エンジン油中でのSUJ2と銅合金の摩擦におけるトライボフィルム生成に及ぼす銅合金組成の影響

抄録

In recent years, the viscosity of engine oils gets lower and cylinder pressure gets higher to improve thermal efficiency of internal combustion engines. Therefore, engine bearings are increasingly used in the boundary lubrication region with the decrease in oil film thickness, and it is necessary to improve seizure resistance and fatigue resistance. On the other hand, MoDTC and ZnDTP are widely used in engine oils to reduce friction and prevent seizure in the boundary lubrication region. It is well known that their effects are different depending on conditions such as sliding materials. However, there are few studies on copper alloys used in engine bearings. So, it is required to understand the effects of copper alloys on friction in engine oils. In this study, effect of chemical composition in copper alloy on tribofilm formation are investigated by using a ball-on-disk type sliding tester in lubricating oils with ZnDTP and MoDTC. As a result, solid solution strengthening components of copper such as Sn, Ni affected tribofilm formation and running-in. In particular, Ni is highly reactive and promoted tribofilm formation. In addition, Bi contained copper alloy can obtain low friction after running-in due to the oriented MoS₂on the top surface.