This study intends to clarify the influence of tribological properties on the efficiency of a Continuously Variable Transmission (CVT) of a metal pushing V-Belt design. Measurements of transmission efficiency and transmittable torque capacity in an actual CVT were carried out by varying clamping forces on the pulley and speed ratio. Using higher torque capacity fluids in CVT units could contribute to reducing the maximum required pulley clamping force. This suggests that it is possible to give lower oil pump load, resulting in the reduction of the total power loss in the CVT unit. The synergy effect of metallic detergents and phosphorus additives could be a key oil formulation technology for the improvement of torque capacity. Transmission efficiency at an upper speed ratio was lower than at a lower ratio. The maximum difference in efficiency with all tested oils reached 3%. Friction losses caused by slipping between the block shoulder and innermost ring and between rings could have a great impact on the whole transmission power loss. Therefore, it is effective for further improving efficiency at lower load conditions to reduce the friction coefficient at low contact pressure.
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