In the whole meshing area of helical gear pair, the meshing point of error free helical 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, machining error and the existence of gear tooth load deformation, the actual helical gear makes its meshing point near the meshing in and meshing out position deviate from the theoretical meshing position, so that the normal speed of the meshing point is not equal, causing meshing impact. Due to the high input speed of the electric vehicle reducer and the large meshing impact, the meshing impact has a greater impact on the overall vibration of the reducer. This chapter analyzes the formation mechanism of meshing impact, derives the meshing impact time by using the geometric relationship at the meshing point of helical gears, and analyzes the influence of system parameter changes on the meshing impact time. The meshing impact velocity and meshing impact force amplitude were calculated by using the theoretical relationship of relevant 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 subsequent analysis of vibration characteristics of high-speed helical gear transmission considering meshing impact
The forming process of meshing impact and its influence on helical gear system are described. First of all, the impact time and impact velocity of meshing are deduced by using the geometric relationship of the impact of helical gear line external meshing. Secondly, the amplitude of meshing impact force is calculated by the mathematical relationship between the parameters in impact mechanics. Finally, according to the meshing impact force amplitude and meshing impact time, the meshing impact force curve is simplified by the sawtooth wave function.