| Hydraulic cylinder is the most typical and widely used hydraulic actuator.The traditional hydraulic cylinder is sealed by sealing ring,which can ensure the volume efficiency of the hydraulic cylinder.However,the problem is that the sealing ring is fragile and the friction characteristic greatly affects the high speed performance of the hydraulic cylinder.Researchers tend to improve the situation by improvements of sealing material and structural.But the problem between friction and leakage is not solved radically.The German Haenchen company has developed a low friction high speed hydraulic cylinder with constant clearance seal technology.This constant clearance seal hydraulic cylinder has the characteristics of small friction and fast speed.However,the internal leakage always exists,and the hydraulic cylinder volume efficiency is obviously decreased with the working pressure increasing.There is a contradiction between the sealing performance and working pressure in the hydraulic cylinder.According to the above problems,this article is based on the previous experiments in the laboratory to improve the volumetric efficiency and the high speed of the gap sealing hydraulic cylinder.The theory of clearance gap seal and hydraulic support surface texture lubrication in the hydraulic cylinder is discussed.A technical scheme for adaptive variable clearance is proposed.The main research is as follows:1.A kind of self-compensation variable-clearance sealing hydraulic cylinder with a thin shell structure is put forward for the problem existing in the sealing hydraulic cylinder and constant clearance seal hydraulic cylinder.The compensation mechanism,compensation effect and adaptability of variable clearance seal are studied.The load analysis model of the piston lip in flow field is established.These provide theoretical basis and technical support for design and manufacture.2.The optimization method of the piston structure of variable clearance hydraulic cylinder is studied and the development design is carried out by combining with engineering applications.The influence of the change of the lip length and thickness on the deformation of the piston lip was analyzed.The selection range of the suitable lip length and thickness was determined.Three different types of piston structures are proposed for the same lip size.And the piston structure with the best sealing effect isdetermined by the comparison of the study.3.In view of engineering application,a simplified model of a variable clearance seal structure is proposed.The mathematical model and calculation method of the clearance flow is built,to provide a effective method for the design of self-compensation variable clearance seal of the hydraulic cylinder.At the same time,the influence of piston eccentricity,hydraulic compressibility,viscosity change and thermal expansion on the clearance flow is analyzed.4.The mechanism of texture lubrication,the morphology characterization method and the key factors are analyzed.The design theory and realization method of hydraulic support surface texture lubrication are studied.A diamond-shaped texture with groove is proposed as the texture unit of the inner wall of the cylinder.And the shapes of groove section and texture unit are designed.To effectively improve the friction characteristics between the cylinder and the piston of the hydraulic cylinder,selection principles of the degree of cell density,the groove depth and the ratio of depth and width ratio of the groove are determined,and the implementation of the processing of the cylinder wall surface texture is put forward.5.Combined with the development demands of the variable clearance hydraulic cylinder,the hydraulic cylinder test system platform is developed and the performance of the hydraulic cylinder is tested.Direct and indirect measurements are adopted to measure the static and dynamic internal leakage respectively.The validity of the theoretical research is verified through tests. |
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