Abstract
Research and/or Engineering Questions/Objective
Improvement in fuel consumption is one of the important subjects. Friction reduction of automotive parts is an effective means for the improvement in fuel consumption. Therefore, friction reduction of engine bearings was carried out. Engine bearings with solid lubricant overlay show low friction compared with engine bearings without solid lubricant overlay in an engine friction test. Clarification of the friction reduction mechanism of the solid lubricant overlay is necessary for applying the overlay to various engines.
Methodology
Hydrodynamic lubrication analysis and a basic friction test is performed for clarifying the mechanism of friction reduction of the solid lubricant overlay in an engine friction test. The minimum oil film thickness between the crankshaft and the bearing is calculated by using hydrodynamic lubrication analysis. A basic friction test in mixed lubrication condition and fluid lubrication condition is performed for friction property of engine bearings with solid lubricant overlay.
Results
Friction reduction of the solid lubricant overlay in the engine friction test is appeared under both low and high rotational velocity. The minimum oil film thicknesses under both high and low rotational velocity predicted by hydrodynamic lubrication analysis are extremely thin because of the combustion pressure of the neighbour cylinder or the rotational inertia force. The basic friction test shows that coefficient of friction of the solid lubricant overlay shows almost the same value as that of an aluminium alloy bearing in fluid lubrication condition. The solid lubricant overlay shows lower coefficient of friction than that of the aluminium alloy bearing in mixed lubrication condition. Therefore, friction reduction of the solid lubricant overlay in the engine is acquired when the oil film between the shaft and the bearing becomes thin and the lubrication condition becomes mixed lubrication condition.
What does the paper offer that is new in the field including in comparison to other work by the authors?
The paper offers the low frictional effect of solid lubricant overlay and its mechanism of friction reduction of the solid lubricant overlay used in automotive engine.
Conclusion
Friction reduction of the solid lubricant overlay is obtained by the solid lubricant effect of MoS2 in the overlay in the case that contacts between the bearings and crankshaft occur under the thin oil film thickness.
KEYWORDS – friction reduction, engine bearing, solid lubricant overlay