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
straight-6-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
straight-6-cylinder engine including preforming steps using such forming apparatus.
BACKGROUND ART
[0002]
A crankshaft is a principal component of a reciprocating engine, by which
power is taken out 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. For straight-6-cylinder engines for
automobiles such as passenger cars, freight cars, and specialized work vehicles, it is
necessary that their crankshafts have high strength and stiffness, and therefore forged
crankshafts, which are more capable of meeting the need, are widely used. For
straight-6-cylinder engines of motorcycles, agricultural machines, marine vessels, and
the like, forged crankshafts are also used.
[0003]
In general, forged crankshafts for straight-6-cylinder engines are manufactured
by using, as a starting material, a billet, and subjecting the billet to the steps of
preforming, die forging, trimming and coining in order. The billet has a circular or
square cross section and has a constant cross-sectional area along the overall length.
The preforming step includes roll for~iiing 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 crankshalt for a straight-6-cylinder engine. A crankshaft 1
illustrated in FIG. I is to be mounted in a straight-6-cylinder engine. It is a
straight-6-cylinder 8-counterweight crankshaft that includes: seven journals J 1 to 57; six
crank pins P1 to P6; a front part Fr; a flange F1; and twelve crank arms (hereinafter
referred to as "arms" to be simple) A I to A 12 that alternatively connect the journals J 1
to 57 and the crank pins PI to P6 to each other. This crankshaft 1 is a
straight-6-cylinder 8-counterweight crankshaft. Among the twelve arms A1 to A12,
first and second arms A1 and A2, and the eleventh and twelfth arms A I 1 and A 12
respectively connecting with the first and sixth crank pins PI and P6 at opposite ends,
and fifth to eighth arms A5 to A8 connecting with central third and fourth crank pins P3
and P4 have balance weights. Hereinafter, when the journals J1 to 57, the crank pins
P1 to P6, and the arms A l to A12 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.
[OOOS]
According to the man~ifacturingm ethod shown in FIG. I , the forged crankshaft
1 is manufactured in the following manner. Firstly, a billet 2 shown in FIG. ](a),
which has been previously cut to a predetermined length, is heated by a heating 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. I(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. I (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 cra~lkshaft( 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 f~~rther
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. I(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 FI, and in some cases the arms A), are slightly pressed with
dies from above and below and formed into a desirgd size and shape. Finally, the
forged crankshaft 1 is manufactured.
[OOOS]
The manufacturing process shown in FIG. 1 is applicable not only to a
straight-6-cylinder-8-counterweight crankshaft as exemplified, but also to a
straight-6-cylinder-12-counterweight crankshaft (hll-counterweight). In a
straight-6-cylinder-12-counterweight crankshaft, all of twelve arms A have balance
weights. 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 improvenient of material utilization. Examples of conventional
techniques that address this object are as follows.
[OO 1 01
For example, Japanese Patent Application Publication No. 2008-155275
(Patent Literature 1 ) and Japanese Patent Application Publication No. 20 1 1-1 61 496
(Patent Literature 2) disclose techniques for manufacturing a crankshaft, by which
journals and crank pins are shaped and arms are roughly shaped. In a 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 used as a blank. Then, a pair
of the 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, the opposing dies are axially
moved toward each other to compressively deform the 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 to place the portion to
be formed into a crank pin into an eccentric position. The above operations are
repeated in succession for all crank throws.
[OOI I]
Further, in a technique of Patent Literature 2, a simple round bar is used as a
blank. Then, one end of the two ends of the round bar is held with a stationary die and
the other end thereof is held with a movable die, and portions to be formed into journals
are held with journal dies and portions to be formed into crank pins are held 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 of 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
[00 1 31
Patent Literature 1 : Japanese Patent Application Publication No. 2008-1 55275
Patent Literature 2: Japanese Patent Application I'ublication No. 20 1 1 - 16 1496
SUMMARY OF INVENTION
TECHNICAL PROBLEM
[OO 1 41
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 stifiess, thus blanks for
the forged crankshaft are not easily deformable. As such, crankshafts that wo~~blde
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 arms are limited to a simple
shape without a balance weight.
[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.
[OO 1 61
The present invention has been made in view of the above-mentioned problems.
Accordingly, in order to manufacture forged crankshafts for straight-6-cylinder 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 straight-6-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 one embodiment of the present invention is
an apparatus for forming, in the process of manufacturing the forged crankshaft for a
straight-6-cylinder engine, the blank for finish forging to be subjected to finish forging
by which a final shape of the forged crankshaft is formed, from a preform blank. 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; and rough crank
arm portions having an axial thickness greater than an axial thickness of crank arms of
the forged crankshaft.
The apparatus for forming a blank for finish forging a forged crankshaft for a
straight-6-cylinder engine according to the present embodiment further has the
following configurations (1) or (2).
[00 1 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 stationary journal dies, movable journal dies,
and movable crank pin dies, described below.
The stationary journal dies are disposed at a location of a central fourth rough
journal portion, configured to hold and retain the fourth rough journal portion
therebetween in the direction perpendicular to the axial direction, and configured to be
constrained from moving in the axial direction while being in contact with side surfaces
of rough crank arm portions through which the rough crank arm portions connect with
the fourth rough journal portion.
The movable journal dies are disposed at locations of the corresponding rough
journal portions excluding the rough journal portion held by the stationary journal dies,
configured to hold and retain the rough journal portions therebetween in the direction
perpendicular to the axial direction, and configured to move axially toward the
stationary journal dies while being in contact with side surfaces of rough crank arm
portions through which the rough crank arm portions connect with the rough journal
portions.
The movable crank pin dies are disposed at locations of the corresponding
rough crank pin portions, configured to be brought into contact with such rough crank
pin portions, and configured to move axially toward the stationary journal dies 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 such rough crank pin portions.
The forming apparatus is configured such that in a state that 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 with 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. 'Thereby, the rough crank arm
portions are compressed in the axial direction so as to reduce the thickness thereof to the
thickness of crank arms of the forged crankshaft, and the rough crank pin portions are
pressed 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 1 91
In the above forming apparatus in (I), it is preferred that 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 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, 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
stationary journal dies and the movable journal dies, and 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 pill dies in the direction perpendicular
to the axial direction is a 100% length of movement thereof, wllell the axial movement
of the nlovable 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 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, 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 while 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 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.
[002 31
(2) Among the rough crank pin portions in the preform blank, the first and sixth
rough crank pin portions at opposite ends and the central third and fourth rough crank
pin portions 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
smaller than a 4312 of an amount of eccentricity of crank pins of the forged crankshaft.
The second and fifth rough crank pin portions have an amount of eccentricity in the
direction perpendicular to the axial direction that is zero, or equal to the amount of
eccentricity of the crank pins of the forged crankshaft in the direction perpendicular to
the eccentric direction of the first and sixth rough crank pin portions and the third and
fourth rough crank pin portions.
The forming apparatus includes stationary journal dies, movable journal dies,
first movable crank pin die, and second movable crank pin die, described below.
The stationary journal dies are disposed at a location of a central fourth rough
journal portion, configured to hold and retain the fourth rough journal portion
therebetween in the direction perpendicular to the axial direction, and configured to be
constrained from moving in the axial direction while being in contact with side surfaces
of rough crank arm portions through which the rough crank arni portions connect with
the fourth rough journal portion.
The movable journal dies are disposed at locations of the corresponding rough
journal portions excluding the rough journal portion held by the stationary journal dies,
configured to hold and retain the rough journal portions therebetween in the direction
perpendicular to the axial direction, and configured to move axially toward the
stationary journal dies while being in contact with side surfaces of rough crank arm
portions through which the rough crank arm portions connect with the rough journal
portions.
The first movable crank pin dies are disposed at locations of the corresponding
second and fifth rough crank pin portions, configured to be brought into contact with the
second and fifth rough crank pin portions, and configured to move axially toward the
stationary journal dies, while being in contact with side surfaces of rough crank arm
portions through which the rough crank arm portions connect with the second and fifth
rough crank pin portions.
The second movable crank pin dies are disposed at locations of corresponding
first, third, fourth, and sixth rough crank pin portions, configured to be brought into
contact with the first, third, fourth, and sixth rough crank pin portions, and configured to
move axially toward the stationary journal dies 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, third, fourth,
and sixth rough crank pin portions.
The forming apparatus is configured such that in a state that the rough journal
portions are held and retained by the stationary journal dies and the movable journal
dies and contacted with the first movable crank pin dies and the second movable crank
pin dies, the movable journal dies and the first movable crank pin dies are moved
axially, and the second movable crank pin dies are moved axially and in the direction
perpendicular to the axial direction. With this, the rough crank arm portions are
axially compressed to reduce their thickness to that of the crank arms of the forged
crankshaft, and the first, third, fourth, and sixth rough crank pin portions are pressed in
the direction perpendicular to the axial direction, but in the opposite direction to each
other, so as to increase the amount of eccentricity to 4312 of the amount of eccentricity
of the crank pins of the forged crankshaft.
[0024]
The manufacturing method according to embodiments of the present invention
is a method for manufacturing a forged crankshaft for a straight-&cylinder engine, and
includes any one of configurations (3) to (6) described below.
[002 51
(3) A method for manufacturing a forged crankshaft for a straight-6-cylinder
engine includes the following successive steps comprising a first preforming step, a
second preforming step, and a finish forging step.
The first preforming step forms the preform blank to be supplied to the above
forming apparatus in ( 1 ) . In the preform blank, among the rough crank pin portions,
the first and sixth rough crank pin portions at opposite ends and the third and fourth
rough crank pin portions in the center have an amount of eccentricity in the direction
perpendicular to the axial direction, but in the opposite direction to each other, the
amount of eccentricity being equal to 4312 of an amount of eccentricity of the crank
pins of the forged crankshaft. The second and fifth rough crank pin portions of the
preform blank have 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
sixth rough crank pin portions, and the third and fourth rough crank pin portions than an
amount of eccentricity of the crank pin of the forged crankshaft.
The second preforming step forms, 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 above forming apparatus described in (1).
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 a forged crankshaft for a straight-6-cylinder
engine includes the following successive steps colnprising a first preforming step, a
second preforming step, a finish forging step, and a twisting step.
The first preforming step forms the preform blank to be supplied to the above
forming apparatus in (I). In the preform blank, among the rough crank pin portions,
the first and sixth rough crank pin portions at opposite ends and the third and fourth
rough crank pin portions in the center have an amount of eccentricity in the 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. The second and fifth rough crank pin portions of the preform blank have
an amount of eccentricity in the direction perpendicular to the axial direction in the
direction opposite to the eccentric direction of the first, third, fourth, and sixth rough
crank pin portions, the amount of eccentricity thereof being smaller than an amount of
eccentricity of the crank pins of the forged crankshaft.
The second preforming step forms, 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 above forming apparatus in (1).
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 a forged crankshaft for a straight-6-cylinder
engine includes the following successive steps comprising a first preforming step, a
second preforming step, and a finish forging step.
The first preformii~g step forins the preform blank to be supplied to the above
forming apparatus in (2). In the preform blank, first and sixth rough crank pin portions
at opposite ends and third and fourth rough crank pin portions in the center among the
rough crank pill portion 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 smaller than a 4312 of an amount of eccentricity of the crank pins of the
forged crankshaft. Second and fifth rough crank pin portions of the preform blank
have an amount of eccentricity of zero in the direction perpendicular to the axial
direction.
The second preforming step forms the blank for finish forging using the above
forming apparatus in (2). In the blank for finish forging, the first and sixth rough
crank pin portions at opposite ends and the third and fourth rough crank pin portions in
the center among the rough crank pin portions 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 4312 of the amount of eccentricity of the
crank pins of the forged crankshaft. The second and fifth rough crank pin portions of
the blank for finish forging remain 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 sixth rough crank pin portions at opposite ends, and
the central third and fourth rough crank pin portions 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 a placement angle of the crank pins.
[002 81
(6) A method for manufacturing a forged crankshaft for a straight-6-cylinder
engine includes the following successive steps comprising a first preforming step, a
second preforming step, and a finish forging step.
The first preforming step forms the preform blank to be supplied to the above
forming apparatus in (2). In the preform blank, first and sixth rough crank pin portions
at opposite ends and third and fourth rough crank pin portions in the center among the
rough crank pin portions 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 sn~allerth an a 4312 of an amount of eccentricity of the crank pins of the
forged crankshaft. Second and fifth rough crank pin portions of the preform blank
have an amount of eccentricity in the direction perpendicular to the axial direction, in a
direction perpendicular to the eccentric direction of the first and sixth rough crank pin
portions and the third and fourth 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 second preforming step forms the blank for finish forging using the above
forming apparatus in (2). In the blank for finish forging, the first and sixth rough
crank pin portions at opposite ends and the third and fourth rough crank pin portions in
the center among the rough crank pin portion 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 4312 of the amount of eccentricity of the
crank pins of the forged crankshaft. The second and fifth rough crank pin portions of
the blank for finish forging remain the same amount of eccentricity in the direction
perpendicular to the axial directioll 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 sixth rough crank pin portions at opposite ends and
the third and fourth rough crack pin portions in the center are horizontally placed,
whereby the first, third, fourth and sixth rough crank pin portions are pressed in the
direction perpendici~lar to the axial direction to form a forged product having a final
shape of the forged crankshaft including a 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
straight-6-cylinder engine having thin arms. When such a blank for finish forging
without a flash is subjected to finish forging, it is possible to obtain a final shape of a
forged crankshaft including the contour shape of arms although some minor amount of
flash is generated. Thus, forged crankshafts for straight-6-cylinder engines can be
manufactured with high material utilization and also with high dimensional accuracy
regardless of their shapes.
BKlEF DESCRlPTlON OF DRAWINGS
[0030]
[FIG. 11 FIG. 1 is a schematic diagram illustrating a typical conventional
process for manufacturing a forged crankshaft for a straight-6 -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 first embodiment.
[FIG. 43 FIG. 4 is a longitudinal sectional view showing a configuration of the
forming apparatus according to the first 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 first
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 finish 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 of the present invention.
[FIG. 93 FIG. 9 is a schematic diagram illustrating a process for manufacturing
a forged crankshaft for a straight-6-cylinder engine according to the second
embodiment.
[FIG. 101 FIG. I0 is a longitudinal sectional view showing a configuration of
the forming apparatus according to the second embodiment.
[FIG. 1 IA] FIG. 11A 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 1 B 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 of a
third embodiment.
[FIG. 131 FIG. 13 is a schematic diagram illustrating a process for
manufacturing a forged crankshaft for a straight-6-cylinder engine 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. 161 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. 171 FIG. 17 is a schematic diagram illustrating a process for
manufacturing a forged crankshaft for a straight-6-cylinder engine according to the
fourth embodiment.
DESCRIPTION OF EMBODIMENTS
1003 I]
The present invention is based on the premise that, in manufacturing a forged
crankshaft for a straight-6-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 straight-6-cylinder engine and the method
for manufacturing a forged crankshaft for a straight-6-cylinder engine including the
preforming steps using such apparatus, of the present invention, embodiments thereof
are described in detail below.
[0032]
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 illustrates how a straight-6-cylinder-8-counterweight crankshaft is manufactured
as an example. Further, in FIG. 2, displays plane views shows 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.
[003 31
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
straight-6-cylinder-8-counterweight shown in FIG. 1 (f) but is generally in a rough
shape. The preform blank 4 includes: seven rough journal portions Jla to J7a; six
rough crank pin portions Pla to P6a; a rough front part portion Fra; a rough flange
portion Fla; and twelve rough crank arm portions Ala to A12a (hereinafter also referred
to simply as "rough arm portions") that alternatively connect the rough journal portions
Jla to J7a, and the rough crank pin portions Pla to P6a to each other. The preform
blank 4 has no flash. Hereinafter, when the rough journal portions Jla to J7a, the
rough crank pin portions Pl a to P6a, and the rough arm portions Ala to A1 2a, 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. Some of the rough arm
portions Aa have roughly shaped balance weights in an integrated manner.
Specifically, the first, second, fifth, sixth, seventh, eighth, eleventh, and twelfth arm
portions A l a, A2a, A5a to A8a, A 1 1 a, and A12a each have a roughly shaped balance
weight in an integrated manner.
[0034]
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 for finish forging 5 includes seven rough journal portions J l b to J7b,
six rough crank pin portions PI b to P6b, a rough front part portion Frb, a rough flange
portion Flb, and twelve rough crank arm portions A 1 b to A 12b (hereinafter also referred
to simply as "rough arm portions") that alternatively connect the rough journal portions
Jl b to J7b, and the rough crank pin portions PI b to P6b to each other. The blank for
finish forging 5 has no flash. Hereinafter, when the rough journal portions Jlb to J7b,
the rough crank pin portions Plb to P6b, and the rough arm portions A1 b to A12b, 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. Some of the
rough arm portions Ab have roughly shaped balance weights in an integrated manner.
Specifically, the first, second, fifth, sixth, seventh, eighth, eleventh, and twelfth arm
portions Alb, A2b, A5b to A8b, A1 lb, and A12b each have a roughly shaped balance
weight in an integrated manner.
[003 51
A forged product 6 of the first embodiment is obtained from the blank for
finish forging 5 described above by finish forging. The forged product 6 includes
seven journals Jlc to J7c, six crank pins PIC to P6c, a front part Frc, a flange Flc, and
twelve crank arms Alc to A12c (hereinafter also referred to simply as "arms") that
alternatively connect the journals Jlc to J7c, and the crank pins Plc to P6c to each other.
Hereinafter, when the journals Jlc to J7c, the crank pins Plc to P6c, and the arms Alc
to A 12c, 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. Some of the arms Ac have balance weights in
an integrated manner. Specifically, the first, second, fifth, sixth, seventh, eighth,
eleventh, and twelfth arms (AIc, A2c, A5c to ASc, A1 1 c, and A12c) each have a balance
weight in an integrated manner.
[0036]
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. I (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 final 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 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). 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
the forged product 6) regardless of whether a balance weight is present or absent.
[003 81
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 sixth rough crank pin portions Pla and P6a
and the central third and fourth rough crank pin portions P3a and P4a 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 and fifth rough crank pin portions P2a and
P5a are configured to have an amount of eccentricity in the direction perpendicular to an
eccentric direction of the first, third, fourth and sixth rough crank pin portions Pla, P3a,
P4a and P6a 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]
The rough arm portions Aa of the preform blank 4 have an axial thickness
greater than that of the rough arm portions Ab of the blank for finish forging 5, i.e., that
of the arms A of the forged crankshaft (arms Ac of forged product 6) regardless of
whether a balance weight is present or absent. Essentially, in comparison with the
blank for finish forging 5 (forged crankshaft and forged product 6, having final shape),
the preform blank 4 has an overall length that is relatively long by the additional
thickness of the rough arm portions Aa, and has a smaller 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 finish forging 5 has such a
configuration that, with respect to the final shapes of the forged crankshaft and the
forged product 6, the rough ann 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 portions Ja and the rough crank
pin portions Pa are accordingly slightly greater.
[004 1 ]
1-2. Process For Manufacturing Forged Crankshaft
FIG. 3 is a schematic diagram illustrating a process for manufacturing a forged
crankshaft for a straight-6-cylinder engine according to the first embodiment. As
shown in FIG. 3, the process for manufacturing the forged crankshaft for the
straight-6-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.
[0042]
The first preforming step is a step in which the preform blank 4 described
above is obtained. In the first preforming step, such a preform blank 4 can be obtained
by using a round billet having a circular cross section as a starting material and applying
a preforming operation to the round billet after it is heated by a heating furnace (for
example, an induction heater, a gas atmosphere filrnace, or the like). In the preforming
operation, for example, the preform blank 4 can be obtained in a manner such that: the
round billet is subjected to roll forming in which it is reduction-rolled 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. 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.
100431
The second preforming step is a step in which the blank for finish forging 5
described above is obtained. In the second preforming step, a preforming operation is
applied by using a forming apparatus described in FIG. 4 below. Thereby, 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 finish forging step, the blank for finish forging 5 is supplied to be
processed by press forging with a pair of upper and lower dies. Thereby, the forged
product 6 having a shape in agreement with the shape of the crankshaft of the forged
crankshaft having the final 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 straight-6-cylinder-8-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 sixth rough crank pin portions, and the
third and fourth 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. The forming apparatus includes a stationary lower pressure pad 20 serving
as a base and an upper pressure pad 2 1, 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 21 via support posts 25. This upper die holder
23 is lowered together with the upper pressure pad 21 by driving the press machine
(ram).
[0047]
In the forming apparatus shown in FIG. 4, the preform blank 4 is placed in the
dies, whereby the preform blank 4 is formed into the blank for finish forging. In this
operation, the preform blank 4 is placed in the dies in a manner such that the first and
sixth rough crank pin portions Pla and P6a, and the third and fourth rough crank pin
portions P3a and P4a are horizontally positioned, and the second and fifth rough crank
pin portions P2a and P5a are positioned in a lower side in the vertical direction. Thus,
the stationary journal dies 9U and 9B, the movable journal dies IOU and IOB, the
movable crank pin dies (second movable crank pin dies) 12, and the auxiliary crank pin
dies 13 are respectively mounted on the lower die holder 22 and the upper die holder 23.
These stationary journal dies 9U and 9B, the movable journal dies 10U and 10B, and
the movable crank pin dies (second movable crank pin dies) 12, and the auxiliary crank
pin die 13 are apart from each other in the axial direction of the preform blank 4,
vertically forming pairs.
[0048]
'The stationary journal dies 9U and 9B, vertically forming a pair, are disposed at
a location of a central fourth rough journal portion J4a among the rough journal portions
Ja of the preform blank 4. The upper and lower of the stationary journal dies 9U and
9B are mounted on the upper die holder 23 and the lower die holder 22, respectively.
Particularly, the stationary journal dies 9U, 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.
[0049]
The stationary journal dies 9U and 9B respectively have first impressions 9Ua
and 9Ba each having a semi-cylindrical shape, and second impressions 9Ub and 9Bb.
The second impressions 9Ub and 9Bb are located adjacent to the first impressions 9Ua
and 9Ba at the front and back (right and left as seen in FIG. 4). The length of the first
impressions 9Ua and 9Ba is equal to the axial length of the fourth rough journal portion
J4b of the blank for finish forging 5. The length of the second impressions 9Ub and
9Rb is equal to the axial thickness of the rough arm portions Ab (the sixth and seventh
rough arm portions A6b and A7b) connecting to the rough journal portion J4b of the
blank for finish forging 5.
[0050]
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 stationary journal dies 9U and
9B are caused to hold and retain the fourth rough journal portion J4a with the first
impressions 9Ua and 9Ba. Concurrently, the stationary journal dies 9U and 9B are
brought into a state in which the second impressions 9Ub and 9Bb, at their first
impressions 9Ua and 9Ba-side surfaces, are in contact with the rough arm portions Aa
(the sixth and seventh rough arm portions A6b and A7b), at their fourth rough journal
portion J4a-side side surface through which the rough arm portions Aa and the fourth
rough journal portion J4a are connected.
[005 1 ]
The movable journal dies 10U and 10B are disposed at locations of the rough
journal portions Ja of the preform blank 4 excluding the rough journal portion Ja thereof
to be held by the stationary journal dies 9U and 9B (the first to third, and fifth to
seventh rough journal portions J I a to J3a and J5a to J7a). The upper and lower of the
movable journal dies IOU and 10B are mounted on the upper die holder 23 and the
lower die holder 22, respectively. Particularly, the movable journal dies IOU and 1 OB,
i.e., both the upper and lower dies, are axially movable toward the stationary journal
dies 9U and 9B on the upper die holder 23 and the lower die holder 22, respectively.
100521
The movable journal dies 10U and 10B have first impressions 10Ua and 1 OBa,
respectively, each having a semi-cylindrical shape and second impressions lOUb and
lOBb, respectively. The second impressions lOUb, lOBb are located in front of or
behind (left or right as seen in FIG. 4) the first impressions 10Ua, 10Ba. The length of
the first impressions 10Ua and lOBa is equal to the axial length of the rough journal
portions Jb (the first to third, and fifth to seventh rough journal portions Jl b to J3b and
J5b to J7b) of the blank for finish forging 5. The length of the second impressions
10Ub and 10Bb is equal to the axial thickness of the rough arm portions Ab (the first to
fifth, and eighth to twelfth rough arm portions Alb to A5b and A8b to A12b)
connecting to the rough journal portions Jb of the blank for finish forging 5.
[0053]
By the downward movement of the press machine, the movable journal dies
IOU and 10B are caused to hold and retain the rough journal portions Ja with the
corresponding first impressions I OUa and 10Ba. Concurrently, the movable journal
dies IOU and I OB are brought into a state in which the second impressions lOUb and
IOBb, at their first impressions lOUa 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 rough arm portions Aa and the corresponding rough journal portions Ja are
connected.
[0054]
The movable journal dies 10U and 10B disposed at locations of the
corresponding first and seventh rough journal portions Jla and J7a 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 first wedges 26, each
located correspondingly to the location of the inclined surfaces 14U and 14B of the
movable journal dies 10U and 10B for the first and seventh rough journal portions Jla
and J7a. Each of the first wedges 26 extends upward penetrating through the lower die
holder 22. The inclined surfaces 14B of the lower movable journal dies 10B, among
the movable journal dies 10U and 10B for the first and seventh rough journal portions
Jla and J7a, are in contact with the slopes of the first 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 the first wedges 26 by the downward movement
of the press machine.
[OOS 51
The movable journal dies IOU and 10B disposed at locations of the second and
sixth rough journal portions J2a and J6a, which are disposed in an inner side of the first
and seventh rough journal portions Jla and J7a, are provided with blocks, not shown,
fixed thereto. The blocks have inclined surfaces 15U and 15B at side sections (front
and back sides of the paper in FIG. 4) apart from the first impressions 10Ua and lOBa
and the second impressions lOUb and lOBb. In relation to this, on the lower pressure
pad 20, there are provided second wedges 27, each located correspondingly to the
location of the inclined surfaces 15U and 15B of the movable journal dies IOU and 10B
for the second and sixth rough journal portions J2a and J6a. Each of the second
wedges 27 extends upward penetrating through the lower die holder 22. The inclined
surfaces 15B of the lower movable journal dies IOB, among the movable journal dies
IOU and 10B for the second and sixth rough journal portions J2a and J6a, are in contact
with the slopes of the second wedges 27 in the initial condition. On the other hand, the
inclined surfaces 15U of the upper movable journal dies IOU are brought into contact
with the slopes of the second wedges 27 by the downward movement of the press
machine. The movable journal dies 10U and 10B disposed at locations of the third and
fifth rough journal portions J3a and J5a, which are disposed in a further inner side of the
first and seventh rough journal portions Jla and J7a, are also provided with similar
wedge mechanisms, not shown.
[0056]
Then, with continued downward movement of the press machine, the upper
movable journal dies IOU are pressed downwardly together with the lower movable
journal dies 1OB. This allows the inclined surfaces 14U and 14B of the movable
journal dies IOU and 10B for the first and seventh rough journal portions J la and J7a,
i.e., both the upper and lower ones, to slide along the slopes of the first wedges 26.
With this, the movable journal dies IOU and 10B move axially toward the stationary
journal dies 9U and 9B for the fourth rough journal portion J4a. Concurrently, the
inclined surfaces 15U and 15B of the movable journal dies IOU and IOB, i.e., both the
upper and lower ones, for the second and sixth rough journal portions J2a and J6a, slide
along slopes of the second wedges 27. With this, the movable journal dies IOU and
10B also move axially toward the stationary journal dies 9U and 9B for the fourth rough
journal portion J4a. The movable journal dies IOU and 10B for the third and fifth
rough journal portions J3a and J5a similarly move axially toward the stationary journal
dies 9U and 9B. Essentially, the movable journal dies IOU and 10B for the first to
third and fifth to seventh rough journal portions Jl a to J3a and J5a to J7a are all capable
of being moved axially by the wedge mechanisms.
[0057]
The movable crank pin dies 12 and the auxiliary crank pin dies 13, which form
upper and lower pairs, are disposed at locations corresponding to the locations of the
rough crank pin portions Pa of the preform blank 4. The upper and lower of the
movable crank pin dies 12 and the auxiliary crank pin dies 13 are mounted on the upper
die holder 23 and the lower die holder 22, respectively. 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 positions of the
corresponding rough crank pin portions Pa in the outside. For example, at the location
of the first rough crank pin portion Pla, the specified position of the first rough crank
pin portion Pla is located in the upper side. Thus, the 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.
1005 81
Particularly, the movable crank pin dies 12 and the auxiliary crank pin dies 13,
i.e., both the upper and lower ones, are axially movable toward the stationary journal
dies 9U and 9B on the lower die holder 22 and the upper die holder 23. 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 (vertical directions in FIG. 4).
[0059]
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.
[0060]
By the downward movement of the press machine, the movable crank pin dies
12 are placed in a state in which their impressions 12a are brought into contact with the
rough crank pin portions Pa, and both side surfaces of 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 the rough crank pin portions Pa
are connected.
[006 1 ]
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 stationary journal dies 10U and 1OB
for the fourth rough journal portion J4a. The movement of 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 12.
[0062]
It should be noted that the axial movement of the niovable 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. The auxiliary crank pin dies 13 may be
integral with one of their adjacent movable journal dies 10U and 10B or the stationary
journal dies 9U and 9B forming pairs.
[0063]
In the initial condition shown in FIG. 4, spaces are provided between the
axially arranged movable journal dies IOU and 10B and stationary journal dies 9U and
9B, and their corresponding movable crank pin dies 12 and auxiliary crank pin dies 13.
The spaces are secured, so as to allow 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 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
rough arm portions Aa of the preform blank 4.
[0064]
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. FIG. 5A shows a forming state at the initial stage and FIG. 5A shows
a forming state at the completion.
100651
The preform blank 4 is placed in the lower movable journal die 10B, the
stationary journal die 9D, 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 the stationary journal dies
9U are brought into contact with the corresponding lower movable journal dies 10B and
the stationary journal dies 9B.
[0066]
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 the stationary journal
dies 9U and 8B from above and below, and the rough crank pin portions Pa are
contacted by 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 IOU and I OB and the 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 movable crank pin dies 12. Further, in this state, the
inclined surfaces 14U and 14B of the movable journal dies 10U and IOB for the first
and seventh rough journal portions J la and J7a are in contact with the slopes of the first
wedges 26, and the inclined surfaces 15U and 15B of the movable journal dies 10U and
10B for the second and sixth rough journal portions J2a and J6a are in contact with the
slopes of the second wedges 27. The inclined surfaces, not shown, of the movable
journal dies 10U and 10B for the third and fifth rough journal portions J3a and J5a are
also in contact with the slopes of wedges, not shown.
[0067]
In this state, the lowering of the press machine is continued. Accordingly, the
inclined surfaces 14U and 14B of the movable journal dies IOU and 10B for the first
and seventh rough journal portions Jla and J7a slide along the slopes of the first wedges
26. By this wedge mechanism, these movable journal dies IOU and 10B are allowed
to move axially toward the stationary journal dies 9U and 9B for the fourth rough
journal portion J4a. Concurrently, the inclined surfaces 15U and 15B of the movable
journal dies IOU and 10B for the second and sixth rough journal portions J2a and J6a
slide along the slopes of the second wedges 27. These wedge mechanisms allow the
movable journal dies 10U and 10B to move axially toward the stationary journal dies
9U and 9B for the fourth rough journal portion J4a. Concurrently, the inclined
surfaces 15U and 15B of the respective movable journal dies IOU and 10B for the
second and sixth rough journal portions J2a and J6a slide along the slopes of the second
wedges 27. These wedge nlechanisms allow the movable journal dies IOU and 10B to
move axially toward the stationary journal dies 9U and 9B for the fourth rough journal
portion J4a. Similarly, the movable journal dies 10U and 10B for the third and fifth
rough journal portions J3a and J5a also move axially toward the stationary journal dies
9U and 9B by the wedge mechanisms. By such axial movement of the movable
journal dies IOU and 10B 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
stationary journal dies 9U and 9B.
[0068]
Accordingly, the spaces between the movable journal dies IOU and 10B and
the stationary journal dies 9U and 9B, and 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 IOU and IOB, the stationary journal dies 9U and 9B, and the
movable crank pin dies 12, so that the thickness of the rough arm portions Aa is reduced
to the thickness of the rough arm portions Ab of the blank for finish forging 5 (see FIG.
5B). At that point, the axial lengths of the rough journal portions Ja and the rough
crank pin portions Pa are maintained. It should be noted that the compression of the
rough arm portions Aa is performed on all of the rough arm portions Aa regardless of
whether a balance weight is present or absent.
[0069]
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, each of the hydraulic cylinders 16 for the movable crank pin dies 12 is operated.
Accordingly, the crank pin dies 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).
[0070]
In this manner, it is possible to form, tko~nth e preform blank 4 without a flash,
the blank for finish forging 5 without a flash. The blank for finish forging 5 has a
shape generally in agreement with the shape of the forged cranks'haft for the
straight-6-cylinder engine having thin arms A (forged final product). 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
straight-6-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 straight-6-cylinder engines can be manufactured with high
material utilization and also with high dimensional accuracy regardless of their shapes.
As illustrated in FIG. 2, FIG. 4 and the like, if, at the stage of preparing the preform
blank, the arm portions are shaped so as to include portions for forming balance weights,
it is even possible to manufacture forged crankshafts having balance weights.
[007 11
In the forming apparatus shown in FIGS. 4, FIG. 5A and FIGSB, the inclined
surfaces 14U and 14B of the movable journal dies IOU and 10B for the first rough
journal portion Jla and its contacting slope of the first wedge 26, and the inclined
surfaces 14U and 14B of the movable journal dies IOU and 10B for the seventh rough
journal portion J7a and its contacting slope of the first wedge 26 are angled in a reverse
relationship relative to a vertical plane. Also, the inclined surfaces 15U and 15B of the
movable journal dies IOU and 10B for the second rough journal portion J2a and its
contacting slope of the second wedge 27, and the inclined surfaces 15U and 15B of the
movable journal dies 10U and 10B for the sixth rough journal portion J6a and its
contacting slope of the second wedge 27 are angled in a reverse relationship relative to a
vertical plane. Furthermore, the angle of the slopes of the first wedges 26 (the angle of
the inclined surfaces 14U and 14B of the movable journal dies IOU and 10B for the first
and seventh rough journal portions Jla and J7a) is greater than the angle of the slopes of
the second wedges 27 (the angle of the inclined surfaces 15U and 15B of the movable
journal dies IOU and 10B for the second and sixth rough journal portions J2a and J6a).
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 IOU and IOB, is to ensure that the rate of deformation at which the rough
arm portions Aa are axially compressed to reduce the thickness thereof stays constant
for all the rough arm portions Aa.
[0072]
In the preform blank 4, which is processed by the forming apparatus shown in
FIGS. 4, FIG. 5A and FIG. 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 prefonn blank 4 is greater
than the cross-sectional area of the rough journal portions Jb of the blank for finish
forging 5, the cross-sectional area of the rough journal portions Ja can be reduced 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 IOU and 10B and by the subsequent axial movement of the
movable journal dies IOU and 10B. Even when the cross-sectional 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 the
movement of the movable crank pin dies 12 in the axial direction and the direction
perpendicular thereto.
[0073]
An issue to be addressed regarding the forming of the blank for finish forging
described above is local formation of fin flaws. The following describes how fin flaws
are formed and how they can be prevented.
[0074]
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.
100751
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), 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 IOU and I 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 IOU and 10R and the
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). 'Illus, 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 the boundaries with adjacent rough arm portions Aa.
[0076]
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.
100771
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 the stationary journal dies 9U and 9B, and the movable
crank pin dies 12, and the auxiliary crank pin dies 13, are filled. Specifically, it may
be configured such that the axial movement of the movable journal dies IOU and I OB 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.
[0078]
For example, the forming operation is started as shown in FIG. 7(a). Then, as
shown in FIG. 7(b), 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 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. Consequently, by this time, the spaces between the movable journal dies
1 OU and 10B and the stationary journal dies 9U and 9B, and 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 the 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.
[0079]
l'he process of movement of the movable crank pin dies in the direction
perpendicular to the axial direction before the conlpletion 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.
[0080]
2. Second Embodiment
A second embodiment is based on the configuration of the first embodiment
described above. The 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.
[008 11
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 illustrates how a
straight-6-cylinder-12-counterweight crankshaft is manufactured as an example. It is
noted that the descriptions of the matters that overlap with the first embodiment shall be
appropriately omitted. This is also the case for third and fourth embodiments
described later.
[0082]
As shown in FIG. 8, a preform blank 4 of the second embodiment has a
crankshaft shape that is approximate to the shape of a forged crankshaft 1 for a
straight-6-cylinder- 12-counterweight, but is generally in rough shape. The preform
blank 4 irlcludes seven rough journal portions Ja, six rough crank pin portions Pa, a
rough front part portion Fra, a rough flange portion Fla, and twelve rough ann portions
Aa. In the preform blank 4, all (first to twelfth) of the rough arm portions Aa have
roughly shaped balance weights in an integrated manner. A blank for finish forging 5
of the second embodiment is formed from the preform blank 4 described above using a
forming apparatus, details of which will be provided later. The blank for finish forging
5 includes seven rough journal portions Jb, six rough crank pin portions Pb, a rough
front part portion Frb, a rough flange portion Flb, and twelve rough arm portions Ab.
In the blank for finish forging 5, all (first to twelfth) of the rough arm portions Ab have
roughly shaped balance weights in an integrated manner. 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 seven journals Jc, six crank pins PC, a
front part Frc, a flange Flc, and twelve arms Ac. In the forged product 6, all (first to
twelfih) of the arms Ac have balance weights in an integrated manner.
[0083]
A twisted product 7 of the second embodiment is obtained from the forged
product 6 described above by twisting. The twisted product 7 includes seven journals
Jld to J7d, six crank pins Pld to P6d, a front part Frd, a flange Fld, and twelve crank
arms Ald to A 12d (hereinafter also referred to simply as "arms") that alternatively
connect the journals Jld to J7d, and the crank pins Pld to P6d to each other.
Hereinafter, when the journals Jld to J7d, the crank pins P Id to P6d, and the arms Ald
to A12d, 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. In the twisted product 7, all (first to twelfth) of
the arms Ad have balance weights in an integrated manner.
[0084]
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 final 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.
[0085]
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
sixth crank pins P 1 c and P6c at opposite ends, and the third and fourth rough crank pin
portions P3c and P4c in the center are eccentric in the same direction perpendicular to
the axial direction. The second and fifth crank pins P2c and P5c are eccentric in the
direction opposite to the eccentric direction of the first, third, fourth, and sixth crank
pins Plc, P3c, P4c, and P6c. 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.
100861
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 rough
crank pin portions Pb 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).
[0087]
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 sixth rough crank pin portions Pla and P6a, and the central third
and sixth rough crank pin portions P3a and P4a 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 and fifth rough crank pin portions P2a and P5a are eccentric in a direction
opposite to an eccentric direction of the first, third, fourth and sixth rough crank pin
portions Pl a, P3a, P4a and P5a with an amount of eccentricity equal to about a half of
an amount of eccentricity in the crank pin P of the forged crankshaft.
[0088]
The rough arm portions Aa of the preform blank 4 have an axial thickness
greater than that of the rough arm portions Ab of the blank for finish forging 5, i.e., that
of the arms A of the forged crankshaft (arms Ac of forged product 6).
[0089]
2-2. Process For Manufacturing Forged Crankshaft
FIG. 9 is a schematic diagram illustrating a process for manufacturing a forged
crankshaft for a straight-6-cylinder engine according to the second embodiment. As
shown in FIG. 9, the process for manufacturing the forged crankshaft for the
straight-6-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.
[0090]
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 is obtained from the preform blank 4 described above by
using a forming apparatus described in FIG. 10 below. The blank for finish forging 5
has the final shape of the forged crankshaft excluding the placement angle of the crank
pins. The finish forging step is a step in which the blank for finish forging 5 is
supplied to be processed by finish forging, and the forged product 6 described above is
obtained. The forged product 6 having the final shape of the forged crankshaft
excluding the placement angle of crank pins.
1009 I ]
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. Thereby the placement angle of the crank pins of the forged
product 6 is adjusted to the placement angle of-the crank pins of the forged crankshaft to
obtain the twisted product 7. 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.
[0092]
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 that is used in manufacturing a straight-6-cylinder-12-counterweight
crankshaft, i.e., 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.
[0093]
In the forming apparatus of the second embodiment shown in FIG. 10, the
preform blank 4 is placed in the dies and is formed into the blank for finish forging 5.
In this operation, the preform blank 4 is placed in the dies in a manner such that the
eccentric direction of the rough crank pin portions I'a is in the vertical direction. For
example, the first and sixth rough crank pin portions Pla and P6a, and the third and
fourth rough crank pin portions P3a and P4a are positioned in the upper side, and the
second and fifth rough crank pin portions P2a and P5a are positioned in the lower side.
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.
[0094]
FIGS. 1 IA and 11B are longit~~dinasel ctional views illustrating a process for
forming the blank for finish forging using the forming apparatus according to the
second embodiment shown in FIG. 10. FIG. 11 A shows a forming state at an initial
stage, and FIG. 11 B shows a forming state at the completion.
[0095]
As shown in FIG. 1 lA, 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 IOU and 10B holding and retaining the rough
journal portions Ja to move axially toward the stationary journal dies 9U and 9B for the
fourth rough journal portion J4a. With this, the movable crank pin dies 12 and the
auxiliary crank pin dies 13 in contact with the rough crank pin portions Pa also move
axially toward the stationary journal dies 9U and 9B. By this operation, in the preform
blank 4, the rough arm portions Aa are axially compressed by the movable journal dies
10U and 10B, the stationary journal dies 9U and 9B, and the movable crank pin dies 12,
so that the thickness of the rough arm portions Aa is reduced to the thickness of the
rough arm portions Ab of the blank for finish forging 5 (see FIG. 11B). In this
operation, the axial lengths of the rough journal portions Ja and the rough crank pin
portions Pa are maintained.
[0096]
Also, in coordination with 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 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 1 1 B).
[0097]
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. The blank for finish forging 5 has thin
arms A and has a shape generally in agreement with the shape of the forged crankshaft
for a straight-6-cylinder engine (forged final product) excluding the placement angle of
the crank pins P. Next, by using such a blank for finish forging 5 without a flash in
finish forging and applying finish forging thereto, it is possible to obtain the forged
product 6 although some minor amount of flash is generated. The forged product 6 has
the final shape in agreement with the shape of the forged crankshaft for the
straight-6-cylinder engine including the contour shape of arms but excluding the
placement angle of the crank pins. Then, by performing the twisting on the forged
product 6, it is possible to obtain the final shape of the forged crankshaft for the
straight-6-cylinder engine including the placement angle of the crank pins. Therefore,
forged crankshafts for straight-6-cylinder engines can be manufactured with high
material utilization and also with high dimensional accuracy regardless of their shapes.
[0098]
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.
LO0991
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 illustrates how a straight-6-cylinder-8-counterweight crankshaft
is manufactured as an example.
[O 1001
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
straight-6-cylinder-8-counterweight, but is generally in a rough shape. The preform
blank 4 includes seven rough journal portions Ja, six rough crank pin portions Pa, a
rough front part portion Fra, a rough flange portion Fla, and twelve rough arm portions
Aa. Some of the rough arm portions Aa of the preform blank 4 have roughly shaped
balance weights in an integrated manner. Specifically, the first, second, fifth, sixth,
seventh, eighth, eleventh, and twelfth arm portions Ala, A2a, A5a to A8a, A1 la, and
A12a each have a roughly shaped balance weight in an integrated manner. The blank
for finish 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 seven rough journal portions Jb, six rough crank
pin portions Pb, a rough front part portion Frb, a rough flange portion Flb, and twelve
rough arm portions Ab. Some of the rough arm portions Ab of the blank for finish
forging 5 have roughly shaped balance weights in an integrated manner. Specifically,
the first, second, fifth, sixth, seventh, eighth, eleventh, and twelfth arm portions Ala,
A2a, A5a to A8a, A 11 a, and A1 2a each have a roughly shaped balance weight in an
integrated manner. The forged product 6 of the third embodiment is obtained from the
blank for finish forging 5 described above by finish forging. The blank for finish
forging 5 includes seven journals Jc, six crank pins PC, a front part Frc, a flange Flc, and
twelve arms Ac. Some of the arms Ac of the blank for finish forging 5 have balance
weights in an integrated manner. Specifically, the first, second, fifth, sixth, seventh,
eighth, eleventh, and twelfth arms each have a balance weight in an integrated manner.
[OI 011
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.
[O 1 021
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 sixth rough crank pin portions PI b and P6b at
opposite ends and the third and fourth rough crank pin portions P3b and P4b in the
center are eccentric in the opposite direction to each other with an amount of
eccentricity equal to d312 of an amount of eccentricity in the crank pins P of the forged
crankshaft. On the other hand, the second and fifth rough crank pin portions P2b and
P5b are 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 1 031
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 finish 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 sixth rough crank pin
portions Pla and P6a, and the central third and fourth rough crank pin portions P3a and
P4a have a smaller amount of eccentricity than that of the rough crank pin portions Pb
of the blank for finish 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 and fifth rough
crank pin portions P2a and P5a have an amount of eccentricity of zero, similar to the
second rough crank pin portion P2b and P5b in the blank for finish forging 5.
[0 1 041
The rough arm portions Aa of the preform blank 4 have an axial thickness
greater than that of the rough arm portions Ab of the blank for finish forging 5, i.e., that
of the arms A of the forged crankshaft (arms Ac of forged product 6).
[0 1051
3-2. Process For Manufacturing Forged Crankshaft
FIG. 13 is a schematic diagram illustrating a process for manufacturing the
forged crankshaft for the straight-6-cylinder engine according to the third embodiment.
As shown in FIG. 13, the process for manufacturing the forged crankshaft 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 1 061
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 is obtained from the preform blank 4 described above by
using a forming apparatus described in FIG. 14 below. The blank for finish forging 5
has the final shape of the forged crankshaft excluding the amount of eccentricity and the
placement angle of all the crank pins.
[0 1071
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 sixth rough crank pin portions, and the third and fourth rough
crank pin portions are horizontally positioned. By this operation, all the rough crank
pin portions are pressed in the vertical direction perpendicular to the axial direction,
whereby the forged product 6 is obtained. The obtained forged product 6 has a shape
in agreement with the shape of the crankshaft of the forged crankshaft having the final
shape including the placement angle of the crank pins.
[0 1081
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.
[0 1 091
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. The
forming apparatus in the third embodiment differs in a manner of placing the preform
blank 4 when the preform blank 4 is placed in the dies and formed into the blank for
finish forging 5. Specifically, the preform blank 4 is placed in the dies in a manner
such that the first and sixth rough crank pin portions Pla and P6a and the third and
fourth rough crank pin portions P3a and P4a which are eccentric in the opposite
direction to each other are vertically positioned. In this forming apparatus, the
movable crank pin dies (first movable crank pin dies) 11 disposed at locations of the
corresponding second and fifth rough crank pin portions P2a and P5a are movable
axially, but constrained from moving in the direction perpendicular to the axial direction.
For this reason, the first movable 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 1 3 forming a pair with the first movable crank pin
die 11 is directly mounted. In FIG. 14, the first movable crank pin die 11 is mounted
to the upper die holder 23 while the auxiliary crank pin die 13 is mounted to the lower
die holder 22.
[Ol lo]
Further, in the forming apparatus of the third embodiment, the second movable
crank pin dies 12 and the auxiliary crank pin dies 13 disposed at locations of the first
and sixth rough crank pin portions Pla and P6a, and the third and fourth rough crank
pin portions P3a and P4a are reversed between the locations of the first and sixth rough
crank pin portions Pl a and P6a, and the location of the third and fourth rough crank pin
portions P3a and P4a. This is because the first and sixth rough crank pin portions Pla
and P6a, and the third and fourth rough crank pin portions P3a and P4a are eccentric in
the opposite direction to each other in the vertical direction. In FIG. 14, the auxiliary
crank pin dies 13 at the locations of the first and'sixth rough crank pin portions Pla and
P6a, and the second movable crank pin dies 12 at the locations of the third and fourth
rough crank pin portions P3a and P4a are positioned in the upper side. The second
movable crank pin dies 12 at the locations of the first and sixth rough crank pin portions
Pla and P6a, and the auxiliary crank pin dies 13 at the locations of the third and fourth
rough crank pin portions P3a and P4a are positioned in the lower side.
[Olll]
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. FIG. 15A shows a forming state at an initial stage, and
FIG. 15B shows a forming state at the completion.
[Oil21
As shown in FIG. 15A, the preform blank 4 is placed in the lower movable
journal die IOB, the stationary journal die 9B, the first movable crank pin dies 11, the
second movable crank pin dies 12, and the auxiliary crank pin dies 13, and then
lowering of the press machine is performed. Then, the movable journal dies IOU 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.
Concurrently, the second and fifth rough crank pin portions P2a and P5a are brought
into a state in which the second and fifth rough crank pin portions P2a and P5a is held
and retained by the first movable crank pin dies 11 and the auxiliary crank pin dies 13
from above and below. In this state, the second movable crank pin dies 12 are brought
into contact with the first, third, fourth, and sixth rough crank pin portions Pla, P3a, P4a,
and P6a. 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 stationary journal dies 9U and 9B of the fourth rough
journal portion J4a. Concurrently, the movable crank pin dies 11 and 12 and the
auxiliary crank pin dies 13 in contact with each rough crank pin portions Pa are moved
axially toward the stationary journal dies 9U and 9B. By this operation, in the preform
blank 4, the rough arm portions Aa are axially compressed by the movable journal dies
10U and 1 OB, the stationary journal dies 9U and 9B, the first movable crank pin dies 11
and the second movable crank pin 12, so that the thickness of the rough arm portions Aa
is reduced to the thickness of the rough arm portions Ab of the blank for finish forging 5
(see FIG. 15B). In this operation, the axial lengths of the rough journal portions Ja and
the rough crank pin portions Pa are maintained.
[0113]
Also, in coordination with the axial movement of the movable journal dies 1 OU
and 10B as well as that of the first movable crank pin dies 11, the movable crank pin
dies 12 and the auxiliary crank pin dies 13, the second movable crank pin dies 12 press
the first, third, fourth and sixth rough crank pin portions Pla, P3a, P4a and P6a 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, third, fourth and
sixth rough crank pin portions Pla, P3a, P4a and P6a of the preform blank 4 are
displaced in the vertical direction perpendicular to the axial direction. As a result, an
amount of eccentricity of the first, third, fourth, and sixth rough crank pin portions Pla,
P3a, P4a, and P6a are in the opposite direction to each other and equal to 4312 of an
amount of eccentricity of the crank pins P of the forged crankshaft (see FIG. 12 and FIG.
15B). On the other hand, the location of the second and fifth rough crank pin portion
P2a and P5a of the preform blank 4 in the vertical direction perpendicular to the axial
direction remain unchanged before and after the forming, thus the amount of
eccentricity thereof remains zero.
[0114]
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. The blank for finish forging 5 has thin
arms A and has a shape generally in agreement with the shape of the forged crankshaft
for a straight-6-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 sixth rough crank pin portions and the third and
fourth rough crank pin portions are horizontally positioned. In this process, all the
rough crank pin portions of the blank for finish forging 5 is pressed in the vertical
direction perpendicular to the axial direction so as to displace them to the specified
positions. Thereby, it is possible to obtain the final shape of the forged crankshaft for
the straight-6-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 straight-6-cylinder engines can be
manufactured with high material utilization and also with high dimensional accuracy
regardless of their shapes.
[0115]
4. Fourth Embodiment
A fourth embodiment includes modifications of the configuration of the third
embodiment.
[0116]
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.
[0117]
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.
[OI 181
In contrast, the blank for finish forging 5 of the fourth embodiment differs from
the blank for finish forging 5 ofthe third embodiment shown in FIG. 12 in the following.
As shown in FIG. 16, the second and fifth rough crank pin portions P2b and P5b in the
center in the blank for finish forging 5 of the fourth embodiment are eccentric in the
direction perpendicular to the eccentric direction of the first and sixth rough crank pin
portions PI b and P6b at opposite ends and the third and fourth rough crank pin portions
P3b and P4b in the center. The amount of eccentricity of the second and fifth rough
crank pin portions P2b and P5b in the center is made equal to that of the crank pins PC
of the forged product 6, i.e., the crank pins P of the forged crankshaft.
[OI 191
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, the second and fifth rough crank pin portions P2a and P5a in the center in the
preform blank 4 of the fourth embodiment are eccentric in the direction perpendicular to
the eccentric direction of the first and sixth rough crank pin portions Pla and P6a at
opposite ends and the third and fourth rough crank pin portions P3a and P4a in the
center. The amount of eccentricity of the second and fifth rough crank pin portions
P2a and P5a in the center is, like the blank for finish forging 5, made equal to that of the
crank pins P of the forged crankshaft (the crank pins PC of the forged product 6).
[O 1201
4-2. Process For Manufacturing Forged Crankshaft
FIG. 17 is a schematic diagram illustrating a process for manufacturing a
forged crankshaft for a straight-6-cylinder engine 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.
[0121]
The first preforming step is a step in which the preform blank 4 described
above is obtained.
[O 1 221
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 FIG. 14, FIG. 15A and FIG. 15B are
used. It should be noted that in the longitudinal sectional view shown in FIG. 14, the
second and fifth rough crank pin portion in the fourth embodiment are in reality located
either in the front or back side of the paper.
[0123]
In the second preforming step of the fourth embodiment, as similarly found in
the third embodiment shown in FIG. 14, FIG. 15A, and FIG. 15B, the preform blank 4
is placed in the lower movable journal dies 1 OB, stationary journal die 9B, first movable
crank pin dies I I, second movable crank pin dies 12, and auxiliary crank pin dies 13,
and then the downward movement of the press machine is performed. By this
operation, in the preform blank 4, the movable journal dies IOU and 10B holding the
rough journal portions Ja, and the movable crank pin dies 11 and 12, and the auxiliary
crank pin dies 13 in contact with the rough crank pin portions Pa move axially toward
the stationary journal dies 9U and 9B for the fourth rough journal portion J4a. With
this, the rough arm portions Aa are axially compressed, and the thickness of the rough
arm portions Aa is reduced to the thickness of the rough arm portions Ab of the blank
for finish forging 5. In this operation, the axial lengths of the rough journal portions Ja
and the rough crank pin portions Pa are maintained.
[0 1241
Further, the first, third, fourth and sixth rough crank pin portions Pla, P3a, P4a
and P6a are pressed by the second movable crank pin dies 12 in the vertical direction
perpendicular to the axial direction. Thereby the first, third, fourth and sixth rough
crank pin portions Pla, P3a, P4a and P6a of the preform blank 4 become eccentric in
the opposite direction to each other with an amount of eccentricity increased to a 6312
of an amount of eccentricity in the crank pins P of the forged crankshaft. On the other
hand, the location of the second and fifth rough crank pin portion P2a and P5a of the
preform blank 4 in the direction perpendicular to the axial direction remain unchanged
before and after the for~ningt,h us an amount of eccentricity thereof remains the same as
that of the crank pin P of the forged crankshaft.
[0 1251
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 described above. The blank for finish
forging 5 has a shape generally in agreement with the shape of the forged crankshaft for
a straight-6-cylinder engine (forged final product) excluding the amount of eccentricity
and the placement angle of the first, third, fourth, and sixth crank pins PI, P3, P4a, and
P6a. The blank for finish forging 5 has thin arms A.
[0 1261
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, third, fourth and sixth
rough crank pin portions are horizontally positioned to obtain the forged product 6. In
this process, the first, third, fourth and sixth rough crank pin portions PI b, P3b, P4b and
P6b of the blank for finish forging 5 are pressed in the vertical direction perpendicular
to the axial direction so as to displace them to the specified positions. 'Thereby it is
possible to obtain the forged product 6 having a shape of the crankshaft of the forged
crankshaft for the straight-6-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. That is, the forged
product 6 has a shape in agreement with the shape of the crankshaft.
[0 1271
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, a servo motor or the like may be employed in
place of the press machine. Furthermore, the mechanism for causing the movable
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.
[0 1281
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.
[O 1 291
Furthermore, in the above embodiments, the auxiliary crank pin dies are
movable only axially, but additionally, they may be made to be movable also in a
direction toward the movable crank pin dies forming pairs, so that the movable crank
pin dies and the auxiliary crank pin dies can hold and retain the rough crank pin
portions Pa therebetween from above and below and ineanwhile move in the direction
perpendicular to the axial direction cooperatively with each other.
[0 1301
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 dies are
changed so as to horizontally press the rough crank pin portions Pa.
[0131]
The present invention is, as described in the embodiments above, applicable to
a crankshaft in which some or all of arms have balance weights in an integrated manner.
In this case, some or all of the rough arm portions of the preform blank may have, as
described in the embodiments above, roughly shaped balance weights in an integrated
manner.
INDUSTRIAL APPLICABILITY
[O 1 321
The present invention is useful in manufacturing forged crankshafts for
straight-6-cylinder engines.
REFERENCE SIGNS LIST
[0133]
1 : forged crankshaft, J, J 1 to 57: journals,
P, PI to P6: crank pins, Fr: front part,
F1: flange, A, A 1 to A 12: crank arrrs,
2: billet,
4: preform blank, Ja, Jl a to J7a: rough journal portions,
Pa, Pl a to P6a: rough crank pin portions,
Fra: rough front part portion, Fla: rough flange portion,
Aa, A 1 a to A 12a: rough crank arm portions,
5: blank for finish forging,
Jb, J 1 b to J7b: rough journal portions of blank for finish forging, .
Pb, P1 b to P6b: 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 A 12b: rough crank arm portions of blank for finish forging,
5a: fin flaws,,
6: forged product, Jc, J lc to J7c: journals of forged product,
PC, P 1 c to P6c: crank pins of forged product,
Frc: front part of forged product, Flc: flange of forged product,
Ac, A1 c to A 12c: crank arms of forged product,
7: twisted product,
Jd, J Id to J7d: journals of twisted product,
Pd, Pld to P6d: crank pins of twisted product,
Frd: front part of twisted product,
Fld: flange of twisted product,
Ad, A 1 d to A 12d: crank anns of twisted product,
9U, 9B: stationary journal die
9Ua, 9Ba: first impression of stationary journal die
9Ub, 9Bb: second impression of stationary journal die
1 OU, 1 OB: movable journal dies,
1 OUa, 10Ba: first impression of movable journal die,
1 OUb, 10Bb: second impression of movable journal die,
11 : first movable crank pin die, I la: impression
12: second movable crank pin die, 12a: impression,
13: auxiliary crank pin die, 13a: impression,
14U, 14B: inclined surfaces of movable journal dies for first and seventh rough journal
portions,
15U, 15B: inclined surfaces of movable journal dies for second and sixth 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: first wedge, 27: second wedge

We claim:
1. An apparatus for forming a blank for finish forging for a forged crankshaft for a
straight-6-cylinder engine, the apparatus configured to form, from a preform blank, in a
process of manufacturing the forged crankshaft for the straight-6-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; and
rough crank arm portions having an axial thickness greater than an axial
thickness of crank arms of the forged crankshaft,
the rough crank pin portions 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:
stationary journal dies disposed at location of a fourth rough journal portion in
the center among the rough journal portions, the stationary journal dies configured to
hold and retain the fourth rough journal portion 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 rough
crank arm portions through which the rough crank arm portions connect with the fourth
rough journal portion;
movable journal dies disposed at locations of the corresponding rough journal
portions excluding the rough journal portion held by the stationary journal dies, 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 stationary journal dies 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; and
movable crank pin dies disposed at locations of the corresponding rough crank
pin portions, the movable crank pin dies configured to be brought into contact with such
rough crank pin portions, the movable crank pin dies configured to move in the axial
direction toward the stationary journal dies 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 such rough crank pin
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 movable crank pin dies are
contacted by the rough crank pin portion, the movable journal dies are moved axially,
the movable crank pin dies are moved axially and in the direction perpendicular to the
axial direction, thereby compressing the rough crank arm portions in the axial direction
so as to reduce a thickness thereof to a thickness of the 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 an amount of eccentricity thereof to an amount of
eccentricity of the crank pins of the forged crankshaft.
2. The apparatus for forming a blank for finish forging for a forged crankshaft for a
straight-6-cylinder engine according to claim 1,
wherein the movable crank pin dies each include an auxiliary crank pin die
disposed at a location outside of the corresponding rough crank pin portion, opposite to
a side where the movable crank pin die is contacted, and
wherein, in conjunction with axial movement of the movable journal dies as well
as that of the movable crank pin dies and the auxiliary crank pin dies, a movement of
the movable crank pin dies in the direction perpendicular to the axial direction is
controlled in a manner such that the rough crank pin portions to be deformed by
pressing reach the auxiliary crank pin dies after spaces between the stationary journal
dies and 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 finish forging for a forged crankshaft for a
straight-6-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
straight-6-cylinder engine according to any one of claims 1 to 3,
wherein the movable crank pin dies, the stationary joi~rnal dies, and, 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 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
straight-6-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
straight-6-cylinder engine according to claim 4 or 5,
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.
7. An apparatus for forming a blank for finish forging for a forged crankshaft for a
straight-6-cylinder engine, the apparatus configured to form, from a preform blank, in a
process of manufacturing the forged crankshaft for the straight-6-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; and
rough crank arm portions having an axial thickness greater than an axial
thickness of crank arms of the forged crankshaft,
among the rough crank pin portions, first and sixth rough crank pin portions at
opposite ends and third and fourth rough crank pin portions in the center having an
amount of eccentricity in a direction perpendicular to the axial direction and 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, second and
fifth rough crank pin portions having an amount of eccentricity of zero in the direction
perpendicular to the axial direction or having an amount of eccentricity in the direction
perpendicular to the eccentric direction of the first and sixth rough crank pin portions
and the third and fourth 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:
stationary journal dies disposed at location of a fourth rough journal portion in
the center among the rough journal portions, the stationary journal dies configured to
hold and retain the fourth rough journal portion 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 rough crank arm portions
through which the rough crank arm portions connect with the fourth rough journal
portion;
movable journal dies disposed at locations of the corresponding rough journal
portions excluding the rough journal portion held by the stationary journal dies, 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 stationary journal dies 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;
first movable crank pin dies disposed at locations of the corresponding second
and fifth rough crank pin portions, configured to be brought into contact with the second
and fifth rough crank pin portions, and configured to move axially toward the stationary
journal dies, while being in contact with side surfaces of rough crank arm portions
through which the rough crank arm portions connect with the second and fifth rough
crank pin portions; and
second movable crank pin dies disposed at locations of the first, third, fourth,
and sixth rough crank pin portions, the movable crank pin dies configured to be brought
into contact with such rough crank pin portions, the movable crank pin dies configured
to move in the axial direction toward the stationary journal dies 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
such rough crank pin portions,
wherein in a state where the rough journal portions held and retained by the
stationary journal dies and the movable journal dies, and the rough crank pin portions
are contacted by the first movable crank pin dies and the second movable crank pin dies,
the movable journal dies and the first ~novablec rank pin dies are moved axially and the
second movable crank pin dies are moved axially and in the direction perpendicular to
the axial direction, thereby compressing the rough crank arm portion in the axial
direction so as to reduce a thickness thereof to a thickness of the crank arms of the
forged crankshaft, and pressing the first, third, fourth, and sixth 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
straight-6-cylinder engine according to claim 7,
wherein the first movable crank pin dies and the second movable crank pin dies
each include an auxiliary crank pin die disposed at a location outside of the
corresponding rough crank pin portion, opposite to a side where the first movable crank
pin dies and the second 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 first movable crank pin dies, the second movable crank pin dies, and
the auxiliary crank pin dies, a movement of the second movable crank pin dies in the
direction perpendicular to the axial direction is controlled in a manner such that the
rough crank pin portions to be deformed by pressing reach the auxiliary crank pin dies
after spaces between the stationary journal dies and the movable journal dies, and the
first movable crank pin dies, the second 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
straight-6-cylinder engine according to claim 8,
wherein provided that a total length of movement of the second 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 the second movable crank pin dies is completed, a length of movement of
the second 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 the second
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
straight-6-cylinder engine according to any one of claims 7 to 9,
wherein the first movable crank pin dies, the second 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 first movable crank pin dies and the second movable crank
pin dies are brought into contact with the rough crank pin portions, and with continued
dow~lward lnovement of the press machine, the movable journal dies are moved axially
by wedge mechanisms, and the first movable crank pin dies and the second movable
crank pin dies are moved axially by the movement of the movable journal dies.
1 1. 'The apparatus for forming a blank for finish forging for a forged crankshaft for a
straight-6-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 1-inish forging for a forged crankshaft for a
straight-6-cylinder engine according to claim 10 or 1 1, .
wherein the second 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 manufacturing a forged crankshaft for a straight-6-cylinder engine,
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 sixth rough crank pin portions at opposite ends and third and fourth rough crank pin
portions in the center among the rough crank pin portions 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 a 4312 of an amount of
eccentricity of the crank pins of the forged crankshaft, and second and fifth rough crank
pin portions have an amount of eccentricity in the direction perpendicular to the axial
direction, in a direction perpendicular to the eccentric direction of the first and sixth
rough crank pin portions and the third and fourth 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 manufacturing a forged crankshaft for a straight-6-cylinder engine,
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 sixth rough crank pin portions at opposite ends and third and fourth rough crank pin
portions in the center among the rough crank pin portions have an amount of
eccentricity in the 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 second and fifth rough crank pin portions have
an amount of eccentricity in the direction perpendicular to the axial direction, in the
opposite direction of an eccentric direction of the first, third, fourth, and sixth 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, by performing finish forging on the blank for finish
forging, forming 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 manufacturing a forged crankshaft for a straight-6-cylinder engine,
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 sixth rough crank pin portions at opposite ends and third and fourth rough crank pin
portions in the center among the rough crank pin portion have an amount of eccentricity
in the direction perpendic~~lator the axial direction in the opposite direction to each
other, the amoulit of eccentricity thereof being smaller than a 4312 of an amount of
eccentricity of the crank pins of the forged crankshaft, and second and fifth rough crank
pin portions have an atnount 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 the first and sixth rough crank pin portions at opposite ends and the third and
fourth rough crank pin portions in the center among the rough crank pin portion 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 and fifth rough crank pin portions remain the amount of ecce~~tricitiyn 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 sixth rough crank
pin portions at opposite ends and the third and fourth rough crank pin portions in the
center are horizontally positioned whereby all the rough crank pin portions are pressed
in the direction perpendicular to the axial direction.
16. A method for manufacturing a forged crankshaft for a straight-6-cylinder engine,
comprising the successive steps of:
a first preforming step of 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 sixth rough crank pin portions at opposite ends and third and fourth rough crank pin
portions in the center among the rough crank pin portions 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 smaller than a 4312 of an amount
of eccentricity of the crank pins of the forged crankshaft, and second' and fifth rough
crank pin portions have an amount of eccentricity in the direction perpendicular to the
axial direction, in a direction perpendici~lar to the eccentric direction of the first and
sixth rough crank pin portions and the third and fourth 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 sixth rough crank pin portions at opposite ends and the third and
fourth rough crank pin portions in the center among the rough crank pin portion 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 and fifth rough crank pin portions remain the 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 sixth rough crank
pin portions at opposite ends and the third and fourth iough crank pin portions in the
center are horizontally positioned whereby the first, third, fourth, and sixth rough crank
pin portions are pressed in the direction perpendicular to the axial direction.