Balancing Dynamic Strength of Gears Operated at Reduced Center Distance

摘要

This paper presents an analytical study on using hob offset to balance the dynamic tooth strength of spur gears operated at a center distance smaller than the standard value because of design needs. The study was limited to the offset values that assure the pinion and gear tooth will neither be undercut nor become pointed. The analysis presented in this paper was performed using a revised version of the NASA gear dynamics code DANST. The dynamic stress of the pinion and gear are affected significantly by varying hob offset values. The significant difference in the tooth stress of the pinion and gear can be minimized by selecting a suitable hob offset. The best offset value to balance the dynamic stresses of the gear and the pinion, subject to different operating conditions, are analyzed. The operating speed of the transmission has a significant influence on the amount of hob offset required to equalize the dynamic stresses in the pinion and gear. In the gears studied, the optimum hob offset was found to fluctuate mostly within a range at any speeds. For gears that must operate over a range of speeds, an average offset value may be used.