Contact Stress Analysis Of Helical Gears In DCT With Backlash

Transmission is one of the most important parts in the power system of cars, and gear system is the main drive part in transmissions. Gear backlash exists inevitably because of tolerances due to manufacturing and assembly, and it also meet the requirement of lubrication and heat dissipation. During the process of gear meshing, the contact status will change and impact will appear due to gear backlash, it has a disadvantage effect on the lifetime and transmission performance of gears.This paper takes the third gear of DCT (Dual Clutch Transmission) as the study object, the main contents includes:(1) The research of contact stress and the mechanical property of gears which considered backlash are reviewed, Hertz contact theory and finite element contact analysis methods were introduced.(2) A parametric model of helical gear pair was built in Pro/e, the assembly and simplification were conducted. The forming reason, classification and influencing factors were analyzed, and mainly focus on the relationship between center distance and gear backlash.(3) The static finite element analysis of contact stress of models which have gear backlash was conducted in ANSYS, the Von Mises equivalent stress was calculated and the changing rule of stress was obtained.(4) The dynamic finite element analysis of contact stress of models which have gear backlash was conducted in ANSYS/LS-DYNA, and the dynamic contact stress of gear pair was calculated and the curve of maximum contact stress-time was obtained.The analysis result shows that the contact stress of helical gear pair and the stress fluctuation increased with the increase of gear backlash, large impact appeared at the beginning and ending time of meshing process and arouse lager contact stress; The stress concentration occurred in the area of gear angel and the root of gear tooth, and it will easily cause fatigue fracture.The model of this paper was built according to the drawing and data from manufacturer and took actual working conditions into consideration, thus the analysis results can provide a reference for gear fail-safe analysis, fatigue stress forecast and deep research of meshing contact, and also provide technical data support for the control of gear backlash and assembly tolerance in practical assembly process.