A study on the design of asymmetric gears for application in gear pumps

This thesis presents a study on the design of spur gears with asymmetric teeth in external gear pump applications. A model is generated for asymmetric gears and for the specified gear pairs, Hertz contact stresses are determined by using analytical approach. The instantaneous flowrate equation is also derived. The process of generating the gear model and calculation of the Hertz contact stress and instantaneous flowrate are automated with a computer program developed in this study. Using the data from the model, tooth contact stress and root bending stress variations during a mesh cycle at certain intervals are investigated by finite element analyses and compared with the results obtained from analytical approach. Drive side pressure angle, coast side pressure angle, profile shift coefficient, number of teeth and module were considered as the performance factors and the effects of these factors on tooth contact stress, bending stress, flowrate and flowrate fluctuation are investigated by testing fifty different spur gear pairs for a specific gear pump. Key Words: involute spur gear, asymmetric teeth, Hertz contact stress, bending stress, finite element method, external gear pump.