Milling of non circular spiral bevel gear

Bevel gear is widely used in vehicle differential, machine tool transmission box and other transmission machinery. The non-circular bevel gear (also known as spherical non-circular gear) can transfer variable transmission ratio. Without changing the original structure of the differential, it can realize the function of limiting slip of vehicle differential. However, due to the difficulty of design and machining, the application of non-circular bevel gear is limited. There are few researches on solving and machining spherical non-circular gears, especially machining methods. Because of the complex structure and shape, the non-circular bevel gears can be processed by wire cutting, molding casting or EDM with forming tools.

The disadvantages of the above methods are: first, the machining accuracy is not high, which depends heavily on the accuracy of the tool; second, the machining efficiency is low, so it is necessary to process the non cone shaped blank first and then use EDM; moreover, the WEDM method can only process the straight bevel gear. Recently, with the development of machining technology, the application research of non-circular bevel gear is increasing gradually. Based on the meshing principle of bevel gear, the method of machining spiral bevel gear with non-circular spiral tooth on CNC machine tool with disc milling cutter is studied. It can not only be directly formed with high precision, but also can improve the contact degree of meshing transmission and make the transmission stable.

According to the pitch curve data and gear meshing theory of non bevel gear, the formula of NC machining spiral tooth non bevel gear with forming disc cutter is deduced. The instantaneous position of a series of disc milling cutter and the wheel blank to be cut is calculated as the control parameter of NC machining program. After tooth profile modification, spiral tooth non bevel gear can be processed by 5-axis NC machine tool. Based on this method, a pair of non bevel gears can be meshed correctly, which proves that the method is feasible. Compared with wire cutting method and ignition processing method, the machining accuracy and efficiency are improved.

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