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A51Oillubrication1OilbathlubricationThisisthemostcommonlyusedoillubricationmethod,andisusedformediumandlowspeeds.Iftheamountofoilistoolarge,heatwillbegeneratedbychurning,andiftheamountistoosmall,seizurewilloccur.Therefore,thecorrectamountofoilmustbemaintained.Whenthemachineisstationary,thecorrectoillevelinthecaseofabearingmountedonahorizontalshaft,isnearthecenterofthelowestrollingelement.Inthecaseofaverticalshaft,about50%ofthesurfacesoftherollingelementsshouldbesub-mergedinoil.Itisdesirabletoprovideanoilgaugesothattheoillevelcanbeeasilycheckedwhilethemachineissta-tionaryorrunning.2OildriplubricationOildrips,whicharefeddownfromasight-feedoileroralongafiberstring,becomeanoilsprayduetowindpressuregeneratedbytherotatingcage,shaft,nut,etc.,ortheystriketherotatingpartsandformanoilspray,whichfillsupthehousingandeveryrequiredpart.Becauseoilsprayremovesfrictionalheat,thismethodhasamoreeffectivecoolingeffectthantheoilbathmethod,andiswidelyusedforhigh-speedrota-tionandmediumloadconditions.Inthecaseofthesight-feedoiler(Fig.21),thenumberofdripscanbeadjusted.However,thisisdifficultusingthestring-feedmethod.Thenumberofdripsdependsonthebearingtype,rotationalspeed,etc.,but5〜6dripsperminuteisgenerallyused.3OilsplashlubricationInthismethod,oilissplashedinalldirectionsbytherotationofthegearordisk.Thiscanbeusedforcon-siderablyhigh-speedrotationswithoutsoakingthebearingdirectlyinoil.Inthegearcasewhereshaftsandbearingsarelubri-catedwiththesameoil,wearparticlesmaybeintro-ducedintothebearingastheymightgetmixedwiththeoil.Inthiscase,apermanentmagnetisprovidedatthebottomofthegearcasetocollectmetalparti-cles,orashieldplateisinstallednexttothebearing.Fig.22showsanothermethodinwhichthesplashed4OilcirculatinglubricationWhenautomaticlubricationismoreeconomicalbecauselubricationisrequiredatmanypoints,orwhencoolingisrequiredforhighrotationalspeed,thismethodisused.Theoilissuppliedwithapump,whichcancontroltheoilpressure,andafilterorcool-er,etc.canbesetupinthecirculationsystem,mak-ingthisanidealmethodoflubrication.AsshowninFig.23,theoilsupplyanddischargeportsarelocatedoppositetoeachother,andthedischargeportismadelargetopreventtheaccumulationofoil.5OilmistlubricationAfterdirtanddustareremovedbyafilter,theoilisturnedintoaspraybydrycompressedair,andthislubricatesthebearing.Whentheairandoilpassthroughthebearing,theaircoolsthebearingandtheoillubricatesit.Inaddition,becausetheairinsidethehousingisatahigherpressurethantheoutsideair,theentryofwaterandforeignparticlesisprevented.Therearemanyotheradvantagesofthismethod,anditissuitableforhighrotationalspeedapplicationssuchashighspeedinternalgrindingspindles.6OiljetlubricationThisisahighlyreliablelubricationmethodandisusedundersevereconditionssuchasultra-highrotationalspeedsandhightemperatures.Thespeedoftheoiljetshouldbemorethan20%oftheperipheralspeedoftheinnerringracewaysurface,sincetheairaroundoilflowsalongthegroovesinthecaseandaccumu-latesintheoilpockets,keepingtheoillevelconstant.Sotheoilissteadilysuppliedtothebearing.Fig.22OilsplashlubricationFig.23OilcirculatinglubricationFig.21Oildriplubrication
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