Manufacturing method of pressed products

Abstract

A technique for reducing manufacturing defects in a pressed product having a corner bulge portion having a top wall and a side wall is disclosed. [Solution] A pressed product 70 manufactured by the manufacturing method of the present disclosure has a corner bulge 80 formed by bulging a portion of the corner between a main body bottom wall 71 and a main body side wall 72 inward, and the corner bulge 80 has a ceiling wall 81 that is approximately parallel to the main body bottom wall 71, and a side wall 82 that is connected to the ceiling wall 81, the main body bottom wall 71, and the main body side wall 72. In the manufacturing method of the present disclosure, a preliminary corner bulge 90 is formed by molding the ceiling wall 81 of the corner bulge 80 into a preliminary ceiling wall 91 that is shaped so as to gradually move away from the main body bottom wall 71 as it moves from the end of the ceiling wall 81 on the side wall 72 side toward a position closer to the end away from the side wall 72, and the preliminary side wall 92 that is connected to the preliminary ceiling wall 91, the main body bottom wall 71, and the main body side wall 72. Then, the preliminary corner bulge 90 is molded into the corner bulge 80.

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a pressed product, wherein the main body of the pressed product has a main body bottom wall and a main body side wall that stands up from the entire outer edge of the main body bottom wall. [Background technology]

[0002] BACKGROUND ART As a manufacturing method of a press product, a method of manufacturing a container-shaped press product from a metal plate is known (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-89139 A (Fig. 1) Summary of the Invention [Problem to be solved by the invention]

[0004] In some press products, a container-shaped main body is required to have a corner bulge that bulges inward at the corner where the bottom wall and side wall of the main body intersect. While a corner bulge with a rounded shape can be formed without any problems, if the corner bulge has a top wall that is approximately parallel to the bottom wall of the main body and a side wall that connects the top wall, bottom wall, and side wall, excessive tension on the side wall during forming can cause a manufacturing defect, resulting in partial breakage. Therefore, this application discloses a technology for reducing manufacturing defects in press products with corner bulges that have a top wall and side wall. [Means for solving the problem]

[0005] A first aspect of the present disclosure made to solve the above problems is a manufacturing method of a pressed product including a main body portion in which a main body side wall rises from the entire outer edge of a main body bottom wall, and a corner bulge portion in which a part of a corner portion between the main body bottom wall and the main body side wall bulges inward, the corner bulge portion having a top wall substantially parallel to the main body bottom wall, and a side wall connected to the top wall, the main body bottom wall, and the main body side wall, The method includes a first press process in which a preliminary corner bulge portion, which is a precursor to the corner bulge portion, is formed, and a second press process in which the preliminary corner bulge portion is formed into the corner bulge portion. a spare ceiling wall having a shape that is inclined so as to gradually move away from the bottom wall of the main body from an end portion on the side wall side of the main body toward a position closer to an end portion on a side farther from the side wall of the main body; and a spare side wall that is connected to the spare ceiling wall, the bottom wall of the main body, and the side wall of the main body. And, before A preliminary bent arc portion having a larger radius of curvature than a bent arc portion between the side wall of the corner bulge portion and the ceiling wall and the main body bottom wall is provided between the preliminary side wall and the preliminary ceiling wall and the main body bottom wall. and in the second pressing step, The preliminary ceiling wall and the preliminary bent arc portion on the main body bottom wall side are pressed in a direction perpendicular to the main body bottom wall, The preliminary ceiling wall is formed into the ceiling wall, and the preliminary bent arc portion is formed into the bent arc portion. This is a manufacturing method for pressed products. [Effects of the Invention]

[0006] In the manufacturing method of the press product of the present disclosure, in order to form a corner bulge portion having a top wall that is substantially parallel to the main body bottom wall and a side wall that is connected to the top wall, the main body bottom wall, and the main body side wall, for a main body portion having a main body side wall that stands from the entire outer edge of the main body bottom wall, first , BookA preliminary corner bulge is formed in the first press step. The preliminary corner bulge includes a preliminary top wall that is inclined so as to gradually move away from the bottom wall of the main body from the end closest to the body side wall toward the end farther from the side wall, and a preliminary side wall connected to the preliminary top wall, the bottom wall, and the side wall of the main body. During this process, a preliminary bent arc portion having a larger radius of curvature than the bent arc portion between the side wall of the corner bulge, the top wall, and the bottom wall of the main body is formed between the preliminary side wall of the preliminary corner bulge and the preliminary top wall and the bottom wall of the main body. Then, in the second press step, the preliminary top wall and the preliminary bent arc portion on the bottom wall side of the main body are pressed in a direction perpendicular to the bottom wall of the main body, thereby forming the preliminary corner bulge into a corner bulge. Because the preliminary top wall of the preliminary corner bulge is inclined, it has a larger area and more material than the top wall of a non-inclined corner bulge. Therefore, the material of the preliminary top wall is more likely to move toward the preliminary side wall. In the second pressing step, the preliminary top wall is pressed to send material toward the preliminary side wall, and the preliminary bent arc portion on the bottom wall of the main body is pressed to pull the preliminary side wall, preventing excessive tension from being applied to the preliminary side wall and reducing the occurrence of manufacturing defects such as breakage of part of the wall as occurs in the conventional case. In other words, the technology disclosed herein can reduce manufacturing defects in pressed products with corner bulges that have a top wall and a side wall. [Brief explanation of the drawings]

[0007] [Figure 1] Figure 1 is a perspective view of a pressed product. [Figure 2] FIG. 2 is an enlarged perspective view of the corner bulge. [Figure 3] Figure 3 is a perspective view of a workpiece in the manufacturing process of a press product. [Figure 4] FIG. 4 is an enlarged perspective view of the auxiliary corner bulge. [Figure 5] FIG. 5A is a side cross-sectional view of a punch and a die for forming a preliminary corner bulge, and FIG. 5B is a front cross-sectional view taken along the AA cross section of FIG. 5A. [Figure 6] FIG. 6A is a side cross-sectional view of a punch and die for forming a corner bulge, and a preliminary corner bulge; FIG. 6B is a side cross-sectional view of a punch and die, and a corner bulge formed by them. [Figure 7] 7A is a front cross-sectional view taken along the line BB in FIG. 6A, and FIG. 7B is a front cross-sectional view taken along the line CC in FIG. 6B. DETAILED DESCRIPTION OF THE INVENTION

[0008] A method for manufacturing a pressed product 70 according to one embodiment of the present disclosure will be described below with reference to Figures 1 to 7. As shown in Figure 1, the pressed product 70 is manufactured by pressing a metal plate, for example, with a press machine, and has a structure in which a main body portion 73 is provided with corner bulges 80.

[0009] The main body 73 has a container structure in which a main body side wall 72 stands upright from the entire outer edge of a main body bottom wall 71. The main body bottom wall 71 is, for example, an elliptical flat plate, and the main body side wall 72 stands upright approximately perpendicularly from the entire outer edge of the main body bottom wall 71. Although not clearly visible in the drawings, a slightly protruding ridge is formed around the entire periphery on the outer surface at the tip of the main body side wall 72, and the tip surface of the ridge forms a cut surface 73K. The tip surface of the main body side wall 72 forms a curved R surface (bent arc surface) that is continuous with the above-mentioned ridge.

[0010] Although the main body 73 of the pressed product 70 of this embodiment has a container structure, it does not have to have a container structure. For example, a through-hole may be formed in the main body bottom wall 71 so that the main body 73 does not function as a container. Furthermore, the main body bottom wall 71 is not limited to an elliptical shape but may be circular, polygonal, or other shapes. Furthermore, the main body bottom wall 71 is not limited to a flat plate shape but may have irregularities at positions away from the corner bulges 80. Furthermore, the main body side walls 72 rise substantially perpendicularly from the main body bottom wall 71 but may be inclined outward as they move away from the main body bottom wall 71. The metal plate constituting the pressed product 70 may be any material, including iron, aluminum, alloys, or plywood made of multiple layers of metal plate. Furthermore, the main body side walls 72 have ridges on their outer leading edge surfaces, forming curved rounded surfaces, but they may not have ridges and instead have cut edges.

[0011] The corner bulge portion 80 is, for example, positioned at the center of the longitudinal direction of the elliptical planar shape of the main body bottom wall 71, and is formed by bulging inward a portion of the corner portion (angle portion) between the main body bottom wall 71 and the main body side wall 72 of the main body portion 73, and has a ceiling wall 81 that is approximately parallel to the main body bottom wall 71, and a side wall 82 that is connected to the ceiling wall 81, the main body bottom wall 71, and the main body side wall 72.

[0012] Specifically, the top wall 81 has a planar shape that is symmetrical trapezoidal and has a pair of side edges that extend straight inward from two locations on the main body side wall 72 and approach each other as they move away from the main body side wall 72, a base edge that connects the two locations on the main body side wall 72, and a tip edge that is substantially parallel to the base edge and faces the base edge. The side walls 82 of the corner bulge 80 are made up of a pair of opposing side walls 84 located on the pair of side edges of the top wall 81 and a tip edge side wall 83 located on the tip edge of the top wall 81, and the opposing side walls 84 and the tip edge side wall 83 are substantially perpendicular to the main body bottom wall 71 and the top wall 81. A circular through hole 81A is formed in the center of the top wall 81 in the width direction (the direction in which the pair of opposing side walls 84 face each other) near the tip of the top wall 81.

[0013] In this embodiment, the main body 73 is provided with only one corner bulge 80, but the main body 73 may be provided with multiple corner bulge 80. The corner bulge 80 has a through-hole 81A, but does not necessarily have to have a through-hole 81A. The top wall 81 has a symmetrical planar shape, but may also have an asymmetrical planar shape. The top wall 81 has a trapezoidal planar shape, but may have any other planar shape, such as a rectangle, a semicircle, a semi-ellipse, a triangle, a square, or any other polygon, or may have a semicircular tip edge.

[0014] The press product 70 is formed through a first press process, a second press process, and a third press process. In the first press process, an oval blank is punched out of sheet metal and then drawn to form a container-shaped workpiece (hereinafter referred to as the "initial workpiece") (not shown). Like the press product 70 described above, the initial workpiece has corner bulges at the corners of the main body of the oval container structure, and also has flanges that protrude laterally from the tips of the main body side walls. Furthermore, the main body side walls and corner bulges of the initial workpiece are lower than those of the press product 70, and the curvature radii of the bending arc portions (corner R) of all corners are larger than those of the press product 70.

[0015] The initial workpiece is then drawn multiple times in a first press process to form the workpiece W1 shown in Fig. 3. The workpiece W1 has a main body 73A, which is the main body 73 of the pressed product 70 to which a flange 74 has been added, and a preliminary corner bulge 90 that is slightly different in shape from the corner bulge 80 of the pressed product 70. Then, in a second press process, the preliminary corner bulge 90 is formed into the corner bulge 80, and in a third press process, a through-hole 81A is drilled in the corner bulge 80 and the flange 74 is cut off, completing the pressed product 70.

[0016] 4, the preliminary corner bulge 90 has a preliminary ceiling wall 91 formed by inclining the ceiling wall 81 of the corner bulge 80 of the press product 70 relative to the main body bottom wall 71, and a preliminary side wall 92 connected to the preliminary ceiling wall 91, the main body bottom wall 71, and the main body side wall 72. The bending arc portions (so-called bending R portions) between the preliminary side wall 92 of the preliminary corner bulge 90 and the preliminary ceiling wall 91 and the main body bottom wall 71 are preliminary bending arc portions 93R1, 93R2, 94R1, and 94R2, which have a larger radius of curvature than the bending arc portions between the side wall 82 of the corner bulge 80 and the ceiling wall 81 and the main body bottom wall 71.

[0017] In detail, the planar shape of the auxiliary ceiling wall 91 of the auxiliary corner bulge portion 90 is a trapezoid similar to the ceiling wall 81 of the corner bulge portion 80, and the auxiliary side wall 92 of the auxiliary corner bulge portion 90, similar to the main body side wall 72 of the corner bulge portion 80, consists of a tip side wall 93 and a pair of opposing side walls 94.

[0018] Furthermore, the auxiliary ceiling wall 91 has a flat plate-like shape that gradually slopes away from the main body bottom wall 71 from the base end edge connecting the two points where a pair of side edges of the trapezoidal planar shape intersect with the main body side wall 72 to a position closer to the tip end edge opposite the base end edge (for example, a position closer to the tip end edge beyond the through hole 81A of the corner bulge portion 80) (see FIG. 5A), and the slope angle is, for example, 5 to 10 degrees.

[0019] 5A , the portion of preliminary ceiling wall 91 closer to the tip edge than the flat inclined portion forms a preliminary bent arc portion 93R1, which is an arc portion continuing from the inclined portion and tip side wall 93, and the radius of curvature of preliminary bent arc portion 93R1 is larger than the radius of curvature of the corresponding bent arc portion 83R1 of corner bulge portion 80. In addition, the radius of curvature of preliminary bent arc portion 93R2, which is an arc portion between tip side wall 93 and main body bottom wall 71, is also larger than the radius of curvature of the corresponding bent arc portion 83R2 of corner bulge portion 80. Furthermore, as shown in FIG. 5B, the radius of curvature of the preliminary bent arc portion 94R1, which is the arc portion between the opposing side wall 94 of the preliminary corner bulge portion 90 and the preliminary ceiling wall 91, is larger than the radius of curvature of the corresponding bent arc portion 84R1 of the corner bulge portion 80, and the radius of curvature of the preliminary bent arc portion 94R2, which is the arc portion between the opposing side wall 94 and the main body bottom wall 71, is also larger than the radius of curvature of the corresponding bent arc portion 84R2 of the corner bulge portion 80. Furthermore, in the preliminary corner bulge portion 90, the radius of curvature of the preliminary bent arc portion 93R1 between the tip side wall 93 and the preliminary ceiling wall 91 is larger than the radius of curvature of the preliminary bent arc portion 94R1 between the opposing side wall 94 and the preliminary ceiling wall 91, while in the corner bulge portion 80, the radius of curvature of the bent arc portion 83R1 between the tip side wall 83 and the ceiling wall 81 is smaller than the radius of curvature of the preliminary bent arc portion 84R1 between the opposing side wall 84 and the ceiling wall 81.

[0020] Figures 5A and 5B show enlarged views of the punch 12A and die 13A in the first press step that form the preliminary corner bulge 90, and Figures 6 and 7 show enlarged views of the punch 12B and die 13B in the second press step that form the preliminary corner bulge 90 into the corner bulge 80.

[0021] When the workpiece W1 is set between the punch 12B and the die 13B in the second pressing step, as shown in Figures 6A and 7A, the main body bottom wall 71, the tip side wall 93, and the opposing side wall 94 overlap the die 13B, and the preliminary top wall 91 and the preliminary bent arc portions 93R2, 94R2 on the main body bottom wall 71 side of the tip side wall 93 and the opposing side wall 94 are floating above the die 13B. In this state, the punch 12B descends, pressing the preliminary top wall 91 and the preliminary bent arc portions 93R2, 94R2 from a direction perpendicular to the main body bottom wall 71, and the preliminary corner bulge 90 is formed into the corner bulge 80, as shown in Figures 6B and 7B. Because the preliminary ceiling wall 91 of the preliminary corner bulge 90 is inclined, it has a larger area and more material than the ceiling wall 81 of the non-inclined corner bulge 80, and therefore the material of the preliminary ceiling wall 91 is more likely to move toward the preliminary side wall 92. Furthermore, between the preliminary side wall 92 of the preliminary corner bulge 90 and the preliminary ceiling wall 91 and main body bottom wall 71, preliminary bent arc portions 93R1, 93R2, 94R1, 94R2 are formed that have a larger radius of curvature than the bent arc portions 83R1, 83R2, 84R1, 84R2 between the side wall 82 of the corner bulge 80 and the ceiling wall 81 and main body bottom wall 71. This also improves the material flow during the second pressing step and improves the material flow when forming the workpiece W1 up to the last three downstream ends, preventing the preliminary side wall 92 from being subjected to excessive tensile force and breaking during the forming of the preliminary corner bulge 90. The preliminary ceiling wall 91 is pressed to send the meat to the preliminary side wall 92 side, and the preliminary bent arc portions 93R2, 94R2 on the main body bottom wall 71 side are pressed to pull the preliminary side wall 92, so that excessive pulling force is prevented from being applied to the preliminary side wall 92, and the occurrence of manufacturing defects such as breakage of a part of the wall as in the conventional case is suppressed.

[0022] Furthermore, since the spare corner bulge 90 is formed with the flange 74 provided, stress concentration at the intersection of the three walls consisting of the spare ceiling wall 91, spare side wall 92, and main body side wall 72 when the spare corner bulge 90 is formed is alleviated by the flange 74, preventing poor molding of the intersection.

[0023] Furthermore, the preliminary bent arc portion 93R1 located at the leading edge of the preliminary ceiling wall 91 has a larger radius of curvature than the preliminary bent arc portion 94R1 located at one of the side edges of the preliminary ceiling wall 91, which makes it easier for the material of the preliminary ceiling wall 91 to flow toward the leading edge, preventing sagging of the material when the preliminary ceiling wall 91 becomes the ceiling wall 81. Then, during the formation of the preliminary corner bulge portion 90 into the corner bulge portion 80, the radii of curvature of the bent arc portion 83R1 located at the leading edge of the ceiling wall 81 and the bent arc portion 84R1 located at one of the side edges of the ceiling wall 81 are reversed, so that the radius of curvature of the bent arc portion 83R1 located at the leading edge of the ceiling wall 81 is smaller than the radius of curvature of the bent arc portion 84R1 located at one of the side edges of the ceiling wall 81. This more reliably removes sagging of the material of the ceiling wall 81.

[0024] As described above, this embodiment can reduce manufacturing defects in the pressed product 70 that includes the corner bulge 80 having the top wall 81 and the side wall 82. In the pressed product 70 of this embodiment, the top wall 81 and the auxiliary top wall 91 have planar shapes that are symmetrical trapezoids with the tip side shorter than the base side. This results in obtuse angles between adjacent side walls (the tip side wall 83 and the opposing side wall 84) and between adjacent auxiliary side walls (the tip side wall 93 and the opposing side wall 94), making it easier for material to flow than when the planar shape of the corner bulge 80 is rectangular. In other words, when the planar shape of the corner bulge 80 is made quadrangular, wall breakage can be reduced by making the planar shape symmetrical trapezoidal rather than rectangular.

[0025] [Other embodiments] The pressed product 70 may be produced in one or more presses or may be produced in a transfer press.

[0026] In the above embodiment, the inclined portion of the preliminary ceiling wall 91 of the preliminary corner bulge 90 is flat, but it may be rounded.

[0027] In the above embodiment, the side wall 82 and the auxiliary side wall 92 are substantially perpendicular to the main body bottom wall 71 , but they may be inclined relative to the main body bottom wall 71 .

[0028] In the above embodiment, the preliminary corner bulge portion 90 is formed into the corner bulge portion 80 by a single press molding, but the preliminary corner bulge portion 90 may be formed into the corner bulge portion 80 by multiple press moldings.

[0029] <Additional Notes> The following describes the group of features extracted from the above embodiment, while indicating, as necessary, the effects, etc. Note that, for ease of understanding, the symbols of specific configurations corresponding to the above embodiment are indicated in parentheses, etc. as appropriate, but these group of features are not limited to the specific configurations indicated in parentheses, etc.

[0030] [Feature 1] A method for manufacturing a press product (70) including a main body portion (73) in which a main body side wall (72) stands from the entire outer edge of a main body bottom wall (71), and a corner bulge portion (80) in which a part of a corner portion between the main body bottom wall (71) and the main body side wall (72) bulges inward, the corner bulge portion (80) having a top wall (81) substantially parallel to the main body bottom wall (71), and a side wall (82) connected to the top wall (81), the main body bottom wall (71), and the main body side wall (72), wherein the top wall (81) is inclined so as to gradually move away from the main body bottom wall (71) from its end on the main body side wall (72) side toward a position closer to its end away from the main body side wall (72), and the top wall (81) is inclined so as to gradually move away from the main body bottom wall (71) A preliminary corner bulge (90) having a radius of curvature larger than that of the bending arc portions (83R1, 83R2, 84R1, 84R2) between the side walls (82) of the corner bulge (80) and the ceiling wall (81) and the main body bottom wall (71) is formed between the preliminary side walls (92) of the preliminary corner bulge (90) and the preliminary ceiling wall (91) and the main body bottom wall (71). A method for manufacturing a pressed product (70), comprising: a first press process in which arc portions (93R1, 93R2, 94R1, 94R2) are formed; and a second press process in which the preliminary ceiling wall (91) and the preliminary bent arc portions (93R2, 94R2) on the main body bottom wall (71) side are pressed in a direction perpendicular to the main body bottom wall (71), thereby forming the preliminary corner bulge portions (90) into the corner bulge portions (80).

[0031] In the method for manufacturing a press product according to Feature 1, to form a corner bulge portion having a ceiling wall substantially parallel to the main body bottom wall and a side wall connected to the ceiling wall, bottom wall, and main body side wall in a main body portion having a main body side wall rising from the entire outer edge of the main body bottom wall, first, a preliminary ceiling wall is formed in a first press step such that the ceiling wall of the corner bulge portion is gradually inclined away from the main body bottom wall from the end of the corner bulge portion closer to the main body side wall toward the end away from the main body side wall, and the preliminary side wall connected to the preliminary ceiling wall, bottom wall, and main body side wall. Furthermore, at this time, a preliminary bent arc portion having a larger radius of curvature than the bent arc portion between the side wall of the corner bulge portion and the ceiling wall and bottom wall is formed between the preliminary side wall of the preliminary corner bulge portion and the preliminary ceiling wall and main body bottom wall. In the second press process, the preliminary top wall and the preliminary bent arc portion on the bottom wall of the main body are pressed in a direction perpendicular to the bottom wall of the main body, forming the preliminary corner bulge into a corner bulge. Because the preliminary top wall of the preliminary corner bulge is inclined, it has a larger surface area and more material than the top wall of a non-inclined corner bulge. Therefore, the material of the preliminary top wall is more likely to move toward the preliminary side wall. In the second press process, the preliminary top wall is pressed, sending the material toward the preliminary side wall, and the preliminary bent arc portion on the bottom wall of the main body is pressed, stretching the preliminary side wall. This prevents excessive tension from being applied to the preliminary side wall, reducing the occurrence of manufacturing defects such as breakage of a portion of the wall, as in the conventional process. Furthermore, in the first pressing step, a preliminary bent arc portion is formed between the preliminary side wall of the preliminary corner bulge portion and the preliminary top wall and main body bottom wall, with a larger radius of curvature than the bent arc portion between the side wall of the corner bulge portion and the top wall and main body bottom wall. This also improves the material flow during the second pressing step and also improves the material flow during the first pressing step, preventing the problem of partial breakage due to excessive tensile force being applied to the preliminary side wall during forming the preliminary corner bulge portion. In other words, feature 1 makes it possible to reduce manufacturing defects in pressed products equipped with a corner bulge portion having a top wall and side walls.

[0032] [Feature 2] The method for manufacturing the pressed product (70) according to Feature 1 includes a third press step in which the side wall (82) and the auxiliary side wall (92) have approximately the same height as the main body side wall (72), the first press step provides an annular flange portion (74) that protrudes laterally outward from the entire tip of the main body side wall (72) and is continuous with the auxiliary top wall (91), and the second press step is followed by a third press step in which the flange portion (74) is cut off from the main body side wall (72).

[0033] In the manufacturing method of the press product of Feature 2, when forming the auxiliary corner bulge, the flange relieves stress concentration at the intersection of the three walls consisting of the auxiliary ceiling wall, the auxiliary side wall, and the main body side wall, preventing poor molding of the intersection.

[0034] [Feature 3] The method for manufacturing a pressed product (70) according to Feature 1, wherein the planar shape of the ceiling wall (81) and the auxiliary ceiling wall (91) is a quadrangle having four sides, including a pair of side edges that extend straight inward from two points on the main body side wall (72) and face each other, a base end edge that connects the two points, and a tip end edge that faces the base end edge.

[0035] The planar shape of the top wall may be, for example, semicircular or semielliptical, or may be polygonal. Furthermore, the planar shapes of the top wall and auxiliary top wall are polygonal compared to semicircular or semielliptical, because the side walls and auxiliary side walls are divided into multiple parts, which makes it difficult for the material to flow smoothly during molding, thereby increasing the effect of the press product manufacturing method of the present disclosure. Specifically, if the top wall has a rectangular planar shape, it is difficult to form a corner bulge without breaking the wall. However, according to the press product manufacturing method of Feature 3, it is possible to form a corner bulge without breaking the wall.

[0036] [Feature 4] The method for manufacturing a pressed product (70) according to Feature 3, wherein the top wall (81) and the auxiliary top wall (91) have a planar shape in which the tip end side is shorter than the base end side and the top wall (81) are symmetrical trapezoidal.

[0037] In Feature 4, the planar shapes of the ceiling wall and auxiliary ceiling wall are trapezoidal, with the tip end shorter than the base end, so that the corners between adjacent side walls and between auxiliary side walls are obtuse, making it easier for the meat to flow than when the planar shape of the corner bulge is rectangular. In other words, when the planar shape of the corner bulge is made quadrangular, making it a symmetrical trapezoid rather than a rectangle can prevent wall breakage.

[0038] [Feature 5] Feature 4: The method for manufacturing the pressed product (70) according to Feature 4, wherein the preliminary bent arc portion (93R1) located at the tip edge of the preliminary ceiling wall (91) has a larger radius of curvature than the preliminary bent arc portions (94R1) located at the pair of side edges of the preliminary ceiling wall (91).

[0039] According to Feature 5, the preliminary bent arc portion located at the tip edge of the preliminary ceiling wall has a larger radius of curvature than the preliminary bent arc portions located at a pair of side edges of the preliminary ceiling wall, so that the material of the preliminary ceiling wall easily flows toward the tip edge side, preventing sagging of the material when the preliminary ceiling wall becomes the ceiling wall.

[0040] [Feature 6] The method for manufacturing a press product according to Feature 5, wherein the bending arc portion (83R1) located at the tip edge of the top wall (81) has a smaller radius of curvature than the bending arc portions (84R1) located at the pair of side edges of the top wall (81).

[0041] In Feature 6, while the preliminary corner bulge is being formed into the corner bulge, the radius of curvature of the curved arc portion located at the tip edge of the ceiling wall and the radius of curvature of the curved arc portion located at one of the side edges of the ceiling wall are reversed, so that the radius of curvature of the curved arc portion located at the tip edge of the ceiling wall is smaller than the radius of curvature of the curved arc portion located at one of the side edges of the ceiling wall. This more reliably removes sagging of the ceiling wall material.

[0042] Although the present specification and drawings disclose specific examples of the technology included in the scope of the claims, the technology described in the claims is not limited to these specific examples, but also includes various modifications and variations of the specific examples, and also includes parts of the specific examples taken out alone. [Explanation of symbols]

[0043] 12, 12A, 12B punch 13, 13A, 13B Dies 70 Press Products 71 Bottom wall of main body 72 Main body side wall 73,73A Main body 74 Tsuba 80 Corner bulge 81 Ceiling Wall 82 Side wall 83R1, 83R2, 84R1, 84R2 bending arc section 90 Spare corner bulge 91 Spare ceiling wall 92 Spare side wall 93R1, 93R2, 94R1, 94R2 Pre-bending arc section

Claims

1. A method for manufacturing a pressed product including a main body portion having main body side walls rising from the entire outer edge of a main body bottom wall, and a corner bulge portion formed by bulging a part of a corner portion between the main body bottom wall and the main body side wall inward, the corner bulge portion having a top wall substantially parallel to the main body bottom wall, and a side wall connected to the top wall, the main body bottom wall, and the main body side wall, a first pressing step in which a preliminary corner bulge portion, which is a precursor to the corner bulge portion, is formed; a second pressing step in which the preliminary corner bulge is formed into the corner bulge; the preliminary corner bulge portion includes a preliminary ceiling wall having a shape that is inclined so as to gradually move away from the main body bottom wall from an end portion on the main body side wall side toward a position closer to an end portion on the side away from the main body side wall, a preliminary side wall that is connected to the preliminary ceiling wall, the main body bottom wall, and the main body side wall, and a preliminary bent arc portion between the preliminary side wall and the preliminary ceiling wall and the main body bottom wall, the radius of curvature of which is larger than that of the bent arc portion between the side wall of the corner bulge portion and the ceiling wall and the main body bottom wall, In the second pressing step, the preliminary ceiling wall and the preliminary bent arc portion on the bottom wall side of the main body are pressed in a direction perpendicular to the bottom wall of the main body, so that the preliminary ceiling wall is formed into the ceiling wall and the preliminary bent arc portion is formed into the bent arc portion.

2. the side wall and the auxiliary side wall have substantially the same height as the main body side wall, In the first pressing step, an annular flange portion is provided that protrudes outward from the entire tip of the main body side wall and is continuous with the preliminary ceiling wall, The method for manufacturing a pressed product according to claim 1 , further comprising a third pressing step in which the flange portion is cut off from the side wall of the main body after the second pressing step.

3. 2. The method for manufacturing a press product according to claim 1, wherein the top wall and the auxiliary top wall have a planar shape that is a quadrangle having four sides: a pair of side edges that extend straight inward from two locations on the main body side wall and face each other, a base end edge that connects the two locations, and a tip end edge that faces the base end edge.

4. The method for manufacturing a press product according to claim 3, wherein the top wall and the auxiliary top wall have a planar shape that is a symmetrical trapezoid with the tip end side shorter than the base end side.

5. The method for manufacturing a press product according to claim 4, wherein the pre-bent arc portion located at the tip edge of the preliminary ceiling wall has a larger radius of curvature than the pre-bent arc portions located at the pair of side edges of the preliminary ceiling wall.

6. The method for manufacturing a press product according to claim 5, wherein the bent arc portion located at the tip edge of the top wall has a smaller radius of curvature than the bent arc portions located at the pair of side edges of the top wall.

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