~.~TheEngineering Society~ ForAdvancing Mobility~ LandSeaAirandSpace 400COMMONWEALTH DRIVEWARRENDALE, PA15096 hnica~ m rrlS 861355 Automotive Traction DriveCVTs­ AnOverview lubomyr O.Hewko PowerSystems Research Dept. General MotorsResearch Laboratories Passenger CarMeellng&Exposilion Dearborn. Michigan September 22-25.1986Downloaded from SAE International by Imperial College London, Saturday, September 08, 2018Theappearance ofthecodeatthebotlomofthefirstpageofthispaperindicates SAE'sconsentthatcopiesofthepapermaybemadeforpersona! orintern;:!use,or forthepersonal orinternaluseofspecificclients.Thisconsent isgivenonthecon~ dition,however, thatthecopierpaythestatedperarticlecopyfeethrough the Copyright Clearance Center,Inc.,Operations Center,P.O.Box765,Schenectady, N.Y.12301,forcopying beyondthatpermitted bySections 107or108oftheU.s. Copyright Law.Thisconsent doesnotextendtootherkindsofcopying suchas copying forgeneral distribution, for.advertising orpromotional purposes, for creating newcollective works,orforresale. Paperspublished priorto1978mayalsobecopiedataperpaperfeeof$2.50 undertheabovestatedconditions. SAEroutinely stocksprintedpapersforaperiodofthreeyearsfollowing dateof publication. DirectyourorderstoSAEOrderDepartment Toobtainquantity reprintrates.permission toreprintatechnical paperorper~ mission tousecopyrighted SAEpublications inotherworks,contact theSAE Publications Division. All$Afp.:pmal'abu;':,lro andinund ilttit,·SAt."GI"bal,I/"Nliry- DJlabau Nopartofthispublication maybereproduced inanyform,in anelectronic retrieval systemorotherwise, without theprior writtenpermission ofthepublisher. ISSNOI48-7191 Copyright ©1987SocietyofAutomotive Engineers,lnc. Thispaper-issubjecttorevision. Stalemertts andopinions ad­ vancedinpapersordiscussion aretheauthor's andarchis responsibility. notSAE's;howcvcr. thepaperhasbecnedited bySALforuniform stylingandformat. Discussion willbe printedwiththepaperifitispublished inSAlTransactions. rorpermission topublishthispaperinfuUorinpart. conta~·t theSAl::Publications Division.Persons wishing tosubmitpaperstobeconsidered forpre­ sentation orpublication through SAEshouldsendthemanu­ scriptora300wordabstract ofaproposed manuscript to: Secretary. [nt-rinccring Activity Board.SA£. PrintedinU.S.A.Downloaded from SAE International by Imperial College London, Saturday, September 08, 2018861355 Automotive Traction DriveCVTs_ AnOverview Lubomyr O.Hewko PowerSystems Research Dept. General MotorsResearch Laboratories ABSTRACT Thispaperisbasedonaprepared discus­ sionwhichwaspresented attheCVTPanel(Ses­ sion#lPC26) duringthe1985SABInternational Congress andExposition. Thepaperreviews the hackground ofthisratherintriguing classof variable-ratio mechanical drivesandbriefly summarizes thepastworldwide research whichled tothedevelopment ofseveral automotive trac­ tiondriveCVTs.ThefttoricnCVT,whichwasa subject ofextensive research anddevelopment effortatGeneral Motorsandelsewhere, isused asanexample forillustrating typicaltraction drivecharacteristics. Further) discussion is presented ofthedesirable attributes oftrac­ tiondrives, aswellasofthevarious technical Concerns arising fromthepowertransfer through traction forcesofarolling contact undercon­ ditions uniquetoautomotive transmission appli­ cations. Thecurrentstate-of-the-art traction drivetechnology andseveral newdevelopments in theareaofautomotive traction driveCVTs, reported inrecentliterature, arealso discussed. TRACTION DRIVESareneither newnorrare.A steelwheelpropelling alocomotive alongarail oratiredriving acaronthepavement are probably theearliest andmostfrequently seen examples oftraction drives. Theseare,how­ ever,fixed-ratio drivesandcanonlybecome continuously variable-ratio transmissions, or CVTs,iftheradiusatwhichthetractive force actscanhevaried. Agoodexample ofasimple traction driveCVTisarubberrollerdriving, bytraction, asteeldisc.Bymovingtheroller further fromorclosertothecenterofthe disc,thedriveratiocanbechanged inacon­ tinuous manner