A study on the hysteresis characteristics of cam loading mechanism in toroidal CVT

For studying the influencing factors of axial force hysteresis in the cam loading mechanism of toroidal continuously variable transmission (CVT), a force analysis on the automatic loading mechanism with both traditional cylindrical and novel tapered rollers is conducted under the action of centrifugal force and friction force induced by the self spinning of rollers, and their hysteresis characteristics of axial force in loading mechanism are analyzed respectively in both standstill and high-speed rotation conditions. The results of numerical calculation show that with cylindrical roller, the real axial forces in input torque increase and decrease process are 80% and 120% of ideal axial force respectively in standstill condition, and the hysteresis phenomenon is more severe due to centrifugal force in high-speed rotation condition with a real axial force being only 50% of ideal one at worst; while with tapered roller, the corresponding figures are 98% and 102% respectively in standstill condition, and the difference between real and ideal axial forces is within 7% in high-speed condition, resulting in significant weakening of axial force hysteresis.