One-sided spot weld 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

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

Background Art

[0002] As a spot welding method, direct spot welding is often used, in which the overlapping portion of a plurality of metal plates is sandwiched between a pair of electrodes and energized. 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 into 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 bringing the ground electrode 140 into contact 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

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the case of one-sided spot welding, since the planned joining portion P is pressed only from above by the welding electrode 130 without being supported from below, the planned joining portion P and its surroundings are likely to be deformed, and when the metal plate is thin, the amount of deformation becomes particularly large. For example, when the width W (see FIG. 8) of the overlapping portion 103 provided with the planned joining portion P is small, as exaggeratedly shown in FIG. 9, the upper plate 102 is pushed downward by the welding electrode 130, and further, the lower plate 101 is pushed downward by the edge 102a of the upper plate 102, so that the edge 101a of the lower plate 101 is greatly separated from the upper plate 102. As a result, the gap between the lower plate 101 and the upper plate 102, specifically, the maximum gap in the region R directly below the welding electrode 130 (hereinafter referred to as "weeping separation gap amount δ") becomes large, and welding defects are likely to occur.

[0006] Therefore, an object of the present invention is to suppress the weeping separation gap amount and prevent welding defects when performing one-sided spot welding.

Means for Solving the Problems

[0007] In order to solve the above problems, the present invention provides a one-sided spot welding method in which welding is performed by energizing while pressing a planned joining portion provided in the vicinity of the edge of the first metal plate only from the side of the second metal plate with an electrode in a overlapping portion of the first metal plate and the second metal plate. A one-sided spot welding method is provided in which a bead is provided in a region of the first metal plate opposite to the edge with respect to the planned joining portion.

[0008] Thus, in the present invention, a bead is provided in a region of the first metal plate (the metal plate that does not contact the electrode) opposite to the edge with respect to the planned joining portion, that is, in a region where bending occurs when pressed from the side of the second metal plate with an electrode, and the rigidity of this region is increased. 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 with an electrode from the side of the second metal plate, the first metal plate is less likely to bend, so that the weeping separation gap amount becomes small and it becomes easier to obtain a desired nugget diameter.

[0009] When beads extending in the direction along the edge are provided on the first metal plate, the rigidity in that direction is increased, so that the bending of the first metal plate in the cross-section in that direction can be suppressed. Further, when beads extending in the direction intersecting the edge are provided on the first metal plate, the rigidity in that direction is increased, so that the bending of the first metal plate in the cross-section in that direction can be suppressed. Further, if first beads and second beads intersecting each other are provided in the region of the first metal plate on the side opposite to the edge with respect to the planned joining portion, the rigidity in all directions of this region can be increased.

[0010] When component mounting holes are provided in the region of the first metal plate on the side opposite to the edge with respect to the planned joining portion, a load is applied to the periphery of the component mounting holes due to the self-weight of the components attached to the component mounting holes. Therefore, it is preferable to extend the above-described beads for reinforcing the periphery of the planned joining portion to the vicinity of the component mounting holes, and reinforce the periphery of the component mounting holes with these beads. Specifically, it is preferable to extend the beads to the side of the component mounting holes rather than the center of the line connecting the planned joining portion and the component mounting holes.

Advantages of the Invention

[0011] As described above, according to the present invention, when performing one-sided spot welding in the vicinity of the edge of the first metal plate among the overlapping portions of the plurality of metal plates, the deformation of the first metal plate is suppressed, so that the weeping gap amount is reduced and welding defects can be prevented.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

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Figure 6

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Figure 8

Figure 9

Embodiments for Carrying Out the Invention

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

[0014] FIG. 1 shows a lower plate 1 as a first metal plate constituting a part (lower back) of an automobile body and an upper plate 2 as a second metal plate (shown by a dotted line in FIG. 1). Bonding planned portions P1 and P2 are provided at the overlapping portion of the lower plate 1 and the upper plate 2. In the illustrated example, the width W of the overlapping portion (the distance between the edge 1a of the lower plate 1 and the edge 2a of the upper plate 2) is small, and the bonding planned 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 a metal plate with which the welding electrode 10 (see FIG. 2) comes into contact, and the lower plate 1 is a metal plate with which the welding electrode 10 does not come into contact, and it is not intended to limit the posture when these metal plates are assembled to the vehicle body. Further, in the following description, the direction along the edge 1a of the lower plate 1 is referred to as the X direction, and in the direction along the surface of the lower plate 1, the direction substantially orthogonal to the edge 1a, specifically, the longitudinal direction of the surface of the lower plate 1 where the bonding planned portions P1 and P2 are provided is referred to as the Y direction (see FIG. 1).

[0015] As shown in FIG. 2, a third metal plate 3 is provided below the bonding planned portions P1 and P2 via a space Q. Since the third metal plate 3 is not provided with a through hole for inserting an electrode, the electrode cannot be brought into contact with the bonding planned portions P1 and P2 from below. As a welding method for such bonding planned portions P1 and P2, indirect spot welding as an 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 than 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] 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 other than the planned joining portions P1 and P2 (the third metal plate 3 in the illustrated example) of the above workpiece (see FIG. 2). Then, the planned joining portion P1 is pressed from above by 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, by providing beads 4 and 5 in the region of the lower plate 1 on the side opposite to the edge 1a in the Y direction with respect to the planned joining portion P1, the rigidity of this region is increased. Specifically, since the X-direction rigidity of the above region of the lower plate 1 is increased by the first bead 4 extending in the X direction, in the X-direction cross section shown in FIGS. 2 and 3, the downward pushing and bending of the X-direction intermediate portion of the lower plate 1 is suppressed. Further, since the Y-direction rigidity of the above region of the lower plate 1 is increased by the second bead 5 extending in the Y direction, in the Y-direction cross section shown in FIGS. 4 and 5, the downward pushing and bending of the vicinity of the edge 1a of the lower plate 1 is suppressed. As described above, by suppressing the bending of the lower plate 1 in the X direction and the Y direction, the lower plate 1 is less likely to separate from the upper plate 2, and the weeping gap amount between the two metal plates 1 and 2 is suppressed.

[0020] In this embodiment, in addition to the above beads 4 and 5, a plurality of recesses 6 are provided in the region of the lower plate 1 including the edge 1a. Thereby, since the rigidity of the region of the lower plate 1 on the edge 1a side rather than the planned joining portions P1 and P2 is increased, the deformation in the vicinity of the edge 1a when the planned joining portion P1 is pressed by the welding electrode 10 is suppressed, and the weeping gap amount between the metal plates 1 and 2 is further suppressed.

[0021] In this way, with the welding electrode 10 pressing the planned joining portion P1 downward, by energizing between the electrodes 10 and 20, a current flows through the current path of welding electrode 10 → upper plate 2 → planned joining portion P1 → lower plate 1 → third metal plate 3 → ground electrode 20. Thereby, a nugget is formed in the planned joining portion P1, and the lower plate 1 and the upper plate 2 are joined via this nugget. At this time, as described above, since the bending of the lower plate 1 is suppressed and the weeping gap amount between the lower plate 1 and the upper plate 2 is suppressed, it becomes easier to obtain a desired nugget diameter.

[0022] Thereafter, with the ground electrode 20 still in contact with the third metal plate 3, the welding electrode 10 is moved to press the planned joining portion P2 (see the dotted line in FIG. 2), and in this state, energization is performed between the electrodes 10 and 20 to form a nugget in the planned joining portion P2. Thus, in indirect spot welding, a plurality of planned joining portions can be welded without moving the ground electrode 20.

[0023] Incidentally, a component mounting portion 7 for attaching other components (such as a bumper) is provided on the lower plate 1 of the workpiece shown in FIG. 1. In the illustrated example, the second bead 5 provided on the lower plate 1 extends from the vicinity of the joining planned portions P1 and P2 to the vicinity of the component mounting portion 7 in the Y direction. Specifically, the second bead 5 extends to the side of the component mounting portion 7 rather than the center of the line connecting the joining planned portions P1 and P2 and the component mounting portion 7 (in the illustrated example, the central portion in the Y direction between the centers of the joining planned portions P1 and P2 and the component mounting portion 7). Thereby, since the vicinity of the component mounting portion 7 can be reinforced by the second bead 5 that reinforces the vicinity of the joining planned portions P1 and P2, deformation of the lower plate 1 due to the weight of other components attached to the component mounting portion 7 can be suppressed.

[0024] The present invention is not limited to the above-described embodiment. Hereinafter, other embodiments of the present invention will be described, but redundant descriptions of the same points as those in the above-described embodiment will be omitted.

[0025] Of the first bead 4 and the second bead 5 provided on the lower plate 1, one of them may be omitted. Also, the recess 6 provided at the edge 1a of the lower plate 1 may be omitted. Further, the number of the beads 4 and 5 and the recess 6 provided on the lower plate 1 may be different from those in the above-described embodiment.

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

[0027] The present invention is not limited to the vehicle body of an automobile, and can be applied regardless of the use of the component as long as one-sided spot welding is performed in the vicinity of the edge of the lower plate among the polymerized portions of the metal plates.

Explanation of Reference Numerals

[0028] 1 Lower plate (first metal plate) 2 Upper plate (second metal plate) 3 Third metal plate 4 First bead 5 Second bead 6 Concave portion 7 Component mounting portion 10 Welding electrode 20 Ground electrode P1, P2 Portions to be joined δ Tear separation gap

Claims

[Claim 1] A one-side spot welding method for welding a joint to be provided in an overlapping portion between a first metal plate and a second metal plate, the joint being provided near an edge of the first metal plate, by passing current through the overlapping portion while pressing the overlapping portion with an electrode only from the second metal plate side, A one-side spot welding method, in which a bead is provided in a region of the first metal plate opposite the edge with respect to the intended joining portion.

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