Fig. 1 (a) and (c) show the dynamic meshing force curves of the front and rear gear pair 1 of the coupling rocker box respectively. The peak value of the dynamic meshing force before the coupling rocker box is 165.96 kn, and the peak value of the dynamic meshing force after the coupling rocker box is 164.02 kn. The absolute error is – 1.94 kn and the relative error is – 1.18%. In order to avoid the contingency of the peak value of dynamic engagement force, the 90th percentile of Fig. 1 (a) and Fig. 1 (c) are calculated, which are 105.33 kn and 103.38 kn respectively.

The absolute error is – 1.95 kn and the relative error is – 1.89%. Figure 3.18 (b) and figure 3.18 (d) show the frequency spectrum of the dynamic meshing force of the front and rear gear pair 1 of the coupling rocker box, which are highly consistent. The main frequency components are the meshing frequency of each gear pair and the excitation frequency of the roller load. Although the gear pair 1 is far away from the second stage planetary gear train, there are still three times of the meshing frequency of the second stage planetary gear train in the meshing force spectrum, which is consistent with the phenomenon in previous studies. There is no frequency component consistent with the deformation of the rocker arm box in the dynamic engagement force spectrum, which is different from the box deformation component of 17.25 Hz in the meshing tooth direction error. The reason will be further analyzed in the future.

Figure 2 Statistics the dynamic load coefficient of the gear pair before and after the coupling rocker box. It can be seen that the dynamic load coefficient of the gear pair after the coupling rocker box may increase or decrease, which is related to the specific position of the gear pair in the rocker box. However, from a quantitative point of view, the dynamic load coefficient of the gear pair before and after the coupling rocker box does not change significantly under rated conditions.