JPS62249348A - High pressure sodium vapor lamp - Google Patents

Abstract

PURPOSE:To prevent cracks from happenning, simplify electrode fabrication and improve lamp characteristics by moulding, in one body a closing member and an electrode axis supported by the closing member with conductive ceramics and by fixing a sintered emitter thereto in addition. CONSTITUTION:A closing member 2 sealing the open end of a luminous tube bulb 1 and the electrode axis part 2a of an electrode supported by the closing member 2 are moulded in one body with conductive ceramics and a sintered emitter 4 consisting of a metal with a high melting point and an electron radioactive material is fixed to the electrode axis part 2a. This eliminates the cases where a difference of thermal expansion coefficient causes cracks to electrode fixing part the closing member 2 and causing the luminous tube to leak. Further, fabrication of electrodes is quite simple since what is reauired is only to fix a sinteied emitter material to the electrode axis part for sintering, and lamp start-up defects and a large increase of lamp voltage during their lives can be prevented since a sufficient volume of electron radioactive material can be contained in the sintered emitter 4.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to high pressure sodium lamps.

(Prior art) Conventionally, in high-pressure sodium lamps that use translucent ceramics as the arc tube pulp, it is difficult to heat and soften the open end and crush and seal it, unlike in the case of quartz glass arc tube pulp. Because there is.

For example, a ceramic closure is used, and the open end is hermetically sealed with a sealing material such as glass solder.

Furthermore, in recent years, as described in Japanese Patent Application Laid-Open No. 52-71695, etc., a technique has been developed in which conductive ceramics are used as the material for the closure body. Since such a conductive ceramic closing body itself also has the role of an electricity introducing body, it can be used as an electricity introducing body for the electrodes in one arc tube, such as a niobium wire or a niobium tube, as in the case of a conventional ceramic closing body. There is no need to airtightly penetrate the closing body through glass solder, and the external introduction body is fixed to the inner surface of the conductive ceramic closing body (inside the arc tube) and the proximal end of the electrode to the outer surface. This eliminates the need for the conventional glass solder described above, which is not only advantageous in terms of preventing arc tube leaks (also, it is preferable in terms of cost since expensive niobium wires and tubes are not required either).

The conductive ceramic closure body normally seals the open end of an arc tube pulp made of a translucent ceramic, such as alumina ceramic, through a glass solder whose main component is alumina, calcia, magnesia, etc. The coefficients of thermal expansion of the lamps must be similar or they will not be able to withstand the severe thermal cycling that occurs during lamp flashing. Therefore, the components of the conductive ceramics forming the closure are subject to restrictions. The conductive ceramic used is, for example, one made of alumina and tungsten, and the tungsten content is generally 10 to 25% by weight. Namely.

When the amount of tungsten exceeds the above range, the coefficient of thermal expansion decreases, resulting in drawbacks such as cracks being likely to occur in the sealing portion of the arc tube, and tungsten precipitating, which tends to impair airtightness.

On the other hand, if the amount of tungsten is too small, the conductivity will decrease.

Therefore, the tungsten content is preferably in the above range, and the thermal expansion coefficient of conductive ceramics with such a composition is 7.
It is around 0 x 10-7/℃.

Further, an electrode is fixed to the inner surface of the closure body, for example, by embedding the proximal end thereof. The electrode is usually formed by winding a tungsten coil around the tip of an electrode shaft made of a high-melting point metal such as tungsten, and coating this coil with an electron-radiating substance such as an alkaline earth metal oxide or tungstate. be done. Therefore, the electrode fixing part of the closure body has the same coefficient of thermal expansion as the closure body made of conductive ceramics with a coefficient of thermal expansion of 70X10/'C<44X10-7/
This is caused by a large difference in coefficient of thermal expansion from the electrode made of tungsten at °C, and has the disadvantage that cracks are likely to occur due to severe thermal cycles during lamp blinking.

In addition, the electrode of the above structure not only requires a complicated assembly process, but also requires a sufficient amount of electron radioactive material to be deposited on the electrode coil, especially in the case of small electrodes for small-capacity lamps. is difficult.

This has resulted in drawbacks such as poor starting, an increase in lamp voltage, and an early decrease in luminous flux.

(Problems to be Solved by the Invention) When a conductive ceramic closure is used as described above, the closure may Disadvantages include cracks occurring in the lamp, resulting in leakage defects in the arc tube, and problems with the structure of the electrodes, such as the complicated assembly process, poor starting, and other poor lamp characteristics. was there.

Therefore, the present invention aims to eliminate the above drawbacks.

It suppresses the occurrence of cracks in the electrode fixing part of the conductive ceramic closure, and it is easy to manufacture the electrode, and
The purpose is to provide a high pressure sodium lamp with excellent lamp characteristics.

[Structure of the invention]

(Means for Solving the Problems) In the high-pressure sodium lamp of the present invention, a closing body that seals the open end of one arc tube pulp and an electrode shaft portion of the electrode held by this closing body are made of conductive ceramics. A sintered emitter made of a high melting point metal and an electron radioactive material is fixed to the electrode shaft portion.

(Function) In the high-pressure sodium lamp of the present invention, a blocker;
Since the electrode shaft portion of the electrode supported by this closing body is integrally molded with the same material, conductive ceramics, the electrode fixing portion of the closing body is different from the conventional one due to the difference in coefficient of thermal expansion between the two. There will be no occurrence of cracks.

In addition, the electrode is manufactured by attaching a mixture of high melting point metal powder and electron radioactive material powder to the electrode shaft part, which is integrally molded with the closure body using conductive ceramics, and then attaching the mixture to the electrode shaft part that is integrally formed with the closure body. Sintering is nano-sized and extremely simple.
Furthermore, since a sufficient amount of electron emitting material can be contained in the sintered emitter, it is possible to prevent lamp startup failure and early deterioration of other characteristics.

(Example) The present invention will be described in detail below based on an example shown in one drawing. FIG. 1 shows a vertical cross-sectional view of one end of the arc tube of a high-pressure sodium lamp with a rated power of 150 W according to the present invention.
) is an arc tube pulp made of a translucent ceramic such as a translucent alumina ceramic, and (2) is a conductive ceramic closure made of a mixed sintered body of alumina and tungsten, for example.

For example, the above-mentioned arc tube pulp (1
The open end of 1 is sealed. A protrusion (2a) corresponding to the electrode shaft portion is integrally molded on one end surface of the closure body (2) inside the arc tube. Sintered emitter made of barium/calcium acid (
4) is fixed, and the electrode (5) is fixed together with the protrusion (2a).
Configure. Although not shown, an external lead wire is attached to the convex portion (2b) formed on the other end surface of the closure body (2).

A predetermined amount of a starting rare gas, such as xenon gas, and sodium amalgam consisting of mercury and sodium is sealed inside such an arc tube, and this arc tube is usually sealed in an outer envelope with a vacuum inside to form a lamp. .

Next, a method for manufacturing the assembly of the closure body (2) and electrode (5) will be outlined. First, a small amount of binder is added to and mixed with a material consisting of 85% alumina powder and 15% tungsten powder in a weight ratio of 2, and this mixture is pressed to form a protrusion corresponding to the electrode shaft part as shown in the second national map. 2
A compression molded body (for two people) of a closed body provided with a) is obtained. Next, a small amount of binder is added to a material consisting of 75% tungsten powder and 25% barium/calcium tungstate powder by weight, mixed, and then pressed to form a sintered cylinder with a bottom as shown in Figure B1. Compression molded emitter (4A
). Next, as shown in FIG.
This assembly was then heated in a hydrogen atmosphere for approximately 1700'
If heated at ℃ for 2 hours, each compression molded product (2A), (
4A) is a closed body (2) made of conductive ceramics which is sintered and integrally formed with a protrusion (2a) corresponding to the electrode axis as shown in the figure (to), and the protrusion (2a) An assembly consisting of an electrode (5) to which a sintered emitter (4) is sintered and fixed is obtained.

In the assembly manufactured in this way, the conductive ceramic closing body (2) not only serves as a closing body for sealing the open end of the arc tube, but also serves as an electricity introduction body. Since the protrusion (2a) that becomes the electrode shaft and the main body of the closure body (2) are integrally molded from the same conductive ceramic material, they naturally have the same coefficient of thermal expansion.
Therefore, it is possible to avoid a situation in which the electrode fixing portion of the closing body cracks due to severe thermal cycles associated with flashing of the lamp as in the conventional case, and it is also possible to avoid the trouble of fixing the electrode shaft of the electrode to the closing body 1τ. Furthermore, the electron radioactive material is not deposited on the electrode coil as in Erasai, but is sintered and fixed to the protruding part corresponding to the electrode axis as a sintered emitter with a high melting point metal, so a sufficient amount can be retained. Therefore, it is also possible to prevent lamp starting failures and significant increases in lamp voltage during the life of the lamp due to lack of electron radioactive substances.

In other words, in the lamp of the second embodiment, there was no arc tube leakage or lamp starting failure caused by cracks in the electrode fixing part of the closing body, and even when the lamp voltage increased during the life of the lamp, the conventional lamp did not turn on for 1,200 hours. Approximately 2 hours
What used to be 5V was able to be reduced to about 8V.

Next, another embodiment will be described with reference to FIG. The figure shows one end of the arc tube, and the same parts as in the previous embodiment are given the same reference numerals and their explanation will be omitted. In the case of this embodiment, the center part (2c) of the closure body (2) is made of conductive ceramics with an integrally provided protrusion (2a) corresponding to the electrode axis, and the outer part surrounding this center part (2c) is made of conductive ceramics. The shell portion (2d) is made of the same ceramic as the arc tube pulp (1). With this configuration, the outer shell part (
Since they are made of the same material as 2d), their coefficient of thermal expansion is exactly the same. Therefore, it is more preferable in terms of improving the strength of this sealing part.

In addition, various materials are known for the arc tube loop, the conductive ceramic closing body, and the sintered emitter, not limited to those in the above examples, but generally, alumina ceramics are used as the arc tube pulp. In view of the coefficient of thermal expansion, the ceramic component of the conductive ceramic should be a sintered body of alumina and tungsten, which is the same as the arc tube pulp, and the sintered emitter should be the same tungsten and alkaline earth metal compound. Most preferred is a combination with an electron radioactive substance consisting of:

〔Effect of the invention〕

As described above, according to the configuration of the present invention, the closing body and the electrode shaft portion of the electrode supported by the closing body are integrally molded from the same material, which is conductive ceramics. In this way, there is no possibility that the electrode fixing portion of the closing body will crack due to the difference in coefficient of thermal expansion between the two, resulting in leakage from one arc tube.

What's more, the manufacturing of the electrode is as simple as attaching the sintered emitter material to the electrode shaft part, which is integrally formed with the closure body using conductive ceramics, and then sintering it.

High-pressure sodium lamps are not only extremely easy to use, but also contain a sufficient amount of electron radioactive material in the sintered emitter, which prevents lamp startup failures and large increases in lamp voltage during the life of the lamp. can be provided.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view of one end of the arc tube of an embodiment of the high pressure IJ Umlumb of the present invention, Fig. 2 is an explanatory diagram of the manufacturing process of the assembly of the closure body and electrode of the arc tube, and Fig. 3 2A and 2B respectively show longitudinal cross-sectional views of one end of the arc tube of other embodiments. (1)... Arc tube pulp, (2)...
Obstruction body.

Claims (2)

[Claims] (1) Equipped with an arc tube formed by sealing the open end of an arc tube pulp made of translucent ceramic with a closing body that supports an electrode, and at least a portion of the closing body and the electrode shaft portion of the electrode are electrically conductive. 1. A high-pressure sodium lamp, which is integrally molded with synthetic ceramics, and has a sintered emitter made of a high-melting point metal and an electron radioactive substance sintered and fixed to the electrode shaft portion. (2) Claim 1, characterized in that the translucent ceramic is a translucent alumina ceramic, the conductive ceramic is alumina ceramic and tungsten, the high melting point metal is tungsten, and the electron radioactive substance is an alkaline earth metal compound. The high-pressure sodium lamp described in item 1.