The cylinder head is mounted on the upper surface of the cylinder block, and seals the cylinder from above to constitute a combustion chamber. It is often in contact with high-temperature and high-pressure gas, and therefore withstands large thermal and mechanical loads. A cooling water jacket is made inside the cylinder head of the water-cooled engine, and the cooling water hole at the lower end surface of the cylinder head is in communication with the cooling water hole of the cylinder block. Circulating water is used to cool high-temperature parts such as the combustion chamber.
Besides,the cylinder head is also equipped with intake and exhaust valve seats and valve duct holes for installing intake and exhaust valves, as well as intake and exhaust channels. The cylinder head of a gasoline engine is processed with a hole for installing a spark plug, and the cylinder head of a diesel engine is processed with a hole for installing an injector. The cylinder head of the overhead camshaft engine is also machined with a camshaft bearing hole for mounting the camshaft.
The cylinder head is generally made of gray cast iron or alloy cast iron. The aluminum alloy has good thermal conductivity and is conducive to improving the compression ratio.
Of course,the cylinder head is a component of the combustion chamber. The shape of the combustion chamber greatly affects the operation of the engine. Due to the different combustion methods of gasoline and diesel engines, the parts of the cylinder head that constitute the combustion chamber are greatly different. The combustion chamber of the gasoline engine is mainly on the cylinder head, while the combustion chamber of the diesel engine is mainly on the recess on the top of the piston.