汽车专业英语 教学课件 黄星 刘春波 黄汽驰 2.ppt

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1、UNIT2IntroductiontoAutomobileEnginePART1TechnicalandPracticalReadingPassageAEngineConstruction(I)Theautomobileisdesignedtotravelonroads.Thetypicalautomobilehasjustaninternalcombustionenginethatoperatesbyburningitsfuelinsidetheengineandmakestheautomobilemove.Soanengineisthehea

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

3、neblock,asshowninFigure2-3,isasinglemachinedcastingunit.Itcontainsthecylindersandthewatercoolantandlubricantpassages.Soitisacomplicatedpartattheheartofanengine.Cylinderblockisusuallymadefromcastironorinmodernengines,aluminiumandmagnesium.Figure2-3aV-engineblockFigure2-3bInlin

4、eengineblockCylinderHeadAcylinderheadisacastinggenerallymadefromironoraluminumthatholdsthevalves,valvespringsandoneortwocamshafts(overheadcamengineonly).Thecylinderheadhasmachinedsurfacestoprovideaprecisionfittomateparts.Inlinefour-andsix-cylinderengineshaveonecylinderhead.V6

5、andV8engineshavetwocylinderheads.Theheadisessentiallyaflatplateofmetalboltedtothetopofthecylinderblockwithagasketinbetween.Seefigure2-4.Figure2-4aCylinderhead(fromside)Figure2-4bCylinderhead(fromtop)CamshaftThekeypartsofanycamshaftarethelobes.Asthecamshaftspins,thelobesopenan

6、dclosetheintakeandexhaustvalvesintimewiththemotionofthepiston.Itturnsoutthatthereisadirectrelationshipbetweentheshapeofthecamlobesandthewaytheengineperformsindifferentspeedranges.Seefigure2-5.Figure2-5aCamshaftFigure2-5bDoubleCamshaftsValvesValves(Figure2-6)areusuallymadefrom

7、asteelalloy.Exhaustvalvesmustwithstandextremelyhightemperaturesupto815degreesCelsiuswithoutdamagingthevalve.Thevalvefacemustseatevenlyagainstthevalveseatinthecylinderheadtopreventleaksfromthecylinderduringthecompressionandpowerstrokes.Manyvalvefacesandseatshaveanangleof45degr

8、ees.Figure2-6aValveAssemblyFigure2-6bCamshaftValveThereareintakevalv