求一篇无级变速器的外文翻译,中英都要,英文要2000~3000词的,谢谢,邮箱:chuwanxinxin@163.com

CVT(CONSTANT VARIABLE TRANSMISSION)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.编辑本段无级变速器和自动变速器的渊源
　　自动变速器是为了简便操作、降低驾驶疲劳而生的,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.编辑本段无级变速器分类
　　为实现无级变速,按传动方式可采用液体传动、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.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 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 of the CVT vehicles already more and more. Editor this section step-less transmission and the origin of the automatic transmission
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 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 technologies. 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), 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. Editor 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 composed 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 The 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, sliding 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 belongs 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 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 ac 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 characteristic 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, maintenance 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 sliding 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 overload and poor, so general suitable for medium and small power transmission. 已发送,望采纳