JP2003007420A - Discharge tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a discharge tube in which a stable discharge initiation potential is obtained even if in case this is actuated at a short interval or in case a surge voltage of an early build up time is applied. SOLUTION: An airtight envelope 16 is formed by air-tightly occluding by a pair of cap members 14, 14 both end opening parts of a case member 12 composed of an insulating material whose both ends are opened, and a prescribed discharge gas is enclosed in the airtight envelope 16, and further a prescribed discharge gap 22 is formed between discharging electrode parts 18, 18 of the cap members 14, 14, and on the inner wall face 24 of the case member 12, a pair of trigger discharge films 28, 28 is formed in plural sets while opposingly arranged separately by a minute discharge gap 26, and further this is the discharge tube 10 wherein an insulating coating film 30 containing alkali iodide is formed on the surface of the discharging electrode part 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge tube, and more particularly to 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 like. The present invention relates to a discharge tube that can be suitably used as a switching spark gap for the purpose of, or as a gas arrester (lightning arrester) for absorbing surge voltage.

[0002]

2. Description of the Related Art As shown in FIG. 4, in a conventional discharge tube 60 of this type, both end openings of a cylindrical case member 62 made of an insulating material such as ceramic whose both ends are open also serve as a discharge electrode. An airtight envelope 66 is formed by hermetically closing with a pair of lid members 64, 64, and a discharge gas is enclosed in the airtight envelope 66. The lid member 64 includes a flat discharge electrode portion 68 that largely projects toward the center of the airtight 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, 68. Further, on the surface of the discharge electrode portion 68, in order to improve discharge generation between the discharge electrode portions 68, 68, carbonate (BaCO ₃ ) or ternary carbonate ([Bs · Sr · Ca]
A coating film 74 containing CO ₃ ) as a main component is formed.

[0003]

DISCLOSURE OF THE INVENTION By the way, the above discharge tube
When 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, so the discharge tube 60 is a high voltage pulse (several hundreds of Hz or more) from a capacitor not shown. ),
It is required to operate with a constant discharge start voltage at intervals as short as several ms. However, the coating film 74 may be formed of carbonate (BaCO ₃ ) or ternary carbonate ([Bs · Sr · Ca] C).
In the case of the conventional discharge tube 60 composed of a material containing O ₃ ) as a main component, the discharge start voltage is not constant and is large even when operated at an interval of a frequency of about 100 Hz (10 ms). There were variations. That is, FIG.
A conventional discharge tube 60 in which the coating film 74 is composed of carbonate (BaCO ₃ ) and the discharge starting voltage is set to 1000V.
Is a chart showing the transition of the discharge start voltage when operated at intervals of a frequency of 100 Hz (10 ms). As shown in the chart, in the conventional discharge tube 60, the discharge start voltage is stable at the rated 1000 V. And there is a large variation between discharges.

Further, when the discharge tube 60 is used as a gas arrester, if the rising time of the applied surge voltage is fast, the discharge starting voltage fluctuates each time the surge voltage is applied, that is, so-called discharge. The "fluctuation" of the starting voltage becomes large, and as a result, there arises a problem that a predetermined surge absorbing function cannot be achieved.

The present invention has been made in view of the above problems of the prior art, and an object thereof is to provide stable operation even when operated at short intervals or when a surge voltage having a fast rise time is applied. It is to realize a discharge tube that can obtain the above described discharge starting voltage.

[0006]

As a result of various studies on the composition material of the film formed on the surface of the discharge electrode, the present inventor has found that the alkali iodide is extremely effective in stabilizing the discharge starting voltage. It was found that the present invention has been completed. That is, the discharge tube according to the present invention has a plurality of discharge electrodes arranged with a discharge gap therebetween, and in a discharge tube in which this is enclosed together with a discharge gas in an airtight envelope, on the surface of the discharge electrode, It is characterized in that a film containing an alkali iodide is formed. Examples of the alkali iodide include potassium iodide (KI),
Sodium iodide (NaI), cesium iodide (Cs
I), rubidium iodide (RbI) alone or as a mixture.

In the discharge tube according to the present invention, since the coating film containing the alkali iodide effective for stabilizing the discharge starting voltage is formed on the surface of the discharge electrode, the discharge tube is operated at a short interval of several ms. In this case, even when a surge voltage with a fast rise time is applied, a stable discharge start voltage can be obtained.

Further, cesium bromide (Ce
Br), rubidium bromide (RbBr), nickel bromide (NiBr ₂ ), indium bromide (InBr ₃ ), cobalt bromide (CoBr ₂ ), iron bromide (FeBr ₂ , FeB)
r ₃ ), barium chloride (BaCl), barium fluoride (BaF), yttrium oxide (Y ₂ O ₃ ), yttrium chloride (YCl ₂ ), yttrium fluoride (Y
F _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 ) and one or more kinds of potassium titanate (K ₂ Ti ₄ O ₉ ) are added, whereby the discharge starting voltage of the discharge tube can be further stabilized.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A discharge tube 10 according to the present invention, as shown in FIG. 1, has both ends of a cylindrical case member 12 made of an insulating material such as ceramic whose both ends are opened and which also serves as a discharge electrode. The airtight envelope 16 is formed by hermetically closing with the pair of lid members 14 and 14, and a predetermined discharge gas is enclosed in the airtight envelope 16.

The lid member 14 includes a flat discharge electrode portion 18 that largely projects toward the center of the airtight 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 four and fourteen discharge electrode portions 18, 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 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.

An insulating film 30 containing an alkali iodide is formed on the surface of the discharge electrode portion 18.
The coating 30 is made of a sodium silicate solution and pure water prepared from a single or mixture of alkali iodides such as potassium iodide (KI), sodium iodide (NaI), cesium iodide (CsI) and rubidium iodide (RbI). It can be formed by applying what is added to the binder to the surface of the discharge electrode portion 18. In this case, a simple substance or a mixture of alkali iodides is mixed in a proportion of 0.01 to 70% by weight, and a binder is mixed in a proportion of 99.99 to 30% by weight. The mixing 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.

Further, in the coating film 30, cesium bromide (C
eBr), rubidium bromide (RbBr), nickel bromide
(NiBr_Two), Indium bromide (InBr_Three), Bromide
Cobalt (CoBr_Two), Iron bromide (FeBr_Two, FeB
r_Three) Etc. add more than one type of bromide
Layer, it is possible to stabilize the discharge starting voltage of the discharge tube 10.
It Barium chloride (BaCl), barium fluoride
(BaF), yttrium oxide (Y_TwoO_Three), Chloride
Thorium (YCl_Two), Yttrium fluoride (Y
F_Three), Potassium molybdate (K_TwoMoO_Four), Tan
Potassium gustenoate (K_TwoWO_Four), Cesium chromate
(Cs_TwoCrO_Four), Praseodymium oxide (Pr₆O
₁₁), Potassium titanate (K_TwoTi_FourO₉) 1 type
The above, together with the bromide, or other than the bromide,
Even if added in the coating film 30 of the discharge start voltage of the discharge tube 10.
Contributes to stabilization. These substances are
In the mixture of the substance alone or the mixture and the binder.
It is added in a blending ratio of 01 to 10% by weight.

The discharge gas sealed in the airtight envelope 16 may be a rare gas such as argon, neon, helium, or xenon, or an inert gas such as nitrogen gas, or a mixed gas. In the discharge gas, halogen, H ₂ , S
By mixing the negative gas such as F ₆ , CO ₂ , O ₂ , and Hg, the continuous flow phenomenon in which the discharge continues can be prevented. 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 follow-up flow is easily induced by such residual ions, but when the negative gas is mixed, Since recombination of ions occurs and the charge disappears, it is possible to effectively prevent the generation of a follow-up current. For example, when the discharge gas is argon, Ar ⁺ is generated as residual ions, but when H ₂ is mixed as the negative polarity gas, H attaches electrons to become negative ions H ⁻ , and as a result, positive ions Ar are generated. ^{The +} and the negative ion H ⁻ are recombined and the electric charge disappears. From the above, argon and H are used as the discharge gas sealed in the airtight envelope 16.
A mixed gas of _2, a mixed gas of argon and CO _2, a mixed gas of argon and SF _6, 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 gas to be mixed (H ₂ , C
O ₂ and SF ₆ ) are 1 to 5 with respect to the discharge gas to be enclosed.
It is made 0% by volume. When H ₂ having a small mass is used as the negative gas, the impact on the discharge electrode portion 18 is small, so that the amount of spatter on the discharge electrode portion 18 can be reduced.

When a voltage equal to or higher than the discharge starting voltage of the discharge tube 10 is applied between the discharge electrode portions 18, 18 of the discharge tube 10 of the present invention having the above-mentioned structure, a minute amount between the trigger discharge films 28, 28 is generated. An electric field is concentrated in the discharge gap 26, whereby electrons are emitted into the minute discharge gap 26, and a creeping corona discharge as a trigger discharge occurs. Then, this creeping corona discharge is converted into glow discharge by the priming effect of electrons. And
This glow discharge is transferred to the discharge gap 22 between the discharge electrode parts 18, 18 and is transferred to the arc discharge as the main discharge. In the discharge tube 10 of the present invention, since the creeping corona discharge, which originally has a high response speed and is generated in the minute discharge gap 26, is used as the trigger discharge, a high response can be realized.

In the discharge tube 10 of the present invention, the discharge electrode section
Since the coating film 30 containing alkali iodide, which is effective in stabilizing the discharge starting voltage, is formed on the surface of the discharge tube 18,
When 10 is used as a switching spark gap, a high voltage pulse (several hundred H
z or more), it becomes possible to stably operate with a constant discharge start voltage at intervals as short as several ms. That is, in FIG. 2, the coating film 30 containing potassium iodide is formed on the surface of the discharge electrode portion 18, and the discharge start voltage is 10
The discharge tube 10 set to 00V, frequency 1000H
3 is a chart showing the transition of the discharge start voltage when operated at z (1 ms) intervals, and as shown in the chart, in the discharge tube 10, the discharge start voltage is always stable at the rated value of about 1000V. You can see that It is needless to say that a stable discharge starting 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.

When the discharge tube 10 of the present invention is used as a gas arrester, even if a surge voltage with a fast rise time is applied, the discharge start voltage fluctuates. It is difficult to cause "fluctuation", and it is possible to operate stably with a constant discharge start voltage. That is, the "fluctuation" phenomenon of the discharge start voltage is
When a surge voltage is applied to the discharge tube 10, the initial electrons and ions as the discharge ignition collide with the discharge gas molecules and ionize them into ions and electrons.The ionized ions are the discharge electrodes. This phenomenon occurs because the secondary electron emission action (γ effect) that collides with the coating film 30 on the surface of the portion 18 and emits secondary electrons is not performed stably. However, in the present invention, since the alkali iodide contained in the coating film 30 has the property of easily ionizing discharge gas molecules, a large amount of ions are present in the hermetic envelope 16. As a result, a stable α effect and a secondary electron emission effect (γ effect) are exhibited, so that “fluctuation” of the discharge start voltage is less likely to occur.

As shown in FIG. 3, the present inventor also conducted an experiment on the relationship between the number of discharges and the discharge starting 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 starting voltage sharply decreases and becomes unusable, whereas in the case of the discharge tube 10 of the present invention, Even when the number of discharges reached about 2 million, the discharge start voltage did not change significantly. In this way, by forming the coating film 30 containing potassium iodide on the surface of the discharge electrode portion 18, the discharge tube
A long service life of 10 is also realized.

[0018]

EFFECTS OF THE INVENTION In the discharge tube according to the present invention, since the coating film containing the alkali iodide, which is effective for stabilizing the discharge starting voltage, is formed on the surface of the discharge electrode, the interval is as short as several ms. Even when operated or when a surge voltage having a fast rise time is applied, a stable discharge start voltage can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing a discharge tube according to the present invention.

FIG. 2 shows a discharge tube according to the present invention with a frequency of 1000 Hz.
6 is a chart showing a transition of a discharge start voltage when operated at intervals of (1 ms).

FIG. 3 is a graph showing the relationship between the number of discharges and the discharge starting voltage in the discharge tube of the present invention and the conventional discharge tube.

FIG. 4 is a cross-sectional view showing a conventional discharge tube.

FIG. 5 shows a conventional discharge tube with a frequency of 100 Hz (10 m
It is a chart which shows the transition of the discharge start voltage when it is made to operate at s) intervals.

[Explanation of symbols]

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

Claims (3)

[Claims] 1. A discharge tube in which a plurality of discharge electrodes are arranged with a discharge gap therebetween, and the discharge electrodes are sealed together with a discharge gas in an airtight envelope, wherein the surface of the discharge electrode contains an alkali iodide. Discharge tube having a formed coating. 2. The alkali iodide is potassium iodide (KI), sodium iodide (NaI), cesium iodide (CsI), or rubidium iodide (RbI) alone or in a mixture. Item 1. The discharge tube according to Item 1. 3. Cesium bromide (CeB) in the coating film.
r), rubidium bromide (RbBr), nickel bromide (N
iBr ₂ ), indium bromide (InBr ₃ ), cobalt bromide (CoBr ₂ ), iron bromide (FeBr ₂ , FeB)
r ₃ ), barium chloride (BaCl), barium fluoride (BaF), yttrium oxide (Y ₂ O ₃ ), yttrium chloride (YCl ₂ ), yttrium fluoride (Y
F _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 ), and one or more kinds of potassium titanate (K ₂ Ti ₄ O ₉ ) are added, The discharge tube according to claim 1 or 2.