汽修畢業(yè)論文外文翻譯--點火系統(tǒng)

1、<p><b>　　外文資料翻譯</b></p><p>　　系 別 中德機電學院 </p><p>　　專 業(yè)汽車檢測與維修技術 </p><p>　　班 級 汽修0902班 </p><p>　　姓 名 XXXXXXXXX </p>&

2、lt;p>　　學 號 XXXXXXX </p><p>　　指導教師 XXXXXXXXXX</p><p><b>　　2012年 4 月</b></p><p>　　Ignition System</p><p>　　The purpose of the ignition syste

3、m 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 i

4、n 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.</p><p>　　The ignition system sends an extremely high voltage to the spark plug

5、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.</p>&

6、lt;p>　　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 e

7、ach cylinder in a specific order, at exactly the right time.</p><p>　　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, th

8、us 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.</p>&

9、lt;p>　　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

10、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 volt

11、age is stepped up, it goes to the secondary circuit which then directs</p><p>　　The Basics</p><p>　　Before we begin this discussion, let’s talk a bit about electricity in general. I know that th

12、is 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.</p><p>　　All automobiles work on DC (Di

13、rect 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 cabl

14、e 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

15、battery can be connected to an</p><p>　　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 s

16、witch. 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,

17、you are connecting the wire from the battery with the wire to the headlamps allowing battery current to go direct</p><p>　　Now, back to the ignition system, the basic principle of the electrical spark igniti

18、on 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.</p><p>　　Currently, there are three distinct types of ignition system. The

19、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

20、 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 imp</p

21、><p>　　Let’s take a detailed look at each system and see how they work.</p><p>　　The Mechanical Ignition System</p><p>　　The distributor is the nerve center of the mechanical ignition

22、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

23、 is under). Second, the distributor is responsible for directing that spark to the proper cylinder (which is why it is called a distributor).</p><p>　　The circuit that powers the ignition system is simple an

24、d 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. Ins

25、ide 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 connec

26、ted </p><p>　　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 ride

27、s 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 revolut

28、ion for every two revolutions of the engine. As it rotates, the cam pushes the points o</p><p>　　Now, we have the voltage necessary to fire the spark plug, but we still have to get it to the correct cylinder

29、. 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 cente

30、r 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 ter</p><p>　　The description I just prov

31、ided 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 t

32、o 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.</p><p>　　The Ignition Switch</p><p>　　There are two separate

33、 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 bat

34、tery 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 k

35、ey is turned to the spring-loaded star</p><p>　　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

36、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.</p><p>　　The Distributor</p><

37、p>　　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 op

38、en 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,

39、 the points would quickly burn up and you would hear heavy static o</p><p>　　The points require periodic adjustments in order to keep the engine running at peek efficiency. This is because there is a rubbing

40、 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 m

41、easuring 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.</p><p>　　On some vehicles, points are adjusted with the

42、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

43、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

44、 feeler gauge</p><p>　　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,

45、 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.</p>&

46、lt;p>　　Ignition Coil</p><p>　　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 o

47、f 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 circui

48、t wire goes into the coil through the positive terminal, loops around the primary windings, then exits thr</p><p>　　The coil secondary winding circuit contains 15,000 to 30,000 turns of fine copper wire, whi

49、ch 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

50、the heat of the current flow, the coil is filled with oil which helps keep it cool.</p><p>　　The ignition coil is the heart of the ignition system. As current flows through the coil a strong magnetic field i

51、s 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 spa

52、rk plugs through the distributor.</p><p>　　Ignition Timing</p><p>　　The timing is set by loosening a hold-down screw and rotating the body of the distributor. Since the spark is triggered at the

53、 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 shaf

54、t that is geared to the engine rotation.</p><p>　　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

55、 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

56、the needs of the engine.</p><p>　　Ignition Wires</p><p>　　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 expos

57、ed 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. I

58、n 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</p><p>　　Spark plug wires are routed around the engine very ca

59、refully. 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

60、 on damp days causing hard starting or a rough running engine.</p><p>　　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

61、 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 t

62、o the correct cylinder.</p><p>　　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 engi

63、ne. 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 wil

64、l tell you the correct firing order and cylinder layout for a particular engine.</p><p>　　The next thing we need to know is what direction the distributor is rotating in, clockwise or counter-clockwise, and

65、which terminal on the distributor caps that #1 cylinder is located. Once we have this information, we can begin routing the spark plug wires.</p><p>　　If the wires are installed incorrectly, the engine may b

66、ackfire, or at the very least, not run on all cylinders. It is very important that the wires are installed correctly.</p><p>　　Spark Plugs</p><p>　　The ignition system’s sole reason for being is

67、 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

68、 the engine.</p><p>　　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 i

69、n a given engine.</p><p>　　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

70、. 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

71、 spark plug is also important and must be set before the spark plug is installed in the engine. If t</p><p>　　The Electronic Ignition System</p><p>　　This section will describe the main differen

72、ces 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 sectio

73、n The Mechanical Ignition System.</p><p>　　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 an

74、d 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

75、to the control module to fire the coil.</p><p>　　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

76、need to have the initial timing adjusted by rotating the distributor housing.</p><p>　　The advantage of this system, aside from the fact that it is maintenance free, is that the control module can handle muc

77、h 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 mechanica

78、l systems. These systems only have a single wire from the ignition switch to the coil since a primary resistor is not longer needed.</p><p>　　On some vehicles, this control module was mounted inside the dist

79、ributor 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 mod

80、ule 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.</p><p>　　The higher voltages th

81、at 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

82、.</p><p>　　The early electronic systems had limited or no computing power, so timing still a centrifugal and vacuum advance built into the distributor.</p><p>　　On some of the later systems, the

83、 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 cams

84、haft 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 n

85、ecessary for the smooth run</p><p>　　The Distributor Ignition System</p><p>　　Newer automobiles have evolved from a mechanical system (distributor) to a completely solid state electronic system

86、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 coi

87、ls 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 fire</p><p><b>　　參考文獻：</b></p>

88、;<p>　　[1] 王欲進,張紅偉.汽車專業(yè)英語[M]. 北京：北京大學出版社，中國林業(yè)出版社，2007.8，55—67</p><p><b>　　點火系統(tǒng)</b></p><p>　　點火系統(tǒng)的作用是產生點燃發(fā)動機氣缸里可燃混合物的火花。在精確時刻和在發(fā)動機每個汽缸工作速率達到每分鐘數(shù)千次下才能產生火花。如果點火時刻不是瞬間，發(fā)動機運行不佳或不運行

89、。</p><p>　　當活塞在其壓縮行程頂部的時候，在每個汽缸里點火系統(tǒng)發(fā)送一個極其高的電壓到火花塞。為了接地每個火花塞的尖端有一個能穿過電壓的間隙。這就是電火花的發(fā)生。</p><p>　　火花塞可接收到的電壓在20，000伏到50，000伏甚至更高。點火系統(tǒng)的任務是在精確時刻從12伏的電源產生高壓電，按特定的順序給每個汽缸提供高電壓。</p><p>　　點火

90、系統(tǒng)執(zhí)行兩個任務。第一，它產生足夠高的電壓穿過火花塞的間隙，因此為了燃燒需要產生足夠強的電壓來點燃可燃混合物。第二，它控制點火時刻以便在精確時刻產生火花并將其發(fā)送到正確的汽缸。</p><p>　　點火系統(tǒng)被分為兩部分：初級線圈和次級線圈。初級線圈的低電壓由電池電壓（12伏至14.5伏）控制，負責在精確地時刻產生點火信號，將點火信號發(fā)送給點火線圈。點火線圈是將12伏電壓信號轉換為高于20000伏電壓信號的器件。一

91、旦電壓被加強就進入次級線圈，然后在正確時刻直接控制對應的火花塞。</p><p><b>　　基礎知識</b></p><p>　　在我們開始討論之前，讓我們大體了解一下電的方面。我知道這是基本材料，但有一段時間你不了解，有些人了解基礎知識以便他們能夠意識到采取什么措施。</p><p>　　所有的汽車用DC（直流電）來運行。這意味著電流朝一個

92、方向移動，從蓄電池的正極到蓄電池的負極。就汽車來說，蓄電池的負極由一根粗的電纜直接連接車身和接在汽車發(fā)動機缸體上。負極與車身或一些金屬部件連接被稱為接地。這意味著電路需要發(fā)送電流回到蓄電池負極與汽車金屬車身任何部分或金屬發(fā)動機缸體連接。</p><p>　　一個好的例子展示前大燈電路中電流是怎樣工作的。前大燈電路由從蓄電池正極到前大燈開關的導線組成。另一根導線從前大燈開關到前大燈的燈泡上的兩端子之一。最后，第三根

93、導線從燈泡的另一個端子到汽車金屬車身。當你打開前大燈時，你將連接從蓄電池到照明燈所允許蓄電池電流直接進入照明燈燈炮的導線。電流穿過燈泡內的燈絲，然后從另一根導線出來接地。電流回到蓄電池的負極形成完整的電路。一旦電流流經照明燈內的燈絲變熱、變亮，產生光。</p><p>　　回到點火系統(tǒng)，電火花點火系統(tǒng)的基本原理約75年沒有改變了?；鸹óa生的方法和如何分配有什么變化。</p><p>　　目

94、前有三種不同類型的點火系統(tǒng)。1975年以前使用機械點火系統(tǒng)。它使用機械和電氣并沒有使用電子。理解早期的點火系統(tǒng)將會更容易理解新的電子和計算機控制的點火系統(tǒng)，所以不要忽視機械點火系統(tǒng)。在70年代初電子點火系統(tǒng)開始在汽車上使用，因能更好的控制變得流行，排放控制的重視來提高可靠性。最后，在80年代中期使用無分電器點火系統(tǒng)。該系統(tǒng)由計算機控制，沒有移動部件，所以可靠性大大提高。除了相隔60，000到100，000英里以上更換火花塞以外這些系統(tǒng)大

95、多數(shù)不需要維修。</p><p>　　讓我們詳細研究每個系統(tǒng)，理解它們是如何工作的。</p><p><b>　　機械點火系統(tǒng)</b></p><p>　　分電器是機械點火系統(tǒng)的核心，執(zhí)行兩個任務。第一，分電器負責起動線圈在精確時刻產生火花（取決于發(fā)動機運轉得多快和根據發(fā)動機的多少負荷）。第二，分電器負責引導火花到正確的汽缸（這是為什么叫分電器

96、的原因）。</p><p>　　直接簡單的向點火系統(tǒng)提供能量的電路。當你在點火開里插入鑰匙，把鑰匙轉到運行位置時，你發(fā)送電流從蓄電池直接到點火線圈的正極（+）。在進入線圈負極（—）之前，線圈內部是一系列環(huán)繞線圈一百圈以上的銅線圈。負責分電器電流的線圈并連接一個特殊的ON/OFF開關，稱為白金觸點。當白金觸點關閉時電流直接接地。當電流流過點火開關時，通過線圈里的繞組，然后到地面，在線圈內部建立一個強大的磁場。<

97、;/p><p>　　白金觸點由一個安裝在分電器內活動底板上的固定觸點和一個固定在觸點臂彈簧末端可移動觸點組成。移動觸點騎在一個有4，6或8個凸輪凸角（取決于發(fā)動機缸體的數(shù)目），騎在分電器里的分電器軸上。發(fā)動機轉動分電器凸輪就轉動，發(fā)動機曲軸每轉兩圈分電器凸輪軸轉一圈。當分電器凸輪軸轉動時，凸輪推動白金觸點打開和關閉。每次白金觸點打開時，通過線圈的電流流動被干擾，因而產生磁場并通過次級線圈釋放高壓電流。電壓電流進出線圈

98、尖端并通過高電壓線圈。</p><p>　　當今，為了點火我們需要充足的電壓，但是我們必須把高電壓送到正確的汽缸。直接連接分電器蓋的中央高壓線。分電器蓋下面是一個固定在分電器軸頂部的分火頭。分火頭尖端有一個金屬條與分電器蓋中央連接。在分電器內部分火頭從中央高壓線接收高壓電，給分火頭的另一端傳送高壓電，分火頭旋轉經過每個火花塞的觸點。當分火頭在分電器軸上轉動時，發(fā)送電壓到正確的分缸線，依次送到火花塞。電壓進入火花塞