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WO2024162905A1 - Inner rotor with surface mounted permanent magnets - Google Patents

Inner rotor with surface mounted permanent magnets Download PDF

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Publication number
WO2024162905A1
WO2024162905A1 PCT/SI2024/050002 SI2024050002W WO2024162905A1 WO 2024162905 A1 WO2024162905 A1 WO 2024162905A1 SI 2024050002 W SI2024050002 W SI 2024050002W WO 2024162905 A1 WO2024162905 A1 WO 2024162905A1
Authority
WO
WIPO (PCT)
Prior art keywords
rotor
fixing
lamellae
groove
lamellar
Prior art date
Application number
PCT/SI2024/050002
Other languages
French (fr)
Inventor
Jakob ŠUŠTAR
Danijel RODIĆ
Original Assignee
Domel, D.O.O.
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 Domel, D.O.O. filed Critical Domel, D.O.O.
Publication of WO2024162905A1 publication Critical patent/WO2024162905A1/en

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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
    • H02K1/28—Means for mounting or fastening rotating magnetic parts on to, or to, the rotor structures
    • 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
    • H02K1/278—Surface mounted magnets; Inset magnets
    • H02K1/2781—Magnets shaped to vary the mechanical air gap between the magnets and the stator

Definitions

  • the object of the invention is a rotor with permanent magnets mounted on the surface of the rotor, whereby the rotor is part of an electronically commutated EC motor.
  • the rotor has permanent magnets arranged circularly at a distance from its main axis and is positioned inside the stator of the same electric motor.
  • the technical problem solved by the invention is the installation and fixing of permanent magnets on the rotor in a way that will ensure a fixed attachment the magnets to the surface of the rotor independent of the speed of rotation of the rotor, while the dimensions and weight of the rotor do not increase compared rotors known so far, and the solution is also simple and economical to manufacture.
  • the magnets are also inserted and glued into the pockets or grooves provided for this purpose in the rotor lamination, and additionally filled with filling compound.
  • the disadvantage of reinforcement with a ring is the relatively high cost of the ring and assembly, and it requires a round shape of the magnets, and at the same time it also causes additional electrical losses on the rotor.
  • the disadvantage of inserting magnets into pockets is that part of the rotor field is short-circuited through the connecting bridges on the rotor, thereby reducing the utilization of the hard magnetic material used (permanent magnets), which consequently reduces the density of the magnetic field in the air gap between the rotor and the stator. This means an additional cost due to the necessary selection of stronger or larger and therefore more expensive magnets.
  • Rotors with inserted magnets are also larger and heavier compared to surface-mounted magnets, if we want to achieve a comparable field density in the air gap.
  • a rotor which includes a rotor core formed from lamellae, each of the lamellae having radially outwardly spaced protrusions around its outer circumference, each protrusion being a pair of positioning tabs , which are separated by a gap.
  • the slots filled with thermoplastic material act as reinforcing ribs, and at the same time, the thermoplastic material in the slots additionally fixes the positioning tabs, which further secures the magnets in the grooves. Since the magnets are spaced around the perimeter with small spacing, this requires the use of magnets with narrow tolerances and thus increased production costs.
  • a rotor with permanent magnets placed on the surface of the rotor wherein the rotor includes a rotor core formed from lamellae, which are connected to each other in a known manner in a package of lamellae so as to form a so-called laminated core.
  • the rotor core has evenly spaced longitudinal rotor grooves that form magnet beds, and the longitudinal rotor grooves are separated from each other by longitudinal rotor separation parts that represent opposite poles of the magnets.
  • Each permanent magnet mounted in the corresponding rotor groove represents one magnetic pole, and each rotor separation part represents the opposite magnetic pole on the periphery of the rotor core.
  • the rotor core is made from fixing lamellae or from fixing and basic lamellae.
  • the individual base lamellae has lamellar separating parts made with positioning tabs, which extend into the interior of the associated lamellar groove and thus into the interior of the rotor grooves.
  • the individual fixing lamellae has lamellar separating parts made with positioning tabs that extend into the interior of the associated lamellar groove and thus into the rotor grooves, whereby at least one positioning tab is designed as a left fixing tab and at least one positioning tab is designed as a right fixing tab, whereby when assembling the lamellae into the rotor core, there is at least one positioning tab located along the individual rotor groove between two fixing tabs .
  • the left fixing tab is a tab made on the left side of the lamellar separating parts as seen in the direction of rotation of the rotor
  • the right fixing tab is a tab made on the right side of the lamellar separating parts as seen in the direction of rotation of the rotor.
  • the positioning tabs enable the formation of an empty space (cavity) between the rotor separating parts and the permanent magnets inserted in the rotor grooves, which is filled with the filling compound. When inserting a permanent magnet into the rotor groove, only the fixing tabs come into contact with the sides of the magnet and fix it in the rotor groove.
  • the shape of the lamellae that make up the rotor core allows for a reduction in the number of the fixing tabs along each rotor groove, thereby reducing magnetic losses, while at the same time providing sufficient force (load-bearing capacity) to hold the permanent magnets in the radial and axial directions even at higher rotational speeds during motor operation.
  • the permanent magnets are designed to fit into each rotor groove, and the permanent magnets have a dovetail cross-section . Since the permanent magnets are fixed in the rotor slots with fixing tabs, there is no need to use permanent magnets with tight dimensional tolerances, therefore cheaper magnets can be used.
  • Figure 1 shows a rotor according to the invention without an inserted magnet in partial section
  • Figure 2 shows a rotor according to the invention with an inserted magnet in partial section
  • FIG. 3 shows detail A of Figure 2 in partial section
  • Figure 4 shows the magnet inserted into the rotor slot
  • Figure 5 shows the base lamellae in cross-section
  • Figure 6 shows an embodiment of the fixing lamellae in cross-section
  • Figure 7 shows the rotated fixing lamellae of Figure 6 when stacked into packag in cross-section
  • Figure 8 shows a cross-section of the rotor core with permanent magnets inserted.
  • An electronically commutated electric motor contains a stator (not shown ) and a rotor 1 arranged axially within it, having a shaft 8, the axis of which coincides with the main axis of the motor, a rotor core 2, which is essentially cylindrical in shape and has a central hole for receiving the shaft 8, and around the circumference of the rotor core 2, a plurality of permanent magnets 3 are arranged at regular intervals, which are separated from each other by rotor separating parts 2a, whereby the permanent magnets 3 have a dovetail shape in cross-section .
  • the rotor core 2 has longitudinally spaced rotor grooves 2b evenly distributed along its perimeter, which are separated from each other by rotor separating parts 2a, whereby the number of rotor grooves 2b and the number of rotor separating parts 2a is always equal to the number of permanent magnets 3.
  • the lower surface of the rotor groove 2b forms a bed for the permanent magnet 3 and fits to the lower surface of the permanent magnet 3.
  • Each permanent magnet 3 placed in the corresponding rotor groove 2b represents one magnetic pole, and each rotor separating part 2a represents the opposite magnetic pole on the periphery of the rotor core 2, whereby the number of rotor separating parts 2a is equal to the number of permanent magnets 3.
  • Dimensions of the permanent magnet 3 and the dimensions of the rotor separation part 2a are determined by magnetic calculation using a commercial program on the basis of finite element method.
  • the rotor core 2 is made of lamellae 4, namely from fixing lamellae 42 or from fixing 42 and basic lamellae 41, whereby the lamellae 4 are made of disc-shaped electrical steel, and are connected to each other in a package of lamellae so as to form lamellar core.
  • the individual lamellae 4 forming the rotor core 2 are made with lamellar separation parts 4a that separate the lamellar grooves 4b, whereby the number of lamellar separation parts 4a is equal to the number of lamellar grooves 4b, and is equal to the number of permanent magnets 3, which are a part of rotor 1 .
  • the individual base lamellae 41 has lamellar separation parts 4a designed in such a way that the lamellar separation parts 4a have positioning tabs 5 in their outer region, viewed in the radial direction of the axis of rotation, on both sides facing the corresponding lamellar groove 4b, which they extend into the interior of each associated lamellar groove 4b, thereby into the interior of the rotor grooves 2b.
  • Each individual fixing lamellae 42 has lamellar separating parts 4a made with positioning tabs 5 that extend into the interior the associated lamellar groove 4b and thus into the interior of the rotor grooves 2b, wherein at least one positioning tab 5 is designed as a left fixing tab 5b and at least one positioning tab 5 designed as a right fixing tab 5a, which extend into the interior of each associated lamellar groove 4b.
  • the left fixing tab 5b is a tab made on the left side of the lamellar separating part 4a
  • the right fixing tab 5a is a tab made on the right side of the lamellar separating part 4a.
  • the number of left fixing tabs 5b is equal to the number of right fixing tabs 5a.
  • the length of the fixing tab 5a, 5b is such that it is sufficiently longer than the length of the positioning tab 5 that when the permanent magnet 3 is inserted into the rotor groove 2b, the fixing tabs 5a, 5b fix the magnet 3.
  • the lamellae 4 When packaging individual lamellae 4 into the rotor core 2, the lamellae 4 are assembled into the rotor core 2 so that along each rotor groove 2b, that is, in the direction of the x-axis of the rotor 1, on one side of the rotor groove 2b, there are at least two right fixing tabs 5a, and on the opposite side, at least two left fixing tabs 5b.
  • the lamellae 4 When packaging individual lamellae 4 into the rotor core 2, the lamellae 4 are assembled into the rotor core 2 so that along each rotor groove 2b, that is, in the direction of the x-axis of the rotor 1, on both sides of the rotor groove 2b between two fixing tabs 5a, 5b, there is at least one positioning tab 5.
  • the magnets 3 have a dovetail shape in cross-section, i.e. with slanted sides.
  • the lower side of the magnet 3 is preferably flat and rests on the bed on the rotor core 2, i.e. on the lower surface of the rotor groove 2b, the opposite, upper side, is lens-shaped, and the two side sides are made at an angle with respect to the lower side, where the mentioned angle is less than 90° and equal to or greater than 80°, so that it has a negligible effect on the reduction of the magnetic field.
  • the positioning tabs 5 are not in contact with the sides of the magnet 3, but their function is primarily to form an empty space 6 between the rotor core 2 and the permanent magnet 3 inserted in the rotor groove 2b, which is filled with the filling compound.
  • the empty space 6 simultaneously prevents the loss of the magnetic field (magnetism) of the individual magnet 3.
  • the lamellae 4 are made of thin sheet metal, when the magnet 3 is inserted into the rotor groove 2b, the fixing tabs 5a, 5b are slightly deformed, which enables good fixing of the magnet 3 in the rotor groove 2b.
  • the fixing tabs 5a, 5b Since only the fixing tabs 5a, 5b are in contact with the magnet 3, the magnetic losses due to contact are smaller, and at the same time, the fixing tabs 5a, 5b represent the reinforcement of the filling compound and, together with the filling compound, provide sufficient force (load capacity) to hold the magnets 3 in the radial and axial direction even at higher rotational speeds during motor operation.
  • the height of the lamellar separating part 4a is lower than the outer radius of the magnet 3. Since the lamellae 4 are steel, it is desirable that the height of the lamellar separating part 4a is lower, as this prevents an excessive reduction of the magnetic field.
  • the rotor core 2 consists only of fixing lamellae 42.
  • the individual fixing lamellae 42 has one positioning tab 5 implemented as a left fixing tab 5b and one positioning tab 5 implemented as a right fixing tab 5a, which extend into the interior of the same associated lamellar groove 4b.
  • the number of lamellar separation parts 4a on the circumference of each lamellae 4 is equal to the number of magnets 3, and the width of the lamellar groove 4b and thus the width of the lamellar separation part 4a depends on the dimensions of the magnets 3 or from the required distance between them to ensure the stated function of the rotor separating part 2a (opposite pole of the magnet).
  • the rotor 1 includes from four to seven permanent magnets 3, whereby the shape of the lamellae 4 (the width of the lamellar groove 4b and the width of the lamellar separating part 4a) is appropriately adapted to the number of magnets 3, so when the lamellae 4 are assembled into the rotor core 2, sufficient width of individual rotor separating parts 2a is ensured, which represent the opposite poles of the permanent magnets 3. In this way, the number of magnets 3 in the rotor 1 can be lower.
  • the manufacturing process of the rotor core 1 takes place in such a way that, when individual fixing lamellae 42 are packed into a package of lamellae, each subsequent fixing lamellae 42 is rotated by an angle a, which represents two poles, i.e. by an angle which includes magnet 3 and rotor separator part 2a.
  • angle a represents two poles, i.e. by an angle which includes magnet 3 and rotor separator part 2a.
  • the angle a is 90°
  • the angle a is 72°
  • six permanent magnets 3 and thus of six separating parts 2a the angle a is 60°, etc.
  • the manufacture of the rotor core 2 and thus the rotor 1 is faster and easier and there is no need for expensive tools.
  • the manufacturing process of the rotor core 1 proceeds similarly, i.e. by rotating each subsequent inserted fixing lamellae 42 by an angle a, and basic lamellae 41 are inserted between the fixing lamellae 42.
  • the shape of the individual lamellae 4, and thus the rotor core 2 enables the use of a smaller number of permanent magnets 3 in the rotor 1 and thus a smaller volume of the rotor 1 for the same loads, and additionally the lower number of the fixing tabs 5a, 5b reduces magnetic losses.
  • the number of the fixing tabs 5a, 5b along the rotor grooves 2b can be variable, it depends on the number of fixing lamellae 42 and on the number of lamellar separation parts 4a with implemented fixing tabs 5a, 5b, and it is always adjusted according to the needs and depends on the centrifugal force due to masses of magnets 3.
  • the rotor 1 After inserting the magnets 3 into the rotor grooves 2b, the rotor 1 is filled with thermoplastic compound from all sides by means of two-component injection technology, thus forming a rotor 1 with a thickness of at least 0.6 mm, which also has a sealing function.
  • the plastic compound also flows into the space 6 between the rotor core 2 and the permanent magnet 3, whereby the fixing tabs 5a, 5b act as reinforcing ribs that additionally support the rotor shell 1, while at the same time the thermoplastic compound in the space 6 additionally fixes the fixing tabs 5a, 5b, which additionally secures the magnets 3 in the rotor grooves 2b.
  • the rotor 1 includes five permanent magnets 3, which are arranged at regular intervals along the circumference of the rotor core 2. Between the permanent magnets 3 are the rotor separating parts 2a, which represent opposite magnetic poles on the circumference of the rotor core 2.
  • the rotor core 1 is composed only of fixing lamellae 42.
  • the individual fixing lamellae 42 forming the rotor core 2 has two adjacent lamellar separating parts 4a which limit the associated lamellar groove 4b, designed so that the left of the two adjacent lamellar separating parts 4a in its upper area, in the radial direction of the axis of rotation, on the side facing the associated lamellar groove 4b, a right-hand fixing tab 5a is made, and on the opposite side a positioning tab 5.
  • the right of the two adjacent lamellar separating parts 4a has in its upper part in the radial direction of the axis of rotation, on the side facing the associated lamellar groove 4b, a left fixing tab 5a is made, and on the opposite side a positioning tab 5.
  • the other lamellar separating parts 4a of the individual fixing lamellae 42 are designed so that the other lamellar separating parts 4a have positioning tabs 5 in their upper area in the radial direction of the axis of rotation, on both sides facing the corresponding lamellar groove 4b.
  • the length of the fixing tabs 5a, 5b is sufficiently longer than the length of the positioning tabs 5 , so that when the magnet 3 is inserted into the rotor groove 2b, the fixing tabs 5a, 5b fix the magnet 3.
  • each rotor groove 2b has at least two fixing tabs 5a, 5b on each side, the number of lamellae 4 must be equal to or greater than twice the number of rotor grooves 2b.
  • the manufacturing process of the rotor core 2 takes place in such a way that when individual fixing lamellae 42 are packed into a package of lamellae, each subsequent fixing lamellae 42 is rotated by an angle of 72°, which represents two poles, i.e. by an angle that includes the magnet 3 and the separating part 2a.
  • an angle of 72° which represents two poles, i.e. by an angle that includes the magnet 3 and the separating part 2a.
  • four positioning tabs 5 are located on each side along the individual rotor groove 2b between two fixing tabs 5a, 5b .

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

Abstract

An inner rotor (1) with surface mounted permanent magnets (3) includes a laminated rotor core. Said rotor core has on its periphery alternating rotor grooves (2b) and rotor separation parts (2a) in axial direction and is made out of a plurality of disc-shaped lamellae. Said lamellae are either fixing lamellae or basic lamellae. Each lamella comprises lamellar separation parts and lamellar grooves. Each lamellar separation part has a positioning tab (5). In circumferential direction is on each left side of each lamellar separation part a left fixing tab (5b) and on each right side a right fixing tab (5a). Each permanent magnet (3) is loaf-shaped and retained in position on the rotor core surface by the right fixing tab (5a) and left fixing tab (5b) of each fixing lamella. The right and left tabs (5a,5b) of the basic lamellae provide a gap (6) in direction of the permanent magnet (3).

Description

INNER ROTOR WITH SURFACE MOUNTED PERMANENT MAGNETS
The object of the invention is a rotor with permanent magnets mounted on the surface of the rotor, whereby the rotor is part of an electronically commutated EC motor. The rotor has permanent magnets arranged circularly at a distance from its main axis and is positioned inside the stator of the same electric motor.
The technical problem solved by the invention is the installation and fixing of permanent magnets on the rotor in a way that will ensure a fixed attachment the magnets to the surface of the rotor independent of the speed of rotation of the rotor, while the dimensions and weight of the rotor do not increase compared rotors known so far, and the solution is also simple and economical to manufacture.
State of the art
The most common solution is gluing magnets to the laminated core of the rotor, but this solution is technologically very demanding, and is only useful for motors with lower rotation speeds and for less demanding applications. For motors with higher rotation speeds, the fixing of the magnets must be better and therefore requires additional mechanical fixing of the magnets.
Current solutions use an additional thin metal ring made of non-magnetic material placed over the magnets, alternativelly reinforcement with glass, carbon or Kevlar fibers impregnated with various epoxy resins is used.
In some cases, the magnets are also inserted and glued into the pockets or grooves provided for this purpose in the rotor lamination, and additionally filled with filling compound.
The disadvantages of gluing solutions are the demanding technological process and the poor long-term reliability of the glued joint.
The disadvantage of reinforcement with a ring is the relatively high cost of the ring and assembly, and it requires a round shape of the magnets, and at the same time it also causes additional electrical losses on the rotor. The disadvantage of inserting magnets into pockets is that part of the rotor field is short-circuited through the connecting bridges on the rotor, thereby reducing the utilization of the hard magnetic material used (permanent magnets), which consequently reduces the density of the magnetic field in the air gap between the rotor and the stator. This means an additional cost due to the necessary selection of stronger or larger and therefore more expensive magnets. Rotors with inserted magnets are also larger and heavier compared to surface-mounted magnets, if we want to achieve a comparable field density in the air gap.
Application WO 2022/045985 describes a rotor which includes a rotor core formed from lamellae, each of the lamellae having radially outwardly spaced protrusions around its outer circumference, each protrusion being a pair of positioning tabs , which are separated by a gap. After overmoulding the rotor with thermoplastic material, the slots filled with thermoplastic material act as reinforcing ribs, and at the same time, the thermoplastic material in the slots additionally fixes the positioning tabs, which further secures the magnets in the grooves. Since the magnets are spaced around the perimeter with small spacing, this requires the use of magnets with narrow tolerances and thus increased production costs.
There was a need for a rotor design where the magnets are placed on the surface of the rotor and there is no need for gluing and additional fasteners, with lower production costs and material costs, the rotor manufacturing process, especially the manufacturing of the rotor core and the assembly of magnets on the rotor core, it is simpler and more environmentally friendly, while at the same time the efficiency of the rotor is improved.
The stated technical problem is solved by a rotor with permanent magnets placed on the surface of the rotor, wherein the rotor includes a rotor core formed from lamellae, which are connected to each other in a known manner in a package of lamellae so as to form a so-called laminated core. The rotor core has evenly spaced longitudinal rotor grooves that form magnet beds, and the longitudinal rotor grooves are separated from each other by longitudinal rotor separation parts that represent opposite poles of the magnets. Each permanent magnet mounted in the corresponding rotor groove represents one magnetic pole, and each rotor separation part represents the opposite magnetic pole on the periphery of the rotor core. The rotor core is made from fixing lamellae or from fixing and basic lamellae. The individual base lamellae has lamellar separating parts made with positioning tabs, which extend into the interior of the associated lamellar groove and thus into the interior of the rotor grooves. The individual fixing lamellae has lamellar separating parts made with positioning tabs that extend into the interior of the associated lamellar groove and thus into the rotor grooves, whereby at least one positioning tab is designed as a left fixing tab and at least one positioning tab is designed as a right fixing tab, whereby when assembling the lamellae into the rotor core, there is at least one positioning tab located along the individual rotor groove between two fixing tabs . The left fixing tab is a tab made on the left side of the lamellar separating parts as seen in the direction of rotation of the rotor, the right fixing tab is a tab made on the right side of the lamellar separating parts as seen in the direction of rotation of the rotor. The positioning tabs enable the formation of an empty space (cavity) between the rotor separating parts and the permanent magnets inserted in the rotor grooves, which is filled with the filling compound. When inserting a permanent magnet into the rotor groove, only the fixing tabs come into contact with the sides of the magnet and fix it in the rotor groove. The shape of the lamellae that make up the rotor core allows for a reduction in the number of the fixing tabs along each rotor groove, thereby reducing magnetic losses, while at the same time providing sufficient force (load-bearing capacity) to hold the permanent magnets in the radial and axial directions even at higher rotational speeds during motor operation. The permanent magnets are designed to fit into each rotor groove, and the permanent magnets have a dovetail cross-section . Since the permanent magnets are fixed in the rotor slots with fixing tabs, there is no need to use permanent magnets with tight dimensional tolerances, therefore cheaper magnets can be used.
The invention will be described in more detail below and presented in the figures showing:
Figure 1 shows a rotor according to the invention without an inserted magnet in partial section
Figure 2 shows a rotor according to the invention with an inserted magnet in partial section
Figure 3 shows detail A of Figure 2 in partial section
Figure 4 shows the magnet inserted into the rotor slot
Figure 5 shows the base lamellae in cross-section
Figure 6 shows an embodiment of the fixing lamellae in cross-section Figure 7 shows the rotated fixing lamellae of Figure 6 when stacked into packag in cross-section
Figure 8 shows a cross-section of the rotor core with permanent magnets inserted.
An electronically commutated electric motor contains a stator ( not shown ) and a rotor 1 arranged axially within it, having a shaft 8, the axis of which coincides with the main axis of the motor, a rotor core 2, which is essentially cylindrical in shape and has a central hole for receiving the shaft 8, and around the circumference of the rotor core 2, a plurality of permanent magnets 3 are arranged at regular intervals, which are separated from each other by rotor separating parts 2a, whereby the permanent magnets 3 have a dovetail shape in cross-section .
The rotor core 2 has longitudinally spaced rotor grooves 2b evenly distributed along its perimeter, which are separated from each other by rotor separating parts 2a, whereby the number of rotor grooves 2b and the number of rotor separating parts 2a is always equal to the number of permanent magnets 3. The lower surface of the rotor groove 2b forms a bed for the permanent magnet 3 and fits to the lower surface of the permanent magnet 3. Each permanent magnet 3 placed in the corresponding rotor groove 2b represents one magnetic pole, and each rotor separating part 2a represents the opposite magnetic pole on the periphery of the rotor core 2, whereby the number of rotor separating parts 2a is equal to the number of permanent magnets 3. Dimensions of the permanent magnet 3 and the dimensions of the rotor separation part 2a are determined by magnetic calculation using a commercial program on the basis of finite element method.
The rotor core 2 is made of lamellae 4, namely from fixing lamellae 42 or from fixing 42 and basic lamellae 41, whereby the lamellae 4 are made of disc-shaped electrical steel, and are connected to each other in a package of lamellae so as to form lamellar core.
The individual lamellae 4 forming the rotor core 2 are made with lamellar separation parts 4a that separate the lamellar grooves 4b, whereby the number of lamellar separation parts 4a is equal to the number of lamellar grooves 4b, and is equal to the number of permanent magnets 3, which are a part of rotor 1 .
The individual base lamellae 41 has lamellar separation parts 4a designed in such a way that the lamellar separation parts 4a have positioning tabs 5 in their outer region, viewed in the radial direction of the axis of rotation, on both sides facing the corresponding lamellar groove 4b, which they extend into the interior of each associated lamellar groove 4b, thereby into the interior of the rotor grooves 2b.
Each individual fixing lamellae 42 has lamellar separating parts 4a made with positioning tabs 5 that extend into the interior the associated lamellar groove 4b and thus into the interior of the rotor grooves 2b, wherein at least one positioning tab 5 is designed as a left fixing tab 5b and at least one positioning tab 5 designed as a right fixing tab 5a, which extend into the interior of each associated lamellar groove 4b. The left fixing tab 5b is a tab made on the left side of the lamellar separating part 4a, the right fixing tab 5a is a tab made on the right side of the lamellar separating part 4a. Preferably, the number of left fixing tabs 5b is equal to the number of right fixing tabs 5a. The length of the fixing tab 5a, 5b is such that it is sufficiently longer than the length of the positioning tab 5 that when the permanent magnet 3 is inserted into the rotor groove 2b, the fixing tabs 5a, 5b fix the magnet 3.
When packaging individual lamellae 4 into the rotor core 2, the lamellae 4 are assembled into the rotor core 2 so that along each rotor groove 2b, that is, in the direction of the x-axis of the rotor 1, on one side of the rotor groove 2b, there are at least two right fixing tabs 5a, and on the opposite side, at least two left fixing tabs 5b.
When packaging individual lamellae 4 into the rotor core 2, the lamellae 4 are assembled into the rotor core 2 so that along each rotor groove 2b, that is, in the direction of the x-axis of the rotor 1, on both sides of the rotor groove 2b between two fixing tabs 5a, 5b, there is at least one positioning tab 5.
As already mentioned, the magnets 3 have a dovetail shape in cross-section, i.e. with slanted sides. The lower side of the magnet 3 is preferably flat and rests on the bed on the rotor core 2, i.e. on the lower surface of the rotor groove 2b, the opposite, upper side, is lens-shaped, and the two side sides are made at an angle with respect to the lower side, where the mentioned angle is less than 90° and equal to or greater than 80°, so that it has a negligible effect on the reduction of the magnetic field.
When the magnet 3 is inserted into the rotor groove 2b, the positioning tabs 5 are not in contact with the sides of the magnet 3, but their function is primarily to form an empty space 6 between the rotor core 2 and the permanent magnet 3 inserted in the rotor groove 2b, which is filled with the filling compound. The empty space 6 simultaneously prevents the loss of the magnetic field (magnetism) of the individual magnet 3. When the magnet 3 is inserted into the rotor groove 2b, only the fixing tabs 5a, 5b come into contact with the sides of the magnet 3 and fix it in the rotor groove 2b. Namely, since the lamellae 4 are made of thin sheet metal, when the magnet 3 is inserted into the rotor groove 2b, the fixing tabs 5a, 5b are slightly deformed, which enables good fixing of the magnet 3 in the rotor groove 2b.
Since only the fixing tabs 5a, 5b are in contact with the magnet 3, the magnetic losses due to contact are smaller, and at the same time, the fixing tabs 5a, 5b represent the reinforcement of the filling compound and, together with the filling compound, provide sufficient force (load capacity) to hold the magnets 3 in the radial and axial direction even at higher rotational speeds during motor operation.
It is desirable that the height of the lamellar separating part 4a is lower than the outer radius of the magnet 3. Since the lamellae 4 are steel, it is desirable that the height of the lamellar separating part 4a is lower, as this prevents an excessive reduction of the magnetic field.
In a preferred embodiment, the rotor core 2 consists only of fixing lamellae 42. The individual fixing lamellae 42 has one positioning tab 5 implemented as a left fixing tab 5b and one positioning tab 5 implemented as a right fixing tab 5a, which extend into the interior of the same associated lamellar groove 4b.
The number of lamellar separation parts 4a on the circumference of each lamellae 4 is equal to the number of magnets 3, and the width of the lamellar groove 4b and thus the width of the lamellar separation part 4a depends on the dimensions of the magnets 3 or from the required distance between them to ensure the stated function of the rotor separating part 2a (opposite pole of the magnet).
Preferably, the rotor 1 includes from four to seven permanent magnets 3, whereby the shape of the lamellae 4 (the width of the lamellar groove 4b and the width of the lamellar separating part 4a) is appropriately adapted to the number of magnets 3, so when the lamellae 4 are assembled into the rotor core 2, sufficient width of individual rotor separating parts 2a is ensured, which represent the opposite poles of the permanent magnets 3. In this way, the number of magnets 3 in the rotor 1 can be lower.
When the rotor core 2 includes only the fixing lamellae 42, the manufacturing process of the rotor core 1 takes place in such a way that, when individual fixing lamellae 42 are packed into a package of lamellae, each subsequent fixing lamellae 42 is rotated by an angle a, which represents two poles, i.e. by an angle which includes magnet 3 and rotor separator part 2a. When using four permanent magnets 3, and thus four separating parts 2a, the angle a is 90°, when using five permanent magnets 3, and thus five separating parts 2a, the angle a is 72°, when using six permanent magnets 3, and thus of six separating parts 2a, the angle a is 60°, etc. In this way, the manufacture of the rotor core 2 and thus the rotor 1 is faster and easier and there is no need for expensive tools.
When the rotor core includes fixing lamellae 42 and basic lamellae 41, the manufacturing process of the rotor core 1 proceeds similarly, i.e. by rotating each subsequent inserted fixing lamellae 42 by an angle a, and basic lamellae 41 are inserted between the fixing lamellae 42.
The shape of the individual lamellae 4, and thus the rotor core 2, enables the use of a smaller number of permanent magnets 3 in the rotor 1 and thus a smaller volume of the rotor 1 for the same loads, and additionally the lower number of the fixing tabs 5a, 5b reduces magnetic losses.
The number of the fixing tabs 5a, 5b along the rotor grooves 2b can be variable, it depends on the number of fixing lamellae 42 and on the number of lamellar separation parts 4a with implemented fixing tabs 5a, 5b, and it is always adjusted according to the needs and depends on the centrifugal force due to masses of magnets 3.
After inserting the magnets 3 into the rotor grooves 2b, the rotor 1 is filled with thermoplastic compound from all sides by means of two-component injection technology, thus forming a rotor 1 with a thickness of at least 0.6 mm, which also has a sealing function. In this process, the plastic compound also flows into the space 6 between the rotor core 2 and the permanent magnet 3, whereby the fixing tabs 5a, 5b act as reinforcing ribs that additionally support the rotor shell 1, while at the same time the thermoplastic compound in the space 6 additionally fixes the fixing tabs 5a, 5b, which additionally secures the magnets 3 in the rotor grooves 2b.
In the embodiment shown in the figures, the rotor 1 includes five permanent magnets 3, which are arranged at regular intervals along the circumference of the rotor core 2. Between the permanent magnets 3 are the rotor separating parts 2a, which represent opposite magnetic poles on the circumference of the rotor core 2. The rotor core 1 is composed only of fixing lamellae 42. The individual fixing lamellae 42 forming the rotor core 2 has two adjacent lamellar separating parts 4a which limit the associated lamellar groove 4b, designed so that the left of the two adjacent lamellar separating parts 4a in its upper area, in the radial direction of the axis of rotation, on the side facing the associated lamellar groove 4b, a right-hand fixing tab 5a is made, and on the opposite side a positioning tab 5. The right of the two adjacent lamellar separating parts 4a has in its upper part in the radial direction of the axis of rotation, on the side facing the associated lamellar groove 4b, a left fixing tab 5a is made, and on the opposite side a positioning tab 5. The other lamellar separating parts 4a of the individual fixing lamellae 42 are designed so that the other lamellar separating parts 4a have positioning tabs 5 in their upper area in the radial direction of the axis of rotation, on both sides facing the corresponding lamellar groove 4b. The length of the fixing tabs 5a, 5b is sufficiently longer than the length of the positioning tabs 5 , so that when the magnet 3 is inserted into the rotor groove 2b, the fixing tabs 5a, 5b fix the magnet 3.
In order to satisfy the condition that each rotor groove 2b has at least two fixing tabs 5a, 5b on each side, the number of lamellae 4 must be equal to or greater than twice the number of rotor grooves 2b.
The manufacturing process of the rotor core 2 takes place in such a way that when individual fixing lamellae 42 are packed into a package of lamellae, each subsequent fixing lamellae 42 is rotated by an angle of 72°, which represents two poles, i.e. by an angle that includes the magnet 3 and the separating part 2a. In this way, when the lamellae 42 are assembled in the rotor core 2, four positioning tabs 5 are located on each side along the individual rotor groove 2b between two fixing tabs 5a, 5b .

Claims

Patent claims
1. A rotor (1) with permanent magnets (3) mounted on a surface of the rotor (1) , wherein the rotor (1) comprises a shaft (8) whose axis coincides with a main axis of a motor, a rotor core (2) having a circumferential arranged mutually equally spaced longitudinal rotor grooves (2b), which are separated from each other by rotor separation parts (2a), and wherein a number of rotor grooves (2b) and a number of rotor separation parts (2a) is each equal to a number of permanent magnets (3), wherein the longitudinal rotor grooves (2b) are adapted to receive permanent magnets (3), which have a dovetail-type cross-section, and the rotor core (2) is made of disc-shaped lamellae (4), made of electro steel, and interconnected into a package of lamellae, characterized in that the rotor core (2) comprises fixing lamellae (42), wherein lamellar separation parts (4a) of individual fixing lamellae (42) are in their upper region in a radial direction of an axis of rotation on both sides, which are facing each respective lamellar groove (4b), made with positioning tabs (5) that extend inside each respective lamellar groove (4b), whereby at least one positioning tab (5) is designed as a left fixing tab (5b), implemented on a left side of the lamellar separating part (4a), and at least one positioning tab (5) is designed as a right fixing tab (5a), implemented on a right side of the lamellar separating part (4a), whereby the lamellae (4) are assembled into the rotor core (2) so that along the individual rotor groove (2b), that is in a direction of an axis (x) of the rotor (1), on one side of the rotor groove (2b) there are at least two right fixing tabs (5a), and on an opposite side, at least two left fixing tabs (5b), and wherein the lamellae (4) are assembled into the rotor core (2) in such a way that along the individual rotor groove (2b) on both sides of the rotor groove (2b) between two fixing tabs (5a, 5b) there is at least one positioning tab (5), and wherein the individual permanent magnet (3) installed in the corresponding rotor groove (2b) represents one magnetic pole, and the individual rotor separation part (2a) represents the opposite magnetic pole on a periphery of the rotor core (1).
2. The rotor (1) according to claim 1, characterized in that the rotor core (2) additionally includes basic lamellae (41), wherein the lamellar separating parts (4a) of individual basic lamellae (41) are in their upper part, in the radial direction of the axis of rotation, on both sides facing the respective lamellar groove (4b), made with positioning tabs (5) that extend into the interior of the respective lamellar groove (4b).
3. The rotor (1) according to claim 1, characterized in that the rotor core (2) consists only of fixing lamellae (42).
4. The rotor (1) according to claim 3, characterized in that the individual fixing lamellae (42) has one positioning tab (5) designed as a left fixing tab (5b) and one positioning tab (5) designed as a right fixing tab (5a), which extend into the interior of the same respective lamellar groove (4b).
5. The rotor (1) according to claims 1 to 4, characterized in that the number of fixing tabs (5a, 5b) along the rotor grooves (2b) is variable and depends on the number of fixing lamellae (42) in the rotor core (2) and on the number of lamellar separating parts (4a) of fixing lamellae (42) with implemented fixing tabs (5a, 5b).
6. The rotor (1) according to claims 1 to 5, characterized in that when the permanent magnet (3) is inserted into the rotor groove (2b), only the fixing tabs (5a, 5b) are in contact with the sides of the magnet (3), whereby a space (6) between the rotor core (2) and the permanent magnet (3) inserted in the rotor groove (2b) is created, which prevents the loss of the magnetic field of the individual permanent magnet (3).
7. The rotor (1) according to claims 1 to 6, characterized in that it additionally includes a rotor shell (1) with a thickness of at least 0.6 mm, made by pouring the rotor (1) from all sides with a thermoplastic compound, whereby the plastic compound flows also into the space (6) between the rotor core (2) and the permanent magnet (3), whereby the fixing tabs (5a, 5b) act as stiffening ribs that additionally support the rotor shell (1), while at the same time the thermoplastic compound in the space ( 6) additionally fixes the fixing tabs (5a, 5b), thereby additionally fixing the permanent magnets (3) in the rotor grooves (2b).
PCT/SI2024/050002 2023-01-30 2024-01-05 Inner rotor with surface mounted permanent magnets WO2024162905A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SIP-202300018 2023-01-30
SI202300018A SI26463A (en) 2023-01-30 2023-01-30 Rotor with permanent magnets mounted on the rotor surface

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001063726A2 (en) * 2000-02-26 2001-08-30 Robert Bosch Gmbh Magnet retainer and method for fixing a magnet on a support element
US6911756B1 (en) * 2004-03-23 2005-06-28 Chio-Sung Chang Rotor core with magnets on the outer periphery of the core having a sine or trapezoidal wave
WO2022218717A1 (en) * 2021-04-14 2022-10-20 Robert Bosch Gmbh Rotor for an electric motor

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001063726A2 (en) * 2000-02-26 2001-08-30 Robert Bosch Gmbh Magnet retainer and method for fixing a magnet on a support element
US6911756B1 (en) * 2004-03-23 2005-06-28 Chio-Sung Chang Rotor core with magnets on the outer periphery of the core having a sine or trapezoidal wave
WO2022218717A1 (en) * 2021-04-14 2022-10-20 Robert Bosch Gmbh Rotor for an electric motor

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