JPH0528965A - Metal halide lamp - Google Patents

Abstract

PURPOSE:To increase the vapor pressure of sealed metal iodide to get light emission characteristic of metal over the whole of the visible range from the near ultraviolet zone by increasing the temperature of a light emitting portion and making it uniform in the light emitting metal halide lamp. CONSTITUTION:The cross section of the molybdenum foil of the upper side sealing portion 7 in a vertical lighting type metal halide lamp is made larger than the cross section of the molybdenum foil of a lower side sealing portion 8. Or thermal capacity of a lower electrode is made smaller than that of an upper electrode. As heat is apt to diffuse to the upper side sealing portion 7, but it is hard to diffuse to the lower side sealing portion 8, the coldest point temperature of a lamp light emitting portion rises up so that it is possible to improve the uniformity of temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical lighting type metal halide lamp used for general lighting, optical equipment and the like.

[0002]

2. Description of the Related Art In recent years, metal halide lamps have been widely used for general lighting such as store lighting and road lighting, and the demand for them is expanding as lighting for automobiles or light sources for optical equipment. An example of the conventional metal halide lamp described above will be described below with reference to the drawings.

FIG. 3 shows the structure of a conventional metal halide lamp. In FIG. 3, 1 is a central light emitting part of a quartz glass arc tube, 2 is a tungsten electrode installed via a molybdenum foil, 3 is a sealing part in which the molybdenum foil is hermetically sealed, and 4 is an external lead. It is a line.

The operation of the metal vapor discharge lamp configured as described above will be described below.

In the metal halide lamp, the metal halide added together with mercury and a rare gas exists as a liquid near the arc tube wall during lighting, while the partially evaporated metal halide vapor forms metal atoms at the center of the arc. Dissociated into halogen atoms, the metal vapor is excited by an arc and emits a spectrum peculiar to the metal. Therefore, the metal halide lamp has an advantage that it is superior in luminous efficiency and color rendering property to the high pressure mercury lamp.

Tl-Na-In, S as a metal iodide
Many metal halide lamps containing c-Na, Dy-Tl, etc. have been put into practical use.

[0007]

Generally, in this kind of metal halide lamp, the emission characteristics of the lamp are determined by the vapor pressure of the enclosed metal halide. That is,
In order to obtain an emission spectrum specific to the enclosed metal, it is necessary to raise the temperature of the coldest part of the arc tube as high as possible and increase the vapor pressure of the metal halide. Therefore, in a metal halide lamp, a method of applying a heat insulating film to the outer surface of the arc tube in the vicinity of the coldest spot of the arc tube is usually used.

By the way, in the vertically-lit type metal halide lamp, the lower part of the lamp light emitting part becomes the coldest point, and the upper part of the light emitting part becomes the highest temperature due to convection in the arc tube.

However, in order to increase the vapor pressure of the metal halide in the lamp, it is necessary to make the temperature in the arc tube as uniform as possible in addition to raising the temperature of the coldest spot as described above. By making the temperature in the lamp light-emitting part as uniform and high as possible, the metal halide present in excess in the lamp will contact not only the coldest spot during lighting but also the inner surface of the arc tube at a higher temperature. The vapor pressure of the halide can be increased.

However, the conventional vertical lighting type metal halide lamp has a drawback in that the vapor pressure of the metal halide cannot be increased due to the large temperature difference between the upper part and the lower part of the lamp light emitting part as described above. It was

On the other hand, in the single-tube type metal halide lamp, the sealing portion of the arc tube must be kept at a temperature as low as possible. This is because in a single-tube type metal halide lamp, the atmosphere penetrates between the external lead wire of the sealing portion and the quartz glass, and the molybdenum foil is oxidized when the temperature of the sealing portion is high.

Therefore, conventionally, a method of preventing the progress of oxidation by increasing the length of the molybdenum foil to lower the temperature of the contact point with the atmosphere has been taken. However, extending the length of the sealing part not only impairs the compactness of the lamp, but also
There is a drawback in that the heat dissipation from the sealing portion is increased, the temperature of the coldest spot is lowered, and the vapor pressure of the metal halide is lowered.

In view of the above problems, the present invention suppresses the dissipation of heat from the lamp sealing portion, maintains the temperature of the lamp arc tube at a high temperature, improves the uniformity of the temperature in the lamp light emitting section, and fills the sealed metal halogen. An object of the present invention is to provide a metal halide lamp having an increased vapor pressure of a compound.

[0014]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention has a vertically lit type having a sealing part that hermetically seals a molybdenum foil to which an electrode is adhered at both ends and a light emitting part in the center. In the metal halide lamp, the molybdenum foil has a cross-sectional area on the upper side of the molybdenum foil that is larger than a cross-sectional area on the lower side, and the heat capacity of the lower electrode of the electrodes is the upper side electrode. The metal halide lamp is characterized by having a smaller heat capacity.

[0015]

According to the present invention, by making the cross-sectional area of the upper molybdenum foil of the vertical lighting type metal halide lamp larger than the cross-sectional area of the lower molybdenum foil, a large amount of heat is transferred from the light emitting part at the center of the arc tube to the upper sealing part. While heat is dissipated, the heat conduction to the lower electrode encapsulation part is small, so that the coldest spot temperature can be prevented from lowering and the inside of the light emitting part can be made hot and uniform.

Further, when the heat capacity of the lower electrode is made smaller than that of the upper electrode, comparing the electrode sealing portion at the lower part of the arc tube and the electrode sealing part at the upper part of the arc tube, from the electrode tip which becomes hot due to arc discharge, Means that a large amount of heat flows through the electrode rod to the lower portion of the arc tube having a small electrode heat capacity. As a result, the coldest spot temperature of the lower part of the arc tube can be raised, and the lamp light emitting part as a whole can be made hot and uniform.

[0017]

【Example】

(Embodiment 1) A metal halide lamp according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a quartz glass metal halide lamp arc tube, in which the cross-sectional area of the molybdenum foil on the upper side of the molybdenum foil sealed in the arc tube sealing portion according to the present invention is made larger than the cross-sectional area of the lower side. is there. 5 is a central light emitting part of a quartz glass arc tube, 6
Is a tungsten electrode, 7 is an upper sealing portion where a molybdenum foil is hermetically sealed, and 8 is a lower sealing portion where a molybdenum foil is hermetically sealed.

The effect of the present invention will be described by comparing the characteristics of the lamp having the structure according to the present invention shown in FIG. 1 and the conventional lamp shown in FIG. While the cross-sectional area of the sealing portion molybdenum foil 3 of the conventional lamp shown in FIG. 3 is 0.10 mm ² at the top and bottom, the sealing portion molybdenum foil 7 on the upper side of the lamp shown in FIG. the cross-sectional area of 0.12 mm ^2, the cross-sectional area of the sealing portion molybdenum foil 8 of the lower side was 0.77 mm ^2. The length of all molybdenum foils was 20 mm.

These lamps were the same except for the cross-sectional area of the molybdenum foil of the sealing part. As an example of dimensions, lamp power 150W, lamp voltage 90V, lamp current 1.7
A, arc length 6.5 mm, tube wall load 38 Wcm ^-2 . In addition, as a starting rare gas, 200 torr of argon, 15 mg of mercury, 3 mg of dysprosium iodide, and 2 mg of cesium iodide were enclosed in the lamp.

The metal halide lamp having the above structure is vertically lit at a lamp power of 150 W as a single tube without providing an outer tube, and the upper lead 9, middle portion 10, lower portion 11 of the lamp light emitting portion and the outer lead of molybdenum foil of the upper electrode sealing portion. Joint with line 12
Was measured for temperature and emission spectrum. The results are shown in (Table 1) and (Fig. 2).

[0021]

[Table 1]

In the metal halide lamp according to the present invention, heat is easily dissipated from the light emitting portion to the upper sealing portion, and heat is less likely to dissipate to the lower sealing portion. Therefore, the temperature of the light emitting portion is higher than that of the conventional example. The uniformity could be improved.

As a result, the vapor pressure of the enclosed metal halide was increased as compared with the conventional example, and as shown in FIG. 2, it was possible to obtain abundant light emission peculiar to the enclosed metal from the near ultraviolet region to the entire visible region. . In FIG. 2, curve 1 is the emission spectrum of the lamp according to the conventional structure, and curve 2 is the emission spectrum of the lamp according to the present invention.

Further, when the temperature of the joint portion of the molybdenum foil of the upper electrode sealing portion with the external lead wire was measured, it was 333 ° C. in the lamp according to the conventional method, whereas in the lamp according to the present invention, the upper sealing portion was sealed. 2 due to large heat dissipation from the part
It was 90 ° C.

When these lamps were subjected to a life test at a lamp power of 150 W in the atmosphere at 40 ° C., oxidation of the molybdenum foil proceeded due to the high temperature of the above-mentioned joint portion in the lamp of the conventional example, and the lamp was heated in 480 hours. The joint was blown.

On the other hand, in the lamp in which the temperature of the joint portion was lowered according to the present invention, the joint portion did not melt even after 2000 hours had elapsed. As described above, when the lamp according to the present invention is used as a single tube, it has the effect of extending the life as well as improving the emission characteristics.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 4 shows a quartz glass metal halide lamp arc tube, which has a structure in which the lower side electrode of the pair of upper and lower electrodes has a smaller heat capacity than the upper side electrode heat capacity. In the figure,
The same members as those in the first embodiment shown in FIG. 1 are designated by the same reference numerals.

The effect of the present invention will be described by comparing the characteristics of the lamp having the structure according to the present invention shown in FIG. 4 and the conventional lamp shown in FIG. In the conventional lamp shown in FIG. 3, the electrodes have a structure in which the upper and lower electrodes have a diameter of 0.8 mm and a coil having a diameter of 0.2 mm is wound around an electrode rod having a length of 12 mm, and the total heat capacity of the electrodes is 0.023.
It is JK ^-1 .

In the lamp according to the present invention shown in FIG. 4, no coil is wound around the lower electrode rod. These lamps were the same except for the presence or absence of the coil of the lower electrode. As an example of dimensions, the lamp power is 150 W, the lamp voltage is 90 V,
Lamp current 1.7A, arc length 6.5mm, tube wall load 3
It is 8 Wcm ^-2 .

The lamp was filled with 200 torr of argon, 15 mg of mercury, 3 mg of dysprosium iodide, and 2 mg of cesium iodide as rare gas for starting. The metal halide lamp having the above structure was vertically turned on with a lamp power of 150 W as a single tube without an outer tube, and the temperature and the emission spectrum of the upper part 9, the middle part 10 and the lower part 11 of the lamp light emitting part were measured. The results are shown in (Table 2) and (Fig. 5).

[0031]

[Table 2]

In the metal halide lamp according to the present invention, the heat capacity of the lower electrode is smaller than that of the upper electrode, and the heat is easily transferred from the tip of the electrode to the coldest spot in the lower portion of the arc tube, so that the coldest spot temperature rises as compared with the conventional example. Further, it was possible to improve the uniformity of temperature in the light emitting section. As a result, the vapor pressure of the enclosed metal halide was increased as compared with the conventional example, and as shown in FIG. 5, it was possible to obtain abundant light emission peculiar to the enclosed metal from the near ultraviolet region to the entire visible region.

In FIG. 5, curve 3 is the emission spectrum of the lamp having the conventional structure, and curve 4 is the emission spectrum of the lamp according to the present invention. In order to reduce the heat capacity of the lower electrode, at least one of the electrode rod diameter, length, coil diameter, and number of turns may be smaller than that of the upper electrode.

[0034]

As described above, the present invention provides a vertical lighting type metal halide lamp which has a sealing part that hermetically seals a molybdenum foil to which electrodes are adhered, and has a light emitting part in the center. Of the lower side molybdenum foil cross-sectional area is smaller than the upper side cross-sectional area, or
By configuring the heat capacity of the lower electrode of the electrodes to be smaller than the heat capacity of the upper electrode, the cold spot temperature of the lamp arc tube is maintained at a high temperature and the uniformity of the temperature in the lamp light emitting part is improved. , The vapor pressure of the enclosed metal halide can be increased.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a metal halide lamp arc tube according to a first embodiment of the present invention.

FIG. 2 is an emission spectrum diagram of a metal halide lamp according to a conventional example and Example 1 of the present invention.

FIG. 3 is an explanatory diagram showing an example of a conventional metal halide lamp arc tube.

FIG. 4 is an explanatory diagram of a metal halide lamp arc tube according to a second embodiment of the present invention.

FIG. 5 is an emission spectrum diagram of a metal halide lamp according to a conventional example and Example 2 of the present invention.

[Explanation of symbols]

1 Quartz Glass Arc Tube Central Light Emitting Section 2 Tungsten Electrode 3 Molybdenum Foil Sealing Section 4 External Lead Wire 5 Quartz Glass Arc Tube Central Light Emitting Section 6 Tungsten Electrode 7 Upper Sealing Section 8 Molybdenum Foil Sealed Molybdenum Foil Airtightly sealed lower sealing part 9 Lamp light emitting part upper part 10 Lamp light emitting part middle part 11 Lamp light emitting part lower part 12 Upper electrode sealing part Joining part of molybdenum foil with external lead wire

Continued front page    (72) Inventor Yuko Ito             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd.

Claims (2)

[Claims] 1. A vertical lighting type metal halide lamp having sealing parts at both ends of which molybdenum foil to which electrodes are adhered is hermetically sealed, and a light emitting part at the center, wherein a lower part of the molybdenum foil is cut off. A metal halide lamp characterized by having an area smaller than the cross-sectional area of the molybdenum foil on the upper side. 2. A vertical lighting type metal halide lamp having a sealing part provided with electrodes at both ends and a light emitting part in the center, wherein the lower electrode has a heat capacity higher than the upper electrode heat capacity. A metal halide lamp characterized by being made smaller.