JPH08150463A - Method for casting ceramic-made port liner - Google Patents

Abstract

PURPOSE: To provide a casting method of a ceramic-made port inner which prevents the breakage of the ceramic-made port liner caused by shrinkage of a metal at the time of casting a cylinder head and encloses an involved stress buffering layer. CONSTITUTION: The port liner 1 with the ceramic and the outer shell 4 with a plate material are manufactured and the outer surface 8 of the port liner 1 is covered with the stress buffering layer 3 composed of the buffering material and also, the outer surface 12 and the end surface 11 of the stress buffering layer 3 and the end surface 10 of the port liner 1 are covered with the outer shell 4. The opening holes 6 at both ends of the port liner 1 are closed with plugs to make a core, and the core is set into a cylinder head mold and molten metal is cast. The opening end surfaces 5 of the outer shell 4 are machined so that the stress buffering layer 3 constituting a heat insulating layer is not exposed to produce the cylinder head 2 inserting the port liner.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for casting a ceramic port liner having a heat shield layer formed on a cylinder head.

[0002]

2. Description of the Related Art Conventionally, regarding the structure of intake and exhaust ports of an engine, a port liner made of a low heat conductive material such as aluminum titanate (Al ₂ TiO ₅ ) is manufactured and cast into a metal material such as an aluminum alloy or Fc. It is known that an intake / exhaust port is formed in a cylinder head.

Further, when a port liner made of a low heat conductive material such as aluminum titanate is cast into a metal material,
A high compressive stress acts on the port liner due to the compressive force due to the contraction of the metal material of Al or Fc after casting. The compressive stress may damage the port liner.
As a measure to prevent damage to the port liner due to shrinkage after casting, it is conceivable to wrap the outer periphery of the port liner with a material such as alumina fiber. For example, in a manufacturing method for forming an intake / exhaust port in a cylinder head, when a ceramic port liner is formed around a cylinder head during casting to form a heat insulating structure, when the cast metal material forming the cylinder head solidifies, In order to prevent the port liner from receiving a compressive stress and being damaged by the contracting force of the metal material, a buffer layer is provided between the cylinder head and the port liner to make the casting line.

For example, as an engine heat insulation device, FIG.
And as shown in FIG. 5, the cylinder head 2 made of metal
In order to cast the ceramic port liner 20 in 2, the buffer layer 21 such as alumina fiber is arranged on the outer surface of the ceramic port liner 20 so that the molten metal does not directly contact the ceramic port liner 20. The end opening 23 of the liner is closed by a plug 25 to produce a core, the core is placed in a cylinder head mold, and the molten metal is poured into the cylinder head 22. A cylinder head having such a structure is disclosed in, for example, Japanese Patent Laid-Open No. 61-7.
There is one disclosed in Japanese Patent Publication No. 9818.

Further, the cylinder head of the internal combustion engine disclosed in Japanese Patent Laid-Open No. 59-108848 is provided with a ceramic layer forming the inner surface of the exhaust port, and a complex body enclosing the outside of the ceramic layer is provided. It is made by wrapping the outside with a heat-resistant material so that there is no gap between it and the ceramics layer.

As a ceramic port liner, for example, there is one disclosed in Japanese Utility Model Laid-Open No. 63-170555. In this ceramic port liner, the outer periphery of a ceramic port liner main body is covered with a ceramic sheet that expands irreversibly by heating.
Further, in the ceramic port liner, the ceramic sheet is composed of vermiculite, ceramic fibers and a trace amount of organic binder.

[0007]

However, in the case where a buffer layer is provided between the cylinder head and the port liner so that the alumina fiber portion is manufactured by casting, the molten metal material during casting is prevented from flowing into the alumina fiber portion. In addition, there is a problem that it is necessary to perform a seam treatment, an end face treatment, and the like, which complicates the treatment process and makes it impossible to perform mass production including dimensional tolerances. Further, in the method of casting a ceramic port liner as shown in FIG. 4, when the end face of the cylinder head 22 is cut, co-processing of the cylinder head 22 and the ceramic port liner 20 occurs. When processing is performed to avoid this co-processing, a recess 26 is formed in the cylinder head 22 at the boundary between the cylinder head 22 and the core. Further, the buffer layer 21 made of alumina fiber or the like is exposed at the end surface of the cylinder head 22, and a part of the buffer layer 21 falls off.
Performance deterioration of the heat shield layer and rattling of the ceramic port liner 20 may occur, and in some cases, the ceramic port liner 20 may be damaged.

An object of the present invention is to solve the above problems, and is a method for producing a port liner having a heat shield structure, in which a ceramic port liner arranged at a port formed in a metal cylinder head is made of alumina. A core is made by covering it with a buffer layer such as fibers with an outer shell, placing the core in a cylinder head mold, casting molten metal to make a cylinder head, and cutting the open end surface of the outer shell. To provide a method of casting a ceramic port liner.

[0009]

In order to achieve the above object, the present invention is configured as follows. That is,
According to the present invention, a step of producing a port liner from ceramics having openings at both ends and an outer shell from a plate material, the outer surface of the port liner being covered with a stress buffer layer made of a buffer material, and the outer surface and the end surface of the stress buffer layer. And a step of covering the end face of the port liner with the outer shell, closing the openings at both ends of the port liner covered with the outer shell and the stress buffer layer with plugs to produce a core, Is placed in a cylinder head mold to cast the molten metal, and a method for casting a ceramic port liner.

Further, in this ceramic port liner casting method, the opening end face of the outer shell that covers the end face of the port liner is cut to such an extent that the stress buffer layer is not exposed, and the cylinder is produced by casting the port liner. The head is manufactured. Further, the stress buffer layer forms a heat shield layer made of ceramic fibers enclosed by the port liner and the outer shell.

[0011]

The method of casting a ceramic port liner according to the present invention is constructed as described above and operates as follows. That is, the casting method of the ceramic port liner is such that the outer surface of the ceramic port liner is covered with a stress buffer layer, and the outer surface and the end surface of the stress buffer layer and the end surface of the port liner are covered with an outer shell to form a core. Made,
Since the core is arranged in the cylinder head mold and the molten metal is cast, the stress and thermal shock force due to the contraction of the metal forming the cylinder head is absorbed by the stress buffer layer, and is not directly applied to the ceramic port liner. The ceramic port liner is not damaged. Further, since the end surface of the ceramic port liner is covered with the outer shell, when the end surface of the cylinder head is cut, co-processing of the cylinder head and the ceramic port liner does not occur, and the ceramic The opening end surface of the outer shell can be partially processed to the extent that the port liner made is not exposed, and the stress buffer layer does not fall off the end surface. Moreover, the stress buffer layer can configure the port liner to have a heat shield structure.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for casting a ceramic port liner according to the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of a method for casting a ceramic port liner according to the present invention, and FIG. 2 is a line A in FIG.
-A is a sectional view and FIG. 3 is a sectional view showing a part of the core in the method of casting the ceramic port liner of FIG.

As shown in FIG. 1, in a cylinder head 2 manufactured by the method for casting a ceramic port liner according to the present invention, a ceramic port liner 1 forming a port 7 is provided with a stress buffer layer 3 and an outer shell 4. It is arranged to intervene. The stress buffer layer 3 functions as a heat shield layer, and is made of ceramic fibers such as alumina fibers, alumina whiskers, and alumina long fibers. The cylinder head 2 is manufactured by casting in a state in which the outer surface of the ceramic port liner 1 is covered with the stress buffer layer 3, and compressive stress caused by shrinkage of the metal material forming the cylinder head 2 generated during casting is suppressed. The stress buffer layer 3 absorbs it, and the ceramic port liner 1 is prevented from cracking or cracking and is prevented from being damaged. The stress buffer layer 3 constitutes a heat shield layer made of ceramic fiber enclosed by the port liner 1 and the outer shell 4, and the port 7 has a heat shield structure. Therefore, in the case of an exhaust port, the stress buffer layer 3 can ensure heat shielding properties, and the ceramic port liner 1 can provide a wall surface having high heat resistance and high heat resistance. Further, regarding the intake port as well, the heat received by the intake air from the cylinder head 2 can be significantly reduced, and the air filling efficiency can be improved.

The casting method of the ceramic port liner according to the present invention is performed as follows. That is, in the method for casting a ceramic port liner according to the present invention, first, the port liner 1 is made of ceramics having openings 6 at both ends, and the outer shell 4 is made of a plate material. The port liner 1 can be produced by forming a compact from a ceramic raw material such as Al ₂ TiO ₅ having low thermal conductivity or heat-resistant and high-strength Si ₃ N ₄ or SiC, and firing the compact. . The outer shell 4 is formed from a metal plate by press working or the like into bent half-cylindrical bodies 4L and 4R, and the flange portions 9 at the edges of the bent half-cylindrical bodies 4L and 4R are welded by projection welding or the like to trim the outer shape. Can be produced. In this case, it is preferable that the flange portions 9 at the edges of the bent semi-cylindrical bodies 4L and 4R be cut to some extent and removed after being welded to each other. Alternatively, when the material forming the cylinder head is made of a low melting point material such as an aluminum alloy, the outer shell 4 may be formed by molding using a plate material such as fiber reinforced plastic.

Therefore, the outer surface 8 of the port liner 1 is covered with the stress buffer layer 3 made of a buffer material. Therefore, the outer surface 12 of the stress buffer layer 3 and its end surface 11 and the end surface 10 of the port liner 1
Are covered with the bent semi-cylindrical bodies 4L and 4R so as to be sandwiched from both sides, and then the flange portions 9 of the bent semi-cylindrical bodies 4L and 4R are welded to form the outer shell 4, and the stress buffer layer 3 and the port liner 1 are formed. And are covered with the outer shell 4. next,
As shown in FIG. 3, the openings 6 at both ends of the port liner 1 covered with the outer shell 4 and the stress buffer layer 3 are closed with plugs 13 to produce a core. Then, the core is placed in the cylinder head mold and the molten metal is cast into the ceramic port liner to complete the casting.

Next, the cylinder head 2 is taken out from the cylinder head mold, and the end portion of the cylinder head 2 including the open end surface 5 of the outer shell 4 covering the end surface 10 of the port liner 1 is exposed to the extent that the stress buffer layer 3 is not exposed. It is possible to manufacture the cylinder head 2 in which the ceramic port liner 1 is cast in by cutting and removing along the reference numeral B in FIG. By cutting the opening end surface 5 of the outer shell 4 at the end surface of the cylinder head 2, a sealing surface of a mounting surface for a manifold and a sealing surface of a valve seat for a valve can be formed.

In consideration of the cutting work of this ceramic port liner, when the outer shell 4 is manufactured to have a thickness of about 3 to 5 mm, even if the outer shell 4 is deformed during casting, the open end surface of the outer shell 1 is formed. 5 has a sufficiently machined surface, and the heat flow path generated in the outer shell 4 can be reduced by cutting the end surface of the outer shell 4. Further, as the outer shell 4, it is preferable to select a material whose outer surface is slightly melted by the molten metal at the time of casting so that the outer shell 4 is welded to the cylinder head 2. For example, a metal such as mild steel is used. Can be made with. Alternatively, the outer shell 4 is 1.2 to 2.2 m
It is made of a plate material having a thickness of about m, and after covering the ceramic port liner 1 and the stress buffer layer 3 with the outer shell 4 to make a core, a plate material of another component is welded to both ends of the outer shell 4. Etc. to form only the opening end face 5 to a thickness of about 4 mm,
It can also be produced by casting it.

[0018]

The method of casting a ceramic port liner according to the present invention is constructed as described above and has the following effects. That is, in this method of casting a ceramic port liner, the outer surface of the ceramic port liner is covered with a stress buffer layer, and the stress buffer layer and the port liner are covered with an outer shell to cast molten metal. The stress due to the contraction of the metal is not directly applied to the ceramic port liner, and the ceramic port liner is not cracked or damaged. In particular, since the end surface of the ceramic port liner is covered with the outer shell, when cutting the end surface of the cylinder head, the opening end surface of the outer shell can be partially processed to the extent that the ceramic port liner is not exposed, The stress buffer layer does not fall off from the end face, the heat insulation of the port does not decrease, the ceramic port liner is firmly incorporated in the cylinder head, and rattling does not occur, resulting in shielding. It is possible to improve durability and reliability with respect to the formation of the stress buffer layer forming the thermal layer.

Further, since the opening end face of the outer shell covering the end face of the port liner is cut to such an extent that the stress buffer layer is not exposed, the cylinder head in which the port liner is cast is manufactured by cutting the end face of the outer shell to produce the cylinder head. Co-processing with the ceramic port liner does not occur, yield in finishing is improved, cutting is facilitated, and manufacturing cost can be reduced. Further, since the stress buffer layer forms a heat shield layer made of ceramic fibers enclosed by the port liner and the outer shell, the heat shield degree of the stress buffer layer is significantly improved.

Since the stress buffer layer is covered with the outer shell at the time of casting, even if the molten metal material for forming the cylinder head is cast, the metal material is melted into the stress buffer layer at the time of casting. Does not flow in, and therefore the heat shield of the stress buffer layer can be effectively exhibited. Further, since ceramics such as aluminum titanate having a low thermal conductivity and alumina fiber can be used as the material forming the stress buffer layer, the heat shielding performance of the exhaust port can be particularly improved. Further, when the cylinder head is manufactured by using the casting method of the ceramic port liner, the manufacturing process is simplified, the casting yield is improved, and the mass production including the dimensional tolerance can be performed.

Therefore, the exhaust port produced by the casting method of the ceramic port liner can secure the heat shielding property by the stress buffer layer, and the ceramic port liner can provide a high temperature and high strength wall surface with high heat resistance. . Further, also in the intake port manufactured by this ceramic port liner casting method, the heat received by the intake air from the cylinder head and the port can be significantly reduced, and the efficiency of air filling can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view illustrating an embodiment of a method for casting a ceramic port liner according to the present invention.

2 is a cross-sectional view taken along the line AA in FIG.

FIG. 3 is a cross-sectional view illustrating a core used in a method for casting a ceramic port liner according to the present invention.

FIG. 4 is a sectional view showing an example of a conventional cylinder head.

FIG. 5 is a cross-sectional view illustrating an example of a conventional ceramic port liner casting method.

[Explanation of symbols]

 1 Ceramic Port Liner 2 Cylinder Head 3 Stress Buffer Layer 4 Metal Outer Shell 5 Open End Face of Metal Outer Shell 6 Opening 7 Port 8 Outer Surface of Ceramic Port Liner 9 Flange 10 End Face of Ceramic Port Liner 11 Stress Buffer Layer End face 12 outer surface of stress buffer layer 13 plug

Claims (3)

[Claims] 1. A step of producing a port liner from ceramics having openings at both ends and an outer shell from a plate material,
Covering the outer surface of the port liner with a stress buffer layer made of a buffer material, and covering the outer surface and the end surface of the stress buffer layer and the end surface of the port liner with the outer shell, covering with the outer shell and the stress buffer layer. A step of closing the openings at both ends of the port liner with plugs to produce a core, arranging the core in a cylinder head mold and casting molten metal, the ceramic port liner characterized in that Casting method. 2. A cylinder head in which the port liner is cast by cutting the opening end surface of the outer shell that covers the end surface of the port liner to the extent that the stress buffer layer is not exposed. Item 1. A method for casting a ceramic port liner according to Item 1. 3. The method for casting a ceramic port liner according to claim 1, wherein the stress buffer layer forms a heat shield layer made of ceramic fibers enclosed by the port liner and the outer shell. .