外文翻譯--動力傳動系a

1、<p><b>　　外文原文：</b></p><p>　　Passage A Power Train</p><p>　　The power train serves two functions: it transmits power from the engine to the drive wheels, and it varies the amount

2、 of torque. The power train includes:1.engine:that produces power;2.transmission:either manual or automatic;3.clutch:used only on manual transmission, or torque converter: used only on automatic transmission;4.drive shaf

3、t: that transmits the power from transmission to differential;5.that carries the power to the two wheel axles.See Fig.5-1.</p><p>　　Manual transmission</p><p>　　The function of a manual transmi

4、ssion, shown in Fig.5-2,is to transfer engine power to the drive shaft and rear wheels. Gears inside the transmission change the car’s drive-wheel speed and torque in relation to engine speed and torque. This keeps the e

5、ngine’s output matched as close as possible to varying road speeds and loads.</p><p>　　A manual transaxle, shown in the Fig.5-3.，is a single unit composed of a manual ansmission, differential, and drive axle

6、s. Most front-wheel-drive（FWD） cars are equipped with a transaxle. Such transaxle are also found on some front-engined or rear-wheel-drive（RWD）,four-wheel-drive（4WD）cars and on rear-engined and rear-wheel-drive cars．<

7、;/p><p>　　A manual transmission requires use of a clutch to apply and remove engine torque to the transmission input shaft. The clutch allows this to happen gradually so that the car can be started from a com

8、plete stop.</p><p>　　Manual transmission usually have four or five speeds, and often have "overdrive", which means that the output shaft can turn faster than the input Shaft for fuel economy on th

9、e highway.When you use it, it will reduce the engine speed by one-third, while maintaining the same road speed.</p><p><b>　　Clutch </b></p><p>　　Driving a car with a manual transmis

10、sion, you depress the clutch, select a gear, and release the clutch while applying power to get the car to move.The clutch allows engine power to be applied gradually when a vehicle is starting out,and interrupts power

11、 to avoid gear crunching when shifting.Engaging the clutch allows power to transfer from the engine to transmission and drive wheel.Disengaging the clutch stops the power transfer and allows the engine to continue turn

12、ing without force to the</p><p>　　The clutch basic components are:the flywheel,clutch disk,pressure plate,release bearing and linkage.See Fig.5-4.</p><p>　　The flywheel is bolted to the cranksha

13、ft of the engine.Its main function is to transfer engine torque from the engine to the transmission.</p><p>　　The clutch disk is basically a steel plate,covered with a frictional material that goes between

14、the flywheel and the pressure plate.</p><p>　　A pressure plate is bolted to the flywheel.It includes a sheet metal cover,heavy release springs,a metal pressure ring that provides a friction surface for the c

15、lutch disk.</p><p>　　The release bearing is the heart of clutch operation.When the clutch pedal is depressed,the throw-out bearing moves toward the flywheel,pushing in the pressure plate’s release fingers a

16、nd moving the pressure plate fingers or levers against pressure plate spring force.</p><p>　　The linkage transmits and multiplies the driver’s leg force to the fork of the clutch pressure plate.A mechanical

17、clutch linkage usually consists of the clutch pedal,a series of linkage rods and arms,or a cable.A hydraulic clutch linkage typically includes a clutch master cylinder and reservoir,a hydraulic line and a slave cylinder

18、.</p><p>　　Automatic transmission</p><p>　　Both an automatic transmission and a manual transmission accomplish exactly the same thing,but they do it in totally different ways.The key difference

19、 between a manual and an automatic transmissions is that the manual transmission locks and unlocks and different sets of gears to the output shaft to achieve the various gear ratios,while in an automatic transmission,the

20、 same set of gears produces all of different gear ratios.The planetary gear-set is the device that makes this possible in an autom</p><p>　　Automatic transmissions are used in many rear-wheel-drive and four-

21、wheel-drive vehicles.Automatic transaxles are used in most front-wheel-drive vehicles.The major components of a transaxle are the same as those in a transmission,except the transaxle assembly includes the final drive and

22、 differential gears,in addition to the transmission.</p><p>　　An automatic transmission receives engine power through a torque converter,which is driven by the engine’s crankshaft.Hydraulic pressure in the

23、converter allows power to flow from the torque converter to the transmission’s input shaft.The input shaft drives a planetary gear set that provides the different forward gears,a neutral position,and one reverse gear.Pow

24、er flow through the gears is controlled by multiple-disk clutches,one-way clutches,and friction bands.</p><p>　　Passage B Power Train</p><p>　　Torque Converter</p><p>　　The key to t

25、he modern automatic transmission is the torque converter.It takes the place of a clutch in a manual transmission to send the power from the engine to the transmission input shaft.The torque converter offers the advantage

26、 of multiplying the turning power provided by the engine.</p><p>　　It has three parts that help multiply the power:an impeller（or pump）conn cted to the engine’s crankshaft,a turbine to turn the turbine shaft

27、 which is connected to the gears,and a stator（or guide wheel）between the two.See Fig. 5-6.</p><p>　　The torque converter is filled with transmission fluid that is moved by impeller blades.When the impeller s

28、pins above a certain speed,the turbine spins,driven by the impeller.</p><p>　　Planetary Gearing</p><p>　　Planetary gears provide for the different gear ratios needed to move a vehicle in the des

29、ired direction at the correct speed.A planetary gear set consists of a sun gear,planet gears,and a internal ring.See Fig. 5-7.</p><p>　　In the center of the planetary gear set is the sun gear.Planet gears su

30、rround the sun gear,just like the earth and other planets in our solar system.These gears are mounted and supported by the planet carrier and each gear spins on its own separate shaft.The planet gears are in constant mes

31、h with the sun and ring gears.The ring gear is the outer gear of the gear set.Its has internal teeth and surrounds the rest of the gear set.Its gear teeth are in constant mesh with the planet gears.The number </p>

32、<p>　　The planetary gear set can provide a gear reduction or overdrive,direct drive or reverse,or a neutral position.Because the gears in constant mesh,gear changes are made without engaging or disengaging gears,as

33、 is required in a manual transmission.Rather, clutches and bands are used to either hold or release different members of the gear set to get the proper direction of rotation and/or gear ratio.</p><p>　　Diff

34、erent </p><p>　　On FWD cars,the differential unit is normally part of the transaxle assembly.On RWD cars,it is part of the rea axle assembly.Located inside the differential case are the differential pinion

35、shafts and gears and the differential side gears. See Fig.5-8</p><p>　　The differential assembly revolves with the ring gear.Axle side gears are splined to the rear axle or front axle drive shafts.</p>

36、;<p>　　When an automobile is moving straight ahead,both wheels are free to rotate. Engine power is applied to the pinion gear,which rotates the ring gear.Beveled pinion gears are carried around by the ring gear an

37、d rotate as one unit.Each axle receives the same power,so each wheel turns at the same speed. See Fig. 5-9.</p><p>　　When the car turns a sharp corner,only one wheel rotates freely.Torque still comes in on t

38、he pinion gear and rotates the ring gear,carrying the beveled pinions around with it.However,one axle is held stationary and the beveled pinions are forced to rotate on their own axis and "walk around"their ge

39、ar.The other side is forced to rotate because it is subjected to the turning force of the ring gear,which is transmitted through the pinions. See Fig. 5-10.</p><p>　　Drive shaft</p><p>　　A drive

40、 shaft and universal joints（U-joints） connect the transmission to the rear drive axle on most rear-wheel-drive vehicles.Many four-wheel-drive vehicles also use drive shafts and universal joints,with one drive shaft bet

41、ween the transfer case and rear drive axle and a second drive shaft between the transfer case and the front drive axle. The drive shaft is sometimes called a propeller shaft.</p><p>　　The drive shaft and U

42、-joints provide a means of transferring engine torque to drive axles.The universal joints allow the drive shaft to move up and down,to allow for suspension travel.Some drive shaft also have a slip joints that allows the

43、drive shaft to make minor length changes as the vehicle suspension height changes.</p><p>　　Gears and gear drive</p><p>　　Gears are the most durable and rugged of all mechanical drives.They can

44、 transmit high power at efficiencies up to 98% and with long service lives. For this reason, gears rather than belts or chains are found in automotive transmissions and most heavy-duty machine drives. On the other hand,

45、gears are more expensive than other drives, especially if they are machined and not made from power metal or plastic.</p><p>　　Gear cost increases sharply with demands for high precision and accuracy. So it

46、is important to establish tolerance requirements appropriate for the application. Gears that transmit heavy loads or than operate at high speeds are not particularly expensive, but gears that must do both are costly.<

47、/p><p>　　Silent gears also are expensive. Instrument and computer gears tend to be costly because speed or displacement ratios must be exact. At the other extreme, gears operating at low speed in exposed locati

48、ons are normally termed no critical and are made to minimum quality standards.</p><p>　　For tooth forms, size, and quality, industrial practice is to follow standards set up by the American Gear Manufactures

49、 Association (AGMA).</p><p>　　Tooth form </p><p>　　Standards published by AGMA establish gear proportions and tooth profiles. Tooth geometry is determined primarily by pitch, depth, and pressur

50、e angle.</p><p>　　Pitch：Standards pitches are usually whole numbers when measured as diametral pitch P. Coarse-pitch gearing has teeth larger than 20 diametral pitch –usually 0.5 to 19.99. Fine-pitch gearing

51、 usually has teeth of diametral pitch 20 to 200.</p><p>　　Depth: Standardized in terms of pitch. Standard full-depth have working depth of 2/p. If the teeth have equal addenda(as in standard interchangeable

52、gears) the addendum is 1/p. Stub teeth have a working depth usually 20% less than full-depth teeth. Full-depth teeth have a larger contract ratio than stub teeth. Gears with small numbers of teeth may have undercut so th

53、an they do not interfere with one another during engagement. Undercutting reduce active profile and weakens the tooth.</p><p>　　Mating gears with long and short addendum have larger load-carrying capacity th

54、an standard gears. The addendum of the smaller gear (pinion) is increased while that of larger gear is decreased, leaving the whole depth the same. This form is know as recess-action gearing.</p><p>　　Pressu

55、re Angle: Standard angles areand.Earlier standards include a 14-pressure angle that is still used. Pressure angle affects the force that tends to separate mating gears. High pressure angle decreases the contact ratio (ra

56、tio of the number of teeth in contact) but provides a tooth of higher capacity and allows gears to have fewer teeth without undercutting.</p><p>　　Backlash: Shortest distances between the non-contacting surf

57、aces of adjacent teeth .</p><p>　　Gears are commonly specified according to AGMA Class Number, which is a code denoting important quality characteristics. Quality number denote tooth-element tolerances. The

58、higher the number, the closer the tolerance. Number 8 to 16 apply to fine-pitch gearing.</p><p>　　Gears are heat-treated by case-hardening, through-hardening, nitriding, or precipitation hardening. In genera

59、l, harder gears are stronger and last longer than soft ones. Thus, hardening is a device that cuts the weight and size of gears. Some processes, such as flame-hardening, improve service life but do not necessarily improv

60、e strength. </p><p>　　Design checklist</p><p>　　The larger in a pair is called the gear, the smaller is called the pinion.</p><p>　　Gear Ratio: The number of teeth in the gear divid

61、e by the number of teeth in the pinion. Also, ratio of the speed of the pinion to the speed of the gear. In reduction gears, the ratio of input to output speeds.</p><p>　　Gear Efficiency: Ratio of output pow

62、er to input power. (includes consideration of power losses in the gears, in bearings, and from windage and churning of lubricant.)</p><p>　　Speed: In a given gear normally limited to some specific pitchline

63、velocity. Speed capabilities can be increased by improving accuracy of the gear teeth and by improving balance of the rotating parts.</p><p>　　Power: Load and speed capacity is determined by gear dimensions

64、and by type of gear. Helical and helical-type gears have the greatest capacity (to approximately 30,000 hp). Spiral bevel gear are normally limited to 5,000 hp, and worm gears are usually limited to about 750 hp.</p&g

65、t;<p>　　Special requirements</p><p>　　Matched-Set Gearing: In applications requiring extremely high accuracy, it may be necessary to match pinion and gear profiles and leads so that mismatch does not

66、exceed the tolerance on profile or lead for the intended application.</p><p>　　Tooth Spacing: Some gears require high accuracy in the circular of teeth. Thus, specification of pitch may be required in additi

67、on to an accuracy class specification.</p><p>　　Backlash: The AMGA standards recommend backlash ranges to provide proper running clearances for mating gears. An overly tight mesh may produce overload. Howeve

68、r, zero backlash is required in some applications.</p><p>　　Quiet Gears: To make gears as quit as possible, specify the finest pitch allowable for load conditions. (In some instances, however, pitch is coars

69、ened to change mesh frequency to produce a more pleasant, lower-pitch sound.) Use a low pressure angle. Use a modified profile to include root and tip relief. Allow enough backlash. Use high quality numbers. Specify a su

70、rface finish of 20 in. or better. Balance the gear set. Use a nonintegral ratio so that the same teeth do not repeatedly engage if bo</p><p>　　Multiple mesh gear</p><p>　　Multiple mesh refers to

71、 move than one pair of gear operating in a train. Can be on parallel or nonparallel axes and on intersection or nonintersecting shafts. They permit higer speed ratios than are feasible with a single pair of gears .</p

72、><p>　　Series trains:Overall ratio is input shaft speed divided by output speed ,also the product of individual ratios at each mesh ,except in planetary gears .Ratio is most easily found by dividing the product

73、 of numbers of teeth of driven gears by the product of numbers of teeth of driving gears.</p><p>　　Speed increasers (with step-up rather than step-down ratios) may require special care in manufacturing and d

74、esign. They often involve high speeds and may creste problems in gear dynamics. Also, frictional and drag forces are magnified which, in extreme cases , may lead to operational problems.</p><p>　　Epicyclic G

75、earing:Normally, a gear axis remains fixed and only the gears rotates. But in an epicyclic gear train, various gears axes rotate about one anther to provide specialized output motions. With suitable clutchse and brakes,

76、an epicyclic train serves as the planetary gear commonly found in automatic transmissions. </p><p>　　Epicyclic trains may use spur or helical gears, external or internal, or bevel gears. In transmissions, th

77、e epicyclic (or planetary) gears usually have multiple planets to increase load capacity.</p><p>　　In most cases, improved kinematic accuracy in a gearset decreases gear mesh excitation and results in lower

78、drive noise. Gearset accuracy can be increased by modifying the tooth involute profile, by substituting higher quality gearing with tighter manufacturing tolerances, and by improving tooth surface finish. However, if gea

79、r mesh excitation generaters resonance somewhere in the drive system, nothing short of a “perfect” gearset will substantially reduce vibration and noise.</p><p>　　Tooth profiles are modified to avoid interfe

80、rences which can result from deflections in the gears, shafts, and housing as teeth engage and disendgage. If these tooth interferences are not compensated for by profile modifications, gears load capacity can be serious

81、ly reduced. In addition, the drive will be noisier because tooth interferences generate high dynamic loads. Interferences typically are eliminated by reliving the tooth tip, the tooth flank, or both. Such profile modific

82、ations are espec</p><p>　　Tighter manufacturing tolerances also produce quietier gears. Tolerances for such parameters as profile error, pitch AGMA quality level. For instance, the graph depicting SPL vs bot

83、h speed and gear quality shows how noise decreases example, noise is reduced significantly by an increase in accuracy from an AGMA Qn 11 quality to an AGNA Qn 15 quality. However, for most commercial drive applications,

84、it is doubtful that the resulting substantial cost increase for such an accuracy improvement can be</p><p>　　Previously, it was mentioned that gears must have adequate clearance when loaded to prevent tooth

85、interference during the course of meshing. Tip and flank relief are common profile modifications that control such interference. Gears also require adequate backlash and root clearance. Noise considerations make backlash

86、 an important parameter to evaluate during drive design. Sufficient backlash must be provided under all load and temperature conditions to avoid a tight mesh, which creates excessive</p><p><b>　　中文譯文：&

87、lt;/b></p><p><b>　　動力傳動系A(chǔ)</b></p><p>　　動力傳動系有兩個作用：它把動力從發(fā)動機(jī)傳送到驅(qū)動輪上，并且改變扭矩的大小。動力傳動系包括：1.發(fā)動機(jī)：制造動力；2.變速器：不是手動就是自動；3.離合器：僅用在手動變速器或者液力變矩器；4.驅(qū)動軸：把動力從變速器傳到差速器；5.差速器：將動力傳到兩個驅(qū)動軸上。</p>

88、<p><b>　　手動變速器</b></p><p>　　手動變速器的作用是，把發(fā)動機(jī)動力傳送到傳動軸和驅(qū)動輪。變速器內(nèi)的齒輪，改變車輛驅(qū)動輪和發(fā)動機(jī)之間轉(zhuǎn)速和扭矩的比例。這樣保持發(fā)動機(jī)的輸出盡可能的靠近改變路面速度和最低速度。</p><p>　　一個手動的驅(qū)動橋，是一個由手動變速器，差速器，傳動軸組成的。大多數(shù)前輪驅(qū)動汽車裝有一個驅(qū)動橋。這樣的驅(qū)動

89、橋也能在一些前置引擎或者后輪驅(qū)動，四輪驅(qū)動的汽車，在后置引擎和后輪驅(qū)動的汽車上看到。</p><p>　　一個手動變速器包括使用一個離合器來消除發(fā)動機(jī)扭矩到變速器輸入軸。離合器允許這樣漸漸發(fā)生以至于汽車能夠啟動。</p><p>　　手動變速器通常有四到五個檔位，而且一般有“超速檔”，對于在路上的燃油經(jīng)濟(jì)性這樣就意味著輸出軸比輸入軸轉(zhuǎn)的更快。當(dāng)你使用變速器的時候，要維持同樣的速度，將減少發(fā)

90、動機(jī)轉(zhuǎn)速的三分之一。</p><p><b>　　離合器</b></p><p>　　駕駛手動擋汽車，你踩下離合器，嚙合了齒輪，然后松掉離合器而汽車會適應(yīng)動力前進(jìn)。離合器可使車輛啟動后發(fā)動機(jī)的動力被逐漸的加載，并可通過切斷動力防止換擋時齒輪被咬碎。離合器嚙合時把發(fā)動機(jī)動力傳送到變速器和驅(qū)動輪。離合器分離停止動力傳輸，在沒有動力傳到驅(qū)動輪上的情況下，發(fā)動機(jī)可以持續(xù)運轉(zhuǎn)。

91、</p><p>　　離合器基本的部件是：飛輪，離合器盤，壓力盤，分離軸承和聯(lián)接裝置。</p><p>　　飛輪被螺栓固定在發(fā)動機(jī)的曲軸上。它的主要作用是傳送發(fā)動機(jī)扭矩從發(fā)動機(jī)到變速器。</p><p>　　離合器盤基本就是一塊鋼板，在飛輪和壓力盤中間覆蓋了一種耐摩擦材料。</p><p>　　離合器盤螺栓連接在飛輪上。它包括一張薄片金屬封蓋

92、，彈簧，一個給離合器盤提供摩擦表面的金屬壓力環(huán)。</p><p>　　分離軸承是離合器操縱機(jī)構(gòu)的中心。當(dāng)離合器踏板踩下時，分離軸承指向飛輪，壓盤推進(jìn)釋放了擋板然后移動壓盤彈簧片到壓盤彈簧彈力頂。</p><p>　　聯(lián)接裝置成倍地傳送駕駛員腿部力量到離合器壓盤的膜片。一個機(jī)械離合器連接裝置通常由離合器踏板，一系列連接桿臂或者一組電纜。一個液壓離合器聯(lián)接裝置大體上是由一個離合器制動缸和儲存器

93、，一組液壓管路和一個從動缸。</p><p><b>　　自動變速器</b></p><p>　　自動變速器和手動變速器嚴(yán)格的講都能完成一樣的工作，但他們完成工作的方法完全不一樣。手動變速器和自動變速器的之間的根本區(qū)別在于手動變速器鎖與不鎖在不同的輸出軸來實現(xiàn)各種傳動比；而在自動變速器上，同一套齒輪裝置能夠提供所有的不同傳動比。行星齒輪副給這樣的自動變速器制造了可能。

94、</p><p>　　自動變速器運用在許多后輪驅(qū)動和四輪驅(qū)動汽車上。自動驅(qū)動橋運用在大多數(shù)前輪驅(qū)動汽車上。一個驅(qū)動橋的主要零部件和一個變速器的差不多，除了驅(qū)動橋擁有主減速器和差速器而變速器沒有。</p><p>　　自動變速器通過液力變矩器接受發(fā)動機(jī)動力，被發(fā)動機(jī)曲軸驅(qū)使。變換器的液壓允許動力從液力變矩器傳到變速器輸入軸。</p><p>　　輸入軸帶動行星齒輪副提

95、供不同的前進(jìn)擋，空擋和倒檔。通過傳動裝置的功率由盤式離合器，單片離合器和摩擦片控制。</p><p><b>　　動力傳動系B</b></p><p><b>　　液力變矩器</b></p><p>　　現(xiàn)代自動變速器的核心是液力變矩器。它代替了手動變速器的離合器來傳輸從發(fā)動機(jī)到變速器輸出軸的動力。液力變矩器提供了有利的成

96、倍轉(zhuǎn)速動力。</p><p>　　液力變矩器有三個部分幫助成倍提高動力：聯(lián)接在發(fā)動機(jī)曲軸上的葉輪，一個渦輪連接在齒輪上的渦輪軸和在兩者之間的導(dǎo)向輪。</p><p>　　液力變矩器里面充滿了變速器液體，那些液體被泵輪葉片驅(qū)動。當(dāng)葉輪旋轉(zhuǎn)到一定速度時，渦輪被葉輪帶動開始旋轉(zhuǎn)。</p><p><b>　　行星齒輪組</b></p>

97、<p>　　行星齒輪組提供不同的齒輪傳動比，使汽車在正確的方向正確的速度上行駛。一個行星齒輪組由一個太陽輪，行星齒輪和一個齒圈組成。</p><p>　　行星齒輪組的中心是太陽輪。行星齒輪圍繞著太陽輪，就像我們的地球和其他行星在我們的太陽系。這些齒輪被安裝在行星齒輪架上而且每個齒輪都在獨立的軸上旋轉(zhuǎn)。行星齒輪是恒定不變的嚙合在太陽輪和齒圈上。齒圈是行星齒輪組遠(yuǎn)離中心的齒。</p><

98、p>　　它有內(nèi)齒而且圍繞著其余的齒輪組。它的齒被恒定不變的嚙合在行星齒輪上。許多星系齒輪根據(jù)變速器所設(shè)計面對的負(fù)荷來運用在行星齒輪組上。對于高負(fù)荷，許多星系齒輪提高比內(nèi)齒更高的負(fù)荷來帶動工作。</p><p>　　星系齒輪組能夠提供一個齒輪減速或者齒輪超速，前進(jìn)擋或者倒檔，或者一個空擋。因為齒輪固定不變的嚙合，變速齒輪被制造了而不再需要接合齒輪或者分離齒輪，它被運用在手動變速器上。相反，離合器被運用的既要保

99、持或者釋放不同的齒輪組數(shù)量又要獲得合適的旋轉(zhuǎn)度和齒輪比。</p><p><b>　　差速器</b></p><p>　　在前輪驅(qū)動汽車上，差速器裝置一般是變速驅(qū)動橋的部分組成。在后輪驅(qū)動橋上，它是后橋的組成部分。在差速器殼內(nèi)，是差速器行星齒輪軸，行星齒輪和差速器齒輪半軸。</p><p>　　差速器圍繞著齒圈旋轉(zhuǎn)。輪軸邊上的齒輪用花鍵聯(lián)接在前