Press Forming Mold And Method For Manufacturing Press Formed Product
Abstract:
A press forming mold equipped with a punch mold a die and a buckling suppression mold wherein a first surface of the buckling suppression mold has pressure receiving parts that receive reaction force for elastically deforming the buckling suppression mold at the end of press forming and buckling suppression pressure increasing parts that protrude toward the pressure receiving parts from a plate part of the punch mold and that when pressed in the pressing direction generate the aforementioned reaction force in the direction opposite the pressing direction.
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c/o NIPPON STEEL & SUMITOMO METAL CORPORATION 6 1 Marunouchi 2 chome Chiyoda ku Tokyo
1008071
Specification
PRESS-FORMING TOOL AND METHOD FOR
MANUFACTURING PRESS-FORMED PRODUCT
[Technical Field of the Invention]
[OOOI]
The present invention relates to a press-forming tool for a metal plate, and a
method for manufacturing a press-formed product which is press-formed using the
press-forming tool. Particularly, the present invention relates to a press-forming tool
and a method for manufacturing a press-formed product for securing improved shape
freezing properties by decreasing springback which is generated after the press
forming is performed.
[Related Art]
[OOO2]
It is possible to form members having various shapes by performing press
forming using a metal plate such as a steel sheet or aluminum alloy plate.
Accordingly, many press-formed products are used in members for an automobile and
the like.
[OOO3]
In the press-formed product, there is a problem relating to a dimension
accuracy defect (a shape freezing defect) due to an angular change or bending of the
press-formed product, which is called springback, generated after the metal plate is
press-formed.
[OOO4]
The springback is generated since the press-formed product is deformed by
elastic recovery after the press forming due to residual stress introduced into the metal
plate during the press forming. When the residual stress introduced into the metal
plate is non-uniformly distributed in a plate thickness direction or an in-plane direction
of the metal plate, the springback is easily generated.
In order to decrease the springback and improve the dimension accuracy of
the press-formed product, in the end phase of the press forming, it is effective to
increase a wrinkle suppression force with respect to a blank material during the press
forming.
However, in order to increase the wrinkle suppression force during the press
forming, a press forming apparatus, which includes a variable die cushion device using
a servo valve or the like, is generally required.
[0007]
With respect to this proble~b,patentD ocument 1 discloses a press-forming
tool in which an elastic body such as a spring is disposed in the press-forming tool.
In this press-forming tool, it is possible to increase the wrinkle suppression force in the
end phase of the press forming without the variable die cushion device.
[OOOS]
Patent Document 2 discloses a press-forming tool in which the disc spring is
disposed in the press-forming tool. In this press-forming tool, since the disc spring
which can generate a high load evcn by a low stroke is used, it is possible to make the
wrinkle suppression force which is increased in the end phase of the press forming be
larger even without the variable die cushion device.
[0009]
Patent Document 3 discloses a press-forming tool in which a wrinkle
suppression mold is divided into a corner portion and a straight side portion. In this
press-forming tool, it is possible to increase the wrinkle suppression force at every
position in which the press forming is performed.
[Prior Art Documenl]
[Patcnt Document]
[OO lo]
[Patent Document 11 Japanese Unexamined Patent Application, First
Publication No. 2002-32101 3
[Patent Document 21 Japanese Unexamined Patent Application, First
Publication No. 2004-344925
[Patent Document 31 Japanese Unexamined Patent Application, First
Publication No. 2003-941 19
[Disclosure of the Invention]
[Problems to be Solved by the Inveqtkn]
[OOll]
In the press-forming tool disclosed in Patent Document 1, even when the
portion which is added an increased the wrinkle suppression force is a part 01 [he entire
wrinltle suppression portion, it is necessary to increase the wrinltle suppression force in
the entire wrinkle suppression portion. That is to say, in order to suppress the
springback of the press-formed product, it is necessary to increase the size of the
spring disposed in the press-forming tool or to increase the number of the springs.
However, a site capable of disposing the spring in the press-forming tool is limited.
Accordingly, when a metal plate having a larger springback such as high tensile
strength steel or high tensile strength aluminum alloy is press-formed as the blank
material, it is difficult to sufficiently increase the wrinkle suppression force.
[0012]
In the press-forming tool disclosed in Patent Document 2, as the spring for
increasing the wrinkle suppression force, the disc spring capable of obtaining the
reaction force of the high load by the low stroke is used. Accordingly, in the end
phase of the press forming at which the increase of the wrinkle suppression force is
needed, it is possiblc to effectively increase the wrinkle suppression force by a slight
stroke. However, also in this press-forming tool, even when the portion which is
added the increased wrinltle suppression force is a part of the entire wrinkle
suppression portion, it is also necessary to increase the wrinlcle suppression force of the
entire wrinlcle suppression portion. Therefore, in recent years, when a metal plate
which is further high-strengthened is press-formed as the blank material, even if the
disc spring is used, the increase ofthe wrinkle suppression force is not sufficient.
[0013]
In the press-forming tool dlscJosed in Patent Document 3, in order to suppress
occurrence of wrinkles (springback) in the corner portion of the press-formed product
which becomes a shrinkage flange deformation region, the wrinltle suppression force
in the early phase of the press-forming is increased. In addition, in order to avoid
occurrence of breakage in the comer portion, the wrinkle suppression force during the
press-forming is decreased. Moreover, in order to remove a shape freezing defect in
the comer portion, the wrinkle suppression force is increased again immediately before
a bottom dead center (press-forming ending point) of the press-forming.
However, in this press-forming tool, in order to change the wrinkle
suppression force in a part of the entire wrinkle suppression portion, the wrinkle
suppression mold is set as a split-type. Since the wrinkle suppression mold is the
split-type, a large spring force is not required, and only the wrinkle suppression force
in the required region is increased
However, generally, compared to an integral-type mold, the split mold has
many problems with respect to manulacturing, operation, maintenance, repair,
replacement, life span, or the like of the mold. Accordingly, since the split mold is
adopted, management of the manufacturing process of the press-formed product
becomes complicated, and the manufacturing cost of the press-formed product may be
increased. Therefore, in a mass production process of press-forming members for an
automobile or the like, i t is more preferable to change the wrinkle suppression rorce in
a part of the entire wrinkle suppression portion not using the split-type wrinkle
suppression mold but using the integral-type wrinkle suppression mold.
In addition, the integral wrinkle suppression mold refers to a wrinkle
suppression mold constituted of the minimum number of components difficult to be
further split, from the viewpoint of the manufacturing of the press mold and the shape
of the press-formed product.
[0014]
Moreover, the press-forming tool disclosed in Patent Document 3 is a pressforming
tool for a drawing of the metal plate and is not suitable to press-form a highstrength
metal plate. Specifically, in the press-forming tool disclosed in Patent
Document 3, a steel sheet is mainly drawn in a deep cylindrical shape.
Accordingly, the shape of the press-formed product obtained by this pressforming
tool is different from the shape of the prcss-formed product in which the highstrength
metal plate is mainly press-formed. In the press mold in which the highstrength
metal plate is used as the blank material drawing and bending processing is
often performed to obtain a press-formed product in which both ends in the
longitudinal direction are opened (hat-shaped cross-section).
When such the high strength metal plate is performed drawing and bending
processing, there are problems which are different from the problems generated when
the metal plate is drawn in a deep cylindrical shape.
[0015]
In the drawing processing of making the metal plate into a deep cylindrical
shape, the drawn corner portion of the press-formed product becomes a shrinkage
flange deformation region. On the other hand, in the drawing and bending processing
of making the high-strength metal plate into the shape (for example, a memhcr part)
having both ends opened in the longitudinal direction, a portion (for example, a flange
portion corresponding to an inner side of a bent portion) of the comer portion of the
press-formed product becomes an extension flange deformation region.
Here, the shrinkage flange deformation refers to deformation in which
extcnsion and shrinkage are simultaneously gerrerated in two axes an in-plane, and the
extension flange deformation refers'tqdeformation in which the extension is generated
in both two axes of the in-plane. That is to say, in the press-formed product drawn by
the press-forming tool disclosed in Patent Document 3, the corner portion which
becomes the extensions flange deformation region such as the member part does not
exist. Moreover, in the drawn press-formed product, the plate thickness of the flange
portion at which the shrinkage flange deformation is generated is not changed or is
increased.
On the other hand, in the press-formed product afler the drawing and bending
processing, the plate thiclcness of the flange portion at which thc extension flange
deformation is generated is significantly decreased. In the region in which the plate
thickness is significantly decreased during the press forming, the wrinkle suppression
force is not easily transmitted to the blank material, and as a result, dimension accuracy
defects such as wall warpage of the press-formed product or waviness of a vertical wall
are easily generated.
Here, the drawing processing refers to press forming (processing) to obtain a
vessel-shaped (cylindrical) press-formed product which does not have the region being
generated the extension flange deformation and which does not have opening portions
on both ends in a direction perpendicular to an advancement direction (pressing
direction) of a punch. Moreover, the drawing and bending processing refers to press
forming (processing) to obtain a member-shaped press-formed product which has the
region being generated the extension flange deformation and has openings on both
ends in the longitudinal direction (the extension direction of the flange portion to
which the wrinkle suppression force is applied).
In the manufacturing process in which the high-slrength metal plate is pressformed
in a member part or the like, development of a press-forming tool capable of
suppressing springback at a portion'which becomes the extension flange deformation
region in addition to the shrinkage flange deformation region is significantly required.
[0016]
In consideration of the above-described circumferences, an object ol'the
present invention is to provide a press-forming tool in which a wrinkle suppression
mold is not a split-type but an integral-type and springback can be suppressed in a
portion which becomes an extension flange deformation region even when a highstrength
metal plate is press-formed as a blank material, and a method for
manufacturing a press-formed product which is press-formed using the press-forming
tool.
That is to say, the present invention provides a press-forming tool and a
method for manufacturing a press-formed product in which a general press forming
apparatus is used without a press forming apparatus having a variable die cushion
device, and a press-formed product having high dimension accuracy can be obtained
by sufficiently increasing a wrinkle suppression force with respect to a blank material
in the end phase of the press forming when a metal plate such as high tensile strength
steel or high strength aluminum alloy in which springback easily occurs is pressformed
as a blank material.
Particularly, another object of the present invention is to provide a pressforming
tool and a method for manufacturing a press-formed product in which a pressformed
product having an extension flange deformation region in addition to a
shrinkage flange deformation region can be press-formed with high dimension
accuracy by a press-forming tool by which a metal plate is performed drawing and
bending processing.
[Means for Solving the Problem]
[0017] ' i
The inventors earnestly reviewed a mold structure in which a wrinkle
suppression force is effectively increased at a portion which is added the increased
wrinkle suppression force, in a press-formed product having an extension flarige
deformation region such as a member part. As a result, the inventors found a
providing of a pressure receiving portion on a portion of a wrinkle suppression mold of
the press-forming tool and providing of a wrinkle suppression force increasing ponion
on a portion of a punch of the press-forming tool.
According to this configuration, in the end phase of the press forming, the
pressure receiving portion and the wrinlcle suppression force increasing portion come
into contact with each other, the wrinlcle suppression mold is elastically deformed and
bent, and thus, the wrinlcle suppression force can be locally added to a portion of the
blank material which is added the increased wrinkle suppression force. Springback of
a press-formed product having the extension flange deformation region such as a
I
member part can be significantly decreased.
Here, the part having the extension flange deformation region such as the
member part refers to a press-formed product having a hat-shaped cross section shape
in which both ends in the longitudinal direction are opened.
[0018]
The gist of the present invention is as follows.
[0019]
(1) According to an aspect of the present invcntion, there is provided a pressforming
tool comprising: a punch which includes a punch portion and a plate portion
which are configured to transfer a shape to a blank material; a die which is paired with
the punch and opposes the punch portion; a wrinkle suppression mold which includes a
first surface which opposes the plate ort ti on and comes into contact with the plate
portion at a press-forming ending point, a second surface which opposes the die and
holds the blank material along with the die, and a third surface which is continuous
between the first surfacc and the second surface and opposes the punch portiou, and is
disposed between the third surface and the punch portion via a gap; a pressure
receiving portion which includes a groove portion and which is disposed on the first
surface of the wrinkle suppression mold; and a wrinkle suppression force increasing ~ portion which is disposed on the plate portion so as to oppose the first surface,
protrudes toward the pressure receiving portion, and generates a reaction force in a
direction opposite to a pressing direction when bcing pressed in the pressing direction
in an end phase of a press forming.
[0020]
(2) In the press-forming tool according to (I), when a region in which a plate
thickness is maximum in a flange portion of a press-formed product is defined as a
plate thickness maximum portion and a region in which the plate thickness is more
than 0% and less than or equal to 97% with respect to the plate thickness maximum
portion is defined as a plate thickness decreasing portion, based on a case where the
pressure receiving portion and the wrinkle suppression force increasing portion are
removed from the press-forming tool, the pressure receiving portion may overlap with
a portion of a region corresponding to the plate thickness decreasing portion in the
blank material when viewed along the pressing direction.
[0021]
(3) In the press-forming tool according to (1) or (2), the pressure receiving
portion is consisted of the groove portion, wherein when a thickness of the wrinkle
suppression mold in a position of the groove portion is defined as L in mm units and a
minimum value of the thickness of k e wrinkle suppression mold in a position which
excludes the groove portion and comes into contact with the blank material is defined
as 13 in mm units, the wrinkle suppression mold may satisfy a following Expression 1
or 2, and when a protruding height of the wrinklc suppression force increasing portion
is defined as G in mm units and a press stroke distance from a press-forming starting
point to the press-forming ending point is defined as PS in mm units, and the
protruding height G of the wrinkle suppression force increasing portion may satisfy a
following Expression 3:
20 < L i 0.8 x H when 40 i H 5 50 (Expression 1)
20 < L i 40 when 50 < H i 80 (Expression 2)
0.02 x PS + H - L i G 5 0.3 x PS + H - L (Expression 3).
[0022]
(4) In the press-lorming tool according to (1) or (2), a portion of a boundary
I which partitions the pressure receiving portion may be the groove portion
[0023]
(5) In the press-forming tool according to any one of (1) to (4), the wrinkle
suppression force increasing portion may include an elastic body which applies the
reaction force.
[0024]
(6) In the press-forming tool according to any one of (1) to (S), the elastic
body may be at least one of a disc spring, a helical spring, and a rubber.
[0025]
(7) According to another aspect of the present invention, there is provided a
method for manufacturing a press-formed product which is press-formed using the
press-forming tool according to any one of (1) t'o (6), including a step of increasing a
wrinkle suppression force with respect to a portion of a blank material in an end phase
of a press forming, which is started from a position at which a press stroke is 2% to
30% and which is ended at a forming end position, when a forming start position of the
press stroke is defined as 100% and the forming end position of the press strolte is
defined as 0% during the press forming of the blank material.
[Effects of the Invention]
[0026]
According to the above-described aspects of the present invention, a pressure
receiving portion is provided on a portion of a wrinkle suppression mold, and a wrinkle
suppression force increasing portion is provided on a portion of a punch. The
pressure receiving portion and the wrinkle suppression force increasing portion come
into contact with each other in the end phase of the press forming, and thus, the
wrinkle suppression mold is elastically deformed. As a result, the wrinkle
suppression force generated from the wrinkle suppression force increasing portion is
sufficiently transmitted to the portion of a blank matcrial which is added the increased
wrinkle suppression force in the end phase of press forming.
That is to say, even when the press-formcd product includes an extension
flange deformation region in addition to a shrinkage flange deformation region,
springback of the press-formed product can be effectively decreased.
[0027]
In a press-formed product which is press-formed using a press-forming tool of
the related art in which the pressure receiving portion and the wrinkle suppression
force increasing portion are removed from thc press-forming tool, when a portion in
which a plate thiclmess of a flange portion is thinned is defined as a plate thickness
decreasing portion, according to the above-described aspects of the present invention, a
portion (a portion which is added arf increased the wrinkle suppression force) of a
region corresponding to the plate thickness decreasing portion of the blank material
and the pressure receiving portion overlap with each other when viewed along the
pressing direction.
Accordingly, the wrinkle suppression force at the portion which is addcd the
increased wrinkle suppression force is preferably increased in the end phase of the
press forming. As a result, even when the press-formed product includes the
extension flange deformation region in addition to the shrinkage flange deformation
region, springhack of the press-formed product can be further decreased.
[0028]
In addition, according to the above-described aspects of the present invention,
even when a metal plate, in which the springback easily occurs, such as high tensile
strength steel or high strength aluminum alloy, is used as the blank material, an
integral-type wrinkle suppression mold, which is a general press forming apparatus
which does not include a variable die cushion device and which is not a split-type is
used, and even when the press-formed product includes the extension flange
deformation region in addition to the shrinkage flange deformation region, it is
possible to obtain a press-formed product having high dimension accuracy.
[Brief Description of the Drawings]
[0029]
FIG. 1A is a view showing a schematic configuration of a press-forming tool
according to a first embodiment of the present invention, and is a perspective view
showing the entirety thereof.
FIG. 1B is a plan view of a punch of the press-forming tool according to the
first embodiment.
FIG. 2 is a view showing a'wwnkle suppression mold of the press-forming
tool according to the first embodiment and is a perspective view when viewed from a
first surface side.
FIG. 3A is an explanatory view schematically showing movements or the
punch, a die, and the wrinkle suppression mold when a blank material is press-formed,
and is a perspective view when the press forming starts.
FIG. 3B is an explanatory view schematically showing the movements of the
punch, the die, and the wrinkle suppression mold when the blank material is pressformed,
and is a perspective view during the press forming.
FIG. 4A is a view showing a wrinkle suppression force increasing portion of
the press-forming tool according to the first embodiment, and a vertical cross-sectional
view showing a state where a wrinkle suppression force is not increased when a
plurality of disc springs are piled.
FIG. 4B is a view showing the wrinkle suppression force increasing portion of
thc press-forming tool according to the first embodiment, and a vertical cross-sectional
view showing a state where the wrinkle suppression force is increased when the
plurality of disc springs are piled.
FIG. 5 is a vertical cross-sectional view when viewed from an arrow I
direction shown in FIG. 2.
FIG. 6A is a perspective view showing a press-formed product which is
formed by the press-forming tool according to the first embodiment.
FIG. 6B is a vertical cross-sectional view when viewed from an arrow A
direction in FIG. 6A.
FIG. 7A is a view showing a schematic configuration of a press-forming tool
according to a second embodiment of the present invention, and is a perspective view
showing the entirety thereof. FIG. 7B is a plan view of a punch of the press-forming tool according to the
second embodiment.
FIG. 8 is a view showing a wrinkle suppression mold of the press-forming
tool according to the second embodiment and is a perspective view when viewed from
a first surface side.
FIG. 9A is a view showing a schematic configuration of a press-forming tool
according to a third embodiment of the present invention, and is a perspective view
showing the entirety thereof.
FIG. 9B is a plan view of a punch of the press-forming tool according to the
third embodiment.
FIG. IOA is a view showing a schematic configuration of a press-forming tool
according to a fourth embodiment of the present invention, and is a perspective view
showing the entirety thereof.
FIG. 10B is a plan view of a punch of the press-forming tool according to the
fourth embodiment.
FIG. 11 is a view showing a wrinkle suppression mold of the press-forming
tool according to the fourth embodiment and is a perspective view when viewed from a
first surface side.
FIG. 12 is a vertical cross-sectional view when viewed in an arrow C direction
shown in FIG. 11
FIG. 13A is a view showing a schematic configuration of a press-forming tool
of the related art which does not include a pressure receiving portion and a wrinkle
suppression force increasing portion and is a perspective view showing the entirety
thereof.
FIG. 13B is a plan view shbying a punch of the press-forming tool of the
related art which does not include the pressure receiving portion and the wrinkle
suppression force increasing portion.
FIG. 14 is an explanatory view showing a plate thickness distribution of a
flange portion in a press-formed product which is formed by the press-forming tool of
the related art shown in FIG. 13A.
FIG. 15 is an explanatory view exemplifying positions at which the pressure
receiving portion and the wrinkle suppression force increasing portion are disposed in
the view showing the plate thickness distribution of the flange portion in the pressformed
product which is formed by the press-forming tool of the related art shown in
FIG. 13A.
FIG. 16A is a perspective view showing the press-formed product after the
finishing processing (restriking processing).
FIG. 16B is a vertical cross-sectional view when viewed from an arrow B
i direction in FIG. 16A
FIG. 17 is a view showing a schematic configuration of a restriking
processing mold performing the finishing processing (restriking processing) and is a
perspective view showing the entirety thereof.
FIG. 18 is a vertical cross-sectional view perpendicular to a longitudinal
direction of the press-lbrmed product which is performed drawing and bending
processing, and an explanatory view showing a generation state of wall warpage
(springback).
FIG. 19 is a vertical cross-sectional view peipendicular to the longitudinal
direction of the press-formed product after the finishing processing (restriking
processing), and an explanatory view showing the generation state of the wall warpage
(springback). FIG. 20 is a perspective view showing the press-formed product after the
finishing processing (restriking processing) and an explanatory view showing a
generation state of wavrness.
FIG. 21A is a perspective view showing the press-formed product after the
finishing processing (restriking processing) and an explanatory view showing a
measurement position of the waviness.
FIG. 21B is a graph showing an example of the measured result of the
waviness in the press-formed product after the finishing processing (restriking
processing).
FIG. 22 is a view showing a contact pressure distribution on a second surface
of the wrinkle suppression mold when a thickness ratio L/H of the wrinkle suppression
mold is 100%.
FIG. 23 is a view showing a contact pressure distribution on the second
surface of the wrinkle suppression mold when the thickness ratio L/H of the wrinkle
suppression mold is 90%.
FIG. 24 is a view showing a contact pressure distribution on the second
surface of the wrinkle suppression mold when the thickness ratio L/H of the wrinkle
suppression mold is 80%.
FIG. 25 is a vicw showing a contact pressure distribution on the second
surface of the wrinkle suppression mold when the thickness ratio LIH of the wrinkle
suppression mold is 70%.
FIG. 26 is a view showing disposed positions of the pressure receiving portion
and the wrinkle suppression force increasing portion of the press-forming tool.
FIG. 27 is a view showing an example of a press-forming tool in which the
thickness of the wrinkle suppressioh mold is not constant, and is a perspective view
showing the entirety thereof.
[Embodiments of the Invention]
[0030]
Hereinafter, each embodiment of the present invention will be described in
detail with reference to the drawings. I-rowever, the present invention is not limited to
only the configurations of the following embodiments, and various modifications may
be applied to the present invention within a scope which does not depart from the gist
of the present invention. Moreover, in the drawings used for the following
description, in order to make the description easier to be understood, for convenience,
a portion becoming a main portion may be shown to be enlarged, and it is not limited
that a dimension ratio of each component or the like is the same as the actual condition.
[003 11
FIGS. 1A and 1B are views showing a schematic configuration ola pressforming
tool according to a first embodiment of the present invention. FIG. 1A is a
perspective view showing the entirety thereof and FIG. 1B is a plan view of a punch
configuring the press-forming tool. In FIG. 1 A, a reference numeral 1 indicates the
press-forming tool according to the present embodiment.
The press-forming tool 1 according to the present embodiment includes a
punch 10, a die 20, and wrinkle suppression molds 25a and 25b. The punch 10
includes a punch portion 12 and a plate portion 14 configured to transfer a shape to a
blank material. The punch portion 12 and the plate portion 14 are fixed to each other
by a fastening member (not shown) and become the punch 10. Alternatively, the
punch portion 12 and the plate portion 14 may integrally form the punch 10.
As shown in FIG. lB, wridklg suppression force increasing portions 16a and
16b are disposed on a surface of the plate portion 14 opposing the wrinkle suppression
molds 25a and 25b. The wrinkle suppression force increasing portions 16a and 16b
protrude toward the wrirdde suppression molds 25a and 25b and generate a reaction
force in a direction opposite to a pressing direction when the wrinkle suppression force
increasing portions are pressed in the pressing direction in the end phase of press
forming.
[0033]
The die 20 is paired with the punch 10 and is disposed so as to oppose the
punch portion 12. The wrinkle suppression molds 25a and 25b are disposed between
the punch 10 and the die 20. The wrinkle suppression molds 25a and 25b according
to the present embodiment are constituted of the minimum number of components,
which is difficult to divide it further, from the viewpoint of a structure of a press mold
and a shape of a press-lormed product. That is to say, the wrinkle suppression molds
25a and 25b are not split-type wrinkle suppression molds but integral-type wrinkle
suppression molds.
The wrinkle suppression molds 25a and 25b include first surfaccs 3 la and 31 b
which oppose the plate portion 14 of the punch 10 and which come into contact with
the plate portion 14 at a press-forming ending point. In addition, the wrinlcle
suppression molds 25a and 25b include second surfaces 32a and 32b which oppose the
die 20 and which hold the blank material along with the die 20.
[0034]
A side surface (third surface) 33a which is continuous between the first
surface 31a and the second surface 32a oppose the punch portion 12 via a
predetermined gap (clearance). Similarly, a side surface (third surface) 33b which is
continuous between the first surface"3Sb and the second surface 32b oppose the punch
portion 12 via a predetermined gap (clearance). By setting the gap appropriately,
occurrence of wrinkles of the press-formed product or cracks of the press-formed
product can be preferably prevented. The setting of the gap may be determ~ned
according to a routine procedure.
FIG. 2 is a perspective view when the wrinkle suppression molds 25a and 25b
are viewed from the first surfaces 3 la and 3 lb sides. As shown in FIG. 2, the wrinkle
suppression molds 25a and 25b include pressure receiving portions (groove portions)
30a and 30b, which receive the reaction force to elastically deform the wrinkle
suppression molds 25a and 25b in the end phase of the press forming, on the first
surfaces 3 la and 3 1b. In the press-forming tool 1 according to the present
embodiment, each of the pressure receiving portions 30a and 30b is formed of a groove
portion. In the end phase of the press forming, the wrinkle suppression force
increasing portions 16a and 16b come into contact with the pressure receiving portions
30a and 30b and are pressed in the pressing direction. If the reaction force is
generated in a direction opposite to the pressing direction, the wrinkle suppression
molds 25a and 25b receive the reaction force and are elastically deformed.
[0036]
FIGS. 3A and 3B are explanatory views schematically showing the
movements of the punch 10, the die 20, and the wrinkle suppression molds 25a and
25b when the blank material 5 is press-formed. FIG. 3A is a perspective view when
the press forming starts, and FIG. 3B is a perspective view during the press forming.
A blank material 5 is disposed on the second surfaces 32a and 32b of the
wrinkle suppression molds 25a and25b in a state where the second surfaces 32a and
32b of the wrinkle suppression molds 25a and 25b and a tip surface 13 of the punch
portion 12 are flush with each other.
[0038]
As shown in FIG. 3A, the die 20 is lowered in the pressing direction, and a
flange portion of the blank material 5 is held by a constant load by the die 20 and the
wrinkle suppression molds 25a and 2%.
[0039]
Moreover, as shown in FIG. 3B, in the state where the blank material 5 is held
by the die 20 and the wrinkle suppression molds 25a and 25b, the die 20 moves in the
pressing direction, that is to say, a direction of the plate portion 14 of the punch 10
(downward in FIG. 3B), and thus, the prcss forming of the blank material 5 is
performed by the punch portion 12.
[0040]
At a predetermined position in the end phase of the press forming, the
pressure receiving portions 30a and 30b provided on the first surfaces 3 1 a and 3 1 b of
the wrinkle suppression molds 25a and 25h come into contact with the wrinkle
suppression force increasing portions 16a and 16b. Moreover, the pressure receiving
portions 30a and 30b press the wrinkle suppression force increasing portions 16a and
16b in the pressing direction in conjunction with the press forming from the
predetermined position of the end phase of the press forming to the press-forming
ending point.
As a result, the reaction force in the direction opposite to the pressing
direction is generated from the wrinkle suppression force increasing portions 16a and
16h. The pressure receiving portions 30a and 30b receive the reaction force, and the
wrinkle suppression force with respect to the blank material 5 in the end phase of the
press forming is increased.
[0041]
FIGS. 4A and 4B are vertical cross-sectional views showing when a plurality
of disc springs overlap with each other as the wrinkle suppression force increasing
portions. FIG. 4A shows a state where the wrinkle suppression force is not increased,
and FIG. 40 shows a state where the wrinkle suppression force is increased.
[0042]
As shown in FIG. 4A, the wrinkle suppression force increasing portion 16a
includes a pin 40a and a disc spring 42a. In this way, the wrinkle suppression force
increasing portion 16a includes an elastic body which applies the reaction force. In
the present embodiment, 12 disc springs 42a pile in parallel and in series. However,
the number and arrangement of the disc springs 42a are not limited to this. For
example, 4 disc springs 42a may pile in series. Although it is not shown, the wrinkle
suppression force increasing portion 16b is similar to the above-described
configuration.
[0043]
Instead of the disc spring 42a, an elastic body such as a helical spring or a
rubber may be used. It is preferable that the disc spring 42a is used since it is
possible to obtain a high load even by a low stroke.
[0044]
As shown in FIG. 4B, the pressure receiving portion 30a provided on the first
surface 3 la of the wrinkle suppression mold 25a presses the pin 40a in the pressing
direction, and thus, the disc spring 42a is compressed. The wrinkle suppression mold
25a receives the reaction force in the direction opposite to the pressing direction from
the disc spring 42a. i
As a result, the reaction force is transmitted to the blank material 5 which is
held between the second surface 32a of the wrinkle suppression mold 25a and the die
20, and thus, the wrinkle suppression force with respcct to the blanlc material 5 can be
increased in the end phase of the press forming.
[0045]
The wrinkle suppression mold 25a which receives the reaction force from the
disc spring 42a includes the pressure receiving portion 30a which is constituted of a
groove portion, and thus, the wrinkle suppression mold 25a is convexly and elastically
deformed to the blank material 5 side and is bent. That is to say, when viewed along
the pressing direction, a portion which is convexly and elastically deformed on the
second surface 32a corresponding to the pressure receiving portion 30a effectively
transmits the reaction force to the blank material 5. Here, the pressure receiving
portion 30a is formed on the first surface 3 la of the wrinkle suppression mold 25a.
I If the wrinkle suppression mold 25a does not include the pressure receiving
portion 30a, the reaction force from the disc spring 42a is distributed to the entire
wrinlcle suppression mold 25a. Accordingly, since the reaction force cannot be
I locally applied to the blank material 5, the transmission efficiency of the reaction force
is decreased.
[0046]
FIG. 5 is a view explaining a thickness of the wrinlcle suppression mold 25a,
and is a vertical cross-sectional view when the wrinkle suppression mold 25a is viewed
from an arrow I direction shown in FIG. 2. As shown in FIG. 5, the thickness of the
wrinkle suppression mold 25a on the pressure receiving portion 30a which is
constituted of a groove portion is defined as L in mm units. Moreover, the thickness
of the wrinkle suppression mold 252 qn the region which excludes the pressure
receiving portion 30a and which comes into contact with the blank material 5 is
defined as H in mm units.
In the press-forming tool 1 according to the present embodiment, thc
thickness H is constant. However, when the thickness is not constant, the minimum
value of the thickness on the region which excludes the pressure receiving portion 30a
and comes into contact with the blank material 5 may be set to H. For example, as
the case where the thickness 13 is not constant, there is a case where a press-formed
product in which the height of the flange surface is not constant is formed, as shown in
FIG. 27.
The lower limit ofthe thickness L is preferably set to 20 mm. If the
thickness I, is less than 20 mm, the wrinkle suppression mold 25a may be plastically
deformed or damaged during drawing and bending processing (during press forming).
On the other hand, in the case of 40 5 H 5 50, the upper limit of the thickness
L is preferably set to 0.8 x 14. If the thickness L exceeds 0.8 x H, even when the
pressure receiving portion 30a receives the reaction force from the wrinkle suppression
force increasing portion 16a, the wrinlcle suppression mold 25a is not elastically
deformed, and thus, the reaction force may not be effectively transmitted to the blanlc
material 5.
In the case of 40 5 H 5 50, the preferable upper limit of the thickness L is 0.6
x N. If the upper limit of the thickness L is 0.6 x H, even when capability of the
wrinkle suppression force increasing portion 16a is small, the reaction force generated
by the wrinkle suppression force increasing portion 16a can be effectively transmitted
to the blank material 5.
[0048]
In the case of 50 < H 5 80, the upper limit of the thickness L is preferably set
to 40 mm regardless of the thickness H. The maximum value of the reaction force:
which is received from the wrinkle suppression force increasing portion 16a to the
pressure receiving portion 30a, is 6.5 MPa. Accordingly, if the thickness L exceeds
40 mm, stiffness of the pressure receiving portion 30a is increased, and the wrinkle
suppression mold 25 may not be elastically deformed even by the maximum value of
the reaction force.
[0049]
If the thiclcness H is less than 40 mm, the stiffness of the entire wrinkle
suppression mold 25a is not suflicient. On the other hand, if the thickness H exceeds
80 mm, the stiflness of the wrinkle suppression mold 25a is increased more than
necessary, and a material cost of the wrinkle suppression mold 25a is also increased.
[0050]
In summary about the thicknesses of the wrinkle suppression mold 25a, a
relationship between the thickness L and the thickness H preferably satisfies the
relationship of the following Expression 1 or 2. Moreover, although it is not shown,
the wrinkle suppression mold 25b is also similar to the above.
2 0 i L i 0 . 8 x H w h e n 4 0 i H i 5 0 (Expression 1)
20 5 L i 40 whcn 50 < H 5 80 (Expression 2)
[0051]
The reaction force from the wrinkle suppression force increasing portion 16a
is generated from contacting the pressure receiving portion 30a provided on the
wrinkle suppression mold 25a with the pin 40a, until the pressure receiving portion 30a
reaches the press-forming ending point. The position of contacting the pressure
receiving portion 30a provided on the,.wri&le suppression mold 25a with the pin 40a
may be a predetermined position in the end phase of the press forming. The position
of contacting the pressure receiving portion 30a with the pin 40a may be controlled by
changing the protruding length (height) of the tip of the pin 40a from the suiiace of the
plate 14.
[0052]
As shown in FIG. 4A, a protruding height G of the tip of the pin 40a from the
surface of the plate 14 may be a height which adds a groove depth (a value which is
obtained by subtracting L from H) of the pressure receiving portion 30a which is
constituted of a groove portion and a distance from the surface of the plate portion 14
to the above-described predetermined position which is added the increased wrinlcle
suppression force in the end phase of the press forming.
[0053]
The protruding height or the tip of the pin 40a of the wrinkle suppression
forcc increasing portion 16a from the surface of the plate 14 is defined as G in mm
units. A press strolte distance from a press-forming starting point, which is a press
stroke position at which the plastic deformation of the blank material 5 starts, to the
press-forming ending point is defined as PS in mm units. At this time, the protruding
height G of the wrinkle suppression force increasing portion 16a may preferably satisfy
the following Expression 3. Moreover, although it is not shown, the wrinkle
suppression force increasing portion 16b is also similar to the above.
0.02 x PS + H - L 5 G 5 0.3 x PS + H - L (Expression 3)
[0054]
The protruding height G of the pin 40a is preferably equal to or more than a
value which adds the groove depth (H-L) of the pressure receiving portion 30a to 2%
of the press strolte distance PS (0.02 x,PS). That is to say, the interval of the press
stroke which increase the wrinkle suppression force in the end phase of the press
forming is preferably equal to or more than 2% of the press strolte distance PS.
If the protruding height G is less than the value (0.02 x PS + 13 - L), Lhe
increase ofthe wrinkle suppression force is not sufficient, and the effects which is
exerted by decreasing the springback may be unstable. In order to further decrease
the springback, the value of the protruding height G is preferably equal to or more than
(0.05 x PS + H - L).
[0055]
On the othcr hand, it is preferable that the protruding height G of the pin 40a
be less than or equal to a value which adds the groove depth (H-L) of the pressure
receiving portion 30a to 30% ofthe press stroke distance PS (0.3 x PS). That is to say,
the interval of the press stroke which increases the wrinkle suppression force in the end
I phase of the press forming is preferably less than or equal to 30% of the press strolce
1 I distance PS.
I If the protruding height G exceeds the value (0.3 x PS + H - L), since the
interval of increasing the wrinlcle suppression force becomes too long, a difference in
the wrinkle suppression force becomes smaller between the press-forming starling
I
point and the press-forming ending point. Accordingly, the effect which is exerted by
increasing the wrinkle suppression force is decreased only in the end phase of the press
forming is decreased, and thus, the springback may occur to the contrary. In order to
further decrease the springback, the value of the protruding height G is preferably less
than or equal to (0.15 x PS + H L ) .
[0056]
So far, it is mainly described regardingthe wrinkle suppression mold 25a and
the wrinkle suppression force increasipg portion 16a. I-Iowever, the wrinkle
suppression mold 25b and the wrinkle suppression force increasing portion 16a are
similar to the above.
[0057]
FIGS. 6A and 6B show the press-formed product which is formed by the
press-forming tool 1 according to the present embodiment. FIG. 6A is a perspective
view, and FIG. 6B is a vertical cross-sectional view when viewed from an arrow A
direction in FIG. 6A. In FIGS. 6A and 6B. a reference numeral 50 indicates the
press-formed product.
[005S]
The press-formed product 50 includes flange portions 54a and 54b, vertical
wall portions 55a and 55b, and a top portion 5%. Moreover, straight side portions
5 la and 5 1 b and a bent portion 52 interposed between the straight side portions 5 1 a
and 5 1b arc provided on both ends of the press-formed product 50.
When viewed from the cross section perpendicular to the longitudinal
direction, the press-formed product 50 has a so-called hat-shaped cross section, and
both ends in the longitudinal direction of the press-lormed product 50 are opened.
Here, when viewed from an arrow A direction in FIG. 6A, the hat-shaped cross section
is a shape which includes the top portion 55c provided on the center portion in the
width direction, the vertical wall portions 55a and 55b provided to be inclined 14om
both ends of the top portion 55c toward one surface side of the top portion 55c, and the
flange portions 54a and 54b provided to be parallel with the top portion 55c fiom the
tips of the vertical wall portions 55a and 55b.
[0059]
When the press forming is performed, according to the shape of the pressformed
product 50, it is generated thata portion in which a plastic flow of the blank
material 5 is easily occurred and a portion in which the plastic flow is not easily
occurred. According to a difference in ease of the generation of the plastic flow, nonuniformity
of residual stress in a plate thickness direction or an in-plane direction of
the press-formed product 50 occurs,
Moreover, due to the non-uniformity of the residual stress, for example,
springback such as warpage, twist, or waviness of the vertical wall portlons 5521 and
55b occurs on the press-formed product 50. Particularly, when the shape of thc pressformed
product 50 has a curved portion, shrinkage flange deformation or extension
flange deformation is applied in the longitudinal direction of the press-lormed product
50. Accordingly, the non-uniformity of the residual stress in the plate thickness
direction or the in-plane direction is increased.
In general, after the drawing and bending processing is performed, finishing
processing (restriking processing) is performed to the press-formed product 50.
According to the restriking processing, when the press-formed product 50 is processed
:: to the shape of a press-formed product 57 shown in FIGS. 16A and 16B described
I
below, remarlcable waviness occurs on the vertical wall portion 55a or the like of the
bent portion 52.
In order to decrease dimension accuracy defects of the press-formed product
57, in general, an advanced estimation of a deformation amount generated by the
springback into mold dimensions at the time of design is often performed. However,
I when the springback is waviness, it is difficult to estimate the deformation amount in
advance.
In addition, since correction of the mo1.d in order to solve the waviness ofthe
press-formed product 57 includes trialand error, a lot of time and costs are required for
the correction of the mold.
[0061]
The waviness is generated since the vertical wall portion 55a of the bent
portion 52 becomes the extension flange deformation region by the drawing and
bending processing (press forming). Accordingly, tensile stress in the longitudinal
direction of the press-formed product 50 is increased, and the non-uniformity of the
residual stress in the plate thickness direction or the in-plane direction of the pressformed
product 50 is promoted.
Due to the non-uniformity of the residual stress of the press-formed product
after drawing and bending processing 50, waviness occurs on the press-formed product
after restriking processing 57. Accordingly, in order to remove the waviness of the
bent portion 52, the wrinltle suppression force applied to the bent portion 52 is
preferably increased in the end phase of the press forming of the draw-bending
processing.
[0062]
In order to increase the wrinltle suppression force applied to the bent portion
52 in the end phase of the press forming compared to the straight side portions 51a and
51 b, as shown in FIGS. 1A to 2, the pressure receiving portion 30a is provided on the
wrinkle suppression mold 25a and the pressure receiving portion 30b is provided on
the wrinkle suppression mold 25b. In order to elastically deform the wrinkle
suppression molds 25a and 25b in the end phase of the press forming, the wrinltle
suppression force increasing portions 16a and 16b are disposed on the plate portion 14.
[0063]
As described above, the wrinkle suppression force is increased in the end
phase of the press forming, and thuS, tension of the vertical wall portion 55a of the bent
portion 52, which is the region in which the extension flange deformation occurs, is
increased. As a result, the non-uniformity of the residual stress in the plate thickness
direction or the in-planc direction, which occurs the springback, of the press-formed
product 50 is decreased
The region in which the shrinkage flange deformation occurs is also similar to
the above. That is to say, as described above, the wrinltle suppression force is
increased in the end phase of the press forming, and thus, tension of the vertical wall
portion 55b of the bent portion 52 which is the region in which the shrinkage flange
deformation occurs is also increased. As a result, the springback at the region in
which the shrinkage flange deformation occurs is also decreased.
LO0641
When the pressure receiving portions 30a and 30b are not provided on the
wrinltle suppression molds 25a and 25b, the wrinltle suppression molds 25a and 25b
are not elastically deformed. The reaction force from the wrinkle suppression force
increasing portions 16a and 16b is distributed on the entire wrinkle suppression molds
25a and 25b. Accordingly, the wrinkle suppression force cannot be locally increased
on the bent portion 52 in the end phase of the press forming, and thus, the wrinkle
suppression force needed in the bent portion 52 cannot be applied.
As a result, tension which is necessary to suppress the springback cannot be
applied on the vertical wall portions 55a and 55b of the bent portion 52. Accordingly,
effects which is exerted by decreasing the springback of the press-formed product 50
are significantly decreased.
In order to decrease the distribution ofthe reaction force from the abovedescribed
wrinkle suppression force! ipcreasing portions 16a and 16b by increasing
capability of the wrinkle suppression force increasing portions 16a and 16b, for
example, it is necessary to increase the diameter of the disc spring 42a or increase the
number of the disc springs 42. In this case, the sizes of the wrinkle suppression force
increasing portions 16a and 16b are increased.
On the other hand, in order to press-form a metal plate having a large plastic
flow resistance and large springback such as high tensile strength steel or high strength
aluminum alloy, since the shape of the press-formed product 50 is curved, it is
particularly necessary to increase the wrinkle suppression force in the end phase ofthe
press forming on the region in which the extension flange deformation or the shrinkage
flange deformation occurs, or the like
Accordingly, when the high tensile strength steel, the high strength aluminum
alloy, or the like is press-formed, and in the case of decreasing the distribution of the
reaction force by increasing the capability of the wrinkle suppression force increasing
portions 16a and 16b, it is necessary to significantly increase the sizes of the wrinkle
suppression force increasing portions 16a and 16b. Accordingly, it is difficult to
dispose the wrinkle suppression force increasing portions 16a and 16b on the pressforming
tool 1.
100671
Next, a press-forming tool according to a second embodiment of the present
invention will be described. FIGS. 7A and 7B are views showing a schematic
configuration of the press-forming tool according to the second embodiment of the
present invention. FIG. 7A is a perspective view showing the entirety thereof and
FIG. 7B is a plan view of a punch configuring the press-forming tool.
FIG. 8 is a perspective view of a wrinkle suppression mold of the pressforming
tool according to the present embodiment when viewed from a first surface
side.
[0068]
A press-forming tool 2 of the present embodiment is the same as the pressforming
tool 1 of the first embodiment except that only the wrinkle suppression force
increasing portion 16b is provided on the plate 14, the pressure receiving portion 30b
formed of a groove portion is disposed only on the wrinkle suppression mold 25b, and
a wrinkle suppression mold 25e does not include the pressure receiving portion.
[0069]
In the press-forming tool 2 according to the present embodiment, the wrinkle
suppression force with respect to the blank material 5 can be increased only on the
region (only the portion which is particularly added the increased wrinlcle suppression
force) in which thc extension flange deformation occurs. That is to say, when the
tensile strength of the blank material 5 is not so high, each of the pressure receiving
portion 30b and the wrinkle suppression force increasing portion 16b may be disposed
according to curvature or the like of the bent portion 52 of the press-formed product 50.
[0070]
Next, a press-forming tool according to a third embodiment of the present
invention will be described. FIGS. 9A and 9B are views showing a schematic
configuration oT the press-forming tool according to the third embodiment of the
present invention. FIG. 9A is a perspective view showing the entirety thereof and
FIG. 9B is a plan view of a punch configuring the press-forming tool.
[0071]
A press-forming tool 3 according to the present embodiment is the same as the
press-forming tool 1 according to the Qrst embodiment except that wrinkle suppression
force increasing portions 16a, 16b, 16c, 16d, 16e, and 16f are disposed on the plate
portion 14.
Moreover, the wrinkle suppression molds 25a and 25b of the press-hrming
tool 3 according to the present embodiment shown in FIG. 9A are the same as the
wrinkle suppression molds 25a and 25b of the press-forming tool 1 according to the
first embodiment shown in FIG. 2.
[0072]
As shown in FIGS. 9A and 9B, the press-forming tool 3 according to the
present embodiment includes the wrinkle suppression force increasing portions 16c to
16f in addition to the wrinkle suppression force increasing portions 16a and 16b which
come into contact with the pressure receiving portions 30a and 30b in the end phase of
the press forming. Accordingly, it is possible to precisely control the wrinkle
supprcssion force with respect to the blank material 5 in the end phase of the press
forming.
However, compared to the wrinkle suppression force increasing portions 16a
and 16b which come into contact with the pressure receiving portions 30a and 30b, in
the wrinkle suppression force increasing portions 16c to 16f which come into contact
with the first surfaces 3 la and 31b not the pressure receiving portions 30a and 30b, the
effect which is exerted by increasing the wrinkle suppression lorce with respect to the
blank material 5 is smaller. That is to say, whether or not disposing the wrinkle
suppression force increasing portions 16c to 16f which come into contact with the first
surface 3 la and 3 lb, which is not the pressure receiving portions 30a and 30h, may be
determined according to the shape of the press-formed product or the structure of the
press mold.
[0073] i
Next, a press-forming tool according to a fourth embodiment of the present
invention will be described. FIGS. 10A and 10B arc views showing a schematic
configuration of the press-forming tool according to the fourth embodiment of the
present invention. FIG. 1OA is a perspective view showing the entirety thereof and
FIG. 10B is a plan view of a punch configuring the press-forming tool.
FIG. 11 is a perspective view when a wrinkle suppression mold of the pressforming
tool according to the fourth embodiment is viewed from a first surlace side.
FIG. 12 is a view explaining the wrinkle suppression mold according to the present
embodiment and is a vertical cross-sectional view of the wrinkle suppression mold
when viewed 12om an arrow C direction shown in FIG. 11.
[0074]
A press-forming tool 4 according to the present embodiment is the same as the
press-forming tool 1 according to the first embodiment except that the pressure
I
I receiving portions 30c and 30d of the wrinkle suppression molds 25c and 25d include
1 groove portions 35c and 35d and the groove portions 35c and 35d, become a portion of
the boundary portion and partition the pressure receiving portions 30c and 30d.
~ In addition, the punch 10 according to the present embodiment shown in FIG.
;I
IOB is the same as the punch 10 according to the first embodiment.
[0075]
The wrinkle suppression molds 25c and 25d according to the present
embodiment are constituted of the minimum number of components which is difficult
to divide it further, from the viewpoint of the structure of the press mold and the shape
of the press-formed product. That is to say, the wrinkle suppression molds 25c and
25d are not split-type wrinkle suppression molds but integral-type wrinkle suppression
molds.
The wrinkle suppression molds 25c and 25d include first surfaces 3 1c and 31d
which oppose the plate portion 14 of the punch 10 and come into contact with the plate
portion 14 at the press-forming ending point. In addition, the wrinkle suppression
molds 25c and 25d includes second surfaces 32c and 32d which oppose the die 20 and
hold the blank material 5 along with the die 20
100761
In the wrinkle suppression molds 25c and 25d, the pressure receiving portions
30c and 30d which receive the reaction force for elastically deforming the wrinkle
suppression molds 25c and 25d in the end phase of the press forn~inga re provided on
the first surfaces 3 1c and 3 Id. The pressure receiving portions 30c and 30d include
the groove portions 35c and 35d. The groove portions 35c and 35d become a poition
of the boundary portion, and the pressure receiving portions 30c and 30d are
partitioned on the first surfaces 3 1 c and 3 id.
Specifically, as shown in FIG. 11, the pressure receiving portions 30c and 30d
are partitioned by the groove portions 35c and 35d and partial edges of the first
surfaces 3 1 c and 3 1d on the first surfaces 3 1 c and 3 1 d.
[0077]
In the end phase of the press forming, the pressure receiving portions 30c and
30d and the wrinkle suppression force increasing portions 16a and 16b come into
contact with each other, and thus, the wrinkle suppression molds 25c and 25d are
elastically deformed. As a result, it is possible to locally add the wrinkle suppression
force to the portion of the blank material 5 which is added the increased wrinkle
suppression force.
Accordingly, the wrinkle suppression force in the shrinkage flange
deformation region or the extensiod W g e deformation region can be locally increased
in the end phase of the press forming, and thus, it is possible to effectively suppress the
springback.
[007S]
In the end phase of the press forming, the wrinltle suppression molds 25c and
25d receive the reaction force from the wrinkle suppression force increasing portions
16a and 16b by the pressure receiving portions 30c and 30d, the wrinkle suppression
molds 25c and 25d include the groove portions 35c and 35d. Accordingly, the
reaction force is not distributed to the entire wrinkle suppression molds 25c and 25d.
If the wrinkle suppression molds 25c and 25d receive the reaction force from
the wrinkle suppression force increasing portions 16a and 16b, the wrinkle suppression
molds 25c and 25d are convexly and elastically deformed to the die 20 (blank material
5) side with the groove portions 35c and 35d as the boundary portion. As aresult, it
is possible to locally and intensively increase the wrinkle suppression force with
respect to the blank material 5.
[0079]
The depths, widths, or the like of the groove portions 35c and 35d of the
present emhodiment are not particularly limited. The groove portions 35c and 35d
may have appropriate dimensions according to the shape of the press-formed product
50 and the structure oT the press mold 4. The thickness L of each of the wrinltle
suppression mold 25c and 25d in the pressure receiving portions 30c and 30d
excluding the groove portions 35c and 35d, and the thickness H of each of the wrinkle
suppression mold 25c and 25d in the region which excludes the pressure receiving
portions 30c and 30d and comes into contact with the blank material 5 are not
particularly limited.
In the present embodiment: 4though it is shown that the aspect in which the
thickness Land the thickness H are the same as each other, it is suflicient that the
thickness L is 20 5 L i H. Moreover, if the thickness L satisfies 20 5 L 5 H, similar
to the first embodiment, it is sufficient that the protruding height G of each of the
wrinkle suppression forcc increasing portions 16a and 16b is 0.02 x PS + H - L i G 5
0.3 xPS+H-L.
[0080]
The press-forming tools 1 to 4 according to the first to fourth embodiments of
the present invention are described above. Next, effective positions to dispose the
wrinkle suppression force increasing portions 16a to 16f and the pressure receiving
portions 30a to 30d will be described.
[OOSl]
FIGS. 13A and 13B are views showing a schematic configuration of a pressforming
tool of the related art which does not include the pressure receiving portion
and the wrinkle suppression force increasing portion. FIG. 13A is a perspective view
showing the entirety thereof, and FIG. 13B is a plan view showing a punch configuring
the press-forming tool of the related art. In FIG. 13A, a reference numeral 91
indicates the press-forming tool of the related art.
[0082]
FIG. 14 is an explanatory view showing a plate thickness distribution of a
flange portion in a press-formed product when the blank material 5 having the plate
thickness of 1.0 mm is performed drawing and bending processing (press-forming)
using the press-forming tool of the related art shown in FIG. 13A.
That is to say, FIG. 14 is a view showing the state of the press-formed product
50 after the blank material 5 is performed drawing and bending processing (pressforming)
using the press-forming tobl,9l shown in FIG. 13A, and is plan view when
viewed along the pressing direction in a state where the die 20 is omitted.
In FIG. 14, the measurement results of the plate thickness of the flange
portions 54a and 54b arc shown. As shown in FIG. 14, the flange portions 34a and
54b include a curved outside portion 6a, a curved inside portion 6b, and straight line
portions 6c, 6d, 6e, and 6f.
[0083]
As shown in FIG. 14, the plate thickness of the curved outside portion 6a is
thick. The curved outside portion 6a becomes a plate thickness maximum portion in
which the plate thiclcness is the maximum in the flange portions 54a and 54b of the
press-formed product 50. On the other hand, the plate thickness of the curved inside
portion 6b is thin.
In this way, in the press-formed product 50 which is press-formed using the
press-forming tool 91 of the related art, the plate thiclcnesses in respective portions in
the flange portions 54a and 54b are not the same as one another. The second surfaces
32e and 32f of wrinkle suppression molds 25e and 25f and the die 20 which hold the
blank material 5 are flat.
Accordingly, in the wrinltle suppression mold 91 in which the pressure
receiving portions 30a to 30d are not provided like the wrinkle suppression molds 25e
and 25f, when the plate thickness of each position in the flange portions 54a and 54b is
changed during the press forming, a portion to which the wrinkle suppression force is
strongly applied and a portion to which the wrinkle suppression force is weakly
applied exist.
If the magnitude of the wrinkle suppression force is changed according to the
portion during the press forming, a balance in the plastic flow of the blank material 5
during the plastic deformation is 10% As a result, dimension accuracy of the pressformed
product 50 after the press forming is decreased.
[0084]
In order to suppress the decrease in the dimension accuracy of the plessformed
product 50 due to the above-described coexistence of the portion to which the
wrinkle suppression force is strongly applied and the portion to which the wrinkle
suppression force is weakly applied, it is preferable to increase the wrinkle suppression
force at the portion at which the plate thickness in the flange portions 54a and 54b is
decreased during the press forming, in the end phase of the press forming.
Specifically, the press-forming tool 91 of the related art in which the pressure
receiving portions 30a to 30d and the wrinkle suppression force increasing portions
16a to 16f are removed from the press-forming tools 1 to 4 is set as a reference. A
region in which the plate thickness becomes the maximum in the flange portions 54a
I and 54b of the press-formed product 50 is defined as a plate thickness maximum
portion, and a region in which the plate thickness is more than 0% and less than or
equal to 97% with respect to the plate thickness maximum portion is defined as a plate
thickness decreasing portion. In this case, when viewed along the pressing direction,
the pressure receiving portions 30a to 30d of the wrinkle suppression molds 25a to 25d
are preferably disposed to overlap with a portion of the plate thickness decreasing
portion on the blank material 5.
As a result, the wrinkle suppression force at the portion at which the plate
thickness in the flange portions 54a and 54b is decreased during the press forming can
be preferably increased in the end phase of the press forming. The wrinkle
suppression force on the plate thickness decreasing portion, in which the plate
thickness is more than 0% and less than or equal to 97% with respect to the plate
thickness maximum portion, is preferqbly increased in the end phase of the press
forming, and thus, the springback orthe press-formed product 50 can be effectively
decreased.
[0085]
FIG. 15 is an explanatory view exemplifying preferable positions at which the
pressure receiving portion and the wrinkle suppression force increasing portion are
disposed in the view showing the plate thickness distribution of the flange portion in
the press-formed product which is formed by the press-forming tool of the related art
shown in FIG. 13A. That is to say, as an example, FIG. 15 is an explanatory view in
which the disposition positions of the pressure receiving portions 30b and 30d and the
wrinkle suppression force increasing portion 16b are overlapped in FIG. 14.
[0086]
As shown in FIG. 15, the pressure receiving portions 30b and 30d are
preferably disposed so that a portion of the curved inside portion 6b (the portion which
becomes the plate thiclcness decreasing portion having the plate thickness of more than
0% and less than or more than 97% with respect to the plate thicltness maximum
portion) overlaps with the curved outside portion 6a (the portion which becomes the
plate thickness maximum portion in the flange portions 54a and 54b of the pressformed
product 50 press-formed by the press-forming tool 91 of the related art).
The wrinkle suppression force increasing portion lbb is preferably disposed
such that the wrinkle suppression force increasing portion 16b protrudes toward the
pressure receiving portions 30b and 30d, and generate the reaction force opposite to the
pressing direction when the wrinkle suppression force increasing portion is pressed in
the pressing direction, and elastically deform the wrinlcle suppression molds 25b and
25d.
As a result, it is possible to' preferably increase the wrinkle suppression force
of the curved inside portion 6b in which the plate thicliness is decreased in the flange
portions 54a and 54b during the press forming, in the end phase of the press forming.
[0087]
In this way, by disposing the pressure receiving portions 30b and 30d and the
wrinkle suppression force increasing portions 16b, the wrinkle suppression molds 25b
and 25d are convexly and elastically deformed to the blank material 5 side by the
pressure receiving portions 30b and 30d in the end phase of the press forming, and thus,
it is possible to locally and intensively increase the wrinkle suppression force on the
curved inside portion 6b,
[OOSS]
The press-forming tools according to each aspect of the present invention
- 41 -
described above are summarized as follows.
(1) The press-forming tools 1 to 4 according to each aspect of the present
invention include the punch 10 which includes the punch portion 12 and the plate
portion 14 configured to transfer a shape to the blank material 5, the die 20 which is
paired with the punch 10 and opposes the punch portion 12, and wrinkle suppression
molds 25a to 25d.
The wrinkle suppression molds 25a to 25d include the first surfaces 3 la to
3 Id, the second surfaces 32a to 32d, and the side surfaces (third surfaces) 37a and 33b
which are continuous between the first surface 3 la to 3 1d and the second surface 32a
to 32d and which oppose the punch portion 12. The wrinkle suppression molds 25a
to 25d are disposed between the side surfaces (third surfaces) 33a and 33b and the
punch portion 12 via a gap.
The first surfaces 3 1 a to 3 1 d oppose ttie plate portion 14 and come into
contact with the plate portion 14 at i hp~res s-forming ending point. The second
surfaces 32a to 32d oppose the die 20 and hold the blank material 5 along with the die
The press-forniing tools 1 to 4 according to each aspect of the presenl
invention include: pressure receiving portions 30a to 30d which include the groove
portion, which receives the reaction force to elastically deform the wrinkle suppression
molds 25a to 25d in the end phase of the press forming, on the first surfaces 31a to 3 1d
of the wrinkle suppression molds 25a to 25d; and wrinkle suppression force increasing
portions 16a and 16b which are disposed on surfaces opposing the first surfaces 3 la to
3 id of the plate portion 14, protrude toward the pressure receiving portions 30a to 30d,
and generate the reaction force in a direction opposite to the pressing direction when
the wrinkle suppression force increasing portions are pressed in the pressing direction
in the cnd phase of press forming.
[0089]
(2) Based on a case where the pressure receiving portions 30a to 30d and the
wrinkle suppression force increasing portions 16a and 16b are removed from the pressforming
tools 1 to 4, the region in which the plate thickness is maximum in the flaigc
portions 54a and 54b of the press-formed product 50 is defined as the plate thickness
maximum portion. The region in which the plate thickness is more than 0% and less
than and equal to 97% with respect to the plate thickness ma~imump ortion is defined
as the plate thicltness decreasing portion. In this case, the pressure receiving portion
30a to 30d may overlap with a portion of the region corresponding to the plate
I thickness decreasing portion in the blank material 5 when viewed along the pressing
direction.
[0090]
(3) The pressure receiving bortions 30a and 30b is constituted of a groove
portion, the thickness of each of the wrinkle suppression molds 25a and 25b in the
positions of the pressure receiving portions (groove portions) 30a and 30b is defined as
L in mm units. The minimum value of the thickness of each of the wrinltle
suppression molds 25a and 25b in the position which excludes the pressure receiving
portions (groove portions) 30a and 30b and comes into contact with the blank material
5 is defined as H in mm units. In this case, each of the wrinkle suppression molds
25a and 25b may satisfy the following Expressions 1 and 2, and when the protruding
height of each of the wrinkle suppression force increasing portions 16a and 16b from
the surface of the plate portion 14 is defined as G in mm units and the press stroke
distance from the press-forming starting point to the press-forming ending point is
defined as PS in mm units, the protruding height G of each of the wrinkle suppression
force increasing portions 16a and 16b may satisfy the following Expression 3.
20 5 L 5 0.8 x H when 40 5 H 5 50 (Expression 1)
20 5 L 5 40 when 50 < H 5 80 (Expression 2)
0.02xPS+H-LiG50.3 xPS+H-L(Expression3)
[0091]
(4) Aportion of the boundary which partitions the pressure receiving portions
30c and 30d may be the groove portions 35c and 35d. Specifically, the pressure
receiving portions 30c and 30d may include the groove portions 35c and 35d, the
groove portions 35c and 35d become a portion ofthe boundary portion, and thus, the
pressure receiving portions 30c and 30d may be partitioned on the first surfaces 31c
and 3 1 d.
[0092]
(5) The wrinkle suppression force increasing portions 1 6a and 16b may
include an elastic body which appli&s\the reaction force.
(6) The elastic body may be at least one of the disc spring 42a, a helical spring,
and rubber.
[0093]
Next, a method for manufacturing the press-formed product 50 which is pressformed
using the press-forming tools 1 to 4 according to the embodiments of the
present invention will be described.
[0094]
A method for manufacturing the press-formed product 50 according to an
aspect of the present invention, including: a step of increasing the wrinkle suppression
force with respect to a portion of the blank material 5 during the press forming in the
end phase of the press forming from the position at which the press stroke is 2% to
30% to the forming end position using the press-forming tools 1 to 4 according the
above-described aspects, and when the forming start position of the press stroke when
the blank material 5 is press-formed is defined as 100% and the forming end position
of the press stroke is defined as 0%.
[0095]
According to the method of manufacturing the press-formed product 50, the
springback is suppressed, and thus, the press-formed product 50 having high
dimension accuracy can be obtained. In the method for manufacturing, if thc position
of the press stroke which is a starting position of increasing the wrinkle suppression
force is less than 2%, the increase in the wrinkle suppression force is not sufficient, and
thus, the effect which is exerted by decreasing the springback may be unstable.
On the other hand, if the position of the press stroke which is a starting
position of increasing the wrinkle suppression force is more than 30%, the interval of
increasing the wrinkle suppression for,ce becomes too long. Accordingly, the
difference in the wrinkle suppression force is decreased between the forming starting
position of the press stroke and the forming ending position of the press stork.
Therefore, the effect which is exerted by increasing the wrinkle suppression
force only in the end phase of the press forming is decreased, and thus, the springback
may occur to the contrary. Moreover, in order to further decrease the springback, the
position of the press stroke which is a starting position of increasing the wrinkle
suppression force is preferably 5% to 15%.
[Example 11
[0096]
Effects of the aspects of the present invention will be further described
according to Examples. However, conditions of Examples are conditions adopted to
coniirm feasibility and effects of the present invention, and the present invention is not
limited to the conditions. The present invention adopts various conditions if
achieving the object of the present invention without departing from the gist of the
prescnt invention.
[0097]
(Example 1)
The blank material 5 was obtained by laser-cutting the high tensile strength
steel sheet in a predetermined shape. The blank material 5 was performed drawing
and bending processing (press-forming) so that the shape became a hat-shaped cross
section. Moreover, after the drawing and bending processing, the blank material was
performed finishing processing (restriking processing). Conditions or the like for
each process are described below.
[0098]
The high tensile strength sted sheet having 1.0 mm in the plate thickness and
590 MPa in the tensile strength was used as the material, the high tensile strength steel
sheet was laser-cut so that the shape after the finishing processing (restriking
processing) became a cross-section width of 60 mm and a height of 80 mm as shown in
FIGS. 16Aand 16B, and thus, the blank material 5 was obtained.
The blank material 5 was performed drawing and bending processing (pressforming)
to have the shape (hat-shaped cross section) shown in FIGS. 6A and 6B using
the press-forming tool 1 FIGS, lA to 2 (the press-forming tool 1 according to the first
embodiment), the press-forming tool 2 shown in FIGS. 7A to 8 (the press-forming tool
2 according to the second embodiment), and the press-forming tool 3 shown in FIGS
9A and 9B (the press-forming tool 3 according to the third embodiment).
[OlOO]
As the wrinkle suppression force increasing portions 16a to 16f, the disc
spring unit which is a combination of disc springs 42a shown in FIG. 4A was used.
The load (reaction force) to which the wrinkle suppression force increasing portions
16a to 16f were applied to the wrinkle suppression molds 25a and 25b in the end phase
of the press forming and were changed according to the number and the combination
method (parallel, series, and parallel series) of the disc springs 42a.
In the press-forming tool 3 (the press-forming tool 3 according to the third
embodiment) shown in FIGS. 9A and 9B, in addition to the pressure receiving portions
30a and 30b, the wrinkle suppression force increasing portions 16c to 16f were
disposed.
[OlOl]
The thicknesses H of the wrinkle suppression molds 25a and 25b on the
region which exclude the pressure