項(xiàng)目3 任務(wù) 1 方向控制閥的認(rèn)知

方向控制閥的認(rèn)知KnowledgeaboutDirectionalControlValve任務(wù)1Task1任務(wù)描述TaskDescription1了解常見方向控制閥的基本工作原理及符號(hào)，進(jìn)一步熟悉方向控制閥的種類，熟悉常見方向控制閥在不同場(chǎng)合的應(yīng)用。Understandthebasicworkingprinciplesandsymbolsofcommondirectionalcontrolvalves,beacquaintedwiththetypesofdirectionalcontrolvalves,andbefamiliarwiththeapplicationsofdirectionalcontrolvalvesindifferentscenarios.液壓閥是用來控制液壓系統(tǒng)中油液的流動(dòng)方向或調(diào)節(jié)其壓力和流量的，因此它可分為方向閥、壓力閥和流量閥三大類。一個(gè)形狀相同的閥，可以因?yàn)樽饔脵C(jī)制的不同，而具有不同的功能。壓力閥和流量閥利用通流截面的節(jié)流作用控制著系統(tǒng)的壓力和流量，而方向閥則利用通油通道的更換控制著油液的流動(dòng)方向。Ahydraulicvalveisusedtocontroltheflowdirectionoforadjustthepressureandflowrateoffluidinahydraulicsystem.Therefore,itisavailableinthreecategories:directionalvalve,pressurevalveandflowvalve.Valvesinthesameshapemayhavedifferentfunctionsduetodifferentmechanismsofaction.Pressurevalvesandflowvalvescontrolthepressureandflowofasystembasedonthethrottlingeffectofpassagecrosssection,whiledirectionalvalvescontroltheflowdirectionoffluidbychangingthefluidpassagechannel.任務(wù)描述TaskDescription1在結(jié)構(gòu)上，所有的閥都有閥體、閥芯（轉(zhuǎn)閥或滑閥）和驅(qū)使閥芯動(dòng)作的元、部件（如彈簧、電磁鐵）組成。Intermsofstructure,allthesevalvesarecomposedofvalvebody,valveelement(rotaryvalveorslidevalve),andcomponentactuatingthevalveelement(e.g.spring,electromagnet).在工作原理上，所有閥的開口大小，閥進(jìn)、出口間壓差以及流過閥的流量之間的關(guān)系都符合孔口流量公式，僅是各種閥控制的參數(shù)各不相同而已。Intermsofworkingprinciple,therelationshipbetweentheopeningsize,valveinlet/outletpressuredifference,andthrough-valveflowofallthesevalvesconformstotheorificeflowformula,althoughdifferenttypesofvalvesdifferincontrolparameters.而方向控制閥是用來改變液壓系統(tǒng)中各油路之間液流通斷關(guān)系的閥類，如單向閥、換向閥及壓力表開關(guān)等。Directionalcontrolvalvesareusedtoalloworstopfluidflowinfluidpathsinahydraulicsystem,includingcheckvalve,reversingvalve,pressuregaugeswitch,etc.單向閥CheckValve2液壓系統(tǒng)中常見的單向閥有普通單向閥和液控單向閥兩種。Commoncheckvalvesinhydraulicsystemincludeordinarycheckvalveandhydrauliccontrolcheckvalve.普通單向閥普通單向閥的作用，是使油液只能沿一個(gè)方向流動(dòng)，不許它反向倒流。圖3-1-1（a）所示是一種管式普通單向閥的結(jié)構(gòu)。Ordinarycheckvalve:Anordinarycheckvalvefunctionstoenablefluidtoflowinonlyonedirectionandpreventitfromflowingbackward.Figure3-1-1(a)showsthestructureofatubularordinarycheckvalve.圖3-1-1單向閥Figure3-1-1CheckValve（a）結(jié)構(gòu)圖（b）職能符號(hào)圖（c）實(shí)物圖

(a)StructureDiagram(b)FunctionalSymbol(c)RealProductPicture1-閥體2-閥芯3-彈簧1-Valvebody2-Valveelement3-Spring單向閥CheckValve2液控單向閥圖3-1-2（a）所示是液控單向閥的結(jié)構(gòu)。當(dāng)控制口K處無壓力油通入時(shí)，它的工作機(jī)制和普通單向閥一樣；壓力油只能從通口P1流向通口P2，不能反向倒流。當(dāng)控制口K有控制壓力油時(shí)，因控制活塞1右側(cè)a腔通泄油口，活塞1右移，推動(dòng)頂桿2頂開閥芯3，使通口P1和P2接通，油液就可在兩個(gè)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.圖3-1-2液控單向閥Figure3-1-2HydraulicControlCheckValve（a）結(jié)構(gòu)圖（b）職能符號(hào)圖（c）實(shí)物圖(a)StructureDiagram(b)FunctionalSymbol(c)RealProductPicture1-活塞2-頂桿3-閥芯1-Piston2-Ejectorrod3-Valveelement換向閥ReversingValve3換向閥利用閥芯相對(duì)于閥體的相對(duì)運(yùn)動(dòng)，使油路接通、關(guān)斷，或變換油流的方向，從而使液壓執(zhí)行元件啟動(dòng)、停止或變換運(yùn)動(dòng)方向。Areversingvalveallowsorstopsfluidfloworchangesfluidflowdirectioninfluidpathsbasedonitsvalveelementmotionrelativetoitsvalvebodytostart,stoporchangemovementdirectionofahydraulicactuator.Table3-1-1ClassificationofReversingValves換向閥ReversingValve3換向閥的工作原理Workingprincipleofreversingvalve在圖示狀態(tài)下，液壓缸兩腔不通壓力油，活塞處于停止?fàn)顟B(tài)。若使閥芯1左移，閥體2的油口P和A連通、B和T連通，則壓力油經(jīng)P、A進(jìn)入液壓缸左腔，右腔油液經(jīng)B、T流回油箱，活塞向右運(yùn)動(dòng)；反之，若使閥芯右移，則油口P和B連通、A和T連通，活塞便向左運(yùn)動(dòng)。Inthestateshowninthefigure,thetwochambersofthehydrauliccylinderdonotallowpressurefluidflow,andthepistonisstationary.Ifthevalveelement(1)ismovedtotheleft,fluidportsPandAofthevalvebody(2)areconnected,portsBandTareconnected,pressurefluidflowsintotheleftchamberofthehydrauliccylinderthroughportsPandA,andfluidintherightchamberflowsbacktothefluidtankthroughportsBandTtomovethepistonrightward.Ifthevalveelementismovedtotheright,theportsPandBareconnected,andportsAandTareconnectedtoallowthepistontomoveleftward.圖3-1-3換向閥的工作原理

Figure3-1-3Workingprincipleofreversingvalve1一閥芯2-閥體1-Valveelement2-Valvebody換向閥ReversingValve3NameStructurePrincipleDiagramGraphicSymbolApplicationScenarioTwo-positiontwo-wayreversingvalveItconnectsfluidandallows/stopsfluidflow(equivalenttoaswitch)Two-positionthree-wayreversingvalveItcontrolsfluidflowdirection(fromonedirectiontoanother)Two-positionfour-wayreversingvalveItdoesnotallowanactuatortostopinanypositionTwo-positionfive-wayreversingvalveItdoesnotallowanactuatortostopinanypositionThree-positionfour-wayreversingvalveItallowsanactuatortostopinanypositionThree-positionfive-wayreversingvalveItallowsanactuatortostopinanyposition換向閥ReversingValve3換向閥的中位機(jī)能Center-positionfunctionofreversingvalve換向閥處于常態(tài)位置時(shí)，其各油口的連通方式稱為滑閥機(jī)能。三位換向閥的常態(tài)為中位，因此三位換向閥的滑閥機(jī)能又稱為中位機(jī)能。不同中位機(jī)能的三位換向閥閥體通用，僅閥芯臺(tái)肩的結(jié)構(gòu)、尺寸及內(nèi)部通孔情況有區(qū)別，但作用區(qū)別又極大。Whenareversingvalveisinthenormalposition,theconnectionmodeofitsfluidportsenablestheslidevalvefunction.Athree-positionreversingvalveisnormallyincenterposition,sotheslidevalvefunctionofathree-positionreversingvalveisalsoknownascenter-positionfunction.Three-positionreversingvalveswithdifferentcenter-positionfunctionshavecommonvalvebodiesanddifferinthestructureandsizeofspoollandandinternalthroughhole,withsignificantdifferenceinfunctions.換向閥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.換向閥ReversingValve3在分析和選擇閥的中位機(jī)能時(shí)，通常考慮以下幾點(diǎn)：Inanalysisandselectionofthecenter-positionfunctionofavalve,thefollowingpointsshouldbeconsideredingeneral:（1）系統(tǒng)保壓。當(dāng)P口被堵塞，系統(tǒng)保壓，液壓泵能用于多缸系統(tǒng)。當(dāng)P口不太通暢地與T口接通時(shí)，系統(tǒng)能保持一定的壓力，供控制油路使用。(1)Systempressuremaintaining:WhenportPisblocked,thesystemmaintainspressureandthehydraulicpumpcanbeusedinamulti-cylindersystem.WhenportPisconnectedtoportTinnon-smoothway,thesystemcanmaintainacertainpressureforthecontrolfluidpath.（2）系統(tǒng)卸荷。P口通暢地與T口接通時(shí)，系統(tǒng)卸荷。(2)Systemunloading:WhenportPisconnectedtoportT,thesystemisunloaded.換向閥ReversingValve3（3）啟動(dòng)平穩(wěn)性。閥芯處于中位時(shí)，液壓缸某腔如通油箱，則啟動(dòng)時(shí)該腔內(nèi)因無油液起緩沖作用，啟動(dòng)不太平穩(wěn)。(3)Startingsmoothness:Whenthevalveelementisinthecenterposition,ifachamberofthehydrauliccylinderisconnectedtothetank,startingwillnotbesmoothenoughasthechamberhasnofluidforbufferinginstarting.（4）液壓缸“浮動(dòng)”和在任意位置上的停止。(4)Hydrauliccylinder"floating"andstoppingatanyposition:換向閥ReversingValve33換向閥的結(jié)構(gòu)Structureofreversingvalve（1）手動(dòng)換向閥。圖3-1-4（b）為自動(dòng)復(fù)位式手動(dòng)換向閥，放開手柄1、閥芯2在彈簧3的作用下自動(dòng)回復(fù)中位，該閥，適用于動(dòng)作頻繁、工作持續(xù)時(shí)間短的場(chǎng)合，操作比較完全，常用于工程機(jī)械的液壓傳動(dòng)系統(tǒng)中。(1)Manualreversingvalve:Figure3-1-4(b)showsanautomaticresettingmanualreversingvalve.Whenthehandle(1)isreleased,thevalveelement(2)automaticallyreturnstothecenterpositionundertheactionofthespring(3).Thisvalveissuitableforscenarioswherethevalvewouldactfrequentlyforshortdurationeachtime,withrelativelycompleteoperation.Thevalveiscommonlyusedinthehydraulictransmissionsystemofconstructionmachinery。如果將該閥，閥芯右端彈簧3的部位改為可自動(dòng)定位的結(jié)構(gòu)形式，即成為可在三個(gè)位置定位的手動(dòng)換向閥。圖3-1-4（a）為職能符號(hào)圖。Ifthespring(3)attherightendofthevalveelementischangedtoastructurethatallowsautomaticpositioning,thevalvebecomesamanualreversingvalvethatcanbepositionedinthreepositions.Figure3-1-4(a)showsitsfunctionalsymbol.換向閥ReversingValve33換向閥的結(jié)構(gòu)Structureofreversingvalve圖3-1-4手動(dòng)換向閥Figure3-1-4ManualReversingValve（a）職能符號(hào)圖（b）結(jié)構(gòu)圖(a)FunctionalSymbol(b)StructureDiagram1-手柄2-閥芯3-彈簧1-Handle2-Valveelement3-Spring換向閥ReversingValve3（2）機(jī)動(dòng)換向閥。機(jī)動(dòng)換向閥又稱行程閥，它主要用來控制機(jī)械運(yùn)動(dòng)部件的行程，它是借助于安裝在工作臺(tái)上的擋鐵5迫使閥芯移動(dòng)，從而控制油液的流動(dòng)方向，機(jī)動(dòng)換向閥通常是二位的，有二通、三通、四通和五通幾種，其中二位二通機(jī)動(dòng)閥又分常閉和常開兩種。(2)Mechanicalreversingvalve:Amechanicalreversingvalve,alsoknownasastrokevalve,ismainlyusedtocontrolthestrokeofmechanicalmovingparts.Itsvalveelementisforcedtomovebymeansofthestopiron(5)installedonthetabletocontrolthefluidflowdirection.Mechanicalreversingvalvesaregenerallyavailableastwo-positiontwo-way,three-way,four-wayandfive-wayvalves.Two-positiontwo-waymechanicalvalvesareavailableintwotypes:normallyclosedandnormallyopenvalves.換向閥ReversingValve3（2）機(jī)動(dòng)換向閥。圖3-1-5（a）為滾輪式二位三通常閉式機(jī)動(dòng)換向閥，在圖示位置閥芯2被彈簧1壓向上端，油腔P和A通，B口關(guān)閉。當(dāng)擋鐵5壓住滾輪4，使閥芯2移動(dòng)到下端時(shí)，就使油腔P和A斷開，P和B接通，A口關(guān)閉。圖3-1-5（b）所示為其職能符號(hào)。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。圖3-1-5機(jī)動(dòng)換向閥Figure3-1-5MechanicalReversingValve1-彈簧2-閥芯3-閥體4-滾輪5-擋鐵

1-Spring2-Valveelement3-Valvebody4-Roller5-Stopiron換向閥ReversingValve3（3）電磁換向閥。(3)Solenoidreversingvalve電磁換向閥是利用電磁鐵的通電吸合與斷電釋放而直接推動(dòng)閥芯來控制液流方向的。Asolenoidreversingvalvecontrolsfluidflowdirectionbyusingtheelectromagnetactionofengagementuponenergizationanddisengagementuponde-energizationtodirectlypushthevalveelement.電磁鐵按使用電源的不同，可分為交流和直流兩種。按銜鐵工作腔是否有油液又可分為“干式”和“濕式”。ElectromagnetscanbedividedintoACandDCelectromagnetsbythepowersupply,andinto"wettype"and"drytype"electromagnetsbypresenceofoilinthearmatureworkingchamberornot.換向閥ReversingValve3（3）電磁換向閥。(3)Solenoidreversingvalve圖3-1-6（a）所示為二位三通交流電磁換向閥結(jié)構(gòu)，在圖示位置，油口P和A相通，油口B斷開；當(dāng)電磁鐵通電吸合時(shí)，推桿1將閥芯2推向右端，這時(shí)油口P和A斷開，而與B相通。而當(dāng)磁鐵斷電釋放時(shí)，彈簧3推動(dòng)閥芯復(fù)位。圖3-1-6（b）所示為其職能符號(hào)。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.圖3-1-6二位三通電磁換向閥Figure3-1-6Two-positionThree-waySolenoidReversingValve（a）結(jié)構(gòu)圖（b）職能符號(hào)圖(a)StructureDiagram(b)FunctionalSymbol1-推桿2-閥芯3-彈簧1-Pushrod2-Valveelement3-Spring換向閥ReversingValve3（3）電磁換向閥。(3)Solenoidreversingvalve電磁換向閥就其工作位置來說，有二位和三位等。二位電磁閥有一個(gè)電磁鐵靠彈簧復(fù)位；三位電磁閥有兩個(gè)電磁鐵，如圖3-1-7所示為一種三位五通電磁換向閥的結(jié)構(gòu)和職能符號(hào)。solenoidreversingvalvesareavailablewithtwopositionsandthreepositionsintermsofworkingposition.Atwo-positionsolenoidvalvehasoneelectromagnetresetbymeansofaspring.Athree-positionsolenoidvalvehastwoelectromagnets.Figure3-1-7showsthestructureandfunctionalsymbolofathree-positionfive-waysolenoidreversingvalve.圖3-1-7三位五通電磁換向閥Figure3-1-7Three-positionFive-waySolenoidReversingValve（a）結(jié)構(gòu)圖（b）職能符號(hào)圖(a)StructureDiagram(b)FunctionalSymbol換向閥ReversingValve3（4）液動(dòng)換向閥。液動(dòng)換向閥是利用控制油路的壓力油來改變閥芯位置的換向閥，圖3-1-8所示為三位四通液動(dòng)換向閥的結(jié)構(gòu)和職能符號(hào)。閥芯是由其兩端密封腔中油液的壓差來移動(dòng)的，當(dāng)控制油路的壓力油從閥右邊的控制油口K2進(jìn)入滑閥右腔時(shí)，K1接通回油，閥芯向左移動(dòng)，使壓力油口P與B相通，A與T相通；當(dāng)K1接通壓力油，K2接通回油時(shí)，閥芯向右移動(dòng)，使得P與A相通，B與T相通；當(dāng)K1、K2都通回油時(shí)，閥芯在兩端彈簧和定位套作用下回到中間位置。(4)Hydraulicreversingvalve:Ahydraulicreversingvalvechangesthepositionofitsvalveelementbyusingpressurefluidinthecontrolfluidpaths.Figure3-1-8showsthestructureandfunctionalsymbolofathree-positionfour-wayhydraulicreversingvalve.Thevalveelementismovedbythepressuredifferenceoffluidinthesealedchambersatbothends.WhenpressurefluidofcontrolfluidpathsflowsintotherightchamberoftheslidevalvefromthecontrolportK2ontherightofthevalve,K1becomesconnectedtoreturnfluidandthevalveelementmovesleftwardtoconnectpressurefluidportsPandB,andconnectportsAandT.WhenK1isconnectedtopressurefluidandK2isconnectedtoreturnfluid,thevalveelementmovesrightwardtoconnectportsPandA,andconnectportsBandT.WhenbothK1andK2areconnectedtoreturnfluid,thevalveelementreturnstothecenterpositionundertheactionofthespringsatbothendsandthelocatingsleeve.換