Resistance welding device

Abstract

The electric resistance welding device welds a plurality of pieces to be welded by applying pressure to a workpiece (100) comprising a plurality of stacked pieces to be welded (101, 102) and supplying power to the workpiece. An electric resistance welding device is provided with an electrode (2) which has a tip surface (211) that comes into contact with a workpiece and which pressurizes and supplies power to the workpiece, and in which slits (41-44) are formed in an intermediate section between the tip surface and the base end of the electrode, the slits (41-44) open on the outer peripheral surface of the electrode and extend in the circumferential direction on a surface intersecting the direction of the center axis (X) of the electrode.

Description

Technical Field

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

[0002] In Patent Document 1, an existing spot welding device is described. The spot welding device includes a robot and a welding gun. The robot holds the welding gun and positions the welding gun at the welding part of the workpiece to be welded. An equalizing mechanism is provided between the welding gun and the robot. The equalizing mechanism absorbs the position deviation of the workpiece to be welded and / or the teaching error of the robot.

[0003] Patent Document 1: Japanese Patent Laid-Open Gazette No. Sho 59-92181 Summary of the Invention

[0004] -Technical Problem to be Solved by the Invention-

[0005] Spot welding is a type of resistance welding. Resistance welding welds a plurality of workpieces to be welded through the following process. That is, (1) The first electrode and the second electrode clamp the workpiece composed of a plurality of workpieces to be welded and apply pressure to the workpiece while supplying power to the workpiece. (2) By applying pressure, the workpieces to be welded come into contact with each other, thereby forming a current path at the joint interface of the workpiece, and generating Joule heat at the joint interface. (3) At the joint interface of the workpiece, the workpieces to be welded melt. (4) The melted workpieces to be welded solidify to form a nugget, and the welding process ends.

[0006] In the resistance welding process, sometimes discharge occurs between the electrode and the workpiece to be welded. This discharge wears the tip of the electrode. During repeated welding, the shape of the electrode tip gradually changes due to wear, resulting in a decrease in welding quality. In the field of resistance welding technology, there is a technical problem that the welding quality decreases due to discharge.

[0007] The technology disclosed herein suppresses the decrease in the welding quality of resistance welding.

[0008] -Technical Solution for Solving the Technical Problem-

[0009] The inventors of the present application found that in the above processes (1) to (4), discharge occurs when the workpiece to be welded softens / melts in (2) and / or (3).

[0010] To explain in more detail, in the welding process, the top surface of the electrode is pressed against the workpiece. The electrode pressed against the workpiece is constrained by the workpiece and the welding torch. In the above (2) and / or (3), when the workpiece to be welded softens / melts, the constraint of the workpiece and the welding torch on the electrode loosens. If the center of the load applied to the electrode is on the central axis of the electrode, then even if the constraint loosens, the top surface of the electrode will not move relative to the surface of the workpiece to be welded, and the electrode remains in the state of being pressed against the workpiece along the direction of the central axis of the electrode. It should be noted that in resistance welding, generally speaking, the central axis of the electrode is orthogonal to the surface of the workpiece.

[0011] However, if the center of the load applied to the electrode is eccentric with respect to the central axis of the electrode or inclined with respect to the central axis, then along with the loosening of the constraint on the electrode, the top surface of the electrode will produce a slight movement in a manner of sliding on the surface of the workpiece to be welded. When this movement occurs, misalignment occurs between the electrode and the workpiece to be welded, and discharge occurs between the electrode and the workpiece to be welded.

[0012] It should be noted that in the following description, the situation where the center of the load applied to the electrode is eccentric with respect to the central axis of the electrode or inclined with respect to the central axis is referred to as "the center of the load deviates from the central axis of the electrode".

[0013] In view of the above discharge generation mechanism, the inventor of the present application focuses on making the electrode elastically bend with respect to the central axis. If the electrode can bend, then even if the center of the load applied to the electrode deviates from the central axis of the electrode, the entire top surface of the electrode can uniformly abut against the surface of the workpiece to be welded through the elastic deformation of the electrode. The electrode can apply a load to the workpiece along the central axis direction. In this case, even if the workpiece to be welded softens / melts and causes the constraint of the workpiece and the welding torch on the electrode to loosen, the top surface of the electrode will not move or hardly move relative to the surface of the workpiece to be welded. It is possible to suppress misalignment between the electrode and the workpiece to be welded and suppress discharge between the electrode and the workpiece to be welded.

[0014] Specifically, the technology disclosed herein relates to a resistance welding device that welds a plurality of workpieces to be welded by pressing a workpiece composed of a plurality of stacked workpieces to be welded and supplying power to the workpiece. The resistance welding device includes an electrode having a top surface that abuts against the workpiece, and pressing and supplying power to the workpiece. A slit is formed in an intermediate portion of the electrode between the top surface and the base end. The slit opens on the outer peripheral surface of the electrode and extends circumferentially on a plane intersecting the central axis direction of the electrode.

[0015] According to this configuration, the top surface of the electrode abuts against the workpiece. The base end of the electrode can be supported by a welding gun, for example. The welding gun presses the top surface of the electrode onto the surface of the workpiece to be welded. The electrode applies pressure to the workpiece in the direction of the central axis of the electrode and supplies power to the workpiece.

[0016] When pressure is applied to the workpiece and power is supplied to soften / melt the workpiece to be welded, the restraint on the electrode pressed against the workpiece becomes loose. When the center of the load applied to the electrode deviates from the central axis of the electrode, when the restraint on the electrode becomes loose, a slight movement occurs on the top surface of the electrode, and sometimes misalignment occurs between the top surface of the electrode and the surface of the workpiece to be welded.

[0017] A slit is formed in the middle part of the electrode. The slit opens on the outer peripheral surface of the electrode and extends circumferentially on a plane intersecting the central axis direction. It should be noted that the plane intersecting the central axis direction is an imaginary plane of the electrode. When the center of the load applied to the electrode deviates from the central axis of the electrode, the slit allows the middle part of the electrode to elastically bend relative to the central axis of the electrode.

[0018] When the middle part of the electrode undergoes elastic deformation, the entire top surface of the electrode can uniformly abut against the surface of the workpiece to be welded. The electrode applies a load to the workpiece through the top surface that uniformly abuts against the surface of the workpiece to be welded. In this case, when the restraint on the electrode becomes loose due to the softening / melting of the workpiece to be welded, the top surface of the electrode does not move or hardly moves relative to the surface of the workpiece to be welded. Although the workpiece to be welded is deformed, the change in the positional relationship between the top surface of the electrode and the surface of the workpiece to be welded that are in mutual contact is suppressed. By suppressing misalignment between the top surface of the electrode and the surface of the workpiece to be welded, discharge between the electrode and the workpiece to be welded is suppressed, and thus wear of the top of the electrode can be suppressed. Since wear can be suppressed, even if welding is repeated, the shape of the top of the electrode will not change or is difficult to change. The resistance welding device can maintain high welding quality. The resistance welding device is also beneficial for the long life of the electrode.

[0019] The resistance welding device has the following advantages: only the electrode has a new structure, and the parts other than the electrode can use the existing resistance welding device.

[0020] It can also be like this, that is: the slit is formed on at least one of the first electrode and the second electrode sandwiching the workpiece, the first electrode is located on the first side, and the second electrode is located on the second side.

[0021] If at least one of the first electrode and the second electrode can undergo elastic deformation, the resistance welding device can stabilize the welding quality. If both the first electrode and the second electrode can undergo elastic deformation, the resistance welding device can make the welding quality more stable.

[0022] Alternatively, the opening of the slit extends circumferentially along a plane orthogonal to the central axis direction on the outer circumferential surface of the electrode.

[0023] When the opening of the slit extends circumferentially along a plane orthogonal to the central axis direction, the middle portion of the electrode can be stably bent relative to the central axis over the entire circumference of the electrode.

[0024] Alternatively, the electrode has a plurality of slits arranged along the central axis direction.

[0025] As the number of slits increases, the elastic modulus of the middle portion of the electrode decreases. By adjusting the number of slits formed on the electrode, the elastic modulus of the middle portion of the electrode is set to an appropriate elastic modulus. The appropriate elastic modulus enables the workpiece to be pressed by the electrode and suppresses misalignment between the top surface of the electrode and the surface of the workpiece to be welded during the welding process.

[0026] Alternatively, a hole extending along the central axis direction is formed at the radially central portion of the electrode. The slit communicates with the hole. The electrode includes a base and columns. The base is formed between a first slit and a second slit adjacent in the central axis direction and is in a ring shape surrounding the hole, and has a thickness that can elastically deform in a manner of flexing along the central axis direction. The columns are respectively formed in the first slit and the second slit, and extend along the central axis direction and are connected to the base.

[0027] The columns in the slit and the base connected to the columns transmit loads in the central axis direction between the top surface and the base end of the electrode. The columns in the slit ensure the rigidity for the electrode to press the workpiece.

[0028] When the base bears the load in the central axis direction through the columns, the base tends to flex in the central axis direction. The slit adjacent to the base allows the base to flex in the central axis direction. When the base flexes in the central axis direction, the slit will be flattened in the central axis direction, so that the middle portion of the electrode can undergo compressive deformation in the central axis direction.

[0029] Alternatively, a plurality of columns are formed at intervals in the circumferential direction in the first slit and the second slit respectively.

[0030] As described above, when the base bears the load in the central axis direction through the columns, the base will deflect in the central axis direction. When the center of the load applied to the electrode deviates from the central axis of the electrode, the load transmitted by a part of the plurality of columns provided with an interval in the circumferential direction will become relatively large. Therefore, in the base, the part connected to the column will deflect relatively largely. As a result, the electrode bends relative to the central axis. That is to say, the plurality of columns provided with an interval in the circumferential direction can make the electrode bend stably relative to the central axis.

[0031] It can also be like this, that is, the columns formed in the first slit and the columns formed in the second slit are staggered from each other in the circumferential direction.

[0032] Since the base is arranged between the first slit and the second slit, and the positions of the columns in the first slit and the columns in the second slit are staggered from each other, the base receives loads from the respective columns at different positions in the circumferential direction. The base can efficiently generate deflection in the central axis direction. As a result, the electrode can elastically bend relative to the central axis. On the other hand, since the electrode can transmit the load in the central axis direction through a plurality of columns whose positions are staggered from each other, the rigidity required for transmitting the load can be ensured. The electrode can reliably press the workpiece.

[0033] It can also be like this, that is, in the radial central part of the electrode, a refrigerant path extending in the central axis direction of the electrode is formed, the slit communicates with the refrigerant path, and the electrode has a suppression part that suppresses the leakage of the refrigerant passing through the slit.

[0034] The slit can cause the electrode to elastically deform. On the other hand, it will cause refrigerant leakage. The electrode has a suppression part. The suppression part suppresses the leakage of the refrigerant passing through the slit. The electrode can elastically deform while ensuring the cooling structure. Therefore, the resistance welding device can suppress the deterioration of the welding quality.

[0035] It can also be like this, that is, the suppression part is a cover installed on the outer peripheral surface of the electrode and covering the opening of the slit.

[0036] Since the cover covers the opening of the slit, the refrigerant leaking from the opening of the slit stays between the electrode and the cover. The leakage of the refrigerant can be suppressed.

[0037] It can also be like this, that is, the electrode has an electrode cap, an electrode rod, and a holder. The electrode cap abuts against the workpiece. The electrode cap is installed at the top of the electrode rod. The holder holds the electrode rod. The slit is formed on the electrode rod or the holder.

[0038] The electrode cap in contact with the workpiece is replaced after the wear increases. The replacement frequency of the electrode cap is higher than that of the electrode rod or the retainer.

[0039] If a slit is formed in the electrode cap, the manufacturing cost of the electrode cap will increase. The increase in the manufacturing cost of the electrode cap with a high replacement frequency will lead to an increase in the maintenance cost of the resistance welding apparatus. In contrast, since the replacement frequency of the electrode rod or the retainer is relatively low, they are suitable as the formation sites of the slit.

[0040] It can also be the case that: the workpiece is composed of a plate-shaped first workpiece to be welded and a non-plate-shaped second workpiece to be welded placed on the first workpiece to be welded. The second workpiece to be welded has a plurality of protrusions in contact with the surface of the first workpiece to be welded. At the positions of the plurality of protrusions, the first workpiece to be welded and the second workpiece to be welded are welded to each other. The first electrode in contact with the first workpiece to be welded has a guide pin that penetrates the first workpiece to be welded and the second workpiece to be welded along the central axis direction. The second electrode in contact with the second workpiece to be welded has a recess for inserting the guide pin on the top end surface.

[0041] The resistance welding apparatus can also perform projection welding. In projection welding, a uniform load is applied to the plurality of protrusions of the second workpiece to be welded through the first electrode and the second electrode, so as to weld a plurality of parts uniformly, thereby improving the welding quality.

[0042] As described above, the electrode having a slit can undergo elastic deformation between the top end surface and the base end of the electrode. The entire top end surface of the electrode uniformly contacts the surface of the workpiece to be welded, and the electrode can uniformly apply a load in the central axis direction to the workpiece to be welded. That is to say, the resistance welding apparatus can uniformly apply a load to the plurality of protrusions of the second workpiece to be welded through the first electrode and the second electrode. The resistance welding apparatus improves the welding quality of projection welding.

[0043] In this way, the resistance welding apparatus disclosed herein can uniformly apply a load to the workpiece through the first electrode and the second electrode. In the case of utilizing this feature, the workpiece as the welding object of the resistance welding apparatus can also be, for example, a workpiece formed by axially butting tubular workpieces to be welded with each other. The above-mentioned resistance welding apparatus can uniformly apply a load through the first electrode and the second electrode to the entire circumference of the joint portion of the workpiece to be welded. The resistance welding apparatus can improve the welding quality.

[0044] The resistance welding apparatus disclosed herein can be applied to ring mash welding. In ring mash welding, the hole formed in the first workpiece to be welded and the second workpiece to be welded whose outer shape is slightly larger than the hole are welded around the entire hole. The above-mentioned resistance welding apparatus can uniformly apply a load to the welding portion around the hole. The resistance welding apparatus improves the welding quality of ring mash welding.

[0045] - Effects of the Invention -

[0046] The above resistance welding device can suppress misalignment between the top surface of the electrode and the surface of the workpiece during the resistance welding process. It can also uniformly apply a load to the workpiece. The resistance welding device can suppress the deterioration of welding quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 Showing a spot welding device;

[0048] Figure 2 Showing the first electrode of the spot welding device;

[0049] Figure 3 Showing the electrode rod of the first electrode;

[0050] Figure 4 The upper figure in [ ] is a top view of the electrode rod, and the lower figure is a cross-sectional view taken along line A - A;

[0051] Figure 5 Showing the manufacturing steps of the slit;

[0052] Figure 6 The upper figure in [ ] shows the state where the electrode rod has undergone elastic deformation, and the lower figure shows a cross-section taken along line B - B;

[0053] Figure 7 Showing the state after the electrode rod is bent;

[0054] Figure 8 Showing a deformation example of the electrode related to the slit;

[0055] Figure 9 Showing a deformation example of the electrode related to the column;

[0056] Figure 10 Showing the welding process of the projection welding device;

[0057] Figure 11 Is an exploded view of the first electrode of the projection welding device;

[0058] Figure 12 Showing the second electrode of the projection welding device. DETAILED DESCRIPTION OF THE INVENTION

[0059] Next, embodiments of the resistance welding device will be described with reference to the drawings. The resistance welding device described here is an example.

[0060] (Overall Structure of the Spot Welding Device)

[0061] Figure 1The overall appearance of a resistance welding device is illustrated. The resistance welding device welds a plurality of workpieces 101 and 102 by pressing a workpiece 100 formed by laminating the plurality of workpieces 101 and 102 and supplying power to the workpiece 100. Figure 1 The resistance welding device in Figure 1 is a so-called spot welding device 1. In

[0062] the spot welding device 1, the pressing direction of the workpiece 100 is the vertical direction of the paper surface. The pressing direction is not limited to the vertical direction. Figure 1 The spot welding device 1 welds the workpieces 101 and 102 that are both plate-shaped. The two workpieces 101 and 102 are metal plates. The two workpieces 101 and 102 can also both be iron-based components. The iron-based components are, for example, steel components with high strength and rigidity like high-tensile steel. The two workpieces 101 and 102 can also, for example, be one iron-based component and the other aluminum-based component. The aluminum-based component is, for example, an aluminum alloy component. It should be noted that in Figure 1 the example, the workpiece 100 is composed of two workpieces 101 and 102, but the workpiece 100 can also be composed of three or more workpieces. In Figure 1 the thicknesses of the two workpieces 101 and 102 are equal, but the thicknesses of the workpieces 101 and 102 can also be unequal.

[0063] Figure 1 The illustrated spot welding device 1 includes a welding gun 11. The welding gun 11 is supported by a robot (not shown), for example. The robot positions the welding gun 11 at the position on the workpiece 100 where welding is to be performed.

[0064] The welding gun 11 supports a first electrode 2 and a second electrode 20. The first arm 111 of the welding gun 11 is supported in a cantilever manner with its base end 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 supported in a cantilever manner, and the second arm 112 supports the second electrode 20 at its free end.

[0065] The first electrode 2 is located on the first side of the workpiece 100. In Figure 1 the first electrode 2 is located on the lower side of 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 on the upper side of the workpiece 100. The first electrode 2 and the second electrode 20 clamp the workpiece 100 along the lamination direction of the workpieces 101 and 102 and press the workpiece 100 in the lamination direction.

[0066] The first electrode 2 is approximately columnar. The second electrode 20 is also approximately columnar. The first electrode 2 and the second electrode 20 face each other in the direction of the central axis X of the electrode.

[0067] The welding gun 11 is provided with a pressing device 14. The pressing device 14 relatively moves the second electrode 20 along the central axis X direction with respect to the workpiece 100. The pressing device 14 is constituted by, for example, including a cylinder, a hydraulic cylinder or a servo motor. In a state where the tip of the first electrode 2 of the welding gun 11 is in contact with the surface of the workpiece 100, the pressing device 14 moves the second electrode 20, whereby the first electrode 2 and the second electrode 20 can clamp the workpiece 100 along the central axis X direction and press the workpiece 100 along the central axis X direction.

[0068] The spot welding device 1 includes a controller 12. The controller 12 controls the pressing and power supply to the workpiece 100 in the spot welding device 1. The controller 12 is a controller based on a well-known microcomputer, and includes a CPU (Central Processing Unit, central processing unit), a memory, and an input / output bus. The CPU is a central arithmetic processing device that executes a computer program. The computer program includes basic control programs such as an OS (Operating System, operating system), and application programs that are started on the OS to achieve specific functions. The memory includes a RAM (Random Access Memory, random access memory) and a ROM (Read Only Memory, read only memory). Various computer programs, data, etc. are stored in the ROM. The 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 and from the controller 12.

[0069] The controller 12 outputs a control signal to the pressing device 14 according to the control program stored in the ROM. The workpiece 100 is pressed by the first electrode 2 and the second electrode 20. 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 20.

[0070] Here, the welding process of the spot welding device 1 will be briefly described.

[0071] (1) While clamping the workpiece 100 along the central axis X direction and pressing the workpiece 100, the first electrode 2 and the second electrode 20 supply power to the workpiece 100.

[0072] (2) By pressing, the workpieces to be welded 101 and 102 are brought into contact with each other, thereby forming an electric conduction path at the joint interface of the workpiece 100 and generating Joule heat at the joint interface of the workpiece 100.

[0073] (3) At the joint interface of the workpiece 100, the workpieces to be welded 101 and 102 are melted.

[0074] (4) The melted workpieces to be welded 101 and 102 solidify to form a nugget, and the welding process ends.

[0075] (Structure of the electrode)

[0076] Figure 2 The structure of the first electrode 2 is illustrated. It should be noted that the structures of the first electrode 2 and the second electrode 20 are the same except for being upside - down. The description of the structure of the second electrode 20 is omitted.

[0077] The electrode cap 21 of the first electrode 2 is located at the top end of the first electrode 2. The electrode cap 21 has a top end face 211 that abuts against the workpiece 100. If the top end face 211 is worn due to repeated welding by the spot welding device 1, the electrode cap 21 will be replaced.

[0078] The electrode cap 21 has a recess 212. The recess 212 opens at the base end face of the electrode cap 21 and depresses along the central axis X of the first electrode 2. As described below, the recess 212 forms a part of the refrigerant path 26.

[0079] The electrode rod 22 extends along the central axis X of the first electrode 2. The electrode cap 21 is mounted at the top end of the electrode rod 22. The electrode rod 22 supports the electrode cap 21. The electrode rod 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 the top end and the base end of the electrode rod 22 respectively. The first hole 221 penetrates the electrode rod 22. The electrode rod 22 is cylindrical (also refer to Figure 3 , Figure 4 ).

[0080] In the state where the electrode cap 21 is mounted at the top end of the electrode rod 22, the first hole 221 is connected to the recess 212 of the electrode cap 21. As described below, the first hole 221 forms a part of the refrigerant path 26.

[0081] An inner tube 222 is provided in 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 electrode rod 22. The inner tube 222 is also inserted into the second hole 231 of a holder 23 described later.

[0082] Slits 41 - 44 are also formed on the electrode rod 22. Figure 2 The illustrated first electrode 2 has a plurality of slits 41 - 44. The details of the shapes of the slits 41 - 44 will be described later.

[0083] The holder 23 is a cylindrical object that extends 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.

[0084] The base end portion of the electrode rod 22 is inserted into the second hole 231 from the top end of the holder 23. The holder 23 supports the electrode rod 22. The second hole 231 of the holder 23 communicates with the first hole 221 of the electrode rod 22.

[0085] Here, as described above, the inner tube 222 extends from the electrode rod 22 to the holder 23. The inner tube 222 forms a supply path 24 for supplying refrigerant to the electrode cap 21. The top end of the inner tube 222 is connected to the recess 212 of the electrode cap 21. Refrigerant is supplied to the recess 212 through the inner tube 222. The refrigerant effectively cools the electrode cap 21 (refer to the arrow in Figure 2 ).

[0086] A part of the refrigerant return path 25 is formed between the first hole 221 of the electrode rod 22 and the inner tube 222. A part of the refrigerant return path 25 is also formed between the second hole 231 of the holder 23 and the inner tube 222. The return path 251 and the return path 252 communicate with each other. The refrigerant supplied to the recess 212 of the electrode cap 21 is reversed in the recess 212 and flows back to the base end of the holder 23 through the return paths 251 and 252. The refrigerant path 26 having a double structure including the supply path 24 and the return path 25 can effectively cool the electrode cap 21.

[0087] (Structure of the slit)

[0088] Figure 3 The left - hand figure in [] is a perspective view of the electrode rod 22. Figure 3 The central figure in [] is a perspective view of the cross - section obtained by cutting the electrode rod 22 at the position of the first slit 41. Figure 3 The right - hand figure in [] is a perspective view of the cross - section obtained by cutting the electrode rod 22 at the position of the second slit 42.

[0089] As described above, the electrode rod 22 has a plurality of slits 41 - 44. More specifically, the electrode rod 22 includes an upper tapered portion 223, a lower tapered portion 224, and an intermediate portion 225. The upper tapered portion 223 tapers upward. The electrode cap 21 is mounted on the top end 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 outer diameter of the intermediate portion 225 is constant.

[0090] The slits 41 - 44 are formed in the intermediate portion 225. The plurality of slits 41 - 44 are arranged along the central axis X of the first electrode 2. The illustrated electrode rod 22 sequentially has a first slit 41, a second slit 42, a third slit 43, and a fourth slit 44 from the top end to the base end.

[0091] Each of the slits 41 to 44 extends in the circumferential direction on a plane that intersects the central axis X direction, more precisely, on a plane orthogonal to the central axis X direction. The plane orthogonal to the central axis X direction is an imaginary plane in the first electrode 2. Each of the slits 41 to 44 opens on the outer peripheral surface of the electrode rod 22. The openings of each of the slits 41 to 44 extend in the circumferential direction of the plane orthogonal to the central axis X direction on the outer peripheral surface of the electrode rod 22. As Figure 3 and Figure 4 shown, each of the slits 41 to 44 communicates with the first hole 221 of the electrode rod 22.

[0092] In Figure 3 and Figure 4 the shown electrode rod 22, each of the slits 41 to 44 has the same width in the central axis X direction. The intervals between adjacent slits 41 to 44 in the central axis X direction are also the same.

[0093] A first base 45 is formed between the first slit 41 and the second slit 42 adjacent in the central axis X direction. Similarly, a second base 46 is formed between the second slit 42 and the third slit 43, and a third base 47 is formed between the third slit 43 and the fourth slit 44. Each of the bases 45 to 47 is in a ring shape surrounding the first hole 221. Since the intervals between adjacent slits 41 to 44 in the central axis X direction are the same, the thicknesses of each of the bases 45 to 47 in the central axis X direction are the same.

[0094] Posts 31 to 33, 34 to 36 are formed in each of the slits 41 to 44. The posts 31 to 36 extend in the central axis X direction within the slits 41 to 44 and are connected to the bases 45 to 47. It should be noted that since there is no base above the first slit 41, the upper ends of the posts 31 to 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 the posts 34 to 36 formed in the fourth slit 44 are connected to the lower wall forming the fourth slit 44.

[0095] Three posts 31 to 36 are formed in each of the slits 41 to 44. More specifically, a first post 31, a second post 32, and a third post 33 are formed in the first slit 41. A first post 31, a second post 32, and a third post 33 are also formed in the third slit 43.

[0096] A fourth post 34, a fifth post 35, and a sixth post 36 are formed in the second slit 42. A fourth post 34, a fifth post 35, and a sixth post 36 are also formed in the fourth slit 44.

[0097] The first post 31 to the sixth post 36 all have as Figure 4The cross-section shown in the above figure is in the same shape of a triangle. The first column 31 to the third column 33 are arranged around the first hole 221. The vertices of the triangles of each column 31 to 33 are located at the radially outer side of the first electrode 2. In the electrode rod 22 of the example, the first column 31 to the third column 33 are spaced 120° apart from each other. A connecting port 37 connecting the slits 41, 43 and the first hole 221 is formed between the first column 31 and the second column 32. Similarly, a connecting port 37 connecting the slits 41, 43 and the first hole 221 is also formed between the second column 32 and the third column 33, and between the third column 33 and the first column 31.

[0098] The fourth to sixth columns 34 to 36 are also arranged around the first hole 221. The vertices of the triangles of the columns 34 to 36 are located at radially outer positions of the first electrode 2. In the electrode rod 22 of the example, the fourth to sixth columns 34 to 36 are spaced 120 degrees apart from each other. The communication ports 37 connecting the slits 42 and 44 to the first hole 221 are formed between the fourth column 34 and the fifth column 35, between the fifth column 35 and the sixth column 36, and between the sixth column 36 and the fourth column 34, respectively.

[0099] The first column 31 and the fourth column 34 are staggered 60° in the circumferential direction. Similarly, the second column 32 and the fifth column 35 are staggered 60° in the circumferential direction, and the third column 33 and the sixth column 36 are staggered 60° in the circumferential direction. Figure 4 As shown in the above figure, the positions of the columns 31 to 36 formed in two adjacent slits 41 to 44 sandwiching any bases 45 to 47 are all offset from each other in the circumferential direction.

[0100] As an example, the slits and posts can be made for the electrode rod 22 as follows. Figure 5 The steps of manufacturing the first slit 41 and the first to third columns 31 to 33 for the electrode rod 22 are shown.

[0101] First, prepare the electrode rod 22 formed with the first hole 221. In step P1, the electrode rod 22 is fixed, and the cutting tool 5 is relatively moved relative to the outer peripheral portion of the electrode rod 22 in a direction orthogonal to the central axis X. As a result, in the cross section of the electrode rod 22, the arcuate portion surrounded by the arc and the chord is cut off by the cutting tool 5. It should be noted that the cutting tool 5 is fed toward the radial inner side of the electrode rod 22 until the position where the chord interferes with the first hole 221 of the electrode rod 22. In step P1, a slit 41 is formed on the electrode rod 22, and the slit 41 opens on the outer peripheral surface of the electrode rod 22 and is connected to the first hole 221.

[0102] Next, in process P2, the electrode rod 22 is rotated 120° about the central axis and the electrode rod 22 is fixed. Similar to process P1, the cutting tool 5 is relatively moved in a direction orthogonal to the central axis X with respect to the outer peripheral portion of the electrode rod 22. Thus, similar to process P1, in the cross-section of the electrode rod 22, the arcuate portion surrounded by the arc and the chord is cut off by the cutting tool 5. A slit 41 is formed, and the slit 41 opens at a position different from the above on the outer peripheral surface of the electrode rod 22 and communicates with the first hole 221. In process P2, the first upright post 31 is also formed.

[0103] Next, in process P3, the electrode rod 22 is further rotated 120° about the central axis and the electrode rod 22 is fixed. Then, similar to process P1, the cutting tool 5 is relatively moved in a direction orthogonal to the central axis X with respect to the outer peripheral portion of the electrode rod 22. Thus, similar to process P1, in the cross-section of the electrode rod 22, the arcuate portion surrounded by the arc and the chord is cut off by the cutting tool 5. A slit 41 is formed, and the slit 41 opens at a position different from the above on the outer peripheral surface of the electrode rod 22 and communicates with the first hole 221. In process P3, the second upright post 32 and the third upright post 33 are also formed. It should be noted that in the electrode rod 22 in the illustrated example, in each of the three processes, the slit 41 is formed, and the slit 41 is connected to each other through the top portions of the first upright post 31, the second upright post 32, and the third upright post 33.

[0104] After the first slit 41 and the first upright post 31 to the third upright post 33 are formed on the electrode rod 22 through processes P1 to P3, the relative position of the electrode rod 22 and the cutting tool 5 in the central axis X direction is changed, and the second slit 42 and the fourth upright post 34 to the sixth upright post 36 are formed on the electrode rod 22 through the above processes P1 to P3. It should be noted that by adjusting the orientation of the electrode rod 22 in the circumferential direction, the positions of the first upright post 31 to the third upright post 33 are staggered by 60° from the positions of the fourth upright post 34 to the sixth upright post 36. With respect to the electrode rod 22, the formation of the third slit 43 and the first upright post 31 to the third upright post 33 and the formation of the fourth slit 44 and the fourth upright post 34 to the sixth upright post 36 can also be performed in the same manner.

[0105] (Elastic deformation of the electrode)

[0106] As described above, the slits 41 to 44 and the upright posts 31 to 36 are formed on the first electrode 2. The slits and the upright posts are also formed on the second electrode 20. The slits 41 to 44 and the upright posts 31 to 36 cause elastic deformation of the first electrode 2 at an intermediate portion between the top end surface 211 and the base end of the first electrode 2.

[0107] Figure 6The example shows a state in which a load in the X direction of the central axis is uniformly applied to the first electrode 2 on a plane orthogonal to the X direction of the central axis. The center of the load applied to the first electrode 2 is located on the central axis X. The load is transmitted in the X direction of the central axis through the columns 31-36 and the bases 45-47 in the electrode rod 22.

[0108] As Figure 6 shown in the lower figure in [ ], the first column 31 to the third column 33 in the first slit 41 are located at equally spaced positions in the circumferential direction. The fourth column 34 to the sixth column 36 in the second slit 42 adjacent to the first slit 41 across the first base 45 are offset from the first column 31 to the third column 33 in the circumferential direction. Since the positions of the first column 31 to the third column 33 on the upper side of the first base 45 are offset from the positions of the fourth column 34 to the sixth column 36 on the lower side of the first base 45, with respect to the first base 45 that expands in a direction orthogonal to the X direction of the central axis, the positions for applying the load in the X direction of the central axis are offset from each other in the circumferential direction as Figure 6 shown by the black arrows in the upper figure of [ ]. As a result, the first base 45 is deflected in the central axis direction as Figure 6 shown by the double-dashed line in the upper figure of [ ]. In other words, the thickness of the first base 45 in the central axis direction is such that it can be deflected when a load is applied.

[0109] Similarly, since the fourth column 34 to the sixth column 36 in the second slit 42 are offset from the first column 31 to the third column 33 in the second slit 43 in the circumferential direction, the second base 46 is deflected in the X direction of the central axis as Figure 6 shown by the double-dashed line in the upper figure of [ ].

[0110] The third base 47 is also deflected in the X direction of the central axis as Figure 6 shown by the double-dashed line in the upper figure of [ ] because the first column 31 to the third column 33 in the third slit 43 are offset from the fourth column 34 to the sixth column 36 in the fourth slit 44 in the circumferential direction. It should be noted that Figure 6 the deflection of each base 45-47 is exaggeratedly depicted.

[0111] The columns 31-36 promote the deflection of the bases 45-47, and the slits 41-44 allow the bases 45-47 to deflect. When the center of the load applied to the first electrode 2 is located on the central axis X, the electrode rod 22 elastically deforms in a manner of contracting in the X direction of the central axis. That is, the electrode rod 22 can transmit the load in the X direction of the central axis and can generate elastic compressive deformation.

[0112] When the center of the load applied to the first electrode 2 is eccentric with respect to the central axis X of the first electrode 2 or inclined with respect to the central axis X, the load is unevenly applied on the plane orthogonal to the direction of the central axis X. In this case, since the loads applied to the bases 45 to 47 through three of the columns 31 to 36 in each of the slits 41 to 44 are not uniform, in the bases 45 to 47, relatively large deflections are locally generated in the direction of the central axis X at the portions where relatively large loads are applied from the columns 31 to 36. For example, Figure 7 shows an example after a compressive load is applied to the first electrode 2 along an axis eccentric to the left side of the paper surface with respect to the central axis X as indicated by the hollow arrow. In this case, since the portions of the slits 41 to 44 on the left side of the paper surface are relatively flattened, the electrode rod 22 is bent, causing the central axis X to incline (refer to the arrow in Figure 7 ). Since the electrode rod 22 is bent, the top surface 211 of the electrode cap 21 maintains the state of being in contact with the surface of the workpiece 100. It should be noted that Figure 7 the bending of the electrode rod 22 is exaggeratedly shown.

[0113] When the workpieces 101 and 102 to be welded are softened / melted in (2) and / or (3) of the above welding process, the electrodes that have been constrained by the welding torch 11 and the workpiece 100 tend to move due to the loosening of the constraint. More specifically, as Figure 1 shown, the first electrode 2 and the second electrode 20 are respectively held on the first arm 111 and the second arm 112 that are cantilever-supported. Therefore, when the workpieces 101 and 102 to be welded are softened / melted, the first electrode 2 and the second electrode 20 tend to move obliquely in the direction indicated by the hollow arrow in Figure 1 .

[0114] At this time, in the electrodes 2 and 20 having the slits 41 to 44 and the columns 31 to 36, the electrode rod 22 is bent as described above, whereby the state in which the top surface 211 of the electrode cap 21 is in contact with the surface of the workpiece 100 can be maintained. As a result, misalignment does not occur between the top surfaces 211 of the electrodes 2 and 20 and the surfaces of the workpieces 101 and 102 to be welded, and discharge between the electrodes 2 and 20 and the workpieces 101 and 102 to be welded can be suppressed. By suppressing the discharge, the tip wear of the electrodes 2 and 20 is suppressed. Therefore, even if the spot welding device 1 performs welding repeatedly, a decrease in welding quality can be suppressed. In addition, since wear of the electrode cap 21 can be suppressed, the life of the electrode cap 21 is prolonged.

[0115] The above spot welding device 1 has the following advantages: only the electrodes 2 and 20 have a new structure, and the parts other than the electrodes 2 and 20 can use the existing spot welding device.

[0116] (Deformation examples of the slit and the column)

[0117] The openings of the slits 41 to 44 extend in the circumferential direction of the surface orthogonal to the central axis X direction on the outer circumferential surfaces of the electrodes 2 and 20. This structure has the following advantages: When the center of the load applied to the electrodes 2 and 20 is offset relative to the central axis X of the electrodes 2 and 20, the electrodes 2 and 20 can be elastically deformed stably in the bending direction in the entire circumferential direction of the electrodes 2 and 20. It should be noted that on the outer circumferential surface of the electrode, the opening of the slit may also extend in the circumferential direction on the surface intersecting the central axis X direction. When the center of the load applied to the electrode is offset from the central axis of the electrode, the electrode of this structure can also cause the electrode to elastically deform in the bending direction.

[0118] By changing the position or number of the slits formed in the electrodes 2 and 20 and / or the position or number of the columns, the elastic modulus of the electrodes 2 and 20 can be changed. Appropriately setting the elastic modulus of the electrodes 2 and 20 according to the welding conditions of the spot welding device 1 enables the workpiece 100 to be pressurized by the electrodes 2 and 20, and the dislocation between the top surface 211 of the electrodes 2 and 20 and the workpiece 100 can be suppressed.

[0119] Regarding the thickness of the bases formed on the electrodes, the multiple bases may be the same or different. In Figure 8 , the thickness H1 of the first base 45 located on the top side of the electrodes 2 and 20 is relatively thick, and the thickness H3 of the third base 47 located on the base end side of the electrodes 2 and 20 is relatively thin. If the thickness of the base is thick, the bending stiffness of the base is high. That is, it is difficult for the base to flex in the central axis X direction. If the thickness of the base is thin, the bending stiffness of the base is low. The base is easy to flex in the central axis X direction. By making the thickness of the first base 45 located on the top side of the electrodes 2 and 20 relatively thick and making the thickness of the third base 47 located on the base end side of the electrodes 2 and 20 relatively thin, the electrodes 2 and 20 elastically deform stably. The dislocation between the top surface 211 of the electrodes 2 and 20 and the surface of the workpiece 100 can be suppressed more effectively.

[0120] It should be noted that in Figure 8 , the thickness H1 of the first base 45, the thickness H2 of the second base 46, and the thickness H3 of the third base 47 become thinner in sequence (H1>H2>H3). The magnitude relationship of the thicknesses of the multiple bases is not limited to the illustrated example. For example, the magnitude relationship of the thicknesses of the multiple bases may be H1=H2>H3, or may be H1>H2=H3.

[0121] The number of bases is not limited to three. It is sufficient for the electrodes 2 and 20 to have at least one base, and correspondingly, it is sufficient for the electrodes 2 and 20 to have at least two slits. The number of slits that can be formed on the electrodes 2 and 20 depends on the length of the electrodes 2 and 20 in the central axis X direction. The electrodes 2 and 20 can have, for example, up to five slits.

[0122] As Figure 6 shown in the example, the circumferential positions of the plurality of upright columns 31 to 36 formed on the electrodes 2 and 20 are all offset from each other, whereby the electrodes 2 and 20 can ensure the rigidity in the central axis X direction required for the electrodes 2 and 20 and can elastically deform stably along the bending direction.

[0123] Figure 9 An example of the electrodes 2 and 20 with the upright column arrangement changed is shown. Figure 9 The electrode rod 220 of the spot welding device 10 shown in the upper figure above is bent midway. The electrode rod 220 with the above shape can avoid interference with the workpiece 100. In Figure 9 , the base end of the electrode rod 220 held by a holder (not shown) and the top end of the electrode rod 220 supporting the electrode cap 21 are offset from each other in the horizontal direction (refer to Figure 9 X1, X2). In the state where the first electrode 2 and the second electrode 20 press the workpiece 100, an eccentric load is always applied to the electrode cap 21 and the electrode rod 220.

[0124] A slit 4 is formed on the electrode rod 220. In the case of the electrode structure where an eccentric load is applied to the electrode cap 21, in order to make the entire top surface 211 of the electrode cap 21 uniformly contact the surface of the workpiece 100, it is preferable to increase the rigidity of the portion of the electrode rod 220 on the right side of the paper surface with respect to the axis X1 and decrease the rigidity of the portion on the left side of the paper surface. Figure 9

[0125] As Figure 9 shown in the lower figure below, the three upright columns 301, 302, and 303 formed in the slit 4 are offset to one side with respect to the axis X1 in the slit 4. The angle between the upright column 301 and the upright column 302 is 90°, and the angle between the upright column 302 and the upright column 303 is also 90°. In this way, the rigidity of the portion of the electrode rod 220 on the right side of the paper surface in Figure 9 is increased, and the rigidity of the portion on the left side of the paper surface is decreased. The electrode cap 21 can stably press the workpiece 100 and can suppress misalignment between the top surface 211 of the electrode cap 21 and the surface of the workpiece 100.

[0126] It should be noted that in Figure 9 ​In the electrode rod 220, the circumferential positions of the three columns 301, 302, and 303 formed in the slit 4 and the columns in the slit 4 adjacent to the slit 4 in the direction of the axis X1 can also be offset from each other.

[0127] The number of columns 31 - 36, 301 - 303 formed in one slit 41 - 44, 4 is not limited to three. However, if there are three columns 31 - 36, 301 - 303, the plane formed by connecting these three columns 31 - 36, 301 - 303 is uniquely determined. Having three columns 31 - 36, 301 - 303 in one slit 41 - 44, 4 has the following advantages: In the electrode structure where multiple slits 41 - 44, 4 overlap axially, the electrodes 2, 20 bend stably.

[0128] It should be noted that in Figure 3 In the electrode rod 22 shown in the example, the radially outermost ends of the columns 31 - 36 (i.e., the vertices of the columns 31 - 36 that are approximately triangular in a top view) are located at positions radially inside the outer peripheral surface of the electrode rod 22. The radially outermost ends of the columns 31 - 36 can also be located at the same position as the outer peripheral surface of the electrode rod 22. Thus, the columns 31 - 36 can also divide the slits 41 - 44 into multiple slits circumferentially.

[0129] The cross-sectional shape of the column is not limited to an approximate triangle. The column can be formed into any shape.

[0130] The slits 41 - 44, 4 are not limited to being formed on the electrode rods 22, 220. The slits 41 - 44, 4 can also be formed on a holder, for example. In addition, the slits 41 - 44, 4 can also be formed on the electrode cap 21. However, if the slits 41 - 44, 4 are to be formed on the electrode cap 21, the manufacturing cost of the electrode cap 21 increases. The increase in the manufacturing cost of the electrode cap 21 with a high replacement frequency will increase the maintenance cost of the spot welding devices 1, 10. Since the electrode rods 22, 220 or the holder 23 have a relatively low replacement frequency, they are suitable as the formation sites of the slits 41 - 44, 4.

[0131] It is also possible not to provide the slits 41 - 44, 4 and the columns 31 - 36, 301 - 303 on both the first electrode 2 and the second electrode 20 of the spot welding devices 1, 10, but to provide the slits 41 - 44, 4 and the columns 31 - 36, 301 - 303 on either the first electrode 2 or the second electrode 20.

[0132] (Structure for suppressing refrigerant leakage)

[0133] Each of the slits 41 to 44 formed on the electrode rod 22 communicates with the first hole 221 forming the refrigerant path 26 via the communication port 37. Therefore, the refrigerant flowing in the return path 25 of the refrigerant path 26 leaks outside the electrodes 2 and 20 through the communication port 37 and the slits 41 to 44.

[0134] The electrodes 2 and 20 include a restraining portion for restraining refrigerant leakage. As Figure 2 shown, the restraining portion is a cover 6 mounted on the electrode rod 22.

[0135] The cover 6 covers the openings of the first slit 41 to the fourth slit 44 formed on the outer peripheral surface of the electrode rod 22. As Figure 2 indicated by the arrow in, the refrigerant leaking outside the electrode 2 from the openings of the first slit 41 to the fourth slit 44 stays inside the cover 6.

[0136] An O-ring 61 is interposed between the electrode rod 22 and the cover 6. The O-ring 61 is respectively mounted on the upper and lower portions of the electrode rod 22. The O-ring 61 restrains the leakage of the refrigerant from the gap between the electrode rod 22 and the cover 6.

[0137] In this way, in the electrodes 2 and 20 having a cooling structure, elastic deformation can be achieved by using the slits 41 to 44, and refrigerant leakage can be restrained.

[0138] It should be noted that the restraining portion only needs to be mounted on the electrodes 2 and 20 on which the slits 41 to 44 and 4 are formed. This is because refrigerant leakage will not occur if there are no slits 41 to 44 and 4.

[0139] (Structure of the projection welding device)

[0140] The technology disclosed herein is not limited to being applied to the spot welding device 1. The electrodes disclosed herein have the function of generating elastic deformation. Therefore, in addition to the function and effect of restraining the misalignment between the top surface 211 of the electrode and the surface of the workpiece 100, the top surface 211 of the electrode can also exert the function and effect of uniformly applying a load to the workpiece 100. This function and effect are useful for a projection welding device, which needs to uniformly weld a plurality of protrusions of the workpieces to be welded. Projection welding is a type of resistance welding.

[0141] Figure 10 Part of the structures of the first electrode 8 and the second electrode 9 of the projection welding device 7 are illustrated. The workpiece 1000 to be welded by the projection welding device 7 is composed of a first workpiece to be welded 1010 and a second workpiece to be welded 1020. The first workpiece to be welded 1010 is in a flat plate shape. The first workpiece to be welded 1010 has a through hole 1011. The through hole 1011 penetrates the first workpiece to be welded 1010 in the thickness direction.

[0142] The second workpiece to be welded 1020 is a nut. The second workpiece to be welded 1020 is not plate-shaped. As shown on the left side of Figure 10 , when viewed from above, the second workpiece to be welded 1020 is approximately square and has a threaded hole 1021 at its center. The second workpiece to be welded 1020 is placed on the first workpiece to be welded 1010 in such a way that the threaded hole 1021 is coaxial with the through hole 1011 of the first workpiece to be welded 1010. The second workpiece to be welded 1020 also has protrusions 1022 at its four corner portions respectively. The four protrusions 1022 are respectively in contact with the surface of the first workpiece to be welded 1010 when the second workpiece to be welded 1020 is placed on the first workpiece to be welded 1010.

[0143] The first electrode 8 has an electrode cap 81 and a guide pin 82. The electrode cap 81 is in contact with the surface of the first workpiece to be welded 1010. The electrode cap 81 has a through hole 811. The through hole 811 penetrates the electrode cap 81 along the central axis X direction.

[0144] The guide pin 82 extends along the central axis X direction of the first electrode 8. The guide pin 82 is inserted into the through hole 811 of the electrode cap 81. The guide pin 82 reciprocates along the central axis X direction by a later-described telescopic actuator 88. Figure 10 The protruding state of the guide pin 82 is shown. The guide pin 82 is inserted into the through hole 1011 of the first workpiece to be welded 1010 and the threaded hole 1021 of the second workpiece to be welded 1020. The tip of the guide pin 82 protrudes from the second workpiece to be welded 1020. The guide pin 82 restricts the relative positions of the first workpiece to be welded 1010 and the second workpiece to be welded 1020 so that the through hole 1011 and the threaded hole 1021 are coaxial. It should be noted that the detailed structure of the first electrode 8 will be described later.

[0145] The electrode cap 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 portion of the electrode cap 91. The first recess 911 opens at the base end of the electrode cap 91 and extends along the central axis X direction of the second electrode 9. As described below, the first recess 911 forms a part of the refrigerant path 93 of the second electrode 9.

[0146] The second recess 912 is formed at the tip portion of the electrode cap 91. The second recess 912 opens at the tip surface 913 of the electrode cap 91. The portion of the tip surface 913 of the electrode cap 91 around the second recess 912 is in contact with the second workpiece to be welded 1020. The second recess 912 extends along the central axis X direction of the second electrode 9. It should be noted that the first recess 911 and the second recess 912 are not connected. When the first electrode 8 and the second electrode 9 clamp the workpiece 1000 along the central axis X direction, the tip of the guide pin 82 is inserted into the second recess 912.

[0147] Here, the welding process of the projection welding device 7 is described.

[0148] (1) The first electrode 8 is abutted against the first workpiece to be welded 1010, and the guide pin 82 protrudes through the through hole 1011 of the first workpiece to be welded 1010 to the second electrode 9 side (refer to Figure 10 P11).

[0149] (2) The second workpiece to be welded 1020 is externally inserted onto the guide pin 82, and the protrusion 1022 of the second workpiece to be welded 1020 is abutted against the first workpiece to be welded 1010 (refer to Figure 10 P12).

[0150] (3) The top surface 913 of the second electrode 9 is abutted against the second workpiece to be welded 1020, and the first electrode 8 and the second electrode 9 clamp the workpiece 1000 along the central axis X direction to pressurize the workpiece 1000, and at the same time supply power to the workpiece 1000 (refer to Figure 10 P13).

[0151] (4) By pressurization, the protrusion 1022 of the second workpiece to be welded 1020 contacts the first workpiece to be welded 1010, a conduction path is formed at the part of the protrusion 1022, and Joule heat is generated. The protrusion 1022 of the second workpiece to be welded 1020 and the part of the first workpiece to be welded 1010 that contacts the protrusion 1022 are melted (refer to Figure 10 P14).

[0152] (5) The melted first workpiece to be welded 1010 and the second workpiece to be welded 1020 solidify to generate a nugget, and the welding process ends.

[0153] The first electrode 8 and the second electrode 9 of the projection welding device 7 can produce elastic deformation. Thereby, a uniform load is applied to the four protrusions 1022 of the second workpiece to be welded 1020, and the projection welding device 7 can weld the four protrusions 1022 uniformly on the first workpiece to be welded 1010. Next, with reference to Figure 11 and Figure 12 , the structures of the first electrode 8 and the second electrode 9 that can produce elastic deformation will be described.

[0154] Figure 11 The exploded view of the first electrode 8 is shown. As described above, the electrode cap 81 of the first electrode 8 has a through hole 811. The guide tube 83 is installed at the base end of the electrode cap 81 and holds the electrode cap 81. The guide tube 83 also has an inner hole for inserting the guide pin 82. The guide tube 83 guides the guide pin 82 to move back and forth.

[0155] The retainer 84 holds the guide tube 83 and the electrode cap 81. The retainer 84 is cylindrical and has a hole 841 for inserting a rod 87 described later. The hole 841 penetrates the retainer 84 along the central axis X direction.

[0156] The first joint 85 is located between the retainer 84 and the electrode cap 81. The first joint 85 is a portion of the first electrode 8 that can elastically deform. The first joint 85 is cylindrical and has a through hole that penetrates the first joint 85 in the direction of the central axis X. The 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 peripheral surface of the first joint 85. The slit 851 extends circumferentially on a plane that intersects the direction of the central axis X, more precisely, on a plane orthogonal to the direction of the central axis X. Figure 11 The illustrated first joint 85 has three slits 851. The three slits 851 are arranged in the direction of the central axis X. It should be noted that the number of slits 851 formed in the first joint 85 is not limited to three. Posts are formed in each slit 851, and bases are formed between the slits 851 adjacent to each other in the direction of the central axis X. The first joint 85 has two bases. The two bases are each annular, surround the through hole of the first joint 85, and have a thickness that can elastically deform in a manner that flexes in the direction of the central axis X. Through these slits 851 and posts, the first joint 85 can elastically deform with respect to a load in the direction of the central axis X.

[0157] The second joint 86 is located 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 and the telescopic actuator 88.

[0158] The telescopic actuator 88 is composed of a cylinder 881 and a piston rod 882. The piston rod 882 is inserted into the retainer 84. When air is supplied to the cylinder 881, the piston rod 882 elongates. Due to the elongation of the piston rod 882, the guide pin 82 projects toward the second electrode 9.

[0159] Therefore, the first electrode 8 has a mechanism for advancing and retracting the guide pin 82 and can elastically deform at the first joint 85 between the tip of the electrode cap 81 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, since the first joint 85 bends, the electrode cap 81 can apply a uniform load to the first workpiece 1010 through the entire tip surface.

[0160] Figure 12 The structure of the second electrode 9 is illustrated. The second electrode 9 has a refrigerant path 93 for cooling the electrode cap 91. As described above, the electrode cap 91 has a first recess 911 and a second recess 912.

[0161] The retainer 92 holds the electrode cap 91. The retainer 92 is cylindrical. The retainer 92 has a holding portion 921 at its top end. The holding portion 921 is a recess that opens on the top end face of the retainer 92. The base end of the electrode cap 91 is inserted into the holding portion 921 of the retainer 92. The first recess 911 of the electrode cap 91 is connected to the holding portion 921 of the retainer 92.

[0162] The inner hole 922 of the retainer 92 communicates with the holding portion 921 and opens at the base end of the retainer 92. The inner hole 922 forms part of the refrigerant path 93. The refrigerant is conveyed through the inner hole 922 and the holding portion 921 to the first recess 911 of the electrode cap 91 and returns from the first recess 911 through the holding portion 921 and the inner hole 922. It should be noted that the refrigerant path 93 can also be formed into a double structure by arranging the above-mentioned inner tube 222 (refer to Figure 2 ) in the inner hole 922 of the retainer 92.

[0163] In the second electrode 9, a slit 923 is formed in the retainer 92. The slit 923 opens on the outer peripheral surface of the retainer 92. The slit 923 extends circumferentially on a plane that intersects the central axis X direction, more precisely, on a plane orthogonal to the central axis X direction. Figure 12 The illustrated second electrode 9 has four slits 923. The four slits 923 are arranged in the central axis X direction. It should be noted that the number of slits 923 formed in the retainer 92 is not limited to four. A base is formed between adjacent slits 923 in the central axis X direction. The retainer 92 has three bases. The three bases are each annular, surround the inner hole 922 forming the refrigerant path 93, and have a thickness that can elastically deform in a manner that flexes along the central axis X direction.

[0164] Although detailed illustrations are omitted in Figure 12 , a plurality of columns are formed in each slit 923. The plurality of columns each extend in the central axis X direction and are connected to the base. The second electrode 9 can elastically deform at the retainer 92 between the top end face 913 of the electrode cap 91 and the base end of the second electrode 9. The retainer 92 elastically deforms such that the top end face 913 of the electrode cap 91 can apply a uniform load to the second workpiece to be welded 1020. The four protrusions 1022 of the second workpiece to be welded 1020 are uniformly welded to the first workpiece to be welded 1010.

[0165] Since the second electrode 9 has the refrigerant path 93, the refrigerant leaks through the slit 923. The second electrode 9 has a suppression portion for suppressing refrigerant leakage. As Figure 12 shown, the suppression portion is a cover 60 mounted on the outer peripheral surface of the retainer 92.

[0166] The cover 60 covers the openings of the four slits 923 formed on the outer peripheral surface of the retainer 92. An O-ring 601 is interposed between the retainer 92 and the cover 60. The O-ring 601 suppresses the leakage of the refrigerant from the gap between the retainer 92 and the cover 60.

[0167] In this way, the second electrode 9 with the cooling structure suppresses the leakage of the refrigerant and achieves elastic deformation by means of the slits 923.

[0168] (Other embodiments)

[0169] The technology disclosed herein is not limited to being applied to the spot welding devices 1, 10 or the projection welding device 7. As described above, the technology disclosed herein can uniformly apply a load to the workpiece through the first electrode and the second electrode. In the case of utilizing this feature, the workpiece to be welded by the resistance welding device can be, for example, a workpiece formed by butt-joining tubular workpieces to be welded to each other in the axial direction. The resistance welding device can uniformly apply a load to the entire circumference of the joint portion of the workpieces to be welded. The resistance welding device can improve the welding quality.

[0170] The technology disclosed herein can be applied to circumferential seam welding. In circumferential seam welding, welding is performed around the entire circumference of a hole formed in a first workpiece to be welded and a second workpiece to be welded whose outer shape is slightly larger than the hole. In this circumferential seam welding, the resistance welding device can uniformly apply a load to the welding portion around the hole. The resistance welding device improves the welding quality of the circumferential seam welding.

[0171] The features described in the above-mentioned multiple embodiments can also be combined within the possible range.

[0172] -Symbol description-

[0173] 100 Workpiece

[0174] 101 Workpiece to be welded

[0175] 102 Workpiece to be welded

[0176] 1000 Workpiece

[0177] 1010 First workpiece to be welded

[0178] 1020 Second workpiece to be welded

[0179] 2 First electrode

[0180] 20 Second electrode

[0181] 21 Electrode cap

[0182] 22 Electrode rod

[0183] 220 Electrode rod

[0184] 221 First hole

[0185] 222 Inner tube

[0186] 23 Retainer

[0187] 24 Supply path

[0188] 25 Return path

[0189] 251 Return path

[0190] 252 Return path

[0191] 26 Refrigerant path

[0192] 31 First column

[0193] 32 Second column

[0194] 33 Third column

[0195] 34 Fourth column

[0196] 4 Slit

[0197] 41 First slit

[0198] 42 Second slit

[0199] 43 Third slit

[0200] 44 Fourth slit

[0201] 45 First base

[0202] 46 Second base

[0203] 47 Third base

[0204] 6 Cover

[0205] 60 Cover

[0206] 61 O-ring

[0207] 610 O-ring

[0208] 8 First electrode

[0209] 81 Electrode cap

[0210] 84 Retainer

[0211] 851 Slit

[0212] 9 Second electrode

[0213] 91 Electrode cap

[0214] 92 Retainer

[0215] 922 Inner hole

[0216] 923 Slit

[0217] 93 Refrigerant circuit

Claims

1. A resistance welding device that welds a plurality of workpieces stacked together by pressing the workpiece composed of the stacked workpieces and supplying power to the workpiece, characterized in that: The resistance welding device includes an electrode having a top surface that abuts against the workpiece and presses and supplies power to the workpiece. A slit is formed in the middle part of the electrode between the top surface and the base end. The slit opens on the outer peripheral surface of the electrode and extends circumferentially on a plane intersecting the central axis direction of the electrode.

2. The resistance welding device according to claim 1, characterized in that: The slit is formed in at least one of the first electrode and the second electrode sandwiching the workpiece. The first electrode is located on the first side and the second electrode is located on the second side.

3. The resistance welding device according to claim 1 or 2, characterized in that: The opening of the slit extends circumferentially on the outer peripheral surface of the electrode along a plane orthogonal to the central axis direction.

4. The resistance welding device according to claim 3, characterized in that: The electrode has a plurality of slits arranged along the central axis direction.

5. The resistance welding device according to claim 4, characterized in that: A hole extending along the central axis direction is formed in the radial central part of the electrode. The slit communicates with the hole. The electrode includes a base and a column. The base is formed between a first slit and a second slit adjacent in the central axis direction, and is annular surrounding the hole, and has a thickness that can elastically deform in a manner of flexing along the central axis direction. The columns are respectively formed in the first slit and the second slit, and extend along the central axis direction and are connected to the base.

6. The resistance welding device according to claim 5, characterized in that: A plurality of columns are formed in the first slit and the second slit respectively with intervals left in the circumferential direction.

7. The resistance welding device according to claim 6, characterized in that: The positions of the columns formed in the first slit and the columns formed in the second slit are staggered from each other in the circumferential direction.

8. The resistance welding device according to any one of claims 1 to 4, characterized in that: A refrigerant path extending along the central axis direction of the electrode is formed in the radial central part of the electrode. The slit communicates with the refrigerant path. The electrode has a suppression part that suppresses the leakage of the refrigerant passing through the slit.

9. The resistance welding device according to claim 8, characterized in that: The suppression part is a cover installed on the outer peripheral surface of the electrode and covering the opening of the slit.

10. The resistance welding device according to any one of claims 1 to 9, characterized in that: The electrode has an electrode cap, an electrode rod, and a holder. The electrode cap abuts against the workpiece. The electrode cap is installed at the top of the electrode rod, and the holder holds the electrode rod. The slit is formed in the electrode rod or the holder.

11. The resistance welding device according to any one of claims 1 to 10, characterized in that: The workpiece is composed of a plate-shaped first workpiece to be welded and a non-plate-shaped second workpiece to be welded placed on the first workpiece to be welded. The second workpiece to be welded has a plurality of protrusions that abut against the surface of the first workpiece to be welded. At the positions of the plurality of protrusions, the first workpiece to be welded and the second workpiece to be welded are welded to each other. The first electrode abutting against the first workpiece to be welded has a guide pin, and the guide pin penetrates through the first workpiece to be welded and the second workpiece to be welded along the central axis direction. The second electrode abutting against the second workpiece to be welded has a recess for inserting the guide pin on the top end surface.

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