>> P.53
(10)FitsBearingsareneverusedontheirown;rather,theyarefittedintoshaftsorhousings.Thefitreferstothemutualdimensionsbetweentheinnerringandshaftandbetweentheouterringandhousing;generally,itisdividedintoclearancefits,intermediatefits,andinterferencefits.FitsThepurposeoffitsistosuppressvibrationduringrotationandtofixthebearinginnerringandshaftandtheouterringandhousing,preventingcreep.Creepreferstoslippingonthefitsurface;itcanleadtothegenerationofabnormalheatandwearpowder.Abnormalheatgenerationcausesrapiddeteriorationofthegreaseinsidethebearing,whileifwearpowderentersthebearingitwillincreasevibrationandnoiseandleadtoshortenedbearinglife.Inthecaseofinterferencefits,theinterferencechangesthebearing'sinternalclearance.Theamountofchangeduetointerferenceinthebearing'sradialclearanceiscalculatedasbelow.(BasedonTimoshenko)InternalclearancedecreaseduetointerferencefitsShaftouterdiameterbeforepress-fittingInnerringouterdiameterbeforepress-fitting•ShaftandinnerringinterferencefitsFig.10-1isasimplediagramshowingbefore(dottedline)andafter(solidline)fitting.Whentheinnerringgroovediameterd2ispress-fitwithinterferencei,δincreases.Thatis,δistheamounttheradialclearancedecreasesduetothefit.Innerringinnerdiameterbeforepress-fittingd1dd2i12δ12ShaftFig.10-122+1-1-1mdd1:Nominalinnerringinnerdiameter,nominalshaftouterdiameter:ShaftinnerdiameterForsolidshaft,(d/d1)2+1(d/d1)2-1=1d2:InnerringgroovediameteriEbEsmbms:Interference(i/2inradialdirection):Young'smodulusofinnerring(outerring):Young'smodulusofshaft:Poisson'snumberofinnerring(outerring):Poisson'snumberofshaft5311dddd2dd2i22+1-1+1mb+EbE22ddddδ=(d2/d)2-1
| < 
| 
> | 
>>
