SHEET METAL FOR THE MANUFACTURE OF A SHEET METAL PACK, IN PARTICULAR A STATOR PACK OR A ROTOR PACK, AND METHOD FOR MANUFACTURING A SHEET METAL PACK

Description

[0001] The present invention relates to a sheet metal core for the manufacture of a stator core or a rotor core. The invention further relates to a method for the manufacture of a sheet metal core, in particular a stator core or a rotor core for an electric machine, especially for an electric motor.

[0002] The operating principle of various electrical machines, and especially electric motors, has long been understood. Particularly in light of the increasing use of electric motors in individualized personal transportation, often referred to as electromobility, the electric motor continues to gain importance. Essential components of every electric motor are a stator and a rotor, with the stator being a stationary part of the motor and the rotor being a moving part.

[0003] One challenge in the provision of electric motors is to increase the efficiency of the electric motor, for example the power provided per volume and / or the efficiency, within an economically reasonable framework.

[0004] One concept for providing efficient electric motors is the production of stators and / or rotors, or parts thereof, as a so-called stator core or rotor core. These components are assembled from individual laminations, also known as laminated cores or lamellar cores. A lamination is a shaped part cut from electrical steel sheet or strip, for example, by stamping. The lamellar cores consist of numerous thin laminations stacked together and electrically insulated from each other, either partially or preferably completely. For such purposes, the use of electrical insulating varnishes, classified into insulation classes, is known in practice.

[0005] The production of such a laminated core always includes the steps of manufacturing laminations and joining the laminations together. The joining is preferably carried out in such a way that the laminations are, after joining, sectionally, and preferably completely, electrically insulated from one another; that is to say, preferably, that two adjacent laminations have no galvanic connection to each other.

[0006] The individual lamellae can be manufactured, for example, by stamping. Joining the stamped lamellae to form a sheet metal stack can be accomplished using a variety of known methods, such as screwing, clamping, welding, or stamping and stacking. However, each of these manufacturing methods, familiar to those skilled in the art, has a detrimental effect on the electromagnetic properties of the finished sheet metal stack after joining due to the mechanical stress generated during the joining process.In particular, mechanical stresses, which are inevitably unavoidable to some extent in a connection produced according to the state of the art, can adversely affect the magnetic properties and the orientation of magnetic field lines within the laminated core, resulting, for example, directly in a detrimental impact on the efficiency of an electric motor manufactured from it. An electrical connection between two or more laminations, which occurs in some joining processes such as stamping or welding, leads to additional losses.

[0007] An elegant way to reduce the detrimental effects of mechanical stress on the lamellae while simultaneously achieving good insulation between them is to use adhesives as bonding agents. These adhesive systems also possess insulating properties similar to electrical insulating varnishes.

[0008] Steel sheets coated with adhesive are described, for example, in US 2018 / 265757 A1 and US 2007 / 231463 A1.

[0009] One method known to those skilled in the art is the use of so-called baking varnishes. The use of baking varnishes for bonding stamped electrical steel sheets is described, for example, in DE 38 29 068 C1. One method for using baking varnish involves coating a sheet, in particular a strip of sheet metal, followed by stamping out individual laminations from the sheet, positioning the individual laminations relative to each other, and subsequently heat-treating the resulting stack of sheets for a defined period and at a defined temperature. In many cases, the laminations are pressed against each other during the heat treatment, for example, by applying force to the end faces, preferably with a uniform surface force, in an axial direction of the stack of sheets, pointing into the interior of the stack.Typical reaction temperatures range from 150°C to 250°C, and typical reaction times for the baking lacquers are 30 to 150 minutes, followed by a cooling phase. The exact parameters, of course, depend on the specific baking lacquer used and the geometry of the component, as, for example, the core temperature within the component influences the baking lacquer process. This method generally allows for excellent electromagnetic properties in stator and / or rotor stacks. However, due to the time-consuming nature of the process, it is immediately apparent that the use of baking lacquers is not, or at least not optimally, suitable for continuous mass production.

[0010] Against the background of the described situation, the object of the invention is to create the conditions for the efficient production of laminated cores, in particular stator cores or rotor cores, in a mechanized production environment.

[0011] In addition, given the desire for further increased efficiency, the invention also aims to provide electromagnetic components and electrical machines with improved conversion of electromagnetic energy into mechanical energy.

[0012] The task is solved using a sheet metal for the production of a stator stack or a rotor stack.

[0013] The term "sheet metal" generally refers to a rolled product made of a metallic material and can, in addition to thin or heavy sheet metal, also specifically refer to metal strip, metal strip or sheet metal made of a soft magnetic material, steel strip, or electrical steel strip. Other manufacturing processes for sheet metal can be used optionally.

[0014] The sheet metal is coated with a thermally activated adhesive. The adhesive contains: 60 parts by weight of an epoxy resin based on its solid resin form, 0.5 to 15 parts by weight of a latent hardener, 1 to 15 parts by weight of a latent accelerator, wherein the latent accelerator contains a urea derivative and the urea derivative is 4,4'-methylene-bis-(phenyldimethylurea).

[0015] Preferably, the adhesive contains 1 to 10 parts by weight of the latent hardener, particularly preferably 2 to 5 parts by weight of the latent hardener.

[0016] The term latent hardener refers to a substance that serves to harden the epoxy resin, but which must be activated for hardening to occur, particularly through the supply of chemical and / or thermal energy. The latent hardener is added to the adhesive, for example, as a solid in powder form.

[0017] The term latent accelerator refers to a substance that accelerates the curing of the epoxy resin by the latent hardener. The attribute "latent" in the context of the accelerator also indicates that it, too, must first be activated by chemical and / or thermal energy to fulfill its function. The latent accelerator is added to the adhesive, for example, as a solid in powder form.

[0018] The composition described above refers to the mixture of the components present as solids in the specified parts by weight to form an adhesive mixture which, in dispersion and / or solution with a suitable liquid, becomes the adhesive capable of forming an adhesive coating. In its usable state, i.e., in a form suitable for coating, the adhesive with the specified components preferably exists as a dispersion of the composition described above in a dispersion medium, particularly an aqueous dispersion.

[0019] By providing a sheet with an adhesive coating made of a thermally activated adhesive, the coated sheet serves as a precursor for flexibly adaptable manufacturing processes for laminated cores, particularly stator cores or rotor cores. Because the adhesive must first be thermally activated, the bonding action can be performed at a desired time or process step after the laminations have been removed from the sheet, for example, by punching. Within a short period after activation, the laminations must be brought together (optionally preferably under partial or full-surface pressure in the press and / or in a subsequent compaction process) so that they bond together during the chemical curing reaction.Only in this way can flawless, non-delaminated and geometrically accurate, mechanically stable packages be produced.

[0020] With the adhesive composition according to the invention, the sheet metal has a surface with a short activation time of, for example, 0.5 to 1 second and a short curing time of only a few seconds. These properties are accompanied by comparatively high temperature resistance and comparatively high insulation and aging resistance.

[0021] The epoxy resin present in the adhesive used according to the invention comprises one or more epoxy resin components with more than one epoxy group, of which preferably at least one epoxy resin has a softening point greater than 50° Celsius.

[0022] Epoxy resins can be aliphatic, cycloaliphatic, or aromatic. Aliphatic epoxy resins contain components that bear both an aliphatic group and at least two epoxy resin groups.

[0023] Examples of aliphatic epoxy resins include butanediol diglycidyl ether, hexanediol diglycidyl ether, dimethyl pentane dioxide, butadiene dioxide, and diethylene glycol diglycidyl ether.

[0024] Cycloaliphatic epoxy resins are, for example, 3-cyclohexenylmethyl-3-cyclohexylcarboxylate diepoxide, 3,4-epoxycyclohexylalkyl-3',4'-epoxycyclohexanecarboxylate, 3,4-epoxy-6-methylcyclohexylmethyl-3',4'-epoxy-o-methylcyclohexanecarboxylate, vinylcyclohexane dioxide, Bis(3,4-epoxycyclohexylmethyl)adipate, dicyclopentadiene dioxide, 1,2-epoxy-6-(2,3-epoxypropoxy)hexahydro-4,7-methanoindane.

[0025] Aromatic epoxy resins include, for example, bisphenol-A epoxy resins, bisphenol-F epoxy resins, phenol-novolac epoxy resins, cresol-novolac epoxy resins, biphenyl epoxy resins, biphenol epoxy resins, 4,4'-biphenyl epoxy resins, divinylbenzene dioxide, 2-glycidylphenyl glycidyl ether, and tetraglycidyl methylenedianiline.

[0026] In a preferred embodiment of the present invention, the epoxy resin is bisphenol A epoxy resin.

[0027] A latent hardener is a substance or a mixture of substances that preferably undergo hardening reactions with the epoxy resins of the adhesive at temperatures in the range of 80° Celsius to 200° Celsius.

[0028] The hardener may contain dicyandiamides, aziridine derivatives, triazine derivatives, imidazolines, imidazoles, o-tolyl biguanide, cyclic amidines, organic hexafluoroantimonate or hexafluorophosphate compounds, or BF3 amine complexes. These compounds may be used individually or in combination.

[0029] Beispiele sind 2-Methylimidazol, 2-Undecylimidazol, 2-Heptadecylimidazol, 1,2-Dimethylimidazol, 2-Ethyl-4-methylimidazol, 2-Phenylimidazol, 2-Phenyl-4-metylimidazol, 1-Benzyl-2-metylimidazol, 1-Benzyl-2-phenylimidazol, 1-Cyanoethyl-2-metylimidazol, 1-Cyanoethyl-2-undecylimidazol, 1-Cyanoethyl-2-ethyl-4-metylimidazol, 1-Cyanoethyl-2-phenylimidazol, 1-Cyanoethyl-2-undecylimidazoliumtrimellitat, 1-Cyanoethyl-2-phenylimidazolium-trimellitat, 2,4-Diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazin, 2,4-Diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazin, 2,4-Diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-2,4-diamino-6-[2"methylimidazolyl-(1')]-ethyl-s-triazin, 2-Phenylimidazol, 2-Phenyl-4,5-dihydroxymetylimidazol, 2-Phenyl-4-methyl-5-hydroxymethylimidazol, 2,3-Dihydro-1H-pyrrolo[1,2-a]benzimidazol, (1-Dodecyl-2-methyl-3-benzyl)imidazoliumchlorid, 2-Methylimidazolin, 2-Phenylimidazolin, 2,4-Diamino-6-vinyl-1,3,5-triazin, 2,4-Diamino-6-vinyl-1,3,5-triazin Isocyansäure-Addukt, 2,4-Diamino-6-methacryloyloxyethyl-1,3,5-triazine, 2,4-diamino-6-methacryloyloxyethyl-1,3,5-triazine isocyanic acid adduct, 1,3,5-triazine, 2,4-diamino-6-methyl-1,3,5-triazine, 2,4-diamino-6-nonyl-1,3,5-triazine, 2,4-diamino-6-phenyl-1,3,5-triazine, 2,4-dimethoxy-6-methyl-1,3,5-triazine, 2,4-dimethoxy-6-phenyl-1,3,5-triazine, 2-amino-4,6-dimethyl-1,3,5-triazine, 2-amino-4-dimethylamino-6-methyl-1,3,5-triazine, 2-Amino-4-ethoxy-6-methyl-1,3,5-triazine, 2-amino-4-ethyl-6-methoxy-1,3,5-triazine, 2-amino-4-methoxy-6-methyl-1,3,5-triazine, 2-amino-4-methyl-6-phenyl-1,3,5-triazine, 2-Chloro-4,6-dimethoxy-1,3,5-triazine, 2-ethylamino-4-methoxy-6-methyl-1,3,5-triazine, 1-o-tolylbiguanide.,

[0030] According to the invention, the accelerator contains a urea derivative, wherein the urea derivative is 4,4'-methylene-bis-(phenyldimethylurea). According to one concept, the accelerator contains an imidazole. The adhesive composition according to the invention may also contain further components.

[0031] In a preferred embodiment of the present invention, the hardener contains a dicyandiamide, an imidazole, a BF3 amine complex or a combination thereof.

[0032] In one embodiment, the adhesive can contain 1 to 10 parts by weight of a latent accelerator, preferably 1 to 5 parts by weight of a latent accelerator, particularly preferably 2 to 5 parts by weight of a latent accelerator, and most preferably 2 to 4 parts by weight of a latent accelerator.

[0033] In another preferred embodiment, the adhesive further comprises 0.2 to 8 parts by weight, preferably 0.2 to 4 parts by weight, of absorption additives. The absorption additives, which may be provided according to this further idea, are selected from the group of carbon blacks and / or from the group of water-soluble dyes.

[0034] The term absorption additive refers to a substance that absorbs thermal radiation. A thermal radiation-absorbing substance offers the particular advantage of enabling more efficient use of a process in which the thermal activation of the adhesive is carried out by means of electromagnetic radiation, especially by irradiation with light in the IR wavelength range, preferably in the NIR wavelength range.

[0035] Preferably, the adhesive contains one or more insulating additives known to those skilled in the art, the term "insulating additives" referring to additives specifically provided to increase the electrical resistance of the adhesive. The insulating additives may be present in the adhesive in amounts of 1 to 10 parts by weight, preferably 1 to 5 parts by weight.

[0036] The latent accelerator contained in the adhesive preferably consists of at least 50 wt.%, more preferably at least 90 wt.%, and more preferably entirely, of urea derivative.

[0037] According to the invention, the urea derivative is a 4,4'-methylene-bis-(phenyldimethylurea).

[0038] The latent accelerator contained in the adhesive preferably consists of at least 50 wt.%, more preferably at least 90 wt.%, more preferably at least 98 wt.%, and especially preferably entirely, of 4,4'-methylene-bis-(phenyldimethylurea).

[0039] According to one concept, a urea derivative is used in which at least one, preferably two, and particularly preferably three hydrogen atoms are replaced, independently of one another, by alkyl groups and / or phenyl groups, which may themselves be substituted. Preferably, the alkyl groups are methyl, ethyl, propyl, or butyl, more preferably methyl; the phenyl group is phenyl or a deeply substituted alkyl group, preferably in position 4, also more preferably than one of the aforementioned alkyl groups. In a further alternative, a difunctional urea derivative is defined as a derivative described above, which has two functional groups. Functional groups are groups of atoms that significantly determine the material properties and, in particular, the reactivity of the compound; in particular, the functional groups undergo reactions.Furthermore, the urea derivative used according to the invention is halogen-free. Alternatively, the urea derivative used according to the invention comprises two urea derivatives as functional groups. Advantageously, this allows epoxy resins to be cured without the presence of dicyanamides as crosslinking agents.

[0040] According to one theory, an asymmetrically substituted urea is also or exclusively used as a urea derivative.

[0041] According to one theory, a mixture of two, three or more of the aforementioned is used.

[0042] A substance can also be a urea derivative. be provided with R: hydrogen or a group according to with n = 0 or 1, preferably 1, X = O or S, preferably O, R1, R2 and R3: each hydrogen, a halogen, nitro group, a substituted or unsubstituted alkyl group, alkoxyl group, aryl group or aryloxyl group, R4: alkyl group, alkenyl group, cycloalkyl group, cycloalkenyl group, aralkyl group optionally substituted by a halogen, hydroxyl or cyano, preferably methyl, ethyl, propyl, butyl, particularly preferably methyl, R5: as R4 or alkoxyl group, R5 optionally forming a heterocyclic ring with R4, or an N,N-dimethyl-N'-(3,4-dichlorophenyl)urea or an N,N-dimethyl-N'-(3-chloro-4-methylphenyl)urea or an N,N-dimethyl-N'-(3-chloro-4-methoxyphenyl)urea or a N,N-Dimethyl-N'(3-chloro-4-ethylphenyl)urea or an N,N-Dimethyl-N'-(4-methyl-3-nitrophenyl)urea or an N-(N'-3,4-dichlorophenylcarbamoyl)morpholine or an N,N-dimethyl-N'(3-chloro-4-methylphenyl)thio-urea;According to the invention, the urea derivative is 4,4'-methylene-bis-(phenyldimethylurea); ; or a mixture of two, three, or more of the aforementioned. Such a mixture preferably contains at least 10%, 25%, more preferably 50%, 60%, 70%, 80%, or 90% 4,4'-methylene-bis-(phenyldimethylurea). The advantage of these urea derivatives arises from the GB 1293142 A The inventors have found that such derivatives are excellent for the production of electromagnetic components.

[0043] The urea derivative can also be a mixture of several of the aforementioned urea derivatives.

[0044] The mean particle size (arithmetic mean) of the urea derivative is preferably between 1 micrometer and 30 micrometers.

[0045] The adhesive coating can be applied to one or both sides of the sheet metal. If an adhesive coating is applied to both sides, the coating thickness can be the same, but different thicknesses are also possible.

[0046] The adhesive can be applied to the sheet metal using known methods, in particular by coil coating (roll to roll).

[0047] The preferred thickness of the adhesive coating, meaning the thickness of the coating on one side for single-sided adhesives and the total thickness of the adhesive coatings on both sides for double-sided adhesives, is between 1 and 20 micrometers, preferably between 2 and 10 micrometers. A total thickness between 4 and 8 micrometers is particularly preferred.

[0048] Applying adhesive to one side of the sheet metal results in simpler manufacturing processes, while applying adhesive to both sides of the sheet metal offers the advantage that when individual lamellae made from the sheet metal are positioned on top of each other, adhesive surface is positioned against adhesive surface, resulting in improved adhesion and thus higher mechanical stability of the electromagnetic component, as demonstrated in experiments and shown below.

[0049] Particularly preferred is the first partial coating of the first sheet surface and the second partial coating of the second sheet surface, with a second thickness, adapted to each other such that the first thickness is at least 1.5 times, preferably 2 times, the second thickness. In such a configuration, the first thickness is responsible for excellent insulation, so that the risk of adhesive gaps is virtually negligible, while the thinner of the two, namely the second partial coating applied with the second thickness, essentially serves to create the excellent adhesion.

[0050] A double-sided coating with a total thickness of both coatings between 4 and 6 micrometers is particularly preferred. Such a small coating thickness is possible with the adhesives used according to the invention or according to further developments of the invention due to their high reactivity, as demonstrated by the manufactured examples. Known back-applied adhesives generally require greater coating thicknesses than 6 micrometers (e.g., back-applied adhesive on both sides, 5 µm per side). This has the advantage that laminated cores, in particular stators or rotors, can be produced from the sheets according to the invention or its further developments, which have a significantly higher iron fill factor than components manufactured using back-applied adhesive processes. The advantage is a somewhat higher efficiency of the electric machine incorporating the component. However, adhesive coatings with a total thickness between 1 and 20 micrometers, preferably 2 and 8 micrometers, can also be provided.

[0051] In another alternative, an insulating varnish layer is arranged between the sheet metal and the adhesive layer and / or only insulating varnish is arranged on the side opposite the adhesive layer.

[0052] Particularly preferably, the sheet is formed as non-grain-oriented electrical steel, also known as NO electrical steel, or is cut from such steel, wherein the non-grain-oriented electrical steel contains, in addition to Fe and unavoidable impurities, the following elements (all values ​​in wt.%): 0.1 to 3.50 Si, 0.01 to 1.60 Al, 0.07 to 0.65 Mn, optionally up to 0.25 P.

[0053] It is understood that the total of all alloy components and impurities adds up to 100 wt.%.

[0054] The following conditions are particularly preferred (all figures in wt.%): 2.3 to 3.40 Si, 0.3 to 1.1 Al, 0.07 to 0.250 Mn, optionally up to 0.030 P, balance Fe and unavoidable impurities.

[0055] It is understood that the total of all alloy components and impurities adds up to 100 wt.%.

[0056] Preferably, the non-grain-oriented electrical steel or non-grain-oriented sheet metal exhibits specific remagnetization losses at P1.0; 50 Hz in the range of 0.7 to 7 W / kg and at P1.5; 50 Hz in the range of 1.8 to 15 W / kg and / or a polarization at J2500 in the range of 1.45 T to 1.71 T and at J5000 in the range of 1.6 T to 1.8 T, determined in accordance with DIN EN 60404-2.

[0057] In a preferred embodiment, the non-grain-oriented electrical steel strip or non-grain-oriented sheet exhibits specific remagnetization losses at P1.0; 50 Hz in the range of 0.8 to 3.5 W / kg and at P1.5; 50 Hz in the range of 1.9 to 8.0 W / kg and / or a polarization at J2500 in the range of 1.47 to 1.71 T and at J5000 in the range of 1.58 to 1.80 T, determined in accordance with DIN EN 60404-2.

[0058] In a further preferred embodiment, the non-grain-oriented electrical steel strip or the non-grain-oriented sheet exhibits specific remagnetization losses at P1.0; 50 Hz in the range of 1.0 to 1.5 W / kg and at P1.5; 50 Hz in the range of 2.2 to 3.3 W / kg and / or a polarization at J2500 in the range of 1.47 to 1.57 T and at J5000 in the range of 1.58 to 1.65 T, determined in accordance with DIN EN 60404-2.

[0059] Preferably, the non-grain-oriented electrical steel strip or the non-grain-oriented sheet exhibits specific remagnetization losses at P1.0; 400 Hz in the range of 8 to 120 W / kg; at P1.5; 400 Hz from 18 to 360 W / kg; and / or a polarization at J2500 in the range of 1.45 T to 1.75 T and at J5000 in the range of 1.45 T to 1.85 T and at J10,000 in the range of 1.50 and 1.95 T determined in accordance with DIN EN 60404-2.

[0060] In a further preferred embodiment, the material exhibits specific remagnetization losses at P1.0; 400 Hz in the range of 10 to 25 W / kg; at P1.5; 400 Hz from 25 to 49 W / kg; and / or a polarization at J2500 in the range of 1.45 T to 1.75 T and at J5000 in the range of 1.45 T to 1.85 T and at J10000 in the range of 1.50 and 1.95 T determined in accordance with DIN EN 60404-2.

[0061] Preferably, the non-grain-oriented electrical steel strip or non-grain-oriented sheet has a longitudinal yield strength of 190 to 610 MPa under standard normal conditions, a maximum tensile strength of 310 to 740 MPa, a minimum elongation at break A80 of 6 to 48% measured in accordance with DIN EN ISO 6892-1, and a hardness Hv5 of 100-250.

[0062] In a particularly preferred embodiment, the material has a longitudinal yield strength at room temperature of 310 to 600 MPa and a maximum tensile strength of 400 to 640 MPa, as well as an elongation at break A80 of 7 to 32 % measured in accordance with DIN EN ISO 6892-1 and a hardness Hv5 of 130-250.

[0063] The material preferably exhibits anisotropy at P1,0; 400 Hz in the range of 5 to 17%.

[0064] Alternatively, a sheet metal made of a soft magnetic material with the following alloying elements can be provided: Fe, in addition to Fe and unavoidable impurities consisting of (all values ​​in wt.%): 0.1 to 4.0 Si, 0.01 to 2.60 Al, 0.07 to 3.0 Mn, optionally up to 0.5 P, optionally up to 0.015 B, optionally up to 0.2 Sb, optionally up to 0.01 Zn, optionally up to 5 Cr, optionally up to 5 Ni, optionally up to 0.25 V, optionally up to 0.5 Sn, optionally up to 0.01 As, optionally up to 0.3 Nb, optionally up to 0.5 W, optionally up to 0.85 Zr, optionally up to 0.2 Mo, optionally up to 1.0 Cu, optionally up to 0.5 Ti, optionally up to 0.5 C, optionally up to 0.01 Ce.

[0065] Suitable and preferred materials include sheet metal, in particular electrical steel, with a thickness between 0.05 and 2.5 mm, with thicknesses between 0.1 and 1.0 mm being preferred. Thicknesses between 0.15 and 0.4 mm are especially preferred.

[0066] Alternatively, the sheet metal can be a multi-layer composite (sandwich) consisting of a sheet layer, for example, one of the electrical tapes described above, and one or more further layers, for example, with an acoustically damping functional layer (e.g., Bondal E). Furthermore, the sheet metal can also be coated on one or both sides with an acoustically damping functional layer (e.g., Half-Bondal E), so that the described adhesive system bonds directly to the acoustically damping functional layer (e.g., chemically based acrylate). It is known from technical experience that epoxy resin systems exhibit good compatibility.

[0067] Alternatively, the sheet metal can have an acoustically damping functional layer on one side and an adhesive layer to be applied according to the invention on the opposite side of the sheet metal.

[0068] Tests have shown that the provision of a sheet according to the invention, or one of its further developments, enables the joining of sheet metal laminations with the highest adhesive reactivity in an outstanding manner, with the further advantage that suitable methods can be provided with which the production of sheet metal stacks is also possible in linear manufacturing processes at high rates of production per unit time. The aforementioned tests are given below as examples.

[0069] The sheet metal provided according to the invention makes it particularly advantageous to produce sheet metal stacks for an electric motor, because, to the knowledge of the developers, for the first time a starting material prepared for further processing has been provided that can be used with high economic efficiency both in inline processes, i.e., processes in continuous processing, and in offline processes, i.e., in a process oriented towards back-bonding.

[0070] In addition to this particularly advantageous combination of properties, it has surprisingly been found that the sheets provided according to the invention also exhibit long-term stability. This means, in particular, that especially in combination with the possibility of inline production of sheet metal stacks, the sheets provided according to the invention meet the basic requirements for integration into typical production processes in the automotive industry, since the long-term stability allows storage over a longer period, at least up to several weeks, and, moreover, due to the temperature stability, also enables processing in the sense of just-in-time delivery, which typically takes place even in the height of summer in non-temperature-controlled trucks and must be able to withstand temperatures of at least 40 degrees Celsius for an extended period.

[0071] Another advantage of the sheets provided according to the invention is that they are mechanically stable, meaning in particular that the adhesive remains dimensionally stable during pressing compared to previously used adhesives from the aforementioned baking varnish processes.

[0072] The adhesion is also temperature-stable, as the examples shown below demonstrate. In contrast to conventional back-applied lacquer systems, the so-called squeezing out of the adhesive system during pressing does not occur, or only to a very limited extent.

[0073] Through the targeted combination of sheet metal, in a further development of specially selected sheet metal for use in electromobility, and specifically chosen adhesive compositions, a previously unknown combination of properties is provided, namely the possibility of supplying sheet metal stacks and electromagnetic components on a large industrial scale, not least for the automotive industry. This provides the person skilled in the art with the implementation of the invention with a flexibility that was previously unknown.

[0074] Potential advantages arise, for example, in the electromagnetic, mechanical, and thermal design of machines, the possibility of selecting different sheet metal types, greater design freedom in the lamella design, and advantages regarding possible component tolerances and media and / or heat management. Further advantages result in component and machine manufacturing (for example, when handling compact and solid components) and machining. Additional advantages of electrical machines with one of the sheets according to the invention or one of its further developments include higher performance and efficiency, a smaller required installation space, improved geometric properties (for example, achievable by post-compression against a stop, particularly with constant surface pressure, with the advantage of improved dimensional accuracy of the electromagnetic component), and, depending on the design, acoustic advantages.

[0075] Another aspect of the invention relates to a method for manufacturing a laminated core for an electric machine, preferably for an electric motor. The laminated core is preferably either a stator core or a rotor core, that is, it is a stator or part of a stator, or a rotor or part of a rotor.

[0076] The procedure consists of the following steps: A) In a first step, a sheet metal sheet according to the invention or one of its further developments is provided. The sheet metal sheet can, for example, be an electrical steel strip or a circuit board cut from a strip of sheet metal. B) The sheet metal sheet is transported into an inline system. The inline system has at least the following stations: a punching tool, means for emitting infrared radiation, and an ejector die.

[0077] The term inline system refers to the fact that a number of processing stations, namely at least those mentioned above, are arranged in a predetermined sequence, and sheet metal, for example electrical steel, fed into the inline system is processed automatically and sequentially at the predetermined stations.

[0078] The punching tool is a tool used to punch out one, or preferably more than one (e.g., four), lamellae from the sheet metal. The punching of the lamellae with the punching tool takes place in step C) and preferably such that a number of connecting webs, for example, three connecting webs, remain between each punched-out lamella and the sheet metal originally transported into the inline system, so that the punched-out lamella is still an integral part of the sheet metal. This serves to enable further transport of the lamellae together with the sheet metal, in particular the sheet metal strip, through the inline system.

[0079] In the above context, the term "lamella" refers to a shaped part obtained by cutting it out of the sheet metal, in particular a shaped part obtained by punching.

[0080] In a preferred alternative, a laminated core, preferably the rotor core, is produced by a conventional stacking process, for example, stamping stacking, and another laminated core, preferably the stator core for the same electric machine as the conventionally produced stator core, is produced using the inventive method described above. This can be done, for example, in a combined process or sequentially. Preferably, stress-relief annealing or recrystallization annealing, and optionally a coating step, an activation step, and / or an inspection step, can be performed before stacking. In this context, activation means the activation of the adhesive used.

[0081] The means for emitting infrared radiation can in particular be designed as NIR emitters, i.e. as light sources designed to emit electromagnetic radiation in the NIR wavelength spectrum, i.e. with wavelengths between 780 nm and 3 µm.

[0082] In a preferred process, the molded parts are illuminated in a near-infrared (NIR) wavelength range, preferably using a wavelength between 0.8 and 1.2 micrometers. A maximum luminous intensity is particularly preferably achieved with NIR radiation at a wavelength between 0.85 and 0.9 micrometers. Activation (irradiation) occurs only in the area of ​​the coated surface that is intended for bonding (is active). The remaining area is shielded with an aperture to activate only the required area. Individual sheet metal stacks are separated once the required height is reached by over-activating individual lamellae, rendering them unreactive and thus preventing bonding.

[0083] Furthermore, as mentioned, the inline system includes an ejection punch. This ejection punch is a punch which, by applying a force perpendicular to the sheet surface, sequentially separates the lamellae, which are still connected to the sheet metal, in particular sheet metal strip, by one or more webs, from the sheet metal by cutting the web(s) and preferably, in the same process step, conveys the lamella into a receiving device arranged below the sheet metal, in which the lamellae are collected.

[0084] Within the inline system, a shaped part, in particular a shaped part designed as a stator lamella or as a rotor lamella, is punched from the sheet metal provided in step A) using the punching tool, wherein preferably one web or several, in particular three, webs have a connection with the sheet metal sufficient for further transport of the shaped part.

[0085] D) The adhesive coating of the molded part formed in step C) is then illuminated with infrared radiation using the infrared radiation emitter to activate the adhesive coating. In other words, a temperature sufficient for activation is generated in the sheet metal and, in particular, in the adhesive, for example, by illumination for a period of between 0.5 and 1 second at an emission power between 5 and 10 kilowatts, which is sufficient for an activation temperature of between 100 degrees Celsius and 250 degrees Celsius in the adhesive.

[0086] E) The molded part is extruded using the extrusion die and, preferably in the same movement, inserted into a receiving device containing a positioning area. The positioning area serves to align the molded part as it falls into the positioning area with respect to the molded parts already present there, so that a stack of aligned molded parts with activated adhesive is obtained.

[0087] The positioning area can, for example, be a cylindrical tube located below the conveying level of the molded part, such that after extrusion, the molded part falls by gravity to an existing stack of molded parts. The alignment of the molded part is achieved by the positioning area, for example, designed as a cylindrical hollow tube with a cross-sectional area that essentially corresponds to the cross-section of the molded part and is aligned with it in the intended position.

[0088] Steps C) to E) are repeated as required until a desired number of molded parts are in the positioning area and form a stack of molded parts. Preferably, the stamping tool and ejector are part of the same press, which offers the advantage of high synchronization of the stamping and ejection processes.

[0089] Particularly preferably, the means for emitting the infrared radiation are arranged between the punching tool and the ejection die and comprise at least one upper light source directed towards the first sheet surface in a punching direction, at least one lower light source located beyond the side of the sheet on which the punching tool is located and directed against a punching direction, or comprise both at least one upper and at least one lower light source. The alignment of the light source with the lamella surface need not be perpendicular, but can also be at another angle.

[0090] Particularly in a case where an upper and a lower light source are present, activation of adhesive on both a first and on the opposite second sheet side is possible in a particularly suitable manner with the advantageous result that excellent adhesion of the sheets to each other can be expected.

[0091] According to a particularly preferred embodiment of the method, after positioning the last forming part with the desired number of forming parts, the resulting sheet metal stack is compacted. This compaction step is carried out by applying a uniform surface pressure to the end face of the sheet metal stack in an axial direction. This compression ensures a particularly strong bond between the individual forming parts and thus contributes to the durability of the sheet metal stack. The subsequent compaction step preferably takes place outside the press in a downstream compaction station. Alternatively, the compaction step can also be achieved by applying, preferably partial or full-surface, pressure from the ejector punch within the stamping die.

[0092] Preferably, steps C) to E) are performed at a stroke rate of at least 80 per minute, preferably at least 100 per minute, particularly preferably at least 120 per minute and / or up to 1000 per minute, preferably up to 300 per minute, particularly preferably up to 220 per minute. This means that a number of molded parts corresponding to the stroke rate are inserted into the positioning area within one minute.

[0093] An alternative process involves, after providing one or more sheets, preferably electrical steel strip, in step B) a number of shaped parts are punched from the sheet provided in step A) using the punching tool. Following this, the shaped parts are positioned and / or angularly aligned on top of each other and then pressed in a separate station, which may be, for example, an oven, and heated to a predetermined temperature or temperatures within a predetermined temperature range for a predetermined period. This procedure is quite similar to the procedure known from the baking lacquer process described at the beginning, but differs in the starting material used, which is specifically one of the materials mentioned at the outset.Only with the materials mentioned at the beginning is it possible to achieve, on the one hand, a long storage period and, on the other hand, to provide sheet metal packages with a certain number of completed sheet metal packages per time, so that, as a result, good use of the process in mass production can be expected.

[0094] Preferably, the specified period is between 10 and 60 minutes, and particularly preferably between 10 and 40 minutes. With the sheets used according to the invention, as mentioned above, this period is entirely sufficient to obtain finished sheet stacks. The specified temperature is particularly preferably between 100 and 200 degrees Celsius, and especially between 100 and 150 degrees Celsius. For example, in laboratory tests, samples were successfully produced with a specified temperature of 120 degrees Celsius and a specified period of 30 minutes. This example also demonstrates one of the advantages of the process according to the invention compared to a conventional baking varnish process, in which both higher temperatures and longer periods are common, for example, annealing at 190 degrees Celsius for a period of 60 minutes.The reason is that it has been possible to develop a sheet metal adhesive with a significantly higher reactivity compared to previously used adhesives. The specific geometry of the component, as the core temperature within the component, for example, influences the bonding process.

[0095] It may be necessary to clean the edges of a sheet metal stack after the manufacturing process is complete, in order to remove any adhesive residue on the stack edge or side. This cleaning can be done chemically and / or mechanically.

[0096] To increase the strength of the adhesive layer, it may be possible to arrange inorganic and / or organic fibers in the adhesive coating. Examples

[0097] Examples of a sheet metal according to the invention and its advantageous behavior for the methods according to the invention are derived from experiments carried out.

[0098] The following samples were produced: circuit boards made from electrical tape M800-50A (according to EN 10027-1) with the material identification number 1.0816 (according to EN 10027-2), thickness 0.5 mm, length x width: 200 x 150 mm.

[0099] Samples 0, 1, 2 and 3 were produced. Samples 0, 1 and 2 are comparison samples; they are coated with an adhesive not according to the invention.

[0100] Probe3 is a probe according to the invention.

[0101] The manufactured samples are circuit boards of the above-mentioned type, coated with adhesive using an application roller according to the following parameters: Sample designation Parts by weight of epoxy resin (present as solid resin) Weight parts Hardener Weight-parts accelerator Selected accelerator Sample 0 60 3,5 4,5 Conventional accelerator (DYHARD URAcc57, brand name) Problem 60 3,5 3,0 Conventional accelerator (DYHARD URAcc13, brand name) Sample 2 60 3,5 3,0 Conventional accelerator (DYHARD URAcc13, brand name) Sample 3 60 3,5 3,0 4,4'-Methylene-bis-(phenyldimethylurea) Layer thicknesses Sample 0: 1st surface: 6 µm, 2nd surface: 0 µm, Sample 1: 1st surface: 6 µm, 2nd surface: 0 µm, Sample 2: 1st surface: 4 µm, 2nd surface: 2 µm, Sample 3: 1st surface: 4 µm, 2nd surface: 2 µm. Several specimens of each sample type were produced. To test long-term stability, 18 sandwich structures of two identical samples each were produced.

[0102] Two identical samples were bonded using a plate press with a 200 mm x 200 mm plate area and a surface pressure of 3 N / mm². The adhesive was activated in an oven by heating to 120 °C and holding at 120 °C for 30 minutes. Subsequently, eight samples were placed in an oven and stored at 40 °C. After each week, one sample was taken and a shear test (in accordance with DIN EN 1465) was performed. Additionally, a shear test was performed weekly on samples stored at room temperature. The test results are presented in Figs. 1a and 1b depicted.

[0103] The results show that at room temperature, the composition used according to the invention exhibits better shear values ​​than the reference samples Sample 0, Sample 1, and Sample 2. Sample 0, tested after six weeks, showed a significantly reduced shear value; after eight weeks, Sample 0 had a shear value of 0.

[0104] Storage at 40 degrees Celsius resulted in a shear value of 0 for the reference sample (Sample 0) after a maximum of one week; therefore, the sample exhibits no storage stability at 40 degrees Celsius. Samples 1 and 2 showed a virtually unchanged, good shear value of over 7.0 N / mm² after two weeks, but began to degrade noticeably after three weeks of storage.

[0105] In all cases, the shear value of sample 2 with a double-sided coated surface is higher than the shear value of sample 1 with a single-sided coated surface.

[0106] In particular, it can be seen that sample 3 exhibits the best storage stability, with a shear value that remains almost unchanged after four weeks of storage at 40 degrees Celsius. A circuit board sandwich was the only sample that still showed a consistently good shear value even after four weeks of storage at 40 degrees Celsius. At the time of registration, the tests were still ongoing.

[0107] Tests were also carried out on the finished sandwiches; they were heated to test temperatures and then, after briefly holding them under heat, also subjected to a shear test. Sample number Sample 2 Sample 3 Shear values ​​[N / mm²<] Each is the average of three tests. [N / mm²<] Standard deviation [N / mm²<] Standard deviation RT 5,55 0,88 6,01 0,26 50°C 5,08 1,32 5,85 0,11 100°C 5,38 0,27 5,59 0,12 150°C 4,89 0,42 5,22 0,08 200°C 4,66 0,46 4,96 0,04

[0108] The results show that both sample 2 and sample 3 can withstand high temperatures of up to 200 °C for a certain period without losing their mechanical stability. In particular, the shear values ​​of sample 3 are significantly higher than those of the comparison sample 2.

[0109] Sample 0 was subjected to temperature testing as a reference, and it was shown that after heating to 150 °C, a shear value of approximately 0.90 N / mm² was obtained. Based on sample 3, it was thus demonstrated that the sheets according to the invention are suitable for producing more temperature-stable sheet stacks compared to previously known sheets.

[0110] An example of a first implementation of the method for manufacturing a laminated core for an electric motor is shown in Fig. 2aThe process is illustrated. A sheet metal strip already coated with a plastic, specifically non-grain-oriented electrical steel 1, is provided. This is transported into an inline system. In a first station, several ejection dies 4 extrude shaped parts 2, which are designed as rotor or stator lamellae. In a subsequent station, the shaped part is illuminated by a device designed as a NIR emitter for emitting infrared radiation 5. The resulting heat activates the adhesive coating of the shaped part. The shaped part is then ejected with the ejection die 6 and collected in a positioning area into a stack 3, aligned in position and / or angle. Finally, in a compaction station, the stack is compacted with a compaction die 7 until the adhesive has cured and the finished sheet metal stack can be removed.

[0111] Fig. 2bA manufacturing process can be derived which is similar to the well-known baking lacquer process. The process of Fig. 2b differs from the procedure of Fig. 2a In particular, the pressing of the molded parts 2 and the formation of the stack 3 take place before the activation of the adhesive coating. The adhesive is only activated last in an oven 8, for example at a temperature between 100 and 200 degrees Celsius, while the sample is simultaneously compacted by means of a plunger 7.

Claims

1. Metal sheet for producing a stator assembly or a rotor assembly, wherein the sheet is coated with an adhesive coating of a thermally activated adhesive, wherein the adhesive contains: 60 parts by weight of an epoxy resin in solid resin form, 0.5 to 15 parts by weight of a latent curing agent, 1 to 15 parts by weight of a latent accelerator, wherein the latent accelerator contains a urea derivative, characterized in that the urea derivative is 4,4'methylene bis-(phenyldimethyl urea).

2. Metal sheet according to Claim 1, characterized in that the adhesive contains: 1 to 10 parts by weight of a latent curing agent, preferably 2 to 5 parts by weight of a latent curing agent.

3. Metal sheet according to one of the preceding claims, characterized in that the epoxy resin bisphenol A epoxy resin.

4. Metal sheet according to any one of the preceding claims, characterized in that the latent curing agent contains a dicyandiamide, an imidazole, a BF3 amine complex or a combination thereof.

5. Metal sheet according to any one of the preceding claims, characterized in that the adhesive contains: 1 to 10 parts by weight of a latent accelerator, preferably 1 to 5 parts by weight of a latent accelerator, particularly preferably 2 to 5 parts by weight of a latent accelerator.

6. Metal sheet according to any one of the preceding claims, characterized in that the adhesive further contains 0.2 to 8 parts by weight absorption additives, selected from the group of lamp blacks and / or from the group of water-soluble dyes.

7. Metal sheet according to any one of the preceding claims, characterized in that the particles of the urea derivative have an average particle size between 1 µm and 30 µm.

8. Metal sheet according to any one of the preceding claims, characterized in that the adhesive coating is applied to both sides of the sheet and is between 1 µm and 20 µm thick in total.

9. Metal sheet according to any one of the preceding claims, characterized in that the adhesive coating is between 2 µm and 8 µm thick in total, preferably between 4 µm and 6 µm thick in total.

10. Metal sheet according to any one of the preceding claims, characterized in that the adhesive coating consists of a first partial coating of the first sheet surface having a first thickness and a second partial coating of the second sheet surface having a second thickness, wherein the first thickness is at least 1.5 times as thick, preferably twice as thick as the second thickness.

11. Metal sheet according to any one of the preceding claims, characterized in that an insulating varnish layer is arranged between sheet and adhesive layer, and / or only insulating varnish is arranged on the side opposite the adhesive layer.

12. Metal sheet according to any one of the preceding claims, characterized in that the sheet is an electrical steel strip, in particular a non-grain oriented electrical steel strip, or has been separated from a non-grain oriented electrical steel strip.

13. Metal sheet according to Claim 12, consisting of, besides Fe and unavoidable impurities: 0.1 to 3.50 Si, 0.01 to 1.60 Al, 0.07 to 0.65 Mn, optionally up to 0.25 P, wherein all values represent percent by weight; preferably consisting of, besides Fe and unavoidable impurities: 2.3 to 3.40 Si, 0.3 to 1.1 Al, 0.07 to 0.250 Mn, optionally up to 0.030 P, wherein all values represent percent by weight.

14. Metal sheet according to any one of the preceding claims, characterized in that the sheet is a soft magnetic, metallic material, for example consisting of, besides Fe and unavoidable impurities: 0.1 to 4.0 Si, 0.01 to 2.60 Al, 0.07 to 3.0 Mn, optionally up to 0.5 P, optionally up to 0.015 B, optionally up to 0.2 Sb, optionally up to 0.01 Zn, optionally up to 5 Cr, optionally up to 5 Ni, optionally up to 0.25 V, optionally up to 0.5 Sn, optionally up to 0.01 As, optionally up to 0.3 Nb, optionally up to 0.5 W, optionally up to 0.85 Zr, optionally up to 0.2 Mo, optionally up to 1.0 Cu, optionally up to 0.5 Ti, optionally up to 0.5 C, optionally up to 0.01 Ce, wherein all values represent percent by weight.

15. Metal sheet according to any one of Claims 12 to 14, having a thickness between 0.05 mm and 2.5 mm, preferably between 0.15 mm and 0.4 mm plus adhesive coating.

16. Metal sheet according to any one of Claims 13 to 15, wherein the sheet is a sandwich or a sheet coated on one or both sides with an acoustically damping functional layer.

17. Method for producing a laminated core for an electric machine, wherein the laminated core is either a stator assembly or a rotor assembly, including the following steps: A) providing a metal sheet furnished with an adhesive coating or a plurality of metal sheets furnished with an adhesive coating according to any one of Claims 1 to 16, B) transporting the sheet into an inline system, including: a stamping tool, means for emitting infrared radiation and an ejector punch, C) stamping a moulded part designed as a stator lamella or rotor lamella out of the sheet metal provided in step A with the stamping tool, D) illuminating the adhesive coating of the moulded part formed in step C with infrared radiation via the means for emitting infrared radiation to activate the adhesive coating of the moulded part, E) extruding the moulded part with the ejector punch, positioning the moulded part in positionally aligned and / or angularly aligned manner in a positioning region, F) repeating steps C) to E) until a desired number of moulded parts has been reached in the positioning region.

18. Method according to Claim 17, characterized in that the production of the laminated core takes place in an inline process, wherein the stamping tool and the ejector punch are components of the same press.

19. Method according to Claim 17 or according to Claim 18, characterized in that the means for emitting infrared radiation are arranged between the stamping tool and the ejector punch, and include: - at least one upper lamp, which is directed towards a first moulded part surface in a stamping direction, or - at least one lower lamp, which is directed towards a second moulded part surface present beyond the stamping tool in the opposite direction to the stamping direction, or - both at least one upper and at least one lower lamp.

20. Method according to any one of Claims 17 to 19, characterized in that, in a compression step downstream of step F, after the last moulded part of the desired number of moulded parts has been positioned, the laminated core obtained is compressed with a contact pressure applied evenly over the frontal face.

21. Method according to any one of Claims 17 to 20, characterized in that steps C to E are performed with a stroke rate of at least 80 / min, preferably between 120 / min and 300 / min.

22. Method for producing a laminated core for an electric machine, wherein the laminated core is preferably either a stator assembly or a rotor assembly, including the following steps: A) providing a metal sheet furnished with an adhesive coating or a plurality of metal sheets furnished with an adhesive coating according to any one of Claims 1 to 16, B) stamping out a number of lamellae with the stamping tool, in particular as moulded parts in the form of stator lamellae or rotor lamellae, from the metal sheet provided in step A, C) positioning the moulded parts one on top of the other in positionally aligned and / or angularly aligned manner, D) pressing the superposed moulded parts, E) heating the superposed moulded parts for a predetermined period of time at a predetermined temperature, F) optionally in a compressing step downstream of step E, after positioning the last moulded part of the desired number of moulded parts, compressing the component obtained with a contact pressure applied evenly over the frontal face in a direction perpendicular to the surface of the moulded part.

23. Method according to Claim 22, wherein the predetermined period of time is between 10 min and 60 min, preferably between 10 and 40 min.

24. Method according to Claim 22 or according to Claim 23, wherein the predetermined temperature is between 100°C and 200°C, preferably between 100°C and 150°C.

25. Laminated core for an electric machine, produced with a method according to any one of Claims 17 to 24.

26. Laminated core according to Claim 25, embodied as a stator or a rotor.

27. Electric machine, in particular an electric motor, including a stator and / or a rotor according to Claim 26.

28. Electric machine according to Claim 27, embodied as an electric motor for a motor car, a lorry, a motorised bicycle, a neighbourhood electric vehicle, an aircraft or a drone.

29. Electric machine having laminated cores according to Claim 25.