JPH087765A - Method for manufacturing metal halide lamp - Google Patents

Abstract

(57) [Summary] (Modified) [Object] The present invention is capable of improving the structure of the embedded portion of the conductive cermet cap and the method of forming the embedded hole, thereby improving the starting characteristics of the lamp, and the arc tube. It is an object of the present invention to provide a method for manufacturing a metal halide lamp that has no fear of blackening, has a long life, and has no variation in life characteristics. A metal halide in which conductive cermet caps 2 and 3 are joined to both ends of a translucent ceramic tube 1, an electrode mandrel 5 is embedded inside the caps and external leads are embedded outside, and a luminescent substance is sealed inside. In the lamp, the buried hole is formed by a die molding method such as press molding or injection molding, and the electrode mandrel 5 and the external lead are inserted into the buried hole and integrally fired to reduce electric resistance loss of the buried portion. To configure.

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 using a translucent ceramic tube or the like as an arc tube, and more particularly to an improvement of a conductive cermet cap joined to its end.

[0002]

2. Description of the Related Art Instead of a quartz arc tube, it comprises a translucent ceramic tube having higher heat resistance than quartz, excellent chemical stability and pressure resistance, and a conductive cermet cap as a current introducing body. Since the metal halide lamp is made of a material having high color rendering properties and high corrosion resistance, it is possible to maintain high color rendering properties for a long time. Further, since the electrode and the external lead as an electric introducer are embedded in the conductive cermet cap, it is important to prevent resistance loss in the embedded portion. However, since the diameters of the electrode mandrel and the external leads are small and a large bonding area cannot be secured, the resistance of the portion tends to increase and the resistance tends to vary. Even if the connection resistance is small when the lamp is completed, the connection resistance tends to gradually increase while the lamp is on. If the resistance of the junction is large, a sufficient starting current does not flow, so that the engine fails to start, and the local heating of the junction evaporates the metal powder and the electrode material, resulting in blackening of the arc tube.

In order to improve the embedded portions of the electrodes of the end caps and the external leads, as shown in Japanese Patent Laid-Open No. 2-242559, uneven portions are formed on the inner surface of the embedded hole to secure the bondability, or to make them even. As in Japanese Patent Laid-Open No. 4-18204, a structure has been proposed in which a fine wire is attached to an electrode or the like and the electrode or the like is inserted into a buried hole. However, even with the above structure, the joint resistance of the buried portion cannot be reduced, and in a small lamp having a small mandrel diameter such as an electrode, the starting tube failure due to the joint resistance or the black color of the arc tube due to the heat generation of the portion. However, there is a problem that

[0004]

Therefore, the inventor has paid attention to a method of forming a buried hole in order to obtain a low resistance at the bonding portion even if the area of the bonding portion of the conductive cermet cap is small. The manufacturing method was examined. The metal network layer of the conductive cermet cap is not used, the buried hole is opened without using mechanical means such as a drill as in the past, and press molding or injection is performed using a die with a pin for forming the buried hole. It was found that it is effective to perform molding and use a conductive cermet cap in which a network layer of cermet material is present on the inner surface of the hole. Then, it can be achieved by removing the binder and pre-baking the cap, and then inserting the electrodes and external leads and integrally baking.

The present invention can improve the starting characteristics of the lamp by improving the structure of the buried portion of the conductive cermet cap joined to the end of the translucent ceramic tube and the method of forming the buried hole. Moreover, it is an object of the present invention to provide a metal halide having a long life and no variation in life characteristics without fear of blackening of the arc tube.

[0006]

According to the present invention, a conductive cermet cap as an electric introducer is joined to both ends of a translucent ceramic tube or a single crystal alumina tube, and an electrode mandrel and an outer side are provided inside the cap. An external lead is embedded and an ionizable gas is sealed inside, and the embedded hole of the conductive cermet cap is formed by a molding method such as press molding or injection molding, and the electrode mandrel and the external lead are inserted into the embedded hole. Is inserted and integrally sintered to reduce the electrical resistance loss of the buried portion. The conductive cermet cap is a ceramic having a metal powder layer whose fine structure forms a three-dimensional network, and the metal powder is a mixture of tungsten, molybdenum and rhenium metals. Furthermore, the outer diameter of the electrode mandrel and the outer lead is 0.1 to 1.0 mm, and the depth of the buried hole of the conductive cermet cap is 0.5 to 2.0 mm.

[0007]

According to the present invention, with the above structure, the resistance of the joint between the cermet cap and the electrode is reduced, a sufficient starting current can be secured, and starting failure does not occur. Further, local heating does not occur, and blackening of the arc tube due to evaporation of the electrode material is prevented.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the illustrated embodiments. FIG. 1 shows a short arc type metal halide lamp in which a conductive cermet cap 2 made of tungsten-alumina is joined to one end of a translucent alumina tube 1 having a spherical central portion and straight tubular ends at both ends by integrally firing. At the other end, a conductive cermet cap 3 is airtightly bonded via a glass frit 4 which is a sealing agent. Also, the electrode mandrel 5 made of tungsten is provided inside the caps 2 and 3.
5 is embedded, and external leads 6 and 6 made of Tung Ten are embedded outside the cap. Then, metal halides such as In, Tl, Li and Dy are enclosed in the interior together with mercury and a rare gas. The lamp is also configured with a tube input of 150W.

Next, the manufacturing method will be described. The raw material of the conductive cermet cap is high-purity alumina of about 1 μm, which is granulated to a size of about 100 μm by spray drying, and 20 wt% of 0.5 μt tungsten powder is dry-coated on the surface of the granules. Using this raw material, a cermet is formed by a press die in which pins for forming embedding holes for electrodes and external leads shown in FIG. Here, 7 is a cylinder, 8 is an upper punch,
9 is a lower punch. The diameter of this hole is formed to be 0.1 to 0.2 mm larger than the diameter of the electrode mandrel and the external lead so that an appropriate shrink fit can be made during the main firing. Further, this cermet molded body is pre-baked at 1500 ° C. in a hydrogen atmosphere furnace through a binder removal step. Then, a tungsten electrode mandrel having a diameter of 0.5 mm and a tungsten lead having a diameter of 1 mm were inserted into the embedding holes of the calcinated cermet, and the calcinated alumina tube was preliminarily set at a predetermined position at the end of the translucent alumina tube. One cermet and the ceramic tube are integrally fired in a hydrogen furnace at ℃. Further, the other cermet is also fired under the same conditions with the electrode mandrel and the external leads inserted as in the above.

Further, a conventional method, that is, a burial hole of a conductive cermet cap was opened by drill machining to prepare a lamp, and a comparative experiment was conducted. 3 and 4 are schematic views of the buried holes of the lamp according to the present invention and the conventional lamp. As shown in FIG. 3, the buried hole 11 of the cermet
Although the inner surface of the is exposed on the surface without cutting the tungsten network layer 13 on the surface of the aluminum granule 12, the network layer is cut by the conventional method.
Further, a flashing lighting test of the lamp was conducted to examine the luminous flux maintenance rate with the lighting time. As is clear from the characteristic diagram of FIG. 5, the variation in the change in the luminous flux maintenance factor between the lamps at each measurement time is small in the present invention, but is large in the conventional lamp. In the case of a lamp having a large change in characteristics, blackening of the inner surface of the arc tube was remarkable.

FIG. 6 is a side view showing another embodiment, which is a small metal halide lamp with a tube input of 50 W. 2 in the figure
Reference numeral 1 is a cylindrical translucent alumina tube, and conductive cermet caps 22 made of tungsten-alumina are joined to both ends of the tube through glass frits 23.
Then, the tungsten electrode 2 is formed on the inner surface of the tube of the cap 22.
4, an outer lead 25 is embedded on the outer surface, and a metal halide such as In, Tl, Li, Dy is enclosed in the interior together with mercury and a rare gas.

In the cermet cap used for the lamp, a burying hole having a diameter of 3 mm is formed by a die with a pin as in the above, and after pre-baking, a tungsten electrode having a diameter of 0.3 mm and a tungsten lead having a diameter of 0.4 mm are inserted. Then, the resistance between the electrode and the lead of the cermet cap alone prepared by the main firing was measured. The results are shown in Table 1. Table 1 shows the resistance of the cermet prepared by the conventional method for comparison. Further, the lamp shown in FIG. 6 was prepared using the cap, and the quality of the starting characteristics thereof is also shown in Table 1. [Hereafter, margin]

[0013]

[Table 1]

As is apparent from Table 1, the lamp according to the present invention has a low resistance of the cermet and a small variation at the time of starting the lamp, and has a good starting characteristic.

[0015]

As described above, the method of manufacturing a metal halide lamp according to the present invention has a relatively simple structure.
Not only the starting characteristics of the lamp can be improved, but also the luminous flux maintenance rate decreases less with the passage of lighting time and the life characteristics are excellent.

[Brief description of drawings]

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

FIG. 2 is likewise an explanatory view showing a mold in a lamp manufacturing process.

FIG. 3 is a diagram schematically showing an embedded hole in the cermet.

FIG. 4 is a view schematically showing an embedding hole of a cermet according to a conventional method.

FIG. 5 is a characteristic diagram showing a change in luminous flux maintenance rate with the passage of lighting time of a metal halide lamp according to the present invention and a conventional lamp.

FIG. 6 is a side view showing another embodiment of the metal halide lamp according to the present invention.

[Explanation of symbols]

 1 Translucent Ceramic Tube 2, 3 Conductive Cermet Cap 4 Glass Frit 5 Electrode Mandrel 6 External Lead 7 Cylinder 8 Upper Punch 9 Lower Punch 11 Cermet Embedding Hole 12 Alumina Granule 13 Tungsten Network Layer 21 Transparent Ceramic Tube 22 Conductive Cermet cap 23 Glass frit 24 Electrode 25 External lead

Claims (3)

[Claims] 1. A conductive cermet cap as an electric introducer is joined to both ends of a translucent ceramic tube or a single crystal alumina tube, an electrode mandrel is embedded inside the cap, and external leads are embedded outside the cap, In a metal halide lamp in which an ionizable gas is sealed, a buried hole of the conductive cermet cap is formed by a molding method such as press molding or injection molding, and an electrode mandrel and an external lead are inserted into the buried hole. A method of manufacturing a metal halide lamp, characterized in that electric resistance loss of the buried portion is reduced by integrally sintering. 2. The metal halide according to claim 1, wherein the conductive cermet cap is a ceramic having a metal powder layer whose fine structure forms a three-dimensional network, and the metal powder is a mixture of tungsten, molybdenum and rhenium metals. Lamp manufacturing method. 3. The outer diameter of the electrode mandrel and the outer lead is 0.
The depth of the buried hole of the conductive cermet cap is 0.5 to 2.0 mm.
A method for manufacturing the described metal halide lamp.