汽車離合器課程畢業(yè)設(shè)計外文文獻(xiàn)翻譯、中英文翻譯、外文翻譯

CLUTCH The engine produces the power to drive the vehicle. The drive line or drive train transfers the power of the engine to the wheels. The drive train consists of the parts from the back of the flywh eel to the wheels. These parts include the clutch, the transmission, the drive shaft, and the final drive assembly (Figure 8-1). The clutch which inc ludes the flywheel, clutch disc, pressure plate, springs, pressure plate cover and the linkage necessary to operate the clutch is a rotating mechanis m between t he engine and the transmission (F igure 8-2). It operates through fr iction which comes from contact between the parts. That is the reason why the clutch is called a frict ion mechanism. After engagement, the clutch must continue to transmit all the engine to rque to the transmission depending on the friction w ithout slippage. The clutch is also used to disengage the engine from the drive train whenever the gears in the transmission are being shifted from one gear ratio to another. To start the engine or shift the gears, the driver has to depress the clutch pedal with the pur pose of disengagement the transmission from the engine. At that time, the driven members connected to the transmission input shaft are either stationary or rotating at a speed that is slowe r or faster tha n the driving members connected to the engine crankshaft. There is no spring pressure on the clutch assembly parts. So there is no frict ion between the driving me mbers and driven me mbers. As the driver lets loose the clutch pedal, spring pre ssure increases on the clutch parts. F riction between the parts also increases. The pressure exerted by the springs on the driven me mbers is controlled by the driver through the clutch pedal and linkage. The positive engagement of the driving and driven me mbers is made possible by the friction between the surfaces of the me mbers. When full spring pressure is applied, the speed of the driving and driven me mbers should be the same. At the moment, the clutch must act as a solid coupling device and transmit al l engine power to the transmission, without slipping. However, the transmission should be engaged to the engine gradually in order to operate the car smoothly and minimize torsional shock on the drive train because an engine at id le just develops litt le power. O therwise, the driving me mbers are connected with the driven members too quickly and the engine would be stalled.  The flyw heel is a major part of the clutch. The flyw heel mounts to the engines crankshaft and transmits engine torque to the clutch asse mbly. The flywheel, when coupled with the clutch disc and pressure plate makes and breaks the flow of power from the engine to the transmission. The flywheel provides a mount ing location for the clutch assembly as well. When the clutch is applied, the flyw heel transfers engine torque to the clutch disc. Because of its weight, the flywheel he lps to smooth engine operation. The flywheel also has a large ring gear at its outer edge, which engages with a pinion gear on the starter motor during engine cranking. The clutch disc fits between the flywheel and the pressure plate. The clutch disc has a splined hub that fits over splines on the transmission input shaft. A splined hub has grooves that match splines on the shaft. These splines fit in the grooves. Thus, t he two parts are held together. However, back-and- forth movement of the disc on the shaft is possible. Attached to the input shaft, At disc turns at the speed of the shaft. The clutch pressure plate is generally made of cast iron. It is round and about the same dia meter as the clutch disc. O ne side of the pressure plate is machined smooth. This side will press the clutch disc facing are against the flywheel. The outer side has various shapes to facilitate attachment of spring and release mechanisms. The two primary types of pressure plate assemblies are coil spring assembly and diaphragm spring (Figure 8-3). In a coil spring clutch the pressure plate is backed by a number of coil springs and housed with them in a pressed -steel cover bolted to the flywheel. The springs push against the cover. Neither the driven plate nor the pressure plate is connected rigidly to the flywheel and both can move either towards it or away. When the clutch pedal is depressed a thrust pad riding on a carbon or ball thrust bearing is forced towards the flywheel. Levers pivoted so that they engage with the thrust pad at one end and the pressure plate at the other end pull the pressure plate back against its springs. This releases pressure on the driven plate disconnecting the gearbox from the engine (Figure 8-4). Diaphragm spring pressure plate assemblies are widely used in most modern cars. The diaphragm spring is a single thin sheet of metal which yie lds when pressure is applied to it. When pressure is removed the metal springs back to its original shape. The centre portion of the diaphragm spring is slit into numerous fingers that act as release levers. When the clutch assembly rotates with the engine these weights are flung outwards by centrifugal forces and cause the levers to pre ss against the pressure plate. During disengagement of the clutch the fingers are moved forward by the release bearing. The spring pivots over the fulcrum ring and its outer rim moves away from the flywheel. The retracting spring pulls the pressure plate a way from the clutch plate thus disengaging the clutch (Figure 8-5). When engaged the release bearing and the fingers of the diaphragm spring move towards the transmission. As the diaphragm pivots over the pivot ring its outer rim forces the pressure plate against the clutch disc so that the clutch plate is engaged to the flywheel.  The advantages of a diaphragm type pres sure plate assembly are its compactness, lower weight, fewer moving parts, less effort to en gage, reduces rotational imbalance by providin g a balanced force around the pressure plate and less chances of clutch slippage.  The clutch pedal is connected to the disengagement mechanis m either by a cable or, more commonly, by a hydraulic system. Either way, pushing the pedal down operates the dise ngagement mechanis m which puts pressure on the fingers of the clutch diaphragm via a release bearing and causes the diaphragm to release the clutch plate. With a hydraulic mechanism, the clutch pedal arm operates a piston in the clutch master cylinder. This forces hydraulic fluid through a pipe to the  clutch release cylinder where another piston operates the clutch disengagement mechanis m. The alternative is to link the clutch pedal to the disengagement mechanism by a cable. The other parts includ ing t he cl utch fork, release bearing, bell- housing, bell housing cover, and pilot bushing are needed to couple and uncouple the transmission. The clutch fork, which connects to the linkage, actually operates the clutch. The release bearing fits between the clutch fo rk and the pressure plate assembly. The bell housing covers the clutch assembly. The bell housing c over fastens to the bottom of the bell housing. This removable cover allows a mechanic to inspect the clutch wit hout removing the transmission and bell housing. A pilot bushing fits into the back of the crankshaft and holds the transmission input shaft. Torque Converter The Basics Just like manual transmission cars, cars with automatic transmissions need a way to let the engine turn while the wheels and gears in the transmission come to a stop. Manual transmission cars use a clutch, which completely disconnects the engine from the transmission. Automatic transmis sion cars use a torque converter. A torque converter is a type of fluid coupling, which allows the  engine to spin somewhat independently of the transmission. If the engine is turning slowly, such as when the car is idling at a stoplight, the amount of torque passed through the torque converter is very small, so keeping the car still requires only a light pressure on the brake pedal. If you were to step on the gas pedal while the car is stopped, you would have to press harder on the brake to keep the car from moving. This is because when you step on the gas, the engine speeds up and pumps more fluid into the torque converter, causing more torque to be transmitted to the wheels. Inside a Torque Converter There are four components inside the very strong housing of the torque converter: 1. Pump;  2. Turbine ;  3. Stator;  4. Transmission fluid. The housing o f the torque converter is bolted to the flyw heel of the engine, so it turns at whatever speed the engine is running at. The fins that make up the pump of the torque converter are attached to the housing, so they also turn at the same speed as the engine.  The cutaway below shows how everything is connected inside the torque converter (Figure 8-6). The pump inside a torque converter is a type of centrifugal pump. As it spins, fluid is flung to the outside, much as the spin cycle of a washing machine flings water and clothes to the outside of the wash tub. As fluid is flung to the outside, a vacuum is created that draws more fluid in at the center. The fluid then enters the blades of the turbine, which is connected to the transmission. The turbine causes the transmission to spin, which basically moves the car. The blades of the turbine are curved. This means that the fluid, which enters the turbine from the outside, has to change direction before it exits the center of the turbine. It is this directional change that causes the turbine to spin. The fluid exits the turbine at the center, moving in a different direction than when it entered. The fluid exits the turbine moving opposite the direction that the pump (and engine) is turning. If the fluid were allowed to hit the pump, it would slow the engine down, wasting power. This is why a torque converter has a stator.  The stator resides in the very center of the torque converter. Its job is to redirect the fluid re turning from the turbine before it hits the pump again. This dramatically increases the efficiency of the torque converter. The stator has a very aggressive blade design that almost completely reverses the direction of the fluid. A one -way clutch (ins ide the stator) connects the stator to a fixed shaft in the transmission. Because of this arrangement, the stator cannot spin with the fluid  - it can spin only in the oppos it e dire c t i o n, forc i n g the flui d to chang e dire c t i o n as it hit s the stato r blade s .  Something a little bit tricky happens when the car gets moving. There is a point, around 40 mph (64 kph), at which both the pump and the turbine are spinning at almost the same speed (the pump always spins slightly faster). At this point, the fluid returns from the turbine, entering the pump already moving in the same direction as the pump, so the stator is not needed. Even though the turbine changes the direction of the fluid and flings it out the back, the fluid  still ends up moving in the direction that the turbine is spinning because the turbine is spinning faster in one direction than the fluid is being pumped in the other direction. If you were standing in the back of a pickup moving at 60 mph, and you threw a ball out the back of that pickup at 40 mph, the ball would still be going forward at 20 mph. This  is similar to what happens in the tur bine: The fluid is being flung out the back in one direction, but not as fast as it was going to start with in the other direction. At these speeds, the fluid actually strikes the back sides of the stator blades, caus ing the stator to freewheel on its one-way clutch so it doesnt hinder the fluid moving through it. Benefits and Weak Points In addition to the very important job of allowing a car come to a complete stop wit hout stalling the engine; the torque converter a ctually gives the car more torque when you accelerate out of a Stop. Modern torque converters can multiply the torque of the engine by two to three times. This effect only happens when the engine is turning much faster than the transmission. At higher speeds, the transmission catches up to the engine, eventually moving at almost the same speed. Ideally, though, the transmission would move at exactly the same speed as the engine, because this difference in speed wastes power. This is part of the reason why cars with automatic transmissions get worse gas mileage than cars with manual transmissions. To counter this effect, some cars have a torque converter with a lockup clutch. When the two halves of the torque converter get up to speed, this clutch locks them together, eliminating the slippage and improving efficiency. 離合器  發(fā)動機(jī)產(chǎn)生動力用以驅(qū)動車輛。動力傳動系將發(fā)動機(jī)動力傳到車輪。傳動系由飛輪后端到車輪之間的零件組成。這些零件包括離合器、變速器、傳動軸和減速器總成。  離合器是位于發(fā)動機(jī)和變速器之間的一個旋轉(zhuǎn)裝置，它包括飛輪、離合器（從動盤）磨擦片、壓盤、壓緊彈簧、離合器蓋及操作離合器所需的連接桿件等。它通過零件間的接觸磨擦工作。這是離合器為什么會稱為磨擦機(jī)構(gòu)的原因。離合器接合后，給變速器傳遞所有的發(fā)動機(jī)轉(zhuǎn)矩磨擦沒有打滑。離合器也被用于在變速器傳動比變換時從傳動系中分離發(fā)動機(jī)。  為了起動發(fā)動機(jī)或換檔，駕駛員必須踩下離合器踏板以便實現(xiàn)變速器和發(fā)動機(jī)的分離。在那時，與變速器輸入軸相聯(lián)的離合器從動件可能處于靜止?fàn)顟B(tài)，也可能以一定的速度旋轉(zhuǎn)，這一速度可能高于或低于與發(fā)動機(jī)相聯(lián)的離合器主動件的旋轉(zhuǎn)速度。沒有彈簧壓力作用于離合器總成器件上。因此在主動件和從動件之間沒有磨擦。當(dāng)駕駛員松開離合器踏板時，彈簧對離合件器件壓力增加。各個器件之間的磨擦也會增加。彈簧對從動件所施加的壓力由駕駛員通過離合器踏板和連桿機(jī)構(gòu) 來控制。主從動件的有效接合是通過其表面的摩擦來實現(xiàn)的。當(dāng)彈簧壓力全部應(yīng)用時，主從動件的轉(zhuǎn)速是相同的。此時，離合器充當(dāng)一個剛性連接裝置，沒有滑轉(zhuǎn)，將發(fā)動機(jī)全部功率傳遞給變速器。  但是，為了使汽車操作平穩(wěn)，變速器應(yīng)該逐漸與發(fā)動機(jī)接合，并減小傳動系的扭轉(zhuǎn)沖擊，因為發(fā)動機(jī)空轉(zhuǎn)時的功率輸出很小。否則，主動件與從動件連接過快，發(fā)動機(jī)會停轉(zhuǎn)。  飛輪是離合器的一個主要部件。飛輪安裝在發(fā)動機(jī)的曲軸上，給離合器總成傳遞發(fā)動機(jī)轉(zhuǎn)矩。飛輪與離合器摩擦片和壓盤結(jié)合在一起來傳遞或中斷發(fā)動機(jī)給變速器的功率流。  飛輪也為離合器總成提供裝配 位置。當(dāng)離合器作用時，飛輪將發(fā)動機(jī)轉(zhuǎn)矩傳遞給離合器從動盤。飛輪重，所以有助于發(fā)動機(jī)的運(yùn)轉(zhuǎn)平穩(wěn)。飛輪外緣還有一個大齒圈，在起動發(fā)動機(jī)時，它與起動機(jī)的小齒輪嚙合。  離合器從動盤安裝在飛輪和壓盤之間，有一個花鍵轂套在變速器輸入軸上的花鍵上?；ㄦI轂上的槽與輸入軸上的花鍵配合?；ㄦI裝配在槽內(nèi)，因此，兩個零件結(jié)合在一起。但是，從動盤可以在軸上前后移動。從動盤連接在輸入軸上，與軸的轉(zhuǎn)速相同。  離合器壓盤一般由鑄鐵制成。它是圓形，與（離合器）從動盤的直徑相同。壓盤一側(cè)被加工平滑。這側(cè)會把離合器摩擦襯面壓到飛輪上。外側(cè)有各種 形狀，以有利于彈簧與分離機(jī)構(gòu)的連接。有兩種主要的壓盤總成分別是螺旋彈簧總成和膜片彈簧總成。  螺旋彈簧離合器中，壓盤背部有許多螺旋彈簧支撐（壓緊），并和它們一起安裝在一個通過螺栓連接到飛輪上的壓制鋼（離合器）蓋中。彈簧推壓離合器蓋。從動盤和壓盤都不是嚴(yán)格連接到飛輪上，兩個都可以相對飛輪前后移動。當(dāng)離合器踏板被踩下時，安放在碳質(zhì)或滾珠推力軸承上的止推墊被壓向飛輪。分離杠桿（在樞軸上）轉(zhuǎn)動，使它們能夠與一側(cè)的止推墊和另一側(cè)的壓盤接合，然后將壓盤拉向彈簧。這會釋放施加在從動盤上的壓力，變速器和發(fā)動機(jī)脫離。  現(xiàn)代轎車 普遍采用膜片彈簧壓盤總成。膜片彈簧是一個薄金屬片，在壓力作用下會彎曲。當(dāng)壓力釋放時，這個金屬彈簧會回到原來的形狀。膜片彈簧的中心部分有許多切開的分離指作為分離杠桿。當(dāng)離合器總成隨著發(fā)動機(jī)旋轉(zhuǎn)時，由于離心力的作用，它們的重量會被甩到膜片彈簧的外緣，從而使分離杠桿對壓盤釋壓。在離合器分離時，分離指在分離軸承作用下向前移動。支撐環(huán)（圈）上的彈簧樞軸和它的外緣從飛輪分離。彈簧收縮將壓盤拉離離合器片，從而將離合器分離。  當(dāng)離合器結(jié)合時，分離軸承和膜片彈簧的分離指向變速器方向移動。當(dāng)膜片樞軸越過支承環(huán)時，它的外緣將壓盤 壓在離合器片上，使離合器片和飛輪接合。  膜片式壓盤總成的優(yōu)點在于它的結(jié)構(gòu)緊湊，重量輕，運(yùn)動部件少，接合費(fèi)力?。ㄝp便），通過對壓盤周圍施加的平衡力來減小轉(zhuǎn)動時的不平衡現(xiàn)象，離合器滑轉(zhuǎn)率小。  離合器踏板可通過繩索或常見的液壓系統(tǒng)連接到分離機(jī)構(gòu)。無論采用哪種方式，踩下踏板，操縱分離機(jī)構(gòu)，通過分離軸承對離合器膜片彈簧指施加壓力，均可解除膜片彈簧對離合器盤的壓緊。如果帶有液壓機(jī)構(gòu)，由離合器踏板臂來操縱離合器主缸中的活塞，將液壓油通過管道壓入到離合器工作（分離）缸，此后由工作缸中的活塞操縱離合器分離機(jī)構(gòu)。另外一種是由繩 索將離合器踏板連接到分離機(jī)構(gòu)的。  其它零部件包括離合器（分離）叉、分離軸承、離合器殼、離合器蓋和導(dǎo)軸襯（套），用來接合和分離變速器。分離叉連接到杠桿機(jī)構(gòu)，實際用來操縱離合器。分離軸承安裝在離合器分離叉和壓盤總成之間。離合器殼用來封閉離合器總成。而離合器蓋固定在離合器殼的底部。這個活動蓋可使技工（維修工）在檢查離合器時不必拆卸變速器和離合器殼。導(dǎo)軸襯安裝在曲軸的后端，用來固定變速器輸入軸。  扭矩變矩器  基礎(chǔ)