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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.

Recent diesel engines require higher performance and longer life. Due to high cylinder pressure, the operating load and temperature of piston pin bushings has become severe. Therefore, high load capacity and wear and corrosion resistance are required for piston pin bushings. To improve the corrosion resistance of copper bushing material, we studied the effects of adding elements to copper alloy. We found that the addition of nickel to copper reduces the sulfide corrosion of copper alloys. In addition, we were able to conclude that copper-nickel alloys can be produced by conventional sintering methods. We also attempted to improve wear resistance by adding hard particles into the copper matrix. The primary goal of the study was to determine the effects of hard particles on wear resistance and the machining process. We found that when a sort of hard particles are added to the copper matrix, the wear resistance improves, but the new matrix is more difficult to machine.

High tin and aluminum alloy bearings can seize easily when used with nodular cast iron shafts. The authors have investigated the process of seizure between such nodular cast iron shafts and high tin and aluminum alloy bearings, and found that the seizures are normally caused by a combination of burrs around the graphite at the surface of the nodular cast iron shafts and abrasive aluminum debris adhering to the shaft. In an attempt to remove the burrs and abrasive aluminum debris, the authors dispersed hard particles in the alloy bearings. The new alloy used has a chemical composition of Al Si 3, Sn 10 and Pb 1.5 and, as a result bearings formed from it do not require a lead-based overlay. This arrangement provides much higher seizure resistance than overlayed copper and lead alloy bearings when used with nodular cast iron shafts. The bearings made with this alloy can be used in all engines with nodular cast iron shafts without any problems whatsoever.