>> P.51
A48ABCDEFGHIJKLMContacttypesealingmethodInthistypeofsealing,theshaftissealedbytheappli-cationofpressureresultingfromtheelasticityofthesealmaterialtothesealingsurfaceoftheshaft,whichrotates,reciprocatesoroscillates.Syntheticrubber,syntheticresinandfeltaregenerallyusedassealingmaterials.1OilsealSyntheticrubberoilsealsarethemostgeneraltypeofsealingused.Thesealingeffectisobtainedwhentheelasticlipcomesintocontactwiththeshaft.Somelipsarespring-loadedtomaintainadequatepressingforce.Theslidingsurfacesofthelipandtheshaftalwaysshowfrictionalbehaviorsuchthattheboundarylubri-cationandfluidlubricationaremixed.Ifthereisaninsufficientamountofoilbetweenthecontactsur-faces,itwillcauseheatgeneration,wearandseizure.Conversely,iftheoilfilmistoothick,itmaycauseoilleakage.GeneraloilsealsarespecifiedinJISB2402-1~5.IKOOilSealsforNeedleRollerBearings(SeepageL1.)havealowsectionalheighttomatchtheNeedleRollerBearings.Nitrilerubberisgenerallyusedasthematerialforoilseallips.Table32showsthematerialsandtheiroperatingtemperatureranges.Thefinishedsurfaceoftheshaftwheretheseallipmakescontactmusthaveanappropriatesurfaceroughness,asshowninTable33,accordingtotheperipheralspeed.Itmustalsohaveaccuratecircular-ity,andtheshafteccentricityshouldbelessthan0.05mm.Toincreasewearresistance,thehardnessoftheslid-ingpartoftheshaftmustbemorethan40HRC.Thiscanbeachievedbyhard-chromeplatingorheattreat-ment.Table32SealmaterialsandoperatingtemperaturesSealmaterialSyntheticrubberNitrilerubberAcrylicrubberSiliconrubberFluororubberTetrafluoethyleneresinOperatingtemperaturerange℃-25〜+120-15〜+130-50〜+180-10〜+180-50〜+220Table33PeripheralspeedandsurfaceroughnessofshaftPeripheralspeed m/sOverIncl.-510510-0.8(3.2)0.4(1.6)0.2(0.8)SurfaceroughnessμmRa(μmRy)2FeltsealBecauseoftheirsimplestructure,feltsealshavelongbeenusedtoprotectgreaselubricationfromdust.Sincefeltabsorbssomegreaseduringoperation,ithardlycausesheatgenerationandseizure,butitcan-notbeusedwhentheperipheralspeedoftheshaftishigh(morethan4m/s).Wherethereisahighcon-centrationofdirtanddust,theymaybecomeattachedtothecontactsurfaceoffelt,sometimesscratchingtheshaftsurface.Topreventthis,twofeltsealsareplacedapartfromeachother,orafeltsealisusedtogetherwithasyntheticrubberseal.1N=0.102kgf=0.2248lbs.1mm=0.03937inch
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