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1、UNIT3LubricationandCoolingSystemPART1TechnicalandPracticalReadingPassageALubricationSystemTheenginelubricationsystemisdesignedtodelivercleanoilatthecorrecttemperatureandpressuretoeverypartoftheengine.Thejobofthelubricationsystemistodistributeoiltothemovingpartstoreducefri
2、ctionbetweensurfaceswhichrubagainsteachother.Thelubricationsystemmainlyconsistsofoilpump,engineoil,oilfilter,oilscreenandoilpan.Seefigure3-1.Figure3-1OilPumpAnoilpumpbeingtheheartofthesystemislocatedintheoilpanonthebottomoftheengine.Thepumpisconnectedbyawormgeartoeitherth
3、ecrankshaftorthecamshaft.Inthisway,whentheengineisturning,theoilpumpispumping.Mostoilpumpshavetwosmallgearsthatmeshwitheachother.Apressure-regulatorvalveinthepumpisusedtopreventthelubricationsystemfromreachingtoohighapressure.Theoilpumppullsoilupfromtheoilpanandmakestheen
4、gineoilcirculatethroughtheengine.Seefigure3-2.Figure3-2EngineOilEngineoilisoftenreferredtoasthelifebloodofanautomobileengine.Anenginerunningwithoutoilwillbejustlikeahumanwithoutblood.Seefigure3-3.Figure3-3Engineoilhasseveralimportantjobsintheengine.First,itmustbecirculate
5、dbetweenmovingenginepartstopreventmetal-to-metalcontact.Withoutoil,metal-to-metalcontactproduceswear.Oilbetweenmovingpartsallowsthemtomoveeasily,withlessfriction.Thelowerthefrictionofanengine,themorepoweritcandevelop.Thecirculatingoilalsocoolstheenginebycarryingheatawayfr
6、omhotenginecomponents,andcleansorflushesdirtanddepositsofftheengineparts.Finally,oilcirculatedonthecylinderwallssealstherings,improvingtheengine’scompression.OilFilterIfengineoilisthelifebloodofanautomobileengine,thentheoilfilteristheliver.Liketheliver,theoilfiltertakesin
7、dirtyoilandremovestheparticulatesandcrud.Thisenginedamagingcrudremainstrappedinthefiltermediaandtheoilfilterreturnsthecleanoilbackintotheengine.Inadditiontoprovidingessentialenginelubricationoil,thisisalsoimportantforscrubbingtheinsideoftheengineclean.Changingtheoilandfil
8、teronaregularintervalgivestheengineafreshtransfusionforlongerlife.Seefigure3-4.Figure3-4OilScree
