汽車專業(yè)畢業(yè)設(shè)計--外文翻譯

1、汽車的基本機械機構(gòu)汽車工業(yè)是一種迅速發(fā)展的工業(yè)。從十八世紀(jì)后期第一輛汽車出現(xiàn)在公路上 后，這一工業(yè)便迅猛發(fā)展起來。如今全世界成千上萬的工廠生產(chǎn)著各種各樣的汽 車。汽車行業(yè)也匯聚了千千萬萬的人。汽車發(fā)動機廣泛地應(yīng)用于配有巨大動力的 機械屮，如農(nóng)業(yè)、建筑業(yè)、制造業(yè)。不同類型的小型發(fā)動機也應(yīng)用于植草機、動 力鋸、除雪機等類似的設(shè)備中。汽車行業(yè)是一個發(fā)展著的、需求著的行業(yè)，似乎 永遠找不到它的盡頭和飽和點。汽車、運輸工具、發(fā)動機有著巨大的需求量。這 一行業(yè)同樣需要受過鍛煉的、有經(jīng)驗的精英，來診斷這些機動車倆的故障、修理 和更新機動車的零件、變速器、推動軸、差分器、車軸、操縱系統(tǒng)、剎車系統(tǒng)、 暫停部件、

2、空調(diào)裝置、發(fā)熱器、機身以及玻璃制造等。汽車由五個基木的機械機構(gòu)或部件組成。它們是：（1）發(fā)動機，它是動力的源泉，包括燃料、潤滑劑、冷卻和電氣系統(tǒng)。（2）框架，它支持發(fā)動機、車輪、操縱和剎車系統(tǒng)，以及機身。（3）傳動系，它將來自發(fā)動機的動力（經(jīng)過離合器、調(diào)速器、傳動軸、差分器和車軸）傳送到車輪。（4）機身。（5）機身附件，它包括加熱器、燈光、擋風(fēng)玻璃擦等等。發(fā)動機是使得汽車運行的動力源泉。它通常叫做一個內(nèi)置的燃燒發(fā)動機， 因為汽油是在發(fā)動機氣缸或燃燒腔內(nèi)被燃燒的。這是相對于外置的發(fā)動機而言的 （如蒸汽發(fā)動機），其燃燒發(fā)生在發(fā)動機的外部。發(fā)動機氣缸內(nèi)的汽油的燃燒產(chǎn) 生了動力。然后動力經(jīng)過傳動系傳送

3、到發(fā)動機再到車輪，這樣車輪轉(zhuǎn)動，汽車便 開始運行。在動力產(chǎn)生的過程中燃料系統(tǒng)起著重要的作用，因為它給發(fā)動機氣缸提供汽 油。在每一個發(fā)動機氣缸里，蒸發(fā)岀來的汽油和空氣組成的混合體進入氣缸，活 塞推進氣缸，壓縮混合體，然后電火花點燃壓縮混合體，這樣活塞被迫向下。當(dāng) 然，在發(fā)動機內(nèi)，活塞沒有完全推到氣缸外面，而是隨著混合體的燃燒，在氣缸 內(nèi)簡單地來回移動。在汽車車輪能夠轉(zhuǎn)動之前，活塞的線性運動必須轉(zhuǎn)變成旋轉(zhuǎn) 運動。發(fā)動機機軸上的連桿和曲柄實現(xiàn)了這一轉(zhuǎn)變。閥門將燃燒過的汽油蒸氣送出氣缸外面，同時把汽油蒸氣和空氣新鮮可燃混 合氣送入氣缸。當(dāng)他們被關(guān)閉或固定時（也就是推到端口上），端口被封閉，這 樣氣體不

4、能流通到端口。當(dāng)他們被打開時，氣體可以流通到端口。閥門是通過發(fā)動凸輪軸上的凸輪被打開的。凸輪有一個最高點，或圓形突出 部分；每次當(dāng)凸輪轉(zhuǎn)動時，突出部分在氣門挺桿之下，使得挺桿向上。挺桿將這 個向上的運動傳動到推桿再傳送到搖桿臂。搖桿臂在它的支撐體上轉(zhuǎn)動并在閥桿 上推下去，使得閥移到低處，也就是說閥被打開了。當(dāng)凸輪轉(zhuǎn)動得足夠使突出部 分移出挺桿z下時，承重的閥門彈簧將閥門退回到自己的位置。彈簧被彈簧座和 鎖附在閥桿的下端。在發(fā)動機凸輪軸上每個閥門都有一個凸輪（每個氣缸兩個凸 輪）。凸輪軸通過齒輪或鏈條齒和齒條受到機軸的驅(qū)動。如果整個循環(huán)過程需耍四次活塞運動，那么該發(fā)動機就叫做四沖程發(fā)動機, 或四

5、行程發(fā)動機。這四個行程是輸入、壓縮、發(fā)動、和排氣。在輸入行程時，進氣閥是被打開的，活塞受到機軸旋轉(zhuǎn)的推動，移到下面。 活塞的這個移動引起了氣缸內(nèi)的局部的真空，同時空氣通過進氣閥推進氣缸，以 填補該真空。當(dāng)空氣向氣缸移動時，它必須經(jīng)過氣化器。那里充滿了汽油蒸氣。 因此當(dāng)活塞在輸入端移至下端時進入氣缸的是空氣和汽油蒸氣的混合體。當(dāng)活塞在進口端移到下止點時，進氣閥關(guān)閉?？刂浦M氣閥的凸輪的突出部 分已經(jīng)從閥門下面移走。因為另一個閥門也是關(guān)閉的，氣缸的上端被關(guān)閉。現(xiàn)在， 當(dāng)轉(zhuǎn)動著的機軸將閥門推上時，已經(jīng)進入氣缸的空氣和汽油蒸氣混合體被壓縮。 直到活塞被推到上止點吋，氣體被壓縮成原來的七分之一或八分之一

6、。這就類似 一加侖的空氣被壓所成一品托。究其原因是由于氣缸內(nèi)部的高壓。在壓縮行程，當(dāng)活塞到達上止點時，氣缸火花塞產(chǎn)生一個電火花?；鸹ㄈ?質(zhì)上是兩個粗鋼絲電極?；鸹ㄓ牲c火系統(tǒng)產(chǎn)生。它點燃了壓縮的空氣和汽油蒸氣 混合體。由于高壓和高溫，發(fā)生了急劇的燃燒。此時，活塞頂端向下的壓力達到 兩噸。這個巨大的推力使得活塞向下，同時巨大的沖力通過連桿和曲柄傳送到機 軸。在動力行程，由于汽油蒸氣的燃燒使得活塞受迫。當(dāng)活塞達到下止點時， 排氣閥被打開。這吋，活塞又一次被返冋，它推動氣缸內(nèi)被燃燒過的氣體。到活 塞到達上止點時，氣缸內(nèi)被燃燒過的氣體被清除掉。排氣閥關(guān)閉，進氣閥開啟。 活塞在下一個輸入行程時再次被返回

7、。發(fā)動機運行時，這四個行程持續(xù)地重復(fù)著。離合器是一種摩擦裝置，它用于從從動機構(gòu)中聯(lián)合和拆分驅(qū)動力。在汽車的 應(yīng)用中，它用于與發(fā)動機調(diào)速輪相連，以提供發(fā)動機和手工傳送之間的平滑結(jié)合 和正常脫離。因此隨著發(fā)動機速度的降低，需要漸進裝載的應(yīng)用，以獲得一個合理的和舒 適的啟動。在裝配有手工傳動的汽車系統(tǒng)中，這可以通過一個機械離合器獲得成 功。離合器是通過摩擦獲得運行的。離合器的主要裝置是一個壓力盤和一個驅(qū)動 板。壓力盤外加有調(diào)速輪，而驅(qū)動板和傳動輸入軸相品配。壓力盤通過彈力壓住 驅(qū)動盤，這樣扭矩由于發(fā)動機和傳送的輸入軸z間的摩擦力而被傳動。汽車一般裝有干式彈力離合器。之所以稱之為干的是因為壓力盤和驅(qū)動

8、板是 干的，相對于油式離合器，它是浸泡在油中運行的。之所以稱之為彈力的是由于 壓力盤和驅(qū)動板是靠彈力相互壓在一起的，同時在某個時刻被釋放到汽車的齒輪 或剎車裝置中。除了壓力盤和驅(qū)動盤，離合器還包含有一個外殼、釋放桿、釋放轆、壓力彈 簧和一個控制連接。離合器外殼是一個鋼鐵沖壓，由螺釘裝載調(diào)速器上。釋放桿 通過支撐螺釘確保在外売內(nèi)部。釋放桿的外部端被放置在壓力盤中。這樣的裝置 允許壓力盤接近或離開外殼，并一直隨著調(diào)速盤而轉(zhuǎn)動。沿壓盤和離合器蓋之間 的圓周均勻分布的彈簧加住壓盤與飛輪之間的從動盤。彈簧的安裝依賴于外殼和壓力盤提供的發(fā)射孔和插槽。為了防治彈簧過熱, 壓力盤插槽配有熱的絕緣墊圈。液壓制動

9、離合器分離裝置由一個踏板、分離彈簧、主氣缸、氣力調(diào)壓器、管 道、軟管、分離叉的桿組成。主氣缸供應(yīng)一個附有杯子的活塞。氣力調(diào)壓器用以 降低踏板力以分離離合器。調(diào)壓器包括內(nèi)置伺服機構(gòu)的兩個機架。機架供應(yīng)氣力 的、水壓的、伺服的活塞。當(dāng)踏板被推上去的時候，來自主氣缸的液壓經(jīng)過管和 軟管被傳到氣力調(diào)壓器的水壓和伺服活塞上。自動離合器理所當(dāng)然被應(yīng)用在美國和歐洲的汽車中。美國發(fā)動機”estick”離 合器消除了踏板物理運行的需要。一個徳國的汽車制造者設(shè)計了一個自動的離合 器系統(tǒng)叫做"hydrak",它由一個液力飛輪連接著一個干燥的轉(zhuǎn)盤。在"e-stick"裝配中，壓

10、力盤杠桿嚙合離合器盤而不是分離的。同樣，當(dāng)變速 器的運動處于正常時，離合器處于閑置狀態(tài)，直到伺服系統(tǒng)被油壓應(yīng)用到的時候。 "hydrak"系統(tǒng)只有杠桿正常時才開始運行。這激勵了一個用以分離離合器轉(zhuǎn)盤的 調(diào)壓器系統(tǒng)。通過釋放輪系統(tǒng)建立了水壓離合器部分，當(dāng)后輪的速度大于發(fā)動機 的速度吋，水壓離合器處于工作狀態(tài)。機械離合器的運行由一個特殊的裝置控制 著，它依賴于后車輪是否處于牽引狀態(tài)或被汽車的推力推動。在克萊斯特汽車和美國通用汽車中，用到了一個不平常的離合器壓盤系統(tǒng)。 叫做半離心式離合器，壓盤有六個圓柱滾輪，它在離心力的作用下向外運動，直 至觸到外殼。當(dāng)發(fā)動機速度增加時，滾輪的楔

11、形物自動進入壓力盤和外殼之間, 這樣離合器轉(zhuǎn)動的越快，施加在壓力盤上的壓力便越大。變速器是安裝在汽車發(fā)動機和驅(qū)動輪之間某個點上的控制速度和功率變化 的裝置。它提供了一種方法，該方法使得在行使的每一個特殊情況下，發(fā)動機每 分鐘的轉(zhuǎn)數(shù)和主動輪每分鐘的轉(zhuǎn)數(shù)達到最好的配合。對于水平路面，如果沒有變速器，汽車可以通過發(fā)動機的加速和離合器的連 接而啟動。然而，這種條件下的啟動不僅慢、有噪聲，而且不舒適。此外，它還 將在發(fā)動機和汽車驅(qū)動部分產(chǎn)生一個巨大的拉伸。這樣為了獲得平滑的啟動并且能過越過和爬上山坡，必須提供一個功率比, 用以對扭矩和發(fā)動機的轉(zhuǎn)動力成倍地增加。同樣需要一個速比以避免高速公路上 過高的發(fā)動

12、機轉(zhuǎn)速/每分鐘。變速器便是實現(xiàn)這些功能。變速器需要設(shè)計的是：改變從發(fā)動機曲軸到傳動軸被傳送的扭矩、使汽車逆 向運動、當(dāng)長時間停車或靠邊行使時將發(fā)動機從驅(qū)動路線上分離生來。當(dāng)慣性大、 牽引阻力小的時候，應(yīng)對車輪施加一個比在一般平路上行使時還要大的扭矩使汽 車全負荷運轉(zhuǎn)或全負荷爬坡。為了配合這些變化的扭矩的需要，用到一個特殊的 齒輪箱。這樣的齒輪箱叫做固定系數(shù)變速器。由主動齒輪和從動齒輪組成的齒輪鏈中，主動齒輪上的扭矩將增加很多倍, 因為主動齒輪的齒數(shù)大于從動齒輪的齒數(shù)。為了滿足變化的操作條件，需要提供不同的扭矩，因此變速器里加入了幾組 不同齒數(shù)比的齒輪。變化。變速器有機殼、輸入軸和齒輪、輸出軸和

13、齒輪、惰輪軸、回轉(zhuǎn)齒輪、齒輪組 及換檔機構(gòu)組成。鐵鑄的機売有一個上蓋和側(cè)蓋并有用于裝軸的孔。底面和另一側(cè)面提供了用 于裝油和排油的孔。輸入軸是剛鑄的，又主動齒輪和輪緣構(gòu)成整體。輸入軸的前端安裝在曲軸的 孔中，而末端在機身前而的孔中做旋轉(zhuǎn)運動。輸入軸這樣布置以便只有主動齒輪 和齒圈安裝在箱體內(nèi)，而伸出變速器外的軸的花鍵部分用來支承離合器從動盤轂。 輸出端是用花鍵連接的，并隨著安裝在輸入軸孔中的滾動軸承的的前端而休息。 輸出端的另一端在變速器機身的滾動軸承中做旋轉(zhuǎn)運動。齒輪軸安放著一組不同齒數(shù)比的齒輪。這組齒輪安裝在輪軸上的滾動軸承上, 或和軸安裝在一起，即機身的孔的軸承屮。閑置的軸始終隨著輸入軸

14、而轉(zhuǎn)動，因 為它們的齒輪是保持嚙合的。冋轉(zhuǎn)齒輪（單個齒輪或兩個齒輪組）由機身上的孔 確保在軸輪上轉(zhuǎn)動。換檔機構(gòu)被設(shè)計用以實現(xiàn)是連接齒輪、使其保持空檔和使其倒檔。沿著輸出 軸齒輪的變換將引起速度的變化。變速器的類型依賴于滑動齒輪的個數(shù)。有兩個 滑動齒輪或同步嚙合套的叫做2范圍，三個齒輪的叫做3范圍。根據(jù)向前的速 度的大小，由3、4、5速度的變速器。換檔機構(gòu)安裝在蓋的頂端上。換檔桿安 裝在蓋上或水平支座的托座上。譯文the basic mechanisms of automobilesthe automobile industry is a fast developing industry. fr

15、om the later 18th century when the first automobile was put on road, this industry has developed tremendously. now there are thousands of factories all over the world manufacturing numerous types of automobiles. this industry employs crores of men and women directly and indirectly in allied industri

16、es. the automobile engines are also being used in engine powered machines for agriculture, construction and manufacturing processes. various types of small engines are also being used in lawn movers, power saws, snow removers and similar equipment. the automobile industry is a developing and demandi

17、ng industry which does not find its end or saturation point. there is a great demand for varied types of automotive products, vehicles and engines.there is also a great demand for trained and experienced persons in this industry for diagnosing motor vehicle troubles, repairing and replacing engines

18、components, transmissions, propeller shafts, differentials, axles, steering system components,brake system components, suspension components, air-conditioners, heaters, body and glass work.the automobile consists of five basic mechanisms, or components. these are :(1) the engine, which is the source

19、 of power, including the fuel, lubricating, cooling, and electric systems(2) the frame, which supports the engine, wheels, steering and brake systems, and body(3) the power train, which carries the power from the engine(through the clutch,transmission, drive shaft, differential, and axles)to the car

20、 wheels(4) the car body(5) car-body accessories, including heater ,lights, windshield wipers, and so forththe engine is the source of power that makes the car move. it is usually called an internal combustion engine because gasoline is burned inside the engine cylinders, or combustion chambers. this

21、 is in contrast to external-combustion engines(such as steam engines),where the combustion takes place outside the engine. the burning of gasoline in the engine cylinders produces the power. the power is then carried from the engine through the power train to the car wheels so that the wheels turn a

22、nd the car moves.the fuel system plays a vital part in the power producing process since it supplies the gasoline to the engine cylinders. in each engine cylinder, a mixture of gasoline vapor and air enters the cylinder, the piston pushes up into the cylinder to compress the mixture, and then an ele

23、ctric spark ignites the compressed mixture so that the piston is forced downward. of course, in the engine the piston is not blown completely out of the cylinder, the piston simply moves up and down in the cylinder-up to compress as the mixture burns. the piston straight-line motion must be changed

24、to rotary motion before it can be used to make the car wheels rotate. a connecting rod and a crank on the engine crankshaft make this change.the engine valves get the burned gasoline vapor out of the engine cylinder and bringing fresh changes of gasoline vapor and air into the cylinder. there are tw

25、o openings ,or ports, in the enclosed end of the cylinder .each containing a valve. the valve are accurately machined plugs on long stems- when they are closed, or seated (that is, moved up into the ports), the ports are sealed off and gas cannot pass through the ports. when the valve is open, gas c

26、an pass through the portthe valves are opened by cams on the engine camshaft. the cam has a high point, or lobe; every time the cam rotates, the lobe comes around under the valve lifter and move it upward. the lifter then carries this upward movement through the pushrod to the rocker arm. the rocker

27、 arm pivots on its support and pushes down on the valve stem, causing the valve to move down, that is, to open. after the cam has turned enough to move the lobe out from under the lifter, the heavy valve spring pulls the valve back into its seat. the spring is attached to the upper end of the valve

28、stem by a spring retainer and lock. there is a cam for each valve (two cams per cylinder) on the engine camshaft. the camshaft is driven off the crankshaft by gears or by sprockets and a chain.when the entire cycle of events requires four piston strokes (two crankshaft revolutions), the engine is ca

29、lled a four-stroke-cycle engine, or a four-cycle engine. the four strokes are intake, compression, power, and exhaust.on the intake stroke, the intake valve is open. the piston moves down, pulled by the rotation of the crankshaft. this piston movement creates a partial vacuum in the cylinder, and ai

30、r rushes into the cylinder past the intake valve to "fill upn this vacuum. as the air moves toward the cylinder, it must pass through the carburetor. there it is charged with gasoline vapor. thus, it is a mixture of air and gasoline vapor that rushes into the cylinder as the piston moves down o

31、n theintake stroke.after the piston moves down to the bottom dead center on the intake stroke, the intake valve closes. the lobe on the cam controlling the intake valve has moved out from under the valve lifte匚 since the other valve is also closed, the upper end of the cylinder is sealed. now, as th

32、e piston is pushed up by the rotating crankshaft, the mixture of air and gasoline vapor that has been drawn into the cylinder is compressed.by the time the piston has moved up to the top dead center, the mixture is compressed to a seventh or an eighth of its original volume. that is like taking a ga

33、llon of air and compressing it to a pin匸 the result is high pressure in the cylinde匚about the time the piston reaches the top dead center on the compression stroke, an electric spark occurs at the cylinder spark plug. the spark plug is essentially two heavy wire electrodes; the spark jumps between t

34、hese electrodes. the spark is produced by the ignition system. it ignites, or sets fire to, the compressed air-gasoline-vapor mixture. rapid combustion takes place; high temperatures and pressures result. at this instant, the downward pressure on the top of the piston may amount to as much as 2tons.

35、 this powerful push forces the piston down, and a power impulse is transmitted to the crankshaft through connecting rod and the crank.the piston is forced down by the pressure of the burning gasoline vapor during the power stroke. when the piston reaches the bottom dead center, the exhaust valve ope

36、ns. now, as the piston starts back up again, it forces the burned gases from the cylinder. by the time the piston has reached the top dead center the cylinder is cleared of the burned gases. the exhaust valve closes and the intake valve opens- then ,the piston starts back down again on the next inta

37、ke stroke. the four cycles, or piston strokes, are continuously repeated while the engine is running.the clutchesa clutch is a friction device used to connect and disconnect a driving force from a driven membe匚 in automotive application, it is used in conjunction with an engine flywheel to provide s

38、mooth engagement and disengagement of the engine and manual transmission.since an internal combustion engine develops little power or torque at low rpm, it must gain speed before it will move the vehicle. however, if a rapidly rotating engine is suddenly connected to the drive line of a stationary v

39、ehicle, a violent shock will result.so gradual application of load, along with some slowing of engine speed, is needed to provide reasonable and comfortable starts. in vehicles equipped with a manual transmission, this is accomplished by means of a mechanical clutch.the clutch utilizes friction for

40、its operation. the main parts of the clutch are a pressure plate, and a driven disk. the pressure plate is coupled with the flywheel, while the driven disk is fitted to the transmission input shaft. the pressure plate is pressed to the disk by the springs so that the torque is transmitted owing to f

41、riction forces from the engine to the input shaft of the transmission. smooth engagement is ensured by slipping of the disk before a full pressure is applied.the automobiles are equipped with a dry spring-loaded clutch. the clutch is termed ndryh because the surfaces of the pressure plate and driven

42、 disks are dry incontrast to oil-bath clutches in which the plate and disks operate in a bath of oil. it is called nspring-loadedn because the pressure plate and the driven disk are always pressed to each other by springs and are released only for a time to shift gears or to brake the automobile.in

43、addition to the plate and disk, the clutch includes a cover, release levers, a release yoke, pressure springs and a control linkage. the clutch cover is a steel stamping bolted to the flywheel. the release levers are secured inside the cover on the supporting bolts. the outer ends of the release lev

44、ers are articulated to the pressure plate. such a construction allows the pressure plate to approach the cover or move away from it, all the time rotating with the flywheel. the springs spaced around the circumference between the pressure plate and the clutch cover clamp the drivendisk between the p

45、ressure plate and the flywheel.the springs are installed with the aid of projections and sockets provided on the cover and pressure plate. the pressure plate sockets have thermal-insulation gaskets for protecting the springs against overheating.the clutch release mechanism can be operated either mec

46、hanically or hydraulically. the mechanicallyoperated release mechanism consists of a pedal,a return spring, a shaft with lever, a rod, a release yoke lever, a release yoke, a release ball bearing with support and a clutch release spring. when the clutch pedalis depressed, the rod and shaft with yoke

47、 shift the released bearing and support assembly. the release bearing presses the inner ends of the release levers, the pressure plate is moved away from, the driven disk and the clutch is disengaged. to engage the clutch, the pedal is released, the release bearing thus releasing the release levers

48、so that the pressure plate is forced by its springs towards the flywheel to clamp the driven disk and engage the clutch.the clutch hydraulically-operated release mechanism consists of a clutch pedal, clutch release spring, a main cylinder, a pneumatic booster, pipelines and hoses and a lever of the

49、clutch release yoke shaft. the main cylinder accommodates a piston with a cup. the pneumatic booster serves to decrease the pedal force required to disengage the clutch. the booster includes two housings with the servo diaphragm clamped in between. the housing accommodates pneumatic, hydraulic and s

50、ervo plungers. when the clutch pedal is pushed, the fluid pressure from the main cylinder is transmitted through the pipelines and hoses to the hydraulic and servo plungers of the pneumatic booste 匚the servo arrangement is intended for automatic change of the air pressure in the pneumatic cylinder p

51、roportionally to the force applied to the pedal. the plunger moves with the diaphragm, the outlet valve closes and the inlet valve opens thus admitting the compressed air to the pneumatic plunger piston. the forces created by the pneumatic and hydraulic plungers are added together and are applied th

52、rough the push rod to the release yoke shaft lever, the lever turns the shaft and the release yoke shaft disengaging the clutch. after the clutch pedal is released,the outlet valve opens and the inlet closes. under the action of the springs thepistons return the plungers to the initial position and

53、the air from the cylinder is let out to the atmosphere.automatic clutches were used in certain u.s. and european cars. american motorsne-stickh clutch eliminated the need for physical operation of the clutch pedal. a german car maker engineered an automatic clutch system called mhydrak, which consis

54、ted of a fluid flywheel connected to a single, dry disk clutch.in the ne-stickn set up, the pressure plate levers "engage” the clutch disk rather than "release” them. also, the clutch remains disengaged until a servo unit is applied by oil pressure when the shift lever is placed "in g

55、ear11 with the engine running.the nhydrakn unit also begins operation when the lever is "in gearh. this activates a booster unit, which disengages the clutch disk. the hydraulic clutch parts are bridged over by a free-wheel unit, which goes into action when the speed of the rear wheels is highe

56、r than the speed of the engine. a special device controls ingagement of the mechanical clutch, depending on whether the rear axle is in traction or is pushed by car momentum.a more-or-less unusual clutch pressure plate set-up is used on late model chrysler and american motors cars. called a semi-cen

57、trifugal clutch, the pressure plate has six cylindrical rollers which move outward under centrifugal force until they contact the cover. as engine speed increases, the rollers wedge themselves between the pressure plate and cover so that the faster the clutch rotates, the greater the pressure exerte

58、d on the pressure plate and disk.automobile transmissiona transmission is a speed and power changing device installed at some point between the engine and driving wheel of the vehicle. it provides a means for changing the ratio between engine rpm ( revol utions per minute) and driving wheels rpm to

59、best meet each particular driving situation.given a level road ,an automobile without a transmission could be made to move by accelerating the engine and engaging the clutch. however, a start under these conditions would be slow, noisy and uncomfortable. in addition, it would place a tremendous strain on the engine and driving parts of the automobile.so in order to get smooth starts and have power to pass and climb hills, a power ratio must be provided to multiply the torqu