JP2005032640A - Discharge tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge tube in which rise of an initial discharge start voltage can be prevented and initial discharge delay is not brought about, and which has a long life. <P>SOLUTION: This is the discharge tube in which an airtight housing 16 is formed by sealing airtightly the both end opening parts of a case member 12 made of an insulating material with both ends open by a pair of lid members 14, 14 working also as the discharge electrode, and a discharge gas is filled in the airtight housing 16 and a prescribed discharge gap 22 is formed between the discharge electrode parts 18, 18 of the lid members 14, 14 arranged in the airtight housing 16, and in which on the inner wall face 24 of the case member 12, linear trigger discharge membranes 28 arranged with a minute discharge gap 26 from the above lid members 14, 14 of which both ends serve as a discharge electrode are formed a plurality of pieces. The above trigger discharge membranes 28 are formed in the range of 8-12 pieces with an equal spacing in the circumferential direction on the inner wall face 24 of the case member 12. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  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.

  As this type of discharge tube, the present applicant has previously proposed Japanese Patent Application Laid-Open No. 2003-7420. As shown in FIGS. 9 and 10, the discharge tube 60 is formed by sealing a cylindrical case member 62 made of an insulating material with both ends opened by a pair of lid members 64 and 64 that also serve as discharge electrodes. A hermetic envelope 66 is formed by sealing with a predetermined discharge gas in the hermetic 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.
In addition, four pairs of trigger discharge films 78 and 78 are formed in the circumferential direction of the inner wall surface 74 of the case member 62 so as to face each other with a minute discharge gap 76 therebetween at intervals of 90 degrees. 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 starting 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.

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, this 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

By the way, when the discharge tube 60 is left for a long time, a small amount of impure gas contained in the discharge gas or impure gas mixed in the sealing process of the hermetic envelope 66 is caused by the discharge electrode portion 68 or the coating 80. The work function of the discharge electrode portion 68 and the coating film 80 is changed by being adsorbed on the surface of the film, and as a result, the initial discharge start voltage increases and an initial discharge delay may occur.
The trigger discharge film 78 is formed to supply a function of preventing the initial discharge delay by supplying the initial electrons, but is spaced 90 degrees in the circumferential direction of the inner wall surface 74 of the case member 62. Thus, the conventional trigger discharge films 78 and 78 formed by four sets cannot always sufficiently prevent the initial discharge delay.

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to realize a long-life discharge tube that can prevent an increase in the initial discharge start voltage and does not cause an initial discharge delay. There is.

  In order to achieve the above object, the discharge tube according to the present invention hermetically seals both end openings of a cylindrical case member made of an insulating material having both ends opened with a pair of lid members also serving as discharge electrodes. Thereby forming a hermetic 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 case member by forming a trigger discharge film whose both ends are spaced apart from the lid member by a minute discharge gap, the trigger discharge film being connected to the inner wall surface of the case member A discharge tube characterized in that it is formed in the range of 8 to 12 at equal intervals in the circumferential direction.

  In the discharge tube according to the present invention, the trigger discharge film is formed in the range of 8 to 12 at equal intervals in the circumferential direction of the inner wall surface of the case member, thereby increasing the initial discharge start voltage. Thus, it is possible to realize a long-life discharge tube that does not cause an initial discharge delay.

  As shown in FIGS. 1 and 2, a discharge tube 10 according to the present invention has 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 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.

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. FIGS. 1 and 2 show the case where eight trigger discharge films 28 are formed at intervals of 45 degrees in the circumferential direction of the inner wall surface 24 of the case member 12. The film 28 is formed in the range of 8 to 12 at equal intervals in the circumferential direction of the inner wall surface 24 of the case member 12.
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.
Incidentally, when the total length L (see FIG. 1) of the case member 12 is 4.6 mm and the inner diameter D1 (see FIG. 2) is 6 mm, the length of the trigger discharge film 28 is set to 3 mm and the width is set to 0.57 mm. The

On the surface of the discharge electrode portion 18, an insulating film 30 containing an alkali iodide effective for stabilizing the discharge starting 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.

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.

The insulating film 30 containing alkali iodide has a function of lowering the 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 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.

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 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 also serving 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, the trigger discharge film 28 is formed in the range of 8 to 12 at equal intervals in the circumferential direction of the inner wall surface 24 of the case member 12. Thus, it is possible to prevent a rise in the initial discharge start voltage and realize a long-life discharge tube that does not cause an initial discharge delay. The initial discharge start voltage refers to the first discharge start voltage when the discharge tube is repeatedly operated, and the second and subsequent discharge start voltages subsequent to the initial discharge start voltage are referred to as follow-up discharge start voltages.
That is, when the number of trigger discharge films 28 formed on the inner wall surface 24 of the case member 12 is seven or less, the supply amount of initial electrons is insufficient, and the initial discharge delay cannot be sufficiently prevented.
On the other hand, when the number of trigger discharge films 28 formed on the inner wall surface 24 of the case member 12 is 13 or more, although the rise of the initial discharge start voltage can be suppressed, the trigger discharge becomes the main discharge between the discharge electrode portions 18 and 18. There is a problem in that the discharge does not shift and the discharge continues in the trigger discharge film 28, and as a result, the follow-up discharge start voltage decreases.
Therefore, as described above, the trigger discharge film 28 is suitably formed in the range of 8 to 12 at equal intervals in the circumferential direction of the inner wall surface 24 of the case member 12.

3 to 5 show the relationship between the number of discharges and the initial discharge start voltage and the relationship between the number of discharges and the follow-up discharge start voltage for the discharge tube 10 of the present invention in which the DC discharge start voltage is set to 800V. It is a graph.
That is, FIG. 3 shows the number of discharges and the initial discharge start voltage in the discharge tube 10 according to the present invention in which eight trigger discharge films 28 are formed at intervals of 45 degrees in the circumferential direction of the inner wall surface 24 of the case member 12. 4 (A in FIG. 3) and the relationship between the number of discharges and the follow-up discharge start voltage (B in FIG. 3). FIG. 4 shows the number of discharges and the initial discharge start voltage in the discharge tube 10 according to the present invention in which ten trigger discharge films 28 are formed at intervals of 36 degrees in the circumferential direction of the inner wall surface 24 of the case member 12. 5 (A in FIG. 4) and the relationship between the number of discharges and the follow-up discharge start voltage (B in FIG. 4). Further, FIG. 5 shows the number of discharges and the initial discharge start voltage in the discharge tube 10 according to the present invention in which 12 trigger discharge films 28 are formed at intervals of 30 degrees in the circumferential direction of the inner wall surface 24 of the case member 12. 6 (A in FIG. 5) and the relationship between the number of discharges and the follow-up discharge start voltage (B in FIG. 5).

6 to 8 are graphs showing the relationship between the number of discharges and the initial discharge start voltage and the relationship between the number of discharges and the follow-up discharge start voltage for a discharge tube as a comparative example for the discharge tube 10 of the present invention. is there.
That is, FIG. 6 shows the number of discharges and the initial discharge start voltage in a discharge tube as a comparative example in which four trigger discharge films 28 are formed at intervals of 90 degrees in the circumferential direction of the inner wall surface 24 of the case member 12. 7 is a graph showing the relationship (A in FIG. 6) and the relationship between the number of discharges and the follow-up discharge start voltage (B in FIG. 6). FIG. 7 shows the number of discharges and the initial discharge start voltage in a discharge tube as a comparative example in which six trigger discharge films 28 are formed at intervals of 60 degrees in the circumferential direction of the inner wall surface 24 of the case member 12. 8 is a graph showing the relationship (A in FIG. 7) and the relationship between the number of discharges and the follow-up discharge start voltage (B in FIG. 7). Further, FIG. 8 shows the number of discharges and the initial discharge start voltage in a discharge tube as a comparative example in which 14 trigger discharge films 28 are formed at intervals of about 26 degrees in the circumferential direction of the inner wall surface 24 of the case member 12. 9 is a graph showing the relationship (A in FIG. 8) and the relationship between the number of discharges and the follow-up discharge start voltage (B in FIG. 8).

As shown in FIGS. 3 to 5, eight (FIG. 3), ten (FIG. 4), and twelve (FIG. 3) trigger discharge films 28 are provided at equal intervals in the circumferential direction of the inner wall surface 24 of the case member 12. 5) In the case of the formed discharge tube 10 of the present invention, even if the number of discharges exceeds 1,000,000, the initial discharge start voltage does not change greatly, and therefore, the life can be extended without causing an initial discharge delay. ing. Further, in the case of the discharge tube 10 of the present invention shown in FIGS. 3 to 5, the follow-up discharge start voltage is also stable.
On the other hand, as shown in FIGS. 6 and 7, four trigger discharge films 28 (FIG. 6) and six (FIG. 7) are formed at equal intervals in the circumferential direction of the inner wall surface 24 of the case member 12. In the case of the discharge tube of the comparative example, the initial discharge start voltage increases from the number of discharges of about 200,000 times, and an initial discharge delay occurs.
Further, as shown in FIG. 8, in the case of a discharge tube of a comparative example in which 14 trigger discharge films 28 are formed at equal intervals in the circumferential direction of the inner wall surface 24 of the case member 12, the discharge tube of the present invention is used. As in FIG. 10, although the increase in the initial discharge start voltage can be suppressed, the follow-up discharge start voltage starts to decrease from the number of discharges of about 600,000 times and is not suitable for use.

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 spaced from the lid members 14 and 14 that also serve as discharge electrodes. 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 the pair of trigger discharge films 78 and 78 are opposed 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 serve as the discharge electrodes, the degree of electric field concentration in the minute discharge gap 26 is suppressed, but as described above, the discharge electrode portion 18 Since the coating 30 containing an alkali iodide having a small work function and excellent electron emission characteristics is formed on the surface, high responsiveness is not impaired.

It is sectional drawing which shows the discharge tube which concerns on this invention. It is BB sectional drawing of FIG. 6 is a graph showing the relationship between the number of discharges and the initial discharge start voltage and the relationship between the number of discharges and the follow-up discharge start voltage in the discharge tube according to the present invention in which eight trigger discharge films are formed. 4 is a graph showing the relationship between the number of discharges and the initial discharge start voltage and the relationship between the number of discharges and the follow-up discharge start voltage in the discharge tube according to the present invention in which ten trigger discharge films are formed. 4 is a graph showing the relationship between the number of discharges and the initial discharge start voltage and the relationship between the number of discharges and the follow-up discharge start voltage in the discharge tube according to the present invention in which 12 trigger discharge films are formed. 4 is a graph showing the relationship between the number of discharges and the initial discharge start voltage and the relationship between the number of discharges and the follow-up discharge start voltage in a discharge tube having four trigger discharge films. 6 is a graph showing the relationship between the number of discharges and the initial discharge start voltage and the relationship between the number of discharges and the follow-up discharge start voltage in a discharge tube having six trigger discharge films. It is a graph which shows the relationship between the frequency | count of discharge and initial stage discharge start voltage, and the relationship between the frequency | count of discharge and follow-up discharge start voltage in the discharge tube which formed 14 trigger discharge films | membranes. It is sectional drawing which shows the conventional discharge tube. It is AA sectional drawing of FIG.

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 coating

Claims (1)

A hermetic envelope is formed by hermetically sealing both end openings of a cylindrical case member made of an insulating material having both ends opened with a pair of lid members that also serve as discharge electrodes. The discharge gas is enclosed in the inside, 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 connected to the lid member on the inner wall surface of the case member. A discharge tube formed by forming a trigger discharge film arranged with a minute discharge gap therebetween, and the trigger discharge film is provided at 8 to 12 at equal intervals in the circumferential direction of the inner wall surface of the case member. A discharge tube characterized by being formed in the range of

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