JPH0519255B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a metal vapor discharge lamp using a translucent ceramic tube as an arc tube bulb.

[Technical background of the invention and its problems]

Conventionally, in metal vapor discharge lamps that use translucent ceramics as arc tube bulbs, it is difficult to heat and soften the end of the tube and crush and seal it, unlike in quartz glass arc tube bulbs. The end of the tube is sealed using a closure made of the metallic niobium or ceramics. Furthermore, in recent years, a technique using conductive ceramics, ie, cermet, as the material for the above-mentioned closing body has been published. In this case, the cermet closing body also serves as an electricity introducing body. For example, Japanese Patent Publication No. 56-29335 discloses that the temperature near the end sealing part of the arc tube, that is, the temperature of the coldest part, is increased by making the electrical resistance of the cermet closure body relatively large. A means to improve lamp efficiency is shown.

In addition, a metal introduction body such as niobium or tantalum is generally used as an electricity introduction body into the translucent ceramic arc tube sealed with the above-mentioned niobium or ceramic closure, but metal halides are used as the filler in the arc tube. When a compound is used, there is a disadvantage that the metal such as niobium is attacked by the halogen, but there is an advantage that such a disadvantage does not occur if a cermet closure body that also serves as an electricity introducing body is used.

However, while the use of a cermet closure has the above-mentioned advantages, it also has the disadvantage that it does not support the electrodes well.

For example, in the above-mentioned Japanese Patent Publication No. 56-29335,
As shown in the figure, the open end of an arc tube bulb 1 made of a translucent ceramic tube is sealed with a cermet closure 3 via a glass solder 2, and an electrode support made of, for example, molybdenum, supports an electrode 4. The electrode support structure attaching 5 to the closure 3 is shown. However, with this method, it is difficult to obtain strong adhesion due to the difference in thermal expansion coefficient between the electrode support 5 and the cermet closure 3, and the electrode support 5 may fall off from the closure 3 or become blocked while the lamp is on. There were drawbacks such as cracks occurring in the body 3 and the gas sealed in the arc tube leaking. Furthermore, as shown in FIG. 2, in Japanese Patent Application Laid-Open No. 57-210560, a male threaded portion 4a is provided at the base of the electrode 4, and the male threaded portion 4a is screwed into a screw receiving portion 3a provided on a cermet closure 3. A method is shown in which the electrode 4 is supported by the closure body 3 by fitting the electrodes 4 together. However, this method requires the labor and effort of cutting threads into the cermet, which has a high degree of hardness, and it is not a practical method in terms of cost, so it has not been put to practical use.

[Purpose of the invention]

The present invention has been made to address the above-mentioned problems, and is a metal vapor discharge lamp having an arc tube sealing part that facilitates and reliably supports electrodes, allows for an increase in the temperature of the coldest part of the arc tube, and is highly resistant to halogen. The purpose is to provide electric light.

[Summary of the invention]

The present invention is a metal vapor discharge lamp equipped with an arc tube in which the opening of a translucent ceramic tube is sealed with a closing body, and the closing body is made of a conductive cermet having a convex portion to which an electrode coil is attached. This is characterized in that the joint surface between the opening of the tube and the closure body is spaced apart from the convex portion.

[Embodiments of the invention]

The details of the invention will be explained below with reference to the illustrated embodiments. Figure 3 shows the structure of one end of a high-pressure sodium lamp arc tube. 1 is an arc tube bulb made of translucent ceramics, such as translucent alumina ceramics, and 3 is a closing body made of cermet, eg, metal powder such as tungsten, and alumina. It consists of a mixed sintered body with ceramics, and a sealing material such as Al ₂ O ₃ ,
The end of the arc tube bulb 1 is hermetically sealed with a glass solder 2 containing CaO or the like as a main component. A convex portion 3b is integrally molded on one end surface of the inner side of the arc tube of this closing body 3 so as to serve as an electrode axis, and this convex portion 3b
An electrode coil 4b is wound around the electrode 4 to form the electrode 4.

According to such a configuration, the cermet closure body 3 serves not only as a closure body for sealing the end of the arc tube but also as an electricity introduction body. Since the main body of the closure body 3 is integrally molded with a cermet material, there is no need for special means for attaching the electrode shaft to the closure body as in the past, and in addition, the electrode shaft does not detach from the closure body or is easily occluded. Naturally, problems such as cracks occurring at the attachment part of the electrode shaft on the body do not occur.

In addition, when a metal halide is sealed in the arc tube like in a metal halide lamp, the electricity introduction body in the part of the arc tube that comes into contact with the halogen is made of cermet, which has high resistance to halogen, as described above. It also has the advantage of not being corroded by halogens, unlike when using niobium or tantalum electrical introduction bodies. Furthermore, according to the above configuration, the electrode coil, which becomes extremely hot, is formed separately from the closing body, and the electrode coil is attached to the joint surface between the opening of the translucent ceramic tube and the closing body. Because it is spaced apart from the convex part, the temperature rise of the sealing material such as glass solder is extremely small when the arc tube is turned on. Therefore, the deterioration of resistance due to the reaction between the encapsulated halogen and the sealing material is greatly reduced. There is also the advantage of being able to do so. FIG. 4 shows another embodiment in which the closure body 3 is composed of two parts made of different materials, and the same parts are given the same reference numerals and the explanation will be omitted.

The one shown in the fourth figure is the part 3 that forms the center of the closure body.
A convex portion 3b serving as an electrode axis is integrally formed on e with cermet, and the outer periphery of the portion 3e forming the center of the closure body is surrounded by an outer shell portion 3f made of ceramics of the same material as the arc tube bulb 1. The outer shell part 3f of the closure body that seals the arc tube bulb 1 and its end via the glass solder 2 is made of the same material, so their thermal expansion coefficients are exactly the same. Therefore, it is extremely effective in preventing the occurrence of cracks due to thermal fluctuations in the sealing portion. Further, the tip of the convex portion 3b serving as the electrode axis may be made to protrude from the electrode coil 4b as shown in the figure.

In the cermet used in the present invention, it is preferable from the viewpoint of airtightness that the ceramic components contained in the cermet be the same as the ceramic material constituting the ceramic forming part of the arc tube bulb or the closure body.

〔Effect of the invention〕

As detailed above, according to the present invention, the closure body is made of a conductive cermet having a convex portion to which an electrode coil is attached, and the joint surface between the opening of the translucent ceramic tube and the closure body is formed by the convex portion. Because of the distance between
It is no longer necessary to attach the electrode shaft to the occluder as in the past, and accidents such as the electrode shaft detaching from the occluder and falling into the arc tube, or cracks occurring from the electrode shaft attachment part of the occluder are eliminated. can also be completely prevented. Furthermore, since the closing body is made of cermet, it can function as a current introduction body and can also increase the temperature of the tube end, that is, the coldest part of the arc tube, thereby improving luminous efficiency. Furthermore, the joint surface between the opening of the translucent ceramic tube and the closure body is spaced apart from the convex part to which the electrode coil is attached, which reduces the temperature of the sealing material. This can prevent deterioration in the durability of the sealing portion due to reactions between the halogen, etc., and the sealing material and thermal effects.

[Brief explanation of the drawing]

1 and 2 are sectional views of one end of a conventional arc tube, FIG. 3 is a sectional view of one end of an arc tube of an embodiment of the present invention, and FIG. 4 is a sectional view of one end of a conventional arc tube. Each shows a cross-sectional view of one end of the tube. 1... Arc tube bulb, 2... Glass solder, 3
...Closing body, 3b...Protrusion, 4...Electrode, 4b...
...electrode coil.

Claims (1)

[Claims] 1. A metal vapor discharge lamp equipped with an arc tube in which the opening of a translucent ceramic tube is sealed with a closing body, the closing body being made of a conductive cermet having a convex portion to which an electrode coil is attached, A metal vapor discharge lamp characterized in that a joint surface between the opening and the closing body is spaced apart from the convex portion.