液压制动控制阀斯图特贝克信息

ObjectivesIdentifypurposeofmeteringvalveIdentifypurposeofproportioningvalveIdentifypurposeofpressuredifferentialvalveExplainoperationofheightsensingproportioningvalveIdentifyOperationofcombinationvalveIntroductionBrakehydraulicsystemsneedvarioustypeofcontroldevicesBrakingperformancemustbeevenandconsistentCombinationdisc/drumsystemsrequiredifferenttypeofvalvesMeteringValvePurposeofValveLocation/constructionofmeteringvalveOperationofmeteringvalveBleedingsystemwithameteringvalveMeteringValveDelaysapplicationoffrontdiscsslightlyLocatedbetweenmastercylinderandfrontdiscbrakes(pg100C)OperationValveisheldopenbyspringClosesat3–30psiOpensat75–300psiOperationhappensinmicroseconds

ProportioningValveProportioningvalvebalancespressureonfrontdisc,reardrumvehiclesRestrictsfluidtotherearbrakesLocatedbetweenMCandrearbrakes(pg100C)SplitpointisthepressurewhenP.V.closesSlopeispercentageofrearpressuretototalpressureTwoproportioningvalvesrequiredondiagonalsplitsystemSome4wheeldiscbrakecarshavetwoProportioningvalvesPage104–105CHeightSensingProportioningValveUsedontrucksandsomecarsReducespressuretorearbrakesforlightloadsTwotypesofvalves linkagetype(pg107C) Gravityball(pg108C)Placementofvalves

Height/LoadSensingValveSomesystemsuseonevalveperrearwheel.PressureDifferentialValveHydraulicallyoperatedswitchLocatedbetweenfrontandrearsystemsSomesystemsusealowfluidlevelswitchinsteadofapressureDiffSwitchCombinationValveCombines2or3functions Meteringvalve Warningswitch Proportioningvalve

Pg111C3FunctionCombinationValveHydraulicSystemBleedingBrakeBleedingandBleederScrewsMustremoveallairfromsystemFivemethodsManualbleedingPressurebleedingVacuumbleedingGravitybleedingSurgebleedingSymptomsofTrappedAirLowandSpongywhenfirstappliedRepeatedpedalpumpingwillmakepedalbecomefirmCanbesimilartodrumbrakesinneedofadjustmentCanperformairentrapmenttesttoverifyairinsystemAirEntrapmentTestWearsafetyglassesPumpbrake10to20timesrapidlyHoldpedalpressureObservereservoirsLetoffpedalIfairinsystem,airwillsquirtfluidBleedingProceduresMustfollowbleedingsequenceandprocedures(pg137L)BenchbleedmastercylinderfirstStartathighpointsinsystemThen,continuefromfarthestpointawayfromMCandworkbacktowardsMC.Watchfluidlevel!UsejarandhosetoobservefluidFrozenBleederScrewUsesixsidedwrenchorsocketAlwaystestbleedersfirstwhendoingbrakeworkSometimesahammerwillbreakbleederfreeSometimesuseappliedheatTappingoncaliperwillalsofreeairbubblesMeteringValveprepMustholdopenvalvewhenpressurebleedingSeveraltoolsavailableWheelBrakeBleedingSequencePressureBleedingSetUpBrakeHydraulicSystemServiceManufacturer’sRecommendations Followbrakeinspectionschedule FollowserviceproceduresProblemsofFlushing SystemshouldberefilledwithfreshfluidIntervalsare15,000to60,000milesBecarefulofstirringsludgeupinsystem!RecenteringaPressureDifferentialValveAfterflushingorworkonbrakesystemvalvebecomesoffcenterMakesureothersourcesnotturningonlightMustdeterminetypeofPressureDifferential ValveValvemaybeseparateorpartofM.C.

Re-centeringSinglePistonValvewithcenteringsprings

Re-centeringsinglepistonvalvewithoutcenteringsprings

Re-centeringTwoPistonValvewithCenteringSpringsServicingHydraulicSystemValvesMeteringValvesBrakeproblemscausedbybadmeteringvalve CanallowfrontbrakestolockprematurelyTestingmeteringvalve InspectbootforleakageMeteringvalvepressuretest(2methods) 1.Applybrakesandfeelstem 2.Pressurizesystemover40psiandopenfrontbleedertoseeifsystemfluidflows(shouldnotflow)ProportioningValveBrakeproblemscausedbybadproportioningvalve MaycausereardrumlockupTestingproportioningvalve Checkforleaks Check“splitpoint”pressureoperation(pg171L)Servicingofproportioningvalve CanonlyoverhaulnonintegralvalvesPg171LHeightSensingProportioningValveBrakeproblems