农用拖拉机车辆课程毕业设计外文文献翻译、中英文翻译、外文翻译

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 农用拖拉机   拖拉机的发展历史很长，在这里不再赘述。拖拉机发展史上的几个里程碑是： 1890 年 内 燃 机 在 美 国 拖 拉 机 上 的 首 次 使 用 ；1901 年 Ivel 拖拉机的问世； 1917 年美国福特拖拉机以及 1923年万国公司 Farmall 拖拉机的相 距出现。 30 年代，低压充气轮胎的应用迅速普及，并且推广了第一批 Forguson 系统的拖拉机，这种拖拉机配有力调节的三点液压悬挂装置。  拖拉机的分类。目前制造的拖拉机可分类如下：  A. 按照获得牵引力及自身推进的方法分：  1.轮式拖拉机  1）  三轮拖拉机。  2）  四轮拖拉机。  2履带式拖拉机  B. 按照用途分：  1通用型，即多用型拖拉机。  2万能型，即中耕型拖拉机。  轮 式 拖 拉 机 ：轮 式 拖 拉 机 是 主 要 的 拖 拉 机 类 型 ，特 别 是 在 农用 方 面 。现 在 制 造 的 轮 式 拖 拉 机 有 三 轮 的 或 四 轮 的 。通 常 的 配 置是在两个后驱动轮及一个 或两个前导向轮。  履 带 式 拖 拉 机 ：履 带 式 拖 拉 机 的 牵 引 机 构 实 质 上 由 两 条 成 为履带的重型封闭金属链条装置构成。每以条履带在两个铁轮上运转 ，其 中 一 个 铁 轮 具 有 链 齿 ，用 作 驱 动 轮 ，另 一 个 用 作 惰 轮。转向是通过履带本身来完成的，即通过减慢其中一条履带的运动速度使之低于另一条的速度的办法来完成的。  通用型即多用型拖拉机：通用型拖拉机基本上是一种传统设计 的 拖 拉 机 ，例 如 普 通 的 四 轮 拖 拉 机 或 履 带 式 拖 拉 机 。这 种 类 型也被成为多用型拖拉机，它仅用来完成一般的拖拉机作业，包括田间作业和皮带作业，例如耕地、耙地、平路、联合收获、饲料 9 粉碎等等。  万 能 型 拖 拉 机 ：万 能 型 拖 拉 机 即 中 耕 型 拖 拉 机 ，用 来 完 成 一般的农场的几乎所有的田间作业和皮带作业，包括中耕作物的播种和中耕在内。  传统的拖拉机通常有两个用发动机驱动的后轮和两个支重的 前 轮 。用 来 为 拖 拉 机 提 供 动 力 的 发 动 机 类 型 是 内 燃 机 。发 动 机是拖拉机的心脏。正是在这里燃料的化学年能被转化为使轮子转动的机械能。  内燃机和外燃机的区别仅仅是在：在内燃机力，势能转化为机械能完全与空气精确的混合，然后在控制的条件下燃烧。这种混合燃烧时就会膨胀，压力增大，推动活塞沿着气缸直线地向下运 动 。我 们 就 说 活 塞 作 直 线 运 动 。该 直 线 运 动 通 过 与 活 塞 连接的连杆和曲柄机构转变为旋转运动。  为了能有效地利用这种能量，对燃烧过程和膨胀压力必须加以控制。为此发动机必须具有：  1.一端密闭的管子即气缸，在这里燃油和空气的混合气被压缩和燃烧  2.活塞，它可以在气缸里只有滑动，但又与气缸配合严密，这 样 ，膨 胀 的 气 体 就 能 推 动 活 塞 沿 着 气 缸 向 下 运 动 而 不 从 周 围 漏掉。  3.气缸的两个同期道：一个是燃料和空气的混合气进入气缸的进气口，另一个是排泄废气的排气口。  4.两 个 阀 门 ：控 制 混 合 气 进 入 气 缸 的 进 气 门 和 控 制 废 气 排 放的排气门。根据阀门的开笔和活塞的位置，使混合气正时点火，就可以使活 塞连续地在气缸里上下运动。  内燃机一旦运动，其工作过程就是指每个气缸里所发生的一系 列 的 动 作 。一 般 有 两 种 不 同 的 循 环 ：四 行 程 循 环 和 二 行 程 循 环 。在四冲程循环中，曲柄转两圈，活塞完成四个行程，一个行程就是指活塞自气缸的一端运动到另一端。在二行程循环中，每一个 10 循环曲柄转一圈，活塞完成两个行程。  拖拉机大概都有一套完整的电系来为电动机、燃料点火和照明 设 备 供 电 。在 有 些 拖 拉 机 的 设 计 上 还 要 为 其 它 一 些 辅 助 线 路 供电。  一套完整的电系包括下面几条线路：（ 1）发 电 线 路 ；（ 2）电起 动 机 线 路 ；（ 3）照 明 线 路 ；（ 4）点 火 线 路 。因 为 蓄 电 池 与 所有这四条主要线路连接并为其供电，所以完全可以把它看作是整个电系的基础。  为了获得适合各种农业工作的速度和牵引力，我们就必须降低发动机较快的转速并将其动力传递给驱动装置。在田间或公路运输时需要较快的前进速度，但在重负荷田间作业时需