JPH0574420A - Metal vapor discharge lamp - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to provide a metal vapor discharge lamp capable of reducing the cross-sectional area of a sealing tube without damaging the arc tube and thereby obtaining good light emission characteristics. [Arrangement] An arc tube 6 having a discharge space 1 in which mercury, a rare gas, and a luminescent metal are enclosed, an electrode 5 embedded, and a sealing tube 2 formed at both ends of the luminescence space 1. The portion 5b of the electrode 5 that is embedded in the sealing tube 2 has a flat plate shape with a bevel portion in the longitudinal direction chamfered. [Effect] Since the portion of the electrode embedded in the sealing tube has a flat plate shape in which the edge portion in the length direction is chamfered, distortion due to the difference in thermal expansion between the electrode and the sealing tube can be reduced, and the sealing can be reduced. Since the cross-sectional area of the stop tube can be reduced, good light emission characteristics can be obtained.

Description

Detailed Description of the Invention

[Object of the Invention]

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal vapor discharge lamp such as a high pressure mercury lamp or a metal halide lamp, and more particularly to a small metal vapor discharge lamp.

[0003]

2. Description of the Related Art Today, small-sized metal vapor discharge lamps are being developed for use in, for example, shop lighting and automobile headlamps. For example, a structure shown in FIG. 3 is known.

That is, as shown in FIG.
In the sealing tube 12 positioned at both ends of the bulb made of quartz glass forming the metal, a tungsten electrode 15 bonded with, for example, a molybdenum foil 14 having an external lead wire 13 mounted thereon.
Are buried in the seal.

In the discharge space 11, a predetermined amount of mercury, a rare gas for starting, a luminescent metal and the like are enclosed by an exhaust pipe 16 attached at the center of the bulb, for example, to be hermetically sealed.

Here, the method of sealing the electrode 15 will be described. A molybdenum foil 14 having external lead wires 13 made of molybdenum, tantalum or the like mounted in a sealing tube 12 at both ends of a bulb forming a discharge space 11. The bonded electrode 15 is inserted, and the sealing tube 12 is heated and melted while rotating to embed the electrode 15, the molybdenum foil 14, and the external lead wire 13 in the sealing tube 12.

By the way, the light emission characteristics of this type of metal vapor discharge lamp are significantly affected by the temperature of the coldest part at the time of lighting, and in order to obtain good light emission characteristics, the heat escaping from the bulb to the sealing part is maximized. It was necessary to reduce the cross sectional area of the sealing tube.

[0008]

By the way, if the wall thickness of the sealing tube is reduced in order to reduce the cross-sectional area of the sealing tube, an electrode composed mainly of a metal such as tungsten and a sealing tube made of quartz are used. Distortion due to the difference in the thermal expansion of the tube may cause the valve to break due to this distortion during lamp lighting.

If the wall thickness of the sealing tube is increased in order to avoid the above problems, not only the desired lamp characteristics will not be obtained, but also the sealing tube is less likely to be melted at the time of sealing. A gap is likely to be created between the electrode and the electrode, and the light emitting metal will enter this gap during lighting to induce poor bonding between the electrode and the metal foil, or the sealing tube will be damaged due to the intrusion of the light emitting metal. There is an obstacle to do.

The present invention has been made in view of the above circumstances, and a metal vapor discharge lamp capable of reducing the cross-sectional area of the sealing tube without damaging the bulb and thereby obtaining good light emission characteristics is provided. It is the one we are trying to provide.

[Constitution of the Invention]

[0012]

In order to solve the above problems, a metal vapor discharge lamp according to the present invention has a discharge space in which mercury, a rare gas, and a luminescent metal are enclosed, and an electrode, and
A light emitting tube having sealing tubes formed at both ends of the light emitting space, wherein the portion of the electrode embedded in the sealing tube has a flat plate shape with chamfered edge portions in the longitudinal direction. It is characterized by being.

[0013]

According to the present invention, since the portion of the electrode embedded in the sealing tube has a flat plate shape with a chamfered edge in the longitudinal direction, it is caused by the difference in thermal expansion between the electrode and the sealing tube. Distortion is less likely to occur, and therefore the wall thickness of the sealing tube is reduced,
Even if the cross-sectional area of the sealing tube is reduced, the bulb will not be damaged during lighting.

[0014]

The details of the present invention will be described below with reference to the illustrated embodiments.

FIG. 1 shows an embodiment of a metal vapor discharge lamp according to the present invention, which forms a discharge space 1, for example, an inner diameter of 4 m.
A bulb made of substantially spheroidal quartz glass having a length of m and a length of 8 mm is filled with, for example, 3 mg of mercury, 200 Torr of argon as a rare gas for starting, and a predetermined amount of metal halide as a luminescent metal.

In the case of the lamp of this embodiment, 4 mg of scandium iodide (ScI) and sodium iodide (NaI) having a composition ratio of 1: 5 are enclosed as light emitting metals.

Further, a tungsten electrode 5 bonded to a molybdenum foil 4 having an external lead wire 3 is sealed and buried in the sealing tubes 2 located on both sides of the discharge space 1.

Here, the manufacturing method of these arc tubes 6 will be described. A substantially central portion of a quartz tube having an inner diameter of 2 mm and a length of 34 mm is heated and melted by, for example, an oxyhydrogen burner, and the inner diameter is 4 mm as described above. A discharge space 1 having a length of 8 mm and a sealing tube 2 having an inner diameter of 2 mm and a length of 13 mm are molded.

Next, the width 1.8 with the external lead wire 3 made of molybdenum wire having a diameter of 0.5 mm shown in FIG. 2 is attached.
mm, length 10 mm, thickness 0.03 mm molybdenum foil 4,
The electrode 5 spot-welded with the molybdenum foil 4 and platinum is inserted into the sealing tube 2 and then attached to a normal glass lathe, and the inside of the bulb is opened via the exhaust tube 7 attached to the central portion of the valve. The vacuum tube is evacuated, and the exhaust tube is heated and melted with an oxyhydrogen burner while rotating the arc tube 6, and the molybdenum foil 4, the external lead wire 3, and the electrode 5 are buried in a sealed manner.

The electrode 5 has a tungsten rod having a diameter of 0.6 mm and a length of 7 mm to which a tungsten coil 5a having a wire diameter of 0.1 mm is attached at one end, and the other end, in other words, a sealing tube. The end portion 5b buried in is processed into a flat plate shape having a length of 5.5 mm and a thickness of 0.3 mm, and the flat plate portion 5b is chamfered in the longitudinal direction. Then, 20 each of the above-configured metal vapor discharge lamps having a rated lamp power of 35 W and 20 lamps of the same lamp power of the conventional configuration were manufactured, and the sealing part and the bulb of each lamp were damaged after sealing. When an experiment was conducted on the situation, the damage situation after long-time lighting, the joining situation of the electrode and the metal foil, etc., the lamp of this example did not show any damage,
Further, while the electrode and the metal foil are well bonded, in some conventional lamps, the bulb was damaged and the electrode and the metal foil were not properly bonded.

Furthermore, when the radiant luminous flux of the lamp of this embodiment and the lamp of the conventional structure were measured, it was confirmed that the luminous flux of this embodiment was improved by about 10%.

As described above, since the metal vapor discharge lamp of the present invention can reduce the strain due to the difference in thermal expansion between the electrode and the sealing tube, it can reduce the cross-sectional area of the sealing tube and is excellent. The light emitting characteristics can be obtained.

In the above embodiments, specific materials and shapes of arc tubes, electrodes, metal foils, etc. are described using numerical values, but the present invention is not limited to these. Other materials and shapes may be used.

Further, with respect to the light emitting metal and the like sealed in the light emitting tube, the same effect can be obtained even when other metal or the like is selected.

By the way, in the above embodiments, an example of the method of manufacturing the arc tube is shown, but the arc tube can be manufactured by the following procedure, for example.

That is, the substantially central part of the quartz tube is heated and melted by, for example, an oxyhydrogen burner to form the discharge space 1 and the sealing tube 2, and then the external lead wire 3, the molybdenum foil 4, and the electrode which are integrated are formed. After inserting 5 into the sealing tube 2, it is attached to a normal glass lathe, one sealing tube (hereinafter referred to as 2a) is connected to an exhaust system to maintain the inside of the arc tube at a vacuum, and the arc tube 6 is attached. While rotating, the other sealing tube (hereinafter referred to as 2b) is heated and melted by an oxyhydrogen burner, and the molybdenum foil 4, the external lead wire 3, and the electrode 5 are sealed and buried.

Then, a predetermined amount of mercury, a luminescent metal, and a rare gas are introduced from the other sealing tube 2a, and the one sealing tube 2b side previously sealed is placed in a cooling tank into which liquid nitrogen or the like is injected. And the mercury, the luminescent metal, and the rare gas are condensed in the arc tube, and the other sealing tube 2a is heated and melted by the oxyhydrogen burner while rotating the arc tube 6 in the same manner as described above. The external lead wire 3 and the electrode 5 are embedded and sealed.

According to the method as described above, the light emitting metal or the like can be sealed from the sealing tube 2, so that the exhaust tube is unnecessary. Therefore, the light distribution of the arc tube can be made uniform, and various problems such as arc curvature, color unevenness, vapor pressure drop of the light emitting metal, etc. due to the exhaust tube which is likely to be the coldest part can be improved.

[0029]

As described above, according to the present invention, the portion of the electrode embedded in the sealing tube has a flat plate shape with a chamfered edge portion in the lengthwise direction. Since the strain due to the difference in thermal expansion of the stop tube can be reduced and the cross-sectional area of the sealing tube can be reduced, good light emission characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a metal vapor discharge lamp of the present invention.

FIG. 2 is a diagram showing essential parts such as electrodes applied to the metal vapor discharge lamp shown in FIG.

FIG. 3 is a diagram showing an example of a conventional metal vapor discharge lamp.

[Explanation of symbols]

1 ... Discharge space 2 ... Sealing tube 3.
..External lead wire 4 ... Molybdenum foil 5 ... Electrode 6
..Light-emitting tube 7 ... Exhaust tube

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akio Watanabe 1-4-2-4 Mita, Minato-ku, Tokyo Toshiba Lighting & Technology Corporation

Claims (1)

[Claims] 1. A metal vapor discharge lamp having a discharge space in which mercury, a rare gas, and a luminescent metal are sealed, and a discharge tube having electrodes and a sealing tube formed at both ends of the discharge space. The metal vapor discharge lamp is characterized in that the portion of the electrode embedded in the sealing tube has a flat plate shape with a beveled portion in the longitudinal direction thereof being chamfered.