THE MAGNITUDE OF THE LOSSES IN THE STEEL PUSHING V-BELT CONTINUOUSLY VARIABLE TRANSMISSION

This paper investigates the reasons why in current passenger vehicles the steel pushing V-belt continuously variable transmission (CVT) has failed to achieve an improvement in fuel economy even though the CVT i s correctly controlled and allows the engine to operate near to its re gion of maximum efficiency. It is shown that the overall efficiency of the transmission is low, especially at the lower vehicle speeds. The main losses are due to the belt torque loss, the hydraulic pump loss a nd the loss due to slip in the belt-pulley system. It is shown that a considerable improvement in vehicle economy is obtainable by controlli ng the transmission so that the sum of these losses is minimized as we ll as seeking to optimize the engine efficiency. This improved overall efficiency is achieved by operating the CYT with much lower pulley cl amping pressures than have previously been considered desirable.