The Optimization Method Of Engine Mounting For Trucks

With the development of automobile industry,the people become more and more concerned about the performance of ride,handling and driving comfort.Engine vibration and road surface are the two main source for vehicle NVH.A proper application in designing engine mounting system can effectively decrease the impact on cab.At the present time,most of national OEMs design their engine mounting by experiences and large number of test.But this kind of method will take too much time and is difficult to control. Commonly there are six direction degrees of freedom which are coupling,and they will lead to big breadth and broad band frequency.If we want to gain a better vibration-isolation result,some more soft mounting cushions are needed.But this will result in big displacement between surrounding parts and will bring collision which will affect the ride performance and decrease the cushion life.Thus in order to catch the target of optimization for engine mounting,we must concern all relevant parameters simultaneously. Before studying the vibration-isolation of engine mounting,we must learn the NVH principles when a vehicle in different running status,and we should consider those unique characteristics in use.Normally the idling circumstance will affect the designing engine mounting prominently and directly.Secondly in uniformity velocity circumstance,road surface impulsion will also affect the engine mounting designing indirectly,because such impulsion will affect the vehicle ride performance which relate to the application between chassis suspension and cab mounting.Furthermore,the tire imbalance also should be concerned for engine mounting. Normally,for those direction degrees of freedom in which there are big impulse forces,small stiffnesses should be chosed in order to isolate the vibration.But for those in which there are small impulse forces,big stiffnesses should be chosed to increase the supporting ability.According the theory of vibration,there are some targets and restrictions for engine mounting in the following. 1.The rigid body mode of power unit should avoid the sensitivity frequency range of human body. 2.The system inherence frequency must no more than the 1 /2times of engine idling impulsing frequency. 3.The distortion value in static status should be 4mm or so. 4.Lay the mounting parts on those nodes of spring vibration. 5.Consider the impulsion from tires. 6.Try to get the result of uncoupling for the mounting system. 7.A big lateral stiffness for power unit benefit to handling. There are some conflicts for above targets.we can not satify all of them.So in the application process,different indexes should be regulated properly. Based on analyzing the papers which study automotive engine mounting system at home and abroad,simultaneously through probing into different principles of NVH for complete truck in different running conditions,various restricting factors for engine mounting system are...