项目2 任务 1 液压马达的认知

液压马达的认知KnowledgeaboutHydraulicMotor任务1Task1任务描述TaskDescription1能够了解常见液压马达的基本工作原理原理及符号，熟悉液压马达的种类，以及常见液压马达在不同场合的应用。Understandthebasicworkingprinciplesandsymbolsofcommonhydraulicmotors,andgetfamiliarwiththetypesofhydraulicmotorsandtheapplicationsofcommonhydraulicmotorsindifferentscenarios.图2-1-1液压马达实物图Figure2-1-1RealProductPictureofHydraulicMotor液压马达的概念及符号ConceptandSymbolofHydraulicMotor2液压马达是一种把液体的压力能转换为机械能的装置。Hydraulicmotorisadevicethatconvertsthepressureenergyoffluidintomechanicalenergy.从结构上讲，同类型的液压泵和液压马达基本上很相似，但由于两者的工作情况不同，使两者在结构上存在些许差异；从原理上讲，液压马达也可以作为液压泵使用，液压泵可以作为液压马达用。Instructure,hydraulicpumpandhydraulicmotorinthesamecategoryareverysimilar,buttheydifferalittleinstructureduetotheirdifferentworkingconditions.Inprinciple,hydraulicmotorcanalsobeusedashydraulicpumpandviceversa.液压马达的概念及符号ConceptandSymbolofHydraulicMotor2两者存在的差别主要有：Themaindifferencesbetweenthemareasfollows:1液压泵一般是单方向旋转的，而液压马达一般需要正反转，所以在内部结构上具有对称性。1Generally,hydraulicpumprotatesinonlyonedirection,buthydraulicmotorperformsforwardandreverserotation.Therefore,theyaresymmetricalininternalstructure.2为减小径向力，减小吸油阻力，一般液压泵的吸油口比出油口的尺寸要大，而液压马达低压腔的压力要稍微高于大气压力。2Toreduceradialforceandfluidsuctionresistance,thesizeofthefluidsuctionportofahydraulicpumpisusuallylargerthanthatofitsfluidoutlet,whilethepressureinthelowpressurechamberofahydraulicmotorisslightlyhigherthantheatmosphericpressure.液压马达的概念及符号ConceptandSymbolofHydraulicMotor23液压马达要求能够在很宽的转速范围情况下能够正常工作，因此，应采用液动轴承或静压轴承。因为当马达速度很低时，如果采用动压轴承，不易形成润滑滑膜。3Hydraulicmotorisrequiredtoworknormallyinawidespeedrange,sohydrodynamicorhydrostaticbearingsshouldbeadopted.Thereasonisthatitishardtoformlubricatingfilmifanydynamicpressurebearingisusedataverylowmotorspeed.4叶片泵依靠叶片和转子一起高速旋转而产生一种离心力，这种离心力能够使叶片始终紧贴定子的内表面，从而起到封油的作用，形成工作容积。若将其当马达使用，则必须在液压马达的叶片根部装上弹簧，以此来保证叶片始终紧贴定子内表面，以便马达能够正常起动。4Relyingonthehigh-speedrotationofitsvaneandrotor,thevanepumpgeneratesacentrifugalforcewhichcankeepthevanecloselytouchwiththeinnersurfaceofthestator,thussealingthefluidandformingaworkingvolume.Ifthevanepumpisusedasamotor,aspringmustbeinstalledatthevanerootofthehydraulicmotortoensurethatthevanecloselytoucheswiththeinnersurfaceofthestator,sothatthemotorcanstartnormally.液压马达的概念及符号ConceptandSymbolofHydraulicMotor25在结构上，液压泵需要保证其具有自吸能力，而对于液压马达来说没有这一要求。5Structurally,itisrequiredtoensuretheself-primingcapacityofahydraulicpump,butforahydraulicmotor,nosuchrequirementexists.6液压马达必须具有较大的起动扭矩。所谓的起动扭矩，就是指马达由静止状态起动时，马达轴上所能输出的扭矩。该扭矩通常大于在同一工作压差时处于运行状态下的扭矩，所以，为了使起动扭矩尽可能接近工作状态下的扭矩，要求马达扭矩的脉动小，内部摩擦小。6Hydraulicmotormusthavealargestartingtorque.Theso-calledstartingtorquereferstothetorquethatcanbeoutputbythemotorshaftwhenthemotorstartsfromastaticstate.Thistorqueisusuallygreaterthanthetorqueofthemotorrunningatthesameworkingdifferentialpressure.Therefore,tomakethestartingtorqueascloseaspossibletothetorqueintheworkingstate,boththetorquefluctuationandinternalfrictionofthemotorshouldbeatalowlevel.液压马达的概念及符号ConceptandSymbolofHydraulicMotor2液压马达根据其额定转速不同，可分为低速液压马达和高速液压马达两大类。额定转速低于500r/min的属于低速液压马达，额定转速高于500r/min的属于高速液压马达。Hydraulicmotorscanbedividedintolow-speedandhigh-speedtypesbyratedspeed.Theoneswitharatedspeedlowerthan500r/minarelow-speedhydraulicmotors,whilethosewitharatedspeedhigherthan500r/minarehigh-speedhydraulicmotors.液压马达也可根据其结构类型的不同，分为齿轮式、叶片式、柱塞式和其他型式。Graphicalsymbolsofhydraulicmotorsaresimilartothoseofhydraulicpumpsandsuchgraphicsymbolsaremainlydividedintothefollowingtwotypes:液压马达的图形符号和液压泵的图形符号类似，主要分为如下两种：Graphicalsymbolsofhydraulicmotorsaresimilartothoseofhydraulicpumpsandsuchgraphicsymbolsaremainlydividedintothefollowingtwotypes:液压马达的概念及符号ConceptandSymbolofHydraulicMotor2表2-1-1液压马达符号Table2-1-1SymbolsofHydraulicMotors液压马达的性能参数PerformanceParametersofHydraulicMotor21排量、流量和容积效率1Displacement,flowrateandvolumetricefficiency通常将马达的轴每转一周，按几何尺寸计算所进入的液体容积，称之为马达的排量V，也称作理论排量、几何排量，即不考虑泄漏损失时的排量。Generally,thevolumeofenteringfluidcalculatedaspergeometricdimensionsforeachrotationofthemotorshaftiscalledthedisplacement(V)ofthemotor,alsocalledtheoreticaldisplacementorgeometricdisplacement,i.e.,thedisplacementwithoutconsideringtheleakageloss.液压马达的性能参数PerformanceParametersofHydraulicMotor2根据液压动力元件的工作原理可知，马达转速n、理论流量qi与排量V之间具有下列关系Itcanbeknownfromtheworkingprincipleofhydraulicpowerelementsthattherelationamongthespeed(n),theoreticalflowrate(qi)anddisplacement(V)ofthemotorisasfollows:式中：qi为理论流量（m3/s）；n为转速（r/min）；V为排量（m3/s）。Where:qiisthetheoreticalflowrate(inm3/s);nisspeed(inr/min);Visdisplacement(inm3/s).为了满足转速要求，通常马达实际输入流量q大于理论输入流量，则有：Tomeetthespeedrequirement,theactualinputflowrate(q)ofthemotorisusuallyhigherthanthetheoreticalflowrate:液压马达的性能参数PerformanceParametersofHydraulicMotor2根据液压动力元件的工作原理可知，马达转速n、理论流量qi与排量V之间具有下列关系Itcanbeknownfromtheworkingprincipleofhydraulicpowerelementsthattherelationamongthespeed(n),theoreticalflowrate(qi)anddisplacement(V)ofthemotorisasfollows:式中：qi为理论流量（m3/s）；n为转速（r/min）；V为排量（m3/s）。Where:qiisthetheoreticalflowrate(inm3/s);nisspeed(inr/min);Visdisplacement(inm3/s).为了满足转速要求，通常马达实际输入流量q大于理论输入流量，则有：Tomeetthespeedrequirement,theactualinputflowrate(q)ofthemotorisusuallyhigherthanthetheoreticalflowrate:式中：Δq为泄漏流量。Where:Δqistheleakageflowrate.液压马达的性能参数PerformanceParametersofHydraulicMotor2所以得实际流量Accordingly,theactualflowrateis:2液压马达输出的理论转矩2Theoreticaltorqueoutputbyhydraulicmotor当液压马达进、出油口之间的压力差为ΔP，输入液压马达的流量为q，液压马达输出的理论转矩为Tt，角速度为ω，如若不计损失，液压马达输入的液压功率应当全部转化成液压马达输出的机械功率，即：givenloadtorque.WiththedifferentialpressureatfluidinletandoutletportsofthehydraulicmotorbeingrecordedasΔP,theinputflowrateofthehydraulicmotorasq,thetheoreticaltorqueoutputbyhydraulicmotorasTtandtheangularvelocityasω,ifnolossiscounted,thehydraulicpowerinputtothehydraulicmotorshouldbecompletelyconvertedintothemechanicalpoweroutputbyit,namely:液压马达的性能参数PerformanceParametersofHydraulicMotor2又因为ω=2πn，所以液压马达的理论转矩为：Andbecauseω=2πn,thetheoreticaltorqueofthehydraulicmotoris:式中：ΔP为马达进出口之间的压力差。Where:ΔPisthedifferentialpressureatfluidinletandoutletportsofthemotor.液压马达的性能参数PerformanceParametersofHydraulicMotor23液压马达的机械效率3Mechanicalefficiencyofhydraulicmotor由于液压马达内部存在不可避免的各种摩擦，实际输出的转矩T总要比理论转矩Tt小一些，即：Duetovarioustypesofinevitablefrictioninsidethehydraulicmotor,theactualoutputtorque(T)isalwayslessthanthetheoreticaltorque(Tt),namely:式中：ηm为液压马达的机械效率（%）。Where:ηmisthemechanicalefficiencyofhydraulicmotor(in%).式4液压马达的启动机械效率ηm4Startingmechanicalefficiency(ηm)ofhydraulicmotor液压马达的性能参数PerformanceParametersofHydraulicMotor2液压马达的启动机械效率指的是液压马达由静止状态开始起动时，马达实际输出的转矩T0与它在同一工作压差时的理论转矩Tt之比。即：Thestartingmechanicalefficiencyofhydraulicmotorreferstotheratioofthehydraulicmotor'sactualoutputtorque(T0)toitstheoreticaltorque(Tt)atthesameworkingdifferentialpressurewhenthemotorstartsfromastaticstate,namely:液压马达的性能参数PerformanceParametersofHydraulicMotor2启动性能最好的是多作用内曲线马达，轴向柱塞马达、曲轴连杆马达和静压平衡马达居中，叶片马达较差，而齿轮马达最差。intermsofstartingperformance,themulti-actinginnercurvemotoristhebest,theaxialplungermotor,crankshaftconnectingrodtypemotorandhydrostaticbalancemotoraregood,thevanemotorispoor,andthegearmotoristheworst.5液压马达的转速5Speedofhydraulicmotor液压马达的转速取决于油液的流量和液压马达本身的排量V，可用下式计算：ThespeedofhydraulicmotordependsontheflowrateofthefluidandthedisplacementVofthehydraulicmotoritself,whichcanbecalculatedwiththefollowingformula:式中：nt为理论转速（r/min）。Where:ntisthetheoreticalspeed(inr/min).液压马达的性能参数PerformanceParametersofHydraulicMotor2由于液压马达内部有泄漏，有一部分液体因泄漏损失掉了，所以并不是所有进入马达的液体都推动液压马达做功，因此液压马达的实际转速要比理论转速低一些。Becausesomefluidislostduetotheleakageinsidethehydraulicmotor,notallthefluidenteringthehydraulicmotordrivesittowork.Asaresult,thehydraulicmotor'sactualspeedislessthanitstheoreticalspeed.式中：n为液压马达的实际转速（r/min）；ηv为液压马达的容积效率（%）。Where:nistheactualspeedofhydraulicmotor(inr/min);ηvisthevolumetricefficiencyofhydraulicmotor(in%).液压马达的性能参数PerformanceParametersofHydraulicMotor26最低稳定转速6Minimumsteadyspeed最低稳定转速是指液压马达在额定负载下，不出现爬行现象的最低转速。所谓爬行现象，指的是当液压马达在工作中转速过低时，往往保持不了均匀的速度，进入时动时停的不稳定状态。Minimumsteadyspeedreferstotheminimumspeedofthehydraulicmotorundertheratedloadwithoutcreeping.Creepingmeansthatwhenthehydraulicmotorrunsataverylowspeedduringoperation,italwaysfailstomaintainataconstantspeedandentersanunstablestatewithintermittentmovementandstop.液压马达的性能参数PerformanceParametersofHydraulicMotor2液压马达在低速时产生爬行现象的原因是：Thereasonswhythehydraulicmotorcreepsatalowspeedareasfollows:①摩擦力的大小不稳定。Thefrictionforceisunstable.②泄漏量大小不稳定。Theleakageamountisunstable.7最高使用转速。7Maximumoperatingspeed液压马达的最高使用转速主要受使用寿命和机械效率的限制。转速提高后，各运动副的磨损加剧，从而使用寿命降低，转速高也就意味着液压马达需要输入的流量大，因此各过流部分的流速相应增大，压力损失也随之增加，从而使机械效率降低。Themaximumoperatingspeedofhydraulicmotorismainlyrestrictedbyitsservicelifeandmechanicalefficiency.Withtheincreaseofspeed,thewearofeachmovingpairisintensified,thusshorteningtheservicelife.Highspeedmeansthatthehydraulicmotorneedsahighinputflow,sotheflowrateofeachflowpassagepartincreasescorrespondinglyandthepressurelossalsorises,thusreducingthemechanicalefficiency.液压马达的性能参数PerformanceParametersofHydraulicMotor28调速范围8Speedregulationrange液压马达的调速范围用最高使用转速和最低稳定转速之比表示，即：Thespeedregulationrangeofhydraulicmotorisexpressedbytheratioofthemaximumoperatingspeedtotheminimumsteadyspeed,namely:液压马达的性能参数PerformanceParametersofHydraulicMotor28调速范围8Speedregulationrange液压马达的调速范围用最高使用转速和最低稳定转速之比表示，即：Thespeedregulationrangeofhydraulicmotorisexpressedbytheratioofthemaximumoperatingspeedtotheminimumsteadyspeed,namely:液压马达的工作原理WorkingPrincipleofHydraulicMotor3图2-1-3所示为叶片液压马达的工作原理图。Figure2-1-3showstheworkingprinciplediagramofavanetypehydraulicmotor.Figure2-1-3WorkingPrincipleDiagramofVaneMotor液压马达的工作原理WorkingPrincipleofHydraulicMotor3当压力为p的油液从进油口进入叶片1和3之间时，叶片2因两面均受液压油的作用，所以不产生转矩。叶片1、3上，一面作用有压力油，另一面为低压油，但由于叶片3伸出的面积大于叶片1伸出的面积，因此作用于叶片3上的总液压力要比作用于叶片1上的总液压力大，于是压力差使得转子产生了顺时针的转矩。同样道理，压力油进入叶片5和7之间时，叶片7伸出的面积大于叶片5伸出的面积，同样也产生顺时针的转矩。这样就把油液的压力能转变成了机械能，这就是叶片马达的工作原理，而当输油方向改变时，液压马达就反转。Whenanyfluidwiththepressureofpflowsbetweenvanes1and3viathefluidinletport,bothsidesofvane2isundertheeffectofhydraulicfluidandnotorqueisgenerated.Asforvanes1and3,pressurefluidexistsononesideandlow-pressurefluidexistsontheotherside.However,becausetheextendingareaofvane3islargerthanthatofvane1,thetotalhydraulicpressureonvane3isgreaterthanthatonvane1andthedifferentialpressuremakestherotorgeneratesaclockwise