A transient elastohydrodynamic lubrication analysis of a cam and follower

The cam and follower of the automobile valve train has proved to be the most difficult component of the internal combustion engine to lubricate. It has been recognized that the extremely thin films which occur during part of the operating cycle will inevitably mean some substantial surface interaction between the components. For this reason the mechanism of lubrication is often described as boundary in nature. During the last decade, however, the importance of a satisfactory design approach incorporating the principles of elastohydrodynamic lubrication has been established. Such design analysis is based upon a quasistatic approach and clearly identifies critical points at which the entraining action of lubricant into the contact ceases to operate and no lubricant film is predicted. In the present paper a transient analysis is described in which the local variation of normal surface velocity may be considered. The protective action of the squeeze-film lubrication mechanism at the critical points is demonstrated enabling an improved design sensitivity.