 11 is arranged in the second groove 9 and embedded in the bonding material to provide a structural connection between the middle part 6 and the hub part 4. The second reinforcement 11 also includes a clip profile 1, which is arranged in the central groove area 7 of the second groove 9. The second reinforcement 11 may also further include non-magnetic particles and / or fibers, such as glass fibers or carbon fibers, which may be arranged to extend mainly in the radial direction. The non-magnetic particles may be, for example, aluminum particles.

[0027] exist Figure 3 In the Figure 1 2. The clamp profile 1 comprises a web 12 which extends in a radial direction across the respective central groove area 7 in cross section. Hook portions 14 are provided at the two lateral ends of the web 12. The hook portions 14 interact with protrusions 15 of the core 2 extending into the respective central groove area 7 to provide a form fit with the outer part 5, the middle part 6 and the hub part 4. In other words, the central groove area 7 is formed to provide an undercut for the hook portion 14 of the clamp profile 1 in the radial direction. The first groove 8 and the second groove 9 further comprise a lateral groove area 16 which extends at the lateral ends. Non-magnetic bonding material is also provided in the lateral groove area 16. An opening 17 extends axially through the core 2, which is arranged in a radial direction in cross section between the lateral groove area 16 of the second groove 9 and the radial outer surface 18 of the core 2.

[0028] The cross-sectional area of ​​the magnet 3 disposed in the second groove 9 is larger than the cross-sectional area of ​​the magnet 3 disposed in the first groove 8. The magnets 3 accommodated in pairs in the first groove 8 and the magnets 3 accommodated in pairs in the second groove 9 are each arranged to form a herringbone in the cross section, wherein the corresponding central groove area 7 forms the tip of the herringbone and the longest extension direction of the magnet 3 in the cross section forms the legs of the herringbone. The first angle B enclosed by the herringbone formed by the magnets 3 disposed in the first groove 8 is larger than the second angle C enclosed by the herringbone formed by the magnets 3 disposed in the second groove 9.

[0029] exist Figure 4, an enlarged detail of a further embodiment of a rotor 20 is shown. Only the first groove 8 is depicted. The clip profile 1 comprises a web 12 extending in the radial direction across the central groove area 7. Alternative hook portions 14 are provided at both lateral ends of the web 12 to interact with the protrusions 15 of the core 2. With the alternative hook portions 14, the clip profile 1 has the form of an I-beam having an H-shaped cross-section.

[0030] exist Figure 5 , an enlarged detail of a further embodiment of a rotor 20 is shown. Only parts of two adjacent first grooves 8 are depicted. The transverse groove area 16 of the first groove 8 extends to the radial outer surface 18 of the core 2, so that the transverse groove area 16 is open towards the air gap between the rotor 20 and the stator 21. A transverse reinforcement 19 is arranged in the transverse groove area 16 of the first groove 8, embedded in the bonding material, to provide a structural connection across the transverse groove area 16 of the first groove 8 in the circumferential direction. The transverse reinforcement 19 also includes a clip profile 1 arranged in the transverse groove area 16 of the first groove 8. In this case, the web 12 of the clip profile 1 extends in the circumferential direction in the cross section and has a hook portion 14 of different shape at the transverse end. The hook portion 14 interacts with a protrusion 15 of the core 2 extending into the transverse groove area 16.

[0031] Reference numerals

[0032] 1 clip profile

[0033] 2 cores

[0034] 3 Magnets

[0035] 4 wheel hub part

[0036] 5 External part

[0037] 6 Middle part

[0038] 7Center groove area

[0039] 8First groove

[0040] 9 Second groove

[0041] 10First reinforcement member

[0042] 11 Second reinforcement

[0043] 12 belly plate

[0044] 14 hook part

[0045] 15 protrusions

[0046] 16 Horizontal groove area

[0047] 17 Opening

[0048] 18 radial outer surface

[0049] 19 Transverse reinforcement

[0050] 20 rotors

[0051] 21 stator

[0052] 22 Winding

[0053] 23 slots

[0054] ARotation axis

[0055] BFirst Angle

[0056] C Second Angle

[0057] DDetails

Claims

1. A rotor for an electric motor, the rotor (20) comprising: A core (2) rotatable about a rotation axis (A), the core (2) comprising an outer portion (5), a first groove (8), an intermediate portion (6), a second groove (9) and a hub portion (4) circumferentially distributed around the rotation axis (A) at decreasing radial distances; A plurality of magnets (3) received in pairs in a first groove (8) and a second groove (9), wherein a central groove region (7) of the first groove (8) and the second groove (9) extends between the magnets (3), and a non-magnetic bonding material is disposed in the central groove region (7); a first reinforcement member (10) disposed in the first recess (8) and embedded in the bonding material to provide a structural connection between the outer portion (5) and the middle portion (6); and A second reinforcement member (11), which is disposed in the second groove (9), is embedded in the bonding material to provide a structural connection between the intermediate portion (6) and the hub portion (4).

2. The rotor according to claim 1, characterized in that At least one of the first reinforcement member (10) and the second reinforcement member (11) is provided as a fiber added to the non-magnetic bonding material.

3. The rotor according to any one of the preceding claims, characterized in that At least one of the first reinforcement member (10) and the second reinforcement member (11) is provided as non-magnetic particles added to the non-magnetic bonding material.

4. A rotor according to any one of the preceding claims, characterized in that At least one of the first reinforcement (10) and the second reinforcement (11) comprises a clip profile (1) arranged in a respective central recessed area (7).

5. The rotor according to claim 4, characterized in that The clip profile (1) comprises a web (12) extending in radial direction across a central groove area (7) and at least one hook portion (14) arranged at at least one transverse end of the web (12).

6. The rotor according to claim 5, characterized in that The hook portion (14) interacts with a protrusion (15) extending into the central recessed region (7) to provide a form fit with one of the outer portion (5), the middle portion (6) and the hub portion (4).

7. Rotor according to one of the preceding claims, characterized in that The central recessed area (7) is formed to provide an undercut in the radial direction for at least one of the first reinforcement member (10) and the second reinforcement member (11).

8. Rotor according to one of the preceding claims, characterized in that A transverse groove region (16) extends at a transverse end of at least one of the first groove (8) and the second groove (9), and a non-magnetic bonding material is disposed in the transverse groove region (16).

9. The rotor according to claim 8, characterized in that The transverse groove area (16) of the first groove (8) extends to the radially outer surface (18) of the core (2).

10. The rotor according to claim 9, characterized in that A transverse reinforcement (19) is arranged in the transverse groove area (16) of the first groove (8), embedded in the bonding material, to provide a structural connection across the transverse groove area (16) of the first groove (8) in the circumferential direction.

11. The rotor according to claim 10, characterized in that The transverse reinforcement (19) comprises a clip profile (1) arranged in a transverse groove region (16) of a first groove (8), the web (12) of the clip profile extending in the circumferential direction.

12. The rotor according to any one of the preceding claims 8 to 11, characterized in that An opening (17) extending axially through the core (2) is arranged in the radial direction between a transverse groove region (16) of the second groove (9) and a radial outer surface (18) of the core (2).

13. A rotor according to any one of the preceding claims, characterised in that The cross-sectional area of ​​the magnet (3) arranged in the second groove (9) is larger than the cross-sectional area of ​​the magnet (3) arranged in the first groove (8).

14. Rotor according to one of the preceding claims, characterized in that The magnets (3) accommodated in pairs in the first grooves (8) and the magnets (3) accommodated in pairs in the second grooves (9) are each arranged in a herringbone shape when viewed in cross section.

15. The rotor according to claim 14, characterized in that A first angle formed by the herringbone shape formed by the magnets (3) arranged in the first groove (8) is greater than a second angle formed by the herringbone shape formed by the magnets (3) arranged in the second groove (9).

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