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外文翻译

汽修专业文献综述外文翻译

时间:2012-11-14 11:32:18  作者:鸿禾娱乐官网注册-鸿禾娱乐怎么注册  来源:鸿禾娱乐官网注册-鸿禾娱乐怎么注册  查看:32  评论:0

 外文资料翻译
       专    业汽车检测与维修技术
       班    级    汽修 
Ignition System
  The purpose of the ignition system is to create a spark that will ignite the fuel-air mixture in the cylinder of an engine. It must do this at exactly the right instant and do it at the rate of up to several thousand times per minute for each cylinder in the engine. If the timing of that spark is off by a small fraction of a second, the engine will run poorly or not run at all.
  The ignition system sends an extremely high voltage to the spark plug in each cylinder when the piston is at the top of its compression stroke. The tip of each spark plug contains a gap that the voltage must jump across in order to reach ground. That is where the spark occurs.
  The voltage that is available to the spark plug is somewhere between 20,000 volts and 50,000 volts or better. The job of the ignition system is to produce that high voltage from a 12 volt source and get it to each cylinder in a specific order, at exactly the right time.
  The ignition system has two tasks to perform. First, it must create a voltage high enough (20,000+) to across the gap of a spark plug, thus creating a spark strong enough to ignite the air/fuel mixture for combustion. Second, it must control the timing of that the spark so it occurs at the exact right time and send it to the correct cylinder.
  The ignition system is divided into two sections, the primary circuit and the secondary circuit. The low voltage primary circuit operates at battery voltage (12 to 14.5 volts) and is responsible for generating the signal to fire the spark plug at the exact right time and sending that signal to the ignition coil. The ignition coil is the component that converts the 12 volt signal into the high 20,000+ volt charge. Once the voltage is stepped up, it goes to the secondary circuit which then directs the charge to the correct spark plug at the right time.
The Basics
  Before we begin this discussion, let’s talk a bit about electricity in general. I know that this is basic stuff, but there was a time that you didn’t know about this and there are people who need to know the basics so that they could make sense of what follows.
  All automobiles work on DC (Direct Current). This means that current move in one direction, form the positive battery terminal to the negative battery terminal. In the case of the automobile, the negative battery terminal is connected by a heavy cable directly to the body and the engine block of the vehicle. The body and any metal component in contact with it is called the ground. This means that a circuit that needs to send current back to the negative side of the battery can be connected to any part of the vehicle’s metal body or the metal engine block.
  A good example to see how this works is the headlight circuit. The headlight circuit consists of a wire that goes from the positive battery terminal to the headlight switch. Another wire goes from the headlight switch to one of two terminals on the headlight bulb. Finally, a third wire goes from a second terminal on the bulb to the metal body of car. When you switch the headlight on, you are connecting the wire from the battery with the wire to the headlamps allowing battery current to go directly to the headlamp bulbs. Electricity passes through the filaments inside the bulb, then out the other wire to the metal body. From there, the current goes back to the negative terminal of the battery completing the circuit. Once the current is flowing through this circuit, the filament inside the headlamp gets hot and glows brightly. Let there be light.
  Now, back to the ignition system, the basic principle of the electrical spark ignition system has not changed for over 75 years. What has changed is the method by which the spark is created and how it is distribute.
  Currently, there are three distinct types of ignition system. The mechanical ignition system was used prior to 1975. It was mechanical and electrical and used no electronics. By understanding these early system, it will be easier to understand the new electronic and computer controlled ignition system, so don’t skip over it. The electronic ignition system started finding its way to production vehicles during the early 70s and became popular when better control and improved reliability became important with the advent of emission controls. Finally, the distributor less ignition system became available in the mid 80s. This system was always computer controlled and contained no moving parts, so reliability was greatly improved. Most of these systems required no maintenance except replacing the spark plugs at intervals from 60,000 to over 100,000 miles.
  Let’s take a detailed look at each system and see how they work.
The Mechanical Ignition System
  The distributor is the nerve center of the mechanical ignition system and has two tasks to perform. First, it is responsible for triggering coil to generate a spark at the precise instant that it is required (which varies depending how fast the engine is turning and how much load it is under). Second, the distributor is responsible for directing that spark to the proper cylinder (which is why it is called a distributor).
  The circuit that powers the ignition system is simple and straight forward. When you insert the key in the ignition switch and turn the key to the Run position, you are sending current from the battery through a wire directly to the positive (+) side of the ignition coil. Inside the coil is a series of copper windings that loop around the coil over a hundred times before exiting out the negative (-) side of the coil. From there, a wire takes this current over to the distributor and is connected to a special on/off switch, called the points. When the points are closed, this current goes directly to ground. When current flows from the ignition switch, through the windings in the coil, then to ground, it builds a strong magnetic field inside the coil.
  The points are made up of a fixed contact point that is fastened to a plate inside the distributor, and a movable contact point mounted on the end of a spring loaded arm. The movable point rides on a 4, 6, or 8 lobe cam (depending on the number of cylinder in the engine) that is mounted on a rotating shaft inside the distributor. This distributor cam rotates in time with the engine, making one complete revolution for every two revolutions of the engine. As it rotates, the cam pushes the points open and closed. Every time the points open, the flow of current is interrupted through the coil, thereby collapsing the magnetic field and releasing a high voltage surge through the secondary coil windings. This voltage surge goes out the top of the coil and through the high-tension coil wire.
  Now, we have the voltage necessary to fire the spark plug, but we still have to get it to the correct cylinder. The coil wire goes from the coil directly to the distributor cap. Under the cap is a rotor that is mounted on top of the rotating shaft. The rotor has a metal strip on the top that is in constant contact with the center terminal of the distributor cap. It receives the high voltage surge from the coil wire and sends it to the other end of the rotor which rotates past each spark plug terminal inside the cap. As the rotor turns on the shaft, it sends the voltage to the correct spark plug wire, which in turn sends it to the spark plug. The voltage enters the spark plug at the terminal at the top and travels down the core until it reaches the tip. It then jumps across the tip of the spark plug, creating a spark suitable to ignite the fuel-air mixture inside that cylinder.
  The description I just provided is the simplified version, but should be helpful to visualize the process, but we left out a few things that make up this type of ignition system. For instance, we didn’t talk about the condenser that is connected to the point, nor did we talk about the system to advance the timing. Let’s take a look at each section and explore it in more detail.
The Ignition Switch
  There are two separate circuits that go from the ignition switch to the coil. One circuit runs through a resistor in order to step down the voltage about 15% in order to protect the points from premature wear. The other circuit sends full battery voltage to the coil. The only time this circuit is used is during cranking. Since the starter draws a considerable amount of current to crank the engine, additional voltage is needed to power the coil. So when the key is turned to the spring-loaded start position, full battery voltage is used. As soon as the engine is running, the driver releases the key to the run position which directs current through the primary resistor to the coil.
  On some vehicles, the primary resistor is mounted on the firewall and is easy to replace if it fails. On other vehicles, most notably vehicles manufactured by GM, the primary resister is a special resister wire and is bundled in the wiring harness with other wires, making it more difficult to replace, but also more durable.
The Distributor
  When you remove the distributor cap from the top of the distributor, you will see the points and condenser. The condenser is a simple capacitor that can store a small amount of current. When the points begin to open the current, flowing through the points looks for an alternative path to ground. If the condenser were not there, it would try to jump across the gap of the point as they begin to open. If this were allowed to happen, the points would quickly burn up and you would hear heavy static on the car radio. To prevent this, the condenser acts like a path to ground. It really is not, but by the time the condenser is saturated, the points are too far apart for the small amount of voltage to jump across the wide point gap. Since the arcing across the opening points is eliminated, the points last longer and there is no static on the radio from point arcing.
  The points require periodic adjustments in order to keep the engine running at peek efficiency. This is because there is a rubbing block on the points that is in contact with the cam and this rubbing block wears out over time changing he point gap. There are two ways that the points can be measured to see if they need an adjustment. One way is by measuring the gap between the open points when the rubbing block is on the high point of the cam. The other way is by measuring the dwell electrically. The dwell is the amount, in degrees of cam rotation that the points stay closed.
  On some vehicles, points are adjusted with the engine off and the distributor cap removed. A mechanic will loosen the fixed point and move it slightly, then retighten it in the correct position using a feeler gauge to measure the gap. On other vehicles, most notably GM cars, there is a window in the distributor where a mechanic can insert a tool and adjust the points using a dwell meter while the engine is running. Measuring dwell is much more accurate than setting the points with a feeler gauge.
  Points have a life expectancy of about 10,000 miles at which time have to be replaced. This is done during a routine major tune up, points, condenser, and the spark plugs are replaced, the timing is set and the carburetor is adjusted. In some cases, to keep the engine running efficiently, a minor tune up would be performed at 5,000 mile increments to adjust the point and reset the timing.
Ignition Coil
  The ignition coil is nothing more that an electrical transformer. It contains both primary and secondary winding circuit. The coil primary winding contains 100 to 150 turns of heavy copper wire. This wire must be insulated so that the voltage does not jump from loop to loop, shorting it out. If this happened, it could not create the primary magnetic field that is required. The primary circuit wire goes into the coil through the positive terminal, loops around the primary windings, then exits through the negative terminal.
  The coil secondary winding circuit contains 15,000 to 30,000 turns of fine copper wire, which also must be insulated from each other. The secondary windings sit inside the loops of the primary windings. To further increase the coils magnetic field the windings are wrapped around a soft iron core. To withstand the heat of the current flow, the coil is filled with oil which helps keep it cool.
  The ignition coil is the heart of the ignition system. As current flows through the coil a strong magnetic field is build up. When the current is shut off, the collapse of this magnetic field to the secondary windings induces a high voltage which is released through the large center terminal. This voltage is then directed to the spark plugs through the distributor.
Ignition Timing
  The timing is set by loosening a hold-down screw and rotating the body of the distributor. Since the spark is triggered at the exact instant that the points begin to open, rotating the distributor body (which the point are mounted on) will change the relationship between the position and the position of the distributor cam, which is on the shaft that is geared to the engine rotation.
  While setting the initial or base timing is important, for an engine to run properly, the timing needs to change depending on the speed of the engine and the load that it is under. If we can move the plate that the points are mounted on, or we could change the position of the distributor cam in relation to the gear that drives it, we can alter the timing dynamically to suit the needs of the engine.
Ignition Wires
  These cables are designed to handle 20,000 to more than 50,000 volts, enough voltage to toss you across the room if you were to be exposed to it. The job of the spark plug wires is to get that enormous power to the spark plug without leaking out. Spark plug wires have to endure the heat of a running engine as well as the extreme changes in the weather. In order to do their job, spark plug wires are fairly thick, with most of that thickness devoted to insulation with a very thin conductor running down the center. Eventually, the insulation will succumb to the elements and the heat of the engine and begins to harden, crack, dry out, or otherwise break down. When that happens, they will not be able to deliver the necessary voltage to the spark plug and a misfire will occur. That is what is meant by “Not running on all cylinders”. To correct this problem, the spark plug wires would have to be replaced.
  Spark plug wires are routed around the engine very carefully. Plastic clips are often used to keep the wires separated so that they do not touch together. This is not always necessary, especially when the wires are new, but as they age, they can begin to leak and crossfire on damp days causing hard starting or a rough running engine.
  Spark plug wires go from the distributor cap to the spark plugs in a very specific order. This is called the “firing order” and is part of the engine design. Each spark plug must only fire at the end of the compression stroke. Each cylinder has a compression stroke at a different time, so it is important for the individual spark plug wire to be routed to the correct cylinder.
  For instance, a popular V8 engine firing order is 1, 8, 4, 3, 6, 5, 7, 2. The cylinders are numbered from the front to the rear with cylinder #1 on the front-left of the engine. So the cylinders on the left side of the engine are numbered 1, 3, 5, 7while the right side are numbered 2, 4, 6, 8. On some engine, the right bank is 1, 2, 3, 4 while the left bank is 5, 6, 7, 8. A repair manual will tell you the correct firing order and cylinder layout for a particular engine.
  The next thing we need to know is what direction the distributor is rotating in, clockwise or counter-clockwise, and which terminal on the distributor caps that #1 cylinder is located. Once we have this information, we can begin routing the spark plug wires.
  If the wires are installed incorrectly, the engine may backfire, or at the very least, not run on all cylinders. It is very important that the wires are installed correctly.
Spark Plugs
  The ignition system’s sole reason for being is to service the spark plug. It must provide sufficient voltage to jump the gap at the tip of the spark plug and do it at the exact right time, reliably on the order of thousands of times per minute for each spark plug in the engine.
  The modern spark plug is designed to last many thousands of miles before it requires replacement. These electrical wonders come in many configurations and heat ranges to work properly in a given engine.
  The heat range of a spark plug dictates whether it will be hot enough to burn off any residue that collects on the tip, but not so hot that it will cause pre-ignition in the engine. Pre-ignition is caused when a spark plug is so hot, that it begins to glow and ignite the fuel-air mixture prematurely, before the spark. Most spark plugs contain a resistor to suppress radio interference. The gap on a spark plug is also important and must be set before the spark plug is installed in the engine. If the gap is too wide, there may not be enough voltage to jump the gap, causing a misfire. If the gap is too small, the spark may be inadequate to ignite a lean fuel-air mixture also causing a misfire.
The Electronic Ignition System
  This section will describe the main differences between the early point & condenser systems and the newer electronic systems. If you are not familiar with the way an ignition system works in general, I strongly recommend that you first read the previous section The Mechanical Ignition System.
  In the electronic ignition system, the points and condenser were replaced by electronics. On these systems, there were several methods used to replace the points and condenser in order to trigger the coil to fire. One method used a metal wheel with teeth, usually one for each cylinder. This is called an armature. A magnetic pickup coil senses when a tooth passes and sends a signal to the control module to fire the coil.
  Other systems used an electric eye with a shutter wheel to send a signal to the electronics that it was time to trigger the coil to fire. These systems still need to have the initial timing adjusted by rotating the distributor housing.
  The advantage of this system, aside from the fact that it is maintenance free, is that the control module can handle much higher primary voltage than the mechanical point. Voltage can even be stepped up before sending it to the coil, so the coil can create a much hotter spark, on the order of 50,000 volts that is common with the mechanical systems. These systems only have a single wire from the ignition switch to the coil since a primary resistor is not longer needed.
  On some vehicles, this control module was mounted inside the distributor where the points used to be mounted. On other designs, the control module was mounted outside the distributor with external wiring to connect it to the pickup coil. On many General Motors engines, the control module was inside the distributor and the coil was mounted on top of the distributor for a one piece unitized ignition system. GM called it high energy ignition or HEI for short.
  The higher voltages that these systems provided allow the use of a much wider gap on the spark plugs for a longer, fatter spark. This larger sparks also allowed a leaner mixture for better fuel economy and still insure a smooth running engine.
  The early electronic systems had limited or no computing power, so timing still a centrifugal and vacuum advance built into the distributor.
  On some of the later systems, the inside of the distributor is empty and all triggering is performed by a sensor that watches a notched wheel connected to either the crankshaft or the camshaft. These devices are called crankshaft position sensor or camshaft position sensor. In these systems, the job of the distributor is solely to distribute the spark to the correct cylinder through the distributor cap and rotor. The computer handles the timing and any timing advance necessary for the smooth running of the engine.
The Distributor Ignition System
  Newer automobiles have evolved from a mechanical system (distributor) to a completely solid state electronic system with no moving parts. These systems are completely controlled by the on-board computer. In place of the distributor, there are multiple coils that each serves one or two spark plugs. A typical 6 cylinder engine has 3 coils that are mounted together in a coil “pack”. A spark plug wire comes out of each side of the individual coil and goes to the appropriate spark plug. The coil fires both spark plugs at the same time. One spark plug fires on the compression stroke igniting the fuel-air mixture to produce power while the other spark plug fires on the exhaust stroke and does nothing. On some vehicles, there is an individual coil for each cylinder mounted directly on top of the spark plug. This design completely eliminates the high tension spark plug wires for even better reliability. Most of these systems use spark plugs that are designed to last over 100,000 miles, which cuts down on maintenance costs.
参考文献:
[1] 王欲进,张红伟.汽车专业英语[M]. 北京:北京大学出版社,中国林业出版社,2007.8,55—67

点火系统
   点火系统的作用是产生点燃发动机气缸里可燃混合物的火花。在精确时刻和在发动机每个汽缸工作速率达到每分钟数千次下才能产生火花。如果点火时刻不是瞬间,发动机运行不佳或不运行。
   当活塞在其压缩行程顶部的时候,在每个汽缸里点火系统发送一个极其高的电压到火花塞。为了接地每个火花塞的尖端有一个能穿过电压的间隙。这就是电火花的发生。
   火花塞可接收到的电压在20,000伏到50,000伏甚至更高。点火系统的任务是在精确时刻从12伏的电源产生高压电,按特定的顺序给每个汽缸提供高电压。
   点火系统执行两个任务。第一,它产生足够高的电压穿过火花塞的间隙,因此为了燃烧需要产生足够强的电压来点燃可燃混合物。第二,它控制点火时刻以便在精确时刻产生火花并将其发送到正确的汽缸。
   点火系统被分为两部分:初级线圈和次级线圈。初级线圈的低电压由电池电压(12伏至14.5伏)控制,负责在精确地时刻产生点火信号,将点火信号发送给点火线圈。点火线圈是将12伏电压信号转换为高于20000伏电压信号的器件。一旦电压被加强就进入次级线圈,然后在正确时刻直接控制对应的火花塞。
基础知识
   在我们开始讨论之前,让我们大体了解一下电的方面。我知道这是基本材料,但有一段时间你不了解,有些人了解基础知识以便他们能够意识到采取什么措施。
   所有的汽车用DC(直流电)来运行。这意味着电流朝一个方向移动,从蓄电池的正极到蓄电池的负极。就汽车来说,蓄电池的负极由一根粗的电缆直接连接车身和接在汽车发动机缸体上。负极与车身或一些金属部件连接被称为接地。这意味着电路需要发送电流回到蓄电池负极与汽车金属车身任何部分或金属发动机缸体连接。
   一个好的例子展示前大灯电路中电流是怎样工作的。前大灯电路由从蓄电池正极到前大灯开关的导线组成。另一根导线从前大灯开关到前大灯的灯泡上的两端子之一。最后,第三根导线从灯泡的另一个端子到汽车金属车身。当你打开前大灯时,你将连接从蓄电池到照明灯所允许蓄电池电流直接进入照明灯灯炮的导线。电流穿过灯泡内的灯丝,然后从另一根导线出来接地。电流回到蓄电池的负极形成完整的电路。一旦电流流经照明灯内的灯丝变热、变亮,产生光。
   回到点火系统,电火花点火系统的基本原理约75年没有改变了。火花产生的方法和如何分配有什么变化。
   目前有三种不同类型的点火系统。1975年以前使用机械点火系统。它使用机械和电气并没有使用电子。理解早期的点火系统将会更容易理解新的电子和鸿禾娱乐官网注册控制的点火系统,所以不要忽视机械点火系统。在70年代初电子点火系统开始在汽车上使用,因能更好的控制变得流行,排放控制的重视来提高可靠性。最后,在80年代中期使用无分电器点火系统。该系统由鸿禾娱乐官网注册控制,没有移动部件,所以可靠性大大提高。除了相隔60,000到100,000英里以上更换火花塞以外这些系统大多数不需要维修。
   让我们详细研究每个系统,理解它们是如何工作的。
机械点火系统
   分电器是机械点火系统的核心,执行两个任务。第一,分电器负责起动线圈在精确时刻产生火花(取决于发动机运转得多快和根据发动机的多少负荷)。第二,分电器负责引导火花到正确的汽缸(这是为什么叫分电器的原因)。
   直接简单的向点火系统提供能量的电路。当你在点火开里插入钥匙,把钥匙转到运行位置时,你发送电流从蓄电池直接到点火线圈的正极(+)。在进入线圈负极(—)之前,线圈内部是一系列环绕线圈一百圈以上的铜线圈。负责分电器电流的线圈并连接一个特殊的ON/OFF开关,称为白金触点。当白金触点关闭时电流直接接地。当电流流过点火开关时,通过线圈里的绕组,然后到地面,在线圈内部建立一个强大的磁场。
   白金触点由一个安装在分电器内活动底板上的固定触点和一个固定在触点臂弹簧末端可移动触点组成。移动触点骑在一个有4,6或8个凸轮凸角(取决于发动机缸体的数目),骑在分电器里的分电器轴上。发动机转动分电器凸轮就转动,发动机曲轴每转两圈分电器凸轮轴转一圈。当分电器凸轮轴转动时,凸轮推动白金触点打开和关闭。每次白金触点打开时,通过线圈的电流流动被干扰,因而产生磁场并通过次级线圈释放高压电流。电压电流进出线圈尖端并通过高电压线圈。
   当今,为了点火我们需要充足的电压,但是我们必须把高电压送到正确的汽缸。直接连接分电器盖的中央高压线。分电器盖下面是一个固定在分电器轴顶部的分火头。分火头尖端有一个金属条与分电器盖中央连接。在分电器内部分火头从中央高压线接收高压电,给分火头的另一端传送高压电,分火头旋转经过每个火花塞的触点。当分火头在分电器轴上转动时,发送电压到正确的分缸线,依次送到火花塞。电压进入火花塞顶端的末端,穿过核心直到火花塞尖端。然后跳过火花塞间隙,在汽缸里产生适合点燃可燃混合气的火花 。
   我提供的描述是简单地看法应该有助于设想进程,但是我们省略一些配置这种类型点火系统的器件。例如,我们没有谈论连接白金触点的电容器,也没有谈论该系统的提前正时。让我们看一看每个部分,更详细地探究。
点火开关
   从点火开关到线圈有两个独立的电路。一个线路贯穿一个为了降低电压15%的电阻,为了防止白金触点过早的磨损。另一个电路发送充足的蓄电池电压到线圈。在起动期间这个电路仅仅使用一次。既然起动装置抽出相当多的电流来转动发动机的曲轴,需要额外的电压为线圈加强动力。所以当钥匙转到带弹簧支承起动位置的时候,饱满的蓄电池电压被使用。发动机一运行驾驶员就释放钥匙回到指引电流进入初级绕组线圈的运行位置。
   在一些汽车上,初级绕组被固定在防火墙上,如果失败了初级绕组容易替代。在其他汽车上,明显地许多汽车被通用制造,初级绕组是一个特殊的电阻,它用束线与其他线圈捆绑,使初级绕组不仅替换更困难而且更耐用。
分电器
   当你从分电器的顶部移走分电器盖时,你将看见白金触点和电容器。电容器是一个简单且能存储小电流的容器。当白金触点开始接通电路时,电流流过白金触点寻找旁路途径接地。如果电容器不在那儿,白金触点开始打接通电路时电流试图跳过白金触电的间隙。如果允许发生,白金触点快速地烧蚀,你将在汽车的无线电设备上听到沉重的静音噪声。为了防止上述情况发生,电容器起的作用就像接地。电容器不是真正地接地而是直到电容器达到饱和状态时,白金触点间隙太大且低电压而不能跳过宽的白金触点间隙。自从通过打开的白金触点的电弧被消除,白金触点持续更长且从触点电弧在无线电装置上没有静音噪声。
   为了保证发动机高效率的运转,白金触点需要定期的调整。因为与凸轮接触的白金触点处有粗纹石板并且这个粗纹石板随着时间的过去不断耗尽来改变触点间隙。如果白金触点需要调整,有两种测量方法。一种方法是当粗纹石板在凸轮凸起时,测量打开触点之间的间隙。另一种是通过用电力测量有规律停顿。凸轮转动的角度很小白金触点保持关闭。
   在一些汽车上,发动机不运行通过分电器盖重新转动来调整白金触点。机修工将松动固定触点并轻微的移动触点,然后在正确的位置使用塞尺测量间隙来重新固定触点。在其他汽车上,大多数显而易见地大众汽车上分电器有一个机修工插入工具的窗口,在发动机运行时使用测量有规律停顿的仪器调整白金触点。测量有规律停顿的仪器比用塞尺设置白金触点更精确。
   白金触点有约10,000英里平均寿命,达到寿命白金触点必须更换。做一个常规的主修调整期,更换白金触点,电容器和火花塞,设置正时和调整化油器。在一些案例里为了保证发动机高效率的运行,在超额5,000英里执行辅修调整,调整白金触点和重新设置正时。
点火线圈
   点火线圈其实是电子变压器。点火线圈包括初级电路和次级电路。初级线圈包含100到150圈粗铜线圈。这个线圈被绝缘以至于电压不能从回路跳到回路,只有短路。如果发生了,它不会产生需要的初级磁场。初级电流进入线圈通过正极端子,环绕初级线圈然后从负极端子出来。
   次级电路的线圈包含15,000到30,000圈细的铜线圈,彼此绝缘。次级线圈位于初级线圈回路里面。进一步增加线圈磁场,线圈包裹一个软铁芯。电流流动产生热,线圈周围充满可以帮助它冷却的油。
   点火线圈产生点火系统的核心。当电流流过线圈时产生强烈的磁场。当电流中断的时候,磁场消失引起次级线圈释放大中央末端高压。然后电压直接通过分电器到火花塞。
点火正时
   正时的设置通过松动一个固定的螺丝钉和旋转分电器的躯体。既然白金触点一开始打开火就产生火花,旋转分电器躯体(被固定的触点)改变分电器位置和分电器凸轮位置之间的关系来适应发动机转动。
   然而设置初始或基本正时是重要的,发动机正确的运转,正时需要改变取决于发动机运转速度和负荷。如果我们移动被固定在活动底板上的触点或改变分电器盖的位置与传动齿轮有关,我们改变动态正时来适应发动机的需求。
点火导线
   这些电缆被设计处理20,000到50,000多伏,如果暴露了足够的电压穿过该空间。火花塞线圈的任务是在没有漏出时给火花塞巨大的能量。火花塞线圈能容忍运行发动机的热量和天气的极端变化。为了做它们的任务火花塞线圈相当粗,大多数粗的有助于隔绝细的导体撞到中心。最后绝缘材料屈服于大自然的力量和发动机热量,开始变硬、开裂、变干或损坏。当发生时它们不能传送必要的电压给火花塞,发生不点火。那意味着“所有汽缸没有一个运行”。为了纠正这个问题火花塞线圈必须更换。
   火花塞线圈给发动机规定周密的路线。塑料夹子经常被使用来分离线圈以便他们在一起没有接触。这是必要的,尤其当导线是新的时,但是当导线老化时,在潮湿的时期导线开始漏电和相互之间串电导致启动困难或发动机运转困难。
   火花塞线圈按特定的顺序从分电器盖到火花塞。这叫做“点火次序”,是发动机设计的部分。每个火花塞在压缩行程末尾点火。每个汽缸的压缩行程在不同时刻,所以对独立的火花塞线圈给出正确的汽缸规定路线是重要的。
   例如一个普通的V8发动机点火顺序是1,8,4,3,6,5,7,2。在,汽缸从前方到发动机左前方的汽缸为一号的后方编号。所以在发动机左侧的汽缸从1,3,5,7编号然而右侧从2,4,6,8编号。在一些发动机上,右岸1,2,3,4而左岸5,6,7,8。修理手册告诉你正确的点火顺序和特定发动机汽缸的布局。
   我们需要知道另一件事是分电器旋转方向,顺时针方向还是逆时针方向,分电器盖的末端位于第一缸。我们一旦有这个信息,我们就开始为火花塞导线规定路线。
   如果导线安装不正确,发动机可能回火或发动机不运行。导线正确安装是重要的。
火花塞
   点火系统存在的原因是服务于火花塞。点火系统提供足够的电压穿过火花塞尖端的间隙,在精确地时刻发动机的每个火花塞每分钟按点火顺序点火数千次。
   在火花塞需要更换之前现代的火花塞被设计能持续上千英里。这些用电的奇物在许多机构里流行,在规定发动机的正确的工作热量范围。
   火花塞的热量范围显示在火花塞尖端是否足够的热以至于烧掉余渣,但是在发动机里不足够的热以至于导致点火延迟。当火花塞如此热以至于火花塞过早地开始发光并点燃可燃混合气时造成点火提前,在点火之前。大多数火花塞包含阻制无线电设备干扰的电阻器。火花塞间隙也是重要的,火花塞安装在发动机之前间隙被设置。如果间隙太宽没有足够的电压跳过间隙造成不点火。如果间隙太小,不适应火花点燃少量可燃混合气也会造成不点火。
电子点火系统
   这个章节描述早期触点式及电容器式点火系统和现代的电子点火系统的主要差异。总而言之,如果你不熟悉点火系统的工作方式,我强烈地推荐你首先读机械点火系统的第一章节。
   在电子点火系统白金触点和电容器被电子取代。在这些系统里为了引起线圈点火,有几种方法用来代替白金触点和电容器。一种方法用一个金属齿轮,通常地每个气缸一个齿轮。这叫做电枢。当齿轮传动和发送信号给控制模块控制点火线圈时磁线圈意识到。
   其他系统使用叶轮电子眼发送信号给电子设备那时是该触发线圈点火的时候。这些系统仍然需要通过旋转分电器外壳来调节初始时刻。
   这个系统的优点除了维修快捷外,控制模块能够比机械式点火系统提供更高的初级电压。在发送到线圈之前电压被加强,所以线圈能产生大约50,000伏火花,与机械点火系统共同。自从初级绕组不再需要时,这些系统仅仅有一个从点火开关到线圈信号线。
   在一些汽车上控制模块被固定在使用白金触点固定的分电器里的位置。在其他设计上控制模块被固定在外部线圈的分电器外,使控制模块与集成线圈连接。在一些通用汽车发动机上控制模块在分电器外,线圈被固定在分电器顶部为一个统一的点火线圈。大众叫它高能量点火或简称HEI。
   这些系统为了更长更大的火花提供允许火花塞使用更宽的间隙的高电压。大的火花也允许更好的燃油经济的混合物仍然确保发动机平顺运行。
   早期的电子点火系统已经限制了或没有电脑控制,所以使离心真空点火提前正时成为分电器的一部分。
   在一些更后的系统中,分电器里面是空的并且所有的起动被一个或者凸轮轴或者曲轴连接锯齿状轮子传感器控制。这些设备叫做凸轮轴位置传感器或曲轴位置传感器。在这些系统里,分电器的任务是通过分电器盖和旋转器分配火花到正确的缸体 。为了发动机平滑运行,鸿禾娱乐官网注册处理正时和正时提前是必要的。
无分电器点火系统
   现代汽车已经从一个机械系统(分电器)向一个完整地没有移动部件的固体状态的电子点火系统演变。这些系统完全由车载电脑控制。代替分电器,有多个线圈每个线圈为一个或两个火花塞服务。一个典型的6缸发动机有三个线圈一起安装在一个线圈包装里。火花塞线圈在独自的线圈的每一侧产生并运行适当的火花塞。在同一时间线圈控制两个火花塞点火。一个火花塞在压缩行程点火点燃可燃混合气产生能量,然而其他的火花塞在进气行程点火不产生能量。在一些汽车上,每个缸体在火花塞上方直接安装独立的线圈。为了更好的可靠性这个设计完全地消除高压火花塞线圈。这些系统的大多数使用这种被设计火花塞持续100,000多英里,减少了维护成本。


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