U.S. patent application number 15/068029 was filed with the patent office on 2016-09-15 for bottomed container and method for manufacturing the same.
This patent application is currently assigned to Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.). The applicant listed for this patent is Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.). Invention is credited to Masatoshi YOSHIDA.
Application Number | 20160263639 15/068029 |
Document ID | / |
Family ID | 56886394 |
Filed Date | 2016-09-15 |
United States Patent
Application |
20160263639 |
Kind Code |
A1 |
YOSHIDA; Masatoshi |
September 15, 2016 |
BOTTOMED CONTAINER AND METHOD FOR MANUFACTURING THE SAME
Abstract
A method includes a main forming step in which a blank in which
creases are formed by a preforming step is set between a die and a
punch such that the die and the punch correspond to the shape of
the blank, and is press-formed to form a square tubular component
as a bottomed container. When, in the main forming step, a rib
protruding outward from between each adjacent two of the vertical
walls of the bottomed container in plan view is formed in press
forming, a slit is provided in each of the corner portions of the
inner side surface of the die.
Inventors: |
YOSHIDA; Masatoshi;
(Kobe-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.) |
Kobe-shi |
|
JP |
|
|
Assignee: |
Kabushiki Kaisha Kobe Seiko Sho
(Kobe Steel, Ltd.)
Kobe-shi
JP
|
Family ID: |
56886394 |
Appl. No.: |
15/068029 |
Filed: |
March 11, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B65D 5/242 20130101;
B21D 51/18 20130101; B21D 22/26 20130101; B21D 51/52 20130101 |
International
Class: |
B21D 22/20 20060101
B21D022/20; B21D 22/26 20060101 B21D022/26; B21D 51/18 20060101
B21D051/18; B65D 1/22 20060101 B65D001/22 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 13, 2015 |
JP |
2015-051445 |
Claims
1. A bottomed container comprising: a bottom portion; and a
plurality of vertical walls rising from the peripheral edge of the
bottom portion, wherein the bottomed container is formed by
press-forming a blank, and has a plurality of corner portions
integral with the bottom portion and the vertical walls adjacent to
each other, the corner portions are each provided with one or more
ribs that protrude outward or inward from between the vertical
walls adjacent to each other in plan view, the ribs are each
composed of a pair of folded flanges that are folded along creases
that are preformed in the blank so as to substantially equally
divide an area that will become one of the corner portions, the
amount of outward or inward protrusion of the ribs becomes larger
from the bottom portion toward the open end of the vertical walls
in side view, and the ribs are provided with no flanges extending
outward from the open ends of the ribs in plan view.
2. The bottomed container according to claim 1, wherein the corner
portions have a substantially arc shape in plan view, and the one
or more ribs formed in each of the corner portions having a
substantially arc shape are two to four ribs.
3. The bottomed container according to claim 2, wherein recesses or
protrusions that are continuous in plan view and that correspond to
the ribs protruding outward or inward from the corner portions
having a substantially arc shape are formed in the bottom
portion.
4. The bottomed container according to claim 3, wherein the
recesses or protrusions provided in the bottom portion are formed
so as to extend radially from the center of each of the corner
portions having a substantially arc shape in plan view.
5. The bottomed container according to claim 1, wherein the
bottomed container is provided with flanges extending outward from
the open ends of the vertical walls.
6. A method for manufacturing the bottomed container according to
claim 1, the method comprising: a preforming step comprising
forming creases in a blank having areas that will become the bottom
portion, the plurality of vertical walls, and the plurality of
corner portions of the bottomed container after press forming using
a preforming die, the creases being formed at borders between an
area that will become the bottom portion and areas that will become
the vertical walls, borders between the areas that will become the
vertical walls and areas that will become the corner portions, and
positions for substantially equally dividing the areas that will
become the corner portions; and a main forming step comprising
setting the blank, in which creases are formed by the preforming
step, between a die and a punch such that the die and the punch
correspond to the shape of the blank, and press-forming said blank
to form the bottomed container, wherein in the main forming step,
when one or more ribs protruding outward from between each adjacent
two of the vertical walls of the bottomed container in plan view
are formed in press forming, slits are provided in corner portions
of the die, and when one or more ribs protruding inward from
between each adjacent two of the vertical walls of the bottomed
container in plan view are formed in press forming, slits are
provided in corner portions of the outer side surface of the
punch.
7. The method for manufacturing a bottomed container according to
claim 6, wherein in the preforming step, the number of creases
formed for substantially equally dividing each of the areas that
will become the corner portions is three to seven.
8. The method for manufacturing a bottomed container according to
claim 6, wherein the inside of each of the corner portions of the
die is formed such that the radius of curvature of the inscribed
circle is R1 in plan view, the corner portions of the outer side
surface of the punch are formed in a shape having a curved surface
having a radius of curvature of R2 in plan view corresponding to
the inscribed circle of each of the corner portions of the die, the
clearance between the punch and the die defined as R1-R2 is set to
100% to 200% of the thickness of the blank, and R1>R2.
9. The method for manufacturing a bottomed container according to
claim 8, wherein in the main forming step, when one or more ribs
protruding outward from between each adjacent two of the vertical
walls of the bottomed container in plan view are formed in press
forming, slits are provided in the corner portions of the bottom
surface of the die, and when one or more ribs protruding inward
from between each adjacent two of the vertical walls of the
bottomed container in plan view are formed in press forming, slits
are provided in the corner portions of the bottom surface of the
punch.
10. The method for manufacturing a bottomed container according to
claim 9, wherein the slits provided in the corner portions of the
bottom surface of the die or the corner portions of the bottom
surface of the punch are formed so as to extend radially from the
center of each corner portion.
11. The method for manufacturing a bottomed container according to
claim 6, wherein flanges extending outward from the outer side
surface other than the corner portions of the punch are provided at
the upper end of the punch.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a bottomed container that
is formed from a blank by press forming and that has a large
forming height, and to a method for manufacturing the same.
[0003] 2. Description of the Related Art
[0004] A fuel tank, a battery tray, and the like mounted on a
vehicle are often bottomed, substantially circular tubular or
square tubular components formed from a plate material by press
deep drawing forming. Such a fuel tank, such a battery tray, and
the like are required to have a watertight structure, and are
therefore integrally formed by press forming. In addition, they are
desired to have as large an internal capacity as possible, and are
therefore desired to have as small a corner R in plan view as
possible, and as large a forming height as possible.
[0005] However, there is a problem in that in the press deep
drawing forming, the smaller the corner R, and the larger the
forming height, the more easily a rupture occurs, and the more
difficult the forming.
[0006] As a technique to solve such a problem, there has been
proposed a technique that reduces the drawing resistance and
improves the forming limit (see, for example, Japanese Patent No.
4985909). This technique holds a material with a blank holder and a
die, provides a recess in part of the die, actively generates a
crease in this part, thereby forms a folded flange, reduces the
drawing resistance of a flange in a corner portion, and thereby
improves the forming limit.
[0007] As another technique to solve the above problem, there has
been proposed a forming method that forms a pair of folded flanges
folded into the inside of a corner portion of a tubular component
without using a blank holder (see, for example, Japanese Patent No.
3454656). This technique can perform manufacture by bending forming
almost without drawing forming, and therefore promises significant
improvement of forming limit.
[0008] However, the technique disclosed in Japanese Patent No.
4985909 has a problem in that because forming is performed by deep
drawing forming, there is a limit on reduction of drawing
resistance, and when forming a very deep product (that is, a
product having a large forming height), a rupture occurs.
[0009] The art disclosed in Japanese Patent No. 3454656 has a
problem in that in order to form a pair of folded flanges folded
into the inside of a corner portion, a die and a punch need to be
provided with a pair of special machined parts, that is, a die
needs to be provided with a special guide protrusion, and a punch
needs to be provided with a clearance groove corresponding thereto.
In addition, a blank itself has no guide serving as a starting
point of bending forming for forming a pair of folded flanges, in
an area that will become a corner portion after completion of press
forming, and therefore, large bending resistance is generated in
the blank itself. A configuration based on such a principle has a
problem in that, in press forming, it is difficult in terms of
shape to prepare a pair of a die and a punch for forming two or
more pairs of folded flanges in a corner portion, and in addition,
the forming itself of folded flanges is unstable.
SUMMARY OF THE INVENTION
[0010] It is an object of the present invention to provide a
bottomed container having a large forming height and a method for
manufacturing the same in which a die and a punch need not be
provided with a pair of special machined parts, and in addition, a
bottomed container can be formed from a blank using cold press
forming, by which mass production is possible, substantially only
by bending forming.
[0011] According to a first aspect of the present invention, a
bottomed container includes a bottom portion, and a plurality of
vertical walls rising from the peripheral edge of the bottom
portion. The bottomed container is formed by press-forming a blank,
and has a plurality of corner portions integral with the bottom
portion and the vertical walls adjacent to each other. The corner
portions are each provided with one or more ribs that protrude
outward or inward from between the vertical walls adjacent to each
other in plan view. The ribs are each composed of a pair of folded
flanges that are folded along creases that are preformed in the
blank so as to substantially equally divide an area that will
become one of the corner portions. The amount of outward or inward
protrusion of the ribs becomes larger from the bottom portion
toward the open end of the vertical walls in side view. The ribs
are provided with no flanges extending outward from the open ends
of the ribs in plan view.
[0012] According to a second aspect of the present invention, in
the first aspect of the present invention, the corner portions have
a substantially arc shape in plan view, and the one or more ribs
formed in each of the corner portions having a substantially arc
shape are two to four ribs. Here, a substantially arc shape means a
curved surface shape having a constant radius of curvature, a
curved surface such that straight line parts are connected
together, or a polygonal shape close to a curved surface. The ribs
are formed so as to protrude from corner portions having such a
substantially arc shape.
[0013] According to a third aspect of the present invention, in the
second aspect of the present invention, recesses or protrusions
that are continuous in plan view and that correspond to the ribs
protruding outward or inward from the corner portions having a
substantially arc shape are formed in the bottom portion. The
definition of the substantially arc shape is as described
above.
[0014] According to a fourth aspect of the present invention, in
the third aspect of the present invention, the recesses or
protrusions provided in the bottom portion are formed so as to
extend radially from the center of each of the corner portions
having a substantially arc shape in plan view. The definition of
the substantially arc shape is as described above.
[0015] According to a fifth aspect of the present invention, in any
one of the first to fourth aspects of the present invention, the
bottomed container is provided with flanges extending outward from
the open ends of the vertical walls.
[0016] According to a sixth aspect of the present invention, a
method for manufacturing the bottomed container according to the
first aspect of the present invention includes a preforming step in
which creases are formed in a blank having areas that will become
the bottom portion, the plurality of vertical walls, and the
plurality of corner portions of the bottomed container after press
forming using a preforming die, the creases being formed at borders
between an area that will become the bottom portion and areas that
will become the vertical walls, borders between the areas that will
become the vertical walls and areas that will become the corner
portions, and positions for substantially equally dividing the
areas that will become the corner portions, and a main forming step
in which the blank in which creases are formed by the preforming
step is set between a die and a punch such that the die and the
punch correspond to the shape of the blank, and is press-formed to
form the bottomed container. In the main forming step, when one or
more ribs protruding outward from between each adjacent two of the
vertical walls of the bottomed container in plan view are formed in
press forming, slits are provided in corner portions of the die,
and when one or more ribs protruding inward from between each
adjacent two of the vertical walls of the bottomed container in
plan view are formed in press forming, slits are provided in corner
portions of the outer side surface of the punch.
[0017] According to a seventh aspect of the present invention, in
the sixth aspect of the present invention, in the preforming step,
the number of creases formed for substantially equally dividing
each of the areas that will become the corner portions is three to
seven.
[0018] According to an eighth aspect of the present invention, in
the sixth or seventh aspect of the present invention, the inside of
each of the corner portions of the die is formed such that the
radius of curvature of the inscribed circle is R1 in plan view, the
corner portions of the outer side surface of the punch are formed
in a shape having a curved surface having a radius of curvature of
R2 in plan view corresponding to the inscribed circle of each of
the corner portions of the die, the clearance between the punch and
the die defined as R1-R2 is set to 100% to 200% of the thickness of
the blank, and R1>R2.
[0019] According to a ninth aspect of the present invention, in the
eighth aspect of the present invention, in the main forming step,
when one or more ribs protruding outward from between each adjacent
two of the vertical walls of the bottomed container in plan view
are formed in press forming, slits are provided in the corner
portions of the bottom surface of the die, and when one or more
ribs protruding inward from between each adjacent two of the
vertical walls of the bottomed container in plan view are formed in
press forming, slits are provided in the corner portions of the
bottom surface of the punch.
[0020] According to a tenth aspect of the present invention, in the
ninth aspect of the present invention, the slits provided in the
corner portions of the bottom surface of the die or the corner
portions of the bottom surface of the punch are formed so as to
extend radially from the center of each corner portion.
[0021] According to an eleventh aspect of the present invention, in
any one of the sixth to tenth aspect of the present invention,
flanges extending outward from the outer side surface other than
the corner portions of the punch are provided at the upper end of
the punch.
[0022] As described above, a bottomed container of the present
invention includes a bottom portion, and a plurality of vertical
walls rising from the peripheral edge of the bottom portion. The
bottomed container is formed by press-forming a blank, and has a
plurality of corner portions integral with the bottom portion and
the vertical walls adjacent to each other. The corner portions are
each provided with one or more ribs that protrude outward or inward
from between the vertical walls adjacent to each other in plan
view. The ribs are each composed of a pair of folded flanges that
are folded along creases that are preformed in the blank so as to
substantially equally divide an area that will become one of the
corner portions. The amount of outward or inward protrusion of the
ribs becomes larger from the bottom portion toward the open end of
the vertical walls in side view. The ribs are provided with no
flanges extending outward from the open ends of the ribs in plan
view. Therefore, a die and a punch need not be provided with a pair
of special machined parts, and in addition, a bottomed container
having a large forming height can be formed from a blank using cold
press forming, by which mass production is possible, substantially
only by bending forming.
[0023] A method for manufacturing a bottomed container of the
present invention includes a preforming step in which creases are
formed in a blank having areas that will become the bottom portion,
the plurality of vertical walls, and the plurality of corner
portions of the bottomed container after press forming using a
preforming die, the creases being formed at borders between an area
that will become the bottom portion and areas that will become the
vertical walls, borders between the areas that will become the
vertical walls and areas that will become the corner portions, and
positions for substantially equally dividing the areas that will
become the corner portions, and a main forming step in which the
blank in which creases are formed by the preforming step is set
between a die and a punch such that the die and the punch
correspond to the shape of the blank, and is press-formed to form
the bottomed container. In the main forming step, when one or more
ribs protruding outward from between each adjacent two of the
vertical walls of the bottomed container in plan view are formed in
press forming, slits are provided in corner portions of the die,
and when one or more ribs protruding inward from between each
adjacent two of the vertical walls of the bottomed container in
plan view are formed in press forming, slits are provided in corner
portions of the outer side surface of the punch. Therefore, a
manufacturing method in which a die and a punch need not be
provided with a pair of special machined parts, and in addition, a
bottomed container can be formed from a blank using cold press
forming, by which mass production is possible, substantially only
by bending forming, can be provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a schematic plan view illustrating a blank before
being formed into a bottomed container of Embodiment 1 of the
present invention;
[0025] FIG. 2 is a partial enlarged perspective view of a
preforming die according to Embodiment 1;
[0026] FIGS. 3A and 3B are partial enlarged views of the blank
before and after preforming according to Embodiment 1, FIG. 3A is
an enlarged view of part IIIA before preforming shown in FIG. 1,
and FIG. 3B is a perspective view after preforming;
[0027] FIG. 4 is a schematic perspective view showing the
positional relationship between a punch, the blank after
preforming, and a die in main forming according to Embodiment
1;
[0028] FIGS. 5A and 5B show the shape and dimensions of the punch
and die shown in FIG. 4;
[0029] FIGS. 6A to 6D show the transformation state of the blank
during main forming according to Embodiment 1;
[0030] FIG. 7 is a schematic plan view illustrating a blank before
being formed into a bottomed container of Embodiment 2 of the
present invention;
[0031] FIG. 8 is a partial enlarged perspective view of a
preforming die according to Embodiment 2;
[0032] FIGS. 9A and 9B are partial enlarged views of the blank
before and after preforming according to Embodiment 2, FIG. 9A is
an enlarged view of part IXA before preforming shown in FIG. 7, and
FIG. 9B is a perspective view after preforming;
[0033] FIG. 10 is a schematic perspective view showing the
positional relationship between a punch, the blank after
preforming, and a die in main forming according to Embodiment
2;
[0034] FIGS. 11A to 11D show the transformation state of the blank
during main forming according to Embodiment 2;
[0035] FIG. 12 is a schematic plan view illustrating a blank before
being formed into a bottomed container of Embodiment 3 of the
present invention;
[0036] FIG. 13 is a partial enlarged perspective view of a
preforming die according to Embodiment 3;
[0037] FIGS. 14A and 14B are partial enlarged views of the blank
before and after preforming according to Embodiment 3, FIG. 14A is
an enlarged view of part XIVA before preforming shown in FIG. 12,
and FIG. 14B is a perspective view after preforming;
[0038] FIG. 15 is a schematic perspective view showing the
positional relationship between a punch, the blank after
preforming, and a die in main forming according to Embodiment
3;
[0039] FIGS. 16A and 16B show the shape and dimensions of the punch
and die shown in FIG. 15; and
[0040] FIGS. 17A to 17E show the transformation state of the blank
during main forming according to Embodiment 3.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0041] Embodiments of the present invention will now be described
in detail.
Embodiment 1
[0042] FIG. 1 is a schematic plan view illustrating a blank before
being formed into a bottomed container of Embodiment 1 of the
present invention. FIG. 2 is a partial enlarged perspective view of
a preforming die according to Embodiment 1. FIGS. 3A and 3B are
partial enlarged views of the blank before and after preforming
according to Embodiment 1, FIG. 3A is an enlarged view of part IIIA
before preforming shown in FIG. 1, and FIG. 3B is a perspective
view of part IIIA after preforming. FIG. 4 is a schematic
perspective view showing the positional relationship between a
punch, the blank after preforming, and a die in main forming
according to Embodiment 1. FIGS. 5A and 5B show the shape and
dimensions of the punch and die shown in FIG. 4. FIGS. 6A to 6D
show the transformation state of the blank during main forming
according to Embodiment 1.
[0043] In FIG. 1, reference sign 1 denotes a blank 800 mm by 1000
mm and 1.0 mm thick made of 6000 series aluminum alloy before cold
press forming (hereinafter also simply referred to as "press
forming"), reference sign 1a denotes an area that will become a
bottom portion of a square tubular component as a bottomed
container after press forming, reference sign 1b denotes areas that
will become a plurality of (four) vertical walls of the square
tubular component after press forming, and reference sign 1c
denotes areas that will become a plurality of (four) corner
portions of the square tubular component after press forming.
[0044] FIG. 2 shows a preforming die 2 for forming creases (for
detail, see FIG. 3B described later) in the blank 1 having the
areas 1a, 1b, and 1c shown in FIG. 1, the creases being formed at
the borders between the area 1a that will become the bottom portion
and the areas 1b that will become the vertical walls, the borders
between the areas 1b that will become the vertical walls and the
areas 1c that will become the corner portions, and positions that
substantially equally divide (into two halves) the areas 1c that
will become the corner portions. In FIG. 2, reference sign 2a
denotes an area of the preforming die 2 corresponding to the area
1a that will become the bottom portion, reference sign 2b denotes
areas of the preforming die 2 corresponding to the areas 1b that
will become the vertical walls, and reference sign 2c denotes areas
of the preforming die 2 corresponding to the areas 1c that will
become the corner portions.
[0045] FIG. 3A is an enlarged view of part IIIA of the blank 1
before preforming shown in FIG. 1. FIG. 3B is a perspective view of
part IIIA of the blank 1 after creases 1d, 1e, and if are formed
(preforming step) in the blank 1 shown in FIG. 1 using the
preforming die 2 shown in FIG. 2, the creases being formed at the
borders between the area 1a that will become the bottom portion and
the areas 1b that will become the vertical walls, the borders
between the areas 1b that will become the vertical walls and the
areas 1c that will become the corner portions, and positions that
substantially equally divide (into two halves) the areas 1c that
will become the corner portions.
[0046] FIG. 4 is a schematic perspective view showing the
positional relationship between a punch 3, the blank 1 after
preforming, and a die 4 in main forming according to Embodiment
1.
[0047] In FIG. 4, the blank 1 in which creases 1d, 1e, and 1f are
formed by the above-described preforming step is set between a die
4 (for detail, see FIG. 5B described later) and a punch 3 (for
detail, see FIG. 5A described later) such that the die 4 and the
punch 3 correspond to the shape of the blank 1, and is press-formed
to form a square tubular component as a bottomed container (main
forming step). In this main forming step, a blank holder need not
be used.
[0048] The die 4 shown in FIG. 4 is provided with a bottom surface
4a, inner side surfaces 4b, and corner portions 4c respectively
corresponding to the area 1a that will become a bottom portion, the
areas 1b that will become vertical walls, and the areas 1c that
will become corner portions, of the blank 1. The corner portions 4c
of the die 4 are each provided with a slit 4f that is used when a
rib 1g (see FIG. 6D described later) that protrudes outward from
between each adjacent two of the vertical walls 1b of the square
tubular component in plan view is formed during press forming.
[0049] The transformation state of the blank 1 after preforming in
the case where the above-described main forming step was performed
on the basis of the blank 1 having creases 1d, 1e, and 1f formed by
the above-described preforming step, the detailed shapes of the
punch 3 and the die 4 shown in FIGS. 5A and 5B, the clearance
between the punch 3 and the die 4 (the thickness of the blank 1 (1
mm)+(20% of the thickness of the blank 1 (1 mm)=0.2 mm)=1.2 mm),
and lubricant (wash oil for steel plate is assumed) and coefficient
of friction .mu.=0.14, was calculated using general-purpose dynamic
explicit method software PAM-STAMP (calculation result is shown in
FIGS. 6A to 6D as deformation state diagrams). The calculation
model was in 1/4 symmetric condition.
[0050] FIGS. 6A to 6D are transformation state diagrams showing the
above-described calculation result. FIGS. 6A, 6B, 6C, and 6D
respectively show the transformation state of the blank 1 after
preforming at a position 70 mm above the bottom dead center (BDC)
(at which the punch 3 is in its lowest position) (hereinafter
referred to as BDC 70 mm UP), BDC 50 mm UP, BDC 20 mm UP, and BDC.
From this, it can be seen that the main forming step progresses
stably. In FIG. 6D, it can be seen that a rib 1g composed of a pair
of folded flanges that protrude outward from between each adjacent
two of the vertical walls 1b of the square tubular component is
formed excellently in each corner portion 1c. That is, a square
tubular component can be formed only by bending without drawing the
corner portions 1c. For this reason, if the height of the square
tubular component is increased, the drawing resistance to the blank
1 does not increase. In other words, a square tubular component
(bottomed container) that is free from rupture can be obtained
without increasing the amount of strain in each parts. This rib 1g
becomes larger from the bottom portion 1a toward the open ends of
the vertical walls 1b in side view, and the rib 1g is provided with
no flanges extending outward from the open end of the rib 1g in
plan view.
[0051] Although, in Embodiment 1, an example in which a rib 1g
protruding outward from between each adjacent two of the vertical
walls 1b of the square tubular component is formed in each corner
portion 1c has been described, the present invention is not limited
to this. For example, when a rib protruding inward from between
each adjacent two of the vertical walls 1b of the square tubular
component is formed in each corner portion 1c, a slit may be
provided in each corner portion of the outer side surface of the
punch 3. Although, in Embodiment 1, an example in which a square
tubular component is formed as a bottomed container has been
described, the present invention is not limited to this. The
present invention can be widely applied, for example, to a
triangular tubular component, and a five or more-sided polygonal
tubular component. Although, in Embodiment 1, an example in which a
rib 1g protruding outward from between each adjacent two of the
vertical walls 1b in plan view is formed in each corner portion 1c
has been described, the present invention is not limited to this.
For example, two or more ribs 1g that protrude outward or inward
from between each adjacent two of the vertical walls 1b in plan
view may be provided in each corner portion 1c (for details, see
Embodiments 2 and 3 described later). Although, in Embodiment 1, an
example in which a blank 1 is made of 6000 series aluminum alloy
has been described, the present invention is not limited to this.
For example, a blank 1 may be made of an aluminum alloy other than
6000 series, a titanium alloy, which is a material difficult to
machine, or an ordinary steel. The advantage that this rib 1g
serves as a reinforcing part resisting against bending deformation
of each corner portion 1c can also be obtained.
[0052] As described above, use of the configuration of the present
invention not only eliminates the need to provide a die and a punch
with a pair of special machined parts, but also makes it possible
to form a bottomed container having a large forming height from a
blank using cold press forming, by which mass production is
possible, substantially only by bending forming.
Embodiment 2
[0053] FIG. 7 is a schematic plan view illustrating a blank before
being formed into a bottomed container of Embodiment 2 of the
present invention. FIG. 8 is a partial enlarged perspective view of
a preforming die according to Embodiment 2. FIGS. 9A and 9B are
partial enlarged views of the blank before and after preforming
according to Embodiment 2, FIG. 9A is an enlarged view of part IXA
before preforming shown in FIG. 7, and FIG. 9B is a perspective
view after preforming. FIG. 10 is a schematic perspective view
showing the positional relationship between a punch, the blank
after preforming, and a die in main forming according to Embodiment
2. FIGS. 11A to 11D show the transformation state of the blank
during main forming according to Embodiment 2. In this embodiment,
the same reference signs will be used to designate the same
components as those of Embodiment 1, detailed description thereof
will be omitted, and only differences will be described in
detail.
[0054] In FIG. 7, the blank 1 is formed in a shape based on the
premise that two ribs are formed in each of the areas 1c that will
become corner portions. That is, the blank 1 is formed in such a
shape that vertical walls 1b are equal in height to two ribs in
side view after main forming (press forming) (see FIG. 9A).
[0055] FIG. 8 shows a preforming die 5 for forming creases (for
detail, see FIG. 9R described later) in the blank 1 having the
areas 1a, 1b, and 1c, shown in FIG. 7, the creases being formed at
the borders between the area 1a that will become the bottom portion
and the areas 1b that will become the vertical walls, the borders
between the areas 1b that will become the vertical walls and the
areas 1c that will become the corner portions, and positions that
substantially equally divide (into four parts) the areas 1c that
will become the corner portions. In FIG. 8, reference sign 5a
denotes an area of the preforming die 5 corresponding to the area
1a that will become the bottom portion, reference sign 5b denotes
areas of the preforming die 5 corresponding to the areas 1b that
will become the vertical walls, and reference sign 5c denotes areas
of the preforming die 5 corresponding to the areas 1c that will
become the corner portions.
[0056] FIG. 10 is a schematic perspective view showing the
positional relationship between a punch 3, the blank 1 after
preforming, and a die 4 in main forming according to Embodiment
2.
[0057] In FIG. 10, the blank 1 in which a crease 1d, a crease 1e,
and three creases 1f are formed by the above-described preforming
step is set between a die 4 and a punch 3 such that the die 4 and
the punch 3 correspond to the shape of the blank 1, and is
press-formed to form a square tubular component as a bottomed
container (main forming step). In this main forming step, a blank
holder need not be used.
[0058] The corner portions 4c of the die 4 shown in FIG. 10 are
each provided with two slits 4f that are used when two ribs 1g (see
FIG. 11D described later) that protrude outward from between each
adjacent two of the vertical walls 1b of the square tubular
component in plan view are formed during press forming.
[0059] The transformation state of the blank 1 after preforming in
the case where the above-described main forming step was performed
on the basis of the blank 1 having a crease 1d, a crease 1e, and
three creases 1f formed by the above-described preforming step, the
punch 3 and the die 4 shown in FIG. 10, the clearance between the
punch 3 and the die 4 (the thickness of the blank 1 (1 mm)+(20% of
the thickness of the blank 1 (1 mm)=0.2 mm)=1.2 mm), lubricant
(wash oil for steel plate is assumed) and coefficient of friction
.mu.=0.14, was calculated using general-purpose dynamic explicit
method software PAM-STAMP (calculation result, is shown in FIGS.
11A to 11D as deformation state diagrams). The calculation model
was in 1/4 symmetric condition.
[0060] FIGS. 11A to 11D are transformation state diagrams showing
the above-described calculation result. FIGS. 11A, 11B, 11C, and
11D respectively show the transformation state of the blank 1 after
preforming at BDC 70 mm UP, BDC 50 mm UP, RDC 20 mm UP, and BDC.
From this, it can be seen that the main forming step progresses
stably. Tn FIG. 11D, it can be seen that two ribs 1g each composed
of a pair of folded flanges that protrude outward from between
adjacent vertical walls 1b of the square tubular component are
formed excellently in the corner portion 1c. That is, a square
tubular component can be formed only by bending without drawing the
corner portions 1c. For this reason, if the height of the square
tubular component is increased, the drawing resistance to the blank
1 does not increase. In other words, a square tubular component
(bottomed container) that is free from rupture can be obtained
without increasing the amount of strain in each parts. However, in
the case of Embodiment 2, a punch 3 and a die 4 that have a very
small corner R in plan view are provided with a plurality of ribs
1g, and therefore the clearance between the punch 3 and die 4 is
large in the slits 4f in each corner portion 4c of the die 4. For
this reason, there is a problem in that the shape of ribs 1g after
press forming is not formed as sharp as the shape of Embodiment 1.
When it is desired to form such ribs 1g more sharply, the corner R
needs to be set slightly larger according to the number of the ribs
1g as in Embodiment 3 described later. The two ribs 1g become
larger from the bottom portion 1a toward the open ends of the
vertical walls 1b in side view, and the two ribs 1g are provided
with no flanges extending outward from the open ends of the ribs 1g
in plan view.
[0061] When two ribs 1g are provided in each corner portion 1c as
in Embodiment 2, the amount of protrusion of the ribs 1g can be
reduced compared to the case where two ribs 1g are provided in each
corner portion 1c as in Embodiment 1. Therefore, the number of ribs
1g provided in each corner portion 1c is preferably two or more.
However, if the number of ribs 1g provided in each corner portion
1c is increased as described above, ends of slits 4f facing the
inside of each corner portion 4c of die 4 overlap. In such a part,
the clearance between the punch 3 and the die 4 is large, and
therefore the shape of ribs 1g is not formed stably. If the width
of the slits 4f is reduced so that the ends of the slits 4f do not
overlap, the volume of the part subjected to deformation load is
also reduced, and it is a challenge to secure the strength of the
die 4. In order to secure a certain width of the slits 4f and to
form a necessary number of relatively sharp ribs 1g, the radius of
curvature R of corner portions 4c needs to be set, larger according
to the number of the ribs 1g. That is, if the number of ribs 1g is
too small, the amount, of protrusion of ribs 1g into or out of each
corner portion 1c is large, and if the number of ribs 1g is too
large, the radius of curvature R of corner portions 4c in plan view
is large. From the viewpoint of shape limitation and securing of
internal capacity, a square tubular component (bottomed container)
that has a relatively small corner R (the radius of curvature R is
about 80 mm or less) and in which the amount of protrusion of ribs
1g out of or into the production is small, is desired. In order to
obtain such a square tubular component (bottomed container), the
number of ribs 1g provided in each corner portion 1c is preferably
four or less.
[0062] As described above, use of the configuration of the present
invention not only eliminates the need to provide a die and a punch
with a pair of special machined parts, but also makes it possible
to form a bottomed container having a large forming height from a
blank using cold press forming, by which mass production is
possible, substantially only by bending forming.
Embodiment 3
[0063] FIG. 12 is a schematic plan view illustrating a blank before
being formed into a bottomed container of Embodiment 3 of the
present invention. FIG. 13 is a partial enlarged perspective view
of a preforming die according to Embodiment 3. FIGS. 14A and 14B
are partial enlarged views of the blank before and after preforming
according to Embodiment 3, FIG. 14A is an enlarged view of part
XIVA before preforming shown in FIG. 12, and FIG. 14B is a
perspective view after preforming. FIG. 15 is a schematic
perspective view showing the positional relationship between a
punch, the blank after preforming, and a die in main forming
according to Embodiment 3. FIGS. 16A and 16B show the shape and
dimensions of the punch and die shown in FIG. 15. FIGS. 17A to 17E
show the transformation state of the blank during main forming
according to Embodiment 3. In this embodiment, the same reference
signs will be used to designate the same components as those of
Embodiments 1 and 2, detailed description thereof will be omitted,
and only differences will be described in detail.
[0064] In FIG. 12, the blank 1 is formed in a shape based on the
premise that four ribs are formed in each of the areas 1c that will
become a corner portions. That is, the blank 1 is formed in such a
shape that vertical walls 1b are equal in height to four ribs in
side view after main forming (press forming) (see FIG. 14A).
[0065] FIG. 13 shows a preforming die 6 for forming creases (for
detail, see FIG. 14B described later) in the blank 1 having the
areas 1a, 1b, and 1c shown in FIG. 12, the creases being formed at
the borders between the area 1a that will become the bottom portion
and the areas 1b that will become the vertical walls, the borders
between the areas 1b that will become the vertical walls and the
areas 1c that will become the corner portions, and positions that
divide equally (into eight parts) the areas 1c that will become the
corner portions. In FIG. 13, reference sign 6a denotes an area of
the preforming die 6 corresponding to the area 1a that will become
the bottom portion, reference sign 6b denotes areas of the
preforming die 6 corresponding to the areas 1b that will become the
vertical walls, and reference sign 6c denotes areas of the
preforming die 6 corresponding to the areas 1c that will become the
corner portions.
[0066] FIG. 15 is a schematic perspective view showing the
positional relationship between a punch 7, the blank 1 after
preforming, and a die 8 in main forming according to Embodiment
3.
[0067] In FIG. 15, the blank 1 in which a crease 1d, a crease 1e,
and seven creases 1f are formed by the above-described preforming
step is set between a die 8 (for detail, see FIG. 16B described
later) and a punch 7 (for detail, see FIG. 16A described later)
such that the die 8 and the punch 7 correspond to the shape of the
blank 1, and is press-formed to form a square tubular component as
a bottomed container (main forming step). In this main forming
step, a blank holder need not be used.
[0068] The inside of each corner portion 8c of the die 8 shown in
FIG. 16B is formed such that the radius of curvature R1 of the
inscribed circle is 66.9 mm. The corner portions 8c are further
provided with four slits 8f that are used when four ribs 1g (see
FIG. 17E described later) that protrudes outward from between
adjacent vertical walls 1b of the square tubular component in plan
view is formed during press forming. The corner portions 7c of the
outer side surface of punch 7 are formed in a shape having a curved
surface having a radius of curvature R2 of 65.7 mm in plan view
corresponding to the inscribed circle of each corner portion 8c of
the die 8. Here, R1>R2. The clearance between punch 7 and die 8
defined as the difference between the radius of curvature R1 of the
inscribed circle and the radius of curvature R2 is 1.2 mm. In the
main forming step, a bottomed container is formed without drawing
forming, only by bending forming, and therefore, the change in
thickness of blank 1 is very small. For this reason, the
above-described clearance can be up to about 100% of the thickness
of blank 1. If the clearance is too large, the shape of ribs 1g is
not formed sharply, and therefore, it can be said that the
clearance is preferably at most 200% (of the thickness of the blank
1). As described above, in the case of a bottomed container formed
by the main forming step, the change in thickness of blank 1 as a
material is very small compared to the case of an ordinary drawn
component. That is, in the case of ordinary drawing forming, the
thickness of the blank 1 decreases in the vicinity of the shoulder
R of the punch 7 and increases on the shoulder R side of the die 8
owing to inflow of material. If the product performance is designed
based on the vicinity of the shoulder R where local reduction in
thickness occurs, the weight of the formed component increases
slightly. A manufacturing method including the main forming step
has the advantage that the change in thickness of the blank 1
associated with forming is small, and therefore, compared to the
above-described drawing forming, the product is lightweight, and
the strength and rigidity of the product can be secured.
[0069] The transformation state of the blank 1 after preforming in
the case where the above-described main forming step was performed
on the basis of the blank 1 in which a crease 1d, a crease 1e, and
seven creases 1f were formed by the above-described preforming
step, the punch 7 and the die 8 shown in FIG. 15, the clearance
between the punch 7 and the die 8 (the thickness of the blank 1 (1
mm)+(20% of the thickness of the blank 1 (1 mm)=0.2 mm)=1.2 mm),
lubricant (wash oil for steel plate is assumed) and coefficient of
friction .mu.=0.14, was calculated using general-purpose dynamic
explicit method software PAM-STAMP (calculation result is shown in
FIGS. 17A to 17E as deformation state diagrams). The calculation
model was in 1/4 symmetric condition.
[0070] FIGS. 17A to 17E are transformation state diagrams showing
the above-described calculation result. FIGS. 17A, 17B, 17C, 17D,
and 17E respectively show the transformation state of the blank 1
after preforming at BDC 70 mm UP, BDC 50 mm UP, BDC 20 mm UP, BDC
10 mm UP, and BDC. From this, it can be seen that the main forming
step progresses further stably compared to Embodiments 1 and 2. In
FIG. 17E, it can be seen that four ribs 1g each composed of a pair
of folded flanges that protrude outward from between adjacent
vertical walls 1b of the square tubular component are formed
excellently in the corner portion 1c. That is, a square tubular
component can be formed more easily only by bending without drawing
the corner portions 1c. For this reason, if the height of the
square tubular component is increased, the drawing resistance to
the blank 1 does not increase. In other words, a square tubular
component (bottomed container) that is free from rupture can be
obtained without increasing the amount of strain in each parts. The
four ribs 1g become larger from the bottom portion 1a toward the
open ends of the vertical walls 1b in side view, and the four ribs
1g are provided with no flanges extending outward from the open
ends of the ribs 1g in plan view.
[0071] When four ribs 1g are provided in each corner portion 1c as
in Embodiment 3, the amount of protrusion of ribs 1g is small
compared to Embodiment 2. The strength of corner portions 1c of
Embodiment 3 is high compared to Embodiment 2.
[0072] As described above, use of the configuration of the present
invention not only eliminates the need to provide a die and a punch
with a pair of special machined parts, but also makes it possible
to form a bottomed container having a large forming height from a
blank using cold press forming, by which mass production is
possible, substantially only by bending forming.
[0073] In the main forming step of Embodiment 3, providing slits in
corner portions of bottom surface 8a of die 8 when one or more ribs
1g protruding outward from between adjacent vertical walls 1b of
square tubular component (bottomed container) in plan view in press
forming, or providing slits in corner portions of bottom surface of
punch 7 when one or more ribs 1g protruding inward from between
adjacent vertical walls 1b of square tubular component (bottomed
container) in plan view in press forming, makes it easier and more
stable to form a square tubular component (bottomed container).
[0074] Forming slits provided in the corner portions 8c of the
bottom surface 8a of the die 8 or the corner portions of the bottom
surface of the punch 7 such that the slits extend radially from the
center of each corner portion makes the forming positions of the
ribs 1g more stable, and makes it much easier and much more stable
to form a square tubular component (bottomed container).
[0075] By providing flanges (not shown) extending outward from the
outer side surface other than the corner portions 7c of punch 7 on
the upper end of the punch 7, flanges (not shown) extending outward
from the open ends of the vertical walls 1b of the square tubular
component (bottomed container) can be provided at the same time in
press forming, without generating strain based on bending
deformation resistance in the ribs 1g.
* * * * *