EP3956412A1 - Core lamination stack and method for the adhesive connecting of core laminations - Google Patents

Abstract

The invention relates to a core lamination stack, comprising a plurality of laminations arranged one above the other and connected to one another by adhesive, wherein the ratio of the mass of the adhesive between the lamination pair held together by the lowest adhesive mass to the mass of the adhesive between the lamination pair held together by the greatest adhesive mass is :5 1 : 1.5, preferably :5 1 : 2, more preferably ≤ 1 : 2.5 and particularly preferably :5 1 : 3. The invention also relates to a method for producing a core lamination stack comprising the following steps: a) providing core laminations, b) providing adhesive in liquid form, c) forming a stack of core laminations such that the surfaces to be glued together are opposite one another, preferably with maximum overlap, d) wetting the stack with adhesive from step b) such that the adhesive is drawn by means of capillary forces into the gaps between each of the laminations to be glued, and e) curing the adhesive between the laminations to be glued.

Description

Stacks of sheet metal lamellas and processes for the technical bonding of

Sheet metal lamellas

The invention relates to a stack of sheet metal lamellas, comprising a plurality of lamellas arranged one above the other, which are connected to one another by adhesive, the mass of the adhesive between the pair of lamellae, which is held together by the smallest adhesive mass, to the mass of the adhesive between the lamella pair, which held together by the largest mass of adhesive is small. The invention also relates to a method for producing a stack of sheet metal lamellas, in particular one with the adhesive situation described.

In order to produce highly efficient electrical machines, it is necessary to realize sheet metal stacks from individual lamellas with thin sheet metal in order to suppress eddy current losses in the stacks as efficiently as possible.

Punch-stacking is a common method of stacking, in which a mechanical interlocking between the individual lamellae leads to the lamellae being connected to form a package. The deformation of the sheets, however, has a negative impact on the magnetic properties of the sheet and thus of the laminated core. In addition to punch packaging, packaging using a laser weld seam is known, in which the magnetic properties are also negatively influenced and eddy current losses also occur more frequently. In order to obtain laminated cores with good strength and good magnetic properties, the laminar stacking process is known, in which an electrical steel strip is coated on both sides with a thin layer of adhesive (baking varnish process). The hardening of the adhesive is achieved either by heating the laminated core after punching in a subsequent hardening step or by briefly heating the individual lamellae before packaging after pre-punching and before punching with transferring the lamella into the package brake, e.g. B. via IR radiation. The disadvantage here is the high energy requirement for hardening and the resulting high cycle times.

There are also adhesive packetizing processes in which the adhesive is applied selectively after the pre-punching and before the punching out and the hardening of the adhesive takes place in the packet brake. This does not result in a full-surface bond with comparatively low bond strengths.

There is also a glue packet method based on the use of an anaerobic glue, the hardening of which z. B. is catalyzed by copper ions. Instead of a liquid activator (solution containing metal ions), the catalytically active copper required for hardening is applied using a physical process. In the monograph “Gluing” by G. habenicht it was mentioned that copper-containing alloys such as brass and bronze, but also low-alloy steels, aluminum with a shiny metallic surface can be anaerobically glued without an activator. In the “Instructions for use General information on the DELO -ML product group”, www.delo.de, DELO_ML_GEBR_ (2) .pdf, it is described that surfaces that are not catalytically active can also be pretreated with a copper-containing brush.

In all the methods described, the adhesive is present on at least one lamella before at least two lamellae are brought into contact.

This method of applying adhesive is very complex, since each sheet must be provided with adhesive separately, either in a flat form by roller application, or in a punctiform / local form by means of printing.

Furthermore, especially if the adhesive or adhesive components are to be applied in the punching process, care must be taken that no adhesive escapes at the edge of the electrical steel sheets. Furthermore, the amount of adhesive must be applied depending on the surface roughness of the electrical steel sheets. The aim is to bring the smallest possible amount of adhesive into the component in order not to lower the stacking factor.

The problem in this context is that there can be flaws in individual metal sheets where the surface roughness is significantly increased. It can also happen that dirt particles or abrasion are in the adhesive gap between the lamellas to be bonded. As a result, the amount of adhesive applied is insufficient to fill the enlarged adhesive gap resulting from the deviation in surface roughness or soiling. This creates a weak point in the bond, which causes increased rejects in the sheet metal stack production.

The situation is similar in cases in which the sheet metal lamellas have even a slight bend. Here, too, the glue gap widens and the standardized amount of glue is not sufficient to close the glue gap. This effect occurs particularly strongly if a subsequent sheet metal lamella is rotated before stacking. This procedure is often used in practice in order to compensate for unequal thicknesses in the sheet metal strip from which it is punched in the stack. If, however, there is even only a slight curvature of the sheet metal lamellas (which, for example, may already have been present in the sheet metal strip from which it was punched), this results in a particularly greatly widened adhesive gap being created by the rotation. At the same time, however, it is possible that there are also places in the glue gap that are reduced in size by such a rotation. Thus, there are actually too little amounts of adhesive in some places within the glue gap, which can lead to the glue escaping from the glue gap and means contamination, and on the other hand too little glue in other places, which can lead to areas in which the Slats that are on top of each other are not adequately bonded with glue.

In the prior art, these problems are often countered by increasing the amount of adhesive between the sheet metal lamellas to such an extent that the adhesive gaps are reliably filled. According to the prior art, the amount of adhesive is not applied according to the amount individually required in each adhesive gap, but rather according to the largest assumed adhesive gap in order to ensure sufficient strength of the resulting bonded sheet metal stack. This leads to a significant reduction in the stacking factor. So-called impregnating resins are used for the packaging, particularly in the construction of laminated transformer cores. These are also applied in the sheet stack, often under pressure after previous evacuation of the stack of sheets. Curing takes place in 1K systems at elevated temperatures. If impregnation is to be carried out at room temperature, 2K systems are used.

The disadvantage here is that the impregnating resins also harden outside the stack of electrical steel sheets, so that the final contour is falsified, especially in the case of rotors and stators for electrical motors. Complex reworking of the electrical sheet stacks is the result.

The object of the present invention was against this background to provide a method by means of which the disadvantages described in the prior art can be mitigated or overcome. In particular, it was a matter of introducing an optimal amount of adhesive into the individual adhesive gaps, in particular avoiding leakage of the adhesive at undesired locations.

This object is achieved according to the invention by a method for producing a stack of sheet metal lamellas comprising the steps: a) providing sheet metal lamellas,

b) providing adhesive in liquid form,

c) Forming a stack from the sheet metal lamellas so that the surfaces to be glued together are opposite one another, preferably with maximum overlap

d) wetting the stack with adhesive from step b), so that the adhesive is drawn into the gaps between the respective lamellae to be bonded by capillary forces and e) curing of the adhesive between the lamellae to be bonded.

With this method it is surprisingly possible to wet closely stacked electrical steel lamellas with an adhesive not only on the edge of the electrical steel stack, but also in the interior as far as possible over the entire surface. This leads in particular to the fact that the scrap is reduced in the production of the sheet metal stacks. The method according to the invention will be discussed in greater detail below.

As already indicated, the increased efficiency of the method according to the invention means that stacks of sheet metal lamellas, which would normally have had to be sorted out at least between individual lamella pairs due to inadequate bonding, now also have an optimal amount of adhesive in these critical adhesive gaps, so that they have sufficient durability feature. Accordingly, part of the invention is also a stack of sheet metal lamellas, comprising a plurality of lamellae arranged one above the other, which are connected to one another by adhesive, the mass of the adhesive between the pair of lamellas, which is held together by the smallest adhesive mass, to the mass of the adhesive between the see Pair of lamellas, which is held together by the largest adhesive mass, in a ratio of <1: 1.5, preferably <1: 2, more preferably <1: 2.5 and particularly preferably <1: 3.

An adhesive within the meaning of the present invention is an adhesive according to DIN EN 923: 2016-03 “Adhesives - terms and definitions”. Preferred adhesives are described below.

It is also described below how the adhesive masses are determined in the individual adhesive gaps (the gaps between the lamellae, i.e. the area that is covered by the two lamellae lying one above the other in a vertical view) (see measurement examples). The method according to the invention makes it possible, as already indicated above, to produce stacks of sheet metal lamellas which would be completely sufficient for the usual requirements, but which would normally not meet the minimum requirements with other methods from the prior art because of insufficient bonding. In other words, the method according to the invention makes it possible to adequately fill the adhesive gaps within the sheet metal stack with adhesive which, for other techniques, would deviate too much from the mean value of the adhesive gaps of the overall stack in terms of their volume. Reasons for these deviations can e.g. that the adjacent lamellas are not optimally aligned, that due to the preceding punching process, the adjacent lamellas cannot be optimally aligned with one another, because one or both of the lamellas themselves are not optimally plan, which can be the case in particular in the edge areas, or that Small (dirt) particles are contained in adhesive gaps, which increase the minimum size of the adhesive gap and / or prevent parallel alignment of the adjacent lamellae to one another.

These and other deviations in the adhesive gap volume compared to the volume of the other adhesive gap are almost automatically compensated for by the method according to the invention in that more adhesive is or is introduced into the gap exactly where it is necessary. fewer. This ensures that the cohesion within the sheet metal stack is improved overall, because the bonding of the potentially weakest point (that of the bonding gap that deviates from the volume) is improved.

Furthermore, stacks of sheet metal stacks bonded by this method are accessible with the greatest stacking factor, because the stacking factor is not reduced by the adhesive according to the prior art, but is only determined by the topography of the individual sheet metal lamellas.

For the purposes of this text, the stacking factor is defined as follows:

F - d Meta II / (dMetall + 2 X d Insolation + d <spalt>) F: Stacking factor d <s _P ait>: gap between each two adjacent lamellae, averaged over the stack of sheet metal lamellas. DMetaii: Thickness of the metal layer of the sheet

Sheet metal thickness: thickness of the metal layer + 2 x insulation layer (if present), whereby this formula preferably applies to sheet metal stacks with> 20 sheet metal lamellas.

Accordingly, a stack of sheet metal lamellae according to the invention is preferred, with a stacking factor of> 97%, preferably> 98%, more preferably> 98.5%.

Adhesive gap thickness preferred according to the invention (d <s ait> are <10 μm, preferably <7 gm, particularly preferably <5 pm. According to the invention, it is preferred that the sheet metal lamellae stack according to the invention has one of the preferred or further preferred adhesive gap thicknesses and / or a preferred or one of the has further preferred stacking factors and at the same time has good tensile shear strength, in particular one which is described below as preferred or further preferred. Just for comparison, it should be mentioned that, for example, in the case of stacks of sheet metal lamellas, which are formed from sheet metal lamellas of a sheet metal thickness of 350 μm with an insulating layer of 1.5 μm on both sides, adhesive gap widths of> 12 μm are usually required in the prior art in order to achieve sufficient tensile shear strength and this leads to a stacking factor of <96%.

In the context of the present invention, a stack of sheet metal lamellas that is only held together by adhesive is preferred. The stacks of sheet metal lamellas are therefore preferably not stacked by punching, alternatively they are preferably not welded, more preferably they are not laser-welded. Furthermore, it is preferred in the context of the present invention that the sheet metal lamellas of the sheet metal lamella stack according to the invention have the same size. The person skilled in the art knows that, of course, small manufacturing tolerances can occur, which, however, in the context of the present invention, must not cause a surface difference of more than 1%. Furthermore, it is preferred in the sense of the present invention that the common cut surfaces of two adjacent sheet metal lamellas of the sheet metal lamella stack according to the invention have the same size in the projection of the surface normals. The person skilled in the art knows that, of course, small manufacturing tolerances can occur, which, however, in the context of the present invention, must not cause an area difference of more than 1%.

The sheet metal lamellas are preferably made of electrical steel, particularly preferred is an at least partially crystalline electrical steel, that is to say an electrical steel whose X-ray diffraction pattern has discrete reflections. For the purposes of the present invention, an electrical steel sheet is preferably a material which has soft magnetic properties and is e.g. is suitable as a material for magnetic cores. Electrical sheet metal is preferably a cold-rolled material made from an iron-silicon alloy, with the lamellae produced therefrom for the production of magnetic circuits for electrical machines, in particular the iron cores of dynamos, generators, electric motors, transformers, relays, contactors, inductors, ignition coils, electricity meters and controllable deflection magnets can be used.

In the context of the present invention, an electrical sheet is particularly preferred as a cold-rolled, non-grain-oriented electrical sheet in the finally annealed state according to DIN EN 10106: 2016-03 or a grain-oriented electrical steel sheet in the final annealed condition according to DIN EN 10107: 2014-07.

The lamellae to be used according to the invention are preferably not amorphous with regard to the material from which they are made, in particular no metallic glasses.

Alloys comprising or preferably consisting of iron and silicon, particularly preferably with a silicon content between 1 and 10%, more preferably between 2 and 6% silicon, are preferably used as materials for the electrical steel sheets.

In the context of the present text, an electrical sheet preferably comprises an insulating layer.

A stack of sheet metal lamellas according to the invention is preferred, the outer edge of the gap between the lamellae being at least partially filled with adhesive.

The outer edge of the gap between the slats can be shaped very differently depending on the shape of the slats. As already defined above, the gap between the lamellae is the area in which the lamellae to be joined face one another. This means that in the gap between the slats, a surface of the opposite slats is always given as a boundary on two sides. The outer edge in this context is the remaining limitation of the gap volume. In the case of round or rectangular plates that represent a continuous surface, this can be the peripheral edge; however, if the sheet metal lamellas are perforated, for example, the outer edge of the gap between the lamellas is jointly the circumferential edge that is defined by the inner hole and the circumferential edge that represents the outer circumference. In this case, the outer edge of the gap between the slats is divided into two.

In many adhesive application methods (e.g. with dotted adhesive application), care is taken as precisely as possible that the outer edge of the gap is not filled with adhesive in order to avoid potential leakage of the adhesive from the adhesive gap and contamination of the manufacturing environment with leaking adhesive. The stacks of sheet metal lamellas according to the invention which are produced by the method according to the invention always have adhesive at at least one point on the outer edge, namely at the point where the stack was wetted (laterally). However, since it is possible to introduce the optimal amount of adhesive between the lamellae with the method according to the invention, it will regularly be the case, even if only in one or a few places the wetting has taken place, the adhesive will occupy larger parts of the outer edge of the adhesive gap.

Accordingly, a stack of sheet metal lamellas is preferred according to the invention, with each of the gaps between the lamellae being> 10% of the running circumference, preferably> 20%, more preferably> 40%, particularly preferably 80% of each of the gaps between the

Lamellae adhesive is located on both sides of the lamellae facing the gap.

This adhesive coverage is regularly an expression of the fact that the method according to the invention has been used. Since the adhesive - without being tied to a theory - gets between the sheet metal lamellas through capillarity in the method according to the invention, a maximum of as much adhesive is drawn into the gap between the sheet metal lamellas that it completely fills the adhesive gap. In other words, there is no need to fear uncontrolled leakage of the adhesive at other locations than the locations where the adhesive was applied.

A stack of sheet metal lamellas according to the invention is preferred, comprising at least 50 lamellas, preferably the number 50-15,000, more preferably 200-2000 and particularly preferably 300-1000 lamellas. These lamella stack sizes are for typical applications such as B. transformers or generators are particularly suitable as coil cores.

In this sense, it is of course preferred that the stacks of sheet metal lamellas are soft magnetic. The method according to the invention (see below) not only has an influence on the adhesive content of the glue gaps compared to one another, but especially in the case of accuracy deviations, bending of the lamellae or dirt, the method according to the invention causes a (desired) strong fluctuation in the layer thickness of the adhesive within a glue gap. This is because it is possible in this way to avoid potential defects using the method according to the invention. Accordingly, a stack of sheet metal lamellae according to the invention is preferred, at least the layer thickness of the adhesive fluctuating in at least one gap between the lamellae by> 20%, preferably> 30% and more preferably> 40%.

These preferred stacks of sheet metal lamellas represent an added value of the method according to the invention, because otherwise, with a generally constant amount of adhesive, gene application according to the state of the art at precisely these gaps (where there is the relatively high fluctuation in the adhesive layer thickness) to find a weak point in the stack of sheet metal lamellas.

A stack of sheet metal lamellas according to the invention is preferred, the adhesive being an adhesive that cures by polymerization, preferably an acrylate-based adhesive. A UV-curing, moisture-curing (e.g. cyanoacrylate) or anaerobically curing adhesive is further preferred or alternatively preferred.

Alternatively preferred is a stack of sheet metal lamellae according to the invention, the adhesive being a silicone-based adhesive, preferably an MS polymer adhesive or silicone adhesive, more preferably a room temperature crosslinking silicone adhesive.

These adhesives are particularly suitable for the method according to the invention.

A stack of sheet metal lamellas according to the invention is preferred, the adhesive having a viscosity of 1 to 1000 mPas, preferably 3 to 500 mPas, particularly preferably 5 to 200 mPas, before curing. In case of doubt, the viscosity is determined according to DIN EN ISO 2884-1: 2006-09, in particular at 20 ° C. using the cone / plate method with a cone with a diameter of 75 mm at 30 rpm.

Adhesives of the preferred viscosity are particularly suitable for the process according to the invention. Of course, this is about the viscosity during application; after curing, such a viscosity no longer exists.

According to the invention, a stack of sheet metal lamellas is preferred, the surface of the sheets to be bonded having a roughness R _z of 0.5 to 15 μm, preferably 1 to 10 μm, preferably 1 to 5 μm.

This surface quality is particularly suitable for the method according to the invention. At the same time, the method according to the invention can still achieve a good adhesive result for the (unwanted) deviations that are regularly present even with a corresponding roughness.

In case of doubt, the value for the roughness R _{z is determined} according to DIN EN ISO 4288. A stack of sheet metal lamellas according to the invention is preferred, the area of the lamellae to be glued in each case being 0.5 to 2000, preferably 5 to 1000, particularly preferably 50 to 500 cm ² .

With these area sizes for the bond, the method according to the invention (see below) shows particularly good results, in particular in terms of reducing rejects. The dimensions for the lamellae to be used according to the invention are suitable for chokes, generators and large motors as well as transformers and electric motors. Of course, smaller and larger sheet metal lamella surfaces are also possible for a large number of applications. A preferred stack of sheet metal lamellas is preferred, the entire stack having a tensile shear strength of> 0.1 MPa, preferably e 1 MPa, particularly preferably 3 MPa.

In case of doubt, this tensile shear strength is measured in accordance with DIN EN 1465: 2009-07 [Adhesives - Determination of the tensile shear strength of overlap bonds, German version EN 1465: 2009]. A corresponding tensile shear strength can also be ensured by the method according to the invention for adhesive gaps that are created using conventional methods would not achieve these values. This actually leads to a reduction in rejects.

A lamellar stack according to the invention is preferred, the lamellae being an electrical steel sheet, preferably made of crystalline electrical steel, more preferably of crystalline soft magnetic electrical steel, particularly preferably of crystalline soft magnetic electrical steel with an insulation coating.

These materials are particularly suitable for the purposes of the present invention.

A stack of lamellas according to the invention is preferred, the entire stack not being destroyed when the stack is suspended; This means that the stack remains unchanged when it is attached to only the topmost lamella and when it is subsequently freely suspended.

As already indicated above, the core of the invention is the method for applying or introducing the adhesive for producing the stack of laminations according to the invention as well as the production of sheet metal stacks. The stacks of sheet metal lamellas described above, which are part of the invention, are in particular the sheet metal lamella stacks that would have been rejected due to the design of the lamellae in conventional processes because the adhesive gaps would not have been ideally filled with adhesive.

The essence of the invention is therefore a method for producing a stack of sheet metal lamellas, comprising the steps: a) providing sheet metal lamellas,

b) providing adhesive in liquid form,

c) Forming a stack from the sheet metal lamellas so that the surfaces to be glued together are opposite one another, preferably with maximum overlap

d) wetting the stack with adhesive from step b), so that the adhesive is drawn into the gaps between the respective lamellae to be bonded by capillary forces and e) curing of the adhesive between the lamellae to be bonded. It is preferred that the method according to the invention also produce a stack of sheet metal lamellas according to the invention, as described above.

As already indicated above, the method according to the invention can ensure that sheet metal lamellae lying close to one another, even when they are under pressure, are supplied with an ideal amount of adhesive in the area between the sheet metal lamellae. As already described above, it is preferred that low-viscosity adhesives are used.

As already indicated above, it is assumed - without being bound by theory - that the wetting of the pressed sheet metal lamellas in the adhesive gap is based on capillarity. The size of the gap is in turn determined in particular by the roughness of the sheet metal lamellae lying on top of one another. In the method according to the invention, it is preferred to work with compression of the stack of sheet metal lamellas, that is to say here, in particular to carry out step d), because this minimizes the area between the respective lamellae (the adhesive gaps) and maximizes the stacking factor. Alternatively, it is preferred that when the adhesive is applied, the stack of sheet metal lamellas is not compressed, in particular there being no vertical pressure actively during the gluing process to the mutually facing surfaces of the lamellas in the stack of lamellas. This can be achieved, for example, by holding the individual slats in position using an alternative clamping device. For rotors and stators, tensioning rollers can be used for this purpose, the diameter of which is increased in the tensioning process. The sheet metal lamellas are suitably aligned for this purpose and threaded onto the non-tensioned roller. The sequence of alignment and threading is arbitrary. The threading onto the tensioning roller can be supported by a further tensioning device which compresses the stack of sheet metal lamellas parallel to the normal to the surface of the lamellae. After threading the stack of sheet metal lamellas, the tension roller is tensioned and the sheet metal lamellae are thus held in position without the need for compression parallel to the surface normal of the lamellae facing each other. Using this method, the height of the stack of sheet metal lamellas can be adjusted in a targeted manner and the adhesive gaps can be enlarged in a targeted manner in order to facilitate the penetration of the adhesive at the same time.

The effect according to the invention depends on the wettability (the surface energy) of the lamellar surfaces to be bonded by the respective adhesive used. Accordingly, a method according to the invention can be preferred in which at least some of the surfaces of the lamellae to be bonded are subjected to a pretreatment before step c) which increases the wettability with the adhesive from step b).

For this purpose, the metal sheets can be subjected to a suitable surface treatment familiar to a person skilled in the art before or after punching (then in lamellar form). In principle, however, the person skilled in the art can of course also set an ideal wetting behavior for the adhesive to be used by using appropriate wetting auxiliaries (see below).

As already indicated above, low-viscosity adhesives are preferred for the method according to the invention. Particularly preferred are anaerobic adhesives which, when they are introduced (between the lamellae), find anaerobic conditions and can thus cure. After curing, the non-crosslinked adhesives on the edge of the stack of electrical steel sheets can be easily removed with a solvent or small residues that have no effect on the final contour of the stack of laminated sheets can be hardened, e.g. B. by means of UV radiation.

The person skilled in the art makes the choice of the anaerobic adhesive based on

sufficiently low adhesive viscosity to achieve the lowest possible layer thicknesses and good wetting speed, sufficiently low surface energy of the adhesive (to increase capillarity),

sufficiently high cohesive strength of the adhesive,

Adequate aging stability of the resulting bond against medial and thermal loads, especially when immersed in 150 ° C gear oil and / or aging at 85 ° C and 85% relative humidity,

for production and minimal cycle time, on the one hand, sufficiently high reactivity of the adhesive and, on the other hand, sufficiently low reactivity for the wetting time. Furthermore, the skilled person has z. B. the possibility of wetting aids such as surfactants

(e.g. fluorosurfactants and silanes), block copolymers with PDMS blocks to reduce the surface energy of the adhesive and thus improve the wetting properties of the adhesive.

The person skilled in the art can also adjust the reactivity of the adhesive within limits by means of the concentration of the catalyst, frequently the copper, on the surface.

To apply the catalyst, it is preferred to work with brushes, blasting or grinding, in each case here in particular for a copper application; at the same time, the lamellar surface can also be roughened.

Alternatively, it is preferred to apply the catalyst, if it is in particular in liquid form, by a spraying process or a roller application or a dipping process or a sponge or brush application.

As also indicated above, depending on the wetting properties of the substrates, it may be necessary to pretreat the substrates, especially if the substrates with a C5 coating are in the non-annealed state. Here, the wetting properties are limited by organic components of the C5 coating and / or punching and / or drawing oils. This pretreatment is typically done with cleaning and / or activating processes.

The cleaning methods are exemplary

Solvent cleaning / US cleaning aqueous cleaning with / without US support

C02 snow jets / pellet jets

To mention laser treatment. A method for improving the wetting properties of adhesives is to add fluorosurfactants (e.g. 3M Novec FC-4430) in a concentration range of 0.01 to 1.00% by weight, preferably 0.05 to 0.10% by weight. -% to call.

The following processes may be mentioned as activating processes, that is to say processes which improve the wetting properties through chemical modification of the surface: Plasma treatment at low pressure or at atmospheric pressure, in particular oxygen-containing plasmas

VUV irradiation, especially Xe excimer lamps and / or low-pressure Hg lamps

(UV) laser treatment

- Flaming

Corona treatment or treatment with dielectrically impeded discharge

In order to set the capillarity in a targeted manner and to ensure a minimum adhesive layer thickness, it can be useful for very smooth (R _z <0.5 μm) substrates to set the topography of the sheets or to install spacers between the individual sheets. The following methods are preferred for setting the topography:

Brushes, in particular brushes with bristles containing copper o When the brush is exposed to tribological stress on the insulation coating of the electrical steel sheet, a transfer film or tribo-film is formed which comprises components of the brush filaments. o Even small amounts of copper (0.05 at% Cu measured with XPS) are sufficient to develop the catalytic effect for hardening the adhesive.

(Vacuum suction) blasting particularly preferably with broken glass, in particular blasting media with a grain size of 5 μm

Laser processes, especially Nd-YAG

Preferred spacers are: inorganic fillers in a lacquer, in particular C5 lacquer

5 μm grains (glass / silicates / bentonites / plastic dispersions (PS)) Preferred methods for applying adhesive are in the process according to the invention:

Application of the adhesive with a sponge or felt or brush or brush or paint roller,

Application by dipping the stack of electrical steel sheets, in particular by rotating the sheet metal stack with a flat amount of adhesive,

- Application by spraying or dripping or flowing.

If not all areas of the sheet metal stack are intended for adhesive wetting, the following areas should preferably be wetted: at the teeth of the sheet metal cut, particularly preferably at the tooth root, i.e. at the transition from the tooth to the circle on which the teeth are located (yoke),

- in sections of the sheet metal cut for the permanent magnets.

Areas in which the adhesive is preferably not applied:

Tooth surfaces of the rotor and / or stator,

cylindrical outer surface of the rotor,

cylindrical inner surface of the stator

Contact areas of the pressing device with the stack of electrical steel sheets. It may also be preferred to apply the adhesive in two or more steps, for example when using a tension roller. In this case, the first step is to apply the adhesive from the outside. After the adhesive has hardened, the tension roller is removed and applied from the inside. This process leads to an enlarged wetting area, ideally to complete wetting and filling of the adhesive gap. Different application methods can also be used in the steps, e.g. first application of the adhesive to the outer surfaces by dipping the stack of electrical steel sheets by rotating the sheet metal stack through a flat amount of adhesive and secondly application of the adhesive to the inner surfaces with a paint roller. A pressing device used is preferably designed in such a way that it has no contact with cutting edges or punching edges of the sheet metal lamellas. This prevents the adhesive from getting between the gaps between the sheet metal lamella and the pressing device that are created during pressing. If this were the case, an undesired hardening of the adhesive between the sheet metal stack and the pressing device could result. Alternatively, the pressing device is preferably designed in such a way that it has contact with cutting edges or punched edges of the sheet metal lamellas, but preferably only in areas where the adhesive is not applied during pressing and the adhesive does not get there due to the lack of a flow path. In this way, unwanted hardening of the adhesive between the sheet metal stack and the pressing device can also be avoided. The length of the flow path describes the path that the adhesive can cover in the bond gap in a defined time, here possibly a pressing time. In addition to capillarity, this is also influenced by the viscosity of the adhesive and the curing speed of the adhesive.

Measures for reducing the viscosity are, for example, increasing the temperature, measures for increasing the viscosity are, for example, lowering the temperature. In addition to the adhesive formulation, measures to increase the reactivity are, for example, increasing the amount of catalyst or choosing a more accelerating catalyst or increasing the temperature, measures to lowering the reactivity are, for example, reducing the amount of catalyst or choosing a less accelerating catalyst or lowering the temperature.

Measures to increase the flow path can also include: - Creation of a pressure difference. The side with higher pressure is the side from which the adhesive is applied and the side with lower pressure is the side to which the adhesive is to flow.

- Setting the stack of sheet metal lamellas, but at least one sheet metal lamella, to vibrate, preferably by means of an ultrasonic sonotrode.

Measures to limit the flow path can also include (capillary barrier): Enlarging the bond gap

Introduction of poorly wettable areas on the sheet metal lamellas, e.g. via coating with silicones or Teflon In general, regardless of what has been said above, adhesives are preferred, with a surface energy of <30 mN / m, preferably <27 mN / m, more preferably <24 mN / m and particularly preferably <20 mN / m. In case of doubt, the surface energy is determined in accordance with DIN 55660-3: 201 1 -12: “Coating materials - wettability - Part 3: Determination of the surface tension of liquids using the hanging drop method”.

The invention is characterized in more detail below by means of examples:

Examples

Measurement examples:

Measurement example 1: Measurement of the amount of adhesive between two lamellae A stack of sheets of metal for a rotor is manufactured according to example 3 (see below).

A scalpel is inserted into the adhesive layer between the top two sheets and the first layer is peeled off from the second layer, analogous to a wedge test. The adhesive generally fails in a complex mixed fracture, i.e. there are adhesive residues on both sides. The stack of sheets is taken apart layer by layer and the order of the sheets is noted. The person skilled in the art ensures that exactly opposite fracture surfaces can be assigned. The weights of each lamella covered with adhesive residue are measured.

Finally, a pair of opposing fracture surfaces are deliberately freed from the adhesive residues with a laser as follows:

Laser type: Coherent COMPexPro ™ 2Q5F

• Laser fluence: 170 mJ / cm ²

• Wavelength: 248 nm

• Pulse duration: 25 ns

• Rep. Rate: 10 Hz

• Laser profile: 2 x 15 mm ² (FlatTop) spectrometer: OCEAN-OPTICS USB4000

• Integration time of the measurement: 5 sec

• Distance lens (focus point): 95 mm

• Angle of measurement to the surface: 45 °

• Filter used: Cut of filter at 280 nm Evaluation: Oriqin

• Measurement of the plasma luminescence by means of temporal integration over 50 individual laser pulses

• Integration range (wavelength) for the evaluation: 250 nm - 850 nm

• The measurement data were determined on the basis of three measurements. The laser treatment is repeated at one point until the light intensity of the optical emission is reduced by 85% of the initial value. Then the next point is stripped. This procedure is repeated until the adhesive has been completely removed from both fracture surfaces.

Finally, the two sheet metal lamellas are weighed again and the weight of the adhesive in the corresponding adhesive layer is determined from the difference.

This procedure is carried out for all further adhesive layers and the mean value and the standard deviation of the weight of the adhesive layers are determined, and the adhesive layer with the lowest weight and the adhesive layer with the highest weight are determined. Measurement example 2: Measurement of the adhesive layer thickness within an adhesive layer

A sheet metal stack of a rotor is manufactured, for example, according to Example 3 (see below).

A scalpel is inserted into the adhesive layer between the top two sheets and the first layer is peeled off from the second layer, analogous to a wedge test. The adhesive generally fails in a complex mixed fracture; H. there is adhesive residue on both sides.

The person skilled in the art ensures that precisely opposite measuring ranges can be assigned.

Both fracture surfaces are examined using laser confocal microscopy: Measuring principle:

Compared to conventional microscopy, laser scanning confocal microscopy (LSCM) generates higher-contrast images with height information. For this purpose, the surface is scanned with a short-wave laser beam (408 nm) and the light reflected back from the surface is collected with the help of optics. By shifting the collecting optics relative to the sample surface and by repeatedly measuring the focal points for different distances, height information in the nm range is achieved.

Measurement parameters and procedure:

The measurements were carried out with a laser scanning confocal microscope of the type VK 9700 from the manufacturer Keyence. The area measured was 270 μm × 202 gm. 3 optical planes were permitted: 1. Interface metal substrate / insulation coating, 2nd interface insulation coating / adhesive, 3rd surface adhesive.

Both fracture surfaces are completely measured by means of a stitching process (stringing together the individual images) and the distribution of the total adhesive layer thickness is determined by adding the adhesive layer thicknesses on both opposing fracture surfaces. The mean value and the standard deviation of the adhesive layer thickness within the examined adhesive layer are determined, as well as the minimum and maximum adhesive layer thickness. In case of doubt, if measurement example 1 cannot be carried out for special adhesives, this procedure can be used to determine the mean value and the standard deviation of the weight of the adhesive layers, and also to determine the adhesive layer with the lowest weight and the adhesive layer with the highest weight. To do this, the procedure described above must be carried out for all further adhesive layers and the adhesive layer thickness converted into the weight of the adhesive of the individual adhesive layers, taking into account the density of the adhesive.

Examples of execution:

Embodiment 1: An electrical sheet stack (electrical sheet M310-50A from the manufacturer Arcelor Mittal with C5 insulation coating from EB 5308 from Rembrandtin) of a rotor sheet section with an inside diameter of 80 mm and an outside diameter of 130 mm and a height of 150 mm (sheet thickness 0 , 3 mm, 500 sheets, roughness Ra = 0.48 + - 0.05 pm / Rz = 4.80 + - 0.45 pm) are brought into position by a holding device so that the sheets are aligned so that they Form a cylinder and the cutouts in the sheet metal cut (in this case for the introduction of permanent magnets) lie one above the other.

To apply the catalyst particles necessary for curing, the substrates are brushed on both sides with a copper brush (according to PCT / EP2018 / 080059 example 4). This simultaneously sets R _z to 4 pm.

This stack is compressed by a pressing device at a pressure of 100 kPa.

When compressed, the cut edges of the stack are wetted by spraying with the DELO ML 5327 adhesive (viscosity 300 mPas).

After 30 min. Curing at room temperature, the stack of electrical steel sheets is removed from the pressing device and the sprayed surfaces are freed from excess (in this case) non-hardened adhesive by solvent cleaning (IPA) in an ultrasonic bath.

The result is a coherent electrical core that is easy to handle. After testing the peel strength (separation of the first sheet from the sheet stack), the fracture surface of the bond can be seen. The flow front shows that the adhesive penetrated 6 mm +/- 2 mm from the edge into the gap between the first and second sheet metal layer and hardened. Embodiment 2:

An electrical sheet stack (electrical sheet M310-50A from manufacturer Arcelor Mittal with C5 insulation coating from EB 5308 from Rembrandtin) of a rotor sheet cut with an inside diameter of 80 mm and an outside diameter of 130 mm and a height of 150 mm (sheet thickness 0.3 mm , 500 sheets, roughness Ra = 0.48 + - 0.05 pm / Rz = 4.80 + - 0.45 pm) are brought into position by a holding device so that the

Metal sheets are aligned so that they form a cylinder and the cutouts in the sheet metal cut (in this case for the introduction of permanent magnets) are on top of each other.

To improve the wetting properties, the substrates are pretreated with the following parameters using atmospheric pressure plasma:

Generator Surfx Atomflo 500

4-lin-g3

Power 100 W

Speed: 3.2 m / min

- Distance between nozzle and substrate 2 mm

Line spacing 10 mm

Cycles 5

Process gas argon 20 l / min oxygen 0.1 l / min

The treatment increases the surface energy of the sheets from 29 mN / m to 67 mN / m (CA measurement of the advancing angle; test liquids: water, diiodomethane, ethylene glycol; evaluation according to Owens-Wendt with values from Rabel and Kaelble)

To apply the catalyst particles necessary for curing, the substrates are brushed on both sides with a copper brush (according to PCT / EP2018 / 080059 example 4). This simultaneously sets R _z to 4 pm. This stack is compressed by a pressing device at a pressure of 100 kPa.

When compressed, the cut edges of the stack are wetted by spraying with the DELO ML 5327 adhesive (viscosity 300 mPas).

After 30 min. Curing at room temperature, the stack of electrical steel sheets is removed from the pressing device and the sprayed surfaces are freed from excess (in this case) non-hardened adhesive by solvent cleaning (IPA) in an ultrasonic bath.

The result is a coherent electrical core that is easy to handle.

After testing the peel strength (separation of the first sheet from the sheet stack), the fracture surface of the bond can be seen. The flow front shows that the adhesive penetrated 10 +/- 2mm from the edge into the gap between the first and second sheet metal layer and hardened.

Embodiment 3:

A stack of electrical steel sheets made of punched lamellas (electrical steel sheet M310-50A from the manufacturer Arcelor Mittal with C5 insulation coating from EB 5308 from Rembrandtin) with a rotor sheet cut with an inner diameter of 80 mm, an outer diameter of 130 mm and recesses for 8 permanent magnets (the Sheet metal section has a 4-fold rotational symmetry), is stacked to a height of 150 mm (sheet thickness 0.3 mm, 500 sheets) and connected to an electrical sheet core as follows: To apply the catalyst particles required for hardening, the electrical sheets are - The stack was brushed on both sides with a copper brush (according to PCT / EP2018 / 080059 example 4). This simultaneously sets Rz to 4 pm.

These brushed electrical sheets are brought into position by a holding device in such a way that they form a cylinder and the cut-outs in the sheet metal cut (in this case for the introduction of permanent magnets) lie one above the other. For all 125 sheets, the rolling direction of the sheets was rotated by 90 ° in order to obtain an electrical sheet stack that was as plane-parallel as possible.

This stack is compressed by a pressing device at a pressure of 100 kPa. In the compressed state, the cut edges of the stack are sufficiently wetted by spraying with Cyberbond RL 65 adhesive (viscosity 10 mPas) so that there is still adhesive on the outside even after the adhesive has been drawn into the adhesive gap.

After 30 min. Curing at room temperature, the stack of electrical steel sheets is removed from the pressing device and the sprayed surfaces are freed from excess (in this case) non-hardened adhesive by solvent cleaning (IPA) in an ultrasonic bath.

The result is a coherent electrical core that is easy to handle. The entire stack is not destroyed when the stack is suspended; This means that the stack remains unchanged when it is attached to only the topmost lamella and when it is subsequently freely suspended.

After testing the peel strength (separation of the first sheet from the sheet stack), the fracture surface of the bond can be seen. The flow front shows that the adhesive has completely penetrated the gap between the first and second sheet metal layer and has cured. This creates a full-surface bond. The determination of the minimum and maximum weight of the 499 adhesive layer layers is carried out according to measurement example 1. The maximum weight of an adhesive layer is 109.3 mg. The minimum weight of an adhesive layer is 47.8 mg.

The determination of the minimum and maximum adhesive layer thicknesses in the uppermost adhesive layer, determined according to measurement example 2, gave, averaged over an area of 200 μm × 2770 μm, a maximum adhesive layer thickness of 10.3 ± 2.6 μm and a minimum adhesive layer thickness of 5.3 ± 0 , 4 pm.

Embodiment 4:

Two electrical sheets with a tensile shear test specimen geometry (25 mm × 100 mm) are brushed with a copper brush to apply the catalyst particles necessary for curing to the sides to be bonded (according to PCT / EP2018 / 080059 Example 4). This simultaneously sets R _z to 4 pm.

These substrates are fixed with an overlap of 1 mm with two clamps so that they result in a tensile shear test specimen according to DIN 1645 and the two brushed sides are brought into contact with one another. The two clamps press these two substrates together with a pressure of 100 kPa.

When compressed, the two cut edges are wetted by brushing with the DELO ML 5327 adhesive (viscosity 300 mPas). After 30 min. Curing at room temperature, the lap shear test specimen is freed from the clamps and the painted surfaces are freed from excess (in this case) non-hardened adhesive by solvent cleaning (IPA) in an ultrasonic bath.

The result is a tensile shear test specimen that is resistant to handling.

The brushed side of the first sheet is brought into contact with the adhesive-coated side of the second sheet and fixed with a clamp. After 1 minute the strength of the bond is sufficient to move the bond (handling strength). After 6 minutes at 40 ° C (typical temperature of the punching tool in operation), the bond already shows tensile shear values of 2.5 ± 0.7 MPa. After 24 hours at room temperature, tensile shear strengths of 4.5 ± 0.8 MPa are achieved. After aging in gear oil at 150 ° C for 150 hours, the tensile shear strength is still 4.2 + - 0.5 MPa. After 1000 hours of aging at 85 ° C. and 85% relative humidity, the tensile shear strength was 4.1 ± 0.2 MPa.

Embodiment 5:

An electrical sheet stack (electrical sheet M310-50A from the manufacturer Arcelor Mittal with C5 insulation coating from EB 5308 from Rembrandtin) of a rotor sheet cut with an inner diameter of 80 mm and an outer diameter of 130 mm and a height of 150 mm (sheet thickness 0, 3 mm, 500 sheets are brought into position by a holding device in such a way that the sheets are aligned in such a way that they form a cylinder and the cut-outs in the sheet metal cut (in this case for the introduction of permanent magnets) lie one above the other.

To improve the wetting properties, 0.1% by weight of a fluorosurfactant (3M Novec FC-4430) was added to the DELO ML 5327 adhesive. This addition of additives significantly lowers the surface tension of the adhesive so that it can be wetted over the entire surface without plasma activation of the substrates.

To apply the catalyst particles necessary for curing, the substrates are brushed on both sides with a copper brush (according to PCT / EP2018 / 080059 example 4). This simultaneously sets Rz to 4 pm.

This stack is compressed by a pressing device at a pressure of 100 kPa.

When compressed, the cut edges of the stack are wetted by spraying with the DELO ML 5327 adhesive with additive. After 30 min. Curing at room temperature, the stack of electrical steel sheets is removed from the press and the sprayed surfaces are freed from excess (in this case) non-hardened adhesive by solvent cleaning (IPA) in an ultrasonic bath.

The result is a coherent electrical core that is easy to handle. The entire stack is not destroyed when the stack is suspended; This means that the stack remained unchanged when it was attached to only the topmost lamella and when it was subsequently hung freely.

After testing the peel strength (separation of the first sheet from the sheet stack), the fracture surface of the bond can be seen. The flow front shows that, starting from the edge, the adhesive penetrated 15 + - 2 mm into the gap between the first and second sheet metal layers and cured.

Claims

Claims 1 . Stack of sheet metal lamellas, comprising a multiplicity of lamellae arranged one above the other, which are connected to one another by adhesive, the mass of adhesive between the lamella pair, which is held together by the smallest adhesive mass, to the mass of adhesive between the lamella pair, which is held together by the largest adhesive mass , in the ratio <1: 1.5, preferably <1: 2, more preferably <1: 2.5 and particularly preferably <1: 3. 2. Stack of sheet metal lamellas according to claim 1, wherein the outer edge of the gap between the lamellae is in each case at least partially filled with adhesive. 3. Laminated sheet stack according to claim 1 or 2, wherein> 10% of the current Around the circumference of each of the gaps between the lamellae, preferably> 20%, more preferably> 40%, particularly preferably 80% of each of the gaps between the lamellae, there is adhesive on both lamellae sides directed towards the gap. 4. Sheet metal lamellae stack according to one of the preceding claims, comprising at least 50 lamellae, preferably the number 50-15,000, more preferably 200-2000 and particularly preferably 300-1000 lamellae. 5. Sheet metal lamellae stack according to one of the preceding claims, wherein at least the layer thickness of the adhesive in at least one gap between the lamellae fluctuates by> 20%, preferably> 30% and more preferably> 40%. 6. Sheet metal lamella stack according to one of the preceding claims, wherein the adhesive is an acrylate-based adhesive, preferably an anaerobically curing adhesive or a cyanoacrylate adhesive, particularly preferably an anaerobically curing adhesive. 7. Stack of sheet metal lamellas according to one of the preceding claims, wherein the adhesive has a viscosity of 15 to 1000 mPas, preferably 3 to 500 mPas, particularly preferably 5 to 200 mPas, before curing. 8. Sheet metal lamella stack according to one of the preceding claims, wherein the surface of the sheets to be bonded has a roughness Rz of 0.5 to 15 pm, preferably 1 to 10 pm, preferably 1 to 5 pm. 9. Sheet metal lamellae stack according to one of the preceding claims, wherein the area of the lamellae to be glued is in each case from 0.5 to 2000, preferably 5 to 1000, particularly preferably 50 to 500 cm ² . 10. Laminated sheet stack according to one of the preceding claims, wherein the entire stack has a tensile shear strength of> 0.1 MPa, preferably> 1 MPa, particularly preferably 3 MPa. 1 1. Laminated sheet stack according to one of the preceding claims, wherein the laminations are each made of electrical steel, preferably of crystalline electrical steel, more preferably of crystalline soft magnetic electrical steel, particularly preferably of crystalline soft magnetic electrical steel with an insulation coating. 12. A method for producing a stack of sheet metal lamellas, comprising the steps: a) providing sheet metal lamellas, b) providing adhesive in liquid form, c) Forming a stack from the sheet metal lamellas so that the surfaces to be glued together are opposite one another, preferably with maximum overlap d) wetting the stack with adhesive from step b), so that the adhesive is drawn into the gaps between the respective lamellae to be bonded by capillary forces and e) curing of the adhesive between the lamellae to be bonded. 13. The method according to claim 12, wherein at least some of the surfaces of the lamellae to be bonded are subjected to a pretreatment before step c) which increases the wettability with the adhesive from step b). 14. The method according to claim 12 or 13, wherein a sheet metal stack according to one of claims 1 to 1 1 is produced.