JP2000030667A - Dielectric barrier discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-cooled dielectric barrier discharge lamp having high cooling efficiency with a small flow at a high flow velocity. SOLUTION: The space 34 between an outer tube 4 made of a dielectric substance transmitting ultraviolet rays and an inner tube 2 is used as a discharge chamber, and a metal pipe 2 having the outer diameter smaller than the inner tube 3 is coaxially arranged in the inner tube 3. A pair of holes 21, 22 are bored on the metal pipe 2 in the direction perpendicular to the axis at an interval in the axial direction, a partition member 1 obstructing a water stream is provided in the metal pipe 2 at the intermediate position of a pair of holes 21, 22, and the narrow space 23 formed between the inner face of the inner tube 3 and the outer face of the metal pipe 2 between a pair of holes 21, 22 is used as a passage of cooling water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-cooled dielectric barrier discharge lamp, and more particularly to a water-cooled dielectric barrier discharge lamp configured to increase the flow rate with a small flow rate to increase the cooling efficiency.

[0002]

2. Description of the Related Art In a conventional dielectric barrier discharge lamp, a cylindrical dielectric material (for example, quartz glass) which transmits two ultraviolet rays having different thicknesses is coaxially arranged as an outer tube and an inner tube. Both ends are hermetically sealed, and the space between the outer tube and the inner tube is used as a discharge chamber. A discharge gas (a rare gas or a mixed gas of a rare gas and a halogen) is sealed in the discharge chamber, and the outside of the outer tube is sealed. Is provided with a mesh-like metal electrode for transmitting light, an electrode is also provided inside the inner tube, and a high frequency and a high voltage are applied between these two electrodes.

The discharge gas sealed in the discharge chamber emits ultraviolet rays by forming excimer molecules by a high frequency voltage applied between both electrodes of the discharge lamp.

In a dielectric barrier discharge lamp, when the temperature of the discharge gas increases due to an increase in input power, the efficiency of forming excimer molecules decreases, and the luminous efficiency decreases.
Further, when the temperature of the transparent dielectric tube wall increases, the ultraviolet transmittance of the tube wall decreases, and the illuminance of emitted light decreases.

[0005]

Conventionally, in order to suppress a rise in the temperature of the dielectric barrier discharge lamp, a cooling method of flowing cooling water inside the inner tube for cooling has been implemented.
The cross-sectional area of the flow path for cooling the discharge lamp is large and the flow velocity is slow, so that a large flow rate is required to increase the velocity of the water flow, and further, there are drawbacks such as easy generation of bubbles.

Therefore, the present invention has been conceived to provide a water-cooled dielectric barrier discharge lamp having good cooling efficiency.

[0007]

According to the dielectric barrier discharge lamp of the present invention, a space 34 between a dielectric outer tube 4 and an inner tube 2 which transmits ultraviolet light is used as a discharge chamber, and the inner tube 3 is used as an inner tube. A metal pipe 2 having an outer diameter smaller than the inner diameter of the metal pipe 3 is coaxially arranged, and a pair of holes 21 and 22 are formed in the metal pipe 2 at intervals in the axial direction and at right angles to the axis. Partition member 1 for preventing water flow into metal pipe 2 at intermediate position between 21 and 22
And a narrow space 23 formed between the inner surface of the inner pipe 3 and the outer surface of the metal pipe 2 between the pair of holes 21 and 22 is used as a cooling water flow path.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in the sectional view of FIG. 1, a dielectric barrier discharge lamp according to the present invention has an inner tube 3 and an outer tube 4 arranged coaxially and sealing both ends in an airtight manner. A space 34 between the outer tube 3 and the outer tube 4 is used as a discharge chamber, and about 20 kPa of xenon gas is sealed as a discharge gas.
The outer pipe 4 is wound around the outer surface of the outer tube 4 with a metal mesh 5 that transmits light.

The inner tube 3 and the outer tube 4 are dielectrics made of a quartz glass tube that transmits ultraviolet light having a wavelength of 172 nm. The inner tube 3 has an inner diameter of 13.5 mm, a wall thickness of 1.2 mm, and an outer tube. No. 4 has an outer diameter of 28.6 mm and a wall thickness of 1.8 mm.

The metal pipe 2 inserted through the inner pipe 3 has an outer diameter of 10.0 mm and a wall thickness of 1.0 mm. The total length of the lamp is approximately 200 mm, and the length of the metal pipe 2 is 260 mm.

The metal pipe 2 is provided with three holes 21 and 170 at intervals of 170 mm at positions symmetrical with respect to the center.
22 have been opened. These holes 21 and 22 are formed at positions where the circumference is divided into three equal parts at right angles to the axial direction, and each hole diameter is 3.0 mm.

Further, the metal pipe 2 is placed at an appropriate position between the holes 21 and 22 formed at intervals of 170 mm, and is 1 m in the center.
A partition member 1 for providing resistance to a water flow having a hole 11 of mφ is provided.

At both ends of the inner tube 3, the inner tube 3
Between the inner surface of the metal pipe 2 and the outer surface of the metal pipe 2
It is sealed to prevent water leakage.

The metal pipe 2 inserted into the inner tube 3 is grounded as an inner electrode, and the outer electrode of the metal net 5 wound around the outer surface of the outer tube 4 is a high voltage electrode. Is applied.

In the dielectric barrier discharge lamp configured as described above, when cooling water flows from one end of the metal pipe 2, a part of the cooling water flows through the hole 11 of the partition member 1 in the metal pipe 2. Most cooling water has three holes in one
From 21 to the space between the inner surface of the inner pipe 3 and the outer surface of the metal pipe 2
After flowing through 23, it enters the metal pipe 2 through the other three holes 22, and is discharged from the other end of the metal pipe 2.

As described above, the metal pipe 2 having an outer diameter of 10 mm slightly smaller than the inner diameter of 13.5 mm of the inner pipe 3 is coaxially arranged on the inner pipe 3 so that the inner surface of the inner pipe 3 and the outer surface of the metal pipe 2 are separated. By forming the narrow space 23 therebetween, it is possible to reduce the cross-sectional area of the flow path of the cooling water, increase the flow velocity even with a small flow rate, and increase the cooling efficiency.

Although the metal pipe 2 is also used as an inner electrode and a cooling pipe of the dielectric barrier discharge lamp, a space 23 exists between the inner pipe 3 and the metal pipe 2 serving as the inner electrode. However, since the dielectric constant of water (about 80) is much higher than that of quartz glass (about 3.5),
The same function can be performed as when the metal pipe 2 is in close contact with the inner surface of the inner pipe 3.

In the metal pipe 2, a hole 11 is formed in the partition member 1. The hole 11 is provided to allow bubbles existing in the metal pipe 2 to escape to the downstream side.

With respect to the dielectric barrier discharge lamp of the present invention, the illuminance of radiated light was measured between the time of non-cooling and the time of cooling. In the case of non-cooling, the temperature of the sealed gas gradually increased from the start of lighting. The illuminance was attenuated by 35% in the lighting time of about 35% as compared with the time of starting lighting. On the other hand, at the time of cooling, almost no decrease in illuminance was observed after lighting for about 15 minutes.

Since it is difficult to directly measure the temperature of the sealed gas, when the surface temperature of the outer tube 4 was measured, the temperature rose to about 300 ° C. in 15 minutes after the start of lighting when no cooling was performed, but increased to 80 ° C. in cooling. Met.

The inner diameter of the inner pipe 3 is 13.5 mm, and the cross-sectional area of the cooling water flowing is 143 mm ² when the metal pipe 2 is not provided.
Is provided, it becomes 64.5 mm ² and the area ratio is 0.4
It becomes 5. Therefore, in order to obtain the same flow rate, about half the flow rate may be used, and about twice the flow rate can be obtained with the same flow rate.

The dimensions of the metal pipe 2, the inner pipe 3, the outer pipe 4, the holes 11, 21, 22 and the like described in the above embodiment are merely examples and are not limited to these dimensions.

[0023]

As is clear from the description based on the above embodiment, in the conventional dielectric barrier discharge lamp, the flow rate of the cooling water is slow, and the generated bubbles are hard to escape.
In addition, when large bubbles remain, the voltage distribution in that part increases, the electric input to the discharge lamp decreases, and the luminous efficiency decreases.In the part where the bubbles exist, the inner surface of the inner tube directly contacts water. However, according to the present invention, the flow rate of the cooling water can be increased with a small amount of water, so that the generated bubbles can be entrained in the flow and quickly discharged, so that the cooling efficiency can be reduced. It is possible to avoid a decrease in the luminous efficiency due to a decrease in the luminous efficiency.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of a dielectric barrier discharge lamp according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Partition member 2 Metal pipe (inside electrode) 3 Inner tube 4 Outer tube 5 Metal net (outer electrode) 6 Silicon rubber stopper 11 holes 21, 22 holes 34 Space (discharge chamber)

[Procedure amendment]

[Submission date] July 31, 1998 (July 7, 1998)
1)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction contents]

The metal pipe 2 inserted through the inner pipe 3 is connected to an inner electrode
Are high voltage electrodes, the outer electrode of the metal net 5 wound around the outer surface of the outer tube 4 is a ground electrode, and a high frequency high voltage is applied between the two electrodes.

Claims (2)

[Claims] 1. A dielectric barrier discharge lamp in which a space between an outer tube and an inner tube made of a dielectric material transmitting ultraviolet light is used as a discharge chamber, a metal pipe having an outer diameter smaller than the inner diameter of the inner tube is provided in the inner tube. A pair of holes are formed coaxially, a pair of holes are formed in the metal pipe at an interval in the axial direction, and at right angles to the axis, and a partition member for preventing water flow is provided in the metal pipe at an intermediate position between the pair of holes. A narrow space formed between the inner surface of the inner tube and the outer surface of the metal pipe between the pair of holes is used as a flow path of cooling water. 2. The dielectric barrier discharge lamp according to claim 1, wherein holes are formed in the partition member to allow bubbles to pass therethrough.