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The load sharing characteristics of the herringbone planetary transmission system are a key indicator for evaluating the bearing stability and reliability of each planet gear in the transmission system. The value of the load sharing coefficient is closely related to the manufacturing error and the assembly error in gear processing and assembly process. Therefore, it is indispensable to study the influence mechanism of these errors on the load sharing characteristics of the transmission system. Nevertheless, researches on the multi-coupling transmission error to the load sharing characteristics of herringbone planetary transmission system did not receive enough attention, but much of the single errors. Based on the centralized parameters theory and the Lagrange method, this research establishes a dynamic model for herringbone planetary transmission system and creatively proposes a study of multi-coupling error which consists of eccentric error, tooth profile error, stagger angle and assembly error. This work shows that the changing regulation of the load sharing characteristics with any one of the above errors is different. However, the load sharing characteristics become worse with the increase of multi-coupling error, in which the eccentric error plays a main role. Therefore, the error control should focus on eccentric error.

In the field of mechanical engineering, involute helical gears are widely used. Compared with the involute spur gear, helical gears have a high bearing strength, more smooth transmission, less impact and less noise. The internal gear pairs have the features of large transmission ratio, low vibration, low noise and low wear and hence are widely used in planetary gear transmission systems. In order to meet the requirements of high strength, high speed of the modern gear transmission systems, a new type of asymmetric involute internal helical gears is designed based on conventional involute gears. This paper discusses the gear shaper cutter modeling for machining this new gear, analyzes the formation principle of asymmetric tooth profile and establishes a three-dimensional modeling by SolidWorks. Through MATLAB simulation, pressure angle, tooth number, coefficient of displacement and contact ratio of conventional and asymmetric gear are compared and analyzed. Using ANSYS, two types of gears are compared on strength in order to demonstrate superiority of asymmetric tooth and further study about the asymmetric internal helical gears.

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