将发动机曲轴及连带的质量(包括所有内部运动部件及飞轮、风扇、发电机等附件)组成的复杂系统,简化成当量系统,以方便分析计算。当量系统由带有当量惯性圆盘的等圆轴组成,即把发动机所有运动部件看作一个绕曲轴中心转动的简单回转体。且简化的当量系统必须保证与原复杂系统在振动过程中的动能和位能均相等及在动力学上的等效性。各惯性圆 The complex system of the engine crankshaft and its associated masses (including all internal moving parts and accessories such as flywheels, fans, generators, etc.) is reduced to an equivalent system to facilitate analysis and calculation. Equivalent systems consist of an equi-circular shaft with an equivalent inertial disk, which treats all moving parts of the engine as a simple rotor that rotates about the center of the crankshaft. The simplified equivalence system must guarantee the equal and dynamic equivalence of kinetic energy and potential energy in the original complex system during vibration. Each inertia circle