農(nóng)用拖拉機(jī)車輛課程畢業(yè)設(shè)計(jì)外文文獻(xiàn)翻譯、中英文翻譯、外文翻譯

1 FARM  TRACTOR The history of tractor development is to lang to relate here .Landmarks along the road include the fires use of an internall combustion engine in a tractor in the United States in 1890;the Ivel tractor of 1901; the American Ford of 1917 , and the International Farmall  of 1923 . During the 1930s , the use of low-pressure pneumatic tyres soon became popular , and the first Ferguson system tracrors incorporating three-point linkage with hydraulic draught control were introduced . Classification of tractor types.Tractors as now manufactured can be classified as follows: A. According to method of securing traction and self-propulsion: 1. Wheel tractors a. Three tractors b. Four wheels 2. Track-type tractors B.  According to utility : 1. General-purpose or utility 2. All-purpose or row-crop type Wheel tractors. The wheel-type tractor is the predomingating type,particularly for agricultural purposes.Wheel tractors are made either with three wheels or with four wheels .The usual arrangement consists of two rear-drive wheels and one or two front steering members. Track-type tractors. The traction mechanism in the  2 track-type tractor  consists essentially of two heavy,endless,metal-linked devices known as tracks themselves by reducing the movement of one track below the speed of the other.  General-purpose or utility tractor.A general-purpose tractor is one ofmore or less conventinal design such as an ordinary four-wheel machine or a track-type machine.This type is also referred to as autility troctor. It is made to perform only the usual tractor jops,including both field and belt work such as plowing ,harrowing,road grading ,combining,feed grinding,and the like. All-purpose tractors.An all-purpose or row-crop type is a tractor designed to handle practically all the field and belt jops on the average farm,including the planting and intertillage of row crops. The conventional tractor consists basically of two engine-driwen wheels,usually at the rear, and two support wheels st the front . The type of the engine used to power the heart of the tractor; it is here that the fuel,the chemical potential energy , is converted into the mechanical emergy which causes the wheels to turn. The difference between n internal and external combustion engine is simply that in an internal combustion engine ,the conversion of potential energy into mechanical energy takes place wholly in the cylinder,whereas with external combustion the fuel is burnt outside the cylinder .A steam engine or a gas turbine is a good example of the latter. How can liquid fuel be changed into rotational mechaanical energy? This is achieved by accurately mixing  3 the fuel with air and then burning it in controlled condition.When this mixture burns ,it expands and pressure builds up ,forcing the piston to move down the cylinder in a straight line. It is said to rotary motion .This linear motion is converted into rotary motion by a connecting rod and crank arrangement joined to the piston. To be able to use this energy effectively, the burning and combustion proce and the force of expansion have to be controlled. To do this , the enginemust have : 1. A tube or cylinder closed at one end ,in which the mixture of fuel and air can be compressed and burnt . 2. A  piston , which slides freely and yet fits closely in the cylinder ,so that the expanding gas force it down the cylinder ,and do not escape past it . 3. Two passages or ports in the cylinder . One for the mixture of fuel and air to enter the cylinder , the inlet prot , and the other to allow the used gases to escape , the exhaust port. 4. Two valves , the inlet valve to control the the movement of the mixture to the cylinder , and the exhaust valve to control the escape of the used gases . By carefully timing the ignition of the mixture in relation of the opening and closing of the valves and the position of the piston , it is possible to make the piston move up and down the cylinder continuously . The working of an internal combusition engine , once it is started , involves a sequence or cycle of operations in  4 each cycle and the two-stroke cycle . In the four-stroke cycle , the crankshaft completes two revolutions and the piston four strokes , a stroke being the movement of the piston from one end of the cylinder to the other . In the two-stroke cycle , the crankshaft makes one revolution and the piston two strokes in each cycle . Your tractor probably has a complete electric system which provides electicuty for the self-starter , for igniting the fuel , and for lights . Insome designs electricity is also used for certain other accessory circuits. Such complete systems comprise several circuits : (1)generator circuit, (2) starting motor circuit , (3) lighing circuit , (4) ignition circuit . The storage battery may well be considered the basis of the complete system bacause it is connected to and works with all four of these principal circuits . We must reduce the relatively fast speed of the engine and transmit its power to the driving menbers to obtain suitable speeds and pulling power for the different farm jops. You may want a fst forward speed for hauling form the field or on the highway but a much slower fortions.Aslo,you msut have some means of reversing the direction of rotation of the driving members. Much of the necessry speed reduction is accomplished by the sliding(speed-changing)gears of the assembly which is ususlly called the “ transmission.” Further reduction is secured at the differential and by the final drive pinions and bull gears(Fig.9).  5 Fig.9 You select the speed you want by shifting one of the sliding gears,which are splined to be transmission shaft.With the gear shift lever,you can move then forward or backward;you can mesh any certain sliding gear with it s mating gear on the counter-shaft. In the schematic diagram(Fig.9),gears C,E,G,ang K are sliding gears.Gear A ,at the end of the drive shaft,and gear B,on the ciuntershaft,are in constant mesh.Hence,the countershaft and all it s rigidly connected gears are in motion whenever the drive shaft revolves. When you disengage the clutch, all gears are at rest and no power is transmittedto the drive wheels. However, when you move one of the sliding gears, such as C,into mesh with D,then by engaging the clutch,you complete the connection  6 bnetween the engine and the drive wheels. Contact between gears C and D(as shown ) would give low,or first, speed; engaging gears E and F would give sceond speed; gear G and H would give third speed. When none of the sliding gers is in mesh with it s countershaft gear, the gears are said to be in “ neutral.”  Reverse speed is obtained by the use of a small/pinion R between the countershaft gear I and the sliding gear K ,which causes the transmission drive shaft ti be driven in the opposite direction. In today s tractors there are still more gear combingations giving more forward speeds; these are needed for the many operations now performed with farm tractors. In some tractor models,an additional speed-reducing and toedue-increasing unit is installed between the engine cluth and the transmision driving gear.This unit is controlled with a separate lever near the tractor seat. When the unit incereases the “ torque”  or pulling force obtained from that speed. When you use this unit,you get a ratio of about three to two between the engine crankshaft and the transmission drive gear (when you are not using it you have the usual direct ratio between these two parts). Because this “ torque amplifier” is ahead of the regular speed-changing gears, it reduces each speed you obtain from the various gear combinations. So it doubles the number of available speeds,Each speed is reduced about one-third and the torque, or pulling force, from such slower speed is increased by 45 per cent . This is very helpful when plowing  7 through tough spots or diskding through wet spots . You can engage the torque amplifier-reduce speed and increase pull-without stopping.And, when through the heavy pull,you can disengage it and return to normal speed without stopping.  8 農(nóng)用拖拉機(jī)   拖拉機(jī)的發(fā)展歷史很長，在這里不再贅述。拖拉機(jī)發(fā)展史上的幾個(gè)里程碑是： 1890 年 內(nèi) 燃 機(jī) 在 美 國 拖 拉 機(jī) 上 的 首 次 使 用 ；1901 年 Ivel 拖拉機(jī)的問世； 1917 年美國福特拖拉機(jī)以及 1923年萬國公司 Farmall 拖拉機(jī)的相 距出現(xiàn)。 30 年代，低壓充氣輪胎的應(yīng)用迅速普及，并且推廣了第一批 Forguson 系統(tǒng)的拖拉機(jī)，這種拖拉機(jī)配有力調(diào)節(jié)的三點(diǎn)液壓懸掛裝置。  拖拉機(jī)的分類。目前制造的拖拉機(jī)可分類如下：  A. 按照獲得牽引力及自身推進(jìn)的方法分：  1.輪式拖拉機(jī)  1）  三輪拖拉機(jī)。  2）  四輪拖拉機(jī)。  2履帶式拖拉機(jī)  B. 按照用途分：  1通用型，即多用型拖拉機(jī)。  2萬能型，即中耕型拖拉機(jī)。  輪 式 拖 拉 機(jī) ：輪 式 拖 拉 機(jī) 是 主 要 的 拖 拉 機(jī) 類 型 ，特 別 是 在 農(nóng)用 方 面 ?，F(xiàn) 在 制 造 的 輪 式 拖 拉 機(jī) 有 三 輪 的 或 四 輪 的 。通 常 的 配 置是在兩個(gè)后驅(qū)動(dòng)輪及一個(gè) 或兩個(gè)前導(dǎo)向輪。  履 帶 式 拖 拉 機(jī) ：履 帶 式 拖 拉 機(jī) 的 牽 引 機(jī) 構(gòu) 實(shí) 質(zhì) 上 由 兩 條 成 為履帶的重型封閉金屬鏈條裝置構(gòu)成。每以條履帶在兩個(gè)鐵輪上運(yùn)轉(zhuǎn) ，其 中 一 個(gè) 鐵 輪 具 有 鏈 齒 ，用 作 驅(qū) 動(dòng) 輪 ，另 一 個(gè) 用 作 惰 輪。轉(zhuǎn)向是通過履帶本身來完成的，即通過減慢其中一條履帶的運(yùn)動(dòng)速度使之低于另一條的速度的辦法來完成的。  通用型即多用型拖拉機(jī)：通用型拖拉機(jī)基本上是一種傳統(tǒng)設(shè)計(jì) 的 拖 拉 機(jī) ，例 如 普 通 的 四 輪 拖 拉 機(jī) 或 履 帶 式 拖 拉 機(jī) 。這 種 類 型也被成為多用型拖拉機(jī)，它僅用來完成一般的拖拉機(jī)作業(yè)，包括田間作業(yè)和皮帶作業(yè)，例如耕地、耙地、平路、聯(lián)合收獲、飼料 9 粉碎等等。  萬 能 型 拖 拉 機(jī) ：萬 能 型 拖 拉 機(jī) 即 中 耕 型 拖 拉 機(jī) ，用 來 完 成 一般的農(nóng)場的幾乎所有的田間作業(yè)和皮帶作業(yè)，包括中耕作物的播種和中耕在內(nèi)。  傳統(tǒng)的拖拉機(jī)通常有兩個(gè)用發(fā)動(dòng)機(jī)驅(qū)動(dòng)的后輪和兩個(gè)支重的 前 輪 。用 來 為 拖 拉 機(jī) 提 供 動(dòng) 力 的 發(fā) 動(dòng) 機(jī) 類 型 是 內(nèi) 燃 機(jī) 。發(fā) 動(dòng) 機(jī)是拖拉機(jī)的心臟。正是在這里燃料的化學(xué)年能被轉(zhuǎn)化為使輪子轉(zhuǎn)動(dòng)的機(jī)械能。  內(nèi)燃機(jī)和外燃機(jī)的區(qū)別僅僅是在：在內(nèi)燃機(jī)力，勢能轉(zhuǎn)化為機(jī)械能完全與空氣精確的混合，然后在控制的條件下燃燒。這種混合燃燒時(shí)就會(huì)膨脹，壓力增大，推動(dòng)活塞沿著氣缸直線地向下運(yùn) 動(dòng) 。我 們 就 說 活 塞 作 直 線 運(yùn) 動(dòng) 。該 直 線 運(yùn) 動(dòng) 通 過 與 活 塞 連接的連桿和曲柄機(jī)構(gòu)轉(zhuǎn)變?yōu)樾D(zhuǎn)運(yùn)動(dòng)。  為了能有效地利用這種能量，對燃燒過程和膨脹壓力必須加以控制。為此發(fā)動(dòng)機(jī)必須具有：  1.一端密閉的管子即氣缸，在這里燃油和空氣的混合氣被壓縮和燃燒  2.活塞，它可以在氣缸里只有滑動(dòng)，但又與氣缸配合嚴(yán)密，這 樣 ，膨 脹 的 氣 體 就 能 推 動(dòng) 活 塞 沿 著 氣 缸 向 下 運(yùn) 動(dòng) 而 不 從 周 圍 漏掉。  3.氣缸的兩個(gè)同期道：一個(gè)是燃料和空氣的混合氣進(jìn)入氣缸的進(jìn)氣口，另一個(gè)是排泄廢氣的排氣口。  4.兩 個(gè) 閥 門 ：控 制 混 合 氣 進(jìn) 入 氣 缸 的 進(jìn) 氣 門 和 控 制 廢 氣 排 放的排氣門。根據(jù)閥門的開筆和活塞的位置，使混合氣正時(shí)點(diǎn)火，就可以使活 塞連續(xù)地在氣缸里上下運(yùn)動(dòng)。  內(nèi)燃機(jī)一旦運(yùn)動(dòng)，其工作過程就是指每個(gè)氣缸里所發(fā)生的一系 列 的 動(dòng) 作 。一 般 有 兩 種 不 同 的 循 環(huán) ：四 行 程 循 環(huán) 和 二 行 程 循 環(huán) 。在四沖程循環(huán)中，曲柄轉(zhuǎn)兩圈，活塞完成四個(gè)行程，一個(gè)行程就是指活塞自氣缸的一端運(yùn)動(dòng)到另一端。在二行程循環(huán)中，每一個(gè) 10 循環(huán)曲柄轉(zhuǎn)一圈，活塞完成兩個(gè)行程。  拖拉機(jī)大概都有一套完整的電系來為電動(dòng)機(jī)、燃料點(diǎn)火和照明 設(shè) 備 供 電 。在 有 些 拖 拉 機(jī) 的 設(shè) 計(jì) 上 還 要 為 其 它 一 些 輔 助 線 路 供電。  一套完整的電系包括下面幾條線路：（ 1）發(fā) 電 線 路 ；（ 2）電起 動(dòng) 機(jī) 線 路 ；（ 3）照 明 線 路 ；（ 4）點(diǎn) 火 線 路 。因 為 蓄 電 池 與 所有這四條主要線路連接并為其供電，所以完全可以把它看作是整個(gè)電系的基礎(chǔ)。  為了獲得適合各種農(nóng)業(yè)工作的速度和牽引力，我們就必須降低發(fā)動(dòng)機(jī)較快的轉(zhuǎn)速并將其動(dòng)力傳遞給驅(qū)動(dòng)裝置。在田間或公路運(yùn)輸時(shí)需要較快的前進(jìn)速度，但在重負(fù)荷田間作業(yè)時(shí)需