Rotor for an electric machine, in particular for a motor vehicle, as well as electric machine, in particular for a motor vehicle

Abstract

The invention relates to a rotor (10) for an electric machine, comprising at least two successive segments (22a, b) in the axial direction of the rotor (10), each of which has a laminated core (24a, b) and at least one permanent magnet (26a, b) supported by the respective laminated core (24a, b), wherein the segments (22a, b) have axial end faces (S1, S2) facing each other in the axial direction of the rotor (10), which extend in a plane perpendicular to the axial direction of the rotor (10). The respective permanent magnet (26a, b) of the respective segment (22a, b) and the respective laminated core (24a, b) of the respective segment (22a, b) terminate in the plane in the axial direction of the rotor (10) towards the respective other segment (22a, b).The permanent magnets (26a, b) are arranged partially offset from each other in the circumferential direction of the rotor (10), so that the respective first sub-areas (T1) of the permanent magnets (26a, b) face each other in the axial direction of the rotor (10) and overlap each other.

Description

[0001] The invention relates to a rotor for an electric machine, in particular of a motor vehicle, according to the preamble of claim 1. Furthermore, the invention relates to an electric machine with such a rotor.

[0002] Such a rotor for an electric machine is, for example, already known from EP 2 216 883 A1. The rotor has at least two segments successive in the axial direction of the rotor, each of which has a laminated core and at least one permanent magnet supported by the respective laminated core.

[0003] Their task is to improve a rotor of the type mentioned at the beginning.

[0004] This problem is solved by a rotor with the features of claim 1 and by an electric machine with the features of claim 4. Advantageous embodiments with expedient further developments of the invention are specified in the remaining claims.

[0005] A first aspect of the invention relates to a rotor for an electric machine, in particular for a motor vehicle. This means that the electric machine, in its fully manufactured state, includes the rotor. For example, the electric machine, in its fully manufactured state, also includes a stator by means of which the rotor can be driven and thus rotated about a machine axis relative to the rotor. The electric machine is preferably designed as a high-voltage component, the electrical voltage of which, in particular its operating or rated voltage, is preferably greater than 50 volts, more particularly greater than 60 volts, and most preferably several hundred volts. In particular, the electric machine can provide a drive torque for propelling the motor vehicle via its rotor.Thus, the motor vehicle, also simply referred to as a vehicle and preferably designed as a motor car, in particular as a passenger car, in its fully manufactured state comprises the electric machine by means of which the motor vehicle can be driven, in particular purely, electrically. The rotor, whose axial direction coincides with the machine's axis of rotation, has at least two segments that are successive in the axial direction of the rotor, in particular directly, namely a first segment and a second segment. The segments are also referred to as rotor segments. When the axial direction is mentioned before and in the following, unless otherwise specified, this is to be understood as the axial direction of the rotor, whose radial direction is perpendicular to the axial direction and thus perpendicular to the machine's axis of rotation.When the radial direction is mentioned before and below, unless otherwise specified, this refers to the radial direction of the rotor, whose circumferential direction is around the axial direction and thus around the machine's axis of rotation, and extends in an imaginary plane of extension that is perpendicular to the axial direction and thus perpendicular to the machine's axis of rotation. When the circumferential direction is mentioned before and below, unless otherwise specified, this refers to the circumferential direction of the rotor. "Axial" refers to the axial direction, and "radial" refers to the radial direction.

[0006] Each segment has, in particular, a specific lamination stack. The lamination stack of the first segment is also referred to as the first lamination stack, and the lamination stack of the second segment is also referred to as the second lamination stack. Specifically, each lamination stack is made of electrical steel. Furthermore, each segment has at least one permanent magnet, also simply referred to as a magnet. The permanent magnet of the first segment is also referred to as the first permanent magnet or first magnet, and the permanent magnet of the second segment is also referred to as the second permanent magnet or second magnet. For example, the stator has a winding, also referred to as the stator winding. By supplying the winding with electrical energy, in particular electric current, a magnetic field, in particular a rotating field, can be generated and thus provided by means of the winding.The rotor can be driven by means of the magnetic field and thereby rotated around the machine's axis of rotation relative to the stator, particularly by the interaction of the magnets with the magnetic field. Specifically, each permanent magnet is designed separately from its respective lamination stack and attached to the lamination stack of the respective segment, in such a way that relative movement between the permanent magnet and the lamination stack of the respective segment is prevented. Thus, each permanent magnet of the respective segment is supported by the lamination stack of the respective segment. Each magnet generates a magnetic field, also referred to as a magnetic flux, the flux of which is also called magnetic flux or flux.

[0007] In order to achieve a particularly advantageous rotor design and a particularly advantageous operation of the electric machine, the invention provides that the segments have axial end faces facing each other in the axial direction of the rotor and, in particular, directly abutting each other in the axial direction of the rotor. These end faces extend in an imaginary plane perpendicular to the axial direction and, in particular, abut each other directly in this plane. The axial end face of the first segment is also referred to as the first axial end face, and the axial end face of the second segment is also referred to as the second axial end face.Furthermore, it is provided that the respective permanent magnet of each segment and the laminated core of each segment, viewed axially towards the other segment, terminate in the plane and thus at the respective axial end face of the respective segment. Similarly, the first permanent magnet and the first laminated core, viewed axially towards the second segment, terminate in the plane and thus at the axial end face of the first segment. Likewise, the second laminated core and the second permanent magnet, viewed axially towards the first segment, terminate in the plane and thus at the axial end face of the second segment. The axial end face of the first segment is also referred to as the first axial end face, and the axial end face of the second segment is also referred to as the second axial end face.The first permanent magnet and the second permanent magnet are arranged circumferentially, in particular exclusively, partially offset from each other, such that their respective first sections, also referred to as overlapping sections, face each other in the axial direction of the rotor and overlap each other, wherein, for example, the first sections extend in the plane and / or wherein, for example, the first sections are in direct contact with each other in the axial direction of the rotor. The first permanent magnet has a second section that extends circumferentially, i.e., in a first connection direction extending around the axial direction, directly adjoining the first section of the first permanent magnet, and which is arranged without overlap with the second permanent magnet.The second permanent magnet has a third section extending circumferentially, i.e., around the axial direction and opposite to the first connection direction, directly adjoining the first section of the second permanent magnet and arranged without overlap with the first permanent magnet. The second lamination stack has a first recess extending axially from the second section of the first permanent magnet, in which a flux barrier is arranged to impede or block the magnetic flux.The first laminated core has a second recess extending axially from the third section of the second permanent magnet to the rotor. This recess contains a second flux barrier to impede or block the magnetic flux of the magnetic field. The electromagnetically insulating axial flux barriers in each laminated core prevent contact between the permanent magnet of each segment and the laminated core of the other segment, thus preventing excessive magnetic leakage flux in that area. This allows the electric machine to deliver a particularly high torque, especially via its rotor, and prevents excessive demagnetization stress on the permanent magnets.Furthermore, compared to conventional solutions, a reduction in the opposing field load can be achieved, thereby reducing the proportion of heavy rare earth elements in the material composite of the respective permanent magnet and thus lowering costs and CO2 emissions. Moreover, the reduced opposing field load, with the same proportion of heavy rare earth elements, allows for a higher operating temperature, thus reducing cooling requirements and enabling particularly high efficiency of the electric machine.The flux barrier reduces the magnetic conductivity between the permanent magnet of each segment and the adjacent lamination stack of the other segment within the area where the flux barrier is located, particularly compared to a state where the flux barrier would not be present. Specifically, this area is a contact zone where the segments abut each other axially and, in particular, make contact with each other.

[0008] Since the permanent magnets of the segments are arranged circumferentially offset from one another, an angular misalignment is created between the permanent magnets. The flux barriers serve to prevent contact between the respective permanent magnets of each segment and the respective lamination stack of the other segment, which would otherwise occur due to this angular misalignment. This is particularly advantageous because the respective lamination stack is made of highly magnetically conductive electrical steel.

[0009] In order to achieve a particularly advantageous rotor design, one embodiment of the invention provides that the respective recess is completely filled with air as the respective flow barrier. This allows for a particularly lightweight rotor design.

[0010] In order to particularly advantageously impede or block the magnetic flux, a further embodiment of the invention provides that a paramagnetic or diamagnetic material is arranged in the respective recess as a flux barrier, in particular such that the respective recess is completely filled with the paramagnetic or diamagnetic material. This enables particularly efficient operation.

[0011] Axial flux barriers between segments or laminated cores that are not offset from each other circumferentially are not strictly necessary, since there is no axial contact between the respective permanent magnet of each segment and the axially adjacent laminated core of the other segment. The axial flux barriers according to the invention can be implemented in addition to conventional flux barriers, which are designed, for example, as magnetic pockets, and can be independent of them.Another possibility for implementing axial flux barriers is to bend the laminated core or the material from which the laminated core is formed, particularly in desired areas, in order to prevent contact between the permanent magnet of the segment and the laminated core of the other segment axially adjacent to it, and, for example, to introduce air into this area.

[0012] The invention is based in particular on the following findings and considerations: The rotor of electric machines, such as permanent magnet synchronous machines (PMSMs), typically comprises several layers of electrical steel, which can be divided into several lamination stacks. Each of these lamination stacks carries its own permanent magnet. To avoid excessive and undesirable harmonics and / or to achieve advantageous noise characteristics, also known as NVH (noise, vibration, and harshness), the individual lamination stacks are often mounted at an angular offset from one another on a rotor shaft, also referred to simply as a shaft. This method is called rotor skew and is a countermeasure in electric machines, particularly in permanent magnet synchronous machines, for traction drives to power motor vehicles.However, the angular misalignment between the permanent magnets of the individual segments can, if no countermeasure is taken, lead to undesirable stray fluxes in the contact areas between the respective permanent magnet and the respective, axially adjacent laminated core. This reduces the torque of the electric machine, as less magnetic flux reaches the stator. Furthermore, the angular misalignment leads to an increase in magnetic conductivity in the contact areas or transitions between the magnet layers. This results in a flux density concentration at the contact areas of the magnets and an increased demagnetization load on the permanent magnets. The aforementioned problems and disadvantages can now be avoided by the invention. All skew variations, such as linear, symmetrical V-skews, asymmetrical V-skews, etc., lead to the aforementioned disadvantages, which can now be avoided by the invention.

[0013] Preferably, the electric machine is designed as a permanent magnet synchronous machine. Preferably, each permanent magnet is a buried magnet arranged in the corresponding magnet pocket of the respective lamination stack of the respective segment. The invention also serves as a solution for all inclined configurations in which the permanent magnets are arranged offset from one another in the circumferential direction. The respective recess, also referred to as the respective cutout, of the respective lamination stack of the respective segment is thus, so to speak, an axial extension of the respective magnet pocket of the respective lamination stack of the other segment, thereby ensuring particularly advantageous operation.

[0014] A second aspect of the invention relates to an electric machine, in particular for a motor vehicle, wherein the electric machine according to the second aspect of the invention comprises a rotor according to the first aspect of the invention. Advantages and advantageous embodiments of the first aspect of the invention are to be regarded as advantages and advantageous embodiments of the second aspect of the invention and vice versa.

[0015] Further advantages, features, and details of the invention will become apparent from the following description of preferred embodiments and from the drawings. The features and combinations of features mentioned above in the description, as well as those mentioned below in the figure description and / or shown in the figures alone, can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention.

[0016] The drawing shows in: Fig. 1 a schematic and perspective top view of a first embodiment of a rotor for an electric machine; Fig. 2 a schematic longitudinal sectional view of the rotor according to the first embodiment; Fig. 3 a schematic front view of the rotor according to the first embodiment; Fig. 4. Partial schematic longitudinal sectional view of a second embodiment of the rotor not belonging to the invention; Fig. 5 a schematic front view of a rotor spacer element according to Fig. 4; and Fig. 6 a schematic longitudinal sectional view of a third embodiment of the rotor not belonging to the invention.

[0017] In the figures, identical or functionally equivalent elements are provided with the same reference symbols.

[0018] Fig. Figure 1 shows a schematic and perspective top view of a rotor 10 of an electric machine, particularly for a motor vehicle. This means that the electric machine, in its fully assembled state, has the rotor 10 and, for example, also a stator, by means of which the rotor 10 can be driven and thus rotated about a machine axis of rotation 12 relative to the stator. Via the rotor 10, whose axial direction coincides with the machine axis of rotation 12 and is illustrated by a double arrow 14, the electric machine can provide a drive torque for propelling the motor vehicle. When the axial direction is mentioned below and before, this refers, unless otherwise specified, to the axial direction of the rotor 10, whose radial direction is illustrated by a double arrow 16 and is perpendicular to the machine axis of rotation 12 and thus perpendicular to the axial direction.When the radial direction is mentioned before and below, unless otherwise specified, this refers to the radial direction of the rotor 10, whose circumferential direction is illustrated by a double arrow 18 and extends in an imaginary plane perpendicular to the axial direction. "Radial" refers to the radial direction, and "axial" refers to the axial direction. When the circumferential direction is mentioned before and below, unless otherwise specified, this refers to the circumferential direction of the rotor 10.

[0019] How particularly good looks Fig. 1 and Fig. As can be seen from Figure 2, the rotor 10 has a rotor shaft 20, also referred to simply as a shaft, and several segments 22a-f, also referred to as rotor segments, arranged on the rotor shaft 20. The segments follow one another in the axial direction. Each segment 22a-f has, in particular, a laminated core 24a-f and at least one permanent magnet 26a-f. The permanent magnet 26a-f is also referred to as the magnet, and the laminated core 24a-f is also referred to as the core. In particular, the magnet of each rotor segment is formed separately from the core of the rotor segment and is connected to the core of the rotor segment, in particular such that relative movements between the magnet of the rotor segment and the core of the rotor segment are prevented.In particular, the respective magnet of each rotor segment is at least partially, and especially at least predominantly and thus at least more than halfway or completely, received in a respective receptacle, also referred to as a magnet pocket, within the respective rotor segment assembly. Segments 22a and 22b form a first segment group G1. Segments 22b and 22c form a second segment group G2, segments 22d and 22e form a third segment group G3, and segments 22e and 22f form a fourth segment group G4. The respective rotor segments of each segment group G1-4 have axially facing end faces S1 and S2, with the respective axial end face S1 also being referred to as the respective first axial end face and the respective axial end face S2 also being referred to as the respective second axial end face.The respective axial end faces S1 and S2 of each segment group G1-4 extend in a respective imaginary plane perpendicular to the axial direction, wherein the planes are spaced apart from each other in the axial direction and arranged consecutively, and wherein the planes run parallel to each other, particularly when considered in pairs. In particular, the respective axial end faces S1 and S2 of each segment group G1-4 abut each other in the respective plane, particularly directly, in the axial direction of the rotor 10. It can be seen that the respective magnet of each rotor segment of each segment group G1-4 and the respective stack of each rotor segment of each segment group G1-4 terminate in the respective plane when viewed in the axial direction of the rotor 10 towards the other rotor segment of each segment group G1-4.Furthermore, the magnets of each segment group G1-4 are arranged circumferentially of the rotor 10, specifically, only partially offset from one another, such that the respective first sub-areas T1 of the magnets of each segment group G1-4, also referred to as overlapping areas, face each other axially and overlap. It can be seen that each magnet of each segment group G1-4 has a first sub-area T1 and a second sub-area T2, which adjoins the first sub-area T1 of the magnet of each segment group G1-4 in the circumferential direction of the rotor 10. Thus, no other sub-area is arranged between the respective sub-areas T1 and T2 in the circumferential direction of the rotor 10.The respective sub-area T2 adjoins the respective sub-area T1 in the circumferential direction in such a way that the respective sub-area T2 of the respective magnet of the respective segment group G1-4 is arranged without overlap with the respective other magnet of the respective segment group G1-4.

[0020] It is also apparent that each sub-area T2 of the respective rotor segment of the respective segment group G1-4 is assigned a respective recess 28, also referred to as a cutout, of the respective package of the respective other rotor segment of the respective segment group G1-4, wherein the respective recess 28 adjoins the respective second sub-area T2, to which the respective recess 28 is assigned, in the axial direction of the rotor 10, as an extension of the second sub-area T2, to which the respective recess 28 is assigned. The respective magnet provides a respective magnetic field, also referred to as a magnetic field, whose magnetic flux is also referred to as magnetic flux or flux.

[0021] In each recess 28, a flux barrier is arranged to impede or block the magnetic flux of the magnetic field of the respective magnet, whose respective sub-area T2 is assigned to the respective recess 28. This ensures particularly efficient operation.

[0022] Fig. Figure 3 shows the rotor 10 according to the first embodiment. It looks particularly good from Fig. 3 The rotor shaft 20, the magnets and the recess 28 and thus the axial flux barriers are recognizable, shown here using the example of segment 22a.

[0023] Fig. Figure 4 shows a partial schematic longitudinal sectional view of a second embodiment of the rotor 10, the second embodiment also being shown in Fig. Figure 5 shows that, in order to reduce the magnetic conductivity between the individual lamination stacks 24a-f of the segments 22a-f, at least the rotor segments of the segment groups G1-4, in particular the or all rotor segments of the rotor 10, especially when considered in pairs, are arranged axially spaced apart from one another, i.e., at a respective axially extending distance from each other. For this purpose, a spacer element 30, formed separately from the rotor segments and provided in addition to the rotor segments, is arranged between two rotor segments arranged adjacent to each other in the axial direction of the rotor 10, so that an axially extending distance is provided between the axially adjacent magnets, in which, for example, air or a paramagnetic or diamagnetic material, in particular a solid, is arranged.

[0024] Out of Fig. As can be seen in Figure 5, the spacer element 30 is designed as a ring, in particular a ring-shaped disk, with an inner diameter ID and an outer diameter AD. Specifically, the respective spacer element 30 is arranged on the rotor shaft 20. The outer diameter AD can be variable. However, the outer diameter AD is smaller in the radial direction than the outer diameter at which, for example, the respective magnet begins, particularly when viewed radially outwards. This ensures that the magnets do not make contact with the respective spacer element 30. Another way to create the spacer is, for example, by using external grooves on the rotor shaft 20, where the external grooves are located, for example, between the individual laminated cores 24a-f.The axial thickness of the spacer element 30 can depend on the geometry of the electrical machine, the angular offset, and material properties, preferably being at least 0.3 millimeters thick. For example, the spacer is or forms an electrically insulating layer. It can be seen that a spacer area extends radially outwards from each spacer, located axially between two magnets arranged adjacent to each other. The spacer layer is, for example, a gap between the axially adjacent magnets, containing, for example, air or the aforementioned paramagnetic or diamagnetic material.In particular, the spacer area is or forms an electromagnetically insulating layer between the individual magnet packs, preventing contact between the individual packs and the axially successive and adjacent magnets, thus preventing the formation of magnetic stray fluxes in this area. In other words, it is preferably provided that the respective magnets of the respective axially successive and adjacent first rotor segments, between which the respective spacer is arranged, completely follow the respective spacer radially outwards, thereby preventing the spacer from being positioned between the respective axially adjacent magnets and thus avoiding any overlap.

[0025] Even at the in Fig.In the third embodiment shown in Figure 6, the spacer elements 30 are arranged, extending radially outwards from the rotor shaft 20 to such an extent that each spacer is also positioned axially between the respective magnets arranged adjacent to one another. The spacer, preferably designed as a solid, is formed, for example, from a paramagnetic or diamagnetic material and has a lower magnetic permeability than the electrical steel sheet from which the respective stack is formed.

[0026] A spacer between segments 22c and 22d, which are angularly offset from each other, is not strictly necessary, as there is no axial contact between the respective magnet and the respective stack. The spacer can be designed separately from the rotor segments, for example, as a separating disc. Alternatively, the spacer could be formed by a coating on at least one of the rotor segments, which are held at the respective axially oriented distance from each other by means of the spacer. In the third embodiment, the spacer element 30 is or forms an electromagnetically insulating layer between the individual rotor segments and prevents direct contact between the respective magnet and the other stack, thereby avoiding excessive stray fluxes. Reference symbol list 10 Rotor 12 Machine rotary axis 14 Double Arrow 16 Double Arrow 18 Double Arrow 20 Rotor shaft 22a-f Segment 24a-f sheet metal package 26a-f Permanent magnet 28 Exclusion 30 spacer elements G1-4 Segment Group S1 axial face S2 axial face T1 first sub-area T2 second sub-area ID inner diameter AD outer diameter QUOTES INCLUDED IN THE DESCRIPTION

[0000] 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

[0000] EP 2 216 883 A1

[0002]

Claims

[1] Rotor (10) for an electric machine, comprising at least two successive segments (22a, b) in the axial direction of the rotor (10), each of which has a laminated core (24a, b) and at least one permanent magnet (26a, b) supported by the respective laminated core (24a, b), characterized by , that: - the segments (22a, b) have axial end faces (S1, S2) facing each other in the axial direction of the rotor (10), which extend in a plane perpendicular to the axial direction of the rotor (10); - the respective permanent magnet (26a, b) of the respective segment (22, b) and the respective laminated core (24a, b) of the respective segment (22a, b) terminate in the axial direction of the rotor (10) towards the respective other segment (22a, b) viewed in the plane; - the permanent magnets (26a, b) are arranged partially offset from each other in the circumferential direction of the rotor (10), such that: ◯ respective first sub-areas (T1) of the permanent magnets (26a, b) are facing each other in the axial direction of the rotor (10) and overlap each other; and ◯ the permanent magnet (26a, b) of the respective segment (22a) has a second sub-section (T2) which is arranged in the circumferential direction of the rotor directly adjacent to the first sub-section of the permanent magnet (26a, b) of the respective segment (22a, b) and which is arranged without overlap with the permanent magnet (26a, b) of the respective other segment (22a, b); - to the respective second sub-area (T2) of the respective permanent magnet (26a, b) of the respective segment (22a, b) a respective recess (28) of the respective lamination stack (24a, b) of the respective other segment (22a, b) is assigned such that the respective recess (28) adjoins the respective second sub-area (T2) to which the respective recess (28) is assigned in the axial direction of the rotor (10), in extension of the respective second sub-area (T2) to which the respective recess (28) is assigned; and - in the respective recess (28) a respective flux barrier is arranged to impede or block a magnetic flux of a respective magnetic field of the respective permanent magnet (26a, b) which has the respective second sub-area (T2) to which the respective recess (28) is assigned. [2] Rotor (10) according to claim 1, characterized by, that the respective recess (28) is completely filled with air as the respective river barrier. [3] Rotor (10) according to claim 1, characterized by , that in the respective recess (28) a paramagnetic or diamagnetic material is arranged as the respective flux barrier. [4] Electric machine, comprising a rotor (10) according to any of the preceding claims.

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