2012 Volume 7 Issue 3 Pages 152-158
Lubricants for metal V-belt type CVTs (B-CVTFs) must be able to produce a higher metal-metal friction coefficient and give excellent anti-shudder properties for lock-up clutch used in B-CVTs. This study intends to optimize various kinds of lubricant additive such as anti-wear additive, detergent and friction modifier (FM) for improving these performances of B-CVTs. In addition, contact mode atomic force microscopy was utilized to investigate links between friction performance and the morphology of tribofilms formed from candidate additives. As a result, an additive formulation consisting of a phosphorus additive, calcium detergent and dispersant showed a higher friction coefficient between the metals. The results of the surface analysis on the wear scar indicate that calcium tribofilm species formed fine depositions on the rubbing surface, which might attribute to a higher friction between the metals. Moreover, it is found that a sort of friction modifier gave an excellent anti-shudder performance for wet clutch with keeping higher friction coefficient between the metals, which would result in improving the performance of B-CVTs.
