Resistance welding method

Abstract

The present invention relates to a resistance welding method, in which a metal conductor and a metal terminal are welded together, wherein the metal terminal (2) is placed on a first electrode (8) with a first surface, and the metal conductor (4) is placed on the bottom of a notch (6), wherein the notch is arranged in a second surface opposite to the first surface, at least two side sliders are placed on the second surface on the side of the notch, the second electrode (10) is moved onto the conductor in the direction of the first electrode, and the conductor is welded together with the terminal in the notch area by a current flowing between the first and second electrodes.

Description

Technical Field

[0001] The present invention relates to a resistance welding method and an apparatus for resistance welding, and a terminal produced by the method. Background Art

[0002] Resistance welding of electrical conductors is well known. In this process, two workpieces to be welded are placed one on top of the other at the interface with their surfaces facing each other. Welding electrodes are then placed on the workpieces on both sides of the interface and a welding current flows between the two electrodes. The welding current can be pulsed continuously or can be set to a desired frequency.

[0003] Due to the increased contact resistance at the interface between the workpieces, increased ohmic losses occur between the workpieces, which generates Joule heat. This causes the workpiece materials to melt at the interface, and then the workpieces form an intermetallic bond. After cooling, a material fit connection is formed.

[0004] Depending on the workpiece material and the material thickness, they melt not only at their interface, but also over a wider area. This leads to material flow at the joint. To avoid this, so-called side slides are used, which are guided laterally to the workpiece before welding. In previous methods, the side slides rest laterally on the side adjacent to the surface to be welded.

[0005] The workpiece to be welded, for example a flat product or a flat component, is placed on the first electrode. The conductor to be welded is placed on the surface of the workpiece opposite the electrode. The side slide is guided to the side wall of the conductor adjacent to the surface to be welded. In this way, the side wall forms a boundary for the molten material during welding. The second electrode is then moved between the side slides onto the conductor to be welded and the above-described resistance welding is then performed.

[0006] However, a problem with the known method is that the width of the second electrode moved between the side slides must correspond to the distance between the side slides. This distance between the side slides is determined by the width of the conductor to be welded. If the width of the electrode is smaller than the distance between the side slides, a cavity is formed between the second electrode and the side slides. This cavity is filled with molten material and can cause the side slides to stick to the workpiece and the conductor through the molten material. This is undesirable.

[0007] The above problems mean that soldering tools must be specially built and equipped for each conductor geometry and terminal width. This results in considerable preparation time and cost. Summary of the invention

[0008] It is therefore an object of the present invention to provide a resistance welding method which is universally applicable to different conductor and terminal geometries.

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

[0010] According to the present invention, it is suggested to weld the metal conductor and the metal terminal together. The metal conductor can be formed of a metal material. The metal material can be copper or a copper alloy in particular. The metal material can also be aluminum or an aluminum alloy.

[0011] The terminal (also referred to as workpiece) is also made of a metal material. The terminal is preferably made of one of the above-mentioned metal materials. It is particularly preferred that the terminal is made of the same metal material as the metal conductor.

[0012] Two electrodes are provided for welding. A metal terminal, in particular a flat component or a flat part, having a polygonal cross section, preferably a rectangular or square cross section, is placed with a first surface on the first electrode. The first surface can be in direct contact with the first electrode. A conductive paste can also be arranged between the first surface and the first electrode to ensure that the contact resistance at the interface between the first surface and the first electrode is as small as possible.

[0013] According to the present invention, the metal terminal has a notch on a second surface opposite to the first surface. The notch is preferably a depression in the second surface. The notch preferably has a bottom. The notch can be formed as a blind hole, a groove or a notch. The bottom can be formed as a groove bottom. The notch is located on the second surface of the terminal. The second surface is located on the side opposite to the first surface. The first surface and the second surface preferably extend parallel to each other.

[0014] In the present invention, the conductor is placed in the notch. In particular, a conductor end, in particular a conductor end that has been stripped of insulation, is placed in the notch. The conductor is preferably placed with one surface on the bottom of the notch. The surface of the conductor is preferably in direct contact with the bottom of the notch. The conductor is preferably arranged in the center of the notch, that is, the conductor is preferably arranged in the notch equidistant from the side edges of the notch.

[0015] As described above, the notch has a bottom. Starting from the bottom, at least two side walls in the notch extend to the second surface. An edge is formed between one side wall and the second surface. At least two edges opposite to each other are arranged on the notch. Preferably, three edges adjacent to each other are arranged on the notch, and the notch extends beyond the side edge of the terminal into the side wall of the notch. Then, from a top view, the notch in the terminal is U-shaped.

[0016] When the conductor has been placed in the notch, it is recommended to place at least two side sliders opposite to each other on the second surface at the sides of the notch. Importantly, unlike the prior art, the side sliders do not rest on the side walls of the conductor opposite to each other, but on the surface in which the notch is formed. Thus, before the actual welding process, the conductor in the notch is placed on the bottom of the notch and the side sliders rest on the surface in which the notch is formed.

[0017] Then the second electrode is preferably moved vertically to the conductor in the direction of the first electrode and placed on the conductor. In this way, a conductive path is formed between the first electrode and the second electrode through the terminal and the conductor. An interface is formed between the terminal and the conductor at the bottom of the gap.

[0018] Directing current through the two electrodes to weld. This current flows from the first electrode to the second electrode (or vice versa, depending on the counting arrow system, ). An increased ohmic resistance is generated at the interface between the conductor and the terminal, which causes Joule heating, which causes the material of the conductor and the terminal to melt at least at the interface. After cooling, the molten material undergoes intermetallic bonding and forms a material fit.

[0019] Since the conductor is placed in the notch, the side walls of the notch form a natural boundary for the material plasticized by the welding process. The molten material, in particular the molten conductor material, flows at least partially within the notch. Since the side walls of the notch form a boundary, the side slides do not come into contact with the plasticized material and therefore no sticking occurs.

[0020] The volume of the notch is preferably at least as large as the volume of the portion of the conductor placed in the notch, in particular the volume of the material of the portion of the conductor placed in the notch, preferably larger. Possible air inclusions in the conductor are not taken into account. If the volumes are approximately the same, the conductor material will remain completely in the notch even if it is completely melted, and will not flow from the edge of the notch to the second surface. This prevents the side slide against the second surface from coming into contact with the plasticized material of the conductor and / or the terminal and adhering to it after cooling.

[0021] Since the side sliders can be placed against the second surface, the distance between them is variable. This has the advantage that the distance between the side sliders can be matched to the second electrode, or the net width of the side sliders can be matched to the width of the second electrode.

[0022] Even in the case where the plasticized material flows over the edge of the notch and comes into contact with the side slide, the contact surface is significantly reduced compared to conventional welding methods. Contact with the molten material occurs only in the transition area between the side slide and the second surface. Any sticking that occurs can be eliminated by applying slight force without damaging the side slide. Material from the molten conductor also does not adhere to the side slide or only slightly.

[0023] According to one embodiment, it is proposed that the conductor is at least partially melted (plasticized) during the welding process. The melting (plasticization) allows the conductor material to flow into the notch or to be distributed in the notch. If the volume of the notch is large enough, the notch can completely accommodate the conductor material and prevent the molten material from reaching the second surface and the side slider through the edge. However, since the side slider only rests on the second surface, it is ensured that even if the molten material reaches the second surface, the adhesion of the side slider can be substantially prevented. Compared with the conventional method, the contact surface between the molten material and the side slider is greatly reduced according to the present invention.

[0024] According to one embodiment, the conductor extends beyond the edge formed between the notch and the second surface before welding. The conductor is preferably arranged in the notch in a manner that keeps a certain distance from the side walls of the notch. The conductor can only be distributed in the notch through welding and the resulting plastic deformation.

[0025] The conductor is plastically deformed and pressed into the notch under the pressure applied by the second electrode to the bottom of the notch. Therefore, not only the plasticization, but also the plastic deformation of the conductor due to the pressure of the second electrode is the reason for ensuring that the conductor basically matches the cross-sectional profile of the notch after welding. Here, the plasticized part of the conductor and the non-plasticized part of the conductor are pressed into the notch, so that the cross-sectional area of ​​the conductor basically corresponds to the cross-sectional area of ​​the notch.

[0026] According to one embodiment, it is suggested that the conductor is arranged in the notch flush with the second surface after welding. If the volume of the notch and the volume of the conductor in the notch are substantially the same, it can be ensured that the conductor is flush with the second surface when welded. This achieves particularly good processability of the connection. It is also possible that the volume of the conductor placed in the notch is smaller than the volume of the notch. This may result in the conductor being arranged offset into the notch after welding. This means that there is a recess between the conductor surface and the second surface, and the conductor is completely located in the notch. Compared with conventional methods, both variants of flush arrangement and arrangement offset into the notch can reduce the structural height of the connection between the conductor and the terminal, which is particularly advantageous for narrow installation spaces.

[0027] According to one embodiment, it is proposed to move the side slider parallel to the second surface, passing the second surface until entering the edge area of ​​the notch. In this case, the distance between the edge and the notch and the surface of the side slider facing the conductor is still ensured. However, the side slider can also be moved directly to the edge of the notch. In the latter case, although the risk of the plasticized material of the conductor coming into contact with the side slider is greater, the second surface of the terminal is prevented from being contaminated by the melted and solidified material of the conductor. The side slider prevents the conductor material from reaching the second surface during the welding process.

[0028] According to one embodiment, it is proposed that the clear width between the side slides before welding substantially corresponds to the width of the second electrode. That is, the side slides are moved toward each other so that the distance between the mutually opposing walls of the side slides corresponds to the distance between the side walls of the electrodes. In this way, the electrodes can be moved between the side slides with almost no gap or with a tolerance of less than one millimeter and welded.

[0029] According to one embodiment, it is proposed that during the welding process, the second electrode is pressed against the conductor with a force. As mentioned above, during the welding process, the conductor is not only plasticized, but also plastically deformed due to the pressing force of the second electrode. The plastic deformation is carried out by the pressing force using the force of the second electrode pressing on the conductor. This plastic deformation can force the conductor into the shape of the notch. After the welding process is completed, the conductor is located in the notch.

[0030] According to one embodiment, it is suggested that at the beginning of the welding process, the second electrode is pressed against the conductor with a first force. This first force should ensure that the conductor and the terminal form a direct contact interface in the area of ​​the bottom of the notch. At this interface, the current can generate sufficiently high Joule heat to plasticize the material of the conductor and / or the terminal. After the welding starts, the electrode will be pressed against the conductor with a second force greater than the first force. This subsequent extrusion will cause the conductor plasticized at the interface and / or the terminal plasticized at the interface to undergo plastic deformation, so that the conductor matches the notch. The second force is applied during the welding process.

[0031] According to one embodiment, it is proposed that the second electrode is lifted from the conductor after a subsequent holding time after welding. The subsequent holding time is preferably selected so that the molten material of the conductor and / or the terminal solidifies again. Its length depends on the materials used, the connection surface between the two workpieces, the size of the welding current and / or the duration of the welding process, etc., and can be selected accordingly. The subsequent holding ensures that a clean and flawless material-fit connection is formed at the interface. During the solidification process, the interface where the material fit is formed is not subjected to mechanical stress due to the subsequent holding, so that a flawless material-fit connection is formed.

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

[0033] As mentioned above, the conductor undergoes plastic deformation during the welding process. This plastic deformation causes the cross section of the conductor to match and be identical to the cross section of the notch after welding. For example, before welding, the conductor may have a circular or oval conductor cross section. After welding, this cross section in the notch region may be polygonal, in particular square or rectangular.

[0034] By plastically deforming the conductor, a material fit connection can be formed between the round conductor and the flat part in the recess, which reduces the overall height of the connection compared to previous methods.

[0035] According to one embodiment, the notch extends from the side edge of the terminal into the central area of ​​the terminal. This can be imagined as a groove extending from the side wall of the terminal to the center of the terminal, but not through. From a top view, the notch is formed in a U shape. Of course, the groove can also be through.

[0036] According to one embodiment, the side slider is made of a non-conductive material, thereby ensuring that when the second electrode contacts the side slider, current does not flow into the terminal through the side slider, thereby forming welding at the interface between the side slider and the terminal.

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

[0038] Since the conductor is inserted into the notch, in particular with its stripped conductor end, and plastically deformed and plasticized during the welding process, no preparation of the conductor edge is required. In particular, it is not necessary to straighten the stripped end edge of the conductor by cutting, nor is it necessary to bring the conductor strands into one plane. This makes the manufacturing process particularly simple.

[0039] According to one embodiment, the width of the notch in the top view is greater than the width of the unwelded conductor. The conductor can be pressed to the bottom by plastic deformation and plasticization during welding. As a result, a particularly large contact surface can be formed between the conductor and the terminal, thereby greatly reducing the contact resistance in the welded state.

[0040] According to one embodiment, it is proposed that the end edge of the conductor rests against the side wall of the notch before welding. The end edge of the conductor rests in particular against the side edge of the notch which is oriented in the direction of the side wall from which the conductor is inserted into the notch.

[0041] By deforming the conductor, it can be flattened in the soldering area, thus achieving a lower structural height. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The present invention will be explained in more detail below with reference to the accompanying drawings which show embodiments.

[0043] In the figure:

[0044] Figure 1a -c shows a welding process according to one embodiment;

[0045] Figure 2a -d shows a top view of the welded conductor;

[0046] Figure 3 A terminal for welding having a notch according to one embodiment is shown;

[0047] Figure 4 A conductor for welding is shown according to one embodiment. DETAILED DESCRIPTION

[0048] Figure 1a A schematic diagram of a terminal 2 to be welded to a conductor 4 is shown.

[0049] For more details on terminal 2, see Figure 3 As can be seen, the terminal 2 has a rectangular cross section with a notch 6. The notch 6 extends from the end face 2a into the central region 2b of the terminal 2. As can be seen, the notch 6 has a bottom 6a and a side wall 6b. The terminal has an upper surface in which the notch 6 forms an edge 6b'. At the edge 6b', the notch 6 is recessed from the upper surface of the terminal 2.

[0050] like Figure 4 As shown, the conductor 4 can be placed in the terminal 2. The conductor 4 can have a stripped end portion 4b. The end surface 4b' of the stripped end portion 4b is against the side wall 6b of the notch 6, and the stripped end portion is placed on the bottom 6a at the same time.

[0051] from Figure 1a This arrangement between terminal 2 and conductor 4 can be seen in Figure 1a It can also be seen in FIG. 1 that the terminal 2 is located on the first electrode 8 .

[0052] A second electrode 10 is provided on the side opposite to the first electrode 8. The electrodes 8 and 10 can move toward each other and away from each other. The electrodes 8 and 10 are made of a conductive material. The same is true for the terminal 2 and the conductor 4. For example, the material (also referred to as raw material) can be copper or a copper alloy. Aluminum or an aluminum alloy can also be used. Other non-ferrous metals can also be used as raw materials.

[0053] After the terminal 2 is placed on the electrode 8, the conductor 4 can be placed into the notch 6 on the side away from the electrode and placed on the bottom 6a. Figure 1a As shown, the conductor 4 is located in the center of the recess 6 .

[0054] On the upper surface away from the electrode 8, the side slider 12 is placed on the terminal 2. The side slider 12 is pressed against the upper surface of the terminal 2 under the action of the pressing force and moves in the direction of the edge 6b'.

[0055] from Figure 1a It can be seen that the distance between the side slides 12, ie their clear width, is large enough so that the electrode 10 can be moved between the side slides 2 towards the conductor.

[0056] like Figure 1bAs shown, after the side slide 12 is placed, the electrode 10 is moved towards the electrode 8 under the action of the force F. In this process, the electrode 8 presses the conductor 4 against the terminal 2, in particular into the notch 6. An electric current is activated between the electrodes 10 and 8, which generates Joule heat at the interface between the terminal 2 and the conductor 4, thereby causing at least partial melting of the material.

[0057] The force F causes the conductor 4 to undergo plastic deformation. The plasticized portion and the deformed conductor 4 can fill the gap 6 together. Figure 1c As shown, after the welding process is completed and maintained for a period of time, the electrode 10 moves away from the electrode 8 along the direction 14. The conductor 4 is welded to the terminal 2. Figure 1c As can be seen from the figure, the surface of the conductor 4 is flush with the upper surface of the terminal 2. However, the surface of the conductor 4 may also be recessed into the notch 6.

[0058] Using the method shown in the figure, the terminal 2 can be connected to different conductors 4. For example, Figure 2a The terminal 2 is shown above, which is connected to the stranded conductor 4. It can be seen that in the top view, the width of the notch 6 is greater than the diameter of the unprocessed stranded conductor 4. This results in a larger contact surface between the terminal 2 and the conductor 4 in the region of the notch 6. A through hole or punching 16 can be provided in the terminal 2.

[0059] Figure 2a Another example is shown below, the only difference being that the conductor 4 is not a stranded conductor but a braided strand.

[0060] Figure 2b Another possibility of a terminal 2 is shown, which is connected to the conductor 4 as a braided strand in two notches 6. In the region of one of the notches 6, a through-hole 16 through which the conductor 4 and the terminal 2 pass can be provided.

[0061] Figure 2c Shown with Figure 2a Similar example, but with the difference that in this case the through-hole 16 is not located completely in the region of the terminal 2, but is arranged to pass through the conductor 4 in the region of the notch 6. This applies both to the stranded conductor (above) and to the braided stranded conductor (below).

[0062] at last, Figure 2d Shown with Figure 2b A corresponding embodiment, but here the conductor 4 is a stranded conductor.

[0063] With the method shown in the figure, conductors can be welded to one another in a particularly advantageous manner without causing adhesion to the side slide in the area of ​​the welding location. At the same time, the terminal surface around the weld seam is protected from contamination by the side slide.

[0064] Description of Reference Numerals

[0065] 2 terminals

[0066] 2a End face

[0067] 2b Central Area

[0068] 4 Conductors

[0069] 4a End

[0070] 4b' end face

[0071] 6 Gap

[0072] 6a Bottom

[0073] 6b Sidewall

[0074] 6b' Edge

[0075] 10,8 Electrode

[0076] 12 Side Sliders

[0077] 14 Direction

Claims

1. Resistance welding method, in which - welding a metal conductor to a metal terminal, wherein - a metallic terminal having a first surface and a second surface opposite to the first surface, and wherein, The notch is arranged in the second surface, and the metal terminal is placed on the first electrode with the first surface, - a metal conductor is placed on the bottom of the notch, - at least two side slides are placed on the second surface at the side of the notch, wherein a spacing is formed between the edge of the notch and the surface of the side slide facing the conductor, and wherein the side slide is moved parallel to the second surface, past the second surface until it enters the region of the edge of the notch, - the second electrode is moved onto the conductor in the direction of the first electrode, and - welding the conductor to the terminal in the region of the notch by means of a current flowing between the first electrode and the second electrode, The side walls of the notch form the boundary of the conductor material plasticized by the welding process, and the side slide blocks do not come into contact with the plasticized material.

2. The resistance welding method according to claim 1, It is characterized in that The conductor is at least partially plasticized during the welding process.

3. The resistance welding method according to claim 1 or 2, It is characterized in that - The conductor protrudes beyond the edge formed between the notch and the second surface before welding.

4. The resistance welding method according to claim 1 or 2, It is characterized in that After welding, the conductor is arranged in the recess flush with the second surface, or after welding, the conductor is arranged offset in the recess relative to the second surface.

5. The resistance welding method according to claim 1, It is characterized in that - The clear width between the sliders before welding is substantially the same as the width of the second electrode.

6. The resistance welding method according to claim 1, It is characterized in that - Press the second electrode firmly against the conductor during welding.

7. The resistance welding method according to claim 1, It is characterized in that - pressing the second electrode against the conductor with a first force at the start of welding, and pressing the second electrode against the conductor with a second force greater than the first force after the start of welding and during welding.

8. The resistance welding method according to claim 1, It is characterized in that - After a subsequent holding time after welding, the second electrode is lifted off the conductor.

9. The resistance welding method according to claim 1, It is characterized in that - After a subsequent holding time after welding, the side slide is moved away from the notch.

10. The resistance welding method according to claim 1, It is characterized in that -The conductor is a stranded conductor or a braided conductor.

11. The resistance welding method according to claim 1, It is characterized in that - The conductors and / or terminals are made of copper or copper alloys.

12. The resistance welding method according to claim 1, It is characterized in that The conductor has a first conductor profile in the region of the notch before welding and has a second conductor profile different from the first conductor profile after welding, in particular the second conductor profile is adapted to the cross-sectional profile of the notch.

13. The resistance welding method according to claim 1, It is characterized in that The notch extends from a side edge of the terminal into a central region of the terminal.

14. The resistance welding method according to claim 1, It is characterized in that - The side slides are formed from a non-conductive material.

15. The resistance welding method according to claim 1, It is characterized in that - Producing through-openings through the conductor and the terminal after welding, in particular drilling or punching holes.

16. The resistance welding method according to claim 1, It is characterized in that - From a top view, the width of the notch is greater than the width of the conductor.

17. The resistance welding method according to claim 1, It is characterized in that Before welding, the end edges of the conductor are placed against the side walls of the recess.

18. The resistance welding method according to claim 1, It is characterized in that - Flatten the conductor in the welding area.

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