Note: Descriptions are shown in the official language in which they were submitted.
~256~65
The present invention relates to a process for manu~ac-
turing a siamese-type cylinder block and more particularly, to
such a process comprising a blank making st.ep of providing a
cylinder block blank in which a sleeve made of a cast iron is
incorporated in each cylinder barrel of a siamese-type cylinder
barrel made of an aluminum alloy and consisting of a plurality of
cylinder barrels connected in ser~es, and a mechanical working or
machining step of ~orming the inner peripheral surface of each
sleeve of the resulting cylinder block blank into a true circle.
Such conventional blank making steps include placing
sleeves in a siamese-type cylinder barrel molding cavity in a
mold and then, pouring a molten metal of aluminum alloy under
pressure into the cavity for casting. Thereby, a casting strain
is produced in the cylinder barrels in the blank due to the cast-
ing pressure and the action of rapid solidification of the alu-
minum alloy. With a sleeve having a smaller thickness and a
lower rigidity, such a casting strain influences the sleeve to
produce a strain therein. To avoid this, the thickness of the
sleeve may be increased, but with a too large thizkness, the
amount of sleeve to be cut is increased in subsequent working
into a true circle, which is uneconomical and causes an increase
in working time. Even if the thickness of the sleeve is
increased, there are the following problems which arise with a
cylinder block resulting from the immediately working of the
inner peripheral surface of the sleeve into a true circle after
the casting of the blank. In the operation of an engine assem-
bled using such cylinder block, the casting strain in the cylin-
der barrel influences the sleeve ~hen the cylinder barrel heated
during the operation has been returned to an ambient temperature
after the stoppage of operation of the engine, thereby causing
the amount of permanent deformation of the inner diameter of the
sleeve to increase. ThuS, a clearance is produced between a pis-
ton ring and the sleeve resulting in an increased amount of blow-
by gas and a useless consumption of oil.
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When the sleeve has increased thickness at an ambient
temperature, the heat of mol-ten metal is absorbed by the sleeve
so that the molten metal close to the sleeve is solidified ear-
lier than the molten metal close to a breakable core for forming
a water jacket. Consequently, the metal structure in the cylin-
der barrel is different from that at the portion close to the
core. In this case, both the metal structures around the sleeves
vary in thickness in the radial direction of the sleeve, and
because the region between the adjacent sleeves is not occupied
by the core, the metal structure between the ad~acent sleeves is
different from both the above metal structures. In addition to
the problem in metal structure, be~ause the shrinkage o~ the
sleeve heated by the molten metal does not follow the solidifica-
tion shrinkage of the molten metal, the casting stress remaining
the sleeve is non-uniform around the circumference of the sleeve.
The absorption of the heat of the molten metal by the
sleeve causes the early solidification of the molten metal to
degrade the close adhesion between the sleeve and the molten
metal, thereby producing a very small clearance between the
sleeve and the cylinder barrel resulting in a poor release of
heat from the sleeve.
Thus, if the casting stress remaininy in the sleeve is
non-uniform around the circumference of the sleeve and the
release of heat from the sleeve is poor, in the operation of an
engine assembled using a cylinder block obtained through the
working of the inner peripheral surface of such sleeve into a
true circle, the amount of sleeve thermally expanded is non-uni-
form around the circumference of the sleeve, causing a clearanceto be produced between a piston ring and the sleeve, resulting in
the same problems as described above.
In providing a blank as described above and including a
water ~acket to which the entire periphery of a siamese-type
cylinder barrel faces, operations which have been adopted include
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placing sleeves and a water-~acket shaplng breakable core sur-
rounding the sleeves into a siamese-type cylinder barrel molding
cavity in a mold and then, pouring a molten metal of aluminum
alloy into the cavity to cast a blank, removing unnecessary por-
tions such as gates and runners from the blank and then, breakingthe breakable core to remove about half thereof by applylng
vibration to the blank, and heating the blank for a period of
about 4 hours at a temperature of 350C or more to burn a binder
contained in the core and enhance the breakabillty of the remain-
der of the core. In the above heating step, the heating causesthe hardness of the aluminum alloy portion in the blank to be
considerably reduced and make it impossible for a cylinder head-
bound surface, a crank ~ournal bearing holder, an oil pan-bound
surface of a crankcase or the like to retain a satisfactory hard-
ness. Therefore, the heating step has been ~ollowed by an opera-
tion comprising subjecting the blank to a T6 treatment, namely to
a thermal treatment of heating the blank for a period of about 2
hours at a temperature of about 500C and then cooling it with
water to provide the recovery of the hardness, breaking the
remainder of the core to remove it from the blank by applying
vibration to the blank, subjecting the blank to cleaning and
checking the resulting blank.
However, the abov~ conventional process is accompanied
by a problem that even if the T6 treatment enables the hardness
of the aluminum alloy portion in the blank to be improved, a non-
uniform stress remains in the sleeve at the coollng step in the
above treatment and thus, a high performance cylinder block can-
not be obtained.
The conventional process also has the disadvantage of
uneconomically increasing the amount of energy consumed due to
two heating steps included therein.
The present invention provides a process for manufac-
turing a siamese-type cylinder block wherein using a highly rigid
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sleeve having a specific thickness, a siamese-typ0 cylinder block
of an improved economy can be obtained with a reduced in~luence
of the casting strain in a cylinder barrel on the sleeve and with
a decreased amount o~ sleeve cut to machine -the inner peripheral
surface of the sleeve into a true circle.
The present invention also provides a process for manu-
; facturing a siamese-type cylinder barrel wherein using a highly
rigid sleeve having a specific thickness, a siamese-type cylinder
block can be produced with a reduced influence of the casting
strain in a cylinder barrel on thl3 sleeve and wi-th the casting
strain in the cylinder barrel being diminished by a thermal
treatment, thereby to substantially reduce the amount of perma-
nent deformation of each sleeve in its inner diameter.
Further, the present invention provides a process for
manufacturing a siamese-type cylinder block wherein using a
highly rigid sleeve having a specific thickness, a siamese-type
cylinder block can be ob~ained with a reduced influence of the
casting strain in a cylinder barrel on the sleeve and with the
casting stress remaining in the sleeve being made substantially
uniform around the circumference of the sleeve while the release
of heat of the sleeve is improved by heating -the sleeve to a
predetermined temperature to castingly incorporate it, so that
the amount of each sleeve thermally expanded may be substantially
uniform around the circumference of the sleeve during the opera-
tion of the engine.
Still further the present invention provides a process
for manufacturing a siamese-type cylinder block wherein a water-
jacket shaping breakable core is removed at ambient temperature
and a thermal treatment is conducted to an extent such that
; strain relieving may be achieved, thus economically producing a
high performance siamese-type cylinder block.
Accorcling to the present invention, there is provided a
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process for manufac-turing a siamese-type cylinder block, compris-
ing a blank making step of providing a cylinder block blank in
which a sleeve made of a cast iron is incorporated in each cylin-
der barrel of a siamese-type cylinder barrel made of an aluminum
alloy and consisting of a plurality of cylinder barrels co~mected
in series, and a mechanically wor]cing or machining step of form-
ing the inner peripheral surface of each sleeve of the resulting
cylinder block blank in-to a true circle, wherein -the blank making
step includes placing highly rigid sleeves each having a thick-
ness of 10~ or more of the inner diameter thereof lnto a siamese-
- type cylinder barrel molding cavity in a mold and then pouring a
molten metal of aluminum alloy under a pressure into the cavity
to effect a casting.
According to the present invention, there is also
provided a process for manufacturing a siamese-type cylinder
block, comprising a blank making step of providing a cylinder
block blank in which a sleeve made of a cast iron is incorporated
in each cylinder barrel of a siamese-type cylinder barrel made of
:20 an aluminum alloy and consisting of a plurality of cylinder bar-
rels connected in series, and a mechanically working or machining
step of forming the inner peripheral surface of each sleeve of
the resulting cylinder blocX blank into a true circle, wherein
the blank making step includes placing highly rigid sleeves each
having a thickness of 10% or more of the inner diameter thereo~
into a siamese-type cylinder barrel molding cavity in a mold and
then pouring a mo~ten metal of aluminum alloy under a pressure
into the cavity to cast a cylinder block blank, and subjecting
the cylinder block blank to a thermal treatment to reduce the
casting strain produced in the cylinder barrel.
Further, according to the present invention, there is
provided a process for manufacturing a siamese-type cylinder
block, comprislng a blank making step of providing a cylinder
block blank in which a sleeve made of a cast iron is incorporated
in each cylinder barrel of a siamese-type cylinder barrel made of
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an aluminum alloy and consisting of a plurallty of cylinder bar-
rels connected in series, and a mechanically working or machining
step of forming the inner peripheral surface of each sleeve of
the resulting cylinder block blank into a true circle, wherein
the blank making step includes heating highly rigid sleeves each
having a thickness of 10% or more of the inner diameter thereof
to a temperature of 150 to 700C, thereafter placing them in a
siamese-type cylinder barrel mold:lng cavlty in a mold and then
pouring a molten metal of aluminum alloy under a pressure into
the cavity to effect a casting.
Yet further, according to the present invention, there
is provided a process for manufacturing a siamese-type cylinder
block, comprising a blank making step of providing a cylinder
block blank in which a sleeve made of a cast iron is incorporated
in each cylinder barrel of a siamese-type cylinder barrel made of
an aluminum alloy and consisting of a plurality of cylinder bar-
- rels connected in series and which includes a water ~acket faced
by the entire periphery of the siamese-type cylinder barrel, and
~` 20 a mechanical working or machining step o~ forming the inner
peripheral surface of each sleeve of the resulting cylinder block
blank into a true circle, wherein the blank making step includes
placing the sleeves and a water-jacket shaping breakable core
surrounding the sleeves in a siamese-type cylinder barrel molding
cavity in a mold and then pouring a molten metal of aluminum
~: alloy into the cavity to cast a cylinder block blank, breaking
: the core at an ambient temperature to remove it from the cylinder
block blank, and sub~ecting the cylinder block blank to anneal-
ing.
According to the procedure of the above process, a
highly rigid sleeve having a thickness of 10% or more o~ the
inner diameter thereof is castingly incorporated in each cylinder
barrel and therefore, the influence of the casting strain in the
cylinder barrel can be diminished on the sleeve and moreover, the
amount of sleeve cut can be reduced when working o~ the inner
s~ s~
peripheral surface of the sl2eve into a true circle to improve
economy.
While the casting incorporation of each thick and
highly rigid sleeve having a thic]cness of 10% or more of the
inner diameter thereof in each cy:Linder barrel results in a
- diminished influence of the casting strain in the cylinder barrel
on the sleeve, the cylinder block blank is then subiected to a
thermal treatment to reduce the casting strain in the cylinder
barrel and thereafter, the inner peripheral surface of the sleeve
is worked into a true circle, so that even if the sleeve is con-
sequently of a smaller thickness and a lower rigidity, the reduc-
tion of the casting strain in each cylinder barrel enable the
influence of such casting strain to be substantially eliminated.
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:: Therefore, in the op~ration of an engine assembled
using such a cylinder block, the amount of permanent deformation
of each sleeve in inner diameter is very small and hence, a
clearance is suppressed to the utmost from ~eing produced between
a piston ring and the sleeve, thus making it possible to overcome
problems of an increase in amount of blow-by gas and a useless
consumption of oil.
In addition, since the influence of the casting strain
: 25 in each cylinder barrel is reduced on each sleeve, it is possible
to place the adjacent sleeves maximally close to each other,
whereby the cylinder block and thus, the entire engine can be
small-sided to achieve a lightweight.
Further, each thick and highly rigid sleeve having a
thickness of 10~ or more of the inner diameter thereof is heated
to a temperature of 150 to 700C and castingly incorporated in
each cylinder barrel and hence, the influence of the casting
strain in the cylinder barrel on the sleeve is reduced, while the
casting stress remaining in the sleeve is substantially uniform
around the circumference of the sleeve and further, the release
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of heat of the sleeve is good. In the operation of an engine
assembled using such a cylinder block, the amount of each sleeve
thermally expanded is substantially uniform around the circumfer-
ence of the sleeve and thus, clearance can be minimized between
the piston ring and the sleeve as in the case described above.
In addition, bscause the ~nfluence of the casting
strain in each cylinder barrel on each sleeve is smaller and the
casting stress remaining in the s:Leeve is substantially uniform
- lO around the circumference of the s:Leeve, it is possible to place
the ad~acent sleeves as close to each other as possible as in the
case described above.
Further, since the water-~acket shaping core is broken
at ambient temperature and removed from the cylinder block blank,
the hardness of the blank cannot be reduced. Thereupon, a T6
treatment i5 not required for recovering the hardness of the
; blank and thus, a high performance cylinder block can be provided
by merely subjecting the blank to an annealing treatment for
strain relief.
Any thermal treatment is also not required for removing
the core, and the above annealing treatment is conducted in a
shorter time at a relatively low temperature, thu9 making it
possible to su~stantially reduce energy consumption and improve
an economy.
The features and advantages of the invention will
become apparent from reading the following description taken in
con~unction with the accompanying drawings, in which:-
Fig.s 1 to 4 illustrate an in-line siamese-type cylin-
der block provided according to the present invention;
Fig. 1 is a perspective view of the apparatus from
above;
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Fig. 2 is a sectional view taken along line II-II in
Fig~ l;
Fig. 3 is a perspective view of the apparatus from
below;
Fig. 4 is a sectional view taken along line IV-IV in
Fig. 2;
Fig. 5 is a perspective view of a siamese-type cylinder
block blank produced in a casting process accordlng to the pre-
sent invention, viewed from above;
Fig. 6 is a front view in vertical section of the cast-
ing apparatus with the mold open;
Fig. 7 is a front view in vertical section of the cast-
ing apparatus with the mold closed;
Fig. 8 is a sectional view taken along line VIII-VIII
in Fig, 7;
Fig. 9 is a sectional view taken along line IX-IX in
Fig. 8;
Fig. 10 is a sectional view taken along line X-X in
Fig. 6;
.
Fig. 11 is a perspective view of a sand core from
above;
Fig. 12 is a sectional view taken along line XII-XII in
Fig. 11;
Fig. 13 is a graph representing the relationship
between time and displacement of plunger and the relationship
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between time and pressure of molten metal;
Fig. 14 is a graph illustrating the relationship
between the depth of sleeve from its cylinder head-bound surface
and the amount of sleeve permanently deformed at inner diameter;
Fig.s 15A to 15C are micrographs showing the metal
structure of the cylinder barrel in the siamese-type cylinder
block obtained according to the present invention, respectively;
Fig.s l~A to 16C are micrographs showing the metal
structure of the cylinder barrel in the siamese-type cylinder
block in the comparatlve example, respectively;
Fig. 17 is a micrograph showing the metal structure of
the deposited portion between the cylinder barrel and the sleeve
in the siamese-type cylinder block obtained according to the pre-
sent invention,
Fig. 1~ is a micrograph showing the metal structure of
the deposited portion batween the cylinder barrel and the sleeve
in the siamese-type cylinder block in the comparative example;
Fig. l9A is a graph illustrating the ~elationship
between the depth of sleeve from its cylinder head-bou~d surface
and the amount of sleeve permanently deformed in inner diameter
in the siamese-type cylinder block obtained according to the pre-
sent invention;
:
Fig. l9B is a graph illustrating the relationship
between the depth of sleeve from its cylinder head-bound surface
and the amount of sleeve permanently deformed in inner diameter
in the siamese-type cylinder block in the comparative example;
and
Fig. 20 is a perspective view of a V-shaped slamese-
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type cylinder block, viewed from above.
Referring to Figs. 1 to ~, therein is shown an in-line
siamese-type cylinder block S obtained according to the present
invention. The cylinder block S is comprised of a cylinder block
body 2 made of an aluminum alloy and a sleeve 3 made of a cast
iron and cast in the body 2. The cylinder block body 2 is con-
stituted of a siamese-type cylinder barrel 1 consisting oE a plu-
rality of, e.g., four (in the illustrated embodiment) cylinder
barrels 11 to 14 connected to one another in series, an outer
wall 4 surrounding the siamese-type cylinder barrel 1, and a
crankcase 5 connected to the lower edges of the outer wall 4.
The sleeve 3 is cast in each of the cylinder barrels 11 to 14 to
define a cylinder bore 3a.
A water jacket 6 is defined between the siamese-type
cylinder barrel 1 and the outer wall 4, so that the entire
periphery of the siamese-type cylinder barrel 1 faces the water
jacket 6. At the opening on the cylinder head blnding side at
the water jacket 6, the siamese-type cylinder barrel 1 is con-
nected with the outer wall 4 by a plurality of reinforcing deck
portions 8, and the space between the ad~acent reinforcing deck
portions 8 functions as a communication port 7 into a cylinder
head. Thereupon, the cylinder block S is constituted into a
closed deck type.
Fig. 5 illustrates a cylinder block blank Sm produced
by the casting, and a sleeve in this blank Sm has an inner diame-
ter of 78 mm and a thickness of 10% or more of the inner diameter
thereof, for example, of 8 mm.
Fig.s 6 to 10 illustrate an apparatus for casting a
cylinder block blank Sm, which apparatus comprises a mold M. The
mold M is constituted of a liftable upper die 9, first and second
laterally split side dies 101 and 12 (see Fig.s 6 and 7) dis-
posed under the upper die 9, and a lower die 11 on which both the
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side dies lOl and l2 are slidably laid.
A clamping recess 12 is provided at the underside of
the upper die 9 to define the upper surface of a first cavity Cl,
and a clamping pro~ection 13 adapted to be fitted in the recess
12 is provided on each of the side dies lOl and l2 The first
cavity ~l consists of a siamese-type cylinder barrel molding cav-
ity Ca defined between a water-jacket molding sand core 59 as a
breakable core and an expansion shell 46, and an outer wall mold-
ing cavity Cb defined between the sand core 59 and both the side
dies lOl and 102, in the clamped condition as shown in Fig. 7.
AS shown in Fig.s 8 and 9, the lower die ll includes a
basin 14 for receiving a molten metal of aluminium alloy from a
furnace (not shown), a pouring cylinder 15 communicating with the
basin 14, a plunger 16 slidably fitted in the pouring cylinder
15, and a pair of runners 17 bifurcated from the basin 14 to
extend in the direction of the cylinder barrels. The lower die
ll also has a molding block 18 projectin~ upwardly between both
of the runners 17, and the molding block 18 defines a second cav-
ity C2 for molding the crankcase 5 in cooperation with both the
side dies 101 and 102. The cavity C2 is in communication at its
upper end with the first cavity Cl and a~ ~ts lower end with both
the runners 17 through a plurality of gates 19.
The molding block 18 is comprised of four first taller
semi-columnar molding portions l8l formed at predetermined inter-
vals, and second protruded molding portions 182 located between
the ad~acent first molding portions l8l and outside both of the
outermost first molding portions l81. Each first molding portion
18l is used for molding a space 20 (see Fig.s 2 and 3) in which a
crankpin and a crankarm are rotated, and each second molding por-
tion 182 is employed to mold a crank journal bearing holder 21
(see Fig.s 2 and 3). Each gate 19 is provided to correspond to
each of the second molding portions l82 and designed to p0rmit
the charging or pouring of a molten metal in larger volume por-
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tion of the second cavity C2 in an early stage.
soth the runners 17 are defined with their bottom sur-
faces stepped in several ascending stairs to stepwise decrease in
section area from the basin 14 toward runner extensions 17a.
Each raised portion 17c connected to each of the stepped portion
17b is angularly formed to be able to smoothly guide molten metal
into each of the gates 19.
With the sectiona] area of the runner 17 decreasing
stepwise in this manner, a larger 'amount of molten metal can be
charged or poured, at the portion larger in sectional area, into
the second cavity C2 through the gate 19 at a slower speed, and
at the portion smaller in sectional area, into the second cavity
through the gate 19 at a faster speed, so that the molten metal
level in the cavity C2 rises substantially equally over the
entire length of the cavity C2 from the lower ends on the oppo-
site sides thereof. Therefore, the molten metal cannot produce
any turbulent flow and thus, a gas such as air can be prevented
from being included into the molten matal to avoid the generation
of mold cavities. In addition, a molten metal pouring operation
is effectively conducted, leading to an improved casting sffi-
ciency.
As shown in Fig.s 6 and 7, a locating projection 22 is
provided on the top of each of the first molding portions 181 and
adapted to be fitted in the circumferential surface of the sleeve
3 of cast iron, and a recess 23 is defined at the central portion
of the locating projection 22. A through hole 24 is made in each
of two first molding portions 181 located on the opposite sides
to penetrate the first molding portion 181 on each of the oppo-
site sides of the locating projection 22. A pair of temporarily
placed pins 2~ are slidably fitted in the through holes 24,
respectively, and are used to temporarily place the water-jacket
molding sand core 59. The lower ends of the pins 25 are fixed on
a mounting plate 26 dlsposed below the molding block 18. Two
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support rods ~7 are inserted through the mounting plate 26, and a
coil spring 28 is provided in compression between the lowex por-
tion of each of the support rods 27 and the lower surface of the
mounting plate 26. During opening of the mold, the mounting
plate 26 is subjected to the resilient force of each of the coil
springs 28 to move up untll it abuts against the stopper 27a on
the fore end of each of the support rods 27. This causes the
fore end of each of the pins 25 to protrude from the top surface
of the first molding portion 181. A recess 25a ls made in the
fore end of each of the pins 25 and adapted to be engaged by the
lower edge of the sand core.
A through hole 29 is macle between the two first molding
portions 181 located on the opposite sides at the middle between
both the through holes 24, and an operating ~in 30 is slidably
~- fitted in the through hole 29. The lower end of the operating
pin 30 is fixed to the mounting plate 26. During opening of the
mold, the fore end of the operating pin 30 protrudes into the
recess 23, and during closing of the mold, it is pushed down by
an expanding mechanism 41, thereby retracting the pins 25 from
the top surfaces of the first molding portions 181o
A core bedding recess 31 for the sand core 59 is
- provided at two places: namely in the central portions of those
walls of the first and second side dies 101 and 12 defining the
second cavity C2. Each of the core bedding recesses 31 consists
of an engaging bore 31a in which the sand ~ore is positioned, and
a clamp surface 31b formed around the outer periphery o~ the
opening of the engaging bore 31a for clamping the sand core.
In the clamping recess 12 of the upper die 9 are a plu-
rality of third cavities C3 opened into the first cavity C1 to
permit the overflow of molten metal and a plurality of fourth
cavities C4 for shaping the communication holes 7. The upper die
9 also has gas vent holes 32 and 33 therein which are communi-
cated with each of the third cavities C3 and each of the fourth
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cavities C4, respectively.
Closing pins 34 and 35 are inserted into the gas vent
holes 32 and 33, respec-tively, and are fi~ed at their upper ends
to a mounting plate 36 disposed above the upper die 9.
The gas vent holes 32 and 33 have smaller diameter por-
tions 32a and 33a, respectively, which extend upwardly a prede-
termined length from the respect:Lve ends of the gas vent holes 32
and 33, communicating with the cavities C3 and C4, and which are
fitted with the corresponding closing pins 34 and 35 so that the
third and fourth cavities C3 and C4 may be closed.
A hydraulic cylinder 39 is disposed between the upper
surface of the upper die 9 and the mounting plate 36 and operates
to move the mounting plate 36 upwardly or downwardly, thereby
causing the individual closing pins 34 and 35 to close the corre-
sponding smaller diameter portions 32a and 33a. It is to be
noted that the reference numeral 40 designates a rod for guiding
the mounting plate 36.
The expanding mechanism 41, which is provided in the
upper die 9 for applying an expansion force to the sleeve 3 cast
in each of the cylinder barrels ll to 14, is constituted in the
following manner.
: A through hole 42 is made in the upper die 9 with its
center line aligned with the extension o~ the axis of the operat-
ing pin 30, and a support rod 43 is loosely lnserted ~nto the
through hole 42. The support rod 43 is fixed at its upper end to
a bracket 44 above the upper surface of the upper die 9, and it
has, as a sealing member, a plate 45 secured at its lower end for
blocking the entry of molten metal. The blocking plate 45 is
formed at its lower surface with a pro~ectlon 45a which is fit-
table in the recess 23 at the top of the first molding portion
181 .
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The hollow expansion shell ~6 has a circular outerperipheral surfac~ and a tapered hole 47 having a downward slope
from the upper portion toward the lower portion. The lower por-
tion of the support rod 43 pro~ecting downwardly from the upper
die g is loosely inserted into the tapered hole 47 of the expan-
sion shell 46 whose upper end sur~Eace bears against a pro;ection
48 disposed as a sealing member on the recess 12 of the upper die
9 and whose lower end ~urface is carried on the blocking plate
45. AS shown in Fig. 10, a plurality of slit grooves 49 are made
in the peripheral wall of the expansion shell 46 ak circumferen-
tially equal intervals to radially extend alternately from the
inner and the outer peripheral surfaces of the expansion shell
46.
A hollow operating or actuating rod 50 is slidably fit-
ted on the support rod 43 substantially over its entire length
for expanding the expansion shell 46, and is comprised of a frus-
toconical portion 50a adapted to be fitted in the tapered hole ~7
of the expansion shell 46, and a truly circular portion 50b con-
tinuously connected to the frustoconical portion 50a so as to be
slidably fitted in the through hole 42 and protruded from the
upper die 9. A plurality of pins 57 protrude from the frustocon-
ical portion 50a and e~ch is inserted into a vertically long pin
hole 58 of the expansion shell 46 to prevent the expansion shell
46 from being rotated while permitting the vertical movement of
the frustoconical portion 50a.
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A hydraulic cylinder 51 is fixedly mounted on the upper
surface of the upper die g and contains a hollow piston 52
therein. Hollow piston rods 531 and 532 are mounted on the upper
and lower end surfaces of the hollow piston 52 and pro~ect there-
from to penetrate the upper and lower end walls of a cylinder
body 54, respectively. The truly circular portion 50b of the
operating rod 50 is inserted into a hole through the hollow pis-
ton 52 and the hollow piston rods 531 and 532~ and anti-slip-off
stoppers 561 and 562 each fitted in an annular groove of the
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truly circular portion 50b are mounted to bear against the upper
end surface of the hollow piston rod 531 and the lower end sur-
face of the hollow piston rod 532~ respectively, so that the hol-
low piston 52 causes the operating rod 50 to be moved up or down.
The four expanding mechanisms 41 may be provided to correspond to
the individual cylinder barrels 11 to 14 of the cylinder block S,
respectively.
Fiy . s 11 and 12 show the water-jacket molding sand core
59 which is constituted of a core body 61 comprising four cylin-
drical portions 601 to 604 corresponding to the four cylinder
barrels 11 to 1~ of the cylinder block S with the peripheral
interconnecting walls of the ad~acent cylindrical portions being
eliminated, a plurality of pro~ections 62 formed on the end sur-
face of the core body 61 on the cylinder head binding side todefine the communication ports 7 for permitt~ng the communication
of the water jackets 6 with the water ~ackets of the cylinder
head, and a core print 63 protrudedly provided on the opposite
(in the direction of the cylinder barrels) outer side surfaces of
the core body 61, e.g, on the opposlte outer side surfaces of two
cylindrical portions 602 and S03 located between the outermost
ones in the iIlustrated embodiment. Each of the core prints 63
is formed of a larger diameter portion 63a integral with the core
body 61, and a smaller diameter portion 63b on the end surface of
the larger diameter portion 63a. In this case, the projection 62
is sized to be loosely fitted in the aforesaid fourth cavity C4.
The sand core 59 is formed, for example, of a resin-coated sand.
Description will now be made of an operation of casting
a cylinder block blank Sm in the above casting apparatus.
First, as shown in Fig. 6, the upper die 9 is moved up
and both the side dies 101 and 12 are mo~ed away from each
other, thus causing the opening of the mold. In the expanding
mechanism 41, each hydraulic cylinder 51 is operated to cause the
hollow piston 52 to move the operatin~ rod 50 downwardly, so that
`.i~
' ~ ' , ' - '
,
-
.,
~ 5~ 6 ~
the downward movement of the frustoconical portion 50a allows the
expansion shell 46 to be co~tracted. In addition, the hydraulic
cylinder 39 of the upper die 9 is operated to move the mounting
plate 36 upwardly. This causes the individual closing pins 34
and 35 to be released from the corresponding smaller diameter
portions 32a and 33a, respectively communicating with the third
and fourth cavlties C3 and C4. Further, the plunger 16 in the
pouring cylinder 15 is moved downwardly.
The substantially truly circular and highly rigid
sleeve 3 of cast iron having a thi~kness as large as ~ mm is
loosely fitted in each expansion shell 46, and the opening at the
upper end of the sleeve 3 is fitted and closed by the pro~ection
48 of the upper die 9. The end surface of the sleeve 3 is
aligned with the lower end surface of the pro;ection 45a on the
blocking plate 45, while the opening at the lower end of the
sleeve 3 is closed by the blocking plate ~5. The hydraulic
cylinder 51 of the expanding mechanism 41 is operated to cause
the hollow piston 52 therein to lift the operating rod 50. The
frustoconical portion 50a is thereby moved upwardly, so that the
expansion shell 46 is expanded. Thereupon, the sleeve 3 is sub-
jected to an expansion force and thus reliably held on the expan-
sion shell 46.
As shown in Fig.s 6 and 12, the lower edges of the
cylindrical portions 601 and 604 on the outermost oppositP sides
in the sand core 59 are each engaged in the recess 25a of each
pin 25 projecting from the top of each of the first molding por-
tions 181 on the opposite sides in the lower die 11, thereby tem-
porarily placing the sand core 59.
The side dies 101 and 12 are moved a predetermined
distance toward each other to engage each core bedding recess 31
with each core print 63, thus really plac~ng the sand core 59.
More specifically, the smaller diameter 63b of each of the core
prints 63 in the sand core 59 is fitted into the engaging hole
- 18 -
,
31a of each of the core bedding recesses 31 to position the sand
core 59, with the end surface of each of the larger diameter por-
tions 63a a parallel to the direction of the cyllnder barrels,
being mated wi-th the clamping surface 31b of each core bedding
recess 31 to clamp the sand core 59 by the clamping surface 31b.
As shown in Fig. 7, the upper dle 9 is moved downwardly
to insert each of the sleeves 3 into each of the cylindrical por-
tions 601 to 604 of the sand core 59, and the projection 45a of
the molten metal-entering blocking plate 45 is fitted into the
~ecess 23 at the top of the first Imolding portion 181. This
causes the pro~ection 45a of the blocking plate 45 to push down
the operating rod 30, so that each of the pins 2s is moved down
and retracted from the top surface of the first molding portion
18~. In addition, the clamping recesses 12 of the upper die 9
are fitted with the clamping projections 13 of both the side dies
101 and 12~ thus effecting the clamping of the mold. This down-
ward movement of the upper die 9 causes the projection 62 of the
sand core 59 to be loosely inserted into the fourth cavity C4,
wh2reby a space is defined around the pro~ection 62. A space 70
for shaping the reinforcing deck portion 8 is also defined
between the end surface of the sand core 59 and the inner surface
of the recess 12 opposed to such end surface.
A molten metal of aluminum alloy is supplied out of a
furnace into the basin 14 of the lower die 11, and the plunger 16
~- is moved up to pass the molten metal through both the runners 17
and pour it into the second cavities C2 and the first cavities Cl
from the opposite lower edges of the second cavities C2 vla the
gates 19. The application of this bottom pouring process allows
a gas such as air in both the cavities Cl and C2 to be forced up
by the molten metal and vented upwardly from the upper die 9 via
- the gas bent holes 32 and 33 in communication with the third and
fourth cavities C3 and C4.
In the present case, both the runners 17 have the run-
-- 19 --
- , . - . -. . .
, , . .. , . . -
. ' . - - - ' ' ' . . ~ ' , '
- .
.
.
-
j5
ner bo-ttom stepped in several upward stairs form the basin 14 so
that the sectional area may decrease stepwise toward the runner
extensions 17a as described above and hence, the upward movement
of the plunger 16 causes a molten m0tal to be passed from both
the runners 17 through the gates 19 and to smoothly rise in the
second cavlties C2 substantlally lmiformly over the entire length
thereof from the opposite side lo~er end thereof. Thus, the
molten metal cannot produce a turbulent flow in both the cavities
Cl and C2, and a gas such as air can be prevented from being
included into the molten metal to avoid the generation of any
mold cavities.
After the molten metal has been poured in the third and
fourth cavities C3 and C4, the hydraulic cylinder 39 on the upper
die 9 is operated to move the mounting plate down, thereby caus-
ing the closing pins 34 and 35 to close the smaller diameter por-
tions 32a and 33a communicating with the cavities C3 and C4,
respectively.
In the above pouring operation, the displacement of the
plunger 16 for pouring the molten metal into the second and first
cavities C2 and Cl and the pressure of the molten metal are con-
trolled as shown in Fig. 13.
More spscifically, the speed of plunger 16 is con-
trolled at three stages of first to third velocities Vl to v3.
In the present embodiment, the first velocity Vl is set at 0.08-
0.12 m/sec., the second velocity V2 is at 0.14-0.18 m/sec., and
the third velocity V3 is at 0.04-0.08 m/sec. to give a substan-
tial deceleration. This control in velocity at three stages pre-
vents the waving of the molten metal and produces a calm molten
metal flow which cannot include a gas such as air thereinto, so
that the molten metal can be poured into both the cavities C2 and
Cl with a good efficiency.
At the first velocity Vl of the plunger 16, the molten
- 20 -
metal merely ~ills both the runners 17 and hence, the pressure Pl
of the molten metal is kept substantially constan-t. At the sec-
ond and third velocities V2 and v3 of the plunger 16, the molten
metal is poured or charged into both the cavities Cl and C2 and
therefore, the pressure P2 of the molten metal rapidly increases.
After the plunger 16 has been moved at the third velocity V3 for
a predetermined period of time, the pressure P3 of the molten
metal is maintained at 150-400 kg/cm2 for a period of about 1.5
seconds, whereby the sand core 5~ is completely enveloped in the
molten metal to form a solidified film of molten metal on the
surface thereof.
After the above time has elaps0d, the plunger 16 is
deceleratively moved at the velocity v4, so that the pressure P4
of the molten metal increases. When the pressure has reached a
level P5 of 200-600 kg/cm2, the movement of the plunger 16 is
stopped, and under this condition, the molten metal is solidi-
fied.
If the pressure of the molten metal is kept constant
for a predetermined period of time to form the solidified ~ilm of
molten metal on the surface of the sand core 59 as described
above, the sand core 59 can be protected by th~ fil~ against
breaking. In addition, the sand core 59 is expanded due to the
molten metal, but because the projection 62 is loosely inserted
in the fourth cavity C4, it follows the expansion of the sand
core 59, whereby the folding of the pro;ection 62 is avoided.
Since the sand core 59 is clamped in an accurate posi-
tion by both the side dies 101 and 12 through each of the core
prints 63, it cannot float up during pouring the molten metal
into the first cavities Cl and during pressing the molten metal
in the cavities Cl. In addition, since the end surface of the
larger diameter portion 63a of each core print 63 mates with the
clamping surface 31b, as the sand core 59 is being expanded, the
deforming force thereof is suppressed by each of the clamping
:.
~56?~65
surfaces 31b to prevent the deformation of the sand core 59.
Thus, a siamese-type cylinder barrel 1 is provided having a uni-
form thickness around each of the sleeves 3.
As discussed abnve, a closed deck-type cylinder block
blank can be cast with substantially the same production effi-
ciency as in a die casting process, by controlling the speed of
plunger 16 and the pressure of the molten metal.
After the completion of solidification of the molten
metal, the hydraulic cylinder 51 of the expanding mechanism 41 is
operated to move the operating rocl 50 down, thereby eliminating
the expansion force of the expansion shell 46 on the sleeve 3.
The mold is opened -to yield a cylinder block blank Sm as shown in
Fig, 5.
In this cylinder block blank Sm, the influence of the
-~ casting strain in each of the cylinder barrels 11 to 14 on each
sleeve 3 is small, because each sleeve 3 is thick and highly
rigid.
Then, the cylinder block blank Sm is sub;ected to a
thermal treatment for a period of 3 hours at a temperature of
220~ to reduce the casting strain produced in each of the cylin-
der barrels 11 to 14~
Thereafter, the protruded portions 64 (Fig. 5) eachincluding the pro~ection 62 of the sand core 59 are cut away from
the cylinder block blank Sm, so that the communication poxts 7
are consequently defined at the portions corresponding to the
projections 62 and the reinforcing deck portions 8 are each also
formed between the adjacent communication ports 7. Subsequently,
the sand extraction is effected to define the water jacket 6, and
the inner peripheral surface of each sleeve 3 is worked into a
true circle to finish it to a thickness of 5 mm and further
another predetermined working operation is conducted to produce a
,:
- 22 -
'' ' , ~ '." : : ' : ~ - ' ' '
, - ' , . ~ .
. , , ~ . , .
, ~ ~
- .
. . ,
cylinder block S as shown in Fig.s 1 to 4~
In Fig. 14, the line a represents the results of mea-
surements obtained by heating the whole of the above ob-tained
cylinder block S for a period of one hour at the temperature
reached during operation of an engine, ~.e., at 200C and deter-
mining the amount of permanent deformation of the inner diameter
of the sleeve at an ambient temperature. The line b represents
the results of measurements obtained in the same manner with the
cylinder block produced in the comparative example from the
: cylinder block blank as cast without the thermal treatment.
As apparent from Fig. 14, in the cylinder block in the
comparative example, the amount of permanent deformation of the
inner diameter of the sleeve Pxhibits a maximum value of 61~m
at the depth of the sleeve of 20 mm from its cylinder head-bound
surface, while in the cylinder block S obtained according to the
present invention, the amount of permanently deformed inner diam-
eter of the sleeve exhibits a maximum value of 15 ~ m at the
depth of the sleevle 30 mm from its cylinder head-bound surface c.
This means that the thermal treatment of the cylinder block blank
Sm after casting enables the amount of permanent deformation of
the sleeve at its inner diameter to be substantially reduced.
It is to be noted that if the thickness of sleeve 3 is
less than 10% of its lnner diameter, riyidity of the sleeve 3 is
reduced, so that the castlng strain in each of the cylinder bar-
rels 11 to 14 may influence each sleeve 3 to produce a strain in
the sleeve 3. Therefore, a thickness less than 10% of the inner
diameter is not pre~erred.
In the above casting operation, if the sleeves 3 are
castingly ~ncorporated in a state previously heated to a tempera-
ture of 150 to 700C, the casting stress remaining in the sleeve
3 can be substantially uniform around the circumference of the
sleeve 3, and a good close adhesion can be ensured between each
- 23 -
~, .
' . .
.:
.
of sleeve 3 and each of the cyl~nder barrels 11 to 14.
Fig.s 15~, 15B and 15C show the metal structure of the
aluminum alloy in micrographs (200 times1 of the cylinder barrels
11 to 14 in the cylinder block S produced in the process of the
present invention, i.e., by previously heating the sleeves 3 to a
temperature of 250 to 500C and casting-in the sleeves, respec-
tively, at the portion close to the sleeves 3 (in Fig. 15A~, the
central portion (in Fig. 15B) and the portion close to the sand
core 59 (in Fig. 15C). As apparent from these Figures, ln the
cylinder barrels 11 to 14, the metal structures are substantially
identical with one another at the portion close to the sleeves 3,
at the central portion and at the portion close to the sand core
59. This is because the heating of the sleeves 3 to a tempera-
15 ture of 250 to 500C followed by the casting-in thereof permits
the speed of the molten metal solidified to be substantially uni-
form around the sleeve 3. The metal structure at the portion
between the adjacent sleeves 3 is substantially identical with
that shown in Fig. 15A. Also due to the fact that the shrinkage
of the sleeve 3 follows the solidification shrinkage of the
molten metal, the casting stress remaining in the sleeve 3 is
substantially uniform around the circumference of the sleeve 3.
` Fig.s 16A, 16B and 16C show the metal structure of the 25 aluminum alloy in the micrographs (200 times) of the cylinder
barrels in the cylinder block obtained in the comparative example
from the incorporation of the sleeves in the cylinder barrels at
an ambient temperature and corresponding to Fig.s 15A, 15s and
15C, respectively. As apparent from these Figures, the use of
the sleeves at an ambient temperature results in different metal
structures at the portion close to the sleeves, the central por-
tion and the portion close to the core, and in substantially the
same metal structure at the portion between the adjacent sleeves
as that shown in Fig. 16A. In addition, the shrlnkage of the
sleeve may not follow the solidification shrinkage of the molten
metal and consequently, the casting stress remaining in the
.,
; - 24 -
, ', . ' ',, ' , ' .
. .
- . .
. , - -
-
sleeve may be non-uniform around its circumference.
Fig. 17 shows th~ metal structure of the cast iron and
the aluminum alloy in the micrograph (400 times) of the deposited
portion between the sleeve 3 and cylinder barrel 11 in the cylin-
der bloc~ S produced according to the present invention. It can
be seen in this Figure that the adhesion between the cast iron
and the aluminum alloy is good at the interface, namely the
deposited portion between the sleeve 3 and the cyllnder barrel
and no clearance is produced between them. This results in a
good release of heat from the sleeve 3.
Fig. 18 shows the metal structure of the cast iron and
the aluminum alloy in the micrograph ~400 times) of the deposited
portion between the sleeve 300 and the cylinder barrel 1001 in
the cylinder block obtained from the incorporation of the sleeve
at an ambient temperature. It can b~ seen in this Figure, that
the adhesion between the casting iron and the aluminum alloy is
inferior at the interface, namely the deposited portion between
the sleeve 300 and the cylinder barrel 1001 and a very small
clearance G is produced between them. As a result, the release
of heat from the sleeve 300 is inferior.
In the cylinder block S produced according to the pre-
sent invention, the casting stress remaining in the sleeve 3 is
substantially uniform around its circumference and the release of
heat of the sleeve 3 is good. Therefore, when an engine assem-
bled using this cylinder block is operated, the amount of each
sleeve thermally expanded is substantially uniform around its
circumference.
After removing each protruded portion 64 formed in
cooperation of each fourth cavity C4 and each pro~ection 62 of
the sand core 59 in the cylinder block blank Sm as shown in Fig.
5 to make each communication port 7 and each reinforcing deck
portlon 8, the cylinder block blank Sm is subjected to sand ex-
- 25 -
,, :;.,
:. .
~2 ~
traction and to anneali.ng in a manner described herelnbelow, thus
making it possible to economically provide a high performance
cylinder block S.
First, the sand core 59 is roughly broken from the com-
munication port 7 and the opening 75 made from each core print 63
of the sand core 59 in the cylinder block blank Sm using a
chisel, punch, drill or the like, and vibration is then applied
to the cylinder block blank Sm to promote ~he breaking of the
sand core 59, followed by the extraction of the sand from the
blank Sm. In this case, the vibration causes the breaking of the
sand core 59 to proceed and hence, approximately 90% of the sand
: core 59 is removed from the cylinder block blank Sm.
Further, utilizing the aforesaid communication port 7
and opening 75, the inside of the cylinder block blank Sm is sub-
jected to a short blasting or sandblasting treatment to com-
pletely remove the sand core 59 from the blank Sm, thus producing
the water ~acket 6.
The cylinder block blank Sm having the sand core 59
thus removed therefrom is subjected to annealing, i.e., a thermal
treatment of heating the blank Sm to a temperature of 220C for a
period of 3.5 hours for strain relief.
: 25
The resulting cylinder block blank Sm is subjected to
cleaning and checking, followed by machining such as working into
:- a true circle for each sleeve 3 to provide a cylinder block S as
shown in Fig.s 1 to 4.
Fig. 19A illustrates the results of the measurements
for the amount of permanent deformation of the inner diameter of
a sleeve at an ambient temperature, when the above cylinder block
S as a whole is heated to the temperature reached during the
operation of the engine of 200 for a period of 1.5 hours, and
Fig. l9B illustrates the results of the similar measurements in
- 26 -
,
.
.
~5~ 5
the case of the cylinder block obtained in the comparative
example from the conven-tional method, i.e., the procedure includ-
ing the heating treatment for the removal of the sand core, the
T6 treatment and the like.
In Fig. l9A, the lines i to iv represent the results of
the measurements of the sleeves 3 in four cylinder barrels 1l to
14, respectively.
n As can be seen in Fig. 19A, the amount of permanent
deformation of the inner diameter of the sleeve in the cylinder
block S produced according to the present invention is of a maxi-
mum value of 20~ m at a depth of 30 to 50 mm from the cylinder
head-bound surface c, and in this way, the amount of sleeve per-
manently deformed is substantially reduced and also less dis-
tributed in the above range of depth. This is attributable to
the fact that the removal of the sand core 59 at an ambient tem-
perature causes the non-uniform stress not to remain in each
sleeve 3.
On the other hand, as can be seen in Fig. l9B, the
amount of permanent deformation of the inner diameter of the
sleeve in the cylinder block in the comparative example exhibits
a maximum value of 55 ~ m at a sleeve depth of 30 mm from the
cylinder head-bound surface of the sleeve, and the amount of per-
manent deformation of the sleeve is largely distributed over the
regions in a range of depth of 10 to 50 mm which are at an
increased temperature during the operation of the engine. This
is due to the fact that the T6 treatment causes non-uniform
stress to remain in each sleeve.
- 27 -
~ .
- .' ' ' ~ : .. : -
: :
.
Fig. 20 shows a V-shaped siamese-type cylinder block S'
including two siamese-type cylinder barrels 1. The cylinder
block S' is also made by the same blank making s-tep and machining
step as described above. In this Figure, the same reference
characters are used to designate the same parts as in the embodi-
ment shown in Fig. 1.
,.; 10
- 2B -
: : ' ' ' '' : ' :
.. ..
-- `
..
.
