PISTON DEVICE FOR INTERNAL COMBUSTION ENGINE

摘要

A gas sealing function and an oil controlling function are provided in a TOP ring, and this enables this single TOP ring to achieve an oil consumption amount and blowby amount in the same level as those obtained by a three-ring set. The TOP ring has a piston body in the outer periphery of which a ring groove is formed leaving a top land section and has a squared C-shaped piston ring formed by connecting an upper leg section and a lower leg section by a base section and installed at the top land section. The width in the axial direction from the boundary between the base section of the piston ring and the upper leg section to the lower surface of the lower leg section is set larger than the width in the axial direction from the upper surface of the top land section of the piston body to the lower surface of the ring groove in which the lower side leg section is installed, or alternatively, a groove is provided on the thrust side of the top land section of the piston body, or still alternatively, a V-shaped annular groove is provided in a second land section of the piston body. The piston ring may be formed to have contact surfaces at the upper periphery with a BF shape and at the lower periphery with a straight or tapered shape.