The piston head need to prevent the high temperature, high pressure gas into the 
crankcase, and prevent oil from entering the combustion chamber; the top of the 
piston absorbed most of the heat also passed to the cylinder through the piston 
head, and then through the cooling medium.
	 The piston head is processed with 
a plurality of grooves which are arranged on the piston ring, and the number of 
the piston rings is determined by the requirements of the seal, which is related 
to the rotation speed of the engine and the cylinder pressure.