JPS5835858A - Compact metal halide lamp - Google Patents

Abstract

PURPOSE:To provide a compact metal halide lamp of improved luminous efficiency, by restricting the size of the electrode sealing part of the lamp to reduce the heat conduction loss and prevent the self-absorption of sodium. CONSTITUTION:The central spherical part 1 of a luminous tube is formed by expansion. Each sealed part 2 of the tube is formed as a bar by tight deformation or vacuum sealing on a molybdenum leaf 4 so that the cross section of the sealed part is nearly circular or elliptic. Prescribed quantities of mercury, scandium iodide and sodium iodide are provided in the sealed central spherical part 1. Argon gas is also provided at prescribed pressure in the sealed central part 1. The cross-sectional area S (mm.<2>) of the sealed part 2 at the molybdenum leaf 4, the consumed electric power P (watt) of the luminous tube, its total length L (mm.) and the distance M (mm.) between the ends of the central spherical part 1 are related to each other as formulaeI, II.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a small metal hashide lamp having an internal volume of an arc tube of 1 c, e or less.

In recent years, highly efficient light sources have been required from the viewpoint of energy conservation. In particular, attention has been paid to the use of metal halide ft-1, which has high efficiency and high color rendering properties, and which has conventionally been mainly used as a light source for outdoor lighting, as a light source for indoor lighting. The conditions for using metal halide lamps as a light source for indoor lighting are that in addition to the advantages of high efficiency, high color rendering, and long life that this type of lamp has, it is also necessary to reduce One example is that it can be used in place of a light bulb or a fluorescent lamp, and a lamp of 100 watts or less, especially 50 watts or less, is required.

However, such metal halide lamps of 100 watts or less, in some cases 50 watts or less, have the disadvantage that they cannot be made as compact as the conventional medium-to-high watt lamp. In other words, within the conventional
If the manufacturing technology of high-wattage lamps were applied analogously to this type of small-sized lamp, the luminous efficiency would decrease significantly as the lamp power became smaller, and this is the reason why the development of small-sized metal halide lamps has been delayed. there were.

The reason why the luminous efficiency decreases significantly as the lamp becomes smaller is because the smaller the lamp, the lower the temperature rise in the coldest part due to the effect of the electrode sealing part, which reduces the evaporation of the enclosed metal. This is because as the lamp becomes smaller, the volume of the sealing portion relative to the discharge space increases, so that heat conduction loss through the sealing portion becomes relatively large. In other words, in conventional large lamps, the sealing part is flattened and sealed, and when this type of crushing sealing technology is applied to small lamps, the volume of the sealing part becomes smaller than the discharge space. It is relatively large.

However, if the dimensions of the sealing section are made extremely small in order to completely reduce the heat conduction loss in the sealing section, the luminous efficiency may conversely decrease. This is because if the coldest and lowest humidity temperature rises too much, and the sodium in the enclosed metal causes self-absorption.

The present invention was made based on the above circumstances, and its purpose is to reduce heat conduction loss in the tube bundle and prevent self-absorption of sodium, thereby increasing luminous efficiency by regulating the size of the electrode sealing part. The object of the present invention is to provide a compact metal halide lamp with improved performance.

The present invention will be explained below based on an embodiment fully shown in the figures.

Figure 1 shows the structure of an arc tube with an internal volume of 1 a,
Reference numeral 1 denotes a central spherical part made by expanding and molding a quartz glass tube, and is literally formed into an almost spherical shape. Electrode sealing portions 2, 2 are formed in the central spherical portion 1, and electrodes 3, 3 are sealed to these sealing portions 2°2VC. Electrode 3゜3 has an electrode coil formed on the electrode axis,
The above pricking part 2. It is connected to a metal foil conductor in z, for example a molybdenum foil 4.4. Note that the molybdenum foil 4.4 is connected to an external lead wire 5.5.

The arc tube has a central spherical part 1 and a sealing part 2. zf It is composed of one silica glass thin tube, and the central spherical part IFi is formed by the above-mentioned through-hole expansion, and the sealing parts 2, 2 are formed by crushing or vacuum sealing the molybdenum foils 4, 4 so that the cross section is approximately circular or It is shaped like a rod with an oval shape.

It should be noted that the molybdenum foils 4, 4 should be of a size that matches the lamp current for each watt, that is, a foil that has a width that can accommodate the lamp current.The thickness of the quartz chips is as follows: Since the internal pressure of the arc tube during lighting of this kind of rung reaches 20 atmospheres or more, a tube of 1 inch or more is used.

Further, in the central spherical portion 1, predetermined amounts of KFi mercury, scandium iodide, and lium iodide are each filled, and argon gas is filled at a predetermined pressure.

However, in the arc tube with such a configuration, the cross-sectional area of the sealing portion 2°2 at the location corresponding to the molybdenum foils 4, 4 is 8 (
■2) Lang power t-P (watts).

When the total length of the arc tube is L (m) and the distance between the inner ends of the central spherical part 1 is t-M (■), 0, IXP≦8≦0.4XP+4... Song...
... Song... Song (1) 1.6 X 10-'≦M
/L≦2.9X10−1 °−°−−−−−−−(2
) is regulated.

These formulas (1) and (2) were obtained based on the inventor's experiments.

First, equation (1) will be explained. Although it is advantageous for the cross-sectional area S of the sealing part 2 to be small in order to reduce heat conduction loss, the sealing part 2 cannot be determined solely from the viewpoint of heat conduction loss, and the molybdenum foil 4. The sealing properties of No. 4 are also dangerous. The size of the molybdenum foil 4.4 differs depending on the rung power because the i-capacity value that allows the rung current to flow is different for each watt. In other words, if the cross-sectional area of the molybdenum foil 4.4 is selected to be at least large enough to allow the lamp current corresponding to the lamp power, then the sealing s2, which corresponds to the size of the molybdenum foils 4, 4, You can choose the minimum cross-sectional area S of 2.
From this point of view, the relationship between the cross-sectional area S of the sealing parts 2 and the lamp voltage P (watts) is expressed as follows:
The results shown in the figure were obtained. In Figure 2, the characteristic person is 8
=0. Even if it corresponds to IXP, VC characteristic B is S=0.4
Corresponds to XP+4. The cross-sectional area S only needs to be an area (shaded area) K surrounded by constraints A and B, and therefore, 0, IXP≦S≦0.4XP+4.

If 8 is less than characteristic A, the quartz glass wall around the molybdenum foil becomes too thin and the molybdenum foil oxidizes, causing foil breakage.If S exceeds characteristic Bt-, the molybdenum foil becomes On the other hand, since the wall thickness of quartz glass is too large, the molybdenum foil and quartz glass do not fit well with each other, and the adhesion between the two cannot be maintained well, causing leaks.

As described above, the cross section m of the sealing portion is limited in reducing its rupture rkJ product from the viewpoint of the sealing function of the molybdenum foil, and must satisfy at least formula (1).

In order to reduce the loss due to thermal conduction of the seal H6x based on the premise of equation (1), the length of the sealing portion must be taken into consideration.

Therefore, the present invention investigated how to select the yi/LO value within the range of formula (1).

A metal halide lamp with a rating of 40 W is used, the distance between the electrodes is 4 cm, and the central spherical part 1 has an inner diameter of about 7 cm (internal volume of about 0.2 cm).
@ ) contains 6■ mercury and 0.3119 scandium iodide. Sodium iodide 1.51by, Alden gas f 200
Torr was enclosed.

The above 40W metal halide lung is shown in Figure 2 and (
From formula 1), the cross-sectional area S of the sealing part 2 is S = 4 m2 ~ 20
It is restricted to snow level 2. Therefore, we changed M/Lt one by one for each of S = 4w + 2゜7m2, 2011112, and investigated the luminous efficiency (M), and obtained the characteristics as shown in Figure 3.In the characteristics shown in Figure 3, M/L (1,
With 6X10-'K, the temperature of the coldest part cannot be obtained sufficiently due to the large heat conduction loss from the sealing part.
Efficiency decreases due to mercury light emission being the main source. However, g/L
When it exceeds 1.6 x 10-' t-, the luminescence of sodium and scandium [accompanyingly, the efficiency gradually increases].

However, once a certain peak is exceeded, self-absorption of sodium begins to occur and the efficiency gradually decreases.
When reaching 10"-'!lc4, the efficiency decreases significantly due to self-absorption of sodium, and M/L (1,6X10
The efficiency is approximately the same as in the area of .

Therefore, the area where efficiency improves above a certain level is M/
L is in the range of 1.6 x 10-' to 2.9 x 10-', and when it is out of this range, the efficiency drops below a certain level. Note that the above-mentioned certain level is the luminous efficiency (tm/N
%'), but there are individual rung levels depending on the value of S.

Figure 4 shows the spectral distribution characteristics, where 8 = 7 m2 in a 40W metal halide lamp, the solid line is g/L = 2.0X10, and the broken line is M/L = 2.
．． 2 x 10-' each spectral distribution shape I! ! 1,
As you can see from this figure, M/L = 2.2 x 10-1
In (the broken line) it is observed that self-absorption of IJium has begun. This confirms the tendency of the characteristics shown in Figure 3. In addition, Figure 5 shows the relationship between M7L and efficiency in a 20W metal-no-ride lamp. ranges from 2 to 12*2.

Therefore, the efficiency was investigated when yI/Lt- was varied between the case of 8=2*2 and the case of 5-12*2. Also in Figure 5, g/L is 1.6X 10
It can be seen that the range of -' to 2.9 x 10-' is a region where luminous efficiency is improved.

Therefore, if it is restricted to 1.6X10''-'≦M/L≦2.9X10-' in the range of formula 0, an improvement in luminous efficiency is recognized.

This shows that the volume of the sealing part is regulated by equations (1) and (2), which suppresses heat conduction loss through the sealing part, and conversely prevents excessive rise in the temperature of the coldest part. TL is essential to deter this.

As detailed above, according to the present invention, the volume of the sealing part is regulated to prevent heat conduction loss, and conversely, an excessive rise in temperature of the coldest part is prevented, thereby improving luminous efficiency. Moreover, it has the advantage of reducing the thermal load on the sealing part and preventing the metal foil from breaking after being lit for a long time.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1... Central spherical part, 2... Sealing part, S... Electrode,
4...Molybdenum foil. Applicant's agent Patent attorney Suzu, Takehiko E Figure 1 Figure 2 P (Watt)

Claims (1)

[Claims] In a metalno-ride lamp with an internal volume of the arc tube of 1 c, e or less, the cross-sectional area S (■) of the metal foil conductor portion in the electrode sealing part is 0 with respect to the Lang power P (watts). IXP≦S≦0.4XP+4, and the ratio of the distance M between the inner ends of the arc tube to the total length of the arc tube M/
L is 1.6 x 10-1≦M/L≦2.9 x 10-
A small metal halide lamp characterized by the following.