# Study on Temperature Characteristics of Lubrication Film of Valve Plate Pair in Axial Piston Pumps
## 1 Introduction  
An axial piston pump provides the benefits of high working pressure and a significant power-to-weight ratio [1]. It is commonly utilized in the military sector, ships, aviation, and construction machinery. Moreover, it can function effectively in high-pressure situations and at varying speeds [2; 3; 4; 5; 6]. The friction pair consisting of the piston cylinder and the valve plate in the axial piston pump is referred to as the valve plate pair. The oil film in the valve plate pair functions to seal and support the load, but it also causes energy loss, affecting the operational efficiency of the piston pump. The factors that affect the lubrication effect of the valve plate pair will result in the efficiency and sustainability of the valve plate pair. In the process of axial piston pump operation, the valve plate pair has high friction due to the influence of uneven forces and off-load moments. At the same time, in the process of work, the pollution of oil [7; 8; 9] and the selection of inappropriate oil will aggravate the friction of the valve plate pair. Aggravating the friction of the valve plate pair affects the efficiency improvement and sustainable work of the valve plate pair while generating a lot of heat, so the film temperature of the valve plate pair will rise. So, studying the temperature characteristics of the valve plate pair is quite important. Many scholars have studied the valve plate pair. [PERSON] et al. [10; 11; 12] studied the lubrication characteristics of the valve plate pair in an axial piston pump, obtained the oil film thickness, pressure, and temperature distribution in the valve plate pair, and analyzed the influence of wedge angle, working pressure, hydraulic oil viscosity, film thickness, and other factors on the film temperature of the valve plate pair. [PERSON] et al. [13] established a thermal elastohydrodynamic lubrication model for slipper pairs, obtained the oil film thickness and pressure distribution of slipper pairs, and studied the influence of different working conditions and structural parameters of slipper pairs on the thermal elastohydrodynamic lubrication performance. Further work studied the power loss characteristics of the slipper pair of an axial piston pump considering thermoelastichydrodynamic deformation and optimized the structural parameters of the slipper pair [14]. [PERSON] et al. [15] established a set of new equations for the pressure distribution, leakage, force, and torque of the seal clearance of the discharge waist groove of the valve plate pair of an axial piston pump, in which the influences of important parameters such as wedge angle, speed, oil film thickness, and silence groove were also considered. In their further study [16], the dynamics of the cylinder block were analyzed, and the relationships between the gap film thickness of the valve plate and the oil pressure and temperature were pointed out. It showed that mixed friction between the cylinder block and valve plate occurred under certain conditions. [PERSON] et al. [17] used a noncontact test scheme to measure the multi-freedom displacement of the cylinder block, indicating that the cylinder block real-timely fluctuates periodically in the multi-freedom displacement. [PERSON] et al. [18] experimentally measured the three-point oil film thickness of the valve plate pair of an axial piston pump, established the oil film shape formula, and inferred that the wedge angle of the valve plate pair was affected by multiple factors. [PERSON] et al. [19] proposed and verified the dynamic seventh-order model to predict the oil film thickness of the valve plate pair in an axial piston pump. [PERSON] et al. [20] studied the aviation axial piston pump and established the thermodynamic model of the slipper pair.