Impact of Organic Sulfur on Frictional Performance 2017-01-1129

The frictional performance of the wet clutch used for automatic transmission is determined by the interaction between the paper-based friction material (D/C), separator plates (S/P), and automatic transmission fluid (ATF). In order to understand the impact of additives in ATF on the frictional performance, commercial ATF was modified by adding 5 types of additives one by one in a specified concentration, and the friction test was conducted for 6 levels of ATF consisting of these 5 modified ATFs plus commercial ATF. The friction test consisted of a dynamic test conducted for 2000 cycles interspersed with a static test conducted once every 100 cycles, in order to measure the coefficient of static friction (μs).As a result, it was found that only in the friction test conducted by using ATF with the addition of sulfur-based friction modifiers, there was an increase of 30% from the existing coefficient of static friction (μs) up to 1500 cycles, but at 2000 cycles, it dropped to the same value as the μs using ATF with no additives. Then, surface analysis was conducted for the frictional surface when the μs was high, as well as when the μs dropped, by X-ray Photoelectron Spectroscopy (XPS) and Time-of-Flight Secondary Mass Spectrometry (TOF-SIMS), in order to clearly identify the relationship between deposits on the frictional surface and μs.