Life and Reliability Examination of Internal Gear and External Gear Contact in Gear Mechanisms

Gear mechanisms are indispensable mechanisms used in many machines as power and motion
transmission elements. What is expected from gear mechanisms is that they can achieve a high cycle
rate in a small area and function for a long time. In this study, safety, life and reliability comparisons of
gear mechanisms in terms of root and flank safety in internal and external gear contact were carried out
using analytical calculations and the KissSoft program. A modular calculation tool for machine element
design, optimization, and verification in accordance with international standards is called
KISSsoft®.The program is also available for evaluating the internal gear. Within the scope of this study,
calculations were made within the scope of ISO 6336 standards. The contributions of internal gear
contact, which is widely used in mechanisms such as harmonic reducers and planetary systems, to life
and reliability are examined. In internal gear contact, there are large differences in contact ratio and load
distribution due to form factor. Studies on internal gear mechanisms are much less than those on external
gear mechanisms. Especially in internal gear mechanisms, profile modification is very open to work. In
this study, the effects of profile shifting and changing the pressure angle in the tooth involute structure,
as basic gear modifications, on gear strength and life were examined. The effects of these elements on
the gear in internal and external gear contact were examined and optimum design parameters were tried
to be obtained. As a result, it has been seen that the internal gear contact is much more efficient than the
external gear contact, both in terms of space coverage and strength. The manufacturability of profile
modifications in the design of real gear mechanisms was also evaluated in the study.