Development of High Torque CVT Fluids

Continuously variable transmissions (CVTs) use starting clutches such as torque converters to perform the same functions as those in conventional automatic transmissions. For high torque applications, CVT fluids require relatively high steel/steel friction. The presence of a torque converter requires that the CVT fluid also provide the same performance as conventional transmission fluids in addition to meeting the requirements for the continuously variable transmission. Often, incorporation of high steel/steel friction can also raise steel/paper friction and lead to shudder or other undesirable properties that can affect the overall performance of the vehicle. This paper describes the development of CVT fluids that fulfill performance requirements for both steel/steel and steel/paper friction.