Research On Tooth-modification Technology Of Fine-forming Straight-tooth Bevel Gear

The teeth of gear named fine forging gear can be formed directly by the forging die without chip-removal machining. Especially for the bevel gear, it was the one of fine forging parts which were developed and applied earlier. Compared with the machining gears, some merits can be obtained to the gears made by fine forging technology as high mechanical performance, long life, energy saving and less materials. But due to the limitation of forming technology and equipments, fine-forging bevel gears with high precision better than 7-grade are hardly manufactured in batch and then their application are out of modern automobile industry. It is proved that the transmission stability, precision and service life of gear box can be improved as well as the vibration and noisy can be lightened with the usage of teeth profile modification technology in manufacturing of gears. It is easy to modify the profile of spur gears, and only minimal modification of profile can be obtained in bevel gears even with some certain location. The modification technology of bevel gears then used seldom. In fact it is efficient and effective to modified the teeth profile of fine forging gears if the modification was printed on the forging die previously.Based on the synthetical analysis of the research and application of the gear modification technology, this thesis put forward and developed the Equidistance Chemical Machining Modification Technology(ECMMT) which is available to the bevel gears modification. The electrode gear, used to form the cavity of fine forging die by the Electrode Discharge Machining(EDM), are modified by the ECMMT. The modification the is "copied" on the die. Large batch of fine forging gears with the special modification therefore are "duplicated" by the unique die. The ECMMT was used in the production of a certain type bevel gear used in the car, as the result, the transmission precision and stability of the bevel gears improved to the 7-grade, the touch area is quite better, the roughness of the teeth face is increased greatly, and the life of forging die is lengthened.By use of ECMMT, both edge modification and the drum area on the gear tooth surface can be implemented easily, as well, the involute characteristic of the modified teeth of bevel gear keeps the normal gear profile.One of the principles of gear teeth modification is researched in this thesis, that is whether the forging gear with teeth modification can be lift out of the die cavity or not. And the calculating model is constructed based on the study of the modified bevel gear structure. Further the universal program is developed and tested effective as the tool to design the figure and the location of modification area.The useful results are obtained by the experiments of chemical milling parameters on copper samples. It's tested that the best chemical milling parameters to reach the excellent machining result are those, the Fe3+ content of electrolyte is 8-12 g/l, the work temperature keeps between 40℃to 60℃, the milling time is not less than 10 minutes. By use of the chemical machining technology with the parameters above, such ideal and operable results as the well-proportioned milling velocity, lower surface roughness and the material equidistance removal of varied surfaces when the milling depth in 0.02-0.05mm.It is necessary to build the comprehensive research way to design the modification area and size precisely for the straight-teeth bevel gear. In this thesis, the 3-D modeling system of equidistance modification bevel gear is developed based the universal CAD software SolidWorks with main help of the tool integrated in SolidWorks-Size Drive Method.