Resistance welding method and apparatus

Abstract

To provide a resistance-welding method that enables a metal body to be resistance-welded by minimizing an influence exerted on the metal body by breakdown of an insulator even when the insulator is interposed in the metal body, and resistance-welding equipment.SOLUTION: In a resistance-welding method, a workpiece having a metal body 7 and an insulator 8 for insulating it is resistance-welded in the state of being sandwiched between upper and lower welding rods. The resistance-welding method includes the steps of: setting a current path leading to a narrow point P1 of the metal body 7, by insulation-breaking down only the narrow point P1 of the insulator 8 at a location where the metal body 7 and the insulator 8 overlap each other in the state of contact with each other; and performing fusion-joining by applying a welding-current to the metal body 7 while applying pressure, in a state in which the current path is secured.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method and an apparatus for resistance welding a weldment having a metal body and an insulator for insulating the metal body.

Background Art

[0002] Generally, as a terminal connection of a metal wire, resistance welding is known in which a metal wire and a terminal block are sandwiched between upper and lower electrodes and a welding current of a large current is passed therethrough for a short time while applying pressure (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when a metal wire (metal body) is coated with a resin (insulator), since the metal wire contains an insulator, it is difficult to join the metal wire as it is. In this case, it is also conceivable to heat with a heater or the like to melt and remove the resin, but in the case of a metal wire such as an aluminum wire or a fine wire, there is a problem that the metal wire is easily cut by heating.

[0005] Also, in the welding of a laminate in which a plurality of thin metal foils (metal bodies) and resins (insulators) are laminated, since an insulator is interposed, it is difficult to ensure conduction of the welding current. Further, even if conduction of the welding current can be ensured, the strength by welding becomes low only by joining the thin metal foils together. On the other hand, if the welding voltage is increased to ensure conduction, the metal foil may be broken (explosion).

[0006] An object of the present invention is to solve the above problems and provide a resistance welding method and a resistance welding apparatus capable of resistance welding a metal body while minimizing the influence on the metal body due to dielectric breakdown of the insulator even when an insulator is interposed between the metal bodies. [Means for solving the problem]

[0007] The resistance welding method and resistance welding apparatus according to the present invention are used to resistance weld a workpiece having a metal body and an insulator that insulates it, by sandwiching it between upper and lower electrode rods. At the point where the metal body and the insulator are in contact and overlap, dielectric breakdown occurs only at the narrow point of the insulator, creating a current path that leads to the narrow point of the metal body. This includes applying a welding current to the metal body while applying pressure, with the current path secured, to perform fusion joining.

[0008] With this configuration, at the point where the metal body and the insulator are in contact and overlap, dielectric breakdown occurs only at the narrow point of the insulator, creating a current path to the narrow point of the metal body. Since the metal body is melted and joined under pressure while the current path is secured, even with an insulator interposed between the metal body and the metal body, the impact on the metal body due to dielectric breakdown of the insulator is minimized, allowing the metal body to be resistance welded.

[0009] In this invention, the narrow point of the insulator may be melted by heating between the upper and lower electrode rods to cause dielectric breakdown. In this case, by adjusting the heating between the upper and lower electrode rods, only the narrow point of the insulator can be melted and the insulator removed from the location of the narrow point, thereby minimizing the impact on the metal body.

[0010] Alternatively, the workpiece to be welded may be a laminate formed by stacking multiple metal bodies and an insulator, and penetration members may be provided on the upper and lower sides of the laminate, and resistance welding may be performed by sandwiching it between the upper and lower electrode rods. In this case, the current path is expanded, allowing the penetration members to penetrate the metal bodies, thereby suppressing the reduction in strength due to welding, and preventing the scattering of metal bodies, which extends the life of the electrode rods.

[0011] Furthermore, the workpiece to be welded may be a laminate formed by stacking multiple metal bodies and insulators, and holes may be made in the stacking direction at narrow points of the multiple insulators and metal bodies using a needle press, so that the holes become current paths for the multiple metal bodies. In this case, as the number of stacked layers of the laminate increases, the resistance of the current path in the welding current increases, so the resistance can be reduced by making holes, making it easier to secure the current path. [Effects of the Invention]

[0012] The present invention enables resistance welding of a metal body and an insulator that insulates it, even when an insulator is interposed between the metal body and the metal body, by minimizing the effect of dielectric breakdown of the insulator on the metal body. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic diagram showing a resistance welding apparatus according to one embodiment of the present invention. [Figure 2] (A) and (B) are diagrams illustrating examples of resistance welding operation. [Figure 3] This figure shows an example of a workpiece to be welded. [Figure 4] Figures (A) to (C) show examples of resistance welding operation. [Figure 5] This figure shows another example of a workpiece to be welded. [Figure 6] (A) and (B) are diagrams illustrating examples of resistance welding operation. [Figure 7] (A) and (B) are diagrams illustrating examples of resistance welding operation. [Modes for carrying out the invention]

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a resistance welding apparatus 1 according to an embodiment of the present invention. This welding apparatus 1 includes a pair of upper and lower electrode bars 5 and 6 that are vertically movable, a power supply unit 2 that passes a welding current through the upper and lower electrode bars 5 and 6, a heater 3 that heats the upper and lower electrode bars 5 and 6, and a pressurizing actuator (not shown) that pressurizes the work piece W sandwiched between the upper and lower electrode bars 5 and 6 in the vertical direction.

[0015] FIG. 2 shows a first embodiment of resistance welding the work piece W1. As shown in FIG. 2(A), the work piece W1 is, for example, a sheet in which metal bodies 7, 7 are formed on both surfaces of a resin (insulator) 8. The metal bodies 7 are joined to each other at narrow points (pinpoints) P1, P1 where the metal body 7 and the insulator 8 contact and overlap.

[0016] As shown in FIG. 2(B), for example, only the narrow points P1, P1 of the insulator 8 are melted by heating with the heater 3 between the upper and lower electrode bars 5, 6 in FIG. 1, and insulation breakdown is caused by removing the insulator 8 from this portion. In that case, the insulator 8 in this portion can also be pushed aside by pressurizing with the upper and lower electrode bars 5, 6.

[0017] Thereby, by adjusting the heating and / or pressurization between the upper and lower electrode bars 5, 6, only the narrow points P1, P1 of the insulator 8 are melted and the insulator 8 is removed from the narrow point positions, so that the influence on the metal body 7 can be minimized.

[0018] Then, the metal bodies 7 are brought into direct contact with each other to form a current path for the welding current reaching both narrow points P1, P1.

[0019] With this current path secured, a high-current welding current is passed through in a short time while pressurizing the metal bodies 7 (FIG. 1), creating nuggets N inside the metal bodies 7 and performing fusion welding.

[0020] Figure 3 shows a second embodiment of resistance welding of a workpiece W2. The workpiece W2 is used, for example, as an electrode plate inside a secondary battery. This workpiece W2 is a laminate 10 in which a thin metal foil (metal body) 11, such as copper foil, is formed on both sides of a resin (insulator) 12, and a plurality of sheets 14, which are copper-plated on this copper foil, are laminated together. In addition to the above-mentioned copper foil, aluminum foil, stainless steel foil, and iron foil can also be used as metal foil for the electrode plate.

[0021] Penetration members 15 are provided above and below the laminate 10. These penetration members 15 are made of a material similar to copper plating. The workpiece W2 is placed between the upper and lower electrode rods 5 and 6 in Figure 1 and resistance welded.

[0022] By providing penetration members 15 on the upper and lower sides of the laminate 10, the current path is expanded, allowing the penetration members 15 to penetrate the metal body 11. This suppresses the reduction in strength due to welding and also reduces the amount of metal body 11 that adheres to the electrode rods 5 and 6, thereby extending the lifespan of the electrode rods 5 and 6.

[0023] Figures 4(A) to 4(C) show the operation of resistance welding in the second embodiment. As shown in Figure 4(A), the metal bodies 11 and insulator 12 are joined together at the narrow points P2, P2 where they are in contact and overlap.

[0024] As shown in Figure 4(B), a needle-shaped press P is used to create holes in only the upper and lower narrow points P2, P2 of the multiple insulators 12 and metal bodies 11 in the stacking direction, causing dielectric breakdown. The multiple metal bodies 11 come into close contact with each other in the stacking direction at the cut edges of these holes, thus ensuring a current path is established that travels along these cut edges to both narrow points P2, P2.

[0025] As the number of layers in the laminate 10 of the workpiece W2 increases, the resistance of the current path in the welding current increases. Therefore, the resistance can be reduced by making holes with the needle-shaped press P, making it easier to secure the current path.

[0026] Furthermore, the insulator 12 is melted by heating with the heater 3 between the upper and lower electrode rods 5 and 6 in Figure 1, and the insulator 12 remaining at the cut end of the hole is removed. In this case, pressure may also be applied to the upper and lower electrode rods 5 and 6 in the same way, and the effect on the metal body 7 can be minimized as much as possible by adjusting the heating and / or pressure between the upper and lower electrode rods 5 and 6. This makes it possible to more reliably secure a current path to both narrow points P2, P2.

[0027] As shown in Figure 4(C), with the current path secured, a large current is passed from the power supply 2 for a short time while pressurizing, creating a nugget N inside the stacked metal body 11 and melting it.

[0028] Depending on the type of material and the number of layers of the laminate 10, the drilling using the needle-shaped press P shown in Figure 4(B) may be omitted.

[0029] Figure 5 shows a third embodiment of resistance welding of the workpiece W3. The workpiece W3 is, for example, an electric wire 20 made of a metal wire (metal body) 21 coated with a resin (insulator) 22, which is used for terminal processing of motor windings. Metal wires such as copper wires and aluminum wires used in motor windings are often coated for pressure resistance and heat resistance.

[0030] As shown in Figure 6(A), the electric wire 20 is resistance-welded to the terminal block 23. For example, heating by the heater 3 between the upper and lower electrode rods 5 and 6 in Figure 1 melts only the narrow points P3, P3 of the insulator 22 of the electric wire 20, causing dielectric breakdown by removing the insulator 22 in this area. In this case, the insulator 22 in this area can also be pushed aside by applying pressure with the upper and lower electrode rods 5 and 6.

[0031] Then, the metal body 21 is brought into direct contact with the terminal block 23 to form a current path leading to both narrow points P3, P3.

[0032] As shown in Figure 6(B), with this current path secured, a large welding current is passed through the metal bodies 21, 21 for a short time while applying pressure (Figure 1), creating a nugget N inside the metal body 21 and terminal block 23 and melting them together.

[0033] Thus, while aluminum wires and fine wires are easily cut by heating, by adjusting the heating and / or pressurization between the upper and lower electrode rods 5 and 6, only the narrow points P3, P3 of the insulator 22 are melted, causing dielectric breakdown that removes the insulator 22 from the narrow point locations, thereby minimizing the impact on the metal body 21.

[0034] Figure 7 shows a modified version of Figure 6, in which the electric wire 20 is resistance-welded to a hook-shaped terminal block 24. Similarly to the above, by adjusting the heating and / or pressurization between the upper and lower electrode rods 5 and 6, only the narrow points P4, P4 of the insulator 22 of the electric wire 20 in Figure 7(A) are melted, causing dielectric breakdown by removing the insulator 22 from the narrow point locations, and the metal body 21 is brought into direct contact with the terminal block 24, creating a current path to both narrow points P4, P4.

[0035] As shown in Figure 7(B), with this current path secured, a high welding current is passed through the metal bodies 21, 21 for a short time while applying pressure (Figure 1), creating a nugget N inside the metal body 21 and terminal block 24 and melting them together. Similarly, only the narrow points P4, P4 of the insulating coating are melted and dielectric breakdown is caused by adjusting the heating and / or pressure, so the impact on the metal body 21 can be minimized as much as possible.

[0036] Other examples of motor windings include the winding type, where the ends of the wire are wrapped around a terminal block and resistance-welded, and the slit type, where the ends of the wire are housed in slits formed on the inner surface of the flange of the drum core around which the wire is wound and then resistance-welded. Similarly, since dielectric breakdown is caused by heating and melting only a narrow point of the insulating coating, the impact on the metal body can be minimized as much as possible.

[0037] Common insulated wires include those with copper, aluminum, nickel, and stainless steel cores that are coated with an insulating material, and are resistance welded in the same manner as described above.

[0038] Thus, in this invention, at the point where the metal body and the insulator are in contact and overlap, dielectric breakdown occurs only at the narrow point of the insulator, creating a current path to the narrow point of the metal body. Since fusion joining is performed under pressure while the current path is secured in the metal body, even if an insulator is interposed in the metal body, the influence on the metal body due to dielectric breakdown of the insulator is minimized, and the metal body can be resistance welded.

[0039] In this invention, by adjusting the heating and / or pressurization between the upper and lower electrode rods, only the narrow points of the insulator are melted, removing the insulator from the location of the narrow points, thereby minimizing the impact on the metal body. Furthermore, when the workpiece to be welded is a laminate consisting of multiple metal bodies and insulators stacked on top of each other, penetration members are provided on the upper and lower sides of the laminate, and resistance welding is performed with the laminate sandwiched between the upper and lower electrode rods. This expands the current path, allowing the penetration members to penetrate the metal body, thereby suppressing the reduction in strength due to welding and preventing the scattering of metal material, thus extending the lifespan of the electrode rods.

[0040] In this invention, when the workpiece to be welded is a laminate formed by stacking multiple metal bodies and insulators, a needle-shaped press is used to create holes in the narrow points of the multiple insulators and metal bodies in the direction of stacking. As the number of layers in the laminate increases, the resistance of the current path in the welding current increases, so these holes can reduce the resistance and more easily secure the current path.

[0041] In this embodiment, the upper and lower electrode rods are heated by a heater, but this is not the only option. For example, a separate AC power source may be used to heat the upper and lower electrode rods.

[0042] The present invention is not limited to the embodiments described above, and various additions, modifications, or deletions are possible without departing from the spirit of the invention. Therefore, such additions and deletions are also included within the scope of the present invention. [Explanation of symbols]

[0043] 1: Resistance welding equipment 2: Power supply section 3: Heater 5: Upper electrode rod 6: Lower electrode rod 7, 11, 21: Metal body 8, 12, 22: Insulators 10: Laminate 13: Plating 15: Blending material P: Needle press P1~P4: Narrow point W1~W3: Work to be welded

Claims

1. A method for resistance welding a workpiece having a metal body and an insulator that insulates it by sandwiching it between upper and lower electrode rods, In a portion where the metal body and the insulator contact and overlap, only a narrow point of the insulator is broken down to form a current path leading to the narrow point of the metal body; With the current path secured, a welding current is applied to the metal body while applying pressure to the metal body to melt and join the metal body. A resistance welding method comprising:

2. In claim 1, A resistance welding method in which the narrow point of the insulator is heated between the upper and lower electrodes to melt and cause dielectric breakdown.

3. In claim 2, A resistance welding method in which the workpiece is a laminate formed by stacking multiple metal bodies and insulators, and penetration members are provided on the upper and lower sides of the laminate, which is sandwiched between the upper and lower electrode rods and resistance welded.

4. In claim 1 or 2, This is a resistance welding method in which the workpiece is a laminated body made up of multiple metal bodies and insulators, and a needle press is used to drill holes in the stacking direction at narrow points of the multiple insulators and metal bodies, and the holes serve as current paths for the multiple metal bodies.

5. A resistance welding apparatus for resistance-welding the workpieces by the resistance welding method according to any one of claims 1 to 4.

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