DESCRIPTION
TITLE OF THE INVENTION
HYDROFORMING METHOD AND HYDROFORMING DEVICE
5
FIELD OF THE INVENTION
[0001]
This invention relates to a hydroforming method for
obtaining a hydroformed product by supplying a forming
10 liquid into the interior of a tube blank placed in a die
assembly to impart an internal pressure load and applying
a compressive load in the tube axial direction, and to a
hydro forming device.
15 BACKGROUND ART
[0002]
Hydroforming has long been known as a method for
forming metal tubes. FIG. 13 is a diagram for explaining
a conventional hydroforming method.
20 [0003]
As shown in FIG. 13(a), ordinary hydroforming uses
upper and lower dies 111 having a cavity 114 of an inner
shape substantially the same as the outer shape of a
tubular hydroformed product split orthogonally to the
25 tube axis, and a sectionally circular tube blank 105
constituting the material of the hydroformed product.
When hydroforming is performed, the tube blank 105 is
first placed in the cavity 114 of the dies 111. Next, as
shown in FIG. 13(b), die-clamping of the upper and lower
30 dies 111 is performed. Then, as shown FIG. 13(c), a
forming liquid 125 is supplied into the interior of the
tube blank 105 to impart an internal pressure load, and a
compressive load is applied in the tube axial direction
by axial pressing punches 151. By this, as shown in FIG.
35 13(d), the tube blank 105 is compressed while being
radially expanded to obtain a hydroformed product 103
whose outer shape conforms to the inner shape of the
- 2 -
cavity 114 of the dies 111. The hydroforming is
advantageous in the point that the wall-thickness
reduction of the tube blank 105 by the radial expansion
can be compensated for by the compression of the tube
5 blank 105 to form a tube of complicated shape with high
precision.
[0004]
In this connection, hydroformed products of various
shapes have come to be required in recent years. FIGS.
10 14(a) and (b) show one example of such a hydroformed
product 103. This hydroformed product 103 is formed to a
sectional shape whose opposite tube end portions 103a in
the tube axial direction are more inwardly narrowed than
the middle portion 103b, and the tube end portions 103a
15 are formed to the square sectional shape that would be
obtained by rotating the sectional shape of the middle
portion 103b of square sectional shape about 45° in the
circumferential direction.
[0005]
20 In order to obtain such a hydroformed product 103,
the cavity 114 of the dies 111 is first formed to a shape
conforming to the outer shape of the hydroformed product
103. Then, as shown in FIG. 14(c), so that the tube blank
105 can be placed in the cavity 114 before clamping of
25 the dies 111, the tube blank 105 is, as a process
upstream of the hydroforming, pressed in the directions
P1 to conduct press-forming. As a result, an intermediate
formed product has generally been obtained whose tube end
portions are formed into a shape conforming to the tube
30 end portions 103a of the hydroformed product 103.
35
CITATION LIST
Patent Document
[0006]
Patent Literature
PLT1: Japanese Patent Publication (A) No. 2003-
290845
- 3 -
SUMMARY OF INVENTION
Technical Problem
[0007]
5 However, with the conventional method, since
separate press-forming is performed as a process upstream
of the aforesaid hydroforming, a troublesome task of
transferring the intermediate formed product from the
dies for press-forming to the dies for hydroforming
10 arises. Further, after the intermediate formed product is
removed from the dies for press-forming, springback
occurs at the press-formed portions of the intermediate
formed product, so that a so-called pinching problem
occurs of it not being possible to perform die-clamping
15 when the hydroformed product is placed in the dies for
hydroforming. Moreover, when the tube end faces of the
intermediate formed product assume a distorted shape
owing to the axial load acting on the tube blank 105
during the press-forming, it becomes necessary for
20 enabling axial pressing by the axial pressing punches 151
to conduct separate cutting, forging or other working of
the end faces of intermediate formed product.
[0008]
In addition, in the conventional hydroforming, the
25 drive mechanism needed to achieve the hydroforming
requires a total of three drive units, namely, a drive
unit for clamping the dies 111 and two drive units for
driving the two axial press punches 151, which gives rise
to a proportional amount of drive unit waste and
30 enlargement of the forming device. Further, the axial
pressing punches 151 have to be given a shape conforming
to the dies 111 so as to be slidable inside the dies 111,
i.e., substantially the same shape as the outer shape of
the tube end portions l03a of the hydroformed product
35 103, which causes a proportional increase in the overall
cost of the forming device.
[0009]
Further, even when press-forming is not required as
a process upstream of the hydroforming, it is still
necessary at the time of performing hydroforming to use a
tube blank 105 of an outer diameter enabling snug
5 insertion into part of the cavity 114 of the dies 111, so
that the diameter of the tube blank 105 that can be
placed in the dies 111 comes to be limited.
[0010]
The present invention was therefore made taking the
10 aforesaid problems into account, and its object is to
provide a hydroforming method and a hydroforming device
that, even in the case where realization of a hydroformed
product requires both hydroforming and press-forming of
end portions of a tube blank, is capable of performing
15 all processes very easily, and in addition of enabling
device simplification and size reduction and further of
enabling improved dimensional freedom of the tube blank.
Solution to Problem
20 [0011]
Following an assiduous study, the inventors invented
the hydroforming method and hydroforming device set out
below in order to overcome the aforesaid problems.
[0012]
25 A hydroforming method according to a first invention
is characterized by comprising a step of placing tube end
portions of a tube blank in entrance portions of a pair
of dies that are formed to have cavities of bottomed hole
shape whose entrance portions are more radially expanded
30 than their bottom portions, are formed between the
entrance portions and the bottom portions with tapered
portions whose shape transforms from the inner shape of
the entrance portions into the inner shape of the bottom
portions, and are arranged so that the entrance portions
35 face each other, a step of press-forming by driving one
of the pair of dies toward the other to press the tube
end portions of the tube blank inward by means of the
tapered portions, and a step of hydroforming the tube
blank by supplying forming liquid into the interior of
the tube blank whose opposite tube end faces are abutted
against the cavity bottom surfaces of the pair of dies to
5 impart an internal pressure load and driving one of the
pair of dies toward the other to apply a compressive load
in the tube axial direction.
[0013]
A hydroforming method according to a second
10 invention is characterized in that, in the press-forming
step of the first invention, press-forming is performed
to give the tube end portions of the tube blank a profile
different from the outer shape profile thereof.
[0014]
15 A hydroforming method according to a third invention
is characterized in that, in the press-forming step of
the first invention or second invention, one of the pair
of dies is driven toward the other to insert backing
members protruding from the cavity bottom surfaces of the
20 dies inside the tube end portions of the tube blank.
[0015]
A hydroforming method according to a fourth
invention is characterized in that in the first invention
or the second invention pairs of dies are used to provide
25 the die cavities in a plurality of sets, and a plurality
of hydroformed products is obtained through the pressforming
process and the hydroforming process.
[0016]
A hydroforming method according to a fifth invention
30 is characterized in that in the third invention pairs of
dies are used to provide the die cavities in a plurality
of sets, and a plurality of hydroformed products is
obtained through the press-forming process and the
hydroforming process.
35 [0017]
A hydroforming device according to a sixth invention
is characterized by comprising a pair of dies that are
- 6 -
formed to have cavities of bottomed hole shape whose
entrance portions are more radially expanded than bottom
portions, are formed between the entrance portions and
the bottom portions with tapered portions whose shape
5 transforms from the inner shape of the entrance portions
into the inner shape of the bottom portions, and are
arranged so that the entrance portions face each other,
drive means for performing press-forming by driving one
of the pair of dies toward the other to press the tube
10 end portions of the tube blank placed in the entrance
portions of the pair of dies inward by means of the
tapered portions, and forming liquid supply means for
supplying forming liquid into the interior of the tube
blank whose opposite tube end faces are abutted against
15 the cavity bottom surfaces of the pair of dies to impart
an internal pressure load.
[0019]
A hydroforming device according to a seventh
invention is characterized in that in the sixth invention
20 the tube blank is hydroformed by causing the forming
liquid supply means to supply forming liquid into the
interior of the tube blank whose opposite tube end faces
are abutted against the cavity bottom surfaces of the
pair of dies to impart an internal pressure load, and
25 causing the drive means to drive one of the pail of dies
toward the other to apply a compressive load in the tube
axial direction.
[0019]
A hydroforming device according to an eighth
30 invention is characterized in that in the sixth invention
or seventh invention the inner shape profile of the
bottom portions of the cavities of the pair of dies is
formed to have a different profile from the outer shape
profile of the tube end'portions of the tube blank.
35 [0020]
A hydroforming device according to a ninth invention
is characterized in that in the sixth invention or the
seventh invention backing members are further provided
that protrude from the cavity bottom surfaces of the pair
of dies and are inserted inside the tube end portions of
the tube blank when one of the pair of dies is driven
5 toward the other.
[0021]
A hydroforming device according to a tenth invention
is characterized in that in the eighth invention backing
members are further provided that protrude from the
10 cavity bottom surfaces of the pair of dies and are
inserted inside the tube end portions of the tube blank
when one of the pair of dies is driven toward the other.
[0022]
A hydroforming device according to an eleventh
15 invention is characterized in that in the sixth invention
or the seventh invention the pair of dies is formed with
a plurality of sets of the die cavities.
[0023]
A hydroforming device according to a twelfth
20 invention is characterized in that in the eighth
invention the pair of dies is formed with a plurality of
sets of the die cavities.
[0024]
A hydroforming device according to a thirteenth
25 invention is characterized in that in the ninth invention
the pair of dies is formed with a plurality of sets of
the die cavities.
Effects of Invention
30 [0025]
In accordance with the first invention to thirteenth
inventions, even in the case where realization of a
hydroformed product requires both hydroforming and pressforming
of end portions`of a tube blank, it is possible
35 to perform all processes very easily, and to a
corresponding degree, to achieve shorter work time, labor
reduction, and yield improvement. Moreover, the number of
drive mechanisms needed to implement hydroforming can be
minimized, and furthermore, since no axial pressing punch
is required, it is possible to realize simplification and
size reduction of the whole hydroforming device, thereby
5 reducing hydroforming device fabrication cost. In
addition, work can be conducted without experiencing a
major limitation on tube blank diameter, so that the
degree of size freedom of the tube blank that can be
placed in the dies is improved to also enhance design
10 freedom.
[0026]
In accordance with the second invention and eighth
invention, it is possible to perform the press-forming
and hydroforming very easily even in the case where the
15 outer shape profile of the tube end portions of the
hydroformed product are to be formed to have a different
profile from the outer shape profile of the tube end
portions of the tube blank.
[0027]
20 In accordance with the third invention and ninth
invention, the tube end faces of the tube blank can be
restrained from deforming in the manner of curling inward
even in the case where the tube blank is pressed
excessively inward by the tapered portions of the
25 cavities during press-forming of the tube blank, whereby
the opposite ends of the tube blank can be sealed
normally when the tube end faces at the opposite ends are
abutted against the cavity bottom surfaces of the pair of
dies.
30 [0029]
In accordance with the fourth invention, fifth
invention, eleventh invention, twelfth invention and
thirteenth invention, a plurality of hydroformed products
can be mass-produced in'''a short time.
35
BRIEF DESCRIPTION OF THE DRAWINGS
[0029]
FIG. 1 is a set of drawings showing an example of a
hydroformed product obtained by a hydroforming method
according a first embodiment. FIG. 1(a) is a perspective
view. FIG. 1(b) is a plan view. FIG. 1(c) is a top
5 sectional view. FIG. 1(d) is a top sectional view showing
the relationship between a hydroformed product and a tube
blank.
FIG. 2 is a set of drawings showing the structure of
a hydroforming device according to a first embodiment.
10 FIG. 2(a) is a side sectional view. FIG. 2(b) is a
sectional view along line A-A of FIG. 2(a). FIG. 2(c) is
a sectional view along line'B-B of FIG. 2(a).
FIG. 3 is a set of drawings explaining the
hydroforming method according to the first embodiment.
15 FIG. 3(a) is a side sectional view showing the state of a
tube blank placed in a cavity of a die. FIG. 3(b) is a
side sectional view showing the state in the course of
press-forming tube end portions of the tube blank.
FIG. 4 is a set of drawings explaining the
20 hydroforming method according to the first embodiment.
FIG. 4(a) is a side sectional view showing the state
after press-forming the tube end portions of the tube
blank. FIG. 4(b) is a sectional view along line C-C of
FIG. 4(a). FIG. 4(c) is a sectional view along line D-D
25 of FIG. 4(a).
FIG. 5 is a set of drawings explaining the
hydroforming method according to the first embodiment.
FT-G. 5(a) is a side sectional view showing the state
after supplying forming liquid to inside the tube blank.
30 FIG. 5(b) is a side sectional view showing the state
after hydroforming the tube blank.
FIG. 6 is a set of drawings showing the structure of
a hydroforming device according to a second embodiment.
FIG. 6(a) is a side sectional view. FIG. 6(b) is a plan
35 view.
FIG. 7 is a set of drawings showing the structure of
a hydroforming device according to a third embodiment.
10 -
FIG. 7(a) is a side sectional view. FIG. 7(b) is a
sectional view along line E-E of FIG. 7(a).
FIG. 8 is a set of drawings explaining a
hydroforming method according to a third embodiment. FIG.
5 8(a) is a side sectional view showing the state in the
course of press-forming tube end portions of a tube
blank. FIG. 8(b) is a side sectional view showing the
state after the press-forming. FIG. 8(c) is a sectional
view along line F-F of FIG. 8(b).
10 FIG. 9 is a set of drawings showing an example of a
hydroformed product obtained by a hydroforming method
according a fourth embodiment. FIG. 9(a) is a perspective
view. FIG. 9(b) is a plan view. FIG. 9(c) is a top
sectional view. FIG. 9(d) is a top sectional view showing
15 the relationship between a hydroformed product and a tube
blank.
FIG. 10 is a set of drawings showing the structure
of a hydroforming device according to a fourth
embodiment. FIG. 10(a) is a side sectional view. FIG.
20 10(b) is a sectional view along line G-G of FIG. 10(a),
FIG. 10(c) is a sectional view along line H-H of FIG.
10(a).
FIG. 11 is a set of drawings showing an example of a
hydroformed product obtained by a hydroforming method
25 according a fifth embodiment. FIG. 10(a) is a perspective
view. FIG. 11(b) is a plan view. FIG. 11(c) is a top
sectional view. FIG. 11(d) is a top sectional view
showing the relationship between a hydroformed product
and a tube blank.
30 FIG. 12 is a set of drawings showing the structure
of a hydroforming device according to a fifth embodiment.
FIG. 12 is a side sectional view. FIG. 12(b) is a
sectional view along line I-I of FIG. 12(a). FIG. 12(c)
is a sectional view along line J-J of FIG. 12(a).
35 FIG. 13 is a set of drawings for explaining a
conventional hydroforming method.
FIG. 14 is a set of drawings showing an example of a
- 11 -
hydroformed product. FIG. 14(a) is a perspective view.
FIG. 14(b) is a plan view. FIG. 14(c) is a diagram for
explaining press-forming performed for obtaining the
hydroformed product.
5
DESCRIPTION OF EMBODIMENTS
[0030]
Examples of modes for implementing the hydroforming
method and hydroforming device embodying the present
10 invention are explained below in detail with reference to
the drawings.
[0031]
A hydroforming method and a hydroforming device
according to first embodiments are explained first.
15 [0032]
FIG. 1 is a set of drawings showing an example of a
hydroformed product 3 obtained by the hydroforming method
according the first embodiment. FIG. 1(a) is a
perspective view thereof. FIG. 1(b) is a plan view. FIG.
20 1(c) is a top sectional view. FIG. 1(d) is a top
sectional view showing the relationship between a
hydroformed product 3 and a tube blank 5.
[0033]
The hydroformed product 3 obtained by the
25 hydroforming method according to the present invention is
one formed in a tubular shape whose middle portion 3b is
more radially expanded than the tube end portions 3a of
the opposite ends. Between the tube end portions 3a and
the middle portion 3b are formed tapered portions 3c
30 provided in a smooth tapered shape to transform from the
sectional shape of the tube end portions 3a into the
sectional shape of the middle portion 3b. The middle
portion 3b of the hydroformed product 3 is formed in a
shape that would be obtained by radially expanding part
35 or all of the circumferential direction of the tube end
portions 3a, and either the degree of taper of the
tapered portions 3c of the hydroformed product 3 is
- 12 -
formed to differ with the region in the circumferential
direction or the degree of taper is formed the same
irrespective of the region in the circumferential
direction. Such a hydroformed product 3 is used, for
5 example, in the frame of a building, automobile, or the
like.
[0034]
In the hydroformed product 3 of the first
embodiment, the middle portion 3b is formed in square
10 sectional shape and the tube end portions 3a at the
opposite ends thereof are formed in the square sectional
shape that would be obtained by rotating the sectional
shape of the middle portion 3b about 45° in the
circumferential direction. In the hydroformed product 3
15 of the first embodiment, the middle portion 3b is formed
in a shape that would be obtained by radially expanding
it with respect to the tube end portions 3a over the
whole range of the circumferential direction. The tapered
portions 3c of the hydroformed product 3 of the first
20 embodiment are sharply tapered at locations along the
tube axial direction from the corners 3d formed by the
sectional shape of the middle portion 3b and are gently
tapered at locations along the tube axial direction from
the midpoint positions between the corners 3d formed by
25 the sectional shape of the middle portion 3b.
[0035]
As shown in FIG. l(d),as the tube blank 5 used to
obtain such a hydroformed product 3 in the hydroforming
method according to the present invention, there is used
30 a tube blank 5 of a shape more radially expanded than the
tube end portions 3a of the hydroformed product 3 at part
or all of the circumferential direction of the tube end
portions 3a. In the first embodiment, there is used as
the tube blank 5 one wherein the outer shape profile of
35 the tube end portions 5a is formed to be a different
profile from the outer shape profile of the tube end
portions 3a of the hydroformed product 3.
- 13 -
[0036]
A hydroforming device 1 for implementing the
hydroforming method according to the first embodiment is
explained next.
5 [0037]
FIG. 2 is a set of drawings showing the structure of
the hydroforming device 1 according to a first
embodiment. FIG. 2(a) is a side sectional view. FIG. 2(b)
is a sectional view along line A-A of FIG. 2(a). FIG.
10 2(c) is a sectional view along line B-B of FIG. 2(a).
[0030]
The hydroforming device 1 according to the present
invention comprises a pair of dies 11, a drive unit 21 as
drive means for driving one of the pair of dies 11 toward
15 the other, and a forming liquid supply unit 23 as forming
liquid supply means for supplying forming liquid into the
interior of the tube blank 5 placed in the pair of dies
11.
[0039]
20 The pair of dies 11 is used to perform both pressforming
and hydroforming of the tube blank 5 with the
same dies. Each of the pair of dies 11 is provided with a
bottomed-hole shaped cavity 14 whose entrance portion 15
is more radially expanded than its bottom portion 16. The
25 cavities 14 are formed between the entrance portions 15
and the bottom portions 16 with tapered portions 17
provided in a smooth tapered shape to transform from the
inner shape of the entrance portions 15 into the inner
shape of the portion 16. By bottom portions 16 here is
30 meant the endmost portions that are the regions among the
regions of the cavities that are most distant from
opposing surfaces 12 described below. The pair of dies 11
is placed with the entrance portions 15 facing each other
and then positioned to align the cavities 14
35 concentrically.
[0040]
The pair of cavities 14 provided in the pair of dies
- 14 -
11 are formed so that their inner shape assumes
substantially the same shape as the outer shape of the
hydroformed product 3 when mutually facing opposing
surfaces 12 of the pair of dies 11 are abutted against
5 each other. This means that the inner shape of the bottom
portions 16 of the cavities 14 is formed to substantially
the same shape as the outer shape of the tube end
portions 3a of the hydroformed product 3, the inner shape
of the entrance portions 15 of the cavities 14 is formed
10 to substantially the same shape as the outer shape of the
middle portion 3b of the hydroformed product 3, and the
inner shape of the tapered,.'portions 17 of the cavities 14
is formed to substantially the same shape as the outer
shape of the tapered portions 3c of the hydroformed
15 product 3. Therefore, the entrance portions 15 of the
cavity 14 come to be formed in the shape that would be
obtained by radially expanding part or all of the
circumferential direction of the bottom portions 16, and
the tapered portions 17 of the cavities 14 either come to
20 be formed to differ in degree of taper with region in the
circumferential direction or come to be formed to be the
same in degree of taper irrespective of the region in the
circumferential direction.
[0041]
25 The entrance portions 15 of the cavities 14 in the
first embodiment are formed in a square sectional shape
and the bottom portions 16 are formed in the square
sectional shape that would be obtained by rotating the
sectional shape of the entrance portions 15 about 45° in
30 the circumferential direction. Further, the tapered
portions 17 of the cavities 14 in the first embodiment
are sharply tapered at locations along the axial
direction from the corners 15a formed by the sectional
shape of entrance portions 15 and are gently tapered at
35 locations along the tube axial direction from the
midpoint positions between the corners 15a formed by the
sectional shape of the entrance portion 15.
- 15 -
[0042]
The drive unit 21 is for driving one of the pair of
dies 11 in directions that make it approach toward and
depart from the other die 11, and is configured from, for
5 example, a hydraulic cylinder, pneumatic cylinder,
electric motor or the like. The drive unit 21 in the
first embodiment is configured to drive the die 11 on the
right side in FIG. 2 toward the die 11 on the left side.
[0043]
10 The forming liquid supply unit 23 is for supplying
water or other forming liquid into the cavities 14
through a forming liquid supply port 19 formed in the
cavity bottom surface 18 of one die 11. In the first
embodiment, the forming liquid supply port 19 is formed
15 in the cavity 14 of the die 11 not driven by the drive
unit 21. By cavity bottom surface 18 here is meant the
endmost surface most distant from the opposing surface
12.
[0044]
20 The hydroforming method of the first embodiment is
next explained in detail.
[0045]
First, the tube blank 5 is placed in the cavities 14
of the pair of dies 11. Specifically, as shown in FIG.
25 3(a), one of the dies 11 is driven to open a space
between the opposing surfaces 12, and one tube end
portion 5a of the tube blank 5 is inserted through the
opening 13 of one or the other of the pair of dies 11 and
into the entrance portion 15. The tube end face 5b of the
30 tube blank 5 inserted into the entrance portion 15 of the
die 11 strikes on the tapered portion 17 to be prevented
from further insertion.
[0046]
As the tube blank 5 here is used a tubular body made
35 of metal, such as a steel tube, aluminum tube or the
like. Moreover, it suffices for the tube blank 5 to be
formed to a shape more radially expanded at part or all
16 -
of the circumferential direction than the inside shape of
the bottom portions 16 of the cavities 14 and to be of a
size insertable in the entrance portions 15 of the
cavities 14, and is not limited to a circular sectional
5 shape as in the first embodiment.
[0047]
Next, the tube end portions 5a of the tube blank 5
are press-formed. Specifically, as shown in FIG. 3(b),
the drive unit 21 drives one of the pair of dies 11
10 toward the other. Owing to this, the tube end faces 5b at
the opposite ends of the tube blank 5 come into contact
with the tapered portions 17 of the cavities 14 of the
pair of dies 11, and from then onward the tapered
portions 17 apply a load that presses inward on part or
15 all of the circumferential direction of the tube blank 5
in contact with the tapered portions 17 of the cavities
14, and the regions that pass through the tapered
portions 17 of the cavities 14 from the side of the tube
end portions 5a toward the side of the middle portion 5c
20 of the tube blank 5 are progressively press-formed.
[0048]
As shown in FIG. 4(a), this press-forming by the
tapered portions 17 of the cavities 14 is performed until
the tube end faces 5b at the opposite ends of the tube
25 blank 5 abut. against the cavity bottom surfaces 1.8 of the
pair of dies 11. The abutment of the tube end faces 5b at
the opposite ends of the tube blank 5 against the cavity
bottom surfaces 18 of the pair of dies 11 seals the
opposite ends of the tube blank 5. It should be noted
30 that FIG. 4(b) is a sectional view along line C-C of FIG.
4(a). And FIG. 4(c) is a sectional view along line D-D of
FIG. 4(a).
[0049]
Here, the pair of dies 11 is adjusted so that an
35 interval L1 is left open between the opposing surfaces 12
of the pair of dies 11 at the point of time when the tube
end faces 5b of the tube blank abut against the cavity
17 -
bottom surfaces 18 of the pair of dies 11. By adjusting
the interval L1 between the opposing surfaces 12, it is
possible to control the push-in depth of the dies 11 in
the hydroforming described later.
5 [0050]
Further, the press-forming of the tube end portions
5a of the tube blank 5 sometimes gives the tube end faces
5b of the tube blank 5 a distorted shape. In this case,
after the tube end faces 5b at the opposite ends of tube
10 blank 5 have abutted against the cavity bottom surfaces
18 of the pair of dies 11, it is advisable from then on
to additionally drive the one of the pair of dies 11
toward the other using the drive unit 21. By this, the
cavity bottom surfaces 18 apply compressive load to the
15 tube end faces 5b of the tube blank 5 in the tube axial
direction, so that the tube end faces 5b of the tube
blank 5 can be made flat to enable thorough sealing of
the opposite ends of the tube blank 5.
[0051]
20 Next, the tube blank 5 is hydroformed. Specifically,
as shown in FIG. 5(a), the forming liquid supply unit 23
supplies forming liquid 25 into the interior of the tube
blank 5 whose opposite tube end faces 5b are abutted
against the cavity bottom surfaces 18 of the pair of dies
25 11 to impart an internal pressure load, and the drive
unit 21 drives one of the pair of dies 11 toward the
other to apply a compressive load in the tube axial
direction. By this, as shown in FIG. 5(b), the tube blank
5 is compressed in the tube axial direction while being
30 radially expanded to conform to the inner shape of the
cavities 14. This hydroforming performed under driving of
the pair of dies 11 by the drive unit 21 is conducted
until the opposing surfaces 12 of the pair of dies 11
contact each other.
35 [0052]
Next, the forming liquid 25 is applied to establish
a still higher internal pressure in the tube blank 5,
- 18 -
whereby the tube blank 5 is brought into tight contact
with the cavities 14 and the tube blank 5 is formed to
conform more closely to the inner shape of the cavities
14. Then one of the pair of dies 11 is driven to open a
5 space between the opposing surfaces 12, whereafter the
hydroformed product 3 formed in the cavities 14 is
removed to complete the series of operations.
[ 0053]
According to the present invention, press-forming
10 and hydroforming can be performed sequentially with the
same pair of dies 11, so that the work of transferring an
intermediate formed product'from dies for press-forming
to dies for hydroforming can be eliminated. Further,
since no intermediate formed product needs to be
15 transferred, occurrence of a springback-induced pinching
problem can be prevented. And if the tube end faces 5b of
the tube blank 5 should assume a distorted shape during
the press-forming, the tube end faces 5b can be flattened
by driving one of the pair of dies 11 toward the other,
20 making it possible to omit the cutting, forging and other
working that has been separately performed. Thus, even in
the case where realization of the hydroformed product 3
requires press-forming of the tube end portions 5a of the
tube blank 5 in addition to the hydroforming, it is still
25 possible to perform all processes very easily, rind to a
corresponding degree, to achieve shorter work time, labor
reduction, and yield improvement.
[0054]
Moreover, in accordance with the present invention,
30 the only drive mechanism needed to achieve the
hydroforming is the drive unit 21 used to drive one of
the pair of dies 11 toward the other, and furthermore,
since no axial pressing punch is required, it is possible
to realize simplification and size reduction of the whole
35 hydroforming device 1, thereby making it possible to
reduce the overall fabrication cost of the hydroforming
device 1.
- 19 -
[0055]
In addition, in accordance with the present
invention, work can be conducted without experiencing a
major limitation on the diameter of tube blank 5, so that
5 the degree of size freedom of the tube blank 5 that can
be placed in the dies 11 is improved to improve also
design freedom. Therefore, in obtaining a hydroformed
product 3 of the desired dimensions, for example, a
hydroformed product of the same dimensions can be
10 obtained using as the tube blank 5 either one of large
wall thickness and small outer diameter or one of small
wall thickness and large outer diameter. Another
possibility is that, for example, where the same pair of
dies. 11 is used, it is possible by changing only the
15 dimensions of the tube blank 5 to obtain hydroformed
products 3 of different wall thickness. In other words,
the present invention improves design freedom.
[0056]
Further, in accordance with the present invention,
20 even in the case of forming the outer shape profile of
the tube end portions 3a of the hydroformed product 3 to
a different profile from the outer shape profile of the
tube end portions 5a of the tube blank 5, the pressforming
and the hydroforming can be performed very
25 easily.
[0057]
A hydroforming method and a hydroforming device
according to second embodiments are explained next. Note
that constituents identical to constituents set out above
30 are assigned the same symbols so as not to require
explanation.
[0058]
FIG. 6 is a set of drawings showing the structure of
a hydroforming device I 'according to the second
35 embodiment. FIG. 6(a) is a side sectional view. FIG. 6(b)
is a plan view.
[0059]
- 20 -
In the hydroforming device 1 according to the second
embodiment, a plurality of pairs of vertically spaced
dies 11 are spaced horizontally. Here, viewed twodimensionally,
the plurality of pairs of dies 11 are
5 spaced apart in the lateral direction and spaced apart in
the depth direction. Thus, paired cavities 14 come to be
provided in a plurality of sets. The upper plurality of
dies 11 is attached to a lower mold holder 31, and the
lower plurality of dies is attached to an upper die
10 holder 33. Further, the upper die holder 33 is vertically
drivable by a drive unit not shown in the drawing. In
addition, in order to supply forming liquid into the
cavities 14 of the lower dies 11 through the forming
liquid supply ports 19 of the dies 11, the lower mold
15 holder 31 is provided with a forming liquid supply hole
35 communicating with the forming liquid supply ports 19
of the dies 11.
[0060]
In the hydroforming method according to the second
20 embodiment, the cavities 14 can be used to obtain a
plurality of hydroformed products 3 through the same
press forming process and hydroforming process as in the
first embodiment. This enables the hydroformed product 3
to be produced in large volume in a short time.
25 [0061]
Moreover, the same effect can also be achieved when
a single pair of dies 11 provided with a plurality of
sets of cavities 14 is used.
[0062]
30 A hydroforming method and a hydroforming device
according to third embodiments are explained next.
[0063]
FIG. 7 is a set of drawings showing the structure of
a hydroforming device 1',1according to a third embodiment.
35 FIG. 7(a) is a side sectional view. FIG. 7(b) is a
sectional view along line E-E of FIG. 7(a).
[0064]
- 21 -
The hydroforming device 1 according to the third
embodiment further comprises backing members 41
protruding from the cavity bottom surfaces 18 of the pair
of dies 11. In order to allow the tube end portions 5a of
5 the tube blank 5 to be inserted between the inner
peripheral surfaces of the bottom portions 16 of the
cavities 14 and the outer peripheral surfaces of the
backing members 41, the backing members 41 are provided
to be spaced away from the inner peripheral surfaces of
10 the bottom portions 16 of the cavities 14 throughout
their circumferential direction. The outer peripheral
surfaces of the backing members 41 are formed to a shape
similar to the inner shape of the bottom portions 16 of
the cavities 14. In order to enable the forming liquid
15 supply unit 23 to supply the forming liquid into the
cavities 14 through the forming liquid supply port 19 of
one die 11, one backing member 41 in the third embodiment
is formed with a forming liquid supply port 43
communicating with the forming liquid supply port 19 of
20 the die 11. It should be noted that the backing members
41 are formed in both of the pair of dies 11.
[0065]
The hydroforming method of the third embodiment is
next explained in detail. Compared with the hydroforming
25 method of the first embodiment, the hydroforming method
of the third embodiment differs only in the press-forming
process.
[0.066]
In the press-forming process, as set forth earlier,
30 the drive unit 21 drives one of the pair of dies 11
toward the other, whereby the regions that pass through
the tapered portions 17 of the cavities 14 from the side
of the tube end portions 5a toward the side of the middle
portion 5c of the tube blank 5 are progressively press-
35 formed. If the tube blank 5 should be pressed excessively
inward by the tapered portions 17 of the cavities 14 at
this time, the tube end faces 5b of the tube blank 5 curl
- 22 -
inward to pose a risk of the tube end faces 5b no longer
abutting normally against the cavity bottom surfaces 18
and the opposite ends of tube blank 5 no longer being
sealed.
5 [0067]
In order to prevent this, in the press-forming
process, as shown in FIG, 8(a) to FIG. 8(c), the backing
members 41 are inserted inside the tube end portions 5a
of the tube blank 5 while one of the pair of dies 11 is
10 being driven toward the other to press-form the tube end
portions 5a of the tube blank 5 with the tapered portions
17 of the cavities 14. Owing to this, the backing members
41 come into contact with the tube end portions 5a of the
tube, blank 5 from the inside, so that such distortion can
15 be inhibited even when the tube end portions 5a of the
tube blank 5 are pressed inward excessively by the
tapered portions 17 of the cavities 14 to make tube end
faces 5b of the tube blank 5 likely to curl inward.
[0068]
20 The hydroforming methods and hydroforming devices of
the fourth embodiments and the fifth embodiments are next
explained in detail. Regarding the fourth embodiments and
the fifth embodiments, cases of producing hydroformed
products 3 of a different shape from those of the first
25 embodiments are explained.
[0069]
FIG. 9 is a set of drawings showing an example of a
hydroformed product 3 obtained by a hydroforming method
according the fourth embodiment. FIG. 9(a) is a
30 perspective view. FIG. 9(b) is a plan view. FIG. 9(c) is
a top sectional view. FIG. 9(d) is a top sectional view
showing the relationship between a hydroformed product
and a tube blank. Further, FIG. 10(a) is a set of
drawings showing the structure of a hydroforming device 1
35 according to the fourth embodiment. FIG. 10(a) is a side
sectional view. FIG. 10(b) is a sectional view along line
G-G of FIG. 10(a). FIG. 10(c) is a sectional view along
- 23 -
line H-H of FIG. 10(a).
[0070]
In the hydroformed product 3 according to the fourth
embodiment, the middle portion 3b is formed in a
5 substantially square shape, the tube end portions 3a at
the opposite ends thereof are of the rectangular
sectional shape that would be obtained by rotating the
sectional shape of the middle portion 3b 45° in the
circumferential direction, and the side surface portions
10 3f formed between the corners 3e formed by the
rectangular sectional shape are formed in a shape
recessed as bowed inward. The tapered portions 3c of the
hydroformed product 3 in the third embodiment are formed
to be sharply tapered at locations along the tube axial
15 direction from the corners 3d formed by the sectional
shape of the middle portion 3b and to be barely tapered
at locations along the tube axial direction from the
midpoint positions between the corners 3d formed by the
sectional shape of the middle portion 3b.
20 [0071]
In the hydroforming device 1 according to the fourth
embodiment, the entrance portions 15 of the cavities 14
are formed in a square sectional shape, the bottom
portions 16 of the cavities 14 are of the rectangular
25 sectional shape that would be obtained by rotating the
sectional shape of the entrance portions 15 about 45° in
the circumferential direction, and the side surface
portions 16b formed between the corners 16a formed by the
rectangular sectional shape are formed in a shape
30 recessed as bowed inward. Further, the tapered portions
17 of the cavities 14 in the fourth embodiment are formed
to be sharply tapered at locations along the axial
direction from the corners 15a formed by the sectional
shape of the entrance portions 15 and to be barely
35 tapered at locations along the axial direction from the
midpoint positions between the corners 15a formed by the
sectional shape of the entrance portions 15.
- 24 -
[0072]
In the hydroforming method according to the fourth
embodiment, the same processes are performed as in the
hydroforming method according to the first embodiment
5 except that as the tube blank 5 is used one of circular
shape of an outer diameter the same as the largest
diameter of the inner shape of the bottom portions 16 of
the cavities 14.
[0073]
10 FIG. 10 is a set of drawings showing an example of a
hydroformed product 3 obtained by the hydroforming method
according the fifth embodiment. FIG. 10(a) is a
perspective view. FIG. 10(b) is a plan view. FIG. 10(c)
is a. top sectional view. FIG. 10(d) is a top sectional
15 view showing the relationship between hydroformed product
3 and the tube blank 5. FIG. 11 is a set of drawings
showing the structure of a hydroforming device 1
according to a fifth embodiment. FIG. 11(a) is a side
sectional view. FIG. 11(b) is a sectional view along line
20 I-I of FIG. 11(a). FIG. 11(c) is a sectional view along
line J-J of FIG. 11(a).
[0074]
In the hydroformed product 3 according to the fifth
embodiment, the middle portion 3b is formed in a
25 substantially circular shape, and the tube end portions
3a at the opposite ends thereof are formed in a
substantially circular shape of smaller diameter than the
middle portion 3b. The degree of taper of the tapered
portions 3c of the hydroformed product 3 in the fifth
30 embodiment is formed the same irrespective of the region
in the circumferential direction.
[0075]
In the hydroforming device 1 according to the fifth
embodiment, the entrance portions 15 of the cavities 14
35 are formed in a circular sectional shape and the bottom
portions 16 of the cavities 14 are formed in a circular
sectional shape of smaller diameter than the sectional
-25-
shape of the entrance portions 15. The degree of taper of
the tapered portions 17 of the cavities 14 in the fifth
embodiment is formed the same irrespective of the region
in the circumferential direction.
5 [0076]
In the hydroforming method according to the fifth
embodiment, the same processes are performed as in the
hydroforming method according to the first embodiment
except that as the tube blank 5 is used one of circular
10 shape of an outer diameter larger than the inner diameter
of the bottom portions 16 of the cavities 14 and smaller
than the inner diameter of the entrance portions 15 of
the cavities 14.
[0077]
15 In the case where, as in the hydroforming method
according to the fifth embodiment, there is used as the
tube blank 5 one of the same profile as the outer shape
profile of the tube end portions 3a of the hydroformed
product 3 and different only in diameter, then, in
20 comparison to the case where there is used as the tube
blank 5 one of the same diameter as the hydroformed
product 3 of the hydroformed product 3, there is the
advantage of it being possible to hold down the diameter
expansion ratio of the tube blank 5 to effectively
25 prevent bursting or buckling during hydroforming.
[0078]
While embodiments of the present invention are set
out in detail in the foregoing, the aforesaid embodiments
are all nothing more than concretely defined examples for
30 illustrating implementation the present invention and are
not to be construed as limiting the technical scope of
the present invention.
[0079]
For example, the shapes of the hydroformed product 3
35 and the cavities 14 of the pair of dies 11 are not
particularly limited insofar as within ranges in which
the object and effect of the present invention are
- 26 -
achieved. In the aforesaid embodiments, explanation was
made with respect to the case where the middle portion 3b
of the hydroformed product 3, the entrance portions 15 of
the cavities 14, and the like, are configured as ones of
5 the same shape irrespective of position in the tube axial
direction, but it is also acceptable for them to be
radially expanded at some portions.
[0080]
To elucidate some dimensional and other examples
10 regarding the constituent elements of the hydroforming
device 1 by way of reference: the cavities 14 of the pair
of dies 11 are, for example', given an overall depth of
50 to 500 mm, inner diameter of the entrance portions 15
of 20 to 100 mm, and internal diameter of the bottom
15 portions 16 of 30 to 150 mm, And, for example, in the
hydroforming method, the driving force by the drive unit
21 during press-forming is made 500 to 1000 kN, the
distance L1 in FIG. 4 between the opposing surfaces 12 of
the pair of dies 11 after completion of the press-forming
20 is made 5 to 50 mm, the driving force by the drive unit
21 during hydroforming is made 500 to 10000 kN, and the
internal pressure produced by the forming liquid is made
30 to 300 Pa.
25 INDUSTRIAL APPLICABILITY
[0081]
As set out above, the present invention makes it
possible to perform all processes very easily even in the
case where both hydroforming and press-forming of the end
30 portions of a tube blank are required. Shorter work time,
labor reduction, and yield improvement can therefore be
achieved. Moreover, in accordance with the present
invention, the number of drive mechanisms can be
minimized, and furthermore, since no axial pressing punch
35 is required, it is possible to realize simplification and
size reduction of the whole hydroforming device. The cost
of fabricating the hydroforming device can therefore be
reduced. Hence, the present invention has high industrial
5
utility value.
Explanation of Reference Symbols
[0082]
1 Hydroforming device
3 Hydroformed product
3a Tube end portion
10 3b Middle portion
3c Tapered portion
3d Corner
3e Corner
3f Side surface portion
15 5 Tube blank
5a Tube end portion
5b Tube end face
5c Middle portion
11 Die
20 12 Opposing surface
13 Opening
14 Cavity
15 Entrance portion
15a Corner
25 16 Bottom portion
16a Corner
16b Side surface portion
17 Tapered portion
18 Cavity bottom surface
30 19 Forming liquid supply port
21 Drive unit
23 Forming liquid supply unit
25 Forming liquid
31 Lower mold holder
35 33 Upper die holder
35 Forming liquid supply hole
41 Backing member
43 Supply port
- 29 -
CLAIMS
1. A hydroforming method characterized by
comprising:
a step of placing tube end portions of a
5 tube blank in entrance portions of a pair of dies that
are formed to have cavities of bottomed hole shape whose
entrance portions are more radially expanded than their
bottom portions, are formed between the entrance portions
and the bottom portions with tapered portions whose shape
10 transforms from the inner shape of the entrance portions
into the inner shape of the bottom portions, and are
arranged so that the entrance portions face each other,
a step of press-forming by driving one of
the pair of dies toward the other to press the tube end
15 portions of the tube blank inward by means of the tapered
portions, and
a step of hydroforming the tube blank by
supplying forming liquid into the interior of the tube
blank whose opposite tube end faces are abutted against
20 the cavity bottom surfaces of the pair of dies to impart
an internal pressure load and driving one of the pair of
dies toward the other to apply a compressive load in the
tube axial direction.
2. A hydroforming method as set out in claim 1,
25 characterized in that in the press-forming step, pressforming
is performed to give the tube end portions of the
tube blank a profile different from the outer shape
profile thereof.
3. A hydroforming method as set out in claim 1 or
30 2, characterized in that in the press-forming step, one
of the pair of dies is driven toward the other to insert
backing members protruding from the cavity bottom
surfaces of the dies inside the tube end portions of the
tube blank.
35 4. A hydroforming method as set out in claim 1 or
2, characterized in that one or more die pairs are used
to provide the die cavities in a plurality of sets, and a
- 30 -
plurality of hydroformed products is obtained through the
press-forming process and the hydroforming process.
5. A hydroforming method as set out in claim 3,
characterized in that one or more die pairs are used to
5 provide the die cavities in a plurality of sets, and a
plurality of hydroformed products is obtained through the
press-forming process and the hydroforming process.
6. A hydroforming device characterized by
comprising:
10 a pair of dies that are formed to have
cavities of bottomed hole shape whose entrance portions
are more radially expanded than bottom portions, are
formed between the entrance portions and the bottom
portions with tapered portions (whose shape transforms
15 from the inner shape of the entrance portions into the
inner shape of the bottom portions, and are arranged so
that the entrance portions face each other,
drive means for performing press-forming
by driving one of the pair of dies toward the other to
20 press the tube end portions of the tube blank placed in
the entrance portions of the pair of dies inward by means
of the tapered portions, and
forming liquid supply means for supplying
forming liquid into the interior of the tube blank whose
25 opposite tube end faces are abutted against the cavity
bottom surfaces of the pair of dies to impart an internal
pressure load.
7. A hydroforming device as set out in claim 6,
characterized in that the tube blank is hydroformed by
30 causing the forming liquid supply means to supply forming
liquid into the interior of the tube blank whose opposite
tube end faces are abutted against the cavity bottom
surfaces of the pair of dies to impart an internal
pressure load, and causing the drive means to drive one
35 of the pair of dies toward the other to apply a
compressive load in the tube axial direction.
8. A hydroforming device as set out in claim 6 or
- 31 -
7, characterized in that the inner shape profile of the
bottom portions of the cavities of the pair of dies is
formed to have a different''profile from the outer shape
profile of the tube end portions of the tube blank.
5 9. A hydroforming device as set out in claim 6 or
7, characterized by further comprising backing members
protruding from the cavity bottom surfaces of the pair of
dies to be inserted inside the tube end portions of the
tube blank when one of the pair of dies is driven toward
10 the other.
10. A hydroforming device as set out in claim 8,
characterized by further comprising backing members
protruding from the cavity bottom surfaces of the pair of
dies. to be inserted inside the,tube end portions of the
15 tube. blank when one of the pair of dies is driven toward
the other.
11. A hydroforming device as set out in claim 6 or
7, characterized in comprising a pair of dies formed with
a plurality of sets of the die cavities or comprising a
20 plurality of the pairs of dies.
12. A hydroforming device as set out claim 8,
characterized in comprising a pair of dies formed with a
plurality of sets of the die cavities or comprising a
plurality of the pairs of dies.
25 13. A hydroformirigdevice as-set out in claim 9,
characterized in comprising a pair of dies formed with a
plurality of sets of the die cavities or comprising a
plurality of the pairs of dies.