Gears are the core components of automotive transmission systems. The transmission performance and meshing characteristics of helical gear systems are key factors affecting the reliability of automotive transmissions, and support stiffness is one of the important factors affecting the normal meshing of helical gears. The bending, twisting, and deformation of the gear shaft can destroy the original meshing state of the helical gear pair, leading to eccentric load during the meshing process and exacerbating its fatigue pitting failure. Surface coating strengthening technology is to cover the surface of helical gears with a solid lubricating layer to reduce friction, in order to improve the contact fatigue strength and fatigue life of helical gears. Therefore, studying the influence of support stiffness and tooth surface coating on the meshing characteristics of helical gear pairs is of great significance.
Due to differences in support stiffness, the transmission helical gears may experience eccentric load pitting failure during meshing. Zheng Guangze et al. studied the influence of the flexible housing on the dynamic meshing characteristics of helical gear pairs by constructing a finite element model of the transmission flexible housing. Chen Ruibo et al. studied the influence of axial eccentric load on the dynamic characteristics of planetary systems by establishing a translational torsional dynamic model of planetary transmission. Wei et al. considered such factors as time-varying meshing stiffness, support stiffness and backlash, established a six degrees of freedom dynamic model, and analyzed the dynamic transmission error and vibration stability of helical gears. In order to improve the phenomenon of eccentric load pitting failure of helical gears, Guo Fan et al. studied the effect of tooth surface modification on the dynamic meshing characteristics of helical gears. Wang et al. analyzed the impact of gear modification on the dynamic characteristics of a helical gearbox by establishing a rigid flexible coupling dynamic model. Li et al. studied the effects of helical gear shaft deformation, tooth profile modification, and torque transmission on the meshing characteristics of spur gears based on the finite element method. In order to further improve the contact fatigue life of helical gears, Wang Liping et al. applied surface coating strengthening technology to the anti fatigue pitting corrosion of gears. Zhou et al. evaluated the contact fatigue life of coated gears under elastohydrodynamic lubrication conditions by establishing a numerical model for contact fatigue life. Xiao et al. studied the influence of the elastic modulus of the coating on the dynamic characteristics of helical gears by establishing a six degrees of freedom model of the coated helical gears. Chen Yong et al. studied the influence of manganese phosphate coating on the contact strength of helical gears by obtaining the surface morphology characteristics of helical gears with/without manganese phosphate coating. In summary, scholars have studied the influence of support stiffness on the meshing characteristics of helical gears and the strengthening effect of coatings on helical gears. However, there has been no systematic study on the mechanism of coatings on improving the bias load of transmission helical gears under large support span conditions after running in.
In order to study the causes of eccentric load failure of helical gear pairs under different support spans and the strengthening effect of surface coatings, a rigid flexible coupling model of helical gear pairs with different support stiffness was established. The meshing misalignment and eccentric load effects of helical gear pairs were studied, and the influence of load and speed on the meshing characteristics of helical gear pairs with different shaft stiffness was analyzed; Use the FCL Å 250H gear precision testing bench to detect the tooth shape and direction parameters of helical gears with/without manganese phosphate coating before and after running in, and combine simulation analysis to explore the influence of coating on the eccentric load condition; Conduct contact fatigue pitting experiments on helical gears, compare and analyze the contact fatigue life before and after pitting failure, and further study the strengthening mechanism and effect of the coating from the perspectives of tooth surface meshing state, surface roughness, and vibration acceleration.