SYNTHESIS AND OPTIMIZATION OF EPICYCLIC-TYPE AUTOMATIC TRANSMISSIONS BASED ON NOMOGRAPHS

Abstract

A new methodology is developed to design and optimize epicyclic-type automatic transmission gear trains using kinematic nomographs. From such nomographs, the kinematic characteristics of an epicyclic gear mechanism can be expressed in terms of the gear ratios of its gear pairs. The main properties of this methodology are that; from a single nomograph, the angular velocities for all of the coaxial links can be estimated and compared directly without specifying the exact size of each gear, the angular velocities can be arranged in a descending sequence without using complicated techniques, and all of the feasible clutching sequences can be enumerated directly. The optimization procedure to find the optimum gear ratios is applicable to any transmission mechanism composed of two or more fundamental gear entities (FGEs) depending on kinematic and geometric constraints.
The reliability of the methodology is established by applying it to the conventionally available three-velocity Simpson gear train for which optimal gear ratios are fully available. The theoretical results are in complete agreement with the practical applications.