JPS58218728A - Manufacture of metal vapor discharge tube - Google Patents

Abstract

PURPOSE:To strengthen a luminous tube itself against a change of temperature and to check generation of leakage at the sealing part of said luminous tube by a method wherein both ends of a translucent ceramic tube are processed by molding to be thicker than the central part while making its inner peripheral surface or outer peripheral surface to be almost circular followed by sticking a blocking body to the processed peripheral surface through adhesive material. CONSTITUTION:In an alumina-ceramic tube 1 or the like whose end part 1b is formed thicker than the tube central part 1c in advance, for instance, the tube end part 1b is formed to be 3mm. in thickness thicker than the thickness 1mm. of the central part 1c, then the outer peripheral surface of said thick tube end part 1b is processed by polishing with a diamond polishing device or the like to mold the outer peripheral surface 1a having a good roundness while making the roundness after processing to be 0.1mm.. Thereafter, a blocking body such as a niobum cap etc. is stuck to the outer peripheral surface 1a of the processed terminal part through adhesives such as glass brazing material or the like in order to seal the luminous tube opening part airtightly. The above processes may secure sufficient strength of tube against any change of temperature and prevent generation of leakage at the sealing part due to unevenness of adhesive layer.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a method of manufacturing a metal vapor discharge lamp having a translucent ceramic arc tube.

[Technical background of the invention]

The arc tube of an IJum lamp is a translucent ceramic tube with excellent heat resistance and corrosion resistance, such as a polycrystalline alumina ceramic tube, which is filled with sodium amalgam and a starting rare gas. The opening is hermetically sealed with a closure such as a niobium cap holding the electrode through an adhesive such as a glass brazing material.

Since such high-pressure sodium lamps have high efficiency and long life, they have recently come to be used in large numbers for lighting in roadway gymnasiums, markets, factories, and the like. In line with this trend, the variety of lamps suitable for various uses is being expanded. However.

For example, lamps with a large power capacity or high color rendering type, etc., have a larger diameter than conventional ones, that is, an inner diameter of 14 or more, especially 2.
There were many cases where products using arc tubes of 0 mm or larger became defective during their lifespan. After various investigations into the cause of this, it was found that it was a leak at the sealing part of the niobium cap at the end of the arc tube.

That is, the large-diameter arc tube pulp, that is, the translucent ceramic tube, has a conventional diameter of about 7 to 8 mm at the time of manufacture.
It is difficult to form a circular cross-sectional shape like a pipe, and the shape tends to be slightly flat, so-called an ellipse. On the other hand,
The material for the closure at the end of the tube, such as niobium, is easy to process into a circular shape.

The thickness of the glass brazing material layer of the adhesive interposed between the oval tube end and the circular niobium cap has thin and thick sections, making it uneven, and the end of the arc tube becomes uneven due to repeated flashing of the lamp. When the temperature changes, a difference occurs in the amount of thermal expansion, and stress is generated in the sealed portion, and this stress causes minute cracks to occur in the glass brazing material. This crack gradually grows larger due to repeated thermal cycles caused by flashing the lamp.
It is thought that leakage will eventually occur in the sealed portion, leading to lamp malfunction.

By the way, the reason why it is difficult to mold the cross-sectional shape of a large-diameter translucent ceramic tube as described above into a circular shape, that is, the roundness deteriorates, is due to the following.

That is, the wall thickness of the tube is usually about 0.5 mm to 1.5 fflω in order to obtain good light transmittance.

This also applies to pipes with large diameters.

Therefore, for large diameter pipes, the wall thickness of the pipe compared to the size of the pipe diameter is thinner than that of conventional small diameter pipes, and deformation occurs during the firing process during pipe manufacturing. This results in poor roundness.

In order to deal with this, a method of improving the roundness by molding the translucent ceramic tube to be thicker than before has been considered, but this method did not yield satisfactory results. This results in the inconvenience of a decrease in light transmittance due to the increased wall thickness.

It could not be an effective method.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a metal vapor discharge lamp using a translucent ceramic tube, which prevents leakage at the tube end sealing portion and has a long life.

[A essential point of the invention]

In the present invention, a translucent ceramic tube is made with both ends thicker than the center, and by processing the thickened ends using an appropriate method, at least the inner peripheral surface or the outer peripheral surface of the end portions can be The method is characterized in that one of the surfaces is brought into a circular shape, and then the obturator is adhered to the circularly processed surface using an adhesive. The end circumferential surface of the ceramic tube and the closing body such as a niobium cap, which has excellent moldability, are both formed into a circular shape with good roundness, so the thickness of the adhesive layer interposed between the bonding surfaces of the two is It becomes uniform and prevents leakage.

[Embodiments of the invention]

The details of the present invention will be explained below with reference to one embodiment shown in the drawings. FIG. 1 shows a partially cutaway front view of an arc tube for a high-pressure sodium lamp embodying the present invention.

(1) is a translucent ceramic tube, such as an alumina ceramic tube, which is filled with an amalgam of sodium and mercury and xenon gas as a starting rare gas; (2) is an outer peripheral surface (1a) of the end of the alumina ceramic tube (1); ) to be airtightly bonded to the glass brazing material (3) whose main components are aluminum oxide, calcium oxide, etc. A closing body that airtightly seals the end opening of the tube (for example, a niobium cap) It is.

(4) is a metal tube that hermetically passes through the center of the niobium cap (2) and is used as a tube for exhausting the tube and filling the amalgam and starting rare gas when manufacturing one arc tube. (5) is an electrode which is held and fixed by the metal tube (4).

Next, a method for manufacturing the above-mentioned arc tube will be explained.

In Figure 2, the tube end (1b) is connected to the tube center (IC) in advance.
Fig. 2(a) is a front view, and Fig. 2(a) is a front view.
(b) is a side view. The tube end (1b) is connected to the tube center (
The wall thickness of lc) is 3.0 mm, which is thicker than the wall thickness of 1.0 m + n.
and its roundness (difference between maximum outer diameter d1 and minimum outer diameter d2) is poor, for example, 0.5 mm or more.
stomach. Next, the outer circumferential surface of the thick-walled tube end (1b) is polished using a diamond polishing machine normally used for processing alumina ceramics, etc., so that the outer circumferential surface is circular, that is, has good roundness ( 1a) K-mold. In FIG. 4, FIG. 3(a) is a front view.

FIG. 3(b) shows side views, and the nine-dot line diagram shows the state before processing. The roundness after processing (the difference between the maximum outer diameter D1 and the minimum outer diameter D2) is improved to 0.1 mm.

After this, as shown in Fig. 1, a closure body such as a niobium cap (2) is adhered to the outer circumferential surface (1!l) of the processed pipe end via an adhesive such as a glass brazing material (3). If the opening of the arc tube is sealed more airtight, the glass brazing material (3) will be uniformly distributed between the tube end outer peripheral surface (1a) of the alumina ceramic tube and the circular inner peripheral surface of the niobium cap (2). It can exist as a layer.

4 to 6 show different embodiments, and the 9-dot line indicates the wall thickness of the end of the alumina ceramic tube before processing, and the same parts as in the above embodiment are designated by the same reference numerals. In the embodiment shown in FIG. 4, the tube end (1b) is formed to be thicker toward the outside as in FIG. 2(a) above, and its inner circumferential surface (
1d) is processed into a circular shape, and the embodiment shown in Figure 5 has the tube end (lb) thickened inward, and its outer peripheral surface (1a) is processed and formed into a circular shape. In both cases, the closure body is adhered to the circularly processed peripheral surface via an adhesive.

Further, in the embodiment shown in FIG. 6, the tube end (1b) is inside.

It is formed thickly in both row directions, and the inner and outer areas (
ld) and (la) are processed into circular shapes, and in this case, the closure body may be glued to only one peripheral surface.

Alternatively, for example, a circular groove may be provided in the closure body, and the tube end portion may be fitted into this groove and bonded to both circumferential surfaces.

In the case of such other embodiments as well, the adhesive can be present as a uniform layer between the rounded tube end curve and the closure body, as in the previous embodiment.

The reason why the peripheral surface of the alumina ceramic tube, especially the tube end, is made circular is that it is better to make the closure member (heat-resistant, corrosion-resistant metal or ceramic such as niobium or tantalum) circular than to form it into other shapes. This is because it is easy to process and the thermal stress distribution is uniform. Also, the reason why the ends of alumina ceramic tubes are pre-formed thickly and then processed later is that the wall thickness at the center of the tube is usually made in consideration of both light transmittance and mechanical strength. 0.5-1. s
Since the tube end is designed to have a wall thickness of about 1.0 mm, if the end of the tube is made to have the same wall thickness and then processed into a circular shape, the wall thickness will be extremely thin in 9 parts, and the wall will be closed using adhesive. This is because if the two arc tubes are bonded together, cracks may occur in the thin tube ends themselves, and the airtightness of the two arc tubes may be impaired.

Furthermore, although the above embodiment describes a high-pressure sodium lamp, the present invention is not limited thereto, and may include an arc tube in which other metals or metal halogenides are sealed in a translucent ceramic tube. It can also be applied to metal vapor discharge lamps, and translucent ceramic tubes are not limited to polycrystalline tubes.

Similar effects can be obtained when using metal-oxide single crystals such as sapphire and ruby.

〔Effect of the invention〕

As detailed above, according to the present invention, in the production of a metal vapor discharge lamp having a translucent ceramic arc tube, the above-mentioned translucent ceramic tube is manufactured by forming both ends of the translucent ceramic tube in advance to be thicker than the central portion. The thick end portion is processed to make at least one of the inner circumferential surface t or outer circumferential surface close to a circular shape. In other words, after making sure the roundness was good, pressure was applied to the processed peripheral surface to bond the obturator through the adhesive, so even when using a large diameter ceramic tube, the adhesive would be applied evenly between the two parts. It is now possible to interpose a layer, which makes it resistant to temperature changes due to repeated blinking of the lamp, and prevents leakage from occurring at the sealed portion of the arc tube due to non-uniformity of the adhesive layer, which was the case in the past.

The following table shows the effects of the present invention. A 4KW high-pressure sodium lamp was created by applying the present invention to a translucent ceramic tube (Lube) with an inner diameter of 24 mm, and a translucent ceramic tube. These are the results of investigating the relationship between one lighting time and the leakage rate for a conventional lamp of the same type in which the tube end is not molded.

It can be seen from the table that the effects of the present invention are extremely significant.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway front view of an arc tube for a high-pressure sodium lamp embodying the present invention, FIGS. 2 and 3 are explanatory diagrams of one embodiment of the present invention, and FIGS. It is an explanatory view of an example of. (1)...Translucent ceramic tube, (lb)...
tube end. (la)...Outer peripheral surface of the tube end, (M)...Inner peripheral surface of the tube end. (IC)...tube center, (2)...obstruction body. (3)...adhesive material, (4)...metal tube. (5)...electrode. Gariri Patent Attorney Noriyuki Chika (and 1 other person) Figure 1 Figure 2 Figure 3 (a) (b) (b) (b
) Figure 4

Claims (1)

[Claims] A step of processing the thick end portions of the translucent ceramic tube, which is formed by forming both ends thicker than the center portion in advance, to make at least one of the inner circumferential surface or the outer circumferential surface close to a circular shape; 1. A method for manufacturing a metal vapor discharge lamp, comprising the step of adhering a closing body to a surface via an adhesive.