DESCRIPTION
TITLE OF INVENTION: MANUFACTURING METHOD AND
MANUFACTURING APPARATUS OF PRESS-FORMED BODY
TECHNICAL FIELD
[0001] The present invention relates to a
manufacturing method and a manufacturing apparatus of
a press-formed body, and specifically, to a
manufacturing method and a manufacturing apparatus of
a press-formed body made of a high-tensile strength
steel sheet with a tensile strength of 390 MPa or
more having approximately a groove-shaped cross
section including a groove bottom par,t, ridge line
parts continuous to the groove bottom part, and side
wall parts continuous to the ridge line parts, and in
which an outward flange is formed at an end part in a
longitudinal direction.
BACKGROUND ART
[0002] A floor of a vehicle body (hereinafter,
referred to just as a 'floor") is not only primary
responsible for torsional rigidity and bending
rigidity of a vehicle body at a vehicle traveling
time, but also responsible for transfer of an impact
load during crash, further it largely affects on a
weight of the vehicle body, and therefore, it is
required to include antinomy characteristics of both
high rigidity and light weight. The floor includes
planar panels (for example, a dash panel, a front
floor panel, a rear floor panel, and so on) which are
- 1 -
welded to be joined wlth each other, long members
(for example, a 'floor cross member, a seat cross
member, and so on) having approximately groove-shaped
cross sections which are fixed to be disposed in a
vehicle width direction of these planar panels by
welding to enhance rigidity and strength of the floor,
and long members (a side sill, a side member, and so
on) having approximately groove-shaped cross sections
which are fixed to be disposed in a vehicle forward
and backward direction to enhance the rigidity and
the strength of the floor. For example, the floor
cross member is normally joined to other members such
as, for example, a tunnel part of the front floor
panel and the side sill via outward flanges formed at
both end parts in a longitudinal direction.
[0003] Fig. 12A, Fig. 12B are explanatory views
illustrating a floor cross member 1. Fig. 12A is a
perspective view, and Fig. 12B is a XI1 arrow view in
Fig. 12A.
In general, the floor cross member 1 is joined to
an upper surface (a surface at an interior side) of a
front floor panel 2. A floor is reinforced by this
floor cross member 1 coupling a tunnel part (notillustrated)
formed by bulging at approximately a
center in a width direction of the front floor panel
2 and side sills 3 spot-welded at both side parts in
a width direction of the front floor panel 2. The
floor cross member 1 has approximately a grooveshaped
cross section, and it is spot-welded to the
tunnel part and the side sills 3 via outward flanges
4 formed at both end parts in a longitudinal
direction thereof, and thereby, rigidity of the floor
and a load transfer characteristic when an impact
load is applied improve.
[0004] Fig. 13A and Fig. 13B are explanatory views
schematically illustrating a conventional pressforming
method of the floor cross member 1. Fig. 13A
is the explanatory view schematically illustrating
drawing in which forming is performed while applying
a binding force at an end of a material by a blank
holder. Fig. 13B is the explanatory view
schematically illustrating bend-forming using a
developed blank 6.
[0005] In the press-forming by the drawing
illustrated in Fig. 13A, an excess part 5a is formed
at a press-forming material 5, the excess part 5a is
cut along a cutting-line 5b, and thereafter, a flange
5c is stood up. Besides, in the press-forming by the
bend-forming illustrated in Fig. 13B, the pressforming
by the bend-forming is performed for the
developed blank 6 having a developed blank shape.
The floor cross member 1 is conventionally formed by
performing the press-forming by the drawing
illustrated in Fig. 13A or the press-forming by the
bend-forming illustrated in Fig. 13B. From a point
of view of improving material yield, the pressforming
by the bend-forming is preferable than the
press-forming by the drawing accompanied by the
cutting of the excess part 5a.
[0006] The floor cross member 1 is an important
structural member which is responsible for the
rigidity improvement of the vehicle body and
absorption of the impact load during side crash (side
impact). Accordingly, in recent years, a thinner and
I higher strength high-tensile strength steel sheet,
i
for example, a high-tensile strength steel sheet with
a tensile strength of 390 MPa or more (a highstrength
steel sheet or a HSS[high tensile strength
steel]) has been used as a material of the floor
cross member 1 from a point of view of reduction in
weight and improvement in crash safety. However,
formability of the high-tensile strength steel sheet
i 1 is not good, and therefore, it is a problem that
I
I flexibility of deslgn of the floor cross member 1 is
low.
[0007] It is concretely described with reference to
Fig. 12A and Fig. 12B. It is desirable to form the
continuous outward flange 4 at a whole periphery of
an end part of the floor cross member 1, and to
obtaln a flange width wlth a certain degree of length
to enhance joining strength and torsional rigidlty
between the floor cross member 1 and the tunnel part
of the front floor panel 2, the side sills 3, and to
enhance the rigidity of the floor and the load
transfer characteristic during crash.
[0008] However, it is difficult to obtain a desired
shape when the continuous outward flange 4 is formed
i at the whole periphery of the end part of the floor
cross member 1, and to obtain the flange width with
the certain degree of length because basically,
stretch flange cracks at a flange part corresponding
to an outer periphery of a ridge line part of the
outward flange 4 (hereinafter, referred to as a
"ridge line part flange portion") and wrinkling at a
proximity part lb of the outward flange 4 at a ridge
line part la occur. These forming failures are easy
to occur as a material strength of the floor cross
member 1 is higher, and as a stretch flange rate at
the forming of a ridge line part flange portion 4a of
the outward flange 4 is higher (namely, for example,
as a cross sectional wall angle (3 in Fig. 12B is
steeper, or as a flange height is higher).
[GO091 The floor cross member 1 tends to be highstrengthened
to reduce the weight of the vehicle body,
and tends to be designed to a shape with high stretch
flange rate from a point of view of performance
thereof and a joint part shape with other members,
and therefore, the forming of the continuous outward
flange 4 including the ridge line part flange portion
4a is difficult to be enabled by the conventional
press-forming method. Accordingly, it is the present
situation in which cutouts cannot but be provided at
the ridge line part flange portion 4a of the outward
flange 4 of the floor cross member 1 made up of the
high-tensile strength steel sheet as illustrated in
Fig. 12A and Fig. 12B from restrictions on the press-
- 5 -
forming technology as stated above even if lowering
of the performance of the floor cross member 1 is
accepted.
[0010] In Patent Literatures 1 to 3, the inventions
are disclosed, in which a shape fixability failure in
a high-strength material press-forming product is
solved by devising a pad mechanism of a metal
forming-tool though it is not intended for the
forming of the floor cross member 1. These
inventions are ones in which deflection is
intentionally generated at a material during the
forming by a positional relationship of the pad
pressing at least a portion of a part (groove bottom
part) where a punch top part and a punch top part
face with each other, to thereby enable improvement
in the shape fixability after the forming.
CITATION LIST
PATENT LITERATURE
[0011] Patent Literature 1: Japanese Patent
Publication No. 4438468
Patent Literature 2: Japanese Laid-open Patent
Publication No. 2009-255116
Patent Literature 3: Japanese Laid-open Patent
Publication No. 2012-051005
SUMMARY OF INVENTION
TECHNICAL PROBLEM
[0012] It is difficult to form the floor cross
member 1 being a press-formed body made of a hightensile
strength steel sheet of 390 MPa or more
having approximately a groove-shaped cross section
including a groove bottom part, ridge line parts, and
side wall parts, and in which an outward flange is
formed at a range across at least a portion of each
of the ridge line part, the groove bottom part and
the side wall part at both sides of the ridge line
part from among an end part in a longitudinal
direction without providing cutouts at the ridge line
part flange portion 4a of the outward flange 4 or
without generating lowering of material yield, even
if the conventional inventions disclosed in Patent
Literatures 1 to 3 are based on.
[0013] An object of the present invention is to
provide a method and an apparatus manufacturing a
press-formed body such as, for example, a floor cross
member made of a high-tensile strength steel sheet of
390 MPa or more having approximately a groove-shaped
cross section including a groove bottom part, ridge
line parts, and side wall parts, and in which an
outward flange is formed at a range across at least a
portion of each of the ridge line part, the groove
bottom part and the side wall part at both sides
thereof, from among an end part in a longitudinal
direction without providing cutouts at a ridge line
part flange portion of the outward flange or without
generating lowering of material yield.
SOLUTION TO PROBLEM
[0014] The present invention is as cited below.
[l] A manufacturing method of a press-formed
body made of a high-tensile strength steel sheet of
390 MPa or more having approximately a groove-shaped
cross section including a groove bottom part, ridge
line parts continuous to the groove bottom part, and
side wall parts continuous to the ridge line parts,
and in which an outward flange is formed at a range
across at least a portion of each of the ridge line
part, the groove bottom part and the side wall part
at both sides thereof, from among an end part in a
longitudinal direction by performing a press-forming
of a press-forming material by a press-forming
i
I apparatus which includes a punch, a die, and a pad
pressing and binding the press-forming material to
the punch, the manufacturing method includes: a first
step of performing the press-forming while the pad
binds a part to be formed into the groove bottom part
and at least a portion of a part to be formed into
the ridge line part at the press-forming material;
and a second step of performing the press-forming of
parts which are not able to be formed by the first
step.
[2] The manufacturing method of the press-formed
body according to [I], wherein the pad binds a part
having a length of one-third or more of a crosssectional
peripheral length of the ridge line part
starting from a connecting part with the groove
bottom part.
(31 The manufacturing method of the press-formed
body according to [I] or [2], wherein the pad binds
the part to be formed into the ridge line part within
a predetermined range from a root part of the outward
flange in a direction where the ridge line part
extends in a longitudinal direction of the part to be
formed into the ridge line part.
[4] The manufacturing method of the pressformed
body according to any one of [I] to [3],
wherein the press-formed body has approximately the
groove-shaped cross section further including curved
parts continuous to the side wall parts, and fldnges
continuous to the curved parts.
[5] The manufacturing method of the press-formed
body according to any one of [l] to [4], wherein the
press-forming is bend-forming.
[6] The manufacturing method of the press-formed
body according to any one of [l] to [41, wherein the
press-forming is drawing.
[7] A manufacturing apparatus of a press-formed
body, manufacturing the press-formed body made of a
high-tensile strength steel sheet of 390 MPa or more
having approximately a groove-shaped cross section
including a groove bottom part, ridge line parts
continuous to the groove bottom part, and side wall
parts continuous to the ridge line parts, and in
which an outward flange is formed at a range across
at least a portion of each of the ridge line part,
the groove bottom part and the side wall part at both
sldes thereof, from among an end part in a
longitudinal direction, the manufacturing apparatus
includes: a punch; a die; and a pad which presses and
binds a press-forming material to the punch, wherein
the pad has a shape binding a part to be formed into
the groove bottom part and at least a portion of a
part to be formed into the ridge line part at the
press-forming material.
I [8] The manufacturing apparatus of the press-
I
:Ii formed body according to [7], wherein the pad has a
shape binding a part having a,length of one-third or
.. . more of a cross-sectional periphera~l length of the
ridge line part starting from a connecting part with
the groove bottom part.
[9] The manufacturing apparatus of the pressformed
body according to [7] or [8], wherein the pad
binds the part to be formed into the ridge line part
within a predetermined range from a root part of the
outward flange in a direction where the ridge line
part extends in a longitudinal direction of the part
to be formed into the ridge line part.
[lo] The manufacturing apparatus of the pressformed
body according to any one of [71 to [91,
wherein the press-formed body has approximately the
groove-shaped cross section further including curved
parts continuous to the side wall parts, and flanges
continuous to the curved parts.
[ll] The manufacturing apparatus of the pressformed
body according to any one of 171 to [ 9 1 ,
wherein the press-forming is bend-forming.
[12] The manufacturing apparatus of the pressformed
body according' to any one of [ 7 ] to [9],
wherein the press-forming is drawing.
Note that the pad according to the inventions
disclosed in the Patent Literatures 1 to 3 is one to
devise a positional relationship between a punch top
part and the pad pressing at least a portion of a
part (groove bottom part) facing the punch top part,
and the pad according to the present invention is
different from the inventions disclosed in the Patent
- . Literatures 1 to 3 in a point in which the pad has a
shape which intentionally presses also the ridge line
part.
11
.I ADVANTAGEOUS EFFECTS OF INVENTION
[0015] According to the present invention, it is
possible to surely form a press-formed body made of a
high-tensile strength steel sheet of 390 MPa or more
having approximately a groove-shaped cross section
including a groove bottom part, ridge line parts, and
side wall parts, and in which an outward flange is
formed at a range across the ridge line part, at
least a portion of each of the groove bottom part and
the side wall part at both sides thereof, from among
an end part in a longitudinal direction without
providing cutouts at a ridge line part flange portion
of the outward flange or without generating lowering
of material yield.
BRIEF DESCRIPTION OF DRAWINGS
[0016] [Fig. lA] Fig. 1A is a view schematically
illustrating a schematic configuration of a
manufacturing apparatus of a press-formed body
according to an embodiment and a first step;
[Fig. lB] Fig. 1B is a sectional view
illustrating a transverse cross-sectional shape of a
press-formed body manufactured in the present
embodiment;
[Fig. lC] Fig. 1C is a perspective view
illustrating a configuration at around a ridge line
pad in the first step;
[Fig. ID] Fig. lD is a view when the pressformed
body manufactured in the present embodiment is
seen from a lateral side in a longitudinal direction;
[Fig. 2A] Fig. 2A is a perspective view of a
press-formed body of an analysis example 1;
[Fig. 2B] Fig. 2B is a I1 arrow view in Fig. 2A;
[Fig. 2C] Fig. 2C is a transverse sectional view
of the press-formed body of the analysis example 1;
[Fig. 3A] Fig. 3A is a perspective view
illustrating a punch, a die, and a press-forming
material at a forming time according to the invented
method;
[Fig. 3B] Fig. 3B is a perspective view
illustrating the punch, a ridge line pad, and the
press-forming material at the forming time according
to the invented method;
[Fig. 3C] Fig. 3C is a perspective view
enlargedly illustrating a square surrounded part in
Fig. 3B;
[Fig. 3D] Fig. 3D is a 111-111 sectional view in
Fig. 3C;
[Fig. 4A] Fig. 4A is a perspective view
illustrating a punch, a die, a pad, and a pressforming
material at a forming time according to a
conventional method;
[Fig. 4B] Fig. 4B is a perspective view
illustrating the punch, the pad, and the pressforming
material at the forming time according to the
conventional method;
[Fig. 4C] Fig. 4C is a perspective view
enlargedly illustrating a square surrounded part in
Fig. 4B;
[Fig. 5A] Fig. 5A is a characteristic diagram
illustrating a numerical analysis result of a
relationship between a pressing angle of the pressforming
material by the pad and a maximum value of a
sheet thickness decrease at an end part of a ridge
line part flange portion of an outward flange in the
analysis example 1;
[Fig. 5B] Fig. 5B is a view illustrating
evaluation positions (a crack threat part) of the
sheet thickness decrease being evaluation objects in
the analysis example 1;
[Fig. 6A] Fig. 6A is a perspective view of a
press-formed body of an analysis example 2;
[Fig. 6B] Fig. 6B is a VI arrow view in Fig. 6A;
[Fig. 6C] Fig. 6C is a transverse sectional view
of the press-formed body of the analysis example 2;
[Fig. 7A] Fig. 7A is a perspective view
illustrating a punch, a die, a ridge line pad, and a
press-forming material at a forming time according to
the invented method;
[Fig. 7B] Fig. 78 is a perspective view
illustrating the punch, the ridge line pad, and the
press-forming material at the forming time according
to the invented method;
[Fig. 7C] Fig. 7C is a perspective view
enlargedly illustrating a square surrounded part in
Fig. 7B;
[Fig. 7D] Fig. 7D is a VII-VII sectional view in
Fig. 7C;
[Fig. 8A] Fig. 8A is a perspective view
illustrating a punch and a die at a forming time
according to the conventional method;
[Fig. 8B] Fig. 8B is a perspective view
illustrating the punch, a pad, and a press-forming
material at the forming time according to the
conventional method;
[Fig. 8C] Fig. 8C is a perspective view
enlargedly illustrating a square surrounded part in
Fig. 8B;
[Fig. 9A] Fig. 9A is a characteristic diagram
illustrating a numerical analysis result of a
relationship between a pressing angle of the pressforming
material by the pad and a minimum value of
sheet thickness decrease in a vicinity of a root part
of a ridge line part flange portion of an outward
- 14 -
flange in the analysis example 2;
[Fig. 9B] Fig. 9B is a view illustrating
evaluation positions (a wrinkling threat part) of the
sheet thickness decrease being evaluation objects in
the analysis example 2;
[Fig. 10AI Fig. 10A is a perspective view of a
press-formed body of an analysis example 3;
[Fig. 10BI Fig. 10B is an X arrow view in Fig.
10A;
[Fig. 10C] Fig. 10C is a transverse sectional
view of the press-formed body of the analysis example
3;
[Fig. 11A] Fig. 11A is a view to explain a
maximum value of a sheet thickness decrease at
evaluation positions (a crack threat part) of a sheet
thickness decrease according to the invented method;
[Fig. 11Bl Fig. 11B is a view to explain a
maximum value of a sheet thickness decrease at
evaluation positions (a crack threat part) of a sheet
thickness decrease according to the conventional
method;
[Fig. 12Al Fig. 12A is a perspective view of a
floor cross member;
[Fig. 12BI Fig. 12B is an XI1 arrow view in Fig.
12A;
[Fig. 13Al Fig. 13A is an explanatory view
schematically illustrating drawing; and
[Fig. 13Bl Fig. 13B is an explanatory view
schematically illustrating bend-forming
DESCRIPTION OF EMBODIMENTS
[0017] Hereinafter, embodiments of the present
invention are described with reference to the
attached drawings.
Fig. 1A to Fig. 1D are explanatory views
conceptually illustrating characteristics of a
manufacturing method and a manufacturing apparatus of
a press-formed body according to an embodiment where
the present invention is applied. Fig. 1A is a view
schematically illustrating a schematic configuration
of the manufacturing apparatus of the press-formed
body according to the embodiment and a first step.
Fig. 1B is a sectional view illustrating a transverse
sectional shape of the press-formed body manufactured
in the present embodiment. Fig. 1C is a perspective
view illustrating a configuration at around a ridge
line pad in the first step. Fig. 1D is a view when
the press-formed body manufactured in the present
embodiment is seen from a lateral side in a
longitudinal direction. Note that in each of Fig. 1B
and Fig. ID, a sheet thickness is represented by a
heavy line.
[0018] 1. Press-Formed Body
As illustrated in Fig. lB, the press-formed body
manufactured in the present embodiment is a pressformed
body 15 which is long and made of a hightensile
strength steel sheet of 390 MPa or more,
having approximately a groove-shaped cross section
including a groove bottom part 15a, ridge line parts
15b, 15b continuous to the groove bottom part 15a,
side wall parts 15c, 15c continuous to the ridge line
parts 15b, 15b, curved parts 15d, 15d continuous to
the side wall parts 15c, 15c, and flanges 15e, 15e
continuous to the curved parts 15d, 15d. An outward
flange 16 is formed at a whole periphery of an end
part in a longitudinal direction, namely, along the
groove bottom part 15a, the ridge line parts 15b, 15b,
the side wall parts 15c, 15c, the curved parts 15d,
15d, and the flanges 15e, 15e.
The press-formed body 15 manufactured in the
present embodiment is a press-formed body which does
not have cutouts at a ridge line part flange portion
16a of the outward flange 16 different from the one
illustrated in Fig. 12A, Fig. 12B.
Besides, the press-formed body 15 manufactured in
the present embodiment has a cross-sectional height
of 20 mm or more. Further, from a point of view of
securing a continuous region for welding such as spot
welding, laser welding, or plasma welding, a flange
width of the outward flange 16 is approximately 5 mm
or more at a flange flat part at a part of at least
the groove bottom part 15a, the ridge line part 15b,
and the side wall part 15c. Besides, at the ridge
line part 15b, the flange width is approximately 2 mm
or more from a point of view of securing performances
such as impact characteristics, torsional rigidity
even if joining is not performed.
[0019] Note that in the present embodiment, a hatshaped
press-formed body having approximately a
groove-shaped cross section illustrated in Fig. 1B is
described, but the present invention is applicable as
long as it is a press-formed body having
approximately a groove-shaped cross section including
at least the groove bottom part 15a, the ridge line
parts 15b, 15b, and the side wall parts 15c, 15c.
Besides, an example in which the outward flange
16 is formed at the whole periphery at the end part
in the longitudinal direction is described, but the
present invention is applicable as long as it is a
press-formed body in which the outward flange 16
including the ridge line part flange portion 16a is
formed, in other words, the outward flange 16 is
formed at a range across the ridge line part 15b, at
least a portion of each of the groove bottom part 15a
and the side wall part 15c at both sides thereof.
[0020] 2. Manufacturing Apparatus of Press-Formed
Body (Press-Forming Apparatus)
As illustrated in Fig. lA, a press-forming
apparatus 10 includes a punch 11, a die 12, and a pad
14 which presses and binds a press-forming material
13 to the punch 11. In the present embodiment, the
pad 14 is to bind not only a part to be formed into
the groove bottom part 15a but also parts to be
formed into the ridge line parts 15b, 15b at the
press-forming material 13, and it is called as a
ridge line pad.
[0021] The ridge line pad 14 has a shape binding the
part to be formed.into the groove bottom part 15a and ~ the parts to be 'formed into the ridge line parts 15b,
15b in a vicinity of the outward flange 16 at the
press-forming material 13.
[0022] A publicly-known pad binds the part to be
formed into the groove bottom part 15a, but does not
bind the parts to be formed into the ridge line parts
I '1 15b, 15b. On the other hand, the ridge line pad 14
I
binds not only the part to beformed into the groove
. . bottom part 15a but also the parts to be formed into
the ridge line parts 15b, 15b in the vicinity of the
outward flange 16. According to the ridge line pad
14, a shape of the ridge line pad 14 is approximately
formed by stretching out only a material at that part.
Moving of the material at around a part where the
ridge line pad 14 is in contact is thereby suppressed,
expansion and shrinkage deformations of a peripheral
material to be a factor of cracks and wrinkling are
suppressed, and t.herefore, it is possible to reduce
occurrences of stretch flange cracks at the ridge
line part flange portion 16a of the flange 16 and
wrinkling at a proximity part of the flange 16 (refer
to a proximity part lb in Fig. 12A) at the ridge line
part 15b.
100231 The ridge line pad 14 is aimed for an effect
suppressing the movlng of the peripheral materlal by
stretching out and forming the shape of the ridge
line part 15b in the vicinity of the outward flange
p:
16. Accordingly, it is desirable to bind a part
having a length of one-third or more of a crosssectional
peripheral length of the ridge line parts
15b, 15b starting from a connecting part 15a-b from
among the part to be formed into the ridge line part
15b, more preferably to bind a whole of the crosssectional
peripheral length of the part to be formed
into the ridge line part 15b. In this case, if it
has a shape of a degree in which only a single part
of the side wall part 15c, for example, a part of the
side wall part 15c having a length of 20 mm or less
in addition to the ridge line part 15b are pressed, a
problem in which a pad load is insufficient and
cannot afford to press is difficult to occur, and
therefore, it is acceptable as a pad in the present
invention.
[0024] Besides, it is preferable that a range bound
by the ridge line pad 14 in a longitudinal direction
of the part to be formed into the ridge line part 15b
("1" illustrated in Fig. ID) is set to be in the
vicinity of the outward flange 16, namely, at least a
portion of a predetermined range from a root part of
the outward flange 16 in a direction where the ridge
line part 15b extends. The predetermined range is
set to be the same degree as a flange width of the
ridge line part flange portion 16a of the outward
flange 16. For example, when the flange width of the
ridge line part flange portion 16a of the outward
flange 16 is 20 mm, the predetermined range is set to
be approximately 20 mm, and when the flange width of
the ridge line part f1,ange portion 16a is 30 mm, the
I predetermined range is set to be approximately 30 mm.
I
j
(I In this case, it is not necessary to bind the part to
be formed into the ridge line part 15bat a whole
area of this predetermined range, and it is no
:;
problem if a part of the predetermined range is bound
I
I [0025] Other elements such as a size and a material
:I of the ridge line pad 14 other than the above-stated
matters may be the same as a publicly-known pad.
[0026] 3. Manu:tacturing Method of. Press-Formed Body
In the press-forming apparatus 10, the pressforming
is performed while binding the part to be
formed into the groove bottom part 15a and the parts
to be formed into the ridge line parts 15b, 15b in
the vicinity of the outward flange 16 at the pressforming
material 13 by using the ridge line pad 14.
[0027] To form parts which cannot be formed by this
press-forming (a first press-forming step), a second
press-forming step being a post-step is perforrncd.
The part which cannot be formed by the first pressforming
step is concretely a part positioning
dlrectly below the rldge line part 15b whlch is bound
by the rldge llne pad 14 as represented by oblique
lines in Fig. ID. The second press-forming step
being the post-step is performed to form the part
represented by the oblique lines in Fig. ID, namely,
parts to be formed lnto a part of the side wall parts
15c, 15c, parts to be formed into a part of the
curved parts 15d, 15d, and parts to be formed lnto a
part of the flanges 15e, l5e.
In the second press-forming step, the pressforming
may be one using only a die and a punch
without using the pad (stamp press-forming), or may
be the normal press-bending using the pad.
[0028] Note that there is a case when a remaining
part of the part to be formed into the ridge line
part 15b which cannot be formed by the first pressforming
step exists depending on the region bound by
the ridge line pad 14. In this case, the remaining
part of the part which is formed into the ridge line
part 15b is also press-formed by the second pressforming
step. For example, when one-third of the
part to be formed into the ridge line part 15b is
formed by the first press-forming step, the remaining
two-thirds of the part to be formed into the ridge
line part 15b is formed by the second press-forming
step.
[0029] As stated above, the press-forming material
13 is press-formed (the first press-forming step, the
second press-forming step) by the press-forming
apparatus including the punch 11, the die 12, and the
ridge line pad 14 pressing and binding the pressforming
material 13 to the punch 11, and thereby, it
is possible to manufacture the press-formed body 15
which is long and made of the high-tensile strength
steel sheet of 390 MPa or more having approximately a
groove-shaped cross section including the groove
bottom part 15a, the ridge line parts 15b, 15b
continuous to the groove bottom part 15a, the side
wall parts 15c, 15c continuous to the ridge line
parts 15b, 15b, the curved parts 15d, 15d continuous
to the side wall parts 15c, 15c, and the flanges 15e,
15e continuous to the curved parts 15d, 15d in which
the outward flange 16 is formed at the whole
periphery of the end part in the longitudinal
direction illustrated in Fig. 1A.
[0030] Note that a concave and convex shape part of
0.1 mm or more is formed at a boundary part between
the ridge line part 15b and the side wall part 15c
corresponding to the end part of the ridge line pad
14 at the press-forming time because two times pressformings
are performed.
[0031] Hereinbelow, a reason why the press-forming
is performed by binding not only the part to be
formed into the groove bottom part 15a but also the
parts to be formed into the ridge line parts 15b, 15b
in the vicinity of the outward flange 16 by using the
ridge line pad 14 is described with reference to a
numerical analysis result by a finite element method.
[0032] [Analysis Example 11
Fig. 2A to Fig. 2C are explanatory views
illustrating a shape of a press-formed body 20 of an
analysis example 1. Fig. 2A is a perspective view of
the press-formed body 20, Fig. 2B is a I1 arrow view
in Fig. 2A, and Fi,g. 2C is a transverse sectional
view of the press-formed body 20 (an outward flange
20f is not illustrated).
[0033] The press-formed body 20 of the analysis
example 1 is made of a high-strength steel sheet (590
MPa class DP ( ~ u a l phase) steel), and a sheet
thickness thereof is 1.4 mm.
The press-formed body 20 includes a groove bottom
part 20a, ridge line parts 20b, 20b continuous to the
groove bottom part 20a, side wall parts 20c, 20c
continuous to the ridge line parts 20b, 20b, curved
parts 20d, 20d continuous to the side wall parts 20c,
20c, and flanges 20e, 20e continuous to the curved
parts 20d, 20d. A curvature radius at a sheet inner
side of the ridge line parts 20b, 20b is 12 mm.
[0034] The outward flanges 20f are formed at a whole
periphery of both end parts in a longitudinal
direction of the press-formed body 20, and a ridge
line part flange portion 20g becomes a curved portion.
A flange width of the outward flange 20f is 25 mm at
a part formed along the groove bottom part 20a, and
30 mm at a part formed along the side wall parts 20c,
20c.
[0035] A cross sectional wall angle of the pressformed
body 20 is 70 degrees, and a cross sectional
height is 100 mm. In the analysis example 1, the
press-formed body 20 is manufactured by the pressforming
by bend-forming using a developed blank.
[0036] Fig. 3A is a perspective view illustrating a
punch (lower forming-tool) 21, a die (upper formingtool)
22, and a press-forming material 24 at a
forming time according to the invented method. Fig.
3B is a perspective view illustrating the punch
(lower forming-tool) 21, a ridge line pad 25, and the
press-forming material 24 at the forming time
according to the invented method. Fig. 3C is a
perspective view enlargedly illustrating a square
surrounded part in Fig. 3B. Fig. 3D is a 111-111
sectional view in Fig. 3C.
[0037] On the other hand, Fig. 4A is a perspective
view illustrating a punch (lower forming-tool) 21, a
die (upper forming-tool) 22, a pad 23, and a pressforming
material 24 at a forming time according to a
conventional method. Fig. 4B is a perspective view
illustrating the punch (lower forming-tool) 21, the
pad 23, and the press-forming material 24 at the
forming time according to the conventional method.
Fig. 4C is a perspective view enlargedly illustrating
a square surrounded part in Fig. 4B.
[0038] Fig. 5A is a characteristic diagram
illustrating a numerical analysis result of a
relationship between a pressing angle of the pressforming
material' 24 by the pads 23, 25 and a maximum
value of a sheet thickness decrease at an end part of
the ridge line part flange portion 209 of the outward
flange 20f formed at the press-formed body 20. In
Fig. 5B, evaluation positions of a sheet thickness
decrease (ranges each surrounded by a dotted line, a
crack threat part) being evaluation objects in the
analysis example 1 are illustrated. The pressing
angle means a center angle of a range of the ridge
- 25 -
line part 20b bound by the pads 23, 25 while setting
a position of a connecting part with the groove
bottom part 20a as "0" (zero) degree from among a
part to be formed into the ridge line part 20b at the
press-forming material 24. Besides, as a maximum
value of the sheet thickness decrease becomes large,
j stretch flange cracks occur.
'I
.! [0039] In the conventional method, namely, in the
bend-forming using the normal pad 23, the pad 23
binds a whole or only a part of the part to be formed
into the groove bottom part 20a at the press-forming
material 24 as illustrated in Fig. 4A to Fig. 4C.
Namely, it is a shape in which a part to be formed
into the ridge line part 20b is not bound, and the
pressing angle is "0" (zero) degree.
[0040] In this case, as illustrated in Fig. 5A, a
maximum value if the sheet thickness decrease at the
end part of the ridge line part flange portion 209 is
a value of approximately 36% which far exceeds 30%,
and it can be seen that a possibility in which the
stretch flange cracks occur is high
[0041] On the other hand, in the invented method,
namely, in the bend-forming using the ridge line pad
25, as illustrated in Fig. 3A to Fig. 3D, the ridge
line pad 25 binds the part to be formed into the
ridge line part 20b in addition to the part to be
formed into the groove bottom part 20a in a vicinlty
of the outward flange 20f (a range w ~ t h i n 10 mm from
a root part of the outward flange 20f in a direction
where the ridge line part 20b extends)
Then, analyses are performed under conditions in
which a region where the ridge line pad 25 binds the
press-forming material 24 is changed into one-third,
two-thirds, and a whole of a cross-sectional
peripheral length of the ridge line part 20b starting
from a connecting part from among the part to be
formed into the ridge line part 20b.
[0042] In this case, as illustrated in Fig. 5A, it
can be seen that a maximum value of the sheet
thickness decrease at the ridge line part flange
portion 209 is suppressed as the region where the
ridge line pad 25 binds the press-forming material 24
(pressing angle) becomes large. In particular, a
suppression effect is remarkable when the binding
region is one-third or more, and it is possible to
avoid the stretch flange cracks.
[0043] [Analysis Example 21
Fig. 6A to Fig. 6C are explanatory views
illustrating a shape of a press-formed body 30 of an
analysis example 2. Fig. 6A is a perspective view of
the press-formed body 30, Fig. 6B is a VI arrow view
in Fig. 6A, and Fig. 6C is a transverse sectional
view of the press-formed body 30 (an outward flange
30f is not illustrated).
[0044] The press-formed body 30 of the analysis
example 2 is made of the high-strength steel sheet
(590 MPa class DP steel), and a sheet thickness
thereof is 1.4 mm.
The press-formed body 30 includes a groove bottom
part 30a, ridge line parts 30b, 30b continuous to the
groove bottom part 30a, side wall parts 30c, 30c
continuous to the ridge line parts 30b; 30b, curved
parts 30d, 30d continuous to the side wall parts 30c,
30c, and flanges 30e, 30e continuous to the curved
parts 30d, 30d. A curvature radius at a sheet inner
side of the ridge line parts 30b, 30b is 12 mm.
[0045] The outward flange 30f is formed at a whole
periphery of both end parts in a longitudinal
direction of the press-formed body 30, and a ridge
line part flange portion 309 becomes a curved portion.
A flange width of the outward flange 30f is 20 mm at
a part formed along the groove bottom part 30a, and
25 mm at a part formed along the side wall parts 30c,
30c.
[0046] A cross sectional wall angle of the pressformed
body 30 is 82 degrees, and a cross sectional
height is 60 mm. In the analysis example 2, the
press-formed body 30 is manufactured by the pressforming
by bend-forming using a developed blank.
[0047] Fig. 7A is a perspective view illustrating a
punch (lower forming-tool) 31, a die (upper formingtool)
32, a ridge line pad 35, and a press-forming
material 34 at a forming time according to the
invented method. Fig. 7B is a perspective view
illustrating the punch (lower forming-tool) 31, the
ridge line pad 35, and the press-forming material 34
at the formed time according to the invented method.
Fig. 7C is a perspecti.ve view enlargedly illustrating
a square surrounded part in Fig. 7B. Fig. 7D is a
VII-VII sectional view in Fig. 7C.
[0048] On the other hand, Fig. 8A is a perspective
view illustrating a punch (lower forming-tool) 31, a
die (upper forming-tool) 32 at a forming time
according to the conventional method. Fig. 8B is a
perspective view illustrating the punch (lower
forming-tool) 31, a pad 33, and a press-forming
material 34 at the forming time according to the
conventional method. Fig. 8C is a perspective view
enlargedly illustrating a square surrounded part in
Fig. 8B.
[a0491 Fig. 9A is a characteristic diagram
illustrating a numerical analysis result of a
relationship between a pressing angle of the pressforming
material 34 by the pads 33, 35 and a minimum
value of a sheet thickness decrease in a vicinity of
a root part of the ridge line part flange portion 30g
of the outward flange 30f formed at the press-formed
body 30. In Fig. 9B, evaluation positions of a sheet
thickness decrease (ranges each surrounded by a
dotted line, a wrinkling threat part) being
evaluation objects in the analysis example 2 are
illustrated. The pressing angle means a center angle
of a range of the ridge line part 30b bound by the
pads 33, 35 while setting a connecting part with the
groove bottom part 30a as "0" (zero) degree from
among a part to be formed into the ridge line part
30b at the press-forming material 34. Besides, as a
minimum value of the sheet thickness decrease becomes
small, a possibil~ty in which wrinkling occurs
becomes high.
[0050] In the conventional method, namely, in the
bend-formlng using the normal pad 33, the pad 33
,;
binds only a part to be formed into the groove bottom
part 30a at the press-forming material 34 as
illustrated in Fig. 8A to Fig. 8C. Namely, it is a
shape in which a part to be formed into the ridge
line part 30b is not bound, and the pressing angle is
"0" (zero) degree.
[00511 In this case, as illustrated in Fig. 9A, a
minimum value of the sheet thickness decrease at the
root part of the ridge line part flange portion 30g
is a value of approximately -65%, and it is obvious
that the winkling occurs at a proximity part 30b-1 of
the flange 30f at the ridge line part 30b.
[0052] On the other hand, in the invented method,
namely, in the bend-forming using the ridge line pad
35, as illustrated in Fig. 7A to Fig. 7D, the ridge
line pad 35 binds the part to be formed into the
ridge line part 30b in addition to the part to be
formed into the groove bottom part 30a in a vicinity
of the outward flange 30f (a range within 10 mm from
a root part of the outward flange 30f in a direction
where the ridge line part 30b extends)
Then, analyses are performed under conditions in
which a region where the ridge line pad 35 binds the
press-forming material 34 is changed into one-third,
I two-thirds, a whole of a cross-sectional peripheral
length of the ridge line part 30b starting from a
connecting part from among the part to be formed into
the ridge line part 30b.
100531 In this case, as illustrated in Fig. 9A, it
can be seen that thickening at the proximity part
30b-1 of the flange 30f at the ridge line part 30b is
suppressed as the region where the ridge line pad 35
binds the press-forming material 34 (pressing angle)
becomes large. In the analysis result, a thickening
amount is large because it is originally a shape
difficult to suppress the wrinkling. Therefore it is
desired to suppress a thickening rate to be less than
20% by setting the region bindlng the ridge line part
30b to be two-thirds or more, but even when the
region binding the ridge line part 30b is
approximately one-third or more, the thickening of a
part where the wrinkling occurrence is concerned is
suppressed to be a half or less compared to the
normal pad, and it can be seen that a thickening
suppression effect by the ridge line pad 35 is very
large.
[0054] [Analysis Example 31
In each of the analysis examples 1, 2, a coldrolled
steel sheet is described, but the present
invention is able to be applied for a hot-rolled
steel sheet.
Fig. 10A to Fig. 10C are explanatory vlews
- 31 -
illustrating a shape 'of a press-formed body 40 of an
analysis example 3. Fig. 10A is a perspective view
of the press-formed body 40, Fig. 10B is a X arrow
view in Fig. 10A, and Fig. 10C is a transverse
sectional view of the press-formed body 40 (an
outward flange 40f is not illustrated).
[0055] The press-formed body 20 of the analysis
example 3 is made of the high-strength steel sheet
(590 MPa class DP steel), and.a sheet thickness
thereof is 2.9 mm.
The press-formed body 40 includes a groove bottom
part 40a, ridge line parts 40b, 40b continuous to the
groove bottom part 40a, and side wall parts 40c, 40c
continuous to the ridge line parts 40b, 40b.
[0056] The outward flange 40f is formed at a whole
periphery of both end parts in a longitudinal
direction of the press-formed body 40, and a ridge
line part flange portion 40g becomes a curved portion.
[0057] A cross sectional wall angle of the pressformed
body 40 is 82 degrees, and a cross sectional
height is 50 mm. In the analysis example 3, the
press-formed body 20 is manufactured by the pressforming
by bend-forming using a developed blank.
[0058] Also in the analysis example 3, the
conventional method using the pad in which a part to
be formed into the groove bottom part 40a is bound,
but parts to be formed into the ridge line parts 40b,
40b are not bound and the invented method using a
ridge line pad in which not only the part to be
formed into the groove bottom part 40a but also the
parts to be formed into the ridge line parts 40b, 40b
I in the vicinity of the outward flange 40f are bound
1 are compared.
1 As illustrated in Fig. 11B, in the conventional
method, a maximum value of the sheet thickness
decrease at the evaluation positions of the sheet
thickness decrease (ranges each surrounded by a
dotted line, a crack threat part) is a value of
approximately 20%. On the other hand, in the
invented method, a maximum value of the sheet
thickness decrease at the evaluation positions of the
sheet thickness decrease (ranges each surrounded by a
dotted line, a crack threat part) is suppressed to a
value of approximately 14%.
[0059] As stated above, the present invention is
described with various embodiments, but the present
invention is not limited only to these embodiments,
and modifications and so on within a range of the
invention are possible
For example, in each of the analysis examples, a
case when the press-forming is the bend-forming is
6 , exemplified, but the present invention is not limited
!,
j j
!!
thereto, and the press-forming may be drawing.
[0060] Besides, a mode in which the lower formingtool
is made up by the punch and the upper formingtool
is made up by the die and the pad is exemplified,
but the present invention is not llmited to the mode.
It goes without saylng that a structure in which the
upper and lower metal forming-tools are reversed,
namely, the upper forming-tool 1s made up by the
punch and the lower forming-tool is made up by the
die and the pad is acceptable.
INDUSTRIAL APPLICABILITY
[0061] The present invention can be used for
manufacturing a press-formed body made of a hightensile
strength steel sheet of 390 MPa or more
having approximately a groove-shaped cross section
including a groove bottom part, ridge line parLs
continuous to the groove bottom part, and side wall
parts continuous to the ridge line parts, and in
which an outward flange is formed at a range across
the ridge part, at least a portion of each of the
groove bottom part and the side wall part at both
sides thereof, from among an end part in a
longitudinal direction, without being limited to a
floor cross member.

WE CLAIM:-
[Clam 1] A manufacturing method of a press-formed
body made of a high-tensile strength steel sheet of
390 MPa or more having approximately a groove-shaped
cross section including a groove bottom part, ridge
line parts continuous to the groove bottom part, and
side wall parts continuous to the ridge line parts,
and in which an outward flange is formed at a range
across the ridge line part, at least a portion of
each of the groove bottom part and the side wall part
at both sides thereof, from among an end part in a
longitudinal direction by performing a press-forming
of a press-forming material by a press-forming
apparatus which includes a punch, a die, and a pad
pressing and binding the press-forming material to
the punch, the manufacturing method comprising:
a first step of performing the press-forming
while the pad binds a part to be formed into the
groove bottom part and at least a portion of a part
to be formed into the ridge line part at the pressforming
material; and
a second step of performing the press-forming of
parts which are not able to be formed by the first
step.
[Claim 2] The manufacturing method of the pressformed
body according to claim 1,
wherein the pad binds a part having a length of
one-third or more of a cross-sectional peripheral
length of the ridge line part starting from a
connecting part with the groove bottom part.
[Claim 3] The manufacturing method of the pressformed
body according to claim 1 or claim 2,
wherein the pad binds the part t o b e formed into
the ridge line part within a predetermined range from
a root part of the outward flange in a direction
where the ridge line part extends in a longitudinal
direction of the part to be formed into the ridge
line part.
[Claim 4] The manufacturing method of the pressformed
body according to any one of claims 1 to 3,
wherein the press-formed body ha's approximately
the groove-shaped cross section further including
curved parts continuous to the side wall parts, and
flanges continuous to the curved parts.
[Claim 5] The manufacturing method of the pressformed
body according to any one of claims 1 to 4,
wherein the press-forming is bend-forming.
[Claim 6] The manufacturing method of the pressformed
body according to any one of claims 1 to 4,
wherein the press-forming is drawing.
[Claim 7] A manufacturing apparatus of a pressformed
body, which manufactures the press-formed body
made of a high-tensile strength steel sheet of 390
MPa or more having approximately a groove-shaped
cross section including a groove bottom part, ridge
line parts continuous to the groove bottom part, and
side wall parts continuous to the ridge line parts,
and in which an outward flange is formed at a range
across the ridge line part, at least a portion of
each of the groove bottom part and the side wall part
at both sides thereof, from among an end part in a
longitudinal direction, the manufacturing apparatus
comprising:
a punch;
a die; and
a pad which presses and binds a press-forming
material to the punch,
wherein the pad has a shape binding a part to be
formed into the groove bottom part and at least a
portion of a part to be formed into the ridge line
part at the press-forming material.
[Claim 8] The manufacturing apparatus of the pressformed
body according to claim 7,
wherein the pad has a shape binding a part having
a length of one-third or more of a cross-sectional
peripheral length of the ridge line part starting
from a connecting part with the groove bottom part.
[Claim 9] The manufacturing apparatus of the pressformed
body according to claim 7 or claim 8,
wherein the pad binds the part to be formed into
the ridge line part within a predetermined range from
a root part of the outward flange in a direction
where the ridge line part extends in a longitudinal
direction of the part to be formed into the ridge
line part.
[Claim 10] The manufacturing apparatus of the pressformed
body according to any one of claims 7 to 9,
wherein the press-formed body has approximately
the groove-shaped cross section further including
curved parts continuous to the side wall parts, aAd
flanges continuous to the curved parts.
[Claim 11] The manufacturing apparatus of the pressformed
body according to any one of claims 7 to 10,
wherein the press-forming is bend-forming.
[Claim 12] The manufacturing apparatus of the pressformed
body according to any one of claims 7 to 10,
wherein the press-forming is drawing.