項目4 任務 2 壓力控制回路的安裝與調試

壓力控制回路的安裝與調試InstallationandCommissioningofPressureControlCircuits任務2Task2任務描述TaskDescription1分析常用的壓力控制回路的方式，能夠講出常用壓力控制回路的原理。Taskdescription:Analyzethepatternsofcommonlyusedpressurecontrolcircuits,andbeabletotelltheprinciplesofcommonlyusedpressurecontrolcircuits.調壓及限壓回路PressureRegulatingandLimitingCircuits2壓力控制回路是用壓力閥來控制和調節(jié)液壓系統(tǒng)主油路或某一支路的壓力，以滿足執(zhí)行元件速度換接回路所需的力或力矩的要求。利用壓力控制回路可實現(xiàn)對系統(tǒng)進行調壓(穩(wěn)壓)、減壓、增壓、卸荷、保壓與平衡等各種控制，當液壓系統(tǒng)工作時，液壓泵應向系統(tǒng)提供所需壓力的液壓油，同時，又能節(jié)省能源，減少油液發(fā)熱，提高執(zhí)行元件運動的平穩(wěn)性。所以，應設置調壓或限壓回路。當液壓泵一直工作在系統(tǒng)的調定壓力時，就要通過溢流閥調節(jié)并穩(wěn)定液壓泵的工作壓力。在變量泵系統(tǒng)中或旁路節(jié)流調速系統(tǒng)中用溢流閥(當安全閥用)限制系統(tǒng)的最高安全壓力。當系統(tǒng)在不同的工作時間內需要有不同的工作壓力，可采用二級或多級調壓回路。調壓及限壓回路PressureRegulatingandLimitingCircuits2Pressurecontrolcircuitsusepressurevalvestocontrolandregulatethepressureofthemainoilpathoracertainbranchofahydraulicsystem,inordertofulfilltheforceortorquerequirementforactuatingcomponentspeedchangeovercircuit.Pressurecontrolcircuitscanrealizemanycontrolsofthesystem,suchaspressureregulation(stabilization),depressurization,pressurization,unloading,pressuremaintainingandbalance.Whenthehydraulicsystemisworking,thehydraulicpumpshallprovidethesystemwithhydraulicfluidofrequiredpressure,whichsavesenergy,reducestheheatoffluid,andalsoimprovesthemovementstabilityofactuatingcomponents.Therefore,pressureregulatingorlimitingcircuitsshallbeprovided.Ifthehydraulicpumpworksatthesetpressureofsystemfromtimetotime,theworkingpressureofhydraulicpumpshallberegulatedandstabilizedbyoverflowvalve.Inavariablepumpsystemorabypassthrottlespeedgoverningsystem,overflowvalve(assafetyvalve)shallbeusedforlimitingthemaximumsafetypressureofthesystem.Whenthesystemrequiresdifferentworkingpressuresindifferentworkinghours,two-stageormulti-stagepressureregulatingcircuitcanbeadopted.調壓及限壓回路PressureRegulatingandLimitingCircuits2單級調壓回路Single-stagePressureRegulatingCircuit如圖4-2-1所示，通過液壓泵1和溢流閥2的并聯(lián)連接，即可組成單級調壓回路。調節(jié)溢流閥的壓力，可以改變泵的輸出壓力。當溢流閥的調定壓力確定后，液壓泵就在溢流閥的調定壓力下工作。從而實現(xiàn)了對液壓系統(tǒng)進行調壓和穩(wěn)壓控制。AsshowninFigure4-2-1,theparallelconnectionofhydraulicpump1andoverflowvalve2formsasingle-stagepressureregulatingcircuit.Regulationoftheoverflowvalvepressurecanchangetheoutputpressureofpump.Aftertheregulationpressureofoverflowvalveisdetermined,thehydraulicpumpworksunderthepressureregulatedbytheoverflowvalve.Thepressureregulationandstabilizationcontrolofhydraulicsystemistherebyachieved.Figure4-2-1Single-stagePressureRegulatingCircuit1-Hydraulicpump2-Direct-actingoverflowvalve3-Shock-proofpressuregauge調壓及限壓回路PressureRegulatingandLimitingCircuits2二級調壓回路Two-stagePressureRegulatingCircuit圖4-2-2（a）所示為典型二級調壓回路。該回路可實現(xiàn)兩種不同的系統(tǒng)壓力控制，由先導式溢流閥4和直動式溢流閥2各調一級。當二位三通電磁換向閥3處于圖示位置時系統(tǒng)壓力由閥4調定。當閥3得電后換位時，系統(tǒng)壓力由閥2調定，這時液壓泵的溢流流量經主閥4回油箱，閥2亦處于工作狀態(tài)，并有油液通過。Figure4-2-2(a)showsatypicaltwo-stagepressureregulatingcircuit.Thiscircuitisabletoachievetwodifferentsystempressurecontrols,wherethepilottypeoverflowvalve4andthedirect-actingoverflowvalve2regulateonestage,respectively.Whenthetwo-positionthree-waysolenoidreversingvalve3isinthepositionshowninthefigure,thesystempressureisregulatedbyvalve4.Whenvalve3isenergizedandchangesposition,thesystempressureisregulatedbyvalve2,wheretheoverflowdischargeofhydraulicpumpreturnstooiltankviathemainvalve4,andvalve2isalsoworkingandhasoilflowingthrough.Figure4-2-1Single-stagePressureRegulatingCircuit1-Hydraulicpump2-Direct-actingoverflowvalve3-Shock-proofpressuregauge調壓及限壓回路PressureRegulatingandLimitingCircuits2Figure4-2-2Two-stagePressureRegulatingCircuit(a)ExampleOneofTwo-stagePressureRegulatingCircuit(b)SchematicDiagramofElectricalControl1-HydraulicPump2-Direct-actingoverflowvalve3-Two-positionthree-waysolenoidreversingvalve4-Pilottypeoverflowvalve5-Shock-proofpressuregauge注意：閥2的調定壓力一定要小于閥4的調定壓力。Note:Regulationpressureofvalve2mustbelessthantheregulationpressureofvalve4.調壓及限壓回路PressureRegulatingandLimitingCircuits2Figure4-2-3Two-stagePressureRegulatingCircuit(a)ExampleTwoofTwo-stagePressureRegulatingCircuit(b)SchematicDiagramofElectricalControl1-Hydraulicpump2-Pilottypeoverflowvalve3-Shock-proofpressuregauge4-Two-positionfour-waysolenoidreversingvalve5-Direct-actingoverflowvalve6-Double-actinghydrauliccylinderwithsinglepistonrod圖4-2-3（a）為二級調壓回路的另一例，活塞下降為工作行程，此時高壓溢流閥2限制系統(tǒng)最高壓力。活塞上升為非工作行程，用低壓溢流閥5限制其最高壓力。本回路常用于壓力機的液壓系統(tǒng)中。Figure4-2-3(a)isanotherexampleoftwo-stagepressureregulatingcircuit,wherethepistondropstotheworkingstrokeandthehigh-pressureoverflowvalve2limitsthemaximumsystempressure.Thepistonrisestonon-workingstrokeandthelow-pressureoverflowvalve5limitsitsmaximumpressure.Thiscircuitiscommonlyusedinthehydraulicsystemofpressmachine.卸荷回路UnloadingCircuits3圖4-2-4（a）中，先導式溢流閥3的遠程控制口直接與二位三通電磁閥4相連，便構成一種用先導式溢流閥遙控口卸荷回路。當換向閥4處于圖示位置時，主油路系統(tǒng)壓力由溢流閥3調節(jié)，當電磁鐵AD1得電閥4換向時，溢流閥3的遠程控制口經閥4與油箱相通，系統(tǒng)壓力卸荷。InFigure4-2-4(a),theremotecontrolinterfaceofpilottypeoverflowvalve3isdirectlyconnectedwithtwo-positionthree-waysolenoidreversingvalve4,inordertoformanunloadingcircuitatremotecontrolinterfaceofpilottypeoverflowvalve.Whenthereversingvalve4isinthepositionshowninthefigure,thesystempressureofmainoilpathisregulatedbyoverflowvalve3;whenelectromagnetAD1isenergizedandthesolenoidvalve4changesdirection,theremotecontrolinterfaceofoverflowvalve3isconnectedwiththeoiltankviavalve4,therebyunloadingthesystempressure.1先導式溢流閥遙控口卸荷回路UnloadingCircuitatRemoteControlInterfaceofPilotTypeOverflowValve卸荷回路UnloadingCircuits31-Hydraulicpump2-Direct-actingoverflowvalve3-Shock-proofpressuregauge4-Two-positionthree-waysolenoidreversingvalve2換向閥卸荷回路

ReversingValveUnloadingCircuit在圖4-2-5（a）中，利用換向閥4使泵卸荷，但切換壓力沖擊大，適用于低壓小流量的系統(tǒng)。InFigure4-2-5(a),thereversingvalve4isusedforunloadingthepump,butthereisagreatchangeoverpressureimpact;sothecircuitissuitableforsmall-flowsystems.減壓回路DepressurizingCircuits4當泵的輸出壓力是高壓而局部回路或支路要求低壓時，可以采用減壓回路。Whenthepumpoutputsahighpressurebutlocalcircuitorbranchrequiresalowpressure,thedepressurizingcircuitcanbeadopted,減壓回路較為簡單，一般是在所需低壓的支路上串接減壓閥。Depressurizingcircuitisrelativelysimple,whichisgenerallyformedbyconnectingareliefvalveinserieswiththebranchtobedepressurized.采用減壓回路雖能方便地獲得某支路穩(wěn)定的低壓，但壓力油經減壓閥口時要產生壓力損失。

Astablelowpressureofcertainbranchcanbeconvenientlyobtainedbyusingadepressurizingcircuit,butthepressurefluidwillbesubjecttopressurelosswhenitpassesthroughthereliefvalve.減壓回路DepressurizingCircuits4圖4-2-6（a）為一典型的減壓回路，主要應用于夾緊回路中。液壓泵供油最高壓力由溢流閥2根據(jù)主油路的需要來調節(jié)。主油路并聯(lián)減壓閥3后，使夾緊缸7獲得較低的壓力，其夾緊壓力由減壓閥3調節(jié)且可保持壓力恒定。單向閥4起短時保壓之用，當主油路壓力低于減壓閥調整壓力時，防止夾緊力降低。Figure4-2-6(a)isatypicaldepressurizingcircuit,whichismainlyusedintheclampingcircuit.Themaximumoilsupplypressureofhydraulicpumpisregulatedbytheoverflowvalve2accordingtothedemandofmainoilpath.Afterthemainoilpathisconnectedinparallelwithreliefvalve3,theclampingcylinder7obtainsalowerpressure,wheretheclampingforcecanberegulatedbyreliefvalve3andmaintainedconstant.The