>> P.60
1-4BearingSelection(12)PreloadandloadIfthepreloadamountandmethodarenotsuitablyselected,thepreloadappliedtothebearingwillcauseitsperformancetodeteriorate(intermsoflife,vibration,noise,heatgeneration,etc.);therefore,itisimportanttoselectapreloadamountandmethodsuitedtotheusageapplication.PreloadpurposeWhenusingthebearinginamotor,etc.,internalclearancewillleadtolargerballplayandreducethebearingrigidity,increasingthebearingrotationvibration.AsshowninFig.12-1,axialdirectionload(Fa)isappliedinadvancetomaketheinternalclearancenegative.Theloadappliedinadvanceintheaxialdirectioniscalledthepreload.Theapplicationofpreloadhelpsimprovenoiseandvibrationperformance.Preloadinvolvesasuitablepreloadamountfortherequiredbearingperformance.Ifthepreloadamountistoolarge,therigiditywillincrease,butitwillalsoleadtoincreasednoiseandvibrationandshortenedlife.Ifthepreloadamountistoosmall,therigiditywillbetoolow,failingtosuppressvibrationandleadingtodamagesuchasfrettingcorrosion.Therefore,whenusingbearings,thepreloadamountsettingisanextremelyimportantelement.QQFaFig.12-1MinebeaMitsumiprovidesvariousunitproducts(PMAproducts)withsuitablepreloadappliedinadvancetothebearings.ForPMAproductsâ–¶60
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