JPH0313704B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a relatively small wattage type metal halide lamp, and to improving the efficiency thereof.

In recent years, there has been a demand for highly efficient lighting from the perspective of energy conservation, and in particular, the indoor use of high-efficiency, high-color-rendering metal halide lamps, which have traditionally been used for outdoor lighting, is attracting attention.
Conditions for indoor use of metal halide lamps are that in addition to the advantages of this type of lamp, such as high efficiency, high color rendering, and long life, low wattage is strongly required. In other words, metal halide lamps are
It is limited to medium to high wattage types in the 250W to 2kW class, and in order to be used as an alternative to incandescent bulbs and fluorescent lamps for indoor lighting in general homes, lamps of 200W or less, especially 100W or less, are required.

However, small metal halide lamps have the disadvantage that the technology for conventional medium- and high-wattage lamps cannot be applied in a similar manner. In other words, if the conventional technology is applied directly to a small wattage lamp, the power output will be 200W or less,
In particular, the smaller the wattage, the lower the lamp efficiency becomes, and the advantage of high efficiency is lost, and for this reason, the development of small wattage metal halide lamps has been delayed.

As a result of various studies on this point, the inventors of the present invention found that the smaller the lamp, the lower the temperature rise in the coldest part due to the influence of the sealing part, which impedes improvement in lamp efficiency. That is, as shown in FIGS. 1a and 1b, a lamp employing the conventional technology as it is has sealing parts 2 formed at both ends of an arc tube 1 by heating and crushing a cylindrical quartz tube. . Main electrodes 5 and 5 and an auxiliary starting electrode 6 are connected. Note that 7, 7 and 8 indicate external lead wires. However, the width of such sealing parts 2, 2 tends to be larger than the outer diameter of the arc tube tube, and therefore the volume of the sealing parts occupies a considerably larger proportion than the discharge space. It is obvious that the discharge space also becomes smaller as the lamp becomes smaller, but the sealing part cannot be made much smaller due to limitations in the processing technology, and the smaller the lamp becomes, the more the sealing part for the discharge space becomes smaller. The volume of will increase relatively. Since this sealing part guides and releases the heat of the main electrode and the discharge space, heat loss through this sealing part becomes extremely large, thus inhibiting the temperature rise of the coldest part and causing a decrease in lamp efficiency. It was something that made me want to do something.

The present invention was made based on the above circumstances, and its purpose is to provide a narrow portion at a specific position of the sealing portion that affects heat loss, and to determine the cross-sectional area of the narrow portion and the lamp input. By defining the relationship, the present invention attempts to provide a metal halide lamp that can improve lamp efficiency without causing problems with the metal foil conductor.

That is, in the present invention, a minimum cross-sectional area is formed between the base of the main electrode and the metal foil conductor in at least one of the sealing parts, and the maximum and minimum values of the cross-sectional area of this minimum cross-sectional area are determined. This is regulated in relation to lamp input.

According to the present application, since the maximum value of the minimum cross-sectional area is regulated, the heat of the electrode is prevented from being transferred to the sealing part, and the heat dissipation from the sealing part is restricted, thereby reducing the temperature of the coldest part. By increasing the temperature to improve lamp efficiency and reduce variations in lamp light color, and by regulating the minimum value of the minimum cross-sectional area, we prevent the electrode heat from transmitting through the electrode axis and overheating the metal foil conductor. death,
Problems such as foil breakage can be prevented.

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

The metal halide lamp shown in FIGS. 2a and 2b has a reduced cross-sectional area of the sealing part 2 located at least on the lower side during lighting, and the base of the main electrode 5, that is, the buried end of the main electrode. A narrow portion, in other words, a minimum cross-sectional area portion 20 is formed between the portion and the metal foil conductor 3. As can be seen from FIG. 2b, the cross-sectional area S (mm ² ) of the minimum cross-sectional area portion 20 is approximately rectangular, so it is calculated by xt.

Therefore, when the cross-sectional area S is regulated within a certain range, lamp efficiency is greatly improved. This was confirmed based on an experiment, and the experiment will be explained below.

First, the inventors conducted an experiment using a 100W metal halide lamp. In other words, the inner diameter of the arc tube located at the tip of the main electrode 5 is 10.5 mm, and the wall thickness is 10.5 mm.
A 100W metal halide lamp with a distance between electrodes of 15mm was fabricated in a 1.2mm quartz tube. 18 mmg of mercury and sodium iodide (NaI) inside the bulb
A total of 10 mmg of a mixture of and scandium iodide (ScI ₃ ) (mixed weight ratio NaI:ScI ₃ =5:1) and 40 Torr of argon gas were sealed. In such a lamp, the minimum cross-sectional area S (mm ² ) of the sealing part 2 is
The lamp efficiencies (lm/W) of each lamp were investigated by changing the lamps sequentially from the conventional one shown in FIG. The results are shown in FIG. The cross-sectional area S of the prior art shown in FIGS. 1a and 1b was 35 mm ² .

As can be seen from Figure 3, in the case of a 100W metal halide lamp, the lamp efficiency is 82lm/W when the minimum cross-sectional area S of the sealing part is ^20mm2 or less, compared to 65lm/W when S = ^35mm2 . compared to about 25
% improvement in efficiency is also recognized. Further, when S is 20 mm ² or less, the efficiency is almost saturated and becomes a constant value.

When we investigated the reason for this, we found the following phenomena. That is, in the above-mentioned lamp, the end of the arc tube is heated by arc discharge and heat from the main electrode 5 during lighting, but since the minimum cross-sectional area portion 20 is formed in the sealing portion 2, this minimum cross-sectional area Heat conduction is blocked by the portion 20, making it difficult for heat to be conducted to the sealed end side of the metal foil conductor 3. In other words, since the minimum cross-sectional area portion 20 has a small cross-sectional area, it restricts the transfer of heat to the tip side of the sealing portion 2, and as a result, the temperature of the base end of the electrode as the coldest portion increases, and the metal halogen Evaporation of compounds is promoted. Therefore, lamp efficiency is increased and variations in lamp light color are reduced.

Note that the tip of the sealing part 2 below the minimum cross-sectional area part 20 has a larger width and cross-sectional area than the minimum cross-sectional area part 20, so it has excellent heat dissipation, and therefore the temperature of the sealing part 2 does not increase. is prevented. In addition, as described above, since the minimum cross-sectional area portion 20 restricts heat from being transferred to the sealing portion 2, the temperature rise in the sealing portion 20 is further suppressed. For this reason, the sealing part 2
Thermal expansion of the metal foil conductor 3 is prevented, peeling of the metal foil conductor 3 is eliminated, and leakage and oxidation of the metal foil conductor 3 are prevented.

In some lamps with S of less than 6.6 mm ² , oxidation and foil breakage of the molybdenum foil occurred during 9000 hours of lighting in some lamps, and lamp life was found to run out in less than 5000 hours.

Examining this, we found that if the cross-sectional area of the minimum cross-sectional area portion 20 is made too small, the temperature of the coldest part and the electrode 5 will rise excessively, and heat will be directly transferred to the metal foil conductor 3 through the electrode axis. transmitted,
The temperature of the metal foil conductor itself increases excessively. It is presumed that this caused the metal foil conductor 3 to peel off, leading to oxidation of the metal foil conductor 3.

From this, it can be seen that the cross-sectional area of the minimum cross-sectional area portion 20 has a minimum range necessary to release the heat that would be directly transmitted to the metal foil conductor 3 through the electrode axis through this minimum cross-sectional area portion 20. I understand.

For this reason, the minimum cross-sectional area portion 20
If the cross-sectional area S is 6.6 mm ² or more, it is considered that problems such as foil breakage will not occur even after lighting for more than 5,000 hours. Therefore, it has been found that by regulating S to a range of 6.6 mm ² to 20 ^{mm 2} for a 100W metal halide lamp, it is possible to improve efficiency by 25% compared to the conventional lamps shown in Figure 1 a and b. did.

Next, the inventors conducted experiments similar to those for the 100W lamp described above using 40W, 250W, and 400W lamps. The results are shown in FIG.

In Figure 4, characteristic A connects the boundary points where lamp efficiency improves in each lamp,
It's almost a straight line. Characteristic B connects the limit points at which the molybdenum foil does not break during its life, and this characteristic is also a substantially straight line. Therefore, it can be seen that if the minimum cross-sectional area S is set within the shaded area surrounded by characteristics A and B, a metal halide lamp with high efficiency and long life can be obtained. Characteristic A is expressed as S=16.6log ₁₀ P−13.2 …(1), and characteristic B is expressed as S=5.6log ₁₀ P−4.6 …(2).

Therefore, the minimum cross-sectional area S (mm ² ) is the lamp input P
(watt), it is sufficient to satisfy 5.6log ₁₀ P−4.6≦S≦16.6log ₁₀ P−13.2 …(3).

Note that the characteristics indicated by the broken line C in FIG. 4 are average values for the conventional type shown in FIGS. 1a and 1b.

If the above equation (3) is satisfied, the lamp efficiency will be 40W.
It has been confirmed that the improvement is 40% for the 100W class, 25% for the 100W class, 15% for the 250W class, and 10% for the 400W class, indicating that the present invention is more effective for smaller wattage types.

Note that in the case of a 700 W or 1 kW metal halide lamp, the volume ratio of the sealing part is small compared to the discharge space (distance between electrodes), so even if the present invention is applied, not much effect can be expected. Therefore, the present invention
This effect is recognized in lamps of 400W class or less.

Note that in the structure shown in FIG. 2, the cross-sectional shape of the minimum cross-sectional area portion 20 is a flat rectangular shape, but the present invention
As shown in FIG. 6 and FIG. 6 as other embodiments, the cross-sectional shape of the minimum cross-sectional area portion 20 may be oval or circular.

As a method of obtaining the minimum cross-sectional area of each shape, it is possible to cut into a predetermined shape using a cutter or laser beam after the conventional crushing and sealing process, or considering mass production. In this case, it is also possible to take measures such as connecting small-diameter tubes by reducing the diameter of the ends of the quartz tubes before sealing.

By the way, according to the present invention as described above, there is also the result that the width of fluctuation in lamp light color can be reduced. In other words, with conventional lamps, the color temperature of the lamp changes greatly even with slight manufacturing variations in the sealing shape of the arc tube, electrode height, etc. There was a difference in temperature of 1500〓. However, in the case of the present invention, the temperature of the coldest part of the arc tube is increased at a higher rate as the smaller the wattage type lamp is, and even within the same allowable variation range as above, the variation in color temperature is 500%.
I was able to keep it within the range of .

In addition, the following advantages are achieved as other effects. In other words, normally in a metal halide lamp, a heat insulating film made of alumina or the like is formed on the end of the arc tube, which is the lower side when the lamp is lit, so as to cover the main electrode. According to the present invention, this heat-retaining film can be omitted or its application area can be reduced, and the amount of alumina used can be reduced. Furthermore, the reduction in luminous flux caused by this alumina heat-retaining film can be eliminated. For example, in the case of the 100W type, the height of the alumina applied to the end of the arc tube is set to be the same height as the electrode height, but according to the present invention, the height of the alumina applied to the end of the arc tube is reduced to at least 1/2 of the electrode height. can do. As a result, the luminous flux can be improved by 5%, and the amount of alumina used is sufficient at 50 to 70% of the conventional amount.

As detailed above, the present invention forms a narrow part in the sealing part located between the buried end of the main electrode and the metal foil, and the relationship between the cross-sectional area S of the narrow part and the lamp input P is expressed as follows. Since log ₁₀ P−4.6≦S≦16.6log ₁₀ P−13.2 is specified, lamp efficiency is improved, lamp life is extended, and variations in lamp light color are reduced. This has the advantage of preventing breakage and leakage from the sealing portion, making it possible to produce a metal halide lamp that can be used as a small or medium Watt type lamp.

[Brief explanation of the drawing]

1A and 1B show a conventional metal halide lamp, FIG. 1A is a front view, FIG. 1B is a sectional view taken along line B-B in FIG. The figures show an embodiment of the present invention, in which Fig. 2a is a front view, Fig. 2b is a sectional view taken along line B-B in Fig. 2a, and Fig. 3 is a lamp efficiency and minimum FIG. 4 is a characteristic diagram showing the relationship between the minimum cross-sectional area and the lamp input, and FIGS. 5 and 6 are cross-sectional views showing modified examples of the cross-sectional shape. DESCRIPTION OF SYMBOLS 1... Arc tube, 2... Sealing part, 3... Metal foil conductor, 5
...Main electrode, 20...Minimum cross-sectional area portion.

Claims (1)

[Scope of Claims] 1. Mercury, metal halides, and a starting rare substance are contained in an arc tube that has a sealing part that embeds and holds a part of the main electrode shaft and seals a metal foil conductor connected to the main electrode. A gas-filled metal halide lamp of 400W class or less, comprising a narrow part formed in the sealing part located between the buried end of the main electrode and the metal foil, and the cross-sectional area of the narrow part is A metal halide lamp characterized in that the relationship between S (mm ² ) and lamp input P (watt) is 5.6log ₁₀ P−4.6≦S≦16.6log ₁₀ P−13.2.