EP2909921A2 - Ensemble stator pour une machine électrique à excitation par aimants permanents - Google Patents

Ensemble stator pour une machine électrique à excitation par aimants permanents

Info

Publication number
EP2909921A2
EP2909921A2 EP13774399.3A EP13774399A EP2909921A2 EP 2909921 A2 EP2909921 A2 EP 2909921A2 EP 13774399 A EP13774399 A EP 13774399A EP 2909921 A2 EP2909921 A2 EP 2909921A2
Authority
EP
European Patent Office
Prior art keywords
permanent magnet
magnetization
arrangement
rotor
rotor assembly
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP13774399.3A
Other languages
German (de)
English (en)
Inventor
Steven Andrew Evans
Jochen Geissler
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Robert Bosch GmbH
Original Assignee
Robert Bosch GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Robert Bosch GmbH filed Critical Robert Bosch GmbH
Publication of EP2909921A2 publication Critical patent/EP2909921A2/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K1/00—Details of the magnetic circuit
    • H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
    • H02K1/22—Rotating parts of the magnetic circuit
    • H02K1/27—Rotor cores with permanent magnets
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K1/00—Details of the magnetic circuit
    • H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
    • H02K1/22—Rotating parts of the magnetic circuit
    • H02K1/27—Rotor cores with permanent magnets
    • H02K1/2706—Inner rotors
    • H02K1/272—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis
    • H02K1/274—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis the rotor consisting of two or more circumferentially positioned magnets
    • H02K1/2753—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis the rotor consisting of two or more circumferentially positioned magnets the rotor consisting of magnets or groups of magnets arranged with alternating polarity
    • H02K1/276—Magnets embedded in the magnetic core, e.g. interior permanent magnets [IPM]
    • H02K1/2766—Magnets embedded in the magnetic core, e.g. interior permanent magnets [IPM] having a flux concentration effect
    • H02K1/2773—Magnets embedded in the magnetic core, e.g. interior permanent magnets [IPM] having a flux concentration effect consisting of tangentially magnetized radial magnets

Definitions

  • the present invention relates to permanent magnet excited electrical machine, in particular a rotor assembly for such an electric machine.
  • Rotor arrangements are known from the state of the art, which have pole pieces which provide a field magnet field generated by permanent magnets in the direction of an air gap to a stator arrangement.
  • the permanent magnets are arranged with their polar direction parallel to the direction of movement of the rotor, so that the pole pieces of the rotor arrangement are located between the permanent magnets.
  • the magnetic field emitted by the permanent magnets is deflected in the direction of the air gap.
  • Such types of rotor assemblies are nowadays used in many permanent magnet-excited electric machines, for example in steering assistance and in cooling devices.
  • substantially parallelepiped-shaped permanent magnets are used, which are simple and can be produced with little effort, with a magnetization anisotropy and a magnetization direction rectified in the direction of the movement of the rotor being aligned.
  • such an arrangement of the permanent magnets is referred to as a spoke arrangement.
  • the polar direction of the permanent magnets runs in the tangential direction.
  • An advantage of such rotor arrangements is that, by suitable dimensioning, an air gap flux density which is greater than the remanent flux density of the permanent magnets used can be achieved. Since the air gap flux density decisively determines the torque density of the electric machine, powerful electric machines with relatively high torque densities can be built thereby.
  • the number of permanent magnets in the rotor is chosen such that its radial width is greater than the tangential width of the pole shoes between the permanent magnets.
  • This arrangement concentrates the magnetic flux into the air gap to produce an air gap flux density that is higher than the remanent flux density of the permanent magnets.
  • the above rotor arrangements are often constructed in combination with permanent magnets of simple, inexpensive magnetic material, in particular magnetic material without rare earth compounds and with relatively low remanence flux density, such as, for example, permanent magnets of sintered ferrite materials of the sixth generation.
  • permanent magnets made of sintered ferrite materials have a relatively low coercive force, so that there is a risk of demagnetization in the case of an opposing magnetic field of sufficiently high field strength.
  • the permanent magnets are made relatively thick in the direction of their material anisotropy and their magnetization to make them more resistant to demagnetization by the stator field of the electric machine.
  • the permanent magnets thus arranged are often twice as thick (in poling direction) as permanent magnets made of ferrite material with their polar direction parallel to the air gap magnetic field, the design only an air gap in their respective flow path exhibit.
  • rotary electric machines with a certain rotor diameter and a predetermined number of poles leads at a
  • a rotor assembly for an electrical machine comprising:
  • An idea of the above rotor arrangement is to provide the permanent magnet with a direction of magnetization different from the arrangement direction, at least in a demagnetization region in which demagnetization of the permanent magnet may occur by the action of a stator magnetic field of a stator assembly.
  • the magnetization of the permanent magnet no longer completely, but only partially precludes the demagnetizing stator magnetic field. Since the direction of magnetization of the permanent magnet deviates in the direction of demagnetization from the direction parallel to the opposing stator magnetic field, a correspondingly reduced demagnetization is effected. This makes it possible for the effect of the demagnetization effect to be weakened in the demagnetization region in which irreversible demagnetization can occur in the case of permissible stator magnetic fields.
  • the permanent magnet is constructed in such a way that a change in direction of the magnetization is provided in the demagnetization region or zones.
  • the magnetization direction is expedient for the magnetization direction to be deflected at least partially in the direction of the air gap. This makes it possible that the deflected magnetization of the permanent magnet contributes in addition to the air gap flux.
  • the profile of the magnetization in the second section of the permanent magnet may correspond to a Halbach magnetization, so that pole faces extend over a plurality of sides of the permanent magnet.
  • the second section is provided at two opposite ends of the permanent magnet in an extension direction transverse to the magnetization direction of the first section. Furthermore, an angle between the arrangement direction of the pole shoes and the course of the magnetization in the second section of the permanent magnet can be greater than 45 °, in particular 90 °.
  • the second portion of the permanent magnet may have a rectilinear magnetization which is perpendicular to the magnetization of the first portion of the permanent magnet.
  • the second portion of the permanent magnet has two regions whose magnetization directions are opposite to each other.
  • the permanent magnet may be formed in one or more parts.
  • first section and the second section adjoin one another in a direction which runs perpendicular to the arrangement direction of the pole shoes.
  • a stator assembly for providing a stator magnetic field and the above rotor assembly is provided, wherein the pole pieces of the rotor assembly are separated by an air gap of the stator assembly, wherein the second portion of the permanent magnet is provided at least in a region in which in an operating state of the electric machine, the direction of the
  • Stator magnetic field is opposite to the magnetization direction of the first section.
  • Figure 1 is a schematic cross-sectional view of an electric machine with a rotor assembly, in which the permanent magnets are arranged in a spoke arrangement; 1 shows a sectional view of the cross-sectional view of the electric machine of FIG. 1 with illustrated field lines, to illustrate the region in which demagnetization of the permanent magnet can occur;
  • FIG. 3 shows a representation of the field lines of the magnetization of the
  • Permanent magnets for use in a rotor arrangement according to a first embodiment of the invention
  • Figure 4 is an illustration of the field lines of the magnetization of a
  • Permanent magnets for use in a rotor arrangement according to a further embodiment of the invention.
  • Figure 5 is an illustration of an embodiment of a permanent magnet for use in a rotor assembly according to another embodiment of the invention.
  • FIGS. 6a and 6b show an arrangement of a plurality of permanent magnets for
  • the electric machine 1 has a cylindrical stator 2.
  • the stator 2 comprises a cylindrical stator yoke region 21, from which stator teeth 22 arranged equidistantly in the circumferential direction project radially inwardly and define with their inwardly directed ends a likewise cylindrical inner recess 3.
  • the stator teeth 22 are provided at their radially inner ends with tooth heads 23, which have an approximately circular segment-shaped, concave outer have contour.
  • the stator teeth 22 are provided with (not shown) stator coils through which a stator magnetic field can be generated when energized.
  • a likewise cylindrical rotor 4 (rotor of the electric machine) is rotatably arranged on a shaft 5 as a rotor arrangement.
  • the rotor 4 has a rotor body 41, which is provided with pole shoes 42, which are connected via webs 43 with an arranged on the shaft 5 in the return region 44.
  • the webs 43 are preferably dimensioned so that they have a sufficient mechanical stability to keep the pole pieces 42 against centrifugal and transverse forces during acceleration or deceleration of the motor and still have a cross section which is sufficiently small to that caused by the permanent magnets 7 magnetic flux through the return region 44 as low as possible.
  • the pockets 6 are arranged, in which permanent magnets 7 are received.
  • the pockets 6 extend substantially obliquely in the radial direction from approximately the outer circumference of the rotor 4 to the return region 44 of the rotor 4. In order to limit the pockets 6 in the radial direction to the outside, have the
  • Pol magnets 45 which engage over the arranged in the pockets 6 permanent magnets 7 and to keep them reliable, even against the action of centrifugal forces upon rotation of the rotor 4, in the pockets 6.
  • Such an electric machine 1 is operated, for example, by an electric motor by the stator coils are energized so that a rotating stator magnetic field is generated, which interacts with the caused by the permanent magnet 7 via the pole pieces 42 exciter magnetic field and thereby exerts a torque on the rotor 4.
  • the permanent magnets 7 are usually manufactured by pressing ferrite powder material and then sintered, wherein the ferrite material is given a magnetization anisotropy during pressing by applying a magnetic field and then magnetizing the sintered material in the direction of anisotropy.
  • the permanent magnets 7 are preferably provided cuboid, with their polar direction in the tangential direction, ie perpendicular to the interfaces between the pole pieces 42 and the pockets 6.
  • Figure 2 the magnetic field of an electric machine 1 is shown under full load. At this particular rotor position, the permanent magnet 7 shown is considerably affected by the force acting on the permanent magnet
  • Stator magnetic field loaded which is represented by the larger distance between the magnetic flux lines in the permanent magnet 7.
  • the larger distance between the magnetic flux lines corresponds to one by the action of the
  • Stator magnetic field reduced flux density which means that the permanent magnet 7 has been partially irreversibly demagnetized in this area by the stator magnetic field.
  • the demagnetization occurs in particular in a demagnetization region of the permanent magnet 7, which is marked in FIG. 2 with DM.
  • the demagnetization region is located at the air gap facing the end of the permanent magnet 7 on the direction of movement of the rotor remote from the permanent magnet 7 and extends over about one-fifth to half the radial length of the permanent magnet 7 and over a tenth to one third of its tangential width.
  • the demagnetization occurs as soon as the magnetic field strength of the stator magnetic field is sufficient to achieve a field strength in corresponding regions of the permanent magnet 7 which has an equal or greater amplitude than corresponds to the coercive force of the permanent magnet 7.
  • magnetization of the permanent magnet 7 can now be provided, as shown in FIG. A shaft 5 facing the first portion 71 of the permanent magnet 7, ie a section facing away from the air gap, a conventional rectilinear Mag- netization in a thickness direction between the pole pieces 42 facing pole faces, parallel to the arrangement direction of the permanent magnets 7 and the pole pieces 42, in the illustrated embodiment, in the tangential direction of the rotor assembly runs.
  • a second section 72 of the permanent magnet 7 facing the air gap may be formed with a two-pole Halbach magnetization.
  • the magnetization of the Halbach type is curved and causes the magnetic poles, which are in conventional permanent magnets exclusively on the opposing surfaces of the permanent magnet 7, extend over an edge on a common side surface, so that there are two magnetic pole regions directly or spaced apart are arranged.
  • the Halbach magnetization is designed so that the magnetic pole areas in the direction of the air gap, d. H. on the side facing the pole shoes, are formed. In this way, the direction of the magnetization of the permanent magnet 7 is curved in this.
  • a substantially rectilinear demagnetizing stator magnetic field which strikes the pole face 42 of the permanent magnet 7 substantially perpendicularly intersects the magnetization lines or the magnetization direction of the Halbach magnetization at an angle ⁇ of 0 ° or 180 ° is different.
  • the field lines of the demagnetizing stator magnetic field at a position A intersect the Halbach magnetization at an angle of 20 ° and at a position B at an angle of 55 °.
  • Stator magnetic field which is aligned in the direction of the Halbach magnetization, decreases with the cosine of ⁇ . It is therefore to be provided that in the demagnetization region DM, in which demagnetization of the permanent magnet 7 can occur, the direction of the magnetic field deviates as much as possible from the direction of the demagnetizing stator magnetic field so as to reduce the demagnetizing effect of the stator magnetic field.
  • Halbach magnetization for the permanent magnet 7 wherein the Halbach magnetization in the direction of the air gap, ie amplified outward in the radial direction, causes the angle between the direction of the anisotropy and the direction of the demagnetizing magnetic field in the area, in which a demagnetization can occur is as large as possible, so that the demagnetizing component is significantly reduced and no longer sufficient to demagnetize the permanent magnet 7.
  • FIG. 4 for a narrower permanent magnet 7 in comparison to the permanent magnet 7 of FIG. 3, it is shown that the demagnetizing stator magnetic field intersects the field lines of the magnetization at a larger angle and thus the degree of demagnetization in the demagnetization region DM can be further reduced.
  • the use of a Halbach magnetization at the air gap directed end of the permanent magnet 7 on a surface between the Hauptpol vom the permanent magnet 7 is the more effective, the smaller the tangential width of the permanent magnet 7.
  • the Halbach magnetization may be semicircular in the second portion of the permanent magnet 7, wherein the first portion of the permanent magnet 7 may be provided with a collimated magnetization.
  • FIG. 5 illustrates a possibility for forming the magnetization of a permanent magnet 7 for use in the rotor arrangement of FIG.
  • a Halbach magnetization at both ends of the permanent magnet 7, ie at the end facing the air gap and at the shaft 5 associated end
  • the insertion of the permanent magnets 7 in the pockets 6 of the rotor assembly is simplified because not on the expression of Magnetization at the ends of the permanent magnet 7 and thus must be paid to its orientation during insertion into the rotor assembly.
  • FIGS. 6a and 6b show a further embodiment of the rotor arrangement.
  • the rotor arrangement provides in each pocket 6 an arrangement of a plurality of partial magnets, which form the permanent magnet 7.
  • a first partial magnet 73 arranged near the shaft 5 has a parallel magnetization in the poling direction, ie in the direction of arrangement of the pole shoes 42 or in the tangential direction in the case of the electrical machine of the described embodiments.
  • a second partial magnet 74 facing the air gap is magnetized in such a way that its direction of magnetization runs at right angles to the direction of the magnetization of the first partial magnet 73.
  • the direction of the magnetization runs in the direction of the air gap.
  • the second partial magnet 74 is designed as a single magnet, with pole regions provided on its end face 76 directed toward the air gap, with a north pole and a south pole, which are aligned in the arrangement direction.
  • the second partial magnet 74 is formed in two parts, wherein the magnetic parts of the second partial magnet 74 are arranged side by side in the arrangement direction, aligned with their pole faces in the direction of the air gap and polar oppositely poled. In both cases, arrangements result in which the direction of the magnetization of the
  • Partial magnets 73, 74 forms perpendicular to the direction of the magnetization of the first part of the magnet 73 and on the end face of the permanent magnet assembly thus formed both a south pole and a north pole.
  • a separating layer 75 which may be formed soft magnetic, so that it serves as a guide to the magnetic flux from the two poles of the second partial magnet 74th or the magnetic parts of the second partial magnet 74 to connect.
  • the separating layer 75 may also be formed as a hard magnetic layer.
  • the demagnetizing stator magnetic field striking substantially laterally on the second partial magnets 74 can not cause demagnetization in the second partial magnet 74 or its magnetic parts.
  • An advantage of the arrangement of FIGS. 6a and 6b is furthermore that the second partial magnets 74 also cause a magnetic excitation field in the insectschuhregion in the air gap. This additional field may create a more sinusoidal air gap field, which may result in reducing vibration and noise, and further reduce the iron losses in the stator 2.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Permanent Field Magnets Of Synchronous Machinery (AREA)

Abstract

L'invention concerne un ensemble stator (4) pour une machine électrique (1), qui comprend: un aimant permanent (7); et au moins deux épanouissements polaires (42) entre lesquels est disposé l'aimant permanent (7), de sorte que sa direction d'aimantation est orientée, dans un premier segment (71) de l'aimant permanent (7), sensiblement dans une direction d'agencement des épanouissements polaires (42); la direction d'aimantation différant de la direction d'agencement, dans un secpnd segment (72) de l'aimant permanent (7).
EP13774399.3A 2012-10-18 2013-10-07 Ensemble stator pour une machine électrique à excitation par aimants permanents Withdrawn EP2909921A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102012218980.7A DE102012218980A1 (de) 2012-10-18 2012-10-18 Läuferanordnung für eine permanentmagneterregte elektrische Maschine
PCT/EP2013/070765 WO2014060228A2 (fr) 2012-10-18 2013-10-07 Ensemble stator pour une machine électrique à excitation par aimants permanents

Publications (1)

Publication Number Publication Date
EP2909921A2 true EP2909921A2 (fr) 2015-08-26

Family

ID=49326657

Family Applications (1)

Application Number Title Priority Date Filing Date
EP13774399.3A Withdrawn EP2909921A2 (fr) 2012-10-18 2013-10-07 Ensemble stator pour une machine électrique à excitation par aimants permanents

Country Status (3)

Country Link
EP (1) EP2909921A2 (fr)
DE (1) DE102012218980A1 (fr)
WO (1) WO2014060228A2 (fr)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3179615A1 (fr) 2015-12-11 2017-06-14 Siemens Aktiengesellschaft Aimant permanent pour un rotor d'une machine à induit extérieur
EP3579383B1 (fr) * 2018-06-07 2020-12-23 maxon international ag Rotor multipolaire à couple de rotation optimisé pour un moteur électrique

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002010547A (ja) * 2000-06-16 2002-01-11 Yamaha Motor Co Ltd 永久磁石回転子及びその製造方法
JP5609689B2 (ja) * 2011-02-08 2014-10-22 株式会社安川電機 回転電機
EP2681829B1 (fr) * 2011-02-28 2020-07-01 Danfoss Power Solutions (US) Company Construction de machine à aimants permanents sans balai autorisant des aimants à faible champ coercitif

Also Published As

Publication number Publication date
WO2014060228A2 (fr) 2014-04-24
DE102012218980A1 (de) 2014-05-08
WO2014060228A3 (fr) 2015-04-23

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