奥迪全系自学手册（SSP）：ssp257_gb.pdf

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1、Service.Self-StudyProgramme257ElectricvacuumpumpforbrakeservounitDesignandFunctionCarsfittedwithapetrolengineincombinationEU4emissionstandard,andcompensatingforthewithanautomaticgearboxwhichcomplywiththegreatertorquefriction(resistanceintorquecon-EU4Standardhaveanel

2、ectricvacuumpump.verter)whichexistsundertheconditionsmentio-Thisisusedforassistingthebrakeservounit.nedabove.Inthisengine-gearboxcombination,thethrottleDependingontheparticularcarmodel,twodiffe-valveisopenedparticularlywidewhentheenginerentversionsoftheelectricvacuu

3、mpumparefit-isstartedfromcold,aswellaswhenitisidlingwithted:adrivepositionengagedandthebrakesapplied.Thisisintendedtoreducethepressuredropin1.open-loopcontrolledvacuumpumpintakemanifold.2.closed-loopcontrolledvacuumpumpThereasonsforthisgreateropeningofthethrottleval

4、veistheheating-upphaseofthecatalyticcon-verterafteracoldenginestart,asrequiredbythePressuredropwhenthrottlevalveopenedIfthethrottlevalveisslightlyopened,ahighvacuumexistsintheintakemanifoldandthusalsoahighvacuumatthevacuumconnectionforthebrakeservounit.Throttlevalve

5、VacuumconnectionS257_002Ifthethrottlevalveisopenedwideandtheengineisrunningatalowspeed,onlyaveryslightvacuumexistsattheconnectionforthebrakeservounitoftheintakemanifold.ThrottlevalveVacuumconnectionS257_003NEWImportantNoteTheSelf-StudyProgrammedescribesthedesignandP

6、leasealwaysrefertotherelevantservicefunctionofnewdevelopments!literatureforup-to-dateinspection,adjustmentThecontentsarenotupdated.andrepairinstructions.2AtaglanceIntroduction..................................4Functionofthebrakeservounit...................4Designand

7、functionoftheelectricvacuumpump....6Designandfunctionofthevanepump.............7Open-loopcontrolledvacuumpump..............8Open-loopcontrolversion........................8Installationposition..............................9Operatingconditions........................

8、...10Functiondiagram..............................10Closed-loopcontrolledvacuumpump............11Closed-loopcontrolversion................