外文資料譯文 1 3.1 Clutc h The engine produces the power to drive the vehic le. The drive line or drive train transfers the power of the engine to the wheels. The drive train cons ists o f the parts fro m t he back of the flywhee l to the w heels. These parts include the clutch, the trans miss ion, the drive shaft, and the final drive assembly. The clutc h which inc ludes the flyw heel, clutc h disc, pressure plate, springs, pressure plate cover and the linkage necessary to operate the clutc h is a rotating mecha nism between the engine and the trans miss ion. It operates through fr ictio n whic h comes fro m contact between the parts. That is the reason why the c lutch is called a fr ict ion mecha nism. A fter engage ment, t he clutch must cont inue to transmit all e ngine torque to transmiss ion depe nd ing on the fr ict ion w itho ut slippage. The clutch is also used to disenga ge the engine from the drive train whene ver the gears in the transmission are being shifted from gear ratio to another. To start the engine or shift the gears, the driver has to depr ess the clutc h pedal w it h the purpose of d isenga geme nt the trans missio n fro m the engine. At that t ime, the driven me mbers connected to the transmiss ion inp ut shaft are eit her stationary or rotating at a speed that is slower of faster than the driving membe rs connected to engine cranksha ft. There is no spring pressure on the clutch asse mbly parts. S o there is no frict ion between the driving members and driven me mbers. As the driver lets loose the c lutc h pedal, spring pressure increase on the clutch parts. F rict ion between the parts also increases. The pressure exerted by the springs on t he drive n members is contro lled by the dr iver through the clutch pedal and linkage. The posit ive engage me nt of the driving a nd drive n members is made possib le the fr ict ion be tween the surfaces of the members. When full spring pressure is applied, the speed of the driving and driven me mbers should be the same. At the 外文資料譯文 2 mo ment, the clutch must act as a coupling device and transmit a ll engine power to the transmission, without slip ping. However, the transmiss ion should be engaged to the engine gradually in order to operate the car smoothly and minimize tens iona l shock on the drive train because an engine at id le just develop litt le power. O therw ise, the driving me mbers are connecte d wit h the driven members too quickly and the engine would be stalled. The flyw heel is a major part of the clutch. The flyw heel mo unts to the engines crankshaft and trans mits engine torque to the clutch assemb ly. T he flyw heel, w hen coup led wit h the c lutc h disc and pressure plate makes and breaks the flow of power the engine to the transmission. The flywhee l provides a mount ing locat ion for the clutch assemb ly as well. When the clutch is applied, the flywhee l transfers engine torque to the clutch d isc. Because of its we ight, the flyw heel he lps to smooth engine operation. T he flyw heel a lso has a large r ing gear at its outer edge, which engages w ith a pinion gear on the starter motor during engine cranking. The clutc h disc fits between the flywhee l and the pressure plate. The clutch d isc has a splinted hub that fits over splints on the transmiss ion input sha ft. A splinted hub has grooves that match splints on the shaft. These splints fit in the grooves. Thus, the two parts held together. However, back and forth move ment of t he disc on the sha ft is possible. Attached to the input sha ft, the d isc turns at the speed of the shaft. The clutch pressure plate is generally made of cast iron. It is round and about the sa me dia meter as the clutch d isc. O ne side of t he pressure plate is machined smooth. This s ide will press the clutch d isc facing are against the flyw heel. T he outer s ide has shapes to facilitate attachment of spring a nd release mechanis m. T he two primary t ypes of pressure plate assemblies are coil spring assembly and diaphragm spring. 外文資料譯文 3 In a coil spring c lutc h the pressure plate is backed by a number of coil springs and housed wit h them in a pressed steed cover bolted to the flyw hee l. The spring pushes against the cover. N eit her the driven plate nor the pressure plate is connected rigid ly to the flywhee l and both can move either towards it o away. When the clutch pedal is depressed a thrust pad riding on a carbon or ba ll thrust bearing is forced towards the flyw heel. Levers pivoted so that they engage wit h the thrust pad at one end and the pressure plate tat the other end pull the pressure plate back against its spr ings. This re leases pressure on the driven plate disconnecting the gearbox from the engine. Diaphragm spring pressure p late assemb lies are w idely used in most mod ern cars. The diaphragm spr ing is a single thin sheet of meta l which yie lds when pressure is applied to it. When pressure is remo ved the metal spring back to its origina l shape. The center portion of the diaphragm spring is s lit int o numerous fingers that act as release le vers. When the clutch assembly rotates wit h the engine these weights are flung outwards by centrifuga l p late and cause the levers to press against the pressure plate. Dur ing d isenga geme nt of t he c lutch the fingers a re moved forward by the release bearing. The spring pivots over the fulcrum r ing a nd its outer rim mo ves away fro m t he flyw heel. The retracting spring pulls the pressure plate away from the clutch plate thus disengaging the clutch. When enga ged the release bearing and t he fingers of t he diaphrag m spring move towards the transmiss ion. As the diaphragm p ivots over the pivot ring its outer rim forces the pressure plate against the clutch disc so that the clutch plate is engaged to flywheel. The advantages of a diaphragm t ype pressure plate assemb ly are its compactness, lower weight, fewer moving parts, less effort to enga ge, reduces rotationa l imbala nce by providing a bala nced force around the pressure plate and less chances of clutch slippage. The clutch peda l is connected to the disengage ment mecha nis m 外文資料譯文 4 either by a cable or, more commonly, by a hydraulic syste m. E ither way, pushing the pedal down operates the dise nga geme nt mechanis m w hich puts pressure on the fingers of t he clutch diaphra gm via a release bearing and causes the diaphragm to release the clutch p late. With a hydraulic mechanis m, the clutch pedal arm operates a piston in the clutc h master cylinder. This forces hydraulic fluid through a pipe to the cutch release cylinder where another operates the c lutc h disenga ge ment mechanism by a cable. The other parts inc luding the clutch fork, release bearing, be ll hous ing, bell hous ing cover, and pilot bushing are needed to couple and uncoup le the trans missio n. The clutch fork, which connects to the linkage, actually operates the clutch. The release bearing fits between the clutch fork and the pressure plate assemb ly. T he bell ho using covers the clutch assemb ly. The bell hous ing cover fastens to the bottom of the bell hous ing. T his removab le cover allows a me chanic to inspect the clutc h wit hout remo ving the transmiss ion and bell ho us ing. A pilot bushing fits into the back of the crankshaft and ho lds the trans miss ion input shaft. 3.2 Brake System The breaking system is the most important system in cars. If the brakes fa il, the result can be disastrous. Brakes are actua lly energy conversion devices, whic h convert the kinet ic energy ( mo ment um) of the vehicle into therma l (heat). When stepping on the brakes, the driver comma nds a stopping force ten t imes as powerfu l as the force that puts the car in motion. The braking system can exert thousands of pounds of pressure on each of the four brakes. The brake system is composed of the follow ing basic compone nts : the “master cylinder” which is located under the hood, and is directly 外文資料譯文 5 connected to the brake pedal, converts driver foots mechanical pressure into hydraulic pressure. Steel “brake lines” and flexible “brake hoses” connect the master cylinder to the “slave cylinders” located at each wheel. Brake fluid, specially designed to work in extreme condition, fills the system. “Shoes” and “Pads” are pushed by the salve cylinders to contact the “drum” and “rotors” thus causing drag, which (hopefully) slows the car. The typ ical brake system cons ists of disk brakes in fro nt and eit her disk or drum brakes in the rear connected by a syste m of tubes and hoses that link the brake at each wheel to the master cylinder. Stepping o n the brake pedal, a plunger is actually been pushing against in the master cylinder which forces hydr aulic oil (brake fluid) through a series of tubes and hoses to the braking unit at each wheel. S ince hydraulic fluid (or any fluid for that matter) cannot be compressed, pushing fluid through a p ipe is just like pushing a steel bar through pipe. Unlike a s teel bar, however, fluid can be directed through many tw ists and turns on its way to its destinat ion, arriving with the exact same motion and pressure that it started wit h. It is very important that the fluid is pure liq uid and that there is no air bubbles in it. A ir can compress which causes sponginess to the pedal and severely reduced braking efficie ncy. If air is suspected, then the system must be bled to remove the air. There are “bleeder screws” at each wheel and caliper for this purpose. O n disk brak es, the fluid from t he master cylinder is forced into a caliper where it pressure against a piston. The piton, in - turn, squeezes two brake pads aga inst the disk (rotor) which is attached to the wheel, forcing it to slow down or stop. This process is simila r to the wheel, caus ing the wheel to stop. In eit her case, the fr ict ion sur face of the pads on a disk brake system, on the shoes on a drum brake convert the forward mot ion of t he vehic le into heat. Heat is w hat causes the fr ict ion surfaces (lining) of the pads and shoes to eventua lly wear out and 外文資料譯文 6 require replacement. Brake fluid is spec ial oil t hat has specifics propert ies. It is designed to withsta nd cold temperatures wit hout thickening as well as very high te mperatures wit hout boiling. (I f the brake fluid sho uld boil, it w ill cause you to have a spongy pedal and the car will be hard to stop). The brake fluid reservoir is on top of t he master cylinder. Most cars today have a transparent reservoir so that yo u can see the leve l wit hout opening the cover. The brake fluid lever w ill drop slight ly as the brake pads wear. This is a nor ma l condit io n and no cause for concern. If t he le ver drops not iceably over a short period of t ime or goes down to about two thirds full, have your brakes checked as soon as possib le. Keep the reservoir covered expect for the amount of t ime you need to fill it and never leave a can of brake fluid uncovered. Brake fluid must ma inta in a very high bo iling point. E xposure to air w ill cause the fluid to absorb moisture which will lower that boiling point. The brake fluid trave ls from t he master cylinder to the whee ls through a series of steel t ubes and reinforced rubber hoses. Rubber hoses are only used in places that require flexib ility, such as at the front w heels, which move up and dow n as well as steer. The rest of the system uses non-corrosive seamless steel tubing wit h specia l fitt ings at attachment points. If a steel line requires a repair, the best procedure is to rep lace the co mplete line. If this is nit practica l, a line can be repaired us ing specia l splice fit t ings that are made for brake system repair. You must never use brass “compression” fittings or copper tubing repair a brake system. They are dangerous and illegal. 3.2.1 Other Components in the Hydraulic System Proportioni ng Valve or Equalizer Valve 外文資料譯文 7 These va lves are mo unted between the master cylinder and the rear wheels. T hey are designed to adjust t he pressure between the front and the rear brakes depending on how hard you are stopping. The shorter you stop, the more of the vehicles weight is transferred to the front wheels, in some cases, causing t he rear to lift and the front to dive. These va lves are designed to direct more pressure to the front and less pressure to the harder you stop. This minimizes the chance of premature lockup at the rear wheels. Pressure Differential Valve This va lve is usua lly mounted just below the master and is responsib le for tur ning the brake warning light on when it detects a ma lfunct ion. It measures the pressure fro m the two sections of the master cylinder and compares the m. S ince it is mo unted ahead of the proportio ning or equalizer valve, the two pressures it detects should be equa l. If it detects a difference, it means that there is probably a brake fluid leak somewhere in the system. 外文資料譯文 8 3 1 離合器 發(fā)動機產(chǎn)生動力 來驅動汽 車，它通過傳 動系把動力 傳遞到車輪 上，傳動系包含從飛輪 到車輪的 所有零件。 這些零件含 離合器、變 速箱，驅動橋和最后的駕 駛總成。 離合器含飛輪、離 合器壓盤、離 合器從動盤、彈 簧 、壓盤蓋和操作離合器所需的 連桿組，連 桿組是引擎 和變速箱之 間的一個旋 轉機構 ，它裝在離合器和變 速器之間 ，離合器通 過來自在兩 零件之間的 接觸的磨擦力來工作 ，這就是 離合器為 什么叫做一 個磨擦機構 。在嚙 合之后 ，離合器一定要依靠 磨擦連續(xù) 傳遞所有的 引擎扭力到 變速箱而中 間不會有滑移。每當變速 箱的齒輪 由于換擋被 移 動時，離 合器就用來 斷開來自引擎的動力。 為了要啟動引擎或 者移動齒 輪，駕駛員 必須踩下離 合器踏板達 到把變速器和引擎 分離的目 的。同時 ,對變速箱 輸入軸的連 接的被動的 構件是或不動或者對 引擎曲軸 被連接的構 件以一個比 較慢的速度 旋轉。沒有彈簧壓力在關 鍵的總成 零件上時， 就沒有主動 的構件和被 動的構件之間的磨擦。駕 駛員松開 離合器踏板 ,離合 器部件上的 彈簧壓力增大，零件之間的磨 擦也增加 。駕駛員通 過控制離合 器踏板和連 桿組來控制彈簧的壓力。 主從動部 件的結合使 他們之間的 摩擦成為可 能。當整個彈簧壓力被應 用的時候 ，主從動部 件之間速度 應該是相同 的。此時，離合器成為一 個聯(lián)結裝 置，傳遞所 有的引擎動 力到變速箱 ，而不會有滑動。 然而，變速箱應該 被逐漸地 連接到引擎 從而能平順 地操作車而 且在駕駛時能獲得較 小的扭轉 陡震因為此 時引擎僅僅 被使用了很 少的動力。另外，主動構 件太快地 與被動的構 件一起連接 ，引擎可能 會被熄滅。 飛輪是離合器的一 個主要部 分。它連接 在引擎曲軸 上并把引擎 動力傳遞到離合器總 成上。飛 輪通過連接 從動盤和壓 盤來傳遞從 引擎到外文資料譯文 9 副箱的動力。 飛輪能很好的為離 合器總成 提供一個合 適的位置。 當離合器被 應用的時候，飛輪把 引擎扭力 轉移到離合 器。因為它 的重量，飛 輪能夠使引擎平順地運 作。飛輪在 它的外部邊 緣有一個齒 圈 ,在起動電動機 上用一個驅動小齒輪 來和它嚙 合。 離合器從動盤裝在 飛輪和壓 盤之間。離 合器從動盤 上有一花鍵 轂和變速箱輸入軸過 盈配合。 花鍵轂和軸 上的花鍵聯(lián) 接。這些花 鍵裝在槽中。因此，這 二個零件就 連在了一起 。然而 ,從動盤在 軸上可能往 前或后圓運動。從動 盤和軸一 起旋轉。 離合器壓盤通常是 用鑄鐵做 成的。它是 圓的，與離 合器從動盤 有相同的直徑。壓盤 的一個邊 是光滑的。 這一個邊將 會壓著的離 合器從動盤壓向飛輪 。外部的 邊有促進 彈簧和分離 機構結合的 輪磨配件 。 這個壓盤總成的主要 的兩個形 式 是螺旋彈 簧總成和膜 片彈簧。 彈簧推動對抗蓋。從動片和壓板都沒有被剛性地被連接到飛輪上，兩者可以向它移動 也可以離 開。當離合 器踏板壓向 止推軸承的 推力軸瓦的時候飛輪被壓 。壓向支 點使他們在 一端以推力 軸瓦連接， 而且壓板另一端把壓板拉 回來壓向 它的彈簧。 這在將齒輪 箱從引擎分 離出來的從動片上釋放壓 力。 膜片彈簧壓板總成 廣泛地被 用于現(xiàn)代的 大多數(shù)汽車 上。當壓力 對它被應用的時候， 膜片彈簧 是一個單薄 的形狀。當 壓力被移動 時它變成最初的形狀。膜 片彈簧的 中央部分進 入擔任釋放 桿的多數(shù)的 手指之內被縱切。當離合 器總成和 引擎輸出軸 一起旋轉那 些重力被離 心板所投而且導致分離桿 桿壓向壓 板。在離合 器的不工作 期間，指端 被分離軸承向前移動，彈 簧支點在 支撐環(huán)上和 輸出軸移動 遠離飛輪， 伸縮彈簧拉著壓板遠離離 合器片使 離合器脫離 工作。 分離軸承工作時膜 片彈簧移 向變速器。 在樞上的隔 膜樞嵌環(huán)它 的外部輞強迫對抗離 合器的壓 板以便離合 器片被連接 到飛輪上。 隔膜型壓板總成 的優(yōu)點是 它的緊湊結 構，比較低的 重量 ,比較少的移動零件 ,比 較少的連接 ,在 壓盤周圍提 供一個平衡 力來降低旋 轉平衡和更少的離合器滑 移幾率。 離合器踏板被連接 到自由機 構或一個高 壓線或 ,更普遍 ,或一個 水外文資料譯文 10 力系統(tǒng)。任一方法 ,踩下 踏板可推 動分離軸承 向前運動進 而壓向壓盤 使離合器與飛輪分離 。由一個 水力的機構 ，離合器踏 板臂在離合 器主泵中操作一個活塞。 其他零件包括離 合器叉 ,分離軸 承 ,離合器殼，離合 器殼蓋 ,分離軸襯連接和分離變速 箱。離合 器叉 ,和連桿組連 接 ,實 際上是操作 離合器的。分離軸承裝在 離合器叉 和壓板總成 之間。離合 器蓋裝在離 合器總成上。離合器蓋緊 固到離合 器殼的底部 。這個可移 動的蓋可以 讓一個機匠不用去除變 速箱和殼 就可以檢驗 離合器。導軸 襯裝在曲軸 的后部 ，并支撐變速箱輸入