Comparison of the size and efficiency of a two-carrier planetary gear train and kinematically equivalent planetary gear trains

Abstract

A two-carrier planetary gear train (PGT) developed for a specific purpose is discussed in this paper. This PGT is suitable for applications which require negative transmission ratios in the range from -3 up to -143. The mechanical and dimensional characteristics of the planetary gear train for nominal negative transmission ratios of -30 and -40 have been considered. Many combinations of ideal torque ratios of the PGT were obtained for the mentioned transmission ratios, from which only the combinations providing the minimum radial dimensions of the planetary gear units were selected. It was found that the minimum radial dimensions of the PGT will be obtained when the ratio of the reference diameters of the planetary unit ring gears of is close to unity, i.e., when the PGT housing is cylindrical rather than stepped. An introduction to single speed two-carrier planetary gear trains is given, in addition to an overview of the application of the DVOBRZ software package used to synthesize different gearboxes for the required transmission ratio. Acceptable gearboxes were selected from all PGTs according to the criteria of minimum dimensions and acceptable efficiency, and their construction concepts were created.