Patent ID: 7854191

Claim:
A three-piece oil ring comprising: a spacer expander, a first side rail disposed at one axial end of the spacer expander, and a second side rail disposed at another axial end of the spacer expander, the spacer expander including an annular body having a radially inner end portion provided with seating tabs protruding in an axial direction of the annular body from one axial end face of the annular body and from another axial end face of the annular body and having radially outer surfaces inclined with respect to an axis of the annular body for urging inner peripheral surfaces of the first side rail and the second side rail, respectively, the annular body having a radially outer end portion provided with side rail support portions projecting in the axial direction from the one axial end face of the annular body and from the another axial end face of the annular body for supporting axial end faces of the first side rail and the second side rail, respectively, wherein the inclined radially outer surface of each seating tab and the axis of the annular body define a seating tab angle ranging from 10 to 20 degrees, and a ratio of 2X/Y is in a range of from 0.04 to 0.15 where 2X is a total projecting length of the side rail support portions in the axial direction, and Y is a distance between distal end faces of the seating tabs in the axial direction.