U.S. patent application number 14/129633 was filed with the patent office on 2014-05-15 for hot-pressing apparatus.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. The applicant listed for this patent is Kenjiro Ishida, Takanobu Suzuki. Invention is credited to Kenjiro Ishida, Takanobu Suzuki.
Application Number | 20140130564 14/129633 |
Document ID | / |
Family ID | 47436690 |
Filed Date | 2014-05-15 |
United States Patent
Application |
20140130564 |
Kind Code |
A1 |
Suzuki; Takanobu ; et
al. |
May 15, 2014 |
HOT-PRESSING APPARATUS
Abstract
This invention relates to a hot-pressing method and a
hot-pressing apparatus capable of quenching a workpiece at a
sufficient cooling rate. In a hot-pressing step, a hot-pressing
apparatus presses and cools a workpiece at the same time. The
hot-pressing apparatus includes a lower die and an upper die whose
forming surfaces face each other. A top surface of the lower die is
provided with a plurality of beads so that a part of the workpiece
difficult to come in contact with the forming surface of the lower
die and the forming surface of the upper die positioned at the
bottom dead center is formed into a stepped shape.
Inventors: |
Suzuki; Takanobu;
(Miyoshi-shi, JP) ; Ishida; Kenjiro; (Nagoya-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Suzuki; Takanobu
Ishida; Kenjiro |
Miyoshi-shi
Nagoya-shi |
|
JP
JP |
|
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi, Aichi
JP
|
Family ID: |
47436690 |
Appl. No.: |
14/129633 |
Filed: |
July 6, 2011 |
PCT Filed: |
July 6, 2011 |
PCT NO: |
PCT/JP2011/065501 |
371 Date: |
December 27, 2013 |
Current U.S.
Class: |
72/342.5 |
Current CPC
Class: |
B21D 22/208 20130101;
B21J 1/06 20130101; B21D 37/16 20130101; C21D 1/673 20130101 |
Class at
Publication: |
72/342.5 |
International
Class: |
B21J 1/06 20060101
B21J001/06 |
Claims
1. (canceled)
2. A hot-pressing apparatus comprising a lower die having a lower
forming surface, and an upper die having an upper forming surface
facing the lower forming surface, which causes the lower die and
the upper die to press a heated workpiece arranged therebetween,
and at the same time, to keep the forming surfaces thereof in
contact with a surface of the workpiece to cool the workpiece,
wherein one of the lower die and the upper die has a protrusion
which protrudes from an intermediate part, in a right-left
direction, of the forming surface thereof toward the forming
surface of the other, and which is continuously formed in a
front-rear direction perpendicular to the right-left direction, the
other of the lower die and the upper die has a recess which is
recessed from an intermediate part, in the right-left direction, of
the forming surface thereof in conformity with a shape of the
protrusion, and which is continuously formed in the front-rear
direction, the forming surface on which the protrusion is formed
includes a top surface extending in the right-left direction at a
protruding end of the protrusion, two lateral surfaces extending in
a direction opposite to that in which the protrusion protrudes from
both ends of the top surface in the right-left direction, and two
base surfaces extending outward in the right-left direction from
extending ends of the lateral surfaces, and the top surface is
formed as a bumpy surface for forming a part of the workpiece
corresponding to the top surface into a stepped shape when the
upper die arrives at a vicinity of a bottom dead center.
3. (canceled)
Description
TECHNICAL FIELD
[0001] The present invention relates to a hot-pressing method and a
hot-pressing apparatus for pressing and cooling a heated workpiece
at the same time.
BACKGROUND ART
[0002] Conventionally, a hot-press forming is widely known in which
a pressing machine to which a pair of dies (an upper die and a
lower die) are attached presses a workpiece, such as a steel plate,
heated to above a temperature at which an austenite structure
appears, and at the same time, brings the dies into contact with
the workpiece to quench the workpiece.
[0003] A technique on the hot-press forming is publicly known which
enables the dies to suitably cool the workpiece during the
quenching by forming water channels through which cooling water
flows inside the dies to cool the dies (for example, see Patent
Literature 1).
[0004] However, when the workpiece is quenched, clearances are
formed between the workpiece and the dies because of variation in
the thickness of the workpiece caused by the press working, a
precision error in the forming surfaces of the dies caused when the
dies are manufactured, flexure of the dies during the press
working, and the like. Consequently, a part of the workpiece where
the clearance between the part and the dies is larger than a
predetermined size has decreased contact areas with the forming
surfaces of the dies when the workpiece is quenched, which causes a
problem that the part is cooled at an insufficient cooling rate,
and hardness of the part is smaller than a predetermined value,
[0005] For example, as shown in FIG. 8, in the case where a flat
plate-like workpiece W is formed into what is called a hat shape,
large clearances tend to form between a top part Wt situated in the
uppermost part of the pressed workpiece W, and the dies. Therefore,
it is probable that hardness of the top part Wt is smaller than a
predetermined value.
CITATION LIST
Patent Literature
[0006] Patent Literature 1: JP 2005-7442 A
SUMMARY OF INVENTION
Problem to Be Solved By the Invention
[0007] The objective of the present invention is to provide a
hot-pressing method and a hot-pressing apparatus capable of
quenching a workpiece at a sufficient cooling rate.
Means for Solving the Problem
[0008] A first aspect of the invention is a hot-pressing method for
pressing and cooling a heated workpiece at the same time, using a
lower die having a lower forming surface, and an upper die having
an upper forming surface facing the lower forming surface. The
hot-pressing method includes a step for pressing the workpiece so
as to form a part of the workpiece difficult to come in contact
with the lower forming surface of the lower die and the upper
forming surface of the upper die positioned at a bottom dead center
into a stepped shape.
[0009] A second aspect of the invention is a hot-pressing apparatus
including a lower die having a lower forming surface, and an upper
die having an upper forming surface facing the lower forming
surface, which causes the lower die and the upper die to press a
heated workpiece arranged therebetween, and at the same time, to
keep the forming surfaces thereof in contact with a surface of the
workpiece to cool the workpiece. In the hot-pressing apparatus, at
least one of the forming surfaces of the lower die and the upper
die is formed as a bumpy surface so that a part of the workpiece
difficult to come in contact with the lower forming surface of the
lower die and the upper forming surface of the upper die positioned
at a bottom dead center is formed in a stepped shape.
[0010] Preferably, one of the lower die and the upper die has a
protrusion which protrudes from an intermediate part, in a
right-left direction, of the forming surface thereof toward the
forming surface of the other, and which is continuously formed in a
front-rear direction perpendicular to the right-left direction. The
other of the lower die and the upper die has a recess which is
recessed from an intermediate part, in the right-left direction, of
the forming surface thereof in conformity with a shape of the
protrusion, and which is continuously formed in the front-rear
direction. The forming surface on which the protrusion is formed
includes a top surface extending in the right-left direction at a
protruding end of the protrusion, two lateral surfaces extending in
a direction opposite to that in which the protrusion protrudes from
both ends of the top surface in the right-left direction, and two
base surfaces extending outward in the right-left direction from
extending ends of the lateral surfaces. The top surface is formed
as the bumpy surface.
Effects of the Invention
[0011] The present invention makes it possible to quench a
workpiece at a sufficient cooling rate, and to prevent hardness of
some parts in the workpiece from being smaller than a predetermined
value.
BRIEF DESCRIPTION OF DRAWINGS
[0012] FIG. 1 illustrates a hot-pressing apparatus according to an
embodiment of the present invention.
[0013] FIG. 2 is a perspective view showing beads.
[0014] FIG. 3 illustrates the hot-pressing apparatus in which an
upper die is at the bottom dead center.
[0015] FIG. 4 illustrates beads which are formed so that the
forming surfaces of dies are recessed.
[0016] FIG. 5 shows a workpiece being pressed.
[0017] FIG. 6 is a perspective view showing another embodiment of
beads.
[0018] FIG. 7 is a perspective view showing another embodiment of
beads.
[0019] FIG. 8 illustrates a conventional hot-pressing
apparatus.
DESCRIPTION OF EMBODIMENTS
[0020] With reference to FIGS. 1 and 2, described below is a
hot-pressing apparatus 1 as an embodiment of a hot-pressing
apparatus according to the present invention.
[0021] The hot-pressing apparatus 1 performs hot-press forming of a
workpiece W.
[0022] The workpiece W is a steel plate to be worked by the
hot-pressing apparatus 1, and is heated to above a temperature at
which an austenite structure appears by ohmic heating and the
like.
[0023] For convenience, a top-bottom direction in FIG. 1 is defined
as a top-bottom direction of the hot-pressing apparatus 1, and a
right-left direction in FIG. 1 is defined as a right-left direction
of the hot-pressing apparatus 1. In addition, this side in FIG. 1
is defined as a front side of the hot-pressing apparatus 1, and the
far side in FIG. 1 is defined as a rear side of the hot-pressing
apparatus 1, thereby a front-rear direction of the hot-pressing
apparatus 1 being defined.
[0024] As shown in FIG. 1, the hot-pressing apparatus 1 includes a
lower die 10 and an upper die 20 whose forming surfaces face each
other.
[0025] The lower die 10 corresponds to the upper die 20. The lower
die 10 is produced by performing numerical control machining of a
predetermined ingot. The lower die 10 is configured so that cooling
water flows thereinside.
[0026] The lower die 10 has a protrusion 11 which protrudes upward
from the forming surface (the upper surface) thereof.
[0027] The protrusion 11 protrudes upward from the forming surface
of the lower die 10. The protrusion 11 is continuously formed in
the front-rear direction in the intermediate part (the
substantially middle part), in the right-left direction, of the
forming surface of the lower die 10.
[0028] The lower die 10 has a top surface 10a extending in the
right-left direction at the protruding end (uppermost part) of the
protrusion 11, two lateral surfaces 10b extending in a direction
opposite to that in which the protrusion 11 protrudes (in the
bottom direction) from both the ends of the top surface 10a in the
right-left direction, and two base surfaces 10c extending outward
in the right-left direction from the extending ends (the bottom
ends) of the lateral surfaces 10b. These surfaces act as what is
called a hat-shaped forming surface of the lower die 10.
[0029] The top surface 10a of the lower die 10 is provided with a
plurality of beads 12.
[0030] As shown in FIG. 2, the bead 12 protrudes upward from the
top surface 10a. The bead 12 has a shape in which a semicircular
section thereof whose arc is situated at the upper part thereof
continues in the front-rear direction from the vicinity of the
front end to the vicinity of the rear end of the protrusion 11. In
other words, the bead 12 has a shape similar to that of one of two
equal parts into which a cylinder with an axis parallel to the
front-rear direction is divided along the axis, and is arranged so
that the flat surface (cutting surface of one of two equal parts
into which a cylinder is divided) comes in contact with the top
surface 10a.
[0031] The plurality of beads 12 (in the present embodiment, three
beads 12) are arranged at predetermined intervals in the right-left
direction.
[0032] The bead 12 is made of the same metal as the lower die 10,
or a metal with hardness larger than that of the lower die 10. The
bead 12 is formed by, after performing buildup welding on the top
surface 10a, performing numerical control machining so that the
buildup part is formed into a predetermined shape, by performing
numerical control machining so that the top surface 10a is formed
into a predetermined shape when producing the lower die 10 from a
predetermined ingot, or by means of a similar technique.
[0033] Thus, the bead 12 is formed in order to change the top
surface 10a of the lower die 10 into a bumpy surface.
[0034] As shown in FIG. 1, the upper die 20 corresponds to the
lower die 10. The upper die 20 is produced by performing numerical
control machining of a predetermined ingot. The upper die 20 is
configured so that cooling water flows thereinside.
[0035] The upper die 20 has a recess 21 recessed upward from the
forming surface (the lower surface) of the upper die 20 in
conformity with the shape of the protrusion 11.
[0036] The recess 21 is formed so that the forming surface of the
upper die 20 is recessed upward. The recess 21 is continuously
formed in the front-rear direction in the intermediate part (the
substantially middle part), in the right-left direction, of the
forming surface of the upper die 20.
[0037] The upper die 20 has a bottom surface 20a extending in the
right-left direction at the innermost part (uppermost part) of the
recess 21, two lateral surfaces 20b extending in a direction
opposite to that in which the recess 21 is recessed (in the bottom
direction) from both the ends of the bottom surface 20a in the
right-left direction, and two base surfaces 20c extending outward
in the right-left direction from the extending ends (the bottom
ends) of the lateral surfaces 20b. These surfaces act as what is
called a hat-shaped forming surface of the upper die 20.
[0038] The hot-pressing apparatus 1 configured as mentioned above
causes the lower die 10 and the upper die 20 to press the heated
plate-like workpiece W arranged between the forming surfaces
thereof to form the workpiece W into what is called a hat shape by
moving the upper die 20 to the bottom dead center so that the upper
die 20 cones close to the lower die 10. At the same time, the
hot-pressing apparatus 1 causes the lower die 10 and the upper die
20 to keep the forming surfaces thereof in contact with the surface
of the workpiece W to cool the workpiece W. Consequently, the
hot-pressing apparatus 1 produces the workpiece W as a product.
[0039] With reference to FIGS. 3 to 7, described below is a
hot-pressing step S1 as an embodiment of a hot-pressing method
according to the present invention.
[0040] The hot-pressing step S1 is a step in which the hot-pressing
apparatus 1 performing the hot-press forming of the workpiece
W.
[0041] In the hot-pressing step S1, by moving the upper die 20 to
the bottom dead center so that the upper die 20 comes close to the
lower die 10, the hot-pressing apparatus 1 causes the lower die 10
and the upper die 20 to press the heated plate-like workpiece W
arranged between the forming surfaces thereof, and at the same
time, brings the lower die 10 and the upper die 20 into contact
with the workpiece W to quench the workpiece W.
[0042] As shown in FIG. 3, since the top surface 10a of the lower
die 10 is provided with the plurality of beads 12, a top part Wt (a
part corresponding to the top surface 10a) situated in the
uppermost part of the pressed workpiece W is formed into a stepped
shape along the shapes of the plurality of beads 12 when the
workpiece W is pressed in the hot-pressing step S1. In other words,
the plurality of beads 12 act as a means which changes the top
surface 10a into a bumpy surface to form a part of the workpiece W
into the stepped shape.
[0043] Note that the "stepped shape" of the workpiece W is a shape
in which the workpiece W is bent to protrude toward the forming
surfaces of the lower die 10 and the upper die 20. In the present
embodiment, the workpiece W is formed into the wavy stepped shape
in which two parts protruding toward the forming surface (the top
surface 10a) of the lower die 10 are formed, and three parts
protruding toward the forming surface (the bottom surface 20a) of
the upper die 20 are formed.
[0044] Since the top part Wt of the workpiece W is formed to
protrude toward the forming surfaces of the lower die 10 and the
upper die 20, compared with the case where the top part Wt is not
formed in the stepped shape, the top part Wt has large contact
areas with a part of the forming surface of the lower die 10 where
the plurality of beads 12 are not formed, and the forming surface
of the upper die 20 when the workpiece W is quenched in the
hot-pressing step S1.
[0045] Moreover, since the top part Wt of the workpiece W is formed
along the shapes of the plurality of beads 12 formed on the top
surface 10a of the lower die 10, the top part Wt comes in contact
with the plurality of beads 12 forming a part of the forming
surface of the lower die 10 along the shapes of the plurality of
beads 12 when the workpiece W is quenched in the hot-pressing step
S1. Thereby, compared with the case where the plurality of beads 12
are not formed on the top surface 10a of the lower die 10, the top
part Wt has large contact area with the forming surface of the
lower die 10.
[0046] These make it possible, when the workpiece W is quenched in
the hot-pressing step S1, to cool the top part Wt of the workpiece
W at a sufficient cooling rate, and to prevent hardness of the top
part Wt from being smaller than a predetermined value.
[0047] In the present embodiment, the top surface 10a of the lower
die 10 is provided with the plurality of beads 12 so that the top
part Wt of the workpiece W is formed into the stepped shape.
[0048] This is because, when the workpiece W formed in the hat
shape is quenched, large clearances tend to form between the top
part Wt of the workpiece W and the dies (see FIG. 8), and hardness
of the top part Wt is more likely to be smaller than a
predetermined value.
[0049] In other words, the top surface 10a of the lower die 10 is
provided with the plurality of beads 12 so that a part of the
workpiece W difficult to come in contact with the forming surfaces
of the lower die 10 and the upper die 20 positioned at the bottom
dead center is formed into the stepped shape.
[0050] Note that the "part difficult to come in contact" with the
forming surfaces of the lower die 10 and the upper die 20
positioned at the bottom dead center in the workpiece W is a part
where an amount of clearance (a distance) between the workpiece W
and conventional dies which does not have the plurality of beads 12
is larger than a predetermined value when the workpiece W is
quenched, namely, a part where hardness thereof is smaller than a
predetermined value (is insufficient) after the hot-press forming.
The part is may previously be found by a simulation and the
like.
[0051] As mentioned above, the top surface 10a of the lower die 10
is provided with the plurality of beads 12, thus enabling to form
the top part Wt difficult to come in contact with the forming
surfaces of the lower die 10 and the upper die 20 positioned at the
bottom dead center into the stepped shape.
[0052] Therefore, it is possible to increase the contact areas
between the top part Wt of the workpiece W, and the forming
surfaces of the lower die 10 and the upper die 20 to prevent the
hardness of the top part Wt from decreasing, and to secure suitable
hardness in the whole workpiece W.
[0053] Consequently, it is possible to do away with the need to
remake the dies so that the dies suitably come in contact with the
workpiece W, and to reduce man-hour required to produce the dies.
In addition, it is possible to reduce the time required to quench
the workpiece W owing to increased contact areas between the
workpiece W and the forming surfaces of the dies, and consequently
to increase speed for producing a product.
[0054] In the present embodiment, only the top surface 10a of the
lower die 10 is provided with the plurality of beads 12, but the
configurations of the dies are limited thereto as long as the top
part Wt is formed into the stepped shape.
[0055] For example, a plurality of beads similar to the plurality
of beads 12 may be provided to the bottom surface 20a of the upper
die 20 in addition to the plurality of beads 12 provided to the top
surface 10a of the lower die 10, or the plurality of beads similar
to the plurality of beads 12 may be provided to only the bottom
surface 20a of the upper die 20.
[0056] As shown in FIG. 4, a plurality of beads 112 and a plurality
of beads 122 which do not protrude from the forming surfaces of the
dies as the plurality of beads 12 but are recessed from the forming
surfaces of the dies may be provided to the lower die 10 and the
upper die 20, respectively.
[0057] The bead 112 is formed on the top surface 10a of the lower
die 10 so that a semicircular section thereof whose are is situated
at the lower part thereof continues in the front-rear direction,
and two beads 112 are arranged at a predetermined interval in the
right-left direction. The bead 112 is formed in order to change the
top surface 10a of the lower die 10 into a bumpy surface.
[0058] The bead 122 is formed on the bottom surface 20a of the
upper die 20 so that a semicircular section thereof whose arc is
situated at the upper part thereof continues in the front-rear
direction, and three beads 122 are arranged at predetermined
intervals in the right-left direction. The bead 122 is formed in
order to change the bottom surface 20a of the upper die 20 into a
bumpy surface.
[0059] The bead 112 and the bead 122 are alternately arranged at
different positions in the right-left direction.
[0060] Note that beads such as the bead 112 and the bead 122 may be
formed by performing numerical control machining to cut the forming
surfaces of the dies.
[0061] In the present embodiment, the dies have the shapes to form
the top part Wt of the workpiece W into the stepped shape. However,
in the case where parts of the workpiece W other than the top part
Wt are difficult to come in contact with the forming surfaces of
the lower die 10 and the upper die 20 positioned at the bottom dead
center, the dies should be formed in the shapes to form the parts
of the workpiece W other than the top part Wt into the stepped
shape. For example, a plurality of beads should be formed on the
base surfaces 10c of the lower die 10.
[0062] In the present embodiment, the plurality of beads 12 are
formed on the top surface 10a which is the surface of the lower die
10 situated in the uppermost part thereof.
[0063] As shown in FIG. 5, in the hot-pressing apparatus 1
configured to move the upper die 20 to the bottom dead center, the
top surface 10a which is the surface of the lower die 10 situated
in the uppermost part thereof comes in contact with the workpiece W
at a relatively early stage when the workpiece W is pressed. In
other words, the part to be finally formed into the top part Wt is
worked at a relatively early stage.
[0064] Thereby, when the upper die 20 arrives at the vicinity of
the bottom dead center (for example, 1 mm above the bottom dead
center), the top part Wt of the workpiece W is formed into the
stepped shape. In other words, the plurality of beads 12 are
arranged at such positions that the top part Wt of the workpiece W
is formed into the stepped shape when the upper die 20 arrives at
the vicinity of the bottom dead center.
[0065] This makes it possible to increase the contact area between
the top part Wt of the workpiece W and the forming surface of the
lower die 10 from a stage where the workpiece W is being pressed,
and to further prevent the hardness of the top part Wt from
decreasing.
[0066] In the present embodiment, three beads 12 each of which has
the shape similar to that of one of two equal parts into which a
cylinder is divided are arranged at predetermined intervals in the
right-left direction (see FIG. 2), but the configurations of the
beads are limited thereto as long as a part of the workpiece W is
formed into the stepped shape.
[0067] For example, as shown in FIG. 6, two flat beads 212 may be
formed at a predetermined interval in the front-rear direction.
[0068] The bead 212 forms a rectangular shape as seen from above.
The bead 212 protrudes upward from the top surface 10a, and has a
flat top surface. The bead 212 is continuously formed from the
vicinity of the left end to the vicinity of the right end of the
top surface 10a of the lower die 10, and is continuously formed
from the vicinity of one end to the vicinity of the middle of the
top surface 10a of the lower die 10 in the front-rear direction.
The bead 212 is formed in order to change the top surface 10a of
the lower die 10 into a bumpy surface.
[0069] As show in FIG. 7, a plurality of semispherical beads 312
may be formed at predetermined intervals.
[0070] The bead 312 has a shape similar to that of one of two equal
parts into which a sphere is divided, and is arranged so that the
flat surface (cutting surface of one of two equal parts into which
a sphere is divided) comes in contact with the top surface 10a.
Three beads 312 are arranged at predetermined intervals in the
right-left direction, and additionally a plurality of sets of the
three beads 312 are arranged at predetermined intervals in the
front-rear direction. The bead 312 is formed in order to change the
top surface 10a of the lower die 10 into a bumpy surface.
[0071] In the present embodiment, the lower die 10 having the
protrusion 11, and the upper die 20 having the recess 21 are used,
but a lower die having a recess, and an upper die having a
protrusion may be used.
[0072] In the present embodiment, the lower die 10 and the upper
die 20 have shapes to form the workpiece W into the hat shape, but
the shapes of the dies are not limited thereto. The dies may have
other shapes.
INDUSTRIAL APPLICABILITY
[0073] The present invention is applied to a hot-pressing method
and a hot-pressing apparatus for pressing and cooling a heated
workpiece at the same time.
REFERENCE SIGNS LIST
[0074] 1: hot-pressing apparatus
[0075] 10: lower die
[0076] 10a: top surface
[0077] 10b: lateral surface
[0078] 10c: base surface
[0079] 11: protrusion
[0080] 12: bead
[0081] 20: upper die
[0082] 20a: bottom surface
[0083] 20b: lateral surface
[0084] 20c: base surface
[0085] 21: recess
* * * * *