JPH0131983B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. DETAILED DESCRIPTION OF THE INVENTION (1) Industrial Field of Application The present invention relates to a Siamese type cylinder block, particularly to each cylinder barrel of a Siamese cylinder barrel made of an aluminum alloy, which is formed by combining a plurality of cylinder barrels. This invention relates to a method of manufacturing a cast iron sleeve.

(2) Conventional technology Conventionally, the Siamese type cylinder block having the above structure has been manufactured by die-casting the cylinder block material in which the sleeves are installed in a mold, and then processing the inner peripheral surface of each sleeve into a perfect circle. ing.

(3) Problems to be Solved by the Invention However, according to the above manufacturing method, since the opposing circumferential wall portions of adjacent sleeves receive strong molten metal filling pressure during filling with molten metal, the long axis of each sleeve is perpendicular to the direction in which the cylinder barrels are arranged. It deforms so that it has a substantially elliptical cross-sectional shape.

In this case, the cross-sectional shape of each cylinder barrel when it contracts as the aluminum alloy solidifies takes on an approximately elliptical shape with its long axis parallel to the direction in which the cylinder barrels are arranged. It attempts to deform to follow the cross-sectional shape of the barrel when it contracts, but the deformed shape during filling with molten metal changes only slightly.

Therefore, the cross-sectional shape of each sleeve and the cross-sectional shape of each cylinder barrel have their long axes offset by 90 degrees, and the casting stress remaining in each sleeve becomes non-uniform around its circumference. If the inner peripheral surface of the sleeve is machined into a perfect circle in this state and an engine is assembled and operated, the amount of thermal expansion around the circumference of the sleeve will be uneven, creating a gap between the piston ring and the sleeve, resulting in blow-by gas. There are problems such as increasing oil consumption and wasting oil.

In view of the above, an object of the present invention is to provide a manufacturing method capable of obtaining a Siamese-type cylinder block in which the amount of thermal expansion around the circumference of each sleeve is substantially uniform during engine operation.

B. Structure of the Invention (1) Means for Solving the Problems The present invention provides a method for pouring molten metal into a mold while applying a diameter expanding force to the sleeve heated to 150 to 700°C installed in the mold. The cylinder block material is cast under pressure, and then after the molten metal has solidified, the diameter expanding force is removed; and the inner peripheral surface of the sleeve is machined into a perfect circle. .

(2) Effect By applying a diameter expanding force to each sleeve when filling with molten metal, deformation of each sleeve due to the filling pressure of molten metal is prevented. In addition, if each sleeve is preheated to 150-700℃, it is possible to reduce the rigidity of each sleeve by heating it to approximately the same temperature with the molten metal during casting, so that after the molten metal has solidified. When the expansion force of each sleeve was removed, each sleeve, which had a low rigidity, was deformed to follow the cross-sectional shape of the cylinder barrel when it was contracted, and the cross-sectional shape of each sleeve was made so that its long axis was parallel to the cylinder barrel arrangement direction. It takes on a roughly elliptical shape.

As a result, the casting stress remaining in each sleeve is made approximately uniform around its circumference, and the stress is well balanced.

In this state, when the inner peripheral surface of each sleeve is machined into a perfect circle and an engine is assembled and operated, the amount of thermal expansion around the circumference of each sleeve becomes approximately uniform.

(3) Embodiment FIGS. 1 to 3 show a Siamese type cylinder block S obtained according to the present invention, which consists of a cylinder block body 2 made of aluminum alloy and a sleeve 3 made of cast iron. The cylinder block body 2 has a plurality of cylinder barrels 1 ₁ to 4 in the illustrated example.
1 ₄ , an outer wall portion 4 surrounding the Siamese cylinder barrel 1, and a crankcase 5 connected to the lower edge of the outer wall portion 4. A water jacket 6 facing the outer periphery of the Siamese cylinder barrel 1 is formed between the Siamese cylinder barrel 1 and the outer wall 4, and each cylinder barrel 1 ₁ to 1 ₄ is connected to the cylinder head side end of the water jacket 6.
and the outer wall portion 4 are partially connected by a plurality of reinforcing deck portions 8 arranged in the circumferential direction, and the space between adjacent reinforcing deck portions 8 functions as a communication port 7 to the cylinder head side of the water jacket 6. do. As a result, the cylinder block S is constructed into a closed deck type. Sleeve 3 is attached to each cylinder barrel 1 ₁ ~
₁₄ , and the sleeve 3 defines a cylinder bore 3a.

Also, the wall thickness t ₁ of each sleeve 3 is the thickness of the adjacent sleeve 3.
The thinnest wall thickness of the cylinder barrels 1 ₁ to 1 ₄ between them is set to 50% or less of the wall thickness t ₂ on the line connecting the centers of adjacent sleeves 3 . In this embodiment, when the thickness t ₂ of the thinnest portion is 4.5 mm, the thickness of each sleeve 3 is set to 3 mm or more.

5 to 9 show a casting device for the cylinder block material Sm shown in FIG.
The mold M is provided with an upper mold 9 that can be raised and lowered, and a first and second side mold 10 ₁ and 10 that are divided into left and right halves in FIGS. 5 and 6. ₂ and 7, it is composed of third and fourth side molds 10 ₃ and 10 ₄ divided into left and right halves, and a lower mold 11 on which each of the side molds 10 ₁ to 10 ₄ is slidably placed.

A mold clamping recess 12 is formed on the lower surface of the upper mold 9 to define a first cavity C ₁ in order to mold the Siamese cylinder barrel ₁ and the outer wall ₄ in cooperation with the upper half of each of the side molds 10 1 to 10 4 . is formed, and its recess 12
The mold clamping convex portion 13 that fits with each side mold 10 ₁ to 1
0 ₄ protrudes from the top surface.

As shown in FIGS. 7 and 8, the lower mold 11 includes a sump 14 that receives molten metal made of aluminum alloy from a melting furnace (not shown), a hot water cylinder 15 communicating with the sump 14, and a hot water supply cylinder 15 that communicates with the sump 14. A plunger 16 that slides onto the hot water supply cylinder 15 and a
branching into the book in the longitudinal direction of the first cavity _C1 ;
In addition, a pair of runners 17 are provided that extend over approximately the same length. Also, the lower mold 11 has both runners 17
It has a molding block 18 projecting upwardly in between, and the molding block 18 is connected to each side mold 10 ₁ to 10 _{4 .}
A second cavity _C2 is formed which forms the crankcase 5 in cooperation with the lower half of the crankcase C2. that cavity
The upper end of C ₂ communicates with the first cavity C ₁ , and the lower ends on both sides communicate with both runners 17 via a plurality of weirs 19 .

The molding block 18 includes four tall semi-cylindrical first molding parts ₁₈₁ formed at predetermined intervals;
Between adjacent first molded parts 18 ₁ and both outermost first molded parts 18 1
It consists _of a convex second molding part ₁₈₂ located outside the molding part 181, and each first molding part ₁₈₁ is for molding the rotation space 20 for the crank pin and crank arm (Figs. 2 and 3). The second molded part 18 ₂ is used for the bearing holder 2 of the crank journal.
1 (Figures 2 and 3). Each weir 19 is provided corresponding to each second forming part 18 ₂ , and is designed to quickly fill the large volume portion of the second cavity C ₂ with molten metal.

The runners 17 are arranged such that the cross-sectional area of both runners 17 gradually decreases from the water reservoir 14 side toward the runner tip 17a.
The bottom surface of 7 is formed in the shape of several steps ascending from the trough portion 14 side. Each rising portion 17c connected to each step portion 17b is formed diagonally so that the molten metal can be smoothly guided to each weir 19.

When the cross-sectional area of the runner 17 is reduced stepwise in this way, a large amount of molten metal is filled into the second cavity _C2 through the weir 19 at a slow speed in the large cross-sectional area, and a small amount is filled in the small cross-sectional area. can be filled into the second cavity C ₂ through the weir 19 at a high speed, so that the cavity C ₂
Inside, the molten metal level rises almost evenly over the entire length from the lower ends of both sides, so that the molten metal rises to the second cavity.
There is no turbulence in C ₂ , and gases such as air are prevented from being drawn into the molten metal, thereby avoiding the formation of cavities. Since this molten metal filling operation is performed efficiently, casting efficiency can be improved.

As shown in FIGS. 5 and 6, each first molding section 18 ₁
A positioning protrusion 22 that fits into the inner peripheral surface of the cast iron sleeve 3 is protruded from the top surface of the cast iron sleeve 3, and a recess 23 is formed in the center of the positioning protrusion 22. Furthermore, in the two first molded parts 18 ₁ located on both sides, through holes 24 are formed that penetrate through the first molded parts 18 ₁ on both sides of the positioning protrusion 22 .
4, a pair of temporary installation pins 28 are slid together, respectively.
These temporary installation pins 25 are used for temporary installation of a sand core for a water jacket. The lower ends of both temporary installation pins 25 are fixed to a mounting plate 26 disposed below the forming block 18. Its mounting plate 26
Two support rods 27 are inserted through the support rods 27, and a coil spring 28 is compressed between the lower part of each support rod 27 and the lower surface of the mounting plate 26. When the mold is opened, the mounting plate 26 receives the elastic force of each coil spring 28 and rises until it comes into contact with the stopper 27a at the tip of each support rod 27, so that the tip of each temporary installation pin 25 is attached to the first molded part 18 ₁ It protrudes from the top. A recess 25a that engages with the lower edge of the sand core is formed on the tip end surface of each temporary installation pin 25.

Further, in the two first molded parts 18 ₁ located on both sides, a through hole 29 is formed that penetrates the first molded part 18 ₁ at a bisecting position between both through holes 24 , and the lower end is inserted into the through hole 29 . An operating pin 30 fixed to the mounting plate 26 is slid together. When the mold is opened, the tip of the operating pin 30 protrudes into the recess 23, and when the mold is closed, it is pushed down by a diameter expanding mechanism, which will be described later, so that both temporary pins 25 are retracted from the top surface of the first molding section ₁₈₁ . It's summery.

The second in the first and second side molds 10 ₁ , 10 ₂
Two core holders 31 are provided at the center of the wall defining the cavity C ₂ for actually installing sand cores. Each core holder 31 includes an engagement hole 31a for positioning the sand core, and a clamping surface 31b formed on the outer periphery of the opening to clamp the sand core.

A first cavity is placed in the mold clamping recess 12 of the upper mold 9.
A plurality of _third cavities C ₃ for overflow and fourth cavities C ₄ for forming communication ports are opened, and each third cavity C 3 is connected to the upper die 9 .
Through holes 32 and 33 communicating with C ₃ and each fourth cavity C ₄ are formed, respectively.

The through holes 32 and 33 have closing pins 34 and 3.
5 are inserted, respectively, and the closing pins 34, 3
The upper end of 5 is a mounting plate 36 disposed above the upper mold 9.
Fixed.

Both cavities C ₃ and C ₄ of each through hole 32 and 34
The small diameter portions 32a, 33a extend upwardly over a predetermined length from the communicating ends of the respective closing pins 34, 3.
5 to close the third and fourth cavities C ₃ and C ₄ , but the diameter of the outer portion is smaller than that of each closing pin 3 .
4, 35, thereby forming air passages 37, 38 between each closing pin 34, 35 and each through hole 32, 33.

A hydraulic cylinder 39 is interposed between the top surface of the upper die 9 and the mounting plate 36, and the operation of the hydraulic cylinder 39 moves the mounting plate 36 up and down to close each closing pin 34, 3.
5 to open and close each small diameter portion 32a, 33a. 40 is a guide rod for the mounting plate 36.

The upper mold 9 has a diameter expanding mechanism 4 for holding the sleeve 3 cast into each cylinder barrel 1 ₁ to 1 _{4 .}
1 is provided, and its mechanism 41 is constructed as follows.

A through hole 42 whose center line coincides with the extension axis of the operating pin 30 is formed in the upper mold 9, and a support rod 43 is loosely inserted into the through hole 42. The upper end of the support rod 43 is fixed to a bracket 44 erected on the top surface of the upper mold 9, and a molten metal intrusion prevention plate 45 is fixed to the lower end. The lower surface of the molten metal intrusion prevention plate 45 is formed with a protrusion 45a that can fit into the recess 23 on the top surface of the first molded part ₁₈₁ in the lower mold 11.

The hollow holding cylinder 46 has a circular outer peripheral surface and a tapered hole 47 with a downward slope from the top to the bottom. The holding cylinder 46 is inserted loosely, and its upper end surface abuts a protrusion 48 protruding from the recess 12 of the upper mold 9, and its lower end surface abuts a molten metal intrusion prevention plate 45. As shown in FIG.
A plurality of slot grooves 49 extending radially from the inner circumferential surface and outer circumferential surface of the circumferential wall are formed alternately and at equal intervals on the circumference.

A hollow actuating rod 50 for expanding the diameter of the holding tube 46 is slid onto the supporting rod 43 over substantially the entire length of the supporting rod 43, and the actuating rod 50 has a tapered shape that fits into the tapered hole 47 of the holding tube 46. Part 50
a, and a perfectly circular portion 50b that is connected to the tapered portion 50a, slides into the through hole 42 of the upper mold 9, and projects from the upper mold 9. A plurality of pins 57 are provided protruding from the tapered portion 50a, and these pins 57 are inserted into pin holes 58 that are long in the vertical direction of the holding tube 46, thereby allowing the rotation of the holding tube 46 while allowing the vertical movement of the tapered portion 50a. A stop is made.

A hydraulic cylinder 51 is fixed to the top surface of the upper die 9, and hollow piston rods 53 ₁ and 53 ₂ projecting from the upper and lower end surfaces of the hollow piston 52 respectively touch the upper and lower end walls of the cylinder body 54. Penetrating. A true circular portion 50b of the actuating rod 50 is inserted into a through hole 55 passing through the hollow piston 52 and the hollow piston rod 53, and a stopper 56 ₁ to prevent removal is fitted into an annular groove of the circular portion 50b.
56 ₂ on the hollow piston rods 53 ₁ and 53 ₂ ,
The actuating rod 50 is raised and lowered by a hollow piston 52, which is brought into contact with the lower end surface. Four diameter expanding mechanisms 41 are provided corresponding to each of the cylinder barrels ₁₁ to ₁₄ of the cylinder block S.

10 and 11 show a sand core 59 for a water jacket, and the sand core 59 has four cylindrical portions 60 ₁ corresponding to the four cylinder barrels 1 ₁ to 1 ₄ of the cylinder block S. - 60 ₄ and a core body 61 which lacks the surrounding walls overlapping their adjacent ones, and a communication port 7 which communicates the water jacket with the water jacket of the cylinder head.
In order to form a plurality of protrusions 62 protruding from the upper end surface of the core body 61 and protrusions protruding from both outer surfaces of the two cylindrical parts 60 ₂ and 60 ₃ located in the middle of the core body 61, respectively. The baseboard 63 is made of Each baseboard 63 has a large diameter portion 63a integrated with the core body 61,
It is formed with a small diameter portion 63b protruding from the end surface thereof. In this case, the protrusion 62 is connected to the fourth cavity.
Its dimensions are set so that it can be inserted loosely into _C4 .

Next, the cylinder block material is made by the casting machine.
I will explain the casting work of Sm.

First, as shown in FIG. 5, the upper mold 9 is raised,
Also, opposing both sides 10 ₁ , 10 ₂ ; 10 ₃ , 1
0 ₄ are moved apart from each other to open the mold. In the diameter expanding mechanism 41, each hydraulic cylinder 51 is operated to lower the actuating rod 50 using the hollow piston 52, and the diameter of the holding cylinder 46 is reduced by moving the tapered portion 50a downward. Also, upper mold 9
The upper hydraulic cylinder 39 is operated to raise the mounting plate 36, thereby connecting the respective closing pins 34, 35 to the overflow cavity _C3 and the communication port forming cavity _C4 .
Make them more detached. Furthermore, the plunger 16 in the hot water supply cylinder 15 is lowered.

Approximately perfect circle and 5mm thick cast iron sleeve 3 for 250~
The sleeve 3 is heated to 400° C. and fitted loosely into each holding cylinder 46, and the upper end opening of the sleeve 3 is fitted into the convex portion 48 of the upper die 9 to close it, and the lower end surface of the sleeve 3 is fitted into the convex portion of the molten metal intrusion prevention plate 45. The lower end opening of the sleeve 3 is closed by the molten metal intrusion prevention plate 45 while matching the lower end surface of the portion 45a. And the hydraulic cylinder 51 of the diameter expansion mechanism 41
is actuated to raise the actuating rod 50 by its hollow piston 52. As a result, the tapered portion 50
Since a moves upward, the holding cylinder 46 expands in diameter, and the sleeve 3 is reliably held in the holding cylinder 46 under the force of expanding the diameter.

As shown in FIGS. 5 and 11, the lower edges of the cylindrical portions 60 ₁ and 60 ₄ on both sides of the sand core 59 are connected to temporary installation pins that protrude from the top surface of the first molding portions 18 ₁ on both sides of the lower mold 11. The sand core 59 is temporarily installed by engaging the recess 25a of the sand core 59.

The two-sided molds 10 ₁ and 10 ₂ are moved a predetermined distance in the direction in which they approach each other, and the small diameter portion 63b of each baseboard 63 of the sand core 59 is fitted into the engagement hole 31a of each core receiver 31, and the sand The core 59 is positioned, and the end face of each large diameter portion 63a is aligned with the clamping surface 3 of each core receiver 31.
1b, thereby accurately positioning the sand core 59 and sandwiching it between the molds 10 ₁ and 10 ₂ on both sides, thereby performing the actual installation of the sand core 59. Also, other double-sided type 10 ₃ , 1
Move 0 ₄ in the same way.

As shown in FIG. 6, the upper die 9 is lowered and each sleeve 3 is inserted into each cylindrical portion 60 ₁ to 60 ₄ of the sand core 59, and the convex portion 45a of the molten metal infiltration prevention plate 45 is first formed. Part 18 ₁ fits into the recess 23 on the top surface. As a result, the operating pins 30 are pushed down by the convex portions 45a of the molten metal intrusion prevention plate 45, so that each temporary installation pin 2
4 descends and retracts from the top surface of the first molded part ₁₈₁ .
Moreover, the mold clamping recess 12 of the upper mold 9 is connected to each side mold 10 ₁ to
The mold clamping is performed by fitting into the mold clamping convex portion 13 of 10 ₄ .

Molten metal made of aluminum alloy is supplied from the melting furnace to the sump 14 of the lower mold 11, and the plunger 16 is raised to allow the molten metal to pass through the weir 19 from both runners 17 and into the cavity C ₂ from both lower edges of the second cavity.
and fill the first cavity _C1 . Gas such as air in both cavities C ₁ and C ₂ is pushed up by the molten metal and escapes above the upper mold 9 through air passages 37 and 38 communicating with the third and fourth cavities C ₃ and C ₄ .

In this case, the bottom surface of the runners is formed in several ascending steps from the trough portion 14 side so that the cross-sectional area of both runners 17 gradually decreases toward the runner tip 17a as described above. As the plunger 16 rises, the molten metal is smoothly pushed up into the cavity C 2 from both runners 17 and through each weir 19 from the lower ends of both sides of the second cavity C ₂ almost uniformly over _its entire length. Therefore, the molten metal has both cavities C ₁ and C ₂
This prevents turbulence within the molten metal, prevents gases such as air from getting into the molten metal, and prevents the formation of cavities.

When the third and fourth cavities C ₃ and C ₄ are filled with molten metal, the hydraulic cylinder 39 on the upper mold 9 is operated to lower the mounting plate 36, and the closing pin 34,
35 closes the small diameter portions 32a and 33a communicating with both cavities C ₃ and C ₄ .

In the pouring work, the second and first cavities
Plunger 16 for filling C ₂ and C ₁ with molten metal
The displacement and molten metal pressure are controlled as shown in FIG.

That is, the plunger 16 changes its moving speed from the first to
The third speed is controlled in three stages, _V1 to _V3 . In this example, the first speed V ₁ is 0.08 to 0.12 m/sec, and the second speed V ₂ is
0.14 to 0.18 m/sec, and the third speed V ₃ is set to 0.04 to 0.08 m/sec to achieve a significant deceleration state. By controlling the speed in these three stages, the molten metal is prevented from rippling and air etc. Forms a quiet flow of molten metal without involving any gases, and directs the molten metal into both cavities.
C ₂ and C ₁ can be efficiently filled.

In addition, at the first speed V ₁ of the plunger 16, the molten metal only fills both runners 17, etc., so the pressure P ₁ of the molten metal is kept approximately constant, and at the second and third speeds V ₂ and V of the plunger 16. In ₃ , the molten metal is in both cavities C ₁ ,
Since C ₂ is filled with molten metal, the pressure P ₂ of the molten metal rises rapidly. After moving the plunger 16 at the third speed _V3 for a predetermined time, the molten metal filling pressure _P3 is increased to 150°C for about 1.5 seconds.
~400 Kg/cm ² , thereby completely covering the sand core 59 with the molten metal and forming a molten metal coagulation film on its surface.

After the above-mentioned time has elapsed, the plunger 16 is moved at a reduced speed _V4 , so the pressure _P4 of the molten metal rises, and when the pressure _P5 reaches 200 to 600 kg/ ^cm2 , the plunger 16 stops moving. solidify the molten metal.

If a molten metal coagulation film is formed on the surface of the sand core 59 by keeping the pressure of the molten metal substantially constant for a predetermined period of time as described above, the sand core 59 will be protected by the film and damaged during the next pressurization of the molten metal. There is no.

Also, the sand core 59 expands due to the molten metal, but since the protrusion 62 is loosely inserted into the fourth cavity _C4 , the protrusion 62 follows the expansion of the sand core 59, thereby preventing the protrusion 62 from breaking. Avoided.

Furthermore, since the sand core 59 is held in an accurate position by the molds 10 ₁ and 10 ₂ on both sides through its baseboards 63, the sand core 59 is held in an accurate position by the molds 10 1 and _{10 2} on both sides. When the molten metal in ₁ is pressurized, the sand core 59 does not float or sag. Furthermore, since the end surfaces of the large diameter portions 63a of each baseboard 63 abut against the clamping surfaces 31b of the core receivers 31 in the double-sided molds 10 ₁ and 10 ₂ , when the sand cores 59 tend to swell, The deformation force is
b, thereby preventing deformation of the sand core 59 and providing a Siamese cylinder barrel 1 with uniform wall thickness around each sleeve 3.

By controlling the moving speed of the plunger 16 and the pressure of the molten metal as described above, a closed deck cylinder block material can be cast with substantially the same production efficiency as die casting.

After the molten metal has solidified, the hydraulic cylinder 51 of the diameter expansion mechanism 41 is operated, the operating rod 50 is lowered to remove the diameter expansion force of the holding cylinder 46 against the sleeve 3, and the mold is opened. The cylinder block material Sm shown is obtained.

In this cylinder block element Sm, the first
As shown in the Talyrond measurement results (100 times magnification) in Figure 3a, the cross-sectional shape of each sleeve 3 is approximately elliptical with its long axis parallel to the arrangement direction of the cylinder barrels 1 ₁ to 1 ₄ . This corresponds to the cross-sectional shape of the barrels 1 ₁ to 1 ₄ when they are contracted.

The reason why such a result is obtained is that the diameter expanding force is applied to each sleeve 3 by the diameter expanding mechanism 41 when filling the molten metal, so each sleeve 3 is prevented from being deformed by the filling pressure of the molten metal, and the molten metal is When the expansion force of each sleeve 3 is removed after the solidification of each sleeve 3 is completed, even if the wall thickness of each sleeve 3 is as thick as 5 mm,
is heated to approximately the same temperature by the molten metal, reducing the rigidity of each cylinder barrel 1 ₁
This is because it deforms to follow the cross-sectional shape of ₁₄ when contracted.

As a result, the casting stress remaining in each sleeve 3 is made substantially uniform over its entire circumference.

FIG. 13b shows a cylinder barrel 100 ₁ to 10 without using a diameter expanding mechanism 41 using a perfectly circular sleeve 300.
₀₄ shows the results of Talyrond measurement of a Siamese-type cylinder block material as a comparative example obtained by casting.As is clear from this figure, the cross-sectional shape of each sleeve 300 has a long axis perpendicular to the arrangement direction of the cylinder barrels. Particularly between adjacent cylinder barrels, the opposing circumferential walls of both sleeves 300 receive the filling pressure of the molten metal and form a concave portion 300a.

FIG. 14a shows the balance of casting stress remaining in each sleeve 3 in the cylinder block material Sm, and the perfect circle c shows the O point of the casting stress. It is clear from this figure that a good degree of balance is ensured over the entire circumference of each sleeve 3 in the material Sm.

FIG. 14b shows each sleeve 3 in the comparative example.
00 indicates the degree of balance of residual casting stress, and there is a peculiar tendency between adjacent cylinder barrels, resulting in poor balance.

After the measurement, the cylinder block material Sm is subjected to a grinding process, and each protrusion 6 is formed by the cooperation of each fourth cavity _C4 and each protrusion 62 of the sand core 59.
4, a communication port 7 is formed by the protrusion 62, and a reinforcing deck portion 8 is formed between adjacent communication ports 7. After that, the water jacket 6 is obtained by removing sand, and each sleeve 3 is further removed.
The inner circumferential surface of is machined into a perfect circle to make the wall thickness t ₁ 3 mm, and further other prescribed processing is performed to obtain the first
~The cylinder block S shown in FIG. 3 is obtained.

A comparative example was also subjected to the same processing to obtain a cylinder block.

Figures 15a and 15b show changes in the inner diameters of both sleeves 3, 300 as expansion amounts when both cylinder blocks are uniformly heated. The amount of expansion is measured at four points a ₁ on the circumference as shown in Figure 16.
The change in inner diameter at _a4 was determined.

Figure 15a shows the case of the cylinder block S obtained according to the present invention, where the difference D ₁ between the maximum expansion amount and the minimum expansion amount at around 190°, which is the heating temperature of the cylinder block during engine operation, is as small as 20μ. There is little variation in the amount of expansion at each point _a1 to _a4 . Moreover, these expansion amounts are close to the theoretical expansion amount T. This is due to the well-balanced casting stress remaining in each sleeve 3 as described above.

Figure 15b shows the case of a comparative example, where the difference D ₂ between the maximum expansion amount and the minimum expansion amount at the same temperature as above.
is as large as 128 μ, and there are variations in the amount of expansion at each point a ₁ to a ₄ . Moreover, 3 points out of those expansion amounts
Those at a ₂ , a ₃ , and a ₄ are separated by a larger distance than the theoretical expansion amount T. This applies to each sleeve 3 as described above.
This is due to the poor balance of casting stress remaining in 00.

C. Effects of the Invention According to the present invention, since molten metal is pressurized and filled into the cavity with a diameter expanding force applied to the sleeve installed in the mold, each sleeve is prevented from being deformed by the filling pressure of the molten metal. is prevented. In addition, since each sleeve is preheated to 150 to 700°C, each sleeve can be heated by the molten metal to approximately the same temperature during casting to reduce its rigidity, so that after the molten metal has solidified, When the expansion force is removed, each sleeve, which has become low in rigidity, deforms to follow the cross-sectional shape of each cylinder barrel when contracted, so that the casting stress remaining in each sleeve is approximately equalized around its circumference, and its The degree of stress balance becomes better.

After that, the inner peripheral surface of each sleeve is machined into a perfect circle, so that the amount of thermal expansion around the circumference of each sleeve is approximately uniform during engine operation, thereby minimizing the formation of gaps between the piston ring and the sleeve. Problems such as increased blow-by gas and wasteful oil consumption can be solved.

In addition, since each sleeve does not deform due to the filling pressure of molten metal, it is possible to make the spacing between adjacent sleeves as close as possible, which makes the cylinder block, and therefore the engine as a whole, smaller and lighter. can be achieved.

[Brief explanation of drawings]

1 to 3 show a Siamese type cylinder block manufactured according to the present invention, FIG. 1 is a perspective view seen from above, FIG. 2 is a sectional view taken along the line of FIG. 1, and FIG. -a line sectional view, 3rd
The figure is a perspective view seen from below, and Figure 4 is a perspective view of the Siamese type cylinder block material seen from above.
Figure 5 is a longitudinal sectional front view of the casting machine when the mold is opened;
The figure is a longitudinal sectional front view of the casting device when the mold is closed, FIG. 7 is a sectional view taken along the line shown in FIG. 6, FIG. 10
The figure is a perspective view of the sand core seen from above, Figure 11 is a sectional view taken along the line XI-XI in Figure 10, Figure 12 is a graph showing the relationship between the displacement of the plunger and the pressure of the molten metal over time, and Figure 13 Figures a and b are measurement diagrams showing the results of Talyrond measurement of the inner diameter shape of the sleeve in the Siamese type cylinder block material obtained by the casting process of the present invention and a comparative example. An explanatory diagram showing the balance of casting stress remaining in the Siamese type cylinder block material obtained in the process and the sleeve in the comparative example, Figures 15a and 15b are the Siamese type cylinder block material obtained by the present invention and the sleeve in the comparative example. FIG. 16 is a graph showing the relationship between the amount of expansion and the heating temperature of the sleeve, and FIG. 16 is an explanatory diagram showing the measurement position of the amount of expansion of the sleeve. M...Mold, S...Cylinder block, Sm...
... Cylinder block material, 1 ₁ to 1 ₄ ... Cylinder barrel, 3 ... Sleeve.

Claims (1)

[Claims] 1. When manufacturing a Siamese-type cylinder block in which a cast iron sleeve is cast into each cylinder barrel of an aluminum alloy Siamese cylinder barrel formed by joining a plurality of cylinder barrels,
Molten metal is pressurized and filled into the mold while applying a diameter expanding force to the sleeve heated to 150 to 700°C installed in the mold, and then, after the molten metal has solidified, the diameter expanding force is applied. A method for manufacturing a Siamese type cylinder block, comprising: a step of casting a cylinder block material to remove it; and a step of machining the inner peripheral surface of the sleeve into a perfect circle.