Method for producing a soft magnetic core material and soft magnetic core material

Abstract

Method for producing a soft magnetic core material (1) for electrical machines and actuators using a 3D printing process, wherein the soft magnetic core material (1) is built up from at least one layer of at least one material component (3.1, 3.2, 3.3), wherein the at least one layer is applied in such a way that, in order to reduce eddy current losses, defined internal cavities (4) are formed within the soft magnetic core material (1), wherein the defined internal cavities (4) are intentionally introduced cavities (4) that are completely enclosed by the at least one material component (3.1, 3.2, 3.3).

Description

[0001] The invention relates to a method for producing a soft magnetic core material for electrical machines and actuators, according to the preamble of claim 1.

[0002] The invention also relates to a soft magnetic core material for electrical machines and actuators.

[0003] Soft magnetic core materials, also known as iron cores or transformer cores, are regularly used in electrical engineering to concentrate the magnetic flux in an alternating field and thereby increase inductance and magnetic flux density.

[0004] Soft magnetic core materials are mostly used in electrical machines, including electric motors, generators and transformers, as well as in actuators such as electric valves.

[0005] A known problem with the use of electrically conductive materials, such as soft magnetic core materials, in an alternating field is that parasitic eddy currents are induced in the material. Such eddy currents also generate a magnetic field that counteracts the original field. This—and other electrical losses—can reduce the energy conversion efficiency of an electrical machine or other device. Furthermore, unwanted heating of components can occur, which can ultimately reduce the service life of the components.

[0006] To eliminate or reduce unwanted eddy current induction, it is common practice in the state of the art to use electrically non-conductive materials in the area of ​​influence of an alternating field. However, it is also known that electrical insulators often do not exhibit magnetic properties suitable for use as soft magnetic core material, i.e., for increasing the magnetic flux density. Ferrites or ferrimagnetic ceramic materials are an exception; however, their processing is technically complex and their low saturation polarization is usually also unsuitable for the corresponding application.

[0007] To reduce alternating field losses, laminated iron cores consisting of transformer laminations (also called "laminated cores") are often used in practice. A soft magnetic core material is manufactured in alternating layers of electrically insulating layers and magnetically well-suited material components.

[0008] To produce such core materials, thin sheets are usually processed by rolling processes, whereby the individual layers are electrically insulated from each other (e.g. by painting).

[0009] For example, DE 25 06 681 A1 shows a stacking device for transformer sheets, which are continuously unrolled from a supply roll and cut to length and shape by a swivel cut shear.

[0010] An alternative is a powder metallurgy process, in which an electrical insulation layer is provided on each individual particle to reduce alternating field losses.

[0011] However, existing solutions only allow for the production of relatively complex geometries. The processing and stacking of the soft magnetic core material is complex and adversely affects the magnetic properties.

[0012] While sheet stacking processes allow for the introduction of electrical insulation, this technology relies on deformable materials. For example, iron alloys with a high silicon content, such as Fe 6.5 wt% Si, cannot be reliably or economically manufactured due to the material's very brittle behavior.

[0013] Often, the insulation layers are not sufficiently temperature-resistant for subsequent heat treatment, which would further improve the material properties of the core material.

[0014] Furthermore, powder metallurgy manufacturing processes do not allow the introduction of electrically insulated intermediate layers, which can cause alternating field losses to spread throughout the entire material.

[0015] The powder composite materials are also uneconomical and have significantly lower permeability than, for example, solid iron.

[0016] Another technique for reducing electrical losses, particularly eddy current losses, is the subsequent introduction of slots into the core material. For background information, see, for example, the scientific publication "Stator Core with Slits in Transverse Flux Rotary Machine to Reduce Eddy Current Loss" by Ji-Young Lee et al. (published in the "Journal of Magnetics 2012": "Koo, Dae-Hyun & Kang, Dohyun & Hong, JP. (2012). Stator Core with Slits in Transverse Flux Rotary Machine to Reduce Eddy Current Loss. Journal of Magnetics. 17. 10.4283 / JMAG.2012.17.1.051.") and US Pat. No. 5,385,410 A. However, the production of such a core material, which thus comprises several very different manufacturing steps (e.g., rolling, sawing, etc.), is extremely complex.

[0017] One possibility for creating recesses in the outer surfaces of a carrier to accommodate permanent magnets is described in WO 2016 / 023 961 A1 and WO 2016 / 023 961 A1. These documents each relate to methods for producing a permanent magnet using additive manufacturing processes.

[0018] For background information regarding additive manufacturing processes, reference is also made to DE 10 2014 212 176 A1, which concerns a powder-bed-based additive manufacturing process in which a layer of powder is repeatedly applied to a powder bed. The powder is then selectively melted with an energy beam, simultaneously forming a layer of a component to be manufactured, thereby creating the component to be manufactured layer by layer in the powder bed.

[0019] For further technological background, please refer to the scientific publications “Fujio Tsumori et al 2016 Jpn. J. Appl. Phys. 55 06GP18” and “Fengli Liu et al 2015 Smart Mater. Struct. 24 035015”.

[0020] The present invention is based on the object of creating a method for producing a soft magnetic core material with which a core material can be produced in which alternating field losses, in particular eddy currents, are avoided better than has previously been possible.

[0021] This object is achieved for the method for producing a soft magnetic core material for electrical machines and actuators according to the features set out in claim 1.

[0022] With regard to an advantageous soft magnetic core material, the object is achieved by the features of claim 15.

[0023] The dependent claims and the features described below relate to advantageous embodiments and variants of the invention.

[0024] In principle, soft magnetic core materials can be used for any application requiring electromagnetic interaction. However, the invention is particularly suitable for the production of a soft magnetic core material for electrical machines and actuators.

[0025] The method for producing a soft magnetic core material provides that the soft magnetic core material for electrical machines and actuators is produced using a 3D printing process.

[0026] 3D printing is an additive manufacturing process. Additive manufacturing processes are often also referred to as generative manufacturing processes.

[0027] According to the invention, the soft magnetic core material is constructed from at least one layer of at least one material component, wherein the at least one layer is applied in such a way that, in order to reduce eddy current losses, defined internal cavities are formed within the soft magnetic core material, which are completely enclosed by the at least one material component.

[0028] Defined internal cavities are, of course, intentional, deliberately introduced cavities and not pores or similar things that arise randomly during the manufacturing process.

[0029] The layers of the material components can be first applied using the 3D printing process and then bonded together. This can be achieved by applying a powder, which is then fused or sintered to the surrounding material through a targeted melting process.

[0030] Because the layers are applied using a 3D printing process, the inventive method also allows for the creation of extremely complex geometries for a soft magnetic core material. For this purpose, a variety of parameters such as layer thickness, number of layers, layer orientation, etc., can be configured to improve the alternating field behavior of a magnetic core material.

[0031] Furthermore, materials that are difficult or impossible to roll, such as iron alloys with a high proportion of elements that increase electrical resistivity, can be additively processed. Alternatively, pure metal (e.g., aluminum) can be used and melted, provided that alloys with high electrical resistivity form between iron and the desired metal (e.g., iron aluminides).

[0032] According to the invention, it is possible to use almost all ferromagnetic materials, in particular iron-silicon alloys in the range 0.5 wt.% to 100 wt.% silicon content, to produce a soft magnetic core material.

[0033] The manufacturing process according to the invention can, in principle, be used for any core geometry made from various material combinations. It is particularly advantageous for applications requiring high saturation polarization of the material combined with low alternating field losses. Such conditions are typically encountered in electric motors, generators, and actuators.

[0034] In particular, the introduction of internal slots is not readily possible with known methods for producing core materials. Using the 3D printing process according to the invention, internal slots can be easily introduced by not applying material at the slots or by not subsequently fusing or solidifying the applied material. This allows the number and shape of slots to be controlled as desired, allowing the core material to be even better tailored to the specific application to reduce eddy current losses.

[0035] In a further development of the invention, it can be provided in particular that the soft magnetic core material is constructed from layers of at least two different material components.

[0036] More than two different material components can also be provided, for example three, four or five.

[0037] The different material components can form the soft magnetic core material in a stack.

[0038] In a further development, it can be provided that at least one of the material components has electrically insulating properties and in particular comprises a mixed crystal, an intermetallic compound, ceramic components and / or polymer components.

[0039] It can also be provided that at least one of the material components has the properties of an electrical semiconductor. Likewise, it can be provided that at least one of the material components has poor electrical conductivity, even though the material component is still classified as a conductor.

[0040] Because at least one of the material components has electrically insulating properties or at least poorly conductive properties, electrical eddy currents within the core material can be locally reduced or even eliminated.

[0041] Preferably, iron, with its high electrical conductivity, can be influenced in its conductivity by adding cobalt, silicon or aluminum, etc. and tailored to the application.

[0042] For example, iron-silicon alloys with 6.5 wt.% Si achieve sufficient saturation polarizations and have a higher electrical resistance than pure iron, which makes the alloy suitable as a material component with “electrically insulating” or at least poorly conductive properties.

[0043] In particular, it may be provided to use at least two different material components with significantly different electrical conductivities.

[0044] In a further development of the invention, it can also be provided that at least one of the material components has soft magnetic properties and in particular comprises pure iron, an iron-silicon alloy, an iron-aluminum alloy, an iron-cobalt alloy and / or an iron-nickel alloy.

[0045] Soft magnetic properties refer in particular to a high saturation polarization and / or a low coercive field strength.

[0046] High saturation polarization can be achieved, for example, using pure iron powder or an iron-cobalt alloy. These have sufficiently high polarizations of approximately two Tesla.

[0047] For additive manufacturing, such powders can be used in the appropriate shape and grain size distribution (e.g., 1 to 200 micrometers). They can be melted together under a protective gas atmosphere.

[0048] Some alloys that are potentially ideal core materials have already been identified as suitable for additive manufacturing processes. For example, see the scientific publication "Metallurgy of high-silicon steel parts produced using Selective Laser Melting" by Michele Garibaldi et al. (published in "Acta Materialia 2016", ELSEVIER) or the publication "Microstructure and Magnetic Properties of Fe-Ni Alloy Fabricated by Selective Laser Melting Fe / Ni Mixed Powders" by Baicheng Zhang et al. (published in "Journal of Materials Science & Technology 2013", ELSEVIER).

[0049] By using iron alloys with a higher proportion of silicon and / or aluminum, the electrical resistance of the material can be increased while reducing the saturation polarization. Iron alloys with a maximum of 3.5 wt.% Si are typically used in the prior art, as the formability of the material can be greatly reduced at higher silicon contents, causing the material to become brittle. However, by using the process according to the invention, iron alloys with higher proportions of silicon and aluminum can now be used.

[0050] The use of diamagnetic, paramagnetic, ferrimagnetic, antiferromagnetic or non-magnetic material components may also be provided.

[0051] In a further development, it can also be provided that the soft magnetic core material is subjected to heat treatment.

[0052] Heat treatment refers, in particular, to a process for heating and subsequently cooling the core material in order to improve its properties. This is often not possible with conventional sheet stacking processes, for example, because the thin electrical insulation layers could otherwise be damaged.

[0053] Heat treatment can lead to the formation of solid solutions, intermetallic phases, an increase in strength, densification and the healing of material defects.

[0054] During heat treatment, internal stresses, inhomogeneity and other negative influences of the additive manufacturing of the soft magnetic core material can be reduced or influenced.

[0055] In particular, it can be provided that existing layers produced by additive manufacturing are subjected to heat treatment following additive manufacturing. Alternatively or additionally, heat treatment is also possible during additive manufacturing or after completion of individual layers.

[0056] It can be provided that the layer layers of the material components have a thickness of 1 to 500 micrometers, preferably 10 to 300 micrometers.

[0057] In particular, it can be provided that the layer layers of the material component which has electrically insulating properties are applied more thinly than the layer layers of the material component which has soft magnetic properties.

[0058] In a particularly preferred embodiment of the soft magnetic core material, iron-silicon alloys with 6.5 wt.% Si or even iron in pure form in a sufficiently free-flowing, e.g., spherical grain size distribution between 1 and 200 micrometers are converted into any desired core geometry in the layered structure and each separated by additively applied electrical insulation layers.

[0059] A large number of thin electrically insulating layers can be provided, which can increase the electrical path lengths for the formation of eddy currents and thus reduce the loss properties of the core material.

[0060] In a further development, it can be provided that recesses, in particular in the form of slots, are introduced into the soft magnetic core material on the outer surfaces.

[0061] By introducing such recesses into the core material, the electrical path length can also be influenced, which can lead to a reduction in eddy current losses.

[0062] The recesses can be created by post-processing, for example by abrasive post-processing, of the soft magnetic core material.

[0063] Preferably, however, the recesses can also be formed during the 3D printing process, by not introducing or fusing any base material at these points. This can even save material.

[0064] In a further development of the invention, it can be provided that the inner cavities are formed in the manner of inner slots.

[0065] For example, a suitable number of internal slots has proven to be sufficient, ranging from 2 to 1000 in a ring body with an outer diameter of 40 millimeters and an inner diameter of 30 millimeters. This exemplary ratio can be scaled by a person skilled in the art for any application or geometry.

[0066] For example, it has also been shown that by introducing 34 slots with a width of 0.5 millimeters and a depth of 4 millimeters in a ring geometry of a core material with an outer diameter of 40 millimeters and an inner diameter of 30 millimeters, it is possible to increase the electrical path length by about 50%.

[0067] By deliberately introducing recesses and / or cavities, the electrical resistance of one or more material components can be increased, which can lead to a reduction in the loss properties of the soft magnetic core material in the alternating field.

[0068] In a further development of the invention, it can also be provided that the recesses on the outer surfaces and / or the cavities within the soft magnetic core material are filled with a material component that has electrically insulating properties.

[0069] By filling the recesses or cavities with a highly permeable material with low electrical conductivity, the behavior of the core material in an alternating field can be further improved. Filling the recesses or cavities can be achieved, for example, by inserting / immersing them in a non-conductive material or directly during additive manufacturing. A further advantage is that this can improve the strength of the core material. Metallic, ceramic, or polymer materials have proven particularly suitable.

[0070] In a particularly advantageous embodiment, a soft magnetic core material with recesses, cavities, or slots can be immersed in a bath of electrically non-conductive material, such as plastic or non-conductive metal, after additive manufacturing. Ceramic intermediate materials can also be used.

[0071] It can also be provided that the recesses on the outer surfaces and / or the cavities within the soft magnetic core material are filled with a material component that has other (special) electrical and / or mechanical properties.

[0072] In a further development, it can be provided that the inner cavities are provided with openings to the outer surfaces of the soft magnetic core material, and a starting material, in particular a powder from the 3D printing process, is removed through the openings.

[0073] Powder from the 3D printing process can thus be blown out or poured out through the openings. An alternative is for the powder to remain loose within the core material.

[0074] In a further development of the invention, it can be provided that the recesses on the outer surfaces and / or the cavities within the soft magnetic core material are introduced or formed in different geometries and / or orientations.

[0075] The recesses, cavities, or slots can be introduced in different orientations, e.g., radial, axial, or in another orientation.

[0076] In particular, it may be provided to introduce recesses or cavities or slots alternately radially and axially in order to efficiently extend the electrical path length.

[0077] Due to the large number of degrees of freedom and manufacturing parameters, the alternating field properties of the resulting core material can be adjusted almost arbitrarily.

[0078] Particularly good magnetic properties of additively manufactured soft magnetic core materials can be achieved by sintering densified cores whose internal porosity is largely minimized. This can be achieved by suitable adjustment parameters during additive manufacturing in combination with a coordinated grain size distribution of the powder and a suitable subsequent heat treatment.

[0079] In a further development of the invention, for example, it can be provided that 1 to 10,000 cavities, preferably 2 to 5,000 cavities, very particularly preferably 2 to 1,000 cavities are formed.

[0080] In a particularly preferred development, it is provided that parameters of the 3D printing process are optimized on the basis of an analysis of the magnetic flux of the soft magnetic core material in order to minimize electrical losses in the alternating field, in particular eddy current losses.

[0081] In a further development, it can also be provided that parameters of the 3D printing process are optimized on the basis of an analysis of the magnetic flux of the magnetic core material, specifying the magnetic permeability of the soft magnetic core material.

[0082] This means that the magnetic permeability of the magnetic core material can be specifically specified, for example in the form of an objective function of an optimization algorithm.

[0083] An analysis refers to any analytical technique used to deterministically and / or heuristically analyze the behavior of the system in which the soft magnetic core material is to be used in an alternating field. Of course, any simulation techniques, optimization algorithms, and mathematical calculation methods are possible.

[0084] A simulation or other analysis can, for example, produce a CAD model or design model, which is then used by the inventive method to manufacture the soft magnetic core material. This allows the electrical power loss or the behavior of the core material in an alternating field to be precisely (pre)determined. Due to the high number of degrees of freedom, particularly in geometry, and the wide range of materials, almost any theoretical properties of the soft magnetic core material can be translated into practice.

[0085] In particular, it can also be provided that a number of recesses and / or cavities with defined widths, depths, geometries, orientations, and spacings are introduced from CAD designs based on simulations or other analysis methods or calculations. An electrical path length and thus an electrical resistance can be defined as a function of the recesses, cavities, or slots relative to a given core geometry.

[0086] In a further development, it can be provided that the parameters to be optimized are a grain size of a starting material of the 3D printing process, an electrical conductivity of one or more material components, a magnetic permeability of one or more material components, a magnetic coercive field strength of one or more material components, a magnetic saturation polarization of one or more material components, the thickness of a layer of one or more material components, a geometry of the soft magnetic core material, a number of layer layers of the soft magnetic core material, the number of different material components, the distribution of the layer layers in the soft magnetic core material, a geometry of the recesses and / or the cavities, a position of the recesses and / or the cavities and / or an orientation of the recesses and / or the cavities.

[0087] The power loss in the alternating field can thus be defined as a function of one or more of the parameters mentioned. The above list is, of course, not exhaustive.

[0088] Knowledge of the properties of the starting powders, including grain size, electrical conductivity, and magnetic characteristics such as permeability, coercive field, and saturation polarization, as well as core properties such as geometry, number of layers, layer thickness, etc., can thus be used to influence the alternating field properties of the core material. This makes application-oriented production of soft magnetic core materials economically feasible.

[0089] It may also be provided to produce a soft magnetic core material from, for example, two layers according to the 3D printing process described above and then to stack several soft magnetic core materials produced in this way and to press them, for example, in a known manner.

[0090] The invention also relates to a soft magnetic core material for electrical machines and actuators, which is provided with internal cavities and is produced by a method according to the above description and claims 1 to 14.

[0091] Exemplary embodiments of the invention are described in more detail below with reference to the drawings. The figures each show preferred exemplary embodiments in which individual features of the present invention are illustrated in combination with one another.

[0092] In the figures, functionally identical elements are provided with the same reference numerals.

[0093] They show schematically: Fig. 1 an isometric representation of a core geometry in ring form with several layers; Fig. 2 a section through the core material of the Fig. 1 with internal cavities; Fig. 3 a section through a core material of a second embodiment with internal cavities; Fig. 4 a section through a core material of a third embodiment with internal cavities; Fig. 5 a section through a core material of a fourth embodiment with internal cavities; Fig. 6 an isometric representation of a core geometry in ring form with radially introduced slots on the outer surfaces; Fig. 7 a plan view of the core material of the Fig. 6; Fig. 8 an isometric representation of a core geometry in ring form with axially introduced slots; Fig. 9 is an isometric view of a core material with internal cavities in a preferred embodiment; Fig. 10 a plan view of the design of the core material of the Fig. 9; and Fig. 11 an isometric representation of a core geometry in ring form with a preferred embodiment of external slots.

[0094] In Fig. Figure 1 shows a soft magnetic core material 1 in ring form, which was produced by a method according to the invention. The core material 1 consists of a stack 2 of seven layers of a first material component 3.1 and a second material component 3.2, which were applied using a 3D printing process and bonded together. The core material 1 has internal slots 4 (not shown, see Figure 1). Fig. 2 to 5 and 9 and 10).

[0095] In Fig. 2 is a section through the core material 1 of the Fig. 1. The seven layers are visible, which are formed in the manner of a stack 2 from the two different material components 3.1, 3.2. It can be provided that a first material component 3.1 has electrically insulating properties and a second material component 3.2 has soft magnetic properties, in particular with regard to a high saturation polarization and / or a low coercive field strength.

[0096] The layer layers of the material components 3.1, 3.2 can, for example, have a thickness of 1 to 500 micrometers, preferably 10 to 300 micrometers.

[0097] It can further be provided that the layers of the electrically insulating first material component 3.1 are applied more thinly than the layers of the second material component 3.2 with the soft magnetic properties, as shown in Fig. 2 is indicated.

[0098] Of course, more than two different material components 3.1, 3.2 can be provided.

[0099] To reduce eddy current losses, the core material 1 shown has intentional, deliberately introduced internal cavities in the form of internal slots 4, which can be formed by the proposed method and which are completely encased by the at least one material component 3.1, 3.2, 3.3. This allows the loss properties of the core material 1 to be further improved.

[0100] The inner slots 4 can extend in particular from one layer of the electrically non-conductive or poorly conductive material component 3.1 to an adjacent or to any further layer of the electrically non-conductive or poorly conductive material component 3.1.

[0101] Of course, the slots 4 can also be provided at any position within the core material 1.

[0102] In Fig. 3 shows an exemplary embodiment in which three different material components 3.1, 3.2, 3.3 are provided.

[0103] In Fig. 3, the first material component 3.1 is provided with the electrically insulating properties, the second material component 3.2 with the soft magnetic properties and a third material component 3.3 with any other material properties.

[0104] Furthermore, in the embodiment of the Fig. Three different layer thicknesses are provided. This allows, for example, the behavior of the soft magnetic core material 1 in an alternating field to be specifically optimized or adjusted based on a simulation or other analysis method.

[0105] The inner cavities or slots 4 can also be introduced into the core material 1 in different orientations. As an example, Fig. 3 shows three vertical or axial slots 4 and one horizontal or radial slot 4.

[0106] The use of a 3D printing process to produce the soft magnetic core material 1 also enables unusual geometries, as in Fig. 4 is shown by way of example with an unusual internal structure of the core material 1. In the embodiment of the Fig. 4, the layer thickness of the first material component 3.1 does not run uniformly within the core material 1, but rather follows a predetermined function. This also allows the behavior of the soft magnetic core material in the alternating field to be adjusted or optimized.

[0107] Also in the execution of the Fig. 4 shows an example and schematically an inner slot 4 which connects the layers of the first material component 3.1 with each other or runs between the layers.

[0108] In Fig. 5 shows - merely for clarification - that the inner cavities or inner slots 4 can also be introduced obliquely within the core material 1 and using a wide variety of geometries.

[0109] In Fig. Figure 6 shows a design of a soft magnetic core material 1 in a ring shape with radially introduced slots 5 on the outer surfaces of the core material 1. The slots 5 can be introduced into the soft magnetic core material 1 by abrasive post-processing, e.g., by sawing. It can also be provided that the slots 5 are already formed during the 3D printing process by not introducing or fusing any base material at these locations.

[0110] By introducing such recesses or slots 5 on the outer surfaces of the core material 1, global eddy currents can be reduced to more local, smaller eddy currents, which can reduce the losses of the core material 1 in the alternating field.

[0111] The electrical path length for a global eddy current may be increased, which similarly increases the electrical resistance and may inhibit the formation of the eddy current.

[0112] In a top view of the execution of the Fig. 6 is in Fig. 7, the electrical path length L is shown in dashed lines. It is clearly visible that the slots 5 significantly increase the electrical path length L.

[0113] In particular, a combination of recesses or slots 5 on the outer surfaces and inner cavities or inner slots 4 within the soft magnetic core material 1 is also possible.

[0114] For example, it can also be provided that an inner cavity or slot 4 opens into a recess or an outer slot 5, whereby pouring out powder is easily possible.

[0115] In Fig. 8 shows a further embodiment of a soft magnetic core material 1 in ring form, in which the outer slots 5 are introduced in the axial direction.

[0116] Any combinations and intermediate forms of axial and radial slots 5 are also possible.

[0117] Finally, the Fig. 9 and Fig. 10 shows a preferred embodiment in which a soft magnetic core material 1 is constructed from a single layer 3.2, wherein a plurality of internal cavities 4 are provided. The cavities 4 are in the Fig. 9 and Fig. 10 is shown in dashed lines within the soft magnetic core material 1. The cavities 4 also open into openings 6 to the outer surfaces of the soft magnetic core material 1, through which, for example, a starting material, in particular a powder from the 3D printing process, can be removed.

[0118] The Fig. Figure 11 shows another example of a soft magnetic core material 1 in ring form, which consists of a single layer 3.2, but can of course also be constructed from multiple layers 3.1, 3.2, 3.3. The soft magnetic core material 1 comprises outer slots 5 that extend alternately from the top and bottom of the soft magnetic core material 1 through the material in a stepped manner. This allows the electrical path length to be effectively influenced. The soft magnetic core material 1 shown additionally has inner slots 4 in the manner described above.

Claims

[1] Method for producing a soft magnetic core material (1) for electrical machines and actuators, using a 3D printing process, wherein the soft magnetic core material (1) is constructed from at least one layer of at least one material component (3.1, 3.2, 3.3), wherein the at least one layer is applied in such a way that, in order to reduce eddy current losses, defined internal cavities (4) are formed within the soft magnetic core material (1), wherein the defined internal cavities (4) are deliberate, specifically introduced cavities (4) which are completely enclosed by the at least one material component (3.1, 3.2, 3.3). [2] Method according to claim 1, characterized by that the soft magnetic core material (1) is constructed from layers of at least two different material components (3.1, 3.2, 3.3). [3] Method according to claim 1 or 2 characterized bythat at least one of the material components (3.1, 3.2, 3.3) has electrically insulating properties, and in particular comprises a mixed crystal, an intermetallic compound, ceramic components and / or polymer components. [4] Method according to claim 1, 2 or 3, characterized by that at least one of the material components (3.1, 3.2, 3.3) has soft magnetic properties, and in particular comprises pure iron, an iron-silicon alloy, an iron-aluminum alloy, an iron-cobalt alloy and / or an iron-nickel alloy. [5] Method according to one of claims 1 to 4, characterized by that the soft magnetic core material (1) is subjected to a heat treatment. [6] Method according to one of claims 1 to 5, characterized by that recesses (5), in particular in the form of slots (5), are introduced into the soft magnetic core material (1) on the outer surfaces. [7] Method according to one of claims 3 to 6, characterized by that the recesses (5) on the outer surfaces and / or the inner cavities (4) within the soft magnetic core material (1) are filled with a material component (3.1, 3.2, 3.3) which has electrically insulating properties. [8] Method according to one of claims 1 to 7, characterized by that the inner cavities (4) are provided with openings to the outer surfaces of the soft magnetic core material (1), and a starting material, in particular a powder of the 3D printing process, is removed through the openings. [9] Method according to one of claims 1 to 8, characterized by that the inner cavities (4) are formed in the manner of inner slots (4). [10] Method according to one of claims 6 to 9, characterized bythat the recesses (5) on the outer surfaces and / or the cavities (4) within the soft magnetic core material (1) are introduced or formed in different geometries and / or orientations. [11] Method according to one of claims 1 to 10, characterized by that 1 to 10,000 cavities (4), preferably 2 to 5,000 cavities (4), very particularly preferably 2 to 1,000 cavities (4) are formed. [12] Method according to one of claims 1 to 11, characterized by that parameters of the 3D printing process are optimized on the basis of an analysis of the magnetic flux of the soft magnetic core material (1) in order to minimize electrical losses in the alternating field, in particular eddy current losses. [13] Method according to one of claims 1 to 12, characterized bythat parameters of the 3D printing process are optimized on the basis of an analysis of the magnetic flux of the soft magnetic core material (1) under specification of the magnetic permeability of the soft magnetic core material (1). [14] Method according to claim 12 or 13, characterized bythat the parameters to be optimized are a grain size of a starting material of the 3D printing process, an electrical conductivity of one or more material components (3.1, 3.2, 3.3), a magnetic permeability of one or more material components (3.1, 3.2, 3.3), a magnetic coercive field strength of one or more material components (3.1, 3.2, 3.3), a magnetic saturation polarization of one or more material components (3.1, 3.2, 3.3), the thickness of a layer of one or more material components (3.1, 3.2, 3.3), a geometry of the soft magnetic core material (1), a number of layers of the soft magnetic core material (1), the number of different material components (3.1, 3.2, 3.3), the distribution of the layer layers in the soft magnetic core material (1), a geometry of the recesses (5) and / or the cavities (4), a position of the recesses (5) and / or the cavities (4) and / or an orientation of the recesses (5) and / or the cavities (4). [15] Soft magnetic core material (1) for electrical machines and actuators, which is provided with internal cavities (4) and is produced by a method according to one of claims 1 to 14.

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