液压与气压系统中英文对照学习资料Word文档下载推荐.docx

液压与气压系统中英文对照学习资料Word文档下载推荐.docx

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Electrical，mechanical．andfluidpower．Mostapplicationsactuallyuseacombinationofthethreemethodstoobtainthemostefficientoverallsystem．Toproperlydeterminewhichprinciplemethodtouse。

itisimportanttoknowthesalientfeaturesofeachtype．Forexample，fluidsystemscalltransmitpowermoreeconomicallyOvergreaterdistancesthanCanmechanicaltypes．However。

fluidsystemsare

restrictedtoshorterdistancesthanareelectricalsystems．

Hydraulicpowertransmissionsystemaleconcernedwiththegeneration,modulation,andcontrolofpressureandflowand,andingeneralsuchsystemsinclude:

1．Pumpswhichconvertavailablepowerfromtheprimemovertohydraulicpowerattheactuator．

2．Valveswhichcontrolthedirectionofpump--flow，thelevelofpowerproduced，andtheamountoffluid一一flowtotheactuators．Thepowerlevelisdeterminedbycontrollingboththeflowandpressurelevel．

3．ActuatorswhichconverthydraulicpowertousablemechanicalpowerOutputatthepointrequired．

4．Themedium，whichisaliquid，providesrigidtransmissionandcontrolaswellas1ubricationofcomponents，sealinginvalves．andcoolingofthesystem．

5．Connectorswhichlinkthevarioussystemcomponents，providepowerconductorsforthefluidunderpressure，andfluidflowreturntotank（reservoir）．．

6、Fluidstorageandconditioningequipmentwhichensuresufficientqualityandquantityaswellascoolingofthefluid．

7、pneumaticssystemsrequiredalubricatortoinject。

averyfinemistofoilintotheairdischargingfromthepressureregulator．Thispreventswearofthecloselyfittingmovingpartsofpneumatic

Hydraulicsystemsaleusedinindustrialapplicationssuchasstampingpresses，steelmills，andgeneralmanufacturing，agriculturalmachines，miningindustry，aviation，spacetechnology，deep—seaexploration,transportation，marinetechnology，andoffshoregasandpetroleumexploration．Inshort，veryfewpeoplegetthroughadayoftheir1iveswithoutsomehowbenefitingfromthetechnologyofhydraulics2．

Theprincipleofelectrical-dischargemachiningalsocalledelectroisorspark-erosionmachining,isbasedontheerosionofmetalsbysparkdischarges.Weknowthatwhentwocurrent-conductinwiresareallowedtotoucheachother,anarcisproduced.Ifwelookcloselyatthepointofcontactbetweenthetwowires,wenotethatasmallportionofthemetalhasbeenerodedaway,leavingasmallcrater.

ThebasicEDMsystemconsistsofashapetoolandtheworkpiece,connectedtoadcpowersupplyandplacedinadielectricfluidthisisoneofthemostwidelyusedmachiningprocesses,particularlyfordie-sinkingoperationswhenthepotentialdifferencebetweenthetoolandtheworkpieceissufficientlyhigh,atransientsparkdischargesthroughthefluid,removingaverysmallamountofmetalfromtheworkpiecesurface.

Thecapacitordischargeisrepeatedatratesofbetween50,withvoltagesusuallyrangingbetween50vand380vandcurrentsfrom0.1Ato500A.

Mechanicalcontrolincludescamsandgovernors.Althoughtheyhavebeenusedforthecontrolofverycomplexmachines,tobecosteffectively,todaytheyareusedforsimpleandfixed-cycletaskcontrol.Someautomatedmachines,suchasscrewmachines,stillusecam-basedcontrol.Mechanicalcontrolisdifficulttomanufactureandissubjecttowear.

Pneumaticcontrolisstillverypopularforcertainapplications.Itusescompressedair,valves,andswitchstoconstructsimplecontrollogic,butiseasilyslow.Becausestandardcompaonentsareusedtoconstructthelogic,itiseasiertobuildthanamechanicalcontrol.Pneumaticcontrolpartsaresubjecttowear.

Asdoesamechanicalcontrol,anelectromechanicalcontrolusesswitches,relays,timescounters,andsoon,toconstructlogic,itisfasterandmoreflexible.Thecontrollersusingelectromechanicalcontrolarecalledrelaydevices.

Thevaluesintheexpresstherelativetooldistancefromthehomeposition.Thisdistanceisshownintherelativeorincrementalcoordinates,UandW.

whenreadingthevaluesinthenotpossibletoknowdirectlyhowfarthetoolisfromthepartorigin.Justhowfaritisfromthehomeposition.mountedonexhaustportsofairvalvesandactuatorstoreducenoiseandpreventoperatingpersonnelfrompossibleinjuryresultingnotonlyfromexposuretonoisebutalsofromhigh—speedairborneparticles.Thesignofthecoordinatesiszeroornegativebecausethetoolcannotmovefartherthanthemachineorigin.thusatpresent,thevaluesarezerosothetoolisatthehomeposition.Thevaluesinthearenormallyusedwhensettingupthetoolsinordertofindtherealtooldistancesfromthepartorigin.

Thevaluesintheabsolutepositionexpresstheabsolutetooldistancefromthepartorigin.Thisdistanceisshowninshowninabsolutecoordinates,xandz.thesignmaybepositiveornegative,dependingonthequadrantsinwhichthetoolismoving.becauseofthecompressibilityofair，

itisimpossibletoobtainprecisecontrolledactuatorvelocitieswithpneumaticsystems．also，precisepositioningcontrolisnotobtainable．Whilepneumaticpressuresarequitesofaristogood.Thisisanimportantpieceofinformationfortheoperatorwhenmaching,sinceanyvalueintheabsolutepositionisdirectlyrelatedtothepart.

Thesecretofhydraulicsystem’sSUCCESSandwidespreaduseisitsversatilityandmanageability．Fluidpowerisnothinderedbythegeometryoperationswhenthepotentialdifferencebetweenthetoolandtheworkpieceissufficientlyhigh,atransientsparkdischargesthroughthefluid,removingaverysmallamountofmetalfromtheworkpieceofthemachineasistheeaseinmechanicalsystems．Also，powercanbetransmittedinalmostlimitlessquantitiesbecausefluidsystemsarenotsolimitedbythephysical1imitationsofmaterialsasaretheelectricalsystems．Forexample，theperformanceofanelectromagnetislimitedbyThesaturationlimitofsteel．Ontheotherhand，thepowerlimitoffluidsystemsis1imitedonlybythestrengthcapacityofthematerial．

Intheexpresstherelativetooldistancefromthehomeposition.Thisdistanceisshownintherelativeorincrementalcoordinates,UandW.whenreadingthevaluesinthenotpossibletoknowdirectlyhowfarthetoolisfromthepartorigin.

Justhowfaritisfromthehomeposition.Thesignofthecoordinatesiszeroornegativebecausethetoolcannotmovefartherthanthemachineorigin.thusatpresent,thevaluesarezerosothetoolisatthehomeposition.Thevaluesinthearenormallyusedwhensettingupthetoolsinordertofindtherealtooldistancesfromthepartorigin.

Industryisgoingtodependmoreandmoreonautomationinordertoincreaseproductivity．Thisincludesremoteanddirectcontrolofproductionoperations，manufacturingprocesses。

andmaterialshandling．

Fluidpoweristhemuscleofautomationbecauseofadvantagesinthefollowingfourmajorcategories．

1．Easeandaccuracyofcontr01．BytheuseofSimpleleversandpushbuttons，theoperatorofafluidpowersystemCallreadilystart，stop，speeduporslowdown，andpositionforceswhichprovideanydesiredhorsepowerWithtolerancesaspreciseasoneten—thousandthOfaninch．Fig．13—1showsafluidpowersystemwhichallowsallaircraftpilottoraiseandlowerhislandinggear．Whenthepilotmovesasmallcontr01valveinonedirection，oilunderpressureflowstooneendofthecylindertolowerthelandinggear．Toretractthelandinggear，thepilot

movesthevalveleverintheoppositedirection，a110wlng0iltoflowintotheotherendofthecylinder．

2．Multiplicationofforce．Afluidpowersystem（withoutusingcumbersomegears，pulleys，andlevers）CanmultiplyforcesSimplyandefficientlyfromafractionofanouncetoseveralhundredtonsofoutput．

3．Constantforceortorque．Onlyfluidpowersystemsarecapableofprovidingconstantforceortorqueregardlessofspeedchanges．Thisisaccomplishedwhethertheworkoutputmovesafewinchesperhour，severalhundredinchesperminute，afewrevolutionsperhour．orthousandsof

revolutionsperminute．

4．Simplicity，safety，economy．general，fluidpowersystemsusefewermovingpartsthan

comparablemechanicalorelectricalsystems．

Thus，theyalesimplertomaintainandoperate．This，inturn，maximizessafety，compactness，andreliability．Forexample，anewpowersteeringcontr01designedhasmadeallotherkindsofpowersystemsobsoleteonmany

off—highwayvehicles．TheSteeringunitconsistsofamanuallyoperateddirectional

controlvalveandmeterinasinglebody．transportation，marinetechnology，andoffshoregasandpetroleumexploration．Inshort，veryfewpeoplegetthroughadayoftheir1iveswithoutsomehowbenefitingfromthetechnologyofhydraulics2．Becausethesteeringunitisfullyfluid1inked，mechanicallinkages，universaljoints。

bearings，reductiongears，etc．areeliminated．Thisprovidesasimple，compactsystem．Inaddition，verylittleinputtorqueisrequiredtoproducethecontrolneededforthetoughestapplications．Thisisimportantwhere1imitationsofcontrolspacerequireasmallsteeringwheelanditbecomesnecessarytoreduceoperatorfatigue．

Thereareseveraltypesofshaftcouplings;

theircharacteristicsdependonthepruposeforwhichtheyareused.Ifanexceptionallylongshaftisrequiredforalineshaftinthemanufacturingplantorapropellershaftonship,itismadeinsectionsthatarecoupledtogetherwithrigidcouplings.

Additionalbenefitsoffluidpowersystemsincludeinstantlyreversiblemotion。

automatic．protectionagainstoverloads，andinfinitelyvariablespeedcontr01．Fluidpowersystemsalsohavethehighesthorsepowerperweightrati0