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The development of the design of spark plugs

Spark plugs, of course, operate in extreme conditions, which only can be found in the car. They are alternately "the epicenter of the explosion" of hot gases with temperatures up to several thousand degrees, then take on a portion of the working mixture, which has just formed from the air (at ambient temperature), and gasoline vapor. All this is repeated dozens of times per second for many hours. The main task of the whole structure is to create a spark gap, which is periodically passed through a powerful electric charge under the stress of 20-30 thousand volts, which creates an arc that ignites the working mixture. Most are small deviations of the parameters leads to unstable operation, especially noticeable at idle, and sometimes to a complete stop or inability to start the engine. The main cause of such deviations are the accumulation of products of combustion of gasoline, spark-plug the gap. Out of this contradictory situation is found for a long time - plug itself should be released from the combustion products. They dozhigayutsya her hot surfaces and washed off a whirlwind of burning gases, falling further into the engine oil, and eventually - in the oil filter or in the form of deposits on the bottom of the crankcase. However, the spark plug must not be heated too much, in this case begins the so-called glow ignition and detonation, when the lights are not working mixture from the discharge current at a given time, and from the hot electrode at the time of contact with the vapor in the chamber. The consequences of this most unfortunate, since the loss of power and increasing emissions of pollutants to the possible destruction of the engine. Nature of the operation of the vehicle determines the enormous range of possible loads on the engine. Thermal regime of its components at work, say, in the city is very different from the motion of heavy duty mountain streamer. All this time the spark plug to provide a precise balance between the accumulation of heat for the self-cleaning and to prevent the diversion of surface ignition. It was established experimentally that such a balance is maintained as true when working surfaces candles are in the range from 400 to 900 degrees. It is well known scheme of heat typical spark plug. About 20% of the 100 derived from the combustion gas passes back into the chamber received a new portion of the working mixture (it comes with almost ambient temperature). 60% passes through the surface contact of the insulator and shell candles then head to the body where they are already "waiting" cooling jacket. 10% received an atmosphere outside of the outer parts of the shell and insulator. It is a combination of design features of the insulator and the shell of spark plugs have identified their division into hot, cold and intermediate. The former have a larger surface facility, outstanding in the camera and "available" to heat the burning gases and a small area of ??transition from prison to the shell. The latter have a much larger area for heat dissipation, and therefore their working surfaces are heated much less. The ability to store heat is called heat range spark. Virtually every manufacturing company applies its system is encoded, so the only way to choose the right candle - use corporate directory or table of interchangeability. Ceramic insulator determines the ability of the candle store heat, and metal core - to give. Without an effective solution of the second component of this equation can not be the right balance, and therefore almost all modern candles are the so-called bimetallic structure. The central electrode is a composite consisting of a persistent erosion of the shell (usually made of chrome-steel nikilevoy) and a copper core, greatly increases the ability to remove heat. Much more rarely do bimetallic electrodes and the side, even more rarely use copper instead of other materials such as silver. Bimetallic central electrode attached to the spark the most important property, known as Thermo. Its design has both a "hot" and "cold" properties. At the time of starting the engine heats up the lower part of the electrode made of chrome-nikilevogo alloy with lower thermal conductivity. This allows you to maintain a higher temperature and, consequently, to provide fast and reliable start. Then, as the mass of warm candle comes in a copper core, intense heat abductor, a candle is a "cold". By reducing turnover, such as idling, more runs chrome nikilevy site, and the candle again becomes "hot" properties. The idea of ??"unattended" vehicle forced designers to look for ways to increase the operating time of a candle. Many of the new U.S. cars now offer 160 thousand miles before the first replacement of consumables (filters, spark). Most of these models are equipped with platinum inserts in the form of discs on the side or on both electrodes. Platinum is much more resistant to corrosion and electrochemical destruction than the traditional chrome-nikilievye alloys. Structures with electrodes made of the entire platinum alloy, are made less frequently. In retail, "candle-centenarians" often staffed by 4.3-electrode side, although there are also platinum paste. Motorists mistakenly believe that four electrodes improve "podzhigaemost" mixture, forming a bridge of four plasma. In fact, the opposite occurs. "Podzhigaemost" as well as the efficiency of combustion even slightly worse, but significantly extend the lifetime of a candle. In the case of the four side electrodes, a spark is formed between the central and the side that is closer. Its surface is a little worn and comes in the next - the one whose distance is minimal. So in turn, and running multiple side electrodes, extending the life of the candle. The combustion of a mixture of working with a few candles side electrodes deteriorates because of its access to the most critical part of the chamber - the spark - is difficult. In addition, the greater the electrode, the intense heat from the candle. For these structures more likely fouling and engine performance is worse for CO and NO. Therefore, designers are actively exploring, another way - candles with a lateral electrode minimum or ... entirely without ground electrode. The latest design in real life can be found only on the sports car. Another way to "escape" from the use of ground electrode offered at the time the company SAAB. In the design of its role fulfilled ... piston. The idea was simple and ingenious. Ignition of a mixture of any gasoline engine occurs when the piston moves upward when it compresses already pre-entered into the camera working mixture. On the surface of the piston was made needle-shaped protrusion, and went with that spark, and then getting to the central electrode of a candle placed in the usual place for it. The advantages of this design are obvious. Not only increased the service "side electrode" (it almost does not burn), but the central electrode and the insulator could be made more durable. Not allowed to introduce such a system ignition problems with the supply and distribution of electric charge. The next step was to improve the geometry of the lateral and central electrode spark of conventional design. If we take as an example of the directory of any of the big firms, then it is possible to find different ways to improve 10-20 sparking. The shape of the central electrode is changing and the most radical example of this can be a model Rapidfire of Delphi. On the surface of the central rod made of 12 ribs with sharp edges. On the edge of the candle goes much easier than with the traditional smooth cylindrical surface of the electrode. This allows, on the one hand, the lower the threshold voltage of the ignition, and the other - to make it safer and more sustainable modes when idling or starting. The main enemy of modern candles on modern engines are ... "Neighbors" of the camera. Structurally, the candle can only be installed in its upper part where the valves are already settled, and, often, different sensors. The transition from two to four and then to five valves per cylinder leaves very little free space. Candle has to "lose weight" in diameter, saving precious space on the inside of the combustion chamber. Thus, in the recent past can be found carved candles with M18, it is now common are M14 and M12 are already there, and even M10. For such a taper is much more difficult to solve the problems of thermal endurance and heat, and there come to the fore issues of material quality, production stability and compliance technology. All manufacturers have their own unique labeling system. For example, nearly the same spark of different manufacturers can be called WR7D, RN9YC, CR43CXLS, CW7LPR or 17R-7DU. The only letter that appears in this case, each combination is R, and this is no accident. It represent a resistor made an integral part of the central electrode. Like many other solutions, it came from the aircraft of those days when out of the internal combustion engine it squeezed the last reserves of efficiency. The resistor should be used on those vehicles that are equipped with electronic systems, located in the engine compartment. Another common letter - C, indicating the copper (Cupper), - or rather, the central copper electrode, and two letters indicate the CC for Champion copper core as the center, and a ground electrode. The most important numerical characteristics of the spark plug heat range is a number, the thread diameter and thread length. Needless to say that the candle should fit on the three parameters of the engine of your car. Even a simple mistake with a length of thread can result in costly sad consequences. If it is shorter than your full-time - the "extra" turns of thread in the head very quickly accumulate the products of combustion, and then for a normal spark would have to punch a special way of tapping. Even worse than the consequences of screwing too long candles. In this case, the combustion products are already settle on its surface, and it will be captured svoebrazny lock. The minimum result of such carelessness - dismantling the engine. Nor should we try to remember the coding system and the glow of threads from different manufacturers. Any reputable seller and the customer has the parts ready Table of interchangeability. For the basic cases Spark plugs, or rather their appearance, are an excellent indicator of the engine. Not only is she ready to plug you "tell" about the possible errors of her choice, but to tell the hidden processes of developing the engine before they declare themselves as black smoke, detonation and unstable. Normal working candle has a serviceable engine clean the electrodes, and the color of the ceramic insulator varies from light gray to brown. The appearance of black oily soot suggests that either a candle for the engine is cold, or begin to show themselves because of wear of piston rings in a cell enters an excessive amount of oil, or the carburetor is adjusted correctly and working mixture pereobogaschena. Overheated the candle is white ceramic. If, however, by removing the spark plug, you will find fused or bombarded with molten aluminum electrodes - a signal has already begun serious trouble (surface ignition, detonation).

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