TITLE OF INVENTION: PRESS FORMING METHOD
TECHNICAL FIELD
[0001] The present invention relates to a press
forming method to form a flat plate-shaped workpiece
into a cup shape.
BACKGROUND ART
[0002] A cup-shaped axially symmetrical component
having a cup vertical wall part and a cup bottom wall
part is known as a component used for a transmission
or the like of a vehicle. If common drawing is used
to obtain a cup-shaped axially symmetrical component,
a cup shoulder part abutting on a shoulder R part of
a drawing punch is thinned. As literatures to
disclose a technique to improve or to avoid the above,
Patent Literatures 1, 2 below are known.
[0003] In Patent Literature 1, first, drawing is
carried out by an apparatus for drawing, to form a
workpiece into a cup shape. Next, in Patent
Literature 1, a cup bottom part of the cup-shaped
workpiece is subjected to coining by an apparatus for
coining, to supply a material from a cup bottom part
to a cup shoulder part having been thinned due to
drawing, so that the cup shoulder part is thickened.
[0004] In Patent Literature 2, a punch is inserted
into a cup-shaped workpiece and an inner wall surface
of a cup vertical wall part is restrained by the
punch. Subsequently, in Patent Literature 2, an
- 1 -
outer wall surface of the cup vertical wall part is
subjected to ironing from a cup opening part side
toward a cup bottom part side by a roller, so that a
cup shoulder part is thickened.
CITATION LIST
PATENT LITERATURE
[0005] Patent Literature 1: Japanese Laid-open
Patent Publication No. 8-141662
Patent Literature 2 : Japanese Laid-open Patent
Publication No. 2007-289989
SUMMARY OF INVENTION
TECHNICAL PROBLEM
[000 6] However, in Patent Literature 1, since the
cup bottom part is subjected to coining when the cup
shoulder part is thickened, there is a problem that
the cup bottom part becomes not planar due to
thickness reduction of a part of the cup bottom part.
In Patent Literature 2, since the cup shoulder part
is thickened by ironing of the cup vertical wall part,
there is a problem tha I t he cup v e r t ica 1 wall par t is
thinned.
[000 7] An object of the present invention is to
provide a cup forming method to contrive suppress ion
of thinning of a cup shoulder part, suppression of
thinning of a cup vertical wall part, and
planarization of a cup bottom part simultaneously at
a time of forming a flat plate-shaped workpiece into
a cup shape.
- 2 -
SOLUTION TO PROBLEM
[0008] (1) In order to solve the above-described
problems, a press forming method according to the
present invention is a press forming method carrying
out press forming to a flat plate-shaped workpiece by
using a press forming die which has a forming punch,
a holding down member disposed along an outer
periphery of the forming punch, a counter punch
disposed to face the forming punch in a center axis
direction, and a die in whose insertion hole part the
counter punch is disposed and one end side inner wall
surface of whose insertion hole part into which the
forming punch is inserted is a die shoulder part,
center axes thereof being coaxially disposed to one
another, the press forming method sequentially
carries out: a first step of pushing the flat plateshaped
workpiece into the insertion hole part via the
die shoulder part by making the forming punch move
relatively in relation to the die and be inserted
into the insertion hole part, thereby to form the
workpiece into a cup-shaped workpiece having a cup
vertical wall part, a cup bottom part, and a cup
shoulder part connecting the cup vertical wall part
and the cup bottom part; a second step of making the
cup-shaped workpiece move relatively in relation to
the forming punch, to a position where a space is
formed between the cup bottom part and the forming
punch by the holding down member abutting on a cup
opening part side end part of the cup vertical wall
- 3 -
part; and a third step of restraining deformation in
a plate thickness direction of the cup vertical wall
part by the forming punch and the die and making the
counter punch approach the forming punch in a state
where a relative position in relation to the forming
punch of the cup vertical wall part is fixed by the
holding down member, to push the cup bottom part to a
forming punch side, to make the cup bottom part
compressed by the forming punch and the counter punc
and to make a material of the cup vertical wall part
flow to the cup shoulder part, thereby to thicken the
cup shoulder part.
[0009] (2) In the press forming method according to
the above-described (1), the holding down member may
be a cylindrical blank holder punch whose inner
peripheral surface in a radial direction orthogonal
to the center axis runs along an outer peripheral
surface of the forming punch and whose outer
peripheral surface in the radial direction runs along
an inner peripheral surface of the insertion hole
part of the die, and .in the third step the cup bottom
part may be c o mpressed by the f orm i ng punch and the
counter punch in a state where a relative position in
relation to the forming punch of the cup vertical
wall part is fixed by the holding down member
inserted between the forming punch and the die and
deformation in the plate thickness direction on a cup
opening part side in the cup vertical wall part is
restrained by the forming punch and the die.
[0010] By such a configuration, since the blank
holder punch which can be moved relatively between
the forming punch and the die is used as the holding
down member, the cup bottom part can be compressed in
a state where the cup opening part side end part of
the cup-shaped workpiece on a distant side of the
insertion hole part is held down by the blank holder
punch, that is, in a state where deformation in the
thickness direction of the cup opening part side in
the cup vertical wall part is restrained by the
forming punch and the die. Thus, it is possible to
make a material flow to the cup shoulder part
securely by compression of the cup bottom part.
[0011] (3) In the press forming method according to
the above-described (1), in the first step, the
forming punch may be moved in a first direction along
the center axis and the forming punch may be inserted
into the die, thereby to form the workpiece into the
cup-shaped workpiece, and in the second step, the
forming punch may be made to recede in a second
direction opposite to the first direction and the
counter punch may be moved in the second direction to
make the cup vertical wall part abut on the holding
dov/n member placed further in the second direction
than the die, thereby to make the cup-shaped
workpiece move relatively to a position where the
space is formed between the cup bottom part and the
forming punch.
[0012] When a cup-shaped workpiece is to be made to
- 5 -
move relatively to a position where a space is formed
between a cup bottom part and a forming punch by
relative movement of a holding down member between
the forming punch and a die after forming of the cupshaped
workpiece, it is necessary to prepare a
holding down member in correspondence with a
thickness (a space between the forming punch and the
die) of the cup-shaped workpiece being a forming
object. Compared with such a configuration,
according to a configuration of- (3), insertion of the
holding down member between the forming punch and the
die is not necessary for the purpose of moving the
cup-shaped workpiece relatively to the position where
the space is formed between the cup bottom part and
the forming punch. Thus, according to the
configuration of (3), forming can be carried out by
using the same holding down member regardless of a
thickness of a cup-shaped workpiece being a forming
object, so that versatility can be improved.
[0013] (4) In the press forming method according to
the above-described (3), an outer diameter of the
holding down member may be larger than an outer
diameter ot the die shoulder part. By such a
configuration, it is possible to carry out forming in
a state where a surface facing the die of the holding
down member is made to abut on the die, and action
control of the form can be carried out easily.
[0014] (5) In the press forming method according to
the above-described (3) or (4),•in the third step,
- 6 -
the counter punch may be moved in the second
direction from a state where a portion in which
deformation in the plate thickness direction is not
restrained exists, the portion being a portion
positioned between the die shoulder part and the
forming punch in the cup vertical wall part, and from
a state where the space exists between the cup bottom
part and the forming punch, and a weighted load of
the counter punch may be monitored, and when the
weighted load reaches a predetermined value, movement
of the counter punch in the second direction may be
halted, thereby to suppress flowing of a material to
the portion positioned between the die shoulder part
and the forming punch in the cup vertical wall part.
ADVANTAGEOUS EFFECTS OF INVENTION
[0015] According to the present invention, it is
possible to provide a press forming method to
contrive suppression of thinning of a cup shoulder
part, suppression of thinning of a cup vertical wall
part, and planarization of a cup bottom part
s imultaneously at a time that a plate-shaped
workpiece is formed into a cup shape.
BRIEF DESCRIPTION OF DRAWINGS
[0016] [Fig. 1] Eig. 1 is a schematic configuration
diagram of a press forming apparatus of a first
embodiment;
[Fig. 2] Fig. 2 is a diagram showing an example
- 7 -
of a forming situation of the press forming
apparatus;
[Fig. 3] Fig. 3 is a diagram showing an example
of the forming situation of the press forming
apparatus ;
[Fig. 4] Fig. 4 is a diagram showing an example
of the forming situation of the press forming
apparatus;
[Fig. 5] Fig. 5 is a diagram showing an example
of a forming completion situation of the press
forming apparatus;
[Fig. 6] Fig. 6 is a diagram showing wrinkling
of a cup bottom part which occurs at a time of
forming into a cup shape;
[Fig. 7] Fig. 7 is a schematic configuration
diagram of a press forming apparatus of a second
embodiment;
[Fig. 8] Fig. 8 is a diagram showing an example
of a forming situation of the press forming
apparatus; and
[Fig. 9] Fig. 9 is a diagram showing an example
of the forming situation of the press forming
appa ratus.
DESCRIPTION OF EMBODIMENTS
[0017] Hereinafter, each embodiment of the present
invention will be described with reference to the
drawings.
(First Embodiment)
Fig. 1 is a schematic configuration diagram of a
press forming apparatus of a first embodiment. A
side cross section of a press forming apparatus la is
axially symmetrical, and Fig. 1 and Fig. 2 to Fig. 9
shown later each show one side part from a center
axis 10 of the press forming apparatus la or lb.
[0018] The press forming apparatus la first forms a
disk-shaped (flat plate-shaped) workpiece A into a
cup shape. A member formed into the cup shape is
referred to as a cup-shaped workpiece B. Next, there
is carried out press forming to thicken a cup
shoulder part B3 of the cup-shaped workpiece B which
has been thinned at a time of forming into the cup
shape. The press forming apparatus la carries out
the press forming by using a press forming die which
has a forming punch 11, a blank holder punch 12
(holding down member), a counter punch 13, and a die
14. The press forming apparatus la consecutively
carries out a step of forming the cup-shaped
workpiece B from the disk-shaped workpiece A and
press forming to thicken the cup shoulder part B3 .of
the cup-shaped workpiece B which has been formed,
without detaching the cup-shaped workpiece B from the
press forming apparatus la. These forming punch 11,
blank holder punch 12, counter punch 13, and die 14
are disposed axially symmetrically (in other words,
coaxially) in relation to the center axis 10, and
each can be moved upward and downward independently.
Note that it is possible that the die 14 is fixed,
- 9 -
with the forming punch 11, the blank holder punch 12,
and the counter punch 13 being moved relatively in
relation to the die 14, for example. Even with the
above configuration, press forming similar to that in
a case of moving the forming punch 11, the blank
holder punch 12, the counter punch 13, and the die 14
upward and downward independently is possible.
[0019] The forming punch 11 is column-shaped, and a
tip surface 111 facing the counter punch 13 is a
plane parallel to an orthogonal direction of the
center axis 10. A tip corner portion of the forming
punch 11 is an R-shaped punch shoulder part 113. The
punch shoulder part 113 connects a peripheral portion
of the tip surface 111 and a lower end portion in an
outer peripheral surface 112 of the forming punch 11.
[0020] The blank holder punch 12 is cylindrical, and
is disposed along the outer peripheral surface 112 of
the forming punch 11. In the blank holder punch 12,
an inner peripheral surface 121 in a radial direction
orthogonal to the center axis 10 runs along the outer
peripheral surface 112 of the forming punch 11, while
an outer peripheral surface 122 in the radial
direction runs along an inner peripheral surface 143
of a later-described insertion hole part 141 of the
die 14. A thickness of a thick portion of the blank
holder punch 12 is a thickness allowing insertion
into between the die 14 and the forming punch 11
which is inserted into the die 14 at a time of
forming of the disk-shaped workpiece A.
10
[0021] The counter punch 13 is column-shaped, and is
disposed in a manner that its tip surface 131 faces
the tip surface 111 of the forming punch 11 in a
center axis 10 direction. In the counter punch 13,
the tip surface 131 facing the tip surface 111 of the
forming punch 11 is a plane parallel to the
orthogonal direction of the center axis 10.
[0022] An upper end surface 144 of the die 14 is
positioned lower than the tip surface 111 of the
forming punch 11 at a start time of forming of the
disk-shaped workpiece A. The die 14 is circular
ring-shaped, and has the insertion hole part 141
extending in an axial direction. The counter punch
13 is disposed inside the insertion hole part 141.
The forming punch 11 and the blank holder punch 12
are inserted into the insertion hole part 141 at the
time of forming of the disk-shaped workpiece A. An
R-shaped die shoulder part 142 which is widened as
going upward is formed in one end side inner wall
surface (tip side inner wall surface) of the
insertion hole part 141 into which the forming punch
11 is inserted at the Lime of forming.
[0023] The die shoulder part 142 connects the inner
peripheral surface 14 3 of the insertion hole part 14 1
and the upper end surface 144. The upper end surface
14 4 is circular ring-shaped in center axis 10
direction view, and is a plane parallel to the
orthogonal direction of the center axis 10. An
inside diameter of the upper end surface 144 is
- 11 -
smaller than an outside diameter of the disk-shaped
workpiece A. Thereby, the upper end surface 144
functions as a supporting surface which supports an
outer edge portion of the disk-shaped workpiece A at
the start time of forming of the disk-shaped
workpiece A. A distance SI between the outer
peripheral surface 112 of the forming punch 11 and
the inner peripheral surface 143 of the die 14 in the
radial direction is a size similar (including an
error) to a thickness of the disk-shaped workpiece A.
[0024] Hereinafter, a forming action (press forming
method) of the press forming apparatus la will be
described. As shown in Fig. 1, the disk-shaped
workpiece A is set on the upper end surface 144 of
the die 14. The press forming apparatus la moves the
forming punch 11 downward so that the forming punch
11 is inserted into the insertion hole part 141,
whereby the disk-shaped workpiece A is pushed into
the insertion hole part 141 via the die shoulder part
142. Thereby, as shown in Fig. 2, the press forming
apparatus la forms the disk-shaped workpiece A into
the cup-shaped workpiece B with a bottomed cylinder
shape which has a cup vertical wall part Bl, a cup
bottom part B2, and a cup shoulder part B3 connecting
the cup vertical wall part Bl and the cup bottom part
B2 (first step). Further, a cup opening part Bill is
formed in the cup-shaped workpiece B. On this
occasion, the cup shoulder part B3 is thinned
compared with a thickness of the disk-shaped
- 12
workpiece A. Incidentally, the blank holder punch 12
is not moved downward but maintains an initial
position apart from the cup-shaped workpiece B.
[0025] Next, as shown in Fig. 3, the press forming
apparatus la moves the blank holder punch 12 downward
while maintaining a position of the forming punch 11
at a position (position shown in Fig. 2) in the first
step. Then, the press forming apparatus la makes the
blank holder punch 12 abut on an end part Bll
(hereinafter, described as a cup opening part side
end part Bll) on a cup opening part Bill side of the
cup vertical wall part Bl, and further pushes the
cup-shaped workpiece B to down below the forming
punch 11 by the blank holder punch 12. Thereby, the
press forming apparatus la makes the cup-shaped
workpiece B move to a position where a space S2 of a
predetermined size is formed between the cup bottom
part B2 and the forming punch 11 {second step).
[0026] On this occasion, the press forming apparatus
la comes into a state where deformation in a plate
thickness direction of the cup vertical wall part Bl
is restrained by the forming punch 11 and the die 14
and upward movement of the cup vertical wall part Bl
is held down by the blank holder punch 12 (a state
where a relative position in relation to the forming
punch 11 of the cup vertical wall part Bl is fixed by
the blank holder punch 12). In this state, as shown
in Fig. 4 , the press forming apparatus la moves the
counter punch 13 upward to make the counter punch 13
13 -
approach the forming punch 11. Thereby, the press
forming apparatus la pushes the cup bottom part B2 to
a forming punch 11 side, to compress the cup bottom
part B2 by the forming punch 11 and the counter punch
13 (third step).
[0027] On this occasion, a peripheral void VI is
formed between a corner part 15 formed by the inner
peripheral surface 143 of the die 14 and the tip
surface 131 of the counter punch 13, and the punch
shoulder part 113 of the forming punch 11. This
peripheral void VI is larger than a size of the cup
shoulder part B3 before forming. Therefore, as shown
in Fig. 5, the press forming apparatus la makes a
material in a neighboring portion of the cup shoulder
part B3 flow into the void VI speedily (prompts
material flow) by pushing the cup bottom part B2 to
the forming punch 11 side in a state where upward
movement of the cup vertical wall part Bl is limited
by the blank holder punch 12. Thereby, the cup
shoulder part B3 is thickened easily. On the other
hand, in the cup vertical wall part Bl, a portion on
a cup opening part Bill s ide in which material flow
does not occur maintains a plate thickness. As
described above, in the present embodiment, since the
cup vertical wall part Bl is not ironed, it is
possible to thicken the cup shoulder part B3 while
preventing thinning of the cup vertical wall part Bl.
[0028] Further, when the disk-shaped workpiece A is
formed into the cup-shaped workpiece B in the first
- 14 -
step, as shown in Fig. 6, there is a case where
projection/recession such as wrinkling occurs in the
cup bottom part B2 , to bring about loss of planeness
of the cup bottom part B2 in a range not hampering
practical use of the cup—shaped workpiece B. In the
present embodiment, since the cup bottom part B2 is
compressed by the planar tip surface 111 of the
forming punch 11 and the planar tip surface 131 of
the counter punch 13, the cup bottom part B2 can be
made planar even in the above case, and the cupshaped
workpiece B can be shape-corrected.
[0029] In the present embodiment, first, the diskshaped
workpiece A is pushed into the die.14 by the
forming punch 11, whereby the disk-shaped workpiece A
is formed into the cup-shaped workpiece B.
Thereafter, the blank holder punch 12 is inserted
between the forming punch 11 and the die 14 to push
the cup-shaped workpiece B out of the forming punch
11, whereby the cup-shaped workpiece B is made to
move to a position where the space S2 is formed
between the cup-shaped workpiece B and the forming
punch 11. Therefore, in the present embodiment, the
consecutive two actions described above can make the
cup-shaped workpiece B move to the position where the
space S2 is formed between the cup-shaped workpiece B
and the forming punch 11, so that man-hour can be
curtailed.
[0030] In the present embodiment, since the blank
holder punch 12 with a small thickness is used as a
15 -
holding down member, the blank holder punch 12 can be
inserted between the forming punch 11 and the die 14.
Therefore, the cup bottom part B2 can be compressed
in a state where the blank holder punch 12 holds down
the cup opening part side end part Bll of the cupshaped
workpiece B on a distant side of the insertion
hole part 141, that is, in a state where the forming
punch 11 and the die 14 restrain deformation in the
thickness direction of the cup opening part Bill side
of the cup vertical wall part Bl of the cup-shaped
workpiece B in the distant side of the insertion hole
part 141. Thus, it is possible to make the material
flow to the cup shoulder part B3 securely by
compression of the cup bottom part B2. Further,
since the cup vertical wall part Bl is maintained to
be in a state of being sandwiched between the forming
punch 11 and the die 14, deformation, for example,
buckling or the like, does not occur in a portion on
the cup opening part Bill side in the cup vertical
wall part Bl.
[0031] (Second Embodiment)
Fig. 7 is a schematic configuration diagram of a
press forming apparatus lb of a second embodiment.
Note that a configuration common to that of the first
embodiment is granted the same reference symbol.
In the present embodiment, a base 16 is used as a
holding down member to hold down a cup vertical wall
part Bl. The base 16 is cylindrical and is disposed
along an outer periphery of a forming punch 11. A
- 16 -
lower end surface of the base 16 is a ring-shaped
holding down surface 161. The ring-shaped holding
down surface 161 is larger than a die shoulder part
142 in outer diameter and faces a die 14 in a center
axis 10 direction. In other words, the base 16
cannot enter between the forming punch 11 and the die
14 .
[0 032] Hereinafter, a forming action of the press
forming apparatus lb of the present embodiment will
be described s imply. As shown in Fig. 8, the press
forming apparatus lb pushes a disk-shaped workpiece A
into an insertion hole part 141 of the-die 14 by the
forming punch 11, so that the disk-shaped workpiece A
is formed into a cup-shaped workpiece B (first step).
[0033] Next, the press forming apparatus lb moves
the base 16 downward to a position where the ringshaped
holding down surface 161 becomes contact with
an upper end surface 144 of the die 14. Further, as
shown in Fig. 9, the press forming apparatus lb moves
the forming punch 11 upward and moves a counter punch
13 upward to lift the cup-shaped workpiece B by the
counter punch 13, so that the cup vertical wall part
Bl is made to abut on the base 16. On this occasion,
the press forming apparatus lb moves the forming
punch 11 upward to a position where a space S2 of a
predetermined size is formed between the forming
punch 11 and a cup bottom part B2 (second step) .
[0034] In other words, in the first step, the press
forming apparatus lb moves the forming punch 11
- 17 -
downward, i.e., in a first direction along a center
axis 10, and the forming punch 11 is inserted into
the die 14, thereby to form the disk-shaped workpiece
A into the cup-shaped workpiece B. Thereafter, in
the second step, the press forming apparatus lb makes
the forming punch 11 recede upward, i.e. in a second
direction being opposite to the first direction and
moves the counter punch 13 upward, to make the cup
vertical wall part Bl abut on the holding down member
16 positioned more above the die 14. Thereby, the
press forming apparatus lb makes the cup-shaped
workpiece B move to the position where the space S2
is formed between the cup bottom part B2 and the
forming punch 11.
[0035] From this state, the press forming apparatus
lb further moves the counter punch 13 upward to push
the cup bottom part B2 to a forming punch 11 side, so
that the cup bottom part B2 is compressed by the
forming punch 11 and the counter punch 13. Thereby,
similarly to in the first embodiment, a material of
the cup vertical wall, part B1 is made to f 1 o w to a
cup shoulder part B3, to thicken the cup shoulder
part B3 (third step).
[0036] It is proved that when the cup bottom part B2
is pushed to the forming punch 11 side from the state
of Fig. 9 and the cup bottom part B2 is further
pushed to the forming punch 11 side after completion
of thickening of the cup shoulder part B3, a weighted
load of the counter punch 13 is increased compared
- l:
with a weighted load at a time of thickening of the
cup shoulder part B3. Besides, it is proved that at
this time the material of the cup-shaped workpiece B
flows to a portion positioned in a void V2 in the cup
vertical wall part Bl. Here, the void V2 means a
space between a corner part 17 formed by an outer
peripheral surface 112 of the forming punch 11 and
the ring-shaped holding down surface 161 of the base
16, and the shoulder part 142.
[0037] In other words, when the counter punch 13 is
to be moved upward from a state where the space S2
exists between the cup bottom part B2 and the forming
punch 11, first, the material flows to the cup
shoulder part B3. It is proved that when the cup
bottom part B2 is further pushed to the forming punch
11 side after completion of thickening of the cup
shoulder part B3, a portion (portion positioned
between the die shoulder prat 142 and the forming
punch 11 in the cup vertical wall part Bl) on a base
16 side where deformation in a plate thickness
direction is not restrained in the cup vertical wall
part Bl buckles.
[0038] Therefore, when the counter punch 13 is to be
moved upward from the state where the space S2 exists
between the cup bottom part B2 and the forming punch
11, the weighted load of the counter punch 13 is
observed, and upper movement of the counter punch 13
is halted when the weighted load reaches a
predetermined value. Thereby, it is possible to
19 -
avoid buckling of the portion on the base 16 side
where deformation in the plate thickness direction is
not restrained in the cup vertical wall part Bl.
Further, it is also possible to prescribe completion
of thickening of the cup shoulder part B3 by a
movement amount of the counter punch 13.
[0039] Note that the above-described weighted load
(predetermined value) and the movement amount
(predetermined value) of the counter punch 13 being
threshold values to halt upward movement of the
counter punch 13 are determined as follows. First,
before forming of the cup-shaped workpiece B, a cup
bottom part B2 of a cup-shaped workpiece B of the
same standard as that of the above cup-shaped
workpiece B is compressed by the counter punch 13
having been moved upward and the forming punch 11,
and on this occasion, a weighted load of the counter
punch 13 is observed.
[0040] Subsequently, in a measurement result of the
weighted load of the counter punch 13, there is
determined a point at which the weighted load of the
counter punch 13 is decreased prominently, that is, a
point at which a portion (portion positioned between
the die shoulder part 142 and the forming punch 11)
on the base 16 side where deformation in' the plate
thickness direction is not restrained in the cup
vertical wall part Bl starts to buckle. Then, the
weighted load at this point and a movement amount
(movement amount of the counter punch 13 from a
- 20 -
position from which the counter punch 13 is started
to move upward in a state where a cup opening part
side end part Bll is held down by the holding down
member to a position of the counter punch 13 at the
above point) of the counter punch 13 at this point
are determined as respective threshold values to halt
upward movement of the counter punch 13.
[0041] As a result of the above procedure, also in
the present embodiment, it is possible to contrive
suppression of thinning of the cup shoulder part B3,
suppression of thinning of the cup vertical wall part
Bl, and planarization of the cup-bottom part B2
simultaneously at the time that the disk-shaped
workpiece A is formed into the cup-shaped workpiece B
Further, in the present embodiment, since the base 16
as the holding down member is not required to be
inserted between the forming punch 11 and the die 14,
forming can be carried out by using the same base 16
regardless of a thickness of a workpiece A being a
forming object, so that versatility can be improved.
[0042] (Modification Example)
In the first and second embodiments, top and
bottom of a tool may be reversed, that is, the
counter punch 13 and the die 14 may be disposed on an
upper side, and the forming punch 11, the holding
down punch 12, and the base 16 may be disposed on a
lower s ide.
In the first step in the first embodiment, the
press forming apparatus la may form the disk-shaped
21 -
workpiece A into the cup-shaped workpiece B by moving
the die 14 upward, to move the forming punch 11
relatively in relation to the die 14 and make the
forming punch 11 inserted into the insertion hole
part 14 1, so. that the disk-shaped workpiece A is
thereby pushed into the insertion hole part 141,
instead of by the aforementioned configuration.
[0043] In the second step in the first embodiment,
the press forming apparatus la may make the cupshaped
workpiece B move to the position where the
space S2 is formed between the cup bottom part B2 and
the forming punch 11 by moving the forming punch 11
upward after making the blank holder punch 12 abut on
the cup opening part side end part Bll of the cup
vertical wall part Bl and supporting the cup bottom
part B2 with the counter punch 13, instead of by the
aforementioned configuration.
[0044] In the third step in the first embodiment,
the press forming apparatus la may make the cup
bottom part B2 compressed by the forming punch 11 and
the counter punch 13 by moving both forming punch 11
and blank holder punch 12 downward while a relative
position to each other is maintained in a state where
the cup bottom part B2 is supported by the counter
punch 13, instead of by the aforementioned
configuration.
[0045] In the second embodiment, there is a case
where the cup vertical wall part Bl is longer than a
length of the die shoulder part 142 in the center
- 22 -
axis 10 direction. In other words, there is a case
where the cup vertical wall part Bl can be held down
by the base 16 positioned abpve the upper end surface
144 of the die 14. In this case, in the third step,
the press forming apparatus lb may make the cup
bottom part B2 compressed by the forming punch 11 and
the counter punch 13 by moving both forming punch 11
and base 16 downward while a relative position to
each other is maintained in a state where the cup
bottom part B2 is supported by the counter punch 13,
instead of by the aforementioned configuration.
[0046] Hereinabove, embodiments and examples of the
present invention are described in detail, but the
embodiments and the examples merely show examples of
concretization in implementing the present invention.
The technical scope of the present invention is not
to be construed in a restrictive manner by these
embodiments. That is, the present invention may be
implemented in various forms without departing from
the technical spirit or main features thereof.
INDUSTRIAL APPLICABILITY
[0047] The present invention is a technique
effective for a press forming method to form a flat
plate-shaped workpiece into a cup shape. Besides,
according to the present invention, it is possible to
contrive suppression of thinning of a cup shoulder
part, suppression of thinning of a cup vertical wall
part, and planarization of a cup bottom part
- 23 -
simultaneously at a time that the plate-shaped
workpiece is formed into a cup shape.

CLAIMS
[Claim 1] A press forming method car
forming to a flat plate-shaped workpi
press forming die which has a forming
holding down member disposed along an
of the forming punch, a counter punch
face the forming punch in a center ax
and a die in whose insertion hole par
punch is disposed and one end side in
of whose insertion hole part into whi
punch is inserted is a die shoulder p
thereof being coaxially disposed to o
press forming method sequentially com
a first step of pushing the flat
workpiece into the insertion hole par
shoulder part by making the forming p
relatively in relation to the die and
into the insertion hole part, thereby
workpiece into a cup-shaped workpiece
vertical wall part, a cup bottom part
shoulder part connecting the cup vert
and the cup bottom part;
a second step of making the cup-shaped workpiece
move relatively in relation to the forming punch, to
a position where a space is formed between the cup
bottom part and the forming punch by the holding down
member abutting on a cup opening part side end part
of the cup vertical wall part; and
a third step of restraining deformation in a
- 25 -
rying out press
ece by using a
punch, a
outer periphery
disposed to
is direction,
t the counter
ner wall surface
ch the forming
art, center axes
ne another, the
prising:
plate-shaped
t via the die
unch move
be inserted
to form the
having a cup
, and a cup
ical wall par t
plate thickness direction of the cup vertical wall
part by the forming punch and the die and making the
counter punch approach the forming punch in a state
where a relative position in relation to the forming
punch of the cup vertical wall part is fixed by the
holding down member, to push the cup bottom part to a
forming punch side, to make the cup bottom part
compressed by the forming punch and the counter punch,
and to make a material of the cup vertical wall part
flow to the cup shoulder part, thereby to thicken the
cup shoulder part.
[Claim 2] The press forming method according to
claim 1,
wherein the holding down member is a cylindrical
blank holder punch whose inner peripheral surface in
a radial direction orthogonal to the center axis runs
along an outer peripheral surface of the forming
punch and whose outer peripheral surface in the
radial direction runs along an inner peripheral
surface of the insertion hole part of the die, and
wherein in the third step the cup bottom part is
compressed by the forming punch and the counter punch
in a state where a relative position in relation to
the forming punch of the cup vertical wall part is
fixed by the holding down member inserted between the
forming punch and the die and deformation in the
plate thickness direction on a cup opening part side
in the cup vertical wall part is restrained by the
forming punch and the die.
- 26 -
[Claim 3] The press forming method according to
claim 1,
wherein in the first step the forming punch is
moved in a first direction along the center axis and
the forming punch is inserted into the die, to form
the workpiece into the cup-shaped workpiece, and
wherein in the second step the forming punch is
made to recede in a second direction opposite to the
first direction and the counter punch is moved in the
second direction to make the cup vertical wall part
abut on the holding down member placed further in the
second direction than the die, to make the cup-shaped
workpiece move relatively to a position where the
space is formed between the cup bottom part and the
forming punch.
[Claim 4] The press forming method according to
claim 3,
wherein an outer diameter of the holding down
member is larger than an outer diameter of the die
shoulder part.
[Claim 5] The press forming method according to
claim 3 or claim 4 ,
wherein in the third step the counter punch is
moved in the second direct.!on from a state where a
portion in which deformation in the plate thickness
direction is not restrained exists, the portion being
a portion positioned between the die shoulder part
and the forming punch in the cup vertical wall part,
and from a state where the space exists between the
- 27
cup bottom part and the forming punch, and a weighted
load of the counter punch is monitored, and
wherein, when the weighted load reaches a
predetermined value, movement of the counter punch in
the second direction is halted, thereby to suppress
flowing of a material to the portion positioned
between the die shoulder part and the forming punch
in the cup vertical wall part.