项目3 任务 1 方向控制阀的认知

方向控制阀的认知KnowledgeaboutDirectionalControlValve任务1Task1任务描述TaskDescription1了解常见方向控制阀的基本工作原理及符号，进一步熟悉方向控制阀的种类，熟悉常见方向控制阀在不同场合的应用。Understandthebasicworkingprinciplesandsymbolsofcommondirectionalcontrolvalves,beacquaintedwiththetypesofdirectionalcontrolvalves,andbefamiliarwiththeapplicationsofdirectionalcontrolvalvesindifferentscenarios.液压阀是用来控制液压系统中油液的流动方向或调节其压力和流量的，因此它可分为方向阀、压力阀和流量阀三大类。一个形状相同的阀，可以因为作用机制的不同，而具有不同的功能。压力阀和流量阀利用通流截面的节流作用控制着系统的压力和流量，而方向阀则利用通油通道的更换控制着油液的流动方向。Ahydraulicvalveisusedtocontroltheflowdirectionoforadjustthepressureandflowrateoffluidinahydraulicsystem.Therefore,itisavailableinthreecategories:directionalvalve,pressurevalveandflowvalve.Valvesinthesameshapemayhavedifferentfunctionsduetodifferentmechanismsofaction.Pressurevalvesandflowvalvescontrolthepressureandflowofasystembasedonthethrottlingeffectofpassagecrosssection,whiledirectionalvalvescontroltheflowdirectionoffluidbychangingthefluidpassagechannel.任务描述TaskDescription1在结构上，所有的阀都有阀体、阀芯（转阀或滑阀）和驱使阀芯动作的元、部件（如弹簧、电磁铁）组成。Intermsofstructure,allthesevalvesarecomposedofvalvebody,valveelement(rotaryvalveorslidevalve),andcomponentactuatingthevalveelement(e.g.spring,electromagnet).在工作原理上，所有阀的开口大小，阀进、出口间压差以及流过阀的流量之间的关系都符合孔口流量公式，仅是各种阀控制的参数各不相同而已。Intermsofworkingprinciple,therelationshipbetweentheopeningsize,valveinlet/outletpressuredifference,andthrough-valveflowofallthesevalvesconformstotheorificeflowformula,althoughdifferenttypesofvalvesdifferincontrolparameters.而方向控制阀是用来改变液压系统中各油路之间液流通断关系的阀类，如单向阀、换向阀及压力表开关等。Directionalcontrolvalvesareusedtoalloworstopfluidflowinfluidpathsinahydraulicsystem,includingcheckvalve,reversingvalve,pressuregaugeswitch,etc.单向阀CheckValve2液压系统中常见的单向阀有普通单向阀和液控单向阀两种。Commoncheckvalvesinhydraulicsystemincludeordinarycheckvalveandhydrauliccontrolcheckvalve.普通单向阀普通单向阀的作用，是使油液只能沿一个方向流动，不许它反向倒流。图3-1-1（a）所示是一种管式普通单向阀的结构。Ordinarycheckvalve:Anordinarycheckvalvefunctionstoenablefluidtoflowinonlyonedirectionandpreventitfromflowingbackward.Figure3-1-1(a)showsthestructureofatubularordinarycheckvalve.图3-1-1单向阀Figure3-1-1CheckValve（a）结构图（b）职能符号图（c）实物图

(a)StructureDiagram(b)FunctionalSymbol(c)RealProductPicture1-阀体2-阀芯3-弹簧1-Valvebody2-Valveelement3-Spring单向阀CheckValve2液控单向阀图3-1-2（a）所示是液控单向阀的结构。当控制口K处无压力油通入时，它的工作机制和普通单向阀一样；压力油只能从通口P1流向通口P2，不能反向倒流。当控制口K有控制压力油时，因控制活塞1右侧a腔通泄油口，活塞1右移，推动顶杆2顶开阀芯3，使通口P1和P2接通，油液就可在两个方向自由通流。Hydrauliccontrolcheckvalve:Figure3-1-2(a)showsthestructureofahydrauliccontrolcheckvalve.WhencontrolportKhasnopressurefluidflowingin,itsworkingmechanismisthesameasanordinarycheckvalve:pressurefluidcanonlyflowfromportP1toportP2andcannotflowreversely.WhencontrolportKhascontrolpressurefluid,asthechamber(a)ontherightsideofthecontrolpiston(1)hasaportthatallowsfluidtopass,thepiston(1)movesrightwardandpushestheejectorrod(2)toopenthevalveelement(3);asaresult,theportsP1andP2areconnected,allowingfluidtoflowfreelyinthetwodirections.图3-1-2液控单向阀Figure3-1-2HydraulicControlCheckValve（a）结构图（b）职能符号图（c）实物图(a)StructureDiagram(b)FunctionalSymbol(c)RealProductPicture1-活塞2-顶杆3-阀芯1-Piston2-Ejectorrod3-Valveelement换向阀ReversingValve3换向阀利用阀芯相对于阀体的相对运动，使油路接通、关断，或变换油流的方向，从而使液压执行元件启动、停止或变换运动方向。Areversingvalveallowsorstopsfluidfloworchangesfluidflowdirectioninfluidpathsbasedonitsvalveelementmotionrelativetoitsvalvebodytostart,stoporchangemovementdirectionofahydraulicactuator.Table3-1-1ClassificationofReversingValves换向阀ReversingValve3换向阀的工作原理Workingprincipleofreversingvalve在图示状态下，液压缸两腔不通压力油，活塞处于停止状态。若使阀芯1左移，阀体2的油口P和A连通、B和T连通，则压力油经P、A进入液压缸左腔，右腔油液经B、T流回油箱，活塞向右运动；反之，若使阀芯右移，则油口P和B连通、A和T连通，活塞便向左运动。Inthestateshowninthefigure,thetwochambersofthehydrauliccylinderdonotallowpressurefluidflow,andthepistonisstationary.Ifthevalveelement(1)ismovedtotheleft,fluidportsPandAofthevalvebody(2)areconnected,portsBandTareconnected,pressurefluidflowsintotheleftchamberofthehydrauliccylinderthroughportsPandA,andfluidintherightchamberflowsbacktothefluidtankthroughportsBandTtomovethepistonrightward.Ifthevalveelementismovedtotheright,theportsPandBareconnected,andportsAandTareconnectedtoallowthepistontomoveleftward.图3-1-3换向阀的工作原理

Figure3-1-3Workingprincipleofreversingvalve1一阀芯2-阀体1-Valveelement2-Valvebody换向阀ReversingValve3NameStructurePrincipleDiagramGraphicSymbolApplicationScenarioTwo-positiontwo-wayreversingvalveItconnectsfluidandallows/stopsfluidflow(equivalenttoaswitch)Two-positionthree-wayreversingvalveItcontrolsfluidflowdirection(fromonedirectiontoanother)Two-positionfour-wayreversingvalveItdoesnotallowanactuatortostopinanypositionTwo-positionfive-wayreversingvalveItdoesnotallowanactuatortostopinanypositionThree-positionfour-wayreversingvalveItallowsanactuatortostopinanypositionThree-positionfive-wayreversingvalveItallowsanactuatortostopinanyposition换向阀ReversingValve3换向阀的中位机能Center-positionfunctionofreversingvalve换向阀处于常态位置时，其各油口的连通方式称为滑阀机能。三位换向阀的常态为中位，因此三位换向阀的滑阀机能又称为中位机能。不同中位机能的三位换向阀阀体通用，仅阀芯台肩的结构、尺寸及内部通孔情况有区别，但作用区别又极大。Whenareversingvalveisinthenormalposition,theconnectionmodeofitsfluidportsenablestheslidevalvefunction.Athree-positionreversingvalveisnormallyincenterposition,sotheslidevalvefunctionofathree-positionreversingvalveisalsoknownascenter-positionfunction.Three-positionreversingvalveswithdifferentcenter-positionfunctionshavecommonvalvebodiesanddifferinthestructureandsizeofspoollandandinternalthroughhole,withsignificantdifferenceinfunctions.换向阀ReversingValve3Table3-1-3ListofFiveCommonCenter-positionFunctionsofThree-positionFour-wayReversingValvesCodeStructuralDiagramSymbolofCenterPositionStatusandCharacteristicsofPortsinCenter-positionConditionOAllfluidportsarefullyenclosed.Thereversingaccuracyishighbutwith

impact,thecylinderislocked,thepumpisnotunloaded,andtheparallelcylinderscanmove

HAllfluidportsarefullyopen.HReversingissmooth,thecylinderfloats,thepumpisunloaded,andothercylinderscannotbeusedinparallelPPortPisclosed,andportsA,BandTareconnected.Reversingisrelativelystable,thecylinderfloats,thepumpisnotunloaded,andtheparallelcylinderscanmoveMPortsPandTportsareconnected,andPortsAandBareclosed.Thereversingaccuracyishighbutwithimpact,thecylinderislocked,thepumpisunloadedandothercylinderscannotbeusedinparallel.换向阀ReversingValve3在分析和选择阀的中位机能时，通常考虑以下几点：Inanalysisandselectionofthecenter-positionfunctionofavalve,thefollowingpointsshouldbeconsideredingeneral:（1）系统保压。当P口被堵塞，系统保压，液压泵能用于多缸系统。当P口不太通畅地与T口接通时，系统能保持一定的压力，供控制油路使用。(1)Systempressuremaintaining:WhenportPisblocked,thesystemmaintainspressureandthehydraulicpumpcanbeusedinamulti-cylindersystem.WhenportPisconnectedtoportTinnon-smoothway,thesystemcanmaintainacertainpressureforthecontrolfluidpath.（2）系统卸荷。P口通畅地与T口接通时，系统卸荷。(2)Systemunloading:WhenportPisconnectedtoportT,thesystemisunloaded.换向阀ReversingValve3（3）启动平稳性。阀芯处于中位时，液压缸某腔如通油箱，则启动时该腔内因无油液起缓冲作用，启动不太平稳。(3)Startingsmoothness:Whenthevalveelementisinthecenterposition,ifachamberofthehydrauliccylinderisconnectedtothetank,startingwillnotbesmoothenoughasthechamberhasnofluidforbufferinginstarting.（4）液压缸“浮动”和在任意位置上的停止。(4)Hydrauliccylinder"floating"andstoppingatanyposition:换向阀ReversingValve33换向阀的结构Structureofreversingvalve（1）手动换向阀。图3-1-4（b）为自动复位式手动换向阀，放开手柄1、阀芯2在弹簧3的作用下自动回复中位，该阀，适用于动作频繁、工作持续时间短的场合，操作比较完全，常用于工程机械的液压传动系统中。(1)Manualreversingvalve:Figure3-1-4(b)showsanautomaticresettingmanualreversingvalve.Whenthehandle(1)isreleased,thevalveelement(2)automaticallyreturnstothecenterpositionundertheactionofthespring(3).Thisvalveissuitableforscenarioswherethevalvewouldactfrequentlyforshortdurationeachtime,withrelativelycompleteoperation.Thevalveiscommonlyusedinthehydraulictransmissionsystemofconstructionmachinery。如果将该阀，阀芯右端弹簧3的部位改为可自动定位的结构形式，即成为可在三个位置定位的手动换向阀。图3-1-4（a）为职能符号图。Ifthespring(3)attherightendofthevalveelementischangedtoastructurethatallowsautomaticpositioning,thevalvebecomesamanualreversingvalvethatcanbepositionedinthreepositions.Figure3-1-4(a)showsitsfunctionalsymbol.换向阀ReversingValve33换向阀的结构Structureofreversingvalve图3-1-4手动换向阀Figure3-1-4ManualReversingValve（a）职能符号图（b）结构图(a)FunctionalSymbol(b)StructureDiagram1-手柄2-阀芯3-弹簧1-Handle2-Valveelement3-Spring换向阀ReversingValve3（2）机动换向阀。机动换向阀又称行程阀，它主要用来控制机械运动部件的行程，它是借助于安装在工作台上的挡铁5迫使阀芯移动，从而控制油液的流动方向，机动换向阀通常是二位的，有二通、三通、四通和五通几种，其中二位二通机动阀又分常闭和常开两种。(2)Mechanicalreversingvalve:Amechanicalreversingvalve,alsoknownasastrokevalve,ismainlyusedtocontrolthestrokeofmechanicalmovingparts.Itsvalveelementisforcedtomovebymeansofthestopiron(5)installedonthetabletocontrolthefluidflowdirection.Mechanicalreversingvalvesaregenerallyavailableastwo-positiontwo-way,three-way,four-wayandfive-wayvalves.Two-positiontwo-waymechanicalvalvesareavailableintwotypes:normallyclosedandnormallyopenvalves.换向阀ReversingValve3（2）机动换向阀。图3-1-5（a）为滚轮式二位三通常闭式机动换向阀，在图示位置阀芯2被弹簧1压向上端，油腔P和A通，B口关闭。当挡铁5压住滚轮4，使阀芯2移动到下端时，就使油腔P和A断开，P和B接通，A口关闭。图3-1-5（b）所示为其职能符号。Figure3-1-5(a)showsarollertypetwo-positionthree-waynormallyclosedmechanicalreversingvalve.Inthepositionshowninthefigure,thevalveelement(2)ispressedbythespring(1)totheupperend,thefluidportsPandAareconnected,andportBisclosed.Whenthestopiron(5)pressestheroller(4)tomovethevalveelement(2)tothelowerend,thefluidportsPandAaredisconnected,portsPandBareconnectedandportAisclosed.Figure3-1-5(b)showsitsfunctionalsymbol。图3-1-5机动换向阀Figure3-1-5MechanicalReversingValve1-弹簧2-阀芯3-阀体4-滚轮5-挡铁

1-Spring2-Valveelement3-Valvebody4-Roller5-Stopiron换向阀ReversingValve3（3）电磁换向阀。(3)Solenoidreversingvalve电磁换向阀是利用电磁铁的通电吸合与断电释放而直接推动阀芯来控制液流方向的。Asolenoidreversingvalvecontrolsfluidflowdirectionbyusingtheelectromagnetactionofengagementuponenergizationanddisengagementuponde-energizationtodirectlypushthevalveelement.电磁铁按使用电源的不同，可分为交流和直流两种。按衔铁工作腔是否有油液又可分为“干式”和“湿式”。ElectromagnetscanbedividedintoACandDCelectromagnetsbythepowersupply,andinto"wettype"and"drytype"electromagnetsbypresenceofoilinthearmatureworkingchamberornot.换向阀ReversingValve3（3）电磁换向阀。(3)Solenoidreversingvalve图3-1-6（a）所示为二位三通交流电磁换向阀结构，在图示位置，油口P和A相通，油口B断开；当电磁铁通电吸合时，推杆1将阀芯2推向右端，这时油口P和A断开，而与B相通。而当磁铁断电释放时，弹簧3推动阀芯复位。图3-1-6（b）所示为其职能符号。Figure3-1-6(a)showsthestructureofatwo-positionthree-wayACsolenoidreversingvalve.Inthepositionshowninthefigure,portsPandAareconnectedandportBisdisconnected.Whentheelectromagnetisengageduponenergization,thepushrod(1)pushesthevalveelement(2)totherightandmeanwhile,thefluidportPbecomesdisconnectedfromportAandconnectedwithportB.Whentheelectromagnetisde-energizedanddisengaged,thespring(3)pushesthevalveelementtoreset.Figure3-1-6(b)showsitsfunctionalsymbol.图3-1-6二位三通电磁换向阀Figure3-1-6Two-positionThree-waySolenoidReversingValve（a）结构图（b）职能符号图(a)StructureDiagram(b)FunctionalSymbol1-推杆2-阀芯3-弹簧1-Pushrod2-Valveelement3-Spring换向阀ReversingValve3（3）电磁换向阀。(3)Solenoidreversingvalve电磁换向阀就其工作位置来说，有二位和三位等。二位电磁阀有一个电磁铁靠弹簧复位；三位电磁阀有两个电磁铁，如图3-1-7所示为一种三位五通电磁换向阀的结构和职能符号。solenoidreversingvalvesareavailablewithtwopositionsandthreepositionsintermsofworkingposition.Atwo-positionsolenoidvalvehasoneelectromagnetresetbymeansofaspring.Athree-positionsolenoidvalvehastwoelectromagnets.Figure3-1-7showsthestructureandfunctionalsymbolofathree-positionfive-waysolenoidreversingvalve.图3-1-7三位五通电磁换向阀Figure3-1-7Three-positionFive-waySolenoidReversingValve（a）结构图（b）职能符号图(a)StructureDiagram(b)FunctionalSymbol换向阀ReversingValve3（4）液动换向阀。液动换向阀是利用控制油路的压力油来改变阀芯位置的换向阀，图3-1-8所示为三位四通液动换向阀的结构和职能符号。阀芯是由其两端密封腔中油液的压差来移动的，当控制油路的压力油从阀右边的控制油口K2进入滑阀右腔时，K1接通回油，阀芯向左移动，使压力油口P与B相通，A与T相通；当K1接通压力油，K2接通回油时，阀芯向右移动，使得P与A相通，B与T相通；当K1、K2都通回油时，阀芯在两端弹簧和定位套作用下回到中间位置。(4)Hydraulicreversingvalve:Ahydraulicreversingvalvechangesthepositionofitsvalveelementbyusingpressurefluidinthecontrolfluidpaths.Figure3-1-8showsthestructureandfunctionalsymbolofathree-positionfour-wayhydraulicreversingvalve.Thevalveelementismovedbythepressuredifferenceoffluidinthesealedchambersatbothends.WhenpressurefluidofcontrolfluidpathsflowsintotherightchamberoftheslidevalvefromthecontrolportK2ontherightofthevalve,K1becomesconnectedtoreturnfluidandthevalveelementmovesleftwardtoconnectpressurefluidportsPandB,andconnectportsAandT.WhenK1isconnectedtopressurefluidandK2isconnectedtoreturnfluid,thevalveelementmovesrightwardtoconnectportsPandA,andconnectportsBandT.WhenbothK1andK2areconnectedtoreturnfluid,thevalveelementreturnstothecenterpositionundertheactionofthespringsatbothendsandthelocatingsleeve.换