SKF工业齿轮箱中的滚动轴承完整版

SKF工业齿轮箱中的滚动轴承完整版 ??Copyright SKF 1997The contents of this publication are thecopyright of the publisher and may notbe reproduced even extracts unlesspermission is granted. Every care hasbeen taken to ensure the accuracy ofthe information contained in this publi-cation but no liability can be acceptedfor any loss or damage whether directindirect or consequential arising out ofthe use of the information containedherein.Publication4560 EPrinted in Denmark on environmentallyfriendly chlorine-free paper MultiartSilk by Scanprint as1Industrial gearboxes – overview2Bearing types for industrial gearboxes3Design of bearing arrangements4Dimensioning the bearing arrangement5Lubrication and maintenance6Recommended fits7Mounting and dismounting bearings8Application examplesRolling bearings in industrial gearboxesRolling bearings inindustrial gearboxesHandbook for the gearbox designerForewordThis Handbook is intended to provide the gearbox designerwith the knowledge required to select bearings for gearboxesand to correctly design gearbox bearing arrangements. Recom-mendations are given based on experience gained by SKFduring decades of cooperation with gearbox manufacturers theworld over.General information regarding the selection calculationmounting and maintenance of ball and roller bearings is givenin the SKF General Catalogue. The questions arising from theuse of rolling bearings in industrial gearboxes are dealt withhere. Data from the General Catalogue are only repeated herewhen it has been thought necessary for the sake of clarity.The application examples described comprise proven gearbox designs from major manufacturers which are worthy of note.Grateful thanks are extended to the companies concernedfor the provision of the detailed information about their prod-ucts and the permission to publish.3Rolling bearings in industrial gearboxes4Types of gearbox............................................................9Geared transmissions....................................................10Demands made on gearboxes......................................14Selecting the gears........................................................14Designing the casing.....................................................15Deep groove ball bearings............................................18Angular contact ball bearings.......................................20Cylindrical roller bearings.............................................22CARB??roller bearings.................................................24Spherical roller bearings...............................................26Taper roller bearings......................................................28Spherical roller thrust bearings....................................30Shafts and gear wheels in spur gearboxes.................33Shafts in bevel gearboxes.............................................44Shafts in worm gearboxes.............................................50Shafts and gear wheels for planetary gearboxes........56Made by SKF??stands for excellence. It symbolises our consistent endeavour to achieve total quality in everything we do. For those who use our products“Made by SKF” implies three main benefits.Reliability– thanks to modern efficient products basedon our worldwide application know-how optimised materials forward-looking designs and the most advanced production techniques.Cost effectiveness– resulting from the favourable ratiobetween our product quality plus service facilities andthe purchase price of the product.Market lead– which you can achieve by taking advantage of our products and services. Increased operating time and reduced down-time as well as improved output and product quality are the key to a successful partnership.Contents5Bearing loads.................................................................65Determination of external forces..................................66Calculation of bearing loads.........................................74Dimensioning the bearing arrangement......................76Grease lubrication..........................................................92Oil lubrication.................................................................95Maintenance..................................... ..............................98Adjustment of angular contact bearings....................109Rolling bearings in industrial gearboxes6SKFis an international industrial Groupoperating in some 130 countries and isworld leader in bearings.The company was founded in 1907following the invention of the self-align-ingball bearing by Sven Wingquist andafter only a few years SKFbegan toexpand all over the world.Today SKFhas some 43000 em-ployees and more than 80 manufactur-ing facilities spread throughout theworld. An international sales network includes a large number of sales com-panies and some 20000 distributorsand retailers. Worldwide availability ofSKFproducts is supported by a com-prehensive technical advisory service.The key to success has been a con-sistent emphasis on maintaining thehighest quality of its products and services. Continuous investment inresearch and development has alsoplayed a vital role resulting in manyexamples of epoch-making innovations.The business of the Group consistsof bearings seals special steel and acomprehensive range of other high-techindustrial components. The ex-perience gained in these various fieldsprovides SKF with the essential know-ledge and expertise required in orderto provide the customers with the mostadvanced engineering products andefficient service.The SKF Group – a worldwide corporationSKF manufacturesball bearings roller bearings and plainbearings. The smal-lest are just a fewmillimetres a frac-tion of an inch indiameter the largestseveral metres. Inorder to protect thebearings effectivelyagainst the ingressof contaminationand the escape oflubricant SKF alsomanufactures oiland bearing seals.SKFs subsidiariesCR and RFT S.p.A.are among the worlds largest pro-ducers of seals.7The SKF house colours are blue and redbut the thinking is green. The latest exampleis the new factory in Malaysia where thebearing component cleaning process con-forms to the strictest ecological standards.Instead of trichloroethylene a water-basedcleaning fluid is used in a closed system.The cleaning fluid is recycled in the factorysown treatment plant.SKFhas developed the Channel concept infactories all over the world. This drasticallyreduces the lead time from raw material toend product as well as work in progress and finished goods in stock. The conceptenables faster and smoother informationflow eliminates bottlenecks and bypassesunnecessary steps in production. TheChannel team members have the know-ledge and commitment needed to share theresponsibility for fulfilling objectives in areassuch as quality delivery time productionflow etc.The SKF Engineering amp Research Centre is situated just outside Utrecht in TheNetherlands. In an area of 17 000 squaremetres 185 000 sq.ft some 150 scientistsengineers and support staff are engaged inthe further improvement of bearing perform-ance. They are developing technologiesaimed at achieving better materials betterdesigns better lubricants and better seals – together leading to an even better unders-tanding of the operation of a bearing in itsapplication. This is also where the SKF New Life Theory was evolved enabling thedesign of bearings which are even morecompact and offer even longer operationallife.1Industrial gearboxes – overviewTypes of gearbox . . . . . . . . . .9Geared transmission . . . . . .10Demands on gearboxes . . .14Selecting the gears . . . . . . .14Designing the casing . . . . . .159Industrial gearboxes –overviewGearboxes are devices for the transmission ortranslation of movement. In industry gearboxesare used to transform the speeds and torquesproduced by the prime mover in order thatthey are appropriate to the machine which is tobe driven. The speeds and torques required bythe machine are dictated by its use. Primemovers can generally only meet these require-ments when combined with gears.Types of gearboxGearboxes are characterised by havingat least three members: the power in-put power take-off and the casing. Thecasing transmits the support momentto the base.In contrast a coupling has y twomembers: the power input and power1Industrial gearboxes –onl overviewTypes of gearboxP1M1PVP2M2n2n1P2P1M2PvM1n1n2take-off. The coupling housing has nopart in the flow of force.The symbols used for powertransmission by gearboxes and coup-lings are shown in figsand .FigFigGearTorqueM1ltM2gtRotational speedn1?n2gtPowerP1P2 PvCouplingTorqueM1M2Rotational speedn1?n2PowerP1P2 Pvwith slipGeared transmissionsGeared transmissions are the mostcommonly used. They transmit powerwithout slip have high operational re-liability and long life require little main-tenance and are characterised by theability to accept overloading small sizeand high efficiency.Spur gearsThe spur gear is the most well-knownand commonly used design of gearedtransmission. The dimensioning andmanufacture of the gear wheels arethe easiest to control. Their kinematicbehaviour also forms the basis of plan-etary gears. Spur gears are in rollingcontact and irrespective of tooth typehave parallel axes.1Industrial gearboxes – overviewGeared transmissions10The main types ofpower transmis-sion equipmentare shown in thefollowing.In addition thereare many com-binations for ex-ample bevel/spurgears spur gearswith belt drive inputor variable tractiondrives combinedwith a planetarygear.Types of gearboxFixed ratio transmissions shift transmissionGeared transmissions?? Spur gears?? Planetary gears?? Bevel gears?? Worm gears?? Hypoid gears?? Helical gearsEccentric drives?? Cyclo drives?? Harmonic drivesTraction drives?? Belt drives?? Chain drivesInfinitely variable transmissionsMechanical transmissions?? Belt drives?? Roller drives?? Ratchet gearsHydraulic transmissions?? Hydrostatic transmissions?? Hydrodyanmic transmissions?Gear wheels with straight cut teeth??figa are simple in designand can be accurately produced.The axial forces generated by in-accuracies and deformations twisting are negligible.?Gear wheels with helical teeth ??figb run more smoothly andcan carry heavier loads than thosewith straight cut teeth. A more elab-orate bearing arrangement is re-quired because of the axial forces.?The double helix or herringbone ??figc allows for large toothwidths and can carry particularlyheavy loads. The axial forces canceleach other out. Deviations in thehelix angle cause axial vibrations.?Internal gearing ??figd hasgreater load carrying capacity thanexternal because of the favourableosculation but is more difficult toproduce. The bearing arrangementis more complicated. The most fre-quent use is in planetary gears.Bevel gearsThe common characteristic of this type of rolling contact gearing is thatthe axes of the wheels intersect eachother. There are three basic designscategorised by the form of the flank.?With straight cut teeth ??figathe mesh begins and ends acrossthe total tooth width. The noise pro-duced considerably limits the use-fulness of straight cut bevel gears.?Bevel gears with helical teeth ??figb have straight flanks.The teeth are usually ground andthe mesh is gradual. The total over-lap is bigger and the noise behav-iour better than with straight cutteeth.?Bevel gears having spirally cut teeth??figc with curved flanks haveclear advantages in respect of loadcarrying capacity. Particularly thosewith ground teeth are quieter thanthe types described above. Forbevel gears which have to transmithigh power the spiral bevel gearsare the most frequently used.Spur gear unitastraight cut teethbhelical teethcdouble helixdinternal gearing111Industrial gearboxes – overviewGeared transmissionsFigFigabcdBevel gear unitastraight cut teethbhelical teethcspirally cut teethabc1Industrial gearboxes – overviewGeared transmissionsWorm gearsThe worm and wheel axes cross eachother at a considerable distance andusually at an angle lt 90???fig.Worm gears are suitable for large single stage speed reduction. Theiroperation is quiet and vibration damp-ing. The efficiency is lower than that ofcompeting bevel/spur and planetarygears because of the higher propor-tion of sliding motion. To reduce thefriction the use of synthetic lubricantsis favoured.The most commonly used design isthe cylindrical worm paired with a glob-oid wheel ??figa. The cylindricalworm can be hardened and groundwhich improves load carrying capacityit is also freely adjustable in the axialdirection so that bearing arrangementand mounting can be simplified. Twoother designs – globoid worm with spurwheel ??figb and globoid wormwith globoid wheel ??figc– arealso used.Depending on the flank form theworm types are classified as follows:?ZA worm: trapezoidal worm threadin the axial cross section?ZN worm: trapezoidal worm threadin the normal cross section?ZK worm trapezoidal tool in normalcross section?ZI worm evolvent thread in end facecross section?ZC worm: concave worm flanksHypoid gearsThe pinion axis is displaced so that theaxes of this type of bevel gear do notintersect but are crossed ??fig.The wheels of hypoid gears are usu-ally spirally cut. The advantages of thistype of gear derive from the larger pin-ionand thus the smaller circumferentialforce for the same torque as well asfrom the axis displacement which oftenallows the pinion to be supported atboth sides so that the bearing arrange-ment is stiffer. The noise behaviour isalso improved by the sliding motion inthe longitudinal direction of the teeth.However the additional sliding motionincreases the friction wear and risk of smearing and requires the use ofhypoid oils with high additive content.12FigHypoid gear unitFigabcWorm gear unitacylindrical wormwith globoidwheelbgloboid wormwith spur wheelcgloboid wormwith globoidwheelHSPZThe ZI and ZC designs are the mostpopular. The ZI worm can be very ac-curately ground whilst the favourableosculation conditions of the ZC wormconcave worm convex wheel bringload carrying advantages.Planetary gearsFrom the point of view of the toothflanks planetary gears are mostly spurgears. In contrast to the spur gear unitsso far described the shafts of whichare supported in stationary casingsthe planetary gear unit has gear wheelswhich circulate. They are also referredto as epicyclic gears.In the simplest design ??figwhich is that most commonly used inindustry the sun wheel drives the plan-etary wheels when acting as a speedreducer. These are supported in thehollow wheel and drive the planetarycarrier from which the power is takenoff.Planetary gears have the followingimportant advantages compared withconventional spur gear units:?the volume weight and centrifugalmass are smaller?the rolling and sliding velocities inthe mesh are lower so that noise isreduced?some of the power is transmitted ascoupling power so that efficiency ishigher.These advantages have led to a continuous increase in the economic importance of planetary gear units inspite of their disadvantages whichinclude more difficult inspection main-tenance and repairs.1Industrial gearboxes – overviewGeared transmissionsSimple planetarygear unit prin-cipleZsun wheelPplanetary wheelHhollow wheelSplanetary carrier13FigDemands made on gearboxesThe most important demands whichmust be fulfilled are:?there must be a sufficient safetymargin in respect of fatigue and/orrequisite life for all components sothat the torques and speeds can bereliably transmitted?there must be sufficient cooling evenunder maximum power transmissionconditions?noise emission should not exceedthe permitted limits.In addition to these demands specialrequirements in respect of operationand design are dictated by the variousapplications. Some examples:?radial and/or axial forces on the in-put and output shafts e.g. for ex-truders?external forces on the casing e.g. inmining?heavy impacts torque peaks e.g.when driven by single cylinder com-bustion engines or when drivingbucket excavators?vibrations e.g. in wire drawing?extreme environmental influences in respect of temperature dirt dustwater e.g. in arctic or tropical opencast mining and in continuous cast-ing plant?seals subjected to pressure.