Study of the Trapping of Fluid in a Gear Pump

In a gear pump, relief grooves are provided on the endplates to avoid the trapping of fluid, and their position has great influence on the performance of a gear pump. However, no definite design has been established on the relief groove position. In order to decide the optimal position of the relief groove, it is necessary to clarify the trapping phenomenon of working fluid in a gear pump. In this study, the pressure in the space trapped by tooth surfaces of the driving and driven gears was measured using a fixed endplate type of external gear pump, specially made, in which a miniature semiconductor type of pressure transducer was installed. The experiment revealed the effects of the relief groove position and the backlash size on the magnitude of the pressure rise in the trapped space and on the performance. The optimal position of the relief groove was made clear.