Abstract
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 is correctly controlled and allows the engine to operate near to its region 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 and the loss due to slip in the belt-pulley system. It is shown that a considerable improvement in vehicle economy is obtainable by controlling the transmission so that the sum of these losses is minimized as well as seeking to optimize the engine efficiency. This improved overall efficiency is achieved by operating the CVT with much lower pulley clamping pressures than have previously been considered desirable.
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