The present invention relates to a cylinder head for an internal combustion engine, and more particularly relates to such a cylinder head for an internal combustion engine, which is particularly improved with regard to the configuration of the coolant passages formed in the body thereof.
The present invention has been described in Japanese Patent Application Serial No. Showa 60-170696 (1985), filed by an applicant the same as the entity assigned or owed duty of assignment of the present patent application; and the present patent application hereby incorporates into itself by reference the text of said Japanese Patent Application and the claim and the drawings thereof; a copy is appended to the present application.
It is per se known in the art for liquid cooled type internal combustion engines to incorporate cylinder heads formed with internal coolant conduits for conducting the flow of coolant near to the parts of said cylinder heads which define the engine combustion chambers, so as to provide cooling for said cylinder heads and said combustion chambers. It is further a known fact in the art that the proper configuration and dimensions of these various coolant conduits is very crucial for determining the characteristics of the internal combustion engine, such as the performance thereof, the mechanical octane value thereof, and the volumetric efficiency obtained therefrom.
In order to improve the mechanical octane value of an internal combustion engine, it is important so to configure the coolant conduits in the cylinder head and the cylinder block thereof as well to cool the combustion chamber wall surface at its portions which present end gas knocking point portions. That is to say, the knocking point of an internal combustion engine is normally not in the central portion of the combustion chambers thereof, but rather is located on the side of the intake ports or on the side of the exhaust ports thereof - in most cases, in fact, on the side of the intake ports, because these tend to have a lower wall temperature than the exhaust ports, as well as experiencing a slow flame propagation speed in their vicinity. Knocking is created by the spontaneous ignition of air-fuel mixture at these regions.
Accordingly, in order to provide a good cooling effect for the above described knocking points so as to enhance the mechanical octane value of the engine, it is desirable that the intake port side region and the exhaust port side region of the cylinder head should be relatively powerfully cooled by the coolant flowing through the coolant flow passages of said cylinder head, and in view of this requirement a cylinder head formed with an improved coolant passage structure, relevant to the present invention, has been described in Japanese Patent Laying Open Publication Serial No. 58-35221 (1983).