JPS59201359A - Compact high pressure metal vapor discharge lamp - Google Patents

Abstract

PURPOSE:To quickly move an arc spot to the tip of an electrode even when it occurs at the base end of the electrode at discharge start and prevent the devitrification, leak, and electrode break of a luminous tube and then provide the captioned lamp with a long life by positioning the tip of the electrode within the specified angular range for the upper part. CONSTITUTION:Electrodes 21 and 21 are provided opposedly in a spherical luminous tube 1 made of quartz glass. The electrodes 21 and 21 are comprised by winding an electrode coil 23 around an electrode axis 22. In addition, the electrode axis 22 is bent upward and electrode tips 21a and 21a are positioned within the range of an angle theta=5 to 30 deg.. The angle theta forms an upward angle that is provided with the end of a sealing section as the vertical angle for a line O1 to O1 in which the ends of the sealing sections of both electrode electrodes 21 and 21. As a result, even when an arc is bent upward for horizontal lighting, since the electrode tips 21a and 21a are always in the arc path and the electrode tips 21a and 21a are heated by the arc and then thermal electrons are easily emitted, the arc spot is easily moved to the electrode tips 21a and 21a.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a small high pressure metal vapor discharge lamp of 100 watt class or less.

[Technical background of the invention and its problems]

BACKGROUND ART Recently, from the viewpoint of power saving, technology has been developed to use surface pressure metal vapor discharge lamps, which have excellent luminous efficiency, in place of incandescent light bulbs, which have been widely used for indoor lighting.

In order to use metal pallite lamps and high-pressure mercury lamps as indoor lighting, it is necessary to downsize these discharge lamps.
Lamps below 100 watts must be developed.

In order to achieve small size and high efficiency in this type of small discharge lamp, the arc tube is made into a spherical or ellipsoidal shape to activate steam convection within the tube and to increase pressure resistance.

On the other hand, in the case of indoor lighting, there are cases where the lamp is forced to be lit horizontally, that is, with the tube axis of the arc tube in a horizontal position, due to ceiling height restrictions and other reasons.

About the small metal paralite lamp, the horizontal lighting condition is $1.
As shown in the figure. The shape of the arc tube 1 is spherical, and this shape promotes convection of the enclosed scandium sodium iodide (Sea, -Nap). Due to the geometry and vapor convection, the arc may be pushed upward to form a curved discharge path.

At the start of discharge, especially when the arc tube is cold, electrode 2
．． Oxide may be attached to the base end of the sealing part 2, making it easy for electrons to be emitted, resulting in the base end becoming an arc spot. The arc from the base end of the electrode curves upward due to the convection, and the arc spot may not move as it is. The fact that the arc spot remains at the base end of the electrode 2°2 is a phenomenon that can only be seen in horizontal lighting, and the reason for this is that the arc is pushed upward! This is thought to be because the electrode tip is not located within the arc, so heating of the electrode tip never occurs, and the base end where a spot occurs at the start of discharge is heated even more, making it easier to generate thermoelectrons.

If an arc spot is generated at the base end of the electrode in this way and the discharge continues without moving to the tip end of the electrode, the sealing part 3.3 of the arc tube 1 near the arc spot
The wall of the arc tube becomes overheated and reacts with the enclosed metal, especially with sodium, causing devitrification of the quartz glass, and also tends to cause cracks and leaks in the arc tube.

Furthermore, the base end of the electrode may also be eroded and the electrode may break at an early stage.

[Purpose of the invention]

The present invention has been developed based on the above circumstances, and its purpose is to quickly move the arc spot to the electrode tip even if it occurs at the base end of the electrode at the start of discharge, and to improve the arc tube. The object of the present invention is to provide a compact high-pressure metal vapor discharge lamp that can prevent devitrification and leakage of the liquid, prevent electrode breakage, and have a long life.

[Summary of the invention]

That is, the present invention is characterized in that the tip of the electrode is positioned within an angle range of 5s to 30° upward with respect to the base of the electrode in order to position the tip in the arc that curves upward. By placing the tip of the electrode in the arc, the tip of the electrode is quickly heated and emits thermoelectrons easily, thereby causing the arc spot to move to the tip of the electrode.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 2 to 4.

The quartz glass spherical arc tube shown in Figure 2! There is an electrode 21 inside
．． 21 are provided facing each other. electrode 21.21
is constructed by winding an electrode coil 23 around an electrode shaft 22. The electrode shaft 22 of this embodiment is bent upward so that the electrode tips 21a, 21a are located within an angle of θ-5° to 30°. The angle θ is defined by a line 0.21 that connects the base ends of both electrodes 21.21 on the sealing part side.
0. This is an angle K made upward with respect to the base end of the sealing portion as the apex angle. Note that the line O8-◯ coincides with the tube axis of the spherical arc tube 1 when the electrode axes 22, 22 are correctly provided on the tube axis. Further, in the figure, 3.3 indicates an arc tube sealing part, 4.4 indicates a high melting point metal foil such as molybdenum, and 5.5 indicates a lead wire.

Inside the arc tube 1, scandium sodium iodide (S
ell・Na■), mercury, and a rare gas for starting are sealed.

If the electrode tips 21m and 21b are positioned upward □ as shown in Figure @2, even if the arc is curved upward due to gas convection and the tube wall shape of the arc tube 1 in horizontal lighting, the electrode tips 21m and 21b is always located within the arc path. For this reason, the electrode tips 21*, 21* are heated by the arc, and thermionic electrons are more likely to be emitted, so that the arc spot is more likely to move to the electrode tips 21m, 21m.

The reason why the electrode tips 21 and 21a are located within the above range of θ-=-56 to 30 degrees is based on the inventor's experiments. The experiment will be explained below with reference to FIGS. 3 and 4.

For metal pallite lamps of 100 watt class or less, the length L of the arc tube 1 along the tube axis direction is regulated to be 12 m or less.

This has been confirmed based on the relationship of relative efficiency, and if L exceeds 12 mm, the relative efficiency will decrease due to factors such as the tube wall load, the distance between electrodes, and the protrusion height.
It is set to be ff111 or less. Further, the electrode height 1lleht is set to 1.5 mm or more. If the electrode height bi fht is 1.5M or less, heating of the quartz glass proceeds as in the case of the arc spot in FIG. 1, causing devitrification and leakage.

Examining the state in which the degree of upward bending of the arc is the least, in a 100-watt lamp with a distance of 1211I111 and an inter-electrode distance l of 9m, both electrodes 2.2 and 2.2 as shown in Figure 3. It turns out that this is the case when an arc spot is formed at the base end of each case, and the tube axis of the arc at this time is 0. The deviation amount δ from -01 is 0.5 m
It was observed that rrr. In this case, θ-tan-'' (is calculated as 0), so 0 is 4.8°.

In addition, looking at an example where the arc curves upward most often, in a 20 watt class lamp where the distance is 5WI + 1 and the interelectrode distance l is set to 2M, one electrode 2 is bent as shown in Figure 4. This was a case where an arc spot was formed at the base end and the tip of the other electrode 2. It was measured that the arc deviation amount δ at this time was about 1 gate.

Therefore, θt = j a n −' +)teFtF is calculated, and θ! is 29.7".

Therefore, from the above experiment, θ shown in the $2 diagram is 4.8° ~
It can be seen that a range of 29.7° is sufficient.

Taking manufacturing variations into consideration, it is sufficient to set the angle in the range of θ-5° to 306 degrees, and the reason why the lower limit is cut at 5° is to take into consideration variations in processing and sealing of the electrode 21 when the angle is less than 5°.

Therefore, even if abnormal lighting occurs in which an arc spot is generated at the electrode base end during horizontal lighting, the electrode tip j! 1m
, 21* are located in the arc path, so the arc spot quickly moves to the tip of the electrode.

In the case of a lamp that is lit with direct current, the cathode 51 shown in FIG. It does not need to be provided. In other words, in a lamp that is lit with alternating current, the polarity of the electrode changes once per cycle, and as a result, the change in polarity causes the arc spot to become closer to the electrode tip 21.
*, there is a chance to move to 21m. In contrast, in DC lighting, the polarity of the cathode 51 does not change, so if an arc spot occurs at the base end, it is difficult to move to the tip 51a, and therefore the tip 11m is placed at an angle of θ-5'' to 30'. It is effective to install the cathode 51 inside the tip 51a.The cathode 51 is not wrapped with an electrode coil and is formed only from an electrode rod, which increases the temperature of the tip 51a and moves the arc spot further to the tip 51a. It is easy to comb.

In each of the above embodiments, the electrode tips 21m and 51* are set at an angle θ-
Although we have described the case where the base of the electrode shaft is bent directly upward in order to position it within the range of 5° to 30°, the present invention basically means that the position of the electrode tip 21m, 51* is θ-511
Since it is sufficient that the angle is within the range of ~30°, for example, as shown in FIG.
Furthermore, the shape of the arc tube 1 is not limited to a spherical shape, but may be an elliptical spherical shape (as shown in FIG. 7).

Although a metal halide lamp was described in the above embodiment, the present invention can also be applied to a high-pressure water chain lamp, etc., as long as it is 100 watts or less, and the arc tube is formed in a spherical or elliptical shape and is lit horizontally. It is.

〔Effect of the invention〕

As described above, in the present invention, even if an arc spot is generated at the base end of the electrode, the tip of the electrode is located in the arc path, so the tip of the gutter is heated by the arc and generates thermoelectrons. As a result, the arc spot quickly moves to the tip. Therefore, normal lighting is maintained, devitrification and leakage of the arc tube is prevented, and 1! Breakage of the poles is also prevented, resulting in a long service life.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a conventional arc tube, FIG. 2 is a sectional view showing an arc tube of the present invention, FIGS. 3 and 4 are explanatory diagrams of a conventional arc tube for explaining experiments, 5 to 7 are cross-sectional views of arc tubes showing other embodiments of the present invention. 1... Arc tube, 21.21... Electrode, 51... Electrode, 52
・@Pole, 21m, 21*, 51a, 61*... Electrode tip, 3... Sealing part. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (3)

[Claims] (1) A spherical or ellipsoidal arc tube equipped with a pair of electrodes is filled with a luminescent metal and a rare gas for starting, and the arc tube is lit with the tube axis horizontal. In a small high-pressure metal vapor discharge lamp, the tip of the electrode is tilted upward by 5° to 30° with respect to the base end on the sealed side of the electrode.
A small high-pressure metal vapor discharge lamp characterized in that the lamp is located within an angular range of . (2) Claim (1) characterized in that in a discharge lamp for direct current lighting, at least the tip of the cathode side electrode is positioned within the range of 4 degrees from 5 degrees to 30 degrees.
Compact high-pressure metal vapor discharge lamp as described in Section 1. (3) The /J% type high-pressure metal vapor discharge lamp according to claim 1 or line 2j, wherein the discharge lamp is a metal halide lamp.