MODERNIZATION of MAIN HELICOPTER GEARBOX with ASYMMETRIC TOOTH GEARS

Transcription

1 Proceedings of the ASME 2013 Interntionl Design Engineering Technicl Conferences & Computers nd Informtion in Engineering Conference IDETC/CIE 2013 August 4-7, 2013, Portlnd, Oregon, USA DETC MODERNIZATION of MAIN HELICOPTER GEARBOX with ASYMMETRIC TOOTH GEARS Sergey I. Shnkin Zporozhye, Ukrine Alexnder A. Stupkov Zporozhye, Ukrine Igor L. Glikson Zporozhye, Ukrine Dr. Vicheslv M. Anniev CIAM Moscow, Russi Dr. Alexnder L. Kpelevich AKGers, LLC Shoreview, MN, USA ABSTRACT This pper descries the reserch nd development of symmetric tooth spur gers for moderniztion of the light multipurpose helicopter gerox mplifying its lod cpcity to utilize more powerful turoshft engines. The pper lso presents numericl design dt relted to development this gerox. INTRODUCTION Erly prior reserch demonstrted the superiority of cermics for erings (1, 2) nd the existence of elstohydrodynmic (ehd) luricnt films t ll nd roller contcts (3), the clcultion of which is now n ccepted prt of ering engineering. These new concepts re now used in the design of luriction systems with solid luricnts tht operte in much more severe environments thn oils nd greses (4, 5). Proprietry computer codes nd unique ptented ering configurtions for optimizing the performnce of ering/solidluricnt systems hve een developed (6, 7 nd 8). In this wy, ptented self-contined solid-luricted ll-steel nd hyrid-cermic ll nd roller erings re now ville for environments tht do not contriute to their luriction, such s in ir or vcuum. trnsmission density, potentilly incresing their lod cpcity, nd reducing size nd weight. However, there re not mny prcticl implementtions of such gers. One of such ppliction of symmetric gers in the turoprop engine gerox is descried in the pper [1]. Then the gerox ws developed from scrtch for new engine nd new ircrft. Although, there re cses of upgrde of existing ircrfts with more powerful engines tht require higher lod cpcity geroxes. One of such cse is descried in this pper. Light multipurpose helicopter ws upgrde with new turoshft engines tht required moderniztion of the min gerox to oost its lod cpcity within existing size, weight, nd lifetime limittions, keeping sufficient sfety fctors nd reliility. This tsk ws solved y implementtion of spur gers with the symmetric tooth profiles in the most loded second nd third stges of the gerox. The pper lso presents design nd performnce dt of modernized symmetric gers in comprison with originl symmetric gers. GEARBOX ARRANGEMENT The helicopter min gerox rrngement [2] is shown in the Fig. 1. NOMENCLATURE Appliction of symmetric tooth gers for erospce propulsion drives llows to considerly increse power 1 Copyright 20xx y ASME

2 Fig. 1. Min gerox rrngement; 1 engine turine shfts, 2 min propeller shft, 3 shft to the til propeller; z 1 1 st stge evel pinions, z 2 1 st stge evel gers, z 3 2 nd stge pinions, z 4 2 nd stge gers, z 5 3 rd stge pinions, z 6 3 rd stge ger, z 7 til drive spur ger, z 8 til drive evel pinion, z 9 til drive evel ger. Power of two turoshft engines is trnsmitted y the turine shfts 1 through the evel gers z 1, z 2 nd then the spur gers z 3, z 4, nd z 5 to the ull ger z 6 connected to the min propeller shft 2. Aout 25% of one of the engine power is used to drive the til propeller through the spur ger z 7 nd the evel gers z 8, z 9. The originl evel ger pirs hd sufficient lod cpcity to withstnd incresed power of new engines nd were not required ny moderniztion. The 2 nd nd 3 rd stge spur gers hd to e redesigned to reduce contct stress level nd sufficient tooth flnk surfce durility. GEAR TOOTH GEOMETRY nd STRESSES The originl spur gers were designed trditionlly using the preselected sic rck nd its ddendum modifiction (Xshift). The modernized spur gers with symmetric teeth were constructed using the Direct Ger Design method [3]. Min prmeters of the originlly designed nd Modernized spur gers re presented in the Tle 1. Tle 1 2nd Stge Numer of Pinion Ger Center Distnce Bsic Rck Module 5.5 N/A Addendum Pinion 0.5 N/A Modifiction Ger N/A Operting Module Bsic Rck Pressure Angle 20 N/A Operting Pressure Angle /20 * Operting Contct Rtio /1.59* 3rd Stge Numer of Pinion Ger Center Distnce Stndrd Module 8.0 N/A Addendum Pinion 0.22 N/A Modifiction Ger N/A Operting Module Stndrd Pressure Angle 28 N/A Operting Pressure Angle /20 * Operting Contct Rtio /1.57* *Drive/Cost tooth flnk, N/A not pplicle Prmeters of symmetric teeth were selected to stisfy the following requirements: - Drive flnk pressure ngle should not exceed 32 o to limit the mximum rdil lod nd keep originl erings; - Minimum drive flnk contct rtio is 1.3; - Minimum tooth tip thickness is 2.3 mm for the 2 nd stge gers nd 3.1 mm for the 3 rd stge gers to void the hrden through tooth tip; - Minimum cost flnk pressure ngle in the 2 nd stge is 20, ecuse the cost flnks of one of the ger ox rnch re used to trnsmit toque to the til propeller; - The tooth root fillet is not ground fter het tretment. Its profile should not interfere with the grinding wheel trjectory. Prior to het tretment, the ger teeth were mchined leving the grinding stock out 0.20 mm on the tooth flnks nd providing finl root fillet profile. Non-ground tooth root fillet remins residul compressive stress fter het tretment, which increse tooth ending strength. This required the ger hos with protuernce. However, due low numer of the pinion teeth of oth the 2 nd nd 3 rd stges these hos could not provide required tooth root fillet surfce finish tht reduces locl stress concentrtion nd crck initition proility. This hppens ecuse the fillet surfce of low tooth numer gers is generted with fewer numer of cuts thn one for gers with greter numer of teeth. In order to solve this issue, the pinion flnks were mchined with conventionl hos (without protuernce) nd then, efore ger het tretment, the pinion root fillets were ground. The 2 nd stge pinion tooth profiles efore nd fter het tretment re shown in the Fig. 2. Fig. 2. The 2 nd stge pinion tooth profiles; originl symmetric, symmetric; 1 fter het tretment nd flnk grinding, 2 efore tretment, 3 root fillet grinding wheel. Prior to het tretment, the gers of oth the 2 nd nd 3 rd stges were mchined with the protuernce hos. The 3 rd stge ger 2 Copyright 20xx y ASME

3 tooth profiles efore nd fter het tretment re shown in the Fig. 3. Fig. 3. The 3 rd stge ger tooth profiles; originl symmetric, symmetric; 1 fter het tretment nd flnk grinding, 2 efore tretment, 3 profile of ho with protuernce. Geometry of symmetric teeth does not llow using the trditionl Lewis eqution to define the tooth ending stress. The FEA suroutine integrted in the Direct Ger Design softwre ws used for comprison symmetric nd symmetric ger tooth ending stresses. Exmples, of the finite element mesh nd stress isogrms re presented in the Fig. 4. Fig. 4. The 3 rd stge pinion tooth finite element mesh nd stress isogrms; originl symmetric, symmetric. The drive flnk contct stresses were clculted y the Hertz eqution. Stress nlysis results re shown in the Tle 2. Tle 2 2nd Stge Numer of Pinion Ger Fce Width Pinion Ger Pinion Torque, Nm Pinion RPM Mx. Contct Stress, MP (-9%) Mx. Bending Pinion (-9%) Stress, MP Ger (-4%) 3rd Stge Numer of Pinion Ger Pinion Ger Pinion Torque, Nm Pinion RPM Mx. Contct Stress, MP (-6%) Mx. Bending Stress, MP Pinion (-4%) Ger (-2%) GEAR MATERIAL nd MANUFACTURING All gers re mde of the forged lnks of the steel 16H3NVFMB (VKS-5, DI-39). Its chemicl composition includes: Fe - se mteril, C %, Si %, Mn %, Cr %, Ni %, S - <0.025%, P - <0.025%, Cu - < 0.30%. The ger lnks position during mchining must provide the symmetric teeth pointed in certin direction (clockwise or counterclockwise). Otherwise, the drive flnk of one ger will e positioned in contct with the cost profile of the mting ger tht mkes ssemly impossile. After the tooth cutting the gers re crurized nd hettreted to chieve tooth surfce hrdness HRC with the cse depth of mm. The core tooth hrdness is HRC. Finl ger mchining includes tooth grinding nd honing. Asymmetric gers require specil setup for oth these opertions. The compound ger tht contins the 2 nd stge ger nd 3 rd stge pinion is shown in the Fig. 5. In this compound ger the 2 nd stge ger is driven nd 3 rd stge pinion is driving. For the symmetric version of compound ger (Fig. 5) this mens tht symmetry directions (tooth inclintions) of those ger nd pinion e opposite nd in reltion to ger rottion direction. This is criticl for proper gerox ssemly. 3 Copyright 20xx y ASME

4 Fll Technicl Meeting, Milwukee, Wisconsin, Octoer 18-19, (10FTM14). Fig. 5. Compound ger; originl design with symmetric teeth, modernized design with symmetric teeth. SUMMARY - Appliction of the symmetric tooth gers in the most loded 2 nd nd 3 rd spur ger stges of the min helicopter gerox llowed to reduce contct stress y 9% nd 6% ccordingly nd rech cceptle drive flnk durility without increse of mjor ger dimensions. - Requirement of the non-ground tooth root fillet did not permit to utilize its profile optimiztion [3] nd, s result, the ending stress reduction provided y symmetric teeth is not significnt. - Replcement the originlly used spur symmetric tooth gers for the gers with symmetric teeth llowed to utilized more powerful nd fuel efficient turoshft engines without complete redesign of the helicopter gerox. - As hs een demonstrted y the similr type of symmetric nd symmetric ger comprtive testing [4], the ctul lod cpcity difference provided y symmetric gers could e noticely greter tht nlyticlly predicted. - Asymmetric tooth gers require the dedicted cutter (ho) for ech of mting gers tht could e considered s limittion for their wider pplictions. REFERENCES [1] A.S. Novikov, A.G. Pikin, V.L. Dorofeyev, V.M. Anniev, A.L. Kpelevich, 2007, Appliction of Gers with Asymmetric in Turoprop Engine Gerox, 10th Interntionl ASME Power Trnsmission nd Gering Conference, Septemer 4-7, Ls Vegs, Nevd, USA. [2] E. B. Vulgkov et l., 1981, Avition Geroxes, Hndook, Mshinostroenie, Moscow, (in Russin). [3] A.L. Kpelevich, 2013, Direct Ger Design, CRC Press, Tylor Frncis Group [4] F.W. Brown, S.R. Dvidson, D.B. Hnes, D.J. Weires, nd A. L. Kpelevich, 2010, Anlysis nd Testing of Gers with Asymmetric Involute Tooth Form nd Optimized Fillet Form for Potentil Appliction in Helicopter Min Drives, AGMA 4 Copyright 20xx y ASME

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