Patent ID: 9303765
Filing Date: 2016-04-05
CPC Classification: F16J

Claim Text:
1. A combined oil control ring comprising: a pair of circular side rails each having a gap; and a spacer expander longitudinally sandwiched by said side rails, and having seating tabs for pushing inner surfaces of said side rails on an inner side, wherein a side rail-pushing surface of each seating tab is provided with one or more grooves extending substantially longitudinally; wherein each of said side rail-pushing surfaces including said one or more grooves being provided with a nitride layer; and wherein the grooves each have a depth d in micrometers that is 1-10 μm, the nitride layer on each of said side rail-pushing surfaces including said one or more grooves each have a surface hardness h as measured by a micro-Vickers hardness test HV0.1 that is 700 or more, the nitride layer on each of said side rail-pushing surfaces including said one or more grooves each have a thickness t in micrometers, and wherein the depth d, surface hardness h and thickness t satisfy the relation according to the following formula: