【作者】 付江华；

【导师】 史文库；

【作者基本信息】 吉林大学 ， 车辆工程， 2011， 博士

【摘要】 随着汽车工业的快速发展和人们生活水平的提高,汽车NVH(Noise, Vibration and Harshness)性能越来越受重视。汽车的振动缩短汽车产品的使用寿命,汽车的噪声污染环境,影响人们的身心健康。在汽车的各大总成和部件之间使用橡胶隔振件可以有效地降低汽车的振动与噪声。动力总成悬置、排气管悬吊和车身悬置可以衰减由发动机和路面等激励引起的振动,减少振动向车内的传递。将动力总成悬置、排气管悬吊和车身悬置这三种橡胶隔振件进行合理匹配,可以大大地提高汽车的乘坐舒适性。因此,本文基于整车模型对动力总成悬置、排气管悬吊和车身悬置进行匹配研究。本文运用多体动力学理论和有限元方法,采用CAE仿真分析和试验相结合的方式建立包含动力总成悬置、排气管悬吊和车身悬置三种橡胶隔振件的整车刚弹耦合模型,然后在整车模型下分别从单种橡胶隔振件的匹配和三种橡胶隔振件的集成优化匹配两个角度对橡胶隔振件进行匹配研究。在研究的过程中紧密结合工程实际,严格控制橡胶隔振件的压剪比,并考虑橡胶隔振件刚度的不确定性,对橡胶隔振系统进行了鲁棒性优化。在进行动力总成悬置研究时,分别基于传统的动力总成悬置系统六自由度模型和整车模型下的动力总成悬置系统模型进行优化,结果表明在整车模型下对动力总成悬置系统进行优化可以获得更优的优化结果。动力总成悬置系统的优化有多种不同的优化目标,本文对动力总成悬置系统六自由度模型分别采用能量解耦法和动力响应法进行优化,并将两者的优化结果代入整车模型以比较车内振动水平,结果表明动力响应法优化结果对应的车内座椅导轨振动小,且动力总成悬置支承处的动反力小。同时从试验的角度进一步研究动力总成悬置系统能量解耦对车内振动的影响,对同一样车装用不同的悬置并测试车内驾驶员座椅导轨、第二排座椅导轨、第四排座椅导轨和最后排座椅导轨的振动,测试结果表明能量解耦好的悬置方案其车内振动并未改善。动力总成悬置系统的能量解耦可以在一定程度降低车内振动,能量解耦好的悬置系统通常不是最佳的方案。为更准确地模拟样车的振动,本文在整车模型中从能量的角度对动力总成悬置系统进行优化,通过减小动力总成悬置支承处传入车架的振动功率来降低车内振动。排气管悬吊的匹配方面,对排气系统进行计算模态分析和试验模态分析,用排气系统试验模态分析结果校准有限元模型。对试验校正后的有限元模型进行排气管悬吊位置优化,选取平均驱动自由度位移较小的位置作为排气管悬吊点,减小排气系统振动向车架的传递。排气管悬吊的刚度影响着排气系统的动力学性能,通过优化悬吊刚度来改变排气系统的固有频率,使排气系统固有频率远离发动机怠速激励频率及发动机经济转速下的激励频率,从而降低车内振动。同时对排气管悬吊进行试验测试与分析,在包含排气系统柔性体的整车环境下以传递到车架的振动加速度为目标,对排气管悬吊进行优化设计,优化过程中排气系统四个悬吊点只采用两种规格的悬吊以节省企业成本。车身悬置的研究方面,通过对样车车内驾驶员座椅导轨、第二排座椅导轨、第四排座椅导轨和最后排座椅导轨进行振动测试,发现车内各测点的振动与发动机、传动轴和车轮的激振有关。本文从优化车身悬置刚度入手,研究车身悬置的各向刚度对车内振动测点的贡献度。建立既有弹性连接又有刚性连接的车身悬置系统模型,对车身悬置系统进行优化设计,在确定车身悬置的设计变量上下限时兼顾汽车操纵稳定性的要求。橡胶隔振件的集成优化设计方面,考虑动力总成悬置、排气管悬吊以及车身悬置之间的相互影响,同时对它们进行优化设计。在优化设计之前,对各橡胶隔振件进行正交试验分析,确定各橡胶隔振件的灵敏度,然后在动力总成悬置系统、排气管悬吊以及车身悬置系统的各自隔振性能达到最优的前提下,以车内振动响应为优化目标对其进行集成优化设计。通常橡胶隔振件的刚度在设计值的±10%范围内波动,本文对橡胶隔振系统进行鲁棒性设计,并对鲁棒性优化过程进行改进,提高了鲁棒性优化效率。在汽车研发过程中,采用试验与仿真相结合的方法可以加快研发进程,建立整车模型可以更准确地进行汽车振动性能的预测与优化。匹配汽车橡胶隔振件时,应从橡胶隔振件的安装空间、加工工艺性和生产成本等多方面进行考虑,不能顾此失彼。本文以动力总成悬置支承处振动输入功率为优化目标,在整车环境下对动力总成悬置系统进行优化,该方法能有效地降低车内振动,与传统的优化目标具有良好的一致性。本文建立了既有弹性连接又有刚性连接的车身悬置系统模型,为其它结构类似的车身悬置系统模型的建立提供参考。汽车橡胶隔振系统相互影响,本文对其进行集成优化设计,然后从工程实际出发对其进行了鲁棒性优化。在橡胶隔振件的设计阶段考虑其刚度的不确定性,可以有效地提高优化目标的稳定性,使设计的产品更好地达到预期的性能目标。更多还原

【Abstract】 Coincident with the development of automotive industry and people’s living standards, the NVH (Noise, Vibration and Harshness) performance of automobile is more and more popular. Vibration reduces the service life of automotive and and its noise pollutes the environment, which is bad for people’s physical and moral integrity. The vibration isolators between the assemblies and components could reduce vehicle vibration and noise effectively. Powertrain mount, exhaust pipe hanger and body mount can attenuate the vibration and shock arising from engine and road, and decrease the vibration transmission to frame. A reasonable match of these isolators may enhance the ride comfort greatly. Therfore, it’s necessary to study the match of powertrain mount, exhaust pipe hanger and body mount.The multi-body dynamics and finite element methods was utilized to establish the rigid-elastic coupling model of full vehicle including powertrain mount, exhaust pipe hanger and body mount in this dissertation, which was validated by the experiment test. Then the match of rubber isolators in the full vehicle model was study from the following aspects: single type isolators’match and integration design of all isolators. During the research process, the isolators’ stiffness ratio of compression to shear was controlled closely combining with engineering practice while the robust optimization of the rubber isolators was carried out for the uncertainty of the isolators’stiffness.In the study of powrtrain mount, the powertrain mount system was optimized based on the traditional six DOF model of powertrain mount system and the mount system under the full vehicle model respectively, and the results demonstrate that the latter could obtain a better effect. There are many different objectives for powertrain mount optimization, the kinetic energy decoupling method and dynamic response method was taken simultaneously to optimize the traditional powertrain mount system in the thesis. Both of the optimized results were simulated in the full vehicle model to compare the vehicle interior vibration. It’s concluded that the mount of dynamic response method causes a smaller vibration in the driver’s seat rail and the dynamic reaction force in the powertrain mount is better. To have a further research on the the relationship between the vehicle interior vibration and the kinetic energy of powertrain mount system, the vibrations of driver’s seat rail, the second seat rail, the fourth seat rail and the last seat rail in the same automotive with different mounts were tested and the results demonstrate that the powertrain mount system with good decoupling level has a worse vibration. The kinetic energy of powertrain mount system can to some extent reduce the vehicle vibration, but it’s usually not the best solution. For a more accurate data of vehicle vibration, the powertrain mount system in a full vehicle model was optimized from the standpoint of energy to cut down the vibration power of the powertrain resulting from the mount supporting position to the frame.As for the match of exhaust pipe hanger, calculating modal analysis and experiment modal analysis of the exhaust system were carried out. The result of the experiment modal analysis was utilized to validate the finite element model of exhaust system, and then hanger position of the exhaust pipe was optimized to find the location with minimum ADDOFD (average driving degree of freedom displacement) in the calibrated model, which could decrease the exhaust system vibration transmission to the frame. The stiffness of exhaust pipe hanger affects the dynamic performance of exhaust system. Altering the stiffness of the hanger could change the natural frequencies of exhaust system which should keep far away from the engine excitation frequency of idle speed and economy speed to reduce the vehicle vibration. Meanwhile the hanger vibration of the exhaust pipe was tested and analyzed. Then exhaust pipe hangers were optimized in a full vehicle model which contained the flexible exhaust system, the vibration acceleration acted as the objective, and at the same time only two types of hanger were used in the four hanger location to save the enterprise cost.With reference to the study of body mount, the vibration of driver’s seat rail, the second seat rail, the fourth seat rail and the last seat rail was tested, and the results show that the vehicle interior vibration is related with engine, drive shaft and wheel. In the dissertation, the contribution of stiffness of each body mount to the vehicle interior vibration was studied and the body mount system model with elastic connection and bolt connection was established. When determining the the design variables limit of body mount, vehicle handling and stability was taken into consideration and then the body mount system was optimized.In respect of integrated design for rubber isolators, the interaction of powertrain mount, exhaust pipe hanger and body mount was taken into account, and all the isolators were optimized at one time. Before the optimization, the orthogonal experimental design of all the isolators was taken to determine the sensitivity of each isolator. Then on the premise that powertrain mount, exhaust pipe hanger and body mount had achieved optimal performance of vibration isolation respectively, the stiffnesses of rubber isolators were optimized integratively with vehicle vibration served as the optimization objective. As a rule actual stiffness of the isolators fluctuate around the target stiffness in a plus or minus 10% range, therefore robust optimization was performed for the isolator and the solution process of optimization was improved to heighten the efficiency of roubust optimization in the dissertation.In the process of vehicle research and development, it can accelerate the development to combine the simulation method with experiment mehtod and establishing a full vehicle model could predict the vibration performance of the automotive more accurately. When matching the rubber isolators of the automotive, comprehensive factors should be taken into account, such as isolators’installation space, machining technics, production cost and so on. The powertrain mount system under the full vehicle model was optimized with the input vibration power at the location of the powertrain mount acted as the objective, and this method could reduce the vehicle vibration effectively, which has good correlations with the traditional objective in the thesis. The body mount system model with elastic connection and bolt connection was established, which could give a reference to other similar body mount system. Rubber isolation of the automobile has a mutual influence, and the integrated design of them was studied. In addition, the robust optimization was carried out according to the engineering practice. Considering the stiffness’s uncertainty of rubber isolators is beneficial to the stability of objective in the design phase, which makes the products achieve the desired performance better.更多还原