scope:

The reduction of component size and oil volume of current automotive and aeronautical transmissions along with the increasing input speed are pushing gear teeth bulk temperatures to their scuffing limit. Although new lubricant additives and coatings are being developed to overcome this obstacle, other problems may also arise as a consequence of high temperatures, such as the decrease in transmission error due to gear's thermal growth, the contact outside the normal path of contact and the non-uniform load distribution.

The present work analyses the effects of the thermal distortion of narrow face width spur gears (b/d < 0.5) on profile geometry and tooth contact parameters in the transverse plane. First, steady-state temperature distribution is calculated from a thermal network model that accounts for the influence of immersion depth, oil sump temperature and lubrication regime in the tooth contact. Then, thermally distorted geometry and tooth contact analysis is computed by means of a 2D finite element model where load distribution, transmission error and backlash are analyzed. The results of the study will allow to set the limits of design backlash to avoid gear jamming and to size the initial profile shift or tooth modifications to reach the desired contact behavior.