Planetaryis mainly composed of central shaft, planetary gear and sun gear. In the gearbox fault, the probability of planetary gear and sun gear fault is 70%, so this paper mainly studies the fault of planetary gear and sun gear. Most of the gear faults are caused by long-time high load operation. In the meshing process, the load on the surface of the planetary gear and the sun gear is very large, which leads to the movement and sliding between the gear surfaces in the running process; At the same time, in the process of sliding, the force point of friction is at the connection point between the tooth surface and the wheel disc, and the force direction on both sides is just opposite, resulting in the force pulse; It is very easy to cause gear wear, broken teeth and other faults when it is in this running condition for a long time.
Gearbox vibration system is a nonlinear system, and its internal vibration model is complex. Before the study of gearbox vibration mechanism, it is usually necessary to simplify the gear pair model to facilitate the research of gearbox fault. The simplified model structure is shown in the figure.
The kinetic formula is as follows
Mx ̈+ Cx ̇+ k(t) = k(t)E1+ k(t)E2(t)
Where m is the equivalent mass, M = m1m2 / M1 + m2; X is the relative displacement of gear; C is the meshing damping; K (T) is the meshing stiffness; E1 is the mean static elastic variant; E2 (T) is the fault function; K (T) e1 is the normal meshing vibration; K (T) E2 (T) is the relationship between side frequency signal and fault.