1、 STD.AGMA SbFTM3-ENGL 1996 Ob87575 OOOLi59 235 96FTM3 Noise Reduction Through Generated Engagement Relief Modification I by: Dr.-Ing. Werner Kie and Stephen Price, Hfler Maschinenbau GmbH TECHNICAL PAPER STD-ALMA SbFTM3-ENGL LS9b b87575 00048b0 T57 Noise Reduction Through Generated Engagement Relief
2、 Modification Dr.-Ing. Werner Kje and Stephen Price, Hfler Maschinenbau GmbH nie statements and opinions contained herein are those of the author and should not be construed as an officiai action or opinion of the American Gear Manufacturers Association. Abstract For years, the international gear ma
3、nufacturing industry has been pushing machine manufacturers to develop an economical realizable tooth flank modification that is made in contact direction, with a soft transfer from the modified to unmodified sections of the tooth. To meet these demands, Hfer has developed, and is already implementi
4、ng, Generated Engagement Relief Modifications. The tooth flank is modified at the areas of engagement only as opposed to the entire tooth flank as is the case with conventional modifications. The paper will disaiss the advantages of this new technology over conventional modifications and discuss how
5、 to produce generated engagement relief modifications. copyright o 19% American Gear Manufacturers Association 1500 King Street, Suite 201 Alexandria, Virginia, 22314 October, 1996 ISBN: 1-55589-670-7 STD - AGMA SbFTM3-ENGL LSb m b87575 D48bL 773 NOISE REDUCTION THROUGH GENERATED ENGAGEMENT RELIEF M
6、ODIFICATIONS Dr. Ing. Werner Kie Stephen Price HFLER Maschinenbau WH D-76275 Ettlingen Introduction It would be impossible to imagine todays world and our society without gears. Gear drive systems are still the most common mechanical element used to transfer power, adjust rotational speeds or change
7、 its direction. Gears can be designed to fulfill every possible axial position, power requirement, rpm, speed or transfer ratio. They are reliable, very efficient and, con- sidering what they deliver, very compact. Despite all of this, the gear manufacturing industry is constantly under pressure to
8、reduce the size, increase the service life, reduce the noise emissions and improve the transmission accuracy of power drive trains. The development of new wear and thermal resistant cutting mate- rials and tool coatings have strengthened the trend towards the fine machining of hardened gears and the
9、 development of new fine machin- ing processes. Deep feed gear grinding, developed for CNC con- trolled index generating gear grind- ers, for instance, has improved the productivity crf these machines many fold. Computer numerical controls (CNC) have replaced almost all mechanical generation couplin
10、gs in gear manufacturing machines. Intel- ligent, multi-axial controls take over the machine setup, including infeed and modification movements. This has resulted in increased accuracy, flexibility and productiv- ity. These benefits are also realized for small workpiece lot sizes and even single gea
11、rs. Gear design and quality assurance are also affected by new develop- ments. Powerful calculating and simulation programs are now in use. These programs are made possible by recent advances in data processing. This is especially true in the areas of programming tools and computer speed. The demand
12、 for reliable, accurate and objective measuring and assessment processes for quality 1 control helped push the development of CNC controlled gear inspection equipment and control software. In connection with these development trends in gear manufacturing machine technology, in the design depart- men
13、ts and in the quality assurance departments, the design and use of tooth flank modifications in power transmission drive systems is a topic of increasing importance. Fine contact topography geometrical modi- fications can now be better calcu- lated, manufactured and verified. Today, tooth flank modi
14、fications are an indispensable design element for modern gear trains. All these developments will keep pressure on gear design engineers and the gear manufacturing industry at large to design and produce geared systems that can transfer more power in less space and make as little noise as possible.
15、This pressure is more likely to increase than decrease. The following will introduce a tooth flank modifica- tion, “Generated Engagement Relief Modification“, that will help the industry meet these goals. The result of numerous experiments and research projects tell us that 60 - 80 % of total gear n
16、oise is produced by gear tooth rigidity , behavior and gear tooth engagement impulses. This is true for different rotational speeds and different levels of power transmission. 2 STD.AGMA SbFTM3-ENGL L97b W b87575 0009Bb3 7bb W Tooth engagement impact is caused by pitch deviations at the beginning of
17、 tooth engagement and, to a lesser degree, tooth flank disengagement. These deviations are caused by a variety of factors such as manufac- turing tolerances and/or load re- lated deviations. Gear box assembly errors , tolerance errors in the gear box housing , gear box deformations and shaft bending
18、 can also contrib- ute to this problem. The initial engagement contact point is shifted, as shown in Figure 1, causing a noise producing impact. A A Actual Beginning of Engagement Engagement Figure 1 Impact point shift To correct this error and reduce gear running noise, tooth profile modif ications
19、 , commonly known as tip relief, are made along the entire width of the tooth flank. This type of modification reduces the, ampli- tude of the initial engagement impact caused by the deformations described above. Tip relief modifi- cations also improve torque transfer uniformity . Using conventional
20、 gear grinding technology, this type of profile modification is made by dressing a special profile into the grinding wheel or correspondingly changing the position of the grinding wheel in respect to the workpiece. Figure 2 illustrates this type of .profile modification. Figure 2 Conventional Profil
21、e modi- f ications I Figure 3 Conventional Lead modifica- tions Normally, modifications produced with the grinding wheel are ground to the same depth and size across the entire width of the tooth flank. This is done, even though we know 3 that gear tooth load and deformation conditions are continuou
22、sly changing as the mating gear elements are rotated. It is especially true for the engagement and meshing relation- ships of helical gears. In order for conventional modifica- tions to be effective, the transfer from the modified to the unmodified portion of the involute must be smooth and spread o
23、ver a large portion of the tooth flank in order to avoid unacceptable, shocklike dynamic loads. This can result in a reduction in the transverse contact ratio. When crowning is introduced (please see Fig.4), the effective face width and, theref ore, the active flank area of the gear is reduced as we
24、ll. Figure 4 Conventional Profile and Lead modifications Crowning, (please see Fig.3) or modifications in lead direction, are normally used to improve the load carrying capacity of power transmis- sions. They also reduce the disloca- tion sensitivity of the gear. Conventional profile and lead modi-
25、fications as shown in Figures 2 and 3 are still the best choice for straight tooth workpieces. Initial tooth engagement or this type of workpiece occurs along the entire tooth width. The entire tooth width must, therefore, be modified to avoid the engagement impact impulse as desired. However, the e
26、ngagement dynamics for helical gears are different. Initial engagement occurs at one point (or corner) of each tooth. It would, therefore, be appropriate to introduce a modification that offers relief at the initial point of contact and follows, or runs parallel to, the line of contact. Generated En
27、uaaement Relief Mod if i- cations For years, the international gear manufacturing industry has been pushing gear grinding machine manufacturers to develop an economi- cally realizable tooth modification technique that would eliminate the serious disadvantages of conven- tional modifications and redu
28、ce operating noise for helical type gear elements. The new modification technique as shown in Figure 5, should entail profile modifications parallel to the line of contact. Tooth entrance Figure 5 Generated engagement relief modification 4 STD-AGMA SbFTM3-ENGL L77b Ob387575 000LiBb5 537 The resultin
29、g mated pair tooth loads must result in a gradual load transfer from modified to unmodified tooth flank surfaces so as to provide a smooth and impact free tooth engagement and disengagement cycle. To meet these demands, Generated Engagement Relief Modifications have been developed. With this techniq
30、ue, the tooth flanks are modified at only the engagement beginning and exit areas, as opposed to the entire tooth face width as is the case with conventional modifications and par- allel to the line of contact. Please see Figure 5. Figure 6 compares the resulting tooth flank contact pressure as a fu
31、nction of the roll angle for two mating gear pair designs of nearly identical design. One gear pair is unmodified and the second is modified with Generated Engagement Relief Modifications . The load dif f erencec , which are caused by the switch from single to double tooth type meshing engagement in
32、 the case of the unmodified set, is substan- tially reduced by the proposed tooth flank modif icationc . The flank relief at the beginning and end of each tooth engagement substantially reduces the effect of remaining pitch errors and running irregulari- ties. B E v v -0,28 -0,2 412 -0,M 0,04 0,12 r
33、ad 0,28 Roll agie w Figure 6 Flank pressure for an uncorrected and a generated engagementrelief modified gear pair (no. of teeth Z1 = 27, Z2= 28, face width 3.1 “, helix angle 160, 3.6 DP, center distance 7.87 “, addendum modification x1 -0.006, xp -0.031), a unmodified pair, b generated engagement
34、relief modified pair, B beginning of engagement, E End of engagement In addition to reducing mesh conventionally modified gears using stresses, the torque transmission the techniques shown in Figures 2, 3 ratio is improved compared to and 4. This allows the design 5 engineer to produce geared power
35、transmission designs that require less volume and weight. Because Generated Engagement Relief Modifi- cations provide for a larger active tooth flank area, the Hertzian pressure is reduced. Total pressure is spread over a larger tooth surface area, thus making increased torque transfer possible. Fig
36、ure 7 illustrates the difference in measured vibration excitation of unmodified and Generated Engagement Relief Modified gears. P p i- n Re- lief Modifications The positive effect that Generated Engagement Relief Modifications, also known as generated end relief modifications or simply modifica- tio
37、ns in contact direction, have on gear running noise, overlap ratios and torque transmission ratios have been known for many years. However, it was previously impossible to create this type of modification, economically, with conventionally built gear grinding machines. The introduction of computer n
38、umerically controlled (CNC) index generating gear grinding machines now make this technology possible. CNC technology allows us to continu- ously change the worktable transla- tion and rotation (profile generation motion) relationship in such a manner that the desired generated modifications are cre
39、ated. Please see Figure 8. Figure 7 Generated Engagement Relief Modification influence on vibration excitation a.) deviation free, unmodified gear, b. ) generated engagement relief modified gear. 6 STD-AGMA SbFTM3-ENGL L79b W Ob87575 00048b7 301 W o Workpieceslide - translation X Figure 8 principle
40、motions, a) for generated engagement relief modifications andb) unmodified gears, f root area, k tip area, w entire generating path. To ensure that the resulting Generated Engagement Relief Modifi- cations are in the correct loca- tions, it is recommended to make several profile and lead diagrams at
41、 exact, predetermined inspection locations along the subject tooth flank, lead and profile. Again, modern CNC controlled gear inspec- tion equipment simplify this task. In Figure 9, the lead and profile charts for the modifications illus- trated in Figure 10 are shown. 1234 5 Figure 9 Inspection res
42、ults for Generated Engagement Relief modifi- cations 7 STD-AGMA SbFTM3-ENGL 177b m b87575 048b8 248 m Figure 10 Generated Engagement Relief Modified Tooth Flank Because of their positive influence on helical gear pair noise levels, overlap ratios and resulting power transmission capabilities, it is
43、predicted that Generated Engagement Relief Modifications will replace conventional modifications within a relatively short period of time. Manufacturing and quality assurance technology, necessary to produce them are available now. b b Tooth prof iles that have been modified with generated engagemen
44、t relief modifications correspond to the actual operating dynamics of meshing helical gears, because they are made parallel to or in line with the actual lines of contact. Using state of the art CNC index generating gear grinding technology, Generated Engagement Relief Modifi- cations are easy and e
45、conomical to produce. The grinding wheel has a simple, double tapered geometric form representing a single tooth in a gear rack. There are no modifica- tions dressed into the grinding wheel. All modifications are ground during the normal grinding process without increasing cycle time. Special machin
46、e control software that guide index generating gear grinding machines through the mo- tions required to produce Generated Engagement Relief Modifications, is available today. 8 STD-AGHA SbFTfl3-ENGL 1SSb = Ob87575 00048bS 184 D Ref ereacec : Schwingungs- und Gerauschanregung bei Stirnradgetrieben (v
47、ibration and noise stimulation in cylindrical gear drive systems), Robert Mller Beanspruchungsgerechte und gerus- choptimierte Stirnradgetriebe,Toler- anzvorgaben und Flankenkorrekturen ( stimulation correct and noise optimized cylindrical gear drive systems, tolerance suggestions and flank modifica
48、tions), Wolfgang Wittke Geziele Verbesserung der Leis- tungsiibertrag von Zahnradgetrieben durch Flankenkorrekturen (specific improvement of gear trans-mission power transmission through flank modifications), Georg Mauer Lastverteilung und Flankenkorrektur in gerad- und schrgverzahnten Stirnradstufen (load distribution and flank modifications for straight and - helical cylindrical gear stages), Thomas Plazcek Verfahrensreserven beim Walzschlei- fen von Stirnrdern (process re- serves for the index generation grinding of cylindrical gears), Dr. Ing. Werner KieS 9
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