DEVICE AND METHOD FOR CONNECTING SHEET METAL PARTS TO FORM LAMINATION STACKS

Abstract

A device and a method for connecting sheet metal parts to form lamination stacks in which sheet metal parts are separated from an electrical steel strip using a stamping stage equipped with a punch, wherein the electrical steel strip has a thermally activatable hot-melt adhesive varnish layer on at least one of its flat sides, the separated sheet metal parts are stacked and integrally bonded to one another to form multiple lamination stacks through activation of the hot-melt adhesive varnish layer, wherein a parting compound is applied to the electrical steel strip and/or separated sheet metal part in order to make it easier to divide the stacked sheet metal parts into lamination stacks. In order to achieve advantageous conditions, it is proposed for the punch of the stamping stage to apply a liquid fluid as a parting compound onto the electrical steel strip and/or separated sheet metal part.

Claims

1. A method for connecting sheet metal parts to form lamination stacks, comprising: separating sheet metal parts from an electrical steel strip with the aid of a stamping stage equipped with a punch, wherein the electrical steel strip has a thermally activatable hot-melt adhesive varnish layer on at least one of its flat sides, and the punch applies a liquid fluid as a parting compound onto the electrical steel strip and/or separated sheet metal part, wherein the parting compound makes it easier to divide the stacked sheet metal parts into lamination stacks, and stacking the separated sheet metal parts and integrally bonding the sheet metal parts to one another to form multiple lamination stacks through activation of the hot-melt adhesive varnish layer.

2. The method according to claim 1, wherein the punch applies the fluid as the sheet metal part is being separated.

3. The method according to claim 2, wherein the punch tightly adjoins the hot-melt adhesive varnish layer with at least one cutting edge during the application of the fluid and the at least one cutting edge therefore at least partially delimits an area on the hot-melt adhesive varnish layer onto which the fluid is applied.

4. The method according to claim 1, wherein the fluid is applied using a contact printing process.

5. The method according to claim 4, wherein the punch has a pressure stamp, which is able to move relative to its punch base and applies the fluid.

6. The method according to claim 1, wherein the fluid is sprayed on.

7. The method according to claim 6, wherein the punch has at least one spray nozzle, which applies the fluid with a rectangular target area.

8. A device for connecting sheet metal parts to form lamination stacks, comprising: a stamping tool, which has a stamping stage with a punch for separating sheet metal parts from an electrical steel strip that is coated on at least one of its flat sides with a thermally activatable hot-melt adhesive varnish layer, a stacking unit for stacking the separated sheet metal parts to form multiple lamination stacks, and a unit, which has a parting compound and is embodied to apply this parting compound onto the electrical steel strip and/or separated sheet metal part in order to thus make it easier to divide the stacked sheet metal parts into lamination stacks, wherein the punch of the stamping stage is equipped with the unit that is embodied to apply the parting compound—which is embodied as a fluid—onto the electrical steel strip and/or separated sheet metal part.

9. The device according to claim 8, wherein the punch has a punch base and at least one cutting edge, which protrudes from the punch base and, together with the hot-melt adhesive varnish layer, is embodied to form a sealing surface for the fluid.

10. The device according to claim 8, wherein the unit has a pressure stamp, which is able to move relative to the punch and applies the fluid, wherein the pressure stamp is provided in a recess in the punch base of the punch.

11. The device according to claim 8, wherein the unit has a nozzle for applying the fluid.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The subject matter of the invention will be described in greater detail by way of example based on an embodiment variant shown in the drawings. In the drawings

[0020] FIG. 1 shows a schematic view of a device for carrying out the method according to the invention,

[0021] FIG. 2 shows a detail view of a stamping stage of the device shown in FIG. 1 in a different movement position,

[0022] FIG. 3 shows a top view of the detail view in FIG. 2, and

[0023] FIG. 4 shows a top view of FIG. 2 showing a differently shaped sheet metal part.

WAY TO IMPLEMENT THE INVENTION

[0024] FIG. 1 schematically depicts a device 1 for carrying out the method according to the invention. This device 1 is used for stacking stamped-out sheet metal parts 2 to form lamination stacks 3. For this purpose, an electrical steel strip 5 that has a heat-hardened hot-melt adhesive varnish layer 8—which in the exemplary embodiment is applied to its entire area—on one of its flat sides 6, 7 is unwound from a coil 4; a layer of a hot-melt adhesive varnish can naturally also be provided on both flat sides 6 and 7, likewise over the entire area.

[0025] Such a thermosetting or heat-hardened hot-melt adhesive varnish is also referred to as a “backlack”. For example, the hot-melt adhesive varnish can be epoxy resin-based. Preferably, the hot-melt adhesive varnish is a bisphenol-based epoxy resin system with a for example dicyandiamide-based hardener. In particular, the above-mentioned hot-melt adhesive varnish can be a bisphenol-A/epichlorohydrin resin system with dicyanamide as a hardener. This two-stage hardening epoxy resin system on the electrical steel strip is in the B state. The partially cross-linked hot-melt adhesive varnish is still reactive. When heat is supplied, the hot-melt adhesive varnish in the B state reacts further and can thus be converted into the fully cross-linked C state, which is also referred to as baking. This partially cross-linked hot-melt adhesive varnish layer typically has a thickness of a few micrometers.

[0026] Multiple sheet metal parts 2 are separated from the hot-melt adhesive varnish-coated electrical steel strip 5 with the aid of a stamping tool 9; it should in general be mentioned that this separating procedure can be a detaching procedure, for example a cutting out, cutting off, notching, trimming, dividing, pushing out, etc. As can also be inferred from FIG. 1, the stamping tool 9, for example a progressive stamping tool or follow-on composite tool here, carries out a detaching procedure with multiple strokes. The stamping tool 9 can thus have more than two stamping stages—which is not shown in the figures.

[0027] With a first stamping stage 10, the electrical steel strip 5 is prepared for a punching-out procedure—for example in that a part is cut out in order to thus form notches on the lamination stack 3. This preprocessing of the electrical steel strip also prepares the sheet metal strip for the separation of the sheet metal parts 2.

[0028] With a second stamping stage 11, the sheet metal parts 2 are then separated from the electrical steel strip 5 by means of a detaching procedure. Such a detaching procedure can—for example—be a cutting out, cutting off, notching, trimming, dividing, pushing out, etc.

[0029] Both stamping stages 10 and 11 have punches 12 and 13, which are part of the upper tool 9.1 of the stamping tool 9. The punches 12 and 13 cooperate with the respective matrixes 14, 15 of the lower tool 9.2 of the stamping tool 9.

[0030] With the aid of the stamping stage 11, the separated sheet metal parts 2 are pushed by the pressure of the upper tool 9.1 into a stacking unit 16 and stacked therein. For this purpose, the stacking unit 16 has a guide in the lower tool 9.2. A brace 10 that is not shown in detail is also provided in the guide.

[0031] The stacking unit 16 can be actively heated, for example in order to thermally activate the preferably latent hot-melt adhesive varnish layer 8 and produce an adhesive bond or integral bond between the sheet metal parts 2—i.e. to convert the thermosetting hot-melt adhesive varnish layer into the C state. In this connection, it is conceivable for this integral bonding, which is also referred to as a baking of the sheet metal parts 2 into a lamination stack 3, to take place in a different tool or in a furnace or by means of a type of energy supply other than heat, which is not shown.

[0032] In order to make the sheet metal parts 2, which exit the stacking unit 16 and are bonded to each other, easier to divide into lamination stacks 3, the electrical steel strip 5 is prepared by applying a parting compound 17—specifically onto the part of the hot-melt adhesive varnish layer 8 on the sheet metal part 2 that is supposed to be the first or last sheet metal part 2 of a lamination stack 3. In the exemplary embodiment, a flowing fluid 17.1, namely a liquid, is used as the parting compound 17.

[0033] By contrast with the prior art, this application takes place in the second stamping stage 11—namely in the one that detaches the sheet metal part 2 from the electrical steel strip 5 and thus carries out the separating procedure. According to the invention, the punch 13 of the second stamping stage 11 applies the fluid 17.1 onto the electrical steel strip 5 and/or separated sheet metal part 4. Preferably, this fluid is applied onto the hot-melt adhesive varnish layer 8. It is also conceivable, though, to apply this fluid to an uncoated flat side of the electrical steel strip 5 and/or sheet metal part 2 or also to apply a different coating to the electrical steel strip 5 and/or sheet metal part 2.

[0034] For this purpose, the punch 13 has a unit 18, which is provided in a recess 19 on the punch bottom 13.1— namely an inward curvature or hollow of the punch bottom 13.1— and applies the fluid 17.1 onto the hot-melt adhesive varnish layer 8 using a contact printing method. Generally speaking, the fluid 17.1 is applied onto the electrical steel strip 5 and/or sheet metal part 2 so that it is then positioned between two stacked sheet metal parts 2.

[0035] A pressure stamp 20, which is visible in FIG. 2 and is also partially visible in a cutaway view in FIG. 3, is saturated—or simply wetted—with the fluid 17.1 and is pressed against the hot-melt adhesive varnish layer 8. For this purpose, the pressure stamp 20 is moved relative to the punch 13, specifically is slid in linear fashion toward the electrical steel strip 5. In order to impregnate the punch 13 with the fluid, it can be embodied as a printing pad or felt.

[0036] As can also be inferred from FIGS. 2 and 3, this parting compound 17 is applied as the sheet metal part 2 is being separated—or in the exemplary embodiment cut out—by the punch 13. As a result, the circumferential cutting edge 13.2 of the punch 13 seals off the contact printing, which prevents the parting compound 17 from escaping. As a result, a sort of cavity forms between the punch bottom 13.1 and the circumferential cutting edge 13.2, which facilitates the contact printing and also ensures a particularly precise printing. This ensures a high degree of reproducibility in order to provide the fluid 17.1 only onto the desired area F.

[0037] The same is true for the sheet metal part 2, which according to FIG. 4 is shaped differently, for example as a rotor. Here, too, the unit 18 provides the fluid 17.1 only on the desired area F.

[0038] In electric machines, for example, the lamination stacks 3 can be used as stators or rotors. But other applications for lamination stacks of this kind are also conceivable, for example when they are used as iron cores for transformers, coils, etc.