【作者】 陈磊；

【导师】 潘公宇；

【作者基本信息】 江苏大学 ， 车辆工程， 2019， 硕士

【摘要】 汽车制动系统的NVH特性关系到整车NVH特性,较差的制动NVH特性将带来消费者的大量抱怨与投诉,由于目前乘用车的前后轮大多采用盘式制动器,所以对于盘式制动器NVH特性的研究具有重要意义。本文选用某乘用车前轴浮钳式通风盘式制动器作为研究对象,根据制动器结构组成特征,提出了六自由度动力学分析模型,基于复特征值分析理论,详细分析了影响系统稳定性的因素并对影响因素做了具体分析。采用有限元复特征值模态分析与噪声台架试验相结合的方式,建立了制动系统尖叫噪声预测模型,提出通过制动背板开槽设计与多层消音片结构设计来降低制动尖叫噪声发生率,进而提高制动系统NVH特性,并结合预测模型与噪声台架试验,验证所提出降噪方法的有效性并对其降噪机理进行分析。通过对制动系统的力学分析发现,制动压力分布的不对称性将影响系统的稳定性,提出了一种新结构卡钳,仿真及试验表明了该结构设计的有效性。首先,在CATIA中建立三维模型,通过HyperMesh划分网格并定义材料等属性,再导入到Ansys/Workbench中进行实模态与复模态分析。通过对关键零部件的实模态仿真分析与实验分析验证了所建立有限元单体模型的有效性,接着在Workbench中编写APDL命令流对系统进行复模态计算,计算结果发现系统共存在七个不稳定模态,该结果与噪声台架试验结果具有较好的一致性,这表明该模型能够较好地预测尖叫噪声的发生。其次,通过制动系统六自由度动力学分析模型可知,制动背板与消音片为影响系统稳定性的两个关键部件。通过试错法发现了在制动背板表面开设横槽有利于系统的稳定性,仿真计算表明,开设三条横向槽的制动背板具有良好的效果,然后台架试验验证了仿真结果的正确性。再者,提出多层结构消音片来改善系统尖叫噪声问题,设计了四种结构形式的消音片进行复模态计算,最终发现IV型消音片(橡胶-钢片-橡胶)使得整体噪声发生率从19.27%降低至了1.27%。最后,通过制动系统力学模型分析发现,制动盘受到的制动压力不平衡将影响系统的稳定性,提出对卡钳结构进行创新性设计,仿真及台架试验结果表明,新结构卡钳的设计能够极大地改善制动系统的稳定性及降低制动尖叫噪声的发生,能够将整体噪声发生率从19.27%降低至3.63%,并通过仿真分析了接触压力分布的特点及通过道路试验对比分析了新结构卡钳的有益效果。更多还原

【Abstract】 The NVH characteristics of automobile brake system concern the characteristics of the whole vehicle NVH,and the poor brake NVH characteristics will bring a large number of complaints from consumers,since most of the front and rear wheels of passenger cars are made of disc brakes,so it is of great significance to study the NVH characteristics of disc brakes.In this paper,the front axle floating clamp type brake of a passenger car is selected as the research object,according to the characteristics of brake structure,a six-DOF dynamic analysis model is proposed.Based on the theory of complex eigenvalue analysis,the factors affecting the stability of the system are analyzed in detail and the influencing factors are analyzed concretely.A prediction model of squeal noise in brake system is established by combining finite element complex eigenvalue modal analysis and noise bench test.It is proposed that the occurrence rate of brake squeal noise can be reduced through the design of brake backplate slotting and insulator multi-layer structure,and the NVH characteristics of brake system can be improved.Combining the prediction model with the noise bench test,the effectiveness of the proposed noise reduction method is verified and the noise reduction mechanism is analyzed.Through the mechanical analysis of the brake system,it is found that the asymmetry of the brake pressure distribution will affect the stability of the system,and a new structure caliper is proposed,and the simulation and test show the effectiveness of the improved structure.Firstly,a three-dimensional model is established in CATIA,the mesh is divided and the properties such as materials are defined by HyperMesh,and then the model is imported into Ansys/Workbench for real modal and complex modal analysis.The validity of the key components finite element model is verified by the real modal experimental analysis.Then the APDL commands are written in Workbench to calculate the complex mode of the system,and the results show that the system there are seven unstable modes in the system.The results are in good agreement with the noise bench test results,which shows that the model can predict the occurrence of squeal noise well.Secondly,through the dynamic analysis model of six-DOF brake system,it can be seen that the brake backplate and insulator are the two key components that affect the stability of the system.It is found that the setting of transverse grooves on the surface of brake backplate is beneficial to the stability of the system through trial-and-error method,and the simulation results show that the braking backplate with three transverse grooves has good effect,and then simulation results are verified by the bench test.Furthermore,a multi-layer structure insulator is proposed to improve the squeal noise of the system,and four kinds of insulator of the structure form are designed for complex modal calculation,and finally the type IV insulator(rubber-steel sheet-rubber)is found to reduce the overall noise incidence from 19.27% to 1.27%.Finally,through the analysis of the mechanical model of braking system,it is found that the unbalance of braking pressure on the brake disc will affect the stability of the system,so the innovative design of the caliper structure,simulation and bench test results show that the design of the new structure caliper can greatly improve the stability of the braking system and reduce the occurrence of squeal noise.The overall noise incidence can be reduced from 19.27% to 3.63%,and the characteristics of contact pressure distribution are analyzed by simulation and the beneficial effect of the new structure caliper is compared and analyzed by road test.更多还原