1 Copyright © 2003 by ASME Proceedings of IMECE2003 2003 ASME INTERNATIONAL MECHANICAL ENGINEERING CONGRESS AND R&D EXPO Washington, D.C – November 15-21, 2003 IMECE2003-43233 CONTACT STRESS IN A GEROTOR PUMP P.Javier Gamez-Montero LABSON - Universitat Politècnica de Catalunya C\ Colom nº 7-11 08222 Terrassa Spain T- 0034937398085/ F- 0034937398633 pjgm@mf.upc.es Esteve Codina LABSON - Universitat Politècnica de Catalunya C\ Colom nº 7-11 08222 Terrassa Spain T- 0034937398664/ F- 0034937398633 ecodina@mf.upc.es ABSTRACT The aim of the first part of this paper is to reach the optimum design parameters of a gear set when it works as part of an internal gear pump type gerotor. The performance of the gear teeth and the whole gear set are evaluated through analytical studies to obtain the maximum contact stress in gear teeth and the volumetric characteristics. Several gear sets have been examined and the results are presented. The aim of the second part of this paper is to document a better understanding of the performance of a crankshaft mounted gerotor pump for IC engines lubrication. Modeling, simulation and experimental work have been examined for a specific unit. A preliminary 2D simulation is carried out by using the Finite Element Method (FEM) to calculate the maximum contact stress. At the testing phase, a prototype model of the gear set provides the maximum contact stress on a pair of teeth by using photoelasticity measurement techniques. The results are exposed and discussed and possible alterations are proposed. Keywords: Internal gear pumps type gerotor, contact stress, volumetric characteristics, FEM, photoelasticity techniques, optimum design parameters INTRODUCTION The trend in industries is toward the improvement of the performance of the hydraulic components. Internal gear pumps present a significant number of advantages and automotive industry has focused on them. The advantages include: less noisy, few components and no sealing units. At the same time, the design of the internal gear pumps has a disadvantage of not having parts that can be adjusted to compensate for wear in the gear set. As a consequence, a sharp reduction of efficiency is generated. It was Colbourne [1,2] who took one of the first approaches to estimate the contact stress. The work presented in this paper is divided into two sections. In the first section of this paper, the authors have concentrated on the performance of the gear teeth through an analytical study of the contact stress in gear teeth and the performance of the whole gear set through an analytical study of the volumetric characteristics when it works as part of an internal gear pump type gerotor. Based on Colbourne’s approach, results of the maximum contact stress in the gear teeth are obtained for several gear sets in function of design parameters. Despite of the fact that the correct selection of the design parameters allows reaching an optimal contact stress, it cannot be forgotten that these geometrical parameters also perform the volumetric characteristics of the pump. Therefore, instantaneous flow, volumetric capacity, delivery irregularity and tooth stress characteristics are presented for various pumps based on several geometrical parameters, on one hand, to know the influence of the design parameters of the gear in order to reduce the maximum contact stress and obtain the optimal volumetric characteristics and, on the other hand, to guide the designer to select the best design parameters in a specific application. In the second section of this paper, the study concentrates on simulation and experimental work for a specific gear set of a unit of gerotor pump for IC engines lubrication. Simulation plays an important role to attain a future optimal behavior in systems and hydraulics components, especially when they are being designed. A series of simulations has been performed using a finite element technique to predict the contact stress in Proceedings of IMECE’03 2003 ASME International Mechanical Engineering Congress Washington, D.C., November 15–21, 2003 IMECE2003-43233 Downloaded From: http://proceedings.asmedigitalcollection.asme.org/ on 10/26/2013 Terms of Use: http://asme.org/terms