Conceptual Design of Pericyclic Non-Traction Continuously Variable Speed Transmissions: Rotorcraft Applications

This paper is a report on an ongoing research effort to develop advanced design architecture for substantially improved high power density, low parts count, pericyclic high power transfer capability, non-traction transmissions that embody motor/generator hardware elements and transfer power at design variable speed ratios. Power is transferred via unique pericyclic kinematics and spherical geometry spiral face gears having very high operating contact ratios, typically greater than 5:1, that can substantially reduce gear meshing vibration excitation and thereby the dynamic transmission error and resulting noise. Basic analysis was performed to estimate the envelope size and weight of both a single speed and variable speed pericyclic continuously variable speed transmission (P-CVT) for replacing 2 stages of a rotorcraft transmission. The results show that based on stated assumptions and methodology, the P-CVT provides a substantial improvement (i.e., 17% weight reduction with approximately 40% reduction in envelope size) over the baseline rotorcraft transmission. In the comparison, the P-CVT face gear tooth tensile stresses were equal to or lower than those of the baseline transmission gears.