JP6090910B2 - Spot welding method - Google Patents

Description

  The present invention relates to a spot welding apparatus.

  As is well known, an automobile body is constituted by joining a plurality of steel plates by welding. As the welding method, direct spot welding using a C-type gun is generally employed from the viewpoint of cost and productivity, and most of the welds are formed by this direct spot welding. However, direct spot welding is a construction method in which a steel plate is energized while being pressed and clamped from both sides by a pair of electrodes of a C-type gun to form a welded portion, so that a hat-shaped section is formed on the steel plate on one side. A portion where the steel plate cannot be sandwiched cannot be welded, and there are some restrictions on the portion where the weld is formed.

  As a welding method in such a case, there is one-side spot welding. One-side spot welding is a method in which a pair of electrodes are pressed and abutted against one surface of a plurality of superposed steel plates, and a weld is formed on the steel plate by this energization heat generation. Spot welding is possible even in the case where the shape portion is formed. In recent years, this one-side spot welding has become one of the welding methods frequently used in the production of automobile bodies from the viewpoint of accessibility. Patent document 1 and patent document 2 show the technique of the preceding one side spot welding.

  For example, in Patent Document 1, by providing a seating surface at a welding position on one surface of a plurality of steel plates to be overlapped, welding is performed by concentrating current by limiting contact points between the steel plates at the welding position. Techniques to do this are disclosed.

  In Patent Document 2, when a plurality of steel plates are overlapped and one-side spot welding is performed, the current amount becomes non-uniform due to the difference in the length of the current path flowing through each steel plate, resulting in poor welding. The technique made to do is disclosed. That is, among a plurality of superposed steel plates, a slit that penetrates all the steel plates except the steel plate on the other side surface is provided between a pair of electrodes that contact the steel plate on one side surface, and the width of the slit is set to the other side. A step is provided in the slit by making it smaller toward the side. In steel plates with slits, electricity is conducted avoiding these slits, so that sufficient current can be passed to steel plates that do not have slits with the longest conduction path, causing poor welding between these steel plates. It is possible to weld without.

JP 2002-239742 A JP2012-096249A

  By the way, in the field of manufacturing automobile bodies, high-strength steel plates are often incorporated into the steel plate assembly constituting the vehicle body in order to reduce the weight. One-side spot welding as described above is also conceivable when direct spot welding cannot be applied due to the formation of a cross-sectional hat-shaped portion on one side of the steel plate at a site where such a high-tensile steel plate is used. However, when one-side spot welding is applied to a high-strength steel plate, this is a method in which the electrode is brought into pressure contact only from one side of the steel plate, so that high-temperature cracking occurs in the steel plate near the contact portion with the electrode. It is known that

  Therefore, the reality is that the one-side spot welding method cannot be applied to high-tensile steel sheets. As described above, since a single-side spot welding method cannot be applied to a workpiece that is a plate assembly in which a high-strength steel plate is incorporated and cannot be welded by a C-type gun welding apparatus, at present, a welded portion is formed by arc welding. To form.

  However, when arc welding is performed on a thin plate such as a steel plate that constitutes a car body, welding defects often occur due to workpiece burnout or plate gap, and there is a need to avoid using arc welding as much as possible. .

  In addition, when a part for one-side spot welding and a part for arc welding are provided in the same workpiece, a plurality of welding apparatuses are required, and the equipment cost increases, and the welding gun is replaced during the welding process. This necessitates a reduction in productivity.

  The present invention is an improvement and removal in view of the above-described problems, and it is possible to perform welding without arc welding even on a portion where direct spot welding or one-side spot welding cannot be performed. An object of the present invention is to provide a spot welding device that can be used.

  The solution to the above problem is when a welding gun having a pair of electrodes arranged in parallel and one electrode of the pair of electrodes is brought into contact with a plurality of stacked steel plates from one side, A first conductive member disposed at a position where the other electrode can contact; and a second conductive member electrically connected to the first conductive member and capable of contacting the plurality of steel plates from the other side. This is achieved by configuring a spot welding apparatus.

  According to this spot welding apparatus, if one-side spot welding is possible, a pair of electrodes provided on the welding gun are brought into contact with a plurality of steel plates from one side, and the pair of electrodes are energized in this state. Thus, a plurality of steel plates can be welded. On the other hand, when one-side spot welding is impossible, for example, when a plurality of steel plates include high-tensile steel plates, one electrode is brought into contact with the plurality of steel plates from one side and the other electrode is contacted with the first conductive member. Further, the second electrode member electrically connected to the first conductive member is brought into contact with the plurality of steel plates from the other side. By energizing between a pair of electrodes in this state, it is possible to form a current path for indirect spot welding, so welding is performed on a plurality of steel plates including high-strength steel plates without causing high-temperature cracks. It becomes possible.

  As described above, according to the spot welding apparatus of the present invention, it is possible to perform welding without using arc welding even for a portion where direct spot welding or one-side spot welding cannot be performed. This makes it possible to avoid problems such as poor welding, increased equipment costs, and reduced productivity.

It is a partial section side view showing one embodiment of a spot welding device of the present invention. It is a side view which shows a mode that welding is performed with the said spot welding apparatus.

  Hereinafter, an embodiment of a spot welding apparatus of the present invention will be described with reference to FIG. In this embodiment, three steel plates, ie, flat steel plates 1 and 2 and a thin steel plate 3 having a hat-shaped cross section are welded. The steel plate 3 has a hat portion 3a having a hat-shaped cross section and a flange portion 3b provided on the periphery of the hat portion 3a. Direct spot welding using a C-type gun (not shown) can be applied to the flange portion 3b. Therefore, direct spot welding is performed by pressing and holding the overlapped flange portion 3b and the steel plates 1 and 2 from above and below with a C-type gun welding apparatus (not shown) provided with a pair of electrodes facing each other in advance. Has already been applied (the welded part is indicated by P).

  The spot welding apparatus 4 according to the present embodiment includes a welding gun 4a and a conductive portion 4b. The welding gun 4a is attached to driving means (not shown) (for example, a robot arm) and can be arranged at an arbitrary three-dimensional position. The welding gun 4a has a pair of electrodes 5 and 6 arranged in parallel at a predetermined distance so as to be able to come into contact with the surface on one side of the steel plate to be welded. The electrodes 5 and 6 are attached to the pressurizing device 7, can move forward and backward with respect to the surface of the steel plate 1, and can be pressed against the steel plate 1 with a constant pressure. In this embodiment, the electrodes 5 and 6 can be individually advanced and retracted by the pressurizing device 7. A current control device 8 is connected to the pair of electrodes 5 and 6 so that the current supplied between the electrodes 5 and 6 during welding is controlled.

  The conductive portion 4b includes a first conductive member 9, a second conductive member 10, and a connection member 11 that electrically connects them. The first conductive member 9 is made of a metal plate such as a copper plate, and is fixed to a work set base (not shown). The second conductive member 10 includes a conductive electrode 10a and a cylinder 10b as driving means for driving the conductive electrode 10a up and down. The connection member 11 electrically connects the first conductive member 10 and the conductive electrode 10a of the second conductive member 10.

  Next, the operation | movement aspect of the spot welding apparatus 4 comprised in this way is demonstrated. As shown in FIG. 2, when spot welding is performed on a region covered from below by the hat portion 3a of the steel plate 3 among the superposed steel plates 1 and 2, direct spot welding cannot be performed. One-side spot welding by the welding gun 4a of the welding apparatus 4 is considered. However, in order to join the steel plates 1 and 2 by one-side spot welding, there are limitations on the material and the plate thickness. For example, when one or both of the steel plates 1 and 2 are partially made of a high-tensile steel plate or are partially thick, one-side spot welding is performed on the same workpiece. There can be sites that can and cannot.

  In this case, one-side spot welding is performed on the portion where one-side spot welding is possible using the welding gun 4a of the spot welding device 4 (see B1 and B2 in FIG. 2). Specifically, the welding gun 4a is moved by the robot arm, and the electrodes 5 and 6 are arranged above the planned welding portions B1 and B2 of the steel plates 1 and 2. And each electrode 5 and 6 is dropped with the pressurization apparatus 7, and the welding scheduled site | parts B1 and B2 are pressurized with a predetermined pressurizing force with the electrodes 5 and 6. FIG. In this state, the steel plates 1 and 2 are welded at the welding scheduled portions B1 and B2 by energizing the electrodes 5 and 6 with the current control device 8.

  On the other hand, indirect welding is performed on a portion where one-side spot welding is impossible by using the welding gun 4a and the conductive portion 4b of the spot welding device 4 described above. Specifically, the welding gun 4a is moved by the robot arm, and one electrode 5 is disposed above the planned welding portion A of the steel plates 1 and 2, and the other electrode 6 is disposed above the first conductive member 9. To do. Then, the pressurizing device 7 presses the one electrode 5 against the planned welding site A from above and presses the other electrode 6 against the first conductive member 9. Further, the second conductive member 10 electrically connected to the first conductive member 9 is brought into contact with the already welded portion P of the flange portion 3b of the steel plate 3 from the lower surface side. At this time, the pressurizing force of one electrode 5 is set to such an extent that the steel plates 1 and 2 are sufficiently brought into contact with each other in the planned welding site A and the steel plates 1 and 2 are not plastically deformed. The pressurizing force of the other electrode 6 and the second conductive member 10 may be such that they can contact the first conductive member 9 and the steel plate 3 to ensure the energized state, and is smaller than the pressurizing force of the one electrode 6. Then, when a welding current is passed between the electrodes 5 and 6 by the current control device 8 in this state, one electrode 5 → the steel plate 1 and the steel plate 2 → the flange portion 3b of the steel plate 3 → the second conductive member 10 → the connecting member 11 → An indirect welding energization path L is formed from the first conductive member 9 to the other electrode 6 (see FIG. 1), whereby the steel plates 1 and 2 are joined at the planned welding site A.

  As described above, according to the spot welding apparatus 4 according to the present invention, even if one or both of the steel plates 1 and 2 of the planned welding site A are high-tensile steel plates, indirect welding is performed via the conductive portion 4b. Therefore, it is possible to weld the planned welding site A without causing high-temperature cracking using the welding gun 4a for one-side spot welding. As a result, welding is performed using the welding gun 4a for one-side spot welding, even at sites where one-side spot welding is possible (scheduled welding sites B1, B2) or sites where one-side spot welding is not possible (scheduled welding site A). Therefore, it is possible to reduce the cost of the welding equipment, and it is not necessary to replace the welding gun, thereby improving productivity.

  The present invention is not limited to the embodiment described above, and appropriate modifications are possible. For example, although the conductive member 9 is fixed in the above embodiment, the conductive member 9 may be movable. For example, when the conductive member 9 is configured to be pivotable or reciprocally movable and one-side spot welding is performed, the conductive member 9 stands by at a position retracted from the workpiece, and only when necessary (ie, when performing indirect spot welding). You may make it arrange | position 9 in the position which the other electrode 6 can contact | abut. In the above embodiment, the conductive electrode 10a of the second conductive member 10 is movable. However, it may be fixed so that it always abuts against the workpiece.

DESCRIPTION OF SYMBOLS 1 ... Steel plate 2 ... Steel plate 3 ... Steel plate 3a ... Hat part 3b ... Flange part 4 ... Spot welding apparatus 4a ... Welding gun 4b ... Conductive part 5 ... One electrode 6 ... The other electrode 9 ... First conductive member 10 ... Second Conductive member A ... Site to be welded P ... Previously welded site

Claims (2)

A spot welding method using a welding gun having a pair of electrodes arranged in parallel ,
The pair of electrodes are brought into contact with the first planned welding site of a plurality of stacked steel plates from one side, and the first welding planned site is not supported from the other side, between the pair of electrodes. One-side spot welding process of energizing and welding ;
One electrode of the pair of electrodes, is brought into contact with the second welding planned site plurality of overlaid steel plates were from one side Rutotomoni, the other electrode of the pair of electrodes, a first conductive is abutted against the member, further, the abutting a second conductive member connected said in electrical first conductive member, the plurality of steel plates, from the other side to a different site and the second welding planned site A spot welding method comprising: an indirect spot welding step of energizing and welding between the pair of electrodes in a state in which the pair of electrodes is welded . The spot welding method according to claim 1, wherein the plurality of steel plates include high-tensile steel plates.

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