1、译文题目：Automobile Transmission汽车变速器学生姓名：学 号：0专 业：机械设计制造及其自动化（现代汽车技术）所在学院： 机 电 工 程 学 院指导教师：职 称：讲 师2012 年 2 月 20 日Automobile TransmissionAs we know , an engine can generate only limited torque at low speeds .Driving condition is very complicated and this required the tractive effort and speed vary in a
2、large scope .And without sufficient torque , moving a heavily loaded vehicle from a standing start is impossible . In any engine , the crankshaft always rotates in the same direction . If the engine transmitted its power directly to the drive axles , the wheels could be driven only in one direction.
3、Given a level road ,an automobile without a transmission could be made to move by accelerating the engine and engaging the clutch . However , a start under these conditions would be slow , noisy and uncomfortable . In condition , it would place a tremendous strain on the engine and driving parts of
4、the automobile.So in order to get smooth starts and have power to pass and climb hills , a power ratio must be provided to multiply the torque and turning effort of the engine . Also required is a speed ratio to avoid the need for extremely high engine rpm at high road speeds . The transmission is g
5、eared to perform these functions . A transmission is a speed and power changing device installed at some point between the engine and driving wheels of the vehicle . It is designed for changing the torque transmitted form the engine crankshaft to the propeller shaft , reversing the vehicle movement
6、and disengaging the engine from the drive line for a long time at parking or coasting . A higher torque should be applied to the wheels to set an automobile in motion or move uphill with a full load than to keep it rolling after it gets under way on level stretches of the road , when inertia is high
7、 and tractive resistance is low . To meet these variable torque requirement , special gear boxes are used . Such gear boxes are called fixedratio transmissions . The transmission consists of a housing , an input shaft and gear , an output shaft and gear , an idler shaft , a reverse gear , a cluster
8、of gears and a gear shift mechanism . The housing is cast of iron which has upper and side covers and bores for the installation of shafts . The bottom and side walls are provided with holes for filling and draining oil . The input shaft is made of steel integral with the driving gear and the rim .
9、The front end of the input shaft is installed on the bearing in the bore of the crankshaft , while the rear end rotates in the bore of the front wall of the housing . The input shaft is arranged so that only the driving gear and the rim are accommodated inside the housing while the splined portion o
10、f the shaft protruding from the transmissions carries the hub of the clutch driven disk . The output shaft is splined and rests with its front end on a roller bearing installed in the bore of the input shaft . The other end of the output shaft rotates in a ball bearing in the transmission housing wa
11、ll . The output shaft splines carry the sliding gear . The output shaft is coaxial with the input shaft . The idler shaft carries a cluster of gears of different sizes . The cluster is mounted in the roller bearings on an axle or , together with the shaft , on bearings in the housing wall bores . Th
12、e idler shaft constantly rotates with the input shaft because their gear in constant mesh . The reverse gear rotates on an axle secured in the holes of the housing walls .The gear shift mechanism is designed for engaging gears , setting them neutral and engaging the reverse speed . The speeds are ch
13、anged by shifting the gear or sleeves along the output shaft . The transmission type depends on the number of the sliding gears or sleeves . The transmission with two sliding gears or synchronizer sleeves is called two-range , with three gears ,three-range . Depending on the number of forward speeds
14、 there are three , four and five-speed transmission . The gear shift mechanism is mounted on the top cover . The shift lever is arranged on the cover or on the bracket of the lever support . The transmission gear are shifted by means of a gear shift mechanism . The gear shift mechanism consists of a
15、 lever , shift rails , shift forks , retainers , locks and a reverse speed safety device . The shift lever mounted on the transmission cover has a spherical bulb housed in a socket in the cover boss . A pin keeps the lever against rotation . The cover drillings accommodate shift rails which carry th
16、e shift forks and shift blocks with slots . The lower end of the lever enters the slots of the shift blocks . The forks fit into the grooves of the sliding gears and synchronizer sleeves . To change a speed , the upper end of the lever is slid to a certain position , the lower end of the lever moves
17、 the shift block and the latter pushes the shift rail with the fork and gear until the required speed is engaged . Retainers keep the gears in the engaged or neutral positions .The retainer consists of a ball and a spring accommodated in a channel drilled in the transmission cover . The shift rail h
18、as slots whose number is equal to that of speeds engaged by the given shift , plus one slot for neutral . When the transmission is in gear or in neutral , the ball is forced into the slot to lock the shift rail . To move the shift rail when changing gear , the force applied to it must be sufficient
19、to push the ball out of the slot . During a gear change , the lower end of the lever may stop between two shift blocks and move two shift rails simultaneously , thereby engaging two speeds at once . As the output shaft cannot rotate at two different speeds simultaneously , this will result in breaki
20、ng the gear teeth . Simultaneous engagement of two gear is prevented by locks . The locks are made in the form of balls of bars located in a horizontal channel between the shift rails . The shift rails gave recesses which align with the channel of the locks when the shift rails are in the neutral po
21、sition . The length of the lock bar plus the diameters of two balls is equal to the distance move any of the shift rails before a part of the ball or the end of the bar snaps into the recess of the other shift rail thus locking the latter .Transmission has a lot of kinds, be roughly divided into man
22、ual transmission, auto transmission and automatic transmission. And for one of the automatic transmission, CVT used more widely. CONSTANT VARIABLE TRANSMISSION (CVT) technology that is stepless speed technology, it USES belt and the work of the Lord diameters driven pulley, cooperated with the power
23、 to deliver, can realize the transmission ratio of the continuous change, and get the TRANSMISSION and engine condition the best match between. Common step-less transmission have hydraulic mechanical step-less transmission and belt type step-less transmission (VDT-CVT), the current domestic market o
24、f the CVT vehicles already more and more. Automatic transmission is easy to operate, reduce fatigue driving, born of the gear drive system, the control method, it can be divided into the hydraulic controlled hydraulic and electric automatic transmission hydraulic automatic transmission; According to
25、 the change of the transmission way and can be divided into have levels of automatic transmission and no levels of automatic transmission. Therefore, step-less transmission is actually a kind of automatic transmission, but it than common automatic transmission is much more complex, more advanced tec
26、hnologies. Step-less transmission and common hydraulic automatic transmission of the biggest differences is on the structure, the latter is by hydraulic control gear drive system structure, still have the gears, it can be realized in between the two block is continuously variable transmission (evt),
27、 and is two groups plate and a belt speed of than traditional automatic transmission, simple structure, smaller. In addition, it is free to change gear ratios, so as to realize the full speed stepless speed change, make more smoothly, without the traditional transmission shift at the “ feeling. Edit
28、or this section step-less transmission classification To realize stepless speed, driving mode can be adopted according to the liquid transmission, power transmission and mechanical drive three ways. Liquid transmission Liquid transmission is divided into two kinds: one kind is hydraulic, mainly is c
29、omposed by the pump and motor or the valve and pump variable speed of transmission device, apply to small and medium-sized power transmission. Another kind is hydraulic type, adopts hydraulic coupler or hydraulic torque of variable speed drive, used in high power (kw). To hundreds of thousands of Th
30、e main characteristics of liquid transmission is: speed range, can absorb the impact and big to prevent transmission efficiency high, overload, long life, easy to realize automation: manufacturing precision demand is high, the price is more expensive, output characteristics for constant torque, slid
31、ing rate is bigger, running vulnerable to leak. Power transmission Power transmission basically is divided into three categories: one kind is electromagnetic sliding type, it is in the asynchronous motor installed in electromagnetic clutch, sliding by changing its exciter current to speed, this belo
32、ngs to a kind of relatively backward speed adjustment way. The characteristics of simple structure, low cost, convenient operation and maintenance, sliding, low efficiency, biggest fever, not suitable for long-term serious load operation, the general used only for small power transmission. Second is
33、 the dc motor type, changes in the magnetic flux or change the armature voltage realize the speed. Its characteristic is speed range, high precision, large and complex, high cost but equipment, maintenance difficulties, are used for medium power range (dozens to hundreds of kw), has gradually been a
34、c motor type instead. Three kinds of ac motor type is, through the change pole, pressure control and frequency conversion for the speed. The most practical application for variable frequency speed regulation, namely deserve using a horns, and then get luffing power drive motor variable speed. Its ch
35、aracteristic is the speed performance is good, range, high efficiency, it can automatic control, small volume, it is suitable for a wide range of power: mechanical properties in single reducing speed constant torque, low efficiency and low speed running smooth enough, the price is higher, maintenanc
36、e should be professional. In recent years, frequency converter as an advanced, excellent variable speed device rapid development of machinery, step-less transmission produced a certain impact. Mechanical transmission The main characteristic of the mechanical transmission is stable, rotate speed slid
37、ing rate, reliable, and has small constant power mechanical properties, the transmission efficiency is high, and simple structure, convenient maintenance, the price is relatively cheap; But parts processing and lubrication to demand higher bearing capacity, low resistance, resistance to impact overl
38、oad and poor, so general suitable for medium and small power transmission.汽车变速器正如我们所知道的,一个引擎在较低速度的情况下只能生成有限的控制力矩。然而对于驾驶条件非常复杂的情况，这就要求汽车的牵引力和速度能够在一个较大的范围内变动。如果没有足够的力矩，将一辆高负荷的汽车从静止开始启动几乎是不可能的。对于任何汽车的引擎，曲轴总是朝着同一个方向旋转，因此当你发动机的功率直接传输到驱动轴上,那么车轮可能仅仅朝着一个方向上驱动。在一平坦的道路上，对于一辆没有变速器的汽车而言,同样可以加速引擎和踩下离合正常行驶。然而，在这些
39、条件下的启动将是缓慢，嘈杂和不舒服的。并且在这种状态下，汽车的发动机和驱动部件将承受着很大的压力。因此，为了得到平稳的启动和足够的爬坡能力，就需要一种装置来提供功率比，用它与扭矩和发动机的转动力矩之积来达到这一目标。并且这种装置还需提供速度比来满足在高速状态下所需的极高的引擎转速。汽车变速器的安装就是用来执行这些功能的。汽车变速器，是一个改变力矩和速度的装置。它被安装在汽车发动机与驱动轮之间。其设计的目的是为了改变发动机曲轴转矩的传播形式，从而改变车辆运动使其能够在停车或滑行时长时间的将发动机与驱动轴分离。对于汽车产生的高转矩，它应当应用于汽车在运动中或满载情况下，而不是应用在惯性很大、牵引阻
40、力较小，能够维持车辆在水平的路面上的行驶的情况。为了满足这些可变转矩的要求，一种特殊的齿轮箱被应用其中。这种齿轮箱被称为固定比例式变速器。一般的变速器由变速器外壳，输入轴及其装置，输出轴及其装置，从动轴，倒档齿轮，齿轮组和齿轮变换机制组成。变速器外壳由钢铁铸成，它由顶部，侧盖和轴安装孔组成。在其底部和侧壁装有提供填充和排放油的细孔。变速器输入轴由整体钢纤组成，包括主动齿轮和轮辋。输入轴前端安装在曲轴轴承孔上，而后端则安装在变速器外壳的侧壁孔内旋转。输入轴的安装导致只有主动齿轮和轮辋被安装在外壳内，而轴的花键部分从变速器向外突出以运载离合器从动盘的轮毂。输出轴与输入轴用花键相连，输出轴前端的滚动
41、轴承安装在输入轴的孔内，其另一端的旋转球轴承安装在变速箱壳体内，输出轴花键滑动齿轮，从而使输出轴与输入轴同轴。变速器的从动轴由一群大小不同的齿轮组成。这些大小不同的齿轮有的安装在车轴的滚子轴承上，有的与轴一起安装在变速器外壳壁孔的轴承上。由于从动轴与输入轴常啮合，所以从动轴一直与输入轴旋转。而倒档齿轮转动轴则固定在变速器外壳上。齿轮变换机制是为接合齿轮而设计的，它可以使汽车处于空挡和倒档。汽车的速度变化通过输出轴移动齿轮或轴套来实现。变速器的类型取决于变速齿轮组的数量或轴套。有两个变速齿轮或同步轴套的变速器称为双距离式变速器，有三个齿轮，三个范围。根据变速器前进速度来区分，变速器则有三，四，五
42、速变速器。齿轮变化机制被安装在变速器的顶壳上，而变速杆则被安排在杆座的盖或支架上。传动齿轮通过齿轮变化机制转向换档。齿轮变化机制由一个杠杆, 拨叉轴，换挡拨叉，定位器,联锁装置和一个反速度安全装置组成。变速杆安装在变速器的盖体上，有一球形灯泡装在盖上的插座内。齿轮变化机制内部装有销来维持杠杆静止，不随齿轮旋转。换挡拨叉安装在变速器盖体孔内，用来实现拨叉与移动块在插槽上的运动。杠杆下端装在移位块的插槽内。换挡拨叉与变速齿轮的凹槽和同步器套筒相匹配。想要改变速度，将杠杆的上端下滑到一定的位置，杠杆下端移动移位块，然后利用拨叉和齿轮来推动拨叉轴，从而达到所需的速度。齿轮变化机制中的固定器起到了保持齿
43、轮运转或出于空挡状态。变速器中的定位器是由一个滚珠和弹簧组成，它们与安装在变速器壳体上的轨道相配合。拨叉轴插槽的数量等于为了得到所需变换速度而参与的插槽数量与一个正处于空挡的插槽数量之和。当变速器处于正常工作状态或者处于空挡时，滚珠被压入插槽,锁止拨叉轴。当变速器处于换挡状态时，则需要有足够的力将插槽中的滚珠推出从而移动拨叉轴。当齿轮变化时, 杠杆的下端会停止在两个滑块的中间同时的移动两个拨叉轴，从而同时实现两个速度的变化。由于输出轴不能够同时的以两种速度旋转，如果这样的话将会导致齿轮损坏。因此，两个齿轮同时结合是不可能的，它们由联锁装置来实现。连锁装置被制成一种球的形式安装在位于拨叉轴之间的
44、一条水平通道上。当拨叉轴处于空挡状态时，他将会与联锁装置相配合。锁定杆的长度和两个球的直径距离之和等于从一根拨叉轴突然将滚珠移动至另一个拨叉轴，从而锁止后者所移动的距离。变速器有很多种，大致可分为手动变速器，半自动变速器和自动变速器。而对于自动变速器中常见的一种，CVT 的应用越来越广泛。CVT 技术即无级变速技术，它采用传动带和工作直径可变的主、从动轮相配合来传递动力，可以实现传动比的连续改变，从而得到传动系与发动机工况的最佳匹配。常见的无级变速器有液力机械式无级变速器和金属带式无级变速器（VDT-CVT），目前国内市场上采用 CVT 的车型已经越来越多。自动变速器是为了简便操作、降低驾驶疲
45、劳而生的，按齿轮变速系统的控制方式，它可以分为液控液压自动变速器和电控液压自动变速器；按传动比的变化方式又可分为有级式自动变速器和无级式自动变速器。因此，无级变速器实际上是自动变速器的一种，但它比常见的自动变速器要复杂得多，技术上也更为先进。无级变速器与常见的液压自动变速器最大的不同是在结构上，后者是由液压控制的齿轮变速系统构成，还是有挡位的，它所能实现的是在两挡之间的无级变速，而无级变速器则是两组变速轮盘和一条传动带组成的，比传统自动变速器结构简单，体积更小。另外，它可以自由改变传动比，从而实现全程无级变速，使车速变化更为平稳，没有传统变速器换挡时那种“顿”的感觉。为实现无级变速，按传动方式
46、可采用液体传动、电力传动和机械传动三种方式。液体传动液体传动分为两类：一类是液压式，主要是由泵和马达组成或者由阀和泵组成的变速传动装置，适用于中小功率传动。另一类为液力式，采用液力耦合器或液力矩进行变速传动，适用于大功率（几百至几千千瓦）。 液体传动的主要特点是：调速范围大，可吸收冲击和防止过载，传动效率较高，寿命长，易于实现自动化：制造精度要求高，价格较贵，输出特性为恒转矩，滑动率较大，运转时容易发生漏油。电力传动电力传动基本上分为三类：一类是电磁滑动式，它是在异步电动机中安装一电磁滑差离合器，通过改变其励磁电流来调速，这属于一种较为落后的调速方式。其特点结构简单，成本低，操作维护方便：滑动
47、最大，效率低，发热严重，不适合长期负载运转，故一般只用于小功率传动。 二类是直流电动机式，通过改变磁通或改变电枢电压实现调速。其特点是调速范围大，精度也较高，但设备复杂，成本高，维护困难，一般用于中等功率范围（几十至几百千瓦），现已逐步被交流电动机式替代。 三类是交流电动机式，通过变极、调压和变频进行调速。实际应用最多者为变频调速，即采用一变幅器获得变幅电源，然后驱动电动机变速。其特点是调速性能好、范围大、效率较高，可自动控制，体积小，适用功率范围宽：机械特性在降速段位恒转矩，低速时效率低且运转不够平稳，价格较高，维修需专业人员。近年来，变频器作为一种先进、优良的变速装置迅速发展，对机械无级变速器产生了一定的冲击。机械传动机械传动的特点主要是：转速稳定，滑动率小，工作可靠，具有恒功率机械特性，传动效率较高，而且结构简单，维修方便，价格相对便宜；但零部件加工及润滑要求较高，承载能力较低，抗过载及耐冲击性较差，故一般适合于中、小功率传动。
