項目3 任務 2 壓力控制閥的認知

壓力控制閥的認知KnowledgeaboutPressureControlValve任務2Task2任務描述TaskDescription1了解常見壓力控制閥的基本工作原理及符號，進一步熟悉壓力控制閥的種類，熟悉常見壓力控制閥在不同場合的應用。Understandthebasicworkingprinciplesandsymbolsofcommonpressurecontrolvalves,beacquaintedwiththetypesofpressurecontrolvalves,andbefamiliarwiththeapplicationsofpressurecontrolvalvesindifferentscenarios.在液壓傳動系統(tǒng)中，控制油液壓力高低的液壓閥稱之為壓力控制閥，簡稱壓力閥。這類閥的共同點是利用作用在閥芯上的液壓力和彈簧力相平衡的原理工作的。Inahydraulictransmissionsystem,thehydraulicvalvecontrollingfluidpressureiscalledpressurecontrolvalveorpressurevalveforshort.Thecommonpointofthesevalvesisthattheyoperateundertheprincipleofbalancinghydraulicpressureandspringforceactingonvalveelement.溢流閥OverflowValve2溢流閥的結構和工作原理Structureandworkingprincipleofoverflowvalve常用的溢流閥按其結構形式和基本動作方式可歸結為直動式和先導式兩種。Commonlyusedoverflowvalvescanbeclassifiedbythestructureandbasicactionintotwotypes:direct-actingandpilot-operatedvalves.（1）直動式溢流閥(1)Direct-actingoverflowvalve溢流閥OverflowValve2直動式溢流閥是依靠系統(tǒng)中的壓力油直接作用在閥芯上與彈簧力等相平衡，以控制閥芯的啟閉動作，圖3-2-1（a）所示是一種低壓直動式溢流閥，P是進油口，T是回油口，進口壓力油經閥芯3中間的阻尼孔a作用在閥芯的底部端面上，當進油壓力較小時，閥芯在彈簧2的作用下處于下端位置，將P和T兩油口隔開。Adirect-actingoverflowvalvereliesonpressurefluidinthesystemtodirectlyactonthevalveelementandbalancethespringforcetocontrolthevalveelementforopeningandclosing.Figure3-2-1(a)showsalow-pressuredirect-actingoverflowvalve,forwhichPisthefluidinlet,andTisthefluidreturnport.Pressurefluidattheinletactsonthebottomendfaceofthevalveelementthroughthedampinghole(a)inthemiddleofthevalveelement(3).Whentheinletfluidpressureislow,thevalveelementisheldatthelowerendundertheactionofthespring(2),separatingportPfromportT.2當油壓力升高，在閥芯下端所產生的作用力超過彈簧的壓緊力F。此時，閥芯上升，閥口被打開，將多余的油液排回油箱，閥芯上的阻尼孔a用來對閥芯的動作產生阻尼，以提高閥的工作平衡性，調整螺帽1可以改變彈簧的壓緊力，這樣也就調整了溢流閥進口處的油液壓力p。Whenthefluidpressureincreases,theforceactingonthelowerendofthevalveelementexceedsthecompressionforceFofthespring.Atthismoment,thevalveelementrises,andthevalveportisopenedtodischargeexcessfluidbacktothetank.Thedampinghole(a)inthevalveelementdampstheactionofthevalveelementtoimprovethebalanceofthevalve.Byadjustingthenut(1),compressionforceofthespringcanbechangedtoadjustthefluidpressurepattheinletoftheoverflowvalve.圖3-2-1低壓直動式溢流閥Figure3-2-1Low-pressureDirect-actingOverflowValve（a）結構圖（b）職能符號圖（c）實物圖

(a)StructureDiagram(b)FunctionalSymbol(c)RealProductPicture1-螺帽2-調壓彈簧3-閥芯1-Nut2-Pressureregulatingspring3-Valveelement溢流閥OverflowValve2圖3-2-2所示為先導式溢流閥的結構示意圖，在圖中壓力油從P口進入，通過阻尼孔e后作用在錐閥芯3上，當進油口壓力較低，導閥上的液壓作用力不足以克服導閥右邊的彈簧2的作用力時，導閥關閉，沒有油液流過阻尼孔，所以錐閥芯3兩端壓力相等，在較軟的主閥彈簧2作用下閥芯3處于最下端位置，溢流閥閥口P和T隔斷，沒有溢流。Figure3-2-2showsastructurediagramofpilot-operatedoverflowvalve.Inthefigure,pressurefluidflowsinfromportPandactsontheconicalvalveelement(3)throughthedampinghole(e).Whenthepressureatthefluidinletislow,thehydraulicforceactingonthepilotvalveisnotstrongenoughtoovercometheactingforceofthespring(2)ontherightsideofthepilotvalve,thepilotvalveisclosedandnofluidflowsthroughthedampinghole,sothepressuresonbothendsoftheconicalvalveelement(3)areequal.Undertheactionofthesoftmainvalvespring(2),thevalveelement(3)isheldatthelowestend,andthevalveportsPandToftheoverflowvalveareseparated,withnooverflow.（2）先導式溢流閥(2)Pilot-operatedoverflowvalve

溢流閥OverflowValve2當進油口壓力升高到作用在導閥上的液壓力大于導閥彈簧作用力時，導閥打開，壓力油就可通過阻尼孔、經導閥流回油箱，由于阻尼孔的作用，使主閥芯上端的液壓力p2小于下端壓力p1，當這個壓力差作用在主閥芯上的力等于或超過主閥預設的彈簧力Fs，主閥芯開啟，油液從P口流入，經主閥閥口由T流回油箱，實現(xiàn)溢流。Whenthefluidinletpressurerisestotheextentthatthehydraulicpressureactingonthepilotvalveisgreaterthantheactingforceofthepilotvalvespring,thepilotvalveopenstoallowpressurefluidtoflowbacktothetankthroughthedampingholeandthepilotvalve.Duetothedampinghole,thehydraulicpressurep2attheupperendofthemainvalveelementislessthanthepressurep1atthelowerend.WhentheforceofthispressuredifferenceactingonthemainvalveelementbecomesequaltoorexceedsthepresetspringforceFsofthemainvalve,themainvalveelementopenstoallowfluidtoflowinfromportPandbacktothetankviathemainvalveportTtoachieveoverflow.溢流閥OverflowValve2當進油口壓力升高到作用在導閥上的液壓力大于導閥彈簧作用力時，導閥打開，壓力油就可通過阻尼孔、經導閥流回油箱，由于阻尼孔的作用，使主閥芯上端的液壓力p2小于下端壓力p1，當這個壓力差作用在主閥芯上的力等于或超過主閥預設的彈簧力Fs，主閥芯開啟，油液從P口流入，經主閥閥口由T流回油箱，實現(xiàn)溢流。Whenthefluidinletpressurerisestotheextentthatthehydraulicpressureactingonthepilotvalveisgreaterthantheactingforceofthepilotvalvespring,thepilotvalveopenstoallowpressurefluidtoflowbacktothetankthroughthedampingholeandthepilotvalve.Duetothedampinghole,thehydraulicpressurep2attheupperendofthemainvalveelementislessthanthepressurep1atthelowerend.WhentheforceofthispressuredifferenceactingonthemainvalveelementbecomesequaltoorexceedsthepresetspringforceFsofthemainvalve,themainvalveelementopenstoallowfluidtoflowinfromportPandbacktothetankviathemainvalveportTtoachieveoverflow.溢流閥OverflowValve2圖3-2-2先導式溢流閥

Figure3-2-2Pilot-operatedoverflowvalve1-調節(jié)螺母2-調壓彈簧3-錐閥芯4-彈簧5-主閥芯1-Adjustingnut2-Pressureregulatingspring3-Conicalvalveelement4-Spring5-Mainvalveelement溢流閥OverflowValve2溢流閥的作用Functionsofoverflowvalve溢流閥OverflowValve在采用定量泵供油的液壓系統(tǒng)中，由流量控制閥調節(jié)進入執(zhí)行元件的流量，定量泵輸出的多余油液則從溢流閥流回油箱。Inahydraulicsystemwhereafixed-displacementpumpisusedtosupplyfluid,theflowcontrolvalveregulatestheflowoffluidintotheactuator,andtheexcessfluidoutputtedbythefixed-displacementpumpflowsbacktothetankfromtheoverflowvalve.(1)作溢流閥用Actingasoverflowvalve2溢流閥的作用Functionsofoverflowvalve溢流閥OverflowValve圖3-2-3(b)所示為一變量泵供油系統(tǒng)，執(zhí)行元件的速度由變量泵自身調節(jié)，系統(tǒng)中無多余油液，系統(tǒng)工作壓力隨負載變化而變化。正常工作時，溢流閥口關閉。一旦過載，溢流閥口立即打開，使油液流回油箱，系統(tǒng)壓力不再升高，以保障系統(tǒng)安全。Figure3-2-3(b)showsavariabledisplacementpumpbasedfluidsupplysystem.Thespeedoftheactuatorisadjustedbythevariabledisplacementpump,withnoexcessfluidinthesystem.Thesystemworkingpressurechangeswiththeload.Duringnormaloperation,theoverflowvalveportisclosed.Oncethesystemisoverloaded,theoverflowvalveportopensimmediately,allowingfluidtoflowbacktothetanksothatthesystempressurewillnolongerrisetoensuresystemsafety.(2)作安全閥用Actingassafetyvalve2溢流閥的作用Functionsofoverflowvalve溢流閥OverflowValve當電磁鐵斷電時，遠程控制口K被堵塞，溢流閥起溢流穩(wěn)壓作用。當電磁鐵通電時，遠程控制口K通油箱，溢流閥的主閥芯上端壓力接近于零，此時溢流閥口全開，回油阻力很小，泵輸出的油液便在低壓下經溢流閥口流回油箱，使液壓泵卸荷，從而減小系統(tǒng)功率損失，故溢流閥起卸荷作用。Whentheelectromagnetisde-energized,theremotecontrolportKisblocked,andtheoverflowvalvefunctionsforoverflowandpressurestabilization.Whenthesolenoidisenergized,theremotecontrolportKisconnectedtothetank,andthepressureattheupperendofthemainvalveelementofoverflowvalveisclosetozero.Atthismoment,theoverflowvalveportisfullyopened,thefluidreturnresistanceissmall,andthefluiddeliveredfromthepumpflowsbackunderlowpressuretothetankthroughtheoverflowvalveporttounloadthehydraulicpump,therebyreducingthepowerlossofthesystem.Therefore,theoverflowvalveactsasunloadingvalve.(3)作卸荷閥用Actingasunloadingvalve2溢流閥的作用Functionsofoverflowvalve溢流閥OverflowValve溢流閥2接在回油路上，可對回油產生阻力，即形成背壓，利用背壓可提高執(zhí)行元件的運動平穩(wěn)性。theoverflowvalve(2)isconnectedtothefluidreturnpath;itcancreateresistancetofluidreturnandformbackpressuretoimprovethemotionsmoothnessoftheactuator.(4)作背壓閥用

Actingascounterbalancevalve圖3-2-3溢流閥的作用

Figure3-2-3Functionsofoverflowvalve3減壓閥ReliefValve減壓閥是使出口壓力（二次壓力）低于進口壓力（一次壓力）的一種壓力控制閥。其作用是降低液壓系統(tǒng)中某一回路的油液壓力，使用一個油源能同時提供兩個或幾個不同壓力的輸出。減壓閥在各種液壓設備的夾緊系統(tǒng)、潤滑系統(tǒng)和控制系統(tǒng)中應用較多。Areliefvalveisapressurecontrolvalvethatenablestheoutletpressure(secondarypressure)tobelowerthantheinletpressure(primarypressure).Itsfunctionistoreducethefluidpressureofacircuitinthehydraulicsystem,andprovidetwoorseveraldifferentpressureoutputswithonefluidsourceatthesametime.Reliefvalvesarewidelyusedinclampingsystems,lubricationsystemsandcontrolsystemsofvariouskindsofhydraulicequipment.3減壓閥ReliefValve此外，當油液壓力不穩(wěn)定時，在回路中串入一減壓閥可得到一個穩(wěn)定的較低的壓力。減壓閥也有直動式和先導式之分，先導式減壓閥應用較多。Inaddition,whenfluidpressurebecomesunstable,areliefvalvecanbeconnectedinseriestothecircuittoachievestablelowpressure.Reliefvalvesarealsoavailableindirect-actingandpilot-operatedvalves.Pilot-operatedreliefvalvesaremorewidelyused.3減壓閥ReliefValve壓力油從閥的進油口進入進油腔P1，經開口為x的減壓閥減壓后，再從出油腔P2和出油口流出。出油腔壓力油經小孔f進人主閥芯5的下端，同時經阻尼小孔e流入主閥芯上端，再經孔c和b作用于錐閥芯3上。當出油口壓力較低時，先導閥關閉，主閥芯兩端壓力相等，主閥芯被平衡彈簧4壓在最下端(圖示位置)，減壓閥口開度為最大，壓降為最小，減壓閥不起減壓作用。PressurefluidflowsintothefluidinletchamberP1fromthefluidinletofthevalve,andafterbeingdepressurizedbythereliefvalvewithportx,flowsoutfromthefluidoutletchamberP2andthefluidoutlet.Pressurefluidfromthefluidoutletchamberflowsintothelowerendofthemainvalveelement(5)throughthesmallholefandmeanwhileflowsintotheupperendofthemainvalveelementthroughthesmalldampingholee,andactsontheconicalvalveelement(3)throughtheholescandb.Whentheoutletpressureislow,thepilotvalveisclosed,thepressuresonbothendsofthemainvalveelementareequal;themainvalveelementispressedtothelowestend(inthepositionshowninthefigure)bythebalancespring(4);theopeningofthereliefvalvereachesthemaximumextentandthepressuredropisthesmallest;thereliefvalvedoesnothavepressurereducingeffect.減壓閥的工作原理Workingprincipleofreliefvalve3減壓閥ReliefValve圖3-2-4減壓閥Figure3-2-4Reliefvalve（a）結構圖（b）實物圖（c）、（d）職能符號圖(a)StructureDiagram(b)RealProductPicture(c),(d)FunctionalSymbol1-調節(jié)螺母2-阻尼孔x3-錐閥芯4-平衡彈簧5-主閥芯L-外泄漏油口1-Adjustingnut2-Dampingholex3-Conicalvalveelement4-Balancespring5-MainvalveelementL-Externaldischargeport3減壓閥ReliefValve當出油口壓力達到先導閥的調定壓力時，先導閥開啟，此時P2腔的部分壓力油經孔e、c、b、先導閥口、孔a和泄漏口L流回油箱。由于阻尼小孔e的作用，主閥芯兩端產生壓力差，主閥芯便在此壓力差作用下克服平衡彈簧的彈力上移，減壓閥口減小，使出油口壓力降低至調定壓力。若由于外界干擾(如負載變化)而使出油口壓力變化，則減壓閥會自動調整減壓閥口的開度以保持出油壓力穩(wěn)定。調節(jié)螺母1即可調節(jié)調壓彈簧2的預壓縮量，從而調定減壓閥出油口壓力。中壓先導式減壓閥的調壓范圍為2.5-8.0MPa，適用于中、低壓系統(tǒng)。Whenthefluidoutletpressurereachesthesetpressureofthepilotvalve,thepilotvalveopens.Atthismoment,partofpressurefluidinthechamberP2flowsbacktothetankthroughholese,candb,pilotvalveholeaanddischargeportL.Duetotheeffectofthesmalldampingholee,pressuredifferenceisformedbetweenbothendsofthemainvalveelement.Undertheeffectofthispressuredifference,themainvalveelementovercomestheelasticforceofthebalancespringandrises;asaresult,thereliefvalveportbecomessmallertoreducethefluidoutletpressuretothesetvalue.Ifthefluidoutletpressurechangesduetoexternalinterference(suchasloadchange),thereliefvalvewillautomaticallyadjustitsportopeningtokeepthefluidpressurestable.Byadjustingthenut(1),thepre-compressionofthepressureregulatingspring(2)canbeadjustedtoregulatethefluidoutletpressureofthereliefvalve.Thepressureregulatingrangeofthemedium-pressurepilot-operatedreliefvalveis2.5-8.0MPa,whichisalsosuitableformedium-andlow-pressuresystems3減壓閥ReliefValve將先導式減壓閥和先導式溢流閥進行比較，它們之間有如下幾點不同之處：Comparisonofapilot-operatedreliefvalveandapilot-operatedoverflowvalveindicatesthefollowingdifferencesbetweenthem:①減壓閥保持出口壓力基本不變，而溢流閥保持進口處壓力基本不變。①Areliefvalvekeepstheoutletpressurebasicallyunchanged,whileanoverflowvalvekeepstheinletpressurebasicallyunchanged.②在不工作時，減壓閥進、出油口互通，而溢流閥進出油口不通。②Whennotinoperation,thefluidinletandoutletofareliefvalveareconnected,butthoseofanoverflowvalvearenotconnected.3減壓閥ReliefValve③為保證減壓閥出口壓力調定值恒定，它的導閥彈簧腔需通過泄油口單獨外接油箱；而溢流閥的出油口是通油箱的，所以它的導閥的彈簧腔和泄漏油可通過閥體上的通道和出油口相通，不必單獨外接油箱。③Toensurethatthesetvalueoftheoutletpressureofareliefvalveisstable,itspilotvalvespringchamberneedstobeconnectedtothetankseparatelythroughthefluiddischargeport.Incomparison,thefluidoutletofanoverflowvalveisconnectedtothetank,sothespringchamberofitspilotvalveandfluidtobedischargedcanbeconnectedtothefluidoutletthroughthechannelonthevalvebody,withoutneedtobeconnectedtothetankseparately.3減壓閥ReliefValve2減壓閥的應用2Applicationofreliefvalve減壓閥在夾緊油路、控制油路和潤滑油路中應用較多。Reliefvalvesarewidelyusedinclampingfluidpath,controlfluidpathandlubricatingoilpath.圖3-2-5減壓閥的應用Figure3-2-5Applicationofreliefvalve4順序閥SequenceValve順序閥是用來控制液壓系統(tǒng)中各執(zhí)行元件動作的先后順序。依控制壓力的不同，順序閥又可分為內控式和外控式兩種。前者用閥的進口壓力控制閥芯的啟閉，后者用外來的控制壓力油控制閥芯的啟閉（即液控順序閥）。順序閥也有直動式和先導式兩種，前者一般用于低壓系統(tǒng)，后者用于中高壓系統(tǒng)。Asequencevalvecontrolsthesequenceofactionofactuatorsinahydraulicsystem.Sequencevalvescanbedividedbythecontrolpressureintotwotypes:internalcontrolledandexternalcontrolledvalves.Theformercontrolstheopeningandclosingofvalveelementbyusinginletpressureofthevalve,whilethelattercontrolstheopeningandclosingofvalveelementbyusingexternalcontrolpressurefluid(i.e.hydrauliccontrolsequencevalve).Sequencevalvesarealsoavailableindirect-actingandpilot-operatedvalves.Theformeraregenerallyusedinlow-pressuresystems,whilethelatterareusedinmedium-andhigh-pressuresystems.4順序閥SequenceValve1順序閥的工作原理Workingprincipleofsequencevalve當進油口壓力p1較低時，閥芯在彈簧作用下處下端位置，進油口和出油口不相通。當作用在閥芯下端的油液的液壓力大于彈簧的預緊力時，閥芯向上移動，閥口打開，油液便經閥口從出油口流出，從而操縱另一執(zhí)行元件或其他元件動作。Whenthefluidinletpressurep1islow,thevalveelementisheldatthelowerendundertheactionofthespring;thefluidinletandoutletarenotconnected.Whenthehydraulicpressureoffluidactingonthelowerendofthevalveelementisgreaterthanthepreloadofthespring,thevalveelementmovesupward,thevalveportopens,andfluidflowsoutfromthefluidoutletthroughthevalveport,therebyoperatinganotheractuatororothercomponentstoact.4順序閥SequenceValve1順序閥的工作原理Workingprincipleofsequencevalve（a）(b)內控外泄式(c)(b)InternalControlledandExternalDischargingType(c)(e)外控外泄式(f)外控內泄式(e)ExternalControlledandExternalDischargingType(f)ExternalControlledandInternalDischargingType圖3-2-6直動式順序閥Figure3-2-6Direct-actingSequenceValve1-下蓋2-活塞3-閥體4-閥芯5-彈簧6-上蓋1-Lowercover2-Piston3-Valvebody4-Valveelement5-Spring6-Uppercover4順序閥SequenceValve順序閥的應用Applicationofsequencevalve圖3-2-7所示為機床夾具上用順序閥實現(xiàn)定工件先定位，后夾緊的順序動作回路。Figure3-2-7showsasequencevalveusedonamachinetoolfixturetoachieveasequentialactionloopofpositioningaworkpiecebefore