目 录
摘要 ············································································································· 2 第一章 序 言 ······················································································· 3
1.1减振器的分类 ······················································································ 3
1.2筒式液阻减振器简介 ············································································· 3
第二章 减振器设计方案的确定 ·································································· 3
2.1减振器设计参数依据 ············································································· 3 2.2汽车振动系统对减振器特性的要求 ··························································· 4 2.3方案的确定 ························································································· 4
第三章 设计计算 ······················································································· 6
3.1载荷的确定 ························································································· 6 3.2减振器阻力与各腔压力的关系 ································································· 6 3.3主要性能参数的确定 ············································································· 6 3.3.1减振器的性能 ···················································································· 7 3.3.2相对阻尼系数Ψ ················································································· 7 3.3.3减振器阻尼系数δ的确定 ····································································· 7 3.3.4最大卸荷力Fs的确定 ·········································································· 8 3.3.5筒式减振器工作缸直径D的确定 ··························································· 8
第四章 阀体选用 ······················································································· 8 第五章 减振器的数学模型 ········································································· 9
5.1拉伸（复原行程）工况下的数学模型 ························································ 9 5.1.1开阀前 ····························································································· 9 5.1.2开阀后 ··························································································· 10 5.2压缩（压缩行程）工况下的数学模型 ······················································ 11 5.3 减振器的外特性模拟计算 ···································································· 13
第六章 减振器的行程与布置 ···································································· 14
6.1减振器的行程选取 ·············································································· 14 6.2减振器行程匹配 ················································································· 15 6.3减振器的行程校核 ·············································································· 16
结论 ··········································································································· 18 致谢 ··········································································································· 19 参考文献 ··································································································· 20
摘 要
本文旨在以一实例阐述筒式液阻减振器设计流程。先在筒式液阻减振器选取两种制造工艺相对成熟结构方案――单筒充气式液力减振器与双筒式液力减振器，进行对比。发现单筒充气式液力减振器相比之下有许多有点，但唯一不足之处在于安装尺寸不合要求，所以采用双筒式液力减振器。减振器设计计算的主要目的在于确定工作缸直径，其他尺寸的确定依赖于一些经验值。本文各项参数的选取和算法主要参照汽车设计手册，进行对减振器设计计算。然后根据前人的减振器数学建模成果，用MATLAB进行外特行计算，并绘制出F-V曲线。再根据曲线修改阀体尺寸及性能参数，再绘制曲线，直到满足设计要求为止。最后进行行程布置和校核计算，由于此项计算对悬架参数的选取依赖性很大，而本人没有找到合适的悬架参数，因此计算的结果意义不大，但这为以后的工作提供了一些资料。
关键词：减振器；数学模型；外特行计算
Abstract
The aim of this thesis is to explain the progress of design of the shock absorber. First, chose tow types of shock absorber which technics of product of is more mature——one solid bowl charged absorber and tow solid bowls absorber. Then compare one with the other one. Though the former have much advantage, it’ s size of assemblage is longer than the request of the design. So I chose the latter. According to the theory of automotive design, I chose the frame of the shock absorber and it’ s part, then calculate the most important parameter which was used to design. I make the F-V curves of the absorber with the mathematics model. At last I complete the calculation of the stroke by which the shock absorber works.
Key words: shock absorber; mathematics model; outer performance calculation
第一章 序 言
1.1减振器的分类
减振器的作用是缓和汽车的振动，提高汽车的行驶平顺性，保护货物，降低车身各部分的动应力，延长车身等部件的寿命。另外，还能增强车轮的附着性，有助于操纵性和稳定性，缓和由于路面不平引起的冲击。减振器从结构上可分为摇臂式减振器和筒式减振器两种。摇臂式减振器是早期产品，现代汽车上已很少用，基本上被淘汰；筒式减振器是主流，它分为被动式和可调式两种。被动式减振器又分为双筒式、单筒充气式、单筒非充气式三种，双筒式减振器按其作用又可分为单向作用式和双向作用式两种。可调式减振器有机械控制式、电子控制式、电流变和磁流变液体减振器四种。
1.2筒式液阻减振器简介
筒式液阻减振器在汽车上有着重要的作用，其阻尼力主要通过油液流经孔隙的节流作用产生。汽车上应用最多的该类减振器是悬架减振器，它能够有效地衰减悬挂质量与非悬挂质量的相对运动，提高汽车的乘坐舒适性、行驶平顺性和操纵稳定性。筒式液阻减振器还用作转向系减振器以及驾驶室、驾驶员座椅、发动机罩等部件的减振装置。随着汽车性能要求的不断提高，筒式液阻减振器的结构和性能亦不断得到改进和提高。在传统被动式减振器技术发展和完善的同时，能够适应不同行驶工况而调节其工作特性的机械控制式可调阻尼减振器、电子控制式减振器以及电流变液体、磁流变液体减振器技术也获得了快速发展。作为筒式液阻减振器技术的重要内容，其设计开发技术也正经历着由基于经验设计一实验修正的传统方法向基于CAD/CAE技术的现代设计开发方法的转变。随着硬件性能和计算分析能力的提高，在设计阶段预测减振器的性能并进行优化设计已成为可能，这对于提高汽车筒式液阻减振器产品的设计开发效率、缩短开发周期具有重要意义。
第二章 减振器设计方案的确定
2.1减振器设计参数依据
车型参数：整车质量1500kg
装载质量500kg 轴距2300mm
质心到前轴距离1100mm 轮距1500mm 质心高度550mm
减振器设计要求：1.活塞有效行程不小于190mm 2.活塞最大压缩时全长不大于310mm 3.复原阻力1000-2800N 4.压缩阻力不大于1000N
2.2汽车振动系统对减振器特性的要求
由路面激励引起的汽车垂直、俯仰以及侧倾等运动都会影响汽车的乘坐舒适性、行驶平顺性。悬架减振器的一个重要作用是衰减因冲击引起的车身的自由振动，并抑制在共振频率附近车身强迫振动的幅值，提高乘坐舒适性。在频域内，由路面激励引起乘员振动加速度的幅频响应特性在系统固有振动频率附近存在峰值，如图1所示。其中车身一悬架系统的固有振动频率在1Hz附近，乘员一座椅系统的固有振动频率在3Hz附近，非悬挂系统的固有振动频率在10Hz附近。在以保证汽车最佳乘坐舒适性为目标的条件下，减振器阻尼系数的选择在于如何有效降低乘员振动响应峰值。对于轿车减振器，当阻尼比在0.3左右，复原压缩行程阻尼力分配为80:20时，通常可以获得较好的乘坐舒适性。
2.3方案的确定
汽车悬架系统最初采用摇臂式液阻减振器，第二次世界大战期间美军吉普车上采用了
筒式液阻减振器并在战场上获得成功，此后筒式液阻减振器很快成为主流产品。它具有工艺性好、成本低、寿命长、质量轻等优点，主要零件采用了冲压、粉末冶金及精密拉管等高效工艺，适于大批量生产。我国在20世纪60年代生产的BJ212、NJ230汽车上开始采用筒式液阻减振器，70年代初解放牌汽车也改用了筒式液阻减振器。
筒式液阻减振器最初采用双筒式结构，如图2a所示，该结构目前仍是悬架减振器中最常见的形式，其优点是工艺简单、成本低廉，缺点是散热困难，且安装角度受到限制。双筒式减振器发展初期不在补偿室内设置背压，在复原行程中油液依靠其自身重力和压缩室负压由补偿室流人压缩室。这类减振器的显著缺点是在高速工况下会出现补偿室向压缩室充油不及时的问题，从而导致减振器工作特性发生畸变，不但影响减振效果，还会导致冲击和噪声。20世纪50年代单筒式充气减振器技术蓬勃发展起来，它采用了浮动活塞结构，在浮动活塞与缸筒的一端之间形成的补偿室内充人一定量的高压(2.0 MPa～2.5 MPa)氮气，
压缩室内油液体积的变化由这部分气体补偿，其典型结构如图2b所示。
单筒充气式液力减振器与双筒式液力减振器的制造工艺相对比较成熟，所以我在这两种方案中选择。前者与后者相比，具有以下优点：1.工作缸筒直接暴露在空气中，冷却效果好；2.在缸筒外径相同的前提下，可采用大直径活塞，活塞面积可增大将近一倍，从而降低工作油压；3.在充气压力作用下，油液不会乳化，保证了小振幅高频振动时的减振效果；4.由于浮动活塞将油、气隔开，因而减振器的布置与安装方向可以不受限制。其缺点