Anti-Shudder Mechanism of ATF Additives (Part 1): Formation of Contact Area Roughness

摘要

The anti-shudder effect of ATF additives and their mechanisms have been investigated. The addition of over-based Ca-sulfonate and friction modifier (FM) remarkably improved the anti-shudder durability of ATF. The surface roughness of the contact area (contact area roughness) of the lock-up clutch plates was measured by an electron probe surface roughness analyzer. It was found that shudder occurrence was strongly correlated with the contact area roughness of the steel plate surface. Large contact area roughness was preferred to prevent shudder. Based on a mixed lubricating theory, it can be considered that the large contact area roughness tends to maintain contact between two surfaces under higher sliding velocity condition, and acts to make a μ-v curve positive. It was suggested that the increase in the contact area roughness was caused by a calcium carbonate contained in the over-based Ca-sulfonate.