Cylinder head structure of engine

Abstract

The first flow-restriction vertical bead narrowing the coolant flow is provided to increase the flow speed at this portion. The coolant passage opens at the flow-in area between the exhaust ports. Thereby, the flow speed of the coolant at this area is increased, so the coolant in the coolant passage can be properly sucked due to the Venturi effect. As a result, the cooling function can be improved.

Description

BACKGROUND OF THE INVENTION [0001] The present invention relates to a cylinder head structure of an engine, particularly to a cylinder head of an engine that can improve the engine cooling function. [0002] An engine valve drive mechanism comprising two intake valves and two exhaust valves provided for each cylinder has been recently adopted to improve an intake and exhaust efficiency of the engine. [0003] The engine equipped with such a valve drive mechanism has been also desired to have a higher power as well as compactness of its engine body. Accordingly, some measures against a severe heat load due to the higher power have been required. [0004] In particular, it is important to improve the cooling function around the combustion chamber and the exhaust ports, and therefore some technologies for those have been proposed. [0005] For example, Japanese Patent Laid-Open Publication 2003-314357 discloses a structure that the cross section area of the plug tower portion (the cylindrical ...

AI Technical Summary

Benefits of technology

The present invention provides a cylinder head structure for an engine that improves cooling function of the exhaust-side portion as well as the intake-side portion, by efficiently flowing coolant through the exhaust-side portion and the ignition-plug hole wall. The structure includes a main water jacket and an exhaust-side sub water jacket that are connected to each other, and a coolant passage that is provided between a pair of exhaust ports. The structure also includes vertical bead portions that are formed at the ignition-plug hole wall and the intake-port wall, and a second vertical bead portion that is formed at the intake-port wall. The smallest cross section of the coolant passage in the main water jacket is larger at the exhaust-side than at the intake-side, and the first vertical bead portion is opposed to the exhaust-port wall. The coolant flow speed is increased by the Venturi effect, improving the cooling function at the exhaust-side portion. The structure also promotes the proper suction of coolant and improves the cooling function at the combustion side.

Problems solved by technology

The art disclosed in the above-described publication, however, just attempts to increase the coolant flow speed at the combustion-chamber side entirely in the water jacket, and so would not provide more appropriate cooling function for respective portions.

Further, it is necessary to reduce properly the temperature around the ignition plug, but the art in the publication would not consider the cooling function of the ignition-plug hole wall itself either.

However, any measures for properly cooling the portion are not disclosed in the above-described art.

Images