Unit-19-Hydraulic-Basic-Circuits-機(jī)電專業(yè)英語(yǔ)-圖文課件

Unit19HydraulicBasicCircuitsContentsNewWords&Expressions

Text&TranslationComplexSentenceAnalysisKeytoExercisesNewWords&Expressionspneumatic[nju:'m?tik]adj.

風(fēng)動(dòng)的，氣動(dòng)的decompression[?di:k?m'pre??n]n.降壓，減壓，釋放regenerative[ri'd?en?reitiv]adj.

再生的，新生的torque[t?:k]n.

轉(zhuǎn)矩，力矩，扭矩lubricator['lu:brikeit?]n.

潤(rùn)滑劑,加油器modification[?m?difi'kei??n]n.

改裝,修訂,更改customize['k?st?maiz]v.

定制;定做;自定義neutral['nju:tr?l]adj.

中立的,中性的;不確定的n.中位psi(poundpersquareinch)氣壓?jiǎn)挝唬?psi=6.89kPa）NewWords&Expressionscylinder['silind?]n.

氣筒;液壓缸,氣缸welder['weld?]n.

焊工;電焊機(jī)parallel['p?r?lel]n.平行,平行線solenoid['s?ulin?id]n.

螺線管energize['en?d?aiz]v.

給與…能量、電壓,使活躍actuate['?ktjueit]v.

開(kāi)動(dòng)（機(jī)器）,驅(qū)動(dòng)compensate['k?mpenseit]v.

補(bǔ)償,賠償traverse['tr?v?:s]v.

橫越,轉(zhuǎn)動(dòng),在軸上旋轉(zhuǎn)momentarily['m?um?n?terili]adv.

短暫地,臨時(shí)地initiate[i'ni?ieit]v.

開(kāi)始;創(chuàng)始Text&Translation[1]Usingschematicsymbolsasbuildingblocks,youcanconstructafunctionaldiagramshowingpipingarrangementsandoperationofanyhydraulicorpneumaticcircuit.Anumberofcircuitsareusedfrequentlyinfluidpowersystemstoperformusefulfunctions.Forexample,meteringcircuitsofferprecisecontrolofactuatorspeedwithoutalotofcomplicatedelectronics,decompressioncircuitsreducepressuresurgeswithinahydraulicsystembycontrollingthereleaseofstoredfluidenergy,andpump-unloadingandregenerativecircuitsmakeasystemmoreenergyefficient.Othercircuitsaredesignedforsafety,sequencingofoperations,andforcontrollingforce,torque,andposition.Stillothercircuitsmayenhancetheapplicationofspecificcomponents,suchaspumps,motors,accumulators,filters,andairlinelubricators.Text&TranslationThecircuitsappearingonthefollowingpagesareprovidedasaresourceofgeneralideas.Theymaybeusedas:aneducationalresourcetoaidunderstandingofcircuitsalreadyinuse,astartingpointfornewdesigns,andasamodificationtoenhanceoperationofexistingequipment.Theycertainlydonothavetobeimplementedasshown.Infact,manyofthecircuitsusepurelymechanicalcomponents,soincorporatingthemintoneworretrofitapplicationsmayinvolveintegratingelectronicfeedbackandcontrolintothecircuitasamodernalternativetomechanicalcontrol.[2]However,manyexistingandnewapplicationsstillgainthegreatestbenefitfrommechanicalcontrol—especiallythoseapplicationswhereelectricitycouldposeathreattohealthandsafety.Text&TranslationHowever,whetherusingmechanicalcontrolorelectronic,perhapsthegreatestbenefitmaybegainedbycustomizingoneofthesecircuitstoservethespecificrequirementsofanapplication.1.Pressure-controlcircuits[3]Whenopen-ortandem-centervalvesareusedincircuitsrequiringpilotpressuretoshiftthevalves,theremustbeameansofmaintainingpressurewhenthevalvesareinneutral.Onemethodistoinstallabackpressurecheckvalveinthetankline.Thecheckvalvemaintainsabackpressureof,say,50psi.Text&TranslationUsingtworeliefvalvesinthiscircuitgivestwoworkingpressures.Ontheupstrokeofthecylinder,thelow-pressurereliefvalvelimitssystempressure.Duringthedownstroke,thehigh-pressurevalvelimitsmaximumpresstonnagefordoingwork.Usingthelow-pressurereliefontheupstrokesavespowerbysupportingthecylinderwithlow-pressurefluid.It’sillustratedbyFig.19-1.Text&TranslationInasystemwithonlyonepump,reducedpressureforonebranchofthecircuitcanbeobtainedwithapressure-reducingvalve.[4]Thiscircuitistypicalforawelder,whichrequireshighclampingforcetobesetbythereliefvalveandreducedforceontheweldingguntobesetbythepressure-reducingvalve.Placingthecheckvalveinparallelwiththepressure-reducingvalveallowsfreereturnflowwhentheweldcylinderretracts.It’sshownasFig.19-2.Text&TranslationFig.19-1 Tworeliefvalvesfortwoworkingpressures Text&TranslationFig.19-2 ReducedpressurecircuitforweldingText&Translation2.RemotecontrolRegulatingpumppressurefromaremotestationcanbeaccomplishedbyusingsmall,pilotreliefvalvesconnectedtothesystemsmainpilot-operatedreliefvalve.InFig.19-3,withthe3-waysolenoidvalvede-energized,systempressureislimitedto1,500psiinthiscircuit.Energizingthe3-waysolenoidvalvepermitsventingthereliefvalvetoeither1,000psior500psi,dependingonthepositionofthe4-wayvalve,whichisdeterminedbythepilotsignalitreceives.Text&TranslationFig.19-3RegulatingpumppressurefromaremotestationText&TranslationInFig.19-4,plot-operatedreliefvalvesprovidetwopressuresforthemold-closecylinderandtheinjectioncylinderofthisplasticmoldingmachinecircuit.Withthemanualvalveinneutral,theair-operatedvalvesareactuatedtoextendthemold-closecylinderatamaximumpressureof2,000psi.Operatingthemanualvalvetoextendtheinjectioncylinderventsthe400-psirelieftotankandventsthe2,000-psireliefat400psi.High-pressurefluidisheldbythecheckvalve.Text&TranslationFig.19-4Plot-operatedreliefvalvesinplasticmoldingmachinecircuitText&Translation3.Pump-unloadingcircuitsWhentheopen-centersystemisinneutral,pumpoutputflowsthroughthedirectionalcontrolvalvetothetank.Whenthissimplecircuithandlesonlylowflowsandthedirectionalvalvespoolhastaperedlands,itprovestobeveryefficient.Ifseveralcylindersareused,thevalvecanbeconnectedinseries—thatis,thetankportofonevalveisconnectedtothepressureportofthenext.Text&Translation4.Pressure-compensatedpumpApressure-compensated,variable-volumepumpiscontrolledbysystempressure.Aspressureincrease,displacementofthepumpdecreasessothatpumpoutputatthepresetpressureisonlysufficienttomakeupforleakage.Usedwithaclosed-centervalve,thepumpisstrokedtominimum(zero)displacementwhenthevalveiscentered.Text&Translation5.Hi-locircuitManysystemsrequireahighvolumeatlowpressureforrapidtraverseofaviseortool,andthenlowvolume,highpressureforclampingorfeeding.InFig.19-5,thiscanbeaccomplishedbyahi-locircuitusingtwopumps.Duringrapidtraverse,bothpumpssupplythesystem.Whenpressurerisesduringclampingorfeed,thelarge-volumemainpumpunloads,andthesmallpumpmaintainspressure.Outputflowofthesmallpumpislowenoughtopreventheatingoftheoil.Insteadofpilotoperation,theunloadingvalvecanbesolenoidcontrolledandactuatedbyapressureswitch.Text&Translation6.SequencingcircuitsCylindersmaybesequencedbyrestrictingflowtoonecylinder.Onemethodofrestrictingflowiswithbackpressurecheckvalves.Theypreventflowuntilasetpressureisreached.InthiscircuitasshownFig.19-6,cylinder1extendsandretractsaheadofcylinder2.Severalcylinderscanbeconnectedtomoveinsequenceonforwardandreturnstrokes.Inthiscircuit,aclampmustclosebeforeadrilldescends.Onthereturnstroke,thedrillmustpulloutoftheworkbeforetheclampopens.Thesequencevalvesarearrangedtocausepressurebuildupwhenonecylindercompletesitsstroke,thevalveopenstoallowflowtotheothercylinder.Text&TranslationFig.19-5 Hi-locircuitwithbothpumpsText&Translation

Fig.19-6 SequencingcircuitsandsequencingvalveText&Translation7.ElectricalcontrolLimitswitchesmomentarilyactuatedbythecylinderscontrolthesolenoidvalvestosequencethiscircuit.Solenoidisenergizedbyapushbuttontoinitiatemovement1.Atthecompletionofmovement1,limitswitchEisactuatedtoenergizesolenoidc,initiatingmovement2.Attheendofmovement2,limitswitchFisactuatedtoenergizesolenoidb,initiatingmovement3.Attheendofthismovement,limitswitchGisactuatedtoenergizesolenoidd,initiatingmovement4.Thesequencevalvespreventapressuredropineithercylinderwhiletheotheroperates.It’sillustratedbyFig.19-7.Text&TranslationFig.19-7 ElectricalcircuitutilizinglimitswitchesandsolenoidvalvesText&Translation利用積木式的示意性符號(hào)，可以建立任意液壓或者氣壓回路的管路系統(tǒng)和操作邏輯圖。大量的回路常常被用于液壓系統(tǒng)中，以實(shí)現(xiàn)有效的功能。例如，在控制存儲(chǔ)能量釋放的液壓系統(tǒng)中，測(cè)量回路為驅(qū)動(dòng)器提供了精確的控制，不需要大量復(fù)雜的電路和減壓回路來(lái)減少壓力沖擊，泵的卸載和循環(huán)回路使得系統(tǒng)具有更高的能量效率。其他回路的設(shè)計(jì)用來(lái)安全保護(hù)，順序動(dòng)作和控制壓扭矩以及位置。還有一些其他回路可以用來(lái)提高特殊元件比如抽水泵、馬達(dá)、壓縮機(jī)、過(guò)濾器和線路潤(rùn)滑器的作用。Text&Translation本文下面提到的這些回路主要作為一般概念的基礎(chǔ)，這些回路可能用于：作為教育資源，輔助理解現(xiàn)有回路；作為新的回路設(shè)計(jì)的開(kāi)端；同時(shí)也可以對(duì)已有設(shè)備進(jìn)行修正，以提高其性能。這些回路不是必須按照現(xiàn)實(shí)的那樣來(lái)執(zhí)行，事實(shí)上，很多回路純粹是使用機(jī)械元件，所以把它們結(jié)合到新的或者改進(jìn)的應(yīng)用中，就會(huì)有除機(jī)械式控制外的另一個(gè)選擇，那就是把集成電子反饋和控制包含到回路中。然而，許多存在的新的應(yīng)用仍然從機(jī)械控制獲得了最大的好處———尤其是那些電氣可能對(duì)健康和安全構(gòu)成威脅時(shí)。Text&Translation然而，是利用機(jī)械控制還是電氣控制，在這些回路中定制去服務(wù)于某個(gè)應(yīng)用的指定需要，或許可以獲益最大。1.壓力控制回路當(dāng)在回路中用換向閥時(shí)，需要壓力來(lái)開(kāi)啟閥，也就是閥在中位的時(shí)候必須要有一個(gè)保持壓力。一個(gè)方法就是在油箱回油路上安裝一個(gè)背壓止回閥，這個(gè)止回閥保持一定的背壓，比如每平方英寸50磅。Text&Translation在回路中使用兩個(gè)安全閥可以提供兩個(gè)工作壓力。在油箱的上升行程中，低壓安全閥限制系統(tǒng)壓力。在下降行程中，高壓安全閥限制壓力機(jī)工作過(guò)程中的最大噸位。在上升行程中使用低壓安全閥可以提供液壓缸低壓液壓油，以節(jié)省能量，如圖19-1所示。在只有一個(gè)液壓泵的系統(tǒng)中，可以利用減壓閥來(lái)減少回路中一個(gè)支路的壓力。對(duì)于焊接裝置來(lái)說(shuō)，需要安裝安全閥，以提供足夠大的夾持力，同時(shí)用低壓閥來(lái)降低焊槍的壓力，此時(shí)減壓回路就是典型的應(yīng)用。將止回閥（單向閥）與減壓閥平行安裝，可以使焊接油缸自由平滑地縮回，如圖19-2所示。Text&Translation圖19-1 兩個(gè)減壓閥提供兩個(gè)工作壓力 圖19-2 焊接的減壓回路Text&Translation2.遙控與主回路先導(dǎo)閥相連接的小的先導(dǎo)閥可以在遙控站調(diào)節(jié)液壓泵的壓力。如圖19-3所示，兩位三通電磁閥失電，系統(tǒng)的壓力被限制在每英寸1500磅。兩位三通電磁閥得電導(dǎo)通，通過(guò)控制兩位四通閥的換向，可以使安全閥的壓力保持在每英寸1000磅或者每英寸500磅。兩位四通電磁閥的動(dòng)作由它接收到的控制信號(hào)來(lái)決定。Text&Translation圖19-3 從遙控站調(diào)節(jié)泵壓力Text&Translation如圖19-4所示，先導(dǎo)型安全閥為塑料模成型機(jī)的沖壓油缸和注射油缸提供兩種壓力。手動(dòng)換向閥處于中位時(shí)，開(kāi)啟氣動(dòng)兩位二通換向閥，沖壓油缸獲得每英寸2000磅的最大壓力。操縱手動(dòng)換向閥，注射油缸獲得每英寸400磅壓力就會(huì)溢流回到油箱，同時(shí)主油路安全壓力由每英寸2000磅降低到每英寸400磅，沖壓油缸由單向閥保持高壓力。Text&Translation圖19-4在塑料模成型機(jī)中的先導(dǎo)型安全閥Text&Translation3.液壓泵卸荷回路當(dāng)中位開(kāi)式液壓系統(tǒng)處于中位時(shí)，泵的輸出流量通過(guò)方向控制閥回到油箱。當(dāng)這個(gè)簡(jiǎn)單的回路僅僅在低流量下工作，方向控制閥的閥芯又是錐形的時(shí)候，中位開(kāi)式液壓系統(tǒng)效率會(huì)比較高。如果有多個(gè)油缸在工作，閥可以串連起來(lái)使用，也就是一個(gè)閥的回油口連到下一個(gè)閥的進(jìn)油口。Text&Translation4.壓力補(bǔ)償泵壓力補(bǔ)償變量泵是由系統(tǒng)壓力控制的。當(dāng)壓力升高，泵的排量降低，這樣液壓泵在設(shè)定壓力下的排量足夠補(bǔ)償泄露。使用一個(gè)中位閉式的閥，當(dāng)閥處于中位時(shí)液壓泵就能夠?qū)⒈玫膲毫φ{(diào)到最小或者零。Text&Translation5.高低回路工具或者夾具的快速行程，使得很多系統(tǒng)在低壓下需要高流量，而在夾緊或者輸送時(shí)，又需要高壓低流量。如圖19-5所示，這通過(guò)使用兩個(gè)泵的高低回路來(lái)實(shí)現(xiàn)。快行程時(shí)，系統(tǒng)中兩個(gè)泵工作。夾緊或輸送時(shí)壓力升高的時(shí)候，大流量主泵卸荷，小流量泵保持壓力。小流量泵的輸出流量足夠防止油溫的升高。相反在引導(dǎo)操作時(shí)，卸荷閥能夠由電磁控制，利用壓力開(kāi)關(guān)驅(qū)動(dòng)。Text&Translation6.順序回路一個(gè)液壓缸的節(jié)流可以使多個(gè)液壓缸順序驅(qū)動(dòng)。節(jié)流的一個(gè)方法就是背壓止回閥（單向閥），它只有當(dāng)壓力達(dá)到一定的時(shí)候才會(huì)開(kāi)始。如圖19-6所示的回路中，液壓缸1在液壓缸2之前伸長(zhǎng)和縮回。Text&Translation圖19-5雙泵高低回路Text&Translation圖19-6順序回路和順序控制閥Text&Translation幾個(gè)液壓缸可以連在一起按照進(jìn)程和回路順序運(yùn)動(dòng)。在這個(gè)回路中，在鉆孔機(jī)下來(lái)之前夾具要夾緊。回程時(shí)，鉆頭必須在夾具松開(kāi)之前拔出。順序閥就是用來(lái)完成蓄壓的，當(dāng)一個(gè)油缸完成工作行程后，順序閥打開(kāi)，使液壓油流向另一個(gè)油缸。7.電控由液壓缸觸發(fā)的限位開(kāi)關(guān)控制電磁閥來(lái)完成順序回路。一個(gè)按鈕觸發(fā)電磁鐵動(dòng)作開(kāi)始動(dòng)作1，動(dòng)作1完成后，限位開(kāi)關(guān)E觸發(fā)使電磁鐵c得電，開(kāi)始動(dòng)作2，在動(dòng)作2完成的時(shí)候，限位開(kāi)關(guān)F觸發(fā)使電磁鐵b得電，開(kāi)始動(dòng)作3，動(dòng)作3完成時(shí)，觸發(fā)限位開(kāi)關(guān)G使電磁鐵d得電，開(kāi)始動(dòng)作4。在一個(gè)液壓缸動(dòng)作時(shí)，順序閥防止另一個(gè)液壓缸的壓力降低，如圖19-7所示。Text&Translation圖19-7利用限位開(kāi)關(guān)和電磁鐵的電控回路ComplexSentenceAnalysis[1]Usingschematicsymbolsasbuildingblocks,youcanconstructafunctionaldiagramshowingpipingarrangementsandoperationofanyhydraulicorpneumaticcircuit.利用積木式的示意性符號(hào)，可以建立任意液壓或者氣壓回路的管路系統(tǒng)和操作邏輯圖。①Usingschematicsymbolsasbuildingblocks：現(xiàn)在分詞短語(yǔ)做狀語(yǔ),表示條件,相當(dāng)于“Ifyouuseschematicsymbols…”②showingpipingarrangementsandoperation：afunctionaldiagram的后置定語(yǔ)，相當(dāng)于“whichshowspipingarrangementsandoperation…”ComplexSentenceAnalysis[2]However,manyexistingandnewapplicationsstillgainthegreatestbenefitfrommechanicalcontrol—especiallythoseapplicationswhereelectricitycouldposeathreattohealthandsafety.然而，許多存在的新的應(yīng)用仍然從機(jī)械控制獲得了最大的好處——尤其是那些電氣可能對(duì)健康和安全構(gòu)成威脅時(shí)。①gainthebenefitfrom：從……獲得好處；獲益②poseathreatto：對(duì)……構(gòu)成威脅。此外，pose還可以與很多名詞搭配，表示“提出，造成，引起”的意思ComplexSentenceAnalysis[3]Whenopen-ortandem-centervalvesareusedincircuitsrequiringpilotpressuretoshiftthevalves,theremustbeameansofmaintainingpressurewhenthevalvesareinneutral.當(dāng)在回路中用換向閥時(shí)，需要壓力來(lái)開(kāi)啟閥，也就是閥在中位的時(shí)候必須要有一個(gè)保持壓力。①requiringpilotpressuretoshiftthevalves：circuits的后置定語(yǔ)，相當(dāng)于“whichrequirepilotpressuretoshiftthevalves”Complex