# Design and Analysis of Internal-External Composite Meshing Hy-Vo Chain
## 6 Conclusions  
1. \(p_{1}=p\) and \(\alpha_{1}=\alpha\) are the necessary conditions for the existence of the internal-external composite meshing Hy-Vo chain. The proper internal meshing profile of the internal-external composite meshing Hy-Vo chain should be a straight line, and its convexity should satisfy Equation (19). Based on the dynamics simulation results, taking the external meshing Hy-Vo chain system as the benchmark, for the internal-external composite meshing Hy-Vo chain system, the meshing performance is improved by an average of 42.38%, the transmission stability is improved by an average of 40.73%, and  
Figure 20: Analysis based on the driven sprocket velocity: (**a**) velocity extent of driven sprocket; (**b**) improving rate of polygon action. the polygon action is improved by an average of 32.72%. For the mixed assembly Hy-Vo chain system, the meshing performance, the transmission stability, and the polygon action are only improved by an average of 13.08%, 8.12%, and 8.60%, respectively;
2. The mixed assembly Hy-Vo chain cannot stably enhance the system meshing performance, transmission stability, and polygon action. According to the dynamics simulation results, compared with the external meshing Hy-Vo chain system, the system meshing performance, transmission stability, and polygon action of the mixed assembly Hy-Vo chain system can only be improved at some special speeds. At other speeds, the system meshing performance, transmission stability, and polygon action for the mixed assembly Hy-Vo chain system will become worse. In the worst case, the system meshing performance is reduced by 23.40%, the system transmission stability is worsened by 37.57%, and the system polygon action is worsened by 47.91% instead. Therefore, the proper internal meshing profile of the mixed assembly Hy-Vo chain is not an arc, and the relative design approach is false;
3. The meshing between the internal-external composite meshing Hy-Vo chain and the involute sprocket is continuous but incomplete; its effect on reducing the polygon action and the transmission performance is limited. The main reason for that is because the tooth shape of the involute sprocket in the Hy-Vo chain transmission system is significantly smaller than that in the round pin jointed silent chain transmission system;
4. The classical meshing theory about the internal-external composite meshing characteristics of the Hy-Vo chain is not completely correct. Under the classical meshing theory, the internal-external composite meshing mechanism should enhance the system meshing performance, transmission stability, and polygon action, as well as the meshing impact between the chain and the sprocket. However, based on the dynamics simulation results in this study, the maximum meshing impact of the internal-external composite meshing Hy-Vo chain system is increased by an average of 51.24%, and the average meshing impact is increased by an average of 6.19% instead. Therefore, we know that using the internal-external composite meshing mechanism can only enhance the system meshing performance, transmission stability, and polygon action but cannot improve the performance of the meshing impact;
5. The system polygon action is not always consistent with the system meshing performance and transmission stability, and the polygon action of the Hy-Vo chain system cannot be evaluated by testing the maximum fluctuation difference of system center distance. In this research, the experiment results show that the system polygon action has the possibility to be improved when the system meshing performance and the system transmission stability are worsened. Due to the limited research time and test cycle, some characteristics of the internal-external composite meshing mechanism of the Hy-Vo chain still need to be further studied, such as the influence of the meshing mechanism on the fatigue life and wear resistance of the chain, the effect of the imperfect meshing on the system noise, etc.