Engine cylinder head. The modern design of the car engi […]
Engine cylinder head. The modern design of the car engine cylinder head is made of aluminum alloy. The cylinder head is both a complex and important casting part, and the combustion chamber, the engine's intake pipe and exhaust pipe are installed in the cylinder head. The working characteristic of the cover in the engine is that it works at a high temperature, and it can withstand a large thermal shock and cause stress concentration, so aluminum alloy has become a popular product. The advantages of using aluminum alloy to make cylinder heads are light weight. Another outstanding advantage is the excellent thermal conductivity. For the engines of cars and light vehicles, the use of aluminum alloy cylinder heads can make the engine thermal efficiency better and avoid overheating of the components in the combustion chamber in the cylinder head.
There are three types of engine cylinder heads, mainly:
1. The function of the cylinder head is to seal the cylinder, form a combustion space with the piston, and bear the role of high temperature and high pressure gas. The cylinder head bears the mechanical load caused by the gas force and tightening of the cylinder bolts, and at the same time, it is exposed to high thermal loads due to contact with high-temperature gas. In order to ensure a good seal of the cylinder, the cylinder head can neither be damaged nor deformed. For this reason, the cylinder head should have sufficient strength and rigidity;
2. Cylinder head materials: Cylinder heads are generally cast from high-quality gray cast iron or alloy cast iron, and gasoline engines used in cars mostly use aluminum alloy cylinder heads. Aluminum alloy has good thermal conductivity, which is conducive to improving the compression ratio of the engine. Secondly, it has excellent casting performance and is suitable for casting parts with complicated structure. But we must pay attention to the cooling of the aluminum alloy cylinder head, and control the temperature of the bottom plane below 300 ℃. Otherwise, overheating of the bottom plane will cause plastic deformation and warpage;
3. Cylinder head 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 (gasoline engine) or fuel injector mounting holes. A water jacket, intake and exhaust passages and a part of the combustion chamber or combustion chamber are also cast in the cylinder head. If the camshaft is installed on the cylinder head, the cam head is also machined with a cam bearing hole or cam bearing seat and its lubricating oil passage;
4. The cylinder head of water-cooled engine has three structural forms: integral type, block type and single type. In a multi-cylinder engine, if all cylinders share a cylinder head, the cylinder head is called an integral cylinder head; if there is a head for every two cylinders or a head for three cylinders, the cylinder head is a block type cylinder head; One cylinder head is a single cylinder head. Air-cooled engines are all single cylinder heads.