液压与气压系统外文文献翻译、中英文翻译、外文翻译

外文资料HYDRAULICANDPNEUMATICSYSTEMHydraulicSystemThereareonlythreebasicmethodsoftransmittingpower:electrical,mechanical,andfluidpower.Mostapplicationsactuallyuseacombinationofthethreemethodstoobtainthemostefficientoverallsystem.Toproperlydeterminewhichprinciplemethodtouse,itisimportanttoknowthesalientfeaturesofeachtype.Forexample,fluidsystemscantransmitpowermoreeconomicallyovergreaterdistancesthancanmechanicaltypes.However,fluidsystemsarerestrictedtoshorterdistancesthanareelectricalsystems.Hydraulicpowertransmissionsystemareconcernedwiththegeneration,modulation,andcontrolofpressureandflow,andingeneralsuchsystemsinclude:(1)Pumpswhichconvertavailablepowerfromtheprimemovertohydraulicpowerattheactuator.(2)Valveswhichcontrolthedirectionofpump-flow,thelevelofpowerproduced,andtheamountoffluid-flowtotheactuators.Thepowerlevelisdeterminedbycontrollingboththeflowandpressurelevel.(3)Actuatorswhichconverthydraulicpowertousablemechanicalpoweroutputatthepointrequired.(4)Themedium,whichisaliquid,providesrigidtransmissionandcontrolaswellaslubricationofcomponents,sealinginvalves,andcoolingofthesystem.(5)Connectorswhichlinkthevarioussystemcomponents,providepowerconductorsforthefluidunderpressure,andfluidflowreturntotank(reservoir)(6)Fluidstorageandconditioningequipmentwhichensuresufficientqualityandquantityaswellascoolingofthefluid.Hydraulicsystemsareusedinindustrialapplicationssuchasstampingpresses,steelmills,andgeneralmanufacturing,agriculturalmachines,miningindustry,aviation,spacetechnology,deep-seaexploration,transportation,marinetechnology,andoffshoregasandpetroleumexploration.Inshort,veryfewpeoplegetthroughadayoftheirliveswithoutsomehowbenefitingfromthetechnologyofhydraulics.Thesecretofhydraulicsystem’ssuccessandwidespreaduseisitsversatilityandmanageability.Fluidpowerisnothinderedbythegeometryofthemachineasisthecaseinmechanicalsystems.Also,powercanbetransmittedinalmostlimitlessquantitiesbecausefluidsystemsarenotsolimitedbythephysicallimitationsofmaterialsasaretheelectricalsystems.Forexample,theperformanceofanelectromagnetislimiteddythesaturationlimitofsteel.Ontheotherhand,thepowerlimitoffluidsystemsislimitedonlybythestrengthcapacityofthematerial.Industryisgoingtodependmoreandmoreonautomationinordertoincreaseproductivity.Thisincludesremoteanddirectcontrolofproductionoperations,manufacturingprocesses,andmaterialshanding.Fluidpoweristhemuscleofautomationbecauseofadvantagesinthefollowingfourmajorcategories.(1)Easeandaccuracyofcontrol.Bytheuseofsimpleleversandpushbuttons,theoperatorofafluidpowersystemcanreadilystart,stop,speeduporslowdown,andpositionforceswhichprovideanydesiredhorsepowerwithtolerancesaspreciseasoneten-thousandthofaninch.Fig.1-1showsafluidpowersystemwhichallowsanaircraftpilottoraiseandlowerhislandinggear.Whenthepilotmovesasmallcontrolvalveinonedirection,oilunderpressureflowstooneendofthecylindertolowerthelandinggear.Toretractthelandinggear,thepilotmovesthevalveleverintheoppositedirection,allowingoiltoflowintotheotherendofthecylinder.(2)Multiplicationofforce.Afluidpowersystem(withoutusingcumbersomegears,pulleys,andlevers)canmultiplyforcessimplyandefficientlyfromafractionofanouncetoseveralhundredtonsofoutput.(3)Constantforceortorque.Onlyfluidpowersystemsarecapableofprovidingconstantforceortorqueregardlessofspeedchanges.Thisisaccomplishedwhethertheworkoutputmovesafewinchesperhour,severalhundredinchesperminute,afewrevolutionsperhour,orthousandsofrevolutionsperminute.(4)Simplicity,safety,economy,Ingeneral,fluidpowersystemsusefewermovingpartsthancomparablemechanicalorelectricalsystems.Thus,theyaresimplertomaintainandoperate.This,inturn,maximizessafety,compactness,andreliability.Forexample,anewpowersteeringcontroldesignedhasmadeallotherkindsofpowersystemsobsoleteonmanyoff-highwayvehicles.Thesteeringunitconsistsofamanuallyoperateddirectionalcontrolvalveandmeterinasinglebody.Becausethesteeringunitisfullyfluid-linked,mechanicallinkages,universaljoints,bearings,reductiongears,etc.areeliminated.Thisprovidesasimple,compactsystem.Inaddition,verylittleinputtorqueisrequiredtoproducethecontrolneededforthetoughestapplications.Thisisimportantwherelimitationsofcontrolspacerequireasmallsteeringwheelanditbecomesnecessarytoreduceoperatorfatigue.Additionalbenefitsoffluidpowersystemsincludeinstantlyreversiblemotion,automaticprotectionagainstoverloads,andinfinitelyvariablespeedcontrol.Fluidpowersystemsalsohavethehighesthorsepowerperweightratioofanyknowpowersource.Inspiteofallthesehighlydesirablefeatureoffluidpower,itisnotapanaceaforallpowertransmissionproblems.Hydraulicsystemsalsohavesomedrawbacks.Hydraulicoilsaremessy,andleakageisimpossibletocompletelyeliminate.Also,mosthydraulicoilscancausefiresifanoilleakinanareaofhotequipment.PneumaticSystemPneumaticsystemsarepressurizedgasestotransmitandcontrolpower.Asthenameimplies,pneumaticsystemstypicallyuseair(ratherthansomeothergas)asthefluidmediumbecauseairisasafe,low-cost,andreadilyavailablefluid.Itisparticularlysafeinenvironmentswhereanelectricalsparkcouldigniteleaksfromsystemcomponents.Inpneumaticsystem,compressorsareusedtocompressandsupplythenecessaryquantitiesofair.Compressorsaretypicallyofthepiston,vaneorscrewtype.Basicallyacompressorincreasesthepressureofagasbyreducingitsvolumeasdescribedbytheprefectgaslaws.Pneumaticsystemsnormallyusealargecentralizedaircompressorwhichisconsideredtobeaninfiniteairsourcesimilartoanelectricalsystemwhereyoumerelyplugontoanelectricaloutletforelectricity.Inthisway,pressurizedaircanbepipedfromonesourcetovariouslocationsthroughoutanentireindustrialplant.Thecompressedairispipedtoeachcircuitthroughanairfiltertoremovecontaminantswhichmightharmthecloselyfittingpartsofpneumaticcomponentssuchasvalveandcylinders.Theairthenflowsthroughapressureregulatorwhichreducesthepressuretothedesiredlevelfortheparticularcircuitapplication.Becauseairisnotagoodlubricant(containsabout20%oxygen),pneumaticssystemsrequiredalubricatortoinjectaveryfinemistofoilintotheairdischargingfromthepressureregulator.Thispreventswearofthecloselyfittingmovingpartsofpneumaticcomponents.Freeairfromtheatmospherecontainsvaryingamountsofmoisture.Thismoisturecanbeharmfulinthatitcanwashawaylubricantsandthuscauseexcessivewearandcorrosion.Hence,insomeapplications,airdriersareneededtoremovethisundesirablemoisture.Sincepneumaticsystemsexhaustdirectlyintotheatmosphere,theyarecapableofgeneratingexcessivenoise.Therefore,mufflersaremountedonexhaustportsofairvalvesandactuatorstoreducenoiseandpreventoperatingpersonnelfrompossibleinjuryresultingnotonlyfromexposuretonoisebutalsofromhigh-speedairborneparticles.Thereareseveralreasonsforconsideringtheuseofpneumaticsystemsinsteadofhydraulicsystems.Liquidsexhibitgreaterinertiathandogases.Therefore,inhydraulicsystemstheweightofoilisapotentialproblemwhenacceleratinganddeceleratingactuatorsandwhensuddenlyopeningandclosingvalves.DuetoNewton’slawofmotion(forceequalsmassmultipliedbyacceleration),theforcerequiredtoaccelerateoilismanytimesgreaterthanthatrequiredtoaccelerateanequalvolumeofair.Liquidsalsoexhibitgreaterviscositythandogases.Thisresultsinlargerfrictionalpressureandpowerlosses.Also,sincehydraulicsystemsuseafluidforeigntotheatmosphere,theyrequirespecialreservoirsandno-leaksystemdesigns.Pneumaticsystemsuseairwhichisexhausteddirectlybackintothesurroundingenvironment.Generallyspeaking,pneumaticsystemsarelessexpensivethanhydraulicsystems.However,becauseofthecompressibilityofair,itisimpossibletoobtainprecisecontrolledactuatorvelocitieswithpneumaticsystems.Also,precisepositioningcontrolisnotobtainable.Whilepneumaticpressurearequitelowduetocompressordesignlimitations(lessthan250psi),hydraulicpressurecanbeashighas10,000psi.Thus,hydraulicscanbehigh-powersystems,whereaspneumaticareconfinedtolow-powerapplications.Industrialapplicationsofpneumaticsystemaregrowingatarapidpace.Typicalexamplesincludestamping,drilling,hoist,punching,clamping,assembling,riveting,materialshandling,andlogiccontrollingoperations.

中文翻译液压与气压系统一、液压系统仅有以下三种基本方法传递动力：电气、机械和流体。大多数应用系统实际上是将三种方法组合起来而得到最有效的最全面的系统。为了合理的确定采取那种方法，重要的是了解各种方法的显著特征。例如液压系统在长距离上比机械系统更能经济地传递动力。然而液压系统与电气系统相比，传递动力的距离较短。液压动力传递系统涉及电动机、调节装置及压力和流量控制，总的来说，该系统包括：泵：将原动机的能力转化成作用在执行部件上的液压能。阀：控制泵产生的流体的运动方向，产生的功率的大小，以及到达执行部件的流体的流量。功率大小取决于对流量和压力大小的控制。执行部件：将液压能转化成可用的机械能。介质即油液：可进行无压缩传递和控制，同时可以润滑部件，使阀体密封和系统冷却。联接件：联接各个系统部件，为压力流体提供功率传输通路，将液体返回油箱（贮藏器）。油液贮存和调节装置：用来确保提供足够质量和数量并冷却的液体。液压系统在工业中应用广泛，例如冲压、钢类工件的磨削及一般加工业、农机、矿业、航天技术、深海勘探、运输、海洋技术，近海天然气和石油勘探等行业，简而言之，在日常生活中很少有人不从液压技术中得到某种益处。液压系统成功而又广泛使用的秘密在于它的通用性和易操作性。液压动力传递不会像机械系统那样受到机械几何形体的制约，另外，液压系统不会像电气系统那样受到材料物理性能的制约，它对传递功率几乎没有量的限制。例如，一个电磁体的性能受到钢的磁饱和极限的限制，相反，液压系统的功率仅仅受材料强度的限制。企业为了提高生产率将越来越依靠自动化，这包括远程和直接的控制生产操作、加工过程和材料处理等。液压动力之所以成为自动化的重要组成部分，是因为它有如下主要的四种优点：(1)控制方便精确通过操作一个简单的操纵杆和按扭，液压系统的操作者便能立即启动、停止、加减速和能提供任意功率、位置精度为万分之一英寸的位置控制力。例如一个飞机驾驶员升起和落下起落架的液压系统，当飞行员向某方向移动控制阀，压力油流入液压缸的某一腔从而降下起落架。飞行员向相反方向移动控制阀，允许油液进入液压缸的另一腔来收回起落架。(2)增力一个液压系统（没有使用笨重的齿轮、滑轮和杠杆）能简单有效地将不到一盎司的力放大产生几百吨力的输出。(3)恒力或恒扭矩只有液压系统能提供不随速度变化而变化的恒力或恒扭矩，它可以驱动对象从每小时移动几英寸到每分钟移动几百英寸，从每小时几转到每分钟几千转。(4)简单、安全、经济总的来说，液压系统比机械或电气系统使用更少的运动部件，因此，它们运行与维护简便