Safety aspects of kinematic planetary precessional transmissions with plastic wheels

Abstract

The planetary precessional transmissions represent a new principle type of the mechanical transmissions. The specificity of the relative sphere-spatial movement of the precessional gearing elements makes the sliding friction persist. The study of the contact between two working surfaces of one gearing is very important, because the safety and the duration of the gearing running, its reliability and efficiency depend on the materials behavior, from which the prehension elements are produced. The study of the kinematical precessional gearing is of a major importance because, in the kinematical precessional gearing, there is slipping friction, which leads to big power losses and to big heat elimination in the contact zone. This paper describes the elaboration of the kinematical planetary precessional transmissions with plastic–steel toothed wheels. To reduce the sliding friction in the gearing of the kinematic precessional transmission, the plastic - steel gearing has been utilized. This fact allowed for increasing the efficiency and a solution of the problems related to the fabrication technologies for the crown gears of the satellite block. The teeth of the central wheel have nonstandard variable convex-concave profile, described by parametric equations according to the fundamental theory of the precessional gear. Because the teeth of the satellite have a circular profile this fact allows its relative simple fabrication. The performed analysis of the state-of-the-art in the field of the technology of fabricating the wheels for the kinematical planetary precessional transmissions demonstrated the need to elaborate the constructive-technological procedures for decreasing the power loses. This work contains a broad justification of the method for plastic materials selection, necessary for toothed wheels fabrication. As well, the plastic material selection and functioning criteria are presented. Also, a range of adequate materials for toothed wheels manufacturing is described.