Characteristics of Piston Ring Friction (Influences of Lubricating Oil Properties)

In reciprocating internal combustion engines, one of the most important issues is to clarify the complicated frictional characteristics between the piston ring and the cylinder liner because of the demand for reduced frictional loss, as well as a solution of problems such as scuffing and wear, that has accompanied the recent progress in engine performance. In the present study, the floating liner method, in which the cylinder liner was supported by means of hydrostatic bearings, was developed to measure accurately the frictional force of the piston assembly as a function of the crank angle in an operating diesel engine. The influences of engine operation conditions (engine speed, cylinder wall temperature, and gas pressure in the cylinder), lubricating oil viscosity, polymer-containing multigrade oils, and a friction modifier on the frictional characteristics were evaluated on the basis of the experimental results obtained using this equipment.