JP2023132920A - welding electrode - Google Patents

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

The present invention relates to a welding electrode, and more particularly to a welding electrode for joining a plurality of plate materials in an overlapping state using a spot welding method.

Spot welding is a method for joining multiple metal plates stacked one on top of the other. This spot welding method is performed using a spot welding device shown in Patent Document 1, for example. The spot welding device has a welding gun whose three-dimensional movement is controlled by a robot. The welding gun has first and second electrodes arranged coaxially and facing each other, and one of the electrodes can move forward and backward in the axial direction. A plurality of stacked metal plates are sandwiched between the first and second electrodes with a predetermined pressure by advancing one electrode, and in this state are joined by passing a predetermined welding current between both electrodes. Ru. Specifically, when welding current is applied, the heat generated by this current flow forms a molten part near the center of the stacked metal plates in the total thickness direction, and this molten part crosses the boundary of the stacked metal plates. It grows and eventually solidifies to form a nugget. This nugget joins metal plates stacked one on top of the other.

By the way, when three or more metal plates are joined by spot welding, if the metal plate at the outermost position is thin and the plate thickness ratio is large, the nugget in which the molten part has solidified is the thin sheet at the outermost position. A welding failure may occur in which the thin metal plate located at the outermost position is insufficiently joined without reaching the metal plate.

JP 2021-154303 Publication

The present invention has been devised under the above-mentioned circumstances, and involves arranging a thin plate to be welded at the outermost position and joining three or more stacked welded plates by a spot welding method. The object of the present invention is to provide a welding electrode that can prevent welding defects due to insufficient bonding of the outermost thin plate to be welded.

In order to solve the above problems, the present invention employs the following technical means.

That is, the welding electrode provided by the present invention has an axis, is a welding electrode for overlapping and joining a plurality of plates to be welded by spot welding, and is located near the center of the tip surface. a first contact portion that protrudes in the axial direction, and a second contact portion that is spaced apart from the first contact portion in the axial direction and protrudes in the axial direction; The second contact portion is characterized in that one of the second contact portions protrudes more than the other in the axial direction.

<When the first contact part protrudes more than the second contact part in the axial direction>
When the electrode is pressed with a constant pressure from the side of the thin plate to be welded onto a stack of, for example, three stacked plates with a thin plate to be welded placed at the outermost position, the first contact part of the electrode will be pressed against the thin plate. By sinking into the surface of the plate to be welded and applying a welding current at a predetermined timing, a molten part is generated near the approximate center of the stacked plate to be welded in the total thickness direction, and this molten part is It grows in the entire thickness direction. At the same time, the first contact portion further sinks into the surface of the thin plate to be welded, and eventually the second contact portion also contacts and sinks into the surface of the thin plate to be welded. At this time, in addition to the current path established between the welding part and the first contact part, a current path is also established between the welding part and the second contact part, and the welding current flowing through this current path causes the melting. The portion grows toward the second contact portion until it reaches the outermost thin plate to be welded. With the nugget formed by the solidified molten portion that has grown in this way, it is possible to join all of the stacked welded plates including the outermost thin plate to be welded.

<When the second contact part protrudes more than the first contact part in the axial direction>
When the electrode is pressed with a constant pressure from the side of the thin plate to be welded onto a stacked body of, for example, three stacked plates with a thin plate to be welded placed at the outermost position, the second contact portion of the electrode will be pressed against the thin plate. By sinking into the surface of the plate to be welded and applying a welding current at a predetermined timing, a molten part is generated near the approximate center of the stacked plate to be welded in the total thickness direction, and this molten part is It grows in the entire thickness direction. At the same time, the second contact portion further sinks into the surface of the thin plate to be welded, but eventually the first contact portion also contacts and sinks into the surface of the thin plate to be welded. At this time, in addition to the current path established between the welding part and the second contact part, a current path is also established between the welding part and the first contact part, and the welding current flowing through this current path causes the melting. The portion grows toward the first contact portion until it reaches the outermost thin plate to be welded. With the nugget formed by the solidified molten portion that has grown in this way, it is possible to join all of the stacked welded plates including the outermost thin plate to be welded.

As described above, by using the electrode according to the present invention, it is possible to achieve the best results by taking simple measures such as devising the shape of the welding electrode, without having to take measures that would increase costs due to a mechanism that complicatedly controls the pressurizing force. In joining a plurality of welded plates in which the thin plates to be welded are disposed at outer positions by the spot welding method, it is possible to avoid welding defects of the outermost thin plates to be welded.

Other features and advantages of the invention will become more apparent from the detailed description given below with reference to the drawings.

1 is a schematic diagram of a spot welder using a welding electrode according to the present invention. FIG. 1 is a side view of a welding electrode according to an embodiment of the present invention. 3 is a bottom view of the welding electrode shown in FIG. 2. FIG. FIG. 3 is a longitudinal cross-sectional view of the welding electrode shown in FIG. 2 (a cross-sectional view taken along line IV-IV in FIG. 3). 5 is a bottom view showing a modification of the welding electrode shown in FIGS. 2 to 4. FIG. 5 is a bottom view showing a modification of the welding electrode shown in FIGS. 2 to 4. FIG. FIG. 5 is an explanatory diagram of the operation when performing spot welding using the welding electrode shown in FIGS. 2 to 4. FIG. FIG. 5 is an explanatory diagram of the operation when performing spot welding using the welding electrode shown in FIGS. 2 to 4. FIG. FIG. 5 is an explanatory diagram of the operation when performing spot welding using the welding electrode shown in FIGS. 2 to 4. FIG. It is a side view of the welding electrode based on other embodiment of this invention. 11 is a bottom view of the welding electrode shown in FIG. 10. FIG. FIG. 11 is a longitudinal cross-sectional view (a cross-sectional view taken along line XII-XII in FIG. 11) of the welding electrode shown in FIG. 10; 13 is a bottom view showing a modification of the welding electrode shown in FIGS. 10 to 12. FIG. 13 is a bottom view showing a modification of the welding electrode shown in FIGS. 10 to 12. FIG. FIG. 13 is an explanatory diagram of the operation when performing spot welding using the welding electrode shown in FIGS. 10 to 12. FIG. FIG. 13 is an explanatory diagram of the operation when performing spot welding using the welding electrode shown in FIGS. 10 to 12. FIG. FIG. 13 is an explanatory diagram of the operation when performing spot welding using the welding electrode shown in FIGS. 10 to 12. FIG.

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

1 to 9 show an overview of a spot welding method using an electrode according to an embodiment of the present invention.

As shown in FIG. 1, a spot welding machine 1 includes a welding gun 2 whose three-dimensional position is controlled by a robot (not shown). Welding gun 2 has an upper electrode 3 and a lower electrode 4. The upper electrode 3 and the lower electrode 4 are arranged facing each other on the same axis L, and the upper electrode 3 is moved forward and backward in the axial direction by a pressure actuator such as a cylinder. The spot welding machine 1 advances the upper electrode 3 to sandwich a stacked body 5 of a plurality of plates to be welded between it and the lower electrode 4 with a predetermined pressure, and then performs a predetermined weld between both electrodes. It is designed to conduct current.

The present invention is applied to the upper electrode 3, and the lower electrode 4 has a dome-like tip shape, which is a common shape.

2 to 6 show embodiment examples of the upper electrode 3. The upper welding electrode basically includes a first contact portion 31 located near the center of the tip surface and protruding in the axial direction, and a first contact portion 31 located at a distance in the radial direction from the first contact portion 31 and extending in the axial direction. The first contact portion 31 is provided with a second contact portion 32 that protrudes, and the first contact portion 31 is configured to protrude more than the second contact portion 32 in the axial direction.

In the embodiments shown in FIGS. 2 to 4, the first contact portion 31 is formed to protrude in a dome shape, and the second contact portion 32 surrounds the first contact portion 31 and protrudes in an annular shape.

In the form shown in FIG. 5, the first contact part 31 is formed in a protruding dome shape similar to the form shown in FIGS. It is formed to protrude in an arc with the center at .

In the form shown in FIG. 6, the first contact part 31 is formed in a protruding dome shape similar to the form shown in FIGS. 2 to 4, and the second contact part 32 is formed in an arc centered on the axis L. , are formed protrudingly at four locations spaced apart by 90 degrees.

An important point common to each of the above embodiments is that, as shown in a longitudinal section in FIG. This is the point.

Next, the operation of spot welding using the electrodes shown in FIGS. 2 to 4 will be described with reference to FIGS. 7 to 9.

Between the upper electrode 3 and the lower electrode 4, a stacked body 5 of three welded plates with a thin welded plate 51 disposed at the outermost position is arranged with the thin welded plate 51 facing upward. (FIG. 7), the upper electrode 3 is moved downward to sandwich the stacked body 5 between both electrodes, and the upper electrode 3 is pressed against the surface of the thin plate-like plate 51 with a constant pressure. Then, the first contact portion 31 of the upper electrode 3 sinks into the surface of the thin plate to be welded 51, and by applying a welding current at a predetermined timing, the first contact portion 31 of the upper electrode 3 sinks into the surface of the thin plate to be welded 51, and by applying a welding current at a predetermined timing, A molten part 6 is formed near the center of the film, and this molten part 6 grows in the entire thickness direction (FIG. 8). At the same time, the first contact portion 31 further sinks into the surface of the thin plate-like plate 51 to be welded, but eventually the second contact portion 32 also comes into contact with the surface of the thin plate-like plate 51 and sinks into the surface. At this time, a current path E is established between the molten part 6 and the second contact part 32, and the welding current flowing through this current path E causes the fusion part 6 to move toward the second contact part 32 to the outermost position. It grows until it reaches the thin plate-like plate 51 (FIG. 9). The nugget formed by solidifying the molten portion 6 that has grown in this way allows all the stacked plates to be welded, including the thin plate-shaped plate 51 at the outermost position, to be stacked and joined.

10 to 14 show other embodiments of the upper electrode 3. The upper electrode 3 basically includes a first contact portion 31 located near the center of the tip surface and protruding in the axial direction, and a first contact portion 31 located at a distance in the radial direction from the first contact portion 31 and protruding in the axial direction. The second contact portion 32 is the same as the above-described embodiment in that the second contact portion 32 is provided with a second contact portion 32 that protrudes from the second contact portion 32, but the second contact portion 32 is different from the first contact portion 31 in that the second contact portion 32 protrudes further in the axial direction.

In the embodiments shown in FIGS. 10 to 12, the first contact portion 31 is formed to protrude in a dome shape, and the second contact portion 32 surrounds the first contact portion 31 and protrudes in an annular shape.

In the form shown in FIG. 13, the first contact part 31 is formed in a protruding dome shape similar to the form shown in FIGS. It is formed to protrude in an arc with the center at .

In the form shown in FIG. 14, the first contact part 31 is formed in a protruding dome shape similar to the form shown in FIGS. 10 to 12, and the second contact part 32 forms an arc centered on the axis. They are formed protrudingly at four locations spaced apart by 90 degrees.

An important point common to each of the above embodiments is that, as shown in a longitudinal section in FIG. This is the point.

Next, the operation of spot welding using the electrodes shown in FIGS. 10 to 12 will be described with reference to FIGS. 15 to 17.

Between the upper electrode 3 and the lower electrode 4, a stacked body 5 of three welded plates with a thin welded plate 51 disposed at the outermost position is arranged with the thin welded plate 51 facing upward. Then, the upper electrode 3 is moved downward to sandwich the stacked body 5 between both electrodes (FIG. 15), and the upper electrode 3 is pressed against the surface of the thin plate-like plate 51 with a constant pressure. Then, the second contact portion 32 of the upper electrode 3 sinks into the surface of the thin plate to be welded 51, and by applying a welding current at a predetermined timing, the entire thickness direction of the stacked body 5 of the plates to be welded is A melted part 6 is formed near the center of the film, and this melted part 6 grows in the entire thickness direction (FIG. 16). At the same time, the second contact portion 32 further sinks into the surface of the thin plate-like plate 51 to be welded, but eventually the first contact portion 31 also comes into contact with the surface of the thin plate-like plate 51 and sinks into the surface. At this time, a current path E is established between the welding part 6 and the first contact part 31, and the welding current flowing through this current path E causes the welding part 6 to move toward the first contact part 31 to the outermost position. It grows until it reaches the thin plate-like plate 51 (FIG. 17). The nugget formed by solidifying the molten portion 6 that has grown in this way allows all the stacked plates to be welded, including the thin plate-shaped plate 51 at the outermost position, to be stacked and joined.

As explained above, in the case where the stacked body 5 of three or more welded plates with the thin welded plate 51 disposed at the outermost position is joined by spot welding, the upper electrode 3 according to each of the above embodiments is By using this, it is possible to avoid welding defects of the thin plate-shaped plate 51 at the outermost position without having to take measures such as complicatedly controlling the pressurizing force that would increase costs.

Of course, the present invention is not limited to the embodiments described above, and any changes within the scope of the claims are included within the scope of the present invention.

L Axis E Current path 1 Spot welder 2 Welding gun 21 Cylinder 3 Upper electrode 31 First contact portion 32 Second contact portion 33 Valley portion 4 Lower electrode 5 Overlapping body of welded plates 51 Thin plate to be welded 52 Welded plate Plate 53 Plate to be welded 6 Melted part

Claims (1)

A welding electrode that has an axis and is used for overlapping and joining multiple plates to be welded using a spot welding method,
A first contact portion located near the center of the tip surface and protruding in the axial direction, and a second contact portion located at a distance from the first contact portion in the axial direction and protruding in the axial direction, The welding electrode, wherein one of the first contact portion and the second contact portion protrudes more than the other in the axial direction.

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