Hamatake Toshiro

Studies on the Mixed Lubrication of Piston Rings

A great deal of attention has been focused on decreasing the piston assembly friction in piston engines, since this friction acounts for the majority of total mechanical power loss in these type of engines. The tribology of the sliding surfaces between piston rings and cylinder liner includes extremely complicated phenomena which will become even more severe with an increase in the engine power. In the present study, the theoretical analysis on the mixed lubrication of piston rings is made. The analysis is comprised of Patir and Chengs average flow model and Greenwood and Tripps asperity interaction model, and is developed to consider the shear thinning effect of non-Newtonian fluid, multigrade oil. The friction characteristics of piston rings for both monograde and multigrade oils are investigated and compared with experimental results obtained by the floating liner method, which can measure the instantaneous friction force of a piston assembly under firing conditions.

Lubrication of a Crosshead-Pin Bearing in a Two-Stroke Cycle Engine : Analysis for the Case of an Elliptical Bearing Surface

The crosshead-pin bearing equipped with axial oilgrooves in a two-stroke cycle diesel engine cannot produce such a thick oilfilm as to hold the bearing to be always free from troubles since the bearing is subjected to high load in a single direction besides a low speed. This paper refers to a theoretical analysis on the lubrication of a crosshead-pin bearing with an elliptical bearing and a circular journal. This bearing can remarkably increase the oilfilm thickness and is superior to the conventional bearing in load-carrying capacity and oilfilm exchanging ability as the wedge film action greatly increases due to the presence of two converging-diverging film shapes in load-carrying film.