| As important part of automotive mechanical transmission, the transmission quality and reliability of spiral bevel gear of the main reducer will determine the quality of vehicle. At present, the service life of bevel gears in heavy truck main reducer working in the complex and harsh condition is too short, which because of low contact strength and can not meet the requirement, therefore, FSH bevel gear, which is also called double circular arc spiral bevel gear, comparing with the spherical involutes bevel gear, has the advantages of high load capacity, long service life, high contact strength and bending strength. On the base of these, it is suggested that the FSH bevel can be applied to the main reducer of heavy truck.The FSH bevel gear is a new technology which applied double arc tooth to the spiral bevel gear and its load capacity is closely related the meshing characteristics. In the gear transmission, the initial location of contact area and the development of contact area may influence the gear meshing characteristics and drive quality. The initial location of contact is determined by the machine tool adjustment parameters, and the development of contact area is determined by the tooth profile design and running-in method. The purpose of this thesis is to put forward the LTCA(Load Tooth Contact Analysis), which is the core technology of the virtual manufacturing, with which reasonable machine tool adjustment parameters can be obtained at the least try-cut, and the method of running-in can be explored quickly and efficiently.The focus of this thesis is on the meshing characteristics of the FSH bevel. Some progress and accomplishment have been made on the key issues such as virtual design and manufacturing system, running-in, strength test and dynamic characteristics. The major works of this thesis are listed as follows:1) According to the differential geometry and meshing principle, the tooth profile design method, which is based on the running-in characteristics, is proposed, and in accordance with circular arc profile feature of FSH bevel gear, the proper method to find curvature radius is proposed.2) According to the conjugate gear tooth surface forming principle, gear processing principle and running-in principle, meshing equation that fitted running-in is deduced. In addition, the induced normal curvature and meshing process are analyzed. The meshing equation and the tooth surface equation of pinion and large wheel are deduced based on FSH bevel gear processing principle. The mathematical relation of running-in rate and tooth surface wear rate are determined.3) On the basis of the spatial engagement principle and TCA principle, the loading contact analysis is made. Based on the TCA and LTCA principle, the meshing characteristic of FSH bevel gear is analyzed, and the method of virtual simulation of machining is proposed. The tooth contact stress FEA is completed base on the machining of digitized gear-tooth surface. The LTCA of FSH bevel gear is completed.4) The running-in theory and test are carried on the meshing gear pairs, the factors that influenced running are analyzed, then, the mathematical model of running-in is established, and the running-in method for FSH bevel gear is proposed. The SLH(Starved-oil Low-speed Hard-load) running-in method is proposed.5) Dynamic testing tap of the bevel gear is designed and constructed to obtain the dynamic characteristic of the FSH and Gleason bevel gear system, and the vibration and noise of running-in pre and post are compared. What is more, the vibration and noise of FSH and Gleason bevel gear are compared.This thesis was supported by National Natural Science Foundation of China"Extraction method of maximum and average densities Unsteady Lubrication space surface meshing characteristics"(No.50875009). |
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