Manufacturing method of press-molded product and mold

Abstract

A method for manufacturing a press-molded product is provided, which is capable of manufacturing a corrugated press-molded product while suppressing the occurrence of cracks. [Solution] A manufacturing method for a press-formed product (90) includes a preparation step of preparing a blank (30) and a forming step. In the forming step, a first mold (10) and a second mold (20) are used. The forming step includes a first forming step and a second forming step. In the first forming step, a first roller (12) is arranged on the second mold (20) side with respect to a first forming surface (111), and a second roller (22) is arranged on the first mold (10) side with respect to a second forming surface (211). The blank (30) is deformed by the first roller (12) and the second roller (22). In the second forming step, the first roller (12) is housed in the first mold body (11), and the second roller (22) is housed in the second mold body (21), and the blank (30) is clamped between the first forming surface (111) and the second forming surface (211).

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a press-molded product, and also to a die for manufacturing the press-molded product. [Background technology]

[0002] Electric vehicles (EVs) and plug-in hybrid vehicles, which have become increasingly popular in recent years, are equipped with large batteries. To protect the battery from impact in the event of a side collision, crashworthy parts are sometimes attached to the side sills, battery cases, etc. Crashworthy parts are, for example, press-molded products that have a corrugated cross-sectional shape.

[0003] Patent Document 1 discloses a method for producing a press-formed product having a wave shape in cross section. In Patent Document 1, the press-formed product has a lattice-like arrangement of concave and convex rows, each of which is made up of alternating concave and convex portions that are smoothly connected, resulting in a wave-like cross section at any position. In Patent Document 1, the press-formed product is produced by press-forming a metal plate using a mold consisting of an upper mold and a lower mold. A plurality of punches that protrude downward are arranged on the lower surface of the upper mold. A plurality of punches that protrude upward are arranged on the upper surface of the lower mold. The punch row of the upper mold is arranged alternately with the punch row of the lower mold. The upper mold and the lower mold are brought close together, and the punch of the upper mold presses the metal plate, thereby forming the concave portions of the press-formed product. Furthermore, the protrusions of the press-formed product are formed by pressing the metal plate with the punch of the lower mold. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-245725 Summary of the Invention [Problem to be solved by the invention]

[0005] When a corrugated press-formed product is formed by pressing a metal plate with an upper die and a lower die as in Patent Document 1, cracks may occur in the press-formed product. In particular, when the press-formed product is long and has a large number of convex portions arranged therein, cracks are likely to occur in the press-formed product during forming. For this reason, a long press-formed product has traditionally been produced by manufacturing multiple short press-formed products with a small number of convex portions and joining them by welding or the like. However, this increases the manufacturing cost of the press-formed product, and the mass of the press-formed product increases in order to ensure a welding allowance.

[0006] An object of the present disclosure is to provide a method for manufacturing a press-formed product that can manufacture a corrugated press-formed product while suppressing the occurrence of cracks. [Means for solving the problem]

[0007] A manufacturing method for a press-formed product according to the present disclosure includes a preparation step and a formation step. In the preparation step, a blank is prepared. In the formation step, the blank is formed into a press-formed product using a first mold and a second mold. The first mold includes a first mold body and a first roller. The first mold body has a first formation surface on which a plurality of convex portions are formed and arranged in parallel at intervals from each other. The first rollers are provided corresponding to the convex portions and are rotatable around rotation axes perpendicular to both the arrangement direction of the convex portions and the press direction. The second mold includes a second mold body and a second roller. The second mold body has a second formation surface on which a plurality of concave portions are formed corresponding to the convex portions and opposed to the first formation surface. The second roller is provided between the concave portions and is rotatable around a rotation axis perpendicular to both the arrangement direction and the press direction. The formation step includes a first formation step and a second formation step. In the first forming step, the first roller is disposed on the second mold side relative to the first forming surface, and the second roller is disposed on the first mold side relative to the second forming surface, and the second mold is brought relatively close to the first mold, and the blank is deformed by the first roller and the second roller. In the second forming step, after the first forming step, the first roller is housed in the first mold body, and the second roller is housed in the second mold body, and the blank is clamped between the first and second forming surfaces. [Effects of the Invention]

[0008] According to the method for manufacturing a press-formed product of the present disclosure, a corrugated press-formed product can be manufactured while suppressing the occurrence of cracks. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view of a press-formed product manufactured by a manufacturing method according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II of FIG. [Figure 3] FIG. 3 is a perspective view schematically showing a mold according to an embodiment. [Figure 4] FIG. 4 is a vertical cross-sectional view schematically showing a mold according to an embodiment. [Figure 5A] FIG. 5A is a schematic view for explaining the manufacturing method according to the embodiment. [Figure 5B] FIG. 5B is a schematic view for explaining the manufacturing method according to the embodiment. [Figure 5C] FIG. 5C is a schematic view for explaining the manufacturing method according to the embodiment. [Figure 5D] FIG. 5D is a schematic view for explaining the manufacturing method according to the embodiment. [Figure 5E] FIG. 5E is a schematic view for explaining the manufacturing method according to the embodiment. [Figure 6] FIG. 6 is a partially enlarged view of the mold and the blank when the first forming step is completed. [Figure 7] FIG. 7 is a partially enlarged view of the mold and the blank when the second forming step is completed. [Figure 8] FIG. 8 is a graph showing the analysis results of the example. DETAILED DESCRIPTION OF THE INVENTION

[0010] A manufacturing method for a press-formed product according to an embodiment includes a preparation step and a formation step. In the preparation step, a blank is prepared. In the formation step, the blank is formed into a press-formed product using a first mold and a second mold. The first mold includes a first mold body and a first roller. The first mold body has a first formation surface on which a plurality of convex portions are formed and arranged in parallel at intervals from each other. The first rollers are provided corresponding to the convex portions and are rotatable around rotation axes perpendicular to both the arrangement direction of the convex portions and the press direction. The second mold includes a second mold body and a second roller. The second mold body has a second formation surface on which a plurality of concave portions are formed corresponding to the convex portions and opposed to the first formation surface. The second roller is provided between the concave portions and is rotatable around a rotation axis perpendicular to both the arrangement direction and the press direction. The formation step includes a first formation step and a second formation step. In the first forming step, the first roller is disposed on the second mold side relative to the first forming surface, and the second roller is disposed on the first mold side relative to the second forming surface, and the second mold is brought relatively close to the first mold, and the blank is deformed by the first roller and the second roller. In the second forming step, after the first forming step, the first roller is housed in the first mold body, and the second roller is housed in the second mold body, and the blank is sandwiched between the first and second forming surfaces (first configuration).

[0011] In the manufacturing method of the first configuration, in the first forming step, the blank prepared in the preparation step is placed between the first mold and the second mold. Then, with the first roller positioned on the second mold side relative to the first forming surface and the second roller positioned on the first mold side relative to the second forming surface, the second mold is moved relatively close to the first mold, causing the first roller and the second roller to contact both sides of the blank. The first roller bends the blank convexly toward the second mold, and the second roller bends the blank convexly toward the first mold. At this time, the blank is pulled toward the inside of the first and second molds while being sandwiched between the first and second rollers. In the second forming step after the first forming step, the first roller is housed in the first mold and the second roller is housed in the second mold, and the blank is sandwiched between the first and second forming surfaces. This results in a corrugated press-formed product formed along the multiple convex portions arranged in parallel on the first forming surface. As described above, in the manufacturing method of the first configuration, a corrugated press-formed product is formed in two steps, a first forming step and a second forming step. In this case, the blank is preliminarily bent by the first roller and the second roller, and then further bent by the first die body and the second die body. Therefore, compared to normal press forming, in which the blank is simply pressed between an upper die and a lower die to form a corrugated press-formed product, the drawing force applied while bending the blank can be reduced.

[0012] In the first manufacturing method, the first roller and the second roller are rotatable around a rotation axis perpendicular to both the arrangement direction of the convex portions and the pressing direction. This allows the first roller and the second roller to rotate in accordance with the movement of the blank when the blank is drawn into the mold during the forming process and moves while being bent by the first roller and the second roller. Therefore, the blank can be formed by the first mold and the second mold including the first roller and the second roller while reducing the frictional force between the blank and the first roller and the second roller.

[0013] As described above, according to the first manufacturing method, in the forming process of a corrugated press-formed product, it is possible to reduce the force that draws in the blank while bending it, and also reduce the frictional force that occurs in the blank, thereby making it possible to manufacture a corrugated press-formed product while suppressing the occurrence of cracks in the blank.

[0014] In the manufacturing method of the first configuration, the length of the blank between adjacent first and second rollers is Lm when the first forming process is completed and Lf when the second forming process is completed, and is 0.6×Lf≦Lm≦1.2×Lf (second configuration).

[0015] A mold according to an embodiment is used to manufacture a press-molded product. The mold includes a first mold and a second mold. The first mold includes a first mold body and a first roller. The first mold body has a first molding surface on which a plurality of convex portions are formed and arranged in parallel at intervals from each other, and a first groove is formed at the position of each of the convex portions. The first roller is provided corresponding to each of the convex portions and is rotatable around a rotation axis perpendicular to both the arrangement direction of the convex portions and the press direction. The first roller is configured to be able to be housed in the first groove. The second mold includes a second mold body and a second roller. The second mold body has a plurality of concave portions formed therein corresponding to the convex portions, and has a second molding surface opposing the first molding surface, and a second groove is formed between the concave portions. The second roller is provided between the concave portions and is rotatable around a rotation axis perpendicular to both the arrangement direction of the convex portions and the press direction. The second roller is configured to be able to be housed in the second groove (third configuration).

[0016] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the same or equivalent components are designated by the same reference numerals, and the same description will not be repeated.

[0017] [Press-molded products] FIG. 1 is a perspective view of a press-formed product 90 manufactured by the manufacturing method according to this embodiment. The press-formed product 90 may be an automobile part. The press-formed product 90 is attached to, for example, a side sill or a battery case of the automobile. In the example of FIG. 1, the press-formed product 90 is a long member.

[0018] The press-formed product 90 has a wave-shaped shape in a side view. The press-formed product 90 includes a plurality of protrusions 91 and a connecting portion 92. The press-formed product 90 includes two or more protrusions 91. The press-formed product 90 includes, for example, three or more protrusions 91. The press-formed product 90 may include 18 or fewer protrusions 91. The protrusions 91 are arranged in parallel and spaced apart from one another. In this embodiment, the protrusions 91 are arranged in the longitudinal direction of the press-formed product 90. The spacing between the protrusions 91 may or may not be constant. The connecting portion 92 connects adjacent protrusions 91. The connecting portion 92 may have a generally flat shape, or may have a generally curved shape.

[0019] FIG. 2 is a vertical cross-sectional view (cross-sectional view taken along line II-II in FIG. 1) of the press-formed product 90. The vertical cross-section of the press-formed product 90 is a cross-section of the press-formed product 90 when cut along the arrangement direction of the protrusions 91 and the vertical direction. The vertical direction is the direction in which the protrusions 91 protrude relative to the connecting portions 92. Referring to FIG. 2, in the vertical cross-sectional view of the press-formed product 90, each of the protrusions 91 has a trapezoidal shape. However, each of the protrusions 91 may have other shapes, such as a rectangular shape or a semicircular shape, in the vertical cross-sectional view of the press-formed product 90. In this embodiment, each of the protrusions 91 includes a top plate 911, two ridge portions 912, two side walls 913, and two ridge portions 914.

[0020] In a vertical cross-sectional view of the press-formed product 90, the side walls 913 are arranged on both sides of the top plate 911. The side walls 913 are connected to the top plate 911 via ridge portions 912, respectively. The ridge portions 912 are corner portions between the top plate 911 and the side walls 913. Each of the ridge portions 912 has, for example, an arc shape in a vertical cross-sectional view of the press-formed product 90. The top plate 911 extends from one ridge portion 912 to the other ridge portion 912 in a vertical cross-sectional view of the press-formed product 90. The top plate 911 may be parallel to the arrangement direction in a vertical cross-sectional view of the press-formed product 90, or may not be parallel to the arrangement direction. The top plate 911 may have an overall flat shape, or may have an overall curved shape.

[0021] In a vertical cross-sectional view of the press-formed product 90, each of the side walls 913 extends from the ridge portion 912 toward the connecting portion 92. The side walls 913 may be parallel or non-parallel in the up-down direction in a vertical cross-sectional view of the press-formed product 90. The side walls 913 are connected to the connecting portion 92 via ridge portions 914, respectively. The ridge portions 914 are corner portions between the side walls 913 and the connecting portions 92. Each of the ridge portions 914 has, for example, an arc shape in a vertical cross-sectional view of the press-formed product 90. In this case, the R end of the ridge portion 914 on the connecting portion 92 side is the boundary between the convex portion 91 and the connecting portion 92.

[0022] If the distance between adjacent protrusions 91 is W1 and the height of each protrusion 91 is h1, h1 / W1 is preferably 2.25 or less, and more preferably 1.00 or less. h1 / W1 may be 0.01 or greater. h1 / W1 is preferably 0.05 or greater, more preferably 0.10 or greater, even more preferably 0.20 or greater, even more preferably 0.30 or greater, and even more preferably 0.41 or greater. The distance W1 between adjacent protrusions 91 is the distance from the center of one protrusion 91 to the center of the other protrusion 91 in the arrangement direction of these protrusions 91. The height h1 is the maximum distance from the center of the thickness of the top plate 911 of each protrusion 91 to the center of the thickness of the connecting portion 92 in the up-down direction. If the heights h1 of adjacent protrusions 91 are different, h1 / W1 is calculated using the larger height h1 of the two protrusions 91.

[0023] [Mold] 3 is a perspective view schematically showing a mold 1 according to this embodiment. The mold 1 is used to manufacture a press-molded product 90 (FIGS. 1 and 2). In this embodiment, the mold 1 corresponds to the long press-molded product 90 and has an elongated shape. The mold 1 includes a first mold 10 and a second mold 20.

[0024] In the example of FIG. 3, the first mold 10 is disposed below the second mold 20. The second mold 20 can move closer to and farther away from the first mold 10. The first mold 10 and the second mold 20 are attached to, for example, a known press machine. The second mold 20 is attached to, for example, a slide (not shown) of the press machine and moves together with the slide. Alternatively, the first mold 10 may be attached to the slide and move together with the slide. Hereinafter, the direction in which the first mold 10 and the second mold 20 move closer to and farther away from each other is referred to as the press direction P. The press direction P is, for example, the vertical direction. The press direction P corresponds, for example, to the up-and-down direction of the press-molded product 90 (FIGS. 1 and 2).

[0025] The first mold 10 includes a first mold body 11 and a plurality of rollers 12 .

[0026] The first mold body 11 has a molding surface 111. The molding surface 111 is provided on the surface of the first mold body 11 that faces the second mold 20. The molding surface 111 has a shape corresponding to the press-molded product 90 (FIGS. 1 and 2). A plurality of protrusions 112 are formed on the molding surface 111.

[0027] The protrusions 112 are arranged in parallel with a gap between them. In this embodiment, the protrusions 112 are arranged in the longitudinal direction of the die 1. Each of the protrusions 112 may extend in a direction substantially perpendicular to the arrangement direction A of the protrusions 112 and the press direction P. In this embodiment, the direction substantially perpendicular to the arrangement direction A of the protrusions 112 and the press direction P is the short side direction of the die 1. The protrusions 112 have a shape corresponding to the protrusions 91 of the press-molded product 90 (FIGS. 1 and 2). The arrangement direction A of the protrusions 112 corresponds to the arrangement direction of the protrusions 91 of the press-molded product 90.

[0028] The rollers 12 are provided corresponding to the protrusions 112. The rollers 12 are arranged in the arrangement direction A of the protrusions 112. Each of the rollers 12 has, for example, a cylindrical or columnar shape. The rollers 12 are rotatable around a rotation axis 121. The rotation axis 121 is an imaginary axis that is perpendicular to both the arrangement direction A of the protrusions 112 and the pressing direction P. In this embodiment, the rotation axis 121 extends in the short direction of the mold 1.

[0029] The second mold 20 includes a second mold body 21 and at least one roller 22. In this embodiment, the second mold 20 includes a plurality of rollers 22.

[0030] The second mold body 21 has a molding surface 211. The molding surface 211 faces the molding surface 111 of the first mold body 11. The molding surface 211 has a shape corresponding to the molding surface 111. Specifically, the molding surface 211 has a plurality of recesses 212 formed thereon corresponding to the protrusions 112 of the molding surface 111.

[0031] The recesses 212 are arranged in parallel with one another at intervals. In this embodiment, the recesses 212 are arranged in the longitudinal direction of the mold 1. The recesses 212 have shapes corresponding to the protrusions 112.

[0032] The rollers 22 are provided between the recessed portions 212. One roller 22 is disposed between adjacent recessed portions 212. The rollers 22 have, for example, a cylindrical or columnar shape. Each roller 22 is rotatable around a rotation axis 221. The rotation axis 221 is an imaginary axis that is perpendicular to both the arrangement direction A of the protrusions 112 and the pressing direction P. In this embodiment, the rotation axis 221 extends in the short direction of the mold 1.

[0033] The configuration of the mold 1 will be further described below with reference to Fig. 4. Fig. 4 is a longitudinal cross-sectional view of the mold 1. The longitudinal cross-section refers to a cross-section cut along the arrangement direction A and the pressing direction P.

[0034] 4, the protrusions 112 of the first mold 10 each have a trapezoidal shape when viewed in vertical cross section of the mold 1. However, the protrusions 112 may have other shapes, such as a rectangular shape or a semicircular shape, when viewed in vertical cross section of the mold 1. In this embodiment, each of the protrusions 112 includes a top surface 1121, two side surfaces 1122, two shoulder portions 1123, and two corner portions 1124.

[0035] The top surface 1121 intersects with the pressing direction P. The top surface 1121 may be substantially perpendicular to the pressing direction P, but may not be perpendicular. The top surface 1121 may have a generally flat shape, or may have a generally curved shape.

[0036] Each of the side surfaces 1122 is connected to the top surface 1121 via a shoulder portion 1123. In a vertical cross-sectional view of the mold 1, the side surfaces 1122 extend from the top surface 1121 toward the opposite side from the second mold 20. In a vertical cross-sectional view of the mold 1, the side surfaces 1122 may extend parallel to the pressing direction P or may be inclined relative to the pressing direction P. In a vertical cross-sectional view of the mold 1, the shoulder portion 1123 is, for example, arc-shaped.

[0037] The molding surface 111 includes at least one connecting surface 113. In this embodiment, the molding surface 111 includes multiple connecting surfaces 113. The connecting surface 113 is located on the opposite side of the second mold 20 from the top surface 1121 of the protrusion 112 in the pressing direction P. The connecting surfaces 113 connect adjacent protrusions 112 to each other. The connecting surfaces 113 are connected to the side surfaces 1122 of one of the adjacent protrusions 112 and the other protrusion 112 via corner portions 1124. The corner portions 1124 are, for example, arc-shaped in a vertical cross-sectional view of the mold 1. In this case, the R end of the corner portion 1124 on the connecting surface 113 side is the boundary between the protrusion 112 and the connecting surface 113.

[0038] The connecting surfaces 113 intersect with the pressing direction P. Each of the connecting surfaces 113 faces one of the rollers 22 of the second mold 20 in the pressing direction P. The connecting surfaces 113 may be substantially perpendicular to the pressing direction P, but they do not have to be perpendicular. The connecting surfaces 113 may have a generally flat shape, or may have a generally curved shape.

[0039] If the distance between adjacent protrusions 112 is W2 and the height of each protrusion 112 is h2, h2 / W2 is preferably 2.25 or less, and more preferably 1.00 or less. h2 / W2 may be 0.01 or greater. h2 / W2 is preferably 0.05 or greater, more preferably 0.10 or greater, even more preferably 0.20 or greater, even more preferably 0.30 or greater, and even more preferably 0.41 or greater. The distance W2 between adjacent protrusions 112 is the distance from the center of one protrusion 112 to the center of the other protrusion 112 in the arrangement direction A of these protrusions 112. The height h2 is the maximum distance from the top surface 1121 of each protrusion 112 to the connecting surface 113 in the pressing direction P. If the heights h2 of adjacent protrusions 112 are different, h2 / W2 is calculated using the larger of the heights h2 of the two protrusions 112. h2 / W2 corresponds to h1 / W1 in the press-formed product 90 (FIG. 2).

[0040] In the first mold body 11, a groove 114 is formed at the position of each of the protrusions 112. The groove 114 is formed in the top surface 1121 of the protrusion 112. The groove 114 has a recessed shape extending from the top surface 1121 toward the inside of the first mold 10.

[0041] The roller 12 is configured to be able to be housed in the groove 114. The roller 12 is supported by, for example, a support member 122 arranged in the groove 114. The support member 122 is a member that is expandable and contractible in the pressing direction P. The support member 122 is, for example, a coil spring, an air spring, a fluid pressure cylinder, or an actuator. The roller 12 is supported while being arranged on the second mold 20 side with respect to the top surface 1121 of the convex portion 112. The radius of the roller 12 may be larger than the radius of curvature of the shoulder portion 1123.

[0042] Each of the recesses 212 of the second mold 20 has a bottom surface 2121 , two side surfaces 2122 , two shoulder portions 2123 , and two corner portions 2124 .

[0043] The bottom surface 2121 is provided corresponding to the top surface 1121. The bottom surface 2121 faces the top surface 1121 in the pressing direction P. The bottom surface 2121 faces one of the rollers 12 of the first mold 10 in the pressing direction P. The bottom surface 2121 may be substantially perpendicular to the pressing direction P, but it does not have to be perpendicular. The bottom surface 2121 may have a generally flat shape, or may have a generally curved shape.

[0044] The side surfaces 2122 are provided corresponding to the side surfaces 1122. Each of the side surfaces 2122 is connected to the bottom surface 2121 via a corner portion 2124. The side surfaces 2122 extend from the bottom surface 2121 toward the first mold 10 in a vertical cross-sectional view of the mold 1. In a vertical cross-sectional view of the mold 1, the side surfaces 2122 may extend parallel to the pressing direction P or may be inclined relative to the pressing direction P. The corner portions 2124 are provided corresponding to the shoulder portions 1123. The corner portions 2124 are, for example, arc-shaped in a vertical cross-sectional view of the mold 1.

[0045] The molding surface 211 includes at least one connecting surface 213. In this embodiment, the molding surface 211 includes a plurality of connecting surfaces 213. The connecting surfaces 213 connect the recesses 212 to each other. Specifically, the connecting surfaces 213 connect the shoulder portions 2123 of adjacent recesses 212 to each other. The shoulder portions 2123 are provided corresponding to the corner portions 1124. The shoulder portions 2123 are, for example, arc-shaped in a vertical cross-sectional view of the mold 1. The connecting surface 213 is located on the first mold 10 side relative to the bottom surfaces 2121 of the recesses 212.

[0046] The connection surface 213 intersects with the pressing direction P. The connection surface 213 may be substantially perpendicular to the pressing direction P, but may not be perpendicular. The connection surface 213 may have a generally flat shape, or may have a generally curved shape.

[0047] In the second mold body 21, grooves 214 are formed between the recesses 212. The grooves 214 are formed in the connection surface 213. The grooves 214 have a concave shape extending from the connection surface 213 toward the inside of the second mold 20.

[0048] The roller 22 is provided at the position of the connection surface 213. The roller 22 is configured to be able to be housed in the groove 214. The roller 22 is supported, for example, by a support member 222 arranged in the groove 214. The support member 222 is a member that is expandable and contractible in the pressing direction P. The support member 222 is, for example, a spring, an air spring, or a fluid pressure cylinder. The roller 22 is supported while being arranged on the first mold 10 side of the connection surface 213. The radius of the roller 22 may be larger than the radius of curvature of the shoulder portion 2123.

[0049] [Method of manufacturing press-molded products] 5A to 5E, an example of a method for manufacturing a press-molded product 90 using the mold 1 will be described. This manufacturing method includes a preparation step and a molding step.

[0050] Referring to FIG. 5A, in the preparation step, a blank 30 is prepared. The blank 30 is a metal plate, typically a steel plate. The blank 30 has a tensile strength of, for example, 270 MPa or more. The tensile strength of the blank 30 may be 590 MPa or more, 780 MPa or more, 980 MPa or more, or 1180 MPa or more. The thickness of the blank 30 may be, for example, 0.1 mm or more and 4.0 mm or less, or 0.8 mm or more and 2.3 mm or less.

[0051] 5B to 5E, in the forming step, the blank 30 is formed into a press-formed product 90 (FIGS. 1 and 2) using a first mold 10 and a second mold 20. The forming step includes a first forming step and a second forming step.

[0052] 5B , in the first molding step, roller 12 is disposed on the second mold 20 side with respect to the molding surface 111, and roller 22 is disposed on the first mold 10 side with respect to the molding surface 211. In this state, second mold 20 is moved relatively close to first mold 10, and blank 30 is deformed by rollers 12 and 22. Specifically, first, first mold 10 and second mold 20 are separated in the press direction P. For example, second mold 20 is disposed at the top dead center. In this state, blank 30 is disposed between first mold 10 and second mold 20. At this time, roller 12 protrudes from first mold body 11 toward second mold 20, and roller 22 protrudes from second mold body 21 toward first mold 10. For example, support members 122 and 222 are respectively in an extended state, so that rollers 12 and 22 are positioned between molding surface 111 of first mold body 11 and molding surface 211 of second mold body 21. The blank 30 is placed on, for example, rollers 12 .

[0053] Next, as shown in FIG. 5C , the second mold 20 is moved relatively closer to the first mold 10 in the pressing direction P. As a result, the rollers 12 and 22 contact the blank 30 from both sides. At this time, the support members 122 and 222 are maintained in an extended state. Therefore, the roller 12 is maintained in a position on the second mold 20 side with respect to the molding surface 111 of the first mold body 11, and the roller 22 is maintained in a position on the first mold 10 side with respect to the molding surface 211 of the second mold body 21. As the second mold 20 is moved relatively closer to the first mold 10, the rollers 12 and 22 deform the blank 30. Specifically, the roller 12 presses the blank 30 toward the second mold 20, causing the blank 30 to bend convexly toward the second mold 20 at the position of the roller 12. Furthermore, the roller 22 presses the blank 30 toward the first mold 10, causing the blank 30 to bend convexly toward the first mold 10 at the position of the roller 22. As a result, the blank 30 is deformed into a wave shape along the rollers 12, 22 in a vertical cross-sectional view of the mold 1. At this time, the blank 30 is pulled inward in the arrangement direction A while being clamped between the rollers 12, 22. Because the rollers 12, 22 are in contact with the blank 30, they rotate around the rotation axes 121, 221, respectively, as the blank 30 moves.

[0054] 5D, the first molding step is completed by sandwiching the blank 30 between the roller 12 and the second mold body 21 and between the roller 22 and the first mold body 11. Upon completion of the first molding step, the blank 30 may be sandwiched between the roller 12 and the bottom surface 2121 and between the roller 22 and the connecting surface 113.

[0055] In the second molding step, after the first molding step, roller 12 is housed in first mold body 11 and roller 22 is housed in second mold body 21, and blank 30 is sandwiched between molding surface 111 and molding surface 211. More specifically, after the first molding step, second mold 20 is brought closer relative to first mold 10. As a result, roller 12 is pressed toward first mold body 11 by second mold body 21, and roller 22 is pressed toward second mold body 21 by first mold body 11. Roller 12 moves toward first mold body 11 as support member 122 contracts, and roller 22 moves toward second mold body 21 as support member 222 contracts. As second mold 20 approaches first mold 10, roller 12 is gradually housed in groove 114 of first mold 10, and roller 22 is gradually housed in groove 214 of second mold 20.

[0056] 5E, ultimately, the roller 12 is entirely housed in the first die body 11, and the roller 22 is entirely housed in the second die body 21. The second molding step is completed when the first die body 11 and the second die body 21 close and the blank 30 is sandwiched between the molding surfaces 111 and 211. In this way, the press-formed product 90 is formed.

[0057] The timing to start storing the rollers 12, 22, i.e., the timing to complete the first forming step (start the second forming step), is preferably set appropriately based on the length of the blank 30 between the adjacent rollers 12, 22. Referring to Figures 6 and 7, the length of the blank 30 between the adjacent rollers 12 and 22 may be 0.6 x Lf ≤ Lm ≤ 1.2 x Lf, where Lm is the length at the completion of the first forming step and Lf is the length at the completion of the second forming step.

[0058] Fig. 6 is a partially enlarged view of the mold 1 and the blank 30 at the completion of the first forming step (Fig. 5D). As shown in Fig. 6, the length Lm at the completion of the first forming step is the length of the blank 30 in the range from the rotation axis 121 of the roller 12 to the rotation axis 221 of the roller 22 in a vertical cross section. More specifically, the length Lm is the line length of the thickness center of the blank 30 from the position of the rotation axis 121 of the roller 12 to the position of the rotation axis 221 of the roller 22 in the vertical cross section of the mold 1 at the completion of the first forming step.

[0059] Fig. 7 is a partially enlarged view of the mold 1 and the blank 30 at the completion of the second forming step (Fig. 5E). As shown in Fig. 7, the length Lf at the completion of the second forming step is the length of the blank 30 in the range from the rotation axis 121 of the roller 12 to the rotation axis 221 of the roller 22 in a vertical cross section. More specifically, the length Lf is the line length of the thickness center of the blank 30 from the position of the rotation axis 121 of the roller 12 to the position of the rotation axis 221 of the roller 22 in the vertical cross section of the mold 1 at the completion of the second forming step.

[0060] [effect] In the manufacturing method according to the embodiment, in the first forming step, the blank 30 prepared in the preparation step is placed between the first mold 10 and the second mold 20. Then, with roller 12 positioned on the second mold 20 side relative to the forming surface 111 and roller 22 positioned on the first mold 10 side relative to the forming surface 211, the second mold 20 is moved relatively close to the first mold 10, whereby rollers 12 and 22 come into contact with both sides of the blank 30. Roller 12 bends the blank 30 convexly toward the second mold 20 side, and roller 22 bends the blank 30 convexly toward the first mold 10 side. At this time, while being sandwiched between rollers 12 and 22, the blank 30 is drawn inward of the mold 1 in the arrangement direction A. In the second forming step after the first forming step, roller 12 is housed in the first mold 10 and roller 22 is housed in the second mold 20, and the blank 30 is sandwiched between the forming surface 111 and the forming surface 211. This forms a corrugated press-formed product 90 that follows the multiple convex portions 112 arranged in parallel on the forming surface 111. In this way, in the manufacturing method according to this embodiment, the corrugated press-formed product 90 is formed in two steps, the first forming step and the second forming step. In this case, the blank 30 is preliminarily bent by the rollers 12 and 22, and then further bent by the first die body 11 and the second die body 21. Therefore, compared to normal press forming in which the blank is simply pressed between an upper die and a lower die to form a corrugated press-formed product, the drawing force applied while bending the blank 30 can be reduced.

[0061] The radius of the rollers 12, 22 may be larger than the radius of curvature of the shoulder portions 1123, 2123. In the first forming step, the blank 30 is bent along the rollers 12, 22 with a relatively large radius of curvature. In the subsequent second forming step, the blank 30 is bent along the shoulder portions 1123, 2123 with a relatively small radius of curvature and is clamped between the forming surface 111 of the first mold body 11 and the forming surface 211 of the second mold body 21. In this way, by forming the blank 30 with the rollers 12, 22 with a relatively large radius of curvature and then forming the blank 30 with the shoulder portions 1123, 2123 with a relatively small radius of curvature, the pulling force applied to the blank 30 while bending it during forming can be further reduced.

[0062] In the manufacturing method according to this embodiment, the rollers 12, 22 that come into contact with the blank 30 during forming are rotatable around rotation axes 121, 221 that are perpendicular to both the arrangement direction A and the press direction P. This allows the rollers 12, 22 to rotate in conjunction with the movement of the blank 30 when the blank 30 is drawn into the mold 1 during the forming process and moves while being bent by the rollers 12, 22. Therefore, the blank 30 can be formed by the first mold 10 and the second mold 20, which include the rollers 12, 22, while reducing the frictional force between the blank 30 and the rollers 12, 22.

[0063] As described above, according to the manufacturing method of this embodiment, in the forming process of the corrugated press-formed product 90, it is possible to reduce the force that draws in the blank 30 while bending it, and also reduce the frictional force that occurs in the blank 30. Therefore, it is possible to manufacture the corrugated press-formed product 90 while suppressing the occurrence of cracks in the blank 30.

[0064] The length of the blank 30 between the rollers 12 and 22 may be 0.6 × Lf ≦ Lm ≦ 1.2 × Lf, where Lm is the length at the completion of the first forming step and Lf is the length at the completion of the second forming step. When 0.6 × Lf ≦ Lm is satisfied, a sufficient amount of blank 30 can be secured inside the mold 1, thereby preventing cracks in the blank 30 and facilitating the formation of a corrugated press-formed product 90. Furthermore, when Lm ≦ 1.2 × Lf is satisfied, the blank 30 is not excessively drawn into the mold 1, making it less likely to wrinkle. If large wrinkles occur in the blank 30, the wrinkles will fold over in portions of the blank 30, increasing their thickness. When the blank 30 in this state is clamped between the first mold 10 and the second mold 20, loads will concentrate on the thickened portions of the blank 30, making the surfaces of the first mold 10 and the second mold 20 more susceptible to dents and damage. In contrast to this, when Lm≦1.2×Lf is satisfied, wrinkles in the blank 30 can be suppressed, and therefore damage to the first mold 10 and the second mold 20 is less likely to occur.

[0065] When using a general press-molding die, that is, a die that does not have rollers 12, 22 as in the present embodiment, the greater the number of protrusions 91, the greater the difficulty of forming the press-molded product 90. For example, when there are three or more protrusions 91, it is difficult to form the press-molded product 90 without cracking using a general press-molding die. In contrast, in the manufacturing method according to the present embodiment, by using a die 1 that has rollers 12, 22, it is possible to simultaneously form more protrusions 91 than when using a general press-molding die. In the manufacturing method according to the present embodiment, it is possible to form the press-molded product 90 while suppressing the occurrence of cracks, even when there are three or more protrusions 91, for example.

[0066] The difficulty of forming the press-formed product 90 also varies depending on the ratio h1 / W1 of the height h1 of the convex portions 91 to the distance W1 between adjacent convex portions 91. When h1 / W1 is large, it is difficult to form the press-formed product 90 even if the number of convex portions 91 is small. In contrast, the manufacturing method according to this embodiment makes it possible to form the press-formed product 90 even when h1 / W1 is relatively large. In the manufacturing method according to this embodiment, by using a mold 1 having rollers 12 and 22, it is possible to simultaneously form more convex portions 91 than when using a general press-forming mold, when compared for the same h1 / W1. h1 / W1 is preferably 2.25 or less, and more preferably 1.00 or less. This makes it easier to ensure the formability of the press-formed product 90.

[0067] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present disclosure. [Example]

[0068] The present disclosure will be described in more detail below with reference to examples, although the present disclosure is not limited to the following examples.

[0069] In order to confirm the effects of the present disclosure, a press forming analysis was performed using general-purpose CAE analysis software (LS-DYNA, manufactured by ANSYS, Inc.). In the analysis, a blank with a tensile strength of 980 MPa and a thickness of 2.0 mm was pressed using a die to form the corrugated press-formed product 90 shown in Figures 1 and 2. The analysis conditions and results are shown in Table 1. The analysis results are also shown in Figure 8.

[0070] [Table 1]

[0071] In Table 1, in the comparative examples where rollers are "absent," the press-formed product 90 was formed by general press forming. Specifically, upper and lower dies without rollers were used, and the press-formed product 90 was formed by simply clamping the blank between the upper and lower dies. On the other hand, in Examples 1 to 5 where rollers are "present," the press-formed product 90 was formed by the manufacturing method according to the present disclosure. In Examples 1 to 5, the press-formed product 90 was formed using a die 1 (FIGS. 3 and 4) including rollers 12, 22. The roll diameter of the rollers 12, 22 was 38.9 mm. The coefficients of friction between the die bodies 11, 21 and the blank and between the rollers 12, 22 and the blank were both 0.1.

[0072] For the comparative example and examples 1 to 5, the thickness reduction rate (%) at the longitudinal center and end portions of the obtained press-formed products 90 was investigated. In this analysis, a thickness reduction rate of less than 13% at both the center and end portions was judged as "Good", and a rate of 13% or more was judged as "Poor". Furthermore, for the comparative example and examples 1 to 5, the presence or absence of cracks in the obtained press-formed products 90 was investigated. In this analysis, a crack was judged as "present" if a crack occurred in at least one of the center and end portions of the press-formed product 90, and a crack was judged as "absent" if a crack did not occur in either the center or end portion. For the center portion, a thickness reduction rate of 13% or more was judged as having a crack in the press-formed product 90, and for the end portions, a thickness reduction rate of 9% or more was judged as having a crack in the press-formed product 90.

[0073] 8, in the comparative example in which a roller was "absent," a press-formed product 90 including two protrusions 91 was formed, while in examples 1 to 5 in which a roller was "present," a press-formed product 90 including two or more protrusions 91 was formed. While cracks occurred in the press-formed product 90 in the comparative example, no cracks occurred in the press-formed product 90 in examples 1 to 5. This shows that the manufacturing method according to the present disclosure can manufacture a corrugated press-formed product 90 while suppressing the occurrence of cracks.

[0074] When comparing the comparative example with examples 4 and 5, which have the same h1 / W1, cracks occurred in the press-formed product 90 in the comparative example, whereas no cracks occurred in the press-formed product 90 in examples 4 and 5. In particular, in example 4, although the number of protrusions 91 was greater than in the comparative example, no cracks occurred in the press-formed product 90. Therefore, it can be seen that the manufacturing method according to the present disclosure makes it possible to manufacture a press-formed product 90 including more protrusions 91 while suppressing the occurrence of cracks. [Explanation of symbols]

[0075] 1: Mold 10: First mold 11: First mold body 111: Molding surface (first molding surface) 112: Convex 114: Groove (1st groove) 12: Roller (first roller) 121: Rotation axis 20: Second mold 21: Second mold body 211: Molding surface (second molding surface) 212: Recess 214: Groove (2nd groove) 22: Laura (2nd Laura) 30: Blank 90: Press-molded products A: Array direction P: Press direction

Claims

1. A method for manufacturing a press-molded product, a preparation step of preparing a blank; a forming step of forming the blank into a press-formed product using a first die including a first die body having a first forming surface on which a plurality of convex portions arranged in parallel at intervals from each other are formed, and first rollers provided corresponding to the convex portions and rotatable around rotation axes perpendicular to both the arrangement direction of the convex portions and the press direction, and a second die including a second die body having a second forming surface facing the first forming surface on which a plurality of concave portions are formed corresponding to the convex portions, and second rollers provided between the concave portions and rotatable around rotation axes perpendicular to both the arrangement direction and the press direction, The molding step includes: a first forming step of moving the second die relatively close to the first die in a state where the first roller is disposed on the second die side with respect to the first forming surface and the second roller is disposed on the first die side with respect to the second forming surface, and deforming the blank with the first roller and the second roller; a second molding step of, after the first molding step, accommodating the first roller in the first mold body and the second roller in the second mold body, and clamping the blank between the first molding surface and the second molding surface.

2. The method of claim 1, A manufacturing method in which the length of the blank between the adjacent first roller and second roller is 0.6 x Lf ≦ Lm ≦ 1.2 x Lf, where Lm is the length at the completion of the first molding process and Lf is the length at the completion of the second molding process.

3. A mold used to manufacture a press-molded product, a first mold including: a first mold body having a first molding surface on which a plurality of convex portions are formed and arranged in parallel at intervals from each other, and a first groove formed at the position of each of the convex portions; and first rollers provided corresponding to each of the convex portions, rotatable around a rotation axis perpendicular to both the arrangement direction of the convex portions and the pressing direction, the first rollers configured to be able to be housed in the first grooves; a second mold body having a plurality of recesses formed corresponding to the protrusions, a second molding surface facing the first molding surface, and a second groove formed between the recesses; and a second roller provided between the recesses and rotatable around a rotation axis perpendicular to both the arrangement direction and the press direction, the second roller configured to be accommodated in the second groove.

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