JPH03101032A - Manufacture of high-pressure sodium lamp - Google Patents

Abstract

PURPOSE:To prevent the infiltration of impurities into a light emitting tube and reduce the dispersion of the lamp voltage by drawing the end section of at least one of electrode support tubes, cleaning the drawn electrode support tube in an organic solvent, and heat-treating the cleaned electrode support tube at the specific temperature. CONSTITUTION:A drawn niobium tube 1 is cleaned with ultrasonic waves in an organic solvent 4, and it is heat treated at the temperature 1400-1500 deg.C in vacuum to obtain a drawn niobium tube 5 removed with impurities 3. An electrode 6 is inserted into the drawn section 2 of the niobium tube 5, the drawn section 2 is caulked and arc-welded to fix the electrode 6, and an electrode support tube 7 and an electrode support tube 8 on the nonexhaust side are formed. The electrode support tube 7 and the electrode support tube 8 on the nonexhaust side are inserted into through holes 11 of end wall sections 10 of a light emitting tube 9, then frit 12 is heated and melted in vacuum, and end wall sections and electrode support tubes 7 and 8 are hermetically sealed. No impurity is left in the light emitting tube 9 after it is sealed, and the dispersion of the lamp voltage is reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a method for manufacturing a high-pressure sodium lamp,
In particular, the present invention relates to a process for processing an electrode support tube whose end portion is subjected to a drawing process.

[Conventional technology]

Ceramic tubes made of translucent alumina, which are generally used as arc tubes for high-pressure sodium lamps, are roughly divided into the following two types in terms of shape. That is, (1) Open type: This type of ceramic tube consists of a cylindrical pipe and two end caps fixed to both ends of the pipe.

■ Monolithic type 12 types of ceramic tubes are
The pipe and end cap of the open type ceramic tube are integrally molded.

When using the above monolithic type ceramic tube as an arc tube, due to its structure, it is difficult to insert an electrode support tube that has an outer diameter larger than the diameter of the through hole formed in the end wall of the ceramic tube into the arc tube. It is possible. Therefore, the maximum outer diameter of the electrode support tube and the maximum outer diameter of the electrode coil supported by the support tube need to be smaller than the outer diameter of the through hole formed in the end wall of the arc tube.

On the other hand, in the so-called exhaust pipe system in which the electrode support tube also serves as an exhaust pipe, a through hole for exhaust must be provided in a portion of the electrode support tube inside the arc tube end wall.

In order to meet the above manufacturing conditions, conventionally, one end of the electrode support tube, which also serves as an exhaust pipe, was drawn.
An electrode is inserted into the drawn end, the drawn end of the electrode support tube is caulked, and arc welding is performed in an argon atmosphere to fix the electrode to the electrode support tube.

At this time, a through hole for exhaust is formed between the electrode and the electrode support tube.

Usually, a niobium tube is used as an electrode support tube, and the end drawing process is performed by rotating a stainless steel jig with a tapered hole, and inserting and pressing the niobium tube into the tapered hole. A predetermined aperture shape is formed.

[Problem to be solved by the invention]

However, the surface of the drawn part of the niobium tube formed in this way contains 0,0, a component of machine oil to prevent heating due to friction during the drawing process, and the composition of stainless steel forming the jig. The element Fe.

Analysis confirmed that a compound containing Ni+Cr etc. was attached.

Such deposits on the surface of the constriction part of the niobium tube are brought into the arc tube as impurities when the arc tube is sealed, and are impurities that can evaporate below the sealing temperature (approximately 1400°C), such as C, Fe, Compounds containing Ni, Cr, etc. evaporate and scatter, and some of them adhere to the inner wall of the arc tube and the electrode surface, while impurities that cannot be evaporated, such as niobium oxide, remain as they are on the surface of the aperture part.

The impurities are released into the arc tube during lamp operation, and react with sodium, which is the luminescent filler, or change the thermal conductivity of the electrode support tube. Therefore, by changing the sodium ratio in the sodium amalgam inside the arc tube and the temperature of the coldest part formed at the outer end of the electrode support tube, the vapor pressure inside the arc tube can be changed, which in turn can greatly increase the variation in lamp voltage. There is a problem with this.

The present invention was made in order to solve the above-mentioned problems in conventional high-pressure sodium, and it is possible to prevent the above-mentioned impurities from entering the arc tube by a simple method and reduce variations in lamp voltage. The purpose of the present invention is to provide a method for manufacturing a sodium lamp.

[Means and effects for solving the problems] In order to solve the above problems, the present invention provides a method for manufacturing a high-pressure sodium lamp, in which at least one end of an electrode support tube sealed at both ends of an arc tube is a drawing step, a step of washing the drawn electrode support tube in an organic solvent, and a step of washing the washed electrode support tube in a vacuum at 1400°C to 150°C.
The electrode support tube sealed in the arc tube is treated with a heat treatment process at a temperature of 0°C.

This simple treatment process makes it possible to remove impurities that adhere to the surface of the niobium tube's constriction section.
No impurities remain in the arc tube after the arc tube is sealed, and the inside of the arc tube remains clean. Therefore, changes in the temperature of the coldest part due to changes in the sodium ratio in the sodium amalgam in the arc tube or changes in the thermal conductivity of the electrode support tube are reduced, and a high-pressure sodium lamp with small variations in lamp voltage can be obtained.

〔Example〕

Examples will be described below with reference to manufacturing process diagrams of arc tubes for high-pressure sodium lamps.

First, as shown in FIG. 1, a niobium tube l for forming an electrode support tube is cut into a predetermined length.

Next, as shown in FIG. 2, one end of the niobium tube 1 is squeezed using a stainless steel jig provided with a tapered hole (not shown) to form a squeezed portion 2.

At this time, C, 0, Fe, Nj+ C
Impurities 3 containing r etc. are attached. Next, the drawn niobium tube 1 is ultrasonically cleaned in an organic solvent 4, as shown in FIG. Then, in vacuum, 1400°C to 150°C
After heat treatment at a temperature of 0°C, impurity 3 was removed as shown in Figure 4.
A drawn niobium tube 5 from which the niobium is removed is obtained. Note that if the temperature of the above heat treatment is lower than 1400°C, impurities may not be completely removed and may remain on the surface.
If the temperature exceeds 500°C, the hardness of niobium becomes high, and there is a risk that the filling material will leak from the electrode support tube portion made of the niobium tube after the arc tube is completed.

Next, as shown in FIG. 5, the electrode 6 is connected to the niobium tube 5.
After inserting it into the constricted part 2, the constricted part 2 is caulked. Next, as shown in FIG. 6, the caulked portion is arc-fused in an argon atmosphere to fix the electrode 6 and obtain the electrode support tube 7. At this time, the temperature is very high during arc melting, so if there are impurities remaining on the surface of the niobium tube, a film of impurities, for example several μm thick, will form on the niobium surface.
However, in the present invention, since impurities and the like are removed in advance, such an oxide film of several micrometers is not formed. Next, the electrode support tube that also serves as an exhaust pipe is left as it is, and the electrode support tube that is used as a non-exhaust pipe is made by sealing the open end of the niobium tube by arc melting in an argon atmosphere as shown in Figure 7. Side electrode support tube 8
form.

Next, after inserting the electrode support tube 7 that also serves as an exhaust pipe and the non-exhaust side electrode support tube 8 into the through hole 11 of the end wall 10 of the monolithic type arc tube 9, as shown in FIG.
The flip 2 is heated and melted at about 1450° C. in a vacuum to airtightly seal the end wall 10 and the electrode support tube 7.8. Next, as shown in FIG.
3 and xenon gas, one end of the arc tube of the electrode support tube 7 is closed by arc melting under the pressure of the xenon gas (15 to 350 Torr) to complete the arc tube. The arc tube manufactured as described above is mounted within an outer bulb (not shown) by conventional means to complete a high-pressure sodium lamp.

Variations in the lamp voltage Vz (V) of high-pressure sodium lamps manufactured using the above manufacturing process, and lamps manufactured using a manufacturing process that does not involve cleaning the niobium tube with conventional drawing processing or vacuum heat treatment. Voltage V
7(V), the data shown in Table 1 below was obtained.

In Table 1, n indicates the number of tests, V indicates the average value of the lamp voltage, and σ indicates the variation (standard deviation).

Table 1 As is clear from Table 1, the variation in lamp voltage of high-pressure sodium lamps produced by the manufacturing method according to the present invention was found to be considerably reduced compared to those produced by the conventional manufacturing method.

〔Effect of the invention〕

As described above based on the embodiments, according to the manufacturing method according to the present invention, the drawn portion of the niobium tube for the electrode support tube is cleaned by cleaning with an organic solvent and vacuum heat treatment after drawing. Impurities attached to the surface are removed. As a result, no impurities remain in the arc tube after the arc tube is sealed, and the inside of the arc tube remains clean. Therefore, changes in the temperature of the coldest part due to changes in the sodium ratio in the sodium amalgam in the arc tube or changes in the thermal conductivity of the electrode support tube are reduced, and as a result, a high-pressure sodium lamp with small variations in lamp voltage can be obtained.

[Brief explanation of drawings]

FIGS. 1 to 9 are diagrams showing the process of manufacturing an arc tube for explaining an embodiment of the method for manufacturing a high-pressure sodium lamp according to the present invention. In the figure, 1 is a niobium tube, 2 is a constriction part, 3 is an impurity, 4 is an organic solvent, 6 is an electrode, 7 is an electrode support tube, 8 is a non-exhaust side electrode support tube, 9 is an arc tube, and IO is an end wall. 11 is a through hole, 12 is a frit, and 13 is a sodium amalgam.

Claims (1)

[Claims] 1. A step of drawing at least one end of an electrode support tube sealed at both ends of an arc tube, a step of cleaning the drawn electrode support tube in an organic solvent, and a step of cleaning the electrode after being cleaned. A method for manufacturing a high-pressure sodium lamp, comprising the step of heat-treating a support tube in a vacuum at a temperature of 1400°C to 1500°C.