High response, stable operation, small volume active vibration damping system and other intelligent hydraulic equipment have become the inevitable trend of future development. A compact low-pulsation gerotor pump is designed to meet these requirements, the theoretical flow pulsation of 8/9 tooth gerotor pump is analysed, and its pressure pulsation characteristics are also studied in this paper. The combined pulsation buffer is placed at the bottom valve plate high-pressure port of pumps. High-pressure oil passes through the honeycomb damping hole and enters the diaphragm volume chamber of the accumulator to form a combined pulsation buffer. Considering the effect of the pulsation buffer structure to reduce flow pulsation at different speeds, a test bench for high-speed gerotor pump pulsation characteristics is built, and the pressure pulsation of the gerotor pump with and without pulsation buffer is analysed at different speeds. Results show that the pressure pulsation frequency increases with pump speed. When the speed reaches 5500 r/min, 8/9 tooth gerotor pump without pulsation buffer outlet pressure pulsation reached 13.797% and that with pulsation buffer outlet pressure pulsation decreased to 9.871%, showing a 28.46% decline rate. At pump rotation speeds are 1500 r/min and 2500 r/min, the pulsation reduction ratios are 37.78% and 35.36%. The pressure pulsation of the gerotor pump can be evidently reduced by designing a combined pulsation buffer in this paper. Therefore, this high-speed and low-pulsation gerotor pump is suitable for active vibration damping system and other intelligent hydraulic equipment.

Internal curve motors (ICMs) are used in construction and port machinery owing to their low speed and strong torque. The internal leakage of an ICM has a direct impact on its working performance; however, research on the internal leakage of ICMs is unclear. A method, based on the Computational Fluid Dynamics (CFD) transient simulation of an ICM, for obtaining the transient pressure in the plunger chamber and combining the mathematical model of internal leakage is calculated, and the internal leakage is proposed. We one-factor analyzed the internal leakage of the ICM and the effect of the valve pair and plunger pair leakage, and conducted multifactor analysis on the effect of the interaction between those two factors on the internal leakage of the ICM. The results show that the internal leakage mechanisms affecting the ICM were, in descending order of impact, the inlet pressure, oil temperature, and rotational speed, and a significant interaction existed between the inlet pressure and oil temperature, whereas the influence of rotational speed was not significant.

The internal curve hydraulic motor valve plate has a clearance self-compensation performance that can effectively improve the working efficiency of the valve plate. However, the dynamic characteristics of the valve plates require further investigation. This study considers the self-compensating ‘floating’ valve plate as the research object, proposes a dynamic characteristic analysis method for the internal curve hydraulic motor valve plate, and explores the changing rule of oil film thickness and surplus pressing force of the valve plate. The results showed that an increase in the inlet pressure and oil temperature led to an increase in the thickness of the oil film, and the amplitude of the oil film thickness was larger, whereas the rotational speed of the oil film thickness of the valve plate pair was not obvious. When the inlet pressure is lower than 8 MPa, and the oil temperature is in the range of 20–30 °C, the oil film is mainly subjected to the squeezing effect of the valve plate, and the displacement of the valve plate decreased with increasing rotational speed. The inlet pressure is the main factor affecting the displacement of the ‘floating’ valve plate, and when the inlet pressure reaches 8.7 MPa, the valve plate is in hydrostatic balance support. In addition, the surplus pressing force coefficient of the valve plate decreased with increasing inlet pressures. This study provides theoretical support for the design of variable pressing force valve plates for internal curve hydraulic motors by investigating the dynamic characteristics of “floating” valve plates.

Non-circular planetary gear motor (NCPGM) is a rotated operating units in hydraulic system, mostly used in low viscosity media. The clearance between NCPGM gear end-face and valve plate has a significant influence on volume efficiency and torque characteristics. Analyze the main leakage way of NCPGM, establish its clearance leakage mathematics model. When the power loss caused by clearance leakage and viscous friction is minimized, there is an optimal clearance. Taking into account the machining deviation of the sun gear, planetary gear and inner ring gear, and the mechanical efficiency of the motor, the design adopted a clearance compensation structure by valve plate deformation. The deformation of valve plate under different working pressures is simulated and analyzed, and the clearance value between valve plate and gear end-face under different working pressures was obtained. The leakage characteristics of the motor under different clearances were calculated. The results show that the maximum deformation of valve plate is 14.3μm and the minimum deformation is 1.6μm under rated working pressure of 20MPa. The machining deviation range of sun gear, planetary gear and internal ring gear was obtained. It has a significant meaning to improving NCPGM volume efficiency. Meanwhile, as the motor volume efficiency increases, the output torque is increased.