ssp gb1242a6底盤昆明陽光汽車維修工作室長期提供各種網(wǎng)址http本站所

Pneumaticself-levellingsuspensionsystem

Thisself-studyprogrammeisdividedintotwoparts:

Principlesofspringsuspension,dampingandairsuspension

Self-levellingsuspension,A6

TherearaxleairsuspensionsystemfortheAudiA6Avantisdescribedhere.

The4-levelairsuspensionoftheAudiallroadquattroisdescribedinself-studyprogram243.

YouwillfindfurtherinformationontheAudiallroadquattroinself-studyprogramme241.

Page

Principles

Vehiclesuspension 4

Thesuspensionsystem 6

Vibration 8

Characteristicvaluesofsprings 12

Conventionalrunninggearwithoutself-levelling 14

Principlesofairsuspension

Self-levellingairsuspension 16

Characteristicvaluesofairspring 21

Vibrationdamping 23

Shockabsorbers(vibrationdampers) 25

PDCshockabsorbers 33

Self-levellingsuspension,A6

Systemoverview 38

Airsprings 40

Airsupplyunit 42

Diagramofpneumaticsystem 43

Compressor 44

Airdryer 47

DischargevalveN111 48

ValveforsuspensionstrutsN150andN151 51

Self-levellingsuspensionsenderG84 52

Self-levellingsuspensioncontrolunitJ197 54

Self-levellingsuspensionwarninglampsK134 55

Functiondiagram 56

Interfaces 57

Thecontrolconcept 58

Otherfeaturesofthecontrolconcept 60

Theself-studyprogrammewillprovideyouwithinformationondesignandfunctions.

NewNote

Important:Note

Theself-studyprogrammeisnotintendedasaworkshopmanual.

Formaintenanceandrepairspleaserefertothecurrenttechnicalliterature.

Pri

cip

les

Vehiclesuspension

Whenavehicletravelsoverirregularroadsurfaces,impactforcesaretransmittedtothewheels.Theseforcespasstothebodyworkviathesuspensionsystemandthewheelsuspension.

Thepurposeofthevehiclesuspensionistoabsorbandreducetheseforces.

Drivingsafety

Drivingcomfort

Whenwetalkaboutthevehiclesuspensionwecanbasicallydistinguishbetweenthesuspensionsystemandthevibrationdampingsystem.

Bymeansoftheinteractionofthetwosystems,thefollowingisachieved:

242_003

Wheelcontactwiththeroadsurface,whichisessentialforbrakingandsteering,ismaintained.

Unpleasantandunhealthystressestovehiclepassengersareminimised,anddamagetofragileloadsisavoided.

Operatingsafety

Thevehiclecomponentsareprotectedagainstexcessivestresses.

Duringdrivingoperation,thevehiclebodyissubjectnotonlytotheforceswhichcausetheupwardanddownwardmotionofthevehicle,butalsothemovementsandvibrationsinthedirectionofthethreespatialaxes.

Alongwiththeaxlekinematics,thevehiclesuspensionhasasignificantinfluenceonthesemovementsandvibrations.

Thecorrectmatchingofthespringsandvibrationdampingsystemisthereforeofgreatsignificance.

Verticalaxis

Longitudinalaxis

Transverseaxis

Pitch

Drift

242_048

Jerking

Tipping(roll)

Swerving(yaw)Risingandsinking

Pri

cip

les

Thesuspensionsystem

As”supporting”componentsofthesuspensionsystem,thesuspensionelementsformtheconnectionbetweenthewheelsuspensionandthebodywork.Thissystemiscomplementedbythespringactionofthetyresandvehicleseats.

Thesuspensionelementsincludesteelsprings,gas/airandrubber/elastomersorcombinationsoftheabove.

Steelspringsuspensionshavebecomewellestablishedinpassengervehicles.Steelspringsareavailableinawidevarietyofdesigns,ofwhichthecoilspringhasbecomethemostwidespread.

Airsuspension,whichhasbeenusedformanyyearsinheavygoodsvehicles,isfindingincreasingapplicationinpassengervehiclesduetoitssystem-relatedadvantages.

Suspensionelement

Inthecaseofthepassengervehiclewecandifferentiatebetweensprungmasses(bodywithdrivetrainandpartsoftherunninggear)andunsprungmasses(thewheels,brakesandpartsoftherunninggearandtheaxleshafts).

Asaresultofthesuspensionsystem,thevehicleformsanoscillatoryunitwithanaturalfrequencyofthebodyworkdeterminedbythesprungmassesandthematchingofthesuspensionsystem

(see”Vibration”chapter).

Sprungmass

Unsprungmass Suspensionelement

Theunsprungmasses

Theaiminprincipleistominimisethevolumeofunsprungmassesandtheirinfluenceonthevibrationcharacteristics(naturalfrequencyofthebodywork).Furthermore,alowinertiaofmassesreducestheimpactloadontheunsprungcomponentsandsignificantlyimprovestheresponsecharacteristicsofthesuspension.Theseeffectsresultinamarkedincreaseindrivercomfort.

Examplesforthereductionofunsprungmasses:

Aluminiumhollowspokewheel

Runninggearparts(swivelbearing,wheelcarrier,linksetc.)madeofaluminium

Aluminiumbrakecallipers

Weight-optimisedtyres

Weightoptimisationofrunninggearparts(e.g.wheelhubs)

213_041

SeealsoSSP213,chapter“Runninggear”.

Pri

cip

les

Vibration

Ifamassonaspringisdeflectedfromitsrestpositionbyaforce,arestoringforcedevelopsinthespringwhichallowsthemasstorebound.Themassoscillatesbeyonditsrestpositionwhichresultsinafurtherrestoringforcebeingexerted.Thisprocessisrepeateduntilairresistanceandtheinternalfrictionofthespringcausesthevibrationtocease.

Thenaturalfrequencyofthebodywork

Thevibrationsaredefinedbythedegreeofamplitudeanditsfrequency.Thenaturalfrequencyofthebodyworkisparticularlyimportantduringmatchingofthesuspension.

Thenaturalfrequencyofunsprungpartsisbetween10Hzand16Hzforamedium-sizevehicle.Appropriatematchingofthesuspensionsystemreducesthenaturalfrequencyofthebodywork(sprungmass)tobetween1Hzand1.5Hz.

Mass

242_021

Thenaturalfrequencyofthebodyworkisessentiallydeterminedbythecharacteristicsofthesprings(springrate)andbythesprungmass.

Greatermassorsofterspringsproducealowernaturalfrequencyofthebodyworkandagreaterspringtravel(amplitude).

Smallermassorharderspringsproduceahighernaturalfrequencyofthebodyworkandalesserspringtravel.

Dependingonpersonalsensitivity,anaturalfrequencyofthebodyworkbelow1Hzcancausenausea.Frequenciesabove1.5Hzimpairdrivingcomfortandareexperiencedasshuddersabovearound5Hz.

Greatermassorsoftersprings

Definitions

Vibration

Upwardanddownwardmotionofthemass(body)

Amplitude

Thegreatestdistanceofthevibratingmassfromtherestposition(vibrationextent,springtravel)

Cycle

Durationofasinglevibration

Frequency

Numberofvibrations(cycles)persecond

Naturalfrequencyofthebodywork

Numberofvibrationsofthesprungmass(body)persecond

Resonance

Themassisdisturbedinitsrhythmbyaforcewhichincreasestheamplitude(build-up).

Springtravel

Lownaturalfrequencyofthebodywork

Time

Smallermassorhardersprings

1cycle

Springtravel

Highnaturalfrequencyofthebodywork

Time

242_072 1cycle 9

Pri

cip

les

Matchingofthenaturalfrequencyofthebodywork

Theaxleloads(sprungmasses)ofavehiclevary,attimesconsiderably,dependingontheengineandequipmentinstalled.

Toensurethatthebodyworkheight(appearance)andthenaturalfrequencyofthebodywork(whichdeterminesthedrivingdynamics)remainspracticallyidenticalforallvehicleversions,differentspringandshockabsorbercombinationsarefittedtothefrontandrearaxlesinaccordancewiththeaxleload.

Forinstance,thenaturalfrequencyofthebodyworkoftheAudiA6ismatchedto1.13Hzonthefrontaxleand1.33Hzontherearaxle(designposition).

Thespringrateofthespringsthereforedeterminesthevalueofthenaturalfrequencyofthebodywork.

Thespringsarecolour-codedtodifferentiatebetweenthedifferentspringrates(seetable).

Thedegreeofdampingofthevibrationdamperhasnosignificantinfluenceonthevalueofthenaturalfrequencyofthebodywork.Itinfluencesonlyhowquicklythevibrationscease(dampingcoefficient).Forfurtherinformation,seechapter“Vibrationdamping”.

Forstandardrunninggearwithoutself-levelling,therearaxleisalwaysmatchedtoahighernaturalfrequencyofthebodyworkbecausewhenthevehicleisloaded,itisprincipallytheloadtotherearaxlewhichincreases,thusreducingthenaturalfrequencyofthebodywork.

SpringratelevelsofthefrontaxlefortheA6

242_073

Naturalfrequencyofthebodywork

Vehicleheight

Usableloadrangeofaspring

Heighttolerance

ComponenttolerancebandNaturalfrequencytoleranceband

1.13Hz

800kg 850kg 900kg 950kg Axleload

Springallocationtable(e.g.A6frontaxle1BA)

PR-No.weightclass,frontaxle

Axleload(kg)

Suspension,leftandright(springrate)

Colourcoding

Standard

OJD

739-766

800411105AN(29.6N/mm)

1violet,3brown

running

OJE

767-794

800411105AP(31.4N/mm)

1white,1brown

gear

OJF

795-823

800411105AQ(33.3N/mm)

1white,2brown

e.g.1BA

OJG

824-853

800411105AR(35.2N/mm)

1white,3brown

OJH

854-885

800411105AS(37.2N/mm)

1yellow,1brown

OJJ

886-918

800411105AT(39.3N/mm)

1yellow,2brown

OJK

919-952

800411105BA(41.5N/mm)

1yellow,3brown

OJL

953-986

800411105BM(43.7N/mm)

1green,1brown

OJM

987-1023

800411105BN(46.1N/mm)

1green,2brown

Sports

OJD

753-787

800411105P(40.1N/mm)

1grey,3violet

running

OJE

788-823

800411105Q(43.2N/mm)

1green,1violet

gear

OJF

824-860

800411105R(46.3N/mm)

1green,2violet

e.g.1BE

OJG

861-899

800411105S(49.5N/mm)

1green,3violet

OJH

900-940

800411105T(53.0N/mm)

1yellow,1violet

OJJ

941-982

800411105AA(56.6N/mm)

1yellow,2violet

OJK

983-1027

800411105AB(60.4N/mm)

1yellow,3violet

Enginecapacity/gearbox/month/yearofmanufacture

Enginecode/gearboxcodeletters

Paintno./interiorequipmentno.

M-equipmentnumber

Weightclassoffrontaxle

Weightclassoftherearaxle

Un-ladenweight/consumptionfigures/CO2emissions

Runninggear

DateofDelivery

Proofofwarranty

Vehicledata

242_108

Pri

cip

les

Characteristicvaluesofsprings

Characteristiccurve/springrateofsprings

Wecanobtainthecharacteristiccurveofaspringbyproducingaforces/traveldiagram.

Thespringrateistheratiobetweentheeffectiveforceandthespringtravel.TheunitofmeasurementforthespringrateisN/mm.Itinformsuswhetheraspringishardorsoft.

Ifthespringrateremainsthesamethroughouttheentirespringtravel,thespringhasalinearcharacteristiccurve.

Asoftspringhasaflatcharacteristiccurvewhileahardspringhasasteepcurve.

Progressivecharacteristiccurve

LinearcharacteristiccurveHardspring

ResilienceF

0

0

Acoilspringisharderdueto: Springtravels 242_018

agreaterwirediameter

asmallerspringdiameter

alowernumberofcoils

LinearcharacteristiccurveSoftspring

a

Ifthespringratebecomesgreaterasthespringtravelincreases,thespringhasaprogressivecharacteristiccurve.

Coilspringswithaprogressivecharacteristiccurvecanberecognisedasfollows:

unevencoilpitch

conicalcoilshape

conicalwirediameter

combinationoftwospringelements(example,seenextpage)

242_019

Reboundstopinsert(inshockabsorber)Un-ladenposition

Designposition

Auxiliaryspringinsert

(Example:Suspensionstrutwithauxiliarypolyurethanesprings).

15

Lowerstop

Upperstop

12

Lowerstop

9

6

3

0

-120

-80 -40 0

Reboundinmm

Parallelspringing

40 80

Compressioninmm

120

Auxiliaryspring

Advantagesofprogressivecharacteristiccurveofspring:

Bettermatchingofthesuspensionsystemfromnormaltofullload.

Thenaturalfrequencyofthebodyworkremainspracticallyconstantduringloading.

Thesuspensionisnotsopronetoimpactsinthecaseofsignificantirregularitiesintheroadsurface.

Betteruseoftheavailablespringtravel.

Pri

cip

les

Conventionalrunninggear(steelsprings)withoutself-levelling

Springtravel

Theoverallspringtravelstotrequiredforrunninggearwithoutself-levellingiscomprisedofthestaticcompressionsstatandthedynamicspringtravelcausedbyvehiclevibrationssdynforbothladenandun-ladenvehicles.

stot=sstat+sdyn(un-laden)+sdyn(fullyladen)

Whenthevehicleisstationary,thevehiclebodyretractsbyacertainspringtraveldependingupontheload.Inthiscase,wespeakofstaticcompression:sstat.

Thedisadvantageofconventionalrunninggearwithoutself-levellingisitsreducedspringtravelatfullload.

Steelsuspension

sstat(un-laden)

HV

H

sstat(fullyladen)

Supportingforceinkn.

10

8

6

4

2

HL

-80mm -40mm 0 +40mm +80mm

242_075

dyn.rebound(un-laden)

sstat

(fullyladen)

fullyladen

DesignpositionUn-ladenposition

Characteristiccurveofspring

HV=heightwhenfullyladenH=designpositionheight

HL=heightwhenun-laden

(un-laden)

dyn.compression

Thestaticcompression...

...isthestartingpoint(zero)forthedynamicspringmovements,compressiontravel(plus)andreboundtravel(minus).

...isdependantuponthespringrateandtheload(sprungmasses).

...resultsfromthedifferencebetweenthestaticcompressionwhenun-laden

sstat(un-laden)andthestaticcompressionwhenfullyladensstat(fullyladen).

sstat=sstat(fullyladen)-sstat(un-laden)

Inthecaseofaflatcharacteristiccurve(softsprings),thedifferenceandtherebythestaticcompressionbetweenfullandun-ladenisverygreat.

Definitions:

Theun-ladenposition...

...isthecompressionexertedontothewheelswhenthevehicleisreadyfortheroad(fueltankcompletelyfilled,sparewheelandvehicletoolspresent).

Thedesignposition...

...isdefinedastheun-ladenpositionplustheadditionalloadofthreepersons,eachweighing68kg.

Inthecaseofasteepcharacteristicspringcurve,thisstateofaffairsisreversedandiscoupledwithanexcessiveincreaseofthenaturalfrequencyofthebodywork.

Hardsprings

Softsprings

Fullyladen

Un-ladenposition

242_076

sstatsoftspringssstathardsprings

Principlesofairsuspension

Self-levellingairsuspension

Airsuspensionisacontrollableformofvehiclesuspension.

Withairsuspension,itissimpletoachieveself-levellinganditisthereforegenerallyintegratedintothesystem.

Thebasicadvantagesofself-levellingare:

Staticcompressionremainsthesame,irrespectiveofvehicleloads(seeoverleaf).Thespacerequirementinthewheelarchesforfreewheelmovementkepttoaminimum,whichhasbenefitsfortheoveralluseofavailablespace.

Thevehiclebodycanbesuspendedmoresoftly,whichimprovesdrivingcomfort.

Fullcompressionandreboundtravelismaintained,whatevertheload.

Groundclearanceismaintained,whatevertheload.

Therearenotrackorcamberchangeswhenvehicleisladen.

Thecwvalueismaintained,asisthevisualappearance.

Lessweartoballjointsduetoreducedworkingangle.

Greaterloadsarepossibleifrequired.

=constant

242_074

Withtheaidofself-levelling,thevehicle(sprungmasses)remainsatonelevel(designposition)becausetheairspringpressureisadaptedaccordingly.

Staticcompressionisthusthesameatalltimesthankstotheself-levellingsystemandneednotbeaccountedforwhendesigningthewheelclearances.

sstat=0

Anotherfeatureofself-levellingairsuspensionisthatthenaturalfrequencyofthebodyworkiskeptvirtuallyconstantbetweenun-ladenandfull-load(seechapter“Airspringcharacteristicvalues”page21).

Inadditiontothemainadvantagesofferedbyself-levelling,itsrealisationbymeansofairsuspension(AudiA6)offersanothersignificantadvantage.

Astheairpressureintheairspringsisadaptedinaccordancewiththeload,thespringratealtersproportionallytothesprungmass.Thepositiveoutcomeisthatthenaturalfrequencyofthebodyworkandtherebydrivingcomfortremainvirtuallyconstant,irrespectiveoftheload.

SupportingforceinkN.

Airsuspension 10

8

242_077

6

H=constant

4

2

Springtravel

Characteristiccurvesofsprings

fullyladenDesignpositionHun-laden

-80mm -40mm

dyn.rebound

0

sstat

+40mm

dyn.compression

+80mm

Principlesofairsuspension

Anotherbenefitistheprinciple-relatedprogressivecharacteristiccurveofanairspring.

Withfullysupportingairsuspensiononbothaxles(Audiallroadquattro),differentvehiclelevelscanbeset,e.g.:

Normaldrivingpositionforcitydriving.

Lowereddrivingpositionforhighspeedstoimprovedrivingdynamicsandairresistance.

Raiseddrivingpositionfortraveloff-roadandonpoorroadsurfaces.

YoucanfindfurtherdetailsinSSP243

“4-LevelairsuspensionintheAudiallroadquattro”.

Fullysupportingmeans:

Self-levellingsystemsareoftencombinedwithsteelorgas-filledspringdeviceswithhydraulicorpneumaticcontrol.Thesupportingforceofthesesystemsresultsfromthesumofbothsystems.Wethereforecallthem“partiallysupporting”(Audi100/

AudiA8).

Intheself-levellingsuspensionsystemsintheAudiA6(ontherearaxle)andintheAudiallroadquattro(rearandfrontaxles)airspringsaretheonlysupportingsuspensionelementsandthesesystemsarethereforedescribedas“fullysupporting”.

242_030

4

242_031

4

Naturalfrequencyofthebodywork

3 3

Springrate

2 2

1 1

0

0

0

10

20

30

0

10

20

30

SupportingforceSteelsprings(linear)Airsprings

SupportingforceSteelsprings(linear)Airsprings

Designoftheairsprings:

Inpassengervehicles,airspringswith

U-bellowsareusedassuspensionelements.Theseallowgreaterspringtravelinrestrictedspaces.

Theairspringsconsistof:

Upperhousingclosure

U-bellows

Piston(lowerhousingclosure)

Retainingrings

TheconstructionoftheU-bellowscanbeseeninfig.242_032.

Theouterandinnersurfacesaremadeofanelastomermaterial.Thematerialisresistanttoallweatherinfluencesandislargelyoil-resistant.Theinnersurfacefinishisdesignedtobeparticularlyair-tight.

Thestabilitysupportsabsorbtheforcesproducedbytheinternalpressureintheairsprings.

Coaxialarrangementoftheairsprings

Upperhousingclosure

Retainingring

Internalsurfacecoating

Woveninsert1

Woveninsert2Externalsurfacecoating

Piston

242_032

Principlesofairsuspension

High-qualityelastomermaterialandpolyamidecordwoveninserts(stabilitysupports)providetheU-bellowswithgoodunrollingcharacteristicsandasensitiveresponseofthespringsystem.

Thenecessarypropertiesareensuredoverawidetemperaturerangebetween

-35°Cand+90°C.

MetalretainingringstensiontheU-bellowsbetweentheupperhousingclosureandthepiston.Theretainingringsaremachine-pressedbythemanufacturer.

TheU-bellowsunrollsontothepiston.

Dependingontheaxledesign,theairspringsareeitherseparatefromtheshockabsorbersorcombinedasasuspensionstrut(coaxialarrangement).

Airspringsmustnotbemovedinanunpressurisedconditionsincetheairbellowscannotunrollonthepistonandwouldbedamaged.

Inavehicleinwhichtheairspringsareunpressurised,therelevantairspringsmustbefilledwiththeaidofthediagnostictester(seeWorkshopManual)beforeraisingorloweringthevehicle(e.g.vehicleliftingplatformorvehiclejack).

Separatearrangementoftheairsprings

Airsprings

Piston

Airspringparameters

Resilience/springrate

Theresilience(supportingforce)FofanairspringisdeterminedbytheeffectivesurfaceAwandtheexcesspressureintheair

springpi.F=pixAw

TheeffectivesurfaceAwisdefinedbytheeffectivediameterdw.

Inthecaseofarigidstructure,suchaspistonandcylinder,theeffectivediametercorrespondstothepistondiameter.

InthecaseofairspringswithU-bellows,theeffectivediameterisdeterminedbythelowestpointofthefold.

Astheformulashows,thesupportingforceofanairspringisindirectrelationtotheinternalpressureandtheeffectivesurface.Itisveryeasytoalterthesupportingstrength(resilience)statically(nomovementofthebodywork)byvaryingthepressureintheairspring.

Thevariouspressures,dependingontheload,resultintherelevantcharacteristiccurvesofthespringsand/orspringrates.Thespringratealtersatthesamerateasthebodyworkweight,whilethenaturalfrequencyofthebodyworkwhichdeterminesthehandlingcharacteristicsremainsconstant.

0

+s

Theairsuspensionisadaptedtoanaturalfrequencyofthebodyworkof1.1Hz.

U-bellows

9bar

2_025

Supportingforce

8bar

7bar

6bar

ladenun-laden

Springtravel

242_078

Principlesofairsuspension

Characteristiccurveofsprings

Owingtothefunctionalprinciple,thecharacteristiccurveofanairspringisprogressive(inthecaseofcylindricalpistons).

Theprogressofthecharacteristiccurveofthespring(flat/steepinclination)isdeterminedbythespringvolume.

Alargespringvolumeproducesaflatprogressionofthecharacteristiccurve(softsprings),asmallspringvolumeproducesasteepprogressionofthecharacteristiccurve(hardsprings).

Theprogressionofthecharacteristiccurveofaspringcanbeinfluencedbythecontourofthepiston.

Changingthecontourofthepistonalterstheeffectivediameterandtherebytheresilience.

SmallspringvolumeLargespringvolume

Supportingweight=weightofthesprungmasses

(+pistonvolume)

9bar

8bar

7bar

6bar

Result

ThefollowingoptionsareavailableformatchingtheairspringsusingU-bellows:

Sizeoftheeffectivesurface

Sizeofspringvolume

Contourofthepiston

-s ±0

Springtravel

+s

242_027

242_084

Exampleofthecontourofapiston

(suspensionstrutintheAudiallroadquattro)

U-bellows

PistonCompressed

242_079

Vibrationdamping

Withoutvibrationdamping,thevibrationofthemassesduringdrivingoperationwouldbeincreasedtosuchanextentbyrepeatedroadirregularities,thatbodyworkvibrationwouldbuildupincreasinglyandthewheelswouldlosecontactwiththeroadsurface.

Thepurposeofthevibrationdampingsystemistoeliminatevibrations(energy)asquicklyaspossibleviathesuspension.

Forthispurpose,hydraulicvibrationdampers(shockabsorbers)arelocatedparalleltothesprings.

Vibrationdampersareavailableindifferentdesignsbuttheirbasicfunctionandpurposearethesame.

Hydraulic/mechanicaldampinghasfoundwidespreadapplicationinmodernvehicledesign.Thetelescopicshockabsorberisnowparticularlyfavouredduetoitssmalldimensions,minimumfriction,precisedampingandsimpledesign.

Sprungmass

Directionoftravel

Unsprungmass

Unevenground

DampedvibrationUn-dampedvibration

242_022

Aspreviouslymentioned,vibrationdampinghasafundamentaleffectondrivingsafetyandcomfort.

However,therequirementsofdrivingsafety(drivingdynamics)anddrivingcomfortareconflicting.

Withincertainlimits,thefollowingappliesinprinciple:

Ahigherrateofdampingimprovesdrivingdynamicsandreducesdrivingcomfort.

Alowerrateofdampinglessensdrivingdynamicsandimprovesdrivingcomfort.

Theterm“shockabsorbers”ismisleadingasitdoesnotpreciselydescribethefunction.

Forthisreasonweshallusetheterm“vibrationdamper”instead.

Shockabsorbers(vibrationdampers).

Dualpipegas-pressureshockabsorber

Thedualpipegas-pressureshockabsorberhasbecomeestablishedasthestandarddamper.

Inthedualpipegas-pressureshockabsorber,theworkingcylinderandthehousingformtwochambers.Thepistonandpistonrodmoveinsidetheworkingchamber,whichiscompletelyfilledwithhydraulicoil.Thering-shapedoilreservoirbetweentheworkingcylinderandthehousingservestocompensatevolumetricchangescausedbythepistonrodsandtemperaturechangesinthehydraulicoil.

Theoilreservoirisonlypartiallyfilledwithoilandisunderapressureof6-8bar,whichreducesthetendencytowardscavitation.

Twodampingvalveunitsareusedfordamping;thepistonvalveandthebottomvalve.Thesecompriseasystemofspringwashers,coilspringsandvalvebodieswiththrottlebores.

Cavitationistheformationcavitiesandthecreationofavacuuminarapidliquidflow.

242_080

Gasfilling

OilreservoirWorkingcylinder

Dampingvalveunit(pistonvalve)

Dampingvalveunit(bottomvalve)

DampervalveNon-returnvalve

Principlesofairsuspension

Function

Duringcompression,dampingisdeterminedbythebottomvalveandtoacertainextentbythereturnflowresistanceofthepiston.

Theoildisplacedbythepistonrodflowsintotheoilreservoir.Thebottomvalveexertsadefinedresistanceagainstthisflow,therebybrakingthemovement.

Duringrebound,thepistonvalvealonecarriesoutthedampingactionandexertsapredeterminedresistanceagainsttheoilflowingdownwards.

Theoilrequiredintheworkingchambercanflowbackunhinderedviathenon-returnvalveinthebottomvalve.

Compression Rebound

Pistonvalve

Oilreservoir

DampervalveNon-returnvalve

242_081

Bottomvalve

Singlepipegas-pressureshockabsorber

Withthesinglepipegas-pressureshockabsorber,theworkingchamberandtheoilreservoirarelocatedinasinglecylinder.Volumetricchangescausedbythepistonrodandthetemperaturechangesintheoilarecompensatedbyanothergaschamberwhichisseparatedfromtheworkingcylinderbyadividingpiston.Thelevelofpressureinthegaschamberisapprox.25-30barandmustbeabletosustainthedampingforcesduringcompression.

Thedampingvalvesforcompressionandreboundareintegratedintothepiston.

Pistonwithdamping

valves

DividingpistonGaschamber

Comparisonofsingle/dualpipegas-pressureshockabsorbers

Dampervalves

Dualpipegas-pressureshockabsorber

Singlepipegas-pressureshockabsorber

Valvefunction

Thetendencytowardscavitationisreducedbythegaspressureintheoilreservoir

Minimaltendencytowardscavitationthankstohighgaspressureandseparationofoilandgas

Characteristiccurves

Any,duetoseparatevalvesforcompressionandrebound

Dependantonthegaspressureduringcompression

Shortdampingstrokes

Good

Better

Friction

Low

Higherduetosealunderpressure

Design

Greaterdiameter

Longerduetogaschamberinthecylinder

Installationposition

Approximatelyvertical

Any

Weight

Heavier

Lighter

Principlesofairsuspension

Function

Duringcompression,oilisforcedoutofthelowerchamberthroughthedischargevalveintegratedintothepistonwhichexertsadefinedresistanceagainsttheoil.Thegascushiontherebycompressesbytheamountof