1993-03-01

A Model for a Planetary - CVT Mechanism: Analysis and Synthesis 930065

This paper describes the strategy for engineering design, modeling, and analysis of a planetary - CVT (Continuously Variable Transmission) system. The uniqueness of this mechanism arrangement resides in the combination of features associated to two conventional systems, namely a planetary gear train and a CVT pulley system, acting as a power circulation control unit. The pulley system features a manually activated control over the variable pitch ratios of the CVT, by means of which the overall system input/output velocity and power ratios can be controlled according the operational requirements.By using the belt drive as a feedback control unit (as opposed to the main driveline), one of the major problems or limitations of conventional CVT arrangements is overcome, namely the belt capacity of the system. Specifically, the output torque obtained through the planetary output shaft is greater than the torque circulating through the pulleys. This feature accomplishes two things, first the gear sizes required to attain variable velocity ratios need not change due to the CVT connection between the gear train and the output shaft, second, the belt capacity no longer limits the maximum torque capacity of the system, since the latter depends on both the planetary gear ratio and the CVT velocity ratio range.

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