Research On Dynamic Pressure Effect Of Middle Pillow Of Hydrostatic Center Rest

Hydrostatic center rack which is used to support for heavy shaft or rotor part is an important component of CNC. It can meet the demand of high process precision. Its lubrication properties directly affect the machining accuracy of work piece. As the technology of hydrostatic center rack is introduced from Germany, ours technology is not very mature and current performance is not very stable. The middle pillow of hydrostatic center rack is easy to be damaged. Therefore, it is necessary to study the oil film of hydrostatic center rack.Firstly, through large amount of reading the related literature and making a summary of radial bearings in china and abroad, the lubrication mechanism and static pressure supportingprinciple of hydrostatic center rack is researched detailedly. The research program of hydrostatic center rack is maked in detail.Secondly, the structure design of middle pillow of hydrostatic center rack is studied detailedly, which including selecting the shape and number of the oil cavity, the arrangement of oil cavity and oil pipe in middle pillow of hydrostatic center rack. The three-dimensional model of middle pillow is established. The basic assumptions and governing equations of CFX finite element analysis software is given. Since it is in turbulent state, the basic equation of turbulence is given.Finally, the oil film of hydrostatic center rack is meshed to hexahedral mesh. The effective bearing area is calculated and the inlet flow formula is derived. The improving suggestion for structure design of middle pillow is provided. By reasonably set the boundary condition, the velocity field,pressure field and dynamic pressure field is simulated. The velocity and pressure distribution, effects of depth of oil cavity, load,viscosity of lubricant oil, width of oil seal edge,spindle speed and relative eccentricity to dynamic pressure are got.Through the simulation of velocity field, pressure field and dynamic pressure field, it can get the flow law of internal flow field of the middle pillow. The critical speed of hydrostatic center rack between stable region and obvious increase region are got. It provides a theoretical basis for the structure optimization of hydrostatic center rack and open type radial sliding bearing in engineering practice.