Patent ID: 7493882

Claim:
A combination of a cylinder liner used for an internal-combustion engine and a piston ring which slides on an inner circumference surface of the cylinder liner at the pressure of 0.03 to 0.2 MPa, wherein the composition of the cylinder liner comprises, (Composition A) silicon: 23.0 to 23.0% by weight, magnesium: 0.80 to 2.0% by weight, copper: 3.0 to 4.5% by weight, iron: 0.25% by weight or less, nickel: 0.01% by weight or less, and the rest: unavoidable impurities and aluminum, or (Composition B) silicon: 23.0 to 28.0% by weight, magnesium: 0.80 to 2.0% by weight, copper: 3.0 to 4,5% by weight, iron: 1.0 to 1.4% by weight, nickel: 1.0 to 5.0% by weight, and the rest: any of avoidable impurities and aluminum; wherein surface roughness profile of the inner circumference surface of the cylinder liner has, a ten-point average roughness Rz=0.5 to 1.0 μm according to JIS B 0601 (1994), a core roughness depth Rk=0.2 to 0.4 μm according to DIN4776 standards, a reduced peak height Rpk=0.05 to 0.1 μm according to DIN 4776, a reduced valley depth Rvk=0.08 to 0.2 according to DIN 4776; meanwhile, wherein the composition of the piston ring comprises carbon: 0.6 to 0.7% by weight, chrome: 13 to 14% by weight, molybdenum: 0.2 to 0.4% by weight, silicon: 0.25 to 0.50% by weight, manganese: 0.2 to 0.5% by weight, and the rest: unavoidable impurities and iron; and the composition includes carbides with a diameter of 5.0 μm or less at the area rate of 4 to 10%, and the surface roughness profile of an outer circumference sliding surface of the piston ring has a ten-point average roughness Rz=0.8 μm or less according to JIS B 0601 (1994), and a reduced peak height Rpk=0.15 μm or less according to DIN 4776.