JP2005025953A - Discharge tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a long-life discharge tube without fear of lowering of following discharge starting voltage. <P>SOLUTION: Both end openings of a case member 12 made of ceramics with both ends open is airtightly sealed with a pair of lid members 14, 14 both serving as discharge electrodes made of oxygen-free high conductivity copper to form an airtight envelope 16, while a given discharge gap 22 is formed between the discharge electrode parts 18, 18 of the lid members 14, 14. Further, a plurality of linear trigger discharge films are formed with their both ends arranged in opposition to the lid members 14, 14 serving as the discharge electrodes with an interposition of a micro discharge gap 26, and an insulating coating film 30 containing alkali iodide is formed on the surface of the discharge electrode part 18, and furthermore, discharge gas consisting of argon is sealed in the airtight envelope 16 with pressure of 0.3 to 5 atms. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a discharge tube, and 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.
[0002]
[Prior art]
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, the discharge tube 60 hermetically seals the opening of both ends of a cylindrical case member 62 made of an insulating material opened at both ends with a pair of lid members 64 and 64 that also serve as discharge electrodes. Thus, an airtight envelope 66 is formed, and a predetermined discharge gas is sealed in the airtight envelope 66.
[0003]
The lid member 64 includes a planar discharge electrode portion 68 projecting greatly toward the center of the hermetic envelope 66 and a joint portion 70 in contact with 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 and 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.
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. 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.
[0004]
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 and 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 and 78. As a result, electrons are emitted into the minute discharge gap 76, and creeping corona discharge as 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 the arc discharge is performed as the main discharge.
[0005]
In this type of conventional discharge tube 60, oxygen-free copper is widely used as a constituent material of the discharge electrode portion 68. The reason is that the discharge electrode portion 68 made of oxygen-free copper does not release an impurity gas such as oxygen when generating discharge, and does not adversely affect the discharge gas composition in the hermetic envelope 66. It is.
[Patent Document 1]
JP 2003-7420 A
[Problems to be solved by the invention]
However, when the discharge electrode portion 68 is made of oxygen-free copper, the follow-up discharge start voltage is lowered, which is a factor for shortening the life of the discharge tube 60.
[0007]
The present invention has been made in view of the above-described conventional problems, and an object thereof is to realize a long-life discharge tube that does not cause a decrease in follow-up discharge starting voltage.
[0008]
[Means for Solving the Problems]
As a result of various investigations regarding the constituent material of the discharge gas and the enclosed gas pressure of the discharge gas, the present inventors have configured the discharge gas as a single element of argon, and the enclosed gas pressure is set to 0.3 to 5 atm. In addition, the inventors have found that a decrease in the follow-up discharge starting voltage can be prevented and is effective in improving the life characteristics of the discharge tube, and the present invention has been completed.
That is, the discharge tube according to the present invention is a discharge tube in which a plurality of discharge electrodes made of oxygen-free copper are arranged with a discharge gap therebetween, and this is enclosed with a discharge gas in an airtight envelope. The discharge gas is composed of argon, and the argon is sealed in an airtight envelope at a pressure of 0.3 to 5 atm.
[0009]
In the discharge tube according to the present invention, the discharge gas is composed of argon, and the argon is enclosed in the hermetic envelope at a pressure of 0.3 to 5 atm. Therefore, a long-life discharge tube can be realized.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
As shown in FIG. 1, a discharge tube 10 according to the present invention includes a pair of lid members 14 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 at 14.
[0011]
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 end face 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. The discharge gap 22 is, for example, about 1.5 mm.
[0012]
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 thereof are opposed to the lid members 14 and 14 serving as discharge electrodes with a minute discharge gap 26 therebetween. Has been. The trigger discharge film 28 is made of a conductive material such as a carbon-based material.
[0013]
The said cover member 14 provided with the discharge electrode part 18 and the junction part 20 is comprised with the oxygen free copper. The discharge electrode portion 18 made of oxygen-free copper does not release an impurity gas such as oxygen during discharge generation, and does not adversely affect the discharge gas composition in the hermetic envelope 16.
[0014]
On the surface of the discharge electrode portion 18, an insulating film 30 containing an alkali iodide effective for stabilizing the discharge start voltage is formed. This coating 30 is made of a simple substance or a mixture of alkali iodides such as potassium iodide (KI), sodium iodide (NaI), cesium iodide (CsI), rubidium iodide (RbI), etc., from a sodium silicate solution and pure water. What is added to the binder to be formed can be formed by applying to the surface of the discharge electrode portion 18.
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.
[0015]
In the coating 30, 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 30 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.
[0016]
The insulating film 30 containing alkali iodide has a function of lowering a discharge start 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 coating 30, the effect of lowering 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.
[0017]
A discharge gas made of argon is enclosed in the hermetic envelope 16 at a pressure of 0.3 to 5 atm.
As described above, when the discharge gas made of argon is sealed in the hermetic envelope 16 at a pressure of 0.3 to 5 atm, the discharge tube 10 according to the present invention is operated repeatedly at regular time intervals. It is possible to prevent a decrease in the discharge start voltage (following discharge start voltage) for the second and subsequent times following the initial discharge start voltage (initial discharge start voltage).
[0018]
The reason why the argon gas pressure in the hermetic envelope 16 is in the range of 0.3 to 5 atm is as follows. That is, when the sealed gas pressure is lower than 0.3 atm, since the gas molecular weight in the hermetic envelope 16 is small, the cation does not collide with the gas molecules at the time of discharge generation, and the discharge electrode portion 18 on the cathode side does not collide. The collision rate increases, and as a result, the sputtering amount of the discharge electrode portion 18 on the cathode side increases. The electrode material of the sputtered cathode-side discharge electrode portion 18 scatters in an atomic state and adheres to the inner wall of the hermetic envelope 16 while adsorbing gas molecules, so that the discharge gas in the hermetic envelope 16 is discharged. The composition is altered, and as a result, the discharge start voltage becomes unstable.
On the other hand, when the sealed gas pressure is higher than 5 atm, a local discharge may be generated at a low voltage between the portions where the electric field concentration of the discharge electrode portions 18 and 18 easily occurs, and the discharge start voltage becomes unstable. .
Therefore, it is appropriate that the enclosed gas pressure of argon is in the range of 0.3 to 5 atmospheres as described above.
[0019]
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, this glow discharge is transferred to the discharge gap 22 between the discharge electrode portions 18 and 18, and shifts to arc discharge as the main discharge. In the discharge tube 10 of the present invention, a creeping corona discharge that is originally generated in the minute discharge gap 26 and has a high response speed is used as a trigger discharge, so that high responsiveness can be realized.
[0020]
It should be noted that both ends of each trigger discharge film 28 of the discharge tube 10 of the present invention are arranged with the micro discharge gap 26 separated from the lid members 14 and 14 that also serve as discharge electrodes, so that both ends of the trigger discharge film 28 are provided. As long as the electrode material that is spattered and scattered by the discharge electrode portion 18 does not adhere to both of the provided small discharge gaps 26, insulation deterioration does not occur. For this reason, the discharge tube 10 of the present invention can suppress the occurrence of insulation deterioration as compared with the conventional discharge tube 60 in which a pair of trigger discharge films 78 and 78 are arranged opposite to each other with a minute discharge gap 76 therebetween. it can.
In this case, since the trigger discharge film 28 is not electrically connected to the lid members 14 and 14 that also function as discharge electrodes, the amount of electrons emitted from the minute discharge gap 26 is suppressed, but on the surface of the discharge electrode portion 18, Since the coating film 30 containing the alkali iodide having a small work function and excellent electron emission characteristics is formed, high responsiveness can be secured.
[0021]
As described above, in the discharge tube 10 of the present invention, the discharge gas composed of argon is sealed in the hermetic envelope 16 at a pressure of 0.3 to 5 atm, thereby causing a decrease in the follow-up discharge start voltage. In this way, a long-life discharge tube can be realized.
[0022]
FIG. 2 shows an operation of a discharge tube 10 according to the present invention in which a discharge gas composed of argon is sealed in an airtight envelope 16 at 2 atm and the DC discharge start voltage is set to 800 V at intervals of 100 ms. It is a chart showing the transition of the DC discharge start voltage in the case of the discharge, and as shown in the chart, it can be seen that in this discharge tube 10, the follow-up discharge start voltage is always stable at a rated level of about 800V. .
On the other hand, FIG. 3 shows a case where a discharge tube composed of argon sealed at 6 atmospheres in an airtight envelope 16 and having a DC discharge start voltage set at 800 V is operated at intervals of 100 ms. As shown in the chart, in this discharge tube, the follow-up discharge start voltage frequently drops below the rated 800 V, and is extremely unstable.
[0023]
FIG. 4 shows a discharge tube 10 according to the present invention in which a discharge gas composed of argon is enclosed in an airtight envelope at 2 atm, argon (40%), neon (40%), and H ₂ (20%). 6 is a graph showing the relationship between the number of discharges and the follow-up discharge start voltage in a discharge tube in which the mixed gas is sealed at 2 atm in the hermetic envelope 16. As shown in this graph, in the case of a discharge tube in which a mixed gas of argon, neon and H ₂ is sealed in the hermetic envelope 16 (graph B in FIG. 4), before the number of discharges reaches 400,000 times. While the follow-up discharge start voltage is lowered and cannot be used, in the case of the discharge tube 10 of the present invention (graph A in FIG. 4), the follow-up discharge start voltage greatly changes even when the number of discharges exceeds 1 million. There is no longer life.
[0024]
【The invention's effect】
In the discharge tube according to the present invention, the discharge gas is composed of argon, and the argon is enclosed in the hermetic envelope at a pressure of 0.3 to 5 atm. Therefore, a long-life discharge tube can be realized.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a discharge tube according to the present invention.
FIG. 2 is a chart showing a transition of a DC discharge start voltage when a discharge tube according to the present invention in which a discharge gas composed of argon is sealed at 2 atm in an airtight envelope is operated at intervals of 100 ms.
FIG. 3 is a chart showing a transition of a DC discharge start voltage when a discharge tube in which a discharge gas composed of argon is sealed at 6 atm in an airtight envelope is operated at intervals of 100 ms.
FIG. 4 shows a discharge tube according to the present invention in which a discharge gas composed of argon is sealed in an airtight envelope at 2 atm, and a mixed gas of argon, neon and H ₂ is sealed in the airtight envelope at 2 atm. It is a graph which shows the relationship between the frequency | count of discharge and a follow discharge start voltage in a discharge tube.
FIG. 5 is a cross-sectional view showing a conventional discharge tube.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Discharge tube 12 Case member 14 Cover member 16 Airtight envelope 18 Discharge electrode part 22 Discharge gap 26 Minute discharge gap 28 Trigger discharge film 30 Coating

Claims (1)

A plurality of discharge electrodes made of oxygen-free copper are arranged with a discharge gap therebetween, and in a discharge tube formed by enclosing it in a hermetic envelope together with a discharge gas, the discharge gas is made of argon, A discharge tube wherein the argon is sealed in an airtight envelope at a pressure of 0.3 to 5 atm.

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