Involute gear has the characteristic that the center distance changes while the transmission ratio remains unchanged, so the center distance error of involute gear is seldom discussed. But from the perspective of dynamics, the change of center distance will change the meshing angle and coincidence degree of gear pair, and these two parameters are related to the dynamic response of gear system, so it is necessary to check the change of center distance of gear pair under the condition of dynamic deformation of cutting part.

Figure 1 compares the instantaneous center distance of gear pair 1 with the theoretical center distance, and defines the difference as the center distance error. Figure 2 (a) and Figure 2 (b) show the peak value and 80th percentile of the center distance error of each gear pair before and after the coupling rocker box. It can be seen that the center distance error of gear pair 1 decreases, the center distance error of gear pair 2 increases, and the center distance error of gear pair 5 changes. The change trend of center distance error of each gear pair has no general rule, which is related to its specific position in the rocker arm box.

From a quantitative point of view, the maximum value of the center distance error of gear pair 1 in the rated condition in Figure 1 is 46.7 μ m, which is almost negligible compared with the theoretical center distance of 315 mm. The theoretical center distance of other gear pairs is greater than that of gear pair 1, and the absolute value of center distance error is less than that of gear pair 1. Therefore, from a quantitative point of view, the coupling rocker box has little effect on the center distance error of each fixed axis gear pair in multi-stage gear transmission. It can be inferred that the coupling rocker box has no obvious effect on the meshing angle and coincidence degree of each fixed shaft gear pair.