JPH07326323A - Metallic vapor discharge lamp - Google Patents

Abstract

PURPOSE:To provide a lengthy type high output metallic vapor discharge lamp for vertical lighting in which the fusion of an electrode is suppressed to improve the life characteristic. CONSTITUTION:This metallic vapor discharge lamp is formed of an arc tube 1 in which the light emitting length L corresponding to the distance between a pair of electrodes 2a, 2b provided on both ends of the arc tube 1 exceeds 15 times the tube bore diameter D of the arc tube 1, and the tube axis is arranged in the vertical direction. When the diameter of the core bar of the electrode arranged on the lower side is d (mm), and the lamp current is I (A), the diameter (d) of the electrode core bar to the lamp current is set so as to satisfy the range of 5<=I/pi(d/2)<2=11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of life characteristics of a vertical lighting metal vapor discharge lamp used for an ultraviolet curing device such as a coating material for an optical fiber.

[0002]

2. Description of the Related Art Generally, in an optical fiber used for optical communication or the like, in order to prevent strength deterioration due to scratches or dust on the surface, immediately after drawing, ultraviolet curable silicone, epoxy, urethane resin, etc. are used. , Thickness of a few μm
Is applied. FIG. 5 is a diagram schematically showing a configuration of such an optical fiber drawing apparatus. As shown in FIG. 5, the drawing device is a preformed fiber base material.
A heating furnace 12 is provided around the periphery of the base material 11, and a wire diameter measuring device 13, a UV curable resin coating device 14, a UV curing device 15, a capstan roller 16, and a winding member are provided from the lower end of the base material 11 in a vertically downward direction. The fibers are led to the take-up drum 17. In FIG. 5, 18 is a UV lamp arranged in the UV curing device 15, 19 is a reflecting plate, and 20 is a quartz tube for N ₂ substitution.

In the thus constructed wire drawing apparatus, the wire drawing speed is usually several tens to several hundreds m / min. In order to realize such a speed, the UV curing device 15 has several k
One or two or more W-class UV lamps 18 are used side by side. Further, as is clear from FIG. 5, the tube axis of the UV lamp 18 installed in the UV curing device 15 is lit and used in a vertical posture parallel to the drawing direction of the optical fiber.

As shown in FIG. 6, a metal vapor discharge lamp used as a UV lamp in such a UV curing device has, as shown in FIG. 6, both ends of an arc tube 21 having a tube inner diameter D of 20 mm.
A pair of electrodes 22a, 22b made of a high melting point material are provided at a distance L of about 25 cm, and in the arc tube 21, in addition to mercury and rare gas, iron, cobalt, nickel, lead, gallium, magnesium, tin, At least one or more halides such as thallium and manganese are added, and they are hermetically sealed via molybdenum foils 23a and 23b for maintaining airtightness and conductivity. Then, it is turned on by an input of about 4 kW and emits light having a wavelength of 250 to 450 mm, which is effective for curing the ultraviolet curable resin.

[0005]

By the way, in the optical fiber drawing apparatus, a UV lamp of about 4 kW is not enough to cure the UV curable resin, so that it is necessary to use a plurality of lamps. In general, UV output control and life control of UV lamps are important factors for quality control of optical fibers. Further, in order to increase the drawing speed of the optical fiber, it is advantageous in terms of quality, cost, and maintenance to use a high-output lamp with a minimum number of lamps. Therefore, UV lamps are required to have a long life, high output, and a long length.

Due to such a request, the emission length is 750 mm,
When a long high-power UV lamp with a lamp power of 12 kW was created and vertically lit, the electrodes located below were severely worn, and after about 300 hours of lighting, more than half of the electrodes melted. It collapsed and accumulated in the cup portion below the arc tube made of quartz glass. The metal mass deposited on the cup is heated by heat conduction from the electrode and radiation from the arc, and softens or crystallizes the surface of the contacting quartz glass. The softened part of the arc tube swells because it receives an internal pressure of several atmospheres during lighting, and there is a problem that it eventually leaks due to a synergistic effect with the crystallization effect, which has the drawback of shortening the life of the lamp. .

Such a problem is caused by a general emission length of 250 m.
It does not occur in a UV lamp with m, tube inner diameter 20 mm, and lamp power 4 kW. To investigate the cause, the electrode core rod diameter is 2 mm, the tube inner diameter D is 20 mm and 27 mm, and the light emission length L is 125 mm.
When a UV lamp having a size of up to 750 mm was prepared and a lighting test was performed, the results shown in Table 1 were obtained.

[0008]

[Table 1]

From the results shown in Table 1, the above problem that the electrode is melted and the life is shortened is that the emission length L is the tube inner diameter D.
It can be seen that this is a peculiar problem that occurs in a comparatively long and narrow lamp that is about 15 times larger than.

The reason why the comparatively elongated lamp having a light emission length of about 15 times or more of the inner diameter of the tube causes a leak and shortens the life of the lamp is considered as follows. That is, in general, when a UV lamp is lit with its tube axis in a vertical posture,
Metal halides are easily affected by convection and gravity and accumulate in the lower side of the arc tube. The longer the emission length of the lamp is, the larger the total amount of the metal halide enclosed is. However, since the emission length is long, convection is less likely to occur, so that the halogen partial pressure near the lower electrode is increased. As a result, the reaction between the electrode and the additive is promoted, and tungsten, which is the material of the tip of the electrode core rod and the coil wound for heat dissipation of the core rod, becomes brittle even if it is repeatedly melted and recrystallized during lighting and collapses. As a result, an irregularly shaped metal block falls into the cup section at the lower end of the arc tube and falls. The collapsed metal lumps start to accumulate around the electrode core rod, which is the lowest point of the cup portion. When the lamp is turned on again in such a state, at the time of start-up, discharge starts from the metal lump portion, and the metal lump overheated by the discharge promotes the temperature rise of the quartz glass in contact with it, causing crystallization and thermal deformation. It is thought that the cup part receives thermal damage on the order of hundreds of hours and eventually leaks, causing the lamp to become a defect. On the other hand, metal vapor is generated and diffused from the arc spot of the metal block with a small thermal capacity, and adheres to the tube wall of the arc tube to reduce the ultraviolet transmittance of the quartz glass,
When it is used in a UV curing device, there is a problem that the ultraviolet ray output required for curing the resin cannot be obtained.

The present invention has been made in order to solve the above-mentioned problems that occur when a relatively elongated metal vapor discharge lamp having a light emission length of 15 times or more the inner diameter of a tube is lit vertically. It is an object of the present invention to provide a long-type high-output metal vapor discharge lamp for vertical lighting, which is suppressed and has improved life characteristics.

[0012]

In order to solve the above problems, the present invention has an emission length corresponding to the distance between electrodes provided at both ends of the arc tube which is more than 15 times the inner diameter of the arc tube. In a metal vapor discharge lamp consisting of an arc tube and lit with its tube axis arranged in the vertical direction, the diameter of the lower electrode core rod is d (mm), and the lamp current is I (A). At this time, the diameter of the electrode core rod with respect to the lamp current is set so as to satisfy the range of 5 ≦ I / π (d / 2) ² ≦ 11.

As described above, by setting the value of I / π (d / 2) ² , that is, the current density of the electrode core rod within the range of 5 to 11 (A / mm ² ), the emission length is set to the tube inner diameter. In a long and high-power metal vapor discharge lamp that exceeds 15 times, even if it is placed vertically and lit, the arc spot moves to the heat radiation coil and the coil melts or spatters at the lower electrode. It is possible to extend the life of the product.

[0014]

EXAMPLES Next, examples will be described. FIG. 1 is a schematic diagram showing an ultraviolet curing metal halide lamp (hereinafter referred to as UV metal halide lamp) of a first embodiment of a metal vapor discharge lamp according to the present invention, and FIG. 2 is an enlarged sectional view showing a lower electrode portion thereof. . In both figures, 1 has a total length of 850 mm
Is a quartz glass arc tube with a tube inner diameter D of 20 mm.
A pair of electrodes 2a and 2b are provided at both ends of the so that the distance L between the electrodes (light emission length) becomes 750 mm, and argon gas and mercury of 10 torr or more and halides of iron and tin are sealed to ensure airtightness. Molybdenum foil 3a for maintaining the conductivity and giving conductivity,
Sealed through 3b, load 160 W / cm, lamp power 12
A UV metal halide lamp having a rating of kW, lamp voltage of 1300 V and lamp current of 10 A is constructed. And
For the electrodes 2a and 2b, a tungsten core rod 4 having a diameter of 1.5 mm and a length of 20 mm is used, and a tungsten wire having a wire diameter of 0.7 mm is coil-length.
The heat-dissipating coil 5 double-wound to 6.5 mm is placed 1.5 mm away from the tip of the core rod 4, and an electron-emitting substance is held in the gap of the coil 5 to facilitate the emission of thermoelectrons. Are configured. In addition, in FIG. 2, 6 is a lower cup part.

The UV metal halide lamp thus constructed has a current density [I / π (d / 2) ² ] of the electrode core rod 4.
Is 5.7 (A / mm ² ), and even after 500 hours of lighting in the vertical direction, phenomena such as sputtering and melting did not occur in the lower electrode.

According to the present invention, in a metal vapor discharge lamp having a light emission length L exceeding 15 times the inner diameter D of the tube, the current density I /
π (d / 2) ² is set in the range of 5 to 11 (A / mm ² ). Next, the experiment conducted for this setting will be described. Except for the diameter of the electrode core rod, the UV metal halide lamp was made to have the same size as that of the above-mentioned first embodiment, and the diameter of the electrode core rod was variously changed.
When the state of the lower electrode after the lighting for a while was examined, the results shown in Table 2 were obtained.

[0017]

[Table 2]

As can be seen from Table 2 above, when the current density I / π (d / 2) ² of the electrode core rod is 4.4 or less, melting of the electrode occurs, which causes a short life of the UV metal halide lamp. When the current density is 12.7 or more, the tungsten sputters from the tip of the electrode core rod violently and adheres to the tube wall of the arc tube to form a blackened portion, which deteriorates the life characteristics of the lamp. And, in the range of current density of about 5-11,
It can be seen that this is a region in which electrode melting and sputtering are unlikely to occur. The reason why the electrode melts at a current density of 4.4 or less is considered to be as follows. That is, when the current density is large, the arc spot is formed on the electrode core rod, but when the current density is small, the thermal gradient between the electrode core rod and the heat radiation coil portion becomes insufficient, and the arc spot is formed on the coil portion. Move to. Since high heat is generated in the arc spot, it is considered that the coil portion formed of a tungsten wire having a small wire diameter is melted.

Therefore, the current density of the electrode core rod is 5 to 11
By setting the diameter of the electrode core rod so as to satisfy (A / mm ² ), the electrode is not melted, the problem of the defect due to the leak from the cup portion 6 under the lamp is solved, and further the spatter is caused. The blackening phenomenon can be suppressed.

Next, a second embodiment will be described. Since the basic configuration of this embodiment is the same as that of the first embodiment,
Illustration is omitted. The UV metal halide lamp of this example uses an arc tube having a total length of 630 mm and a tube inner diameter D of 27 mm.
A pair of electrodes is installed at both ends so that the distance L between electrodes (light emission length) is 500 mm. Similarly, argon gas of 10 torr and mercury, and halides of iron and tin are enclosed, and a load of 240
It has a rating of W / cm, lamp power of 12 kW, lamp voltage of 900 V, and lamp current of 15 A. The electrode has a diameter of 1.5 mm and a length of 20 as in the first embodiment.
A 0.7 mm tungsten wire with a coil diameter of 6.5 mm is wound on a tungsten core rod with a diameter of 6.5 mm, and a heat dissipation coil is placed 1.5 mm away from the tip of the core rod. It is constructed by holding a substance.

In the UV metal halide lamp thus constructed, the current density [I / π (d / 2) ² ] of the electrode core rod is
It was 8.5 (A / mm ² ), and even after 500 hours of lighting in the vertical direction, no phenomenon such as sputtering or melting occurred in the lower electrode.

Also in this embodiment, a UV metal halide lamp having various diameters of the electrode core rod was prepared,
When the state of the lower electrode after vertical lighting for 500 hours was examined, the results shown in Table 3 were obtained.

[0023]

[Table 3]

As can be seen from Table 3, when the current density of the electrode core rod is 4.8 or less, melting of the electrode occurs, which causes a short life, and when it is 13.3 or more, tungsten spatters from the tip of the electrode. It occurs violently and adheres to the wall of the arc tube to form a blackened portion, which deteriorates the life characteristics of the lamp. Then, similar to the experiment conducted on the first embodiment,
It can be seen that the region where the current density is approximately 5 to 11 is the region where electrode melting and sputtering are unlikely to occur. Therefore, even in the UV metal halide lamp having a large load as in the second embodiment, the current density is 5 to 11 (A /
By setting the diameter of the electrode core rod so as to satisfy mm ² ), the electrode does not melt and the problem of defects due to leakage from the cup under the lamp is solved, and the blackening phenomenon due to spatter Can be suppressed.

Next, in the UV metal halide lamp of the second embodiment and the experiment carried out with respect to the second embodiment, the UV output maintenance rate was measured for the electrode core rod diameters of 1.2 mm, 2.0 mm and 2.4 mm. The results (UV output maintaining process) are shown in FIG. 3, and the results of measuring the residual ratio (residual ratio process) are shown in FIG. In each figure, the curve a is U according to the second embodiment.
V metal halide lamp, curve b has an electrode core rod diameter of 1.2
mm, lamps with curves c ₁ and c ₂ have an electrode core rod diameter of 2.0
The characteristics of the lamp are shown in mm and 2.4 mm. As can be seen from the curve b in Fig. 3, the electrode core current density is 11 (A / mm
^For lamps exceeding ² ), the UV output is largely reduced due to electrode sputtering, and as can be seen from the curves c ₁ and c _{2 in} FIG. 4, lamps with an electrode core rod current density of less than 5 (A / cm ² ). Causes a leak in the above process, so 20
Even with a lamp that did not leak due to a poor residual rate at 00 hours, the UV output range was unstable due to sputtering from the molten metal ingot, as shown by the curves c ₁ and c ₂ in FIG.

Next, a third embodiment will be described. Since the basic configuration of this embodiment is the same as that of the first embodiment,
Illustration is omitted. The UV metal halide lamp of this embodiment uses an arc tube having a total length of 600 mm and a tube inner diameter D of 20 mm.
A pair of electrodes is installed at both ends so that the distance L between electrodes (light emission length) is 500 mm. Similarly, argon gas of 10 torr or more, mercury, and halides of iron and tin are enclosed, and a load of 160
It has a rating of W / cm, lamp power of 8 kW, lamp voltage of 700 V, and lamp current of 13 A. The electrode has a diameter of 1.5 mm and a length of 20 as in the first embodiment.
A 0.7 mm tungsten wire with a coil diameter of 6.5 mm is wound on a tungsten core rod with a diameter of 6.5 mm, and a heat dissipation coil is placed 1.5 mm away from the tip of the core rod. It is constructed by holding a substance.

In the UV metal halide lamp thus configured, the current density [I / π (d / 2) ² ] of the electrode core rod is
The value was 7.4 (A / mm ² ), and no phenomenon such as sputtering or melting occurred in the lower electrode even after the lamp was placed vertically and lighted for 500 hours.

Also in this example, a UV metal halide lamp having various diameters of the electrode core rod was prepared,
When the state of the lower electrode after vertical lighting for 500 hours was examined, the results shown in Table 4 were obtained.

[0029]

[Table 4]

As can be seen from Table 4 above, when the current density of the electrode core rod is 4.6 or less, the electrode melts and causes a short life, and when it is 11.5 or more, tungsten spatters from the tip of the electrode. It is generated and adheres to the tube wall of the arc tube to form a blackened portion, which deteriorates the life characteristics of the lamp. Then, similarly to the experiment conducted on the first embodiment, it is understood that the range where the current density is approximately 5 to 11 is a region in which melting or sputtering of the electrode is unlikely to occur.

In the experiments relating to the first, second and third embodiments, the load on the arc tube was 160 W / cm and 240 W / cm.
However, when the experiment was carried out with the load of the arc tube set to a value other than the above, the current density of the electrode core rod was about 5 to 11 (A / m
It was confirmed that melting and sputtering of the electrode did not occur when the range was set to m ² ).

In the UV metal halide lamp according to the present invention, the electrode on the upper side when arranged in the vertical direction causes a problem in characteristics even if the above-mentioned limitation of current density is not provided. However, if the upper and lower electrode core rods have different diameters, it is difficult to visually recognize the appearance of the lamp, and manufacturing mistakes and installation mistakes are likely to occur, so the upper and lower electrodes should have the same dimensions. Is desirable.

[0033]

As described above on the basis of the embodiments,
According to the present invention, in a vertical lighting metal vapor discharge lamp having a light emission length of 15 times or more the inner diameter of the tube, by setting the current density of the electrode core rod within the range of 5 to 11 (A / mm ² ), It is possible to provide a metal vapor discharge lamp with improved longevity characteristics, long output and stable life characteristics. Further, by using as a light source of an ultraviolet curing device for an optical fiber, the output of the light source can be increased and the length thereof can be improved to improve the maintainability, and the running cost can be reduced to contribute to the cost reduction of the optical fiber manufacturing. can get.

[Brief description of drawings]

FIG. 1 is a U of a first embodiment of a metal vapor discharge lamp according to the present invention.
It is a schematic diagram showing a V metal halide lamp.

FIG. 2 is an enlarged sectional view showing a lower electrode portion of the first embodiment shown in FIG.

FIG. 3 is a diagram showing a UV output maintenance rate range of the UV metal halide lamp of the second embodiment and the lamp in which the current density of the electrode core rod used in the experiment is out of the specified range.

FIG. 4 is a diagram showing the remaining rate range of the UV metal halide lamp of Example 2 and the lamp in which the current density of the electrode core rod used in the experiment was outside the specified range.

FIG. 5 is a schematic view showing a conventional optical fiber drawing device.

FIG. 6 is a schematic diagram showing a configuration example of a metal vapor discharge lamp generally used as a UV lamp.

[Explanation of symbols]

1 arc tube 2a, 2b electrode 3a, 3b molybdenum foil 4 electrode core rod 5 heat dissipation coil 6 cup part 11 fiber base material 12 heating furnace 13 wire diameter measuring instrument 14 UV curable resin coating device 15 UV curing device 16 capstan roller 17 Winding drum 18 UV lamp 19 Reflector 20 N ₂ replacement quartz tube

Claims (1)

[Claims] 1. A metal which comprises a light emitting tube having a light emitting length corresponding to a distance between electrodes provided at both ends of the light emitting tube exceeding 15 times an inner diameter of the light emitting tube, and which is lit with a tube axis arranged in a vertical direction. In the vapor discharge lamp, the diameter of the lower electrode core rod is
(Mm) and the lamp current is I (A), 5 ≦ I
A metal vapor discharge lamp characterized in that the diameter of the electrode core rod with respect to the lamp current is set so as to satisfy the range of / π (d / 2) ² ≦ 11.