JP3718142B2 - Discharge tube - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
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 metal halide lamp of a projector or an automobile, or an ignition plug of a gas cooker, Or it is related with the discharge tube which can be used conveniently as a gas arrester (lightning arrester) for absorbing a surge voltage.
[0002]
[Prior art]
As shown in FIG. 4, a conventional discharge tube 60 of this type includes a pair of lid members 64 that serve as discharge electrodes at both ends of a cylindrical case member 62 made of an insulating material such as ceramic that is open at both ends. , 64 is hermetically closed to form a hermetic envelope 66, and discharge gas is sealed in the hermetic envelope 66.
The lid member 64 includes a planar discharge electrode portion 68 that protrudes largely 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 portions 68 and 68.
Further, on the surface of the discharge electrode portion 68, carbonate (BaCO ₃ ) or ternary carbonate ([Bs · Sr · Ca] CO ₃ ) is used in order to improve discharge generation between the discharge electrode portions 68 and 68. Is formed as a main component.
[0003]
[Problems to be solved by the invention]
By the way, when the discharge tube 60 is used as a switching spark gap, it is necessary to stably supply a constant voltage for lighting to a high-pressure discharge lamp or the like. Therefore, the discharge tube 60 has a high voltage pulse from a capacitor (not shown). In response to (several hundred Hz or more), it is required to operate at a constant discharge start voltage at short intervals of several ms. However, in the case of the conventional discharge tube 60 in which the coating 74 is made of a material mainly composed of carbonate (BaCO ₃ ) or ternary carbonate ([Bs · Sr · Ca] CO ₃ ), the frequency is 100 Hz ( Even when the operation is performed at intervals of about 10 ms), the discharge start voltage is not constant and a large variation occurs. That is, FIG. 5 shows a case where a conventional discharge tube 60 in which the coating film 74 is made of carbonate (BaCO ₃ ) and the discharge start voltage is set to 1000 V is operated at a frequency of 100 Hz (10 ms). It is a chart showing the transition of the discharge start voltage, and as shown in the chart, in the conventional discharge tube 60, the discharge start voltage is not stabilized at the rated 1000 V, and there is a large variation for each discharge. .
[0004]
In addition, when the discharge tube 60 is used as a gas arrester, if the rise time of the applied surge voltage is fast, the discharge start voltage varies every time the surge voltage is applied. As a result, the “fluctuation” is increased, and as a result, there is a problem that a predetermined surge absorbing function cannot be achieved.
[0005]
The present invention has been made in view of the above-described problems, and the object of the present invention is to start stable discharge even when operated at short intervals or when a surge voltage with a fast rise time is applied. It is to realize a discharge tube capable of obtaining a voltage.
[0006]
[Means for Solving the Problems]
As a result of various investigations on the composition material of the coating film formed on the surface of the discharge electrode, the present inventor found that alkali iodide is extremely effective for stabilizing the discharge starting voltage, and completed the present invention. It is a thing.
[0007]
That is, the discharge tube according to the present invention is a discharge tube in which a plurality of discharge electrodes are arranged with a discharge gap and enclosed in a hermetic envelope together with a discharge gas, on the surface of the discharge electrode, A film containing an alkali iodide is formed, and in the film, cesium bromide (CsBr), rubidium bromide (RbBr), nickel bromide (NiBr ₂ ), indium bromide (InBr ₃ ), bromide Cobalt (CoBr ₂ ), iron bromide (FeBr ₂ , FeBr ₃ ), 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 ), potassium tungstate (K ₂ WO ₄ ), cesium chromate (Cs ₂ CrO) ₄ ), one or more kinds of praseodymium oxide (Pr ₆ O ₁₁ ) and potassium titanate (K ₂ Ti ₄ O ₉ ) are added.
[0008]
Examples of the alkali iodide include potassium iodide (KI), sodium iodide (NaI), cesium iodide (CsI), and rubidium iodide (RbI) alone or in a mixture.
[0009]
In the discharge tube according to the present invention, a film containing alkali iodide that is effective for stabilizing the discharge starting voltage is formed on the surface of the discharge electrode. Even when a surge voltage with a fast rise time is applied, a stable discharge start voltage can always be obtained.
[0010]
In the discharge tube of the present invention, cesium bromide (CsBr), rubidium bromide (RbBr), nickel bromide (NiBr ₂ ), indium bromide (InBr ₃ ), cobalt bromide (CoBr ₂₎ ), Iron bromide (FeBr ₂ , FeBr ₃ ), 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 ), potassium tungstate (K ₂ WO ₄ ), cesium chromate (Cs ₂ CrO ₄ ), praseodymium oxide (Pr ₆ O ₁₁ ), potassium titanate (K ₂ Ti ₄ O ₉ ) By adding one or more of the above, it is possible to further stabilize the discharge start voltage of the discharge tube.
[0011]
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 an insulating material such as ceramic that is open at both ends. An airtight envelope 16 is formed by airtightly closing at 14, and a predetermined discharge gas is sealed in the airtight envelope 16.
[0012]
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.
A plurality of pairs of trigger discharge films 28, 28 are formed on the inner wall surface 24 of the case member 12 so as to face each other with a minute discharge gap 26 therebetween. The trigger discharge film 28 is made of a conductive material such as a carbon-based material. Of the pair of trigger discharge films 28, 28, one trigger discharge film 28 is electrically connected to one discharge electrode portion 18, and the other trigger discharge film 28 is electrically connected to the other discharge electrode portion 18. It is connected.
[0013]
On the surface of the discharge electrode portion 18, an insulating film 30 containing alkali iodide 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. It can be formed by applying to the surface of the discharge electrode portion 18 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.
[0014]
Further, in the coating film 30, cesium bromide (C s Br), rubidium bromide (RbBr), nickel bromide (NiBr ₂ ), indium bromide (InBr ₃ ), cobalt bromide (CoBr ₂ ), bromide When one or more kinds of bromides such as iron (FeBr ₂ , FeBr ₃ ) are added, the discharge start voltage of the discharge tube 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 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 discharge tube 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.
[0015]
The discharge gas sealed in the hermetic envelope 16 corresponds to a rare gas such as argon, neon, helium, xenon, or an inert gas such as nitrogen gas or a mixed gas.
In addition, by mixing a negative gas such as halogen, H ₂ , SF ₆ , CO ₂ , O ₂ , or Hg in the discharge gas, it is possible to prevent a continuation phenomenon in which the discharge continues. That is, when the discharge tube 10 is used at a high frequency, a large amount of ions generated at the time of discharge remain, and a continuity is easily induced by such residual ions. Since recombination of ions occurs and charges disappear, it is possible to effectively prevent generation of a continuation flow. For example, when the discharge gas is argon, Ar ⁺ is generated as residual ions, but when H ₂ is mixed as the negative gas, for example, H attaches electrons and becomes negative ions H ⁻ , resulting in positive ions Ar ⁺ And the negative ion H ⁻ are recombined and the charge disappears.
From the above, the discharge gas sealed in the hermetic envelope 16 includes a mixed gas of argon and H _2, a mixed gas of argon and CO _2, a mixed gas of argon and SF _{6, and} a mixed gas of nitrogen gas and H ₂ . A mixed gas of nitrogen gas and CO _{2 and} a mixed gas of nitrogen gas and SF ₆ are preferable. In this case, the negative polarity gas (H ₂ , CO ₂ , SF ₆ ) to be mixed is 1 to 50% by volume with respect to the enclosed discharge gas. When H ₂ having a small mass is used as the negative gas, since the impact when colliding with the discharge electrode portion 18 is small, the sputtering amount of the discharge electrode portion 18 can be reduced.
[0016]
When a voltage equal to or higher than the discharge start voltage of the discharge tube 10 is applied between the discharge electrode portions 18 and 18 of the discharge tube 10 of the present invention having the above-described configuration, the minute discharge gap 26 between the trigger discharge films 28 and 28 is applied. As a result, the electric field concentrates, and 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. 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.
[0017]
In the discharge tube 10 of the present invention, the coating 30 containing an alkali iodide effective for stabilizing the discharge starting voltage is formed on the surface of the discharge electrode portion 18, so that the discharge spark tube 10 is connected to the switching spark gap. , When receiving a high voltage pulse (several hundreds Hz or more) from a capacitor (not shown), it becomes possible to always operate stably at a constant discharge start voltage at a short interval of several ms.
That is, in FIG. 2, the discharge tube 10 in which the coating 30 containing potassium iodide is formed on the surface of the discharge electrode portion 18 and the discharge start voltage is set to 1000 V is operated at a frequency of 1000 Hz (1 ms). In this discharge tube 10, the discharge start voltage is always stable at a rated value of about 1000 V, as shown in the chart. It should be noted that a stable discharge start voltage can be obtained even when the discharge tube 10 according to the present invention is operated at a frequency of 1000 Hz (1 ms) or less, for example, 400 Hz (2.5 ms). Absent.
[0018]
In addition, when the discharge tube 10 of the present invention is used as a gas arrester, even when a surge voltage with a fast rise time is applied, a so-called “fluctuation” of the discharge start voltage that fluctuates in the discharge start voltage is generated. It is difficult to occur and can stably operate at a constant discharge start voltage.
That is, when the surge voltage is applied to the discharge tube 10, the initial electrons and ions as a discharge igniter collide with the discharge gas molecules and turn them into ions and electrons. This is a phenomenon that occurs because the α effect that causes ionization and the secondary electron emission action (γ effect) that causes ionized ions to collide with the coating 30 on the surface of the discharge electrode portion 18 to emit secondary electrons are not performed stably. .
However, in the present invention, since the alkali iodide contained in the coating 30 has the property of easily ionizing the discharge gas molecules, a large amount of ions are present in the hermetic envelope 16, As a result, since the stable α effect and secondary electron emission effect (γ effect) are exhibited, the “fluctuation” of the discharge start voltage is less likely to occur.
[0019]
Further, as shown in FIG. 3, the inventor conducted an experiment on the relationship between the number of discharges and the discharge start voltage for the discharge tube 10 of the present invention and the conventional discharge tube 60. As a result, in the case of the conventional discharge tube 60, when the number of discharges exceeds about 50,000 times, the discharge start voltage rapidly decreases and cannot be used, whereas in the case of the discharge tube 10 of the present invention, Even when the number of discharges was about 2 million, there was no significant change in the discharge start voltage. Thus, by forming the coating 30 containing potassium iodide on the surface of the discharge electrode portion 18, the life of the discharge tube 10 can be extended.
[0020]
【The invention's effect】
In the discharge tube according to the present invention, a film containing alkali iodide that is effective for stabilizing the discharge starting voltage is formed on the surface of the discharge electrode. Even when a surge voltage with a fast rise time is applied, a stable discharge start voltage can always be obtained.
In the discharge tube of the present invention, cesium bromide (CsBr), rubidium bromide (RbBr), nickel bromide (NiBr ₂ ), indium bromide (InBr ₃ ), cobalt bromide (CoBr ₂₎ ), Iron bromide (FeBr ₂ , FeBr ₃ ), 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 ), potassium tungstate (K ₂ WO ₄ ), cesium chromate (Cs ₂ CrO ₄ ), praseodymium oxide (Pr ₆ O ₁₁ ), potassium titanate (K ₂ Ti ₄ O ₉ ) By adding one or more of the above, it is possible to further stabilize the discharge start voltage of the discharge tube.
[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 the transition of the discharge start voltage when the discharge tube according to the present invention is operated at a frequency of 1000 Hz (1 ms).
FIG. 3 is a graph showing the relationship between the number of discharges and the discharge start voltage in the discharge tube of the present invention and a conventional discharge tube.
FIG. 4 is a cross-sectional view showing a conventional discharge tube.
FIG. 5 is a chart showing a transition of a discharge start voltage when a conventional discharge tube is operated at a frequency of 100 Hz (10 ms).
[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 (2)

In a discharge tube in which a plurality of discharge electrodes are arranged with a discharge gap and sealed together with a discharge gas in an airtight envelope, a film containing alkali iodide is formed on the surface of the discharge electrode. In addition, in the coating, cesium bromide (CsBr), rubidium bromide (RbBr), nickel bromide (NiBr) ₂ ), Indium bromide (InBr) ₃ ), Cobalt bromide (CoBr) ₂ ), Iron bromide (FeBr) ₂ , FeBr ₃ ), 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 ), Potassium tungstate (K ₂ WO ₄ ), Cesium chromate (Cs ₂ CrO ₄ ), Praseodymium oxide (Pr) ₆ O ₁₁ ), Potassium titanate (K ₂ Ti ₄ O ₉ A discharge tube characterized by adding one or more of the following. The alkali iodide is a simple substance or a mixture of potassium iodide (KI), sodium iodide (NaI), cesium iodide (CsI), and rubidium iodide (RbI). Discharge tube.

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