汽车专业英语 黄星 刘春波 黄汽驰 2

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1、UNIT2IntroductiontoAutomobileEnginePART1TechnicalandPracticalReadingPassageAEngineConstruction(I)Theautomobileisdesignedtotravelonroads.Thetypicalautomobilehasjustaninternalcombustionenginethatoperatesbyburningitsfuelinsidetheengineandmakestheautomobilemov

2、e.Soanengineistheheartofanautomobile.Seefigure2-1.Figure2-1aV-engineFigure2-1bInline-engineAtypicalautomobileengineconsistsofcylinderblock,cylinderhead,camshaft,valves,sparkplug,pistonandpistonrings,connectingrod,crankshaft，flywheelandoilpan.Seefigure2-2.F

3、igure2-2CylinderBlockCylinderblockorengineblock,asshowninFigure2-3,isasinglemachinedcastingunit.Itcontainsthecylindersandthewatercoolantandlubricantpassages.Soitisacomplicatedpartattheheartofanengine.Cylinderblockisusuallymadefromcastironorinmodernengines,

4、aluminiumandmagnesium.Figure2-3aV-engineblockFigure2-3bInlineengineblockCylinderHeadAcylinderheadisacastinggenerallymadefromironoraluminumthatholdsthevalves,valvespringsandoneortwocamshafts(overheadcamengineonly).Thecylinderheadhasmachinedsurfacestoprovide

5、aprecisionfittomateparts.Inlinefour-andsix-cylinderengineshaveonecylinderhead.V6andV8engineshavetwocylinderheads.Theheadisessentiallyaflatplateofmetalboltedtothetopofthecylinderblockwithagasketinbetween.Seefigure2-4.Figure2-4aCylinderhead(fromside)Figure2-

6、4bCylinderhead(fromtop)CamshaftThekeypartsofanycamshaftarethelobes.Asthecamshaftspins,thelobesopenandclosetheintakeandexhaustvalvesintimewiththemotionofthepiston.Itturnsoutthatthereisadirectrelationshipbetweentheshapeofthecamlobesandthewaytheengineperforms

7、indifferentspeedranges.Seefigure2-5.Figure2-5aCamshaftFigure2-5bDoubleCamshaftsValvesValves(Figure2-6)areusuallymadefromasteelalloy.Exhaustvalvesmustwithstandextremelyhightemperaturesupto815degreesCelsiuswithoutdamagingthevalve.Thevalvefacemustseatevenlyag

8、ainstthevalveseatinthecylinderheadtopreventleaksfromthecylinderduringthecompressionandpowerstrokes.Manyvalvefacesandseatshaveanangleof45degrees.Figure2-6aValveAssemblyFigure2-6bCamshaftValveThereareintakevalv