车辆工程专业毕业论文 外文翻译2

车辆工程专业毕业论文 外文翻译2车辆与动力工程学院毕业设计说明书 Of all transmission technologies, the manual gearbox is the most efficient; around 96 per cent of the energy that is put in comes out of the other end. But not everyone can drive one or wants to. Because you have to dip the clutch pedal, it is less comfortable to drive in heavy traffic. It makes the driver tired and the torque interruptions head-nod effect on passengers can be wearing.The drivers clutch control and corresponding torque interruptions are also the manuals weak point. When accelerating up through the gearbox, each up-shift requires the driver to cut the torque momentarily by lifting the gas pedal and dipping the clutch. It may just take a second to complete the operation, but during this time the vehicle is losing speed and acceleration.At the opposite end of the spectrum is the traditional automatic. The modern transmission is by far, the most complicated mechanical component in todays automobile. It is a type of transmission that shifts itself .A fluid coupling or torque converter is used instead of a manually operated clutch to connect the transmission to the engine.There are two basic types of automatic transmissions based on whetherthe vehicle is rear wheel drive . On a rear wheel drive car , the transmission is usually mounted to the back of the engine and is located under the hump in the center of the floorboard alongside the gas pedal position . A drive shaft connects the rear of the transmission to the final drive which is located in the rear axle and is used to send power to the rear wheel. Power flow on this system is simple and straight forward going from the engine, through the torque converter , then through the transmission and driver shaft until it reaches the final driver where it is split and sent to the two rear wheel .On a front wheel drive car, the transmission is usually combined .With the final drive to from what is called a transaxle. The engine on a front wheel driver car is usually mounted sideways in the car with the transaxle tucked under it on 1车辆与动力工程学院毕业设计说明书the side of the engine facing the rear of the car. Front axles are connected directly to the transaxle and provide power to the front wheels. In this example, power flows from the engine through the torque converter to a large chain that sends the power through a 180 degree turn to the transmission that is along side the engine. From there，The power is routed through the transmission to the final drive where it is split and sent to the two front wheels through the drive axles. There are a number of other arrangements including front drive vehicles where the engine is mounted front to back instead of sideways and there are other systems that drive all four wheels but the two systems described here are by far the most popular. A must less popular rear drive arrangement has the transmission mounted to the final drive at the rear and is connected by a drive shaft to the torque converter which is still mounted on the engine. This system is found on the new corvette and is used in order to balance the weight evenly between the front and rear wheels for improved performance and handling. Another rear drive system mounts everything, the engine, transmission and final drive in the rear. This rear engine arrangement is popular on the Porsche.The modern automatic transmission consists of many components and systems that are designed to work together in a symphony of planetary gear sets, the hydraulic system, seals and gaskets, the torque converter, the governor and the modulator or throttle cable and computer consider being an art form.On the automobile planet gear mainly uses in two places, one is the driving axle reduction gear, two is the automatic transmission. Very many net friends all want to know that, the planet gear has any function, why automobile must have it . We knew very well the gear major part all rotates the spool thread fixed gear. For example mechanical type clock and watch, above all gears although all in make the rotation, but their rotation center (with center of a circle position superposition) often installs through the bearing on the cabinet, therefore, their rotating axis all is the relative cabinet fixed, thus also is called "dead axle gear" . Has must have surely moves, the corresponding place, some kind of not that manner knows very well is called "planet gear" the gear, their rotation spool thread is not fixed, but is installs the support which may rotate in (blue color) on 2车辆与动力工程学院毕业设计说明书(in chart black part is shell, yellow expression bearing). The planet gear (green) besides can look like the dead axle gear such to revolve own rotating axis (B-B) to rotate, their rotating axis also (is called planet) along with the blue color support to circle other gears the spool thread (A-A) to rotate. Circles oneself spool thread the rotation to be called "rotation", circles other gear spool threads the rotation to be called "revolution", looks like in solar system planet such, therefore acquires fame.The spool thread fixed gear drive principle is very simple, meshes mutually in a pair in the gear, some gear takes the driving pulley, the power spreads from its there, another gear takes the driven wheel, the power outputs from it toward outside. Also some gears only take the stopover station, at the same time meshes with the driving pulley, one side meshes in addition with the driven wheel, the power passes from its there.In contains the planet gear in the gear system, the situation was different. Because has the planet frame, in other words, may have three rotating axes permissions power input/Output, but also may use the coupling or the brake and so on method. in needs time limits axis the rotation, is left over two axes to carry on the transmission, as the matter stands, meshes mutually between the gear relations may have the many kinds of combinations: The power from sun gear input, outputs from other sun gear, the planet put through brake mechanism has checked dies; Power from sun gear input, from planet output, moreover a sun gear ecks dies; The power from a planet input, outputs from sun gear, moreover a sun gear checks dies; Two powers separately from two sun gears inputs, after synthesis from planet output; Two powers separately from the planet and sun gear input, after the synthesis output from other sun gear; The power from sun gear input, divides two groups outputs from other sun gear and the planet frame; The power from a planet input, divides two groups to output from two sun gears;Its shift quality is good thanks to its torque converter, but efficiency is relatively poor despite recent advances. Because of this, a lot of the current research is trying to find an efficient alternative to the conventional automatic. The main technologies are continuously variable transmissions (CVTs); dual 3车辆与动力工程学院毕业设计说明书clutch transmissions (DCTs) and automated manual transmission (AMTs).They all offer different benefits over the conventional planetary automatic.The CVT uses a belt chain or torodial shaped dish drive to vary an infinite number of gear ratios. It has improved efficiency and cost when compared to conventional automatics. Its advantage comes from its simplicity. It consists of very few components；usually a rubber or metal-link belt；a hydraulically operated driving pulley, a mechanical torque-sensing driving pulley, microprocessors and some sensors.The transmission works by varying the distance between the face of the two main pulleys. The pulleys have Vshaped grooves in which the connecting the belt rides. One side of the pulley is fixed axially; the other side moves, actuated by hydraulics.When actuated, the cylinder can increase or reduce the amount of space between the two sides of the pulley. This allows the belt to ride lower or higher along the walls of the pulley, depending on driving conditions. This changes the gear ratio. A torodial-type design works in a similar way but runs an discs and power- rollersThe "step less" nature of its design is CVTs biggest draw for automotive engineers .Because of this, a CVT can work to keep the engine in its optimum power range, thereby increasing efficiency and mileage. A CVT can convert every point on the equines operating curve to a corresponding point on its own operating curve.The transmission is most popular with Japanese carmakers and Japanese supplier JATCO is a major producer. But in the US and Europe driving styles are different. Uptake has been slow despite Audi and other manufacturers having Offered CVT operations on their ranges.The DCT is, in effect, two manual gearboxes coupled together. Gear shifts are made by switching from one clutch on one gearbox to another clutch on the other. The shift quality is equal to a conventional automatic, but slip, fluid drag and hydraulic losses in the system result in only slightly improved efficiency and acceleration over the conventional planetary automatic. Developing the control 4车辆与动力工程学院毕业设计说明书strategy is costly too."Resent advances in conventional automatic technology have weakened the argument to develop and set up production for CVT or DCT," says Bill Martin, managing director of transmission firm Zeroshift "Some carmakers have cancelled DCT projects because of the cost."The cheapest way to build an automatic is with an AMT. AMTs use actuators to replace the clutch pedal and gear stick of a conventional manual. They keep the high efficiency and acceleration of a manual gearbox, but the shift quality on some models is lacking. Torque interruptions and the head-nod effect are the most common complaint.SO what is the alternative? There are always new ideas in transmissions, but Zeroshift says that its technology has efficiency benefits over a manual, delivering fuel economy improvements to city driving. Shift quality can also be equal to that of a refined automatic.Zeroshifts approach is an upgrade to the AMT. The synchromesh is replaced with an advanced dog engagement system.Dog engagement has been used for many years in motor sport to allow fast shifts. Conventional dog Boxes are unsuitable for road use as the large spaces between the drive lugs or dogs" create backlash, an uncomfortable shunt caused by the sudden change in torque direction.Zeroshifts technology solves this problem by adding a second set of drive dogs. It has also made each of The two sets of dogs only capable of transmitting torque in one or otheropposing directions By controlling the engagement and disengagement of the two sets you can shift into the new gear before disengaging the previous gear," says Martin "The shift quality is smoother than a typical modern six-speed automatic luxury car"The shift is instant and the torque is not interrupted. This philosophy is used for both up and down shifts."In conventional AMT there is an emissions spike during a shift due to the need to back off and reintroduce throttle, this is eliminated by going seamless," says Martin.” This also reduces fuel consumption. “5车辆与动力工程学院毕业设计说明书It is a relative newcomer to the transmission sector, but the firm says that it is already attracting the attention of major European and US carmakers. The big draw is as a low-cost alternative to DCT, says Martin.Because the manual gearbox architecture is largely maintained, production costs and complexity are not greater than for a conventional AMT. Development of tile controls side is also considerably cheaper. Music to the ears of engineers trying to cut emissions and costs."Most of the carmakers have seen the system at least once," says Martin "Some signed us up immediately some have said not yet. None have said no." That may be the clearest sign yet that when it comes to power train developments, carmaker are starting to focus on the transmission.How zeroshift works? The hardware consists of two sets of bullets mounted and actuate on two independent bullet rings. Both set of bullets run on the common hub, which is attached to the shaft with splints.Each bullet has a special profile. On one side they have an angled face for engagement. These are diagonally opposed, allowing the bullet to have a drive function for one gear and an overrun function for the other gear. The engagement faces taper backwards slightly to ensure the bullet latches onto the engaged under load.The opposite corners have a ramp, which pushes the bullet out of the previous gear once the new gear has been engaged.In neutral both bullet rings are positioned midway between the ratios. To select first gear, the bullets are moved into mesh with the engagement dogs. The bullets are actuated via shift forks connected to the shift actuators.6车辆与动力工程学院毕业设计说明书变速器 所有变速箱技术中，手动变速器的效益最高，输出功率可达到输入功率的96%，但并不是所有的人都能驾驭手动变速箱，也不是所有人愿意用它。因为用手动变速器需要踩离合器，这是在交通繁忙的时候很不舒服，驾驶员容易疲劳，而由扭矩中断导致的“点头”效应也会使乘客很难受。由驾驶员操纵离合器而产生的扭矩中断是手动变速器主要的缺点。在换档加速时，驾驶员都必须通过松开油门并踩下离合器来使扭矩中断，完成整个过程大概需要一秒，但在这段时间里车辆会暂时停止加速，速度也会降低。与此截然不同的是自动变速箱，到目前为止现代汽车自动变速器是汽车上最复杂的元件。它是一种可以自己换挡的变速器。力矩转换器或流体联合器被用来代替手动离合器连接发动机。汽车上变后轮驱动或前轮驱动是车辆自动变速器的两种基本类型。在一个后轮驱动的速器通常放在发动机后面凸起后长板旁边气体踏板下方的位置。驾驶杆连接变速器后端，最终驾驶的准确位置在后轴，用操纵力控制后轮。发动机的动力简单连续的在这个系统中循环，在通过变速器时改变力矩，通过传动轴后在主减速器分流到两后轮。在前轮驱动汽车中，变速器常常兼有最终驱动叫做变速驱动桥。前轮驱动汽车通常在发动机的后下方安装有横向变速驱动桥。前桥直接连接在发动机的变速驱动桥上为前轮提供动力，动力从发动机出发转过一个大链条后经180转变传给变速器。从而，将主动力通过变速器后分流传到驱动轴再送到两前轮。也有一些其他方式的前轮驱动车辆，车架前方代替另一边的其他系统驱动四轮，但在这儿仅对其中的两个系统进行说明。相对于前轮驱动来说最流行的是后轮驱动，在发动机上连接一个输出轴，将改变后的力矩传给后驱动轮。这个系统是探寻前后轴实施改进的新的节能动力平衡装置。另一个驱动系统是把所有的驱动零件都按在后轮上。这种排列方式发动机通常后置。现代自动变速器由许多的部件和系统组成，它们有行星齿轮组、液压系统、密封圈和密封衬垫、变矩器、油压调节器、调制器、节气门拉线、电子 7车辆与动力工程学院毕业设计说明书控制装置等，经精心设计运转协调，其中的电子控制装置经历了多年的发展，已经以巧妙的形式溶入了许多人性化的设计。汽车上的行星齿轮主要用在两个地方，一是驱动桥减速器、二是自动变速器。很多网友都想知道，行星齿轮有什么功能，为什么汽车少不了它。我们熟知的齿轮绝大部分都是转动轴线固定的齿轮。例如机械式钟表，上面所有的齿轮尽管都在做转动，但是它们的转动中心（与圆心位置重合）往往通过轴承安装在机壳上，因此，它们的转动轴都是相对机壳固定的，因而也被称为"定轴齿轮"。轴线固定的齿轮传动原理很简单，在一对互相啮合的齿轮中，有一个齿轮作为主动轮，动力从它那里传入，另一个齿轮作为从动轮，动力从它往外输出。也有的齿轮仅作为中转站，一边与主动轮啮合，另一边与从动轮啮合，动力从它那里通过。在包含行星齿轮的齿轮系统中，情形就不同了。由于存在行星架，也就是说，可以有三条转动轴允许动力输入/输出，还可以用离合器或制动器之类的手段，在需要的时候限制其中一条轴的转动，剩下两条轴进行传动，这样一来，互相啮合的齿轮之间的关系就可以有多种组合：动力从其中一个太阳轮输入，从另外一个太阳轮输出，行星架通过刹车机构刹死；动力从其中一个太阳轮输入，从行星架输出，另外一个太阳轮刹死；动力从行星架输入，从其中一个太阳轮输出，另外一个太阳轮刹死；两股动力分别从两个太阳轮输入，合成后从行星架输出；两股动力分别从行星架和其中一个太阳轮输入，合成后从另外一个太阳轮输出；动力从其中一个太阳轮输入，从另外一个太阳轮和行星架分两路输出；动力从行星架输入，分两路从两个太阳轮输出。由于采用了变矩器，这种变速器的换档质量不错但效率相对较差虽然目前有所改进。因此，目前进行了许多研究，试图发现传统变速器的有效的代替方案。主要的技术还是无级变速器（CVT）、双离合变速（DCT）和手自一体（AMT）变速器。它们在不同的方面优于传统的行星齿轮式自动变速器。无级变速器采用带、链或锥盘滚轮来产生无限多种速比，与传统自动变速器相比其效率和成本都有所改善。之所以有这些优点，是因为它结构简单，这种变速器的零部件很少，通常只有一根橡胶或金属传动带、一个液压作用的驱动带轮、一个机械扭矩感应式驱动带轮、一些微处理器和传感器等。这种变速器的工作原理是改变两个主带轮表面之间的距离，带轮上挂传 8车辆与动力工程学院毕业设计说明书动带的地方开了V形槽，一侧的带轮沿轴向固定，另一侧的带轮可在液压的作用下移动。在驱动轮后，液压缸可增加或减少带轮两侧之间的距离，这样会使传动带在带轮侧壁上的位置上下变动，变动的方式取决于驾驶情况。这样就会使变速比改变。锥盘滚轮型变速器的工作原理与此类似但用的是驱动盘和动力滚轮。CVT（无极）变速器的特点对技术人员最具有吸引力。因为这样没有档位，CVT可使发动机保持在最佳的功率范围9车辆与动力工程学院毕业设计说明书Zeroshift公司通过增加第二套驱动犬牙来解决这一问题，这种技术还使每组犬牙只能传递两种相反方向扭矩中的一种。“通过对两套犬牙的啮合和分离，可在上一个档位没有分离的情况下换入新的档位。”马丁说，“换档质量超过采用现代化的6档变速器的豪华轿车。”换档可在瞬间完成，而扭矩不发生中断，而且这种方法既可用于升档又可用于降档。“在使用传统的AMT变速器时，由于需要关闭并重新打开油门，换档过程中排放会达到高峰，而通过这种无过渡的换档方式可以消除这种现象。”马丁说，“这样还能降低燃油消耗。”“尽管在技术上变速器领域还比较新，但公司称已经引起了欧美各大汽车制造商的注意，最大的吸引力在于其成本比DCT低”，马丁说。由于可以保留大部分手动变速器的结构，这种变速器的成本和复杂性都不会高于传统的AMT变速箱。控制系统的成本也会大大降低，这对试图减少排放和削减成本的工程师来说是个好消息。“大部分制造商都来参观过，”马丁说，“有些公司马上就和我们签合同，另一些未作决定，拒绝的一个都没有。”这再清楚不过的表明了汽车制造商现在正在将动力系统开发的重点转移到变速箱上。Zeroshift公司的变速系统是怎样工作的呢？它的硬件部分包括两套犬牙，安装在两个独立的犬牙环上并受其驱动，两套犬牙有一个共同的盖，盖和一个花键轴相连。每个犬牙都有特殊的轮廓。在一侧是用于啮合的直角面。这些直角面是沿对角线相对的，这样的犬牙在对某一个档位具有驱动功能的同时，对另一个档位具有超越传动的功能。啮合面有轻微的后向锥度，以保证犬牙能在加载时锁定在啮合齿轮上。相对角上有一个斜坡，可在新档位啮合后将犬牙从前一个档位推离。 在空档时，两个犬牙环处于变速比的中间位置。选一档时，犬牙会发生移动并和犬牙啮合面发生啮合。犬牙通过与换档执行器相连的换档拨叉驱动。驱动犬牙将一档齿轮与输出轴锁定在一起，将扭矩从齿轮传递到输出轴。一档的超越传动犬牙也会移动并将齿轮以相反的方向和输出轴锁定。这样可以在油门关闭且发动机倒拖时将扭矩从齿轮传递到输出轴。这样就消除了犬牙啮合式变速器常见的后坐现象。10车辆与动力工程学院毕业设计说明书在加大油门换档时，一档齿轮的超越传动犬牙卸载后和二档齿轮啮合。然后换入二档时，前一个驱动环卸载。如果犬牙之间不能完全啮合，即实现两个犬牙面之间的啮合，由于相对速度差的存在，二档齿轮会打开一个啮合缺口。在犬牙抵住啮合面后，在拨叉和执行器的共同作用下，储存的能量会将犬牙送入缺口内。此时，一档超越传动犬牙成为二档的驱动犬牙。在换入二档后，一档的驱动犬牙随即卸载。这时候，这些犬牙不再受其固定面固定，可以被执行器或犬牙上的斜面推离档位。 11