Optimization Design For The Vehicle Engine Mounting System

Vehicle vibration comes from two main sources: engine and road surface, powertrain mounting system plays a vital role in isolating the vibration. The reasonable design of powertrain mounting system could not only improve the vehicle comfort, but also improve the reliability and durability of the engine and related parts around it. It can be proved from the engineering practice that the design of the powertrain mounting system is not a simple task because there is contradiction in itself: on the one hand, the mounting system is hoped to be stiffer just to constrain the movement of engine;on the other hand, in order to play a better role in vibration isolation, the stiffness of mounting system is constrained. Based on the vibration isolation basic principle and optimization design theory and method, we conducted a optimization design and research on the vehicle powertrain mounting system.Therefore, the main contents in this paper are as followed:(1)An engine mounting system optimization model was established based on the multi-objective optimization theory and the maximum energy decoupling rate of main vibration directions had been obtained by reasonable setting of mounting stiffness and position parameters. A 6 DOFs model for mounting system was constructed with the maximization of energy decoupling rate of vertical and crankshaft rotation directions as objectives, mounting stiffness parameters and position parameters as design variables. Taking into account of constraint of natural frequency and engine mounting system parameters and using non-dominated sorting genetic algorithm, a multi-objective optimization was conducted.(2)According to the vibration isolation requirement, the engine mounting system modal decoupling and dynamic response was comprehensively considered and the corresponding optimization method was established. An engine mounting system optimization model was established with the maximization of mounting decoupling rate of vertical direction and the minimum of the amplitude of the sum of the reaction in each direction of four mountings as objectives, decoupling rate of crankshaft rotation direction and the sum of the reaction of crankshaft rotation direction of four mountings along with natural frequency and mounting stiffness as constrains. A multi-objective optimization was conducted using non-dominated sorting genetic algorithm.(3)Taking into account of the influencing characteristic of the exciting force to the dynamic stiffness and damping coefficient, the optimization model of mounting system was perfected. Choosing the sum of integral of vibration transmissibility of vertical direction in the vibration frequency range scope as objective, vertical direction static stiffness parameters of four mountings as design variables, natural frequency of 6 DOFs mounting system as constraints, substituting the relationship between the mount dynamic stiffness and static stiffness at the vibration frequency range into the optimization model, an optimization was conducted using genetic algorithm.