Press forming apparatus and method for manufacturing press-formed product

Abstract

A press molding device (100, 100A, 100B, 100C, 100D) is provided with a punch (10, 10D), blank holders (30, 30B, 30C), and dies (20, 20C). Each punch shoulder (12) includes a curved part (121). Each curved part (121) curves concavely toward the inside of the punch (10, 10D) when viewed from a punch side surface (13). The blank holders (30, 30B, 30C) and the dies (20, 20C) are disposed adjacent to the curved part (121) when viewed from the pressing direction (P). When viewed from the pressing direction (P), at least one of a pressing surface (21) and a holder top surface (31) of the dies (20, 20C) has a smaller length along the extending direction of the punch shoulder (12) than the punch shoulder (12).

Description

[Technical Field]

[0001] The present disclosure relates to a press-forming apparatus and a method for manufacturing a press-formed product. [Background technology]

[0002] For example, press-formed products are used as structural members for automobiles. Press-formed products are manufactured by press-forming a blank using a press-forming device including a punch and a die. The blank is clamped between the punch and the die, which approach each other in the pressing direction, and formed into a desired shape.

[0003] Patent Document 1 discloses a technique for manufacturing a press-formed product using a pad in addition to a punch and a die. In Patent Document 1, the side surface of the punch and the side surface of the die cooperating with the punch include curved surfaces. In Patent Document 1, a blank that has been given a step shape in advance is clamped between the punch and the pad, and the die is moved relative to the punch along the side surface of the punch. In this way, a press-formed product is formed from the blank.

[0004] Patent Document 2 also discloses a technique for manufacturing a press-formed product using a punch, a die, and a pad. In Patent Document 2, the edge of the top surface of the punch has a shape with a recess in the center in a plan view. The die has a shape corresponding to the punch. In Patent Document 2, a blank placed on the upper surface of the punch is pressed with a pad to form a bead on the blank. The blank is then bent by the punch and die to form a press-formed product. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6052478 [Patent Document 2] Patent No. 6202059 Summary of the Invention [Problem to be solved by the invention]

[0006] When the punch shoulder includes a curved portion in a side view of the punch, stretch flange deformation occurs at the end of the blank that is bent along the curved portion of the punch shoulder. More specifically, when the punch shoulder has a curved portion that curves concavely toward the inside of the punch when viewed from the side, the end of the blank is stretched in the direction of extension of the curved portion at the position of the curved portion of the punch shoulder, and the blank thickness decreases. Therefore, there is a risk of fracture at the end of the blank.

[0007] An object of the present disclosure is to provide a press forming apparatus that can suppress the occurrence of breakage of a blank. [Means for solving the problem]

[0008] The press forming apparatus according to the present disclosure includes a punch, a blank holder, and a die. The punch includes a punch top surface, a punch shoulder, and a punch side surface. The punch top surface intersects with the press direction. The punch shoulder is continuous with the punch top surface. The punch side surface is continuous with the punch shoulder. The punch side surface is connected to the punch top surface via the punch shoulder. The punch shoulder includes a first curved portion. The first curved portion is curved concavely toward the inside of the punch when viewed from the punch side surface side. The blank holder is disposed next to the first curved portion when viewed from the press direction. The blank holder includes a holder top surface, a holder shoulder, and a holder side surface. The holder top surface intersects with the press direction. The holder shoulder is continuous with the holder top surface on the first curved portion side. The holder shoulder includes a second curved portion corresponding to the first curved portion. The holder side surface is continuous with the holder shoulder. The holder side surface is connected to the holder top surface via the holder shoulder. The die is positioned next to the first curved portion when viewed from the press direction. The die includes a pressing surface, a die shoulder, and a die side surface. The pressing surface faces the holder top surface. The die shoulder is continuous with the pressing surface on the first curved portion side. The die shoulder includes a third curved portion corresponding to the first curved portion. The die side surface is continuous with the die shoulder. The die side surface is connected to the pressing surface via the die shoulder. When viewed from the press direction, at least one of the pressing surface and the holder top surface has a length along the extension direction of the punch shoulder that is shorter than that of the punch shoulder. [Effects of the Invention]

[0009] According to the press forming apparatus according to the present disclosure, it is possible to suppress the occurrence of breakage of the blank. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view showing a schematic configuration of a press forming apparatus according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the press-forming apparatus shown in FIG. [Figure 3] FIG. 3 is a side view of the press-forming apparatus shown in FIG. [Figure 4] FIG. 4 is another side view of the press-forming apparatus shown in FIG. [Figure 5]FIG. 5 is a view of the press-forming apparatus shown in FIG. 1 as seen from the pressing direction. [Figure 6] FIG. 6 is another view of the press-forming apparatus shown in FIG. 1, seen from the pressing direction. [Figure 7A] FIG. 7A is a schematic diagram for explaining a method for manufacturing a press-formed product using the press-forming apparatus according to the first embodiment. [Figure 7B] FIG. 7B is a schematic diagram for explaining a method for manufacturing a press-formed product using the press-forming apparatus according to the first embodiment. [Figure 7C] FIG. 7C is a schematic view for explaining a method for manufacturing a press-formed product using the press-forming apparatus according to the first embodiment. [Figure 8] FIG. 8 is a diagram for explaining press forming of a blank accompanied by stretch flange deformation. [Figure 9] FIG. 9 is a side view of the press forming apparatus according to the second embodiment. [Figure 10] FIG. 10 is a side view of a press forming apparatus according to the third embodiment. [Figure 11] FIG. 11 is a side view of a press forming apparatus according to the fourth embodiment. [Figure 12] FIG. 12 is a view of the press-forming apparatus shown in FIG. 11 as seen from the pressing direction. [Figure 13] FIG. 13 is a side view of the press forming apparatus according to the fifth embodiment. [Figure 14] FIG. 14 is a view of the press-forming apparatus shown in FIG. 13 as seen from the pressing direction. [Figure 15] FIG. 15 is a view of a blank holder according to a modified example of the first embodiment, viewed from the pressing direction. [Figure 16] FIG. 16 is a view of a blank holder according to another modified example of the first embodiment, viewed from the pressing direction. [Figure 17] FIG. 17 is a view of a blank holder according to yet another modified example of the first embodiment, viewed from the pressing direction. [Figure 18] FIG. 18 is a view of a blank holder according to yet another modified example of the first embodiment, viewed from the pressing direction. [Figure 19] FIG. 19 is a perspective view of a press-forming apparatus according to yet another modified example of the first embodiment. [Figure 20] FIG. 20 is a view of a press-forming apparatus according to yet another modified example of the first embodiment, viewed from the pressing direction. [Figure 21] FIG. 21 is a perspective view of a press-forming apparatus according to yet another modified example of the first embodiment. [Figure 22] FIG. 22 is a partial cross-sectional view of a press-forming apparatus according to yet another modified example of the first embodiment. [Figure 23] FIG. 23 shows the results of the press forming analysis. DETAILED DESCRIPTION OF THE INVENTION

[0011] A press forming apparatus according to an embodiment includes a punch, a blank holder, and a die. The punch includes a punch top surface, a punch shoulder, and a punch side surface. The punch top surface intersects with the press direction. The punch shoulder is continuous with the punch top surface. The punch side surface is continuous with the punch shoulder. The punch side surface is connected to the punch top surface via the punch shoulder. The punch shoulder includes a first curved portion. The first curved portion is curved concavely toward the inside of the punch when viewed from the punch side surface side. The blank holder is disposed next to the first curved portion when viewed from the press direction. The blank holder includes a holder top surface, a holder shoulder, and a holder side surface. The holder top surface intersects with the press direction. The holder shoulder is continuous with the holder top surface on the first curved portion side. The holder shoulder includes a second curved portion corresponding to the first curved portion. The holder side surface is continuous with the holder shoulder. The holder side surface is connected to the holder top surface via the holder shoulder. The die is positioned next to the first curved portion when viewed from the pressing direction. The die includes a pressing surface, a die shoulder, and a die side surface. The pressing surface faces the holder top surface. The die shoulder is continuous with the pressing surface on the first curved portion side. The die shoulder includes a third curved portion corresponding to the first curved portion. The die side surface is continuous with the die shoulder. The die side surface is connected to the pressing surface via the die shoulder. When viewed from the pressing direction, at least one of the pressing surface and the holder top surface has a length along the extension direction of the punch shoulder that is shorter than that of the punch shoulder (first configuration).

[0012] In the press forming apparatus according to the embodiment, the punch includes a first curved portion at the punch shoulder. The first curved portion is curved concavely toward the inside of the punch when viewed from the side of the punch. In this case, when the blank is bent along the punch shoulder during press forming, stretch flange deformation occurs at the end of the blank near the first curved portion. However, a die and a blank holder are disposed adjacent to the first curved portion of the punch shoulder. The die and blank holder clamp the end of the blank near the first curved portion of the punch shoulder and can apply compressive stress in the thickness direction to the end of the blank. In particular, when viewed from the press direction, the length of at least one of the pressing surface of the die and the holder top surface in the extension direction of the punch shoulder is shorter than that of the punch shoulder. Therefore, the pressing surface of the die and the holder top surface locally press the end of the blank that is stretched in the extension direction of the first curved portion and experiences a thickness reduction. This reduces blank strain near the first curved portion of the punch shoulder and suppresses thickness reduction in the blank. This prevents breakage of the blank.

[0013] In the press forming apparatus according to the first configuration, when viewed from the pressing direction, the length of the pressing surface in the extension direction of the punch shoulder may be greater than the length of the holder top surface in the extension direction (second configuration).

[0014] The press forming apparatus according to the first or second configuration may further include a pad facing the top surface of the punch (third configuration).

[0015] According to the third configuration, the blank can be formed by the punch, die, and blank holder while the blank is sandwiched between the punch top surface and the pad, which makes it difficult for wrinkles to occur in the blank and enables a press-formed product to be formed from the blank with high precision.

[0016] In the press forming apparatus according to any one of the first to third configurations, when viewed from the pressing direction, the distance between the die shoulder and the holder shoulder on a line perpendicular to the direction in which the die shoulder extends may vary along the die shoulder. In this case, the distance is preferably smallest at the third curved portion of the die shoulder (fourth configuration).

[0017] During press forming, the blank is drawn toward the die shoulder and bent along the punch shoulder. In the press forming apparatus according to the embodiment, the die shoulder has a third curved portion corresponding to the first curved portion of the punch shoulder. In this case, the portion of the blank drawn toward the third curved portion of the die shoulder is stretched as it is drawn toward the third curved portion, and its thickness tends to decrease. In contrast, in the fourth configuration, when viewed from the press direction, the distance between the die shoulder and the holder shoulder is smallest at the third curved portion. Therefore, the portion of the blank drawn toward the third curved portion can be clamped by the die and blank holder up to the vicinity of the third curved portion. In other words, compressive stress is applied in the thickness direction to the portion of the blank with reduced thickness up to the vicinity of the third curved portion. This makes it less likely for the blank to break.

[0018] In the fourth configuration, when viewed from the press direction, the distance between the die shoulder and the holder shoulder varies along the extension direction of the die shoulder. More specifically, the point where the distance between the die shoulder and the holder shoulder is smallest is located at the third curved portion of the die shoulder, and the distance between the die shoulder and the holder shoulder is large elsewhere. Therefore, during press forming, the blank is pressed by the die and blank holder up to the vicinity of the die shoulder at the point where the distance between the die shoulder and the holder shoulder is smallest, while the blank is not pressed up to the vicinity of the die shoulder at the point adjacent to that point. This allows metal to flow into the thinned portion of the blank during press forming, thereby mitigating the thinning of the blank's thickness. This makes the blank even less likely to break.

[0019] In the press forming apparatus according to the fourth configuration, the distance may increase as the distance from the third curved portion increases when viewed from the pressing direction (fifth configuration).

[0020] In the press forming apparatus according to the fourth configuration, the die shoulder may include a convex portion that protrudes outward from the die when viewed from the side of the die. The convex portion may consist of only the third curved portion. In this case, when viewed from the pressing direction, the distance may be greatest at the end of the third curved portion (sixth configuration).

[0021] In a press forming apparatus according to any one of the fourth to sixth configurations, it is preferable that the line length of the part of the holder shoulder that has the smallest spacing when viewed from the press direction is 0.76 to 10.92 times the line length of the third curved portion (seventh configuration).

[0022] A manufacturing method for a press-formed product according to an embodiment includes a step of clamping a blank between a die and a blank holder, and a step of pressing the blank in a press direction with a punch. The punch includes a punch top surface, a punch shoulder, and a punch side surface. The punch top surface intersects with the press direction. The punch shoulder is continuous with the punch top surface. The punch side surface is continuous with the punch shoulder. The punch side surface is connected to the punch top surface via the punch shoulder. The punch shoulder includes a first curved portion. The first curved portion is concavely curved toward the inside of the punch when viewed from the punch side surface side. The blank holder is positioned next to the first curved portion when viewed from the press direction. The blank holder includes a holder top surface, a holder shoulder, and a holder side surface. The holder top surface intersects with the press direction. The holder shoulder is continuous with the holder top surface on the first curved portion side. The holder shoulder includes a second curved portion corresponding to the first curved portion. The holder side surface is continuous with the holder shoulder. The holder side surface is connected to the holder top surface via a holder shoulder. The die is arranged next to the first curved portion when viewed from the pressing direction. The die includes a pressing surface, a die shoulder, and a die side surface. The pressing surface faces the holder top surface. The die shoulder is continuous with the pressing surface on the first curved portion side. The die shoulder includes a third curved portion corresponding to the first curved portion. The die side surface is continuous with the die shoulder. The die side surface is connected to the pressing surface via the die shoulder. When viewed from the pressing direction, at least one of the pressing surface and the holder top surface has a shorter length along the extension direction of the punch shoulder than the punch shoulder (eighth configuration).

[0023] In the manufacturing method of a press-molded product relating to the eighth configuration, when viewed from the press direction, the length of the pressing surface in the extension direction of the punch shoulder may be greater than the length of the holder top surface in the extension direction (ninth configuration).

[0024] The method for manufacturing a press-formed product according to the eighth or ninth configuration may further include a step of clamping the blank between a pad and a punch (tenth configuration).

[0025] In the method for manufacturing a press-formed product according to any one of the eighth to tenth configurations, when viewed from the pressing direction, the distance between the die shoulder and the holder shoulder on a line perpendicular to the direction in which the die shoulder extends may vary along the die shoulder. In this case, the distance is preferably smallest at the third curved portion of the die shoulder (eleventh configuration).

[0026] In the method for manufacturing a press-formed product according to the eleventh configuration, the interval may increase as the distance from the third curved portion increases when viewed from the pressing direction (twelfth configuration).

[0027] In the method for producing a press-formed product according to the eleventh aspect, the die shoulder may include a convex portion that protrudes outward from the die as viewed from the side of the die. The convex portion may consist of only the third curved portion. In this case, the distance may be greatest at the end of the third curved portion as viewed from the pressing direction (thirteenth aspect).

[0028] In the manufacturing method of a press-molded product according to any one of the 11th to 13th configurations, it is preferable that the line length of the part of the holder shoulder that has the smallest spacing when viewed from the press direction is 0.76 to 10.92 times the line length of the third curved portion (14th configuration).

[0029] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the same or equivalent components are designated by the same reference numerals, and the same description will not be repeated.

[0030] First Embodiment [Press molding equipment] FIG. 1 is a schematic perspective view of a press forming apparatus 100 according to a first embodiment. As shown in FIG. 1, the press forming apparatus 100 includes a punch 10, a die 20, a blank holder 30, and a pad 40. In the example shown in FIG. 1, the dies 20 are arranged on both sides of the punch 10. These dies 20 may be separate bodies or may be integrally formed. In this embodiment, the spaces between these dies 20 may be referred to as die holes. The blank holder 30 is provided corresponding to each of the dies 20. The pad 40 is arranged between the dies 20.

[0031] The punch 10 and the blank holder 30 are configured to be movable relative to the die 20 and the pad 40 in the press direction P. In the press forming apparatus 100, the punch 10 and the blank holder 30 may be moved in the press direction P by a drive mechanism (not shown) such as a fluid pressure cylinder, or the die 20 and the pad 40 may be moved in the press direction P. The blank holder 30 is movable relative to the punch 10 in the press direction P by a drive mechanism (not shown) such as a cushion. Although not particularly limited, the press direction P is, for example, a vertical direction.

[0032] Fig. 2 is a cross-sectional view of the press forming apparatus 100 shown in Fig. 1. The cross-section of the press forming apparatus 100 is a cross-section obtained by cutting the press forming apparatus 100 along a plane perpendicular to the longitudinal direction of the punch 10. The direction perpendicular to the press direction P on the cross-section of the press forming apparatus 100 is referred to as the width direction of the press forming apparatus 100. For ease of explanation, Fig. 2 shows only one side of the widthwise center line CL of the cross-section of the press forming apparatus 100.

[0033] Referring to FIG. 2, punch 10 includes a punch top surface 11 , a punch shoulder 12 , and a punch side surface 13 .

[0034] The punch top surface 11 is a surface that intersects with the press direction P. In a cross-sectional view of the press forming apparatus 100, the punch top surface 11 extends substantially in the width direction. The punch shoulder 12 is continuous with the punch top surface 11. In a cross-sectional view of the press forming apparatus 100, the punch shoulder 12 has, for example, a substantially arc-shaped shape. The punch side surface 13 is continuous with the punch shoulder 12 on the side opposite to the punch top surface 11. The punch side surface 13 is connected to the punch top surface 11 via the punch shoulder 12. In a cross-sectional view of the press forming apparatus 100, the punch side surface 13 extends from the punch shoulder 12 substantially in the press direction P. In a cross-sectional view of the press forming apparatus 100, the punch side surface 13 may be parallel to the press direction P or may be inclined with respect to the press direction P.

[0035] The die 20 includes a pressing surface 21, a die shoulder 22, and a die side surface 23. The pressing surface 21 is a surface for pressing the blank together with the blank holder 30 during press forming. The pressing surface 21 intersects with the press direction P. The die shoulder 22 is continuous with the end of the pressing surface 21 on the punch 10 side in a cross-sectional view of the press forming apparatus 100. The die shoulder 22 has, for example, a substantially arc shape in a cross-sectional view of the press forming apparatus 100. The die side surface 23 is connected to the pressing surface 21 via the die shoulder 22. In a cross-sectional view of the press forming apparatus 100, the die side surface 23 extends from the die shoulder 22 substantially in the press direction P. The die side surface 23 has a shape corresponding to the punch side surface 13.

[0036] The blank holder 30 is disposed outside the punch 10 in the width direction of the press forming apparatus 100. The blank holder 30 is disposed so as to face the die 20 in the pressing direction P. The blank holder 30 includes a holder top surface 31, a holder shoulder 32, and a holder side surface 33.

[0037] The holder top surface 31 faces the pressing surface 21 of the die 20. The holder shoulder 32 is continuous with the end of the holder top surface 31 on the punch 10 side in a cross-sectional view of the press forming apparatus 100. The holder shoulder 32 has, for example, a substantially arc shape in a cross-sectional view of the press forming apparatus 100. The holder side surface 33 is connected to the holder top surface 31 via the holder shoulder 32. In a cross-sectional view of the press forming apparatus 100, the holder side surface 33 extends from the holder shoulder 32 substantially in the pressing direction P. At least a portion of the holder side surface 33 faces the punch side surface 13 in the width direction of the press forming apparatus 100.

[0038] The pad 40 faces the punch top surface 11. The pad 40 moves relative to the die 20 in the pressing direction P by an elastic member 50 such as a fluid pressure cylinder or a spring.

[0039] Pad 40 includes a pressing surface 41. Pressing surface 41 is a surface for pressing a blank during press forming. Pressing surface 41 faces punch top surface 11 in the press direction P. Pressing surface 41 has a shape corresponding to punch top surface 11. In other words, pressing surface 41 is formed into a shape that engages with punch top surface 11 so that the blank can be sandwiched between pressing surface 41 and punch top surface 11.

[0040] In this embodiment, the press-forming apparatus 100 has a shape that is symmetrical about the width center line CL in a cross-sectional view. However, the cross-sectional shape of the press-forming apparatus 100 may be asymmetrical about the width center line CL.

[0041] 3 and 4 are side views of the press-forming apparatus 100. FIG. 3 is a view of the punch 10, the die 20, and the blank holder 30 as viewed from the blank holder 30 side, and FIG. 4 is a view of the die 20 and the blank holder 30 as viewed from the punch 10 side. In FIG. 4, the punch 10 is indicated by a two-dot chain line. FIGS. 5 and 6 are views of the press-forming apparatus 100 as viewed from the press direction P. More specifically, FIGS. 5 and 6 are views of the press-forming apparatus 100 projected onto a plane perpendicular to the press direction P. FIG. 5 shows the punch 10, the die 20, and the blank holder 30 as viewed from the blank holder 30 side, and FIG. 6 shows the punch 10, the die 20, and the blank holder 30 as viewed from the die 20 side. FIGS. 5 and 6 show one of the two punch shoulders 12 of the punch 10, as well as the corresponding die 20 and blank holder 30. The relationship between the punch 10, the die 20, and the blank holder 30 will be described in more detail below with reference to FIGS.

[0042] As shown in FIG. 3 , in the punch 10, the punch shoulder 12 includes a curved portion 121 and straight portions 122 and 123. The curved portion 121 is curved concavely toward the inside of the punch 10 when viewed from the punch side surface 13. When viewed from the punch side surface 13, the curved portion 121 extends with a radius of curvature of 400 mm or less. When viewed from the punch side surface 13, the curved portion 121 may extend with a radius of curvature of 5 mm or more, or may extend with a radius of curvature of 10 mm or more. The curved portion 121 may have a constant radius of curvature or may have a variable radius of curvature. For example, when viewed from the punch side surface 13 side, the radius of curvature of an arc passing through three points, that is, the point and the points on either side of the point, is measured for each point arranged at 5 mm intervals on the edge of the punch shoulder 12 on the die 20 side, and the section where the radius of curvature is 400 mm or less can be defined as a curved section 121, and the section where the radius of curvature is 400 mm or more can be defined as a non-curved section (straight section).

[0043] The straight portions 122, 123 are provided continuously at both ends of the curved portion 121. When viewed from the punch side surface 13 side, the straight portions 122, 123 extend from the curved portion 121 so as to become more distant from each other as they move away from the curved portion 121. When viewed from the punch side surface 13 side, the straight portions 122, 123 may be located on tangents to both ends of the curved portion 121.

[0044] When viewed from the punch side surface 13 side, the punch shoulder 12 is recessed in the pressing direction P away from the die 20 at the positions of the curved portion 121 and the straight portions 122, 123. The punch top surface 11 (FIG. 2) also includes a portion corresponding to the punch shoulder 12 that is recessed in the pressing direction P away from the die 20.

[0045] 4, in the die 20, the die shoulder 22 includes a curved portion 221 and straight portions 222, 223. The curved portion 221 corresponds to the curved portion 121 of the punch shoulder 12. More specifically, in a side view of the press forming apparatus 100, the curved portion 221 of the die shoulder 22 is curved in substantially the same direction as the curved portion 121 of the punch shoulder 12. In a side view of the press forming apparatus 100, the curved portion 221 is curved so as to be convex toward the punch 10.

[0046] Like the curved portion 121 of the punch shoulder 12, the curved portion 221 extends with a radius of curvature of 400 mm or less when viewed from the die side surface 23. When viewed from the die side surface 23, the curved portion 221 may extend with a radius of curvature of 5 mm or more, or may extend with a radius of curvature of 10 mm or more. The curved portion 221 may have a constant radius of curvature or a variable radius of curvature. For example, when viewed from the die side surface 23, the radius of curvature of an arc passing through three points, including each point and two adjacent points, is measured at each point located at 5 mm intervals on the edge of the die shoulder 22 on the punch 10 side. The section with a radius of curvature of 400 mm or less can be defined as the curved portion 221, and the section with a radius of curvature of 400 mm or more can be defined as a non-curved portion (straight portion).

[0047] The straight portions 222, 223 are provided continuously at both ends of the curved portion 221. When viewed from the die side surface 23 side, the straight portions 222, 223 extend from the curved portion 221 so as to become increasingly separated from each other as they move away from the curved portion 221. The straight portions 222, 223 correspond to the straight portions 122, 123 of the punch shoulder 12. More specifically, when viewed from the side of the press forming apparatus 100, the straight portions 222, 223 of the die shoulder 22 extend along the straight portions 122, 123 of the punch shoulder 12, respectively.

[0048] When viewed from the die side surface 23 side, the straight portions 222, 223 may be located on tangents to both ends of the curved portion 221. The angle formed by the tangents to both ends of the curved portion 221 is the included angle θ of the curved portion 221. The included angle θ may be 1 / 3π (rad) or more and 2 / 3π (rad) or less.

[0049] The die shoulder 22 protrudes in the press direction P toward the punch 10 at the positions of the curved portion 221 and the straight portions 222, 223. The pressing surface 21 of the die 20 ( FIG. 2 ) also corresponds to the die shoulder 22 and includes a portion that protrudes in the press direction P toward the punch 10. In the example of this embodiment, the entire die shoulder 22 is parallel to the punch shoulder 12 in a side view of the press forming apparatus 100. However, at least a portion of the die shoulder 22 may be non-parallel to the punch shoulder 12 in a side view of the press forming apparatus 100.

[0050] Referring to FIG. 5 , the die 20 is disposed adjacent to the curved portion 121 of the punch shoulder 12 when viewed from the press direction P. More specifically, when viewed from the press direction P, a portion of the pressing surface 21 of the die 20 is disposed adjacent to the curved portion 121 of the punch shoulder 12. The die shoulder 22 is continuous with the pressing surface 21 on the curved portion 121 side. When viewed from the press direction P, the punch 10 and the die 20 are disposed side by side so that the curved portion 221 of the die shoulder 22 faces the curved portion 121 of the punch shoulder 12. In the example shown in FIG. 5 , when viewed from the press direction P, the entire die shoulder 22 is parallel to the punch shoulder 12. However, at least a portion of the die shoulder 22 may be non-parallel to the punch shoulder 12.

[0051] Returning to FIG. 4 , in the blank holder 30, the holder shoulder 32 includes a curved portion 321. The curved portion 321 corresponds to the curved portion 121 of the punch shoulder 12. More specifically, in a side view of the press forming apparatus 100, the curved portion 321 of the holder shoulder 32 curves in substantially the same direction as the curved portion 121 of the punch shoulder 12 and the curved portion 221 of the die shoulder 22. In a side view of the press forming apparatus 100, the curved portion 321 is curved so as to be concave toward the side away from the die 20. The holder top surface 31 ( FIG. 2 ) also corresponds to the holder shoulder 32 and includes a portion that is concave toward the side away from the die 20 in the pressing direction P. The holder top surface 31 has a shape that corresponds to the pressing surface 21 of the die 20 ( FIG. 2 ). In other words, the holder top surface 31 of the blank holder 30 is formed in a shape that engages with the pressing surface 21 of the die 20 so that the blank can be clamped between the holder top surface 31 and the pressing surface 21 of the die 20.

[0052] 6, the blank holder 30 is disposed adjacent to the curved portion 121 of the punch shoulder 12 when viewed from the press direction P. More specifically, when viewed from the press direction P, at least a portion of the holder top surface 31 is disposed adjacent to the curved portion 121 of the punch shoulder 12. The holder shoulder 32 is continuous with the holder top surface 31 on the curved portion 121 side. When viewed from the press direction P, the punch 10 and the blank holder 30 are disposed side by side so that the curved portion 321 of the holder shoulder 32 faces the curved portion 121 of the punch shoulder 12.

[0053] When viewed from the press direction P, the holder top surface 31 has a length along the extension direction of the punch shoulder 12 that is shorter than that of the punch shoulder 12. The holder top surface 31 does not reach both ends of the punch 10 in the extension direction of the punch shoulder 12. In other words, when viewed from the press direction P, the holder top surface 31 is disposed inside both ends of the punch 10 in the extension direction of the punch shoulder 12. In this embodiment, the entire blank holder 30 is disposed inside both ends of the punch 10 in the extension direction of the punch shoulder 12. The punch 10 is separate from the blank holder 30 and is configured so as not to overlap with the blank holder 30 in the extension direction of the punch shoulder 12. In this embodiment, when viewed from the press direction P, the length of the pressing surface 21 ( FIG. 5 ) of the die 20 is longer than the length of the holder top surface 31 ( FIG. 6 ) in the extension direction of the punch shoulder 12. In this embodiment, the length of the pressing surface 21 of the die 20 is approximately the same as the length of the punch top surface 11 when viewed from the pressing direction P.

[0054] 5 and 6, when viewed from the press direction P, a gap C is generated between the holder shoulder 32 and the die shoulder 22. The gap C is the gap between the holder shoulder 32 and the die shoulder 22 on a line perpendicular to the extension direction of the die shoulder 22 when viewed from the press direction P. The line perpendicular to the extension direction of the die shoulder 22 is a line perpendicular or normal to the edge of the die shoulder 22 on the punch 10 side when viewed from the press direction P. The line perpendicular to the extension direction of the die shoulder 22 roughly coincides with the direction in which the blank is drawn into the die hole when the blank is formed using the press forming apparatus 100 (FIGS. 1 and 2).

[0055] In this embodiment, when viewed from the press direction P, the distance C between the holder shoulder 32 and the die shoulder 22 varies along the die shoulder 22. That is, the distance C between the holder shoulder 32 and the die shoulder 22 is not constant over the entire length of the holder shoulder 32. When viewed from the press direction P, the distance C between the holder shoulder 32 and the die shoulder 22 is smallest at the curved portion 221 of the die shoulder 22. In this case, if a perpendicular line is drawn from a position on the die shoulder 22 where the distance from the holder shoulder 32 is smallest when viewed from the press direction P, the perpendicular line will pass through the curved portion 221. The minimum value of the distance C is smaller than the clearance between the punch shoulder 12 and the die shoulder 22, for example. The minimum value of the distance C may be 0 mm. In this embodiment, when the minimum value of the distance C is 0 mm, the holder shoulder 32 and the die shoulder 22 overlap at the point where they are closest to each other when viewed from the press direction P, and in other points, the edge of the die shoulder 22 is located on the punch 10 side relative to the edge of the holder shoulder 32. On the other hand, when the minimum value of the distance C is greater than 0 mm, the entire edge of the holder shoulder 32 is located on the opposite side of the punch 10 from the edge of the die shoulder 22 when viewed from the press direction P.

[0056] The linear length of the portion of the holder shoulder 32 where the distance C from the die shoulder 22 is smallest when viewed from the press direction P can be, for example, 0.76 to 10.92 times the linear length of the curved portion 221 of the die shoulder 22. The linear length of the portion of the holder shoulder 32 where the distance C from the die shoulder 22 is smallest when viewed from the press direction P is preferably 0.79 to 5.43 times, and more preferably 0.80 to 4.00 times, the linear length of the curved portion 221 of the die shoulder 22. The linear length of the portion of the holder shoulder 32 where the distance C from the die shoulder 22 is smallest when viewed from the press direction P can be measured, for example, along the end of the R of the holder shoulder 32 on the holder top surface 31 side. The linear length of the curved portion 221 of the die shoulder 22 is, for example, the product of the included angle θ (rad) and the radius of curvature of the curved portion 221. When the radius of curvature of the curved portion 221 varies, the radius of curvature of the curved portion 221 can be, for example, the average value of the radii of curvature measured at 5 mm intervals as described above.

[0057] 5 and 6, the distance C between the holder shoulder 32 and the die shoulder 22 is minimum and constant in a partial section of the curved portion 221 of the die shoulder 22. In other words, when viewed from the press direction P, the holder shoulder 32 is substantially parallel to the die shoulder 22 in a partial section of the curved portion 221 of the die shoulder 22. When viewed from the press direction P, the distance C between the holder shoulder 32 and the die shoulder 22 increases with increasing distance from the curved portion 221. The distance C widens at the straight portions 222, 223 of the die shoulder 22.

[0058] [Method of manufacturing press-molded products] Next, a method for manufacturing a press-formed product using the press-forming apparatus 100 will be described with reference to FIGS. 7A to 7C.

[0059] Referring to FIG. 7A , in manufacturing a press-formed product, first, a blank 200 is prepared. The blank 200 can be obtained, for example, by blanking a metal strip. The blank 200 is formed, for example, into the shape of a developed version of the desired press-formed product. The blank 200 may be a steel plate. The blank 200 is preferably a high-tensile steel plate. The tensile strength of the blank 200 is, for example, 440 MPa or more. The tensile strength of the blank 200 may be 590 MPa or more, or 780 MPa or more. The tensile strength of the blank 200 may be 1300 MPa or more. The plate thickness of the blank 200 is, for example, 0.4 mm or more and 6.0 mm or less.

[0060] The method for manufacturing a press-formed product according to this embodiment includes a step of clamping the blank 200 between the die 20 and the blank holder 30, and a step of pressing the blank 200 in the pressing direction P with the punch 10. The method for manufacturing a press-formed product may further include a step of clamping the blank 200 between the pad 40 and the punch 10. When manufacturing the press-formed product, the blank 200 is placed between the punch 10 and the blank holder 30, and the die 20 and the pad 40. For example, the blank 200 is placed on the punch top surface 11. Alternatively, the blank 200 may be placed on the pressing surface 21 of the die 20.

[0061] Next, the die 20 and pad 40 are brought relatively close to the punch 10 and blank holder 30 in the pressing direction P. As a result, the blank 200 is pressed by the pressing surface 41 of the pad 40, as shown in FIG. 7B. The blank 200 is sandwiched between the punch top surface 11 and the pressing surface 41 of the pad 40. The blank 200 is also sandwiched between the pressing surface 21 of the die 20 and the holder top surface 31.

[0062] Referring to FIG. 7C , with the blank 200 sandwiched between the die 20 and the blank holder 30, the die 20 is further moved relatively closer to the punch 10 in the pressing direction P. This causes the blank 200 to be pressed into the die 20 side (die hole) by the punch 10. As the blank 200 is pressed by the punch 10, it is drawn toward the die hole. In FIG. 7C , the direction in which the blank 200 is drawn is indicated by arrow D. In this embodiment, the pressing (forming) by the punch 10 is completed after the blank 200 is completely pulled out from between the die 20 and the blank holder 30. However, forming may be completed with a portion of the blank 200 still sandwiched between the die 20 and the blank holder 30. When the pressing by the punch 10 is completed, the blank 200 is formed into a press-formed product.

[0063] [effect] 8, when the blank 200 is bent along the punch shoulder 12, stretch flange deformation occurs at the end of the blank 200 near the curved portion 121 of the punch shoulder 12. Near the curved portion 121, strain is concentrated in the blank 200 as shown by the arrows in FIG. 8, and the blank 200 is stretched, resulting in a decrease in its thickness.

[0064] In contrast, in the press forming apparatus 100 according to this embodiment, the die 20 and the blank holder 30 are disposed adjacent to the curved portion 121 of the punch shoulder 12. Therefore, the end of the blank 200 can be clamped between the die 20 and the blank holder 30 near the curved portion 121, allowing compressive stress to be applied to the end of the blank 200 in the thickness direction. In particular, in this embodiment, when viewed from the pressing direction P, the length of the holder top surface 31 in the extension direction of the punch shoulder 12 is shorter than that of the punch shoulder 12. This allows the pressing surface 21 of the die 20 and the holder top surface 31 to apply a concentrated pressing force to a portion of the blank 200 located near the curved portion 121 where a thickness reduction occurs. This reduces strain in the blank 200 near the curved portion 121, thereby suppressing a thickness reduction in the blank 200. As a result, the occurrence of breakage of the blank 200 during press forming can be suppressed.

[0065] This embodiment relates to a developed method for suppressing cracking of the blank 200 by applying compressive stress to a thickness-reduced portion of the blank 200 using a blank holder 30 when drawing is performed using a punch 10 having a curved portion 121 on the punch shoulder 12. When flange-up forming is performed using a punch 10 having a curved portion 121 that is concave in side view on the punch shoulder 12, the thickness of the blank 200 decreases near the curved portion 121 of the punch shoulder 12 and the corresponding curved portion 221 of the die shoulder 22. During press forming, the punch 10 pushes the blank 200 into the die hole and the blank 200 is drawn toward the die shoulder 22. From the perspective of the developed method, it is desirable for the die 20 and blank holder 30 to press the blank 200 up to the vicinity of the curved portion 221 of the die shoulder 22. On the other hand, from the viewpoint of metal flow, if the die 20 and the blank holder 30 do not press the periphery of the thickness-reduced portion of the blank 200, metal will flow into the thickness-reduced portion of the blank 200, thereby mitigating the reduction in the thickness of the blank 200. Therefore, in this embodiment, from the viewpoints of both the developed method and metal flow, the distance C between the holder shoulder 32 and the die shoulder 22 when viewed from the press direction P is varied along the die shoulder 22. That is, when viewed from the press direction P, the holder shoulder 32 extends along the die shoulder 22 but is not parallel to the die shoulder 22. When viewed from the press direction P, the distance C between the holder shoulder 32 and the die shoulder 22 is minimum at the curved portion 221 of the die shoulder 22. As a result, during press forming, the blank 200 is pressed by the die 20 and the blank holder 30 up to the vicinity of the die shoulder 22 at the location where the distance C is minimum, whereas the blank 200 is not pressed up to the vicinity of the die shoulder 22 at a location adjacent to the minimum distance C. Therefore, compressive stress can be applied in the thickness direction to the thickness-reduced portion of the blank 200, and metal can be allowed to flow in. Therefore, the blank 200 is less likely to break.

[0066] In this embodiment, when viewed from the pressing direction P, the distance C between the holder shoulder 32 and the die shoulder 22 increases as the distance increases from the curved portion 221. This allows the blank holder 30 to press the entire portion of the blank 200 that is drawn into the curved portion 221 closer to the die hole than the portion that is drawn into the straight portions 222, 223, while facilitating the flow of metal from the periphery of the portion that is drawn into the curved portion 221 into that portion.

[0067] In this embodiment, when viewed from the pressing direction P, the linear length of the portion of the holder shoulder 32 where the distance C from the die shoulder 22 is smallest is preferably 0.76 to 10.92 times the linear length of the curved portion 221. This makes it possible to effectively prevent the blank 200 from breaking.

[0068] Second Embodiment 9 is a side view of a press forming apparatus 100A according to the second embodiment. The press forming apparatus 100A according to this embodiment differs from the press forming apparatus 100 according to the first embodiment in that it further includes blank holders 60 and 70.

[0069] 9, the blank holders 60 and 70 are arranged on both sides of the blank holder 30 in a side view of the press forming apparatus 100A. The blank holders 60 and 70 are separate from the blank holder 30. The blank holders 30, 60, and 70 are provided in the press forming apparatus 100A so as to move in the pressing direction P independently of each other.

[0070] The blank holders 60 and 70, together with the blank holder 30, have shapes corresponding to the die 20. Like the blank holder 30, the blank holders 60 and 70 are configured to clamp the blank between themselves and the die 20 during press forming. However, the blank holders 30, 60, and 70 are separate bodies and can move independently in the press direction P. Therefore, even if the blank thickness is reduced near the curved portion 121 of the punch shoulder 12, the blank holder 30 can independently follow the blank and firmly press the reduced thickness portion of the blank together with the die 20. Therefore, similar to the first embodiment, distortion of the blank near the curved portion 121 is reduced, and the reduction in the blank thickness is suppressed. As a result, the occurrence of breakage of the blank during press forming can be suppressed.

[0071] <Third embodiment> 10 is a side view of a press forming apparatus 100B according to the third embodiment. The press forming apparatus 100B according to this embodiment differs from the press forming apparatus 100 according to the first embodiment in the configuration of the blank holder 30B.

[0072] In the first embodiment, the blank holder 30 is provided so as to correspond to only a part of the punch 10 (FIGS. 3 to 6). On the other hand, in the present embodiment, as shown in FIG. 10, the blank holder 30B is provided over the entire length of the punch 10.

[0073] In this embodiment, in a side view of the press forming apparatus 100B, a convex portion 34 is provided on the surface of the blank holder 30B facing the die 20. The top surface of this convex portion 34 is the holder top surface 31. The edge of the convex portion 34 facing the punch 10 is the holder shoulder. As in the other embodiments, when viewed from the press direction P, the pressing surface 21 of the die 20 extends beyond the holder top surface 31. When viewed from the press direction P, the length of the holder top surface 31 along the extension direction of the punch shoulder 12 is shorter than the extension length of the punch shoulder 12. In this embodiment, too, the holder top surface 31 does not reach both ends of the punch 10 in the extension direction of the punch shoulder 12. In other words, when viewed from the press direction P, the holder top surface 31 is located inside both ends of the punch 10 in the extension direction of the punch shoulder 12. Therefore, during press forming, the holder top surface 31 and the die 20 can locally press the blank near the curved portion 121 of the punch shoulder 12. Therefore, similarly to the other embodiments, distortion of the blank is reduced near the curved portion 121, and a reduction in the thickness of the blank is suppressed. As a result, it is possible to suppress the occurrence of breakage of the blank during press forming.

[0074] <Fourth embodiment> Fig. 11 is a side view of a press forming apparatus 100C according to the fourth embodiment. Fig. 12 is a view of the press forming apparatus 100C as viewed from the pressing direction P. Fig. 12 shows the punch 10, die 20C, and blank holder 30C as viewed from the blank holder 30C side. The press forming apparatus 100C according to this embodiment differs from the press forming apparatus 100 according to the first embodiment in the configurations of the die 20C and blank holder 30C.

[0075] In the first embodiment, when viewed from the press direction P, the length of the holder top surface 31 along the extension direction of the punch shoulder 12 is smaller than that of the punch shoulder 12. On the other hand, in the present embodiment, when viewed from the press direction P, the length of the pressing surface 21 of the die 20C along the extension direction of the punch shoulder 12 is smaller than that of the punch shoulder 12. In the example shown in Figures 11 and 12, when viewed from the press direction P, the length of the holder top surface 31 along the extension direction of the punch shoulder 12 is larger than the length of the pressing surface 21 of the die 20C.

[0076] In a side view of the press forming apparatus 100C, a convex portion 24 is provided on the surface of the die 20C facing the blank holder 30C. The top surface of this convex portion 24 serves as the pressing surface 21 of the die 20C. The pressing surface 21 does not reach both ends of the punch 10 in the extension direction of the punch shoulder 12. In other words, when viewed from the press direction P, the pressing surface 21 is located more inward than both ends of the punch 10 in the extension direction of the punch shoulder 12. The shape of the pressing surface 21 when viewed from the press direction P can be the same as the shape of the holder top surface 31 of the blank holder 30 of the first embodiment ( FIG. 5 ), for example. Furthermore, the distance C between the holder shoulder 32 and the die shoulder 22 when viewed from the press direction P can also be set in the same way as in the first embodiment.

[0077] 11 and 12, when viewed from the pressing direction P, the holder top surface 31 extends along the punch shoulder 12 and beyond the pressing surface 21 of the die 20C. For example, the holder top surface 31 extends a length approximately equal to that of the punch shoulder 12 when viewed from the pressing direction P. However, when viewed from the pressing direction P, the length of the holder top surface 31 in the extension direction of the punch shoulder 12 may be equal to or shorter than the length of the convex pressing surface 21 of the die 20C.

[0078] In the present embodiment, too, the blank can be locally pressed by the holder top surface 31 and the pressing surface 21 of the die 20C near the curved portion 121 of the punch shoulder 12 during press forming. Therefore, as in the other embodiments, distortion of the blank is reduced near the curved portion 121, and a reduction in the thickness of the blank is suppressed. As a result, breakage of the blank can be suppressed during press forming.

[0079] Fifth Embodiment Fig. 13 is a side view of a press forming apparatus 100D according to the fifth embodiment. Fig. 14 is a view of the press forming apparatus 100D as seen from the pressing direction P. The press forming apparatus 100D according to this embodiment differs from the press forming apparatus 100 according to the first embodiment in the configurations of a punch 10D and a die 20D.

[0080] 13, in this embodiment, the punch shoulder 12 includes a concave portion consisting only of a curved portion 121. The die shoulder 22 also includes a convex portion consisting only of a curved portion 221 corresponding to the punch shoulder 12. The convex portion is a portion of the die shoulder 22 that protrudes outward from the die 20D (toward the punch 10D) when viewed from the die side surface 23 side.

[0081] 14, when viewed from the press direction P, the distance C between the die shoulder 22 and the holder shoulder 32 is small at the center in the extension direction of the curved portion 221 and is large at the end. The distance C may gradually increase toward the end in the extension direction of the curved portion 221. When viewed from the press direction P, the distance C is largest at the end in the extension direction of the curved portion 221. The distance C is smallest, for example, in a portion of the curved portion 221 where it is expected that the thickness of the blank will be significantly reduced during press forming.

[0082] When viewed from the press direction P, the holder shoulder 32 is provided so as to correspond to, for example, only a portion of the die shoulder 22. When the curved portion 221 occupies a large area of ​​the die shoulder 22, as in this embodiment, when a perpendicular line is drawn to the end of the curved portion 221 when viewed from the press direction P, the perpendicular line may not intersect with the blank holder 30. In this case, when viewed from the press direction P, the distance C between the end of the curved portion 221 and the holder shoulder 32 in the direction perpendicular to the curved portion 221 becomes infinite. In this case, too, it can be said that the distance C is largest at the end of the curved portion 221.

[0083] Even when the convex portion of the die shoulder 22 consists only of the curved portion 221 as in this embodiment, blank breakage can be effectively suppressed by narrowing the distance C between the die shoulder 22 and the holder shoulder 32 at a portion of the curved portion 221. That is, when a blank that is drawn into the curved portion 221 of the die shoulder 22 during press forming has a portion where the thickness is particularly reduced, by bringing the die shoulder 22 and the holder shoulder 32 closest to each other at the portion where the thickness is reduced, compressive stress can be applied in the thickness direction to the portion where the thickness is reduced, thereby promoting metal flow. Therefore, when drawing is performed using a die 20D whose die shoulder 22 consists only of the curved portion 221, blank cracking can be suppressed.

[0084] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present disclosure.

[0085] In the above embodiment, an example has been described in which the holder top surfaces 31 of the blank holders 30 and 30B and the pressing surface 21 of the die 20C have a substantially trapezoidal shape when viewed from the pressing direction P. However, the shapes of the pressing surfaces of the dies and the holder top surfaces are not limited to this.

[0086] 15 and 16 , when the blank has a portion where the thickness is particularly reduced at the portion drawn into the curved portion 221 of the die shoulder 22, the die shoulder 22 and the holder shoulder 32 can be brought closest to each other at the portion where the thickness is significantly reduced. The distance C between the holder shoulder 32 and the die shoulder 22 as viewed from the pressing direction P may be smallest, for example, at the apex (center) of the curved portion 221 of the die shoulder 22. In this case, the distance C between the holder shoulder 32 and the die shoulder 22 may increase from the center toward both ends of the curved portion 221. It is preferable that the distance C increases with increasing distance from the curved portion 221. This allows compressive stress to be applied in the thickness direction to the portion of the blank where the thickness is significantly reduced and promotes metal flow. Furthermore, the blank is pressed for a long period at the curved portion 221 of the die shoulder 22 and the corresponding curved portion 121 of the punch shoulder 12, thereby reducing distortion of the blank. Therefore, the strain generated at the end of the blank tends to be uniform, and breakage of the blank is easily suppressed.

[0087] For example, the shape of the blank holder 30 when viewed from the press direction P may be as shown in FIGS. 17 and 18. In the example of FIG. 17, the holder shoulder 32 is closest to the die shoulder 22 at the position of a curved portion 221 when viewed from the press direction P, and the distance C between the holder shoulder 32 and the die shoulder 22 increases linearly outside the section where the holder shoulder 32 is closest to the die shoulder 22. When viewed from the press direction P, the section of the holder shoulder 32 that moves away from the die shoulder 22 extends, for example, at an angle α from the section where the holder shoulder 32 is closest to the die shoulder 22. The angle α may be 90° or less. On the other hand, in the example of FIG. 18, the holder shoulder 32 is closest to the die shoulder 22 at the position of a curved portion 221 when viewed from the press direction P, and the distance C between the holder shoulder 32 and the die shoulder 22 increases while curving outside the section where the holder shoulder 32 is closest to the die shoulder 22.

[0088] The shape of the blank holder 30 shown in FIGS. 15 to 18 can also be applied to the blank holder 30B having the holder top surface 31 on the convex portion 34 as in the third embodiment, and to the pressing surface 21 of the die 20C in the fourth embodiment.

[0089] The first to fifth embodiments can also be implemented in combination with one another. For example, the blank holders 30 and 30B in the first to third and fifth embodiments can also be used in combination with the die 20C in the fourth embodiment. That is, the press forming apparatus according to the present disclosure may include the punch 10 or 10D, the die 20C, and the blank holder 30 or 30B. In this case, the end of the blank is clamped near the curved portion 121 of the punch shoulder 12 by the holder top surface 31 of the blank holder 30 or 30B and the pressing surface 21 of the die 20C.

[0090] In the first embodiment described above, an example has been described in which the die 20 and the blank holder 30 are provided on both sides of the punch 10 as viewed from the press direction P. However, as shown in Fig. 19 , the die 20 and the blank holder 30 may be provided on only one side of the punch 10 as viewed from the press direction P. Similarly, in other embodiments, the die and the blank holder may be provided on only one side of the punch as viewed from the press direction P.

[0091] In each of the above embodiments, the curved portion 121 of the punch shoulder 12 has a symmetrical shape when viewed from the punch side surface 13. However, the curved portion 121 may have an asymmetrical shape when viewed from the punch side surface 13. Similarly, the curved portion 221 of the die shoulder 22 and the curved portion 321 of the holder shoulder 32 may also be symmetrical or asymmetrical when viewed from the side of the press forming apparatus.

[0092] 15 to 18, the holder top surfaces 31 of the blank holders 30 and 30B and the pressing surface 21 of the die 20C have shapes that are symmetrical when viewed from the pressing direction P. However, the holder top surfaces 31 and the pressing surface 21 may be symmetrical or asymmetrical when viewed from the pressing direction P.

[0093] In each of the above embodiments, the punches 10, 10D have a rectangular shape when viewed from the press direction P. However, the overall shape of the punches 10, 10D is not limited to this. For example, as shown in FIG. 20 , the punch 10 may have a curved shape when viewed from the press direction P. Similarly, the punch 10D may also have a curved shape when viewed from the press direction P. The punches 10, 10D may have a shape that branches in multiple directions when viewed from the press direction P. The shape of the punches 10, 10D can be changed as appropriate to suit the desired press-formed product.

[0094] In each of the above embodiments, each of the multiple punch shoulders 12 includes a curved portion 121. However, as shown in FIG. 21 , for example, the punch 10 or 10D may include at least one punch shoulder 12 including a curved portion 121. When the multiple punch shoulders 12 each include a curved portion 121, the positions of the curved portions 121 may be substantially the same among the punch shoulders 12 or may be different. Furthermore, the shapes of the curved portions 121 may be substantially the same among the punch shoulders 12 or may be different.

[0095] For example, as shown in FIG. 22 , the press forming apparatus 100 according to the first embodiment may further include a plate-shaped shim 80. The shim 80 is disposed between the blank holder 30 and the die 20. Because the shim 80 is disposed between the blank holder 30 and the die 20, the thickness of the end portion of the blank 200 is not less than the thickness of the shim 80. In other words, the shim 80 can prevent the blank holder 30 and the die 20 from excessively pressing the blank 200. The shim 80 may be provided on the holder top surface 31 or on the pressing surface 21 of the die 20. The shim 80 may be formed integrally with the blank holder 30 or the die 20, or may be a separate body. Although not shown, the press forming apparatuses 100A, 100B, 100C, and 100D according to other embodiments may also include the shim 80.

[0096] In the first embodiment, the press forming apparatus 100 includes a punch 10, a die 20, a blank holder 30, and a pad 40. The pad 40 presses the blank 200 during press forming, making it less likely for wrinkles to occur in the blank 200 and enabling a press-formed product to be formed from the blank 200 with high precision. However, the press forming apparatus 100 does not necessarily need to include a pad. Similarly, the press forming apparatuses 100A, 100B, 100C, and 100D according to other embodiments may or may not include a pad. [Example]

[0097] The present disclosure will be described in more detail below with reference to examples, although the present disclosure is not limited to the following examples.

[0098] When viewed from the press direction, if the section where the die shoulder and the holder shoulder are closest to each other is extremely short, it is believed that the difference in effect between bending without using a blank holder and the method according to the present disclosure will be small. On the other hand, when viewed from the press direction, if the section where the die shoulder and the holder shoulder are closest to each other is extremely long, it is believed that the difference in effect between ordinary drawing and the method according to the present disclosure will be small. Therefore, the inventors performed press forming analysis using commercially available software (LS-DYNA, manufactured by ANSYS) and investigated the appropriate length of the section where the distance between the die shoulder and the holder shoulder is shortest.

[0099] The inventors decided to express the length (linear length) of the section where the distance between the die shoulder and the holder shoulder is the smallest when viewed from the press direction as the ratio to the extension length (linear length) of the curved portion included in the die shoulder.

[0100] In this analysis, the curved portion of the die shoulder in the side view of the press forming device was assumed to extend with a constant radius of curvature. The extension length (linear length) of the curved portion was defined as the product of the angle (included angle θ (rad)) at which the tangents to both ends of the curved portion intersect and the radius of curvature of the curved portion. If the ratio of the length (linear length) of the section where the distance between the die shoulder and the holder shoulder is smallest when viewed from the press direction to the linear length of the curved portion is smaller than 1.0, this means that the edge of the die and the edge of the blank holder are closest to each other in a portion of the curved portion. If the ratio of the length (linear length) of the section where the distance between the die shoulder and the holder shoulder is smallest to the linear length of the curved portion is 1.0, this means that the edge of the die and the edge of the blank holder are closest to each other throughout the entire curved portion. If the ratio of the length (linear length) of the section where the distance between the die shoulder and the holder shoulder is smallest to the linear length of the curved portion is larger than 1.0, this means that the edge of the die and the edge of the blank holder are closest to each other throughout the entire curved portion and in a portion of the straight portion adjacent to the curved portion.

[0101] The inventors expressed the magnitude of damage to the edge of the flange of a press-formed product after forming as a damage value I, which is expressed by the following formula: The inventors also evaluated the magnitude of the effect of the present disclosure in terms of the reduction rate (%) of the damage value I compared to normal drawing.

[0102]

number

[0103] The press forming analysis was carried out using a blank holder having a square shape when viewed from the press direction as shown in Fig. 17, with angles α of 30° and 90°.

[0104] The results of this analysis are shown in Figure 23. As can be seen from Figure 23, when press forming according to the present disclosure was performed, the damage value I was generally reduced compared to conventional drawing. When the line length of the section where the distance between the die shoulder and the holder shoulder is the smallest (closest approach section) / line length of the curved portion was 0.76 or more and 10.92 or less, the reduction rate of the damage value I compared to conventional drawing was significantly improved. When the line length of the closest approach section / line length of the curved portion was in the range of 0.79 or more and 5.43 or less, the reduction rate of the damage value I was further improved, and when it was in the range of 0.80 or more and 4.00 or less, the reduction rate of the damage value I was further improved.

[0105] Therefore, when viewed from the pressing direction, the linear length of the part of the holder shoulder that is the shortest distance from the die shoulder is preferably 0.76 to 10.92 times the linear length of the curved portion provided on the die shoulder, more preferably 0.79 to 5.43 times, and even more preferably 0.80 to 4.00 times. [Explanation of symbols]

[0106] 100, 100A, 100B, 100C, 100D: Press molding equipment 10,10D: Punch 11: Punch top surface 12: Punch shoulder 121: Curved section 13: Punch side 20,20C: Die 21: Pressing surface 22: Die shoulder 221: Curved section 23: Die side 30, 30B, 30C: Blank holder 31: Holder top surface 32: Holder shoulder 321: Curved section 33: Holder side 40: Pad P: Press direction

Claims

1. a punch including a punch top surface intersecting a pressing direction, a punch shoulder continuous with the punch top surface, and a punch side surface continuous with the punch shoulder and connected to the punch top surface via the punch shoulder, wherein the punch shoulder includes a first curved portion that is curved concavely toward the inside of the punch when viewed from the punch side surface side; a blank holder disposed adjacent to the first curved portion as viewed from the press direction, the blank holder including: a holder top surface intersecting the press direction; a holder shoulder continuing from the holder top surface on the first curved portion side and including a second curved portion corresponding to the first curved portion; and a holder side surface continuing from the holder shoulder and connected to the holder top surface via the holder shoulder; a die disposed adjacent to the first curved portion as viewed from the pressing direction, the die including: a pressing surface facing the holder top surface; a die shoulder continuing from the pressing surface on the first curved portion side and including a third curved portion corresponding to the first curved portion; and a die side surface continuing from the die shoulder and connected to the pressing surface via the die shoulder; Equipped with When viewed from the pressing direction, at least one of the pressing surface and the holder top surface has a length along the extension direction of the punch shoulder that is shorter than the length of the punch shoulder.

2. The press forming apparatus according to claim 1, When viewed from the pressing direction, the length of the pressing surface in the direction in which the punch shoulder extends is greater than the length of the holder top surface in the direction in which the punch shoulder extends.

3. The press forming apparatus according to claim 1 or 2, further comprising: a pad facing the top surface of the punch; A press forming apparatus comprising:

4. The press forming apparatus according to claim 1, When viewed from the press direction, a distance between the die shoulder and the holder shoulder on a line perpendicular to the extension direction of the die shoulder varies along the die shoulder and is smallest at the third curved portion.

5. The press forming apparatus according to claim 4, When viewed from the pressing direction, the distance increases as the distance increases from the third curved portion.

6. The press forming apparatus according to claim 4, the die shoulder includes a convex portion that protrudes outward from the die as viewed from the die side surface side and is formed only of the third curved portion, When viewed from the pressing direction, the distance is greatest at an end of the third curved portion.

7. The press forming apparatus according to any one of claims 4 to 6, A press forming apparatus, wherein the line length of the portion of the holder shoulder where the gap is smallest when viewed from the press direction is 0.76 to 10.92 times the line length of the third curved portion.

8. A method for manufacturing a press-molded product, a step of clamping the blank between a die and a blank holder; a step of pressing the blank in a pressing direction with a punch; Equipped with the punch includes a punch top surface intersecting the pressing direction, a punch shoulder continuous with the punch top surface, and a punch side surface continuous with the punch shoulder and connected to the punch top surface via the punch shoulder, the punch shoulder includes a first curved portion that is curved concavely toward the inside of the punch when viewed from a side surface of the punch, the blank holder is disposed adjacent to the first curved portion when viewed from the pressing direction, The blank holder includes a holder top surface intersecting the press direction, a holder shoulder continuing to the holder top surface on the side of the first curved portion and including a second curved portion corresponding to the first curved portion, and a holder side surface continuing to the holder shoulder and connected to the holder top surface via the holder shoulder, the die is disposed adjacent to the first curved portion when viewed from the pressing direction, the die includes a pressing surface facing the holder top surface, a die shoulder that is continuous with the pressing surface on the side of the first curved portion and includes a third curved portion that corresponds to the first curved portion, and a die side that is continuous with the die shoulder and is connected to the pressing surface via the die shoulder, When viewed from the pressing direction, at least one of the pressing surface and the holder top surface has a length along the extension direction of the punch shoulder that is smaller than that of the punch shoulder.

9. The method for manufacturing a press-molded product according to claim 8, When viewed from the pressing direction, the length of the pressing surface in the extension direction of the punch shoulder is greater than the length of the holder top surface in the extension direction of the punch shoulder.

10. The method for producing a press-formed product according to claim 8, further comprising: a step of clamping the blank between a pad and the punch; A manufacturing method comprising:

11. The method for manufacturing a press-molded product according to claim 8, When viewed from the pressing direction, the distance between the die shoulder and the holder shoulder on a line perpendicular to the extension direction of the die shoulder varies along the die shoulder and is smallest at the third curved portion.

12. The method for manufacturing a press-molded product according to claim 11, When viewed from the pressing direction, the distance increases as the distance increases from the third curved portion.

13. The method for manufacturing a press-molded product according to claim 11, the die shoulder includes a convex portion that protrudes outward from the die as viewed from the die side surface side and is formed only of the third curved portion, When viewed from the pressing direction, the distance is greatest at an end of the third curved portion.

14. The method for manufacturing a press-molded product according to any one of claims 11 to 13, A manufacturing method in which the line length of the part of the holder shoulder where the gap is smallest when viewed from the pressing direction is 0.76 to 10.92 times the line length of the third curved portion.

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