New release ports applicable to high-pressure gear pumps and their effectiveness.

The authors introduced two kinds of new pressure-release ports for improving the performance of gear pumps with involute profiles. High-pressure gear pumps as well as low pressure ones were used for verifying the effectiveness of the new release ports. In the case of the low-pressure pumps, the total efficiency of the pump with the new release ports was higher by about 10% when compared with the one having conventional release ports. However, when the improved conventional release ports, which were found in a gear pump currently available on the market, were used, the increase reduced from 10% to about 4% at a delivery pressure of about 700 kPa. Running noise and vibration of the gear pumps with the new release ports were appreciably smaller than those of the one with the conventional release ports. In the case of the high-pressure gear pumps, the increase in the total efficiency was about 5% at a delivery pressure of about 10 MPa. The reason for the improvement in the total efficiency was clearly explained by the maximum pressure measured in the semienclosed tooth space between two mating gears of the gear pumps with different release ports.