JPH10283990A - High pressure discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high pressure discharge lamp capable of providing a light output that is stable over a long time. SOLUTION: In a high pressure discharge lamp having a pair of electrodes 2, 3 therein and lighted in a vertical position, the upper electrode has a convex- gas limiting member 4 placed at an interval from the side face of the electrode and formed to surround the electrode. Further, the limiting member 4 is made of tantalum, niobium, zirconium, and titanium, has getter action, and is formed into a coil shape from a linear material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] The present invention relates to a high pressure discharge lamp. In particular, it relates to a vertically operated high pressure discharge lamp.

[0002]

2. Description of the Related Art In a high pressure discharge lamp, mercury and an inert gas are sealed in an arc tube. Then, depending on the intended use, a so-called vertical operation is performed in which one of the electrodes is arranged and operated so as to be higher than the other electrode. Such vertical lighting is performed by an optical system mirror or the like, and vertical operation is performed to achieve gas convection.

FIG. 4 shows a conventional high pressure discharge lamp. An anode 2 and a cathode 3 are arranged on the arc tube 1 so as to face each other, and are arranged vertically with the anode 2 facing upward. This high-pressure discharge lamp has an anode 2
The tip of the electrode becomes extremely hot due to the arc discharge formed between the anode and the cathode 3, and the heated gas rises along the anode axis and reaches near the top inside the arc tube. The gas descends along the tube wall of the arc tube 1. (Indicated by A in the figure)

On the other hand, in recent years, the power of discharge lamps has been increasing, and accordingly, the size of electrodes has also increased. In particular, the anode generates a large amount of heat due to collision of electrons emitted from the cathode and arc discharge. For this reason, a considerably large one is used because it is necessary to secure a sufficient heat capacity. As the size of the electrode increases, the temperature of the gas, which rises along the anode axis, is regulated by the large-volume electrode, and the convection direction is regulated. As shown in FIG. 5, it is bent by the anode 2 and collides at the central portion of the arc tube 1.

At the tip of the cathode 3, abrasion of the tungsten material occurs during the operation of the lamp, and the worn material is caused to flow along the convection as vapor, and finally the arc tube 1 is located at an undesired position. Will stain the inside. For this reason, as the size of the anode 2 increases, the evaporant easily adheres to the central portion of the arc tube 1, which also affects the amount of emitted light.

[0006]

An object of the present invention is to provide a high-pressure discharge lamp capable of obtaining a stable light output for a long time.

[0007]

According to the present invention, there is provided a high-pressure discharge lamp having a pair of electrodes therein and operated vertically, having the following configuration. (1) Of the above-mentioned electrodes, the electrode located above has a convection gas direction regulating member which is arranged with a gap from the side surface and formed so as to surround the electrode. For this reason, a path for sending the gas near the top through the gap between the electrode and the direction regulating member is formed, so that the convective gas does not cause the evaporation substance to adhere to an undesired position. (2) Further, in the invention according to the above (1), the convection gas direction regulating member is made of tantalum, niobium, zirconium, and titanium and also has a getter function. For this reason, not only the position where the convection gas collides with the inner surface of the arc tube can be controlled, but also the impurities contained in the convection gas can be satisfactorily captured. In addition, the impurity gas can be adsorbed by this member, and impurities generated by abrasion evaporation of the cathode can be carried to the vicinity of the top of the arc tube 1 where light is not emitted and accumulated there. Therefore, it is possible to prevent light from attenuating for a long time. (3) Further, in the invention of the above (1), the convective gas direction regulating member may be a coil made of a linear material of the above-mentioned material. Thereby, the surface area can be increased.

[0008]

FIG. 1 is an explanatory sectional view showing an example of a short arc type high pressure discharge lamp according to the present invention. The short arc type discharge lamp comprises a glass arc tube 1 in which sealing portions 11 are formed at both ends of a discharge space surrounding portion 10 surrounding a discharge space 5, and a substantially cylindrical shape is formed in the discharge space surrounding portion 10. The anode 2 and the cathode 3 are arranged so as to face each other on the tube axis of the arc tube 1.

The anode 2 is connected to an internal lead 12 arranged along the tube axis of the arc tube 1. The internal lead 12 is supported by one sealing portion 11 of the arc tube 1, It is connected to a metal foil 13 buried hermetically in the part 11. This metal foil 13 is connected to an external lead 14 extending outward from one sealing portion 11. On the other hand, the cathode 3
It is supported by the other sealing portion 11 of the arc tube 1 and is connected to a metal foil 13 buried hermetically in the one sealing portion 11. The metal foil 13 is connected to an external lead 14 extending outward from the other sealing portion 11. Here, the sealing portion 11 includes not only the portion covering the metal foil 13 but also both end portions thereof (the portion excluding the discharge space surrounding portion 10).

The anode 2 has a truncated conical shape having a flat portion at the tip end as shown in FIG.
Its size is, for example, maximum outer diameter φ25 mm, length 30
mm (the part excluding the internal lead). However, the shape of the anode 2 is not limited to such a shape, and a shape having a semi-spherical tip can be applied.

Around the anode 2, a convection gas direction regulating member 4 (hereinafter also referred to as a "regulating member") is arranged. The regulating member 4 is a plate-shaped metal member formed into a cylindrical shape, and is passed between the regulating member 4 for gas convection in the arc tube 1 and the anode 2 so as to be in the vicinity of the base of the anode 2, that is, surrounding the light emitting space. It can be guided to the vicinity of the top of the part 10. By attaching and installing the regulating member 4, impurities contained in the convection gas can be satisfactorily adhered to a region which becomes a blind spot as a light emitting region or an inner surface of the direction regulating member 4. Also,
Impurity gas can also be adsorbed on the inner surface of the regulating member 4,
By preventing the deterioration of both electrodes due to the impurity gas, a stable arc discharge operation can be maintained for a long time. FIG. 2B shows a view of the anode 2 shown in FIG. Such a discharge lamp is useful for a high-pressure discharge lamp in which mercury is sealed.
To several KW. Other structures are the same as those of the conventional high-pressure discharge lamp, and a detailed description thereof will be omitted.

FIG. 3 shows a joint structure between the anode 2 and the regulating member 4. The joining of the regulating member 4 to the anode 2 is spot-welded by a fixing member 20 as shown in FIG. The location, number, and shape of the spot welding are not particularly limited, but it is desirable that the number of the spot welding is 3 to 4 locations on the upper side (sealing portion side) as much as possible in consideration of the influence of temperature and the like. The regulating member 4 preferably has a length corresponding to the side surface of the anode 2, but may be longer or shorter than the side surface of the anode 2 as long as the convective gas inside the arc tube 1 can be effectively guided upward. No problem. However, if it is too long, it blocks light.

Such a regulating member 4 is made of, for example, Ta.
(Tantalum), Nb (niobium), Zr (zirconium), Ti (titanium), or the like can be used. Since these have a getter function, they are advantageous in that they not only regulate the convection direction of the gas but also adsorb impurities and impurity gases. Further, the regulating member 4 can make the linear substance into a coil shape.

FIG. 6 illustrates the light output maintenance ratio of the discharge lamp of the present invention. The vertical axis indicates the relative value of the light output when the initial value is 100, and the horizontal axis indicates the operation time. In the drawing, a shows the characteristics of the discharge lamp provided with the direction regulating member according to the present invention, and b shows the characteristics of the conventional discharge lamp without the direction regulating member. The lamp used in the experiment had a current of 20
A, voltage 25 V, discharge gap (arc length) 3 mm, xenon gas pressure about 30 atm. FIG. 6 shows that the discharge lamp of the present invention maintains a light output of 90% or more of the initial value even after the operation for 2,000 hours, whereas the conventional discharge lamp has a light output of 2,000 hours. After passing through the above operation, the voltage attenuates to about 70% of the initial value.

[0015]

According to the present invention, the gas heated to a high temperature by the operation of the lamp is sent to the vicinity of the top of the arc tube through the gap between the electrode and the direction regulating member. No evaporation material is deposited at undesired locations. Further, since the impure gas is adsorbed on the regulating member, it is possible to prevent deterioration of both electrodes due to the impure gas for a long time.

[Brief description of the drawings]

FIG. 1 shows the entire discharge lamp of the present invention.

FIG. 2 shows an electrode located above a discharge lamp according to the invention.

FIG. 3 shows a welding portion of a regulating member to an electrode located above a discharge lamp of the present invention.

FIG. 4 shows an overall view of a conventional discharge lamp.

FIG. 5 shows another overall view of a conventional discharge lamp.

FIG. 6 shows the effect of the discharge lamp of the present invention.

[Explanation of symbols]

 1 arc tube 2 anode 3 cathode 4 regulating member

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yasuhiko Wakahata 1194, Sado, Bessho-cho, Himeji City, Hyogo Prefecture Inside (72) Inventor Hikaru Toda 1194, Sado, Bessho-cho, Himeji City, Hyogo Prefecture Inside

Claims (3)

[Claims] 1. A high-pressure discharge lamp which has a pair of electrodes inside and is vertically lit, wherein a convection gas is formed on an upper electrode with a gap from a side surface thereof and formed so as to surround the electrode. A high-pressure discharge lamp having a direction regulating member. 2. A high-pressure discharge lamp according to claim 1, wherein said convection gas direction regulating member is made of tantalum, niobium, zirconium, and titanium and has a getter function. 3. The high-pressure discharge lamp according to claim 1, wherein the convective gas direction regulating member is formed by forming a linear substance into a coil shape.