DE102019110261A1 - Stack of sheet metal lamellas and processes for the adhesive connection of sheet metal lamellas - Google Patents

Abstract

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 the adhesive between the lamella pair, which is held together by the smallest adhesive mass, to the mass of the 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.

Description

The invention relates to 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 lamellae, which is held together by the smallest adhesive mass, to the mass of the adhesive between the pair of lamellae, which is supported by the largest adhesive mass is held together 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 brush containing copper.

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 emerges 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 sheets where the surface roughness is significantly increased. It can also happen that dirt particles or abrasion in the glue gap between the slats to be glued. 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. However, if there is even only a slight curvature of the sheet metal lamellas (which may already have been present in the sheet metal strip from which the punching was carried out), this leads to 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 sufficiently bonded with adhesive.

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 the sheet stack has been evacuated beforehand. 1K systems harden 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.

1. a) Bereitstellen von Blechlamellen,
2. b) Bereitstellen von Klebstoff in flüssiger Form,
3. c) Bilden eines Stapels aus den Blechlamellen, sodass die miteinander zu verklebenden Flächen einander gegenüberliegen, bevorzugt mit maximaler Überdeckung,
4. d) Benetzen des Stapels mit Klebstoff aus Schritt b), sodass der Klebstoff durch Kapillarkräfte in die Spalten zwischen den jeweilig zu verklebenden Lamellen gezogen wird und
5. e) Aushärten des Klebstoffes zwischen den zu verklebenden Lamellen.

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

1. a) Provision of sheet metal lamellas,
2. b) providing adhesive in liquid form,
3. 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,
4. d) wetting the stack with adhesive from step b), so that the adhesive is drawn into the gaps between the respective lamellae to be glued by capillary forces and
5. 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 multiplicity of lamellae arranged one above the other, which are connected to one another by adhesive, the mass of the adhesive between the lamella pair, which is held together by the smallest adhesive mass, to the mass of the adhesive between the lamella pair, 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.

The sheet metal lamellas are preferably made of electrical steel. 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 DIN EN 10106: 2016-03 or a grain-oriented electrical steel sheet in the final annealed condition DIN EN 10107: 2014-07 .

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

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 apply the optimal amount of adhesive between the lamellae with the method according to the invention, it will regularly be the case that even if the wetting has only occurred in one or a few places, the adhesive has larger parts of the outer edge of the adhesive gap will prove.

Accordingly, according to the invention, a stack of sheet metal lamellas is preferred, whereby at ≥ 10% of the running circumference of each of the gaps between the lamellae, preferably ≥ 20%, more preferably ≥ 40%, particularly preferably 80% of each of the gaps between the lamellas, there is adhesive on both lamella sides facing the gap is located.

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 bound to a theory - gets between the sheet metal lamellas through capillarity in the method according to the invention, the gap between the sheet metal lamellae is A maximum of enough glue has been drawn so that it completely fills the glue 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 lamellae, preferably 50-15,000 in number, more preferably 200-2000 and particularly preferably 300-1000 lamellae. 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 lamellas 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 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 a weak point in the sheet metal lamella stack would be found with a generally constant amount of adhesive applied according to the prior art at precisely these gaps (where there is the relatively high fluctuation in adhesive layer thickness).

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.

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 15 to 1000 mPas, preferably 3 to 500 mPas, particularly preferably 5 to 200 mPas, before curing.

In case of doubt, the viscosity according to the DIN EN ISO 2884-1: 2006-09 determined, in particular at 20 ° C in 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 according to DIN EN ISO 4288 certainly.

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 1 MPa, particularly preferably 3 MPa.

In case of doubt, this tensile shear strength is determined according to DIN EN 1465: 2009-07 measured [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 glue gaps which would not achieve these values using conventional methods. This actually leads to a reduction in rejects.

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 essence of the invention is the method for applying or introducing the adhesive for producing the stack of sheet metal lamellas according to the invention and, in principle, for producing stacks of sheet metal lamellas. 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.

1. a) Bereitstellen von Blechlamellen,
2. b) Bereitstellen von Klebstoff in flüssiger Form,
3. c) Bilden eines Stapels aus den Blechlamellen, sodass die miteinander zu verklebenden Flächen einander gegenüberliegen, bevorzugt mit maximaler Überdeckung,
4. d) Benetzen des Stapels mit Klebstoff aus Schritt b), sodass der Klebstoff durch Kapillarkräfte in die Spalten zwischen den jeweilig zu verklebenden Lamellen gezogen wird und
5. e) Aushärten des Klebstoffes zwischen den zu verklebenden Lamellen.

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

1. a) Provision of sheet metal lamellas,
2. b) providing adhesive in liquid form,
3. 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,
4. d) wetting the stack with adhesive from step b), so that the adhesive is drawn into the gaps between the respective lamellae to be glued by capillary forces and
5. 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 lamellas lying close to one another are supplied with an ideal amount of adhesive in the area between the sheet metal lamellas, even when they are under pressure. 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.

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 can be removed have no effect on the final contour of the stack of sheet metal lamellas. B. by means of UV radiation.

• - ausreichend niedrigen Viskosität des Klebstoffes zur Einstellung möglichst geringer Schichtdicken und guter Benetzungsgeschwindigkeit,
• - ausreichend geringen Oberflächenenergie des Klebstoffes (zur Steigerung der Kapillarität),
• - ausreichend hohen kohäsiven Festigkeit des Klebstoffes,
• - ausreichenden Alterungsstabilität der resultierenden Klebung gegenüber medialer und thermischer Belastung, insbesondere bei Immersion in 150 °C heißem Getriebeöl und/oder Alterung bei 85 °C und 85 rel% Luftfeuchtigkeit,
• - für die Produktion und minimale Taktzeit einerseits ausreichend hohen Reaktivität des Klebstoffes und andererseits eine für die Benetzungsdauer ausreichend niedrige Reaktivität.

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

• - Sufficiently low viscosity of the adhesive for setting the smallest possible layer thicknesses and good wetting speed,
• - Sufficiently low surface energy of the adhesive (to increase capillarity),
• - sufficiently high cohesive strength of the adhesive,
• - Sufficient 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,
• - On the one hand, sufficiently high reactivity of the adhesive for production and minimal cycle time and, on the other hand, sufficiently low reactivity for the wetting time.

Furthermore, the skilled person has z. B. the possibility of using wetting aids such as surfactants (e.g. fluorosurfactants and silanes), block copolymers with PDMS block 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 through the concentration of the catalyst, often 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.

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.

• - Lösungsmittelreinigung / US-Reinigung
• - wässrige Reinigung mit/ohne US-Unterstützung
• - CO2-Schneestrahlen / Pelletstrahlen
• - Laserbehandlung

zu nennen.The cleaning methods are exemplary

• - Solvent cleaning / US cleaning
• - aqueous cleaning with / without US support
• - CO2 snow jets / pellet jets
• - laser treatment

to call.

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.

• - Plasmabehandlung im Niederdruck oder bei Atmosphärendruck, insbesondere sauerstoffhaltige Plasmen
• - VUV-Bestrahlung, insbesondere Xe-Excimer-Strahler und/oder Niederdruck-Hg-Strahler
• - (UV-) Laserbehandlung
• - Beflammung
• - Coronabehandlung oder Behandlung mit dielektrisch behinderter Entladung

The following processes should be mentioned as activating processes, i.e. processes that improve the wetting properties through chemical modification of the surface:

• - Plasma treatment at low pressure or at atmospheric pressure, especially 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 adjust the topography of the sheets or to install spacers between the individual sheets.

• - Bürsten, insbesondere Bürsten mit kupferhaltigen Borsten
  • ◯ Bei der tribologischen Beanspruchung der Isolationsbeschichtung des Elektroblechs durch die Bürste kommt es zur Ausbildung eines Transferfilms oder Tribo-Films, der Bestandteile der Bürstenfilamente umfasst.
  • ◯ Bereits geringe Mengen des Kupfers (0,05 at% Cu gemessen mit XPS) reichen aus, um die katalytische Wirkung zur Härtung des Klebstoffs zu entfalten.

• - (Vakuumsaug-)Strahlen besonders bevorzugt mit Glasbruch, insbesondere Strahlmittel mit 5 µm Körnung
• - Laserverfahren, insbesondere Nd-YAG

The following methods are preferred for setting the topography:

• - Brushes, especially brushes with bristles containing copper
  • ◯ When the brush is subjected to tribological stress on the insulation coating of the electrical steel sheet, a transfer film or tribo-film is formed that includes components of the brush filaments.
  • ◯ 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, especially blasting media with a grain size of 5 µm
• - Laser processes, especially Nd-YAG

• - anorganische Füllstoffe in einem Lack, insbesondere C5-Lack
• - 5 µm große Körner (Glas / Silikate / Bentonite / Kunststoff-Dispersionen (PS))

The preferred spacers are:

• - Inorganic fillers in a paint, especially C5 paint
• - 5 µm grains (glass / silicates / bentonites / plastic dispersions (PS))

• - Auftrag des Klebstoffes mit einem Schwamm oder Filz,
• - Auftrag über Tauchen des Elektroblechstapels, insbesondere über eine Rotation des Blechstapels durch eine flache Klebstoffmenge,
• - Auftrag über Sprühen.

Preferred methods for applying adhesive in the process according to the invention are:

• - Application of the adhesive with a sponge or felt,
• - Application by dipping the stack of electrical steel sheets, in particular by rotating the sheet metal stack with a flat amount of adhesive,
• - Application via spray.

• - an den Zähnen des Blechschnittes, besonders bevorzugt an der Zahnwurzel, also am Übergang vom Zahn zu dem Kreis, auf dem die Zähne sitzen,
• - in Ausschnitten des Blechschnittes für die Permanentmagnete.

If not all areas of the sheet metal stack are intended for adhesive wetting, the following areas should preferably be wetted:

• - on the teeth of the sheet metal cut, particularly preferably on the tooth root, i.e. at the transition from the tooth to the circle on which the teeth sit,
• - in sections of the sheet metal cut for the permanent magnets.

• - Zahnoberflächen von Rotor und/ oder Stator,
• - zylindrische Außenfläche desRotors,
• - zylindrische Innenfläche des Stators
• - Kontaktbereiche der Pressvorrichtung mit dem Elektroblechstapel.

Areas in which the adhesive is preferably not applied:

• - tooth surfaces of 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.

The pressing device 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.

Generally independent of what has been said above, adhesives with a surface energy of 30 mN / m, preferably 27 mN / m, more preferably 24 mN / m and particularly preferably 20 mN / m are preferred. In case of doubt, the surface energy is determined in accordance with DIN 55660-3: 2011-12: "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 slats

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, 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 ™ 205F • Laser fluence: 170 mJ / cm ² • Wavelength: 248 nm • Pulse duration: 25 ns • Rep. Rate: 10 Hz • Laser profile: 2 × 15 mm ² (FlatTop) Spectrometer: OCEAN-OPTICSUSB4000 • 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: Origin • 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 based on 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 measured area was 270 µm × 202 µm. Three optical levels were permitted: 1. Metal substrate / insulation coating interface, 2. Insulation coating / adhesive interface, 3. Adhesive surface.

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.

Embodiments:

Embodiment 1:

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 µm / Rz = 4.80 + - 0.45 µm) are brought into position by a holding device so that the sheets are aligned so 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 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 µm.

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 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.

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 µm / Rz = 4.80 + - 0.45 µm) are brought into position by a holding device so that the sheets are aligned so 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.

• - Generator Surfx Atomflo 500
• - 4-lin-g3
• - Power 100 W
• - Geschwindigkeit: 3,2 m/min
• - Abstand Düse Substrat 2 mm
• - Zeilenabstand 10 mm
• - Zyklen 5
• - Prozessgas Argon 20 l/min Sauerstoff 0,1 l/min

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

• - Surfx Atomflo 500 generator
• - 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 µm.

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 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.

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 layers 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 necessary for hardening, the electrical sheets are of the stack Brushed on both sides with a copper brush (according to PCT / EP2018 / 080059 example 4). This simultaneously sets Rz to 4 µm.

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 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 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 µm.

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 µm.

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 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 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 cutouts 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 µm.

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.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Non-patent literature cited

• DIN EN 923: 2016-03 [0021]
• DIN EN 10106: 2016-03 [0025]
• DIN EN 10107: 2014-07 [0025]
• DIN EN ISO 2884-1: 2006-09 [0039]
• DIN EN ISO 4288 [0043]
• DIN EN 1465: 2009-07 [0047]

Claims (13)

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 the adhesive between the lamella pair, which is held together by the smallest adhesive mass, to the mass of the adhesive between the lamella pair, which is held together by the largest adhesive mass , in the ratio 1: 1.5, preferred 1: 2, more preferably 1: 2.5 and particularly preferably 1: 3. Sheet metal stack after Claim 1 , wherein the outer edge of the gap between the lamellae is in each case at least partially filled with adhesive. Sheet metal stack after Claim 1 or 2 , where on ≥ 10% of the running 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 facing the gap. Sheet metal lamella stack according to one of the preceding claims, comprising at least 50 lamellas, preferably the number 50-15,000, more preferably 200-2000 and particularly preferably 300-1000 lamellas. Stack of sheet metal lamellas 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%. 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. Stack of sheet metal lamellae 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. Stack of sheet metal lamellas according to one of the preceding claims, the surface of the sheets to be glued having a roughness Rz of 0.5 to 15 µm, preferably 1 to 10 µm, preferably 1 to 5 µm. Stack of sheet metal lamellas according to one of the preceding claims, the area of the lamellae to be glued in each case from 0.5 to 2000, preferably 5 to 1000, particularly preferably 50 to 500 cm ² . Stack of sheet metal lamellas according to one of the preceding claims, the entire stack having a tensile shear strength of ≥ 0.1 MPa, preferably ≥ 1 MPa, particularly preferably 3 MPa. A method for producing a stack of sheet metal lamellas, comprising the steps: a) Provision of 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 glued by capillary forces and e) curing of the adhesive between the lamellae to be bonded. Procedure according to Claim 11 , 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). Procedure according to Claim 11 or 12 , wherein a stack of laminations according to one of the Claims 1 to 9 will be produced.