JPH05334997A - Metallic vapor electric discharge lamp - Google Patents

Abstract

PURPOSE:To prevent cracking of a blocking cap and enable sealing of a metal halide in an arc tube so as to increase emission efficiency and luminous color characteristics by permitting a pipe having thin walls to absorb stress that acts on the portion of the blocking cap in contact with the pipe during sintering. CONSTITUTION:A metallic vapor electric discharge lamp has a translucent ceramic tube 112 both ends of which are opened and a blocking cap 114 made of conductive cermet, provided at both end openings of the translucent ceramic tube 112. The metallic vapor electric discharge lamp also has pipes 120 having thin walls, made from a halogen-resistant metal and planted on both the inside and outside of the blocking cap 114, and an electrode core bar 116 welded to an end portion of the pipe 120 planted on the inside of the blocking cap 114, the end portion not being embedded in the blocking cap 114.

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 structure of a metal vapor discharge lamp, and more particularly to a metal vapor discharge lamp containing a metal halide.

[0002]

2. Description of the Related Art A metal vapor discharge lamp used in a high pressure sodium lamp or the like, in which various metal halides are enclosed in an arc tube made of translucent ceramics, is excellent in luminous efficiency and color rendering property. Sometimes research and development are actively carried out. The use of translucent ceramics for the arc tube allows higher operating temperature than the arc tube made of quartz glass, and the corrosion resistance of alumina, which is the material for the translucent ceramics, is high for long-term use. This is because even in the above, the life characteristics are excellent, such as a small change in emission color.

However, when a metal halide is enclosed in the arc tube used in the high-pressure sodium lamp, the electrode support portion of the arc tube is made of niobium, so that the electrode support portion is eroded by the halogen enclosed at a high temperature during lighting. It was impossible to put into practical use. The reason why the electrode supporting portion is made of niobium is that the coefficient of thermal expansion is substantially the same as that of the translucent ceramic. Therefore, in order to enable the encapsulation of the metal halide, an arc tube having a structure shown in FIG. 2 has been conventionally proposed. The arc tube 10 shown in the figure includes a translucent ceramic tube 12, a closing cap 14 for closing both ends of the translucent ceramic tube 12,
Electrode mandrel 16 implanted inside the closing cap 14.
And a lead rod 18 implanted outside the closing cap 14.

Here, the closing cap 14 is made of a conductive cermet, and is formed by integrally firing the electrode mandrel 16 inside the closing cap 14 and the lead rod 18 outside. There is. In general, tungsten is used as the material of the electrode mandrel 16 and alumina-tungsten cermet is used as the material of the closing cap 14, and each of these materials has excellent halogen resistance even at high temperatures. By enclosing a metal halide in the arc tube 10, lighting is possible.

[0005]

However, as described above, the electrode mandrel 16 and the lead rod 18 are fired and shrink-fitted in the closing cap 14 in a state of being embedded in the closing cap 14, and in the firing, Closure cap 14
A minute crack is generated in the implanted portion of the electrode mandrel 16 and the lead rod 18. That is, due to the difference in the materials of the electrode mandrel 16 and the lead rod 18 and the closing cap 14, there is a difference in the coefficient of thermal expansion during firing, and a crack is generated due to the stress acting on the planted portion. Of. Then, the liquid-phase metal halide sealed in the arc tube 10 when the discharge lamp is lit enters the crack,
There is a problem in that the emission color of the discharge lamp is changed.

Further, since the contact resistance in the planted portion is large, the crack may become larger due to heat shock caused by repeated lighting and extinction of the discharge lamp, which may cause arc tube leakage. To solve the above problems, the electrode mandrel 16 and the lead rod 18
At the same time, a wire that is thinner than them is attached to the closing cap 14 for shrink fitting, or a notch is provided in the implanting portion of the electrode mandrel 16 for shrink fitting to prevent cracks that absorb the stress of the closing cap 14. A method is being considered,
The electrode mandrel 16 has fallen down during shrink fitting, cracks cannot be completely prevented, and so on.

Further, a structure in which a metal plate is wound around an electrode mandrel to be attached to a closing body and the end of the winding portion is attached to the closing body is disclosed in Japanese Utility Model Laid-Open No. 63-160662. However, there is a problem in that the winding work is difficult and the assembly is troublesome. The present invention has been made in view of the above-mentioned problems of the prior art, and an object thereof is an electrode mandrel planted in a closing cap made of a conductive cermet, and a lead rod, in a portion where the closing cap is fired. It is an object of the present invention to provide a metal vapor discharge lamp that is free from cracks and can be easily assembled.

[0008]

In order to achieve the above object, a metal vapor discharge lamp according to claim 1 of the present application is a translucent ceramic tube having openings at both ends, and the translucent ceramic tube. A closing cap made of a conductive cermet provided at both ends, and a pipe made of a halogen-resistant metal and seamlessly formed on both inner and outer sides of the closing cap, respectively. An electrode mandrel welded to a tip end portion of the pipe implanted inside the closing cap, which is not embedded in the closing cap. Further, in the metal vapor discharge lamp according to claim 2, the depth of the planting portion of the pipe planted in the closing cap is 2 mm to 4 mm, and the wall thickness of the pipe is 0.05 mm to 0.2 mm. It is characterized by being.

[0009]

In the metal vapor discharge lamp according to the present invention, as described above, the electrode mandrel is welded to the tip portion of the pipe embedded inside the closing cap, which is not embedded, and the pipe embedded on the outer surface is attached. Used as a lead rod. Further, since the thickness of the pipe planted in the closing cap is thin and formed seamlessly, even if the materials of the closing cap and the pipe are different, the difference in coefficient of thermal expansion when the closing cap is fired. The pipe absorbs the stress caused by the above and the like, and the generation of cracks in the planted portion can be prevented. Further, the depth of the planting portion of the pipe planted in the closure cap is set to 2 mm to 4 mm.
In addition, by forming the wall thickness of the pipe to be 0.05 mm to 0.2 mm, it becomes possible to absorb the stress more effectively, and the mechanical shock of the electrode mandrel welded to the pipe causes It is also possible to prevent tilting.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic structure of an arc tube of a metal vapor discharge lamp according to an embodiment of the present invention. It should be noted that the reference numeral 100 is added to the portions corresponding to those in FIG. 2 and the description thereof will be omitted. The arc tube 110 shown in the figure is a translucent ceramic tube 112 having both ends opened, a closing cap 114 made of a conductive cermet for closing the opening of the translucent ceramic tube 112, and the closing cap. 1
Pipes 120a, 120b made of halogen-resistant metal, which are implanted on both inner and outer sides of 14, and means for plasma welding or the like on the tip of the pipe 120a implanted inside, which is not embedded in the closing cap 114. And an electrode mandrel 116 connected by.

The pipe 120b implanted outside the closing cap 114 is used as a lead rod, and the tip of the pipe 120a implanted inside is wound with a coil 122. Discharge is performed in the section. The material of the conductive cermet forming the closing cap 114 is preferably a tungsten-alumina cermet obtained by adding a small amount of tungsten to alumina ceramics. Further, as the material of the pipe 120, it is preferable to use molybdenum having excellent halogen resistance characteristics so that even if a metal halide is enclosed in the arc tube 110, it is not corroded by the halogen.

The above is the schematic configuration of the metal vapor discharge lamp according to the present embodiment. Next, a specific method of forming the closing cap 114 in which the pipe 120 is implanted will be described. First, the constituent material of the closing cap 114 is changed to the closing cap 1
14 is pressed. Here, the tips of the pipes 120a and 120b are buried in the above-mentioned predetermined positions during the pressure molding so that the pipes 120a and 120b are buried in the predetermined positions.
a and 120b are fixed to the closing cap 114.
Then, the closing cap 1 to which the pipe 120 is fixedly attached.
Sinter 14 at high temperature. The closing cap 114
Which is one of the constituent materials of the pipe, and the pipe 120
Molybdenum, which is a constituent material of the above, forms a solid solution during the sintering at the high temperature, so that the plugging portion of the closing cap 114 and the seamless pipe 120 is integrated and becomes mechanically and electrically strong.

Here, when the closing cap 114 is sintered, stress due to thermal contraction acts near the contact surface of the closing cap 114 with the pipe 120, and cracks often occur near the contact surface. Therefore, in this embodiment, the pipe 120 is made thin so that the stress acting on the closing cap 114 is absorbed by the pipe 120 to prevent the closing cap 114 from cracking. Then, the wall thickness of the pipe 120 is formed so as to effectively absorb the stress in consideration of the depth of embedding in the closing cap 114.

Here, when the closing cap 114 is fired at a high temperature, the structure of the metal forming the pipe 120 becomes coarse and the pipe 120 becomes brittle. If it is formed to be extremely thin, the electrode mandrel 11 is subject to a mechanical impact on the arc tube or the like.
There is a possibility that the electrode mandrel 116 may fall down at the welded portion with 6. Therefore, the wall thickness and the embedding depth of the pipe 120 must be set to a value that absorbs the stress within a range having a strength that does not allow the electrode mandrel 116 to fall. Then, in order to find an appropriate value of the wall thickness and the embedding depth of the pipe 120, generation of cracking occurs when the closing cap in which the pipe 120 is embedded is baked by changing the wall thickness and the embedding depth. Also, it was examined whether or not the pipe 120 was tilted. The results are shown in Table 1.
The outer diameters of the pipes 120 are all 1.4 mm.

[0015]

[Table 1] ──────────────────────────────────── Pipe thickness Embedding depth Firing of closed caps Rear state (mm) (mm) ──────────────────────────────────── 0.1 2. 5 ○ 0.05 2.5 ○ 0.2 2.5 ○ 0.02 2.5 Crack on pipe 0.3 2.5 Crack on cap 0.5 2.5 Crack on cap 0.1 1.0 Pipe Tilt 0.1 5.0 Crack on cap 0.1 8.0 Crack on cap ──────────────────────────────── ─────

As is clear from Table 1, the pipe 120
It is understood that it is preferable to form the wall thickness of 0.05 mm to 0.2 mm and the embedding depth in the closing cap 114 to 2 mm to 4 mm. As described above, the metal vapor discharge lamp according to the present embodiment does not directly implant the electrode mandrel 116 and the lead rod 18 shown in FIG. Since the pipe 120 formed to have a wall thickness that absorbs electricity is planted, it is possible to prevent the occurrence of cracks in the closing cap 114. Further, by using a seamless pipe made of a material having excellent halogen resistance such as molybdenum as the pipe 120, the electrode supporting portion becomes mechanically and electrically strong, and the assembly is easy. Then, by enclosing the metal halide in the arc tube 110 and lighting it, it becomes possible to obtain a metal vapor discharge lamp excellent in luminous efficiency and color rendering.

[0017]

As described above, according to the metal vapor discharge lamp of the present invention, the wall thickness of the pipe embedded in the closing cap to a depth within a specific range is thin within the specific range. Therefore, it becomes possible to prevent the occurrence of cracks in the closing cap by absorbing stress acting on the contacting portion of the closing cap with the pipe during sintering. Further, since the pipe is formed of a halogen-resistant metal seamlessly, a metal halide can be enclosed in the arc tube, and further, the assembly of the electrode is easy and mechanically and electrically strong. It is possible to obtain a metal vapor discharge lamp having the same.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a schematic configuration of a metal vapor discharge lamp according to an embodiment of the present invention.

FIG. 2 is a schematic configuration explanatory view of a conventional metal vapor discharge lamp.

[Explanation of symbols]

 10, 110 ... Arc tube 12, 112 ... Translucent ceramic tube 14, 114 ... Closing cap 16, 116 ... Electrode mandrel 120 ... Pipe

Claims (2)

[Claims] 1. A translucent ceramic tube having both ends opened, a closing cap made of a conductive cermet provided at both ends of the translucent ceramic tube, and both inner and outer sides of the closing cap. A thin pipe made of halogen-resistant metal and formed seamlessly, and welded to the tip of the pipe implanted inside the closing cap, which is not embedded in the closing cap. A metal vapor discharge lamp comprising: a metal halide containing mercury and a rare gas in the translucent ceramic tube. 2. The metal vapor discharge lamp according to claim 1, wherein the depth of the planting portion of the pipe planted in the closing cap is 2 mm to 4 mm, and the wall thickness of the pipe is 0.05.
A metal vapor discharge lamp having a diameter of 0.2 mm to 0.2 mm.