>> P.59
1N=0.102kgf=0.2248lbs.1mm=0.03937inchABCDEFGHIJKLMAllowablerotationalspeedtherollingbearingsrotationalspeedofAsisincreased,thebearingtemperaturealsoincreasesduetotheheatgeneratedatthecontactsurfacesbetweenthecage,racewaysandrollingelements,untilitfinallyleadstobearingseizure.Itisthereforenecessarytomaintaintherotationalspeedofabear-ingbelowacertainlimitvaluetoensuresafeopera-tionforlongperiods.Thislimitvalueiscalledtheallowablerotationalspeed.Sincetheamountofheatgeneratedisapproximatelyproportionaltotheslidingspeedatthecontactarea,thisslidingspeedisanapproximateguideindicatingthelimitofthebearingrotationalspeed.Theallowablerotationalspeedofbearingsthusvariesaccordingload,methodoflubrication,radialclearance,andothersuchfactors.Theallowablerotationalspeedsshowninthetableofdimensionsareempiricalvalues.Theyarenotabsolutevaluesandcanbechangedaccordingtothebearinguseconditions.Dependingonthestructureandaccuracyaroundthebearing,thelubricantandthelubricationmethod,itispossibleforsomebear-ingstobeoperatedatmorethantwicetheallowablerotationalspeedgiveninthetablewithouttrouble.type,size,bearingthebearingtoisinfluencedbyComparedwithslidingbearings,thestarting(static)frictionforrollingbearingsissmall,andthedifferencebetweenthestarting(static)frictionandthekineticfrictionisalsosmall.Thelossofpowerandtempera-tureriseinmachinesarethusreduced,improvingthemechanicalefficiency.thebearingtype,Frictionaltorqueload,rotationalspeed,lubricantcharacteris-bearingtics,etc.Itvariesaccordingtothelubricantwhenoperatedunderlight-loadsandhigh-speedconditions,andaccordingloadwhenoperatedunderheavy-loadsandlow-speedconditions.torqueofrollingbearingsiscomplicatedFrictionalforbecauseconvenience,itcanbeexpressedapproximatelybythefollowingequations.influencedbyvariousfactors,butthetoisitd2・RadialbearingsM=μP……………………(37)・ThrustbearingsM=μP……………………(38)dm2where,M:Frictionaltorque, N-mmμ:CoefficientoffrictionPddm:Meanvalueofbearingboreand:Bearingload, N:Bearingborediameter, mmoutsidediameters, mmFrictionandAllowableRotationalSpeedFrictionTheapproximatecoefficientsofIKOBearingsunderoperatingconditions,inwhichlubrica-tionandmountingarecorrectandwhereloadsarerel-ativelylargeandstable,areshowninTable40.frictionofTable40CoefficientoffrictionBearingseriesμNeedlerollerbearingswithcageFullcomplementneedlerollerbearingsThrustneedlerollerbearingsThrustrollerbearings0.0010〜0.00300.0030〜0.00500.0030〜0.00400.0030〜0.0040A56
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