The structure and function of the cylinder head

1. Working conditions and requirements for cylinder head

The cylinder head is subjected to mechanical loads caused by gas forces and tightening of cylinder head bolts, as well as high thermal loads due to contact with high-temperature gas. To ensure the sealing ability of the cylinder, the cylinder head must not be damaged or deformed. The cylinder head should have sufficient strength and stiffness for this purpose. In order to make the temperature distribution of the cylinder head as uniform as possible and to avoid thermal cracks between the intake and exhaust valve seats, cylinder head should have a good cooling capacity. 

2. Cylinder head material

Cylinder heads are generally made of high-quality gray cast iron or alloy cast iron, and gasoline cars often use aluminum alloy cylinder heads. 

3. Cylinder head construction

The cylinder head is a complex box shaped component, and it often cosists of intake and exhaust valve seat holes, valve guide holes, spark plug installation holes (for gasoline engines) or injector installation holes (for diesel engines). It also has a water jacket, intake and exhaust duct, and a combustion chamber or part of the combustion chamber cast inside the cylinder head. If the camshaft is installed on the cylinder head, there are also cam bearing holes or cam bearing seats and their lubricating oil channels machined on the cylinder head. 

The cylinder head of a water-cooled engine has three structural forms: integral, segmented, and individual. In a multi cylinder engine, if all cylinders share one cylinder head, the cylinder head is called an integral cylinder head; If there is one cover for every two cylinders or one cover for every three cylinders, the cylinder head is a segmented cylinder head; If there is one head per cylinder, it is a single cylinder head. Air cooled engines are all single cylinder heads.