JPS62237660A - High pressure sodium lamp - Google Patents

Abstract

PURPOSE:To prevent the leakage of sodium in a luminous tube to the outside of the tube during operation by through sealing an electric conductor provided with magnesium oxide film on the outside surface in the aperture of the end of an alumina tube with ceramic cement containing calcium oxide. CONSTITUTION:An alumina tube 1 and an end disk 2 and an electric conductor 6 are sealed together with rings of ceramic cement 8 by heating up to a high temperature and melting the said cement. During the heating aluminum oxide and magnesium oxide are dissolved in the ceramic cement 8 and crystallized partially under the existence of calcium oxide. Thereby the magnesium oxide film 7 and the ceramic cement 8 are adhered strongly, and the sealed portions between the hole 3 of the end disk 2 and the conductor 6 and between the alumina tube l and the end disk 2 can be made sufficiently airtight. Therefore the leakage of the sodium or the like in the luminous tube to the outside of the tube during the operation of the lamp can be prevented.

Description

[Detailed description of the invention] Industrial applications The present invention relates to high pressure sodium lamps.

BACKGROUND OF THE INVENTION High-pressure sodium lamps have an efficiency approximately twice as high as mercury lamps, and are attracting attention as suitable for the new era of energy conservation, and are increasingly being used. This high-pressure sodium lamp consists of a translucent alumina body with electrodes at both ends, and has an arc tube with sodium etc. sealed inside.Electricity is supplied to the electrodes through a hole in the end of the arc tube. A conductor for this purpose is passed through and hermetically sealed with ceramic cement.

Problems to be Solved by the Invention However, such conventional conductors and ceramic cements sometimes have insufficient airtightness, and inclusions such as sodium in the arc tube may leak from the areas lacking in airtightness. There was a problem in that the lamp leaked outside the tube, resulting in an increase in the lamp current and an increase in the temperature of the ballast, leading to burnout.

The present invention was made to solve these problems, and it prevents sodium from leaking out of the arc tube.
The present invention provides a high-pressure sodium lamp that does not cause accidents such as ballast burnout.

Means for Solving the Problem In order to solve this problem, the present invention comprises an arc tube made of a translucent alumina body having electrodes at both ends, with sodium sealed inside, and an electric discharge tube attached to the electrode. A magnesium oxide film is formed on the outer surface of an electric conductor for supplying the electric current, and the electric conductor is penetrated and sealed into a hole provided at the end of the arc tube through a cement containing at least calcium oxide. It features a high-pressure sodium lamp.

With this configuration, magnesium oxide melts into the ceramic cement from the magnesium oxide film formed on the outer surface of the conductor, and partially forms crystals with calcium oxide contained in the ceramic cement. Therefore, the airtightness is sufficient, and the sodium inside the arc tube will not leak out of the tube during the operation of the lamp.

Embodiment FIG. 1 is a longitudinal sectional view of an arc tube of a high-pressure sodium lamp which is an embodiment of the present invention. In FIG. 1, the arc tube of this high-pressure sodium lamp consists of a single-crystalline or polycrystalline alumina tube 1 and an end disk 2 made of single-crystalline or polycrystalline alumina provided at one end of the tube. hole 3 provided in the end disk 2
A conductor e made mainly of niobium and having an electrode 4 held by titanium 6 at its tip passes through it. Inside the arc tube,
n) Metals for buffer gas such as IJum and mercury and rare gas for starting are sealed. A magnesium oxide film 7 is formed on the outer surface of the conductor 6. And conductor 6
is penetrated into the hole 3 of the end disk 20 and hermetically sealed with a ceramic cement 8 whose main components are aluminum oxide (BOS) + calcium oxide (CaO), strontium oxide (3rO), and yttrium oxide (Y2O2). (See Figure 2).The alumina tube 1 and end disk 2 are hermetically sealed with the same ceramic cement 8.The structure of the end of the arc tube (not shown) is the same as that of one end. It's the same.

In an IJum lamp, the alumina tube 1, end disk 2, and conductor 6 are heated to high temperature using a ring of ceramic cement 8. Each is sealed by heating and melting. During heating, alumina tube 1
, aluminum oxide from the end disk 2 and magnesium oxide from the magnesium oxide film 7.
The solution is dissolved into the cement 8, in which aluminum oxide and magnesium oxide partially form crystals in the presence of calcium oxide.

Therefore, the yttrium oxide film 7 formed on the outer surface of the conductor 6 and the ceramic cement 8 are firmly bonded, and the sealing area between the hole 3 of the end disk 2 and the conductor 6 is sufficiently airtight. Furthermore, the sealing area between the alumina tube 1 and the end disk 2 is sufficiently airtight, and as a result, leakage of sodium, etc. inside the arc tube to the outside of the arc tube is prevented during movement.

The location where the magnesium oxide film is applied is not limited to a part of the conductor as shown in Figure 1, but may be the entire outer surface of the conductor, or the base of the conductor (
It may be the entire outer surface excluding the outside of the arc tube.

Next, an experimental example in which the effects of the present invention were confirmed will be described.

The alumina tube 1 of the arc tube is made of polycrystalline alumina, has an inner diameter of 7.51 mm, a total length of 114 mm, and an arc length of 68 mm.

The end disk 2 is made of polycrystalline alumina and has a conductor 6.
is 0.25 thick containing about 1% zirconium (Zr)
The electrode 4 is made of a tungsten coil coated with an electron radioactive material and is fixed with titanium 9 at its tip. A magnesium oxide film 7 is formed on the outer surface of the conductor 6.

This magnesium oxide film 7 is formed using a vapor phase evaporation method in which magnesium oxide is formed by electron beam evaporation in a vacuum, and has a thickness of about 2 microns. The alumina tube 1 and the end disk 2, and the end disk 2 and the conductor 6 are made of aluminum oxide, calcium oxide, and strontium oxide.

Each is hermetically sealed with a ceramic cement 8 made of yttrium oxide. Inside the arc tube, there are 2 mg of sodium, 1 s mg of mercury, and about 2 s of xenon gas.
0 Torr is enclosed.

Approximately 1Q of such high-pressure sodium lamps were manufactured, and the input was 4.
When we conducted a life test at 00W (repeatedly turning off the light for 0.6 hours and turning it on for 6.6 hours), we found that even after 20,000 hours, there was no leakage of sodium inside the arc tube to the outside of the tube, and therefore the light color did not change. There was no increase in lamp current.

It goes without saying that the present invention is applicable not only to alumina bodies having the shape and structure shown in FIG. 1, but also to those shown in FIGS. 3 to 6, for example.

The one shown in Figure 3 is the same as the one in Figure 1 in that the alumina body is composed of an alumina tube 1 and an end disk 2, but the shape of the end disk 2 is different; It is completely inserted into the inner surface of the end.

In the case shown in FIG. 4, the alumina body is composed of an alumina tube 1 and an end disk 2, similar to those in FIGS. 1 and 3, but the alumina tube 1 has a bottom at the end. ,
An end disk 2 is provided on the outer surface of this bottom surface.

In the case shown in FIG. 6, the alumina body is made of a single piece, and a conductor 6 is sealed in a hole 3 of an alumina tube 1 with a narrowed end.

The conductor may be not only a niobium tube but also a niobium wire, and its material is not only niobium, but also tantalum, tantalum, etc.
Tungsten etc. can be used.

As described in detail, the present invention is formed by forming a magnesium oxide film on the outer surface of a conductor for supplying electricity to an electrode, and at least calcium oxide film is formed in the hole provided at the end of the alumina body. By sealing the conductor through the ceramic cement that contains the light, it is possible to prevent the sodium inside the light tube from leaking out of the light tube during the movement, and as a result, the light color does not change. Of course, since the phenomenon of increase in lamp current does not occur, it is possible to provide a high-pressure sodium lamp that is free from the risk of inducing burnout of the ballast.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a main part of an arc tube of a high-pressure sodium lamp which is an embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view of the main part,
Figures 3 to 6 show other embodiments of the present invention (high pressure)
It is a sectional view of the main part of the arc tube of IJ Umrambu. 1... Alumina tube, 2... End disk, 3... Hole, 4... Electrode, 6...
...Titanium, 6...Conductor, 7...
・Magnesium oxide film, 8...Ceramic cement. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 3
figure

Claims (1)

[Claims] It is made of a translucent alumina body with electrodes at both ends, and is equipped with an arc tube in which at least sodium is sealed, and a magnesium oxide film is formed on the outer surface of a conductor for supplying electricity to the electrodes. A high-pressure sodium lamp, characterized in that the conductor is sealed through a hole provided at the end of the arc tube through a cement containing at least calcium oxide.