汽车专业实用英语 教学课件 作者 陈晟闽 04-ignition system.ppt

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1、WelcomeToIgnitionSystemOperation&DiagnosisSECTION4ObjectivesDescribethethreemajorfunctionsofanignitionsystem.Nametheoperatingconditionsofanenginethataffectignitiontiming.Namethetwomajorelectricalcircuitsusedinignitionsystemsandtheircommoncomponents.Describetheopera

2、tionofignitioncoils,sparkplugs,andignitioncables.continued…ObjectivesExplainhowhighvoltageisinducedinthecoilsecondarywinding.Describethevarioustypesofsparktimingsystems,includingelectronicswitchingsystemsandtheirrelatedenginepositionsensors.Explainthebasicoperation

3、ofacomputer-controlledignitionsystem.continued…ObjectivesExplainhowthefuelinjectionsystemmayrelyoncomponentsoftheignitionsystem.Describetheoperationofdistributor-basedignitionsystems.Describetheoperationofdistributorlessignitionsystems.continued…PurposesoftheIgniti

4、onSystemItmustgeneratesparkwithenoughheattoignitetheair/fuelmixture.Itmustmaintainthesparklongenoughtoallowforcompletecombustion.Itmustdeliverthesparksocombustioncanbeginattheprecisetime.continued…FactorsThatAffectTimingEnginespeed(rpm)Athigherrpms,thecrankshafttur

5、nsthroughmoredegreesinagivenperiodoftime.Ifcombustionistobecompletedby10ºATDC,ignitiontimingmustoccursoonerorbeadvanced.continued…FactorsThatAffectTimingcontinued…FactorsThatAffectTimingEngineloadUnderlightloadsahighvacuumorlowpressureexistsandlessair/fuelmixturedr

6、awnintothecylindersproducinglesscombustionpressureandcombustiontimeisslow.Tocompletecombustionby10ºATDC,ignitiontimingmustbeadvanced.Underheavyloads,thevacuumislowandalargermassofair/fuelmixturecanbedrawnin.Highcombustionpressureandrapidburningresultsandtheignition

7、timingmustberetardedtopreventcompleteburningbefore10ºATDC.continued…FactorsThatAffectTimingFiringorderExamplesoftypicalfiringorderscontinued…IgnitionSystemPrimaryCircuitComponentsBatteryIgnitionswitchBallastresistor(oldersystems)IgnitioncoilprimarywindingTriggering

8、deviceSwitchingdeviceorcontrolmodulecontinued…IgnitionSystemPrimarycircuitoperationBatterycurrentflowsthroughtheignitionswitchandtheprimarywindin