Internal-combustion engines – Particular piston and enclosing cylinder construction – Cylinder head
Reexamination Certificate
2000-04-18
2001-12-18
McMahon, Marguerite (Department: 3747)
Internal-combustion engines
Particular piston and enclosing cylinder construction
Cylinder head
Reexamination Certificate
active
06330871
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cylinder block of an internal combustion engine integrally having a cylinder head and particularly to a cylinder head-integrated cylinder block having liner portions of cylinders made of reinforced aluminum members with heat resistance and wear resistance and a process for manufacturing the cylinder head-integrated cylinder block.
2. Prior Art
In a conventional internal combustion engine, a cylinder head is fastened to a cylinder block through cylinder head bolts and a gasket is provided between the cylinder head and the cylinder block to seal in combustion gas. In this structure, because the cylinder head bolts receive force of expansion caused by combustion, there is a possibility that sealing in of gas cannot be ensured if fastening force of the cylinder head bolts decreases. When rigidity of the cylinder block is not ensured, stress generated in the cylinder block in fastening may cause deformation of liners against which pistons slide. Furthermore, the number of parts is large, which increases the volume of work in assembly.
Because the above problems were caused by separate structures of the cylinder head and the cylinder block in the internal combustion engine, an internal combustion engine having an integral cylinder head-cylinder block structure was proposed in recent years.
There is an integrally-molded engine having an integral cylinder head-cylinder block structure by using cast iron as disclosed in Japanese Utility Model Application Laid-open No. 60-159857, for example. As material for a casting structure, material using casting aluminum which is lightweight and has cooling effect is known in addition to cast iron.
There is one in which cylinder liners in a cylinder block are formed as separate bodies and are coupled to a lower portion of a cylinder head to form an integral structure as disclosed in Japanese Patent Application Laid-open No. 5-26100. The invention of Japanese Patent Application Laid-open No. 5-26100 prevents deformation of the cylinder liners by fitting lower ends of the cylinder liners projecting from the lower end of the cylinder head into a recessed portion of the cylinder block.
Moreover, in the conventional internal combustion engine with the integral structure, dry liners having wear-resistant inner peripheral faces are inserted into cylinder barrels or inner peripheral faces of the cylinder barrels are directly chrome plated.
The casting aluminum has a problem of insufficient strength at a high temperature and it is necessary to increase a thickness of a combustion chamber portion which receives combustion pressure under a high temperature condition in the internal combustion engine using the casting aluminum. However, in a case of making a device of Japanese Utility Model Application Laid-open No. 60-159857 by using the casting aluminum, weight increases because the thickness of an inner wall of the combustion chamber portion is necessary to be increased for insuring strength in the conventional internal combustion engine.
Although the invention of Japanese Patent Application Laid-open No. 5-26100 has a structure for making up the insufficiency of the strength of the liners, the invention does not solve the insufficient strength at the high temperature at its source. Therefore, it is necessary to increase the thickness of the inner wall of the combustion chamber portion to insure the strength, thereby increasing weight.
Furthermore, if the wear-resistant dry liners are inserted through inner peripheral faces of the cylinder-barrels or the inner peripheral faces are directly chrome plated, the number of parts increases, which increases the volume of work in assembly.
SUMMARY OF THE INVENTION
The present invention has been accomplished with the above problems in view, and it is an object of the invention to provide a cylinder head-integrated cylinder block which is easy to assemble, lightweight and has strength at a high temperature without increasing a thickness of the aluminum member even if an integral cylinder head is molded by using an aluminum member and a process for manufacturing the cylinder head-integrated cylinder block.
To achieve the above object, the invention employs the following means.
In other words, a cylinder block of the invention is a cylinder head-integrated cylinder block in which a cylinder head portion having an intake port and an exhaust port and a cylinder block portion whose end face opening is closed by the cylinder head portion are molded integrally by casting.
The cylinder block includes a cylindrical cup-shaped member having a bottom and a surrounding member in which the cup-shaped member is wrapped.
The cup-shaped member forms a head inner wall portion forming a combustion chamber and a liner portion which is adjacent to the head inner wall portion and against which a piston can slides. The cup-shaped member is integrally molded of reinforced aluminum members having heat resistance and wear resistance. The surrounding member is formed of a casting aluminum member and the cup-shaped member is molded in the surrounding member by enveloped casting.
According to the invention, because the head inner wall portion and the liner portion constituting the cup-shaped member are molded integrally of the reinforced aluminum member and the cup-shaped member is molded in the casting aluminum member by enveloped casting, a thickness of an inner wall can be reduced as compared with a case in which the cylinder head and the cylinder block are simply molded integrally by using the casting aluminum material by an aluminum casting method and weight can be reduced.
Because the cylindrical reinforced aluminum member which has the bottom and is the cup-shaped member is molded in the surrounding member by enveloped casting such that the cylinder head and the cylinder block are integrated, a gas seal such as a gasket is unnecessary and the number of parts can be decreased, thereby facilitating assembly.
Here, the reinforced aluminum member constituting the cup-shaped member may have different aluminum characteristics at the head inner wall portion and the liner portion.
For example, the head inner wall portion of the invention is molded of an aluminum forged member with a high-strength aluminum characteristic and the liner portion is molded of an aluminum forged member with a wear-resistant aluminum characteristic. In other words, different parts of the cylinder may have aluminum characteristics with different required performance. If at least the liner portion is made of the aluminum forged member with the wear-resistant aluminum characteristic, it is possible to reduce the thickness to a proper degree, thereby further facilitating weight reduction while providing high strength.
It is possible to provide the different characteristics to the different parts of an integral body, i.e., provide the high-strength aluminum characteristic to the head inner wall portion and the wear-resistant aluminum characteristic to the liner portion by changing a formula of metallic additives added to the aluminum material used for the respective parts. In this case, preparation can be carried out relatively easily by using aluminum powder. Needless to say, if the head inner wall portion and the liner portion are molded with equal formulas of the metallic additives, the characteristics of the reinforced aluminum members of the head inner wall portion and liner portion may be equalized with each other.
Furthermore, according to the invention, a corner portion where a bottom portion and an inner peripheral face portion at a periphery of the bottom portion of the cylindrical shape with the bottom of the head inner wall portion intersecting each other may be formed into an arc shape. With this structure, combustion pressure is received by the arc shape and it is possible to prevent combustion stress from concentrating on a point of the corner portion. Because the corner portion is formed into the arc shape and the integral cylindrical shape having the bottom is formed
Furukubo Tatsumi
Hirooka Akihiko
Imai Yasuo
Jufuku Yasunobu
Ueno Makoto
Kenyon & Kenyon
McMahon Marguerite
Toyota Jidosha & Kabushiki Kaisha
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