JPH0917380A - Large capacity short arc metal halide lamp - Google Patents

Abstract

PURPOSE: To stop a crack in a sealing part of an arc tube within a lamp unlighted range by selecting a cross sectional shape of the sealing part of the light emitting tube so as to satisfy a specific condition. CONSTITUTION: A recessed part is formed over its whole circumference on the outer periphery of a boundary part between a swelling part 2 and a sealing part 3 of an arc tube, and an end part of a main electrode 5 composed of an electrode core bar 5b having a coil part 5a on the tip of the sealing part 3 and an end part of molybdenum foil 6 are connected to each other by welding. When the cross-sectional area of the sealing part positioned on the barrel center side of the main electrode embedded in the recessed part is denoted by A and the cross-sectional area of the sealing part containing a connecting part of the main electrode and the molybdenum foil is denoted by B, they are selected in a range of the ratio (A/B<=0.8). Therefore, a crack of the light emitting tube generated with the lapse of lamp lighting time can be stopped within a range of the sealing part, and the crack does not develop up to a barrel center part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a large-capacity short arc metal halide lamp, and to an improvement of the arc tube sealing portion thereof.

[0002]

2. Description of the Related Art In recent years, as a lamp adapted to illuminate a large sports area such as a soccer field without waste and to be suitable for color broadcasting, the arc length is about 30 mm between the electrodes of the arc tube and the capacity is large. Therefore, a short arc metal halide lamp having a high luminous efficiency and a high color rendering property has been proposed. By placing the lamp in a fixture designed to be compact, it is considered not to cause light pollution in the surrounding area, and it is particularly suitable as a large ground lighting lamp.

[0003]

When manufacturing this type of lamp, several types of quartz tubes are arranged in concentric circles, and an electrode mount constituted by connecting an electrode and a molybdenum foil is positioned at the center, and once the whole is mounted, After evacuating, the place to be sealed is heated with a burner to gradually melt the quartz, thereby sealing the outside air and the light emitting part hermetically. Then, a metal halide is enclosed together with a starting auxiliary gas and mercury in the arc tube thus created to manufacture a short arc metal halide lamp.

However, during the life of the lamp, the contact resistance increases due to the metal halide infiltrating into the sealing portion, which is the connecting portion between the main electrode and the molybdenum foil, and a large current flows through the connecting portion. As a result of excessive heating of the sealing portion, so-called cracks may occur, and eventually the cracks may reach the inside of the body of the bulging portion, which is the light emitting portion, and the arc tube may burst. Then, there is a problem that the front glass or the like of the compact instrument is damaged or the reflecting mirror in the instrument is deteriorated.

The present invention has been made in view of the above, and in the sealing portion of the arc tube manufactured by the fusion-sealing method, the cross-sectional areas of the recesses formed at both ends of the arc tube, the electrode core rod, and the molybdenum foil are formed. By selecting the cross-sectional area of the part including the connection part within a predetermined range, by preventing cracks in the arc tube sealing part that may occur during or at the end of the lamp life, long life, high efficiency and It is an object of the present invention to provide a large-capacity short arc metal halide lamp which has a high color rendering and is optimal for lighting such as a ground.

[0006]

In order to achieve the above object, the present invention is to seal at least a main electrode on both ends of a quartz arc tube, and the arc tube is integrally formed on a central bulge and both ends thereof. And a molybdenum foil are connected to the electrode core rods at both ends of the arc tube and are integrally embedded in the sealing part, and the rated current is 10 A or more and an outer tube is used. In a short arc metal halide lamp that is turned on without a recess, a recess is formed over the entire circumference of the boundary between the bulging part and the sealing part, and the recess is located on the inner side of the body of the main electrode embedded part. A / B ≦ 0.8, where A is the cross-sectional area of the sealed portion and B is the cross-sectional area of the sealed portion including the connection between the main electrode and the molybdenum foil.

[0007]

With the above structure, even if a metal halide enters the arc tube sealing portion during lamp lighting and a crack occurs at the connecting portion between the electrode core rod and the molybdenum foil, the bulging portion of the light emitting portion is not affected. No cracks occur in the middle of the body,
There is no accidental rupture of the arc tube.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side view of the arc tube. A quartz arc tube 1 is provided with a substantially elliptical bulging portion 2 which is a light emitting portion, and sealing portions 3 and 3 are formed at both ends thereof. There is. or,
Recesses 4 and 4 are formed along the entire circumference of the boundary between the bulging portion 2 and the sealing portion 3. The main electrodes 5 and 5 are sealed at both ends of the arc tube, the electrode cores 5b and 5b of the main electrodes and the molybdenum foils 6 and 6 are connected by welding, and the sealing parts 3 and 3 are integrally formed. It is buried. Further, a pair of caps 7, 7 are fixed to the ends of the sealed portion of the arc tube, and terminals 9, 9 for power supply are connected via external lead wires 8, 8. In addition, a heat insulating film 10 made of white heat-resistant oxide is applied to the outer periphery of the main electrode of the arc tube.

Then, in the arc tube, 12 mg of a halide containing dysprosium iodide, neodymium iodide, and cesium iodide in a weight ratio of (4: 2: 3) and 100 g of argon as a starting trapping gas are used. About 60 mg of mercury as a buffer gas is enclosed together with Thor. The arc tube 1 of the present embodiment has a bulging portion 2 which is a substantially elliptical light emitting portion having a maximum diameter of 40 mm in outer diameter and 32 mm in inner diameter. In addition, φ made of a tungsten rod as the main electrode 5
A coil wire 5a having a diameter of 1.2 mm is wound around an electrode core rod 5b having a length of 2.0 mm and a length of 25 mm, the length thereof is 10 mm, and a coil portion 5a is provided 2.5 mm away from the tip of the core rod. doing. The main electrode 5 is electrically connected to the molybdenum foil 6 and is connected to the external lead wire, and is connected to the terminal 9 via the base 7 and the external lead wire 8 so that power is supplied by both terminals 9, 9. It is ready to receive power. Further, the base 7 is structured so that it can be accurately mounted in the lighting equipment, so that proper light distribution can be obtained when it is correctly mounted in the lighting equipment.

Next, the arc tube sealing portion to which the main electrode and the molybdenum foil are electrically connected to each other by welding will be described with reference to FIG. Swelling part 2 of arc tube
A concave portion 4 is formed on the entire outer periphery of the boundary between the sealing portion 3 and the sealing portion 3, and the sealing portion 3 has a main electrode 5 composed of an electrode core rod 5b provided with a coil portion 5a at its tip. The end portion and the end portion of the molybdenum foil 6 are connected by welding. Then, a ratio when the cross-sectional area of the sealing portion located on the inner side of the main electrode embedded in the recess is A and the cross-sectional area of the sealing portion including the connecting portion between the main electrode and the molybdenum foil is B. A / B ≦
It is selected in the range of 0.8. In the above-mentioned embodiment, the cross-sectional area B located at the connecting portion is 2 cm ² , and the minimum cross-sectional area A of the concave portion on the side closer to the body is 1.5 cm ² . In this case, A / B = 0.75.

A specific experimental example will be described. As described above, the minimum sectional area A of the arc tube sealing portion is set to the other sectional area B
A short arc metal halide lamp consisting of an arc tube selected to be 80% or less of the above and lit without using an outer tube is provided with a tube input of 2 kW and a lamp voltage of 110.
When the life test was performed with V and rated current turned on at 20 A, 13 of 50 samples were 3,000 hours in which the connection between the main electrode and the molybdenum foil was corroded by the metal halide and became the sealing part. A crack occurred and finally became a flaw. However, this crack is settled within the range of the sealing portion of the sealing portion of the arc tube shown in FIG. 2 which is closer to the inside of the barrel, and the crack does not propagate to the inside portion of the barrel. Was avoided. On the other hand, a lamp with the same specifications as the above with a conventional structure (a lamp having the same cross-sectional area as the sealing portion including the welded portion without narrowing the sealing portion near the inside of the body)
In the same life test as described above, not only 12 of 50 cracks but also 9 of which caused the arc tube to rupture.

As described above, by making the cross-sectional area of the concave portion near the inside of the barrel 80% or less of the cross-sectional area of the sealing portion including the welded portion, the halide is kept in the sealing portion during the life of the lamp. Since the contact resistance is increased by entering the connection portion and a large current flows through the connection portion, the arc tube is not ruptured due to the crack in the sealing portion which is generated due to the contact resistance. When the sealing portion is formed so that the A / B ratio has a cross-sectional area of 80% or more, the arc tube may be ruptured due to cracks as in the conventional case. Further, in a lamp having a rated current of 10 A or less, cracks due to excessive heat generation in the sealing portion are rarely generated, and the lamp current is 1
The effect is recognized in the short arc metal halide lamp in which a large current of 0 A or more is used as the design condition.

[0013]

As is apparent from the above description, in the large-capacity short arc metal halide lamp according to the present invention, the cross-sectional shape of the arc tube sealing portion is devised, and the cross-sectional area ratio is selected within a certain range. By doing so, it is possible to prevent cracks in the sealed portion of the arc tube that occur with the lapse of the lamp lighting time within the range of the lamp imperfections, and there is no risk of an accident resulting from the burst of the arc tube. Further, there is an advantage that it has an excellent lamp characteristic that is compact, highly efficient, and has a high color rendering property, which is optimum for illumination of a ground or the like.

[Brief description of the drawings]

FIG. 1 is a side view showing an embodiment of a short arc metal halide lamp according to the present invention.

FIG. 2 is likewise an explanatory view showing a main part of an arc tube.

[Explanation of symbols]

 1 arc tube 2 bulging part 3,3 sealing part 4,4 recess 5,5 main electrode 5a electrode core 5b electrode coil part 6,6 molybdenum foil 7,7 base 8,8 external lead wire 9,9 terminal 10 , 10 Insulating film

Claims (1)

[Claims] 1. A quartz arc tube is sealed with at least a main electrode at both ends thereof, and the arc tube is composed of a central bulge portion and sealing portions integrally formed at both ends thereof, and both ends of the arc tube. In the short arc metal halide lamp, in which the electrode core rod and the molybdenum foil are connected to each other and embedded in the sealing portion, and the rated current is 10 A or more and the lamp is lit without using an outer bulb, the bulging portion A concave portion is formed on the entire outer circumference of the boundary portion between the main electrode and the sealing portion, and the cross-sectional area of the sealing portion located inside the main electrode embedded portion of the concave portion is A, and the main electrode and molybdenum are separated. A / B ≦ 0.8, where B is the cross-sectional area of the sealing portion including the connection portion with the foil, and is a large capacity short arc metal halide lamp.