JP3430972B2 - Metal halide lamp - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal halide lamp used for high ceiling lighting or the like.

[0002]

2. Description of the Related Art Conventionally, such a metal halide lamp has electrodes made of tungsten at both ends thereof and scandium iodide at both ends thereof in order to prevent a large decrease in luminous flux maintenance rate, that is, blackening of the inner surface of the arc tube. , Sodium iodide, and thorium iodide or metal thorium are enclosed in a quartz arc tube.

As described above, by enclosing thorium iodide or metal thorium in the arc tube, the metal thorium adheres to the tip of the electrode during lighting of the lamp, and the work function of the electrode is lowered. As a result, the temperature of the tip of the electrode is lowered, the evaporation of tungsten can be suppressed, and the blackening of the arc tube can be prevented.

[0004]

However, in the conventional device, when an excessive amount of thorium iodide or metal thorium is enclosed in the arc tube, the vapor voltage of the metal thorium is high, so that the lamp voltage rises and disappears. There was a problem of causing it.

The present invention has been made in order to solve such a problem, and provides a metal halide lamp which improves the luminous flux maintenance factor and prevents the lamp from extinguishing due to an increase in the lamp voltage.

[0006]

The metal halide lamp of the present invention has electrodes at both ends, and at least internal scandium iodide, sodium iodide, thorium iodide, and the free energy of iodide thereof are iodide-containing. An arc tube in which a metal higher than sodium and lower than thorium iodide is encapsulated, and the thorium iodide is 3 wt% with respect to the total amount of metal iodide encapsulated in the arc tube.
˜5 wt%, and the amount of the metal enclosed is a molar ratio of 1.4 to 20 with respect to the thorium iodide.

This makes it possible to reduce the decrease in the luminous flux maintenance factor and prevent the extinction caused by the increase in the lamp voltage.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

A rated power 700 according to an embodiment of the present invention
The metal halide lamp of W has a length 1 with electrodes 1a made of tungsten provided at both ends as shown in FIG.
A quartz arc tube 1 having a diameter of 30 mm and a maximum outer diameter of 30 mm is supported and fixed by metal plates 3 and 4 inside a hard glass outer tube 2 having a total length of 360 mm and a maximum outer diameter of 140 mm. The distance between the electrodes 1a is 66 mm.

In the arc tube 1, the free energy of mercury, a mixed gas of neon and argon, scandium iodide, sodium iodide, thorium iodide, and their iodides is higher than that of sodium iodide. As a lower metal, for example, scandium (hereinafter referred to as metal scandium) is sealed in a predetermined amount.

The outer tube 2 is filled with a mixed gas of neon and nitrogen.

In FIG. 1, numeral 5 indicates a base.

Next, a method of lighting such a metal halide lamp will be described.

First, when the power is turned on, the bimetal 6 is in a closed state, and a current flows through the lighting tube 7. Therefore, the lighting tube 7 and about 470
A secondary voltage is applied to the low resistance 8 of Ω, and a pulse voltage is generated in the lighting tube 7. This pulse voltage causes a discharge between the electrode 1a and the auxiliary electrode 10 through a high resistance 9 of about 10 kΩ, and then an arc discharge is generated between the electrodes 1a to light the lamp.

Such a metal halide lamp (hereinafter,
In the present invention product), thorium iodide is used as the arc tube 1.
3 wt% to the total amount of metal iodide enclosed in
It is preferable to fill the inside of the arc tube 1 so as to be 5 wt%. The reason will be described as follows.

In the product of the present invention, 10 mg of scandium iodide and 50 mg of sodium iodide were placed in the arc tube 1.
A lamp in which a scandium metal is used in an amount such that the molar ratio is 1.4 with respect to thorium halide described below, and thorium iodide is variously changed within a range of 2 to 6 wt% with respect to the total amount of metal iodide. When the lamp was manufactured and the luminous flux maintenance factor of each lamp after the lighting of 9000 hours was examined, the results as shown in Table 1 were obtained.

The default value of the lamp voltage is 130.
V.

[0018]

[Table 1]

As is clear from Table 1, in the lamp in which thorium iodide is contained in an amount of 3 wt% to 5 wt% with respect to the total amount of metal iodides, the luminous flux maintenance factor of 55%, which is practically sufficient, can be obtained. . On the other hand, when the thorium iodide is 2 wt% with respect to the total amount of metal iodides, the luminous flux maintenance factor is 5
It was 0% or less, which was not sufficient for practical use. Further, when thorium iodide was 6 wt% with respect to the total amount of metal iodides, the lamp voltage increased by 24 V, the lamp was extinguished after 7,000 hours of lighting, and no lighting was achieved.

As described above, by enclosing 3 wt% to 5 wt% of thorium iodide with respect to the total amount of metal iodide in the arc tube 1, the enclosed amount of thorium iodide can be optimized, that is, the electrode 1a. Since the vapor pressure of the metal thorium in the arc tube 1 can be prevented from rising excessively while the temperature is reduced, the luminous flux maintenance factor can be improved and extinction can be prevented.

Here, the reason for enclosing a metal that is a metal iodide higher than the free energy of sodium iodide and lower than the free energy of thorium iodide will be described.

In the metal halide lamp of the present invention, in order to attach the metal thorium to the electrode 1a, it is necessary to decompose the enclosed thorium iodide and take out the metal thorium. Therefore, by encapsulating, for example, metal scandium as a metal whose free energy of iodide is higher than that of sodium iodide and lower than that of thorium iodide, thorium iodide and metal scandium react with each other to form scandium iodide. Once formed, the metallic thorium can be removed. However, as is conventionally known, when metal scandium is excessively enclosed, it reacts with quartz and the luminous flux maintenance factor decreases.

Therefore, in order to improve the luminous flux maintenance factor,
It is preferable to define the metal having a free energy of iodide higher than that of sodium iodide and lower than that of thorium iodide in a molar ratio of 1.4 to 20 with respect to thorium iodide. The reason will be described as follows.

In the invention product, 10 mg of scandium iodide, 50 mg of sodium iodide, and 3 wt% of thorium iodide with respect to the total amount of metal iodide in the arc tube 1,
The scandium metal is in a molar ratio of 0.3 to thorium iodide.
Lamps each having various changes in the range of 5 to 22 were manufactured, and the luminous flux maintenance factor after each lamp was operated for a rated life of 9000 hours was examined, and the results shown in Table 2 were obtained.

[0025]

[Table 2]

As is clear from Table 2, in the lamp in which metal scandium is enclosed in thorium iodide in an amount of 1.4 to 20, a luminous flux maintenance factor of 55% which is practically sufficient can be obtained. On the other hand, when the scandium metal has a molar ratio of 0.5 to thorium iodide, the luminous flux maintenance factor is 45.
%, Which was not sufficient for practical use. Further, for example, when the scandium metal has a molar ratio of 22 to thorium iodide, the luminous flux maintenance factor is 50%, which is not practically sufficient.

As described above, by enclosing metal scandium in the arc tube 1 in a molar ratio of 1.4 to 20 with respect to thorium iodide, the enclosed amount of metal scandium can be optimized, and the luminous flux maintenance factor can be improved. Can be improved.
Further, in order to further improve the luminous flux maintenance factor, it is preferable to encapsulate metal scandium in a molar ratio of 6 to 17 with respect to thorium iodide.

In the above-mentioned embodiment, the case where scandium is used as a metal iodide which is higher than the free energy of sodium iodide and lower than the free energy of thorium iodide has been described, but dysprosium, The same effect as above can be obtained by using thulium metal.

In the above embodiment, the rated power 70
Although the case of the metal halide lamp of 0 W has been described, the same effect as above can be obtained also in the case of a metal halide lamp having a rated power of 100 W or 1000 W.

[0030]

As described above, the present invention provides a metal halide lamp capable of improving the luminous flux maintenance factor and suppressing the rise of the lamp voltage to prevent extinction. Is something that can be done.

[Brief description of drawings]

FIG. 1 is a perspective view of a metal halide lamp having a rated power of 700 W, which is an embodiment of the present invention.

[Explanation of symbols]

1 arc tube 1a electrode

─────────────────────────────────────────────────── --- Continuation of the front page (56) Reference JP-A-55-124937 (JP, A) JP-A-63-136454 (JP, A) JP-A-2-265158 (JP, A) JP-A-6- 162994 (JP, A) JP-A-7-21981 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01J 61/20

Claims (3)

(57) [Claims] 1. Free energy of scandium iodide, sodium iodide, thorium iodide, and the iodide thereof is higher than that of sodium iodide and lower than that of thorium iodide, which has electrodes at both ends. An arc tube in which a metal is sealed is provided, and the thorium iodide is 3 w with respect to the total amount of metal iodide sealed in the arc tube.
A metal halide lamp, characterized in that the content of the metal is from t% to 5 wt% and the molar amount of the metal is 1.4 to 20 with respect to the thorium iodide. 2. The metal halide lamp according to claim 1, wherein the metal has a molar ratio of 6 to 17 with respect to the thorium iodide. 3. The metal halide lamp according to claim 1, wherein the metal is scandium.