Resistance welding device and resistance welding method

Abstract

The resistance welding device (1) comprises a first electrode (2) having a first contact surface (21) in contact with the workpiece (100) and a second electrode (3) having a second contact surface (31) in contact with the workpiece, the first contact surface having at least one first overlapping portion (22) and at least one first non-overlapping portion (23), the second contact surface has a second overlapping portion (32) and at least one second non-overlapping portion (33), the first overlapping portion and the second overlapping portion overlap in the lamination direction, and the first non-overlapping portion and the second non-overlapping portion do not overlap in the lamination direction.

Description

Technical Field

[0001] The technology disclosed herein relates to a resistance welding device and a resistance welding method. Background Art

[0002] Patent document 1 describes an electrode for resistance spot welding. The welding electrode is used for single-sided resistance spot welding. In single-sided resistance spot welding of a workpiece consisting of a first plate and a second plate, the welding electrode is brought into contact with the surface of the first plate to apply pressure to the surface of the first plate, and the ground electrode is connected to the second plate in a manner that allows electricity to flow. If current flows between the welding electrode and the ground electrode, a nugget is formed at the junction where the first plate and the second plate are joined. In single-sided resistance spot welding, since the welding electrode and the ground electrode are not necessarily opposite to each other, as shown in the figure in patent document 1, the current path in the workpiece is sometimes inconsistent with the pressure direction of the electrode.

[0003] Patent document 2 describes a resistance welding device including a first electrode and a second electrode. The first electrode and the second electrode are respectively composed of an inner electrode and an outer electrode. The resistance welding device first conducts electricity between the inner electrode and / or the outer electrode in a state where either the inner pressure or the outer pressure is greater than the other pressure, thereby softening at least one of the multiple welded parts. After softening, electricity is conducted between the inner electrode and / or the outer electrode in a state where the inner pressure is greater than the outer pressure, thereby welding the multiple welded parts to each other at the position where the inner pressure acts. The resistance welding device is not prone to poor joining, and is therefore suitable for welding, for example, iron-based parts and aluminum-based parts.

[0004] Patent Document 1: Japanese Patent Publication No. 2012-55925

[0005] Patent document 2: Japanese Patent Publication No. 2021-41441 Summary of the invention

[0006] -Technical problem to be solved by the invention-

[0007] For example, in order to achieve light weight and / or optimize functions, various materials are used in the body of an automobile. As a result, a multi-material joining technology is required. The welding technology described in Patent Document 2 is one of the multi-material joining technologies.

[0008] Creating an appropriate interface state in welding multiple materials can stabilize the welding quality. The interface state mentioned here includes, for example, the melting amount of each material or the interface temperature. In order to stabilize the welding quality of multiple materials, it is necessary to manage the interface state with high precision.

[0009] After repeated welding, the tip shape of the electrode used for so-called spot welding may change due to wear, for example. Hereinafter, the change in the state of the tip of the electrode caused by wear or other reasons is collectively referred to as electrode degradation. Electrode degradation changes the current path in the workpiece, and the change in the current path changes the current density. If the current density changes, the heating state of the joint interface will change. Electrode degradation makes it difficult to manage the state of the joint interface with high precision, making the welding quality of multiple materials unstable.

[0010] In addition, electrode degradation may cause the following undesirable conditions not only in multi-material welding, but also in general resistance welding. That is, with existing spot welding technology, the heating state caused by electrode degradation will change each time spot welding is performed, so the heating state is allowed to change within a range that can ensure the desired welding quality. If the number of welding times exceeds the specified number, the desired welding quality cannot be ensured, so the electrode must be repaired or replaced. In order to maintain the electrode, the production line must be stopped. If the electrode is easily degraded, the frequency of stopping the production line will increase. In addition, in order to ensure the desired quality even if the electrode has degraded, the power supply during welding is sometimes increased in advance. High power supply will lead to energy loss.

[0011] The technology disclosed herein suppresses the degradation of electrodes used for resistance welding.

[0012] -Technical solutions to solve technical problems-

[0013] The inventors of the present application have studied the mechanism of electrode degradation in resistance welding. Fig.15 The following is a diagram showing a state in which a conventional resistance welding device 10 is welding a workpiece 100. The resistance welding process is composed of the following steps (1) to (4).

[0014] (1) The workpiece 100 is clamped by the first electrode 20 and the second electrode 30 mounted on the welding gun and pressurized in the stacking direction, and power is supplied to the workpiece 100 through the first electrode 20 and the second electrode 30 (see Fig.15 The workpiece 100 is composed of a plurality of stacked welding materials 101 and 102. The stacking direction is Fig.15 The paper direction corresponds to the top and bottom direction. Fig.15 In the resistance welding device 10, the pressurizing direction is consistent with the power supply direction.

[0015] (2) The workpiece 100 is heated due to Joule heat generated at the bonding interface 103 in the workpiece 100 , and the workpiece 100 is cooled due to a part of the heat being transferred to the first electrode 20 and the second electrode 30 .

[0016] (3) The workpiece 100 softens and melts due to the heat, thereby causing the workpiece 100 to undergo plastic deformation.

[0017] (4) The molten metal at the joint interface 103 of the workpiece 100 solidifies to form a nugget, and the welding of the workpiece 100 is completed.

[0018] According to the research of the inventors of the present application, it is understood that when the workpiece undergoes plastic deformation in the above-mentioned step (3), arc discharge is generated between the electrode surface and the workpiece surface, and the arc discharge causes degradation of the electrode. In more detail, the arm of the welding gun bends during the pressurization of the workpiece. When the workpiece undergoes plastic deformation and the electrode sinks into the workpiece, the stress of the arm is released. The electrode slides relative to the workpiece surface due to the stress release, or the electrode tilts relative to the workpiece surface due to the stress release. As a result, the contact state between the electrode and the workpiece surface changes. The change in the contact state between the electrode and the workpiece surface causes the current path between the electrode and the workpiece to change sharply, thereby generating arc discharge between the electrode surface and the workpiece surface.

[0019] Having obtained new insights into the electrode degradation mechanism, the inventors of the present application focused on suppressing changes in the contact state between the electrode and the workpiece surface when the workpiece undergoes plastic deformation. The inventors of the present application devised an electrode structure and completed the technology disclosed herein.

[0020] Specifically, if Fig.15 As shown, in the conventional resistance welding device 10, the first electrode 20 and the second electrode 30 perform pressurization and power supply to the workpiece 100 in an integrated manner. Therefore, when the first electrode 20 and the second electrode 30 pressurizing the workpiece 100 sink into the workpiece 100 as the workpiece 100 undergoes plastic deformation, the contact state between the first electrode 20 and the second electrode 30 and the workpiece 100 changes as the workpiece 100 sinks.

[0021] Therefore, the inventors of the present application separated the pressurizing function and the power supply function of the first electrode and the second electrode, thereby suppressing the first electrode and / or the second electrode from sinking into the workpiece.

[0022] The technology disclosed herein relates to a resistance welding device that pressurizes a workpiece consisting of a plurality of stacked materials to be welded in a stacking direction and supplies power to the workpiece, thereby welding the plurality of materials to be welded. The resistance welding device includes: a first electrode and a second electrode,

[0023] The first electrode is located on a first side of the stacking direction relative to the workpiece,

[0024] The second electrode is located on a second side of the stacking direction relative to the workpiece, and the second electrode sandwiches the workpiece between the first electrode and the second electrode.

[0025] The first electrode has a first contact surface in contact with the workpiece,

[0026] The second electrode has a second contact surface in contact with the workpiece,

[0027] The first contact surface has at least one first overlapping portion and at least one first non-overlapping portion,

[0028] The second contact surface has at least one second overlapping portion and at least one second non-overlapping portion,

[0029] The first overlapping portion and the second overlapping portion overlap in the stacking direction, and the first non-overlapping portion and the second non-overlapping portion do not overlap in the stacking direction.

[0030] According to this configuration, the first electrode and the second electrode of the resistance welding device pressurize the workpiece in the laminating direction and supply power to the workpiece.

[0031] The first electrode has a first contact surface in contact with the workpiece, the first contact surface has at least one first overlapping portion and at least one first non-overlapping portion. Similar to the first electrode, the second electrode also has a second contact surface in contact with the workpiece, the second contact surface has at least one second overlapping portion and at least one second non-overlapping portion.

[0032] The first overlapping portion overlaps with the second overlapping portion in the stacking direction. It should be noted that overlapping in the stacking direction means that when the second electrode (or the first electrode) is observed from the first electrode side (or the second electrode side) along the axis extending in the stacking direction, the first overlapping portion overlaps with the second overlapping portion, rather than that the first overlapping portion is in direct contact with the second overlapping portion. When the first electrode and the second electrode clamp the workpiece and pressurize the workpiece, the first overlapping portion and the second overlapping portion constitute a pressurizing portion that is opposite to each other in the stacking direction and actually pressurizes the workpiece. In the first electrode and the second electrode, the portion that actually pressurizes the workpiece is a portion of the first contact surface and a portion of the second contact surface, and the area of ​​the first overlapping portion and the second overlapping portion is smaller than the overall area of ​​the first contact surface and the second contact surface. It should be noted that the first overlapping portion and the second overlapping portion may have the function of supplying power to the workpiece, or may not have the function of supplying power to the workpiece.

[0033] The first non-overlapping portion and the second non-overlapping portion do not overlap in the stacking direction. When the first electrode and the second electrode clamp the workpiece and press the workpiece, the first non-overlapping portion and the second non-overlapping portion do not press the workpiece or hardly press the workpiece. The first non-overlapping portion and the second non-overlapping portion mainly function as power supply portions for supplying power to the workpiece.

[0034] In this resistance welding device, the function of each of the first electrode and the second electrode to pressurize the workpiece is separated from the function of supplying power to the workpiece.

[0035] When the first electrode and the second electrode clamp the workpiece and pressurize the workpiece, and power is supplied to the workpiece, the materials to be welded contact each other at the joint interface corresponding to the first overlapping portion and the second overlapping portion, forming a current path. Joule heat is generated at this location, and the workpiece softens and melts. The range of softening and melting of the workpiece is roughly the range corresponding to the first overlapping portion and the second overlapping portion. When the workpiece undergoes plastic deformation due to the softening and melting of the workpiece, in each of the first electrode and the second electrode, the overall area of ​​the first contact surface and the second contact surface is relatively large relative to the area of ​​the first overlapping portion and the second overlapping portion. The first electrode and the second electrode are suppressed from sinking into the workpiece. Since the change in the contact state between the electrode and the workpiece surface is suppressed, the occurrence of arc discharge between the electrode and the workpiece is suppressed. That is, the degradation of the electrode is suppressed.

[0036] In addition, since the area of ​​the first overlapping portion and the second overlapping portion of the first electrode and the second electrode of the above structure is relatively small, the amount of heat transferred from the workpiece to the first electrode or the second electrode is reduced. At the same time, since the volume of the first electrode and the second electrode having the first non-overlapping portion and the second non-overlapping portion is relatively large, the heat capacity of the first electrode or the second electrode is relatively large. As a result, the first electrode and the second electrode can be prevented from becoming high temperature due to the heat from the workpiece, and the degradation of the electrode such as alloying of the electrode surface or deformation of the electrode surface can be prevented.

[0037] The electrode degradation is suppressed, and as a result, the resistance welding device can perform high-precision management of the bonding interface state. The resistance welding device, for example, stabilizes the welding quality of multiple materials. In addition, in the resistance welding device, the stop frequency of the production line is reduced, which is conducive to reducing the manufacturing cost. Moreover, since it is not necessary to increase the power supply during welding in advance in consideration of the degradation of the electrode, the resistance welding device can also suppress energy loss.

[0038] In addition, the first non-overlapping portion and the second non-overlapping portion do not sink into the workpiece during welding, but are in stable contact with the surface of the workpiece. When the welded material thermally expands as the workpiece softens and melts, the first non-overlapping portion and the second non-overlapping portion press the thermally expanded welded material. The resistance welding device can suppress deformation of the workpiece after welding.

[0039] Moreover, the first contact surface and the second contact surface respectively include an overlapping portion and a non-overlapping portion, so the area is relatively large. The first electrode and the second electrode will not be tilted relative to the surface of the workpiece, and can stably contact the surface of the workpiece. The stable contact of the electrodes realizes stable pressurization and stable power supply of the first electrode and the second electrode. Stable pressurization and stable power supply are conducive to stabilization of welding quality.

[0040] A line connecting the first non-overlapping portion and the second non-overlapping portion may intersect a line connecting the first overlapping portion and the second overlapping portion near the joining interface of the workpieces.

[0041] The part where the line connecting the first overlapping part and the second overlapping part intersects with the joint interface of the workpiece is the part where the materials to be welded come into contact with each other by the pressure of the first overlapping part and the second overlapping part to form a current path, and this part is the predetermined welding part. By making the line connecting the first non-overlapping part and the second non-overlapping part intersect with the predetermined welding part forming the current path, the first electrode and the second electrode can efficiently generate Joule heat at the predetermined welding part of the workpiece, wherein the first non-overlapping part and the second non-overlapping part supply power to the workpiece. The above-mentioned resistance welding device takes into account both the stabilization of resistance welding and the suppression of electrode degradation.

[0042] Alternatively, the first non-overlapping portion may be located on a first side in a direction perpendicular to the stacking direction relative to the first overlapping portion, and the second non-overlapping portion may be located on a second side in a direction perpendicular to the stacking direction relative to the second overlapping portion.

[0043] A wire connecting the first overlapping portion and the second overlapping portion is sandwiched between the first non-overlapping portion and the second non-overlapping portion, and the first non-overlapping portion and the second non-overlapping portion are located on both sides in a direction orthogonal to the stacking direction.

[0044] Since the first non-overlapping portion and the second non-overlapping portion are located on both sides of a line connecting the first overlapping portion and the second overlapping portion in a direction perpendicular to the stacking direction, the first electrode and the second electrode can stably contact the surface of the workpiece.

[0045] Alternatively, the first contact surface has a circular shape, and the second contact surface has a circular ring shape whose center coincides with the center of the first contact surface.

[0046] The first overlapping portion is an annular shape located at the outer periphery of the first contact surface, and the first non-overlapping portion is a circular shape located inside the annular first overlapping portion.

[0047] The second overlapping portion is annular in shape and located at an inner circumference of the second contact surface, and the second non-overlapping portion is annular in shape and located outside the annular second overlapping portion.

[0048] According to this structure, the shape of the current path formed at the joint interface of the workpieces is annular. The electrode can heat the welding target portion uniformly from the entire circumference.

[0049] Alternatively, the first contact surface may have a triangular shape, and the second contact surface may have a triangular shape obtained by reversing the direction of the triangle of the first contact surface with respect to a line connecting the first overlapping portion and the second overlapping portion.

[0050] The centroid of the triangle of the first contact surface coincides with the centroid of the triangle of the second contact surface in the stacking direction.

[0051] By overlapping the inverted triangles, the first non-overlapping portion is formed at each vertex near the three vertices of the triangle, and the second non-overlapping portion is also formed at each vertex near the three vertices of the triangle. The current path formed at the joint interface by pressurizing the first overlapping portion and the second overlapping portion is arranged in a manner that surrounds the line connecting the first overlapping portion and the second overlapping portion in the circumferential direction. Since the predetermined welding portion is evenly heated from the entire circumference, the quality of resistance welding is stabilized.

[0052] Alternatively, the center of gravity of the first contact surface may be included in the first overlapping portion.

[0053] The position of the center of gravity of the second contact surface is included in the second overlapping portion.

[0054] Since the center of gravity of the first contact surface and the center of gravity of the second contact surface are respectively included in the overlapped portion of the first electrode and the second electrode in the stacking direction, the pressure density of the first electrode and the second electrode when pressing the workpiece in the stacking direction is increased. High pressure density is conducive to improving the joining quality of the workpiece.

[0055] Alternatively, the area of ​​the first contact surface is greater than 120% of the area of ​​the first overlapping portion.

[0056] The area of ​​the second contact surface is greater than 120% of the area of ​​the second overlapping portion.

[0057] When the area of ​​the first overlapping portion is large relative to the entire first contact surface, the position of the center of gravity of the first contact surface is easily included in the first overlapping portion. When the area of ​​the first overlapping portion is large, the area of ​​the first non-overlapping portion becomes smaller. When the area of ​​the first non-overlapping portion is small, the pressure application function and the power supply function of the first electrode are substantially inseparable. The same is true for the second contact surface.

[0058] When the area of ​​the first contact surface is 120% or more of the area of ​​the first overlapping portion, the area of ​​the first non-overlapping portion can be sufficiently increased. The first electrode can separate the pressurizing function from the power supply function and ensure the high pressurizing density described above.

[0059] Similarly, the area of ​​the second non-overlapping portion can be sufficiently increased by making the area of ​​the second contact surface 120% or more of the area of ​​the second overlapping portion. The second electrode can separate the pressurizing function from the power supply function and ensure the high pressurizing density described above.

[0060] It should be noted that the upper limit of the area of ​​the first contact surface and the upper limit of the area of ​​the second contact surface are respectively determined by the restrictions that the position of the center of gravity of the first contact surface must be included in the first overlapping portion and the position of the center of gravity of the second contact surface must be included in the second overlapping portion.

[0061] Another resistance welding device disclosed herein includes a first electrode and a second electrode,

[0062] The first electrode is located on a first side of the stacking direction relative to the workpiece, and the first electrode has a first contact surface that contacts the workpiece.

[0063] The second electrode is located on a second side of the stacking direction relative to the workpiece, and the second electrode has a second contact surface that contacts the workpiece, and the second electrode sandwiches the workpiece between the first electrode and the second electrode,

[0064] The first electrode has a first inhibiting portion at a portion of the first contact surface, the first inhibiting portion inhibiting the first electrode from sinking toward the workpiece when power is supplied.

[0065] The second electrode has a second inhibiting portion at a portion of the second contact surface, and the second inhibiting portion inhibits the second electrode from sinking toward the workpiece during the power supply.

[0066] According to this structure, the first electrode having the first inhibition portion is suppressed from sinking into the workpiece, and the second electrode having the second inhibition portion is also suppressed from sinking into the workpiece. Since the change in the contact state between the electrode and the workpiece surface is suppressed, the occurrence of arc discharge between the electrode surface and the workpiece surface is suppressed. In other words, the degradation of the electrode is suppressed.

[0067] The technology disclosed herein relates to a resistance welding method, which uses a first electrode and a second electrode to pressurize a workpiece consisting of a plurality of stacked materials to be welded in a stacking direction and supply power to the workpiece, thereby welding the plurality of materials to be welded. In the resistance welding method,

[0068] The first electrode has a first contact surface, the first contact surface contacts the workpiece, and the first contact surface includes at least one first overlapping portion and at least one first non-overlapping portion.

[0069] The second electrode has a second contact surface, the second contact surface contacts the workpiece, and the second contact surface includes at least one second overlapping portion and at least one second non-overlapping portion.

[0070] The first overlapping portion and the second overlapping portion overlap in the stacking direction, and the first non-overlapping portion and the second non-overlapping portion do not overlap in the stacking direction,

[0071] In the resistance welding method,

[0072] pressurizing the workpiece in the stacking direction by using the first overlapping portion and the second overlapping portion,

[0073] Power is supplied to the workpiece using at least the first non-overlapping portion and the second non-overlapping portion.

[0074] According to the resistance welding method, the first electrode and the second electrode are suppressed from pressing and supplying electricity to the workpiece, and when the workpiece undergoes plastic deformation due to softening and melting of the workpiece, the first electrode and the second electrode are suppressed from sinking into the workpiece. Since the change in the contact state between the electrode and the workpiece surface is suppressed, the occurrence of arc discharge between the electrode surface and the workpiece surface is suppressed. That is, the deterioration of the electrode is suppressed.

[0075] The electrode degradation is suppressed, and as a result, the resistance welding method can stabilize the welding quality of multiple materials, for example. In addition, in the resistance welding method, the frequency of stopping the production line is reduced, which is conducive to reducing the manufacturing cost. Moreover, since it is not necessary to increase the power supply in advance in consideration of the degradation of the electrode, the resistance welding method can also suppress energy loss.

[0076] - Effects of the Invention -

[0077] A resistance welding device and a resistance welding method are provided that can suppress degradation of electrodes. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Figure 1 An integral resistance welding device is shown;

[0079] Figure 2 It shows the state of the resistance welding device welding the workpiece;

[0080] Figure 3 The welding process of the resistance welding device is shown;

[0081] Figure 4 A first electrode and a second electrode are shown;

[0082] Figure 5 A first electrode and a second electrode are shown;

[0083] Figure 6 A first electrode and a second electrode are shown;

[0084] Figure 7 A first electrode and a second electrode are shown;

[0085] Figure 8 A first electrode and a second electrode are shown;

[0086] Fig. 9 A first electrode and a second electrode are shown;

[0087] Fig.10 A first electrode and a second electrode are shown;

[0088] Fig.11 A first electrode and a second electrode are shown;

[0089] Fig.12 A first electrode and a second electrode are shown;

[0090] Fig.13 Shown include Fig.12 A state in which a resistance welding device with a first electrode and a second electrode welds a workpiece;

[0091] Fig.14 The change of the inter-electrode resistance value in the case of the conventional electrode and Figure 4 Changes in inter-electrode resistance in the case of electrodes;

[0092] Fig.15 A conventional resistance welding device is shown. DETAILED DESCRIPTION

[0093] Hereinafter, embodiments of a resistance welding device and a resistance welding method will be described with reference to the accompanying drawings. The resistance welding device and the resistance welding method described here are examples.

[0094] (Overall structure of resistance welding device)

[0095] Figure 1 The overall resistance welding device 1 is exemplified. The resistance welding device 1 welds a plurality of materials to be welded 101 and 102 by pressing the workpiece 100 in the stacking direction and supplying power to the workpiece 100, wherein the workpiece 100 is composed of a plurality of stacked materials to be welded 101 and 102. The resistance welding device 1 is a so-called spot welding device. Figure 1 In the resistance welding device 1, the stacking direction is the up-down direction on the paper. The stacking direction is not limited to the up-down direction.

[0096] The two welded materials 101 and 102 are metal plates, for example, one is an iron component and the other is an aluminum component. The iron component is a high-strength and high-rigidity steel component such as high-tensile strength steel, and the aluminum component is an aluminum alloy component. It should be noted that both the welded materials 101 and 102 can also be iron components. Figure 1 In the example, the workpiece 100 is composed of two materials to be welded 101 and 102, but the workpiece 100 may also be composed of three or more materials to be welded. Figure 1 In the embodiment, the thicknesses of the two materials to be welded 101 and 102 are equal, but the thicknesses of the materials to be welded 101 and 102 may not be equal.

[0097] Figure 1 The illustrated resistance welding device 1 includes at least a welding gun 11 , a controller 12 , and a power source 13 .

[0098] The welding gun 11 is supported by, for example, a robot (not shown). The robot positions the welding gun 11 at a position on the workpiece 100 where welding is to be performed.

[0099] The welding gun 11 supports the first electrode 2 and the second electrode 3. The first electrode 2 is located on the first side of the stacking direction relative to the workpiece 100. Figure 1 In the embodiment, the first electrode 2 is located on the upper side of the workpiece 100. The second electrode 3 is located on the second side of the stacking direction relative to the workpiece 100. Figure 1 In the embodiment, the second electrode 3 is located at the lower side of the workpiece 100. The first electrode 2 and the second electrode 3 sandwich the workpiece 100 in the stacking direction and press the workpiece 100 in the stacking direction.

[0100] The first electrode 2 is a columnar shape extending in the stacking direction. The second electrode 3 is also a columnar shape extending in the stacking direction. The first electrode 2 and the second electrode 3 face each other in the stacking direction.

[0101] The welding gun 11 has a pressurizing device 14. The pressurizing device 14 moves the first electrode 2 relative to the workpiece 100 in the stacking direction. The pressurizing device 14 is composed of, for example, an air cylinder, a hydraulic cylinder, or a servo motor. When the welding gun 11 makes the front end of the second electrode 3 contact the surface of the workpiece 100, the pressurizing device 14 moves the first electrode 2, thereby the first electrode 2 and the second electrode 3 can clamp the workpiece 100 in the stacking direction and pressurize the workpiece 100 in the stacking direction.

[0102] In the resistance welding device 1, the controller 12 controls the pressurization and power supply to the workpiece 100. The controller 12 is a controller based on a well-known microcomputer, including a CPU (Central Processing Unit), a memory, and an input-output bus. The CPU is a central processing unit that executes computer programs. Computer programs include basic control programs such as OS (Operating System) and application programs that are started on the OS to implement specific functions. The memory includes RAM (Random Access Memory) and ROM (Read Only Memory). Various computer programs, data, etc. are stored in the ROM. RAM is a memory provided with a processing area used when the CPU performs a series of processes. The input-output bus inputs and outputs electrical signals to the controller 12.

[0103] The controller 12 outputs a control signal to the pressurizing device 14 according to a control program stored in the ROM, thereby pressurizing the workpiece 100 using the first electrode 2 and the second electrode 3 .

[0104] The controller 12 also supplies the welding current from the power source 13 to the workpiece 100 through the first electrode 2 and the second electrode 3. The current sensor 121 outputs a measurement signal corresponding to the welding current to the controller 12. The controller 12 can obtain the resistance value between the first electrode 2 and the second electrode 3 according to the measurement signal of the current sensor 121. The controller 12 adjusts the welding current supplied to the workpiece 100 based on the resistance value between the first electrode 2 and the second electrode 3.

[0105] (Basic Structure of First Electrode and Second Electrode)

[0106] Figure 2 The basic structure of the first electrode 2 and the second electrode 3 is illustrated. The first electrode 2 and the second electrode 3 have a feature that a voltage application function and a power supply function are separated.

[0107] The first electrode 2 has a first contact surface 21. The first contact surface 21 is in contact with the surface of the workpiece 100, more specifically, with the surface of the material to be welded 101. The first contact surface 21 is, for example, a flat surface. The first contact surface 21 is not limited to a flat surface.

[0108] The first contact surface 21 has a first overlapping portion 22 and a first non-overlapping portion 23. That is, the first overlapping portion 22 is a part of the first contact surface 21, and the first non-overlapping portion 23 is a part of the first contact surface 21 other than the first overlapping portion 22.

[0109] The second electrode 3 has a second contact surface 31. The second contact surface 31 also contacts the surface of the workpiece 100, more specifically, the surface of the material to be welded 102. The second contact surface 31 is, for example, a flat surface. The second contact surface 31 is not limited to a flat surface.

[0110] The second contact surface 31 has a second overlapping portion 32 and a second non-overlapping portion 33. That is, the second overlapping portion 32 is a part of the second contact surface 31, and the second non-overlapping portion 33 is a part of the second contact surface 31 excluding the second overlapping portion 32.

[0111] The first overlapping portion 22 and the second overlapping portion 32 overlap each other in the stacking direction (see Figure 2 The first non-overlapping portion 23 and the second non-overlapping portion 33 do not overlap each other in the stacking direction. More specifically, the first non-overlapping portion 23 is located on the first side of the direction orthogonal to the stacking direction relative to the first overlapping portion 22. The first side is Figure 2 The second non-overlapping portion 33 is located on the second side of the direction orthogonal to the stacking direction relative to the second overlapping portion 32. The second side is Figure 2 The first non-overlapping portion 23 and the second non-overlapping portion 33 are located on both sides of a line connecting the first overlapping portion 22 and the second overlapping portion 32 in a direction perpendicular to the stacking direction.

[0112] When the first electrode 2 and the second electrode 3 pressurize the workpiece 100 in the stacking direction, the first contact surface 21 and the second contact surface 31 overlap in the stacking direction only with the first overlapping portion 22 and the second overlapping portion 32. The first overlapping portion 22 and the second overlapping portion 32 constitute the pressurizing portion that actually pressurizes the workpiece 100. In the first electrode 2 and the second electrode 3, the portion that actually pressurizes the workpiece 100 is a portion of the first contact surface 21 and a portion of the second contact surface 31. The area of ​​the first overlapping portion 22 and the second overlapping portion 32 is smaller than the area of ​​the first contact surface 21 and the second contact surface 31.

[0113] The first non-overlapping portion 23 and the second non-overlapping portion 33 do not overlap each other in the stacking direction. Figure 2 In the structural example, the second electrode 3 does not exist at a position opposite to the first non-overlapping portion 23 in the stacking direction, and the first electrode 2 does not exist at a position opposite to the second non-overlapping portion 33 in the stacking direction. When the first electrode 2 and the second electrode 3 press the workpiece 100 in the stacking direction, the first non-overlapping portion 23 and the second non-overlapping portion 33 do not press the workpiece 100. The first non-overlapping portion 23 and the second non-overlapping portion 33 mainly function as a power supply portion for supplying power to the workpiece 100.

[0114] The line connecting the first non-overlapping portion 23 and the second non-overlapping portion 33 intersects with the line connecting the first overlapping portion 22 and the second overlapping portion 32 near the bonding interface 103 of the workpiece 100 (see Figure 2 In the workpiece 100, a current path is formed in a manner connecting the first non-overlapping portion 23 and the second non-overlapping portion 33 (see Figure 2 dashed arrow).

[0115] In this way, the function of applying pressure to the workpiece 100 and the function of supplying power to the workpiece 100 are separated from each other, respectively, of the first electrode 2 and the second electrode 3 .

[0116] Figure 3 The example shows a welding process performed by a resistance welding device 1 including a first electrode 2 and a second electrode 3. The welding process includes five steps S1 to S5. It should be noted that: Figure 3 The upper section of the diagram illustrates the relationship between the first electrode 2, the second electrode 3 and the workpiece 100 in each step. Figure 3 The middle section of the diagram illustrates the state near the bonding interface 103 in each step. Figure 3 The lower graph 301 shows an example of the change in the inter-electrode resistance value over time during the welding process.

[0117] The first step S1 is a step of moving the first electrode 2 toward the upper surface of the workpiece 100 while the second electrode 3 is in contact with the lower surface of the workpiece 100. The first electrode 2 and the second electrode 3 sandwich the workpiece 100 in the stacking direction and press the workpiece 100 in the stacking direction.

[0118] The second step S2 is a step of supplying power to the workpiece 100 through the first electrode 2 and the second electrode 3 while the first electrode 2 and the second electrode 3 pressurize the workpiece 100 in the stacking direction. At this time, as described above, the first overlapping portion 22 and the second overlapping portion 32 act as pressurizing portions to pressurize the workpiece 100 in the stacking direction. At the portion of the joint interface 103 of the workpiece 100 corresponding to the first overlapping portion 22 and the second overlapping portion 32, the two welded materials 101 and 102 come into contact, thereby forming a current path 105 in the workpiece 100. It should be noted that Figure 3 In the example, power is supplied not only to the first non-overlapping portion 23 and the second non-overlapping portion 33, but also to the first overlapping portion 22 and the second overlapping portion 32. In this state, there is a peripheral portion A of the first electrode 2 and a peripheral portion B of the second electrode 3, and the peripheral portions A and B are separated from each other with respect to the current path 105 at the bonding interface 103.

[0119] The third step S3 is to generate Joule heat at a portion of the bonding interface 103 of the workpiece 100 corresponding to the first overlapping portion 22 and the second overlapping portion 32, such as Figure 3As shown by the black arrow, a step of thermal expansion occurs at this part. With respect to this thermal expansion, since the peripheral parts A and B are separated from each other, the positional displacement of the first electrode 2 and the second electrode 3 caused by the thermal expansion is suppressed.

[0120] The fourth step S4 is a step of forming a current path 105 at the joint interface 103 of the workpiece 100 along with the heat generation and thermal expansion in the third step S3. A nugget is then generated in the current path 105. In this state, the current path 105 at the pressurized portion of the joint interface 103 is narrowed compared to the current path 105 in the second step S2 where pressurized and energized is applied.

[0121] The fifth step S5 is a step in which the welding materials 101 and 102 are melted at the joint interface 103 of the workpiece 100 to expand the current path 105 .

[0122] After the fifth step S5, the molten materials to be welded 101, 102 solidify to form a nugget, thereby completing the welding process. Figure 3 It should be noted that even in the state of the fourth step S4 and the fifth step S5, the positional deviation of the peripheral portions A and B separated from the nugget is small relative to the deformation of the workpiece 100 caused by the nugget.

[0123] like Figure 2 As shown, in each of the first electrode 2 and the second electrode 3, the area of ​​the first overlapping portion 22 and the second overlapping portion 32 that presses the workpiece 100 is relatively small. Therefore, in the fourth step S4 to the fifth step S5, the first electrode 2 and the second electrode 3 are suppressed from sinking into the workpiece 100 when the workpiece 100 undergoes plastic deformation.

[0124] In other words, since the first electrode 2 and the second electrode 3 have the first non-overlapping portion 23 and the second non-overlapping portion 33, respectively, the first electrode 2 and the second electrode 3 are suppressed from sinking into the workpiece 100. The first non-overlapping portion 23 and the second non-overlapping portion 33 are the first suppression portion and the second suppression portion, respectively, which suppress the first electrode 2 and the second electrode 3 from sinking toward the workpiece 100.

[0125] exist Fig.15 In the example of the conventional resistance welding device 10 , since the first electrode 20 and the second electrode 30 are sunk into the workpiece 100 , arc discharge occurs between the electrode surfaces and the workpiece surface, causing electrode degradation.

[0126] Figure 2 The resistance welding device 1 suppresses the first electrode 2 and the second electrode 3 from sinking into the workpiece 100, thereby suppressing the occurrence of arc discharge between the electrode surface and the workpiece surface. That is, the degradation of the electrode is suppressed.

[0127] In addition, the areas of the first overlapping portion 22 and the second overlapping portion 32 of the first electrode 2 and the second electrode 3 are relatively small, so the amount of heat transferred from the workpiece 100 to the first electrode 2 or the second electrode 3 during welding is reduced. In addition, since the volumes of the first electrode 2 and the second electrode 3 having the first non-overlapping portion 23 and the second non-overlapping portion 33 are relatively large, the heat capacity of the first electrode 2 or the second electrode 3 is relatively large. As a result, the first electrode 2 and the second electrode 3 are also suppressed from becoming high in temperature due to the heat from the workpiece 100, causing alloying of the electrode surfaces, or deformation of the electrode surfaces.

[0128] The electrode degradation is suppressed, and as a result, the resistance welding device 1 can perform high-precision management of the bonding interface state. High-precision management of the bonding interface state, for example, stabilizes the welding quality of multiple materials. In addition, since the resistance welding device 1 suppresses the degradation of the electrode, the stop frequency of the production line is reduced, which is conducive to reducing the manufacturing cost. Moreover, since there is no need to increase the power supply during welding in advance in consideration of the degradation of the electrode, the resistance welding device 1 can also suppress energy loss.

[0129] In addition, the first non-overlapping portion 23 and the second non-overlapping portion 33 do not sink into the workpiece 100 during welding, but stably contact the surface of the workpiece 100. When the welded materials 101 and 102 undergo thermal expansion in step S2, the first non-overlapping portion 23 and the second non-overlapping portion 33 press the thermally expanded welded materials 101 and 102. As a result, deformation of the workpiece 100 after welding is suppressed.

[0130] Here, the area of ​​the overlapping portion of the first electrode 2 and the second electrode 3 may account for 10% to 90% of the total area of ​​the contact surface. In this way, the first electrode 2 and the second electrode 3 can effectively suppress the electrode from sinking, thereby suppressing degradation.

[0131] The position where the line connecting the first overlapping portion 22 and the second overlapping portion 32 intersects with the joint interface of the workpiece 100 is the position where the welding materials 101 and 102 contact each other by the pressure of the first overlapping portion 22 and the second overlapping portion 32 to form a current path, and this position is the predetermined welding position. By making the line connecting the first non-overlapping portion 23 and the second non-overlapping portion 33 intersect with the predetermined welding position forming the current path, the first electrode 2 and the second electrode 3 can efficiently generate Joule heat at the predetermined welding position of the workpiece 100, wherein the first non-overlapping portion 23 and the second non-overlapping portion 33 supply power to the workpiece 100.

[0132] In addition, the first non-overlapping portion 23 and the second non-overlapping portion 33 are arranged symmetrically with respect to the line connecting the first overlapping portion 22 and the second overlapping portion 32, thereby, the first non-overlapping portion 23 and the second non-overlapping portion 33 can efficiently supply power to the portion corresponding to the first overlapping portion 22 and the second overlapping portion 32 and the portion where the welded materials 101 and 102 contact each other. The energy loss of resistance welding is reduced. In addition, the first electrode 2 and the second electrode 3 can stably contact the surface of the workpiece 100.

[0133] (Specific Structure of the First Electrode and the Second Electrode)

[0134] (first example)

[0135] Figure 4 Specific structures of the first electrode 2 and the second electrode 3 are exemplified. Figure 4 (a) is a cross-sectional view of the first electrode 2, Figure 4 (b) is a top view of the first electrode 2, Figure 4 (c) is a top view of the second electrode 3, Figure 4 (d) is a cross-sectional view of the second electrode 3, Figure 4 (e) shows the shape of the nugget 104 of the workpiece 100 joined using the first electrode 2 and the second electrode 3 . Figure 4 The double-dashed line in (e) is a line formed by projecting the shapes of the first contact surface 21 and the second contact surface 31 onto the workpiece 100. It should be noted that the following description Figure 5 to Figure 12 The same applies to each of (a) to (e).

[0136] The first electrode 2 and the second electrode 3 have cylindrical shapes with equal diameters, respectively. The first electrode 2 and the second electrode 3 are located on the same axis.

[0137] The first contact surface 21 of the first electrode 2 and the second contact surface 31 of the second electrode 3 each have a fan-shaped shape. However, the diameter of the fan-shaped shape is larger than the diameter of the cylindrical first electrode 2 and the second electrode 3. The axis of the first electrode 2 and the axis of the second electrode 3 are located inside the first contact surface 21 and the second contact surface 31.

[0138] The first electrode 2 and the second electrode 3 are reversed relative to the axis. At the front end of the first electrode 2, as Figure 4 As shown in (a), the portion other than the first contact surface 21 is the first recessed portion 24. Similarly, at the front end of the second electrode 3, as shown in Figure 4 As shown in (d) of FIG. 1 , the portion other than the second contact surface 31 is a second recessed portion 34 . These recessed portions 24 , 34 do not contact the surface of the workpiece 100 .

[0139] When the first electrode 2 and the second electrode 3 are opposite to each other, the overlapped portion of the first contact surface 21 and the second contact surface 31 is Figure 4 (b) Figure 4 The cross-hatched area in (c) is a quadrilateral area including the axis. This area is the first overlapping portion 22 and the second overlapping portion 32. In addition, in the first contact surface 21 and the second contact surface 31, the areas other than the first overlapping portion 22 and the second overlapping portion 32 are the first non-overlapping portion 23 and the second non-overlapping portion 33. The first non-overlapping portion 23 and the second non-overlapping portion 33 do not overlap in the stacking direction.

[0140] The first non-overlapping portion 23 is located on a first side in a direction perpendicular to the stacking direction relative to the first overlapping portion 22, and the second non-overlapping portion 33 is located on a second side in a direction perpendicular to the stacking direction relative to the second overlapping portion 32. The first non-overlapping portion 23 and the second non-overlapping portion 33 are located symmetrically on both sides in a direction perpendicular to the stacking direction across a line connecting the first overlapping portion 22 and the second overlapping portion 32.

[0141] By using Figure 4 The first electrode 2 and the second electrode 3 are connected to form a substantially quadrilateral nugget 104 on the workpiece 100 .

[0142] (Second example)

[0143] Figure 5 The first electrode 2 has a first contact surface 21 shaped like a semicircle. Similarly to the first electrode 2, the second electrode 3 has a second contact surface 31 shaped like a semicircle. The first electrode 2 and the second electrode 3 are reversed relative to the axis. At the front end of the first electrode 2, as shown in FIG. Figure 5 As shown in (a), the portion other than the first contact surface 21 is the first recessed portion 24. Similarly, at the front end of the second electrode 3, as shown in Figure 5 As shown in (d) of FIG. 1 , the portion other than the second contact surface 31 is a second recessed portion 34 . These recessed portions 24 , 34 do not contact the surface of the workpiece 100 .

[0144] When the first electrode 2 and the second electrode 3 are opposite to each other, the overlapped portion of the first contact surface 21 and the second contact surface 31 is Figure 5 (b) Figure 5 The cross-hatched portion in (c) is a linear portion including the axis. This portion is the first overlapping portion 22 and the second overlapping portion 32. In addition, in the first contact surface 21 and the second contact surface 31, the portion other than the first overlapping portion 22 and the second overlapping portion 32 is the first non-overlapping portion 23 and the second non-overlapping portion 33. The first non-overlapping portion 23 and the second non-overlapping portion 33 do not overlap in the stacking direction.

[0145] The first non-overlapping portion 23 is located on a first side in a direction perpendicular to the stacking direction relative to the first overlapping portion 22, and the second non-overlapping portion 33 is located on a second side in a direction perpendicular to the stacking direction relative to the second overlapping portion 32. The first non-overlapping portion 23 and the second non-overlapping portion 33 are located symmetrically on both sides in a direction perpendicular to the stacking direction across a line connecting the first overlapping portion 22 and the second overlapping portion 32.

[0146] By using Figure 5 The first electrode 2 and the second electrode 3 are connected to form a linear nugget 104 on the workpiece 100. The nugget 104 has a directionality. Having a directionality means that the length of the nugget 104 in the first direction is sufficiently longer than the length in the second direction. By appropriately setting the direction of the nugget 104 according to the workpiece 100, the necessary strength can be ensured. Figure 5 The width of the weld nugget 104 in the horizontal direction of the paper is narrow, so it is possible to weld a narrow part of the workpiece 100. The linear weld nugget 104 can obtain an advantage such as being able to narrow the width of the flange of the welding object. It should be noted that the width of the weld nugget 104 can be appropriately adjusted by adjusting the width of the first overlapping portion 22 and the second overlapping portion 32.

[0147] (Third example)

[0148] Figure 6 The first electrode 2 has a circular first contact surface 21. Different from the first electrode 2, the second electrode 3 has a ring-shaped second contact surface 31. Figure 6 In the example, the first contact surface 21 and the second contact surface 31 have different shapes. It should be noted that the shape of the first contact surface 21 of the first electrode 2 and the shape of the second contact surface 31 of the second electrode 3 can be interchangeable. Figure 6 As shown in (a), the portion other than the first contact surface 21 is the first recessed portion 24. Similarly, at the front end of the second electrode 3, as shown in Figure 6 As shown in (d) of FIG. 1 , the portion other than the second contact surface 31 is a second recessed portion 34 . These recessed portions 24 , 34 do not contact the surface of the workpiece 100 .

[0149] When the first electrode 2 and the second electrode 3 are opposite to each other, the overlapped portion of the first contact surface 21 and the second contact surface 31 is Figure 5 (b) Figure 5The cross-hatched portion in (c) is a circular ring-shaped portion centered on the axis. This portion is the first overlapping portion 22 and the second overlapping portion 32. The first overlapping portion 22 is a circular ring-shaped portion located on the outer periphery of the first contact surface 21. The second overlapping portion 32 is a circular ring-shaped portion located on the inner periphery of the second contact surface 31. In addition, in the first contact surface 21, the circular-shaped portion located on the inner side of the first overlapping portion 22 is the first non-overlapping portion 23, and in the second contact surface 31, the circular ring-shaped portion located on the outer side of the second overlapping portion 32 is the second non-overlapping portion 33. The first non-overlapping portion 23 and the second non-overlapping portion 33 do not overlap in the stacking direction.

[0150] exist Figure 6 In the cross section shown in (a), the first non-overlapping portion 23 is located on the first side in the direction orthogonal to the stacking direction, that is, on the radially inner side, relative to the first overlapping portion 22. Figure 6 In the cross section shown in (d), the second non-overlapping portion 33 is located on the second side in the direction orthogonal to the stacking direction, i.e., radially outward, relative to the second overlapping portion 32. The first non-overlapping portion 23 and the second non-overlapping portion 33 are located on both sides in the direction orthogonal to the stacking direction across the line connecting the first overlapping portion 22 and the second overlapping portion 32.

[0151] By using Figure 6 The first electrode 2 and the second electrode 3 are connected to form a ring-shaped weld nugget 104 on the workpiece 100.

[0152] (Fourth example)

[0153] Figure 7 The first electrode 2 has a first contact surface 21 in a triangular shape. Similarly to the first electrode 2, the second electrode 3 has a second contact surface 31 in a triangular shape. More precisely, the first contact surface 21 and the second contact surface 31 are in the shape of regular triangles. It should be noted that the first electrode 2 and the second electrode 3 are reversed relative to the axis. The center of gravity of the triangle of the first contact surface 21 and the center of gravity of the triangle of the second contact surface 31 coincide with each other in the stacking direction. At the front end of the first electrode 2, as shown in FIG. Figure 7 As shown in (a), the portion other than the first contact surface 21 is the first recessed portion 24. Similarly, at the front end of the second electrode 3, as shown in Figure 7 As shown in (d) of FIG. 1 , the portion other than the second contact surface 31 is a second recessed portion 34 . These recessed portions 24 , 34 do not contact the surface of the workpiece 100 .

[0154] When the first electrode 2 and the second electrode 3 are opposite to each other, the overlapped portion of the first contact surface 21 and the second contact surface 31 is Figure 7 (b) Figure 7The cross-hatched portion in (c) is a regular hexagonal portion centered on the axis. This portion is the first overlapping portion 22 and the second overlapping portion 32. In addition, in the first contact surface 21, the three triangular portions other than the first overlapping portion 22, that is, the portions near the vertices of the triangle of the first contact surface 21 are the first non-overlapping portions 23, and in the second contact surface 31, the three triangular portions other than the second overlapping portion 32, that is, the portions near the vertices of the triangle of the second contact surface 31 are the second non-overlapping portions 33. The three first non-overlapping portions 23 and the three second non-overlapping portions 33 do not overlap in the stacking direction. Figure 7 The first electrode 2 and the second electrode 3 have a plurality of first non-overlapping portions 23 and a plurality of second non-overlapping portions 33 .

[0155] By using Figure 7 The first electrode 2 and the second electrode 3 are connected to form a hexagonal nugget 104 on the workpiece 100.

[0156] Here, when the first electrode 2 and the second electrode 3 pressurize the workpiece 100 in the stacking direction, the pressure at the portion corresponding to the portion where the edge of the first contact surface 21 overlaps the edge of the second contact surface 31 in the joint interface of the workpiece is likely to increase, and Joule heat is likely to be generated after a current path is formed at this portion. Figure 7 In the electrode, since Joule heat is easily generated at each vertex of the hexagon of the first overlapping portion 22 and the second overlapping portion 32, multiple heat generating portions are evenly arranged in the circumferential direction centered on the axis. Since the welding predetermined portion can be evenly heated from its surroundings, Figure 7 The electrode has the advantage of stabilizing the heating of the workpiece 100 .

[0157] In addition, since multiple first non-overlapping portions 23 and second non-overlapping portions 33 are arranged at equal intervals around the first overlapping portion 22 and the second overlapping portion 32, when the workpiece 100 expands thermally, the multiple first non-overlapping portions 23 and the multiple second non-overlapping portions 33 can effectively press the thermally expanded welded material.

[0158] It should be noted that the shapes of the first contact surface 21 and the second contact surface 31 are not limited to regular triangles. The shapes of the first contact surface 21 and the second contact surface 31 may be, for example, isosceles triangles. In addition, the shapes of the first contact surface 21 and the second contact surface 31 may also be polygonal shapes other than triangles.

[0159] (Fifth Example)

[0160] Figure 8The electrode of the third example and the fourth example are combined. That is, similarly to the fourth example, the first electrode 2 has a triangular first contact surface 21. Similar to the third example, the second electrode 3 has a circular second contact surface 31. The outer diameter of the second contact surface 31 is consistent with the diameter of the circumscribed circle of the triangle of the first contact surface 21, and the inner diameter of the second contact surface 31 is consistent with the diameter of the inscribed circle of the triangle of the first contact surface 21.

[0161] When the first electrode 2 and the second electrode 3 are opposite to each other, the overlapped portion of the first contact surface 21 and the second contact surface 31 is Figure 8 (b) Figure 8 The cross-hatched areas in (c) are areas near the vertices of the triangle. These areas are the first overlapping area 22 and the second overlapping area 32. Figure 8 The first electrode 2 and the second electrode 3 have a plurality of first overlapping portions 22 and a plurality of second overlapping portions 32. In addition, in the first contact surface 21, the portion of the inscribed circle excluding the first overlapping portion 22 is the first non-overlapping portion 23, and in the second contact surface 31, the portion of a part of the circle excluding the second overlapping portion 32 (i.e., the arcuate portion) is the second non-overlapping portion 33. The first non-overlapping portion 23 and the three second non-overlapping portions 33 do not overlap in the stacking direction.

[0162] By using Figure 8 The first electrode 2 and the second electrode 3 are connected to form a plurality of weld nuggets 104 on the workpiece 100 .

[0163] It should be noted that the relationship between the triangle of the first contact surface 21 and the circular ring of the second contact surface 31 is not limited to the relationship between the circumscribed circle and the inscribed circle of the above triangle.

[0164] In addition, the first contact surface 21 of the first electrode 2 is not limited to a triangle, and may also be other polygons.

[0165] Furthermore, the shape of the first electrode 2 and the shape of the second electrode 3 may be interchangeable.

[0166] (Sixth Example)

[0167] Fig. 9 The first electrode 2 has a circular first contact surface 21, and similarly to the first electrode 2, the second electrode 3 has a circular second contact surface 31. For both the first electrode 2 and the second electrode 3, the entire front end surface of the cylindrical electrode serves as a contact surface.

[0168] The first electrode 2 and the second electrode 3 are arranged coaxially. The first electrode 2 and the second electrode 3 are opposite to each other in such a way that a part of the first contact surface 21 overlaps a part of the second contact surface 31. The overlapping part of the first contact surface 21 and the second contact surface 31 is Fig. 9(b) Fig. 9 The cross-hatched portion in (c) is an elliptical portion. This portion is the first overlapping portion 22 and the second overlapping portion 32. In addition, in the first contact surface 21 and the second contact surface 31, the portion other than the first overlapping portion 22 and the second overlapping portion 32 is the first non-overlapping portion 23 and the second non-overlapping portion 33. The first non-overlapping portion 23 and the second non-overlapping portion 33 do not overlap in the stacking direction.

[0169] The first non-overlapping portion 23 is located on a first side in a direction perpendicular to the stacking direction relative to the first overlapping portion 22, and the second non-overlapping portion 33 is located on a second side in a direction perpendicular to the stacking direction relative to the second overlapping portion 32. The first non-overlapping portion 23 and the second non-overlapping portion 33 are located symmetrically on both sides in a direction perpendicular to the stacking direction across a line connecting the first overlapping portion 22 and the second overlapping portion 32.

[0170] By using Fig. 9 The first electrode 2 and the second electrode 3 are connected to form a substantially elliptical nugget 104 on the workpiece 100 .

[0171] It should be noted that the first contact surface 21 and the second contact surface 31 are not limited to circular shapes, and may be, for example, elliptical shapes. The elliptical first contact surface 21 and the second contact surface 31 may partially overlap in their major axis direction or in their minor axis direction.

[0172] (Seventh Example)

[0173] Fig.10 The first electrode 2 has a quadrilateral first contact surface 21, and the second electrode 3 has a quadrilateral second contact surface 31 similarly to the first electrode 2. The entire front end surface of the first electrode 2 and the second electrode 3, which are both quadrangular prism-shaped electrodes, serves as a contact surface.

[0174] The first electrode 2 and the second electrode 3 are arranged coaxially. The first electrode 2 and the second electrode 3 are opposite to each other in such a way that a part of the first contact surface 21 overlaps a part of the second contact surface 31. The overlapping part of the first contact surface 21 and the second contact surface 31 is Fig.10 (b) Fig.10 The cross-hatched area in (c) is a rectangular area. This area is the first overlapping area 22 and the second overlapping area 32. In addition, in the first contact surface 21 and the second contact surface 31, the areas other than the first overlapping area 22 and the second overlapping area 32 are the first non-overlapping area 23 and the second non-overlapping area 33. The first non-overlapping area 23 and the second non-overlapping area 33 do not overlap in the stacking direction.

[0175] The first non-overlapping portion 23 is located on a first side in a direction perpendicular to the stacking direction relative to the first overlapping portion 22, and the second non-overlapping portion 33 is located on a second side in a direction perpendicular to the stacking direction relative to the second overlapping portion 32. The first non-overlapping portion 23 and the second non-overlapping portion 33 are located symmetrically on both sides in a direction perpendicular to the stacking direction across a line connecting the first overlapping portion 22 and the second overlapping portion 32.

[0176] By using Fig.10 The first electrode 2 and the second electrode 3 are connected to form a rectangular nugget 104 on the workpiece 100. In this case, the nugget 104 also has directivity as in the second example described above.

[0177] (Example 8)

[0178] Fig.11 The first electrode 2 has a triangular first contact surface 21, and similarly to the first electrode 2, the second electrode 3 has a triangular second contact surface 31. For the first electrode 2 and the second electrode 3, the entire front end surface of the triangular prism-shaped electrode is the contact surface. The directions of the first electrode 2 and the second electrode 3 are reversed with respect to the axis.

[0179] The first electrode 2 and the second electrode 3 are arranged coaxially. The first electrode 2 and the second electrode 3 are opposite to each other in such a manner that a portion of the first contact surface 21 overlaps a portion of the second contact surface 31. More specifically, a portion near the vertex of the first contact surface 21 and a portion near the vertex of the second contact surface 31 overlap each other. The overlapping portion of the first contact surface 21 and the second contact surface 31 is Fig.11 (b) Fig.11 The cross-hatched area in (c) is a diamond-shaped area. This area is the first overlapping portion 22 and the second overlapping portion 32. In addition, in the first contact surface 21 and the second contact surface 31, the areas other than the first overlapping portion 22 and the second overlapping portion 32 are the first non-overlapping portion 23 and the second non-overlapping portion 33. The first non-overlapping portion 23 and the second non-overlapping portion 33 do not overlap in the stacking direction.

[0180] The first non-overlapping portion 23 is located on a first side in a direction perpendicular to the stacking direction relative to the first overlapping portion 22, and the second non-overlapping portion 33 is located on a second side in a direction perpendicular to the stacking direction relative to the second overlapping portion 32. The first non-overlapping portion 23 and the second non-overlapping portion 33 are located symmetrically on both sides in a direction perpendicular to the stacking direction across a line connecting the first overlapping portion 22 and the second overlapping portion 32.

[0181] By using Fig.11 The first electrode 2 and the second electrode 3 are connected to form a diamond-shaped weld nugget 104 on the workpiece 100.

[0182] It should be noted that the first contact surface 21 and the second contact surface 31 are not limited to the quadrilateral shape of the seventh example or the triangular shape of the eighth example, and may also be other polygonal shapes or regular polygonal shapes.

[0183] (Case 9)

[0184] Fig.12 and Fig.13 Shows Figure 4 The first contact surface 21 of the first electrode 2 and the second contact surface 31 of the second electrode 3 are both fan-shaped. However, the diameter of the fan-shaped shape is larger than that of the first contact surface 21 of the first electrode 2 and the second contact surface 31 of the second electrode 3. Figure 4 The fan-shaped diameters of the first contact surface 21 and the second contact surface 31 of the electrode are small.

[0185] More specifically, Figure 4 The first contact surface 21 of the first electrode 2 extends to the peripheral portion of the first electrode 2. Similarly, Figure 4 The second contact surface 31 of the second electrode 3 extends to the peripheral portion of the second electrode 3 .

[0186] In contrast, Fig.12 The first electrode 2 is provided with an inclined surface 25. The inclined surface 25 is formed between the periphery of the first electrode 2 and the first contact surface 21 and is inclined relative to the axis of the first electrode 2. The inclined surface 25 reduces the area of ​​the first contact surface 21 and brings the center of gravity 26 of the fan-shaped first contact surface 21 closer to the center of the first electrode 2.

[0187] Similarly, in Fig.12 The second electrode 3 has an inclined surface 35 formed thereon. The inclined surface 35 reduces the area of ​​the second contact surface 31 and brings the center of gravity 36 of the fan-shaped second contact surface 31 closer to the center of the second electrode 3.

[0188] It should be noted that Fig.12 The recessed portion 24 of the first electrode 2 is constituted by a surface inclined with respect to the axis of the first electrode 2 , and the recessed portion 34 of the second electrode 3 is also constituted by a surface inclined with respect to the axis of the second electrode 3 .

[0189] In making Fig.12 When the first electrode 2 and the second electrode 3 are opposite to each other, the overlapped portion of the first contact surface 21 and the second contact surface 31 is Fig.12 (b) Fig.12 The cross-hatched area in (c) is a quadrilateral area including the axis. This area is the first overlapping portion 22 and the second overlapping portion 32. In addition, in the first contact surface 21 and the second contact surface 31, the areas other than the first overlapping portion 22 and the second overlapping portion 32 are the first non-overlapping portion 23 and the second non-overlapping portion 33. The first non-overlapping portion 23 and the second non-overlapping portion 33 do not overlap in the stacking direction.

[0190] As mentioned above, due to Fig.12 The area of ​​the first contact surface 21 and the second contact surface 31 in the electrode is smaller than Figure 4 The area of ​​the first contact surface 21 and the second contact surface 31 of the electrode is relatively small, so the area of ​​the first non-overlapping portion 23 and the second non-overlapping portion 33 is also relatively small. When the first electrode 2 and the second electrode 3 are used to supply power to the workpiece 100, if the current is the same, the current density will increase by the amount of reduction in the area of ​​the first non-overlapping portion 23 and the second non-overlapping portion 33 (see Fig.13 The high current density improves the joining quality of the workpiece 100. In addition, the high current density enables efficient heating of the joining interface of the workpiece 100. Fig.12 The first electrode 2 and the second electrode 3 are advantageous for power saving in resistance welding.

[0191] In addition, since the position of the center of gravity 26 of the first contact surface 21 is near the center of the first electrode 2, the center of gravity 26 is included in the first overlapping portion 22. Since the position of the center of gravity 36 of the second contact surface 31 is also near the center of the second electrode 2, the center of gravity 36 is included in the second overlapping portion 32 (see Fig.12 (b) Fig.12 (c)). By making the area of ​​the first contact surface 21 and the second contact surface 31 relatively small and making the positions of the centers of gravity 26 and 36 of the first contact surface 21 and the second contact surface 31 close to the centers of the first electrode 2 and the second electrode 3, the pressing density when the first electrode 2 and the second electrode 3 press the workpiece 100 in the stacking direction is increased. The high pressing density improves the joining quality of the workpiece 100.

[0192] In addition, since the distance between the position of the center of gravity 26, 36 and the central axis of the electrodes 2, 3 is short, when the workpiece 100 softens and melts due to heat, the moment acting on the first electrode 2 and the second electrode 3 is small. The small moment suppresses the electrodes 2, 3 from sliding relative to the surface of the workpiece 100 or the electrodes 2, 3 from tilting relative to the surface of the workpiece 100, thereby suppressing the degradation of the first electrode 2 and the second electrode 3.

[0193] Here, when the area of ​​the first contact surface 21 and the second contact surface 31 is too small, the area of ​​the first non-overlapping portion 23 and the second non-overlapping portion 33 becomes too small, and the pressure-applying function and the power-supplying function of the first electrode 2 and the second electrode 3 are not substantially separated. The area of ​​the first contact surface 21 can also be made more than 120% of the area of ​​the first overlapping portion 22. Similarly, the area of ​​the second contact surface 31 can also be made more than 120% of the area of ​​the second overlapping portion 32. In this way, the pressure-applying function and the power-supplying function of the first electrode 2 and the second electrode 3 are separated, so that the resistance welding device 10 can obtain the above-mentioned effect and can improve the current density. It should be noted that when the area of ​​the first contact surface 21 is too large relative to the area of ​​the first overlapping portion 22, the position of the center of gravity of the first contact surface 21 will deviate from the first overlapping portion 22. The upper limit of the area of ​​the first contact surface 21 is determined by the restriction that the position of the center of gravity of the first contact surface 21 must be included in the first overlapping portion 22. Likewise, the upper limit of the area of ​​the second contact surface 31 is determined by the restriction that the position of the center of gravity of the second contact surface 31 is included in the second overlapping portion 32 .

[0194] (Example)

[0195] Fig.14 An example in which the effect of suppressing electrode degradation is confirmed is shown. Fig.14 The figure above compares the use of Fig.15 The shown graphs show the change in inter-electrode resistance over time at the first welding and the change in inter-electrode resistance over time at the 101st welding when spot welding was repeatedly performed using conventional electrodes. Fig.14 The following figure compares the use of Figure 4 The illustrated graph shows the change in inter-electrode resistance over time at the first welding and the change in inter-electrode resistance over time at the 101st welding when the electrodes of the present invention were repeatedly spot welded.

[0196] from Fig.14 As can be seen from the above figure, in the conventional electrode, the inter-electrode resistance value at the beginning of welding at the 101st welding is significantly lower than the inter-electrode resistance value at the beginning of welding at the 1st welding. The decrease in inter-electrode resistance value is due to the deterioration of the electrode as spot welding is repeated.

[0197] In contrast, from Fig.14 As can be seen from the figure below, in the electrode of the present application, the inter-electrode resistance value at the beginning of welding at the 101st welding is almost unchanged from the inter-electrode resistance value at the beginning of welding at the 1st welding. That is, the electrode of the present application suppresses the degradation of the electrode.

[0198] Here, as a standard for the press density or current density in resistance welding, the standard established by RWMA (Resistance Welding Manufacturing Alliance) is known. Even in the case of resistance welding using the electrodes of the first to ninth examples, the press density or current density can be determined according to the RWMA standard.

[0199] Specifically, the pressure density in the resistance welding device 1 disclosed herein can be 4 to 10 kgf / mm 2 In addition, the current density can be 200-500A / mm 2 .

[0200] It should be noted that the above embodiments are merely examples and are not intended to limit the scope of the present invention. The scope of protection of the present invention is determined by the scope of the claims, and modifications and variations within the equivalent scope of the claims are included in the scope of the present invention.

[0201] - Explanation of symbols -

[0202] 1 Resistance welding device

[0203] 100 Workpieces

[0204] 101, 102 Welding materials

[0205] 103 Bonding interface

[0206] 2. First electrode

[0207] 21 First contact surface

[0208] 22 First overlapping part

[0209] 23 First non-overlapping portion (first suppression portion)

[0210] 26 Center of Gravity

[0211] 3 Second electrode

[0212] 31 Second contact surface

[0213] 32 Second overlapping part

[0214] 33 Second non-overlapping portion (second suppression portion)

[0215] 36 Center of Gravity

Claims

1. A resistance welding device, which welds a plurality of materials to be welded by pressurizing a workpiece composed of a plurality of materials to be welded stacked in a stacking direction and supplying power to the workpiece, characterized in that: The resistance welding device comprises a first electrode and a second electrode, The first electrode is located on a first side of the stacking direction relative to the workpiece, The second electrode is located on a second side of the stacking direction relative to the workpiece, and the second electrode sandwiches the workpiece between the first electrode and the second electrode, The first electrode has a first contact surface in contact with the workpiece, The second electrode has a second contact surface in contact with the workpiece, The first contact surface has at least one first overlapping portion and at least one first non-overlapping portion, The second contact surface has at least one second overlapping portion and at least one second non-overlapping portion, The first overlapping portion and the second overlapping portion overlap in the stacking direction, and the first non-overlapping portion and the second non-overlapping portion do not overlap in the stacking direction.

2. The resistance welding device according to claim 1, characterized in that: A line connecting the first non-overlapping portion and the second non-overlapping portion intersects a line connecting the first overlapping portion and the second overlapping portion near a joining interface of the workpieces.

3. The resistance welding device according to claim 2, characterized in that: The first non-overlapping portion is located on a first side in a direction orthogonal to the stacking direction relative to the first overlapping portion, and the second non-overlapping portion is located on a second side in a direction orthogonal to the stacking direction relative to the second overlapping portion. A wire connecting the first overlapping portion and the second overlapping portion is sandwiched between the first non-overlapping portion and the second non-overlapping portion, and the first non-overlapping portion and the second non-overlapping portion are located on both sides in a direction orthogonal to the stacking direction.

4. The resistance welding device according to claim 2, characterized in that: The first contact surface has a circular shape, and the second contact surface has a circular ring shape whose center coincides with the center of the first contact surface. The first overlapping portion is an annular shape located at the outer periphery of the first contact surface, and the first non-overlapping portion is a circular shape located inside the annular first overlapping portion. The second overlapping portion is annular in shape and located at an inner circumference of the second contact surface, and the second non-overlapping portion is annular in shape and located outside the annular second overlapping portion.

5. The resistance welding device according to claim 1, characterized in that: The first contact surface has a triangular shape, and the second contact surface has a triangular shape obtained by reversing the direction of the triangle of the first contact surface with respect to a line connecting the first overlapping portion and the second overlapping portion. The first contact surface and the second contact surface are arranged so that the center of gravity of the triangle of the first contact surface coincides with the center of gravity of the triangle of the second contact surface in the stacking direction.

6. The resistance welding device according to claim 1, characterized in that: The position of the center of gravity of the first contact surface is included in the first overlapping portion, The position of the center of gravity of the second contact surface is included in the second overlapping portion.

7. The resistance welding device according to claim 6, characterized in that: The area of ​​the first contact surface is greater than 120% of the area of ​​the first overlapping portion. The area of ​​the second contact surface is greater than 120% of the area of ​​the second overlapping portion.

8. A resistance welding device that welds a plurality of materials to be welded by pressurizing a workpiece composed of a plurality of materials to be welded stacked in a stacking direction and supplying power to the workpiece, wherein: The resistance welding device comprises a first electrode and a second electrode, The first electrode is located on a first side of the stacking direction relative to the workpiece, and the first electrode has a first contact surface that contacts the workpiece. The second electrode is located on a second side of the stacking direction relative to the workpiece, and the second electrode has a second contact surface that contacts the workpiece, and the second electrode sandwiches the workpiece between the first electrode and the second electrode, The first electrode has a first inhibiting portion at a portion of the first contact surface, the first inhibiting portion inhibiting the first electrode from sinking toward the workpiece when power is supplied. The second electrode has a second inhibiting portion at a portion of the second contact surface, and the second inhibiting portion inhibits the second electrode from sinking toward the workpiece during the power supply.

9. A resistance welding method, using a first electrode and a second electrode, pressurizing a workpiece consisting of a plurality of stacked materials to be welded in a stacking direction and supplying power to the workpiece, thereby welding the plurality of materials to be welded, characterized in that: The first electrode has a first contact surface, the first contact surface contacts the workpiece, and the first contact surface includes at least one first overlapping portion and at least one first non-overlapping portion. The second electrode has a second contact surface, the second contact surface contacts the workpiece, and the second contact surface includes at least one second overlapping portion and at least one second non-overlapping portion. The first overlapping portion and the second overlapping portion overlap in the stacking direction, and the first non-overlapping portion and the second non-overlapping portion do not overlap in the stacking direction, pressurizing the workpiece in the stacking direction by using the first overlapping portion and the second overlapping portion, Power is supplied to the workpiece using at least the first non-overlapping portion and the second non-overlapping portion.

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