JPS6334590B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an incandescent light bulb, and more particularly to an improvement in an incandescent light bulb that includes a tungsten coil filament that has a long life and good vibration resistance in an airtight container. Traditionally, the tungsten coil filament built into the airtight container of an incandescent light bulb is heated by coiling tungsten wire and then heating it indirectly in a hydrogen furnace or electric furnace, or by heating the coil or by energizing it after completing the incandescent light bulb. In addition to removing distortion during coiling, the tungsten wire is secondary recrystallized so that the stable shape of the tungsten coil filament is maintained during lighting. Burning out of the tungsten coil filament of an incandescent light bulb is very often caused by uneven temperature distribution in the tungsten wire. The crystal orientation of the surface of the tungsten wire is different, so the emissivity of light from the tungsten wire is not uniform, resulting in temperature unevenness. In order to prevent this, it is possible to make the secondary recrystallization structure of the tungsten wire finer to reduce the temperature difference, but if the recrystallization structure of the entire tungsten coil filament is made finer, the vibration resistance strength of the tungsten coil filament decreases. There is a drawback that it does. The present invention was made to solve these drawbacks.
It is an object of the present invention to provide an incandescent light bulb that eliminates uneven temperature distribution of a tungsten wire and is equipped with a tungsten coil filament that has high vibration resistance. The invention will now be described in detail with reference to the accompanying drawings. As mentioned above, the present inventors have discovered that in order to reduce the uneven temperature distribution of the tungsten wire, which accounts for most of the causes of tungsten coil filament burnout, and to increase the vibration resistance, it is necessary to We thought that it would be better to make the recrystallized structure finer and to increase the crystalline structure inside the tungsten wire, and after various trials and errors, we arrived at the following method and conducted tests. FIG. 1 is a partially cutaway side view of an example of the tungsten coil filament heat treatment apparatus used in the above test, in which a cylindrical body 1 made of quartz glass or ceramic is connected at both ends with rubber plugs 2, 2. The plugs 2, 2 are hermetically sealed, and conductive wires 3, 3 hermetically pass through them to hold the tungsten coil filament 4. Inside the cylinder body 1, which is kept airtight, is an exhaust pipe 5.
It is evacuated and maintained in a vacuum. Note that the inside of the cylinder 1 may be an inert gas or hydrogen atmosphere. A high-frequency heating coil 6 is provided on the outer periphery of the cylinder 1 so as to surround the position of the tungsten coil filament 4 inside the cylinder 1 . (The high-frequency heating coil is shown with a portion thereof cut away, and the high-frequency oscillation device and the conductive wire and power source that feed it are not shown.) With this device, the conductive wire 3, 3 to heat the tungsten coil filament 4, and a high frequency heating coil 6 applies high frequency to the tungsten coil filament 4. Next, the test method will be described. Tungsten coil filament is 100V,
Used 750W single coil filament. The diameter of the tungsten wire is 0.25mm. For the heat treatment, tungsten coil filaments having the above ratings were heat treated using the following three heating methods. () A tungsten coil filament is heated to 1600℃ by electricity, and a 20MHz high frequency is rapidly applied to it. () A tungsten coil filament is heated to 1600℃ by electricity, and a 1MHz high frequency is rapidly applied to it. () Tungsten coil filament is heated to 1600°C by energizing, without applying high frequency. In both () and () above, the temperature of the tungsten coil filament was set to reach approximately 2200°C, which corresponds to the secondary recrystallization temperature of the tungsten wire. FIG. 2 shows a 200 times enlarged view of the surface of the tungsten coil filament heat-treated in the above test. In Figure 2, a is the above ()
b was heat-treated by the method (), c was heat-treated by the method (),
As is clear from FIG. 2, the surface structure of specimen a is finer than that of specimens b and c. By using tungsten coil filament that has been heat treated as above () or (), each 100V750W incandescent bulb with halogen is produced.
was manufactured and its lifespan was tested. The sealed halogen is bromine Br and the inert gas is argon A70.
A mixed gas of ₃₀ % nitrogen and nitrogen was sealed at 700 torr. In addition, 10 of each of the same halogen bulbs with tungsten coil filaments that had been heat-treated as described in () or () above were increased in height by 5 cm and dropped onto a wooden board in the direction of the bulb axis. The vibration resistance was adjusted until the wire broke. Table 1 below shows 10 each.
The average value is shown.

[Table] From the above results, it can be seen that () and (), which were heat-treated with high-frequency electromagnetic waves, are superior in both lifespan and vibration resistance compared to (), which was not heat-treated with high-frequency electromagnetic waves. Let's further consider heat treatment using high-frequency electromagnetic waves. Angular frequency of high frequency electromagnetic waves ω=
2πf (f: same frequency C/S), electrical conductivity σ(・cm
^-1 ), the penetration length of high-frequency electromagnetic waves into the tungsten wire δ (cm) when the speed of electromagnetic waves is C (cm/S).
is given by the following formula. δ=C/(2πσω) ^1/2 (cm) From the above formula, the penetration depth in the above heat treatment () and () becomes the value shown in Table 2 below.

[Table] As mentioned above, the direct diameter of the tungsten wire used in the test was 0.25 mm, so the high-frequency electromagnetic waves penetrated the entire area of the tungsten wire during the heat treatment, which caused the secondary recrystallization of the tungsten wire to become fine. As shown in Table 1, the lifespan is
It can be seen that the vibration resistance was a low value of 30 cm after 1000 hours or less. Then, in the heat treatment using 20MHz high-frequency electromagnetic waves, the penetration length of the high-frequency electromagnetic waves into the tungsten wire is 0.09 mm, and the high-frequency electromagnetic waves with a diameter of 0.25 − 0.09 × 2 = 0.07 mm penetrate into the center. Because it has parts that do not have a fine secondary recrystallized structure, it has strong vibration resistance and a long life, and the surface has a fine secondary recrystallized structure. It is thought that the unevenness of the temperature distribution on the surface of the tungsten wire was eliminated, and therefore the cause of burning out the tungsten coil filament was eliminated. The effects of the present invention cannot be fully achieved unless there is even a small portion left in the center of the tungsten wire where high-frequency electromagnetic waves do not reach, so the penetration depth must be smaller than 1/2 of the diameter of the tungsten wire. The present invention is an incandescent light bulb in which a tungsten coil filament made of tungsten wire that has been heat-treated with high-frequency electromagnetic waves having a frequency calculated from this value using the above formula is housed in an airtight container. As detailed above, the present invention provides a method for storing a tungsten coil filament of a tungsten wire heated by high-frequency electromagnetic waves at a frequency such that the penetration length of the electromagnetic wave into the tungsten wire is smaller than 1/2 of the diameter of the tungsten wire. This incandescent light bulb has an excellent effect of eliminating the uneven temperature distribution on the surface of the tungsten wire, which was the cause of conventional tungsten coil filament burnout, and providing an incandescent light bulb with strong vibration resistance. are doing. In addition, although the test results of halogen light bulbs were explained in the examples, the present invention is not limited to halogen light bulbs, but is effective when applied to incandescent light bulbs in general. Although the heat treatment in the form of a filament has been explained, it may also be performed after the incandescent light bulb is constructed, and the above heat treatment method has the same effect even if a high-frequency electromagnetic current is directly passed through the tungsten coil filament. .

[Brief explanation of the drawing]

Figure 1 is a partially cutaway side view of an example of the tungsten coil filament heat treatment apparatus used in the present invention, and Figures 2 a, b, and c are enlarged views of the surface of the tungsten coil filament obtained by three types of heat treatment methods. be. 1... Cylindrical body, 2... Plug, 3... Conductive wire, 4... Tungsten coil filament, 6... High frequency heating coil.

Claims (1)

[Claims] 1 A tungsten coil filament is built in an airtight container, and the tungsten wire constituting the tungsten coil filament emits high-frequency electromagnetic waves at a frequency such that the penetration length of the electromagnetic waves into the tungsten wire is less than 1/2 of the diameter of the tungsten wire. An incandescent light bulb characterized by being heat-treated by.