JP2012096249A - One-side spot welding method - Google Patents

Abstract

Three or more metal plates are joined with sufficient strength by spot welding on one side.
A slit S that penetrates an upper metal plate 1 and an intermediate metal plate 2 is provided between a pair of electrodes 10 and 20, and the width of the slit 2 a of the intermediate metal plate 2 is set to be equal to the upper metal plate 1. By making it smaller than the width of the slit 1a, a step S0 is provided between the slit 1a and the slit 2a.
[Selection] Figure 1

Description

  The present invention relates to a one-side spot welding method, and more particularly to a one-side spot welding method for joining three or more metal plates.

  One-side spot welding is known as a method of welding a plurality of metal plates (for example, Patent Document 1). In one-side spot welding, a pair of electrodes are brought into contact with one surface of a plurality of stacked metal plates and energized, and the metal plates are heated by resistance heat generated by this energization, and the metal plates are bonded to each other by the applied pressure of the electrodes. By pressing, metal plates are joined together. As described above, the one-side spot welding can be suitably performed by bringing the electrode into contact with only one surface of the overlapped metal plates, and therefore is suitably applied when the electrode cannot be accessed on the other surface.

JP 2002-239742 A

  However, in one-side spot welding, most of the current flows through the metal plate with the pair of electrodes in contact with each other, and only a small amount of current can flow through the other metal plate. There is a possibility that it cannot be joined.

  The present applicant has proposed single-side spot welding as shown in FIG. 4 in Japanese Patent Application No. 2010-42121. In this method, a slit 101a that penetrates the upper metal plate 101 is provided between the pair of electrodes 110 and 120, and the energization is performed by bypassing the slit 101a, whereby the path of the energization path L1 that passes through the upper metal plate 101. The length is long. As a result, the energization resistance of the energization path L <b> 1 is increased, and a current flows relatively easily through the energization path L <b> 2 that passes through the lower metal plate 102, so that a sufficient current flows through the joint P.

  When there are two metal plates, they can be joined by one-side spot welding by providing the slits as described above. However, when there are three or more metal plates, a metal plate that is far from the electrodes, especially the electrodes are brought into contact. Since it becomes difficult for current and heat to be transmitted to the metal plate on the surface opposite to the surface, there are cases where bonding cannot be performed simply by providing a slit. When joining the three metal plates 101, 102, and 103 shown in FIG. 5 by one-side spot welding, the inventors connect the upper metal plate 101 and the intermediate metal plate 102 between the pair of electrodes 110 and 120. Passing slits 101a and 102a having the same width were provided to verify the quality of the bonded state. As a result, the upper metal plate 101 and the intermediate metal plate 102 are bonded with sufficient strength (the bonding portion is indicated by P), but the intermediate metal plate 102 and the lower metal plate 103 are not bonded. It was.

  A technical problem to be solved by the present invention is to join three or more metal plates with sufficient strength by one-side spot welding.

  When the metal plates of the three metal plates are joined by one-side spot welding by trial and error of the present inventors, the width of the slit 2a formed in the intermediate metal plate 2 is set to the upper side as shown in FIG. It has been found that the three metal plates 1, 2, 3 can be firmly joined by making the step S 0 between the slits 1 a, 2 a smaller than the width of the slit 1 a formed in the metal plate 1. The reason why the junction Q is formed in this way is that the step S0 is provided so that the energization path L3 from the electrodes 10 and 20 to the lower metal plate 3 avoids the junction P having a large energization resistance and is on the slit side. It can be assumed that a sufficient current flows through the lower metal plate 3 due to this.

  From this, when joining three or more metal plates by one-side spot welding, by reducing the width of the slit toward the other side and providing a step between the slits formed in the adjacent metal plates, all It can be said that the metal plate can be firmly joined. That is, the present invention is a one-side spot welding method in which a pair of electrodes are brought into contact with a metal plate on one surface among three or more stacked metal plates and are energized to join these metal plates. In addition, by providing a slit that passes through all the metal plates except the metal plate on the surface on the other side between the pair of electrodes, and by reducing the width of the slit toward the other side, adjacent metal at least in the vicinity of the electrode It can be characterized as a one-side spot welding method characterized by providing a step between the slits formed in the plate.

  When the three metal plates joined by the above method were observed, as shown in FIG. 1, the intermediate metal plate 2 and the lower metal plate 2 were lower than the joint P between the upper metal plate 1 and the intermediate metal plate 2. The joint Q with the side metal plate 3 was closer to the slit S. This is probably because the energization path L3 passing through the lower metal plate 3 is provided on the slit side while avoiding the joint portion P as described above.

  As described above, according to the one-side spot welding method of the present invention, it is possible to firmly join three or more metal plates.

It is sectional drawing of the three metal plates joined by the one side spot welding method which concerns on one Embodiment of this invention. It is a top view of the said 3 metal plate. It is sectional drawing of the four metal plates joined by the one-side spot welding method which concerns on other embodiment of this invention. It is the (a) top view and (b) sectional view of two metal plates joined by the single side spot welding method shown by the previous application. It is sectional drawing which shows the state which formed the slit of uniform width in the upper two metal plates among three metal plates.

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

  FIG. 1 shows three metal plates 1, 2, 3 joined by a one-side spot welding method according to an embodiment of the present invention and electrodes 10, 20 used for welding. In the following, in order to facilitate understanding of the relative positional relationship between the members, description will be given using the vertical direction of FIG.

  Each of the electrodes 10 and 20 used in the present embodiment has a circular flat surface and a tapered surface whose diameter is increased upward from the flat surface at the tip. The shape of the electrode is not limited to this, and for example, the tip may be spherical.

  The upper metal plate 1 and the intermediate metal plate 2 are previously formed with slits S penetrating them. The slit S includes a slit 1 a formed in the upper metal plate 1 and a slit 2 a formed in the intermediate metal plate 2. The slit S is provided between the pair of electrodes 10 and 20 and extends in a direction orthogonal to the direction connecting the electrodes 10 and 20 (see FIG. 2).

  The slit 2 a of the intermediate metal plate 2 has a smaller width in the direction connecting the pair of electrodes 10 and 20 than the slit 1 a of the upper metal plate 1. Thereby, the intermediate metal plate 2 protrudes from the edge of the slit 1a of the upper metal plate 1 toward the center side in the slit width direction, and a step S0 is formed between the slit 1a and the slit 2a. In the present embodiment, as shown in FIG. 2, a slit 2a that is slightly smaller than the slit 1a is formed, and an annular step S0 is formed between the slit 1a and the slit 2a.

  The one-side spot welding method of this embodiment is performed as follows. First, the pair of electrodes 10 and 20 is brought into contact with the metal plate on one surface (the upper metal plate 1) of the stacked metal plates 1, 2, and 3. Specifically, a pair of electrodes 10 and 20 are brought into contact with both sides of the slit S in the upper metal plate 1. Then, the electrodes 10 and 20 are energized between the electrodes 10 and 20 in a state where the three metal plates 1, 2 and 3 are pressurized from above.

  The current that flows between the pair of electrodes 10 and 20 flows roughly through the three energization paths L1, L2, and L3. The first energization path L1 is an energization path that mainly flows through the upper metal plate 1. The second energization path L <b> 2 is an energization path that mainly flows through the intermediate metal plate 2 via the upper metal plate 1. The third energization path L3 is an energization path that mainly flows through the lower metal plate 3 via the upper metal plate 1 and the intermediate metal plate 2.

  As described above, since the slits S (slit 1a and slit 2a) are provided between the electrodes 10 and 20, the first energization path L1 passing through the upper metal plate 1 is slit as shown in FIG. It is formed around 1a. Similarly, the second energization path L2 flowing through the intermediate metal plate 2 is formed around the slit 2a. Thus, since the path lengths of the first energization path L1 and the second energization path L2 are increased by forming the slits 1a and 2a, the path length of the third energization path L3 is relatively shortened, and the lower side An electric current easily flows through the metal plate 3.

  In the present embodiment, as shown in FIG. 1, the slit 2a of the intermediate metal plate 2 is made smaller than the slit 1a of the upper metal plate 1, and a step S0 is formed between the slit 1a and the slit 2a. Since the intermediate metal plate 2 protrudes from the edge of the slit 1a of the upper metal plate 1 to the center side in the slit width direction, the third current-carrying path L3 includes the upper metal plate 1 and the intermediate metal plate 2 It is provided on the slit S side avoiding the joint P. The joining portion P has a high resistance due to high temperature due to heating and pressure bonding. However, the joining portion P flows to the lower metal plate 3 by forming the third conduction path L3 while avoiding the joining portion P. The amount of current can be increased.

  As described above, sufficient current flows through the second energization path L2 and the third energization path L3, so that the joints P and Q are formed below the electrodes 10 and 20, respectively, and the three metal plates 1, 2, and 3 are formed. Strongly joined. At this time, the joint portion Q between the intermediate metal plate 2 and the lower metal plate 3 is not directly below the joint portion P between the upper metal plate 1 and the lower metal plate 2 but is slit more than the joint portion P. It is formed at a position biased toward the S side.

  As shown in FIG. 1, the electrodes 10 and 20 are brought into contact with the metal plate 1 at a position as close as possible to the slit S, thereby forming the first and second energization paths L1 and L2 by forming the slit S. The difference in path length with the third energization path L3 is increased, and the amount of current flowing through the lower metal plate 3 can be increased. In addition, by bringing the electrodes 10 and 20 close to the slit S and forming the joints P and Q in the immediate vicinity of the slit S, particularly when the metal plates 1, 2 and 3 are curved, the joints P and A situation in which a gap is formed between the metal plates on the slit S side with respect to Q can be prevented.

  The joints P and Q are joined by so-called solid-phase joining in which the contact portions of adjacent metal plates are joined in a solid state by heating and pressure bonding. According to the solid phase bonding, the amount of current is sufficient to soften the contact portion between the metal plates, and therefore it is easy to bond even at a location where current is difficult to flow, such as the third energization path L3. On the other hand, when a part of adjacent metal plates is melted and solidified to form a nugget and the metal plates are joined to each other via the nugget, it is necessary to completely melt the contact portion between the metal plates. Therefore, it is necessary to increase the amount of current flowing between the electrodes. For this reason, the amount of current flowing through the metal plate that is in direct contact with the electrode becomes excessive, and there is a risk of generation of dust and falling off of the metal plate. Therefore, in particular, when three or more metal plates are joined by one-side spot welding, the current amount is set so that adjacent metal plates, particularly metal plates at positions away from the electrodes, are joined by solid phase joining. It is preferable to set an energization pattern.

  The present invention is not limited to the above embodiment. For example, although the case where three metal plates are joined is shown in the above embodiment, the one-side spot welding method of the present invention can be applied to the case where four or more metal plates are joined. For example, as shown in FIG. 3, when four metal plates 1 to 4 are joined, a slit S that penetrates the upper three metal plates 1 to 3 is formed. The slit S is formed so that the slit width narrows downward, and specifically, the width W1 of the slit 1a of the uppermost metal plate 1 and the width of the slit 2a of the metal plate 2 adjacent to the lower side thereof. W2 and the width W3 of the slit 3a of the metal plate 3 adjacent to the lower side thereof are formed such that W1> W2> W3. Thereby, the metal plate 2 adjacent to the lower side from the edge of the slit 1a of the uppermost metal plate 1 protrudes toward the center side in the slit width direction, and a step S0 is formed between the slit 1a and the slit 2a. Similarly, the metal plate 3 adjacent to the lower side from the edge of the slit 2a of the metal plate 2 protrudes toward the center side in the slit width direction, and a step S0 is formed between the slit 2a and the slit 3a. When the pair of electrodes 10 and 20 are brought into contact with the uppermost metal plate 1 and are energized while being pressed downward, joints P, Q, and R are formed below the electrodes 10 and 20, respectively. The plates 1 to 4 are firmly joined. At this time, the joints P, Q, and R are arranged on the slit S side toward the lower side, specifically, the joint Q is arranged on the slit S side of the joint P, and further on the slit S side of the joint Q. A joint R is disposed.

  In the above embodiment, the electrodes 10 and 20 both function as welding electrodes, and a joint portion is formed below each electrode. However, the present invention is not limited to this. For example, one electrode may be a welding electrode. And the other electrode may function as a ground electrode, and a joint may be formed only below the welding electrode (not shown). In this case, the step S0 formed in the slit S may be formed only on the welding electrode side, and the edge of the slit S on the ground electrode side may be flush. Of course, similar to the above embodiment, a step may be provided on both electrodes on the inner surface of the slit S.

  Further, in the above embodiment, the case where the step S0 is formed on the entire inner periphery of the slit S is shown, but it is not always necessary to provide the step on the entire periphery, and at least in the vicinity of the electrodes 10 and 20, Specifically, it is only necessary that the step S0 is formed in a cross section (cross section in FIGS. 1 and 3) including at least the contact portion between the electrodes 10 and 20 and the metal plate.

1, 2, 3 Metal plates 1a, 2a Slit 10, 20 Electrodes L1, L2, L3 Current path P, Q Junction S Slit S0 Step

Claims (1)

Among the three or more stacked metal plates, a one-side spot welding method for joining the three or more metal plates by energizing a pair of electrodes in contact with a metal plate on one surface,
Provided between the pair of electrodes is a slit penetrating all the metal plates except the metal plate on the other surface, and by reducing the width of the slit toward the other side, adjacent metal plates at least in the vicinity of the electrodes A one-side spot welding method, wherein a step is provided between the slits formed on the substrate.

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