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    当前位置:网站美女AV > 英语毕业论文 > 其他相关论文 > 双离合器变速器结构工作原理外文翻译及原文

    双离合器变速器结构工作原理外文翻译及原文

        作者:新论文网    [ 2013-10-26 14:57:20 ]

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      淮 阴 工 学 院
    毕业设计(论文)外文资料翻译

    系  (院): 交通工程学院
    专    业: 汽车服务工程
    姓    名: 
    学    号: 
    外文出处: How Dual-clutch Transmissions Work
    by William Harris
    (用外文写) 
    附    件: 1.外文资料翻译译文;2.外文原文。

           
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        注:请将该封面与附件装订成册。附件1:外文资料翻译译文
    双离合器变速器结构工作原理
       大多数人都知道汽车的变速器分为两种基本类型:手动和自动。手动变速器要求驾驶员踩下离合器踏板并使用换挡杆来实现换挡;而自动变速器可以使用离合器、变矩器和行星齿轮组为驾驶员完成全部换挡工作。 但是还有一种介于二者之间并综合了二者各自优点的变速器:双离合器变速器。这种变速器也称为半自动变速器、“无离合”手动变速器和自动手动变速器。
       在赛车领域,半自动变速器(例如顺序手动变速器)多年来一直占据主导地位。 但是在量产车中,这还是一种相对较新的技术。被称作双离合器变速器或直接换挡变速器的这些特定设计采用的就是这种技术。
       本文将探讨双离合器变速器的工作原理、它与其他两种变速器的对比,以及为何有人预言这种变速器代表了未来的发展趋势。
       一.手动操作还是自动操作
       双离合器变速器在一个变速器中实现了两个手动变速器的功能。 为了帮助您理解这句话的含义,我们可以回顾一下传统的手动变速器的工作原理。 在使用标准换挡杆换挡的汽车中,如果驾驶员要从一个挡位换到另一个挡位,他先要踩下离合器踏板。 此动作可以操作一个离合器,使发动机与变速器断开连接,中断输送到变速器的动力。 然后,驾驶员使用换挡杆选择新的挡位,这个过程涉及到将齿形联轴器从一个齿轮移动到另一个不同大小的齿轮。 称为“同步器”的设备会让齿轮在结合之前相匹配以防止磨齿。 一旦换入了新的挡位,驾驶员就可以松开离合器踏板,从而使发动机重新连接到变速器,并将动力传送给车轮。
       由此可见,在传统的手动变速器中,从发动机到车轮没有连续的动力输出。 在换挡的过程中,动力传送将从“有”到“无”再到“有”进行变化,这样就会导致“换挡冲击”或“扭矩中断”现象。 对于技术不熟练的驾驶员,这种现象会导致车上的乘客在换挡过程中感到前后摇晃。
       对比之下,双离合器变速器使用两个离合器,但没有离合器踏板。先进的电子系统和液压系统像控制标准自动变速器那样对离合器进行控制。 但在双离合器变速器中,各离合器单独运转。 一个离合器控制奇数挡(一挡、三挡、五挡和倒挡),另一个离合器控制偶数挡(二挡、四挡和六挡)。 这样,不需要中断从发动机到变速器的动力传送就可以换挡。 其工作方式如下:
       驾驶员也可以选择完全自动模式,从而将所有换挡工作交给计算机完成。 在这种模式下,驾驶体验非常类似于普通自动挡车。 由于双离合器变速器可以“逐渐退出”一个挡位并“逐渐接入”另一个挡位,因此减少了换挡冲击。 更重要的是,换挡是在负载下完成的,因此可以始终维持动力输出。
       独创性的双轴构造使奇数挡和偶数挡分离,从而使这一切成为可能。 我们将在下一节了解有关这两个轴的知识。
       二.变速器轴和多片离合器
       在双离合器变速器的中央是一个由两个部分构成的变速器轴。 普通的手动变速器将所有挡位的齿轮安放在一根输入轴上,与此不同的是,双离合器变速器将奇数挡齿轮和偶数挡齿轮分别安放到两根输入轴上。 这是如何实现的呢? 外轴是中空的,其中留有嵌套内轴的空间。 外部的中空轴为二挡和四挡提供动力,而内轴为一挡、三挡和五挡提供动力。
       由于双离合器变速器与自动变速器类似,因此,您可能会认为,双离合器变速器会像自动变速器一样需要一个变矩器,以用来将发动机扭矩从发动机传送到变速器。 但是,双离合器变速器不需要变矩器。 市场上当前的双离合器变速器使用的是湿式多片离合器。 “湿式”离合器是指将离合器组件浸泡在润滑液中以减少摩擦并限制发热的离合器。 有几家制造商正在开发使用干式离合器(像那些通常与手动变速器关联的离合器那样)的双离合器变速器,但现在装备双离合器变速器的所有量产车使用的都是湿式离合器。 许多摩托车使用了单一的多片离合器。
       
       湿式多片离合器和变矩器一样,都是使用液压来驱动齿轮。 液体作用于离合器活塞内部,如上图所示。 当离合器结合后,活塞内部的液压迫使一组螺旋弹簧分离,从而将一系列离合器片和摩擦盘推向固定的压板。 摩擦盘有内部齿形,其大小和形状可与离合器从动鼓上的花键啮合。 而动鼓又连接到将接收传动力的齿轮。 奥迪的双离合器变速器在其湿式多片离合器中既有一个小的螺旋弹簧,又有一个大的膜片弹簧。
       为了使离合器分开,活塞内部的液压会减少。 这样就可以让活塞弹簧松弛下来,从而减少离合器总成和压板上的压力。
       三.双离合器变速器的优缺点
       希望您现在已经清楚为什么会将双离合器变速器归类为自动手动变速器。双离合器变速器的操作大体上与标准的手动变速器类似: 双离合器变速器使用了输入轴和辅助轴来安放齿轮、同步器和离合器。 由于实际的换挡工作是由计算机、电磁阀和液压系统完成的,因此双离合器变速器没有离合器踏板。 即使没有离合器踏板,驾驶员仍然可以通过翘板开关、按钮或换挡杆“告诉”计算机何时采取动作。
       轻松的驾驶体验仅仅是双离合器变速器带来的众多优点之一。 由于升挡仅需要8毫秒,很多人都认为,双离合器变速器在市场上现有的任何车辆中可以提供最为凌厉的加速度。 由于双离合器变速器消除了手动变速器中伴随换挡带来的换挡冲击(甚至有些自动变速器中也存在),自然可以提供平稳的加速。 最为突出的优点是,双离合器变速器可以让驾驶员自由选择是自己控制换挡还是交由计算机来完成。
       双离合器变速器最为引人关注的优点可能是节油。 由于从发动机到变速器的动力传送不会发生中断,因此可以显著降低油耗。 有些专家认为,六速双离合器变速器与传统的五速自动变速器相比,最多可以节油10%。
       很多汽车制造商都对双离合器变速器技术感兴趣。 不过,有些汽车制造商对于因改造生产线以提供新型变速器而带来的附加成本还存有顾虑。 这些附加成本最初会增加装备双离合器变速器汽车的成本,而这可能不会受到精明的消费者的欢迎。
       此外,有些制造商已经在替代变速器技术上投入了巨资。 最值得注意的一项技术就是无级变速器,即CVT。CVT是一种自动变速器,可使用移动的滑轮系统和皮带或链条,在一个很宽的范围内无级调节齿数比。 CVT还可以减少换挡冲击,并且可以显著降低油耗。 但CVT无法满足高性能汽车的高扭矩要求。
       双离合器变速器则没有这类问题,因而是高性能汽车的理想之选。 在欧洲,手动变速器凭借其性能和节油的优势成为人们的首选,因此有人预言,双离合器变速器将会占据25%的欧洲市场。 到2012年,西欧生产的汽车中将只有1%会安装CVT。
         
    附件2:外文原文
    How Dual-clutch Transmissions Work
       Most people know that cars come with two basic transmission types: manuals, which require that the driver change gears by depressing a clutch pedal and using a stick shift, and automatics, which do all of the shifting work for drivers using clutches, a torque converter and sets of planetary gears. But there's also something in between that offers the best of both worlds -- the dual-clutch transmission, also called the semi-automatic transmission, the "clutchless" manual transmission and the automated manual transmission.
       
       In the world of racecars, semi-automatic transmissions, such as the sequential manual gearbox (or SMG), have been a staple for years. But in the world of production vehicles, it's a relatively new technology -- one that is being defined by a very specific design known as the dual-clutch, or direct-shift, gearbox.
       This article will explore how a dual-clutch transmission works, how it compares to other types of transmissions and why some predict that it is the transmission of the future.
       
       Hands-On or Hands-Off
       A dual-clutch transmission offers the function of two manual gearboxes in one. To understand what this means, it's helpful to review how a conventional manual gearbox works. When a driver wants to change from one gear to another in a standard stick-shift car, he first presses down the clutch pedal. This operates a single clutch, which disconnects the engine from the gearbox and interrupts power flow to the transmission. Then the driver uses the stick shift to select a new gear, a process that involves moving a toothed collar from one gear wheel to another gear wheel of a different size. Devices called synchronizers match the gears before they are engaged to prevent grinding. Once the new gear is engaged, the driver releases the clutch pedal, which re-connects the engine to the gearbox and transmits power to the wheels.
       So, in a conventional manual transmission, there is not a continuous flow of power from the engine to the wheels. Instead, power delivery changes from on to off to on during gearshift, causing a phenomenon known as "shift shock" or "torque interrupt." For an unskilled driver, this can result in passengers being thrown forward and back again as gears are changed.
       
       A dual-clutch gearbox, by contrast, uses two clutches, but has no clutch pedal. Sophisticated electronics and hydraulics control the clutches, just as they do in a standard automatic transmission. In a DCT, however, the clutches operate independently. One clutch controls the odd gears (first, third, fifth and reverse), while the other controls the even gears (second, fourth and sixth). Using this arrangement, gears can be changed without interrupting the power flow from the engine to the transmission. Sequentially, it works like this:
       Dual-clutch Transmission Shafts
       A two-part transmission shaft is at the heart of a DCT. Unlike a conventional manual gearbox, this houses all of its gears on a single input shaft, the DCT splits up odd and even gears on two input shafts. How is this possible? The outer shaft is hollowed out, making room for an inner shaft, which is nested inside. The outer hollow shaft feeds second and fourth gears, while the inner shaft feeds first, third and fifth.
       
       Because a dual-clutch transmission is similar to an automatic, you might think that it requires a torque converter, which is how an automatic transfers engine torque from the engine to the transmission. DCTs, however, don't require torque converters. Instead, DCTs currently on the market use wet multi-plate clutches. A "wet" clutch is one that bathes the clutch components in lubricating fluid to reduce friction and limit the production of heat. Several manufacturers are developing DCTs that use dry clutches, like those usually associated with manual transmissions, but all production vehicles equipped with DCTs today use the wet version. Many motorcycles have single multi-plate clutches.
       
       Like torque converters, wet multi-plate clutches use hydraulic pressure to drive the gears. The fluid does its work inside the clutch piston, seen in the diagram above. When the clutch is engaged, hydraulic pressure inside the piston forces a set of coil springs part, which pushes a series of stacked clutch plates and friction discs against a fixed pressure plate. The friction discs have internal teeth that are sized and shaped to mesh with spines on the clutch drum. In turn, the drum is connected to the gear set that will receive the transfer force. Audi's dual-clutch transmission has both a small coil spring and a large diaphragm spring in its wet multi-plate clutches.
       
       To disengage the clutch, fluid pressure inside the piston is reduced. This allows the piston springs to relax, which eases pressure on the clutch pack and pressure plate.
       We'll look at the pros and cons of dual-clutch transmissions next.
       Pros and Cons of Dual-clutch Transmissions
       Hopefully it's becoming clear why the DCT is classified as an automated manual transmission. In principle, the DCT behaves just like a standard manual transmission: It's got input and auxiliary shafts to house gears, synchronizers and a clutch. What it doesn't have is a clutch pedal, because computers, solenoids and hydraulics do the actual shifting. Even without a clutch pedal, the driver can still "tell" the computer when to take action through paddles, buttons or a gearshift.
       Driver experience, then, is just one of the many advantages of a DCT. With up shifts taking a mere 8 milliseconds, many feel that the DCT offers the most dynamic acceleration of any vehicle on the market. It certainly offers smooth acceleration by eliminating the shift shock that accompanies gearshifts in manual transmissions and even some automatics. Best of all, it affords drivers the luxury of choosing whether they prefer to control the shifting or let the computer do all of the work.
       Perhaps the most compelling advantage of a DCT is improved fuel economy. Because power flow from the engine to the transmission is not interrupted, fuel efficiency increases dramatically. Some experts say that a six-speed DCT can deliver up to a 10 percent increase in relative fuel efficiency when compared to a conventional five-speed automatic.
       
       Many car manufacturers are interested in DCT technology. However, some automakers are wary of the additional costs associated with modifying production lines to accommodate a new type of transmission. This could initially drive up the costs of cars outfitted with DCTs, which might discourage cost-conscious consumers.
       In addition, manufacturers are already investing heavily in alternate transmission technologies. One of the most notable is the continuously variable transmission, or CVT. A CVT is a type of automatic transmission that uses a moving pulley system and a belt or chain to infinitely adjust the gear ratio across a wide range. CVTs also reduce shift shock and increase fuel efficiency significantly. But CVTs can't handle the high torque demands of performance cars.
       DCTs don't have such issues and are ideal for high-performance vehicles. In Europe, where manual transmissions are preferred because of their performance and fuel efficiency, some predict that DCTs will capture 25 percent of the market. Just one percent of cars produced in Western Europe will be fitted with a CVT by 2012.
        

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