機(jī)械專業(yè)英語(yǔ)課件

單詞復(fù)習(xí)：1.enginelathe2.carriage/stop4.piston5.turret6.Crossslide7.forging/barstock8.collet/chuck上一課回顧1單詞復(fù)習(xí)：上一課回顧1Lesson10MotorsandDrivers

電機(jī)和驅(qū)動(dòng)

重點(diǎn)詞匯：diesel[?di:z?l]n.柴油機(jī)synchronous/asynchronous[ei?si?kr?n?s]

angularvelocitystrip帶、條slider-crank曲柄滑塊gasolineengines汽油機(jī)pneumatic[nju(:)?m?tik]氣動(dòng)的2Lesson10MotorsandDriverParagraph1Allofthemechanismswillrequiresomedriverstoprovidetheinputmotionandenergy.Therearemanypossibilities.所有機(jī)構(gòu)都需要某種形式的驅(qū)動(dòng)裝置提供動(dòng)力和運(yùn)動(dòng)。有許多種選擇。Ifthedesignrequiresacontinuousrotaryinputmotion,suchasforaslider-crank(曲柄滑塊)oracam-follower(凸輪隨動(dòng)件),thenamotoristhelogicalchoice.像曲柄滑塊機(jī)構(gòu)、凸輪機(jī)構(gòu)，如果需要輸入連續(xù)的旋轉(zhuǎn)運(yùn)動(dòng)，那么選擇發(fā)動(dòng)機(jī)是合理的。

3Paragraph1AllofthemechanisParagraph2:

Motorscomeinawidevarietyoftypes.Themostcommonenergysourceforamotoriselectricity,butcompressedairandpressurizedhydraulicfluidarealsousedtopowerairandhydraulicmotors.發(fā)動(dòng)機(jī)有各種各樣的類型。發(fā)動(dòng)機(jī)最一般的能源是電，壓縮空氣和具有一定壓力的液體也常用于氣動(dòng)和液壓馬達(dá)。4Paragraph2:

Motorscomeina

Gasolineordieselengines(汽油和柴油機(jī))areanotherpossibility.Electricmotorsaremadeinseveraldesigns,amongwhichareAC,DC,servo,andstepping.汽油機(jī)和柴油機(jī)是另一選擇。電機(jī)也有像交流/直流電機(jī)、伺服電機(jī)步進(jìn)電機(jī)幾種形式。

5Gasolineordieselengines(汽油Paragraph3:

ACandDCrefertoalternatingcurrentanddirectcurrentrespectively.ACistypicallysuppliedbythepowercompany(動(dòng)力公司)and,intheU.S.,willbealternatingat60hertz,atabout±110voltsor±220volts.AC和DC分別指交流電和直流電。交流電一般由電廠（電力公司）提供，在美國(guó)交流電是60HZ、±110V或±220V。6Paragraph3:

ACandDCrefertParagraph4:

ACmotorsarethemostinexpensivesolutiontocontinuousrotarymotion,andthereareavarietyoftorque-speedcurves(扭矩速度曲線)tosuitvariousapplications.交流電機(jī)是得到連續(xù)旋轉(zhuǎn)運(yùn)動(dòng)的最經(jīng)濟(jì)選擇，有各種轉(zhuǎn)矩—速度曲線適應(yīng)不同載荷。Theyarelimitedtoafewspeeds,whichareafunctionofthe60HzAClinefrequency.交流電機(jī)有有限的幾種速度，這是60HZ交流電源的作用結(jié)果。7Paragraph4:

ACmotorsaretheThemostcommonACmotornoloadspeedsare1725and3450revolutionperminute(RPM),whichrepresentsomeslippage(轉(zhuǎn)差率)fromthemoreexpensivesynchronousACmotorspeedsof1800and3600rpm.最普通的交流電機(jī)零負(fù)載時(shí)速度為1725和3450rPm，這同較貴的速度為1800rPm和3600rPm的同步交流電機(jī)比有一定的轉(zhuǎn)差率。Ifotherspeedsareneeded,agearboxspeedreducer(減速器)isattachedtothemotor’soutputshaft.如果需要輸出其它速度，可在電機(jī)輸出軸上裝一齒輪減速器來(lái)解決。

8ThemostcommonACmotornolParagraph5

DCmotorsaremadeindifferentelectricalconfigurations,whichprovidedifferingtorque-speedcharacteristics.Thetorque-speedcurveofamotordescribeshowitwillrespondtoanappliedload.直流電機(jī)有幾種不同的配置，提供幾種不同的轉(zhuǎn)矩—速度特性。轉(zhuǎn)矩—速度描述了直流電機(jī)如何與負(fù)載一致。9Paragraph5

DCmotorsaremadeFigure1ashowssuchacurveforapermanentmagnet(PM永磁的)DCmotor.Notethatthetorquevariesgreatlywithspeed,rangingfrommaximumtorqueatzerospeedtozerotorqueatmaximumspeed.圖1a所示為永磁直流電機(jī)特性曲線。轉(zhuǎn)矩隨速度變化較大，范圍從零轉(zhuǎn)速時(shí)最大轉(zhuǎn)矩到最大轉(zhuǎn)速時(shí)的零轉(zhuǎn)矩。

(a)Speed-Torque

characteristicofaPMelectricmotorFigure1Speed-TorquecurveParagraph610Figure1ashowssuchacurvefThisrelationshipcomesfromthefactthatPower=Torque×AngularVelocity.

Sincethepoweravailablefromthemotorislimited,anincreaseintorquerequiresadecreaseinangularvelocityandviceversa.這種關(guān)系來(lái)自于關(guān)系式：動(dòng)力=轉(zhuǎn)矩×角速度因?yàn)閯?dòng)力是一定的，轉(zhuǎn)矩增大要求角速度減小，反之亦然。

viceversa

[?vaisi?v?:s?]

反之亦然Wegossipaboutthemandviceversa(=theygossipaboutus).11ThisrelationshipcomesfromtParagraph7Figure1bshowafamilyofloadlinessuperposedonthetorquespeedcurveofthemotor.圖1b所示為在電機(jī)轉(zhuǎn)矩—速度曲線上的一組負(fù)載線。(b)Loadlinessuperposedonaspeed-TorquecurveFigure1Speed-Torquecurve12Paragraph7Figure1bshowafaTheseloadlinesrepresentachangingloadappliedtoamechanism,whichthemotormustsupply.這些負(fù)載曲線表示電機(jī)提供的作用到機(jī)構(gòu)上的載荷變化。

Theproblemcomesfromthefactthatastherequiredtorque(load)increase,themotormustreducespeedtosupplyit.這一變化的根據(jù)是：隨著需要的負(fù)載轉(zhuǎn)矩增加，電機(jī)輸出的速度必須減小來(lái)適應(yīng)這種變化。13TheseloadlinesrepresentacThustheinputspeedwillvaryinresponsetoloadvariation.這樣速度將隨著負(fù)載變化。Ifconstantspeedisdesired,thisisunacceptable.若需要速度恒定是不現(xiàn)實(shí)的。

1414Onepossiblesolutionistouseaspeed-controllerDCmotorwhichcontainscircuitry(回路)thatincreaseanddecreasethecurrenttothemotorinthefaceofchangingloadtotrytomaintainconstantspeed.一種可能的解決方案是使用速度控制的直流電動(dòng)機(jī)，它有一電路系統(tǒng)隨著電機(jī)負(fù)載的變化增大或減小輸入給電機(jī)的電流以試圖保持恒定的速度。Paragraph815OnepossiblesolutionistousTheseDCmotorwillrunfromanACsourcesincethecontrollerconvertsACtoDC.Thecostofthissolutionishigh,however.控制器將交流電轉(zhuǎn)化為直流電，因此這些直流電機(jī)的運(yùn)行需要交流電源，成本較高。Anothersolutionistoprovideaflywheelontheinputshaft,whichwillstorekineticenergyandhelpsmoothoutthespeedvariationsintroducedbytheloadvariations.另一種方案是在輸入軸上安裝飛輪，儲(chǔ)存動(dòng)能來(lái)平緩負(fù)載變化引起的速度波動(dòng)。16TheseDCmotorwillrunfromaParagraph9TheseACandDCmotorsaredesignedtoprovidecontinuousrotaryoutput.Thoughtheycanbestalledagainstaload,theywillnottolerateafull-current,zero-velocitystallformorethanafewminuteswithoutoverheating.這些交流和直流電機(jī)用于輸出連續(xù)的旋轉(zhuǎn)運(yùn)動(dòng)。雖然電機(jī)負(fù)載增大時(shí)速度可降低，但不可能實(shí)現(xiàn)全電流、零速度停車超過(guò)幾分鐘而不過(guò)熱。

17Paragraph9TheseACandDCmotParagraph10

Servomotorsarefastresponse,closed-loop(閉環(huán))controlledmotorscapableofprovidingaprogrammedfunctionofaccelerationorvelocity,aswellasholdingafixedpositionagainstaload.伺服電機(jī)是一種快速反應(yīng)，閉環(huán)控制的電機(jī)，具有可編程控制速度、加速度的功能，也可以通過(guò)固定位置來(lái)應(yīng)對(duì)載荷變化。

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ServomotorsarefClosedloopmeansthatsensorsontheoutputdevicebeingmovedfeedbackinformationonitsposition,velocity,andacceleration.

閉環(huán)的意思是移動(dòng)輸出裝置上的傳感器能給出位置、速度、加速度的反饋信息。Circuitryinthemotorcontrollerrespondstothefedbackinformationbyreducingorincreasing(orreversing)thecurrentflowtothemotor.電機(jī)控制裝置中電路通過(guò)增加或減?。ǚ聪颍┻M(jìn)入電機(jī)的電流，對(duì)反饋信息作出反應(yīng)。

19ClosedloopmeansthatsensorsThusprecisepositioningoftheoutputdeviceispossible,asiscontrolofthespeedandtheshapeofitstimerespondstochangesinloadorinputcommands.這樣輸出裝置處于精確的位置是可能的。同時(shí)控制了速度、對(duì)載荷變化和輸入指令的反應(yīng)時(shí)間。

20ThusprecisepositioningoftTheseareveryexpensivedevicesandcommonlyusedinapplicationssuchasmovingtheflightcontrolsurfacesinaircraftandguidedmissiles.這是一種很昂貴的裝置，一般用在像移動(dòng)在飛行器和巡航導(dǎo)彈中的飛行控制操作臺(tái)。ThesearerelativelysmallandhavelowerpowerandtorquecapacitycomparedtolargerAC/DCmotors.和大直流/交流電機(jī)相比，這種電機(jī)體積小、功率和輸出轉(zhuǎn)矩也較小。

21TheseareveryexpensivedevicSteppingmotorsaredesignedtopositionanoutputdevice.Unlikeservomotors,theseareopenloop,meaningtheyreceivenofeedbackasto（至于，關(guān)于）whethertheoutputdevicehasrespondedasrequired.

步進(jìn)電機(jī)用于定位輸出裝置。不像伺服電機(jī)它是開環(huán)控制，意思是無(wú)論輸出裝置是否按要求動(dòng)作，都沒有反饋。

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22SteppingmotorsaredesignedtTheirinternalconstructionconsistsofanumberofmagneticstrips（磁條）arrangedaroundthecircumferenceofboththerotorandthestator.內(nèi)部結(jié)構(gòu)包括在定子和轉(zhuǎn)子的圓周上分布的很多磁條。Whenenergized,therotorwillmoveonestep,tothenextmagnet,foreachpulsereceived.每接收一個(gè)脈沖，轉(zhuǎn)子轉(zhuǎn)動(dòng)一步（一定角度）到達(dá)下一個(gè)磁體。23TheirinternalconstructioncoThustheseareintermittentmotiondevicesanddonotprovidecontinuousrotarymotionlikeothermotors.這樣它成為一個(gè)間歇運(yùn)動(dòng)裝置，不像其它電機(jī)一樣提供連續(xù)的旋轉(zhuǎn)運(yùn)動(dòng)。Thenumberofmagneticstripsdeterminestheresolution(typicallyafewdegreesperstep).

磁條的數(shù)量決定了分度大小。24ThustheseareintermittentmoTheyarerelativelysmallcomparedtoAC/DCmotorsandhavelowtorquecapacity.Theyaremoderatelyexpensiveandrequirespecialcontrollers.和交直流電機(jī)相比，體積小、輸出轉(zhuǎn)矩小。它不算太貴，要求特殊的控制器。25TheyarerelativelysmallcompParagraph12

Airandhydraulicmotorshavemorelimitedapplicationthanelectricmotors,simplybecausetheyrequiretheavailabilityofcompressedairorhydraulicsource.氣動(dòng)和液壓馬達(dá)和電機(jī)相比應(yīng)用很有限，是因?yàn)樗枰獕嚎s空氣和液壓源。

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AirandhydraulicBothofthesedevicesarelessenergyefficientthandirectelectrictomechanicalconversionofelectricmotors,becauseoflossesassociatedwiththeconversionoftheenergyfirstfromchemicalorelectrictofluidpressureandthentomechanicalform.同利用電機(jī)直接轉(zhuǎn)化為機(jī)械能相比，這些裝置的能量利用率較低，這是因?yàn)槭紫然瘜W(xué)的或電的能量轉(zhuǎn)化為流體壓力，然后轉(zhuǎn)化為機(jī)械能，這些相關(guān)的轉(zhuǎn)換會(huì)有損耗。

27BothofthesedevicesarelesEveryenergyconversioninvolvessomelosses.Airmotorsfindwidestapplicationinfactoriesandshops,wherehigh-pressurecompressedairisavailableforotherreasons.每種能量轉(zhuǎn)換都會(huì)有一些損失。在工廠和車間里，高壓空氣因有其它用途，可以方便獲取，所以氣動(dòng)馬達(dá)得到廣泛應(yīng)用。Acommonexampleistheairimpactwrenchusedinautomotiverepairshop.一個(gè)最普通的例子是在自動(dòng)化維修車間使用的氣動(dòng)扳手。

28EveryenergyconversioninvolAlthoughindividualairmotorsandaircylindersarerelativelycheap,thesepneumaticsystems（氣動(dòng)系統(tǒng)）arequiteexpensivewhenthecostofalltheancillaryequipmentisincluded.雖然氣壓缸和氣動(dòng)馬達(dá)都比較便宜，但計(jì)入所有輔助裝置的成本，這些氣動(dòng)系統(tǒng)是很貴的。

29AlthoughindividualairmotorHydraulicmotorsaremostoftenfoundwithinmachinesorsystemssuchasconstructionequipment(cranes),aircraft,andships,wherehigh-pressurehydraulicfluidisprovidedformanypurposes.液壓馬達(dá)常用于像建筑設(shè)備（起重機(jī)）、飛行器和輪船等機(jī)器和系統(tǒng)中，在這些系統(tǒng)中高壓液體有多種用途。

30HydraulicmotorsaremostofteHydraulicsystemsareveryexpensivewhenthecostofalltheancillaryequipmentisincluded.計(jì)入所有輔助設(shè)備的成本，液壓系統(tǒng)也是很貴的。

31HydraulicsystemsareveryexpParagraph13

Airandhydrauliccylinderarelineractuators(pistonincylinder),whichprovidealimitedstroke,straightlineoutputfromapressurizedfluidinputofeithercompressedairorhydraulicfluid(oil).氣壓和液壓缸是一線性執(zhí)行機(jī)構(gòu)（活塞在缸體內(nèi)），它可實(shí)現(xiàn)有限行程的直線運(yùn)動(dòng)，由工作介質(zhì)為壓縮空氣或液壓油的加壓流體驅(qū)動(dòng)。32Paragraph13

AirandhydraulicTheyarethemethodofchoice