電液比例控制技術(shù)課件：比例電磁鐵

1/56比例電磁鐵Theproportionalelectromagnet比例電磁鐵Theproportionalelectromagnet2.1Functionandformofelectricmachineryconversioncomponent2.2Structureandworkingprincipleofelectromagnet2.3Characteristicofproportionalelectromagnet2.4Classificationandapplicationoftheproportionalelectromagnet2.5Thepreliminarydesignofproportionalelectromagnet2.6Theuseandmaintenanceofproportionalelectromagnet2.1電—機(jī)械轉(zhuǎn)換元件的作用及形式2.2電磁鐵的結(jié)構(gòu)和工作原理2.3比例電磁鐵的特性分析2.4比例電磁鐵的分類與應(yīng)用2.5比例電磁鐵的初步設(shè)計(jì)2.6比例電磁鐵的使用與維護(hù)2.1電-機(jī)械轉(zhuǎn)換元件的作用及形式Functionandformofelectricmachineryconversioncomponent2.1.1Theformoftheelectricmachineryconversioncomponent

Theelectricmachineryconversioncomponentappliedinproductionmostlyadoptselectromagneticdesignatpresentandutilizesequilibriumelectricmachineryprincipleofelectromagneticforceandspringforcetoachieveproportionalconversion.Dcservomotors,steppingmotors,torquemotors,moving-coilforcemotorsandmoving-ironforcemotorsaremostwidelyused.Thelatteraremoregenerallycalledproportionalelectromagnets.Themostwidelyused(electricmachinerycomponents)aretheproportionalelectromagnetsincurrentsituation,whichhasalreadybecamethemainelectricmachineryconversionone.2.1.1電-機(jī)械轉(zhuǎn)換元件的形式目前，生產(chǎn)上應(yīng)用的電—機(jī)械轉(zhuǎn)換元件大多采用電磁式設(shè)計(jì)，并且利用電磁力與彈簧力相互平衡的原理，實(shí)現(xiàn)電—機(jī)械的比例轉(zhuǎn)換。最常見的有直流伺服電機(jī)、步進(jìn)電機(jī)、力矩馬達(dá)、動(dòng)圈式力馬達(dá)以及動(dòng)鐵式力馬達(dá)。后者更一般的稱為比例電磁鐵。從目前的使用情況來看，應(yīng)用最為廣泛的還是比例電磁鐵，它目前已經(jīng)成為最主要的電—機(jī)械轉(zhuǎn)換元件。2.1.2電—機(jī)械轉(zhuǎn)換元件的要求在電液比例技術(shù)中，對作為閥的驅(qū)動(dòng)裝置的電—機(jī)械轉(zhuǎn)換元件的基本要求有以下六點(diǎn)：（1）具有水平吸力特性，即輸出的機(jī)械力與電信號大小成比例，與銜鐵的位移無關(guān)；（2）有足夠的輸出力和行程，結(jié)構(gòu)緊湊、體積?。唬?）線性好，死區(qū)小，靈敏度高，滯環(huán)??；2.1.2DemandsofelectricmachineryconversioncomponentThebasicdemandsoftheconversioncomponentasvalvedrivingdeviceareasfollowsinelectro-hydraulicproportionaltechnology:(1)Itisinpossessionofaclinicattractioncharacteristic-itsoutputforceisproportionaltostrengthofelectricalsignalandhasnothingtodowiththedisplacementofthekeeper.(2)Theremustbeenoughoutputforceandstrokewithcompactstructureandsmallbulkingatthesametime.(3)Itmustpossessthequalityoffinelinearity,littledeadzone,highsensitivityandtinyhysteresis.（4）動(dòng)態(tài)性能好，響應(yīng)速度快；（5）長期工作中溫升不會過大，并在允許溫升下仍能工作；（6）能承受液壓系統(tǒng)高壓，抗干擾性好。(4)Itmustpossessthequalityofgooddynamicperformanceandfastresponse.(5)Thetemperaturerisemustnotbetoohighduringlongworkingtime,anditshouldworknormallyatthestateofpermittedtemperaturerise.

(6)Itcanbearthehighpressureofhydraulicsystemandtheresistancetodisturbancemustbestrong.

2.1.3Thesummaryoftheproportionalelectromagnet

Thekeycomponentofproportionalcontroltechnologyistheproportionalvalve.Itsinputunitistheelectricmachineryconversiondevicewhichconvertstheinputelectricalsignalintomechanicalone.TheproportionalelectromagnetwhichisdesignedaccordingtoFaradayelectromagneticinductionprinciplecanmakemechanicalsignal(force,torqueanddisplacement)proportionaltoinputelectricalsignal(current),anditcancontrolthepositionofspoolsuccessively.Theabovecharacteristicswillmakesurethatthepressure,directionandflowofhydraulicsystemchangecontinuously.2.1.3比例電磁鐵的概述比例控制的核心是比例閥。比例閥的輸入單元是電－機(jī)械轉(zhuǎn)換器，它將輸入信號轉(zhuǎn)換成機(jī)械量。比例電磁鐵根據(jù)法拉第電磁感應(yīng)原理設(shè)計(jì),能使其產(chǎn)生的機(jī)械量(力或力矩和位移)與輸入電信號(電流)的大小成比例，再連續(xù)地控制液壓閥閥芯的位置，實(shí)現(xiàn)連續(xù)地控制液壓系統(tǒng)的壓力、方向和流量。

圖2.1耐高壓比例電磁鐵

1.導(dǎo)套；2.限位片；3.推桿；4.工作間隙；5.非工作間隙；6.銜鐵；7.軸承環(huán)；8.限磁環(huán)當(dāng)前，應(yīng)用最廣泛的比例電磁鐵是耐高壓直流比例電磁鐵如圖2.1。Currently,themostwidelyusedhighvoltagedirectcurrentproportionalsolenoidisproportionalsolenoidinFigure2.1.Figure2.1highpressureproportionalsolenoid1Guidesleeve;2.Limittablets;3.Putter;4.Workinggap;

5Non-workingspace;6.Armature;7.Bearingring;8.Limitring

Theproportionalelectromagnetwhichissimilartothetorquemotororforcemotoroftheservovalveinelectro-hydraulicservosystemisakindofconvertersconvertingelectricalsignaltoforceanddisplacement(signal).Theproportionalelectromagnetisalinkbetweenelectronictechnologyandhydraulictechnology.TheproportionalelectromagnetisakindofDCstrokeelectromagnets.Itgeneratesanoutputsignal(forceanddisplacement)whichisproportionaltotheinputsignal(current).Itsperformancehasanextremelyimportanteffectonthecharacteristicsoftheelectro-hydraulicproportionalvalve.比例電磁鐵同電液伺服系統(tǒng)中伺服閥的力矩馬達(dá)或力馬達(dá)相似，是一種將電信號轉(zhuǎn)換成機(jī)械力和位移的電－機(jī)械轉(zhuǎn)換器。比例電磁鐵是電子技術(shù)與液壓技術(shù)的連接環(huán)節(jié)。比例電磁鐵是一種直流行程式電磁鐵，它產(chǎn)生一個(gè)與輸入量（電流）成比例的輸出量：力和位移。它的性能的好壞，對電液比例閥的特性有著舉足輕重的作用。2.2電磁鐵的結(jié)構(gòu)與工作原理Structureandworkingprincipleofelectromagnet2.2.1Theordinarysolenoidelectromagnet

TheordinaryshelltypesolenoidelectromagnetshowninFig.2-2ismadeupofashell2,abaffle4,aarmature6andafieldcoil3.WhenflowedthroughbyDC,thecoilgeneratesmagneticfieldinthecorewhichformsaclosemagneticcircuit.Therearetwogapsintheelectromagnet.Oneisworkinggap5andtheotherisnon-workinggap1.2.2.1普通螺線管型電磁鐵甲殼型螺線管電磁鐵如圖2.2所示，由外殼2、擋鐵4、銜鐵6、普通激磁線圈3組成。當(dāng)線圈通有直流電i時(shí)，線圈便在鐵芯中產(chǎn)生磁場，并形成閉合的磁力線路。電磁鐵存在兩個(gè)間隙，一個(gè)工作間隙5，另一個(gè)非工作間隙1。

圖2.2普通螺線管型電磁鐵1.非工作間隙；2.外殼；3.激磁線圈；4.擋板；5.工作間隙；6.銜鐵Figure2.2Theordinarysolenoidelectromagnet1.Nonworkinggap；2.Shell；3.Fieldcoil；4.Baffle；5.Workinggap；6.ArmatureTwochangingfluxesarecreated.Oneiscalledthemainmagneticflux∮andtheotheriscalledthechangingmagneticflux∮L.Thesuctionimposingonthearmature6iscomposedoftwoparts.Oneisthefaceforcecreatedbythemainmagneticfluxandtheotherissolenoidforcecreatedbythechangingmagneticflux.Thedirectionsofthetwoforcesarethesame.Theresultantforceofthetwoforcesisthetotalelectromagneticforce.在電磁鐵吸合過程中形成兩個(gè)變化的磁通，即主磁通∮和變化的磁通∮L。銜鐵6所受到的吸力主要由兩部分組成。主磁通產(chǎn)生的力稱為端面力，而漏磁通產(chǎn)生的力稱為螺管力。對圖示結(jié)構(gòu)這兩個(gè)力的方向是一致的。這兩個(gè)力的合力就構(gòu)成了總的電磁力。2.2.2Theone-wayproportionalelectromagnet

TheDCproportionalelectromagnetisthemostwidelyusedelectricity-machineconversioncomponentamongelectro-hydraulicproportionalcontroldevices.Itisarmoredsolenoidelectromagnetandmoving-ironmotorbecauseitsmovingpartisthearmature.Itcanexportgreaterforceanddisplacementwithsimplestructure,lowpriceandlargepower/weightratio.Theproportionalelectromagnetsaredividedintoone-waydirectoperatedelectromagnetandtwo-waydirectoperatedelectromagnetaccordingtoitsformofoutputdisplacement.Therotaryproportionalelectromagnetisseldomused.2.2.2單向比例電磁鐵

直流比例電磁鐵是電液比例控制器件中應(yīng)用最廣泛的電一機(jī)械轉(zhuǎn)換器。它也是裝甲式螺管電磁鐵，由于可動(dòng)部分是銜鐵，所以是一種動(dòng)鐵式馬達(dá)，具有結(jié)構(gòu)簡單，價(jià)格低，功率／重量比大，能夠輸出較大的力和位移等特點(diǎn)。按比例電磁鐵輸出位移的形式，除最常見的單向直動(dòng)式外，還有雙向直動(dòng)式?；剞D(zhuǎn)式比例電磁鐵應(yīng)用較少。Afterthecoilisenergized,thefollowingmagneticcircuitgeneratesbevelsuctionbygoingthroughtheshell,conepointoftheguidesleeveandthentheyokeiron;theotheroutputforceoftheyokeironisgeneratedbythearmatureface.(inFigure2.3).

線圈通電后形成的磁路經(jīng)殼體、導(dǎo)向套錐端到軛鐵而產(chǎn)生斜面吸力；另一路是直接由銜鐵端面到軛鐵的輸出力（見圖2.3）。圖2.3單向比例電磁鐵1.軛鐵；2.導(dǎo)向套錐端；3.銜鐵；4.線圈；5.導(dǎo)向套；6.殼體Figure2.3Theone-wayproportionalelectromagnet1.Yokeiron;2.Coneendofguidesleeve;3.Armature;4.Coil;5.Guidesleeve;6.Shell2.3比例電磁鐵的特性分析Characteristicsofproportionalelectromagnet2.3.1

Attractingcharacteristicofproportionalelectromagnet

Theelectromagnet(linearforcemotor)isakindofelectricdevicewhichmakesthearmaturedoworkbytheelectromagneticforcegeneratedintheelectromagneticsystem.ItsbasiccharacteristicscanbeexpressedastherelationshipbetweenelectromagneticforceFmworkingonthemovingarmatureandthedisplacementxofthearmature,namely

Fm＝f(x).Therelationshipiscalledtheattractioncharacteristic.Theproportionalelectromagnetneedstopossesstheaclinicattractioncharacteristic.2.3.1電磁鐵的吸力特性電磁鐵（直線力馬達(dá)）是一種依靠電磁系統(tǒng)產(chǎn)生的電磁吸力，使銜鐵對外做功的一種電動(dòng)裝置。其基本特性可表示為銜鐵在運(yùn)動(dòng)中所受到的電磁力Fm與它的行程（位移）x之間的關(guān)系，即Fm＝f(x)。這個(gè)關(guān)系稱為吸力特性。對比例電磁鐵，要求它具有水平的吸力特性。比例電磁鐵基本結(jié)構(gòu)：如圖2.4可知，比例電磁鐵主要由推桿、銜鐵、軸承環(huán)、隔磁環(huán)、導(dǎo)套、限位環(huán)組成。導(dǎo)套前后兩段由導(dǎo)磁材料制成，中間用一段非導(dǎo)磁材料（隔磁環(huán)）焊接。銜鐵前端有推桿，用于輸出力或者位移；后端裝有由彈簧和調(diào)節(jié)螺釘組成的調(diào)零機(jī)構(gòu)，可在一定范圍內(nèi)對比例電磁鐵特性曲線進(jìn)行調(diào)整。Thebasicstructureoftheproportionalelectromagnetisshowninfigure2.4.Theproportionalelectromagnetismadeupofpushrod,keeper,bearingcollar,septalmagneticcollar,guidesleeve,limitcollar.Thefrontandbackoftheguidesleeveismadeofconductionmaterialwhosemiddlepartisweldedwithnonconductionmaterial(septalmagneticcollar).Thepushrodinfrontofthekeeperexportsforceordisplacement;Theadjustingzeromechanismiscomposedofthespringandadjustingscrewsothatthekeepercangovernthecharacteristiccurveoftheproportionalelectromagnetinacertainrange.圖2.4比例電磁鐵基本結(jié)構(gòu)Ⅰ吸合區(qū)；Ⅱ工作行程區(qū)；Ⅲ空行程區(qū)1.推桿2.工作氣隙3.非工作氣隙4.銜鐵5.軸承環(huán)6.隔磁環(huán)7.導(dǎo)套8.限位環(huán)Fig.2.4BasicstructureofproportionalelectromagnetⅠAttractingzone；ⅡWorkingzone；ⅢIdlezone1.Pushrod2.Workinggap3.Non-workinggap4.Keeper5.Bearingcollar6.Septalmagneticcollar7.Guidesleeve8.Limitcollar

比例電磁鐵基本原理：當(dāng)給比例電磁鐵控制線圈一定電流時(shí)，在線圈電流控制磁勢的作用下，形成兩條磁路（如圖2.5a所示），一條磁路由前端蓋盆形極靴底部，沿軸向工作氣隙，進(jìn)入銜鐵，穿過導(dǎo)套后段和導(dǎo)磁外殼回到前端蓋極靴。

Thebasicprincipleoftheproportionalelectromagnet:Whenthecontrolcoiloftheproportionalelectromagnetispowered/energized,twomagneticcircuitsareformedbythemagneticpotentialofthecoilcurrent(asshowninFig.2.5a).Onemagneticcircuitreturnstothefrontendcoverpoleshoeviathebottomoffrontendcoverbasinshapepoleshoe,workinggap,armature,backofguidesleeveandconductionshell.圖2.5比例電磁鐵基本原理a--Φ1、Φ2的磁路示意圖b--位移-力特性Fig.2.5Basicprincipleoftheproportionalelectromagneta--MagneticcircuitofΦ1andΦ2b--Characteristicdiagramofdisplacementandforcesab另一磁路經(jīng)盆形極靴錐形周邊（導(dǎo)套前段），徑向穿過工作氣隙進(jìn)入銜鐵，而后與前一條磁路相匯合。由于電磁作用，主磁通產(chǎn)生了通常的端面力，漏磁通則產(chǎn)生了附加軸向力（如圖2.5b所示），兩者的綜合，就得到了整個(gè)比例電磁鐵的輸出力。在工作區(qū)域內(nèi)，電磁力，相對于銜鐵位移基本呈水平力特性關(guān)系。

Theotheroneiscombinedwithviaconicalsurroundingofbasinshapepoleshoe(frontofguidesleeve),workinggapandarmature.fluxgeneratesthefaceforcebecauseofelectromagneticwhilefluxgeneratesacertainamountofadditionalaxialforce(asshowninFig.2-5b).Thecombinationofthetwoistheoutputforceoftheproportionalelectromagnet.Electromagneticforceismainlyconstantforcerelativetothedisplacementofarmatureinworkingstrokezone.

圖2.6所示為普通電磁鐵與比例電磁鐵的靜態(tài)吸力特性。所謂靜態(tài)吸力特性就是在穩(wěn)態(tài)過程中得到的吸力特性。與它相對應(yīng)的是動(dòng)態(tài)特性。比例電磁鐵必須具有水平吸力特性，即在工作區(qū)內(nèi)，其輸出力的大小只與電流成正比，而與銜鐵位移無關(guān)

ThestaticattractivecharacteristicsoftheordinaryandproportionalelectromagnetisshowninFig.2.6.Thestaticattractivecharacteristicisobtainedinasteadyprocess.Thecorrespondingoneisdynamiccharacteristic.Theproportionalelectromagnetneedstopossessaclinicattractioncharacteristicwhichmeansthattheoutputforceisonlyrelativetothecurrentandhasnothingtodowiththedisplacementofthearmatureintheworkingstrokezone.圖2.6比例電磁鐵的靜態(tài)吸力–位移特性1—比例電磁鐵;2—普通電磁鐵;3—彈簧負(fù)載曲線Fig.2.6Staticsuction-displacementcharacteristicoftheproportionalelectromagnet1.Proportionalelectromagnet;2.Ordinaryelectromagnet;3.Springloadcurve

若電磁鐵的吸力不顯水平特性，彈簧曲線與電磁力曲線族只有有限的幾個(gè)交點(diǎn)，這意味著不能進(jìn)行有效的位移控制。在工作范圍內(nèi)，不與彈簧曲線相交的各電磁力曲線中，對應(yīng)的電流在彈簧曲線以下，不會引起銜鐵位移；在彈簧曲線以上時(shí)，若輸出這樣的電流，電磁力將超過彈簧力，將銜鐵一直拉到極限位置為止。相反，若電磁鐵具有水平特性，那么在同樣的彈簧曲線下，將與電磁力曲線族產(chǎn)生許多交點(diǎn)。在這些交點(diǎn)上，彈簧力與電磁力相等，就是說，逐漸加大輸入電流時(shí)，銜鐵能連續(xù)地停留在各個(gè)位置上。

Iftheproportionalelectromagnetdoesnotpossesstheaclinicattractioncharacteristic,thespringcurveandelectromagneticforcecurvefamilywillintersectatlimitedspots.Displacementcontrolwillnotbeeffective.Thearmaturewillnotmovewhenthecurrentcurveisamemberofthecurrentcurveswhichareunderspringcurveinthewholeworkingzone;thearmaturewillbeatthelimitpositionifthecurrentcurveoftheexactcurrentisabovethespringcurve.Onthecontrary,iftheproportionalelectromagnetpossessestheaclinicattractioncharacteristicandthespringisthesameone,thespringcurveandelectromagneticforcecurvefamilywillintersectatmanyspots.Thespringforceisequaltoelectromagneticforceatthesespots.Thearmaturewillbecontinuouslystoppedatallthepositionsthatthespotsrepresentwhenthecurrentbecomeslargerandlarger.2.3.2

Loadcharacteristicofelectromagnet

Duringmoving,theelectromagnethastoovercomemechanicalloadandresistanceanddowork.Itisdemandedthatelectromagneticattractionforceislargerthanloadreactionfortheordinaryelectromagnet.Theproportionalelectromagnetworksnormallybecausethearmaturekeepstheelectromagneticattractionforceandtheloadreactionbalance.Attractioncharacteristicshouldbematchedwithloadcharacteristictomaketheelectromagnetreliable.ThecurveofcommonloadreactioncharacteristicisshowninFig.2.7.2.3.2電磁鐵的負(fù)載特性在電磁鐵的運(yùn)動(dòng)過程中，必然要克服機(jī)械負(fù)載和阻力而做功。對于普通電磁鐵，一般都要求電磁吸力大于負(fù)載反力；而對于比例電磁鐵，則銜鐵處于電磁吸力與負(fù)載反力平衡狀態(tài)，只有這樣，電磁鐵才能正常工作。為使電磁鐵可靠的工作，應(yīng)使吸力特性與負(fù)載特性有良好的配合。常見的負(fù)載反力的特性如圖2.7所示。圖2.7典型負(fù)載反力特性a.恒力負(fù)載特性；b.彈簧負(fù)載特性；c.多級彈簧負(fù)載特性Fig.2.7Curveoftypicalloadreactioncharacteristica—Constantforceloadcharacteristic;b—Springloadcharacteristic;c—Multistagespringloadcharacteristic

對于吸合型電磁鐵，在吸合過程中，電磁吸力特性曲線應(yīng)在負(fù)載反力曲線的上方；而在釋放運(yùn)動(dòng)中，負(fù)載反力必須大于電磁產(chǎn)生的剩磁力。比例電磁鐵在工作過程中電磁力總是與負(fù)載力相平衡，吸力特性曲線有很多條，而負(fù)載多為彈性負(fù)載，所以它工作時(shí)吸力特性與負(fù)載特性的配合情況如圖2.8所示。

Thecurveofelectromagneticattractioncharacteristicshouldbeabovethecurveofloadreactionforthesuctionelectromagnetduringsuctionprocess;theloadreactionmustbelargerthantheremainingelectromagneticforceduringreleaseprocess.

Theelectromagneticforceshouldalwaysbeequaltotheloadforceduringtheworkingprocessoftheelectromagnet.Therearemanyattractioncharacteristiccurvesbutfewloadcharacteristiccurves.Theloadisnormallyelasticload.ItsattractioncharacteristiccurvesmatchedwithloadcharacteristiccurvesisshowninFig.2.8.圖2.8比例電磁鐵的靜態(tài)吸力–位移特性1.比例電磁鐵;2.普通電磁鐵;3.彈簧負(fù)載曲線Fig.2.8Staticsuction-displacementcharacteristicoftheproportionalelectromagnet1.Proportionalelectromagnet;2.Ordinaryelectromagnet;3.Springloadcurve負(fù)載彈簧的特性曲線與多條吸力特性曲線相交。對應(yīng)不同的輸入電流，電磁力的曲線水平上下平移，而它與彈簧特性曲線的相交點(diǎn)便是對應(yīng)電流下的工作點(diǎn)。由圖中可以看出，當(dāng)電流改變時(shí)工作點(diǎn)也改變，比例電磁鐵正是利用這一特性來實(shí)現(xiàn)電—機(jī)械信號的比例轉(zhuǎn)換。Thecurveofloadspringcharacteristicintersectwithmanyattractioncharacteristiccurves.Electromagneticforcecurvewillbemovingupanddownasthecurrentchanging.Theintersectionofspringcharacteristiccurveandloadcharacteristiccurveistheworkingpointofcorrespondingcurrent.Itcanbeseenthattheworkingpointcanbechangedwhenthecurrentischanged.Theproportionalelectromagnetmakeelectricity-mechanicalsignaltransferbythewayofthischaracteristics.2.4比例電磁鐵的分類與應(yīng)用Classificationandapplicationoftheproportionalelectromagnet

Theworkingprincipleoftheproportionalelectromagnetofvariouskindsismostlythesame.Theyaredevelopedbythecontrollingrequirementsoftheproportionalvalves

Theproportionalelectromagnetcanbedividedintotwotypesofhigh-pressureresistantandhigh-pressurenonresistant,accordingtoitspressureresistancelevel.

Theproportionalelectromagnetcanbedividedintolinearmotiontypeandrotarymotiontypeaccordingtoitsoutputmotionparameters.Thelinearmotiontypeisthemostwidelyusedone.

比例電磁鐵種類繁多，但工作原理基本相同。它們都是根據(jù)比例閥的控制需要開發(fā)出來的。根據(jù)所承受的壓力等級，可分為耐高壓和不耐高壓的比例電磁鐵。根據(jù)所輸出的運(yùn)動(dòng)參數(shù)，可分為直線運(yùn)動(dòng)的比例電磁鐵和旋轉(zhuǎn)運(yùn)動(dòng)的比例電磁鐵(角位移式)。直線運(yùn)動(dòng)的比例電磁鐵應(yīng)用最為廣泛。根據(jù)參數(shù)的調(diào)節(jié)方式和它們與所驅(qū)動(dòng)閥芯的聯(lián)接形式，比例電磁鐵可分為力控制型、行程控制型和位置調(diào)節(jié)型三種基本類型。本節(jié)按照這三種情況分類敘述各自的特點(diǎn)和應(yīng)用。此外，還有雙向極化式耐高壓比例電磁鐵、插裝閥式比例電磁鐵、防爆比例電磁鐵、內(nèi)裝集成比例放大器的比例電磁鐵等等。

Theproportionalelectromagnetcanbedividedintoforcecontroltype,strokecontroltypeandpositioncontroltypeaccordingtoitsparameters’accommodationmodeandconnectionformofthedrivingvalvespool.Thecharacteristicsandapplicationofthethreetypesareshownrespectivelyinthisdivision.

Inaddition,therearebidirectionalpolarizedenduringhighpressuretype,cartridgevalvetype,explosion-prooftypeandinnerintegrationtypeandsoon.2.4.1Forcecontroltype

Thebasiccharacteristicoftheforcecontroltypeisforce-strokecharacteristic.Thestrokeofthekeeperisunconspicuouslychanged.TheoutputelectromagneticforcecanbeadjustedbychangingcurrentI.Becauseofthecurrentfeedbacklinksetinelectronicamplifier,themagneticfluxcanremainunchangedwhencurrentsetvalueisconstantandreluctanceischanging,thuskeepingelectromagneticforceaconstant.2.4.1力控制型比例電磁鐵力控制型比例電磁鐵的基本特性是力—行程特性。在力控制型比例電磁鐵中，銜鐵行程沒有明顯變化時(shí)，改變電流I，就可以調(diào)節(jié)其輸出的電磁力。由于在電子放大器中設(shè)置電流反饋環(huán)節(jié)，在電流設(shè)定值恒定不變而磁阻變化時(shí)可使磁通量不變，進(jìn)而使電磁力保持不變。

在控制電流不變時(shí)，電磁力在其工作行程內(nèi)保持不變。如圖2.9所示，這類電磁鐵的有效工作行程約為1.5mm。由于行程較小，力控制型電磁鐵的結(jié)構(gòu)很緊湊。正由于其行程小，可用于比例壓力閥和比例方向閥的先導(dǎo)級，將電磁力轉(zhuǎn)化為液壓力。這種比例電磁鐵，是一種可調(diào)節(jié)型直流電磁鐵，在其銜鐵腔中，充滿工作油液。

Whencontrolcurrentisconstant,electromagneticforceremainunchangedinworkingstrokezone.AsshowninFig.2-9,effectiveworkingstrokeofforcecontroltypeisabout1.5mm.

Thestructureofforcecontroltypeiscompactbecauseofitsshortstroke.Becauseofitsshortstroke,itcanbeusedaspilotstageofproportionalpressurevalveandproportionaldirectionvalvewhichconvertelectromagneticforceintohydraulicpressure.

ThiskindofproportionalelectromagnetisakindofadjustableDCelectromagnet.Thechamberofthekeeperisfilledwithworkingoil.(1)力控制型比例電磁鐵原理圖和力—行程曲線(1)Principlediagramandforce-strokecurveofforcecontroltype圖2.10力控制型比例電磁鐵力—行程曲線圖2.9力控制型比例電磁鐵原理圖Fig.2.10Force-strokecurveofforcecontroltypeFig.2.9Principlediagramofforcecontroltype(2)力控制型比例電磁鐵與閥芯的連接方式

力控制型比例電磁鐵直接輸出力，它的工作行程短，可直接與閥芯或通過傳力彈簧與閥芯連接。(2)

Connectionformofvalvespoolandforcecontroltype

Theforcecontrollingelectromagnetexportsforcedirectly,anditsworkingstrokeisshort.Itcanbedirectlyconnectedtothevalvespoolwithorwithoutaspring.圖2.11力控制型比例電磁鐵與閥芯的連接方式

a）比例電磁鐵通過傳力彈簧作用在閥芯上b）比例電磁鐵直接作用在閥芯上Fig.2.11Connectionformofvalvespoolandforcecontroltypea)Connectedbytransferspringb)Connecteddirectly2.4.2Strokecontroltype

Thepositionofthearmatureisadjustedbyacloseloopinthestrokecontroltype.Aslongastheelectromagnetisworkinginitspermittedzone,thepositionofitsarmaturekeepsunchangedandhasnothingtodowiththereaction.Byusingthestrokecontroltype,thevalvespoolofproportionalflowvalve,proportionaldirectionvalveandproportionalpressurevalvecanbepushedandstoppedatanyposition.Thestrokeofelectromagnetisdifferentbecauseofitsspecification.Itisnormallybetween3mmand5mm.2.4.2行程控制型比例電磁鐵在行程控制型比例磁鐵中，銜鐵的位置由一個(gè)閉環(huán)調(diào)節(jié)回路進(jìn)行調(diào)節(jié)。只要電磁鐵在其允許的工作區(qū)域內(nèi)工作，其銜鐵位置就保持不變，而與所受反力無關(guān)。使用行程調(diào)節(jié)型比例電磁鐵，能夠直接推動(dòng)諸如比例方向閥、流量閥及壓力閥的閥芯，并將其控制在任意位置上。電磁鐵的行程，因其規(guī)格而異，一般在3~5mm之間。

如前所述，行程控制型比例電磁鐵，主要用來控制四通比例方向閥。配上電反饋環(huán)節(jié)后，電磁鐵的滯環(huán)及重復(fù)誤差均較小。此外，作用在閥芯上的液動(dòng)力也受到抑制（與各種可能產(chǎn)生的干擾力相比，電磁力較小）。在先導(dǎo)閥中，受控壓力作用在一個(gè)較大的控制面積上，因此供使用的調(diào)節(jié)力要大得多，而干擾力影響的百分比并不大。因此，先導(dǎo)式比例閥也可不帶電反饋機(jī)構(gòu)。

Aswhatmentionedbefore,thestrokecontroltypeismainlyusedtocontrolfour-wayproportionaldirectionvalve.Itshysteresisandrepetitiveerrorareallquitesmallwiththeusingofelectricfeedback.Inaddition,theflowforceexertingonvalvespoolcanberestrained(theelectromagneticforceisquitesmallcomparedwithotherpossibledisturbingforces).

Duetothefactthatthecontrolledpressureexertsonalargerareainthepilotvalve,theavailableadjustingforceismuchlargerthanthatinthevalvesmentionedbefore,butthepercentageoftheeffectofinterferenceforceisnotsolarge.Thus,thepilotproportionalvalvecanalsoworkwithoutelectricfeedbackmechanism.(1)行程控制型比例電磁鐵原理圖(1)Principlediagramofstrokecontroltype圖2.12行程控制型比例電磁鐵原理圖Fig.2.12Principlediagramofstrokecontroltype(2)行程控制型比例電磁鐵示意圖

行程控制型比例電磁鐵是在力控制型比例電磁鐵的基礎(chǔ)上，將彈簧布置在閥芯的另一端得到的。(2)Schematicdiagramofstrokecontroltype

Basedontheforcecontroltype,thestrokecontroltypeisobtainedbythespringequippedontheothersideofthevalvespool.圖2.13行程控制型比例電磁鐵示意圖a）單個(gè)使用的行程控制型比例電磁鐵b)成對使用的行程控制型比例電磁鐵Fig.2.13Theschematicdiagramofstrokecontroltypea)Singleusingb)Pairsusing2.4.3Thepositioncontroltype

Thepositionofproportionalelectromagnetisdetectedbydisplacementsensoranditconstitutesafeedbacksystemwithproportionalamplifier.Theseformthepositioncontroltype.Aslongastheelectromagnetisworkinginitspermittedworkingrange,thepositionofitsarmaturekeepsunchangedandhasnothingtodowiththereactingforce.Itsloadstiffnessislarge.2.4.3位置調(diào)節(jié)型比例電磁鐵

比例電磁鐵銜鐵的位置通過位移傳感器檢測，與比例放大器一起構(gòu)成位置反饋系統(tǒng)，就形成了位置調(diào)節(jié)型比例電磁鐵。只要電磁鐵運(yùn)行在允許的工作區(qū)域內(nèi)，其銜鐵就保持與輸入電信號相對應(yīng)的位置不變，而與所受反力無關(guān)，即它的負(fù)載剛度很大。Thepositioncontroltypeisoftenusedontheproportionalvalvewhosecontrolprecisionisdemandedhigher.Thestructureofthistypeisthesameastheothertypesexceptthatitsarmatureislinkedwithdisplacementsensor(thedynamicrodofdisplacementsensorisfixedwitharmature).這類位置調(diào)節(jié)型比例電磁鐵多用于控制精度要求較高的比例閥上。在結(jié)構(gòu)上，除了銜鐵的一端接上位移傳感器(位移傳感器的動(dòng)桿與銜鐵固定聯(lián)接)外，其余與力控制型、行程控制型比例電磁鐵基本相同。位置調(diào)節(jié)型比例電磁鐵在比例方向閥和比例流量閥上，可控制閥口開度，用在比例壓力閥上，可獲得精確的輸出力。這種比例電磁鐵具有很高的定位精度，負(fù)載剛度大，抗干擾能力強(qiáng)。由于這類比例電磁鐵是一個(gè)位置反饋系統(tǒng)，故要與配套的比例放大器一起使用。

Aswhatmentionedbefore,thestrokecontroltypeismainlyusedtocontrolfour-wayproportionaldirectionvalveoffunctiontype.Itshysteresisandrepetitiveerrorareallquitesmallwiththeusingofelectricfeedback.Inaddition,theflowforceexertingonvalvespoolcanberestrained(theelectromagneticforceisquitesmallcomparedwithotherpossibledisturbingforce).

Duetothefactthatthecontrolledpressureexertsonalargerareainthepilotvalve,theavailableadjustingforceismuchlargerthanthatinthevalvesmentionedbefore,butthepercentageoftheeffectofinterferenceforceisnotsolarge.Thus,thepilotproportionalvalvecanalsoworkwithoutelectricfeedbackmechanism.(1)位置調(diào)節(jié)型比例電磁鐵結(jié)構(gòu)圖(1)Thestructurediagramofpositioncontroltype圖2.14位置調(diào)節(jié)型比例電磁鐵結(jié)構(gòu)圖Fig.2.14Thestructurediagramofpositioncontroltype(2)位置調(diào)節(jié)型比例電磁鐵示意圖(2)Schematicdiagramofpositioncontroltype圖2-15位置調(diào)節(jié)型比例電磁鐵示意圖Fig.2.15Theschematicdiagramofpositioncontroltype2.5比例電磁鐵的初步設(shè)計(jì)Thepreliminarydesignofproportionalelectromagnet

Thebasicequationsconcerningthepreliminarydesignofproportionalelectromagnetareasfollows.Theyareelectromagneticsuctionequation,magneticpotentialequation,voltageequationandheatingequation.Theseequationsreflectthebasicrelationshipbetweenstructuresizeandphysicalparameters.Inaddition,thereisstilltherelationalexpressionindicatingreasonablenumericalvaluerangeofelectromagnetsizeparameters,whichwillbetalkedaboutseparatelyasfollows.(1)Theelectromagneticsuctionequation

Aspreliminarycalculation,thecomputingbaseisMaxwellformularandequivalentgasgapmagneticconductivitymethodisadoptedtobesimple.比例電磁鐵的初步設(shè)計(jì)主要涉及的基本方程有四個(gè)，即電磁吸力方程、磁勢方程、電壓方程和發(fā)熱方程。這些方程反映了結(jié)構(gòu)尺寸和物理參數(shù)之間的基本關(guān)系。此外還有表征電磁鐵尺寸參數(shù)的合理取值范圍的關(guān)系式，下面分別討論。(1)電磁鐵的吸力方程作為初步計(jì)算,計(jì)算基礎(chǔ)為麥克斯韋公式,采用等效氣隙磁導(dǎo)法較為簡便。

式中

——等效氣隙處的磁感應(yīng)強(qiáng)度（T）；——等效氣隙端面積（㎡

）；

——空氣導(dǎo)磁率（H/m）。where

——Themagneticinductionintensityatequivalentgasgap;

——Theareaatequivalentgasgapend;

——Airpermeability.（2-1）（2-1）(2)磁勢方程磁勢方程反映了電磁鐵正常工作時(shí)所需要的激磁勢值，利用磁勢方程可求出線圈所需要的激磁安匝數(shù)：(2)Themagneticpotentialequation

Themagneticpotentialequationshowstheneededshockmagneticpotentialvalveduringthenormalworkingofelectromagnet.Excitingampereturnscanbecalculatedbyusingtheequation.（2-2）式中Rp，Rg——?dú)庀洞抛韬蛯?dǎo)磁體磁阻。（2-2）where

Rp，Rg——Thereluctanceofgasgapandmagnetizer.(3)電壓方程電流通過線圈便產(chǎn)生磁勢,并引起發(fā)熱。為了確定線圈的參數(shù):圈數(shù)、線徑、線圈電流等，使線圈能夠在額定電壓下，產(chǎn)生足夠的磁勢(IN)。這時(shí)需要用到線圈電壓方程：(3)Thevoltageequation

Whenthecurrentgoesthroughcoil,themagneticpotentialisgeneratedandleadtoheating.Thevoltageequationisneededinordertodeterminecoilparameters(laps,diameterandcurrent),andmakethecoilunderratedvoltageandcreateenoughmagneticpotential：式中g(shù)x

——導(dǎo)線截面積（㎡

）；

Rx

——線圈總電阻（Ω）；

I——線圈電流（A）；Dx

——線圈平均直徑（m）；

Dw——線圈外徑（m）；DN

——線圈內(nèi)徑（m）；N——線圈圈數(shù)；ρx

——導(dǎo)線在相應(yīng)溫度下電阻率（Ω/m）。wheregx——Thesectionalareaofwire;Rx——Theresistanceofcoil;

I——Thecoilcurrent;Dx

——Themeandiameterofcoil;

Dw——Theexternaldiameterofcoil;DN

——Theinnerdiameterofcoil;

N——Thecoillaps;ρx

——Theresistivityofwireundercorrespondingtemperature.（2-3）（2-3）(４)發(fā)熱方程發(fā)熱方程是為了校核電磁鐵線圈在長期工作下，溫升是否超過其允許值。比例電磁鐵通常按長期工作計(jì)算。(4)TheheatingequationTheheatingequationisusedtocheckwhethertemperaturerisingexceeditspermittedvaluewhenelectromagnetcoilisunderlongtermoperation.Theproportionalelectromagnetisoftencalculatedonthebasisofitslongtermoperationcondition.式中:μs

——散熱系數(shù)；ft——線圈填充系數(shù)；bs——線圈厚度；ls——線圈長度（m）ρs

——工作溫度下的電阻率（Ω/m），查表可得。where

μs

——Heatreleasecoefficient;ft——Coilfilledcoefficient;

bs——Thethicknessofcoil;

ls——Thelengthofcoil;

ρs——Theresistivityunderworkingtemperature,look-uptable.（2-4）（2-4）比例電磁鐵的設(shè)計(jì)步驟：

設(shè)計(jì)的已知條件通常是：最大電磁吸力Fm，初始?xì)庀鼎?，推桿直徑d0，線圈電壓U0及允許溫升[θ]。綜上所述，設(shè)計(jì)步驟如下：(1)求出結(jié)構(gòu)因素Ｋφ，查出電磁感應(yīng)強(qiáng)度Ｂ０。(2)求出銜鐵的外徑d1和盆底極靴（導(dǎo)套）的外徑d2。半徑間隙δ由實(shí)驗(yàn)確定，初步設(shè)

計(jì)取δ＝0.02。Thedesignstepsofproportionalelectromagnet:

Thedesignedknownconditionsareoften:maximumelectromagneticattractionFminitialgasgapδ0,roddiameterd0,coilvoltageU0andpermittedtemperaturerising

[θ].Tosumup,thedesignstepsareasfollows：(1)FindoutstructuralfactorsＫφandelectromagneticintensityＢ０.(2)Findouttheouterdiameterd1ofkeeper

andtheouterdiameterd2ofbasinbottompoleshoe(guid