U.S. patent application number 16/155222 was filed with the patent office on 2019-04-11 for press-molded product, press-molded product producing method, and press-molded product producing apparatus.
This patent application is currently assigned to NIPPON STEEL & SUMITOMO METAL CORPORATION. The applicant listed for this patent is NIPPON STEEL & SUMITOMO METAL CORPORATION. Invention is credited to Yasuhiro ITO, Yoshiaki NAKAZAWA.
Application Number | 20190105697 16/155222 |
Document ID | / |
Family ID | 52688664 |
Filed Date | 2019-04-11 |
View All Diagrams
United States Patent
Application |
20190105697 |
Kind Code |
A1 |
NAKAZAWA; Yoshiaki ; et
al. |
April 11, 2019 |
PRESS-MOLDED PRODUCT, PRESS-MOLDED PRODUCT PRODUCING METHOD, AND
PRESS-MOLDED PRODUCT PRODUCING APPARATUS
Abstract
The objective is to provide a press-molded product including an
inward continuous flange and capable of improving performance
involved with the bonding strength between a reinforcing member and
the other member or the rigidity of a vehicle body without forming
a notch in a ridge-portion flange so as to prevent a defect
generated during a press-molding process. Provided is a
press-molded product of a metal plate which is formed by a steel
plate having a tensile strength of 340 MPa or more and includes a
ridge portion extending in a predetermined direction and first and
second surface portions respectively extending from both ends of a
ridge line formed by the ridge portion, the press-molded product
including: an inward continuous flange which is obtained by
continuously forming a ridge-portion flange formed inward in an end
portion of the ridge portion, a first flange formed inward in at
least a part of an area of an end portion of the first surface
portion, and a second flange formed inward in at least a part of an
area of an end portion of the second surface portion. Regarding a
plate thickness of an edge portion of the ridge-portion flange, the
ridge-portion flange has a plate thickness distribution in which a
plate thickness of a portion of each of areas on both sides of a
circumferential center area is equal to or larger than a plate
thickness of the center area.
Inventors: |
NAKAZAWA; Yoshiaki; (Tokyo,
JP) ; ITO; Yasuhiro; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NIPPON STEEL & SUMITOMO METAL CORPORATION |
Tokyo |
|
JP |
|
|
Assignee: |
NIPPON STEEL & SUMITOMO METAL
CORPORATION
Tokyo
JP
|
Family ID: |
52688664 |
Appl. No.: |
16/155222 |
Filed: |
October 9, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14911587 |
Feb 11, 2016 |
10124387 |
|
|
PCT/JP2014/072281 |
Aug 26, 2014 |
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16155222 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B21D 22/26 20130101;
B21D 22/02 20130101; B21D 22/20 20130101; B21D 53/88 20130101 |
International
Class: |
B21D 22/02 20060101
B21D022/02; B21D 53/88 20060101 B21D053/88; B21D 22/20 20060101
B21D022/20; B21D 22/26 20060101 B21D022/26 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 20, 2013 |
JP |
2013-195951 |
Claims
1. A press-molded product producing method for a work which is
formed by a steel plate having a tensile strength of 340 MPa or
more and includes a ridge portion extending in a predetermined
direction and first and second surface portions respectively
extending from both ends of a ridge line formed by the ridge
portion, a flange being formed in at least one end portion of the
work in the predetermined direction, the press-molded product
producing method comprising: an installation step of supporting an
area excluding the end portion of the work from an inner area of
the work; and a bending step of, using a bending tool having a
protrusion portion, bringing the protrusion portion into contact
with a predetermined position of the ridge portion in the end
portion of the work from an outer area of the work and then
relatively moving the bending tool in a plate thickness direction
of the predetermined position in a direction toward the inner area
so as to form the flange.
2. The press-molded product producing method according to claim 1,
wherein in the bending step, the flange is formed in a manner that
the protrusion portion of the bending tool presses the
predetermined position of the ridge portion in the end portion in
accordance with the movement of the bending tool so as to bend the
predetermined position in a plate thickness direction and then a
portion other than the protrusion portion of the bending tool
sequentially presses another portion excluding the predetermined
position in the end portion so as to bend the other portion in a
plate thickness direction.
3. The press-molded product producing method according to claim 1,
wherein the predetermined position is an area substantially having
a width of a plate thickness and including a circumferential center
portion and both sides of the circumferential center portion of the
ridge portion, and wherein the protrusion portion presses the
predetermined position in a plate thickness direction of the center
portion.
4. A press-molded product producing apparatus comprising: a work
supporting tool which supports a work including a ridge portion
extending in a predetermined direction and first and second surface
portions respectively extending from both ends of a ridge line
formed by the ridge portion from an inner area of the work; and a
bending tool which relatively moves in a direction toward the inner
area of the work while contacting an end portion of the work in the
predetermined direction so as to bend the end portion in a
direction toward the inner area, wherein the bending tool includes
a protrusion portion which contacts a predetermined position in the
end portion of the ridge portion and presses the predetermined
position in a plate thickness direction of the predetermined
position in accordance with the movement.
5. The press-molded product producing apparatus according to claim
4, wherein when the bending tool is viewed in the predetermined
direction, a width of the protrusion portion decreases in a
direction toward a front end portion and the front end portion
forms a curve.
6. The press-molded product producing apparatus according to claim
4, wherein a height (h) of the protrusion portion and a curvature
radius (rf) of a curvature of the ridge portion satisfy Equation
(2) below: 0.5.times.rf.ltoreq.h.ltoreq.3.0.times.rf (2).
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Divisional of co-pending patent
application Ser. No. 14/911,587 filed Feb. 11, 2016, which is the
National Phase under 35 U.S.C. .sctn. 371 of International
Application No. PCT/JP2014/072281 filed Aug. 26, 2014, which claims
the benefit under 35 U.S.C. .sctn. 119(a) to Patent Application No.
2013-195951 filed in Japan on Sep. 20, 2013, all of which are
hereby expressly incorporated by reference into the present
application.
TECHNICAL FIELD
[0002] The present invention relates to a press-molded product
having excellent rigidity and strength and appropriately used as,
for example, a vehicle body reinforcing member and also relates to
a press-molded product producing method and a press-molded product
producing apparatus used to produce the press-molded product.
BACKGROUND ART
[0003] A vehicle body has a structure in which a plurality of
molding panels is bonded into a box shape by, for example,
resistance spot-welding while edge portions of the molding panels
overlap one another. A reinforcing member or a strengthening member
(hereinafter, generally referred to as a "reinforcing member") is
bonded to the box-shaped structure by, for example, resistance
spot-welding. As such vehicle body reinforcing members, there are a
bumper reinforcement, a locker (side sill), a beltline, a cross
member, and a side member.
[0004] Each of these reinforcing members is formed as, for example,
a press-molded member that has a substantially hat-shaped or
groove-shaped cross-section and includes a ceiling plate, two ridge
lines connected to the ceiling plate, and two flanges connected to
two ridge lines. An end portion opened in the extension direction
of the ridge line of such a reinforcing member is bent inward or
outward so as to form a flange in the end portion. When the flange
overlaps the other member and the flange and the other member are
bonded to each other by, for example, resistance spot-welding, a
vehicle body reinforcing member is assembled. Depending on the
plate thickness of the material, arc-welding may be used instead of
spot-welding.
[0005] Here, in the specification, an area in which an angle formed
by two surfaces respectively connected to both ends of the ridge
line is smaller than 180.degree. will be referred to as an inner
area, and a flange obtained by bending the end portion of the
reinforcing member toward the inner area will be referred to as an
inward flange. Further, an area in which an angle formed by two
surfaces respectively connected to both ends of the ridge line is
larger than 180.degree. will be referred to as an outer area, and a
flange obtained by bending the end portion of the reinforcing
member toward the outer area will be referred to as an outward
flange.
[0006] When the inward flange is formed in the end portion of the
reinforcing member, a ridge-portion flange located on the extension
line of the ridge line is molded as a flange by shrinking, and
hence wrinkles are generated in the ridge-portion flange. For that
reason, when such an inward flange overlaps the other member and
the inward flange and the other member are bonded to each other by
spot-welding, a gap is generated between the inward flange and the
other member due to the wrinkles, and hence there is a concern that
an assembling problem may occur. Thus, when the reinforcing member
having the inward flange formed at the end portion is used, there
is a need to weld the reinforcing member to the other member by
using the inward flange as a bonding edge while avoiding the
generation of wrinkles by, for example, forming a notch in the
ridge-portion flange.
[0007] However, when the notch is formed in the inward
ridge-portion flange so that the flange is not continuous, the
performance of the vehicle body reinforcing member involved with
torsional rigidity or load transfer efficiency is essentially
degraded. Thus, in order to ensure the performance demanded for the
reinforcing member by bonding the reinforcing member to the other
member through the inward flange, there is a need to mold the
shrinking flange while suppressing the generation of wrinkles in
the ridge-portion flange without any notch formed in the inward
flange.
[0008] In addition, in the specification, the "notch formed in the
flange" indicates a state where the notch is formed in the entire
flange in the width direction so that the flange is not continuous.
Further, the width of the flange is used as the meaning of the
height of the flange. Thus, when the width of the flange is
partially decreased so that a part of the flange is left, the notch
is not formed in the flange.
[0009] So far, a technique of suppressing the generation of
wrinkles during the shrinking flange molding process has been
proposed. For example, Patent Literature 1 discloses a technique of
forming an unevenness shape, absorbing a difference in length
between a front end portion and a base portion in a shrinking
flange portion, in a roof panel having a sunroof opening. Further,
Patent Literature 2 discloses a technique of preventing the
generation of wrinkles by providing a specific drawing bead in a
shrinking flange portion during a rectangular tube drawing process.
Furthermore, Patent Literature 3 discloses a technique of
suppressing the generation of wrinkles by performing a molding
process while applying a pressure to a shrinking flange portion
using a cam structure.
[0010] Further, Patent Literature 4 discloses a plate member
molding method in which a flange corresponding portion extending in
a direction interesting a bending load direction is formed in a
portion to be used as a bent portion and the flange corresponding
portion is stretched into a flange so as to have a desired shape.
Such a plate member molding method is used to suppress tearing
caused by the wrinkles in the flange.
[0011] Patent Literature 5 discloses a method in which a plane
metal member is bent, upright portions of both side portions are
bent outward, and both inclined side portions are strongly pressed
by a processing roller of a pressing surface of a side surface of a
receiving die so as to be sequentially raised. Such a processing
method is used to reduce the distortion or the wrinkles of the
upright portion.
PRIOR ART LITERATURE(S)
Patent Literature(s)
[0012] [Patent Literature 1] JP 2554768B [0013] [Patent Literature
2] JP 2560416B [0014] [Patent Literature 3] JP H4-118118A [0015]
[Patent Literature 4] JP S59-144530A [0016] [Patent Literature 5]
JP H1-104420A
SUMMARY OF THE INVENTION
Problem(s) to be Solved by the Invention
[0017] The techniques disclosed in Patent Literatures 1 and 2 are
used to absorb the extra line length causing the generation of
wrinkles and excessive padding by an excessive portion formed in
advance. Thus, the spot-welding is not easily performed on the
excessive portion and the excessive portion disturbs the
spot-welding of the other portion. In such a case, it is difficult
to perform the techniques disclosed in Patent Literatures 1 and
2.
[0018] Further, the technique disclosed in Patent Literature 3 can
suppress the generation of wrinkles of the flange portion of the
large-curvature-radius portion having, for example, a curvature
radius of 2100 mm and having a feature that the shrinkage rate of
the flange portion and the reaction force for the cam structure are
small. However, it is difficult to suppress the generation of
wrinkles of the flange portion of the small-curvature-radius
portion having, for example, a curvature radius of 5 mm and having
a feature that the shrinkage rate of the flange portion and the
reaction force for the cam structure are large. Particularly, when
a high-tensile steel plate having a large tensile strength is used,
excessive wrinkles are generated, and hence the reaction force from
the flange portion increases. For that reason, the cam structure
disclosed in Patent Literature 3 cannot suppress the generation of
wrinkles.
[0019] Further, the technique disclosed in Patent Literature 4 is
used to suppress the generation of wrinkles by the stretching
process. Thus, the plate thickness of the obtained flange is
decreased. As a result, there is a concern that the rigidity of the
reinforcing member or the strength of the flange portion may be
degraded.
[0020] Further, the technique disclosed in Patent Literature 5 is
used to form the upright portion by sequentially strongly pressing
a plurality of processing rollers. Here, a product in which the
curvature radius of the bent portion of the plane metal member is
comparatively large is considered as a target. Thus, it is
difficult to suppress the generation of wrinkles of, for example,
the flange portion of the small-curvature-radius portion having a
curvature radius of 5 mm.
[0021] In this way, in the member having a substantially hat-shaped
or groove-shaped cross-section, it is difficult to form the inward
flange without forming the notch in the end portion opened in the
extension direction of the ridge portion from the viewpoint of
press-moldability. Particularly, Patent Literatures 1 to 5 above
are not contrived in consideration of the formation of the flange
in the high-tensile steel plate having a tensile strength of 340
MPa or more. For that reason, there is no example in which a
press-molded product formed by a high-tensile steel plate and
including a continuous, inward flange without a notch in a
ridge-portion flange is used as the vehicle body reinforcing member
so far.
[0022] In a press-molded product having an outward flange, a
hat-shaped or groove-shaped cross-section cannot be enlarged to the
fullest extent of the design cross-section by the area of the
outward flange. In other words, when the press-molded product can
be bonded to the other member through the inward flange instead of
the outward flange, the cross-section of the press-molded product
can be enlarged to the fullest extent of the design cross-section
by the area in which the outward flange is not provided. For that
reason, it is possible to improve the bonding strength between the
vehicle body reinforcing member and the other member or the bending
rigidity or the torsional rigidity of the vehicle body. Thus, there
is a desire to realize a press-molded product formed by a
high-tensile steel plate and including an inward continuous
flange.
[0023] An object of the invention is to provide a press-molded
product including an inward continuous flange without a notch and
capable of improving performance involved with the bonding strength
between a reinforcing member and the other member or the rigidity
of a vehicle body without forming a notch in a ridge-portion flange
so as to prevent a defect generated during a press-molding process.
Further, another object of the invention is to provide a
press-molded product producing method and a press-molded product
producing apparatus.
Means for Solving the Problem(s)
[0024] In order to solve the above problems, according to an aspect
of the present invention, there is provided a press-molded product
of a metal plate which is formed by a steel plate having a tensile
strength of 340 MPa or more and includes a ridge portion extending
in a predetermined direction and first and second surface portions
respectively extending from both ends of a ridge line formed by the
ridge portion, the press-molded product including: an inward
continuous flange in at least one end portion in the predetermined
direction. The inward continuous flange is obtained by continuously
forming a ridge-portion flange formed inward in an end portion of
the ridge portion, a first flange formed inward in at least a part
of an area of an end portion of the first surface portion, and a
second flange formed inward in at least a part of an area of an end
portion of the second surface portion. Regarding a plate thickness
of an edge portion of the ridge-portion flange, the ridge-portion
flange has a plate thickness distribution in which a plate
thickness of a portion of each of areas on both sides of a
circumferential center area is equal to or larger than a plate
thickness of the center area.
[0025] The ridge-portion flange may have a maximal plate thickness
at three positions of the center area and the areas on the both
sides, and the plate thickness of the positions of the areas on the
both sides having a maximal plate thickness may be larger than the
plate thickness of the position of the center area having a maximal
plate thickness.
[0026] A flange width of at least a part of the ridge-portion
flange may be smaller than a flange width of each of the first
flange and the second flange.
[0027] A flange width (Lf) of the ridge-portion flange and a
curvature radius (rf) of the ridge portion may satisfy Equation (1)
below:
0.2.times.rf.ltoreq.Lf.ltoreq.rf (1).
[0028] A cross-section of the press-molded product when viewed in
the predetermined direction may be a substantially hat-shaped or
groove-shaped opened cross-section or a closed cross-section.
[0029] The press-molded product may be a vehicle body reinforcing
member.
[0030] In order to solve the above problems, according to another
aspect of the present invention, there is provided a press-molded
product producing method for a work which is formed by a steel
plate having a tensile strength of 340 MPa or more and includes a
ridge portion extending in a predetermined direction and first and
second surface portions respectively extending from both ends of a
ridge line formed by the ridge portion, a flange being formed in at
least one end portion of the work in the predetermined direction,
the press-molded product producing method including: an
installation step of supporting an area excluding the end portion
of the work from an inner area of the work; and a bending step of,
using a bending tool having a protrusion portion, bringing the
protrusion portion into contact with a predetermined position of
the ridge portion in the end portion of the work from an outer area
of the work and then relatively moving the bending tool in a plate
thickness direction of the predetermined position in a direction
toward the inner area so as to form the flange.
[0031] In the bending step, the flange may be formed in a manner
that the protrusion portion of the bending tool presses the
predetermined position of the ridge portion in the end portion in
accordance with the movement of the bending tool so as to bend the
predetermined position in a plate thickness direction and then a
portion other than the protrusion portion of the bending tool
sequentially presses an other portion excluding the predetermined
position in the end portion so as to bend the other portion in a
plate thickness direction.
[0032] The predetermined position may be an area substantially
having a width of a plate thickness and including a circumferential
center portion and both sides of the circumferential center portion
of the ridge portion. The protrusion portion may press the
predetermined position in a plate thickness direction of the center
portion.
[0033] In order to solve the above problems, according to still
another aspect of the present invention, there is provided a
press-molded product producing apparatus including: a work
supporting tool which supports a work including a ridge portion
extending in a predetermined direction and first and second surface
portions respectively extending from both ends of a ridge line
formed by the ridge portion from an inner area of the work; and a
bending tool which relatively moves in a direction toward the inner
area of the work while contacting an end portion of the work in the
predetermined direction so as to bend the end portion in a
direction toward the inner area. The bending tool includes a
protrusion portion which contacts a predetermined position in the
end portion of the ridge portion and presses the predetermined
position in a plate thickness direction of the predetermined
position in accordance with the movement.
[0034] When the bending tool is viewed in the predetermined
direction, a width of the protrusion portion may decrease in a
direction toward a front end portion and the front end portion may
form a curve.
[0035] A height (h) of the protrusion portion and a curvature
radius (rf) of the ridge portion may satisfy Equation (2)
below:
0.5.times.rf.ltoreq.h.ltoreq.3.0.times.rf (2).
Effect(s) of the Invention
[0036] According to the invention, it is possible to suppress the
generation of wrinkles in an inward continuous flange without
forming a notch in a ridge-portion flange in order to prevent a
defect generated during a press-molding process in a press-molded
product formed by a high-tensile steel plate. Thus, when the
press-molded product is used as a vehicle body reinforcing member,
it is possible to improve performance involved with the bonding
strength between the reinforcing member and the other member or the
rigidity of a vehicle body.
BRIEF DESCRIPTION OF THE DRAWING(S)
[0037] FIG. 1 is a perspective view schematically illustrating a
press-molded product having a hat-shaped cross-section according to
a first embodiment of the invention.
[0038] FIG. 2A is an explanatory diagram schematically illustrating
a shape of an inward continuous flange and FIG. 2B is an
explanatory diagram illustrating a ridge-portion flange when viewed
from the front side.
[0039] FIGS. 3A-3D are an explanatory diagram illustrating examples
of cross-section shapes of press-molded products according to the
same embodiment.
[0040] FIG. 4 is a graph illustrating an example of a plate
thickness distribution of a ridge-portion flange.
[0041] FIG. 5 is a schematic diagram schematically illustrating an
entire configuration example of a press-molded product producing
apparatus for a bending process.
[0042] FIG. 6 is an explanatory diagram schematically illustrating
an example of a drawing device.
[0043] FIG. 7 is an explanatory diagram schematically illustrating
an example of a bending device.
[0044] FIG. 8A is a diagram illustrating a state where a work is
attached to a work supporting tool, FIG. 8B is a diagram
illustrating a state where a bending process starts, FIG. 8C
illustrates a state where the bending process is being performed,
and FIG. 8D is a diagram illustrating a state where the bending
process ends.
[0045] FIG. 9 is an explanatory diagram illustrating a state where
a protrusion portion provided in a surface of a bending tool
contacts an end portion of a ridge portion.
[0046] FIG. 10A is a perspective view illustrating an end portion
of a work to be bent, FIG. 10B is a perspective view illustrating
the end portion of the work of which a ridge portion is being bent,
and FIG. 10C is a perspective view illustrating the end portion of
the work when the bending process ends.
[0047] FIG. 11A is a diagram schematically illustrating a shape of
a bending tool with a protrusion portion and FIG. 11B is an
explanatory diagram illustrating a flange deformation state in the
vicinity of a ridge-portion flange.
[0048] FIG. 12A is a diagram schematically illustrating a shape of
a straight bending tool without a protrusion portion and FIG. 12B
is an explanatory diagram illustrating a flange deformation state
in the vicinity of a ridge-portion flange.
[0049] FIG. 13 is a graph illustrating a plate thickness increase
rate of a ridge-portion flange in accordance with a bending
process.
[0050] FIG. 14A and FIG. 14B are external views illustrating a
shape of a press-molded product having an inward continuous
flange.
[0051] FIG. 15 is a graph illustrating a plate thickness
distribution of a ridge-portion flange.
MODE(S) FOR CARRYING OUT THE INVENTION
[0052] Hereinafter, referring to the appended drawings, preferred
embodiments of the present invention will be described in detail.
It should be noted that, in this specification and the appended
drawings, structural elements that have substantially the same
function and structure are denoted with the same reference
numerals, and repeated explanation thereof is omitted.
1. First Embodiment
[0053] First, a press-molded product according to a first
embodiment of the invention will be described.
[0054] (1-1. Entire Configuration)
[0055] FIG. 1 is a perspective view schematically illustrating a
press-molded product 100 according to the embodiment. FIG. 2A is an
explanatory diagram schematically illustrating a shape of an inward
continuous flange 118 of the press-molded product 100. FIG. 2B is a
view (a front view of a ridge-portion flange 115a) when viewed from
A in FIG. 1 and is an enlarged view of an area surrounded by the
dashed line in FIG. 2A.
[0056] The press-molded product 100 according to the embodiment is
a press-molded product of a metal plate which is formed by a
high-tensile steel plate having a tensile strength of 340 MPa or
more and includes ridge portions 112a and 112b which extend in a
predetermined direction and first surface portions 113a and 113b
and a second surface portion 114 which respectively extend from
both ends of the ridge lines formed by the ridge portions 112a and
112b.
[0057] Such a press-molded product 100 includes, in at least one
end portion in a predetermined direction, the inward continuous
flange 118 obtained by continuously forming ridge-portion flanges
115a and 115b which are formed in the end portions of the ridge
portions 112a and 112b so as to be directed inward, first flanges
116a and 116b which are formed in at least a part of the area of
the end portions of the first surface portions 113a and 113b so as
to be directed inward, and a second flange 117 which is formed in
at least a part of the area of the end portion of the second
surface portion 114 so as to be directed inward.
[0058] Regarding the plate thickness of the edge portions of the
ridge-portion flanges 115a and 115b of the press-molded product
100, the ridge-portion flanges 115a and 115b have a plate thickness
distribution in which portions of areas on both sides of the center
area in the circumferential direction have plate thicknesses equal
to or larger than the plate thickness of the center area. For
example, as illustrated in FIG. 2B, the center area of the edge
portion of the ridge-portion flange 115a in the circumferential
direction is defined as an area X including a center portion Rc as
the intermediate point of positions R1 and R2 in which the plate
thickness starts to increase from both ends of the edge portion of
the ridge-portion flange 115a in the circumferential direction.
Such a center area X can be set as a center area X when the area
from the position R1 to the position R2 in the edge portion of the
ridge-portion flange 115a is divided into three parts in the
circumferential direction.
[0059] The press-molded product according to the embodiment is a
molded product obtained by press-molding a steel plate. Such a
press-molded product is suitable for, for example, a vehicle body
reinforcing member such as a bumper reinforcement, a locker (side
sill), a beltline, and a cross member. The press-molded product
used for such an application may be obtained by press-molding a
high-tensile steel plate having a tensile strength of 340 MPa or
more and desirably 590 MPa or more. The tensile strength is a value
measured by the tensile test based on JIS Z 2241. Further, the
plate thickness of the blank formed by the steel plate may be, for
example, in the range of 0.8 to 2.0 mm.
[0060] In the embodiment, the longitudinal direction of the
press-molded product 100 or the blank corresponds to the extension
direction of the ridge portions 112a and 112b of the press-molded
product 100, but the extension direction of the ridge portions 112a
and 112b is not limited to the longitudinal direction of the
press-molded product 100. Further, in the embodiment, a
predetermined direction in which the ridge portions 112a and 112b
extend is not limited to a direction which is recognized as a
straight line. A direction which is recognized as a curved shape
(curve) other than the straight line found in many vehicle body
reinforcing members is also included in the predetermined
direction. When the predetermined direction is recognized as a
curve, the predetermined direction includes, for example, a
direction which is curved in the left and right direction or the up
and down direction of the reinforcing member or a direction
obtained by the combination of these directions. Further, the
entire length in the predetermined direction includes, for example,
all kinds of length from the length of about 1000 mm of a bumper or
a side member to the length of about 100 mm of a cubic
bulkhead.
[0061] FIGS. 3A-3D are an explanatory diagram illustrating an
example of a cross-section shape of the press-molded product 100 in
a cross-section orthogonal to the longitudinal direction of the
press-molded product 100. The cross-section shape of the
press-molded product 100 according to the embodiment can be set to
a hat-shaped cross-section illustrated in FIG. 3A or a
groove-shaped cross-section illustrated in FIG. 3B, but the
invention is not limited thereto. As illustrated in FIG. 3C or FIG.
3D, the cross-section shape of the press-molded product 100
includes a cross-section shape in which a convex shape 100b or a
concave shape (not illustrated) is provided in a wall surface 100a
in a hat-shaped or groove-shaped cross-section.
[0062] Further, the cross-section shape of the press-molded product
100 also includes, for example, a substantially rectangle-shaped
closed cross-section shape other than the opened cross-section
shapes illustrated in FIGS. 3A-3D. In addition, the press-molded
product 100 is not limited to these cross-section shapes. For
example, a press-molded product having a cross-section shape
including a ridge portion and a first surface portion and a second
surface portion respectively extending from both ends of the ridge
line formed by the ridge portion and called a V-shaped
cross-section may be used. The press-molded product 100 illustrated
in FIG. 1 is the press-molded product 100 having a hat-shaped
cross-section. Hereinafter, the press-molded product 100 having a
hat-shaped cross-section will be described as an example.
[0063] As illustrated in FIG. 1, the press-molded product 100
includes the ridge portions 112a and 112b, the first surface
portions 113a and 113b, and the second surface portion 114. Both
ridge portions 112a and 112b are formed so as to extend in the
longitudinal direction of the press-molded product 100. One first
surface portion 113a is connected to the ridge portion 112a and is
formed so as to extend in the first direction intersecting the
longitudinal direction of the press-molded product 100. The other
first surface portion 113b is connected to the ridge portion 112b
and is formed so as to extend in the first direction intersecting
the longitudinal direction of the press-molded product 100. The
first direction as the extension direction of one first surface
portion 113a and the first direction as the extension direction of
the other first surface portion 113b may be different from each
other.
[0064] The second surface portion 114 is connected to the ridge
portions 112a and 112b and is formed so as to intersect the
longitudinal direction of the press-molded product 100 and to
extend in a second direction different from the first direction.
The second surface portion 114 is formed between the ridge portions
112a and 112b. In this way, the press-molded product 100 has a
substantially hat-shaped opened cross-section including the ridge
portions 112a and 112b which extend in the longitudinal direction
of the press-molded product 100 and including the first surface
portions 113a and 113b and the second surface portion 114 which are
continuous to the ridge portions 112a and 112b.
[0065] (1-2. Inward Continuous Flange)
[0066] The press-molded product 100 includes the ridge-portion
flanges 115a and 115b, the first flanges 116a and 116b, and the
second flange 117 provided in at least one outer end portion 100A
in the longitudinal direction. The ridge-portion flanges 115a and
115b are formed at the outer end portion 100A in the longitudinal
direction of the ridge portions 112a and 112b. The first flanges
116a and 116b are formed in at least a part of the area of the
outer end portion 100A in the longitudinal direction of the first
surface portions 113a and 113b. Further, the second flange 117 is
formed in at least a part of the area of the outer end portion 100A
in the longitudinal direction of the second surface portion 114. In
the embodiment, the first flanges 116a and 116b and the second
flange 117 are formed in the entire area of the outer end portion
100A of each of the first surface portions 113a and 113b and the
second surface portion 114.
[0067] The ridge-portion flanges 115a and 115b, the first flanges
116a and 116b, and the second flange 117 are all formed
continuously as the inward flange. The ridge-portion flanges 115a
and 115b, the first flanges 116a and 116b, and the second flange
117 constitute the inward continuous flange 118. Since the flange
provided in the end portion of the press-molded product 100 is
formed as the inward continuous flange 118, for example, the
cross-section of the vehicle body reinforcing member can be
enlarged to the fullest extent of the design cross-section. Thus,
it is possible to further improve the bonding strength between the
reinforcing member and the other member or the rigidity of the
vehicle body.
[0068] The press-molded product 100 according to the embodiment
includes the inward continuous flange 118 provided in the
longitudinal outer end portion 100A so as to be continuous in the
entire length of the first surface portions 113a and 113b, the
ridge portions 112a and 112b, and the second surface portion 114.
Here, the first flanges 116a and 116b and the second flange 117 may
be continuous to the ridge-portion flanges 115a and 115b and the
inward continuous flange 118 is not necessarily continuous in the
entire length. For example, the first flanges 116a and 116b or the
second flange 117 may be formed in a part of the area of the outer
end portion 100A of the first surface portions 113a and 113b or the
second surface portion 114. When the second flange 117 is not
formed in the entire area of the second surface portion 114, two
divided inward continuous flanges 118 are formed.
[0069] When the press-molded product 100 is used as the vehicle
body reinforcing member, the press-molded product 100 and the other
member can overlap each other with the inward continuous flange 118
interposed therebetween. Then, the press-molded product 100 and the
other member are bonded to each other by, for example, spot-welding
the inward continuous flange 118.
[0070] In addition, when a spot-welding process is performed on the
press-molded product 100, for example, the welding process may be
performed as below. First, the press-molded product 100 is made to
abut on the side surface of the other member and then the inward
continuous flange 118 is welded by a C-type spot-welding gun.
Subsequently, a closing plate is welded while abutting on the
flanges provided in the end portions of the first surface portions
113a and 113b of the press-molded product 100 in a direction
intersecting the extension direction of the ridge portions 112a and
112b. Accordingly, the opening portion of the hat-shaped
press-molded product 100 is closed and the press-molded product 100
is assembled. The same applies to the welding of the closing plate
in the other member. When the press-molded product 100 cannot be
fixed by the spot-welding gun, the other welding means such as
one-way welding, TIG welding, laser welding, and adhering may be
used.
[0071] (1-3. Ridge-Portion Flange)
[0072] In the press-molded product 100 according to the embodiment,
it is desirable that the width Lf and the curvature radius rf of
each of the ridge-portion flanges 115a and 115b satisfy Equation
(1) as below.
0.2.times.rf.ltoreq.Lf.ltoreq.rf (1)
[0073] When the width Lf of each of the ridge-portion flanges 115a
and 115b is equal to or smaller than the curvature radius rf, the
moldability of the inward continuous flange 118 becomes
satisfactory while the generation of wrinkles is suppressed.
Further, when the width Lf of each of the ridge-portion flanges
115a and 115b is equal to or larger than 0.2 times the curvature
radius rf, it is possible to ensure the rigidity of the
ridge-portion flanges 115a and 115b and to ensure the strength of
the press-molded product 100 suitable for the vehicle body
reinforcing member.
[0074] When the width Lf and the curvature radius rf of each of the
ridge-portion flanges 115a and 115b satisfy Equation (1) above, the
flange width of each of the ridge-portion flanges 115a and 115b may
be set to be small so that the ridge-portion flanges do not reach
the inner surfaces of the ridge portions 112a and 112b. That is,
the width Lf of each of the ridge-portion flanges 115a and 115b may
be smaller than the widths Lfs1 and Lfs2 of each of the first
flanges 116a and 116b or the second flange 117. Particularly, when
a work formed by a high-tensile steel plate or a steel plate having
a large plate thickness is used, it is desirable to decrease the
flange width Lf of each of the ridge-portion flanges 115a and
115b.
[0075] In the press-molded product 100 according to the embodiment,
a concave portion 119 is provided in each of the ridge-portion
flanges 115a and 115b. Accordingly, the width Lf of each of the
ridge-portion flanges 115a and 115b is smaller than the widths Lfs1
and Lfs2 of each of the first flanges 116a and 116b and the second
flange 117 in an area corresponding to the vertex of each of the
ridge lines formed by the ridge portions 112a and 112b. Further,
the width of the flange indicates a flat portion except for a
curved portion formed in the base portion in which the flange is
uprightly formed from the ridge portion, the first surface portion,
or the second surface portion.
[0076] For example, in the ridge-portion flange 115a, as
illustrated in FIG. 2B, the width Lf of the ridge-portion flange
115a indicates the width Lf of a flat portion 115aa except for a
curved portion 115ab formed so as to be continuous to the ridge
portion 112a in the longitudinal outer end portion 100A. Since the
width Lf of each of the ridge-portion flanges 115a and 115b is
smaller than the widths of the first flanges 116a and 116b and the
second flange 117, the extra extension amount of the front end of
the flange of each of the ridge-portion flanges 115a and 115b is
small, and hence the generation of wrinkles is reduced.
[0077] (1-4. Plate Thickness Distribution)
[0078] Here, the plate thickness distribution of the ridge-portion
flanges 115a and 115b of the press-molded product 100 according to
the embodiment will be described. FIG. 4 is a graph illustrating an
example of the plate thickness distribution for the end portion of
the ridge-portion flange 115a in the width direction. The vertical
axis indicates a plate thickness increase rate (%). The plate
thickness increase rate indicates the plate thickness increase rate
of the end portion of the flange in the width direction based on
the plate thickness of the blank to be press-molded.
[0079] Further, the horizontal axis indicates the distance (mm) of
the edge portion of the ridge-portion flange 115a. The "distance of
the edge portion of the flange" indicates a position in the
circumferential direction from a position in which the plate
thickness of the edge portion of the ridge-portion flange 115a
starts to increase along the ridge line, serving as the starting
point 0, to a position in which the plate thickness stops to
increase. Specifically, as illustrated in FIG. 2B, the distance
indicates a position in the circumferential direction from a plate
thickness increase start position R1 to a plate thickness increase
end position R2 in the end portion of the ridge-portion flange 115a
in the width direction. In the example of FIG. 2B, the plate
thickness increase start position R1 is located near the first
surface portion 113a, and the plate thickness increase end position
R2 is located near the second surface portion 114. However, the
plate thickness increase start position R1 and the plate thickness
increase end position R2 may be located at the reverse positions.
The intermediate point between the plate thickness increase start
position R1 and the plate thickness increase end position R2
indicates a circumferential center portion Rc of the edge portion
of the ridge-portion flange 115a in the width direction.
[0080] As illustrated in FIG. 4, the ridge-portion flange 115a of
the press-molded product 100 according to the embodiment includes
positions C1 and C2 which are provided at both sides of the center
area including the circumferential center portion Rc, the plate
thickness of the edge portion of the positions C1 and C2 being
larger than the plate thickness of the edge portion of the center
portion Rc. Specifically, the plate thickness distribution
illustrated in FIG. 4 includes a position A which is located at the
circumferential center portion Rc so that the plate thickness is
maximal, positions B1 and B2 which are located at both sides of the
position A so that the plate thickness is minimal, and positions C1
and C2 which are located outside the positions B1 and B2 so that
the plate thickness is maximal. That is, the plate thickness is
maximal at three positions of the ridge-portion flange 115a in the
circumferential direction. The plate thickness of each of positions
C1 and C2 on both sides between which the center area is interposed
is larger than the plate thickness of the circumferential center
portion Rc (A).
[0081] Since the ridge-portion flanges 115a and 115b have such a
plate thickness distribution, wrinkles generated by the
ridge-portion flanges 115a and 115b are distributed. Accordingly,
it is possible to suppress a problem in which buckling wrinkles are
intensively generated in the circumferential center area of each of
the ridge-portion flanges 115a and 115b. Thus, when the
press-molded product 100 and the other member are bonded to each
other by spot-welding through the inward continuous flange 118, a
gap is not easily formed between each of the ridge-portion flanges
115a and 115b and the other member. As a result, the bonding
strength can be improved.
[0082] Further, it is desirable that a ratio between the maximum
value of the position A having a maximal plate thickness in the
circumferential center area and the maximum value of each of the
positions C1 and C2 provided at both sides of the center area so as
to have a maximal plate thickness be substantially in the range of
1.0 to 1.5. Such a ratio can be changed by the curvature radius rf
of each of the ridge portions 112a and 112b or the strength and the
work-hardening coefficient of the metal plate (for example, the
high-tensile steel plate having a tensile strength of 340 MPa or
more) as the blank material of the press-molded product 100.
[0083] Since the above-described ratio is in the range of 1.0 to
1.5, the degree of wrinkles generated in the ridge-portion flanges
115a and 115b decreases. Thus, a gap is not easily formed when the
press-molded product 100 is bonded to the other member by
spot-welding through the ridge-portion flanges 115a and 115b, and
hence degradation in bonding strength can be suppressed.
[0084] As described above, the press-molded product 100 according
to the embodiment can be bonded to the other member through the
inward continuous flange 118 instead of the outward flange. Thus,
the hat-shaped cross-section or the groove-shaped cross-section can
be enlarged to the fullest extent of the design cross-section by
the area in which the outward flange is not provided. Further, in
the press-molded product 100 according to the embodiment, the
generation of wrinkles in the inward continuous flange 118 is
suppressed without any notch formed in the ridge-portion flanges
115a and 115b. Thus, when the press-molded product 100 is used as,
for example the vehicle body reinforcing member, it is possible to
improve the bonding strength between the press-molded product 100
and the other member and to improve the performance involved with
the rigidity or the load transfer efficiency of the reinforcing
member.
2. Second Embodiment
[0085] Next, an example of a method of producing the press-molded
product 100 according to a second embodiment of the invention will
be described along with a configuration example of an apparatus of
producing the press-molded product 100. A method and an apparatus
of producing the press-molded product 100 according to the
embodiment are used to produce, for example, the press-molded
product 100 according to the first embodiment. Hereinafter, an
apparatus (hereinafter, also referred to as the "press-molding
apparatus") of producing the press-molded product 100 according to
the embodiment will be described and then a method of producing the
press-molded product 100 using the press-molding apparatus will be
described.
[0086] (2-1. Press-Molding Apparatus)
[0087] FIG. 5 is a schematic diagram schematically illustrating an
entire configuration example of a press-molding apparatus 20
according to the embodiment. As illustrated in FIG. 5, the
press-molding apparatus 20 includes a work supporting tool 24 and
first to third bending tools 21a, 21b, and 22. The work supporting
tool 24 is used to fix and support a work 140 having a U-shaped
cross-section. The outer surface of the work supporting tool 24 has
a shape corresponding to the shape of the inner surface of the work
140 to be supported. The work supporting tool 24 supports the work
140 from the inner area while the end portion forming the flange of
the work 140 protrudes outward.
[0088] In order to form the inward flange in the end portion of the
work 140, the first to third bending tools 21a, 21b, and 22 are
used to press-insert the end portion from the outer area to the
inner area of the work 140 so that the work is bent inward. Each of
the first to third bending tools 21a, 21b, and 22 is formed by, for
example, a bending blade.
[0089] The first to third bending tools 21a, 21b, and 22 move
forward and backward with respect to the work supporting tool 24 so
as not to contact the work supporting tool 24. Such a forward and
backward movement is realized by, for example, a cam structure (not
illustrated). When the first to third bending tools 21a, 21b, and
22 move forward relatively, at least a part of the bending tools
face a side surface 24b in a portion causing the end portion of the
work 140 to protrude outward in the side surface of the work
supporting tool 24. In accordance with such a forward movement, the
first to third bending tools 21a, 21b, and 22 bend the end portion
of the work 140 inward.
[0090] Further, when the first to third bending tools 21a, 21b, and
22 move backward relatively, the bending tools move backward to a
position not facing the side surface 24b. At such a backward
movement position, the first to third bending tools 21a, 21b, and
22 are disposed so as not to be located on the extension line in
the longitudinal direction of the work 140. In the press-molding
apparatus 20 according to the embodiment, the side surface 24b of
the work supporting tool is formed on one flat surface, and the
first to third bending tools 21a, 21b, and 22 are provided so as to
be movable relatively within a plane parallel to the side surface
24b.
[0091] The first and second bending tools 21a and 21b are provided
so as to correspond to shoulder portions 25a and 25b supporting
ridge portions 142a and 142b of the work 140 in the work supporting
tool 24. The first and second bending tools 21a and 21b move
forward and backward in a direction in which the shoulder portions
25a and 25b are divided into two parts in the circumferential
direction, that is, a direction in which the ridge lines formed by
the ridge portions 142a and 142b of the work 140 are divided into
two parts.
[0092] Further, the third bending tool 22 is provided at the
substantial center between the first bending tool 21a and the
second bending tool 21b. Such a third bending tool 22 moves forward
and backward in a direction orthogonal to a support surface 24a of
the work supporting tool 24 supporting a second surface portion 144
of the work 140. As described above, the first to third bending
tools 21a, 21b, and 22 are used to press the end portion of the
work 140 protruding from the work supporting tool 24 and do not
contact the work supporting tool 24.
[0093] In a state where the first to third bending tools 21a, 21b,
and 22 move forward relatively so as to face the side surface 24b
of the work supporting tool 24, it is desirable that the distance x
of the gap between each of the first to third bending tools 21a,
21b, and 22 and the work supporting tool 24 satisfy Equation (3) as
below.
1.00.times.t.ltoreq.x.ltoreq.1.40.times.t (3)
[0094] t: plate thickness (mm) of blank
[0095] w: distance (mm) of gap
[0096] Since the distance x of the gap satisfies Equation (3)
above, it is possible to suppress the plate thickness of the inward
continuous flange 118 from being smaller than the plate thickness
before the press-molding process. Further, since the distance x of
the gap satisfies Equation (3) above, it is possible to suppress an
increase in plate thickness causing the generation of wrinkles in
the ridge-portion flanges 115a and 115b.
[0097] Here, the first and second bending tools 21a and 21b include
protrusion portions 23a and 23b provided at the surfaces in the
forward movement direction. Such protrusion portions 23a and 23b
press the end portions of the ridge portions 142a and 142b in the
end portion of the work 140 protruding from the work supporting
tool 24 in the plate thickness direction. The end portion of the
work 140 protruding from the work supporting tool 24 is a portion
bent in the inward continuous flange 118. Further, the end portions
of the protruding ridge portions 142a and 142b are portions formed
in the ridge-portion flanges 115a and 115b.
[0098] The first and second bending tools 21a and 21b are disposed
so that the protrusion portions 23a and 23b contact a part of the
end portions of the ridge portions 142a and 142b from the outer
area when the bending process starts. Subsequently, the first and
second bending tools 21a and 21b move forward relatively toward the
inner area in the plate thickness direction of the portions
contacting the protrusion portions 23a and 23b. In the end portions
of the ridge portions 142a and 142b, the portions contacting the
protrusion portions 23a and 23b are pressed in the plate thickness
direction of the contact portions. Meanwhile, the other parts of
the end portions of the ridge portions 142a and 142b are pressed in
a direction intersecting the plate thickness directions of the
respective portions.
[0099] In this way, when the end portions of the ridge portions
142a and 142b are pressed by the first and second bending tools 21a
and 21b with the protrusion portions 23a and 23b, a difference in
deformation speed is generated between a portion pressed by the
protrusion portions 23a and 23b and the other portion. Thus, a
deformation field obtained when the ridge-portion flanges 115a and
115b are formed in the end portions of the ridge portions 142a and
142b is changed from a shrinking deformation field to a shearing
deformation field. That is, it is supposed that the deformation
state of the ridge-portion flanges 115a and 115b is changed from
the shrinking deformation field (strain ratio .beta.
(.epsilon.2/.epsilon.1)<-1: increased plate thickness) to the
shearing deformation field (strain ratio .beta.
(.epsilon.2/.epsilon.1).apprxeq.-1: uniform plate thickness). Thus,
it is possible to suppress an increase in plate thickness causing
the generation of wrinkles in the end portions of the ridge
portions 142a and 142b.
[0100] At this time, when the height h of each of the protrusion
portions 23a and 23b is too small, the shearing deformation field
formed in the end portions of the ridge portions 142a and 142b
protruding from the work supporting tool 24 during the bending
process performed by the first and second bending tools 21a and 21b
is not sufficient. As a result, there is a case in which an effect
of suppressing an increase in plate thickness decreases. Meanwhile,
when the height h of each of the protrusion portions 23a and 23b is
too large, there is a concern that the protrusion portions 23a and
23b may be damaged. Thus, it is desirable that the height h of each
of the protrusion portions 23a and 23b satisfy Equation (2) as
below. Further, the sign rf in Equation (2) below indicates the
curvature radius of each of the ridge portions 112a and 112b.
0.5.times.rf.ltoreq.h.ltoreq.3.0.times.rf (2)
[0101] In the embodiment, in the shearing deformation field formed
during the bending process performed by the first and second
bending tools 21a and 21b, the strain ratio .beta.
(.epsilon.2/.epsilon.1) of the maximal strain portions of the
ridge-portion flanges 115a and 115b satisfies the inequation of
-1.5<(.epsilon.2/.epsilon.1)<0.9. In other words, the
protrusion portions 23a and 23b can give a shearing deformation
field in which the strain ratio .beta. (.epsilon.2/.epsilon.1) of
the maximal strain portions of the ridge-portion flanges 115a and
115b satisfies the inequation of
-1.5<(.epsilon.2/.epsilon.1)<0.9.
[0102] In addition, the press-molding apparatus 20 may be provided
as, for example, a drawing device which draws a blank so as to form
the work 140 including the ridge portions 142a and 142b and the
first surface portions 143a and 143b and the second surface portion
144 being continuous to the ridge portions 142a and 142b. For
example, the press-molding apparatus 20 according to the embodiment
may be provided as an existing drawing device 50 including a die
51, a punch 53, and a blank holder 55 illustrated in the example of
FIG. 6. Alternatively, the press-molding apparatus 20 according to
the embodiment may be provided as an existing bending device 60
including a die 61 and a punch 63 illustrated in the example of
FIG. 7.
[0103] In this case, the press-molding apparatus 20 is provided in
a manner that the first to third bending tools 21a, 21b, and 22 are
disposed near the side surface of the die 51 or 61 and the bending
tools 21a, 21b, and 22 are set to be movable relative to the punch
53 or 63. According to such a press-molding apparatus 20, since the
punch serves as the work supporting tool 24, there is no need to
use the dedicated work supporting tool 24. Thus, it is possible to
reduce the producing cost and the number of the production steps of
the press-molded product 100 compared with the case where the
dedicated work supporting tool 24 is used.
[0104] Further, the press-molding apparatus 20 according to the
embodiment is provided as a bending device for bending the work 140
with two ridge portions 142a and 142b. Such a press-molding
apparatus 20 includes the first and second bending tools 21a and
21b which bend the end portions of the ridge portions 142a and 142b
and the third bending tool 22 which bends the end portion of the
second surface portion 144 of the work 140. Here, the press-molding
apparatus 20 is not limited to such an example.
[0105] For example, the third bending tool 22 which bends the end
portion of the second surface portion 144 may be omitted when the
width of the second surface portion 144 is small. Further, for
example, when a work having a V-shaped cross-section with one ridge
portion is bent, the press-molding apparatus may not include the
third bending tool 22. In this case, in order to press the end
portion of the ridge portion so that the end portion is bent
inward, the press-molding apparatus may include only the first
bending tool 21a with the protrusion portion 23a.
[0106] (2-2. Press-Molded Product Producing Method)
[0107] Next, a method of producing the press-molded product 100 by
bending the end portion of the work 140 having a U-shaped
cross-section using the press-molding apparatus 20 according to the
embodiment will be described.
[0108] FIGS. 8A-8D are an explanatory diagram schematically
illustrating a state where the press-molded product 100 is produced
from the work 140 by the method of producing the press-molded
product 100 according to the embodiment. FIG. 8A illustrates a
state where the work 140 is attached to the work supporting tool 24
and FIG. 8B illustrates a state where the bending process for the
work 140 starts. Further, FIG. 8C illustrates a state where the
work 140 is bent and FIG. 8D illustrates a state where the bending
process for the work 140 ends.
[0109] Further, FIG. 9 is an explanatory diagram illustrating a
state where the protrusion portions 23a and 23b provided in the
surfaces of the first and second bending tools 21a and 21b contact
the work 140 and the protrusion portions 23a and 23b press the
contact portion of the work 140 in the plate thickness direction.
In addition, FIGS. 10A-10C are a perspective view illustrating a
state where the end portion of the work 140 is deformed by the
method of producing the press-molded product 100 according to the
embodiment. FIG. 10A illustrates the end portion of the work 140 to
be bent, FIG. 10B illustrates the end portion of the work 140 of
which the ridge portion is being bent, and FIG. 10C illustrates the
end portion of the work 140 when the bending process ends.
[0110] As illustrated in FIG. 8A, the work 140 has a U-shaped
cross-section with the ridge portions 142a and 142b extending in
the longitudinal direction and the first surface portions 143a and
143b and the second surface portion 144 being continuous to both
ends of the ridge lines formed by the ridge portions 142a and 142b.
In a state where the longitudinal end portion 140a of such a work
140 protrudes from the work supporting tool 24, the work 140 is
fixed and supported while being covered by the work supporting tool
24. The protruding end portion 140a is a portion to be bent in the
inward continuous flange 118. As illustrated in FIG. 10A, the end
portion of the work 140 is not bent at the step in which the
bending process is not started yet.
[0111] At that time, as illustrated in FIGS. 8A and 9, the first
and second bending tools 21a and 21b are disposed so that the front
ends of the protrusion portions 23a and 23b provided in the
respective surfaces of the first and second bending tools 21a and
21b contact the end portions of the ridge portions 142a and 142b of
the work 140. In the embodiment, the protrusion portions 23a and
23b contact the center portion dividing the ridge line into two
parts in the end portions of the ridge portions 142a and 142b.
Further, the third bending tool 22 is disposed so as to contact the
substantial center portion of the end portion of the second surface
portion 144 interposed between two ridge portions 142a and
142b.
[0112] Next, as illustrated in FIG. 8B, the first and second
bending tools 21a and 21b are moved from the outer area toward the
inner area of the work 140 in the inclination direction inclined
with respect to the vertical direction by, for example, a cam
mechanism (not illustrated). Accordingly, the front ends of the
protrusion portions 23a and 23b press the circumferential center
portions of the end portions of the ridge portions 142a and 142b in
the plate thickness direction. That is, as indicated by the white
arrow of FIG. 8B, the first and second bending tools 21a and 21b
move in the inclination direction substantially dividing the ridge
lines of the end portions of the ridge portions 142a and 142b into
two parts.
[0113] Accordingly, the circumferential center areas of the end
portions of the ridge portions 142a and 142b start to be deformed
earlier than the other areas. At the same time, the third bending
tool 22 is similarly moved in the vertical direction by a cam
mechanism (not illustrated), and the front end of the third bending
tool 22 contacts the center portion of the end portion of the
second surface portion 144. At this time, it is desirable that the
protrusion portions 23a and 23b of the first and second bending
tools 21a and 21b press a part or the entirety of an area
substantially having a width of the plate thickness and including
the circumferential center portion and both sides of the
circumferential center portion of each of the end portions of the
ridge portions 142a and 142b in the plate thickness direction of
the corresponding portion.
[0114] With such a bending process, positions having a maximal
plate thickness and formed in each of the edge portions of the
ridge-portion flanges 115a and 115b in the width direction can be
easily distributed evenly in the circumferential direction of the
ridge-portion flanges 115a and 115b. Thus, the generation of
wrinkles in the ridge-portion flanges 115a and 115b is further
suppressed. From such a viewpoint, it is more desirable to press
and bend the circumferential center portions of the ridge portions
142a and 142b in the plate thickness direction by the protrusion
portions 23a and 23b.
[0115] Next, as illustrated in FIGS. 8C and 8D, the first to third
bending tools 21a, 21b, and 22 are moved in the directions
indicated by the white arrows so as to bend the end portions of the
work 140. That is, when the third bending tool 22 is moved, the end
portion of the second surface portion 144 is bent inward in the
plate thickness direction. Further, when the first and second
bending tools 21a and 21b are moved, the circumferential center
portions of the end portions of the ridge portions 142a and 142b
are bent in the plate thickness direction. Further, in accordance
with the movement of the first and second bending tools 21a and
21b, the other portion except for the circumferential center
portions of the end portions of the ridge portions 142a and 142b
are sequentially pressed from the center portions at the timing
later than the timing of pressing the circumferential center
portions. Accordingly, the other portions except for the center
portions of the ridge portions 142a and 142b are sequentially bent
in a direction intersecting the plate thickness direction of the
corresponding portion.
[0116] That is, in the method of producing the press-molded product
100 according to the embodiment, as illustrated in FIG. 10B, the
end portion of the ridge portion 142b among the end portions of the
work 140 is bent first. Subsequently, as illustrated in FIG. 10C,
the end portions of the first surface portion 143b and the second
surface portion 144 are sequentially bent so as to form the inward
continuous flange 118.
[0117] In the method of producing the press-molded product 100
according to the embodiment, the circumferential center areas of
the end portions of the ridge portions 142a and 142b start to be
deformed earlier than the other areas, so that the deformation
speed of the center area becomes different from the deformation
speed of the portion other than the center area. For that reason,
the deformation field of each of the ridge-portion flanges 115a and
115b is changed from the deformation field as the shrinking flange
deformation field having a large increase in plate thickness to the
pure shearing deformation field, and hence an increase in plate
thickness easily causing the generation of wrinkles is suppressed.
In this way, it is possible to obtain the press-molded product 100
with the inward continuous flange 118 in which each of the
ridge-portion flanges 115a and 115b is not provided with the notch
and the generation of wrinkles is suppressed.
[0118] In the description above, an example is described in which
the protrusion portions 23a and 23b press the circumferential
center portions of the end portions of the ridge portions 142a and
142b of the work 140 in the plate thickness direction, but the
embodiment is not essentially limited to such an example. As long
as the circumferential center areas of the end portions of the
ridge portions 142a and 142b are guaranteed, the positions other
than the center portions dividing the ridge lines into two parts
may be pressed in the plate thickness direction.
[0119] According to the method and the apparatus of producing the
press-molded product 100 according to the embodiment, a shearing
deformation field is formed in each of the ridge-portion flanges
115a and 115b formed in the end portions of the ridge portions 142a
and 142b of the work 140 during the bending process. Thus, it is
possible to effectively suppress an increase in plate thickness of
the ridge-portion flanges 115a and 115b caused by the shrinking
deformation in accordance with the bending deformation.
[0120] In addition, when the press-molding apparatus 20 is provided
by using the existing drawing device or the bending device
illustrated in FIG. 6 or 7, it is possible to mold the work 140 and
the inward continuous flange 118 according to a series of processes
as below. For example, first, the work 140 is molded by drawing or
bending a blank. Next, in a state where the work 140 is not
separated from the press-molding apparatus 20, the longitudinal end
portion of the work 140 is bent inward by the first to third
bending tools 21a, 21b, and 22 disposed near the side surface of
the die 51 or 61 by using the punch 53 or 63 as the work supporting
tool 24.
[0121] In this way, it is possible to obtain the press-molded
product 100 with the inward continuous flange 118 through a series
of processes. In this way, since the press-molded product 100 is
produced by using the single press-molding apparatus 20, it is
possible to produce the press-molded product 100 at low cost and a
small number of steps.
[0122] Further, in order to process (hereinafter, "trim") each of
the ridge-portion flanges 115a and 115b into a predetermined shape
when the concave portion 119 is formed in each of the ridge-portion
flanges 115a and 115b, for example, the press-molded product 100
can be produced according to the following procedures.
[0123] (1) The work 140 having a predetermined cross-section shape
is molded, the longitudinal end portions of the ridge portions 142a
and 142b of the work 140 are trimmed, and then the end portions of
the work 140 are bent inward.
[0124] (2) The work 140 is molded and trimmed from the blank so as
to mold the work 140 of which the longitudinal end portions of the
ridge portions 142a and 142b are processed into a predetermined
shape, and then the end portions of the work 140 are bent
inward.
[0125] (3) A portion molded into the ridge-portion flange in the
blank is trimmed so as to process the blank into a predetermined
shape, the work 140 is then molded from the blank, and the end
portion of the work 140 is bent inward.
EXAMPLES
[0126] Hereinafter, Examples of the invention will be described
with reference to a numerical analysis result based on the finite
element method.
Examples 1 to 5 and Comparative Examples 1 to 5
[0127] First, a work having a V-shaped cross-section and formed by
a high-tensile steel plate with a plate thickness of 1.6 mm and a
tensile strength of 980 MPa was used, and the end portion of the
work was bent according to the procedure illustrated in FIGS. 5 to
9 so as to produce a press-molded product having an inward
continuous flange. The deformation behavior of each of a
ridge-portion flange and adjacent first and second flanges during
the production of the press-molded product was analyzed by a
numerical analysis.
[0128] FIGS. 11A-11B are an explanatory diagram illustrating
Example of the invention in which a bending process is performed by
the first bending tool 21a with the protrusion portion 23a. FIG.
11A is a diagram illustrating a shape of the first bending tool
21a. In the first bending tool 21a, the height h of the protrusion
portion 23a is 7 mm, and the curvature radius of the front end of
the protrusion portion 23a is 6 mm. FIG. 11B is an explanatory
diagram illustrating the deformation state of the ridge-portion
flange 115, the first flange 116, and the second flange 117 of the
press-molded product in Examples 1 to 5. At the upper left side of
the drawing of FIG. 11B, a V-shaped angle (hereinafter, also
referred to as a "ridge inner angle") formed by the first surface
portion 113 and the second surface portion 114 is illustrated.
[0129] FIGS. 12A-12B are an explanatory diagram illustrating
Comparative Example in which a bending process is performed by a
straight bending tool 31 without a protrusion portion. FIG. 12A is
an explanatory diagram illustrating a shape of the bending tool 31.
FIG. 12B is an explanatory diagram illustrating the deformation
state of a ridge-portion flange 115', a first flange 116', and a
second flange 117' of Comparative Examples 1 to 5. At the upper
left side of the drawing of FIG. 12B, a V-shaped ridge inner angle
formed by a first surface portion 113' and a second surface portion
114' is illustrated.
[0130] In Example 1 and Comparative Example 1, the ridge inner
angle of the press-molded product is 60.degree.. In Example 2 and
Comparative Example 2, the ridge inner angle of the press-molded
product is 70.degree.. In Example 3 and Comparative Example 3, the
ridge inner angle of the press-molded product is 90.degree.. In
Example 4 and Comparative Example 4, the ridge inner angle of the
press-molded product is 120.degree.. In Example 5 and Comparative
Example 5, the ridge inner angle of the press-molded product is
150.degree..
[0131] FIG. 13 is a graph in which the plate thickness increase
rates of the edge portions of the ridge-portion flanges 115 and
115' in the width direction are respectively correlated with
Example and Comparative Example. The vertical axis indicates the
maximum value of the plate thickness increase rate, and the
horizontal axis indicates the ridge inner angle. The plate
thickness increase rate indicates the plate thickness increase rate
after the bending process based on the plate thickness (1.6 mm) of
the blank.
[0132] As illustrated in FIGS. 11B and 12B, in the press-molded
products of Examples 1 to 5, the plate thickness increase rate of
the ridge-portion flange 115 is suppressed so as to be small
compared with the press-molded products having the same ridge inner
angle of Comparative Examples 1 to 5. Further, as illustrated in
the graph of FIG. 13, in the press-molded products of Examples 1 to
5, the plate thickness increase rate of the ridge-portion flange
115 is largely suppressed compared with the press-molded products
having the same ridge inner angle of Comparative Examples 1 to 5.
Thus, according to the invention, it is understood that the
press-molded product having the inward continuous flange 118 with a
satisfactory shape can be produced while an increase in plate
thickness of the ridge-portion flange 115 is small and a difference
in plate thickness distribution is small.
Examples 6 and 7
[0133] Next, in Example 6, a work having a V-shaped cross-section
and formed by a high-tensile steel plate with a plate thickness of
1.0 mm and a tensile strength of 980 MPa was used, and a
press-molded product having an inward continuous flange was
produced according to the procedure illustrated in FIGS. 5 to 9.
Further, in Example 7, a work having a U-shaped cross-section and
formed by a high-tensile steel plate with a plate thickness of 1.0
mm and a tensile strength of 980 MPa was used, and a press-molded
product having an inward continuous flange was produced according
to the procedures illustrated in FIGS. 5 to 9. The plate thickness
distribution of the edge portion of the ridge-portion flange in the
width direction during the production of the press-molded product
was analyzed by a numerical analysis.
[0134] FIGS. 14A and 14B are external views illustrating
press-molded products 120 and 130 in which the inward continuous
flanges are formed by a bending process. FIG. 15 is a graph
illustrating the plate thickness distribution in the width
direction of the edge portion of the inward continuous flange 118
formed in the end portion in the extension direction of the ridge
portion 112 of the press-molded product 120 or 130. In the graph of
FIG. 15, the vertical axis indicates the plate thickness increase
rate (%). Further, the horizontal axis indicates the distance (mm)
of the edge portion of the ridge-portion flange 115.
[0135] As illustrated in the graph of FIG. 15, according to the
press-molded product producing method of the invention, it is
proved that the plate thickness increase rate of a part of both
sides of the center portion is larger than the plate thickness
increase rate of the circumferential center portion Rc in the edge
portion of the inward ridge-portion flange 115. Further, it is
understood that the plate thickness increase rate of the edge
portion of the inward ridge-portion flange 115 is maximal at three
positions. Thus, the press-molded product producing method of the
invention can suppress the generation of buckling wrinkles at the
circumferential center area of the ridge-portion flange 115.
Accordingly, when the press-molded product is used as, for example,
the vehicle body reinforcing member, it is possible to improve the
bonding strength between the press-molded product and the other
member and to improve the performance involved with the rigidity or
the load transfer efficiency of the reinforcing member.
REFERENCE SIGNS LIST
[0136] 20 press-molding apparatus
[0137] 21a first bending tool
[0138] 21b second bending tool
[0139] 22 third bending tool
[0140] 23a, 23b protrusion portion
[0141] 24 work supporting tool
[0142] 24a support surface
[0143] 24b side surface
[0144] 25a, 25b shoulder portion
[0145] 31 bending tool
[0146] 50 drawing device
[0147] 60 bending device
[0148] 100, 120, 130 press-molded product
[0149] 100A outer end portion
[0150] 112a, 112b ridge portion
[0151] 113a, 113b first surface portion
[0152] 114 second surface portion
[0153] 115, 115', 115a, 115b ridge-portion flange
[0154] 115aa flat portion
[0155] 115ab curved portion
[0156] 116, 116', 116a, 116b first flange
[0157] 117, 117' second flange
[0158] 118 inward continuous flange
[0159] 119 concave portion
[0160] 140 work
[0161] 140a longitudinal end portion
[0162] 142a, 142b ridge portion
[0163] 143a, 143b first surface portion
[0164] 144 second surface portion
* * * * *