目的 针对目前某些封口机减速箱中齿轮设计不合理等问题，提出改善齿轮振动特性的新思路，改变齿轮的变位系数。方法 通过模态分析来确定机构的固有频率和振型等系数，以直齿轮的变位系数为自变量，利用SolidWorks进行齿轮三维建模，将模型导入Ansys Workbench中进行模态分析，最后将得到的数据导入Matlab进行分析，进行多项式拟合。结果 直齿轮的固有频率会随着变位系数的增加而减小，且在变位系数为0处会出现突变，固有频率随着变位系数的增加在小范围里先减后增，变化曲线可用十次曲线精确拟合。结论 为研究齿轮固有频率、振型以及对封口机减速箱进行优化设计提供了参考。

This work aims to present a method of promoting the vibration performance of the gear and change the variation coefficient with respect to some unreasonable designs for gear of reduction gearbox in capper. Natural frequency and vibration mode were confirmed by modal analysis. 3D modeling was conducted by Solidworks with variation coefficient of spur gear as independent variable. Then Ansys Workbench was used to do modal analysis. At last, experiment data were imported into Matlab for analysis and polynomial fitting. The natural frequency of spur gear decreased with the increase of the variation coefficient and had a sudden change when the variation coefficient was zero. It decreased firstly and increased then in a small range with the increase of the variation coefficient. The change curves could be accurately fitted with ten fitting curves. In conclusion, the work can be used as a useful reference for the study of the natural frequency and vibration mode of gear and the optimization design of the reduction gearbox for capper.