자동차용 파워트레인 마운팅 시스템의 동적 해석 및 최적설계

Abstract

Technology of vehicle industry has been developing and it is required a better vehicle performance than before. Therefore, the consumers are asking not only an economic efficiency, functionality, polished design, ride comfort, and silence but also a driving stability. The ride comfort, silence and driving stability are influenced by the size of vehicle room and various facilities. But the principal factor is a room noise and vibration sensed by a driver and passenger. Thus, the NVH(Noise, Vibration and Harshness) of vehicle has been raised and used as a principal factor for evaluation of vehicle performance. The primary objective of this study is an optimized design of powertrain mounting system. We analyzed an engine exciting force as a source of a vehicle NVH. To understand the engine exciting force, we developed a theoretical equation of single cylinder engine that the equations are incorporated into a in-line 4 cylinders engine. The theoretical equations were programmed using MATALB so that the engine exciting force were analyzed using MSC.ADAMS. We also used ADAMS/Engine and ADAMS/View module. Based on these three analysis, we predicted the engine exciting force. The predicted engine exciting force can be used as a design parameter of powertrain mounting system in a dynamic analysis. A dynamic characteristics of hydraulic mount widely used in the powertrain mount system was investigated. The hydraulic mount is the one used an elastic force of rubber and a damping force of fluid simultaneously. In powertrain mount system, it is necessary that the mount need a high damping at engine shake for ride comfort and a low dynamic spring constant when it is idle. However, a general rubber mount could not be satisfactory for these desired conditions. To satisfy these conditions, the hydraulic mount has been widely used up to date. The hydraulic mount shows "frequency dependent nonlinear characteristics" at both low frequency-high amplitude and high frequency-low amplitude. To resolve this, the hydraulic mount may be used. For an optimized design of hydraulic mount, we studied "nonlinear characteristics" using dynamic analysis of powertrain mounting system considering the engine exciting force. For this, we analyzed the dynamic spring constant and loss factor using a lumped parameter model. It is programmed by MATLAB. A spring constant of coil spring mount in the active control mount was determined. To do this, we developed a new theoretical equation and calculated using a finite element method using MATLAB. Using MSC.Nastran, the spring constant of coil spring was analyzed. We also conducted three spring constant experiments. We can compare all the results from three types of analysis. We conducted a dynamic analysis of powertrain mounting system from the engine exciting force previously calculated and a dynamic analysis of engine shake. To understand the dynamic analysis of powertrain mounting system, we used MSC.Nastran and MSC.Patran as a pre-post processor. To apply for nonlinear characteristics of mount, a CBUSH element and Field function used. A powertrain specification, mount characteristic, mounting position and mounting angle were considered as design parameters. Based on this analysis, the design parameter of powertrain mounting system can be characterized and optimized. These optimized design parameters will be used parameters for an optimized design of powertrain mounting systems. We are optimized the powertrain mounting system using MSC.Nastran optimization modules. We investigated results of dynamic analysis for powertrain mounting system. By these results, we applied the design variables by 12 dynamic spring constant. And the weighting factor according to translational displacement and rotational displacement applied 3 cases. The objective function applied to minimize displacement of powertrain. And the design variable constraint was imposed dynamic spring constant ratio. The constraint of design variable for objective function was imposed bounce displacement for powertrain. All these processes result in the optimization of the powertrain mounting system. 1) The engine exciting forces could predict by theoretical equation, ADAMS/Engine and ADAMS/View software. And the torsional damper and balance shaft was influenced to the engine exciting force. 2) The dynamic characteristics of hydraulic mount could predict by lumped parameter model. The dynamic characteristics are dynamic spring constant and loss factor of hydraulic mount. These showed "frequency dependent nonlinear characteristics". And the optimum design of hydraulic mount can designed by dynamic characteristics using lumped parameter model. 3) In dynamic analysis of powertrain mounting system for TRA 4-point mounting system, the engine mount and transmission mount were applied to "frequency dependent nonlinear characteristics". The reaction forces of front roll mount and rear roll mount are stronger than that of engine mount and transmission mount. This is control of roll behavior at front roll mount and rear roll mount. And the reaction force of transmission mount is stronger than that of engine mount. This is affect of reaction forces for front roll mount and rear roll mount. We have need to consider that reaction force and mode decouple ratio in dynamic analysis of powertrain mounting system. 4) In optimum design of powertrain mounting systems system for TRA 4-point mounting system, we optimized reaction force of mount and displacement behavior of powertrain. We obtained powertrain mounting system of decoupled mode. The results show that the optimum design can reduce the reaction force at each mount. We have need to consider that translational displacement and rotational displacement for objective function.