Optimum Tooth-Surface Modification for Axis-Displaced Involute Helical Gear Drive With Parallel Axes
Gear drives, which have larger misalignment than the maximum tolerance of misalignment for gear drives with parallel axes in the Standard of Japanese Gear Manufacture’s Association (JGMA Standard 114-02), are designated as axis-displaced gear drives in this study. So, axis-displacement is used in place of the misalignment. And tooth-surface modification for axis-displaced gear drives has been studied by the authors. In this study, design system for optimum tooth-surface modification is developed for axis-displaced involute helical gear drives, which are sensitive to gear misalignment, to reduce the sensitivity to misalignment and to provide the high productivity and reliability. The system is composed of; (1) Virtual rack, which is conjugate to mating standard helical gear pair in their standard relative motion, is defined for pinion and gear tooth-surface generation. And axis-displacement is relative displacement between the virtual rack and each gear, or between pinion and gear. (2) Axis-displaced tooth-surface of each gear is defined as the envelope of virtual rack tooth-surface family in their regular motion transmission (zero transmission error) under an axis-displacement. (3) Basic tooth-surface of each gear is built by combining the axis-displaced tooth-surfaces under various axis-displacements. (4) Basic rack tooth-surface for each gear is obtained as the envelope of the basic tooth-surface family in their regular relative motion. (5) It is illustrated how to get optimum rack tooth-surface from the basic rack tooth-surface. (6) Optimum tooth-surface of each gear is generated as the envelope of the optimum rack tooth-surface family in their regular relative motion. (7) Undercut around dedendum, and tooth thickness on tip circle of the optimum pinion tooth-surface are checked. (8) The performances of testing gear drive with the optimum tooth-surface of each gear are analyzed by TCA (Tooth Contact Analysis) program developed for analysis of meshing and bearing contact. The above-mentioned system is illustrated with its application for testing involute helical gear drive. As a result, it is ascertained that the system can provide the gear drive favorable tooth bearing contact and motion transmission, even in 10 times misalignment of the maximum tolerance in JGMA Standard 114-02.