Fluid Film Lubrication in Automobile Valve Trains

Abstract

It is nearly twenty years since the so-called energy crisis of the 1970s. This stimulated an increased awareness of the scarcity of natural resources and the necessity for their efficient and effective use. During the intervening period there has also been a mounting pressure from the ‘green’ lobby to recognize the fragility of the environment. The automobile is a significant factor world-wide with regard to both these aspects because of fuel consumption and exhaust considerations. These developments have led to intensive studies of the lubricated machine elements which are vital to the functioning of the internal combustion engine—the piston assembly, the bearings and the valve train. This paper will focus upon the valve train and in particular the fluid film lubrication of its most significant part, the cam and follower. The important role of lubricant additives, the formation of reaction films, boundary lubrication, contaminants and wear and failure mechanisms will not be addressed. In part the paper will review the background to the current position and understanding. However, attention will also be paid to a new study of a modern automobile engine valve train—that in the Ford Zeta engine. The research work described has revealed novel tribological understanding which will aid the design of future valve trains through technology transfer.