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The mechanism considered here, combines the functions of a planetary gear train and a continuously variable transmission (CVT) system, through a circulating power control unit, which results by connecting the sun-gear shaft and the ring-gear rotation through a variable pitch pulley system. The mechanism is simple and does not require clutches for its operation. Three basic configurations are presented, two of them produce a power feedback effect and a third one produces a power split forward, without a “geared neutral” condition. Parametric analysis is carried out in relation to the circulating power split feature in order to to assist in the design of an optimum configuration for light-weight applications. A parametric approach is used to generate a model that can be used to perform parametric sensitivity analysis.

Continuously variable transmissions, commonly known as CVT's, have been shown to be feasible alternatives to the conventional multi-step gear transmissions (standard or automatic) typically used in automotive applications. Most CVT applications, however, rely on a shaft-to-shaft transmission arrangement, in which the belt-sheave action limits the load capacity of the transmission, particularly at the high power ranges (low speed, high torque). In this paper, a system based on a combined planetary gear train and a continuously variable pulley system is presented. The uniqueness of this arrangement is that the variable pulleys provide a power/torque split and recirculation function, which, when combined with the planetary gear train function, produces a continuously variable power split transmission system.