Theory Study Of Non-Backlash Double-Roller Enveloping Hourglass Worm Gearing

After long-term research and explore, a new kind of non-backlash worm gear sets, namely double-roller enveloping hourglass worm gearing, is proposed by Professor Wang Jing-ge. That is applied for the realization of worm-drive without gear backlash. A study on this drive is significant in theory and valuable in practice for developing a kind of non-backlash worm gear sets with high precision and heavy load capacity. Manily from the theoretical perspective, this dissertation investigates the meshing theory, worm geometry features, meshing performance and how to construct the numerical model of double-roller enveloping hourglass worm gearing. The content of this research is as follows:The structure and the work principle of this worm gearing have been introduced. According to the theories of differential geometry and gear meshing, a perfect set of meshing system of the double-roller enveloping hourglass worm gearing in an ideal state is established using kinematics method. We deduced the meshing function of this drive and worm tooth surface equations. And, the formulas of contacting parameters which include induced normal curvature, lubrication angle, rotation angle and relatively entrainment velocity are derived.The geometry features of the worm of this drive, which include the tooth-surface features, mating surfaces, tooth profile of axial cross sections, tooth profile of radial cross sections and normal cross section, first boundary curve and undercut curve on the tooth surface, and the helix angle of tooth face, are analyzed by applying of numerical technology. The worm tooth surfaces are constructed by contacting lines and helical lines. And, the calculation formula and computation method of tooth thickness, the equations of undercut curve on worm tooth surfaces and helix angle are derived. Systematic study and research are done to the geometry parameters impacting the drive performance. Based on numerical calculation software, the author developed a set of program used for engagement analysis, which according to the meshing theories of this drive. After lots of numerical calculations, the main characteristics and the main parameters which impact the engagement performance of this transmission are analyzed. The results provide theoretical guide for reasonable selecting of geometric design parameters of double-roller enveloping hourglass worm gearing.Through analysis of parameters, one pair of double-roller enveloping hourglass worm drive, which central distance is 160 millimeter and drive ratio is 36, is designed. Consulting the design of planar enveloping hourglass worm drive, we work out the calculation formulas of geometry parameters of this new transmission.The solid model of worm gear and worm are constructed. In the environment of Pro/Engineering, two methods of tooth surface generation are researched. And their respective advantages and disadvantages are compared. Finally, the analysis results of assembly interference and assembly clearance show that the numerical models established have high degree of precision. That can be used as a reference for the profile of cutter and the virtual design of double-roller enveloping hourglass worm reducer.