JPH10334852A - Metal halide lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal halide lamp, wherein quantity of metal halide aggregating on an outer end part of a pipe made of metal can be reduced, without lowering of luminous efficiency or changes in luminescent color, and life characteristics are superior by decreasing conductance for the metal halide to reach the outer end part of the pipe made of metal. SOLUTION: Both ends of a luminous tube 1 made of light-transmitting ceramic each closed by a ceramic plug 3a, 3b, jointed bodies of electrode stems 4 to metallic current conductors 2, 6 passing through the ceramic plugs 3a, 3b, the metallic current conductors 2, 6 sintered with the fixed to the ceramic plugs 3a, 3b, at least a metal halide enclosed within the luminous tube 1, at least one of the metallic current conductors 2, 6 made up of a thin-walled pipe 6 made of a metal and disposed as an exhaust pipe 7 near the middle in the luminous tube axial direction, a metal rod 8 being inserted into the metallic pipe 6 via a fine clearance, one end of the metal rod 8 is brought into contact with an end part of the electrode stem 4, and an outer end part of the pipe 6 made of metal is melted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in the life characteristics of an arc tube in a metal halide lamp using an arc tube made of a translucent ceramic.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. Hei 8-250068 discloses a metal halide lamp using a light-transmitting ceramic, which is provided with a metal pipe as a current conductor that passes through the center of a ceramic plug sealed to the end of an arc tube. No. 6
No. 511592 and JP-A-8-83568 are disclosed.

[0003] The basic configuration of the above publication is to add a material having a different thermal expansion coefficient such as a metal to ceramic to prepare a ceramic plug which approximates the thermal expansion coefficient of a metal pipe which is both a current conductor and an exhaust pipe. Then, the joined body of the electrode mandrel and the metal pipe is passed through the ceramic plug and sintered integrally, and then the outer end of the metal pipe is hermetically sealed with a laser beam or the like after adding an additive. A technique for performing this is disclosed.

The structure of a conventional arc tube is as shown in FIG. The material of the arc tube 11 is translucent alumina. At both ends, a ceramic plug 12 made of molybdenum-alumina cermet in which molybdenum powder is dispersed in alumina is hermetically sealed by solid phase sintering. Current conductors 13 and 14 are welded to the electrode mandrel 16 inside the main body through the center of the ceramic plug.

[0005] At least one of the current conductors is made of a molybdenum pipe 13 and the other is made of a molybdenum wire 14. The interface between the current conductors 13 and 14 and the ceramic plug 12 made of cermet is made airtight by sintering shrinkage of the ceramic plug 12 by integral sintering. A frit glass layer 15 is formed around the current conductors 13 and 14 protruding from the ceramic plug 12. From the molybdenum pipe 13, metal halide pellets, mercury and a starting gas are introduced. Thereafter, the end of the molybdenum pipe 13 is melted and sealed by TIG welding or a YAG laser beam.

[0006]

However, when a flash cycle test of turning on the arc tube for 7 hours and extinguishing the lamp for 30 minutes is performed, the metal halide is reduced to about 300 hours in the molybdenum pipe having the lowest temperature in the arc tube. Aggregates on the outer edge. Since the aggregated metal halide does not return to the discharge space, it does not contribute to the light emission, and as a result, there is a problem that the light emission efficiency is reduced and the light emission color is changed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to reduce the conductance of a metal halide to reach the outer end of a metal pipe so that the metal aggregates at the outer end of the metal pipe. An object of the present invention is to provide a metal halide lamp which can reduce the amount of a halide, does not lower the luminous efficiency or changes the luminescent color, and has excellent life characteristics.

[0008]

According to the present invention, both ends of a light-transmitting ceramic arc tube are closed with ceramic plugs, and a joined body of an electrode mandrel and a metal current conductor passes through the ceramic plug. The metal current conductor is fixed to the ceramic plug by sintering, at least a metal halide is sealed inside the arc tube, and at least one of the metal current conductors is formed of a thin metal pipe. Arranged near the center, a metal rod is inserted into the metal pipe through a minute gap, and one end of the metal rod and the end of the electrode mandrel are abutted, and the outer end of the metal pipe is It will melt.

The invention according to claim 2 is characterized in that the metal rod is made of a high melting point metal such as molybdenum. The invention according to claim 3 is characterized in that the inner diameter of the metal pipe and the outer diameter of the metal rod are different from each other. Is set to be 0.05 mm ≦ d ≦ 0.1 mm.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an arc tube of a metal halide lamp according to the present invention. The arc tube has a total length of 35 mm, both ends open, an inner diameter of 10 mm at the center, and an inner diameter of 3.5 m at the end.
A translucent alumina tube 1 having an inner diameter of 0.7 m and an inner volume of 0.7 ml is used, and the arc length is 5 mm.

One end of the translucent alumina tube 1 is made of a mixture of tungsten and alumina or molybdenum and alumina so as to reduce the difference in thermal expansion between the translucent alumina tube 1 and the molybdenum wire 2. Outer diameter 3.2m
A ceramic plug 3a having a length of 5 mm and a length of 5 mm is hermetically sealed without using a sealing material by integral sintering with the translucent alumina tube 1. At the center of the ceramic plug 3a, a joined body of a tungsten electrode mandrel 4 having an outer diameter of 0.5 mm and a molybdenum wire 2 having an outer diameter of 0.30 mm penetrates. The outer end surface of 3a is hermetically sealed with frit glass 5.

At the other end of the arc tube, a similar ceramic plug 3b is hermetically sealed without using a sealing material by integral sintering with the translucent alumina tube 1. In the center of the plug 3b, a tungsten electrode mandrel 4 having an outer diameter of 0.5 mm, an outer diameter of 0.8 mm, and a wall thickness of 0.1 m
m and a joined body with the molybdenum pipe 6 penetrates, and the length of the pipe 6 protruding from the outer end of the ceramic plug 3b is set to 6 mm. The end of the electrode mandrel 4 is fixed to the inner end of the pipe 6 by welding.
And the outer end face of the ceramic plug 3b
Is hermetically sealed.

At the time of manufacture, the molybdenum pipe 6
From the outer end opening, a metal halide compound pellet or mercury is sealed as a luminescent substance into a luminous tube through an exhaust hole 7 formed at the distal end thereof, and a molybdenum rod 8 is inserted into the molybdenum pipe 6. It comes into contact with the end of the electrode mandrel 4. Then, after sealing argon gas as a starting gas, TIG welding or YA is performed to hermetically seal the arc tube.
The outer end of the molybdenum pipe 6 is simultaneously melt-sealed with the outer end of the molybdenum rod 8 by the G laser beam. In addition,
Argon gas is sealed by enclosing a metal halide pellet or the like, evacuating the quartz chamber in which the arc tube is placed, and then filling the gas with argon gas to a predetermined pressure.

In the present invention, a thin metal pipe is specified.
m or less. By making the wall thin, leakage of the filling material from the frit glass portion is eliminated, and cracking of the metal pipe at the time of fusion sealing can be prevented. Also,
The gap d between the inner diameter of the metal pipe and the outer diameter of the metal rod
Is defined as 0.05 mm ≦ d ≦ 0.1 mm, for the following reason. A molybdenum rod with a diameter of 0.75 mm can be numerically inserted into a pipe with an inner diameter of 0.8 mm with respect to an inner diameter of 0.8 mm of a molybdenum pipe. It is difficult to insert due to the curvature, and it is the limit value that can be mass-produced in actual production.

In the case of a molybdenum rod having a diameter of 0.6 mm, as shown in FIG. 3A, the gap between the molybdenum pipe 6 and the molybdenum rod 8 is large, and the molybdenum rod 8 is displaced in the molybdenum pipe 6 after insertion. Molybdenum melted at the time of melting the end of the molybdenum pipe enters into the gap with a large gap, and when the molybdenum pipe is solidified, distortion remains on the wall surface 9 of the molybdenum pipe, and a vertical crack may occur in the molybdenum pipe. On the other hand, for φ0.7 mm, FIG.
As shown in (2), since the molybdenum melted at the end of the molybdenum pipe does not enter the pipe and is solidified, no distortion remains on the wall 9 of the molybdenum pipe, and the crack does not occur.

FIG. 4 shows the change in the luminous flux maintenance rate with the diameter of the molybdenum rod inserted into the molybdenum pipe as a parameter. The diameter of the molybdenum rod is φ0.7mm φ
It can be seen that the luminous flux maintenance factor is larger than that of 0.6 mm.

The length of the molybdenum rod is such that it can be inserted into the molybdenum pipe 3 mm or more from the outer end. This is because the molybdenum rod is longer than the molybdenum pipe or 3 m from the outer end of the molybdenum pipe.
When inserted below m, the molybdenum pipe and the molybdenum rod cannot both be melted at the same time, so they cannot be melted over the entire circumference of the molybdenum pipe and may not be hermetically melted and sealed. , The outer end surface of the molybdenum rod is 3 mm from the end of the molybdenum pipe
When the molybdenum pipe is inserted deeper, only the molybdenum pipe can be melted, and the seal can be reliably hermetically sealed.

[0018]

As described above, in the arc tube of the present invention, the metal halide reaches the end of the molybdenum pipe by inserting the metal rod into the thin molybdenum pipe having both the exhaust pipe and the current introducing body. By reducing the conductance at the time, the amount of metal halide aggregated at the end of the molybdenum pipe can be reduced, and it is possible to prevent a decrease in luminous efficiency and a change in luminescent color of the lamp. Cracking of the molybdenum metal pipe can be prevented, and a metal halide lamp having excellent life characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an arc tube of the present invention.

FIG. 2 is a schematic configuration diagram of a conventional arc tube.

FIG. 3 is a schematic view of a fusion sealing portion of a molybdenum pipe.

FIG. 4 is a diagram showing a change in a luminous flux maintenance ratio with a parameter of a diameter of a molybdenum rod inserted into a molybdenum pipe.

[Explanation of symbols]

 1,11 translucent alumina tube 2,14 molybdenum wire 3a, 3b, 12 ceramic plug 4,16 electrode mandrel 5,15 frit glass 6,13 molybdenum pipe 7 exhaust hole 8 molybdenum rod 9 molybdenum pipe wall

Claims (3)

[Claims] 1. A light-transmitting ceramic arc tube is closed at both ends with ceramic plugs, a joined body of an electrode mandrel and a metal current conductor penetrates the ceramic plug, and the metal current conductor and the ceramic plug are fired. At least one of the metal current conductors is formed of a thin metal pipe, and is disposed near the center of the arc tube in the axial direction as an exhaust pipe. A metal rod is inserted into the metal pipe through a minute gap, and one end of the metal rod is in contact with the end of the electrode mandrel to melt the outer end of the metal pipe. 2. The metal rod according to claim 1, wherein said metal rod is made of a high melting point metal such as molybdenum or tungsten.
The metal halide lamp according to 1. 3. The method according to claim 1, wherein a gap d between an inner diameter of the metal pipe and an outer diameter of the metal rod is set to 0.05 mm ≦ d ≦ 0.1 mm. The described metal halide lamp.