On the Optimal Shape of Gear Teeth End Gaps for Hydraulic Gear Pumps and Motors

In order to improve the efficiency of hydraulic gear pumps or motors especially for high operating pressure or temperature, power losses due to viscous friction acting on and leak flow through gear teeth end-gaps are considered in this paper. Formulas of the viscous friction and leak flow through a gap are derived and then the optimal gaps minimizing the power loss for pumps and motors with uniform heights of gaps are analyzed first. And the effect of the shapes of gaps with unequal heights on the power loss are discussed by simulation study. Considering that the outer shell facing gear teeth may expand due to high internal pressure or thermal stress, the results drawn in this paper can be used for the design of high efficiency pumps and motors.