JPS6139357A - Metal-vapor discharge lamp - Google Patents

Abstract

PURPOSE:To improve the starting characteristics and to prevent beam lowering due to the blackening of tube wall, by convering an electrode axis with an insulating material so as to keep it away from the direct contact with a sealed wire power source while enclosing a radioactive substance in the form of sealed wire power source within a luminous tube. CONSTITUTION:A sealing material containing a pair of electrode 2, starting rare gas and mercury is enclosed in a valve 1 made of quartz-glass, and also, a sealed wire power source 12 consisting of a ceramic material dispersed with a radioactive material is inserted into the side of an electrode 2b facing downward at lighting time, moreover, a luminous tube for metal-vapor discharge lamp is formed while keeping a sealed wire power source 12 away form its contact by covering the axis of electrode 2b with a small-quartz tube 10. While supposing that the diameter of electrode-coil is ''d'', the distance to the tube wall is ''L'', the distance up to the sealing end is ''h'', the diameter of sealed wire power source 12 is ''D'', and the length of the small tube 10 is ''l'', setting is made to satisfy L>D, l=h-d. Accordingly, it is possible to prevent the blackening phenomenon of the tube wall while improving the starting characteristics.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to metal vapor discharge lamps.

[Technical background of the invention and its problems]

Although metal vapor discharge lamps such as metal hashide lamps and high-pressure sodium lamps have excellent luminous efficiency, their starting voltage is high, so it is necessary to apply a sufficiently high voltage to start them. However, recently.

Lamps have been developed that are compatible with high-pressure mercury lamps by starting them using low-cost, light-duty mercury lamp ballasts; A means to enable this is required.

Furthermore, due to recent energy saving trends, there is a strong desire to develop small metal vapor discharge lamps that can replace low-efficiency incandescent light bulbs. A problem arises in that it is difficult to install the electrodes in terms of space.

As a means of lowering the starting voltage.

JP-A-56-126248, JP-A-57-904
Publication No. 7 discloses that a radioactive substance or a radioactive substance dispersed and sealed in a ceramic body, for example, is sealed in an arc tube for safety in handling.

Each item is shown to have a significant effect.

However, if such measures are taken.

If the shape of the ceramic body in which the radioactive substance is dispersed is too large due to manufacturing variations, or if the arc tube is downsized and the height of the electrode is lowered accordingly, the ceramic body is sealed so that it can move freely. Contact between the radioactive substance and the electrode, which becomes hot during lamp operation, may occur. In such a case, a high melting point metal such as tungsten or molybdenum, which is an electrode constituent material, reacts with the radioactive particles and scatters on the inner surface of the arc tube, causing early blackening and causing a decrease in luminous flux. For this reason, for example, if the radioactive material-dispersed ceramic body is made very small, it may be possible to prevent contact with the electrode, but the amount of radioactive material will inevitably decrease, making it difficult to achieve the original purpose of improving the starting voltage. .

As a means to deal with such inconvenience,
Publication No. 83338 discloses that the arc tube container is provided with a storage section that communicates with the inside of the arc tube, and the radioactive material is stored in this storage section to prevent contact9 reactions between the radioactive material and the electrodes. . Although this method is extremely effective in achieving that goal.

It takes time and effort to provide a storage section in the arc tube container.

An even simpler method was desired1゜ [Purpose of the invention] The present invention has been made in consideration of the above circumstances.

A metal vapor discharge lamp that prevents the radioactive material sealed in the arc tube from coming into contact with the electrodes by simply adding a simple means, eliminates the reduction in luminous flux due to blackening of the arc tube wall, and improves the starting characteristics. The purpose is to provide

[Summary of the invention]

The present invention provides a pair of electrodes facing the light emitting 'U bulb,
It is equipped with an arc tube in which a starter cloth gas and an enclosure containing at least mercury are sealed, and a radioactive substance made into a dense M-ray source is enclosed in the arc tube, and the lamp is located at the lower side at least when the lamp is turned on. This is a metal vapor discharge lamp in which the surface of the electrode shaft of the electrode is coated with an electrical insulator to prevent direct contact between the sealed source of the radioactive substance and the '&L pole.

[Embodiments of the invention]

The details of the present invention will be explained below with reference to the illustrated embodiments.

(Example ■) Figure 1 shows an arc tube of a 100W small metal halide lamp, and (1) shows an inner diameter of 10.5. This is an arc tube bulb made of ILM's quartz glass, and inside it contains 100 Torr of starting rare gases, such as 100 Torr of argon, 20 Torr of mercury, 0.1 Torr of scandium metal, and a total of 10 Torr of scandium iodide and sodium iodide as metal halides. It is enclosed. (2a) and (2b) are arc tube bulbs (1)
A pair of electrodes are placed opposite each other with a distance of 17 mm at both ends of the starting electrode (3), which is an auxiliary starting electrode placed close to one electrode (2a).

Each of the above electrodes (2a)l (2b)? (3) is the sealing part (4) of the arc tube.

(5) Airtightly sealed with 2 widths, maximum thickness approximately 28μm
are connected to external lead wires (7a), (7b), and (7C) via molybdenum foils (6a), (6b), and (6c), respectively.

Further, the surface of the electrode (2b) located on the lower side when the lamp is lit, on the side of the sealed end (9) of the electrode shaft (8), is covered with an electrical insulator (a) such as a quartz tube. More specifically, the electrode (2b) has a diameter of about 9.31111°, a length of 9.31111°, and a length of 9.3111°, and a length of 1.8 mm from the tip of the electrode shaft (8). Outer diameter 1. Made by winding tungsten wire in multiple layers.
The second electrode coil ←υ is wound, and the distance h (m) from the lower end of the electrode coil aυ to the sealed end (9) is about 3 degrees. Note that a'a is a sealed source of radioactive material,
A radioactive substance such as promethium 147 (Pm) is sealed in an arc tube as a spherical ceramic body with a diameter of 1.0 mm in which a radioactive amount of 0.05 μm is dispersed.

The arc tube formed in this way has a vacuum or nitrogen gas inside.
The lamp is completed by sealing it inside an outer tube filled with an inert gas or the like. Although the electrical circuit of this lamp is not shown, the external lead wires (7a) and (7b) of the arc tube are connected via a ballast.
, (7c) to electrode (2a) and starting auxiliary electrode (3)
A voltage is applied between both electrodes (2a) and t (2b) to turn on the light, but if the starting voltage is higher than the normal power supply voltage, a high voltage pulse is further applied at the time of starting as necessary. The lamp has a radioactive substance dispersed ceramic body α2 housed in the arc tube.

Initial electrons, which serve as a trigger for discharge, that is, seeds, are then released into the arc tube, resulting in rapid starting and a low starting voltage. That is, the initial electrons emitted from the radioactive substance ionize the argon gas in the vicinity, and without this ionization, ionized gas cannot be generated, making it difficult to start. In other words, in this case, the discharge will not start until ionized gas is generated by cosmic rays or natural radiation from the earth, etc. Moreover, the natural radiation is extremely small and the startup waiting time is very long. When the electrode shaft is not covered with an electrical insulator (conventional example 2.
), for example, when the light is turned on vertically, the radioactive material comes into contact with the electrode located below, and at the same time as the first discharge, the reaction products of the radioactive material and the electrode constituent materials such as tungsten and molybdenum are scattered and covered on the tube wall near the electrode. This darkening causes blackening, which causes a large drop in lamp luminous flux, and this blackened part also acts as a heat insulating film, causing an undesirable increase in the temperature of the coldest part, which was originally designed, and reducing the lamp voltage, etc. The characteristics of the tsumegome kaiseki dansenrei lamp also changed, which was undesirable.

Next, (Example 1) of the present invention, (Conventional example 1) and (
Table 1 shows the characteristic measurement results for each lamp of Conventional Example 2) after 100 hours of lighting and 2,000 hours of lighting.

Table 1 (Pulse width is about 1.25 μm) It can be seen from Table 1 that there are cases where the effects of the present invention are remarkable. As described above, in the lamp of the present invention, there is no fear of direct contact between the radioactive material-dispersed ceramic body and the electrodes, so that a sufficient amount of radioactive material can be used to lower the starting voltage.

(Example 2.) Inner diameter 20111. A total of 309% of sodium iodide, thallium iodide, and indium iodide and 50% of mercury were placed in a normal cylindrical quartz glass arc tube container with an interelectrode distance of 42%.
IV. Regarding a 400 W metal halide lamp filled with 25 Torr of argon gas, a ceramic body impregnated with a radioactive substance 22Na dispersed in a radioactive amount of 0.05 microcuries was sealed in the arc tube in the same manner as in the previous example, and the lamp was lit for 2 hours. The electrode axis of the side electrode was covered with an electrical insulator to form an arc tube.

These lamps include a lamp that does not use any radioactive materials (Conventional Example 3), and a two-tube lamp in which the Na-dispersed and impregnated ceramic body is enclosed in the arc tube, but the electrode shaft is not covered with an electrical insulator (Conventional Example 4). Table 2 shows the results of two lighting tests for each 100 lamps.

The applied voltage is a pulse voltage of 1500V and a pulse of -1il.
It was 1.25 μs, and the luminous flux maintenance rate after 3000 hours of lighting was set at 85%.

Table 2 Table 2 shows the use of radioactive substances (conventional example 4 and example 2)
) has a remarkable effect on lowering the starting voltage, and the lamp of the present invention, in which the electrode shaft is coated with an electrical insulator to prevent direct contact with radioactive materials, has a particularly superior luminous flux maintenance rate compared to Conventional Example 4. I know that there is. The reason for this improvement in the luminous flux maintenance rate is thought to be that the movement of radioactive substances can prevent contact with the electrodes, as in the case of the small lamp of Example 1. In the case of lamps, one thing is obvious, but it's not obvious.

In each of the above embodiments, a coil-wound electrode was used, but a rod-shaped electrode without a coil may also be used.

As described above, at least the surface of the electrode shaft of the electrode located on the lower side when the lamp is lit is coated with an electrical insulator over a part or the entire area, including the end of the sealing part. Although it was possible to prevent the blackening of the shear lamp by eliminating direct contact between the shear lamp and the electrode, it is more preferable to follow the 9th-order dimensional regulation in the case of an electrode provided with an electrode fill.

That is, FIG. 2 shows a longitudinal cross-sectional view of one end of the arc tube that becomes the lower side during lighting, and the outer diameter of the electrode coil αυ is d (im
), the shortest distance between the electrode coil 0〃 and the arc tube wall is L(g
m), the distance from the lower end of the electrode coil a3) to the end of the sealing part (9) is h (m), and the maximum length of the sealed radiation source, for example, the radioactive substance dispersed ceramic body α2, is D (gg).

L) D ・・・・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・・・・
In (1), the length of the electrode shaft (8) from the sealed end (9) covered with the electrical insulator 00 is l(
am).

l≧h−d ・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・・・・
Set so that (2) is satisfied.

Equation (1) above means that the radioactive substance-dispersed ceramic body (6) cannot pass through the gap between the electrode coil α and the arc tube wall and gets caught, and the electrode (2b) is not covered with an electrical insulator. This is to avoid a situation where the electrode coil αυ portion and the ceramic body←2 come into direct contact and react, causing the wall of the arc tube 9 to become black.

The regulation of formula (2) is based on the following reasons. That is, the pressure inside the arc tube of a metal vapor discharge lamp is at a low pressure of 1 atm or less immediately after starting, so discharge starts with a short discharge distance. However, over two hours, the temperature K inside the arc tube rises, and the pressure inside the tube rises, reaching a high pressure of 1 atm or more at rated lighting, for example, around 10 atm or more in the case of a metal halide 2 lamp. Therefore, for the discharge to remain stable.

The arc spot moves from the sealed end of the electrode shaft to the electrode tip, satisfying the well-known law Pd = const, (P is pressure, d' is discharge distance), and the discharge distance d becomes shorter. move in the direction. This phenomenon is caused by the fact that in the case of AC lighting, both electrodes act as both cathode and anode in each half cycle, so when the electrode is anode, the arc concentrates on the entire electrode and the tip of the electrode is also heated. When the pressure increases and the temperature of the electrode tip rises to a level sufficient to emit electrons, the arc moves to the electrode tip. However, since the heat capacity of an electrode provided with an iE electrode coil is large, it takes a long time for the arc spot to move to the tip of the electrode.

Therefore, even if a part of the electrode shaft is covered with an electrical insulator to prevent the radioactive substance-dispersed ceramic body from directly contacting the electrode shaft, the ceramic body and the exposed part of the electrode shaft that is not covered with an electrical insulator may If the distance is short,
Immediately after discharge, the exposed electrode shaft portion -tb<h-ti
If an arc spot is generated in the area > and then the arc spot does not move toward the electrode tip for a long time, the temperature of the ceramic body near the arc spot will rise excessively and the inside of the ceramic body will rise excessively. As a result of releasing the contained impurity gas into the arc tube, lamp characteristics, particularly starting voltage and life characteristics, may be adversely affected.

The inventors have determined that the covering length J (m) of the electrical insulator on the S pole axis
As a result of conducting tests with various changes, the above formula (2), ie.

If the coating satisfies the relationship l≧h−d, no arc spot will be formed on the electrode shaft below the electrode coil, or even if it is formed, the arc will come into contact with a part of the electrode coil, so it will instantly It was confirmed that the arc spot migrated to the tip of the electrode, and it was found that this did not have any adverse effect on the lamp characteristics.

In addition, when the two arc tubes are lit in a horizontal position, or when lit in an inclined or vertical position, the electrode axes of both electrodes should be made of electrically insulating material as shown above so that either side of the electrode may be facing downward. It may be covered.

Note that the present invention is not limited to the metal halide lamp shown in the above embodiments, but can also be applied to other metal vapor discharge lamps, such as high-pressure sodium lamps filled with a starting rare gas, mercury, and sodium, and a high-pressure sodium lamp filled with a starting rare gas and mercury. This also applies to high-pressure mercury lamps, etc. However, while the arc tube container of a metal halide lamp is made only of quartz glass, in the case of a high-pressure sodium lamp, the arc tube container is made of a translucent ceramic tube and a metal or ceramic tube that airtightly closes the openings at both ends of the tube. When connecting the electrode to the closing body, it is preferable to take measures such as covering the electrode shaft with a thin tube made of an insulating material such as quartz or ceramics in advance.

In addition, in the case of high-pressure mercury lamps, their starting characteristics are inherently superior to those of the metallolide lamps, high-pressure sodium lamps, etc., but when making the arc tube more compact, it is necessary to set an auxiliary electrode for starting. Due to space limitations,
Further, when the engine is used in cold regions, the starting characteristics deteriorate, so the present invention is effective in such cases.

It is preferable that the radioactive substance has a relatively short half-life, such as carbon-14 (14C), sodium A22 (22Na), etc.
)y Calcium 45 (45Ca), Iron 55 (51sFe
), cobalt 60 (60CO), nickel 63 ("N
i) Zinc 65 (65Zn), Manganese 54 (54
Mn), Strontium 90 (90Sr), #f
=Rum 106 ("'Ru), Silver 110 ("'Ag)
+ Antimony 125 (125Sb), Cesium 13
4 (13'CI)tCesium-137(13?C3),
Basaum 133 (133Ba), Cerium 144 (
144CB).

Promethium 147 ("7Pm), Eurobiu A 1
54 (1541i) u) Europium 155 (155E
u), gold 195 (195Au), thallium 204 (
20'TI), “Actinium 227 (227AC>
, Agilum 226 (22'Ra), 5Dium 228 (
228Rkt), Thorium 228 (228Th)
At least one of these is selected and used. In addition, ceramics include non-metallic oxides such as oxides, aluminum oxide, sodium oxide, magnesium oxide, and peryl oxide.

Metal oxides such as titanium oxide and calcium oxide.

Metal carbides such as aluminum carbide, sodium carbide, calcium carbide, aluminum nitride, sodium nitride,
Metal nitrides such as magnesium nitride are used.

Note that sealed sources of radioactive materials are not limited to those in which radioactive materials are dispersed and sealed in ceramics, which are metal carriers, as described above, but also materials that contain radioactive materials that are naturally present in the arc tube, such as metals such as scandium. Alternatively, it may be coated and sealed with a halogenide or oxide of these metals.

Sealing here refers to not peeling off in a smear test, and means that no radiation is detected when a sealed radiation source is wiped with a filter paper and examined using a counter, etc., to see if radiation is emitted from the surface of the filter paper. .

This means that virtually no radioactive substances migrate from the sealed source to the filter paper.

, [Effects of the Invention] As detailed above, according to the present invention, direct contact between the radioactive substance sealed in the arc tube and the electrode can be avoided by simple means.9 Based on the blackening of the wall of the arc tube. It is possible to prevent a decrease in luminous flux and improve starting characteristics.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of a small metal noride Gimp arc tube according to an embodiment of the present invention, and (2) FIG. 2 is a longitudinal cross-sectional view of one end of the arc tube, which is also the main part. (1)... Arc tube bulb, (2a), (2b)...
·electrode. (3)...Auxiliary electrode for starting (4), (5)・
...Sealing part. (8)... Electrode shaft, (9)... Sealing end. Ql...Electrical insulator. a2...Representative for radioactive material dispersion ceramic body Patent attorney Noriyuki Chika - Yushu → Figure 1

Claims (3)

[Claims] (1) An arc tube is provided with a pair of electrodes facing the bulb, and an enclosure containing a starting rare gas and at least mercury is enclosed inside the arc tube, and a sealed radiation source is provided within the arc tube. What is claimed is: 1. A metal vapor discharge lamp characterized by enclosing a radioactive substance and covering at least the surface of an electrode shaft of an electrode located on the lower side with an electrical insulator so as not to come into direct contact with the sealed radiation source. (2) The electrode consists of an electrode shaft and an electrode coil wrapped around a part of the electrode shaft, the outer diameter of the electrode coil is D (mm), and the shortest distance between the electrode coil and the wall of the arc tube is L (mm). , the length of the electrode axis from the lower end of the electrode coil to the electrode sealing end is h (m
m), when the maximum length of the sealed source is D (mm), L>D and the length from the sealed end of the electrode shaft covered with the electrical insulator is l (mm). The metal vapor discharge lamp according to claim 1, wherein 1≧h−d. (3) Claim (1) characterized in that the sealed radiation source is one in which a radioactive substance is dispersed and sealed in ceramics.
The metal vapor discharge lamp described in Items 1 and 2).