Digitalization of Radial Piston Pumps through Internal Mechanically Actuated Designs

Digital hydraulics is a technology gaining perceptible growth in fluid power research. The advantages of digital fluid power systems can be realized through improved system efficiencies, energy savings, increased productivity, and system performance compared to traditional fluid power systems. Conventional check valve pumps use differential pressures to deliver pressurized flow to the system. Digital fluid power pumps enable conventional check valve pumps to achieve variable displacements by enhancing the controllability of the inlet and outlet valves through digital hydraulic technologies and techniques. The benefit of this technology is the use of positive sealing check valves with lower leakage losses compared to typical variable displacement pumps, increasing the unit's overall efficiency. The primary focus of prior digital pump/motor research has been on digital actuation using electronic solenoids to actuate or latch the valves. While these electrical systems provide a platform for digital hydraulic techniques, they come with a cost: added energy sources, advanced controls, and expensive data acquisition systems. Research has also shown that minor valve timing inconsistencies can limit the potential energy savings of digital pumps in electrically actuated systems. A system configuration that promotes the advantages of digital hydraulics while mitigating the disadvantages associated with electrical systems is mechanically actuated systems. This work discusses variable cams and their advantages/disadvantages in digital radial piston pump/motor technologies. The significance of this work is the investigation of the digitalization of radial piston pumps through mechanically actuated valving systems, which has yet to be implemented in prior research. This paper evaluates various design concepts for commercializing digital radial piston pumps using mechanically actuated cams. A two-quadrant pump and a four-quadrant pump/motor design are simulated to assess their potential efficiency across the bandwidth of their displacement. The results show that the two systems can achieve relatively high efficiencies across their displacement bandwidth but show room for further improvement by optimizing these systems. This study is the first step in designing an integrated mechanically actuated variable cam system in digital radial piston pumps.