The production processing of the top of the piston head understand the ring groove for installing the piston ring. The number of piston rings depends on the requirements of the tightness. The low-pressure casting processing factory is related to the speed ratio of the engine the working pressure of the cylinder. The number of rings of high-speed engine is less than that of low-speed engine, that of gasoline engine is less than that of diesel engine. Generally, two gas rings one oil ring are used for gasoline engine; three gas rings one oil ring are used for diesel engine; three to four gas rings are used for low-speed diesel engine. In order to reduce the friction damage, it is necessary to reduce the height width ratio of a part of the ring as much as possible, strive to reduce the number of rings under the standard of ensuring the tightness.
All the parts below the piston ring groove are called piston skirt. Its function is to correctly guide the piston to move repeatedly in the cylinder bear the pressure. When the engine is working, because of the effect of the air pressure of the main cylinder, the piston will be bent deformed. When the piston is hot, because there are many metal materials at the piston pin, its surging volume exceeds that of other parts. In addition to the production manufacturing of low-pressure casting parts, the piston will also cause extrusion deformation under the effect of pressure. The comprehensive result of the deformation causes the cross section of the piston journal to become an ellipse of the short shaft in the direction of the piston pin. In addition, because the temperature quality of the piston along the centerline are even, the thermal deformation of each cross section is small.