JPS6313648Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a high-pressure metal vapor discharge lamp in which an auxiliary electrode is provided in the vicinity of at least one of the main electrodes arranged oppositely in the arc tube.

Conventionally, for example, high-pressure mercury vapor discharge lamps (hereinafter abbreviated as mercury lamps) have been equipped with an auxiliary lamp that is connected to a high-resistance element in close proximity to at least one of the main electrodes arranged oppositely in the arc tube in order to facilitate starting. It is common to have poles.

However, in the case of such a mercury lamp, the main electrode sputters during operation of the mercury lamp, and electrode material, etc. is deposited along the sealing part where the main electrode and the auxiliary electrode are sealed, and the emitted light is mixed with this. The mercury sealed in the tube forms an amalgam, resulting in electrical continuity between the main electrode and the auxiliary electrode, making it difficult to start the mercury lamp.

Therefore, in order to prevent a short circuit between the main electrode and the auxiliary electrode, the main electrode and the auxiliary electrode were formed on both sides of the arc tube axis, and the distance between the main electrode and the auxiliary electrode was increased. something is proposed.

However, in this proposal, the main electrode is formed offset from the arc tube axis toward the tube wall, which results in the arc coming closer to the arc tube wall, especially when the lamp is lit horizontally. This has the disadvantage of causing the tube wall to devitrify and shortening its lifespan. In addition, since the sealing part on the auxiliary electrode side is far from the main electrode, the coldest spot is formed at the sealing part, which is lower in temperature than a normal mercury lamp with the main electrode formed on the tube axis. ,
Therefore, there is a drawback that the tube voltage decreases, resulting in a decrease in light output and a negative effect on the ballast.

This idea was made in view of the above drawbacks,
The purpose of the present invention is to obtain a high-pressure metal vapor discharge lamp that prevents short circuits between the main electrode and the auxiliary electrode without shortening the service life, reducing light output, or adversely affecting the ballast.

An embodiment of this invention will be described below based on the drawings. In the figure, 1 is a quartz glass arc tube filled with rare gas and mercury to assist in starting;
As shown in FIG. 1, 2 and 3 are cylindrical parts 4 and 5 having right cylindrical inner walls at both ends on the tube axis 1a of the arc tube 1, and a tip 6 from the tips 4a and 5a of the cylindrical parts 4 and 5.
8 and 9 are tungsten coils in which an electrode material is coated on the tips of tungsten core rods 10 and 11; The main electrodes 8, 9 are fitted in the cylindrical portions 4, 5, and the coils 12, 13 are inserted into the cylindrical portions 4, 5 at a height of 1/2 of the height of the main electrodes 8, 9.
It protrudes so that it is surrounded by. Reference numeral 14 denotes an auxiliary electrode made of tantalum wire that is sealed to the inclined portion 6 so that its tip protrudes into the arc tube 1, and the main electrodes 8 and 9 are external lead wires 17 welded to molybdenum foils 15 and 16. , 18 to the outside. Similarly, the auxiliary pole 14 is connected to the outside via a molybdenum foil 19 and an external lead wire 20.

Here, the cylindrical portions 4 and 5 whose inner walls are right cylindrical do not include those whose inner walls are conical as shown in Utility Model Publication No. 50-19896, and the inner diameter of the cylindrical portions 4 and 5 is in the longitudinal direction of the cylinder. It refers to a shape that is approximately the same throughout.

The high pressure metal vapor discharge lamp constructed in this way is
Since the creepage distance of the sealing portion 2 connecting the main electrode 8 and the auxiliary electrode 14 is long, a series of amalgams will not be formed therebetween. Furthermore, since the cylindrical parts 4 and 5 of the sealing parts 2 and 3 surround the coils 12 and 13 of the main electrodes 8 and 9, they receive heat during the operation of the main electrodes 8 and 9, and also receive heat during operation of the main electrodes 8 and 9. Since the tips 6a, 7a of 7 extend upward (towards the center of the arc tube) than the tips 4a, 5a of the cylindrical parts 4, 5, they easily receive the heat of the arc, increasing the temperature of the entire sealing part 2, The temperature at the coldest point will also be increased. In addition, the main electrodes 8, 9
is sealed on the tube axis 1a of the arc tube 1, so
Even if the lamp is lit horizontally, the arc will not touch the wall of the arc tube 1. Therefore, short circuit between the main electrode 8 and the auxiliary electrode 14 can be prevented without shortening the life or reducing the tube voltage. In addition, here, the height of the coils 12 and 13, that is, the distance L in the cylinder length direction and the coil 1 where the cylinder parts 4 and 5 are the main electrodes 8 and 9.
The effect of the ratio to the distance l in the cylinder length direction surrounding the cylinders 2 and 13 on the starting voltage will be explained with reference to FIG.

Figure 2 shows the distance between the tips of opposing coils.
la is 70mm, the inner diameter of the arc tube is 18.5mm, and the amount of mercury enclosed is
73mg, coil height L is 7.8mm, coil diameter is 3.5
-10 after lighting a mm 400W mercury lamp for 1000 hours
It shows the starting characteristics in an atmosphere of ℃, where the vertical axis is the starting voltage V _s , and the horizontal axis is the height l of the coil surrounded by the cylindrical part relative to the height L of the coil (l/L).
are shown respectively.

As is clear from the figure, when the value of l/L is less than 0.5, the starting voltage V _s rises along a relatively gentle curve, and the value is at most 180 [V] or less, which poses no problem in practical use. When l/L becomes larger than 0.5, the starting voltage V _s increases along a rather steep curve. Generally, an ambient temperature of -10° C. is considered to be the harshest operating environment temperature when this type of mercury lamp is used.

Therefore, considering that there is a practical problem if the starting voltage exceeds 180 [V], it can be understood that the above-mentioned value of l/L is preferably 0.5 or less.

Furthermore, when the inclined parts 6 and 7 were located below the tips of the cylindrical parts 4 and 5 (on the arc tube end side), a coldest spot having an undesirably low temperature was formed at that part.

By the way, since the shape of the inner wall of the cylindrical parts 4 and 5 is a right cylindrical shape, the temperature near the upper part of the cylindrical parts 4 and 5 can be increased by the heat from the main electrodes 8 and 9, so that after the lamp is turned off, the cylindrical part Cooling is slower near the tip portions 4a and 5a than in other locations. Therefore, the cylindrical portion tip 4
Mercury no longer aggregates near a and 5a.
In addition, an auxiliary pole 14 is provided on the inclined portion 6 connected to the cylindrical portions 4 and 5.
Since the auxiliary electrode 14 and the main electrode 8 are protruded, the creepage distance between the auxiliary electrode 14 and the main electrode 8 is large, and a short circuit between the two electrodes due to the amalgam is effectively prevented.

In the above embodiments, the auxiliary electrodes are formed on one side of the main electrodes 8 and 9, but the same effect can be obtained even if the auxiliary electrodes 14 are formed on both sides. Furthermore, it is clear that the main electrode 9 without the auxiliary electrode 14 provided nearby may be sealed regardless of the shape of the sealing part 2 of the above embodiment.

As explained above, this idea consists of a cylindrical part that surrounds less than half of the coil of the main electrode placed oppositely on the tube axis of the arc tube, and a cylindrical part whose inner wall is in the shape of a right cylinder. In addition, a sealing part is formed with the sloping part whose tip is slanted toward the center of the tube, and an auxiliary electrode is provided on the slanted part, so that the sealing position between the main electrode and the auxiliary electrode can be maintained without changing the sealing position of the main electrode. This makes it possible to increase the creepage distance and increase the temperature of the sealing part, so that the cylindrical part can be removed after the lamp is turned off, without impairing its life, reducing the light output due to a drop in tube voltage, or adversely affecting the ballast. It is possible to prevent mercury from condensing near the tip, which has the effect of preventing short circuits between the main electrode and the auxiliary electrode.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an embodiment of the high-pressure metal vapor discharge lamp of this invention. FIG. 2 is a characteristic diagram of the starting voltage of the device shown in FIG. In the figure, 1 is the arc tube, 1a is the tube axis, 2, 3
is a sealing part, 4 and 5 are cylinder parts, 4a and 5a are cylinder part tips, 6 and 7 are slope parts, 6a and 7a are slope part tips,
8 and 9 are main electrodes, 12 and 13 are coils, and 14 is an auxiliary pole.

Claims (1)

[Scope of utility model registration request] The arc tube is provided with a main electrode facing on the tube axis and an auxiliary electrode near at least one of the main electrodes, which surrounds 1/2 or less of the coil part of the main electrode and has a cylindrical part with an inner wall in the shape of a right cylinder. , a sealing part is formed by a sloped part that is connected to the cylinder part and whose tip is inclined toward the center of the tube from the tip of the cylinder part, and the auxiliary electrode is made to protrude from the slope part. A high-pressure metal vapor discharge lamp.