Shudder Durability of a Wet Launch Clutch Part I – Thermal Study and Development of Durability Test Profile

Under the initiative of the United States Council for Automotive Research LLC (USCAR^§) Transmission Working Group, a collaborative effort was made with LuK USA LLC to study the influence of the friction interface parameters on the shudder durability of a wet launch clutch. A test bench was designed. Clutch configurations with different combinations of four friction materials (A, B, C and D), three groove patterns (waffle, radial and waffle–parallel) and two separator plate conditions (nitrided and non–nitrided) were considered. Considerable improvement in performance was seen by changing from CVT fluid* to DCT fluid*. A thermal analysis based on thermal model predictions and measurement correlations was conducted. Comparisons of clutch configurations with four and five friction plates were done. The waffle and radial groove pattern showed better heat transfer than the waffle–parallel groove pattern. The friction material type and separator plate conditions do not show any significant influence. The separator plate temperatures were the highest for the waffle–parallel pattern. Using this analysis, a test profile with 110 kJ energy per test cycle and four friction plate configuration was developed for durability testing.