The cavity in which the piston is placed in the block of an internal combustion engine. Is the piston movement of the track, in which the gas combustion and expansion, through the cylinder wall can also disperse part of the gas to the explosion of waste heat, so that the engine to maintain the normal working temperature. Cylinder types are integral and single - cast. Single - cast type is divided into dry and wet two. Cylinder and cylinder block cast into a whole is called integral cylinder; When the cylinder and cylinder block are cast separately, the single cast cylinder is called the cylinder sleeve. Cylinder liner and cooling water direct contact is called wet cylinder liner; Those not in direct contact with cooling water are called dry cylinder jackets. In order to maintain the tightness of the contact between the cylinder and the piston and reduce the friction loss of the piston in which the movement, the inner wall of the cylinder should have higher processing accuracy and accurate shape