JPH0429484Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a small metal halide lamp that is operated horizontally using a power source such as direct current that does not have polarity reversal.

[Technical background of the invention and its problems]

In recent years, from the viewpoint of energy conservation, the development of metal vapor discharge lamps with excellent luminous efficiency, such as metal halide lamps, which can be used in place of incandescent lamps with low luminous efficiency, has been actively promoted. These metal vapor discharge lamps are usually lit via a ballast using a general power supply of AC 100V or 200V with a commercial frequency of 50Hz or 60Hz, and the ballast is installed in a separate location from the discharge lamp. A method is being taken. However, considering it as an alternative to incandescent light bulbs, which are often used in general homes, stores, and vehicle headlights, it is a small lamp of less than 100W (watts), and the lamp and ballast are integrated, and the ballast is small and lightweight. , low cost is an essential condition.However, it is considered difficult to satisfy the above condition with the currently common ballast using a chiyoke coil.

In recent years, with the development of transistors, ICs, etc., it has become possible to construct an electronic circuit as a ballast that can satisfy the above conditions. Possible methods for such electronic circuits include DC lighting and high-frequency lighting, but high-frequency lighting causes a phenomenon called acoustic resonance in a specific frequency band, which causes the arc to fluctuate and cause the lamp to go out. In particular, in the case of metal halide lamps, the frequency band in which acoustic resonance occurs is extremely wide due to the shape of the arc tube and the inclusions, making high-frequency lighting methods inappropriate.
Therefore, as an electronic ballast for a metal halide lamp, it is desirable to use a lighting method using a voltage such as direct current that does not reverse polarity.

When a metal halide lamp is lit with a voltage such as direct current that does not have polarity reversal, the temperature of the anode becomes considerably higher than that of the cathode during lighting. This is because the energy of electrons accelerated by the cathode drop voltage generated around the cathode is mainly consumed at the anode. This phenomenon appears even more clearly with electric lights. Therefore, when an arc tube is used with horizontal lighting, the temperature of the arc tube near the cathode becomes lower than that near the anode, creating the coldest part on the wall of the arc tube near the cathode, and in small metal halide lamps, the temperature of the arc tube becomes lower than that near the anode, and in small metal halide lamps, the temperature of the arc tube becomes lower than that near the anode. The remaining metal halide will adhere to the arc tube tube near the cathode. In addition, under such lighting conditions, the partial pressure of the metal halide during lighting is low, so the ionized luminescent metal is attracted to the cathode, and eventually the metal's light emission can only be seen near the cathode, while mercury near the anode A phenomenon occurs in which only the light emitted by the light is visible, that is, color separation occurs. Moreover, since the mercury emission intensity near the anode is stronger than in AC lighting, the color separation phenomenon is even more pronounced. Furthermore, since the luminous intensity of mercury increases, the color temperature of the lamp as a whole increases, making it look very different from conventional incandescent light bulbs, making it unsuitable as a replacement.

[Purpose of invention]

This invention was developed in response to the above circumstances.
We provide a compact metal halide lamp of 100W or less that does not cause color separation when lit horizontally at a voltage with no polarity reversal, such as direct current or pulsating current, and whose color temperature does not differ significantly from incandescent or halogen bulbs. The purpose is to

[Summary of the idea]

The present invention is a small horizontally lit metal halide lamp characterized by having a light-shielding film coated on the outer surface of the anode side of the arc tube bulb.

[Example of idea]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the inside of the arc tube of a 35W class metal halide lamp. Although such an arc tube is not shown in the drawings, it is normally housed in an outer bulb to constitute the lamp.

In Fig. 1, reference numeral 1 is an arc tube bulb made of quartz glass, which is formed into an elliptical shape with a distance between the inner ends of both end sealing parts 2a and 2b of about 8 mm, and an inner diameter of about 6 mm. A fixed amount of a starting noble gas such as argon gas, mercury and the metal halides sodium iodide and scandium iodide are enclosed. 3 is a cathode, and 4 is an anode, which are installed facing each other at a distance of 5 mm, and the cathode 3 has a protrusion length of 1 mm inside the arc tube.
The protrusion length d of the tungsten rod and anode 4 is 2 mm.
A tungsten coil is wound around a tungsten rod, and is connected to external lead wires 7 and 8 via molybdenum foils 5 and 6, respectively. Reference numeral 9 denotes a light-shielding film formed on the outer surface of the arc tube bulb 1 on the anode 4 side, for example, a film made of a heat-resistant metal oxide such as alumina or silica is deposited on top of a carbon black film. Ru. The effective length l of the light shielding film 9 (the straight line distance from the sealed end of the anode 4 along the direction of its protrusion length) is set to 3 mm, and the protrusion length d of the anode 4 of the above effective length l (mm) is set to 3 mm. (mm)
The ratio to that is l/d=3mm/2mm=1.5.

A small metal halide lamp 10 equipped with such an arc tube is connected to an AC power source 12 via a DC lighting electronic circuit ballast 11, as shown in FIG. The above stabilizer 11 is AC/DS converter 1
3. A current detection circuit 14 is provided. 15 is a starting circuit which applies a pulse voltage to the cathode 3 and anode 4 at the time of starting. Such a ballast 11 and starting circuit 1
5, the lamp 10 is lit, and the lamp input is controlled to be 35W when stable. When the small metal halide lamp 10 was lit horizontally using such a lighting device, the color separation was almost undetectable from the outside of the lamp, and the color temperature was approximately 3300K, even though the light shielding film 9 was not provided. The temperature was about 6500K, but compared to that, we were able to get it much closer to incandescent or halogen light bulbs. That is, since the arc tube bulb on the anode 4 side where only mercury emission can be seen is covered with a light-shielding film 9, the mercury emission in this area cannot be detected from outside the lamp, and therefore the visual color is The separation phenomenon is eliminated. In addition, since mercury light emission, which has a particularly strong light emission in the blue region, is blocked, the color temperature of the lamp as a whole is lower than the conventional 6000K and can be brought closer to incandescent or halogen light bulbs of 2850 to 3100K. In the case of the present invention, since a light-shielding film is provided on the arc tube bulb, a slight decrease in luminous flux is unavoidable, but this is not the case for incandescent bulbs and halogen bulbs used indoors, stores, or vehicle headlights. Considering that it is a substitute, although the luminous flux is reduced, it is far superior to these bulbs, and as mentioned above, it eliminates the visual color separation phenomenon and further brings the color temperature closer. This has the practical effect of being able to do the following.

Next, regarding the same type of lamp as in the above embodiment, the light shielding film 9
FIG. 3 shows the results of testing the relationship with lamp characteristics by varying the ratio l/d between the effective length l (mm) of the anode 4 and the protrusion length d (mm) of the anode 4. In FIG. 3, the horizontal axis represents l/d, the vertical axis represents color temperature on the left, and luminous efficiency (lm/W) on the right. It can be seen from the figure that the installation of the light-shielding film 9 is extremely effective in lowering the color temperature and bringing it closer to the color of a light bulb. On the other hand, as a matter of course, there appears to be an effect of reducing the luminous efficiency. However, since the luminous efficiency of metal halide lamps is originally several times better than that of light bulbs, a slight decrease is not so much of a problem; for example, even if l/d increases to 1.75, the luminous efficiency remains
40lm/W or more can be obtained, which is significantly superior to the 13-14lm/W of incandescent bulbs near the same 35W and the approximately 20lm/W of halogen bulbs, and the color temperature is almost the same as these bulbs of 2,850K to 3,100K. It can be seen that a certain amount can be obtained. On the other hand, as the effective length l of the light-shielding film 9 becomes shorter and l/d becomes smaller, the luminous efficiency increases, but the color temperature also increases accordingly. By the way, the sense of incongruity with light bulbs due to the difference in color temperature is less noticeable when the color temperature is higher than when it is lower, so there is almost no problem if you keep it at around 2,800K to 3,500K. Therefore, the smaller l/d is
It is preferable to set it to about 1.25.

Note that there was almost no problem with visual color separation when observing this lamp from the outside as long as l/d was set to exceed 1.0.

In addition, although scandium iodide was used as the metal halide in the above example, the present invention is not limited to this, and combinations of sodium iodide and other rare earth metal iodides, or the well-known sodium iodide, Exactly the same effect can be obtained by a combination of indium and thallium iodides.

[Effect of idea]

As detailed above, according to the present invention, a light-shielding film is coated on the outer surface of the anode side of the light-shielding tube bulb, so even when lit horizontally, the luminous efficiency is far superior to incandescent or halogen bulbs. It is possible to provide a small metal halide lamp that maintains the characteristics, has a color temperature comparable to the above-mentioned light bulb, and does not give a sense of discomfort, and can sufficiently replace the above-mentioned light bulb without causing any visual perception of color separation. .

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view of a small metal halide lamp arc tube that is an embodiment of the present invention, Fig. 2 is a schematic diagram of the lighting device of the lamp, and Fig. 3 is a diagram showing the relationship between the light-shielding film and the lamp characteristics. It is. 1... Arc tube bulb, 3... Cathode, 4... Anode, 9... Light shielding film, d... Projection length of anode, l...
Effective length of light shielding film.

Claims (1)

[Claims for Utility Model Registration] (1) Equipped with an arc tube in which an anode and a cathode are sealed opposite to each other at both ends of the arc tube bulb, and a rare gas for starting, mercury, and metal halide are sealed inside. ,
100W lit horizontally with voltage without polarity reversal
(WATCH) The following small metal halide lamp is characterized in that a light-shielding film is coated on the outer surface of the anode side of the arc tube bulb. (2) A practical device characterized in that the light-shielding film is deposited in a range where l/d is 1.25 to 1.75, where the effective length is l (mm) and the protrusion length of the anode is d (mm). A small metal halide lamp according to claim 1 of the patent registration claim.