外文翻译-汽车悬架系统的设计及仿真

本科毕业设计(论文)外文翻译（附外文原文） 学 院： 机械与控制工程学院 课题名称： 汽车悬架系统的设计及仿真 专业(方向)： 机械设计制造及其自动化 （机械装备设计与制造） 班 级： 机械11-2班 学 生： 蓝秀美 指导教师： 沈中华 日 期： 2015年1月23日 汽车悬架如何工作威廉哈里斯密歇根大学当人们考虑汽车性能的时候,他们通常想到的是马力,扭矩, 0至60的加速度时间。如果司机无法控制汽车，即使所有的能量由活塞式发动机提供也是没有意义的。这就是为什么汽车工程师将他们的注意力转向对悬架系统的研究，几乎如同已掌握的四冲程内燃机一样。汽车悬架的作用是最大限度地增加轮胎与路面之间的摩擦,提供操纵稳定性,并确保乘客的舒适性。在这篇文章,让我们一起来探讨悬架是如何工作的,悬架的发展历程和未来发展方向。如果一条路是平坦的,悬架是不必要的。但是路不可能是平坦的，即使是刚铺好的公路也有瑕疵，根据牛顿运动定律,所有力都是有幅值和方向的，当汽车经过一个障碍物时,车轮会上下跳动。没有一个介于中间的结构,所有车轮的垂直能量都会转移到车架上，在同一方向移动。在这种情况下,车轮会与道路完全失去接触，然后在重力的作用下,车轮又会紧压路面。你需要的就是那种系统,可以吸收垂直加速轮的能量,允许汽车即使在颠簸的路面上也依然能平稳的行驶。车辆动力学研究汽车在行驶中受到的力被称为汽车动力学。为了更好地理解为什么要把悬架放在首位，你需要了解一些概念，大多数汽车工程师从两个角度来考虑汽车动力学。行驶:车辆行驶不平路面的平顺性。操控:车辆安全加速,制动和转弯的能力。这两个特点,可以进一步说明,在三个重要的原则道路隔离、道路控制和转弯。下面描述了这些原则和工程师如何试图解决每一个独特的挑战。底盘系统悬挂实际上是汽车底盘的一部分，包括所有位于汽车身体下面的重要系统。这个系统包括：框架结构，承载组件，支持汽车的引擎和车身，反过来又受到悬挂的支持。 悬挂系统支持重量，吸收振动并且保证轮胎的接触。 转向系统底盘，使驾驶员直接引导车辆。 轮胎保证车轮和地面的抓紧力。 因此悬架系统在任何车辆里都是主要的系统之一。下面该看悬架系统的三个基本组成件： 弹簧、阻尼和扭杆。弹簧现如今,弹簧系统都基于四种基本设计形式.螺旋弹簧：弹簧的常用形式，本质上讲，螺旋弹簧相当于围绕在轴线周围的一中高载负性能的扭杆螺旋弹簧，利用伸缩来缓冲车轮的位移。钢板弹簧：这种形式的弹簧是由若干个叶片形金属捆绑而成，并作为一个独立的元件使用的。起初，钢板弹簧用在四轮马车上，直到1985年才广泛用于汽车上。 扭杆弹簧：像螺旋弹簧一样，不过扭杆弹簧利用金属杆的扭曲特性工作的。它是将金属杆的一端铰接在车架上，另一端连接在叉骨架上来工作的。叉骨架类似一个杠杆，它与扭杆的运动方向相垂直，当车轮颠簸时，这种垂直的运动传到叉骨架，通过这种杠杆的作用在扭杆上，然后扭杆沿着轴线发生扭曲而产生弹力。欧洲汽车制造商曾广泛的应用这种弹簧，在20世纪50-60年代美国的Packard和chrgsler也采用了这种弹簧。 空气弹簧：空气弹簧主要是由放置在车轮和车身的柱形气室组成，它利用空气的压缩性能去吸收车轮的振动。这种空气弹簧的概念已经有一个多世纪了，在双轮的马车上就有其存在，在那个时候，空气弹簧用充气的皮革制作，直到20世纪30年代被橡胶气弹簧取代。 根据弹簧在车轮与车架之间放置位置的不同，工程技术人员为了方便将其分为弹簧和簧下质量。弹簧和簧下质量承载弹簧是一种支撑车体的弹簧,而非承载弹簧却是道路和悬架之间松弛的弹簧。当汽车在行驶中弹簧的刚度对承载弹簧有影响。而像林肯之类的高档汽车用的是非承载弹簧,可以吸收缓冲提供高稳定的行驶。可是这种车在加速和刹车的时候容易出现点头和后坐现象，在汽车拐弯的时候也很容易摇晃。像运动形这种承载弹簧类的车,对路面的颠簸要求小,它需要的是在高速行驶时即使是在拐弯的时候,尽可能的减小车身的移动.所以像弹簧这样看起来很简单的装置,在一辆汽车上设计和安装要平衡其舒适度是一件很复杂的工作。更为复杂的是弹簧本身不能提供平顺的行驶。为什么呢?这是因为弹簧能很好的吸收能量却不能释放能量。所以我们需要另一种结构,那就是减振器。减振器减振器和弹簧共同作用，吸收振动并释放出去，直到能量完全释放弹簧才能回到原来的位置，它可以补偿因地面引起的颠簸。由于减振器的存在,它减小并平缓了振动的幅值,将汽车的动能转化成热能并散发到油液中。减振器就象是一个油泵放置在车架和车轮之间。减振器的上部连接在车架上,而下部连接在车轮附近的车桥上。减振器的主要形式是双筒式减振器。它的最上部连接在活塞杆，然后连接活塞,管内充满着油液。其中内部管叫做压力管,外部管叫做贮存管，贮存管内有过量的油液。当车轮在路上颠簸时引起弹簧伸缩,能量传到减振器上部,再传到活塞。减振器在上下运动时油液通过阻尼孔，由于小孔特别小加上压力,使活塞速度减慢,近而弹簧振动速度减慢。减振器有两个工作行程，一个是压缩行程,一个是膨胀行程。 压缩行程发生于活塞向下运动,压缩油液进入活塞下的气室。 膨胀行程发生于活塞向上运动压缩油液进入活塞上部的气室。典型的汽车和轻卡车膨胀行程要大于压缩行程。可以这样理解,压缩行程发生在非承载弹簧的车上, 膨胀行程发生在承载弹簧的车上。当代的减振器对速度是敏感的-悬架动的越快,减振器提供的阻尼就越大。这使得减振器能根据路面的情况去控制车辆,平顺汽车的颠簸,摇摆,前倾和后蹲。支柱和扭杆另一种较常见的减振结构是支柱,基本上是这样的，一个减振器安装在螺旋弹簧内。支柱有两项功能:一是它们提供缓冲功能,如吸振系统。二是他们为汽车悬架提供结构性支持。这意味着它比吸振器吸收的更多, 但是他们只控制速度,而不是重量本身.由于冲击和压杆和一辆汽车的可控性有很大的相关, 他们可被视为是评定安全特征的重要因素。 磨损冲击和压杆可以让过度的车载重量从一侧转向另一侧，从前方到后方，这就降低了轮胎对地面的附着力,以及操纵和制动性能。扭杆扭杆(又称抗侧滚杆)和减振器一起增强车辆在行驶时的稳定性。 扭杆是一个金属杆,横跨整个车桥,有效地将两边的减振器连接在一起。当一个轮子的减振器忽上忽下时,扭杆将运动转移到另外一个车轮上， 这将创建更多的平顺性行驶并减小了汽车摆动。 尤其是它克服了在汽车转弯时的滚动。 基于这个原因,现如今几乎所有的车装都有扭杆作为标准装备,但如果它们没有,在任何时候利用工具箱也会很容易的安装上。悬架类型：前悬目前为止,我们讨论的重点是弹簧和阻尼如何作用于车轮上。但四轮车一起成了两个独立的系统前两个轮子是通过前桥相连的，后两个轮子是通过后桥相连的。这意味着一辆车可以在前方与后方有不同类型的悬架并多少取决了刚性约束车轴车轮或车轮间的独立移动。 前布置被称为独立系统,而后者的布置被称为非独立系统.。在以下章节中, 我们也会学习一些常见的主流汽车上的前后悬架。前悬非独立系统前悬架非独立系统利用刚性前轴连接前轮。 基本上就好像一个坚实的杆放置在汽车的后前方, 装备钢板弹簧和减振器。这些年来通用卡车一直没使用前悬非独立悬架。前悬独立系统前悬架独立系统允许车轮单独运动。麦弗逊式悬架,典型的独立悬架，由厄尔国会商量通用汽车公司在1947年发展起来的，是应用最广泛的前悬架系统,特别是生产于欧洲的汽车。麦弗逊式悬架将减振器和螺旋弹簧结合成一个单位。这提供了一个更紧凑更轻便的悬架系统,通常应用于前轮驱动车辆。双横臂独立悬架,是另一种常见的独立前悬架。虽然有几个不同的配置,但是这样的设计通常是用两个横臂去定位车轮。每个横臂,其中的两端一端连接在车架，另一端连接在车轮。减振器和螺旋弹簧用来吸收振动，双横臂悬架,更多的是控制车轮的倾角，描述车轮倾斜到何种程度。它们还有助于减少滚动或摇摆并为其提供一个更加一致的转向感觉。由于这些特点,双横臂独立悬架是常用于前轮较大的汽车.现在让我们看看一些常见的后悬架.后悬架：非独立悬架用一个固体轴连接一辆小轿车的车轮后方,根据钢板弹簧或是螺旋弹簧，这种悬挂通常很简单。 在刚开始的设计中,弹簧钢板直接钳接驱动桥，减振器连接弹簧轴。由于这种结构简单易行，多年来,美国汽车制造商喜欢采用这种设计结构。相同的基本设计,可以实现与钢板弹簧更换叶片。在这种情况下,弹簧和减振器可以挂载作为一个单一的单位或者作为单独的组件使用。当他们分开时,弹簧可以变的更小,减少了空间的占用。后悬架：独立悬架如果汽车前后悬架是独立的, 那么所有的轮子都进行过单独的安装，可以用在前面的车也可以在后方,可以发现在后轴上节所述的各种版本的前后独立系统。当然,在车的后面, 转向架-其中包括行星齿轮车轮,使车轮从一侧向另一侧旋转。这意味着后部独立悬架可以简化为前部独立悬架,虽然现有的基本原则不变。过去数年汽车悬架虽然对弹簧和避震器有加强和该进, 但是该系统的基本设计并未发生重大改变。但所有这一切即将改变，由于采用了全新的悬架设计构思- Bose,Bose因为其在技术方面的创新而闻名。 一些专家甚至说Bose是汽车悬架最大的一个全独立设计的进步。其工作原理是什么? Bose系统采用直线电机(为LEM ) ,应用于每个车轮以代替传统的冲击和弹簧设置。放大器是提供电力的电动机，电动机向用户提供电力马达,且电机是不被固有常规惯性限制的流体阻尼器。其结果是一个LEM可以扩展和压缩在一个更大的速度，从根本上消除在客舱的所有振动，且可以精细控制该车车轮的运动，不管发生什么事车身依然保持在水平状态。该LEM还可以抵消汽车的身体运动，同时加速，制动和转弯，让驾驶者控制感更强。不幸的是，这种模式暂时将无法使用，直到2009年，它才会提供应用于一个或多个高档豪华型轿车。这时，司机将不得不依赖于尝试了几个世纪具有平滑颠簸的真正的悬挂方式。 How Car Suspensions WorkBy William HarrisUniversity of MichiganWhen people think of automobile performance, they normally think of horsepower, torque and zero-to-60 acceleration. But all of the power generated by a piston engine is useless if the driver cant control the car. Thats why automobile engineers tu- rned their attention to the suspension system almost as soon as they had mastered the four-stroke internal combustion engine.The job of a car suspension is to maximize the friction between the tires and the road surface, to provide steering stability with good handling and to ensure the comfort of the passengers. In this article, well explore how car suspensions work, how theyve evolved over the years and where the design of suspensions is headed in the future. Vehicle Dynamics If a road were perfectly flat, with no irregularities, suspensions wouldnt be nece ssary. But roads are far from flat. Even freshly paved highways have subtle imperfections that can interact with the wheels of a car. Its these imperfections that apply forces to the wheels. According to Newtons laws of motion, all forces have both magnitude and direction. A bump in the road causes the wheel to move up and down perpendicular to the road surface. The magnitude, of course, depends on whether the wheel is striking a giant bump or a tiny speck. Either way, the car wheel experiences a vertical acceleration as it passes over an imperfection. Without an intervening structure, all of wheels vertical energy is transferred to the frame, which moves in the same direction. In such a situation, the wheels can lose contact with the road completely. Then, under the downward force of gravity, the wheels can slam back into the road surface. What you need is a system that will absorb the energy of the vertically accelerated wheel, allowing the frame and body to ride undisturbed while the wheels follow bumps in the road. The study of the forces at work on a moving car is called vehicle dynamics, and you need to understand some of these concepts in order to appreciate why a suspension is necessary in the first place. Most automobile engineers consider the dynamics of a moving car from two perspectives: Ride - a cars ability to smooth out a bumpy road Handling - a cars ability to safely accelerate, brake and corner A cars suspension, with its various components, provides all of the solutions described. Lets look at the parts of a typical suspension, working from the bigger picture of the chassis down to the individual components that make up the suspension proper. The Chassis The suspension of a car is actually part of the chassis, which comprises all of the important systems located beneath the cars body. These systems include: The frame-structural, load-carrying component that supports the cars engine and b-ody, which are in turn supported by the suspension. The suspension system - setup that supports weight, absorbs and dampens shock and helps maintain tire contact.The steering system-mechanism that enables the driver to guide and direct the vehicle.The tires and wheels - components that make vehicle motion possible by way of grip and/or friction with the road .So the suspension is just one of the major systems in any vehicle. With this big-picture overview in mind, its time to look at the three fundamental components of any suspension: springs, dampers and anti-sway bars. Springs Todays springing systems are based on one of four basic designs: Coil springs - This is the most common type of spring and is, in essence,heavy-duty torsion bar coiled around an axis. Coil springs compress and expand to absorb the motion of the wheels.Leaf springs - This type of spring consists of several layers of metal (called leaves) bound together to act as a single unit. Leaf springs were first used on horse-drawn carriages and were found on most American automobiles until 1985. They are still used today on most trucks and heavy-duty vehicles. Torsion bars - Torsion bars use the twisting properties of a steel bar to provide coil-spring-like performance. This is how they work: One end of a bar is anchored to the vehicle frame. The other end is attached to a wishbone, whichacts like a lever that moves perpendicular to the torsion bar. When the wheel hits a bump, vertical motion is transferred to the wishbone and then, through the levering action, to the torsion bar. The torsion bar then twists along its axis to provide the spring force. European carmakers used this system extensively, as did Packard and Chrysler in the United States, through the 1950s and 1960s. Air springs - Air springs, which consist of a cylindrical chamber of air positioned between the wheel and the cars body, use the compressive qualities of air to absorb wheel vibrations. The concept is actually more than a century old and could be found on horse-drawn buggies. Air springs from this era were made from air-filled, leather diaphragms, much like a bellows; they were replaced with molded-rubber air springs in the 1930s. Based on where springs are located on a car., between the wheels and the frame engineers often find it convenient to talk about the sprung mass and the unsprung mass.Springs: Sprung and Unsprung Mass The sprung mass is the mass of the vehicle supported on the springs, while the unsprung mass is loosely defined as the mass between the road and the suspension springs. The stiffness of the springs affects how the sprung mass responds while the car is being driven. Loosely sprung cars, such as luxury cars (think Lincoln Town Car), can swallow bumps and provide a super-smooth ride; however, such a car is prone to dive and squat during braking and acceleration and tends to experience body sway or roll during cornering. Tightly sprung cars, such as sports cars (think Mazda Miata), are less forgiving on bumpy roads, but they minimize body motion well, which means they can be driven aggressively, even around corners. So, while springs by themselves seem like simple devices, designing and implementing them on a car to balance passenger comfort with handling is a complex task. And to make matters more complex, springs alone cant provide a perfectly smooth ride. Why? Because springs are great at absorbing energy, but not so good at dissipating it. Other structures, known as dampers, are required to do this. Dampers: Shock Absorbers Unless a dampening structure is present, a car spring will extend and release the energy it absorbs from a bump at an uncontrolled rate. The spring will continue to bounce at its natural frequency until all of the energy originally put into it is used up. A suspension built on springs alone would make for an extremely bouncy ride and, depending on the terrain, an uncontrollable car. Enter the shock absorber, or snubber, a device that controls unwanted spring motion through a process known as dampening. Shock absorbers slow down and reduce the magnitude of vibratory motions by turning the kinetic energy of suspension movement into heat energy that can be dissipated through hydraulic fluid. To understand how this works, its best to look inside a shock absorber to see its structure and function. A shock absorber is basically an oil pump placed between the frame of the car and the wheels. The upper mount of the shock connects to the frame (i.e., the sprung weight), while the lower mount connects to the axle, near the wheel (i.e., the unsprung weight). In a twin-tube design, one of the most common types of shock absorbers, the upper mount is connected to a piston rod, which in turn is connected to a piston, which in turn sits in a tube filled with hydraulic fluid. The inner tube is known as the pressure tube, and the outer tube is known as the reserve tube. The reserve tube stores excess hydraulic fluid. When the car wheel encounters a bump in the road and causes the spring to coil and uncoil, the energy of the spring is transferred to the shock absorber through the upper mount, down through the piston rod and into the piston. Orifices perforate the piston and allow fluid to leak through as the piston moves up and down in the pressure tube. Because the orifices are relatively tiny, only a small amount of fluid, under great pressure, passes through. This slows down the piston, which in turn slows down the spring. Shock absorbers work in two cycles - the compression cycle and the extension cycle. The compression cycle occurs as the piston moves downward, compressing the hydraulic fluid in the chamber below the piston. The extension cycle occurs as the piston moves toward the top of the pressure tube, compressing the fluid in the chamber above the piston. A typical car or light truck will have more resistance during its extension cycle than its compression cycle. With that in mind, the compression cycle controls the motion of the vehicles unsprung weight, while extension controls the heavier, sprung weight. All modern shock absorbers are velocity-sensitive - the faster the suspension moves, the more resistance the shock absorber provides. This enables shocks to adjust to road conditions and to control all of the unwanted motions that can occur in a moving vehicle, including bounce, sway, brake dive and acceleration squat. Dampers: Struts and Anti-sway BarsAnother common dampening structure is the strut - basically a shock absorber mounted inside a coil spring. Struts perform two jobs: They provide a dampening function like shock absorbers, and they provide structural support for the vehicle suspension. That means struts deliver a bit more than shock absorbers, which dont support vehicle weight - they only control the speed at which weight is transferred in a car, not the weight itself. Because shocks and struts have so much to do with the handling of a car, they can be considered critical safety features. Worn shocks and struts can allow excessive vehicle-weight transfer from side to side and front to back. This reduces the tires ability to grip the road, as well as handling and braking performance. Anti-sway Bars Anti-sway bars (also known as anti-roll bars) are used along with shock absorbers or struts to give a moving automobile additional stability. An anti-sway bar is a metal rod that spans the entire axle and effectively joins each side of the suspension together.When the suspension at one wheel moves up and down, the anti-sway bar transfers movement to the other wheel. This creates a more level ride and reduces vehicle sway. In particular, it combats the roll of a car on its suspension as it corners. For this reason, almost all cars today are fitted with anti-sway bars as standard equipment, although if theyre not, kits make it easy to install the bars at any time. Suspension Types: Front So far, our discussions have focused on how springs and dampers function on any given wheel. But the four wheels of a car work together in two independent systems - the two wheels connected by the front axle and the two wheels connected by the rear axle. That means that a car can and usually does have a different type of suspension on the front and back. Much is determined by whether a rigid axle binds the wheels or if the wheels are permitted to move independently. The former arrangement is known as a dependent system, while the latter arrangement is known as an independent system. In the following sections, well look at some of the common types of front and back suspensions typically used on mainstream cars. Front Suspension - Dependent Systems Dependent front suspensions have a rigid front axle that connects the front wheels. Basically, this looks like a solid bar under the front of the car, kept in place by leaf springs and shock absorbers. Common on trucks, dependent front suspensions havent been used in mainstream cars for years. Front Suspension - Independent Systems In this setup, the front wheels are allowed to move independently. The MacPherson strut, developed by Earle S. MacPherson of General Motors in 1947, is the most widely used front suspension system, especially in cars of European origin. The MacPherson strut combines a shock absorber and a coil spring into a single unit. This provides a more compact and lighter suspension system that can be used for front-wheel drive vehicles. The double-wishbone suspension, also known as an A-arm suspension, is another common type of front independent suspension. While there are several different possible configurations, this design typically uses two wishbone-shaped arms to locate the wheel. Each wishbone, which has two mounting positions to the frame and one at the wheel, bears a shock absorber and a coil spring to absorb vibrations. Double-wishbone suspensions allow for more control over the camber angle of the wheel, which describes the degree to which the wheels tilt in and out. They also help minimize roll or sway and provide for a more consistent steering feel. Because of these characteristics, the double-wishbone suspension is common on the front wheels of larger cars. Now lets look at some common rear suspensions. Suspension Types: RearRear Suspension - Dependent SystemsIf a solid axle connects the rear wheels of a car, then the suspension is usually quite simple - based either on a leaf spring or a coil spring. In the former design, the leaf springs clamp directly to the drive axle. The ends of the leaf springs attach directly to the frame, and the shock absorber is attached at the clamp that holds the spring to the axle. For many years, American car manufacturers preferred this design because of its simplicity. The same basic design can be achieved with coil springs replacing the leaves. In this case, the spring and shock absorber can be mounted as a single unit or as separate components. When theyre separate, the springs can be much smaller, which reduces the amount of space the suspension takes up. Rear Suspension - Independent Suspensions If both the front and back suspensions are independent, then all of the wheels are mounted and sprung individually, resulting in what car advertisements tout as four-wheel independent suspension. Any suspension that can be used on the front of the car can be used on the rear, and versions of the front independent systems described in the previous section can be found on the rear axles. Of course, in the rear of the car, the steering rack - the assembly that includes the pinion gear wheel and enables the wheels to turn from side to side - is absent. This means that rear independent suspensions can be simplified versions of front ones, although the basic principles remain the same. The Future of Car Suspensions While there have been enhancements and improvements to both springs and shock absorbers, the basic design of car suspensions has not undergone a significant evolution over the years. But all of thats about to change with the introduction of a brand-new suspension design conceived by Bose - the same Bose known for its innovations in acoustic technologies. Some experts are going so far as to say that the Bose suspension is the biggest advance in automobile suspensions since the introduction of an all-independent design.How does it work? The Bose system uses a linear electromagnetic motor (LEM) at each wheel in lieu of a conventional shock-and-spring setup. Amplifiers provide electricity