JP2004362925A - Surge absorbing element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surge absorbing element with long life, utilizing creeping corona discharge as a trigger means against atmospheric discharge, capable of restraining deterioration of insulation. <P>SOLUTION: An airtight envelope 16 is formed by airtightly sealing openings at both end parts of a case member 12 made of an insulation material by a pair of lid members 14, 14 serving as discharge electrodes, discharge gas is sealed in the airtight envelope 16, and a prescribed discharge gap 22 is formed between discharge electrodes 18, 18 of the lid members 14, 14 disposed inside the airtight envelope 16. Further, a plurality of linear trigger discharge films 28 of which both ends are arranged in opposition so as to separate the lid member 14, 14 serving as the discharge electrodes from minute discharge gaps 26, are formed on inner wall faces 24 of the case member 12, and a film 30 having an insulation property containing alkaline iodide is formed on the surface of the discharge electrodes 18. Since the both ends of the trigger discharge films are arranged so as to have a minute discharge gaps against the lid members serving as the discharge electrodes, the insulation property is not deteriorated unless an electrode material of the discharge electrodes scattered by the discahrge electrode parts being sputtered is adhered on both of the minute discharge gaps arranged at both ends of the trigger discharge films. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a surge absorbing element for preventing damage to an electronic device by absorbing a surge such as an induced lightning by utilizing a discharge phenomenon in a discharge gap enclosed in an airtight envelope. The present invention relates to a surge absorbing element using a surface corona discharge as a trigger means for a discharge.
[0002]
[Prior art]
Conventionally, varistors composed of high-resistance elements with non-linear voltage characteristics and gas arresters with discharge gaps housed in airtight containers have been used as surge absorbing elements to protect electronic circuits of electronic equipment from surges such as induced lightning. In addition, various surge absorbing elements have been used. Among such surge absorbing elements, a surge absorbing element using a creeping corona discharge as a trigger discharge is often used in order to realize high responsiveness.
As a surge absorbing element (discharge tube) of this type, the present applicant has previously proposed Japanese Patent Application Laid-Open No. 2003-7420. As shown in FIG. 4, the surge absorbing element (discharge tube) 60 has a pair of lid members 64, 64 which also serve as discharge electrodes, by opening both ends of a cylindrical case member 62 made of an insulating material having both ends opened. The hermetic enclosure 66 is formed by airtightly closing with a gas, and a predetermined discharge gas is sealed in the hermetic enclosure 66.
[0003]
The lid member 64 includes a flat discharge electrode portion 68 protruding largely toward the center of the hermetic envelope 66 and a joining 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.
On the inner wall surface 74 of the case member 62, a plurality of pairs of a pair of trigger discharge films 78, 78 which are opposed to each other with a minute discharge gap 76 therebetween, are formed. Of the pair of trigger discharge films 78, 78, one trigger discharge film 78 is electrically connected to one discharge electrode unit 68, and the other trigger discharge film 78 is electrically connected to the other discharge electrode unit 68. It is connected.
On the surface of the discharge electrode section 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 single gas or a mixed gas of a rare gas such as argon, neon, helium, xenon, or an inert gas such as nitrogen gas corresponds. In addition, a mixed gas of a single or mixed gas of a rare gas or an inert gas and a negative gas such as H ₂ is applicable.
[0004]
Thus, when a surge is applied to the surge absorbing element 60, an electric field concentrates in the minute discharge gap 76 between the trigger discharge films 78, 78, whereby electrons are emitted to the minute discharge gap 76 and trigger discharge occurs. Generates a creeping corona discharge. Next, the creeping corona discharge shifts to a glow discharge due to a priming effect of electrons. Then, the glow discharge is transferred to the discharge gap 72 between the discharge electrode portions 68, 68, and shifts to an arc discharge as a main discharge to absorb the surge.
[0005]
In the above-described conventional surge absorbing element 60, a surge 80 having a fast rise time can be formed by forming a coating 80 containing an alkali iodide effective for stabilizing a discharge starting voltage on the surface of the discharge electrode section 68. Even when the voltage is applied, a stable discharge starting voltage can be obtained.
In addition, in the discharge tube 60, even when the number of discharges reaches about 2 million, there is no significant change in the discharge start voltage, and the life of the discharge tube 60 can be extended.
[Patent Document 1]
JP-A-2003-7420
[Problems to be solved by the invention]
Incidentally, in the surge absorbing element 60, the trigger discharge films 78, 78 are electrically connected to the lid members 64, 64 provided with the discharge electrode portions 68, 68, and a pair of trigger discharge films are separated by a minute discharge gap 76. Since the discharge films 78 and 78 are disposed to face each other, the degree of electric field concentration in the minute discharge gap 76 is high, and a large amount of electrons are emitted, which contributes to a reduction in the discharge starting voltage. The electrode material that is sputtered and scattered from the electrode portion 68 adheres to the minute discharge gap 76 between the pair of trigger discharge films 78 and 78 that are opposed to each other and easily causes insulation deterioration between the trigger discharge films 78 and 78.
[0007]
The present invention has been made in view of the above problems, and an object of the present invention is to realize a long-life surge absorbing element capable of suppressing occurrence of insulation deterioration.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the surge absorbing element according to the present invention is configured such that an opening at both ends of a case member made of an insulating material having both ends opened is hermetically sealed with a pair of lid members also serving as discharge electrodes. Along with forming an airtight envelope, filling a discharge gas in the airtight envelope, and forming a discharge gap between the discharge electrode portions of the lid member disposed in the airtight envelope, On the inner wall surface of the case member, a trigger discharge film whose both ends are opposed to each other with a minute discharge gap from the lid member is formed, and further, a film containing an alkali iodide is formed on the surface of the discharge electrode portion. It is characterized by having been formed.
[0009]
In the surge absorbing element of the present invention, since both ends of the trigger discharge film are arranged with the minute discharge gap separated from the lid member also serving as the discharge electrode, the minute discharge gap provided at both ends of the trigger discharge film is provided. As long as the electrode material that is sputtered and scattered on the discharge electrode portion does not adhere to both of them, the insulation does not deteriorate. For this reason, the surge absorbing element of the present invention suppresses the occurrence of insulation deterioration as compared with the conventional surge absorbing element 60 in which a pair of trigger discharge films 78, 78 are arranged to face each other with a minute discharge gap 76 therebetween. Therefore, the life of the surge absorbing element 10 can be extended.
In the surge absorbing element of the present invention, the amount of electrons emitted in the minute discharge gap is suppressed because the trigger discharge film is not electrically connected to the lid member also serving as the discharge electrode. Since a film containing an alkali iodide having a small work function and excellent electron emission characteristics is formed, high responsiveness can be secured.
[0010]
As the alkali iodide, for example, a simple substance or a mixture of potassium iodide (KI), sodium iodide (NaI), cesium iodide (CsI), and rubidium iodide (RbI) corresponds.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
As shown in FIG. 1, the surge absorbing element 10 according to the present invention includes a pair of lid members 14 serving also as discharge electrodes, which are formed by opening both ends of a cylindrical case member 12 made of ceramic as an insulating material having both ends opened. , 14 to form an airtight enclosure 16 by hermetically sealing.
[0012]
The lid member 14 includes a flat discharge electrode portion 18 that protrudes largely toward the center of the hermetic envelope 16 and a joint portion 20 that contacts the end surface of the case member 12. A predetermined discharge gap 22 is formed between the discharge electrode portions 18.
The lid member 14 including the discharge electrode part 18 and the joint part 20 is made of oxygen-free copper or zirconium copper containing zirconium (Zr) in oxygen-free copper.
Note that the end face of the case member 12 and the joint 20 of the lid member 14 are hermetically sealed via a sealing material (not shown) such as silver solder.
[0013]
Further, on the inner wall surface 24 of the case member 12, a plurality of linear trigger discharge films 28 whose both ends are opposed to the lid members 14 serving also as discharge electrodes with a minute discharge gap 26 therebetween are formed. Have been. 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.
[0014]
A predetermined discharge gas is sealed in the hermetic envelope 16. As the discharge gas, for example, a single gas or a mixed gas of a rare gas such as argon, neon, helium, xenon, or an inert gas such as nitrogen gas corresponds. In addition, a mixed gas of a single or mixed gas of a rare gas or an inert gas and a negative gas such as H ₂ is applicable.
[0015]
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. The coating 30 is made of a single or mixture of alkali iodides such as potassium iodide (KI), sodium iodide (NaI), cesium iodide (CsI), and rubidium iodide (RbI) prepared from a sodium silicate solution and pure water. It can be formed by applying a material added to the binder to the surface of the discharge electrode portion 18.
In this case, the alkali iodide alone or as a mixture is mixed at 0.01 to 70% by weight, and the binder is mixed at 99.99 to 30% by weight. The mixing ratio of the sodium silicate solution and 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 pure water.
[0016]
Cesium bromide (CsBr), rubidium bromide (RbBr), nickel bromide (NiBr ₂ ), indium bromide (InBr ₃ ), cobalt bromide (CoBr ₂ ), iron bromide (FeBr ₂ ) , FeBr ₃ ) or the like, the discharge starting voltage of the surge absorbing element 10 can be further stabilized.
In addition, 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 silicate (K ₂ WO ₄ ), cesium chromate (Cs ₂ CrO ₄ ), praseodymium oxide (Pr ₆ O ₁₁ ), and potassium titanate (K ₂ Ti ₄ O ₉ ), together with the bromide or In addition to the bromide, addition to the coating 30 contributes to stabilization of the discharge starting voltage of the surge absorbing element 10.
These substances are added in a mixing ratio of 0.01 to 10% by weight to a mixture of the above-mentioned alkali iodide alone or a mixture thereof with a binder.
[0017]
The insulating film 30 containing an alkali iodide has a small work function and is excellent in electron emission characteristics, and thus has an action of lowering a discharge starting voltage. 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 firing voltage is remarkable.
FIG. 2 shows the mixing ratio (% by weight) of potassium iodide added to a binder composed of a sodium silicate solution and pure water (the mixing ratio of sodium silicate solution and pure water is 1: 1), and the DC discharge of the surge absorbing element 10. 4 is a graph showing a relationship with a starting voltage. The surge absorbing element 10 used was one in which argon was sealed as a discharge gas at a gas pressure of 120 kPa, and a discharge gap 22 between the discharge electrodes 18 was 0.55 mm.
As is clear from the graph of FIG. 2, as the mixing ratio of potassium iodide added to the binder composed of sodium silicate solution and pure water (the mixing ratio of sodium silicate solution and pure water is 1: 1) increases, DC discharge starts. The voltage decreases.
[0018]
FIG. 3 shows the mixing ratio (% by weight) of potassium iodide added to a binder composed of a sodium silicate solution and pure water (the mixing ratio of sodium silicate solution and pure water is 1: 1), 6 is a graph showing a relationship with an impulse discharge starting voltage. As the surge absorbing element 10, an argon gas as a discharge gas is sealed at a gas pressure of 120 kPa, and a discharge gap 22 between the discharge electrode portions 18 is formed to be 0.55 mm. The measurement was performed by applying an impulse voltage of 2.5 kV.
As is clear from the graph of FIG. 3, as the mixing ratio of potassium iodide added to the binder composed of sodium silicate solution and pure water (the mixing ratio of sodium silicate solution and pure water is 1: 1) increases, the impulse discharge starts. The voltage decreases.
[0019]
If the mixing ratio of potassium iodide to be 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 cannot be further dissolved. The mixing ratio of potassium iodide is preferably in the range of 0.1% by weight to 40% by weight, and when the mixing ratio of potassium iodide is 40% by weight, the effect of lowering the firing voltage is maximized. .
[0020]
When a surge is applied to the surge absorbing element 10 of the present invention via the lid members 14 serving also as discharge electrodes, an electric field is applied to the minute discharge gap 26 between both ends of the trigger discharge film 28 and the lid members 14. Are concentrated, whereby electrons are emitted into the minute discharge gap 26 to generate a creeping corona discharge as a trigger discharge. Next, the creeping corona discharge shifts to a glow discharge due to a priming effect of electrons. 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 main discharge, thereby absorbing surge.
[0021]
Thus, in the surge absorbing element 10 of the present invention, since both ends of each trigger discharge film 28 are arranged with the minute discharge gap 26 separated from the lid members 14 serving also as discharge electrodes. As long as the electrode material which is spattered and spattered from the discharge electrode portion 18 does not adhere to both of the minute discharge gaps 26 provided at both ends of the trigger discharge film 28, the insulation does not deteriorate. For this reason, the surge absorbing element 10 of the present invention suppresses the occurrence of insulation deterioration as compared with the conventional surge absorbing element 60 in which a pair of trigger discharge films 78, 78 are arranged to face each other with a minute discharge gap 76 therebetween. Therefore, the life of the surge absorbing element 10 can be extended.
[0022]
Since the trigger discharge film 28 is not electrically connected to the lid members 14 serving also as discharge electrodes, the amount of emitted electrons in the minute discharge gap 26 is suppressed. Since the coating 30 containing an alkali iodide having a small function and excellent electron emission characteristics is formed, high responsiveness can be secured.
[0023]
【The invention's effect】
In the surge absorbing element of the present invention, since both ends of the trigger discharge film are arranged with the minute discharge gap separated from the lid member also serving as the discharge electrode, the minute discharge gap provided at both ends of the trigger discharge film is provided. As long as the electrode material that is sputtered and scattered on the discharge electrode portion does not adhere to both of them, the insulation does not deteriorate. For this reason, the surge absorbing element of the present invention suppresses the occurrence of insulation deterioration as compared with the conventional surge absorbing element 60 in which a pair of trigger discharge films 78, 78 are arranged to face each other with a minute discharge gap 76 therebetween. Therefore, the life of the surge absorbing element 10 can be extended.
Further, in the surge absorbing element of the present invention, since the trigger discharge film is not electrically connected to the lid member also serving as the discharge electrode, the amount of emitted electrons in the minute discharge gap is suppressed. Since a film containing an alkali iodide having a small work function and excellent electron emission characteristics is formed, high responsiveness can be secured.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a surge absorbing element according to the present invention.
FIG. 2 is a graph showing a relationship between a mixing ratio of potassium iodide and a DC discharge starting voltage.
FIG. 3 is a graph showing a relationship between a mixing ratio of potassium iodide and an impulse discharge starting voltage.
FIG. 4 is a sectional view showing a conventional surge absorbing element.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Surge absorption element 12 Case member 14 Cover member 16 Hermetic envelope 18 Discharge electrode part 22 Discharge gap 26 Micro discharge gap 28 Trigger discharge film 30 Coating

Claims (2)

Both ends of a case member made of an insulating material having both ends opened are hermetically sealed with a pair of lid members serving also as discharge electrodes, thereby forming an airtight envelope and discharging into the airtight envelope. A gas is sealed, and a discharge gap is formed between the discharge electrode portions of the lid member disposed in the hermetic envelope. A trigger discharge film which is opposed to the discharge electrode portion, and a coating containing an alkali iodide is formed on the surface of the discharge electrode portion. 2. The alkali iodide is a simple substance or a mixture of potassium iodide (KI), sodium iodide (NaI), cesium iodide (CsI), and rubidium iodide (RbI). Surge absorbing element.

Images