Rotor for an electric machine

Abstract

Rotor (20) for an electrical machine, in particular an electric motor, which extends along a rotation axis (R), comprising at least one recess (30), wherein in the region of the at least one recess (30) at least one first retaining web (40) is provided for absorbing centrifugal forces in the rotor (20), characterized in that the at least one first holding web (40) has at least one first holding section (42) which is supported on a second holding section (52) to absorb the centrifugal forces, and wherein a locking section (70) is provided between the first holding section (42) and the second holding section (52), and wherein the holding sections (42; 52) are positioned relative to one another such that the locking section (70) is substantially subjected to pressure upon rotation of the rotor (20) about the rotation axis (R).

Description

[0001] The present invention relates to a rotor, in particular for an electrical machine, and to an electrical machine, in particular an electric motor having a rotor with internal permanent magnets.

[0002] Rotors with internal or embedded permanent or permanent magnets are used, for example, in permanent-magnet synchronous machines. This type of motor is particularly interesting in the low- and medium-power range, for example, for auxiliary and vehicle drives. To control or influence the magnetic flux within the rotor, corresponding flux barriers in the form of openings or recesses are provided in the area or between the magnets. To ensure sufficiently high strength and stability, even at high and extremely high speeds, it is common practice to provide webs in the area of ​​the flux barriers or recesses or openings. These absorb the tensile forces that arise from the centrifugal force generated by the mass of the magnets and the rotor material behind them when the rotor rotates.However, these ribs are problematic in that some of the magnets' field lines close prematurely in the rotor rather than via the stator. This creates a stray flux, which is why these ribs are also called stray ribs. Part of the magnetic mass thus serves only to "feed" this stray flux and is not effective for the magnetic circuit. This is all the more problematic because the materials used for the magnets are expensive and difficult to obtain. However, simple "isolation" or interruption of the magnetic flux is not feasible here, as the corresponding materials lack the necessary tensile strength.

[0003] US 2015 / 0 137 632 A1 concerns a rotor with V-shaped magnets. The laminated core has continuous recesses that serve as flux barriers.

[0004] It is therefore an object of the present invention to provide a rotor and an electric machine that meet the highest speed requirements with the best possible efficiency and lowest costs. This object is achieved by a rotor according to claim 1 and by an electric machine according to claim 11. Further advantages and features emerge from the subclaims as well as the description and the accompanying figures.

[0005] According to the invention, a rotor for an electrical machine, in particular for an electric motor, wherein the rotor extends along a rotational axis, comprises at least one recess, wherein in the region of the at least one recess at least one first holding web is provided for absorbing centrifugal forces in the rotor, wherein the at least one first holding web has at least one first holding section which is supported on a second holding section for absorbing the centrifugal forces, and wherein a locking section is provided between the first holding section and the second holding section, and wherein the holding sections are positioned relative to one another in such a way that the locking section is substantially subjected to pressure when the rotor rotates about the rotational axis.According to a preferred embodiment, the rotor is a rotor constructed or assembled from a plurality of, in particular punched or laser-cut, sheets, for example, electrical steel. The at least one recess, which can have a wide variety of cross-sectional shapes, preferably penetrates the rotor completely along the axis of rotation, which (initially) leads to a weakening of the rotor due to the removal of material. Advantageously, however, at least one first retaining web is provided in the area of, in other words, in particular within, the recess, which extends, as it were, away from a wall section of the recess, in particular radially—into the recess—with the first retaining section of the first retaining web interacting with the second retaining section in such a way that, as the rotor rotates about the axis of rotation, the aforementioned wall section is, so to speak, "held."In particular, by appropriately angled or deflected at least one first retaining web according to one embodiment, it is achieved that the locking section arranged or provided between the retaining sections is subjected to compressive stress. This force deflection makes it possible to use materials for the locking section that can primarily withstand compressive stress, but possibly not tensile stress. Typical materials are, for example, plastic or ceramic materials. Preferably, a non-magnetizable material is used, whereby an interruption of the magnetic circuit can be effected by means of the locking section. Advantageously, the locking section is designed such that it has low or as low a permeability as possible for magnetic fields. Expediently, the magnetic permeability is at least lower than that of the (surrounding) rotor, the rotor laminated core or the rotor iron.Preferred values ​​for magnetic permeability µ. r of the barrier section or the material of the barrier section are, for example, in a range of approximately 1. The magnetic permeability of iron is, for comparison, in a range of approximately 300 to 10,000.

[0006] According to a preferred embodiment, the rotor comprises a plurality of recesses, in particular arranged essentially in a circle, wherein the recesses are designed, at least in part, as flux barriers. The recesses preferably each comprise two V-shaped magnetic pockets, wherein the "V" opens towards an outer circumference of the rotor. Appropriate permanent magnets, for example in the form of bar magnets, are expediently arranged in the magnetic pockets. The flux barriers serve in particular to prevent the magnetic flux from closing in the rotor or to influence the course of the field lines. For this purpose, the recesses or the magnetic pockets are expediently designed such that, with respect to the axis of rotation, inner and outer flux barriers are formed. The inner flux barrier means, for example, the part of the recess which is arranged in the "V".In this area, at least one first holding web is also preferably provided, whereby the tensile forces generated by the mass of the magnets and the material behind them of the rotor during its rotation can advantageously be absorbed. Because the two holding sections engage with each other via the locking section, the stray flux can be significantly reduced and the entire magnetic material is optimally effective for the useful magnetic circuit. Depending on the design, it is possible to save up to 20% of magnetic material, which leads to corresponding cost savings. In preferred embodiments, neodymium-iron-boron magnets are used as magnets, which are very expensive, so any material savings on this side proves to be extremely advantageous.

[0007] The holding sections are expediently formed by holding surfaces that are oriented substantially perpendicular to the axis of rotation. In other words, the holding sections or holding surfaces are aligned substantially radially to the axis of rotation, thereby optimally absorbing centrifugal forces. The holding sections or holding surfaces expediently extend substantially straight or along the axis of rotation, but may also have interruptions along this axis, so they do not necessarily have to be continuous. The actual design depends in particular on the mass of the rotor, the masses to be supported, and in particular the desired maximum speed of the corresponding rotor or electric motor.

[0008] The aforementioned holding surfaces can be essentially straight or flat or planar, but alternatively also concave or convex, viewed along the axis of rotation.

[0009] The holding sections are expediently arranged substantially opposite one another or facing one another, viewed along the rotation axis. In particular, the holding sections or holding surfaces are arranged at a distance, wherein this distance is essentially closed by the blocking section. The dimensioning of the distance or the thickness of the blocking section depends on the size of the electrical machine and is approximately 1-50 mm in various embodiments. According to an alternative embodiment, the blocking section can also be understood as merely a very thin layer or ply, such as a coating, which is arranged between the holding sections; however, this coating must be designed to provide the necessary blocking effect.

[0010] The blocking section is expediently formed from a material of low magnetic permeability, in particular from a potting compound of low magnetic permeability, which is provided at least partially in the recess. Low permeability is understood to mean, for example, a permeability µ r in a range of approximately 1, or lower or slightly higher. In particular, the magnetic permeability of the blocking section is expediently lower than that of the rotor or the rotor core. Preferred materials are, for example, glass, ceramic, and / or suitable plastics with low magnetic permeability. Suitable plastic materials characterized by low or low magnetic permeability are expediently used as the potting compound. Such materials can, depending on the design, be provided with, for example, glass fiber reinforcement.

[0011] Conveniently, the blocking section can also be a strip-shaped, piece-like material which is inserted into the rotor at the corresponding position, i.e. between the corresponding holding sections.

[0012] According to one embodiment, the at least one first retaining web extends at least partially toward the rotational axis, in other words, substantially radially with respect to the rotational axis, with the first retaining section being oriented away from the rotational axis, or vice versa. For example, the first retaining web can also extend at least partially away from the rotational axis, with the corresponding first retaining section of this first retaining web then being oriented toward the rotational axis. This geometry advantageously allows the aforementioned force deflection to be realized.

[0013] The second holding section is expediently formed or shaped on a wall section of the at least one recess or on a second holding web.

[0014] According to one embodiment, the second retaining web extends, at least in sections, substantially radially to the rotational axis and terminates in the second retaining section. The first retaining web and the second retaining web expediently form a kind of "spreading web," but without the disadvantages, since the blocking section is provided between the retaining webs.

[0015] Conveniently, the first retaining web and the second retaining web each comprise a hook-shaped section, wherein the retaining sections are formed on the hook-shaped sections or at their ends. Accordingly, the first retaining web and the second retaining web each comprise a longitudinal section, wherein the longitudinal section extends substantially radially with respect to the rotation axis.

[0016] According to one embodiment, the at least one first retaining web comprises a longitudinal section and a transverse section, with two first retaining sections being formed on the transverse section. Viewed along the rotation axis, the at least one first retaining web of this embodiment has a T-shape, so to speak, with this "T" preferably being arranged such that the longitudinal section, which adjoins a wall section of the recess or, in particular, the inner flow barrier, extends radially inward, towards the rotation axis, and merges into the transverse section. In this embodiment, the retaining sections are expediently formed directly on corresponding wall sections of the recess.

[0017] The invention also relates to an electrical machine, in particular an electric motor, comprising a rotor according to the invention. There are fundamentally no restrictions regarding the type of electrical machine or electric motor. The proposed rotor design can be used for all rotors that have corresponding recesses or openings. According to a preferred embodiment, however, the electric motor is in particular a permanent magnet synchronous motor with embedded or buried magnets in a V-arrangement.

[0018] Advantageously, up to 20% of magnetic material can be used, resulting in cost savings. In addition, higher torques and speeds can be achieved without increasing leakage flux, thus enabling highly efficient high-speed machines, for example, for vehicle drives, especially in the passenger car sector.

[0019] Further advantages and features will become apparent from the following description of preferred embodiments with reference to the accompanying figures. Different features can be combined within the scope of the invention.

[0020] They show: Fig. 1: a conventional design of a rotor according to the state of the art; Fig. 2: a comparison of a conventional spreading bar with an embodiment of a first and a second holding bar; Fig. 3: an embodiment of a rotor comprising a T-shaped first retaining web.

[0021] Fig. 1 shows, as seen along an axis of rotation R, a sectional view of a stator 10, within which a rotor 20 is rotatably arranged or mounted. The rotor 20 comprises a plurality of recesses 30 distributed around the circumference, each of the recesses 30 (not all of which are provided with reference symbols) comprising an inner flux barrier 33 and two outer flux barriers 34, and wherein magnetic pockets 31 are formed in between, in which corresponding (permanent) magnets 32, which extend along the axis of rotation R, are arranged or fastened. The respective magnetic pockets 31 are arranged essentially in a V shape, with the "V" opening towards an outer circumference of the rotor 20. The inner flux barrier 33 arranged in the "V" is interrupted by a scattering web 80, or the scattering web 80 extends within this.The stray webs 80 absorb the tensile forces generated by the centrifugal force due to the mass of the magnets 32 and the material of the rotor 20 located behind them. In a magnetic sense, these webs 80 are at least partially disruptive, since some of the field lines passing through the magnets 32 do not close over the stator 10, but rather prematurely in the rotor 20. This is indicated by the (schematic) field lines F and F' shown. This is stray flux. Part of the magnetic mass thus serves merely to "feed" this stray flux and is not effective for the useful magnetic circuit; see the schematic field line F. This section is sketched with the reference numeral 36.

[0022] Fig. 2 shows, in its right-hand half, the interaction of a first holding web 40 with a second holding web 50, wherein the two holding webs 40 and 50 each have a longitudinal section 60 and a hook-shaped section 64. Both holding webs 40 and 50 end accordingly in a first holding section 42 and a second holding section 52, wherein a locking section 70 is provided or arranged between these holding sections 42 and 52. This geometric configuration can advantageously be used to realize a force deflection, by means of which, upon rotation of the corresponding rotor (not shown here), the locking section 70 is subjected to pressure. For comparison, a conventional scattering web 80 is shown in the left-hand half of the image, wherein a possible position of a rotation axis is sketched with the reference symbol R for orientation.The interaction of the first holding web 40 and the second holding web 50 expediently provides a mechanical strength similar to that provided by the scattering web 80 shown on the left. However, the provision of the blocking section 70 ensures the progression of a field line F, as shown in the . Fig. 1 is prevented, whereby, depending on the size and design of the corresponding electric motor, for example, the magnet mass can be reduced.

[0023] Fig. 3 shows a sectional view of a configuration of a rotor 20 comprising a recess 30, wherein a first retaining web 40 is arranged within the recess 30. The first retaining web 40 comprises a substantially radially extending longitudinal section 60, which merges into a transverse section 62. Two first retaining sections 42 are arranged or formed on the transverse section 62, which are positioned substantially opposite two second retaining sections 52. The two second retaining sections 52 are arranged or formed on a wall section of the recess 30. Between the retaining sections 42 and 52, locking sections 70 are provided, which are subjected to pressure or substantially pressure due to the configuration of the first retaining web 40 or due to the arrangement of the retaining sections 42 and 52 when the rotor 20 rotates about a rotation axis not shown here.The recess 30 essentially comprises two V-shaped magnetic pockets 31, in each of which a bar magnet 32 ​​is arranged. The recess 30 is designed such that outer flux barriers 34 are formed which, together with an inner flux barrier 33, into which the first holding web 40 extends, prevent, among other things, the magnetic flux from closing in the rotor. Depending on the embodiment, the entire area of ​​the inner flux barrier 33 can be filled with potting compound, whereby corresponding pressure-loaded blocking sections 70 are automatically formed. Alternatively, the corresponding blocking sections 70 are also provided only in the area of ​​the pressure load, as in the . Fig. 3 shown. List of reference symbols 10 Stator 20 rotors 30 recess 31 magnetic pocket 32 (permanent) magnet 33 inner river barrier 34 outer river barrier 36 non-effective magnet section 40 first stop bridge 42 first stopping section 50 second landing stage 52 second stopping section 60 Longitudinal section 62 cross section 64 hook-shaped section 70 restricted section 80 spreading bridge F, F' field lines R rotation axis

Claims

[1] Rotor (20) for an electrical machine, in particular an electric motor, which extends along a rotation axis (R), comprising at least one recess (30), wherein in the region of the at least one recess (30) at least one first retaining web (40) is provided for absorbing centrifugal forces in the rotor (20), characterized by , that the at least one first holding web (40) has at least one first holding section (42) which is supported on a second holding section (52) to absorb the centrifugal forces, and wherein a locking section (70) is provided between the first holding section (42) and the second holding section (52), and wherein the holding sections (42; 52) are positioned relative to one another such that the locking section (70) is substantially subjected to pressure upon rotation of the rotor (20) about the rotation axis (R). [2] Rotor according to claim 1, comprising a plurality of recesses (30), wherein the recesses (30), at least in regions, are designed as flow barriers (33; 34). [3] Rotor according to claim 1 or 2, wherein the holding sections (42; 52) are formed by holding surfaces which are oriented substantially perpendicular to the axis of rotation (R). [4] Rotor according to one of the preceding claims, wherein the holding sections (42; 52) are arranged substantially opposite or facing each other. [5] Rotor according to one of the preceding claims, wherein the blocking section (70) is formed by a material of low magnetic permeability, in particular by a potting compound of low magnetic permeability, which is provided at least in regions in the at least one recess (30). [6] Rotor according to one of the preceding claims, wherein the at least one first holding web (40) extends at least partially towards the axis of rotation (R), and wherein the first holding portion (42) is oriented away from the rotation axis (R), or vice versa. [7] Rotor according to one of the preceding claims, wherein the second holding portion (52) is formed / shaped on a wall portion of the at least one recess (30) or on a second holding web (50). [8] Rotor according to claim 7, wherein the second holding web (50) extends at least in sections substantially radially to the axis of rotation (R) and ends in the second holding section (52). [9] Rotor according to one of claims 7-8, wherein the first retaining web (40) and the second retaining web (50) each comprise a hook-shaped portion (64), and wherein the holding sections (42; 52) are formed on the hook-shaped sections (64). [10] Rotor according to one of the preceding claims, wherein the at least one first retaining web (40) comprises a longitudinal section (60) and a transverse section (62), and wherein two first holding sections (42) are formed on the transverse section (62). [11] Electrical machine, in particular electric motor, comprising a rotor according to one of the preceding claims.

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