点火系统外文文献翻译中英文翻译外文翻译.docx

1、点火系统外文文献翻译中英文翻译外文翻译Ignition SystemThe 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.

2、 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

3、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

4、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 contr

5、ol 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

6、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 di

7、rects the charge to the correct spark plug at the right time.The BasicsBefore we begin this discussion, lets talk a bit about electricity in general. I know that this is basic stuff, but there was a time that you didnt know about this and there are people who need to know the basics so that they cou

8、ld 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 bo

9、dy 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 vehicles metal body or the metal engine block.A good exa

10、mple 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 term

11、inal 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

12、 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

13、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

14、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 dont skip over it. The electronic ignition system started finding its way to production vehicles during the early 70s and became pop

15、ular 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

16、of these systems required no maintenance except replacing the spark plugs at intervals from 60,000 to over 100,000 miles.Lets take a detailed look at each system and see how they work.The Mechanical Ignition SystemThe distributor is the nerve center of the mechanical ignition system and has two task

17、s 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 (whi

18、ch 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 igni

19、tion 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

20、 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

21、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 complet

22、e 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 winding

23、s. 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

24、 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 insi

25、de 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,

26、 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 didnt talk about the cond

27、enser that is connected to the point, nor did we talk about the system to advance the timing. Lets take a look at each section and explore it in more detail.The Ignition SwitchThere are two separate circuits that go from the ignition switch to the coil. One circuit runs through a resistor in order t

28、o 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 n

29、eeded 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 resisto

30、r 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.Ignition Coi

31、lThe 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 thi

32、s 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 fi

33、ne 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 i