REAPPRAISAL OF GEARS LUBRICATION IN LIGHT OF ELASTOHYDRODYNAM1C THEORIES

Document Type : Original Article

Authors

1 Professor,Head of Mech. Dept.,Zagazig University.

2 Associate Professor, Dept. of Mechanical Design and Prod. Eng.,Cairo University.

3 Col.Eng.,Military Tech. Research Center.

Abstract

The present work comprises a computer-aided analysis of the lubrication performance of Involute and Novikov gears. Due to the complexity of gears geometry and their kinematics, gears meshing is simulated by equivalent cylinders loaded and moving in such a way to fairly describe gears load sharing effect and the combined rolling/sliding speeds along the line of action. Different theories to describe Elastohydrodynamic lubrication (EHD) have been considered. Both oil film thickness and coefficient of friction are chosen to represent the lubrication performance characteristics due to their paramont effect on major modes of gear failure. The trend to increase power and efficiency, especially in military applications, has created the need for a more accurate, efficient and quality gears. One of such development is the introduction of circular-are gear, known as Novikov/Wildhaber or Circ-arc gears. This type of gears has been herein analysed. Results show that efficient lubrication (maximum oil film thic-kness and minimum frictional loss) could be attained whenever the involute gears geometry renders higher pressure angles and smaller tooth modules. However, the Novikov gears are more advantageous over the common involute gears as they render oil film thickness ten times greater and a relatively reduced coefficient of friction under the same loading conditions. Lower values for both pressure angles and helix angles are prefered in case of Novikov gears.