Resistance welding equipment

Abstract

To inhibit deterioration of welding quality in resistance welding.SOLUTION: A resistance welding device welds a plurality of laminated to-be-welded members 101, 102 by pressurizing a workpiece 100 that comprises the plurality of to-be-welded members and supplying electric power to the workpiece. The resistance welding device includes an electrode 2 configured to abut on the workpiece, pressurize the workpiece, and supply electric power to the workpiece. The electrode is provided with: a refrigerant passage 26 extending in a center axis direction of the electrode at a center part in a radial direction; and slits 41 to 44 that communicate with the refrigerant passage, are open on an outer peripheral surface of the electrode, and extend in a circumferential direction on a plane that intersects the central axis direction. The electrode has an inhibition part (a cover 6) which inhibits leakage of a refrigerant through the slits.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The technology disclosed herein relates to a resistance welding apparatus.

Background Art

[0002] Patent Document 1 describes a spot welding apparatus. The spot welding apparatus includes a robot and a welding gun. The robot holds the welding gun and positions the welding gun at the welding location of the workpiece to be welded. An equalizing mechanism is provided between the welding gun and the robot. The equalizing mechanism absorbs the displacement of the workpiece to be welded and / or the teaching error of the robot.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Spot welding is one type of resistance welding. Resistance welding welds a plurality of workpieces to be welded by going through the following process. That is, (1) The first electrode and the second electrode sandwich a workpiece composed of a plurality of workpieces to be welded and supply power to the workpiece while applying pressure to the workpiece. (2) When the workpieces to be welded come into contact with each other due to the applied pressure, an energization path is formed at the bonding interface of the workpiece, and Joule heat is generated at the bonding interface. (3) The workpieces to be welded melt at the bonding interface of the workpiece. (4) The melted workpieces to be welded solidify to form nuggets, and the welding process is completed.

[0005] In the resistance welding process, electrical discharges can occur between the electrode and the workpiece. Such discharges cause wear on the electrode tip. A challenge in the field of resistance welding is that, as the shape of the electrode tip gradually changes due to wear during repeated welding, the weld quality deteriorates.

[0006] The technology disclosed herein suppresses the deterioration of welding quality in resistance welding. [Means for solving the problem]

[0007] The inventors of the present invention have found that the discharge occurs when the material to be welded softens / melts in process (2) and / or (3) of the processes (1) to (4) described above.

[0008] To explain in more detail, during the welding process, the tip of the electrode is pressed against the workpiece. The electrode pressed against the workpiece is constrained by the workpiece and the welding gun. When the material to be welded softens / melts in (2) and / or (3) above, the constraint of the electrode by the workpiece and the welding gun loosens. If the center of the load applied to the electrode is on the electrode's central axis, even if the constraint loosens, the tip of the electrode does not move relative to the surface of the material to be welded, and the electrode remains pressed against the workpiece in the direction of the electrode's central axis. In resistance welding, the electrode's central axis is generally perpendicular to the surface of the workpiece.

[0009] However, if the center of the load applied to the electrode is eccentric or tilted relative to the electrode's central axis, the electrode's restraint loosens, causing the electrode's tip to move slightly, sliding across the surface of the workpiece. During this movement, a displacement occurs between the electrode and the workpiece, resulting in a discharge between them.

[0010] In the following, when the center of the load applied to the electrode is eccentric or tilted relative to the electrode's central axis, it is referred to as "the center of the load being offset from the electrode's central axis."

[0011] In view of the discharge generation mechanism described above, the inventors of the present invention focused on the point of elastically bending the electrode with respect to its central axis. If the electrode can be bent, even if the center of the load applied to the electrode is offset from the electrode's central axis, the elastic deformation of the electrode causes the entire tip surface of the electrode to uniformly contact the surface of the workpiece, and the electrode can apply a load to the workpiece in the direction of the central axis. In this case, even if the workpiece softens / melts and the restraint of the electrode by the workpiece and welding gun loosens, the tip surface of the electrode does not move, or moves very little, relative to the surface of the workpiece. This suppresses the occurrence of displacement between the electrode and the workpiece, and suppresses the generation of discharge between the electrode and the workpiece.

[0012] Because the electrode has a flexible structure, it is conceivable to form a slit on the outer surface of the electrode. However, if a slit is formed in the electrode, the coolant used to cool the electrode will leak through that slit.

[0013] Therefore, the technology disclosed herein is characterized by suppressing the leakage of refrigerant through the slit.

[0014] Specifically, the technology disclosed herein relates to a resistance welding apparatus that welds a workpiece consisting of a plurality of stacked workpieces by applying pressure to the workpiece and supplying power to the workpiece. This resistance welding apparatus is The electrode is provided to contact the workpiece and to apply pressure and supply power to the workpiece, The electrode has, In the radial central portion, a refrigerant passage extends in the direction of the central axis of the electrode, A slit is formed which communicates with the refrigerant passage and opens to the outer surface of the electrode, and which extends circumferentially on a plane intersecting the central axis direction, The electrode has a suppression portion that suppresses the leakage of refrigerant through the slit.

[0015] In this configuration, the tip surface of the electrode is in contact with the workpiece. The base end of the electrode may be supported, for example, by a welding gun. The welding gun presses the tip surface of the electrode against the surface of the material to be welded. The electrode applies pressure to the workpiece in the direction of the electrode's central axis and also supplies power to the workpiece.

[0016] When the material to be welded softens / melts due to pressure and power supply to the workpiece, the restraint of the electrode pressed against the workpiece loosens. If the center of the load applied to the electrode is offset from the electrode's central axis, the loosening of the electrode's restraint may cause the electrode's tip surface to move slightly, resulting in a misalignment between the electrode's tip surface and the surface of the material to be welded.

[0017] A slit is formed in the aforementioned electrode. The slit opens on the outer surface of the electrode and extends circumferentially on a plane that intersects with the central axis. Note that the plane that intersects with the central axis is a virtual plane on the electrode. The slit allows the electrode to bend elastically with respect to its central axis when the center of the load applied to the electrode is offset from the electrode's central axis.

[0018] When the electrode undergoes elastic deformation, the entire tip surface of the electrode can make uniform contact with the surface of the workpiece. The electrode applies a load to the workpiece through the tip surface that is uniformly in contact with the surface of the workpiece. In this case, when the constraint on the electrode loosens due to the softening / melting of the workpiece, the tip surface of the electrode does not move, or moves very little, relative to the surface of the workpiece. The workpiece deforms, but the change in the positional relationship between the tip surfaces of the electrodes that are in contact with each other and the surface of the workpiece is suppressed. Suppressing the displacement between the tip surface of the electrode and the surface of the workpiece suppresses the generation of discharge between the electrode and the workpiece, and therefore suppresses wear of the electrode tip. Because wear is suppressed, the shape of the electrode tip does not change, or changes very little, even after repeated welding. The resistance welding apparatus described above can maintain high welding quality. Furthermore, the resistance welding apparatus described above is also advantageous for extending the lifespan of the electrode.

[0019] The slit formed in the electrode enables elastic deformation of the electrode while causing leakage of the refrigerant. The electrode has a suppression portion. The suppression portion suppresses the leakage of the refrigerant through the slit. Since the electrode can be elastically deformed while ensuring the cooling structure, the resistance welding apparatus can suppress deterioration of the welding quality.

[0020] The slit is formed in at least one of the first electrode located on the first side sandwiching the workpiece and the second electrode located on the second side. The suppression portion may be attached to the electrode in which the slit is formed.

[0021] If at least one of the first electrode and the second electrode is elastically deformable, the resistance welding apparatus can stabilize the welding quality. If both the first electrode and the second electrode are elastically deformable, the resistance welding apparatus can further stabilize the welding quality. [[ID=​​​​​​​​​​​​​​​​​​​​​​​​

[0027] The slit extends circumferentially in a plane perpendicular to the central axis direction, The electrode is Multiple slits aligned in the direction of the central axis, A base formed by the first and second slits adjacent to each other in the central axis direction, which is an annular shape surrounding the refrigerant passage and has a thickness that is elastically deformable so as to bend in the central axis direction, The structure includes columns formed within the first slit and the second slit, respectively, and extending in the direction of the central axis and connected to the base. ru.

[0028] The column within the slit, and the base to which the column is connected, transmit the load in the central axis direction between the tip and base of the electrode. The column within the slit ensures the rigidity required for the electrode to press down on the workpiece.

[0029] When the base is subjected to a load in the axial direction through the column, it tends to bend in the axial direction. The slit adjacent to the base allows the base to bend in the axial direction. As the base bends in the axial direction, the slit collapses in the axial direction, allowing the electrode to be compressed in the axial direction.

[0030] The electrode comprises a cap tip that contacts the workpiece, a shank to which the cap tip is attached, and a holder that holds the shank. The slit is formed in the shank or the holder, The suppression portion may be attached to the shank or holder in which the slit is formed.

[0031] The cap tip that contacts the workpiece is replaced when it becomes worn. The frequency of cap tip replacement is higher than the frequency of shank replacement or holder replacement.

[0032] Forming slits in the cap tip increases the manufacturing cost of the cap tip. High manufacturing costs for cap tips, which are replaced frequently, increase the maintenance costs of resistance welding equipment. In contrast, the shank or holder are suitable locations for slit formation because they are replaced relatively infrequently. [Effects of the Invention]

[0033] The aforementioned resistance welding apparatus can suppress the occurrence of slippage between the electrode tip surface and the surface of the workpiece during resistance welding, thereby suppressing a decrease in welding quality during resistance welding. Furthermore, the resistance welding apparatus can suppress refrigerant leakage. [Brief explanation of the drawing]

[0034] [Figure 1] Figure 1 shows a spot welding apparatus. [Figure 2] Figure 2 shows the first electrode of the spot welding apparatus. [Figure 3] Figure 3 shows the shank of the first electrode. [Figure 4] The upper part of Figure 4 is a top view of the shank, and the lower part is a cross-sectional view of AA. [Figure 5] Figure 5 shows the procedure for creating the slit. [Figure 6] The upper part of Figure 6 shows the shank in an elastically deformed state, while the lower part shows the BB cross-section. [Figure 7] Figure 7 shows the shank in a bent state. [Figure 8] Figure 8 shows a modified example of the electrode related to the slit. [Figure 9] Figure 9 shows a modified example of an electrode related to a column. [Figure 10] Figure 10 shows the welding process of a projection welding apparatus. [Figure 11] Figure 11 is an exploded view of the first electrode of a projection welding apparatus. [Figure 12] Figure 12 shows the second electrode of the projection welding apparatus. [Modes for carrying out the invention]

[0035] The following describes an embodiment of a resistance welding apparatus with reference to the drawings. The resistance welding apparatus described herein is illustrative.

[0036] (Overall structure of spot welding equipment) Figure 1 illustrates an overall resistance welding apparatus. The resistance welding apparatus welds multiple workpieces 101 and 102, which are stacked and consist of a workpiece 100, by applying pressure to the workpiece 100 and supplying power to the workpiece 100. The resistance welding apparatus in Figure 1 is a so-called spot welding apparatus 1. In the spot welding apparatus 1 of Figure 1, the direction of pressure applied to the workpiece 100 is the vertical direction in the plane of the paper. The direction of pressure is not limited to the vertical direction.

[0037] The spot welding apparatus 1 welds two plate-shaped workpieces 101 and 102. The two workpieces 101 and 102 are metal plates. The two workpieces 101 and 102 may both be iron-based materials. Iron-based materials are steel materials with high strength and rigidity, such as high-tensile steel. Alternatively, one of the two workpieces 101 and 102 may be an iron-based material and the other an aluminum-based material. An aluminum-based material is, for example, an aluminum alloy material. In the example in Figure 1, the workpiece 100 consists of two workpieces 101 and 102, but the workpiece 100 may consist of three or more workpieces. Also, in Figure 1, the two workpieces 101 and 102 have the same thickness, but the thicknesses of the workpieces 101 and 102 may be different.

[0038] The spot welding apparatus 1 illustrated in Figure 1 includes a welding gun 11. The welding gun 11 is supported by, for example, a robot (not shown). The robot positions the welding gun 11 on the workpiece 100 at the welding location.

[0039] The welding gun 11 supports a first electrode 2 and a second electrode 20. The first arm 111 of the welding gun 11 is cantilevered, with its base fixed and its tip unfixed, and the first arm 111 supports the first electrode 2 at its free end. The second arm 112 is also cantilevered, and the second arm 112 supports the second electrode 20 at its free end.

[0040] The first electrode 2 is located on the first side of the workpiece 100. In Figure 1, the first electrode 2 is located below the workpiece 100. The second electrode 20 is located on the second side of the workpiece 100. In Figure 1, the second electrode 20 is located above the workpiece 100. The first electrode 2 and the second electrode 20 sandwich the workpiece 100 in the stacking direction of the materials to be welded 101 and 102, and apply pressure to the workpiece 100 in the stacking direction.

[0041] The first electrode 2 is roughly columnar in shape. The second electrode 20 is also roughly columnar in shape. The first electrode 2 and the second electrode 20 are opposite each other in the direction of the electrode's central axis X.

[0042] The welding gun 11 has a pressurizing device 14. The pressurizing device 14 moves the second electrode 20 relative to the workpiece 100 in the direction of the central axis X. The pressurizing device 14 is configured to include, for example, an air cylinder, a hydraulic cylinder, or a servo motor. With the welding gun 11 in contact with the surface of the workpiece 100, the pressurizing device 14 moves the second electrode 20, so that the first electrode 2 and the second electrode 20 can clamp the workpiece 100 in the direction of the central axis X and pressurize the workpiece 100 in the direction of the central axis X.

[0043] The spot welding apparatus 1 is equipped with a controller 12. The controller 12 controls the pressurization and power supply to the workpiece 100 in the spot welding apparatus 1. The controller 12 is a well-known microcomputer-based controller and includes a CPU (Central Processing Unit), 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 the OS (Operating System), and application programs that are launched on the OS to realize specific functions. The memory includes RAM (Random Access Memory) and ROM (Read Only Memory). ROM stores various computer programs and data. RAM is a memory in which a processing area is provided for use when the CPU performs a series of processes. The input / output bus provides input and output of electrical signals to the controller 12.

[0044] The controller 12 outputs a control signal to the pressurizing device 14 according to the control program stored in the ROM. The workpiece 100 is pressurized by the first electrode 2 and the second electrode 20. The controller 12 also supplies welding current from the power supply 13 to the workpiece 100 through the first electrode 2 and the second electrode 20.

[0045] Here, we will briefly explain the welding process using spot welding equipment 1. (1) The first electrode 2 and the second electrode 20 clamp the workpiece 100 in the direction of the central axis X and supply power to the workpiece 100 while applying pressure to it. (2) When the materials to be welded 101 and 102 come into contact with each other due to the pressurization, an electrical path is formed at the joint interface of the workpiece 100, and Joule heat is generated at the joint interface of the workpiece 100. (3) At the joint interface of the workpiece 100, the materials to be welded 101 and 102 melt. (4) The molten materials 101 and 102 to be welded solidify to form a nugget, and the welding process is completed.

[0046] (Electrode structure) Figure 2 illustrates the structure of the first electrode 2. Note that the structures of the first electrode 2 and the second electrode 20 are identical, except for the inversion of their orientation. A description of the structure of the second electrode 20 is omitted.

[0047] The cap tip 21 of the first electrode 2 is located at the tip of the first electrode 2. The cap tip 21 has a tip surface 211 that contacts the workpiece 100. If the tip surface 211 wears down due to repeated welding by the spot welding device 1, the cap tip 21 is replaced.

[0048] The cap tip 21 has a recess 212. The recess 212 opens to the base end face of the cap tip 21 and is recessed from the base end face along the central axis X of the first electrode 2. The recess 212 forms part of the refrigerant passage 26, as will be described later.

[0049] The shank 22 extends along the central axis X of the first electrode 2. The cap tip 21 is attached to the tip of the shank 22. The shank 22 supports the cap tip 21. The shank 22 has a first hole 221. The first hole 221 extends along the central axis X of the first electrode 2. The first hole 221 opens at both the tip and the base of the shank 22. The first hole 221 penetrates the shank 22. The shank 22 has a cylindrical shape (see also Figure 3).

[0050] With the cap tip 21 attached to the end of the shank 22, the first hole 221 is connected to the recess 212 of the cap tip 21. As will be described later, the first hole 221 forms part of the refrigerant passage 26.

[0051] An inner tube 222 is positioned within the first hole 221. The inner tube 222 extends along the central axis X of the first electrode 2. The inner tube 222 protrudes from the base end of the shank 22. The inner tube 222 is also inserted into the second hole 231 of the holder 23, which will be described later.

[0052] The shank 22 also has slits 41 to 44 formed therein. The first electrode 2 illustrated in Figure 2 has multiple slits 41 to 44. Details of the shape of slits 41 to 44 will be described later.

[0053] The holder 23 is a cylindrical object extending along the central axis X of the first electrode 2. The holder 23 has a second hole 231. The second hole 231 extends along the central axis X of the first electrode 2. The second hole 231 penetrates the holder 23.

[0054] The proximal end of the shank 22 is inserted into the second hole 231 from the tip of the holder 23. The holder 23 supports the shank 22. The second hole 231 of the holder 23 and the first hole 221 of the shank 22 are in communication.

[0055] As mentioned earlier, the inner tube 222 spans both the shank 22 and the holder 23. The inner tube 222 forms a supply path 24 for supplying refrigerant to the cap tip 21. The end of the inner tube 222 is connected to a recess 212 in the cap tip 21. The refrigerant is supplied through the inner tube 222 into the recess 212. The refrigerant effectively cools the cap tip 21 (see arrow in Figure 2).

[0056] The space between the first hole 221 of the shank 22 and the inner tube 222 forms part of the refrigerant return path 25. Similarly, the space between the second hole 231 of the holder 23 and the inner tube 222 also forms part of the refrigerant return path 25. The return paths 251 and 252 are in communication with each other. The refrigerant supplied into the recess 212 of the cap tip 21 reverses within the recess 212 and returns to the base end of the holder 23 through the return paths 251 and 252. The double-layered refrigerant path 26, including the supply path 24 and the return path 25, can efficiently cool the cap tip 21.

[0057] (Slit structure) The left image in Figure 3 is a perspective view of the shank 22. The center image in Figure 3 is a perspective view showing a cross-section of the shank 22 cut at the position of the first slit 41. The right image in Figure 3 is a perspective view showing a cross-section of the shank 22 cut at the position of the second slit 42.

[0058] As mentioned above, the shank 22 has a number of slits 41-44. More specifically, the shank 22 consists of an upper tapered portion 223, a lower tapered portion 224, and an intermediate portion 225. The upper tapered portion 223 tapers upward. A cap tip 21 is attached to the tip of the upper tapered portion 223. The lower tapered portion 224 tapers downward. The base end of the lower tapered portion 224 is supported by the holder 23. The intermediate portion 225 is located between the upper tapered portion 223 and the lower tapered portion 224. The intermediate portion 225 has a constant outer diameter.

[0059] Slits 41-44 are formed in the intermediate portion 225. The multiple slits 41-44 are aligned in the direction of the central axis X of the first electrode 2. In the illustrated example, the shank 22 has the first slit 41, the second slit 42, the third slit 43, and the fourth slit 44, in order from the tip to the base.

[0060] Each slit 41-44 extends circumferentially on a plane that intersects the central axis X, or more precisely, on a plane perpendicular to the central axis X. The plane perpendicular to the central axis X is a hypothetical plane on the first electrode 2. Each slit 41-44 opens onto the outer circumferential surface of the shank 22. The openings of each slit 41-44 extend circumferentially on the outer circumferential surface of the shank 22 in a direction perpendicular to the central axis X. Each slit 41-44 also communicates with the first hole 221 of the shank 22, as shown in Figures 3 and 4.

[0061] In the shank 22 shown in Figures 3 and 4, each slit 41 to 44 has the same width in the direction of the central axis X. Furthermore, the spacing between adjacent slits 41 to 44 in the direction of the central axis X is also the same.

[0062] The first base 45 is formed by the first slit 41 and the second slit 42, which are adjacent to each other in the direction of the central axis X. Similarly, the second base 46 is formed by the second slit 42 and the third slit 43, and the third base 47 is formed by the third slit 43 and the fourth slit 44. Each base 45 to 47 is an annular shape surrounding the first hole 221. Also, since the spacing between adjacent slits 41 to 44 in the direction of the central axis X is the same, the thickness of each base 45 to 47 in the direction of the central axis X is the same.

[0063] Each of the slits 41-44 has columns 31-33 and 34-36 formed within it. Columns 31-36 extend in the direction of the central axis X within the slits 41-44 and are connected to bases 45-47. Since there is no base above the first slit 41, the upper ends of columns 31-33 formed in the first slit 41 are connected to the upper wall forming the first slit 41. Similarly, since there is no base below the fourth slit 44, the lower ends of columns 34-36 formed in the fourth slit 44 are connected to the lower wall forming the fourth slit 44.

[0064] Each of the slits 41 to 44 has three columns 31 to 36 formed within it. More specifically, the first slit 41 has a first column 31, a second column 32, and a third column 33 formed within it. The third slit 43 also has a first column 31, a second column 32, and a third column 33 formed within it.

[0065] The second slit 42 has a fourth column 34, a fifth column 35, and a sixth column 36 formed therein. The fourth slit 44 also has a fourth column 34, a fifth column 35, and a sixth column 36 formed therein.

[0066] The first to sixth columns 31 to 36 all have the same shape, with a roughly triangular cross-section, as shown in the upper diagram of Figure 4. The first to third columns 31 to 33 are arranged around the first hole 221, enclosing it. The vertices of the triangles of each column 31 to 33 are located radially outward from the first electrode 2. In the shank 22 of the example shown, the first to third columns 31 to 33 are spaced 120° apart from each other. A communication opening 37 is formed between the first column 31 and the second column 32, connecting the slits 41 and 43 to the first hole 221. Similarly, communication openings 37 are formed between the second column 32 and the third column 33, and between the third column 33 and the first column 31, connecting the slits 41 and 43 to the first hole 221.

[0067] The fourth to sixth columns 34 to 36 are also arranged around the first hole 221, surrounding it. The vertices of the triangles formed by each column 34 to 36 are located radially outward from the first electrode 2. In the illustrated example shank 22, the fourth to sixth columns 34 to 36 are spaced 120° apart from each other. Communication openings 37 are formed between the fourth column 34 and the fifth column 35, between the second column 32 and the third column 33, and between the third column 33 and the first column 31, respectively, connecting the slits 42 and 44 to the first hole 221.

[0068] The first column 31 and the fourth column 34 are offset by 60° in the circumferential direction. Similarly, the second column 32 and the fifth column 35 are offset by 60° in the circumferential direction, and the third column 33 and the sixth column 36 are offset by 60° in the circumferential direction. Therefore, as shown in the upper diagram of Figure 4, all columns 31 to 36 formed in two adjacent slits 41 to 44 with any bases 45 to 47 in between are offset in the circumferential direction.

[0069] The creation of slits and columns in the shank 22 can be carried out as follows, for example. Figure 5 shows the procedure for creating the first slit 41 and the first to third columns 31 to 33 in the shank 22.

[0070] First, a shank 22 having a first hole 221 is prepared. In step P1, the shank 22 is fixed, and the cutting tool 5 is moved relative to the outer circumference of the shank 22 in a direction perpendicular to the central axis X. As a result, the bow-shaped area enclosed by the arc and chord in the cross-section of the shank 22 is cut away by the cutting tool 5. The cutting tool 5 is advanced radially inward of the shank 22 until the chord interferes with the first hole 221 of the shank 22. In step P1, a slit 41 is formed in the shank 22, opening to the outer circumference of the shank 22 and communicating with the first hole 221.

[0071] Next, in step P2, the shank 22 is rotated 120° around its central axis and fixed in place. Similar to step P1, the cutting tool 5 is moved relative to the outer circumference of the shank 22 in a direction perpendicular to the central axis X. As a result, similar to step P1, the arc-shaped portion enclosed by the arc and chord in the cross-section of the shank 22 is removed by the cutting tool 5. A slit 41 is formed on the outer surface of the shank 22, opening at a different location than described above and communicating with the first hole 221. Also in step P2, the first column 31 is formed.

[0072] Next, in step P3, the shank 22 is rotated another 120° around its central axis to fix it in place. Then, similar to step P1, the cutting tool 5 is moved relative to the outer circumference of the shank 22 in a direction perpendicular to the central axis X. As a result, similar to step P1, the arc-shaped portion enclosed by the arc and chord in the cross-section of the shank 22 is removed by the cutting tool 5. A slit 41 is formed on the outer surface of the shank 22, opening at a different location than described above and communicating with the first hole 221. Also in step P3, the second column 32 and the third column 33 are formed. In the shank 22 of the illustrated example, the slit 41 is formed individually in each of the three steps, but the slits 41 are connected to each other through the tips of the first column 31, the second column 32, and the third column 33, respectively.

[0073] By processes P1 to P3, once the first slit 41 and the first to third columns 31 to 33 are formed in the shank 22, the relative position of the shank 22 and the cutting tool 5 in the direction of the central axis X is changed, and the second slit 42 and the fourth to sixth columns 34 to 36 are formed in the shank 22 by the aforementioned processes P1 to P3. Note that by adjusting the circumferential orientation of the shank 22, the positions of the first to third columns 31 to 33 and the positions of the fourth to sixth columns 34 to 36 are shifted by 60°. The formation of the third slit 43 and the first to third columns 31 to 33, and the formation of the fourth slit 44 and the fourth to sixth columns 34 to 36 on the shank 22 can be carried out similarly.

[0074] (Elastic deformation of electrodes) As mentioned above, the first electrode 2 has slits 41-44 and columns 31-36 formed therein. The second electrode 20 also has slits and columns formed therein. The slits 41-44 and columns 31-36 cause elastic deformation of the first electrode 2 in the intermediate portion between the tip surface 211 and the base end of the first electrode 2.

[0075] Figure 6 illustrates a state in which a load in the direction of the central axis X is uniformly applied to the first electrode 2 in a plane perpendicular to the central axis X. The center of the load applied to the first electrode 2 is equivalent to being on the central axis X. The load is transmitted in the direction of the central axis X through the columns 31-36 and the bases 45-46 in the shank 22.

[0076] As shown in the lower part of Figure 6, the first to third columns 31 to 33 of the first slit 41 are positioned at equal intervals in the circumferential direction. Also, the fourth to sixth columns 34 to 36 of the second slit 42, which is adjacent to the first slit 41 across the first base 45, are circumferentially offset from the first to third columns 31 to 36. Because the positions of the first to third columns 31 to 33 on the upper side of the first base 45 and the positions of the fourth to sixth columns 34 to 36 on the lower side of the first base 45 are offset, the position at which a load is applied in the direction of the central axis X to the first base 45, which extends in a direction perpendicular to the central axis X, is circumferentially shifted as illustrated by the black arrow in the upper part of Figure 6. As a result, the first base 45 flexes in the direction of the central axis, as illustrated by the dashed line in the upper part of Figure 6. In other words, the thickness of the first base 45 in the direction of the central axis is such that flexing occurs when a load is applied.

[0077] Similarly, because the fourth to sixth columns 34 to 36 of the second slit 42 and the first to third columns 31 to 33 of the third slit 43 are misaligned in the circumferential direction, the second base 46 bends in the direction of the central axis X, as illustrated by the dashed line in the upper diagram of Figure 6.

[0078] Furthermore, the third base 47 also flexes in the direction of the central axis X, as illustrated by the dashed line in the upper part of Figure 6, because the first to third columns 31 to 33 of the third slit 43 and the fourth to sixth columns 34 to 36 of the fourth slit 44 are misaligned in the circumferential direction. Note that Figure 6 exaggerates the flexure of each base 45 to 47.

[0079] Columns 31-36 promote the deflection of bases 45-47, while slits 41-44 allow the deflection of bases 45-47. The shank 22 undergoes elastic deformation to contract in the direction of the central axis X when the center of the load applied to the first electrode 2 lies on the central axis X. In other words, the shank 22 is elastically compressible while transmitting the load in the direction of the central axis X.

[0080] If the center of the load applied to the first electrode 2 is eccentric or tilted relative to the central axis X of the first electrode 2, the load will be applied unevenly in a plane perpendicular to the direction of the central axis X. In this case, the load applied to the base 45-47 through the three columns 31-36 of each slit 41-44 will be uneven, and the areas of the base 45-47 where a relatively large load is applied from columns 31-36 will locally bend significantly in the direction of the central axis X. For example, Figure 7 shows an example where a compressive load is applied to the first electrode 2 along an axis eccentric to the left side of the plane relative to the central axis X, as indicated by the white arrow. In this case, the left side of the plane in the slits 41-44 will be relatively crushed, so the shank 22 will bend so that the central axis X is tilted (see arrow in Figure 7). Because the shank 22 bends, the tip surface 211 of the cap tip 21 maintains contact with the surface of the workpiece 100. Note that Figure 7 exaggerates the curvature of the shank 22.

[0081] In steps (2) and / or (3) of the welding process described above, when the materials to be welded 101 and 102 soften / melt, the electrodes that were restrained by the welding gun 11 and the workpiece 100 tend to move as the restraint loosens. More specifically, the first electrode 2 and the second electrode 20 are held by the cantilevered first arm 111 and second arm 112, respectively, as shown in Figure 1. Therefore, when the materials to be welded 101 and 102 soften / melt, the first electrode 2 and the second electrode 20 tend to move in the direction indicated by the white arrows in Figure 1.

[0082] In this case, with electrodes 2 and 20 having slits 41 to 44 and columns 31 to 36, the shank 22 bends as described above, allowing the tip surface 211 of the cap tip 21 to maintain contact with the surface of the workpiece 100. As a result, no slippage occurs between the tip surface 211 of electrodes 2 and 20 and the surfaces of the workpieces 101 and 102, and the generation of electrical discharge between electrodes 2 and 20 and the workpieces 101 and 102 is suppressed. Since the wear of the tips of electrodes 2 and 20 is suppressed by the suppression of electrical discharge, this spot welding apparatus 1 can suppress the deterioration of welding quality even when welding is repeated. In addition, since the wear of the cap tip 21 is suppressed, the lifespan of the cap tip 21 is extended.

[0083] Furthermore, the aforementioned spot welding apparatus 1 has the advantage that only electrodes 2 and 20 have a new structure, while parts other than electrodes 2 and 20 can utilize the same design as a conventional spot welding apparatus.

[0084] (Variations of slits and columns) The openings of the slits 41-44 extend circumferentially on the outer surface of electrodes 2 and 20 in a direction perpendicular to the central axis X. This configuration has the advantage that when the center of the load applied to electrodes 2 and 20 is offset from the central axis X of electrodes 2 and 20, electrodes 2 and 20 can be stably elastically deformed in the bending direction in all circumferential directions. The openings of the slits may also extend circumferentially on the outer surface of the electrodes in a plane intersecting the central axis X. Electrodes with this structure can also be elastically deformed in the bending direction when the center of the load applied to the electrodes is offset from the central axis of the electrodes.

[0085] The elastic modulus of electrodes 2 and 20 can be changed by changing the position or number of slits formed in electrodes 2 and 20, and / or the position or number of columns. By appropriately setting the elastic modulus of electrodes 2 and 20 according to the welding conditions of the spot welding apparatus 1, it is possible to suppress the occurrence of slippage between the tip surface 211 of electrodes 2 and 20 and the workpiece 100 while enabling pressurization of the workpiece 100 through electrodes 2 and 20.

[0086] The thickness of the base formed on the electrode may be the same or different for multiple bases. Figure 8 shows that the thickness H1 of the first base 45 located on the tip side of electrodes 2 and 20 is relatively thick, and the thickness H3 of the third base 47 located on the base side of electrodes 2 and 20 is relatively thin. When the base is thick, the bending rigidity of the base is high. In other words, the base is less likely to bend in the direction of the central axis X. When the base is thin, the bending rigidity of the base is low. The base is more likely to bend in the direction of the central axis X. By making the thickness of the first base 45 located on the tip side of electrodes 2 and 20 relatively thick, and the thickness of the third base 47 located on the base side of electrodes 2 and 20 relatively thin, electrodes 2 and 20 can be stably elastically deformed. The slippage between the tip surface 211 of electrodes 2 and 20 and the surface of the workpiece 100 can be more effectively suppressed.

[0087] In Figure 8, the thicknesses of the first base 45 (H1), the second base 46 (H2), and the third base 47 (H3) are progressively thinner (H1 > H2 > H3). The relative thicknesses of the multiple bases are not limited to the example shown. For example, the relative thicknesses of the multiple bases could be H1 = H2 > H3, or H1 > H2 = H3.

[0088] Furthermore, the number of bases is not limited to three. Electrodes 2 and 20 only need to have at least one base, and consequently, electrodes 2 and 20 only need to have at least two slits. The number of slits that can be formed in electrodes 2 and 20 depends on the length of the electrode 2 and 20 in the direction of its central axis X. Electrodes 2 and 20 may have, for example, up to five slits.

[0089] As illustrated in Figure 6, since all of the columns 31 to 36 formed on electrodes 2 and 20 are offset in the circumferential direction, electrodes 2 and 20 can stably undergo elastic deformation in the bending direction while ensuring the required rigidity in the central axis X direction.

[0090] Figure 9 illustrates electrodes 2 and 20 with a modified column arrangement. In the spot welding apparatus 10 shown in the upper part of Figure 9, the shank 220 is bent in the middle. This shape of shank 220 can avoid interference with the workpiece 100. In Figure 9, the base end of the shank 220 held by a holder (not shown) and the tip of the shank 220 supporting the cap tip 21 are horizontally offset (see X1 and X2 in Figure 9). When the first electrode 2 and the second electrode 9 are pressing on the workpiece 100, an eccentric load is constantly applied to the cap tip 21 and the shank 220.

[0091] The slit 4 is formed in the shank 220. In the case of an electrode structure in which an eccentric load is applied to the cap tip 21, in order to uniformly contact the entire tip surface 211 of the cap tip 21 with the surface of the workpiece 100, it is preferable to make the rigidity of the shank 220 higher on the right side of the paper in Figure 9 than the axis X1, and lower on the left side of the paper.

[0092] As shown in the lower part of Figure 9, the three columns 301, 302, and 303 formed in the slit 4 are positioned biased to one side of the slit 4, straddling the axis X1. The angle between column 301 and column 302 is 90°, and the angle between column 302 and column 303 is also 90°. This makes the shank 220 rigid on the right side of the paper in Figure 9 and rigid on the left side. The cap tip 21 can stably pressurize the workpiece 100, and slippage between the tip surface 211 of the cap tip 21 and the surface of the workpiece 100 is suppressed.

[0093] Furthermore, in the shank 220 of Figure 9, the three columns 301, 302, and 303 formed in the slit 4 may be offset in the circumferential direction from the columns of the slit 4 adjacent to the slit 4 in the direction of axis X1.

[0094] The number of columns 31-36 and 310-330 formed in a single slit 41-44,4 is not limited to three. However, if there are three columns 31-36 and 310-330, the plane to which these three columns are connected is uniquely determined. Having three columns 31-36 and 310-330 in a single slit 41-44,4 has the advantage that electrodes 2 and 20 can bend stably in an electrode structure where multiple slits 41-44,4 overlap in the axial direction.

[0095] In the shank 22 illustrated in Figure 3, the outermost radial ends of columns 31-36 (i.e., the vertices of the roughly triangular columns 31-36 in a plan view) are located radially inward from the outer surface of the shank 22. The outermost radial ends of columns 31-36 may be at the same position as the outer surface of the shank 22. As a result, columns 31-36 may divide the slits 41-44 into multiple slits in the circumferential direction.

[0096] Furthermore, the cross-sectional shape of the column is not limited to a roughly triangular shape. The column can be formed into any shape.

[0097] Furthermore, the slits 41-44 and 4 are not limited to being formed on the shanks 22 and 220. The slits 41-44 and 4 may also be formed on the holder, for example. Alternatively, the slits 41-44 and 4 can be formed on the cap tip 21. However, forming the slits 41-44 and 4 on the cap tip 21 would increase the manufacturing cost of the cap tip 21. The increased manufacturing cost of the cap tip 21, which is frequently replaced, would increase the maintenance cost of the spot welding equipment 1 and 10. The shanks 22 and 220 or the holder 23 are suitable locations for forming the slits 41-44 and 4 because they are replaced relatively infrequently.

[0098] Furthermore, even if slits 41-44 and columns 31-36 and 310-330 are not provided on both the first electrode 2 and the second electrode 20 of the spot welding apparatus 1 and 10, slits 41-44 and columns 31-36 and 310-330 may be provided on either the first electrode 2 or the second electrode 20.

[0099] (Structure designed to suppress refrigerant leakage) Each of the slits 41-44 formed in the shank 22 is in communication with the first hole 221 that forms the refrigerant passage 26 via a communication port 37. As a result, the refrigerant flowing through the return passage 25 of the refrigerant passage 26 leaks out of the electrodes 2 and 20 through the communication port 37 and the slits 41-44.

[0100] The electrodes 2 and 20 are equipped with a suppression section to prevent refrigerant leakage. The suppression section is a cover 6 attached to the shank 22, as shown in Figure 2.

[0101] The cover 6 covers the openings of the first to fourth slits 41 to 44 formed on the outer circumferential surface of the shank 22. As indicated by the arrows in Figure 2, the refrigerant that leaks out of the electrode 2 through the openings of the first to fourth slits 41 to 44 remains inside the cover 6.

[0102] An O-ring 61 is interposed between the shank 22 and the cover 6. The O-ring 61 is attached to both the upper and lower parts of the shank 22. The O-ring 61 prevents refrigerant leakage from the gap between the shank 22 and the cover 6.

[0103] In this way, in electrodes 2 and 20 having a cooling structure, both elastic deformation due to slits 41 to 44 and suppression of refrigerant leakage are achieved.

[0104] Furthermore, the suppression unit only needs to be installed on electrodes 2 and 20 where slits 41-44 and 4 are formed. This is because refrigerant leakage will not occur if slits 41-44 and 4 are not present.

[0105] (Structure of projection welding equipment) The technology disclosed herein is not limited to application to spot welding apparatus 1. Because the electrode disclosed herein has the function of elastic deformation, in addition to the effect of suppressing slippage between the electrode tip surface 211 and the workpiece surface 100, it can also exert the effect of allowing the electrode tip surface 211 to apply a uniform load to the workpiece 100. This effect is useful for projection welding apparatuses that require uniform welding of multiple protrusions on the workpiece. Projection welding is a type of resistance welding.

[0106] Figure 10 illustrates a part of the structure of the first electrode 8 and the second electrode 9 of the projection welding apparatus 7. The workpiece 1000 to be welded by the projection welding apparatus 7 consists of a first workpiece 1010 and a second workpiece 1020. The first workpiece 1010 is flat. The first workpiece 1010 has a through hole 1011. The through hole 1011 penetrates the first workpiece 1010 in the thickness direction.

[0107] The second workpiece 1020 is a nut. The second workpiece 1020 is not plate-shaped. As shown on the left of Figure 10, the second workpiece 1020 is approximately square in plan view and has a screw hole 1021 in the center. The second workpiece 1020 is placed on top of the first workpiece 1010 such that the screw hole 1021 is coaxial with the through hole 1011 of the first workpiece 1010. The second workpiece 1020 also has protrusions 1022 at each of its four corners. Each of the four protrusions 1022 contacts the surface of the first workpiece 1010 when the second workpiece 1020 is placed on top of the first workpiece 1010.

[0108] The first electrode 8 has a cap tip 81 and a guide pin 82. The cap tip 81 contacts the surface of the first workpiece 1010. The cap tip 81 has a through hole 811. The through hole 811 penetrates the cap tip 81 in the direction of the central axis X.

[0109] The guide pin 82 extends in the direction of the central axis X of the first electrode 8. The guide pin 82 is inserted into the through hole 811 of the cap tip 81. The guide pin 82 reciprocates in the direction of the central axis X by an extension actuator 88, which will be described later. Figure 10 shows the protruding state of the guide pin 82. The guide pin 82 is inserted into the through hole 1011 of the first workpiece 1010 and the screw hole 1021 of the second workpiece 1020. The tip of the guide pin 82 protrudes from the second workpiece 1020. The guide pin 82 regulates the relative position of the first workpiece 1010 and the second workpiece 1020 so that the through hole 1011 and the screw hole 1021 are coaxial. The details of the structure of the first electrode 8 will be described later.

[0110] The cap tip 91 of the second electrode 9 has a first recess 911 and a second recess 912. The first recess 911 is formed at the base end of the cap tip 91. The first recess 911 opens at the base end of the cap tip 91 and extends in the direction of the central axis X of the second electrode 9. As will be described later, the first recess 911 forms part of the refrigerant passage 93 of the second electrode 9.

[0111] The second recess 912 is formed at the tip of the cap tip 91. The second recess 912 opens onto the tip surface 913 of the cap tip 91. The area around the second recess 912 on the tip surface 913 of the cap tip 91 abuts against the second workpiece 1020. The second recess 912 extends in the direction of the central axis X of the second electrode 9. The first recess 911 and the second recess 912 are not in communication. The tip of the guide pin 82 is inserted into the second recess 912 when the first electrode 8 and the second electrode 9 clamp the workpiece 1000 in the direction of the central axis X.

[0112] Here, we will explain the welding process using the projection welding apparatus 7. (1) The first electrode 8 is in contact with the first workpiece 1010, and the guide pin 82 protrudes through the through hole 1011 in the first workpiece 1010 toward the second electrode 9 (see P11 in Figure 10). (2) The second workpiece 1020 is fitted onto the guide pin 82, and the projection 1022 of the second workpiece 1020 rests on the first workpiece 1010 (see P12 in Figure 10). (3) The tip surface 913 of the second electrode 9 contacts the second workpiece 1020, and the first electrode 8 and the second electrode 9 clamp the workpiece 1000 in the direction of the central axis X, applying pressure to the workpiece 1000 while supplying power to the workpiece 1000 (see P13 in Figure 10). (4) Due to the pressurization, the projection 1022 of the second workpiece 1020 comes into contact with the first workpiece 1010, forming an electrical path at the location of the projection 1022 and generating Joule heat. The projection 1022 of the second workpiece 1020 and the portion of the first workpiece 1010 in contact with the projection 1022 melt (see P14 in Figure 10). (5) The molten first workpiece 1010 and the second workpiece 1020 solidify to form a nugget, and the welding process is completed.

[0113] The first electrode 8 and the second electrode 9 of the projection welding apparatus 7 are elastically deformable. This allows a uniform load to be applied to the four protrusions 1022 of the second workpiece 1020, enabling the projection welding apparatus 7 to uniformly weld the four protrusions 1022 to the first workpiece 1010. The structure of the elastically deformable first electrode 8 and the second electrode 9 will be described below with reference to Figures 11 and 12.

[0114] Figure 11 shows an exploded view of the first electrode 8. The cap tip 81 of the first electrode 8 has a through hole 811, as previously described. The guide pipe 83 is attached to the base end of the cap tip 81 and holds the cap tip 81. The guide pipe 83 also has an internal hole into which the guide pin 82 is inserted. The guide pipe 83 guides the reciprocating movement of the guide pin 82.

[0115] The holder 84 holds the guide pipe 83 and the cap tip 81. The holder 84 is cylindrical and has a hole 841 into which the rod 87, described later, is inserted. The hole 841 penetrates the holder 84 in the direction of the central axis X.

[0116] The first joint 85 is interposed between the holder 84 and the cap tip 81. The first joint 85 is an elastically deformable portion of the first electrode 8. The first joint 85 is cylindrical and has a through hole that penetrates in the direction of the central axis X. A guide pin 82 is inserted into this through hole. A slit 851 is formed in the first joint 85. The slit 851 opens on the outer circumferential surface of the first joint 85. The slit 851 extends circumferentially on a plane that intersects the direction of the central axis X, or more precisely, on a plane perpendicular to the direction of the central axis X. The first joint 85 illustrated in Figure 11 has three slits 851. The three slits 851 are aligned in the direction of the central axis X. Note that the number of slits 851 formed in the first joint 85 is not limited to three. A column is formed within each slit 851, and a base is formed between adjacent slits 851 in the direction of the central axis X. The first joint 85 has two bases. Each of the two bases is an annular shape surrounding the through-hole of the first joint 85 and has a thickness that allows it to be elastically deformed so as to flex in the direction of the central axis X. These slits 851 and columns allow the first joint 85 to be elastically deformed in response to a load in the direction of the central axis X.

[0117] The second joint 86 is interposed between the guide pin 82 and the rod 87. The second joint 86 connects the guide pin 82 and the rod 87. The rod 87 extends in the direction of the central axis X. The rod 87 connects the guide pin 82 to the telescopic actuator 88.

[0118] The telescopic actuator 88 consists of an air cylinder 881 and a piston rod 882. The piston rod 882 is inserted into a holder 84. When air is supplied to the air cylinder 881, the piston rod 882 extends. As the piston rod 882 extends, the guide pin 82 protrudes toward the second electrode 9.

[0119] Therefore, the first electrode 8 has a mechanism for advancing and retracting the guide pin 82, and is elastically deformable at the first joint 85 between the tip of the cap tip 21 and the base end of the first electrode 8. When the center of the load is offset from the central axis X of the first electrode 8, the first joint 85 bends, allowing the cap tip 81 to apply a uniform load to the entire tip surface of the first workpiece 1010.

[0120] Figure 12 illustrates the structure of the second electrode 9. The second electrode 9 has a coolant passage 93 for cooling the cap tip 91. As described above, the cap tip 91 has a first recess 911 and a second recess 912.

[0121] The holder 92 holds the cap tip 91. The holder 92 is cylindrical. The holder 92 has a retaining portion 921 at its tip. The retaining portion 921 is a recess that opens onto the tip surface of the holder 92. The base end of the cap tip 91 is inserted into the retaining portion 921 of the holder 92. The first recess 911 of the cap tip 91 connects to the retaining portion 921 of the holder 92.

[0122] The inner bore 922 of the holder 92 communicates with the retaining portion 921 and opens at the base end of the holder 92. The inner bore 922 forms part of the refrigerant passage 93. The refrigerant is sent through the inner bore 922 and the retaining portion 921 to the first recess 911 of the cap tip 91, and returns from the first recess 911 through the retaining portion 921 and the inner bore 922. The refrigerant passage 93 may be made into a double structure by placing the aforementioned inner tube 222 (see Figure 2) in the inner bore 922 of the holder 92.

[0123] In the second electrode 9, a slit 923 is formed in the holder 92. The slit 923 opens to the outer circumferential surface of the holder 92. The slit 923 extends circumferentially on a plane that intersects the central axis X direction, or more precisely, on a plane perpendicular to the central axis X direction. The second electrode 9 illustrated in Figure 12 has four slits 923. The four slits 923 are aligned in the central axis X direction. Note that the number of slits 923 formed in the holder 92 is not limited to four. A base is formed between adjacent slits 923 in the central axis X direction. The holder 92 has three bases. Each of the three bases is an annular shape surrounding the inner hole 922 that forms the refrigerant passage 93, and has a thickness that allows for elastic deformation so as to flex in the central axis X direction.

[0124] Although not shown in detail in Figure 12, multiple columns are formed in each slit 923. Each of the multiple columns extends in the direction of the central axis X and is connected to the base. The second electrode 9 is elastically deformable in the holder 92 between the tip surface 913 of the cap tip 91 and the base end of the second electrode 9. By the elastic deformation of the holder 92, the tip surface 913 of the cap tip 91 can be subjected to a uniform load on the second workpiece 1020. The four protrusions 1022 of the second workpiece 1020 are uniformly welded to the first workpiece 1010.

[0125] Since the second electrode 9 has a refrigerant passage 93, refrigerant leaks through the slit 923. The second electrode 9 has a suppression part that inhibits refrigerant leakage. The suppression part is a cover 60 attached to the outer circumferential surface of the holder 92, as shown in Figure 12.

[0126] The cover 60 covers the openings of each of the four slits 923 formed on the outer circumferential surface of the holder 92. An O-ring 601 is interposed between the holder 92 and the cover 60. The O-ring 601 prevents refrigerant leakage from the gap between the holder 92 and the cover 60.

[0127] In this way, the second electrode 9, which has a cooling structure, is able to undergo elastic deformation by the slit 923 while suppressing refrigerant leakage.

[0128] (Other embodiments) The technology disclosed herein is not limited to application to spot welding apparatus 1, 10 or projection welding apparatus 7. As described above, the technology disclosed herein can apply a uniform load to the workpiece through the first electrode and the second electrode. Utilizing this feature, the workpiece to which the resistance welding apparatus is applied may be, for example, a workpiece where two cylindrical workpieces are butted together in the axial direction. The resistance welding apparatus can apply a uniform load through the first electrode and the second electrode over the entire circumference of the joint of the workpieces. The resistance welding apparatus can improve welding quality.

[0129] Furthermore, the technology disclosed herein can be applied to ring mash welding. The resistance welding apparatus can uniformly apply load to the welding area around the hole in ring mash welding, in which a hole formed in a first workpiece and a second workpiece having an outer diameter slightly larger than the hole are welded around the hole. The resistance welding apparatus improves the welding quality of ring mash welding.

[0130] Furthermore, the features described in the aforementioned embodiments can be combined to the extent possible. [Explanation of symbols]

[0131] 100 Work 101 Material to be welded 102 Material to be welded 1000 work 1010 First workpiece 1020 Second workpiece to be welded 2 1st electrode 20 2nd electrode 21 Cap Tips 22 Shank 220 Shank 221 Hole 1 222 Inner tube 23 Holder 24 Passageway 25 The return journey 251 The return journey 252 The return journey 26 Refrigerant passage 31 Column 1 32 Column 2 33 Third Column 34. 4th Column 4 slits 41. First Slit 42. Second Slit 43 Third Slit 44. Fourth Slit 45 1st Base 46. ​​Second base 47 Third Base 6 Covers 60 Cover 61 O-rings 610 O-ring 8 1st electrode 81 Cap Tip 84 Holder 851 Slit 9 Second electrode 91 Cap Tip 92 Holder 922 Internal bore 923 Slit 93 Refrigerant path

Claims

1. A resistance welding apparatus for welding multiple workpieces, which consists of multiple stacked workpieces, by applying pressure to the workpiece and supplying power to the workpiece, The electrode is provided to contact the workpiece and to apply pressure and supply power to the workpiece, The electrode has, In the radial central portion, a refrigerant passage extends in the direction of the central axis of the electrode, A slit is formed which communicates with the refrigerant passage and opens to the outer surface of the electrode, and which extends circumferentially in a plane perpendicular to the central axis direction, The electrode is Multiple slits aligned in the direction of the central axis, A base formed by the first and second slits adjacent to each other in the central axis direction, which is an annular shape surrounding the refrigerant passage and has a thickness that is elastically deformable so as to bend in the central axis direction, A column formed in the first slit and the second slit, extending in the direction of the central axis and connected to the base, A resistance welding apparatus having a suppression unit that suppresses the leakage of refrigerant through the aforementioned slit.

2. In the resistance welding apparatus according to claim 1, The slit is formed in at least one of the electrodes, the first electrode located on the first side of the workpiece and the second electrode located on the second side. The suppression part is attached to the electrode in which the slit is formed, in a resistance welding apparatus.

3. In the resistance welding apparatus according to claim 1, The suppression part is a cover attached to the outer circumferential surface of the electrode and covers the opening of the slit in a resistance welding apparatus.

4. In the resistance welding apparatus according to claim 1, The refrigerant passage has an inner tube that extends to the tip of the electrode and forms a refrigerant supply path. The refrigerant passage has a double structure in which a refrigerant return passage is formed on the outside of the inner pipe. The slit is in communication with the return path, and the resistance welding apparatus.

5. In the resistance welding apparatus according to any one of claims 1 to 4, The electrode comprises a cap tip that contacts the workpiece, a shank to which the cap tip is attached, and a holder that holds the shank. The slit is formed in the shank or the holder, The suppression part is a resistance welding device attached to the shank or holder, in which the slit is formed.