Analysis of Forces and Moments in Gerotor Pumps

Abstract

This article presents the analyses of the forces and moments between gears in contact with a gerotor pump. The objective was to reach a more accurate solution for the problems related to load distribution in trochoidal pumps with fixed shaft axes. Calculation of contact forces is complex due to the simultaneous contact of several trochoidal teeth during the load transfer and additional compressive fluid forces that act on the teeth flanks. A simple physical model and a suitable analytical model are used for this analysis. Compressive fluid forces are simulated with single force applied in the middle of the line that separates the suction and upward pressure zone. During the teeth engagement there is also a change in fluid volumes between teeth. This creates pressure change that needs to be considered and calculated at an arbitrary moment of the engagement process. Finite element analysis (FEA) was used to determine the reaction forces that depend on instantaneous moments as well. Analysis shows that if a chamber pressure variation is taken into account, higher values of driving moment and support reaction forces will be generated. Designers can use the obtained results to develop a higher efficiency gerotor pumps.