WELDING ELECTRODE, METHOD, AND DEVICE FOR WELDING SANDWICH PANELS

Abstract

A welding electrode may comprise a welding electrode body and a welding electrode cap that is connected or connectable to the welding electrode body for making contact between the welding electrode and a component for producing a welded connection. The problem of achieving an efficient heating of the sandwich sheet to be welded in a compact layout with the fewest possible modifications of the welding electrodes used heretofore is solved in that an electrically conductive resistance element integrated, or which can be integrated, in the welding electrode and which is connected or connectable in an electrically-conductive manner to the welding electrode body and the welding electrode cap is provided for the heating of the component. Furthermore, a method and a device with the welding electrode and a use are disclosed.

Claims

1.-15. (canceled)

16. A welding electrode comprising: a welding electrode body; a welding electrode cap that is connected or connectable to the welding electrode body and is configured to make contact with a component to produce a welded connection; and an electrically conductive resistance element for heating the component, wherein the electrically conductive resistance element is integrated or configured to be integrated in the welding electrode, wherein the electrically conductive resistance element is connected or connectable in an electrically conductive manner to the welding electrode body and the welding electrode cap.

17. The welding electrode of claim 16 wherein the electrically conductive resistance element is integrated or configured to be integrated in the welding electrode in a region intended to contact the component.

18. The welding electrode of claim 16 wherein the electrically conductive resistance element is integrated or configured to be integrated in the welding electrode body.

19. The welding electrode of claim 16 wherein the electrically conductive resistance element is integrated or configured to be integrated in the welding electrode cap.

20. The welding electrode of claim 16 further comprising a first material for conducting a welding current, wherein an electrical resistivity of the electrically conductive resistance element is greater than an electrical resistivity of the first material for conducting the welding current.

21. The welding electrode of claim 20 wherein at least one of the welding electrode body or the welding electrode cap comprise the first material for conducting the welding current.

22. The welding electrode of claim 21 wherein the first material is copper or a copper alloy.

23. The welding electrode of claim 16 further comprising an electrically conductive welding electrode jacketing that at least partly surrounds the welding electrode body and is electrically insulated from the welding electrode body.

24. The welding electrode of claim 23 wherein the electrically conductive welding electrode jacketing is comprised of metal.

25. The welding electrode of claim 23 wherein the electrically conductive welding electrode jacketing is comprised of copper or a copper alloy.

26. The welding electrode of claim 23 further comprising an electrical insulation that at least partly surrounds the welding electrode body, wherein the electrical insulation is disposed between the electrically conductive welding electrode jacketing and the welding electrode body.

27. The welding electrode of claim 23 wherein the welding electrode body is connected or connectable in an electrically conductive manner to the welding electrode jacketing across the electrically conductive resistance element and the welding electrode cap.

28. The welding electrode of claim 16 wherein the electrically conductive resistance element comprises metal, wherein an electrical resistivity of the electrically conductive resistance element is larger than an electrical resistivity of copper.

29. The welding electrode of claim 16 wherein the welding electrode body comprises cooling channels for cooling the welding electrode.

30. A method for resistance welding a metallic component to a sandwich sheet that comprises a thermoplastic layer disposed between two metallic cover layers, the method comprising: heating a region of the sandwich sheet to be welded such that the thermoplastic layer softens; displacing the softened thermoplastic layer in the region by pressing together the two metallic cover layers; and welding the two metallic cover layers and the metallic component together by a flow of electric current in a first circuit through a first welding electrode disposed on a side of the sandwich sheet and a second welding electrode disposed on a side of the metallic component, wherein the first welding electrode comprises a welding electrode body, a welding electrode cap that is connected or connectable to the welding electrode body and is configured to make contact with the metallic component to produce a welded connection, and an electrically conductive resistance element for heating the metallic component, wherein the electrically conductive resistance element is integrated or configured to be integrated in the first welding electrode, wherein the electrically conductive resistance element is connected or connectable in an electrically conductive manner to the welding electrode body and the welding electrode cap, wherein heating the region of the sandwich sheet to be welded is performed by way of a current flow in a second circuit comprising the welding electrode body, the electrically conductive resistance element, and the welding electrode cap of the first welding electrode.

31. A device for resistance welding a metallic component to a sandwich sheet that comprises a thermoplastic layer disposed between metallic cover layers, the device comprising: a first welding electrode positionable on a side of the sandwich sheet, wherein the first welding electrode comprises a welding electrode body, a welding electrode cap that is connected or connectable to the welding electrode body and is configured to make contact with the metallic component to produce a welded connection, and an electrically conductive resistance element for heating the metallic component, wherein the electrically conductive resistance element is integrated or configured to be integrated in the first welding electrode, wherein the electrically conductive resistance element is connected or connectable in an electrically conductive manner to the welding electrode body and the welding electrode cap; a second welding electrode positionable on a side of the metallic component; a first circuit configured to pass a welding current across the first and second welding electrodes; and means for displacing the thermoplastic layer of the sandwich sheet from a region of the sandwich sheet to be welded, wherein a second circuit comprises the welding electrode body, the electrically conductive resistance element, and the welding electrode cap of the first welding electrode, wherein the region of the sandwich sheet to be welded can be heated by passing current through the second circuit.

Description

[0040] Furthermore, the invention shall be explained more closely by means of exemplary embodiments in connection with the drawing. The drawing shows:

[0041] FIG. 1a, in longitudinal section, a schematic exploded representation of a first exemplary embodiment of a welding electrode according to the invention without the welding electrode cap;

[0042] FIG. 1b, in longitudinal section, a schematic representation of the first exemplary embodiment of a welding electrode including the welding electrode cap;

[0043] FIG. 2a, in longitudinal section, a schematic exploded representation of a second exemplary embodiment of a welding electrode according to the invention without the welding electrode cap;

[0044] FIG. 2b, in longitudinal section, a schematic representation of the second exemplary embodiment of a welding electrode including the welding electrode cap;

[0045] FIG. 3, a schematic representation of an exemplary embodiment of a device according to the invention for carrying out an exemplary embodiment of a method according to the invention;

[0046] FIG. 4a, a magnified view of the region to be welded making use of the welding electrode from FIG. 1;

[0047] FIG. 4b, a magnified view of the region to be welded making use of the welding electrode from FIG. 2.

[0048] FIG. 1a first of all shows in longitudinal section a schematic exploded representation of a first exemplary embodiment of a welding electrode according to the invention without the welding electrode cap. The welding electrode 1 comprises a welding electrode body 2. This is designed as a sleeve, substantially elongated, with a first end 4 and a second end 6. At its first end 4 the welding electrode body 2 comprises a recess 7 for receiving an electrically conductive resistance element 8. The resistance element 8 and the seat 7 are adapted to each other, so that the resistance element 8 can be integrated in the welding electrode body 2 and connected in electrically conductive manner to the welding electrode body 2.

[0049] The welding electrode body 2 in this case is made from a first material, a copper alloy, for conducting a welding current. The resistance element 8 is made of tungsten and comprises an electrical resistivity which is thus greater than the first material of the welding electrode body 2. Thus, the resistance element 8 comprises a greater electrical resistivity than that of copper.

[0050] The welding electrode 1 furthermore comprises an electrically conductive welding electrode jacketing 10, at least partly surrounding the welding electrode body 2 and electrically insulated from the welding electrode body 2. The electrically conductive welding electrode jacketing 10 consists of metal, in this case, of a copper alloy such as brass. For the insulation, the welding electrode 1 comprises between the electrically conductive welding electrode jacketing 10 and the welding electrode body 2 an electrical insulation 12 at least partly surrounding the welding electrode body 2. The welding electrode jacketing 10 furthermore comprises a connection region 14 in the region of the second end 6 of the welding electrode body 2 for attachment of a current return.

[0051] For the cooling of the welding electrode 1, the welding electrode body 2 comprises cooling channels 16, which substantially extend from the second end 6 to the first end 4 along the length of the welding electrode body 2.

[0052] FIG. 1b shows in longitudinal section a schematic representation of the first exemplary embodiment of a welding electrode from FIG. 1, also representing a welding electrode cap 18. The welding electrode cap 18 like the welding electrode body likewise consists of the first material for conducting the welding current, in this case a copper alloy. The welding electrode cap 18 is designed for making contact with a component to be welded. Because the welding electrode body 2 is adapted to the resistance element 8 and the resistance element 8 is integrated in the welding electrode body 2, the welding electrode body 2 with the resistance element 8 for the welding electrode cap 18 behaves like a standard welding electrode body. In this way, it is possible to use a welding electrode cap 18 which does not need to be modified, despite the integration of the resistance element 8 in the welding electrode 1. Instead, the welding electrode cap 18 can be mounted as usual on the welding electrode body 2 in the direction of the arrow. For this, the welding electrode cap 18 comprises a recess 19, in which the welding electrode body 2 can be introduced by its first end 4 with the resistance element 8.

[0053] The welding electrode cap 18 is designed so that it can be connected in electrically conductive manner to the resistance element 8 integrated in the welding electrode body 2 and the welding electrode jacketing 10.

[0054] FIG. 2a shows in longitudinal section a schematic exploded representation of a second exemplary embodiment of a welding electrode 1′ according to the invention without the welding electrode cap. The welding electrode 1′ here is designed similar to the welding electrode 1. Accordingly, reference is made to the description of the welding electrode 1. In contrast to the welding electrode 1, however, the welding electrode 1′ comprises no resistance element.

[0055] As shown in FIG. 2b, the resistance element 8 is integrated in the welding electrode cap 18′. FIG. 2b shows in longitudinal section a schematic representation of the second exemplary embodiment of a welding electrode 1′ including the welding electrode cap 18′. Like the first welding electrode cap 18, the welding electrode cap 18′ apart from the resistance element 8 consists of a copper alloy. The resistance element 8, in turn, consists of tungsten, a material with higher electrical resistivity. Because the welding electrode cap 18′ is adapted to the resistance element 8 and the resistance element 8 is integrated in the welding electrode cap 18′, the welding electrode cap 18′ with the resistance element 8 for the welding electrode body 2′ behaves like a standard welding electrode cap. In this way, a welding electrode body 2′ can be used which despite the integration of the resistance element in the welding electrode 1′ does not need to be modified. Instead, the welding electrode cap 18′ can be mounted as usual on the welding electrode body 2′.

[0056] Like the welding electrode cap 18, the welding electrode cap 18′ is designed so that it can be connected in electrically conductive manner to the welding electrode body 2 and the welding electrode jacketing 10.

[0057] Furthermore, FIG. 2b shows another exemplary embodiment of a welding electrode cap 18″. The resistance element 8 here is integrated in the welding electrode cap 18″ such that the resistance element 8 can make contact with the component to be welded.

[0058] FIG. 3 shows a schematic representation of an exemplary embodiment of a device 20 according to the invention for carrying out an exemplary embodiment of a method according to the invention.

[0059] Here, for example, the welding electrodes 1, 1′ shown in FIGS. 1 and 2 can be used. The device 20 is designed for the resistance welding of a sandwich sheet 22 to at least one other metallic component 24. The sandwich sheet 22 comprises a thermoplastic plastic layer 22c arranged between metallic cover layers made preferably of steel 22a, 22b. The other component 24 is likewise fashioned as a metal sheet, such as a steel sheet. The device 20 comprises a first welding electrode 26a arranged on the side of the sandwich sheet 22 and a second welding electrode 26b arranged on the side of the other metallic component 24. As the first welding electrode 26a, an exemplary embodiment of a welding electrode according to the invention is used, such as one of the welding electrodes 1 or 1′ as shown in FIG. 1 or FIG. 2. For the second welding electrode 26b, likewise a welding electrode as shown in FIG. 1 or 2 can be used, but the second welding electrode does not need to comprise any electrically conductive resistance element.

[0060] Furthermore, the device 20 comprises with a current source 28 and electrical conductors 30 means of providing a first circuit 32, which lead a welding current I.sub.S at least across the first welding electrode 26a and the second welding electrode 26b. The first circuit 32 comprises the current source 28, the electrical conductors 30, the first welding electrode 26a, the sandwich sheet 22, the other component 24 and the second welding electrode 26b. Furthermore, the device 20 with the first welding electrode 26a comprises means of displacing the plastic layer 22c of the sandwich sheet 22 from the region of the sandwich sheet 22 to be welded.

[0061] Furthermore, a second circuit 34 is provided for conducting a preheating current I.sub.V. The second circuit 34 comprises the current source 28, the electrical conductors 30, the first welding electrode 26a, the electrical conductors 36 and the second welding electrode 26b. In regard to the first welding electrode 26a, the second circuit 34 comprises the welding electrode body, the resistance element, the welding electrode cap and the welding electrode jacketing of the first welding electrode 26a (also see FIG. 4), so that the region of the sandwich sheet 22 to be welded can be heated by a current flow in the second circuit 34. Alternatively, it is conceivable for the second circuit 34 to also return directly to the current source 28 for example from the first welding electrode 26a by means of the electrical conductors 36 without using the second welding electrode 26b.

[0062] With the device 20, a method for the resistance welding of the sandwich sheet 22 to the other metallic component 24 can be carried out. In the method, the region of the sandwich sheet 22 to be welded is heated such that the thermoplastic plastic layer 22c softens and is displaced from the welding region by pressing together the cover layers 22a, 22b. For this, means of applying force to the welding electrodes can be provided, such as welding tongs. The region of the sandwich sheet 22 to be welded is heated by a preheating current flow I.sub.V in the second circuit 34. As already represented, the second circuit 34 comprises the welding electrode body, the resistance element, the welding electrode cap and the welding electrode jacketing of the first welding electrode 26a. Thanks to the electrical resistivity of the resistance element, the current flow through the resistance element can heat the first welding electrode 26a and thus the region of the sandwich sheet 22 to be welded, so that the thermoplastic plastic layer 22c softens and can be displaced.

[0063] Now, since an electrically conductive connection exists between the welding electrodes 26a, 26b across the components 22, 24, the cover layers 22a, 22b can afterwards be welded to each other with the other component 24 by an electrical welding current flow I.sub.S in the first circuit 32 across the first welding electrode 26a and the second welding electrode 26b.

[0064] FIG. 4a shows a magnified view of the region to be welded making use of the welding electrode 1 from FIG. 1. The preheating current I.sub.V flows in the second circuit 34 across the electrical conductor 36 and the connection region 14 of the welding electrode jacketing 10. Thanks to the contacting of the welding electrode cap 18 with the welding electrode jacketing 10, furthermore the preheating current I.sub.V flows across the welding electrode cap 18, the resistance element 8 integrated in the welding electrode body and the welding electrode body 2. The increased electrical resistance of the resistance element 8 and the transition resistance between the resistance element 8 and the welding electrode cap 18 or the welding electrode body 2 produces the necessary heat to locally heat the plastic layer 22c.

[0065] FIG. 4b shows a magnified view of the region to be welded making use of the welding electrode 1′ from FIG. 2. Here as well, the resistance element 8, being integrated here in the welding electrode cap 18′, is connected on the one hand across the welding electrode cap 18′, the welding electrode jacketing 10, the connection region 14 and the electrical conductor 36 and on the other hand across the welding electrode body 2′ and the electrical conductor 30 to the current source 28. In this case as well, the increased electrical resistance of the resistance element 8 and the transition resistance between the resistance element 8 and the welding electrode cap 18′ or the welding electrode body 2′ produces the necessary heat to locally heat the plastic layer 22c.