Dynamic Analysis Of Transmission Gear System With Consideration Of Hydrodynamic Lubrication

Gear transmission system needs good lubrication when the manual transmission runsin the practical working process. Gear teeth interact with each other on the form ofnonlinear oil film force when gear tooth surfaces contact by lubricant. Due to nonlinearfactors such as the oil film damping, backlash and time-varying meshing stiffness,strong nonlinear dynamic characteristics of the gear transmission system are presented,which directly affect various performance indicators of the transmission. So themodeling and analysis of the gear transmission system considering hydrodynamiclubrication are discussed in this paper, and helical gear system with temperature effect isstudied.Considering the squeezing motion of lubricant between gear teeth, the oil filmdamping force can be obtained based on half-Sommerfeld boundary conditions.Dynamic models of spur gear and helical gear transmission systems with the oil filmdamping force are built by using centralized mass method which take the backlash,time-varying meshing stiffness, time-varying contact length and contact ratio intoaccount. Based on above modeling method, the model of helical gear transmissionsystem with temperature effect is established, and the influence of temperature on thelubricant viscosity and backlash is considered. The numerical solution is carried out byemploying improved Newmark method, and bifurcation diagram and other analysismethods are used to analyze the system motion characteristics. The results show that thetorque fluctuation frequency and temperature have obvious impacts on the responses ofgear system where chaotic motion appeares with the change of parameters and theresponses of spur gear system are simpler than helical gear system.A new gear rattle index is proposed and the change rules of transmissioncharacteristics with different parameters are analyzed. The results indicate that backlashand temperature are major factors which affect the transmission precision of gearsystem, and meshing frequency components occur in the system responses with theincrease of load torque or the decrease of the torque fluctuation. Gear rattlephenomenon happens when the gear is light-loaded or torque fluctuation is large. Inaddition, gear rattle is related with gear speed, lubricant viscosity, module, helical angleand temperature, and gear rattle phenomenon in the spur gear system is more obviousthan the helical gear system. Also, the power losses of gear system are greatly influenced by gear rotational speed, lubricant viscosity and temperature.