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(17)LubricantsBearinglubricationnormallyusesgreaseoroil.Forminiatureandsmall-diameterrollingballbearings,theinitiallyinsertedlubricantcanalmostalwaysbeusedthroughoutthedevicelifewithoutreplacement.Therefore,lubricantsmustbeselecteduponsufficientconsiderationoflife,torque,rotationperformance,noiseperformance,andsoon.OilOilscanberoughlydividedintomineraloil,syntheticoil,andmixedoilcombiningthetwo.Asitisfluidandnotusedinlargequantities,itenablesreducedtorquebutalsorequiresconsiderationwithregardtolife.Itisalsousedasthebaseoilofgrease.GreaseAsolidorsemi-solidformedbydiffusingthickenerinbaseoil.Composedofbaseoil,thickener,andadditive,itspropertiesaredeterminedbytheircombination.•BaseoilBaseoilscanberoughlydividedintomineraloil,syntheticoil,andmixedoilcombiningthetwo.•ThickenerThickenerisaddedinordertodiffuseinthebaseoilandformsemi-solids(ingrease).Thissubstanceisimportantindeterminingthepropertiesandperformanceofgrease.Thickenerscanbedividedintosoap-basedtypeswhichusemetalsoaps(lithium,etc.)andnon-soap-basedtypeswhichdoTypesofgreasenot(urea,etc.).•AdditivesAdditivesareaddedtoimprovethephysicalandchemicalperformanceofthegrease.Typesofadditivesincludeantioxidants,rust-proofingagents,corrosioninhibitors,extreme-pressureadditives,andsoon.Greaseisdividedintovarioustypesbythickener,asshownonthefollowingpageinTable17-1"Lubricanttypes."Therepresentativecharacteristicsofgreasearebelow.•Lithiumsoapgrease•FluorinegreaseLithiumsoapgreasehasexcellentlow-noisepropertiesanddurability,andisthemostwidelyusedasauniversalgreaseingeneralindustry,automobiles,andhouseholdappliances.Itiscomparativelyinexpensive.•UreagreaseUreagreasehasexcellentheatresistance,highspeed,andwaterresistance,andisfrequentlyusedinautomotiveelectricalproducts,vacuumcleanermotors,andventilationfans.Aswell,incombinationwithsyntheticoil,othergreaseshaveexcellentenvironmentalstresscracking(ESC)resistance.Fluorinegreasehasexcellentchemicalstabilityandisusedinhigh-temperatureenvironmentsaroundautomobileengines.Itisalsousedinvacuumenvironments.Thisgreaseisextremelyexpensive.•ConductivegreaseConductivegreasehasconductivityandenablesconductionofelectricitywithinthebearing,foruseindevicessuchascopierswhereelectricaldischargemustbeavoided.73
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