JP2021191661A - Method of manufacturing vehicle frame - Google Patents

Abstract

To easily manufacture a frame structure having a high torsional rigidity without welding defects.SOLUTION: First and second press molded bodies 2, 3 are obtained by press-molding a steel plate P1 into a cross-sectional U-shape such that two folding lines 2a and two folding lines 3a are formed and that an internal angle α of a folded portion where each of the folding lines 2a, 3a is formed satisfies α>90°. The open sides of the first and second press molded bodies 2, 3 are opposed to each other, and thus end surfaces 2c extending in a longitudinal direction of the first press molded body 2 and end surfaces 3c extending in a longitudinal direction of the second press molded body 3 face each other. An inner edge portion of one of both the end surfaces 2c, 3c opposed to each other is disposed to face an inner edge portion of the other of both the end surfaces 2c, 3c. Meanwhile, an outer edge portion of one of both the end surfaces 2c, 3c opposed to each other is separated from an outer edge portion of the other of both the end surfaces 2c, 3c. By continuously or discontinuously welding the opposed portions of the first and second press molded bodies 2, 3 from the outer side, a side member 1a having a closed cross-section is obtained.SELECTED DRAWING: Figure 7

Description

The present invention relates to, for example, a method for manufacturing a frame used in an automobile.

Conventionally, an automobile has a frame structure (chassis structure) at the lower part of the vehicle, which is composed of a pair of side members extending in the front-rear direction of the vehicle and a plurality of cross members extending in the width direction of the vehicle bridging the side members. The ones that have been prepared are known. These frame structures are required to be lightweight and rigid in order to improve the steering stability of automobiles, and in recent years, it has become common to assemble them with a closed cross-section frame having a hollow inside. ing. For example, in the closed cross-section frame disclosed in Patent Document 1, a steel plate is press-molded into a U-shaped cross section to obtain long first and second press-formed bodies, respectively, and then the first and second presses are performed. The end faces of the side walls extending in the longitudinal direction of the first press molded body and extending in parallel to each other and the end faces of the side walls extending in the longitudinal direction of the second press molded body, and parallel to each other, so that the molded bodies face each other with their open sides facing each other. By abutting the end faces of the side wall portions extending to the above, and then continuously welding the abutted portions of the first and second press-molded bodies from the outside of the first and second press-molded bodies to integrate them. I am trying to get a closed cross section frame.

Japanese Unexamined Patent Publication No. 11-34914

By the way, in recent years, there has been a demand for an automobile having a lighter weight and a higher safety structure, and in response to this demand, the frame structure of a vehicle as described above has been manufactured from a hard and light high-strength steel plate. It's coming.

However, for example, when a press-molded body having a U-shaped cross section constituting a closed cross-section frame as in Patent Document 1 is obtained from a high-strength steel plate, so-called springbacks in which both side wall portions facing each other expand in a V shape after the completion of molding are performed. It is known that this phenomenon is likely to occur, and the dimensional accuracy after press molding for the target shape deteriorates. Therefore, when an attempt is made to manufacture a closed cross-section frame from the first and second press-molded bodies having the side wall portions extending in parallel with each other as in Patent Document 1, the end face of each side wall portion of the first press-molded body and the second press molding are attempted. When the end faces of each side wall of the body are butted against each other, the positions of the end faces are displaced from each other, and welding defects occur during continuous welding, resulting in rigidity of the closed cross-section frame after completion. It may decrease.

Further, the frame structure obtained by combining a plurality of frames as in Patent Document 1 has high torsional rigidity because a large load is applied to the portion where the frames are connected to each other when the vehicle is running, that is, the end portion of the frame. There is a demand for a structure.

The present invention has been made in view of these points, and an object of the present invention is to easily manufacture a frame structure having high torsional rigidity without causing welding defects.

In order to achieve the above object, the present invention presents a method of bending a steel sheet at the time of press molding, and when integrating the first and second press-molded bodies, at the time of welding the first and second press-molded bodies. It is characterized by devising the way of matching each end face.

Specifically, the following solutions have been taken in the method of manufacturing a vehicle frame.

That is, in the first invention, the steel plate is formed so that one or more bending lines extending in the longitudinal direction are formed and the internal angle α of the bending portion where each of the bending lines is formed satisfies α> 90 °. After press-molding into a U-shaped or V-shaped cross section to obtain long first and second press-molded bodies, the first and second press-molded bodies are placed so that their open sides face each other. Each end face extending in the longitudinal direction of the first press-molded body and each end face extending in the longitudinal direction of the second press-molded body are made to correspond to each other, and one inner edge portion of one end face corresponding to each other is attached to the other end face. On the other hand, one outer edge portion of both end faces corresponding to each other is fixed to the first jig in a state of being separated from the other of both end faces, and then each butt portion of the first and second press molded bodies is fixed. The first frame having a closed cross-sectional structure is obtained by continuously or intermittently welding the first and second press-molded bodies from the outside to be integrated.

The second invention is characterized in that, in the first invention, the first and second press-molded bodies are press-molded so as to have two or more bending lines, respectively.

In the third invention, in the second invention, the edge portion at one end in the longitudinal direction corresponds to the outer peripheral surface of the first frame at a position extending so as to intersect with at least one of the bent lines and the welded lines. A second frame having a long closed or open cross-section structure having a shape was prepared, and the first and second frames were placed on the outer peripheral surface of the first frame with one end in the longitudinal direction of the second frame. It is characterized in that a frame structure is obtained in which the continuous portions of the first and second frames are integrally fixed by fillet welding after being fixed to a second jig in a state.

In the first invention, when molding the first and second press-molded bodies, it is not necessary to bend the opposite side wall portions to positions extending in parallel with each other, so that the molding accuracy of the first and second press-molded bodies is good. Become. Therefore, when the first and second press-molded bodies are set on the jig and the first and second press-molded bodies are integrated by welding, the second press-molded body with respect to each side wall portion of the first press-molded body is used. The position of each side wall portion is less likely to shift, and the occurrence of welding defects can be suppressed. Further, when the first and second press-molded bodies are integrated by continuous or intermittent welding, the entire end face of each side wall portion of the first press-molded body and each side wall of the second press-molded body are formed. It is no longer necessary to abut the entire end face of the portion, and it is sufficient to abut one inner edge portion of each of the corresponding end faces against the other of both end faces. Therefore, when the end faces of the side wall portions of the first press molded body and the end faces of the side wall portions of the second press molded body are associated with each other, the molding accuracy of the first and second press molded bodies is poor and they correspond to each other. Even if the position of one end face is slightly deviated from the position of the other end face, welding is possible, and the occurrence of welding defects can be suppressed. Further, in the frame structure, the number of bent lines formed by press forming is two or more in total, and the number of weld lines formed by continuous welding is two in total. Therefore, the internal angle of the bent portion in the completed frame structure becomes a shape in which stress concentration is difficult to exceed 90 °, while the cross section around the weld line formed in two places in the frame structure has an angle. Since the welded portion becomes more rigid, stress concentration in the portion can be avoided. In this way, the frame of the closed cross-section structure after completion has a polygonal cross-section structure, but it is difficult for stress to be concentrated on each vertex portion, so that the torsional rigidity of the entire frame structure can be increased.

In the second invention, since the apex portion of the polygon of the cross section in the completed frame structure is increased, the stress applied to each bent portion when a load is applied to the completed frame structure is dispersed, and further twisted. It is possible to make a frame structure with high torsional rigidity.

In the third invention, the continuous portion of the second frame with the first frame has a U-shaped cross section or a curved cross section in a side view. Therefore, the positioning of the second frame with respect to the first frame becomes easy, and even if heat is applied to the first and second frames during welding, the positional deviation of the second frame with respect to the first frame due to thermal strain is unlikely to occur. Therefore, the dimensional accuracy of the frame structure after completion can be improved.

It is a schematic perspective view which shows the vehicle which provided the frame structure manufactured by the manufacturing method in embodiment of this invention. FIG. 3 is a cross-sectional view taken along the line II-II of FIG. It is a block diagram of the production line to which the production method which concerns on embodiment of this invention is applied. It is a schematic cross-sectional view which shows the state immediately after the steel plate was carried into the forming die of a pressing process. After FIG. 4, it is a figure which shows the state immediately after molding a press-molded body by closing a die for molding. After FIG. 5, it is a figure which shows the state just before opening a die for molding and carrying out a press-molded article. It is a figure which shows the state in the process of obtaining the side member by integrating the 1st and 2nd press molded bodies fixed to the jig of the 1st assembly process by welding. FIG. 7 is an enlarged view of part VIII of FIG. It is a figure which shows the state immediately after obtaining the frame structure of the lower part of an automobile by integrating the cross member with the side member fixed to the jig of the 2nd assembly process by welding.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the following description of the preferred embodiment is essentially merely an example.

FIG. 1 shows a frame structure 1 manufactured by the manufacturing method according to the embodiment of the present invention and an automobile 10 to which the frame structure 1 is attached. The frame structure 1 is a suspension member (suspension cross) having a substantially ladder shape in a plan view, and bridges a pair of side members 1a (first frame) having a long shape extending in the front-rear direction of the vehicle and both side members 1a. It is composed of a pair of long cross members 1b (second frame) extending in the width direction of the entwined vehicle, and is arranged on the rear side of the vehicle at the bottom of the vehicle 10.

As shown in FIG. 2, the side member 1a is a frame having a closed cross-section structure having a decagonal cross section, and is composed of a first press molded body 2 and a second press molded body 3 having a U-shaped cross section.

The first press-molded body 2 is obtained by press-molding a steel plate P1 and has four bending lines 2a extending in the longitudinal direction.

_{The internal angles α 1 to} α ₄ of the bent portion where the bending line 2a is formed in the first press-molded body 2 _{satisfy α 1 to} α ₄ > 90 °, and in the case of the embodiment of the present invention, α _{1 to} α ₄ are all at the same angle. Therefore, the side wall portions 2b of the first press molded body 2 have a shape that expands in a C shape in a cross-sectional view.

The second press-molded body 3 is obtained by press-molding a high-strength steel plate, and four bending lines 3a extending in the longitudinal direction are formed.

_{The internal angles α 5 to} α ₈ of the bent portion where the bending line 3a is formed in the second press-molded body 3 _{satisfy α 5 to} α ₈ > 90 °, and in the case of the embodiment of the present invention, α _{5 to} α ₈ are all at the same angle. Therefore, the side wall portions 3b of the second press-molded body 3 have a shape that expands in a C shape in a cross-sectional view.

The side member 1a extends from each end surface 2c extending in the longitudinal direction of the first press molded body 2 so that the open sides of the first press molded body 2 and the second press molded body 3 face each other, and the longitudinal length of the second press molded body 3. It is obtained by forming a welded portion 4 at a portion where each end surface 3c (see FIG. 8) extending in the direction is butted with each other to integrate the first press-molded body 2 and the second press-molded body 3.

_{The internal angles β 1} and β ₂ of the portion of the side member 1a where the welded portion 4 (welded line) is formed have an obtuse angle and, in the case of the embodiment of the present invention, the same angle.

The cross member 1b has a closed cross-sectional structure having a rectangular cross section, and a position where the opening peripheral edge of the end portion intersects and extends with respect to the bending line 2a, the bending line 3a, and the welded portion 4 formed on the side surface of the side member 1a. There is no corresponding shape in. That is, as shown in FIG. 9, the end edge portion of the cross member 1b has a substantially U-shape in a side view so as to cover the outer peripheral surface of the side member 1a.

As shown in FIGS. 4 to 6, the first press-molded body 2 is molded by using a press-molding apparatus 5 equipped with a molding die 50.

The press forming apparatus 5 includes a base 51 installed on the floor surface F and a liftable lift 52 arranged to face the base 51 above the base 51, and a metal is placed on the lower surface of the lift 52. While the upper mold 53 of the mold 50 is fixed, the lower mold 54 of the mold 50 is fixed to the upper surface of the base 51.

The upper mold 53 is formed with an upper molded surface 53a having a substantially convex cross section that projects downward, and the upper molded surface 53a has a shape corresponding to the inner surface of the first press molded body 2.

On the other hand, the lower mold 54 is formed with a lower molded surface 54a having a concave cross section, and the lower molded surface 54a has a shape corresponding to the outer surface of the first press molded body 2.

Then, in the press forming apparatus 5, when the elevating table 52 moves up and down, the die 50 closes or opens, and the first press molded body 2 is obtained from the steel plate P1.

Although not shown, the second press-molded body 3 is molded using a press-molding device equivalent to the press-molding device 5.

As shown in FIGS. 7 and 8, the side member 1a is assembled in the first assembly device 6 provided with the first jig 60.

The first jig 60 has an upper fixing block 61 having an upper fixing surface 61a having a shape corresponding to the upper surface of the side member 1a, and a lower having a lower fixing surface 62a having a shape corresponding to the lower surface of the side member 1a. Each end face 2c extending in the longitudinal direction of the first press molded body 2 and the second press molding are provided with a side fixing block 62 so that the first press molded body 2 and the second press molded body 3 face each other with their open sides facing each other. Each end face 3c extending in the longitudinal direction of the body is associated with each other, and one inner edge of the corresponding end faces 2c, 3c is abutted against the other of both end faces 2c, 3c, while the end faces 2c, 3c corresponding to each other are abutted against each other. It is possible to fix one outer edge portion in a state of being separated from the other of the end faces 2c and 3c.

A welding torch 7 for performing arc welding is arranged on the side of the first jig 60. The welding torch 7 is attached to the arm tip of an industrial robot (not shown), and the first press molded body 2 and the second press molding fixed to the first jig 60 while continuously supplying the wire 7a from the torch tip. Each butt portion of the body 3 is welded continuously or intermittently from the outside of the first press molded body 2 and the second press molded body 3 to form a welded portion 4, thereby forming a closed cross section. The side member 1a of the structure is obtained.

As shown in FIG. 9, the frame structure 1 is assembled in a second assembly device 8 provided with a second jig 80.

The second jig 80 includes a first fixing unit 81 for fixing the side member 1a and a second fixing unit 82 for fixing the cross member 1b, and the side member 1a is fixed by the first fixing unit 81 and the cross member. By fixing 1b with the second fixing unit 82, the outer peripheral surface of the side member 1a is configured so that one end in the longitudinal direction of the cross member 1b is in contact with the outer peripheral surface of the side member 1a.

Similar to the first assembly device 6, a welding torch 7 is arranged on the side of the second jig 80, and the second jig 80 is continuously supplied with the wire 7a from the tip of the torch of the welding torch 7. By fillet welding the continuous portions of the side member 1a and the cross member 1b fixed to the welded portion 9 to form a welded portion 9, a frame structure 1 in which the side member 1a and the cross member 1b intersect with each other can be obtained. ing.

Next, the manufacture of the frame structure 1 will be described in detail.

As shown in FIG. 3, the production line of the frame structure 1 is provided with a pressing process S1, a first assembly process S2, and a second assembly process S3 in order.

First, in the pressing step S1, as shown in FIG. 4, the steel plate P1 is inserted between the upper mold 53 and the lower mold 54 in the state of being opened in the press forming apparatus 5, and the steel plate P1 is placed on the lower mold 54. Place on top.

Next, the elevating table 52 is lowered to close the upper mold 53 and the lower mold 54. Then, as shown in FIG. 5, the first press-formed body 2 in which the steel plate P1 is deformed along the upper forming surface 53a of the upper die 53 and the lower forming surface 54a of the lower die 54 to form a U-shaped cross section is formed. It is molded. Then, as shown in FIG. 6, the elevating table 52 is raised to open the upper mold 53 and the lower mold 54, so that the completed first press molded body 2 is taken out from the first jig 60. At this time, the first press-molded body 2 is formed with four bending lines 2a extending in the longitudinal direction, and both side wall portions 2b are molded so as to expand in a C shape in a cross-sectional view.

In the press step S1, the second press-molded body 3 is also molded using the same apparatus as the press-molding apparatus 5. In the molded second press-molded body 3, four bending lines 3a extending in the longitudinal direction are formed, and both side wall portions 3b are molded so as to expand in a C shape in a cross-sectional view.

Next, in the first assembly step S2, as shown in FIG. 7, the second press-molded body 3 is set on the lower fixing surface 62a of the lower fixing block 62 so that the open side faces upward, and the first The press-molded body 2 is set on the upper fixing surface 61a of the upper fixing block 61 so that the open side faces downward. Then, each end face 2c of the first press molded body 2 and each end face 3c of the second press molded body 3 are at corresponding positions, and one inner edge portion of the end faces 2c and 3c corresponding to each other is at both end faces 2c. , 3c is abutted against the other, while the outer edges of one of the end faces 2c and 3c corresponding to each other are separated from the other of both end faces 2c and 3c.

After that, as shown in FIG. 8, the first press molded body 2 and the second press molded body fixed to the first jig 60 while moving the welding torch 7 by operating an industrial robot (not shown). The first press molded body 2 is formed by welding each of the butt portions of 3 continuously or intermittently from the outside of the first press molded body 2 and the second press molded body 3, respectively, to form a welded portion 4. And the second press molded body 3 are integrated into a side member 1a having a closed cross-sectional structure.

As described above, since the first press-molded body 2 and the second press-molded body 3 obtained by press molding in the embodiment of the present invention have a cross-sectional C shape, the first press-molded body 2 and the second press-molded body 2 and the second press-molded body 3 have a cross-section C shape. When molding the press-molded body 3, it is not necessary to bend the opposite side wall portions 2b and 3b to positions extending in parallel with each other, and the molding accuracy of the first press-molded body 2 and the second press-molded body 3 is improved. Therefore, when the first press molded body 2 and the second press molded body 3 are set on the first jig 60 and the first press molded body 2 and the second press molded body 3 are integrated by welding, the first press is performed. The position of each side wall portion of the second press molded body 3 with respect to each side wall portion of the molded body 2 is less likely to shift, and the occurrence of welding defects can be suppressed. Further, when the first press-molded body 2 and the second press-molded body 3 are integrated by continuous or intermittent welding, the entire end surface 2c of the side wall portion 2b of the first press-molded body 2 and the first It is no longer necessary to abut the entire end surface 3c of each side wall portion 3b of the 2 press molded body 3, and it is only necessary to abut one inner edge portion of the end surfaces 2c and 3c against the other of both end faces 2c and 3c. Therefore, when the end surface 2c of each side wall portion 2b of the first press molded body 2 and the end surface 3c of each side wall portion 3b of the second press molded body 3 are made to correspond to each other, the first press molded body 2 and the second press Even if the molding accuracy of the molded body 3 is poor and the positions of one end faces corresponding to each other are slightly deviated from the positions of the other end faces, welding is possible and the occurrence of welding defects is suppressed. Can be done.

Next, in the second assembly step S3, as shown in FIG. 9, the side member 1a is fixed to the first fixing unit 81, and the cross member 1b is fixed to the second fixing unit 82. Then, one end of the cross member 1b in the longitudinal direction is in contact with the outer peripheral surface of the side member 1a.

After that, as shown in FIG. 9, the continuous portion of the side member 1a and the cross member 1b fixed to the second jig 80 is cornered while moving the welding torch 7 by operating an industrial robot (not shown). By performing fillet welding to form the welded portion 9, the side member 1a and the cross member 1b are integrated to obtain the frame structure 1.

As described above, since the opening peripheral edge of the end portion of the cross member 1b has a corresponding shape at a position extending so as to intersect the bending line 2a, the bending line 3a and the welded portion 4 formed on the side surface of the side member 1a. , The continuous portion of the cross member 1b with the side member 1a forms a U-shaped cross section in the side view. Therefore, the positioning of the cross member 1b with respect to the side member 1a becomes easy, and even if heat is applied to the side member 1a and the cross member 1b during welding, the position of the cross member 1b with respect to the side member 1a is displaced due to thermal strain. It becomes difficult and the dimensional accuracy of the frame structure 1 after completion can be improved.

Further, in the frame structure 1 manufactured by the manufacturing method of the present invention, the bent lines 2a and 3a formed by press molding have a total of two or more places, and the welded parts 4 formed by continuous welding. Will be in two places in total. _{Therefore, while the internal angles α 1 to} α ₈ of the bent portion in the completed frame structure 1 each have a shape in which stress concentration exceeding 90 ° is difficult, the cross section around the welded portion 4 formed in two places in the frame structure 1 has an internal angle β. _The structure has 1 and β ₂ , but since the portion has rigidity due to the welded portion 4, stress concentration in the portion can be avoided. As described above, the side member 1a after completion has a polygonal cross-sectional structure, but stress is less likely to be concentrated on each apex portion, so that the torsional rigidity of the entire frame structure 1 can be increased.

Further, in the side member 1a of the embodiment of the present invention, a total of eight bending lines 2a and 3a are formed. In this way, when the apex portion of the polygon of the cross section in the completed frame structure 1 increases, the stress applied to each bent portion when the load is applied to the completed frame structure 1 becomes dispersed. The frame structure 1 having high torsional rigidity can be obtained.

The first press-molded body 2 and the second press-molded body 3 in the embodiment of the present invention are press-molded so that four bending lines 2a and 3a are formed, respectively, but the present invention is not limited to this. If the internal angle α of the bent portion where the bending lines 2a and 3a are formed satisfies α> 90 °, the first press-molded body 2 and the second press-molded body 3 each have one bending line 2a and 3a. It suffices if it is formed as above.

_{Further, in the embodiment of the present invention, the internal angles α 1 to} α ₄ of the bent portion where the bending line 2a is formed in the first press molded body 2 have the same angle, respectively, and the bending line 3a in the second press molded body 3 is _{The internal angles α 5 to} α ₈ of the bent portion to be formed have the same angle, but they may have different angles. _{Further, the internal angles β 1} and β _{2 of} the portion of the side member 1a where the welded portion 4 is formed have the same angle, but may be different angles.

Further, in the embodiment of the present invention, the first press-molded body 2 and the second press-molded body 3 are press-molded into a U-shaped cross section, but those press-molded into a V-shaped cross section may be used.

Further, in the embodiment of the present invention, arc welding is used for the connection between the first press molded body 2 and the second press molded body 3 and the connection between the side member 1a and the cross member 1b, but MIG. Welding, TIG welding, or laser welding may be used.

Further, in the embodiment of the present invention, the first jig 60 is of a type in which the first press-molded body 2 and the second press-molded body 3 are sandwiched and fixed from above and below, but the present invention is not limited to this, and for example, positioning. It may be of a type that positions and fixes the first press-molded body 2 and the second press-molded body 3 with a pin. Similarly, the second jig 80 may be of a type in which the side member 1a and the cross member 1b are positioned and fixed by the positioning pin.

Further, in the embodiment of the present invention, the cross member 1b has a closed cross-sectional structure, but the present invention is not limited to this, and for example, an open cross-sectional structure having a U-shaped cross section may be used.

Further, in the embodiment of the present invention, the edge portion of the cross member 1b has a substantially U-shape in a side view, but it may have a curved shape that bends gently.

Further, the frame having a closed cross-sectional structure obtained by the manufacturing method of the embodiment of the present invention can be applied not only to the frame structure of an automobile other than the suspension member but also to the frame structure of a vehicle other than the automobile. be.

The present invention is suitable, for example, for a method for manufacturing a frame used in an automobile.

1 frame structure 1a side member (1st frame)
1b Cross member (2nd frame)
2 1st press molded body 2a Bending line 2b Side wall part 2c End face 3 2nd press molded body 3a Bending line 3b Side wall part 3c End face 4 Welded part (welded line)
60 1st jig 80 2nd jig

Claims (3)

The steel plate is U-shaped or V-shaped in cross section so that one or more bending lines extending in the longitudinal direction are formed and the internal angle α of the bending portion where each of the bending lines is formed satisfies α> 90 °. After obtaining long first and second press-molded bodies, respectively,
Each end face extending in the longitudinal direction of the first press molded body is made to correspond to each end face extending in the longitudinal direction of the second press molded body so that the open sides of the first and second press molded bodies face each other. At the same time, the inner edges of one of the end faces corresponding to each other are abutted against the other of the end faces, while the outer edges of one of the end faces corresponding to each other are separated from the other of the end faces on the first jig. Fixed and
After that, the butt portions of the first and second press-molded bodies are welded continuously or intermittently from the outside of the first and second press-molded bodies to be integrated to form a closed cross-sectional structure. A method for manufacturing a frame for a vehicle, which comprises obtaining the first frame of the above. In the method for manufacturing a vehicle frame according to claim 1,
A method for manufacturing a frame for a vehicle, wherein the first and second press-molded bodies are each press-molded so as to have two or more bending lines. In the method for manufacturing a vehicle frame according to claim 2.
A long closed or open cross section having a shape corresponding to the outer peripheral surface of the first frame at a position where the edge portion at one end in the longitudinal direction intersects and extends with respect to at least one of the bent lines and the welded lines. Prepare the second frame of the structure,
The first and second frames are fixed to the second jig with one end in the longitudinal direction of the second frame facing the outer peripheral surface of the first frame.
After that, a method for manufacturing a frame for a vehicle, which comprises obtaining a frame structure in which continuous portions of the first and second frames are integrally crossed by fillet welding.

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