DE102019215324A1 - Rotor of a permanent magnet excited electrical machine - Google Patents

Abstract

A rotor (RO) for a permanently excited electrical machine (EM) is described which comprises a rotor body (RK) with a central axis (A) and with a circumferential surface (U) directed towards a stator (ST). The rotor (R) forms a plurality of rotor poles (RP), each of which has at least one permanent magnet (PM3) held radially inside the rotor body (RK) in a pocket (T). The permanent magnet is arranged on the rotor (RO), viewed in the axial direction, with a main direction of extent in a tangential or circumferential view. The rotor is characterized in that at least one recess (C41, C42) is formed in a radial area of the rotor body (RK) between the permanent magnet (PM3) and the circumferential surface (U).

Description

The invention relates to a rotor of a permanent magnet electrical machine according to the preamble of patent claim 1 as this already exemplified with the DE 11 2016 004 949 T5 , the DE 10 2017 206 928 A1 or the US 2012/0200186 A1 has become known.

The rotors described in the aforementioned prior art have a multi-layer arrangement of the permanent magnets, the magnets there being arranged in a V-configuration that spreads out toward an outer circumference of the rotor to form a rotor pole and within the between the V -Legs formed area centrally at least one further, tangentially aligned magnet is used to the outer circumference. In a foot area of the two V-legs, a recess is designed as a flux barrier, which is radially opposite the centrally arranged magnet.

During the operation of an electrical machine with such a rotor, it has been found that the torque of the electrical machine has a pronounced non-uniformity, in particular a significant ripple. In the case of a distributed winding, this torque ripple occurs more intensely with an order which corresponds to the number of teeth present on the stator.

The object of the invention is to improve a generic rotor of a permanent magnet-excited electrical machine in such a way that torque ripple when operating an electrical machine equipped therewith is further reduced. Furthermore, an electrical machine with such a rotor is to be shown.

The above-mentioned object is achieved according to a first aspect by a rotor with the features specified in claim 1 and according to a further aspect by an electrical machine using such a rotor according to claim 10.

Advantages and advantageous configurations and developments of the invention can be found in the dependent claims and the description of the figures.

A rotor for a permanently excited electrical machine is thus proposed which comprises a rotor body with a central axis and with a circumferential surface directed towards a stator. The rotor forms a plurality of rotor poles, each of which has at least one permanent magnet received radially inside the rotor body in a pocket. This permanent magnet is arranged on the rotor, viewed in the axial direction, with a main direction of extent in the tangential or in the circumferential direction. The rotor is characterized in that at least one recess is formed in a radial area of the rotor body between the permanent magnet and the circumferential surface.

By providing flux barriers designed as recesses on the rotor, more precisely radially in a zone between a permanent magnet buried in the radially outer edge area of the rotor in the laminated core and the circumferential surface of the rotor facing the stator, a magnetic flux density effective for a stator can be achieved in the area of a rotor pole be spatially modulated in the circumferential direction in a manner favorable to attenuating a torque ripple. The improvement achieved in this way can be felt immediately when the rotor rotates. Furthermore, the proposed modification can also noticeably reduce the noise associated with the torque ripple.

The invention is explained below by way of example using an embodiment shown in the figures.

• 1 eine schematische Ansicht einer permanenterregten elektrischen Maschine mit einem mit Permanentmagneten ausgebildeten Rotor;
• 2 eine stirnseitige Teilansicht des Rotors von 1 mit darin ausgebildeten Taschen zur Aufnahme von Permanentmagneten in einer vergrößerten Darstellung;
• 3 eine stirnseitige Teilansicht des Rotors von 1 mit in den Taschen aufgenommenen Permanentmagneten in einer vergrößerten Darstellung.

Show it:

• 1 a schematic view of a permanently excited electrical machine with a rotor formed with permanent magnets;
• 2 a front partial view of the rotor of 1 with pockets formed therein for receiving permanent magnets in an enlarged view;
• 3 a front partial view of the rotor of 1 with permanent magnets received in the pockets in an enlarged view.

The 1 shows an end view in the axial direction of a permanently excited electrical synchronous machine EM which is provided, for example, for installation and for use in a drive train of an electric or hybrid vehicle and provides a driving force for moving the vehicle. The electric machine EM can be operated both as a motor and as a generator. The electric machine EM includes a stator ST , one inside rotatable about an axis A. arranged with permanent magnets PM equipped rotor RO and one between the stator ST and the rotor RO located radial air gap LS , over which a magnetic field to generate a rotary movement of the rotor RO or to generate an induced voltage in the stator ST can spread. The stator ST is only here shown schematically and greatly simplified. This comprises a laminated core formed in a customary manner with stator teeth on which a stator winding for interaction with the rotor magnets PM is appropriate. The stator ST can in the present case, for example, have a total of 48 stator teeth and likewise 48 stator slots, in which a distributed stator winding, for example a 3-phase hairpin winding, is inserted. The stator ST forms 8 stator poles, which each effectively extend over 6 stator teeth and which also have a total of 8 rotor poles RP work together. In 1 are simplified only 8 stator teeth SZ shown.

The rotor RO has a rotor body RK on, in the present case from individual, in one direction along an axis of rotation A. stacked slats L. is made from an electrical sheet, like this with excerpts 2 is shown. The electrical steel sheet used can consist of a known material, for example with the designation N030-15. Instead of a lamella set produced in this way, the rotor body RK also be designed as a solid part, for example made of a sintered material.

At the rotor RO are a variety of permanent magnets PM in a radial space area between an axis of rotation or a central axis A. and an outer peripheral surface U , that is, an outer edge of the rotor R. within axially extending pockets T arranged. There is thus a rotor RO with buried magnets PM before, which is designed as an internal rotor in the exemplary embodiment. The rotor is for a clearer representation RO initially in 2 only with the pockets T , but without the permanent magnets and in 3 with in the pockets T permanent magnets used PM shown.

The permanent magnets PM or magnets are not subject to any special features or restrictions with regard to the material system. For example, the magnets can contain rare earth elements and in particular belong to the neodymium-iron-boron (Nd-Fe-B) material system.

With 1 illustrated arrangement of the pockets T and the magnets PM shows eight identical groups, each representing a 45 ° sector of the rotor R. or occupy an eighth of a circle, each group having a rotor pole RP trains. The following description therefore only refers to one of the rotor poles RP Referenced.

With view on 2 , 3 includes each rotor pole RP three permanent magnets PM1-3, which generally have a cuboid shape and which in the shown rectangular cross-section with a long side M1 and a short side M2 are trained. The page M1 forms the main direction of extent and can be facing 3 as a width and the side M2 as a height of one of the permanent magnets PM be considered. The aspect ratio M1 / M2 of these pages is presently equal to or greater than 3: 1. Furthermore, the magnets PM1-3 have an extension or side M3 in the axial direction as a depth, which, however, is not shown in the figures. The magnets PM can be segmented to suppress eddy currents in the axial direction with the formation of individual magnet blocks and mutually electrically isolated, with the rotor RO several such blocks can follow one another axially. As with 3 The magnets PM1-3 of a rotor pole are visible RP formed with the same cross section.

The illustrated rotor cross section comprises eight rotor poles RP and thus a total of 24 magnets PM . The magnets PM each have a magnetic north pole and a south pole, which are defined by the parallel opposite long sides M1 are formed. The magnets PM The penetrating magnetic flux exits or enters the longitudinal sides perpendicularly and runs in the direction of the surface normals of the sides M1 .

As already mentioned, each permanent magnet PM1-3 is housed in a pocket T1-3 ( 2 , 3 ), which is the cross-section of a magnet PM at least corresponds to or which compared to a magnet used there PM is formed enlarged.

Magnet receiving areas TM1-3 are provided within the pockets T1-3, of which one edge R1-3 with two parallel sides, at least on the long sides M1 the magnets PM is applied. The bags T are in the field of magnets PM dimensioned and designed so that these axially into the laminated core or the rotor body RK can be inserted and jammed there. At opposite the magnets PM pockets with larger cross-sections T are for this purpose at the magnet reception areas TM Holding projections HV provided. The magnets PM are thereby fixed against operational forces in particular in the radial direction, ie within the plane of the drawing and in the axial direction.

The rotor described here RO is with a multi-layer arrangement of permanent magnets PM educated. Here are to form a rotor pole RP two pockets T1, T2, each with a magnet PM1, PM2, arranged in a V-configuration that spreads out towards an outer circumference of the rotor, with each pocket T with a magnet PM forms a V-leg. As in 3 visible, the pockets T1, T2 are opposite the Magnets PM1, PM2 are enlarged and have next to the magnet receiving areas TM on both sides adjacent to the short side M2 the magnets PM each have recesses C11, C12, C21, C22, which prevent or weaken the spread of a magnetic flux in these areas and thus the flux in other areas of the rotor R. urges.

The two pockets T1, T2 and magnets PM1, PM2 of the V configuration are on the sheet metal lamella L. with respect to a radius line RR of the rotor R. arranged mirror-symmetrically and close an angle on the circumference α1 of about 30 ° a ( 2 ). The magnets PM1, PM2 are at an angle α2 about 60 ° to each other ( 3 ). In this arrangement, it is therefore at least approximately α2 = 2x α1.

The pockets T1, T2 are closer together radially on the inside than radially on the outside and close in a radially inner foot region F. of the two V-legs two webs S1, S2 and a central recess C1, which forms a flow barrier. The recess C1 is symmetrical to the permanent magnets PM1, PM2.

In an area radially outside of the recess C1, the further permanent magnet PM3 lies opposite this, which is arranged centrally between the magnets PM1, 2 and in particular between radially outer sections of the magnets PM1, 2. The magnet PM3 is with its long side M1 in the tangential direction or in the circumferential direction of the rotor R. aligned. The radial distance of the permanent magnet PM3 to the circumferential surface U is approximately equal to or less than the height of the permanent magnet PM3. The extension of the recess C1 in the tangential direction or in the circumferential direction corresponds approximately to the extension of the magnet PM3 in this direction. In the radial direction, the recess C1 is larger than the side M2 and smaller than the side M1 of the magnet PM1 and subsequently also the magnets PM1, 2.

Further recesses C31, C32 are provided on both sides of the magnet PM3 in the circumferential direction, which also serve for the purpose of targeted flux guidance. The recesses are separated from the pocket T3 by means of separators S3, S4 and are larger in the radial direction than the short side M2 of the magnet PM3 is formed. The recesses C31, C32 project beyond the magnet PM3 in the radial direction to the outer circumferential surface U of the rotor R. down. The recesses C31, C32 are also approximately equal to or smaller than one side in the circumferential direction M2 of the magnet PM3.

One between the rotor RO and the stator ST The effective magnetic field is in the area of the rotor poles RP and stator poles are particularly strong compared to circumferentially intermediate areas, so that the electrical machine EM when the rotor rotates R. absorbed or output torque is subject to fluctuations and a ripple of the torque is perceived. An improvement in the sense of reducing the torque ripple can be achieved by introducing further flux barriers in the immediate vicinity of the circumferential surface U of the rotor R. be achieved.

For this purpose, in the present exemplary embodiment, radially in a zone between that in the radially outer edge region of the rotor RO arranged magnet PM3 and the peripheral surface U of the rotor R. further recesses C41, C42 introduced into the laminated core. The recesses C41, C42 are formed in the circumferential direction symmetrically to the magnet PM3 and furthermore also symmetrically to the recesses C31, C32, wherein in the circumferential direction the distance between the adjacent recesses C41; C42 is slightly smaller than the distances between the recesses C41; C42 to the laterally adjacent recesses C31; C32. Alternatively, the distances between two mutually adjacent recesses C31, C32, C41; C42 should be at least about the same size.

In the circumferential direction outside the recesses C31, C32 a further recess C43, C44 is provided, which together with the recesses C41, C42 and a radially outer edge of the recesses C31, C32 at least approximately on the same pitch circle diameter TK are arranged. Furthermore, there is also at least approximately a radially outer edge of the recesses C11, C21 on this pitch circle diameter TK . The recesses C43, C44 are arranged closer to the recesses C31, C32 in the circumferential direction. The recesses C41, C42, C43, C44 are designed identically in the example discussed here and are also designed to be visibly smaller in cross section than the recesses C31, C32. In the present case, those are close to the outer edge U located recesses C41, C42, C43, C44 approximately rectangular shaped, the longer side of such a rectangle in the circumferential direction of the rotor R. extends. In the view shown, the ratio corresponds to a height of the recesses C41, C42, C43, C44 running approximately in the radial direction in relation to the short magnet side M2 approximately equal to 1: 5. Furthermore, the ratio of a width of the recesses running approximately in the circumferential direction is C41, C42, C43, C44 in relation to the short magnet side M2 approximately equal to 1: 3.

The magnets PM1, PM2 forming the V-legs and the magnet PM3 arranged centrally between them can be used in the with 1 , 2 Cross-section shown in each case from several magnets PM put together and within a common pocket T be arranged. Instead of a common pocket, separate pockets with separating webs located between them can also be provided to represent such an arrangement.

List of reference symbols

A.

Center axis, axis of rotation

C.

Recess

EM

Electric machine

F.

Foot area

L.

Lamella

LS

Air gap

M1

long magnetic side

M2

short magnetic side

PM

magnet

RO

rotor

R.

edge

RK

Rotor body

RP

Rotor pole

RR

Radius line

S.

web

SZ

Stator tooth

ST

stator

T

Magnetic pocket, pocket

TK

Pitch circle

TM

Magnet receiving area

U

Circumferential surface

α1

angle

α2

angle

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 112016004949 T5 [0001]
• DE 102017206928 A1 [0001]
• US 2012/0200186 A1 [0001]

Claims (11)

Rotor (RO) for a permanently excited electrical machine (EM) comprising, - a rotor body (RK) with a central axis (A) and with a circumferential surface (U) directed towards a stator (ST), - several rotor poles (RP) each with at least a permanent magnet (PM3) received radially inside the rotor body (RK) in a pocket (T), which is arranged on the rotor (RO) viewed in the axial direction with a main direction of extent in tangential or circumferential view, characterized in that - in a radial Area of the rotor body (RK) between the permanent magnet (PM3) and the peripheral surface (U) at least one recess (C41, C42) is formed. Rotor after Claim 1 , characterized in that the permanent magnet (PM) is rectangular, trapezoidal or arc-shaped and has a long side (M1) and a short side (M2), the long side (M1) forming the main direction of extent. Rotor after Claim 1 or 2 , characterized in that the radial distance between the permanent magnet (PM3) and the peripheral surface (U) is approximately equal to or less than the height of this permanent magnet (PM3). Rotor after one of the Claims 1 - 3 , characterized in that adjacent recesses (C31, C32) are provided on both sides of the permanent magnet (PM3) in the circumferential direction. Rotor after Claim 4 , characterized in that further recesses (C43, C44) are provided in the circumferential direction outside the recesses (C31, C32). Rotor after Claim 5 , characterized in that the further recesses (C43, C44) are arranged together with the recesses (C41, C42) and a radially outer edge of the recesses (C31, C32) approximately on one and the same pitch circle diameter (TK). Rotor after one of the Claims 1 - 6th , characterized in that on one of the rotor poles (RP) symmetrically to the permanent magnet (PM3) two further permanent magnets (PM1, PM2) are arranged in a V-configuration spreading towards the circumferential surface (U), the permanent magnet (PM3) being centered between the further permanent magnets (PM1, PM2) is arranged. Rotor after Claim 7 , characterized in that recesses (C11, C12, C21, C22) are provided adjacent to a short side (M2) of the two further permanent magnets (PM1, PM2) on both sides. Rotor after Claim 7 or 8th , characterized in that a recess (C1) is formed symmetrically between the further permanent magnets (PM1, PM2) in a foot region (F) of the V configuration. Electrical machine (EM) with a stator (ST) and a rotatable to this mounted rotor (RO), which after one of the Claims 1 - 9 is trained. Electric machine after Claim 10 , characterized in that the rotor (RO) has 8 rotor poles (RP) and the stator (ST) has 48 stator teeth (SZ).

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