Piston ring

Abstract

To provide a piston ring for an internal combustion engine, particularly a second compression ring, which has excellent wear resistance and can achieve both lower fuel consumption and efficient combustion. The above-described problem is solved by a piston ring () for an internal combustion engine formed so as to have a tapered shape by a peripheral surface () that gradually projects outward from a top to a bottom, and a radial cross-sectional shape of a Napier ring. The peripheral surface () is constituted by an outer edge end portion () that has a non-tapered shape and comes into sliding contact, as a peripheral sliding surface, with a mating material, an outer peripheral tapered part () formed at a predetermined taper angle (α) above the outer edge end portion (), a curved surface part () having a diameter that gradually decreases inward from the outer edge end portion () to a lower end in an axial direction, and a lower end portion () forming a section of the curved surface part (). A distance (d) between a position (A) of the outer edge end portion () and a position (C) of the lower end portion () in a ring axial direction is within a range of 0.001 mm to 0.05 mm, and a contact width (d) of the outer edge end portion () in the ring axial direction is within a range of 0.01 mm to 0.3 mm.