Abstract: An oil scraper piston ring includes an inner circumferential surface; an outer circumferential surface adapted to contact and slide along an inner wall of an engine cylinder; a radial wall thickness defined by a radial distance between the inner and outer circumferential surfaces; and a plurality of circumferentially distributed recesses each extending radially from the inner circumferential surface toward the outer circumferential surface to reduce the radial wall thickness. Each recess has a first recess region open at the inner circumferential surface and extending radially toward the outer circumferential surface and a second recess region merging into the first recess region. The two recess regions have different shapes, and the area of the second recess region is larger than the area of the first recess region.

Abstract: An oil scraper piston ring includes an inner circumferential surface; an outer circumferential surface adapted to contact and slide along an inner wall of an engine cylinder; a radial wall thickness defined by a radial distance between the inner and outer circumferential surfaces; and a plurality of circumferentially distributed recesses each extending radially from the inner circumferential surface toward the outer circumferential surface to reduce the radial wall thickness. Each recess has a first recess region open at the inner circumferential surface and extending radially toward the outer circumferential surface and a second recess region merging into the first recess region. The two recess regions have different shapes, and the area of the second recess region is larger than the area of the first recess region.

Abstract: A single-piece oil scraper piston ring includes a ring axis and first, second and third axially mutually spaced runner webs having a respective first, second and third runner face adapted to slidingly engage an engine cylinder wall during operation. The first and third runner webs flank the second runner web. A first connecting web couples the first runner web to the second runner web and a second connecting web couples the third runner web to the second runner web. First and second throughgoing oil outflow holes are provided in the first and second connecting webs, respectively. The piston ring further includes a first groove having a first side wall forming part of the first runner web and a second side wall; and a second groove axially spaced from the first groove and having a first side wall and a second side wall which forms part of the third runner web. First and second hose springs are received in the first and second grooves, respectively.