Spot screws and electrodes

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

[0005] ,

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

Background Art

[0002] Resistance welding is a method of connecting two metal workpieces to be welded by sandwiching the welding portion with electrodes in a state where at least two metal workpieces to be welded are overlapped, applying pressure while passing an electric current, and connecting the workpieces to be welded with Joule heat generated at the welding portion. When one of the two workpieces to be resistance welded is a screw, the screw is called a "spot screw". Spot screws include male spot screws and female spot bosses.

[0003] As a method of welding a spot screw to a metal plate, for example, there is a method described in Patent Document 1. This document describes a method of "inserting a stepped portion formed at the lower end of the boss into an insertion hole of a sheet metal, bringing the curved surface formed on the stepped portion into line contact with the sheet metal, and passing a welding current while pressing the boss and the sheet metal, thereby pressure-welding the line-contact portion using resistance heating".

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, conventional spot screws have the problems described below. As shown in Figure 8, in the case of a spot screw 100 having a flange 101 at the end that is welded to the member to be welded 60, the distance L between the electrode contact surface (i.e., the power supply surface) to which the electrode 150 contacts and the welding surface (the surface that becomes the molten part) of the member to be welded 60 is short, which has the advantage of generating less resistive heat and being less likely to damage the screw itself. In contrast, as shown in Figure 9, in the case of a spot screw 110 without a flange, the electrode contact surface to which the electrode 160 contacts is the surface opposite to the surface on the member to be welded 60 side, so the distance L between it and the welding surface of the member to be welded 60 becomes longer, which has the disadvantage of generating more resistive heat and being more likely to damage the screw itself. Note that the arrows in Figures 8 and 9 indicate the direction in which the current i flows.

[0006] Furthermore, because spot screws are generally small in shape, stable welding is difficult unless the precision of electrode application is maintained to a high degree.

[0007] This invention has been made in view of the above circumstances, and aims to provide a spot screw and electrode that can reduce the amount of resistive heat generation even in a spot screw without a flange, 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 apparatus and welded to a metal workpiece by Joule heat generated at the welding site when an electric current is passed between the electrode and the workpiece while under pressure. The spot screw has a cylindrical shape, with threads formed on its outer circumference from one end on the shank side to the other end on the opposite side, and a hole is formed that is sized to fit the tip of the electrode, and is recessed in the direction from the center of the one end to the center of the other end, and the bottom of the hole is formed in a tapered shape that narrows towards the other end, and a projection is formed in the center of the surface of the other end.

[0009] According to the above structure, a hole sized to fit the tip of the electrode is provided in the spot screw, thus shortening the distance between the tip of the electrode and the other end of the spot screw, and thus reducing the amount of resistive heat generated. In other words, even spot screws without a flange can have their resistive heat generated reduced.

[0010] Furthermore, by providing a hole in the spot screw into which the tip of the electrode can be fitted, the precision with which the electrode is applied to the spot screw is improved, enabling stable welding.

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

[0012] The spot screw of the present invention is a female-type spot screw that is held by an electrode attached to the tip of the shank of a resistance welding apparatus and welded to a metal workpiece by Joule heat generated at the welding site when an electric current is passed between the electrode and the workpiece while under pressure. The spot screw has a cylindrical shape, and a hole is formed in the center of one end of the shank side, sized to fit the tip of the electrode, extending toward the center of the other end. The bottom of the hole is tapered, narrowing toward the other end. A screw is formed on the inner circumferential surface from one end of the hole toward the other, excluding the tapered portion, and a projection is formed in the center of the surface on the other end.

[0013] According to the above structure, a hole sized to fit the tip of the electrode is provided in the spot screw, thus shortening the distance between the tip of the electrode and the other end of the spot screw, and thus reducing the amount of resistive heat generated. In other words, even spot screws without a flange can have their resistive heat generated reduced.

[0014] Furthermore, by providing a hole in the spot screw into which the tip of the electrode can be fitted, the precision with which the electrode is applied to the spot screw is improved, enabling stable welding.

[0015] Furthermore, by matching the shape of the bottom of the spot screw hole with the shape of the electrode tip, the contact area between the spot screw and the electrode can be increased, making it possible to further reduce the amount of resistive 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 apparatus and welded to a metal workpiece by Joule heat generated at the welding site when an electric current is passed between the electrode and the workpiece while under pressure, and has a cylindrical shape, with threads formed on the outer circumference from one end on the shank side to the other end on the opposite side, and the portion on the one end is sized to fit the tip of the electrode, A first hole is formed in the direction toward the other end, the bottom of the first hole is tapered and narrows toward the other end, and the periphery of the first hole is formed as a protruding annular shape. A second hole is formed in the other end portion, which is sized to fit the tip of the electrode, and is recessed in the direction toward the one end, the bottom of the second hole is tapered and narrows toward the one end, and the periphery of the second hole is formed as a protruding annular shape.

[0017] According to the above structure, a first hole sized to fit the tip of the electrode is provided at one end of the spot screw, thereby shortening the distance between the electrode tip and the other end of the spot screw, and reducing the amount of resistive heat generated. In other words, even a spot screw without a flange can have its resistive heat generated reduced.

[0018] Furthermore, by providing a hole in the spot screw into which the tip of the electrode can be fitted, the precision with which the electrode is applied to the spot screw is improved, enabling stable welding.

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

[0020] Similarly, since a second hole sized to fit the tip of the electrode is provided in the other end portion of the spot screw, the distance between the tip of the electrode and one end of the spot screw can be shortened, and the amount of heat generated by resistance can be reduced. That is, even a spot screw without a flange portion can reduce the amount of heat generated by resistance.

[0021] The spot screw of the present invention can be used in either the upper or lower direction.

[0022] In addition, by providing a first hole (second hole) into which the tip portion of the electrode can be fitted in the spot screw, the accuracy of applying the electrode to the spot screw is improved, and stable welding becomes possible.

[0023] Also, 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 portion of the electrode, the contact area between the spot screw and the electrode can be widened in each case, and the amount of heat generated by resistance can be further reduced.

[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, the rear end portion of the main body can be fitted to the tip portion of the shank holder of the resistance welding device, and the tip portion of the main body has an electrode portion sized to fit 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 such that the tip portion of the main body is in close contact with the bottom of the hole of the spot screw.

[0026] According to the above structure, by matching the shape of the tip portion of the electrode portion with the shape of the bottom of the hole of the spot screw, the tip portion of the electrode portion can be brought into contact with 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] The above structure makes it possible to hold the spot screws without them falling.

[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 to the metal component to be welded. [Effects of the Invention]

[0031] According to the present invention, even spot screws without a flange can have their resistance heat generation kept to a minimum, and the precision of electrode application can be maintained at a high level. [Brief explanation of the drawing]

[0032] [Figure 1] Side view showing the external appearance of a resistance welding apparatus according to one embodiment of the present invention. [Figure 2] Figure 1 is a cross-sectional view showing the structure of the shank holder, shank, electrode, and stud screw used in a resistance welding apparatus. [Figure 3] Figure 1 shows a cross-sectional view illustrating the structure of the shank, electrode, and stud screw used in a resistance welding apparatus. [Figure 4] Figure 1 shows the studs loaded into a stud feeder used in a resistance welding machine. [Figure 5] Figure 1 shows a cross-sectional view illustrating the structure of the shank, electrode, and stud boss used in a resistance welding apparatus. [Figure 6] Figure 1 shows a cross-sectional view illustrating the structure of the shank, electrode, and stud screw used in a resistance welding apparatus. [Figure 7] (a), (b) Diagrams showing the appearance of the stud screws in Figure 6. [Figure 8] A diagram showing the welding process of a spot screw with a flange. [Figure 9] A diagram showing the welding process of a spot screw without a flange. [Modes for carrying out the invention]

[0033] Hereinafter, preferred embodiments for carrying out the present invention will be described in detail with reference to the drawings.

[0034] Figure 1 is a side view showing the external 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 comprises a vertically oriented welding gun (so-called a "vertical gun") 2, a table electrode 3, a support column 13, a support arm 14, a frame 15, a welding transformer 16, a power supply cable 17, and a control device 18.

[0035] The welding gun 2 comprises a shank holder 5, a crankshaft 6, a gun shaft 7, a gun holder 8, a handle 9, a pressurizing device 10, and a power supply device 11. An electrode 40 is mounted on the shank holder 5 via a shank 30. The shank holder 5, crankshaft 6, and 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 on the support arm 14 via the gun holder 8. The welding gun 2 is supported so that it can move vertically in a direction perpendicular to the planar direction of the table electrode 3, and also so that it can move in the planar direction of the table electrode 3. The welding gun 2 is also held in a state where it is lifted up with a constant tension by a lifting mechanism 20 disposed at the tip of the support arm 14. The lifting mechanism 20 allows the welding gun 2 to be fixed in any position in the vertical direction. The welding gun 2 is also capable of rotating around the axis of the gun holder 8.

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

[0038] The pressurizing device 10 is positioned on the upper surface of the tip of the support arm 14. The pressurizing device 10 pressurizes the gun shaft 7 downwards (towards the table electrode 3), and when compressed air is supplied during welding, it grips the gun shaft 7 and pushes it downwards (towards the table electrode 3). The power supply device 11 supplies power from the welding transformer 16 to the welding gun 2. The power supply device 11 has two built-in contacts (not shown), and these contacts become contacted (on) or not contacted (off) depending on the injection and discharge of air from the outside. The power supply device 11 is turned on during welding by the control device 18. When the power supply device 11 is turned on, power from the welding transformer 16 is supplied to the welding gun 2.

[0039] The table electrode 3 is formed from a conductive metal material (mainly copper) into a roughly square, flat plate shape. The table electrode 3 is positioned below the welding gun 2, perpendicular to the height direction of the main body of the equipment. A metal workpiece, the member to be welded 60 (see Figure 2), is placed on the table electrode 3. The stand 15 is a platform used for welding work. The table electrode 3 is placed on this stand 15.

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

[0041] The support arm 14 is positioned at the upper end of the column 13 in the direction of vertical installation, perpendicular to the direction of vertical installation of the column 13. The support arm 14 has a multi-joint structure that allows for horizontal rotation with the connection point with the column 13 as the pivot point. The control device 18 receives a welding command from the operation of a start switch (not shown) installed on the welding gun 2 and applies pressure and power to the welding gun 2. Specifically, upon receiving a welding command, the control device 18 activates the pressure device 10 to pressurize the welding gun 2 toward the table electrode 3, and also turns on the power supply device 11 to supply power to the 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 and power supply cable 17, etc., have a structure for circulating the cooling water.

[0043] Figure 2 is a cross-sectional view showing the structure of a shank holder 5, shank 30, electrode 40, and stud screw (a type of spot screw) 50 used in a 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 stud screw 50 is held by the electrode 40. 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 from the electrode 40. The stud screw 50 is welded to a metal workpiece 60.

[0044] Figure 3 is a cross-sectional view showing the structure 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, narrowing towards 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 has a hole 40c formed therein for fitting the electrode 40 into the tip portion 30a of the shank 30 and for storing cooling water flowing through the shank 30. The hole 40c is tapered, narrowing towards the tip of the electrode 40. Also, The bottom of hole 40c is flat. Formed in a tapered shape This allows the electrode 40 to be firmly fitted onto the tip portion 30a of the shank 30.

[0045] On the other hand, the lower end portion 40b of the electrode 40 is formed in a convex shape with a diameter that decreases in two stages. The first convex portion 40b2 has threads formed on its outer surface. The second convex portion 40b3 is sized to fit into a hole 50a formed in the stud screw 50 (details will be described later) and is tapered so as to be in close contact with the bottom surface of the hole 50a. In addition, the lower end portion 40b of the electrode 40 is 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 a screw 40b5 is formed on the inner circumferential surface of its upper end portion. The screw 40b5 formed on the support portion 40b4 is designed to screw into a screw 40b6 formed on the outer circumferential surface of the first convex portion 40b2 of the lower end portion 40b of the electrode 40. In this way, screws (screw 40b5, screw 40b6) are formed on the outer circumferential surface of the first convex portion 40b2 of the lower end portion 40b of the electrode 40 and on the inner circumferential surface of the support portion 40b4, respectively, enabling the support portion 40b4 to be attached to and detached from the electrode 40.

[0047] Since the support portion 40b4 is insulating, it is possible to prevent current from flowing through the support portion 40b4 to the metal welded member 60.

[0048] The stud screw 50 has a cylindrical shape and does not have a flange. The stud screw 50 has one end on the shank 30 side. (Top end side) From the other end opposite to the one end (lower end side) A screw 50b is formed on the outer surface over a certain distance, and the second convex portion 40b3 of the lower end portion 40b of the electrode 40 is sized to fit into one end of the stud screw 50. (Top end side) From the central part to the other end (lower end side) A recessed hole 50a is formed in the direction toward the central part. The bottom of the hole 50a is Stud screws 50 It is formed in a conical shape with the apex at the other end. The shape of the bottom of the hole 50a is conical to match the shape of the second convex portion 40b3 of the lower end portion 40b of the electrode 40, but it is sufficient if it is tapered and narrows towards the other end.

[0049] A conical projection 50c is formed in the center of the other end face of the stud screw 50, serving as a projection. Note that no threads are formed in the hole 50a of the stud screw 50.

[0050] The stud screw 50 is held by the electrode 40 and, while being pressed, is welded to the workpiece 60 by the Joule heat generated at the welding point when an electric current is passed between the electrode 40 and the workpiece 60, which is the welding target.

[0051] As described above, the stud screw 50 used in the resistance welding apparatus 1 according to this embodiment has a hole 50a that is sized to fit the second convex portion 40b3 of the lower end portion 40b of the electrode 40, so the distance L (see Figure 3) between the tip of the electrode 40 and the other end of the stud screw 50 (That is, the distance L between the electrode contact surface in contact with the electrode 40 and the welding surface of the member to be welded 60) This allows for a reduction in length, and even with stud screws 50 that do not have a flange, the amount of resistive heat generated can be kept to a minimum.

[0052] Furthermore, by providing the stud screw 50 with a hole 50a into which the second convex portion 40b3 of the lower end portion 40b of the electrode 40 can be fitted, the accuracy of contact between the electrode 40 and the stud screw 50 can be maintained with high precision, 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 increased, making it possible to further reduce the amount of resistive heat generated.

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

[0055] Furthermore, by providing a hole 50a in the stud screw 50, when multiple stud screws 50 are loaded into a feeder (a device that supplies stud screws 50), the projections 50c of all stud screws 50 except the leading stud screw 50 will enter the hole 50a of the stud screw 50 immediately preceding them, thus preventing damage from contact with the preceding stud screw 50. Figure 4 shows the state when three stud screws 50A to 50C are loaded into the feeder 200. As shown in the figure, the projection 50c of stud screw 50B is in the hole 50a of stud screw 50A, and the projection 50c of stud screw 50C is in the hole 50a of stud screw 50B.

[0056] In this embodiment, the support portion 40b4 of the electrode 40 used in the resistance welding apparatus 1 was made of an insulating material, but it may also 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 that can handle stud screws 50, it is of course possible to have a structure that can handle stud bosses. The electrode having a structure that can handle stud bosses will be described below.

[0058] (Variation 1) Figure 5 is a cross-sectional view showing the structure 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 common to Figure 3 are given the same reference numerals.

[0059] In Figure 5, the stud boss 70 is a female-type spot screw, has a cylindrical shape, and does not have a flange. The stud boss 70 has one end on the shank 30 side. (Top end side) In the center of the other end (lower end side)A hole 70a is formed in the direction toward the center of the electrode 40, sized to fit the second convex portion 40b3 of the lower end 40b of the electrode 40. The bottom of the hole 70a is formed in a conical shape with the apex at the other end. The shape of the bottom of the hole 70a is conical to match the shape of the convex portion 40b3 of the lower end 40b of the electrode 40, but it is sufficient if it is tapered and narrows towards the other end.

[0060] The stud boss 70 has threads 70b formed on its inner surface, excluding the tapered portion in the direction from one end to the other of the hole 70a. Since the stud boss 70 is a female-type spot screw, the depth of the hole 70a, which becomes the screw hole, is approximately 1.5 to 2 times the diameter of the screw.

[0061] Furthermore, the stud boss 70 has a conical projection 70c formed in the center of the other end surface as a projection.

[0062] As described above, the stud boss 70 has a hole 70a that is sized 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 to which the electrode 40 is in contact and the welding surface of the member to be welded 60) This allows for a reduction in length, making it possible to minimize the amount of heat generated by resistance even with a stud boss 70 that does not have a flange.

[0063] Furthermore, by providing a hole 70a in the stud boss 70 into which the convex portion 40b3 of the lower end 40b of the electrode 40 can be fitted, the precision of contact between the electrode 40 and the stud boss 70 is improved, enabling stable welding.

[0064] Furthermore, since the bottom of the hole 70a of the stud boss 70 is shaped like a cone, similar to the shape of the tip of the convex portion 40b3 of the lower end portion 40b of the electrode 40, the contact area with the electrode 40 can be increased, making it possible to further reduce the amount of resistive heat generated.

[0065] Furthermore, since the stud boss 70 also has a hole 70a, when multiple stud bosses 70 are loaded into the feeder, the projections 70c of all stud bosses 70 except the leading stud boss 70 will enter the hole 70a of the stud boss 70 immediately preceding them, thus preventing damage from contact with the preceding stud boss 70.

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

[0067] In Figure 6, the stud screw 90 is a male spot screw, has a cylindrical shape, and does not have a flange. The stud screw 90 has one end on the shank 30 side. (Top end side) From the other end opposite to the one end (lower end side) A screw thread 90c is formed on the outer surface over the entire length, and a first hole 90a is formed at one end of the shank 30, sized to fit the tip portion 80b2 of the electrode 80. The tip portion 80b2 of the electrode 80 is tapered, narrowing towards the other end. The first hole 90a is conical to match the shape of the tip portion 80b2 of the electrode 80. However, the tip portion 80b2 of the electrode 80 may be conical with its apex at the other end, rather than tapered towards the other end.

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

[0069] Figures 7(a) and 7(b) show the external appearance of the stud screw 90 shown in 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 annular shape. Thus, since the stud screw 90 has the same shape at both ends, it can be used in either an up or down orientation.

[0070] Although the peripheral edges 90a1 of the first hole 90a and 90b1 of the second hole 90b are shown as annular projections, the projections may be arranged in an annular pattern along the circumferential direction. Furthermore, the support section 80b4 has a magnet 80b1 built into it.

[0071] As described above, the stud screw 90 has a first hole 90a at one end that is sized to fit the tip portion 80b2 of the electrode 80, thus shortening the distance between the tip of the electrode 80 and the other end of the stud screw 90, and making it possible to reduce the amount of resistive heat generation even with a stud screw 90 that does not have a flange. Furthermore, the other end of the stud screw 90 also has a second hole 90b that is sized to fit the tip portion 80b2 of the electrode 80, thus shortening the distance between the tip of the electrode 80 and one end of the stud screw 90, and making it possible to reduce the amount of resistive heat generation.

[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 in the resistance welding apparatus 1 according to the above embodiment, the reduction in resistance heat generation cannot be achieved compared to the stud screw 50 in the resistance welding apparatus 1 according to the above embodiment.

[0073] Furthermore, by providing a first hole 90a (second hole 90b) in the stud screw 90 into which the tip of the electrode 80 can be fitted, the precision with which the electrode 80 contacts 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 the first hole 90a and the second hole 90b of the stud screw 90, the contact area between the stud screw 90 and the electrode 80 can be increased, making it possible to further reduce the amount of resistive heat generated. [Industrial applicability]

[0075] The present invention can be applied to a resistance welding apparatus that connects at least two metal members to be welded by overlapping them, sandwiching the welding area between electrodes, applying pressure, and passing an electric current, thereby using Joule heat generated at the welding area. [Explanation of symbols]

[0076] 1. Resistance welding equipment 2. Welding gun 3 Table electrodes 5 Shank holder 6 Crankshaft 7 Gun Shaft 8 Gun holster 9 handles 10 Pressurizing device 11 Power supply device 13 Posts 14 Support Arms 15. 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 Upper end of 40a, 80a electrodes Lower end of electrodes 40b, 80b 40b1, 80b1 Magnets 40b2 The first convex portion at the lower end of the electrode 40b3 The second convex portion at the lower end of the electrode 40b4 Support part 40b5, 40b6 screws 50, 50A, 50B, 50C Stud screws 50a hole 50b Screw 50c protrusion 60 Metal components to be welded 70 Stud Boss 70a hole 70b Screw 70c protrusion 80b2 Electrode tip 80b4 Support part 80b5, 80b6 screws 90 Stud Screws 90a First hole 90b Second hole 90a1 Periphery of the first hole 90b1 Periphery of the second hole 90c screw 200 feeders

Claims

1. A male spot screw is welded to a metal workpiece by Joule heat generated at the welding point when an electric current is passed between the electrode, which is attached to the tip of the shank of a resistance welding device, and the electrode is held in place and pressurized. It has a cylindrical shape, with threads formed on its outer surface from one end of the shank to the other end opposite to the shank, and a hole formed therein that is large enough to fit the tip of the electrode, recessed from the center of the one end to the center of the other end, the bottom of the hole is tapered towards the other end, and a projection is formed in the center of the surface of the other end. Spot screws.

2. A male spot screw is welded to a metal workpiece by Joule heat generated at the welding point when an electric current is passed between the electrode, which is attached to the tip of the shank of a resistance welding device, and the electrode is held in place and pressurized. The device has a cylindrical shape, with threads formed on its outer surface from one end of the shank to the other end opposite to the first end. A first hole is formed at the first end, sized to fit the tip of the electrode, and recessed in the direction from the first end to the other end. The bottom of the first hole is tapered, narrowing towards the other end. The periphery of the first hole is formed as a protruding annular shape. A second hole is formed at the other end, sized to fit the tip of the electrode, and recessed in the direction from the other end to the first end. The bottom of the second hole is tapered, narrowing towards the first end. The periphery of the second hole is also formed as a protruding annular shape. Spot screws.

3. An electrode to which a spot screw according to claim 1 or claim 2 can be attached, The rear end portion of the main body can be fitted onto the tip portion of the shank holder of the resistance welding device, and the tip portion of the main body has an electrode portion that is sized to fit into the hole of the spot screw, A support portion that contacts the outer surface of the spot screw and supports the spot screw, It has, The electrode portion is formed in a tapered shape such that the tip portion of the main body is in close contact with the bottom of the hole of the spot screw. The support portion is made of an insulating material containing resin. electrode.

4. The support portion includes a magnet for attracting the spot screw. The electrode according to claim 3.

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