As the power density of gear sets increases, mesh deflections increase, and the variations in those deflections, which
result primarily from mesh stiffness variation, become increasingly significant. This is because these variations translate
directly into transmission error and provide the excitation that generates the periodic inertial load supplement called“the
dynamic increment of load”. In addition to subtracting from the useful torque capacity, the dynamic increment is the
main generator of gear noise.
To minimize these undesirable effects, designers of power tain gear pairs have traditionally specified various forms of
profle modification, the most common of which is tip and/or root relief. The problem with these conventional
modifications is that they give only alimited reduction in transmission ertor ata particular roll angle and load (the“design
]oad”) but produce increases in transmission error at other roll angles and loads.
A new system of modifications, however, bas recently been devised that substantially eliminates mesh stiffness
variations throughout the entire engagement angle regardless of wbat torque load is being transmitted. This new system
of modifications is described and confirmatory test results are reported.