Abstract
Lubricants for metal V-belt pushing type continuously variable transmissions (B-CVTFs) are required to give greater transmittable torque capacity between the belt and pulley in the CVT. In this study, the impact of base stocks used in B-CVTFs on the torque capacity of a B-CVT was experimentally investigated using a commercial CVT unit with a metal belt assembly and pulley design. As a result, synthetic naphthene base stock (SN) demonstrated 10 % greater than polyalphaolefin (PAO) under the conditions of secondary pulley clamping force from 17 to 34 kN and oil temperature 45 to 100℃ at a reduction speed ratio. Furthermore, the traction characteristic of tested oils was evaluated utilizing a rolling/sliding type tribometer at contacting pressure of 400 MPa, corresponding to the pressure between the belt segment and pulley. The traction coefficient of sample SN increased with increasing slip ratio while PAO did not show a distinct increase in the traction coefficient. This result implies that the difference in torque capacity between the two base stocks depends on the oil film shearing stress caused by slipping between the belt and pulley in the CVT.
