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1、 本科畢業(yè)設(shè)計(論文) 外文翻譯（附外文原文） 學(xué) 院： 機(jī)械與控制工程學(xué)院 課題名稱： 汽車懸架系統(tǒng)的設(shè)計及仿真 專業(yè)(方向)： 機(jī)械設(shè)計制造及其自動化 （機(jī)械裝備設(shè)計與制造） 班 級： 機(jī)械11-2班 學(xué) 生： 藍(lán)秀美 指導(dǎo)教師： 沈中華

2、 日 期： 2015年1月23日 汽車懸架如何工作 威廉?哈里斯 密歇根大學(xué) 當(dāng)人們考慮汽車性能的時候,他們通常想到的是馬力,扭矩, 0至60的加速度時間。如果司機(jī)無法控制汽車，即使所有的能量由活塞式發(fā)動機(jī)提供也是沒有意義的。這就是為什么汽車工程師將他們的注意力轉(zhuǎn)向?qū)壹芟到y(tǒng)的研究，幾乎如同已掌握的四沖程內(nèi)燃機(jī)一樣。 汽車懸架的作用是最大限度地增加輪胎與路面之間的摩擦,提供操縱穩(wěn)定性,并確保乘客的舒適性。在這篇文章,讓我們一起來探討懸架是如何工作的,懸架的發(fā)展歷程和未來發(fā)展方向。 如果一條路是平

3、坦的,懸架是不必要的。但是路不可能是平坦的，即使是剛鋪好的公路也有瑕疵，根據(jù)牛頓運(yùn)動定律,所有力都是有幅值和方向的，當(dāng)汽車經(jīng)過一個障礙物時,車輪會上下跳動。 沒有一個介于中間的結(jié)構(gòu),所有車輪的垂直能量都會轉(zhuǎn)移到車架上，在同一方向移動。在這種情況下,車輪會與道路完全失去接觸，然后在重力的作用下,車輪又會緊壓路面。你需要的就是那種系統(tǒng),可以吸收垂直加速輪的能量,允許汽車即使在顛簸的路面上也依然能平穩(wěn)的行駛。 車輛動力學(xué) 研究汽車在行駛中受到的力被稱為汽車動力學(xué)。為了更好地理解為什么要把懸架放在首位，你需要了解一些概念，大多數(shù)汽車工程師從兩個角度來考慮汽車動力學(xué)。 行駛:車輛行駛不平路面的平

4、順性。 操控:車輛安全加速,制動和轉(zhuǎn)彎的能力。 這兩個特點,可以進(jìn)一步說明,在三個重要的原則—道路隔離、道路控制和轉(zhuǎn)彎。下面描述了這些原則和工程師如何試圖解決每一個獨特的挑戰(zhàn)。 底盤系統(tǒng) 懸掛實際上是汽車底盤的一部分，包括所有位于汽車身體下面的重要系統(tǒng)。 這個系統(tǒng)包括： 框架—結(jié)構(gòu)，承載組件，支持汽車的引擎和車身，反過來又受到懸掛的支持。 懸掛系統(tǒng)—支持重量，吸收振動并且保證輪胎的接觸。 轉(zhuǎn)向系統(tǒng)—底盤，使駕駛員直接引導(dǎo)車輛。 輪胎—保證車輪和地面的抓緊力。 因此懸架系統(tǒng)在任何車輛里都是主要的系統(tǒng)之一。 下面該看懸架系統(tǒng)的三個基本組成件：

5、彈簧、阻尼和扭桿。 彈簧 現(xiàn)如今,彈簧系統(tǒng)都基于四種基本設(shè)計形式. 螺旋彈簧：彈簧的常用形式，本質(zhì)上講，螺旋彈簧相當(dāng)于圍繞在軸線周圍的一中高載負(fù)性能的扭桿螺旋彈簧，利用伸縮來緩沖車輪的位移。 鋼板彈簧：這種形式的彈簧是由若干個葉片形金屬捆綁而成，并作為一個獨立的元件使用的。起初，鋼板彈簧用在四輪馬車上，直到1985年才廣泛用于汽車上。 扭桿彈簧：像螺旋彈簧一樣，不過扭桿彈簧利用金屬桿的扭曲特性工作的。它是將金屬桿的一端鉸接在車架上，另一端連接在叉骨架上來工作的。叉骨架類似一個杠桿，它與扭桿的運(yùn)動方向相垂直，當(dāng)車輪顛簸時，這種垂直的運(yùn)動傳到叉骨架，通過這種杠桿的作用在扭桿上，然

6、后扭桿沿著軸線發(fā)生扭曲而產(chǎn)生彈力。歐洲汽車制造商曾廣泛的應(yīng)用這種彈簧，在20世紀(jì)50-60年代美國的Packard和chrgsler也采用了這種彈簧。 空氣彈簧：空氣彈簧主要是由放置在車輪和車身的柱形氣室組成，它利用空氣的壓縮性能去吸收車輪的振動。這種空氣彈簧的概念已經(jīng)有一個多世紀(jì)了，在雙輪的馬車上就有其存在，在那個時候，空氣彈簧用充氣的皮革制作，直到20世紀(jì)30年代被橡膠氣彈簧取代。 根據(jù)彈簧在車輪與車架之間放置位置的不同，工程技術(shù)人員為了方便將其分為彈簧和簧下質(zhì)量。 彈簧和簧下質(zhì)量 承載彈簧是一種支撐車體的彈簧,而非承載彈簧卻是道路和懸架之間松弛的彈簧。當(dāng)汽車在行駛

7、中彈簧的剛度對承載彈簧有影響。而像林肯之類的高檔汽車用的是非承載彈簧,可以吸收緩沖提供高穩(wěn)定的行駛。可是這種車在加速和剎車的時候容易出現(xiàn)點頭和后坐現(xiàn)象，在汽車拐彎的時候也很容易搖晃。像運(yùn)動形這種承載彈簧類的車,對路面的顛簸要求小,它需要的是在高速行駛時即使是在拐彎的時候,盡可能的減小車身的移動. 所以像彈簧這樣看起來很簡單的裝置,在一輛汽車上設(shè)計和安裝要平衡其舒適度是一件很復(fù)雜的工作。更為復(fù)雜的是彈簧本身不能提供平順的行駛。為什么呢?這是因為彈簧能很好的吸收能量卻不能釋放能量。所以我們需要另一種結(jié)構(gòu),那就是減振器。 減振器 減振器和彈簧共同作用，吸收振動并釋放出去，直到能量完全釋放彈簧才

8、能回到原來的位置，它可以補(bǔ)償因地面引起的顛簸。 由于減振器的存在,它減小并平緩了振動的幅值,,將汽車的動能轉(zhuǎn)化成熱能并散發(fā)到油液中。 減振器就象是一個油泵放置在車架和車輪之間。減振器的上部連接在車架上,而下部連接在車輪附近的車橋上。減振器的主要形式是雙筒式減振器。它的最上部連接在活塞桿，然后連接活塞,管內(nèi)充滿著油液。其中內(nèi)部管叫做壓力管,外部管叫做貯存管，貯存管內(nèi)有過量的油液。 當(dāng)車輪在路上顛簸時引起彈簧伸縮,能量傳到減振器上部,再傳到活塞。減振器在上下運(yùn)動時油液通過阻尼孔，由于小孔特別小加上壓力,使活塞速度減慢,近而彈簧振動速度減慢。 減振器有兩個工作行程，一個是壓縮行程,一個是膨脹

9、行程。 壓縮行程發(fā)生于活塞向下運(yùn)動,壓縮油液進(jìn)入活塞下的氣室。 膨脹行程發(fā)生于活塞向上運(yùn)動壓縮油液進(jìn)入活塞上部的氣室。典型的汽車和輕卡車膨脹行程要大于壓縮行程?？梢赃@樣理解,壓縮行程發(fā)生在非承載彈簧的車上, 膨脹行程發(fā)生在承載彈簧的車上。 當(dāng)代的減振器對速度是敏感的---懸架動的越快,減振器提供的阻尼就越大。這使得減振器能根據(jù)路面的情況去控制車輛,平順汽車的顛簸,搖擺,前傾和后蹲。 支柱和扭桿 另一種較常見的減振結(jié)構(gòu)是支柱,基本上是這樣的，一個減振器安裝在螺旋彈簧內(nèi)。支柱有兩項功能:一是它們提供緩沖功能,如吸振系統(tǒng)。二是他們?yōu)槠噾壹芴峁┙Y(jié)構(gòu)性支持。這意味著它比吸振器吸收的更多, 但是他

10、們只控制速度,而不是重量本身. 由于沖擊和壓桿和一輛汽車的可控性有很大的相關(guān), 他們可被視為是評定安全特征的重要因素。 磨損沖擊和壓桿可以讓過度的車載重量從一側(cè)轉(zhuǎn)向另一側(cè)，從前方到后方，這就降低了輪胎對地面的附著力,以及操縱和制動性能。 扭桿 扭桿(又稱抗側(cè)滾桿)和減振器一起增強(qiáng)車輛在行駛時的穩(wěn)定性。 扭桿是一個金屬桿,橫跨整個車橋,有效地將兩邊的減振器連接在一起。 當(dāng)一個輪子的減振器忽上忽下時,扭桿將運(yùn)動轉(zhuǎn)移到另外一個車輪上， 這將創(chuàng)建更多的平順性行駛并減小了汽車擺動。 尤其是它克服了在汽車轉(zhuǎn)彎時的滾動。 基于這個原因,現(xiàn)如今幾乎所有的車裝都有扭桿作為標(biāo)準(zhǔn)裝備,但如果它們沒有,在任何

11、時候利用工具箱也會很容易的安裝上。 懸架類型：前懸 目前為止,我們討論的重點是彈簧和阻尼如何作用于車輪上。但四輪車一起成了兩個獨立的系統(tǒng)—前兩個輪子是通過前橋相連的，后兩個輪子是通過后橋相連的。這意味著一輛車可以在前方與后方有不同類型的懸架并多少取決了剛性約束車軸車輪或車輪間的獨立移動。 前布置被稱為獨立系統(tǒng),而后者的布置被稱為非獨立系統(tǒng).。在以下章節(jié)中, 我們也會學(xué)習(xí)一些常見的主流汽車上的前后懸架。 前懸非獨立系統(tǒng) 前懸架非獨立系統(tǒng)利用剛性前軸連接前輪。 基本上就好像一個堅實的桿放置在汽車的后前方, 裝備鋼板彈簧和減振器。這些年來通用卡車一直沒使用前懸非獨立懸架。 前懸獨立系統(tǒng)

12、前懸架獨立系統(tǒng)允許車輪單獨運(yùn)動。麥弗遜式懸架,典型的獨立懸架，由厄爾國會商量通用汽車公司在1947年發(fā)展起來的，是應(yīng)用最廣泛的前懸架系統(tǒng),特別是生產(chǎn)于歐洲的汽車。 麥弗遜式懸架將減振器和螺旋彈簧結(jié)合成一個單位。這提供了一個更緊湊更輕便的懸架系統(tǒng),通常應(yīng)用于前輪驅(qū)動車輛。 雙橫臂獨立懸架,是另一種常見的獨立前懸架。 雖然有幾個不同的配置,但是這樣的設(shè)計通常是用兩個橫臂去定位車輪。每個橫臂,其中的兩端一端連接在車架，另一端連接在車輪。減振器和螺旋彈簧用來吸收振動，雙橫臂懸架,更多的是控制車輪的傾角，描述車輪傾斜到何種程度。它們還有助于減少滾動或搖擺并為其提供一個更加一致的轉(zhuǎn)向感覺。由于這些特

13、點,雙橫臂獨立懸架是常用于前輪較大的汽車. 現(xiàn)在讓我們看看一些常見的后懸架. 后懸架：非獨立懸架 用一個固體軸連接一輛小轎車的車輪后方,根據(jù)鋼板彈簧或是螺旋彈簧，這種懸掛通常很簡單。 在剛開始的設(shè)計中,彈簧鋼板直接鉗接驅(qū)動橋，減振器連接彈簧軸。由于這種結(jié)構(gòu)簡單易行，多年來,美國汽車制造商喜歡采用這種設(shè)計結(jié)構(gòu)。 相同的基本設(shè)計,可以實現(xiàn)與鋼板彈簧更換葉片。在這種情況下,彈簧和減振器可以掛載作為一個單一的單位或者作為單獨的組件使用。當(dāng)他們分開時,彈簧可以變的更小,減少了空間的占用。 后懸架：獨立懸架 如果汽車前后懸架是獨立的, 那么所有的輪子都進(jìn)行過單獨的安裝，可以用在前面的車也可以在

14、后方,可以發(fā)現(xiàn)在后軸上節(jié)所述的各種版本的前后獨立系統(tǒng)。當(dāng)然,在車的后面, 轉(zhuǎn)向架--其中包括行星齒輪車輪,使車輪從一側(cè)向另一側(cè)旋轉(zhuǎn)。這意味著后部獨立懸架可以簡化為前部獨立懸架,雖然現(xiàn)有的基本原則不變。 過去數(shù)年汽車懸架雖然對彈簧和避震器有加強(qiáng)和該進(jìn), 但是該系統(tǒng)的基本設(shè)計并未發(fā)生重大改變。但所有這一切即將改變，由于采用了全新的懸架設(shè)計構(gòu)思-- Bose,Bose因為其在技術(shù)方面的創(chuàng)新而聞名。 一些專家甚至說Bose是汽車懸架最大的一個全獨立設(shè)計的進(jìn)步。 其工作原理是什么? Bose系統(tǒng)采用直線電機(jī)(為LEM ) ,應(yīng)用于每個車輪以代替?zhèn)鹘y(tǒng)的沖擊和彈簧設(shè)置。放大器是提供電力的電動機(jī)，電動機(jī)向

15、用戶提供電力馬達(dá),且電機(jī)是不被固有常規(guī)慣性限制的流體阻尼器。其結(jié)果是一個LEM可以擴(kuò)展和壓縮在一個更大的速度，從根本上消除在客艙的所有振動，且可以精細(xì)控制該車車輪的運(yùn)動，不管發(fā)生什么事車身依然保持在水平狀態(tài)。該LEM還可以抵消汽車的身體運(yùn)動，同時加速，制動和轉(zhuǎn)彎，讓駕駛者控制感更強(qiáng)。 不幸的是，這種模式暫時將無法使用，直到2009年，它才會提供應(yīng)用于一個或多個高檔豪華型轎車。這時，司機(jī)將不得不依賴于嘗試了幾個世紀(jì)具有平滑顛簸的真正的懸掛方式。 How Car Suspensions Work By William Harris

16、University of Michigan When people think of automobile performance, they normally think of horsepow er, torque and zero-to-60 acceleration. But all of the power generated by a piston engine is useless if the driver can't control the car. That's why automobile engineers tu- rned their attention t

17、o 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 th

18、is article, we'll explore how car suspensions work, how they've 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 wouldn't be nece ssary. But roads are far from flat. Even fr

19、eshly paved highways have subtle imperfections that can interact with the wheels of a car. It's these imperfections that apply forces to the wheels. According to Newton's laws of motion, all forces have both magnitude and direction. A bump in the road causes the wheel to move up and down perpendicul

20、ar 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 wheel's vertical energy is transferred

21、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 w

22、heel, 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. Mo

23、st automobile engineers consider the dynamics of a moving car from two perspectives: Ride - a car's ability to smooth out a bumpy road Handling - a car's ability to safely accelerate, brake and corner A car's suspension, with its various components, provides all of the solutions descri

24、bed. Let's 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 locate

25、d beneath the car's body. These systems include: The frame-structural, load-carrying component that supports the car's 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 cont

26、act. 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

27、 big-picture overview in mind, it's time to look at the three fundamental components of any suspension: springs, dampers and anti-sway bars. Springs Today's springing systems are based on one of four basic designs: Coil springs - This is the most common type of spring and is, in essence,hea

28、vy-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 an

29、d 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 vehi

30、cle 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

31、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 car's body, use the compressive

32、 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. Bas

33、ed 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

34、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, suc

35、h 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 aggressiv

36、ely, 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 can't provide a perfectly smooth ride. Why? Because springs are

37、 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 spr

38、ing 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 cont

39、rols 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, it's best to l

40、ook 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

41、., 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

42、 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

43、 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 spri

44、ng. 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, c

45、ompressing 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 vehicle's unsprung weight, while extension controls the heavier, spr

46、ung 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,

47、 brake dive and acceleration squat. Dampers: Struts and Anti-sway Bars Another 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 f

48、or the vehicle suspension. That means struts deliver a bit more than shock absorbers, which don't 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

49、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 tire's ability to grip the road, as well as handling and braking performance. Anti-sway Bars Anti-sway bars (also known as anti-roll

50、 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 transfe

51、rs 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 they're not, kits make it eas

52、y 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 connec

53、ted 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 t

54、he latter arrangement is known as an independent system. In the following sections, we'll 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 th

55、e 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 haven't been used in mainstream cars for years. Front Suspension - Independent Systems In this setup, the front w

56、heels 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. Th

57、is 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 des

58、ign 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, wh

59、ich 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 let's look at some common rear susp

60、ensions. Suspension Types: Rear Rear Suspension - Dependent Systems If 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

61、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 lea

62、ves. In this case, the spring and shock absorber can be mounted as a single unit or as separate components. When they're 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 s

63、uspensions 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 des

64、cribed 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 versio

65、ns 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 that

66、's 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