Lubrication failure is one of the main failure forms of gear failure. Time varying meshing stiffness is an important factor affecting the dynamic behavior of gears. However, the influence of oil film stiffness is usually ignored in the research process. In this paper, according to the meshing characteristics of double involute gears, based on the non-Newtonian thermal EHL theory, a new calculation method of normal and tangential oil film stiffness for double involute gears is established by the idea of subsection method. The oil film stiffness difference between double involute gears and common involute gears is analyzed, and the influence of tooth waist order parameters, working conditions, and thermal effect on the oil film stiffness are studied. The results reveal that there are some differences between normal and tangential oil film stiffness between double involute gears and common involute gears, but there is little difference. Compared with the torque, rotation speed and initial viscosity of the lubricating oil, the tooth waist order parameters have less influence on the oil film stiffness. Thermal effect has a certain influence on normal and tangential oil film stiffness, which indicates that the influence of thermal effect on the oil film can not be ignored. This research proposes a calculation method of normal and tangential oil film stiffness suitable for double involute gears, which provides a theoretical basis for improving the stability of the transmission.
To slow down the surface wear process of double involute gears (DIG), the surface adhesive wear model and wear life prediction model are established according to its meshing characteristics, combined with the modified Archard wear model and mixed EHL model. This paper studies the surface wear and wear life of DIG, compares it with common involute gears (CIG), and discusses the influence of different factors on its surface wear. Results show that the adhesive wear distribution of DIG is similar to that of CIG. Properly reducing l* and increasing y* can reduce surface wear and prolong wear life. The reasonable selection of lubrication states and working conditions can beneficial to enhance its tooth surface wear resistance.
In order to accurately obtain the dynamic characteristics of double involute gears, according to the characteristics of its tooth profile, the idea of "subsection method" is proposed to establish a novel tribo-dynamic model by the coupling relationship between thermal effect, lubrication characteristics and dynamic characteristics. In the process of iterative solution of the model, an analytical model of lubricant film deformation is established and a time-varying meshing stiffness calculation model considering the coupling effects of multiple factors is established. The influence of different factors on its dynamic behaviors and the difference of dynamic characteristics between double involute gears (DIGs) and common involute gears (CIGs) are comparative analyzed. The results show that the thermal effect and tooth friction can intensify the dynamic response of the gear transmission. The change of rotational velocity and torque have significant impact on the dynamic behaviors of DIGs, the variation of tooth waist order parameters have little effect on its dynamic characteristics, and the dynamic characteristics between DIGs and CIGs exist difference, but the difference is not obvious. Additionally, the theoretical model is verified through experiments.
The tooth of double involute gear (DIG) is considered as a cantilever beam on the tooth root circle, considering the real tooth profile of DIG, an improved energy method is used to solve the time-varying mesh stiffness. The influence of tooth waist order parameters and the difference of time-varying mesh stiffness between DIG and common involute gear(CIG) are studied. The results show that the time-varying mesh stiffness of the single tooth pair is less than that of CIG with the same parameters when the contact line passing through the tooth waist grading position, and the comprehensive time-varying mesh stiffness of DIG is less than that of CIG. The tooth waist order parameters will affect the time-varying mesh stiffness of DIG, and compared with the tooth waist altitude coefficient (l*), the tooth waist tangential modification coefficient (y*) has little effect on the time-varying mesh stiffness.
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