JPH0316207Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a translucent alumina ceramic arc tube used in high-output, high-pressure sodium lamps used for special purposes such as the chemical industry.

In the polymer chemical industry, polymerization reactions are carried out using light as activation energy.
In this case, a huge amount of light energy is required. For this reason, high-pressure mercury lamps and metal halide lamps, which have high conversion efficiency into light energy, are used.
However, in the current era where energy conservation is required, there is a strong desire to develop a lamp that is more efficient than the above two types of lamps.

For this reason, high-pressure sodium lamps, which are already used for road lighting, have more than twice the illumination efficiency of mercury lamps, and have the highest efficiency among existing white light sources, making it difficult to use high-pressure sodium lamps for photopolymerization. It has been tried.

However, for this practical use, a lamp output of 20 to 60 KW is required, which is much larger than that of a normal high-pressure sodium lamp for lighting. For this reason, the arc tube used in the lamp also needs to have an outer diameter of 20 to 50 mm and a length of 1 to 3 m, and because of the large outer diameter and length, it has not been put to practical use.

In mercury lamps and metal halide lamps, quartz tubes are used as luminous tubes, and by using quartz tubes, the dimensions of quartz tubes for lighting lamps of about 400 W are scaled up due to the thermoformability of quartz. , high output lamps can be easily obtained. However, quartz cannot be used as a material for the arc tube of high-pressure sodium lamps due to heat resistance and sodium resistance, and translucent alumina is the only material available.
Although large pipes with a length of 1 to 3 m can be produced,
If the conventional shape was scaled up as it is, it would have many problems such as the following, making it unusable.

In other words, the structure of conventional arc tubes for lighting is
As shown in the figure, both ends of a simple straight alumina tube 1 with an outer diameter of 9 mm and a length of 110 mm are sealed with a cap 2 made of the same material through a glass frit 3. An electrode 4 is provided with a glass frit 3 interposed therebetween.

If this kind of dimensional structure for lighting is made into a large lamp as it is as a photopolymerization lamp,
The following difficulties arose at both ends, and a large lamp suitable for practical use could not be obtained.

Due to the large outer diameter of 20 to 50 mm, a rapid temperature rise occurs at both ends when the lamp is lit, and the ceramic tube cannot withstand the stress caused by the thermal shock, causing breakage near the ends. .

If the outer diameter is large, the sealing area of the glass frit used to seal both ends becomes large, and the sodium gas sealed inside the arc tube tends to leak, making it impossible to manufacture a reliable lamp.

Glass frit and alumina have slightly different coefficients of thermal expansion, so when sealing the cap and electrode, thermal strain remains near the electrode, which reduces the resistance to thermal stress, especially as the outside diameter of the ceramic tube increases. The residual strain becomes large and the arc tube is likely to break.

The present invention was developed to eliminate the above-mentioned drawbacks.In a translucent alumina ceramic tube in which the light emitting part and the electrode holding parts at both ends are integrally formed, the length between the electrode holding parts is 1 to 3 m, the length of each electrode holding part is 5 to 50 mm, and the outer diameter d of the electrode holding part is the outer diameter D of the central part of the light emitting part.
smaller, and the ratio (d/D) is 0.2 to 0.5.

The details of the present invention will be explained below with reference to the drawings.

As shown in FIG. 2, in the arc tube 5 for a high-output, high-pressure sodium lamp, the tube wall of the light emitting section 6 and the electrode holding sections 7, 7' for discharging at both ends thereof are made of a translucent alumina material. It is integrally formed without any seams. This seamless shape is not limited to one in which the electrode holding parts 7 and 7' for discharge are formed with a straight taper from the light emitting part 6 shown in FIG. 2, and the shape shown in FIG. It may also be formed in an arc shape as shown. The distance between the electrode holding parts 7 and 7', that is, the length L, is in the range of 1 to 3 m. In this range, if it is 1 m or less, there are relatively few problems even with the above-mentioned lighting lamp, that is, a straight cylindrical shape, but if it is 3 m or more, the heat loss of the lamp's discharge characteristics is large and the efficiency is degraded, and the manufacturing equipment for ceramic arc tubes This is because the amount becomes excessive.

The length l of the electrode holding parts 7, 7' is in the range of 5 to 50 mm. This range is intended to facilitate holding and sealing the electrode; if it exceeds 50 mm, the length of the electrode becomes too long and is not economical.

Further, the outer diameter d of the electrode holding parts 7 and 7' is smaller than the outer diameter D of the central part of the light emitting part 6.

In other words, the central part of the tube, which is the light emitting part, reaches the highest temperature when the high-pressure sodium lamp is lit, and the vapor of the enclosed material (mainly sodium) reacts with the translucent alumina that makes up the arc tube, reducing the luminous efficiency and causing the lamp to heat up. shorten the lifespan of Therefore, the outer diameter of the central portion is configured to be larger than the outer diameter of the tube end near the coldest point to which the discharge electrode is attached.

Outer diameter d of the electrode holding part and outer diameter D of the central part of the light emitting part
The ratio of is selected in the range 0.2 to 0.5. This ratio is 0.2
In the following cases, the diameter of the electrode becomes extremely thin.
It is not practical for passing large amounts of current. If it is 0.5 or more, the change in diameter is smaller than that at the center, and as described above, defects occur due to the large diameter, making it impossible to obtain the effects of the present invention.

The electrode holding parts 7, 7' are provided with straight tube-shaped through holes, that is, electrode holding holes 8, 8', and the electrode 1 is inserted into the electrode holding holes 8, 8' through a glass frit 9.
0,10' are provided. The internal diameter of the electrode holding holes 8, 8' is determined according to the desired size of the electrodes determined by the lamp characteristics, and is usually between 2 and 5 mm.

To hold the electrode, as shown in FIG. 3, a ceramic cap 11 having electrode holding holes 8, 8' is sealed in the through hole of the electrode support part 7 with a glass frit 9 interposed therebetween. It is also possible to seal the electrode 10 at 8' with a glass frit 9. The thickness of the electrode holding parts 7, 7' is the same as that of the light emitting part 6.
The thickness may be the same as that of the light emitting part 6, but it may be made larger than that of the light emitting part 6 in order to increase the supporting strength of the electrode.

As is clear from the above explanation, the arc tube for high-output, high-pressure sodium lamps of the present invention is configured so that the outer diameter of the electrode holding part is smaller than the outer diameter of the central part of the tube, which is the light emitting part, and when the lamp is lit, This invention has a significant effect on improving the life of the lamp because it prevents destruction due to thermal shock and eliminates the leakage of sodium gas from both ends, and this invention contributes to the development of industry.

[Brief explanation of drawings]

Fig. 1 is a partial cross-sectional view of an arc tube for a high-pressure sodium lamp for illumination, Fig. 2 is a partially cutaway front view of an arc tube for a high-output high-pressure sodium lamp of the present invention, and Fig. 3
The figure is a sectional view of a main part of another embodiment of the present invention. 1... Alumina tube, 2... Cap, 3... Glass frit, 4... Electrode, 5... Arc tube for high output high pressure sodium lamp, 6... Light emitting part, 7, 7'... Electrode holding part, 8, 8'... Electrode holding hole , 9...Glass frit, 10,10'...electrode, 11...ceramic cap, L...length between electrode holding parts, l...length of electrode holding part, D...outer diameter of light emitting part, d...of electrode holding part Outer diameter.

Claims (1)

[Scope of utility model registration request] In a translucent alumina ceramic tube in which a light emitting part and electrode holding parts at both ends are integrally formed, the length between the electrode holding parts is 1 to 3 m, and the length of each electrode holding part is 5 to 50 mm. An arc tube for a high-output, high-pressure sodium lamp, characterized in that the outer diameter d of the electrode holding part is smaller than the outer diameter D of the central part of the light emitting part, and the ratio (d/D) is 0.2 to 0.5.