JP3453252B2 - Core for engine water jacket - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is related to the child in for a water jacket of the engine.

[0002]

2. Description of the Related Art A cylinder block is a basic component of an engine, and its main functions are to guide a reciprocating motion of a piston, support a crankshaft, and cool a cylinder. A water jacket is arranged 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 made as small as possible (8-
11mm), no water jacket between the bores,
So-called Siamese type cylinder blocks have been widely adopted in recent years. Since cooling water does not flow between the bores in this engine block, the cooling between the bores is insufficient compared to the full jacket type.

If the cooling between the bores is insufficient, the bore is distorted due to the rise of the wall temperature, and the oil in the oil pan flows into the combustion chamber and is discharged as gas. Further, there is also a problem that when the temperature of the bore wall is large, the amount of nitrogen oxides (NOx) and smoke in the exhaust gas increases.

The water jacket is formed by a core when the cylinder block is formed by casting. Therefore, it suffices if the water jacket core is integrally formed with a thin portion for casting the gap between the bores, and a flat hole for passing cooling water can be formed between the bores during casting of the cylinder block. However, when the conventional core is used, high temperature (approximately 1400 °
In C), the size on the small diameter side of the hole which can prevent the insertion (feeding), cracks and the like at the time of casting to cast the cylinder block with a good yield was about 2.2 mm. In addition, a core that can be formed with a hole with a size on the small diameter side of approximately 2.2 mm by casting requires careful handling in order to prevent damage to the thin-walled part, and is easy to work with. There is also the problem of being bad.

Instead of casting holes for cooling water through a sand core, a flat pipe with a thickness of 1 mm (width: 17 mm, thickness: 3 mm) is provided at a position corresponding to the space between the bores of the water jacket core. Is arranged and the pipe is arranged in the partition wall between the bores in the state of cast gurumi to form holes for passing cooling water. Further, in JP-A-5-141307, as shown in FIG. 8, a slit 64 is formed between the bore 62 of the cylinder block 61 from the upper deck 63 side, and a plurality of holes 66 communicating with the water jacket 65 are provided. What is formed by a drill is disclosed.

[0007]

However, in the case of the prior art in which a flat pipe is cast between the bores in the state of cast walnut instead of using the sand core, the pipe is placed at a predetermined position of the core for the water jacket. It takes time to embed. In addition, since the flat pipe has a thin wall thickness of 1 mm, if the pipe is cast in an empty state, the pressure of the molten metal acting on the pipe causes the pipe to be deformed. It is necessary to cast in a filled state and remove the filling after casting. Therefore, the number of steps is increased and a special flat pipe is required, which increases the manufacturing cost.

On the other hand, in the case of the conventional technique disclosed in Japanese Patent Laid-Open No. 5-141307, the cooling effect can be enhanced by increasing the number of holes 66. However, since a large number of drilling processes are performed with a drill, there is a problem that the number of processing steps increases and the manufacturing cost increases.

The width of the cooling water passage to be formed between the cylinder bores is very narrow as compared with the width of the water jacket. Therefore, even if a small amount of so-called graduation (insertion), which is a defect on the surface of the casting that occurs due to the molten metal entering the sand grain gap during casting, even a defect that is allowed in the water jacket is not allowed in the cooling water passage. In addition, since the width of the cooling water passage is very narrow, it is very difficult to remove the scale marks formed on the inner surface of the cooling water passage by post-processing, and the cylinder block with the scale marks becomes a defective product. The yield at the time of manufacturing the block is deteriorated.

When a core for a water jacket is formed, when the casting portion between the cylinder bores is formed integrally with the water jacket by using the same core sand, the thickness limit is almost as described above. It is 2.2 mm, which makes it difficult to thin the partition wall between the cylinder bores.

The present invention has been made in view of the above conventional problems, and an object thereof is to form by a conventional molding method using a core for a water jacket between the bores of a cylinder block of the Siamese type. and to provide a child in a water jacket of the engine that can Nuku cast the ultrathin flat holes for cooling water passage can not.

[0012]

In order to achieve the above object, in the invention according to claim 1, a cylinder bore adjacent to a water jacket core body used when a cylinder block of an engine is manufactured by casting is provided. A core piece separate from the core body for forming holes for passage of cooling water in the partition wall between the core body for water jacket and a material different from the core body. And a core piece was disposed at a position corresponding to a position where the partition wall was to be formed.

According to a second aspect of the present invention, the core core is
The amount of resin is about 5% .

According to a third aspect of the present invention, in the first or second aspect of the invention, the water jacket core body has a convex portion at a position corresponding to the upper ends of both ends of each core piece. Are respectively projected toward the upper side.

According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the length of the core piece in the vertical direction is gradually increased from the central portion side toward both sides. It is formed to be large.

According to a fifth aspect of the invention, in the invention according to any one of the first to third aspects, the lower edge of the core piece is formed in an arch shape. In the invention according to claim 6, any one of claims 1 to 5
In the invention described in the paragraph (2), the core piece is formed such that the center of the upper part thereof is located above the upper surface of the core body for the water jacket.

[0017]

[0018]

The core for a water jacket of the invention according to any one of claims 1 to 6 has a core body for a water jacket for forming a water jacket and a hole for passing cooling water in a partition wall between the cylinder bores. The core piece to be formed is formed separately and is made of a different material. And, the material of the core piece 3 is more resin than the core body.
It is made of a material containing a lot of materials. Therefore, the core piece can be made thin so that it can withstand the thermal shock during casting and does not cause eye marks or seizure.Cylinder blocks can be cast under the same conditions as before, and the space between adjacent cylinder bores can be reduced. An extremely small (ultra-thin) hole for passing cooling water is formed in the partition wall of the.

[0020]

According to the third aspect of the present invention, in the state where the cylinder block is cast, the core piece forms a portion corresponding to the convex portions formed at the positions corresponding to the upper ends of both ends of each core piece. The holes communicate with the holes for passing cooling water. Then, by utilizing the holes formed by the convex portions, it is possible to confirm the cast-out state of the holes for passing the cooling water.

In the invention according to claim 4, since the core piece is formed so that the length in the vertical direction gradually increases from the central portion side to both sides, it collapses when the mold is released after casting. The core sand thus formed easily comes out of the holes for passing the cooling water.

According to the fifth aspect of the invention, since the lower edge of the core piece is formed in an arch shape, the resistance to thermal shock during casting is enhanced. Also, by forming it in an arched shape, the width (distance between the upper edge and the lower edge) of the core piece becomes larger on both end sides than in the vicinity of the center, and the core piece collapses during mold release after casting. The sand easily escapes from the holes for passing the cooling water.

In the invention according to claim 6, since the core piece is formed so that the center of the upper part thereof is located above the upper surface of the core body for the water jacket, the space between the bores of the cast cylinder block. The upper part of the bore is efficiently cooled by the cooling water flowing through the hole formed in the hole.

[0025]

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic perspective view of a water jacket core used when manufacturing a four-siamese type cylinder block of an engine. As shown in FIG. 1, a water jacket core 1 is composed of a water jacket core body 2 and a core piece 3 for forming a cooling water passage hole in a partition wall between adjacent cylinder bores. ing. The water jacket core body 2 is formed with a pair of fitting grooves 4 that are open at the upper side and at the lateral sides, respectively, at positions facing each other at the upper portions 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 the spaces between the adjacent cylinder bores.

As shown in FIG. 2, the core piece 3 has a convex portion 3a formed at the center of the upper edge thereof and an arched lower edge 3b thereof. The core piece 3 is formed such that its width (distance between the upper edge and the lower edge) W is larger on both end sides than in the vicinity of the center. That is, the core piece is formed such that the length in the vertical direction gradually increases from the central portion side to both sides. The thickness t of the core piece 3 is 1.0
It is formed to be about 1.8 mm. Both ends of the upper edge of the core piece 3 are located on the same plane as the upper surface of the core body 2 for the water jacket, and the convex portion 3a has the core body 2 for the water jacket.
Is attached to the water jacket core body 2 so as to be located above the upper surface of the.

Further, on the core body 2 for the water jacket, the convex portions 5 are respectively provided so as to project upward at positions corresponding to the upper ends of both ends of each core piece 3, that is, in the vicinity of the fitting groove 4. . After the cylinder block is cast, the convex portion 5 is for forming a hole used for confirming whether or not the hole for passing cooling water is surely cast out by the core piece 3 between the bores. .

As the material of the core body 2 for the water jacket, core sand similar to the conventional one, for example, resin coated sand (shell sand) having a resin content of about 2% is used. On the other hand, the core piece 3 is made of a material different from that of the water jacket core body 2. When cast iron at around 1400 ° C is cast into the material of the core piece 3, seizure and grading do not occur, it has high strength capable of preventing cracks due to thermal shock, and low expansion. A material satisfying the requirement of being present and the requirement of having the strength that the core piece 3 is not damaged when the core piece 3 is handled at room temperature is used.

In this embodiment, as the material of the core piece 3, resin coated sand (hereinafter, simply referred to as coated sand) whose main aggregate is artificial SiO ₂ is used. More detailed description has the following composition.

Main material: 100-200 mesh of crystalline silica (crystalline silicon dioxide (Si O ₂ )) Sub material: 100 mesh of Al ₂ O ₃ (2.5%), more than main material of SiO ₂ Crystal silica with small particle size (3.5%), MgO (1%) Additives: resin (phenolic resin) (5%), hexamethylenetetramine aqueous solution (2%), calcium stearate aqueous solution (1%) % Of auxiliary materials and additives is 1 including the main material
The weight% is defined as 00%, and the rest is% of the main material.

This coated sand is adjusted on the premise that the conventional conditions for manufacturing cores for water jackets and casting conditions for cylinder blocks can be used as they are.

Crystal silica of 100 to 200 mesh, which is the main material, plays a role of making the core piece 3 have a low expansion property and a non-seizure property, and at the same time, preventing the occurrence of eye-grip. The 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 of further suppressing the occurrence of a grain in casting.

Al ₂ O ₃ used as an auxiliary material plays a role of enhancing the disintegration 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 disintegration property of the core piece 3 after casting is deteriorated. 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 that of crystal silica, the difference in coefficient of thermal expansion between 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 it easily collapses.

When the coated sand is adjusted by adding the same amount of resin (2 to 3%) as that of the conventional core sand to the aggregate having this composition, it cannot be molded because it is too smooth. Therefore, by increasing the amount of resin about twice as much as the conventional amount, the moldability and the strength at room temperature that can prevent damage when handling the core piece 3 are secured.

Next, an example of 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 the piece material and a manufacturing process of the core piece 3 using the coated sand.

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

(Second Step) Powdery resin is added to the mixture obtained in the first step, and the mixture is stirred to uniformly mix. (Third step) The mixture obtained in the second step was added to about 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 auxiliary material.

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

The coated sand thus prepared has appropriate fluidity and is excellent in moldability by a mold. Next, a method of manufacturing the core piece 3 using the coated sand manufactured as described above will be described with reference to FIGS. A die-cutting plate 6 as shown in FIG. 3 is used for manufacturing the core piece 3. The die-cutting plate 6 is made of stainless steel, and a plurality of die portions 6a corresponding to the shape of the core piece 3 are provided in a transparent manner. The die-cutting plate 6 has a thickness of 1.0-1 ..
It is formed to a preset value of 8 mm.

The core piece 3 is manufactured through the steps shown in FIGS. 4 (a) to 4 (f). (First Step) As shown in FIG. 4A, the bottom plate 7
The die-cutting plate 6 is disposed on the above, and the coated sand 8 is supplied to the portions of the die-cutting plate 6 corresponding to the die portions 6a in a state of being raised from the die portions 6a.

(Second Step) As shown in FIG. 4 (b),
The roller 9 is moved while being pressed against the upper surface of the die-cutting plate 6, and the coated sand 8 is pushed into the die portion 6a with a predetermined pressure. At this time, since the coated sand is in a state similar to that of appropriately moist sand, the coated sand 8 is pressed into a shape corresponding to the shape of the mold portion 6a without losing its shape.

(Third Step) As shown in FIG.
The scraper 10 is moved along the upper surface of the die-cutting plate 6 to remove the coated sand in the portion protruding from the die 6a.

(Fourth Step) As shown in FIG.
The bottom plate 7 and the die-cutting plate 6 are put in the furnace 12 with the lid 11 covered, and heated 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.

(Fifth Step) As shown in FIG.
The bottom plate 7 and the die-cutting plate 6 are taken out of the furnace 12 and naturally cooled (about 10 minutes). Due to the difference in coefficient of thermal expansion between the core piece 3 and the die-cutting plate 6, the core piece 3 is naturally separated from the die 6a and the bottom plate 7 by cooling.

(Sixth Step) As shown in FIG.
The core piece 3 is removed from the die-cutting plate 6. Since the core piece 3 is separated from the die 6a and the bottom plate 7 in the fifth step, the die cutting work becomes extremely easy.

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

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

After the core piece 3 formed as described above is fitted into the fitting groove 4 of the core body 2 for water jacket, the core body 2 for water jacket and the core piece 3 are coated with a coating material. And are fixed to form the water jacket core 1. Since the core piece 3 has a high strength at room temperature, the damage during handling can be greatly reduced without paying much attention to the handling of the core piece 3. Further, instead of the worker manually attaching the core piece 3 to the water jacket core body 2, it is possible to automatically attach the core piece 3 with a robot.

The water jacket core 1 configured as described above is assembled with other cores and then housed in the mold. In that state, cast iron heated to around 1400 ° C is poured into the mold. Then, the mold release is performed after several tens of minutes. Then, the mold sand adhering to the casting surface and the 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 on the core piece 3 is removed by blowing compressed air.

FIG. 5 is a partial schematic plan view of the cylinder block 13 formed as described above, and FIG. 6 is a plan view of FIG.
It is a schematic sectional drawing in the VI-VI line. As shown in FIG. 5, a water jacket 16 is formed around the cylinder bore 14 except for a partition wall 15 that partitions the adjacent cylinder bores 14. Minimal (extremely thin) as a hole for passing cooling water at a position corresponding to the partition wall 15
The cooling water passage 17 has water jackets 1 at both ends.
The partition wall 15 is formed by casting so as to communicate with 6. Further, holes 18 communicating with the cooling water passages 17 are formed at positions corresponding to both ends of the partition wall 15 so as to open on the upper surface of the cylinder block 13. This hole 18 is formed by the convex portion 5 of the water jacket core body 2. This hole 18 is used when inspecting whether or not the casting of the cooling water passage 17 between the cylinder bores 14 has been reliably performed.

Since the particle size-controlled crystal silica is used as the main material of the core piece 3, the core piece 3 is prevented from being deformed or cracked due to thermal shock during casting, and at the same time, seizure or rubbing can be prevented. Generation is prevented, and the cooling water passage 17 is reliably formed at a predetermined position between the cylinder bores. The proportion of resin in the coated sand of the core piece 3 is significantly higher than the proportion of resin in the core sand of the water jacket core body 2. Therefore, the amount of gas generated by the decomposition of the resin during casting increases. But,
Since the absolute amount of the coated sand of the core piece 3 is much smaller than the absolute amount of the core sand of the core body 2 for the water jacket, the increase in the total gas amount is small and does not adversely affect the casting. .

The particles constituting the aggregate of the core piece 3 are held in a state of being pressed against each other by thermal expansion during casting, but the thermal expansion coefficient of Al ₂ O ₃ and crystal silica is maintained during cooling after casting. Due to the difference between the _two , a gap is generated between the Al ₂ O ₃ particles and the crystal silica particles, and the particles easily collapse. Therefore, the core sand is surely removed from the inside of the cooling water passage 17 by blowing the compressed air after releasing the mold.

This embodiment has the following effects. (A) The material of the water jacket core body 2 and the material of the core piece 3 for forming the cooling water passage 17 in the partition wall 15 between the cylinder bores 14 are made of different materials. Therefore, even if the core piece 3 has a small thickness, it is possible to prevent the sighting and seizure during casting and to withstand the thermal shock, and the partition wall 15 between the adjacent cylinder bores 14 has a thickness of 1.0. An extremely small (ultra-thin) cooling water passage 17 of up to 1.8 mm can be formed.

(B) In the core piece 3, the main material of the aggregate is secured to prevent the occurrence of the grain and seizure at the time of casting, and the auxiliary material is to ensure the disintegration after casting. Therefore, the sand that has formed the core piece can be reliably removed from the cooling water passage 17 after casting, and the cooling water passage 17 having an opening ratio of 100% can be formed.

(C) When the same amount of resin as the conventional one is added to the main material containing crystal silica as a main component, it is difficult for the coated sand to be smoothly inserted into the mold to form the core piece 3, so that Even if the core piece 3 is formed, the corners and the like are easily damaged when the core piece 3 is handled in order to fix the core piece 3 for the water jacket. However, due to the increase in the amount of resin, the strength at room temperature is secured, the core piece 3 is easily handled, and the core damage ratio (defective) can be significantly reduced.

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

(D) As an aggregate of the core piece 3, an artificial sand (crystal body SiO ₂ ), whose main and auxiliary materials are completely controlled in grain size, and an artificial aggregate made of Al ₂ O ₃ and Mg O are used. It is used. Therefore, unlike conventional shell sand and cold sand (aggregate is natural silica sand or blended sand of artificial sand such as cera beads), variations in characteristics such as transverse rupture strength of the manufactured core piece 3 are very small. Therefore, the incidence of defective products can be significantly reduced.

(E) Since the main material of the core piece 3 is crystal silica, it is the same as silicon dioxide which is the main component of the shell sand which is the material of the core body 2 for the water jacket. Therefore, there is no problem even if the core sand for the water jacket core body 2 mixed with the core sand for the core piece 3 is used as the return sand for the core sand for the water jacket core body 2 when the mold is released. .

(F) Core body 2 for water jacket
Is the same as the conventional one except for the fitting groove 4 and the convex portion 5, and can be used by slightly modifying the conventional manufacturing equipment. (G) As shown in FIG. 6, in the manufactured cylinder block 13, the upper end of the cooling water passage 17 is located at a position corresponding to the upper pressure ring (compression ring) 20 when the piston 19 is located at the top dead center. Since it has reached, the cooling water can pass through the position corresponding to the upper part of the cylinder bore 14, and the upper part of the cylinder bore 14 can be efficiently cooled by the cooling water.

(H) Since the core piece 3 is formed such that the length in the vertical direction gradually increases from the central portion side to both sides, the collapsed core sand is cooled when the mold is released after casting. It becomes easy to get out of the water passage 17.

(B) Since the lower edge 3b of the core piece 3 is formed in an arch shape, the resistance to thermal shock during casting is enhanced. In addition, the core piece 3 has a width (distance between the upper edge and the lower edge) by being formed in an arch shape.
W becomes larger on both end sides than in the vicinity of the center, and when the mold is released after casting, the collapsed core sand has a cooling water passage 17
It is easy to get out of the inside.

(N) The cast cylinder block 13
Since holes 18 are formed near both ends of the cooling water passage 17, the opening ratio of the cooling water passage 17 is 100 by utilizing the holes 18.
%, That is, it is easy to confirm that there is no graduation during casting and that part of the core sand does not remain.

The present invention is not limited to the above embodiment, but may be embodied as follows, for example. (1) When a coated sand containing artificial SiO ₂ as the main aggregate is used as the material of the core piece 3, those having different particle size distributions of the main material and the sub-material are used, or the main material,
You may change the ratio of a submaterial and an additive suitably. For example, Al ₂ O, which plays a role of improving disintegration among the auxiliary materials
The amount of ₃ is 1 to 7%, preferably 1.5 to 4.0%,
More preferably, it is 2.0 to 3.2%. If the amount of Al ₂ O ₃ is less than 1%, the disintegration property deteriorates, and it becomes difficult to remove the material of the core piece 3 from the cooling water passage 17 after casting. If it is more than 7%, the moldability of the core piece 3 is deteriorated. The particle size of Al ₂ O ₃ is not limited to 100 mesh, and may be larger or smaller.

The amount of crystal silica having an average particle size smaller than that of SiO _{2 as the} main material is 1 to 7%, preferably 2.5.
˜4.3%, and more preferably 3.0 to 3.8%.
If the amount of crystal silica is less than 1%, it is easy for a grain to be generated during casting. If it is more than 7%, the transverse rupture strength decreases.

The amount of resin is 3.5 to 8%, preferably 4.0 to 7.0%, more preferably 4.5 to 6.0%. If the amount of the resin is less than 3.5%, the material becomes dry and the molding becomes difficult. If the amount of the resin is more than 7.0%, it becomes too sticky and difficult to be formed, and more gas is generated during casting, and bubbles are formed.

(2) In addition, an essential one of the auxiliary materials is Al ₂ O ₃ (provided that the coefficient of thermal expansion is almost equal to that of Al ₂ O ₃ which plays a role of improving the disintegration property of the core piece 3 after casting. (For example, zirconia (ZrO ₂ ) or the like may be substituted), and crystal silica or MgO having an average particle size smaller than that of the main material SiO ₂ may not be used.

(3) As a resin or a curing agent as an additive which functions as a binder, a thermosetting resin other than phenol resin (for example, urea resin) or a curing agent other than hexamethylenetetramine may be used. Further, a binder other than the synthetic resin binder may be used as the binder (binder).

(4) The material of the core piece 3 is artificial SiO 2.
Not limited to coated sand with ₂ as the main aggregate, 1400
Any material can be used as long as it does not cause seizure, rubbing or deformation when cast iron of about ° C is cast, and can be collapsed by air blow after the mold is released. For example, a graphite sheet mainly containing carbon may be used. Since graphite has poor wettability with respect to the molten metal, it is less likely to cause grading as compared with coated sand having artificial SiO ₂ as a main aggregate.

(5) Instead of attaching the core piece 3 to the water jacket core body 2 via the fitting groove 4, the core piece 3 is fitted in a predetermined position without forming the fitting groove, The core piece 3 may be attached to the water jacket core body 2 by using an adhesive.

(6) The shape of the core piece 3 is not limited to that of the above-mentioned embodiment, and may be changed appropriately. For example, in FIG.
As shown in (a) and (b), the upper edge is linear and the lower edge 3b is
Has an arched shape. In this case, similarly to the above-described embodiment in which the lower edge 3b has an arched shape, the strength against the thermal shock at the time of casting is large, and the core sand collapsed at the time of casting after the casting is easily released from the cooling water passage 17. . In the case of the core piece 3 shown in (b), the lower end of the arch is the core piece 3
Since it reaches the both ends of the core piece 3, the core sand is more likely to come out of the cooling water passage 17 than in the core piece 3 of FIG. When the upper edge and the lower edge have an arched shape as shown in FIGS. 7C and 7D, in addition to the effect corresponding to the core piece 3 shown in FIGS. 7A and 7B, In the manufactured cylinder block 13, the cooling water can pass through the position corresponding to the upper part of the cylinder bore 14, and the upper part of the cylinder bore 14 can be efficiently cooled by the cooling water.

Further, as shown in FIG. 7 (e), both sides of the upper part of the core piece 3 of the above embodiment may be cut off obliquely. In this case, as compared with the core piece 3 of the embodiment, the core sand becomes easier to escape from the cooling water passage 17. Further, as shown in FIG. 7 (f), the lower edge 3b
May not have an arch shape, but may have a shape including a horizontal central portion and inclined portions that extend obliquely toward both sides. Also,
The core piece 3 may have a simple rectangular shape, or the lower edge 3b may be horizontal and the convex portion 3b may be formed on the upper side.
Further, as shown in FIG. 7 (g), a long hole 3c may be formed in a part of the core piece 3. When the long hole 3c is formed, the strength of the partition wall 15 of the manufactured cylinder block 13 increases.

Inventions other than those described in the claims that can be grasped from the above-described embodiments and modifications will be described below along with their effects. (1) the material of the middle terminal piece and resin-coated sand, galling at the time of casting the main material of the aggregate (sand), and a material capable of preventing aiming, secondary material can be secured at least disintegration after casting Including materials. In this case, since the main material has the respective functions of maintaining the strength during casting and the sub-material having the function of ensuring the disintegration, the range of selection of materials satisfying the performance required for the core piece is expanded.

(2) The main material is a crystal body S whose grain size is controlled.
iO ₂ is used, and the auxiliary material is Al ₂ O ₃ or Al ₂ O ₃ whose average particle size is smaller than that of the main material and whose particle size is controlled. In this case, the main material is the same as the main component of the shell sand that is the material for the core body for the water jacket, so there is no problem if it is used as return sand after unmolding for the core sand for the water jacket core body. .

(3) In the invention of (1) or (2), the amount of resin of the core piece material is made larger than that of the core material for the water jacket. In this case, the moldability of the core piece and the bending strength at room temperature are improved, and the core piece is easily handled.

(4) A method of manufacturing a cylinder block for casting a cylinder block of an engine using the core for a water jacket according to any one of claims 1 to 6. In this case, an extremely thin cooling water passage can be cast out between the cylinder bores, the cost for forming the extremely thin cooling water passage can be reduced, and the manufacturing cost of the entire cylinder block can be reduced.

[0077]

As described in detail above, the first to sixth aspects of the invention are described.
The use of child in the invention described in, rhinoceros Amy between's type cylinder block bore, tiny 1.0~1.8mm can not be formed in the molding method using the conventional water jacket core for (Ultrathin) flat holes for passing cooling water can be cast out.

[0078] In the invention described in 請 Motomeko 3, since the cast cylinder block bore near both ends of the hole for the cooling water passage (coolant passage) is formed, the cooling water by utilizing the hole It becomes easy to confirm that the opening ratio of the passage is 100%, that is, that there is no gaze during casting and that some of the core sand does not remain.

In the invention according to claim 4, since the core piece is formed so that the length in the vertical direction gradually increases from the central portion side to both sides, it collapses when the mold is released after casting. The core sand easily comes out of the holes for passing the cooling water.

In the invention according to claim 5, since the lower edge of the core piece is formed in an arch shape, resistance to thermal shock during casting is enhanced. Further, by forming the arched shape, the core piece is easily moved in the direction in which it is discharged from the hole due to the weight of the core piece material on both end sides thereof, and the collapsed core sand is generated when the mold is released after casting. It becomes easy to come out from the hole for passing the cooling water.

According to the sixth aspect of the invention, the upper portion of the cooling water passage hole can be formed so as to extend to a position corresponding to the upper portion of the cylinder bore between the cylinder bores, and the cooling efficiency of the cooling water on the upper side of the cylinder bore is improved. To do.

[0082]

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a core for a water jacket.

FIG. 2 is a perspective view of a core piece.

FIG. 3 is a perspective view of a die cutting plate.

FIG. 4 is a schematic view showing a manufacturing process of a core piece.

FIG. 5 is a schematic plan view of a cylinder block.

6 is a sectional view taken along line VI-VI of FIG.

FIG. 7 is a front view of a core piece of a modified example.

8A is a partial plan view of a conventional cylinder block, and FIG. 8B is a sectional view taken along line BB of FIG. 8A.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Core for water jacket, 2 ... Core body for water jacket, 3 ... Core piece, 3b ... Lower edge, 4 ... Fitting groove, 5 ... Convex part, 13 ... Cylinder block, 14 ... Cylinder bore, 15 ... Partition wall, 17 ... Cooling water passage as a hole for passing cooling water.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Toshio Sano, 2-chome, Toyota-cho, Kariya City, Aichi Prefecture Toyota Industries Corporation (72) Inventor, Tsujihiko Yasuda 107, Takanedai, Midori-ku, Nagoya-shi, Aichi (56) ) Reference Japanese Unexamined Patent Publication No. 5-169184 (JP, A) Actually opened 63-66547 (JP, U) Actually opened 63-47048 (JP, U) Actually opened 59-6037 (JP, U) Japan Foundry Association Edited, Casting Handbook 4th Edition, January 20, 1986, p. 124 (58) Fields investigated (Int.Cl. ⁷ , DB name) B22C 1/00-9/30 F02F 1/14

Claims (6)

(57) [Claims] 1. A core body for a water jacket used when a cylinder block of an engine is manufactured by casting, the core body for forming a hole for passing cooling water in a partition wall between adjacent cylinder bores. Separate core piece from the material of the core body for the water jacket,
A core for a water jacket of an engine, which is made of a material containing a larger amount of resin than that of the core body, and in which the core piece is arranged at a position corresponding to a position where the partition wall is to be formed. 2. The amount of resin in the core piece is about 5%
A core for a water jacket of an engine according to claim 1. 3. The core body for a water jacket is provided with convex portions projecting upward at positions corresponding to upper ends of both ends of each core piece. Core for the water jacket of the engine. 4. The engine according to claim 1, wherein the core piece is formed such that the length in the vertical direction gradually increases from the central portion side toward both sides. Core for water jacket. 5. The core for a water jacket of an engine according to claim 1, wherein a lower edge of the core piece is formed in an arch shape. 6. The engine according to claim 1, wherein the core piece is formed so that the center of the upper part thereof is located above the upper surface of the core body for the water jacket. Core for water jacket .