Balance Characteristic Analysis And Mount Matching Of Three Cylinder Engine

China’s fourth-stage fuel consumption regulations stipulate that the average fuel consumption of passenger cars in 2020 must reach 5L /(100 km).The three-cylinder engine,which can meet the requirements of low fuel consumption and power conditions and has small installation space,has ushered in new development space.Compared with the traditional four-cylinder engine,the three-cylinder engine has large torque fluctuations and the reciprocating inertia moment imbalance characteristic causes the powertrain vibration to deteriorate,and the vibration transmitted to the vehicle through the suspension is also large,causing the driver to intuitively feel the three-cylinder The machine is generally more violent than the four-cylinder machine,and the comfort of the whole vehicle is deteriorated.In-cylinder direct injection,turbocharging and other technologies have greatly increased the power of the three-cylinder engine,and the vibration has become more intense.Vibration control has important engineering significance for the development of high-comfort passenger cars.Adding balancing devices and optimizing the suspension system are two typical technical measures to improve riding comfort.In the matching process of the traditional three-cylinder engine powertrain mounting system,less attention is paid to the requirements of the engine balancing strategy for the excitation force and the decoupling rate of the mounting system,or the balancing scheme is adopted after the matching of the mounting system is completed.The effect of vibration control becomes worse,affecting the NVH performance evaluation of the entire vehicle.Firstly,the dynamic and kinematic analysis of the central crank connecting rod mechanism is done,and the reciprocating inertial force of the piston assembly and the rotating inertial force of the crank connecting rod mechanism are used to calculate the excitation force and torque of the machine body.The new imbalance factors that will be introduced illustrate the calculation of the optimal balance ratio.The actual cylinder pressure data is integrated to determine the output torque of the single-cylinder engine,and then the excitation torque of the three-cylinder engine is determined according to the vector superposition of the excitation.Secondly,the mathematical model of the powertrain suspension was established in MATLAB.The accuracy of its modeling was verified using the multi-body dynamic model established in ADAMS / VIEW.The natural frequencies and decoupling rates of various orders of the built models were compared.Distribution,the results of the two are in good agreement.Latin hypercube sampling was used to establish an approximate relationship model between the mounting stiffness,mounting system decoupling rate and natural frequency.Using the determination coefficient as an evaluation index,the accuracy of the constructed approximate model is evaluated.From the overall model,the accuracy of the constructed approximate model is high,which can replace the original model for optimization analysis.Under the premise of considering the excitation characteristics,taking the reasonable configuration of the system natural frequency as the constraint condition to improve the decoupling rate of the suspension system,the design optimization of the suspension stiffness improves the decoupling rate of the system.The approximate model is used to analyze the robustness of the mounting stiffness,and the influence of the discreteness of the mounting stiffness on the decoupling rate of the system is studied.The results show that the system is robust and the solution has engineering significance.Finally,the Newmark-β algorithm was used to analyze the vibration response of the matched suspension system,and the dynamic reaction force and torque of the suspension before and after optimization were calculated and compared.It can be seen from the calculation results that as the speed increases,the vibration reduction effect is obvious,and the joint application of the balancing strategy and the suspension matching is effective.