Piston ring set
View Patent ↗A piston ring set according to one aspect includes a top ring and an oil ring, and is inserted into a cylinder bore of an internal combustion engine, the top ring has an annular main body portion including an inner peripheral surface, an outer peripheral surface, one side surface and the other side surface substantially perpendicular to the inner peripheral surface, and a first joint end portion and a second joint end portion that face each other to form a joint portion, the oil ring has a pair of rails facing each other, a joint flow area of the top ring is 0.1 mm 2 or less, and the oil ring has an outer peripheral conformability coefficient of 0.3 or more.
1 . A piston ring set comprising a top ring and an oil ring, wherein the piston ring set is inserted into a cylinder bore of an internal combustion engine while attached to a piston,
wherein the top ring comprises an annular main body portion,
wherein the annular main body portion comprises:
an inner peripheral surface;
an outer peripheral surface;
a first side surface and a second side surface substantially perpendicular to the inner peripheral surface; and
a first joint end portion and a second joint end portion that face each other to form a joint portion,
wherein the oil ring comprises a pair of rails facing each other,
wherein a joint flow area of the top ring is 0.1 mm 2 or less,
wherein an outer peripheral conformability coefficient of the oil ring is 0.3 or more,
wherein the main body portion comprises:
a first joint chamfered surface located between the first joint end portion and the outer peripheral surface;
a second joint chamfered surface located between the second joint end portion and the outer peripheral surface, and
an outer peripheral lower surface chamfered surface located between one of the first side surface and the second side surface and the outer peripheral surface, and
wherein, when the top ring and the oil ring are inserted into the cylinder bore while attached to the piston:
a first joint chamfered portion is formed between an inner surface of the cylinder bore and the first joint chamfered surface;
a second joint chamfered portion is formed between the inner surface and the second joint chamfered surface; and
an outer peripheral lower surface chamfered portion is formed between the inner surface and the outer peripheral lower surface chamfered surface;
the joint flow area is expressed as s1×g1×f+C1+C2+2×C3, where a gap between the first joint end portion and the second joint end portion is s1, a gap between an outer surface of the piston and the inner surface of the cylinder bore is g1, a correction coefficient based on an inner diameter of the cylinder bore is f, a size of the first joint chamfered portion is C1, a size of the second joint chamfered portion is C2, and a size of the outer peripheral lower surface chamfered portion is C3; and
the outer peripheral conformability coefficient is expressed as 3/2×Ft×(d1−a1) 2 /(E×h12×a1 3 ), where a tension of the oil ring is Ft, the inner diameter of the cylinder bore is d1, a thickness of each of the pair of rails along a radial direction of the cylinder bore is al, an elastic modulus of a material forming each of the pair of rails is E, and a width of each of the pair of rails along an axial direction of the cylinder bore is h12.
2 . The piston ring set according to claim 1 ,
wherein the outer peripheral conformability coefficient of the oil ring is 0.8 or less.
3 . The piston ring set according to claim 1 ,
wherein a dimension of the outer peripheral lower surface chamfered portion along the radial direction is smaller than a dimension of the outer peripheral lower surface chamfered portion along the axial direction.
4 . The piston ring set according to claim 1 , further comprising a second ring,
wherein the second ring comprises an annular second main body portion comprising a third joint end portion and a fourth joint end portion that face each other to form a second joint portion, and
wherein a ratio of a gap between the third joint end portion and the fourth joint end portion to a gap between the first joint end portion and the second joint end portion is 1.8 or less.
5 . The piston ring set according to claim 1 ,
wherein each outer peripheral surface of the pair of rails has either a tapered face shape or a bullet face shape.
6 . A piston ring set comprising a top ring and an oil ring, wherein the piston ring set is inserted into a cylinder bore of an internal combustion engine while attached to a piston,
wherein the top ring comprises an annular main body portion,
wherein the annular main body portion comprises:
an inner peripheral surface;
an outer peripheral surface;
a first side surface and a second side surface substantially perpendicular to the inner peripheral surface; and
a first joint end portion and a second joint end portion that face each other to form a joint portion,
wherein the oil ring comprises a pair of rails facing each other,
wherein a joint flow area of the top ring is 0.1 mm 2 or less,
wherein an outer peripheral conformability coefficient of the oil ring is 0.3 or more,
wherein the piston ring set further comprises a second ring,
wherein the second ring comprises an annular second main body portion comprising a third joint end portion and a fourth joint end portion that face each other to form a second joint portion, and
wherein a ratio of a gap between the third joint end portion and the fourth joint end portion to a gap between the first joint end portion and the second joint end portion is 1.8 or less.