Piston ring assembly for automotive internal combustion engine

A piston ring assembly for an automotive internal combustion engine, comprising:

• a first compression ring disposed in a first groove formed in the outer circumferential surface of the head portion of the piston reciprocating in sliding contact with a cylinder inner surface, said first compression ring being provided with double-stepped mating ends;
• and
• a second compression ring disposed in a second groove formed in said outer circumferential surface at a position spaced apart from said first groove in the direction opposite to the combustion chamber of said engine, said second compression ring being constructed in the form of a double-ring structure which comprises:
• a front ring provided with an inner circumferential chamfered portion, said front ring being adapted to be disposed in sliding contact with said cylinder inner surface;
• and
• a rear ring provided with an outer circumferential chamfered portion adapted to be disposed, under tension, in contact with said inner circumferential chamfered portion of said front ring;
• and
• said double-ring structure being positioned in close contact with the lower and upper surfaces of said second groove, under the influence of the tension of said rear ring. in contact with said inner circumferential chamfered portion of said front ring.