Patent ID: 7396018

Claim:
A combination oil wiping ring and piston for an internal combustion engine, comprising: a piston having a piston crown, a ring groove and cylinder wall; a lamella consisting of strip steel, provided with parallel walls, and having a working surface with a vertex line that extends over a circumference of the lamella; and a spreading spring disposed in the ring groove and having one spring groove wall facing away from a piston crown side and one spring groove wall facing a piston crown side, said spring pressing the lamella radially against the cylinder wall, wherein at least one of the spring groove walls runs at a slant radially outward up to an end of the spreading spring facing the cylinder wall, at an angle relative to a piston axis, wherein the working surface of the lamella is configured so that it corresponds to an almost worn end contour in a run-in engine state, wherein when the oil ring is assembled in the piston, the vertex line of the working surface is disposed towards the ring groove wall that faces away from the piston crown side; and wherein the working surface of the lamella, in cross-section, (a) follows an asymmetrical shape of a polynomial of the second order in a first segment (I), with h(x)=ax+bx 2 , wherein x=working surface coordinates in the Cartesian coordinate system in mm, and a, b are coefficients, with a being defined by the ratio of axial wall play of the lamellae relative to a width of the lamellae; b being defined as an amount of the working surface curvature; (b) has a supporting vertex (II) h(x=0) configured as an edge, and (c) in a third segment (III) follows the asymmetrical shape of the function h(x)=cx 2 , with c as a multiple of b.