WO2024209532A1 - Method for manufacturing press-molded article - Google Patents

Abstract

The present invention provides a method for manufacturing a press-molded article, the method comprising inserting a blank (200) between a die (20) and a blank holder (30) and pressing the blank (200) in a press direction (P) by means of a punch (10). When viewed from the press direction (P), an edge (24) of the die (20) includes a curved part (241) and an edge (201) of the blank (200) includes a curved part (211). The interval (w) between the blank edge curved part (211) and the edge (24) of the die (20) differs between one end portion (211a) and the other end portion (211b) of the blank edge curved part (211). The blank holder (30) holds a portion of the edge (201) of the blank (200) together with the die (20). The interval (d) between an edge (34) of the blank holder (30) and the edge (201) of the blank (200) held between the blank holder (30) and the die (20) changes along the edge (201) of the blank (200). The interval (d) is the largest at the blank edge curved part (211).

Description

Manufacturing method of press-molded products

This disclosure relates to a method for manufacturing press-molded products.

For example, press-formed products are used as structural components for automobiles. Press-formed products are manufactured by press-forming a blank using a punch and die. The blank is pressed into the die by the punch and formed into the desired shape.

Patent Document 1 discloses a method for manufacturing a press-formed product that uses a pad in addition to a punch and die. In Patent Document 1, the side of the punch and the side of the die that cooperates with it 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 of the punch. In this way, a press-formed product is formed from the blank.

Patent No. 6052478

In Patent Document 1, the edge of the die on the punch side includes a curved portion. The curved portion is a portion that is curved convexly toward the punch side in a plan view of the die. In this case, when the blank is pressed by the punch during press forming and the blank is drawn toward the edge of the die on the punch side, the portion of the blank that is drawn toward the curved portion is stretched in the extension direction of the curved portion. If the blank is stretched and its plate thickness is reduced, cracks may occur in the blank.

The objective of this disclosure is to prevent cracks from occurring in blanks during the manufacture of press-molded products.

The manufacturing method of the press-formed product according to the present disclosure includes sandwiching a blank between a die and a blank holder, and pushing the blank in the press direction with a punch. When viewed from the press direction, the punch-side edge of the die includes a die edge convex portion protruding toward the punch side, and the die edge convex portion includes a die edge curved portion that is convexly curved toward the punch side and extends with a radius of curvature of 400 mm or less. When viewed from the press direction, the edge of the blank includes a blank edge curved portion that is concavely curved toward the punch side and extends with a radius of curvature of 400 mm or less, the distance between the blank edge curved portion and the edge of the die on a perpendicular line in the extension direction of the edge of the die is different between one end and the other end of the blank edge curved portion, and the blank holder sandwiches a part of the edge of the blank together with the die. When viewed from the press direction, the edge of the blank holder on the punch side has a convex shape toward the edge of the die, and the distance between the edge of the die and the edge of the blank holder on a perpendicular line in the extension direction of the edge of the die changes along the edge of the blank holder. When viewed from the press direction, the distance between the edge of the blank holder and the edge of the blank sandwiched between the blank holder and the die, perpendicular to the direction of extension of the edge of the blank, varies along the edge of the blank. When viewed from the press direction, this distance is greatest at the blank edge curvature.

According to this disclosure, it is possible to suppress the occurrence of cracks in blanks during the production of press-molded products.

FIG. 1 is a schematic perspective view of a press molding apparatus used in the manufacturing method according to the first embodiment. FIG. 2 is a vertical sectional view of the press molding apparatus shown in FIG. FIG. 3 is a diagram showing a schematic diagram of the relationship between the punch, the die, and the blank holder included in the press forming apparatus shown in FIG. 1 when viewed from the pressing direction. FIG. 4A is a schematic diagram for explaining the method for manufacturing a press-formed product according to the first embodiment. FIG. 4B is a schematic diagram for explaining the method for manufacturing a press-formed product according to the first embodiment. FIG. 4C is a schematic diagram for explaining the manufacturing method of the press-formed product according to the first embodiment. FIG. 4D is a schematic diagram for explaining the method for manufacturing a press-formed product according to the first embodiment. FIG. 4E is a schematic diagram for explaining the manufacturing method of the press-formed product according to the first embodiment. FIG. 4F is a schematic diagram for explaining the manufacturing method of the press-formed product according to the first embodiment. FIG. 4G is a schematic diagram for explaining the manufacturing method of the press-formed product according to the first embodiment. FIG. 4H is a schematic diagram for explaining the manufacturing method of the press-formed product according to the first embodiment. FIG. 5A is a diagram illustrating a schematic relationship between a punch, a die, and a blank holder included in a press-forming apparatus used in a manufacturing method according to a second embodiment, when viewed from the press direction. FIG. 5B is a diagram illustrating a schematic relationship between a punch, a die, and a blank holder included in a modified press-forming apparatus used in the manufacturing method according to the second embodiment, when viewed from the pressing direction. FIG. 6 is a diagram showing a schematic view of the relationship between a punch, a die, and a blank holder included in a press-forming apparatus used in a manufacturing method according to the third embodiment, as viewed from the pressing direction. FIG. 7 is a diagram showing a schematic view of the relationship between a punch, a die, and a blank holder included in a press-forming apparatus used in a manufacturing method according to the fourth embodiment, when viewed from the pressing direction. FIG. 8 is a diagram showing a schematic view of the relationship between a punch, a die, and a blank holder included in a press-forming apparatus used in a manufacturing method according to the fifth embodiment, when viewed from the pressing direction. FIG. 9 is a diagram showing a schematic view of the relationship between a punch, a die, and a blank holder included in a press-forming apparatus used in a manufacturing method according to the sixth embodiment, as viewed from the pressing direction. FIG. 10 is a schematic perspective view of a press molding apparatus according to a modified example of the above embodiment. FIG. 11 is a vertical sectional view of the press molding apparatus shown in FIG. FIG. 12 is a diagram showing a punch and a die used in normal press molding, projected onto a plane perpendicular to the pressing direction. FIG. 13 is a diagram showing the analysis results when the forming is completed by pulling out the blank from between the die and the blank holder. FIG. 14 is a diagram showing the analysis results when forming is completed with the blank still sandwiched between the die and the blank holder.

When press forming is performed using a punch and a die, the blank is drawn toward the edge of the punch side of the die. When viewed from the press direction, the edge of the punch side of the die includes a curved portion that extends in a convex curve in the direction in which the blank is drawn, and press forming in which the blank is drawn toward this curved portion is called stretch flange forming. In stretch flange forming, as the blank is drawn toward the edge of the punch side of the die, the portion of the blank that is drawn toward the curved portion is stretched in a direction transverse to the direction in which it is drawn. On the other hand, if the edge of the punch side of the die includes a straight portion adjacent to the curved portion, the portion of the blank that is drawn toward the straight portion is not stretched in a direction transverse to the direction in which it is drawn. The blank is stretched in the region enclosed by the curved portion at the edge of the punch side of the die and the perpendicular lines to the edge of the punch side of the die that pass through both ends of the curved portion. These are common technical knowledge for those skilled in the art.

However, the inventors have noticed that stretching that does not fall under the above-mentioned stretching occurs on the edges of the blank. This is explained in detail below with reference to Figure 12.

Figure 12 shows the punch 91 and die 92 used in normal press forming, and the blank 200 to be press formed, projected onto a plane perpendicular to the press direction. As shown in Figure 12, the edge 920 on the punch 91 side of the die 92 includes a convex portion 921 that protrudes toward the punch 91 side. This convex portion 921 includes a curved portion 921a and straight portions 921b provided on both sides of the curved portion 921a. The edge 201 of the blank 200 includes a curved portion 211 (indicated by the thick line in Figure 12) that extends concavely toward the edge 920 on the punch 91 side of the die 92, and a straight portion 212 adjacent to the curved portion 211.

As shown by the arrow A1 in FIG. 12, during press forming, the edge 201 of the blank 200 is pulled toward the edge 920 of the die 92 on the punch 91 side. Specifically, each portion of the edge 201 of the blank 200 is pulled in the normal or perpendicular direction to the edge 920 of the die 92. When the blank 200 is pulled toward the straight portion 921b at the edge 920 of the die 92, the edge 201 of the blank 200 is not substantially deformed. On the other hand, when the curved portion 211 of the edge 201 of the blank 200 is pulled toward the curved portion 921a at the edge 920 of the die 92, the line length of the curved portion 211 at the edge 201 of the blank 200 is extended when comparing before and after press forming. In FIG. 12, the edge 201' of the blank 200 during press forming is shown by a dashed line, and the line length of the curved portion 211 at the edge 201' of the blank 200 during press forming is shown by a double arrow A2. Press forming increases the line length of the curved portion 211 at the edge 201 of the blank 200, so there is a risk that the edge 201 of the blank 200 may crack at the curved portion 211.

The problem of cracking of edge 201 of blank 200 occurs when curved portion 211 is inside convex portion 921 of edge 920 of die 92. More specifically, if curved portion 211 of edge 201 of blank 200 is in region S1 surrounded by convex portion 921 and perpendicular lines La, Lb of edge 920 of die 92 that pass through both end portions 920a of convex portion 921, edge 201 of blank 200 is stretched during press forming, making edge 201 prone to cracking. In particular, when the distance w1 between one end 211a of the curved portion 211 of the blank 200 and the edge 920 of the die 92 on the punch 91 side of the die 92 on the perpendicular line in the extension direction of the edge 920 of the die 92, is different from the distance w2 between the other end 211b of the curved portion 211 of the blank 200 and the edge 920 of the die 92, the curved portion 211 of the edge 201 of the blank 200 is stretched unevenly during press forming, and the curved portion 211 is likely to crack. Therefore, the inventors came up with the idea of applying a compressive stress in the thickness direction to the part of the edge 201 of the blank 200 that is stretched and reduced in thickness during press forming in order to suppress cracks in the blank 200, especially cracks in the edge 201, and completed a manufacturing method for a press-molded product according to the embodiment.

The manufacturing method of the press-formed product according to the embodiment includes sandwiching a blank between a die and a blank holder, and pushing the blank in the press direction with a punch. When viewed from the press direction, the punch-side edge of the die includes a die edge convex portion protruding toward the punch side, and the die edge convex portion includes a die edge curved portion that is convexly curved toward the punch side and extends with a radius of curvature of 400 mm or less. When viewed from the press direction, the edge of the blank includes a blank edge curved portion that is concavely curved toward the punch side and extends with a radius of curvature of 400 mm or less, and the distance between the blank edge curved portion and the edge of the die on a perpendicular line in the extension direction of the edge of the die is different between one end and the other end of the blank edge curved portion, and the blank holder sandwiches a part of the edge of the blank together with the die. When viewed from the press direction, the edge of the blank holder on the punch side has a convex shape toward the edge of the die, and the distance between the edge of the die and the edge of the blank holder on a perpendicular line in the extension direction of the edge of the die changes along the edge of the blank holder. When viewed from the press direction, the distance between the edge of the blank holder and the edge of the blank sandwiched between the blank holder and the die on a line perpendicular to the extension direction of the edge of the blank varies along the edge of the blank. When viewed from the press direction, this distance is greatest at the blank edge curvature (first configuration).

When the edge of the die on the punch side as viewed from the press direction includes a convex portion (die edge convex portion), this die edge convex portion includes a curved portion (die edge curved portion), and the edge of the blank includes a curved portion (blank edge curved portion) that is recessed toward the punch side, the sheet thickness of the blank edge becomes thinner as the blank is drawn toward the die edge curved portion. More specifically, if the distance between one end of the blank edge curved portion and the edge of the die in the distance on the perpendicular line between the edge of the blank and the edge of the punch side of the die in the extension direction of the edge of the die is different from the distance between the other end of the blank edge curved portion and the edge of the die, the blank edge curved portion is stretched unevenly during press forming, and the sheet thickness of the blank edge curved portion decreases.

In contrast, in the manufacturing method of the press-formed product according to the first configuration, when viewed from the press direction, the blank holder clamps a part of the edge of the blank together with the die, and the edge of the blank holder has a convex shape toward the edge of the die, the distance between the edge of the die and the edge of the blank holder on the perpendicular line in the extension direction of the edge of the die changes along the edge of the blank holder, and further, the distance between the edge of the blank holder on the punch side and the edge of the blank sandwiched between the blank holder and the die is maximum at the blank edge curved portion. Therefore, the blank edge curved portion that is drawn into the vicinity of the die edge convex portion is clamped by the die and blank holder, and compressive stress can be applied to the blank edge curved portion in the plate thickness direction until the end of the press forming. This makes it possible to suppress the occurrence of cracks in the blank, more specifically, cracks in the edge of the blank, in the manufacturing of press-formed products.

In the first configuration, the distance between the edge of the blank holder on the punch side and the edge of the blank sandwiched between the blank holder and the die changes along the extension direction of the edge of the blank, as viewed from the press direction. More specifically, the blank edge curved portion has a point where the distance between the edge of the blank holder and the blank holder is maximum, and the distance between the edge of the blank holder and the blank holder is small at other points. Therefore, during press forming, the blank is pressed by the die and the blank holder until the end of forming at the point where the distance between the edge of the blank holder and the blank edge curved portion is maximum, while the blank is not pressed until the end of forming at the point adjacent to the point where the distance is maximum. As a result, during press forming, material can be flowed from other points into the point where the distance between the edge of the blank holder is large, that is, the point where the plate thickness reduction is expected, and the plate thickness reduction of the edge of the blank can be mitigated. Therefore, the occurrence of cracks on the edge of the blank can be further suppressed.

In the above-mentioned method for manufacturing a press-molded product, the die edge convex portion may consist only of the die edge curved portion (second configuration).

In the above-mentioned method for manufacturing a press-molded product, when viewed from the pressing direction, the die edge convex portion may be composed of a curved die edge portion and a straight die edge portion that is continuous with one side of the curved die edge portion and extends with a radius of curvature greater than 400 mm (third configuration).

In the above-mentioned method for manufacturing a press-molded product, when viewed from the pressing direction, the die edge convex portion may be composed of a curved die edge portion and a straight die edge portion that is continuous with both sides of the curved die edge portion and extends with a radius of curvature greater than 400 mm (fourth configuration).

In the above-mentioned method for manufacturing a press-molded product, when viewed from the press direction, the line length of the edge of the blank sandwiched between the blank holder and the die may be 0.67 to 2.50 times the line length of the blank edge curved portion (fifth configuration). In this case, it is preferable that all of the edges of the blank sandwiched between the blank holder and the die are blank edge curved portions (sixth configuration). Alternatively, it is preferable that all of the blank edge curved portions are sandwiched between the blank holder and the die (seventh configuration).

Below, an embodiment of the present disclosure will be described with reference to the drawings. In each drawing, the same or equivalent components are given the same reference numerals, and the same description will not be repeated.

First Embodiment
[Press molding equipment]
FIG. 1 is a schematic perspective view of a press forming apparatus 100 used in the manufacturing method of a press-formed product according to the first embodiment. As shown in FIG. 1, the press forming apparatus 100 includes a punch 10, a die 20, and a blank holder 30. Although only one die 20 is shown with respect to the imaginary line CL in FIG. 1, the die 20 may be disposed on both sides of the punch 10. These dies 20 may be separate bodies or may be integrally formed. In this embodiment, the space between these dies 20 may be referred to as a die hole. The blank holder 30 is provided corresponding to each of the dies 20.

The punch 10 and the blank holder 30 are configured to be movable relative to the die 20 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 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. If the press direction P is a vertical direction, it is easy to place the blank 200 (FIG. 4A) described later between the punch 10 and the die 20.

Figure 2 is a vertical cross-sectional view of the press forming apparatus 100 shown in Figure 1. The vertical cross-section of the press forming apparatus 100 is a cross-section of the press forming apparatus 100 cut along a plane parallel to the press direction P and perpendicular to the longitudinal direction of the punch 10. The direction perpendicular to the press direction P on the vertical cross-section of the press forming apparatus 100 is called the width direction of the press forming apparatus 100. As with Figure 1, Figure 2 shows only one side of the press forming apparatus 100 relative to the imaginary line CL. The imaginary line CL is, for example, the center line of the press forming apparatus 100 in the width direction.

As shown in FIG. 2, the punch 10 includes a punch top surface 11, a punch shoulder 12, and a punch side surface 13.

The punch top surface 11 is a surface that intersects with the press direction P. The punch top surface 11 may be perpendicular to the press direction P. The punch top surface 11 extends substantially in the width direction in a vertical cross-sectional view of the press forming apparatus 100. The punch shoulder 12 is continuous with an end of the punch top surface 11. The punch shoulder 12 has, for example, a substantially arc shape in a vertical cross-sectional view of the press forming apparatus 100. If the punch shoulder 12 is sharp, there is a risk that the punch shoulder 12 will cut the blank 200 (FIG. 4A) during press forming. The radius of curvature of the punch shoulder 12 may be 1.0 mm or more. The punch side surface 13 is connected to the punch top surface 11 via the punch shoulder 12. The punch side surface 13 extends from the punch shoulder 12 in the press direction P in a vertical cross-sectional view of the press forming apparatus 100. In a vertical 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.

The die 20 includes a plate pressing surface 21, a die shoulder 22, and a die side surface 23. The plate pressing surface 21 of the die 20 is, for example, a flat surface substantially perpendicular to the press direction P. The die shoulder 22 is continuous with the end of the plate pressing surface 21 on the punch 10 side in a vertical cross-sectional view of the press forming apparatus 100. The die shoulder 22 has, for example, a substantially arc shape in a vertical cross-sectional view of the press forming apparatus 100. If the die shoulder 22 is sharp, there is a risk that the blank 200 (FIG. 4A) will be cut by the die shoulder 22 during press forming. The radius of curvature of the die shoulder 22 may be 1.0 mm or more. The die side surface 23 is connected to the plate pressing surface 21 via the die shoulder 22. The die side surface 23 extends from the die shoulder 22 in the press direction P in a vertical cross-sectional view of the press forming apparatus 100. The die side surface 23 has a shape corresponding to the punch side surface 13.

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

The blank holder 30 has a blank pressing surface 31 that faces the blank pressing surface 21 of the die 20 in the press direction P. The blank pressing surface 31 is, for example, a flat surface that is substantially perpendicular to the press direction P. The holder shoulder 32 is continuous with the end of the blank pressing surface 31 on the punch 10 side in a vertical cross-sectional view of the press forming apparatus 100. The holder side surface 33 is connected to the blank pressing surface 31 via the holder shoulder 32. The holder side surface 33 extends from the holder shoulder 32 in the press direction P in a vertical cross-sectional view of the press forming apparatus 100. The holder side surface 33 faces the punch side surface 13 in the width direction of the press forming apparatus 100.

The press molding device 100 may have a shape that is symmetrical about the width center line CL when viewed in vertical cross section, or may have a shape that is asymmetrical about the width center line CL.

FIG. 3 is a diagram showing the relationship between the punch 10, the die 20, and the blank holder 30 when viewed from the press direction P. In other words, FIG. 3 is a diagram showing the punch 10, the die 20, and the blank holder 30 when projected onto a plane perpendicular to the press direction P. In FIG. 3, the edge 14 of the punch 10 is shown by a dotted line, the edge 24 of the die 20 is shown by a dashed line, and the edge 34 of the blank holder 30 is shown by a broken line. To make it easier to distinguish between the die 20 and the blank holder 30, the blank holder 30 is hatched. Also, in FIG. 3, the edge 14 of the punch 10 is shown by a dashed line. The edge 14 of the punch 10 in FIG. 3 is the punch side surface 13 that is on the same plane as the sheet pressing surface 21 of the die 20.

As shown in FIG. 3, when viewed from the press direction P, the edge 14 of the punch 10 on the die 20 side extends along the edge 24 of the die 20 on the punch 10 side. The edge 24 of the die 20 is a die shoulder 22. The edge 14 of the punch 10 has a shape corresponding to the edge 24 of the die 20. For example, when viewed from the press direction P, the edge 14 of the punch 10 is substantially parallel to the edge 24 of the die 20 over the entirety. The clearance between the edge 14 of the punch 10 and the edge 24 of the die 20 when viewed from the press direction P is equal to or greater than the plate thickness of the blank, which is the material for press molding, so as not to impede the relative movement of the punch 10 and the die 20 in the press direction P. When viewed from the press direction P, the edge 24 of the die 20 includes a die edge protrusion 240 protruding toward the punch 10 side. The die edge protrusion 240 includes a die edge curved portion 241 and die edge straight portions 242 and 243.

When viewed from the press direction P, the die edge curved portion 241 is curved convexly toward the punch 10. When viewed from the press direction P, the die edge curved portion 241 extends with a radius of curvature of 400 mm or less. The die edge curved portion 241 may have a constant radius of curvature or may have a variable radius of curvature. In this disclosure, when viewed from the press direction P, for each point arranged at intervals of 5.0 mm on the edge 24 (die edge convex portion 240) of the die 20, the radius of curvature of an arc passing through the three points, that is, the point and the two adjacent points, is measured, and the section with a radius of curvature of 400 mm or less is regarded as the die edge curved portion 241, and the section with a radius of curvature greater than 400 mm is regarded as a non-curved portion (straight portion).

The die edge straight portions 242, 243 are provided continuously on both ends of the die edge curved portion 241. When viewed from the press direction P, the die edge straight portions 242, 243 extend from the die edge curved portion 241 so as to move away from each other as they move away from the die edge curved portion 241. When viewed from the press direction P, the die edge straight portions 242, 243 may be located on the tangents to both ends of the die edge curved portion 241.

The blank holder 30 is provided, for example, to correspond to only a portion of the edge 24 of the die 20. When viewed from the press direction P, it is preferable that at least a portion of the blank holder 30 is disposed within the die edge convex portion 240. More preferably, the blank holder 30 is disposed at a position corresponding to the die edge curved portion 241 when viewed from the press direction P. In this embodiment, the blank holder 30 has a shape that is substantially tapered toward the punch 10 when viewed from the press direction P. In the example shown in FIG. 3, the blank holder 30 has a roughly triangular shape when viewed from the press direction P. However, the shape of the blank holder 30 is not limited to this.

In this embodiment, the edge 34 of the blank holder 30 on the punch 10 side has a convex shape toward the edge 24 of the die 20 (e.g., the die edge convex portion 240 or the die edge curved portion 241) when viewed from the press direction P. When viewed from the press direction P, the distance between the edge 24 of the die 20 and the edge 34 of the blank holder 30 changes along the edge 34 of the blank holder 30. That is, the distance between the edge 24 of the die 20 and the edge 34 of the blank holder 30 is not constant over the entire length of the edge 24 of the die 20. This distance is the distance between the edge 24 of the die 20 and the edge 34 of the blank holder 30 on a perpendicular line to the extension direction of the edge 24 of the die 20 when viewed from the press direction P. In other words, this distance is the distance from the edge 24 of the die 20 to the edge 34 of the blank holder 30 in the normal direction of the curved portion 241 or the perpendicular direction of the straight portions 242, 243 when viewed from the press direction P. The perpendicular line in the extension direction of the edge 24 of the die 20 is a perpendicular line or normal line to the edge of the die shoulder 22 (FIG. 2) on the punch 10 side when viewed from the press direction P. The perpendicular line in the extension direction of the edge 24 of the die 20 roughly coincides with the direction in which the blank is drawn toward the die hole when the blank is formed using the press forming device 100 (FIGS. 1 and 2). The edge 34 of the blank holder 30 is the edge of the holder shoulder 32 (FIG. 2) on the punch 10 side when viewed from the press direction P.

In the example shown in Figure 3, when viewed from the press direction P, the distance between the edge 24 of the die 20 and the edge 34 of the blank holder 30 increases as it moves away from the die edge curved portion 241.

[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. 4A to 4H.

As shown in FIG. 4A, in manufacturing a press-formed product, first, a blank 200 is prepared. The blank 200 can be obtained, for example, by blanking a rolled steel plate. The blank 200 is formed, for example, in the shape of the target press-formed product when it is unfolded. That is, the blank 200 has an edge 201 in the shape of the target press-formed product when it is unfolded. The shape of the target press-formed product when it is unfolded can be obtained, for example, by using a function of deriving the blank shape before molding from the shape of the molded product in finite element analysis software that analyzes press molding. 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 980 MPa or more, 1180 MPa or more, or 1300 MPa or more. The thickness of the blank 200 may be, for example, 0.4 mm or more and 6.0 mm or less, or 1.0 mm or more and 4.0 mm or less.

The manufacturing method for the press-formed product includes clamping the blank 200 between the die 20 and the blank holder 30, and pressing the blank 200 in the pressing direction P with the punch 10.

As shown in FIG. 4B, first, the blank 200 is placed between the punch 10 and the blank holder 30, and the die 20. For example, the blank 200 is placed on the punch top surface 11 and the plate pressing surface 31 of the blank holder 30. Alternatively, the blank 200 may be placed on the plate pressing surface 21 (FIG. 2) of the die 20.

After placing the blank 200 between the punch 10 and blank holder 30 and the die 20, as shown in FIG. 4C, the blank holder 30 and the die 20 are brought relatively close to each other in the press direction P, and the blank 200 is sandwiched and pressed between the plate pressing surface 21 of the die 20 and the plate pressing surface 31 of the blank holder 30.

Here, we will explain the relationship between the die 20, blank holder 30, and blank 200 when viewed from the press direction P, as shown in Figure 4D. Figure 4D is a schematic diagram showing the die 20, blank holder 30, and blank 200 when projected onto a plane perpendicular to the press direction P before press forming. In Figure 4D, the edge 24 of the die 20 is shown by a dashed line, the edge 34 of the blank holder 30 is shown by a dashed line, and the edge 201 of the blank 200 is shown by a solid line. The punch 10 is omitted in Figure 4D.

When viewed from the press direction P, the edge 201 of the blank 200 extends in roughly the same direction as the edge 24 of the die 20. The edge 201 of the blank 200 includes a blank edge curved portion 211 (thick line portion in FIG. 4D) and blank edge straight portions 212, 213. The blank edge straight portions 212, 213 are provided continuously at both ends of the blank edge curved portion 211. Specifically, the distance w between the blank edge curved portion 211 and the edge 24 of the die 20 changes along the extension direction of the blank edge curved portion 211. In other words, the distance w between the blank edge curved portion 211 and the edge 24 of the die 20 is not constant over the entire length of the blank edge curved portion 211. This distance w is the distance between the blank edge curved portion 211 and the edge 24 of the die 20 on a perpendicular line to the extension direction of the edge 24 of the die 20 when viewed from the press direction P. In other words, the interval w is the distance from the blank edge curved portion 211 to the edge 24 of the die 20 in the normal direction of the curved portion 241 of the die 20 or in the perpendicular direction of the straight portions 242 and 243 when viewed from the press direction P. The interval w between the blank edge curved portion 211 and the edge 24 of the die 20 is different between one end 211a and the other end 211b of the blank edge curved portion 211. In the example shown in FIG. 4D, the interval w1 between one end 211a of the blank edge curved portion 211 and the edge 24 of the die 20 is larger than the interval w2 between the other end 211b of the blank edge curved portion 211 and the edge 24 of the die 20.

Furthermore, the blank edge straight portion 212 extends parallel to the die edge straight portion 242, and the blank edge straight portion 213 extends parallel to the die edge straight portion 243. The distance between the blank edge straight portion 212 and the die edge straight portion 242 is greater than the distance between the blank edge straight portion 213 and the die edge straight portion 243. However, the blank edge straight portion 212 may be inclined with respect to the die edge straight portion 242. The blank edge straight portion 213 may be inclined with respect to the die edge straight portion 243.

In the example shown in FIG. 4D, the blank edge curved portion 211 is disposed at a position corresponding to the die edge curved portion 241 when viewed from the press direction P, for example. When viewed from the press direction P, the blank edge curved portion 211 is curved concavely toward the punch 10 (FIG. 3). When viewed from the press direction P, the blank edge curved portion 211 extends with a radius of curvature of 400 mm or less. The blank edge curved portion 211 may have a constant radius of curvature or may have a variable radius of curvature. In this disclosure, when viewed from the press direction P, for each point arranged at intervals of 5.0 mm on the edge 201 of the blank 200, the radius of curvature of the arc passing through the three points, that is, the point and the points located on both sides of the point, is measured, and the section with a radius of curvature of 400 mm or less is regarded as the blank edge curved portion 211, and the section with a radius of curvature larger than 400 mm is regarded as a non-curved portion (straight line portion).

When viewed from the press direction P, the blank edge straight portions 212, 213 extend from the blank edge curved portion 211 so as to move away from each other as they move away from the blank edge curved portion 211. When viewed from the press direction P, the blank edge straight portions 212, 213 may be located on the tangents of both ends 211a, 211b of the blank edge curved portion 211.

When viewed from the press direction P, the blank edge curved portion 211 is disposed in an area S1 surrounded by two perpendicular lines La, Lb and the die edge convex portion 240. When viewed from the press direction, the perpendicular lines La, Lb are perpendicular lines to the die edge convex portion 240 passing through both ends 240a, 240b of the die edge convex portion 240. In this embodiment, one end 240a of the die edge convex portion 240 is an end of the die edge straight portion 242 that continues to the die edge curved portion 241, and the other end 240b of the die edge convex portion 240 is an end of the die edge straight portion 243 that continues to the die edge curved portion 241. For example, the blank edge curved portion 211 may be disposed in an area surrounded by a straight line that passes through both ends 240a, 240b of the die edge convex portion 240 and the die edge convex portion 240 when viewed from the press direction P.

When the distance w between the blank edge curved portion 211 and the edge 24 of the die 20 is different between one end 211a and the other end 211b of the blank edge curved portion 211, deformation as shown in FIG. 12 occurs. In order to deal with deformation as shown in FIG. 12, in this embodiment, the blank holder 30 is arranged relative to the die 20 and blank 200 as follows.

When viewed from the press direction P, the blank holder 30 is arranged so as to sandwich a portion of the edge 201 of the blank 200 together with the die 20. More specifically, in press forming, the blank holder 30 sandwiches at least a portion of the blank edge curved portion 211 together with the die 20. For example, the edge 34 of the blank holder 30, like the blank edge curved portion 211, is arranged within the region S1 surrounded by the die edge convex portion 240 and its perpendicular lines La, Lb. When viewed from the press direction P, at least a portion of the edge 34 of the blank holder 30 is arranged between the die edge convex portion 240 and the blank edge curved portion 211.

In this embodiment, when viewed from the press direction P, the edge 201 of the blank 200 intersects with the edge 34 of the blank holder 30 on the punch 10 (Figure 4C) side at both ends 211a, 211b of the blank edge curved portion 211. Therefore, the entire blank edge curved portion 211 is sandwiched between the blank holder 30 and the die 20. In addition, the entire edge 201 of the blank 200 sandwiched between the blank holder 30 and the die 20 is the blank edge curved portion 211.

When viewed from the press direction P, the distance d between the edge 34 of the blank holder 30 on the punch 10 (FIG. 3) side and the edge 201 of the blank 200 sandwiched between the blank holder 30 and the die 20 changes along the edge 201 of the blank 200. In other words, the distance d between the edge 34 of the blank holder 30 and the portion of the edge 201 of the blank 200 sandwiched between the blank holder 30 and the die 20 is not constant over the entire length of that portion. The distance d is the distance between the edge 34 of the blank holder 30 and the edge 201 of the blank 200 on a line perpendicular to the extension direction of the edge 201 of the blank 200 when viewed from the press direction P. In other words, the distance d is the distance from the edge 34 of the blank holder 30 to the edge 201 of the blank 200 in the perpendicular or normal direction of the edge 201 of the blank 200 when viewed from the press direction P.

When viewed from the press direction P, the distance d between the edge 34 of the blank holder 30 and the edge 201 of the blank 200 is largest at the blank edge curved portion 211. In other words, when viewed from the press direction P, if a position where the distance between the edge 34 of the blank holder 30 is largest is selected in the portion of the edge 201 of the blank 200 that is sandwiched between the blank holder 30 and the die 20 and a perpendicular line is drawn to the edge 201 of the blank 200, the perpendicular line will pass through the blank edge curved portion 211.

When viewed from the press direction P, the line length of the edge 201 of the blank 200 sandwiched between the blank holder 30 and the die 20 can be, for example, 0.67 to 2.50 times the line length of the blank edge curved portion 211. Here, each line length is the line length of the blank 200 before press forming. The line length of the blank edge curved portion 211, that is, the length in the extension direction of the blank edge curved portion 211, can be the product of the included angle θ and the radius of curvature of the blank edge curved portion 211. The included angle θ is the angle formed by the tangents to both end portions 211a, 211b of the blank edge curved portion 211 when viewed from the press direction P. The included angle θ may be 1/3π (rad) or more and 2/3π (rad) or less. If the radius of curvature of the blank edge curved portion 211 varies, the radius of curvature of the blank edge curved portion 211 can be, for example, the average value of the radii of curvature measured at 5.0 mm intervals as described above.

In the example shown in FIG. 4D, when viewed from the press direction P, the distance d between the punch side edge 34 of the blank holder 30 and the edge 201 of the blank 200 sandwiched between the blank holder 30 and the die 20 is maximum at the bottom of the blank edge curved portion 211. The distance d becomes smaller as it moves away from the bottom of the blank edge curved portion 211. In other words, the distance d changes within the range of the edge 201 of the blank 200 sandwiched between the blank holder 30 and the die 20. However, the distance d does not necessarily have to be maximum at the bottom of the blank edge curved portion 211.

As shown in FIG. 4E, while the blank 200 is sandwiched between the die 20 and the blank holder 30, the die 20 and the punch 10 are brought relatively closer together in the press direction P. This causes the blank 200 to be pushed into the die 20 side (die hole) by the punch 10. As the blank 200 is pushed by the punch 10, it is drawn toward the die hole. As the punch 10 pushes the blank 200, the edge 201 of the blank 200 is drawn toward the die hole. In FIG. 4E, the direction in which the blank 200 is drawn is indicated by arrow D. In this embodiment, the pushing (forming) by the punch 10 is completed after the edge 201 of the blank 200 is completely pulled out from 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 300, for example, as shown in FIG. 4F. The press-formed product 300 includes a top plate 301, a ridge portion 302, and a wall 303.

In the example shown in FIG. 4F, in a plan view of the top plate 301 of the press-molded product 300 viewed vertically, the side edges of the top plate 301 have a concave portion on the inside in the width direction. The top plate 301 is formed so that the width of the central portion in the longitudinal direction is smaller than the width of both ends in the longitudinal direction. In other words, the top plate 301 is formed so that the central portion in the longitudinal direction is narrowed inward in a plan view. The top plate 301 may have a flat shape overall, or may have an uneven shape in part. The top plate 301 may have a through hole formed therein.

A ridge portion 302 is provided continuously on the side edge in the width direction of the top plate 301. The wall 303 is connected to the side edge of the top plate 301 via the ridge portion 302. The wall 303 is provided so as to be continuous with the ridge portion 302 and to stand up from the top plate 301. The ridge portion 302 and the wall 303 extend along the side edge of the top plate 301. In the example shown in FIG. 4F, the height of the wall 303 is not constant. Specifically, the height of the wall 303 is lowered in a part of the side edge of the top plate 301. The lowered part of the wall 303 corresponds to the blank edge straight portion 213. In this case, the height of the wall 303 may be uniformed by trimming a part of the wall 303 after press molding using the press molding device 100.

As described above, in the example shown in FIG. 4E, the pushing (forming) by the punch 10 is completed after the edge 201 of the blank 200 is completely pulled out from between the die 20 and the blank holder 30. However, as shown in FIG. 4G, forming may be completed with the edge 201 of the blank 200 still sandwiched between the die 20 and the blank holder 30. In this case, the press-formed product 300 includes a top plate 301, a ridge portion 302, a wall 303, and a flange 304, as shown in FIG. 4H. The height of the wall 303 is constant along the side edge of the top plate 301, and the flange 304 protrudes from the wall 303. The amount of protrusion of the flange 304 is not constant, and is smaller in some parts. The portion of the flange 304 where the amount of protrusion is smaller corresponds to the blank edge straight portion 213 described above.

The tensile strength of the press-formed product 300 is, for example, 440 MPa or more. The tensile strength of the press-formed product 300 may be 590 MPa or more, or 780 MPa or more. The tensile strength of the press-formed product 300 may be 980 MPa or more, 1180 MPa or more, or 1300 MPa or more. The plate thickness of the press-formed product 300 may be, for example, 0.4 mm or more and 6.0 mm or less, or 1.0 mm or more and 4.0 mm or less.

The press-formed product 300 can be used, for example, as an automobile part. The press-formed product 300 may be an automobile body part, chassis part, or panel part. Examples of body parts include side sills, roof side rails, front pillars, center pillars, lock pillars, kickline forces, side members, etc. The chassis parts are, for example, suspension arm parts or link parts. Examples of arm parts or link parts include subframes, lower arms, upper arms, trailing arms, etc. Examples of panel parts include door inner panels, side panels, floor panels, etc.

In this embodiment, processing marks such as pressing marks or abrasion marks remain at the locations of the press-formed product 300 that are locally pressed by the blank holder 30. These processing marks do not adversely affect the mechanical properties of the press-formed product. For example, in the press-formed product 300 of Figure 4F, processing marks remain on the back side of the flange 303, which is not exposed in the figure.

[effect]
When viewed from the press direction P, the blank edge curved portion 211 is positioned within a region S1 surrounded by the die edge convex portion 240 and two perpendicular lines La, Lb passing through both end portions 240a, 240b of the die edge convex portion 240, and the distance w between the blank edge curved portion 211 and the edge 24 of the die 20 is different between one end portion 211a and the other end portion 211b of the blank edge curved portion 211, then as the blank 200 is pulled toward the die edge curved portion 241, the line length of the blank edge curved portion 211 expands non-uniformly and the plate thickness decreases non-uniformly. However, in the manufacturing method of the press-formed product according to the present embodiment, the edge 34 of the blank holder 30 has a convex shape toward the edge 24 of the die 20, the distance between the edge 24 of the die 20 and the edge 34 of the blank holder 30 changes along the edge 34 of the blank holder 30, and the distance d between the edge 34 of the blank holder 30 on the punch 10 side and the edge 201 of the blank 200 sandwiched between the blank holder 30 and the die 20 is maximum at the blank edge curved portion 211. Therefore, when the blank 200 is pushed into the die hole by the punch 10 to be formed, the blank edge curved portion 211 can be clamped until the end of forming to apply compressive stress in the plate thickness direction. This makes it possible to suppress the occurrence of cracks in the blank 200, particularly cracks in the edge 201 of the blank 200, in the manufacture of the press-formed product 300.

When forming the blank 200 into the press-formed product 300, in order to continue pressing the blank edge curved portion 211 until the end of the forming process, it is desirable to press the blank edge curved portion 211 with the die 20 and the blank holder 30 up to the vicinity of the die edge curved portion 241. On the other hand, from the viewpoint of material flow, if the die 20 and the blank holder 30 do not press the periphery of the thickness reduction portion of the blank 200, material will flow into the thickness reduction portion of the blank 200, and the reduction in the thickness of the blank 200 can be mitigated. Therefore, in this embodiment, the distance d between the edge 34 of the blank holder 30 and the edge 201 of the blank 200 sandwiched between the blank holder 30 and the die 20 is changed along the extension direction of the edge 201. The distance d is maximum at the blank edge curved portion 211. As a result, during press forming, the blank 200 is pressed by the die 20 and the blank holder 30 until the end of forming at the blank edge curved portion 211 where the distance d is maximum, while the blank 200 is not pressed until the end of forming at the portion adjacent to the blank edge curved portion 211. Therefore, compressive stress can be applied to the blank edge curved portion 211 in the plate thickness direction and material can be allowed to flow in. Therefore, the occurrence of cracks in the edge 201 of the blank 200 can be suppressed.

In this embodiment, when viewed from the press direction P, it is preferable that the line length of the edge 201 of the blank 200 sandwiched between the blank holder 30 and the die 20 is 0.67 to 2.50 times the line length of the blank edge curved portion 211. This makes it possible to effectively suppress cracking of the blank 200.

Second Embodiment
FIG. 5A is a diagram of a press forming apparatus 100A used in the manufacturing method of a press-formed product according to the second embodiment, and is a diagram showing the relationship between the die 20A, the blank holder 30, and the blank 200A when viewed from the press direction P. In other words, FIG. 5A is a schematic diagram showing the die 20A, the blank holder 30, and the blank 200A when projected onto a plane perpendicular to the press direction P before press forming. In FIG. 5A, the edge 24 of the die 20A is shown by a dashed line, the edge 34 of the blank holder 30 is shown by a dashed line, and the edge 201 of the blank 200A is shown by a solid line. In addition, in order to make it easier to understand the range of the blank edge curved portion 211 at the edge 201 of the blank 200A, the blank edge curved portion 211 is shown by a thick line. In FIG. 5A, the punch is omitted.

The press forming apparatus 100A of this embodiment has basically the same configuration as the press forming apparatus 100 of the first embodiment (FIGS. 1 to 3). However, the press forming apparatus 100A of this embodiment differs from the press forming apparatus 100 of the first embodiment in the shape of the edge 24 of the die 20A and the edge 201 of the blank 200A.

As shown in FIG. 5A, when viewed from the press direction P, the edge 24 of the die 20A includes a die edge convex portion 240A. The die edge convex portion 240A is composed of a die edge curved portion 241 and a die edge straight portion 243. The die edge straight portion 243 is provided continuous to one side of the die edge curved portion 241. Although not substantially involved in the molding of the press-molded product, the die edge convex portion 240A may include a die edge straight portion 242 (FIGS. 3 and 4D) that is continuous to the die edge straight portion 243 on the opposite side of the die edge curved portion 241, similar to the die edge convex portion 240 of the first embodiment.

The edge 201 of the blank 200A is provided to correspond to the die edge protrusion 240A. Specifically, the edge 201 of the blank 200A includes a blank edge curved portion 211 and a blank edge straight portion 213. The edge 201 of the blank 200A further includes a blank edge side portion 214. The blank edge side portion 214 extends from one end 211a of the blank edge curved portion 211 toward one end 240Aa of the die edge protrusion 240A. The blank edge straight portion 213 is provided continuously with the other end 211b of the blank edge curved portion 211, as in the blank 200A of the first embodiment. The distance w between the blank edge curved portion 211 and the edge 24 of the die 20 is different between the one end 211a and the other end 211b of the blank edge curved portion 211. In the blank 200A, the blank edge curved portion 211 is located in an area S1 surrounded by the die edge convex portion 240A and two perpendicular lines La, Lb passing through both ends 240Aa, 240Ab of the die edge convex portion 240A.

In this embodiment, as in the first embodiment, all of the blank edge curved portions 211 are sandwiched between the blank holder 30 and the die 20A. Also, all of the edges 201 of the blank 200A sandwiched between the blank holder 30 and the die 20A are blank edge curved portions 211. However, all of the blank edge curved portions 211 do not necessarily have to be sandwiched between the blank holder 30 and the die 20A. Also, all of the edges 201 of the blank 200A sandwiched between the blank holder 30 and the die 20A do not necessarily have to be blank edge curved portions 211. It is sufficient that the blank holder 30 and the die 20A are configured to sandwich at least a portion of the blank edge curved portions 211.

As in the first embodiment, when viewed from the press direction P, the distance d between the punch side edge 34 of the blank holder 30 and the edge 201 of the blank 200A sandwiched between the blank holder 30 and the die 20A on the perpendicular line to the extension direction of the edge 201 of the blank 200A varies along the edge 201 of the blank 200A. This distance d is largest at the blank edge curved portion 211.

The manufacturing method using the press molding device 100A in this embodiment can achieve the same effects as the first embodiment.

[Modification]
FIG. 5B is a diagram of a modified press forming apparatus 100B used in the manufacturing method of a press-formed product according to the second embodiment, and is a diagram showing the relationship between the die 20B, the blank holder 30, and the blank 200B when viewed from the press direction P. In other words, FIG. 5B is a schematic diagram showing the die 20B, the blank holder 30, and the blank 200B when projected onto a plane perpendicular to the press direction P before press forming. In FIG. 5B, the edge 24 of the die 20B is shown by a dashed line, the edge 34 of the blank holder 30 is shown by a dashed line, and the edge 201 of the blank 200B is shown by a solid line. In addition, in order to make it easier to understand the range of the blank edge curved portion 211 at the edge 201 of the blank 200B, the blank edge curved portion 211 is shown by a thick line. In FIG. 5B, the punch is omitted.

As shown in FIG. 5B, when viewed from the press direction P, the edge 24 of the die 20B includes a die edge convex portion 240B. The die edge convex portion 240B is composed of a die edge curved portion 241 and die edge straight portions 242, 243. The die edge straight portions 242, 243 are provided continuously at both ends of the die edge curved portion 241. The die edge straight portion 243 is shorter than the die edge straight portion 243 of the first embodiment (FIGS. 3 and 4D). Although it is not substantially involved in the molding of the press-molded product, the die edge straight portion 243 of the die edge convex portion 240B may be of the same length as the die edge straight portion 243 of the first embodiment.

The edge 201 of the blank 200B is provided to correspond to the die edge protrusion 240B. Specifically, the edge 201 of the blank 200B includes a blank edge curved portion 211 and a blank edge straight portion 212. The edge 201 of the blank 200B further includes a blank edge side portion 215. The blank edge side portion 215 extends from the other end 211b of the blank edge curved portion 211 toward the other end 240Bb of the die edge protrusion 240B. The blank edge straight portion 212 is provided continuously with one end 211a of the blank edge curved portion 211, as in the blank 200A of the first embodiment. The distance w between the blank edge curved portion 211 and the edge 24 of the die 20 is different between the one end 211a and the other end 211b of the blank edge curved portion 211.

The manufacturing method using the press molding device 100B in this modified example can achieve the same effects as the first embodiment.

Third Embodiment
FIG. 6 is a diagram of a press forming apparatus 100C used in the manufacturing method of a press-formed product according to the third embodiment, and is a diagram that shows a relationship between a die 20C, a blank holder 30, and a blank 200C when viewed from the press direction P. In other words, FIG. 6 is a schematic diagram showing the die 20C, the blank holder 30, and the blank 200C when projected onto a plane perpendicular to the press direction P before press forming. In FIG. 6, the edge 24 of the die 20C is shown by a dashed line, the edge 34 of the blank holder 30 is shown by a dashed line, and the edge 201 of the blank 200C is shown by a solid line. In addition, in order to make it easier to understand the range of the blank edge curved portion 211 at the edge 201 of the blank 200C, the blank edge curved portion 211 is shown by a thick line. In FIG. 6, the punch is omitted.

The press forming apparatus 100C of this embodiment has basically the same configuration as the press forming apparatus 100 of the first embodiment (FIGS. 1 to 3). However, the press forming apparatus 100C of this embodiment differs from the press forming apparatus 100 of the first embodiment in the shape of the edge 24 of the die 20C and the edge 201 of the blank 200C.

As shown in FIG. 6, when viewed from the press direction P, the edge 24 of the die 20C includes a die edge convex portion 240C. The die edge convex portion 240C is composed only of a die edge curved portion 241. Although not substantially involved in the molding of the press-molded product, the die edge convex portion 240C may also include die edge straight portions 242, 243 (FIGS. 3 and 4D) that are continuous with both ends of the die edge curved portion 241, similar to the die edge convex portion 240 of the first embodiment.

The edge 201 of the blank 200C is provided to correspond to the die edge protrusion 240C. Specifically, the edge 201 of the blank 200A includes a blank edge curved portion 211. The edge 201 of the blank 200C further includes blank edge side portions 214, 215. The blank edge side portion 214 extends from one end 211a of the blank edge curved portion 211 toward one end 240Ca of the die edge protrusion 240C. The blank edge side portion 215 extends from the other end 211b of the blank edge curved portion 211 toward the other end 240Cb of the die edge protrusion 240C. The distance w between the blank edge curved portion 211 and the edge 24 of the die 20 is different between the one end 211a and the other end 211b of the blank edge curved portion 211. In blank 200C, blank edge curved portion 211 is located within region S1 surrounded by two perpendicular lines La, Lb passing through both ends 240Ca, 240Cb of die edge convex portion 240C and die edge convex portion 240C.

In this embodiment, as in the first embodiment, all of the blank edge curved portions 211 are sandwiched between the blank holder 30 and the die 20C. Also, all of the edges 201 of the blank 200C sandwiched between the blank holder 30 and the die 20C are blank edge curved portions 211. However, all of the blank edge curved portions 211 do not necessarily have to be sandwiched between the blank holder 30 and the die 20C. Also, all of the edges 201 of the blank 200C sandwiched between the blank holder 30 and the die 20C do not necessarily have to be blank edge curved portions 211. It is sufficient that the blank holder 30 and the die 20C are configured to sandwich at least a portion of the blank edge curved portions 211.

As in the first embodiment, when viewed from the press direction P, the distance d between the punch side edge 34 of the blank holder 30 and the edge 201 of the blank 200C sandwiched between the blank holder 30 and the die 20C on the perpendicular line to the extension direction of the edge 201 of the blank 200C varies along the edge 201 of the blank 200C. This distance d is largest at the blank edge curved portion 211.

The manufacturing method using the press molding device 100C in this embodiment can achieve the same effects as the first embodiment.

Fourth Embodiment
FIG. 7 is a diagram of a press forming apparatus 100D used in a manufacturing method of a press-formed product according to a fourth embodiment, and is a diagram showing a relationship between the die 20, the blank holder 30D, and the blank 200 when viewed from the press direction P. In other words, FIG. 7 is a schematic diagram showing the die 20, the blank holder 30D, and the blank 200 when projected onto a plane perpendicular to the press direction P before press forming. In FIG. 7, the edge 24 of the die 20 is shown by a dashed line, the edge 34D of the blank holder 30D is shown by a dashed line, and the edge 201 of the blank 200 is shown by a solid line. In addition, in order to make it easier to understand the range of the blank edge curved portion 211 at the edge 201 of the blank 200, the blank edge curved portion 211 is shown by a thick line. In FIG. 7, the punch is omitted.

The press forming apparatus 100D of this embodiment has basically the same configuration as the press forming apparatus 100 of the first embodiment (FIGS. 1 to 3). However, the press forming apparatus 100D of this embodiment differs from the press forming apparatus 100 of the first embodiment in the blank holder 30D. The width of the blank holder 30D in this embodiment is smaller than that of the blank holder 30 in the first embodiment (FIG. 4D). The width of the blank holder 30D is the length of the blank holder 30D in the direction in which a straight line passing through both ends 240a, 240b of the die edge convex portion 240 extends.

As shown in FIG. 7, when viewed from the press direction P, the punch-side edge 34D of the blank holder 30D intersects with the edge 201 of the blank 200. Specifically, the edge 34D of the blank holder 30D intersects with the blank edge curved portion 211 and the blank edge straight portion 213. Therefore, in press forming, a portion of the blank edge curved portion 211 is sandwiched between the blank holder 30D and the die 20. Also, the portion of the edge 201 of the blank 200 sandwiched between the blank holder 30D and the die 20 is the blank edge curved portion 211. Even in this case, the same effect as in the first embodiment can be achieved.

Fifth Embodiment
FIG. 8 is a diagram of a press forming apparatus 100E used in the manufacturing method of a press-formed product according to the fifth embodiment, and is a diagram that shows a relationship between the die 20, the blank holder 30E, and the blank 200 when viewed from the press direction P. In other words, FIG. 8 is a schematic diagram showing the die 20, the blank holder 30E, and the blank 200 when projected onto a plane perpendicular to the press direction P before press forming. In FIG. 8, the edge 24 of the die 20 is shown by a dashed line, the edge 34E of the blank holder 30E is shown by a dashed line, and the edge 201 of the blank 200 is shown by a solid line. In addition, in order to make it easier to understand the range of the blank edge curved portion 211 at the edge 201 of the blank 200, the blank edge curved portion 211 is shown by a thick line. In FIG. 8, the punch is omitted.

The press forming apparatus 100E of this embodiment has basically the same configuration as the press forming apparatus 100 of the first embodiment (FIGS. 1 to 3). However, the press forming apparatus 100E of this embodiment differs from the press forming apparatus 100 of the first embodiment in the blank holder 30E. The width of the blank holder 30E in this embodiment is smaller than the blank holder 30 (FIG. 4D) in the first embodiment, as in the fourth embodiment.

As shown in FIG. 8, when viewed from the press direction P, the edge 34E on the punch side of the blank holder 30E intersects with the edge 201 of the blank 200. Specifically, the edge 34E of the blank holder 30E intersects with the blank edge curved portion 211 near each of the two ends 211a, 211b of the blank edge curved portion 211. For this reason, in press forming, a part of the blank edge curved portion 211 is sandwiched between the blank holder 30E and the die 20. Also, the entire edge 201 of the blank 200 sandwiched between the blank holder 30E and the die 20 becomes the blank edge curved portion 211. In order for the entire edge 201 of the blank 200 sandwiched between the blank holder 30E and the die 20 to become the blank edge curved portion 211, it is sufficient that the extension length of the blank edge curved portion 211 is equal to or greater than the extension length of the portion of the edge 201 of the blank 200 that is sandwiched between the blank holder 30E and the die 20. In this embodiment, the extension length of the blank edge curved portion 211 is greater than the extension length of the portion of the edge 201 of the blank 200 that is sandwiched between the blank holder 30E and the die 20.

Even with the manufacturing method using the press forming apparatus 100E in this embodiment, the same effects as in the first embodiment can be achieved. In particular, in this embodiment, the width of the blank holder 30E is smaller than the width of the die edge protrusion 240. In such a case, by making the entire edge 201 of the blank 200 sandwiched between the blank holder 30E and the die 20 into the blank edge curved portion 211, the effect of suppressing the reduction in plate thickness and cracking of the blank edge curved portion 211 during press forming can be improved.

Sixth Embodiment
FIG. 9 is a diagram of a press forming apparatus 100F used in the manufacturing method of a press-formed product according to the sixth embodiment, and is a diagram showing the relationship between the die 20, the blank holder 30F, and the blank 200 when viewed from the press direction P. In other words, FIG. 9 is a schematic diagram showing the die 20, the blank holder 30F, and the blank 200 when projected onto a plane perpendicular to the press direction P before press forming. In FIG. 9, the edge 24 of the die 20 is shown by a dashed line, the edge 34F of the blank holder 30F is shown by a dashed line, and the edge 201 of the blank 200 is shown by a solid line. In addition, in order to make it easier to understand the range of the blank edge curved portion 211 at the edge 201 of the blank 200, the blank edge curved portion 211 is shown by a thick line. In FIG. 9, the punch is omitted.

The press forming apparatus 100F of this embodiment, like the fifth embodiment, has basically the same configuration as the press forming apparatus 100 of the first embodiment (FIGS. 1 to 3). However, the width of the blank holder 30F in this embodiment is larger than the width of the blank holder 30F in the fourth embodiment.

As shown in FIG. 9, when viewed from the press direction P, the punch side edge 34F of the blank holder 30F intersects with the edge 201 of the blank 200. Specifically, the edge 34F of the blank holder 30F intersects with the blank edge straight portions 212, 213 near both ends 211a, 211b of the blank edge curved portion 211. The extension length of the blank edge curved portion 211 is less than the extension length of the portion of the edge 201 of the blank 200 that is sandwiched between the blank holder 30F and the die 20. In this embodiment, the entire blank edge curved portion 211 is sandwiched between the blank holder 30F and the die 20.

The manufacturing method using the press forming apparatus 100F in this embodiment can achieve the same effect as the first embodiment. In this embodiment, the width of the blank holder 30F is relatively large compared to the width of the die edge protrusion 240. In such a case, by sandwiching the entire blank edge curved portion 211 between the blank holder 30F and the die 20, the effect of suppressing the reduction in plate thickness and cracking of the blank edge curved portion 211 during press forming can be improved.

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

In the manufacturing method of the press-formed product according to this embodiment, punches, dies, and blank holders of various shapes can be used, not limited to those described in the above embodiment. When press forming is performed using the punch, die, and blank holder, it is sufficient that the edge of the blank holder on the punch side and the edge of the blank are in an appropriate positional relationship. That is, when viewed from the press direction P, the distance between the edge of the blank holder on the punch side and the edge of the blank sandwiched between the blank holder and the die changes along the edge of the blank and is maximum at the blank edge curved portion. When press forming is performed using the punch, die, and blank holder, it is sufficient that the edge of the die on the punch side and the blank edge curved portion are in an appropriate positional relationship. That is, the distance between the blank edge curved portion and the edge of the die is different at one end and the other end of the blank edge curved portion.

For example, when an existing press forming apparatus is modified to implement the manufacturing method of a press-formed product according to the present disclosure, a plate can be installed on the sheet pressing surface of the blank holder provided in the existing press forming apparatus. In the existing press forming apparatus, when viewed from the press direction, the punch side edge of the blank holder faces almost the entire punch side edge of the die, and the distance between the edge of the blank holder and the edge of the die is constant. In such an existing press forming apparatus, a plate is installed on the sheet pressing surface of the blank holder. As a result, the punch side edge of the plate when viewed from the press direction can be regarded as the edge of the blank holder. When viewed from the press direction, the distance on the perpendicular line between the punch side edge of the plate and the edge of the blank sandwiched between the blank holder and the die changes along the edge of the blank, and is largest at the blank edge curved portion. This can achieve the same effect as the above embodiment. In addition, instead of a plate, a convex portion may be formed by cutting out the sheet pressing surface of the blank holder. In this case, the edge of the convex portion formed on the sheet pressing surface of the blank holder can be regarded as the edge of the blank holder.

In the above first embodiment, an example has been described in which the die 20 and the blank holder 30 are provided on both sides of the punch 10 in the width direction of the press forming apparatus 100. However, the die 20 and the blank holder 30 may be provided only on one side of the punch 10 in the width direction of the press forming apparatus 100. Alternatively, the blank holder 30 may be provided on one side of the punch 10 in the width direction of the press forming apparatus 100, and one of the blank holders 30A to 30E may be provided on the other side. The number and positions of the blank holders can be changed as appropriate, for example, depending on the number and positions of the die edge curved portions 241.

As shown in Figures 10 and 11, the press forming apparatus 100 in the first embodiment may further include a pad 50 that faces the punch 10 in the press direction P. In the manufacture of a press-formed product, the pad 50 approaches the punch 10 relatively in the press direction P and can press the blank 200 on the punch 10. Similarly, the press forming apparatuses 100A, 100B, 100C, 100D, and 100E in the other embodiments may also include a pad 50.

The present disclosure will be explained in more detail below with reference to examples. However, the present disclosure is not limited to the following examples.

The inventors conducted press forming analysis and investigated the appropriate ratio of the area of the blank edge curved portion to the area of the blank edge sandwiched between the blank holder and the die. The inventors decided to express the length (line length) of the blank edge sandwiched between the blank holder and the die as viewed from the press direction, as the ratio to the extension length (line length) of the blank edge curved portion included in the blank edge.

In this analysis, the curved blank edge portion is assumed to extend with a constant radius of curvature when viewed from the press direction. The extension length (line length) of the curved blank edge portion is the product of the angle (included angle) θ (Fig. 4D) at which the tangents to both ends of the curved blank edge portion intersect and the radius of curvature of the curved blank edge portion.

If the line length of the blank edge sandwiched between the blank holder and the die/the line length of the blank edge curved portion is smaller than 1.0, it means that all of the blank edges sandwiched between the blank holder and the die are blank edge curved portions, and part of the blank edge curved portion is sandwiched between the blank holder and the die. On the other hand, if the line length of the blank edge sandwiched between the blank holder and the die/the line length of the blank edge curved portion is greater than 1.0, it means that part of the blank edges sandwiched between the blank holder and the die are blank edge curved portions, and all of the blank edge curved portions are sandwiched between the blank holder and the die. If the line length of the blank edge sandwiched between the blank holder and the die/the line length of the blank edge curved portion is 1.0, it means that all of the blank edges sandwiched between the blank holder and the die are blank edge curved portions, and all of the blank edge curved portions are sandwiched between the blank holder and the die.

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

The press forming analysis was performed for two cases: one in which the edge of the blank is pulled out from between the die and the blank holder to complete the forming, and one in which the edge of the blank is left sandwiched between the die and the blank holder to complete the forming. The analysis was also performed for cases in which the included angle θ of the curved part of the edge of the die when viewed from the press direction was 60°, 90°, and 120°.

Figure 13 shows the analysis results when the blank is pulled out from between the die and the blank holder to finish forming. Figure 14 shows the analysis results when forming is finished with the blank still sandwiched between the die and the blank holder. As can be seen from Figures 13 and 14, when press forming according to the present disclosure is performed, the damage value I is reduced compared to normal drawing forming. When the line length of the edge of the blank sandwiched between the blank holder and the die/the line length of the curved part of the blank edge is 0.67 or more and 2.50 or less, the reduction rate of the damage value I compared to normal drawing forming is significantly improved.

Therefore, when viewed from the press direction, it is preferable that the line length of the edge of the blank sandwiched between the blank holder and the die is 0.67 to 2.50 times the line length of the blank edge curved portion provided on the edge of the blank.

100, 100A, 100B, 100C, 100D, 100E, 100F: Press forming device 10: Punch 20, 20A, 20B, 20C: Die 24: Die edge 240, 240A, 240B, 240C: Die edge convex portion 240a, 240b, 240Aa, 240Ab, 240Ba, 240Bb, 240Ca, 240Cb: End portion 241: Die edge curved portion 242, 243: Die edge straight portion 30, 30D, 30E, 30F: Blank holder 34, 34D, 34E, 34F: Edge 200, 200A, 200B, 200C: Blank 201: Edge 211: Blank edge curved portion 211a: One end portion 211b: other end La, Lb: perpendicular line S1: area d: interval w, w1, w2: interval P: press direction 300: press-molded product

Claims (7)

Clamping the blank between a die and a blank holder; and pushing the blank in a pressing direction with a punch.
Equipped with
When viewed from the press direction,
The edge of the die on the punch side includes a die edge protrusion protruding toward the punch side,
The die edge convex portion includes a die edge curved portion that is convexly curved toward the punch side and extends with a curvature radius of 400 mm or less,
The edge of the blank includes a blank edge curved portion that is concavely curved toward the punch side and extends with a curvature radius of 400 mm or less,
A distance between the blank edge curved portion and the edge of the die on a perpendicular line in an extension direction of the edge of the die is different between one end and the other end of the blank edge curved portion,
the blank holder, together with the die, clamps a portion of the edge of the blank;
The edge of the blank holder on the punch side has a convex shape toward the edge of the die, and a distance between the edge of the die and the edge of the blank holder on a perpendicular line in an extension direction of the edge of the die varies along the edge of the blank holder;
a distance between the edge of the blank holder and the edge of the blank sandwiched between the blank holder and the die on a perpendicular line in an extension direction of the edge of the blank, the distance varying along the edge of the blank, and the distance being largest at a curved portion of the blank edge. The method for manufacturing a press-molded product according to claim 1, wherein the die edge convex portion consists only of the die edge curved portion. The method for manufacturing a press-molded product according to claim 1, wherein, when viewed from the pressing direction, the die edge convex portion is composed of the die edge curved portion and a die edge straight portion that is continuous with one side of the die edge curved portion and extends with a curvature radius greater than 400 mm. The method for manufacturing a press-molded product according to claim 1, wherein, when viewed from the pressing direction, the die edge convex portion is composed of the die edge curved portion and a die edge straight portion that is continuous with both sides of the die edge curved portion and extends with a curvature radius greater than 400 mm. The method for manufacturing a press-formed product according to any one of claims 1 to 4, wherein the line length of the edge of the blank sandwiched between the blank holder and the die is 0.67 to 2.50 times the line length of the blank edge curved portion when viewed from the press direction. The method for manufacturing a press-formed product according to claim 5, wherein all of the edges of the blank sandwiched between the blank holder and the die are the blank edge curved portions. The method for manufacturing a press-formed product according to claim 5 , wherein the entire blank edge curved portion is sandwiched between the blank holder and the die.

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