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1、04FTM13 Superfinishing Motor Vehicle Ring and Pinion Gears by:L. Winkelmann, J. Holland and R. Nanning, REM Chemicals, Inc. TECHNICAL PAPER American Gear Manufacturers Association Copyright American Gear Manufacturers Association Provided by IHS under license with AGMA Licensee=IHS Employees/1111111
2、001, User=Wing, Bernie Not for Resale, 04/18/2007 11:25:45 MDTNo reproduction or networking permitted without license from IHS -,-,- Superfinishing Motor Vehicle Ring and Pinion Gears Lane Winkelmann, Jerry Holland and Russell Nanning, REM Chemicals, Inc. The statements and opinions contained herein
3、 are those of the author and should not be construed as an official action or opinion of the American Gear Manufacturers Association. Abstract Today,themotorvehiclemarketisfocusingon”lubedforlife”differentialsrequiringnoserviceforthelifeofthe vehicle. Still,differentialsarepronetodevelopproblemsofon
4、esortoranothersincetheyareusedtotransmit aheavytorquethrougharightangle. Oneweakpointinthedifferentialistheringandpiniongearset. Assuch, a proper break-in period is essential to attain the required service life. Break-in is an attempt to smooth the contact surfaces of the gears and bearings through
5、controlled or limited metal-to-metal contact.The roughness of the contact surfaces is reduced during this process until a lower and relatively stable surface roughness is reached. The lower surface roughness is advantageous, but irreversible metallurgical and lubricant damage occurs since break-in a
6、lways results in stress raisers, metal debris and an extreme temperature spike. Break-in and its negative effects can be eliminated with chemically accelerated vibratory finishing. When this method isused tosuperfinish ground(AGMA Q10)or lapped(AGMA Q8)ring andpinion gearsets to less than 10 min.Ra,
7、 the life of the lubricant, bearings and gears is significantly increased. Just a few years ago, this technology was considered impractical for high production volume OEM ring and pinion gearsets due to lengthy processing times. This superfinishing technology also had difficulties preserving the geo
8、metry of rough lapped gears, which required more stock removal than finely ground aerospace gears (AGMA Q12+). As a result the transmission error of these gears was increased leading to unacceptable noise. The superfinishing technology discussed in this paper overcomes these obstacles and meets the
9、needs of the motor vehicle industry.Gear metrology, contact patterns, transmission error and actual performance data for superfinished gearsets will be presented along with the superfinishing process. Copyright 2004 American Gear Manufacturers Association 500 Montgomery Street, Suite 350 Alexandria,
10、 Virginia, 22314 October, 2004 ISBN: 1-55589-836-X Copyright American Gear Manufacturers Association Provided by IHS under license with AGMA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 04/18/2007 11:25:45 MDTNo reproduction or networking permitted without license from IHS -,
11、-,- 1 Superfinishing Motor Vehicle Ring and Pinion Gears Lane Winkelmann, Jerry Holland and Russell Nanning, REM Chemicals, Inc. Introduction Break-In Process Vehicular differentials are apt to develop problems of one sort or another since they are used to trans- mitaheavytorquethrougharightangle. A
12、differen- tial consists of a ring gear, pinion gear, side gears, spider gears, and bearings. See Figure 1. The spi- ral bevel or hypoid gearsets can be a weak point in the differential since they need to withstand large sliding pressures and shock loading.Over the years, many improvements have been
13、made to dif- ferentials such that now many require no mainte- nance (i.e., “lubed for life”). New ring and pinion gears are not normally ground after carburization, but rather are lapped at the factory and maintained as a matched gearset. Lapping partially corrects the distortion which occurs during
14、 carburization, and therefore somewhat reduces the operating temperature,wearandnoise. Itisimpractical,how- ever, to perform the lapping under the same loads asthosewhichareexperiencedunderactualdriving conditions.Therefore, ring and pinion gearsets must alwaysgo througha “break-in”cycle, whichis pr
15、ofessed by car experts as the magic potion for preventing future failure. As one expert puts it, im- proper break-in results in a differential lasting 90,000miles,andproperbreak-inresultsinadiffer- ential lasting, 180,000 miles. Key 1Ring 2Pinion 3Shims 4Housing 5Side gears 6Spider gears Figure 1. E
16、xploded view of a differential pointing out the various parts discussed in this paper. Copyright American Gear Manufacturers Association Provided by IHS under license with AGMA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 04/18/2007 11:25:45 MDTNo reproduction or networking p
17、ermitted without license from IHS -,-,- 2 Break-in is an attempt to create a smooth surface on the contact surfaces of the gears and bearings through controlled or limited metal-to-metal con- tact.The roughness of the contact surfaces changes during this process until a lower and rela- tively stable
18、 surface roughness is reached. During the break-in cycle, it is hoped that the lubrication of the ring and pinion gearset is maintained. In fact, this is vital to the life of the differential. During the initial start-up of the break-in cycle, an oil film is formedonthesurfacebetweenthegearteeth. Th
19、is filmisreferredtoasHydrodynamicorFullFluidFilm Lubrication, which completely separates the ring from the pinion so that there is no metal-to-metal contact.As the speed of the ring and pinion in- creases, the hydrodynamic layer thickens as well. Asaload,however,isplacedonthegearset,thehy- drodynami
20、c layerdecreases. At thesame time,the temperature rises and the viscosity of the lubricant decreases, which further decreases the film thick- ness. As the load and/or temperature continue to increase, the lubricant film becomes too thin to pro- videtotalseparation. Contactbetweenthepeakas- perities
21、occurs, which results in higher frictional forces and the concomitant temperature rise. This is referred to as the Boundary Lubrication or Thin Film Lubrication regime. The break-in process is an attempt to maintain the temperature low enough toprovideboundarylubricationuntilthepeakasper- ities are
22、worn away leaving the lower and relatively stable surface roughness on the contact surfaces. In order to understand the shortcomings and mis- conceptionsconcerningbreak-in,itisworthwhileto briefly examine what advice the experts are giving totheenduser. Althougheveryexperthashisorher own recipe for
23、break-in, the following is fairly typical: All new ring (2) measurements of the contact patterns; and (3) single flank testing. Direct Measurement of Stock Removal Figure 4 shows the relative stock removal normal- ized to unity across the flank of the gearsets super- finished using Media A and Media
24、 B. From these charts,itisapparentthatMediaAdistortstheprofile by removing more stock from the flank of the gear nearer the tip than the root, but does not negatively affectthespiral. Therefore,itisexpectedthatgears superfinished with this media mixture will have a higher transmission error leading
25、to an increase in noise. On the other hand, Media B does not distort thespiralortheprofile,butremovesstockuniformly from the tip to the root and across the spiral. The small variations seen in the Media B charts are due toslightmeasurementinaccuracies. Therefore,itis expected that the transmission e
26、rror will not be in- creased. This will be shown and discussed in more detail later. Copyright American Gear Manufacturers Association Provided by IHS under license with AGMA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 04/18/2007 11:25:45 MDTNo reproduction or networking per
27、mitted without license from IHS -,-,- 6 Figure 4: Relative stock removal normalized to unity using Media A and Media B. Contact Patterns GroupIcontactpatternsweremeasuredforthefour gearsets to ensure proper alignment and position- ing. The gearsets were theninstalled ina DANA44 housing which had bee
28、n modified for use in the Loaded Bevel Gear Test Rig at the Gear Dynamics and Gear NoiseResearch Laboratoryat OhioState University.General Motors marking grease was used to coat the gearsets. They were then rotated by hand in both the forward and reverse directions until a clear contact pattern was
29、developed on the ringgear. The contactpattern foreach gearsetwas then checked to determine if the superfinishing had altered or caused a contact pattern to become un- Copyright American Gear Manufacturers Association Provided by IHS under license with AGMA Licensee=IHS Employees/1111111001, User=Win
30、g, Bernie Not for Resale, 04/18/2007 11:25:45 MDTNo reproduction or networking permitted without license from IHS -,-,- 7 acceptable. Though there were some very slight deviations from the baseline contact pattern, all contact patterns before and after superfinishing were found to be acceptable. Gro
31、up II gearsets were superfinished identically to those tested at the Gear Dynamics and Gear Noise Research Laboratory. The contact patterns of be- fore and after superfinished gearsets were mea- sured at The GleasonWorks. Again, thelaboratory reported no change in the contact patterns aftersu- perfi
32、nishing. The contact patterns are displayed in Figure 5. Figure 5. Contact patterns of Group II gearsets as determined at The Gleason Works. Single Flank Testing Single flank transmission error testing was con- ducted on Group I gearsets at the Gear Dynamics and Gear NoiseResearch Laboratoryat OhioS
33、tate University. Their Loaded Bevel Gear Test Rig was used to measure the transmission error (TE) with the gearsets mounted in an actual differential hou- sing. This was donein orderto measurethe TEun- derlight loadas wellas underloading sothat theef- fect of friction on noise/vibration could also b
34、e determined.Unfortunately, technical difficulties Copyright American Gear Manufacturers Association Provided by IHS under license with AGMA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 04/18/2007 11:25:45 MDTNo reproduction or networking permitted without license from IHS -,
35、-,- 8 were encountered such that the TE could only be measuredunder lightloading. Only aranking ofthe TEcouldbederivedfromtheirdata. Ablindtestwas conducted such that the testing laboratory did not know the history of the gearsets. See Table 2. Although variation in the test results were reported fr
36、om the assembly/disassembly and alignmentpro- cesses, the rankings are noteworthy and expected. The gearset with non-uniform stock removal by superfinishing with Media A had the highest TE. Interestingly, gearsets No.3 and 4 with uniform stock removal by superfinishing with Media B had the lowest TE
37、, and were even better than the raw lappedgear. Atthistime,thereisno explanationfor this latter result. In an effort to verify the previously measured noise/ vibrationresults,TheGleasonWorksmeasuredthe TE on the Group II gearsets beforeand aftersuper- finishingusingthe552GleasonSingleFlankTester. Th
38、e changes in transmission error (TE Before Su- perfinishing TE After Superfinishing) is shown in the last chart of Figure 6. It is apparent that Media A significantly increases theTE. Ontheotherhand,MediaBhasproventhat even a 4.0 min. Racan be achievedwithout anyper- ceptible noise level. It is also
39、 clear that an accept- ablecontactpatternisnoguaranteethattheTEhas not increased. Table 2: Results of Single Flank Testing on Group I gearsets at the Gear Dynamics and Gear Noise Research Laboratory Description of Surfaces Tested Transmission Error Ranking LowestHighest 1234 Raw Lapped Baseline3 Sup
40、erfinished using Media A to a 4.0 min. Ra. 4 Superfinished using Media B to a 10.0 min. Ra. 2 Superfinished using Media B to a 4.0 min. Ra. 1 Figure 6. TE measurements of Group II gearsets by The Gleason Works. Copyright American Gear Manufacturers Association Provided by IHS under license with AGMA
41、 Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 04/18/2007 11:25:45 MDTNo reproduction or networking permitted without license from IHS -,-,- 9 Performance Testing Laboratory Testing: Automotive OEM Ring and Pinion:Several years ago, ring and pinion gearsets were superfin- ishe
42、d using Media A for an OEM automotive ap- plication to evaluate the effect of superfinishing on operating temperature. This superfinished gearset was compared toa standardcarburized andlapped gearset using the L-37 (ASTM D6121) Perfor- mance of Gear Lubricants at High Speed, Low Torque, Followed by
43、Low Speed, High Torque. The L-37 test is used by individual OEMs, the Military, and Federal Government, to measure five parame- ters that are the result of distress on gears. The re- sults are shown in Figure 7.The superfinished gearset had apeak temperatureof 124C whilethe standard gear had a peak
44、temperatureof 165C. It is assumed that the slight temperature increase in the initial phase of the testing of the superfinished gearset is attributable to bearing break-in. The ab- sence of a large temperature spike during break-in eliminatesthepossibilityofanythermaldegradation ofthelubrication. It
45、 isalso indicativethat thesuper- finishedgearsetdoesnotgeneratedamagingmetal debris and will have significantly lower wear throughout its service life. This same phenomenon was observed a number of years ago for superfin- ished bearings by The Timken Company. 8 9 In a separate study 6, Sikorsky Airc
46、raft Corpora- tion tested superfinished second stage spiral bevel gears (Q12+), third stage pinion gears and the bull gearoftheirS-76C+,LowNoiseTransmissiontoan Raof less than 4.0 min. The standard ground sur- faces of these gears have a nominal Raof approxi- mately15min. Theresultsofthestandardtwo-
47、hour Acceptance Test Procedure (ATP) are shown in Figure 8. This test is mandatory for all gearboxes priortoflightapproval. Assuch,thebaselineresults shownarefromthreestandardproductiongearbox- es. The superfinishedgearbox wasrun throughthe ATP three separate times. This is indicated by the multiple
48、 data points at the same torque loading. It should be noted that this test is conducted using an oil recirculation system and an externalcooler. The temperature is measured on the outflow side. Again, it is seen that the superfinished gears had a very significant temperature drop in comparison withgearshavingthestandardgroundsurface. The superfinished gears showed no damage or wear uponfinalinspection. As aresult oftheir testing,Si- korsky has licensed this flight certified superfinish- ing technology. This data is presented here to ex- empl