Rotor for an electric machine, electric machine, and method for manufacturing such a rotor

Abstract

The invention relates to: a rotor (10) for an electric machine (12); an electric machine (12); and a method for manufacturing such a rotor (10), the rotor comprising a main body (14), on the radially outer circumference (15) of which a plurality of rotor magnets (20) are arranged, wherein the rotor magnets (20) are fixed on the main body (14) by means of a rotor sleeve (30) made of metal, wherein the rotor sleeve (30) has limited thermally treated regions (32) which radially brace the rotor sleeve (30) on the main body (14).

Description

[0001] Description

[0002] title

[0003] Rotor for an electrical machine, an electrical machine, and method for producing such a rotor

[0004] The invention relates to a rotor for an electrical machine, as well as to an electrical machine and to a method for producing such a rotor according to the preamble of the independent claims.

[0005] State of the art

[0006] DE 10 2007 029 719 A1 discloses a rotor for an electrical machine in which "buried magnets" are arranged in magnetic pockets of the rotor that are closed radially outward. The magnetic poles of the rotor are determined by the shape of the radially outer tangential web, which closes the magnetic pocket radially outward. Therefore, in this design, the exact positioning of the magnets within the magnetic pocket in the tangential direction is relatively uncritical and does not have a significant influence on the rotor's cogging torque.

[0007] CN 104659941 A discloses another rotor in which the magnets are positioned on the surface of the rotor body using radial retaining webs. A tape is then glued to the magnets and pressed against the curved circumferential surface of the magnets. With this design, the assembly process for attaching the tape is very cumbersome, as gluing processes in the assembly line quickly lead to contamination. This disadvantage is to be remedied by the solution according to the invention.

[0008] Disclosure of the invention Advantages of the invention

[0009] The device according to the invention and the method according to the invention with the features of the independent claims have the advantage that the local heating of limited areas of the rotor sleeve after its cooling creates a tensile residual stress in the sleeve material, which leads to the rotor sleeve contracting radially. As a result, the rotor sleeve, which can previously be pushed onto the rotor magnets in particular with a clearance fit, is pressed radially against the rotor magnets after the thermally treated areas have been formed. This has the advantage that the rotor sleeve can be pushed onto the rotor magnets without pressing, which also eliminates the need for an insertion phase at one axial end of the rotor sleeve. By omitting the insertion phase, the maximum outer diameter of the rotor sleeve can be reduced, or remachining of the insertion phase can be dispensed with.In this case, the limited areas of the rotor sleeve are preferably heated to such an extent that the material of the rotor sleeve melts, so that the shrinkage process of the rotor sleeve when the dissolved material resolidifies reduces the inner diameter of the rotor sleeve to such an extent that the rotor magnets are pressed against the base body and thus remain securely fixed during operation of the electrical machine.

[0010] The measures listed in the dependent claims enable advantageous refinements and improvements of the designs specified in the independent claims. To reduce the inner diameter of the rotor sleeve as much as possible, the limited thermally treated areas are formed as heat seams that extend axially parallel to the rotor axis. If these heat seams extend substantially over the entire axial length of the rotor sleeve, the inner diameter of the rotor sleeve is reduced evenly over its entire axial length, causing the rotor sleeve to conform evenly to the surface of the rotor magnet.

[0011] In a preferred embodiment, the rotor magnets extend essentially over the entire axial extent of the rotor base body. Likewise, the rotor sleeve extends essentially over the entire axial length of the base body. In this embodiment, the axial heat seams are particularly advantageously formed between two adjacent rotor magnets in the circumferential direction, so that the rotor magnets are not damaged when the sleeve material is heated. Thus, the axial heat seams are formed radially directly above the base body—or above the radial webs formed on the base body—whereby heating of the base body has no damaging effects.

[0012] For precise positioning of the rotor magnets on the base body, radial retaining webs are formed on the base body, against which the rotor magnets can be supported in the circumferential direction. Spring elements can also be incorporated into the retaining webs, which can compensate for manufacturing tolerances and temperature fluctuations. The radial retaining webs and / or the spring elements can be easily punched out of the sheet metal laminations as a single piece. The radial extension of the radial webs is less than the maximum radial extension of the rotor magnets, so that the rotor sleeve rests firmly against the outer surface of the rotor magnets as its diameter decreases.

[0013] The cross-section of the rotor magnets is particularly advantageously shaped such that the radial circumferential surfaces are curved or circular. The radial inner surfaces of the magnets, on the other hand, are preferably designed as straight, flat base surfaces that lie fully against the flat contact surfaces of the rotor base body. The cross-section of the rotor magnets transverse to the axial direction is advantageously designed in the shape of a "loaf of bread," in which the curved radial outer surface is connected to the flat radial inner surface by means of two tangentially opposite side surfaces. These side surfaces preferably run approximately perpendicular to the base surface, but can alternatively also extend approximately in the radial direction to the base body.Two opposing side surfaces of two adjacent magnets can be supported on the base body in the tangential direction to reliably position and fix the rotor magnets with respect to the tangential direction. The rotor sleeve rests against the central area of ​​the radially outer surface of the rotor magnets, at least with respect to the circumferential direction, to press the rotor magnets radially against the contact surfaces.

[0014] The rotor sleeve can be manufactured using a deep-drawing process, which is particularly simple and cost-effective. A metal sheet is used, the thickness of which is selected to achieve the desired radial shrinkage of the rotor sleeve after cooling of the localized, thermally treated areas. Likewise, the material of the rotor sleeve can be selected to achieve sufficient shrinkage of its inner diameter. For example, the rotor sleeve can be made of steel or aluminum, but preferably of a non-magnetically conductive metal.

[0015] To reduce weight and ensure optimal magnetic flux of the rotor, the rotor base advantageously features radial webs extending radially from a central hub to an outer yoke ring. The hub can be pushed – preferably pressed – onto the rotor shaft. The contact surfaces for the rotor magnets, which are particularly flat, are formed on the outer circumference of the yoke ring. The radial retaining webs are arranged in the tangential areas between two adjacent rotor magnets and are preferably located in the circumferential areas of the radial webs.

[0016] The rotor according to the invention is particularly suitable for use in an electrically commutated EC motor, in which the rotor is designed as an internal rotor motor. The rotor is arranged within a stator, in which an electronically commutable electrical winding is arranged within a stator housing. The rotor sleeve according to the invention ensures that the rotor magnets remain reliably positioned on the rotor and are protected from being thrown off.

[0017] To assemble the rotor according to the invention, the cold rotor sleeve is pushed axially onto the rotor, on whose base body the rotor magnets have previously been positioned. The material of the rotor sleeve is then heated to such an intense level using an external heat source in the locally defined areas that, after cooling, the material of the rotor sleeve contracts in these areas. By appropriately arranging the locally defined, thermally treated areas, a shrinkage residual stress can be generated in the locally defined areas during cooling, which presses the rotor sleeve radially against the rotor magnets.

[0018] Particularly advantageous is the very precise heating, and in particular melting, of the material in the defined areas using a laser beam. The laser beam can be guided along the surface of the rotor sleeve with many degrees of freedom to create appropriately shaped, thermally treated areas. The applied energy and the focus of the laser beam can be adjusted accordingly to the sleeve material and the material thickness of the rotor sleeve.

[0019] It is particularly advantageous if the laser beam is guided in the axial direction, preferably over the entire axial length of the rotor sleeve, in order to form axial heat seams thereon. These heat seams are preferably formed between two rotor magnets in the circumferential direction, with, for example, an axial heat seam being formed between each rotor magnet. In this case, a shrinkage residual stress can be generated, particularly in the tangential direction, between the rotor magnets, which causes the inner diameter of the rotor sleeve to shrink more at these points than in the area of ​​the maximum radial extension of the rotor magnets.

[0020] With this assembly process, the rotor sleeve can be designed particularly advantageously without an insertion phase, as the rotor sleeve can be pushed onto the radially outer surfaces of the rotor magnets with some clearance. By omitting the insertion phase, the rotor has a smaller outer diameter after assembly, and material machining during the insertion phase after the rotor sleeve has been pushed on can be omitted. In contrast to the conventional shrink-fitting of a sleeve, circumferential stresses can be generated subsequently after the sliding on, so that on the one hand the rotor sleeve can be pushed onto the rotor magnets with a clearance fit, and then a sufficient radial contact force can be generated on the rotor magnets through the local melting of the rotor sleeve. The degree of the radial contact force of the rotor sleeve can be influenced by the number and the areal extent of the heat seams.Since the rotor magnets are preferably already radially magnetized, they are held in place by the magnetic force on the contact surfaces of the rotor body when the rotor sleeve is pushed on. Melting the rotor sleeve material with a laser beam does not impair the magnetic properties of the rotor magnets.

[0021] In an alternative embodiment, the locally defined areas of the rotor sleeve can be heated inductively, whereby, for example, several limited thermally treated areas can be created on the rotor sleeve simultaneously. The power of the inductive heater can be set high enough to melt the corresponding material of the rotor sleeve.

[0022] Short description of the drawings

[0023] Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description.

[0024] They show:

[0025] Fig. 1 is a sectional view of a first embodiment of a rotor according to the invention in longitudinal section,

[0026] Fig. 2 is a side view of the embodiment according to Fig. 1, and

[0027] Fig. 3 shows a further embodiment of a rotor in an electrical machine in cross-section. Fig. 1 shows a rotor 10 of an electrical machine 12, which has a base body 14, on the outer circumference 15 of which contact surfaces 16 are formed. Rotor magnets 20 are arranged on the contact surfaces 16 and preferably extend over the entire axial length 13 of the base body 14. The rotor magnets 20 are arc-shaped in the circumferential direction 9 and have an inner base surface 26 and a radial outer surface 24. A rotor sleeve 30 bears against the radial outer surfaces 24 and serves as anti-skid protection for the rotor magnets 20. The rotor sleeve 30 is made, for example, from a metal sheet, in particular by means of a deep-drawing process. For assembly, the rotor sleeve 30 is first pushed with play onto the radial outer surfaces 24 of the rotor magnets 20 in the axial direction 8.Thereafter, locally defined areas 32 are thermally treated in such a way that they contract upon cooling and generate residual tensile stress. This reduces the inner diameter 29 of the rotor sleeve 30, whereby the rotor sleeve 30 is pressed in the radial direction 7 against the radial outer surface 24 of the rotor magnets 20. As a result, the rotor magnets 20 are pressed radially at their base surface 26 against the contact surfaces 16 of the base body 14. This allows the rotor magnets 20 to be securely fixed to the base body 14 without the rotor sleeve 30 having to be pushed onto the rotor magnets 20 by means of a press fit. In Fig. 1, a laser beam 40 is used as the heat source 42 for the thermal treatment of the defined areas 32, by means of which the locally defined areas 32 are preferably melted.If the laser beam 40 is guided from the outside over the rotor sleeve 30, so-called heat seams 34 are formed thereon, which preferably extend in the axial direction 8 of the rotor sleeve 30.

[0028] Distributed around the circumference, a plurality of heat seams 34 are formed as limited thermally treated regions 32, as shown, for example, in Fig. 2. The heat seams 34 preferably extend over the entire axial length 31 of the rotor sleeve 30. The number of these heat seams 34 can influence the radial contact force with which the rotor sleeve 30 presses against the rotor magnets 20. For example, the heat seams 34 are each formed between two rotor magnets 20 with respect to the circumferential direction 9. This can prevent the magnetic material of the rotor magnets 20 from being impaired during the thermal treatment of the rotor sleeve 30.

[0029] Fig. 3 shows a cross-section through an electric machine 12 as a further exemplary embodiment. The rotor 10 is arranged within a stator 11, which preferably has an electrically commutable winding that interacts with the rotor magnets 20 of the rotor 10. The rotor body 14 here has a hub 54 that is arranged on the rotor shaft 57. Radial webs 56 extend radially outward from the hub 54 to a yoke ring 55 that is closed in the circumferential direction 9. Recesses 52 are formed between the radial webs 56, which reduce the weight of the rotor 10. The base body 14 can, for example, be composed of individual sheet metal laminations that are arranged axially one above the other and connected to one another - in particular by means of stamped packages 51. On the outer circumference 15 of the yoke ring 55, the contact surfaces 16 for the rotor magnets 20 are formed as flat surfaces in the circumferential direction 9.The rotor magnet 20 is placed on this flat contact surface 16 with its flat base surface 26. The rotor magnets 20 preferably have a "loaf-shaped" cross-section 23, with side surfaces 25 being formed between a curved radial outer surface 24 and the flat inner base surface 26. Radial holding webs 22 are formed on the base body 14 between the rotor magnets 20 in the circumferential direction 9. These radial holding webs 22 serve to correctly position the rotor magnets 20 and can optionally also be designed as spring elements 21 that fix the rotor magnets 20 between the holding webs 22 in the circumferential direction 9. The rotor magnets 20 are preferably magnetized in the radial direction 7, with adjacent rotor magnets 20 then forming opposite magnetic poles. The yoke ring 55 serves as a magnetic yoke between two adjacent rotor magnets 20. In the embodiment in Fig.3, the curvature of the radial outer surface 24 of the rotor magnets 20 deviates from a circular ring around the center point 50 of the rotor 10. The radial extension of the radial retaining webs 22 is less than the radial extension of the side surfaces 25 of the rotor magnets 20. If, after the rotor sleeve 30 has been axially pushed on, the limited thermally treated regions 32 are formed tangentially between the rotor magnets 20, these generate a shrinkage residual stress that presses the rotor sleeve 30 against the rotor magnets 20 in the radial direction 7. The rotor sleeve 30 rests radially against the rotor magnets 20 in the region of the curved radial outer surfaces 24. In the tangential circumferential area between two adjacent rotor magnets 20, the limited thermally treated areas 32 of the rotor sleeve 30 have a radial distance from the radial retaining webs 22.Due to the residual shrinkage stress of the thermally treated regions 32, the rotor sleeve 30 conforms radially to the surface of the rotor 10, whereby the rotor sleeve 30, in particular after its thermal treatment, deviates from an exact circular shape around the center point 50. The limited thermally treated regions 32 are also preferably formed here as axial heat seams 34, which extend along the side surfaces 25 of the rotor magnets 20 in the axial direction 8. The material of the rotor sleeve 30 is preferably magnetically non-conductive, so that the magnetic field lines of the rotor poles extend radially outward from the rotor magnets 20 to the stator 11. An air gap is formed between the outer circumference of the rotor sleeve 30 and the stator 11 so that the rotor 10 can rotate unhindered within the stator 11.Preferably, an axial heat seam 34 is formed between all rotor magnets 20, wherein the rotor 10 has, for example, six or ten or twelve or eighteen rotor magnets 20, which extend essentially over the entire axial extent 13 of the base body 14. The electric machine 12 is designed, for example, as an electrically commutated EC motor in which an output element is arranged on the rotor shaft 57. The rotor magnets 20 remain securely fixed to the base body 14 by the rotor sleeve 30, even if the rotor magnets 20 are damaged during operation.

[0030] It should be noted that, with regard to the exemplary embodiments shown in the figures and in the description, a wide variety of combinations of the individual features are possible. For example, the specific design and arrangement of the contact surfaces 16 and the rotor magnets 20 can be varied. For example, the rotor magnets 20 can also be bowl-shaped or cuboid-shaped instead of having a loaf of bread cross-section. Likewise, the specific design and the number of radial retaining webs 22 can be adapted to the requirements of the electrical machine 12. The deformability - and thus the contact forces generated thereby - of the rotor sleeve 30 can be adjusted by the material used and its wall thickness and by the number and extent of the limited thermally treated regions 32.As an alternative heat source 42, the thermally treated regions 32 can also be generated by means of an inductive heater, in which, in particular, several heat seams 34 can be formed simultaneously. The invention is particularly suitable for use in an EC motor designed as an internal rotor, in particular for the rotary drive of components or the adjustment of parts in a motor vehicle, but is not limited to this application.

Claims

Claims 1. Rotor (10) for an electrical machine (12), comprising a base body (14) on whose radially outer circumference (15) a plurality of rotor magnets (20) are arranged, wherein the rotor magnets (20) are fixed to the base body by means of a rotor sleeve (30) made of metal (14) are fixed, wherein the rotor sleeve (30) has limited thermally treated areas (32) which radially clamp the rotor sleeve (30) on the base body (14).

2. Rotor (10) according to claim 1, characterized in that the thermally treated regions (32) are designed as axial heat seams (34) which extend in particular over the entire axial length (31) of the rotor sleeve (30).

3. Rotor (10) according to claim 1 or 2, characterized in that the rotor magnets (20) extend substantially over the entire axial length (13) of the base body (14) and the axial heat seams (34) are arranged in the circumferential direction (9) between two adjacent rotor magnets (20).

4. Rotor (10) according to one of the preceding claims, characterized in that in the circumferential direction (9) between flat contact surfaces (16) for the rotor magnets (20) on the base body (14) radial holding webs (22) for the rotor magnets (20) are formed, which in particular each bear tangentially on opposite side surfaces (25) of two adjacent rotor magnets (20).

5. Rotor (10) according to one of the preceding claims, characterized in that the rotor magnets (20) have a "loaf-shaped" cross-section (23) and each have a base surface (26) that lies flat against the contact surfaces (16), and a radial outer surface (24) is curved, against which arcuate sections (36) of the rotor sleeve (30) radially rest. and press the rotor magnets (20) radially against the contact surfaces (16).

6. Rotor (10) according to one of the preceding claims, characterized in that the rotor sleeve (30) is manufactured in the circumferential direction (9) as a continuous ring, and in particular is manufactured by means of deep drawing.

7. Rotor (10) according to one of the preceding claims, characterized in that the base body (14) has a central hub (54) which is pressed onto a rotor shaft (57), and has a circumferential yoke ring (55), on the outside of which the contact surfaces (16) for the rotor magnets (20) are formed - wherein radial webs (56) extend in particular between the hub (54) and the yoke ring (55).

8. Electrical machine (12) with a rotor (10) according to one of the preceding claims, which is rotatably arranged within a stator (11) having an electronically commutated winding.

9. A method for producing a rotor (10) for an electrical machine (12), preferably according to one of the preceding claims, characterized by the following steps: - Axial sliding of the rotor sleeve (30) over the rotor magnets (20) - Local heating of the rotor sleeve (30) to form the limited thermally treated areas (32) - Cooling of the rotor sleeve (30), whereby the thermally treated Areas (32) generate a shrinkage residual stress which presses the rotor magnets (20) in the radial direction (8) against the contact surfaces (16).

10. The method according to claim 9, characterized in that the thermally treated areas (32) are heated - in particular locally melted - by means of a laser beam (40).

11. Method according to claim 9 or 10, characterized in that the laser beam (40) is guided radially from the outside along the axial extension (31) of the rotor sleeve (30) in order to form the axial heat seams (34).

12. Method according to claim 9 to 11, characterized in that the rotor sleeve (30) is pushed onto the rotor magnets (20) with a clearance fit without an insertion phase, and only after the local heating of the thermally treated areas of the rotor sleeve (30) does a press fit between the rotor sleeve (30) and the rotor magnets (20) form.

13. Method according to claim 9 or 12, characterized in that the limited thermally treated areas (32) are heated by means of an inductive heater - in particular several axial heat seams (34) simultaneously.

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