COIL AND METHOD FOR PRODUCING AN ELECTRICAL STRIP LAMINATE COILED INTO A COIL

Description

Technical area

[0001] The invention relates to a coil and a method for producing an electrical steel strip laminate wound into a coil, in which at least two electrically insulated metallic electrical steel strips are joined together to form an electrical steel strip laminate and, in a further step, are wound into a coil. State of the art

[0002] Coils made of self-bonding lacquer-coated electrical steel strip are known from the prior art. These coils are used, among other things, to cut self-bonding lacquer-coated sheet metal parts for laminated cores, for example, in electrical machines. The production time for such laminated cores is significantly determined by the cutting of the individual sheet metal parts.

[0003] To minimize this time expenditure, DE3033378A1 proposes a coil made of a multilayer electrical steel laminate. This electrical steel laminate is produced, for example, by bonding two electrical steel strips, each electrically insulated from each other by a coating. The coating proposed is a selection from a group comprising phosphate glass, magnesium silicate, and phosphate glass over magnesium silicate. To bond these coated electrical steel strips, an adhesive is used, which can be, for example, a phenolic adhesive, epoxy adhesive, or synthetic resin-based adhesive. As DE3033378A1 further explains, this adhesive must ensure a sufficiently strong bond between the coatings of the electrical steel to enable flawless further processing of the electrical steel laminate, for example, coiling into a coil.Defects at the joining point can lead to damage to the laminate during further processing and, due to short circuits between the electrical steel sheets, to impaired magnetic or electromagnetic properties of the electrical steel laminate. Therefore, increased care must be ensured when joining the coated electrical steel, which complicates the manufacturing process and prevents comparatively high reproducibility.

[0004] WO2007 / 116047A1 discloses a method in which three electrical strips are bonded together to form an electrical strip laminate. For this purpose, an adhesive layer is applied to both sides of a middle electrical strip of the three electrical strips.

[0005] In addition, lacquer-coated electrical sheets are known from DE69611009T2. Description of the invention

[0006] The invention therefore aims to simplify a process for producing a coil from an electrical steel laminate and thus ensure high reproducibility. Furthermore, the coil should exhibit high stability.

[0007] The invention solves the problem with regard to the method by the features of claim 1.

[0008] If the electrical steel strips, each of which is electrically insulated on at least one flat side by a bonding varnish layer, are joined together via mutually facing bonding varnish layers, increased short-circuit protection can initially be achieved because the mutually facing flat sides each have an electrically insulating layer before being joined. In contrast to the prior art, these two coatings also eliminate the need for an additional adhesive to firmly join the electrical steel strips because the electrical steel strips are firmly bonded to one another to form an electrical steel strip laminate by activating the chemical crosslinking of the two bonding varnish layers. Because the application of additional adhesive to the joining area between the electrically insulating coatings can be omitted, the risk of joining defects can also be reduced.Furthermore, chemical crosslinking of both bonding varnish layers ensures a particularly uniform, cohesive bond between the electrical steel strips – which in turn particularly benefits damage-free winding of the electrical steel strip laminate into a coil. Further use of such an electrical steel strip laminate can therefore take place with a lower risk of short circuits, which is why deterioration in the electromagnetic properties of the wound electrical steel strip laminate is not to be expected. The cohesive bonding of two bonding varnish-coated electrical steel strips into an electrical steel strip laminate according to the invention – without the need for additional adhesive – therefore ensures a particularly simple and cost-effective process with comparatively high reproducibility.

[0009] In general, it is stated that a coil can be understood as a metal strip wound or reeled into a bundle, which is then unwound or unwound as a material for further processing.

[0010] In general, thermoplastic and / or thermosetting bonding varnishes can be used. Bonding varnishes based on polyvinyl butyral, polyamide, or epoxy resin are also generally conceivable. Electrical steel strip can include electrical steel strip, silicon steel strip, etc.

[0011] The bonding of the two bonding varnish layers can be accelerated by applying a catalyst, particularly an amine, to at least one of the bonding varnish layers. In this context, spraying the catalyst has proven particularly effective, as this allows for particularly uniform application.

[0012] In this case, 1-methylimidazole, 2-methylimidazole and / or 1,2-diaminocyclohexane can be particularly suitable as an amine.

[0013] If the bonding varnish layers are thermally activated for their chemical cross-linking, the process can be further simplified in its handling.

[0014] If coated electrical steel strips are combined to form an electrical steel strip laminate, at least one of which is electrically insulated on both of its flat sides with a bonding varnish layer, it can prove advantageous for further processing of the electrical steel strip laminate if the activation temperature for chemically crosslinking the bonding varnish layers on the facing flat sides is lower than the activation temperature of the bonding varnish layer on the opposite flat side. This can ensure, among other things, that the electrical steel strip laminate wound into a coil can be unwound and further processed without damage.

[0015] If coated electrical steel strips are joined together to form an electrical steel strip laminate, of which at least one electrical steel strip has a cross-linked, polymeric and electrical insulation layer on the flat side opposite the flat side coated with baking varnish, this can also prove to be advantageous with regard to the further processing of the electrical steel strip laminate if the activation temperature for the chemical cross-linking of the baking varnish layers on the mutually facing flat sides is below the softening temperature of the polymeric electrical insulation layer.

[0016] Further improvements in the formation of a stable, bonded joint can be achieved by pressing the electrical steel strips together during the bonding process. This can promote more uniform chemical crosslinking of both bonding varnish layers. The compression can be achieved in a simple process, preferably with at least one pair of opposing rollers to ensure a continuous process. It can also be advantageous if the electrical steel strips are pressed together with their flat sides aligned. It is generally stated that multiple pairs of rollers, especially with different roller gaps, can improve the uniformity of the bonded joint between the bonding varnish layers.

[0017] The parameters of the material connection can be further improved if the rollers of at least one roller pair have a roller crown.

[0018] If the rolls of one roll pair have a concave crown and the rolls of another roll pair have a convex crown, this can further improve the bonding of the electrical steel strips. These roll pairs can preferably follow one another in the series of roll pairs.

[0019] The electrical short-circuit strength of the electrical steel laminate can be increased if at least one of the facing bonding varnish layers contains an incompressible and, in particular, abrasive-free filler. Among other things, this can ensure damage-free winding of the electrical steel laminate into a coil. Furthermore, this filler can increase the short-circuit strength between the electrical steel strips during punching of the electrical steel laminate. For this purpose, the filler preferably contains barium sulfate and / or lithopone.

[0020] The method according to the invention can be particularly advantageous when used to produce a coil with an electrical steel laminate. This can lead to a particularly stable coil with an electrical steel laminate, comprising a cohesive, chemically cross-linked bond between at least two electrical steel strips. A coil with an electrical steel laminate comprising a cohesive, chemically cross-linked bond consisting of at least one bonding varnish layer between at least two electrical steel strips is particularly advantageous.

[0021] The magnetic short-circuit strength of the coil or its electrical steel laminate can be increased if the material connection has an incompressible and, in particular, abrasive-free filler.

[0022] The above can be further increased by the cohesive bonding of several chemically cross-linked bonding lacquer layers, although in general a single chemically cross-linked bonding lacquer layer between two electrical steel strip laminates can be sufficient to create such a cohesive bond.

[0023] On the flat side facing away from the flat side with the cohesive connection, the electrical steel laminate has either a baked enamel layer whose activation temperature is above the activation temperature for chemical crosslinking of the cohesive connection, or a crosslinked, polymeric and electrical insulation layer whose softening temperature is above the activation temperature for chemical crosslinking of the cohesive connection.

[0024] The coil described above can be particularly suitable if several laminate parts punched out of its electrical steel laminate are used for a magnetically conductive component. Short description of the drawings

[0025] The figures show, for example, the subject matter of the invention based on an embodiment variant. Fig. 1 a schematic view of a device for producing an electrical steel laminate wound into a coil and Fig. 2 an enlarged detailed view of the Fig. 1 . Way to implement the invention

[0026] According to the Fig. 1 In the schematically illustrated device 1, it can be seen that two coils 2, 3, each consisting of a coated electrical strip 4, 5 - in the exemplary embodiment - are unwound, connected and combined to form a coil 6. The connection of the coated electrical strips 4, 5 is materially bonded, thereby creating an electrical strip laminate 7. In addition, the connected electrical strips 4, 5 are insulated from each other - namely by Fig. 2 have a coating 8 shown in more detail. In order to avoid damage to the electrical steel laminate 7 during winding, for example due to an inadequate material-to-material joining process, the electrical steel strips 4, 5, each of which is electrically insulated on at least one flat side 9, 10 with a bonding varnish layer 11, 12, are joined to one another via bonding varnish layers 11, 12 facing one another and are bonded to one another to form an electrical steel laminate 7 by activating the chemical crosslinking of both bonding varnish layers 11, 12.

[0027] As particularly in Fig. 2 As can be seen, no additional adhesive is required between the two bonding varnish layers 11, 12. The two bonding varnish layers 11, 12 are fed to one another and bond to form a stable electrical insulation between the two electrical steel strips 4 and 5. This ensures a comparatively high short-circuit resistance of the electrical steel strip laminate 7 - even if the electrical steel strip laminate 7 is significantly deformed, reshaped, separated, etc. during further processing. In addition, the chemical crosslinking of both bonding varnish layers 11, 12 offers advantages with regard to the joining area 13 - in particular with regard to the uniform texture, high mechanical strength, etc. This facilitates, among other things, the winding of the electrical steel strip 7 into a coil 6.

[0028] This chemical cross-linking of the two backing layers 11, 12 is, as in Fig. 1 As indicated, this reaction is accelerated by spraying an amine 14 as a catalyst. 1-Methylimidazole has proven to be excellent for this purpose, although 2-methylimidazole and / or 1,2-diaminocyclohexane can also be used.

[0029] As also in Fig. 1 As can be seen, the baking varnish layers 11, 12 are thermally activated for their chemical cross-linking by being irradiated with infrared 17 from a heat source 15 in the area of ​​the inlet 16 of the coated electrical sheets 4, 5.

[0030] As in Fig. 2 As shown, both flat sides 9, 90 and 10, 100 of the respective electrical strips 4, 5 are coated. Any coating 8 is conceivable, in particular, it should fulfill an electrically insulating function. For example, these coatings 8 of the flat sides 90, 100 can also represent a baked enamel layer 18 and / or a cross-linked, polymeric, and electrically insulating layer 19.

[0031] If a bonding varnish layer 18 is used as an electrically insulating coating of the electrical steel strip 4, when joining the bonding varnish layers 11, 12 on the facing flat sides 9, 10, an activation temperature for chemically crosslinking the bonding varnish layers 11, 12 to be joined is set below the activation temperature of the bonding varnish layer 18 provided on the opposite flat side 90 - or a bonding varnish with a correspondingly higher activation temperature is selected for the flat side 90. This simply and effectively prevents the electrical steel strip laminate 7 from sticking together in the wound state.

[0032] In the case of an external coating of the electrical steel strips 4, 5 with a cross-linked, polymeric and electrical insulation layer 19, the activation temperature for chemically cross-linking the bonding lacquer layers 11, 12 on the mutually facing flat sides 9, 10 is set below the softening temperature of the polymeric electrical insulation layer 19. This also prevents the electrical steel strip laminate 7 from sticking together in the wound state.

[0033] It is of course not excluded that the coatings 8 on the flat sides 90, 100 of the electrical strips 4, 5 facing away from the material-to-material joining may consist of the same material, although this has not been shown in more detail.

[0034] When bonding the two electrical steel strips 4, 5, they are pressed together with their flat sides 9, 10 aligned, using opposing rollers 20, 21 and 24, 25, respectively, which form successively arranged roller pairs 23, 24. This makes the electrical steel strip laminate 7 relatively highly resilient.

[0035] Rolls 20, 21 have a concave crown (not shown in detail), and rolls 24, 25 have a convex crown, which improves the stability of the bonded connection 27 between the electrical steel strips 4, 5 – especially when these two pairs of rolls follow one another. However, other roll crowns, or rolls without crowns, are also conceivable.

[0036] The short-circuit tendency of the electrical strips 4, 5 during subsequent reuse, in particular caused by punching, is reduced in this embodiment by barium sulfate as an incompressible filler 22 in the baked enamel layer 11 - as is the case with the Fig. 2 can be removed.

[0037] In general, it is conceivable that, in a further embodiment not shown, three or more electrical steel strips are joined together in a single process step. This can also be advantageous for producing desired material combinations, such as two hard cover layers and a more ductile intermediate layer, in the electrical steel strip laminate.

Claims

1. A method for producing an electric strip laminate (7) wound into a coil (6), in which at least two metallic electric strips (4, 5) that are electrically insulated from each other are integrally bonded to form an electric strip laminate (7) and in another step, are wound into a coil (6), characterized in that the electrical strips (4, 5), which are each electrically insulated with a baked enamel layer (11, 12) on at least one flat side (9, 10), are joined to each other by means of baked enamel layers (11, 12) facing each other and are integrally bonded to form an electric strip laminate (7) by activating the chemical cross-linking of the two baked enamel layers (11, 12), wherein the baked enamel layers (11, 12) are thermally activated in order to produce their chemical cross-linking, wherein coated electric strips (4, 5) are joined together to form an electric strip laminate (7), of which at least one electric strip (4) is electrically insulated with a baked enamel layer (11, 18) on both of its flat sides (9, 90) and the activation temperature for chemically cross-linking the baked enamel layers (11, 12) on the flat sides (9, 10) facing each other is below the activation temperature of the baked enamel layer (18) provided on the flat side (90) facing away, and / or of which at least one electric strip laminate (7) has a cross-linked polymer electrical insulation layer (19) on the flat side (100) opposite from the flat side (10) that is coated with baked enamel and wherein the activation temperature for chemically cross-linking the baked enamel layers (11, 12) on the flat sides (9, 10) facing each other is below the softening temperature of the polymer electrical insulation layer (19).

2. The method according to claim 1, characterized in that a catalyst, more particularly an amine (14), is applied, more particularly sprayed, onto at least one baked enamel layer (11).

3. The method according to claim 2, characterized in that 1-methylimidazole, 2-methylimidazole, and / or 1,2-diaminocyclohexane is used as the amine (14).

4. The method according to one of claims 1 through 3, characterized in that during the integral bonding of the electric strips (4, 5), they are pressed together, more particularly with at least one roller pair (23, 26) composed of opposing rollers (20, 21 or 24, 25).

5. The method according to claim 4, characterized in that the rollers (20, 21 or 120, 21) of at least roller pair (23, 26) have a roller camber.

6. The method according to claim 5, characterized in that the rollers (20, 21) of one roller pair (23) have a concave roller camber and the rollers (24, 25) of another roller pair (26) have a convex roller camber and these roller pairs (23, 26) preferably come one after the other in the series of roller pairs.

7. The method according to one of claim(7)s 1 through 6, characterized in that at least one of the baked enamel layers (11, 12) facing each other has an incompressible and more particularly abrasive-free filler (22), preferably containing barium sulfate and / or lithopone.

8. A coil with an electric strip laminate (7), having an integral, chemically cross-linked bond (27) composed of at least one baked enamel layer (11, 12) between at least two electric strips (4, 5), wherein the electric strip laminate (7) on the flat side (90, 100) facing away from the flat side (9 or 10) with the integral bond (27), has either a baked enamel layer (18), whose activation temperature is above the activation temperature for the chemical cross-linking of the integral bond (27), or has a cross-linked polymer electrical insulation layer (19), whose softening temperature is above the activation temperature for the chemical cross-linking of the integral bond (27).

9. The coil according to claim 8, characterized in that the integral bond (27) has an incompressible and more particularly abrasive-free filler (22).

10. The coil according to claim 8 or 9, characterized in that the integral bond (27) has a plurality of baked enamel layers (11, 12) that are chemically cross-linked to one another.

11. A use of several laminate parts that are stamped from an electric strip laminate (7) of the coil (6) according to claim 8, 9 or 10 for a magnetically conductive component.