JP2006024422A - Discharge tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a long-life discharge tube capable of suppressing deterioration of a discharge-delay prevention function even if triggering discharge films are peeled off by spatter. <P>SOLUTION: The discharge tube is constituted such that: an airtight envelope 16 is formed by hermetically closing openings at both ends of a cylindrical case member 12 made of an insulating material opened at its both ends with a pair of cap members 14, 14, that also perform as a discharge electrode; the airtight envelop 16 is with encapsulated a predetermined discharge gas: a predetermined discharge gap 22 is formed between opposing discharge electrode portions 18, 18 of both cap members 14, 14 disposed in the airtight envelope 16; a plurality of linear triggering discharge films 28 are formed while being separated from the cap members 14, 14 whose both ends are also used as discharge electrodes with a small discharge space 26 on the inner wall surface 24 of the case member 12. A conductive film 30 made of titanium is formed on the discharge electrode portions 18, 18. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a discharge tube, in particular, as a switching spark gap for supplying a constant voltage for lighting or ignition to a high pressure discharge lamp such as a projector or a metal halide lamp of an automobile, or an ignition plug of a gas cooker, or The present invention relates to a discharge tube that can be suitably used as a gas arrester for absorbing surge voltage.

  As this type of discharge tube, the present applicant has previously proposed Japanese Patent Application Laid-Open No. 2003-7420. As shown in FIG. 5, this discharge tube 60 is hermetically sealed with a pair of lid members 64, 64 that also serve as discharge electrodes, at both ends of a cylindrical case member 62 made of an insulating material that opens at both ends. Thus, an airtight envelope 66 is formed, and a predetermined discharge gas is sealed in the airtight envelope 66.

The lid member 64 includes a flat discharge electrode portion 68 that protrudes greatly toward the center of the hermetic envelope 66, and a joint portion 70 that contacts the end surface of the case member 62. A predetermined discharge gap 72 is formed between the discharge electrode portions 68 and 68.
A plurality of pairs of trigger discharge films 78, 78 are formed on the inner wall surface 74 of the case member 62 so as to face each other with a minute discharge gap 76 therebetween. Of the pair of trigger discharge films 78, 78, one trigger discharge film 78 is electrically connected to one discharge electrode portion 68, and the other trigger discharge film 78 is electrically connected to the other discharge electrode portion 68. It is connected. The trigger discharge film 78 is made of a conductive material such as a carbon-based material.
On the surface of the discharge electrode portion 68, an insulating film 80 containing an alkali iodide effective for stabilizing the discharge start voltage is formed.
As the discharge gas sealed in the hermetic envelope 66, for example, a rare gas such as argon, neon, helium, xenon, or an inert gas such as nitrogen gas or a mixed gas is applicable. Also, a single or mixed gas of a rare gas or an inert gas, a mixed gas of negative polarity gas such as H ₂ corresponds.

When a voltage equal to or higher than the discharge start voltage of the discharge tube 60 is applied between the discharge electrode portions 68, 68 of the discharge tube 60 having the above-described configuration, an electric field is generated in the minute discharge gap 76 between the trigger discharge films 78, 78. As a result, electrons are emitted into the minute discharge gap 76, and creeping corona discharge as a trigger discharge is generated. Next, this creeping corona discharge shifts to glow discharge due to an electron priming effect. Then, the glow discharge is transferred to the discharge gap 72 between the discharge electrode portions 68 and 68, and is transferred to arc discharge as the main discharge.
JP 2003-7420 A

  The trigger discharge film 78 is formed to supply a function of preventing initial delay by supplying initial electrons. Gradually deteriorated.

The present invention has been made in view of the above-described conventional problems, and its object is to
An object of the present invention is to realize a long-life discharge tube that can suppress deterioration of the discharge delay preventing function of the trigger discharge film even if the trigger discharge film is peeled off by sputtering.

  In order to achieve the above object, the discharge tube according to the present invention is hermetically sealed by hermetically sealing both end openings of a case member made of an insulating material having both ends open with a pair of lid members that also serve as discharge electrodes. Forming an envelope, enclosing a discharge gas in the hermetic envelope, and forming a discharge gap between the discharge electrode portions of the lid member disposed in the hermetic envelope; A discharge tube formed on the inner wall surface of the member by forming a trigger discharge film whose both ends are spaced from the lid member by a minute discharge gap, wherein the conductive film is formed on the surface of the discharge electrode portion. Features.

  The conductive film can be made of titanium, for example.

  In the discharge tube according to the present invention, since the conductive film is formed on the surface of the discharge electrode portion, a part of the conductive material that is spattered and scattered by the impact during discharge is separated from the trigger discharge film. Can be compensated by adhering to the location. As a result, deterioration of the discharge delay preventing function of the trigger discharge film is suppressed, and a long-life discharge tube can be realized.

When the conductive film is made of titanium, since titanium has a getter function, it absorbs impure gases such as oxygen (O ₂ ) and carbon dioxide (CO ₂ ) released from the discharge electrode portion by discharge, and discharges. The deterioration of the gas composition with time can be prevented.

  As shown in FIGS. 1 and 2, a discharge tube 10 according to the present invention includes a pair of lids that serve as discharge electrodes at both ends of a cylindrical case member 12 made of ceramic as an insulating material having both ends open. The hermetic envelope 16 is formed by hermetically sealing with the members 14 and 14.

The lid member 14 includes a planar discharge electrode portion 18 projecting greatly toward the center of the hermetic envelope 16, and a joint portion 20 in contact with the end surface of the case member 12. A predetermined discharge gap 22 is formed between the discharge electrode portions 18 and 18. The discharge gap 22 is, for example, about 1.5 mm.
The lid member 14 provided with the discharge electrode portion 18 and the joint portion 20 is made of oxygen-free copper or zirconium copper containing oxygen-free copper containing zirconium (Zr). Note that the end surface of the case member 12 and the joint portion 20 of the lid member 14 are hermetically sealed through a sealing material (not shown) such as silver solder.

A predetermined discharge gas is sealed in the hermetic envelope 16. As this discharge gas, for example, a rare gas such as argon, neon, helium, or xenon, or an inert gas such as nitrogen gas or a mixed gas is applicable. In addition, a single gas or a mixed gas of a rare gas or an inert gas and a mixed gas of a negative gas such as H ₂ are applicable.

In addition, a plurality of linear trigger discharge films 28 are formed on the inner wall surface 24 of the case member 12 so that both ends of the case member 12 are spaced apart from the lid members 14 and 14 that also serve as discharge electrodes and a minute discharge gap 26. ing.
The trigger discharge film 28 is made of a conductive material such as a carbon-based material. The trigger discharge film 28 can be formed, for example, by rubbing a core material made of a carbon-based material.

On the surface of the discharge electrode portion 18, a conductive film 30 is formed by depositing titanium (Ti) as a conductive material. The thickness of the conductive film 30 is, for example, about 1 to 5 μm.
The conductive film 30 is provided to supplement the trigger discharge film 28 peeled off by sputtering. That is, like the trigger discharge film 28, the conductive film 30 is also sputtered by an impact at the time of discharge, and titanium as its constituent material is scattered in various directions, but a part of the scattered titanium is As a result, the trigger discharge film 28 adheres to the peeled portion and is compensated for, and as a result, deterioration of the discharge delay prevention function of the trigger discharge film 28 is suppressed. Since the conductive film 30 is formed by vapor-depositing a conductive material (titanium), it is easily sputtered by an impact during discharge.
When the conductive film 30 is made of titanium as described above, since titanium has a getter action, oxygen (O ₂ ), carbon dioxide (CO ₂ ), etc. released from the discharge electrode portion 18 by discharge. The impure gas can be adsorbed and deterioration of the discharge gas composition with time can be prevented. Of course, the conductive film 30 may be formed of a conductive material other than the titanium (for example, a carbon-based material).

  In the discharge tube 10 of the present invention, when a voltage equal to or higher than the discharge start voltage of the discharge tube 10 is applied between the pair of lid members 14 and 14 that also serve as discharge electrodes, the trigger discharge film 28 The electric field concentrates in the minute discharge gap 26 between the both ends and the lid members 14 and 14, whereby electrons are emitted into the minute discharge gap 26 to generate creeping corona discharge as a trigger discharge. Next, this creeping corona discharge shifts to glow discharge due to an electron priming effect. Then, the glow discharge is transferred to the discharge gap 22 between the discharge electrode portions 18 and 18, and the arc discharge is performed as the main discharge.

  Thus, in the discharge tube 10 of the present invention, since the conductive film 30 is formed on the surface of the discharge electrode portion 18, the conductive material (titanium) that the conductive film 30 is sputtered and scattered by an impact during discharge. A part of can adhere to the peeled portion of the trigger discharge film 28 and can be supplemented. As a result, deterioration of the discharge delay preventing function of the trigger discharge film 28 is suppressed, and a long-life discharge tube can be realized.

FIG. 3 shows the number of discharges and the DC discharge start voltage in the discharge tube 10 according to the present invention in which the conductive film 30 is formed on the surface of the discharge electrode 18 and the discharge tube in which the conductive film 30 is not formed on the surface of the discharge electrode 18. It is a graph which shows the relationship with (rating 800V).
As shown in this graph, in the case of a discharge tube in which the conductive film 30 is not formed on the surface of the discharge electrode portion 18 (graph B in FIG. 3), the DC discharge start voltage gradually increases and a discharge delay occurs. However, the number of discharges is about 300,000 times, and the DC discharge start voltage exceeds 1000 V, making it unsuitable for use. On the other hand, in the case of the discharge tube 10 of the present invention (graph A in FIG. 3), even if the number of discharges exceeds 500,000, there is no significant change in the DC discharge start voltage, and therefore a discharge delay occurs. There is no longer life.

FIG. 4 shows a modified example of the discharge tube 10 according to the present invention. An insulating film 32 containing an alkali iodide effective for stabilizing the discharge starting voltage is formed on the surface of the conductive film 30. It has the characteristics in the point.
Note that the conductive film 30 is sputtered together with the insulating film 32 containing alkali iodide, and the sputtered conductive material (titanium) is scattered in various directions in the hermetic envelope 16. The portion adheres to the peeling portion of the trigger discharge film 28 and can supplement the trigger discharge film 28.

The coating 32 is made of a simple substance or a mixture of alkali iodides such as potassium iodide (KI), sodium iodide (NaI), cesium iodide (CsI), and rubidium iodide (RbI) from a sodium silicate solution and pure water. It can be formed by applying to the surface of the conductive film 30 what is added to the binder.
In this case, the alkali iodide alone or a mixture is mixed at a blending ratio of 0.01 to 70% by weight, and the binder is 99.99 to 30% by weight. Moreover, the compounding ratio of the sodium silicate solution and the pure water in the binder is 0.01 to 70% by weight for the sodium silicate solution and 99.99 to 30% by weight for the pure water.

In the coating 32, cesium bromide (CsBr), rubidium bromide (RbBr), nickel bromide (NiBr ₂ ), indium bromide (InBr ₃ ), cobalt bromide (CoBr ₂ ), iron bromide (FeBr ₂ ). , FeBr ₃ ) and other bromides can be added to further stabilize the discharge start voltage of the surge absorber 10.
Incidentally, barium chloride (BaCl), barium fluoride (BaF), yttrium oxide (Y ₂ O ₃ ), yttrium chloride (YCl ₂ ), yttrium fluoride (YF ₃ ), potassium molybdate (K ₂ MoO ₄ ), tungsten One or more of potassium acid (K ₂ WO ₄ ), cesium chromate (Cs ₂ CrO ₄ ), praseodymium oxide (Pr ₆ O ₁₁ ), potassium titanate (K ₂ Ti ₄ O ₉ ) together with the bromide, or In addition to the bromide, addition to the coating 32 also contributes to stabilization of the discharge start voltage of the surge absorber 10.
These substances are added at a blending ratio of 0.01 to 10% by weight in the alkali iodide alone or a mixture of the mixture and the binder.

The insulating film 32 containing alkali iodide has an action of lowering the discharge starting voltage because of its small work function and excellent electron emission characteristics, and in particular, potassium iodide (KI). Is added to a binder composed of a sodium silicate solution and pure water to form the film 32, the action of reducing the discharge start voltage is remarkable.
In this case, when the compounding ratio of potassium iodide added to the binder (the mixing ratio of sodium silicate solution and pure water is 1: 1) exceeds 40% by weight, the solubility of potassium iodide in the binder becomes saturated and is not dissolved any more. Therefore, the blending ratio of potassium iodide is preferably in the range of 0.1 wt% to 40 wt%. When the blending ratio of potassium iodide is 40 wt%, the action of decreasing the discharge start voltage is the largest. Become.

It is a schematic sectional drawing which shows the discharge tube which concerns on this invention. It is an AA schematic sectional drawing of FIG. It is a graph which shows the relationship between the frequency | count of discharge and DC discharge start voltage in the discharge tube which formed the electrically conductive film in the surface of the discharge electrode part, and the discharge tube which does not form a electrically conductive film in the surface of the discharge electrode part. It is a schematic sectional drawing which shows the modification of the discharge tube which concerns on this invention. It is sectional drawing which shows the conventional discharge tube.

Explanation of symbols

10 discharge tube
12 Case material
14 Lid member
16 Airtight envelope
18 Discharge electrode
22 Discharge gap
26 Micro discharge gap
28 Trigger discharge membrane
30 Conductive film
32 coating

Claims (2)

  An airtight envelope is formed by hermetically sealing the opening at both ends of the case member made of an insulating material having both ends opened with a pair of lid members that also serve as discharge electrodes, and a discharge is generated in the airtight envelope. Gas is sealed, and a discharge gap is formed between the discharge electrode portions of the lid member disposed in the hermetic envelope, and both ends of the case member are disposed on the inner wall surface of the case member. A discharge tube formed by forming a trigger discharge film disposed at a distance from each other, wherein a conductive film is formed on the surface of the discharge electrode portion. The discharge tube according to claim 1, wherein the conductive film is made of titanium.

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