Press-formed products, joining structures for press-formed products, and sheet frames

Abstract

To suppress spring back of a curved-surface-like part that has a circular-arc-shaped cross section.SOLUTION: A seat back frame 12 includes a side frame 18 that is a press molded product. The side frame 18 includes: a curved-surface-like part 20 having a circular-arc-shaped cross section; and circumferential bead sections 22, 24, 26 formed by swelling part of the curved-surface-like part 20 on a radial outside of the curved-surface-like part 20 and extending along a circumferential direction of the curved-surface-like part 20.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a press-formed product and its joining structure, and a sheet frame to which the joining structure is applied.

Background Art

[0002] Patent Document 1 below discloses a press-forming method for forming a metal plate by the relative linear movement of a die and a punch. In this press-forming method, an intermediate product of a metal plate in which a plurality of embossments are arranged at a portion to be an elongation flange forming portion is formed, and when this intermediate product is press-formed, these embossments are crushed with an embossment-crushing punch before the bottom dead center of the press in the final press process, and a compressive stress is applied to the elongation flange forming portion. Further, before the bottom dead center of the press in the final press process, a plurality of surplus beads are formed with a surplus bead forming punch at a portion to be a shrinkage flange forming portion, and a tensile stress is applied to the shrinkage flange forming portion to equalize the residual stress of the press-formed product. Thereby, a press-formed product is obtained without causing three-dimensional shape defects such as angular changes, ridge line warping (surface warping), and torsion due to springback.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The above prior art improves the dimensional accuracy of a press-formed product having a flat flange forming portion, and does not consider improving the dimensional accuracy of a press-formed product having a curved surface portion with an arcuate cross section.

[0005] In consideration of the above facts, the present invention aims to provide a press-formed product, a joining structure for a press-formed product, and a sheet frame that can suppress the springback of a curved portion having an arc-shaped cross-section. [Means for solving the problem]

[0006] The press-formed product of the first embodiment has a curved portion having an arc-shaped cross-section, and a circumferential bead portion formed by a part of the curved portion bulging radially outward from the curved portion and extending along the circumferential direction of the curved portion.

[0007] In the press-formed product of the first embodiment, a portion of the curved surface having an arc-shaped cross-section bulges radially outward from the curved surface, forming a circumferential bead. The circumferential bead extends along the circumferential direction of the curved surface. This circumferential bead can suppress the springback of the curved surface.

[0008] The press-formed product of the second embodiment has, in the first embodiment, a plurality of circumferential bead portions arranged at intervals from each other in the axial direction of the curved portion, and an axial bead portion provided between adjacent circumferential bead portions in the curved portion, formed by a part of the curved portion bulging radially outward from the curved portion, and extending along the axial direction of the curved portion.

[0009] In the press-formed product of the second embodiment, axial bead portions are provided between adjacent circumferential bead portions in the curved portion. The axial bead portion is formed when a part of the curved portion bulges radially outward from the curved portion and extends along the axial direction of the curved portion. This makes it possible to suppress the bulging radially outward in the portion between adjacent circumferential bead portions in the curved portion due to springback.

[0010] The joining structure of a press-formed product according to claim 1 or 2 comprises a joining mating member having a cylindrical surface, and a press-formed product according to claim 1 or 2 having a plurality of circumferential bead portions arranged at intervals from each other in the axial direction of the curved portion, the curved portion being coaxially arranged on the outside of the cylindrical surface, and the portions between the plurality of circumferential bead portions on the curved portion being joined to the cylindrical surface.

[0011] In the third embodiment of the press-formed product joining structure, the curved portion of the press-formed product is coaxially arranged on the outside of the cylindrical surface of the mating member. Multiple circumferential bead portions are formed on this curved portion, spaced apart from each other in the axial direction. The portions between these multiple circumferential bead portions on the curved portion are joined to the cylindrical surface. Since this press-formed product is of the first or second embodiment, springback of the curved portion can be suppressed. As a result, it becomes easier to ensure the dimensional accuracy of the curved portion for joining it to the cylindrical surface.

[0012] A seat frame according to a fourth embodiment comprises an upper frame constituting the upper part of a seat back frame and a side frame constituting the side of the seat back frame, wherein the upper frame, which is the mating member, and the side frame, which is a press-formed product, are joined by the press-formed product joining structure described in claim 3.

[0013] In the seat frame of the fourth embodiment, the upper frame, which is a mating member forming the upper part of the seat back frame, and the side frame, which is a press-formed product forming the side of the seat back frame, are joined by the press-formed product joining structure of the third embodiment. Therefore, the same effects as in the third embodiment can be obtained. [Effects of the Invention]

[0014] As described above, the press-formed product, the joining structure for the press-formed product, and the sheet frame according to the present invention can suppress the springback of the curved portion having an arc-shaped cross-section. [Brief explanation of the drawing]

[0015] [Figure 1] This is a side view showing a part of the sheet frame according to the embodiment. [Figure 2] This is a cross-sectional view showing an enlarged view of the cross-section along line AA in Figure 1. [Figure 3] This is a cross-sectional view showing an enlarged view of the cross-section along line BB in Figure 1. [Figure 4] This is a side view showing a portion of the sheet frame relating to the comparative example. [Figure 5] This is a cross-sectional view showing an enlarged view of the cross-section along the CC line in Figure 4. [Figure 6] This is a cross-sectional view showing an enlarged view of the cross-section along the DD line in Figure 4. [Figure 7] This is a cross-sectional view corresponding to Figure 2, which shows a modified example of the embodiment. [Modes for carrying out the invention]

[0016] The following describes a seat frame 10 according to one embodiment of the present invention with reference to Figures 1 to 7. The arrows FR and UP shown in Figure 1 indicate the front and top of the seat frame 10, respectively. Hereafter, when simply using the directions front, back, left, right, up, and down, these directions refer to the direction relative to the seat frame 10.

[0017] As shown in Figure 1, a seat frame 10 according to one embodiment of the present invention comprises a seat back frame 12 that constitutes the frame of the seat back of a vehicle seat, and a seat cushion frame (not shown) that constitutes the frame of the seat cushion of the vehicle seat. The seat back frame 12 comprises an upper frame 14 that constitutes the upper part of the seat back frame 12, and left and right side frames 18 (the right side frame 18 is not shown) that constitute the left and right sides of the seat back frame 12. The upper frame 14 and the left and right side frames 18 are joined by applying a press-formed product joining structure according to one embodiment of the present invention.

[0018] The upper frame 14 corresponds to the "joint mating member" in the present invention and has a cylindrical cylindrical surface. This upper frame 14 is manufactured by bending a metal pipe material and has an inverted U shape when viewed in the front-rear direction. The left and right side portions 16 of the upper frame 14 (the right side portion 16 is not shown) extend downward.

[0019] The left and right side frames 18 each correspond to the "press-formed product" in the present invention. These side frames 18 are manufactured by press-forming a metal plate material and have a long plate shape with the left-right direction as the plate thickness direction and the up-down direction as the longitudinal direction. The metal plate, which is the material of the left and right side frames 18, is here a high-tensile steel plate, and while being made thinner than the material of the conventional side frame, ensuring rigidity and weight reduction are achieved.

[0020] On the upper portions of the left and right side frames 18, semi-cylindrical curved surface portions 20 are formed. As shown in FIG. 2, each curved surface portion 20 has an arc-shaped (substantially C-shaped) cross section when viewed from the up-down direction, and the inside in the left-right direction is open. The lower portions of the left and right side portions 16 of the upper frame 14 are coaxially inserted inside each curved surface portion 20. Each curved surface portion 20 is coaxially arranged outside the outer peripheral surface (cylindrical surface) of the left and right side portions 16.

[0021] Each curved surface portion 20 has multiple (in this case, three) circumferential bead portions 22, 24, and 26, and multiple (in this case, three) axial bead portions 28, 30, and 32. As shown in Figures 1 and 3, the circumferential bead portions 22, 24, and 26 are each formed by multiple locations (in this case, three locations) of the curved surface portion 20 bulging radially outward, and have an arc-shaped cross-section when viewed from the circumferential direction of the curved surface portion 20. These circumferential bead portions 22, 24, and 26 extend along the circumferential direction of the curved surface portion 20 and are spaced apart from each other in the axial direction of the curved surface portion 20. The circumferential bead portion 22 is formed at the upper end of the curved surface portion 20, the circumferential bead portion 24 is formed at the vertical center of the curved surface portion 20, and the circumferential bead portion 26 is formed at the lower end of the curved surface portion 20.

[0022] The axial bead portions 28, 30, and 32 are formed on the curved portion 20 between adjacent circumferential bead portions 22 and 24. As shown in Figure 2, the axial bead portion 28 is formed at one circumferential end of the curved portion 20, the axial bead portion 30 is formed at the circumferential center of the curved portion 20, and the axial bead portion 32 is formed at the other circumferential end of the curved portion 20. These axial bead portions 28, 30, and 32 are formed by a part (multiple locations) of the curved portion 20 bulging radially outward from the curved portion 20, and extend along the axial direction of the curved portion 20. The axial bead portion 30 has an arc-shaped cross-section when viewed from the axial direction of the curved portion 20. The axial bead portions 28 and 32 have a shape that, when viewed from the axial direction of the curved portion 20, is like the axial bead portion 30 being cut in half in the circumferential direction of the curved portion 20.

[0023] The curved portion 20 is joined to the outer circumferential surface (cylindrical surface) of the side portion 16 of the upper frame 14 at two joints 34 and 36 provided between the circumferential bead portions 22 and 24, and at two joints 38 and 40 provided between the circumferential bead portions 24 and 26. The joining method for these joints 34, 36, 38, and 40 is described as laser welding, but is not limited to this. Arc welding, spot welding, adhesive joining, friction stir welding, crimping, etc., may also be used. Furthermore, the number of joints 34, 36, 38, and 40 is not limited to the above and can be changed as appropriate.

[0024] Next, the operation and effects of this embodiment will be described.

[0025] In this embodiment, the upper frame 14 that constitutes the upper part of the seat back frame 12 is made of metal pipe material, and the side frame 18 that constitutes the side of the seat back frame 12 is made of metal press-formed product. A curved portion 20 having an arc-shaped cross-section is formed on the upper part of the side frame 18. The curved portion 20 is arranged coaxially on the outside of the outer peripheral surface (cylindrical surface) of the side portion 16 of the upper frame 14. Multiple circumferential bead portions 22, 24, and 26 are formed on the curved portion 20. The circumferential bead portions 22, 24, and 26 are formed by multiple locations (three locations in this case) of the curved portion 20 bulging radially outward from the curved portion 20. These circumferential bead portions 22, 24, and 26 each extend along the circumferential direction of the curved portion 20 and are spaced apart from each other in the axial direction of the curved portion 20. Furthermore, the portions between the circumferential bead portions 22, 24, and 26 in the curved portion 20 are joined to the outer circumferential surface of the side portion 16 at the joint portions 34, 36, 38, and 40. In this embodiment, the circumferential bead portions 22, 24, and 26 suppress the springback of the curved portion 20. As a result, it becomes easier to ensure the dimensional accuracy of the curved portion 20 for joining it to the cylindrical surface.

[0026] Furthermore, in this embodiment, axial bead portions 28, 30, and 32 are provided between adjacent circumferential bead portions 22 and 24 in the curved portion 20. These axial bead portions 28, 30, and 32 are formed by multiple locations (three locations in this case) of the curved portion 20 bulging radially outward, and extend along the axial direction of the curved portion 20. This suppresses the bulging radially outward due to springback in the portion between adjacent circumferential bead portions 22 and 24 in the curved portion 20 (see the dashed line in Figure 3).

[0027] The effects described above will be further explained using Comparative Example 100 shown in Figures 4 to 6. In Comparative Example 100, circumferential bead portions 22, 24, 26 and axial bead portions 28, 30, 32 are not formed on the curved portion 20 of the side frame 18. In Comparative Example 100, the configuration other than that described above is the same as in this embodiment, and the side frame 18 is made of high-tensile steel plate. Therefore, in Comparative Example 100 as well, it is possible to thin the side frame 18 while ensuring rigidity and reducing weight. However, high-tensile steel plate is hard and has a large springback during press forming, making it difficult to ensure the dimensional accuracy of the curved portion 20 for joining it to the side portion 16. As a result, a gap is created between the curved portion 20 and the side portion 16, making it difficult to join the curved portion 20 and the side portion 16. In particular, when the side frame 18 is thinned and welded to the upper frame 14, it becomes necessary to prevent the side frame 18 from melting down due to heat input during welding. Therefore, if laser welding, which has a lower heat input than arc welding, is used, the gap margin becomes smaller than with arc welding, making laser welding between the curved portion 20 and the side portion 16 difficult.

[0028] In this embodiment, the three circumferential bead portions 22, 24, and 26 suppress the springback of the curved portion 20, making it easier to ensure the dimensional accuracy of the curved portion 20, and thus facilitating laser welding of the curved portion 20 and the side portion 16. Moreover, in this embodiment, the three axial bead portions 28, 30, and 32 suppress the portion of the curved portion 20 between the circumferential bead portions 22 and 24 from bulging radially outward due to springback. This also facilitates laser welding of the curved portion 20 and the side portion 16.

[0029] In the above embodiment, the curved portion 20 is configured to have three circumferential bead portions 22, 24, and 26 and three axial bead portions 28, 30, and 32. However, the number of circumferential and axial bead portions can be changed as appropriate. Alternatively, the curved portion may be configured so that no axial bead portions are formed.

[0030] Furthermore, in the above embodiment, the axial bead portions 28 and 32 are configured to have a shape that is half the size of the axial bead portion 30, but this is not the only configuration. For example, as shown in Figure 7, the axial bead portions 28 and 32 may be configured to have a substantially cylindrical (C-shaped) curl. The curl shape of the axial bead portions 28 and 32 can be set in a range greater than 0 degrees and less than 360 degrees.

[0031] Furthermore, the present invention can be implemented with various modifications without departing from its spirit. Of course, the scope of the present invention is not limited to the embodiments described above. [Explanation of Symbols]

[0032] 10 Seat Frames 12 Seat back frame 14. Upper frame (mutually connected component) 18. Side frame (press-formed part) 20 Curved part 22, 24, 26 Circumferential bead section 28, 30, 32 Axial bead section

Claims

1. Press-formed product, A curved surface portion formed in a semi-cylindrical shape with a roughly C-shaped cross-section and one side in the radial direction open, A portion of the curved surface is formed to bulge radially outward from the curved surface, and a circumferential bead portion extends along the circumferential direction of the curved surface, A press-formed product having [a certain characteristic].

2. A plurality of circumferential bead portions are arranged at intervals from each other in the axial direction of the curved portion, A portion of the curved surface is provided between adjacent circumferential bead portions, and a part of the curved surface is formed by bulging radially outward from the curved surface, and an axial bead portion extends along the axial direction of the curved surface. A press-formed article according to claim 1, having the following characteristics:

3. A mating member having a cylindrical surface, A press-formed product according to claim 1 or claim 2, having a plurality of circumferential bead portions arranged at intervals from each other in the axial direction of the curved portion, the curved portion being coaxially arranged on the outside of the cylindrical surface, and the portions between the plurality of circumferential bead portions on the curved portion being joined to the cylindrical surface, A joining structure for press-formed products equipped with the following features.

4. The upper frame that makes up the upper part of the seat back frame, The side frame that constitutes the side of the seat back frame, Equipped with, A seat frame in which the upper frame, which is the mating member, and the side frame, which is a press-formed product, are joined by the press-formed product joining structure described in claim 3.

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