Combination of piston rings, and combination structure of piston and piston rings

A combination structure of a piston and piston rings in a spark ignition engine, comprising the piston fitted in a cylinder in the spark ignition engine and a combination of a plurality of piston rings assembled to the piston, the combination of the plurality of piston rings including:

• a first compression ring assembled at a position closest to a combustion chamber, a second compression ring assembled at a position close to the combustion chamber next to the first compression ring, an oil ring assembled at a position farthest from the combustion chamber, and a third compression ring assembled at a position between the second compression ring and the oil ring, wherein an axial width of the first compression ring is h1(1), an axial width of the second compression ring is h1(2), an axial width of the third compression ring is h1(3), and an axial width of the oil ring is h1(4), wherein h1(1)≥h1(2) and h1(1)≥h1(3),
• wherein h1 (TOTAL)=h1(1)+h1(2)+h1(3)+h1 (4), 10 mm≥h1 (TOTAL)≥3.1 mm,
• the piston has an outer peripheral surface that is formed with a first ring groove in which the first compression ring is fitted, a second ring groove in which the second compression ring is fitted, a third ring groove in which the third compression ring is fitted, and an oil ring groove in which the oil ring is fitted,
• wherein a length from an end face of the first ring groove on a combustion chamber side to an end face of the oil ring groove on a crank chamber side in an axial direction of the piston is Lp, wherein Lp≥5.1 mm,
• wherein a length, in the axial direction of the piston, of a second land portion that is a region defined between the first ring groove and the second ring groove in the outer peripheral surface of the piston is Lp2, and a length, in the axial direction of the piston, of a fourth land portion that is a region defined between the third ring groove and the oil ring groove is Lp4, wherein Lp2>Lp4, and
• wherein 1.8 mm≥h1(1), 1.2 mm≥h1(2), and 1.0 mm≥h1(3).

A combination structure of a piston and piston rings in a spark ignition engine, comprising the piston fitted in a cylinder in the spark ignition engine and a combination of a plurality of piston rings assembled to the piston, the combination of the plurality of piston rings including:

• a first compression ring assembled at a position closest to a combustion chamber, a second compression ring assembled at a position close to the combustion chamber next to the first compression ring, an oil ring assembled at a position farthest from the combustion chamber, and a third compression ring assembled at a position between the second compression ring and the oil ring, wherein an axial width of the first compression ring is h1(1), an axial width of the second compression ring is h1(2), an axial width of the third compression ring is h1(3), and an axial width of the oil ring is h1(4), wherein h1(1)≥h1(2) and h1(1)≥h1(3),
• wherein h1 (TOTAL)=h1(1)+h1(2)+h1(3)+h1(4), 10 mm≥h1 (TOTAL)≥3.1 mm,
• the piston has an outer peripheral surface that is formed with a first ring groove in which the first compression ring is fitted, a second ring groove in which the second compression ring is fitted, a third ring groove in which the third compression ring is fitted, and an oil ring groove in which the oil ring is fitted,
• wherein a length from an end face of the first ring groove on a combustion chamber side to an end face of the oil ring groove on a crank chamber side in an axial direction of the piston is Lp, wherein Lp≥5.1 mm,
• wherein a length, in the axial direction of the piston, of a second land portion that is a region defined between the first ring groove and the second ring groove in the outer peripheral surface of the piston is Lp2, and a length, in the axial direction of the piston, of a fourth land portion that is a region defined between the third ring groove and the oil ring groove is Lp4, wherein Lp2>Lp4, and
• wherein a volume of a fourth space that is a space surrounded by the piston, the cylinder, the third compression ring, and the oil ring is V4, a diameter of a cylinder bore of the spark ignition engine is d1 and Vp=(d1/2)2×π×Lp, wherein V4/Vp≥0.00027.