畢業(yè)設計---汽車轉向機構英文翻譯資料

1、<p>　　Automobile Transmissions and Power Steering</p><p>　　Automobiles, trucks, buses, and tractors all depend on transmissions to deliver power from the engine to the wheels, The gasoline and diesel en

2、gines that power these vehicles cannot be connected directly to the wheels, because the engines must keep turning at a certain seed to keep from stalling. Also, different amount of torque (turning force) must be delivere

3、d to the wheels at different times. A large amount of force is needed to get a car moving from a standstill. Less force is needed to keep</p><p>　　The heart of any transmission——even an automatic one—is a se

4、t of gears. Gears do not change the power of an engine, but they can increase the torque by decreasing the speed. They can also increase the speed by decreasing the torque.</p><p>　　The automobile transmissi

5、on uses a series of gears which enables the engine to continue to operate at maximum efficiency when the vehicle’s speed is altered. Setting an automobile in motion requires a large amount of power to overcome the inerti

6、a of the vehicle’s weight. This process requires high engine speed, needed for high power, and a gradual increase in a vehicle’s speed to avoid a jerky start. To do this, a low gear ratio is allows the crankshaft to revo

7、lve several times in order to turn </p><p>　　The manual transmission system permits the driver to select the desired gear ratio by manipulating a shift lever. Besides the forward speed gears, additional gear

8、ing is incorporated to permit the vehicle to operate in reverse. Manually operated passenger car transmission used in the United States and Canada usually have there speeds forward and one in reverse. Trucks, tractors, b

9、uses, and other heavy-duty vehicles have as many as 10 forward speeds and 2 in reverse. These units are basically five</p><p>　　The automatic transmission system changes gear ratios automatically in response

10、 to changes in engine speed or throttle setting. The use of automatic transmissions increased tremendously after World War Ⅱ, and they are installed in more than half of the automobile produced in the United States. Auto

11、mobiles equipped with an automatic transmission have a control lever which allows the driver to select neutral, low, drive, and reverse. The engine is started in neutral, and the lever is moved to “dri</p><p&g

12、t;　　It is used for climbing steep grades, in mud, or at other tomes when maximum power is needed. Some units have a “park” position, which locks the transmission to prevent a parked car from rolling. The automatic transm

13、ission makes it easier to drive a car, but it is less efficient than a manually shifted unit and increase gasoline consumption. For this reason, the automatic transmission is not as common in Europe, where economy of ope

14、ration is a prime sales factor.</p><p>　　Four basic types of automatic transmissions have been developed to the point where they have been installed in production vehicles. The first consists of a standard m

15、echanical transmission and clutch which is automatically shifted by pneumatic, hydraulic or electric power units. The second type uses a hydraulic torque converter plus a planetary gear system to increase engine torque.

16、The third system combines a hydraulic coupling with an automatically shifted mechanical gearbox to provide torque </p><p>　　Automatic transmission shift in response to signals from speed sensing and throttle

17、 position sensors. The units incorporating hydraulic torque converters use the hydraulic fluid, under pressure, to engage and disengage planetary gear trains.</p><p>　　Power steering system 也是汽車重要的一部分，</p

18、><p>　　The car of today is larger and heavier than earlier cars; the tyres are wider, further apart and inflated to lower pressures .In addition, the trend of development has been to place more than half the we

19、ight on the front wheels, especially the weight of the engine , which itself is larger and heavier than in the early days.</p><p>　　To make cars easier to steer, the gear ratio in the steering box at the end

20、 of the steering column was changed to that turning the wheel required less torque, but this increased the number of turns of the steering wheel required on modern cars without power steering compared to 2.5 or 3 turns f

21、or cars built before 1940. Modern cars with power steering only require about three turns.</p><p>　　Power assisted steering was first developed in the 1920s; one of the first devices was developed by an engi

22、neer at Pierce Arrow, an American make of luxury cars. The Cadillac division of General Motors was going to offer power steering as optional equipment on some models in the early 1930s, but the depression interfered with

23、 development. During World War Ⅱ power steering was fitted to military vehicles; in 1952 Chrysler began offering it , and it is now standard equipment on many of the biggest</p><p>　　Electric devices were tr

24、ied , but power steering today is always hydraulic , with oil pressure of perhaps 1000 psi (70kg/cm2) maintained by a pump driven by the engineer of the car . The system is a servomechanism, or servo loop, which makes a

25、correction to compensate for the torque applied to the steering wheel by the driver. It consists of an actuator and a control valve. The actuator is a hydraulic cylinder with a piston, or ram, which is free to travel in

26、either direction from the center. Th</p><p>　　Hydrostatic systems, designed for off-the-road vehicles, are exception to some of this, because they dispense with the steering column and the steering box , and

27、 the steering wheel and the steered wheels are connected only by hydraulic tubes or hoses.</p><p>　　The power steering system includes a reservoir to hold the oil. Oil pressure is always provided when the en

28、gine is running, but when the system is at rest, that is when the steering wheel is not being turned, equal pressure is available to each side of the piston in the actuator, so that it does not move.</p><p>

29、　　There are basically two types of power steering system: those which have the control valve located within the steering box, in which case it is usually a rotary valve, and those in which the valve is integral with actu

30、ator, when it is an axial spool valve.</p><p>　　汽車傳動系與動力轉向裝置</p><p>　　轎車、卡車、公交車以及拖拉機都靠汽車傳動系將動力從發(fā)動機輸送到車輪上。為機動車輛提供動力的汽油或柴油發(fā)動機不能直接與車輪相連，因為發(fā)動機必須以一定的速度運轉以防熄火停車。而且，在不同的時刻，需要由不同大小的力矩（旋轉力）傳遞到車輪上。當車輛從靜止開

31、始運動的時候需要較大的力矩，而一旦啟動后要維持車輛行走則需要較小的力矩。當車輛以比較高的速度爬坡的時候，還需要額外的驅動力。傳動系的作用就是在需要的時候傳遞特定大小的力矩。傳動系統(tǒng)也能夠使機動車輛后退——雖然汽油或者柴油發(fā)動機只能夠按一個方向旋轉，但是傳遞系統(tǒng)可以改變力矩的方向。當車輛停止運動時，傳動系統(tǒng)能夠使發(fā)動機保持運動而車輪不運動。</p><p>　　即使是自動的，任何一個汽車傳動系統(tǒng)的核心都是一系列齒輪

32、裝置。齒輪不改變發(fā)動機的功率大小，但它可以通過降低轉速來增大轉矩；也可通過減小轉矩來提高轉速。</p><p>　　汽車傳動系是用一系列齒輪，在車速改變時，該系統(tǒng)能使發(fā)動機繼續(xù)以最高效率運轉。起動汽車需要大功率以克服車輛本身的慣性。啟動過程要求發(fā)動機的轉速高，即大功率所必需的轉速，同時還要求汽車逐步加速，以免造成顛簸起動。為此，低速比可使曲軸傳動數周而后輪軸只轉一周。低速比用于起動，爬陡坡及其他需要大功率的場合。

33、當功率需要減小時，就用較高的變速比，此變速比使曲軸以較少的轉數帶動后輪軸。隨著車速的增大，要繼續(xù)地使用更高的變速比，直至發(fā)動機到后輪軸的傳動經過傳動裝置時無需減速為止。傳動裝置主要由兩類：手動的和自動的。</p><p>　　手動傳動系要求駕駛員熟練地操縱變速桿以選擇所需的變速比。汽車一般除裝有前進變速齒輪外，還有輔助齒輪裝置，以便倒車。在美國和加拿大，客車的手動傳動系有三個前進檔和一個倒車檔?？ㄜ?、拖拉機、公共

34、汽車及其他重型車輛都有十個前進擋和兩個倒車檔。這些機構主要有五速傳動機構和一個二速輔助齒輪箱。那些使汽車在行進中可變速的傳動系都裝有同步齒輪變速機構，以防止齒輪嚙合時碰撞。同步齒輪變速機構使齒輪速度同步，這樣，在這些齒輪進入嚙合時，能同速轉動。</p><p>　　自動傳動系隨發(fā)動機的速度變化或調速氣門的變化而自動地改變速比。第二次世界大戰(zhàn)后，應用自動換擋的車輛迅速增加。美國現今生產的汽車多半都裝有自動換擋裝置。

35、裝自動換擋的汽車都有一操縱桿，駕駛員可用它選擇空擋、低速、行駛和倒車速度。發(fā)動機以空擋起動，操縱桿移至“行駛”擋為正常向前運行。掛“行駛”擋時，只要踩下加速踏板，汽車便可從靜止加速到最大速度。低檔位置可防止變速機構變速超出較低的變速比范圍。</p><p>　　抵擋用于爬陡坡、泥路或者其他需要大功率的場合。有的車還裝有“停車”擋，它可鎖住變速機構以防止已停止的汽車溜動。使用自動換擋裝置使駕車更加容易，然而，它沒有

36、手動變速效率高，而且汽車油耗量增大。因此自動變速機構在歐洲用的并不普遍，因為在那里經濟實惠是汽車銷售的首要因素。</p><p>　　現已研制處四種基本自動換擋裝置，并已達到在汽車上安裝使用的程度。第一種是標準的機械傳動裝置及靠氣傳動。液力或電力裝置自動換擋的離合器。第二種是液力變矩器加行星齒輪機構，以增加發(fā)動機的扭矩。第三種是把液力聯(lián)軸器與自動換擋機械齒輪箱結合在一起以增大扭矩。第四種是用一級或多級的液力變矩器

37、以增大扭矩。</p><p>　　自動換擋是隨著來自速度傳感器和調速氣門位置傳感器的變化而變速的。該裝置與液力變矩器相合并，利用高壓液流使行星齒輪嚙合或分離。</p><p>　　動力轉向裝置也是汽車上重要的一部分，現今的汽車比早期的汽車大得多也重的多。為了降低壓力，加寬了輪胎，也加大了輪胎間距，并給輪胎充了氣。此外，汽車的發(fā)展趨勢主要是把一多半的重量，特別是發(fā)動機的重量，由前輪承受，發(fā)動

38、機本身也比早期的既大又重。</p><p>　　為使汽車容易轉向，改變了轉向柱末端轉向箱的傳動比，結果只需較小的扭矩轉動方向盤。然而，這與1940年以前制造的汽車需要兩周半或三周的傳數相比，現在無動力轉向裝置的轉向盤所需的轉數增加了，而有動力轉向裝置的現代汽車其轉數只需三周左右。 動力轉向裝置早在20世紀20年代首次研制出來；最初的裝置之一是由皮爾斯.埃羅汽車長的一位工程師、美國豪華汽車制造商研制出來的。在

39、20世紀30年代初期，美國通用汽車公司卡迪萊克汽車分部打算提供動力轉向裝置作為某些型號汽車的備選裝置，但是經濟蕭條妨礙了其發(fā)展。在第二次世界大戰(zhàn)期間，動力轉向裝置曾裝在軍用車輛上。1952年克萊斯勒公司開始提供這種裝置?，F在這種動力轉向裝置是美國許多大型汽車的一種標準配置。</p><p>　　雖然曾經試過電動裝置，但現在用的動力轉向裝置常是液壓的，由汽車發(fā)動機驅動一臺泵，該泵使油壓維持在1000泵/平方英寸（7

40、00公斤/平方厘米）。該系統(tǒng)叫做私服機構或私服回路，其作用是進行調整以補償駕駛員施加于轉向盤的扭矩。私服回路系統(tǒng)由一傳動裝置和一控制閥組成。該傳動裝置即是一個裝有活塞或柱塞的油缸，此油缸的活塞可以從油缸中央向兩個方向自由移動?？刂崎y的作用是通過開動油缸兩端處的小閥對方向盤的扭矩做出反應。設計這一私服系統(tǒng)由助于轉向聯(lián)動裝置，而不是代替轉向裝置。該系統(tǒng)不能完成全部轉向動作，而其余動作則是由司機完成。這樣如果液壓系統(tǒng)一旦失靈，盡管司機要費些力

41、氣，汽車任然可以開動。而且對路面的感覺始終可由汽車前輪機械傳地傳到駕駛員握著的方向盤的雙手。而這是能安全駕駛的一個重要因素。動力轉向裝置對安全駕駛做出的另一個有益的貢獻在于：如果駕駛員碰到路面上的一個小障礙物或在快速行駛重輪胎泄氣，該動力轉向裝置使汽車更容易控制。許多安裝了寬而堅硬的徑向線網層輪胎的大型汽車，如果沒有動力轉向裝置，當汽車以停車時速度慢行時，幾乎不可能對汽車進行轉向操作。</p><p>　　為不在

42、公路上行駛的一些運輸車輛設計的液壓系統(tǒng)與這種液壓系統(tǒng)有所不同，因為這種液壓系統(tǒng)不用轉向柱和轉向箱，而方向盤和轉向車輪只用液壓油管或液壓軟管連接。</p><p>　　動力轉向系統(tǒng)包括一個盛油的儲油箱，在發(fā)動機工作時，始終保持著油壓不變。但當轉向系統(tǒng)不工作時，即轉向盤不轉動時，傳動裝置油缸中活塞兩側的壓力相等，因此活塞不動。</p><p>　　動力轉向機構，有兩種基本類型：一種是在轉向箱內