PISTON FOR MEDIUM AND HEAVY DUTY SPARK IGNITION LEAN BURN ENGINE

摘要

PURPOSE: A piston for a medium and heavy duty spark ignition lean burn engine is provided to increase a squish area and secure a sufficient flame area by optimizing a shape of a head part of a piston, thereby securing strong turbulence strength and realizing combustion stability. CONSTITUTION: A piston head part(12) has a bowl type indented part(19) to form a part of a combustion chamber. A ring part(20) has a plurality of ring grooves(21) at predetermined intervals in association with an outer peripheral surface of an upper end of a piston. A compression ring or an oil ring is inserted into each ring groove. A skirt part(23) is formed at a lower end of the piston for receiving a side pressure when the piston reciprocates up and down. A side wall of the bowl type indented part includes a first inclined part(14) inclining downward at a predetermined angle with an upper end surface of the piston head part, a vertical part(16) vertical to the upper end surface of the piston head, and a second inclined part(18) inclining downward at a predetermined angle with the vertical part.