Development of an Analytical Model for Prediction of Drag Torque Characteristics of Disengaged Wet Clutches in High Speed Region

Reduction of the drag torque and longevity of the clutch assembly are the most important factors for vehicle transmission improvement. The decreasing trend of the drag torque with speed after its peak is a common characteristic of the clutch assembly. Several theoretical models have been presented by the researchers describing the drag torque characteristics at lower clutch speed region. However, very little study has been made on the drag torque behavior at very high clutch speed region (6000~10000⁺ rpm). The unwanted occurrence of drag torque jump up at high speed operating condition remains unexplained till date. In this paper, we have investigated the possible reasons of torque jump up at high rotation speed and solution to overcome this problem. We have presented an analytical correlation of torque jump up with the excessive decrease of local static pressure and assumed that vacuum formation is one of the possible reasons of high speed torque rising and associated vibration. Result shows that when the separator plates are free for axial movement, a remarkable torque jump is observed. However, the drag torque jump up at higher speed can be eliminated by controlling the axial movement of separator plates by using separation springs or screws.