Method for manufacturing a magnetic carrier

Abstract

Method for manufacturing a magnetic carrier (MT) for an electric machine, comprising the following steps: - Providing a sheet metal stack (BP) with at least one recess (AN) for receiving at least one magnetic element (ME); - Inserting at least one elastic retaining element (HE1, HE2) into the at least one recess (AN); - Inserting the at least one magnetic element (ME) into the at least one recess (AN) after the at least one elastic retaining element (HE1, HE2) has been inserted into the at least one recess (AN), wherein the at least one retaining element (HE1) is pulled in the insertion direction of the at least one magnetic element (ME) when inserting the at least one magnetic element (ME) into the at least one recess (AN).

Description

Technical area:

[0001] The invention relates to a method for producing a magnet carrier for an electrical machine. State of the art:

[0002] Electrical machines, especially permanent-magnet synchronous machines, comprise a stator and a rotor, with the stator and rotor, respectively, comprising a magnet carrier. The magnet carrier, in turn, comprises a laminated core with permanent magnets attached to or within it. These permanent magnets are made of brittle sintered magnets and are therefore brittle and fragile.

[0003] Due to the brittle nature and magnetic force of permanent magnets, attaching them to or within the laminated core is complex and costly in terms of manufacturing. Furthermore, permanent magnets are easily broken during operation of electrical machines due to strong vibrations and centrifugal forces.

[0004] DE 10 2012 016 927 A1 discloses an assembly method for securing permanent magnets in a rotor of an electric machine. This method involves pressing a clamping element onto the permanent magnet and partially compressing it before inserting the permanent magnet into the recess. After insertion, the permanent magnet is radially secured by a clamping force acting in the radial direction.

[0005] DE 10 2011 119 512 A1 discloses a method for manufacturing a rotor for a permanent-magnet electric machine. Before inserting a permanent magnet into a tubular recess, the permanent magnet is coated with a thermally expandable coating material.

[0006] It is an object of the invention to provide a method for producing a rotor in which a permanent magnet can be inserted and fixed in a recess of the rotor in a material-saving manner. Description of the invention:

[0007] This problem is solved by the subject matter of the independent claims. Advantageous embodiments are the subject matter of the dependent claims.

[0008] According to a first aspect of the invention, a method for producing a magnet carrier for an electrical machine is provided. According to the method, a laminated core is provided with at least one recess for receiving at least one magnetic element. At least one elastic retaining element is then inserted into this at least one recess. After the at least one elastic retaining element has been inserted into the at least one recess, the at least one magnetic element is inserted into the at least one recess.

[0009] A magnet carrier is a laminated core with built-in magnetic elements that will form a stator or rotor, or parts thereof, or a stator or rotor itself that comprises a laminated core with built-in magnetic elements. Depending on the perspective, a magnet carrier is thus an intermediate or final product of a stator or rotor of an electrical machine, especially a permanent magnet synchronous machine.

[0010] A recess means a groove-shaped depression (such as a dovetail groove) on the outer circumference of the laminated core or a through or blind hole in the laminated core in which a magnetic element is arranged and fastened.

[0011] The magnetic element can be a (fully magnetized) permanent magnet containing a hard magnetic material. Alternatively, the magnetic element can also be a (not yet fully magnetized) magnetizable element made of the hard magnetic material, which can also only be (fully) magnetized once it is arranged or fastened in the recess. The magnetization of the magnetic element can occur, for example, through the (repeated) action of a magnetic field on the magnetic element. The at least one elastic holding element contains, for example, elastomer and is thus soft and spring-elastic. The holder element is placed between the magnetic element and the inner wall of the recess so that it holds the magnetic element softly and resiliently in the recess and thus prevents the magnetic element from slipping out of the recess during operation of the electrical machine or from breaking due to vibrations or centrifugal forces.

[0012] In particular, two or more holder elements are inserted into a recess, which are then placed spatially separated from one another between the magnetic element and the inner wall of the recess, so that they support the magnetic element from two or more sides and can be held softly and resiliently in the center of the recess, electrically separated from the laminated core under the influence of compressive stresses.

[0013] The holding elements are preferably designed as extruded profiles, which can be easily and cost-effectively manufactured from an elastomer in an extrusion process.

[0014] When inserting the magnetic elements into the recesses filled with the retaining elements, the retaining elements maintain a gap between the (possibly brittle) magnetic elements and the hard inner walls of the recesses or the laminated core, thus preventing the magnetic elements from colliding with the laminated core and breaking. Furthermore, the soft and spring-elastic retaining elements yield when the magnetic elements are inserted, thus allowing the magnetic elements to be inserted into the respective recesses without breakage, even without exerting a great deal of force.

[0015] In addition, the spring-loaded retaining elements hold the magnetic elements in their respective recesses softly and resiliently, thus preventing them from slipping out of the recesses. Furthermore, the retaining elements compensate for vibrations and centrifugal forces that act on the magnetic elements during operation of the electrical machine, thus protecting the magnetic elements from breakage caused by vibrations and centrifugal forces.

[0016] This demonstrates a possibility of producing magnetic carriers or electrical machines more easily and cost-effectively, while also being stable.

[0017] According to the invention, when the at least one holding element is inserted into the at least one recess, the at least one holding element that is already located in the at least one recess is pulled in the insertion direction of the at least one holding element, so that the at least one holding element stretches in the insertion direction of the at least one holding element. For this purpose, tensile stresses are preferably applied to both axial ends of the holding element, viewed in the insertion direction. Due to the elasticity, the holding element is lengthened in the insertion direction under the action of the tensile stresses and the cross-section of the holding element transverse to the insertion direction is reduced (and the holding element thus becomes slimmer). As a result, the free space in the corresponding recess is enlarged. The at least one magnetic element is then inserted into this enlarged space.

[0018] After the at least one magnetic element has been inserted into the at least one recess or into the enlarged space within this recess, the at least one holding element is (again) relaxed, preferably in the direction of insertion, for example by removing the tensile stresses. After the relaxation or removal of the tensile stresses, the at least one holding element contracts in the direction of insertion and attempts to return to its original shape. The cross-section of the at least one holding element increases in size, and the at least one holding element fills the still free space (not occupied by the magnetic element) in the at least one recess. As a result, frictional or positive-locking connections are created between the holding element and the magnetic element, or between the holding element and the inner wall of the recess, whereby the magnetic element is held softly and resiliently in the recess.

[0019] The retaining element is preferably designed to be softer than the magnetic element, so that when the magnetic element is inserted into the recess or when external forces act on the retaining element and the magnetic element, e.g., during operation of the electrical machine, the retaining element always yields and deforms, thereby compensating for the external forces acting on it. This protects the magnetic element from deformation or breakage.

[0020] In the following, exemplary embodiments of the invention are explained in more detail with reference to the accompanying drawings. In the drawings: Fig. 1A, Fig. 1B in respective schematic cross-sectional representations a rotor of a permanent magnet synchronous machine; Fig. 2A, Fig. 2B, Fig. 2C, Fig. 2D in respective schematic cross-sectional representations a recess of a Fig. 1A, Fig. 1B shown rotor including an inserted magnetic element.

[0021] Fig. 1A shows a rotor RT of a permanent magnet synchronous machine in a schematic cross-sectional view transverse to its rotor axis RA, which is perpendicular to the plane of the figure.

[0022] The rotor RT comprises a magnet carrier MT, which in turn comprises a laminated core BP with a number of recesses AN. The recesses AN extend in the direction of the rotor axis RA from one axial end to another opposite axial end of the laminated core BP and thus form individual through-holes in the laminated core BP. The recesses AN are arranged in a circular distribution in the radial edge region RB of the laminated core BP, viewed in the direction of the rotor axis RA. In each of the recesses AN, a magnetic element made of an iron-cobalt-nickel alloy and at least two holding elements made of a dielectric elastomer are arranged, which are described below with reference to Fig. 2A to 2D are described in detail.

[0023] Fig. 1B shows a rotor RT of a permanent magnet synchronous machine, also in a schematic cross-sectional view transverse to its rotor axis RA, which is perpendicular to the plane of the figure.

[0024] In this embodiment, the recesses AN in the radial edge region RB of the laminated core BP are distributed and placed at an angle to one another in such a way that, viewed in the direction of the rotor axis RA, they simulate the shape of the corners of a multi-pointed star, such as a Star of David or an asterisk. Also arranged in the recesses AN are a magnetic element made of an iron-cobalt-nickel alloy and at least two holding elements made of a dielectric elastomer, which are also described below with reference to Fig. 2A to 2D are described in detail.

[0025] The different designs of the recesses, the magnetic elements and the holding elements of a Fig. 1A and Fig. 1B shown rotor RT are in Fig. 2A, Fig. 2B, Fig. 2C and Fig. 2D detailed image.

[0026] Fig. 2A shows a first embodiment of recesses AN and holding elements HE1.

[0027] In this embodiment, the recess AN has in its cross-section (transverse to the rotor axis RA) a substantially rectangular base area GF and four substantially circular corner areas EF at the four corners of the base area GF.

[0028] In a cuboid-shaped cavity HR11 defined by the quadrangular base area GF, a magnetic element ME is inserted, which is rod-shaped in its longitudinal direction, which runs parallel to the rotor axis RA, and has a substantially rectangular cross-section.

[0029] In each of four cylindrical cavities HR12 defined by the four circular corner surfaces EF, a holding element HE1 is arranged, which is also rod-shaped in its longitudinal direction, which runs parallel to the rotor axis RA, and substantially circular in its cross section.

[0030] The four retaining elements HE1 form-fit the respective cylindrical cavities HR12 and press the magnetic element ME located in the cuboidal cavity HR11 at its four corners toward the axial center of the recess AN. As a result, the four retaining elements HE1 fix the magnetic element ME in the center of the recess AN with a soft, resilient grip. At the same time, the four retaining elements HE1 hold the magnetic element ME at a distance from the entire inner wall IW of the recess AN, thus also electrically separating / insulating it from the laminated core BP.

[0031] Fig. 2B shows a second embodiment of the recesses AN and the holding elements HE1.

[0032] In this embodiment, the recess AN - viewed in the direction of the rotor axis RA - has a substantially dumbbell-shaped cross-section, which in turn has a substantially rectangular central surface MF and a substantially trapezoidal side surface SF at each of the two ends of the central surface MF.

[0033] A rod-shaped magnetic element ME is inserted into a cuboid-shaped cavity HR21 defined by the central surface MF. A holding element HE1 is inserted into each of the two cavities HR22 defined by the trapezoidal side surfaces SF. The holding element HE1 has a substantially C-shaped or double-L-shaped cross-section and positively fills the respective cavities HR22.

[0034] Viewed in their respective longitudinal directions, which run parallel to the rotor axis RA, the two retaining elements HE1 form-fit one of the two edge regions BR of the magnetic element ME and press the magnetic element ME toward the axial center of the recess AN. As a result, the two retaining elements HE1 fix the magnetic element ME softly and resiliently in the center of the recess AN and simultaneously keep it spaced from the entire inner wall IW of the recess AN, thus electrically insulating it from the laminated core BP.

[0035] Fig. 2C shows a third embodiment of the recesses AN and the holding elements HE1.

[0036] In this embodiment, the recess AN has a substantially rectangular cross-sectional area. In each of the two opposite side regions SB of the recess AN, a holding element HE1 is arranged, which extends in a rod-like manner in the direction of the rotor axis RA. In the center of the recess AN, a magnetic element ME is arranged, which also extends in a rod-like manner in the direction of the rotor axis Ra. The two holding elements HE1 fill the spaces in the two side regions SB between the magnetic element ME and the inner wall IW of the recess AN in a form-fitting manner and press the magnetic element ME towards the axial center of the recess AN. This creates form-fitting and friction-fitting connections between the inner wall IW of the recess AN and the two holding elements HE1, or between the two holding elements HE1 and the magnetic element ME.Thus, the two holding elements HE1 fix the magnetic element ME in the center of the recess AN in a resilient and resilient manner and at the same time keep the magnetic element ME at a certain distance from the entire inner wall IW of the recess AN and thus electrically insulated from the laminated core BP.

[0037] Fig. 2D shows a fourth embodiment of recesses AN and holding elements HE2.

[0038] In this embodiment, the recess AN also has a substantially rectangular cross-sectional area. The inner wall IW of the recess AN is coated with a protective arrangement SA made of a dielectric elastomer. The protective arrangement SA comprises an insulating element IE that completely covers the inner wall IW of the recess AN in a layered manner. On the surface OF facing the center of the recess AN, the protective arrangement SA has a rough or wavy surface structure that forms a plurality of holding elements HE2 that protrude from the surface OF toward the center of the recess AN and simultaneously extend in a rib-like manner in the direction of the rotor axis RA.

[0039] A magnetic element ME is arranged in the recess AN or in the cavity HR3 bordered by the surface OF of the protective arrangement SA. The magnetic element ME displaces the retaining elements HE2, which elastically yield and deform. This creates frictional and positive connections between the magnetic element ME and the retaining elements HE2, which secure the magnetic element ME in the recess AN. The insulating element IE also electrically insulates the magnetic element ME from the laminated core BP.

[0040] The following procedures are described with which the magnetic elements ME are inserted into the Fig. 2A to 2D and from the recesses AN described in Fig. 2A to 2D described holding elements HE1, HE2 are held in the respective recesses AN.

[0041] For those in Fig. 2A, Fig. 2B and Fig. 2C will be explained below using the example of the embodiment shown in Fig. The method indicated above is described in the embodiment shown in Figure 2B.

[0042] First, two holding elements HE1 made of a dielectric elastomer are inserted in their longitudinal directions parallel to the rotor axis RA into the cavities HR22 at the corners of the recesses AN.

[0043] The retaining elements HE1 are then pulled in their respective longitudinal directions by applying tensile forces to their two axial ends. Under the influence of these tensile stresses, the retaining elements HE1 expand in their respective longitudinal directions. Due to their elasticity, the cross-sections of the respective retaining elements HE1 become narrower, and consequently, the central area MF and thus also the cavity HR21 in the center of the recess AN also increase in size.

[0044] While the holding elements HE1 are still subjected to tensile stress, the magnetic element ME is inserted into the recess AN or into the enlarged cavity HR21 in an insertion direction parallel to the direction of the rotor axis RA and the longitudinal direction of the magnetic element ME. Due to the enlarged central area MF of the recess AN, the magnetic element ME can be inserted unhindered into the enlarged cavity HR21 without touching the inner wall IW of the recess AN.

[0045] After the magnetic element ME has been placed in the recess AN or in the enlarged cavity HR21, the two holding elements HE1 or their axial ends are relaxed again by removing the tensile stresses. Once the tensile stresses are removed, the two holding elements HE1 return to their original shapes due to their elasticity or attempt to return to their original shapes. The cross-sections of the holding elements HE1 increase in size again and the holding elements HE1 fill the two lateral cavities HR22 and the spaces between the magnetic element ME and the two lateral cavities HR22. The two holding elements HE1 press the magnetic element ME towards the center of the recess AN and thus hold the magnetic element ME firmly in the recess AN with a soft springback.

[0046] If the magnetic element ME is not yet magnetized, it is magnetized after being secured in the recess AN. For this purpose, the magnetic element ME is repeatedly exposed to a magnetic field in a manner known to those skilled in the art.

[0047] In the case of Fig. In the embodiment shown in Figure 2D, the inner wall IW of the recess AN is first overmolded with a dielectric elastomer, which, after hardening, forms a protective arrangement SA comprising a layered insulating element IE with a rough or wavy surface OF. The insulating element IE is made sufficiently thick so that it is not punctured when a magnetic element ME is inserted. The rough or wavy surface OF of the insulating element IE forms elastic retaining elements HE2, which protrude from the surface OF into the center of the recess and simultaneously extend in the direction of the rotor axis RA.

[0048] After the protective assembly SA has hardened, a magnetic element ME is inserted into the recess AN in an insertion direction parallel to the direction of the rotor axis RA and the longitudinal direction of the magnetic element ME. The magnetic element ME displaces the soft retaining elements HE2 of the protective assembly SA, which then yield through elastic deformation and adapt to the outer contour of the magnetic element ME. This creates positive and frictional connections between the retaining elements HE2 and the magnetic element ME. Thanks to these positive and frictional connections, the magnetic element ME is held firmly in the recess AN.

[0049] If the magnetic element ME is not yet magnetized, the magnetic element ME is magnetized after being fastened in the recess AN as described above.

Claims

[1] Method for producing a magnetic carrier (MT) for an electrical machine, comprising the following steps: - Providing a laminated core (BP) with at least one recess (AN) for receiving at least one magnetic element (ME); - Inserting at least one elastic holding element (HE1, HE2) into the at least one recess (AN); - Inserting the at least one magnetic element (ME) into the at least one recess (AN) after the at least one elastic holding element (HE1, HE2) has been inserted into the at least one recess (AN), wherein the at least one holding element (HE1) is pulled in the insertion direction of the at least one magnetic element (ME) when inserting the at least one magnetic element (ME) into the at least one recess (AN). [2] The method of claim 1, further comprising the step of: - Relaxing the at least one holding element (HE1) in the insertion direction of the at least one magnetic element (ME) after the at least one magnetic element (ME) has been inserted into the at least one recess (AN). [3] A method according to any one of the preceding claims, further comprising the step of: - Magnetizing the at least one magnetic element (ME) after the at least one magnetic element (ME) has been inserted into the at least one recess (AN).

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