汽車發(fā)動機車身全系列專業(yè)英語

Itiswell-knownthattheautomobileiscomposedoffoursectionssuchasengine,chassis,bodyandelectricalsystem.眾所周知，汽車都由發(fā)動機、底盤、車身以及電氣系統(tǒng)四部分組成。Theenginewhichiscalledthe"heart"ofavehicleisusedtosupplypowerforanautomobile.Itincludesthefuel,lubricating,cooling,ignitionandstartingsystems.Generally,anautomobileisoperatedbyinternalcombustionengine.Theinternalcombustionengineburnsfuelwithinthecylindersandconvertstheexpandingforceofthecombustionor"explosion"intorotaryforceusedtopropelthevehicle.發(fā)動機是汽車的心臟，向汽車提供動力。它包含有燃料系統(tǒng)、潤滑系統(tǒng)、冷卻系統(tǒng)、點火系統(tǒng)和起動系統(tǒng)。汽車一般采用內(nèi)燃發(fā)動機。內(nèi)燃發(fā)動機在汽缸里燃燒燃料將內(nèi)燃所產(chǎn)生的膨脹力轉(zhuǎn)變成旋轉(zhuǎn)力，用以推動車輛前進。Thechassisisaframeworkusedtoassembleautocomponentsonit.Thechassisitselfisdividedintofoursystemsliketransmissionsystem,suspensionsystem,steeringsystemandbrakesystem.底盤是一個用以總裝汽車部件的框架。底盤本身可以分成四個系統(tǒng)，即傳動系統(tǒng)、懸架系統(tǒng)、轉(zhuǎn)向系統(tǒng)和制動系統(tǒng)。Thetransmissionsystemappliestothecomponentsneededtotransferthedrivefromtheenginetotheroadwheels.Themaincomponentsareclutch,gearbox,driveshaft,finaldriveanddifferential.傳動系統(tǒng)運用所需部件將發(fā)動機產(chǎn)生的動力傳遞到車輪。它的主要部件有離合器、變速器、傳動軸、后橋和差速器。Theprimarypurposeofthesuspensionsystemistoundefinedincreasestrengthanddurabilityofcomponentsandtomeetcustomers'requirementsforridingcomfortanddrivingsafety.Inautomobilesuspension,themajorcomponentissprings.Thespringsusedontoday'svehiclesareengineeredinawidevarietyoftypes,sizes,ratesandcapacities.Springtypesincludeleafsprings,coilspringsandtorsionbars.Springsarepairedoffonvehiclesinvariouscombinations,andareattachedtovehiclebydifferentmountingtechniques.懸架系統(tǒng)的主要目的是提高零部件的強度和壽命，并滿足顧客對車輛乘坐舒適性和駕駛安全性的需求。汽車懸架上的主要部件是彈簧。在當(dāng)今車輛上使用的彈簧被設(shè)計制造成許多不同的型號、大小、標(biāo)準(zhǔn)及負(fù)載。彈簧類型包括鋼板彈簧、螺旋彈簧和扭力彈簧。彈簧以各種組合形式在車輛上配套使用，并用不同的裝配技術(shù)將彈簧裝在車輛上。Thefunctionofthesteeringsystemistoprovidethedriverwithameansforcontrollingthedirectionofthevehicleasitmoves.Thesteeringsystemconsistsofsteeringwheel,steeringshaft,worm,gearsector,pitmanarm,draglink,steeringknucklearm,kingpin,steeringarms,tierod,frontaxleandsteeringknuckle.Theyenablethecartochangethedirectionbymeansofturningandmovingforthandback.轉(zhuǎn)向系統(tǒng)的用途是在駕駛員的操縱下控制汽車行駛的方向。轉(zhuǎn)向系統(tǒng)包括轉(zhuǎn)向盤、轉(zhuǎn)向軸、蝸桿、扇形齒輪、轉(zhuǎn)向搖臂、直拉桿、轉(zhuǎn)向節(jié)臂、主銷、轉(zhuǎn)向臂、轉(zhuǎn)向橫拉桿、前軸和轉(zhuǎn)向節(jié)。這些零部件前后移動或轉(zhuǎn)動，可以使汽車改變運動方向。Theautomobilebrakesystemisafrictiondevicetochangepowerintoheat.Whenthebrakesareapplied,theyconvertthepowerofmomentumofthemovingvehicle{kineticenergy)intoheatbymeansoffriction,thusretardingthemotionofthevehicle.Structurally,anautomotivebrakesystemcontainsthesemajorpartslikebrakedrum,brakeshoe,brakelining,etc.Functionally,anautomotivebrakesystemcanbedividedintowheelbrakemechanismandparkingbrakemechanism.汽車制動系統(tǒng)是一種將動力轉(zhuǎn)變?yōu)闊崃康哪Σ裂b置。當(dāng)使用制動器時，制動器通過摩擦將行駛車輛的動量力轉(zhuǎn)變成熱量，從而使車輛運動停滯。從結(jié)構(gòu)上講，汽車制動系含有幾個主要部件，如制動鼓、制動蹄片、制動器摩擦襯片等。從功能上講，汽車制動系可分為行車制動機構(gòu)和停車制動機構(gòu)。Theautomobilebodyservestheobviouspurposeofprovidingshelter,comfortandprotectionfortheoccupants.Thebodyisgenerallyclassifiedintofoursections:thefront,therear,thetopandtheunderbody.Thesesectionscanfurtherfallintoalotofassembliesandparts,suchasthehood,thefenders,theroofpanels,thedoor,theinstrumentpanel,thebumpersandtheluggagecompartment.車身的基本功能就是向乘員提供保護，使其乘坐舒適并保證安全。車身一般分為四個部分:車前部、車后部、車頂部和車下部。這些部分可以進一步分為許多的分總成和部件，如發(fā)動機蓋板、擋泥板、車身頂板、車門、儀表板、汽車保險杠和行李箱。Theelectricsystemsupplieslightinganddrivingpowerfortheautomobile.Itcranksmeengineforstarting.Itsuppliesthehigh-voltagesurgesthatignitethecompressedair-fuelmixtureinthecombustionchambers.Theelectricsystemincludesthebattery,generator,startingsystem,ignitionsystem,lightingsystem,hornsystem,radioandotherdevices.電氣系統(tǒng)向汽車提供照明與驅(qū)動電力。它能起動發(fā)動機、提供高壓電脈沖點燃燃燒室中空氣和燃油的高壓混合氣等。電氣系統(tǒng)包括電池、發(fā)電機、起動系統(tǒng)、點火系統(tǒng)、照明系統(tǒng)、喇叭、收音機以及其他裝置。Theautodescriptionaboveseemstoconcludethatthoughautomobilesarequitedifferentindesign,theyarebasicallysimilarinstructure.綜上所述，盡管汽車的設(shè)計變化很大，然而汽車的構(gòu)造基本上是一樣的。TextFour-stage-engineOperationTherearevarioustypesofenginessuchaselectricmotors,steamenginesandinternalcombustionengines.But,theinternalcombustionengineseemstobetheonemostcommonlyusedintheautomotivefield.Accordingtothefuelenergyused,internalcombustionenginesarefurtherdividedintogasolineengines,keroseneengines,dieselengines,etc.四行程發(fā)動機工作過程發(fā)動機有各種各樣的類型，如電動機、蒸汽機和內(nèi)燃機。但是，在汽車領(lǐng)域里內(nèi)燃機似乎是用得最為普遍的發(fā)動機。根據(jù)所用燃料，內(nèi)燃機還可分為汽油機、煤油機、柴油機等。Theinternalcombustionengine,asitsnameindicates,burnsfuelwithinthecylindersandconvertstheexpandingforceofthecombustionintorotaryforceusedtopropelthevehicle.Theactionstakingplaceintheenginecylindercanbeclassifiedintofourstages,orstrokes."Stroke"referstopistonmovement;astrokeoccurswhenthepistonmovesfromonelimitingpositiontotheother.TheupperlimitofpistonmovementiscalledTDC(topdeadcenter).ThelowerlimitofpistonmovementiscalledBDC(bottomdeadcenter).AstrokeispistonmovementfromTDCtoBDCorfromBDCtoTDC.Inotherwords,thepistoncompletesastrokeeachtimeitchangesitsdirectionofmotion.顧名思義，內(nèi)燃發(fā)動機是在汽缸里燃燒燃料，將內(nèi)燃的膨脹力轉(zhuǎn)變成推動汽車前進的旋轉(zhuǎn)力。發(fā)動機汽缸內(nèi)的工作過程可以分為四個過程或行程。(沖程)行程是指活塞的運動，即活塞從某一限定位置到另一限定位置的運動?；钊\動的上限稱為TDC(上止點)，下限稱為BDC(下止點)。一個行程就是活塞從上止點到下止點，或從下止點到上止點的運動。換句話說，活塞每完成一個行程，就改變一次其運動的方向。Wheretheentirecycleofeventsinthecylinderrequiresfourstrokes(ortwocrankshaftrevolutions),theengineiscalledafour-stroke-cycleengine.Thefour-stroke-cycleengineisalsocalledtheOttocycleengine,inhonoroftheGermanengineer,Dr.NikolausOtto,whofirstappliedtheprinciplein1876.Thefourpistonstrokesareintake,compression,powerandexhaust.Intakestroke.Ontheintakestroke,theintakevalvehasopened,thepistonismovingdownward,andamixtureofairandvaporizedgasolineisenteringthecylinderthroughthevalveport.Themixtureofairandvaporizedgasolineisdeliveredtothecylinderbythefuelsystemandcarburetor.Compressionstroke.AfterthepistonreachesBDC,orthelowerlimitofitstravel,itbeginstomoveupward.Asthishappens,theintakevalvecloses.Theexhaustvalveisalsoclosed,sothatthecylinderissealed.Asthepistonmovesupward(pushednowbytherevolvingcrankshaftandconnectingrod),theair-fuelmixtureiscompressed.BythetimethepistonreachesTDC,themixturehasbeencompressedtoaslittleasone-tenthofitsoriginalvolume,orevenless.Whentheair-fuelmixtureiscompressed,notonlydoesthepressureinthecylindertoup,butthetemperatureofthemixturealsoincreases.Powerstroke.AsthepistonreachesTDConthecompressionstroke,anelectricsparkisproducedatthesparkplug.Theignitionsystemdeliversahigh-voltagesurgeofelectricitytothesparkplugtoproducethespark.Thesparkignitestheair-fuelmixture.Itnowbeginstobumveryrapidly,andthecylinderpressureincreasestoasmuchas3~5MPaorevenmore.Thisterrificpushagainstthepistonforcesitdownward,andapowerimpulseistransmittedthroughtheconnectingrodtothecrankpinonthecrankshaft.Thecrankshaftisrotatedasthepistonispusheddownbythepressureaboveit.Exhauststroke.AsthepistonreachesBDCagain,theexhaustvalveopens.Now,asthepistonmovesupontheexhauststroke,itforcestheburnedgasesoutofthecylinderthroughtheexhaust-valveport.Then,whenthepistonreachesTDC,theexhaustvalveclosesandtheintakevalveopens.Now,afreshchargeofair-fuelmixturewillbedrawnintothecylinderasthepistonmovesdownagaintowardBDC.Thisfourstrokecycleofpistonwithinthecylinderisrepeatedtimeandagaintoputthevehicleforward.發(fā)動機汽缸中的全部工作過程分為四個沖程的(即曲軸旋轉(zhuǎn)兩周的)，叫做四沖程循環(huán)發(fā)動機，或四循環(huán)發(fā)動機。為紀(jì)念德國工程師尼科拉斯、奧托搏士于1876年首次運用四行程循環(huán)原理，四行程循環(huán)發(fā)動機也叫奧托循環(huán)發(fā)動機。發(fā)動機的四個活塞行程是進氣、壓縮、做功和排氣。進氣沖程:在進氣行程中，進氣門打開，活塞向下移動，可燃混合氣通過進氣門進入汽缸。適當(dāng)濃度的可燃混合氣是由燃料系統(tǒng)和化油器提供的。壓縮沖程:在活塞到達(dá)下止點時或者是活塞下限時，活塞開始向上運動。同時，進氣門關(guān)閉，排氣門也關(guān)閉，所以這時的汽缸是封閉的。當(dāng)活塞向上運動時(這時是由轉(zhuǎn)動的曲軸和連桿推動活塞)，可燃混合氣被壓縮。當(dāng)活塞到達(dá)上止點時，可燃混合氣被壓縮到有原體積的十分之下甚至更少。當(dāng)油氣混合燃料被壓縮時，不僅汽缸里的壓力上升，可燃混合氣的溫度也隨之增加了。做功沖程:當(dāng)活塞到達(dá)壓縮行程的上止點時，火花塞產(chǎn)生電火花。電火花是由點火系統(tǒng)向火花塞提供高壓電脈沖而產(chǎn)生的。電火花點燃可燃混合氣。可燃混合氣開始發(fā)生劇烈燃燒，汽缸內(nèi)壓力達(dá)到3-5兆帕，甚至更高。作用于活塞上強大的推動力推動活塞向下運動，并將這一推力通過連桿傳到曲軸上的連桿軸頸上。因此，當(dāng)活塞受壓向下運動時，推動曲軸轉(zhuǎn)動。排氣沖程:當(dāng)活塞再一次到達(dá)下止點時，排氣門打開。同時，活塞向上移動，將廢氣經(jīng)排氣門排出汽缸。隨后，活塞達(dá)到上止點，排氣門關(guān)閉，進氣門打開。當(dāng)活塞又一次向下移動到達(dá)下止點時，新的可燃混合氣被吸入汽缸。汽缸活塞的四個沖程不斷重復(fù)，推動著汽車前進。ThePowerMechanismoftheEngineInareciprocatingengine,thepowermechanismiscalledthecrankshaftandconnectingrodassembly.Inthisassembly,allofthemajorunitssuchastheenginecrankcaseandcylinderblock,thepistonandconnectingrod(seeFigure3.1),thecrankshaftandflywheelworktogethertoconvertthermalenergyintomechanicalenergyusedtodrivethevehicle.Theenginecrankcaseandblockareusuallycastintoonepieceandthereforecanbeseemedasthelargestandmostintricatepieceofmetalinautomobile.Theyareusuallymadeofhigh-gradecastalloyirontoimprovewearcharacteristicsofthecylinder.Thismajorunitmustbestrongandrigidenoughtowithstandanybendingordistortion.Thepistonconvertsthepotentialenginesofthefuelintothekineticenergythatturnsthecrankshaft.Thepistonisacylindricalshapedhollowpartthatmovesupanddowninsidetheenginescylinder.Thepistoniscomposedofpistonhead,pistonrings,pistonlands,pistonskirtandpistonpinhole.Thepistonheador"crown"isthetopsurfaceagainstwhichtheexplosiveforceisexerted.Itmaybeflat,concave,andconvexoranyoneofagreatvarietyofshapestopromoteturbulenceorhelpcontrolcombustion.Insomeapplication,anarrowgrooveiscutintothepistonabovethetopringtoserveasaheatdamtoreducetheamountofheatreachingthetopring.Thepistonringscarriedintheringgrooveareoftwobasictypes:compressionringsandoff-controlring.Theupperringorringsaretopreventcompressionleakage;thelowerringorringscontroltheamountofoilbeingdepositedonthecylinderwall.Thelowergrooveorgroovesoftenhaveholesorslotsinthebottomofthegroovestopermitsoildrainagefrombehindtherings.Thepistonlandsarepartsofpistonbetweentheringgrooves.Thelandsprovideaseatingsurfaceforthesidesofpistonrings.Themainsectionofapistonisknownastheskirts.Itformsabearingareaincontactwiththecylinderwall.Thepistonpinholeinthepistonalsoservesasabearingforthepistonpin,whichisusedtoconnecttheconnectingrod.Inaddition,becausepistonsoperateunderexceedinglydifficultmechanicalandthermalconditions,pistonmustbestrongenoughtostandtheforceoftheexpansion,yetlightenoughtoavoidexcessiveinertiaforceswhentheirdirectionoftravelisreversedtwiceeachrevolution.Pistonmustbeabletowithstandtheheatfromtheburningair-fuelmixture,plustheheatgeneratedbyfriction.Theconnectingrodisattachedtothecrankshaftatoneend(bigend)andtothepistonattheotherend(smallend).Inoperation,theconnectingrodissubjectedtobothgaspressureandinertialoads,andtherefore,itmustbeadequatelystrongandrigidandlightinweightaswell.Sotheyaregenerallyfabricatedfromhighqualitysteel.Theconnectingrodisinformofabarwithringshapedheadsatitsend.Theyarecomposedofconnectingrodsmallend,connectingrodshank,connectingrodbigend,connectingrodcap,andconnectingrodbearinghalfshells.ShankoftheconnectingrodisprovidedwithanI-crosssectiontogivetherodmaximumrigiditywiththeminimumofweight.Thebigendoftherodissplitsothatitcanbeconnectedtothecrankshaft.Toavoidmisplacingtherodcapsduringassembly,theconnectingrodsandtheirmatingcapsaremarkedononesidewithserialnumbers,startingwiththefirstrodfromtheradiator,toidentifytheirlocationintheengine.Someconnectingrodshaveanoilspurtholeintheyokeoratthecap-matingsurfacetoprovidecylinderwalllubrication.Thesmallendoftheconnectingrodisattachedtothepistonbyapistonpin.Insomecasesthesmallendoftherodisclampedtothepinorhasabushinginittoallowthepinandrodoscillation.Inotherdesignsthepinisboltedtotherod.Connectingrodsareusuallydrilledtoprovidelubricationtothepistonpinandalsotosprayoilintothebottomofthepistonforpistoncoolingonsomedesigns.Thecrankshaftservestochangethereciprocatingmotionofthepistonintorotarymotionandhandlestheentirepoweroutput.Theperiodicgasandinertiaforcestakenbythecrankshaftmaycauseittosufferwearandbendingandtensionalstrains.Thecrankshaftthereforemustbeadequatelystrongandwear-resistant.Sothecrankshaftiseitherforgedfromahighqualitysteelorcastinahigh-strongiron.Thecrankshaftisactuallymadeupofvariouspartssuchasmainbearingjournals,rodjournal,crankarmbearing,counter-balancedweightandflywheelend.Thecrankshaftrevolvesinbearingslocatedintheenginecrankcase,butthenumberofbearingsusedusuallydependsonthenumberofcylindersintheengineandthedesignoftheengine.Mechanically,acrankshaftwithoutspecialbalancedweightwouldhaveseverevibrationwhenrevolving.Inordertoreduceoreliminatesuchvibration,itmustbeprovidedwithcounterbalancedweightsthatextendradiallyfromthecrankshaftcenterlineintheoppositedirectionofthecrankarms.Inthatway,theforcesactingonthecrankshaftarebalancedandvibrationisreduced.Therodjournalsareboredhollowinordertoreducethecrankshaftinertia.Drilleddiagonallythroughthecrankarmsareoilholestosupplyoiltotherodjournals.Theflywheelisarelativelyheavymetalwheel,whichisfirmlyattachedtothecrankshaft.Itsfunctionistohelptheenginetorunsmoothlybyabsorbingsomeoftheenergyduringthepowerstrokeandreleasingitduringtheotherstrokes.Inthefrontfaceoftheflywheel,thereisashallowindentationusedtodeterminethepositionofthepistoninthefirstcylinder.Whenthisindentationisalignedwithaspecialholeprovidedinthebellhousing,thepistonisattopdeadcenter（TDC）orindicatesthestartoffuelinjectionintothefirstcylinder.Theflywheelsofsomeenginesalsocarrymarksindicatingtheserialnumbersofthecylinderswherethecompressionoccurs.Theflywheelmarksandindentationareusedforsettingthevalveandignitionsystemsrelativetoprescribedpositionsofthecrankshaft.Inconclusion,theconnectingrodandcrankshaftmechanismoftheengineiscomposedofvariousunits,andeachoftheseunitshasitsownfunctionsinproducingpowerforvehicles.發(fā)動機的能量轉(zhuǎn)換裝置曲柄連桿機構(gòu)就是往復(fù)式發(fā)動機的能量轉(zhuǎn)換裝置。曲柄連桿機構(gòu)主要的組件，如曲軸箱和缸體、連桿和活塞、曲軸和飛輪，協(xié)同工作把熱能轉(zhuǎn)化為機械能，從而推動汽車行駛。通常發(fā)動機的曲軸箱和缸體澆鑄為了體。曲軸箱缸體是汽車中最大、?最復(fù)雜的金屬件，一般由優(yōu)質(zhì)合金鑄鐵制成，以增強其耐磨性。（曲軸箱缸體）這個主要組件必須有足夠的強度和剛度，承受所有彎曲和扭曲變形?；钊讶剂系膬?nèi)能（化學(xué)能）轉(zhuǎn)化為動能使曲軸旋轉(zhuǎn)?；钊菆A柱形的中空的機件，在汽缸內(nèi)上下運動?；钊身敳?、活塞環(huán)、環(huán)槽岸部、裙部和活塞銷組成。活塞頂部或冠都是活塞的上表面，（燃燒所產(chǎn)生的）爆炸作用力就作用于此?；钊敳靠梢宰龀善降?、凹的、凸的或是能夠促進渦流幫助燃燒的任何形狀。某些發(fā)動機中，最上道活塞環(huán)的上方開出一窄槽作為絕熱槽，以減少熱量的傳遞。位于活塞環(huán)槽內(nèi)的活塞環(huán)分為氣環(huán)和油環(huán)。上面的（氣環(huán)）防止漏氣，下面的（油環(huán)）可以控制積聚在汽缸壁的機油量?；钊h(huán)槽內(nèi)通常鉆有油孔或油槽，以從活塞環(huán)后面泄油?；钊h(huán)槽之間的部位稱為槽岸，槽岸為活塞環(huán)側(cè)面提供了艾承面。活塞最主要的部位是裙部，裙部形成活塞與缸壁的接觸支承面?；钊N座支撐活塞銷，而活塞銷連接活塞和連桿。此外，由于活塞在非?？量痰臋C械條件和很高的溫度下工作，其強度必須足以承受膨脹作用力。一個工作循環(huán)活塞上下運動兩次，因此活塞自重應(yīng)盡可能輕以減小慣性作用。活塞應(yīng)當(dāng)能夠承受燃燒混合氣和摩擦熱量。連桿一端（大頭）與曲軸相連，另一端（小頭）和活塞配合。連桿工作時受到氣體壓力和慣性作用，因此必須有足夠的強度和剛度，質(zhì)量盡可能輕。連桿一般由優(yōu)質(zhì)鋼制成，其桿身兩端為環(huán)形。連桿由小頭、桿身、大頭、連桿蓋和軸瓦組成。連桿桿身斷面為工字型，這樣可以同時獲得最大剛度和最小質(zhì)量。連桿大頭一般為剖分式，以便和曲軸相連。為防止裝配時裝錯連桿蓋，在連桿和與其相配合的連桿蓋的某一側(cè)標(biāo)有序號，從靠水箱側(cè)為第一缸，以確認(rèn)各缸的位置。一些連桿在大頭軸頭處或在連桿蓋配合面上鉆有噴油孔潤滑汽缸壁。連桿小頭通過活塞銷與活塞相連。一些發(fā)動機的連桿小頭與活塞銷夾在一起，即連桿小頭有襯套，使活塞銷和連桿一起運動。而在另一些設(shè)計中用螺栓連接活塞銷和連桿。通常連桿上鉆出油道潤滑活塞銷，有些設(shè)計中連桿上的油道也向活塞底部噴油實現(xiàn)冷卻。曲軸用于把活塞的往復(fù)運動轉(zhuǎn)化為旋轉(zhuǎn)運動并控制全部動力輸出。曲軸所受到的周期性的氣體壓力和慣性力導(dǎo)致曲軸磨損、產(chǎn)生彎曲和扭轉(zhuǎn)變形。因此曲軸應(yīng)當(dāng)有足夠的強度和耐磨。曲軸由優(yōu)質(zhì)鋼鍛造或通過高強度鑄鐵鑄造而成。事實上曲軸由主軸頸、連桿軸頸、曲柄臂軸承、平衡塊和飛輪端這些主要部件所組成。曲軸在位于曲軸箱內(nèi)的主軸承上旋轉(zhuǎn)，所使用的主軸承數(shù)量取決于發(fā)動機汽缸數(shù)和發(fā)動機的設(shè)計。如果沒有專門的平衡塊，曲軸在旋轉(zhuǎn)時會產(chǎn)生劇烈的振動。為了減少甚至消除振動，在曲軸中心線的延長線上與曲柄臂相反方向配有平衡塊。這樣，作用于曲軸的作用力得到了平衡，減少了振動。連桿軸頸內(nèi)部銳空目的是減少曲軸慣性。穿過曲柄臂斜向鉆出的油孔提供連桿軸頸的潤滑。飛輪是一個相當(dāng)重的金屬輪盤，飛輪與曲軸緊相連。它的作用是在做功行程吸收能量，在其他工作行程釋放能量，從而有助于發(fā)動機平穩(wěn)工作。在飛輪前斷面有一淺的缺口，用來確定一缸活塞位置。當(dāng)缺口與飛輪殼體上的小孔對齊時，一缸活塞位于上止點或表明一缸開始噴油。有些發(fā)動機的飛輪標(biāo)有在壓縮行程的汽缸序號。飛輪上的記號和缺口用來調(diào)整與曲軸特定位置相關(guān)的配氣機構(gòu)和點火系統(tǒng)?？傊?，發(fā)動機曲柄連桿機構(gòu)由各個不同的組件構(gòu)成，在產(chǎn)生汽車動力時每個組件具有特定的功能。ValvesandValveTrainThevalvegearofaninternalcombustionengineprovidestimelyadmissionofthefreshchargeintothecylindersandexhaustofspentgasesfromthem.Forthispurposethevalvesatdefinitemomentsopenandclosetheintakeandexhaustportsinthecylinderhead,throughwhichthecylinderscommunicatewiththeintakeandexhaustmanifold.Thevalvegeariscomposedoftiminggears,acamshaft,tappets,valves,springwithfastenersandvalveguides.Thetiminggearsinmostenginesarehousedinaspecialcasefittedatthefrontendoftheengine.Thesearenecessarytotransmitrotationfromthecrankshafttothecamshaft,fuelinjectionpumpshaft,andtooilpumpandothermechanisms.Thegearsaremadeofsteelandusehelicalteethtoreducenoise.Camshaft'sfunctionistoopentheenginevalvespositivelyandtimely,inadefinitesequence,andtocontroltheirclosingagainstthereturnactionofthevalvesprings.Theshaftismadeintegralwithitscamsandbearingjournals.Eachcamcontrolsasinglevalve,eitherintakeorexhaust.Insomeautomobileengines,thecamshaftismadeintegralwithfuelpumpeccentricwheelandoilpumpdrivegear.Thecamshaftbearingsarelubricatedwithoilsuppliedunderpressurefromthemaingalleryinthecylinderblock.Thetappetsservetotransmittheforcefromthecamshafttothepushrods.Thetappetsaresmallcylindricalboresreceivingthepushrods.Theyaremadeofcastironorsteelandlocatedintheguides,whichmaybemadeintegralwiththecylinderblockorremovableasintheengine.Whentheenginesoperate,thetappetscontinuouslyrotateabouttheiraxesforuniformwear.Therotationisensuredbyaconvexsurfaceoftheirbottomsandaslantedsurfaceofthecams.Thepushrodstransmitstheforcefromthetappetstotherockerandaremadeassteelstemswithhardenedtipsorduralumintubeswithsphericalsteeltipspress-fittedat.bothends.Thepushrodtipsbearagainstthetappethollowatoneendagainstthesphericalsurfaceofrockeradjustingscrewatother.Therockerstransmittheforcefromthepushrodtothevalve.Therockersaremadefromsteelandareinstalledonahollowfulcrum.Abronzebushispressfittedintotherockerholetoreducefriction.Thehollowfulcrumissupportedbystandardsonthecylinderhead.Endplayoftherockerispreventedbyacoilspring.Therockerarmisabellcrankmadeofsteel.Atthemiddleoftherockerarm,thereisabosswithaboreintowhichispressedthebushing.Ahardenedcurvedpadisprovidedontheendoftherockerwhereitcontactsthevalvestemtip,whileathreadedholeismachinedinitsotherendtoreceivetheadjustingscrewusedtosetthevalveclearance,theclearancebetweentherockercontactpadandthevalvestemtip,sothatthevalvewillbetightlypressedagainstitsseatwhenhot.Therockerarmfreelyoscillatesabouttherocker-armshaftsupportedbyaseriesofpedestalsorbrackets,whichareboltedtothetopdeckofthecylinderhead.Anenginevalveisadevicedesignedtoopenapassagewhenmovinginonedirectionandtocloseitwhenmovingintheoppositedirection.Eachcylinderofafour-stroke-cycledieselorgasouneengineiscommonlyequippedwithanintakevalveandanexhaustvalve.Thepurposeoftheintakevalveistoallowtheairfuelmixtureorairtoenterthecylinder.Afterthecombustionprocesshasbeencompleted,theburnedgasesarepermittedtoescapefromthecylinderthoughtheexhaustvalve.Toobtainsufficientvalvearea,someautomobileshavetwointakevalvesandtwoexhaustvalves.Avalveconsistsofaheadandstem.Thevalveheadhasanarrowchamferof45°or30°referredtoasvalveface.Thevalvefacefitstightlyagainsttheseat,whichisachievedbygrinding.Forbetterenginebreathing,theinletvalvehasalargerdiameterthantheexhaustone.Asthevalvesarenotequallyheatedintherunningengine,theyaremadefromdifferentmaterials.Theinletvalvesaremadefromchromiumsteel,theexhaustvalvesareofsilchromeheat-resistantsteel.Thecylinderstemofthevalvehasarecessattheupperendforfasteningthevalvespring.Thevalvestemsslideinthecast-ironorcerametallicvalveguides.Thevalvespringprovidestheforcenecessarytoclosethevalveandholdittightlyagainstitsseat.Someenginesusetwospringsoneachvalve,whichreducethesizeofthesprings,improvestheirreliability,andmakestheiroperatingconditionslessarduous.Valveguidesupportsthevalvestemandguidesitsmovementsothatthevalvefaceremainsperfectlyconcentricwiththevalveseatandfitsitwithoutanyskewing.Replaceablevalveguidesarefabricatedfromcastironoracermetsmaterialandpressedinthecylinderhead.Todecreaseoilpenetrationalongthevalvestemtothecombustionchambers,theseatingcollarsarefittedwithrubberringsortheseatsareprovidedwithrubbercaps.Moreuniformheatingandwearofthevalveareensuredwiththevalvesrotatingduringtheoperationoftheengine.Ingeneral,therearetwowaysofrotating:oneisfreerotatetheotherispositiverotate.Asthevalveisopened,springiscompressedanditsincreasingloadcausestheflexiblewashertoflattenoutandforceballsdowntheirrampsagainsttheresistanceofferedbytheirreturnsprings.Astheballsrolldown,theyturnthroughsomeangletheflexiblewasher,seatingcollarandvalvespringtogetherwiththevalve;whenthevalveisclosed,thevalvespringloaddecrease,theflexiblewasherdeflectstoacquireitsinitialconicalshapeandabuttingagainstashoulderinhousing,releasestheballswhicharethenforcedbytheircoilspringstoreturntotheirstartingposition.配氣機構(gòu)內(nèi)燃機的配氣機構(gòu)保證新鮮混合氣可以適時進入汽缸，同時燃燒后的廢氣及時排出。為實現(xiàn)這一目的，氣門在一定的時刻打開和關(guān)閉汽缸蓋上的進排氣道，汽缸通過進排氣歧管與進排氣管相溝通。配氣機構(gòu)由正時齒輪、凸輪軸、挺柱、氣門、帶有鎖緊裝置的彈簧和氣門導(dǎo)管組成。大多數(shù)發(fā)動機的正時齒輪裝在專門的殼體內(nèi)，正時齒輪殼體位于發(fā)動機前端。必須使用正時齒輪將曲軸的旋轉(zhuǎn)傳遞到凸輪軸，驅(qū)動噴油泵軸、機油泵和其他的裝置。正時齒輪由鋼制成，采用螺旋狀齒以減少噪聲。凸輪軸的功用是按特定的順序準(zhǔn)確適時地打開氣門并通過氣門彈簧的回位作用控制氣門的關(guān)閉。凸輪軸與凸輪、軸頸制為一體。每個凸輪控制一個氣門:進氣門或排氣門。有些汽車發(fā)動機的凸輪軸也與驅(qū)動燃油泵的偏心輪和機油泵的驅(qū)動齒輪做成一體。缸體內(nèi)主油道的機油在壓力作用下到達(dá)凸輪軸軸頸提供潤滑。挺柱用來把凸輪軸的作用力傳遞給推桿。挺柱為圓柱形小筒，里面插入推桿。挺柱材料為鑄鐵或鋼，定位于導(dǎo)管內(nèi)，挺柱導(dǎo)管可以是與缸體一體的或者是可拆卸的。發(fā)動機工作時，為使磨損均勻，挺柱總是繞其軸線旋轉(zhuǎn)。挺柱的旋轉(zhuǎn)是由挺柱凸起的下表面和凸輪傾斜面所保證的。推桿將挺柱傳來的推力傳給搖臂。推桿由頂部淬火的鋼柱或由兩端壓入配合的帶球形鋼頭的硬鋁管制成。推桿的兩端一頭支撐在挺柱的空腔內(nèi)，另一頭與搖臂調(diào)整螺釘端的球形表面配合。搖臂把推桿的作用力傳遞到氣門。搖臂由鋼制成，安裝于空心的樞軸。搖臂空內(nèi)裝有青銅襯套以減少摩擦。中空的搖臂軸通過支架固定于汽缸蓋。搖臂上的螺旋彈簧防止產(chǎn)生軸向竄動。搖臂是鋼制的雙臂杠桿。搖臂中部有一帶孔的凸臺，孔內(nèi)壓裝有襯套。搖臂的一端是經(jīng)過淬火的圓弧狀長臂，與氣門桿尾端接觸，而車有螺紋孔的另一端安裝有調(diào)整螺釘，用來調(diào)整搖臂與氣門桿尾端之間的氣門間隙，從而保證氣門在受熱后緊緊壓在氣門座上。搖臂可以繞搖臂軸自由擺動，搖臂軸通過一系列支座支撐，支座用螺栓固定于汽缸蓋上表面。發(fā)動機氣門向某一萬向運動時開啟-通道，而它向相反方向移動時則關(guān)閉此通道。四行程汽油機或柴油機的每缸一般都裝有進氣門和排氣門。%氣門的作用是使空氣燃油混合氣進入汽缸。燃燒過程完成后廢氣通過排氣門排出汽缸。為了獲得足夠的充氣面積，有些發(fā)動機采用兩個進氣門和兩個排氣門。氣門由頭部和桿身組成。氣門頭部相對于氣門平面之間存在45?；?0。的錐角。通過研磨使氣門平面與氣門座緊密貼合。為使發(fā)動機更好地?fù)Q氣，進氣門（頭部）直徑大于排氣門。在發(fā)動機工作時由于進、排氣門受熱不均等，因此它們采用不同的材料制成。進氣門采用鉻鋼，排氣門采用耐熱硅鉻鋼。圓柱氣門桿身的上部有一凹槽用來固定氣門彈簧。氣門桿身在鑄鐵或金屬陶瓷氣門導(dǎo)管內(nèi)運動。氣門彈簧提供氣門關(guān)閉時所需要的作用力，保證氣門與氣門座緊密貼合。有些發(fā)動機的每個氣門裝有兩根彈簧，可以減小所使用的彈簧大小，增加可靠性，使工作更平穩(wěn)。氣門導(dǎo)管支撐氣門桿身，對其運動起導(dǎo)向作用，以保證氣門X閉時能準(zhǔn)確地與氣門座貼合而不產(chǎn)生偏移。可拆卸式氣門導(dǎo)管采用鑄鐵或金屬陶瓷材料制成，壓入汽缸蓋上的（氣門導(dǎo)管。為防止機油從氣門桿滲進燃燒室，在氣門導(dǎo)管上裝有橡膠環(huán)或橡膠皮碗。發(fā)動機工作時通過氣門的旋轉(zhuǎn)可以使氣門獲得更均勻的受熱和磨損。通常有兩種實現(xiàn)氣門旋轉(zhuǎn)的方式：自由旋轉(zhuǎn)和強制旋轉(zhuǎn)。當(dāng)氣門開啟時，彈簧被壓縮，彈力增加，將彈性墊圈壓平，迫使鋼球克服回位彈簧的阻力沿斜坡滾動。當(dāng)鋼球滾下時，帶動彈性墊圈、氣門彈簧與氣門一起轉(zhuǎn)過一個角度;當(dāng)氣門關(guān)閉時，氣門彈簧彈力減小，彈性墊圈變形為原來的圓錐狀，支撐于殼體的支撐板，鋼球在回位彈簧作用下回到原來位置。EngineFuelSystemThefuelsystemiscriticaltooperation.Thesystemconsistsofthefueltank,lines,pump,filter,carburetor,andinjectors.FuelFlowThefuelinthefueltankisreadytobeusedwhentheengineneedsit.Thefuelpumpdrawfuelfromthetankandsendsittothecarburetor.Thecarburetoristokeepthefuelattherightair-fuelratio.Foraelectricfuel-injectedengine,thefuelispressurizedandsenttothefuelfeedpipe,throughafuelfilter,andintothefuelinjectors.Foradieselfuelgoestothefuelinjectorpump,ratherthantothecarburetor,thentothefuelnozzles.FuelTankThefueltankisusedtostorethefuelofengineneeded.Itisusuallylocatedinrearofthevehicle.Thefueltankisdesignedtofitaroundframeandtobeprotectedfromimpacts.Theseareseveralbafflesinsidesthefueltanktorestrictfuelmovementduringrapidstartsandstops,cornering,andsoon.Thefuelcaponthefueltankisusedtokeepthefuelfromsplashingout,releasethevacuumcreatedbythefuelremoving,andpreventvaporsfromescapingdirectlyintotheatmosphere.Thefuellevelsaremeasuredbyafuel-meteringunit.Onestyleoftheunithasahingedfloatinsidethetank.Asthefloatpositionchangeswithdifferentlevelsoffuel,theneedlepositiononthedashboardgaugechanges.FuelPumpGasolineenginepumpiseithermechanicalorelectrical.Themechanicalfuelpumpisusedonmanyvehicleswithcarburetorsanddrivenbythecamshaft.Thereisacamoraneccentriclobeonthecamshaft.Asthecamshaftturns,thelobeliftsaleverupanddown,causingapumpingaction.Fuelisdrawnfromthetankbyavacuumandsenttothecarburetor.Electricalfuelpumpcanbeusedinsteadofmechanicaltypes.Thetypesoftheelectricalfuelpumpsemployedincludethebellowandtheimpellerorrollervane.Inthebellows-typeelectricalfuelpump,ametalbellowsisusedinsteadofadiaphragm.Itoperatesfromthemovementofthearmatureinthemagneticcoil.Thebellowsisstretchedandsqueezedtocausethevacuumandpressure.Therollervaneelectricalfuelpumpsareusedonnewervehicles.Astheelectricmotorturnsanimpeller,fuelisdrawninattheinletportofthepump.Itispressurizedandsentoutthedischargeportfordeliverytotheengine.Theimpellerattheinletendservesasavaporseparator.Apressurereliefvalvekeepsfuelpumppressureataconstantlevel.Fuelsystemsthathaveelectricalfuelpumpsandfuelinjectorsmayuseafuelpressureregulatortokeepthefuelpressureconstant.FuelFiltersFuelfilersareusedtostopanycontaminationfromgettingintothefuelsystemofbothgasolineanddieselengines.Thegasolineenginesmayhaveoneortwofiltersinthefuelsystem.Thefirstfilterisusuallyplacedinsidethefueltanktopreventlargepiecesofcontaminantfromdamagingthefuelpump.Thesecondoneisanin-linetypeoranin-carburetortypeusedtofilteroutsmalldirtparticles.Manydieselenginesusedinautomotiveapplicationshaveonlyonefilter,whichiscalledtheprimaryfilter.Onsomeengines,asecondaryfilterisadoptedandcombinedwithprimaryonetobuildintoasinglefilter.CarburetorCarburetorsusedongasolineenginearedesignedtomixtheairandfuelatthecorrectratio.Themostcorrectair-fuelratiois14.8partsofairto1partoffuel.Ontheintakestoke,thepistonmovesdownandtheintakevalveisopened,avacuumisproducedandcausesairtobedrawnorpulledintotheengine.Theairpassesthroughthecarburetorandventuriasitgoesintotheengine.Aventuriisastreamlinedrestrictionthatpartlyclosesthecarburetorbore.Theairenteringtheventuriisforcedtospeedup.Thegreaterthevelocityofairpassedthoughtheventuri,thegreaterthevacuumproduced,andthemorefuelisdrawnin.Theflowofairandfuelthroughthecarburetoriscontrolledwithathrottleplate.Thethrottleplateisplacedbelowtheventuriandconnectedtotheaccelerationpedal.Asthedriver'sfootonthepedalisdepressed,thethrottleplateopens,andthereisverylittlerestrictionofairandfuel.Theloadandspeedisincreased.發(fā)動機燃料供給系統(tǒng)燃料供給系統(tǒng)對于發(fā)動機的工作是至關(guān)重要的。燃料供給系統(tǒng)由燃油箱、燃油管、燃油泵、燃油濾清器、化油器和噴油器組成。燃油的流動燃油箱可以提供發(fā)動機需要的燃油。燃油泵將燃油從油箱吸出并送至化油器?；推鞅３趾线m的空燃比的混合氣。在電控燃油噴射式發(fā)動機中，燃油被加壓送至輸油管，經(jīng)過燃油濾清器最終到達(dá)噴油器。對于柴油機而言，燃油進入噴油泵而不是化油器，最后到達(dá)噴油器。燃油箱燃油箱用于儲存發(fā)動機所需的燃油。燃油箱通常位于車輛后方。燃油箱安裝在車架旁，保護油箱不致受到?jīng)_擊。燃油箱內(nèi)有隔板，以減輕車輛起動、急剎車、轉(zhuǎn)彎等情況下燃油的振蕩。燃油箱蓋用來保持燃油不致濺出，釋放因使用燃油造成的真空，防止燃油蒸汽泄入大氣。燃油平面的高低由燃油面指示裝置來測量。有一種類型的燃油面指示裝置采用-浮子鉸接到油箱內(nèi)。燃油面的高低會改變浮子的位置，儀表板上燃油表的指針的位置也隨之發(fā)生了改變。燃油泵燃油泵汽油機燃油泵為機械驅(qū)動式或電動式機械驅(qū)動燃油泵用于許多化油器式車輛，它由凸輪軸驅(qū)動。凸輪軸上有一凸輪或偏心輪。當(dāng)凸輪旋轉(zhuǎn)時，（凸輪或偏心輪的）凸尖頂起拉桿上下運動，使燃油泵工作。燃油在真空作用下從油箱中被吸入壓送到化油器。電動燃油泵可以代替機械式燃油泵。常用的電動燃油泵包括波紋管式和葉輪式。在波紋管式電動燃油泵中，金屬波紋管取代了膜片。金屬波紋管在磁場線圈的電樞作用下工作。波紋管被伸長、擠壓，從而產(chǎn)生真空和壓力。葉輪式電動燃油泵用于新型車輛。電機帶動葉輪轉(zhuǎn)動，燃油被吸到燃油泵的進油道。燃油得到加壓，從油室到達(dá)發(fā)動機。進油端的葉輪起到油氣分離器的作用。（燃油泵中的）卸壓閥使燃油泵壓力保持一定。采用電動燃油泵的燃料供給系統(tǒng)要使用燃油壓力調(diào)節(jié)器來保證油壓恒定。燃油濾清器燃油濾清器用來阻止汽油機或柴油機的燃油系統(tǒng)受到污染。汽油機的燃油系統(tǒng)可以有一個或兩個濾清器。第一個濾清器通常在燃油箱內(nèi)，防止較大污物進入損壞燃油泵。第二個濾清器串接在油路中或在化油器中，以去除較小污物微粒。大多數(shù)車用柴油機只有一個燃油濾清器，稱為初級濾清器。有些發(fā)動機將次級濾清器和初級濾清器組合在一起?；推髌蜋C中使用的化油器用來將空氣和燃油以適當(dāng)?shù)谋嚷驶旌?，最佳空燃比?4.8:1。在進氣行程，活塞下行，進氣門開啟，產(chǎn)生真空使空氣被吸進發(fā)動機?？諝膺M入發(fā)動機要流經(jīng)化油器和文氏管（化油器喉管人文氏管（化油器喉管）部分關(guān)閉了化油器孔徑，有效限制了氣流?？諝饬鹘?jīng)文氏管（化油器喉管）時流速增加。流經(jīng)文氏管（化油器喉管）的氣流速度越快，產(chǎn)生的真空度就越大，吸進的燃油就越多。通過化油器的空氣和燃油的量是由節(jié)氣門控制的。節(jié)氣門位于喉管下方，與加速踏板（油門）相連。當(dāng)司機踩下油門時，節(jié)氣門打開，空氣和燃油的流動幾乎不受限制，負(fù)荷和車速增加。EngineCoolingSystemThepurposeofthecoolingsystemistokeeptheengineatitsmostefficientoperatingtemperatureatallspeedsunderalldrivingconditions.Asfuelisburnedintheengine,aboutone-thirdoftheheatenergyinthefuelisconvertedintopower.Anotherthirdgoesoutthroughtheexhaustpipeunused,andtheremainingthirdmustbehandledbythecoolingsystem.Thismeansthattheenginecanworkeffectivelyonlywhentheheatenergyisequallyhandledsoastokeeptheenginetemperatureinbalance:So,thetemperatureisquiteessentialforanenginetoproducepower.Noenginecanworkwellwithoutsuitableoperatingtemperatures.Iftheenginerunstoohot,itmaysufferfrompre-ignition,whiletheair-fuelchargeisignitedprematurelyfromexcessivecombustionchambertemperature.Viscosityoftheoilcirculatinginanoverheatingengineisreduced.HotoilalsoformsvarnishandcarbondepositsmaybedrawnintothecombustionchamberwhereitincreasesHCemission.Thisalsocausespoorperformanceandprematurewear,andmayevenresultinenginedamage.What'smore,thebehaviorofthemetalsatexcessivelyhightemperaturealsodiffersfromthatatnormaltemperatures.Iftheenginerunstoocold,thefuelwillnotvaporizeproperly.Ifliquidfuelreachesthecylinders,itwillreducelubricationbywashingtheoilfromthecylinderwallsanddilutingtheengineoil.Thiscausesalossofperformance,anincreaseinHCemissions,andprematureenginewear.Forthesereasons,acoolingsystemofsomekindisnecessaryinanyinternalcombustionengine.Therearegenerallytwodifferenttypesofcoolingsystem:water-coolingsystemandair-coolingsystem.Water-coolingsystemiscommon.Thecoolingmedium,orcoolant,inthemiseitherwaterorsomelow-freezingliquid,calledantifreeze.Awater-coolingsystemconsistsoftheenginewaterjacket,thermostat,waterpump,radiator,radiatorcap,fan,fandrivebeltandnecessaryhoses.Awater-coolingsystemmeansthatwaterisusedasacoolingagenttocirculatethroughtheenginetoabsorbthehotandcarryittotheradiatorfordisposal.