Single-sided spot welding method

Abstract

To provide a one-sided spot weld method which reduces amount of parting gap to prevent poor weld.SOLUTION: A one-sided spot weld method welds a planned weld zone P1 through energization while pressing down the planned weld zone P1 in the vicinity of an edge 1a of a lower plate 1 only from an upper plate 2 side by an electrode 10 among an overlapped part between the lower plate 1 and the upper plate 2. Beads 4, 5 are arranged in regions opposite to the edge 1a relative to the planned weld zone P1 in the lower plate 1.SELECTED DRAWING: Figure 1

Description

Technical Field

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[0001] The present invention relates to a one-sided spot welding method.

Background Art

[0002] As a spot welding method, direct spot welding in which a plurality of overlapping portions of metal plates are sandwiched between a pair of electrodes and energized is often used. However, as shown in FIG. 6, when the planned joining portion P provided in the overlapping portion 103 of the lower plate 101 and the upper plate 102 is covered with a metal plate 104 having a hat-shaped cross section, the planned joining portion P cannot be sandwiched between a pair of electrodes 110 and 120. For example, as shown in FIG. 7, if a through hole 105 is formed in the metal plate 104 having a hat-shaped cross section and the electrode 120 is inserted through this through hole 105, the planned joining portion P can be sandwiched from both sides in the thickness direction by a pair of electrodes 110 and 120. However, when a through hole 105 is formed in the metal plate 104 having a hat-shaped cross section, the rigidity of this metal plate 104 decreases, so it is necessary to increase the wall thickness or form it with a high-strength material, resulting in high costs.

[0003] Therefore, when welding such a part, "one-sided spot welding" in which current is passed with an electrode pressed against only one side in the thickness direction of the planned joining portion may be applied (see, for example, Patent Document 1). Specifically, as shown in FIG. 8, while pressing the planned joining portion P from above with the welding electrode 130 and contacting the ground electrode 140 with another part of the workpiece, current is passed between the two electrodes 130 and 140 to weld the planned joining portion P.

Prior Art Documents

Patent Documents

[0006] Therefore, the present invention aims to prevent welding defects by reducing the amount of gap when performing spot welding on one side. [Means for solving the problem]

[0007] To solve the above problems, the present invention provides a one-sided spot welding method in which welding is performed by applying current while pressing an electrode with the joint portion located near the edge of the first metal plate in the overlapping portion of the first metal plate and the second metal plate from only the second metal plate side, The present invention provides a one-sided spot welding method in which a bead is provided in the region of the first metal plate opposite to the edge with respect to the portion to be joined.

[0008] Thus, in this invention, a bead is provided in the region of the first metal plate (the metal plate that does not come into contact with the electrode) that is opposite to the edge of the planned joining area, that is, the region in which deflection occurs when pressed from the second metal plate side with the electrode, thereby increasing the rigidity of this region. As a result, when the vicinity of the edge of the first metal plate in the overlapping portion of the two metal plates is pressed from the second metal plate side with the electrode, the first metal plate becomes less likely to deflect, reducing the separation gap and making it easier to obtain the desired nugget diameter.

[0009] By providing a bead extending along the edge of the first metal plate, the rigidity in that direction is increased, thereby suppressing the curvature of the first metal plate in the cross-section in that direction. Furthermore, by providing a bead extending in a direction intersecting the edge of the first metal plate, the rigidity in that direction is increased, thereby suppressing the curvature of the first metal plate in the cross-section in that direction. In addition, by providing a first bead and a second bead intersecting each other in the region of the first metal plate opposite the edge to the planned joining portion, the rigidity in all directions of this region can be increased.

[0010] If a component mounting hole is provided in the first metal plate in the region opposite to the edge of the planned joint, the weight of the component attached to this mounting hole will apply a load to the area around the mounting hole. Therefore, it is preferable to extend the bead that reinforces the area around the planned joint to the vicinity of the component mounting hole, thereby reinforcing the area around the component mounting hole as well. Specifically, it is preferable to extend the bead to the side of the component mounting hole beyond the midpoint of the line connecting the planned joint and the component mounting hole. [Effects of the Invention]

[0011] As described above, according to the present invention, when performing one-sided spot welding near the edge of the first metal plate in the overlapping portion of multiple metal plates, deformation of the first metal plate is suppressed, so that the gap between the plates becomes smaller and welding defects can be prevented. [Brief explanation of the drawing]

[0012] [Figure 1] This is a plan view of a workpiece to which a one-sided spot welding method according to one embodiment of the present invention is applied. [Figure 2] This is a cross-sectional view in the X direction along line II-II in Figure 1. [Figure 3] This is a cross-sectional view in the X direction along line III-III in Figure 1. [Figure 4] This is a cross-sectional view in the Y direction along the line IV-IV in Figure 1. [Figure 5] This is a cross-sectional view in the Y direction along the VV line in Figure 1. [Figure 6]This is a cross-sectional view of a workpiece having a metal plate with a hat-shaped cross-section. [Figure 7] This is a cross-sectional view showing how direct spot welding is performed on a metal plate with a hat-shaped cross-section by creating through holes. [Figure 8] This is a cross-sectional view showing the process of indirect spot welding being performed on a workpiece having a metal plate with a hat-shaped cross-section. [Figure 9] This is an enlarged cross-sectional view of the overlapping portion of the lower and upper plates in Figure 8 when pressed with an electrode. [Modes for carrying out the invention]

[0013] Hereinafter, embodiments of the present invention will be described based on the drawings.

[0014] Figure 1 shows a lower plate 1 as a first metal plate and an upper plate 2 (shown as a dotted line in Figure 1) as a second metal plate that constitute a part of the car body (lower back). Joining portions P1 and P2 are provided at the overlapping portion between the lower plate 1 and the upper plate 2. In the illustrated example, the width W of the overlapping portion (distance between the edge 1a of the lower plate 1 and the edge 2a of the upper plate 2) is small, and the joining portions P1 and P2 are provided near the edge 1a of the lower plate 1 and the edge 2a of the upper plate 2. Note that the upper plate 2 is the metal plate that the welding electrode 10 (see Figure 2) contacts, and the lower plate 1 is the metal plate that the welding electrode 10 does not contact, and this is not intended to limit the orientation of these metal plates when they are assembled to the car body. Furthermore, in the following explanation, the direction along the edge 1a of the lower plate 1 is referred to as the X direction, and the direction along the surface of the lower plate 1 that is approximately perpendicular to the edge 1a, specifically the longitudinal direction of the surface of the lower plate 1 where the planned joint portions P1 and P2 are provided, is referred to as the Y direction (see Figure 1).

[0015] As shown in Figure 2, a third metal plate 3 is provided below the planned joining portions P1 and P2, with a space Q in between. Since the third metal plate 3 does not have through holes for inserting electrodes, it is not possible to bring the electrodes into contact with the planned joining portions P1 and P2 from below. As a welding method for such planned joining portions P1 and P2, indirect spot welding, which is one embodiment of the one-sided spot welding according to the present invention, is applied.

[0016] In the lower plate 1, beads are provided in a region on the opposite side of the edge 1a in the Y direction with respect to the planned joining portions P1 and P2 (in FIG. 1, the region lower left of the planned joining portions P1 and P2) (see FIG. 1). A bead is an elongated convex portion (a concave portion when viewed from the opposite side) formed on the lower plate 1 by bending or drawing. In the present embodiment, a plurality of beads extending in directions intersecting each other are provided on the lower plate 1. Specifically, a first bead 4 extending in the X direction and a second bead 5 extending in a direction intersecting the X direction (the Y direction in the illustrated example) are provided on the lower plate 1. In the illustrated example, the first bead 4 and the second bead 5 are continuously formed integrally, and the top surfaces of both beads 4 and 5 are provided on the same plane (see FIGS. 1 and 4). In the illustrated example, a plurality of (two in the illustrated example) second beads 5 are provided (see FIGS. 1 and 3).

[0017] [[ID= 5]] In the region of the lower plate 1 including the edge 1a, a plurality of recesses 6 spaced apart in the X direction are formed (see FIGS. 1, 2, and 5). The region 8 between the plurality of recesses 6 in the X direction and the region 9 between the plurality of recesses 6 and the first bead 4 in the Y direction are provided on the same plane, and the planned joining portions P1 and P2 are provided on this plane (see FIG. 1). In the illustrated example, the planned joining portions P1 and P2 are provided in the region 8 between the plurality of recesses 6 in the X direction.

[0018] When welding the planned joining portions P1 and P2, first, the ground electrode 20 is brought into contact with a portion of the above workpiece other than the planned joining portions P1 and P2 (the third metal plate 3 in the illustrated example) (see FIG. 2). Then, the planned joining portion P1 is pressed from above with the welding electrode 10 shown by the solid line. Due to the pressing force of the welding electrode 10 at this time, the overlapping portion of the lower plate 1 and the upper plate 2 is pushed downward and deformed.

[0019] In this embodiment, as described above, beads 4 and 5 are provided on the lower plate 1 in the region opposite to the edge 1a in the Y direction from the planned joining portion P1, thereby increasing the rigidity of this region. Specifically, the first bead 4 extending in the X direction increases the rigidity of the region of the lower plate 1 in the X direction, so that the middle portion of the lower plate 1 in the X direction shown in the cross-section in the X direction in Figures 2 and 3 is suppressed from being pushed down and bending. Also, the second bead 5 extending in the Y direction increases the rigidity of the region of the lower plate 1 in the Y direction, so that the area near the edge 1a of the lower plate 1 is suppressed from being pushed down and bending in the cross-section in the Y direction shown in Figures 4 and 5. As described above, by suppressing the bending of the lower plate 1 in the X and Y directions, the lower plate 1 becomes less likely to separate from the upper plate 2, and the gap between the two metal plates 1 and 2 is reduced.

[0020] In this embodiment, in addition to the beads 4 and 5 described above, the lower plate 1 is provided with a plurality of recesses 6 in the region including the edge 1a. As a result, the rigidity of the region of the lower plate 1 closer to the edge 1a than the planned joining portions P1 and P2 is increased, thereby suppressing deformation near the edge 1a when the planned joining portion P1 is pressed with the welding electrode 10, and further reducing the gap between the metal plates 1 and 2.

[0021] With the welding electrode 10 pushing the joint P1 downwards, current is passed between electrodes 10 and 20, causing current to flow through the path: welding electrode 10 → upper plate 2 → joint P1 → lower plate 1 → third metal plate 3 → ground electrode 20. This forms a nugget on the joint P1, and the lower plate 1 and upper plate 2 are joined via this nugget. At this time, as described above, the curvature of the lower plate 1 is suppressed, and the gap between the lower plate 1 and upper plate 2 is reduced, making it easier to obtain the desired nugget diameter.

[0022] Subsequently, while the ground electrode 20 remains in contact with the third metal plate 3, the welding electrode 10 is moved to press against the planned joining area P2 (see dotted line in Figure 2), and in this state, current is passed between electrodes 10 and 20 to form a nugget on the planned joining area P2. In this way, indirect spot welding allows welding of multiple planned joining areas without moving the ground electrode 20.

[0023] Incidentally, the lower plate 1 of the workpiece shown in Figure 1 is provided with a component mounting section 7 for attaching other parts (for example, a bumper). In the illustrated example, the second bead 5 provided on the lower plate 1 extends from the vicinity of the planned joining sections P1 and P2 to the vicinity of the component mounting section 7 in the Y direction. Specifically, the second bead 5 extends further towards the component mounting section 7 than the center of the line connecting the planned joining sections P1 and P2 and the component mounting section 7 (in the illustrated example, the Y-direction center between the planned joining sections P1 and P2 and the center of the component mounting section 7). As a result, the vicinity of the component mounting section 7 can be reinforced by the second bead 5 that reinforces the vicinity of the planned joining sections P1 and P2, thereby suppressing deformation of the lower plate 1 due to the weight of other parts attached to the component mounting section 7.

[0024] The present invention is not limited to the embodiments described above. Other embodiments of the present invention will be described below, but redundant explanations of points similar to those described above will be omitted.

[0025] One of the first bead 4 and the second bead 5 provided on the bottom plate 1 may be omitted. Also, the recess 6 provided on the edge 1a of the bottom plate 1 may be omitted. Furthermore, the number of beads 4, 5 and recess 6 provided on the bottom plate 1 may differ from that of the above embodiment.

[0026] The present invention is not limited to indirect spot welding, but can also be applied to series spot welding. For example, the planned joining parts P1 and P2 shown in Figure 2 may be joined simultaneously by pressing them from above with a pair of electrodes 10, shown by solid and dotted lines, and then applying current between these electrodes. In this case, the ground electrode 30 is not required.

[0027] This invention is not limited to automobile bodies, but can be applied to any part regardless of its intended use, as long as spot welding is performed on one side near the edge of the lower plate in the overlapping portion of metal plates. [Explanation of Symbols]

[0028] 1. Bottom plate (first metal plate) 2. Upper plate (second metal plate) 3. Third metal plate 4. First bead 5. The second bead 6 recesses 7. Parts mounting section 10 Welding electrodes 20 Ground electrode P1, P2 planned joint area δ Separation gap

Claims

[Claim 1] In a one-sided spot welding method in which a planned joining portion, located near the edge of the first metal plate, is applied to the overlapping portion of a first metal plate and a second metal plate by applying current while pressing the portion with an electrode only from the second metal plate side, A one-sided spot welding method in which, of the first metal plate, a plurality of beads extending in directions that intersect each other are provided in the region opposite to the edge with respect to the planned joining portion.

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