Small Size Hydraulic Pumps with Low Heat Generation for Electro Hydrostatic Actuation of Humanoid Robots

Abstract

In this research, we suggest a method to reduce the loss of the pump aiming to develop small and high-pressure pump for EHA. To reduce the loss of the pump, we focused on the internal leakage loss and the viscous friction loss. We formulated each loss and found that it is effective for loss reduction to make gaps inside the pump narrower and increase the discharge amount per 1 rad making the radius of the gear small. Based on the above, we developed the improved involute external gear pump. Compared with conventional trochoid pump, the internal leakage loss of developed pump is reduced by 22.4% at 10MPa and the viscous friction loss is reduced by 85.6% at 10MPa. Also, there is a problem that internal leakage increases when the internal pressure becomes high. This problem is caused by the deformation of the pump-casing under high pressure. We developed highly rigid ceramics-casing to reduce the increase of the internal leakage. Compared with the pump using aluminum-casing, the pump using ceramics-casing reduced 56.2% in internal leakage loss when the internal pressure increased from 3MPa to 6MPa.