Abstract
Al-Sn-Si alloy bearings, widely used as main bearing and con-rod bearing in gasoline and compact diesel engines for passenger car, have such better characteristics as possibility with no overlay due to its conformability of tin, excellent corrosion resistance, reasonable prices and lower contents of lead as one of the hazardous substances for the environment, than conventional copper lead alloy bearings with lead based alloy overlay. Engine bearings have to exhibit excellent performance of anti-seizure and anti-wear property under further severe condition of higher specific load onto bearings and of thinner oil film formation between bearing and crankshaft in operation caused by satisfying such recent engine requirements as lower fuel consumption and clean exhaust gas for global environment. Especially, recent issue makes clear that wear of the bearing alloy may extraordinarily increase in an engine operated under frequent start-stop condition, adopted from the viewpoint of global environment, that causes insufficient oil film formation. Based upon these backgrounds, a new lead-free Al-Sn-Si alloy bearing was developed, which had superior both anti-wear and anti-seizure property to conventional Al-Sn-Si alloy bearing. The bearing performances were achieved by increasing amount of Si dispersed in the form of hard particles in the alloy, focused on characteristic of Si, less adhesion to steel, which gives good anti-seizure property. A newly developed Al-Sn-Si alloy bearing was verified to have the excellent performances through evaluation of rig tests and bench test in actual engine compared with conventional.
Keywords: Engine bearing, Aluminum alloy, Lead-free, Silicon particle, Wear