考虑连杆惯性参数的三缸发动机激励建模与分析

针对传统曲柄滑块简化方法无法准确计算三缸发动机振动激励的问题，提出了一种新的三缸发动机激励建模计算方法。首先，考虑了连杆等部件的惯性参数，基于拉格朗日乘子法推导了三缸发动机振动激励的理论表达式，并代入了实车数据，计算了其激励后发现：三缸发动机在三个方向上都存在数量级相当的不平衡惯性力矩，而传统简化方法不会出现绕z轴的激励。然后建立了考虑液压悬置频变特性的动力总成悬置系统仿真模型，分别将本文方法和传统简化方法计算出的激励施加于仿真模型，计算了各悬置点的振动加速度响应。最后，为间接验证激励计算准确性，进行了某三缸发动机样车怠速振动实验，测量了各悬置点振动加速度响应，与仿真值进行了对比，结果表明，考虑连杆等部件的惯性参数后，可得到更为准确的三缸发动机激励，可应用于计算精度要求较高的场合。
Abstract：To reduce the inaccuracy in excitation calculation of a three-cylinder engine,a new modeling calculation method was proposed.Considering the inertial parameters of connecting rods and other components,a theoretical expression for the vibration excitation of the three-cylinder engine was deduced based on the Lagrangian multiplier method.Then the excitation of the engine was calculated,unbalance inertia moments in all three directions were found,whereas the excitation around the z-axis will not appear,if calculating by traditional simplified methods.A model for the powertrain mounting system was built considering the frequency-dependent characteristics of the hydraulic engine mount,and the vibration accelerations at mount locations were simulated.Then the vibrating accelerations were measured through the idle vibration experiments on a sample car.By comparing the simulation results with measured values,the accuracy and superiority of the method considering inertial parameters of connecting rods was verified.The method can be used in the situation where high accuracy is needed.