In the whole meshing area of gear pair, the meshing point of error free gear transmission is always on its theoretical meshing line, so the transmission ratio is stable and the transmission process is stable. However, due to the installation error, manufacturing error and load-bearing deformation of gear teeth, the meshing points near the meshing in and meshing out positions deviate from the theoretical meshing position, which makes the normal velocity of the meshing points unequal and causes meshing impact. Due to the high input speed of the electric vehicle reducer, the meshing impact is large, and the impact of meshing impact on the overall vibration of the reducer is also greater.
The formation mechanism of meshing impact is analyzed. The meshing impact time is deduced by using the geometric relationship of gear meshing point. The influence of system parameters on meshing impact time is analyzed. The velocity and amplitude of meshing impact force are calculated by using the theoretical relationship of related variables in impact mechanics. According to the meshing impact time and the meshing impact force amplitude, the meshing impact force curve is expressed by sawtooth wave. It lays a foundation for the vibration characteristic analysis of high-speed helical gear transmission considering meshing impact.
The formation principle of dynamic excitation of time-varying meshing stiffness is described. The calculation methods of time-varying meshing stiffness based on material mechanics method and finite element method are introduced. The calculation method of time-varying meshing stiffness based on improved LTCA method is proposed. Then, taking the input gear pair of an electric vehicle reducer as an example, the time-varying meshing stiffness curve of the gear pair is calculated. Finally, by comparing the results of the three methods, the time-varying meshing stiffness results based on the improved LTCA method are determined.