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Manual Transmission
It’s no secret that cars with manual transmissions are usually more fun to drive than the automatic-equipped counterparts. If you have even a passing interest in the act of driving, then chances are you also appreciate a fine-shifting manual gearbox. But how does a manual transmission actually work?
A history hows that manual transmissions preceded automatics by several decades. In fact, up until General Motors offered an automatic in 1938, all cars were of the shift-it-yourself variety. While it’s logical for many types of today’s vehicles to be equipped with an automatic---such as a full-size sedan, SUV or pickup----the fact remains that nothing is more of a thrill to drive than a tautly suspended sport sedan, sport coupe or two-seater equipped with a precise-shifting five-or six-speed gearbox.
We know which types of cars have manual trannies. Now let’s take a look at how they work. From the most basic four-speed manual trannies. Now let’s take a look at how they work.From the most basic four-speed manual in a car from the’60s to the most high-tech six-speed one in a car of today, the principles of a manual gearbox are the same. The driver must shift from gear to gear. Normally, a manual transmission bolts to a clutch housing ,in turn, bolts to the back of the engine. If the vehicle has front-wheel drive, the transmission still attaches to the engine in a similar fashion but is usually referred to as a transaxle. This is because the transmission, differential and drive axles are one complete unit. In a front-wheel-drive car, the transmission also serves as part of the front axle for the front wheels. In the remaining text, a transmission and a transaxle will both be referred to using the term transmission.
The function of any transmission is transferring engine power to the driveshaft and rear wheels . Gears inside the transmission change the vehicle’s drive-wheel speed and torque in relation to inside the transmission change the vehicle’s drive-wheel speed and torque in relation to engine speed and torque. Lower gear ratios serve as torque multipliers and help the engine to develop enough power to accelerate from a standstill.
Initially, power and torque from the engine comes into the front of the transmission and rotates the main drive gear, which meshes with the cluster or counter shaft gear----a series of gears forged into one piece that resembles a cluster of gears. The cluster-gear assembly rotates any time the clutch is engaged to a running engine, whether or not the transmission is in gear or in neutral.
There are two basic types of manual transmissions. The sliding-gear type and the constant-mesh design. With the basic---and now obsolete---sliding-gear type, nothing is turning inside the transmission case except the main drive gear and cluster gear when the trans is in neutral. In order to mesh the gears and apply engine power to move the vehicle, the driver presses the clutch pedal and moves the shifter handle, which in turn moves the shift linkage and forks to slide a gear along the mainshaft, which is mounted directly above the cluster. Once the gears are meshed, the clutch pedal is released and the engine’s power is sent to the drive wheels. There can be several gears on the mainshaft of different diameters and tooth counts, and the transmission shift linkage is designed so the driver has to unmesh one gear before being able to mesh another. With these older transmissions, gear clash is a problem because the gears are all rotating at different speeds.
All modern transmissions are of the constant-mesh type, which still uses a similar gear arrangement as the sliding-gear type. However, all the mainshaft gears are in constant mesh with the cluster gears. This is possible because the gears on the mainshaft are not splined to the shaft, but are free to rotate on it. With a constant-mesh gearbox, the main drive gear, cluster gear and all the mainshaft gears are always turning, even when the transmission is in neutral.
Alongside each gear on the mainshaft is a dog clutch, with a hub that’s positively splined to the shaft and an outer ring that can slide over against each gear. Both the mainshaft gear and the ring of the dog clutch have a row of teeth. Moving shift linkage moves the dog clutch against the adjacent mainshaft gear, causing the teeth to interlock and solidly lock the gear to the mainshaft.
To prevent gears from grinding or clashing during engagement, a constant-mesh, fully “synchronized”manual transmission is equipped with synchronizers. A synchronizer typically consists of an inner-splined hub, an outer sleeve, shifter plates, lock rings and blocking rings. The hub is splined onto the mainshaft between a pair of main drive gears. Held in place by the lock rings, the shifter plates position the sleeve over the hub while also holding the floating blocking rings in proper alignment.
A synchro’s inner hub and sleeve are made of steel, but the blocking ring----the part of the synchro that rubs on the gear to change its speed----is usually made of a softer material, such as brass. The blocking ring has teeth that match the teeth on the dog clutch. Most synchros perform double duty----they push the synchro in one direction and lock one gear to the mainshaft. Push the synchro the other way and it disengages from the first gear, passes through a neutral position, and engages a gear on the other side.
That’s the basics on the inner workings of a manual transmission. As for advances, they have been extensive over the years, mainly in the area of additional gears. Back in the’60s,four-speeds were common in American and European performance cars. Most of these transmissions had 1:1 final-drive ratios with no overdrives. Today, overdriven five-speeds are standard on practically all passenger cars available with a manual gearbox.
Overdrive is an arrangement of gearing that provides more revolutions of the driven shaft than the driving shaft. For example, a transmission with a fourth-gear ratio of 1:1 and a fifth-gear ratio of 0.70:1 will reduce engine rpm by 30 percent, while the vehicle maintains the same road speed. Thus, fuel efficiency will improve and engine wear will be notably reduced. Today, six-speed transmissions are becoming more and more common. One of the first cars sold in America with a six-speed was the’89Corvette. Designed by Chevrolet and Zahnradfabrik Friedrichshafen and built by ZF in Germany, this tough-as-nails six-speed was available in the Corvette up to the conclusion of the’96 model year. Today, the Corvette uses a Tremec T56 six-speed mounted at the back of the car.
Many cars are available today with six-speeds, including the Mazda Miata, Porsche Boxster S and 911, Dodge Viper, Mercedes-Benz SLK320, Honda S2000,Toyota Celica GT-S and many others. Some of these gearboxes provide radical 50-percent sixth-gear overdrives such as in the Viper and Corvette, while others provide tightly spaced gear ratios like in the S2000 and Celica for spirited backroad performance driving. While the bigger cars mentioned above such as the Viper and Vette often have two overdrive ratios the smaller cars like the Celica and S2000 usually have one overdriven gear ratio and fifth is 1:1.
Clearly a slick-shifting manual transmission is one of the main components in a fun-to-drive car, along with a powerful engine, confidence-inspiring suspension and competent brakes.
手動(dòng)變速器
駕駛手動(dòng)變速器汽車(chē)比駕駛自動(dòng)裝置的汽車(chē)更有樂(lè)趣，這顯然已經(jīng)不是什么秘密了。如果你有駕駛興趣，那么你就會(huì)更喜歡手動(dòng)變速箱。但是手動(dòng)變速箱到底是如何工作的呢？
手動(dòng)變速器要早于自動(dòng)變速器幾十年。事實(shí)上，直到1938年通用汽車(chē)公司提供自動(dòng)變速器以前，所有的轎車(chē)都采用的手動(dòng)變速器。現(xiàn)在的很多車(chē)輛都裝備了自動(dòng)變速器，如全尺寸轎車(chē)，運(yùn)動(dòng)型多功能車(chē)或皮卡車(chē)——事實(shí)上是沒(méi)有什么能比駕駛配備了五擋或六擋變速箱的跑車(chē)或運(yùn)動(dòng)雙座跑車(chē)更令人興奮的了。
我們知道哪些類(lèi)型的車(chē)配備有手動(dòng)變速箱?，F(xiàn)在讓我們來(lái)看看他們是如何工作的。我們從最基本的六十年代的四擋手動(dòng)變速箱到今天最高技術(shù)的六擋變速箱來(lái)看，其手動(dòng)變速箱的工作原理是相同的。駕駛員必須從一檔換到另一檔。通常，從一個(gè)手動(dòng)變速器的螺栓到離合器殼體，反過(guò)來(lái)，從螺栓到發(fā)動(dòng)機(jī)的背面。如果車(chē)輛前輪驅(qū)動(dòng)，變速器仍依附于發(fā)動(dòng)機(jī)工作，但通常又被送交給變速驅(qū)動(dòng)橋。這是因?yàn)樽兯倨鳎钏倨骱万?qū)動(dòng)軸是一個(gè)完整的裝置。在剩下的文章中，變速器和變速驅(qū)動(dòng)橋都將由術(shù)語(yǔ)傳動(dòng)裝置來(lái)表示。
變速器的功能是將發(fā)動(dòng)機(jī)的動(dòng)力傳送到傳動(dòng)軸和后輪。變速器中的傳動(dòng)裝置以及與變速器內(nèi)部相關(guān)聯(lián)的扭矩改變了汽車(chē)驅(qū)動(dòng)輪的轉(zhuǎn)速。低扭矩齒輪可使扭矩倍增，并且?guī)椭鎻撵o止?fàn)顟B(tài)加速來(lái)發(fā)出足夠的動(dòng)力。
起初，來(lái)自于發(fā)動(dòng)機(jī)的動(dòng)力和扭矩進(jìn)入到變速器的前部，并且使主驅(qū)動(dòng)齒輪旋轉(zhuǎn)，它與齒輪組或副軸齒輪——一組單片齒輪組成的齒輪組共同嚙合。齒輪組旋轉(zhuǎn)時(shí)離合器就開(kāi)始運(yùn)行引擎，無(wú)論是否在傳送動(dòng)力中的齒輪還是處于空擋中的齒輪。
手動(dòng)變速箱的基本類(lèi)型有兩種?；瑒?dòng)齒輪類(lèi)型和常嚙合設(shè)計(jì)類(lèi)型。隨著基礎(chǔ)型號(hào)滑動(dòng)齒輪式的淘汰，當(dāng)傳動(dòng)裝置設(shè)置在空擋時(shí)，除了主動(dòng)齒輪和齒輪組以外，其余皆沒(méi)有什么變化。為了嚙合齒輪并使發(fā)動(dòng)機(jī)提供動(dòng)力來(lái)移動(dòng)車(chē)輛，司機(jī)按下離合器踏板以及移動(dòng)換檔手柄，從而改變聯(lián)動(dòng)，使撥叉沿主軸移動(dòng)。一旦齒輪嚙合時(shí)，離合器踏板被釋放，發(fā)動(dòng)機(jī)的動(dòng)力便被傳送到了驅(qū)動(dòng)輪。這里可以有若干不同直徑和齒數(shù)的齒輪，變速器換擋桿被設(shè)計(jì)成在能夠嚙合另一個(gè)齒輪前，使這個(gè)齒輪處于非嚙合狀態(tài)。隨著這些舊變速箱，齒輪沖突是一個(gè)問(wèn)題，因?yàn)樗械凝X輪都在以不同的速度旋轉(zhuǎn)著。
所有現(xiàn)代的傳輸都是常嚙合類(lèi)型，仍然使用的是滑動(dòng)齒輪式的安排。但是，所有的主軸齒輪都以齒輪組的形式常嚙合。這是很有可能的，因?yàn)辇X輪在主軸上不是用花鍵鏈接，只要能夠自由旋轉(zhuǎn)就可以了。以常嚙合變速箱，即使是處于空擋狀態(tài)，主傳動(dòng)齒輪、所有中間軸齒輪和主軸齒輪總是轉(zhuǎn)動(dòng)。
在主軸上的每個(gè)齒輪旁邊是牙嵌式離合器，用這輪轂和外環(huán)可以針對(duì)每個(gè)齒輪滑動(dòng)通過(guò)樞紐。主軸齒輪和牙嵌式離合器有一排齒。移動(dòng)的聯(lián)動(dòng)裝置使與主軸齒輪相對(duì)的牙嵌式離合器移動(dòng)，導(dǎo)致齒互鎖并牢固地鎖定齒輪的主軸。
為了防止在工作中的研磨和沖突，常嚙合完全使手動(dòng)變速箱齒輪與同步器配備相協(xié)調(diào)。同步器通常由花鍵轂，外套筒，換檔板，鎖環(huán)和阻斷環(huán)組成。該輪轂是在一對(duì)主動(dòng)齒輪之間的花鍵上鏈接。同時(shí)保持浮動(dòng)的鎖環(huán)適當(dāng)?shù)恼{(diào)整。
一個(gè)同步器的中心和套筒是由鋼鐵制成，但鎖環(huán)----同步器上的一部分在齒輪上的摩擦來(lái)改變它的速度——鎖環(huán)通常是由較軟的材料制成，如黃銅。阻斷環(huán)上的齒與牙嵌式離合器上的齒相匹配。大多數(shù)同步器執(zhí)行雙重任務(wù)----他們推向一個(gè)方向同步并將一個(gè)齒輪鎖定在主軸上。同步推進(jìn)的其他方式，它從一檔脫離接觸，通過(guò)空檔，并嚙合到另一側(cè)的齒輪上。
這是關(guān)于手動(dòng)變速箱的內(nèi)部運(yùn)作的基本知識(shí)。至于進(jìn)展，他們已經(jīng)發(fā)展多年，主要是在齒輪領(lǐng)域。早在六十年代，四速變速箱在美國(guó)和歐洲的汽車(chē)中就普遍使用。大多數(shù)的變速箱都是一比一的傳動(dòng)比，無(wú)超速傳動(dòng)。今天，超速轉(zhuǎn)動(dòng)的五速變速箱是幾乎所有手動(dòng)變速箱的標(biāo)準(zhǔn)配置。
超速傳動(dòng)是為了提供給驅(qū)動(dòng)軸更多的轉(zhuǎn)數(shù)。例如，一個(gè)1:1的第四齒輪和一個(gè)傳動(dòng)比0.70:1第五齒輪傳動(dòng)比將減少百分之三十發(fā)動(dòng)機(jī)轉(zhuǎn)速，而保持同樣的道路車(chē)輛的速度。因此，燃油效率就會(huì)提高，發(fā)動(dòng)機(jī)的磨損會(huì)明顯減少。今天，六速變速箱正變得越來(lái)越普遍。在美國(guó)出售的配備有六速變速箱汽車(chē)是89Corvette。這款車(chē)是由雪佛蘭和Zahnradfabrik Friedrichshafen在德國(guó)建立的。這種六速變速器是在克維特牌轎車(chē)96年車(chē)型上使用的。如今，克爾維特在車(chē)的后座上使用Tremec T56六速變速箱。
今天許多汽車(chē)配備有六速變速箱，包括馬自達(dá)Miata，保時(shí)捷的Boxster S和911，道奇Viper，奔馳SLK320，本田S2000，豐田Celica的GT - S和其他品牌車(chē)輛。這些變速箱的六擋超速擋能夠達(dá)到百分之五十的傳動(dòng)比，如Viper和科威特這類(lèi)汽車(chē)，而其他變速器則提供間隔緊密的齒輪比，如S2000和賽利卡這樣的汽車(chē)。然而，上面提到的這些較大Viper和科威特汽車(chē)有兩個(gè)超速擋，而小型的汽車(chē)像塞利卡和S2000這樣的汽車(chē)通常有一個(gè)是超速擋，而第五擋的傳動(dòng)比為1：1。
顯然，對(duì)于一輛駕駛起來(lái)有樂(lè)趣的車(chē)來(lái)說(shuō)，一個(gè)靈活的手動(dòng)變速箱是其主要組成部分之一，與此同時(shí)，一個(gè)強(qiáng)大的引擎以及令人充滿(mǎn)信心和激情的懸掛和剎車(chē)能力也是駕駛員的樂(lè)趣所在。
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