Improved Design Of A Commercial Vehicle Powertrain Mounting System

This subject takes a high-speed logistics model developed by our company as the research object.NVH test was carried out on the target vehicle.According to the test results,it was found that the vibration intensity of engine end suspension in the right X direction was 2 times greater than that of the left side,and "negative vibration isolation"appeared in the Y direction of transmission end.At the same time,there is resonance between the suspension system and the cab system in the vicinity of 23Hz when the vehicle is rising in situ.In view of the large difference in vibration isolation rate between the left and right sides of the engine end suspension,the problems of "negative vibration isolation" at the transmission end and the resonance between the suspension system and the cab system in idle speed are presented.In this paper,the vibration isolation theory is used to analyze the testing problem.It is proposed that the distribution of the powertrain's center of mass causes the difference of the left and right suspension excitation forces,the position of the right and left support points of the suspension support frame is inconsistent,the component of the y-direction stiffness of the transmission is unreasonable,and the stiffness of the right passive support of the transmission causes resonance.Based on the "six degrees of freedom" suspension system design theory,the decoupling rate of the suspension system is determined as the optimization goal,and the dynamic stiffness of the suspension block as the optimization variable to improve the design scheme.By using the company's rotary inertia test bench and coordinate measuring instrument and other test resources to test the position of the inertia and center of mass of the powertrain,the accurate quality characteristics of the powertrain are obtained.Abaqus software was used to conduct modal analysis on the stiffness of the connecting frame of the engine before improvement,and the optimization design was carried out according to the optimization target of the first-order mode greater than 400Hz.Using ADAMS software to create a dynamic analysis model,the decoupling rate of the suspension system and the dynamic stiffness of the glue block are optimized by multi-objective analysis,and the dynamic stiffness of the glue block is obtained when the decoupling rate is more than 90%.Through the test and verification of the improved scheme,the results show that the vibration isolation rate of the improved suspension system is 40%-70%,and the improved effect is very obvious.From the evaluation results,the test results of the improved design meet the use requirements.Although the improvement of vibration isolation rate is not obvious as reflected in the cab attachment,the suspension system has met the set target requirements.In particular,the problem of "negative vibration isolation" at the transmission end is solved.It is very important to solve the problem of systematic vibration.The practice proves that the ideas and methods of improving the design of the suspension system discussed in this paper can be applied to engineering practice.