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1、Unit9SafetyAirbagandSeatbeltSystemPart ITechnicalandPracticalReadingPassageASafetyAirbagWhenacarcrashes,theforcerequiredtostopanobjectisverygreatbecausethecar’smomentumhaschangedinstantlywhilethepassengers’hasnot—thereisnotmuchtimetoworkwith.Thegoalofthesupple
2、mentalrestraintsystem(SRS)istohelpstopthepassengerwhiledoingaslittledamagetohimaspossible.SRSincludessafetyairbagandsafetybelt.Seefigure9-1.Figure9-1SafetyAirbagAsamatteroffact,airbagsaredesignedtokeepyourhead,neck,andchestfromslammingagainstthedashboard,steer
3、ingwheelorwindshieldinafront-endcrash.Anairbagisaninflatablecushion,containingairorsomeothergas.Airbagsaremostcommonlyusedforcushioning,inparticularafterveryrapidinflationinthecaseofanautomobilecollision.Seefigure9-2.Figure9-2Theairbagsystemconsistsofthreebasi
4、cparts:anairbagmodule,crashsensorsandadiagnosticunit.1.Thedriverairbagmoduleisfoldedintothesteeringwheel,andthepassengerairbagmoduleislocatedinthedashboardor,morerecently,intheseatordoor.Anairbagmodulehasthreemainparts:theairbag,theinflator,andthepropellant.Th
5、ebagitselfismadeofathin,nylonfabric.Theinflatorismadefromeitherstainlesssteelorcastaluminum.Theinflatorfitsintoamodulewithawovennylonbagandabreak-awayplastichornpadcover.Seefigure9-3.Figure9-3InflatorThemodule,inturn,fitsintothesteeringwheelfordriver’s-sideapp
6、licationsandabovetheglovecompartmentforfrontpassengerapplications.Thepropellantisprimarilysodiumazidecombinedwithanoxidizerandistypicallylocatedinsidetheinflator.Seefigure9-4.Figure9-4AirBagInflationDevice2.Thesensoristhedevicethattellsthebagtoinflate.Vehicles
7、canhaveoneormorecrashsensors.Theyarelocatedeitherinthefrontofthevehicleand/orinthepassengercompartment.Thesensorsaretypicallyactivatedbyforcesgeneratedinsignificantfrontalornear-frontalcrashes.Seefigure9-5.Figure9-5CrashSensor3.Thediagnosticunitmonitorstheread
8、inessoftheairbagsystem.Theunitisactivatedwhenthevehicle’signitionisturnedon.Iftheunitidentifiesaproblem,awarninglightalertsthedrivertotakethevehicleforexaminationoftheairbagsystem.
