Abstract: A ring groove for a two-piece oil ring of a piston is provided that has ring body equipped with a coil expander, wherein the ring body has an upper outer surface and a lower outer surface, both orthogonal to the axial direction of the piston. The ring groove also has an upper inner surface and a lower inner surface, both orthogonal to the axial direction of the piston; a radially inward-most, bottom surface connecting the upper and lower inner surfaces; and oil drain holes, each having an opening thereof located on the bottom surface. The ring groove has an axial width slightly greater than the width of the two-piece oil ring.

Abstract: A ring groove for a two-piece oil ring of a piston is provided that has ring body equipped with a coil expander, wherein the ring body has an upper outer surface and a lower outer surface, both orthogonal to the axial direction of the piston. The ring groove also has an upper inner surface and a lower inner surface, both orthogonal to the axial direction of the piston; a radially inward-most, bottom surface connecting the upper and lower inner surfaces; and oil drain holes, each having an opening thereof located on the bottom surface. The ring groove has an axial width slightly greater than the width of the two-piece oil ring.

Abstract: According to an embodiment of the present invention, a ring groove 11 for a two-piece oil ring 10, of a piston 20, is provided that has a ring body 5 equipped with a coil expander 6, where the ring body 5 has an upper outer surface and a lower outer surface, both orthogonal to the axial direction of the piston 20. The ring groove 11 has an upper inner surface 13 and a lower inner surface 14, both orthogonal to the axial direction of the piston 20; a radially inward-most, bottom surface 12 connecting the upper and lower inner surfaces 13, 14; and oil drain holes 18 each having an opening 19 thereof located on the bottom surface 12. The ring groove 11 has an axial width slightly greater than the width of the two-piece oil ring 10.