Incandescent lamp is an electric light source, which heats the filament to incandescent state and emits visible light through thermal radiation. Starting from 1879, T.A. Edison of the United States made carbon fiber (carbon filament) incandescent lamps. With the continuous improvement of filament material, filament structure and filling gas, the luminous efficiency of incandescent lamps is also improved accordingly. 1959, based on incandescent lamps, the United States developed tungsten halogen lamps with small volume and adjustable light. The development trend of incandescent lamps is mainly to develop energy-saving bulbs. Incandescent lamps with different uses and requirements have different structures and components. Incandescent lamps have low light efficiency, but good light color and light collection performance. It is the largest output and the most widely used electric light source.
/kloc-in the second half of the 0/9th century, people began to trial-produce incandescent bulbs, and heated the filament with current in vacuum. 1879, T.A. Edison of the United States made the carbon fiber (carbon filament) incandescent lamp, and sent the electric light source into the home for the first time. 1907, A. Justin invented the drawing tungsten wire and made it into a tungsten filament incandescent lamp. Soon after, I Langmuir of the United States invented the spiral tungsten wire, and filled the glass bulb with inert gas nitrogen to inhibit the evaporation of tungsten wire; In 19 15, a mixture of argon and nitrogen is filled. 19 12 years, in order to minimize the contact surface between filament and gas, Junyi, a Japanese Mihura, developed the tungsten filament from single helix to double helix, which greatly improved the luminous efficiency. 1935, A. Claude of France filled the bulb with krypton and xenon, which further improved the luminous efficiency. From 65438 to 0959, the United States developed tungsten halogen lamps with the smallest volume and the smallest light attenuation on the basis of incandescent lamps. The history of incandescent lamps is the history of improving the luminous efficiency of light bulbs. The production efficiency of incandescent lamps has also increased rapidly. In 1980s, the output of ordinary incandescent lamp high-speed production line has reached 8000 pieces/hour, and computer has been used for quality control.
It is generally believed that the inventor of electric light is the great inventor Edison. In fact, the experimental research in this field began long before Edison.
In the patent document of US 1845, Starr of Cincinnati proposed that carbon wires can be used in vacuum bubbles. According to this idea, Swann in Britain used carbonized paper as a filament, trying to make current pass through it and emit light. However, due to the poor vacuum pumping technology at that time, the filament was quickly burned out by the residual air in the bulb. Therefore, the life of this lamp is quite short, only one hour, and it has no practical value. 1878, the appearance of vacuum pump made Swan carry out the research on incandescent lamps again. 1879 65438+ 10, the incandescent lamp he invented was successfully tested in public and won favorable comments.
1879, Edison also began to study electric lights. He believes that the key to prolong the life of incandescent lamps is to improve the vacuum degree of bulbs and use heat-resistant materials with low power consumption, strong luminescence and low price as filaments. Edison tried 1600 kinds of heat-resistant materials successively, and the results were not satisfactory. 1879 10+265438+. Results The light emitted by carbonized cotton thread was bright and stable, lasting for more than 10 hour. In this way, the carbonized cotton filament incandescent lamp was born, and Edison obtained a patent for it.
Success did not stop Edison. He continues to look for heat-resistant materials that are stronger and more durable than carbon cotton. 1880, Edison developed a carbonized bamboo filament lamp, which greatly prolonged the filament life. In the same year, in 10, Edison set up his own factory in New Jersey and started mass production. This is the earliest commercialized incandescent lamp in the world, and Swann of Britain also set up a factory in Benwell, a suburb of Newcastle, in 18 1.
The invention of incandescent lamp is usually attributed to Edison in America and Swan in England. In Britain, the centenary of the invention of electric light was held in 1978+00, while in the United States it was held one year later in 1 10.
The competition between the two inventors is fierce, and patent disputes are almost inevitable. Later, the two reached an agreement to set up a joint venture Edison Swan Electric Company to produce incandescent lamps in Britain.
Modern tungsten filament incandescent lamp was successfully trial-produced by American inventor Coolidge in 1908. The luminous body is a filament drawn from tungsten metal. The most valuable feature of this material is its high melting point, that is, it can remain solid at high temperature. In fact, the filament temperature of a lighted incandescent lamp is as high as 3000℃. It is precisely because the hot filament produces light radiation that the electric lamp emits bright light. Because some tungsten atoms will evaporate into gas at high temperature and deposit on the glass surface of the bulb, making the bulb black, incandescent lamps are made into a "paunchy" appearance, which is to let the deposited tungsten atoms spread to a larger surface. Otherwise, the light bulb will turn black in a short time. Because the filament continues to sublimate, it will gradually become thinner until it is finally disconnected, when the life of a light bulb is over.
Among all the lighting lamps that use electricity, incandescent lamp has the lowest efficiency, and only a small part of the electric energy it consumes, that is, 12%- 18% can be converted into light energy, and the rest is lost in the form of heat energy. As for the lighting time, the service life of this kind of electric lamp usually does not exceed 1000 hours. At this point, halogen lamps are much longer than ordinary incandescent lamps. Halogen lamp is usually a tiny glass tube. Compared with incandescent lamps, halogen lamps are special in that tungsten filaments can "self-regenerate". In fact, the filament and glass shell of this lamp are filled with some halogen elements, such as iodine and bromine. When the filament is heated, tungsten atoms evaporate and move towards the glass tube wall. When they approach the glass tube, the tungsten vapor is "cooled" to about 800℃ and combines with halogen atoms to form tungsten halides (tungsten iodide, tungsten bromide). Tungsten halide moved to the center of the glass tube and landed on the corroded filament. Because tungsten halide is unstable, it will decompose into halogen vapor and tungsten when heated, so that tungsten will be deposited on the filament to make up for the evaporation. This cycle will prolong the service life of the filament. Therefore, the filament of halogen lamp can be made relatively small and the lamp body is very compact. Halogen lamps are generally used in places where spotlight is needed, such as local lighting in writing desks or living rooms.
Recently, the Australian government launched a plan to gradually adopt energy-saving fluorescent lighting equipment to reduce greenhouse gas emissions, and incandescent bulbs will be banned from 20 10.
This is the first plan to eliminate incandescent light bulbs in the world. In order to save energy and protect the environment, incandescent bulbs will die!
According to reports, the price of compact fluorescent lamps is about 10 times that of incandescent bulbs, but their life span is six times that of the latter. For products with the same brightness, the power consumption of fluorescent lamps is less than a quarter of that of incandescent bulbs. With the continuous emergence of new products, new light sources are also being born. For example, LED is a semiconductor solid-state light-emitting device, which is called the fourth generation lighting source or green light source. It has the characteristics of energy saving, environmental protection, long service life and small size. Its service life can reach 60,000 to 65,438+10,000 hours, which is more than 10 times of the traditional light source. The electro-optical power conversion is close to 100%, and the same light efficiency is more than 80% less than that of the traditional light source.
Incandescent light bulbs have been used for 128 years. When it comes to incandescent light bulbs, people will inevitably think of Edison. In fact, before Edison, J. Swan, a British electrical engineer, began to study electric lights as early as the late 1940s. After nearly 30 years' efforts, Swan finally found a kind of carbon filament suitable for filament. 1878 18 February 18, Swan successfully trial-produced the first incandescent light bulb. Shortly thereafter, he also showed his carbon filament light bulb at the Newcastle Chemical Society. When his experimental report on incandescent lamps was published in the United States, it also gave Edison direct help. Unlike Edison, Swan didn't apply for a patent until 1880 after he invented the incandescent lamp. It was not officially put into production until 188 1. After the light bulb was put into production, he failed to build the corresponding power station and transmission network like Edison. In this way, Edison came from behind and became a recognized inventor of incandescent lamps.
During Edison's development of filament materials for incandescent bulbs, cotton thread, thin strips of wood, straw, gauze paper, thread, Manila hemp rope, horse hair, fishing line, chestnuts, hard rubber, cork, rattan, corn fiber and even human beard and hair were tested.
1879, 10, 2 1 In the evening of June, Edison and his assistants successfully put the carbon filament into the light bulb. According to Edison's instructions, a German glass expert pumped the air in the light bulb to only one millionth of atmospheric pressure, sealed it, and Edison switched on the current. The scene they were looking forward to day and night finally appeared in front of them: the light bulb gave off golden light! After 45 hours of continuous use, the filament of this kind of electric lamp was burned out, which is the first kind of electric lamp with wide practical value. Later, people designated this day as the invention day of electric light. Since then, Edison has been working on the improvement of incandescent lamps. In order to improve the quality of light bulbs and prolong their life, Edison tried his best to find suitable materials for filament. By early May 1880, he had tested about 6,000 kinds of plant fiber materials. For a long time, Edison sent many people around the world to find bamboo suitable for filament. During the nine years from 65438 to 0908, Japanese bamboo has been the main raw material for supplying carbon fiber.
The incandescent light bulb invented by Edison has made great contributions to human civilization, but in order to save energy and protect the environment, it can only be withdrawn from the historical stage!
Supplement: Incandescent lamps have an advantage that most other types of luminous products do not have, that is, they are suitable for frequent starting occasions.
This is an ordinary incandescent lamp, which is mainly composed of glass shell, filament, wire, induction column, lamp holder and so on.
The glass shell is made into a sphere, and the material is heat-resistant glass, which separates the filament from the air, which can not only transmit light, but also play a protective role. When the incandescent lamp works, the temperature of the glass bulb can reach about 100℃.
The filament is made of tungsten filament which is much thinner than the hair, and it is made into a spiral shape. It seems that the filament is very short, but in fact, this extremely thin spiral tungsten wire is drawn into a straight line, and the length exceeds 1 meter.
These two lines are simple on the surface, but in fact they are composed of three parts: internal line, Dumex line and external line. The inner conductor is used for conducting electricity and fixing the filament, and is made of copper wire or nickel-plated iron wire; A short red line in the middle is called Dumex line, which is required to be closely combined with glass without air leakage; The outer conductor is copper wire, and the task is to connect the lamp holder with electricity.
The trumpet-shaped glass part is an induction column, which is connected to the glass shell and plays the role of fixing the metal part. The air in the glass bulb is pumped out by the exhaust pipe, and then the lower end is welded and sealed, so that the lamp will not leak.
The lamp holder is a metal piece connecting the lamp holder and the power supply, and it is bonded with the glass shell with solder paste.
It is particularly necessary to talk about filament here, because it is the lamp that shines.
The tungsten filament in an incandescent lamp, like the carbon filament, is afraid of air. If the glass bulb is filled with air, when the temperature of the tungsten wire rises above 2000℃ after being electrified, the air will attack it mercilessly, so that it will burn out quickly, and at the same time, a yellow-white tungsten trioxide will be generated, which will adhere to the inner wall of the glass bulb and the inside of the lamp.
If there is less air left in the glass bulb, the above process will proceed slowly, and tungsten will combine with oxidation in the air to form a thin blue mixture of tungsten trioxide and tungsten oxide.
These are all tricks played by the air-oxygen in the air oxidizes the high-temperature tungsten wire.
Therefore, tungsten filament bulbs should be evacuated to remove all air.
Sometimes, I am afraid that the air pump is not clean, so I have to apply a little red phosphorus to the induction column of the light bulb. Red phosphorus will become white phosphorus when heated, and white phosphorus will easily react with oxygen to generate solid phosphorus pentoxide, which will "eat" oxygen and destroy the residual oxygen in the glass shell.
However, this does not solve all the problems. Incandescent lamps will turn black when used for a long time and burn out after a while. Do you know why?
Indeed, the evaporation rate of tungsten wire in vacuum is much slower than that of carbon wire. However, when the lighting temperature of incandescent lamp rises very high, the evaporation of tungsten is still very serious.
Long-term high temperature makes the tungsten atoms on the surface of the tungsten filament evaporate and diffuse like water vapor, and then deposit on the inner surface of the glass shell layer by layer, which makes the glass shell slowly turn black and become more and more opaque.
The evaporation of tungsten also makes the tungsten filament thinner and thinner and finally burns out.
The higher the working temperature of filament, the faster the evaporation of tungsten and the shorter the life of incandescent lamp.
Is there any way to reduce evaporation and prolong the service life of filament under vacuum condition?
The only way to prolong life is to lower the temperature and lower the filament temperature. When the working temperature of tungsten wire is as high as 2700℃, the bulb will go out in less than 1 hour. The working temperature of tungsten wire is reduced to 1700℃, and the service life can be extended to more than 1000 hours.
However, this is not a good idea. Reducing the working temperature of tungsten filament, that is, reducing its incandescence, will reduce the luminous efficiency of incandescent lamp, which is far less bright than that at high temperature.
Therefore, the problem is clearly in front of people: if incandescent lamps want to emit more light, they must increase the working temperature of the filament; If you want to reduce the evaporation of tungsten wire to prolong the life of the lamp, you have to lower its body temperature. "This is a contradiction.
Our requirements are not only high luminous efficiency, but also reducing the evaporation of tungsten wire.
After years of research, people have noticed that when the bulb is filled with air, although the filament will be oxidized soon, the evaporation of tungsten will slow down.
The reason is actually very simple: air is composed of many components, and only oxygen tungsten oxide accounts for 1/5 of the total air; As for the remaining 4/5 nitrogen, not only did it not participate in destroying tungsten, but it also did something good-hindered the movement of tungsten molecules and slowed down the evaporation rate of tungsten.
So people found a good friend to defend tungsten wire-nitrogen. There is nitrogen in the air, and it accounts for most of the air. It can be said that "I can't find a place to get it, and I don't have to work hard to get it."
In the past, in order to ensure the life of incandescent lamps, we had to evacuate the air from glass bulbs as cleanly as possible. Now, for the same purpose, we have to do the opposite, that is, fill the glass bulb with gas, and the gas will not react chemically with tungsten.
Nitrogen is a lazy guy who likes to wander around by himself and doesn't like to deal with anyone. It is useless in many places, but it can be used in incandescent lamps.
If the bulb is vacuum, then when the tungsten wire is connected to the power supply and the temperature rises, the molecules of tungsten will "be ready to move", leave the filament in large numbers and run around "like nobody's business" until they are sucked to the glass shell wall.
Once the glass bulb is filled with nitrogen, a thin and stable gas protective layer will be formed around the incandescent filament, just like a living "fence". Every nitrogen molecule is a brave warrior, guarding around the tungsten wire, rude and violent against those tungsten molecules who try to break away from the collective and run around, and tell them to return to their jobs and continue to serve the light. In this way, the evaporation rate of tungsten wire is much slower.
The result is an incandescent light bulb filled with nitrogen.
19 13, Langmuir filled the glass bulb with nitrogen for the first time, which was another major innovation of incandescent lamp after the filament was changed from carbon filament to tungsten filament. Up to now, aeration is still the basic measure to inhibit the evaporation of tungsten wire.
However, it should be noted that oxygen or water vapor will react with tungsten wire when working, so there are very strict requirements on the oxygen content and water content of inflation, otherwise the life of the bulb will be greatly shortened.
Aeration slows down the evaporation rate of tungsten filament, and the filament can work at higher temperature under the same service life, so the luminous efficiency of inflatable bulb is higher than that of vacuum bulb. Generally speaking, the luminous efficiency of inflatable bulbs is higher than that of vacuum bulbs 1/3 or more.