The automatic transmission has a mechanism that transmits the power of engine to the driving system of the vehicle and it is operated by hydraulic pressure. Recently, reducing the power loss of automatic transmissions, which have a great effect on fue...
The automatic transmission has a mechanism that transmits the power of engine to the driving system of the vehicle and it is operated by hydraulic pressure. Recently, reducing the power loss of automatic transmissions, which have a great effect on fuel efficiency, is an important issue. Many researchers were studied the reduction of power loss. The power losses in automatic transmissions are largely divided into oil pump losses, clutch drag torque losses, seal drag losses and gear churning losses. One of them, clutch drag loss accounts for more than 30% of total clutch losses. Previous research have been studied the factors that affect clutch drag torque, but drag torque was investigated mainly on uniaxial rotation in the clutch. In this study, we developed mathematical model which predicts drag torque depending on relative velocity. The drag torque is measured by the absolute speed change in the relative rotation of the input and output of the clutch for the verifying the mathematical model, experimentally. Also, we measured and analyzed the drag torque according to the factor by which, absolute rotating speed, ATF flow rate, and ATF temperature affecting the drag torque at the relative rotation.