Abstract: The adoption of hydraulic pump to drive the hydraulic cylinders in closed circuit is a research hotspot in the field of current electro-hydraulic control technology. This technology is well applied in the control of symmetric cylinders, yet the effect is not that satisfactory for widely used differential cylinders. Therefore, the principle of adopting three assignment windows axial piston pump to directly drive the differential cylinder in closed circuit is proposed according to the concept of asymmetrical cylinder controlled with asymmetrical valve technology. The scheme is to transform the oil suction window of the existing axial piston pump into two parallel windows. When in use, a piston is added to the universally adopted 9-piston pump, then the 10 pistons are separated into two groups, the oil suction and discharge windows of each group are in the staggered position in the radial direction and are respectively corresponding to the two assignment windows in the valve plate. With the software SimulationX, a hydraulic pump simulation model, which takes into consideration the single piston motion characteristics and the change of assignment area with the rotary angle, is established. The pump key parameters, especially the sizes of the cylinder body and the unloading groove of the valve plate, are determined through digital simulation. Then the prototype pump is designed and made. The basic characteristics such as pressure, flow and noise of the pump at different rotation speeds are tested, thus verifying the correctness of the principle.

Key words: Axial piston pump, Parallel connection, Pump controlled differential cylinder