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ear 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. Next, we39。ll look at the suspensions of specialty cars. Historical Suspensions Sixteenthcentury wagons and carriages tried to solve the problem of feeling every bump in the road by slinging the carriage body from leather straps attached to four posts of a chassis that looked like an upturned table. Because the carriage body was suspended from the chassis, the system came to be known as a suspension a term still used today to describe the entire class of solutions. The slungbody suspension was not a true springing system, but it did enable the body and the wheels of the carriage to move independently. Semielliptical spring designs, also known as cart springs, quickly replaced the leatherstrap suspension. Popular on wagons, buggies and carriages, the semielliptical springs were often used on both the front and rear axles. They did, however, tend to allow forward and backward sway and had a high center of gravity. By the time powered vehicles hit the road, other, more efficient springing systems were being 本科生畢業(yè)設計(論文) 24 developed to smooth out rides for passengers. 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 kiic energy of suspension movement into heat energy that can be dissipated through hydraulic fluid. To understand how this works, it39。s 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 (., the sprung weight), while the lower mount connects to the axle, near the wheel (., the unsprung weight). In a twintube design, one of the most mon 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. 本科生畢業(yè)設計(論文) 25 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 pression cycle and the extension cycle. The pression cycle occurs as the piston moves downward, pressing the hydraulic fluid in the chamber below the piston. The extension cycle occurs as the piston moves toward the top of the pressure tube, pressing the fluid in the chamber above the piston. A typical car or light truck will have more resistance during its extension cycle than its pression cycle. With that in mind, the pression cycle 本科生畢業(yè)設計(論文) 26 controls the motion of the vehicle39。s unsprung weight, while extension controls the heavier, sprung weight. All modern shock absorbers are velocitysensitive 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. 翻譯 汽車懸架是如何工作的 如果車身與車輪之間沒有中間結構的話,汽車在行駛時所有車輪的垂直震動都將被傳遞到車身,并且都沿著相同的方向 傳遞 。在這種情況下,車輪可能會與道路完全分離。然后 ,在地心引力的作用下,車輪又回到路面。我們所需要的是一種系統(tǒng), 能吸收車輪垂直加速能量,使車架和車身在顛簸道路上行駛時,能不受干擾。 研究車在移動時受力情況的學科叫做車輛 動力學,您需要了解一些 概念 ,以 明白為什么懸架擺在首位是必要的 。大部分汽車工程師考慮動態(tài)行駛 汽車從兩個角度進行: 行駛 — 汽車在不平坦的道路上行駛的能力。 操控性 — 具有安全加速,剎車和轉彎的能力。 這兩個特點,可以進一步被體現在以下三種情況中 — 減 震 能力、抓地力、轉 本科生畢業(yè)設計(論文) 27 彎性能。下面的表格描述了這些原則,以及工程師如何嘗試解決每一個方面 的 問題。 項目 定義 目標 方法 減震 汽車吸收和阻斷來自地面的震動對乘客和車身部件的沖擊的能力。 能使汽車在不平路面上不受干擾的行駛。 吸收來自地面沖撞產生的能量并設法消耗掉避免車身過分震動。 抓地力 汽車在不斷 改 變行駛方向時和 定向 行駛時 保持 與路面的接觸的能力 (例如:在制動 時, 汽車將重量從后輪向前方的輪胎作用, 因汽車 車頭向下載 , 汽車 這種類型運動 ,被稱為 “ 制動俯沖 ” 。相反的 情況就叫 “ 加速后仰 ” 發(fā)生在加速 , 汽車重量從前面的輪胎向 后轉移。 ) 使輪 胎始終保持與路面接觸,因為輪胎與地面的摩擦力影響著汽車的轉向能力 ,制動能力和加速能力。 使汽車重量從側面到側面以及從前到后的轉移最小化,因為這種重量的轉移減少了輪胎的抓地力。 駕車轉彎 汽車在彎路上行駛的能力。 減少車身的跳動。轉彎時離心力 作用在中心上,使得車身一邊高于另一邊。 在轉彎時將汽車的重量從高的一邊轉移到低的一邊。 一輛車的懸架,其各組成部分,以及提供所有的解決方案的描述。 讓我們看看,一個典型的懸架的工作狀況,從大的底盤環(huán)境 到組成懸架的 每個零件。 汽車懸架,其實是底盤的一部分 ,位于汽車下方,其中包括了很多重要的系統(tǒng)。獨立后 懸架 懸架類型 : 后懸架 如果是一個后橋與后輪直接相連的汽車,那么它的懸架系統(tǒng)一般來說都比較簡單 — 基于鋼板彈簧或者是螺旋彈簧之上。在賽車的懸架設計中,鋼板彈簧直接與車軸相連。鋼板彈簧的末端與車架相連,減震器 與鋼板彈簧相連。多年來,美國汽車制造商的首選這種設計就是因為它簡單。 基本設計相同 的情況下 ,才能實現螺旋彈簧取代鋼板。在這種情況下,彈簧和減振器可以安裝 成 一個單一的單位或作為單獨的組件。當他們分開,彈簧體積可以制造的小 得 多,從而降低了懸架占用的空間。 本科生畢業(yè)設計(論文) 28 非獨立后 懸架 如果前橋懸架和后橋懸架都是獨立懸架的話,那么所有的車輪都可以單獨的安裝,不干涉的振動,這便是廣告中所說的四輪獨立懸架。任何懸架,可用于汽車前橋的便可以用在后橋,以上描述的獨立懸架的類型能在后橋上 找到。在汽車尾部,汽車轉向裝置 —— 其中包括小齒輪,使 車輪 從一側轉向另一側。這意味著,雖然基本原理保持不變 ,后獨立懸可以比前獨立懸架簡單 。 接下來,我們將看看專業(yè)車的懸架系統(tǒng)。 懸架的歷史 16世紀的車廂