Welding method

Abstract

To provide a spot electrode capable of preventing a poor weld state in which a thin welded plate in an outermost position is insufficiently joined, when the three or more welded plates, which overlap one another in such a manner that the thin plate-like welded plate is arranged in the outermost position, are joined together by a spot welding method.SOLUTION: A welding electrode 3, which has an axis line L and which is used to overlap-join a plurality of welded plates 51, 52 and 53 together by a spot welding method, comprises a first contact part 31 that is positioned near the center of an apical surface and that is protruded in the direction of the axis line, and a second contact part 32 that is positioned with a space in a radial direction from the first contact part 31 and that is protruded in the direction of the axis line. Either of the first and second contact parts 31 and 32 is further protruded in the direction of the axis line X than the other one of them.SELECTED DRAWING: Figure 9

Description

Technical Field

[0004] , , , , , ,

[0001] The present invention relates to welding method and, more particularly, to welding for joining a plurality of sheet materials in a stacked state by spot welding method method.

Background Art

[0002] As a method of joining a plurality of stacked metal sheet materials, there is a spot welding method. This spot welding method is performed using, for example, a spot welding apparatus shown in Patent Document 1. The spot welding apparatus has a welding gun that is three-dimensionally moved and controlled by a robot. The welding gun has first and second electrodes arranged coaxially and opposed to each other, and one of the electrodes is movable forward and backward in the axial direction. The plurality of stacked metal sheet materials are sandwiched between the first and second electrodes with a predetermined pressing force by advancing one of the electrodes, and are joined by passing a predetermined welding current between both electrodes in this state. Specifically, when the welding current is passed, a molten portion is formed near the center in the total thickness direction of the stacked metal sheet materials due to the heat generated by this current passage, and this molten portion grows beyond the boundary of the stacked metal sheet materials and eventually solidifies to form a nugget. This nugget joins the stacked metal sheet materials together.

[0003] By the way, when joining three or more metal sheet materials by spot welding, if the outermost metal sheet material is thin and the thickness ratio is large, the nugget formed by solidification of the molten portion may not reach the thin metal sheet material at the outermost position, and there may occur a welding defect in which the joining of the thin metal sheet material at the outermost position is insufficient.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention was conceived under the circumstances described above, and when three or more plates to be welded are joined by spot welding with a thin plate to be welded placed at the outermost position, it is possible to prevent welding defects where the thin plate to be welded at the outermost position is not joined properly. method The challenge is to provide [this]. [Means for solving the problem]

[0006] To solve the above problems, the present invention employs the following technical means.

[0007] In other words, the welding method provided by the present invention is A welding gun having a first electrode and a second electrode arranged opposite each other on the same axis is used to create a stack of three or more superimposed bodies, including a thin plate-like workpiece located at the outermost position on the first electrode side. By spot welding Riju Joining welding method And, The first electrode described above has a central axis and, at its tip surface, is convexly curved around the axis. A protruding first contact portion, and the first contact portion The outer edge adjacent to the periphery is smoothly extended in the axial direction as described above. It comprises a protruding second contact portion. And, The process of clamping the overlapping body between the first electrode and the second electrode includes the step of applying a welding current between the first electrode and the second electrode when the entire surface of the first contact portion of the second electrode comes into contact with the thin plate-like welded plate. It is characterized by the following: [Effects of the Invention]

[0008] <When the first contact portion protrudes more axially than the second contact portion> When the electrode is pressed with a constant pressure from the thin sheet side onto an stack of, for example, three stacked sheets of plates to be welded, with a thin sheet of plate placed at the outermost position, the first contact portion of the electrode sinks into the surface of the thin sheet of plate to be welded. When a welding current is applied at a predetermined timing, a molten area is formed near the approximate center of the overall thickness of the stacked sheets of plates, and this molten area grows in the overall thickness direction. At the same time, the first contact portion sinks further into the surface of the thin sheet of plate to be welded, and eventually the second contact portion also contacts and sinks into the surface of the thin sheet of plate to be welded. At this time, in addition to the current path established between the molten area and the first contact portion, a current path is also established between the molten area and the second contact portion, and the welding current flowing through this current path causes the molten area to grow toward the second contact portion until it reaches the outermost thin sheet of plate to be welded. The nugget formed by the solidified molten portion in this manner allows all overlapping weld plates, including the outermost thin plate-shaped plate, to be joined together.

[0009] <When the second contact portion protrudes more axially than the first contact portion> When the electrode is pressed with a constant pressure from the thin sheet side onto an stack of, for example, three stacked sheets of plates to be welded, with a thin sheet of plate placed at the outermost position, the second contact portion of the electrode sinks into the surface of the thin sheet of plate to be welded. When a welding current is applied at a predetermined timing, a molten area is created near the approximate center of the overall thickness of the stack of plates to be welded, and this molten area grows in the overall thickness direction. At the same time, the second contact portion sinks further into the surface of the thin sheet of plate to be welded, and eventually the first contact portion also contacts and sinks into the surface of the thin sheet of plate to be welded. At this time, in addition to the current path established between the molten area and the second contact portion, a current path is also established between the molten area and the first contact portion, and the welding current flowing through this current path causes the molten area to grow toward the first contact portion until it reaches the outermost thin sheet of plate to be welded. The nugget formed by the solidified molten portion in this manner allows all overlapping weld plates, including the outermost thin plate-shaped plate, to be joined together.

[0010] Thus, the present invention Welding methodBy using this method, without taking measures that would lead to cost increases due to a mechanism for complex control of the pressing force, a simple measure such as devising the shape of the welding electrode can avoid welding defects in the thin plate-shaped workpieces to be welded located at the outermost position in the spot welding of multiple workpieces to be welded with the thin plate-shaped workpieces to be welded arranged at the outermost position. and the timing of the power supply

[0011] Other features and advantages of the present invention will become clearer from the detailed description given below with reference to the drawings.

Brief Description of the Drawings

[0012] [[ID=!12]] [Figure 1] It is a schematic diagram of a spot welding machine using the welding method according to the present invention. [Figure 2] It is a side view of a welding electrode used in an embodiment of the present invention. [Figure 3] It is a bottom view of the welding electrode shown in FIG. 2. [Figure 4] It is a longitudinal sectional view of the welding electrode shown in FIG. 2 (a sectional view taken along line IV-IV of FIG. 3). [Figure 5] It is a bottom view showing a modified example of the welding electrode shown in FIGS. ²⁻⁴. [Figure 6] It is a bottom view showing a modified example of the welding electrode shown in FIGS. ²⁻⁴. [Figure 7] It is an explanatory diagram of the operation when performing spot welding using the welding electrodes shown in FIGS. ²⁻⁴. [Figure 8] It is an explanatory diagram of the operation when performing spot welding using the welding electrodes shown in FIGS. ²⁻⁴. [Figure 9] It is an explanatory diagram of the operation when performing spot welding using the welding electrodes shown in FIGS. ²⁻⁴. [Figure 10] It is a side view of a welding electrode used in another embodiment of the present invention. [Figure 11] It is a bottom view of the welding electrode shown in FIG. 10. [Figure 12] It is a longitudinal sectional view of the welding electrode shown in FIG. 10 (a sectional view taken along line XII-XII of FIG. 11). [Figure 13] Note: There seems to be an error in line ID=12 where it should be `` instead of `[[ID=!12]]`. The translation is done as accurately as possible based on the provided text. [Figure 13] It is a bottom view showing a modified example of the welding electrode shown in FIGS. 10 to 12. [Figure 14] It is a bottom view showing a modified example of the welding electrode shown in FIGS. 10 to 12. [Figure 15] It is an explanatory diagram of the operation when performing spot welding using the welding electrode shown in FIGS. 10 to 12. [Figure 16] It is an explanatory diagram of the operation when performing spot welding using the welding electrode shown in FIGS. 10 to 12. [Figure 17] It is an explanatory diagram of the operation when performing spot welding using the welding electrode shown in FIGS. 10 to 12.

Embodiment for Carrying out the Invention

[0013] Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the drawings.

[0014] FIGS. 1 to 9 show the outline of a welding method according to an embodiment of the present invention. dissolve 接法の概要を示す。

[0015] As shown in FIG. 1, the spot welder 1 has a welding gun 2 whose three-dimensional position is controlled by a robot (not shown). The welding gun 2 has an upper electrode 3 and a lower electrode 4. These upper electrode 3 and lower electrode 4 are arranged to face each other on the same axis L, and the upper electrode 3 can be moved forward and backward in the axial direction by a pressurizing actuator such as a cylinder. The spot welder 1 is configured to sandwich a stack 5 of a plurality of welded plates between the upper electrode 3 and the lower electrode 4 with a predetermined pressing force by advancing the upper electrode 3, and then pass a predetermined welding current between the two electrodes.

[0016] The present invention is applied to the upper electrode 3, and the lower electrode 4 has a dome-shaped tip shape in a general form.

[0017] Figures 2 to 6 show examples of embodiments of the upper electrode 3. The upper welding electrode basically has a central axis and comprises a first contact portion that protrudes in a convex curved shape around the axis at the tip surface, and a second contact portion that protrudes in the axial direction on the outside adjacent to the peripheral edge of the first contact portion, with the first contact portion 31 protruding more in the axial direction than the second contact portion 32.

[0018] The configuration shown in Figures 2 to 4 is such that the first contact portion 31 is Convex curve The second contact portion 32 is formed to protrude in a ring shape, surrounding the first contact portion 31.

[0019] In the configuration shown in Figure 5, the first contact portion 31 is similar to the configurations shown in Figures 2 to 4. Convex curve The second contact portion 32 is formed to protrude in a certain shape, and in two radially opposing regions, it is formed to protrude in an arc centered on the axis L.

[0020] In the configuration shown in Figure 6, the first contact portion 31 is similar to the configurations shown in Figures 2 to 4. Convex curve The second contact portion 32 is formed to protrude in a certain shape, and it is formed to protrude at four locations separated by 90 degrees, forming an arc with the axis L as the center.

[0021] An important point common to all of the above embodiments is that, as shown in the vertical cross-section in Figure 4, a valley 33 is formed between the first contact portion 31 and the second contact portion 32, which is lower than the second contact portion 32.

[0022] Next, using the electrodes shown in Figures 2 to 4 By the method of the present invention The operation of spot welding will be explained with reference to Figures 7 to 9.

[0023] A stacked body 5 of three weldable plates, with the thin plate 51 positioned at the outermost position, is placed between the upper electrode 3 and the lower electrode 4, with the thin plate 51 facing upwards (Figure 7). The upper electrode 3 is moved downwards to sandwich the stacked body 5 between the two electrodes, and the upper electrode 3 is pressed against the surface of the thin plate 51 with constant pressure. As a result, the first contact portion 31 of the upper electrode 3 sinks into the surface of the thin plate 51, and when a welding current is applied at a predetermined timing, a molten portion 6 is created near the approximate center of the overall thickness direction of the stacked body 5 of the weldable plates, and this molten portion 6 grows in the overall thickness direction (Figure 8). At the same time, the first contact portion 31 sinks further into the surface of the thin plate 51, and eventually the second contact portion 32 also contacts and sinks into the surface of the thin plate 51. At this time, an electric current path E is established between the molten portion 6 and the second contact portion 32, and the welding current flowing through this electric current path E causes the molten portion 6 to grow toward the second contact portion 32 until it reaches the outermost thin plate-shaped weld plate 51 (Figure 9). The nugget formed by the solidified molten portion 6 in this way allows all the overlapping weld plates, including the outermost thin plate-shaped weld plate 51, to be joined together.

[0024] Figures 10 to 14 show other embodiments of the upper electrode 3. This upper electrode 3 is basically the same as the embodiment described above in that it comprises a first contact portion 31 located near the center of the tip surface and protruding in the axial direction, and a second contact portion 32 located radially apart from the first contact portion 31 and protruding in the axial direction, but differs in that the second contact portion 32 protrudes more axially than the first contact portion 31.

[0025] The configuration shown in Figures 10 to 12 is such that the first contact portion 31 Convex curve The second contact portion 32 is formed to protrude in a ring shape, surrounding the first contact portion 31.

[0026] In the configuration shown in Figure 13, the first contact portion 31 is similar to the configurations shown in Figures 10 to 12. Convex curve The second contact portion 32 is formed to protrude in a certain shape, and in two radially opposing regions, it is formed to protrude in an arc centered on the axis L.

[0027] In the configuration shown in Figure 14, the first contact portion 31 is similar to the configurations shown in Figures 10 to 12. Convex curve The second contact portion 32 is formed to protrude in a certain shape, and it is formed to protrude at four locations separated by 90 degrees, forming an arc with respect to the axis.

[0028] An important point common to all of the above embodiments is that, as shown in the vertical cross-section in Figure 12, a valley 33 is formed between the first contact portion 31 and the second contact portion 32, which is lower than the first contact portion 31.

[0029] Next, using the electrodes shown in Figures 10 to 12 According to the present invention The mechanism for spot welding will be explained with reference to Figures 15 to 17.

[0030] A stacked body 5 of three weldable plates, with the thin plate 51 positioned at the outermost position, is placed between the upper electrode 3 and the lower electrode 4, with the thin plate 51 facing upwards. The upper electrode 3 is then moved downwards to sandwich the stacked body 5 between the two electrodes (Figure 15), and the upper electrode 3 is pressed against the surface of the thin plate 51 with constant pressure. As a result, the second contact portion 32 of the upper electrode 3 sinks into the surface of the thin plate 51, and when a welding current is applied at a predetermined timing, a molten portion 6 is created near the approximate center of the overall thickness direction of the stacked body 5 of the weldable plates, and this molten portion 6 grows in the overall thickness direction (Figure 16). At the same time, the second contact portion 32 sinks further into the surface of the thin plate 51, and eventually the first contact portion 31 also contacts and sinks into the surface of the thin plate 51. At this time, an electric current path E is established between the molten portion 6 and the first contact portion 31, and the welding current flowing through this electric current path E causes the molten portion 6 to grow toward the first contact portion 31 until it reaches the outermost thin plate-shaped weld plate 51 (Figure 17). The nugget formed by the solidified molten portion 6 in this way allows all the overlapping weld plates, including the outermost thin plate-shaped weld plate 51, to be joined together.

[0031] As explained above, when joining three or more overlapping plates 5, each with a thin plate-shaped plate 51 positioned at the outermost position, by spot welding, using the upper electrode 3 according to each of the above embodiments makes it possible to avoid welding defects in the outermost thin plate-shaped plate 51 without having to take measures that increase costs, such as complex control of the pressing force.

[0032] Of course, the present invention is not limited to the embodiments described above, and any modifications within the scope of the claims are included within the scope of the present invention. [Explanation of Symbols]

[0033] L axis E current path 1 Spot welding machine 2. Welding gun 21 Cylinder 3 Upper electrode 31 1st contact part 32 Second contact part 33 Tanibe 4 Lower electrode 5. Overlapping welded plates 51 Thin plate-shaped welded sheet 52 Welded Plates 53 Plate to be welded 6. Molten part

Claims

[Claim 1] A welding method for joining three or more overlapping bodies, including a thin plate-like plate to be welded located at the outermost position on the first electrode side, by spot welding, using a welding gun having a first electrode and a second electrode arranged opposite to each other on the same axis, The first electrode has a central axis and comprises a first contact portion that protrudes in a convex curved shape from its tip surface with respect to the axis, and a second contact portion that protrudes smoothly in the axial direction, adjacent to the peripheral edge of the first contact portion and continuing outward. A welding method characterized by including the step of applying a welding current between the first electrode and the second electrode when the entire surface of the first contact portion of the first electrode comes into contact with the thin plate-shaped plate to be welded, during the process of clamping the overlapping body between the first electrode and the second electrode.

Images