Thermal Elastohydrodynamic Analysis of a Worm Gear
Marko Tošić, Roland Larsson, Karsten Stahl, Thomas Lohner
Abstract
This study explores the elastohydrodynamic lubrication (EHL) between the contacting tooth flanks of a worm gear with nonconjugate meshing action. The contact is characterized by a slender-like elliptical shape and high sliding. The geometry and contact conditions for the considered worm gear were obtained using tooth contact analysis. Based on that, the complete area of the worm gear contact was analyzed using a validated numerical EHL model considering non-Newtonian, thermal, and transient effects. The geometrical and kinematic design factors that influence EHL film formation in worm gears were identified and discussed. The results show the specific characteristics of worm gear EHL contacts, such as the very slender contact in the tooth root flank area, which diminishes the effect of the entrainment speed on film thickness. EHL film formation could be supported by increasing conformity between the flanks to make the contact less slender. By comparing the film thickness results against analytically obtained ones, relatively large differences were observed except for one formula for minimum film thickness.