The digital valve distribution axial piston pump is a swashplate rotary piston pump, the force on slippers is different from that of traditional axial piston pump. At the same time, the control strategy of the distribution valve will affect the pressure in the piston cavity, and then affect the oil film lubrication. According to these characteristics, the modeling method of oil film thickness field was proposed, and the force model of slipper pair and the numerical solution model of oil film lubrication of digital valve distribution axial piston pump were further established. The influence of swashplate rotation speed, swashplate inclination angle, and distribution valve control strategy on the characteristics of oil film lubrication were solved. The results show that the established thickness field model of oil film conforms to the stress characteristics of the slipper of the valve distribution pump. Increasing the swashplate rotation speed and the swashplate inclination angle is beneficial to optimize the oil film lubrication performance. The discharge valve should be opened in advance or closed in delay, which is beneficial to prevent eccentric wear and adhesion wear of slippers. The research results can provide theoretical basis for the optimal design of valve distribution axial piston pump.

Abstract. To study the flow characteristics of a new swashplate rotary valve distribution double-row axial piston pump, an instantaneous flow model was developed for the pump, the influences of structural parameters on the flow pulsation and uneven coefficient of flow were determined, and the ideal plunger distribution parameters were derived. On this basis, a valve distribution model was developed for the pump, the flow superposition process in the plunger cavity was analyzed, and the high-speed switching valve's control strategy was optimized. Additionally, the effects of parameters such as the plunger motion frequency, the plunger cavity's dead zone volume, the spool valve's preloading force, and the spool's equivalent mass on the flow characteristics were studied. The results show that the new pump had a small flow pulsation when there were five plungers in both the inner and outer rows and the dislocation angle was 18∘. The plunger's reverse-suction effect at the moment when the discharge valve opened and the suction valve closed and the plunger cavity's dead zone volume size were the primary factors affecting the size of the pump's flow spike. The discharge valve's opening was delayed by 3 ms to be consistent with the suction valve's closing time; for this case, the flow peak was small and the volumetric efficiency was the highest. The discharge valve began to close 2 ms early and closed completely at the critical point when the plunger transferred from the discharge stroke to the suction stroke, which helped the suction valve to open on time and improved the pump's oil absorption capacity. The active opening and closing control of the discharge valve improved the coordination of the flow distribution to a large extent, reduced the hysteresis of the suction valve, and ultimately improved the pump's volumetric efficiency and flow stability. The results of this study can provide theoretical guidance for the flow control of balanced double-row axial piston pumps with valve distribution.