WO2019179863A1

WO2019179863A1 - Rotor of a permanent-magnet-excited electric machine

Info

Publication number: WO2019179863A1
Application number: PCT/EP2019/056378
Authority: WO
Inventors: Matthias BERINGER; Stephan TENNER; Matthias Cudok; Philipp NEIDHARDT; Walter Wolf
Original assignee: Zf Friedrichshafen Ag
Priority date: 2018-03-21
Filing date: 2019-03-14
Publication date: 2019-09-26
Also published as: DE102018204300A1

Abstract

The invention relates to a rotor (R) for a permanent-magnet-excited electric machine, comprising a rotor body (RK) having a central axis (A) and an outer peripheral surface (U), wherein a plurality of pockets (T) with permanent magnets (PM) arranged therein are provided in a radial region between the central axis (A) and the peripheral surface (U), and wherein the permanent magnets (PM) have edges (K) extending axially within the rotor body (RK). According to the invention, the pockets (T) have recesses (C2) in the region of the edges (K) and the edges (K) are released in this way.

Description

Rotor of a permanent-maaneterreaten electrical machine

The invention relates to a rotor of a permanent magnet-excited electrical machine according to the preamble of patent claim 1, as has already become known by way of example with DE 10 2008 059 347 A1.

The object of the invention is to present a rotor equipped with permanent magnets of an electrical machine with a high magnetic power density. Furthermore, such a rotor is to be represented, in which the magnets are additionally reliably supported even under high speeds, in particular occurring in a drive train of a vehicle relative to operational centrifugal forces and wherein the rotor has a high dimensional stability even under such a speed influence and the permanent magnets are secured shatterproof. In particular, these requirements should also be met beyond the stated range, in particular in a range above approximately 7,000 revolutions to approximately 20,000 revolutions per minute. At the same time, the mass moment of inertia of the rotor should be kept comparatively low.

At least one of the above objects is achieved by a rotor having the features specified in claim 1 and by an electric machine using such a rotor according to claim 6.

Advantages and advantageous embodiments and developments of the invention are the dependent claims and the description of the figures removed.

The invention will be explained by way of example with reference to an embodiment shown in the figures.

Show it:

1 is a partial end view of a permanent magnet rotor with pockets formed therein for receiving permanent magnets.

FIG. 2 is a partial end view of the permanent magnet rotor of FIG. 1 with permanent magnets disposed in pockets; FIG. Fig. 3 shows the arrangement of Fig. 2 with further registered feature names.

The figures show a frontal plan view of a rotor R for a permanent magnet excited electric machine, in which a plurality of permanent magnets PM completely in a radial space between a rotation axis and a center Z and an outer peripheral surface U and a Outside ßeren edge of the rotor R are arranged. Thus, there is a rotor R with buried magnets, which in the exemplary embodiment is designed as an internal rotor. The rotor R has a rotor body RK, which in the present case is made of individual laminations L stacked in one direction along the axis of rotation and made of an electrical sheet. In this case, Fig. 1 shows a section of the rotor R and also in sections the formation of a single lamination L. The used electric sheet may consist of a known material, for example with the well-known in the art designation NO30-15. Instead of a laminated core thus produced, the rotor body RK can also be formed as a solid part, for example of a sintered material.

The permanent magnets PM or short magnets are not subject to any special features or restrictions with regard to the material system. For example, the magnets may contain rare earth elements and in particular belong to the material system neodymium-iron-boron (Nd-Fe-B). In addition to the rotor, an electric machine basically also comprises a stator with a stator winding, which is designed to enter into a magnetic interaction with the rotor explained in more detail below. On a representation and detailed description of the stator is omitted, since this is not a subject of the invention treated here and its basic structure is well known to those skilled in the art. An electric machine based on the proposed rotor R can be operated both as a motor and as a generator, and can be used, for example, as a drive source in an electric or hybrid vehicle. FIGS. 1-3 each show a 45.degree. Sector of the rotor R or an octet circle thereof. The arrangement shown occurs on the rotor R or on a lamination L thus a total of 8 times. The existing in the entire sector SE geometric arrangement of magnets and recesses forms a geometric motif. So a total of 8 motives are formed on a full circle, which can be converted into each other by a rotation by one-eighth of the rotor axis or by reflection at an axial plane.

The permanent magnets PM1 -6 used generally have a cuboid shape and are formed in the rectangular cross-section shown with a long side M1 and a short side M2. In the extension, which is not shown here in the axial direction of the rotor R, the magnets PM have an axial extent or a depth M3. The edges K extending in the axial direction in the abutting region of the sides M1 and M2 may be rounded off to form an edge radius PMR. The magnets PM can be segmented for the suppression of eddy currents in the axial direction to form individual magnetic blocks and be mutually electrically isolated, wherein the rotor R several such blocks can follow each other axially. To form a motif, similar magnets PM1 -6 or blocks are advantageously used, at least in cross-section, whereby the manufacturing costs of a rotor R can be limited. The illustrated rotor cross-section thus comprises a total of 48 magnets PM. The magnets PM each have a magnetic north pole and a south pole, which are each formed by a long side M1. The magnetic flux permeating the magnets PM emerges vertically from the longitudinal sides or into them and runs in the direction of the surface normals of the sides M1.

It can be seen in the figures that each permanent magnet PM1 -6 is accommodated in a magnetic pocket T1 -6. For this purpose, magnet receiving areas TM1 -6 are provided within the pockets T, of which an edge R1 -6 abuts at least on the longitudinal sides M1 of the magnets PM. The number of pockets T or the number of magnet receiving areas TM corresponds to the number of magnets PM. The pockets T are sized and in the range of magnets PM designed that the magnets PM can be axially inserted into the laminated core or the rotor body RK and clamped there. The magnets PM are thereby fixed in particular in the radial and in the axial direction against operational forces.

The magnets PM and the pockets T are recognizably arranged in two radially staggered V-shaped groups V1, V2, which form a first group V1 with magnets PM1, 2 and a second group 2 with magnets PM3-6. The pockets T of a group V or the two legs V1 .1, V1 .2; V2.1, V2.2 of a V are arranged inclined to each other. Each pocket T has, for the purpose of forming a magnet receiving region TM at its boundary R, two mutually parallel sides RM which interact with the longitudinal sides M1 and in this way virtually coincide. The pockets T of each group V are radially inwardly closer together than radially outward and close in the radially innermost region in each case a web S1, S2 with mutually parallel sides S1 .1, S1 .2; S2.1, S2.2, where, however, instead of parallel straight lines, alternatively or additionally, curved boundary lines can also be implemented. The angle between two associated V-limbs V1 .1, V1 .2 or V2.1, V2.2 can basically be an acute, a right, a blunt or even an extended angle.

The first, radially outer V-shaped group V1 comprises two pockets T1, T2, which include a sector SE1 with an angle a1 (alpha 1), which in the exemplary embodiment is about 90 °. Each of the two V-legs of this group V1 is formed by exactly one pocket T. The two pockets T1, T2 of the first group V1 are arranged on the lamination L with respect to a radius vector RR1 of the rotor R mirror-symmetrical and positioned at an angle of approximately 45 ° to the radius vector RR1.

The second, radially inner V-shaped group V2 comprises a total of four pockets T3-T6, which include a sector SE2 with an angle a2 (alpha 2), which in the figure is about 82 °. In the present case, therefore, the angle is cd> a2 (alpha 1> alpha 2). Each of the two V-legs V2.1, V2.2 of this group V2 is determined by two pockets T3, T4; T5, T6, which follow one another along a straight line in each case in the direction of the long side M1. The four pockets T of the second group V2 are also arranged mirror-symmetrically on the lamination L relative to the radius vector RR1 and are positioned at an angle of approximately 41 °, that is to say smaller than 45 ° to the radius vector RR1.

On a lamination L, the two groups V1, V2 are arranged such that their mirror plane coincides with an axial plane and the radius vector RR1 passing through it.

The pockets T3-T6 and the magnets PM3-PM6 of the second group V2 thus span a spatial region or the sector SE2, in which the magnets PM1, 2 of the first group V1 are arranged. In other words, the magnets PM of the first group V1 are enclosed by the magnets PM of the second group V2, the sector SE2 being bounded by an associated area of the outer circumference U of the rotor R. Furthermore, two adjacent to the cross section shown in the circumferential direction adjacent motives are arranged in mirror image, the mirror plane coincides with a radius vector RR2.

In the present case, an inner radius IR of the laminated core is about 2 length units and an outer radius OR is about 7 linear units, so that the laminated core has a radial extent of about 5 length units. The side M1 of a magnet PM in this case is about 1 to 1, 6, in particular about 1, 3 units of length. The quantities M1, ID and OD thus relate to one another such as (1 .... 1, 6): 2: 7.

As can be seen in the figures, the pockets T are enlarged relative to the magnets PM and, in addition to the magnet receiving areas TM and thus adjacent to the short side M2 of the magnets PM on both sides, have recesses or recesses C2, C20 and C4, respectively. Furthermore, recesses C1, C30 are provided in the vicinity of magnets PM, which are formed separately from the pockets T and which will be explained in detail below. The recesses C extend in the axial direction through the rotor. In the figures, it can initially be seen that a recess C1 is formed in the sector SE1 which is stretched open by the first group V1 and occupies therein a comparatively large area of a lamination L or of the rotor body RK. This recess C1 is formed with respect to an axial section plane symmetrical to the two adjacent magnets PM1, PM2 and in the radial direction approximately centrally to a shortest connecting line 11 of the magnets PM1, PM2 and the outer boundary U of the lamination L and the rotor R arranged (Fig. 3). In the present case, the recess C1 is formed as a rounded triangle, wherein in principle other shapes are possible.

The recess C1 serves to reduce the mass inertia of the rotor R overall and in particular to reduce the mass of the rotor body RK enclosed between the magnets PM1, PM2 of the first group V1. The recess C1 thus acts as a mass relief opening and is formed radially outside of the web S1, which space the two magnets PM 1, PM2 and the pockets T1, T2 in the circumferential direction. In this case, the web S1 supports a space region of the rotor body RK which is radially outside this and is enclosed by the two magnets PM1, PM2 against forces acting on it. In the exemplary embodiment shown, the cross-section of the recess C1 behaves like the area enclosed by the web S1 and enclosed by the adjacent or associated magnets PM1, 2, such as 1: 5. Depending on the arrangement of the magnets and the constructive conditions available in each case, said ratio can also be smaller and larger, and in particular in a range from about 1: 7 or greater.

Instead of a single recess C1, it is alternatively also possible for a plurality of mass-relieving recesses to be embodied in the area mentioned, with the said area ratio correspondingly likewise being able to be realized. The web S1 forms an inner support section, which together with one each formed between the radially outer portions of a magnet and the edge region further web S3, S4 supports said region. The further webs S3, S4 form outer support areas. The area between the magnets PM1, PM2 is thus held by a total of three support areas S1, S3, S4.

As a result of the mass relief of the web S1 can thus be made weaker and in particular in the circumferential direction of the rotor R narrower. At the same time, the magnets PM1, PM2 adjacent to the recess C1 can thereby be displaced further outward in the radial direction into the edge region of the rotor R near the peripheral surface U. It can be seen in the figures that the distance of the magnets PM1, PM2 from the edge region U of the rotor R is smaller than a width of the web S1 and is only approximately half the web width.

In this way, the magnets PM1, PM2 of the first group V1 overall can be brought closer together in the circumferential direction, whereby the magnetic power density, the efficiency and the maximum achievable torque of the electric machine can be markedly increased. The recess C1 is arranged outside a main magnetic flux passing through the rotor R, which would propagate there in the absence of a recess C1. In particular, the recess is arranged in a region with a magnetic flux which is small relative to a main magnetic flux or in a region which is essentially free of magnetic flux. Thus, the recesses C1 do not constitute flow barriers for selectively influencing the magnetic flux within the rotor body.

The geometric design and the positioning of the recess C1 in the illustrated and explained manner thus lead in comparison to a closed there rotor body to only a small and minimized influence of the magnetic flux, the above-mentioned positive aspects significantly outweigh. In general, the provision of recesses and the associated mass reduction in a radially outer area of the rotor are associated with a positive effect, especially at high speeds. In the exemplary embodiment, the recesses C1 are provided in particular in a radial region above or from about 6/7 of the radius OR and in particular between about 6/7 and 7/7 of the radius OR. As already mentioned above, the magnets PM are fixed in a frictional manner by clamping within the magnet receiving areas TM.

The clamping can form an exclusive method of attachment. If required, however, an adhesion of the magnets PM can take place alternatively and / or additionally. In order to avoid mechanical stress peaks and a resulting brittle fracture of the magnets PM, which may occur in particular under the influence of high rotational speeds, comparatively small recesses C2 are provided at edge positions of the magnet receiving areas TM or in the end areas of the parallel sides M1 exemplified for the magnet PM3 in Fig. 2 and designated there. Corresponding recesses C2 are provided on all pockets T1 -6. These recesses C2 are formed in regions of the edges K of the magnets PM formed by the sides M1, M2 and extending along M3, and each have a curved contour with comparatively small radii. The said edges K of the magnets PM are thus free and do not abut the edges R of the pockets T. As a result, the magnets PM are not exposed to increased mechanical loads in these particularly fracture-sensitive zones even under operating conditions.

Adjacent to the radially outer regions of the four magnets PM1 -4 of the second group V2, recesses C20 are made over the entire width of side M2, which interconnect the recesses C2 present at the edges K (FIG. 2). The sides M2 are thus completely free. The magnets PM may be K eckig or with an edge radius in the region of these edges. In the latter case, the radius can at least fall on the order of magnitude of the edge radius of the magnets.

It can be seen from the figures that the permanent magnets PM are joined over their entire sides with their sides M1 to the rotor body RK. More specifically, the permanent magnets PM are joined only to the sides M1 to the rotor body RK and the two sides M2 are free. According to a preferred fastening The permanent magnets PM are exclusively positively frictionally joined to the rotor body RK, in particular pressed in.

Through the recesses C2 and in the following also through the recesses C20 a higher mounting and operational safety of the magnets PM is realized. Even an optionally applied on the surface of the magnets PM insulating coating can be spared as possible and preserved from damage.

For effective and in particular for targeted spatial guidance of a magnetic flux within the rotor R further recesses C3 are provided, which act as obstacles in the propagation of the magnetic flux. In this way, unwanted magnetic short circuits in the rotor R can be avoided and simultaneously achieved that the magnetic flux can propagate in a defined manner on a desired path between the rotor R and a stator. Such recesses C3 are provided in the embodiment discussed in a radially outer region of the rotor R and thus close to the outer peripheral surface U. For the formation of such flux barriers, the pockets T1, T2 of the first group V1 have extensions whose radially outer boundary is formed at least approximately parallel to the outer peripheral surface U of the rotor and thus bounds the webs S3, S4. In the present case, these extensions or recesses C3 are in particular approximately triangular in shape. In principle, other forms can also be used.

The radially outer pockets T3, T6 of the second group V2 have a larger radial distance to the outer peripheral surface U of the rotor R than the pockets T1, T2 of the first group V1. In this case, the respectively assigned recesses C30 and flux barriers are designed separately from the magnetic pockets T3, T6. The recesses C30 are also formed approximately triangular with an at least approximately parallel to the outer peripheral surface U of the rotor R extending radially outer boundary, whereby there are webs S9, S10. As can be seen in Fig. 2, between the recesses C20 and C30 are more Webs S5, S6 are provided, which adjoin with two parallel edges to said recesses. Between the pockets T3, T4 and T5, T6 further webs S7, S8 are formed.

Further, as flow barriers serving recesses or recesses C4 are also provided on the respective radially innermost pockets T1, T2 and T4, T5 of the first and second group V1, 2, in particular in a foot region F of the respective V arrangement, to which the magnets PM of a group V in the circumferential direction closest together. The webs S1, S2 are thus also in the respective Fu ßbereich F1, F2 is. These recesses C4 generally have an asymmetrical shape and in the exemplary embodiment are approximately asymmetrically drop-shaped. With reference to the figures, it can be seen that the recesses C4 have a main extension direction approximately at the center of the rotor R. In other words, the maximum extent C4R of the recesses C4 located outside a magnet PM in the radial direction is appreciably greater than its maximum extent C4U in the circumferential direction of the rotor body RK (FIG. 1). In the present case, the ratio is about 1.8: 1. Particularly advantageous is a ratio from about 1, 3: 1 and larger. In order to form a web S1, S2, parallel edges S1 .1, S1 .2 are respectively provided on two recesses C4 adjacent in the circumferential direction. S2.1, S2.2 provided, which thus extend substantially in the direction of the radius vector RR1. By means of a web S1, S2, the respectively radially outer structural regions of the rotor R are mechanically supported. Even with these recesses C4 rounded contour lines are formed to avoid mechanical stress peaks. However, the maximum radii used in this case are based on the previously explained recesses C2, C20, C3,

C30 comparatively large. In particular, the path of the magnetic flux in these areas is extended by the drop-shaped formation of the recesses C4 and reduces the formation of short circuits. This measure also causes a higher speed stability of the rotor R. The embodiments of the various types of recesses explained above can take place on a rotor, taken alone or in any combination.

Bezuaszeichen

A center axis, rotation axis RR2 radius vector

C1 recess edge radius

C2 recess S1 -10 bridge

C3 recess 51 .1 side

C4 recess 51 .2 side

C4R radial extent 52.1 side

C4U perimeter extension 52.2 page

C20 recess SE sector

C30 recess SE1 sector

F1, 2 foot SE2 sector

IR inner radius T 1 -6 Magnetic pocket, ash

K edge TE edge position

L Lamelle TM1 -ßMagnetaufnahmebereich

11 distance U circumferential surface

M1 magnet side V1 first group

M2 magnet side V2 second group

M3 magnet side V1 .1 V-leg

OR outer radius V1 .2 V-leg

PM magnet V2.1 V-leg

PMR edge radius V2.2 V-leg

R rotor Z center

R1 -6 edge

RK rotor body al angle

RM side a2 angle

RR1 radius vector

Claims

claims

A rotor (R) for a permanent magnet electric machine comprising a rotor body (RK) having a central axis (A) and an outer peripheral surface (U), wherein in a radial region between the central axis (A) and the peripheral surface (U) a plurality of pockets (T) with permanent magnets (PM) arranged therein are provided, and wherein the permanent magnets (PM) have edges (K) which extend axially within the rotor body (RK),

characterized in that the pockets (T) in the region of the edges (K) recesses (C2) and the edges (K) are thereby released.

Second rotor (R) according to claim 1, characterized in that the permanent magnets (PM) are formed with a substantially rectangular cross-section and in a radial plane of the rotor (R) has a long side (M1) and a shorter side ( M2), wherein on one side (M2) formed recesses (C2) are interconnected by a further recess (C20) and the side (M2) is completely free.

3. rotor (R) according to claim 1 or 2, characterized in that the permanent magnets (PM) are substantially over the entire surface with their sides (M1) joined to the rotor body (RK).

4. rotor (R) according to one of claims 1 to 3, characterized in that the permanent magnets (PM) are joined exclusively with the sides (M1) to the rotor body and both sides (M2) are free

5. Rotor (R) according to one of claims 1 to 4, characterized in that the permanent magnets (PM) are joined only frictionally to the rotor body (RK).

6. Permanent-magnet electric machine with a stator and a rotatably mounted to this rotor (R), which is designed according to one of the claims 1-5.