JP7111057B2

JP7111057B2 - Press molding method

Info

Publication number: JP7111057B2
Application number: JP2019091808A
Authority: JP
Inventors: 祐輔藤井; 正樹卜部
Original assignee: JFE Steel Corp
Current assignee: JFE Steel Corp
Priority date: 2019-05-15
Filing date: 2019-05-15
Publication date: 2022-08-02
Anticipated expiration: 2039-05-15
Also published as: JP2020185591A

Description

本発明は、プレス成形方法に関し、特に、天板部、縦壁部及びフランジ部を有する断面ハット形状であり、側面視で長手方向に沿って高さ方向に凸状に湾曲する部位を有するプレス成形品のプレス成形方法に関する。 TECHNICAL FIELD The present invention relates to a press forming method, and in particular, a press having a hat-shaped cross section having a top plate portion, a vertical wall portion, and a flange portion, and having a portion convexly curved in the height direction along the longitudinal direction when viewed from the side. The present invention relates to a press molding method for a molded product.

プレス成形は、鋼板等の金属板（ブランク材）を一対の金型の間に挟んで挟圧して該金属板を金型の形状に倣うよう成形することで、該金属板を様々な形状の部品（プレス成形品）に加工する方法である。しかしながら、天板部と縦壁部とフランジ部とを有する断面ハット形状であって長手方向に沿って高さ方向に湾曲するプレス成形品（以下、「湾曲部品」という場合がある。）のプレス成形においては、フランジ部や天板部にしわが発生する場合がある。特に、近年では高張力鋼板を用いたプレス成形品が増えており、鋼板の強度が増加するに伴ってプレス成形品にしわが発生しやすくなるという問題がある。そのため、高張力鋼板を用いた場合にあっては、しわの発生をいかに抑制しながらプレス成形を行うかが課題となっている。 Press molding involves pressing a metal plate (blank material) such as a steel plate between a pair of dies and pressing the metal plate so as to follow the shape of the dies, thereby forming the metal plate into various shapes. This is a method of processing into parts (press-molded products). However, pressing a press-formed product (hereinafter sometimes referred to as a "curved part") that has a hat-shaped cross section having a top plate portion, a vertical wall portion, and a flange portion and is curved in the height direction along the longitudinal direction. During molding, wrinkles may occur in the flange portion and the top plate portion. In particular, in recent years, the number of press-formed products using high-strength steel sheets has increased, and there is a problem that press-formed products tend to be wrinkled as the strength of steel sheets increases. Therefore, in the case of using a high-strength steel sheet, the problem is how to perform press forming while suppressing the occurrence of wrinkles.

これまでに、しわを抑制して湾曲部品をプレス成形する技術がいくつか提案されている。
例えば、特許文献１には、長手方向の平面外で屈曲部を有する金属製断面ハット型形状部材を成形するに際し、天板部と縦壁部が形成する稜線部に、又は、該稜線部及び縦壁部とフランジ部が形成する角部の両方にフィレット部を形成することで、しわを抑制する技術が開示されている。
また、特許文献２には、天面部の幅方向端縁が長手方向に沿って湾曲する断面ハット状の湾曲プレス部品をプレス成形するに際し、平板状のブランク材の幅方向の端部にビードや折曲部などの高剛性部を設ける予備成形工程と、該高剛性部を残した状態で天面部と側壁部とを成形する本成形工程により、フランジ部におけるシワを抑制する技術が開示されている。
さらに、特許文献３には、上下方向に湾曲した湾曲部品に対し、パッドでブランクのパンチ底を板厚方向に加圧しながら該ブランクの端部をダイとホルダとで挟持してドロー成形を行うことで、しわを抑制する技術が開示されている。 Several techniques have been proposed so far for press-molding curved parts while suppressing wrinkles.
For example, in Patent Document 1, when forming a metal hat-shaped cross-sectional member having a bent portion out of the plane in the longitudinal direction, the ridge formed by the top plate portion and the vertical wall portion, or the ridge portion and A technique for suppressing wrinkles by forming fillet portions at both the corners formed by the vertical wall portion and the flange portion is disclosed.
Further, in Patent Document 2, when press-molding a curved press part having a hat-shaped cross section in which the width direction edge of the top surface portion is curved along the longitudinal direction, a bead or the like is formed at the width direction end of a flat plate-shaped blank material. A technique for suppressing wrinkles in the flange portion is disclosed by a preforming step of providing a highly rigid portion such as a bent portion and a main forming step of molding the top surface portion and the side wall portion while leaving the highly rigid portion. there is
Furthermore, in Patent Document 3, draw molding is performed by pinching the end of the blank between a die and a holder while pressing the punch bottom of the blank in the plate thickness direction with a pad for a curved part that is curved in the vertical direction. Therefore, a technique for suppressing wrinkles is disclosed.

特許４９０７５９０号公報Japanese Patent No. 4907590 特許５９６５１５９号公報Japanese Patent No. 5965159 特許５７３３４７５号公報Japanese Patent No. 5733475

しかしながら、特許文献１に開示されている技術は、１工程で金属製断面ハット型形状部材を成形するものであり、フィレット部を充分に押し潰すことができずに残ってしまい、目標形状の部品の剛性を低下させる要因になりやすいという問題がある。 However, the technique disclosed in Patent Document 1 forms a metal hat-shaped cross-sectional member in one step, and the fillet portion cannot be sufficiently crushed and remains, resulting in a part of the target shape. There is a problem that it tends to be a factor that lowers the rigidity of the

また、特許文献２に開示されている技術は、本成形工程に続くフランジ部平坦化工程において、ブランク材の幅方向の端部に形成されたビードや折曲部を平坦に押し潰すものであるが、該ビードや折曲部が十分に平坦に押し潰されない場合があった。 In addition, the technique disclosed in Patent Document 2 is to flatten the beads and bent portions formed at the ends of the blank in the width direction in the flange portion flattening step following the main forming step. However, in some cases, the beads and bent portions were not sufficiently flattened.

さらに、特許文献３に開示されている技術は、凹状湾曲部の天板や凸状湾曲部のフランジにおけるしわを抑制するため、パッドでブランクのパンチ底を板厚方向に加圧しながら該ブランクの端部をダイとホルダとで挟持して縦壁部を絞り加工で成形するため、該縦壁部においてはスプリングバックによる壁の反りが生じて問題となる場合があった。 Furthermore, in the technique disclosed in Patent Document 3, in order to suppress wrinkles in the top plate of the concave curved portion and the flange of the convex curved portion, the blank is pressed while pressing the punch bottom of the blank in the plate thickness direction with a pad. Since the vertical wall portion is formed by drawing while the end portion is sandwiched between a die and a holder, the vertical wall portion may warp due to springback, which poses a problem.

本発明は、上記のような課題を解決するためになされたものであり、天板部、縦壁部及びフランジ部を有する断面ハット形状であり、長手方向に沿って高さ方向に凸状に湾曲するプレス成形品を、しわを抑制してプレス成形することができるプレス成形方法を提供することを目的とする。 The present invention has been made to solve the above problems, and has a hat-shaped cross section having a top plate portion, a vertical wall portion, and a flange portion, and is convex in the height direction along the longitudinal direction. It is an object of the present invention to provide a press-molding method capable of press-molding a curved press-molded product while suppressing wrinkles.

＜発明に至った経緯＞
図１（ａ）に一例として示すような、天板部３と、天板部３から連続する縦壁部５と、縦壁部５から連続するフランジ部７とを有する断面ハット形状であり、側面視で天板部３とフランジ部７とが長手方向に沿って高さ方向に凸状に湾曲する凸状湾曲部位９を有するプレス成形品１を、従来技術のように１工程でプレス成形すると、しわがフランジ部７に生じやすく、特に、湾曲の大きい凸状湾曲部位９に生じやすい。 <Circumstances leading to the invention>
As shown in FIG. 1(a) as an example, it has a cross-sectional hat shape having a top plate portion 3, a vertical wall portion 5 continuous from the top plate portion 3, and a flange portion 7 continuous from the vertical wall portion 5, A press-formed product 1 having a convex curved portion 9 in which the top plate portion 3 and the flange portion 7 are convexly curved in the height direction along the longitudinal direction in a side view is press-formed in one step as in the conventional technology. As a result, wrinkles are likely to occur in the flange portion 7, particularly in the convex curved portion 9 having a large curvature.

これは、金属板である平板状のブランク材をその垂直方向に向かって凸状に湾曲させるため、縦壁部５からフランジ部７に向かう材料流れが凸状湾曲部位９に集中する結果、しわが発生するためである。したがって、しわを抑制するためには、プレス成形過程において縦壁部５からフランジ部７への材料流れを生じさせないようにすることが必要となる。 This is because the flat plate-shaped blank material, which is a metal plate, is curved in a convex shape in the vertical direction, so that the material flow from the vertical wall portion 5 toward the flange portion 7 concentrates on the convex curved portion 9, resulting in It is because I arise. Therefore, in order to suppress wrinkles, it is necessary to prevent material from flowing from the vertical wall portion 5 to the flange portion 7 during the press molding process.

そこで、本発明者は、長手方向に沿って凸状に湾曲するプレス成形品１をプレス成形するに際し、その縦壁部５からフランジ部７への材料流れを生じさせないようにする方法を鋭意検討した。その結果、まずは目標形状よりも長手方向中央から端部に至るほど平坦に押し潰された中間形状にプレス成形し、続いて該中間形状のプレス成形品をフォーム成形することにより曲げ成形のみで目標形状にプレス成形することにより、縦壁部５からフランジ部７への材料流れを抑制することを想到した。 Therefore, the present inventors diligently studied a method of preventing the material from flowing from the vertical wall portion 5 to the flange portion 7 when press-molding the press-molded product 1 curved in a convex shape along the longitudinal direction. did. As a result, the target shape was first press-molded into an intermediate shape that was flattened from the center in the longitudinal direction to the end, and then the press-molded product of the intermediate shape was formed to form the target shape only by bending. It was conceived of suppressing material flow from the vertical wall portion 5 to the flange portion 7 by press-molding into the shape.

次に、目標形状よりも平坦な中間形状をどのように決定するかについて検討した。検討においては、金属板の端部側は中央に比べて変形が容易であることに着目した。そこで、目標形状のプレス成形品をその長手方向の両端から中央に向かって圧縮させることで、断面線長を維持したまま天板部と縦壁部の開き角度が大きくなって縦壁部の縦壁高さが小さくなること、さらには、長手方向の中央に比べて端部側の方が開き角度は大きく縦壁高さは低くなることを見出した。そして、このような中間形状をフォーム成形することで、しわを抑制して目標形状にプレス成形できるという知見が得られた。 Next, we examined how to determine an intermediate shape that is flatter than the target shape. In the study, attention was paid to the fact that the edge side of the metal plate deforms more easily than the central portion. Therefore, by compressing the press-formed product of the target shape from both ends in the longitudinal direction toward the center, the opening angle between the top plate portion and the vertical wall portion is increased while maintaining the cross-sectional line length. It was found that the wall height is reduced, and furthermore, the opening angle is larger and the vertical wall height is lower at the ends than at the center in the longitudinal direction. Then, it was found that by forming such an intermediate shape, wrinkles can be suppressed and press-molded into the target shape.

本発明は係る知見に基づいてなされたものであり、具体的には、以下の構成を備えてなるものである。 The present invention has been made based on such findings, and specifically includes the following configurations.

（１）本発明に係るプレス成形方法は、天板部と、該天板部から連続する縦壁部と、該縦壁部から連続するフランジ部とを有する断面ハット形状であり、前記天板部及び／又は前記フランジ部が側面視で長手方向に沿って高さ方向に凸状に湾曲する凸状湾曲部位を有するプレス成形品をプレス成形するものであって、前記プレス成形品の目標形状に比べて、長手方向長さが短くて前記凸状湾曲部位が前記目標形状よりも大きく湾曲し、かつ該凸状湾曲部位における前記天板部と前記縦壁部との開き角度が大きくて前記縦壁部の縦壁高さが低い中間形状のプレス成形品をプレス成形する中間形状成形工程と、該中間形状のプレス成形品をフォーム成形により目標形状にプレス成形する目標形状成形工程と、を備えたことを特徴とするものである。 (1) The press molding method according to the present invention has a hat-shaped cross section having a top plate portion, a vertical wall portion continuous from the top plate portion, and a flange portion continuous from the vertical wall portion, and the top plate and/or the flange portion press-forms a press-formed product having a convex curved portion that curves convexly in the height direction along the longitudinal direction in side view, wherein the target shape of the press-formed product , the length in the longitudinal direction is shorter, the convex curved portion curves more than the target shape, and the opening angle between the top plate portion and the vertical wall portion at the convex curved portion is large, and the An intermediate shape forming step of press-forming an intermediate-shaped press-formed product in which the vertical wall height of the vertical wall portion is low, and a target-shape forming step of press-forming the intermediate-shaped press-formed product into a target shape by form forming. It is characterized by having

（２）上記（１）に記載のものにおいて、前記中間形状成形工程における前記中間形状は、前記目標形状と同一形状の成形品モデルを設定し、該成形品モデルの長手方向の両端面に中央に向かう荷重又は変位を与えて成形解析を行うことにより決定することを特徴とするものである。 (2) In the method described in (1) above, the intermediate shape in the intermediate shape forming step is set by setting a molded product model having the same shape as the target shape, and centering on both end faces in the longitudinal direction of the molded product model. It is characterized by determining by performing a forming analysis by giving a load or displacement toward.

（３）上記（２）に記載のものにおいて、前記中間形状成形工程における前記中間形状は、前記成形解析後の中間形状モデルについて、その長手方向の端部側をさらに平坦にする逆解析を行うことにより決定することを特徴とするものである。 (3) In the above (2), the intermediate shape in the intermediate shape forming step is subjected to inverse analysis to further flatten the longitudinal end side of the intermediate shape model after the forming analysis. It is characterized in that it is determined by

（４）上記（１）に記載のものにおいて、前記中間形状成形工程における前記中間形状は、前記目標形状と同一形状の成形品モデルを設定し、該成形品モデルについてその長手方向の端部側を平坦にする逆解析を行い、該逆解析した後の中間形状モデルの長手方向の両端面に中央に向かう荷重又は変位を与えて成形解析を行うことにより決定することを特徴とするものである。 (4) In the above (1), the intermediate shape in the intermediate shape forming step is a molded product model having the same shape as the target shape. is flattened, and a load or displacement toward the center is applied to both end faces in the longitudinal direction of the intermediate shape model after the inverse analysis to determine by forming analysis. .

本発明においては、天板部と、該天板部から連続する縦壁部と、該縦壁部から連続するフランジ部とを有する断面ハット形状であり、前記天板部及び／又は前記フランジ部が側面視で長手方向に沿って高さ方向に凸状に湾曲する凸状湾曲部位を有するプレス成形品をプレス成形するものであって、前記プレス成形品の目標形状に比べて、長手方向長さが短くて前記凸状湾曲部位が前記目標形状よりも大きく湾曲し、かつ該凸状湾曲部位における前記天板部と前記縦壁部との開き角度が大きくて前記縦壁部の縦壁高さが低い中間形状のプレス成形品をプレス成形する中間形状成形工程と、該中間形状のプレス成形品をフォーム成形により目標形状にプレス成形する目標形状成形工程と、を備えたことにより、プレス成形過程における縦壁部からフランジ部への材料流れを抑制し、フランジ部におけるしわを抑制することができる。 In the present invention, the top plate portion, the vertical wall portion continuing from the top plate portion, and the flange portion continuing from the vertical wall portion have a hat-shaped cross section, and the top plate portion and / or the flange portion is for press-molding a press-formed product having a convex curved portion that is convexly curved in the height direction along the longitudinal direction in a side view, and the length in the longitudinal direction is greater than the target shape of the press-formed product is short, the convex curved portion is curved more than the target shape, and the opening angle between the top plate portion and the vertical wall portion at the convex curved portion is large, and the vertical wall height of the vertical wall portion is large. An intermediate shape forming step of press forming an intermediate shape press-formed product with a low thickness, and a target shape forming step of press forming the intermediate shape press-formed product into a target shape by form forming. It is possible to suppress material flow from the vertical wall portion to the flange portion in the process and suppress wrinkles in the flange portion.

本発明の実施の形態に係るプレス成形方法において、（ａ）成形対象とする目標形状のプレス成形品の一例と、（ｂ）中間形状成形工程でプレス成形する中間形状のプレス成形品の一例、を説明する図である（その１）。In the press-forming method according to the embodiment of the present invention, (a) an example of a target-shaped press-formed product to be formed, (b) an example of an intermediate-shaped press-formed product to be press-formed in the intermediate-shape forming step, (Part 1). 本発明の実施の形態に係るプレス成形方法において、（ａ）成形対象とする目標形状のプレス成形品の他の例と、（ｂ）中間形状成形工程でプレス成形する中間形状のプレス成形品の他の例、を説明する図である。In the press-forming method according to the embodiment of the present invention, (a) another example of a target-shaped press-formed product to be formed, and (b) an intermediate-shaped press-formed product to be press-formed in the intermediate-shape forming step. FIG. 10 is a diagram for explaining another example; 実施例１において、成形対象とする目標形状のプレス成形品の斜視図である。1 is a perspective view of a target-shaped press-formed product to be formed in Example 1. FIG. 実施例１において、成形対象とする目標形状のプレス成形品の断面図である。1 is a cross-sectional view of a target-shaped press-formed product to be formed in Example 1. FIG. 実施例２において、成形対象とする目標形状のプレス成形品の斜視図である。FIG. 10 is a perspective view of a target-shaped press-formed product to be formed in Example 2;

本発明の実施の形態に係るプレス成形方法は、図１（ａ）に示すように、長手方向に沿って高さ方向に湾曲するプレス成形品１をプレス成形するものであって、図１（ｂ）に示すような中間形状のプレス成形品１１に成形する中間形状成形工程と、中間形状のプレス成形品１１をフォーム成形により目標形状のプレス成形品１にプレス成形する目標形状成形工程と、を備えたものである。以下、各工程について説明する。
なお、本発明において、長手方向に沿って高さ方向に凸状に湾曲するとは、側面視において凸状に湾曲した円弧の中心がフランジ部７側に位置することをいう。 As shown in FIG. 1(a), the press-molding method according to the embodiment of the present invention is for press-molding a press-molded product 1 curved in the height direction along the longitudinal direction. An intermediate shape forming step of forming an intermediate shaped press-formed product 11 as shown in b), and a target shape forming step of press-forming the intermediate shaped press-formed product 11 into a target shaped press-formed product 1 by form forming, is provided. Each step will be described below.
In the present invention, to curve convexly in the height direction along the longitudinal direction means that the center of the convexly curved arc in a side view is located on the flange portion 7 side.

＜中間形状成形工程＞
中間形状成形工程は、図１（ｂ）に示すように、プレス成形品１の目標形状に比べて、長手方向長さLが短くて凸状湾曲部位１９が前記目標形状よりも大きく湾曲し、かつ凸状湾曲部位１９における天板部１３と縦壁部１５との開き角度が大きくて縦壁部１５の縦壁高さが低い中間形状のプレス成形品１１をプレス成形する工程である。 <Intermediate shape forming process>
In the intermediate shape forming step, as shown in FIG. 1(b), the length L in the longitudinal direction is shorter than the target shape of the press-formed product 1, and the convex curved portion 19 is curved more than the target shape. This is a step of press-molding the intermediate-shaped press-formed product 11 in which the opening angle between the top plate portion 13 and the vertical wall portion 15 at the convex curved portion 19 is large and the vertical wall portion 15 has a low vertical wall height.

ここで、凸状湾曲部位１９が前記目標形状よりも大きく湾曲する形状とは、図１（ａ）に示すように目標形状の凸状湾曲部位９の長手方向の両端面に中央に向かう荷重を与えることにより、長手方向長さLが目標形状の長手方向長さL₀よりも短くなって目標形状の凸状湾曲部位９の曲率よりも大きくなった形状のことをいう。 Here, the shape in which the convex curved portion 19 curves more than the target shape means that, as shown in FIG. It means a shape in which the longitudinal length L is shorter than the longitudinal length _L0 of the target shape and larger than the curvature of the convex curved portion 9 of the target shape.

また、天板部１３と縦壁部１５との開き角度は、天板部１３と縦壁部１５のなす角度のうち断面ハット形状の内側における角度であり、縦壁部１５の縦壁高さは、高さ方向における縦壁部１５の高さである（後述する図３中の縦壁高さHに該当）。 Further, the opening angle between the top plate portion 13 and the vertical wall portion 15 is the angle on the inner side of the cross-sectional hat shape among the angles formed by the top plate portion 13 and the vertical wall portion 15, and is the vertical wall height of the vertical wall portion 15. is the height of the vertical wall portion 15 in the height direction (corresponds to the vertical wall height H in FIG. 3, which will be described later).

そして、中間形状のプレス成形品１１における凸状湾曲部位１９の長手方向長さL（図１（ｂ））は、目標形状のプレス成形品１における凸状湾曲部位９の長手方向長さL₀（図１（ａ））に対する変化割合(＝(L₀－L)／L₀)が10%以上であることが好ましい。 The longitudinal length L (FIG. 1(b)) of the convex curved portion 19 in the intermediate-shaped press-formed product 11 is the longitudinal length L ₀ of the convex curved portion 9 in the target-shaped press-formed product 1 . It is preferable that the rate of change (=(L ₀ −L)/L ₀ ) with respect to (FIG. 1(a)) is 10% or more.

なお、中間形状成形工程における中間形状の具体的な決定方法については後述する。
また、中間形状成形工程は、ドロー成形又はフォーム成形のいずれであってもよい。 A specific method for determining the intermediate shape in the intermediate shape forming process will be described later.
Also, the intermediate shape forming process may be either draw molding or foam molding.

＜目標形状成形工程＞
目標形状成形工程は、中間形状のプレス成形品１１をフォーム成形により目標形状のプレス成形品１にプレス成形する工程である。 <Target shape forming process>
The target shape forming step is a step of press-forming the intermediate-shaped press-formed product 11 into the target-shaped press-formed product 1 by form forming.

＜中間形状の決定方法＞
中間形状成形工程における中間形状は、以下の（ａ）～（ｃ）に示す方法により決定することができる。 <How to determine the intermediate shape>
The intermediate shape in the intermediate shape forming step can be determined by the methods shown in (a) to (c) below.

（ａ）目標形状のプレス成形品と同一形状の成形品モデルを設定し、該成形品モデルの長手方向の両端面に中央に向かう荷重又は変位を与えて成形解析を行うことにより決定する。 (a) A molded product model having the same shape as the press-molded product having the target shape is set, and a load or displacement toward the center is applied to both longitudinal end faces of the molded product model to perform forming analysis.

成形解析後の中間形状モデルは、目標形状よりも長手方向長さが短くなって凸状湾曲部位（プレス成形品１１の凸状湾曲部位１９に相当）の高さ方向に大きく湾曲する。さらに、成形解析後の中間形状モデルは、目標形状における断面線長を維持したまま、天板部（プレス成形品１１の天板部１３に相当）と縦壁部（プレス成形品１１の縦壁部１５に相当）との開き角度が目標形状に比べて大きくなって縦壁部の縦壁高さが低くなる。さらに、成形解析後の中間形状モデルにおいては、長手方向の中央に比べて端部側の方が、天板部と縦壁部との開き角度が大きくて縦壁高さが低い。
このような成形解析後の中間形状モデルの形状を、中間形状成形工程における中間形状として決定する。 The intermediate shape model after forming analysis has a length in the longitudinal direction shorter than that of the target shape, and is greatly curved in the height direction of the convex curved portion (corresponding to the convex curved portion 19 of the press-formed product 11). Furthermore, the intermediate shape model after the forming analysis has the top plate portion (corresponding to the top plate portion 13 of the press-formed product 11) and the vertical wall portion (the vertical wall of the press-formed product 11) while maintaining the cross-sectional line length in the target shape. 15) becomes larger than the target shape, and the vertical wall height of the vertical wall portion becomes low. Furthermore, in the intermediate shape model after forming analysis, the opening angle between the top plate portion and the vertical wall portion is larger and the vertical wall height is lower at the ends than at the center in the longitudinal direction.
The shape of the intermediate shape model after such forming analysis is determined as the intermediate shape in the intermediate shape forming step.

（ｂ）上記（ａ）と同様に、目標形状のプレス成形品と同一形状に設定した成形品モデルの成形解析を行い、該成形解析を行った成形品モデルについてその長手方向の端部側をさらに平坦にする逆解析を行うことにより決定する。 (b) In the same manner as in (a) above, a molded product model set to have the same shape as the press-molded product of the target shape is subjected to molding analysis, and the longitudinal end side of the molded product model subjected to the molding analysis is measured. It is determined by further flattening inverse analysis.

逆解析とは、成形対象とする目標形状にプレス成形されたプレス成形品を、プレス成形前の平板状のブランク材またはその途中の形状に戻す解析である。具体的には、例えば、成形対象とする目標形状のプレス成形品を要素分割した成形品モデルを設定し、これをひずみエネルギーが最小または所定値まで低減するように（要素同士が重なることなく、また各要素の変形が最小または所定値まで低減するように）することで、プレス成形前の平板状のブランク材または中間形状に展開する。 Inverse analysis is an analysis of returning a press-formed product, which has been press-formed into a target shape to be formed, to a flat plate-like blank material before press-forming or a shape in the middle thereof. Specifically, for example, a molded product model obtained by dividing the press-formed product of the target shape to be molded into elements is set, and the strain energy is reduced to the minimum or a predetermined value (without overlapping the elements, In addition, by reducing the deformation of each element to a minimum or to a predetermined value, it develops into a flat plate-like blank material or an intermediate shape before press forming.

まず、目標形状の成形品モデルについて成形解析を行うことにより、前述のとおり、目標形状に比べて長手方向の両端から中央に向かって圧縮されて長手方向長さが短くなり、該成形品モデルにおける凸状湾曲部位（プレス成形品１１の凸状湾曲部位１９に相当）は、目標形状よりも大きく湾曲した形状の成形解析後の成形品モデルが得られる。
そして、該成形解析後の成形品モデルについてその長手方向の端部側を平坦にする逆解析を行うことにより、天板部（プレス成形品１１の天板部１３に相当）と縦壁部（プレス成形品１１の縦壁部１５に相当）との開き角度はさらに大きくなって縦壁部の縦壁高さは低くなった形状の逆解析後の中間形状モデルが得られる。そして、このような逆解析後の中間形状モデルの形状を、中間形状成形工程における中間形状として決定する。 First, by performing molding analysis on the molded product model of the target shape, as described above, compared to the target shape, it is compressed from both ends in the longitudinal direction toward the center, and the length in the longitudinal direction becomes shorter. For the convex curved portion (corresponding to the convex curved portion 19 of the press-formed product 11), a molded product model after molding analysis having a shape curved larger than the target shape is obtained.
Then, the top plate portion (corresponding to the top plate portion 13 of the press-formed product 11) and the vertical wall portion ( An intermediate shape model after inverse analysis of a shape in which the opening angle with respect to the vertical wall portion 15 of the press-formed product 11 is further increased and the vertical wall height of the vertical wall portion is decreased is obtained. Then, the shape of the intermediate shape model after such inverse analysis is determined as the intermediate shape in the intermediate shape forming step.

当該（ｂ）の方法により決定される中間形状は、上記（ａ）の方法により決定された中間形状と同様に、目標形状に比べて長手方向長さが小さく、高さ方向にさらに凸状に湾曲した形状であることに加え、長手方向の中央に比べて端部側が平坦な形状をより適切に決定することができる。 Similar to the intermediate shape determined by the method (a), the intermediate shape determined by the method (b) has a smaller length in the longitudinal direction than the target shape and is more convex in the height direction. In addition to the curved shape, a shape that is flatter at the ends than in the middle in the longitudinal direction can be determined more appropriately.

なお、一般的に逆解析は、プレス成形品の全領域を解析対象として平板状のブランク材に展開する。しかしながら、本発明における逆解析は、プレス成形品をモデル化した成形品モデルのうち少なくとも長手方向の端部側の所定の範囲が平坦化またはその途中の形状となるように展開するものである。そのため、本発明での逆解析においては、平坦化またはその途中形状とする長手方向の端部側における所定の範囲は、適宜設定すればよい。 In addition, inverse analysis is generally performed on a flat plate-shaped blank material with the entire region of the press-formed product as the analysis target. However, the reverse analysis in the present invention develops a molded product model obtained by modeling a press molded product so that at least a predetermined range on the end side in the longitudinal direction is flattened or has a shape in the middle. Therefore, in the inverse analysis of the present invention, the predetermined range on the end portion side in the longitudinal direction to be flattened or shaped in the middle thereof may be appropriately set.

（ｃ）目標形状と同一形状に設定した成形品モデルについて、その長手方向の端部側を平坦にする逆解析を行う。続いて、逆解析を行った中間形状モデルの長手方向の両端面に中央に向かう荷重又は変位を与えて成形解析を行う。そして、成形解析した中間形状モデルの形状を、中間形状成形工程における中間形状として決定する。 (c) Perform reverse analysis to flatten the ends in the longitudinal direction of the molded product model set to have the same shape as the target shape. Subsequently, forming analysis is performed by applying a load or displacement toward the center to both end surfaces in the longitudinal direction of the intermediate shape model subjected to inverse analysis. Then, the shape of the intermediate shape model subjected to molding analysis is determined as the intermediate shape in the intermediate shape molding process.

当該（ｃ）の方法により決定される中間形状は、前述の（ｂ）の方法と同様に、目標形状に比べて、長手方向長さが短くて高さ方向に大きく湾曲した形状であることに加え、長手方向の中央に比べて端部側がさらに平坦な形状である。 The intermediate shape determined by the method (c) is, as in the method (b) described above, a shape having a shorter length in the longitudinal direction and a greater curvature in the height direction than the target shape. In addition, the shape is flatter at the ends than at the center in the longitudinal direction.

なお、上記（ａ）乃至（ｃ）のいずれかの方法で決定された中間形状のプレス成形品１１は、前述のとおり目標形状のプレス成形品１の長手方向の両端から中央に向かって圧縮され、凸状湾曲部位１９が目標形状よりも湾曲したものである。そのため、中間形状のプレス成形品１１において、天板部１３と縦壁部１５との間の曲げ稜線部１４の稜線長さ、及び、縦壁部１５とフランジ部１７との間の曲げ稜線部１６の稜線長さはそれぞれ、目標形状のプレス成形品１の天板部３と縦壁部５との間の曲げ稜線部４の稜線長さ、及び、縦壁部５とフランジ部７との間の曲げ稜線部６の稜線長さに等しいものと考えられる。 The intermediate-shaped press-formed product 11 determined by any one of the above-described methods (a) to (c) is compressed toward the center from both ends in the longitudinal direction of the target-shaped press-formed product 1 as described above. , the convex curved portion 19 is curved more than the target shape. Therefore, in the intermediate-shaped press-formed product 11, the ridgeline length of the bending ridgeline portion 14 between the top plate portion 13 and the vertical wall portion 15, and the bending ridgeline portion between the vertical wall portion 15 and the flange portion 17 The ridgeline lengths of 16 are the ridgeline length of the bending ridgeline portion 4 between the top plate portion 3 and the vertical wall portion 5 of the press-formed product 1 of the target shape, and the ridgeline length between the vertical wall portion 5 and the flange portion 7. It is considered to be equal to the ridgeline length of the bending ridgeline portion 6 between.

すなわち、中間形状のプレス成形品１１は、目標形状の曲げ稜線部４及び曲げ稜線部６それぞれの稜線長さを維持したまま、長手方向の両端から中央に向かって圧縮させて凸状湾曲部位１９を目標形状よりも大きく湾曲させた形状である。 That is, the press-formed product 11 of the intermediate shape is compressed from both ends in the longitudinal direction toward the center while maintaining the respective ridge lengths of the bending ridge 4 and the bending ridge 6 of the target shape. is curved more than the target shape.

＜しわを抑制することができる理由＞
本実施の形態に係るプレス成形方法により、側面視で長手方向に沿って高さ方向に凸状に湾曲するプレス成形品を、しわを抑制してプレス成形することができる理由について説明する（図１参照）。 <Reason why wrinkles can be suppressed>
The reason why the press-molding method according to the present embodiment can press-mold a press-molded product that curves convexly in the height direction along the longitudinal direction in a side view while suppressing wrinkles will be described (Fig. 1).

前述のとおり、中間形状成形工程においてプレス成形する中間形状のプレス成形品１１は、目標形状のプレス成形品１に比べて、天板部１３と縦壁部１５との開き角度が大きくて縦壁部１５の縦壁高さが低いものである。１工程で目標形状のプレス成形品１をプレス成形する場合に比べて、中間形状成形工程においては縦壁部１５からフランジ部１７への縦壁高さの変化が緩やかになるため、材料の変形は広く分散し、かつ、金型で材料流れを抑えることが容易となる。 As described above, the intermediate-shaped press-formed product 11 press-formed in the intermediate-shaped forming process has a larger opening angle between the top plate portion 13 and the vertical wall portion 15 than the target-shaped press-formed product 1, and the vertical wall The vertical wall height of the portion 15 is low. Compared to the case where the press-formed product 1 having the target shape is press-formed in one process, the change in the height of the vertical wall portion 15 from the flange portion 17 to the flange portion 17 becomes gentler in the intermediate shape forming process, so the deformation of the material is reduced. is widely dispersed, and it becomes easy to suppress the material flow in the mold.

そして、続く目標形状成形工程は、中間形状のプレス成形品１１における天板部１３と縦壁部１５との間の曲げ稜線部１４と、縦壁部１５とフランジ部１７との間の曲げ稜線部１６を曲げ成形するものである。そのため、目標形状成形工程においては、縦壁部５からフランジ部７への材料流れを抑制して目標形状のプレス成形品１が成形される。その結果、フランジ部７におけるしわを抑制することができる。 Then, in the subsequent target shape forming process, the bending ridgeline portion 14 between the top plate portion 13 and the vertical wall portion 15 and the bending ridgeline between the vertical wall portion 15 and the flange portion 17 in the intermediate-shaped press-formed product 11 The portion 16 is formed by bending. Therefore, in the target shape forming process, the press-formed product 1 having the target shape is formed by suppressing the material flow from the vertical wall portion 5 to the flange portion 7 . As a result, wrinkles in the flange portion 7 can be suppressed.

さらに、本実施の形態に係るプレス成形方法は、前述の特許文献２に開示されている技術のように、ブランク材の幅方向の端部にビードや折曲部を形成するものではない、そのため、本実施の形態に係るプレス成形方法によれば、このようなビードや折曲部が十分に押し潰されずに平坦にならないおそれがなく、フランジ部を平坦な形状に成形することができる。 Furthermore, the press molding method according to the present embodiment does not form beads or bent portions at the ends of the blank material in the width direction, unlike the technique disclosed in Patent Document 2 described above. According to the press forming method according to the present embodiment, the flange portion can be formed into a flat shape without the risk that such beads and bent portions will not be flattened due to insufficient crushing.

また、本実施の形態に係るプレス成形方法は、中間形状のプレス成形品１１をフォーム成形により曲げ成形のみで目標形状に成形するものである。そのため、前述の特許文献３に開示されている絞り成形による技術で問題とされていたスプリングバックによる縦壁部５の壁反りは、本実施の形態に係るプレス成形方法では防ぐことができる。 Further, the press-molding method according to the present embodiment forms the intermediate-shaped press-formed product 11 into a target shape only by bending by form-forming. Therefore, the press forming method according to the present embodiment can prevent wall warpage of the vertical wall portion 5 due to springback, which has been a problem in the draw forming technique disclosed in the aforementioned Patent Document 3.

なお、公知文献（ＷＯ２０１７／０１０４７０号公報）には、前工程においてプレス成形部品形状（本発明の中間形状に相当）にプレス成形し、該前工程のプレス成形部品形状を最終部品形状（本発明の目標形状に相当）にプレス成形する技術が開示されている。当該技術における前工程のプレス成形部品形状は、プレス成形部品の最終部品形状を展開する途中で得られる展開途中形状から設定した形状であるとされている。しかしながら、目標形状のフランジ部を部品外側方向に開く途中で得られる展開途中形状から前工程のプレス成形品形状を設定するものであり、長手方向長さについては何ら規定されていない。 In addition, in a known document (WO2017/010470), a press-molded part shape (equivalent to an intermediate shape of the present invention) is press-molded in a previous process, and the press-molded part shape of the previous process is a final part shape (the present invention (corresponding to the target shape of ) is disclosed. The shape of the press-formed part in the preceding process in this technology is said to be a shape set from a mid-development shape obtained during development of the final part shape of the press-formed part. However, the shape of the press-formed product in the previous step is set from the mid-development shape obtained while the flange portion of the target shape is being opened in the outward direction of the part, and the length in the longitudinal direction is not defined at all.

さらに、本実施の形態に係るプレス成形方法は、上述のとおり、長手方向に荷重又は変位を与えて成形解析を行うことにより中間形状を決定するものである。そして、このように決定された中間形状のプレス成形品は、長手方向の中央に比べて端部側の方がより開いた形状である。これにより、しわをさらに抑制できると考えられる。しかしながら、上記の参考文献に記載されている発明においては、長手方向における開きの度合いの違いについては何ら開示も示唆もされていない。 Furthermore, in the press forming method according to the present embodiment, as described above, the intermediate shape is determined by applying a load or displacement in the longitudinal direction and performing forming analysis. The thus determined intermediate-shaped press-formed product has a shape that is more open at the ends than at the center in the longitudinal direction. It is believed that this can further suppress wrinkles. However, the inventions described in the above references do not disclose or suggest any difference in the degree of opening in the longitudinal direction.

＜対象とするプレス成形品の目標形状＞
なお、本発明において成形対象とするプレス成形品の目標形状は、凸状湾曲部位の曲率半径Rが30mm以上5000mm以下であり、縦壁部の縦壁高さHが10mm以上300mm以下のものであることが好ましい。 <Target shape of target press-formed product>
The target shape of the press-formed product to be molded in the present invention is such that the radius of curvature R of the convex curved portion is 30 mm or more and 5000 mm or less, and the vertical wall height H of the vertical wall portion is 10 mm or more and 300 mm or less. Preferably.

曲率半径Rが30mm未満、又は、縦壁高さHが300mmより大きいと、高強度鋼板を用いてプレス成形したときにフランジ部におけるしわや天板部における割れが顕著になり、プレス成形が困難になる場合がある。
また、曲率半径Rが5000mmより大きい、又は、縦壁高さHが10mm未満であると、本発明を用いなくても、しわを抑制して目標形状にプレス成形することできる。 If the radius of curvature R is less than 30 mm or the vertical wall height H is greater than 300 mm, wrinkles in the flange and cracks in the top plate become noticeable when press forming using high-strength steel sheets, making press forming difficult. may become
Further, when the curvature radius R is larger than 5000 mm or the vertical wall height H is smaller than 10 mm, wrinkles can be suppressed and the target shape can be press-molded without using the present invention.

したがって、本発明に係るプレス成形方法は、湾曲の曲率半径Rと縦壁高さHとの比R／Hが0.1以上500以下である目標形状のプレス成形品に対して好適に適用することができる。湾曲の曲率半径Rと縦壁高さHとの比R／Hの好適範囲については、後述する実施例において実証する。 Therefore, the press-forming method according to the present invention can be suitably applied to a press-formed product having a target shape in which the ratio R/H of the curvature radius R to the vertical wall height H is 0.1 or more and 500 or less. can. A preferable range of the ratio R/H of the radius of curvature R of the curve and the height H of the vertical wall will be demonstrated in Examples described later.

なお、上記の説明においては、側面視で高さ方向に凸状に湾曲した凸状湾曲部位９のみを有するプレス成形品１について説明した。もっとも、本発明はこのようなプレス成形品１のみを対象とするものではなく、図２に示すように、天板部２３と縦壁部２５とフランジ部２７とを有する断面ハット形状であり、長手方向に沿って高さ方向に凸状に湾曲する凸状湾曲部位２９と、長手方向に沿って高さ方向に凹状に湾曲する凹状湾曲部位３１とを有するプレス成形品２１や、凸状湾曲部位の長手方向の端部から外方に直線状に延出する直線部位を有するプレス成形品（図示なし）であってもよい。
なお、長手方向に沿って高さ方向に凹状に湾曲するとは、側面視において凹状に湾曲した円弧の中心が天板部３側に位置することをいう。 In the above description, the press-formed product 1 having only the convex curved portion 9 that is convexly curved in the height direction when viewed from the side has been described. However, the present invention is not intended only for such a press-formed product 1, but as shown in FIG. A press-formed product 21 having a convex curved portion 29 that is convexly curved in the height direction along the longitudinal direction and a concave curved portion 31 that is concavely curved in the height direction along the longitudinal direction. It may be a press-formed product (not shown) having a linear portion extending linearly outward from the longitudinal end of the portion.
It should be noted that to curve concavely in the height direction along the longitudinal direction means that the center of the concavely curved arc in a side view is located on the top plate portion 3 side.

そして、図２に示すような凸状湾曲部位２９と凹状湾曲部位３１を有するプレス成形品や、凸状湾曲部位と直線部位を有するプレス成形品の場合、長手方向の端面から中央に向かって圧縮されて長手方向長さを短くする場合、中間形状成形工程における中間形状は、中間形状の凸状湾曲部位の長手方向長さと目標形状の凸状湾曲部位の長手方向長さとの差が10%以上であることが好ましい。 In the case of a press-formed product having a convex curved portion 29 and a concave curved portion 31, or a press-formed product having a convex curved portion and a straight portion as shown in FIG. When the longitudinal length is shortened by the intermediate shape forming process, the intermediate shape in the intermediate shape forming process has a difference of 10% or more between the longitudinal length of the convex curved portion of the intermediate shape and the longitudinal length of the convex curved portion of the target shape. is preferably

なお、凸状湾曲部位の長手方向長さは、該凸状湾曲部位の長手方向における両端間の距離とすればよい。そして、凸状湾曲部位の長手方向の端部に凹状湾曲部位や直線部位が接続している場合、凸状湾曲部位の長手方向の端は、該凸状湾曲部位と凹状湾曲部位又は直線部位との湾曲の変曲点の位置とすればよい。 The length in the longitudinal direction of the convex curved portion may be the distance between both ends of the convex curved portion in the longitudinal direction. When the concave curved portion and the straight portion are connected to the longitudinal ends of the convex curved portion, the longitudinal ends of the convex curved portion are connected to the convex curved portion, the concave curved portion, or the straight portion. may be the position of the inflection point of the curvature of .

また、図１に示すプレス成形品１における凸状湾曲部位９は天板部３とフランジ部７の双方が側面視で高さ方向に凸状に湾曲するものであり、また、図２に示すプレス成形品２１における凸状湾曲部位２９も同様に天板部２３とフランジ部２７の双方が側面視で高さ方向に凸状に湾曲するものであった。
もっとも、本発明は、天板部又はフランジ部のいずれか一方が、長手方向に沿って高さ方向に凸状に湾曲するプレス成形品を成形対象とするものであっても、しわを抑制してプレス成形することができる。 1, both the top plate portion 3 and the flange portion 7 are convexly curved in the height direction when viewed from the side. Similarly, both the top plate portion 23 and the flange portion 27 of the press-formed product 21 were convexly curved in the height direction when viewed from the side.
However, the present invention suppresses wrinkles even when a press-formed product in which either the top plate portion or the flange portion is convexly curved along the longitudinal direction and in the height direction. can be press molded.

本発明に係るプレス成形方法の作用効果について検証するため、具体的な実験を行ったので、以下に説明する。 In order to verify the effects of the press molding method according to the present invention, specific experiments were conducted, which will be described below.

実験は、図３に示すように、長手方向に沿って高さ方向に凸状に湾曲する凸状湾曲部位９を有するプレス成形品１を目標形状とする場合（実施例１）と、図５に示すように、長手方向に沿って高さ方向に凸状に湾曲する凸状湾曲部位２９と高さ方向に凹状に湾曲する凹状湾曲部位３１とが連続するプレス成形品２１を目標形状とする場合（実施例２）のそれぞれについて行った。
なお、実施例１及び実施例２において、プレス成形に供した材料として、以下の表１に示す材料Ａ又はＤの鋼板を用いた。 As shown in FIG. 3, the experiment was carried out when the target shape was a press-formed product 1 having a convex curved portion 9 convexly curved in the height direction along the longitudinal direction (Example 1). , the target shape is a press-formed product 21 in which a convex curved portion 29 that curves convexly in the height direction along the longitudinal direction and a concave curved portion 31 that curves concavely in the height direction are continuous. It was performed for each of the cases (Example 2).
In addition, in Example 1 and Example 2, the steel plate of material A or D shown in Table 1 below was used as the material subjected to press forming.

＜実施例１＞
図３に示すように、天板部３と縦壁部５とフランジ部７とを有する断面ハット形状であり、側面視で天板部３とフランジ部７の双方が長手方向に沿って高さ方向に凸状に湾曲する凸状湾曲部位９を有するプレス成形品１を成形対象とした。 <Example 1>
As shown in FIG. 3, the top plate portion 3, the vertical wall portion 5, and the flange portion 7 have a hat-shaped cross section. A press-formed product 1 having a convex curved portion 9 curved in a convex shape in a direction was used as a molding object.

プレス成形品１の寸法は、図４に断面形状を示すように、長手方向長さを500mm、天板部３と縦壁部５の開き角度を長手方向の全長にわたって110°一定とした。さらに、凸状湾曲部位９のフランジ部７側における湾曲の曲率半径Rを30～5000mm、縦壁部５の縦壁高さHを10～300mmの範囲で変更した。 As for the dimensions of the press-formed product 1, as shown in the cross-sectional shape of FIG. 4, the length in the longitudinal direction was 500 mm, and the opening angle between the top plate portion 3 and the vertical wall portion 5 was constant at 110° over the entire length in the longitudinal direction. Furthermore, the radius of curvature R of the convex curved portion 9 on the side of the flange portion 7 was changed in the range of 30 to 5000 mm, and the vertical wall height H of the vertical wall portion 5 was changed in the range of 10 to 300 mm.

実施例１においては、目標形状のプレス成形品１に比べて、凸状湾曲部位１９における天板部１３と縦壁部１５との開き角度が大きくて縦壁部１５の縦壁高さが低い中間形状のプレス成形品１１（図１（ｂ）参照）をプレス成形し、次いで中間形状のプレス成形品１１を目標形状にフォーム成形したものを発明例とした。そして、目標形状のプレス成形品１の長手方向長さL₀に対する中間形状のプレス成形品１１の長手方向長さLの変化割合（＝(L₀－L)／L₀）を5%～20%とした。実施例１では、目標形状のプレス成形品１の長手方向の両端面に中央に向かう荷重を与える成形解析により中間形状を定めた。 In Example 1, the opening angle between the top plate portion 13 and the vertical wall portion 15 at the convex curved portion 19 is large, and the vertical wall height of the vertical wall portion 15 is low, compared to the press-formed product 1 having the target shape. An invention example was obtained by press-molding an intermediate-shaped press-molded product 11 (see FIG. 1(b)) and then forming the intermediate-shaped press-molded product 11 into a target shape. Then, the rate of change of the longitudinal length L of the press-formed product 11 of the intermediate shape with respect to the longitudinal length L ₀ of the press-formed product 1 of the target shape (=(L ₀ −L)/L ₀ ) is 5% to 20%. %. In Example 1, the intermediate shape was determined by forming analysis in which a load directed toward the center was applied to both longitudinal end faces of the press-formed product 1 having the target shape.

なお、実施例１において、中間形状成形工程でのプレス工法はドロー成形とし、目標形状成形工程でのプレス工法はフォーム成形とした。 In addition, in Example 1, the press method in the intermediate shape forming step was draw forming, and the press method in the target shape forming step was form forming.

そして、目標形状にプレス成形したプレス成形品におけるしわの有無を評価した。
ここで、しわが無い場合は「○」、微小なしわがある場合は「△」、明らかなしわがある場合は「×」と評価した。 Then, the presence or absence of wrinkles in the press-formed product press-formed into the target shape was evaluated.
Here, it was evaluated as "◯" when there were no wrinkles, as "Δ" when there were minute wrinkles, and as "X" when there were obvious wrinkles.

さらに、比較対象として、１工程で目標形状のプレス成形品にプレス成形したものを従来例とし、発明例と同様にしわを評価した。
表２に、中間形状のプレス成形品の押し込み割合（長手方向長さの変化割合）、目標形状の凸状湾曲部位９の湾曲の曲率半径Rと縦壁部の縦壁高さHの比R／H、及びしわの評価結果を示す。 Further, for comparison, a press-molded product having a target shape was obtained as a conventional example in one process, and wrinkles were evaluated in the same manner as the invention example.
Table 2 shows the indentation ratio (rate of change in length in the longitudinal direction) of the intermediate shape press-formed product, the ratio R of the curvature radius R of the convex curved portion 9 of the target shape and the vertical wall height H of the vertical wall portion /H, and evaluation results of wrinkles.

表２より、従来例１においては明らかなしわが見られたのに対し、発明例１～４においてはしわを抑制してプレス成形できることが示された。
さらに、目標形状の凸状湾曲部位９の湾曲の曲率半径Rと縦壁部５の縦壁高さHの比R／Hが好適範囲である0.1以上500以下の場合においては、しわの発生が一切見られず、良好な結果であった。なお、発明例４では、発明例３の中間形状のプレス成形品に対して長手方向の端部を逆解析によりさらに平坦とした中間形状を用いた。 From Table 2, it was shown that, while clear wrinkles were observed in Conventional Example 1, press molding was possible with wrinkles suppressed in Inventive Examples 1 to 4.
Furthermore, when the ratio R/H of the curvature radius R of the convex curved portion 9 of the target shape and the vertical wall height H of the vertical wall portion 5 is in the preferred range of 0.1 or more and 500 or less, wrinkles do not occur. Nothing was found, which was a good result. In addition, in Example 4 of the invention, an intermediate shape was used in which the ends in the longitudinal direction of the press-formed product of the intermediate shape of Example 3 were further flattened by inverse analysis.

＜実施例２＞
図５に示すように、天板部２３と縦壁部２５とフランジ部２７とを有する断面ハット形状であり、側面視で天板部２３とフランジ部２７の双方が長手方向に沿って高さ方向に凸状に湾曲する凸状湾曲部位２９と、長手方向に沿って高さ方向に凹状に湾曲する凹状湾曲部位３１を有するプレス成形品２１を成形対象とした。 <Example 2>
As shown in FIG. 5, the top plate portion 23, the vertical wall portion 25, and the flange portion 27 have a hat-shaped cross section. A press-formed product 21 having a convex curved portion 29 curved in a convex shape in the longitudinal direction and a concave curved portion 31 curved in a concave shape in the height direction along the longitudinal direction was used as a molding object.

プレス成形品２１の寸法は、長手方向長さを800mm、凸状湾曲部位２９の長手方向長さを400mm、天板部２３と縦壁部２５の開き角度を長手方向の全長にわたって110°一定とした。さらに、凸状湾曲部位２９のフランジ部２７側における湾曲の曲率半径R₁を30～5000mm、縦壁部２５の縦壁高さHを10～300mmの範囲で変更した。また、凹状湾曲部位３１の湾曲の曲率半径R₂は、凸状湾曲部位２９の湾曲の曲率半径R₁と等しいものとした。 The press-formed product 21 has a longitudinal length of 800 mm, a convex curved portion 29 of 400 mm, and an opening angle between the top plate 23 and the vertical wall 25 of 110° over the entire longitudinal length. did. Furthermore, the radius of curvature R ₁ of the convex curved portion 29 on the side of the flange portion 27 was changed in the range of 30 to 5000 mm, and the vertical wall height H of the vertical wall portion 25 was changed in the range of 10 to 300 mm. Also, the radius of curvature R ₂ of the curvature of the concave curved portion 31 is equal to the radius of curvature R ₁ of the curvature of the convex curved portion 29 .

実施例２においては、目標形状のプレス成形品２１に比べて、凸状湾曲部位２９における天板部２３と縦壁部２５との開き角度が大きくて縦壁部２５の縦壁高さが低い中間形状のプレス成形品４１（図２（ｂ）参照）をプレス成形し、次いで中間形状のプレス成形品４１を目標形状にフォーム成形したものを発明例とした。そして、目標形状のプレス成形品２１の凸状湾曲部位における長手方向長さL₀に対する中間形状のプレス成形品４１の凸状湾曲部位における長手方向長さLの変化割合（＝(L₀－L)／L₀）を5%又は10%とした。実施例２では、目標形状のプレス成形品２１の長手方向両端面に中央に向かう変位を与える成形解析により中間形状を定めた。 In Example 2, the opening angle between the top plate portion 23 and the vertical wall portion 25 at the convex curved portion 29 is large, and the vertical wall height of the vertical wall portion 25 is low, compared to the target-shaped press-formed product 21. An invention example was obtained by press-molding an intermediate-shaped press-molded product 41 (see FIG. 2(b)) and then forming the intermediate-shaped press-molded product 41 into a target shape. Then, the rate of change in the longitudinal length L at the convex curved portion of the press-formed product 41 of the intermediate shape with respect to the longitudinal length L ₀ of the convex curved portion of the press-formed product 21 of the target shape (=(L ₀ −L )/L ₀ ) was set to 5% or 10%. In Example 2, the intermediate shape was determined by a forming analysis in which both longitudinal end faces of the press-formed product 21 having the target shape were displaced toward the center.

なお、本実施例において、中間形状成形工程でのプレス工法はドロー成形とし、目標形状成形工程でのプレス工法はフォーム成形とした。 In this example, the press method in the intermediate shape forming step was draw forming, and the press method in the target shape forming step was form forming.

さらに、比較対象として、１工程で目標形状のプレス成形品にプレス成形したものを従来例とし、発明例と同様にしわを評価した。
表３に、中間形状のプレス成形品４１の凸状湾曲部位における長手方向長さの変化割合、目標形状の凸状湾曲部位２９の湾曲の曲率半径R₁と縦壁部２５の縦壁高さHの比R₁／H、及びしわの評価結果を示す。 Further, for comparison, a press-molded product having a target shape was obtained as a conventional example in one process, and wrinkles were evaluated in the same manner as the invention example.
Table 3 shows the rate of change in the longitudinal length of the convex curved portion of the intermediate-shaped press-formed product 41, the curvature radius _R1 of the convex curved portion 29 of the target shape, and the vertical wall height of the vertical wall portion 25. The ratio R ₁ /H of H and evaluation results of wrinkles are shown.

表３より、従来例２、３においては明らかなしわが見られたのに対し、発明例５～９においてはしわを抑制してプレス成形できることが示された。
さらに、目標形状の凸状湾曲部位２９の湾曲の曲率半径R₁と縦壁部５の縦壁高さHの比R₁／Hが好適範囲である0.1以上500以下の場合、しわの発生が一切見られず、良好な結果であった。 Table 3 shows that while conventional examples 2 and 3 clearly show wrinkles, invention examples 5 to 9 can be press-molded with wrinkles suppressed.
Furthermore, when the ratio R ₁ /H of the curvature radius R ₁ of the curvature of the convex curved portion 29 of the target shape and the vertical wall height H of the vertical wall portion 5 is in the preferred range of 0.1 or more and 500 or less, wrinkles are generated. Nothing was found, which was a good result.

１目標形状のプレス成形品
３天板部
５縦壁部
７フランジ部
９凸状湾曲部位
１１中間形状のプレス成形品
１３天板部
１５縦壁部
１７フランジ部
１９凸状湾曲部位
２１目標形状のプレス成形品
２３天板部
２５縦壁部
２７フランジ部
２９凸状湾曲部位
３１凹状湾曲部位
４１目標形状のプレス成形品
４３天板部
４５縦壁部
４７フランジ部
４９凸状湾曲部位
５１凹状湾曲部位 1 Press-formed product of target shape 3 Top plate portion 5 Vertical wall portion 7 Flange portion 9 Convex curved portion 11 Press-formed product of intermediate shape 13 Top plate portion 15 Vertical wall portion 17 Flange portion 19 Convex curved portion 21 Target shape Press-formed product 23 Top plate portion 25 Vertical wall portion 27 Flange portion 29 Convex curved portion 31 Concave curved portion 41 Press-formed product of target shape 43 Top plate portion 45 Vertical wall portion 47 Flange portion 49 Convex curved portion 51 Concave curved portion

Claims

A hat-shaped cross section having a top plate portion, a vertical wall portion continuing from the top plate portion, and a flange portion continuing from the vertical wall portion, wherein the top plate portion and/or the flange portion are longitudinal in side view A press-molding method for press-molding a press-molded product having a convex curved portion that is convexly curved in the height direction along the direction,
Compared to the target shape of the press-formed product, the length in the longitudinal direction is shorter and the convex curved portion curves more than the target shape, and the top plate portion and the vertical wall portion at the convex curved portion The opening angle of the vertical wall portion is large and the vertical wall height of the vertical wall portion is low. and the bending ridgeline length between the top plate portion and the vertical wall portion and the bending ridgeline length between the vertical wall portion and the flange portion are the same as the target shape of the press-formed product. an intermediate shape forming step of press-molding a certain intermediate-shaped press-formed product;
The intermediate-shaped press-formed product is subjected to form molding to form a bent ridgeline portion between the top plate portion and the vertical wall portion and between the vertical wall portion and the flange portion in the intermediate-shaped press-formed product. A press forming method, comprising: a target shape forming step of bending a bent ridge portion, suppressing material flow from the vertical wall portion to the flange portion, and press forming into a target shape.

For the intermediate shape in the intermediate shape forming step, a molded product model having the same shape as the target shape is set, and the molding analysis is performed by applying a load or displacement toward the center to both longitudinal end faces of the molded product model. 2. The press molding method according to claim 1, wherein the determination is made by:

3. The intermediate shape in the intermediate shape forming step is determined by performing an inverse analysis of the intermediate shape model after the forming analysis to further flatten the ends in the longitudinal direction thereof. The press molding method.

For the intermediate shape in the intermediate shape forming step, a molded product model having the same shape as the target shape is set, and an inverse analysis is performed to flatten the longitudinal end side of the molded product model, and the reverse analysis is performed. 2. The press forming method according to claim 1, wherein the determination is made by applying a load or displacement toward the center to both end faces in the longitudinal direction of the subsequent intermediate shape model and performing forming analysis.