汽车制动系统(机械、车辆工程毕业论文 英文文献及翻译).pdfVIP

AutomobileBrakeSystem汽车制动系统

Thebrakingsystemisthemostimportantsystemincars.Ifthebrakesfail,theresult

canbedisastrous.Brakesareactuallyenergyconversiondevices,whichconvertthe

kineticenergy(momentum)ofthevehicleintothermalenergy(heat).Whenstepping

onthebrakes,thedrivercommandsastoppingforcetentimesaspowerfulasthe

forcethatputsthecarinmotion.Thebrakingsystemcanexertthousandsofpoundsof

pressureoneachofthefourbrakes.

Twocompleteindependentbrakingsystemsareusedonthecar.Theyaretheservice

brakeandtheparkingbrake.

Theservicebrakeactstoslow,stop,orholdthevehicleduringnormaldriving.They

arefoot-operatedbythedriverdepressingandreleasingthebrakepedal.Theprimary

purposeofthebrakeistoholdthevehiclestationarywhileitisunattended.The

parkingbrakeismechanicallyoperatedbywhenaseparateparkingbrakefootpedal

orhandleverisset.

Thebrakesystemiscomposedofthefollowingbasiccomponents:the“master

cylinder”whichislocatedunderthehood,andisdirectlyconnectedtothebrakepedal,

convertsdriverfoot’smechanicalpressureintohydraulicpressure.Steel“brakelines”

andflexible“brakehoses”connectthemastercylindertothe“slavecylinders”located

ateachwheel.Brakefluid,speciallydesignedtoworkinextremeconditions,fillsthe

system.“Shoes”and“pads”arepushedbytheslavecylinderstocontactthe“drums”

and“rotors”thuscausingdrag,which(hopefully)slowsthecar.

Thetypicalbrakesystemconsistsofdiskbrakesinfrontandeitherdiskordrum

brakesintherearconnectedbyasystemoftubesandhosesthatlinkthebrakeateach

wheeltothemastercylinder(Figure).

Basically,allcarbrakesarefrictionbrakes.Whenthedriverappliesthebrake,the

controldeviceforcesbrakeshoes,orpads,againsttherotatingbrakedrumordisksat

wheel.Frictionbetweentheshoesorpadsan