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无级
调速
提升
绞车
设计
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- 资源描述：
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无级调速提升绞车设计
46页-15000字数+说明书+开题报告+任务书+外文翻译+4张CAD图纸
中英文摘要.doc
任务书.doc
原创性声明.doc
变速系统图.dwg
外文翻译--汽车制动系统.doc
总装图.dwg
无级调速提升绞车设计开题报告.doc
无级调速提升绞车设计说明书.doc
论文封面.doc
输入轴.dwg
零件图.dwg
目 录
前 言
1传动方案的拟定和选择
1．1 拟定方案2
1．1．1具体方案的拟定和比较2
1.2 方案的确定6
2 电动机的选择
2. 1 主电动机的选择7
2．1．1 电动机类型和结构形式选择7
2．1. 2选择电动机容量7
2. 2 无级变速电动机的选择8
2．2．1分析绞车的工作过程：8
2．2．2 分析电动机的具体工作情况8
2．2．3 电动机容量的计算10
2．2．4 电动机类型的选择11
3 交流变频调速系统
3.1 调速系统介绍11
3.2 不同交流电动机调速系统的优缺点12
3．3 变频控制方式的选择14
3．4 确定变频器15
3．5 JPS变频器的功能、原理、技术参数等15
3.5.1概述15
3.5.2型号意义16
3.5.3 技术参数及性能17
3.5.4 外形及安装尺寸18
3.5.5 使用维护注意事项18
4 行星齿轮的计算
4.1 行星齿轮基本参数的计算19
4.1.1 传动装置的总传动比及分配19
4.1.2 行星齿轮传动的配比计算20
4.1.3 轮齿数的选择22
4.2 行星齿轮传动设计与计算22
4.3 选择材料、齿轮、传动比23
4.4 无级变速电动机输入齿轮传动计算33
5 传动系统的其他设计
5.1均载机构设计37
5.2 行星架的设计37
5.3 箱体的基本参数38
5.4 变速轴的设计38
总 结40
参考文献41
致 谢42
摘要
该系统主要是以行星齿轮传动和变频交流调速电动机调速为核心，由主电动机、变频交流调速电动机和行星齿轮传动三大部分组成。绞车的工作情况由以下三种情况：一是启动，即启动加速阶段；二是正常运转，即绞车匀速提升或下降阶段；三是停车，即绞车减速停止阶段。绞车起动和停止是无级变速的，由交流变频器和三相力矩异步电动机组成无级变速装置，通过差动轮系实现输出轴的无级变速；绞车的提升阶段，调速电动机处于堵转阶段，只有主电动机和2K-H行星轮处于工作状态。
本次设计主要任务是进行传动方案的选择与确定，传动装置的运动、动力的计算和传动零件的设计计算。提升绞车传动系统中的主要机械部分是差动式行星齿轮减速器，为了提高传动效率，减小机构的尺寸和重量，采用的是2K-H单排行星齿轮机构和调速齿轮组成的差动轮系。在该轮系中2K-H行星齿轮传动是绞车匀速运行的核心，因此也就成为本次设计的主题了，在设计中主要是进行以下几方面的工作：1、传动比计算；2、齿数选择；3、传动的几何计算；4、传动的受力分析；5、强度计算；还有行星架结构的选择、均载机构的设计、减速箱体结构尺寸的设计等等。 绞车的无级调速是由变频交流调速电动机来完成的，其主要完成绞车的启动、停止。电气部件主要是变频器，调速系统采用正弦脉冲宽度调置（SPWM）型变频器和YLJ系列三相异步力矩电动机组成。对电气部分的设计主要是进行变频器的类型、参数选择，还有电动机的类型和容量选择
该系统采用电气和机械组合，集结了机电两大方面的优点于一身，使得该系统的总体性能得到很大的提高，从而使得该产品有着更广阔的前景。
关键词：差速器、无级调速、绞车
II、毕 业设计(论文)使用的原始资料(数据)及设计技术要求：
1. 绞车提升速度：0.5～4.5m/s；
2. 绞车滚筒直径：1200mm；
3. 最大提升重量：1000Kg；
4. 提升速度可无级变速；
5. 有制动装置。
- 内容简介：
-
无 级 变 速 提 升 绞 车学生姓名：程晓军 班级：0881054指导教师：朱保利摘要 该系统主要是以行星齿轮传动和变频交流调速电动机调速为核心，由主电动机、变频交流调速电动机和行星齿轮传动三大部分组成。绞车的工作情况由以下三种情况：一是启动，即启动加速阶段；二是正常运转，即绞车匀速提升或下降阶段；三是停车，即绞车减速停止阶段。绞车起动和停止是无级变速的，由交流变频器和三相力矩异步电动机组成无级变速装置，通过差动轮系实现输出轴的无级变速；绞车的提升阶段，调速电动机处于堵转阶段，只有主电动机和2K-H行星轮处于工作状态。 本次设计主要任务是进行传动方案的选择与确定，传动装置的运动、动力的计算和传动零件的设计计算。提升绞车传动系统中的主要机械部分是差动式行星齿轮减速器，为了提高传动效率，减小机构的尺寸和重量，采用的是2K-H单排行星齿轮机构和调速齿轮组成的差动轮系。在该轮系中2K-H行星齿轮传动是绞车匀速运行的核心，因此也就成为本次设计的主题了，在设计中主要是进行以下几方面的工作：1、传动比计算；2、齿数选择；3、传动的几何计算；4、传动的受力分析；5、强度计算；还有行星架结构的选择、均载机构的设计、减速箱体结构尺寸的设计等等。 绞车的无级调速是由变频交流调速电动机来完成的，其主要完成绞车的启动、停止。电气部件主要是变频器，调速系统采用正弦脉冲宽度调置（SPWM）型变频器和YLJ系列三相异步力矩电动机组成。对电气部分的设计主要是进行变频器的类型、参数选择，还有电动机的类型和容量选择该系统采用电气和机械组合，集结了机电两大方面的优点于一身，使得该系统的总体性能得到很大的提高，从而使得该产品有着更广阔的前景。 关键词：差速器、无级调速、绞车 指导教师签名：stepless gearshift take-up winchStudent name: xiaojun cheng class: 0881054Supervisor: baoli zhuAbstract：Spherical gearing and changing speed by the motor of variant frequency and periodic juice is the core of this system, which is made up of central motor, the motor of variant frequency and periodic juice and spherical gearing. There are three procedures. Now it is described as follows. The first one is to switch on the machine, which means to start the case of acceleration. The second one is well-regulated operation. In this case, the machine can uprear and drop in an equable speed. The third one is the case of deceleration until to stop the winch, which is called straightforwardly to shut down it. Starting and stopping use stepless gearshift. The stepless gearshift device is made up of the transducer of variant frequency and periodic juice and the motor of trinomial asynchronism moment, moreover, the stepless gearshift of is accomplished by series of different spherical gear. phase，timing plug up revolution. The most important task in this design is to choose and confirm the gearing schema, the operation of the driving device, the calculation of power and driving part. The mainly mechanical segment of this driving system is the different spherical gear creeper gear. In order to improve the efficiency, lessen the weight and shorten the measure of the mechanic, series of different spherical gear, which is composed of 2K-H single-row spherical gear machine and the regulative gears, is used. In the gear course, 2K-H spherical gear driving is the core of operation of the machine in an equable speed. So, that becomes the motive of this design. There are some aspects to be done in this design as follows. The first one is the calculation of driving ratio. The second one is the choice of quantity of gear. The third one is the geometrical calculation of the gearing. The forth one is the analysis about the driving vigor. The fifth one is the calculation of degree. Besides the former aspects to have been described, the choice of the structure of the spherical rack, design of proportional loading and the structural measure of the creeper gear etc. must be contained in the design. The winchs stepless gearshift is accomplished by the motor of variant frequency and periodic juice. It mainly accomplishes the starting and drop of the machine. Electrical accessory primarily consists of the instrument variant frequency, adjustment-system uses sine wave pulse width modulate（SPWM）transducer and YLJ courses trinomial asynchronism moment. The design about electrical segment mainly chooses not only the variant frequency-motors parameter and type but also the motors type and capability. The system adopts the assemblage between electricity and mechanic. It combines the virtues of them, which improves the overall capacity of the instrument and makes this product have a more prospective perspective. Keywords: Differential stepless gearshift Winch Signature of supervisor：毕业设计（论文）任务书I、毕业设计(论文)题目： 无级调速提升绞车设计II、毕 业设计(论文)使用的原始资料(数据)及设计技术要求：1. 绞车提升速度：0.54.5m/s；2. 绞车滚筒直径：1200mm；3. 最大提升重量：1000Kg；4. 提升速度可无级变速；5. 有制动装置。III、毕 业设计(论文)工作内容及完成时间：1. 收集资料、开题报告 2周2. 无级调速原理方案设计 3周3. 传动系统的运动和动力计算 6周4. 装配图及零部件图设计 3周5. 外文翻译 1周6. 毕业设计论文 2周 、主 要参考资料：1 璞良贵，纪名刚主编.机械设计.第七版.北京：高等教育出版社，20012 孙桓，陈作模主编.机械原理.第七版.北京：高等教育出版社，20063 江耕华，胡来瑢，陈启松等编.机械传动设计手册. 北京：煤炭工业出版社,19924 王昆等主编. 机械设计课程设计手册.北京：高等教育出版社，20045 Ye Zhonghe, Lan Zhaohui. Mechanisms and Machine Theory. Higher Education Press, 2001.7 航空与机械工程 系 机械设计制造及自动化 专业类 0881054 班学生： 填写日期： 年 月 日指导教师：助理指导教师(并指出所负责的部分)： 机械设计制造及其自动化 教研室主任：学士学位论文原创性声明本人声明，所呈交的论文是本人在导师的指导下独立完成的研究成果。除了文中特别加以标注引用的内容外，本论文不包含法律意义上已属于他人的任何形式的研究成果,也不包含本人已用于其他学位申请的论文或成果。对本文的研究作出重要贡献的个人和集体，均已在文中以明确方式表明。本人完全意识到本声明的法律后果由本人承担。作者签名： 日期：学位论文版权使用授权书本学位论文作者完全了解学校有关保留、使用学位论文的规定，同意学校保留并向国家有关部门或机构送交论文的复印件和电子版，允许论文被查阅和借阅。本人授权南昌航空大学科技学院可以将本论文的全部或部分内容编入有关数据库进行检索，可以采用影印、缩印或扫描等复制手段保存和汇编本学位论文。 作者签名： 日期：导师签名： 日期：汽车制动系统制动系统是汽车中最重要的系统。 如果制动失灵，结果可能是损失惨重的。制 动器实际就是能量转换装置，它将汽车的动能（动量）转化成热能（热量）。当 驾驶员踩下制动踏板，所产生的制动力是汽车运动时动力的 10 倍。制动系统能 对四个刹车系统中的每个施加数千磅的力。 每辆汽车上使用两个完全独立的制动系统，即行车制动器和驻车制动器。 行车制动器起到减速、停车、或保持车辆正常行驶。制动器是由司机用脚踩、松 制动器踏板来控制的。驻车制动器的主要作用就是当车内无人的时候，汽车能够 保持静止。当独立的驻车制动器踏板或手杆，被安装时，驻车制动器就会被机 械地操作。 制动系统是由下列基本的成分组成:位于发动机罩下方，而且直接地被连接到制 动踏板的“制动主缸”把驾驶员脚的机械力转变为液压力。钢制的“制动管路”和有 柔性的“制动软管”把制动主缸连接到每个轮子的“制动轮缸”上。 制动液, 特别地 设计为的是工作在极端的情况，填充在系统中。“制动盘”和“衬块”是被制动轮缸 推动接触“圆盘”和“回转体”如此引起缓慢的拖拉运动, (希望)使汽车减慢速度。 典型的制动系统布置有前后盘式，前盘后鼓式，各个车轮上的制动器通过一套 管路系统连接到制动主缸上。 基本上讲，所有的汽车制动器都是摩擦制动器。当司机刹车时，控制装置会迫使 制动蹄，或制动衬片与车轮处的旋转的制动鼓或制动盘接触。接触后产生的摩擦 使车轮转动减慢或停止，这就是汽车的制动。 在最基本的制动系统中，有一个制动主缸，这个主缸内部填充制动液，并包含两 个部分，每个部分里都有一个活塞，两个活塞都连接驾驶室里的制动踏板。当制 动踏板被踩下时，制动液会从制动主缸流入轮缸。在轮缸中，制动液推动制动蹄 或制动衬片与旋转的制动鼓或制动盘接触。 静止的制动蹄或制动衬片与旋转的制 动鼓或制动盘之间产生摩擦力使汽车的运动逐渐减缓或停止。 制动液的装置位于主缸的顶部。 目前大多数的车都有一个容易看见的装制动液的 装置，为的是不用打开盖子就可以看得见制动液的油面。随着制动踏板的运动制 动液就会缓慢的下降，正常情况下是这样的。如果制动液在很短的时间内下降得 明显或者下降了三分之二，那么就要尽快的检查你的制动系统了。保持制动液装置充满制动液除非你需要维修它，制动液必须保持很高的沸点。位于在空气中的 制动液就会吸收空气中的潮气引起制动液低于沸点。 制动液通过一系列的管路从主缸到达各车轮。橡胶软管只用在需要弹力的地方， 比如应用在前轮。在车的行进中上下来回运动。系统的其它部分在所有的连接点 上都应用了无腐蚀性的无缝钢管。如果钢线需要修理的话，最好的方法就是代替 这条线。如果这不符合实际，那么为了制动系统可以用特殊的装置修理它。你不 可以用铜管来修理制动系。它们是危险也是不正确的。 鼓式制动器包括制动鼓，一个轮缸，回拉弹簧，一个制动底版，两个带摩擦层的 制动蹄。制动底版固定在轮轴外部的法兰或转向节。制动鼓固定在轮毂上。制动 鼓的内部表面与制动蹄的内层之间有空隙。 要使用制动器时， 司机就要踩下踏板， 这时轮缸扩大制动片，对其施加压力，是制动蹄触碰制动鼓。制动鼓与摩擦片之 间产生的摩擦制动了车轮，从而使汽车停止。要释放制动器时，司机松开踏板， 回拉弹簧拉回制动片，这样车轮会自由转动。 盘式制动器包括制动盘而不是鼓， 在它的两面上各有一个薄的制动片或叫盘式制 动器的制动片。制动片是靠挤住旋转的制动盘来停住汽车。制动主缸里流出的制 动液迫使活塞向里部的金属盘移动，这便使摩擦片紧紧地贴住制动盘。这时制动 片与制动盘产生的摩擦使汽车减速、 停止， 出现了制动行为。 活塞分金属或塑料。 盘式制动器主要有三种，即：浮动卡钳型、固定卡钳型和滑动卡钳型。浮动卡钳 型和滑动卡钳型盘式制动器使用单活塞。 固定卡钳型盘式制动器既可以使用两个 活塞有可以使用四个活塞。 制动系统是由机械能，液压能或气压能装置驱动的。在机械杠杆适合所有的汽 车的驻车制动器中使用。当踩下制动踏板时，杠杆就会推动制动器主缸的活塞给 制动液施加压力，制动液通过油管流入轮缸。制动液的压力施加到轮缸活塞以使 制动片被压到制动鼓或制动盘上。如果松开踏板，活塞回到原来的位置上，回拉 弹簧拉回制动片，制动液返回制动主缸，这样制动停止。 驻动制动器的主要作用是车内无人时，使汽车静止不动。如果车内安装的是独 立的驻车制动器，那么驻车制动器是由司机手动的控制。驻车制动器正常是当车 已经停止时使用的。向后拉手闸，并把手柄卡在正确的位置上。现在，即使离开 汽车也不用害怕它会自己滑走。如果司机要再次启车时，他必须在松开手杆之前 按下按钮。在行车制动器失灵的情况下，手闸必须能停住车。正因为这样，手闸 与脚闸分开，手闸使用的是绳索或杠杆而不是液力系统。防抱死制动系统是使汽车制动更安全、更方便的制动装置，它既有调节制动系统 的压力来防止车轮被完全抱死的功能， 又有防止轮胎在滑的路面上行驶或紧急停 车时的滑动。 防抱死制动系统最早应用在航空飞行器上，而且在二十世纪 90 年代一些国内的 汽车内也安装了这种系统。 近来， 几个汽车制造商引进了更为复杂的防抱死系统。 欧洲使用这种系统已有几十年的时间，通过对其的调查，一位汽车制造商坦言， 如果所有的汽车都安装上防抱死制动系统， 那么交通事故的发生率会降低 7.5%。 同时，一些权威人士预测这种系统会提高汽车的安全性。 防抱死制动系统可以在一秒钟内调节几次制动时车轮上的受力， 使车轮的滑移受 到控制，而且所有的系统基本上都以相同的方式完成。每个车轮都会有一个传感 器，电子控制装置能连续检测来自车轮传感器传来的脉冲电信号，并将它们处理 转换成和轮速成正比的数值；如果其中一个传感器的信号不断下降，那么这就表 明了相应的轮胎趋于抱死， 这时电子控制装置向该车轮的制动器发出降低压力的 指令。当信号显示车轮转速恢复正常时，电子控制装置会增加制动器的液压。这 种循环像司机一样调节制动器，但它的速度更快，达到了每秒循环数次。 防抱死制动系统除了上面基本操作，还有两个特点。首先，当制动系统的压力上 升到使轮胎抱死或即将抱死的时候，防抱死制动系统才会启动；当制动系统在正 常情况下，防抱死制动系统停止运作。其次，如果防抱死制动系统有问题时，制 动器会独立地继续运行。但控制板上的指示灯亮起提醒司机系统出现问题。 目前欧洲汽车生产商，如：宝马、奔驰、宝时捷等广泛使用的是波许（Bosch） 防抱死制动系统。这种系统基本组成包括车轮转速传感器，电子控制装置和调节 装置。 每个有一个向电子控制装置发出车轮转动情况的信号的传感器， 它一般由磁感应 传感头和齿圈组成。前面的传感器安在轮毂上，齿圈安在轮网上。后面的传感器 安在后部的监测系统上，齿圈安在轮轴上。传感器本身是缠绕电磁核的电线圈， 电磁核才线圈的周围产生磁场。 当齿圈的齿移动到磁场时， 就会改变线圈的电流。 电子控制装置会监测这种变化，然后判断车轮是否即将抱死。 电子控制装置有三个作用，即：信号的处理，编辑和安全防护。信号的处理起 到转换器的作用，它是将接受的脉冲电信号处理转换成数值，为编辑做准备。编辑就是分析这些数值，计算出需要制动压力。如果检测出车轮即将抱死，电控装 置就会计算出数值向调节装置发出指令。 调节装置 当接受到电子控制装置的指令后，液压执行装置会调节制动轮缸的液压的大小。 调节装置能保持或减小来自制动主缸的液压，而装置本身是不能启用制动器的。 这种装置有三个高速率的电磁阀， 两个油液存储器和一个带有内外检测阀的传动 泵。调节装置中的电子连接器隐藏在塑料盖下。 每个电磁阀都是其独立控制的，并作用于前轮。后部的制动轮缸受到一个电磁阀 控制，并依照-的原理进行调节。当防抱死制动系统运行时，电子控制装置会 使电磁阀循环运作，这样既能收回又能释放制动器的压力。当压力释放时，它会 释放到液压单元。前部的制动器电路有一个单元。存储器低压存储器，它在低压 下存储油液，直到回流泵打开，油液流经制动轮缸进入制动主缸 。Automobile Brake SystemThe braking system is the most important system in cars. If the brakes fail, the result can be disastrous. Brakes are actually energy conversion devices, which convert the kinetic energy (momentum) of the vehicle into thermal energy (heat).When stepping on the brakes, the driver commands a stopping force ten times as powerful as the force that puts the car in motion. The braking system can exert thousands of pounds of pressure on each of the four brakes. Two complete independent braking systems are used on the car. They are the service brake and the parking brake. The service brake acts to slow, stop, or hold the vehicle during normal driving. They are foot-operated by the driver depressing and releasing the brake pedal. The primary purpose of the brake is to hold the vehicle stationary while it is unattended. The parking brake is mechanically operated by when a separate parking brake foot pedal or hand lever is set. The brake system is composed of the following basic components: the “master cylinder” which is located under the hood, and is directly connected to the brake pedal, converts driver foots mechanical pressure into hydraulic pressure. Steel “brake lines” and flexible “brake hoses” connect the master cylinder to the “slave cylinders” located at each wheel. Brake fluid, specially designed to work in extreme conditions, fills the system. “Shoes” and “pads” are pushed by the slave cylinders to contact the “drums” and “rotors” thus causing drag, which (hopefully) slows the car. The typical brake system consists of disk brakes in front and either disk or drum brakes in the rear connected by a system of tubes and hoses that link the brake at each wheel to the master cylinder (Figure). Basically, all car brakes are friction brakes. When the driver applies the brake, the control device forces brake shoes, or pads, against the rotating brake drum or disks at wheel. Friction between the shoes or pads and the drums or disks then slows or stops the wheel so that the car is braked.In most modern brake systems (see Figure 15.1), there is a fluid-filled cylinder, called master cylinder, which contains two separate sections, there is a piston in each section and both pistons are connected to a brake pedal in the drivers compartment. When the brake is pushed down, brake fluid is sent from the master cylinder to the wheels. At the wheels, the fluid pushes shoes, or pads, against revolving drums or disks. The friction between the stationary shoes, or pads, and the revolving drums or disks slows and stops them. This slows or stops the revolving wheels, which, in turn, slow or stop the car. The brake fluid reservoir is on top of the master cylinder. Most cars today have a transparent r reservoir so that you can see the level without opening the cover. The brake fluid level will drop slightly as the brake pads wear. This is a normal condition and no cause for concern. If the level drops noticeably over ashort period of time or goes down to about two thirds full, have your brakes checked as soon as possible. Keep the reservoir covered except for the amount of time you need to fill it and never leave a cam of brake fluid uncovered. Brake fluid must maintain a very high boiling point. Exposure to air will cause the fluid to absorb moisture which will lower that boiling point. The brake fluid travels from the master cylinder to the wheels through a series of steel tubes and reinforced rubber hoses. Rubber hoses are only used in places that require flexibility, such as at the front wheels, which move up and down as well as steer. The rest of the system uses non-corrosive seamless steel tubing with special fittings at all attachment points. If a steel line requires a repair, the best procedure is to replace the compete line. If this is not practical, a line can be repaired using special splice fittings that are made for brake system repair. You must never use copper tubing to repair a brake system. They are dangerous and illegal. Drum brakes, it consists of the brake drum, an expander, pull back springs, a stationary back plate, two shoes with friction linings, and anchor pins. The stationary back plate is secured to the flange of the axle housing or to the steering knuckle. The brake drum is mounted on the wheel hub. There is a clearance between the inner surface of the drum and the shoe lining. To apply brakes, the driver pushes pedal, the expander expands the shoes and presses them to the drum. Friction between the brake drum and the friction linings brakes the wheels and the vehicle stops. To releasebrakes, the driver release the pedal, the pull back spring retracts the shoes thus permitting free rotation of the wheels. Disk brakes, it has a metal disk instead of a drum. A flat shoe, or disk-brake pad, is located on each side of the disk. The shoes squeeze the rotatin g disk to stop the car. Fluid from the master cylinder forces the pistons to move in, toward the disk. This action pushes the friction pads tightly against the disk. The friction between the shoes and disk slows and stops it. This provides the braking action. Pistons are made of either plastic or metal. There are three general types of disk brakes. They are the floating-caliper type, the fixed-caliper type, and the sliding-caliper type. Floating-caliper and sliding-caliper disk brakes use a single piston. Fixed-caliper disk brakes have either two or four pistons. The brake system assemblies are actuated by mechanical, hydraulic or pneumatic devices. The mechanical leverage is used in the parking brakes fitted in all automobile. When the brake pedal is depressed, the rod pushes the piston of brake master cylinder which presses the fluid. The fluid flows through the pipelines to the power brake unit and then to the wheel cylinder. The fluid pressure expands the cylinder pistons thus pressing the shoes to the drum or disk. If the pedal is released, the piston returns to the initialposition, the pull back springs retract the shoes, the fluid is forced back to the master cylinder and braking ceases. The primary purpose of the parking brake is to hold the vehicle stationary while it is unattended. The parking brake is mechanically operated by the driver when a separate parking braking hand lever is set. The hand brake is normally used when the car has already stopped. A lever is pulled and the rear brakes are approached and locked in the “on” position. The car may now be left without fear of its rolling away. When the driver wants to move the car again, he must press a button before the lever can be released. The hand brake must also be able to stop the car in the event of the foot brake failing. For this reason, it is separate from the foot brake uses cable or rods instead of the hydraulic system. Anti-lock Brake SystemAnti-lock brake systems make braking safer and more convenient, Anti-lock brake systems modulate brake system hydraulic pressure to prevent the brakes from locking and the tires from skidding on slippery pavement or during a panic stop. Anti-lock brake systems have been used on aircraft for years, and some domestic car were offered with an early form of anti-lock braking in late 1990s. Recently, several automakers have introduced more sophisticated anti-lock system. Investigations in Europe, where anti-lock brakin g systems have been available for a decade, have led one manufacture to state that the number of traffic accidents could be reduced by seven and a half percent if all cars had anti-lock brakes. So some sources predict that all cars will offer anti-lock brakes to improve the safety of the car. Anti-lock systems modulate brake application force several times per second to hold the tires at a controlled amount of slip; all systems accomplish this in basically the same way. One or more speed sensors generate alternating current signal whose frequency increases with the wheel rotational speed. An electronic control unit continuously monitors these signals and if the frequency of a signal drops too rapidly indicating that a wheel is about to lock, the control unit instructs a modulating device to reduce hydraulic pressure to the brake at the affected wheel. When sensor signals indicate the wheel is again rotating normally, the control unit allows increased hydraulic pressure to the brake. This release-apply cycle occurs several time per second to “pump” the brakes like a driver might but at a much faster rate. In addition to their basic operation, anti-lock systems have two other things in common. First, they do not operate until the brakes are applied with enough force to lock or nearly lock a wheel. At all other times, the system stands ready to function but does not interfere with normal braking. Second, if the anti-lock system fail in any way, the brakes continue to operate without anti-lock capability. A warning light on the instrument panel alerts the driver when a problem exists in the anti-lock system. The urrel osc component Anti-lock Braking System (ABS), is a secon generation0design wild聬 used by European utooajer schas BWM, MeRcedes-Bejz and Porsche. ABS system consists of : four heelspeed sensor, electronic bontrol unit and m聯dulator assembly.A speed sensor is!fitted av each wheel sends signals about wheel rotation to control unht. Each speed sensor consists of a sensor unit and a gear wheel. The front sensor mounts to the steering knuckle and its gear wheel is pressed onto the stub axle that rotates with the wheel. The rear sensor mounts the rear suspension member and its gear wheel is pressed onto the axle. The sensor itself is a winding with a magnetic core. The core creates a magnetic field around the win
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