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機(jī)電工程學(xué)院
畢業(yè)設(shè)計(jì)外文資料翻譯
設(shè)計(jì)題目: JD1121載貨汽車(chē)總體及底盤(pán)布置設(shè)計(jì)
譯文題目: 汽車(chē)底盤(pán)構(gòu)造
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正文：（汽車(chē)底盤(pán)）
汽車(chē)底盤(pán)構(gòu)造
汽車(chē)型號(hào)的不同使汽車(chē)的設(shè)計(jì)也有所不同，一輛私家車(chē)可以承載人數(shù)的上限是八個(gè)人，一般需要四個(gè)座位。
汽車(chē)設(shè)計(jì)的布局如圖1-1所示，它體現(xiàn)了這輛汽車(chē)各個(gè)主要部件的布置，它是由位于汽車(chē)前邊的發(fā)動(dòng)機(jī)、接著是離合器、變速器、傳動(dòng)軸、萬(wàn)向節(jié)、差速器、后橋等部件布置構(gòu)成。汽車(chē)散熱器位于汽車(chē)發(fā)動(dòng)機(jī)的前邊，圖中其他的各種不同的汽車(chē)零件則分別是發(fā)電機(jī)、喇叭、轉(zhuǎn)向機(jī)、風(fēng)扇、正時(shí)齒輪、化油器、空氣濾清器、齒輪傳動(dòng)控制裝置、方向盤(pán)、汽缸、汽油油槽、后橋主動(dòng)及被動(dòng)齒輪、后車(chē)橋。驅(qū)動(dòng)力由變速器輸出，通過(guò)一個(gè)短軸輸送到到前邊傳動(dòng)軸的萬(wàn)向節(jié)上，再?gòu)膫鲃?dòng)軸輸出，經(jīng)過(guò)一個(gè)接頭形式的、可滑動(dòng)花鍵輸送到傳動(dòng)軸后部，然后帶動(dòng)傳動(dòng)軸軸上的錐齒輪，這個(gè)錐齒輪再與一個(gè)大的錐齒輪相嚙合，這個(gè)大的錐齒輪經(jīng)過(guò)一個(gè)差速齒輪驅(qū)動(dòng)著后橋的半軸。
圖1-1 車(chē)的總布置
1-車(chē)架 ; 2-車(chē)輪 ; 3-散熱器 ; 4-發(fā)動(dòng)機(jī) ; 5-離合器和變速器; 6-傳動(dòng)軸 ; 7-萬(wàn)向節(jié) ; 8-差速器, 后橋 ; 9-油箱;10-前橋 ; 11-轉(zhuǎn)向器; 12- 鋼板彈簧 ; 13-排氣管/消音器
這個(gè)總布置設(shè)計(jì)同時(shí)還包括獨(dú)立的1/4橢圓的樹(shù)業(yè)形狀的獨(dú)立懸架系統(tǒng)的設(shè)計(jì)，還包括轉(zhuǎn)向桿的錐齒輪控制系統(tǒng)和液力制動(dòng)系統(tǒng).
能量的單元是由發(fā)動(dòng)機(jī)構(gòu)成的，他通常安裝在車(chē)底盤(pán)的較低點(diǎn)。離合器以及變速器安置在它之后，這三個(gè)部分,發(fā)動(dòng)機(jī),離合器和變速器組裝成一個(gè)獨(dú)立的單位。
底盤(pán)
汽車(chē)底盤(pán)是指對(duì)汽車(chē)底部所有結(jié)構(gòu)的描述?，F(xiàn)代汽車(chē)的主要結(jié)構(gòu)就是底盤(pán)結(jié)構(gòu)。大量的設(shè)計(jì)要求是在發(fā)動(dòng)機(jī)，輪胎，車(chē)軸組件，變速器，轉(zhuǎn)向機(jī)構(gòu)，制動(dòng)器和懸架安裝在鋼制框架上。在底盤(pán)的制造過(guò)程中主要取決于螺栓的靈活性。底盤(pán)基本框架的主要組成部分是，發(fā)動(dòng)機(jī)，動(dòng)力傳動(dòng)系統(tǒng)，輪胎，轉(zhuǎn)向裝置，制動(dòng)器，懸架和汽車(chē)轉(zhuǎn)向所需要的所有部件。此外，其他幾個(gè)系統(tǒng)是也被安裝在底盤(pán)上。懸架系統(tǒng)無(wú)論是對(duì)穿越崎嶇道路的旅行車(chē)輛輪胎還是對(duì)在正確公路上行駛的汽車(chē)輪胎都有吸收道路沖擊的作用。當(dāng)馬路不平引起汽車(chē)顛簸時(shí)，它也能允許輪胎上下移動(dòng)。
另一個(gè)重要的底盤(pán)部分是轉(zhuǎn)向系統(tǒng)，它是駕駛員用來(lái)控制汽車(chē)行駛方向的系統(tǒng)。駕駛員控制的方向盤(pán)被連接在變速器上，使駕駛員的控制力變強(qiáng)。這個(gè)變速器是被連接到車(chē)輛的前輪上。
汽車(chē)底盤(pán)的另一個(gè)主要組成部分是制動(dòng)系統(tǒng)，它的作用是能使行駛車(chē)輛減速，使車(chē)輛停止，如果車(chē)輛已停止將保持平穩(wěn)狀態(tài)。當(dāng)駕駛員踩動(dòng)剎車(chē)踏板時(shí)，液壓油被迫離開(kāi)主缸傳到四個(gè)輪子中，由液壓運(yùn)動(dòng)產(chǎn)生的鼓狀和盤(pán)式制動(dòng)器作用使汽車(chē)的輪胎放慢或停止。
發(fā)動(dòng)機(jī)
柴油發(fā)動(dòng)機(jī)效率比汽油發(fā)動(dòng)機(jī)的高35%-40% ，生產(chǎn)更多的電力單位燃料的燃燒。 The efficiency of the diesel engine has been greatly enhanced by the use of turbochargers and charged-air cooling, which has resulted in increased power and performance at minimum fuel consumption rates.效率的柴油發(fā)動(dòng)機(jī)已大大加強(qiáng)，使用渦輪增壓器和帶電空氣冷卻，從而導(dǎo)致更多的功率和性能，最低燃油消耗率。 Advancements in engine design also mean diesel is no longer considered a "dirty" fuel.先進(jìn)的發(fā)動(dòng)機(jī)設(shè)計(jì)也意味著柴油已不再被視為“骯臟”的燃料。 Fuel injection and control strategies have produced the "smokeless" diesel.燃油噴射和控制戰(zhàn)略已產(chǎn)生的“無(wú)煙”柴油。發(fā)動(dòng)機(jī)的作用是使輸入汽缸的燃料燃燒而發(fā)出動(dòng)力?，F(xiàn)代汽車(chē)廣泛應(yīng)用往復(fù)活塞式內(nèi)燃機(jī)，它一般有機(jī)體，配氣機(jī)構(gòu)，曲柄連桿機(jī)構(gòu)，燃油供油系統(tǒng)，冷卻系統(tǒng)，點(diǎn)火系統(tǒng)，啟動(dòng)系統(tǒng)等部分組成。地盤(pán)接受發(fā)動(dòng)機(jī)的動(dòng)力，使汽車(chē)產(chǎn)生運(yùn)動(dòng)，并保證汽車(chē)按照駕駛員的操縱正常行駛。
離合器
離合器的主要功用是切斷和實(shí)現(xiàn)發(fā)動(dòng)機(jī)對(duì)傳動(dòng)系的動(dòng)力傳遞，保證汽車(chē)起步時(shí)使發(fā)動(dòng)機(jī)和傳動(dòng)系平順的接合，確保汽車(chē)平穩(wěn)起步；在換擋時(shí)將發(fā)動(dòng)機(jī)和傳動(dòng)系分離，減少變速器中換擋齒輪之間的沖擊；在工作中受到較大的動(dòng)載荷時(shí)，能限制傳動(dòng)系所承受的最大轉(zhuǎn)矩，以防止傳動(dòng)系各部分零件因過(guò)載而損壞；有效地降低傳動(dòng)系中的振動(dòng)和噪音。
變速器
變速器是一個(gè)速力變化裝置,安裝在車(chē)輛的發(fā)動(dòng)機(jī)和驅(qū)動(dòng)輪之間.變速器用以改變發(fā)動(dòng)機(jī)與驅(qū)動(dòng)輪轉(zhuǎn)速間的比率關(guān)系.以適應(yīng)每種行駛狀況. 傳輸裝置連接到背面的發(fā)動(dòng)機(jī)發(fā)出的功率,從發(fā)動(dòng)機(jī)驅(qū)動(dòng)車(chē)輪. 這樣在一定的范圍內(nèi)汽車(chē)發(fā)動(dòng)機(jī)的運(yùn)行也會(huì)處于最佳狀態(tài)。
前橋
前橋是用來(lái)控制與固定在車(chē)橋兩端上的部件并通過(guò)相互連接的在前車(chē)橋末端的轉(zhuǎn)向節(jié)上進(jìn)行轉(zhuǎn)動(dòng)。為減輕整車(chē)的質(zhì)量,讓整車(chē)結(jié)構(gòu)更緊湊,采用膜片彈簧離合器,高速旋轉(zhuǎn)時(shí)其性能 穩(wěn)定，膜片彈簧離合器與螺旋彈簧離合器相比有以下優(yōu)點(diǎn),傳遞的轉(zhuǎn)矩較大而且平穩(wěn)，結(jié)構(gòu)簡(jiǎn)單緊湊，操縱輕便,使用壽命長(zhǎng)。
轉(zhuǎn)向器
轉(zhuǎn)向器以及轉(zhuǎn)向拉桿將兩根轉(zhuǎn)向軸連接起來(lái)并通過(guò)與轉(zhuǎn)向節(jié)相連的轉(zhuǎn)向盤(pán)轉(zhuǎn)向輪來(lái)轉(zhuǎn)動(dòng)他們，轉(zhuǎn)向盤(pán)通過(guò)一根軸連接到了轉(zhuǎn)向搖臂的一端，變速器以及一個(gè)合適的連接軸通過(guò)駕駛員的操作而被執(zhí)行。先前的單個(gè)橋是通過(guò)彈簧來(lái)支持汽車(chē)，在這里的布置還了解到采用獨(dú)立前懸已經(jīng)取代了車(chē)軸和彈簧的所一起布置形成的系統(tǒng)。在采用獨(dú)立懸架內(nèi)彈簧的控制下，車(chē)輪就可以獨(dú)立于其他自由的上下彈動(dòng)了。
驅(qū)動(dòng)橋
為了安裝好后邊的車(chē)輪，用半軸套管將半軸在輪子被使用的時(shí)候開(kāi)始通過(guò)合適的軸承來(lái)驅(qū)動(dòng)后橋，在發(fā)動(dòng)機(jī)和兩個(gè)驅(qū)動(dòng)車(chē)輪之間，為了促使驅(qū)動(dòng)橋內(nèi)的驅(qū)動(dòng)齒輪提供最終轉(zhuǎn)速，它在驅(qū)動(dòng)橋中心的轉(zhuǎn)速不斷增大，這種方向改變的驅(qū)動(dòng)放把前部和后部到排列成一條直線的傳動(dòng)軸的軸槽也是由這種部件提供的，它被稱為后置驅(qū)動(dòng)橋.
差速器就是一種將發(fā)動(dòng)機(jī)輸出扭矩一分為二的裝置，允許轉(zhuǎn)向時(shí)輸出兩種不同的轉(zhuǎn)速。在現(xiàn)代轎車(chē)，包括許多四輪驅(qū)動(dòng)汽車(chē)上，都能找到差速器。這些四輪驅(qū)動(dòng)車(chē)的每組車(chē)輪之間都需要差速器。同樣，其兩前輪和兩后輪之間也需要一個(gè)差速器。這是因?yàn)樵谄?chē)轉(zhuǎn)彎時(shí)，前輪和后輪對(duì)比后輪，走過(guò)的距離是不相同的。 部分四輪驅(qū)動(dòng)車(chē)前后輪之間沒(méi)有差速器。相反的，他們被固定聯(lián)結(jié)在一起，以至于前后輪轉(zhuǎn)向時(shí)能夠以同樣的平均轉(zhuǎn)速轉(zhuǎn)動(dòng)。
每個(gè)車(chē)輪都設(shè)有自己?jiǎn)为?dú)的半軸，通過(guò)差速器的差速齒輪連接到一起并在驅(qū)動(dòng)橋的中心匯合，車(chē)輪都可以以不同的速度自由轉(zhuǎn)動(dòng)，雖然他們都靠不同的齒輪提供同樣的驅(qū)動(dòng).
制動(dòng)器
控制或者阻止汽車(chē)運(yùn)動(dòng)，高效率的制動(dòng)系統(tǒng)是汽車(chē)所不可缺少的，通過(guò)四個(gè)車(chē)輪起到剎車(chē)作用的部件有兩種類(lèi)型，最起初的類(lèi)型，一對(duì)剎車(chē)片被固定在一個(gè)固定的板子上，被擴(kuò)大然后連接到安裝在輪子上旋轉(zhuǎn)式的制動(dòng)鼓上，這樣可以控制到鼓的執(zhí)行動(dòng)作。在現(xiàn)代的剎車(chē)類(lèi)型上，一對(duì)或者多對(duì)的墊片被放置在一個(gè)靠在車(chē)橋或者車(chē)輪支撐連接的卡鉗上，被安裝在輪胎上側(cè)面的制動(dòng)盤(pán)以用來(lái)緊緊的抓住這些墊片，通過(guò)在踏板施加壓力來(lái)實(shí)現(xiàn)剎車(chē)。手動(dòng)杠桿的作用是通過(guò)一個(gè)單獨(dú)的連接來(lái)鎖定定位器。
在制動(dòng)器的操作方面，無(wú)論是機(jī)械式的制動(dòng)系統(tǒng)還是液壓制動(dòng)系統(tǒng)都可以被使用。機(jī)械式的制動(dòng)系統(tǒng)需要通過(guò)機(jī)械傳動(dòng)和流體液壓等過(guò)程進(jìn)行液壓制動(dòng)來(lái)進(jìn)行應(yīng)用。
傳動(dòng)軸和萬(wàn)向節(jié)
讓變速器的輸出軸連接到后橋，這個(gè)被使用的長(zhǎng)軸被稱之為傳動(dòng)軸，這個(gè)傳動(dòng)軸被一個(gè)管型套所密封或者被一個(gè)萬(wàn)向節(jié)所打開(kāi)并裝在每個(gè)萬(wàn)向節(jié)的末端，以用來(lái)通過(guò)因地面不同的變化而導(dǎo)致的各種形狀的傳動(dòng)軸的連接的上下變化。萬(wàn)向節(jié)不能消除，即使有最終傳動(dòng)齒輪是安裝在固定在車(chē)輪獨(dú)立懸架的彈簧的車(chē)架上。即可以避免因路上的顛簸未對(duì)準(zhǔn)而導(dǎo)致的汽車(chē)構(gòu)造的變形，又可以保證沒(méi)有它們的時(shí)候軸的準(zhǔn)確性。
為了阻止在不平坦的路面上產(chǎn)生的振動(dòng)傳輸?shù)狡?chē)內(nèi)部，這里在汽車(chē)的車(chē)橋上采用了彈簧用來(lái)支持汽車(chē)保證汽車(chē)行駛的平順性。
為了使垂直運(yùn)動(dòng)的車(chē)輪相對(duì)車(chē)架以及允許的部分軸在不同的角度進(jìn)行運(yùn)動(dòng),另外，越來(lái)越多的這樣布置已經(jīng)被應(yīng)用推廣。由驅(qū)動(dòng)齒輪和差速器組成的一個(gè)系統(tǒng)在驅(qū)動(dòng)橋殼軸管內(nèi)通過(guò)車(chē)輪上的獨(dú)立的并起彈簧作用的部件連接在車(chē)架上，這樣能把軸和部件連接在一起的裝置稱為萬(wàn)向節(jié).
車(chē)輪
一共有四個(gè)輪子分別被安裝在汽車(chē)底盤(pán)的下面，用以承載汽車(chē)和乘客的重量，同時(shí)也能夠驅(qū)動(dòng)汽車(chē)使汽車(chē)能夠行駛。他們與橡膠輪胎相適應(yīng)，橡膠輪胎中充滿了由橡膠管在一定壓力的有效壓力下充入的空氣，這個(gè)壓力對(duì)承擔(dān)負(fù)載是非常必要的，這樣來(lái)汽車(chē)輪胎內(nèi)有了足夠的壓力足以用于裝載運(yùn)送東西，同時(shí)能夠承受吸收由于路面不平整而產(chǎn)生的顛簸。憑借安裝在輪子與車(chē)輛之間的鋼板彈簧以及允許做垂直上下顛簸運(yùn)動(dòng)的車(chē)輛，在大部分的不均勻路面將會(huì)得到較好的行駛條件。
當(dāng)按曲線行駛的時(shí)候，內(nèi)輪相對(duì)于外輪在轉(zhuǎn)彎的時(shí)候不得不行駛短一些的距離，但是后邊的兩個(gè)車(chē)輪當(dāng)他們連接到一個(gè)軸的時(shí)候?qū)⑥D(zhuǎn)動(dòng)的速度將達(dá)到一致，通過(guò)兩個(gè)車(chē)輪一起旋轉(zhuǎn)通過(guò)在路面造成的輪胎過(guò)度磨損而將會(huì)導(dǎo)致其中的一個(gè)或兩個(gè)輪子將會(huì)在路面上慢慢滑動(dòng)，并會(huì)導(dǎo)致額外的車(chē)輪磨損以及軸上嚴(yán)重的扭轉(zhuǎn)負(fù)荷。除此之外，兩個(gè)車(chē)輪的完全相同的直徑(即通常不是如此)能在同一個(gè)速度行駛的時(shí)候車(chē)輪沒(méi)有打滑在一條筆直的路上。輪胎安裝在兩個(gè)對(duì)立面,可能會(huì)產(chǎn)生不同位置的磨損,甚至輪胎是相同的直徑，但由不同或相同的制造商在實(shí)際尺寸上可能有所不同，或者未必完全相同。由于改變滾動(dòng)半徑(距車(chē)輪中心與地面)的有效尺寸，輪胎將因?yàn)椴煌呐蛎泬毫Χ淖兇笮 ?
汽車(chē)性能的優(yōu)劣不僅取決于組成汽車(chē)的各部件的性能，而且在很大程度上取決于各部件的協(xié)調(diào)和配合，取決于總體布置；總體設(shè)計(jì)水平的高低對(duì)汽車(chē)的設(shè)計(jì)質(zhì)量、使用性能和產(chǎn)品的生命力起決定性的影響。
Automobile chassis structure
The layout of different types of vehicles is different. A private car which is to carry upto eight persons is generally four seats.
The layout of a car is shown in (Figure1). It shows the position of the main parts of an automobile. It consists of engine located at the front of the vehicle, followed by a clutch, gear box, propeller shaft, universal joint, differential, back axle ect. The radiator is located in front of the engine. Various other parts of the vehicle shown in the layout are dynamo, horn, steering box, fan, timing gear, carburetor, air filter, gear control, steering wheel, cylinder, petrol tank, rear axle, back axle. The drive from the gear box is conveyed through a short shaft to the front universal joint of the propeller shaft.From the propeller shaft.it is conveyed to the rear universal joint through a sliding splined type of joint.The bevel gear of the short shaft is driven by the rear universal joint.This bevel gear meshes with a larger bevel gear which drives the tow rearaxle shafts through a differential gear.
Figure 1 layout of a car
1-Frame ; 2-Wheels ; 3-Radiator ; 4-Engine ; 5-Clutch and gearbox ；6-Propeller shaft ; 7-Uniwersal joint ; 8-Differential , Rear Axle ; 9-Fuel tank ;10-Front axle ; 11-Steering ; 12- Road springs ; 13-Exhaust/silencer
The layout also consists of independent front-wheel springing with quarter-elliptic leaf springs,steering column bevel-gear control and hvdraulic braking system.
Power unit consists of an internal combustion engine.It is usually mounted at the point end of the car.The clutch and the gear box are placed immediately behind it.The three components,engine,clutch and gear box are assembled into a single unit.
Chassis
The term chassis describes all the parts of the automobile under the body .The chassis forms the main structure of the modern automobile .A large number of designs in pressed-steel frame form a skeleton on which the engine ,wheels ,axle assemblies ,transmission ,steering mechanism ,brakes ,and suspension members are mounted .During the manufacturing process the body is flexibly bolted to the chassis . The major components of the basic chassis are the frame ,engine, drivetrain ,wheels ,tires ,steering , brakes ,suspension and steering-everything needed to drive the car .In addition, several other systems are mounted to the chassis assembly .The wheels of the automobile are connected to the frame t by a system of springs ,shock absorbers ,and linkages that make up the car’s suspension system .The suspension system absorbs road shocks as the vehicle travels over rough roads and holds the tire and wheel in correct alignment with the car and the road .It also allows the tires and wheels to move up and down relative to the body over bumps and chuckholes.
Another important chassis component is the steering system ,which allows the driver to control the direction the car travels. The steering wheel ,which the driver controls , is connected to a gearbox that multiplies the driver’s effort .The gearbox is linked to the front wheel of the vehicle.
The last major chassis component is the braking system the function ,the function of which is to either reduce the vehicle’s speed ,bring the vehicle to a halt ,or keep it stationary if already halted. When the driver pushes on the brake pedal,hydraulic fluid is forced out of a master cylinder to each of the four wheels .The resulting hydraulic pressure operates a drum or disk brake assembly to slow or stop the car’s wheels.
Engine
Diesel engines are substantially more efficient than gasoline engines by an estimate of 35-40 percent, producing more power per unit of fuel burned. The efficiency of the diesel engine has been greatly enhanced by the use of turbochargers and charged-air cooling, which has resulted in increased power and performance at minimum fuel consumption rates. Advancements in engine design also mean diesel is no longer considered a "dirty" fuel. Fuel injection and control strategies have produced the "smokeless" diesel. The role of the engine cylinder is to enable the importation of fuel combustion and a driving force. Hyundai Motor wider use of Reciprocating Engine, which generally organisms, with gas, crank linkage, fuel oil supply systems, cooling systems, ignition systems, launch systems and other components. Site to accept the engine driving force, so that a sports car, and to ensure that the driver of the vehicle in accordance with the manipulation of normal traffic.
Clutch
The main function of clutch is cut off and realize the transmission of engine power transmission to ensure that when the car started the engine and transmission smooth joint, to ensure a smooth start car in the shift when the engine and transmission of separation, to reduce transmission of the shift Gear between the impact in their work by the larger dynamic load, we can limit transmission of the largest faced by the torque to prevent the transmission of some parts due to the overload and damage to effectively reduce the transmission of noise and vibration .
Gear Box
A gear box is a speed and power changing device installed at some point between the engine and driving wheels of the vehicle.It provides a means for changing the ration between engine and driving wheels rpm to best meet each particular driving situation. The gear box is a device that is connected to the back of the engine and e same average speed. This is why these vehicles are hard to turn on concrete when the four-wheel-drive system is engaged.
Each wheel is sends the power from the engine to the drive wheels. An automobile engine runs at its best at a certain range.
Front Axle
Front axlw is used for steering front wheels carried on stubaxles swiveling upon king pins at the axle extremities.
Seering Systems
Steering arms and a track rod link the two stub axles together for swiveling them by a steering wheel about the king pins.The steering wheel linked to one of the stub axles by a shaft,a gear box and a suitable linkage is opeated by the driver’s hand wheel.Previously the axle-a onepiece beam was used to support the vehicle through springs,An arrangement known ad independent front suspension has replaced the axle and spring arrangement.Under the control of springs,the wheels are free to rise and fall vertically independently of each other.
Drive Axle
For fixing rear wheels,a tube like shaft enclosing driving shafts with suitable bearings for rotating the wheels is useds.It is enlarged at the center for enclosing the final drive gears used for providing main speed reduction between the engine and the driving wheels. The change of direction of the drive trom the fore and aft line of the propeller shaft to the transverse line of the axle shafts is also provided by this tube known as rear axle.
The differential is a device that splits the engine torque two ways, allowing each output to spin at a different speed. It is found on all modern cars, and also in many all-wheel-drive vehicles. These all-wheel-drive vehicles need a differential between each set of drive wheels, and they need one between the front and the back wheels as well, because the front wheels travel a different distance through a turn than the rear wheels. Part-time four-wheel-drive systems don't have a differential between the front and rear wheels; instead, they are locked together so that the front and rear wheels have to turn at thprovided with its own separate halfshaft connected by a differential gear and meeting at about the center of the axle.The wheels are free to rotate at different speeds although they are provided with equal by the differential gear.
Bake System
For controlling the movement of the vehicles or to stop them,efficient braking system is a necessity for a vehicle.Brakes attached to each of the four wheels are of two types.In the initial type,a pair of shoes carried on a stationary plate is expanded in contact with a rotating drum mounted on the wheels to arrest the motion of the drum.In the modern type of brakes,one or more pairs of pads are carried in a caliper attached to the axle or wheel supporting linkage.The sides of the disk mounted on the wheel are griped by these pads.By applying pressure on a pedal,the brakes are applied.A hand lever acting through a separate linkage and locked in the on position is used.
For operating the brake,either mechanical or hydraulic system is used.Mechanical system requiring gearing system for mechanical and hydraulic fluid for the hydraulic brakes are used
Propeller Shaft And Uniwersal Joint
For connecting the output shaft of the gear box to the rear axle,a long shaft known as propeller shaft is used.This shaft is either enclosed in a tubular casing or kept exposed or opened with a universal joint fitted at each end for allowing the changes in the shaft alignment with the rise and fall of the rear axle due to road surface variations.Universal joints cannot be eliminated even if the final drive gears are fixed to the frame with the wheel springing independently.Neither the misalignment resulting from the flexing of the vehicle structure over bumpy road surfaces can be avoided nor the precise alingnment of shaft can be ensured without them.
For preventing the transmission of shock from uneven road surfaces to the vehicle,springs are used to support the vehicle on the axle.
In order to allow for the vertical movements of the wheels relative to the frame as well as to allow the parts of the shaft to operate at different angle,another increasingly used arrangement is used.It consists of mounting the final-drive gears and the differential gear in a casing attached to the frame with independently sprung wheels attached to them by means of shafts through devices called universal joints.
Wheels
The wheels which are four in number are fitted below the car chassis to support the load of the vehicle and passengers as well as to run the car.They arefitted with hollow rubber tyres filled with air in rubber tubes under sufficient pressure necessary for carrying the load.Theshocks caused by road irregularities are absorbed by them.By fitting springs between the wheels and the vehicle allowing the vertical movement of wheels in relation to vehicle,greater part of unevenness of road surfaces is taken care of.
When going round a curve,the inner wheel has to travel a smaller distance in comparison to the outer wheel.But both the rear wheels would rotate at the same speed if they are connected by a shaft.This rotation of both the wheels would result in slipping of one or both of them on the road surface causing excessive tyre wear as well as severe twisting loads on the shaft.Moreover,the two wheels of the exactly similar diameter(which is not usually so)can only turn at the same spdde witheout slip on the straight road.Tyres fitted on the opposite sides may be of different states of wear and even tyre of same nominal diameter made by different or same manufacturer may differ in actual dimensions or may not be exactly similar.Due to change of rolling radius(the distance from the wheel center to the ground)the effective size of the tyre many be altered by different inflation pressure also.
Through the above exposition know, Vehicle performance depends not only on the merits of the auto component parts of the performance, and to a large extent depend on the components of the coordination and cooperation depends on the overall layout; The overall design of the level of vehicle design quality, performance and vitality products play a decisive impact.
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