working principle:
(1) The cylinder head is subjected to high temperature and high pressure gas, and bears a large bolt pre-tightening force, resulting in high mechanical stress.
(2) The structure of the cylinder head is complex, and the temperature field is severely uneven, resulting in large thermal stress. In severe cases, it will cause cracks and overall deformation of the cylinder head.
Therefore, the design requirements for the cylinder head are
(1) It has sufficient rigidity and strength, small working deformation, and guarantees sealing.
(2) Reasonably arrange the combustion chamber, valve and air passage to ensure the working performance of the engine.
(3) Good manufacturability, and the temperature field is as uniform as possible to reduce thermal stress and avoid thermal cracking.
structure
The cylinder head is a box-shaped part with a complicated structure. There are inlet and exhaust valve seat holes, valve guide holes, spark plug mounting holes or fuel injector mounting holes processed on it. In the cylinder head, there are also cast water jackets, intake and exhaust ducts, and combustion chambers or parts of combustion chambers. If the camshaft is installed on the cylinder head, the cylinder head is also machined with a cam bearing hole or a cam bearing seat and its lubricating oil passage.
Cylinder heads of water-cooled engines have three structural forms: integral type, block type and single-piece type. In a multi-cylinder engine, if all the cylinders share one cylinder head, the cylinder head is called an integral cylinder head; if every two cylinders has one head or three cylinders and one head, the cylinder head is a block cylinder head; One cylinder head is a single-piece cylinder head. Air-cooled engines are all single-piece cylinder heads.
