WO2024106512A1 - Structure around through-holes in metal sheet, and blank and automotive part - Google Patents

Structure around through-holes in metal sheet, and blank and automotive part Download PDF

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Publication number
WO2024106512A1
WO2024106512A1 PCT/JP2023/041313 JP2023041313W WO2024106512A1 WO 2024106512 A1 WO2024106512 A1 WO 2024106512A1 JP 2023041313 W JP2023041313 W JP 2023041313W WO 2024106512 A1 WO2024106512 A1 WO 2024106512A1
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WO
WIPO (PCT)
Prior art keywords
hole
flat surface
metal plate
thickness direction
flat
Prior art date
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PCT/JP2023/041313
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French (fr)
Japanese (ja)
Inventor
諒 漆畑
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日本製鉄株式会社
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Application filed by 日本製鉄株式会社 filed Critical 日本製鉄株式会社
Priority to JP2024517001A priority Critical patent/JP7506354B1/en
Publication of WO2024106512A1 publication Critical patent/WO2024106512A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D28/00—Shaping by press-cutting; Perforating
    • B21D28/02—Punching blanks or articles with or without obtaining scrap; Notching
    • B21D28/10—Incompletely punching in such a manner that the parts are still coherent with the work
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D28/00—Shaping by press-cutting; Perforating
    • B21D28/24—Perforating, i.e. punching holes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D53/00—Making other particular articles
    • B21D53/88—Making other particular articles other parts for vehicles, e.g. cowlings, mudguards

Definitions

  • the present invention relates to a peripheral structure for a through hole in a metal plate, a blank, and an automobile part.
  • Metal plates used as materials for automotive parts may be punched.
  • stress concentration occurs around the punched area (hole edge). This can cause cracks to occur in the punched area, leading to fatigue failure. For this reason, in order to improve the fatigue durability of automotive parts, it is important to prevent fatigue cracks from occurring in the punched areas.
  • Patent Document 1 discloses a punching method that improves the stretch flangeability of the punched end surface.
  • the die used in the punching method disclosed in Patent Document 1 has a cutting edge that is located a predetermined distance below the flat part on the top surface of the die in the punching direction, and the cutting edge portion is chamfered.
  • Patent Document 1 the improvement of stretch flangeability is examined. However, no study is made of the stress concentration that occurs around the punched portion when the entire metal plate is deformed. In other words, no study is made of the fatigue durability of the metal plate having the punched portion.
  • the present invention aims to improve the fatigue durability of metal plates in which through holes are formed by punching.
  • the gist of the present invention is the peripheral structure of a through hole in a metal plate, a blank, and an automobile part described below.
  • the flat plate portion includes a first flat surface surrounding the processed portion on the one side of the flat plate portion, the processed portion includes a wall surface extending in the thickness direction and constituting an inner wall of the through hole, a ring-shaped second flat surface that is located inside the first flat surface when viewed from the thickness direction and on the one side of the first flat surface in the thickness direction, and extends from an edge of the wall surface on the one side in a direction intersecting the thickness direction, and an inclined surface that connects an outer edge of the second flat surface and an inner edge of the first flat surface and is inclined with respect to the thickness direction,
  • the through hole includes a curved portion that is curved in an arc shape so as to be convex toward an outside of the through hole,
  • W is the length (mm) of the inclined surface in a direction perpendicular to the thickness direction
  • R is the radius of curvature (mm) of the part of the curved portion corresponding to the cross section
  • t is the thickness (mm) of the metal plate
  • H is the distance (mm) between the first flat surface and the second flat surface in the thickness direction.
  • H is the distance (mm) between the first flat surface and the second flat surface in the thickness direction
  • R is the radius of curvature (mm) of the part of the curved portion corresponding to the cross section
  • t is the thickness (mm) of the metal plate.
  • the present invention makes it possible to improve the fatigue durability of a metal plate having through holes formed therein.
  • FIG. 1 is a diagram showing an example of a metal plate in which through holes are formed by punching.
  • FIG. 2 is a diagram showing another example of a metal plate in which through holes are formed by punching.
  • FIG. 3 is a diagram showing an analytical model of a metal plate used in the simulation.
  • FIG. 4 is a diagram showing another example of the analytical model of a metal plate.
  • FIG. 5 is a diagram showing an analytical model of a metal plate for comparison.
  • FIG. 6 is a diagram showing the analysis results.
  • FIG. 7 is a diagram showing the analysis results.
  • FIG. 8 is a schematic diagram showing an example of a die for performing hole punching.
  • FIG. 9 is a diagram showing the state of the die and the blank just before the blank is cut.
  • FIG. 9 is a diagram showing the state of the die and the blank just before the blank is cut.
  • FIG. 10 is a diagram for explaining a state in which a burr is formed when a blank is cut.
  • FIG. 11 is a diagram showing the analysis results.
  • FIG. 12 is a diagram showing another example of a metal plate in which through holes are formed by punching.
  • FIG. 13 shows a modified example of the die.
  • FIG. 14 shows a modified example of the die.
  • FIG. 1 is a diagram showing an example of a metal plate in which through holes are formed by punching, where (a) is a perspective view showing the metal plate, and (b) is a cross-sectional view of a portion surrounded by a dashed line in (a).
  • the metal plate 100 shown in FIG. 1 has a flat plate portion 102 and a processed portion 104.
  • the thickness direction of the flat plate portion 102 is indicated by an arrow A.
  • the thickness direction of the flat plate portion 102 will also be simply referred to as the thickness direction A.
  • the processed portion 104 is formed by punching so as to rise from the flat portion 102 to one side in the thickness direction A.
  • a through hole 104a is formed in the center of the processed portion 104. When viewed from the thickness direction A, the through hole 104a has a circular shape.
  • the flat plate portion 102 has a flat surface 102a provided on one side in the thickness direction A, and a flat surface 102b provided on the other side in the thickness direction A.
  • the flat surfaces 102a and 102b are each provided so as to surround the periphery of the processed portion 104.
  • the processed portion 104 has a wall surface 400, an inclined surface 402, and an inclined surface 404.
  • the wall surface 400 extends in the thickness direction A and constitutes the inner wall of the through hole 104a.
  • the wall surface 400 includes a shear surface 400a and a fracture surface 400b.
  • the inclined surface 402 is formed in a ring shape as viewed from the thickness direction A so as to connect the edge on one side of the wall surface 400 in the thickness direction A to the inner edge of the flat surface 102a.
  • the inclined surface 404 is sagging and is formed in a ring shape as viewed from the thickness direction A so as to connect the edge on the other side of the wall surface 400 in the thickness direction A to the inner edge of the flat surface 102b.
  • the inventor therefore conducted research into ways to prevent such stress concentration from occurring. Specifically, he investigated the relationship between the shape of the end of the processed part and the stress that occurs at the edge of the through hole.
  • FIG. 2 shows another example of a metal plate in which through holes are formed by punching, where (a) is a perspective view of the metal plate, and (b) is a cross-sectional view of the part surrounded by the dashed line in (a). The method of manufacturing the metal plate shown in FIG. 2 will be described later.
  • the metal plate 200 shown in FIG. 2 differs from the metal plate 100 shown in FIG. 1 in that a processed portion 204 is formed instead of the processed portion 104. Also, the processed portion 204 differs from the processed portion 104 in that a flat surface 406 and a sloped surface 408 are formed instead of the sloped surface 402.
  • the flat surface 406 and the sloped surface 408 are each formed in an annular shape when viewed from the thickness direction A.
  • the flat surface 406 is formed so as to extend from one edge of the wall surface 400 in the thickness direction A in a direction intersecting the thickness direction A.
  • the sloped surface 408 connects the outer edge of the flat surface 406 and the inner edge of the flat surface 102a and is sloped with respect to the thickness direction A.
  • the present inventors have studied the stress generated at the edge of the through hole 104a when bending deformation is applied to the metal plate 100 and the metal plate 200. Specifically, the present inventors performed a simulation by FEM analysis using a computer to investigate the stress generated at the edge of the through hole 104a.
  • FIG. 3 is a diagram showing an analytical model of the metal plate 100 in FIG. 1
  • FIG. 4 is a diagram showing an analytical model of the metal plate 200 in FIG. 2.
  • (a) is a plan view of the analytical model
  • (b) is a front view of the analytical model
  • (c) is a cross-sectional view of the part surrounded by the dashed line in (a).
  • the analytical models 300 and 310 the parts having the configuration corresponding to the metal plates 100 and 200 are given the same reference numerals as the metal plates 100 and 200.
  • the shapes of the processed parts 104 and 204 are simplified in the analytical models 300 and 310.
  • the material properties of a hot-rolled steel plate with a tensile strength of 780 MPa were set for the analytical models 300 and 310 and the analytical model 350 described later.
  • W indicates the length (mm) of the inclined surfaces 402, 408 in a direction perpendicular to the thickness direction A
  • R indicates the radius of curvature (mm) of the through hole 104a as viewed from the thickness direction A
  • t indicates the thickness (mm) of the flat plate portion 102 (metal plate).
  • H indicates the distance (mm) between the flat surface 102a and the tip of the processed portion 104 in the thickness direction A
  • H indicates the distance (mm) between the flat surface 102a and the flat surface 406 in the thickness direction A.
  • F indicates the length of the flat surface 406 in a direction perpendicular to the thickness direction A.
  • multiple analysis models 300, 310 were created by changing the length W, the ratio R/t of the radius of curvature R to the thickness t, and the distance H, and FEM analysis was performed.
  • the length and width of the analysis models 300, 310 were 90 mm and 30 mm.
  • the length W was set to 1.0 to 3.0 mm
  • the ratio R/t was set to 1.56 to 2.17
  • the distance H was set to 0.1 to 1.0 mm.
  • the length W was set to 1.0 to 5.0 mm
  • the ratio R/t was set to 1.25 to 3.13
  • the distance H was set to 0.1 to 1.0 mm.
  • the length F was set to 0.1 mm.
  • FIG. 5 shows the analytical model for comparison, where (a) is a plan view of the analytical model, and (b) is a cross-sectional view showing the b-b portion of (a).
  • the analytical model 350 has a configuration in which a through hole 350a is simply formed in the center of a metal plate, and no inclined surface is formed around the through hole 350a. In other words, the analytical model 350 has a flat shape overall.
  • multiple analytical models 350 were created by changing the ratio R/t of the radius of curvature R and the thickness t of the through hole 350a.
  • the length and width of the analytical model 350 are 90 mm and 30 mm, similar to the analytical models 300 and 310.
  • the analytical models 300, 310, and 350 were restrained at a 25 mm x 30 mm region 300a (hereinafter referred to as the one end 300a) on one end side in the length direction and at a 25 mm x 30 mm region 300b (hereinafter referred to as the other end 300b) on the other end side.
  • the position of the one end 300a was fixed and the position of the other end 300b was moved to apply bending deformation to the analytical models 300, 310, and 350.
  • the other end 300b was rotated 2° around the center of the analytical models 300, 310, and 350, the stress generated at the edge of the through holes 104a and 350a on the outer surface side of the bend was investigated.
  • the inventor first compared the stress (maximum value of the maximum principal stress) generated at the edge of the through hole 104a, 350a for the analysis models 310, 350 with the same ratio R/t. Then, the length W and distance H when the stress generated at the edge of the through hole 104a is lower than the stress generated at the edge of the through hole 350a were clarified.
  • Tables 1 and 2 The results of the investigation are shown in Tables 1 and 2 below.
  • "A" and "B” indicate that the stress generated at the edge of the through hole 104a was lower than the stress generated at the edge of the through hole 350a
  • “A” indicates that the stress generated at the edge of the through hole 104a was 90% or less of the stress generated at the edge of the through hole 350a.
  • “C” indicates that the stress generated at the edge of the through hole 104a was equal to or greater than the stress generated at the edge of the through hole 350a.
  • the upper limit values of the length W and distance H of analysis model 310 with ratio R/t of 1.92 are 4.0 mm (length W) and 0.8 mm (distance H), rather than 4.0 mm (length W) and 0.9 mm (distance H).
  • the upper limit values of length W and distance H were determined so that the total number of "A"s and "B"s in the comparison results was maximized. For example, when the ratio R/t is 2.17, the combination of the upper limit values of length W and distance H that maximizes the total number of "A"s and “B”s in the comparison results is an upper limit value of length W of 3.0 mm and an upper limit value of distance H of 0.6 mm. Therefore, when the ratio R/t is 2.17, the upper limit values of length W and distance H are 3.0 mm and 0.6 mm, respectively.
  • FIG. 6 shows the relationship between the upper limit of length W and the ratio R/t
  • FIG. 7 shows the relationship between the upper limit of distance H and the ratio R/t.
  • FIG. 6 and FIG. 7 show the approximation curves obtained by the least squares method from multiple data (length W and distance H) obtained by analysis. As described above, in the analysis using analysis model 310, length W was set to 1.0 to 5.0 mm, and distance H was set to 0.1 to 1.0 mm.
  • the comparison result may be "B" or "A” even if the length W exceeds 5.0 mm or the distance H exceeds 1.0 mm.
  • the combination of the upper limit values of the length W and the distance H may be determined by values equal to or less than the minimum set values of the length W and the distance H. Taking these points into consideration, the data for ratios R/t of 1.25, 1.56, and 3.13 were excluded to obtain the approximation curves shown in Figures 6 and 7.
  • the inventor compared the stress (maximum value of maximum principal stress) occurring at the edge of through-hole 104a, 350a for analytical models 300, 350 with the same ratio R/t. Then, similar to the above case, the upper limit values of length W and distance H were obtained to make the stress occurring at the edge of through-hole 104a of analytical model 300 lower than the stress occurring at the edge of through-hole 350a of analytical model 350. As a result, the upper limit values of length W and distance H of analytical model 300 when ratio R/t was 2.17 were 1.0 mm and 0.1 mm, respectively. Moreover, the upper limit values of length W and distance H of analytical model 300 when ratio R/t was 1.56 were 1.0 mm and 1.0 mm, respectively.
  • analysis model 310 in which flat surface 406 is formed at the tip of processing portion 204, can reduce the value of stress generated at the edge of through hole 104a compared to analysis model 300 (see Figure 3), in which flat surface 406 is not formed.
  • the angle between the wall surface 400 and the inclined surface 402 of the analytical model 300 is significantly smaller than the angle between the wall surface 400 and the flat surface 406 of the analytical model 310.
  • the tip of the processed portion 104 of the analytical model 300 is sharper than that of the analytical model 310. This is thought to make it easier for stress concentration to occur at the edge of the through hole 104a (the tip of the processed portion 104) in the analytical model 300 than in the analytical model 310. From the above results, it can be seen that by providing a flat surface 406 at the tip of the processed portion 204, as in the metal plate 200 of FIG. 2, it is possible to suppress stress concentration at the edge of the through hole 104a.
  • Fig. 8 is a schematic diagram showing an example of a die for manufacturing the metal sheet 200.
  • the die 10 includes a punch 12, a die 14, and a blank holder 16.
  • the punch 12 is formed in a columnar shape (cylindrical in this embodiment) and is provided so as to be movable forward and backward in the vertical direction (press direction).
  • the die 14 has a hollow shape so that the punch 12 can be inserted.
  • the die 14 has a flat and annular support surface 40 that supports the blank (metal plate) 18, a tubular (cylindrical in this embodiment) inner peripheral surface 42 extending downward from the inner peripheral edge of the support surface 40, a flat and annular (circular in this embodiment) flange surface 44 extending from the lower edge of the inner peripheral surface 42 toward the inside of the inner peripheral surface 42, and a tubular (cylindrical in this embodiment) inner peripheral surface 46 extending downward from the inner peripheral edge of the flange surface 44.
  • the blank holder 16 is formed hollow so that the punch 12 can be inserted, and has an annular lower surface 60 facing the support surface 40 of the die 14.
  • the inner peripheral edge of the support surface 40 and the inner peripheral edge of the flange surface 44 each have a circular shape.
  • Figure 9 shows the state of the die 10 and the blank 18 immediately before the blank 18 is cut. As shown in Figure 9, when the die 10 cuts a predetermined area of the blank 18, the blank 18 is cut using the shoulder of the punch 12 and the inner edge of the flange surface 44 of the die 14 as cutting blades.
  • a step is provided between the support surface 40 and the flange surface 44. Therefore, the portion of the blank 18 located inside the inner peripheral edge of the support surface 40 is pressed toward the flange surface 44. As a result, as shown in FIG. 2, a processed portion 204 is formed so as to rise from the flat portion 102 in the thickness direction A.
  • the distance H (see FIG. 2) between the flat surface 102a and the flat surface 406 in the thickness direction A is approximately equal to the distance h (see FIG. 8) between the support surface 40 and the flange surface 44 in the press direction (up and down direction) of the die 10. Therefore, the distance H between the flat surface 102a and the flat surface 406 in the thickness direction A can be adjusted by adjusting the distance h between the support surface 40 and the flange surface 44.
  • the length W (see FIG. 2) of the inclined surface 408 in the direction perpendicular to the thickness direction A can be adjusted by adjusting the length w (see FIG. 8) of the flange surface 44 in the direction perpendicular to the press direction of the die 10.
  • the clearance CL (see FIG. 9) between the punch 12 and the die 14 (the inner peripheral edge of the flange surface 44) may be appropriately set according to the thickness of the blank 18, but is set to, for example, 18% or less of the thickness of the blank 18, and preferably 15% or less.
  • Figure 10 is a diagram for explaining the situation in which burrs are formed when the blank 18 is cut.
  • the inventor therefore created an axisymmetric model of two-dimensional solid elements for the die 10 and the blank 18, and conducted FEM analysis to investigate the conditions for the occurrence of the inflection point P.
  • the inventor created multiple analytical models by changing the ratio R1/t1 between the radius of curvature R1 (not shown) of the outer peripheral surface of the punch 12 and the thickness t1 of the blank 18, and conducted FEM analysis.
  • the distance d between the inflection point P and the support surface 40 in the press direction was investigated.
  • the ratio R1/t1 was set to 1.25 to 6.25
  • the distance h was set to 1.0 mm
  • the length w of the flange surface 44 in the direction perpendicular to the press direction was set to 1.0 mm.
  • the ratio CL/t1 between the clearance CL (see FIG. 9) of the punch 12 and the die 14 and the thickness t1 of the blank 18 was set to 12.5%.
  • the material properties of the blank 18 were set to the same as those of the above-mentioned analytical model 300.
  • Figure 11 shows the relationship between the ratio R1/t1 and the distance d.
  • the dotted line shows an approximation curve calculated by the least squares method from the distance d obtained by analysis.
  • the dashed line shows a straight line that is parallel to the approximation curve and passes through the point corresponding to the distance d when the ratio R1/t1 is 1.25.
  • the distance h between the support surface 40 and the flange surface 44 in the press direction should be equal to or less than the distance d between the inflection point P and the support surface 40 obtained by the above FEM analysis.
  • the distance H between the flat surface 102a and the flat surface 406 in the thickness direction A is approximately equal to the distance h. Therefore, by performing the punching process so that the distance H between the flat surface 102a and the flat surface 406 in the thickness direction A is equal to or less than the distance d obtained by the above FEM analysis, the flat surface 406 (see FIG.
  • the through hole 104a of the metal plate 200 is formed by the die 10
  • the radius of curvature R of the through hole 104a is approximately equal to the radius of curvature R1 of the outer circumferential surface of the punch 12.
  • the thickness t of the flat plate portion 102 of the metal plate 200 is approximately equal to the thickness t1 of the blank 18. Therefore, by forming the through hole 104a so as to satisfy the following formula (iii), the flat surface 406 (see FIG. 2) can be more appropriately formed and the occurrence of excessive burrs can be sufficiently suppressed. It is more preferable to form the through hole 104a so as to satisfy the following formula (iv).
  • H indicates the distance (mm) between the flat surface 102a and the flat surface 406 in the thickness direction A
  • R indicates the radius of curvature (mm) of the through hole 104a as viewed from the thickness direction A
  • t indicates the thickness (mm) of the flat plate portion 102 (metal plate).
  • the peripheral structure of a through hole in a metal plate is characterized in that, in the peripheral structure of a through hole 104a in a metal plate 200 shown in Fig.
  • a cross-sectional shape of a processed portion 204 that is parallel to the thickness direction A and passes through the center of the through hole 104a satisfies the following formulas (i) and (ii): 1.0 ⁇ W ⁇ 3.8314 ⁇ (R/t)+11.47 ⁇ 5.0 (i) 0.1 ⁇ H ⁇ 0.6604 ⁇ (R/t)+2.0489 ⁇ 1.0 (ii)
  • W is the length (mm) of the inclined surface 408 in a direction perpendicular to the thickness direction A
  • R is the radius of curvature (mm) of the through hole 104a
  • t is the thickness (mm) of the metal plate 200
  • H is the distance (mm) between the flat surface 102a and the flat surface 406 in the thickness direction A.
  • the structure surrounding the through hole of the metal plate according to this embodiment is formed, for example, using a material (steel plate, aluminum plate, etc.) with a thickness of 1.6 mm to 4.0 mm and a tensile strength of 590 MPa or more.
  • a material with a thickness of less than 1.6 mm or greater than 4.0 mm may also be used, and a material with a tensile strength of less than 590 MPa may also be used.
  • the flat surface 102a corresponds to the first flat surface
  • the flat surface 406 corresponds to the second flat surface
  • the wall surface 400 of the through hole 104a corresponds to the curved portion.
  • the radius of curvature of the through hole 104a means the radius of curvature of the sheared surface 400a as viewed from the thickness direction A. The radius of curvature of the through hole 104a can be measured using a spherometer.
  • the flat surface 406 is formed to extend in a direction perpendicular to the thickness direction A.
  • the tip of the processed portion 204 does not have a sharp shape, it is possible to sufficiently prevent stress concentration from occurring at the edge of the through hole 104a.
  • the length of the flat surface 406 in a direction perpendicular to the thickness direction A is 0.1 mm or more.
  • the flat surface 406 is provided perpendicular to the thickness direction A, but the flat surface 406 does not have to be strictly perpendicular to the thickness direction A.
  • “the flat surface extends in a direction perpendicular to the thickness direction A” includes the case where the flat surface is inclined at 0 to 10 degrees with respect to the direction perpendicular to the thickness direction A. Even in this case, it is possible to sufficiently prevent stress concentration from occurring at the edge of the through hole 104a.
  • flat surface 102a is also formed to extend in a direction perpendicular to thickness direction A, similar to flat surface 406.
  • the wall surface 400 includes a shear surface 400a that extends in a direction perpendicular to the flat surface 102a.
  • the wall surface 400 is provided so as to extend in a direction perpendicular to the flat surface 102a, but the wall surface 400 does not have to be strictly perpendicular to the normal direction of the flat surface 102a.
  • “the shear surface extends in a direction perpendicular to the flat surface” includes the case where the shear surface is inclined at an angle of 0 to 10 degrees with respect to the normal direction of the flat surface.
  • the portion between the shear surface 400a and the flat surface 406 in the wall surface 400 (the fracture surface 400b in this embodiment) is provided so as to be located outside the shear surface 400a in the radial direction D of the through hole 104a.
  • the portion between the shear surface 400a and the flat surface 406 in the wall surface 400 does not protrude toward the inside of the through hole 104a beyond the shear surface 400a when viewed from the thickness direction A.
  • the inclined surface 408 is provided so as to be located outside the outer edge of the flat surface 406 in the radial direction D of the through hole 104a.
  • the inclined surface 408 does not extend toward the through hole 104a side beyond the outer edge of the flat surface 406 when viewed from the thickness direction A.
  • the shape of the periphery of the processed portion 204 is smooth, it is possible to sufficiently suppress the occurrence of stress concentration around the through hole 104a. This can improve the fatigue durability of the metal plate 200.
  • the shape of the through hole as viewed from the thickness direction A is not limited to a circular shape. If the shape of the through hole as viewed from the thickness direction A is not circular, the radial direction of the through hole means the direction perpendicular to the central axis of the through hole.
  • the cross-sectional shape of the processed portion 204 which is parallel to the thickness direction A and passes through the center of the through hole 104a, satisfies the following formula (iii).
  • the flat surface 406 (see FIG. 2) can be more appropriately formed, and the occurrence of excessive burrs can be sufficiently suppressed.
  • H 0.0975 ⁇ (R/t)+0.3009 (iii)
  • R is the radius of curvature (mm) of the through hole 104a
  • t is the thickness (mm) of the metal plate 200.
  • the present invention is applied to a metal plate 200 in which a circular through hole 104a is formed as viewed from the thickness direction A, but the shape of the through hole 104a is not limited to a circular shape.
  • the through hole formed in the processed portion may have one or more (four in this embodiment) straight portions and one or more curved portions as viewed from the thickness direction of the flat plate portion.
  • the through hole 104a may have an oval shape.
  • the through hole 104a shown in FIG. 12(a) has two straight portions 50 and two curved portions 52.
  • the through hole 104a may have a polygonal shape with curved portions 52 provided at the corners.
  • the curved portions 52 are curved in an arc so as to be convex toward the outside of the through hole 104a.
  • the above formulas (i) and (ii) are satisfied in the cross section of the processed portion 204 that is parallel to the thickness direction A and passes through the center of the through hole 104a and the curved portion 52.
  • R in the above formulas (i), (ii), (iii), and (iv) indicates the radius of curvature (mm) of the portion of the curved portion 52 that corresponds to the above cross section.
  • the metal plate according to the present invention includes not only flat metal plates, but also various molded products (e.g., automobile parts) manufactured using flat metal plates as blanks.
  • the peripheral structure of the through hole in the metal plate according to the present invention can be used in blanks used as materials for various molded products (such as automobile parts), and in various molded products.
  • examples of automobile parts according to the present invention include suspension parts (lower arms, upper arms, trailing links, subframes, etc.) that have the peripheral structure of the above-mentioned through holes, body parts, and ladder frames.
  • connection between the inner circumferential surface 42 and the flange surface 44 may be curved in an arc.
  • the durability of the die 14 can be improved.
  • connection between the support surface 40 and the inner peripheral surface 42 may be curved in an arc.
  • the connection between the support surface 40 and the inner peripheral surface 42 may be curved in an arc.
  • connection between the support surface 40 and the inner circumferential surface 42 and the connection between the inner circumferential surface 42 and the flange surface 44 may each be curved in an arc. In this case, the durability of the metal plate 200 and the die 14 can be improved.
  • the inner circumferential surface 42 may be inclined with respect to the support surface 40 and the flange surface 44.
  • the durability of the metal plate 200 and the die 14 can be improved.
  • the durability of the die 14 can be further improved by curving the connection between the inner circumferential surface 42 and the flange surface 44 in an arc shape.
  • the durability of the metal plate 200 (the rising portion of the inclined surface 408) can be further improved by curving the connection between the support surface 40 and the inner circumferential surface 42 in an arc shape.
  • the die does not need to be equipped with a blank holder.
  • the manufacturing method of the metal plate 200 is not limited to the above-mentioned method, and if the metal plate 200 (processing section 204) can satisfy the above formulas (i) and (ii), the metal plate 200 may be manufactured using a die having a shape and dimensions different from those of the above-mentioned die. Therefore, the shape and dimensions of the die can be appropriately changed depending on the material and dimensions of the metal plate 200 so that the metal plate 200 (processing section 204) satisfies the above formulas (i) and (ii).
  • the present invention can improve the fatigue durability of metal plates with through holes. Therefore, the present invention can be suitably used in the raw metal plates of various automobile parts.

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  • Shaping Metal By Deep-Drawing, Or The Like (AREA)

Abstract

In the present invention, a metal sheet 200 has a flat sheet part 102 and a processed part 204 in which a through-hole 104a is formed in the center part thereof. The processed part 204 includes a flat surface 406 formed on one side with respect to the thickness direction A relative to the flat surface 102a of the flat sheet part 102, and an inclined surface 408 extending from the flat surface 406 towards the flat surface 102a, and "1.0≤W≤–3.8314×(R/t)+11.47≤5.0" and "0.1≤H≤–0.6604×(R/t)+2.0489≤1.0". In the above relationships, W is the length (mm) of the inclined surface 408 in a direction orthogonal to the thickness direction A, R is the curvature radius (mm) of the through-hole 104a as viewed from the thickness direction A, t is the thickness (mm) of the metal sheet 200, and H is the distance (mm) between the flat surface 102a and the flat surface 406 in the thickness direction A.

Description

金属板の貫通孔の周辺構造、ブランクおよび自動車部品Peripheral structures for through holes in metal sheets, blanks and automotive parts
　本発明は、金属板の貫通孔の周辺構造、ブランクおよび自動車部品に関する。 The present invention relates to a peripheral structure for a through hole in a metal plate, a blank, and an automobile part.
　近年、二酸化炭素排出規制の厳格化を受け、自動車車体の軽量化が求められている。これに伴い、自動車部品として使用される金属板の高強度薄肉化が進んでいる。一方で、自動車部品には、優れた疲労耐久性が要求される。 In recent years, in response to stricter carbon dioxide emission regulations, there is a demand for lighter automobile bodies. Accordingly, metal plates used in automobile parts are becoming stronger and thinner. At the same time, automobile parts are required to have excellent fatigue durability.
　自動車部品の素材として利用される金属板には、穴抜き加工が施される場合がある。このような金属板からなる自動車部品に変形が加えられると、穴抜き加工部（穴縁）の周辺において応力集中が生じる。これにより、穴抜き加工部からき裂が発生し、疲労破壊する場合がある。このため、自動車部品の疲労耐久性を向上させるためには、穴抜き加工部において疲労き裂が発生することを防止することが重要である。 Metal plates used as materials for automotive parts may be punched. When automotive parts made of such metal plates are deformed, stress concentration occurs around the punched area (hole edge). This can cause cracks to occur in the punched area, leading to fatigue failure. For this reason, in order to improve the fatigue durability of automotive parts, it is important to prevent fatigue cracks from occurring in the punched areas.
　従来、穴抜き加工部におけるき裂の発生を防止するための方法が提案されている。例えば、特許文献１には、打ち抜き加工端面の伸びフランジ性を向上させる打ち抜き加工方法が開示されている。特許文献１に開示された打ち抜き加工方法で使用されるダイは、ダイ上面の平坦部から打ち抜き方向に所定距離下がった位置に刃先が設けられ、かつ、刃先部分が面取りされている。 　Methods have been proposed to prevent cracks from occurring in the punched area. For example, Patent Document 1 discloses a punching method that improves the stretch flangeability of the punched end surface. The die used in the punching method disclosed in Patent Document 1 has a cutting edge that is located a predetermined distance below the flat part on the top surface of the die in the punching direction, and the cutting edge portion is chamfered.
　特許文献１の方法によって打ち抜き加工された金属板では、打ち抜きが終了した時点で、打ち抜き方向に被加工材が曲がることになる。このため、打ち抜き後に打ち抜き方向と同一方向にフランジアップ加工をする場合には、打ち抜き端面がフランジアップ加工初期の時点で既にある程度フランジアップされた形状となる。この場合、フランジアップ加工をする際に、伸びフランジ変形による端面の塑性歪量を少なくすることができる。これにより、打ち抜き加工端面の伸びフランジ性を向上させることができ、打ち抜き端面における割れの発生を防止することができる。 In a metal plate punched by the method of Patent Document 1, the workpiece bends in the punching direction when punching is completed. For this reason, when flange-up processing is performed in the same direction as the punching direction after punching, the punched end face will already have a flange-up shape to a certain extent at the beginning of the flange-up processing. In this case, the amount of plastic strain on the end face due to stretch flange deformation can be reduced when performing flange-up processing. This can improve the stretch flangeability of the punched end face and prevent the occurrence of cracks on the punched end face.
特開２００９－２５５１６７号公報JP 2009-255167 A
　特許文献１においては、上記のように、伸びフランジ性の向上については検討が行われている。しかしながら、金属板全体に変形が加えられた際に穴抜き加工部の周辺に生じる応力集中については検討が行われていない。すなわち、穴抜き加工部を有する金属板の疲労耐久性については検討が行われていない。 As mentioned above, in Patent Document 1, the improvement of stretch flangeability is examined. However, no study is made of the stress concentration that occurs around the punched portion when the entire metal plate is deformed. In other words, no study is made of the fatigue durability of the metal plate having the punched portion.
　そこで、本発明は、穴抜き加工によって貫通孔が形成された金属板の疲労耐久性を向上させることを目的としている。 The present invention aims to improve the fatigue durability of metal plates in which through holes are formed by punching.
　本発明は、下記の金属板の貫通孔の周辺構造、ブランクおよび自動車部品を要旨とする。 The gist of the present invention is the peripheral structure of a through hole in a metal plate, a blank, and an automobile part described below.
（１）金属板に形成された貫通孔の周辺の構造であって、
　平板部と、前記平板部から前記平板部の厚み方向における一方側に立ち上がりかつ中心に前記貫通孔が形成された加工部と、を有し、
　前記平板部は、前記平板部の前記一方側において前記加工部の周囲を囲む第１平坦面を含み、
　前記加工部は、前記厚み方向に延びかつ前記貫通孔の内壁を構成する壁面と、前記厚み方向から見て前記第１平坦面よりも内側でかつ前記厚み方向において前記第１平坦面よりも前記一方側で前記壁面の前記一方側の縁から前記厚み方向に交差する方向に延びる環状の第２平坦面と、前記第２平坦面の外縁と前記第１平坦面の内縁とを接続しかつ前記厚み方向に対して傾斜する傾斜面とを含み、
　前記厚み方向から見て、前記貫通孔は、前記貫通孔の外側に向かって凸となるように弧状に湾曲する湾曲部を含み、
　前記厚み方向に平行でかつ前記貫通孔の中心および前記湾曲部を通る前記加工部の断面において、下記（ｉ）式および（ii）式を満たす、金属板の貫通孔の周辺構造。
　１．０≦Ｗ≦－３．８３１４×（Ｒ／ｔ）＋１１．４７≦５．０　・・・（ｉ）
　０．１≦Ｈ≦－０．６６０４×（Ｒ／ｔ）＋２．０４８９≦１．０　・・・（ii）
　ただし、上記（ｉ）式および（ii）式において、Ｗは、前記厚み方向に直交する方向における前記傾斜面の長さ（ｍｍ）であり、Ｒは、前記湾曲部のうち前記断面に対応する部分の曲率半径（ｍｍ）であり、ｔは、前記金属板の厚み（ｍｍ）であり、Ｈは、前記厚み方向における前記第１平坦面と前記第２平坦面との距離（ｍｍ）である。 (1) A structure around a through hole formed in a metal plate,
A flat plate portion and a processed portion rising from the flat plate portion to one side in a thickness direction of the flat plate portion and having the through hole formed at a center thereof,
The flat plate portion includes a first flat surface surrounding the processed portion on the one side of the flat plate portion,
the processed portion includes a wall surface extending in the thickness direction and constituting an inner wall of the through hole, a ring-shaped second flat surface that is located inside the first flat surface when viewed from the thickness direction and on the one side of the first flat surface in the thickness direction, and extends from an edge of the wall surface on the one side in a direction intersecting the thickness direction, and an inclined surface that connects an outer edge of the second flat surface and an inner edge of the first flat surface and is inclined with respect to the thickness direction,
When viewed from the thickness direction, the through hole includes a curved portion that is curved in an arc shape so as to be convex toward an outside of the through hole,
A peripheral structure of a through hole in a metal plate, which satisfies the following formulas (i) and (ii) in a cross section of the processed portion that is parallel to the thickness direction and passes through the center of the through hole and the curved portion.
1.0≦W≦−3.8314×(R/t)+11.47≦5.0 (i)
0.1≦H≦−0.6604×(R/t)+2.0489≦1.0 (ii)
However, in the above formulas (i) and (ii), W is the length (mm) of the inclined surface in a direction perpendicular to the thickness direction, R is the radius of curvature (mm) of the part of the curved portion corresponding to the cross section, t is the thickness (mm) of the metal plate, and H is the distance (mm) between the first flat surface and the second flat surface in the thickness direction.
（２）前記第２平坦面は、前記厚み方向に直交する方向に延びる、上記（１）に記載の金属板の貫通孔の周辺構造。 (2) The peripheral structure of the through hole of the metal plate described in (1) above, in which the second flat surface extends in a direction perpendicular to the thickness direction.
（３）前記壁面は、前記第１平坦面に対して直交する方向に延びるせん断面を含む、上記（１）または（２）のいずれかに記載の金属板の貫通孔の周辺構造。 (3) The peripheral structure of a through hole in a metal plate described in either (1) or (2) above, in which the wall surface includes a shear surface extending in a direction perpendicular to the first flat surface.
（４）前記断面において、前記壁面のうち前記せん断面と前記第２平坦面との間の部分は、前記貫通孔の中心軸に直交する方向において前記せん断面よりも外側に収まるように設けられ、かつ前記傾斜面は、前記直交する方向において前記第２平坦面の前記外縁よりも外側に収まるように設けられている、上記（３）に記載の金属板の貫通孔の周辺構造。 (4) The peripheral structure of the through hole in the metal plate described in (3) above, in which, in the cross section, the portion of the wall surface between the sheared surface and the second flat surface is arranged so as to be located outside the sheared surface in a direction perpendicular to the central axis of the through hole, and the inclined surface is arranged so as to be located outside the outer edge of the second flat surface in the perpendicular direction.
（５）前記断面において、下記（iii）式を満たす、上記（１）から（４）のいずれかに記載の金属板の貫通孔の周辺構造。
　Ｈ≦０．０９７５×（Ｒ／ｔ）＋０．３００９　・・・（iii）
　ただし、上記（iii）式において、Ｈは、前記厚み方向における前記第１平坦面と前記第２平坦面との距離（ｍｍ）であり、Ｒは、前記湾曲部のうち前記断面に対応する部分の曲率半径（ｍｍ）であり、ｔは、前記金属板の厚み（ｍｍ）である。 (5) A peripheral structure of a through hole of a metal plate according to any one of (1) to (4) above, which satisfies the following formula (iii) in the cross section:
H≦0.0975×(R/t)+0.3009 (iii)
However, in the above formula (iii), H is the distance (mm) between the first flat surface and the second flat surface in the thickness direction, R is the radius of curvature (mm) of the part of the curved portion corresponding to the cross section, and t is the thickness (mm) of the metal plate.
（６）前記断面において、下記（iv）式を満たす、上記（５）に記載の金属板の貫通孔の周辺構造。
　Ｈ≦０．０９７５×（Ｒ／ｔ）＋０．２３８１　・・・（iv）
　ただし、上記（iv）式において、Ｈは、前記厚み方向における前記第１平坦面と前記第２平坦面との距離（ｍｍ）であり、Ｒは、前記湾曲部のうち前記断面に対応する部分の曲率半径（ｍｍ）であり、ｔは、前記金属板の厚み（ｍｍ）である。 (6) A peripheral structure of the through hole of the metal plate described in (5) above, which satisfies the following formula (iv) in the cross section:
H≦0.0975×(R/t)+0.2381 (iv)
However, in the above formula (iv), H is the distance (mm) between the first flat surface and the second flat surface in the thickness direction, R is the radius of curvature (mm) of the part of the curved portion corresponding to the cross section, and t is the thickness (mm) of the metal plate.
（７）前記貫通孔は、前記厚み方向から見て、円形状を有している、上記（１）から（６）のいずれかに記載の金属板の貫通孔の周辺構造。 (7) The peripheral structure of a through hole in a metal plate described in any one of (1) to (6) above, wherein the through hole has a circular shape when viewed in the thickness direction.
（８）上記（１）から（７）のいずれかに記載の金属板の貫通孔の周辺構造を備える、ブランク。 (8) A blank having a peripheral structure for a through hole in a metal plate described in any one of (1) to (7) above.
（９）上記（１）から（７）のいずれかに記載の金属板の貫通孔の周辺構造を備える、自動車部品。 (9) An automobile part having a peripheral structure for a through hole in a metal plate described in any one of (1) to (7) above.
　本発明によれば、貫通孔が形成された金属板の疲労耐久性を向上させることができる。 The present invention makes it possible to improve the fatigue durability of a metal plate having through holes formed therein.
図１は、穴抜き加工によって貫通孔が形成された金属板の一例を示す図である。FIG. 1 is a diagram showing an example of a metal plate in which through holes are formed by punching. 図２は、穴抜き加工によって貫通孔が形成された金属板の他の例を示す図である。FIG. 2 is a diagram showing another example of a metal plate in which through holes are formed by punching. 図３は、シミュレーションで用いた金属板の解析モデルを示す図である。FIG. 3 is a diagram showing an analytical model of a metal plate used in the simulation. 図４は、金属板の解析モデルの他の例を示す図である。FIG. 4 is a diagram showing another example of the analytical model of a metal plate. 図５は、比較対象の金属板の解析モデルを示す図である。FIG. 5 is a diagram showing an analytical model of a metal plate for comparison. 図６は、解析結果を示す図である。FIG. 6 is a diagram showing the analysis results. 図７は、解析結果を示す図である。FIG. 7 is a diagram showing the analysis results. 図８は、穴抜き加工を行うための金型の一例を示す概略図である。FIG. 8 is a schematic diagram showing an example of a die for performing hole punching. 図９は、ブランクが切断される直前の、金型およびブランクの状態を示す図である。FIG. 9 is a diagram showing the state of the die and the blank just before the blank is cut. 図１０は、ブランクが切断される際にバリが形成される状況を説明するための図である。FIG. 10 is a diagram for explaining a state in which a burr is formed when a blank is cut. 図１１は、解析結果を示す図である。FIG. 11 is a diagram showing the analysis results. 図１２は、穴抜き加工によって貫通孔が形成された金属板のその他の例を示す図である。FIG. 12 is a diagram showing another example of a metal plate in which through holes are formed by punching. 図１３は、ダイの変形例を示す図である。FIG. 13 shows a modified example of the die. 図１４は、ダイの変形例を示す図である。FIG. 14 shows a modified example of the die.
　（本発明者による検討）
　図１は、穴抜き加工によって貫通孔が形成された金属板の一例を示す図であり、（ａ）は、金属板を示す斜視図であり、（ｂ）は、（ａ）において一点鎖線で囲んだ部分の断面図である。図１に示す金属板１００は、平板部１０２および加工部１０４を有している。なお、図１においては、平板部１０２の厚み方向を矢印Ａで示している。以下、平板部１０２の厚み方向を、単に厚み方向Ａとも記載する。 (Study by the inventor)
1 is a diagram showing an example of a metal plate in which through holes are formed by punching, where (a) is a perspective view showing the metal plate, and (b) is a cross-sectional view of a portion surrounded by a dashed line in (a). The metal plate 100 shown in FIG. 1 has a flat plate portion 102 and a processed portion 104. In FIG. 1, the thickness direction of the flat plate portion 102 is indicated by an arrow A. Hereinafter, the thickness direction of the flat plate portion 102 will also be simply referred to as the thickness direction A.
　加工部１０４は、穴抜き加工によって、平板部１０２から厚み方向Ａにおける一方側に立ち上がるように形成されている。加工部１０４の中心には、貫通孔１０４ａが形成されている。厚み方向Ａから見て、貫通孔１０４ａは円形状を有している。 The processed portion 104 is formed by punching so as to rise from the flat portion 102 to one side in the thickness direction A. A through hole 104a is formed in the center of the processed portion 104. When viewed from the thickness direction A, the through hole 104a has a circular shape.
　平板部１０２は、厚み方向Ａにおける一方側に設けられる平坦面１０２ａと、厚み方向Ａにおける他方側に設けられる平坦面１０２ｂとを有する。平坦面１０２ａ，１０２ｂはそれぞれ、加工部１０４の周囲を囲むように設けられている。 The flat plate portion 102 has a flat surface 102a provided on one side in the thickness direction A, and a flat surface 102b provided on the other side in the thickness direction A. The flat surfaces 102a and 102b are each provided so as to surround the periphery of the processed portion 104.
　図１（ｂ）に示すように、加工部１０４は、壁面４００、傾斜面４０２および傾斜面４０４を有する。壁面４００は、厚み方向Ａに延びかつ貫通孔１０４ａの内壁を構成する。壁面４００は、せん断面４００ａおよび破断面４００ｂを含む。傾斜面４０２は、壁面４００の厚み方向Ａにおける一方側の縁と平坦面１０２ａの内縁とを接続するように、厚み方向Ａから見て環状に形成されている。傾斜面４０４は、だれであり、壁面４００の厚み方向Ａにおける他方側の縁と平坦面１０２ｂの内縁とを接続するように、厚み方向Ａから見て環状に形成されている。 As shown in FIG. 1(b), the processed portion 104 has a wall surface 400, an inclined surface 402, and an inclined surface 404. The wall surface 400 extends in the thickness direction A and constitutes the inner wall of the through hole 104a. The wall surface 400 includes a shear surface 400a and a fracture surface 400b. The inclined surface 402 is formed in a ring shape as viewed from the thickness direction A so as to connect the edge on one side of the wall surface 400 in the thickness direction A to the inner edge of the flat surface 102a. The inclined surface 404 is sagging and is formed in a ring shape as viewed from the thickness direction A so as to connect the edge on the other side of the wall surface 400 in the thickness direction A to the inner edge of the flat surface 102b.
　上記のような金属板１００を素材とする自動車部品等においては、加工部１０４の周辺において、矢印Ｂで示すような曲げ変形が加えられる場合がある。本発明者による検討の結果、金属板１００においてこのような曲げ変形が加えられた場合には、貫通孔１０４ａの縁部に応力集中が生じることが分かった。 In automobile parts and the like made of the above-mentioned metal plate 100, bending deformation as shown by arrow B may be applied around the processed portion 104. As a result of the inventor's investigation, it was found that when such bending deformation is applied to the metal plate 100, stress concentration occurs at the edge of the through hole 104a.
　そこで、本発明者は、このような応力集中の発生を抑制するための検討を行った。具体的には、加工部の端部の形状と、貫通孔の縁部に発生する応力との関係を調査した。 The inventor therefore conducted research into ways to prevent such stress concentration from occurring. Specifically, he investigated the relationship between the shape of the end of the processed part and the stress that occurs at the edge of the through hole.
　図２は、穴抜き加工によって貫通孔が形成された金属板の他の例を示す図であり、（ａ）は、金属板を示す斜視図であり、（ｂ）は、（ａ）において一点鎖線で囲んだ部分の断面図である。なお、図２に示す金属板の製造方法については後述する。 FIG. 2 shows another example of a metal plate in which through holes are formed by punching, where (a) is a perspective view of the metal plate, and (b) is a cross-sectional view of the part surrounded by the dashed line in (a). The method of manufacturing the metal plate shown in FIG. 2 will be described later.
　図２に示す金属板２００が図１に示す金属板１００と異なるのは、加工部１０４の代わりに加工部２０４が形成されている点である。また、加工部２０４が加工部１０４と異なるのは、傾斜面４０２の代わりに、平坦面４０６および傾斜面４０８を有する点である。平坦面４０６および傾斜面４０８はそれぞれ、厚み方向Ａから見て環状に形成されている。平坦面４０６は、壁面４００の厚み方向Ａにおける一方側の縁から厚み方向Ａに交差する方向に延びるように形成されている。傾斜面４０８は、平坦面４０６の外縁と平坦面１０２ａの内縁とを接続しかつ厚み方向Ａに対して傾斜している。 The metal plate 200 shown in FIG. 2 differs from the metal plate 100 shown in FIG. 1 in that a processed portion 204 is formed instead of the processed portion 104. Also, the processed portion 204 differs from the processed portion 104 in that a flat surface 406 and a sloped surface 408 are formed instead of the sloped surface 402. The flat surface 406 and the sloped surface 408 are each formed in an annular shape when viewed from the thickness direction A. The flat surface 406 is formed so as to extend from one edge of the wall surface 400 in the thickness direction A in a direction intersecting the thickness direction A. The sloped surface 408 connects the outer edge of the flat surface 406 and the inner edge of the flat surface 102a and is sloped with respect to the thickness direction A.
　（シミュレーション）
　本発明者は、金属板１００および金属板２００に対して曲げ変形を加えた際に、貫通孔１０４ａの縁部に発生する応力について検討を行った。具体的には、本発明者は、コンピュータを用いたＦＥＭ解析によるシミュレーションを行い、貫通孔１０４ａの縁部に発生する応力を調査した。 (simulation)
The present inventors have studied the stress generated at the edge of the through hole 104a when bending deformation is applied to the metal plate 100 and the metal plate 200. Specifically, the present inventors performed a simulation by FEM analysis using a computer to investigate the stress generated at the edge of the through hole 104a.
　図３は、図１の金属板１００の解析モデルを示す図であり、図４は、図２の金属板２００の解析モデルを示す図である。図３および図４において、（ａ）は、解析モデルの平面図であり、（ｂ）は解析モデルの正面図であり、（ｃ）は、（ａ）において一点鎖線で囲んだ部分の断面図である。なお、解析モデル３００，３１０において、金属板１００，２００に対応する構成を有する部分については、金属板１００，２００と同一の符号を付している。ただし、図３（ｃ）および図４（ｃ）に示すように、解析モデル３００，３１０においては、加工部１０４，２０４の形状は簡略化した。解析モデル３００，３１０および後述の解析モデル３５０には、引張強さが７８０ＭＰａ級の熱延鋼板の材料特性を設定した。 3 is a diagram showing an analytical model of the metal plate 100 in FIG. 1, and FIG. 4 is a diagram showing an analytical model of the metal plate 200 in FIG. 2. In FIG. 3 and FIG. 4, (a) is a plan view of the analytical model, (b) is a front view of the analytical model, and (c) is a cross-sectional view of the part surrounded by the dashed line in (a). In the analytical models 300 and 310, the parts having the configuration corresponding to the metal plates 100 and 200 are given the same reference numerals as the metal plates 100 and 200. However, as shown in FIG. 3(c) and FIG. 4(c), the shapes of the processed parts 104 and 204 are simplified in the analytical models 300 and 310. The material properties of a hot-rolled steel plate with a tensile strength of 780 MPa were set for the analytical models 300 and 310 and the analytical model 350 described later.
　図３および図４において、Ｗは、厚み方向Ａに直交する方向における傾斜面４０２，４０８の長さ（ｍｍ）を示し、Ｒは、厚み方向Ａから見た貫通孔１０４ａの曲率半径（ｍｍ）を示し、ｔは、平板部１０２（金属板）の厚み（ｍｍ）を示す。また、図３においてＨは、厚み方向Ａにおける平坦面１０２ａと加工部１０４の先端との距離（ｍｍ）を示し、図４においてＨは、厚み方向Ａにおける平坦面１０２ａと平坦面４０６との距離（ｍｍ）を示す。また、図４において、Ｆは、厚み方向Ａに直交する方向における平坦面４０６の長さを示す。本シミュレーションでは、長さＷ、曲率半径Ｒと厚みｔとの割合Ｒ／ｔ、および距離Ｈを変えて複数の解析モデル３００，３１０を作成し、ＦＥＭ解析を実施した。解析モデル３００，３１０の長さおよび幅は、９０ｍｍおよび３０ｍｍとした。なお、解析モデル３００では、長さＷは、１．０～３．０ｍｍに設定し、割合Ｒ／ｔは、１．５６～２．１７に設定し、距離Ｈは、０．１～１．０ｍｍに設定した。解析モデル３１０では、長さＷは、１．０～５．０ｍｍに設定し、割合Ｒ／ｔは、１．２５～３．１３に設定し、距離Ｈは、０．１～１．０ｍｍに設定した。また、解析モデル３１０において、長さＦは、０．１ｍｍとした。 3 and 4, W indicates the length (mm) of the inclined surfaces 402, 408 in a direction perpendicular to the thickness direction A, R indicates the radius of curvature (mm) of the through hole 104a as viewed from the thickness direction A, and t indicates the thickness (mm) of the flat plate portion 102 (metal plate). In addition, in FIG. 3, H indicates the distance (mm) between the flat surface 102a and the tip of the processed portion 104 in the thickness direction A, and in FIG. 4, H indicates the distance (mm) between the flat surface 102a and the flat surface 406 in the thickness direction A. In addition, in FIG. 4, F indicates the length of the flat surface 406 in a direction perpendicular to the thickness direction A. In this simulation, multiple analysis models 300, 310 were created by changing the length W, the ratio R/t of the radius of curvature R to the thickness t, and the distance H, and FEM analysis was performed. The length and width of the analysis models 300, 310 were 90 mm and 30 mm. In the analysis model 300, the length W was set to 1.0 to 3.0 mm, the ratio R/t was set to 1.56 to 2.17, and the distance H was set to 0.1 to 1.0 mm. In the analysis model 310, the length W was set to 1.0 to 5.0 mm, the ratio R/t was set to 1.25 to 3.13, and the distance H was set to 0.1 to 1.0 mm. In the analysis model 310, the length F was set to 0.1 mm.
　また、本シミュレーションでは、比較対象となる解析モデルを作成した。図５は、比較対象の解析モデルを示す図であり、（ａ）は、解析モデルの平面図であり、（ｂ）は（ａ）のｂ－ｂ部分を示す断面図である。図５に示すように、解析モデル３５０は、金属板の中心部に単に貫通孔３５０ａを形成した構成を有し、貫通孔３５０ａの周囲に傾斜面は形成されていない。すなわち、解析モデル３５０は、全体として平坦な形状を有している。なお、解析モデル３００，３１０と同様に、貫通孔３５０ａの曲率半径Ｒと厚みｔとの割合Ｒ／ｔを変えて複数の解析モデル３５０を作成した。解析モデル３５０の長さおよび幅は、解析モデル３００，３１０と同様に、９０ｍｍおよび３０ｍｍである。 Furthermore, in this simulation, an analytical model for comparison was created. FIG. 5 shows the analytical model for comparison, where (a) is a plan view of the analytical model, and (b) is a cross-sectional view showing the b-b portion of (a). As shown in FIG. 5, the analytical model 350 has a configuration in which a through hole 350a is simply formed in the center of a metal plate, and no inclined surface is formed around the through hole 350a. In other words, the analytical model 350 has a flat shape overall. Note that, similar to the analytical models 300 and 310, multiple analytical models 350 were created by changing the ratio R/t of the radius of curvature R and the thickness t of the through hole 350a. The length and width of the analytical model 350 are 90 mm and 30 mm, similar to the analytical models 300 and 310.
　ＦＥＭ解析では、解析モデル３００，３１０，３５０の長さ方向における一端側の２５ｍｍ×３０ｍｍの領域３００ａ（以下、一端部３００ａと記載する。）、および他端側の２５ｍｍ×３０ｍｍの領域３００ｂ（以下、他端部３００ｂと記載する。）を拘束した。また、図３（ｂ）、図４（ｂ）および図５（ｂ）に矢印Ｃで示すように、一端部３００ａの位置を固定した状態で、他端部３００ｂの位置を移動させて、解析モデル３００，３１０，３５０に曲げ変形を加えた。そして、他端部３００ｂが、解析モデル３００，３１０，３５０の中心に対して２°回転したときに、解析モデル３００，３１０，３５０の曲げの外面側において貫通孔１０４ａ，３５０ａの縁部に生じている応力を調査した。 In the FEM analysis, the analytical models 300, 310, and 350 were restrained at a 25 mm x 30 mm region 300a (hereinafter referred to as the one end 300a) on one end side in the length direction and at a 25 mm x 30 mm region 300b (hereinafter referred to as the other end 300b) on the other end side. As shown by the arrow C in Figures 3(b), 4(b), and 5(b), the position of the one end 300a was fixed and the position of the other end 300b was moved to apply bending deformation to the analytical models 300, 310, and 350. Then, when the other end 300b was rotated 2° around the center of the analytical models 300, 310, and 350, the stress generated at the edge of the through holes 104a and 350a on the outer surface side of the bend was investigated.
　具体的には、まず、本発明者は、割合Ｒ／ｔが互いに等しい解析モデル３１０，３５０について貫通孔１０４ａ，３５０ａの縁部に生じる応力（最大主応力の最大値）を比較した。そして、貫通孔３５０ａの縁部に生じる応力よりも、貫通孔１０４ａの縁部に生じる応力が低くなるときの、長さＷおよび距離Ｈを明らかにした。調査結果を下記の表１および表２に示す。なお、表１および表２において、「Ａ」および「Ｂ」は、貫通孔１０４ａの縁部に生じた応力が貫通孔３５０ａの縁部に生じた応力よりも低かったことを示し、特に「Ａ」は、貫通孔１０４ａの縁部に生じた応力が貫通孔３５０ａの縁部に生じた応力の９０％以下であったことを示している。また、「Ｃ」は、貫通孔１０４ａの縁部に生じた応力が貫通孔３５０ａの縁部に生じた応力以上であったことを示している。 Specifically, the inventor first compared the stress (maximum value of the maximum principal stress) generated at the edge of the through hole 104a, 350a for the analysis models 310, 350 with the same ratio R/t. Then, the length W and distance H when the stress generated at the edge of the through hole 104a is lower than the stress generated at the edge of the through hole 350a were clarified. The results of the investigation are shown in Tables 1 and 2 below. In Tables 1 and 2, "A" and "B" indicate that the stress generated at the edge of the through hole 104a was lower than the stress generated at the edge of the through hole 350a, and in particular, "A" indicates that the stress generated at the edge of the through hole 104a was 90% or less of the stress generated at the edge of the through hole 350a. In addition, "C" indicates that the stress generated at the edge of the through hole 104a was equal to or greater than the stress generated at the edge of the through hole 350a.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　本発明者は、表１および表２に示した結果から、解析モデル３１０の貫通孔１０４ａの縁部に生じる応力を、解析モデル３５０の貫通孔３５０ａの縁部に生じる応力よりも低くするための、長さＷおよび距離Ｈの上限値を求めた。下記の表３に、各割合Ｒ／ｔについての、長さＷおよび距離Ｈの上限値を示す。 From the results shown in Tables 1 and 2, the inventors have determined the upper limit values of length W and distance H to make the stress generated at the edge of through hole 104a in analytical model 310 lower than the stress generated at the edge of through hole 350a in analytical model 350. Table 3 below shows the upper limit values of length W and distance H for each ratio R/t.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　なお、各割合Ｒ／ｔにおいて、長さＷおよび距離Ｈがそれぞれ特定の値以下であれば、上記の表１，２において、すべての比較結果が「Ａ」および「Ｂ」のいずれかとなる。そのような特定の値を上限値という。例えば、割合Ｒ／ｔが１．９２の解析モデル３１０について説明すると、表２に示すように、長さＷが４．０ｍｍの場合には、距離Ｈが０．１～０．９ｍｍの範囲で、比較結果が「Ｂ」となっている。しかしながら、表１に示すように、長さＷが１．０ｍｍでかつ距離Ｈが０．９ｍｍの場合には、比較結果は「Ｃ」となっている。したがって、割合Ｒ／ｔが１．９２の解析モデル３１０の長さＷおよび距離Ｈの上限値は、４．０ｍｍ（長さＷ）および０．９ｍｍ（距離Ｈ）ではなく、４．０ｍｍ（長さＷ）および０．８ｍｍ（距離Ｈ）となる。 Note that, for each ratio R/t, if the length W and distance H are equal to or less than a specific value, all comparison results will be either "A" or "B" in Tables 1 and 2 above. Such a specific value is called the upper limit. For example, in the case of analysis model 310 with ratio R/t of 1.92, as shown in Table 2, when the length W is 4.0 mm, the comparison result is "B" when the distance H is in the range of 0.1 to 0.9 mm. However, as shown in Table 1, when the length W is 1.0 mm and the distance H is 0.9 mm, the comparison result is "C". Therefore, the upper limit values of the length W and distance H of analysis model 310 with ratio R/t of 1.92 are 4.0 mm (length W) and 0.8 mm (distance H), rather than 4.0 mm (length W) and 0.9 mm (distance H).
　また、長さＷおよび距離Ｈの上限値は、比較結果の「Ａ」および「Ｂ」の合計の数が最も多くなるように決定した。例えば、割合Ｒ／ｔが２．１７の場合、比較結果の「Ａ」および「Ｂ」の合計の数が最も多くなる長さＷの上限値および距離Ｈの上限値の組み合わせは、長さＷの上限値が３．０ｍｍで、距離Ｈの上限値が０．６ｍｍである。このため、割合Ｒ／ｔが２．１７の場合の長さＷおよび距離Ｈの上限値はそれぞれ、３．０ｍｍおよび０．６ｍｍとなる。 The upper limit values of length W and distance H were determined so that the total number of "A"s and "B"s in the comparison results was maximized. For example, when the ratio R/t is 2.17, the combination of the upper limit values of length W and distance H that maximizes the total number of "A"s and "B"s in the comparison results is an upper limit value of length W of 3.0 mm and an upper limit value of distance H of 0.6 mm. Therefore, when the ratio R/t is 2.17, the upper limit values of length W and distance H are 3.0 mm and 0.6 mm, respectively.
　図６に、長さＷの上限値および割合Ｒ／ｔの関係を示し、図７に、距離Ｈの上限値および割合Ｒ／ｔの関係を示す。図６および図７には、解析によって得られた複数のデータ（長さＷおよび距離Ｈ）から最小二乗法によって求めた近似曲線を示している。なお、上述したように、解析モデル３１０を用いた解析では、長さＷは、１．０～５．０ｍｍに設定し、距離Ｈは、０．１～１．０ｍｍに設定した。ここで、長さＷの上限値および距離Ｈの上限値の組み合わせが、５．０ｍｍ（長さＷの最大設定値）および１．０ｍｍ（距離Ｈの最大設定値）となる場合（すなわち、Ｒ／ｔ＝１．２５およびＲ／ｔ＝１．５６のときの組み合わせ）は、長さＷおよび距離Ｈの上限値の組み合わせを適切に表していない可能性がある。具体的には、表１および表２に示すように、割合Ｒ／ｔが、１．２５および１．５６の場合には、長さＷが１．０～５．０ｍｍおよび距離Ｈが０．１～１．０ｍｍの範囲において、全ての比較結果が「Ｂ」または「Ａ」となった。この点を考慮すると、割合Ｒ／ｔが、１．２５および１．５６の場合には、長さＷが５．０ｍｍ超または距離Ｈが１．０ｍｍ超でも、比較結果が「Ｂ」または「Ａ」となる可能性がある。また、長さＷの上限値および距離Ｈの上限値の組み合わせが、１．０ｍｍ（長さＷの最小設定値）および０．１ｍｍ（距離Ｈの最小設定値）となる場合（すなわち、Ｒ／ｔ＝３．１３のときの組み合わせ）も、長さＷおよび距離Ｈの上限値の組み合わせを適切に表していない可能性がある。具体的には、長さＷおよび距離Ｈの最小設定値以下の値によって、長さＷおよび距離Ｈの上限値の組み合わせが決定される可能性がある。これらの点を考慮して、割合Ｒ／ｔが、１．２５、１．５６および３．１３の場合のデータは除外して、図６および図７に示した近似曲線を求めた。 6 shows the relationship between the upper limit of length W and the ratio R/t, and FIG. 7 shows the relationship between the upper limit of distance H and the ratio R/t. FIG. 6 and FIG. 7 show the approximation curves obtained by the least squares method from multiple data (length W and distance H) obtained by analysis. As described above, in the analysis using analysis model 310, length W was set to 1.0 to 5.0 mm, and distance H was set to 0.1 to 1.0 mm. Here, when the combination of the upper limit of length W and the upper limit of distance H is 5.0 mm (the maximum setting value of length W) and 1.0 mm (the maximum setting value of distance H) (i.e., the combination when R/t = 1.25 and R/t = 1.56), there is a possibility that the combination of the upper limit of length W and distance H is not appropriately represented. Specifically, as shown in Tables 1 and 2, when the ratio R/t is 1.25 and 1.56, all comparison results are "B" or "A" in the range of the length W of 1.0 to 5.0 mm and the distance H of 0.1 to 1.0 mm. Considering this point, when the ratio R/t is 1.25 and 1.56, the comparison result may be "B" or "A" even if the length W exceeds 5.0 mm or the distance H exceeds 1.0 mm. In addition, when the combination of the upper limit value of the length W and the upper limit value of the distance H is 1.0 mm (the minimum set value of the length W) and 0.1 mm (the minimum set value of the distance H) (i.e., the combination when R/t = 3.13) may not appropriately represent the combination of the upper limit values of the length W and the distance H. Specifically, the combination of the upper limit values of the length W and the distance H may be determined by values equal to or less than the minimum set values of the length W and the distance H. Taking these points into consideration, the data for ratios R/t of 1.25, 1.56, and 3.13 were excluded to obtain the approximation curves shown in Figures 6 and 7.
　本シミュレーション結果から、図２に示す金属板２００において、下記（ｉ）式および（ii）式を満たすことによって、貫通孔１０４ａの縁部に生じる応力を低減できることが分かった。この場合、金属板２００に対して曲げ変形が加えられても、貫通孔１０４ａの縁部において応力集中が生じることを抑制できるので、貫通孔１０４ａの縁部においてき裂が発生することを防止できる。これにより、金属板２００の疲労耐久性を向上させることができる。
　１．０≦Ｗ≦－３．８３１４×（Ｒ／ｔ）＋１１．４７≦５．０　・・・（ｉ）
　０．１≦Ｈ≦－０．６６０４×（Ｒ／ｔ）＋２．０４８９≦１．０　・・・（ii） From the results of this simulation, it was found that in the metal plate 200 shown in Fig. 2, by satisfying the following formulas (i) and (ii), the stress occurring at the edge of the through hole 104a can be reduced. In this case, even if bending deformation is applied to the metal plate 200, the occurrence of stress concentration at the edge of the through hole 104a can be suppressed, and therefore the occurrence of cracks at the edge of the through hole 104a can be prevented. This allows the fatigue durability of the metal plate 200 to be improved.
1.0≦W≦−3.8314×(R/t)+11.47≦5.0 (i)
0.1≦H≦−0.6604×(R/t)+2.0489≦1.0 (ii)
　次に、本発明者は、割合Ｒ／ｔが互いに等しい解析モデル３００，３５０について貫通孔１０４ａ，３５０ａの縁部に生じる応力（最大主応力の最大値）を比較した。そして、上記の場合と同様に、解析モデル３００の貫通孔１０４ａの縁部に生じる応力を、解析モデル３５０の貫通孔３５０ａの縁部に生じる応力よりも低くするための、長さＷおよび距離Ｈの上限値を求めた。その結果、割合Ｒ／ｔが２．１７のときの解析モデル３００の長さＷおよび距離Ｈの上限値はそれぞれ、１．０ｍｍおよび０．１ｍｍであった。また、割合Ｒ／ｔが１．５６のときの解析モデル３００の長さＷおよび距離Ｈの上限値はそれぞれ、１．０ｍｍおよび１．０ｍｍであった。これらの上限値と、表３に示した解析モデル３１０の上限値とを比較すると、貫通孔１０４ａの縁部に生じる応力を解析モデル３５０の貫通孔３５０ａの縁部に生じる応力よりも低くすることができる長さＷおよび距離Ｈの範囲は、解析モデル３００よりも解析モデル３１０の方が広いことが分かる。 Next, the inventor compared the stress (maximum value of maximum principal stress) occurring at the edge of through- hole 104a, 350a for analytical models 300, 350 with the same ratio R/t. Then, similar to the above case, the upper limit values of length W and distance H were obtained to make the stress occurring at the edge of through-hole 104a of analytical model 300 lower than the stress occurring at the edge of through-hole 350a of analytical model 350. As a result, the upper limit values of length W and distance H of analytical model 300 when ratio R/t was 2.17 were 1.0 mm and 0.1 mm, respectively. Moreover, the upper limit values of length W and distance H of analytical model 300 when ratio R/t was 1.56 were 1.0 mm and 1.0 mm, respectively. Comparing these upper limits with the upper limits of analytical model 310 shown in Table 3, it can be seen that the range of length W and distance H for which the stress generated at the edge of through hole 104a can be made lower than the stress generated at the edge of through hole 350a in analytical model 350 is wider in analytical model 310 than in analytical model 300.
　この結果から、加工部２０４の先端部に平坦面４０６を形成した解析モデル３１０（図４参照）の方が、平坦面４０６が形成されていない解析モデル３００（図３参照）に比べて、貫通孔１０４ａの縁部に発生する応力の値を小さくできることが分かる。 From these results, it can be seen that analysis model 310 (see Figure 4), in which flat surface 406 is formed at the tip of processing portion 204, can reduce the value of stress generated at the edge of through hole 104a compared to analysis model 300 (see Figure 3), in which flat surface 406 is not formed.
　なお、図３および図４を比較して分かるように、解析モデル３００の壁面４００と傾斜面４０２との間の角度は、解析モデル３１０の壁面４００と平坦面４０６との間の角度に比べて、大幅に小さい。言い換えると、解析モデル３００では、解析モデル３１０に比べて、加工部１０４の先端部が尖った形状となっている。これにより、解析モデル３００では、解析モデル３１０に比べて、貫通孔１０４ａの縁部（加工部１０４の先端部）において応力集中が生じやすくなったと考えられる。以上の結果から、図２の金属板２００のように、加工部２０４の先端部に平坦面４０６を設けることによって、貫通孔１０４ａの縁部の応力集中を抑制できることが分かる。 As can be seen by comparing FIG. 3 and FIG. 4, the angle between the wall surface 400 and the inclined surface 402 of the analytical model 300 is significantly smaller than the angle between the wall surface 400 and the flat surface 406 of the analytical model 310. In other words, the tip of the processed portion 104 of the analytical model 300 is sharper than that of the analytical model 310. This is thought to make it easier for stress concentration to occur at the edge of the through hole 104a (the tip of the processed portion 104) in the analytical model 300 than in the analytical model 310. From the above results, it can be seen that by providing a flat surface 406 at the tip of the processed portion 204, as in the metal plate 200 of FIG. 2, it is possible to suppress stress concentration at the edge of the through hole 104a.
　（金属板の製造方法）
　次に、金属板２００の製造方法について説明する。図８は、金属板２００を製造するための金型の一例を示す概略図である。図８に示すように、金型１０は、パンチ１２、ダイ１４およびブランクホルダ１６を備えている。パンチ１２は、柱状（本実施形態では、円柱状）に形成され、上下方向（プレス方向）に進退可能に設けられている。 (Metal plate manufacturing method)
Next, a method for manufacturing the metal sheet 200 will be described. Fig. 8 is a schematic diagram showing an example of a die for manufacturing the metal sheet 200. As shown in Fig. 8, the die 10 includes a punch 12, a die 14, and a blank holder 16. The punch 12 is formed in a columnar shape (cylindrical in this embodiment) and is provided so as to be movable forward and backward in the vertical direction (press direction).
　ダイ１４は、パンチ１２を挿入できるように中空形状を有している。本実施形態では、ダイ１４は、ブランク（金属板）１８を支持する平坦かつ環状の支持面４０と、支持面４０の内周縁から下方に延びる筒状（本実施形態では、円筒状）の内周面４２と、内周面４２の下縁から内周面４２の内側に向かって延びる平坦かつ環状（本実施形態では、円環状）のフランジ面４４と、フランジ面４４の内周縁から下方に向かって延びる筒状（本実施形態では、円筒状）の内周面４６とを有している。ブランクホルダ１６は、パンチ１２を挿入できるように中空状に形成されており、ダイ１４の支持面４０に対向する環状の下面６０を有している。本実施形態では、支持面４０の内周縁およびフランジ面４４の内周縁はそれぞれ、円形状を有している。 The die 14 has a hollow shape so that the punch 12 can be inserted. In this embodiment, the die 14 has a flat and annular support surface 40 that supports the blank (metal plate) 18, a tubular (cylindrical in this embodiment) inner peripheral surface 42 extending downward from the inner peripheral edge of the support surface 40, a flat and annular (circular in this embodiment) flange surface 44 extending from the lower edge of the inner peripheral surface 42 toward the inside of the inner peripheral surface 42, and a tubular (cylindrical in this embodiment) inner peripheral surface 46 extending downward from the inner peripheral edge of the flange surface 44. The blank holder 16 is formed hollow so that the punch 12 can be inserted, and has an annular lower surface 60 facing the support surface 40 of the die 14. In this embodiment, the inner peripheral edge of the support surface 40 and the inner peripheral edge of the flange surface 44 each have a circular shape.
　図８に示すように、ブランク１８に対して穴抜き加工を行う場合には、まず、ダイ１４の支持面４０上にブランク１８を置く。その後、ブランクホルダ１６によってブランク１８を押さえた状態で、パンチ１２を下方に移動させて、パンチ１２およびダイ１４によってブランク１８の所定領域を切断（せん断加工）する。これにより、図２に示すように、貫通孔１０４ａを有する金属板２００が得られる。 As shown in FIG. 8, when punching a blank 18, first, the blank 18 is placed on the support surface 40 of the die 14. Then, while the blank 18 is held down by the blank holder 16, the punch 12 is moved downward, and a predetermined area of the blank 18 is cut (sheared) by the punch 12 and the die 14. This results in a metal plate 200 having a through hole 104a, as shown in FIG. 2.
　図９は、ブランク１８が切断される直前の、金型１０およびブランク１８の状態を示す図である。図９に示すように、金型１０によってブランク１８の所定領域を切断する際には、パンチ１２の肩部およびダイ１４のフランジ面４４の内周縁をそれぞれ切断刃として、ブランク１８が切断される。 Figure 9 shows the state of the die 10 and the blank 18 immediately before the blank 18 is cut. As shown in Figure 9, when the die 10 cuts a predetermined area of the blank 18, the blank 18 is cut using the shoulder of the punch 12 and the inner edge of the flange surface 44 of the die 14 as cutting blades.
　ここで、本実施形態では、支持面４０とフランジ面４４との間には、段差が設けられている。このため、ブランク１８のうち支持面４０の内周縁よりも内側に位置する部分は、フランジ面４４側に押し込まれる。これにより、図２に示すように、平板部１０２から厚み方向Ａに立ち上がるように加工部２０４が形成される。 In this embodiment, a step is provided between the support surface 40 and the flange surface 44. Therefore, the portion of the blank 18 located inside the inner peripheral edge of the support surface 40 is pressed toward the flange surface 44. As a result, as shown in FIG. 2, a processed portion 204 is formed so as to rise from the flat portion 102 in the thickness direction A.
　また、図９に示すように、ブランク１８が切断される際には、ブランク１８の一部が、フランジ面４４に押し付けられて塑性変形する。これにより、図２に示すように、加工部２０４に平坦面４０６を形成することができる。 Also, as shown in FIG. 9, when the blank 18 is cut, a portion of the blank 18 is pressed against the flange surface 44 and plastically deformed. This allows a flat surface 406 to be formed in the processed portion 204, as shown in FIG. 2.
　なお、金属板２００において、厚み方向Ａにおける平坦面１０２ａと平坦面４０６との距離Ｈ（図２参照）は、金型１０のプレス方向（上下方向）における支持面４０とフランジ面４４との距離ｈ（図８参照）に略等しくなる。したがって、厚み方向Ａにおける平坦面１０２ａと平坦面４０６との距離Ｈは、支持面４０とフランジ面４４との距離ｈを調整することによって調整できる。また、金属板２００において、厚み方向Ａに直交する方向における傾斜面４０８の長さＷ（図２参照）は、金型１０のプレス方向に直交する方向におけるフランジ面４４の長さｗ（図８参照）を調整することによって調整できる。なお、パンチ１２とダイ１４（フランジ面４４の内周縁）とのクリアランスＣＬ（図９参照）は、ブランク１８の厚みに応じて適宜すればよいが、例えば、ブランク１８の厚みの１８％以下に設定され、好ましくは、１５％以下に設定される。 In the metal plate 200, the distance H (see FIG. 2) between the flat surface 102a and the flat surface 406 in the thickness direction A is approximately equal to the distance h (see FIG. 8) between the support surface 40 and the flange surface 44 in the press direction (up and down direction) of the die 10. Therefore, the distance H between the flat surface 102a and the flat surface 406 in the thickness direction A can be adjusted by adjusting the distance h between the support surface 40 and the flange surface 44. In addition, in the metal plate 200, the length W (see FIG. 2) of the inclined surface 408 in the direction perpendicular to the thickness direction A can be adjusted by adjusting the length w (see FIG. 8) of the flange surface 44 in the direction perpendicular to the press direction of the die 10. In addition, the clearance CL (see FIG. 9) between the punch 12 and the die 14 (the inner peripheral edge of the flange surface 44) may be appropriately set according to the thickness of the blank 18, but is set to, for example, 18% or less of the thickness of the blank 18, and preferably 15% or less.
　金属板２００の製造方法について本発明者がさらに検討を進めたところ、金型１０において、プレス方向における支持面４０とフランジ面４４との距離ｈが大きくなると、バリが発生しやすくなることが分かった。図１０は、ブランク１８が切断される際にバリが形成される状況を説明するための図である。 As the inventors further investigated the manufacturing method of the metal plate 200, they found that burrs are more likely to occur when the distance h between the support surface 40 and the flange surface 44 in the pressing direction of the die 10 increases. Figure 10 is a diagram for explaining the situation in which burrs are formed when the blank 18 is cut.
　図１０に示すように、本発明者による検討の結果、ブランク１８が切断される際に、支持面４０とフランジ面４４との間においてブランク１８の下面に変曲点Ｐが生じ、ブランク１８のうち変曲点Ｐとフランジ面４４との間の部分が外側に膨らむように変形する場合があることが分かった。この場合、変曲点Ｐとパンチ１２の肩部との間（一点鎖線で示す部分）において破断が生じ、平坦面４０６（図２参照）を適切に形成できなかったり、過大なバリが発生したりするおそれがあることが分かった。 As shown in Figure 10, as a result of investigations by the inventors, it was found that when the blank 18 is cut, an inflection point P occurs on the underside of the blank 18 between the support surface 40 and the flange surface 44, and the portion of the blank 18 between the inflection point P and the flange surface 44 may be deformed so as to bulge outward. In this case, it was found that a break occurs between the inflection point P and the shoulder of the punch 12 (the portion shown by the dashed dotted line), and there is a risk that the flat surface 406 (see Figure 2) may not be formed properly or that excessive burrs may be generated.
　そこで、本発明者は、金型１０およびブランク１８について、二次元ソリッド要素の軸対称モデルを作成し、ＦＥＭ解析を行うことにより、変曲点Ｐの発生条件を調査した。具体的には、パンチ１２の外周面の曲率半径Ｒ１（図示せず）とブランク１８の厚みｔ１との割合Ｒ１／ｔ１を変えて複数の解析モデルを作成し、ＦＥＭ解析を実施した。そして、各解析モデルにおいて、プレス方向における変曲点Ｐと支持面４０との距離ｄを調査した。なお、割合Ｒ１／ｔ１は、１．２５～６．２５に設定し、距離ｈは、１．０ｍｍに設定し、プレス方向に直交する方向におけるフランジ面４４の長さｗは１．０ｍｍに設定した。パンチ１２およびダイ１４のクリアランスＣＬ（図９参照）とブランク１８の厚みｔ１との割合ＣＬ／ｔ１は、１２．５％に設定した。また、ブランク１８の材料特性は、上述の解析モデル３００と同様に設定した。 The inventor therefore created an axisymmetric model of two-dimensional solid elements for the die 10 and the blank 18, and conducted FEM analysis to investigate the conditions for the occurrence of the inflection point P. Specifically, the inventor created multiple analytical models by changing the ratio R1/t1 between the radius of curvature R1 (not shown) of the outer peripheral surface of the punch 12 and the thickness t1 of the blank 18, and conducted FEM analysis. Then, for each analytical model, the distance d between the inflection point P and the support surface 40 in the press direction was investigated. The ratio R1/t1 was set to 1.25 to 6.25, the distance h was set to 1.0 mm, and the length w of the flange surface 44 in the direction perpendicular to the press direction was set to 1.0 mm. The ratio CL/t1 between the clearance CL (see FIG. 9) of the punch 12 and the die 14 and the thickness t1 of the blank 18 was set to 12.5%. The material properties of the blank 18 were set to the same as those of the above-mentioned analytical model 300.
　図１１に、割合Ｒ１／ｔ１と距離ｄとの関係を示す。なお、図１１には、解析によって得られた距離ｄから最小二乗法によって求めた近似曲線を点線で示している。さらに、図１１には、上記近似曲線に平行でかつ割合Ｒ１／ｔ１が１．２５のときの距離ｄに対応する点を通る直線を一点鎖線で示している。 Figure 11 shows the relationship between the ratio R1/t1 and the distance d. Note that in Figure 11, the dotted line shows an approximation curve calculated by the least squares method from the distance d obtained by analysis. Furthermore, in Figure 11, the dashed line shows a straight line that is parallel to the approximation curve and passes through the point corresponding to the distance d when the ratio R1/t1 is 1.25.
　穴抜き加工時に変曲点Ｐを発生させないためには、プレス方向における支持面４０とフランジ面４４との距離ｈを、上記のＦＥＭ解析で求められた変曲点Ｐと支持面４０との距離ｄ以下にすればよいと考えられる。この点に関して、上述したように、金属板２００において、厚み方向Ａにおける平坦面１０２ａと平坦面４０６との距離Ｈは、距離ｈに略等しくなる。したがって、厚み方向Ａにおける平坦面１０２ａと平坦面４０６との距離Ｈが、上記のＦＥＭ解析で求められた距離ｄ以下になるように穴抜き加工を行うことによって、平坦面４０６（図２参照）をより適切に形成でき、かつ過大なバリの発生を十分に抑制することができる。なお、金型１０によって金属板２００の貫通孔１０４ａを形成した場合、貫通孔１０４ａの曲率半径Ｒは、パンチ１２の外周面の曲率半径Ｒ１に略等しくなる。また、金属板２００の平板部１０２の厚みｔは、ブランク１８の厚みｔ１に略等しい。したがって、下記（iii）式を満たすように貫通孔１０４ａを形成することによって、平坦面４０６（図２参照）をより適切に形成でき、かつ過大なバリの発生を十分に抑制することができる。なお、下記（iv）式を満たすように貫通孔１０４ａを形成することがより好ましい。この場合、平坦面４０６の面積を十分に大きくすることができる。
　Ｈ≦０．０９７５×（Ｒ／ｔ）＋０．３００９　・・・（iii）
　Ｈ≦０．０９７５×（Ｒ／ｔ）＋０．２３８１　・・・（iv）
　ただし、上記式において、Ｈは、厚み方向Ａにおける平坦面１０２ａと平坦面４０６との距離（ｍｍ）を示し、Ｒは、厚み方向Ａから見た貫通孔１０４ａの曲率半径（ｍｍ）を示し、ｔは、平板部１０２（金属板）の厚み（ｍｍ）を示す。 In order to prevent the inflection point P from occurring during the punching process, it is considered that the distance h between the support surface 40 and the flange surface 44 in the press direction should be equal to or less than the distance d between the inflection point P and the support surface 40 obtained by the above FEM analysis. In this regard, as described above, in the metal plate 200, the distance H between the flat surface 102a and the flat surface 406 in the thickness direction A is approximately equal to the distance h. Therefore, by performing the punching process so that the distance H between the flat surface 102a and the flat surface 406 in the thickness direction A is equal to or less than the distance d obtained by the above FEM analysis, the flat surface 406 (see FIG. 2) can be more appropriately formed and the occurrence of excessive burrs can be sufficiently suppressed. Note that when the through hole 104a of the metal plate 200 is formed by the die 10, the radius of curvature R of the through hole 104a is approximately equal to the radius of curvature R1 of the outer circumferential surface of the punch 12. In addition, the thickness t of the flat plate portion 102 of the metal plate 200 is approximately equal to the thickness t1 of the blank 18. Therefore, by forming the through hole 104a so as to satisfy the following formula (iii), the flat surface 406 (see FIG. 2) can be more appropriately formed and the occurrence of excessive burrs can be sufficiently suppressed. It is more preferable to form the through hole 104a so as to satisfy the following formula (iv). In this case, the area of the flat surface 406 can be made sufficiently large.
H≦0.0975×(R/t)+0.3009 (iii)
H≦0.0975×(R/t)+0.2381 (iv)
However, in the above formula, H indicates the distance (mm) between the flat surface 102a and the flat surface 406 in the thickness direction A, R indicates the radius of curvature (mm) of the through hole 104a as viewed from the thickness direction A, and t indicates the thickness (mm) of the flat plate portion 102 (metal plate).
　（本発明の実施形態の説明）
　本発明は、上記の知見に基づいてなされたものである。具体的には、本発明の一実施形態に係る金属板の貫通孔の周辺構造は、図２に示した金属板２００の貫通孔１０４ａの周辺構造において、厚み方向Ａに平行でかつ貫通孔１０４ａの中心を通る加工部２０４の断面形状が、下記（ｉ）式および（ii）式を満たすことを特徴とする。
　１．０≦Ｗ≦－３．８３１４×（Ｒ／ｔ）＋１１．４７≦５．０　・・・（ｉ）
　０．１≦Ｈ≦－０．６６０４×（Ｒ／ｔ）＋２．０４８９≦１．０　・・・（ii）
　ただし、上記（ｉ）式および（ii）式において、Ｗは、厚み方向Ａに直交する方向における傾斜面４０８の長さ（ｍｍ）であり、Ｒは、貫通孔１０４ａの曲率半径（ｍｍ）であり、ｔは、金属板２００の厚み（ｍｍ）であり、Ｈは、厚み方向Ａにおける平坦面１０２ａと平坦面４０６との距離（ｍｍ）である。 (Description of the embodiment of the present invention)
The present invention has been made based on the above findings. Specifically, the peripheral structure of a through hole in a metal plate according to one embodiment of the present invention is characterized in that, in the peripheral structure of a through hole 104a in a metal plate 200 shown in Fig. 2, a cross-sectional shape of a processed portion 204 that is parallel to the thickness direction A and passes through the center of the through hole 104a satisfies the following formulas (i) and (ii):
1.0≦W≦−3.8314×(R/t)+11.47≦5.0 (i)
0.1≦H≦−0.6604×(R/t)+2.0489≦1.0 (ii)
However, in the above equations (i) and (ii), W is the length (mm) of the inclined surface 408 in a direction perpendicular to the thickness direction A, R is the radius of curvature (mm) of the through hole 104a, t is the thickness (mm) of the metal plate 200, and H is the distance (mm) between the flat surface 102a and the flat surface 406 in the thickness direction A.
　なお、本実施形態に係る金属板の貫通孔の周辺構造は、例えば、厚みが１．６ｍｍ～４．０ｍｍで、引張強さが５９０ＭＰａ級以上の素材（鋼板、アルミニウム板等）を用いて形成される。ただし、厚みが１．６ｍｍ未満または４．０ｍｍよりも大きい素材を用いてもよく、引張強さが５９０ＭＰａ級未満の素材を用いてもよい。 The structure surrounding the through hole of the metal plate according to this embodiment is formed, for example, using a material (steel plate, aluminum plate, etc.) with a thickness of 1.6 mm to 4.0 mm and a tensile strength of 590 MPa or more. However, a material with a thickness of less than 1.6 mm or greater than 4.0 mm may also be used, and a material with a tensile strength of less than 590 MPa may also be used.
　本実施形態では、平坦面１０２ａが第１平坦面に対応し、平坦面４０６が第２平坦面に対応し、貫通孔１０４ａの壁面４００が湾曲部に対応する。また、本実施形態では、貫通孔１０４ａの曲率半径とは、厚み方向Ａから見たせん断面４００ａの曲率半径を意味する。貫通孔１０４ａの曲率半径は、球面計を用いて測定することができる。 In this embodiment, the flat surface 102a corresponds to the first flat surface, the flat surface 406 corresponds to the second flat surface, and the wall surface 400 of the through hole 104a corresponds to the curved portion. In this embodiment, the radius of curvature of the through hole 104a means the radius of curvature of the sheared surface 400a as viewed from the thickness direction A. The radius of curvature of the through hole 104a can be measured using a spherometer.
　なお、本実施形態では、平坦面４０６は、厚み方向Ａに直交する方向に延びるように形成されている。この場合、加工部２０４の先端部が鋭利な形状とならないので、貫通孔１０４ａの縁部において応力集中が生じることを十分に防止することができる。厚み方向Ａに平行でかつ貫通孔１０４ａの中心を通る加工部２０４の断面（図２に示す断面）において、厚み方向Ａに直交する方向における平坦面４０６の長さ（図４（ｃ）の長さＦに相当）は、０．１ｍｍ以上であることが好ましい。なお、図２に示した金属板２００では、平坦面４０６は、厚み方向Ａに対して直交するように設けられているが、平坦面４０６が厚み方向Ａに対して厳密に直交していなくてもよい。本明細書において「平坦面が厚み方向Ａに直交する方向に延びる」には、平坦面が厚み方向Ａに直交する方向に対して０～１０°傾斜している場合が含まれる。この場合でも、貫通孔１０４ａの縁部において応力集中が生じることを十分に防止することができる。なお、本実施形態では、平坦面１０２ａも、平坦面４０６と同様に、厚み方向Ａに直交する方向に延びるように形成されている。 In this embodiment, the flat surface 406 is formed to extend in a direction perpendicular to the thickness direction A. In this case, since the tip of the processed portion 204 does not have a sharp shape, it is possible to sufficiently prevent stress concentration from occurring at the edge of the through hole 104a. In a cross section (cross section shown in FIG. 2) of the processed portion 204 that is parallel to the thickness direction A and passes through the center of the through hole 104a, it is preferable that the length of the flat surface 406 in a direction perpendicular to the thickness direction A (corresponding to the length F in FIG. 4(c)) is 0.1 mm or more. In the metal plate 200 shown in FIG. 2, the flat surface 406 is provided perpendicular to the thickness direction A, but the flat surface 406 does not have to be strictly perpendicular to the thickness direction A. In this specification, "the flat surface extends in a direction perpendicular to the thickness direction A" includes the case where the flat surface is inclined at 0 to 10 degrees with respect to the direction perpendicular to the thickness direction A. Even in this case, it is possible to sufficiently prevent stress concentration from occurring at the edge of the through hole 104a. In this embodiment, flat surface 102a is also formed to extend in a direction perpendicular to thickness direction A, similar to flat surface 406.
　また、本実施形態では、壁面４００は、平坦面１０２ａに対して直交する方向に延びるせん断面４００ａを含む。なお、図２に示した金属板２００では、壁面４００は、平坦面１０２ａに対して直交する方向に延びるように設けられているが、壁面４００が平坦面１０２ａの法線方向に対して厳密に直交していなくてもよい。本明細書において「せん断面が、平坦面に対して直交する方向に延びる」には、せん断面が、平坦面の法線方向に対して０～１０°傾斜している場合が含まれる。 In addition, in this embodiment, the wall surface 400 includes a shear surface 400a that extends in a direction perpendicular to the flat surface 102a. In the metal plate 200 shown in FIG. 2, the wall surface 400 is provided so as to extend in a direction perpendicular to the flat surface 102a, but the wall surface 400 does not have to be strictly perpendicular to the normal direction of the flat surface 102a. In this specification, "the shear surface extends in a direction perpendicular to the flat surface" includes the case where the shear surface is inclined at an angle of 0 to 10 degrees with respect to the normal direction of the flat surface.
　また、本実施形態では、壁面４００においてせん断面４００ａと平坦面４０６との間の部分（本実施形態では、破断面４００ｂ）は、貫通孔１０４ａの径方向Ｄにおいてせん断面４００ａよりも外側に収まるように設けられている。言い換えると、壁面４００においてせん断面４００ａと平坦面４０６との間の部分は、厚み方向Ａから見てせん断面４００ａよりも貫通孔１０４ａの内側に向かって突出していない。さらに、傾斜面４０８は、貫通孔１０４ａの径方向Ｄにおいて平坦面４０６の外縁よりも外側に収まるように設けられている。言い換えると、傾斜面４０８は、厚み方向Ａから見て平坦面４０６の外縁よりも貫通孔１０４ａ側に向かって延びていない。この場合、加工部２０４の周辺の形状が滑らかな形状となるので、貫通孔１０４ａの周辺において応力集中が生じることを十分に抑制することができる。これにより、金属板２００の疲労耐久性を向上させることができる。なお、後述する図１２で説明するように、厚み方向Ａから見た貫通孔の形状は、円形状に限定されない。厚み方向Ａから見た貫通孔の形状が円形状ではない場合には、貫通孔の径方向とは、貫通孔の中心軸に直交する方向を意味する。 In addition, in this embodiment, the portion between the shear surface 400a and the flat surface 406 in the wall surface 400 (the fracture surface 400b in this embodiment) is provided so as to be located outside the shear surface 400a in the radial direction D of the through hole 104a. In other words, the portion between the shear surface 400a and the flat surface 406 in the wall surface 400 does not protrude toward the inside of the through hole 104a beyond the shear surface 400a when viewed from the thickness direction A. Furthermore, the inclined surface 408 is provided so as to be located outside the outer edge of the flat surface 406 in the radial direction D of the through hole 104a. In other words, the inclined surface 408 does not extend toward the through hole 104a side beyond the outer edge of the flat surface 406 when viewed from the thickness direction A. In this case, since the shape of the periphery of the processed portion 204 is smooth, it is possible to sufficiently suppress the occurrence of stress concentration around the through hole 104a. This can improve the fatigue durability of the metal plate 200. As described later in FIG. 12, the shape of the through hole as viewed from the thickness direction A is not limited to a circular shape. If the shape of the through hole as viewed from the thickness direction A is not circular, the radial direction of the through hole means the direction perpendicular to the central axis of the through hole.
　なお、本実施形態では、厚み方向Ａに平行でかつ貫通孔１０４ａの中心を通る加工部２０４の断面形状が、下記（iii）式を満たすことが好ましい。この場合、平坦面４０６（図２参照）をより適切に形成でき、かつ過大なバリの発生を十分に抑制することができる。
　Ｈ≦０．０９７５×（Ｒ／ｔ）＋０．３００９　・・・（iii）
　ただし、上記（iii）式において、Ｈは、厚み方向Ａにおける平坦面１０２ａと平坦面４０６との距離（ｍｍ）であり、Ｒは、貫通孔１０４ａの曲率半径（ｍｍ）であり、ｔは、金属板２００の厚み（ｍｍ）である。 In this embodiment, it is preferable that the cross-sectional shape of the processed portion 204, which is parallel to the thickness direction A and passes through the center of the through hole 104a, satisfies the following formula (iii). In this case, the flat surface 406 (see FIG. 2) can be more appropriately formed, and the occurrence of excessive burrs can be sufficiently suppressed.
H≦0.0975×(R/t)+0.3009 (iii)
However, in the above formula (iii), H is the distance (mm) between the flat surface 102a and the flat surface 406 in the thickness direction A, R is the radius of curvature (mm) of the through hole 104a, and t is the thickness (mm) of the metal plate 200.
　なお、貫通孔の周囲の全ての領域において、上述の（ｉ）式および（ii）式が満たされることが好ましいが、貫通孔の周囲の一部のみにおいて、上述の（ｉ）式および（ii）式が満たされていてもよい。上述の（iii）式についても同様である。なお、上述の（ｉ）式および（ii）式が満たされていれば、上述の（iii）式は満たされていなくてもよい。 It is preferable that the above formulas (i) and (ii) are satisfied in the entire area around the through hole, but the above formulas (i) and (ii) may be satisfied only in a portion of the area around the through hole. The same applies to the above formula (iii). It is noted that as long as the above formulas (i) and (ii) are satisfied, the above formula (iii) does not have to be satisfied.
　また、上述の実施形態では、厚み方向Ａから見て円形状の貫通孔１０４ａが形成された金属板２００に本発明を適用する場合について説明したが、貫通孔１０４ａの形状は円形状に限定されない。加工部に形成された貫通孔が、平板部の厚み方向から見て、１または複数（本実施形態では４つ）の直線部と、１または複数の湾曲部とを備えていてもよい。例えば、図１２（ａ）に示すように、貫通孔１０４ａが長円形状を有していてもよい。なお、図１２（ａ）に示す貫通孔１０４ａは、２つの直線部５０と、２つの湾曲部５２とを有している。また、図１２（ｂ）および図１２（ｃ）に示すように、貫通孔１０４ａが、角部に湾曲部５２が設けられた多角形状を有していてもよい。なお、湾曲部５２は、貫通孔１０４ａの外側に向かって凸となるように弧状に湾曲している。この場合、厚み方向Ａに平行でかつ貫通孔１０４ａの中心および湾曲部５２を通る加工部２０４の断面において、上述の（ｉ）式および（ii）式が満たされていればよい。上述の（iii）式についても同様である。また、この場合には、上述の（ｉ）式、（ii）式、（iii）式および（iv）式におけるＲは、湾曲部５２のうち上記断面に対応する部分の曲率半径（ｍｍ）を示す。 In the above embodiment, the present invention is applied to a metal plate 200 in which a circular through hole 104a is formed as viewed from the thickness direction A, but the shape of the through hole 104a is not limited to a circular shape. The through hole formed in the processed portion may have one or more (four in this embodiment) straight portions and one or more curved portions as viewed from the thickness direction of the flat plate portion. For example, as shown in FIG. 12(a), the through hole 104a may have an oval shape. Note that the through hole 104a shown in FIG. 12(a) has two straight portions 50 and two curved portions 52. Also, as shown in FIG. 12(b) and FIG. 12(c), the through hole 104a may have a polygonal shape with curved portions 52 provided at the corners. Note that the curved portions 52 are curved in an arc so as to be convex toward the outside of the through hole 104a. In this case, it is sufficient that the above formulas (i) and (ii) are satisfied in the cross section of the processed portion 204 that is parallel to the thickness direction A and passes through the center of the through hole 104a and the curved portion 52. The same applies to the above formula (iii). In this case, R in the above formulas (i), (ii), (iii), and (iv) indicates the radius of curvature (mm) of the portion of the curved portion 52 that corresponds to the above cross section.
　なお、本発明に係る金属板には、平板状の金属板だけでなく、平板状の金属板をブランクとして用いて製造される種々の成形品（例えば、自動車部品）が含まれる。すなわち、本発明に係る金属板の貫通孔の周辺構造は、種々の成形品（自動車部品等）の素材として用いられるブランク、および種々の成形品において利用できる。例えば、本発明に係る自動車部品としては、上記の貫通孔の周辺構造を備えたサスペンション部品（ロアアーム、アッパーアーム、トレーリングリンク、サブフレーム等）、ボディ部品、およびラダーフレームを挙げることができる。 The metal plate according to the present invention includes not only flat metal plates, but also various molded products (e.g., automobile parts) manufactured using flat metal plates as blanks. In other words, the peripheral structure of the through hole in the metal plate according to the present invention can be used in blanks used as materials for various molded products (such as automobile parts), and in various molded products. For example, examples of automobile parts according to the present invention include suspension parts (lower arms, upper arms, trailing links, subframes, etc.) that have the peripheral structure of the above-mentioned through holes, body parts, and ladder frames.
（金型の変形例）
　図８～図１０に示した金型１０のダイ１４においては、支持面４０と内周面４２とが互いに直交するように接続され、内周面４２とフランジ面４４とが互いに直交するように接続されているが、ダイ１４の形状は上述の例に限定されない。 (Modifications of the mold)
In the die 14 of the mold 10 shown in Figures 8 to 10, the support surface 40 and the inner circumferential surface 42 are connected so as to be perpendicular to each other, and the inner circumferential surface 42 and the flange surface 44 are connected so as to be perpendicular to each other, but the shape of the die 14 is not limited to the above-mentioned example.
　例えば、図１３（ａ）に示すように、内周面４２とフランジ面４４との接続部が、弧状に湾曲していてもよい。このように内周面４２とフランジ面４４との接続部に丸みを持たせることによって、ダイ１４の耐久性を向上させることができる。 For example, as shown in FIG. 13(a), the connection between the inner circumferential surface 42 and the flange surface 44 may be curved in an arc. By rounding the connection between the inner circumferential surface 42 and the flange surface 44 in this manner, the durability of the die 14 can be improved.
　また、例えば、図１３（ｂ）に示すように、支持面４０と内周面４２との接続部が、弧状に湾曲していてもよい。このように傾斜面４０８（図２参照）を形成する部分に丸みを持たせることによって、製造された金属板２００において、傾斜面４０８の立ち上がり部分４０８ａ（図２（ｂ）参照）の周辺の耐久性を向上させることができる。 Also, for example, as shown in FIG. 13(b), the connection between the support surface 40 and the inner peripheral surface 42 may be curved in an arc. By rounding the portion that forms the inclined surface 408 (see FIG. 2) in this way, the durability of the area around the rising portion 408a (see FIG. 2(b)) of the inclined surface 408 in the manufactured metal plate 200 can be improved.
　また、例えば、図１３（ｃ）に示すように、支持面４０と内周面４２との接続部および内周面４２とフランジ面４４との接続部がそれぞれ弧状に湾曲していてもよい。この場合、金属板２００およびダイ１４の耐久性を向上させることができる。 Also, for example, as shown in FIG. 13(c), the connection between the support surface 40 and the inner circumferential surface 42 and the connection between the inner circumferential surface 42 and the flange surface 44 may each be curved in an arc. In this case, the durability of the metal plate 200 and the die 14 can be improved.
　また、例えば、図１４（ａ）に示すように、内周面４２が支持面４０およびフランジ面４４に対して傾斜していてもよい。この場合も、金属板２００およびダイ１４の耐久性を向上させることができる。なお、図１４（ｂ）および（ｄ）に示すように、内周面４２とフランジ面４４との接続部を弧状に湾曲させることによって、ダイ１４の耐久性をさらに向上させることができる。また、図１４（ｃ）および（ｄ）に示すように支持面４０と内周面４２との接続部を弧状に湾曲させることによって、金属板２００（傾斜面４０８の立ち上がり部分）の耐久性をさらに向上させることができる。 Also, for example, as shown in FIG. 14(a), the inner circumferential surface 42 may be inclined with respect to the support surface 40 and the flange surface 44. In this case, the durability of the metal plate 200 and the die 14 can be improved. Note that, as shown in FIGS. 14(b) and (d), the durability of the die 14 can be further improved by curving the connection between the inner circumferential surface 42 and the flange surface 44 in an arc shape. Also, as shown in FIGS. 14(c) and (d), the durability of the metal plate 200 (the rising portion of the inclined surface 408) can be further improved by curving the connection between the support surface 40 and the inner circumferential surface 42 in an arc shape.
　なお、金属板２００（加工部２０４）が上記の（ｉ）式および（ii）式を満たすことができるのであれば、金型がブランクホルダを備えていなくてもよい。また、金属板２００の製造方法は上述の方法に限定されず、金属板２００（加工部２０４）が上記の（ｉ）式および（ii）式を満たすことができるのであれば、上述した金型とは異なる形状および寸法の金型を用いて金属板２００を製造してもよい。したがって、金属板２００（加工部２０４）が上記の（ｉ）式および（ii）式を満たすように、金属板２００の素材および寸法等に応じて、金型の形状および寸法を適宜変更することができる。 Note that, if the metal plate 200 (processing section 204) can satisfy the above formulas (i) and (ii), the die does not need to be equipped with a blank holder. Furthermore, the manufacturing method of the metal plate 200 is not limited to the above-mentioned method, and if the metal plate 200 (processing section 204) can satisfy the above formulas (i) and (ii), the metal plate 200 may be manufactured using a die having a shape and dimensions different from those of the above-mentioned die. Therefore, the shape and dimensions of the die can be appropriately changed depending on the material and dimensions of the metal plate 200 so that the metal plate 200 (processing section 204) satisfies the above formulas (i) and (ii).
　本発明によれば、貫通孔が形成された金属板の疲労耐久性を向上させることができる。したがって、本発明は、種々の自動車部品の素材金属板において好適に利用できる。 The present invention can improve the fatigue durability of metal plates with through holes. Therefore, the present invention can be suitably used in the raw metal plates of various automobile parts.
　１０２　平板部
　１０２ａ　平坦面（第１平坦面）
　１０４ａ　貫通孔
　２００　金属板
　２０４　加工部
　４００　壁面
　４００ａ　せん断面
　４００ｂ　破断面
　４０６　平坦面（第２平坦面）
　４０８　傾斜面 102 Flat plate portion 102a Flat surface (first flat surface)
104a: through hole 200: metal plate 204: processed portion 400: wall surface 400a: shear surface 400b: fracture surface 406: flat surface (second flat surface)
408 Inclined surface

Claims (9)

  1. 　金属板に形成された貫通孔の周辺の構造であって、
    　平板部と、前記平板部から前記平板部の厚み方向における一方側に立ち上がりかつ中心に前記貫通孔が形成された加工部と、を有し、
    　前記平板部は、前記平板部の前記一方側において前記加工部の周囲を囲む第１平坦面を含み、
    　前記加工部は、前記厚み方向に延びかつ前記貫通孔の内壁を構成する壁面と、前記厚み方向から見て前記第１平坦面よりも内側でかつ前記厚み方向において前記第１平坦面よりも前記一方側で前記壁面の前記一方側の縁から前記厚み方向に交差する方向に延びる環状の第２平坦面と、前記第２平坦面の外縁と前記第１平坦面の内縁とを接続しかつ前記厚み方向に対して傾斜する傾斜面とを含み、
    　前記厚み方向から見て、前記貫通孔は、前記貫通孔の外側に向かって凸となるように弧状に湾曲する湾曲部を含み、
    　前記厚み方向に平行でかつ前記貫通孔の中心および前記湾曲部を通る前記加工部の断面において、下記（ｉ）式および（ii）式を満たす、金属板の貫通孔の周辺構造。
    　１．０≦Ｗ≦－３．８３１４×（Ｒ／ｔ）＋１１．４７≦５．０　・・・（ｉ）
    　０．１≦Ｈ≦－０．６６０４×（Ｒ／ｔ）＋２．０４８９≦１．０　・・・（ii）
    　ただし、上記（ｉ）式および（ii）式において、Ｗは、前記厚み方向に直交する方向における前記傾斜面の長さ（ｍｍ）であり、Ｒは、前記湾曲部のうち前記断面に対応する部分の曲率半径（ｍｍ）であり、ｔは、前記金属板の厚み（ｍｍ）であり、Ｈは、前記厚み方向における前記第１平坦面と前記第２平坦面との距離（ｍｍ）である。     A structure around a through hole formed in a metal plate,
    A flat plate portion and a processed portion rising from the flat plate portion to one side in a thickness direction of the flat plate portion and having the through hole formed at a center thereof,
    The flat plate portion includes a first flat surface surrounding the processed portion on the one side of the flat plate portion,
    the processed portion includes a wall surface extending in the thickness direction and constituting an inner wall of the through hole, a ring-shaped second flat surface that is located inside the first flat surface when viewed from the thickness direction and on the one side of the first flat surface in the thickness direction, and extends from an edge of the wall surface on the one side in a direction intersecting the thickness direction, and an inclined surface that connects an outer edge of the second flat surface and an inner edge of the first flat surface and is inclined with respect to the thickness direction,
    When viewed from the thickness direction, the through hole includes a curved portion that is curved in an arc shape so as to be convex toward an outside of the through hole,
    A peripheral structure of a through hole in a metal plate, which satisfies the following formulas (i) and (ii) in a cross section of the processed portion that is parallel to the thickness direction and passes through the center of the through hole and the curved portion.
    1.0 ≦ W≦−3.8314×(R/t)+11.47≦5.0 (i)
    0.1≦H≦−0.6604×(R/t)+2.0489≦1.0 (ii)
    However, in the above formulas (i) and (ii), W is the length (mm) of the inclined surface in a direction perpendicular to the thickness direction, R is the radius of curvature (mm) of the part of the curved portion corresponding to the cross section, t is the thickness (mm) of the metal plate, and H is the distance (mm) between the first flat surface and the second flat surface in the thickness direction.
  2. 　前記第２平坦面は、前記厚み方向に直交する方向に延びる、請求項１に記載の金属板の貫通孔の周辺構造。 The peripheral structure of a through hole in a metal plate according to claim 1, wherein the second flat surface extends in a direction perpendicular to the thickness direction.
  3. 　前記壁面は、前記第１平坦面に対して直交する方向に延びるせん断面を含む、請求項１または２に記載の金属板の貫通孔の周辺構造。 The peripheral structure of a through hole in a metal plate according to claim 1 or 2, wherein the wall surface includes a shear surface extending in a direction perpendicular to the first flat surface.
  4. 　前記断面において、前記壁面のうち前記せん断面と前記第２平坦面との間の部分は、前記貫通孔の中心軸に直交する方向において前記せん断面よりも外側に収まるように設けられ、かつ前記傾斜面は、前記直交する方向において前記第２平坦面の前記外縁よりも外側に収まるように設けられている、請求項３に記載の金属板の貫通孔の周辺構造。 The peripheral structure of a through hole in a metal plate according to claim 3, wherein in the cross section, the portion of the wall between the sheared surface and the second flat surface is arranged so as to be located outside the sheared surface in a direction perpendicular to the central axis of the through hole, and the inclined surface is arranged so as to be located outside the outer edge of the second flat surface in the perpendicular direction.
  5. 　前記断面において、下記（iii）式を満たす、請求項１から４のいずれかに記載の金属板の貫通孔の周辺構造。
    　Ｈ≦０．０９７５×（Ｒ／ｔ）＋０．３００９　・・・（iii）
    　ただし、上記（iii）式において、Ｈは、前記厚み方向における前記第１平坦面と前記第２平坦面との距離（ｍｍ）であり、Ｒは、前記湾曲部のうち前記断面に対応する部分の曲率半径（ｍｍ）であり、ｔは、前記金属板の厚み（ｍｍ）である。     The surrounding structure of the through hole of the metal plate according to claim 1 , wherein the cross section satisfies the following formula (iii):
    H≦0.0975×(R/t)+0.3009 (iii)
    However, in the above formula (iii), H is the distance (mm) between the first flat surface and the second flat surface in the thickness direction, R is the radius of curvature (mm) of the part of the curved portion corresponding to the cross section, and t is the thickness (mm) of the metal plate.
  6. 　前記断面において、下記（iv）式を満たす、請求項５に記載の金属板の貫通孔の周辺構造。
    　Ｈ≦０．０９７５×（Ｒ／ｔ）＋０．２３８１　・・・（iv）
    　ただし、上記（iv）式において、Ｈは、前記厚み方向における前記第１平坦面と前記第２平坦面との距離（ｍｍ）であり、Ｒは、前記湾曲部のうち前記断面に対応する部分の曲率半径（ｍｍ）であり、ｔは、前記金属板の厚み（ｍｍ）である。     The surrounding structure of the through hole of the metal plate according to claim 5 , wherein the cross section satisfies the following formula (iv):
    H≦0.0975×(R/t)+0.2381 (iv)
    However, in the above formula (iv), H is the distance (mm) between the first flat surface and the second flat surface in the thickness direction, R is the radius of curvature (mm) of the part of the curved portion corresponding to the cross section, and t is the thickness (mm) of the metal plate.
  7. 　前記貫通孔は、前記厚み方向から見て、円形状を有している、請求項１から６のいずれかに記載の金属板の貫通孔の周辺構造。 The peripheral structure of a through hole in a metal plate according to any one of claims 1 to 6, wherein the through hole has a circular shape when viewed in the thickness direction.
  8. 　請求項１から７のいずれかに記載の金属板の貫通孔の周辺構造を備える、ブランク。 A blank having a peripheral structure for a through hole in a metal plate according to any one of claims 1 to 7.
  9. 　請求項１から７のいずれかに記載の金属板の貫通孔の周辺構造を備える、自動車部品。 An automobile part having a peripheral structure for a through hole in a metal plate according to any one of claims 1 to 7.
PCT/JP2023/041313 2022-11-16 2023-11-16 Structure around through-holes in metal sheet, and blank and automotive part WO2024106512A1 (en)

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JPH06238360A (en) * 1993-02-15 1994-08-30 Sekisui House Ltd Device for embossing and punching
JP2001347331A (en) * 2000-06-06 2001-12-18 Koshin Giken:Kk Method and apparatus for forming stock for rotary part from plate material
JP2014202292A (en) * 2013-04-05 2014-10-27 未来工業株式会社 Open-hole structure, supporting member fixing structure, method for fixing the supporting member to column member and punching tool

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JP5494449B2 (en) 2010-12-03 2014-05-14 新日鐵住金株式会社 Method and apparatus for punching metal plate and method for manufacturing rotary electric iron core
JP6238360B2 (en) 2014-06-16 2017-11-29 日本電信電話株式会社 Manufacturing method of nanostructure
JP2019155436A (en) 2018-03-14 2019-09-19 トヨタ紡織株式会社 Manufacturing method of component having tooth part

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH06238360A (en) * 1993-02-15 1994-08-30 Sekisui House Ltd Device for embossing and punching
JP2001347331A (en) * 2000-06-06 2001-12-18 Koshin Giken:Kk Method and apparatus for forming stock for rotary part from plate material
JP2014202292A (en) * 2013-04-05 2014-10-27 未来工業株式会社 Open-hole structure, supporting member fixing structure, method for fixing the supporting member to column member and punching tool

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