DESCRIPTION
TITLE OF INVENTION:
PRESS-FORMING APPARATUS, METHOD FOR PRODUCING PRESSFORMED
PRODUCT USING THE FORMING APPARATUS, AND PRESSFORMED
PRODUCT
TECHNICAL FIELD
[OOOI ]
The present invention relates to a press-formed product having an external
shape that curves in an L shape along a longitudinal direction in a planar view.
More specifically, the present invention relates to a press-forming apparatus for
producing a press-formed product having a cross-sectional fonn that is a hat shape, a
method for producing a press-formed product using the forming apparatus, and a
press-formed product.
BACKGROUND ART
[0002]
The body of an automobile includes various structural members (for example,
a front pillar lower outer reinforcement, a front pillar inner, a side sill outer
reinforcement rear, a side sill inner and a rear side member). Press-formed products
are frequently used as the structural members. In many cases, the cross-sectional
form of a press-fornled product that is used as a structural member is a hat shape or a
groove shape.
[0003]
FIGS. 1 (a) and (b) are views that schematically illustrate an example of a
press-formed product having a hat-shaped cross section. Among these figures, FIG.
1 (a) shows a side view, and FIG. I (b) shows a cross-sectional view along a line A-A
in FIG. l(a). As shown in FIG. l(b), a press-formed product 90 includes a top plate
portion 90a, vertical wall portions 90b and 90c, and flange portions 90d and 90e.
The vertical wall portions 90b and 90c are connected to two side portions of the top
plate portion 90a, respectively. The flange portions 90d and 90e are connected to
the vertical wall portions 90b and 90c, respectively. The press-fonned product 90
shown in FIGS. I (a) and (b) extends linearly along the longitudinal direction in a
planar view.
[0004]
The above described type of press-formed product having a hat-shaped cross
section is formed by press working using a punch and die. At the time of pressforming,
a blank holder is sometimes used to hold the edge of a metal plate (for
example, a steel plate) that is a starting material. Press forming that uses a blank
holder is also referred to as "drawing". Further, in press-forming (drawing), a pad
is sometimes used together with a blank holder.
[0005]
FIG. 2(a) to FIG. 2(f) are cross-sectional views that schematically illustrate
working processes of conventional common press-forming (drawing). Among
these figures, FIG. 2(a) illustrates a state before the start of forming. FIG. 2(b)
illustrates a state in which a blank metal plate is sandwiched by blank holders. FIG.
2(c) illustrates a state in which the blank metal plate is sandwiched using a pad.
FIGS. 2(d) and (e) sequentially illustrate states during a process of pushing a punch
into a die. FIG. 2(f) illustrates a state when forming is completed. The working
processes illustrated in FIGS. 2(a) to (f) illustrate a case in which press working is
performed on a blank metal plate 70 to form a press-formed product having a hatshaped
cross section. The press-formed product has a top plate portion, a vertical
wall portion and a flange portion.
[0006]
A press-forming apparatus 20 is equipped with an upper die 40 and a lower
die 30. The upper die 40 includes a die 50 and a pad 41. The lower die 30
includes a punch 3 I , and blank holders 32 and 33 that are adjacent to two side
portions of the punch 3 1, respectively.
[0007]
The punch 3 1 has a die impression in which the shape of the press-formed
product is reflected. In other words, as shown in FIG. 2(a), the punch 31 has an end
face 3 1 a that has a shape that corresponds to a top plate portion of the press-formed
product. Further, the punch 3 1 has outer side faces 3 I b and 3 I c that have a shape
that corresponds to a vertical wall portion of the press-formed product.
[OOOS]
The die 50 has a die impression in which the shape of the press-formed
product is reflected. In other words, the die 50 has guide faces 50c and 50d that
have a shape that corresponds to a flange portion of the press-formed product,
respectively. In addition, the die 50 has inner side faces 50a and 50b that have a
shape that corresponds to a vertical wall portion of the press-formed product. The
pad 41 constitutes one part of the die 50, and has an end face that has a shape that
corresponds to the top plate portion of the press-formed product.
[0009]
The pad 41 is mounted to the die 50 via a pad pressurizing mechanism (for
example, a spring, rubber, a gas cylinder or a hydraulic cylinder) 42. By this means,
the pad 41 is slidable in a pressing direction. Therefore the pad 41 is individually
slidable with respect to the die 50. The end face of the pad 41 faces the end face
3 1 a of the punch 3 1. Note that, in some cases the pad 41 is mounted to a die or a
fixing jig or the like that is integrated with a ram (not illustrated in the drawings) of
the press-forming apparatus and makes the same movement as the ram.
[OO 1 01
The blank holders 32 and 33 are slidably supported in a pressing direction by
blank holder pressurizing mechanisms (for example, a spring, rubber, a hydraulic
cylinder or a gas cylinder) 36 and 37, respectively. In this case, the term "pressing
direction" refers to a direction in which the punch 3 1 and the die 50 relatively move
at the time of press-forming. In the press-forming apparatus 20 illustrated in FIGS.
2(a) to (f), the vertical direction is the pressing direction.
[OOl 11
The press-formed product having a hat-shaped cross section that is shown in
FIG. 1 is produced by the following processes using the press-forming apparatus 20
configured as described above. As shown in FIG. 2(a), in a state in which the upper
die 40 is withdrawn to the upper side, the blank metal plate 70 is placed on top of the
lower die 30. In this state, the upper die 40 descends. Thereupon, as shown in
FIG. 2(b), the guide faces 50c and 50d of the die 50 butt against the blank holders 32
and 33 via the blank metal plate 70, and the blank holder pressurizing mechanisms
36 and 37 move downward while imparting a restoring force in the upward direction.
The blank holders 32 and 33 are pressed against the blank metal plate 70 by the
restoring force of the blank holder pressurizing mechanisms 36 and 37. By this
means, the blank metal plate 70 is sandwiched by the die 50 and the blank holders 32
and 33.
[OO 1 21
When the upper die 40 descends further, as shown in FIG. 2(c), the pad 41
butts against the punch 3 1 via the blank metal plate 70, and the pad pressurizing
mechanism 42 contracts. The pad 41 is pressed against the blank metal plate 70 by
the restoring force of the pad pressurizing mechanism 42. By this means, the blank
metal plate 70 is sandwiched by the punch 3 1 and the pad 41.
[00 1 31
In a state in which the blank metal plate 70 is sandwiched in this way, the
upper die 40 descends further. Thereupon, as shown in FIGS. 2(d) and (e), the
punch 3 1 and the die 50 move relatively, and the punch 3 1 is pushed into the die 50.
As a result, both side portions in the width direction of the blank metal plate 70 move
towards the center along the guide faces 50c and 50d of the die 50, and in
accompaniment therewith one portion of the blank metal plate 70 is pushed into the
die impression of the die 50.
[00 1 41
Subsequently, as shown in FIG. 2(f), the upper die 40 arrives at bottom dead
center. As a result, the top plate portion is finished by the end face 3 1 a of the punch
31 and the pad 41, and the vertical wall portions are finished by the outer side faces
3 1 b and 3 1 c of the pullch 3 1 and the inner side faces 50a and 50b of the die 50.
Further, the flange portions are finished by the guide faces 50c and 50d of the die 50
and the blank holders 32 and 33. By performing press-forming in this manner, a
press-formed product having a hat-shaped cross section is produced.
[00 1 51
The following technology is available as prior art for forming a press-formed
product having a hat-shaped cross section.
[00 1 61
Japanese Patent Application Publication No. 2009-255 1 16 (Patent Literature
I) discloses technology that uses a pad when performing press-forming by means of
a punch and die. According to the technology disclosed in Patent Literature 1, a
punch position, a die position and a pad position during press-forming are measured.
Based on the measurement values, the position of the pad is controlled so that a
relative displacement between the pad and the punch stays within a range of 10 to 20
mm until a relative displacement between the die and the pad from the start of
forming becomes zero. By controlling the position of the pad in this way, slackness
is formed in the blank metal plate between the punch and the pad, and the slackness
that is formed is crushed out in a later stage of the press-forming. By this means,
the technology described in Patent Literature 1 enlarges a bending region so that, as a
result, spring back can be reduced.
[OO 1 71
International Application Publication No. W02011/145679 (Patent Literature
2) discloses technology relating to a press-forming method that uses a die, a bending
die and a pad. A press-formed product that is produced using the technology
disclosed in Patent Literature 2 has an external shape that curves in an L shape along
a longitudinal direction in a planar view. The press-formed product includes a top
plate portion, vertical wall portions connected to the top plate portion, and flange
portions connected to the vertical wall portions. Specifically, among two side
portions of the top plate portion, a vertical wall portion is formed across an entire
area at a side portion on a curved inner side. At a side portion on a curved outer
side of the top plate portion, a vertical wall portion is formed only in an area from
one edge until a position at which the side portion curves. In other words, the
press-formed product described in Patent Literature 2 has an incomplete hat-shaped
cross section in which a vertical wall portion is missing over a wide area on the
curved outer side of the top plate portion.
[00 1 81
According to the technology disclosed in Patent Literature 2, a blank metal
plate is disposed between a die and pad and a bending die, and press-forming is
performed in a state in which the pad is brought adjacent to or into contact with the
blank metal plate. At such time, vertical wall portions and flange portions are
formed while sliding at least one part of the blank metal plate over a region
corresponding to the top plate portion among the entire region of the die. By this
means, according to Patent Literature 2, a configuration is adopted that enables
suppression of the occurrence of cracks in a flange portion and also enables
suppression of the occurrence of wrinkles in a top plate portion in a curved region of
a press-formed product.
CITATION LIST
PATENT LITERATURE
[0019]
Patent Literature 1 : Japanese Patent Application Publication No. 2009-255 1 16
Patent Literature 2: International Application Publication No. W020111145679
SUMMARY OF INVENTION
TECHNICAL PROBLEM
[0020]
Vehicle body structural members (front pillar portion, side sill portion and the
like) are constituted by individual press-formed products, or are constituted by
joining a plurality of press-formed products by spot welding or the like. A lower
end of a front pillar portion is joined to a front end of a side sill portion. In the front
pillar portion, the portion thereof that is joined to the side sill portion is constituted
by a front pillar lower outer reinforcement and a front pillar inner. A press-formed
product having a hat-shaped cross section is used for the front pillar lower outer
reinforcement. A press-formed product disclosed in the above described Patent
Literature 2 may be mentioned as one example thereof.
[002 1 ]
Such a front pillar lower outer reinforcement is made in a shape that curves in
an L shape along the longitudinal direction. This shape is adopted in order to
improve performance such as vehicle body rigidity as well as collision safety
performance.
[0022]
FIGS. 3(a) and (b) are views that scl~ematicallyil lustrate a different example
of a press-formed product having a hat-shaped cross section. Among these figures,
FIG. 3(a) shows a plan view, and FIG. 3(b) shows a cross-sectional view along a line
B-B in FIG. 3(a). The press-formed product shown in FIGS. 3(a) and (b) is applied
to a front pillar lower outer reinforcement, and has an external shape that curves in
an L shape along the longitudinal direction in a planar view, and has a hat-shaped
cross section across the entire area in the longitudinal direction. Hereunder, a pressformed
product of this shape is also referred to as a "specific press-formed product".
Note that, in FIGS. 3(a) and (b), to facilitate the description, a press-fonned product
that is used as a fi-ont pillar lower outer reinforcement is illustrated as an example, a
lower end side thereof that is joined to a side sill portion is referred to as "back" in
the longitudinal direction (see reference character "B" surrounded by a circle in FIG.
3(a)), and a top end side that is opposite to the "back" is referred to as "front" in the
longitudinal direction (see reference character "F" surrounded by a circle in FIG.
3(a)).
[0023]
As shown in FIG. 3(b), the press-formed product 10 includes a top plate
portion 1 Oa, a first vertical wall portion 1 Ob, a second vertical wall portion 1 Oc, a
first flange portion 10d and a second flange portion 10e. The top plate portion 1 Oa
has an L-shaped curved region. The first vertical wall portion lob is connected to
the entire area of a side portion on the curved inner side among two side portions of
the top plate portion 10a. The second vertical wall portion 10c is connected to the
entire area of a side portion on the curved outer side among the two side portions of
the top plate portion 10a. The first flange portion 10d is connected to the first
vertical wall portion lob. The second flange portion 10e is connected to the second
vertical wall portion 1 Oc.
[0024]
As shown in FIGS. 3(a) and (b), a boundary portion 1 Of between the top plate
portion 10a and the first vertical wall portion 1 Ob has a substantially quarter arcshaped
region 10j (hereunder, also referred to as "first arc-shaped region of the top
plate portion") that curves along a curved region of the top plate portion 10a (see
thick line in FIG. 3(a)). Further, a boundary portion log between the top plate
portion 10a and the second vertical wall portion 10c also has a substantially quarter
arc-shaped region 10k (hereunder, also referred to as "second arc-shaped region of
the top plate portion") that curves along a curved region of the top plate portion 1 Oa
(see thick line in FIG. 3(a)).
[0025]
The specific press-formed product 10 can be produced by press-forming using
a punch, a die and a blank holder. However, when using a high-strength metal plate,
for example, a metal plate having a tensile strength (TS) of 590 MPa or more, as a
blank metal plate, cracks or wrinkles are liable to occur in the press-formed product
10.
[0026]
On the other hand, even in the case of using a metal plate having a tensile
strength (TS) of less than 590 MPa as a blank metal plate, if a depth dl of the first
vertical wall portion lob or a depth d2 of the second vertical wall portion 10c is deep,
cracks or wrinkles are liable to occur in the press-formed product 10. Further,
cracks or wrinkles are also liable to occur in the press-formed product 10 in a case
where the radius of curvature of the first arc-shaped region 10j of the top plate
portion is small or a case where the radius of curvature of the second arc-shaped
region 10k of the top plate portion is small.
100271
FIGS. 4(a) to (c) are views that illustrate the distribution of a plate thickness
decrease rate when the specific press-formed product is produced by press-forming.
Among these figures, FIG. 4(a) illustrates a case where the specific press-formed
product shown in the above described FIG. 3 is produced by drawing using a punch,
a die and a blank holder. FIG. 4(b) illustrates a case where a specific press-formed
product having a shape in which one end in the longitudinal direction is closed is
produced by the same drawing as that used in the case illustrated in FIG. 4(a). FIG.
4(c) illustrates a case where the specific press-formed product shown in the above
described FIG. 3 is produced by drawing using a pad in addition to a punch, a die and
a blank holder. In FIGS. 4(a) to (c), the plate thickness decrease rates are indicated
by degrees of shading, and the contour shape of the blank metal plate 70 before
press-fonning is shown by a solid line. The plate thickness decrease rate is a rate of
decrease (%) in the plate thickness based on the thickness of the blank metal plate 70.
[0028]
The plate thickness decrease rate was determined by FEM analysis. At that
time, a 980 MPa-class dual-phase, high strength steel plate having a plate thickness
of 1.6 mm was used as the blank metal plate. The dimensions and shape of the
press-fonned product were the same as in examples that are described later. The
plate thickness decrease rate rtb (%) was calculated by the following Formula (1).
rtb = (tb - t)/tb x 100 ...( 1)
In the above Formula (I), tb represents the plate thickness (mm) of the blank
metal plate, and t represents the plate thickness (mm) of the press-formed product.
[0029]
As shown in FIG. 4(a), in the case where the specific press-formed product
was produced by drawing using a punch, a die and a blank holder, a noticeable
thickness reduction occurred in an X region of the curved inner side of the second
arc-shaped region of the top plate portion. In this case, because of the
characteristics of the material adopted for the blank metal plate, if the plate thickness
decrease rate is more than around 18%, cracks are generated in the actual formed
product that is obtained by the press-forming. Therefore, in the specific pressformed
product shown in FIG. 4(a), cracks are generated in the X region. Note that,
the X region includes the second arc-shaped region of the top plate portion that
adjoins the X region as well as the vicinity of this arc-shaped region.
[0030]
Further, in the case of the specific press-formed product shown in FIG. 4(a),
in a Y region on the curved outer side of the first arc-shaped region of the top plate
portion, the plate thickness decrease rate repeatedly increases and decreases at a short
cycle along the longitudinal direction. This means that wrinkles are generated in
the actual formed product that is obtained by the press-forming. Therefore, in the
specific press-formed product shown in FIG. 4(a), wrinkles are generated in the Y
region. Note that, the Y region includes the first arc-shaped region of the top plate
portion adjoining the Y region as well as the vicinity of this arc-shaped region.
[003 1 ]
As shown in FIG. 4(b), in a case where the specific press-formed product
having a shape in which one end in the longitudinal direction is closed was produced
by drawing perfomled in the same manner as in the case of the specific press-formed
product illustrated in FIG. 4(a), a thickness reduction occurred in the same X region
as in FIG. 4(a). However, because the amount of the thickness reduction decreased
relative to the specific press-formed product illustrated in FIG. 4(a), the occurrence
of cracks is reduced. Further, in the specific press-formed product shown in FIG.
4(b), wrinkles are generated in the same Y region as in FIG. 4(a). Note that,
because the specific press-formed product shown in FIG. 4(b) has a shape in which
the first vertical wall portion and the second vertical wall portion are connected at the
rear end in the longitudinal direction, the shapes of the punch, the die and the blank
metal plate were changed to match to this shape.
LO0321
As shown in FIG. 4(c), in a case where the specific press-formed product was
produced by drawing performed using a pad in addition to a punch, a die and a blank
holder, a noticeable thickness reduction occurred in the same X region as in FIG.
4(a). Therefore, cracks are generated in the X region. Further, in the specific
press-formed product shown in FIG. 4(c), the occurrence of wrinkles is suppressed in
the Y region.
[0033]
In the specific press-formed products shown in FIGS. 4(a) to (c), a large
amount of excess metal is provided in a Z region (see the above described FIG. 3(a))
of the first flange portion on the curved inner side that corresponds to the curved
region of the top plate portion. This excess metal is obtained by expanding the
width of the blank metal plate. In a case where this excess metal is not provided, as
shown in the above described FIG. 3(a), cracks are liable to arise in the Z region.
The Z region includes an arc-shaped region (hereunder also referred to as "first arcshaped
region of the flange portion") that adjoins the Z region among the entire area
of the boundary portion between the first flange portion and the first vertical wall
portion, as well as the vicinity of this arc-shaped region.
[0034]
As a method for suppressing the occurrence of such cracks or wrinkles, it is
conceivable to apply the technology disclosed in the aforementioned Patent
Literature 1 to drawing of the specific press-formed product. In this case, since a
pad is used in press-forming by a punch and die, it is possible to reduce wrinkles in
the Y region to some extent. However, on the other hand, wrinkles will arise in a
W region (see the above described FIG. 3(a)) in the second flange portion on the
curved outer side that corresponds to the curved region of the top plate portion. The
W region includes an arc-shaped region (hereunder also referred to as "second arcshaped
region of the flange portion") that adjoins the W region among the entire area
of the boundary portion between the second flange portion and the second vertical
wall portion, as well as the vicinity of this arc-shaped region.
[003 51
Further, a press-formed product that is adopted as an object of production
with the technology disclosed in the aforementioned Patent Literature 2 is a pressformed
product having an incomplete hat-shaped cross section in which a vertical
wall portion is missing over a wide range. Consequently, it is difficult to apply the
technology disclosed in Patent Literature 2 to drawing of the specific press-formed
product. If, for instance, the technology disclosed in Patent Literature 2 were
applied to drawing of the specific press-formed product, wrinkles would arise in the
W region (see the aforementioned FIG. 3(a)) of the second flange portion.
[0036]
The present invention has been conceived in consideration of the actual
circumstances that are described above. An objective of the present invention is to
provide a press-forming apparatus having a characteristic described hereunder with
regard to a press-formed product that has an external shape that curves in an L shape
along a longitudinal direction in a planar view and also has a hat-shaped cross
section across approximately an entire area in the longitudinal direction, a method for
producing a press-formed product using the forming apparatus, and a press-formed
product:
obtainment of a press-formed product in which cracks and wrinkles are
reduced.
SOLUTION TO PROBLEM
[003 71
A press-forming apparatus according to one embodiment of the present
invention is a press-forming apparatus for producing a press-formed product having
an external shape that curves in an L shape along a longitudinal direction in a planar
view.
The press-formed product includes:
a top plate portion including an L-shaped curved region;
a first vertical wall portion that is connected to a side portion on a curved
inner side among two side portions of the top plate portion;
a second vertical wall portion that is connected to a side portion on a curved
outer side among the two side portions of the top plate portion;
a first flange portion that is connected to the first vertical wall portion; and
a second flange portion that is connected to the second vertical wall portion.
[003 81
The press-forming apparatus includes a punch, a first blank holder, a second
blank holder, a die, a pad, a preceding portion and a restriction mechanism.
The punch has an end face, a first outer side face and a second outer side face
that have shapes that correspond to the top plate portion, the first vertical wall
portion and the second vertical wall portion, respectively.
The first blank holder is adjacent to a curved inner side of the punch, and is
slidable in a pressing direction.
The second blank holder is adjacent to a curved outer side of the punch, and is
slidable in the pressing direction.
The die fonns a pair with the punch, the first blank holder, and the second
blank holder, and includes a first inner side face and a second inner side face that
have shapes that correspond to the first vertical wall portion and the second vertical
wall portion, respectively, and a first guide face and a second guide face that face the
first blank holder and the second blank holder, respectively.
The pad constitutes one part of the die and is slidable in the pressing direction,
and among an entire region of the end face of the punch, faces at least a region that
corresponds to the curved region of the top plate portion.
The preceding portion constitutes one part of the die and is slidable in the
pressing direction, and among an entire region of the first guide face and the first
inner side face, includes at least a region that corresponds to the curved region of the
top plate portion.
[0039]
Operations of the press-forming apparatus are as described below.
When pushing the punch into the die by relatively moving the punch and the
die in the pressing direction to form a metal plate into the press-formed product, the
first guide face of the preceding portion precedes the second guide face of the die,
and the first vertical wall portion and the first flange portion are formed. Thereafter,
sliding of the first blank holder and the preceding portion relative to the punch is
restricted by the restriction mechanism, and pushing of the punch into the die is
continued in the restricted state and the second vertical wall portion and the second
flange portion are formed.
[0040]
The above described press-forming apparatus can have a configuration that
hrther includes a cushion and a stopper.
The cushion slidably supports the first blank holder in the pressing direction
via a cushion pin.
The stopper limits sliding of the first blank holder.
In the case of this configuration, by separating the cushion pin and the first
blank holder while limiting sliding of the first blank holder with the stopper, the
restriction mechanism restricts sliding of the first blank holder, and restricts sliding
of the preceding portion following restriction of the first blank holder.
LO04 11
The above described press-forming apparatus can adopt a configuration that
further includes a pressurizing mechanism instead of the above described
configuration.
The pressurizing mechanism slidably supports the first blank holder in the
pressing direction.
In the case of this configuration, the restriction mechanism restricts the first
blank holder by limiting sliding of the first blank holder, and restricts sliding of the
preceding portion following restriction of the first blank holder.
[0042]
A method for producing a press-formed product according to one embodiment
of the present invention is a method that, when producing the above described pressformed
product from a metal plate by press-forming, executes formation of the first
vertical wall portion and the first flange portion prior to formation of the second
vertical wall portion and the second flange portion.
[0043]
The described production method can adopt the following configuration.
The method for producing the press-formed product uses the above described
press-forming apparatus, and includes a holding process and a forming process.
In the holding process, in a state in which the first guide face of the preceding
portion precedes the second guide face of the die, the metal plate is sandwiched by
the first blank holder, the second blank holder and the pad.
In the forming process, by relatively moving the punch and the die in the
pressing direction, the punch is pushed into the die to form the metal plate into the
press-formed product.
The forming process includes a first step and a second step.
In the first step, in a state in which the first guide face of the preceding portion
precedes the second guide face of the die, pushing of the punch into the die is
performed to form the first vertical wall portion and the first flange portion.
In the second step, sliding of the first blank holder and the preceding portion
relative to the punch is restricted by the restriction mechanism, and pushing of the
punch into the die is continued in the restricted state to form the second vertical wall
portion and the second flange portion.
[0044]
A press-formed product according to one embodiment of the present
invention has an external shape that curves in an L shape along a longitudinal
direction in a planar view.
The press-formed product includes:
a top plate portion including an L-shaped curved region;
a first vertical wall portion that is connected to a side portion of a curved inner
side among two side portions of the top plate portion;
a second vertical wall portion that is connected to a side portion of a curved
outer side among the two side portions of the top plate portion;
a first flange portion that is connected to the first vertical wall portion; and
a second flange portion that is connected to the second vertical wall portion;
wherein, a tensile strength thereof is 590 MPa or more.
ADVANTAGEOUS EFFECT OF INVENTION
[0045]
A press-forming apparatus, a method for producing a press-fonned product
using the forming apparatus, and a press-formed product of the present invention
have the following remarkable advantageous effect:
obtainment of a press-formed product in which cracks and wrinkles are
reduced.
BRIEF DESCRIPTION OF DRAWINGS
[0046]
[FIG. 11 FIGS. l(a) and (b) are views that schematically illustrate one example of a
press-formed product having a hat-shaped cross section.
[FIG. 21 FIG. 2(a) to FIG. 2(f) are cross-sectional views that schematically illustrate
working processes of conventional common press-forming.
[FIG. 31 FIGS. 3(a) and (b) are views that schematically illustrate a different example
of a press-formed product having a hat-shaped cross section.
[FIG. 41 FIGS. 4(a) to (c) are views that illustrate the distribution of a plate thickness
decrease rate when a specific press-formed product is produced by press-forming.
[FIG. 51 FIG. 5 is a cross-sectional view that schematically illustrates a pressforming
apparatus of a first embodiment of the present invention.
[FIG. 61 FIGS. 6(a) to (e) are cross-sectional views that schematically illustrate
working processes of press-forming by the press-forming apparatus of the first
embodiment of the present invention.
[FIG. 71 FIGS. 7(a) to (e) are cross-sectional views that schematically illustrate
working processes of press-forming by a press-forming apparatus of a second
embodiment of the present invention.
[FIG. 81 FIG. 8 is a cross-sectional view that schematically illustrates an upper die in
a press-forming apparatus of a third embodiment of the present invention.
[FIG. 91 FIG. 9 is a plan view of a press-formed product that schematically illustrates
an example of a region which a preceding portion butts against at bottom dead center.
[FIG. 101 FIG. 10 is a plan view of a press-formed product that schematically
illustrates an example of a region which a pad butts against at bottom dead center.
[FIG. 111 FIGS. 1 l(a) to (g) are cross-sectional views that schematically illustrate
working processes according to press-forming of a fourth embodiment of the present
invention.
[FIG. 121 FIG. 12 is a plan view that schematically illustrates a press-formed product
that is produced by press-forming of Example 1.
[FIG. 131 FIG. 13 is a view that illustrates the distribution of a plate thickness
decrease rate when a specific press-formed product is produced by the press-forming
of Example 1.
[FIG. 141 FIG. 14 is a view that illustrates an example of the distribution of a plate
thickness decrease rate when a specific press-formed product is produced by pressforming
of Example 2.
[FIG. 151 FIGS. 15(a) to (c) are views that illustrate a relation between a stroke
difference between dies and a plate thickness decrease rate as results of Example 2.
DESCRIPTION OF EMBODIMENTS
[0047]
To achieve the above described objective, the present inventors preformed
various experiments and conducted concentrated studies. As a result, as shown in
FIG. 5 that is described later, the present inventors discovered that when pressforming
(drawing) using blank holders 32 and 33 together with the pad 41, it is
advantageous for the guide face (first guide face) 50c on the curved inner side of the
die to precede the guide face (second guide face) 50d on the curved outer side thereof.
In this case, a curved inner side of a curved region of the top plate portion, more
specifically, the first vertical wall portion and the first flange portion, are finished
prior to other portions. As a result, the blank metal plate leans to the curved inner
side. Consequently, compared to a case where the first guide face 50c does not
precede, a state is entered in which there is a surplus of the blank metal plate in the
vicinity of the second arc-shaped region 10k of the top plate portion. In this state,
the curved outer side of the curved region of the top plate portion, more specifically,
the second vertical wall portion and the second flange portion are finished. By this
means, a thickness reduction in the X region of the curved inner side of the second
arc-shaped region 10k of the top plate portion can be reduced, and as a result it is
possible to reduce the occurrence of cracks.
[0048]
Further, by using the blank holders 32 and 33 together with the pad 4 1, the
generation of wrinkles in the Y region of the curved outer side of the first arc-shaped
region 10j of the top plate portion can be reduced. As a result, it is possible to
reduce changes in the plate thickness of the press-formed product.
[0049]
Hereunder, embodiments of the present invention are described while
referring to the drawings.
[OOS 01
[First Embodiment]
FIG. 5 is a cross-sectional view that schematically illustrates a press-forming
apparatus of a first embodiment of the present invention. A press-forming
apparatus 20 of the first embodiment is used in drawing for producing the specific
press-formed product 10 that is shown in the above described FIG. 3. Note that the
cross-section shown in FIG. 5 is a cross-section along a line B-B in the above
described FIG. 3(a). The same applies with respect to a second embodiment and a
third embodiment which are described later.
[005 11
The press-forming apparatus 20 includes a ram 61, an upper die 40, a lower
die 30, a bolster 62 and a cushion 35. The ram 61 slides in a pressing direction
(vertical direction). The cushion 35 is arranged below the bolster 62. The cushion
35 generates a uniform pressure in the upward direction by means of a spring or a
fluid pressure or the like. Note that a blank metal plate 70 is also shown in FIG. 5.
[0052]
The lower die 30 includes a punch 3 1, a first blank holder 32 and a second
blank holder 33. The punch 3 1 has a die impression in which the shape of the
press-formed product 10 is reflected. In other words, the punch 3 1 has an end face
3 1 a which has a shape that corresponds to the top plate portion 1 Oa of the pressformed
product 10. In addition, the punch 3 1 has a first outer side face 3 1 b which
has a shape that corresponds to the first vertical wall portion 1 Ob, and also has a
second outer side face 3 1 c which has a shape that corresponds to a second vertical
wall portion 10c. Accordingly, similarly to the press-formed product 10, the shape
in a planar view of the punch 3 1 is a shape that curves in an L shape along the
longitudinal direction.
[0053]
The first blank holder 32 is arranged on a curved inner side of the punch 3 1,
and is adjacent to the punch 3 1. The second blank holder 33 is arranged on a
curved outer side of the punch 3 1, and is adjacent to the punch 3 1.
[0054]
The first blank holder 32 and the second blank holder 33 are mounted at an
upper end of a cushion pin 34, respectively. The cushion pins 34 penetrate through
the bolster 62 and are supported so as to be individually movable in the pressing
direction (vertical direction). The lower ends of the cushion pins 34 are pressed
against the cushion 35. Therefore, the first blank holder 32 and the second blank
holder 33 are slidably supported in the pressing direction while an upward restoring
force is imparted thereto by the cushion 35 via the cushion pins 34.
[0055]
A stopper 56 that is fixed to the press-forming apparatus and that is used for
limiting a sliding movement of the first blank holder 32 is provided on the cushion
pin 34 that supports the first blank holder 32. The stopper 56 constitutes a
restriction mechanism that restricts sliding of the first blank holder 32, and also
restricts sliding of a preceding portion 54 of a die that is described later. The first
blank holder 32 is mounted to the cushion pin 34 in a state in which the first blank
holder 32 is detachable from the cushion pin 34.
[0056]
The upper die 40 includes a die 50 (51 to 53) and the pad 41. The die 50 is
constituted by a die plate 5 1, a first die 52 and a second die 53, and has a die
impression in which the shape of the press-formed product 10 in a state in which
these dies are integrated is reflected. In terms of the die impression, the pad 41
constitutes one part of the die 50, and has an end face having a shape that
corresponds to the top plate portion 1 Oa of the press-formed product 10. In other
words, the pad 41 is arranged facing the end face 3 1 a of the punch 3 1.
[0057]
The first die 52 faces the first blank holder 32. In other words, the first die
52 is arranged on the curved inner side of the punch 3 1 (press-formed product 10).
The first die 52 has a first guide face 50c which has a shape that corresponds to the
first flange portion 10d of the press-formed product 10. In addition, the first die 52
has a first inner side face 50a which has a shape that corresponds to the first vertical
wall portion lob of the press-formed product 10. The first inner side face 50a is
also a shape that corresponds to the first outer side face 3 1b of punch 3 1 .
[0058]
The second die 53 faces the second blank holder 33. In other words, the
second die 53 is arranged on the curved outer side of the punch 3 1 (press-formed
product 10). The second die 53 has a second guide face 50d which has a shape that
corresponds to the second flange portion 1 Oe of the press-formed product 10. In
addition, the second die 53 has a second inner side face 50b which has a shape that
corresponds to the second vertical wall portion 10c of the press-formed product 10.
The second inner side face 50b is also a shape that corresponds to the second outer
side face 3 1 c of the punch 3 1.
[0059]
The preceding portion 54 is provided in the first die 52 that is arranged on the
curved inner side of the punch 3 1 (press-formed product 10). Among the entire
region of the first guide face 50c and the first inner side face 50a, the preceding
portion 54 includes at least a region that corresponds to the curved region of the top
plate portion 10a of the press-formed product 10. In other words, the preceding
portion 54 constitutes one part of the first guide face 50c and the first inner side face
50a of the first die 52. As described using FIG. 9 that is described later, a boundary
portion 1 Oh between the first flange portion 10d and the first vertical wall portion
1 Ob of the press-formed product 10 includes a substantially quarter arc-shaped region
101 (first arc-shaped region of the flange portion) that curves along a curved region
of the top plate portion 1Oa. For example, the first guide face 50c of the preceding
portion 54 corresponds to a region 1 On that includes a region on a curved inner side
of the first arc-shaped region 101 of the flange portion.
[OOGO]
The preceding portion 54 may be integrated with the first die 52, or may be a
portion that is separated and independent from the first die 52. In FIG. 5, an
example is illustrated in which the preceding portion 54 is integrated with the first
die 52. The preceding portion 54 (first die 52) is supported via a preceding portion
pressurizing mechanism (for example, a spring, rubber, a gas cylinder or a hydraulic
cylinder) 55. By this means, the preceding portion 54 is slidable in the pressing
direction. On the other hand, the second die 53 is fixed by, for example, a bolt to
the die plate 5 1. Accordingly, the first guide face 50c of the preceding portion 54 is
slidable relative to the second guide face 50d of the second die 53.
[OOG 1 ]
The pad 41 is supported via a pad pressurizing mechanism (for example, a
spring, rubber, a gas cylinder or a hydraulic cylinder) 42. By this means, the pad 41
is slidable in the pressing direction. Of the entire region of the end face 3 1 a of the
punch 3 1, the pad 41 faces at least a region that corresponds to the curved region of
the top plate portion 10a of the press-formed product 10. In other words, the pad 41
constitutes one part of the die 50. For example, as described using FIG. 10 that is
described later, the pad 4 1 corresponds to a region 1 Om that includes a region on a
curved outer side of the first arc-shaped region 10j of the top plate portion of the
press-formed product 10. In the top plate portion 1 Oa of the press-formed product
10, the region 1 Om that corresponds to the pad 4 1, and particularly a region of the
region 1 Om which is adjacent to the first arc-shaped region 10j of the top plate
portion, is a region in which wrinkles are liable to arise (hereunder, also referred to
as "wrinkle occurrence region").
LO0621
The specific press-fonned product 10 illustrated in the above described FIG. 3
is produced through the following processes using the press-forming apparatus 20
having the above described configuration.
[0063]
FIGS. 6(a) to (e) are cross-sectional views that schematically illustrate
working processes of press-forming (drawing) by. the press-forming apparatus of the
first embodiment of the present invention. Among these figures, FIG. 6(a)
illustrates a state before the start of forming. FIG. 6(b) illustrates a state in which a
blank metal plate is sandwiched by the blank holders. FIG. 6(c) illustrates a state in
which the blank metal plate is sandwiched using the pad. FIG. 6(d) illustrates a
state at a time point at which the preceding portion is restricted. FIG. 6(e)
illustrates a state when forming is completed.
[0064]
In the state before forming, as shown in FIG. 6(a), the upper die 40 is at top
dead center, and is separated in the upward direction from the lower die 30. In this
state, with regard to the upper die 40, the end face of the pad 41 and the second guide
face 50d of the second die 53 are arranged at the same height position. However,
the end face of the pad 41 may also be arranged at a higher position than the second
guide face 50d of the second die 53. The first guide face 50c of the preceding
portion 54 (first die 52) is arranged at a lower position than the second guide face
50d of the second die 53. On the other hand, with regard to the lower die 30, the
first blank holder 32 and the second blank holder 33 are arranged at a higher position
than the punch. Further, the first blank holder 32 is arranged at a higher position
than the second blank holder 33. According to this arrangement of the upper die 40,
at the time of press-forming, the first guide face 50c of the preceding portion 54
precedes the second guide face 50d of the second die 53. Further, the blank metal
plate 70 is placed on the lower die 30 (strictly speaking, on the first blank holder 32
and the second blank holder 33).
LO0651
From this state, the upper die 40 descends and the punch 3 1 and the die 50
move relatively in the pressing direction. Thereupon, as shown in FIG. 6(b), the
first guide face 50c of the first die 52 and the preceding portion 54 butts against the
first blank holder 32 via the blank metal plate 70. In accompaniment therewith, the
second guide face 50d of the second die 53 butts against the second blank holder 33
via the blank metal plate 70. By this means the blank metal plate 70 is sandwiched
by the preceding portion 54 (first die 52) and the first blank holder 32, and is also
sandwiched by the second die 53 and the second blank holder 33. At such time, a
restoring force of the cushion 35 is imparted through the cushion pins 34 to the first
blank holder 32 and the second blank holder 33. Further, a restoring force of the
preceding portion pressurizing mecllanism 55 is imparted to the preceding portion 54.
[0066]
Next, the upper die 40 descends further. Thereupon, as shown in FIG. 6(c),
the pad 41 butts against the punch 3 1 via the blank metal plate 70. As a result, the
blank metal plate 70 is sandwiched by the punch 3 1 and the pad 41. At such time, a
restoring force of the pad pressurizing mechanism 42 is imparted to the punch 3 1.
[0067]
The restoring force of the preceding portion pressurizing mechanism 55 that is
imparted to the preceding portion 54 is greater than the restoring force of the cushion
35 that is imparted to the first blank holder 32. Consequently, the first blank holder
32 is pushed downward by the preceding portion 54, and as shown in FIG. 6(c), a
state in which the first guide face 50c of the preceding portion 54 precedes the
second guide face 50d of the second die 53 is maintained.
[0068]
In the state in which the blank metal plate 70 is sandwiched in this manner,
the upper die 40 descends further. Thereupon, in the state in which the first guide
face 50c of the preceding portion 54 precedes the second guide face 50d of the '
second die 53, the punch 3 1 is pressed into the die 50, and the blank metal plate 70 is
worked. In due course, as shown in FIG. 6(d), the blank metal plate 70 is pressed
against the first outer side face 3 I b of the punch 3 1 to thereby substantially complete
forming of the first vertical wall portion lob in the blank metal plate 70. Forming
of the first vertical wall portion lob is also performed by the first inner side face 50a
of the first die 52 (preceding portion 54) being pressed against the blank metal plate
70. Further, forming of the first flange portion 10d in the blank metal plate 70 by
the preceding portion 54 and the first blank holder 32 is substantially completed.
On the other hand, since the state is one in which the first guide face 50c of the
preceding portion 54 precedes the second guide face 50d of the second die 53,
forming of the second vertical wall portion 10c and the second flange portioil 10e is
continuing.
[0069]
When the first vertical wall portion lob and first flange portion 10d are
formed in advance from the blank metal plate 70, the blank metal plate 70 is drawn
to the preceding portion 54 side (first die 52 side) on the curved inner side. More
specifically, the blank metal plate 70 is drawn in a direction indicated by a solid line
arrow in the above described FIG. 3.
[0070]
As shown in FIG. 6(d), in a state in which forming of the first vertical wall
portion lob and the first flange portion 10d is completed, sliding of the first blank
holder 32 and the preceding portion 54 is restricted by the restriction mechanism
(stopper) 56. By this means, a further change in the shape of the formed first
vertical wall portion lob and first flange portion 10d is prevented. Following
restriction of sliding of the first blank holder 32 in this way, sliding of the preceding
portion 54 relative to the punch 3 1 is also restricted.
[007 1 ]
The upper die 40 then descends further. Thereupon, because sliding of the
first blank holder 32 and the preceding portion 54 relative to the punch 3 1 is
restricted, the first blank holder 32 and the cushion pin 34 separate fkom each other,
and the preceding portion 54 is pressed to the die plate 51 side. On the other hand,
the second die 53 descends, and working of the second vertical wall portion 10c and
the second flange portion 10e continues.
[0072]
Subsequently, as shown in FIG. 6(e), the upper die 40 reaches bottom dead
center. By this means, forming of the second vertical wall portion 1 Oc and the
second flange portion 10e is completed. By performing press-forming in this way,
the specific press-formed product 10 illustrated in the above described FIG. 3 is
produced.
[0073]
According to the press-forming of the present embodiment, when forming of
the first vertical wall portion lob and the first flange portion 10d is substantially
completed, the blank metal plate 70 is drawn in towards the preceding portion 54
side (first die 52 side) on the curved inner side. By this means, a state is entered in
which there is a surplus of the blank metal plate 70 in the second arc-shaped region
10k of the top plate portion and the vicinity thereof. From this state, forming of the
second vertical wall portion 10c by the end face 3 1 a and the second outer side face
3 1 c of the punch 3 1 progresses and is completed. Therefore, even when a highstrength
metal plate, for example, a metal plate having a tensile strength (TS) of 590
MPa or more is used as the blank metal plate 70, a thickness reduction in the X
region (top plate portion 10a; see FIG. 4) on the curved inner side of the second arcshaped
region 10k of the top plate portion can be decreased, and as a result the
occurrence of cracks can be reduced. In accompaniment therewith, a thickness
reduction can also be decreased in the second vertical wall portion 10c on the curved
outer side of the X region.
[0074]
Further, according to the press-forming of the present embodiment, the pad 41
butts against the blank metal plate 70 on at least the curved outer side of the first arcshaped
region 10j of the top plate portion. As a result of the blank metal plate 70
being sandwiched by the pad 41 and the punch 3 1, the formation of wrinkles can be
reduced in the Y region (top plate portion 10a; see FIG. 4) on the curved outer side
of the first arc-shaped region 10j of the top plate portion. In addition, since drawing
is performed in a state in which the blank metal plate 70 is sandwiched using the first
blank holder 32 and the second blank holder 33, tension that is generated in the width
direction of the blank metal plate 70 increases. By this means also, formation of
wrinkles in the Y region can be reduced.
[0075]
In particular, by using the second blank holder 33, formation of wrinkles in
the W region (see FIG. 3) on the curved outer side of the second arc-shaped region of
the flange portion can also be reduced.
[0076]
The occurrence of cracks in the Z region (see FIG. 3) on the curved inner side
of the first arc-shaped region of the flange portion is reduced by expanding the width
of the blank metal plate 70. This is because, at the time of press-forming, a region
located on the back side in the longitudinal direction of the blank metal plate 70 is
liable to flow in towards the Z region and the periphery thereof, and as a result a
portion having excess metal is formed on the curved inner side of the first flange
portion 1 Od. A press-formed product of a desired shape can be obtained by
removing the portion having excess metal by trimming after press-forming.
[0077]
As described above, according to the press-forming of the present
embodiment, since a thickness reduction in the press-formed product 10 is decreased,
the occurrence of cracks can be reduced. Furthermore, wrinkles can be reduced.
Consequently, a change in the plate thickness of the press-formed product 10 can be
reduced. Therefore, it is possible to obtain the press-formed product 10 in which
cracks and wrinkles are reduced. The press-formed product 10 is formed using the
blank metal plate 70 which has a tensile strength of 590 MPa or more by the pressforming
of the present embodiment. Accordingly, the tensile strength of the pressformed
product 10 is 590 MPa or more, preferably 980 MPa or more, and further
preferably 1 180 MPa or more.
[007 81
The press-forming of the present embodiment is also applicable to a case
where a low-strength metal plate is used as the blank metal plate 70. In such a case,
even if the radius of curvature of the first arc-shaped region 10j of the top plate
portion is small, the press-formed product 10 in which a change in the plate thickness
as well as cracks and wrinkles are reduced can be obtained. Naturally, a problem
will not arise even if the radius of curvature of the second arc-shaped region 1 Ok of
the top plate portion is small. Furthermore, a problem will not arise even if the
depth dl of the first vertical wall portion lob or the depth d2 of the second vertical
wall portion 10c is deep. Accordingly, the degree of freedom in designing the
shape of a press-formed product is increased by using the press-forming of the
present embodiment.
[0079]
[Second Embodiment]
FIGS. 7(a) to (e) are cross-sectional views that schematically illustrate
working processes in press-forming (drawing) by a press-forming apparatus
according to a second embodiment of the present invention. Each of these drawings
illustrates a similar state as the respective drawings of FIGS. 6(a) to (e) that are
described above.
[0080]
The press-forming apparatus 20 of the second embodiment is based on the
configuration of the press-forming apparatus 20 of the first embodiment illustrated in
the above described FIG. 6. The same applies with respect to a third and fourth
embodiment that are described later. A difference between the press-forming
apparatus 20 of the second embodiment and the press-forming apparatus 20 of the
first embodiment is that the shape of the restriction mechanism is changed. In the
second embodiment, the first blank holder 32 is slidably supported in the pressing
direction by a first blank holder pressurizing mechanism 36 instead of a cushion pin.
For example, a spring, rubber, a gas cylinder or a hydraulic cylinder or the like can
be employed as the first blank holder pressurizing mechanism 36.
[OOS 1 ]
In the second embodiment, sliding of the first blank holder 32 is limited by
the stopper 56 through the first blank holder pressurizing mechanism 36. The first
blank holder 32 is restricted as a result of such limiting, and sliding of the preceding
portion 54 is restricted following such restriction of the first blank holder 32.
[0082]
[Third Embodiment]
FIG. 8 is a cross-sectional view that schematically illustrates an upper die in a
press-forming apparatus according to a third embodiment of the present invention.
A difference between the press-forming apparatus 20 of the third embodiment and
the press-forming apparatus 20 of the first and second embodiments is that the shape
of the upper die 40 is changed. In the third embodiment, the first die 52 is
constituted by a first die main body 52a and a preceding portion 54. The preceding
portion 54 of the third embodiment constitutes the entire area in the width direction
with regard to the first guide face 50c, and constitutes one portion in the vicinity of
the first guide face 50c with regard to the first inner side face 50a. The first die
main body 52a constitutes the remainder of the first inner side face 50a excluding the
preceding portion 54. The first die main body 52a is fixed to the die plate 51. The
preceding portion 54 is supported through the preceding portion pressurizing
mechanism 55 that is fixed to the first die main body 52a.
[0083]
In the case of the third embodiment, a die parting line exists between the
preceding portion 54 and the first die main body 52a. There is a risk that the die
parting line will be transferred onto the press-formed product 10. Therefore, from
the viewpoint of ensuring the surface quality of the press-formed product 10, it is
preferable to adopt the preceding portion 54 as described in the foregoing first and
second embodiments.
[0084]
In the above described first to third embodiments, the preceding portion 54
constitutes the entire area in the width direction of the first guide face 50c.
However, as long as press-forming (drawing) of the blank metal plate 70 can be
performed, a form may also be adopted in which the preceding portion 54 constitutes
one part in the width direction of the first guide face 50c.
[0085]
Further, although the preceding portion 54 may be provided across the entire
area in the longitudinal direction of the first die 52, a configuration may also be
adopted in which the preceding portion 54 is partially provided in the longitudinal
direction of the first die 52. If the preceding portion 54 is partially provided, a die
parting line will exist. The die parting line may be appropriately set, for example,
in accordance with constraints with respect to the surface quality of the press-formed
product 10, and hrthermore, in accordance with an offset load applied to a die and a
press machine. Indeed, from the viewpoint of ensuring the surface quality of the
press-formed product 10, it is preferable that the preceding portion 54 is provided
across the entire area in the longitudinal direction of the first die 52.
[0086]
FIG. 9 is a plan view of a press-formed product that schematically illustrates
one example of a region that the preceding portion butts against at bottom dead
center. The preceding portion 54 butts against at least a region 1 On (see hatched
portion in FIG. 9) on the curved inner side of the first arc-shaped region 101 of the
flange portion (thick line in FIG. 9). This is to decrease a thickness reduction in the
X region (see FIG. 4) on the curved inner side of the second arc-shaped region 10k of
the top plate portion. Together therewith, it is to reduce the occurrence of cracks in
the Z region (see FIG. 3) of the first flange portion 10d.
[0087]
FIG. 10 is a plan view of a press-formed product that schematically illustrates
an example of a region that the pad butts against at bottom dead center. The pad 41
butts against at least a region 1 Om (see hatched portion in FIG. 10) on the curved
outer side of the first arc-shaped region 10j of the top plate portion (see thick line in
FIG. 10). This is to reduce wrinkles in the Y region (see FIG. 4) of the top plate
portion 10a. As shown in FIG. 10, the region 1 Om that the pad 41 butts against may
include, among the entire region of the top plate portion 1 Oa, a frontward region in
the longitudinal direction of the curved region. Further, the region 1 Om that the pad
41 butts against may be the entire region of the top plate portion 1Oa. In this case,
as necessary, the pad 41 may be arranged in a divided state in the longitudinal
direction.
[0088]
In short, the pad 41 is arranged so as to butt against at least the wrinkle
occurrence region of the top plate portion 1 Oa. In many cases, the wrinkle
occurrence region exists in the Y region (see FIG. 4) on the curved outer side of the
first arc-shaped region 10j of the top plate portion (see the thick line in FIG. 10).
The wrinkle occurrence region can be ascertained by FEM analysis. Further, the
wrinkle occurrence region can also be ascertained by producing a press-formed
product by a conventional common press-forming method, and examining the
surface properties of the press-formed product.
[0089]
In this case, as described above, the occurrence of cracks in the Z region (see
FIG. 3) on the curved inner side of the first arc-shaped region of the flange portion
can be reduced by expanding the width of the blank metal plate 70 and fornling a
portion having excess metal on the curved inner side of the first flange portion 1 Od.
In such a case, at the time of press-forming, a region that is located on the back side
in the longitudinal direction of t6e blank metal plate 70 flows in towards the Z region
and the periphery thereof. To prevent the aforementioned inflow from being
obstructed, in a case where the pad 41 is caused to butt against the region located on
the back side in the longitudinal direction of the blank metal plate 70, it is preferable
to appropriately set the pressing force of the pad 41.
[0090]
In the press-forming of the present embodiment, the first guide face 50c of the
preceding portion 54 is arranged so as to precede the second guide face 50d of the
second die 53. A preceding amount m (unit: mm; see FIG. 5) of the preceding
portion 54 is set by taking as an index a ratio (hereunder, also referred to as
"preceding amount ratio") R that the preceding amount m occupies with respect to
the depth d2 (unit: mm; see FIG. 3(b)) of the second vertical wall portion 1 Oc. The
preceding amount m of the preceding portion 54 is appropriately set in accordance
with the shape of the press-formed product 10 and the material quality of the blank
metal plate 70, and for example is set so that the preceding amount ratio R is 3 to
100%. From the viewpoint of further reducing the occurrence of cracks in the X
region (see FIG. 4), the viewpoint of an offset load that is loaded on the die and the
press machine, and the viewpoint of reducing the occurrence of wrinkles while
improving production efficiency, it is preferable to set the preceding amount m of the
preceding portion 54 so that the preceding amount ratio R is 10 to 70%. The
preceding amount m can also be said to be a stroke difference between the preceding
portion 54 and the second die 53 (that is, a difference between the respective
remaining strokes until bottom dead center) during a pushing-in process.
[009 1 ]
The arrangement of the preceding portion 54 at an early stage of a pushing-in
process can be evaluated by means of a height difference n (unit: mm; see the above
described FIG. 5) between the first guide face 50c of the preceding portion 54 and
the second guide face 50d of the second die 53. The height difference n takes a
positive value in a state in which the first guide face 50c of the preceding portion 54
protrudes relative to the second guide face 50d of the second die 53, as shown in the
aforementioned FIG. 5,' and takes a negative value in a state in which the second
guide face 50d protrudes relative to the first guide face 50c of the preceding portion
54.
[0092]
In the press-forming of the present embodiment, whatever value the height
difference n between the first guide face 50c and the second guide face 50d is among
a positive value, 0 (zero) and a negative value, the occurrence of cracks in the X
region can be reduced. From the viewpoint of reducing the occurrence of cracks in
the X region to a greater extent, preferably the height difference n between the first
guide face 50c and the second guide face 50d is made a positive value, and the state
in the early stage of the pushing-in process is a state in which the first guide face 50c
of the preceding portion 54 protrudes relative to the second guide face 50d of the
second die 53. On the other hand, from the viewpoint of an offset load that is
loaded on the die and the press machine as well as from the viewpoint of reducing
the occurrence of wrinkles while improving the production efficiency, preferably the
height difference n between the first guide face 50c and the second guide face 50d is
made a smaller value than the depth dl of the first vertical wall portion lob.
[0093]
A boundary portion 10i between the second vertical wall portion 10c and the
second flange portion 10e of the press-formed product 10 includes a substantially
quarter arc-shaped region 10q (second arc-shaped region of the flange portion) that
curves along a curved region of the top plate portion 10a (see FIG. 12 that is
described later). In the press-forming of the present embodiment, a distance
between the second blank holder 33 and the second die 53 is preferably maintained
in a state in which the distance is greater than the plate thickness of the blank metal
plate 70 at least in a region on the curved outer side of the second arc-shaped region
10q of the flange portion. By this means, it is possible to promote an inflow into
the die impression of the die 50 of a region of the blank metal plate 70 that butts
against the second blank holder 33. As a result, a thickness reduction in the X
region (see FIG. 4) of the press-formed product 10 can be decreased. Furthermore,
a thickness reduction can also be decreased in the second vertical wall portion 10c on
the curved outer side of the X region.
100941
A configuration that maintains a distance between the second blank holder 33
and the second die 53 in a state in which the distance is greater than the plate
thickness of the blank metal plate 70 can be realized, for example, by providing a
step height in mutually facing surfaces of the second blank holder 33 and the second
die 53. Further, for example, such a configuration can be realized by providing,
between the second blank holder 33 and the second die 53, a distance block that
serves as a die surface contacting portion of the second blank holder 33 and the
second die 53. Such a configuration can also be realized by combining the second
blank holder 33 and the second die 53.
100951
In the case of adopting a configuration that maintains a distance between the
second blank holder 33 and the second die 53 in a state in which the distance is
greater than the plate thickness of the blank metal plate 70, if the distance between
the second blank holder 33 and the second die 53 is too large, there is a risk that
wrinkles will arise in the W region (see FIG. 3). Therefore, it is sufficient to
appropriately set the distance between the second blank holder 33 and the second die
53 to a level such that wrinkles do not arise in the W region. The distance d (mm)
between the second blank holder 33 and the second die 53 can be set, for example, so
as to satisfy the following Formula (2).
tb x 1 .O1 5 d 5 tb x 1.50 ...( 2)
In the above Formula (2), tb represents the plate thickness (mm) of the blank
metal plate.
[0096]
As described above, in a case where cracks in the Z region (see FIG. 3) is
reduced by forming a portion having excess metal on a curved inner side of the first
flange portion 1 Od, it is more preferable to maintain a distance between the second
blank holder 33 and the second die 53 in a state in which the distance is greater than
the plate thickness of the blank metal plate 70 in a region (see hatched portion
denoted by reference character "lop" in FIG. 12 that is described later) that, among
the entire region of the second flange portion 1 Oe, is rearward in the longitudinal
direction from the second arc-shaped region 10q of the flange portion. In addition,
it is more preferable to maintain a distance between the first blank holder 32 and the
first die 52 (preceding portion 54) in a state in which the distance is greater than the
plate thickness of the blank metal plate 70 in a region (see hatched portion denoted
by reference character "1 00" in FIG. 12 that is described later) that, among the entire
region of the first flange portion 1 Od, is rearward in the longitudinal direction from
the first arc-shaped region 101 of the flange portion.
[0097]
By this means, a thickness reduction in the X region (see FIG. 4) of the pressformed
product 10 can be decreased, and a thickness reduction can also be decreased
in the second vertical wall portion 10c on the curved outer side of the X region.
Furthermore, an effect that reduces cracks in the Z region (see FIG. 3) is enhanced.
[0098]
In the press-forming of the present embodiment there is not limitation with
respect to the order of sandwiching the blank metal plate 70. Sandwiching using
the pad 41 may be executed after sandwiching by the first blank holder 32 and
second blank holder 33 as in the working processes illustrated in the above described
FIG. 6 and FIG. 7, or sandwiching may be executed in the reverse order thereto.
[0099]
Although in the press-forming apparatus illustrated in the above described
FIG. 5 to FIG. 8 a configuration is adopted in which a die and a pad are arranged as
an upper die, and a punch and blank holders are arranged as a lower die, a
configuration may also be adopted in which the arrangement of the upper and lower
dies is inverted in the vertical direction.
[Ol 001
Note that, a restriking process may be added after the press-forming of the
present embodiment. In the restriking process a region having an incomplete shape
(for example, a minute R portion or the like) is finished into a final shape.
[OIOI]
The specific press-formed product 10 that is produced by the press-forming of
the present embodiment is applied not only to a front pillar lower outer reinforcement,
but also to structural members such as a side sill inner, a side sill outer reinforcement
rear, a front side member and a rear side member.
[O 1 021
In the case of a specific press-formed product that is applied to the
aforementioned structural members, a central angle of the first arc-shaped region 1 Oj
of the top plate portion and the second arc-shaped region 10k of the top plate portion
is designed to be, for example, 15 to 120'. Further, the radius of curvature of the
first arc-shaped region 10j of the top plate portion is designed to be, for example, 30
to 600 mm. The radius of curvature of the second arc-shaped region 10k of the top
plate portion is designed to be, for example, 10 to 600 mm, or a (a straight line).
The depth dl of the first vertical wall portion lob is designed to be, for example, 20
to 300 mm, and the depth d2 of the second vertical wall portion 1 Oc is designed to be,
for example, 20 to 300 mm.
[0 1 031
More specifically, in a case of using the specific press-formed product as a
rear side member, the central angle of the arc-shaped regions 10j and 1 Ok is set to,
for example, 15 to 85O. Further, the radius of curvature of the first arc-shaped
region l0j of the top plate portion is set to, for example, 30 to 600 mm. The radius
of curvature of the second arc-shaped region 10k of the top plate portion is set to, for
example, 30 to 600 inm. The depth dl of the first vertical wall portion is set to, for
example, 30 to 300 mm, and the depth d2 of the second vertical wall portion is set to,
for example, 30 to 300 mm.
[0 1 041
In a case of using the specific press-formed product as a front pillar lower
outer reinforcement, the central angle of the arc-shaped regions 10j and 10k is set to,
for example, 60 to 120". Further, the radius of curvature of the first arc-shaped
region l0j of the top plate portion is set to, for example, 30 to 200 mm. The radius
of curvature of the second arc-shaped region 10k of the top plate portion is set to, for
example, 10 to 200 mm. The depth dl of the first vertical wall portion and the
depth d2 of the second vertical wall portion are set to, for example, 20 to 200 mm.
[0 1 051
In the case of using the specific press-formed product as a front pillar inner,
the central angle of the arc-shaped regions 10j and 1 Ok is set to, for example, 60 to
120". Further, the radius of curvature of the first arc-shaped region 10j of the top
plate portion is set to, for example, 30 to 200 mm. The radius of curvature of the
second arc-shaped region 1 Ok of the top plate portion is set to, for example, 10 to 200
mm. The depth dl of the first vertical wall portion and the depth d2 of the second
vertical wall portion are set to, for example, 20 to 200 mm.
[O 1 061
In the case of using the specific press-formed product as a side sill outer
reinforcement rear, the central angle of the arc-shaped regions 10j and 10k is set to,
for example, 15 to 85". Further, the radius of curvature of the first arc-shaped
region l0j of the top plate portion is set to, for example, 30 to 400 mm. The radius
of curvature of the second arc-shaped region 10k of the top plate portion is set to, for
example, 70 to oo (a straight line) mm. The depth dl of the first vertical wall
portion and the depth d2 of the second vertical wall portion are set to, for example,
20 to 200 mm.
[0 1071
[Fourth Embodiment]
FIGS. 11 (a) to (g) are cross-sectional views that schematically illustrate
working processes according to press-forming of a fourth embodiment of the present
invention. In the fourth embodiment, the working processes of the press-forming
are divided into two stages. Although a press-formed product that is ultimately
obtained by the press-forming of the fourth embodiment is the same as the pressformed
product obtained by the press-forming of the first to third embodiments, the
press-formed product obtained according to the fourth embodiment is formed into a
finished product afier undergoing a first stage and a second stage in order. In other
words, separate press-forming apparatuses are used for each stage, with an
intermediate product being formed from a blank metal plate in the first stage, and the
intermediate product being finished into a finished product in the second stage.
Although the intermediate product is a product in which the top plate portion, the
first vertical wall portion on the curved inner side of the top plate portion, and the
first flange portion that is connected to the first vertical wall portion are co~npletely
formed, the intermediate product is also a product in which the second vertical wall
portion on the curved outer side of the top plate portion as well as the second flange
portion that is connected to the second vertical wall portion are partly formed.
[0 1 081
FIGS. 11 (a) to (d) illustrate working processes in the first stage. Among
these figures, FIG. 1 ](a) illustrates a state before the start of forming in the first stage.
FIG. I 1 (b) illustrates a state in which a blank metal plate is sandwiched by the blank
holders. FIG. 1 I (c) illustrates a state in which the blank metal plate is sandwiched
using the pad. FIG. 1 l(d) illustrates a state when forming in the first stage is
completed. FIGS. I l(e) to (g) illustrate working processes in the second stage.
Among these figures, FIG. 1 l(e) illustrates a state before the start of forming in the
second stage. FIG. 1 l(f) illustrates a state when forming starts. FIG. 1 I (g)
illustrates a state when forming in the second stage is completed.
[0 1 091
As shown in FIGS. 1 1 (a) to (d), a press-forming apparatus 20A that is used in
the first stage differs from the press-forming apparatus 20 of the first and second
embodiments in the following respects. With regard to the upper die 40 and the die
50, the first die 52 and the preceding portion 54 that are arranged on the curved inner
side of the punch 3 I are integrated and fixed to the die plate 51. In other words, the
preceding portion pressurizing mechanism 55 included in the first to third
embodiments is not provided. Similarly to the first to third embodiments, the die
impression of the first die 52 and the preceding portion 54 is a portion in which the
shape of the finished product is reflected.
[Ol lo]
Further, in the first stage, the second die 53 that is arranged on the curved
outer side of the punch 3 1 is fixed to the die plate 5 1, similarly to the first to third
embodiments. However, the die impression of the second die 53 is a portion in
which the shape of the finished product is partly reflected. In other words, the
depth in the pressing direction of the inner side face 50b of the second die 53 is
shallower than the depth of the second vertical wall portion of the finished product.
[OI 111
With regard to the lower die 30 used in the first stage, the stopper 56 that
limits a sliding movement of the first blank holder 32 as described in the first to third
embodiments is not provided.
[0112]
As shown in FIGS. 1 l(e) to (g), a press-forming apparatus 20B that is used in
the second stage differs from the press-forming apparatus 20 of the first and second
embodiments in the following respects. With regard to the upper die 40 and the die
50, the first die 52 and the preceding portion 54 that are arranged on the curved inner
side of the punch 3 1 are integrated in a manner that includes the pad 41. The
integrated first die 52, preceding portion 54 and pad 41 are supported through the pad
pressurizing mechanism 42. The preceding portion pressurizing mechanism 55
provided in the first to third embodiments is not provided. Similarly to the first to
third embodiments, a die impression of the first die 52, the preceding portion 54 and
the pad 41 is a portion in which the shape of the finished product is reflected.
[0113]
Further, in the second stage, similarly to the first to third embodiments, the
second die 53 that is arranged on the curved outer side of the punch 3 1 is fixed to the
die plate 5 1. Furthermore, similarly to the first to third embodiments, the die
impression of the second die 53 is a portion in which the shape of the finished
product is reflected.
[OI 141
With regard to the lower die 30 that is used in the second stage, the first blank
holder 32 that is adjacent to the curved inner side of the punch 3 I is integrated with
the punch 3 I . In other words, the cushion pin 34 that supports the first blank holder
32 in the configurations of the first to third embodiments is not provided.
[OllS]
As shown in FIGS. 1 l(a) to (d), in the press-forming by the press-forming
apparatus 20A in the first stage, the upper die 40 descends and the punch 3 1 and the
die 50 move relatively in the pressing direction. In accompaniment therewith,
similarly to the first to third embodiments, the first guide face 50c of the preceding
portion 54 (first die 52) precedes the second guide face 50d of the second die 53.
The shapes of the first vertical wall portion lob and the first flange portion 10d are
then formed in the blank metal plate 70. In addition, the shapes of the second
vertical wall portion 10c and the second flange portion 10e are partly formed in the
blank metal plate 70. An intermediate product 71 is fonned by such press-forming
of the first stage.
[OI 161
As shown in FIGS. 1 l(e) to (g), in the press-forming by the press-fonning
apparatus 20B in the second stage, the upper die 40 descends and the punch 3 1 and
die 50 move relatively in a pressing direction. In accompaniment therewith,
similarly to the first to third embodiments, sliding of the first blank holder 32 and the
preceding portion 54 is restricted. In addition, corresponding to descent of the
second die 53, the shapes of the second vertical wall portion 10c and the second
flange portion 10e are formed. The specific press-formed product 10 illustrated in
the above described FIG. 3 is produced by the press-forming in which the first stage
and the second stage are performed in order in this way.
[0117]
In the fourth embodiment also, because forming of the first vertical wall
portion lob and the first flange portion 10d precedes fornling of the second vertical
wall portion 10c and the second flange portion 1 Oe, the same advantageous effects as
in the first to third embodiments are obtained.
EXAMPLES
[0118]
FEM analysis as described in the following Examples 1 and 2 was performed
to verify the effect of the present invention.
[0119]
[Example 11
In the FEM analysis of Example 1, a blank metal plate was formed into a
specific press-formed product using the press-forming apparatus of the above
described first embodiment. The plate thickness decrease rate, cracks and wrinkles
in respective portions were evaluated with respect to the press-fonned product that
was obtained.
[0120]
A dual-phase, high strength steel plate having a tensile strength of the 980
MPa-class and a plate thickness of 1.6 mm was adopted as the blank metal plate.
The shape of the blank metal plate was set so that a portion having excess metal with
a width of a maximum of around 97 mm is formed on the curved inner side of the
first flange portion having a width of approximately 15 mrn in the press-formed
product that is obtained.
[012 11
The radius of curvature of the first arc-shaped region of the top plate portion
of the press-formed product was set as 80 mm. The radius of curvature of the
second arc-shaped region of the top plate portion of the press-formed product was set
as 36 mm. The depth dl of the first vertical wall portion was set as 44 mm, and the
depth d2 of the second vertical wall portion was set as 51 mrn.
[OI 221
The preceding portion was arranged so that the preceding amount m was 25
mm, and the height difference n between the first guide face and the second guide
face was set as 18 mm. The pressing force of the pad was set as approximately 100
kN. The pressing forces of the first blank holder and second blank holder were set
in accordance with the actual length in the longitudinal direction of the first flange
portion and the second flange portion, respectively, with the pressing force of the
first blank holder being set to approximately 160 kN and the pressing force of the
second blank holder being set to approximately 260 kN. The pressing force of the
preceding portion was set to approximately 600 kN.
[O 1231
The preceding portion was provided across the entire area in the longitudinal
direction of the first die. On the other hand, the pad was provided in the region 1 Om
shown in the above described FIG. 10. A step height of 0.1 mm was provided in
one part of the top face of the first blank holder, and a distance between the first
blank holder and the preceding portion (first die) was maintained in a state in which
the distance was greater than the plate thickness of the blank metal plate. A step
height of 0.1 mm was provided in one part of the top face of the second blank holder,
and a distance between the second blank holder and the second die was maintained in
a state in which the distance was greater than the plate thickness of the blank metal
plate.
[0 1241
FIG. 12 is a plan view that schematically illustrates a press-formed product
produced by press-forming according to Example 1. A region 100 that is indicated
by a hatched portion among the entire region of the first flange portion 10d is a
region at which the distance between the first blank holder and the preceding portion
(first die) is maintained in a state in which the distance is greater than the plate
thickness of the blank metal plate by means of the step height provided on the top
face of the first blank holder. A region lop that is indicated by a hatched portion
among the entire region of the second flange portion 10e is a region at which the
distance between the second blank holder and the second die is maintained in a state
in which the distance is greater than the plate thickness of the blank metal plate by
means of the step height provided on the top face of the second blank holder.
[0125]
The region 100 of the first flange portion 1 Od is taken as a region on the
curved inner side of the first arc-shaped region 101 of the flange portion, the entire
region that is rearward in the longitudinal direction from the arc-shaped region 101,
and a neighboring region to the front in the longitudinal direction of the arc-shaped
region 101. The region lop of the second flange portion 1 Oe is taken as a region on
the curved outer side of the second arc-shaped region 10q of the flange portion, the
entire region that is rearward in the longitudinal direction from the arc-shaped region
1 Oq, and a neighboring region to the front in the longitudinal direction of the arcshaped
region 10q.
101261
FIG. 13 is a view that illustrates the distribution of a plate thickness decrease
rate when the specific press-formed product was produced by press-forming
according to Example 1. In FIG. 13, the plate thickness decrease rates are indicated
by degrees of shading, and the shape of the blank metal plate 70 prior to pressforming
is indicated by a solid line. The plate thickness decrease rate rtb (%) was
calculated by the above described Formula (1). The plate thickness decrease rate is
a rate of decrease (%) in the plate thickness based on the thickness of the blank metal
plate 70.
[0 1 271
The results shown in FIG. 13 indicate the following facts. In the X region of
the top plate portion, a thickness reduction was decreased, and the occurrence of
cracks was suppressed. In the Y region of the top plate portion, the occurrence of
wrinkles was suppressed. In the Z region of the first flange portion, the occurrence
of cracks was suppressed. In the W region of the second flange portion, the
occurrence of wrinkles was suppressed. The plate thickness decrease rate for the
entire press-formed product was from - 10 to 1 1 %, and thus a change in the plate
thickness was reduced.
101281
[Example 21
In the FEM analysis of Example 2, the specific press-formed product was
formed using a similar press-forming apparatus and blank metal plate as in Example
1, and the preceding amount m of the preceding portion, that is, the stroke difference
between the preceding portion and the second die was changed to various values.
The plate thickness decrease rate, cracks and wrinkles in respective portions were
evaluated with respect to the press-formed product that was obtained. Note that, in
the press-formed product of Example 2, the depth dl of the first vertical wall portion
and the depth d2 of the second vertical wall portion were made deeper than the
corresponding depth dl and depth d2 in the press-formed product of Example 1. In
other words, in the press-formed product of Example 2, the depth dl of the first
vertical wall portion was made 55 mm and the depth d2 of the second vertical wall
portion was made 60 mm.
[0129]
FIG. 14 is a view that illustrates one example of the distribution of the plate
thickness decrease rate when the specific press-formed product was produced by the
press-forming of Example 2. FIGS. 15(a) to (c) are views that illustrate the relation
between a stroke difference between dies and the plate thickness decrease rate as
results of Example 2. Among these figures, FIG. 15(a) illustrates the result for the
Z region of the first flange portion. FIG. 15(b) illustrates the result for the X region
of the top plate portion. FIG. 15(c) illustrates the result for the Y region of the top
plate portion.
[0130]
The results shown in FIG. 14 and FIGS. 15(a) to (c) indicate the following
facts. In a region in which the stroke difference between the preceding portion and
the second die was in a range of 10 to 40 mm, cracks did not arise in the Z region and
X region, and there was also no occurrence of wrinkles in the Y region. The stroke
difference, that is, the preceding amount m, being 10 to 40 mm corresponds to the
preceding amount ratio R (ratio which the preceding amount m occupies with respect
to the depth d2 of the second vertical wall portion) being 10 to 70%. Thus, it was
found that under conditions such that the preceding amount ratio R becomes 10 to
70%, cracks and wrinkles at respective portions of the press-formed product are
reduced.
INDUSTRIAL APPLICABILITY
[0131]
The present invention can be effectively used in the production of structural
members of an automobile body.
REFERENCE SIGNS LIST
[0132]
10: Press-formed product
10a: Top plate portion
lob: First vertical wall portion
10c: Second vertical wall portion
10d: First flange portion
10e: Second flange portion
20,20A, 20B: Press-forming apparatus
30: Lower die
3 1 : Punch, 3 1 a: End face of punch
3 1 b: First outer side face of punch
3 1 c: Second outer side face of punch
32: First blank holder
33: Second blank holder
34: Cushion pin, 35: Cushion
36: First blank holder pressurizing mechanism
37: Second blank holder pressurizing mechanism
40: Upper die
41: Pad
42: Pad pressurizing mechanism
50: Die
50a: First inner side face of die
50b: Second inner side face of die
50c: First guide face of die
50d: Second guide face of die
5 1 : Die plate
52: First die
52a: First die main body
53: Second die
54: Preceding portion
55: Preceding portion pressurizing mechanism
56: Stopper
70: Blank metal plate

We claim:
1. A press-forming apparatus for producing a press-fonned product having an
external shape that curves in an L shape along a longitudinal direction in a planar
view,
wherein the press-fonned product coniprises:
a top plate portion including an L-shaped curved region;
a first vertical wall portion that is connected to a side portion on a curved
inner side among two side portions of the top plate portion;
a second vertical wall portion that is connected to a side portion on a curved
outer side among the two side portions of the top plate portion;
a first flange portion that is connected to the first vertical wall portion; and
a second flange portion that is connected to the second vertical wall portion,
the press-forming apparatus comprising:
a punch having an end face, a first outer side face and a second outer side face
that have shapes that correspond to the top plate portion, the first vertical wall
portion and the second vertical wall portion, respectively;
a first blank holder that is adjacent to a curved inner side of the punch, and is
slidable in a pressing direction;
a second blank holder that is adjacent to a curved outer side of the punch, and
is slidable in the pressing direction;
a die that forms a pair with the punch, the first blank holder, and the second
blank holder, and that has a first inner side face and a second inner side face having
shapes that correspond to the first vertical wall portion and the second vertical wall
portion, respectively, and has a first guide face and a second guide face that face the
first blank holder and the second blank holder, respectively;
a pad that constitutes one part of the die and is slidable in the pressing
direction, and among an entire region of the end face of the punch, faces at least a
region that corresponds to the curved region of the top plate portion;
a preceding portion that constitutes one part of the die and is slidable in the
pressing direction, and among an entire region of the first guide face and the first
inner side face, includes at least a region that corresponds to the curved region of the
top plate portion; and
a restriction mechanism,
and wherein, when pushing the punch into the die by relatively moving the
punch and the die in the pressing direction to for111 a metal plate into the pressformed
product, after the first guide face of the preceding portion precedes the
second guide face of the die and the first vertical wall portion and the first flange
portion are fonned, sliding of the first blank holder and the preceding portion relative
to the punch is restricted by the restriction mechanism, and pushing of the punch into
the die is continued in the restricted state and the second vertical wall portion and the
second flange portion are formed.
2. The press-forming apparatus according to claim I , further comprising:
a cushion that slidably supports the first blank holder in the pressing direction
via a cushion pin; and
a stopper that limits sliding of the first blank holder,
wherein, by separating the cushion pin and the first blank holder while sliding
of the first blank holder is being limited by the stopper, the restriction mechanism
restricts sliding of the first blank holder, and restricts sliding of the preceding portion
following restriction of the first blank holder.
3. The press-forming apparatus according to claim I, further comprising:
a pressurizing mechanism that slidably supports the first blank holder in the
pressing direction;
wherein the restriction mechanism restricts the first blank holder by limiting
sliding of the first blank holder, and restricts sliding of the preceding portion
following restriction of the first blank holder.
4. A method for producing a press-formed product having an external shape that
curves in an L shape along a longitudinal direction in a planar view,
the press-formed product comprising:
a top plate portion including an L-shaped curved region;
a first vertical wall portion that is connected to a side portion on a curved
inner side among two side portions of the top plate portion;
a second vertical wall portion that is connected to a side portion on a curved
outer side among the two side portions of the top plate portion;
a first flange portion that is connected to the first vertical wall portion; and
a second flange portion that is connected to the second vertical wall portion,
wherein, when producing the press-formed product from a metal plate by
press-forming, forming of the first vertical wall portion and the first flange portion is
executed prior to forming of the second vertical wall portion and the second flange
portion.
5. The method for producing a press-formed product according to claim 4, that
uses a press-forming apparatus according to any one of claims 1 to 3, including:
a holding process of, in a state in which the first guide face of the preceding
portion precedes the second guide face of the die, sandwiching the metal plate by
means of the first blank holder, the second blank holder and the pad, and
a forming process of pushing the punch into the die by relatively moving the
punch and the die in a pressing direction to form the metal plate into the pressformed
product,
wherein the forming process includes:
a first step of, in a state in which the first guide face of the preceding portion
precedes the second guide face of the die, pushing the punch into the die to form the
first vertical wall portion and the first flange, and
a second step of restricting sliding of the first blank holder and the preceding
portion relative to the punch by means of the restriction mechanism, and continuing
pushing of the punch into the die in the restricted state to form the second vertical
wall portion and the second flange portion.
6. A press-formed product having an external shape that curves in an L shape
along a longitudinal direction in a planar view, comprising:
a top plate portion including an L-shaped curved region;
a first vertical wall portion that is connected to a side portion on a curved
inner side among two side portions of the top plate portion;second vertical wall portion that is connected to a side portion on a curved
outer side among the two side portions of the top plate portion;
a first flange portion that is connected to the first vertical wall portion; and
a second flange portion that is connected to the second vertical wall portion,
wherein a tensile strength thereof is 590 MPa or more.
7. The press-formed product according to claim 6, wherein a tensile strength
thereof is 980 MPa or more.
8. The press-fonned product according to claim 6, wherein a tensile strength
thereof is 1 180 MPa or more.