Research Of Planetary Gear Range Group For Heavy Commercial Vehicle Transmission

In order to achieve the group's strategic goals of "the twelfth five years plan" and sustainable development of our company, the leader decided to develop and design the heavy duty truck transmissions with multi-gear, high torque and high speed ratio. According to market developments, the kinds of our company's transmission are increasing. So pre-series production, modular operation and integrated designation should be considerate. Auxiliary range section as the transmission of heavy duty truck is an important component, which structure and carrying capacity will affect the transmission's economical and reliability. The advantages of auxiliary range section with planet mechanism are compact structure, high carrying capacity, high transmission efficiency, high speed ratio and reliable capability. Therefore, in order to enhancing the competitiveness of our products, it is significant to research the auxiliary range section with planet mechanism, optimize its structure and improve its performance.This paper starts with the analysis of the structural principle of various transmissions. Heavy duty truck's transmission needs to fulfill the engines'high-power and high torque, so structure and composition are different in domestic and international manufacturer in the highest flight. There are three typical structures: the twin-countershaft in the middle box & setup of planetary gear in the auxiliary range section, twin-countershaft in the middle box & auxiliary range section and single-countershaft in the middle box & auxiliary range section. Auxiliary range section is the main part of the transmission carrying of heavy duty truck, also the focus of this paper. Planet mechanism is superior to twin-countershaft or single-countershaft in aspects of power split, gear stress, the main failure mode and carrying capacity .So for automotive transmission designation, the auxiliary range section with planet mechanism should be chose for its advantages on the structure. But planet mechanism is very high costs, cost control is necessary. Optimize its structure, make its bulk smaller and lightweight in a certain carrying capacity, thus reducing the use of raw materials and lower manufacturing costs. In this paper, the NGW planet mechanism's structure and working principle in auxiliary range section of 2K-H are analyzed and this provide a theoretical basis for the following optimization.Set the minimum volume of setup of planetary gear in auxiliary range section as the objective function, according to its structural parameters, identified design variables. According to speed ratio, concentric conditions, adjacent conditions, meshing relationship, geometrical features of deflection, force characteristics of components and strength characteristics, interrelated constraints in the establishment of a mathematical model should be identified. Focus on the constraints in detail for analysis to ensure that constraints are established contact with the objective function closely. Number of critical constraints can not be too small, or the accuracy of the results will be affected. While constraints should be selected that little effect on the objective function, or too many constraints will make optimum analysis become intricate, or even no solution.After the establishment of constraints, the setup of auxiliary range section with planet mechanism is calculated and optimized by MATLAB optimization toolbox.By the analysis of products of our company, the result of volume than the original volume is reduced by 16%, and that achieved minimum goal. A three-dimensional mathematical model is built with optimized parameters by Pro / ENGINEER Wildfire 2.0 software, focusing on the method of involutes planetary gear's three-dimensional model. And modeling methods of sun gear and planet carrier are similar to the planetary gear. Three-dimensional models of each component in the established setup of planetary gear are assembled at last, and further validates the parameters of the optimization is feasible, without interference, correctly assembled. This provides facilitation for the following analysis of heat balance.After the fulfillment of minimum volume of setup of planetary gear in auxiliary range section, its transmission efficiency is analyzed and calculated, and the auxiliary range section's cooling effect is verified by heat balance calculation in theory. Analysis result of this structure cooling efficiency is low, so proposed to take oil bath and compulsive lubrication. And then take the heat balance checking of this auxiliary range section for the selected pump. The paper has the signification of polestar in our company's designation on the future. The method of heat balance analysis mentioned in this paper can be referred for gearbox designer.