Oil ring

It is a main object of the present invention to provide an oil ring which is capable of reducing sliding friction even in a high speed revolution region of a piston, and capable of reducing the consumption of oil. To achieve the object, the present invention provides an oil ring which is formed into cross-section substantially of an I-shape that two rails are connected at a columnar portion thereof, wherein a sliding projection formed in each of the two rails comprises an outer side surface of sliding projection which forms an outer portion of the sliding projection, a inner side surface of sliding projection which forms an inner portion of the sliding projection, and a sliding surface which slides on a cylinder inner wall and forms a tip end of the sliding projection; wherein a taper angle of the outer side surface of sliding projection is in a range of 10° to 60°; and wherein the outer edge portion, where the outer side surface of sliding projection and the sliding surface are joined to each other, is formed into the curved surface, and the sliding surface has the curved surface sliding portion which is joined to the outer side surface of sliding projection and formed into a gently curved surface.