JPH10144262A - Sealing structure for metal vapor arc tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely fix an electrode to the holding member (cap) of the metal vapor arc tube with no welding required. SOLUTION: A tungsten electrode 3 is inserted into an aluminum sleeve 2, and the base end part of the tungsten electrode 3 is inserted into a niobium pipe 1. After that, the portion of the niobium pipe 1, in which the tungsten electrode 3 is inserted, is crushed with pressure, after the outer side surface of the tungsten electrode 3 has been closely brought into contact with the inner circumferential surface of the niobium pipe 1, they are sintered so as to be joined together by means of solid phase diffusion. Subsequently, a metallic bar 4 is inserted into the niobium pipe 1 at the other end, after the tip end part of the niobium pipe 1 has been crushed with pressure, they are heated under a prescribed condition so as to allow the inner side surface of the niobium pipe 1 at its tip end to be joined with the metallic bar 4 by means of liquid phase diffusion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal vapor arc tube sealing structure incorporated in a high-intensity discharge lamp such as a metal halide lamp or a high-pressure sodium lamp.

[0002]

2. Description of the Related Art A high-luminance discharge lamp (HI) having a high luminous efficiency is used as a light source of a lighting device for a road or a tunnel, a light source of a lighting device in a building, a light source of an OHP or a color liquid crystal projector.
D) is attracting attention. In this high-intensity discharge lamp, an opening formed at one end in a light-transmitting arc tube is sealed with a sealing body (cap) provided with an electrode, and then Sc is inserted from the opening at the other end.
After metal halides such as I ₃ and NaI are charged, the opening at the other end is sealed with a sealing body having electrodes, and a high voltage is applied between the electrodes to generate an arc discharge in the arc tube. Then, the enclosed metal halide is evaporated by the heat of the arc discharge, dissociated into metal and halogen, and light emission having a color unique to the metal is performed.

As a structure for preventing leakage of a luminescent substance from an opening, a sealing body is formed of niobium (Nb), which is a metal having a thermal expansion coefficient relatively close to that of an arc tube made of alumina or the like. There is one in which a tungsten electrode is attached to a sealed body. In such a configuration, since the thermal expansion coefficients of the sealing body and the arc tube are close to each other, leakage of the luminescent substance from the opening can be prevented, and since the sealing body itself is conductive, power supply to the electrodes is not performed. It can be done reliably.

[0004]

In the above-described structure for sealing the opening of the arc tube, the method of attaching the electrode to the sealing member includes a method of welding the electrode to the sealing member using a brazing material, and a method of attaching the electrode to the sealing member. There is a method in which a hole is formed in a body and an electrode is pressed into the hole. In the case of the former method, the electrode can be positioned and securely fixed to the sealing body, but it is troublesome and causes an increase in cost. In the case of the latter method, the position of the electrode may shift after press-fitting due to a difference in thermal expansion coefficient over time.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a sealing member for sealing an opening of a light-transmitting luminous tube having an interior as a discharge space, in an airtight manner. It is composed of a holding member such as niobium and an electrode rod made of tungsten or the like whose base end is inserted into a hole formed in the holding member. Further, the outer periphery of the electrode rod and the inner periphery of the hole of the holding member are fixed. Bonded by phase diffusion.

[0006] Incidentally, when the portion joined by solid phase diffusion is vaporized, impurities are scattered in the light emitting space, and when the portion joined by solid phase diffusion is melted, there is a possibility that electrode displacement may occur. Therefore, it is preferred that these do not occur, for example by solid phase diffusion at a temperature higher than the maximum temperature reached by the junction when the arc tube is lit.

Further, if a metal pipe is used as the holding member, it is not necessary to form a hole for inserting an electrode. However, there is a risk of leakage through the through hole of the metal pipe. Therefore, a metal rod having a lower melting point than the metal pipe is inserted into a portion inside the through hole of the metal pipe and outside the solid-phase diffusion portion with the electrode rod, and preferably a portion of the metal pipe into which the metal rod is inserted. Is crushed from the outside, and the metal rod and the metal pipe are joined by liquid phase diffusion. Metal rods include Pt (platinum), Rh (rhodium), Ir (iridium), Re (rhenium), Zr (zirconium), Ti
(Titanium) and Pd (palladium) are suitable.

The insertion depth can be determined by flattening and crushing the outer portion of the metal pipe protruding from the opening of the translucent light emitting tube.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a sectional view of a main part of a metal vapor arc tube to which a sealing structure according to the present invention is applied, and FIG.
(E) is a figure explaining the manufacturing process of the sealing body.

The manufacturing process will be described with reference to FIG. 2. First, as shown in FIG. 2A, a niobium pipe 1, an alumina sleeve 2, and a tungsten electrode 3 as a holding member (cap) are prepared. The thickness of the niobium pipe 1 is 0.
25 mm to 2.0 mm, and the relationship between the inner diameter Φ _{1 of the} niobium pipe 1 and the inner diameter Φ ₂ of the tungsten electrode 3 is 2 ≦ Φ ₂
/ Φ ₁ ≦ 7 is desirable. If 2> Φ ₂ / Φ ₁ , the contact pressure between the niobium pipe and the tungsten electrode will be insufficient, and the solid phase diffusion performed in the subsequent step will be insufficient. If Φ ₂ / Φ ₁ > 7, the glass melt after sealing is performed. Cracks are likely to occur at the joint.

Next, as shown in FIG. 2B, a tungsten electrode 3 is inserted into the alumina sleeve 2, and a base end of the tungsten electrode 3 is inserted into the niobium pipe 1.
It is desirable that the insertion length of the tungsten electrode 3 be accurately determined by a jig.

Thereafter, as shown in FIG. 2C, the portion of the niobium pipe 1 into which the tungsten electrode 3 is inserted is crushed from the outside at a pressure of 10 to 250 kg / cm ² , and the outer surface of the tungsten electrode 3 and the niobium pipe 1 are crushed. After contacting the inner peripheral surface of the substrate closely, the temperature is set to 1800 to 2000 ° C. and 5 × 10 ⁻⁵ Torr.
Solid phase diffusion is carried out by holding for ５5 hours.

Next, as shown in FIG. 2D, a metal rod 4 is inserted from the other end of the niobium pipe 1. Pt (platinum), Rh (rhodium), Ir (iridium), Re (rhenium), Zr having a lower melting point than niobium are used as materials for the metal rod 4.
(Zirconium), Ti (titanium), Pd (palladium)
And

Next, as shown in FIG. 2 (e), after the tip of the niobium pipe 1 is crushed flat at a pressure of 50 to 1000 kg / cm ² , the melting point of the metal rod 4 ± 100 ° C. (Pt)
In the case of (1650-1850 ° C.), the temperature is maintained at 5 × 10 ⁻⁵ Torr for 0.5 to 3 hours, so that the inner surface of the tip of the niobium pipe 1 and the metal rod 4 are liquid-phase diffused. In this embodiment, the solid phase diffusion and the liquid phase diffusion are performed in different steps, but it is also possible to perform the solid phase diffusion and the liquid phase diffusion by one firing.

As shown in FIG. 1, the sealing body 5 obtained in the above steps is fitted into the opening 7 of a light-transmitting luminous tube 6 made of ceramic such as alumina or YAG. The space between the sealing body 5 and the sealing body 5 is sealed with the sealing glass 8 to complete the arc tube.
When the sealing body 5 is fitted into the opening 7, the tip of the sealing body 5 is flattened and crushed to form a step, so that the step functions as a stopper, The insertion depth of the sealing body 5 is automatically set.

FIG. 3 is a cross-sectional view of a main part of a metal vapor arc tube to which a sealing structure according to another embodiment is applied. In this embodiment, a step portion 9 is formed in an opening 7 of the arc tube 6. Steps 10 are also formed on the alumina sleeve 2 for protecting the niobium pipe 1 from halogen, and the steps 9 and 10 set the insertion depth of the sealing body.

In this embodiment, the niobium pipe 1 does not protrude from the opening 7, and instead, the Pt-Rh
The metal rod 11 made of is also usable as an external electrode.
The inner peripheral surface of the through hole formed in the niobium pipe 1 and the outer peripheral surface of the tungsten electrode 3 undergo solid phase diffusion, and the inner peripheral surface of the through hole formed in the niobium pipe 1 and the outer peripheral surface of the metal rod 11 also undergo solid phase diffusion. I have.

FIG. 4 is a sectional view of a main part of a metal vapor arc tube to which a sealing structure according to still another embodiment is applied. In the above embodiment, a metal pipe (niobium pipe) is shown as a holding member. However, in this embodiment, a metal rod 12 made of niobium or the like is used as a holding member instead of a pipe, and the electrode 3 is formed in a hole 13 formed in the metal rod 12.
And insert the hole 13 and the electrode 3 by the method described above.
And solid phase diffusion.

That is, in this embodiment, the step of forming the hole 13 is required, but the step of diffusing the liquid phase in the above embodiment is not required.

[0020]

As described above, according to the metal vapor arc tube sealing structure according to the present invention, the sealing body for sealing the opening of the arc tube is made of niobium or the like which is fitted in the opening in an airtight manner. And an electrode rod made of tungsten or the like, the base end of which is inserted into a hole formed in the holding member, wherein the outer periphery of the electrode rod and the inner periphery of the hole of the holding member are fired. In this case, since the electrodes are joined by solid-phase diffusion, the electrodes can be securely fixed to the holding member without a welding step.

In particular, if the firing temperature for solid-phase diffusion is higher than the maximum temperature reached by the joint when the arc tube is turned on, the solid-phase diffusion portion does not vaporize or melt, so that the impurity in the light-emitting space is reduced. There is no risk of the particles being scattered or the electrode being displaced.

If a metal pipe is used as the holding member, it is not necessary to form a hole for inserting an electrode. If a metal pipe is used, inserting a metal rod into the pipe outside the solid phase diffusion part and joining the metal rod and the metal pipe by liquid phase diffusion further improves the leakage prevention effect. I do.

When a metal pipe is used, if the outer portion of the metal pipe is crushed flat, the insertion depth of the sealing body can be determined.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a metal vapor arc tube to which a sealing structure according to the present invention is applied.

FIGS. 2A to 2E are views for explaining a manufacturing process of a sealed body;

FIG. 3 is a cross-sectional view of a main part of a metal vapor arc tube to which a sealing structure according to another embodiment is applied.

FIG. 4 is a cross-sectional view of a main part of a metal vapor arc tube to which a sealing structure according to another embodiment is applied.

[Explanation of symbols]

1 ... niobium pipe (holding body), 2 ... alumina sleeve,
3 ... electrode, 4,11 ... metal rod, 5 ... sealed body, 6 ... translucent luminous tube, 7 ... opening, 8 ... sealing glass, 12 ... metal rod, 13 ... hole.

Claims (6)

[Claims] In a metal vapor arc tube sealing structure in which an opening of a translucent light emitting tube whose inside is a discharge space is sealed with a sealing member, the sealing member is fitted in the opening in an airtight manner. A holding member to be inserted, and an electrode rod into which a base end is inserted into a hole formed in the holding member. The outer periphery of the electrode rod and the inner periphery of the hole of the holding member are joined by solid phase diffusion. A sealing structure for a metal vapor arc tube. 2. The sealed structure of a metal vapor arc tube according to claim 1, wherein the portion joined by the solid phase diffusion is subjected to solid phase diffusion under conditions that do not vaporize or melt when the arc tube is used. A sealed structure for a metal vapor arc tube. 3. The metal vapor arc tube sealing structure according to claim 2, wherein the condition is that the solid-phase diffusion is performed at a temperature higher than the maximum temperature reached by the joint when the arc tube is used. Sealing structure for vapor arc tube. 4. The metal vapor arc tube sealing structure according to claim 1, wherein the holding member is a metal pipe, and is located inside a through hole of the metal pipe and outside of a solid-phase diffusion portion with an electrode rod. A metal rod having a melting point lower than that of the metal pipe is inserted into the portion to be formed, and the metal rod and the metal pipe are joined by liquid phase diffusion. 5. The metal vapor arc tube sealing structure according to claim 4, wherein an outer portion of the metal pipe protruding from an opening of the translucent arc tube is crushed flat. Metal vapor arc tube sealing structure. 6. The metal vapor arc tube sealing structure according to claim 4, wherein said metal pipe is made of Nb (niobium), said electrode bar is made of W (tungsten), and said metal bar is Pt (platinum). ), Rh (rhodium), Ir (iridium), Re (rhenium), Zr (zirconium), Ti
A metal vapor arc tube sealing structure comprising at least one of (titanium) and Pd (palladium).