TECHNICAL FIELD
looor]
The present invention relates to an apparatus and a method for
manufacturing a crankshaft by hot forging.
BACKGROUND ART
looozl
A reciprocating engine to be employed in a motor vehicle, a
motorcycle, an agricultural machine, a marine vessel or the like requires a
crankshaft to extract po\iler by converting reciprocating motions of pistons
to rotational motion. There are two types of crankshafts: the type
manufactured by die forging and the type manufactured by casting.
Especially when high strength and high stiffness are required, die forged
crankshafts (which will hereinafter be referred to as forged crankshafbs) are
ofben employed.
looosl
A forged crankshaft is generally manufactured by using a billet as a
starting material. The billet has a circular or square cross section, and the
cross-sectional area is constant throughout the length. A method for
manufacturing a forged crankshafb includes a preforming step, a die forging
step, and a trimming step. When a process to fi.nish the interim product
into a finished shape and fi.nished size is needed, a coining step is performed
after the trimming step. Tþpically, the preforming step includes a rolling
step and a bending step, and the die forging step includes a rough forging
step and a finish forging step.
looo¿l
FIGS. 1A to lF are schematic diagrams illustrating a conventional
process for manufacturing a common forged crankshaft. The crankshafb 1
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shown in FIG. lF is a four-cylinder eight-counterweight crankshaft to be
mounted in a four-cylinder engine. The crankshaft 1 includes fi.ve journals
Jl to J5, four pins P1 to P4, a front part Fr, a fLange Fl, and eight crank
arms (hereinafter referred to simply as "arms") A1 to 48. The eight arms
A1 to A8 connect the journals Jl to J5 respectively to the pins Pl to P4.
The eight arms A1 to A8 have counterweights (hereinafter referred to
simply as "weights") Wl to W8, respectively. The weights Wl to W'8 are
integrally formed with the arms A1 to 48, respectively.
looosl
The four pins P1 to P4 are decentered from the journals Jl to J5.
The phases of the pins Pl to P4 are set such that the pins P1 to P4 arc
positioned plane symmetrically with respect to the journal JB positioned in
the center in the length direction of the crankshaft 1. Accordingly, the
arms A4 and A5 connecting with the central journal J3 are plane
symmetrical with respect to the central journal J3. Thus, the two arms A4
and A5 both connect with one journal JB and connect with the pins P2 and
P3, respectively, which are in the same phase.
looool
In the following paragraphs, when the journals J1 to J5, the pins P1
to P4, the arms A1 to 48, and the weights Wl to W8 are each collectively
referred to, a reference character rtJrr is used for the journals, a reference
character "P" for the pins, a reference character rrArt for the arms, and a
reference character "W'" for the weights. A pin P and a couple of arms A
(including weights W) connecting with the pin P are collectively referred to
as a "throw".
looozl
According to the manufacturing method shown in FIGS. 1A to lF,
the forged crankshaft 1 is manufactured in the following manner. First, a
billet 2 with a predetermined length as shown in FIG. 1A is heated in a
heating furnace or a gas atmosphere furnace and then undergoes rolling.
In the rolling step, the billet 2 is rolled and drawn by grooved rolls.
Thereby, the volume of the billet 2 is distributed in the longitudinal
direction, and a rolled blank 3, which is an intermediate material, is formed
3
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(see FIG. 1B). Next, in the bending step, the rolled blank 3 is partially
pressed in a direction perpendicular to the longitudinal direction. Thereby,
the volume of the roller blank 3 is distribute, and a bent blank 4, which is a
secondary intermediate material, is formed (see FIG. 1C).
loooel
Next, in the rough forging step, the bent blank 4 is press forged by a
pair of upper and lower dies, whereby a rough forged blank 5 is formed (see
FIG. 1D). The rough forged blank 5 has a general shape of the crankshaft
(finished product). Then, in the finish forging step, the rough forged blank
5 is further press forged by a pair of upper and lower dies, whereby a finish
forged blank 6 is formed (see FIG. 1E). The finish forged blank 6 has a
shape in agreement with the shape of the finished. crankshaft. In the
rough forging and the finish forging, excess material flows out from between
the mutually opposed parting surfaces of the dies, thereby forming flash.
Therefore, the rough forged blank 5 and the finish forged blank 6 have large
flash 5a and 6a around the shape of the crankshafb.
looogl
In the trimming step, while the finish forged btank 6 with flash 6a is
held by a pair of dies, the flash is punched by a cutting die. Thereby, the
flash 6a is removed from the finish forged blank 6. In this manner, a finish
forged blank with no flash is obtained, and the finish forged blank with no
flash has almost the same shape as the forged crankshaft 1 shown in FIG.
lF. The forged blank with no flash includes rough journals J', rough pins P,
rough crank arms A' and rough weights 'W, which correspond to the
journals J, the pins P, the arms A and the weights W, respectively, of the
forged crankshaft.
loorol
In the coining step, principal parts of the forged blank with no flash
are slightly pressed by dies from above and below and shaped to have the
correct size and shape of the finished product. In this regard, the principal
parts of the forged blank with no flash are, e.g., the rough journals J', the
rough pins P', the rough arms A' and the rough weights W''. The principal
parts of the forged blank with no flash further include shaft parts such as a
+
rough front part and a rough fLange, which correspond to the front part Fr
and the fLange part FI of the crankshaft, respectively. In this manner, the
forged crankshafb 1 is manufactured.
loortl
The process shown in FIGS. 1A to lF is applicable not only for
manufacturing a four-cylinder eight-counterweight crankshaft as
illustrated in FIG. lF but also for manufacturing various other types of
crankshafts. For example, the process is applicable for manufacturing a
four-cylinder four-counterweight crankshafb.
loorzl
In a four-cylinder four-counterweight crankshaft, only some of the
eight ârms A incorporate a weight W. For example, the leading first arm
41, the trailing eighth arm ,A.8, and the two central arms (the fourth armA4
and the fifth arm A5) incorporate a weight W.
loorsl
The process shown in FIGS. 1A to lF can be applied for
manufacturing crankshafts that are to be mounted in a three-cylinder
engine, an inline six'cylinder engine, a V-type six-cylinder engine, an
eight-cylinder engine and the like. It is noted that, when adjustment of the
placement angles of the pins is necessary, a twisting step is added after the
trimming step.
loor¿l
An exemplary process flow of the manufacturing process shown in
FIGS. 1A to lF is described with reference to the drawings.
loorsl
FIGS. Zy''to 2D arc diagrams showing an exemplâry process fl,ow of
a conventional coining step. FIG. 2A shows a time when a forged blank
with no flash has been carried in, FIG. 28 shows a state where the forged.
blank with no flash is being reduced, FIG. 2C shows a time when an upper
die has been moved up, and FIG. 2D shows a time when the forged blank
with no flash is to be taken out. In FIGS. 2[to 2D, an apparatus 10 to
apply coining and a forged blank with no flash 70 t}nat is a workpiece are
shown.
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looral
The coining apparatus 10 shown in FIGS. Zy''to 2D includes a first
Iower die 20 and a second upper die 30 paired with each other, a carry-in
robot arm 13 (see FIG. 2A), a take-out robot arm L4 (see FIG. 2D), and a
knock-out member 15. The first die 20 and the second die 30 are to apply
coining to the forged blank with no flash 70. The knock-out member 15 is
to release the coined forged blank from the dies.
loorzl
In the coining step executed by use of the manufacturing apparatus
10, while the first die 20 and the second die 30 are arü¡ay from each other, a
forged blank with no flash 70 is carried in onto the first lower die 20 by the
robot arm 13 (see FIG. 2A).
loorsl
Then, the first die 20 and the second die 30 are moved toward each
other and thereby reduce the forged blank with no flash 70. In this way,
coining is applied to the forged blank with no flash 70 (see FIG. 2B).
Thereafter, the first die 20 and the second die 30 are separated from each
other (see FIG. 2C).
loorgl
Next, the knock-out member 15 is moved up by a lifting device (not
shown) and thereby releases the forged blank with no flash from the dies.
The processed forged blank 71 is taken out and fed to the next stage by the
robot arm 14.
loozol
In recent years, there has been a need. for weight reduction of
reciprocating engines, particularly those for motor vehicles, in order to
improve the fuel economy. Accordingly, there is also an ever-increasing
demand for weight reduction of crankshafbs to be mounted in reciprocating
engines. The following techniques are known as \¡¡ays to reduce the weight
of a forged crankshaft.
loozrl
Patent Literatures 1 and 2 disclose an arm having a recess in the
journal-facing surface. These literatures also disclose a method for
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manufacturing a crankshafb including an arm having â recess. The recess
of the arm is formed to lie on a straight line connecting the axis of the
journal and the axis of the pin (which will hereinafter be referred to as an
"arm centerline"), and the recess is made deep toward the pin. This arm is
reduced in weight by an amount corresponding to the volume of the recess.
The weight reduction of the arm leads to a weight reduction of the weight
paired with the arm, thereby resulting in a weight reduction of the whole
forged crankshaft. The arm having a recess has thick portions on both
sides of the arm centerline in the region near the pin, which ensures
stiffness (¡ottr torsional rigidity and fLexural rigidity).
îoozzl
Thus, thickening both side portions of an arm and thereby forming a
recessed portion in the journal-facing surface of the arm ensure weight
reduction and stiffness.
loozsl
It is, however, difficult to manufacture such a forged crankshafb
with such arms having a unique shape by a conventional manufacturing
method. The reason is as follows. When a recess is to be formed in the
surface of an arm in the die forging step, the draft of the die will become a
reverse draft at the site of the recess, and therefore, the formed forged blank
will not be able to be released. from the die.
loozql
To avoid such situations, the manufacturing methods disclosed in
Patent Literatures I and 2 ate configured as follows. In the die forging
step, the arm is shaped to be small with no recess formed in the surface of
the arm, and after the trimming step, a punch is pushed into the surface of
the arm to form a recess.
CITIffION LIST
PATENT LITERATI.IRE
looz¡l
Patent Literature 1: Japanese Patent Application Publication No.
20t2-7726
+
-/-
Patent Literature 2: Japanese Patent Application Publication No.
2010-230027
SLIMMARY OF INVETION
TECHNICAL PROBLEMS
loozol
As disclosed in Patent Literatures 1 and 2, by forming a recess in
the journal-facing surface of an arm, it is possible to thicken both side
portions of the arm. This permits manufacture of a forged crankshaft with
a reduced weight and assured stiffness.
loozzl
In the manufacturing methods d.isclosed in Patent Literatures 1 and
2, however, in forming a recess, a surface of an arm is strongly punched and
is deformed entirely, and a great force is necessary for the punching.
Therefore, a special mechanism for supplying a great force to a punch is
required, and it is also necessary to give attention to the durability of the
punch.
loozsl
Then, the inventors suggested forming a recess in the journal-facing
surface of an arm by bending an excess portion (pCt¡.lpZO14l005835).
SpeciÍ.cally, in a die forging step, a forged blank that includes a rough arm
having excess portions protruding from the outer peripheries of both side
portions in a region near an adjacent rough pin is formed. In a coining step,
the excess portions are bent toward the rough-journal-facing surface of the
rough arm by a pair of upper and lower dies. In this case, there is no need
to supply a great force to form a recess, and a forged crankshaft having a
reduced. weight and assured. stiffness can be manufactured. easily.
loozgl
Also, the inventors suggested crashing the excess portions, instead
of bending, to form a recess in the journal-facing surface of the arm
(pcrrupzo14/oo5s5o).
loosol
However, in a case where bending or crashing of excess portions is
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carried out during the conventional process flow of a coining step shown by
FIGS. 2A to 2D, when the forged blank with no flash 70 is placed on the
lower die (the first die 20 in FIG. 2Ð, the posture of the forged blank with
no flash 70 becomes unstable. This is because the forged blank with no
flash 70 includes protruding excess portions. Then, there is a possibility
that the rough pin decentering direction (the direction in which the rough
pins are decentered from the rough journals) of the forged blank with no
flash 70 will not be perpendicular to the reducing direction in which the
first die 20 and the second die 30 apply force for reduction. In this case,
the first die 20 and the second die 30 may fail to apply desired coining to the
forged blank with no flash 70 by the reduction. This may cause a problem
that the forged blank after processed in the coining step is twisted.
loosr]
An object of the present invention is to provide a forged crankshafb
manufacturing apparatus and a forged crankshafb manufacturing method
that deliver stable performance to deform excess portions of a forged blank
with no fl.ash.
SOLUTIONS TO PROBLEMS
looszl
A forged crankshaft manufacturing apparatus according to an
embodiment of the present invention is to process a forged blank with no
flash in a process of manufacturing a forged crankshafb. The forged
crankshaft includes journals serving as an axis of rotation, pins decentered
from the journals, and crank arms connecting the journals and the pins.
The forged blank includes rough journals, rough pins and rough crank arms
corresponding to the journals, the pins, and the crank arms, respectively, of
the forged crankshaft- At least one of the rough crank arms includes an
excess portion protruding from the outer periphery of a side portion thereof.
The manufacturing apparatus includes a fi.rst die and a second die paired
with each other, a retaining device, and a moving device. The first die and
the second dies are to bend or crash the excess portion. The retaining
device is to retain at least one of the rough journals or at least one of the
1
rough pins of the forged blank such that a rough pin decentering direction
in which the rough pins are decentered from the rough journals is
perpendicular to a reducing direction in which the first die and the second
die apply force for reduction. The moving device is to support the retaining
device such that the retaining device is movable along the reducing
direction.
loogsl
A forged crankshaft manufacturing method according to an
embodiment of the present invention is a method for manufacturing a
forged crankshaft including journals serving as an axis of rotation, pins
decentered from the journals, and crank arms connecting the journals and
the pins. The manufacturing method includes a fi.rst step and. a second
step. By the first step, a forged blank with no flash is obtained. The
forged blank includes rough journals, rough pins and rough crank arms
corresponding to the journals, the pins and the crank arms, respectively, of
the forged crankshafb. At least one of the rough crank arms includes an
excess portion protruding from an outer periphery of a side portion thereof.
In the second step, the excess portion of the forged blank with no flash is
bent or crashed. In the second step, the above'described manufacturing
apparatus is used. In the second step, the excess portion of the rough
crank arm is deformed, whereby the rough crank arm is shaped into a crank
arm with a thick side portion.
ADVANTAGEOUS EFFECTS OF INVENTION
loos¿l
The forged crankshaft manufacturing apparatus according to the
present invention includ.es a. retaining d.evice. Therefore, the
manufacturing apparatus according to the present invention can retain a
forged blank with no flash including an excess portion in a specified posture.
The manufacturing apparatus according to the present invention further
includes a moving device. Therefore, the forged blank with no fl.ash can be
reduced by the first die and the second die while being kept in the specified
posture. Thus, the forged crankshaft manufacturing apparatus and the
to
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forged crankshafb manufacturing method can deliver stable performance to
bend or crash the excess portion of a forged blank with no flash.
BRIEF DESCRIPTION OF DRAWINGS
loossl
[f'IC.m] f'IC. 1A is a schematic diagram of a billet during a
conventional process of manufacturing a forged crankshaft.
[n'tC. 1B] FIG. 18 is a schematic diagram of a rolled blank during
the conventional process of manufacturing a forged crankshaft.
[nC. lC] FIG. 1C is a schematic diagram of a bent blank during the
conventional process of manufacturing a forged crankshaft.
[f'IC. lD] FIG. lD is a schematic diagram of a rough forged blank
during the conventional process of manufacturing a forged crankshaft.
[f'IC. lE] FIG. lE is a schematic diagram of a finish forged blank
during the conventional process of manufacturing a forged crankshaft.
[f'IC. lF] FIG. 1F is a schematic diagram of a crankshaft during the
conventional process of manufacturing a forged crankshaft.
[f'IC. 2A] FIG. 2A is a diagram showing a time when a forged blank
with no flash has been carried in during a conventional coining step.
[f'tC. 2B] FIG. 28 shows a state where the forged blank with no
flash is being reduced during the conventional coining step.
[f'IC. 2C] FIG. 2C shows a time when an upper die has been moved
up during the conventional coining step.
[f'IC. 2D] FIG. 2D shows a time when the forged blank with no flash
is to be taken out during the conventional coining step.
[f'IC. 3A] FIG. SAis a perspective view showing the shape of an arm
of a crankshaft after processed in the coining step, the arm having a first
exemplary confi.guration.
[f'tC. 38] FIG. 38 is a front view of the arm of the crankshaft after
processed in the coining step, the arm having the first exemplary
configuration and the front view showing the shape viewed from a journal
side.
[f'tC. 3C] FIG. 3C is a view foom a direction indicated by the dashed
ri
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arrow in FIG. 3B.
ltr'lC. 3D] FIG. 3D is a sectional view along the line IIID-IIID in FIG.
38.
[f'tG. 4A] FIG. 4Ais a perspective view showing the shape of a rough
arm of a forged blank before processed in the coining step, the rough arm
being for the arm having the first exemplary configuration.
[f'IC. 4B] FIG. 48 is a front view of the rough arm of the forged
blank before processed in the coining step, the rough arm being for the arm
having the first exemplary configuration and the front view showing the
shape viewed from a rough journal side.
[f'lC. 4C] FIG. 4C is a view from a direction indicated by the dashed
arrow in FIG. 4C.
[n'IC. 4D] FIG. 4D is a sectional view along the Iine IVD-IVD in FIG.
48.
[f'tC. 5A] FIG. 5A is a front view of an arm of a crankshaft after
processed in the coining step, the ârm having a second exemplary
configuration and the front view showing the shape viewed from a pin side.
[fIC. 58] FIG. 5B is a sectional view along the line VB-VB in FIG.
54.
[f'lC. 6A] FIG. 6A is a front view of a rough arm of a forged blank
before processed in the coining step, the rough arm being for the arm having
the second exemplary confi.guration and the front view showing the shape
viewed from a rough pin side.
[f'IC. 68] FIG. 6B is a sectional view along the line VIB-VIB in FIG.
64.
[f'lC. 7A] FIG. TAis a perspective view showing the shape of an arm
of a crankshaft after processed in the coining step, the arm having a third
exemplary confi.guration.
[f'lC. 7B] FIG. 78 is a front view of the arm of the crankshafb after
processed in the coining step, the arm having the thfud exemplary
confi.guration and the front view showing the shape viewed from a pin side.
[f'tG. 7C] FIG. 7C is a view from a direction indicated by the dashed
arrovr/ in FIG. 78.
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[f'tC. zO] mC. 7D is a sectional view along the line VIID-VIID in
FIG. 78.
[f'lC. 8A] FIG. 8A is a front view of a rough arm of a forged blank
before processed in the coining step, the rough arm being for the arm having
the third exemplary configuration, the front view showing the shape viewed
from a rough pin side.
[¡'lC. 8B] FIG. 8B is a view from a direction indicated by the dashed
arrovi¡ in FIG. 84.
[f'lC. SC] FIG. 8C is a sectional view along the line VIIIC-VIIIC in
FIG.88.
[f'fG. 9] FIG. 9 is a sectional view schematically showing an
exemplary con-figuration of a forged crankshaft manufacturing apparatus.
[f'tC. 104] FIG. 10Ais a sectional view showing, in a coining step by
use of the forged crankshaft manufacturing apparatus, a time when a
forged blank has been set in the manufacturing apparatus.
[f'lC. 108] FIG. 108 is a sectional view showing, in the coining step
by use of the forged crankshaft manufacturing apparatus, a state where a
knock-out member is in a retracting position.
[f'IC. 10C] FIG. 10C is a sectional view showing, in the coining step
by use of the forged crankshaft manufacturing apparatus, a state where
second elastic members are connected to holders.
[fIC. 10D] FIG. 10D is a sectional view showing, in the coining step
by use of the forged crankshaft manufacturing apparatus, a time when the
second die has reached the bottom dead point.
[f'IC. 10E] FIG. 10E is a sectional view showing, in the coining step
by use of the forged crankshaft manufacturing apparatus, a state where
thfud dies are separated from each other.
[f'IC. 10F] FIG. 10F is a sectional view showing, in the coining step
by use of the forged crankshaft manufacturing apparatus, a time when the
second die has reached the top dead point.
[FIG. 10G] FIG. 10G is a sectional view showing, in the coining step
by use of the forged crankshaft manufacturing apparatus, a state where the
knock-out member is in an upper position.
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DESCRIPTION OF EMBODIMENTS
loosol
A forged crankshaft manufacturing apparatus according to an
embodiment of the present invention is to process a forged blank with no
flash during a process of manufacturing a forged crankshaft. The forged
crankshaft includes journals serving as an axis of rotation, pins decentered
from the journals, and crank arms connecting the journals and the pins.
The forged blank includes rough journals, rough pins and rough crank arms
corresponding to the journals, the pins, and the crank arms, respectively, of
the forged crankshaft. At least one of the rough crank arms includes an
excess portion protruding from the outer periphery of a side portion thereof.
The manufacturing apparatus includes a first die and a second die paired
with each other, a retaining device, and a moving device. The first die and
the second die are to bend or crash the excess portion. The retaining
device is to retain at least one of the rough journals or at least one of the
rough pins of the forged blank such that a rough pin decentering direction
in which the rough pins are decentered from the rough journals is
perpendicular to a reducing direction in which the first die and the second
die apply force for reduction. The moving device is to support the retaining
device such that the retaining device is movable along the reducing
direction.
looszl
The moving device preferably moves the retaining device such that
the forged blank is positioned in the center between the first die and the
second die while contacting both the first die and the second die.
loossl
In the manufacturing apparatus, the retaining device preferably
includes a third pair of dies, and a holder. In this case, the third pair of
dies supports the rough journals or the rough pins by nipping the rough
journals or the rough pins from both sides. The holder holds the third pair
of dies such that the third dies are movable a\l¡ay from and toward each
other. The moving device includes a first elastic member that is
t\?
stretchable in the reducing direction. The fi.rst elastic member connects
the first die to the holder.
[oosg]
It is preferred that the manufacturing apparatus further includes a
second elastic member that is stretchable in the reducing direction. In this
case, the second elastic member is configured to connect and disconnect the
second die to and from the holder. Further, the manufacturing apparatus
preferably applies coning to the forged blank.
loo¿ol
A forged crankshaft manufacturing method according to an
embodiment of the present invention is a method for manufacturing a
forged crankshafi including journals serving â.s an axis of rotation, pins
decentered from the journals, and crank arms connecting the journals and
the pins. The manufacturing method includes a first step and a second
step. By the first step, a forged blank with no flash is obtained. The
forged blank includes rough journals, rough pins and rough crank arms
corresponding to the journals, the pins and the crank arms, respectively of
the forged crankshaft. At least one of the rough crank arms includes an
excess portion protruding from the outer periphery of a side portion thereof.
In the second step, the excess portion of the forged blank with no flash is
bent or crashed. The above manufacturing apparatus is used in the second
step. The excess portion of the rough crank arm is deformed in the second
step, whereby the rough crank arm is shaped into a crank arm with a thick
side portion.
loo¿rl
In the manufacturing method, the excess portion may be a first
excess portion protruding from the outer periphery of a side portion in a
region near an adjacent rough pin. In this case, the first excess portion of
the rough crank arm is deformed in the second step, whereby the rough
crank arm is shaped into a crank arm with a thick side portion in the region
near the adjacent pin.
Íoo+21
In the manufacturing method, the excess portion may be a second
(5
excess portion protruding from the outer periphery of a side portion in a
region near an adjacent rough journal. In this case, the second excess
portion of the rough crank arm is deformed in the second step, whereby the
rough crank arm is shaped into a crank arm with a thick side portion in the
region near the adjacent journal.
loo+sl
In the above-described manufacturing method, preferably, coining is
applied to the forged blank in the second step.
loo¿¿l
A case where the forged crankshaft manufacturing apparatus and
the forged crankshaft manufacturing method according to the present
invention are adopted in a coining step wiII hereinafter be described with
reference to the drawings.
loo¿sl
1. Shape of Crankshafb
A forged crankshafb according to the present embodiment includes
journals serving as an axis of rotation, pins decentered from the journals,
and crank arms connecting the pins and the journals. The forged
crankshaft may include an arm having a first exemplary configuration as
shown in FIGS. 3A to 3D. The forged crankshaft may include an arm
having a second exemplary configuration as shown in FIGS. 5A and 58, or
may include an arm having a third exemplary configuration as shown in
FIGS.7[to7D.
loo¿ol
FIGS. 3A to 3D are diagrams showing the shape of an arm of a
crankshaft after processed in the coining step, the arm having a first
exemplary confi.guration according to the present invention. FIG. 3A is a
perspective view, FIG. 38 is a front view from the journal side, FIG. 3C is a
side view, and FIG. 3D is a sectional view along the line IIID-IIID in FIG.
38. In FIGS. 3A to 3D, an arm (with a weight) of the crankshaft is
representatively shown, and the other arms are omitted. FIG. 3C is a view
from the direction indicated by the dashed arrorn/ in FIG. 38.
[oo+À
IL
v
The arm A having the first exemplary confi.guration, as shown in
FIGS. 3A to 3D, has a recess in the journal J-facing surface, in a region near
a pin P adjacent thereto, in an area As inside of both side portions Aa and
Ab. The side portions Aa and Ab in the region near the adjacent pin P
bulge toward the journal J. The thicknesses of the side portions Aa andAb
are greater than the thickness of the recess in the inner area As.
loo¿sl
In the fi.rst exemplary configuration, the arm A has thick side
portions Aa andAb in the region near the adjacent pin P, and has a recess in
the journal J-facing surface. According to the present embodiment, the
recess made in the arm A leads to a weight reduction of the forged
crankshaft. Besid.es, the thick side portions Aa and Ab of the arm A ensure
stiffness.
loo+gl
In the arm A having the first exemplary configuration, both side
portions Aa and Ab in the region near the adjacent pin P are thick.
However, only one side portion of the arm A in the region near the adjacent
pin P may be thick. Even in this case, the thick portion of the armAin the
region near the adjacent pin P ensures the armAstiffness.
loosol
As shown in FIGS. 3A to 3D, a case where the arm having the first
exemplary configuration is an arm with a weight has been described. AII
of the arms of the crankshaft may have the first exemplary configuration.
At least one of the arms of the crankshafb may have the first exemplary
configuration. There is no limit to the shapes of the other arms than the
arms having the first exemplary configuration. For example, the other
arms than the arms having the first exemplary configuration may have a
weight or alternatively may have no weight. The other arms than the
arms having the first exemplary configuration may have a second
exemplary confi.guration and/or a third exemplary configuration, which will
be described below.
loosrl
FIGS. 4A to 4D arc diagrams showing the shape of a rough arm of
l?
the forged blank with no flash before processed in the coining step, the
rough arm being for the arm having the fi.rst exemplary configuration
according to the present invention. FIG. 4A is a perspective view, FIG. 48
is a front view from the rough journal side, FIG. 4C is a side view, and FIG.
4D is a sectional view along the line IVD-IVD in FIG. 48. In FIGS. 4A to
4D, a rough arm (with a rough weight) of the forged blank with no flash is
representatively shown, and the other rough arms are omitted. FIG. 4C is
a view from the direction indicated by the dashed arro'ev in FIG. 48.
loorzl
The rough arm A' before processed in the coining step, as shown in
FIGS. 4|to 4D, has the same surface shape as the finished product after
processed in the coining step, in the rough-journal J'-facing surface, in a
region near a rough pin P' adjacent thereto, in an area As inside of both side
portions Aa' and Ab'. The surface shape extends smoothly to the side
portions Aa' and Ab' in the region near the adjacent rough pin P'.
Accordingly, the thicknesses of the side portions Aa' and Ab' are smaller
than the thicknesses of the side portions of the finished product after
processed in the coining step.
loorsl
The rough arm A' has excess portions Aaa and Aba protruding from
the outer peripheries of the side portions Aa' and Ab' in the region near the
adjacent rough pin P'. Such ân excess portion provided to a rough arm and
protruding from the outer periphery of a side portion of the rough arm in a
region near a rough pin P' adjacent to the rough arm will hereinafber be
referred to as a fi.rst excess portion. The first excess portions Aaa and Aba
are plate-shaped, and are disposed along the outer periphery of the side
portion Aa' and the outer periphery of the side portion Ab', respectively, in
the region near the adjacent rough pin P'. The thicknesses of the first
excess portions Aaa and Aba are comparable to or less than the thicknesses
of the side portionsAa'andAb'which are the bases thereof.
loor¿l
In the forged blank with no fl.ash, every one of the rough arms A'
may have the first excess portions Aaa and Aba, or at least one of the rough
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arms A' may have the first excess portions Aaa and Aba. In the first
exemplary configuration, the rough arm A' has two first excess portions Aaa
and Aba. However, the rough arm A' may have only one first excess
portion. In this case, in the finished crankshafb, the arm has one thick side
portion.
looml
The rough arm shown in FIGS. 4Ato 4D for the arm having the first
exemplary configuration is a rough arm with a rough weight. All of the
rough ârms of the forged blank may have the first exemplary confi.guration.
At least one of the rough arms of the forged blank may have the first
exemplary configuration. There is no limit to the shapes of the other rough
arms than the rough arms for the arms having the first exemplary
configuration. For example, the other rough arms than the rough arms for
the arms having the first exemplary configuration may have a rough weight
or alternatively may have no rough weight. The side portions of the other
rough arms than the rough arms for the arms having the first exemplary
confi.guration need not be thickened. The other rough arms than the rough
arms for the arms having the first exemplary confi.guration may have a
second exemplary configuration and/or a third exemplary confi.guration,
which will be described below. Thus, the shape of the forged blank with no
flash is determined according to the shape of the crankshafb.
loosal
In the above-described first exemplary configuration, the excess
portions protrude from the outer peripheries of the side portions of the
rough arm A' in the region near the adjacent rough pin P'. However, the
excess portions may protrude from the outer peripheries of the side portions
in a region near a rough journal J' adjacent thereto. In this case, in the
finished crankshaft, the arm has thick sid.e portions in a region near a
journal adjacent thereto. Such an excess portion provided to a rough arm
and protruding from the outer periphery of a side portion of the rough arm
in a region near a rough journal J' adjacent to the rough arm will
hereinafber be referred to as a second excess portion.
loorzl
lq
v
FIGS. 5A and 5B are diagrams showing an arm of a crankshaft after
processed in the coining step, the arm having à second exemplary
configuration according to the present invention. FIG. 5A is a front view
from the pin side, and FIG. 5B is a sectional view along the line VB-VB in
FIG. 54. In the second exemplary confi.guration, the crankshaft includes a
plurality of arms, and at least one of the arms has no weight integrated
therewith. In FIGS. 5A and 58, an arm with no weight of the crankshaft is
representatively shown, and the other arms of the crankshaft are not
shown.
loorsl
In the second exemplary configuration, as in the first exemplary
con-figuration, the arm A has thick side portions in the region near the
adjacent pin P and has a recess in the journal J-facing surface, though it is
not shown in the drawings. The arm A having the second exemplary
configuration further has another recess in the pin P-facing surface, in a
region near a journal J adjacent thereto, in an area At inside ofboth side
portions Ac and Ad. The side portions Ac and Ad in the region near the
adjacent journal J bulge toward the adjacent pin P. The thicknesses of the
side portions Ac and Ad are greater than the thickness of the recess in the
areaAt.
loo¡gl
The armAhaving the second exemplary confi.guration has thick side
portions in the region near the adjacent pin P and has a recess in the
journal J'facing surface. Further, the arm A has thick side portions Ac and
Ad in the region near the adjacent journal J and has another recess in the
pin P-facing surface. In the second exemplary confi.guration, the recesses
formed in the journal J-facing surface and the pin P'facing surface of the
armAlead to a further weight reduction of the forged crankshaft. Besides,
the thick side portions in the region near the adjacent pin P and the thick
side portions Ac and Ad in the region near the journal J ensure the arm A
stiffness.
looaol
9o
In the second exemplary configuration, both side portions of the arm
A in the region near the adjacent pin P are thick, and both side portions Ac
and Ad of the arm A in the region near the adjacent journal J are thick.
However, only one side portion of the arm A in the region near the adjacent
pin P may be thick, and only one side portion of the arm Ain the region near
the adjacent journal J may be thick. Also, not all of the arms A with no
weights need to have thick side portions in the region near the adjacent pin
P and in the region near the adjacent journal J.
looarl
All of the arms with no weights may have the second exemplary
configuration. At least one of the arms with no weights may have the
second exemplary configuration. The arms with no weights do not need to
have the second exemplary configuration. For example, when the arms
with weights have the first exemplary configuration or the third exemplary
configuration, the arms with no weights do not need to have thick side
portions.
looozl
FIGS. 6A and 6B are diagrams showing the shape of a rough arm of
a forged blank before processed in the coining step, the rough arm being for
the arm having the second exemplary configuration according to the present
invention. FIG. 6Ais a front view from the rough pin side, and FIG. 6B is a
sectional view along the line VIB-VIB in FIG. 64. In FIGS. 6A and 68, a
rough arm with no rough weight is representatively shown, and the other
arms are not shown.
loooel
As in the first exemplary configuration, the rough arm A' before
processed in the coining step has the same surface shape as the finished
product afber processed in the coining step, in the rough'journal J'-facing
surface, in a region near a rough pin P' adjacent thereto, in an area inside of
both side portions Aa' and Ab'. Further, as in the first exemplary
configuration, the rough arm A' has first excess portions Aaa and Aba
protruding from the outer peripheries of the side portions Aa' and Ab' in the
region near the adjacent rough pin P'.
Ìi
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looa¿l
Unlike in the fi.rst exemplary configuration, the rough arm A'before
processed in the coining step, as shown in FIGS. 6A and 68, has the same
surface shape as the finished product after processed in the coining step, in
the rough-pin P'-facing surface, in a region near a rough journal J' adjacent
thereto, in an area At inside of both side portions Ac' and Ad'. The surface
shape extends smoothly to the side portions Ac' and Ad' in the region near
the adjacent rough journal J'. Accordingly, the thicknesses of the side
portions Ac' and Ad' are smaller than the thicknesses of the side portions of
the fi.nished product after processed in the coining step.
[ooas]
The rough arm A' has second. excess portions Aca and Ada
protruding from the outer peripheries of the side portions Ac' and Ad' in the
region near the adjacent rough journal J'. The second excess portions Aca
andAda are plate-shaped, and are disposed along the outer periphery of the
side portion Ac' and the outer periphery of the side portion Ad', respectively,
in the region near the adjacent rough journal J'. The thicknesses of the
second excess portions Aca and Ada are comparable to or less than the
thicknesses of the side portions Ac' andAd' which are the bases thereof.
loooal
In the forged blank with no fLash, every one of the rough arms A'
with no rough weights may have the second excess portions Aca andAda, or
at least one of the rough arms A' with no rough weights may have the
second excess portions Aaa and Aba. In the second exemplary
configuration, the rough arm A' has two fi.rst excess portions Aaa and Aba
and two second excess portions Aca and Ada. However, the rough arm A'
may have only one first excess portion and only one second excess portion.
When the rough arm A'has only one second excess portion, in the finished
crankshaft, the arm has one thick side portion in the region near the
adjacent journal. Also, at least one of the rough arms with no rough
weights may have one or two first excess portions or one or two second
excess portions. Further, at least one of the rough arms with no rough
weights may have neither the first excess portions nor the second excess
9-2-
v
podions.
[oooz]
AII of the rough arms with no rough weights may have the second
exemplary configuration. At least one of the rough arms with no rough
weights may have the second exemplary configuration. The rough arms
with no rough weights do not need to have the second s¡smplary
configuration. For example, when the rough arms with rough weights
have the first exemplary configuration or the thiïd exemplary confi.guration,
none of the rough arms with no rough weights needs to have the first excess
portions or the second excess portions.
looosl
FIGS. 7A to 7D are d.iagrams showing the shape of an arm of a
crankshaft afber processed in the coining step, the arm having a third
exemplary con-figuration. FIG. 7A is a perspective view, FIG. 7B is a front
view from the pin side, FIG. 7C is a side view, and FIG. 7D is a sectional
view along the line VIID-VIID in FIG. 78. In FIGS. TAto 7D, an arm (with
a weight) of the crankshaft is representatively shown, and the other ârms
are not shown. FIG. 7C is a view from the direction indicated by the
dashed arro\M in FIG. 78.
looegl
As in the first exemplary configuration, the arm having the third
exemplary configuration has thick side portions in a region near a pin P
adjacent thereto and has a recess in the journal J-facing surface. In the
third exemplary configuration, the arm A, which has a weight W integrated
therewith, has thick side portions Ac and Ad in a region near a journal J
adjacent thereto, and has another recess in the pin P-facing surface, in the
region near the adjacent journal J, in an area At inside of both side portions
Ac and Ad.
loozol
In the third exemplary configuration, the recesses formed in the
journal J-facing surface and the pin P-facing surface of the arm A lead to a
further weight reduction of the forged crankshaft. Besides, the thick side
portions Aa and Ab in the region near the adjacent pin P and the thick side
F.
F
Ë:,
!-9
portions Ac and Ad in the region near the journal J ensure the arm A
stiffness.
loozrl
In the third exemplary configuration, both side portions of the arm A
in the region near the adjacent pin P are thick, and both side portions Ac
and Ad of the arm A in the region near the adjacent journal J are thick.
However, only one side portion of the arm A in the region near the adjacent
pin P may be thick, and only one side portion of the arm A in the region near
the adjacent journal J may be thick.
[ootz]
All of the arms of the
configuration. At least one
exemplary con-fi guration.
[oozg]
FIGS. 8A to 8C are diagrams showing the shape of a rough arm of a
forged blank with no flash before processed in the coining step, the rough
arm being for the arm having the third exemplary configuration. FIG. 8A
is a front view from the rough pin side, FIG. 88 is a side view, and FIG. 8C
is a sectional view along the line VIIIC'VIIIC in FIG. 84. In FIGS. 8A to
8C, a rough arm (with a rough weight) of the forged blank with no flash is
representatively shown, and the other rough arms are not shown. FIG. 8B
is a view from the direction indicated by the dashed arrolv in FIG. 84.
[ooz+]
In the third exemplary configuration, the rough arm A' before
processed in the coining step, as in the first exemplary configuration, has
the same surface shape as the finished product after processed in the
coining step, in the rough-journal J''facing surface, in a region near a rough
pin P' adjacent thereto, in an area As inside of both side portions Aa'- and Ab'.
Further, as in the first exemplary confi.guration, the rough arm A'has first
excess portions Aaa and Aba protruding from the outer peripheries of the
side portions Aa' andAb' in the region near the adjacent rough pin P'.
[oozs]
In the forged blank with no flash before processed in the coining step,
crankshaft may have the third exemplary
of the crankshaft may have the thiïd
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the arm A', which has a rough weight W' integrated therewith, has the same
surface shape as the finished product after processed in the coining step, in
the rough-pin P''facing surface, in a region near a rough journal J' adjacent
thereto, in an area At inside of both side portions Ac' and Ad'. The surface
shape extends smoothly to the side portions Ac' and Ad' in the region near
the adjacent rough journal J'. Also, the rough arm A' with the rough
weight W'' integrated therewith has second excess portions Aca and Ada
disposed in the side portions Ac' and Ad', respectively, in the region near the
adjacent rough journal J'. The second excess portions Aca and Ada
protrude from the outer peripheries of the side portions Ac' and Ad' in the
region near the adjacent roughjournal J'.
loozol
In the forged blank with no fLash, every one of the rough arms A'
with rough weights may have the first excess portions Aaa and Aba and the
second excess portions Aca and Ada, or at least one of the rough arms A'
with rough weights may have the first excess portions Aaa and Aba and the
second excess portions Aca and Ada. In the thfud exemplary configuration,
the rough arm A'with a rough weight has two first excess portions Aaa and
Aba and two second excess portions Aca and Ada. However, the rough arm
A'with a rough weight may have only one first excess portion and only one
second excess portion.
loottl
AII of the rough arms of the forged blank may have the third
exemplary confi.guration. At least one of the rough arms may have the
thfud exemplary configuration. There is no limit to the shapes of the other
rough arms than the rough arms for the arms having the third exemplary
confi.guration. The shape of the forged blank with no flash is determined
according to the shape of the crankshaft.
loozsl
Some examples of rough arms of a forged blank with no flash to be
processed by the manufacturing apparatus according to the present
embodiment have been described in connection with the fi.rst to the thfud
exemplary confi.gurations. The rough arms of the forged blank to be
l;
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25
f,
i:
processed by the manufacturing apparatus according to the present
embodiment do not need to have the fi.rst to the third exemplary
configurations. In short, the forged blank with no flash has a shape that
causes the forged blank with no flash to be put into an unstable posture
when the forged blank with no flash is placed on the lower die. In other
words, the forged blank with no flash to be processed by the manufacturing
apparatus according to the present embodiment includes at least one rough
arm having at least one first excess portion or at least one second excess
portion.
loozgl
2. Forged Crankshafb Manufacturing Apparatus
FIG. 9 is a sectional view of a forged crankshaft manufacturing
apparatus having an exemplary configuration according to the present
invention. The manufacturing apparatus 10 shown in FIG. 9 includes a
first die 20, a second die 30, a retaining device 50, a moving device 60 and a
knock-out member 15. The following description is of a case where the
manufacturing apparatus is used in a coining step.
loosol
The first die 20, which is a lower die, and the second die 30, which is
an upper die, shown in FIG. 9 are paired with each other, and apply coining
to a forged blank with no fl.ash. The first die 20 and the second die 30 also
apply bending or crashing to the protruding excess portions. To this end,
the first die 20 and the second die 30 have impressions. The impressions
refLect the shape of the crankshaft except some parts of the crankshaft.
loosrl
Specifically, when a recess is to be formed in the journal-facing
surface of an arm (see FIGS. 3A to 3D), the impressions do not reflect the
recess to be formed in the journal-facing surface of the arm. When a recess
is to be formed in the pin'facing surface of an arm (see FIGS. 54, 5B and
FIGS. 7A to 7D), the impressions do not refl.ect the recess to be formed in
the pin-facing surface of the arm. If the impressions reflect the shapes of
these recesses, some parts of the impressions will have a reverse draft.
looazl
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In order to receive third dies 53, the first die 20 and the second die
30 have open spaces 20a and 30a, respectively. The open spaces 20a and
30a are wide open along the pin decentering direction. The first lower die
20 is wide open downward to receive the knock-out member 15.
loossl
The retaining device 50 retains at least one of the rough journals or
at least one of the rough pins of the forged blank with no flash. When the
forged blank with no fl.ash is retained by the retaining der¡ice 50, the rough
pin decentering direction in which the rough pins are decentered from the
rough journals is perpendicular to the reducing direction (up-down direction
in FIG. 9) in which the first die 20 and the second die 30 apply force for
reduction.
loos¿l
The retaining device 50 shown in FIG. 9 includes third dies 53 and
holders 51. The third dies 53 form a pair of dies. The third dies 53 nip a
rough journal or a rough pin to be retained from both sides. The holders 51
hold the third dies 53 such that the third dies 53 are movable away from
and toward each other in the direction perpendicular to the reducing
direction, that is, movable in the direction indicated by the hatched arrow in
FIG. 9. The movements of the thfud dies 53 can be achieved, for example,
by use of hydraulic cylinders 52.
looesl
The moving device 60 supports the retaining device 50 such that the
retaining device 50 is movable in the reducing direction. The moving
device 60 shown in FIG. 9 includes first elastic members 61 and second
elastic members 62. The first elastic members 61 connect the first die 20
and the holders 51. Specifically, each of the first elastic members 61 has a
first end connected to the first die 20 and a second end connected to one of
the holders 51. The first elastic members 61 are stretchable in the
reducing direction. As the first elastic members 61, for example, coil
springs, air cylinders and the like can be used. In the present embodiment,
the fi.rst elastic members 61 are directly connected to the first die 20.
However, the first elastic members 61 may be connected to any other
2-k
iì-'
/
component, such as a bed (not shown) for the manufacturing apparatus,
supporting the first die 20.
looael
Each of the second elastic members 62 has a fi.rst end connected to
the second die 30 and a second end that can be connected to one of the
holders 51 by contact therewith. The second elastic members 62 are
configured to connect and disconnect the second die 30 to and from the
holders 51. Specifically, the second ends of the second elastic members 62
come into contact with the holders 51 and thereby connect with the holders
51, and the second ends of the second elastic members 62 move away from
the holders 51 and thereby separate from the holders 51. The second
elastic members 62 are stretchable in the reducing direction. As the
second elastic members 62, for example, coil springs, air cylinders and the
like can be used. In the present embodiment, the second elastic members
62 are directly connected to the second die 30. However, the second elastic
members 62 may be connected to any other component, such as a ram (not
shown) for the manufacturing apparatus, supporting the second die 30. In
sum, it is only necessary that the retaining device 50 should be supported to
be movable together with the second die 30.
looszl
In a state where the second elastic members 62 connect the second
die 30 and the holders 51, the moving device 60 operates such that the
amount of expansion or contraction of the first elastic members 61
accompanying a movement of the second die 30 in the reducing direction
becomes equal to the amount of expansion or contraction of the second
elastic members 62. Thereby, the retaining device 50 is moved such that
the forged blank with no fl.ash is positioned in the center between the first
die 20 and the second die 30. On the other hand, in a state where the
second elastic members 62 keep the second die 30 away from the holders 51,
even when the second die 30 is moved in the reducing direction, the distance
between the first die 20 and the forged blank with no flash retained by the
retaining device 50 is kept constant.
loosel
È.
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2_v
F
The knock-out member 15 shown in FIG. 9 is located inside the fi.rst
die (Iower die) 20, and can be moved in the reducing direction by a lifting
device (not shown). The knock-out member 15 has a recessed portion for
receiving the forged blank with no flash. Tko or more such knock-out
members 15 are provided to support some of the rough journals and some of
the rough pins, though not all of the knock-out members 15 are shown in
the drawings. In this way, the forged blank with no flash is placed in the
manufacturing apparatus 10.
looegl
Next, an exemplary process fLow of the coining step by use of the
forged crankshaft manufacturing apparatus according to the present
embodiment is described with reference to the drawings.
loogol
FIGS. 104 to 10G are sectional views showing the exemplary
process fl.ow of the coining step by use of the forged crankshafb
manufacturing apparatus according to the present embodiment. FIG. 10A'
shows the time when a forged blank with no flash has been set in the
manufacturing apparatus. FIG. 108 shows a state where the knock-out
members are in retracting positions. FIG. 10C shows a state where the
second elastic members are connected to the holders. FIG. 10D shows a
time when the second die has reached the bottom dead point. FIG. 108
shows a state where the third dies are separate from each other. FIG. 10F
shows a time when the second die has reached the top dead point. FIG.
10G shows a state where the knock-out members are in upper positions.
FIGS. 10A' to 10G show the exemplary process flow using the forged
crankshaft manufacturing apparatus shown in FIG- 9. To make the
drawings easy to understand, the excess portions of the forged blank with
no fLash 7O are not shown.
loogrl
In the exemplary process flow shown in FIGS. lOAto 10G, when the
coining step is to be executed, the second die (upper die) gO is moved to the
top dead point. Also, the knock-out members 15 are moved up, and the
thfud dies 53 are separated from each other and retracted. In this state, a
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forged blank with no flash 70, which is a workpiece, is set on the knock-out
members 15 by a carry-in robot arm 13 (see FIG. 10Ð.
loogzl
Next, the third dies 53 are moved toward each other, and the rough
journals and/or the rough pins of the forged blank with no flash 7O arc
nipped by the third pair of dies 53 from both sides. Then, while the forged
blank with no flash 70 is held by the third pair of dies 53, the knock-out
members 15 are retracted downward (see FIG. 108).
loogel
After the knock-out members 15 are retracted downward, reduction
of the forged blank with no flash 70 by use of the first die 20 and the second
die 30 is started. In the exemplary process fl.ow shown in FIGS. 104 to
10G, the second die (upper die) gO is moved down. Before the downward
movement of the second die 30, the second die 30 is sufficiently distant from
the first die 20 and is separate from the holders 51. Therefore, none of the
holders 51, the thfud dies 53 and the forged blank with no flash 70 moves,
and the distances from these components to the first die 20 are kept
constant. When the distance between the first die 20 and the holders 51
becomes equal to the distance between the second die 30 and the holders 51
as the second die 30 is moving down, the lower ends of the second elastic
members 62 come into contact with the holders 51. Then, the second die 30
is connected to the holders 51 by the second elastic members 62 (see FIG.
10c).
loog¿l
'When the second die 30 is moved further down while the second die
30 is connected to the holders 51 by the second elastic members 62, the first
elastic members 61 and the second elastic members 62 arc contracted. The
amount of contraction of the first elastic members 61 and the amount of
contraction of the second elastic members 62 along with the downward
movement of the second die 30 are controlled to be equal to each other.
Thereby, the distance between the first die 20 and the holders 51 is kept
equal to the distance between the second die 30 and the holders 51. Thus,
the holders 51, the third dies 53 and the forged blank with no flash 70 are
!o
positioned in the center between the first die 20 and the second die 30 at aII
times.
loogrl
Meanwhile, along with the downward movement of the second die
30, the forged blank with no flash 70 come into contact with both the first
die 20 and the second die 30 and thereby is reduced. Then, the forged
blank with no flash 70 undergoes coining. The forged blank with no flash
70 includes excess portions (not shown), and the excess portions are bent or
crashed.
loogol
The second die 30 reaches the bottom dead point as shown in FIG.
10D. At the time, the third dies 53 are moved away from each other (see
FIG. 108). Thereby, the retaining device 50 stops retaining the forged
blank with no flash 70. Meanwhile, the forged blank with no flash 70 is
kept reduced by the first die 20 and the second die 30. In the present
embodiment, when the second die 30 reaches the bottom dead point, the
third dies 53 are moved a\May from each other. However, the third dies 53
may be moved away from each other after the second die 30 starts moving
upward after having reached the bottom dead point.
loogzl
Next, as shown in FIG. 10F, the second die 30 is moved to the top
dead point. At the time, the forged blank with no fl.ash 70 stays on the first
die 20 without moving up. While the second die 30 is connected to the
holders 51by the second elastic members 62,tlne holders 51 are moved up to
be positioned in the center between the first die 20 and the second die 30.
Thereafter, the second die 30 is disconnected from the holders 51. Then,
the holders 51 no longer move up, and stay in the same position.
loogsl
When the second die 30 reaches the top dead point, the knock'out
members 51 are moved up. Thereby, the processed forged blank 71 is
released from the first die 20. Then, the rough pins and/or the rough
journals of the processed forged blank '7L are supported on the recessed
portions of the knock-out members 15. The processed forged blank 71
3t
moves up together with the knock-out members 15. Next, a take-out robot
arm 14 takes out the processed forged blank 17 (see FIG. 10G).
looggl
As described above, the forged crankshaft manufacturing apparatus
according to the present embodiment includes a retaining device 50.
Therefore, the forged crankshaft manufacturing apparatus can keep a
forged blank with no flash 70 in a specified posture even when the forged
blank 70 has excess portions. The forged crankshaft manufacturing
apparatus further includes a moving device 60, and the forged blank with
no fLash 70 can be reduced by the first die 20 and the second die 30 while
being kept in the specifi.ed posture. Thus, the forged crankshaft
manufacturing apparatus can certainly bend or crash the excess portions of
the forged blank while applyrng coining to the forged blank. Therefore,
trouble such as twisting of the forged blank can be prevented.
lorool
In the exemplary configuration shown in FIG. 9, the manufacturing
apparatus l-0 includes second elastic members 62. However, the forged
crankshaft manufacturing apparatus according to the present embodiment
need not include the second elastic members 62. In this case, the forged
blank with no flash 70 is pressed down by the second die 30, and thereafter,
comes into contact with the first die 20, whereby the forged blank 70 is
reduced. In this process, the forged blank with no flash 70 can be kept in
the specified posture by the third dies 53, and therefore, the forged blank
with no flash 70 can certainly undergo the coining and the crashing or
bending of the excess portions.
lororl
The moving device 60, as shown in FIGS. 104 to 10G, preferably
moves the retaining device 50 such that the forged blank with no flash 70 is
positioned in the center between the fi.rst die 20 and the second die 30 while
both the first die 20 and the second die 30 are in contact with the forged
blank with no flash 70. This is because uniform reduction of the forged
blank with no flash 70 by the first die 20 and the second die 30 allows an
improvement of the processing accuracy.
i,
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32-
lorozl
As shown in FIG. 9, the retaining device 50 may include a pair of
third dies 53, and holders 51. The moving device 60 may include first
elastic members 61. The pair of third dies 53 may support all of the rough
journals and the rough pins of the forged blank with no flash. As long as
the forged blank with no flash is retained such that the rough pin
decentering direction is perpendicular to the reducing direction, not all of
the rough journals and the rough pins need to be supported. For example,
the third dies 53 may support only the rough journals of the forged blank
with no flash. Alternatively, the third dies 53 mây support only the rough
pins of the forged blank with no flash. The third dies 53 may support only
some of the rough journals, or the third dies 53 may support only some of
the rough pins. The third dies 53 may support some of the rough journals
and some of the rough pins. In sum, there is no limit to the number of
rough journals and rough pins to be supported by the third dies 53 as long
as the support provided by the third dies 53 can control the posture ofthe
forged blank with no flash.
lorosl
'When the forged blank with no flash 70 is moved to the center
between the first die 20 and the second die 30 by the moving device 60, the
moving device 60 may further include second elastic members 62. In this
case, the second elastic members 62 can connect and disconnect the second
die 30 to and from the holders 51. The second. elastic members 62 arc
stretchable in the reducing direction. In the exemplary configuration
shown in FIG. 9, one end of each of the second elastic members 62 is
contactable with one of the holders 51. The manufacturing apparatus
according to the present embodiment may have any other configuration.
For example, each of the second elastic members 62 may have one end
connected to one of the holders 51, and another end contactable with the
second die 30.
[oro¿]
As the moving device 60, stretchable hydraulic cylinders may be
used rather than the first and the second elastic members. In this case,
33
each of the hydraulic cylinders has one end connected to the first die or the
second die, and another end connected to one of the holders 51. By
adjusting the lengths of the hydraulic cylinders with a downward movement
of the second die, the moving device 60 can place the forged blank with no
flash 70 in the center between the first die 20 and the second die 30.
lorosl
The manufacturing apparatus according to the present embodiment
is used to manufacture a forged crankshaft including arms having any of
the first to the thfud exemplary configurations.
[oroa]
The forged crankshaft manufacturing apparatus according to the
present embodiment may include a fourth die to come into contact with the
rough-journal-facing surface of a rough arm except the side portions in the
region near the adjacent rough pin. The fourth die is to retain the surface
shape which the fourth die contacts. The forged crankshaft manufacturing
apparatus may further include a fifth die to come into contact with the
rough-pin-facing surface of a rough arm with no rough weight except the
side portions in the region near the adjacent rough journal. The fifth die is
to retain the surface shape which the fourth die contacts. The forged
crankshaft manufacturing apparatus may furthermore include a sixth die
to come into contact with the rough'pin-facing surface of a rough arm with a
rough weight except the side portions in the region near the adjacent rough
journal. The sixth die is to retain the surface shape which the fourth die
contacts.
lorozl
In the above paragraphs, a case in which the manufacturing
apparatus according to the present embodiment is used in the coining step
has been described. However, the manufacturing apparatus according to
the present embodiment can be used in any other step than the coining step.
For example, when another processing step is added before the coining step,
the manufacturing apparatus accorúing to the present embodiment may be
used in the processing step. In sum, the manufacturing apparatus
according to the present embodiment is used to process the excess portions
3+
v
of a forged blank with no flash.
lorosl
3. Forged Crankshaft Manufacturing Method
According to the present embodiment, a method for manufacturing a
forged crankshaft includes a first step and a second step. The first step
and the second step are hot working to be performed successively. By the
first step, a forged blank with no flash 70 as shown in FIGS. 4A to 4D is
obtained. The forged blank with no flash 70 has almost the same shape as
the forged crankshaft. Specifically, the forged blank with no flash 70
includes rough journals J', rough pins P' and rough arms A'. At least one of
the rough arms A' of the forged blank with no flash 70 has first excess
portions Aaa and Aba protruding from the outer peripheries of side portions
Aa' and Ab' in a region near a rough pin P' adjacent thereto.
[orog]
The fi.rst step to obtain such a forged blank with no flash can be
executed, for example, by executing a preforming step, a die forging step
and a trimming step in this order, as in a conventional method for
manufacturing a common forged crankshaft. 'When adjustment of the
placement angles of the rough pins is necessary, a twisting step is added
after the trimming step.
[orro]
In the second step, the forged blank with no flash obtained by the
first step undergoes bending or crashing of the first excess portions. In
this step, the above-described forged crankshafb manufacturing apparatus
according to the present embodiment is used. In the bending or crashing of
the first excess portions, the first excess portions Aaa and Aba of the rough
crank arm are deformed, whereby the rough rank arm is shaped into an
arm A with thick side portions Aa and Ab in the region near the adjacent pin
P. Accordingly, a crankshaft having a reduced weight and assured stiffiness
as shown in FIGS. SAto 3D can be obtained.
lorrrl
In the forged crankshaft manufacturing method according to the
present embodiment, bending or crashing of the excess portions is
3Y
performed stably by use of the above-described manufacturing apparatus
according to the present embodiment. Therefore, it is possible to prevent
trouble, such as twisting, in the manufactured forged crankshafb.
lorrzl
The manufacturing method according to the present embodiment is
applicable for manufacturing a forged crankshaft including arms having the
second exemplary confi.guration shown in FIGS. 5A and 58. The forged
crankshaft includes arms Awith no weights and arms with weights.
lorrsl
In this case, what is obtained by the first step is a forged blank with
no flash including a rough arm A'with no rough weight, and the rough arm
A' with no rough weight additionally has second excess portions Aca and
Ada as shown in FIGS. 6A and 68. The second excess portions Aca and
Ada are disposed on the outer peripheries of both side portions of the rough
arm A' with no rough weight in a region near a rough journal J' adjacent
thereto. The second excess portions Aca and Ada protrude from the outer
peripheries of both side portions of the rough arm A' with no rough weight
in the region near the adjacent rough journal J'.
lorr¿l
In the second step, while the first excess portions Aaa and Aba are
being processed, the second excess portions Aca and Ada are also bent or
crashed. Thereby, the second excess portions Aca and Ada of the rough
arm A' with no rough weight are deformed. Consequently, in the
crankshaft, the arm A with no weight has thick side portions Ac and Ad in
the region near the adjacent journal J. Accordingly a crankshaft with a
rnore reduced weight and assured stiffness as shown in FIGS. 5A and 58
can be obtained.
lorrsl
The manufacturing method according to the present embodiment is
applicable for manufacturing a forged crankshaft including an arm having
the third exemplary configuration as shown in FIGS. 7A to 7D. In the
forged crankshaft, the arm, which has a weight integrated therewith, has a
recess in the pin P-facing surface, in a region near a journal J adjacent
3ç
li
:
thereto, in an area At inside of both side portions Ac and Ad.
[orra]
In this case, what is obtained by the first step is a forged blank with
no flash including a rough arm A'with a rough weight, and the rough arm
A' with a rough weight has second excess portions Aca and Ada in addition
to the fi.rst excess portions Aaa and Aba. The second excess portions Aca
and Ada are disposed on the outer peripheries of both side portions of the
rough arm A' with a rough weight in a region near a rough journal J'
adjacent thereto. The second excess portions Aca and Ada protrude from
the outer peripheries of both side portions of the rough arm A' with a rough
weight in the region near the adjacent rough journal J'.

We claim:
1. A manufacturing apparatus for processing a forged blank ivith no
flash in a process of manufacturing a forged crankshaft including journals
serving as an axis ofrotation, pins decentered from the journals, and crank
arms connecting the journals and the pins, rilherein:
the forged blank includes rough journals, rough pins and rough
crank arms corresponding to the journals, the pins and the crank arms,
respectively, of the forged crankshafti and
at least one of the rough crank arms includes an excess portion
protruding from an outer periphery of a side portion thereofi
the manufacturing apparatus comprising:
a first die and a second die paired with each other, the first die and
the second die configured to bend or crash the excess portioni
a retaining device configured to retain at least one of the rough
journals or at least one of the rough pins such that a rough pin decentering
direction in which the rough pins are decentered from the rough journals is
perpendicular to a reducing direction in which the first die and the second
die apply folce for reductioni and
a moving device configured to support the retaining device such that
the retaining device is movable along the reclucing direction.
2. The manufacturing apparatus according to claim 1, wherein
the moving device configured to move the retaining device such that
the forged blank is positioned in a center between the first die and, the
second die whiLe contacting both the first die and the second die.
3. The manufacturing apparatus according to claim ! or Z,wherein:
the retaining device includes:
a thiïd pair of dies confrgured to support at least one of the rough
journals or at least one of the rough pins by nipping the rough journal or the
rouþh þin from both sidesi and
a holder holding the third pair of dies such that the dies in the third
t+o
/
pair are movable toward and away from each otheri and
the moving device includes a first elastic member stretchable in the
reducing direction, the first elastic member connecting the first die to the
holder.
4. The manufacturing apparatus according to claim 3, wherein:
the moving device further includes a second elastic member
stretchable in the reducing direction, the second elastic member configured
to connect and disconnect the second die to and foom the holder.
5. The manufacturing apparatus according to any one of claims 1 to 4,
wherein
the manufacturing apparatus is configured to apply coining to the
forged blank.
6. A manufacturing method for manufacturing a forged crankshafb
including journals serving as an axis of rotation, pins decentered from the
journals, and crank arms connecting the journals and the pins, the
manufacturing method comprises :
a first step of obtaining a forged blank with no fLash, the forged
blank including rough journals, rough pins and rough crank arms
corresponding to the journals, the pins and the crank arms, respectively, of
the forged crankshaft, at least one of the rough crank arms including an
excess portion protruding from an outer periphery of a side portion thereof;
and
a second step ofbending or crashing the excess portion ofthe rough
crank arm of the forged blank with no flash, wherein:
in the second step, the manufacturing apparatus according to any
one of claims I to 4 is used to deform the excess portion of the rough crank
arm, whereby the rough crank arm is shaped into a crank arm with a thick
side portion.
7. The forged crankshaft manufacturing method according to claim 6,
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ft
È
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/
wherein:
the excess portion includes a first excess portion
outer periphery of a side poltion of the rough cranli alrn
adjacent one ofthe rough pinsi and
in the Lecond step, the first excess portion of the
deformed, whereby the rough crank arm is shaped into
thicli side portion in a region near an adjacent pin.
protruding fi'orn an
in a legion neal an
rough cranl< arm is
a crank arm with a
8. The manufacturing method according to claim 6 or 7 , wherein:
the excess portion includes a second excess portion'protruding from
an outer periphery of a side portion of the rough crank arm in a region near
an adjacent one of the rough journalsi and
in the second step, the second excess portion ofthe rough crank arm
is deformed, whereby the rough crank arm is shaped into a crank arm with
a thick side portion in a region near an adjacent journal.
9. The forged crankshaft manufacturing method according to any one
of claims 6 to 8, wherein
in the second step, coining is applied to the forged blank.