Using the large-scale finite element general software ANSYS and ANSYS / LS-DYNA, this paper analyzes the influence of the contact stress, tooth backlash and support shaft stiffness of the helical gear of a heavy truck transmission on the dynamic contact stress of the helical gear in the meshing process from both static and dynamic aspects. At the same time, in order to improve the serious problem of stress concentration in the meshing process of the helical gear pair, the tooth profile and tooth direction of the small and medium gears of the helical gear pair are modified, The conclusions are as follows:
1) The finite element analysis models of four common local teeth and full teeth with and without flange are established, and the static and dynamic contact stress of helical gear are analyzed. The results show that in the static analysis, whether the rim exists or not, the calculation error of the five tooth model is smaller and the accuracy is higher than that of the corresponding three tooth model; In the dynamic analysis, no matter the three tooth or five tooth local tooth model, the calculation error of the model with flange is much smaller than that of the model without flange;
2) The nonlinear contact finite element static simulation of involute helical gear is carried out by using ANSYS finite element analysis software. The analysis results show that the stress concentration caused by tooth sharp angle is serious, which makes the maximum contact static strength of helical gear exceed the allowable strength of material;
3) The nonlinear dynamic contact stress of involute helical gear is studied by using the explicit dynamic finite element analysis module ANSYS / LS-DYNA, and the equivalent stress distribution of helical gear at different times in the meshing process is obtained. The results show that the dynamic analysis result is slightly larger than the static analysis result, and the stress concentration caused by the sharp angle of helical gear is more serious than the static result;
4) The effects of different backlash and support shaft stiffness on the dynamic contact stress of helical gear pair are studied. The results show that the contact stress increases with the increase of backlash; The support shaft is easy to produce bending deformation in the meshing process of helical gear, and its deformation is easy to cause the meshing instability of helical gear and produce large stress;
5) Aiming at the problem that the stress concentration caused by the sharp angle of the tooth makes the maximum contact strength of the helical gear exceed the allowable strength of the material, the tooth profile and tooth direction of the small and medium-sized gears of the helical gear pair are modified, the dynamic contact finite element analysis model of the modified helical gear is established, and the dynamic contact simulation of the contact stress of the helical gear is carried out under the influence of the stiffness of the support shaft. The results show that the contact stress of the modified helical gear is significantly reduced, and the stress decreases of tooth profile modification and drum modification are 70% and 58% respectively; After modification, the meshing impact is eliminated, the contact stress is evenly distributed, and the stress concentration phenomenon has been greatly improved. The modified helical gears meet the strength requirements.