Previous studies have shown that the sound pressure of air radiation generated by no-load knocking of gears is proportional to the impact load. Maximum dynamic meshing force and root mean square value can provide theoretical basis for studying knocking noise of gear transmission system.

In 1-8 gear, the maximum dynamic engagement force and the root mean square value of the unloaded gear are shown in the figure.In the figure, the transverse coordinates 1-4 represent each external engagement gear pair of the unloaded planetary row, 5-8 represents each internal engagement gear pair of the unloaded planetary row, and 9-11 represents the engagement pair of the unloaded fixed shaft gear.It can be seen from the diagram that the maximum and root mean square values of dynamic engagement force of no-load gear pair basically coincide with the change trend of gear position.

Under gear 1-4, the maximum dynamic engagement force and root mean square value of no-load gears gradually decrease with gear increase.The change trend of gears 5-8 is similar to that of gears 1-4.From a quantitative point of view, the dynamic meshing force maximum and mean square root of each inner and outer gear pair of planetary gear drive are significantly smaller than that of fixed shaft gear drive.Among them, the maximum dynamic engagement force and root mean square value of gears 1 and 5 are generally large, which indicates that the no-load knocking noise of gears 1 and 5 is large.