Spot screw and electrode

Abstract

To provide a spot screw that can keep a low resistance heating amount even if the same is a spot screw having no flange part, and further, can maintain high accuracy of electrode application.SOLUTION: A stud screw 50 is provided with: a thread 50b on an outer peripheral surface from one end side on a shank 30 side to the other end side opposite to one end side; and a hole 50a which has such a size that a tip part of an electrode fits, and is recessed in a direction toward a central part on the other end side of the stud screw 50 from a central part on one end side on the shank 30 side. A bottom of the hole 50a is tapered toward the other end side of the stud screw 50, and a projection 50c is formed at a midship part on the other end side surface of the stud screw 50.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a spot screw used in spot welding and an electrode for supplying power when welding the spot screw. [Background technology]

[0002] Resistance welding involves overlapping at least two metal workpieces, clamping the welding point with electrodes, applying pressure and passing an electric current through them, and connecting the workpieces together using the Joule heat generated at the welding point. When one of the two workpieces being resistance welded is a screw, the screw is called a "spot screw." There are male spot screws and female spot bosses for spot screws.

[0003] One method for welding a spot screw to a metal plate is described in, for example, Patent Document 1. This document describes a method in which "a stepped portion formed at the lower end of a boss is inserted into an insertion hole in the sheet metal, and in a state in which the curved surface formed in the stepped portion and the sheet metal are in line contact, a welding current is passed through while applying pressure to the boss and the sheet metal, thereby pressure-welding the line-contact area using resistance heating." [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-228705 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventional spot screws have the following problems. As shown in Figure 8, a spot screw 100 having a flange 101 at the end that is welded to the workpiece 60 has a short distance L between the electrode contact surface (i.e., the power supply surface) with which the electrode 150 contacts and the welding surface of the workpiece 60 (the surface that becomes the molten zone), which has the advantage of reducing the amount of resistance heat generated and making the screw itself less likely to be damaged. In contrast, as shown in Figure 9, a spot screw 110 that does not have a flange has a long electrode contact surface with the electrode 160, which is the surface opposite the surface that faces the workpiece 60, which increases the distance L from the welding surface of the workpiece 60, resulting in a greater amount of resistance heat generated and making the screw more likely to be damaged. Note that the arrows in Figures 8 and 9 indicate the direction in which current i flows.

[0006] In addition, because spot screws are generally small, stable welding is difficult unless high precision is maintained in applying the electrode.

[0007] The present invention has been made in consideration of the above circumstances, and aims to provide a spot screw and electrode that can keep the amount of resistance heat generated low even when the spot screw does not have a flange portion, and that can maintain high accuracy in applying the electrode. [Means for solving the problem]

[0008] The spot screw of the present invention is a male spot screw that is held by an electrode attached to the tip of the shank of a resistance welding device, and is welded to the metal workpieces that are the welding destination by Joule heat generated at the welding point when an electric current is passed between the electrode and the metal workpieces that are the welding destination while being pressurized; the spot screw is cylindrical, with a thread formed on the outer peripheral surface from one end on the shank side to the other end opposite the one end, and a hole formed therein that is recessed in a direction from the center of the one end toward the center of the other end and is sized to fit the tip of the electrode, the bottom of the hole being tapered toward the other end, and a protrusion formed in the center of the surface on the other end side.

[0009] According to the above structure, the spot screw has a hole large enough to fit the tip of the electrode, which shortens the distance between the tip of the electrode and the other end of the spot screw, making it possible to keep the amount of resistance heat generated low. In other words, it is possible to keep the amount of resistance heat generated low even with a spot screw that does not have a flange.

[0010] In addition, by providing a hole in the spot screw into which the tip of the electrode can be fitted, the accuracy of contacting the electrode with the spot screw is improved, enabling stable welding.

[0011] Furthermore, by matching the shape of the bottom of the hole of the spot screw with the shape of the tip of the electrode, the contact area between the spot screw and the electrode can be made larger, making it possible to further reduce the amount of resistance heat generated.

[0012] The spot screw of the present invention is a female spot screw that is held by an electrode attached to the tip of the shank of a resistance welding device, and is welded to the metal workpieces that are the welding destination by Joule heat generated at the welding point when an electric current is passed between the electrode and the metal workpieces that are the welding destination while being pressurized; the spot screw has a cylindrical shape, and a hole of a size that allows the tip of the electrode to fit into is formed in the center of one end of the shank, extending in the direction toward the center of the other end, the bottom of the hole is formed in a tapered shape that narrows toward the other end, and a thread is formed on the inner surface of the hole in the direction from one end to the other end, excluding the tapered portion, and a protrusion is formed in the center of the surface on the other end.

[0013] According to the above structure, the spot screw has a hole large enough to fit the tip of the electrode, which shortens the distance between the tip of the electrode and the other end of the spot screw, making it possible to keep the amount of resistance heat generated low. In other words, it is possible to keep the amount of resistance heat generated low even with a spot screw that does not have a flange.

[0014] In addition, by providing a hole in the spot screw into which the tip of the electrode can be fitted, the accuracy of contacting the electrode with the spot screw is improved, enabling stable welding.

[0015] Furthermore, by matching the shape of the bottom of the hole of the spot screw with the shape of the tip of the electrode, the contact area between the spot screw and the electrode can be made larger, making it possible to further reduce the amount of resistance heat generated.

[0016] The spot screw of the present invention is a male spot screw that is held by an electrode attached to the tip of the shank of a resistance welding device, and is welded to the metal workpieces that are the welding destination by Joule heat generated at the welding point when an electric current flows between the electrode and the metal workpieces that are the welding destination while being pressurized, and has a cylindrical shape, with a thread formed on the outer circumferential surface from one end on the shank side to the other end opposite to the one end side, and a thread is formed on the one end side of the screw that is sized to fit the tip of the electrode, and A first hole is formed in the other end, recessed from the other end toward the one end, the bottom of the first hole is tapered toward the other end, and the peripheral edge of the first hole is formed in a protruding ring shape.A second hole is formed in the other end, recessed in the direction from the other end toward the one end, large enough to fit the tip of the electrode, and the bottom of the second hole is tapered toward the one end, and the peripheral edge of the second hole is formed in a protruding ring shape.

[0017] According to the above structure, a first hole large enough to fit the tip of the electrode is provided on one end of the spot screw, which shortens the distance between the tip of the electrode and the other end of the spot screw, making it possible to keep the amount of resistance heat low. In other words, it is possible to keep the amount of resistance heat low even with a spot screw that does not have a flange.

[0018] In addition, by providing a hole in the spot screw into which the tip of the electrode can be fitted, the accuracy of contacting the electrode with the spot screw is improved, enabling stable welding.

[0019] Furthermore, by matching the shape of the bottom of the hole of the spot screw with the shape of the tip of the electrode, the contact area between the spot screw and the electrode can be made larger, making it possible to further reduce the amount of resistance heat generated.

[0020] Similarly, a second hole large enough to fit the tip of the electrode is provided at the other end of the spot screw, shortening the distance between the tip of the electrode and one end of the spot screw and making it possible to keep the amount of resistance heat low. In other words, it is possible to keep the amount of resistance heat low even with a spot screw that does not have a flange.

[0021] The spot screw of the present invention can be used in either the up or down orientation.

[0022] In addition, by providing a first hole (second hole) into which the tip of the electrode can be fitted into the spot screw, the accuracy of contacting the electrode with the spot screw is improved, enabling stable welding.

[0023] Furthermore, by matching the shape of the bottom of each of the first and second holes of the spot screw with the shape of the tip of the electrode, the contact area between the spot screw and the electrode can be made larger, making it possible to further reduce the amount of resistance heat generated.

[0024] In the above structure, it is desirable that the first hole and the second hole have the same shape.

[0025] The electrode of the present invention is an electrode to which the spot screw can be attached, and the rear end portion of the main body can be fitted into the tip portion of the shank holder of a resistance welding device, and the electrode portion has a size such that the tip portion of the main body fits into the hole of the spot screw, and a support portion that contacts the outer peripheral surface of the spot screw and supports the spot screw, and the electrode portion is formed in a tapered shape so that the tip portion of the main body fits tightly against the bottom of the hole of the spot screw.

[0026] According to the above structure, by matching the shape of the tip of the electrode part with the shape of the bottom of the hole of the spot screw, it is possible to make the tip of the electrode part contact the bottom of the spot screw over a wide area.

[0027] In the above structure, the support portion includes a magnet that attracts the spot screw.

[0028] According to the above structure, it is possible to hold the spot screw without it falling off.

[0029] In the above structure, the support portion is made of an insulating material containing resin.

[0030] According to the above structure, it is possible to prevent current from flowing through the support portion to the metal workpieces to be welded. [Effects of the Invention]

[0031] According to the present invention, even with a spot screw that does not have a flange, the amount of resistance heat generated can be kept low, and high accuracy in contacting the electrode can be maintained. [Brief explanation of the drawings]

[0032] [Figure 1] FIG. 1 is a side view showing the appearance of a resistance welding device according to an embodiment of the present invention. [Figure 2] A cross-sectional view showing the structure of the shank holder, shank, electrode, and stud screw used in the resistance welding device of Figure 1. [Figure 3] A cross-sectional view showing the structure of the shank, electrode, and stud screw used in the resistance welding device of Figure 1. [Figure 4] A diagram showing the state where the stud screw is loaded into the stud screw feeder used in the resistance welding device of Figure 1. [Figure 5] A cross-sectional view showing the structure of the shank, electrode, and stud boss used in the resistance welding device of Figure 1. [Figure 6] A cross-sectional view showing the structure of the shank, electrode, and stud screw used in the resistance welding device of Figure 1. [Figure 7] (a) and (b) are diagrams showing the appearance of the stud screw in Figure 6. [Figure 8] A diagram showing the state of welding a spot screw with a flange [Figure 9] A diagram showing the welding of a spot screw without a flange DETAILED DESCRIPTION OF THE INVENTION

[0033] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0034] 1 is a side view showing the appearance of a resistance welding apparatus 1 according to one embodiment of the present invention. In the figure, the resistance welding apparatus 1 according to this embodiment includes a vertically oriented welding gun 2 (also called a "vertical gun"), a table electrode 3, a support column 13, a support arm 14, a stand 15, a welding transformer 16, a power supply cable 17, and a control device 18.

[0035] The welding gun 2 includes a shank holder 5, a crankshaft 6, a gun shaft 7, a gun holder 8, a handle 9, a pressure device 10, and a power supply device 11. An electrode 40 is attached to the shank holder 5 via a shank 30. The shank holder 5, the crankshaft 6, and the gun shaft 7 are each cylindrical rods made of a conductive metal material (mainly copper). The gun shaft 7 is inserted into the gun holder 8.

[0036] The welding gun 2 is supported by a support arm 14 via a gun holder 8. The welding gun 2 is supported so as to be movable up and down in a direction perpendicular to the planar direction of the table electrode 3, and also so as to be movable in the planar direction of the table electrode 3. The welding gun 2 is held in a raised state with a constant tension by an elevating mechanism 20 disposed at the tip of the support arm 14. The action of the elevating mechanism 20 allows the welding gun 2 to be held at any desired position in the vertical direction. The welding gun 2 is also rotatable around the axis of the gun holder 8.

[0037] Gun holder 8 is shaped like a cylindrical rod and is disposed on the underside of the tip of support arm 14, perpendicular to the arm direction of support arm 14. Gun shaft 7 is inserted into gun holder 8. Handle 9 is used to operate welding gun 2. By operating handle 9, welding gun 2 can be rotated and moved up and down. A push-button start switch (not shown) is provided on handle 9, and operating this start switch outputs a welding command to control device 18.

[0038] The pressure device 10 is disposed on the upper surface of the tip of the support arm 14. The pressure device 10 applies pressure to the gun shaft 7 downward (toward the table electrode 3), and during welding, it receives a supply of compressed air to grip the gun shaft 7 and push it downward (toward the table electrode 3). The power supply device 11 supplies power from a welding transformer 16 to the welding gun 2. The power supply device 11 has two built-in contacts (not shown), and these contacts are placed in a contact state (ON state) or a non-contact state (OFF state) by injecting or expelling air from the outside. The power supply device 11 is turned ON by control of the control device 18 during welding. When the power supply device 11 is turned ON, power is supplied from the welding transformer 16 to the welding gun 2.

[0039] Table electrode 3 is made of a conductive metal material (mainly copper) and is formed into a generally square, flat plate. Table electrode 3 is disposed below welding gun 2, perpendicular to the height direction of the equipment body. A metal workpiece 60 to be welded (see FIG. 2) is placed on table electrode 3 as a workpiece. Stand 15 is a stand used for welding work. Table electrode 3 is placed on stand 15.

[0040] Welding transformer 16 supplies power to welding gun 2, with one electrode (not shown) connected to table electrode 3 and the other electrode (not shown) connected to power supply device 11 via power supply cable 17 or the like. Welding transformer 16 is built into stand 15.

[0041] Support arm 14 is disposed at a right angle to the upright direction of support column 13 at the upper end portion of support column 13. Support arm 14 has an articulated structure that allows it to rotate horizontally around the connection point with support column 13 as a fulcrum. Control device 18 applies pressure and supplies power to welding gun 2 upon receiving a welding command through operation of a start switch (not shown) disposed on welding gun 2. That is, upon receiving the welding command, control device 18 activates pressure device 10 to pressurize welding gun 2 in the direction toward table electrode 3, and also turns on power supply device 11 to supply power to welding gun 2.

[0042] The resistance welding apparatus 1 is equipped with a cooling unit (not shown), which cools the cooling water circulating inside the resistance welding apparatus 1. The welding gun 2, the power supply cable 17, etc. have a structure for circulating the cooling water.

[0043] 2 is a cross-sectional view showing the structures of the shank holder 5, shank 30, electrode 40, and stud screw (a type of spot screw) 50 used in the resistance welding apparatus 1. In the figure, the shank 30 is fitted into the shank holder 5, and the electrode 40 is fitted into the tip of the shank 30. The electrode 40 holds the stud screw 50. A magnet 40b1 is built into the tip of the electrode 40. The magnet 40b1 attracts the stud screw 50 to prevent it from falling off the electrode 40. The stud screw 50 is welded to a metal workpiece 60.

[0044] 3 is a cross-sectional view showing the structures of the shank 30, electrode 40, and stud screw 50 used in the resistance welding apparatus 1. In the figure, the tip portion 30a of the shank 30 is tapered toward the tip. The electrode 40 is cylindrical and consists of an upper end portion 40a that fits into the tip portion 30a of the shank 30, and a lower end portion 40b that holds the stud screw 50. The upper end portion 40a of the electrode 40 is formed with a hole 40c for fitting the electrode 40 into the tip portion 30a of the shank 30 and for storing cooling water that flows through the shank 30. The hole 40c is tapered toward the tip of the electrode 40. Also, The bottom of the hole 40c is flat. Tapered shape This allows the electrode 40 to be firmly fitted to the tip portion 30 a of the shank 30 .

[0045] Meanwhile, the lower end 40b of the electrode 40 is formed with a convex cross section whose diameter decreases in two stages. The first-stage convex portion 40b2 has a thread formed on its outer periphery. The second-stage convex portion 40b3 is sized to fit into a hole 50a (details of which will be described later) formed in the stud screw 50, and is tapered so as to fit closely to the bottom of the hole 50a. The lower end 40b of the electrode 40 is also provided with a support portion 40b4 that contacts the outer surface of the stud screw 50 and supports the stud screw 50.

[0046] The support portion 40b4 is made of an insulating material containing resin, and has a thread 40b5 formed on the inner peripheral surface of its upper end portion. The thread 40b5 formed on the support portion 40b4 is adapted to mesh with a thread 40b6 formed on the outer peripheral surface of the first-step convex portion 40b2 of the lower end portion 40b of the electrode 40. In this way, threads (threads 40b5, 40b6) are formed on both the outer peripheral surface of the first-step convex portion 40b2 of the lower end portion 40b of the electrode 40 and the inner peripheral surface of the support portion 40b4, enabling the support portion 40b4 to be attached to and detached from the electrode 40.

[0047] The support portion 40b4 has insulating properties, and therefore, it is possible to prevent current from flowing through the support portion 40b4 to the metal member to be welded 60.

[0048] The stud screw 50 has a cylindrical shape and does not have a flange. (Top end side) From the other end opposite to the one end (lower end side) A thread 50b is formed on the outer peripheral surface of the electrode 40 from the bottom end 40b to the bottom end 40b of the electrode 40. The ... of the electrode 40. The thread 50b is formed on (Top end side) From the center to the other end (lower end side) The bottom of the hole 50a is recessed in the direction toward the center of the hole 50a. Stud screw 50 The hole 50a is formed in a conical shape with a vertex at the other end. The shape of the bottom of the hole 50a is conical to match the shape of the second-stage convex portion 40b3 of the lower end 40b of the electrode 40, but it may be tapered toward the other end.

[0049] A conical projection 50c is formed as a projection in the center of the surface on the other end side of the stud screw 50. The hole 50a of the stud screw 50 is not threaded.

[0050] The stud screw 50 is held by the electrode 40 and pressurized while a current is passed between the stud screw 50 and the workpiece 60 to be welded, and is welded to the workpiece 60 by Joule heat generated at the welding point.

[0051] As described above, the stud screw 50 used in the resistance welding apparatus 1 according to this embodiment has a hole 50a large enough to fit the second-stage convex portion 40b3 of the lower end 40b of the electrode 40, so the distance L (see FIG. 3) between the tip of the electrode 40 and the other end of the stud screw 50 is (That is, the distance L between the electrode contact surface with which the electrode 40 contacts and the welding surface of the workpiece 60) This allows the length to be shortened, and even with a stud screw 50 that does not have a flange, it is possible to keep the amount of resistance heat generation low.

[0052] Furthermore, since the stud screw 50 has a hole 50a into which the second-stage convex portion 40b3 of the lower end 40b of the electrode 40 can be fitted, high precision can be maintained when the electrode 40 is brought into contact with the stud screw 50, enabling stable welding.

[0053] Furthermore, by making the bottom surface of the hole 50a of the stud screw 50 conical, the contact area with the electrode 40 can be made larger, making it possible to further reduce the amount of resistance heat generation.

[0054] Furthermore, the support portion 40b4 has a magnet 40b1 that attracts the stud screw 50, making it possible to hold the stud screw 50 without it dropping.

[0055] Furthermore, by providing holes 50a in the stud screws 50, when multiple stud screws 50 are loaded into a feeder (a device that supplies stud screws 50), the protrusions 50c of all stud screws 50 except for the first stud screw 50 fit into the hole 50a of the stud screw 50 immediately preceding it, preventing damage from hitting the stud screw 50 immediately preceding it. Figure 4 shows the state in which three stud screws 50A to 50C have been loaded into feeder 200. As shown in the figure, the protrusion 50c of stud screw 50B fits into the hole 50a of stud screw 50A, and the protrusion 50c of stud screw 50C fits into the hole 50a of stud screw 50B.

[0056] Although the support portion 40b4 of the electrode 40 used in the resistance welding apparatus 1 according to this embodiment is made of an insulating material, it may be made of a metal material such as stainless steel that has been given insulating properties by a surface coating treatment called KCF (also called "special stainless steel").

[0057] Furthermore, although the electrode 40 used in the resistance welding apparatus 1 according to this embodiment has a structure capable of handling the stud screw 50, it is of course also possible to use a structure capable of handling a stud boss. An electrode having a structure capable of handling a stud boss will be described below.

[0058] (Variation 1) 5 is a cross-sectional view showing the structures of the shank 30, electrode 40, and stud boss 70 used in the resistance welding apparatus 1 according to the above embodiment. In this figure, parts that are common to those in FIG. 3 are given the same reference numerals.

[0059] 5, the stud boss 70 is a female spot screw, has a cylindrical shape, and does not have a flange. (Top end side) At the center of the other end (lower end side)A hole 70a is formed in the bottom of the electrode 40 in a direction toward the center of the electrode 40, the hole being large enough to fit the second-stage convex portion 40b3 of the lower end 40b of the electrode 40. The bottom of the hole 70a is formed in a cone shape with an apex at the other end. The shape of the bottom of the hole 70a is cone-shaped to match the shape of the convex portion 40b3 of the lower end 40b of the electrode 40, but it may be tapered toward the other end.

[0060] Threads 70b are formed on the inner circumferential surface of the stud boss 70, excluding the tapered portion from one end of the hole 70a toward the other end. Note that, because the stud boss 70 is a female spot thread, the depth of the hole 70a that will become the screw hole is approximately 1.5 to 2 times the diameter of the screw.

[0061] The stud boss 70 also has a conical projection 70c formed in the center of the surface on the other end side.

[0062] As described above, the stud boss 70 has a hole 70a large enough to fit the convex portion 40b3 of the lower end 40b of the electrode 40, so the distance L between the tip of the electrode 40 and the other end of the stud boss 70 is (That is, the distance L between the electrode contact surface with which the electrode 40 contacts and the welding surface of the workpiece 60) This allows the length to be shortened, and even with a stud boss 70 that does not have a flange, it is possible to keep the amount of resistance heat generated low.

[0063] In addition, by providing the stud boss 70 with a hole 70a into which the convex portion 40b3 of the lower end 40b of the electrode 40 can be fitted, the accuracy with which the electrode 40 is brought into contact with the stud boss 70 is improved, enabling stable welding.

[0064] Furthermore, the shape of the bottom of the hole 70a of the stud boss 70 is conical, similar to the shape of the tip of the convex portion 40b3 of the lower end 40b of the electrode 40, which allows for a wider contact area with the electrode 40 and further reduces the amount of resistance heat generated.

[0065] Furthermore, because the stud bosses 70 also have holes 70a, when multiple stud bosses 70 are loaded into the feeder, the protrusions 70c of all stud bosses 70 except for the leading stud boss 70 fit into the holes 70a of the stud boss 70 immediately preceding them, preventing damage from hitting the stud boss 70 immediately preceding them.

[0066] (Variation 2) 6 is a cross-sectional view showing the structures of the shank 30, electrode 80, and stud screw 90 used in the resistance welding device 1 according to the above embodiment. In this figure, parts that are common to those in FIG. 3 are given the same reference numerals.

[0067] 6, the stud screw 90 is a male spot screw, has a cylindrical shape, and does not have a flange. (Top end side) From the other end opposite to the one end (lower end side) A thread 90c is formed on the outer peripheral surface extending from the end of the electrode 80 to the end of the electrode 80, and a first hole 90a is formed in one end portion on the shank 30 side, the first hole 90a being large enough to fit the tip portion 80b2 of the electrode 80. The tip portion 80b2 of the electrode 80 is tapered toward the other end. The first hole 90a is conical in shape to match the shape of the tip portion 80b2 of the electrode 80. The tip portion 80b2 of the electrode 80 may have a conical shape with an apex at the other end, rather than being tapered toward the other end.

[0068] The periphery of the first hole 90a is formed in a protruding ring shape, which acts as a projection. The stud screw 90 has a second hole 90b of the same shape as the first hole 90a formed at one end on the shank 30 side and the other end on the opposite side.

[0069] Figures 7(a) and 7(b) are diagrams showing the appearance of the stud screw 90 of Figure 6. As shown in the figures, the peripheral edge 90a1 of the first hole 90a and the peripheral edge 90b1 of the second hole 90b are both formed in a protruding ring shape. As such, one end and the other end of the stud screw 90 have the same shape, so it can be used either facing up or down.

[0070] Although the peripheral edge 90a1 of the first hole 90a and the peripheral edge 90b1 of the second hole 90b are each shaped as annular projections, protrusion pieces may be arranged in an annular shape along the circumferential direction. Furthermore, the support portion 80b4 has a magnet 80b1 built in.

[0071] As described above, the stud screw 90 has a first hole 90a at one end that is large enough to fit the tip portion 80b2 of the electrode 80, which shortens the distance between the tip of the electrode 80 and the other end of the stud screw 90, making it possible to keep the amount of resistance heat generated low even with a stud screw 90 that does not have a flange. In addition, the other end of the stud screw 90 has a second hole 90b that is large enough to fit the tip portion 80b2 of the electrode 80, which shortens the distance between the tip of the electrode 80 and one end of the stud screw 90, making it possible to keep the amount of resistance heat generated low.

[0072] Furthermore, since the distance between the tip of the electrode 80 and the other end (or one end) of the stud screw 90 is longer than that of the stud screw 50 of the resistance welding device 1 according to the above embodiment, the amount of resistance heat generated cannot be reduced compared to that of the stud screw 50 of the resistance welding device 1 according to the above embodiment.

[0073] Furthermore, by providing the first hole 90a (second hole 90b) into which the tip of the electrode 80 can be fitted in the stud screw 90, the accuracy with which the electrode 80 is brought into contact with the stud screw 90 is improved, enabling stable welding.

[0074] Furthermore, by matching the shape of the tip of the electrode 80 to the shape of the bottom of each of the first hole 90a and second hole 90b of the stud screw 90, the contact area between the stud screw 90 and the electrode 80 can be made larger, making it possible to further reduce the amount of heat generated by resistance. [Industrial Applicability]

[0075] The present invention can be applied to a resistance welding device in which at least two metal workpieces to be welded are overlapped, the welding point is sandwiched between electrodes, pressure is applied and an electric current is passed through, and the workpieces are connected to each other by Joule heat generated at the welding point. [Explanation of symbols]

[0076] 1 Resistance welding equipment 2 welding guns 3 Table Electrodes 5 Shank holder 6 crankshaft 7 Gunshaft 8 Gun Holder 9 Handle 10. Pressure device 11 Power supply equipment 13 Posts 14 Support arm 15 Mounting stand 16 Welding transformer 17 Power supply cable 18 Control Device 20 Lifting mechanism 30 shank 30a Shank tip 40,80 electrodes 40c,80c hole 40a, 80a Upper end of electrode 40b, 80b Lower end of electrode 40b1,80b1 magnet 40b2 First step convex portion at the bottom end of the electrode 40b3 Second step convex portion at the bottom end of the electrode 40b4 Support part 40b5, 40b6 screws 50, 50A, 50B, 50C stud screws 50a hole 50b screw 50c protrusion 60 Metallic welded parts 70 Stud Boss 70a hole 70b screw 70c protrusion 80b2 Tip of electrode 80b4 Support part 80b5,80b6 screws 90 stud screws 90a First Hole 90b Second hole 90a1 Periphery of the first hole 90b1 periphery of second hole 90c screws 200 feeders

Claims

1. A male spot screw is welded to a metal workpiece by Joule heat generated at a welding point by passing an electric current between the metal workpiece and the electrode attached to the tip of the shank of a resistance welding device while being held and pressurized, The electrode has a cylindrical shape, a thread is formed on the outer circumferential surface from one end side on the shank side to the other end side opposite the one end side, and a hole is formed in a size into which the tip portion of the electrode fits, recessed in a direction from the center of the one end side to the center of the other end side, the bottom of the hole is formed in a tapered shape that tapers toward the other end side, and a protrusion is formed in the center of the surface on the other end side. Spot screws.

2. A male spot screw is welded to a metal workpiece by Joule heat generated at a welding point by passing an electric current between the metal workpiece and the electrode attached to the tip of the shank of a resistance welding device while being held and pressurized, a cylindrical shape, a thread formed on the outer circumferential surface from one end side on the shank side to the other end side opposite the one end side, a first hole formed in the one end side to a size in which the tip portion of the electrode fits and recessed in a direction from the one end side to the other end side, a bottom of the first hole formed in a tapered shape that tapers toward the other end side, and a peripheral portion of the first hole formed in a protruding annular shape, and a second hole formed in the other end side to a size in which the tip portion of the electrode fits and recessed in a direction from the other end side to the one end side, a bottom of the second hole formed in a tapered shape that tapers toward the one end side, and a peripheral portion of the second hole formed in a protruding annular shape; Spot screws.

3. A female spot screw is welded to a metal workpiece by Joule heat generated at a welding point by passing an electric current between the metal workpiece and the electrode attached to the tip of the shank of a resistance welding device while being held and pressurized, The electrode has a cylindrical shape, and a hole is formed in the center of one end of the shank side toward the center of the other end, the hole being large enough to fit the tip of the electrode, and the bottom of the hole is tapered toward the other end. A screw is formed on the inner circumferential surface of the hole from one end toward the other end to a portion excluding the tapered portion, and a protrusion is formed in the center of the surface on the other end. Spot screws.

4. An electrode to which the spot screw according to any one of claims 1 to 3 can be attached, an electrode portion having a rear end portion of a body that can be fitted to a front end portion of a shank holder of a resistance welding device, and a front end portion of the body that is sized to fit into a hole of the spot screw; A support portion that contacts an outer peripheral surface of the spot screw and supports the spot screw; having The electrode portion is formed in a tapered shape such that a tip portion of the main body is in close contact with a bottom portion of the hole of the spot screw, The support portion is made of an insulating material containing a resin. electrode.

5. The support portion includes a magnet that attracts the spot screw.

5. The electrode of claim 4.

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