Wet Clutch Friction Properties and Tribofilm Characterization from Lubricant Additives in Automatic Transmission Fluids

摘要

The aim of this study is to clarify how lubricant additives applied to Automatic Transmission Fluids (ATFs) control the friction coefficient versus sliding velocity properties (μ-V curve) between the friction plate and the steel plate employed in lock-up clutch. Friction properties of some kinds of dispersant and metallic detergent used in ATF were experimentally investigated using a Low Velocity Friction Apparatus (LVFA) based on JASO M349. The sample composed of base oil plus dispersant gave 20% higher friction coefficient at a higher sliding speed condition in comparison with base oil alone. The difference in the friction coefficient between the tested dispersants might be affected by trobofilm morphology formed on the steel plate. Moreover, a sort of calcium detergent was found to be an effective agent for improving anti-shudder durability. Calcium detergent which finely disperses in oil solution could minimize abrasion wear and clogging against the friction materials, resulting in a longer anti-shudder durability for lock-up clutch system.