Gear Tooth Stress of an End-Relieved Spur Gear

In the nose-suspended type traction gears, the angle between the projected lines of axes of pinion and gear on pitch plane often becomes equal to about 10' and end tooth bearing happens, leading to tooth failures. In JNR, as the countermeasure for these failures, heavily crowned gears are used for nose-suspended type traction gears. The calculation method for such heavily crowned gear was already introduced by one of the authors. In some types of traction gears, the positions of pinion and gear axes are comparatively stable, but even in these cases, due to distortions of gear case and bogie frame, error of gear alignment, etc, the axes of gears become non-parallel slightly. For this reason, such gears of JNR are relieved at the tooth end in order to avoid end tooth bearing. Up to this time, the gear tooth stress of such end-relieved gear has been calculated with uniform loading assumed over the total facewidth. But it has become clear through experiments that the stress of end-relieved gear grows considerably larger than that under uniform loading, and the authors proposed a calculation method for the stress of end-relieved gear. For practical application, it is sufficient that the factor of stress increase induced by end relief is considered for the tooth stress when uniform load is applied over the total facewidth, and they gave diagrams for deciding the stress increase factor. By experiments they demonstrated that introduction of this factor in stress calculation would be very reasonable.