Selection of bearing type

Transcription

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2 Selection of ering type Aville spce Lods Mgnitude of lod Direction of lod Mislignment Precision Speed Quiet running Stiffness Axil displcement Mounting nd dismounting Cylindricl ore Tpered ore Integrl sels Mtrix: Bering types design nd chrcteristics

3 Selection of ering type Ech ering type displys chrcteristic properties, sed on its design, which mkes it more, or less, pproprite for given ppliction. For exmple, deep groove ll erings cn ccommodte moderte rdil lods s well s xil lods. They hve low friction nd cn e produced with high precision nd in quiet running vrints. Therefore they re preferred for smll nd medium-sized electric motors. Sphericl nd toroidl roller erings cn crry very hevy lods nd re self-ligning. These properties mke them populr for exmple for hevy engineering pplictions, where there re hevy lods, shft deflections nd mislignments. In mny cses, however, severl fctors hve to e considered nd weighed ginst ech other when selecting ering type, so tht no generl rules cn e given. The informtion provided here should serve to indicte which re the most importnt fctors to e considered when selecting stndrd ering type nd thus fcilitte n pproprite choice lso depends on the pplied prelod nd the operting speed, which is influenced y the precision of the ering nd its ssocited components s well s y the cge design. In spite of its limittions, the mtrix on pges 46 nd 47 should enle n pproprite choice of ering type to e mde. It should lso e considered tht the totl cost of ering rrngement nd inventory considertions could lso influence the finl choice. Other importnt criteri to e oserved when designing ering rrngement including lod crrying cpcity nd life, friction, permissile speeds, ering internl clernce or prelod, luriction nd seling re delt with in depth in seprte sections of this ctlogue. The complete SKF product rnge is not shown in this Generl Ctlogue. Specific ctlogues nd rochures re ville for erings not covered here plese consult SKF. ville spce lods mislignment precision speed quiet running stiffness xil displcement mounting nd dismounting integrl sels. A comprehensive overview of the stndrd ering types, their design chrcteristics nd their suitility for the demnds plced on given ppliction cn e found in the mtrix on pges 46 nd 47. Detiled informtion on the individul ering types, including their chrcteristics nd the ville designs, cn e found in the sections deling with individul ering types. Bering types tht re not included in the mtrix re generlly only used for few welldefined pplictions. The mtrix permits only reltively superficil clssifiction of ering types. The limited numer of symols does not llow n exct differentition nd some properties do not depend solely on ering design. For exmple, the stiffness of n rrngement incorporting ngulr contct ll erings or tper roller erings 34

4 Aville spce In mny cses, one of the principl dimensions of ering the ore dimeter is predetermined y the mchine s design nd the shft dimeter. For smll-dimeter shfts ll types of ll erings cn e used, the most populr eing deep groove ll erings; needle roller erings re lso suitle ( fig. 1). For lrgedimeter shfts, cylindricl, tper, sphericl nd toroidl roller erings re ville, s well s deep groove ll erings ( fig. 2). When rdil spce is limited, erings with smll cross section, prticulrly those with low cross-sectionl height, should e chosen, i.e. erings in the 8 or 9 Dimeter Series. Needle roller nd cge ssemlies, drwn cup needle roller erings nd needle roller erings without or even with n inner ring ( fig. 3) re very pproprite ( SKF ctlogue Needle roller erings ), s well s certin series of deep groove nd ngulr contct ll erings, cylindricl, tper, sphericl nd toroidl roller erings. Fig. 1 Fig. 2 Fig. 3 35

5 Selection of ering type When xil spce is limited, certin series of cylindricl roller erings nd deep groove ll erings cn e used for rdil or comined lods respectively ( fig. 4), s well s the vrious types of comined needle roller erings ( fig. 5). For purely xil lods, needle roller nd cge thrust ssemlies (with or without wshers) s well s thrust ll erings nd cylindricl roller thrust erings cn e used ( fig. 6). Fig. 4 Fig. 5 Fig. 6 36

6 Fig. 7 Lods Mgnitude of lod The mgnitude of the lod is one of the fctors tht usully determines the size of the ering. Generlly, roller erings re le to support hevier lods thn similr sized ll erings ( fig. 7) nd erings hving full complement of rolling elements cn ccommodte hevier lods thn the corresponding cged erings. Bll erings re mostly used where lods re light or moderte. For hevy lods nd where shft dimeters re lrge, roller erings re usully the more pproprite choice. Direction of lod Fig. 8 Rdil lod NU nd N design cylindricl roller erings, needle roller erings nd toroidl roller erings cn only support pure rdil lods ( fig. 8). All other rdil erings cn ccommodte some xil lods in ddition to rdil lods ( Comined lod ). Axil lod Thrust ll erings nd four-point contct ll erings ( fig.9) re suitle for light or moderte lods tht re purely xil. Single direction thrust ll erings cn only ccommodte xil lods cting in one direction; for xil lods cting in oth directions, doule direction thrust ll erings re needed. Fig. 9 37

7 Selection of ering type Fig. 10 Fig. 11 Angulr contct thrust ll erings cn support moderte xil lods t high speeds; here, the single direction erings cn lso ccommodte simultneously cting rdil lods, while doule direction erings re normlly used only for purely xil lods ( fig. 10). For moderte nd hevy xil lods cting in one direction, needle roller thrust erings, cylindricl nd tper roller thrust erings re suitle, s re sphericl roller thrust erings ( fig. 11). Sphericl roller thrust erings cn lso ccommodte simultneously cting rdil lods. For hevy lternting xil lods, two cylindricl roller thrust erings or two sphericl roller thrust erings cn e mounted djcent to ech other. Comined lod A comined lod comprises rdil nd n xil lod cting simultneously. The ility of ering to crry n xil lod is determined y the ngle of contct the greter the ngle, the more suitle the ering for xil lods. An indiction of this is given y the clcultion fctor Y, which ecomes smller s the contct ngle increses. The vlues of this fctor for ering type or for individul erings cn e found in the introductory text of the product tle sections, or in the ctul product tles. The xil lod crrying cpcity of deep groove ll ering depends on its internl design nd the internl clernce in the ering ( section Deep groove ll erings, strting on pge 287). For comined lods, single nd doule row ngulr contct ll erings nd single row tper roller erings re most commonly used, lthough deep groove ll erings nd sphericl roller erings re suitle ( fig. 12). In ddition, self-ligning ll erings nd NJ nd NUP design cylindricl roller erings s well s NJ nd NU design cylindricl roller erings with HJ ngle rings cn e used for comined lods where the xil component is reltively smll ( fig. 13). Single row ngulr contct ll erings, tper roller erings, NJ design cylindricl roller erings, NU design cylindricl roller erings HJ ngle ring nd sphericl roller thrust erings cn ccommodte xil lods cting in one direction only. For xil lods of lternting direction these erings must e comined with second ering. For this reson, single 38

8 Fig. 12 row ngulr contct ll erings re ville s erings for universl mtching nd single row tper roller erings cn e supplied s mtched sets comprising two single row erings ( sections Single row ngulr contct ll erings, strting on pge 409, nd Pired single row tper roller erings, strting on pge 671). When the xil component of comined lods is lrge, it my e supported independently from the rdil lod y seprte ering. In ddition to thrust erings, some rdil erings, e.g. deep groove ll erings or fourpoint contct ll erings ( fig. 14) re suitle for this tsk. To mke sure tht the ering is only sujected to the xil lod in such cses, the ering outer ring must e mounted with rdil clernce. Fig. 13 Fig

9 Selection of ering type Moment lod When lod cts eccentriclly on ering, tilting moment will occur. Doule row erings, e.g. deep groove or ngulr contct ll erings, cn ccommodte tilting moments, ut pired single row ngulr contct ll erings or tper roller erings rrnged fce-to-fce, or etter still ck-to-ck, re more suitle ( fig. 15). Mislignment Angulr mislignments etween the shft nd housing occur, for exmple, when the shft ends (flexes) under the operting lod, when the ering setings in the housing re not mchined to the sme height or when shfts re supported y erings in seprte housings tht re too fr prt. Rigid erings, i.e. deep groove ll erings nd cylindricl roller erings cnnot ccommodte ny mislignment, or cn only ccommodte very minor mislignments, unless y force. Self-ligning erings, i.e. self-ligning ll erings, sphericl roller erings, toroidl roller erings nd sphericl roller thrust erings ( fig. 16), on the other hnd, cn ccommodte mislignment produced under operting lods nd cn lso compenste for initil mislignment resulting from mchining or mounting errors. Vlues for the permissile mislignments re provided in the introductory text of the tle section. If the expected mislignment exceeds the permissile vlues, plese contct the SKF ppliction engineering service. Thrust ll erings with sphered housing wshers nd seting rings, Y-ering units nd lignment needle roller erings ( fig. 17) cn compenste for initil mislignment rising from mchining or mounting errors. Precision Berings with higher precision thn Norml re required for rrngements tht must hve high running ccurcy (e.g. mchine tool spindle rrngements) s well s those pplictions where very high speeds re required. The introductory text to ech tle section contins informtion out the tolernce clsses to which the erings in tht section re produced. SKF produces comprehensive rnge of high-precision erings, including single row ngulr contct ll erings, single nd doule row cylindricl roller erings nd single nd doule direction ngulr contct thrust ll erings ( SKF ctlogue High-precision erings ). 40

10 Fig. 15 Fig. 16 Fig

11 Selection of ering type Speed The permissile operting temperture limits the speed t which rolling erings cn e operted. Bering types with low friction nd correspondingly low het genertion inside the ering re therefore the most suitle for high-speed opertion. The highest speeds cn e chieved with deep groove ll erings nd self-ligning ll erings ( fig. 18) when lods re purely rdil nd with ngulr contct ll erings ( fig. 19) for comined lods. This is prticulrly true of high-precision ngulr contct ll erings or deep groove ll erings with cermic rolling elements. Becuse of their design, thrust erings cnnot ccommodte s high speeds s rdil erings. Fig. 18 Fig. 19 Quiet running In certin pplictions, e.g. smll electric motors for household pplinces or office mchinery, the noise produced in opertion is n importnt fctor nd cn influence the ering choice. SKF deep groove ll erings re produced specificlly for these pplictions. Stiffness The stiffness of rolling ering is chrcterized y the mgnitude of the elstic deformtion (resilience) in the ering under lod. Generlly, this deformtion is very smll nd cn e neglected. In some cses, however, e.g. spindle ering rrngements for mchine tools or pinion ering rrngements, stiffness is importnt. Becuse of the contct conditions etween the rolling elements nd rcewys, roller erings, e.g. cylindricl or tper roller erings ( fig. 20), hve higher degree of stiffness thn ll erings. Bering stiffness cn e further enhnced y pplying prelod ( section Bering prelod, strting on pge 206). Fig

12 Fig. 21 Fig. 22 Fig. 23 Axil displcement Shfts, or other rotting mchine components, re generlly supported y locting nd nonlocting ering ( section Bering rrngements, strting on pge 160). Locting erings provide xil loction for the mchine component in oth directions. The most suitle erings for this re those tht cn ccommodte comined lods, or cn provide xil guidnce in comintion with second ering ( mtrix on pges 46 nd 47). Non-locting erings must permit shft movement in the xil direction, so tht the erings re not overloded when, for exmple, therml expnsion of the shft occurs. The most suitle erings for the non-locting position include needle roller erings nd NU nd N design cylindricl roller erings ( fig. 21). NJ design cylindricl roller erings nd some full complement design cylindricl roller erings cn lso e used. In pplictions where the required xil displcement is reltively lrge nd lso the shft my e misligned, CARB toroidl roller ering is the est choice s non-locting ering ( fig. 22). All of these erings permit xil displcement of the shft with respect to the housing within the ering. Vlues for the permissile xil displcement within the ering re provided in the relevnt product tles. If non-seprle erings, e.g. deep groove ll erings or sphericl roller erings ( fig. 23) re used s non-locting erings, one of the ering rings must hve loose fit ( section Rdil loction of erings, strting on pge 164). 43

13 Selection of ering type Mounting nd dismounting Cylindricl ore Berings with cylindricl ore re esier to mount nd dismount if they re of seprle design rther thn non-seprle, prticulrly if interference fits re required for oth rings. Seprle erings re lso preferle if frequent mounting nd dismounting re required, ecuse the ring with rolling element nd cge ssemly of these seprle erings cn e fitted independently of the other ring, e.g. fourpoint contct ll erings, cylindricl, needle nd tper roller erings ( fig. 24), s well s ll nd roller thrust erings. Fig. 24 Tpered ore Berings with tpered ore ( fig. 25) cn esily e mounted on tpered journl or on cylindricl shft seting using n dpter or withdrwl sleeve ( fig. 26). Fig. 25 Fig

14 Integrl sels Fig. 27 The selection of sel is of vitl importnce to the proper performnce of the ering. SKF supplies erings with integrl shields ( fig. 27) low-friction sels ( fig. 28) contct sels ( fig. 29) tht cn provide n economic nd spce-sving solution for mny pplictions. A lrge numer of sizes re ville for deep groove ll erings ngulr contct ll erings self-ligning ll erings cylindricl roller erings needle roller erings sphericl roller erings CARB toroidl roller erings cm rollers Y-erings nd Y-ering units. Fig. 28 All erings with integrl sels on oth sides re filled with grese of pproprite qulity nd quntity. Fig

15 Selection of ering type Angulr contct ll erings, single row seprle Deep groove ll erings non-seperle Bering type self-ligning tpered ore Symols excellent good fir poor unsuitle single direction s doule direction shields or sels The mtrix cn only provide rough guide so tht in ech individul cse it is necessry Bering types design nd chrcteristics to mke more qulified selection referring to the informtion provided on the preceding pges or the detiled informtion in the text preceding ech tle section. If severl designs of the ering type re shown djcent to ech other, the relevnt informtion is Design indicted y the sme smll letter used to identify the individul design., c mtched single row, doule row c four-point contct Self-ligning ll erings Cylindricl roller erings, with cge full complement, single row full complement, doule row c Needle roller erings, with steel rings c ssemlies/drwn cups comined erings d d c, c c c Tper roller erings mtched single row Sphericl roller erings CARB toroidl roller erings, with cge full complement Thrust ll erings with sphered housing wsher Needle roller thrust erings Cylindricl roller thrust erings Sphericl roller thrust erings 46 d c, c

16 Chrcteristics Suitility of erings for purely rdil lod purely xil lod comined lod moment lod high speed high running ccurcy high stiffness quiet running low friction compenstion for mislignment in opertion compenstion for errors of lignment (initil) locting ering rrngements non-locting ering rrngements xil displcement within ering s s s s s s s s s s c d s c d s c d s c c d s c d s s s c s s c c s c c s s c c s s s s s 47