中英文文獻翻譯

英文原文Hydraulicactuationsystemdesignandcomputation1.clearingaboutthedesignrequesttocarryontheoperatingmodeanalysis.Whendesignhydraulicsystembelow,firstshouldbeclearaboutthequestion,andtakesitasthedesignbasis.Mainengineuse,technologicalprocess,overalllayoutaswellastohydraulicgearpositionandspatialsizerequest;Themainenginetothehydraulicsystemperformancerequirement,liketheautomaticity,thevelocitymodulationscope,themovementstability,thecommutationpointingaccuracyaswellastherequestwhichtothesystemefficiency,warmpromotes;Hydraulicsystemworkingconditions,liketemperature,humidity,vibrationimpactaswellaswhetherhassituationandsooncorrosivenessandheat-sensitivematerialexistence.Inintheaboveworkfoundation,shouldcarryontheoperatingmodeanalysistothemainengine,theoperatingmodeanalysisincludingthemovementanalysisandthemechanicalanalysis,alsomustestablishtheloadandtheoperatingcyclecharttothecomplexsystem,fromthisunderstoodthehydrauliccylinderortheoilmotorloadandthespeedchangeasnecessarytherule,belowmakestheconcreteintroductiontotheoperatingmodeanalysiscontentmovementsanalysesThemainenginefunctionalelementaccordingtothetechnologicalrequirementmovementsituation,mayusethedisplacementcirculationchart(L—t),thespeedcirculationchart(v—t),orthespeedandthedisplacementcirculationchartindicated,fromthiscarriesontheanalysistothemovementrule.displacementscirculationattemptsL—tThechart1.1isthehydraulicpresshydrauliccylindermovesthecirculationchart,they-coordinateLexpressionpistonmoves,thex-coordinatetexpressionstartsfromthepistontotherepositiontime,therateofcurveexpressionmovementofplungerspeed.、speedscirculationchartv—t(orv—L)Intheprojectthehydrauliccylindermovementcharacteristicmayinduceisthreekindoftypes.Thechartisthreekindoftypeshydrauliccylindersv—tchart,thefirstkindoflikechart1.2centersolidlinesshow,thehydrauliccylinderstartstomaketheuniformacceleratedmotion,thenuniformmotion,

Chart1.2speedscirculationchartFinallyuniformretardedmotiontoendpoint;Thesecondkind,thehydrauliccylinderprecedingpartlymakestheuniformacceleratedmotionintheoveralltravellingschedule,inanotheronepartlymakestheuniformretardedmotion,alsotheaccelerationvalueisequal;Thethirdkind,thehydrauliccylinderonemostabovemakestheuniformacceleratedmotionintheoveralltravellingschedulebyasmalleracceleration,thenuniformdeceleratestothetravellingscheduleendpoint.V—tchartthreevelocitycurve,notonlyclearlyhasindicatedthreekindoftypeshydrauliccylindersmovementrule,alsoindirectlyhasindicatedthreekindofoperatingmodesdynamicperformance.mechanicalanalyseshydrauliccylindersloadsanddutycyclecharthydrauliccylindersloadstrengthcomputations(1.1)Whentheoperatingmechanismmakesthestraightreciprocatingmotion,thehydrauliccylindermustovercometheloadiscomposedbysixparts(1.1)F=F+F+F+F+F+FcfigmbIntheformula:FcInordertoresistancetocutting;FfInordertofrictiondrag;FiForinertiaresistance;FgForgravity;FmInordertosealtheresistance;FbInordertodraintheoiltheresistance.hydrauliccylinderscycleofmotionvariousstagesoverallloadstrengthThehydrauliccylindercycleofmotionvariousstagesoverallloadstrengthcomputation,generallyincludesthestartacceleration,quicklyenters,thelaborenters,quicklydrawsback,deceleratesappliesthebrakeandsoonseveralstages,eachstageoverallloadstrengthhasthedifference.(1)startstheaccelerationperiod:Bynowthehydrauliccylinderorthepistonwereinfromstaticenoughtostartsandacceleratestothecertainspeed,itsoverallloadstrengthincludingguiderailfrictionforce,packingassemblyfrictionforce(accordingtocylindermechanicalefficiencyqm=0.9computation),gravityandsoonitem,namely:F二F二七+F+F+F+Fb(1.2)faststage:(1.3)thelaborentersthestage:F=F+^+F+F+F (1.4)decelerates:F=氣+F+F+F+Fb (1.5)Tothesimplehydraulicsystem,theabovecomputationprocessmaysimplify.Forexampleusesthesingleproportioningpumptosupplytheoil,onlymustcalculatethelabortoenterthestagetheoverallloadstrength,ifthesimplesystemusesthelimitingpressuretypevariabledisplacementpumporapairofassociationpumpsfortheoil,thenonlymustcalculatethefaststageandthelaborentersthestagetheoverallloadstrength.

oilmotorsloadWhentheoperatingmechanismmakestherotarymotion,theoilmotormustovercometheoutsideloadis:M=M+Mf+M (1.6)operatingdutiesmomentofforceMe.Theoperatingdutymomentofforceispossiblyadefinitevalue,alsopossiblyasnecessarychanges,shouldcarryontheconcreteanalysisaccordingtothemachineworkingcondition.frictionmoments.Inordertorevolvethepartjournalplacefrictionmoment,itsformulais:Mf=GFR(N-M) (1.7)Intheformula:Gisrevolvesthepartweight(N);Fistherubbingfactor,whenthestartforthefactor,afterthestartformovestherubbingfactor;Risthejournalradius(m).momentofinertiaMi.Themomentofinertiawhichinordertorevolvethepartaccelerationordecelerateswhenproduces,itsformulais:(1.8)Intheformula:sIstheangleacceleration(r/sIntheformula:sIstheangleacceleration(r/s2);Atistheaccelerationordeceleratesthetime(s);Jis1GD2：4Grevolvesthepartrotationinertia(Kg-m2),1GD2：4GIntheformula:GD2Inordertorotatetheparttheflywheeleffect(N-M2).Eachkindmaylookup<MachinedesignHandbook>Accordingtothetype(1.6),separatelyfiguresouttheoilmotorinaoperatingcyclevariousstagesloadsize,thenmaydrawuptheoilmotorthedutycyclechartdeterminationshydraulicsystemmainparameterhydrauliccylindersdesigncalculationsinitiallydecidesthehydrauliccylinderworkingpressureInthehydrauliccylinderworkingpressuremainbasiscycleofmotionvariousstagesbiggestoverallloadstrengthdetermined,inadditionbelow,butalsoneedstoconsiderthefactor:eachkindofequipmentdifferentcharacteristicandusesituation.considerationseconomiesandtheweightfactor,thepressureelectslowly,thenpartsizebig,theweightisheavy;Thepressurechooseshighsomewhat,thenpartsizesmall,theweightislight,buttothepartmanufactureprecision,thesealingpropertyrequestshigh.Therefore,thehydrauliccylinderworkingpressurechoicehastwoways:One,electsaccordingtothemechanicaltype;Two,accordingtocutstheloadtoelect.Ifthetable2.1,thetable2.2shows.Thetable2.1pressestheloadtochoosetheexecutionfiletheworkingpressureLoad/N<5000500?1000010000?2000020000?3000030000?50000>50000Workingpressure/MPa<0.8-11.5?22.5?33?44?5>5Thetable2.2pressesthemechanicaltypetochoosetheexecutionfiletheworkingpressureMechanicaltypeEnginebedFarmmachineryProjectmachineryGrinderAggregatemachine-toolDragonGatedigsthebedBroachingmachineWorkingpressure/MPaa<23?5<88?1010?1620?32oilmotorsdesigncalculationcomputationsoilmotordisplacementUnderoilmotordisplacementaccordingtothetypedecidedthat,V=6.28T/AP門.(m3/r) (2.1)AP「Intheformula:Tistheoilmotorloadmomentofforce(N,m); Foroilmotorimportandexportpressuredifference(n/m3);istheoilmotormechanicalefficiency,thecommongearandtheplungermotortakes0.9?0.95,theleafblademotortakes0.8?0.9.computationsoilmotorneedsthecurrentcapacityoilmotorthemaximumcurrentcapacityq=Vn (m3/s) (2.2)Intheformula:Vistheoilmotordisplacement(m3/r);nistheoilmotorhighestrotationalspeed(r/s).hydraulicpressurepartschoicehydraulicpumpsdeterminationswithneedthepowerthecomputationdeterminesthehydraulicpumpthebiggestworkingpressure.Thehydraulicpressurepumpingstationmusttheworkingpressuredetermination,mainlyactsaccordingtothehydrauliccylinderintheoperatingcyclevariousstagestohavemosttremendouspressurep1,inadditiontheoilpumplosesSigmaDeltaptheoilmouthtothecylinderplacealwayspressureSA,pnamelyPb=p+ZAP (3.1)

YaD1△△Ploses,thepipelineincludingtheoilaftertheflowvalveandotherpartslocalpressuresalongtheregulationlossandsoon,beforesystempipelinedesign,mayactaccordingtothesimilarsystemexperiencetoestimate,commonpipelinesimplethrottlevalvevelocitymodulationsystemZAis(2~5)x105Pa,withthevelocitymodulationvalveandpipelinecomplexsystemZapis(5velocitymodulationvalveandpipelinecomplexsystemZapis(5?15)x105Pa,Zapalsomayonlyconsiderflowsaftervariouscontrolvalvespressureloss,butignoresthecircuitryalongtheregulationloss,variousvalvesratedpressurelosesmaysearchesfromthehydraulicpressureparthandbookortheproductsample,Alsomayrefertothetable1.3selectionsThetable3.1iscommonlyused,thelowpressureeachkindofvalvepressureloses(Ip)ValveApn(x105Pa)ValveApn(x105Pa)ValveApn(x105Pa)ValveApn(x105Pa)Cone-wayvalve0.3?0.5Cone-wayvalve3?8Cone-wayvalve1.5?2Cone-wayvalve1.5?2Crossvalve1.5?3Crossvalve2?3Crossvalve1.5?3Crossvalve3?5determinesthehydraulicpumpcurrentcapacityqBPumpsthecurrentcapacityqbasisfunctionalelementoperatingcyclemustthemaximumcurrentcapacityqandthesystemdivulgesthedeterminationAtthesametimewhenmorethanhydrauliccylindersmovement,thehydraulicpumpcurrentcapacitymustbebiggerthanthemaximumcurrentcapacitywhichatthesametimethemovementseveralhydrauliccylinders(ormotor)needs,andshouldconsiderthesystemdivulgingwearsthevolumetricefficiencydropafterthehydraulicpump,namelyqB=K(zq) (m3/s) (3.2)Intheformula:Kisthesystemleakagecoefficient,generallytakes1.1?1.3,thegreatcurrentcapacitytakesthesmallvalue,thesmallcurrentcapacitytakesthegreatvalue(Zq) ;Foratthesametimemaxmovementhydrauliccylinder(ormotor)isbiggest(m3/s).choosesthehydraulicpumpthespecificationTable3.2hydraulicpumpsoveralleffectivenessindicesHydraulicpumpGearpumptypeThescrewrodVanepumpRampumppumps

HydraulicpumpGearpumptypeOveralleffectiveness0.6Overalleffectiveness0.6?0.7index0.65?0.800.60?0.750.80?0.85Rotationalspeedandpumpswhichaccordingtotheabovepower,mayselectthestandardelectricmotorfromtheproductsample,againcarrieson,causeswhentheelectricmotorsendsoutthemaximumworkrate,inpermissionscope.valvesclasspartschoicechoicesbasesThechoicebasisis:Ratedpressure,maximumcurrentcapacity,movementway,installmentfixedway,pressurelossvalue,operatingperformanceparameterandworkinglifeandsoon.selectorvalvesclasspartsshouldpayattentionquestionshouldselectthestandardstereotypiaproductasfaraspossible,onlyifdoesnothavealreadytimeonlythenindependentlydesignsspecial-purpvalvesclasspartsspecificationmainbasisclassafterthisvalvefatliquormosttremendouspressureandmaximumcurrentcapacityselection.Whenchoosestheoverflowvalve,shouldaccordingtothehydraulicpumpmaximumcurrentcapacityselection;Whenchoosesthethrottlevalveandthevelocitymodulationvalve,shouldconsideritsminimumstablecurrentcapacitysatisfiesthemachinelow-speedperformancetherequestaccumulatorschoicesaccumulatorsuseintosupplementwhenthehydraulicpumpsuppliestheoilinsufficiency,itsdischargeablecapacityisV=ZALK一qt(m3) (3.3)ii BIntheformula:Aisthehydrauliccylinderactivesurface(m2);Listhehydrauliccylindertravellingschedule(m);Kisthehydrauliccylinderlosscoefficient,whentheestimatemaytakeK=1.2;Suppliestheoilcurrentcapacityforthehydraulicpump(m3/s);Tistheoperatingtime(s).accumulatorsmaketheemergencyenergy,itsdischargeablecapacityis:V=ZAL一qt(m3) (3.4)iiBWhentheaccumulatorusesinabsorbsthepulsationtorelaxthehydraulicpressureimpact,shouldtakeitasinthesystemalinkiftobeconnectedpartiallytogethersynthesizesconsidersitsdischargeablecapaciAccordingtothedischargeablecapacitywhichextractsandconsideredotherrequests,thenchoosestheaccumulatortheformpipelineschoicesdrilltubingstypeschoiceInthehydraulicsystemusesthedrilltubingdividesthehardtubeandthehose,thechoicedrilltubingshouldhaveenoughpassesflowsthesectionandthebearingpressureability,simultaneously,shouldreducethepipelineasfaraspossible,avoidstheextremeturnandthesectionsuddenchange.steelpipes:Centerthehightensionsystemselectstheseamlesssteelpipe,thelowpressuresystemselectstheweldedsteelpipe,thesteelpipepricelowly,performancegood,theuseiswidespreadcopperpipes:Thecoppertubeworkingpressurebelow6.5~10MPa,theinstabletune,isadvantageousfortheassembly;Yellowcopperpipewithstandingpressurehigher,reaches25MPa,wasinferiortothecoppertubeiseasytobecurving.Copperpipepricehigh,earthquakeresistanceabilityweak,iseasytocausethefatliquoroxidation,shouldasfaraspossiblelittleuse,onlyusesinthehydraulicunittomatchmeetsnottheconvenientspot.drilltubingssizesdeterminationdrilltubingsinsidediametersdpressesdownthetypecomputationIntheformula:Qispassesthedrilltubingthemaximumcurrentcapacity(mWs);Vspeedofflowwhichpermitsforthepipelinein(m/s).Thecommonoilsuctionpipetakes0.5~5(m/s);Thepressureoilpipetakes~5(m/s);Theoilreturnpipetakes1.5~2(m/s).drilltubings<5sizesdetermination8 >P?—(Q) (3-5)2Intheformula:Pisinthetubethebiggestworkingpressure;Whennisthesafetycoefficient,steelpipep<7MPa,takesn=8;Whenp<17.5MPa,takesn=6;Whenp>17.5MPa,takesn=4.Accordingtodrilltubinginsidediameterandwallthicknesswhichcalculates,looksupthehandbookselectionstandardspecificationdrilltubingfueltankdesignThefueltankfunctionistheoilstorage,dispersestheoildischargethequantityofheat,intheprecipitationoiltheimpurity,isleisurelyintheoilthegasfueltanksdesignsmainpointfueltanksshouldhavetheenoughvolumetosatisfytheradiation,simultaneouslyitsvolumeshouldguaranteeinthesystemthefatliquorcompletelyflowswhenthefueltankdoesnotseepout,thefatliquorliquidlevelshouldnotsurpassthefueltankhighly80%.suctionboxestubesandtheoilreturnpipespacingshouldbeasfaraspossiblebigfueltanksbasesshouldhavethesuitableascent,releasestheoilmouthtosettothemostlowspot,inordertodrainstheoiloilfilterschoicesChoosestheoilfilterthebasistohavefollowingseveralbearingcapacitiesAccordingtosystempipelineworkingpressuredetermination.filterstheprecision:Accordingtoisprotectedtheparttheprecisionrequestdeterminationflowtheability:Accordingtothroughmaximumcurrentcapacitydetermination.resistancepressuredrops:Shouldthesatisfiedfiltermaterialintensityandthecoefficientrequest.hydraulicsystemsperformanceInordertojudgethehydraulicsystemthedesignquality,needstolosetothesystempressure,togiveoffheat,theefficiencyandsystemdynamiccharacteristicandsooncircuitriespressurelosesAfterhydraulicpressurepartspecificationmodelandpipelinesizedetermination,maythemoreaccuratecomputingsystempressureloss,thepressurelossinclude:Theoilloses,△p^thelocalpressureafterthepipelineApalongtheregulationpressuredamagesflowsafterthevalveclasspartpressurelossAP^,namely:AP=AP^+APC+AP^ (4.1)Systemadjustmentpressure:P0>P+AP (4.2)Intheformula:PQForhydraulicpumpworkingpressureorlegadjustmentpressure;PJnordertoexecutionworkingpressure.IfcalculatesAPintheprimaryelectionsystemworkingpressuretimetheissketchierthandesignationpressuretoloseismuchbiggerthan,shouldremoveentirerelatedpart,auxiliaryspecification,againdefinitepipelinesize.systemsgiveoffheatThesystemgivesoffheatoriginatesfromthesysteminteriorenergyloss,likethehydraulicpumpandthefunctionalelementpowerloss,theoverflowvalveoverflowloses,thehydraulicvalveandthepipelinepressurelossandsoon.ThesystemgivesoffheatthepowerPcomputationP=P(1-n)(W) (4.3)BIntheformula:PBisthehydraulicpumppowerinput(W);nIsthehydraulicpumpoveralleffe(indexIfinaoperatingcyclehasseveralworkingprocedures,thenmayactaccordingtoeachworkingprocedurethecalorificcapacity,extractsthesystemunittimetheaveragecalorificcapacity:1P=—YPb(1-n叫(W) (4.4)i=1 1 1Intheformula:Tistheoperatingcyclecycle(s);qForiworkingprocedureoperatingtime(s);piisinthecirculationtheiworkingprocedurepowerinput(W).systemsefficiencyThehydraulicsystemefficiencyisbythehydraulicpump,thefunctionalelementandthehydraulicpressurereturnrouteefficiencydeterminedThehydraulicpressure^ returnrouteefficiencygenerallymayusethetypetocalculate:(4.5)Pq+P&+..…nc='Pq2+2Pqb1b2 b2b2(4.5)Intheformula:p1,q1；p2，q2； Foreachfunctionalelementworkingpressureandcurrentcapacity;pB1，qB1；pB2，qB2iseachhydraulicpumpsuppliestheoilpressureandthecurrentcapacity.Hydraulicsystemoveralleffectivenessindex:(4.6)Intheformula:門^Forhydraulicpumpoveralleffectivenessindex;門Inordertofunctionalelementoveralleffectivenessindex;門ForreturnrouteefficiencydrawsuptheregularworkermappingandthecompilationtechnologydocumentPassesthroughafterthehydraulicsystemperformanceandtheessentialrevision,thenmaydrawuptheregularworkermapping,itincludingplanhydraulicsystemschematicdiagram,systempipelineassemblydrawingandeachkindofnon-standardpartdesigndrawing.Intheofficialhydraulicsystemschematicdiagrammustmarkvarioushydraulicpressurepartthemodelspecification.Regardingautomaticityhigherenginebed,butalsoshouldincludethemovementpartthecycleofmotionchartandtheelectro-magnet,thepressureswitchactivestatus.determinationshydraulicsystemparameterMayknowbytheoperatingmodeanalysisin,thelaborentersthestagetheloadstrengthtobebiggest,therefore,thehydrauliccylinderworkingpressureaccordingtothisloadstrengthcomputation,accordingtothehydrauliccylinderandtheloadrelations,p1=40x105Pa.Thisenginebedforthedrillholeaggregatemachine-tool,forpreventeddrillsthroughbeforewhenoccursflushesthephenomenon,thehydrauliccylinderoildischargecavityshouldhavethebackpressure,、p2=6x105Pa,forcausesquicklytoenterquicklydrawsbackthespeedtobeequal,selects=2A2thedifferentialmotioncylinder,thehypothesisquicklyenterstheoildischargepressurewhich,quicklydrawsbacktoloseforAp=7x105Pa.choiceshydraulicpressurepartchoosesthehydraulicpumpandtheelectricmotordeterminesthehydraulicpumptheworkingpressure.Fronthaddeterminedthehydrauliccylinderthebiggestworkingpressurefor40x105Pa,selectstheintakepiperoadpressuretoloseAp=8x105Pa,itsadjustmentpressureisgenerallybiggerthanthesystembiggestworkingpressure5x105Pa,thereforepumpsworkingpressurePB=(40+8+5)x105=53x105PaThisistheworkingpressurewhichthehigh-pressuredsmallcurrentcapacitypumps.Thehydrauliccylinderquicklydrawsbackwhentheworkingpressurequicklyenterswhenisbiggerthan,takesitspressuretoloseDeltap'=4x105Pa,thenquicklydrawsbacktimepumpstheworkingpressureis:PB=(16.4+4)x105=20.4x105PaThisistheworkingpressurewhichthelowpressuregreatcurrentcapacitypumps.hydraulicpumpscurrentcapacities.Quicklyenterswhenthecurrentcapacityisbiggest,itsvalueis30L/min,thequantityenterswhenthelabor,itsvalueis0.51L/min,takesK=1.2,Then: qB=1.2x0.5x10-3=36L/minBecausetimetheoverflowvalvesteadyworkmostissmallis3L/min,thereforeslightlypumpsthecurrentcapacitytotake3.6L/minCalculatesaccordingtoabove,selectstheYYB-AA36/6Bdoublejointvanepumpdefinitepipelinessizes:Accordingtotheworkingpressureandthecurrentcapacity,accordingtothetype(3.5),thetype(3.6)determinethepipelineinsidediameterandwallthickness,(Omits)determinationsfuel-tankcapacityfuel-tankcapacitymayaccordingtotheempiricalformulaestimate,takeV=(5?7)q.Inthisexample:V=6q=6(6+36)=252Lrelatedsystemperformanceomits.中文翻譯中文翻譯液壓傳動系統(tǒng)設計與計算1.明確設計要求進行工況分析在設計液壓系統(tǒng)時，首先應明確以下問題，并將其作為設計依據。主機的用途、工藝過程、總體布局以及對液壓傳動裝置的位置和空間尺寸的要求；主機對液壓系統(tǒng)的性能要求，如自動化程度、調速范圍、運動平穩(wěn)性、換向定位精度以及對系統(tǒng)的效率、溫升等的要求；液壓系統(tǒng)的工作環(huán)境，如溫度、濕度、振動沖擊以及是否有腐蝕性和易燃物質存在等情況。在上述工作的基礎上，應對主機進行工況分析，工況分析包括運動分析和動力分析，對復雜的系統(tǒng)還需編制負載和動作循環(huán)圖，由此了解液壓缸或液壓馬達的負載和速度隨時間變化的規(guī)律，以下對工況分析的內容作具體介紹。1.1運動分析主機的執(zhí)行元件按工藝要求的運動情況，可以用位移循環(huán)圖(L—t)，速度循環(huán)圖(v—t)，或速度與位移循環(huán)圖表示，由此對運動規(guī)律進行分析。1.1.1位移循環(huán)圖L-t圖1.1為液壓機的液壓缸位移循環(huán)圖，縱坐標L表示活塞位移，橫坐標t表示從活塞啟動到返回原位的時間，曲線斜率表示活塞移動速度。1.1.2速度循環(huán)圖v—t(或v—L)工程中液壓缸的運動特點可歸納為三種類型。圖1.2為三種類型液壓缸的v—t圖，第一種如圖1.2中實線所示，液壓缸開始作勻加速運動，然后勻速運動，最后勻減速運動到終點；第二種，液壓缸在總行程的前一半作勻加速運動，在另一半作勻減速運動，且加速度的數值相等；第三種，液壓缸在總行程的一大半以上以較小的加速度作勻加速運動，然后勻減速至行程終點。v—t圖的三條速度曲線，不僅清楚地表明了三種類型液壓缸的運動規(guī)律，也間接地表明了三種工況的動力特性。1.2動力分析動力分析，是研究機器在工作過程中，其執(zhí)行機構的受力情況，對液壓系統(tǒng)而言，就是研究液壓缸或液壓馬達的負載情況。1.2.1液壓缸的負載及負載循環(huán)圖液壓缸的負載力計算工作機構作直線往復運動時，液壓缸必須克服的負載由六部分組成：F=F+F+F+F+F+Fcfigmb (1.1)式中：Fc為切削阻力；Ff為摩擦阻力；Fi為慣性阻力；Fg為重力；Fm為密封阻力；Fb為排油阻力。液壓缸運動循環(huán)各階段的總負載力液壓缸運動循環(huán)各階段的總負載力計算，一般包括啟動加速、快進、工進、快退、減速制動等幾個階段，每個階段的總負載力是有區(qū)別的。啟動加速階段：這時液壓缸或活塞處于由靜止到啟動并加速到一定速度，其總負載力包括導軌的摩擦力、密封裝置的摩擦力(按缸的機械效率門=0.9計算)、重力和慣性力等項，即：TOC\o"1-5"\h\z\o"CurrentDocument"F=F+F+F+F+F (1.2)快速階段：\o"CurrentDocument"F=F+F+F+F (1.3)工進階段：□\o"CurrentDocument"F=F+F+F+F+Fb (1.4)減速：\o"CurrentDocument"F=F+F+F+F+F (1.5)對簡單液壓系統(tǒng)，上述計算過程可簡化。例如采用單定量泵供油，只需計算工進階段的總負載力，若簡單系統(tǒng)采用限壓式變量泵或雙聯(lián)泵供油，則只需計算快速階段和工進階段的總負載力。1.2.2液壓馬達的負載工作機構作旋轉運動時，液壓馬達必須克服的外負載為：TOC\o"1-5"\h\z\o"CurrentDocument"M=M+M$+M (1.6)工作負載力矩Me。工作負載力矩可能是定值，也可能隨時間變化，應根據機器工作條件進行具體分析。摩擦力矩Mf。為旋轉部件軸頸處的摩擦力矩，其計算公式為：\o"CurrentDocument"Mf=GFR(N-M) (1.7)式中：G為旋轉部件的重量(N)；f為摩擦因數，啟動時為靜摩擦因數，啟動后為動摩擦因數；R為軸頸半徑(m)。慣性力矩M。為旋轉部件加速或減速時產生的慣性力矩，其計算公式為：\o"CurrentDocument"M=J心(N-M) (1.8)式中：￡為角加速度(r/s2)；電為角速度的變化(r/s)；At為加速或減速時間(s)；J為旋轉部件的轉動慣量(Kg-m2)，。J=1GD2.4G式中：GD2為回轉部件的飛輪效應(N-M2)。各種回轉體的GD2可查《機械設計手冊》。根據式(1.6)，分別算出液壓馬達在一個工作循環(huán)內各階段的負載大小，便可繪制液壓馬達的負載循環(huán)圖2確定液壓系統(tǒng)主要參數2.1液壓缸的設計計算2.1.1初定液壓缸工作壓力液壓缸工作壓力主要根據運動循環(huán)各階段中的最大總負載力來確定，此外，還需要考慮以下因素：各類設備的不同特點和使用場合?？紤]經濟和重量因素，壓力選得低，則元件尺寸大，重量重；壓力選得高一些，則元件尺寸小，重量輕，但對元件的制造精度，密封性能要求高。所以，液壓缸的工作壓力的選擇有兩種方式：一是根據機械類型選；二是根據切削負載選。如表2.1、表2.2所示。表2.1按負載選執(zhí)行文件的工作壓力負載/N<5000500?1000010000?2000020000?3000030000?50000>50000工作壓力/MPa<0.8-11.5?22.5?33?44?5>5表2.2按機械類型選執(zhí)行文件的工作壓力機械類型機 床農業(yè)機械工程機械磨床組合機床龍門刨床拉床工作壓力/MPaa<23?5<88?1010?1620?322.2液壓馬達的設計計算2.2.1計算液壓馬達排量液壓馬達排量根據下式決定:V=6.28T/'AP門.(m3/r) (2.1)式中：T為液壓馬達的負載力矩(N-m)；△匕為液壓馬達進出口壓力差(Nm3)；門min為液壓馬達的機械效率，一般齒輪和柱塞馬達取0.9?0.95，葉片馬達取0.8?0.93液壓元件的選擇3.1液壓泵的確定與所需功率的計算3.1.1液壓泵的確定確定液壓泵的最大工作壓力。液壓泵所需工作壓力的確定，主要根據液壓缸在工作循環(huán)各階段所需最大壓力P1，再加上油泵的出油口到缸進油口處總的壓力損失ZAp，即(3.1)p=p+ZAP(3.1)Zap包括油液流經流量閥和其他元件的局部壓力損失、管路沿程損失等，在系統(tǒng)管路未設計之前，可根據同類系統(tǒng)經驗估計，一般管路簡單的節(jié)流閥調速系統(tǒng)ZAP為(2?5)x105Pa，用調速閥及管路復雜的系統(tǒng)ZAP為(5?15)x105Pa，ZAP也可只考慮流經各控制閥的壓力損失，而將管路系統(tǒng)的沿程損失忽略不計，各閥的額定壓力損失可從液壓元件手冊或產品樣本中查找，也可參照表1.3選取。表3.1常用中、低壓各類閥的壓力損失心?)閥名△pn(x105Pa)閥名△pn(x105Pa)閥名△pn(x105Pa)閥名△pn(x105Pa)單向閥0.3?0.5背壓閥3?8行程閥1.5?2轉閥1.5?2換向閥1.5?3節(jié)流閥2?3順序閥1.5?3調速閥3?53.1.2確定液壓泵的流量qB泵的流量qB根據執(zhí)行元件動作循環(huán)所需最大流量qmax和系統(tǒng)的泄漏確定。多液壓缸同時動作時，液壓泵的流量要大于同苻動作的幾個液壓卸或馬達)所需的最大流量，并應考慮系統(tǒng)的泄漏和液壓泵磨損后容積效率的下降，即q=K(Zq) (m3/s) (3.2)B max式中：K為系統(tǒng)泄漏系數，一般取1.1?1.3，大流量取小值，小流量取大值；(Zq)max為同時動作的液壓缸(或馬達)的最大總流量(m3/s)。選擇液壓泵的規(guī)格：根據上面所計算的最大壓力pB和流量qB，查液壓元件產品樣本，選擇與PB和qB相當的液壓泵的規(guī)格型號。表3.2液壓泵的總效率液壓泵類型齒輪泵螺桿泵葉片泵柱塞泵總效率0.6?0.70.65?0.800.60?0.750.80?0.85按上述功率和泵的轉速，可以從產品樣本中選取標準電動機，再進行驗算，使電動機發(fā)出最大功率時，其超載量在允許范圍內。3.2閥類元件的選擇3.2.1選擇依據選擇依據為：額定壓力，最大流量，動作方式，安裝固定方式，壓力損失數值，工作性能參數和工作壽命等。3.2.2選擇閥類元件應注意的問題應盡量選用標準定型產品，除非不得已時才自行設計專用件。閥類元件的規(guī)格主要根據流經該閥油液的最大壓力和最大流量選取。選擇溢流閥時，應按液壓泵的最大流量選??；選擇節(jié)