Water contamination effect in wet clutch system

Abstract

Water contamination in wet clutch systems can be a problem since both torque characteristics and wear resistance can be influenced by the presence of water. The present paper reveals the effect of externally added water on the wet clutch frictional performance. Commercially available standard paper-based friction plates and steel separator plates lubricated with commercially available automatic transmission fluid were investigated in a recently developed automated test rig using a well-confined experimental approach. Frictional response was observed for three different situations with different amounts of water and different exposure times. An undesirable friction increase is observed with increasing amounts of water in the system. The rate of increase in friction coefficient does not linearly depend on the amount of added water, and this is a noticeable outcome from the common possible water contamination effects, such as change in lubricant viscosity, inadequate additive performance and weakening of the friction material. The greater reduction in the separator plates’ surface roughness (Ra) in a water contaminated clutch system compared to an uncontaminated one may be a reason for the change in friction. It is also shown that different water exposure time has no great impact on the change in friction level and the separator plates’ roughness.