1994-03-01

Parametric Modeling and Analysis of a Planetary Gear-CVT Mechanism 940519

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. In the optimization process, a parametric characterization is made based on the most significant parameters and functional ratios of the system to evaluate the performance of the variable transmission and power control unit. Three different transmission ratios and two independent design parameters fully define the configuration of the system. These are: the planetary gear train ratio (Fg), the CVT transmission ratio (Fc), and the control to output gear ratio (Fgc). The two independent parameters can be selected from the radii of two groups of elements (one from each), that include a) the planetary gear carrier, the sun gear, the internal ring gear and b) the control ring gear, and the output gear.

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