In the process of gear transmission and meshing, there are many reasons that affect the vibration of gear, including large period error and small period error. The main factors causing large period vibration are motion eccentricity and geometric eccentricity in the process of gear processing and poor alignment in the process of installation; the main factors causing small period vibration are rotation error of main shaft in the process of gear processing, change of meshing stiffness, meshing in and out impact of gear, as well as tooth break, root fatigue crack, tooth surface wear, pitting and peeling off in the process of operation Serious gluing, etc. Among them, the periodic change of meshing stiffness is one of the important exciting sources of gear system vibration. Its periodic change is mainly caused by the following two reasons: first, with the change of the position of the meshing point, the stiffness of the single gear engaging in meshing changes; second, the number of teeth engaging in meshing changes.
As shown in Figure 1-1, at the beginning of meshing (point a), the active gear 1 is meshed at the tooth root, with less elastic deformation; the passive gear 2 is meshed at the tooth top, with large elastic deformation, while at the end of meshing (point d), the opposite is true. If the meshing stiffness of pair I is K1 and that of pair П is K2, then the total meshing stiffness is k = K1 + K2. It can be seen from Figure 1-1 that the total meshing stiffness changes periodically from single meshing area to double meshing area.