Method for manufacturing frame parts formed by roll forming

Abstract

Provided is a manufacturing method for frame parts formed by roll forming, which can manufacture highly rigid frame parts having a plurality of closed cross-sectional portions with good productivity, and can suppress springback in a simple manner to increase welding accuracy. [Solution] The method includes a cutting step S1 for cutting a metal plate material 5, a forming step S2 for forming a frame part having a T-shaped joint 12 with a T-shaped cross section and at least two closed cross sections, a temporary joining step S3, a waiting step S4, and a final joining step S5. The cutting step S1 is performed either before the forming step S2 or after the temporary joining step S3 and before the waiting step S4. While the frame part is being formed in the forming step S2, the other frame part is final joined.

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing roll-formed frame components. [Background technology]

[0002] Parts mounted on vehicles such as automobiles need to be supported by strong frame parts. In order to increase the rigidity of the frame parts, it is possible to provide the frame parts with a closed cross-sectional portion in which a plurality of frames with a rectangular cross-sectional shape are continuously arranged. Such a frame part is described, for example, in Patent Document 1. The frame part disclosed in Patent Document 1 uses a plurality of plate materials to form the above-mentioned closed cross-sectional portion. That is, the frame part is formed by a first plate material having a molded portion with an S-shaped cross-section, and second and third plate materials welded to both sides of the first plate material.

[0003] On the other hand, a frame part having multiple frames with a rectangular cross section is described in, for example, Patent Document 2. The frame part disclosed in Patent Document 2 is formed by bending a single plate material into a substantially B-shaped cross section by roll forming. One end and the other end of the plate material are butted together at the bottom of the B and welded by high-frequency welding. Also, the vertical middle part of the B is formed to have a recess that opens toward the left side of the B. The bottom part of this recess is made of overlapping plate materials and spot welded. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-96385 A [Patent Document 2] U.S. Patent No. 7,197,824 Summary of the Invention [Problem to be solved by the invention]

[0005] The frame parts disclosed in Patent Document 1 had a problem in that when forming a closed cross-sectional portion in which multiple adjacent rectangular cross-sectional frames are lined up in succession, such as a closed cross-sectional portion with a cross-section shaped like a character "H" or "E", the number of manufacturing steps, such as positioning and welding of multiple plate materials, was large, resulting in low productivity. The frame part disclosed in Patent Document 2 has a recess formed in the vertical middle part of the B shape, so that the rigidity is insufficient and it cannot be used as a frame for accommodating an automobile battery.

[0006] Furthermore, when welding one end and the other end of the plate material of the frame part shown in Patent Document 2 by high-frequency welding, a jig may be required to prevent the one end and the other end from being separated due to springback and to improve welding accuracy. One possible jig is a box-shaped welding jig that holds the frame part from both the left and right sides in a B shape. For this reason, when manufacturing frame parts by roll forming, there is a demand for a simple method to suppress springback and improve welding accuracy.

[0007] An object of the present invention is to provide a method for manufacturing frame parts formed by roll forming, which can produce highly rigid frame parts having multiple closed cross-sectional portions with high productivity, and which can suppress springback in a simple manner to improve welding accuracy. [Means for solving the problem]

[0008] In order to achieve this object, the manufacturing method of the present invention for manufacturing a frame part formed by roll forming includes a cutting process for cutting a metal plate material to a predetermined length, a forming process for forming a frame part having a T-shaped joint with one end abutted against it and at least two closed cross-sectional portions including two closed cross-sectional portions sandwiching the T-shaped joint by applying roll forming to the plate material so as to surround one end of the plate material, a temporary joining process for performing a temporary joining process to maintain the shape of the frame parts, a waiting process for keeping the frame parts after the temporary joining process on standby, and a final joining process for consistently welding the frame parts waiting in the waiting process, wherein the cutting process is performed either before the forming process or after the temporary joining process but before the waiting process, and while the frame parts are being formed in the forming process, the final joining is performed on the other frame parts.

[0009] The present invention may be directed to a method for manufacturing a frame part formed by roll forming, wherein the frame part has a ladle-shaped portion formed in a ladle-like cross section with one end located at an open end of the ladle, and an outer frame portion formed in a cup-like cross section for accommodating the ladle and forming the two closed cross-sectional portions that sandwich the T-shaped joint in cooperation with the ladle, and the temporary joining step may be performed by performing the temporary joining process on at least a portion where the outer frame portion overlaps the bottom of the ladle and a portion where the outer frame portion overlaps the handle of the ladle.

[0010] The present invention may further provide a method for manufacturing a frame component formed by roll forming, wherein a drilling step is carried out prior to the forming step to drill rivet holes at positions in the plate material where the temporary joining process is to be performed, and the temporary joining process is carried out by driving rivets into the rivet holes using a rivet driving device installed downstream in the feed direction of the frame component from a roll forming device that carries out the forming step.

[0011] The present invention may be directed to a method for manufacturing a frame component formed by roll forming, in which the roll forming in the forming process applies a forming stress so that the frame component is compressively deformed, and the temporary joining process in the temporary joining process may be performed when the frame component has restored to its normal shape by springback caused by the forming stress.

[0012] The present invention may also provide a method for manufacturing a frame component formed by roll forming, in which a groove forming process is carried out in the plate material to form a groove into which the one end fits, before roll forming is performed on the plate material in the forming process, and in the forming process, the T-shaped joint is formed into its final shape by fitting the one end into the groove.

[0013] The present invention may also provide a method for manufacturing a frame component formed by roll forming, in which a step forming process is carried out to form a step in the plate material so that a portion of the plate material is biased to one side in the thickness direction before roll forming is performed on the plate material in the forming process, and in the roll forming process, the T-shaped joint is formed into its final shape by engaging the one end with the step.

[0014] In the present invention, in the method for manufacturing a frame component formed by roll forming, the temporary joining process in the temporary joining step may be performed in a state where the T-shaped joint portion is formed into the final shape.

[0015] In the present invention, in the method for manufacturing a frame component formed by roll forming, the main joining step may be performed by welding the T-shaped joint portion by laser welding from the outside of the frame component.

[0016] In the present invention, in the manufacturing method of a frame component formed by roll forming, the laser welding may also be performed at a position longitudinally adjacent to the frame component and the rivet driven by the rivet driving device in the temporary joining process.

[0017] The present invention may also provide a method for manufacturing a frame component formed by roll forming, wherein the cutting step is performed before the forming step is performed, and the temporary joining process performed in the temporary joining step is performed by clamping the portions where the plate materials are overlapped at both longitudinal ends of the frame component with clamps.

[0018] In the present invention, in the manufacturing method of frame parts formed by roll forming, the temporary joining process carried out in the temporary joining step may be carried out by clamping and binding one outer end portion and the other outer end portion of the frame parts with a clamping member so that the other end portion of the plate material is sandwiched. Effect of the Invention

[0019] According to the present invention, it is possible to provide a manufacturing method for frame parts formed by roll forming, which can produce highly rigid frame parts having multiple closed cross-sectional portions with high productivity, and which can suppress springback in a simple manner to improve welding accuracy. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a flow chart for explaining an embodiment of a method for manufacturing a frame component molded by roll forming according to the present invention. [Diagram 2] FIG. 2 is a side view of the roll forming machine. [Diagram 3] FIG. 3 is a block diagram showing the storage location and the configuration of this welding machine. [Figure 4] FIG. 4 is a cross-sectional view of a frame component. [Diagram 5] FIG. 5 is a perspective view of the frame components. [Figure 6] FIG. 6 is a cross-sectional view of a plate material showing the roll forming process in stages. [Figure 7] FIG. 7 is a cross-sectional view of a plate material showing the roll forming process in stages. [Figure 8] FIG. 8 is a cross-sectional view of a plate material showing the roll forming process in stages. [Figure 9] FIG. 9 is a cross-sectional view for explaining springback. [Figure 10] FIG. 10 is a cross-sectional view of the frame parts after the temporary joining process has been carried out. [Figure 11] FIG. 11 is a flow chart showing a manufacturing method of a frame part including a drilling step. [Figure 12] FIG. 12 is a cross-sectional view for explaining the temporary bonding step. [Figure 13] FIG. 13 is a cross-sectional view of the frame parts compressed during the molding process. [Figure 14] FIG. 14 is a front view showing the positions of rivet holes when the compressive deformation is restored. [Figure 15] FIG. 15 is a cross-sectional view showing a modified example of a T-shaped junction. [Figure 16] FIG. 16 is a cross-sectional view showing a modified example of a T-shaped junction. [Figure 17] FIG. 17 is a flowchart showing a manufacturing method of a frame component having a groove forming step. [Figure 18] FIG. 18 is a cross-sectional view for explaining a method for forming a groove. [Figure 19] FIG. 19 is a cross-sectional view showing a moving path of the groove when one end of a plate material is fitted into the groove. [Figure 20] FIG. 20 is a flow chart for explaining a manufacturing method of a frame component having a step forming step. [Figure 21] FIG. 21 is a cross-sectional view for explaining the shape of a welded portion formed by laser welding. [Figure 22] FIG. 22 is a perspective view of the frame components after the main joining process has been completed. [Diagram 23] FIG. 23 is a perspective view of a frame component with laser welds between multiple temporary joints. [Figure 24]FIG. 24 is a side view of a roll forming machine for carrying out a method of manufacturing a frame component in which a cutting step is carried out after a temporary joining step. [Diagram 25] FIG. 25 is a flow chart for explaining a method of manufacturing a frame component in which the cutting step is performed after the temporary joining step. [Figure 26] FIG. 26 is a perspective view of frame parts that have been temporarily joined using clamps that hold the overlapping portions of the plate materials. [Figure 27] FIG. 27 is a front view of frame parts that have been temporarily joined using clamps that hold the overlapping portions of the plate materials. [Figure 28] FIG. 28 is a front view of the frame parts that have been temporarily joined with a clamp that holds the entire frame part. [Figure 29] FIG. 29 is a cross-sectional view showing another example of the frame part. [Diagram 30] FIG. 30 is a cross-sectional view showing another example of a frame part having a groove into which one end of a plate material is fitted. [Diagram 31] FIG. 31 is a cross-sectional view showing another example of a frame part having a step portion with which one end of a plate material is engaged. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] (First embodiment) Hereinafter, a method for producing a frame component molded by roll forming according to the present invention will be described in detail with reference to Figs. (Outline of manufacturing method for frame parts) The manufacturing method for frame parts formed by roll forming according to this embodiment is a method in which a cutting process S1, a forming process S2, a temporary joining process S3, a waiting process S4, and a main joining process S5 are carried out in this order, as shown in the flow chart of Fig. 1. Frame parts manufactured by this manufacturing method can be used as parts for supporting on-board parts of an automobile or the like (not shown), or as parts constituting part of the framework of the vehicle body.

[0022] The cutting process S1, the forming process S2, and the temporary joining process S3 are performed by a roll forming machine 1 shown in Fig. 2. The waiting process S4 is performed in a storage location 2 (see Fig. 3), and the main joining process S5 is performed by a main welding machine 3 (see Fig. 3). The roll forming machine 1 feeds a metal plate material 5 to the right in Fig. 1 from a cutting device 4 located at the leftmost position in Fig. 2 to manufacture a product of a predetermined shape. The cutting device 4 is a device for carrying out a cutting step S1. This cutting device 4 has a function of cutting a metal plate material 5 having a predetermined width to a predetermined length, a function of performing drilling, groove processing, press processing, etc. on the plate material 5, and a function of feeding the plate material 5 downstream in the feeding direction.

[0023] A multi-stage roll forming machine 6 is disposed downstream of the cutting device 4 in the feeding direction of the plate material 5, and a temporary joining device 7 is disposed downstream of the multi-stage roll forming machine 6 in the feeding direction of the plate material 5. The multi-stage roll forming machine 6 is a device for carrying out the forming step S2. In this embodiment, the multi-stage roll forming machine 6 corresponds to the "roll forming device" of the present invention. This multi-stage roll forming machine 6 uses many rolls 6a to bend the plate material 5 into a predetermined shape by roll forming, forming the frame part 8 shown in Figs. 4 and 5. Fig. 4 shows a cross-sectional view of the frame part 8 cut along imaginary plane A shown in Fig. 5. Imaginary plane A shown in Fig. 5 is hatched downward to the left. The roll forming will be described later.

[0024] The temporary joining device 7 is a device for carrying out the temporary joining step S3. This temporary joining device 7 performs a temporary joining process in which the shape of the frame parts 8 formed by the multi-stage roll forming machine 6 is maintained. The temporary joining device 7 according to this embodiment is constituted by a rivet driving device 9. The temporary joining process according to this embodiment is riveting of the portions where the plate materials 5 are overlapped with each other. The temporary joining process will be described in detail later.

[0025] After the temporary joining process by the temporary joining device 7 is completed, the frame parts 8 are removed from the roll forming machine 1 and moved to the storage location 2. The multi-stage roll forming machine 6 continuously produces frame parts 8 after the temporary joining process has been completed. For this reason, as shown in Fig. 3, a plurality of frame parts 8 are stored in the storage location 2 to await processing in the next process, the main joining process S5. The process in which the frame parts 8 await the next processing in the storage location 2 in this manner becomes the waiting process S4. In the main joining process S5, the frame parts 8 waiting in the storage location 2 are supplied to the main welding machine 3, and main joining is performed on the frame parts 8 to prevent deformation of the frame parts 8. In the main joining process S5 according to this embodiment, laser welding is performed. A detailed description of laser welding will be given later.

[0026] (Specific explanation of manufacturing method of frame parts) (Description of molding process S2) The frame component 8 shown in Fig. 4 is formed by applying roll forming to a plate material 5 so as to surround one end 11 of the plate material 5. By performing roll forming in this manner, a T-shaped joint 12 having a T-shaped cross section where one end 11 of the plate material 5 abuts is formed. The T-shaped joint 12 is laser welded in a main joining process S5, which will be described in detail later. For the sake of convenience, when describing each part of the frame component 8, the upper side of Fig. 4 will be referred to as the upper part of the frame component 8, and the left side of Fig. 4 will be referred to as the left side of the frame component 8.

[0027] The roll forming according to this embodiment is carried out so as to form a first closed cross-sectional portion 13 and a second closed cross-sectional portion 14 which sandwich a T-shaped joint portion 12, and a third closed cross-sectional portion 15 which is located below the frame component 8 shown in Fig. 4. When forming the first to third closed cross-sectional portions 13 to 15, first, a ladle-shaped portion 16 having a ladle-shaped cross section including one end 11 of the plate material 5 is formed in the early stage of the roll forming. The ladle-shaped portion 16 has one end 11 of the plate material 5, and is composed of a first horizontal wall 21 extending from the one end 11 to the left side in Fig. 4, a first vertical wall 22 extending downward from the left end of the first horizontal wall 21, a second horizontal wall 23 extending right from the lower end of the first vertical wall 22, and a second vertical wall 24 extending downward from the right end of the second horizontal wall 23. The ladle-shaped portion 16 is formed so that one end 11 of the plate material 5 is located at the open end of the ladle, the first vertical wall 22 forms the bottom of the ladle, and the second vertical wall 24 forms the handle of the ladle.

[0028] Since the frame component 8 according to this embodiment has three closed cross-sectional portions (first to third closed cross-sectional portions 13-15), after the ladle-shaped portion 16 is formed, the outer peripheral frame 17 is formed so as to cooperate with the ladle-shaped portion 16 to form the first to third closed cross-sectional portions 13-15. The outer peripheral frame 17 includes an outer frame portion 18 having a cup-shaped cross-section that accommodates the ladle of the ladle-shaped portion 16. The outer frame portion 18 cooperates with the ladle of the ladle-shaped portion 16 to form two closed cross-sectional portions (first and second closed cross-sectional portions 13, 14) that sandwich a T-shaped joint.

[0029] The outer peripheral frame 17 is formed so as to surround the ladle-shaped portion 16 from the lower end of the second vertical wall 24 (the tip of the handle of the ladle), passing through the bottom side of the ladle and the opening side of the ladle. In detail, the outer peripheral frame 17 is formed by a third horizontal wall 25 extending leftward from the lower end of the second vertical wall 24, a third vertical wall 26 extending upward from the left end of the third horizontal wall 25 and overlapping with the first vertical wall 22, a fourth horizontal wall 27 extending rightward from the upper end of the third vertical wall 26, and a fourth vertical wall 28 extending downward from the right end of the fourth horizontal wall 27 and overlapping with one end 11 of the plate material 5 and the second vertical wall 24. The outer frame portion 18 is composed of a third vertical wall 26, a fourth horizontal wall 27, and a fourth vertical wall .

[0030] The forming sequence when forming the frame component 8 shown in Fig. 4 by the roll forming method is, for example, as shown in Fig. 6(A)-(G), Fig. 7(A)-(D), and Fig. 8(A)-(D). The roll forming is performed by the multi-stage roll forming machine 6 of the roll forming machine 1 shown in Fig. 1. Fig. 6(A)-(G), Fig. 7(A)-(D), and Fig. 8(A)-(D) are cross-sectional views of the plate material 5 as viewed from the longitudinal direction.

[0031] To form the frame part 8, first, the ladle-shaped portion 16 is formed as shown in Fig. 6(A) to Fig. 7(B). That is, the first horizontal wall 21 including one end 11 of the flat plate material 5 is bent, and the first vertical wall 22, the second horizontal wall 23, and the second vertical wall 24 are formed in this order. The radius of curvature of the curved portion 29 (see Fig. 4) between each wall can be adjusted by the multi-stage roll forming machine 6 according to the rigidity and collision performance. Then, as shown in Fig. 7(C) to Fig. 8(D), the third horizontal wall 25, the third vertical wall 26, the fourth horizontal wall 27, and the fourth vertical wall 28 are formed in this order.

[0032] More specifically, in the step shown in Fig. 7(D), the third vertical wall 26 and the first vertical wall 22 are overlapped to form a double wall. Then, in the step shown in Figs. 8(A)-(B), the third vertical wall 26 is bent while forming a curved portion 29 to form a fourth horizontal wall 27. Thereafter, in the step shown in Figs. 8(C)-(D), the fourth vertical wall 28 is overlapped with one end 11 of the plate material 5 and the second vertical wall 24 to form the T-shaped joint portion 12. After overlapping the third vertical wall 26 with the first vertical wall 22 in the step shown in Fig. 7(D), a step can be added in which the third vertical wall 26 is bent to the left in the figure as shown in Fig. 7(E) to form a frame 17a having a square cross section at the upper left side of the outer peripheral frame 17 in the figure.

[0033] This rectangular cross-sectional frame 17a is formed by bending the third vertical wall 26 clockwise in the figure, and finally, the third vertical wall 26 is formed so that it overlaps with the part bent to the left as it extends downward, adding a closed cross section to the outside. After forming the rectangular cross-sectional frame 17a in this way, the third vertical wall 26 is bent so that its tip faces rightward in the figure, resulting in the state shown in Figure 8(B). When roll forming is performed in this manner, springback occurs at the curved portion 29, and the frame part 8 may be deformed after forming as shown in Fig. 9. When springback occurs, the fourth vertical wall 28 separates from one end 11 of the plate material 5 and the second vertical wall 24, and the first vertical wall 22 separates from the third vertical wall 26. If this deformation occurs, it will be impossible to perform laser welding on the T-shaped joint 12 in a later process. In order to prevent such deformation due to springback, a temporary joining process S3 is performed after the forming process S2.

[0034] (Explanation of temporary joining process S3) The temporary joining step S3 is performed by performing a temporary joining process on at least a first overlapping portion 31 (see FIG. 4) where the outer frame portion 18 (third vertical wall 26) overlaps with the bottom of the ladle (first vertical wall 22) of the ladle-shaped portion 16, and a second overlapping portion 32 where the outer frame portion 18 (fourth vertical wall 28) overlaps with the handle of the ladle (second vertical wall 24). In this embodiment, the temporary joining step S3 is performed using a rivet driving device 9 installed downstream in the feed direction of the frame parts 8 from the multi-stage roll forming machine 6 that performs the forming step S2.

[0035] The rivet driving device 9 performs riveting using a blind rivet 33, as shown in Fig. 10. Fig. 10 is a cross-sectional view of the frame part 8 shown in Fig. 5 cut along imaginary plane B. Imaginary plane B shown in Fig. 5 is hatched downward to the right. The riveting is performed by inserting the blind rivet 33 into a rivet hole 34 in the frame part 8 from the outside of the frame part 8. The rivet hole 34 can be drilled at a predetermined position in the plate material 5 by the cutting device 4. That is, the cutting step S1 according to this embodiment is performed including a drilling step S1A for drilling the rivet hole 34, as shown in Fig. 11.

[0036] The rivet holes 34 are composed of outer rivet holes 34a formed in the outer frame portion 18 (third and fourth vertical walls 26, 28) of the frame component 8, and inner rivet holes 34b formed in the first and second vertical walls 22, 24. The hole diameter of the outer rivet hole 34a is larger than the hole diameter of the inner rivet hole 34b. 12(A) to 12(C), the blind rivet 33 is made up of a cylindrical main body 35 and a shaft 36 that is movably inserted into the main body 35. A flange 35a is provided at one end of the main body 35. The shaft 36 passes through the main body 35. A head 36a whose outer diameter is equal to the outer diameter of the main body 35 is provided at the end of the shaft 36 that protrudes on the side opposite the flange 35a of the main body 35.

[0037] To carry out the temporary joining step S3 using this blind rivet 33, first, as shown in Fig. 12(A), the blind rivet 33 is inserted into the rivet hole 34 from the outside of the frame component 8, and the shaft portion 36 is pulled toward the outside of the frame component 8 with the flange 35a pressed against the third and fourth vertical walls 26, 28. By pulling the shaft portion 36 in this manner, the tip 35b of the main body portion 35 is spread apart by the head portion 36a, as shown in Fig. 12(B). Thereafter, the shaft portion 36 is pulled further a predetermined length until the tip 35b of the main body portion 35 is significantly deformed as shown in Fig. 12(C), and the shaft portion 36 is cut off at the portion protruding from the flange 35a. By performing this temporary joining process, deformation due to springback thereafter is restricted, and one end 11 of the plate material 5 is held in abutted position against the fourth vertical wall 28 at the T-shaped joint 12.

[0038] Springback begins when forming by the multi-stage roll forming machine 6 is completed. Therefore, springback that occurs before the temporary joining process is performed may cause misalignment between the outer rivet hole 34a and the inner rivet hole 34b. In this embodiment, the outer rivet hole 34a is formed to have a larger hole diameter than the inner rivet hole 34b, so a wide tolerance can be provided for misalignment due to springback.

[0039] In order to prevent the outer rivet hole 34a from being misaligned with the inner rivet hole 34b due to springback that occurs before the temporary joining process is performed, it is possible to apply a forming stress to the frame part 8 so that it is compressed and deformed from its normal shape during roll forming. That is, when forming the outer rim 17 of the frame part 8, a part of the frame part 8 is elastically deformed as shown in FIG. 13, and the frame part 8 is formed so that it will have a normal shape during the springback process due to stress release after forming. In the frame part 8 shown in FIG. 13, the first and second side walls 21, 23 of the ladle-shaped part 16 are inclined downward to the right, and the lower part of the frame part 8 is deformed as if it has been crushed in the left and right directions due to compression. In FIG. 13, the frame part 8 is drawn deformed more than it actually is in order to make the deformation easier to understand.

[0040] By performing roll forming in this way while taking into consideration stress relief after forming, frame component 8 returns to its normal shape, i.e., the shape shown in Fig. 4, due to springback caused by stress relief after forming. When frame component 8 is compressively deformed by roll forming, there is a misalignment between outer rivet hole 34a and inner rivet hole 34b immediately after forming, as shown in Fig. 14(A). However, when frame component 8 returns to its normal shape due to springback, the misalignment between outer rivet hole 34a and inner rivet hole 34b is eliminated, as shown in Fig. 14(B). By performing a temporary joining process at this time, riveting using blind rivet 33 is performed correctly.

[0041] In order to perform riveting in this manner, the temporary joining device 7 may be disposed so that the frame parts 8 are restored to their normal shape while being sent from the multi-stage roll forming machine 6 to the temporary joining device 7. In order to achieve this, it is considered that the distance D (see FIG. 2) between the multi-stage roll forming machine 6 and the temporary joining device 7 is set to the distance that the frame parts 8 move after being formed until they are restored to their normal shape. By adopting this configuration, the temporary joining process is performed when the frame parts 8, which have been compressively deformed by roll forming, are restored to their normal shape by springback caused by stress release.

[0042] When the frame part 8 is compressed and deformed by roll forming, in order to ensure that one end 11 of the plate material 5 is abutted against the fourth vertical wall 28 at the T-shaped joint 12 during the process of the frame part 8 being restored, it is possible to adopt the configurations shown in Figures 15 and 16. The T-shaped joint 12 shown in FIG. 15 has a structure in which one end 11 of the plate material 5 fits into a groove 37 formed in the fourth vertical wall 28. The groove 37 shown in FIG. 15 is formed by a guide shape portion 38 continuing to the inner side surface 28a of the fourth vertical wall 28 and a groove bottom portion 39 connected to the guide shape portion 38. The guide shape portion 38 is formed by an inclined surface extending from the side surface 28a toward the inside of the groove 37. The inclined surface is inclined so that the opening width of the groove 37 gradually becomes wider toward the outside of the groove 37. The groove bottom portion 39 is composed of a side surface 39a extending in the depth direction of the groove 37 and a bottom surface 39b that becomes the groove bottom, and is formed so that the cross-sectional shape is an angular C-shaped groove. The groove width of the groove bottom portion 39 is a width in which one end 11 of the plate material 5 fits.

[0043] The groove 37 shown in Fig. 15 can be formed by cutting or molding. The groove forming step of forming the groove 37 in the fourth vertical wall 28 by cutting or molding is performed before the roll forming of the plate material 5 is performed in the molding step S2. For example, as shown in Fig. 17, the groove forming step S6 can be performed between the cutting step S1 and the molding step S2. When the grooves 37 are formed by cutting, a rotating cutting tool 41 is pressed against the plate material 5 as shown in Fig. 18(A). The cutting tool 41 can be provided in the cutting device 4, or can be disposed between the cutting device 4 and the multi-stage roll forming machine 6.

[0044] When the groove 37 is formed by molding, a groove forming roll 42 is pressed against the plate material 5 as shown in FIG. 18(B). The groove forming roll 42 can be provided at a position before the roll forming of the multi-stage roll forming machine 6 is performed. A groove processing part 43 is provided on the outer periphery of the roll 42. By pressing the roll 42 against the plate material 5 and rotating it, the shape of the groove processing part 43 is transferred to the plate material 5 to form the groove 37. The groove 37 is formed in a shape in which a part of the inner surface (side surface 28a) of the fourth vertical wall 28 is recessed, but a convex shape may be exposed on the outer surface of the part where the recess is formed. When the convex shape is exposed in this way, it becomes a mark for laser welding.

[0045] In the T-shaped joint 12 shown in Fig. 15, as the fourth vertical wall 28 approaches one end 11 of the plate material 5 by roll forming, a corner portion 44 of the one end 11 fits into a corner portion 45 of the groove bottom 39 immediately after passing through the guide shape portion 38, as shown in Fig. 19. Then, the fourth vertical wall 28 tilts clockwise in the figure around this corner portion 45, and the one end 11 of the plate material 5 fits into the groove bottom 39. By fitting the one end 11 of the plate material 5 into the groove 37 in this way, the T-shaped joint 12 in its final shape is formed.

[0046] The T-shaped joint 12 shown in Fig. 16 has a structure in which one end 11 of the plate material 5 engages with a step 46 formed in the fourth vertical wall 28. The step 46 is formed in the fourth vertical wall 28 such that a portion of it is positioned offset to one side in the thickness direction. The step 46 shown in Fig. 16 is formed such that a portion of the fourth vertical wall 28 that is located above the one end 11 of the plate material 5 is positioned offset to the left. This step 46 can be formed by press molding using the press function of the cutting device 4.

[0047] The step forming step of forming the step 46 in the fourth vertical wall 28 is performed before the roll forming of the plate material 5 in the forming step S2. For example, as shown in Fig. 20, a step forming step S7 can be performed between the cutting step S1 and the forming step S2. One end 11 of the plate material 5 engages with the step 46 formed in the fourth vertical wall 28, thereby forming the T-shaped joint 12 in its final shape.

[0048] (Description of main joining process S5) The main joining process S5 is performed by sequentially feeding the frame components 8 that have been subjected to the temporary joining process and moved to the storage location 2 into the main welding machine 3. That is, in the main joining process S5, while the frame components 8 are being formed in the forming process S2, laser welding is performed on the other frame components 8 waiting in the waiting process S4 (other frame components 8 in the waiting process S4). The laser welding is performed consistently using the same welding method on the frame components 8 waiting in the waiting process S4. In the main joining step S5, it is preferable to perform laser welding simultaneously on a plurality of frame components 8 using a plurality of main welding machines 3. The reason for this is that the joining (laser welding) that regulates the cross-sectional shape of a frame component having two closed cross sections on both sides of a T-shaped joint requires a longer operation time than roll forming, and by performing laser welding simultaneously on a plurality of frame components 8, productivity can be increased. Laser welding is performed by irradiating the T-shaped joint 12 with laser light L from the outside of the frame part 8 (from the opposite side to the first lateral wall 21) as shown in Fig. 21. Fig. 21 shows the T-shaped joint 12 when the groove 37 is used, but the same applies to the case where the groove 37 is not used.

[0049] The laser light L is irradiated to the outer surface 28b of the fourth vertical wall 28 at a position corresponding to the first horizontal wall 21 (one end 11 of the plate material 5). By irradiating the T-shaped joint 12 with the laser light L in this manner, a part of the fourth vertical wall 28 and a part of the first horizontal wall 21 melt and mix together, and are welded together. By performing laser welding, a warhead-shaped melted portion 47 is generated, as shown by hatching downward to the left in FIG. 21. The warhead shape of the melted portion 47 is a convex shape extending from the laser irradiation surface (outer surface 28b) toward the first horizontal wall 21. The warhead-shaped melted portion makes the first horizontal wall 21 more likely to collapse under a load from the laser irradiation direction, and the collapse of the first horizontal wall 21 makes it easier for the load to concentrate on the curved portion 29, increasing the amount of shock absorption.

[0050] The laser welding is performed continuously from one end to the other end in the longitudinal direction of the frame part 8, as shown by the welded portion designated by reference numeral 48 in FIG. By completing the main joining step S5, a frame component 51 is completed in its final shape with no change in shape being allowed. Laser welding can also be performed on a position of the frame component 8 adjacent in the longitudinal direction to the blind rivet 33 driven by the rivet driving device 9 in the temporary joining step S3, as shown in Figure 23. Laser welding has been performed on the frame component 8 shown in Figure 23 so that a linear weld 52 is formed between a plurality of temporary joining treatment portions (blind rivets 33) that are lined up at a predetermined interval in the longitudinal direction.

[0051] (Explanation of Effects of the First Embodiment) The manufacturing method for frame parts formed by roll forming in this embodiment includes a cutting process S1 in which a metal plate material 5 is cut to a predetermined length, a forming process S2 in which the plate material 5 is roll formed to form a frame part 8 having a T-shaped cross-section of a T-shaped joint 12 and first, second closed cross-sectional portions 13, 14 and a third closed cross-sectional portion 15 sandwiching the T-shaped joint 12, a temporary joining process S3 in which a temporary joining process is performed to maintain the shape of the frame part 8, a waiting process S4 in which the frame part 8 is kept on standby, and a final joining process S5 in which final welding is consistently performed on the frame parts 8 waiting in the waiting process S4, and while the frame part 8 is being formed in the forming process S2, final welding is performed on the other frame parts 8 in the waiting process S4.

[0052] According to this manufacturing method, it is possible to form a plurality of adjacent closed cross sections (first and second closed cross-sectional portions 13, 14) that sandwich the T-shaped joint portion 12, making it possible to manufacture a highly rigid frame component 51. This frame component 51 can be used as a side frame of a battery case that houses a battery for an electric vehicle. Since the temporary joining process is performed after the roll forming, the frame parts 8 will not be deformed by springback even if the waiting step S4 is performed after the roll forming. Therefore, the accuracy of the main welding after the roll forming can be improved by a simple method that does not use a box-shaped welding jig or the like.

[0053] The joining (laser welding) time required to regulate the cross-sectional shape of the frame parts, which have two closed cross sections on both sides of the T-shaped joint, is longer than the time required for roll forming. Therefore, by providing a waiting process S4, production is possible without reducing the roll forming speed, thereby improving productivity. Therefore, according to this embodiment, it is possible to provide a manufacturing method for frame parts formed by roll forming, which can produce highly rigid frame parts having multiple closed cross-sectional portions with high productivity, and which can suppress springback in a simple manner to improve welding accuracy.

[0054] Frame component 8 formed by the manufacturing method for a frame component according to this embodiment has a ladle-shaped portion 16 formed in a ladle-like cross section with one end 11 of plate material 5 located at the open end of the ladle, and an outer frame portion 18 formed in a cup-like cross section for accommodating the ladle and forming two closed cross-sectional portions (first and second closed cross-sectional portions 13, 14) that cooperate with the ladle to sandwich a T-shaped joint. The temporary joining step S3 is performed by performing a temporary joining process on at least the portion where outer frame portion 18 overlaps the bottom of the ladle and the portion where outer frame portion 18 overlaps the handle of the ladle.

[0055] In this embodiment, a drilling step S1A is carried out prior to the forming step S2, in which rivet holes 34 are drilled in the plate material 5 at positions where temporary joining processing will be performed. The temporary joining step S3 is carried out by driving blind rivets 33 into the rivet holes 34 using a rivet driving device 9 installed downstream in the feed direction of the frame components 8 from the multi-stage roll forming machine 6 that carries out the forming step S2. Since roll forming can form complex closed cross sections, it is easy to create complex closed cross sections including the T-shaped joint 12. However, the parts that cannot be overbended are in a state of compressive deformation of the cross section, and will return to their original shape due to springback. Therefore, these parts are temporarily joined by a temporary joining process. That is, the bending points around the T-shaped joint 12 (the connection part between the second vertical wall 24 and the third horizontal wall 25, and the connection part between the fourth horizontal wall 27 and the fourth vertical wall 28) cannot be overbended after the T-shaped joint 12 is formed, so there is a possibility that they will become more open than the normal position due to springback. Therefore, the opening of the ladle is configured to be the T-shaped joint 12, and the part that will become the bottom of the ladle and the part that will become the handle are temporarily joined to suppress springback. A complex closed cross section including a T-shaped joint 12 cannot be temporarily joined by pinch spot welding, but one-sided joining is possible by using a rivet. Even when temporary joining is performed on both sides of the frame part 8, the rivet can be driven from both sides of the frame part 8 by the rivet driving device 9, so the time required for temporary joining can be short. By performing temporary joining on both sides of the frame part 8, the strength of the temporary joint is stabilized.

[0056] The roll forming in the forming step S2 according to this embodiment is considered to impart forming stress so as to compressively deform the frame component 8. The temporary joining process in the temporary joining step S3 is performed when the frame component 8 restores to its normal shape due to springback caused by stress release. According to this embodiment, since laser welding can be performed on frame components 8 having a regular shape in the main joining step S5, high-quality frame components can be manufactured.

[0057] In this embodiment, when a groove 37 into which one end 11 fits is formed in the plate material 5 and the one end 11 of the plate material 5 is fitted into the groove 37 in the forming step S2, it is possible to prevent the T-shaped joint 12 from failing to join due to spring back. Also, fitting is possible while performing roll forming within a closed cross section.

[0058] In this embodiment, when the step 46 is formed in the plate material 5 so that a part of it is positioned offset to one side in the thickness direction, and one end 11 of the plate material 5 is engaged with the step 46 in the forming step S2, it is possible to prevent the T-shaped joint 12 from failing to be joined due to spring back. Also, it becomes possible to engage the plate material 5 while performing roll forming within a closed cross section.

[0059] In this embodiment, the temporary joining process in the temporary joining step S3 is performed in a state where the T-shaped joint portion 12 is formed into its final shape. Therefore, the product shape with a closed cross section adjacent to the T-shaped joint portion 12 can be maintained.

[0060] The main joining step S5 according to this embodiment is performed by welding the T-shaped joint 12 from the outside of the frame part 8 by laser welding. Although the T-shaped joint 12 is located inside the closed cross section, laser welding makes it possible to weld from one side of the frame component 8. Therefore, a frame component with high rigidity can be manufactured.

[0061] In this embodiment, when laser welding is also performed on the rivet and the frame part 8 at positions adjacent in the longitudinal direction, it is possible to reliably prevent the shape of the final product from being changed.

[0062] (Second embodiment) The cutting step S1 can be performed after the molding step S2. An embodiment in which this configuration is adopted will be described with reference to Figures 24 and 25. In Figures 24 and 25, members that are the same as or equivalent to those described with reference to Figures 1 to 23 are given the same reference numerals, and detailed description thereof will be omitted.

[0063] The method for producing a frame part formed by roll forming in this embodiment is carried out as shown in the flow chart of FIG. 25 using a roll forming machine 61 shown in FIG. The roll forming machine 61 sends the metal sheet 5 to the right side in Fig. 24 from the uncoiler 62 located at the leftmost position in Fig. 24, and produces a product of a predetermined shape. The metal sheet 5 is attached to the uncoiler 62 in a state where it is wound in a coil shape.

[0064] Downstream of the uncoiler 62 in the feeding direction of the plate material 5, devices such as a pre-hole press 63, a multi-stage roll forming machine 64, a temporary joining device 65 and a cutting machine 66 are arranged in this order. The pre-hole press 63 performs machining such as drilling, cutting, and pressing on the plate material 5. The rivet holes 34, grooves 37, step portions 46, etc. can be formed by this pre-hole press 63.

[0065] The cutting machine 66 cuts the cylindrically formed plate material 5 to a predetermined length after the temporary joining process. The plate material 5 is cut by the cutting machine 66 to form frame components 8 that will become the frame components 51. The frame components 8 are sent to the storage location 2 shown in FIG. 3 and are sequentially fed into the main welding machine 3. When this configuration is adopted, the cutting step S1 is performed after the molding step S2 and the temporary joining step S3 are completed, and then the waiting step S4 and the main joining step S5 are performed in sequence, as shown in Fig. 23. That is, the cutting step S1 is performed either after the temporary joining step S3 and before the waiting step S4 as shown in this embodiment, or before the molding step S2 as in the above-mentioned embodiment. By performing the cutting step S1 after the temporary joining step S3, the plate material 5 formed into a cylindrical shape can be cut in a state in which deformation due to springback is suppressed.

[0066] (Another embodiment of the temporary bonding process) When the first embodiment is adopted, the temporary joining process is performed using blind rivets 33. However, the temporary joining process can be performed using clamps 71, 72 as shown in Figures 26 to 28. In Figures 26 to 28, members that are the same as or equivalent to those described with reference to Figures 1 to 23 are given the same reference numerals and detailed description thereof will be omitted as appropriate.

[0067] The frame part 8 shown in Fig. 26 is formed in the forming step S2 from the plate material 5 cut to a predetermined length before the forming step S2 is performed, and has clamps 71 attached to both ends in the longitudinal direction. As shown in Fig. 27, the clamps 71 hold the overlapping portions of the plate materials 5 in the thickness direction and hold the plate materials 5 in close contact with each other. The clamps 71 shown in Fig. 27 are attached to the overlapping portions of the first vertical wall 22 and the third vertical wall 26 of the frame part 8 and to the overlapping portions of the second vertical wall 24 and the fourth vertical wall 28 of the frame part 8.

[0068] The clamp 72 shown in FIG. 28 corresponds to the "clamping member" of the present invention, and has a structure in which one outer end 8a (left end) and the other outer end 8b (right end) of the frame component 8 are clamped and bound so that the other end 73 (the lower end of the fourth vertical wall 28) of the plate material 5 is clamped. The temporary joining process using the clamp 72 shown in FIG. 28 can be performed even when the plate material 5 is not cut into the individual frame components 8, and can also be performed after the plate material 5 is cut into the individual frame components 8. In other words, the temporary joining process using the large clamp 72 shown in FIG. 28 can be performed in either case where the cutting step S1 is performed before the forming step S2, or where the cutting step S1 is performed after the temporary joining step S3 and before the waiting step S4.

[0069] (Modification of frame part 8) In each of the above-described embodiments, an example has been shown in which a frame component 8 having first to third closed cross-sectional portions 13 to 15 is formed by roll forming. However, the present invention is also applicable to a case in which a frame component 83 having only first and second closed cross-sectional portions 81, 82 located on both sides of a T-shaped joint 12 is formed by roll forming, as shown in Figs. 29 to 31. In Figs. 29 to 31, members that are the same as or equivalent to those described with reference to Figs. 1 to 23 are given the same reference numerals, and detailed descriptions thereof will be omitted as appropriate.

[0070] In the frame part 83 shown in Figs. 29 to 31, after forming the first horizontal wall 21, the first vertical wall 22, and the second horizontal wall 23, the plate material 5 is bent upward to form a fifth vertical wall 84 so as to overlap with the tip of the first horizontal wall 21 (one end 11 of the plate material 5). Then, after forming a fifth horizontal wall 85 parallel to the first horizontal wall 21, a sixth vertical wall 86 extending downward is formed. The lower end of the sixth vertical wall 86 becomes the other end of the plate material 5. This sixth vertical wall 86 is formed so as to overlap with the first vertical wall 22. In this embodiment, a temporary joining process is performed in a temporary joining step S3 on an overlapping portion 87 where the first vertical wall 22 and the sixth vertical wall 86 overlap.

[0071] A groove 37 into which one end 11 of the plate material 5 fits is formed in the fifth vertical wall 84 of the frame part 83 shown in Fig. 30. A step 46 into which one end 11 of the plate material 5 engages is formed in the fifth vertical wall 84 of the frame part 83 shown in Fig. 31. Even when molding a frame part 83 having only first and second closed cross-sectional portions 81, 82 as shown in Figures 29 to 31, it is possible to productively manufacture a highly rigid frame part having multiple closed cross-sectional portions as in the embodiment shown in Figures 1 to 28, and it is possible to provide a manufacturing method for frame parts molded by roll forming that can suppress springback in a simple manner and improve welding accuracy.

[0072] The temporary joining process can be performed using the blind rivets 33 and the clamps 71 and 72 as described above, or can be performed using an adhesive (not shown). The main joining process, which involves welding in an integrated manner, may be laser welding, MIG welding, friction stir welding, or the like. In the above-described embodiment, the frame part 8 has an outer peripheral frame 17 formed so as to surround the ladle-shaped part 16 from the tip of the handle of the ladle through the bottom side and the opening side of the ladle, but the frame part 8 may surround the ladle-shaped part 16 through the opening side and the bottom side of the ladle, and may have an opening, without being limited to the outer peripheral frame 17. For example, after forming the ladle-shaped part 16, the outer frame part 18 is formed by performing roll forming in the order of the fourth vertical wall 28, the fourth horizontal wall 27, and the third vertical wall 26. The outer frame part 18 is formed in a cup-like cross section that opens downwards and accommodates the ladle of the ladle-shaped part 16, and forms two closed cross-sectional parts (first and second closed cross-sectional parts 13, 14) that sandwich the T-shaped joint part 12 in cooperation with the ladle. In the above embodiment, the third closed cross-sectional portion 15 is provided on the left side of the dipper handle (second vertical wall 24), but it may be provided on the right side of the dipper handle, and the fourth and fifth closed cross-sectional portions may be provided above and below or to the left and right. Also, the dipper-shaped portion 16 is roll-formed clockwise, but it may also be roll-formed counterclockwise. [Explanation of symbols]

[0073] 5...plate material, 8,51,83...frame parts, 9...rivet driving device, 11...one end, 12...T-shaped joint, 13...first closed cross-sectional portion, 14...second closed cross-sectional portion, 15...third closed cross-sectional portion, 16...ladle-shaped portion, 17...peripheral frame, 18...outer frame portion, 31...first overlapping portion, 32...second overlapping portion, 33...blind rivet, 34...rivet hole, 37...groove, 46...step portion, 71...clamp, 72...clamp (clamping member), S1...cutting process, S1A, drilling process, S2...forming process, S3...temporary joining process, S4...waiting process, S5...actual joining process, S6...groove forming process, S7...step forming process.

Claims

1. A cutting process of cutting a metal plate material to a predetermined length; a forming process for forming a frame part having a T-shaped joint having a T-shaped cross section where the one end of the plate material is butted against the T-shaped joint, and at least two closed cross-sectional portions including two closed cross-sectional portions sandwiching the T-shaped joint by performing roll forming on the plate material so as to surround one end of the plate material; a temporary joining process for performing a temporary joining process in which the frame parts are held in shape; a waiting process in which the frame components after the temporary joining process are kept waiting; a main joining process for consistently welding the frame parts waiting in the waiting process, the forming step is carried out such that a wall having the one end of the plate material is shared by the two closed cross-sectional portions and serves as a boundary between the two closed cross-sectional portions; The temporary joining process is a joining process for holding the overlapping plate materials in a state of close contact without melting and mixing the plate materials, In the main joining step, a welding is performed in which a part of the wall including the one end of the plate material and a part of the wall of the plate material against which the one end is abutted are melted and mixed together, The cutting step is performed either before the molding step or after the temporary joining step and before the waiting step; A method for manufacturing a frame component formed by roll forming, characterized in that while the frame component is being formed in the forming process, the welding in the main joining process is performed on another frame component in the waiting process.

2. 2. The method for producing a frame component formed by roll forming according to claim 1, the frame part has a ladle-shaped portion having a ladle-shaped cross section and one end located at an open end of the ladle, and an outer frame portion having a cup-shaped cross section for accommodating the ladle and cooperating with the ladle to form the two closed cross-sectional portions that sandwich the T-shaped joint, A manufacturing method for a frame part molded by roll forming, characterized in that the temporary joining step is carried out by performing the temporary joining process on at least a portion where the outer frame part overlaps the bottom of the ladle and a portion where the outer frame part overlaps the handle of the ladle.

3. 3. The method for producing a frame component formed by roll forming according to claim 2, Furthermore, a drilling step is carried out prior to the forming step to drill rivet holes at positions in the plate material where the temporary joining process is performed, a roll forming device that performs the molding process, and a rivet driving device that drives a rivet into the rivet hole, the rivet driving device being installed downstream in the feed direction of the frame component from the roll forming device that performs the molding process.

4. 4. The method for producing a frame component formed by roll forming according to claim 3, In the roll forming process, a forming stress is applied so that the frame parts are compressively deformed, A method for manufacturing a frame part formed by roll forming, characterized in that the temporary joining process in the temporary joining step is performed when the frame part restores to its normal shape due to springback caused by the forming stress.

5. 5. The method for producing a frame component formed by roll forming according to claim 4, Before the roll forming process is performed on the plate material in the forming process, a groove forming process is performed to form a groove in the plate material into which the one end is fitted, A method for manufacturing a frame component formed by roll forming, characterized in that in the forming process, the T-shaped joint is formed into a final shape by fitting the one end into the groove.

6. 5. The method for producing a frame component formed by roll forming according to claim 4, Before the roll forming process is performed on the plate material in the forming process, a step forming process is performed to form a step in the plate material such that a part of the plate material is positioned to one side in a thickness direction, A method for manufacturing a frame component formed by roll forming, characterized in that in the forming process, the one end engages with the step portion to form the T-shaped joint into a final shape.

7. The method for producing a frame component formed by roll forming according to claim 5 or 6, A method for manufacturing a frame component formed by roll forming, characterized in that the temporary joining process in the temporary joining step is performed in a state where the T-shaped joint portion is formed into the final shape.

8. The method for producing a frame component formed by roll forming according to claim 7, A method for manufacturing a frame part formed by roll forming, characterized in that the main joining step is performed by welding the T-shaped joint portion by laser welding from the outside of the frame part.

9. 9. The method for producing a frame component formed by roll forming according to claim 8, A method for manufacturing a frame component formed by roll forming, characterized in that the laser welding is also performed at a position longitudinally adjacent to the frame component and the rivet driven by the rivet driving device in the temporary joining process.

10. 2. The method for producing a frame component formed by roll forming according to claim 1, The cutting step is performed before the molding step is performed, A manufacturing method for a frame part formed by roll forming, characterized in that the temporary joining process is performed by clamping the portions where the plate materials are overlapped at both longitudinal ends of the frame part with clamps.

11. 2. The method for producing a frame component formed by roll forming according to claim 1, a method for manufacturing a frame part formed by roll forming, characterized in that the temporary joining process carried out in the temporary joining step is carried out by clamping and binding one outer end portion and the other outer end portion of the frame part with a clamping member so that the other end portion of the plate material is sandwiched between the two outer end portions.

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