1)I~SCRlP'TlON
PRESSED AK?'ICI_I? MANUJ:ACTURING MEl'HOl) AND PRESS MOT,D
Technical Field
[0001] The present invention relates to a manufacturing mcthod for a pressed article, and a
press mold.
Background Art
[0002] As is widely known, automotive bodies include what are ltnown as monocoqne
structures. Namely, automotive bodies are configured by body shells in which reinforcement
framework members are joincd to relevant portions such as portions on which stress acts, and
portions that support hcavy objects, in a box shaped structural body in which multiple molded
panels are superimposed on each other and joined together.
[0003] Fig. 12A to Fig. 12D are explanatory diagrams respectively illustrating framework
members 1 to 4, to be disposed at relevant portions of a body sl~ell. As illustrated in Fig.
12A to Fig. 12D, the framework members 1 to 4 are generally manufactured as hat shaped
members with hat shaped lateral cross-section profiles by pressing blanks, these being stock
materials, using a punch and a die. More specifically, the framework members 1 to 4 are
each configured including a top plate 5 (first wall), two ridge lines 6% 6b formed along two
edges of the top plate 5, two vertical walls 7a, 7b (second walls) respectively linked to the two
ridge lines 6a, 6b, two bend lines 8% 8b respectively linked to the two vertical walls 7a, 7b,
and two flanges 9a, 9b (thud walls) respectively linked to the two bend lines 8a,8b. Note
that Fig. 12D illustrates a case in which the framework member 4 has been spot welded to a
closing plate P through the flanges 9a, 9b.
[0004] As part of vehicle body weight reduction in order to both reduce C02 emissions
further, and also improve crash safety, there has been a recent trend toward making the
framework members 1 to 4 even stronger and thinner. Accordingly, the framework members
1 to 4 are, for example, configured from sheet steel stock material with a tensile strength of
590 MPa or greater, 780 MPa or greater, and in some cases, 980 MPa or greater.
[0005] Fig. 13A to Fig. 13C are explanatory diagrams illustrating the occurrence of spring
back (also referred to as "vertical wall warping" in the present specification) arising in the
vertical walls 7a, 7b when dcmolding the framework members 1 to 4 after pressing.
Specifically, Fig. 13A is a cross-section illustrating how the framework members 1 to 4 are
prcssed. Fig. 13B is a contour diagram illustrating moment distribution in the vertical walls
7a, 7b of the framework members 1 to 4 after pressing. Fig. 13C is a cross-section
illustrating vertical wall warping in the framework members 1 to 4.
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[0006] As illustrated ill Fig. 1 3A1 when pressing the fra~iieworkm cinbers 1 to 4, portions B 1,
n2 ofa blank R that are fornicd into the vertical walls 7a, 7b arc subjecled to bending, and
bend-back, dcfornlation by a punch 10 and a dic 11 during the pressing process.
Accordingly, as illustrated in Fig. 13B, accompanying the increased strength oI' the framework
members 1 to 4, moments due to stress differencesin the sheet thickness direction of the
blank B (stress differences between stress at an outer side face (front face) end an inner side
face (back face)) arise in the formed vertical walls 7a, 7b. More specifically, after forming,
compressive stress acts on an outer side face (front face), and tensile stress acts on an inner
side face (back face) at base end side port.ions of the vertical walls 7a, 7b. Accordingly, a
moment (referred to below as "inward warp moment") that would cause the base end side
portioils of the vertical walls 7a, 7b to warp so as to become convex on the front face side of
the vertical walls 7a, 7b (curl around toward the inside of the framework members 1 to 4)
arises in the base end side portions of the vertical walls 7a, 7b due to the difference between
the stress in the outer side faces and the stress in the inner side faces ofthe vertical walls 7a,
7b.
[0007] By contrast, after forming, tensile stress acts on the outer side face (front face), and
compressive stress acts on the inner side face (back face) at leading end side portions of the
vertical walls 7a, 7b. Accordingly, a moment (referred to below as "outward warp moment")
that would cause the leading end side portions of the vertical walls 7a, 7b to warp so as to
become convex on the back face side of the vertical walls 7a, 7b (curl around toward the
outside of the framework members 1 to 4) arises in the leading end side portions of the
vertical walls 7a, 7b due to the difference between the stress in the outer side faces and the
stress in the inner side faces of the vertical walls 7a, 7b. Moreover, as illustrated in Fig. 13C,
when the pressure applied to the framework members 1 to 4 by the punch 10 and the die 11 is
removed during demolding following pressing, vertical wall warping is liable to occur in
which, due to elastic deformation recovery, the two vertical walls 7a, 7b depart from the shape
they take on when applied with pressure (a manufactured article shape), and return to an
opened-out shape (a shape in which the two flanges 9a, 9b have moved apart from each
other).
[0008] As a countermeasure thereto, as illustrated in Fig. 14.4 to Fig. 14C, technology is
known in which vertical wall warping is suppressed by providing beads 12, steps 13, or the
like to parts of the vertical walls 7a, 7b. Moreover, for example, Japanese Patent No.
4984414 (Patent Documeut 1) describes technology in which vertical walls are formed with a
continuous undulating shape in order to suppress spring back.
[0009] Moreover, Japanese Patent Application Laid-Open (JP-A) No. 2007-1 11725 (Patent
Doc~uiient2 ) dcscribcs technology to reduce spring back in a prcsscd article that is pressccl
plural times. For cxaiuple, as illr~stratedi n Fig. 15, technology is dcscrihed in which a
pressed article that been prcssed a lirst time (see thc lcft side of Fig. 15) is pressed a second
time using a punch with a larger width dimension (see the right side of Fig. 15) in order to
reduce spring back in the pressed article.
SUMMARY OF INVENTION
Technical Problem
[0010] However, the technology described in the related technology illustrated in Fig. 14A
to Fig. 14C, and in the technology in Patent Document I, do not suppress or eliminate the
actual moments arising in the vertical walls. In particular, the inward warp lnoment arising
in the base end portions of the vertical walls is not suppressed or eliminated. Moreover, in
the related technology illustrated in Fig. 14A to Fig. 14C, it is necessary to form the beads 12
or the steps 13 in the vertical walls 7a, 7b, and in the technology described in Patent
Document 1, it is necessary to form the vertical walls in undulating shapes. Accordingly,
such technology cannot be applied to the framework members 1 to 4 in cases in which the
design does not permit the formation of the beads 12 or the steps 13, or formation of
undulating shapes in the vertical walls.
[0011] Likewise, the technology described in Patent Document 2 does not suppress or
eliminate the actual moments arising in the vertical walls 7a, 7b. In particular, the inward
warp moment arising in the base end portions of the vertical walls 7a, 7b is not suppressed or
eliminated. As described above, such technology therefore leaves room for improvement
with regard to suppressing or eliminating the inward warp moment arising in the base end
portions of the vertical walls.
[0012] In consideration of the above circumstances, the present disclosure relates to
obtaining a pressed article manufacturing method and a press mold capable of suppressing the
occurrence of wall warping in a base end portion of a second wall in a pressed article having a
high strength of, for example, 590 MPa or greater, 780 MPa or greater, or in some cases 980
MPa or greater.
Solution to Problem
[0013] Apressed article manufacturing method of the present disclosure employs a press
mold equipped with a punch and a die to manufacture a pressed article including a first wall, a
second wall extending out from an end portion on at least one length direction side of the first
wall toward a back face side of the first wall, and a third wall extending out from a leading
end portion of the second wall toward a front face side of the second wall. The
manufactnring method includes using the punch and the die to apply pressure to and grip a
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portion on a base end side of the second wall in a first warp shape in which tllc base end side
portion is warped so as to bc convex on a back face sidc of the second wall as viev:ed in
lateral cross-section in a state prior to dcmolding from the press mold.
[0014j In the pressed article manufacturing method addressing the issue described above,
the prcssed article formed using the manufacturing direction includcs the first wall, the second
wall extending out from an end portion on at least one length direction side ol'the first wall
toward a back facc side of the first wall, and the third wall extending out from the leading end
portion of the second wall toward the front face side of the second wall. Namely, the lateral
cross-section profile of the pressed article is what is referred to as hat shaped or Z-shaped
(crank shaped). Note that when manufacturing a presscd article with a lateral cross-section
profile such as that described above using a punch and a die, after forming, coinpressive stress
acts on the front face (outer sidc facc), and tensile stress acts on the back face (inner side face)
of the base end side portion (portion on the first wall side) of the second wall. Accordingly,
a moment that would cause the base end side portions of the second wall to warp so as'to
become convex on the front face (outer side face) side of the second wall (warp so as to curl
around toward the inside of the pressed article) (this moment is referred to below as "inward
warp moment") arises in the base end side portion of the second wall due to the difference in
stress in the sheet thickness direction of the base end side portion of the vertical wall (the
difference between the stress in the front face (outer side face) and the stress in the back face
(inner side face) of the base end side portion of the second wall).
[0015] The punch and the die are employed to apply pressure to and grip the base end side
portion of the second wall in the first warp shape, in which the base end side portion is
warped so as to be convex on the back face side of the second wall as viewed in lateral
cross-section in a state prior to demolding from the press mold. Accordingly, in the pressed
article prior to demolding from the press mold, the base end side portion of the second wall,
which is attempting to warp so as to become convex on the front face side of the second wall
(the outside of the pressed article) due to the inward warp moment, is corrected by the first
warp shape that is warped so as to be convex on the back face side of the second wall (the
inside of the pressed article). Accordingly, the inward warp moment arising in the second
wall is cancelled out. As a result, when the pressure applied by the punch and the die is
removed during demolding from the press mold, strain difference in the sheet thickness
direction of the base end side portion of the vertical wall is reduced, thereby enabling the
occurrence of wall warping in the base end portion of the vertical wall to be suppressed.
[0016] Apress mold of the present disclosure is a press mold for manufacturing a pressed
article including a first wall, a second wall extending out from an end portion on at least one
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length direction side ol'the first wall towa1.d a back face side of ihc first wall. and a third wall
extending out froin a leading elid portion of the second wall toward a front race side of the
second wall. The press mold includes a punch and a die that form the pressed article by
moving relative to each othcr in a direction approaching each other. A first pressure
applicat~ons ection is formed at the punch and the die, the first pressure applicatloi: section
applying pressure to and gripping a portion on a base end side of the second wall in a first
warp shape in which the base cnd side portion is warped so as to be convex on a back facc
side of the second wall as viewed in lateral cross-section in a statc prior to demolding from
the punch and the die.
[0017] In the press mold addressing the above issue, the first pressure application section is
formed at the punch and the dic, the first pressure application section applying pressure to and
gripping the base end side portion of the second wall in the first warp shape in which the base
end side portion is warped so as to be convex on a back face side of the second wall as viewed
in lateral cross-section in a state prior to demoiding from the punch and the die. Accordingly,
similarly to as described above, in the pressed article prior to demolding from the press mold,
the base end side portion of the second wall, which is attempting to warp so as to become
convex on the front face side of the second wall (the outside of the pressed article) due to the
inward warp moment, is corrected by the first warp shape that is warped so as to be convex on
the back face side of the second wall (the inside of the pressed article). Accordingly, the
inward warp moment arising in the second wall is cancelled out. As a result, when the
pressure applied by the punch and the die is removed during dcmolding from the press mold,
strain difference in the sheet thickness direction of the base end side portion of the vertical
wall is reduced, thereby enabling the occurrence of wall warping in the base enti portion of
the vertical wall to be suppressed.
Advantageous Effects of Invention
[0018] The pressed article manufacturing method and the press mold of the present
disclosure enable the occurrence of wall warping in the base end portion of the vertical wall to
be suppressed.
BRIEF DESCRIPTION OF DRAWINGS
[0019] Fig. 1A is a cross-section illustrating configuration of an example of a press mold
according to an exemplary embodiment.
Fig. IB is a cross-section illustrating configuration of another example of a press mold
according to an exempltuy cmnbodiment.
Fig. 2 is an enlarged cross-section (in which region A in Fig. 1A is enlarged) illustrating the
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periphery ofa punch sidc concave curved face portion and a die side convcx curved Sace
portion orthe press Inold illustrated in Fig. 1A.
Fig. 3 is an cxplanatory diagranl to cxplain thc shape of a pressed articlc forrned using a press
mold according to the present exclnplary embodirnent.
Fig. 4A is an explanatory diagram illustrating the occurrence of vcrtical wall warping in a
pressed ariicle after completion of a first pressing, and aftcr dcmolding.
Fig. 4B is an explanatory diagram illustrating the occurrence of vertical wall warping in a
pressed article after a second pressing, performed as required, and after demolding.
Fig. 5A is a cross-section illustrating a state immediately prior to fonning a blank with the
press mold illustrated in Fig. 1A.
Fig. 5B is a cross-section illustrating a statc in which a punch has been moved relatively
toward a die side from the state illustrated in Fig. 5A.
Fig. 6A is an explanatory diagram illustrating a shape of a pressed article manufactured in
Example 1.
Fig. 6B is an explanatory diagram illustrating dimensions of the pressed article in Fig. 6A.
Fig. 7 is a table evaluating pressed articles manufactured in Example 1 and Example 2 and
pressed articles of comparative examples.
Fig. 8 is a graph summarizing curvature of vertical wall warping in pressed articles of
respective comparative examples and Example 1, for respective cases employing DP steel
with 980 MPa grade tensile strength as a blank.
Fig. 9 is a graph summarizing curvature of vertical wall warping in respective pressed articles
of comparative examples and Example 1, in cases employing blanks of three classes of tensile
strength as a stock material.
Fig. 10 is a graph summarizing curvature of vertical wall warping in respective pressed
articles of comparative examples and Example 2, for respective cases employing DP steel
with 980 MPa grade tensile strength as a blank.
Fig. 1 I is a graph summarizing curvature of vertical wall warping in respective pressed
articles of comparative examples and Example 2 in cases employing blanks of three classes of
tensile strength as a stock material.
Fig. 12A is an explanatory diagram illustrating a framework member to be disposed at a
relevant portion of a body shell.
Fig. 12B is an explanatoq diagram illustrating another example of a framework membcr to bc
disposed at a relevant portion of a body shell.
Fig. 12C is an explanatory diagram illustrating another example of a framework member to be
disposed at a relevant portion of a body shell.
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Fig. 121) is an explanatory diagram illustrating another example of a framework member to be
disposehi a relevant portion of a body shell.
Fig. 13A is a cross-section illustrating pressing of the framework nlcrnbers in Fig. 12A to Fig.
12D.
Fig. 13B is a contour diagram illustrating rnomcnt distribution in vertical walls of the
frarne~vorlmi embers in Fig. 12A to Fig. 12D.
Fig. 13C is a cross-section illustrating vertical wall warping in the framework members in Fig.
12A to Fig. 12D.
Fig. 14A is an explanatory diagram to explain related technology.
Fig. 14B is an explanatory diagram to explain rclated technology.
Fig. 14C is an explanatoly diaglam to explain related technology.
Fig. 15 is an explanatory diagram illustrating technology described in Patent Document 2
DESCRIPTION OF EMBODIMENTS
[0020] First, explanation follows regarding a pressed article 26 formed using a pressed
article manufacturing method according to an exemplary embodiment. Explanation will
then he given regarding a press mold for forming the pressed article 26. Note that the
pressed article 26 is configured by a molded article in a state in which the press mold has been
opened, described later.
[0021] Pressed Article 26
As illustrated in Fig. 3, the pressed article 26 is formed in a shape having what is
referred to as a hat shaped lateral cross-section profile. Namely, the pressed article 26 is
configured including a top plate 21, serving as a "first wall" with its length direction along a
width direction of the pressed article 26 (along the arrow W direction in Fig. 3), a pair of ridge
lines 22a, 22b respectively linked to both length direction end portions of the top plate 21, a
pair of vertical walls 23a, 23b, serving as "second walls" that are respectively linked to the
pair of ridge lines 22a, 22b and that extend out from the respective ridge lines 22a, 22h toward
one sheet thickness direction side (a back face side) of the top plate 21, a pair of bend lines
24a, 24b respectively linked to leading end portions (lower end portions) of the pair of
vertical walls 23a, 23b, and a pair of flanges 25a, 25b, serving as "third walls" respectively
linked to the pair of bend lines 24a, 24b and respectively extending out from the bend lines
24a, 24b toward both length direction sides of the top plate 21 (front face sides of the veltieal
walls 23a, 23b). Note that in the following explanation, a front face side of the pressed
article 26 is referred to as the outside of the pressed article 26, and a back face side of the
pressed article 26 is referred to as the inside of the pressed article 26.
[0022] The pair of ridge lines 22a, 22h are curved in substantially circular arc shapes that are
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couves toward the outside of thc prcsscd at-Licle 26, Namely, the two ridge lincs 22a, 22h
configure corncr pot-tions that arc couvex toward the outside of thc pressed articlc 26.
Moreovel; the pair of bend lines 24a, 24b are curved in substantially circular arc shapes that
are convex toward the inside orthe pressed articlc 26. The ve~ticawl alls 23a, 23b are
inclined toward both length direction sides (the outside) of the top plate 21 on progression
toward their leading end sides when the pressed article 26 is viewed in latcral cross-section.
In other words, the two vertical walls 23a, 23b are inclined in directions away from each other
on progression toward their leading end sides. Accordingly, in [he pressed article 26, leading
end portions of the vertical walls 23a, 23b are formed spreading apart toward the length
direction outer sides of the top plate 21, and angles formed between the top platc 21 and the
vertical walls 23a, 23b are set as obtuse angles.
[0023] Note that the pressed article 26 of the present disclosure is not limited to the above
shape. For example, the pressed article 26 may similarly be applied with shapes having a
lateral cross-section profile (specifically, a Z-shape (crank shape)). Namely, in such cases,
the pressed article 26 is configured including the top plate 21, a single ridge line 22a linked to
one length direction side end portion of the top plate 21, a single vertical wall 23a linked to
the ridge line 22a and extending out from the ridge line 22a toward one sheet thickness
direction side of the top plate 2 1, a single bend line 24a linked to the vertical wall 23a, and a
single flange 25a that is linked to the bend line 24a and extends from the bend line 24a toward
one length direction side of the top plate 21.
[0024] The pressed article 26 with the hat shaped lateral cross-section profile described
above has a left-right symmetrical shape about a line at the width direction center of the
pressed article 26. However, the pressed article 26 may have a left-right asymmetrical shape.
Moreover, in the pressed article 26 with the hat shaped lateral cross-section profile described
above, as an example, the angles formed between the top plate 21 and the vertical walls 23a,
23b are set as obtuse angles. However, in the pressed article described later, in cases in
which the pressed article 26 is configured using a cam bending method, for example, the
angles formed between the top plate 21 and the vertical walls 23a, 23b may be set as
substantially right angles, or acute angles.
[0025] The pressed articlc 26 of the present disclosure is obtained by cold or warm pressing
(first pressing) a blank or a blank that has been subjected to additional processing using the
pressed article manufacturing method described later. The pressed article 26 of the present
disclosurc may also be obtained by restriking (second pressing) as necessary following the
first piessing mentioned abovc.
[0026] The tensile strength of the blank, this being a forming stock material for the pressed
8
ai-ticlc 26, 01- ofthe pressed articlc 26, is 590 MPa or greater. is prcfcrably 780 MPa or greater
and is cvcn more preferably 980 Ml'a or greater. This is since at tcilsilc strengths or below
590 MPa, vertical wall warping, this being the issue addressed by the present invention, is
unliltely to occul; with verlical wall wa~yingb ecoming more liltely to occur the higher the
tensile strength. From this perspective, there is no need to specify an upper liinit to the
tensile strength of the blank or thc pressed article 26; however, when considering the upper
limit of practical press loads, the tensile strength is preferably 2000 Ml'a or lower.
[0027] Note that in the following explanation, for convenience, Llle pressed article in a state
prior to demolding from the press mold, described later, is allocated the reference numeral 20,
and a distinction is made between the pressed article in the state prior to demolding and the
pressed article in the state after demolding from the press mold.
[0028] Press Mold
Fig. 1A illustrates a press mold 30A in a case in which the pressed article 26 is
illanufactured by performing clrawing on a blark during the first pressing, described later.
Fig. 1B illustrates a press mold 30B in a case in which the pressed article 26 is manufactured
by performing bending on a blank during the first pressing, described later. Note that in Fig.
1A and Fig. lB, the width direction of the pressed article 20 corresponds to the width
direction of the press molds 30A, 30B.
[0029] As illustrated in Fig. 1 A, the press mold 30Aemployed when the blank is drawn
during the first pressing is configured including a punch 3 1, a die 32, and a pair of blank
holders 33. Specifically, the die 32 configures an upper section of the press mold 30A, and
is formed with a recessed shape opening toward the lower side as viewed in lateral
cross-section. The punch 31 is disposed at the lower side of the recess of the die 32, and is
formed in a protruding shape projecting toward the upper side. The punch 31 is configured
capable of relative movement toward the upper side with respect to the die 32. The pair of
blank holders 33 are disposed on both width direction sides of the punch 3 I, and are
configured such that portions of the blank that will be formed into the flanges 25a, 25b are
gripped by the blank holders 33 and the die 32.
[0030] As illustrated in Fig. lB, the press mold 30B employed when the blank is bent during
the first pressing is configured including a punch 3 1, a pair of dies 32, and a die pad 34.
Specifically, the pair of dies 32 configure an upper section of the press mold 30B, and form an
overall recessed shape opening toward the lower side. The punch 3 1 is disposed at the lower
side of the dies 32, and is foiined in a protruding shape projecting toward the upper side.
The dies 32 are configured capable of relative movement toward the lower side with respect
to the punch 3 1. The die pad 34 is disposed between the pair of dies 32, and is configured
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such that a portion or the blailk that will be fornied into thc top plate 21 is grippcd by the
blanli holders 33 and the punch 3 1.
1003 11 As illustrated in Fig. 1 A and Fig. lB, thc punch 3 1 has an outer surface protile
matching respective parts of the top plate 21, thc ridge lines 22a, 22b, and the vertical walls
23a, 23b of the pressed article 20. The dies 32 have inner surfacc profiles matching outer
surface profiles of respective parts ofthe lop plate 21, the ridge lincs 22a, 22b, and the
vertical walls 23a, 23b of the pressed article 20.
[0032] In the pressed article 26, since the angles formed between the top plate 21 and the
vertical walls 23a, 23b are set as obtuse angles, as illustrated in Fig. SA, corner portions 32A
of the die 32 arc disposed further apart from each other, toward width direction outer sides of
the press inold 30A (30B), than corner portions 3 1A of the punch 31. A distance in the width
direction of the press mold 30A (30B) between one of the comer portions 3 1A ofthe punch 3 1
(an intersection point between a forming face that forms the top plate 21 and a forming face
that forms the vertical wall 23a or 23b as viewed in lateral cross-section) and the
corresponding corner portion 32A ofthe die 32 (an intersection point hetween a forming face
that forms the vertical wall 23a or 23b and a forming face that forms the flange 25a or 25b as
viewed in lateral cross-section) is denoted distance X.
[0033] Note that in the press mold 30A (30B) of the present disclosure, portions ofthe
punch 3 1 and the die 32 that form the vertical walls 23a, 23b are formed with undulating
pressure application sections. This thereby reduces strain difference in the vertical walls 23%
23b ofihe pressed article 26 in the sheet thickness direction of the vertical walls 23a, 23b
after the pressed article 20 has been formed by the punch 31 and the die 32 and demolded
from the press mold 30A (30B). This will be described in detail below.
[0034] Portions of the punch 31 that form base end side portions of the vertical walls 23a,
23b (portions toward the side of the top plate 21 and ridge lines 22a, 22b) are formed with
punch side concave curved face portions 31B, serving as "first pressure application sections".
The punch side concave curved face portions 3 1B are formed in concave curved face shapes
indented toward the width direction inner side orthe punch 3 1 (the inside of the pressed
article 20).
[0035] Portions of the punch 3 1 that form leading end side portions of the vertical walls 23a,
23b (portions toward the side of the bend lines 24a, 24b and the flanges 2Sa, 25h) are formed
with punch side convex curved face portions 3 1C, serving as "second pressure application
sections". The punch side convex curved face portions 3 1C are formed in convex curved
face shapes that protrude towaid the width direction outer side of the punch 3 1 (the outside of
the pressed article 20).
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[0036] T'ortions of the dic(s) 32 that l'orm base end side poi-tions of the vertical ~valls2 3a.
23b are ihrriieci with die side convex curved face portions 32H: serving as "lirsl pl.essure
application sections". 'Tie die side convex curvcd Sacc portions 328 are formed in convex
curved face shapes that protrude toward the width direction inner side ofthe die 32 (the inside
of the pressed article 20). Accordingly, when forming the vertical walls 23a, 23b with the
punch 3 1 and the die 32, base end side portions of the vertical walls 23a, 23b are applied with
pressure and gripped by the punch side concave curved face portions 3 1B and the die side
convex curved face portions 32B (see Fig. 1A).
[0037] Portions of the die 32 that form leading end side portions of the vertical walls 23a,
23b are formed with die side concave curved face portioils 32C, serving as a "second pressure
application section". The die side concave curved face portions 32C are fonned in concave
curved face shapes indented toward the width direction outer sides of the die 32 (the outside
of the pressed article 20). Accordingly, when forming the vertical walls 23a, 23b with the
punch 3 1 and the die 32, leading end side portions of the vertical walls 23a, 23b are applied
with pressure and gripped by the punch side convex curved face portions 3 1C and the die side
concave curved face portions 32C (see Fig. 1A).
LO0381 Accordingly, as illustrated in Fig. 1A and Fig. IB, in the pressed article 20, after
completion of pressing using the punch 3 1 and the die 32, and before demolding from the
press mold 30A (30B), the base end side portions of the pair of vertical walls 23a, 23b are
applied with pressure and gripped by the punch 31 and the die 32 in first warp shapes 23a-1,
23b-1 that are convex toward the inside of the pressed article 26 (the back face side of the
vertical walls 23% 23b). Moreover, in the pressed article 20, the leading end side portions of
the pair of vertical walls 23a, 23b are applied with pressure and gripped by the punch 3 1 and
the die 32 in second warp shapes 23a-2,23b-2 that are convex toward the outside of the
pressed article 26 (the front face side of the vertical walls 23a, 23b). Namely, in this state of
the pressed article 20, the two vertical walls 23a, 23b are applied with pressure and gripped by
the punch 3 1 and the die 32 so as to form an S-shaped lateral cross-section profile.
Accordingly, as will be described in detail later, configuration is made so as to correct warp of
the vertical walls 23a, 23b across the overall extension direction of the vertical walls 23a, 23b.
Note that depending on the specifications of the pressed article and the like, the press mold
30A (30B) of the present disclosure may, for example, be configured without providing the
punch side convex curved face portions 3 1 C and the die side concave curved face portions
32C. Namely, the punch side convex curved face portions 3 1C and the die side concave
curved face portions 32C may be formed with flat place shapes.
[0039] The first warp shapes 23a-1,23b-1 and the second warp shapes 23a-2,23b-2 of the
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pressed article 20 are configured as shapes having uniform curvature. Specifically, the
p~~nscihdc concave curved facc portions 3 I T3, the punch sidc convex curved face portions
31C, the die side convex curved Sace portions 32B, and the die side concave cnrvcd face
portions 32C are formed sucll that the radii of curvdturc of both the first waly shapes 23a-1,
23h-1 and the second warp shapes 23a-2,23b-2 are from 10 mnl to 800 mm. If the radius of
curvature is below 10 mm, bending marks remain in the vertical walls 23a, 23b of the pressed
article 26, and bending cracks may occur in cases in which the tensile strength of the blank is
590 MPa or greater. If the radius of curvature is greater than 800 mm, the effect of
correcting strain difference in the sheet thickness direction of the vertical walls 23a, 23h of
the pressed article 26 becomes small, and it may not be possible to reduce spring back (wall
warp) of the vertical walls 23a, 23b. Note that the first warp shapes 23a-1,23b-1 and the
second warp shapes 23a-2,23b-2 may be shapes having plural curvatures, such as elliptical
arc shapes.
[0040] The respective sums of cross~sectionp eripheral lengths of the first warp shapes 23a-I,
23b-1 and cross-section peripheral lengths of the second warp shapes 23a-2,23b-2 are set to
not less than 50% of the cross-section peripheral lengths of the vertical walls 23a, 23b of the
pressed article 26. If the sum is less than 50% of the cross-section peripheral length of the
respective vertical walls 23a, 23b, the effect of correcting strain difference in the sheet
thickness direction of the vertical walls 23a, 23b becomes small, and it may not be possible to
reduce spring back (wall warping) in the vertical walls 23% 23b.
[0041] As illustrated in Fig. 1A and Fig. IB, the portions of the punch 31 and the die 32 that
form the vertical walls 23a, 23b may be configured such that the first warp shapes 23a-1,
23b-1 and the second warp shapes 23a-2,23b-2 are formed continuously to one another.
Alternatively, the portions of the punch 3 1 and the die 32 that form the vertical walls 23a, 23b
may he configured such that, for example, respective straight line shaped portions or curved
line shaped portions are interposed between the first warp shapes 23a-1,23b-1 and the second
warp shapes 23a-2,23b-2.
[0042] The cross-section peripheral length of each of the first warp shapes 23a-1,23b-1 is
set so as to be not less than the distance X between the rcspective corner portions 3 1A of the
punch 3 1 and the respective comer portions 32A of the die 32 in the width direction of the
press mold 30A (30B), and is set equal to or less than 112 the cross-section peripheral length
of the respective vertical walls 23a, 23b. Namely, when forming the vertical walls 23a, 23b,
the veit~cawl alls 23a, 23b are iormed by bending the blank about origins at the portions
pressed by the comer portions 3 1A of the punch 3 1. Accordingly, the cross-section
peripheral length of the respective first warp shapes 23a-1, 23b-1 is preferably set to not less
12
than the distance X. moreo over. when forniiiig tllc vcrtical \walls 23a, 23b, the blank is pulled
in at portions that will form the vertical walls 23a, 23b. Accordingly, in consideration of
pulling in thc blank, Lhe cross-scction peripheral length of the first warp shapes 23a-1, 23b-1
is set to a lcngth equal to or less than 112 that of the respective vertical walls 23a, 23b.
LO0431 The placemcnt of the lirst warp shapes 23a-1,23b-1 is set as follows Namely, as
illustrated in Fig. 2, first, a line passing through an upper edge of the lirst warp shapc 23b-I
(23a-1) (an intersection point with the ridge line 22'0 (22a)), and running along the up-down
direction of the pressed article 26 (the sheet thickness direction of the top plate 21), is denotcd
as a reference line L. Then, a line passing through an upper edge of the first warp shape
23b-1 (23a-1) and tangential to the first warp shape 23b-1 (23a-1) is denoted as langcnt line
L1. The tangent line Ll is inclincd toward the width direction outer side of the presscd
article 20 on progression toward the leading end side of the vertical wall 23b (23a). In other
words, if an inclination angle of the tangent line L1 with respect to the reference line L is
denoted by 01, the inclination angle is set such that 01 does not become a negative value.
Namely, if the inclination angle 0 were to become a negative value, the tangent line L1 would
be inclined toward the width direction inner sidc of the pressed article 20 on progression
toward the leading end side of the vertical wall 23b (23a). Accordingly, in such cases, when
forming the pressed article 20 using the punch 31 and the die 32, parts of the punch sidc
concave curved face portions 3 1B and the die side convex curved face portions 32B would
adopt a state overlapping (superimposed on) the first warp shape 23b-1 (23a-1) in the
up-down direction. Accordingly, when opening the punch 31 and the die 32 in the up-down
direction, the first warp shape 23b-1 (23a-1) would be wrenched by the punch side concave
curved face portions 31B and the die side convex curved face portions 32B, potentially
damaging the pressed article 26. Accordingly, in order to prevent damage to the pressed
article 26, the inclination angle is set such that 01 docs not become a negative value.
[0044] Prior to forming the vertical walls 23a, 23b into the S-shaped lateral cross-section
profile, portions of the blank intended to form the vertical walls do not have to have a straight
line shaped lateral cross-section, and, for example, may be formed into recess shapes, curved
shapes, or the like prior to forming the S-shaped lateral cross-section profile.
[0045] Next, explanation follows regarding operation and advantageous effects of the
pressed article manufacturing method of the present disclosure, while explaining the pressed
article manufacturing method.
[0046] The pressed article manufacturing method includes the first pressing. During the
first pressing, the pressed article 26 is manufactured by pressing in which the blank is
subjected to drawing using the punch 3 1, the die 32, and the blank holders 33 as illustrated in
13
Fig. IA, or ~~~anufactubrye dp rcssing in which the blank is sub,jectecl to bcnding using the
p~unch 31. the die 32, and the dic pad 34, as illustl.ated in Fig. 1R. Xote that othcr niethods
may also be employcd in ihe iirst pressing. Examples thereof includc a pad drawing method
employing a punch, a die and die pad, and blank holders, a stamping method employing a
punch and a die, or a can1 bending method employing a punch, and a die and die pad.
100471 ?'hen, to use the example or the first pressing in which the blank is subjected to
drawing, illustrated in Fig. 1 A, during the first pressing both length direction end portions of
the blank are gripped by the pair of blank holders 33 and the die 32. Then, as illustrated in
Fig. 5A, the punch 3 1 is moved toward the upper side so as to approach the die 32. Then, as
illustrated in Fig. 5B, the punch 31 is moved further toward the upper side from this state, so
as to be inserted into the recess of the die 32. Accordingly, the blank is bent by the corner
portions 31A of the punch 3 1, and bent by the corner portions 32A of ihe die 32. When this
is performed, since the corner portions 31A of the punch 3 1 and the corner portions 32A of
the die 32 are at a separation to each other in the width direction of the press mold 30A, 30B,
portions of the blank that will form the base end sides of the vertical walls 23a, 23b are curved
so as to become convex toward radial direction outer sides of the comer portions 3 1 A of the
punch 3 1, and portions of the blank that will form the leading end sides of the vertical walls
23a, 23b are curved so as to become convex toward radial direction outer sides of the corner
portions 32A of the die 32.
[0048] The punch 31 is then moved further toward the upper side, and the blank is applied
with pressure and gripped by the punch 31 and the die 32, thereby forming the pressed article
20 (see Fig. 1A). Accordingly, the blank that has been bent by the comer portions 31Aof
the punch 3 1 (see Fig. 5B) and the comer portions 32A of the die 32 (see Fig. 5R) is bent back
to form the vertical walls 23a, 23b. In this manner, during forming of the vertical walls 23a,
23b, the blank is sub.jected to bending, and bend-back, deformation by the punch 31 and the
die 32, and moments arise in the vertical walls 23a, 23b due to stress differences (differences
between stress at the front faces (outer side faces) and stress at the back faces (inner side
faces) of the vertical walls 23a, 23b) in the sheet thickness direction of the vertical walls 23a,
23b.
[0049] Specifically, compressive stress acts in the front faces (outer side faces), and tensile
stress acts in the back faces (inner side faces) of the base end side portions of the vertical
walls 23a, 23b after forming. Accordingly, due to the difference between the stress at the
front faces (outer side faces) and the stress at the back faces (inner side faces) of the vertical
walls 23a, 23b, moment (inward warp moment) that would cause the base end side portions of
the respective vertical walls 23a, 23b to warp so as to curl around toward the inside of the
14
pressed article 20 (in other words, that would cause the vertical \valIs 23a. 23b to warp so as
to bccomc convex on the front Fdcc side) arises in the base end side portions of the vertical
walls 23a, 23b (see thc base end side portions of the vcrtical walls 23a, 23b illustrated by the
dashed lines in Fig. 3).
[0050] By contrast, tensile stress acts in the frontfaces (outer side faces), and compressive
stress acts in the back faces (inner side faces) orthe leading end side portions of the vcrtical
walls 23a, 23b after forming. Accordingly, due to the difference between the stress at the
front faces (outer side faces) and the stress at the back faces (inner side faces) of the vertical
walls 23a, 23b, moment (outward warp moment) that would cause the leading end side
portions of the respective vertical walls 23a, 23b to warp so as to curl around towa~dth e
outside of the pressed article 20 (in other words, that would cause the vertical walls 23a, 23b
to warp so as to become convex on the back face side) arises in the leading end side portions
of the vertical walls 23a, 23b (see the leading end side portions of the vertical walls 23a, 23b
illustratzd by the dotted lines in Fig. 3).
[0051] Note that the portions of the punch 31 that form the base end side portions of the
vertical walls 23a, 23b (portions on the side of the top plate 21 and the ridge lines 22a, 22b)
are formed with the punch side concave curved face portions 31 B, and portions of the punch
3 1 that form the leading end side portions of the vertical walls 23a, 23 b (portions on the side
of the bend lines 24a, 24b and flanges 25a, 25b) are formed with the punch side convex
curved face portions 31C. Portions of the die 32 that form the base end side portions of the
vertical walls 23a, 23b are formed with the die side convex curved face portions 32B, and
portions ofthe die 32 that form the leading end side portions of the vertical walls 23a, 23b are
formed with the die side concave curved face portions 32C.
100521 Accordingly, as illustrated in Fig. 1A and Fig. IB, in a state after the first pressing
has been completed, and before demolding from the press mold 30A, the base end side
portions of the pair of vertical walls 23a, 23b are applied with pressure and gripped by the
punch side concave curved face portions 31B and the die side convex curved face portions
32B in the first warp shapes 23a-1,23b-1 that are convex on the back face side of the vertical
walls 23a, 23b. The leading end side portions of the pair of vertical walls 23a, 23b are
applied with pressure and gripped by the punch side convex curved face portions 3 1C and the
die side concave curved face portions 32C in the second warp shapes 23a-2,23b-2 that are
convex on the Gont face side of the vertical walls 23a, 23b. Namely, in the pressed article 20
prior to demolding from the mold, the pair of vertical walls 23a, 23b are applied with pressure
and gripped by the punch 3 1 and the die 32 so as to adopt an S-shaped lateral cross-section
prof le.
15
/0053] Accordingly, in the presscd article 20 prior to demolding from 111e press lllold 30A.
the base end sidc portions of the vertical walls 23a, 23b, which arc atternpiing to warp so as to
bccome convex on the fiont face side of the vertical walls 23a, 23b (the outside of the pressed
article 20) due to the inward warp moment, are corrected by the lirsl warp shapes 23a-1,
23b-1 that are warped so as to be convcx on the back face side of the vertical walls 23a, 23b.
Moreover, in the pressed article 20, the leading end side portions of the vertical ~valls2 3a, 23b.
which are attempting to warp so as to become convex on the back face side of the vertical
walls 23a, 23b (the inside of the pressed article 20) due to the outward warp moment, are
corrected by the second warp shapcs 23a-2,23b-2 warped so as to be convex on the front face
side of the vertical walls 23a, 23b. Accordingly, the inwa~dw arp moment arising in the base
end side po~tionso f the vertical walls 23a, 23b are cancellcd out, and the outward warp
moment arising in the leading end side portions of the vertical walls 23a, 23b are cancelled
out. As a result, as illustrated in Fig. 4A, when the pressure applied by the punch 31 and the
d ~3e2 is removed from the pressed article 20 when demolding from the press mold 30A, the
strain difference in the sheet thickness direction is reduced at the base end side portions and
the leading end side portions of the vertical walls 23a, 23b, thereby enabling the occurrence of
wall warping in the vertical walls 23a, 23b (only the vertical wall 23b is illustrated in Fig. 4A)
to be suppressed.
100541 In cases in which the shape of the pressed article 26 illustrated in Fig. 4A satisfies the
shape of the manufactured article, the pressed article 26 may be used as it is as the finished
manufactured article. However, in cases in which it is necessary to push the ridge lines 22a,
22b of the pressed article 26 in further, the pressed article 26 may be restruck after the first
pressing so as to form the pressed article into the finished manufactured article. Namely,
after the first pressing, a restriking punch and a restriking die may be employed to restrike the
ridge lines 22a, 22b in a second pressing to push the ridge lines 22a, 22b in further, thereby
configuring a finished manufactured article with the desired cross-section profile, illustrated
in Fig. 4B (only the vertical wall 23b is illustrated in Fig. 4B). Note that in the restriking
punch and the restriking die employed when restriking the pressed article 26, faces that form
the vertical walls 23a, 23b are formed with flat plane shapes (straight line shapes as viewed in
lateral cross-section).
[0055] In this manner, the pressed article manufacturing method of the present disclosure
enables the pressed article 26 to be manufactured without forming beads or steps in the
vertical walls 23a, 23b, while spring back (vertical wall warping) of the vertical walls 23a,
23b is eliminated in practice, when the pressed article 26 has a high tensile strength of, for
example, 590 MPa or greater, 780 MPa or greater, or in some cases 980 MPa or greater.
16
/0056] 'Yhc p~iuch side concave cul-ved face portions 3 IR, the punch side convex curvcd face
portions 3 IC. the die side collvcx curved Face portions 32B. and thc die side concave curved
face portions 32C are formed such that the radii of curvature ol'both the first waq shapes
23a-1,23b-1 and the second warp shapes 23a-2, 23b-2 of the pressed article 20 are from 10
n ~ mto 800 mm. This thereby enables a good reduction in wall warping in the overall
vertical walls 23a, 23b of the pressed article 26.
100571 Moreover, the respective sums of the cross-section peripheral lengths of the
respective first warp shapes 23a-1,23b-1 and the cross-section peripheral lengths of the
respective second warp shapes 23a-2,23b-2 of the pressed article 20 are set to not less than
50% of the cross-section peripheral length of the respective vertical walls 23a, 23b of the
pressed article 26. This thereby enables an effective reduction in wall warping in the overall
vertical walls 23a, 23b of the pressed article 26.
[0058] Moreover, the cross-section peripheral lengths of the respective first warp shapes
23a-1,23b-1 of the pressed article 20 are set not less than the distance X between the
respective corner portions 3 1A of the punch 3 1 and the respective corner portions 32A of the
die 32 in the width direction of the press mold 30A (30B), and is set equal to or less than 112
the cross-section peripheral length of the vertical walls 23a, 23b. This thereby enables a
reduction in wall warping of the vertical walls 23a, 23b of the pressed article 26 that can be
applied to the bending, drawing, or the like during the first pressing.
[0059] Example 1
Example 1 is an example in which the pressed articles 26 were manufactured with
hat shaped lateral cross-section profiles. Specifically, the pressed articles 26 were
manufactured employing the press mold 30A illustrated in Fig. 1Afor the first pressing, using
rectangular blanks configured by three classes of steel (length 250 mm, width 27 mm, sheet
thickness 1.2 mm; material: DP steel with 1180 MPa grade tensile strength (steel A), DP steel
with 980 grade tensile strength (steel B), DP steel with 590 grade tensile strength (steel C)).
Fig. 6A is a perspective view illustrating the pressed article 26 after demolding, and Fig. 6B
illustrates dimensions of the pressed article 26 after demolding.
[0060] Several of the pressed articles 26 (Example 1-(1) to Example 1-(9) in the table in Fig.
7) were manufactured, varying the angles of the vertical walls 23a, 23b of the pressed article
20 (vertical wall angles, more specifically, the angles of the vertical walls 23a, 23b with
respect to the reference line I,) prior to demolding from the press mold 30A, and varying the
respective radii of curvature of tile first warp shapes 23a-1,23b-1 and the second warp shapes
23a-2,23 b-2, as shown in the table in Fig. 7.
[0061] Then, as illustrated in Fig. 6A and Fig. 6B, thc radii of curvature passing though
17
measul.ernent positions 27 to 29 at three rcspcctivc locations of an upper portion.. a central
portion, and a lower portion ofthe vertical wall 23b of each denioldcd prcssed article 26 were
measured, and spring back of thc vertical wall 23b (wall warping ol'the vertical walls 23a,
23b) was evaluated against comparative examples. Note that in the comparative examples,
the punch side concave curved face portions 3 1B and the punch side convex curved face
portions 3 1C were not provided to the punch 3 1 of the press mold 30A, and the die side
convex curved face portions 32B and the die side concave curved face portions 32C were not
provided to the die 32 of the press mold 30A. Namely, in the pressed articles of the
comparative examples, the vertical walls 23a, 23b are formed in substantially straight line
shapes prior to demolding from the press mold 30A, and are not formed with the first warp
shapes 23a-1,23b-1, nor with the second warp shapes 23a-2,23b-2.
[0062] Fig. 8 is a graph illustrating relative values of the respective radii of curvature
measured for Comparative Examples 1 to 3 and for Examples 1-(1) to 1-(9), for respective
cases in which DP steel with 980 MPa grade tensile strength (steel B) was used astheblank.
The radius of curvature measured for Comparative Example 3 is set to 1.
[0063] Fig. 9 is a graph illustrating relative values of the respective radii of curvature
measured for Comparative Examples 2 and 3 and for Examples 1-(3) and 1-(5), for cases in
which blanks configured from the three tensile strength classes described above (steel h to
steel C) were used as the stock material. The radius of curvature measured for Comparative
Example 3 when configured using steel A is set to 1.
[0064] As illustrated in the graph of Fig. 8, it can be seen that the curvature of the pressed
articles 26 of Examples 1-(1) to 1-(9) was less than approximately 115 the curvature of the
pressed articles of Comparative Examples 1 to 3. Namely, it can be seen that in the pressed
articles 26 of Example 1-(1) to 1-(9), wall warping of the vertical walls 23a, 23b was greatly
suppressed in comparison to Comparative Examples 1 to 3, and was eliminated in practice.
[0065] Moreover, as illustratcd in the graph of Fig. 9, although there is some difference in
curvature between the pressed articles 26 of Examples 1 -(3) and 145) depending on the
tensile strength of the blank, it can be seen that the curvatures of the pressed articles 26 of
Examples 1 -(3) and 1-(5) were greatly reduced in comparison to the curvature of the pressed
articles of Comparative Examples 2 and 3. Namely, it can be seen that in the pressed articles
26 of Examples 1-(3) and 1-(5), wall warping of the vertical walls 23a, 23b was greatly
suppressed in comparison to Comparative Examples 2 and 3, and was eliminated in practice.
[0066] As described above, the pressed article manufacturing method employing the press
molds 30A, 30B enables wall warping in the vertical walls 23a, 23b of the presscd article 26
to be reduced.
18
100671 Example 2
Similarly to in Example 1, in Example 2, pressed articlcs 26 were manufactured
employing the press mold 30.4 illustrated in Fig. 1A for the first pressing, using rectangular
blanlts manufactured from three classcs of stecl. Howcver, in Example 2, the press mold
30A was not provided with the punch side convex curved face portions 3 1C of the punch 31,
and was not provided with thc die side concave curved face portions 32C of the die 32.
Namely, prior to demolding, in the pressed article 20, only the base end side portions of the
vertical walls 23a, 23b were pressed into the first warp shapes 23a-1, 23b-1, and the leading
end side portions of the vertical walls 23a, 23b were pressed into substantially straight line
shapes as viewed in lateral cross-se~tion. Note that the blaiilcs employed in Example 2 were
similar to the blanks employed in Example 1, and the pressed articles 26 of Example 2 had the
same dimensions as those of Examplc 1.
[0068] Similarly to in Example 1, several of the pressed articles 26 (Example 2-(1) to
Example 2-(4) in the table in Fig. 7) were manufactured, varying the angles (vertical wall
angles) of the vertical walls 23a, 23b of the pressed article 20 prior to demolding, and varying
the radii of curvature of the first warp shapes 23a-1,23b-I, as shown in the table in Fig. 7.
[0069] In Example 2, the radii of curvature passing through measurement positions 27A to
29A (see Fig. 3) at three locations of an upper portion, a central portion, and a lower portion
of the base end side portion (a portion corresponding to the first warp shape 23b-1 of the
pressed article 20) of the vertical wall 23b of each demolded pressed article 26 were measured
in order to evaluate wall warping ofthe base end side portion of the vertical wall 23b together
with the Comparative Examples introduced above.
[0070] Fig. 10 is a graph illustrating relative values for the respective radii of curvature at
the measurement positions 27A to 29A measured for Comparative Examples 1 to 3 and for the
Examples 2-(1) to 2-(4), for respective cases in which DP steel with 980 MPa grade tensile
strength (steel B) was used as the blank. The radii of curvature for Comparative Example 3
at the measurement positions 27A to 29A are set to 1.
[0071] Fig. 11 is a graph illustrating relative values lor the respective radii of curvature
measured for the measurement positions 27 to 29 in Comparative Examples 2 and 3 and in
Examples 2-(2) and 2-(3), for cases in which blanks configured from the three tensile strength
classes described above (steel A to steel C) were used as the stock material. The radii of
curvature at the measurement positions 27A to 29A for Comparative Example 3 when
configured using steel A is set to I .
[0072] As illustrated in the graph of Fig. 10, in Examplc 2, it can be seen once again that
wall warping of the vertical walls 23a, 23b of the pressed articlcs 26 of Examples 2-(1) to
19
2-(4) was suppl.essed in comparison to Comparative Examples 1 to 3, and was eli~iiiiiaied in
practice. Y~lall warping of ihe pressed article 26 of Example 2-(4) in 13articular was great11
suppressed in coiliparison to Compzaraiive Examples I to 3.
100731 As illustrated in the graph o-l'Fig. 11, it can be seen that thc curvature ofthe vertical
walls 23a, 23b of the pressed articles 26 of Examples 2-(2) and 2-(3) was smaller than the
curvature of the pressed articles of Comparative Examples 2 and 3 for the blanks of each
tensile strength. Namely, it can be seen that in the pressed articles 26 of Examples 2-(2) and
2-(3), wall warping of the vertical walls 23a, 23b was suppressed in comparison to the
Comparative Examples 2 and 3, and was eliminated in practice.
to0741 As described above, wall warping of the vertical walls 23a, 23b at the base end
portions of the pressed article 26 can still be reduced even when onlythe base end side
portions of the vertical walls 23a, 23b of the pressed article 20 are applied with pressure and
gripped in the first warp shapes 23a-1, 23b-1 using the press mold 30A (30B).
[0075] -The disclosure of Japanese Patent Application No. 2014-131901, filed on June 26,
2014, is incorporated in its entirety by reference herein.
[0076] Supplementary Explanation
Apressed article manufacturing method of the present disclosure employs a press
mold equipped with a punch and a die to manufacture a pressed article including a first ,wall, a
second wall extending out from an end portion on at least one length direction side of the first
wall toward a back face side of the first wall, and a third wall extending out from a leading
end portion of the second wall toward a front face side of the second wall. The
manufacturing method includes using the punch and the die to apply pressure to and grip a
portion on a base end side of the second wall in a first warp shape in which the base end side
portion is warped so as to be convex on a back face side of the second wall as viewed in
lateral cross-section in a state prior to demolding from the press mold.
[0077] The pressed article manufacturing method of the present disclosure preferably further
includes using the punch and the die to apply pressure to and grip a portion on a leading end
side of the second wall in a second warp shape in which the leading end side portion is
warped so as to be convex on the front face side of the second wall as viewed in lateral
cross-section in a state prior to demolding from the press mold.
[0078] In the pressed article manufacturing method of the present disclosure, preferably
radii of curvature of the first warp shape and the second warp shape are from 10 mm to 800
rnrn as viewed in lateral cross-se~tlonin a state prior to demolding from the press mold.
[0079] In the pressed article manufacturing method of the present disclosure, preferably the
sum of a cross-section peripheral length of the first warp shape and a cross-section peripheral
20
length of the second warp shape is not lcss than 50% of a cross-section peripheral lcngth of
the second well as viewed in lateral cross-scctioii in a state prior to demoldi~lgfr om the pl-ess
mold.
[0080] In the pressed articlc manufacturing method of the present disclosure, preferably a
cross-section peripheral length of the first warp shape is set so as to be not lcss than a distance
in a width direction of the press mold between a comer portion of the punch and a corner
portion of the die, and so as to be not greater than 112 of a cross-section peripheral length of
the second wall, as viewed in lateral cross-section in a state prior to demolding from the press
mold.
[0081] In the pressed article manufacturing method of the present disclosure, preferably the
tensile strength of the pressed article is 590 MPa or greater.
[0082] Apress mold of the present disclosure is a press mold for manufacturing a pressed
article including a first wall, a second wall extending out from an end portion on at least one
length direction side of the first wall toward a back face side of the first wall, and a third wall
extending out from a leading end portion of the second wall toward a front face side of the
second wall. The press mold includes a punch and a die that form the pressed article by
moving relative to each other in a direction approaching each other. A first pressure
application section is formed at the punch and the die, the first pressure application section
applying pressure to and gripping a portion on a base end side of the second wall in a first
warp shape in which the base end side portion is warped so as to be convex on a back face
side of the second wall as viewed in lateral cross-section in a state prior to demolding from
the punch and the die.
[0083] In the press mold of the present disclosure, preferably a second pressure application
section is formed at the punch and the die, the second pressure application section applying
pressure to and gripping a portion on a leading end side of the second wall in a second warp
shape in which the leading end side portion is warped so as to be convex on the front face side
of the second wall as viewed in lateral cross-section in a state prior to deinolding from the
punch and the die.
[0084] In the press mold of the prcsent disclosure, preferably the first pressure application
section and the second pressure application section are formed such that radii of curvature of
the first warp shape and the second warp shape are from 10 mm to 800 mm as viewed in
lateral cross-section in a state prior to demolding from the punch and the die.
[0085] 111 the press mold of the present disclosure, prefcrably cross-section peripheral
lengths of the first pressure application section and the second pressure applicatioll section are
set such that the sum of a cross-section peripheral length of the first warp shape and a
cross-section peripheral lengtlh of thc sccond warp shape is not less than 50% of a
cross-section peripheral length of the vcrtical wall as viewed in lateral cross-seclion in a slate
prior to demolding fiorn the punch and the die.
[0086] In the press mold of the present disclosure, preferably a lcngth of the lirst pressure
application section is set such that a cross-section peripheral length of the first warp shape is
not less than a distance in a width direction of the press mold between a comer portion ofthe
punch and a corner portion of the die, and is not greater than 112 of a cross-section peripheral
length of the second wall, as viewed in lateral cross-section in a state prior to demolding from
the punch and the die.
[0087] In the pressed article manufacturing method of the present disclosure, a first pressing
is performed using a first punch and a first die to configure a blank into a molded article with
a lateral cross-section configured by a top plate, a ridge line linked to the top plate, a vertical
wall linked to the ridge line, a bend line linked to the vertical wall, and a flange linked to the
bend line. The vertical wall has a11 S-shaped lateral cross-section profile including a convex
shaped portion that is formed on the ridge line side and that is configured by a line that curves
toward the inside of the lateral cross-section profile, and a convex shaped portion that is
formed on the bend line side and that is configured by a line that curves toward the outside of
the lateral cross-section profile. The molded article is then demolded.
[0088] The press mold of the present disclosure is a pressed article manufacturing apparatus
including a first punch and a first die that perform a first pressing to form a blank into a
molded article with a lateral cross-section configured by a top plate, a ridge line linked to the
top plate, a vertical wall linked to the ridge line, a bend line linked to the vertical wall, and a
flange linked to the bend line. The vertical wall has an S-shaped lateral cross-section profile
including a convex shaped portion that is formed on the ridge line side and that is configured
by a line that curves toward the inside of the lateral cross-section profile, and a convex shaped
portion that is formed on the bend line side and that is configured by a line that curves toward
the outside of the lateral cross-section profile. The first punch has an outer surface profile of
the same shape as an inner surface profile of the top plate, the ridge line, and part of the
vertical wall respectively, and the first die has an inner surface profile of the same shape as an
outer surface profile of the top plate, the ridge line, and part of the vertical wall respectively.
The radii of curvature of the convex shaped portion configured by the line that curves toward
the inside, and the convex shaped porlion configured by the line that curves toward the
outside, are both from 10 mm to 800 mm.
CLAIMS
I . A pressed article nianufacturing mcthod employing a press mold cquipped with a punch
and a die to lnanufacture a pressed article including a first wall, a sccond wall extending out
from an end portion on at least one length direction side of the first wall toward a back facc
side ofthe first wall, and a third wall cxtending out from a leading end portion or the second
wall toward a front face side of the second wall, the inmufacturing method comprising:
using the punch and the die to apply pressure to and grip a portion on a base end side
of the second wall in a first warp shape in which the base end side portion is warped so as to
be convex on a back face side of the second wall as viewed in lateral cross-section in a state
prior to demolding from the press mold.
2. The pressed article manufacturing method or claim 1, further comprising using the punch
and the die to apply pressure to and grip a portion on a leading end side of the second wall in
a second warp shape in which the Ieadiilg end side portion is warped so as to be convex on the
front face side of the second wall as viewed in lateral cross-section in a state prior to
demolding from the press mold.
3. The pressed article manufacturing method of claim 2, wherein radii of curvature of the
first warp shape and the second warp shape are from 10 mm to 800 mm as viewed in latcral
cross-section in a state prior to demolding from the press mold.
4. The pressed article manufacturing method of either claim 2 or claim 3, wherein a sum of
a cross-section peripheral length of the first warp shape and a cross-section peripheral length
of the second warp shape is not less than 50% of a cross-section peripheral length of the
second wall as viewed in lateral cross-section in a state prior to demolding from the press
mold.
5. The pressed article manufacturing method of any one of claim 2 to claim 4, wherein a
cross-section peripheral length of the first warp shape is set so as to he not less than a distance
in a width direction of the press mold between a comer portion of the punch and a comer
portion of the die, and so as to be not greater than 112 of a cross-section peripheral length of
the second wall, as viewed in lateral cross-section in a state prior to demolding from the press
mold.
6. The pressed article manufacturing method of any one of claim 1 to claim 5, wherein a
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tcilsilc strcilgth of the pressed article is 590 MPa or greater
7. A press mold fol. manufacturing a pressed article including a first wall, a second wall
extending out from an end portion on at least one length direction side of the first wall toward
a back face side of the iirst wall, and a third wall extending out from a leading end portion of
the second wall toward a front face side of the second wall, the press mold comprising:
a punch and a die that form the pressed article by moving relative to each other in a
direction approaching each other,
wherein a first pressure application section is formed at the punch and the die, the
first pressure application section applying pressure to and gripping a portion on a base end
side of the second wall in a first warp shape in which the base end side portion is warped so as
to be convex on a back face side of the second wall as viewed in lateral cross-section in a state
prior to demolding from the punch and the die.
8. The press mold of claim 7, wherein a second pressure application section is formed at the
punch and the die, the second pressure application section applying pressure to and gripping a
portion on a leading end side of the second wall in a second warp shape in which the leading
end side portion is warped so as to be convex on the front face side of the second wall as
viewed in lateral cross-section in a state prior to demolding from the punch and the die.
9. The press mold of claim 8, wherein the first pressure application section and the second
pressure application section are formed such that radii of curvature of the first warp shape and
the second warp shape are from 10 mm to 800 mm as viewed in lateral cross-section in a state
prior to demolding from the punch and the die.
10. The press mold of either claim 8 or claim 9, wherein cross-section peripheral lengths of
the first pressure application section and the second pressure application section are set such
that a sum of a cross-section peripheral length of the first waiF shape and a cross-section
peripheral length of the second warp shape is not less than 50% of a cross-section peripheral
length of the second wall as viewed in lateral cross-section in a state prior to demolding from
the punch and the die.
11. The press mold of any one of claim 8 to claim 10, wherein a length of the fiist pressure
application section is set such that a cross-section peripheral length of the first warp shape is
not less than a distance in a width direction of the press mold between a coiner portion ofthe
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punch and a corner povtioil of tlie die, and is not greater than 1/2 of a cross-section peripheral
length of the second wall, as viewed in lateral cross-section in a state prior to deillolding fl-om
the punch and the die.