Three-part oil scraper ring

A three-part oil scraper ring, comprising an upper scraper ring, a lower scraper ring, wherein the scraper rings are held at a distance by an expander spring, which is configured as an MF spring, and pressed radially outwards, wherein the upper scraper ring comprises a ring body having

• an upper flank,
• a lower flank,
• a ring inner surface and
• a ring outer surface which has a ring outer contour in cross-section in axial direction (A),
• wherein the ring body has a height H which, when viewed in axial direction (A), corresponds to the greatest distance of the upper flank from the lower flank, wherein the ring outer contour forms a running surface which has a radius of curvature R which is smaller than the height H of the upper scraper ring by a factor between 1.5 to 6,
• wherein the upper scraper ring has a curvature (R) at the pivot point which goes over continuously and smoothly into the lower flank and forms a tangent to the radius of curvature (R), wherein the curvature extends over more than 90° so that the pivot point of the ring outer contour of the running surface is formed by the curvature (R) with the result that the pivot point is located at the distance (R) above the lower flank, the curvature (R) then goes over directly continuously and smoothly into a straight section which in turn goes over into an upper radius of curvature (Ro) which is tangential both to the tangential section and also to the line of intersection of the upper flank, wherein the radius (Ro) is smaller than the radius (R), wherein in the cross-section of the upper scraper ring, the mid points of the radii of curvature R and Ro lie on a straight line (G) which lies parallel to an axial direction (A) of the upper scraper ring and wherein the lower scraper ring is symmetrically spherical in the region of the pivot point, the pivot point is located from the lower flank at an axial height between 47 and 54% or between 55 and 75% of the height H of the lower scraper ring and the radius R lies between 0.05 and 0.15 mm.