Bead formation method

Abstract

To provide a bead formation method that can suppress warpage caused by bead formation more effectively.SOLUTION: A bead formation method includes: a beading process in which a bead (Wb) is formed on a plate (W); and a correction process in which a prescribed correction range (K) that is separated from the bead (Wb) with a correction line (P2a), which bites to the bead (Wb) side by only a distance (α) from a connection line (P1a) between a flat part (Wp) and the bead (Wb), as an inner end, in the plate (W) with the bead (Wb) formed thereon is pinched and crushed in a thickness direction.SELECTED DRAWING: Figure 2A

Description

[Technical Field]

[0001] The present invention relates to a bead forming method. [Background technology]

[0002] Patent Document 1 describes a bead forming method in which a bead is formed on a metal plate by beading, and then a coining process is performed on the connection between the outer surface of the bead and the flat portion. This method is said to be able to suppress warping when a product having a bead is cut out, because the internal stress generated by the beading process is homogenized by the coining process. Patent Document 2 describes that the beading process is performed using a roll forming mold, which is a rotating roller-shaped die and punch. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-60957 [Patent Document 2] Patent No. 3708175 Summary of the Invention [Problem to be solved by the invention]

[0004] The bead forming method described in Patent Document 1 may not be able to sufficiently suppress warpage when the bead width is large. Therefore, there is a demand for a bead forming method that can better suppress warpage that occurs during bead formation. [Means for solving the problem]

[0005] In order to solve the above-mentioned problems, one aspect of one or more embodiments of the present invention is a bead forming method including: a beading step of forming a bead on a plate material; and a straightening step of sandwiching and crushing a predetermined straightening range away from the bead in the thickness direction of the plate material on which the bead has been formed, with the inner end of a straightening line that has dug into the bead side by a predetermined distance from a connection line that connects a flat portion and the bead. [Effects of the Invention]

[0006] According to the bead forming method according to one or more embodiments of the present invention, it is possible to obtain an effect that warpage that occurs due to bead formation can be more effectively suppressed. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram for explaining the beading process using a roll forming die. [Figure 2A] FIG. 2A is a first view showing warpage reduction processing using a warpage reduction single mold set 2 according to one embodiment of the present invention. [Figure 2B] FIG. 2B is a second view showing the warpage reduction process using the warpage reduction single mold set 2. As shown in FIG. [Figure 3] 3A and 3B are enlarged cross-sectional views showing the vicinity of the bead connection position P1 before and after the warpage reduction processing, with FIG. 3A showing the state before the warpage reduction processing and FIG. 3B showing the state after the warpage reduction processing. [Figure 4] FIG. 4 is a plan view showing the plate material W after the warpage reduction process has been performed on the formed bead Wb. [Figure 5] FIG. 5 is a diagram for explaining the relationship between the amount of penetration α in warpage reduction processing and the distribution of the amount of warpage, where FIG. 5(a) shows the case without warpage reduction processing, FIG. 5(b) shows the case where α=0.45 mm, FIG. 5(c) shows the case where α=0.65 mm, and FIG. 5(d) shows the case where α=0.85 mm. [Figure 6A] FIG. 6A is Table 1 showing the results of measuring the amount of warpage. [Figure 6B] FIG. 6B is Table 2 showing the results of Table 1 organized with the central portion A of the plate material W as the reference. [Figure 6C] FIG. 6C is a graph showing the average values ​​in Table 2. [Figure 7A] FIG. 7A is a diagram showing warp reduction processing using the warp reduction double mold set 3. As shown in FIG. [Figure 7B] FIG. 7B is a partially cutaway cross-sectional view showing the cross-sectional shape of the plate material W after undergoing warpage reduction processing using the warpage reduction double mold set 3. [Figure 8A] FIG. 8A is a side view illustrating a state in which beading processing and warpage reduction processing are performed using the composite mold set 5. FIG. [Figure 8B] FIG. 8B is a bottom view for explaining the dimensional relationship between the beading mold set 50 and the warp reduction mold set 60 of the composite mold set 5. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0008] A bead forming method according to one aspect of one or more embodiments of the present invention will be described. This bead forming method includes a beading process (see FIG. 1) for forming a bead Wb on a sheet material W, and a warpage reduction process for the sheet material W on which the bead Wb has been formed. The beading process is not limited to a specific process, and the method described here is a method performed using a roll forming die set described in Patent Document 2.

[0009] As shown in FIG. 1, the roll forming die set 1 used in one embodiment of the present invention is a set of a lower roll die 1D and an upper roll die 1P. The roll forming die set 1 is formed symmetrically with respect to a center line CL1 extending vertically in FIG. 1. The lower roll die 1D rotates about a rotation axis line CL1D extending horizontally, and integrally has a push-up roll 1D2 and bottom pressure rolls 1D1 and 1D3. The push-up roll 1D2 is formed with a curved surface that protrudes maximally radially outward so that the axial peripheral surface shape has a maximum diameter at the center, and bottom pressure rolls 1D1 and 1D3, each having the same outer diameter, are connected to both axial ends of the push-up roll 1D2.

[0010] The upper roll die 1P is disposed above the lower roll die 1D so that it can be raised and lowered by a drive unit (not shown). The upper roll die 1P is formed as a roll that rotates about a horizontally extending rotation axis CL1P. The upper roll die 1P has an escape shaft portion 1P2 and upper pressure rolls 1P1 and 1P3 at positions corresponding to the push-up roll 1D2 and lower pressure rolls 1D1 and 1D3 of the lower roll die 1D, respectively.

[0011] When performing beading, the workpiece, that is, the sheet material W, is inserted between the lower roll die 1D and the raised upper roll die 1P. Then, the upper roll die 1P descends, sandwiching the sheet material W between it and the lower roll die 1D, while relatively moving the roll forming die set 1 in the direction in which the bead Wb extends. As a result, the portion between the upper pressure rolls 1P1 and 1P3 is lifted by the push-up roll 1D2, forming the bead Wb. The bead Wb may be formed by fixing the roll forming die set 1 and moving the sheet material W, or by fixing the sheet material W and moving the roll forming die set 1. Alternatively, the bead Wb may be formed by moving both the roll forming die set 1 and the sheet material W.

[0012] As shown in Figure 1, the sheet material W is sandwiched between the upper pressure rolls 1P1, 1P3 and the lower pressure rolls 1D1, 1D3, and the relief shaft portion 1P2 is formed with a small diameter so as not to interfere with the bead Wb formed by the push-up roll 1D2, allowing it to escape from the bead Wb. The inner end positions of the upper pressure roll 1P1 and the upper pressure roll 1P3 form a bead connection position P1 at the boundary (shape change position) between the bead Wb and the flat portion Wp. A connection line P1a, which is a bent line in the extension direction of the bead Wb, is formed at the bead connection position P1.

[0013] In one embodiment of the bead forming method, warpage reduction processing is performed after the beading processing described above. Next, this warpage reduction processing will be described with reference to Figs. 2A to 4. Fig. 2A is a first view showing warpage reduction processing using a warpage reduction single die set 2 in one embodiment of the present invention. Fig. 2B is a second view showing warpage reduction processing using the warpage reduction single die set 2. Fig. 3 is an enlarged cross-sectional view showing the vicinity of the bead connection position P1 before and after warpage reduction processing, Fig. 3(a) shows the state before warpage reduction processing, and Fig. 3(b) shows the state after warpage reduction processing. Fig. 4 is a plan view showing the sheet material W after warpage reduction processing has been performed on the formed bead Wb.

[0014] In one embodiment of the bead forming method, the warpage reduction process is performed using, for example, a warpage reduction single die set 2 (hereinafter simply referred to as single die set 2) shown in FIG. 2A.

[0015] The single die set 2 is a set consisting of a lower roll die 2D and an upper roll die 2P. The lower roll die 2D rotates about a horizontally extending rotation axis CL2D and has a lower pressure roll 2D2 with a constant outer diameter, and shafts 2D1 and 2D3 at both ends of the lower pressure roll 2D2 that are smaller in diameter and extend in the axial direction. The upper roll die 2P is raised and lowered by a drive unit (not shown) and rotates about a rotation axis CL2P that extends parallel to the rotation axis CL2D. The upper roll die 2P has an upper pressure roll 2P2 with a constant outer diameter and shafts 2P1 and 2P3 at both ends of the upper pressure roll 2P2 that are smaller in diameter and extend in the axial direction.

[0016] With the upper roll die 2P of this single die set 2 raised, the sheet material W on which the bead Wb has been formed is inserted between it and the lower roll die 2D with the extension direction of the bead Wb (the direction perpendicular to the plane of the paper in FIG. 2A) perpendicular to the rotation axis CL2D, and positioned as follows: That is, the axial position of the upper roll die 2P is set to a correction position P2 where one edge of the upper roll die 2P is positioned further inward into the bead Wb than one bead connection position P1 of the bead Wb. The distance (amount) of this penetration is set to the penetration amount α, as shown in FIG. 3(b).

[0017] The position of the upper roll die 2P in the direction in which the bead Wb extends is approximately the end of the bead connection position P1 on one side in the width direction of the bead Wb. Next, the upper roll die 2P is lowered (see arrow DR2), and while the flat portion Wp of the sheet material W is sandwiched between the upper pressure roll 2P2 and the lower pressure roll 2D2, the single die set 2 is moved relative to the sheet material W in the direction in which the bead Wb extends. With the upper roll die 2P lowered, the heightwise gap between the upper pressure roll 2P2 and the lower pressure roll 2D2 is set to be the same as or slightly smaller than the thickness of the sheet material W.

[0018] As a result, the upper pressure roll 2P2 and the lower pressure roll 2D2 rotate as shown in FIG. 2B, flattening the portion of the bead Wb from the bead connection position P1 to the inwardly indented correction position P2. Here, "straightening" refers to a process of crushing the sheet material W to its original thickness or a thickness slightly smaller than that. For example, the crushing amount set as the lowering position of the upper pressure roll 2P2 is approximately 0.2 mm. In this case, the amount of crushing (compression) actually reflected in the sheet material W after the crushing process is approximately 0.1 mm for a sheet thickness of 1.0 mm. In other words, the sheet thickness is crushed and compressed by approximately 10%. The portion where this warpage reduction process was performed is conveniently indicated as the range LN indicated by a thick solid line in FIG. 2B. After the correction of the bead connection position P1 on one side is completed, the correction of the bead connection position P1 on the opposite side of the bead Wb in the width direction is performed using a similar procedure.

[0019] As shown in Fig. 3(a), the shape of the top surface W1, which is the outer surface of the bead Wb before the warpage reduction process, is bent in cross section at a bead connection position P1, which is the boundary between the flat portion Wp and the curved bead Wb, and the bead Wb side rises sharply. In contrast, the cross-sectional shape of the top surface W1 at the same portion after the warpage reduction process with a bite amount α has a correction line P2a, which is a bent line extending in the extension direction of the bead Wb (a direction perpendicular to the paper surface), at a correction position P2, which is located inward from the bead connection position P1 by the bite amount α. The warpage reduction process plastically deforms the area between the connection line P1a formed at the bead connection position P1 and the correction line P2a, making it approximately flat.

[0020] 3(a), the lower surface W2, which is the inner surface of the sheet material W, before the warpage reduction process is performed, has a flat area M, which is the area that becomes flat due to the pushing action of the push-up roll 1D2, and extends to a position Q1 outside the bead connection position P1 (on the opposite side from the bead Wb). The lower surface W2 is a curved surface that rises from the position Q1 toward the bead Wb so that the sheet thickness gradually decreases.

[0021] In contrast, as shown in Figure 3(b), the lower surface W2 of the same portion subjected to warpage reduction processing with a penetration depth α is pressed against the lower pressure roll 2D2 by the upper pressure roll 2P2 up to the straightening position P2, so the flat region M extends to a position Q2 corresponding to the straightening position P2. This shape change indicates that part of the metal that was forced to plastically flow toward the center of the bead Wb as indicated by the arrow DR3a due to the beading processing now plastically flows from the bead Wb side toward the original flat portion Wp as indicated by the arrow DR3b due to the warpage reduction processing. Therefore, it is inferred that the warpage reduction processing partially releases and reduces the residual stress that was generated in the vicinity of the bead connection position P1 due to the beading processing.

[0022] As shown in FIGS. 3(b) and 4, a correction line P2a caused by the edge of the upper pressure roll 2P2 remains as a mark at the correction position P2 on the bead Wb that has been subjected to warpage reduction processing. Also, as shown in FIG. 4, a correction range K, which is a crushing range corresponding to the contact area of ​​the upper pressure roll 2P2, is a predetermined range away from the bead Wb as the inner end of the correction line P2a, and this range is crushed so that it is slightly visible. As described above, the correction range K is a portion where the sheet thickness is compressed by, for example, about 10%. The width of the correction range K corresponds to the width of the upper pressure roll 2P2. The larger (wider) this width is, the more uniformly the metal that has plastically flowed from the bead Wb side toward the flat portion Wp side is smoothed, resulting in a greater residual stress reduction effect. When a single mold set 2 is used for warp reduction processing, processing is performed on the bead connection position P1, which is one widthwise edge of the bead Wb, and the bead connection position P1, which is the other widthwise edge, and warp reduction processing is not performed on the curved portions at both ends of the bead Wb.

[0023] In order to confirm the assumption that the above-mentioned warpage reduction processing reduces residual stress, a test was conducted to confirm the change in the warpage reduction effect when warpage reduction processing was performed by changing the amount of penetration α for the bead Wb of the same shape. This will be explained below. The test was also conducted on a comparison product that was not subjected to warpage reduction processing.

[0024] The details of the test to confirm the warpage reduction effect are as follows. (Plate material W) Material: SECC (electro-galvanized steel plate) Dimensions: 130mm x 300mm Plate thickness: 1.0 mm

[0025] (Formed bead Wb) Length: 240mm Width: 12.7mm Height: Maximum 3.0mm Number of pieces: 2 Pitch: 80mm The width of the bead Wb is the distance in the width direction between a pair of bead connection positions P1 of the bead Wb.

[0026] (measurement item) Comparison example: No warpage reduction processing (beading processing only) Product 1: Warpage reduction processing applied α=0.45mm Product 2: Warpage reduction processing applied α=0.65mm Product 3: Warpage reduction processing applied α=0.85mm

[0027] (Measuring instrument) Keyence 3D scanner type three-dimensional measuring instrument VL-500

[0028] (Measurement method) The product to be measured is placed on the stage of the measuring instrument with the convex side of the bead Wb facing up, and the height distribution of the product is measured. Four measurement points are extracted from the height distribution: the center A of the product and the heights of the four corners B1 to B4. The thickness of the product to be measured is subtracted from the value obtained at each measurement point to determine the warpage value at each measurement point. Therefore, the warpage value may be negative because the thickness is affected by processing.

[0029] The distribution of warpage values ​​obtained in the confirmation test is shown in Figures 5(a) to (d). Figure 5(a) shows a comparison product without warpage reduction processing, Figure 5(b) shows the case of implemented product 1 (α = 0.45 mm), Figure 5(c) shows the case of implemented product 2 (α = 0.65 mm), and Figure 5(d) shows the case of implemented product 3 (α = 0.85 mm). The distribution of warpage values ​​is displayed in the following three stages for all parts except bead Wb. Bead Wb is not displayed as its distribution is large due to its large deformation. First range AR1: Less than +1.0 mm Second range AR2: +1.0 mm or more, less than +2.0 mm Third range AR3: +2.0 mm or more

[0030] As shown in Figure 5(a), in the comparison product, large warping in the third range AR3 occurs near both edges of the bead Wb of the plate material W in the extension direction, and warping in the second range AR2 occurs over a wide area inside each of the third ranges AR3. In contrast, in the implementation products 1 and 2 shown in Figures 5(b) and (c), warping of the second range AR2 occurs only at one end of the plate material W, but warping of the other ranges is suppressed to the first range AR1, and it is clear that warping is significantly suppressed compared to the comparison product.

[0031] Furthermore, in the example product 3 shown in Figure 5(d), warping is suppressed compared to the comparison product, and the second range AR2 occurring at one end of the plate material W is further reduced, but the second range AR2 occurs in the center, and a tendency for so-called reverse warping is observed.

[0032] Fig. 6A is Table 1 showing the warpage values ​​of the center A and the four corners B1 to B4, which are the four measurement points shown in Figs. 5(a) to (d). Fig. 6B is Table 2 showing the warpage values ​​of the corners B1 to B4 when the center A is used as the reference, that is, the differences between the warpage values ​​of the corners B1 to B4 and the warpage value of the center A, and their average values ​​(AVE). Fig. 6C is a graph of the average values ​​in Table 2.

[0033] As is clear from Figure 6C, by performing warp reduction processing with the penetration amount α in the range of up to 0.85 mm, the overall warp of the plate material W can be reduced to less than half of the warp value when no warp reduction processing is performed. Furthermore, it is clear that the larger the penetration amount α, the more likely reverse warp occurs. In this example, when the penetration amount α is in the range of 0.45 mm to 0.65 mm, the warp can be reduced to a small value in a more balanced manner. As described above, although the tendency toward reverse warp increases with increasing penetration amount α, it was confirmed that as long as the penetration amount α is less than twice the plate thickness of the plate material W, the warp reduction effect can be obtained compared to when no warp reduction processing is performed.

[0034] As described above, according to the bead forming method of one aspect of one or more embodiments of the present invention, warping that occurs in a plate-shaped product due to bead formation can be more effectively suppressed.

[0035] One aspect of one or more embodiments of the present invention is not limited to the configurations described above, and may be modified without departing from the spirit of the present invention.

[0036] (Variation 1) The single die set 2 used in the warp reduction processing may be a warp reduction double die set 3 (hereinafter referred to as double die set 3). The double die set 3 will now be described with reference to Figs. 7A and 7B. Fig. 7A is a diagram showing warp reduction processing using the double die set 3. Fig. 7B is a partially broken cross-sectional view showing the plate material W after warp reduction processing using the double die set 3.

[0037] While the single die set 2 corrects only the vicinity of the bead joining position P1 on one side of the bead Wb, the double die set 3 can simultaneously correct the bead joining position P1 on both sides of the bead Wb. As shown in Fig. 7A, the double die set 3 is a set of a lower roll die 3D and an upper roll die 3P. The double die set 3 is formed symmetrically with respect to a center line CL3 extending vertically in Fig. 7A.

[0038] The lower roll mold 3D is a lower pressure roll having a constant outer diameter and rotates about a horizontally extending rotation axis CL3D. The upper roll mold 3P is raised and lowered by a drive unit (not shown) and rotates about a rotation axis CL3P extending parallel to the rotation axis CL3D. The upper roll mold 3P is integrally formed with upper pressure rolls 3P1 and 3P3, which have a constant outer diameter and are arranged axially spaced apart, and a connecting shaft 3P2 that connects them with a smaller outer diameter. The lower roll mold 3D is formed with a length that exceeds the length between both ends of the upper pressure rolls 3P1 and 3P3, and is arranged opposite to each other so as to include that range of length.

[0039] Specifically, a width L4, which is the axial distance between the straightening positions P3, P3, which are the inner edges of the upper pressure rolls 3P1, 3P3, is set shorter than a width L3, which is the distance between the bead connection positions P1, P1 in the width direction of the bead Wb. More specifically, the width L4 is shorter than the width L3 by twice the amount of penetration α2. In the warpage reduction process, the double mold set 3 is positioned and disposed so as to penetrate into the bead Wb by the amount of penetration α2 into each of the bead connection positions P1, P1 on both sides in the width direction.

[0040] In warpage reduction processing using the double die set 3, as in the case of using the single die set 2, with the upper roll die 3P of the double die set 3 raised, the sheet material W on which the bead Wb has been formed between it and the lower roll die 3D is inserted so that the extending direction of the bead Wb (the direction perpendicular to the plane of the paper in FIG. 7A) is perpendicular to the rotation axis CL3D, and positioned as follows: That is, the upper roll die 3P is positioned in the axial position so that it is inserted inward by a penetration amount α2 from both bead connection positions P1 of the bead Wb. Also, the positions of the rotation axes CL3D and CL3P in the extending direction of the bead Wb are approximately at the ends of the linear bead connection positions P1 of the bead Wb. Next, the upper roll die 3P is lowered (see arrow DR5 in FIG. 7A), and while the flat portion Wp of the sheet material W is sandwiched between the upper pressure rolls 3P1, 3P3 and the lower roll die 3D, the double die set 3 is moved relative to the sheet material W in the direction in which the bead Wb extends. With the upper roll die 3P lowered, the gap in the height direction between the upper pressure rolls 3P1, 3P3 and the lower roll die 3D is set to be the same as or slightly smaller than the thickness of the sheet material W.

[0041] As a result, the upper pressure rolls 3P1, 3P3 and the lower roll die 3D rotate around their respective rotation axes CL3P, CL3D as shown by arrows DR6 in Fig. 7A, while simultaneously performing straightening on the bead connection positions P1 on both sides of the bead Wb in the width direction. During the straightening, the portions from the respective bead connection positions P1 to the straightening position P3, which is inwardly cut by a cutting amount α2, are straightened to be flat, forming a straightening line P3a. This reduces the time required for warpage reduction processing by half.

[0042] By making it possible to adjust the axial distance between the upper pressure rolls 3P1 and 3P3, warpage reduction processing can be performed simultaneously near the bead connection position P1 on both sides of the bead Wb with any width and any penetration amount α, thereby improving the versatility of the double mold set 3.

[0043] (Variation 2) The roll forming die set 1 used for beading processing and the double die set 3 used for warpage reduction processing may be integrated into a composite die set 5. Next, the composite die set 5 will be described with reference to Figs. 8A and 8B. Fig. 8A is a side view illustrating processing using the composite die set 5. Fig. 8B is a view illustrating the difference between width L5, which is the roll spacing of the beading die set 50 of the composite die set 5, and width L6, which is the roll spacing of the warpage reduction die set 60.

[0044] 8A, the composite mold set 5 has a frame body 53, a beading mold set 50, and a warpage reduction mold set 60. The frame body 53 is formed in a frame shape and supports the beading mold set 50 on the upstream side in the relative conveying direction (arrow DR6) of the plate material W, and supports the warpage reduction mold set 60 on the downstream side thereof.

[0045] The beading mold set 50 has a lower roll mold 5D fixed to a support frame 52 of a frame body 53, and an upper roll mold 5P supported by an elevator frame 51 of the frame body 53 so as to be able to move up and down freely. The upper roll mold 5P is raised and lowered by a drive unit (not shown). The warpage reduction mold set 60 has a lower roll mold 6D fixed to a support frame 62 of the frame body 53, and an upper roll mold 6P supported by an elevator frame 61 of the frame body 53 so as to be able to move up and down freely. The upper roll mold 6P is raised and lowered by a drive unit (not shown), independently of the raising and lowering of the upper roll mold 5P.

[0046] The beading die set 50 has the same configuration as the roll forming die set 1, and the warpage reduction die set 60 has the same configuration as the double die set 3. That is, the upper roll die 5P of the beading die set 50 has upper pressure rolls 5P1 and 5P3 corresponding to the upper pressure rolls 1P1 and 1P3. The lower roll die 5D has lower pressure rolls 5D1 and 5D3 and a push-up roll 5D2. On the other hand, the warpage reduction die set 60 has upper pressure rolls 6P1 and 6P3 corresponding to the upper pressure rolls 3P1 and 3P3, and a lower roll die 6D corresponding to the lower roll die 3D.

[0047] As shown in Fig. 8B, the beading mold set 50 and the warpage reduction mold set 60 are arranged so that their respective rotation axes CL5D, CL5P, CL6D, and CL6P are parallel to each other. Furthermore, they are arranged so as to be symmetrical in the up-down direction in Fig. 8B with respect to the center line CL5, which is the center in the axial direction of each. Furthermore, compared to the width L5, which is the separation distance between the upper pressure rolls 5P1 and 5P3 in the direction of the rotation axes CL5P, the width L6, which is the separation distance between the upper pressure rolls 6P1 and 6P3 in the direction of the rotation axes CL6P, is set to be shorter by twice the amount of penetration α2, which is the amount of penetration on one side.

[0048] As shown in Fig. 8A, a flat plate material W, which is a workpiece, is inserted into the composite die set 5 from the beading die set 50 side and moved relative to the composite die set 5, whereby a bead Wb is first formed by the beading die set 50. This bead Wb is shown as a bead Wba in Fig. 8A. The warp reduction die set 60, which is arranged adjacently and downstream of the beading die set 50, immediately performs warp reduction processing on both sides of the bead Wba in the vicinity of the bead connection position P1 in the width direction, thereby correcting the bead Wba and forming a correction line P6a (see range LN in Fig. 8A).

[0049] In this way, by using the composite mold set 5, the beading process and the warpage reduction process can be carried out substantially simultaneously in one process, so that the product can be manufactured in a shorter time.

[0050] The composite mold set 5 may be configured so that the distance between the upper pressure rolls 5P1, 5P3 of the beading mold set 50 in the direction of the rotation axis CL5P and the distance between the upper pressure rolls 6P1, 6P3 of the warp reduction mold set 60 in the direction of the rotation axis CL6P can be adjusted as desired. This improves the versatility of the composite mold set 5, allowing the formation of a bead Wb of any width and the execution of warp reduction processing with any desired penetration amount α2. Furthermore, each of these can be performed essentially in one processing run.

[0051] The beading process is not limited to the one performed using the roll forming die set described above. The warpage reduction process is also not limited to the method of squashing the correction area by sandwiching it between a pair of rolls described above. For example, a method of squashing the correction area by coining multiple times along the bead Wb may be used.

[0052] As described above in detail, the bead forming method according to one or more embodiments of the present application includes a beading process for forming a bead Wb on a plate material W, and a correction process for squeezing a predetermined correction range K outside a correction line P2a that has dug into the bead Wb side by a predetermined distance α from a connection line P1a connecting the flat portion Wp and the bead Wb in the plate material W on which the bead Wb has been formed, in the thickness direction.

[0053] According to this, the residual stress in the plate material W is effectively released by the straightening process, and the warpage that occurs with the formation of the bead can be more effectively suppressed.

[0054] Furthermore, in the above-described embodiment, the straightening process may be such that the sheet material W is sandwiched between a first roll 2P2 that rolls along the bead Wb on the first surface W1 on the side where the bead Wb is convex, and a second roll 2D2 that is arranged opposite the first roll 2P2 and rolls along the bead Wb on the second surface W2 opposite the first surface W1, with the edge of the first roll 2P2 positioned at the straightening line P2a, and is crushed and moved relatively in the direction in which the bead Wb extends.

[0055] This allows the warp reduction process to be carried out continuously by the relative movement of the plate material W, thereby shortening the time required for the warp reduction process.

[0056] Furthermore, the first rolls 2P2 may be disposed on both sides of the bead Wb in the width direction, so that both correction ranges K in the width direction of the bead Wb are simultaneously crushed in the correction process.

[0057] This allows a pair of correction ranges K on both sides of the bead Wb in the width direction to be crushed with a single relative movement, thereby further shortening the time required for warp reduction processing.

[0058] Furthermore, when the bead Wb is formed by the roll forming die set 1 and the first roll 2P2 and the second roll 2D2 are included in the warpage reduction die set 2, the roll forming die set 1 and the warpage reduction die set 2 may be integrally arranged in series in the relative movement direction of the sheet material W, so that both the beading process and the straightening process can be performed by a single relative movement of the sheet material W.

[0059] This allows both the formation of the bead Wb and the warp reduction processing to be performed with a single relative movement of the plate material W, thereby shortening the overall processing time including the beading processing and the warp reduction processing. [Explanation of symbols]

[0060] 1 Roll forming die set 1D lower roll die 1D1,1D3 Lower pressure roll 1D2 Upward Roll 1P Upper roll mold 1P1, 1P3 Upper pressure roll 1P1a,1P3a Edge 1P2 Relief shaft 2. Warpage reduction single mold set (single mold set) 2D lower roll die 2D1,2D3 Shaft part 2D2 Lower pressure roll (second roll) 2P upper roll mold 2P1,2P3 shaft part 2P2 Upper pressure roll (1st roll) 2P2a edge 3. Warpage reduction double mold set (double mold set) 3D lower roll mold 3P upper roll mold 3P1, 3P3 Upper pressure roll 3P1a,3P3a edge 3P2 connection shaft 5 Composite mold set 50 Beading mold set 5P upper roll mold 5P1, 5P3 Upper pressure roll 5D lower roll mold 5D1 Lower pressure roll 5D2 Upward Roll 51,61 Lifting frame 52,62 Support frame 53 Frame 60 Warpage reduction mold assembly 6P upper roll mold 6P1, 6P3 Upper pressure roll 6P1a, 6P3a Edge 6D lower roll mold A Central section AR1~AR3 1st range~3rd range B1~B4 corner CL1,CL3,CL5 Center line CL1D, CL1P, CL2D, CL2P, CL3D, CL3P, CL5D, C K Correction range L5P, CL6D, CL6P Rotation axis LN Range L3, L4, L5, L6 width M Flat Range P1 Bead connection position P1a connecting wire P2,P3 correction position P2a,P3a,P6a Correction line Q1,Q2 position W plate material Wb,Wba bead Wp flat area W1 Top surface (outer surface) (first surface) W2 Bottom surface (inner surface) (2nd surface) α,α2 Amount of penetration

Claims

1. a beading process for forming a bead on the plate material; a straightening process in which a predetermined straightening range in the plate material on which the bead has been formed is sandwiched and crushed in a thickness direction, with the inner end being a straightening line that has dug into the bead side by a predetermined distance from a connection line connecting the flat portion and the bead; A bead forming method comprising:

2. The straightening step includes:

2. The bead forming method according to claim 1, wherein the plate material is sandwiched between a first roll that rolls along the bead on a first surface on the side where the bead is convex, and a second roll that is disposed opposite the first roll and rolls along the bead on a second surface opposite to the first surface, with the edge of the first roll positioned to be on the straightening line, and the plate material is moved relatively in the extending direction of the bead while being crushed.

3. 3. The bead forming method according to claim 2, wherein the first rolls are disposed on both sides of the bead in the width direction, and the straightening step simultaneously crushes the straightening ranges on both sides of the bead in the width direction.

4. The bead is formed using a roll forming die set; When the first roll and the second roll are included in a warp reduction die set, 4. The bead forming method according to claim 3, wherein the roll forming die set and the warp reduction die set are integrally arranged in series in the relative movement direction of the plate material, so that both the beading process and the straightening process can be performed by a single relative movement of the plate material.

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