Introduction of Cylinder Head
The cylinder head is also equipped with intake and exhaust valve seat, valve guide hole, for the installation of intake and exhaust valves, and intake and exhaust channels, etc.. The cylinder head of the gasoline engine has a hole for the installation of spark plugs, and the cylinder head of the diesel engine has a hole for the installation of fuel injectors. The cylinder head of the overhead camshaft engine also has a camshaft bearing hole to install the camshaft.
Cylinder head is generally made of gray cast iron or alloy cast iron, aluminum alloy has good thermal conductivity, which helps to improve the compression ratio.
Cylinder head is a component of the combustion chamber, the shape of the combustion chamber on the engine’s work, due to the gasoline engine and diesel engine combustion mode is different, the cylinder head composition of the combustion chamber part of the big difference. Gasoline engine’s combustion chamber is mainly in the cylinder head, and diesel engine’s combustion chamber is mainly in the piston top pit.
Measures for Cylinder Head Cracks
1、The cylinder head bolts should be tightened evenly and the oil supply time should be adjusted correctly.
2、The water tank should be filled with soft water, and change water as little as possible.
3, the engine should avoid long-term work under overload.
4, the engine is working and the water tank occasionally lack of water, shall not immediately shut down, but should be low speed running slowly add water. Do not add cold water after the engine is hot, after parking should wait for the water temperature to 40 ℃ or less before releasing water. Winter season start can not immediately add boiling water, but should first heat water and add boiling water.
5, assembly should check whether the cooling water hole is smooth. Regularly clean the cooling system with alkaline solution and remove the scale and oil in time.
Cylinder Head Creep
Cylinder head for 4tne94 in the work of low circumference thermal fatigue damage, high circumference thermal fatigue damage and creep damage, its life and reliability is an important indicator of the engine. In the engine start-stop process (start cycle), the cylinder head is sharply heated and cooled, resulting in a large cycle of thermal stress, by low circumference thermal fatigue damage. In the engine after the start of each work cycle (suction – compression – work – exhaust cycle process), the cylinder head occurs in a smaller temperature change, suffer high circumferential thermal fatigue damage. The local material of the cylinder head works for a long time in an environment higher than the creep temperature and suffers from creep damage.
1) from the theoretical analysis of the cylinder head low circumference thermal fatigue damage, high circumference thermal fatigue damage and creep damage, causing cylinder head failure is mainly low circumference thermal fatigue damage, the number of starts is its main life index.
2) creep on the cylinder head of the direct damage is small, but can affect the average stress of low circumference thermal fatigue, so yanmar 3 cylinder diesel engine rebuild kit the engine creep – low circumference thermal fatigue can be equivalent to constant strain amplitude, a certain average stress thermal – mechanical fatigue, with thermal mechanical fatigue test instead of creep – thermal fatigue test can greatly reduce the test time.
Processes of Cylinder Head
Engine head is one of the most critical parts of the engine, its high precision requirements, complex machining process, the quality of processing directly affects the overall performance and quality of the engine, therefore, the engine head processing is particularly important, the key parts of the valve seat ring and the processing of the duct hole is the most important.
Engine intake and exhaust valve seat ring is an important part of the control of gas inhalation and exhaust gas discharge, its work process will be at high temperatures under the impact of airflow erosion and valve friction, working conditions are very harsh: normal operation, valve seat ring long-term in (600 ~ 800) ℃ high temperature, high-temperature gas corrosion and parts deformation and other factors will cause the valve guide and seat taper breakage intensified, resulting in valve seal is not tight, so the valve is not tight. So that the valve seal is not tight, a lot of energy with the discharge of high-temperature gas and wasted, thus greatly reducing the engine power. Therefore, the valve seat ring and conduit hole should have good high temperature wear resistance, corrosion resistance, heat transfer and high temperature strength, high temperature creep resistance, and with the cylinder head to match the coefficient of thermal expansion. At the same time, the engine work if the valve center and valve seat ring center deviation is too large, in the engine power down, fuel consumption increases at the same time, will also accelerate the valve and duct hole wear. Therefore, the valve seat ring and the processing accuracy of the duct hole, especially the valve seat ring working cone on the duct hole runout provides a strict tolerance limit.
Engine head valve seat ring and the general requirements of the processing accuracy of the conduit hole: gasoline engine coaxiality tolerance requirements for (0.015 ~ 0.025) mm; and diesel engines are only (0.01 ~ 0.015) mm, cone runout for (0.03 ~ 0.05) mm, hole accuracy level requirements are generally H7 level.