Experimental Study of Drag Torque between Wet Clutch Discs

Abstract

The development of automatic gearbox control systems contributes to their increasing popularity. By raising the number of gears and sophisticated algorithms, the reduction of fuel consumption is feasible regarding traditional manual transmissions. The continuously variable transmissions (CVT) are also growing their share of the market. Wet clutches are employed in all types of automatic transmissions, but because of oil viscosity, when such a type of clutch is disengaged, the drag torque phenomenon occurs. This deteriorates the global efficiency of the transmission system. To recognize the nature of this drag torque and how it is influenced by the main parameters (distance between plates, value of oil flow rate lubricating clutch, oil temperature, rotational speed between plates), a new test stand has been designed and assembled. The value of rotational speed has been studied up to 7000 rpm which is novel in literature. Due to strongly nonlinear dependences, the achieved results can contribute to designing more efficient clutch systems due to the strongly nonlinear nature of observed phenomena.