JPH1029036A - Manufacture of core piece for forming hole as cast - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a flat core piece of <=2mm in thickness with high yield. SOLUTION: The coated sand 9 which is the material of a core piece 3 is fed in the material feed process in a condition the sand overflows from each die part 6a of a die 8 provided with a plurality of die parts 6a whose upper part is opened. After the coated sand 9 fed to the die parts 6a is pressed by a roller 10 with the prescribed pressure in the pressing process, the coated sand 9 overflowed from the die part 6a after the pressing is removed by a scraper 11 in the removal process. The coated sand 9 in the die 8 subjected to the removal process is calcined in the calcination process, and the calcined coated sand 9 is cooled together with the die 8. The core piece 3 is knocked out of the die 8 in the knock-out process after the cooling to complete the manufacture of the core piece 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a core piece for forming a cast hole, and more particularly to a core for forming a cast hole suitable for casting a flat hole (hole) having a thickness of 2 mm or less. The present invention relates to a method for manufacturing a piece.

[0002]

2. Description of the Related Art A cylinder block is a basic component of an engine, and its main role is to guide a reciprocating motion of a piston, support a crankshaft, cool a cylinder, and the like. A water jacket is provided around the cylinder bore for cooling the cylinder.

In order to reduce the weight and size of the engine, the thickness of the partition wall between the cylinder bores is reduced as much as possible (8 to 8).
11mm), no water jacket between the bores,
A so-called Siamese type cylinder block has been widely used in recent years. In this engine block, since cooling water does not flow between the bores, the cooling between the bores is insufficient compared to the full jacket type.

[0004] If the cooling between the bores is insufficient, the bores are distorted due to an increase in the wall temperature, and the oil in the oil pan spills into the combustion chamber and is discharged as gas. There is also a problem that if the bore wall temperature rises significantly, nitrogen oxides (NOx) and smoke in the exhaust gas increase.

[0005] The water jacket is formed by a core when the cylinder block is formed by casting. Therefore, it is sufficient that a thin portion for casting between the bores is formed integrally with the core for the water jacket so that a flat hole for passing the cooling water can be formed between the bores when casting the cylinder block. However, when a conventional core is used, a high temperature (about 1400 °
The thickness of the core capable of casting a cylinder block with a good yield by preventing insertion (looking), cracks and the like during casting in C) was limited to approximately 2.2 mm. In addition, a core capable of forming a hole having a small diameter of approximately 2.2 mm by casting requires careful handling in order to prevent the thin-walled portion from being damaged at the time of handling, and has a problem of poor workability. is there.

The inventor of the present invention has solved the above-mentioned problem and has a flat hole for cooling water passage between the bores of a cylinder block of a siamese type, which cannot be formed by a conventional molding method using a core for a water jacket. A method of casting a steel was invented. According to the invention, the core body for the water jacket and the core piece constituting the cast portion between the cylinder bores are formed of different materials. Therefore, 1.0 to 2.0
It is necessary to manufacture a flat core piece with a thickness of mm.

As a method for manufacturing a plate-shaped core piece, a shell molding method has conventionally been used. In this method, FIG.
As shown in FIG. 1, a mold 62 having a heater 61 is disposed below a tank 63. Then, shell sand (coated sand) 64 filled in the tank 63 is blown into the piece-shaped space 62a formed in the mold 62 heated from the blowing port 65 by the pressure of the compressed air, and the core piece is removed. Form. Then, after the shell sand 64 is fired for a predetermined time to bond and harden the phenol resin on the surface, the core piece is released and the core piece is taken out. As a method of heating the mold 62, there is a method of heating with a gas.

As a method other than the shell mold method, there is a method called a cold box method. In this method, the coated sand is blown into the mold space without heating the mold to fill the space, and then a hardening gas (triethylamine gas) is blown into the core to form a core piece.

[0009]

According to the conventional manufacturing method, a core piece having a stable quality can be obtained up to a core piece thickness of about 7 to 8 mm. However, it is difficult to apply the present invention to a thin core piece having a thickness of 2 mm or less, which is the object of the present invention.

This is because, in the case of the shell molding method, shell sand is blown into a very narrow space with the mold 62 being heated, so that the shell sand adheres to the wall surface of the mold 62 and is not sufficiently filled. It often hardens. In addition, in the cold box method, poor flowability of the coated sand, which is a feature of the cold box method, leads to poor filling, and it is difficult to manufacture core pieces of a predetermined shape with high yield.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a core for forming a cast hole capable of manufacturing a flat core piece having a thickness of 2 mm or less with a high yield. An object of the present invention is to provide a method for manufacturing a piece.

[0012]

In order to achieve the above object, according to the first aspect of the present invention, a resin coated sand, which is a material of a core piece, is provided with an upper opening and a depth of a core piece. A material supply step of overflowing from each mold part of the mold having a plurality of mold parts corresponding to the thickness of the mold, a pressing step of pressing the resin-coated sand supplied to the mold part, and a mold after pressing. A removing step of removing the resin-coated sand overflowing from the portion, a firing step of firing the resin-coated sand in the mold after the removing step, and a cooling step of cooling the fired resin-coated sand together with the mold, Removing the core piece from the mold after cooling.

According to the second aspect of the present invention, the mold includes a mold body having a mold portion formed as a through hole, and a bottom plate in contact with the mold body. According to a third aspect of the present invention, in the first or second aspect of the invention, in the pressing step, the roller is relatively moved while pressing the roller along the upper surface of the mold.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the firing step includes disposing a metal heat transfer plate on an open side of a mold.
In this state, the mold and the heat transfer plate are sandwiched between the heating plates and heated.

According to a fifth aspect of the present invention, in the fourth aspect of the invention, the material of the mold and the heat transfer plate is aluminum. In the invention according to claim 6, a main body side mold having a mold portion filled with the material of the core piece,
A filling step of blowing resin-coated sand into the mold part in a state where the lid-side mold covering the open part of the mold part is matched, and firing the resin-coated sand filled by heating the mold Firing step, a mold separating step of separating the main body side mold and the lid side mold, and blowing the gas toward the mold by connecting the separated main body side mold to a compressed gas injection nozzle. Removing the core piece from the mold portion.

According to a seventh aspect of the present invention, in the first aspect of the present invention, the resin-coated sand comprises crystalline silicon dioxide whose particle size is controlled as a main material of the aggregate. The secondary material used is at least Al ₂ O ₃ or a ceramic having a coefficient of thermal expansion substantially equal to that of Al ₂ O ₃ .

According to an eighth aspect of the present invention, in the first aspect of the present invention, the shape of the mold corresponds to a cooling water passage to be formed between the bores of the cylinder block. Shape.

According to the first to fifth aspects of the present invention, in the material supply step, the resin-coated sand, which is the material of the core piece, is provided with a plurality of mold parts having a plurality of mold parts whose upper parts are open. It is supplied in a state overflowing from. Next, after the resin-coated sand supplied to the mold section is pressed in the pressing step, the resin-coated sand overflowing from the mold section even after the pressing in the removing step is removed. The resin-coated sand in the mold after the removal step is fired in a firing step, and the fired resin-coated sand is cooled together with the mold. Then, after cooling, the core piece is removed from the mold in a mold removal step, and the manufacture of the core piece is completed.

According to the second aspect of the present invention, since the mold includes a mold body having a mold portion formed as a through hole and a bottom plate abutting on the mold body, the work of the mold removing step is performed. Becomes easier.

According to the third aspect of the present invention, in the pressing step, the rollers are relatively moved while being pressed along the upper surface of the mold, and the resin-coated sand is pushed into the mold section with a uniform pressure.

According to a fourth aspect of the present invention, in the first aspect of the present invention, a metal heat transfer plate is disposed on the open side of the mold during the firing step. Is done. Then, in the firing step, heating is performed in a state where the mold and the heat transfer plate are sandwiched between the heating plates.

According to a fifth aspect of the present invention, in the fourth aspect of the invention, since the material of the mold and the heat transfer plate is aluminum, the heat conduction is improved and the firing time is shortened.

In the invention according to claim 6, the mold includes a main body-side mold having a mold portion filled with the material of the core piece, and a lid-side mold covering an open portion of the mold portion. I have. In the filling step, resin-coated sand is blown into the mold portion of the mold in a state where the main body side mold and the lid side mold are matched. After filling, the mold is heated in a firing step, and the filled resin-coated sand is fired. Next, the main body side mold and the lid side mold are separated. In the mold removing step, the separated main body side mold is connected to the compressed gas injection nozzle, and gas is blown toward the mold portion, so that the core piece receives a uniform force and is smoothly removed from the mold portion.

According to a seventh aspect of the present invention, in the first aspect of the present invention, the resin-coated sand uses crystalline silicon dioxide whose particle size is controlled as a main material of the aggregate. And at least A
It contains ceramics having a coefficient of thermal expansion almost equal to that of l ₂ O ₃ or Al ₂ O ₃ . Therefore, 1400 ° like cast iron casting
Seizure of the molten metal at a high temperature around C is prevented, and the occurrence of gaze is prevented, and the desired shape can be obtained after casting. Moreover, the collapse property of the sand after casting is good.

According to the present invention, a core piece having a shape corresponding to the cooling water passage to be formed between the bores of the cylinder block can be obtained.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) A first embodiment in which the present invention is embodied in the case of manufacturing a core piece for forming a cast hole between cylinder bores of an engine will be described below with reference to FIGS.

FIG. 3 is a schematic perspective view of a core for a water jacket used in manufacturing a cylinder block of an engine. As shown in FIG. 3, the core 1 for a water jacket is used.
Is composed of a core body 2 for a water jacket and a core piece 3 for forming a cooling water passage hole in a partition wall between adjacent cylinder bores. The water jacket core main body 2 is formed with a pair of fitting grooves 4 which are open at the top and at the sides, respectively, at positions opposing each other in the upper portion corresponding to between the adjacent cylinder bores. Both ends of the core piece 3 are fitted in the fitting grooves 4 and are arranged at predetermined positions corresponding to adjacent cylinder bores.

As shown in FIG. 4, the core piece 3 has a convex portion 3a formed at the center of the upper edge and a lower edge 3b formed in an arch shape. The core piece 3 is formed such that its width (the distance between the upper edge and the lower edge) W is larger at both ends than near the center. The core piece 3 has a thickness t of 1.
It is formed in a range of 0 to 1.8 mm. The core piece 3 is attached to the core body 2 for a water jacket such that both ends of the upper edge thereof are flush with the upper surface of the core body 2 for a water jacket.

Also, in the core body 2 for a water jacket, convex portions 5 project upward from positions corresponding to the upper ends of the respective core pieces 3, that is, in the vicinity of the fitting grooves 4. . This projection 5 is formed after the cylinder bracket is cast.
This is for forming a hole used for confirming whether or not the hole for passing the cooling water is reliably cast out between the bores by the core piece 3.

The water jacket core 1 configured as described above is assembled in another core and then stored in a mold. In that state, the cast iron heated to about 1400 ° C. is poured into the mold. After several tens of minutes, the mold is separated. Thereafter, mold sand adhering to the casting surface and core sand remaining in the internal space are removed. The core sand is mainly removed by shot blasting, but it is difficult to perform shot blasting because the core piece 3 has a narrow gap. Therefore, the sand is removed from the core piece 3 by blowing compressed air.

As the material of the core body 2 for the water jacket, the same core sand as the conventional one, for example, a resin-coated sand (shell sand) having a resin content of about 2% is used. On the other hand, the material of the core piece 3 is different from the material of the core body 2 for the water jacket. When cast iron of about 1400 ° C. is cast into the material of the core piece 3, seizure and gaze are not generated, high strength capable of preventing cracks due to thermal shock, and low expansion property. A material that satisfies a certain requirement and a requirement that the core piece 3 has such strength that it is not damaged when handling the core piece 3 at normal temperature is used.

In this embodiment, as the material of the core piece 3, a resin-coated sand (hereinafter simply referred to as coated sand) using artificial SiO ₂ as a main aggregate is used. More specifically, the composition is as follows.

Main material: 100-200 mesh crystal silica (crystalline silicon dioxide (SiO 2)) Secondary material: 100 mesh Al ₂ O ₃ (2.5%), average grain size from main material SiO ₂ Crystal silica with small diameter (3.5%), MgO (1%) Additives: resin (phenolic resin) (5%), hexamethylenetetramine aqueous solution (2%), calcium stearate aqueous solution (1%) The percentage of materials and additives is 1
The percentage by weight indicates the value of 00%, and the remainder is the percentage of the main material.

The coated sand is adjusted on the premise that the conventional manufacturing of the core for the water jacket and the casting conditions of the cylinder block can be used as they are.

The crystal silica of 100 to 200 mesh, which is the main material, plays a role of giving the core piece 3 a low expansion property and a non-seizure property and also preventing the occurrence of eyes. Crystal silica having a small average particle size used as a sub-material fills the gaps between the particles of the main material and plays a role in suppressing the occurrence of eyes at the time of casting.

Al ₂ O ₃ used as an auxiliary material plays a role in enhancing the collapse property of the core piece after casting. When the aggregate is composed only of crystal silica, the particles are in pressure contact with each other, and the collapse of the core piece 3 after casting deteriorates. However, if you mixed for Al ₂ O ₃ secondary material, a state in which the particles were present Al ₂ O ₃ between crystal silica particles. Since the coefficient of thermal expansion of Al ₂ O ₃ is larger than the coefficient of thermal expansion of crystal silica, a difference between the coefficients of thermal expansion of the two causes a difference between the particles of Al ₂ O _{3 and} the particles of crystal silica during cooling after casting. A gap is generated and collapses easily.

When the same amount (2 to 3%) of resin as that of the conventional core sand is added to the aggregate having the above composition to prepare a coated sand, it is too smooth to be formed. Therefore, the moldability and ease of handling were ensured by increasing the resin amount to about twice that of the conventional resin.

Next, a method of manufacturing the core piece 3 will be described.
The core piece 3 is manufactured through a manufacturing process of a coated sand for a piece material and a manufacturing process of the core piece 3 using the coated sand.

The coated sand for the piece material is manufactured through the following steps. (First step) The powdery main material and sub-material are stirred and uniformly mixed.

(Second Step) A powdery resin is added to the mixture obtained in the first step, and the mixture is stirred and uniformly mixed. (Third Step) The mixture obtained in the second step was mixed with almost 140
Heat at ° C for 1 hour. By this treatment, a resin film is formed on the surfaces of the particles of the main material and the sub-material.

(Fourth Step) The resin-coated mixture obtained in the third step is charged with an aqueous solution of hexamethylenetetramine and mixed well with stirring. (Fifth step) An aqueous solution of calcium stearate is added to the mixture obtained in the fourth step, and the mixture is stirred and mixed well.

The coated sand thus adjusted has an appropriate fluidity and is excellent in moldability. Next, a method of manufacturing the core piece 3 using the coated sand manufactured as described above will be described with reference to FIGS. The core piece 3 is manufactured by using a die-cut plate 6 as shown in FIG. The mold release plate 6 as a mold body is made of stainless steel, and a plurality of mold portions 6a corresponding to the shape of the core piece 3 are formed as through holes. The thickness of the die-cut plate 6 is set to a predetermined value of 1.0 to 1.8 mm corresponding to the thickness of the core piece 3 to be manufactured. The die plate 6 is combined with the bottom plate 7 which is in contact with one side of the die plate 6 to form a die 8 having an open upper part of the die part 6a.

The core piece 3 is manufactured through the steps shown in FIGS. 1 (a) to 1 (f). (Material Supplying Step) As shown in FIG. 1A, the die cutting plate 6 is disposed on the bottom plate 7, and the coated sand 9 is placed on the die cutting plate 6 at a position corresponding to each die part 6a. It is supplied in a raised state from the section 6a.

(Pressing Step) As shown in FIG.
The roller 10 is moved while being pressed against the upper surface of the die-cutting plate 6 to push the coated sand 9 into the die 6a with a predetermined pressure.

(Removal Step) As shown in FIG.
The scraper 11 is moved along the upper surface of the die cutting plate 6 to remove the portion of the coated sand that protrudes from the die 6a.

(Firing Step) As shown in FIG.
It is placed in a furnace 13 with the lid 12 covered from above the bottom plate 7 and the die-cutting plate 6, and baked at 180 ° C. for 1 hour. By this treatment, the resin coated on the surface of the coated sand is hardened and the sand grains are bonded to each other.

(Cooling Step) As shown in FIG.
The bottom plate 7 and the die-cut plate 6 are taken out of the furnace 13 and naturally cooled (about 10 minutes). Due to the difference in the thermal expansion coefficient between the core piece 3 and the die-cutting plate 6, the core piece 3 is easily separated from the die part 6a and the bottom plate 7 by cooling.

(Die Removal Step) As shown in FIG. 1 (f), the core piece 3 is removed from the die release plate 6. Since the core piece 3 is easily separated from the mold portion 6a and the bottom plate 7 in the cooling step, the die-cutting operation becomes extremely easy.

Through the above steps, the manufacture of the core piece 3 is completed. In order to compare the strength of the core piece 3 at room temperature and at high temperature with a core piece manufactured using a conventional coated sand, a test piece (10 × 10 × 60) was manufactured at room temperature and 1000 ° C. A bending strength test (three-point bending strength test) was performed in an atmosphere based on JIS.

As a result, the transverse rupture strength at normal temperature was 1.5 times and the transverse rupture force at high temperature (1000 ° C.) was about 1.2 times that of the conventional shell sand. The transverse force was compared by comparing the average values. When the conventional shell sand was used as a raw material, the range of variation was large in the measurement results at a high temperature, but when the coated sand of this embodiment was used as a raw material, the range of variation was small. That is, when the conventional shell sand is used as a raw material, the reliability is lowered and the yield is deteriorated.

This embodiment has the following effects. (B) The thickness of the flat core piece 3 becomes the depth of the mold portion 6a, and the mold portion 6a is formed so that the area of the open portion of the mold 8 is increased.
Are formed, it is easy to fill the coated sand 9 into the mold portion 6a.

(B) The coated sand 9 supplied into the mold portion 6a is pressed by the roller 10 at a predetermined pressure.
Since the mold portion 6a is uniformly filled in a state where it receives a uniform pressing force in the thickness direction, the strength of the core piece 3 after firing is made uniform.

(C) Since the die 8 is composed of the die cutting plate 6 in which the die portion 6a is formed as a through hole and the bottom plate 7 abutting on one side thereof, Due to the difference in the coefficient of thermal expansion of the coated sand 9, the core piece 3 is easily separated from the mold portion 6a during cooling after firing, and the mold is easily removed.

(D) Since crystalline silicon dioxide whose particle size is controlled is used as the main material of the aggregate of the resin-coated sand 9, seizure, gaze or deformation during casting is prevented. In addition, since Al ₂ O ₃ is contained as an auxiliary material, the collapse property after casting is ensured, and the sand that has formed the core piece can be reliably removed from the cooling water passage after casting, and the cooling rate of 100% of the opening ratio A water passage can be formed.

(E) Since the amount of the resin of the coated sand 9 is about twice as large as that of the usual case, the moldability at the time of molding with a mold is good, and the strength at room temperature is large. With little care, damage during handling is greatly reduced. If the same amount of resin as the conventional resin is added to the main material mainly composed of crystal silica, it is difficult to form the core piece 3 by putting the coated sand into the mold, and if the core piece 3 However, when the core piece 3 is handled to fix the core piece 3 to the core body 2 for a water jacket, corners and the like are easily damaged. However, by increasing the resin amount, the strength at room temperature is secured, the handling of the core piece 3 becomes easy, and the core failure rate (defective) can be greatly reduced.

Although the ratio of the resin amount of the core piece 3 is larger than the ratio of the resin amount used for the conventional core sand for water jackets, the coated sand amount of the core piece 3 is larger than that of the water jacket. Since the amount of the coated sand of the entire use core 1 is insignificant, there is no problem even if the gas amount increases during casting.

(Second Embodiment) Next, a second embodiment will be described with reference to FIGS. In this embodiment, the configuration of the mold and the sintering step are different from those of the above-described embodiment, and the other steps are basically the same. As shown in FIG.
The stamping plate 6 constituting the mold 8 has a larger number of mold portions 6a than in the above-described embodiment, and the stamping plate 6
The whole is formed large. Also, the die-cut plate 6
Is made of stainless steel as in the above embodiment, but the bottom plate 7 is changed to aluminum.

Then, as shown in FIGS. 5A to 5C, the material supply step, the pressing step, and the removing step are performed in the same manner as in the above embodiment. Next, as shown in FIG. 5D, a firing step is performed in a state where the aluminum heat transfer plate 14 is placed on the upper surface of the mold 8 from which the coated sand protruding from the mold portion 6a has been removed. . In the firing step, as shown in FIG. 5 (e), the mold 8 and the heat transfer plate 14 are heated at a predetermined temperature for a predetermined time while the mold 8 and the heat transfer plate 14 are sandwiched between a pair of upper and lower heating plates 15a and 15b. The heating plates 15a and 15b are provided with a heater 16 so that the heating temperature can be adjusted. The heating condition is, for example, 20
8 minutes at 0 ° C, 6 minutes at 220 ° C, 4 minutes at 240 ° C,
It takes 2 minutes at 260 ° C.

After the firing step, as shown in FIG. 5F, cooling is performed with the heat transfer plate 14 placed on the mold 8 (cooling step). Next, as shown in FIG. 5 (g), the core piece 3 is removed from the mold 8 in the mold releasing step, and the manufacture of the core piece 3 is completed.

The number of core pieces 3 fired at one time is preferably 30 to 40 in consideration of the material supply step to the removal step. In this embodiment, (a) in the above embodiment is used.
In addition to the effects of (e), the following effects are obtained.

(F) Since the mold 8 is heated at a higher temperature than the furnace 13 by sandwiching the mold 8 between the heating plates 15a and 15b in the firing step, the firing step is completed in a short time, and the productivity is improved. (G) Since the bottom plate 7 and the heat transfer plate 14 are made of aluminum whose thermal conductivity is ten and several times larger than that of stainless steel, the heating efficiency by the heating plates 15a and 15b is increased.

(H) Since the die-cutting plate 6 constituting the die 8 is made of stainless steel and the bottom plate 7 is made of aluminum, the thermal expansion coefficients of the die-cutting plate 6 and the bottom plate 7 are different. And the bottom plate 7 is assisted.

(Third Embodiment) Next, a third embodiment will be described with reference to FIGS. In this embodiment, the filling of the coated sand into the mold is performed by the blow-in method as in the related art, and the point that the mold is formed in a block shape as in the conventional mold. It is very different from the form.

The mold 17 includes a body-side mold 18 having a mold portion 18a and a lid-side mold 19 that covers an open portion of the mold portion 18a. The portion of the main body side mold 18 facing the mold portion 18a is a ventilation portion 18b through which gas can be blown toward the mold portion and coated sand cannot enter. The ventilation part 18b is formed of a slit block having slits (manufactured by Mitsui Engineering & Shipbuilding Co., Ltd.) or a sintered body having good ventilation.

Then, as shown in FIG. 7, the mold 17 is disposed below the tank 21 provided with the blowing port 20 as in the case of the shell molding method, and the coated sand in the tank 21 is discharged from the blowing port 20 through the mold. The part 18a is filled by blowing (filling step). Next, the mold 17 is placed in a furnace and heated for a predetermined time to fire the coated sand (firing step). Thereafter, the mold 17 is taken out of the furnace and separated into a main body mold 18 and a lid mold 19. The core piece 3 is the main body side mold 18
Is left in the mold portion 18a.

Next, the main body side mold 18 is inverted, and the ventilation portion 18 a is arranged at a position where it comes into contact with the injection port 22 a of the compressed air injection nozzle 22 as shown in FIG. In this state, compressed air is injected from the injection nozzle 22, and the core piece 3 is separated from the mold portion 18a. Since the core piece 3 receives the force of the compressed air uniformly on the surface facing the ventilation portion 18a, the mold portion 18
Detach smoothly from a. And the mold 17 is 100 ° C
After cooling to the extent, the mold 1
7 is arranged at a predetermined position of the tank 21, and a similar process is repeated.

In this embodiment, similarly to the prior art, the filling of the space of the mold portion 18a with the coated sand is performed by blowing the coated sand not in the thickness direction but in the width direction of the core piece 3. Therefore, the roller 10
It is difficult to uniformly press the coated sand in the mold portion 18a to increase the strength as compared with the above-described two embodiments in which the large area of the mold portion 6a is pressed. However, unlike the shell molding method, since the coated sand is not blown while the mold 17 is actively heated, the resin of the coated sand does not melt and adhere to the mold 17. When the manufacturing cycle of the core piece 3 is repeated, the coated sand is blown into the mold portion 18a in a state where the temperature of the mold 17 is cooled to about 100 ° C., but the resin of the coated sand does not melt at this temperature. . By blowing the coated sand at a temperature of the mold 17 of about 100 ° C., the mold 17 is fired in the firing step after the blow.
The amount of energy used for heating can be reduced.

In the prior art, when the core piece is removed from the mold, the core piece is partially pressed by a takeout pin or the like, so that the thin plate-shaped core piece has a high probability of being damaged. However, the entire core piece 3 is compressed with compressed air.
In this embodiment of pressing the core piece 3 away from the mold part 18a, the core piece 3
Damage probability is reduced.

Further, a part of the conventional apparatus, for example, a tank provided with a blowing port can be used as it is. The present invention is not limited to the above embodiments, and may be embodied as follows, for example.

(1) In the second embodiment, FIG.
(A) As shown in FIG.
Of the mold 8 and the heat transfer plate 14 to the heating plate 15a,
It may be heated by sandwiching it between 15b. In this case, the number of core pieces 3 that can be fired at one time can be increased without increasing the areas of the die-cutting plate 6 and the heating plates 15a and 15b. When a large number of sets are stacked, the heating efficiency of the core piece 3 of the mold arranged in the middle part is deteriorated.
The number of layers is preferably two. Also, instead of placing the heat transfer plate 14 on each of the die-cutting plates 6, as shown in FIG. The heat transfer plate 14 is arranged, and the other molds 8 are the bottom plate 7 of the mold 8 arranged on the upper side.
May serve as the heat transfer plate 14. In this case, the number of heat transfer plates 14 may be small.

(2) In the pressing steps of the first and second embodiments, instead of moving the roller 10 while pressing the roller 10 toward the die-cutting plate 6, the die 8 is moved. For example, a roller is provided above the conveyor device so as to be rotatable and urged toward the conveyor device side at a predetermined pressure, and the mold 8 after the material supply step is engaged with the roller by the conveyor device. It may be configured to pass below the roller. In this case, if the scraper 11 is provided downstream of the rollers of the conveyor device, it is easy to perform the pressing step and the removing step by a series of operations.

(3) In the pressing steps of the first and second embodiments, instead of pressing the coated sand in the mold portion 6a with a roller, the coated sand may be pressed from above the mold portion 6a with a flat plate. For example, a flat plate is attached to the tip of the piston rod of the air cylinder, and the coated sand is pressed with a predetermined pressure by the flat plate by the operation of the air cylinder.

Further, the coated sand is supplied while protruding from the mold portion 6a, and the scraper moving with the one end abutting on the mold removal plate 6 is moved to a portion corresponding to the scraper advancing direction of the mold removal plate 6 by a scraper. May be moved in a state where the angle formed by the angle is acute. In this case, the pressing step and the removing step are performed at the same time, and the manufacturing step is simplified.

(4) Also in the first embodiment, the bottom plate 7 may be made of aluminum, and in the second embodiment, the bottom plate 7 may be made of stainless steel. Further, in the first and second embodiments, the entire die 8, that is, the die-cutting plate 6 and the bottom plate 7 may be made of aluminum. When the entire mold 8 is made of aluminum, the heating efficiency in the sintering process is further improved.

(5) The die 8 may have a structure in which the die release plate 6 and the bottom plate 7 are integrally formed. (6) The firing time is appropriately changed depending on the thickness of the core piece 3, the number of core pieces 3 fired at one time, the firing temperature, and the like.

(7) The proportions of the main material, the auxiliary material and the additive in the coated sand used as the material of the core piece 3 may be changed as appropriate. The essential material among the sub-materials is Al ₂ O which plays a role in improving the collapse property of the core piece 3 after casting.
₃ (however, those Al ₂ O ₃ and the thermal expansion coefficient approximately equal, for example, zirconia (Zr O ₂₎ may be replaced by, or the like.) Alone, an average particle size smaller crystal silica than Si O ₂ of the main material Or MgO is not required.

(8) The resin serving as an additive serving as a binder may be a thermosetting resin (for example, a urea resin) other than a phenol resin, or a curing agent other than hexamethylenetetramine may be used as a curing agent. Further, a binder other than the synthetic resin binder may be used as the binder (binder).

(9) The shape of the core piece 3 is not limited to that of the above-described embodiment. For example, as shown in FIGS. 10 (a) and 10 (b), the upper edge is straight and the lower edge 3b is arched. The shape may be a shape in which the upper edge and the lower edge are arched as shown in FIGS. 10C and 10D, or a shape in which both sides of the upper portion extend obliquely as shown in FIG. FIG.
As shown in (f), the shape may be such that the width gradually increases from the center toward both sides, or a simple rectangle. In the case where the width of both sides of the core piece 3 is larger than that of the center part, the sand of the core piece 3 that has collapsed after the cylinder block casting is easily discharged from the cooling water passage. When formed in the shape of an arch, the strength against thermal shock during casting increases.

(10) The core piece 3 is not limited to the one used for casting the cooling water passage to be formed between the bores of the cylinder block, and may be used for casting a flat hole or hole having a thickness of 2 mm or less. It may be applied to a core for use.

The inventions other than those described in the claims, which can be understood from the above embodiments and modifications, will be described below together with their effects. (1) In the invention described in claim 4, in the firing step, a plurality of molds are stacked and sandwiched by a heating plate to perform heating.
In this case, the number of core pieces that can be fired at one time can be increased without increasing the areas of the die-cutting plate and the heating plate, and the productivity is improved.

(2) In the invention according to claim 2,
The mold body and the bottom plate are formed of metals having different coefficients of thermal expansion. In this case, separation of the core piece and the bottom plate is assisted in the cooling step.

[0082]

As described in detail above, claims 1 to 8 are provided.
According to the invention described in (1), a flat core piece having a thickness of 2 mm or less can be manufactured with high yield.

According to the second aspect of the present invention, the work of the mold releasing step becomes easy. According to the third aspect of the present invention, the coated sand supplied into the mold portion is pressed by the roller at a predetermined pressure, and is uniformly filled in the mold portion under a uniform pressing force in the thickness direction. Therefore, the strength of the core piece after firing is made uniform.

According to the fourth aspect of the present invention, in the firing step, the mold is heated by sandwiching it between the heating plates, so that the heating is performed more efficiently than the heating in the furnace, and the firing step is completed in a short time to improve the productivity. .

According to the fifth aspect of the present invention, since the bottom plate and the heat transfer plate are made of aluminum whose thermal conductivity is ten times larger than that of stainless steel, the heating efficiency by the heating plate is further increased.

According to the sixth aspect of the present invention, when the fired core piece is removed from the mold portion of the blow-fill type mold,
Since the whole core piece is extruded in the direction away from the mold part with compressed air, the probability of damaging the thin plate-shaped core piece is reduced compared to the conventional technology in which the core piece is partially extruded with a takeout pin, etc. Productivity is improved.

In the invention according to the seventh aspect, since crystalline silicon dioxide whose particle size is controlled is used as a main material of the aggregate of the resin-coated sand, the occurrence of seizure, gaze or deformation during casting is prevented. Is done. In addition, since Al ₂ O ₃ is contained as an auxiliary material, the disintegration after casting is ensured, and the sand forming the core piece can be reliably removed from the flat holes or holes of the casting after casting.

According to the present invention, a core piece having a shape corresponding to a cooling water passage to be formed between the bores of the cylinder block can be manufactured with high productivity.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a manufacturing process of a core piece according to the first embodiment.

FIG. 2 is a perspective view of a mold.

FIG. 3 is a schematic perspective view of a core for a water jacket.

FIG. 4 is a perspective view of a core piece.

FIG. 5 is a schematic view illustrating a manufacturing process of a core piece according to the second embodiment.

FIG. 6 is a perspective view of the mold.

FIG. 7 is a schematic cross-sectional view illustrating a relationship between a mold and a tank according to a third embodiment.

FIG. 8 is a schematic cross-sectional view of the same demolding step.

FIG. 9 is a schematic cross-sectional view of a firing step according to a modified example.

FIG. 10 is a front view of a core piece of a modified example.

FIG. 11 is a schematic cross-sectional view showing a relationship between a mold and a tank according to the related art.

[Explanation of symbols]

2 ... Core body for water jacket, 3 ... Core piece,
6: die-cutting plate, 6a, 18a: die, 7: bottom plate, 8, 17: die, 9: (resin) coated sand, 10: roller, 14: heat transfer plate, 15a, 15
b: heating plate, 18: body side mold, 19: lid side mold, 22: injection nozzle.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Toshio Sano 2-1-1 Toyotamachi, Kariya, Aichi Prefecture Inside Toyota Industries Corporation (72) Inventor Tsujihiko Yasuda 107, Takanedai, Midori-ku, Nagoya-shi, Aichi Prefecture 72) Inventor Akiyoshi Sano No. 230, Okita-cho, Nakamura-ku, Nagoya-shi, Aichi, Japan Chubu Sukegawa Kogyo Co., Ltd.

Claims (8)

[Claims] 1. A resin coated sand, which is a material of a core piece, overflows from each mold part of a mold having a plurality of mold parts whose upper side is opened and whose depth corresponds to the thickness of the core piece. A material supplying step of supplying the resin-coated sand in a state, a pressing step of pressing the resin-coated sand supplied to the mold section, a removing step of removing the resin-coated sand overflowing from the mold section even after the pressing, and a metal having passed through the removing step. A firing step of firing the resin-coated sand in the mold, and a cooling step of cooling the fired resin-coated sand together with the mold,
Removing the core piece from the mold after cooling. 2. The core piece for forming a blanked hole according to claim 1, wherein the mold includes a mold body having a mold portion formed as a through hole, and a bottom plate abutting on the mold body. Manufacturing method. 3. The method of manufacturing a core piece for forming a cast hole according to claim 1, wherein in the pressing step, the rollers are relatively moved while pressing along the upper surface of the mold. 4. The sintering step is performed by disposing a metal heat transfer plate on the open side of the mold, and holding the mold and the heat transfer plate by a heating plate and heating the plate. A method for manufacturing the core piece for forming a cast hole according to any one of claims 1 to 3. 5. The method according to claim 4, wherein the material of the mold and the heat transfer plate is aluminum. 6. A resin in a mold portion of a mold in a state where a main body side mold having a mold portion filled with a material of a core piece and a lid side mold covering an open portion of the mold portion are combined. A filling step of blowing and filling the coated sand, a firing step of heating the mold and firing the filled resin coated sand, a mold separating step of separating the main body side mold and the lid side mold, and separation. Removing the core piece from the mold portion by connecting the later main body side mold to the compressed gas injection nozzle and blowing gas toward the mold portion, thereby manufacturing a core piece for forming a cast hole. . 7. The resin-coated sand uses crystalline silicon dioxide having a controlled particle size as a main material of the aggregate, and a ceramic having a thermal expansion coefficient at least approximately equal to Al ₂ O ₃ or Al ₂ O ₃ as a secondary material. Claim 1 which includes
A method for manufacturing the core piece for forming a cast hole according to claim 6. 8. The casting hole forming method according to claim 1, wherein said mold portion has a shape corresponding to a cooling water passage to be formed between bores of a cylinder block. Method of manufacturing child pieces.