Study on Mechanism of Lubricating Oil Consumption Caused by Cylinder Bore Deformation

Abstract

It is a well-known fact that cylinder bore deformations in engine operation involves a number of problems in terms of lubrication, and the deterioration of piston ring conformability to the bore, in particular, increases the lubricating oil consumption (LOC). It is also verified through the cylinder bore deformation measurements carried out by the research laboratory that bore deformations occur in engine operation which can not be ignored. Although some studies on the mechanism and the reduction of such deformations have been conducted, only few analyses have been conducted on the mechanism of the increase in LOC, whereas it is vital to clarify the mechanism under the current situation where the reduction of LOC is urged in terms of purification of exhaust emissions also. This study has been conducted for the clarification of the mechanism of LOC increased by cylinder bore deformation, with emphasis of analysis placed mainly on the following two points: (1) the development of a theoretical calculation method for the behavior of the oil film between a piston ring and the cylinder bore taking into account of the deformed bore profile and the ring elastic deformation, based on the piston ring dynamic lubrication theory developed by Furuhama, analysismore » of the relationship between the oil film behavior and lubricating oil flow-out rate against the deformed bore profile; (2) measurements of LOC and ring conformability to the bore deformation, using cylinder liners having various types of bore profiles and rings with local clearances on their sliding surfaces. Based on the analyses stated above, qualitatively and quantitatively evaluations of the LOC attributable to the bore deformations have been conducted. The details of the mechanism of LOC determined by the above is reported.« less