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The recent demands for higher performance and lower fuel consumption of automotive engines require the bearings to operate under severe conditions. One of the problems with conventional aluminum alloy bearings used under these conditions is the low wear resistance. A new aluminum alloy bearing that allows a higher wear resistance is developed by controlling Si particle size and lining hardness. The mechanism to upgrade the wear resistance are the concentration of enlarged Si particles on the sliding surface and to prevent falling off Si that are held by sufficient lining hardness. Wear resistance of this bearing is 4-5 times better compared with the conventional bearings and seizure resistance is two times better than the conventional bearings.

In a common rail type fuel injection system installed in recent diesel engines, a supply pump is needed to accumulate high pressure fuel. In this supply pump, a bushing is used for the outer cam system. The bushing is lubricated by diesel fuel with relatively low viscosity and unit load of the bushing is higher. Therefore, lubricating film thickness of the bushing is extremely thin. In order to ensure the bushing function under such severe sliding conditions, the bushing is required higher seizure resistance and higher fatigue resistance. Conventionally, lead bronze alloys are applied for the bushing material. We developed a new high performance copper alloy material without lead, which is one of substances of environmental concern. The newly developed bushing contains bismuth instead of lead for tribological component.

Two types of new conceptual lead free overlays are developed for automotive internal combustion(IC) engine bearings. The overlays are consisted of molybdenum disulfide(MoS2) and polyamideimide(PAI) resin for binding. One of the overlays is suitable for diesel engines with higher unit load and the other overlay is suitable for gasoline engines with higher sliding velocity. Both overlays indicate good corrosion resistance and wear resistance comparing with conventional lead base overlay. Moreover, higher fatigue resistance is obtained in combination with high performance lead free bearing alloy. These new bearings have the potential to become alternative materials to conventional copper lead bearings with lead base overlay.