High-strength Spiral Bevel Gear Design And Experimental Study

The design and manufacture methods of high-strength spiral bevel gears andhypoid gears are researched in this thesis. Due to the transmitting smoothing and higherstrength, the spiral bevel gears and hypoid gears have widely been used in automobiles,aeronautical engineering, astronautical engineering, engineering mechanics, miningmachinery', machine tool, instrument and so on. With the development of modernscience and technology, the spiral bevel gears and hypoid gears are required with higherstrength and lower noise; at the same time, the new research platform of the spiral bevelgears and hypoid gears is constructed. Thus the research on the strength and noise of thespiral bevel gears and hypoid gears is hot topics and paid attention by a number ofexperts. By using the local synthesis method, tooth contact analysis, loaded toothcontact analysis, finite element method and with the aid of the Natural ScienceFoundation of China and, the Science Foundation of Chinese Aeronautical Engineering,the method of improving the strength of spiral bevel gears and hypoid gears is studied.Some conclusions and creative contents are listed as follows:(1) With the aid of the local synthesis method, the tooth cutting of non-zeromodified spiral bevel gears is researched. By using the finite element method, thebending stress, tooth profile and tooth thickness are analyzed. The computer simulationand computational analysis show that the maximum tensile bending stress and themaximum tooth surface contact stress of the non-zero modified spiral bevel gears withpositive modification coefficients are markedly reduced. On the condition of invariantouter diameter of gear and the geometric parameters of the cutters, tooth root thicknessof the non-zero modified spiral bevel gears with positive modification coefficients isthicker than the spiral bevel gears designed by Gleason method.(2) The modified pitch cone method of the hypoid gear manufactured by HFT isintroduced. The tooth-cutting design of the hypoid gears designed by the modified pitchcone method is studied with the aid of the local synthesis method. The computersimulation and computational analysis show that the root chordal tooth thickness of thepinion designed by the modified pitch cone method becomes thicker, and pinion outerdiameter becomes longer; the tooth surface contact stress, the maximum tensile bendingstress and the maximum compressive bending stress of the pinion designed by newmethod can be markedly reduced. The tooth machining experiment and the comparativeexperiment for strength of hypoid gears designed by the modified pitch cone methodand Gleason method respectively show that the hypoid gears designed by the modifiedpitch cone method are manufactured successfully by using the general machine-tool andcutter, and the changing of bending stress, tooth profile and tooth thickness areconsistent with theoretical design and analysis. As the application of the modified pitchcone method, the hypoid gears of high-speed ratio (tooth number of pinion is 3 or 4) are designed successfully.(3) Unsymmetrical strength design of the hypoid gear is presented. In the design ofhypoid gear, the pressure angle of forward running tooth surface is modified, thus thebending strength of forward running tooth surface is improved and the tensile bendingstress is reduced.(4) The topic of optimal tooth surface of hypoid gears is studied. The profile angleof pinion cutter blade at mean point (here we consider profile angle of cutter blade atmean point as a continuous variable), the proportion of length of major axis ofinstantaneous contact ellipse to gear face width, first derivative of transmission errorfunction, and coordinates of mean contact point are considered as the optimal variables,the third order contact shortcomings are eliminated and the control of engagementquality is realized. The optimal method of the tooth profile at tooth root, control oftooth-depth, testing of undercut and testing tooth top interference are presented.(5) The method of the rough-machining and overcutting test of therough-machining to the hypoid gear, which machine-tool settings are derived by usingthe local synthesis method, are introduced, the software is designed. With the aids of thesoftware, the distributing of the finish-machining allowance can be shown. This methodhas been verified by tooth machining experiment in Dong Feng vehicle-bridge CO.,LTD.(6) The topic of Top-Rein profile blade is discussed. In order to improve bendingstrength and avoid the interference between the tooth root of pinion with tooth tip ofgear, the method and formulae of maximal edge radius of Top-Rem profile blade, whichis used to manufacture the bevel gear, are introduced. And the bending stress andcontact stress of hypoid gear which the pinion is manufactured by using cutter with theTop-Rem profile blade are discussed with the aid of LTCA and FEM.