Spot welding method and spot welding apparatus

Abstract

To provide a spot welding method and a spot welding device which secure conductivity in a weld part and can suppress welding failure, and can suppress formation of a gap between panels.SOLUTION: A spot welding method for sandwiching a first panel 51 and a second panel 52 that are overlapped with each other with a pair of electrodes 12 and 14, performing energization between electrodes 12 and 14, and thereby welding the panels 51 and 52 includes the steps of: forming a projection 51a on a surface that is a welding part of the first panel 51 and faces the second panel 52, and forming a recess 52a with such a depth that a tip of the projection 51a comes in contact with a bottom on a surface that is a welding part of the second panel 52 and faces the projection 51a; and sandwiching the welding parts of the first and second panels 51 and 52 with the pair of electrodes 12 and 14 in a state where the projection 51a is inserted to the recess 52a, and performing energization between the electrodes 12 and 14.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a spot welding method and a spot welding apparatus for welding by sandwiching two panels between a pair of electrodes and passing an electric current between the electrodes.

Background Art

[0002] As a method of welding metal panels, resistance welding is known in which a plurality of panels are overlapped and energized with a large current, and the panels are welded to each other by the heat generated.

[0003] In spot welding, which is one type of resistance welding, the panels overlapped by a pair of electrodes are sandwiched and pressed, so that the panels are brought into contact with each other at the welding portion to ensure electrical conductivity. However, if the contact is not sufficient, it may cause poor welding. In particular, when a viscous material such as a weld bond is applied between two panels, the viscous material applied around the welding portion may enter the welding portion when the two panels are pressed against each other, thereby inhibiting the flow of electric current.

[0004] Thus, if the panels are not sufficiently brought into contact with each other at the welding portion, current may flow outside the welding portion of the panel, forming a shunt path, which may cause problems such as explosion and flying.

[0005] As a method of ensuring electrical conductivity and welding two panels, Patent Document 1 discloses projection welding in which a projection is formed on a first panel and an electric current is passed between the first and second panels while pressing the projection against a flat second panel.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] In the projection welding described above, a protrusion formed on the first panel is brought into contact with the surface of the second panel, allowing current to flow from the protrusion to the second panel. However, when the panels are set, a gap equal to the height of the protrusion is created, and welding is performed with this gap present, which affects the accuracy of the product.

[0008] The present invention has been made in view of the above problems, and aims to provide a spot welding method and spot welding apparatus that can ensure electrical conductivity in the welded area to suppress welding defects and suppress the formation of gaps between panels. [Means for solving the problem]

[0009] To achieve the above objective, one embodiment of the present invention is In a spot welding method in which overlapping first and second panels are clamped between a pair of electrodes and current is passed between the electrodes to weld the panels together, A step of applying a viscous material between the first and second panels and overlapping the first and second panels, In the welded joint of the overlapping first and second panels, Panel 1 Before A protrusion is formed on the surface facing the second panel, and the second panel Before A step of forming a recess on the surface opposite to the protrusion, having a depth such that the tip of the protrusion abuts against the bottom, After the convex portion and the concave portion are formed, The recessed portion but Insert re Furthermore, while the viscous material has not hardened, the welded portions of the first and second panels are clamped between the pair of electrodes and current is passed between the electrodes. Includes, In the process of forming the convex portion and the concave portion, the first and second panels, which are stacked on top of each other, are placed between a male mold having a tapered rod-shaped member and a female mold having a groove into which the tip of the rod-shaped member fits, and the convex portion and the concave portion are formed by press work in which the rod-shaped member is pushed toward the groove. The second panel has a larger section modulus than the first panel, and due to the springback of the second panel after press working, the depth of the recess is The height of the aforementioned protrusion is greater than small formed, In the process of applying current, the tip of the protrusion is brought into contact with the bottom surface of the recess, and current is applied between the pair of electrodes while the viscous material present between them is pushed aside.

[0010] In order to achieve the above object, one embodiment of the present invention is A method of welding panels by sandwiching a first panel, which is superimposed on the first panel, and a second panel, which has a larger section modulus than the first panel, between a pair of electrodes and passing an electric current between the electrodes, The process of forming a protrusion on the welded surface of the first panel facing the second panel, and forming a recess on the welded surface of the second panel facing the protrusion, having a depth such that the tip of the protrusion abuts against the bottom, A step of applying a viscous material between the first and second panels before or after forming the convex and concave portions and then overlapping the first and second panels, The steps include inserting the protrusion into the recess and, while the viscous material has not hardened, clamping the welded portions of the first and second panels with the pair of electrodes and applying current between the electrodes, Includes, The height of the protrusion is greater than the depth of the recess. In the process of applying current, the tip of the protrusion is brought into contact with the bottom surface of the recess, and the viscous material present between them is pushed aside, and current is applied between the pair of electrodes. used in a spot welding method In a spot welding apparatus , a fixed electrode fixed to the apparatus main body, a movable electrode that can approach and separate from the fixed electrode 、 before a processing mechanism movable between a processing position where the first and second panels are subjected to pressing and a non-processing position retreated from the processing position and, and includes the processing mechanism is a tapered rod-shaped member provided near the movable electrode and movable in the moving direction of the movable electrode by a driving unit that moves the movable electrode at the processing position, a die provided near the fixed electrode, having a concave groove corresponding to the tip shape of the rod-shaped member, and on which the first and second panels are placed at the processing position A male moving mechanism moves the rod-shaped member between a processing position located coaxial with the movable electrode and below the movable electrode, and a non-processing position off-axis from the movable electrode. A die moving mechanism moves the die between a machining position located on the axis of the fixed electrode and above the fixed electrode, and a non-machining position off the axis of the fixed electrode. and includes the tip of the rod-shaped member and the concave groove are each substantially conical, and the central angle of the cone is set larger for the concave groove than for the tip of the rod-shaped member.

Advantages of the Invention

[0011] According to the spot welding method and the spot welding apparatus according to the present invention, it is possible to ensure the electrical conductivity at the welded portion and suppress welding defects, and it is also possible to suppress the formation of a gap between the panels.

Brief Description of the Drawings

[0012] [Figure 1] This is a schematic side view showing the main components of a spot welding apparatus, which is one embodiment of the present invention. [Figure 2] This is a side view showing the operation of a spot welding machine. [Figure 3A] This is a cross-sectional view showing the process of forming the convex and concave portions. [Figure 3B] A cross-sectional view showing the process of forming the convex and concave portions. [Figure 4] This is a side view showing the operation of a spot welding machine. [Figure 5] This flowchart shows the procedure for joining the first and second panels. [Figure 6] These are cross-sectional views of the first and second panels. [Figure 7A] This is a cross-sectional view showing the process of welding the first and second panels together. [Figure 7B] This is a cross-sectional view showing the process of welding the first and second panels together. [Figure 7C] This is a cross-sectional view showing the process of welding the first and second panels together. [Figure 8] This is a cross-sectional view illustrating the contact state between the first and second panels during welding. [Modes for carrying out the invention]

[0013] Figure 1 is a schematic side view showing the main parts of a spot welding apparatus 10, which is one embodiment of the present invention. The spot welding apparatus 10 is used, for example, in the manufacturing process of vehicles such as automobiles (for example, joining panels that make up the vehicle body). The spot welding apparatus 10 is a device that can weld multiple metal panels 51, 52, which are at least partially overlapped, together by clamping them with a pair of electrodes and passing current between the electrodes.

[0014] In this embodiment, a first metal panel 51 and a second metal panel 52 are described as an example of a workpiece 50 to be spot-welded. In the workpiece 50 to be spot-welded, an adhesive 54, which is a viscous material, is applied between each panel 51 and 52, as shown in Figure 7A. In this embodiment, a thermosetting adhesive 54 such as Weldbond is used. Each panel 51 and 52 may have the same thickness or different thicknesses, and in this embodiment, the thickness of the second panel 52 is greater than the thickness of the first panel 51.

[0015] As shown in Figure 1, the spot welding apparatus 10 comprises an apparatus body 11, a fixed electrode 12 and a movable electrode 14 held by the apparatus body 11, a drive mechanism 20 for moving the movable electrode 14, a processing mechanism 16 for press working on the workpiece 50, and a control device (control unit) 18. Figure 1 shows the parts of the apparatus body 11 to which the fixed electrode 12, the movable electrode 14, and the processing mechanism 30 are attached. The control device 18 is electrically connected to the power supply unit (not shown), the drive mechanism 20, and the processing mechanism 16 for each electrode 12 and 14.

[0016] In this embodiment, the movable electrode 14 is configured to be movable in the uniaxial Y direction by the drive mechanism 20, and this Y direction coincides with the up and down direction in Figure 1. In the spot welding apparatus 10 shown in Figure 1, the symbols U and D indicate up and down, and the symbols Fr and Rr indicate forward and backward. In Figure 1, the X direction, which is perpendicular to the Y direction, coincides with the front and back direction. Also, in Figure 1, the Z direction, which is perpendicular to the Y and X directions, coincides with the depth direction of the paper in Figure 1, and in the following description, in the Z direction, the far side of the paper in Figure 1 will be referred to as the left, and the near side of the paper will be referred to as the right.

[0017] The fixed electrode 12 is fixed to the device body 11, and in this embodiment, it is fixed to the tip of the lower support bracket 11b of the device body 11. The movable electrode 14 is positioned opposite the fixed electrode 12 such that its central axis is coaxial with the central axis of the fixed electrode 12, and is configured to move closer to and further away from the fixed electrode 12 by the driving force of the drive mechanism 20.

[0018] The drive mechanism 20 comprises an actuator 22 and a rod 24 connected to the actuator 22 and extending in the Y direction. The actuator 22 is fixed to the upper support bracket 11a of the device body 11. The actuator 22 can be configured as, for example, an air cylinder, a servo cylinder, or a servo motor. The rod 24 moves back and forth in the axial Y direction by the driving force of the actuator 22.

[0019] The movable electrode 14 is provided at the tip of the rod 24 of the drive mechanism 20. The movable electrode 14 moves between a retracted position, which is moved upward in Figure 1, and a pressure welding position, which is moved downward in Figure 1, contacting the surface of the first panel 51 of the set workpiece 50 and applying pressure to the first panel 51. The fixed electrode 12 and the movable electrode 14 are connected to a power supply unit (not shown). This power supply unit is electrically connected to a control device 16 and receives signals from the control device 16 to supply current between the electrodes 12 and 14.

[0020] The processing mechanism 16 performs press working on the workpiece 50. As shown in Figures 3A and 3B, the processing mechanism 16 forms a convex portion 51a on the first panel 51 on the surface facing the second panel 52, and a concave portion 52a on the second panel 52 on the surface facing the convex portion 51a. The processing mechanism 16 comprises a male mold portion 30 attached to the upper support bracket 11a of the device body 11, and a female mold portion 40 attached to the lower support bracket 11b. The male mold portion 30 is equipped with a tapered rod-shaped member as a processing tool. In this embodiment, a punch 32 is used as an example of this rod-shaped member. The male mold portion 30 further comprises a male mold moving mechanism 34 for moving the punch 32. The female mold portion 40 comprises a die 42 that constitutes the female mold, and a female mold moving mechanism 44 for moving the die 42. In the following description, the male mold section 30, the male mold moving mechanism 34, the female mold section 40, and the female mold moving mechanism 44 will be referred to as the punch section 30, the punch moving mechanism 34, the die section 40, and the die moving mechanism 44, respectively.

[0021] The punch section 30 is attached to the upper support bracket 11a so as to be located near the movable electrode 14. The punch 32 is configured to move between a processing position where processing is performed on the workpiece 50, as shown in Figure 1, and a non-processing position retracted from the processing position, as shown in Figure 2, by a punch movement mechanism 34. In the processing position, the axis of the punch 32 is positioned coaxially with the movable electrode 14, and the punch 32 is positioned below the movable electrode 14 (i.e., on the fixed electrode side). In the non-processing position, the punch 32 is off-axis from the movable electrode 14, and in this embodiment, it is located in front of the movable electrode 14.

[0022] In this embodiment, the punch moving mechanism 34 is attached to the rod 24 of the drive mechanism 20 using a mounting fixture 31. The punch moving mechanism 34 comprises a plate 35 to which a punch 32 is attached, and a punch actuator 37 and a support arm 38 connected to the plate 35. The base end of the support arm 38 is fixed to the mounting fixture 31 and extends downward from this base end. In this embodiment, the support arm 38 is formed in a bent shape, and the tip of the support arm 38 is positioned to the left in the Z direction (towards the back of the paper in Figure 1) so as to be off the axis of the rod 24. The punch actuator 37 is fixed to the mounting fixture 31 via the support arm 38 and has a drive rod 37a that is extendable and retractable in the Y direction.

[0023] The plate 35 is formed in a roughly triangular shape. The first corner of the plate 35 is rotatably connected to the tip of the support arm 38, and the second corner is rotatably connected to the tip of the drive rod 37. The third corner of the plate 35 has a planar pressing surface 35a that faces the die 42 at the machining position shown in Figure 1.

[0024] The punch 32 is attached to the plate 35 via a linear motion member 35b. The linear motion member 35b causes the punch 32 to move linearly in the axial direction. In this embodiment, a linear guide is used as an example of the linear motion member 35b. The base end of the punch 32 is held by a holder 36 which is linearly movably attached to the linear motion member 35. The linear motion member 35b is attached to the plate 35 such that, at the machining position shown in Figure 1, its linear motion direction coincides with the Y direction. At this machining position, the holder 36 is on the axis of the movable electrode 14 and is positioned below the movable electrode 14, and the punch 32 extends downward from the holder 36.

[0025] The punch 32 moves to the machining position shown in Figure 1 when the drive rod 37a of the punch actuator 37 extends, and to the non-machining position shown in Figure 2 when the drive rod 37a retracts. In the non-machining position, the punch portion 30 is located above the movable electrode 14.

[0026] The die section 40 is attached to the lower support bracket 11b so as to be located near the fixed electrode 12. The die 42 is configured to be movable between the machining position shown in Figure 1 and the non-machining position shown in Figure 2 by a die movement mechanism 44. In the machining position, the die 42 is positioned on the axis of the fixed electrode 12 and above the fixed electrode 12. In this machining position, the fixed electrode 12 supports the die 42 from below. In the non-machining position, the die 42 is off the axis of the fixed electrode 12 and, in this embodiment, is located behind the fixed electrode 12.

[0027] In this embodiment, the die moving mechanism 44 includes a holding member 45 for holding the die 42, a die actuator 47 for powering the holding member 45, and a first link 48a and a second link 48b for movably supporting the holding member 45 with respect to the support bracket 11b. The die actuator 47 is formed in a cylindrical shape, with its base end rotatably connected to the support bracket 11b and its tip end having an extendable drive rod 47a. The first and second links 48a and 48b have their base ends rotatably connected to the support bracket 11b and their tips rotatably connected to the holding member 45.

[0028] The die 42 moves to the machining position shown in Figure 1 when the drive rod 47a of the die actuator 47 extends, and to the non-machining position shown in Figure 2 when the drive rod 47a retracts. In the non-machining position, the die portion 40 is located below the fixed electrode 12.

[0029] As shown in Figures 1 and 2, the die 42 has a groove 43 formed on the surface facing the punch 32 during processing, with a shape corresponding to the tip shape of the punch 32. As shown in Figure 3A, the punch 32 has a substantially conical tip. The tip of the punch 32 is rounded. The groove 43 of the die 42 is formed in a substantially conical shape to correspond to the tip shape of the punch 32. In this embodiment, the conical shape of the groove 43 is formed such that the central angle of the cone is larger than that of the conical shape of the punch 32. Note that the tip shape of the punch 32 and the shape of the groove 43 are not limited to a conical shape, but may be, for example, substantially hemispherical.

[0030] The processing mechanism 16 described above allows the punch 32 to be moved downward in the Y direction, which is the direction of movement of the movable electrode 14, by the drive mechanism 20 that moves the movable electrode 14, while the punch portion 30 and the die portion 40 are in the processing position shown in Figure 1. Specifically, when the movable electrode 14 is moved downward by the drive mechanism 20 in the processing position shown in Figure 1, the movable electrode 14 comes into contact with the holder 36, as shown in Figure 4. As described above, the holder 36 and the punch 32 are configured to be movable in the Y direction relative to the plate 35 by the linear motion member 35b. Therefore, when the movable electrode 14 is in contact with the holder 36, and the drive mechanism 20 moves the movable electrode 14 further downward, the holder 36 and the punch 32 are pressed by the movable electrode 14 and move downward. This applies pressure to the punch 32, allowing it to be pushed towards the groove 43 of the die 42.

[0031] The control device 18 is configured to include, for example, an information processing unit such as a CPU, a storage unit such as RAM or ROM, and an input / output interface. Based on a program stored in the storage unit (for example, the positions of the punch 32 and die 42 at each timing, the Y-direction position and pressure of the punch 32 during press working, the Y-direction position and pressure of the movable electrode 14 at each timing, and the current supplied to the fixed electrode 12 and movable electrode 14 at each timing), the control device 18 controls the movement of the punch 32, die 42 and movable electrode 14, the pressure applied to the workpiece 50, and the current value of the welding current supplied to each electrode 12 and 14.

[0032] Next, a spot welding method using the spot welding apparatus 10 described above will be explained. The first and second panels 51 and 52 of this embodiment are joined using adhesive 54 and spot welding, and are joined through an overlapping step of overlapping the panels 51 and 52 to which adhesive 54 has been applied, a recessed portion forming step of forming convex and concave portions on the welded portions of each panel 51 and 52 by press working, a welding step of performing spot welding on the welded portions, and an adhesive curing step of curing the adhesive 54. The joining procedure for the first and second panels 51 and 52 will be explained below according to the flowchart shown in Figure 5.

[0033] First, adhesive 54 is applied to the first panel 51 and / or the second panel 52, and with the adhesive 54 applied between the panels 51 and 52, the first and second panels 51 and 52 are placed on top of each other (step S11).

[0034] Next, the workpiece 50, formed by overlapping the first and second panels 51 and 52, is set in the spot welding device 10 (step S12). The workpiece 50 is set in the spot welding device 10 while the adhesive 54 is not yet hardened (unhardened state of the adhesive 54). At this time, the spot welding device 10 is set with the processing mechanism 16 in the processing position, as shown in Figure 1. The workpiece 50 is set so that the second panel 52 is positioned on the die 42 side, and the welded parts on the first and second panels 51 and 52 to be spot welded are positioned on the grooves 43 of the die 42.

[0035] Subsequently, the workpiece 50 is press-formed using the processing mechanism 16 to form a convex portion 51a and a concave portion 52b on the opposing surfaces of the first panel 51 and the second panel 52 (step S13). The press-forming is performed while the adhesive 54 has not yet hardened. During the press-forming, the drive mechanism 20 is activated to extend the rod 24 as shown in Figure 4. This causes the pressing surface 35a of the plate 35 to contact the upper surface of the first panel 51, pressing the workpiece 50 toward the die 42. Furthermore, as the rod 24 is extended, the movable electrode 14 contacts the holder 36, and the holder 36 and the punch 32 are pushed downward below the plate 35 by the pressing force received from the movable electrode 14. As a result, as shown in Figures 3A and 3B, the workpiece 50 is subjected to the pressing force of the punch 32 from the first panel 51 side toward the die 42. This pressing process creates a convex portion 51a on the first panel 51 that protrudes toward the second panel 52, and a recessed portion 52a on the second panel 52 that is recessed toward the first panel 51. At this time, the uncured adhesive 54 is pushed aside around the convex portion 51a and the recessed portion 52a.

[0036] In this embodiment, the thickness of the second panel 52 is greater than the thickness of the first panel 51, and the section modulus of the second panel 52 is greater than that of the first panel 51. As a result, the amount of springback in the machined portion of the second panel 52 is greater than that of the first panel 51. Consequently, as shown in Figure 6, the height h of the convex portion of the first panel 51 (height from the surface facing the second panel 52) is greater than the depth d of the concave portion 52a of the second panel 52.

[0037] Next, the processing mechanism 16 is moved to a non-processing position, and spot welding is performed on the welded portion of the workpiece 50 while the adhesive 54 has not yet hardened (step S14). Figures 7A, 7B, and 7C are cross-sectional views showing the process of welding the first and second panels 51 and 52. Note that in Figures 7A, 7B, 7C, and 8, each electrode 12 and 14 is shown in a non-cross-sectional state.

[0038] As shown in Figures 7A and 7B, welding is performed with the protrusion 51a of the first panel 51 inserted into the recess 52a of the second panel 52. During the welding process, the welded area, where the protrusion 51a and recess 52a are formed, is clamped and pressurized by a fixed electrode 12 and a movable electrode 14, and current is passed between the electrodes 12 and 14 in this state. As shown in Figure 8, when the workpiece 50 is clamped and pressurized by the electrodes 12 and 14, the adhesive 54 is in an uncured state and is pushed aside around the protrusions 51a and 52a. Also, as shown in Figure 6, since the height h of the protrusion 51a is greater than the depth of the recess 52a, the tip 56 of the protrusion 51a contacts the bottom surface of the recess 52a. By passing current between the electrodes 12 and 14 in this state, the conductivity of the welded area of ​​the first and second panels 51 and 52 is ensured.

[0039] As welding progresses, a nugget 51 is formed between the first and second panels 51 and 52, as shown in Figure 7C. Furthermore, the convex portion 51a and concave portion 52a are flattened by the melting of each panel 51 and 52 and the pressure applied by each electrode 12 and 14. This minimizes the impact on the appearance and strength of the welded workpiece 50 due to the formation of the convex portion 51a and concave portion 52a.

[0040] After spot welding is performed, the adhesive 54 on the workpiece 50 is cured (step S15). Specifically, the workpiece 50 is transported from the spot welding apparatus 10 to a heating furnace (not shown), and the adhesive 54 is cured by heating the workpiece 50 in the heating passage. This allows the first and second panels 51 and 52 to be joined by the adhesive 54 and spot welding.

[0041] As described above, in the spot welding method of this embodiment, a recess 52a is formed in the second panel 52 into which the protrusion 51a of the first panel 51 is inserted. Therefore, when the first and second panels 51 and 52 are superimposed, it is possible to suppress the occurrence of a gap between the panels 51 and 52. This suppresses the impact on product accuracy caused by welding with a gap. Furthermore, since the recess 52a is formed to a depth into which the protrusion 51a abuts, when the first and second panels 51 and 52 are clamped and pressed by a pair of electrodes 12 and 14 during welding, the protrusion 51a of the first panel 51 can be brought into contact with the recess 52a of the second panel 52. This ensures electrical conductivity at the weld joint and suppresses the occurrence of welding defects in the workpiece 50 to which the uncured adhesive 54 is applied between the panels 51 and 52.

[0042] Furthermore, in this embodiment, by pressing the punch 32 into the overlapping first and second panels 51 and 52, a convex portion 51a and a recess 52a corresponding to the shape of the convex portion 51a can be easily formed on the opposing surfaces of the first and second panels 51 and 52.

[0043] Furthermore, in this embodiment, when the thicknesses of the panels 51 and 52 are different, by performing press working so that a recess 52a is formed on the side of the second panel 52 which has a greater thickness, the depth d of the recess 52a can be made smaller than the height h of the protrusion 51a by utilizing the springback after press working. Note that even when the thicknesses of the first and second panels 51 and 52 are the same, the processing area of ​​the second panel 52 is larger than that of the first panel 51, so the amount of springback of the second panel 52 will be greater than that of the first panel.

[0044] Furthermore, in this embodiment, a processing mechanism 16 for press working is provided in the spot welding apparatus 10, and a drive mechanism 20 for moving the movable electrode 14 can be used to apply pressure during press working, thereby reducing the equipment cost for press working. In addition, in the spot welding apparatus 10 of this embodiment, after press working, the processing mechanism 16 can be moved to a non-processing position, and spot welding can be performed immediately on the set workpiece, resulting in excellent manufacturing efficiency.

[0045] It should be noted that the present invention is not limited to the embodiments or modifications described above, and various modifications are possible without departing from the spirit of the invention.

[0046] For example, the workpiece 50 to be spot-welded may not have adhesive 54 applied to it.

[0047] Furthermore, in the spot welding method, the protrusion 51a of the first panel 51 and the recess 52a of the second panel 52 are not formed simultaneously, but may be formed individually by a press device separate from the spot welding apparatus 10. In this case, the recess 52a is formed to a depth such that the tip of the protrusion 51a abuts against the bottom, and during welding, the weld portion is welded by a pair of electrodes with the protrusion 51a inserted into the recess 52a. [Explanation of Symbols]

[0048] 10 Spot welding equipment 12 Fixed electrode 14. Movable electrodes 16 Processing mechanism 18 Control device 20 Drive mechanism 30 Punch section 32. Punch (rod-shaped member) 34 Punch movement mechanism 40 Die section 42 Dies 43. Grooves 44 Die transfer mechanism 50 Work 51 Panel 1 51a Convex part 52. Second Panel 52a Recess 54 Adhesives

Claims

1. In a spot welding method in which overlapping first and second panels are clamped between a pair of electrodes and current is passed between the electrodes to weld the panels together, A step of applying a viscous material between the first and second panels and overlapping the first and second panels, In the welded joint of the overlapping first and second panels, a protrusion is formed on the surface of the first panel facing the second panel, and a recess is formed on the surface of the second panel facing the protrusion, having a depth such that the tip of the protrusion abuts against the bottom. After the convex portion and the concave portion are formed, the convex portion is inserted into the concave portion and the viscous material has not hardened, and the welded portions of the first and second panels are clamped between the pair of electrodes and current is passed between the electrodes, Includes, In the process of forming the convex portion and the concave portion, the first and second panels, which are stacked on top of each other, are placed between a male mold having a tapered rod-shaped member and a female mold having a groove into which the tip of the rod-shaped member fits, and the convex portion and the concave portion are formed by press work in which the rod-shaped member is pushed toward the groove. The second panel has a larger section modulus than the first panel, and due to the springback of the second panel after press working, the depth of the recess is formed to be smaller than the height of the protrusion. A spot welding method characterized in that, in the process of applying current, the tip of the protrusion is brought into contact with the bottom surface of the recess, and the viscous material present between them is pushed aside to the periphery, and current is applied between the pair of electrodes.

2. The spot welding method according to claim 1, characterized in that the thickness of the second panel is greater than or equal to the thickness of the first panel.

3. A method for welding panels together by sandwiching a first panel and a second panel having a larger section modulus than the first panel with a pair of electrodes and passing an electric current between the electrodes, The process involves forming a protrusion on the welded surface of the first panel facing the second panel, and forming a recess on the welded surface of the second panel facing the protrusion, having a depth such that the tip of the protrusion abuts against the bottom. A step of applying a viscous material between the first and second panels and overlapping the first and second panels before or after forming the convex and concave portions, The steps include inserting the protrusion into the recess and, while the viscous material has not hardened, clamping the welded portions of the first and second panels with the pair of electrodes and applying current between the electrodes, Includes, The height of the protrusion is greater than the depth of the recess. In a spot welding apparatus used in a spot welding method in which, in the process of applying current, the tip of the protrusion is brought into contact with the bottom surface of the recess, and the viscous material present between them is pushed aside to the periphery, and current is applied between the pair of electrodes, A fixed electrode fixed to the main body of the device, A movable electrode that can move closer to and further away from the fixed electrode, The device comprises a processing mechanism that can move between a processing position for press working on the first and second panels and a non-processing position retracted from the processing position, The aforementioned processing mechanism is A tapered rod-shaped member is provided near the movable electrode and, at the processing position, is movable in the direction of movement of the movable electrode by a drive unit that moves the movable electrode, A die provided near the fixed electrode and having a groove corresponding to the tip shape of the rod-shaped member, on which the first and second panels are placed at the processing position, A male moving mechanism moves the rod-shaped member between a processing position located coaxial with the movable electrode and below the movable electrode, and a non-processing position off-axis from the movable electrode. The die is moved by a female die moving mechanism that moves the die between a machining position located on the axis of the fixed electrode and above the fixed electrode, and a non-machining position off the axis of the fixed electrode. A spot welding apparatus characterized in that the tip of the rod-shaped member and the groove are both substantially conical in shape, and the central angle of the cone is set to be larger for the groove than for the tip of the rod-shaped member.

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