Design Optimization Of Powertrain Mounting System Of Internal Combustion Engine

Powertrain engine is one of the main automobile source of vibration and noise. With the improvement of living standard, people are having increasingly demanding on automobile safety and comfort products. How to increase the efficiency of powertrain mounting system vibration damping and vibration isolation, a very valuable problem, is crucial for the development and progress of automobile industry. Setting reasonable mounting system and optimizing it’s performance can not only make cars more robust and reduce energy consumption, but also increase the lifespan of components of the vehicle, more importantly, increase safety.This paper aims to optimize the powertrain mounting system and improve the NVH performance of the car. What we have done are brief introduced as follows.First,we described the basic functionality of the powertrain mounting system, as well as domestic and foreign status, then analyzed the excitation force acting on the single cylinder crank mechanism and inline six-cylinder engine. On the basis of the above, we made a balance analysis on excitation force and moment of the existing models, and then get the unbalanced moments.Second, we established physical model and mathematical model of mounting system. Though solving differential equations of free vibration, we obtained stiffness matrix, the natural frequencies and other inherent characteristics. Though solving differential equations of forced vibration, we obtained the displacement and velocity of the system in the main inertial frame, lay the foundation for subsequent optimization.Third, calculated and analyzed the inherent characteristics of the existing models. Applying the fgoalattain method in Matlab to optimizing the decoupling rate of mounting system. The results show when the decoupling rate is higher than 90%, the allocation of natural frequency is more reasonable. However, as the car running, stiffness of the suspension system will change, decoupling rate will be changed consequentially.Fourth, as for such a suspension system, that is to say, coupled vibration system for more freedom, decoupling is the most effective general practice to reduce and control vibration. However, decoupling rate is the inherent characteristics in case of the system is not excited by the excitation force. As the car running, powertrain is excited by the force all the time, so it’s need to optimize the dynamic characteristics of the powertrain mounting system. Vibration intensity is also an important indicator to estimate the vibration isolation performance of the system. Vibration intensity can represent vibration strength more intuitively. Vibration intensity reflects the number of the total energy which contains each harmonic vibration wave energy, it is often used to measure the intensity of vibration intensity. To optimize the suspension system again, using vibration intensity as the optimization target, suspension stiffness, the mounting position as the optimization parameters. The results show vibration displacement, velocity and acceleration of the system has all reduced, the change gets mild as the time going. Each operating mode vibration intensity all reduced, at a speed of 2200 r per minute in rated conditions, vibration intensity reduced from 35.5542 mm per second to 28.9692 mm per second. Thus, we reached the optimization goal to reduce the vibration intensity, vibration performance improved significantly.