Gear transmission error outside the normal path of contact due to corner and top contact

This paper is devoted to a phenomenon known as corner contact, or contact o utside the normal path of contact, which can occur in spur and helical gear transmission systems under certain conditions. In this case, a change in p osition of the driven gear with respect to its theoretical position takes p lace, thus inducing a transmission error referred to here as the transmissi on error outside the normal path of contact (TEo.p.c.). The paper deals with spur gears only, but the results are directly applicab le to helical gears. It systematizes previous knowledge on this subject, su ggests some further developments of the theory and introduces the novel phe nomenon of top contact. The theoretical results are compared with experimen tal measurements using a single flank tester and a back-to-back dynamic tes t rig for spur and helical gears, and they are in good agreement. Convenient approximate equations for calculation of TEo.p.c. suggested here are important for analysis of experimental data collected in the form of H arris maps. This will make possible the calculation of tooth stiffness valu es needed for use in theoretical models for spur and helical gear transmiss ion systems.