JPH01220362A - Metal vapor discharge lamp - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a metal vapor discharge lamp, such as a metal halide lamp, in which the electrode structure is changed.

(Prior Art) For example, metal halide lamps have excellent efficiency and color rendering properties, and have recently become popular for display lighting in stores and the like. As such devices become more popular, there is a demand for smaller devices, and for this reason metal halide lamps, which serve as the light source, are being made smaller. For example 150W
Class metal halide lamps with a distance between electrodes of about 6 to 7 fins have been developed.

In the case of such a small metal halide lamp, the shape of the arc tube is close to an ellipse, and in the case of the above-mentioned 150W class metal halide lamp, the inner diameter in the long axis direction is about 15 to 17 degrees, and the inner diameter in the short axis direction is about 9 to 12+n. become.

However, for such a small and elliptical arc tube, if the valve structure is made to have a crush-sealed valve structure at both ends, which has been commonly used in the past, it would take time and effort to mold the bulb, and the crush-sealed portion would become large, so the overall It has the disadvantage of being large.

For this reason, this type of arc tube employs a one-end crush-sealed structure, as shown in FIG. That is, the long sleeve direction of the elliptical arc tube bulb l made of quartz glass is the bulb axis, and a crush seal [2 is formed at one end in the short axis direction perpendicular to the bulb axis. A pair of electrodes 3 are spaced apart and opposed to each other along the valve axis direction within the bulb l.
．． 3 are both sealed to the one-end crushing sealing portion 2.

The electrodes 3, 3 are composed of, for example, an electrode shaft portion 4 and an electrode coil portion 5 for increasing heat capacity.
5 are spaced apart and opposed to each other along the bulb axis direction, and the electrode shaft portions 4.4 are respectively connected to metal foil conductors 7.7 made of Mo or the like sealed to the crushing sealing portion 2. .

The metal foil conductors 7.7 are each connected to an external lead wire 8.8.

Note that a predetermined amount of mercury, metal halides such as sodium, thallium, and indium, and a starting rare gas are sealed in the bulb l.

According to such a structure, since there is only one crushing sealing part 2, the number of relatively large crushing sealing parts for a relatively small discharge space is reduced, and the overall structure of the bulb becomes compact. It is something.

By the way, in the case of the arc tube l having the above structure, two metal foil conductors 7, 7 are juxtaposed and sealed in one crushed sealing part 2,
The widthwise dimension of the crushing sealing part 2 cannot be made unnecessarily large in order to make the whole compact. In addition, in order to maintain good airtightness between the quartz glass and the two metal foil conductors 7.7, the two metal foil conductors 7. It cannot be sealed if it is removed.

Therefore, the distance S between the two metal foil conductors 7, 7 cannot be set large.

Therefore, when the electrodes 3, 3 connected to these metal foil conductors 7.7 are configured such that the pair of electrode shaft portions 4.4 are substantially parallel to each other as shown in FIG. Part 4.
4 and the bulb wall A of the arc tube bulb l along the bulb axis direction becomes relatively large.

If the distance X between the tip of the electrode shaft 4.4 and the wall of the arc tube bulb is large, the coldest part of the discharge space is a portion A facing the back of the tip of the electrode shaft 4.4. occurs in This coldest part A is relatively far from the electrode, so the temperature is low.
Therefore, the vapor pressure becomes low, leading to problems such as a decrease in luminous efficiency and a decrease in color rendering properties.

In order to prevent such problems, when trying to reduce the dimension along the bulb axis direction of the arc tube bulb l, that is, the dimension in the long axis direction, the width direction dimension of the crushing sealing part 2 becomes small (and the metal foil conductor 7, 7 are too close to the ends in the width direction of the crushed sealing part 2, causing oxidation during sealing or inhibiting the melt flow of the quartz glass, resulting in a disadvantage that good sealing cannot be achieved.

For this reason, it is conceivable to configure the pair of electrode shaft portions 4, 4 connected to the metal foil conductor 7.7 so that their distal ends are expanded from each other (see FIG. 1).

In this way, the tip of the electrode shaft portion 4.4 can be brought close to the bulb wall along the bulb axis direction, and the distance X from the arc tube bulb wall can be reduced.
The temperature of the coldest part A of the discharge space can be increased, thereby making it possible to improve luminous efficiency and color rendering.

Moreover, in this case, the distance S between the two metal foil conductors 7.7
There is no need to increase the width of the crush sealing portion 2, and the width of the crush sealing portion 2 can be reduced.

(Subject to be Solved by the Invention) However, in the case of the above-described configuration, since the electrode shaft portions 4.4 of the pair are formed such that their distal ends are expanded, these electrode shaft portions 4, The distance between the proximal ends sealed to the crushing sealing part 2 of No. 4 becomes closer.

When electrode coil parts 5.5 are formed at the tip of the electrode shaft part 4.4 so as to face each other, these electrode coil parts 5.5.
5, that is, the distance between the electrodes 11, the distance ftlI2 between the sealed ends of the electrode shaft portions 4.4 may be shorter (p"t in 2 >. In such a case, In this case, no discharge occurs between the electrode coil parts 5.5 and 5.5 N'l,
G2 between the sealed ends of the electrode shaft parts 4, 4, which is the shortest distance
There is a possibility that it may occur.

As a result, problems such as breakage of the electrode shaft portions 4, 4, overheating of the crushed sealing portion and generation of cracks, and shortening of the life span may occur.

The present invention aims to provide a metal vapor discharge lamp that prevents discharge from occurring between the sealed ends of the electrode shaft, eliminates breakage of the electrode shaft and cracks in the crushed seal, and has a longer life. That is.

[Structure of the Invention] (Means for Solving the Problems) The present invention accommodates a pair of electrodes in the end of an arc tube that has one end closed and a crushed seal formed at the other end. A metal vapor discharge lamp in which electrode shaft portions are sealed to the crushing sealing portion, and the tip portions of these electrode shaft portions are wider than between the sealed ends sealed to the crushing sealing portion. It is characterized in that an electrically insulating coating is provided on the sealed end of the electrode shaft.

(Function) According to the present invention, since the electrically insulating coating is provided on the sealed ends of the electrode shafts, electrical insulation can be achieved even if the distance g2 between the sealed ends of the pair of electrode shafts is shorter than other parts. The coating prevents discharge from occurring.

(Example) The present invention will be described below based on an example shown in FIG.

Most of the configuration of this embodiment may be the same as the conventional one, so the same members as the conventional one will be given the same numbers and the explanation thereof will be omitted.

The electrodes 3.3 installed inside the arc tube bulb l are each composed of an electrode shaft portion 4 made of tungsten wire and an electrode coil portion 5 provided at the tip of the electrode shaft portion 4.
These electrode shafts 4, 4 are connected to a metal foil conductor 7.7 sealed to the crushing seal 2.

These metal foil conductors7. - The pair of electrode shaft portions 4.4 connected to the electrode shaft portions 7 are configured such that their tip portions extending into the arc tube bulb 1 are spread out from each other. In other words, the electrode shaft portions 4, 4
is inclined at an angle θ with respect to the vertical axis in the drawing.

Electrical insulating coatings 10 and 10 made of, for example, quartz glass tubes are formed on the sealed base end portions of these electrode shaft portions 4, 4 that are sealed to the crush sealing portions 2, respectively.

The operation of the embodiment with such a configuration will be explained.

Since the electrode shaft portions 4.4 have their distal ends diverged from each other, these distal ends can be brought close to the bulb wall, and the distance X from the arc tube bulb wall A can be reduced.

Therefore, the temperature of the coldest part A of the discharge space can be increased, and luminous efficiency and color rendering properties can be improved.

Furthermore, in this case, there is no need to increase the distance between the two metal foil conductors 7, 7, or the dimension S, and the width of the crush sealing portion 2 can also be reduced.

Furthermore, since each of the sealed proximal end portions of these electrode shaft portions 4.4 sealed in the crush sealing portion 2 is formed with an electrically insulating coating 10.10 made of, for example, a quartz glass tube, Even if the distance g2 between these sealed ends becomes shorter than the distance between other parts between the electrodes, generation of discharge between N2 between these sealed ends is prevented.

As a result, the electrode shaft portion 4.4 may break or the crushed sealing portion 2.
This prevents failures such as overheating and cracks, and extends the service life.

Note that the electrically insulating coating 10 is not limited to being formed of a quartz glass tube, and may be coated with glass or ceramic powder to cover the electrode shaft portion 4.4.

Further, the present invention is not limited to metal halide lamps, but may be any discharge lamp in which a crushed seal is formed only at one end of the bulb; therefore, other metal vapor discharge lamps such as high-pressure mercury lamps may be used. Good too.

[Effects of the Invention] As explained above, according to the present invention, since the electrically insulating coating is provided on the sealed ends of the electrode shafts, the distance g2 between the sealed ends of the pair of electrode shafts is Even if the length is equal to or shorter than the length, the electrical insulating coating prevents discharge from occurring. Therefore, breakage of the electrode shaft portion is prevented, and overheating of the crushed sealing portion is also prevented, so that cracks do not occur and the life of the electrode is extended.

[Brief explanation of the drawing]

FIG. 1 is a side view of a metal halide lamp showing an embodiment of the present invention, and FIG. 2 is a side view of a conventional metal halide lamp. l... Arc tube bulb, 2... Crushing sealing part, 3...
Electrode, 4... Electrode shaft portion, 5... Electrode coil portion, 7.
... Metal foil conductor, 8... External lead wire, lO... Electrical insulation coating. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Scope of Claims] A pair of electrodes are housed inside an arc tube whose one end is closed and a crushing seal is formed at the other end, and each of these electrodes has an electrode shaft portion sealed to the crush seal. , and these electrode shaft parts are electrically insulated at the sealed ends of the electrode shaft parts in a metal vapor discharge lamp in which the distal end portions are wider than the sealed end parts sealed to the crush sealing part. A metal vapor discharge lamp characterized by being provided with a covering.