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Manual transmission
1.Introduction
The purpose of the transmission in an automobile is to transfer the power created by the engine to the wheels via a drive shaft or half-axles. Differing gears in the transmission allow for different levels of torque to be applied to the wheels depending on the speed at which the vehicle is traveling. In order to change the level of torque the gears in the transmission need to be shifted either manually or automatically. In the beginning all transmissions were manual.French inventors Louis-Rene Panhard and Emile Levassor are credited with the development of the first modern manual transmission. They demonstrated their three-speed transmission in 1894 and the basic design is still the starting point for most contemporary manual transmissions.Panhard and Levassor used a chain drive on their original transmission. In 1898 auto maker Louis Renault used their basic design, but substituted a drive shaft for the drive chain and added a differential axle for the rear wheels to improve performance of the manual transmission.By the beginning of the 20th century most cars manufactured in the United States featured a non-synchronized manual transmission based on the Panhard/Levassor/Renault design. The next major innovation occurred in 1928 when Cadillac introduced the synchronized manual transmission, which significantly reduced gear grinding and made shifting smoother and easier.Manual transmissions were the standard on most vehicle for the first half of the 20th century, but automatic transmissions were being developed as far back as 1904. General Motors introduced the clutchless automatic transmission under the moniker, Hydra-Matic, in 1938, but the first true fully automatic transmission didn't appear until 1948 with the Buick Dynaflow transmission.
2.Background
Americans tend to prefer automatic transmission in their vehicles while Western Europe is--and is expected to remain--the largest market for manual transmissions through 2014. Eastern Europe and Asia are also large markets for manual transmission although Japan appears to be embracing more automatic transmissions. In the United States, more manual transmissions are found in the Northern states than in the Southern states. It is surmised that manual transmissions give better control on icy roads and are thus more useful in the North where the winters are more harsh.
Sports cars are often equipped with manual transmissions because they offer more direct driver involvement and better performance, though this is changing as many automakers move to faster dual-clutch transmissions, which are generally shifted with paddles located behind the steering wheel. For example, the 991 Porsche 911 GT3 uses Porsche's PDK. Off-road vehicles and trucks often feature manual transmissions because they allow direct gear selection and are often more rugged than their automatic counterparts.
Conversely, manual transmissions are no longer popular in many classes of cars sold in North America, Australia and some parts of Asia, although they remain dominant in Europe, Asia, Africa and Latin America. Nearly all cars are available with an automatic transmission option, and family cars and large trucks sold in the US are predominantly fitted with automatics, however in some cases if a buyer wishes he/she can have the car fitted with a manual transmission at the factory. In Europe most cars are sold with manual transmissions. Most luxury cars are only available with an automatic transmission. In most cases where both transmissions are available for a given car, automatics are an at cost option, but in some cases the reverse is true. Some cars, such as rental cars and taxis, are nearly universally equipped with automatic transmissions in countries such as the US, but the opposite is true in Europe. As of 2008, 75.2% of vehicles made in Western Europe were equipped with manual transmission, versus 16.1% with automatic and 8.7% with other.
Some trucks have transmissions that look and behave like ordinary car transmissions—these transmissions are used on lighter trucks, typically have up to 6 gears, and usually have synchromesh.
3. Composition for Manual Transmission.
Manual transmissions often feature a driver-operated clutch and a movable gear stick. Most automobile manual transmissions allow the driver to select any forward gear ratio ("gear") at any time, but some, such as those commonly mounted on motorcycles and some types of racing cars, only allow the driver to select the next-higher or next-lower gear. This type of transmission is sometimes called a sequential manual transmission.
In a manual transmission, the flywheel is attached to the engine's crankshaft and spins along with it. The clutch disk is in between the pressure plate and the flywheel, and is held against the flywheel under pressure from the pressure plate. When the engine is running and the clutch is engaged (i.e., clutch pedal up), the flywheel spins the clutch plate and hence the transmission. As the clutch pedal is depressed, the throw out bearing is activated, which causes the pressure plate to stop applying pressure to the clutch disk. This makes the clutch plate stop receiving power from the engine, so that the gear can be shifted without damaging the transmission. When the clutch pedal is released, the throw out bearing is deactivated, and the clutch disk is again held against the flywheel, allowing it to start receiving power from the engine.Manual transmissions are characterized by gear ratios that are selectable by locking selected gear pairs to the output shaft inside the transmission.
Contemporary automobile manual transmissions typically use four to six forward gear ratios and one reverse gear, although consumer automobile manual transmissions have been built with as few as two and as many as seven gears. Transmissions for heavy trucks and other heavy equipment usually have 8 to 25 gears so the transmission can offer both a wide range of gears and close gear ratios to keep the engine running in the power band. Operating aforementioned transmissions often use the same pattern of shifter movement with a single or multiple switches to engage the next sequence of gear selection.
3.1 Transmission shaft
Like other transmissions, a manual transmission has several shafts with various gears and other components attached to them. Typically, a rear-wheel-drive transmission has three shafts: an input shaft, a countershaft and an output shaft. The countershaft is sometimes called a layshaft.In many transmissions the input and output components of the mainshaft can be locked together to create a 1:1 gear ratio, causing the power flow to bypass the countershaft. The mainshaft then behaves like a single, solid shaft: a situation referred to as direct drive.Even in transmissions that do not feature direct drive, it's an advantage for the input and output to lie along the same line, because this reduces the amount of torsion that the transmission case has to bear.Under one possible design, the transmission's input shaft has just one pinion gear, which drives the countershaft. Along the countershaft are mounted gears of various sizes, which rotate when the input shaft rotates. These gears correspond to the forward speeds and reverse. Each of the forward gears on the countershaft is permanently meshed with a corresponding gear on the output shaft. However, these driven gears are not rigidly attached to the output shaft: although the shaft runs through them, they spin independently of it, which is made possible by bearings in their hubs.
3.2 Synchromesh
Most modern manual-transmission vehicles are fitted with a synchronized gear box. Transmission gears are always in mesh and rotating, but gears on one shaft can freely rotate or be locked to the shaft. The synchronizer has to overcome the momentum of the entire input shaft and clutch disk when it is changing shaft rpm to match the new gear ratio. It can be abused by exposure to the momentum and power of the engine, which is what happens when attempts are made to select a gear without fully disengaging the clutch. This causes extra wear on the rings and sleeves, reducing their service life. When an experimenting driver tries to "match the revs" on a synchronized transmission and force it into gear without using the clutch, the synchronizer will make up for any discrepancy in RPM. The success in engaging the gear without clutching can deceive the driver into thinking that the RPM of the layshaft and transmission were actually exactly matched. Nevertheless, approximate rev. matching with clutching can decrease the difference in rotational speed between the layshaft and transmission gear shaft, therefore decreasing synchro wear.
In a synchromesh gearbox, to correctly match the speed of the gear to that of the shaft as the gear is engaged the collar initially applies a force to a cone-shaped brass clutch attached to the gear, which brings the speeds to match prior to the collar locking into place. The collar is prevented from bridging the locking rings when the speeds are mismatched by synchro rings (also called blocker rings or baulk rings, the latter being spelled balk in the U.S.). The synchro ring rotates slightly due to the frictional torque from the cone clutch. In this position, the dog clutch is prevented from engaging. The brass clutch ring gradually causes parts to spin at the same speed. When they do spin the same speed, there is no more torque from the cone clutch and the dog clutch is allowed to fall into engagement. In a modern gearbox, the action of all of these components is so smooth and fast it is hardly noticed.
3.3 Reverse
Reverse gear is usually not synchromesh, as there is only one reverse gear in the normal automotive transmission and changing gears into reverse while moving is not required—and often highly undesirable, particularly at high forward speed.
3.4 Clutch
Among many different types of clutches, a dog clutch provides non-slip coupling of two rotating members. It is not at all suited to intentional slipping, in contrast with the foot-operated friction clutch of a manual-transmission car.
The gear selector does not engage or disengage the actual gear teeth which are permanently meshed. Rather, the action of the gear selector is to lock one of the freely spinning gears to the shaft that runs through its hub. The shaft then spins together with that gear. The output shaft's speed relative to the countershaft is determined by the ratio of the two gears: the one permanently attached to the countershaft, and that gear's mate which is now locked to the output shaft.
Locking the output shaft with a gear is achieved by means of a dog clutch selector. The dog clutch is a sliding selector mechanism which is splined to the output shaft, meaning that its hub has teeth that fit into slots (splines) on the shaft, forcing that shaft to rotate with it. However, the splines allow the selector to move back and forth on the shaft, which happens when it is pushed by a selector fork that is linked to the gear lever. The fork does not rotate, so it is attached to a collar bearing on the selector. The selector is typically symmetric: it slides between two gears and has a synchromesh and teeth on each side in order to lock either gear to the shaft.
4.Fuel Economy
The manual transmission couples the engine to the transmission with a rigid clutch instead of the torque converter on an automatic transmission or the v-belt of a continuously variable transmission, which slip by nature. Manual transmissions also lack the parasitic power consumption of the automatic transmission's hydraulic pump. Because of this, manual transmissions generally offer better fuel economy than automatic or continuously variable transmissions; however the disparity has been somewhat offset with the introduction of locking torque converters on automatic transmissions. Increased fuel economy with a properly operated manual transmission vehicle versus an equivalent automatic transmission vehicle can range from 5% to about 15% depending on driving conditions and style of driving. The lack of control over downshifting under load in an automatic transmission, coupled with a typical vehicle engine's greater efficiency under higher load, can enable additional fuel gains from a manual transmission by allowing the operator to keep the engine performing under a more efficient load/RPM combination. This is especially true as between manual and automatic versions of older models, as more recent advances including variable valve timing reduce the efficiency disadvantages of automatic transmissions by allowing better performance over a broader RPM range. In recognition of this, many current models (2010 and on) come with manual modes, or overrides on automatic models, although the degree of control varies greatly by the manufacturer. Also, manual transmissions do not require active cooling and because they are, mechanically, much simpler than automatic transmissions, they generally weigh less than comparable automatics, which can improve economy in stop-and-go traffic.[16] However this gap in economy is being rapidly closed, and many mid to higher end model automatic cars now get better economy than their standard spec counterparts[citation needed]. This is in part due to the increasing impact of computers co-ordinating multiple systems, particularly in hybrid models in which the engine and drive motors must be managed.
手動變速器
1.說明
汽車傳動的目的是通過驅(qū)動軸或半軸將發(fā)動機驅(qū)動車輪的動力傳遞給車輪。在變速器中不同的齒輪允許不同程度的扭矩被施加到車輪上，這取決于車輛行駛的速度。為了改變變速器中的齒輪的轉(zhuǎn)矩的水平，需要手動或自動移動。在開始時，所有的傳輸都是手動的。法國發(fā)明家路易斯雷內(nèi)潘哈德和埃米爾勒瓦索被認為是第一個促進現(xiàn)代手動變速器的發(fā)展的人。他們在1894年展示了他們的三擋變速器，其基本的設(shè)計仍然是現(xiàn)代的手動變速器的起點。潘哈德和勒瓦索在原來傳輸?shù)幕A(chǔ)上改用鏈傳動。1898年，汽車制造商路易斯雷諾使用他們的基本設(shè)計，但是使用了驅(qū)動軸取代了驅(qū)動鏈，并在后橋增加了一個差速器，以提高手動變速器性能。在第二十世紀初美國制造的大多數(shù)汽車采用了美國特色的非同步手動變速器都是基于潘哈德/勒瓦索/雷諾設(shè)計。下一個重大創(chuàng)新發(fā)生在1928年，當凱迪拉克推出同步手動變速器，這大大減少齒輪磨削，使換檔更順暢，更容易。在二十世紀上半年手動變速器的標準被大多數(shù)車輛采用，但自動變速器的開發(fā)可追溯到1904年。在1938年，通用汽車為生產(chǎn)的離合器自動變速器取名為Hydra-Matic，但第一個真正的全自動變速器的出現(xiàn)直到1948年的別克流體動力傳輸?shù)某霈F(xiàn)。
2.背景
2014年調(diào)查顯示，美國人更傾向于在他們的車上安裝自動變速器，而西歐預計保持最大的手動變速器市場。東歐和亞洲也有大量的手動變速器市場，日本似乎擁有更多的自動變速器。在美國，手動變速器在北方各州比在南部各州更廣為使用。據(jù)推測，手動變速器可以更好地控制在結(jié)冰的路面上的行駛，從而更有效的適應更惡劣的北方冬天。
跑車往往配備手動變速箱，因為他們提供更多的直接驅(qū)動的參與和更好的性能，盡管這是許多汽車制造商將更快的雙離合器變速箱的變化，它通常是位 于方向盤槳移。例如，991保時捷911 GT3使用保時捷的PDK。越野車和卡車經(jīng)常采用手動變速器，因為它們允許直接齒輪的選擇，而且往往比他們的自動變速器更堅固耐用。
相反，在北美 國、澳大利亞以及亞洲的一些地區(qū)，手動變速器不再流行，雖然它們在歐洲、亞洲、非洲和拉丁美洲都是占主導地位的美國。幾乎所有的汽車都可以與自動變速器的 選擇，家庭轎車和大卡車在美國銷售的主要配備自動化，但是在某些情況下，如果買方希望他/她能把車裝在工廠的手動變速器。在歐洲，大多數(shù)汽車都是用手動變 速器出售的。大多數(shù)豪華車只能用一種自動變速器。在大多數(shù)情況下，傳輸，可用于一個給定的汽車，自動變速器是一個在成本的選擇，但在某些情況下是正確的。 一些汽車，如出租汽車和出租車，幾乎全世界都配備了自動變速器，如美國，但相反的是真實的，在歐洲，2008，75.2%的車輛在西歐，配備手動變速器， 與16.1%與自動和其他8.7%。一些卡車變速器的外觀和行為像普通汽車變速器這些傳輸用于輕卡車，通常有6個齒輪，通常有同步。
3.變速器組成.
手動變速器通常有一個驅(qū)動操縱離合器和一個可移動的撥叉。大多數(shù)汽車的手動變速器允許司機在任何時候選擇任何前進檔位，但有些，如一般安裝在摩托車和某些類型的賽車，只允許司機選擇下一個或下一個較低的檔位。這種類型的傳輸有時被稱為順序手動變速器。在一個手動變速器，飛輪是連接到發(fā)動機的曲軸和旋轉(zhuǎn)一起。離合器盤在壓力板與飛輪之間，并在壓力下與飛輪保持在一起。當發(fā)動機運轉(zhuǎn)時，離合器接合，飛輪轉(zhuǎn)動離合器盤。由于離合器踏板是凹陷的，這會導致壓力板停止向離合器盤施加壓力。這使得離合器停止接收發(fā)動機的功率，使變速器可以換擋，而不損壞傳輸。當離合器踏板被釋放時，分離軸承被停用，離合器盤再次被與飛輪接合，允許它開始從發(fā)動機接收功率。手動變速器的特點是通過鎖定選定的齒輪副的傳動比，從而決定傳輸?shù)妮敵鲚S的齒輪比。
現(xiàn)代汽車的手動變速器通常采用（4+1）檔，或者（6+1）檔。雖然消費者的汽車手動變速器已經(jīng)建立了七個檔位。而且重型卡車和其他重型設(shè)備的變速器通常有8至25個檔位，因此變速器可以同時提供一個較大范圍的齒輪比，以保持發(fā)動機在最佳功率運行。操作上述變速器經(jīng)常使用相同的模式。即選用一個或者多個操縱桿來進行檔位的選擇。
3.1 變速器軸
與其它變速器一樣，手動變速器軸上包含不同的齒輪和其它連接部件。通常情況下，后輪驅(qū)動的變速器有三個軸：輸入軸、中間軸和輸出軸。副軸有時被稱為中間軸。許多變速器的輸入和輸出的主軸組件可以被鎖在一起，創(chuàng)建一個1:1的傳動比，使功率流繞過副軸。主軸然后像一個單一的實心軸：這種情況稱為直接驅(qū)動。直接驅(qū)動時輸入和輸出沿一條直線是一個很大的優(yōu)勢，因為這降低了扭矩，變速箱承受量。一個可能的設(shè)計，變速器的輸入軸只有一個小齒輪，從而帶動副軸。沿中間軸安裝不同尺寸的齒輪，輸入軸轉(zhuǎn)動時。這些齒輪對應的正向速度和反向。每一個前進檔中間軸上永久嚙合輸出軸上的相應齒輪。然而這些從動齒輪不剛性連接到輸出軸：雖然軸運行通過他們，他們獨立地旋轉(zhuǎn)，這時由軸承在高速旋轉(zhuǎn)。
3.2 變速器同步器
大多數(shù)現(xiàn)代的手動變速器都配有一個同步齒輪箱。變速器齒輪總是在嚙合和旋轉(zhuǎn)，但在一個軸上的齒輪可以自由旋轉(zhuǎn)或被鎖定到軸上。同步器克服了整個輸入軸和離合器盤在改變軸的轉(zhuǎn)速來匹配新的齒輪比。它可以通過暴露于發(fā)動機的動力選擇一個齒輪來換擋，但沒有完全分離離合器。這會導致環(huán)和套筒額外的磨損，減少他們的使用壽命。當司機試圖嘗試換擋，匹配的轉(zhuǎn)速在同步傳輸和力成齒輪不使用離合器，同步將彌補換擋時轉(zhuǎn)速的差異。不過近似配合，能降低中間軸和傳動齒輪軸之間的轉(zhuǎn)速差，因此降低同步磨損。
在一個同步器變速箱，正確匹配的齒輪轉(zhuǎn)速，軸的齒輪嚙合齒圈最初施加力到錐形黃銅離合器連接到齒輪，它匹配的齒圈鎖定到之前帶來的速度。衣領(lǐng)是防止連接鎖定環(huán)時速度不匹配同步環(huán)。同步環(huán)輕微旋轉(zhuǎn)，由于摩擦扭矩從錐形離合器到這個位置，離合器被阻止接合。黃銅離合器環(huán)逐漸使零件以相同的速度旋轉(zhuǎn)。當它們旋轉(zhuǎn)相同的速度，有沒有更多的扭矩從錐形離合器和離合器被允許進入接觸。在現(xiàn)代的齒輪箱，所有這些組件的作用是如此的平穩(wěn)和快速，幾乎沒有注意到。
3.3 倒檔
倒檔齒輪通常是不同步的，因為普通的汽車變速器只有一個倒檔，并且汽車正常行駛時不需要經(jīng)常換到倒檔，尤其是在高速行駛時。
3.4 離合器
在眾多不同類型的離合器中，齒式離合器是提供非滑動耦合的雙旋轉(zhuǎn)的成員。它不限滑的，相反，干式摩擦離合器的手動變速器是限滑的。
同步器不接合或脫離永久嚙合齒輪齒。同步器的作用是把一個自由旋轉(zhuǎn)的齒輪鎖定在軸上，通過它的中心，然后軸與齒輪一起旋轉(zhuǎn)。輸出軸的速度相對于副軸是由兩齒輪的比值決定：一個永久連接到中間軸，且相嚙合的齒輪現(xiàn)在鎖定到輸出軸。鎖定輸出軸與齒輪是通過一個離合器實現(xiàn)。離合器的機理是通過花鍵與輸出軸實現(xiàn)，這意味著它的樞紐已融入槽齒（花鍵）在軸上，通過軸轉(zhuǎn)動它。然而，花鍵允許花鍵轂在軸上來回移動，當它被一個與齒輪桿相連的撥叉推的時候，撥叉不旋轉(zhuǎn)，所以它是連接到一個衣領(lǐng)軸承上的選擇器。選擇器器通常是對稱的：它位于兩檔齒輪之間并有一個同步器把每側(cè)齒輪鎖到齒輪軸。
4.燃油經(jīng)濟性
手動變速器與離合器剛性連接，而不是像自動變速器、無級變速器的帶液力變矩器傳輸引擎。手動變速器也缺乏自動變速器的液壓泵的保存功率消耗功能。因此，手動變速器一般提供比自動或無級變速器更好的燃油經(jīng)濟性；然而，差距已經(jīng)有所抵消，引進的自動變速器鎖定扭矩轉(zhuǎn)換器。增加燃油經(jīng)濟性與適當?shù)牟倏v技巧，手動變速器汽車等效自動變速器的車輛，根據(jù)駕駛條件和駕駛風格可以在5%到15%的范圍。在低檔載荷下自動變速器控制的不足，再加上一個典型的汽車發(fā)動機的效率更高的負載，可以使手動變速器從額外的收益燃料允許經(jīng)營者保持引擎執(zhí)行U在一個更有效的負荷/轉(zhuǎn)速組合。這是特別真實的手動和自動版本的舊機型，隨著越來越多的最新進展，包括可變氣門正時減少自動變速器的效率的缺點，允許更好的性能在更廣泛的轉(zhuǎn)速范圍。認識到這一點，許多現(xiàn)有的模型（2010）來自手動模式、自動模式或重寫，雖然控制程度差別很大。另外，手動變速器不需要主動冷卻，因為他們是機械，比自動變速器簡單得多，一般體重小于可比的自動化，從而提高經(jīng)濟在走走停停的交通。但是這種經(jīng)濟差距正在迅速關(guān)閉，很多中高端的模型自動車現(xiàn)在得到比標準規(guī)格的同行更好的經(jīng)濟。這部分是由于計算機協(xié)調(diào)多個系統(tǒng)的影響越來越大，特別是在混合動力車型的發(fā)動機和驅(qū)動電機必須管理。