Abstract
The needs for increases in transmitting capacity of CVTs will become greater. The important factor in attempting to increase transmitting capacity is ensuring the dynamic strength of the metal pushing V-belt. Dynamic strength cannot be determined simply from the maximum input torque, but must be determined experimentally in relation to the shift ratio, pulley piston pressure as well as the maximum rated speed. This is because it is generally difficult to measure element stress, a factor that is indispensable in determining the strength of the belt in actual CVT operation. It is therefore both technically and procedurally difficult to optimize the shape of the belt for higher-speed operation, making it necessary to develop a theoretical method of determining the effect of the shape of the belt, and in particular the shape of the elements, on dynamic strength. A simulation method enabling simultaneous prediction of dynamic behavior and stress distribution on element has been developed for durability evaluation of dynamic strength of metal pushing V-belts. The finite-element-method that enables contact analyses in time history with large-scale model was adopted to reproduce the dynamic behavior of the V-belt in high rotational speed range of CVT. This paper focuses on the element strength in actual operation of CVT, and also discusses modifications made to the previously reported simulation method to enable the prediction of detailed stress. A new technique named inertia-relief is introduced needless of applying the constraint conditions when calculating the detailed stress on element in respectively. This results in allowing the stress distribution on any element to be found at any position on the trajectory of the V-belt and the elastic deformation of the element to be identified. Using this technique, it has been found that the stress on the necks of elements at the entrance and exit of the pulleys affects the dynamic strength of the V-belt. Furthermore, a method of evaluating this stress was also determined. In addition, consideration was given to the effect of the concave shape at the element tail side on the dynamic strength of the V-belt.
KEYWORDS - Continuously Variable Transmission, Metal V-belt, Dynamic behaviour, Stress simulation, Fatigue strength