Prediction of oil film thickness in trochoidal pump

Abstract

A model for predicting the oil film thickness between the contact surfaces of the gerotor pump teeth is given in this paper. Gerotor pumps are rotary pumps with inner trochoidal gearing. The working process of the pump is followed by mechanical losses due to friction that occurs between the coupled surfaces. To reduce these losses and avoid wearing of the teeth’s active surfaces, it is necessary to provide a minimum thickness of the oil film between the contact surfaces. The minimum thickness of the oil film depends on many different factors, but in this paper for its determination, the Hamrock and Dowson empirical equation is used. Previously, the mathematical model that follows the change of relative velocities in contact, sliding velocity, rolling velocity, and contact force at the contact points of the coupled teeth profiles is developed. The influence of different parameters on the lubrication regime has been analyzed, and it has been shown that the trochoidal pump operates most with the limit EHD lubrication regime. The most unfavorable period occurs when the resulting rolling velocity decreases significantly, and this period dominates during coupling. The results of this research provide guidelines for the design of the tooth profile’s shape and the choice of operating parameters of the pump with high reliability.