外文翻译液压助力转向系统节选.docx
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外文翻译液压助力转向系统节选.docx
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外文翻译液压助力转向系统节选
中文3000单词,2000单词,1万英文字符
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Theconventionalhydraulically-assistedpowersteeringusedinmostcarsissoontobereplacedwithelectricpowersteering.Already,manymanufacturersareusingelectronicallycontrolledhydraulicsystems,whilesomecarmanufacturershaverecentlyintroducedpurelyelectricsystemstotheirvehicles.Inadditiontoreducingengineloads,fullelectricpowersteeringallowssteeringresponsivenesstobeautomaticallyvarieddependingonspeed,roadconditions-andeventhedriver'sability!
TraditionalHydraulicPower-AssistedSteering
HydraulicPowerAssistedSteeringhasbeenusedinautomotiveapplicationsforabout50years.Thesystemsuseanengine-drivenhydraulicpump,acontrolvalve,steeringcylinderandconnectinghydraulichoses.Thepumpisusuallyofavanedesignwithanintegratedinternalbypass.Itissizedsothat-evenatidlerpm-itdeliversenoughoilflowtoprovideasuitabledegreeofpowerassistance.
Thecontrolvalveusesaflexibletorque-measuringdevice(suchasatorsionbar,spiralspringorleafspring)toconvertthesteeringtorqueintoasmallcontrolmovement.Thismovementistransferredtoavalvethatregulatesfluidflowtothepowerassistancemechanism.Inrackandpinionsteering,adouble-endedhydraulicrammountedparalleltotherack(withintherackassembly)isused,whilerecirculatingballsystemsincorporatethemechanismintothesteeringbox.NotethatintheNissansystemshownhere,thefluidreservoirisincorporatedintothepump.
Amajorproblemwithsimpleconventionalhydraulicsteeringsystemsisthattheassistancelevelisnotreducedathighspeeds,givingalackofsteeringfeel.AmericancarsoftheFiftiesandSixtieswereparticularlywellknownfortheirfeather-lightsteeringeffortduringparking,acharacteristicwhichresultedinextremevaguenessathighspeeds.Toovercomethisproblem,mostconventionalhydraulicsteeringsystemsofthelastfewdecadeshaveincorporatedmechanismsthatreducesteeringassistanceaseitherenginespeedincreases,or(lessfrequently)asroadspeedincreases.Thereasonthatenginespeedwasmore
commonlyusedasisthatsuchasystemcanremainpurelyhydraulic,whereasusingroadspeedasthecontrolvariablerequirestheuseofanelectronicsystem.
Electronically-ControlledHydraulicSteering
Theintroductionofelectronicspeedometers-andsubsequently,fullenginemanagement-meantthatanelectronicroadspeedsignalbecameavailable,allowingthewidespreaduseofelectronically-controlledhydraulicsteeringsystems.Thesevarysteeringeffortdependingonroadspeedandalso,insomecases,otherfactorsaswell.
Anumberofdifferenthydraulicapproachestoregulatingsteeringassistanceareused.Theseare:
FlowControl
Asolenoidvalveislocatedonthedischargeportofthehydraulicpump.Electroniccontrolisusedtocontrolthesolenoidvalveopening,soregulatingthefluidflow.Theflowisreducedathighroadspeeds,reducingthedegreeofassistanceprovided.
CylinderBypass
Asolenoidvalveandassociatedbypasslineislocatedbetweenthetwochambersofthehydrauliccylinder,allowingthereductionofthepressuredifferencebetweenthem.Thesolenoidvalveopeningiscontrolledelectronically,itsopeningbeinggreaterathighroadspeeds.Thisreducesthedegreeofassistancethatisprovided.
HydraulicReactionForce
Ahydraulicforceisenabledthatworksagainstthepowerassistance.Asspeedincreases,thereactionforceisincreased.Sincefluidflowtothepowercylinderisnotaffected,thesteeringresponseratecanremainhighwithoutreductionsoccurringinfeel.
Intheirelectronically-controlledhydraulicsteeringsystem,HyundaiuseanECUequippedwithan8-bitmicroprocessor.Twomajorinputs-vehiclespeedandthespeedofsteeringwheelmovement-areused.Fromtheseinputs,theECUdeterminesthedrivingconditionandviaa3-dimensionallook-upmap,providestheappropriatecurrentflowtoahydraulicsolenoidvalve.
Threedifferentdrivingconditionsarerecognised:
Parking-maximumcurrentissuppliedtothesolenoidvalve,resultinginmaximumsteeringassistance.
HighSpeed-minimumcurrentissuppliedtothesolenoidvalve,resultinginminimumsteeringassistance.
EvasiveSteering-alargeandsuddensteeringinputcausestheECUtosupplyacurrenttothesolenoidproportionaltothespeedofthesteeringinput.
Thereareplentyofspeed-sensitivehydraulicsteeringsystemsaround.ThisdiagramshowsthelayoutofaMazdaMX6systemwherethedegreeofassistanceisbasedonroadspeedandsteeringangle.
(1)steeringwheel;
(2)steeringshaft;(3)intermediateshaft;(4)steering
gearassembly;(5)pressurehose;(6)returnhose;(7)oilpump;(8)solenoidvalve;(9)ECU;
(10)reservetank;(11)steeringanglesensor;(12)checkconnector.
HybridHydraulic/ElectricPowerSteeringSystems
Hybridhydraulicsteeringsystemsuseanelectricmotortodrivethehydraulicpump,ratherthanhavingthepumpdrivendirectlybytheengine.Thisapproachallowsthesteeringefforttobeeasilycontrolledbyvaryingthepumpspeed.Becauseflowcanbebettermatchedtoactualrequirements,thepowerdrainisreduced-fueleconomysavingsofupto0.2litres/100kmarepossible.
Thecontrolapproachthatistakencanbeofthreetypes-
DrivingMode-wheredrivingconditions(suchascity,country,highway,etc)areautomaticallyjudgedwithappropriatelevelsofassistancethenprovided.
SteeringWheelInputMode-wherethespeedofthesteeringwheelmovementisusedtodeterminethedegreeofassistancerequired.
SteeringLoadMode-wheredemandforpowerassistanceisindicatedbythecounter-pressureofthehydraulicfluid,sensedthroughvariationsinthemotorcurrentload.
TheGeneralMotorshybridhydraulicsteeringsystemshownhereusesSteeringLoadModetodeterminetheactualsteeringloadsandsothedegreeofassistancethatneedstobeprovided.The3-phasebrushlessDCmotor(12)issuppliedpowerbytheMotorPowerCircuit.TheEHPScontrolprovidesacontrolsignaltotheMotorPowerCircuitinresponsetoinputsignalsfrom
themotoranglesensor,motorcurrentsensorandbatterycurrentsensoraswellasoperatingsystemvoltage.Thetemperatureofthehydraulicfluidisalsomonitored.
ElectricPower-AssistedSteering
ElectricPower-AssistedSteeringcompletelyreplacesthehydraulicsystemthatpreviouslyhasalwaysbeenassociatedwithpowersteering.Electricpowersteeringsystemsassistdrivereffortbytheuseofanelectricmotorwhichactsthroughareversiblegearboxandinsomecases,alsoanelectromagneticclutch.Anelectroniccontrolunitdeterminesthedegreeofassistancethatisrendered.
Electricpowersteeringhassomesignificantadvantagesoveranyformofconventionalhydraulicsteering,bothfortheownerofthecaranditsmanufacturer.Thereductioninengineloadofanelectricpowersteeringsystem(itcanbeaslowas4wattswhenthecarisbeingdriveninastraightline)meansthatthefueleconomyofacarequippedwithelectricpowersteeringisverysimilartothatofacarwithnoformofpowersteering.Analysesprovidedbymanufacturersofelectricpowersteeringsystemsindicatepotentialfuelsavingsof4-8percentovercarsequippedwithconventionalhydraulicsteering,withthelightermassofanelectricpowersteeringalsohavinganimpacthere.Theindependenceofthesystemfromengineoperationalsomeansthatshouldtheenginestall,steeringassistancedoesnotchange.
Fromamanufacturer'sperspective,usingelectricpowersteeringreducesassemblylinetime,allowstheeasysoftwaretuningofthesteeringassistancecharacteristicstosuitavarietyofcars(egasportscaroralimousine-moreonthisinaminute),andhasthepotentialtoimprovereliability-53percentofallpowersteeringwarrantyclaimsarefrompumpandhoseproblems.Environmentalgainsarealsopossiblefromthedecreasedproductionanddisposalofhydraulicfluid(worldwide,anestimated40millionlitresofpowersteeringfluidwasinusein1995)andfromthedecreasedrequirementforthenon-recyclablepolymersusedinhydraulichoses.
Features
Benefits
Engineindependence
Reducedenginepowerdrain
Improvedfueleconomyandacceleration
Instant-onpowersteering
Assistanceavailableevenshouldtheenginestall
Eliminationofpump,hoses,fluid,drivebeltandpulley
Simplifiedpackaging
Environmentalcompatibility
Reducedmass
Modulardesignandintegratedcontroller
Reducedassemblytime
Designandpackagingflexibility
Multivehicleuse
Designandpackagingflexibility
Softwaretuning
Wideassistancerange
In-vehiclelaptopPCtuning
Tuningprocessreducedfrommonthstohours
Cost-effectiveadvancedfeatures
Variableeffortsteering,
AssistedreturntocentreSteeringdampingcapability
Dependingonthelocationoftheelectricassistunit,theelectricdriveassistancecanbetransmittedtothesteeringmechanismbyanumberofmeans.Theseare:
Method
ElectricAssistUnitLocation
PowerTransmission
Pinionassist
Underthedashboardonthesteeringcolumn
Motor>wormgear>columnshaft>pinionshaft
Onthesteeringrackinputpinion
Motor>geartrain>pinionshaft
Rackassist
Onthesteeringrack
Motor>ballscrew>rackshaft
Onasecondpiniononthesteeringrack
Motor>planetarygeartrain>anothershaftpinion>rackshaft
So,HowGoodisYourDriving?
Oneofthemostinterestingaspectsofelectricpowersteeringistheabilitythatthemanufacturerhastotunethesystem'sresponsiveness.Asindicatedearlier,thisallowstheeasysoftwarem
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