RESISTANCE WELDING PROCESS

Description

[0001] The subject matter relates to a resistance welding method and a device for resistance welding, as well as a terminal produced by such a method.

[0002] Resistance welding of electrical conductors is well known. Two workpieces to be welded are placed on top of each other at an interface, facing each other. Welding electrodes are then applied to both sides of the interface, and a welding current flows between the two electrodes. The welding current can be constant, pulsed, or set at a desired frequency.

[0003] Due to the increased contact resistance at the interface between the workpieces, increased ohmic loss and thus Joule heat occur between the workpieces. This leads to melting of the workpiece materials at the interface, so that they subsequently form an intermetallic bond. After cooling, a material-to-material bond is formed. US 2003 / 226823 A1 discloses the preamble of claim 1.

[0004] Depending on the material and thickness of the workpieces, they may melt not only at their interfaces, but also across a wider area. This leads to the materials flowing apart at the joint. To prevent this, so-called side shifters are used, which are moved laterally to the workpieces before welding. In previous processes, the side shifters rested on the sides of the side surfaces adjacent to the surfaces to be welded.

[0005] A workpiece to be welded, such as a flat product or flat part, is placed on a first electrode. A conductor to be welded is placed on the surface of the workpiece opposite the electrode. Side shifters are moved up to the side walls of the conductor, which are adjacent to the surface to be welded. The side walls thus form boundaries for the materials melting during welding. The second electrode is then moved between the side shifters up to the conductor to be welded, and the resistance welding process described above takes place.

[0006] The problem with the known method, however, is that the second electrode, which is moved between the side slides, must have a width that corresponds to the distance between the side slides. This distance between the side slides is defined by the width of the conductor to be welded. If the electrode were narrower than the distance between the side slides, a cavity would form between the second electrode and the side slides. This cavity would be filled by the molten material, and the molten material would cause the side slides to stick to the workpiece and the cable. This is undesirable.

[0007] The problem described above requires a welding tool to be specifically set up and prepared for each conductor geometry and terminal width. This results in significant setup times and costs.

[0008] The object of the invention was therefore to provide a resistance welding process that can be used universally for a wide variety of conductors and terminal geometries.

[0009] This object is achieved by a resistance welding method according to claim 1.

[0010] In the present invention, it is proposed that a metallic conductor be welded to a metallic terminal. The metallic conductor may be made of a metallic material. The metallic material may, in particular, be copper or a copper alloy. It is also possible for the metallic material to be aluminum or an aluminum alloy.

[0011] The terminal (also referred to as the workpiece) is also made of a metallic material. Preferably, the terminal is made of one of the metallic materials mentioned above. Particularly preferably, the terminal is made of the same metallic material as the metallic conductor.

[0012] Two electrodes are provided for welding. The metallic terminal, which is in particular a flat part or flat piece, in particular with a polygonal cross-section, preferably a rectangular or square cross-section, is placed with a first surface onto the first electrode. This can result in direct contact between the first surface and the first electrode. It is also possible to provide a conductive paste between the first surface and the first electrode to ensure the lowest possible contact resistance at the interface between the first surface and the first electrode.

[0013] The metallic terminal has a recess on a second surface opposite the first surface. This recess is preferably a depression in the second surface. The recess has a bottom. The recess can be formed as a blind hole, groove, or fold. The bottom can be formed as a groove base. The recess is arranged on the second surface of the terminal. This second surface lies on the side opposite the first surface. The first and second surfaces preferably run parallel to one another.

[0014] A conductor is inserted into the recess. In particular, a conductor end, in particular a stripped conductor end, is inserted into the recess. The conductor is preferably placed with one surface on the bottom of the recess. Direct contact preferably occurs between the surface of the conductor and the bottom of the recess. The conductor is preferably arranged centrally in the recess, i.e., the conductor is preferably arranged in the recess at equal distances from the side edges of the recess.

[0015] As mentioned, the recess has a base. Starting from the base, at least two side walls extend in the recess to the second surface. An edge forms between one side wall and the second surface. At least two opposing edges are arranged on a recess. Preferably, three adjacent edges are provided on the recess, and the recess extends beyond a side edge of the terminal into a side wall recess. In a plan view, the recess in the terminal is then U-shaped.

[0016] Once the conductor is inserted into the recess, it is proposed that at least two opposing side sliders be placed on the second surface to the side of the recess. It is important that, in contrast to the prior art, the side sliders are not placed on the opposing side walls of the conductor, but rather on the surface in which the recess is formed. Thus, before the actual welding process, the conductor is placed in the recess on the bottom of the recess, and the side sliders rest on the surface in which the recess is formed.

[0017] Subsequently, a second electrode is moved, preferably perpendicularly, toward the first electrode and placed on the conductor. This creates an electrically conductive path between the first electrode and the second electrode via the terminal and the conductor. An interface forms between the terminal and the conductor at the bottom of the recess.

[0018] To weld, a current is passed through the two electrodes. This current flows from the first electrode to the second electrode (or vice versa, depending on the counting arrow system). At the interface between the conductor and the terminal, an increased ohmic resistance will occur, resulting in Joule heating, which causes the materials of the conductor and terminal to melt, at least at the interface. After cooling, the molten materials form an intermetallic bond, forming a material bond.

[0019] Due to the fact that the conductor is inserted into the recess, the side walls of the recess form natural boundaries for the materials that are plasticized during the welding process. The molten materials, in particular the molten material of the conductor, flow at least partially into the recess. Since the side walls of the recess form a boundary, according to the invention, the side slides do not come into contact with the plasticized material, thus preventing adhesion.

[0020] Preferably, the volume of the recess is at least as large as, and preferably larger than, the volume of the conductor portion placed in the recess, in particular the volume of the material of the conductor portion placed in the recess. Any air inclusions in the conductor are disregarded. If the volumes are approximately equal, the conductor material remains completely within the recess even upon complete melting and does not flow over the edges of the recess onto the second surface. This prevents the side slides resting on the second surface from coming into contact with the plasticized material of the conductor and / or terminal and sticking to it after cooling.

[0021] Since the side shifters can rest on the second surface, their spacing is variable. This has the advantage that the spacing of the side shifters can be adjusted to the second electrode, or the clear width of the side shifters can be adjusted to the width of the second electrode.

[0022] Even if plasticized material flows over the edge of the recess and comes into contact with the side shifters, the contact surface is significantly reduced compared to conventional welding processes. Contact with the molten material only occurs in the transition area between the side shifter and the second surface. Any adhesion that may occur can be broken by applying slight force without damaging the side shifters. Furthermore, there is little or no adhesion of the molten conductor material to the side shifter.

[0023] According to one embodiment, it is proposed that the conductor is at least partially melted (plasticized) during welding. As a result of the melting (plasticizing), the conductor material can flow into the recess or be distributed within the recess. If the volume of the recess is sufficiently large, the recess can completely accommodate the conductor material and molten material is prevented from passing over the edge onto the second surface and thus onto the side slides. However, due to the fact that the side slides only rest on the second surface, it is ensured that even if molten material does reach the second surface, adhesion of the side slides is essentially avoided. The contact surface between the molten material and the side slide is significantly reduced compared to conventional methods.

[0024] According to one embodiment, it is proposed that the conductor protrudes beyond the edge formed between the recess and the second surface prior to welding. The conductor is preferably arranged in the recess at a distance from the side walls of the recess. Only through welding and the associated plastic deformation can the conductor be distributed within the recess.

[0025] The contact pressure exerted by the second electrode on the conductor toward the bottom of the recess causes the conductor to be plastically deformed and pressed into the recess. Thus, not only the plasticizing process, but also the plastic deformation of the conductor due to the contact pressure of the second electrode is responsible for ensuring that the conductor is essentially adapted to the cross-sectional profile of the recess after welding. In this process, a plasticized part of the conductor and a non-plasticized part of the conductor are pressed into the recess in such a way that the cross-section of the conductor essentially corresponds to the cross-section of the recess.

[0026] According to one embodiment, it is proposed that the conductor is arranged flush with the second surface in the recess after welding. If the volume of the recess and the volume of the conductor arranged in the recess are substantially identical, it can be ensured that the conductor, when welded, is flush with the second surface. This leads to particularly good processability of the connection. It is also possible for the volume of the conductor inserted into the recess to be smaller than the volume of the recess. In this case, it can happen that after welding the conductor is arranged offset into the recess. This means that a step results between the surface of the conductor and the second surface and the conductor lies completely in the recess.Both variants, the flush arrangement and the arrangement offset into the recess, result in a lower installation height of the connection between conductor and terminal than in conventional methods, which is particularly advantageous for confined installation spaces.

[0027] According to the invention, it is proposed that the side sliders are moved parallel to the second surface over the second surface into the region of the edge of the recess. In this case, a distance is still ensured between the edge of the recess and the surface of the side sliders facing the conductor. However, according to an unclaimed alternative, it is also possible for the side sliders to be moved directly to the edge of the recess. In the latter case, although there is a greater risk that plasticized conductor material will come into contact with the side sliders, this prevents the second surface of the terminal from becoming contaminated by melted and solidified conductor material. The side sliders prevent the conductor material from coming into contact with the second surface during welding.

[0028] According to one embodiment, it is proposed that the clear width between the side slides before welding essentially corresponds to the width of the second electrode. This means that the side slides are moved toward each other such that the distance between the facing walls of the side slides corresponds to the distance between the side walls of the electrode. The electrode can then be moved between the side slides with virtually no play or with a clearance of less than one millimeter, and the welding can be performed.

[0029] According to one embodiment, it is proposed that the second electrode be pressed against the conductor with a force during welding. As already explained, the conductor is not only plasticized during welding, but also plastically deformed by the contact force of the second electrode. The plastic deformation occurs due to the contact pressure and the force with which the second electrode is pressed against the conductor. This plastic deformation allows the conductor to be forced into the shape of the recess. After the welding process, the conductor thus lies in the recess.

[0030] According to one embodiment, it is proposed that at the start of welding, the second electrode is pressed against the conductor with a first force. This first force is intended to ensure that the conductor and the terminal form a directly contacting interface in the region of the bottom of the recess. At this interface, the current can generate sufficiently high Joule heat to plasticize the materials of the conductor and / or terminal. After welding has begun, the electrode is then pressed against the conductor with a second force that is greater than the first force. This continued pressure plastically deforms the conductor and / or terminal, which is plasticizing at the interface, so that the conductor adapts to the recess. The second force is applied during the welding process.

[0031] According to one embodiment, it is proposed that after a holding time, after welding, the second electrode is lifted from the conductor. The holding time is preferably selected such that the molten material of the conductor and / or terminal has solidified again. The duration depends, among other things, on the material used, the surface of the connection between the two workpieces, the level of the welding current and / or the duration of the welding process and can be selected accordingly. The holding ensures that a clean, defect-free material-to-material connection is formed at the interface. The interface in which the material bond is formed is not mechanically stressed by the holding during solidification, so that a defect-free material-to-material connection is created.

[0032] According to one embodiment, it is proposed that the conductor is a stranded conductor or a braided conductor.

[0033] As already mentioned, the conductor undergoes plastic deformation during welding. This plastic deformation results in the conductor's cross-section being adjusted to the cross-section of the recess after welding, which is identical to the cross-section of the recess. For example, before welding, the conductor may have a round or oval cross-section. In the recess area, this cross-section may be polygonal after welding, particularly square or rectangular.

[0034] By plastically deforming the conductor, a circular conductor can be firmly bonded to a flattened portion in the recess. This reduces the height of the connection compared to previous methods.

[0035] According to one embodiment, it is proposed that the recess extends from a side edge of the terminal into a central region of the terminal. This can be imagined as a groove that extends from a side wall of the terminal to the center of the terminal, but is not continuous. In a top view, the recess is then U-shaped. The groove can, of course, also be continuous.

[0036] According to one embodiment, it is proposed that the side shifter be made of an electrically non-conductive material. This ensures that, in the event that the second electrode touches the side shifter, a current cannot flow through the side shifter into the terminal, thus preventing a weld from forming at the interface between the side shifter and the terminal.

[0037] According to one embodiment, it is proposed that, after welding, a through-hole is formed through the conductor and the terminal. This can be done, in particular, by drilling or punching. The through-hole can, in particular, be provided at least partially in the area of ​​the weld.

[0038] Because the conductor is inserted into the recess, particularly with its stripped end, and is plastically deformed and plasticized during welding, edge preparation of the conductor is unnecessary. In particular, it is not necessary to straighten the stripped end edge of the conductor by cutting or to align the strands of a conductor. This makes the manufacturing process particularly simple.

[0039] According to one embodiment, it is proposed that the width of the recess, viewed from above, be larger than the width of the unwelded conductor. Due to the plastic deformation and plasticization during welding, the conductor can be pressed onto the ground. This allows a particularly large contact surface to be formed between the conductor and the terminal, which significantly reduces the contact resistance in the welded state.

[0040] According to one embodiment, it is proposed that, prior to welding, an end edge of the conductor be placed against a side wall of the recess. In particular, the end edge of the conductor is placed against the side edge of the recess, which is oriented toward the side wall from which the conductor is inserted into the recess.

[0041] By deforming the conductor, it can be flattened in the area of ​​the welding, thus achieving a low installation height.

[0042] The subject matter is explained in more detail below using a drawing showing exemplary embodiments. The drawing shows: Fig. 1a-c show a welding process according to an embodiment; Fig. 2a-d show top views of welded conductors; Fig. 3 shows a terminal for welding with a recess according to an embodiment; Fig. 4 shows a conductor for welding according to an embodiment.

[0043] Fig. 1a shows a schematic representation of a terminal 2 which is to be welded to a conductor 4.

[0044] Terminal 2 is in Fig. 3 shown in more detail. It can be seen that the terminal 2 has a rectangular cross-section with a recess 6. The recess 6 extends from an end face 2a to a central region 2b of the terminal 2. As can be seen, the recess 6 has a base 6a and side walls 6b. The terminal has an upper surface, and the recess 6 forms edges 6b' in the upper surface. At the edges 6b', the recess 6 recesses back from the upper surface of the terminal 2.

[0045] In this terminal 2 a conductor 4, as shown in the Fig. 4 shown. The conductor 4 may have a stripped end 4b. The stripped end 4b is placed with its end face 4b' against a side wall 6b of the recess 6 and simultaneously placed on the base 6a.

[0046] This arrangement between Terminal 2 and Conductor 4 is in the Fig. 1a Furthermore, the Fig. 1a It can be seen that the terminal 2 is placed on a first electrode 8.

[0047] A second electrode 10 is provided on the side opposite the first electrode 8. The electrodes 8, 10 can be moved toward and away from each other. The electrodes 8, 10 are made of an electrically conductive material. The same applies to terminal 2 and conductor 4. A material (also called a working material) can be, for example, copper or a copper alloy. Aluminum or an aluminum alloy can also be provided. Other non-ferrous metals can also be used as a working material.

[0048] After the terminal 2 has been placed on the electrode 8, the conductor 4 can be inserted into the recess 6 on the side facing away from the electrode and placed on the base 6a. As shown in the Fig. 1a As can be seen, the conductor 4 is arranged centrally in the recess 6.

[0049] On the upper surface facing away from the electrode 8, side sliders 12 are placed on the terminal 2. The side sliders 12 are pressed against the upper surface of the terminal 2 with a pressure force and moved in the direction of the edges 6b'.

[0050] As in the Fig. 1a As can be seen, the distance between the side slides 12, i.e. their clear width, is sufficiently large so that the electrode 10 can be moved between the side slides 2 towards the conductor.

[0051] After the side shifters 12 are placed, as shown in the Fig. 1b shown, the electrode 10 is moved with a force F in the direction of the electrode 8. The electrode 8 presses the conductor 4 onto the terminal 2, in particular into the recess 6. A current flow is activated between the electrodes 10, 8, which leads to Joule heat at the interface between terminal 2 and conductor 4 and thus to at least partial melting of the materials.

[0052] The force F causes the conductor 4 to be plastically deformed. The plasticized part together with the deformed conductor 4 can fill the recess 6. After the welding process and a holding time, the electrode 10 is moved away from the electrode 8 in direction 14, as shown in the Fig. 1c The conductor 4 is welded to the terminal 2. Here, as shown in the Fig. 1c As can be seen, the surface of the conductor 4 is flush with the upper surface of the terminal 2. However, it is also possible that the surface of the conductor 4 springs back into the recess 6.

[0053] Using the method shown, it is possible to connect terminals 2 to different conductors 4. Fig. 2a For example, the figure above shows a terminal 2 connected to a stranded conductor 4. It can be seen that, in a top view, the recess 6 is wider than the diameter of the unprocessed stranded conductor 4. This allows for a large contact surface between terminal 2 and conductor 4 in the area of ​​the recess 6. A through-hole or punching 16 can be provided in terminal 2.

[0054] Fig. 2a shows another example below with the only difference that conductor 4 is not a stranded conductor but a stranded braid.

[0055] Fig. 2b shows another possibility of a terminal 2, which is connected to conductors 4 as a braided wire in two recesses 6. In the area of ​​one of the recesses 6, a through-opening 16 can be provided through the conductor 4 and the terminal 2.

[0056] Fig. 2c shows a similar example, how Fig. 2a , whereby the through-opening 16 is not arranged exclusively in the area of ​​the terminal 2, but through the conductor 4 in the area of ​​the recess 6. This can apply to both stranded wires (above) and braided wires (below).

[0057] Finally, Fig. 2d one to Fig. 2b corresponding embodiment, but here the conductors 4 are formed as stranded conductors.

[0058] Using the method shown, it is possible to weld conductors together in a particularly advantageous manner without causing adhesions with side shifters in the area of ​​the weld. At the same time, the terminal surface around the weld seam is protected by the side shifters and is not contaminated. Bezugszeichenliste

[0059] 2Terminal 2aEnd face 2bCentral area 4Conductor 4aEnd 4b'End face 6Recess 6aBottom 6bSide wall 6b'Edge 10, 8Electrode 12Side shift 14Direction

Claims

1. Resistance welding method in which - a metallic conductor (4) is welded to a metallic terminal (2), wherein - the metallic terminal (2) is placed with a first surface onto a first electrode (8), - the metallic conductor (4) is placed on a bottom (6a) of a recess (6), wherein the recess (6) is arranged in a second surface opposite the first surface, characterized in that - at least two side sliders (12) are placed on the second surface lateral of the recess (6) wherein a distance is formed between an edge (6b') of the recess (6) and a surface of the side sliders (12) facing the conductor (4), and wherein the side slides (12) are moved in parallel to the second surface over the second surface into the region of the edge (6b') of the recess (6), a second electrode (10) is moved in the direction (14) of the first electrode (8) onto the conductor (4), and - the conductor (4) is welded to the terminal (2) in the region of the recess (6) by means of a current flowing between the first and the second electrode (8, 10), wherein the side walls (6b) of the recess (6) form a boundary for the material of the conductor (4) which is plasticized by the welding operation, and the side sliders (12) do not come into contact with the plasticized material.

2. Resistance welding method according to claim 1, characterized in - that the conductor (4) is at least partially plasticized during the welding.

3. Resistance welding method according to claim 1 or 2, characterized in - that the conductor (4) projects beyond the edge (6b'), which is formed between the recess (6) and the second surface, before welding.

4. Resistance welding method according to claim 1 or 2, characterized in - that the conductor (4) is arranged in the recess (6) flush with the second surface after welding, or that the conductor (4) is arranged offset into the recess (6) with respect to the second surface after welding.

5. Resistance welding method according to one of the preceding claims, characterized in - that the clear width between the side sliders (12) before welding essentially corresponds to the width of the second electrode (10).

6. Resistance welding method according to one of the preceding claims, characterized in - that during welding the second electrode (10) is pressed against the conductor (4) with a force, in particular - that at the start of welding the second electrode (10) is pressed against the conductor (4) with a first force and that after the start of and during welding the second electrode (10) is pressed against the conductor (4) with a second force which is greater than the first force.

7. Resistance welding method according to one of the preceding claims, characterized in - that after a dwell time after the welding, the second electrode (10) is lifted off from the conductor (4) and / or - that after a dwell time after the welding, the side sliders (12) are moved away from the recess (6).

8. Resistance welding method according to one of the preceding claims, characterized in - that the conductor (4) is a stranded conductor or a braided conductor.

9. Resistance welding method according to one of the preceding claims, characterized in - that the conductor (4) and / or the terminal (2) are formed from copper or a copper alloy and / or - that the side slider (12) is formed from an electrically non-conductive material.

10. Resistance welding method according to one of the preceding claims, characterized in - that the conductor (4) in the region of the recess (6) has a first conductor profile before welding and has a second conductor profile after welding, which is different from the first, in particular that the second conductor profile is matched to a cross-sectional profile of the recess (6).

11. Resistance welding method according to one of the preceding claims, characterized in - that the recess (6) extends from a side edge of the terminal (2) into a central region (2b) of the terminal (2).

12. Resistance welding method according to one of the preceding claims, characterized in - that after the welding, a through-opening is formed, in particular drilled or punched, through the conductor (4) and the terminal (2).

13. Resistance welding method according to one of the preceding claims, characterized in - that, in a plan view, the width of the recess (6) is greater than the width of the conductor (4).

14. Resistance welding method according to one of the preceding claims, characterized in - that prior to the welding, an end edge of the conductor (4) is placed against a side wall (6b) of the recess (6).

15. Resistance welding method according to one of the preceding claims, characterized in - that the conductor (4) is flattened in the area of the weld.