项目4 任务 2 压力控制回路的安装与调试

压力控制回路的安装与调试InstallationandCommissioningofPressureControlCircuits任务2Task2任务描述TaskDescription1分析常用的压力控制回路的方式，能够讲出常用压力控制回路的原理。Taskdescription:Analyzethepatternsofcommonlyusedpressurecontrolcircuits,andbeabletotelltheprinciplesofcommonlyusedpressurecontrolcircuits.调压及限压回路PressureRegulatingandLimitingCircuits2压力控制回路是用压力阀来控制和调节液压系统主油路或某一支路的压力，以满足执行元件速度换接回路所需的力或力矩的要求。利用压力控制回路可实现对系统进行调压(稳压)、减压、增压、卸荷、保压与平衡等各种控制，当液压系统工作时，液压泵应向系统提供所需压力的液压油，同时，又能节省能源，减少油液发热，提高执行元件运动的平稳性。所以，应设置调压或限压回路。当液压泵一直工作在系统的调定压力时，就要通过溢流阀调节并稳定液压泵的工作压力。在变量泵系统中或旁路节流调速系统中用溢流阀(当安全阀用)限制系统的最高安全压力。当系统在不同的工作时间内需要有不同的工作压力，可采用二级或多级调压回路。调压及限压回路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.调压及限压回路PressureRegulatingandLimitingCircuits2单级调压回路Single-stagePressureRegulatingCircuit如图4-2-1所示，通过液压泵1和溢流阀2的并联连接，即可组成单级调压回路。调节溢流阀的压力，可以改变泵的输出压力。当溢流阀的调定压力确定后，液压泵就在溢流阀的调定压力下工作。从而实现了对液压系统进行调压和稳压控制。AsshowninFigure4-2-1,theparallelconnectionofhydraulicpump1andoverflowvalve2formsasingle-stagepressureregulatingcircuit.Regulationoftheoverflowvalvepressurecanchangetheoutputpressureofpump.Aftertheregulationpressureofoverflowvalveisdetermined,thehydraulicpumpworksunderthepressureregulatedbytheoverflowvalve.Thepressureregulationandstabilizationcontrolofhydraulicsystemistherebyachieved.Figure4-2-1Single-stagePressureRegulatingCircuit1-Hydraulicpump2-Direct-actingoverflowvalve3-Shock-proofpressuregauge调压及限压回路PressureRegulatingandLimitingCircuits2二级调压回路Two-stagePressureRegulatingCircuit图4-2-2（a）所示为典型二级调压回路。该回路可实现两种不同的系统压力控制，由先导式溢流阀4和直动式溢流阀2各调一级。当二位三通电磁换向阀3处于图示位置时系统压力由阀4调定。当阀3得电后换位时，系统压力由阀2调定，这时液压泵的溢流流量经主阀4回油箱，阀2亦处于工作状态，并有油液通过。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调压及限压回路PressureRegulatingandLimitingCircuits2Figure4-2-2Two-stagePressureRegulatingCircuit(a)ExampleOneofTwo-stagePressureRegulatingCircuit(b)SchematicDiagramofElectricalControl1-HydraulicPump2-Direct-actingoverflowvalve3-Two-positionthree-waysolenoidreversingvalve4-Pilottypeoverflowvalve5-Shock-proofpressuregauge注意：阀2的调定压力一定要小于阀4的调定压力。Note:Regulationpressureofvalve2mustbelessthantheregulationpressureofvalve4.调压及限压回路PressureRegulatingandLimitingCircuits2Figure4-2-3Two-stagePressureRegulatingCircuit(a)ExampleTwoofTwo-stagePressureRegulatingCircuit(b)SchematicDiagramofElectricalControl1-Hydraulicpump2-Pilottypeoverflowvalve3-Shock-proofpressuregauge4-Two-positionfour-waysolenoidreversingvalve5-Direct-actingoverflowvalve6-Double-actinghydrauliccylinderwithsinglepistonrod图4-2-3（a）为二级调压回路的另一例，活塞下降为工作行程，此时高压溢流阀2限制系统最高压力。活塞上升为非工作行程，用低压溢流阀5限制其最高压力。本回路常用于压力机的液压系统中。Figure4-2-3(a)isanotherexampleoftwo-stagepressureregulatingcircuit,wherethepistondropstotheworkingstrokeandthehigh-pressureoverflowvalve2limitsthemaximumsystempressure.Thepistonrisestonon-workingstrokeandthelow-pressureoverflowvalve5limitsitsmaximumpressure.Thiscircuitiscommonlyusedinthehydraulicsystemofpressmachine.卸荷回路UnloadingCircuits3图4-2-4（a）中，先导式溢流阀3的远程控制口直接与二位三通电磁阀4相连，便构成一种用先导式溢流阀遥控口卸荷回路。当换向阀4处于图示位置时，主油路系统压力由溢流阀3调节，当电磁铁AD1得电阀4换向时，溢流阀3的远程控制口经阀4与油箱相通，系统压力卸荷。InFigure4-2-4(a),theremotecontrolinterfaceofpilottypeoverflowvalve3isdirectlyconnectedwithtwo-positionthree-waysolenoidreversingvalve4,inordertoformanunloadingcircuitatremotecontrolinterfaceofpilottypeoverflowvalve.Whenthereversingvalve4isinthepositionshowninthefigure,thesystempressureofmainoilpathisregulatedbyoverflowvalve3;whenelectromagnetAD1isenergizedandthesolenoidvalve4changesdirection,theremotecontrolinterfaceofoverflowvalve3isconnectedwiththeoiltankviavalve4,therebyunloadingthesystempressure.1先导式溢流阀遥控口卸荷回路UnloadingCircuitatRemoteControlInterfaceofPilotTypeOverflowValve卸荷回路UnloadingCircuits31-Hydraulicpump2-Direct-actingoverflowvalve3-Shock-proofpressuregauge4-Two-positionthree-waysolenoidreversingvalve2换向阀卸荷回路

ReversingValveUnloadingCircuit在图4-2-5（a）中，利用换向阀4使泵卸荷，但切换压力冲击大，适用于低压小流量的系统。InFigure4-2-5(a),thereversingvalve4isusedforunloadingthepump,butthereisagreatchangeoverpressureimpact;sothecircuitissuitableforsmall-flowsystems.减压回路DepressurizingCircuits4当泵的输出压力是高压而局部回路或支路要求低压时，可以采用减压回路。Whenthepumpoutputsahighpressurebutlocalcircuitorbranchrequiresalowpressure,thedepressurizingcircuitcanbeadopted,减压回路较为简单，一般是在所需低压的支路上串接减压阀。Depressurizingcircuitisrelativelysimple,whichisgenerallyformedbyconnectingareliefvalveinserieswiththebranchtobedepressurized.采用减压回路虽能方便地获得某支路稳定的低压，但压力油经减压阀口时要产生压力损失。

Astablelowpressureofcertainbranchcanbeconvenientlyobtainedbyusingadepressurizingcircuit,butthepressurefluidwillbesubjecttopressurelosswhenitpassesthroughthereliefvalve.减压回路DepressurizingCircuits4图4-2-6（a）为一典型的减压回路，主要应用于夹紧回路中。液压泵供油最高压力由溢流阀2根据主油路的需要来调节。主油路并联减压阀3后，使夹紧缸7获得较低的压力，其夹紧压力由减压阀3调节且可保持压力恒定。单向阀4起短时保压之用，当主油路压力低于减压阀调整压力时，防止夹紧力降低。Figure4-2-6(a)isatypicaldepressurizingcircuit,whichismainlyusedintheclampingcircuit.Themaximumoilsupplypressureofhydraulicpumpisregulatedbytheoverflowvalve2accordingtothedemandofmainoilpath.Afterthemainoilpathisconnectedinparallelwithreliefvalve3,theclampingcylinder7obtainsalowerpressure,wheretheclampingforcecanberegulatedbyreliefvalve3andmaintainedconstant.The