Characteristics of Piston Ring Friction. Influences of Piston Ring Specifications.

In internal combustion engines, one of the most important issues is to clarify the friction characteristics between the piston ring and the cylinder liner because of the demand for improved fuel economy through the reduction of friction loss. In the present study, the floating liner method is used to measure the piston assembly friction force in a diesel engine. The piston assembly friction demonstrates that fluid film lubrication is dominant at midstroke, but a friction peak due to boundary lubrication is observed at dead center. A decrease in either the number or the width of piston rings is effective in reducing total friction loss, but this increases the maximum friction peak at the beginning of the power stroke. However, the friction peak can be reduced by using a ceramic-coated piston ring. The influence of the compression ring tension on friction loss is dependent on the oil ring tension.