Design and analysis of hollow tapered roller thrust bearings for PDM

Key words:  positive displacement motor(PDM)  thrust bearing  hollow tapered roller  finite element  stress concentration

Abstract:

A hollow tapered roller thrust bearing was designed for solving the failure problem which often happens in the thrust bearing group of positive displacement motor(PDM). The finite element model of the bearing was established, and a reasonable hollow structure of the roller was selected through the analysis. Finally, a deep cavity hollow tapered roller was designed. The effects of hollow degree and axial load on the mechanical properties of the bearing were studied. The results show that equal ratio hollow structure is suitable for the tapered roller. The stress concentration phenomenon exists at both ends of the tapered roller. The greater the hollow degree, the more uneven the equivalent stress distribution along the axial direction and the inner wall of the roller becomes. The equivalent stress of the roller changes little when the hollow degrees are less than 65％. The bigger the axial load, the greater the stress concentration at the ends of the roller becomes. The analysis results show that with the increase of the cavity depth and cavity diameter, the stresses at the ends of the roller decrease, but the stresses of the middle part increase gradually. The cavity structure can improve the "edge effect" effectively, and avoid the premature fatigue failure at both ends.