Technical Paper
ATF Friction Properties and Shift Quality
2004-10-25
2004-01-3027
Multiple plate disk clutches are used extensively for shifting gears in automatic transmissions. In a shift from one gear to another one or more clutches is engaging or disengaging. In these active clutches the automatic transmission fluid (ATF) and friction material experience large changes in pressure P, temperature T, and sliding speed v. The coefficient of friction, μ, of the ATF and friction material depends on v, P and T, and also changes during clutch engagement. Changes in μ can lead to vibration and poor shift quality if the ATF and clutch friction material are improperly selected. An in-depth theoretical understanding of the cause of vibration in shifting clutches is crucial in the development of a suitable ATF to work with a particular friction material.