三軸四擋低速載貨汽車變速器的設(shè)計【全套含20張CAD圖紙】
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機(jī)械設(shè)計制造及其自動化專業(yè)外文翻譯
How Automatic Transmissions Work
by Karim Nice
Introduction to How Automatic Transmissions Work
If you have ever driven a car with an automatic transmission, then you know that there are two big differences between an automatic transmission and a manual transmission:
There is no clutch pedal 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 transmission (plus its torque converter) and a manual transmission (with its clutch) accomplish exactly the same thing, but they do it in totally different ways. It turns out that the way an automatic transmission does it is absolutely amazing!
Automatic Transmission Image Gallery
In this article, we'll work our way through an automatic transmission. We'll start with the key to the whole system: planetary gearsets. Then we'll see how the transmission is put together, learn how the controls work and discuss some of the intricacies involved in controlling a transmission.
Just like that of a manual transmission, the automatic transmission's primary job is to allow the engine to operate in its narrow range of speeds while providing a wide range of output speeds.
Photo courtesy DaimlerChrysler
Mercedes-Benz CLK, automatic transmission, cut-away model
Without a transmission, cars would be limited to one gear ratio, and that ratio would have to be selected to allow the car to travel at the desired top speed. If you wanted a top speed of 80 mph, then the gear ratio would be similar to third gear in most manual transmission cars.
You've probably never tried driving a manual transmission car using only third gear. If you did, you'd quickly find out that you had almost no acceleration when starting out, and at high speeds, the engine would be screaming along near the red-line. A car like this would wear out very quickly and would be nearly undriveable.
So the transmission uses gears to make more effective use of the engine's torque, and to keep the engine operating at an appropriate speed.
The key difference between a manual and an automatic transmission is that the manual transmission locks and unlocks different 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 different gear ratios. The planetary gearset is the device that makes this possible in an automatic transmission.
Let's take a look at how the planetary gearset works.
Planetary Gearsets & Gear Ratios
When you take apart and look inside an automatic transmission, you find a huge
· An ingenious planetary 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 incredibly odd hydraulic system that controls the clutches and bands
· A large gear pump to move transmission fluid around
The center of attention is the planetary gearset. 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 transmission is there to help the planetary gearset do its thing. This amazing piece of gearing has appeared on HowStuffWorks before. You may recognize it from the electric screwdriver article. An automatic transmission contains two complete planetary gearsets folded together into one component. See How Gear Ratios Work for an introduction to planetary gearsets.
From left to right: the ring gear, planet carrier, and two sun gears
Any planetary gearset has three main components:
· The sun gear
· The planet gears and the planet gears' carrier
· The ring gear
Each of these three components can be the input, the output or can be held stationary. Choosing which piece plays which role determines the gear ratio for the gearset. Let's take a look at a single planetary gearset.
One of the planetary gearsets from our transmission has a ring gear with 72 teeth and a sun gear with 30 teeth. We can get lots of different gear ratios out of this gearset.
Input
Output
Stationary
Calculation
Gear Ratio
A
Sun (S)
Planet Carrier (C)
Ring (R)
1 + R/S
3.4:1
B
Planet Carrier (C)
Ring (R)
Sun (S)
1 / (1 + S/R)
0.71:1
C
Sun (S)
Ring (R)
Planet Carrier (C)
-R/S
-2.4:1
Also, locking any two of the three components together will lock up the whole device at a 1:1 gear reduction. Notice that the first gear ratio listed above is a reduction -- the output speed is slower than the input speed. The second is an overdrive -- the output speed is faster than the input speed. The last is a reduction again, but the output direction is reversed. There are several other ratios that can be gotten out of this planetary gear set, but these are the ones that are relevant to our automatic transmission. You can try these out in the animation below:
So this one set of gears can produce all of these different gear ratios without having to engage or disengage any other gears. With two of these gearsets in a row, we can get the four forward gears and one reverse gear our transmission needs. We'll put the two sets of gears together in the next section.
Compound Planetary Gearset
This automatic transmission uses a set of gears, called a compound planetary gearset, that looks like a single planetary gearset but actually behaves like two planetary gearsets combined. It has one ring gear that is always the output of the transmission, but it has two sun gears and two sets of planets.
Let's look at some of the parts:
How the gears in the transmission are put together
Left to right: the ring gear, planet carrier, and two sun gears
The figure below shows the planets 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.
Planet carrier: Note the two sets of planets.
Next you can see the inside of the planet carrier. The shorter gears are engaged only by the smaller sun gear. The longer planets are engaged by the bigger sun gear and by the smaller planets.
Inside the planet carrier: Note the two sets of planets.
Automatic Transmission Gears
First Gear
In 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 clutch (which only allows rotation in the clockwise direction) 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 = -2.4:1
So the rotation is negative 2.4:1, which means that the output direction would be opposite the input direction. But the output direction is really the same as the input direction -- this is where the trick with the two sets of planets comes in. The first set of planets engages the second set, and the second set turns the ring gear; this combination reverses the direction. You can 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 direction of the turbine (counterclockwise).
Second Gear
This transmission does something really neat in order to get the ratio needed for second gear. It acts like two planetary gearsets connected to each other with a common planet carrier.
The first stage of the planet carrier actually uses the larger sun gear as the ring gear. So the first stage consists of the sun (the smaller sun gear), the planet carrier, and the ring (the larger sun gear).
The input is the small sun gear; the ring gear (large sun gear) is held stationary by the band, and the output is the planet carrier. For this stage, with the sun as input, planet carrier as output, and the ring gear fixed, the formula is:
1 + R/S = 1 + 36/30 = 2.2:1
The planet carrier turns 2.2 times for each rotation of the small sun gear. At the second stage, the planet carrier acts as the input for the second planetary gear set, the larger sun gear (which is held stationary) acts as the sun, and the ring gear acts as the output, so the gear ratio is:
1 / (1 + S/R) = 1 / (1 + 36/72) = 0.67:1
To get the overall reduction for second gear, we multiply the first stage by the second, 2.2 x 0.67, to get a 1.47:1 reduction. This may sound wacky, but it works.
Third Gear
Most automatic transmissions have a 1:1 ratio in third gear. You'll remember from the previous section 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 engage the clutches that lock each of the sun gears to the turbine.
If both sun gears turn in the same direction, the planet gears lockup because they can only spin in opposite directions. This locks the ring gear to the planets and causes everything to spin as a unit, producing a 1:1 ratio.
Overdrive
By definition, an overdrive has a faster output speed than input speed. It's a speed increase -- the opposite of a reduction. In this transmission, engaging the overdrive accomplishes two things at once. If you read How Torque Converters Work, you learned about lockup torque converters. In order to improve efficiency, some cars have a mechanism that locks up the torque converter so that the output of the engine goes straight to the transmission.
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 the planet carrier. The small sun gear freewheels, and the larger sun gear is held by the overdrive band. Nothing is connected to the turbine; the only input comes from the converter housing. Let's go back to our chart again, this time with the planet carrier for input, the sun gear fixed and the ring gear for output.
Ratio = 1 / (1 + S/R) = 1 / ( 1 + 36/72) = 0.67:1
So the output spins once for every two-thirds of a rotation of the engine. 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 speed stays nice and slow.
Reverse
Reverse is very similar to first gear, except that instead of the small sun gear being driven by the torque converter turbine, the bigger sun gear is driven, and the small one freewheels in the opposite direction. The planet carrier is held by the reverse band to the housing. So, according to our equations from the last page, we have:
Ratio = -R/S = 72/36 = 2.0:1
So the ratio in reverse is a little less than first gear in this transmission.
Gear Ratios
This transmission has four forward gears and one reverse gear. Let's summarize the gear ratios, inputs and outputs:
Gear
Input
Output
Fixed
Gear Ratio
1st
30-tooth sun
72-tooth ring
Planet carrier
2.4:1
2nd
30-tooth sun
Planet carrier
36-tooth ring
2.2:1
Planet carrier
72-tooth ring
36-tooth sun
0.67:1
Total 2nd
1.47:1
3rd
30- and 36-tooth suns
72-tooth ring
1.0:1
OD
Planet carrier
72-tooth ring
36-tooth sun
0.67:1
Reverse
36-tooth sun
72-tooth ring
Planet carrier
-2.0:1
After reading these sections, you are probably wondering how the different inputs get connected and disconnected. This is done by a series of clutches and bands inside the transmission. In the next section, we'll see how these work.
Clutches and Bands in an Automatic Transmission
In the last section, we discussed how each of the gear ratios is created by the transmission. For instance, when we discussed overdrive, we said:
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 the planet carrier. The small sun gear freewheels, and the larger sun gear is held by the overdrive band. Nothing is connected to the turbine; the only input comes from the converter housing.
To get the transmission into overdrive, lots of things have to be connected and disconnected by clutches and bands. The planet carrier gets connected to the torque converter housing by a clutch. The small sun gets disconnected from the turbine by a clutch so that it can freewheel. The big sun gear is held to the housing 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 disengaging. Let's take a look at a band.
Bands
In this transmission there are two bands. The bands in a transmission are, literally, steel bands that wrap around sections of the gear train and connect to the housing. They are actuated by hydraulic cylinders inside the case of the transmission.
One of the bands
In the figure above, you can see one of the bands in the housing of the transmission. The gear train is removed. The metal rod is connected to the piston, which actuates the band.
The pistons that actuate the bands are visible here.
Above you can see the two pistons that actuate the bands. Hydraulic pressure, routed into the cylinder by a set of valves, causes the pistons to push on the bands, locking that part of the gear train to the housing.
The clutches in the transmission are a little more complex. In this transmission there are four clutches. Each clutch is actuated by pressurized hydraulic fluid that enters a piston inside the clutch. Springs make sure that the clutch releases when the pressure is reduced. Below you can see the piston and the clutch drum. Notice the rubber seal on the piston -- this is one of the components that is replaced when your transmission gets rebuilt.
One of the clutches in a transmission
The next figure shows the alternating layers of clutch friction material and steel plates. The friction material is splined on the inside, where it locks to one of the gears. The steel plate is splined on the outside, where it locks to the clutch housing. These clutch plates are also replaced when the transmission is rebuilt.
The clutch plates
The pressure for the clutches is fed through passageways in the shafts. The hydraulic system controls which clutches and bands are energized at any given moment.
FROM: http://auto.howstuffworks.com/automatic-transmission.htm
24
自動變速器的工作原理
耐斯·卡瑞姆
介紹自動變速器的工作原理
如果你駕駛過帶有自動變速器的汽車，那么你一定知道手動變速器與自動變速器之間存在兩個很大的區(qū)別：
· 自動變速器中沒有離合器踏板
· 自動變速器中沒有換檔手柄，一旦讓變速器傳遞動力，那么接下來的一切都是自動完成的了。
雖然自動變速器（包括液力變矩器）與手動變速器（包括離合器）完成的功能是相同的，但它們卻是以完全不同的方式來實(shí)現(xiàn)的。最終證實(shí)，自動變速器的工作方式令人驚異。
自動變速器概圖
本文是通過一個具體的自動變速器來闡述其中的原理，我們從整個系統(tǒng)的關(guān)鍵——行星齒輪系入手，然后我們將看到自動變速器是如何組裝在一起的，學(xué)習(xí)控制裝置是如何工作的，討論在自動變速器控制方面的一些復(fù)雜的關(guān)系。
自動變速器和手動變速器一樣，主要功能就是允許發(fā)動機(jī)工作在小范圍變速的速度內(nèi)，變速器卻能夠輸出較大變速范圍的速度。
Mercedes-奔馳 CLK, 自動變速器,剖面立體圖
如果沒有變速器，汽車將被限制在一種傳動比，并且那個傳動必須被選擇作為汽車的最高期望速度。 如果您想要以80英里/小時的最高速度行駛，則傳動比類似于手動變速器汽車的第三檔。
您大概從未嘗試僅使用第三檔駕駛一輛手動變速的汽車。 如果您嘗試過，您馬上會發(fā)現(xiàn)啟動時幾乎沒有加速過程，而是直接以很高的速度啟動，引擎是工作在警戒線附近的。這樣汽車很快就會損害，而且?guī)缀鯚o法駕駛。
因此變速器是利用齒輪來更有效地利用發(fā)動的扭矩的，并且使得發(fā)動機(jī)工作在適當(dāng)?shù)乃俣取?
手動和自動變速器之間的關(guān)鍵性區(qū)別在于：手動變速器采用鎖止或打開不同的齒輪，從而使輸出軸獲得不同傳動比，而在自動變速器中，同樣是這些齒輪，但是能得到一定范圍內(nèi)所有的不同的傳動比。而行星齒輪系是使此成為可能的裝置。
讓我們來看一下行星齒輪系是如何工作的。
行星齒輪系和齒輪傳動比
當(dāng)您拆散自動變速器往里面觀察，可以發(fā)現(xiàn)，在一個相對狹小的空間里布滿了很多零件。在這些零件中有：
? 一個精巧的行星齒輪系
? 一套鎖止齒輪的鋼帶
? 三個鎖住另外一些齒輪的濕式片式離合器
? 控制離合器和鋼帶的復(fù)雜液壓系統(tǒng)
? 為變速器提供液壓的齒輪泵
關(guān)注的重點(diǎn)是行星齒輪系。 變速器所產(chǎn)生的所有不同的傳動比決定于齒輪系尺寸的大小。變速器里其他的零部件是協(xié)助行星輪系產(chǎn)生不同傳動比的。這套裝置曾經(jīng)出現(xiàn)在《材料的工作方式》中。 您可以從《電螺絲刀》中找到。 一個自動變速器中包含有由兩套行星齒輪系組合在一起而成的一個部件。其介紹可以參見《齒輪系工作方式》。
從左到右：內(nèi)齒圈，行星架，和兩個太陽輪
行星齒輪系有三個主要的組成部分：
? 太陽輪
? 行星輪和行星架
? 內(nèi)齒圈
這三個組成中的任何一組成都可以作為輸入或輸出，或者被固定。哪些組成充當(dāng)何種角色取決于行星齒輪系的速度比。下面的動畫可以顯示出其中的關(guān)系。
這是變速器中其中的一個行星齒輪系，內(nèi)齒圈齒數(shù)為72，太陽輪齒數(shù)為30。我們可以從中的到很多不同的速比。
輸入
輸出
固定
計算
齒輪速比
A
太陽輪(S)
行星架(C)
內(nèi)齒圈(R)
1 + R/S
3.4:1
b
行星架(C)
內(nèi)齒圈(R)
太陽輪(S)
1/(1 + S/R)
0.71:1
C
太陽輪(S)
內(nèi)齒圈(R)
行星架(C)
- R/S
-2.4:1
并且，鎖住三個組成中的任何兩個組成將鎖止整個個行星系，而此時速比為1：1。從表中可以看出，第一個中方案的速比為減速——輸出速度小于輸入。第二種方案為加速——輸出速度高于輸入。最后一種方案也是減速，但輸出速度的方向相反。這個行星齒輪系還可以得到其他很多的速比，而剛才的這些速比僅和我們的自動變速器有關(guān)。
因此這一套行星齒輪系可以產(chǎn)生所有需要的不同的齒輪傳動比，卻不需要接合或不接合其他齒輪。把兩套行星齒輪系置于一行，我們可以得到四個前進(jìn)檔和一個后退檔。下一部分內(nèi)容我們將這兩個齒輪系組裝在一起。
復(fù)合行星齒輪系
自動變速器中使用了一系列的行星齒輪系，我們稱之為復(fù)合行星齒輪系，看起來好像只有一個簡單的行星齒輪系，實(shí)際上卻實(shí)現(xiàn)這兩套齒輪系的功能。其中包含一個總是作為輸出的內(nèi)齒圈、兩個太陽和兩套行星裝置。
讓我們看其中的一些零件：
變速器中的齒輪的組裝
從左到右：內(nèi)齒圈，行星架，和兩個太陽輪
下圖中，行星輪裝在行星架上，可以看到，右邊的行星輪低于左邊的行星輪。右邊的行星輪不與內(nèi)齒圈嚙合——它和另一個行星輪嚙合。而只有左邊的行星輪與內(nèi)齒圈嚙合。
行星架：兩個行星輪
在下個圖中，您可看到在行星架的內(nèi)部，短行星輪與小太陽輪嚙合，長行星輪同時與大太陽輪和小太陽輪嚙合。
行星架內(nèi)部：兩個行星輪
自動變速檔位
第一檔
在一檔，小太陽輪在變矩器的渦輪驅(qū)動下順時針旋轉(zhuǎn)。行星架將自動做逆時針轉(zhuǎn)動，但是被離合器阻止了（離合器只允許單向旋轉(zhuǎn)），從而內(nèi)齒圈變成了輸出。小太陽輪有30齒，內(nèi)齒圈72齒，則速比為：
Ratio = -R/S = - 72/30 = -2.4:1
因此旋轉(zhuǎn)速率為負(fù)的2.4:1，這意味著輸出方向同輸入的方向是相反的。但事實(shí)上，輸出方向是與輸入方向相同的，這就是要引入兩套行星齒輪系的原因。第一套與第二套嚙合，而第二套輸出至內(nèi)齒圈，這樣的組合把方向轉(zhuǎn)回原先輸入的方向。這樣還是使得大太陽輪自轉(zhuǎn)，而這時的離合器是不作用的，大太陽輪以同渦輪相反的方向（逆時針）自轉(zhuǎn)。
第二檔
變速器做一些單獨(dú)的事情來獲得二檔所需的傳動比。它像相互連接的兩套行星輪和共同的行星架相連接。
行星架的第一級事實(shí)上是把大太陽輪用作內(nèi)齒圈。所以第一級包括太陽輪（小太陽輪）、行星架和“內(nèi)齒圈”（大太陽輪）。輸入是小太陽輪，內(nèi)齒圈(大太陽輪)由鋼帶保持靜止，輸出是行星架。對于一級，太陽輪作為輸入，行星架作為輸出，而內(nèi)齒圈固定，其公式為：
1 + R/S = 1 + 36/30 = 2.2:1
小太陽輪旋轉(zhuǎn)一圈，行星架則轉(zhuǎn)過2.2圈。在第二級，行星架作為第二套行星齒輪系的輸入，大太陽輪（被固定）作為太陽輪，而內(nèi)齒圈則作為輸出，其齒輪速比為：
1 / (1 + S/R) = 1 / (1 + 36/72) = 0.67:1
要得到二檔的減速比，我們把第一級減速比和第二級減速比相乘， 2.2 x 0.67，得到1.47:1。 這也許聽起來有些怪，但卻是這么運(yùn)作的。
第三檔
絕大多數(shù)的自動變速器在第三檔是1：1的速比。您還記得前面我們已經(jīng)得到速比為1：1的方法——三個組成中鎖住任何兩個組成。這樣的裝置實(shí)現(xiàn)就比較容易——我們所要做的就是接合離合器來鎖住太陽輪中的一個。 如果兩個太陽輪以同一方向旋轉(zhuǎn)，行星輪則被鎖定，因?yàn)樗鼈兎聪蛐D(zhuǎn)。內(nèi)齒圈和行星輪固定使得它們作為一個整體旋轉(zhuǎn)，從而產(chǎn)生1：1的速比。
加速檔
根據(jù)定義，輸出的速度要高于輸入的速度。它是速度的增加——減速的對立面。在變速器中，加速時在同一時刻完成兩件事情。如果您看過《變矩器是如何工作的》，就知道變矩器的鎖止的情況。為了提高效率，一些汽車用機(jī)械方式鎖住變矩器，使得發(fā)動機(jī)的扭矩直接輸出到變速器。
變速器中，當(dāng)加速時，聯(lián)接到變矩器的外殼（用螺栓連接到發(fā)動機(jī)的飛輪）的軸通過離合器的接合連接到行星架，小太陽輪和大太陽輪與加速鋼帶同步，渦輪不接其他東西，而變矩器的外殼作為輸出。我們回顧一下，此時行星架作為輸入，太陽輪固定，而內(nèi)齒圈作為輸出。
Ratio = 1 / (1 + S/R) = 1 / ( 1 + 36/72) = 0.67:1
可得到，發(fā)動機(jī)輸入旋轉(zhuǎn)速度為輸出的三分之二。例如，如果發(fā)動機(jī)轉(zhuǎn)速為每分鐘2000轉(zhuǎn)，輸出轉(zhuǎn)速就為3000轉(zhuǎn)每分鐘。這就允許發(fā)動機(jī)以相對合適的速度運(yùn)轉(zhuǎn)，汽車也能夠在高速公路上行駛。
倒檔
倒檔和一檔非常類似，區(qū)別在于，不是小太陽輪被驅(qū)動，而是大太陽輪被驅(qū)動，而小行星輪以相反方向旋轉(zhuǎn)。行星架與變矩器外殼同步，則根據(jù)上述的公式可以得到：
Ratio = -R/S = 72/36 = 2.0:1
可見，變速器倒檔的傳動比比一檔稍小一些。
齒輪傳動比
此變速器有四個前進(jìn)檔和一個倒檔，讓我們用傳動比、輸入和輸出總結(jié)一下：
檔 位
輸 入
輸 出
固 定
齒輪傳動比
第1 檔
30齒太陽輪
72齒內(nèi)齒圈
行星架
2.4:1
第2檔
30齒太陽輪
行星架
36齒內(nèi)齒圈
2.2:1
行星架
72齒內(nèi)齒圈
30齒太陽輪
0.67:1
兩級總比
1.47:1
第3 檔
30和36齒太陽
72齒內(nèi)齒圈
1.0:1
加速檔
行星架
72齒內(nèi)齒圈
36齒太陽
0.67:1
倒 檔
30齒太陽輪
72齒內(nèi)齒圈
行星架
-2.0:1
在讀完這部分之后，您大概想知道不同的輸入是怎么接合與斷開的。這是由變速器中的離合器和鋼帶完成的。在下一部分中，我們將看到它們是如何工作的。
變速器中的離合器和鋼帶
在上一部分，我們討論了變速器是如何得到不同檔位的傳動比的。例如，討論加速檔是，我們說：
變速器中，當(dāng)加速時，聯(lián)接到變矩器的外殼（用螺栓連接到發(fā)動機(jī)的飛輪）的軸通過離合器的接合連接到行星架，小太陽輪和大太陽輪與加速鋼帶同步，渦輪不接其他東西，而變矩器的外殼作為輸出。
要讓變速器工作在加速檔，很多零部件要通過離合器和鋼帶連接或斷開。行星架通過離合器與變矩器外殼連接。小太陽輪通過離合器斷開與渦輪連接，使其空轉(zhuǎn)。大太陽輪利用鋼帶與外殼同步，使其無法旋轉(zhuǎn)。像這樣通過離合器與鋼帶的接合或不接合，每個齒輪運(yùn)動都會觸發(fā)一系列的事件。讓我們看一下鋼帶。
鋼帶
變速器中有兩條鋼帶，這兩條鋼帶事實(shí)上是包貼在齒輪組切面周圍的，并且連接到外殼，由變速器的液壓缸推動執(zhí)行的。
其中的鋼帶
在上圖中，您可以看到在變速器外殼上其中的一條鋼帶。此時齒輪都已經(jīng)被移走了，金屬推桿與活塞相連，用來推動鋼帶。
活塞推動鋼帶
上圖可看到驅(qū)動鋼帶的兩個活塞。油壓通過液壓閥控制進(jìn)入液壓缸，驅(qū)動活塞推動鋼帶，從而使得齒輪系中的某個組成與外殼鎖止。
變速器中的離合器共有四個，而且相對來說要復(fù)雜一些。被壓縮的液壓油進(jìn)入離合器內(nèi)部的活塞，從而驅(qū)動離合器。當(dāng)油壓降低時，彈簧確保離合器分離后回復(fù)原位。下圖所示為活塞和離合器從動鼓，還要注意到活塞上的密封橡膠圈，當(dāng)變速器被重新修理裝配時，要求更換這個橡膠圈。
變速器中的一個離合器
下圖所示的是離合器中相互交替的摩擦片與金屬片。摩擦片內(nèi)側(cè)由花鍵聯(lián)接，與輪系的其中一個組成鎖止。金屬片外側(cè)用花鍵與離合器外殼固接。同樣，變速器被修理時，這些離合器片要被更換。
離合器片
離合器的油壓是通過經(jīng)由軸內(nèi)通道來供應(yīng)的。在任一時刻，離合器和鋼帶的運(yùn)動都是有液壓系統(tǒng)控制的。
注：本文來源: http://auto.howstuffworks.com/automatic-transmission.htm
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