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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=气+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门.(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:门^Forhydraulicpumpoveralleffectivenessindex;门Inordertofunctionalelementoveralleffectivenessindex;门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.中文翻译中文翻译液压传动系统设计与计算1.明确设计要求进行工况分析在设计液压系统时，首先应明确以下问题，并将其作为设计依据。主机的用途、工艺过程、总体布局以及对液压传动装置的位置和空间尺寸的要求；主机对液压系统的性能要求，如自动化程度、调速范围、运动平稳性、换向定位精度以及对系统的效率、温升等的要求；液压系统的工作环境，如温度、湿度、振动冲击以及是否有腐蚀性和易燃物质存在等情况。在上述工作的基础上，应对主机进行工况分析，工况分析包括运动分析和动力分析，对复杂的系统还需编制负载和动作循环图，由此了解液压缸或液压马达的负载和速度随时间变化的规律，以下对工况分析的内容作具体介绍。1.1运动分析主机的执行元件按工艺要求的运动情况，可以用位移循环图(L—t)，速度循环图(v—t)，或速度与位移循环图表示，由此对运动规律进行分析。1.1.1位移循环图L-t图1.1为液压机的液压缸位移循环图，纵坐标L表示活塞位移，横坐标t表示从活塞启动到返回原位的时间，曲线斜率表示活塞移动速度。1.1.2速度循环图v—t(或v—L)工程中液压缸的运动特点可归纳为三种类型。图1.2为三种类型液压缸的v—t图，第一种如图1.2中实线所示，液压缸开始作匀加速运动，然后匀速运动，最后匀减速运动到终点；第二种，液压缸在总行程的前一半作匀加速运动，在另一半作匀减速运动，且加速度的数值相等；第三种，液压缸在总行程的一大半以上以较小的加速度作匀加速运动，然后匀减速至行程终点。v—t图的三条速度曲线，不仅清楚地表明了三种类型液压缸的运动规律，也间接地表明了三种工况的动力特性。1.2动力分析动力分析，是研究机器在工作过程中，其执行机构的受力情况，对液压系统而言，就是研究液压缸或液压马达的负载情况。1.2.1液压缸的负载及负载循环图液压缸的负载力计算工作机构作直线往复运动时，液压缸必须克服的负载由六部分组成：F=F+F+F+F+F+Fcfigmb (1.1)式中：Fc为切削阻力；Ff为摩擦阻力；Fi为惯性阻力；Fg为重力；Fm为密封阻力；Fb为排油阻力。液压缸运动循环各阶段的总负载力液压缸运动循环各阶段的总负载力计算，一般包括启动加速、快进、工进、快退、减速制动等几个阶段，每个阶段的总负载力是有区别的。启动加速阶段：这时液压缸或活塞处于由静止到启动并加速到一定速度，其总负载力包括导轨的摩擦力、密封装置的摩擦力(按缸的机械效率门=0.9计算)、重力和惯性力等项，即：TOC\o"1-5"\h\z\o"CurrentDocument"F=F+F+F+F+F (1.2)快速阶段：\o"CurrentDocument"F=F+F+F+F (1.3)工进阶段：□\o"CurrentDocument"F=F+F+F+F+Fb (1.4)减速：\o"CurrentDocument"F=F+F+F+F+F (1.5)对简单液压系统，上述计算过程可简化。例如采用单定量泵供油，只需计算工进阶段的总负载力，若简单系统采用限压式变量泵或双联泵供油，则只需计算快速阶段和工进阶段的总负载力。1.2.2液压马达的负载工作机构作旋转运动时，液压马达必须克服的外负载为：TOC\o"1-5"\h\z\o"CurrentDocument"M=M+M$+M (1.6)工作负载力矩Me。工作负载力矩可能是定值，也可能随时间变化，应根据机器工作条件进行具体分析。摩擦力矩Mf。为旋转部件轴颈处的摩擦力矩，其计算公式为：\o"CurrentDocument"Mf=GFR(N-M) (1.7)式中：G为旋转部件的重量(N)；f为摩擦因数，启动时为静摩擦因数，启动后为动摩擦因数；R为轴颈半径(m)。惯性力矩M。为旋转部件加速或减速时产生的惯性力矩，其计算公式为：\o"CurrentDocument"M=J心(N-M) (1.8)式中：£为角加速度(r/s2)；电为角速度的变化(r/s)；At为加速或减速时间(s)；J为旋转部件的转动惯量(Kg-m2)，。J=1GD2.4G式中：GD2为回转部件的飞轮效应(N-M2)。各种回转体的GD2可查《机械设计手册》。根据式(1.6)，分别算出液压马达在一个工作循环内各阶段的负载大小，便可绘制液压马达的负载循环图2确定液压系统主要参数2.1液压缸的设计计算2.1.1初定液压缸工作压力液压缸工作压力主要根据运动循环各阶段中的最大总负载力来确定，此外，还需要考虑以下因素：各类设备的不同特点和使用场合。考虑经济和重量因素，压力选得低，则元件尺寸大，重量重；压力选得高一些，则元件尺寸小，重量轻，但对元件的制造精度，密封性能要求高。所以，液压缸的工作压力的选择有两种方式：一是根据机械类型选；二是根据切削负载选。如表2.1、表2.2所示。表2.1按负载选执行文件的工作压力负载/N<5000500〜1000010000〜2000020000〜3000030000〜50000>50000工作压力/MPa<0.8-11.5〜22.5〜33〜44〜5>5表2.2按机械类型选执行文件的工作压力机械类型机 床农业机械工程机械磨床组合机床龙门刨床拉床工作压力/MPaa<23〜5<88〜1010〜1620〜322.2液压马达的设计计算2.2.1计算液压马达排量液压马达排量根据下式决定:V=6.28T/'AP门.(m3/r) (2.1)式中：T为液压马达的负载力矩(N-m)；△匕为液压马达进出口压力差(Nm3)；门min为液压马达的机械效率，一般齿轮和柱塞马达取0.9〜0.95，叶片马达取0.8〜0.93液压元件的选择3.1液压泵的确定与所需功率的计算3.1.1液压泵的确定确定液压泵的最大工作压力。液压泵所需工作压力的确定，主要根据液压缸在工作循环各阶段所需最大压力P1，再加上油泵的出油口到缸进油口处总的压力损失ZAp，即(3.1)p=p+ZAP(3.1)Zap包括油液流经流量阀和其他元件的局部压力损失、管路沿程损失等，在系统管路未设计之前，可根据同类系统经验估计，一般管路简单的节流阀调速系统ZAP为(2〜5)x105Pa，用调速阀及管路复杂的系统ZAP为(5〜15)x105Pa，ZAP也可只考虑流经各控制阀的压力损失，而将管路系统的沿程损失忽略不计，各阀的额定压力损失可从液压元件手册或产品样本中查找，也可参照表1.3选取。表3.1常用中、低压各类阀的压力损失心?)阀名△pn(x105Pa)阀名△pn(x105Pa)阀名△pn(x105Pa)阀名△pn(x105Pa)单向阀0.3〜0.5背压阀3〜8行程阀1.5〜2转阀1.5〜2换向阀1.5〜3节流阀2〜3顺序阀1.5〜3调速阀3〜53.1.2确定液压泵的流量qB泵的流量qB根据执行元件动作循环所需最大流量qmax和系统的泄漏确定。多液压缸同时动作时，液压泵的流量要大于同苻动作的几个液压卸或马达)所需的最大流量，并应考虑系统的泄漏和液压泵磨损后容积效率的下降，即q=K(Zq) (m3/s) (3.2)B max式中：K为系统泄漏系数，一般取1.1〜1.3，大流量取小值，小流量取大值；(Zq)max为同时动作的液压缸(或马达)的最大总流量(m3/s)。选择液压泵的规格：根据上面所计算的最大压力pB和流量qB，查液压元件产品样本，选择与PB和qB相当的液压泵的规格型号。表3.2液压泵的总效率液压泵类型齿轮泵螺杆泵叶片泵柱塞泵总效率0.6〜0.70.65〜0.800.60〜0.750.80〜0.85按上述功率和泵的转速，可以从产品样本中选取标准电动机，再进行验算，使电动机发出最大功率时，其超载量在允许范围内。3.2阀类元件的选择3.2.1选择依据选择依据为：额定压力，最大流量，动作方式，安装固定方式，压力损失数值，工作性能参数和工作寿命等。3.2.2选择阀类元件应注意的问题应尽量选用标准定型产品，除非不得已时才自行设计专用件。阀类元件的规格主要根据流经该阀油液的最大压力和最大流量选取。选择溢流阀时，应按液压泵的最大流量选取；选择节