Abstract
The piston-cylinder pair is the key friction pairs in the piston pump. Its performance determines the volume efficiency of piston pump. With the increase of load pressure, the leakage at the clearance of piston-cylinder pair will also increase. In order to reduce leakage, the clearance of the piston-cylinder pair of the ultra-high pressure piston pump is smaller than that of the medium-high pressure piston pump. In order to explore whether the piston will stuck in the narrow gap, it is necessary to study the oil film characteristics of the piston-cylinder pair under the condition of ultra-high pressure, so as to provide a theoretical basis for the optimal design of the piston-cylinder pair of ultra-high pressure axial piston pump. In this paper, an ultra-high pressure axial piston pump is taken as the research object, and its structural characteristics are analyzed. The mathematical model of the oil film thickness of the piston-cylinder pair is established by using the cosine theorem in the cross section of the piston. The finite volume method is used to discretize the Reynolds equation of the oil film of the piston-cylinder pair, and the over relaxation iteration method is used to solve the discrete equations, and the mathematical model of the oil film pressure of the piston-cylinder pair is obtained. The mathematical model of oil film thickness and pressure field of piston-cylinder pair is solved by programming. The dynamic change process of oil film thickness and pressure field of the plunger pair of the ultra-high pressure axial piston pump under the load of 20 MPa and 70 MPa is obtained. Under the two conditions, the thinnest area of the oil film reaches 3 μm and 2 μm dangerous area respectively; the oil film pressure reaches 20 MPa and 70 MPa respectively when the swashplate rotates 10° and continues to increase with the increase of swashplate rotation angle. When the rotation angle reaches 90°, the oil film pressure also reaches the maximum value, but there is no pressure spike phenomenon. The oil film pressure characteristics of ultra-high pressure axial piston pump under conventional and ultra-high pressure conditions were obtained by modification and experimentation.
Highlights
Compared with other transmission modes, hydraulic transmission system has been widely accepted because of its advantages of large power-mass ratio, convenient control, and smooth transmission [1,2,3]
In order to prevent the above situation of the piston-cylinder pair under ultra-high pressure condition, it is necessary to analyze the oil film characteristics of the piston-cylinder pair
In 2009, Zhang Bin of Zhejiang University discussed the experimental method based on the oil film characteristics of the piston-cylinder pair under actual working conditions, and established the virtual prototype simulation model of the axial piston pump
Summary
Compared with other transmission modes, hydraulic transmission system has been widely accepted because of its advantages of large power-mass ratio, convenient control, and smooth transmission [1,2,3]. In 2009, Zhang Bin of Zhejiang University discussed the experimental method based on the oil film characteristics of the piston-cylinder pair under actual working conditions, and established the virtual prototype simulation model of the axial piston pump. Xu Bing and Zhang Junhui of Zhejiang University describe the piston state of oblique axial piston pump of electro-hydrostatic actuator accurately by solving the discrete oil film Reynolds equation and force balance equation iteratively, and obtain the leakage of piston-cylinder pair under high speed and pressure. It provides appropriate theoretical guidance for the design of EHA pump [19]. Under different working conditions are characteristics of the piston-cylinder pairpressure are obtained through
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