NUMERICAL AND EXPERIMENTAL STUDIES ON FRICTION REDUCTION BY SURFACE MODIFICATION IN TEHL CONTACTS

摘要

According to HOLMBERG et al. [1], around one fifth of the fuel energy in passenger cars is used to overcome friction in the engine, of which, for example, approximately 15 % is consumed in the valve train. Total friction losses could be reduced by taking advantage of new technologies such as surface modifications. The latter can, for instance, be done by applying micro-textures (GACHOT et al. [2]) or amorphous carbon coatings (DONNET and ERDEMIR [3]) onto the rubbing surfaces of lubricated tribological contacts. Both approaches have been studied intensively in literature. For example Marian et al. [4], TREMMEL et. al. [5] and DOBRENIZKI et al. [6] studied the fabrication and tribological performance of micro-textures and diamond-like carbon (DLC) coatings applied onto bucket tappets in the thermo-elastohydrodynamically lubricated (TEHL) cam/tappet contact. Although the basic idea of micro-texturing and applying DLC-coatings is very similar, i. e. to improve the energy efficiency of the tribological contact without affecting other components by, for example, design changes, the two approaches are often considered separately. In addition, many studies are limited to specific contact and lubrication conditions. However, dynamic conditions and thus different friction mechanisms are present in real applications.