Pulleys' Axial Movement Mechanism for Electro-Mechanical Continuously Variable Transmission

Abstract

Pulley-based continuously variable transmission (CVT) with Metal Pushing V-belt (V-belt) is a type of automotive transmission that is widely applied currently by many car manufacturers worldwide. Unlike the conventional automotive transmissions, in a pulley-based CVT with V-belt, the transmission ratio (CVT ratio) is changed continuously without the use of discrete gears. Instead, the CVT ratio is varied through the simultaneous axial movement of the primary pulley and the secondary pulley. By axially moving both pulleys simultaneously, the radius of the V-belt on both pulleys will be changed accordingly, resulting in the change of the CVT ratio. The existing pulley-based CVTs in the market use electro-hydro-mechanical (EHM) actuation system to change and to maintain the desired CVT ratio through the hydraulic pressure. However, the application of EHM actuation system leads to some disadvantages, particularly in term of the high power consumption from the engine needed to maintain the desired CVT ratio. This reduces the efficiency of the powertrain system, which eventually increases the fuel consumption of the vehicles. In addition to that, the existing pulley-based CVTs also use single acting pulley mechanism to axially move the pulleys for changing the CVT ratio. Therefore, the issue of V-belt's misalignment, which shortens the lifespan of the V-belt, is inevitable here. In this paper, the pulleys' axial movement mechanism that uses electro-mechanical (EM) actuation system is proposed. Consequently, the working principle of the proposal is described and its potential benefits are discussed.