机械专业外文翻译自动变速器的工作原理分析解析

1、How Automatic Transmissions Workby Karim NiceIn troductio n to How Automatic Tran smissi ons WorkIf you have ever driven a car with an automatic transmission, then you know that there are two big differe nces betwee n an automatic tran smissi on and a man ual tran smissi on:There is no clutch pedal

2、in an automatic transmission car.There is no gear shift in an automatic transmission car. Once you put the transmission into drive, everything else is automatic.Both the automatic tran smissi on (plus its torque con verter) and a manual tran smissi on (with its clutch) accomplish exactly the same th

3、ing, but they do it in totally differe nt ways. It turns out that the way an automatic tran smissi on does it is absolutely amaz ing!Automatic Tran smissi on Image GalleryQ7000穷Irin 如杭In this article, well work our way through an automatic transmission. Well start with the key to the whole system: p

4、lanetary gearsets. Then well see how the transmission is put together, learn how the controls work and discuss some of the intricacies involved in con troll ing a tran smissi on.Just like that of a manual tran smissi on, the automatic tran smissi ons primary job is to allow the engine to operate in

5、its narrow range of speeds while providing a wide range of output speeds.Photo courtesy DaimlerChryslerMercedes-Be nz CLK, automatic tran smissi on, cut-away modelWithout a tran smissi on, cars would be limited to one gear ratio, and that ratio would have to be selected to allow the car to travel at

6、 the desired top speed. If you wan ted a top speed of 80 mph, then the gear ratio would be similar to third gear in most manual transmission cars.Youve probably never tried driving a manual transmission car using only third gear. If you did, youd quickly find out that you had almost no acceleration

7、when starting out, and at high speeds, the engine would be scream ing along n ear the red-li ne. A car like this would wear out very quickly and would be n early un driveable.So the tran smissi on uses gears to make more effective use of the engin es torque, and to keep the engine operating at an ap

8、propriate speed.The key differenee between a manual and an automatic transmission is that the manual tran smissi on locks and uni ocks differe nt sets of gears to the output shaft to achieve the various gear ratios, while in an automatic transmission, the same set of gears produces all of the differ

9、e nt gear ratios. The pla netary gearset is the device that makes this possible in an automatic tran smissi on.Lets take a look at how the pla netary gearset works.Pla netary Gearsets & Gear RatiosWhen you take apart and look in side an automatic tran smissi on, you find a huge An ingenious pla neta

10、ry gearset A set of bands to lock parts of a gearset A set of three wet-plate clutches to lock other parts of the gearset An in credibly odd hydraulic system that con trols the clutches and bands A large gear pump to move tran smissi on fluid arou ndThe center of attention is the planetary gearset.

11、About the size of a cantaloupe, this one part creates all of the different gear ratios that the transmission can produce. Everything else in the tran smissi on is there to help the pla netary gearset do its thing. This amaz ing piece of geari ng has appeared on HowStuffWorks before. You may recog ni

12、ze it from the electric screwdriver article. An automatic tran smissi on contains two complete pla netary gearsets folded together into one comp onent. See How Gear Ratios Work for an in troduct ion to pla netary gearsets.From left to right: the ring gear, planet carrier, and two sun gearsAny pla ne

13、tary gearset has three main comp onen ts: The sun gear* The pla net gears and the pla net gears carrier The ring gearEach of these three comp onents can be the in put, the output or can be held stati on ary.Choosing which piece plays which role determines the gear ratio for the gearset. Lets take a

14、look at a sin gle pla netary gearset.One of the pla netary gearsets from our tran smissi on has a ring gear with 72 teeth and a sun gear with 30 teeth. We can get lots of differe nt gear ratios out of this gearset.In putOutputStatio naryCalculatio nGear RatioASun (S)Pla net Carrier (C)Ring (R)1 + R/

15、S3.4:1BPla net Carrier (C)Ring (R)Sun (S)1 / (1 + S/R)0.71:1!CSun (S)Ring (R)Pla net Carrier (C)-R/S-2.4:1Also, lock ing any two of the three comp onents together will lock up the whole device at a 1:1 gear reducti on. Notice that the first gear ratio listed above is a reduct ion - the output speed

16、is slower tha n the in put speed. The sec ond is an overdrive - the output speed is faster than the in put speed. The last is a reduct ion aga in, but the output direct ion is reversed.There are several other ratios that can be gotte n out of this pla netary gear set, but these are the ones that are

17、 releva nt to our automatic tran smissi on. You can try these out in the ani mati on below:F-LlputGear Rartlin (S)Planet Carrier (C)Rl飓岡!.4;1nPirinel Crtrner 心Rin (R)Sun |S0.71：10SuntS)Rir)g(R)Piawt Carrier(C)-3.4:1StopW CTQ f * FlhE 阳皿Animation of rhe diffeient geki i alios related to auto ma 竹 c 1

18、1 加将 niissioiMClick on the buttons on ths left in the table above.So this one set of gears can produce all of these differe nt gear ratios without hav ing to en gage or dise ngage any other gears. With two of these gearsets in a row, we can get the four forward gears and one reverse gear our tran sm

19、issi on n eeds. Well put the two sets of gears together in the n ext sect ion.Compo und Pla netary GearsetThis automatic tran smissi on uses a set of gears, called a compo und pla netary gearset, that looks like a sin gle pla netary gearset but actually behaves like two pla netary gearsets comb in e

20、d. It has one ring gear that is always the output of the tran smissi on, but it has two sun gears and two sets of pla nets.Lets look at some of the parts:How the gears in the transmission are put togetherLeft to right: the ring gear, planet carrier, and two sun gearsThe figure below shows the planet

21、s in the planet carrier. Notice how the planet on the right sits lower than the planet on the left. The planet on the right does not engage the ring gear -it engages the other planet. Only the planet on the left engages the ring gear.匏士 Wvriis-Th is pFanet engages the ring： gaar and Is sogafod by th

22、 inrr sun genrThis planettheother planet and Is engaged by the snnallAr unPlanet carrier: Note the two sets of planets.Next you can see the in side of the pla net carrier. The shorter gears are en gaged only by the smaller sun gear. The Ion ger pla nets are en gaged by the bigger sun gear and by the

23、 smaller pla nets.In side the pla net carrier: Note the two sets of pla nets.Automatic Tran smissi on GearsFirst GearIn first gear, the smaller sun gear is driven clockwise by the turbine in the torque converter. The planet carrier tries to spin counterclockwise, but is held still by the one-way clu

24、tch (which only allows rotatio n in the clockwise direct ion) and the ring gear turns the output. The small gear has 30 teeth and the ring gear has 72, so the gear ratio is:Ratio = -R/S = - 72/30 = -2.4:1So the rotatio n is n egative 2.4:1, which means that the output direct ion would be opposite th

25、e in put direct ion. But the output directi on is really the same as the in put direct ion - this is where the trick with the two sets of planets comes in. The first set of planets engages the sec ond set, and the sec ond set turns the ring gear; this comb in ati on reverses the directi on. You can

26、see that this would also cause the bigger sun gear to spin; but because that clutch is released, the bigger sun gear is free to spin in the opposite direct ion of the turb ine (co un terclockwise).MftVA fihlfiVBr 10 Rfift tow kthin,JflL *fe IransmlKiimSecond GearThis transmission does something real

27、ly neat in order to get the ratio needed for second gear. It acts like two pla netary gearsets conn ected to each other with a com mon pla net carrier.The first stage of the planet carrier actually uses the larger sun gear as the ring gear. So the first stage con sists of the sun (the smaller sun ge

28、ar), the pla net carrier, and the ring (the larger sun gear).The in put is the small sun gear; the ring gear (large sun gear) is held stati onary by the band, and the output is the pla net carrier. For this stage, with the sun as in put, pla net carrier as output, and the ring gear fixed, the formul

29、a is:1 + R/S = 1 + 36/30 = 2.2:1The planet carrier turns 2.2 times for each rotation of the small sun gear. At the second stage, the pla net carrier acts as the in put for the sec ond pla netary gear set, the larger sun gear (which is held stati on ary) acts as the sun, and the ring gear acts as the

30、 output, so the gear ratio is:1 / (1 + S/R) = 1 / (1 + 36/72) = 0.67:1To get the overall reduct ion for sec ond gear, we multiply the first stage by the sec ond, 2.2 x 0.67, to get a 1.47:1 reduct ion. This may sound wacky, but it works.Third GearMost automatic transmissions have a 1:1 ratio in thir

31、d gear. Youll remember from the previous sect ion that all we have to do to get a 1:1 output is lock together any two of the three parts of the planetary gear. With the arrangement in this gearset it is even easier - all we have to do is en gage the clutches that lock each of the sun gears to the tu

32、rb ine.If both sun gears turn in the same directi on, the pla net gears lockup because they can only spin in opposite directi ons. This locks the ring gear to the pla nets and causes everyth ing to spin as a un it, produc ing a 1:1 ratio.OverdriveBy defi niti on, an overdrive has a faster output spe

33、ed tha n in put speed. Its a speed in crease -the opposite of a reduct ion. In this tran smissi on, en gag ing the overdrive accomplishes two things at on ce. If you read How Torque Con verters Work, you lear ned about lockup torque con verters .In order to improve efficie ncy, some cars have a mech

34、a nism that locks up the torque con verter so that the output of the engine goes straight to the tran smissi on.In this transmission, when overdrive is engaged, a shaft that is attached to the housing of the torque converter (which is bolted to the flywheel of the engine) is connected by clutch to t

35、he pla net carrier. The small sun gear freewheels, and the larger sun gear is held by the overdrive band. Nothi ng is conn ected to the turbi ne; the only in put comes from the converter housing. Lets go back to our chart again, this time with the planet carrier for in put, the sun gear fixed and th

36、e ring gear for output.Ratio = 1 / (1 + S/R) = 1 / ( 1 + 36/72) = 0.67:1So the output spins once for every two-thirds of a rotati on of the engin e. If the engine is turning at 2000 rotations per minute (RPM), the output speed is 3000 RPM. This allows cars to drive at freeway speed while the engine

37、speed stays nice and slow.ReverseReverse is very similar to first gear, except that in stead of the small sun gear being drive n by the torque con verter turb ine, the bigger sun gear is drive n, and the small one freewheels in the opposite direct ion. The pla net carrier is held by the reverse band

38、 to the hous ing. So, accord ing to our equati ons from the last page, we have:Ratio = -R/S = 72/36 = 2.0:1So the ratio in reverse is a little less than first gear in this transmission.Gear RatiosThis tran smissi on has four forward gears and one reverse gear. Lets summarize the gear ratios, in puts

39、 and outputs:GearIn putOutputFixedGear Ratio1st30-tooth sun72-tooth ringPla net carrier2.4:12nd30-tooth sunPla net carrier36-tooth ring2.2:1Pla net carrier72-tooth ring36-tooth sun0.67:1Total 2nd1.47:13rd30- and 36-tooth suns72-tooth ring1.0:1ODPla net carrier72-tooth ring36-tooth sun0.67:1Reverse36

40、-tooth sun72-tooth ringPla net carrier-2.0:1After readi ng these sect ions, you are probably won deri ng how the differe nt in puts get conn ected and disc onn ected. This is done by a series of clutches and bands in side the tran smissi on. In the n ext secti on, well see how these work.Clutches an

41、d Bands in an Automatic Tran smissi onIn the last sect ion, we discussed how each of the gear ratios is created by the tran smissi on. For in sta nee, whe n we discussed overdrive, we said:In this transmission, when overdrive is engaged, a shaft that is attached to the hous ing of the torque con ver

42、ter (which is bolted to the flywheel of the engine) is connected by clutch to the planet carrier. The small sun gear freewheels, and the larger sun gear is held by the overdrive band. Noth ing is conn ected to the turb ine; the only in put comes from the con verter hous ing.To get the transmission i

43、nto overdrive, lots of things have to be connected and disconnected by clutches and ban ds. The pla net carrier gets conn ected to the torque con verter hous ing by a clutch. The small sun gets disc onn ected from the turb ine by a clutch so that it can freewheel. The big sun gear is held to the hou

44、s ing by a band so that it could not rotate. Each gear shift triggers a series of events like these, with different clutches and bands engaging and dise ngagi ng. Lets take a look at a band.BandsIn this tran smissi on there are two ban ds. The bands in a tran smissi on are, literally, steel bands th

45、at wrap around sect ions of the gear train and conn ect to the hous ing. They are actuated by hydraulic cyli nders in side the case of the tran smissi on.One of the bandsIn the figure above, you can see one of the bands in the hous ing of the tran smissi on. The gear train is removed. The metal rod

46、is connected to the piston, which actuates the band.The pist ons that actuate the bands are visible here.Above you can see the two pist ons that actuate the ban ds. Hydraulic pressure, routed into the cyli nder by a set of valves, causes the pist ons to push on the ban ds, lock ing that part of the

47、gear train to the hous ing.The clutches in the tran smissi on are a little more complex. In this tran smissi on there are four clutches. Each clutch is actuated by pressurized hydraulic fluid that en ters a pist on in side the clutch. Springs make sure that the clutch releases whe n the pressure is

48、reduced. Below you can see the pist on and the clutch drum. Notice the rubber seal on the pist on -this is one of the comp onents that is replaced whe n your tran smissi on gets rebuilt.Rubber昶打PMonOne of the clutches in a tra nsmissi onThe next figure shows the alternating layers of clutch friction

49、 material and steel plates. The frictio n material is spli ned on the in side, where it locks to one of the gears. The steel plate is spli ned on the outside, where it locks to the clutch hous ing. These clutch plates are also replaced whe n the tran smissi on is rebuilt.The clutch platesThe pressur

50、e for the clutches is fed through passageways in the shafts. The hydraulic system con trols which clutches and bands are en ergized at any give n mome nt.FROM: nsmissi on .htm自动变速器的工作原理耐斯卡瑞姆介绍自动变速器的工作原理如果你驾驶过带有自动变速器的汽车，那么你一定知道手动变速器与 自动变速器之间存在两个很大的区别：-自动变速器中没有离合器踏板-自动变速器中没有换档手柄，一旦让变速器传递动力，那么接下来 的一切都是

51、自动完成的了。虽然自动变速器（包括液力变矩器）与手动变速器（包括离合器）完 成的功能是相同的，但它们却是以完全不同的方式来实现的。最终证实， 自动变速器的工作方式令人惊异。自动变速器概图本文是通过一个具体的自动变速器来阐述其中的原理，我们从整个系 统的关键一一行星齿轮系入手，然后我们将看到自动变速器是如何组装在 一起的，学习控制装置是如何工作的，讨论在自动变速器控制方面的一些 复杂的关系。自动变速器和手动变速器一样，主要功能就是允许发动机工作在小范 围变速的速度内，变速器却能够输出较大变速范围的速度。Mercedes-奔驰CLK,自动变速器,剖面立体图如果没有变速器，汽车将被限制在一种传动比，

52、并且那个传动必须被 选择作为汽车的最高期望速度。如果您想要以80英里/小时的最高速度行驶，则传动比类似于手动变速器汽车的第三档。您大概从未尝试仅使用第三档驾驶一辆手动变速的汽车。如果您尝试过，您马上会发现启动时几乎没有加速过程，而是直接以很高的速度启动， 引擎是工作在警戒线附近的。这样汽车很快就会损害，而且几乎无法驾驶。因此变速器是利用齿轮来更有效地利用发动的扭矩的，并且使得发动 机工作在适当的速度。手动和自动变速器之间的关键性区别在于：手动变速器采用锁止或打 开不同的齿轮，从而使输出轴获得不同传动比，而在自动变速器中，同样 是这些齿轮，但是能得到一定范围内所有的不同的传动比。而行星齿轮系 是

53、使此成为可能的装置。让我们来看一下行星齿轮系是如何工作的。行星齿轮系和齿轮传动比当您拆散自动变速器往里面观察，可以发现，在一个相对狭小的空间 里布满了很多零件。在这些零件中有：? 一个精巧的行星齿轮系? 一套锁止齿轮的钢带?三个锁住另外一些齿轮的湿式片式离合器?控制离合器和钢带的复杂液压系统?为变速器提供液压的齿轮泵关注的重点是行星齿轮系。变速器所产生的所有不同的传动比决定于 齿轮系尺寸的大小。变速器里其他的零部件是协助行星轮系产生不同传动 比的。这套装置曾经出现在 材料的工作方式中。您可以从电螺丝刀 中找到。一个自动变速器中包含有由两套行星齿轮系组合在一起而成的一 个部件。其介绍可以参见齿轮

54、系工作方式。从左到右：内齿圈，行星架，和两个太阳轮行星齿轮系有三个主要的组成部分：?太阳轮?行星轮和行星架?内齿圈这三个组成中的任何一组成都可以作为输入或输出，或者被固定。哪 些组成充当何种角色取决于行星齿轮系的速度比。下面的动画可以显示出 其中的关系。InputOutputStatlcnaryGbbv Ratto ESun (S)Plamt Carrier (C)剛ns何3.4:1prahet corner (C)Ring(F?)Sa $0,71:J0Sun|SRjng(ft)Planet Carrier (C)-2.4:1自动变速器中不同齿轮速比的濾示动画 单击左边的按钮这是变速器中其中的

55、一个行星齿轮系，内齿圈齿数为72,太阳轮齿数为30。我们可以从中的到很多不同的速比。输入输出固定计算齿轮速比A太阳轮(S)行星架(C)内齿圈(R)1 + R/S3.4:1b行星架(C)内齿圈(R)太阳轮(S)1/(1 + S/R)0.71:1C太阳轮(S)内齿圈(R)行星架(C)-R/S-2.4:1并且，锁住三个组成中的任何两个组成将锁止整个个行星系，而此时 速比为1:1。从表中可以看出，第一个中方案的速比为减速 输出速度 小于输入。第二种方案为加速 输出速度高于输入。最后一种方案也是 减速，但输出速度的方向相反。这个行星齿轮系还可以得到其他很多的速 比，而刚才的这些速比仅和我们的自动变速器有

56、关。因此这一套行星齿轮系可以产生所有需要的不同的齿轮传动比，却不 需要接合或不接合其他齿轮。把两套行星齿轮系置于一行，我们可以得到 四个前进档和一个后退档。下一部分内容我们将这两个齿轮系组装在一起。复合行星齿轮系自动变速器中使用了一系列的行星齿轮系，我们称之为复合行星齿轮 系，看起来好像只有一个简单的行星齿轮系，实际上却实现这两套齿轮系 的功能。其中包含一个总是作为输出的内齿圈、两个太阳和两套行星装置让我们看其中的一些零件:变速器中的齿轮的组装从左到右：内齿圈，行星架，和两个太阳轮下图中，行星轮装在行星架上，可以看到，右边的行星轮低于左边的行星轮。右边的行星轮不与内齿圈啮合 它和另一个行星轮啮

57、合。而只有左边的行星轮与内齿圈啮合。星轮与内齿囲 啮含，由大太阳鸵 駆动鬆昴轮覇行星匕曰，Q 3090)How Sttff WortB行星架：两个行星轮在下个图中，您可看到在行星架的内部，短行星轮与小太阳轮啮合, 长行星轮同时与大太阳轮和小太阳轮啮合。行星架内部：两个行星轮自动变速档位第一档在一档，小太阳轮在变矩器的涡轮驱动下顺时针旋转。行星架将自动 做逆时针转动，但是被离合器阻止了（离合器只允许单向旋转），从而内 齿圈变成了输出。小太阳轮有 30齿，内齿圈72齿，则速比为：Ratio = -R/S = - 72/30 = -2.4:1因此旋转速率为负的2.4:1，这意味着输出方向同输入的方向是相反的。但 事实上，输出方向是与输入方向相同的，这就是要引入两套行星齿轮系的 原因。第一套与第二套啮合，而第二套输出至内齿圈，这样的组合把方向