Spherical Roller Bearings

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Spherical Roller Bearings

Spherical Roller Bearings1. Types, construction and characteristicsSpherical roller bearings consist of an outer ring having acontinuous spherical raceway within which operates tworows of barrel-shaped rollers which are in turn guided by aninner ring with two raceways separated by a center rib.(Refer to Diagram 1) This bearing has self-aligningproperties, and therefore is suited for use wheremisalignment between the inner and outer rings occurs fromhousing installation error or shaft flexure.Spherical roller bearings have a large capacity for radialloads, axial loads in either direction, and complex loads.They are also suited for applications where vibration andshock loads are encountered. When operating under axialloads, however, it is desirable to maintain conditions so thatFaFr2e in order to prevent sliding movement along therow of rollers not receiving the axial load. (For the value of e,refer to dimension tables.)As shown in Table 1, in addition to standard type there arevarious other types of spherical roller bearings. Amongthese, Type E has a particularly high load capacity.In addition to bearings with cylindrical bore, those withtapered bore are also available. Bearings with tapered boreare specified by attaching the suffix "K" to the end of thebearing's basic number. The standard taper ratio is 1:12 forbearings with a "K" suffix, but for bearings in series 240 and241 the suffix "K30" indicates the taper ratio for a bearing is1:30. Most tapered bore bearings incorporate the use ofadapters and withdrawal sleeves for shaft mounting.Diagram 1.AllowablemisalignmentTable 1 Types of spherical roller bearingsType Standard type (B type) C type 213 type E typeConstructionBearing seriesDoes not include C typeSeries 222, 223, and 213with bore dia. of 50 mm orless; series 24024 to 24038.Series 213 with boredia. of 55 mm or moreSeries 22211 to 22218RollersRoller guidemethodcage typeAsymmetrical Symmetrical Asymmetrical SymmetricalUnified inner ringcenter ribPressed cage;machined cageBy guide ring betweenthe 2 rows of rollersBy guide ring betweenrows of rollers on outerring racewayHigh precision cage(no guide ring, center rib)Pressed cage Machined cage Molded resin cageB-219


Spherical Roller Bearings2. Standard cage typesStandard cage types for spherical roller bearings areshown in Table 2. In general, pressed cages are standardfor small sized bearings, and machined cages are standardfor large sized bearings.E type bearings use as their standard cage type a cagemolded from a newly developed glass fiber reinforcedpolyamide 46 resin which has excellent heat resistancequalities (allowable operating temperatures up to150˚C), strength, as well as unsurpassed oil resistance.A standard cage may however not be able to be used forhigh-speed specifications, in high temperature atmospheres,or under excessive vibration/impact conditions. For moreinformation concerning such conditions, please contact NTNEngineering.Table 2 Standard cage typesBearingseries239230240231241222232213223Molded resin cage Pressed cage Machined cage22211E 22218E23022B 23048B24024C 24038C23120B 23136B22208C 22210C22211B 22236B21308C 21310C22308C 22310C22311B 22328B23932 239/140023052B 230/1120B24024B 240/1120B23138B 231/900B24122B 241/710B22238B 22264B23218B 232/750B21311 2132222330B 22360BTable 3 Oil inlet and oil groove dimensionsNominal bearingwidthover including3045608010012016020031530456080100120160200315Oil groovewidthW67911141620273342Table 4 Oil inlet numberNominal bearingouter diameter mmover up to including3201 0103201 010hOil inletdiameter4812d345681012162025Units mmOil groove depthhWidth series Width series1, 2, 3 41.21.51.52.02.53.03.55.06.07.01.01.11.31.52.02.53.03.55.06.5If a pin is necessary to prevent outer ring rotation, contactNTN Engineering.WZOil inletnumberZd3. Oil inlets and oil groove dimensionsSpherical roller bearings with an outer diameter of 320mmor more are provided with an oil inlet and oil groove on theouter ring for the purpose of supplying lubricant to thebearing's moving parts. When necessary, oil inlets and oilgrooves can also be provided on bearings with outerdiameters less than 320 mm. In such cases, please add thesupplementary suffix code "D1" to the end of the bearingnumber, and contact NTN Engineering. (Refer to page A-29)Table 3 lists dimensions for oil inlets and oil grooves.Table 4 contains information about the number of oil inlets.4. Allowable misalignmentSpherical roller bearings possess the same self-aligningproperties as other self-aligning bearings. The allowablemisalignment angle will vary according to dimension seriesand load conditions, but the following misalignment anglesare generally standard:Normal load (loads equivalentto 0.09 Cr): ⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯0.009rad 0.5˚Light load: ⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯0.035rad 2˚B-220


Spherical Roller Bearings5. Adapters and withdrawal sleevesAdapters are used for installation of bearings with taperedbore on cylindrical shafts. Withdrawal sleeves are also usedto install and disassemble bearings with tapered bore ontoand off of cylindrical shafts. In disassembling the bearingfrom the shaft, the nut is pressed down against the edge ofthe inner ring utilizing the bolt provided on the withdrawalsleeve, and then the sleeve is drawn away from the bearing'sinner diameter surface. (Precision of adapter and withdrawalsleeve are stipulated JIS B 1552 and JIS B 1556).For bearings with a bore diameter of 200 mm or more, highpressure oil (hydraulic) type adapters and withdrawal sleeveshave been standardized to make installation anddisassembly easier. As shown in Diagram 2 construction isdesigned to reduce friction by injecting high pressure oilbetween the surfaces of the adapter sleeve and bearinginner bore by means of a pressure fitting.If the oil supply inlet is attached in the nut side of theadapter, the supplementary suffix "HF" should be added tothe bearing number; if the oil supply inlet is attached on theopposite side, the suffix "HB" should be added to the bearingnumber. For adapter sleeves, the supplementary suffix "H" isadded to the bearing's number in both cases.The hydraulic sleeve nut is equipped with holes for boltsused for mounting and dismounting and holes for hydraulicpiping. The suffix SP or SPB is added to the bearing numberof the nut.6. LH seriesIn recent years, conditions under which spherical rollerbearings are used have become increasingly severe. Inparticular, longer life is now demanded for use in hightemperature environments.Taking the global environment into account, NTNEngineering has developed a type of steel (STJ2) that offerslonger life in a wide range of temperatures, from roomtemperature all the way up to 250˚C. The steel is standardlyused in NTN Engineering's LH series of spherical rollerbearings.Features are as follows (in comparison with SUJ2):(1) Longer life in wide range of temperatures.¡3.5 times longer life at room temperature.¡30 times longer life at high temperature (250˚C).(2) Resists surface damage.¡7 times stronger resistance to peeling¡1.4 times stronger resistance to smearing¡2.5 times stronger resistance to wear(3) Dimensions stability at high temperatures.¡Almost no dimensional variation when maintained at250˚C.(4) Enhanced cracking fatigue strength.¡2 times longer cracking fatigue life under hightemperatures or tight fitting stress.¡2 times better operating cracking fatigue strength.(5) Simplified service part stock management.¡Applications ranging from room temperature to 250˚Ccan be handles with a single type of standardbearing.Diagram 2.Items with LH preceding the basic number in thedimensions table are LH series and are gradually beingswitched.Bearing numbers without LH can be manufacturedaccording to size. For information, please contact NTNEngineering.B-221

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