JPH11154491A - Discharge lamp and its electrode mount - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the pressure proof performance of a discharge lamp by airtightly firmly sealing an electrode mount inserted into a tube end portion, and suppressing the occurrence of crack in glass around an electrode rod resulting from the linear expansion coefficient difference between the electrode rod of the electrode mount and a glass tube in the case of the sealing of the tube end portion of the glass tube to be arc tube material through heat softening. SOLUTION: A glass bead 9 is sealed on the rear end side of the electrode rod 4 of an electrode mount 3 in advance, and airtightness between the glass bead 9 and the electrode rod 4 is previously secured so that the tube end portion 7 is sealed with good airtightness just by sealing to the glass bead 9 without sealing the tube end portion 7 of a glass tube 1 to the electrode rod 4. Thereby, the occurrence of crack in glass around the electrode rod 4 of the tube end portion 7 is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp suitable as a power-saving small light source used for a liquid crystal projector or the like, and an electrode mount thereof.

[0002]

2. Description of the Related Art A light source for a liquid crystal projector or an overhead projector, etc. includes a mercury alone or a halogen-added power of 500 W or less, an arc length of 3 to 10 mm or less, and a power-saving small high-voltage operated at high pressure or ultra-high pressure. Metal vapor discharge lamps have been used.

[0003] In this type of discharge lamp, as shown in FIG. 3, a spherical expanded portion 31 serving as a discharge space S is formed in the center of a glass tube 30 serving as an arc tube material.
0, a pair of electrode mounts 32, 32 formed by connecting an electrode rod 33, a molybdenum foil 34, and a lead wire 35 in series by welding means are inserted from the electrode rod 33 side, respectively. A pinch seal in which the tube ends 36, 36 of the glass tube 30 are crushed and crushed while being heated with a flame of a gas burner to form a hermetically sealed state, with the front end of the glass tube 30 protruding into the discharge space S. The tube ends 36, 36 are heated and shrunk in the radial direction by applying a negative pressure to the tube ends 36, 36 to form a hermetic seal. The side and the molybdenum foil 34 and the lead wire 35 are sealed to form an air-tight discharge space S for confining the arc.

[0004]

[SUMMARY OF THE INVENTION Incidentally, the sealing portion of the glass tube 30 was sealed with the electrode mount 32, the discharge space vapor partial pressure during the lighting is 10 ⁵ Pa ~10 ⁶ Pa or more high-pressure or ultrahigh-pressure It is required to have a pressure resistance enough to withstand the internal pressure of S and maintain airtightness.

For this reason, a molybdenum foil 34 that is hermetically sealed to quartz glass as a glass tube material when sealing the tube end 36 of the glass tube 30 is used for the electrode mount 32. As the lead wire 35, a molybdenum lead wire effective for maintaining airtightness is used.

However, the pressure resistance performance of the seal portion is most greatly influenced by the sealing state between the rear end of the electrode rod 33 whose front end protrudes into the discharge space S where the pressure is high or ultra-high and the quartz glass. For example, in order to increase the airtightness between the electrode rod 33 and the quartz glass, the heating temperature of the glass tube 30 is set to be high and the quartz glass is tightly sealed around the electrode rod 33. And a linear expansion coefficient (20 ° C.) between the electrode rod 33 made of metal such as tungsten and quartz glass during slow cooling.
, Tungsten 4 × 10 ^-6 : quartz glass 0.5 × 10
Due to the difference of ^-6 ), a number of fine cracks are generated in the quartz glass around the electrode rod, the pressure resistance is impaired, and there is a risk of explosion during lighting.

[0007] If strict temperature control is performed during slow cooling, it is possible to suppress the occurrence of cracks. However, the control means for performing the temperature control becomes very complicated. The slow cooling operation takes a long time, and the production efficiency of the discharge lamp is significantly reduced.

On the other hand, if the heating temperature of the glass tube 30 is set lower, the temperature control for slow cooling can be simplified and the slow cooling time can be shortened, but the sealing between the electrode rod 33 and the quartz glass can be performed. At the same time, the state is weakened and the pressure resistance is reduced, and at the same time, there is a possibility that a large gap is formed in the sealing portion and the airtightness is impaired.

For this reason, it has been proposed that the surface roughness of the electrode rod is specified or that the surface of the electrode rod is subjected to a surface treatment such as an oxidation treatment so that quartz glass is firmly sealed to the electrode rod. No results were obtained. Further, even if manufacturing conditions such as making the thickness of the quartz glass tube to be processed into the glass tube 30 constant are difficult, it is difficult to obtain a good pressure resistance exceeding a certain value.

Therefore, according to the present invention, when the tube end of the glass tube is sealed, the electrode rod of the electrode mount inserted into the tube end can be tightly sealed with good airtightness.
It is a technical problem to suppress the occurrence of cracks without strict temperature control during slow cooling.

[0011]

In order to solve the above-mentioned problems, according to the present invention, there is provided an expanded tube portion serving as a discharge space in the center of a glass tube serving as an arc tube material, and an electrode is formed from both ends of the glass tube. A pair of electrode mounts formed by connecting a rod, a molybdenum foil, and a lead wire in series are inserted from the electrode rod side, respectively, and a glass is formed in a state in which the tip end side of the electrode rod protrudes into the discharge space. In a discharge lamp sealed at the tube end by a heating closing process for sealing the tube end of the tube, both or one of the electrode mounts is provided at the rear end side of the electrode rod, and the electrode rod is provided at a bead hole. In a state where the passed glass beads are sealed, it is inserted into the tube end of the glass tube, and the rear end side of the electrode rod is sealed to the tube end of the glass tube via the glass beads. Features.

In the discharge lamp of the present invention, when a tube end of a glass tube serving as an arc tube material is sealed by heating closing, the tube end and an electrode rod of an electrode mount inserted into the tube end are sealed. And the rear end side thereof is sealed via glass beads previously sealed to the electrode rod.

That is, the end of the glass tube directly sealed is not the electrode rod made of metal such as tungsten, but the glass beads sealed to the electrode rod. Are compatible with each other, so that they can be tightly sealed with good airtightness by heating closing processing for sealing the end of the glass tube.

Further, if the glass tube and the glass beads are made of the same glass material having the same coefficient of linear expansion, there is no possibility that cracks will be generated in the sealed portions of the two at the time of slow cooling. Therefore, it is not necessary to perform strict temperature control, and it is possible to shorten the annealing time and increase the production efficiency of the discharge lamp.

Further, the glass beads are sealed in advance with the electrode rod to ensure the airtightness between the electrode rod and the electrode rod. There is no need to seal beads and electrode rods together. In addition, since the heat generated during heating and closing the end of the glass tube is not easily transmitted to the electrode rod to which the glass beads are sealed, the difference in the coefficient of linear expansion between the electrode rod and the glass beads causes the electrode of the glass beads to have an electrode. There is no risk of cracks around the bar.

[0016]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a sectional view showing an example of a discharge lamp according to the present invention, and FIG. 2 is a plan view showing an example of an electrode mount used for the discharge lamp.

In the discharge lamp shown in FIG. 1, an expanded tube portion 2 serving as a discharge space S is formed at the center of a glass tube 1 serving as an arc tube material, and an electrode rod 4 made of tungsten is formed from both ends of the glass tube 1. Molybdenum foil 5 and lead wire 6 made of molybdenum
Are connected in series to form a pair of electrode mounts 3, 3,
A pinch seal or a shrink for sealing the tube ends 7, 7 of the glass tube 1 in a state where the end portions of the electrode rods 4 are inserted from the electrode rod 4 side and project into the discharge space S, respectively. The tube ends 7, 7 are sealed by heat closing such as sealing.

As shown in FIG. 2, a tungsten coil 8 is wound around the tip of the electrode rod 4 and the electrode rod 4 is beaded on the rear end of the electrode rod 4, as shown in FIG. Glass beads 9 passing through holes 10 are sealed.

Then, the electrode mount 3 is connected to the glass tube 1.
By performing the above-mentioned heating closing process in a state of being inserted into the tube end portion 7 as shown in FIG.
The glass tube 1 is sealed to the tube end 7 via the glass beads 9 sealed to the electrode rod 4.

The glass tube 1 is made of quartz glass having good translucency. The glass beads 9 are made of quartz glass of the same quality as the glass tube 1 and are slightly smaller than the inner diameter of the tube end 7 of the glass tube 1. It is molded into a small cylindrical shape.

Before connecting the rear end of the electrode rod 4 to the front end of the molybdenum foil 5 by welding, the electrode mount 3 passes the rear end of the electrode rod 4 through the bead hole 10 of the glass bead 9. The electrode rod 4 is heated by an induction heating device or the like in a state where the electrode rod 4 is protruded from the bead hole 10 by a length of a welding margin required for connection with the molybdenum foil 5, so that the rear end side of the electrode rod 4 Glass beads 9 are hermetically sealed.

The configuration of the discharge lamp and its electrode mount shown in FIG. 1 and FIG. 2 has been described above. Next, their operation will be described. Glass tube 1 with electrode mount 3 inserted
When the tube end 7 is sealed by a heating closing process, the tube end 7 is not directly sealed to the electrode rod 4, and the glass beads previously sealed to the rear end side of the electrode rod 4. 9 is sealed.

Since the glass beads 9 are made of quartz glass of the same quality as the glass tube 1, the tube end 7 of the glass tube 1 and the glass beads 9 are tightly and airtightly sealed by a pinch seal or a shrink seal. Can be done, and
The sealing portion does not have a risk of cracking due to a difference in linear expansion coefficient during slow cooling.

Since the glass beads 9 are previously sealed to the electrode rod 4, when the tube ends 7 of the glass tube 1 are sealed by heating with a gas burner or the like, the tube ends 7 are sealed with the glass beads. It is not necessary to heat the tube end 9 to such a high temperature that the electrode rod 4 is sealed, and the glass beads 9 are interposed between the tube end 7 and the electrode rod 4 so that the tube end 7 can be sealed. Since heat is not easily transmitted to the electrode rod 4, there is no possibility that cracks may be generated in the sealing portion between the glass beads 9 and the electrode rod 4 due to a difference in linear expansion coefficient.

Accordingly, the tube end 7 of the glass tube 1 is hermetically sealed, and at the same time, the pressure resistance of the sealed portion is significantly improved.

It should be noted that the discharge lamp of the present invention has a glass tube 1
The glass beads 9 may be sealed to only one of the electrode mounts 3, 3 inserted into the tube ends 7, 7.

[0027]

According to the present invention, the electrode rod of the electrode mount inserted into the tube end of the glass tube serving as the sealing portion of the arc tube can be tightly sealed with good airtightness. At the same time, there is a very excellent effect that cracks can be reliably prevented from being generated at the places where the electrode bars are sealed, and the pressure resistance of the discharge lamp can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a discharge lamp according to the present invention.

FIG. 2 is a plan view showing an example of an electrode mount according to the present invention.

FIG. 3 is a sectional view showing a conventional discharge lamp.

[Explanation of symbols]

 1 ... Glass tube 3 ... Electrode mount 4 ... Electrode bar 5 ... Molybdenum foil 6 ... Lead wire 7 ... Glass tube tube End 9 ... Glass beads 10 ... Bead hole

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Atsushi Machida 1-1, Ichiriyama-cho, Gyoda-shi, Saitama Iwasaki Electric Co., Ltd. Saitama Works

Claims (2)

[Claims] 1. A tube portion serving as a discharge space is formed in the center of a glass tube serving as an arc tube material, and a pair of electrodes formed by connecting an electrode bar, a molybdenum foil, and a lead wire in series from both ends of the glass tube. The electrode mounts are inserted from the electrode rod side, respectively, and in a state where the tip end side of the electrode rod is protruded into the discharge space, the tube end is sealed by heating and closing the tube end of the glass tube. In the discharge lamp sealed in the above, both or one of the electrode mounts (3, 3) is provided on the rear end side of the electrode rod (4) with the electrode rod (4).
Is inserted into the tube end (7) of the glass tube (1) with the glass bead (9) passed through the bead hole (10) sealed, and the rear end side of the electrode rod (4) is A discharge lamp characterized by being sealed to a tube end (7) of a glass tube (1) via glass beads (9). 2. An electrode mount comprising an electrode rod, a molybdenum foil, and a lead wire connected in series, inserted into a tube end of a glass tube serving as a discharge tube material of a discharge lamp and sealed to the tube end. A glass bead (9) having the electrode rod (4) passed through a bead hole (10) is provided on the rear end side of the electrode rod (4).
An electrode mount characterized by being sealed.