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Research on Higher Stiffness Aerostatic Bearing

Author: ZhangJunAn
Tutor: FangZongDe
School: Northwestern Polytechnical University
Course: Mechanical Design and Theory
Keywords: Aerostatic bearing Self-controlled Restrictor Pressure groove Higher stiffness Finite difference
CLC: TH133.3
Type: PhD thesis
Year: 2006
Downloads: 879
Quote: 16
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Abstract

Aerostatic bearing is one of the essential elements of precision andultra-precision machines. With the development of precision andultra-precise technology, the aerostatic bearings with excellentstiffness, accuracy and the stability are needed urgently. Because thegas may be compression, especially to enhance the aerostatic bearingstiffness to bring the very major difficulty. Therefore, enhances theaerostatic bearing the stiffness is the aerostatic bearing research areaof one of difficulty and hot spots, belongs to the front question. Thisarticle develops the research work take the project application as thefinal goal, chooses by the traditional advanced version and from thecontrol reducing expenses aerostatic bearing took the research content,the prominent project application characteristic, the theory, theexperiment and the application closely unifies. Mainly from the structure,the parameter improvement and reduces expenses two aspects from thecontrol to do the research work. The research, designed a kind to be ableeffectively to enhance the aerostatic bearing stiffness new from theself-controlled restrictor bearing.This article compared the domestic and foreign each kind in theanalysis to enhance the aerostatic bearing stiffness method in thefoundation, take the pressure groove to carry out the system research asthe key point.The aerostatic thrust bearing with the nozzle hole restrictor is anexample, from the theoretical analysis, the establishment governingequation, the numerical analysis and the experimental aspect studied hasthe pressure groove to enhance the stiffness through two times flow restriction effects the size effect and the design calculation principle,produced has the pressure groove bearing the structural design principleand the performance numerical analysis method. Three examples successesapplications are produced.Applies the equivalent network method, systematically has analyzedeach kind of successful higher stiffness aerostatic bearing basicprinciple, summarizes the idea new changeable restrictor realizationinfinite stiffness bearing 4 characteristics:Ⅰ. The changeablerestrictor should lie aside in the load bearing gas film surface, thisis the aerostatic bearing characteristic requests;Ⅱ. The changeablerestrictor should be gas chamber the internal installation only then hasthe use value;Ⅲ. The changeable restrictor may design the multi-levelrestrictor module which constitutes many classes the restrictor groupsynthesizes;ⅣThe gas film surface pressure through the elastic thinmembrane loading surface feedback, the structure is simple, respondsquickly.The concept of the elastic changeable section pressure groove isproposed. And three in specific way new bearings are proposed with thisconcept as the core: The air pressure reaction in the thrust bearing gapon load makes annular membrane elastically deform. The elasticdeformation brings about changes of throttling area and pressure groovedepth of the bearing; Elastic annular membrane and the rigidity pressuregroove constitute the thrust bearing structure; the air pressure reactionin the journal bearing gap on load makes Lengthwise membrane elasticallydeform. The elastic deformation brings about changes of throttling areaand pressure groove depth of the bearing.The elastic membrane finite difference computation model has beenestablished. The coupling computation process has been designed about the aerostatic bearing computation model with pressure groove and the elasticmembrane finite difference computation model. And has carried on thecoupling computation, obtains the stiffness distinct enhancement thecomputed result. Has explored solves four steps partial differentialequations with the multi-layer grid method (elastic membrane deformedgoverning equation) the iterative process, obtains the success, furtherenhances one of operation efficiency important algorithms.The new type laboratory equipment of the aerostatic thrust bearingfor testing performance has been developed. This is one kind precise alsothe higher automation test laboratory equipment, has in the testautomation bearing gas film gap the pressure distribution, the loadingcapacity as well as gas film thickness function. The exerting the loadnovel spring system for the laboratory equipment has realized continuousand the stable exerting the load, also ease of operationThe new type laboratory equipment of the aerostatic and dynamicaljournal bearing for testing performance has been developed. This is onekind precise also the automation high test system, has in the testautomation bearing gap to the internal pressure distribution, the loadingcapacity as well as gas film thickness function, spindle rotational speedand flow quantity capacity and so on. The exerting the load novel springsystem with the changeable loading direction designs for the laboratoryequipment, causes the examination system module greatly is thesimplification, to build the foundation for high speed rotation theaerostatic and dynamic testing, the data acquisition automation is high,the precision is advantageous for the control. To was measured the bearingdynamic characteristic examination indicated, develops the experimentalsystem could in the more accurate examination bearing rotation processthe spindle center perturbation situation, build the foundation for the development high speed bearing examination.The experimental result hasproven the new bearing system principleaccuracy. The annular membrane elastic deformation on the new thrustbearing the examination result to indicate that, The annular membranewidth and depth all can produce along with the design pressure changesatisfies the control request the criterion change, explained this kindof structure the design and the manufacture and the examination all aresuccessful. The changeable restrictor with the elastic annular membranecombined with changeable section pressure groove action thrust bearingload characteristic examination result realization indicated that,bearing stiffness is everywhere high about the examination scope insideall quite, k=100(N/μm)achieves. To use in the load to change a biggersituation is the possibility with the better use prospect. The elasticannular membrane pressure groove and the rigidity pressure grooveconstitute function the thrust bearing load characteristic examinationresult to indicate that, the bearing stiffness change is bigger in theexamination scope, the most stiffness main point k=100(N/μm) alsoachieves. The bearing is suitable in load no changeable and high precisionand measurement room environment.

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