TITLE OF INVENTION
APPARATUS FOR FORMING A BLANK FOR FINISH FORGING FOR A
FORGED CRANKSHAFT FOR A THREE-CYLINDER ENGINE AND METHOD
FOR MANUFACTURING A FORGED CRANKSHAFT FOR A THREECYLINDER
ENGINE USING THE SAME
TECHNICAL FIELD
[OOO 1)
The present invention relates to techniques for manufacturing, by hot forging,
a crankshaft (hereinafter also referred to as a "forged crankshaft") for a three-cylinder
engine. In particular, the present invention relates to an apparatus for forming, in
the process of manufacturing a forged crankshaft, a blank for finish forging to be
subjected to finish forging by which a final shape of the forged crankshaft is obtained,
and a method for manufacturing a forged crankshaft for a three-cylinder engine
including preforming steps using such forming apparatus.
BACKGROUND ART
[0002)
In engines of passenger cars, motorcycles, agricultural machines, and the like,
a crankshaft is required for taking out power by converting reciprocating motion of
pistons to rotary motion. Generally, there are two types of crankshafts: those that
are manufactured by forging and those that are manufactured by casting, and the
former forged crankshafts superior in terms of strength and stiffness are more widely
used. In recent years, in order to improve fuel economy performance and meet
emission regulations, downsizing of engine displacement becomes popular, and a
three-cylinder engine is attracting wide attention.
[0003]
In general, forged crankshafts for three-cylinder engines are manufactured by
using, as a stMing material, a billet having a circular or square cross section and
having a constant cross-sectional area along the entire length, and subjecting the
billet to the steps of preforming, die forging, trimming and coining in order. The
preforming step includes roll forming and bending, and the die forging step includes
block forging and finish forging.
[0004]
FIG. 1 is a schematic diagram illustrating a typical conventional process for
manufacturing a forged crankshaft for a three-cylinder engine. A crankshaft 1
illustrated in FIG. 1 is to be mounted in a three-cylinder engine. It is a threecylinder
four-counterweight crankshaft that includes: four journals J1 to 54; three
crank pins P1 to P3; a front part Fr; a flange F1; and six crank arms (hereinafter
referred to as "arms" to be simple) A1 to A6 that alternatively connect the journals J1
to 54 and the crank pins P1 to P3 to each other, wherein among the six arms A1 to
A6, first and second arms A1 and A2, and fifth and sixth arms A5 and A6
respectively connecting to first and third crank pins P1 and P3 at opposite ends, have
balance weights. The third and fourth arms A3 and A4 connecting with the second
crank pin P2 in the center have no balance weight, therefore having oval shapes.
Hereinafter, when the journals J1 to J4, the crank pins P1 to P3, and the arms A1 to
A6 are each collectively referred to, a reference character "J" is used for the journals,
a reference character "P" for the crank pins, and a reference character "A" for the
arms. An arm having a balance weight is also referred to as a weighted arm when
distinguished from an arm having no balance weight. On the other hand, an arm
having no balance weight is also referred to as a non-weighted arm or an oval arm.
[0005]
According to the manufacturing method shown in FIG. 1, the forged
crankshaft 1 is manufactured in the following manner. Firstly, a billet 2 shown in
FIG. l(a), which has been previously cut to a predetermined length, is heated by a
furnace and then is subjected to roll forming. In the roll forming step, the billet 2 is
rolled and reduced in cross section by grooved rolls, for example, to distribute its
volume in the longitudinal direction, whereby a rolled blank 103, which is an
intermediate material, is formed (see FIG. l(b)). In the bending step, the rolled
blank 103 obtained by the roll forming is partially pressed in a press in a direction
perpendicular to the longitudinal direction to distribute its volume, whereby a bent
blank 104, which is a secondary intermediate material, is formed (see FIG. l(c)).
[0006]
Then, in the block forging step, the bent blank 104 obtained by bending is
press forged with a pair of upper and lower dies, whereby a forged blank 105 having
a general shape of a crankshaft (forged final product) is formed (see FIG. l(d)).
Then, in the finish forging step, the block forged blank 105 obtained by the block
forging is further processed by press forging the block forged blank 105 with a pair
of upper and lower dies, whereby a forged blank 106 having a shape in agreement
with the shape of the crankshaft is formed (see FIG. l(e)). In the block forging and
the finish forging, excess material flows out as a flash from between the parting
surfaces of the dies that oppose each other. Thus, the block forged blank 105 and
the finish forged blank 106 have large flashes 105a and 106a, respectively, around
the formed shape of the crankshaft.
[0007]
In the trimming step, the finish forged blank 106 with the flash 106a, obtained
by the finish forging, is held by dies from above and below and the flash 106a is
trimmed by a cutting die. In this manner, the forged crankshaft 1 is obtained as
shown in FIG. l(f). In the coining step, principal parts of the forged crankshaft 1,
from which the flash has been removed, e.g., shaft parts such as the journals J, the
crank pins P, the front part Fr, and the flange Fl, and in some cases the arms A, are
slightly pressed with dies from above and below and formed into a desired size and
shape. Finally, the forged crankshaft 1 is manufactured.
[OOOS]
It should be noted that, when adjustment of a placement angle of the crank
pins is necessary, a step of twisting is added after the trimming step.
[0009]
With such a manufacturing method, however, it is inevitable that material
utilization decreases since large amounts of unnecessary flash, which is not a part of
the end product, are generated. Thus, in the manufacturing of a forged crankshaft,
it has been so far an important object to inhibit the generation of flash to the extent
possible and achieve improvement of material utilization. Examples of
conventional techniques that address this object are as follows.
[OO 1 O]
For example, Japanese Patent Application Publication No. 2008-1 55275
(Patent Literature 1) and Japanese Patent Application Publication No. 201 1-1 61496
(Patent Literature 2) disclosure techniques for manufacturing a crankshaft, by which
journals and crank pins are shaped and crank arms are roughly shaped. In the
technique of Patent Literature 1, a stepped round bar having reduced diameter
regions at portions to be formed into journals and crank pins of a crankshaft is a
round bar used as a blank. Then, a pair of portions to be formed into journals,
between which a portion to be formed into a crank pin is disposed, are held with dies.
In this state, opposing dies are axially moved toward each other to compressively
deform a round bar blank. Concurrently with imparting this deformation, punches
are pressed against the portion to be formed into a crank pin in a direction
perpendicular to the axial direction, whereby the portion to be formed into a crank
pin is placed into an eccentric position. This operation is repeated in succession for
all crank throws.
[OOl 11
In the technique of Patent Literature 2, a simple round bar is used as a blank.
One end of the two ends of the round bar is held with a stationary die and the other
end thereof with a movable die, and portions to be formed into journals are held with
journal dies and portions to be formed into crank pins with crank pin dies. In this
state, the movable die, the journal dies, and the crank pin dies are axially moved
toward the stationary die to compressively deform the round bar blank.
Concurrently with imparting this deformation, the crank pin dies are moved in an
eccentric direction perpendicular to the axial direction to place the portion to be
formed into the crank pin into an eccentric position.
[OO 121
With both the techniques disclosed in Patent Literatures 1 and 2, no flash will
be generated, and therefore a significant improvement in material utilization can be
expected.
CITATION LIST
PATENT LITERATURE
[0013]
Patent Literature 1 : Japanese Patent Application Publication No. 2008-1 55275
Patent Literature 2: Japanese Patent Application Publication No. 201 1-1 61496
SUMMARY OF INVENTION
TECHNICAL PROBLEM
100 141
As described above, according to the techniques disclosed in Patent
Literatures 1 and 2, a round bar blank is directly processed into a crankshaft shape.
However, forged crankshafts are required to have high strength and high stiffness,
thus blanks for the forged crankshaft are not easily deformable. As such,
crankshafts that would be practically manufacturable are inevitably limited to the
ones having arms of large thickness and crank pins with a small amount of
eccentricity, and therefore having a relatively gentle crankshaft shape. Moreover,
all the crank arms are limited to a simple shape without a balance weight, that is, an
oval arm.
[00 1 51
In addition, according to the techniques disclosed in Patent Literatures 1 and 2,
the shape of arms is formed by free expansion of a round bar blank in a direction
perpendicular to the axial direction in conjunction with its axial compressive
deformation and by tensile deformation of the round bar blank in conjunction with
the movement of portions to be formed into crank pins in an eccentric direction.
Because of this, the contour shape of the arms tends to be unstable, and thus
dimensional accuracy cannot be ensured.
[0016]
The present invention has been made in view of the above-mentioned
problems. Accordingly, in order to manufacture forged crankshafts for threecylinder
engines with high material utilization and also with high dimensional
accuracy regardless of their shapes, it is an object of the present invention to provide
an apparatus for use in forming a blank for finish forging to be subjected to finish
forging on the premise that, in the process of manufacturing the forged crankshaft,
finish forging for forming its final shape is performed. Further, it is another object
of the present invention to provide a method for manufacturing forged crankshafts
for three-cylinder engines with high material utilization and also with high
dimensional accuracy regardless of their shapes.
SOLUTION TO PROBLEM
[00 1 71
A forming apparatus according to embodiments of the present invention is an
apparatus for forming, from a preform blank, in the process of manufacturing the
forged crankshaft for a three-cylinder engine, the blank for finish forging to be
subjected to finish forging by which a final shape of the forged crankshaft is formed.
In the forged crankshaft, third and fourth crank arms connecting with a second
crank pin in a center have no balance weights, and remaining crank arms have
balance weights.
The preform blank includes:
rough journal portions having an axial length equal to an axial length of
journals of the forged crankshaft;
rough crank pin portions having an axial length equal to an axial length of
crank pins of the forged crankshaft;
third and fourth rough crank arm portions corresponding to the third and
fourth crank arms of the forged crankshaft, having an axial thickness equal to an
axial thickness of such crank arms; and
weighted rough crank arm portions corresponding to weighted crank arms
having the balance weights of the forged crankshaft, having an axial thickness
greater than an axial- thickness of such crank arms.
The apparatus for forming a blank for finish forging a forged crankshaft for a
three-cylinder engine according to the present embodiment further has the following
structures (1) or (2).
[OOl 81
(1) The rough crank pin portions in the preform blank have a smaller amount
of eccentricity in the direction perpendicular to the axial direction than an amount of
eccentricity of the crank pins of the forged crankshaft.
The forming apparatus includes a reference crank pin die, movable crank pin
dies, and stationary and movable journal dies, described below.
The reference crank pin die is disposed at a location of a second rough crank
pin portion, configured to be brought into contact with the second rough crank pin
portion, and configured to move in the direction perpendicular to the axial direction,
but be constrained from moving in the axial direction, while being in contact with
side surfaces of a third and a fourth rough crank arm portions through which the
rough crank arm portions connect with the second rough crank pin portion.
The movable crank pin dies are disposed at locations of the corresponding
first and third rough crank pin portions at opposite ends, configured to be brought
into contact with the first and third rough crank pin portions, and configured to move
axially toward the reference crank pin die and in the direction perpendicular to the
axial direction, while being in contact with side surfaces of the rough crank arm
portions through which the rough crank arm portions connect with the first and third
rough crank pin portions.
The stationary journal dies are disposed at locations of the rough journal
portions connecting with the third and fourth rough crank arm portions, configured to
hold and retain such rough journal portions therebetween in the direction
perpendicular to the axial direction, and configured to be constrained from moving
axially while being in contact with side surfaces of the third and fourth rough crank
arm portions.
The movable journal dies are disposed at locations of the corresponding rough
journal portion excluding the rough journal portions connecting with the third and
fourth rough crank arm portions, configured to hold and retain such rough journal
portions therebetween in the direction perpendicular to the axial direction, and
configured to move axially toward the reference crank pin die while being in contact
with side surfaces of the rough crank arm portions through which the rough crank
arm portions connect with such rough journal portions.
The forming apparatus is configured such that in a state that the rough journal
portions are held and retained by the stationary and movable journal dies and the
rough crank pin portions are contacted with the reference crank pin die and the
movable crank pin dies, the movable journal dies are moved axially, the movable
crank pin dies are moved axially and in the direction perpendicular to the axial
direction, and the reference crank pin die is moved in the direction perpendicular to
the axial direction, thereby compressing the weighted rough crank arm portions in
the axial direction so as to reduce the thickness thereof to the thickness of weighted
crank arms of the forged crankshaft, and pressing the rough crank pin portions in the
direction perpendicular to the axial direction so as to increase the amount of
eccentricity thereof to the amount of eccentricity of the crank pins of the forged
crankshaft.
[00 191
In the above forming apparatus in (I), it is preferred that the reference crank
pin die and the movable crank pin dies each includes an auxiliary crank pin die
disposed at a location outside of the corresponding rough crank pin portion, opposite
to the side where the reference crank pin die and the movable crank pin dies are
contacted, and in conjunction with the axial movement of the movable journal dies as
well as that of the movable crank pin dies and the auxiliary crank pin dies forming
pairs therewith, a movement of the movable crank pin dies in the direction
perpendicular to the axial direction is controlled in a manner that the rough crank pin
portions to be deformed by pressing reach to the auxiliary crank pin dies after spaces
between the movable journal dies, the reference crank pin die, the movable crank pin
dies, and the auxiliary crank pin dies are filled.
[0020]
This forming apparatus preferably has a configuration such that, provided that
a total length of movement of the movable crank pin dies in the direction
perpendicular to the axial direction is a 1000/0 length of movement thereof, when the
axial movement of the movable journal dies that are adjacent to such movable crank
pin dies is completed, a length of movement of such movable crank pin dies in the
direction perpendicular to the axial direction is 90% or less of the total length of
movement, and thereafter, the movement of such movable crank pin dies in the
direction perpendicular to the axial direction is completed.
[002 11
Further, the above forming apparatus in (1) may have a configuration such
that the reference crank pin die, the movable crank pin dies, and the stationary and
movable journal dies are mounted on a press machine that is capable of being moved
downward along the direction perpendicular to the axial direction and, by the
downward movement of the press machine, the stationary and movable journal dies
are caused to hold and retain the rough journal portions therebetween while the
reference crank pin die and the movable crank pin dies are brought into contact with
the rough crank pin portions, and with continued downward movement of the press
machine, the movable journal dies are moved axially by wedge mechanisms, and the
movable crank pin dies are caused to move axially by the movement of the movable
journal dies.
[0022]
In case of this forming apparatus, it is preferred that the wedge mechanisms
have different wedge angles for each movable journal die. Furthermore, it is
preferred that the reference crank pin die and the movable crank pin dies are coupled
to hydraulic cylinders and caused to move in the direction perpendicular to the axial
direction by driving the hydraulic cylinders.
[0023]
(2) First and third rough crank pin portions at opposite ends in the preform
blank have an amount of eccentricity in a direction perpendicular to an axial
direction in the opposite direction to each other, the amount of eccentricity thereof
being less than a 4312 of an amount of eccentricity of the crank pins of the forged
crankshaft, and a second rough crank pin portion in the center in a preform blank has
an amount of eccentricity in the direction perpendicular to the axial direction of zero
or has the same amount of eccentricity in a direction perpendicular to an eccentric
direction of the first and third rough crank pin portions as an amount of eccentricity
of the crank pin of the forged crankshaft.
The forming apparatus includes a reference crank pin die, movable crank pin
dies, and journal dies, described below.
The reference crank pin die is disposed at a location of the second rough
crank pin portion, configured to be brought into contact with the second rough crank
pin portion, and configured to be constrained from moving in the axial direction
while, being in contact with side surfaces of the third and fourth rough crank arm
portions through which the rough crank arm portions connect with the second rough
crank pin portion.
The movable crank pin dies are disposed at locations of the corresponding
first and third rough crank pin portions, configured to be brought into contact with
the first and third rough crank pin portions, and configured to move axially toward
the reference crank pin die and in the direction perpendicular to the axial direction,
while being in contact with side surfaces of the rough crank arm portions through
which the rough crank arm portions connect with the first and third rough crank pin
portions.
The stationary journal dies are disposed at locations of the rough journal
portions connecting with the third and fourth rough crank arm portions, configured to
hold and retain such rough journal portions therebetween in the direction
perpendicular to the axial direction, and configured to be constrained from moving
axially while being in contact with side surfaces of the third and fourth rough crank
arm portions.
The movable journal dies are disposed at locations of the corresponding rough
journal portion excluding the rough journal portions connecting with the third and
fourth rough journal portions, configured to hold and retain such rough journal
portions therebetween in the direction perpendicular to the axial direction, and
configured to move axially toward the reference crank pin die while being in contact
with side surfaces of the rough crank arm portions through which the rough crank
arm portions connect with such rough journal portions.
The forming apparatus in a state that the rough journal portions are held and
retained by the stationary and movable journal dies and the rough crank pin portions
are contacted with the reference crank pin die and the movable crank pin dies, the
movable journal dies are moved axially and the movable crank pin dies are moved
axially and in the direction perpendicular to the axial direction, thereby compressing
the weighted rough crank arm portions in the axial direction so as to reduce the
thickness thereof to the thickness of weighted crank arms of a forged crankshaft, and
pressing the first and third rough crank pin portions in the direction perpendicular to
the axial direction, but in the opposite direction to each other, so as to increase the
amount of eccentricity thereof to the4312 of the amount of eccentricity of crank pins
of the forged crankshaft.
LO0243
The manufacturing method according to embodiments of the present
invention is a method for manufacturing a forged crankshaft for a three-cylinder
engine, and includes any one of configurations (3) to (6) described below.
[0025]
(3) A method for manufacturing includes the following successive steps
comprising a f ~ sptre forming step, a second preforming step, and a finish forging
step.
The first preforming step forms a preform blank to be supplied to the above
forming apparatus in (1). First and third rough crank pin portions at opposite ends
in a preform blank have an amount of eccentricity in a direction perpendicular to an
axial direction in the opposite direction to each other, the amount of eccentricity
thereof being equal to a 4312 of an amount of eccentricity of crank pins of the forged
crankshaft. A second rough crank pin portion in the center in a preform blank has a
smaller amount of eccentricity in the direction perpendicular to the axial direction in
the direction perpendicular to an eccentric direction of the first and third rough crank
pin portions than an amount of eccentricity of the crank pin of the forged crankshaft.
The second preforming step forms, using the above forming apparatus
described in (I), a blank for finish forging. The blank for finish forging has the
final shape of the forged crankshaft including the placement angle of the crank pins.
In the finish forging step, finish forging is performed on the blank for finish
forging to form a forged product having the final shape of the forged crankshaft
including the placement angle of the crank pins.
[0026]
(4) A method for manufacturing includes the following successive steps
comprising a first preforming step, a second preforming step, a finish forging step,
and a twisting step.
The first preforming step forms a preform blank to be supplied to the above
forming apparatus in (1). First and third rough crank pin portions at opposite ends
in a preform blank have a smaller amount of eccentricity in a direction perpendicular
to an axial direction in the same direction than an amount of eccentricity of crank
pins of the forged crankshaft. A second rough crank pin portion in the center in a
preform blank has a smaller amount of eccentricity in the direction perpendicular to
the axial direction in the direction opposite to an eccentric direction of the first and
third rough crank pin portions than an amount of eccentricity of the crank pin of the
forged crankshaft.
The second preforming step forms a blank for finish forging using the above
forming apparatus described in (1). The blank for finish forging has the final shape
of the forged crankshaft excluding the placement angle of the crank pins.
In the finish forging step, finish forging is performed on the blank for finish
forging to form a forged product having the final shape of the forged crankshaft
excluding the placement angle of the crank pins.
In the twisting step, the placement angle of the crank pins of the forged
product is adjusted to the placement angle of the crank pins of the forged crankshaft.
[0027]
(5) A method for manufacturing includes the following successive steps
comprising a first preforming step, a second preforming step, and a finish forging
step.
The first preforming step forms a preform blank to be supplied to the above
forming apparatus in (2). First and third rough crank pin portions at opposite ends
in a preform blank have an amount of eccentricity in a direction perpendicular to an
axial direction in the opposite direction to each other, the amount of eccentricity
thereof being less than a 4312 of an amount of eccentricity of the crank pins of the
forged crankshaft. A second rough crank pin portion in the center in a preform
blank has an amount of eccentricity in the direction perpendicular to the axial
direction of zero.
The second preforming step forms, using the above forming apparatus
described in (2), a blank for finish forging. The first and third rough crank pin
portions at opposite ends in a blank for finish forging have an amount of eccentricity
in the direction perpendicular to the axial direction in the opposite direction to each
other, the amount of eccentricity thereof being equal to the 43/2 of the amount of
eccentricity of the crank pins of the forged crankshaft. The second rough crank pin
portion in the center in a blank for finish forging remains the same amount of
eccentricity in the direction perpendicular to the axial direction as the preform blank.
In the finish forging step, finish forging is performed on the blank for finish
forging in a state that the first and third rough crank pin portions at opposite ends are
horizontally placed, whereby all the rough crank pin portions are pressed in the
direction perpendicular to the axial direction to form a forged product having a final
shape of the forged crankshaft including the placement angle of the crank pins.
[0028]
(6) A method for manufacturing includes the following successive steps
comprising a first preforming step, a second preforming step, and a finish forging
step.
The first preforming step forms a preform blank to be supplied to the above
forming apparatus in (2). First and third rough crank pin portions at opposite ends
in a preform blank have an amount of eccentricity in a direction perpendicular to an
axial direction in the opposite direction to each other, the amount of eccentricity
thereof being less than a 4312 of an amount of eccentricity of the crank pins of the
forged crankshaft. A second rough crank pin portion in the center in a preform
blank has an amount of eccentricity in the direction perpendicular to the axial
direction in the direction perpendicular to an eccentric direction of the first and third
rough crank pin portions, the amount of eccentricity thereof being the same as an
amount of eccentricity of the crank pin of the forged crankshaft.
The second preforming step forms a blank for finish forging using the above
forming apparatus described in (2). The first and third rough crank pin portions at
opposite ends in a blank for finish forging have an amount of eccentricity in the
direction perpendicular to the axial direction in the opposite direction to each other,
the amount of eccentricity thereof being equal to the 4312 of the amount of
eccentricity of the crank pins of the forged crankshaft. The second rough crank pin
portion in the center in a blank for finish forging remains the same amount of
eccentricity in the direction perpendicular to the axial direction as the preform blank.
In the finish forging step, finish forging is performed on the blank for finish
forging in a state that the first and third rough crank pin portions at opposite ends are
horizontally placed, whereby the first and third rough crank pin portions are pressed
in the direction perpendicular to the axial direction to form a forged product having a
final shape of the forged crankshaft including the placement angle of the crank pins.
ADVANTAGEOUS EFFECTS OF INVENTION
[0029]
With the forming apparatus of the present embodiment and the manufacturing
method including the preforming steps in which such apparatus is used, it is possible
to form, from a preform blank without a flash, a blank for finish forging without a
flash which has a shape generally in agreement with a shape of a forged crankshaft
for a three-cylinder engine having thin arms, even with the weighted arms. By
subjecting such a blank for finish forging without a flash to finish forging, it is
possible to obtain the final shape of the forged crankshaft including the contour
shape of crank arms although some minor amount of flash is generated. Thus,
forged crankshafts for three-cylinder engines can be manufactured with high material
utilization and also with high dimensional accuracy regardless of their shapes.
BRIEF DESCRIPTION OF DRAWINGS
[0030]
[FIG. 11 FIG. 1 is a schematic diagram illustrating a typical conventional
process for manufacturing a forged crankshaft for a three-cylinder engine.
[FIG. 21 FIG. 2 is a diagram schematically showing the shapes of a preform
blank to be processed by the forming apparatus, a blank for finish forging formed
therefrom, and a forged product after finish forging, in the manufacturing method of
a first embodiment.
[FIG. 31 FIG. 3 is a schematic diagram illustrating a process for
manufacturing a forged crankshaft according to the fust embodiment.
[FIG. 41 FIG. 4 is a longitudinal sectional view showing a configuration of the
forming apparatus according to the fust embodiment.
[FIG. 5A] FIG. 5A is a longitudinal sectional view illustrating a process for
forming a blank for finish forging using the forming apparatus according to the first
embodiment shown in FIG. 4, with a forming state at an initial stage shown therein.
[FIG. 5B] FIG. 5B is a longitudinal sectional view illustrating a process for
forming a blank for finish forging using the forming apparatus according to the fust
embodiment shown in FIG. 4, with a forming state at the completion shown therein.
[FIG. 61 FIG. 6 is a diagram illustrating how fin flaws occur in forming a
blank for finish forging using the forming apparatus.
[FIG. 71 FIG. 7 is a diagram illustrating how fin flaws are prevented by taking
a measure in forming a blank for fmish forging using the forming apparatus.
[FIG. 81 FIG. 8 is a diagram schematically showing the shapes of a preform
blank to be processed by the forming apparatus, a blank for finish forging formed
therefrom, a forged product after finish forging, and a twisted product after twisting,
in the manufacturing method of a second embodiment.
[FIG. 93 FIG. 9 is a schematic diagram illustrating a process for
manufacturing a forged crankshaft according to the second embodiment.
[FIG. 101 FIG. 10 is a longitudinal sectional view showing a configuration of
the forming apparatus according to the second embodiment.
[FIG. 1 1A] FIG. 1 1A is a longitudinal sectional view illustrating a process for
forming a blank for finish forging using the forming apparatus according to the
second embodiment shown in FIG. 10, with a forming state at an initial stage shown
therein.
[FIG. 1 1 B] FIG. 1 1B is a longitudinal sectional view illustrating a process for
forming a blank for finish forging using the forming apparatus according to the
second embodiment shown in FIG. 10, with a forming state at the completion shown
therein.
[FIG. 121 FIG. 12 is a diagram schematically showing the shapes of a preform
blank to be processed by the forming apparatus, a blank for finish forging formed
therefrom, and a forged product after finish forging, in the manufacturing method af
a third embodiment.
[FIG. 131 FIG. 13 is a schematic diagram illustrating a process for
manufacturing a forged crankshaft according to the third embodiment.
[FIG. 141 FIG. 14 is a longitudinal sectional view showing a configuration of
the forming apparatus according to the third embodiment.
[FIG. 15A] FIG. 15A is a longitudinal sectional view illustrating a process for
forming a blank for finish forging using the forming apparatus according to the third
embodiment shown in FIG. 14, with a forming state at an initial stage shown therein.
[FIG. 15B) FIG. 15B is a longitudinal sectional view illustrating a process for
forming a blank for finish forging using the forming apparatus according to the third
embodiment shown in FIG. 14, with a forming state at the completion shown therein.
[FIG. 16-1 FIG. 16 is a diagram schematically showing the shapes of a preform
blank to be processed by the forming apparatus, a blank for finish forging formed
therefrom, and a forged product after finish forging, in the manufacturing method of
a fourth embodiment.
[FIG. 17) FIG. 17 is a schematic diagram illustrating a process for
manufacturing a forged crankshaft according to the fourth embodiment.
DESCRIPTION OF EMBODIMENTS
LOO3 11
The present invention is based on the premise that, in manufacturing a forged
crankshaft for a three-cylinder engine, finish forging is performed in the
manufacturing process. The forming apparatus of the present invention is used for
forming, in a step prior to finish forging, a blank for finish forging to be subjected to
the finish forging, from a preform blank. With regard to the apparatus for forming a
blank for finish forging for a forged crankshaft for a three-cylinder engine and the
method for manufacturing a forged crankshaft for a three-cylinder engine including
the preforming steps using such apparatus, of the present invention, embodiments
thereof are described in detail below.
LOO321
1. First Embodiment
1-1. Preform Blank, Blank For Finish Forging, and Forged Product
FIG. 2 is a diagram schematically showing the shapes of a preform blank to
be processed by the forming apparatus, a blank for finish forging formed therefrom,
and a forged product after finish forging, in the manufacturing method of the first
embodiment. FIG. 2 shows how a three-cylinder four-counterweight crankshaft is
manufactured as an example. In addition, FIG. 2 shows plane views showing an
outside appearance of the crankshaft and drawings depicting an arrangement of crank
pins with a view along an axial direction side by side to facilitate understanding of
the shapes of the blanks in each step.
[0033]
As shown in FIG. 2, a preform blank 4 of the first embodiment has a
crankshaft shape that is approximate to a shape of a forged crankshaft 1 for a threecylinder
four-counterweight shown in FIG. 1 (f) but is generally in a rough shape.
The preform blank 4 includes: four rough journal portions Jl a to J4a; three rough
crank pin portions Pla to P3a; a rough front part portion Fra; a rough flange portion
Fla; and six rough crank arm portions A1 a to A6a (hereinafter also referred to simply
as "rough arm portions") that alternatively connect the rough journal portions Jla to
J4a, and the rough crank pin portions Pla to P3a to each other. The third and fourth
rough arm portions A3a and A4a connecting with the second rough crank pin portion
P2a in the center have no balance weight, therefore having oval shapes. The
preform blank 4 has no flash. Hereinafter, when the rough journal portions Jla to
J4a, the rough crank pin portions Pla to P3a, and the rough arm portions Ala to A6a,
of the preform blank 4, are each collectively referred to, a reference character "Ja" is
used for the rough journal portions, a reference character "Pa" for the rough crank
pin portions, and a reference character "Aa" for the rough arm portions. The first,
second, fifth, and sixth rough arm portions Ala, A2a, A5a, and A6a having balance
weights are also referred to as weighted rough arm portions Aa. On the other hand,
the third and fourth rough arm portions A3a and A4a having no balance weight are
also referred to as non-weighted rough arm portions Aa, or oval rough arm portions
Aa.
A blank for finish forging 5 of the first embodiment is formed from the
preform blank 4 described above using a forming apparatus, details of which will be
provided later. The blank far finish forging 5 includes four rough journal portions
Jlb to J4b, three rough crank pin portions Plb to P3b, a rough front part portion Frb,
a rough flange portion Flb, and six rough crank arm portions Alb to A6b (hereinafter
also referred to simply as "rough arm portions") that alternatively connect the rough
journal portions Jlb to J4b, and the rough crank pin portions Plb to P3b to each other.
The third and fourth rough arm portions A3b and A4b connecting with the second
rough crank pin portion P2b in the center have no balance weight, therefore having
oval shapes. The blank for finish forging 5 has no flash. Hereinafter, when the
rough journal portions Jlb to J4b, the rough crank pin portions Plb to P3b, and the
rough arm portions Alb to A6b, of the blank for finish forging 5, are each
collectively referred to, a reference character "Jb" is used for the rough journal
portions, a reference character "Pb" for the rough crank pin portions, and a reference
character "Ab" for the rough arm portions. The first, second, fifth, and sixth rough
arm portions Alb, A2b, A5b, and A6b having balance weights are also referred to as
weighted rough arm portions Ab. On the other hand, the third and fourth rough arm
portions A3b and A4b having no balance weight are also referred to as non-weighted
rough arm portions Ab, or oval rough arm portions Ab.
[0035]
A forged product 6 of the first embodiment is obtained from the blank for
finish forging 5 described above by fmish forging. The forged product 6 includes
four journals Jl c to J4c, three crank pins Plc to P3c, a front part Frc, a flange Flc,
and six crank arms Alc to A6c (hereinafter also referred to simply as "arms") that
alternatively connect the journals Jlc to J4c, and the crank pins Plc to P3c to each
other. The third and fourth arms A3c and A4c connecting with the second rough
crank pin portion P2c in the center have no balance weight, therefore having oval
shapes. Hereinafter, when the journals Jlc to J4c, the crank pins Plc to P3c, and
the arms Alc to A6c, of the forged product 6, are each collectively referred to, a
reference character "Jc" is used for the journals, a reference character "PC" for the
crank pins, and a reference character "Ac" for the arms. The first, second, fifth, and
sixth arms Alc, A2c, A5c, and A6c having balance weights are also referred to as
weighted arms Ac. On the other hand, the third and fourth arms A3c and A4c
having no balance weight are also referred to as non-weighted arms Ac, or oval arms
Ac.
COO361
The forged product 6 has a shape that is in agreement with a shape of a
crankshaft (forged final product) including a placement angle of the crank pins PC
and corresponds to a forged crankshaft 1 shown in FIG. 1 (f). Specifically, the
journals Jc of the forged product 6 have an axial length equal to that of journals J of
the forged crankshaft having the final shape. The crank pins PC of the forged
product 6 have an axial length equal to that of crank pins P of the forged crankshaft
having the final shape. Further, the crank pins PC of the forged product 6 have the
same amount of eccentricity in a direction perpendicular to an axial direction and the
same placement angle of 120" as the crank pins P of the forged crankshaft having the
final shape, thus they are placed at the specified positions. The arms Ac of the
forged product 6 have an axial thickness equal to that of arms A of the forged
crankshaft having the fmal shape.
[0037]
The blank for finish forging 5 has a shape that is generally in agreement with
the shape of the forged product 6 and corresponds exactly to a block forged blank
105 shown in FIG. l(d) with a difference therebetween being a flash 105a.
Specifically, the rough journal portions Jb of the blank for finish forging 5 have an
axial length equal to that of the journals J of the forged crankshaft having the fmal
shape (journals Jc of forged product 6). The rough crank pin portions Pb of the
blank for finish forging 5 have an axial length equal to that of the crank pins P of the
forged crankshaft having the fmal shape (crank pins PC of forged product 6).
Further, the crank pins Pb of the blank for finish forging 5 have the same amount of
eccentricity in the direction perpendicular to the axial direction and the same
placement angle of 120" as the crank pins P of the forged crankshaft having the final
shape, thus they are placed at the specified positions. The rough arm portions Ab of
the blank for finish forging 5 have an axial thickness equal to that of the arms A of
the forged crankshaft having the final shape (arms Ac of forged product 6).
[0038]
In contrast, the rough journal portions Ja of the preform blank 4 have an axial
length equal to that of the rough journal portions Jb of the blank for finish forging 5,
i.e., that of the journals J of the forged crankshaft (journals Jc of forged product 6).
The rough crank pin portions Pa of the preform blank 4 have an axial length equal to
that of the rough crank pin portions Pb of the blank for finish forging 5, i.e., that of
the crank pins P of the forged crankshaft (crank pins PC of forged product 6), but
have a smaller amount of eccentricity than that of the rough crank pin portions Pb of
the blank for finish forging 5. Specifically, the first and third rough crank pin
portions Pl a and P3a at opposite ends among the rough crank pin portions Pa of the
preform blank 4 have an amount of eccentricity in the opposite direction to each
other, the amount of eccentricity thereof being equal to a 4312 of an amount of
eccentricity in the crank pins P of the forged crankshaft. On the other hand, the
second rough crank pin portion P2a in the center is configured to have an amount of
eccentricity in the direction perpendicular to an eccentric direction of the first and
third rough crank pin portions Pla and P3a, the amount of eccentricity thereof being
approximately equal to a half of an amount of eccentricity in the crank pin P of the
forged crankshaft.
[0039]
Among the rough arm portions Aa of the preform blank 4, the weighted rough
arm portions Aa (the first, second, fifth and sixth rough arm portions Ala, A2a, A5a,
and A6a) have an axial thickness greater than that of the respective weighted rough
arm portions Ab of the blank for finish forging 5, i.e., weighted arms A of the forged
crankshaft (the weighted arms Ac of the forged product 6). On the other hand, the
oval rough arm portions Aa of the preform blank 4 (the third and fourth rough arm
portions A3a and A4a) have an axial thickness equal to that of the respective oval
rough arm portions Ab af the blank for finish forging 5, i.e., the oval arms A (the
oval arm Ac of the forged product 6) of the forged crankshaft. In brief, compared
to the blank for finish forging 5 (the forged crankshaft having the fmal shape and the
forged product 6), the preform blank 4 has an overall length that is relatively long by
the additional thickness of the weighted rough arm portions Aa, and has a relatively
small amount of eccentricity of the rough crank pin portions Pa. Thus, the preform
blank 4 has a relatively gentle crankshaft shape.
[0040]
However, strictly speaking, the blank for fmish forging 5 has such a
configuration that, with respect to the final shapes of the forged crankshaft and the
forged product 6, the rough arm portions Ab are made slightly thinner and therefore
the axial lengths of the rough journal portions Jb and the rough crank pin portions Pb
are accordingly slightly greater. This is intended to ensure that the blank for finish
forging 5 can be easily received by the dies when finish forging is performed and
thereby prevent the occurrence of scoring. Correspondingly, the preform blank 4,
too, has such a configuration that, with respect to the final shapes of the forged
crankshaft and the forged product 6, the axial lengths of the rough journal potions Ja
and the rough crank pin portions Pa are accordingly slightly greater.
[0041]
1-2. Process For Manufacturing Forged Crankshaft
FIG. 3 is a schematic diagram illustrating a process for manufacturing a
forged crankshaft according to the first embodiment. As shown in FIG. 3, the
process for manufacturing the forged crankshaft for the three-cylinder engine of the
first embodiment includes a first preforming step, a second preforming step, and a
finish forging step, and also includes a trimming step and a coining step as necessary.
[W21
The first preforming step is a step in which the preform blank 4 described
above is obtained. In the first preforming step, by using a round billet having a
circular cross section as a starting material, a preforming operation is applied to the
round billet after it is heated by an induction heater or a gas atmosphere furnace.
For example, the round billet is subjected to roll forming in which it is reductionrolled
by grooved rolls to distribute its volume in the longitudinal direction; and the
resulting rolled blank is repeatedly subjected to bending in which it is partially
pressed in a press from a direction perpendicular to the longitudinal direction to
distribute its volume. In this manner, the preform blank 4 can be obtained. Also,
the preform blank 4 may be obtained by using the techniques disclosed in Patent
Literatures 1 and 2. Furthermore, cross roll forging, fully-enclosed die forging or
the like may also be employed.
[0043]
The second preforming step is a step in which the blank for finish forging 5
described above is obtained. In the second preforming step, operation is applied by
using a forming apparatus described in FIG. 4 below. In this manner, the blank for
finish forging 5 having the final shape of the forged crankshaft including the
placement angle of crank pins can be obtained from the preform blank 4 described
above.
[0044]
The finish forging step is a step in which the forged product 6 described
above is obtained. In the fmish forging step, the blank for finish forging 5 is
supplied to be processed by press forging with a pair of upper and lower dies,
whereby the forged product 6 having a shape in agreement with the shape of the
crankshaft of the forged crankshaft having the fmal shape including the placement
angle of the crank pins can be obtained.
[0045]
1-3. Apparatus For Forming Blank For Finish Forging
FIG. 4 is a longitudinal sectional view showing a configuration of the forming
apparatus according to the first embodiment. FIG. 4 illustrates, as an example, a
forming apparatus that is used in manufacturing a three-cylinder four-counterweight
crankshaft, i.e., a forming apparatus configured to form the blank for finish forging 5
from the preform blank 4 shown in FIG. 2. It should be noted that in the
longitudinal sectional view shown in FIG. 4, the first and third rough crank pin
portions are in reality extended in a front-back direction, where either one of them is
located in the front side of the paper and the other one is located in the back side of
the paper, however they are illustrated on the same plane for convenience.
[0046]
As shown in FIG. 4, the forming apparatus is configured to utilize a press
machine and includes a stationary lower pressure pad 20 serving as a base and an
upper pressure pad 21, which is lowered by driving a ram of the press machine. A
lower die holder 22, located over the lower pressure pad 20, is resiliently supported
via a resilient member 24. This lower die holder 22 is vertically movable. As the
resilient member 24, disc springs, coil springs, air springs, or the like may be
employed, or a hydraulic spring system may be employed. An upper die holder 23
is secured under the upper pressure pad 2 I via support posts 25. This upper die
holder 23 is lowered together with the upper pressure pad 2 1 by driving the press
machine (ram).
[0047]
In the forming apparatus shown in FIG. 4, the preform blank 4 is placed in the
dies in a manner such that the first and third rough crank pin portions Pl a and P3a
are horizontally positioned and the second rough crank pin portion P2a is positioned
in a lower side in the vertical direction. The preform blank 4 placed in such a
manner is formed into the blank for finish forging. Thus, vertically forming pairs,
i.e., the stationary journal dies 9U and 9B, the movable journal dies 10U and lOB,
the reference crank pin die 1 I and the auxiliary crank pin die 13, and the movable
crank pin dies 12 and the auxiliary crank pin dies 13, are apart from each other in the
axial direction of the preform blank 4, and the lower and upper ones are respectively
mounted on the lower die holder 22 and the upper die holder 23.
[0048]
The reference crank pin die 1 1 and the auxiliary crank pin die 13, vertically
forming a pair, are disposed serving as a reference among the rough crank pin
portions Pa of the preform blank 4, the location of the second rough crank pin
portion P2a in the center, with the upper one mounted on the upper die holder 23 and
the lower one mounted on the lower die holder 22. The reference crank pin die 11
of the first embodiment is disposed on the opposite side of a specified position of
second rough crank pin portions P2a, whereas its counterpart, the auxiliary crank pin
die 13 is disposed in the same side of the specified position of the second rough
crank pin portion P2a in the outside. For example, at the location of the second
rough crank pin portion P2a, the second rough crank pin portion P2a is positioned in
the lower side. Thus the specified position thereof is located in the lower side, as a
result, the reference crank pin die 11 is mounted on the upper die holder 23, and its
counterpart, the auxiliary crank pin die 13 is mounted on the lower die holder 22.
[0049]
Particularly, the reference crank pin die 1 1 and the auxiliary crank pin die 13,
i.e., both the upper and lower dies, are constrained from moving in the axial direction
on the upper die holder 23 and the lower die holder 22, respectively. Only the
reference crank pin die 11 is movable in the direction perpendicular to the axial
direction, i.e., the direction toward the specified position of the rough crank pin
portion Pa (downward direction in FIG. 4).
[OOSO]
The reference crank pin die 1 1 and the auxiliary crank pin die 13 respectively
have impressions 1 1 a and 13a having a semi-cylindrical shape. The length of the
impressions 1 1 a and 13a is equal to the axial length of the rough crank pin portion
P2b of the blank for finish forging 5.
[0051]
By the lowering of the upper die holder 23 caused by driving the press
machine, is., the downward movement of the press machine, the reference crank pin
die 1 1 is brought into a state in which the impression 1 la is brought into contact with
the second rough crank pin portion P2a. Concurrently, both side surfaces of the
reference crank pin die 1 1 are in contact with the third and fourth rough arm portions
A3a and A4a at a second rough crank pin portion P2a-side side surfaces through
which the third and fourth rough arm portions A3a and A4a and the second rough
crank pin portion P2a are connected.
LO0521
The movable crank pin dies 12 and the auxiliary crank pin dies 13, vertically
forming pairs with each other, are disposed is in contact, the locations of the first
and third rough crank pin portions Pla and P3a, with the upper ones mounted on the
upper die holder 23 and the lower ones mounted on the lower die holder 22. The
movable crank pin dies 12 of the first embodiment are disposed on the opposite side
of specified positions of the corresponding rough crank pin portions Pa, whereas
their counterparts, the auxiliary crank pin dies 13 are disposed on the same side of
the specified positiops of the corresponding rough crank pin portions Pa in the
outside. For example, at the location of the frst rough crank pin portion Pla, the
specified position of the first rough crank pin portion Pla is located in the upper side.
Thus the corresponding movable crank pin die 12 is mounted on the lower die holder
22, and its counterpart, the auxiliary crank pin die 13 is mounted on the upper die
holder 23.
[0053]
Particularly, all the movable crank pin dies 12 and the auxiliary crank pin dies
13, i.e., both the upper and lower dies, are axially movable toward the reference
crank pin die 11 on the lower die holder 22 and the upper die holder 23, respectively.
Only the movable crank pin dies 12 are movable in the direction perpendicular to the
axial direction, i.e., the direction toward the specified positions of the rough crank
pin portions Pa (upward direction in FIG. 4).
[0054]
The movable crank pin dies 12 and the auxiliary crank pin dies 13
respectively have impressions 12a and 13a having a semi-cylindrical shape. The
length of the impressions 12a and 13a is equal to the axial length of the rough crank
pin portions Pb of the blank for finish forging 5.
[0055]
Tbe stationary journal dies 9U and 9B are disposed at locations of the
corresponding rough journal portion Ja of the preform blank 4 (the second and third
rough journal portions J2a and J3a) connecting with the rough oval arm portion Aa
(the third and fourth rough arm portions A3a and A4a), with the upper ones mounted
on the upper die holder 23 and the lower ones mounted on the lower die holder 22.
Particularly, the stationary journal dies 9U and 9B, i.e., both the upper and lower
ones, are completely secured to the upper die holder 23 and the lower die holder 22,
respectively, and constrained from moving in the axial direction.
[0056]
The stationary journal dies 9U and 9B have first impressions 9Ua and 9Ba,
respectively, each having a semi-cylindrical shape and second impressions 9Ub and
9Bb, and third impressions 9Uc and 9Bc, respectively, each located at the front and
back (right and left as seen in FIG. 4) the first impressions 9Ua and 9Ba and adjacent
thereto. The length of the first impressions 9Ua and 9Ba is equal to the axial length
of the rough journal portions Jb (the second and third rough journal portions J2b and
J3b) of the blank for finish forging 5. The length of the second impressions 9Ub
and 9Bb is equal to the axial thickness of the weighted rough arm portions Ab (the
second and fifth rough arm portions A2b and A5b) connecting to the rough journal
portions Jb of the blank for finish forging 5. The length of the third impressions
9Uc and 9Bc is equal to the axial thickness of the rough oval arm portions Ab (the
third and fourth rough arm portion A3b and A4b) connecting to the rough journal
portions Jb of the blank for finish forging 5.
[0057]
By the downward movement of the press machine, the stationary journal dies
9U and 9B are caused to hold and retain the rough journal portions Ja with the
corresponding first impressions 9Ua and 9Ba therebetween from above and below.
Concurrently, the stationary journal dies 9U and 9B are brought into a state in which
the second impressions 9Ub and 9Bb and the third impressions 9Uc and 9Bc, at their
first impressions 9Ua and 9Ba-side surfaces, are in contact with the weighted rough
arm portions Aa and the rough oval arm portions Aa connecting with the
corresponding rough journal portions Ja, at their rough journal portion Ja-side side
surfaces.
[0058]
The movable journal dies 10U and 10B are disposed at locations of the
corresponding the rough journal portions Ja (first and fourth rough journal portions
Jla and J4a) of the preform blank 4 excluding the rough journal portions Ja (second
and third rough journal portions J2a and J3a) connecting with the rough oval arm
portions Aa (third and fourth rough arm portions A3a and A4a), with the upper ones
mounted on the upper die holder 23 and the lower ones mounted on the lower die
holder 22. Particularly, the movable journal dies 10U and 1 OB, i.e., both the upper
and lower dies, are axially movable toward the reference crank pin die 11 to the
upper die holder 23 and the lower die holder 22, respectively.
[0059}
The movable journal dies 10U and 1 OB respectively have first impressions
lOUa and 1 OBa having a semi-cylindrical shape and respectively have second
impressions 10Ub and lOBb, located adjacent to the first impressions 10Ua and lOBa
at the front and back (right and left as seen in FIG. 4). The length of the first
impressions 1 OUa and 10Ba is equal to the axial length of the rough journal portions
Jb (first and fourth joumal portions Jl b and J4b) of the blank for finish forging 5.
The length of the second impressions 10Ub and 10Bb is equal to the axial thickness
of the weighted rough arm portions Ab (first and sixth rough arm portions A1 b and
A6b) connecting to the rough journal portions Jb of the blank for fmish forging 5.
[00601
By the lowering of the upper die holder 23 caused by driving a press machine,
i.e., the downward movement of the press machine, the movable journal dies 1OU
and 10B are caused to hold and retain the respective rough journal portions Ja from
the upper and lower sides with the first impressions lOUa and 10Ba. Concurrently,
the movable journal dies 10U and 10B are brought into a state in which the second
impressions 10Ub and 1 OBb, at their first impression 10Ua and 10Ba-side surfaces,
are in contact with the rough arm portions Aa, at their rough journal portion Ja-side
side surfaces through which the weighted rough arm portions Aa and the respective
rough journal portions Ja are connected.
[0061]
In this operation, by the downward movement of the press machine, the
reference crank pin die 1 1 and the movable crank pin dies 12 are placed in a state in
which the iinpressions 1 1 a and 12a are brought into contact with the rough crank pin
portions Pa, and both side surfaces of the reference crank pin die 1 1 and the movable
crank pin dies 12 are in contact with the rough arm portions Aa at their rough crank
pin portion Pa-side side surfaces through which the rough arm portions Aa and rough
crank pin portions Pa are connected.
[0062]
The movable journal dies 10U and 10B disposed at locations of the
corresponding first and fourth rough journal portions Jla and J4a at opposite ends
have end surfaces, which are respectively referred to as inclined surfaces 14U and
14B. In relation to this, on the lower pressure pad 20, there are provided wedges 26,
each located correspondingly to the location of the inclined surfaces 14U and 14B of
the movable journal dies 1 OU and 10B for the first and fourth rough journal portions
Jla and J4a. Each of wedges 26 extends upward penetrating through the lower die
holder 22. The inclined surfaces 14B of the lower movable journal dies lOB,
among the movable journal dies 10U and 10B for the first and fourth rough journal
portions Jla and J4a, are in contact with the slopes of wedges 26 in the initial
condition. On the other hand, the inclined surfaces 14U of the upper movable
journal. dies IOU are brought into contact with the slopes of wedges 26 by the
downward movement of the press machine.
[0063]
Then, with continued downward movement of the press machine, the upper
movable journal. dies 10U are pressed downwardly together with the lower movable
journal dies 10B. This allows the movable journal dies 10U and 10B for the first
and fourth rough journal portions Jla and J4a, i.e., both the upper and lower ones, to
move axially toward the reference crank pin die 1 1 for the second rough crank pin
portion P2a serving as a reference, as their inclined surfaces 14U and 14B slide along
the slopes of the first wedges 26. Essentially, the movable journal dies IOU and
10B are all capable of being moved axially by the wedge mechanisms.
[0064]
Then, the movable crank pin dies 12 and the auxiliary crank pin dies 13 are
pressed downwardly together with continued downward movement of the press
machine. Accordingly, with the axial movement of the movable journal dies 10U
and 10B as described above, the movable crank pin dies 12 and the auxiliary crank
pin dies 13 are moved axially along with them toward the reference crank pin die 1 1
for the second rough crank pin portion P2a serving as a reference. The movement
of the reference crank pin die 11 and the movable crank pin die 12 in the direction
perpendicular to the axial direction is accomplished by driving the hydraulic
cylinders 16 coupled to the crank pin dies 1 1 and 12.
[0065]
It should be noted that the axial movement of the movable crank pin dies 12
and the auxiliary crank pin dies 13 may be forcibly caused using a wedge mechanism
similar to the one for the movable journal dies IOU and 10B or a separate mechanism
such as a hydraulic cylinder or a servo motor or the like. The auxiliary crank pin
dies 13 may be integral with one of their adjacent movable journal dies IOU and 1 OB
or the stationary journal dies 9U and 9B forming pairs.
[0066]
In the initial condition shown in FIG. 4, spaces are provided between the
axially arranged movable journal dies 1 OU and 10B and the stationary journal dies
9U and 9B, and their corresponding movable crank pin dies 12 and auxiliary crank
pin dies 13. The spaces are provided so as to allow the axial movement of the
movable journal dies 1 OU and 10B as well as that of the movable crank pin dies 12
and the auxiliary crank pin dies 13. The size of the spaces represents the difference
between the thickness of the rough arm portions Ab of the blank for finish forging 5
and the thickness of the weighted rough arm portions Aa of the preform blank 4.
LO0671
Next, descriptions are given as to how the blank for finish forging is formed
using the thus configured forming apparatus.
FIG. 5A and FIG. 5B are longitudinal sectional views illustrating a process
for forming a blank for finish forging using the forming apparatus of the first
embodiment shown in FIG. 4. Among these figures, FIG. 5A shows a forming state
at the initial stage and FIG. 5B shows a forming state at the completion.
[0068]
The preform blank 4 is placed in the lower movable journal die 1 OB,
stationary journal die 9B, the movable crank pin dies 12, and the auxiliary crank pin
dies 13, shown in FIG. 4, and then lowering of the press machine is started. Then,
as shown in FIG. 5A, the upper movable journal dies 10U and stationary journal dies
9U are brought into contact with the corresponding lower movable journal dies 10B
and stationary journal dies 9B.
[0069]
Thus, the preform blank 4 is brought into a state in which the rough journal
portions Ja are held by the movable journal dies 10U and 10B and stationary journal
dies 9U and 9B from above and below, and the rough crank pin portions Pa are
contacted by the reference crank pin die 1 1 and the movable crank pin dies 12. In
this state, in the preform blank 4, the rough arm portions Aa, at their rough journal
portion Ja-side side surfaces, are in contact with the movable journal dies 10U and
10B and stationary journal dies 9U and 9B, and the rough arm portions Aa, at their
rough crank pin portion Pa-side side surfaces, are in contact with the reference crank
pin die 11 and the movable crank pin dies 12. Further, in this state, the inclined
surfaces 14U and 14B of the movable journal dies IOU and 10B for the fxst and
fourth rough journal portions Jla and J4a are in contact with the slopes of wedges 26.
[0070]
In this state, the lowering of the press machine is continued. Accordingly,
the inclined surfaces 14U and 14B of the movable journal dies 10U and 10B for the
first and fourth rough journal portions Jl a and J4a slide along the slopes of the first
wedges 26, and by this wedge mechanism, these journal dies IOU and 10B are
allowed to move axially toward the reference crank pin die 11 for the second rough
crank pin portion P2a. By such axial movement of the movable journal dies 1 OU
and IOB caused by the wedge mechanism, the movable crank pin dies 12 and the
auxiliary crank pin dies 13 are also allowed to move axially toward the reference
crank pin die 1 1.
[0071]
Accordingly, the spaces between the movable journal dies 10U and 10B and
stationary journal dies 9U and 9B, the movable crank pin dies 12, and the auxiliary
crank pin dies 13 are gradually narrowed, and finally filled. In this process, in the
preform blank 4, the rough arm portions Aa are axially compressed by the movable
journal dies 10U and 10B and stationary journal dies 9U and 9B, the reference crank
pin die 1 1, and the movable crank pin dies 12, while the axial lengths of the rough
journal portions Ja and the rough crank pin portions Pa are maintained, so that the
thickness of the weighted rough arm portions Aa is reduced to the thickness of the
weighted rough arm portions Ab of the blank for finish forging 5 (see FIG. 5B).
[0072]
Also, in coordination with the axial movement of the movable journal dies
1 0U and 10B as well as that of the movable crank pin dies 12 and the auxiliary crank
pin dies 13, each of the hydraulic cylinders 16 for the reference crank pin die 1 1 and
the movable crank pin dies 12 is operated. Accordingly, the crank pin dies 1 1 and
12 press the corresponding rough crank pin portions Pa of the preform blank 4 in the
direction perpendicular to the axial direction. Thus, the rough crank pin portions Pa
of the preform blank 4 are displaced in the vertical direction perpendicular to the
axial direction, and an amount of eccentricity thereof is increased to an amount of
eccentricity of the rough crank pin portions Pb of the blank for finish forging 5,
bringing into a state in which all the rough crank pin portions Pb are disposed in their
specified positions (see FIGS. 2 and 5B).
[0073]
In this manner, it is possible to form, from the preform blank 4 without a flash,
the blank for finish forging 5 without a flash, which has a shape generally in
agreement with the shape of the forged crankshaft for the three-cylinder engine
having thin arms A (forged final product), even with the weighted arms A. By
supplying such a blank for finish forging 5 without a flash for finish forging, and
performing finish forging with it, it is possible to obtain the final shape of the forged
crankshaft for the three-cylinder engine including the contour shape of arms and the
placement angle of the crank pins, although some minor amount of flash is generated.
Therefore, forged crankshafts for three-cylinder engines can be manufactured with
high material utilization and also with high dimensional accuracy regardless of their
shapes.
[0074]
In the forming apparatus shown in FIGS. 4,5A and 5B, the inclined surfaces
14U and 14B of the movable journal dies 10U and 10B for the first rough journal
portion Jl a and its contacting slope of wedge 26, and the inclined surfaces 14U and
14B of the movable journal dies 10U and 10B for the fourth rough journal portion
J4a and its contacting slope of wedge 26 are angled in a reverse relationship relative
to a vertical plane. The purpose of varying, for each of the movable journal dies
IOU and 1 OB, the wedge angle of the wedge mechanism, which causes the axial
movement of the movable journal dies 10U and 1 OB, is to ensure that the rate of
deformation at which the weighted rough arm portions Aa are axially compressed to
reduce the thickness thereof stays constant for all the weighted rough arm portions
Aa.
[OQ75]
In the preform blank 4, which is processed by the forming apparatus shown in
FIGS. 4,5A and 5B, the rough journal portions Ja have a cross-sectional area that is
equal to or greater than that of the rough journal portions Jb of the blank for finish
forging 5, i.e., that of the journals J of the forged crankshaft. Similarly, the rough
crank pin portions Pa of the preform blank 4 have a cross-sectional area that is equal
to or greater than that of the rough crank pin portions Pb of the blank for finish
forging 5, i.e., that of the crank pins P of the forged crankshaft. Even when the
cross-sectional area of the rough journal portions Ja of the preform blank 4 is greater
than the cross-sectional area of the rough journal portions Jb of the blank for fmish
forging 5, it is possible to reduce the cross-sectional area of the rough journal
portions Ja to the cross-sectional area of the rough journal portions Jb of the blank
for finish forging 5. This is caused by the holding and retaining of the rough
journal portions Ja by the movable journal dies 10U and 10B and by the subsequent
axial movement of the movable journal dies 10U and 1 OB. Even when the crosssectional
area of the rough crank pin portions Pa of the preform blank 4 is greater
than the cross-sectional area of the rough crank pin portions Pb of the blank for finish
forging 5, the cross-sectional area of the rough crank pin portions Pa can be reduced
to the cross-sectional area of the rough crank pin portions Pb of the blank for finish
forging 5 This is caused by, in addition to the movement of the reference crank pin
die 11 in the direction perpendicular to the axial direction, the movement of the
movable crank pin dies 12 in the axial direction and the direction perpendicular
thereto.
[0076]
An issue to be addressed regarding the forming of the blank for finish forging
described above is local formation of fin flaws against the weighted rough arm
portion Aa. The following describes how fin flaws are formed and how they can be
prevented.
[0077]
FIG. 6 is a diagram illustrating how fin flaws occur in forming a blank for
finish forging using the forming apparatus, and FIG. 7 is a diagram illustrating how
fin flaws are prevented by taking a measure. In FIGS. 6 and 7, there are shown (a)
a forming state at an initial stage, (b) a forming state during the process, (c) a
forming state at the completion, and (d) a blank for finish forging, which is removed
from the forming apparatus after the completion of forming.
[0078]
As shown in FIG. 6(a), upon the start of the forming operation, the movable
journal dies IOU and 10B move axially, and the movable crank pin dies 12 and the
auxiliary crank pin dies 13 move axially and in the direction perpendicular to this
direction. Then, as shown in FIG. 6(b), in the weighted rough arm portions Aa, if
the rough crank pin portions Pa in the process of pressing deformation in the
direction perpendicular to the axial direction reach the auxiliary crank pin dies 13
before the completion of the axial movement of the movable journal dies 10U and
1 OB, and the movable crank pin dies 12 and the auxiliary crank pin dies 13, i.e.,
before the spaces between the movable journal dies 10U and 10B and the stationary
journal dies 9U and 9B, and their corresponding movable crank pin dies 12 and
auxiliary crank pin dies 13 are filled, a problem to be described below will occur.
The fillings of the rough crank pin portions Pa flow into the spaces between the
auxiliary crank pin dies 13 and the movable journal dies 10U and 10B and stationary
journal dies 9U and 9B. Although the fillings that have flowed thereinto are
thinned with the progress of the forming operation, they stay there even after the
forming operation is completed as shown in FIG. 6(c). Thus, as shown in FIG. 6(d),
fin flaws 5a, coming out of the rough crank pin portions Pb of the blank for finish
forging 5, are formed locally at tbe boundaries with adjacent weighted rough arm
portions Aa.
100791
In the subsequent finish forging step, the fin flaws 5a will be struck into the
finished product, resulting in causing overlaps. Therefore, in order to ensure
product quality, it is necessary to prevent the formation of the fin flaws.
[0080]
One measure to prevent the formation of the fin flaws may be to control the
movement of the movable crank pin dies 12 in the direction perpendicular to the
axial direction so that the rough crank pin portions Pa to be processed for
deformation by pressing reach the auxiliary crank pin dies 13 after the spaces
between the movable journal dies 10U and 10B and stationary journal dies 9U and
9B, the movable crank pin dies 12, and the auxiliary crank pin dies 13 in weighted
rough arm portions Aa, are filled. Specifically, it may be configured such that the
axial movement of the movable journal dies 10U and 10B as well as that of the
movable crank pin dies 12 and the auxiliary crank pin dies 13 forming pair with the
movable crank pin dies 12 is completed, thereafter the movement of the movable
crank pin dies 12 in the direction perpendicular to the axial direction is completed.
For example, when the total moved distance of the movable crank pin dies 12 in the
direction perpendicular to the axial direction is designated as a 100% moved distance
thereof, it is preferred that, when the axial movement of the movable journal dies
10U and 10B that are adjacent to the movable crank pin dies 12 is completed, the
moved distance of the movable crank pins die 12 in the direction perpendicular to the
axial direction is 90% or less (more preferably 83% or less, and even more preferably
60% or less) of the total moved distance. Thereafter, the movement of the movable
crank pin dies 12 in the same direction may be completed.
[0081]
For example, the forming operation is started as shown in FIG. 7(a). And
then, as shown in FIG. 7(b), the axial movement of the movable journal dies 1 OU and
10B as well as that of the movable crank pin dies 12 and the auxiliary crank pin dies
13 are completed before the length of movement of the movable crank pin dies 12 in
the direction perpendicular to the axial direction reaches 90% of the total length of
movement in weighted rough arm portions Aa. Consequently, by this time, the
spaces between the movable journal dies IOU and 10B and stationary journal dies 9U
and 9B, the movable crank pin dies 12, and the auxiliary crank pin dies 13 have been
filled, whereas the rough crank pin portions Pa to be processed for deformation by
pressing have not reached the auxiliary crank pin dies 13. Subsequently, along with
the movement of the movable crank pin dies 12 in the direction perpendicular to the
axial direction, the rough crank pin portions Pa reach the auxiliary crank pin dies 13,
and with the completion of the movement, the forming is completed as shown in FIG.
7(c). Thus, no such problem occurs as the fillings of the rough crank pin portions
Pa flow into the spaces between the auxiliary crank pin dies 13 and the movable
journal dies 10U and 10B and stationary journal dies 9U and 9B. As a result, as
shown in FIG. 7(d), a high quality blank for finish forging 5 without the fin flaws can
be obtained.
[0082]
The process of movement of the movable crank pin dies in the direction
perpendicular to the axial direction before the completion of the axial movement of
the movable journal dies may be varied as desired. For example, the movement of
the movable crank pin dies in the direction perpendicular to the axial direction may
be started simultaneously with the start of the axial movement of the movable journal
dies or in advance of that, or conversely, it may be started after the axial movement
of the movable journal dies has progressed to some extent. Also, the movement of
the movable crank pin dies in the direction perpendicular to the axial direction may
be stopped temporarily after its start, at positions a certain distance away from their
initial positions, and it may be resumed after the completion of the axial movement
of the movable journal dies.
[0083]
2. Second Embodiment
A second embodiment is based on the configuration of the first embodiment
described above. A second embodiment includes a twisting step in a process of
manufacturing a forged crankshaft as well as modifications of the configuration
related to this step.
[0084]
2-1. Preform Blank, Blank For Finish Forging, Forged Product, and Twisted Product
FIG. 8 is a diagram schematically showing the shapes of a preform blank to
be processed by the forming apparatus, a blank for finish forging formed therefrom, a
forged product after finish forging, and a twisted product after twisting, in the
manufacturing method of the second embodiment. FIG. 8 shows how a threecylinder
four-counterweight crankshaft is manufactured, as seen in FIG. 2. This is
also the case for third and fourth embodiments described later.
[0085]
As shown in FIG. 8, a prefonn blank 4 of the second embodiment has a
crankshaft shape that is approximate to the shape of a forged crankshaft 1 for a threecylinder
four-counterweight, but is generally in rough shape. The preform blank 4
includes four rough journal portions Ja, three rough crank pin portions Pa, a rough
front part portion Fra, a rough flange portion Fla, and six rough arm portions Aa. A
blank for finish forging 5 of the second embodiment is formed from the prefonn
blank 4 described above using a forming apparatus, details of which will be provided
later. The blank for finish forging 5 includes four rough journal portions Jb, three
rough crank pin portions Pb, a rough front part portion Frb, a rough flange portion
Flb, and six rough arm portions Ab. A forged product 6 of the second embodiment
is obtained from the blank for finish forging 5 described above by finish forging.
The forged product 6 includes four journals Jc, three crank pins PC, a front part Frc, a
flange Flc, and six arms Ac.
[0086]
A twisted product 7 of the second embodiment is obtained from the forged
product 6 described above by twisting. The twisted product 7 includes four journals
Jl d to J4d, three crank pins Pl d to P3d, a front part Frd, a flange Fld, and six crank
arms A1 d to A6d (hereinafter also referred to simply as "arms") that alternatively
connect the journals Jld to J4d, and the crank pins Pld to P3d to each other.
Hereinafter, when the journals Jld to J4d, the crank pins Pld to P3d, and the arms
Ald to A6d, of the twisted product 7, are each collectively referred to, a reference
character "Jd" is used for the journals, a reference character "Pd" for the crank pins,
and a reference character "Ad" for the arms.
[0087]
The twisted product 7 has a shape that is in agreement with a shape of a
crankshaft (forged final product) including a placement angle of the crank pins Pd.
Specifically, the journals Jd of the twisted product 7 have an axial length equal to
that of the journals J of the forged crankshaft having the h a 1 shape. The crank pins
Pd of twisted product 7 have an axial length equal to that of the crank pins P of the
forged crankshaft having the final shape. Further, the crank pins Pd of the twisted
product 7 have the same amount of eccentricity in the direction perpendicular to the
axial direction and the same placement angle of 120" as the crank pins P of the
forged crankshaft having the final shape, thus they are placed at the specified
positions. The arms Ad of the twisted product 7 have an axial thickness equal to
that of arms A of the forged crankshaft having the final shape.
[OOSS]
The forged product 6 has a shape that is in agreement with the shape of the
crankshaft (forged final product) excluding the placement angle of the crank pins PC.
Specifically, the journals Jc of the forged product 6 have an axial length equal to that
of the journals J of the forged crankshaft having the final shape. The crank pins PC
of the forged product 6 have an axial length equal to that of the crank pins P of the
forged crankshaft having the final shape, and an amount of eccentricity in the
direction perpendicular to the axial direction is the same between them. However,
the placement angle of the crank pins PC of the forged product 6 is deviated from
specified positions. Specifically, among the crank pins PC of the forged product 6,
the first and third crank pins Plc and P3c at opposite ends are eccentric in the
direction perpendicular to the axial direction in the same direction. The second
crank pins P2c in the center is eccentric in the direction opposite to an eccentric
direction of the first and third crank pins Pl c and P3c. The arms Ac of the forged
product 6 have an axial thickness equal to that of arms A of the forged crankshaft
having the final shape.
[0089]
The blank for finish forging 5 has a shape that is generally in agreement with
the shape of the forged product 6. Specifically, the rough journal portions Jb of the
blank for finish forging 5 have an axial length equal to that of the journals J of the
forged crankshaft having the final shape ('journals Jc of forged product 6). The
rough crank pin portions Pb of the blank for finish forging 5 have an axial length
equal to that of the crank pins P of the forged crankshaft having the final shape
(crank pins PC of forged product 6), and the amount of eccentricity in the direction
perpendicular to the axial direction is the same between them. However, the
placement angle of the blank for finish forging 5 is, like the forged product 6,
deviated from the specified positions. The rough arm portions Ab of the blank for
finish forging 5 have an axial thickness equal to that of the arms A of the forged
crankshaft having the final shape (arms Ac of forged product 6).
[0090]
In contrast, the rough journal portions Ja of the preform blank 4 have an axial
length equal to that of the rough journal portions Jb of the blank for finish forging 5,
i.e., that of the journals J of the forged crankshaft ('journals Jc of forged product 6).
The rough crank pin portions Pa of the preform blank 4 have an axial length equal to
that of the rough crank pin portions Pb of the blank for finish forging 5, i.e., that of
the crank pins P of the forged crankshaft (crank pins PC of forged product 6), but
have a smaller amount of eccentricity than that of the rough crank pin portions Pb of
the blank for finish forging 5. Specifically, among the rough crank pin portions Pa
of the preform blank 4, the first and third rough crank pin portions Pla and P3a at
opposite ends are eccentric in the same direction with an amount of eccentricity
thereof equal to about a half of an amount of eccentricity in the crank pins P of the
forged crankshaft. On the other hand, the second rough crank pin portion P2a in the
center is eccentric in a direction opposite to an eccentric direction of the first and
third rough crank pin portions Pl a and P3a with an amount of eccentricity equal to
about a half of an amount of eccentricity in the crank pin P of the forged crankshaft.
[009 11
Among the rough arm portions Aa of the preform blank 4, the weighted rough
arm portions Aa (the first, second, fifth and sixth rough a m portions Ala, A2a, A5a,
and A6a) have an axial thickness greater than that of the respective weighted rough
arm portions Ab of the blank for fmish forging 5, i.e., weighted arms A of the forged
crankshaft (the weighted arms Ac of the forged product 6). On the other hand, the
oval rough arm portions Aa of the preform blank 4 (the third and fourth rough arm
portions A3a and A4a) have an axial thickness equal to that of the respective oval
rough arm portions Ab of the blank for finish forging 5, i.e., the oval arms A of the
forged crankshaft (the oval arm Ac).
100921
2-2. Process For Manufacturing Forged Crankshaft
FIG. 9 is a schematic diagram illustrating a process for manufacturing a
forged crankshaft according to the second embodiment. As shown in FIG. 9, the
process for manufacturing the forged crankshaft for the three-cylinder engine of the
second embodiment includes a first preforming step, a second preforming step, a
finish forging step, and a twisting step, and also includes a trimming step before the
twisting step and a coining step after the twisting step as necessary.
100931
The first preforming step is a step in which the preform blank 4 described
above is obtained. The second preforming step is a step in which the blank for
finish forging 5 described above having the final shape of the forged crankshaft
excluding the placement angle of crank pins is obtained from the preform blank 4
described above by using a forming apparatus described in FIG. 10 below. The
finish forging step is a step in which the blank for fmish forging 5 is supplied to be
processed by fmish forging, whereby the forged product 6 described above having
the fmal shape of the forged crankshaft excluding the placement angle of crank pins
is obtained.
100941
The twisting step is a step in which the twisted product 7 described above is
obtained. In the twisting step, in a state in which the journals and the crank pins of
the forged product 6 described above are held and retained, the journals are twisted
around these axial centers in order to adjust the placement angle of the crank pins of
the forged product 6 to the placement angle of the crank pins of the forged crankshaft.
In this manner, the twisted product 7 having a final shape that is in agreement with
the shape of the crankshaft of the forged crankshaft including the placement angle
can be obtained.
[0095]
2-3. Apparatus For Forming Blank For Finish Forging
FIG. 10 is a longitudinal sectional view showing a configuration of the
forming apparatus according to the second embodiment. FIG. 10 illustrates, as an
example, the forming apparatus configured to form the blank for finish forging 5
from the preform blank 4 shown in FIG. 8. It should be noted that in the
longitudinal sectional view shown in FIG. 10, all parts of the rough crank pin
portions are actually on the same plane.
[0096]
In the forming apparatus of the second embodiment shown in FIG. 10, the
preform blank 4 is placed in the dies in a manner such that an eccentric direction of
the rough crank pin portions Pa is in the vertical direction. For example, the
preform blank 4 is placed in a manner such that the first and third rough crank pin
portions Pla and P3a are positioned in the upper side and the second rough crank pin
portion P2a is positioned in the lower side. The preform blank 4 placed in such a
manner is formed into the blank for fmish forging 5. Other than this, the same
configuration is shared with the forming apparatus of the first embodiment shown in
FIG. 4, thus the detailed description thereof will be omitted.
[0097]
FIGS. 11A and 1 IB are longitudinal sectional views illustrating a process for
forming the blank for finish forging using the forming apparatus according to the
second embodiment shown in FIG. 10. Among these figures, FIGS. 11A shows a
forming state at an initial stage and 11B shows a forming state at the completion.
[0098]
As shown in FIG. 11 A, the preform blank 4 is placed in the lower movable
journal dies 10B, stationary journal die 9B, movable crank pin dies 12, and auxiliary
crank pin dies 13, and then the downward movement of the press machine is
performed. This allows the movable journal dies 10U and 10B holding and
retaining each rough journal portion Ja to move axially toward the reference crank
pin die 11 in contact with the second rough crank pin portion P2a. Concurrently,
the movable crank pin dies 12 and the auxiliary crank pin dies 13 in contact with the
first and third rough crank pin portions Pla and P3a are moved axially toward the
reference crank pin die 1 1. By this operation, in the preform blank 4, the weighted
rough arm portions Aa are axially compressed by the movable journal dies 1 OU and
10B, the stationary journal dies 9U and 9B, the reference crank pin die 1 1, and the
movable crank pin dies 12, while the axial lengths of the rough journal portions Ja
and the rough crank pin portions Pa are maintained. Then, the thickness of the
weighted rough arm portions Aa is reduced to the thickness of the weighted rough
arm portions Ab of the blank for finish forging 5 (see FIG. 1 1B).
[0099]
Also, in coordination with the axial movement of the movable journal dies
IOU and 10B as well as that of the movable crank pin dies 12 and the auxiliary crank
pin dies 13, the reference crank pin dies 1 1 and the movable crank pin dies 12 press
the rough crank pin portions Pa of the preform blank 4 in the direction perpendicular
to the axial direction by the operation of each hydraulic cylinders 16. By this
operation, the rough crank pin portions Pa of the preform blank 4 are displaced in the
direction perpendicular to the axial direction, thus despite that the placement angle of
the rough crank pin portions Pa is deviated from the specified positions, the amount
of eccentricity thereof is increased to the amount of eccentricity of the rough crank
pin portions Pb of the blank for finish forging 5 (see FIGS. 8 and 11B).
[O loo]
In this manner, it is possible to form, from the preform blank 4 without a flash,
the blank for finish forging 5 without a flash, which has a shape generally in
agreement with the shape of the forged crankshaft for the three-cylinder engine
(forged final product) excluding the placement angle of the crank pins P. By
supplying such a blank for finish forging 5 without a flash for finish forging, and
performing finish forging with it, it is possible to obtain the forged product 6 having
the final shape of the forged crankshaft for the three-cylinder engine but excluding
the placement angle of the crank pins, although some minor amount of flash is
generated. Then, by performing the twisting on the forged product 6, it is possible
to obtain the final shape of the forged crankshaft for the three-cylinder engine
including the placement angle of the crank pins. Therefore, forged crankshafts for
three-cylinder engines can be manufactured with high material utilization and also
with high dimensional accuracy regardless of their shapes.
[OlOl]
3. Third Embodiment
A third embodiment is based on the configuration of the first and second
embodiments described above. The third embodiment includes modifications in the
relevant parts of the configuration, so that a final shape of a forged crankshaft can be
formed as desired in finish forging step without applying the twisting step in a
process of manufacturing the forged crankshaft.
[O 1021
3-1. Preform Blank, Blank For Finish Forging, and Forged Product
FIG. 12 is a diagram schematically showing the shapes of a preform blank to
be processed by the forming apparatus, a blank for finish forging formed therefrom,
and a forged product after finish forging, in the manufacturing method of the third
embodiment. FIG. 12 shows, similar to FIGS 2 and 8 above, how a three-cylinder
four-counterweight crankshaft is manufactured.
[0 1031
As shown in FIG. 12, the preform blank 4 of the third embodiment has a
crankshaft shape that is approximate to the shape of a forged crankshaft 1 for the
three-cylinder four-counterweight, but is generally in a rough shape. The prefonn
blank 4 includes four rough journal portions Ja, three rough crank pin poftions Pa, a
rough front part portion Fra, a rough flange portion Fla, and six rough arm portions
Aa. The blank for fmish forging 5 of the third embodiment is formed from the
preform blank 4 described above using a forming apparatus, details of which will be
provided below. The blank for finish forging 5 includes four rough journal portions
Jb, three rough crank pin portions Pb, a rough front part portion Frb, a rough flange
portion Flb, and six rough arm portions Ab. The forged product 6 of the third
embodiment is obtained from the blank for finish forging 5 described above by finish
forging. The forged product 6 includes four journals Jc, three crank pins PC, a front
part Frc, a flange Flc, and six arms Ac.
The forged product 6 has a shape that is in agreement with the shape of the
crankshaft (forged final product) including a placement angle of the crank pins PC.
Specifically, the journals Jc of the forged product 6 have an axial length equal to that
of the journals J of the forged crankshaft having the final shape. The crank pins PC
of the forged product 6 have an axial length equal to that of the crank pins P of the
forged crankshaft having the final shape. Further, the crank pins PC of the forged
product 6 have the same amount of eccentricity in a direction perpendicular to an
axial direction and the same placement angle of 120" as the crank pins P of the
forged crankshaft having the final shape, thus they are placed at the specified
positions. The arms Ac of the forged product 6 have an axial thickness equal to that
of arms A of the forged crankshaft having the final shape.
[0 1 051
In contrast, the rough journal portions Jb of the blank for finish forging 5 have
an axial length equal to that of the journals Jc of forged product 6, i.e., that of the
journals J of the forged crankshaft. The rough crank pin portions Pb of the blank
for finish forging 5 have an axial length equal to that of the crank pins PC of forged
product 6, i.e., that of the crank pins P of the forged crankshaft, but both the amount
of eccentricity and the placement angle of the rough crank pin portions Pb are
deviated from the specified positions. Specifically, among the rough crank pin
portions Pb of the blank for finish forging 5, the first and third rough crank pin
portions Plb and P3b at opposite ends are eccentric in the opposite direction to each
other with an amount of eccentricity equal to a 4312 of an amount of eccentricity in
the crank pins P of the forged crankshaft. On the other hand, the second rough
crank pin portion P2b is not eccentric and has an amount of eccentricity of zero.
The rough arm portions Ab of the blank for finish forging 5 have an axial thickness
equal to that of the arms A of the forged crankshaft having the final shape (arms Ac
of forged product 6).
[0 1061
Also, the rough journal portions Ja of the preform blank 4 have an axial length
equal to that of the rough journal portions Jb of the blank for finish forging 5, i.e.,
that of the journals J of the forged crankshaft (journals Jc of forged product 6). The
rough crank pin portions Pa of the preform blank 4 have an axial length equal to that
of the rough crank pin portions Pb of the blank for fmish forging 5, i.e., that of the
crank pins P of the forged crankshaft (crank pins PC of forged product 6). However,
among the rough crank pin portions Pa of the preform blank 4, the first and third
rough crank pin portions Pla and P3a have a smaller amount of eccentricity than that
of the rough crank pin portions Pb of the blank for fmish forging 5, and are eccentric
in the opposite direction to each other with an amount of eccentricity less than the
4312 of the amount of eccentricity in the crank pins P of the forged crankshaft. On
the other hand, the second rough crank pin portion P2a has an amount of eccentricity
of zero, similar to the second rough crank pin portion P2b in the blank for finish
forging 5.
[0 1 071
Among the rough arm portions Aa of the preform blank 4, the weighted rough
arm portions Aa (the first, second, fifth and sixth rough arm portions Ala, A2a, A5a,
and A6a) have an axial thickness greater than that of the respective weighted rough
arm portions Ab of the blank for finish forging 5, i.e., weighted arms A of the forged
crankshaft (the weighted arms Ac of the forged product 6). On the other hand, the
oval rough arm portions Aa of the preform blank 4 (the third and fourth rough arm
portions A3a and A4a) have an axial thickness equal to that of the respective oval
rough arm portions Ab of the blank for finish forging 5, i.e., the oval arms A of the
forged crankshaft (the oval arm Ac).
[0 1081
3-2. Process For Manufacturing Forged Crankshaft
FIG. 13 is a schematic diagram illustrating a process for manufacturing the
forged crankshaft according to the third embodiment. As shown in FIG. 13, the
process for manufacturing the forged crankshaft for the three-cylinder engine of the
third embodiment includes a first preforming step, a second preforming step, and a
finish forging step, and also includes a trimming step and a coining step as necessary.
[0 1 091
The first preforming step is a step in which the preform blank 4 described
above is obtained. The second preforming step is a step in which the blank for
finish forging 5 described above having the final shape of the forged crankshaft is
obtained from the preform blank 4 described above excluding the amount of
eccentricity and the placement angle of all the crank pins, by using a forming
apparatus described in FIG. 14 below.
[Ol 101
The finish forging step is a step in which the forged product 6 described
above is obtained. In the finish forging step, the blank for finish forging 5
described above is supplied to be processed by press forging with a pair of upper and
lower dies in a state in which the first and third rough crank pin portions are
horizontally positioned, whereby all rough crank pin portions are pressed in the
vertical direction perpendicular to the axial direction. By this operation, the forged
product 6 having a shape in agreement with the shape of the crankshaft of the forged
crankshaft having the final shape can be obtained including the placement angle of
the crank pins.
[Olll]
3-3. Apparatus For Forming Blank For Finish Forging
FIG. 14 is a longitudinal sectional view showing a configuration of the
forming apparatus according to the third embodiment. FIG. 14 illustrates, as an
example, the forming apparatus that is used in forming the blank for finish forging 5
from the preform blank 4 shown in FIG. 12. It should be noted that in the
longitudinal sectional view shown in FIG. 14, all parts of the rough crank pin
portions are actually on the same plane.
[0112]
The forming apparatus of the third embodiment shown in FIG. 14 differs from
the forming apparatus of the first embodiment shown in FIG. 4 and the forming
apparatus of the second embodiment shown in FIG. 10 largely in the following. In
the forming apparatus of the third embodiment, the preform blank 4 is placed in the
dies in a manner such that the first and third rough crank pin portions Pla and P3a
which are eccentric in the opposite direction to each other are vertically positioned.
The preform blank 4 in this manner is formed into the blank for finish forging 5. In
this process, the reference crank pin die 1 1 disposed in the location of the second
rough crank pin portion P2a is constrained from moving not only in the axial
direction but also in the direction perpendicular to the axial direction. For this
reason, the reference crank pin die 11 of the third embodiment is, unlike the one in
the first and second embodiments, not coupled to a hydraulic cylinder, instead,
directly mounted to one of the upper die holder 23 and the lower die holder 22. To
the other one, the auxiliary crank pin die 13 forming a pair with the reference crank
pin die 11 is directly mounted. FIG. 14 shows a mode in which the reference crank
pin die 1 1 is mounted to the upper die holder 23 while the auxiliary crank pin die 13
is mounted to the lower die holder 22.
[0113]
Further, in the forming apparatus of the third embodiment, the movable crank
pin dies 12 and the auxiliary crank pin dies 13 are disposed at locations of the rough
crank pin portions Pla and P3a. However, a vertical arrangement of the movable
crank pin dies 12 and the auxiliary crank pin dies 13 is reversed between the
locations of the first and third rough crank pin portions Pla and P3a. This is
because the first and third rough crank pin portions Pla and P3a are eccentric in the
opposite direction to each other in the vertical direction. FIG 14 shows a mode in
which the auxiliary crank pin die 13 at the location of the first rough crank pin
portion Pl a and the movable crank pin die 12 at the location of the third rough crank
pin portion P3a are disposed on the upper side while the movable crank pin die 12 at
the location of the first rough crank pin portion Pla and the auxiliary crank pin die
13 at the location of the third rough crank pin portion P3a are disposed on the lower
side.
[0114]
FIGS. 15A and 15B are longitudinal sectional views illustrating a process for
forming a blank for finish forging using the forming apparatus according to the third
embodiment shown in FIG. 14. Among these figures, FIG. 15A shows a forming
state at an initial stage and 15B shows a forming state at the completion.
[0115]
As sho-wn in FIG. 15A, the preform blank 4 is placed in the lower movable
journal dies 1 OB, stationary journal die 9B, movable crank pin dies 12, and auxiliary
crank pin dies 13, and then the downward movement of the press machine is
performed. Then, the movable journal dies 10U and 10B and the stationary journal
dies 9U and 9B are caused to hold and retain the rough journal portions Ja of the
preform blank 4 therebetween from above and below, and concurrently, the reference
crank pin die 1 1 and the auxiliary crank pin dies 13 are caused to hold and retain the
second rough crank pin portion P2a therebetween from above and below, bringing
into a state in which the first and third rough crank pin portions Pla and P3a are in
contact with the movable crank pin dies 12. In this state, the lowering of the press
machine is continued. This allows the movable journal dies 10U and 10B holding
and retaining each rough journal portion Ja to move axially toward the reference
crank pin die 1 1 holding and retaining the second rough crank pin portion P2a.
Concurrently, the movable crank pin dies 12 and the auxiliary crank pin dies 13 in
contact with the first and third rough crank pin portions Pl a and P3a are moved
axially toward the reference crank pin die 1 1. By this operation, in the preform
blank 4, the weighted rough arm portions Aa are axially compressed by the movable
journal dies 10U and 1 OB, the stationary journal dies 9U and 9B, the reference crank
pin die 1 1, and the movable crank pin dies 12, while the axial lengths of the rough
journal portions Ja and the rough crank pin portions Pa are maintained. Then, the
thickness of the weighted rough arm portions Aa is reduced to the thickness of the
weighted rough arm portions Ab of the blank for finish forging 5 (see FIG. 15B).
[0116]
Also, in coordination with the axial movement of the movable journal dies
IOU and 10B as well as that of the movable crank pin dies 12 and the auxiliary crank
pin dies 13, the movable crank pin dies 12 press the first and third rough crank pin
portions Pla and P3a of the preform blank 4 in the vertical direction perpendicular to
the axial direction by the operation of each hydraulic cylinders 16. By this
operation, the first and third rough crank pin portions Pl a and P3a of the preform
blank 4 are displaced in the vertical direction perpendicular to the axial direction,
thus the amount of eccentricity thereof in the opposite direction to each other is
increased to an amount of eccentricity equal to a d3/2 of an amount of eccentricity in
the crank pins P of the forged crankshaft (see FIGS. 12 and 15B). On the other
hand, the location of the second rough crank pin portion P2a of the preform blank 4
in the vertical direction perpendicular to the axial direction remains unchanged
before and after the forming, thus the amount of eccentricity thereof remains zero.
[0117]
In this manner, it is possible to form, from the preform blank 4 without a flash,
the blank for finish forging 5 without a flash, which has a shape generally in
agreement with the shape of the forged crankshaft for the three-cylinder engine
(forged final product) excluding the amount of eccentricity and the placement angle
of all the crank pins P. Such a blank for finish forging 5 without a flash is supplied
for finish forging, and finish forging is performed with it in a state in which the first
and third rough crank pin portions Pla and P3a are horizontally positioned. In this
process, by pressing all the rough crank pin portions of the blank for finish forging 5
in the vertical direction perpendicular to the axial direction so as to displace them to
the specified positions, it is possible to obtain the final shape of the forged crankshaft
for the three-cylinder engine including the contour shape of arms, and the amount of
eccentricity and the placement angle of the crank pins, although some minor amount
of flash is generated. Therefore, forged crankshafts for three-cylinder engines can
be manufactured with high material utilization and also with high dimensional
accuracy regardless of their shapes.
[0118]
4. Fourth Embodiment
A fourth embodiment includes modifications of the configuration of the third
embodiment.
[0119]
4-1. Preform Blank, Blank For Finish Forging, and Forged Product
FIG. 16 is a diagram schematically showing the shapes of a preform blank to
be processed by the forming apparatus, a blank for finish forging formed therefrom,
and a forged product after finish forging, in the manufacturing method of the fourth
embodiment.
[O 1 201
As shown in FIG. 16, the forged product 6 of the fourth embodiment
maintains the same shape as the forged product 6 of the third embodiment shown in
FIG. 12.
[0121]
In contrast, the blank for finish forging 5 of the fourth embodiment differs
from the blank for finish forging 5 of the third embodiment shown in FIG. 12 in the
following. As shown in FIG. 16, central second rough crank pin portion P2b of the
blank for finish forging 5 of the fourth embodiment is configured to be eccentric in a
direction perpendicular to an eccentric direction of the f ~ satn d third rough crank pin
portions Plb and P3b at opposite ends with an amount of eccentricity equal to that of
the crank pin PC of the forged product 6, i.e., that of the crank pin P of the forged
crankshaft.
[O 1221
Further, the preform blank 4 of the fourth embodiment differs from the
preform blank 4 of the third embodiment shown in FIG. 12 in the following. As
shown in FIG. 16, central second rough crank pin portion P2a of the preform blank 4
of the fourth embodiment is configured to be eccentric in a direction perpendicular to
an eccentric direction of first and third rough crank pin portions Pla'and P3a at
opposite ends with an amount of eccentricity equal to that of the crank pin P of the
forged crankshaft (crank pin PC of forged product 6), the configuration similar to that
of the blank for finish forging 5.
[0 1231
4-2. Process For Manufacturing Forged Crankshaft
FIG. 17 is a schematic diagram illustrating a process for manufacturing a
forged crankshaft according to the fourth embodiment. As shown in FIG. 17, the
process for manufacturing the forged crankshaft of the fourth embodiment, similar to
the third embodiment shown in FIG. 13, includes a first preforming step, a second
preforming step, and a the finish forging step, and also includes a trimming step and
a coining step as necessary.
[0 1241
The f ~ sptre forming step is a step in which the preform blank 4 described
above is obtained.
[0 1251
The second preforming step is a step in which the blank for finish forging 5
described above is obtained. In the second preforming step, the same forming
apparatus used in the third embodiment shown in FIGS. 14, 15A and 15B is used.
It should be noted that in the longitudinal sectional view shown in FIG. 14, the
second rough crank pin portion in the fourth embodiment is in reality located either
in the front or back side of the paper.
[0 1261
In the second preforming step of the fourth embodiment, as similarly found in
the third embodiment shown in FIGS. 14, 15A, and 15B, the preform blank 4 is
placed in the lower journal die 10B, the stationary journal dies 9B, the movable
crank pin die 12, and the auxiliary crank pin dies 13, and then the downward
movement of the press machine is performed. This allows the movable journal dies
IOU and 10B holding and retaining each rough journal portion Ja, and the movable
crank pin dies 12 and the auxiliary crank pin dies 13 in contact with the first and
third rough crank pin portions Pla and P3a to move axially toward the reference
crank pin die 1 1 herding and retaining the second rough crank pin portion P2a. In
conjunction with this movement, in the preform blank 4, the weighted rough arm
portions Aa are axially compressed while the axial lengths of the rough journal
portions Ja and the rough crank pin portions Pa are maintained. Then, the thickness
of the weighted rough arm portions Aa is reduced to the thickness of the weighted
rough arm portions Ab of the blank for finish forging 5.
[0127]
Further, the first and third rough crank pin portions Pla and P3a are pressed
by the movable crank pin dies 12 in the vertical direction perpendicular to the axial
direction. In this manner, the first and third rough crank pin portions Pla and P3a
of the preform blank 4 become eccentric in the opposite direction to each other with
an amount of eccentricity increased to a 4312 of an amount of eccentricity in the
crank pins P of the forged crankshaft. On the other hand, the location of the second
rough crank pin portion P2a of the preform blank 4 in the direction perpendicular to
the axial direction remains unchanged before and after the forming, thus an amount
of eccentricity remains the same as that of the crank pin P of the forged crankshaft.
[0128]
In this manner, it is possible to form, from the preform blank 4 without a flash,
the blank for finish forging 5 without a flash, which has a shape generally in
agreement with the shape of the forged crankshaft for the three-cylinder engine
(forged final product) excluding the amount of eccentricity and the placement angle
of the first and third crank pins P1 and P3.
[0129]
The finish forging step is a step in which the forged product 6 described
above is obtained. In the finish forging step, the blank for finish forging 5 is
supplied to be processed for finish forging in a state that in which the first and third
rough crank pin portions are horizontally positioned. In this process, by pressing
the first and third rough crank pin portions Plb and P3b of the blank for finish
forging 5 in the vertical direction perpendicular to the axial direction so as to
displace them to the specified positions, it is possible to obtain the forged product 6
having a shape in agreement with the shape of the crankshaft of the forged crankshaft
for the three-cylinder engine having the final shape including the contour shape of
arms, and the amount of eccentricity and the placement angle of the crank pins,
although some minor amount of flash is generated.
[0130]
The present invention is not limited to the embodiments described above, and
various modifications may be made without departing from the spirit and scope of
the present invention. For example, the mechanism for causing the movable journal
dies to move axially is not limited to the one described in the above embodiments, in
which a wedge mechanism of a press machine is employed. Alternatively, a link
mechanism may be employed, or a hydraulic cylinder or a servo motor or the like
may be employed in place of the press machine. Furthermore, the mechanism for
causing the crank pin dies to move in the direction perpendicular to the axial
direction is not limited to a hydraulic cylinder, and it may be a servo motor.
[0131]
In the embodiments described above, the inclined surfaces are provided to the
end surface of the movable journal dies, as wedge mechanisms to move axially the
movable journal dies, and wedges are provided correspondingly to these inclined
surfaces. As wedge mechanisms instead to this, a block having an inclined surface
may be fixed to a side section outside the first impression and the second impression
of the movable journal die, and a wedge may be provided correspondingly to the
inclined surface of this block.
Furthermore, the embodiments described above have such a configuration that
the upper die holder is secured to the upper pressure pad while the lower die holder is
resiliently supported on the lower pressure pad on which the wedges are installed,
and the upper and lower movable journal dies are allowed to move by the wedges,
but alternatively, the functions of the upper section and the lower section may be
reversed. The configuration may also be such that the upper and lower die holders
are resiliently supported on the corresponding pressure pads, and that wedges are
installed on both pressure pads so that the upper and lower movable journal dies are
caused to move by their corresponding wedges.
[0133]
Furthermore, in the above embodiments, the auxiliary crank pin dies are
movable only axially, but they may be made to be movable also in a direction toward
the crank pin dies forming pairs. In this case, the crank pin dies and the auxiliary
crank pin dies hold and retain the rough crank pin portions Pa therebetween from
above and below and meanwhile move in the direction perpendicular to the axial
direction cooperatively with each other.
[0134]
Furthermore, the embodiments described above have such a configuration that
the rough crank pin portions Pa are pressed in the vertical direction by moving the
crank pin dies in the direction perpendicular to the axial direction, however the
configuration may also be such that the locations of the crank pin dies and the journal
8
dies are changed so as to horizontally press the rough crank pin portions Pa.
INDUSTRIAL APPLICABILITY
[0135]
The present invention is useful in manufacturing forged crankshafts for threecylinder
engines.
REFERENCE SIGNS LIST
[0136]
1 : forged crankshaft
J, J1 to 54: journals
P, Pl to P3: crank pins
Fr: front part
F1: flange
A, A1 to A6: crank arms
2: billet
4: preform blank
Ja, Jla to J4a: rough journal portions
Pa, Pla to P3a: rough crank pin portions
Fra: rough front part portion
Fla: rough flange portion
Aa, A1 a to A6a: rough crank arm portions
5: blank for finish forging
Jb, Jl b to J4b: rough journal portions of blank for finish forging
Pb, Plb to P3b: rough crank pin portions of blank for finish forging
Frb: rough front part portion of blank for finish forging
Flb: rough flange portion of blank for finish forging
Ab, A1 b to A6b: rough crank arm portions of blank for finish forging
5a: fin flaws
6: forged product
Jc, Jlc to J4c: journals of forged product
PC, Plc to P3c: crank pins of forged product
Frc: front part of forged product
Flc: flange of forged product
Ac, Alc to A6c: crank arms of forged product
7: twisted product
Jd, Jl d to J4d: journals of twisted product
Pd, Pld to P3d: crank pins of twisted product
Frd: front part of twisted product
Fld: flange of twisted product
Ad, A1 d to A6d: crank arms of twisted product
9U, 9B: stationary journal dies
9Ua, 9Ba: first impression of stationary journal die
9Ub, 9Bb: second impression of stationary journal die
9Uc, 9Bc: third impression of stationary journal die
1 OU, 10B: movable journal dies
1 OUa, 10Ba: first impression of movable journal die
1 OUb, 10Bb: second impression of movable journal die
1 1 : reference crank pin die
1 1 a: impression
12: movable crank pin die
12a: impression
13: auxiliary crank pin die
13a: impression
14U, 14B: inclined surfaces of journal dies for first and fourth rough journal portions
16: hydraulic cylinder
20: lower pressure pad
2 1 : upper pressure pad
22: lower die holder
23: upper die holder
24: resilient member
25: support post
26: wedge

We claim:
1. An apparatus for forming a blank for finish forging for a forged crankshaft for
a three-cylinder engine in which third and fourth crank arms connecting with a
second crank pin in a center have no balance weights and remaining crank arms have
balance weights, the apparatus configured to form, from a preform blank, in a
process of manufacturing the forged crankshaft for a three-cylinder engine, the blank
for finish forging to be subjected to finish forging by which a final shape of the
forged crankshaft is obtained,
the preform blank including:
rough journal portions having an axial length equal to an axial length of
journals of the forged crankshaft;
rough crank pin portions having an axial length equal to an axial length of
crank pins of the forged crankshaft;
third and fourth rough crank arm portions corresponding to the third and
fourth crank arms of the forged crankshaft, having an axial thickness equal to an
axial thickness of such crank arms; and
weighted rough crank arm portions corresponding to weighted crank arms
having the balance weights of the f6rged crankshaft, having an axial thickness
greater than an axial thickness of such crank arms,
the rough crank pin portions of the preform blank having a smaller amount of
eccentricity in a direction perpendicular to an axial direction than an amount of
eccentricity of the crank pins of the forged crankshaft,
the forming apparatus comprising:
a reference crank pin die disposed at a location of the second rough crank pin
portion, the reference crank pin die configured to be brought into contact with the
second rough crank pin portion, the reference crank pin die configured to move in a
direction perpendicular to the axial direction, but be constrained from moving axially,
while being in contact with side surfaces of the third and fourth rough crank a m
portions through which the third and fourth rough crank arm portions connect with
the second rough crank pin portion;
movable crank pin dies disposed at locations of the corresponding first and
third rough crank pin portions at opposite ends, the movable crank pin dies
configured to be brought into contact with the first and third rough crank pin portions,
the movable crank pin dies configured to move axially toward the reference crank
pin die and in the direction perpendicular to the axial direction, while being in
contact with side surfaces of the rough crank arm portions through which the rough
crank arm portions connect with the first and third rough crank pin portions;
stationary journal dies disposed at locations of the rough journal portions
connecting with the third and fourth rough crank arm portions, the stationary journal
dies configured to hold and retain such rough journal portions therebetween in the
direction perpendicular to the axial direction, the stationary journal dies configured
to be constrained from moving axially while being in contact with side surfaces of
the third and fourth rough crank arm portions; and
movable journal dies disposed at locations of the corresponding rough journal
portion excluding the rough journal portions connecting with the third and fourth
rough crank arm portions, the movable journal dies configured to hold and retain
such rough journal portions therebetween in the direction perpendicular to the axial
direction, the movable journal dies configured to move axially toward the reference
crank pin die while being in contact with side surfaces of the rough crank arm
portions through which the rough crank arm portions connect with such rough
journal portions,
wherein, in a state where the rough journal portions are held and retained by
the stationary journal dies and the movable journal dies, and the rough crank pin
portions are contacted by the reference crank pin die and the movable crank pin dies,
the movable journal dies are moved axially, the movable crank pin dies are moved
axially and in the direction perpendicular to the axial direction, and the reference
crank pin die is moved in the direction perpendicular to the axial direction, thereby
compressing the weighted rough crank arm portions in the axial direction so as to
reduce the thickness thereof to the thickness of the weighted crank arms of the forged
crankshaft, and pressing the rough crank pin portions in the direction perpendicular
to the axial direction so as to increase the amount of eccentricity thereof to the
amount of eccentricity of the crank pins of the forged crankshaft.
2. The apparatus for forming a blank for fmish forging for a forged crankshaft
for a three-cylinder engine according to claim 1,
wherein the reference crank pin die and the movable crank pin dies each
includes an auxiliary crank pin die disposed at a location outside of the
corresponding rough crank pin portion, opposite to the side where the reference
crank pin die and the movable crank pin dies are contacted, and
wherein in conjunction with the axial movement of the movable journal dies
as well as that of the movable crank pin dies and the auxiliary crank pin dies forming
pairs therewith, a movement of the movable crank pin dies in the direction
perpendicular to the axial direction is controlled in a manner that the rough crank pin
portions to be deformed by pressing reach the auxiliary crank pin dies after spaces
between the movable journal dies, and the movable crank pin dies and the auxiliary
crank pin dies are filled.
3. The apparatus for forming a blank for fmish forging for a forged crankshaft
for a three-cylinder engine according to claim 2,
wherein, provided that a total length of movement of the movable crank pin
dies in the direction perpendicular to the axial direction is a 100% length of
movement thereof, when the axial movement of the movable journal dies that are
adjacent to such movable crank pin dies is completed, a length of movement of such
movable crank pin dies in the direction perpendicular to the axial direction is 90% or
less of the total length of movement, and thereafter, the movement of such movable
crank pin dies in the direction perpendicular to the axial direction is completed.
4. The apparatus for forming a blank for finish forging for a forged crankshaft
for a three-cylinder engine according to any one of claims 1 to 3,
wherein the reference crank pin die, the movable crank pin dies, the stationary
journal dies, and the movable journal dies are mounted on a press machine that is
capable of being moved downward along the direction perpendicular to the axial
direction, and
wherein, by the downward movement of the press machine, the stationary
journal dies and the movable journal dies are caused to hold and retain the rough
journal portions therebetween, the reference crank pin die and the movable crank pin
dies are brought into contact with the rough crank pin portions, and with continued
downward movement of the press machine, the movable journal dies are moved
axially by wedge mechanisms, and the movable crank pin dies are caused to move
axially by the movement of the movable journal dies.
5. The apparatus for forming a blank for finish forging for a forged crankshaft
for a three-cylinder engine according to claim 4,
wherein the wedge mechanisms have different wedge angles for each of the
movable journal dies.
6. The apparatus for forming a blank for finish forging for a forged crankshaft
for a three-cylinder engine according to claim 4 or 5,
wherein the reference crank pin die and the movable crank pin dies are
coupled to hydraulic cylinders and caused to move in the direction perpendicular to
the axial direction by driving the hydraulic cylinders.
7. An apparatus for forming a blank for finish forging for a forged crankshaft for
a three-cylinder engine in which third and fourth crank arms connecting with a
second crank pin in a center have no balance weights and remaining crank arms have
balance weights, the apparatus configured to form, from a preform blank, in a
process of manufacturing the forged crankshaft for a three-cylinder engine, the blank
for finish forging to be subjected to finish forging by which a final shape of the
forged crankshaft is obtained,
the preform blank including:
rough journal portions having an axial length equal to an axial length of
journals of the forged crankshaft;
rough crank pin portions having an axial length equal to an axial length of
crank pins of the forged crankshaft;
third and fourth rough crank arm portions corresponding to the third and
fourth crank arms of the forged crankshaft, having an axial thickness equal to an
axial thickness of such crank arms; and
weighted rough crank arm portions corresponding to weighted crank arms
having the balance weights of the forged crankshaft, having an axial thickness
greater than an axial thickness of such crank arms,
the first and third rough crank pin portions at opposite ends of the preform
blank having an amount of eccentricity in a direction perpendicular to the axial
direction in the opposite direction to each other, the amount of eccentricity thereof
being smaller than a 4312 of an amount of eccentricity of the crank pins of the forged
crankshaft, the second rough crank pin portion in the center of the preform blank
having an amount of eccentricity of zero in the direction perpendicular to the axial
direction or having an amount of eccentricity in a direction perpendicular to an
eccentric direction of the first and third rough crank pin portions, the amount of
eccentricity thereof being equal to the amount of eccentricity of the crank pins of the
forged crankshaft,
the forming apparatus comprising:
reference crank pin die disposed at a location of the second rough crank pin
portion, the reference crank pin die configured to be brought into contact with the
second rough crank pin portion, the reference crank pin die configured to be
constrained from moving axially while being in contact with side surfaces of the
third and fourth rough crank arm portions through which the rough crank arm
portions connect with the second rough crank pin portion;
movable crank pin dies disposed at locations of the corresponding first and
third rough crank pin portions, the movable crank pin dies configured to be brought
into contact with the first and third rough crank pin portions, the movable crank pin
dies configured to move axially toward the reference crank pin die and in the
direction perpendicular to the axial direction, while being in contact with side
surfaces of the rough crank arm portions through which the rough crank arm portions
connect with the first and third rough crank pin portions;
stationary journal dies disposed at locations of the rough journal portions
connecting with the third and fourth rough crank arm portions, the stationary journal
dies configured to hold and retain such rough journal portions therebetween in the
direction perpendicular to the axial direction, the stationary journal dies configured
to be constrained from moving axially, while being in contact with side surfaces of
the third and fourth rough crank arm portions; and
movable journal dies disposed at locations of the corresponding rough journal
portion excluding the rough journal portions connecting with the third and fourth
rough crank arm portions, the movable journal dies configured to hold and retain
such rough journal portions therebetween in the direction perpendicular to the axial
direction, the movable journal dies configured to move axially toward the reference
crank pin die while being in contact with side surfaces of the rough crank arm
portions through which the rough crank arm portions connect with such rough
journal portions,
wherein, in a state where the rough journal portions are held and retained by
the stationary journal dies and the movable journal dies, and the rough crank pin
portions are contacted by the reference crank pin die and the movable crank pin dies,
the movable journal dies are moved axially and the movable crank pin dies are
moved axially and in the direction perpendicular to the axial direction, thereby
compressing the weighted rough crank arm portions in the axial direction so as to
reduce the thickness thereof to the thickness of the weighted crank arms of the forged
crankshaft, and pressing the first and third rough crank pin portions in the direction
perpendicular to the axial direction but in an opposite direction to each other, so as to
increase an amount of eccentricity thereof to the 4312 of an amount of eccentricity of
the crank pins of the forged crankshaft.
8. The apparatus for forming a blank for finish forging for a forged crankshaft
for a three-cylinder engine according to claim 7,
wherein the reference crank pin die and the movable crank pin dies each
includes an auxiliary crank pin die disposed at a location outside of the
corresponding rough crank pin portion, opposite to the side where the reference
crank pin die and the movable crank pin dies are contacted, and
wherein in conjunction with the axial movement of the movable journal dies
as well as that of the movable crank pin dies and the auxiliary crank pin dies forming
pairs therewith, a movement of the movable crank pin dies in the direction
perpendicular to the axial direction is controlled in a manner that the rough crank pin
portions to be deformed by pressing reach the auxiliary crank pin dies after spaces
between the movable journal dies, and the movable crank pin dies and the auxiliary
crank pin dies are filled.
9. The apparatus for forming a blank for finish forging for a forged crankshaft
for a three-cylinder engine according to claim 8,
wherein, provided that a total length of movement of the movable crank pin
dies in the direction perpendicular to the axial direction is a 100% length of
movement thereof, when the axial movement of the movable journal dies that are
adjacent to such movable crank pin dies is completed, a length of movement of such
movable crank pin dies in the direction perpendicular to the axial direction is 90% or
less of the total length of movement, and thereafter, the movement of such movable
crank pin dies in the direction perpendicular to the axial direction is completed.
10. The apparatus for forming a blank for finish forging for a forged crankshaft
for a three-cylinder engine according to any one of claims 7 to 9,
wherein the reference crank pin die, the movable crank pin dies, the stationary
journal dies, and the movable journal dies are mounted on a press machine that is
capable of being moved downward along the direction perpendicular to the axial
direction, and
wherein, by the downward movement of the press machine, the stationary
journal dies and the movable journal dies are caused to hold and retain the rough
journal portions therebetween, the reference crank pin die and the movable crank pin
dies are brought into contact with the rough crank pin portions, and with continued
downward movement of the press machine, the movable journal dies are moved
axially by wedge mechanisms, and the movable crank pin dies are caused to move
axially by the movement of the movable journal dies.
1 1. The apparatus for forming a blank for fmish forging for a forged crankshaft
for a three-cylinder engine according to claim 10,
wherein the wedge mechanisms have different wedge angles for each of the
movable journal dies.
12. The apparatus for forming a blank for finish forging for a forged crankshaft
for a three-cylinder engine according to claim 10 or 1 1,
wherein the movable crank pin dies are coupled to hydraulic cylinders and
caused to move in the direction perpendicular to the axial direction by driving the
hydraulic cylinders. .
13. A method for forming a forged crankshaft for a three-cylinder engine in
which third and fourth crank arms connecting with a second crank pin in a center
have no balance weights and remaining crank arms have balance weights,
comprising the successive steps of
a first preforming step for forming, as the preform blank to be supplied to the
forming apparatus according to any one of claims 1 to 6, a preform blank in which
first and third rough crank pin portions at opposite ends have an amount of
eccentricity in a direction perpendicular to the axial direction in the opposite
direction to each other, the amount of eccentricity thereof being equal to a 4312 of an
amount of eccentricity of the crank pins of the forged crankshaft, and a second rough
crank pin portion in the center has an amount of eccentricity in the direction
perpendicular to the axial direction, in a direction perpendicular to an eccentric
direction of the first and third rough crank pin portions, the amount of eccentricity
thereof being smaller than the amount of eccentricity of the crank pins of the forged
crankshaft;
a second preforming step for forming, as the blank for finish forging, a blank
for finish forging in which a final shape of the forged crankshaft is formed including
a placement angle of the crank pins using the forming apparatus according to any one
of claims 1 to 6; and
a finish forging step for, by performing finish forging on the blank for finish
forging, forming a forged product having the final shape of the forged crankshaft
including the placement angle of the crank pins.
14. A method for forming a forged crankshaft for a three-cylinder engine in
which third and fourth crank arms connecting with a second crank pin in a center
have no balance weights and remaining crank arms have balance weights,
comprising the successive steps of:
a first preforming step for forming, as the preform blank to be supplied to the
forming apparatus according to any one of claims 1 to 6, a preform blank in which
first and third rough crank pin portions at opposite ends have an amount of
eccentricity in a direction perpendicular to the axial direction in the same direction,
the amount of eccentricity thereof being smaller than an amount of eccentricity of the
crank pins of the forged crankshaft, and a second rough crank pin portion in the
center has an amount of eccentricity in the direction perpendicular to the axial
direction, in the opposite direction of an eccentric direction of the first and third
rough crank pin portions, the amount of eccentricity thereof being smaller than the
amount of eccentricity of the crank pins of the forged crankshaft;
a second preforming step for forming, as the blank for finish forging, a blank
for finish forging in which a final shape of the forged crankshaft is formed excluding
a placement angle of the crank pins using the forming apparatus according to any one
of claims 1 to 6;
a finish forging step for forming, by performing finish forging on the blank
for finish forging, a forged product having the final shape of the forged crankshaft
excluding the placement angle of the crank pins; and
a twisting step for adjusting the placement angle of the crank pins of the
forged product to the placement angle of the crank pins of the forged crankshaft.
15. A method for forming a forged crankshaft for a three-cylinder engine in
which third and fourth crank arms connecting with a second crank pin in a center
have no balance weights and remaining crank arms have balance weights,
comprising the successive steps of:
a first preforming step for forming, as the preform blank to be supplied to the
forming apparatus according to any one of claims 7 to 12, a preform blank in which
the first and third rough crank pin portions at opposite ends have an amount of
eccentricity in a direction perpendicular to the axial direction in the opposite
direction to each other, the amount of eccentricity thereof being smaller than a d3/2
of an amount of eccentricity of the crank pins of the forged crankshaft, and the
second rough crank pin portion in the center has the amount of eccentricity of zero in
the direction perpendicular to the axial direction;
a second preforming step for forming, using the forming apparatus according
to any one of claims 7 to 12, as the blank for finish forging, a blank for finish forging
in which first and third rough crank pin portions at opposite ends have an amount of
eccentricity in the direction perpendicular to the axial direction in the opposite
direction to each other, the amount of eccentricity thereof being equal to the 4312 of
the amount of eccentricity of the crank pins of the forged crankshaft, and a second
rough crank pin portion in the center remains the same amount of eccentricity in the
direction perpendicular to the axial direction as the preform blank; and
a finish forging step for forming a forged product having a final shape of the
forged crankshaft including a placement angle of the crank pins by performing finish
forging on the blank for finish forging in a state in which the first and third rough
crank pin portions at opposite ends are horizontally positioned whereby all the rough
crank pin portions are pressed in the direction perpendicular to the axial direction.
16. A method for forming a forged crankshaft for a three-cylinder engine in
which third and fourth crank arms connecting with a second crank pin in a center
have no balance weights and remaining crank arms have balance weights,
comprising the successive steps of:
a first preforming step for forming, as the preform blank to be supplied to the
forming apparatus according to any one of claims 7 to 12, a preform blank in which
first and third rough crank pin portions at opposite ends have an amount of
eccentricity in a direction perpendicular to the axial direction in the opposite
direction to each other, the amount of eccentricity thereof being smaller than a 43/2
of an amount of eccentricity of the crank pins of the forged crankshaft, and a second
rough crank pin portion in the center has an amount of eccentricity in the direction
perpendicular to the axial direction, in a direction perpendicular to an eccentric
direction of the first and third rough crank pin portions, the amount of eccentricity
thereof being equal to the amount of eccentricity of the crank pins of the forged
crankshaft;
a second preforming step for forming, using the forming apparatus according
to any one of claims 7 to 12, as the blank for finish forging, a blank for finish forging
in which the first and third rough crank pin portions at opposite ends have an amount
of eccentricity in the direction perpendicular to the axial direction in the opposite
direction to each other, the amount of eccentricity thereof being equal to the 4312 of
the amount of eccentricity of the crank pins of the forged crankshaft, and the second
rough crank pin portion in the center remains the same amount of eccentricity in the
direction perpendicular to the axial direction as the preform blank; and
a finish forging step for forming a forged product having a final shape of the
forged crankshaft including a placement angle of the crank pins by performing finish
forging on the blank for finish forging in a state in which the first and third rough
crank pin portions at opposite ends are horizontally positioned whereby the f ~ satn d
third rough crank pin portions are pressed in the direction perpendicular to the axial
direction.