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1、UNIT5AutomotiveIgnitionSystemPartITechnicalandPracticalReadingPassageAConventionalIgnitionSystemThepurposeoftheignitionsystemistocreateasparkthatwillignitethefuel-airmixtureinthecylinderofanengine.Theignitionsystemhastwotaskstoperform.First,itmustcreateavoltagehigheno
2、ugh(20,000+)tojumpacrossthegapofasparkplug,thuscreatingasparkstrongenoughtoignitetheair-fuelmixtureforcombustion.Second,itmustcontrolthetimingofthespark,soitoccursattheexactrighttimeandsendittothecorrectcylinder.Seefigure5-1.Figure5-1IgnitionSystemCurrently,therearetw
3、odistincttypesofignitionsystems: theconventionalignition(CI)systemandtheelectronicignition(EI)system.Theignitionsystemisdividedintotwosections,theprimarycircuit(low-voltagecircuit)andthesecondarycircuit(high-voltagecircuit).Theprimarycircuitconsistsofthebattery,igniti
4、onswitch,coilprimarywinding,distributorcontactpoint,andconnectingwiring.Thesecondarycircuitconsistsofignitioncoilsecondarywindings,distributorcap,distributorrotor,sparkplugsandsparkplugwires.Seefigure5-2.Figure5-2DistributorThedistributor,seefigure5-3,isthenervecenter
5、oftheignitionsystem.Itcontainsarotatingcam,asetofbreakerpoints,acondenser,arotorandadistributorcap.Thedistributorhastwotaskstoperform.First,itisresponsiblefortriggeringtheignitioncoiltogenerateasparkatthepreciseinstant.Second,thedistributorisresponsiblefordirectingtha
6、tsparktothepropercylinder.Figure5-3IgnitionCoilExternaltothedistributoristheignitioncoil.Itisnothingmorethananelectricaltransformer.Itcontainsbothprimaryandsecondarywindingcircuits.Thecoilprimarywindingcontains100to150turnsofcopperwire.Theprimarycircuitwiregoesintothe
7、coilthroughthepositiveterminal,loopsaroundtheprimarywindings,thenexitsthroughthenegativeterminal.Thecoilsecondarywindingcircuitcontains15,000to30,000turnsoffinecopperwire,whichalsomustbeinsulatedfromeachother.Thesecondarywindingssitinsidetheloopsoftheprimarywindings.T
8、ofurtherincreasethecoils’magneticfieldthewindingsarewrappedaroundasoftironcore.Theignitioncoilistheheartoftheignitionsystem.
