JP2716956B2 - Manufacturing method of automobile outer panel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an outer panel of an automobile.

[0002]

2. Description of the Related Art There are two types of methods for manufacturing an automobile body. One is a method of forming the final shape of the body by joining several divided pressed parts by means such as welding (split method), and the other is using a large steel sheet from the beginning. This is a method of integrally pressing (integrated method).

[0003]

In the division method, the yield of materials is good, but the number of parts increases, so that the number of molds and the number of joining steps increase accordingly. In addition, every time the design is changed, many dies must be manufactured. In addition, because it is inevitable that the appearance is deteriorated by the joint of the joint, in a member that is easily visible from the outside such as the outer panel,
Careful finishing must be applied to the joints to improve their appearance. For example, as shown in FIG. 8 (a), when a front panel (2) and a rear panel (3) are joined at two upper and lower parts to produce a side panel outer (1), it is noticeable to the user. Particularly elaborate finishing operations have to be carried out on the upper weld (P), which is easily accessible. Traditionally,
The upper weld (P) is brazed by MIG welding with a lap joint (see FIG. 3B). However, in MIG welding, the amount of distortion and excess after welding are large, and the heat effect Since the width is wide, the number of finishing steps required to obtain good surface accuracy is excessive, and the productivity is reduced.

[0004] In addition, in the integrated system, the number of molds and the number of steps related to the above-mentioned joining are reduced, so that an advantage in terms of reduction of manufacturing cost is claimed. However, there is a possibility that equipment cost and equipment space may be increased, for example, as a result of the integration increasing the size of the parts and requiring a larger press equipment than before. Further, for example, it is pointed out that it is difficult to standardize component designs in an integrated body.

Accordingly, an object of the present invention is to provide a construction method capable of solving each of the problems of the division method and the integration method at once. That is, an object of the present invention is to enable low-cost molding of two or more types of automobile outer panels including a common portion and different shapes as a whole.

[0006]

According to the present invention, when two or more panels are welded to obtain a three-dimensional automobile outer panel, each of the panels is press-formed into a three-dimensional shape. Then, a pre-strain is applied to the welded end of each panel in a direction to cancel the heat shrinkage distortion caused by welding, and the welded ends of each panel are laser-welded with a butt joint using filler wires, and welded. After completion, the torch-side surface of the weld was finished.

[0007] Laser welding can reduce the spot light as compared with MIG welding, so that the amount of heat distortion, the amount of extra heat, and the width of heat influence after welding can be reduced. Finishing can be performed easily and accurately.
The reason for using the filler wire is to prevent undercut of the welded portion because a gap is easily generated in the welded portion in the three-dimensional shape.

Further, when two or more panels are welded to obtain two or more kinds of automobile outer panels having different three-dimensional shapes, a common divided panel obtained by dividing a common portion of each outer panel and a remaining divided panel having a different shape are used. Each deformed split panel is press-formed into a three-dimensional shape, and a pre-strain is applied to the welded ends of each panel in a direction to cancel the heat shrinkage distortion caused by welding, and filler wires are used at the welded ends of each panel. Laser welding may be performed with a butt joint while the welding is completed, and the torch-side surface of the welded portion may be finished.

In this case, the size of the mold and the press can be reduced as compared with the integrated system, and the common divided panel can be formed by one type of the mold and the press. And so on.

[0010] The pre-strain can be imparted by bending the welded end of the panel to the torch side.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. As shown in FIG. 7, in the present invention, when the front panel (2) can be shared by different vehicle types, for example, a wagon vehicle and a sedan vehicle, the common front panel (2) (common split panel) has a different shape. Two types of body panels (1a) (1b) were obtained by welding with two types of rear panels (3a) (3b) (deformed split panels). According to this method, the molds can be divided, so that the individual molds can be made smaller than in the case of the integrated system, and the molds at the front part can be shared. It is possible to suppress molding costs by eliminating mold costs and storage space waste.

By the way, of the joints (P) (P ') between the front panel (2) and the rear panels (3a) (3b), at least the upper joint (P) is easily visible to the user. In MIG welding using a lap joint which is often used in such a case, there are many problems in terms of finishing accuracy.

Accordingly, in the present invention, as shown in FIG.
At least the upper welded portion (P) of the joint between the front panel (2) and the rear panel (3) of the side panel outer (1) is laser-welded with a butt joint. Compared to MIG welding, laser welding has advantages in that thermal distortion is small, a margin is small, and a heat affected width is small. Therefore, good surface accuracy can be ensured by simple finishing. Further, laser welding has an advantage that sufficient strength can be obtained even with a butt joint and high-speed welding can be easily performed since a stronger bonding strength than that of the base material can be secured.

In such butt laser welding, it is an important point to determine the quality of welding by how to match the steel plates at the butt surface without any gap. In the case of joining two-dimensional panels, that is, flat panels, good butting can be easily obtained by a method such as using a plate material with high end face accuracy. However, as in the case of the side panel outer (1), In the case of a panel having a simple three-dimensional shape, that is, a panel in which the welding line is displaced every time in the thickness direction of the panel with respect to the horizontal plane, the end face accuracy is required due to the press forming of the front panel (2) and the rear panel (3) into a three-dimensional shape. Is not easy to manage, and therefore, it is considered that there are many cases where the size of the gap is generated, resulting in poor welding.

Therefore, in such a case, it is desirable to use a filler wire. This makes it possible to replenish the welded portion with the amount of the molten metal that is insufficient due to the gap, so that it is possible to prevent an undercut and obtain a good welded portion.

FIG. 3 shows the roof rail portion of the side panel outer (1) joined and integrated by MIG welding, and the roof rail portion of the side panel outer (1) joined and integrated by laser welding using a filler wire (both are butt welding). FIG. 9 is a diagram showing the results of comparative measurement of the surface shape of a current integrated panel (a panel integrally formed from a single plate). The horizontal axis in the figure represents the coordinates (mm) in the front-rear direction of the roof rail, and the vertical axis represents the surface position (mm) in the thickness direction when both ends of the test piece are set to 0. The welding conditions for laser welding are as follows.

Steel plate thickness: 0.8 [mm] Laser output: 3.2 [kw] Welding speed: 4.0 [m / min] Wire speed: 2.1 [m / min] Defocus amount ... 0 [mm] Shielding gas: Ar, 20 "liter / min" From the results of this experiment, the laser welded panel was compared to the MIG welded panel in the original panel ( (Currently integrated panel), it was confirmed that the heat distortion amount, the extra height (Hl), and the heat affected width (Wl) were all lower values (M
The extra height of IG welding is Hm and the heat affected width is Wm).

In general, at the time of welding, there is a problem that deformation (portion B in FIG. 3) due to heat shrinkage occurs on the surface of the base metal adjacent to the welding line. As shown in FIG. 4A, this modification (B)
The bead width differs between the front and back surfaces of the base material as well as the result of the press forming of the panel, and as a result, the solidification shrinkage of the base material is different between the front and back surfaces (front> back surface). . This solidification shrinkage occurs not only in the direction perpendicular to the bead but also in the direction along the bead (5) as shown in FIG.

When such deformation occurs, at the stage of finishing processing, it is not enough to process only the front side, and correction work such as hitting a recessed portion from the back side is required.
Finish man-hours increase.

In order to solve this problem, according to the present invention, a pre-strain is applied to each of the welded ends of the two members to be welded in a direction to cancel the heat shrinkage strain caused by welding. FIG. 2 (a) shows a specific example in which a pre-strain is given by bending the welded end surfaces of both panels toward the torch (7) side by means of press molding or punching out after pressing to plastically deform. is there. In this state, when the panels are welded to each other by irradiating a laser beam from the torch (7) as shown in FIG. 7 (b), the pre-strain of the bent portion (9) cancels out the heat shrinkage strain. Deformation is prevented from occurring. After the welding is completed, as shown in FIG. 3 (c), the outer panel (1) having high surface accuracy is formed by finishing the surface of the welded portion with a polishing machine (10) or the like.
Since there is no deformation, man-hours during finishing can be reduced.

FIG. 5 is a diagram showing a change in the shape of the panel surface in an experiment in which a pre-strain was imparted by punching for each process. (C) In the figure, the curve represents the surface shape when the bent part (9) is formed by punching out both the welded ends of the roof rail part to the torch side with the punching tool (11), and the curve is a laser. Represents the surface shape immediately after welding. The curve represents the surface shape when finishing is performed after welding. As is clear from this figure, if laser welding is performed with pre-strain applied, the occurrence of deformation can be almost certainly avoided (curve). Therefore, if the finish processing is performed thereafter, it is almost the same as the current integrated panel. It can be formed into a shape.

FIG. 6 shows a comparison experiment on how the difference in the finishing process affects the surface accuracy of the panel. That is, as shown in FIG. 1 (a), the welding end face of the test panel is struck out with a punching tool (11) to give a pre-strain (), and the welding end faces are butt-welded to each other by laser welding (). The surface shape was measured after the finishing process (-1 and -2). Of these, Samples A and C were subjected to finishing such as polishing only from the surface, and Sample A took about 15 times as long as Sample C. On the other hand, the sample B is obtained by alternately performing punching from the back surface by the punching tool (11) and finishing such as polishing from the front surface, and the finishing time is substantially the same as that of the sample A. According to the experimental results, in Sample A, the surface shape was smooth, but there was no hit from the back surface, so that the pressing force of the finishing tool (10) resulted in a concave shape having a larger curvature than the current panel as a whole due to the pressing force of the finishing tool (10).
In sample B, since the processing time is short, the entire panel is unlikely to be dented, and thus has almost the same curvature as the current panel, but sufficient surface accuracy cannot be obtained because the surface has irregularities. On the other hand, in the sample B, since the punching-out tool (11) hits from the back surface and the processing time is sufficient, the surface shape of the sample B can be made to substantially match the current surface shape of the integrated panel. From the above, it can be understood that at the time of finishing, it is desirable to alternately repeat tapping from the back surface and surface finishing.

In the experiment, the bent portion (9) of the welded end face is formed by using a punching tool (11). However, the bent portion (9) is formed by other forming means, for example, a press. May be formed. With the press, the bent portion (9) can be formed simultaneously with the press forming of the body panel, so that there is no need to add a process for forming a new bent portion (9) in the line, and low cost is achieved. Thus, the bent portion (9) can be formed. Of course, it is also possible to insert the process of bending and forming only the end of the panel already formed as a separate process instead of simultaneously. Of course, each of the above-described welding methods is not limited to the outer panel of an automobile, and can be applied to welding of various two-dimensional members.

[0024]

According to the present invention, the following effects can be obtained. Since the two-dimensionally shaped two members are laser-welded with a butt joint, for example, compared to MIG welding or the like, thermal distortion, extra volume,
The heat affected width can be reduced, and therefore, good surface accuracy can be ensured by simple finishing.

[0025] For a three-dimensionally shaped welded part in which a gap is likely to be generated, if laser welding is performed using a filler wire,
A good product without undercut can be obtained.

When two members are welded to obtain one welded product, after applying a pre-strain to a welding end portion of each member in a direction to cancel a heat shrinkage strain caused by welding, laser welding is performed using a butt joint. Since the occurrence of deformation can be prevented, the labor required for the finishing work can be reduced.

The pre-strain can be easily applied by bending the end in a direction to cancel the deformation of the member after welding.

In obtaining two or more types of welding products having different shapes, a common part of each welding product is divided into a common split piece, and the common split piece and the deformed split pieces having different shapes are respectively welded. If two or more types of welded products are obtained by using this method, the individual press dies and press devices can be made smaller than in the case of the integrated system, and the dies for the common split pieces are partially omitted. Therefore, waste of space and mold costs is reduced, and molding costs can be suppressed.

When the common split piece and the deformed split piece are welded by any one of the above-described laser welding methods, two or more types of weld products having different shapes as a whole while including the common part are obtained. Molding can be performed at low cost, and good surface accuracy can be ensured even after welding with a simple finishing operation. That is, it is possible to combine the advantages of the integrated system with good surface accuracy with the advantages of the split system with small molds and press equipment and good material yield. The above effects can be obtained similarly when the welding product is an outer panel of an automobile.

[Brief description of the drawings]

FIG. 1A is a perspective view showing an embodiment of the present invention, and FIG. 1B is a sectional view thereof.

FIG. 2 is a cross-sectional view showing a welding procedure when prestrain is applied.

FIG. 3 is a diagram illustrating surface accuracy of a MIG welding panel and a laser welding panel.

4A is a cross-sectional view showing a cause of deformation, and FIG. 4B is a plan view of the same.

FIG. 5 (a) is an enlarged perspective view of a roof rail portion,
(B) is a process diagram when applying a pre-strain (A- in FIG.
(C) is a diagram (a cross-sectional view taken along line BB in FIG. (A)) showing the panel surface shape in each step.

FIG. 6 (a) is a view showing a finishing process (FIG. 5 (a)).
5A is a cross-sectional view taken along line AA), and FIG. 5B is a view showing a surface shape of the panel formed by each finishing process (B-B in FIG. 5A).
FIG. 7 is a sectional view taken along line B).

FIG. 7 is a perspective view showing an embodiment of the present invention.

FIG. 8A is a perspective view of a conventional split-type side panel outer, and FIG. 8B is a cross-sectional view illustrating a conventional welding method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Side panel outer (outer panel) 2 Front panel (Common split piece) 3 Rear panel 3a / 3b Deformed split piece 5 Bead 7 Torch 9 Bending part 10 Finishing tool 11 Launching tool

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kimitoshi Yamamoto 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (72) Inventor Koichi Ishihara 1 Okimura Okimura Nishiharu-cho, Nishikasugai-gun, Aichi Prefecture No. Sanyo Kiko Co., Ltd. (56) References JP-A-5-84585 (JP, A) JP-A-5-50275 (JP, A) JP-A-6-671 (JP, A) JP-A-4-71794 (JP, A) JP-A-1-104488 (JP, A) JP-A-7-32176 (JP, A) JP-A-6-179086 (JP, A) "Welding technology" Vol. Hoho Publishing Co., Ltd., published on November 1, 1994, pp. 69-74

Claims (3)

(57) [Claims] 1. When two or more panels are welded to obtain a three-dimensional automobile outer panel, each of the panels is press-formed into a three-dimensional shape, and a heat shrinkage accompanying welding is formed on a welded end of each panel. Apply pre-strain in the direction to cancel the strain, laser weld the welded ends of each panel with a butt joint using filler wire, and after finishing welding, finish the torch side surface of the welded part A method for manufacturing an automobile outer panel, comprising: 2. When two or more panels are welded to obtain two or more types of automobile outer panels having different three-dimensional shapes, a common divided panel obtained by dividing a common portion of each outer panel and a remaining divided shape different from each other. Each deformed split panel is press-formed into a three-dimensional shape, and a pre-strain is applied to the welded end of each panel in a direction to cancel the heat shrinkage distortion caused by welding. A method for manufacturing an automobile outer panel, comprising: performing laser welding with a butt joint while performing welding, and after finishing welding, performing a finishing process on a torch-side surface of a welded portion. 3. The method of manufacturing an automobile outer panel according to claim 1, wherein the prestrain is provided by bending a welded end of the panel toward a torch.