>> P.43
1N=0.102kgf=0.2248lbs.1mm=0.03937inchas∆T,thetemperaturedifferencebetweentheinnerringandtheshaftcanbeestimatedtobe(0.1〜0.15)∆T.Accordingly,theamountofreductionoftheinnerringinterferenceisobtainedbythefollowingequation. ∆dT=(0.1〜0.15)∆Tαd≒0.0015∆Td×10-3…(32)where, ∆dT: Reductionamountofinnerringtemperaturetointerferenceduedifference, mm Temperaturedifferencebetweentheinsideofthebearingandtheoutsideofthehousing,°C Coefficientofforbearingsteellinearexpansion ∆Tα :: ≒12.5×10-61/°C Borediameterofinnerring,mm:d 4ShaftfinishgradeandinterferenceSincepeaksofsurfaceroughnessofthefittedsurfacearecrusheddownwhenfittingthebearing,theeffec-tiveinterferencebecomessmallerthantheapparentinterferenceobtainedbymeasurements,anditisgen-erallyobtainedbythefollowingequations.・Forgroundshaftdd ∆de=∆df…………………………(33)d+2・Formachinedshaft ∆de=∆df…………………………(34)d+3where,∆de: Effectiveinterferenceofinnerring, mm d: Borediameterofinnerring, mm∆df Apparentinterference, mm:tothefittedwithinterferenceto5MinimuminterferenceandmaximuminterferenceWhentheloaddirectionisrotatinginrelationinnerring,theinnerringistheshaft.Forsolidgroundsteelshafts,theminimuminterfer-ence(requiredapparentinterference)∆dfisexpressedbythefollowingequationwhichisdeducedfromequa-tions(30)or(31),(32)and(33).∆df≧(∆dF+0.0015∆Td×10-3)…(35)d+2dItisdesiredthatthemaximuminterferenceshouldbelessthan1/1000oftheshaftdiameter.Inthecaseoftheouterring,theeffectiveinterferencevariesaccord-ingtothehousingmaterial,thickness,shape,etc.,soitisdeterminedempirically.A40ABCDEFGHIJKLMConditionsfordeterminationoffitWhendeterminingasuitablefitforabearing,itisnec-essarytoconsidervariousconditionssuchasnatureandmagnitudeoftheload,temperature,requiredrota-tionalaccuracy,material/finishgrade/thicknessoftheshaftandhousing,easeofmountinganddismounting,etc.1NatureofloadandfitBasically,theappropriatefitdependsonwhethertheloaddirectionisrotationalorstationaryinrelationtotheinnerandouterrings.Therelationshipbetweenthenatureofradialloadsandthefitis,ingeneral,basedonTable20.2LoadamountandinterferenceThegreatertheload,thelargertheinterferencemustbe.Whenselectinganinterferencebetweentheinnerringandtheshaft,itisnecessarytoestimatethereductionofinterferenceduetotheradialload.Theamountofreductionofisobtainedbythefollowingequations.interference∆dF=0.08Fr×10-3………………(30)dB・WhenFr>0.2C0∆dF=0.02×10-3FrB……………………(31)・WhenFr≦0.2C0where, FrC0∆dF dB:Radialloadappliedtobearing, N:Basicstaticloadrating, N:Amountofreductionofringinterference, mm:Borediameterofinnerring, mm:Widthofinnerring, mminnertemperaturedifferencebetween3TemperatureconditionsandchangeofinterferenceTheinterferenceoffittedsurfacesisalsoinfluencedbythethebearingandtheshaftandhousing.Forexample,whensteamisflowingthroughahollowshaft,orwhenthehousingismadeoflightmetal,itisnecessarytotakeintoconsid-erationthecoefficientoflinearexpansionandothersuchfactors.theinnerringdecreasesUsually,increasesduringopera-astion.Ifthetemperaturedifferencebetweentheinsideofthebearingandtheoutsideofthehousingistakeninterferenceoftemperaturethedifferencestemperature,thebearingthein
| < 
| 
> | 
>>
