JP2006134584A - Discharge tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge tube having a long life, wherein an initial discharge starting voltage is prevented from rising, and no initial discharge delay is caused. <P>SOLUTION: Opening parts at both ends of a case member 12 is airtightly sealed by a pair of lid members 14, 14 also serving as discharge electrodes to form an airtight envelope 16, a discharge gas is filled in the airtight envelope 16, and a discharge gap 22 is formed between the discharge electrode parts 18, 18 of the lid members 14, 14. A plurality of trigger discharge films 28 both ends of which are disposed with a minute discharge gap 26 parted from the lid members 14, 14 are formed on the inner wall face 24 of the case member 12, and in addition, a coat 30 containing a mixture of cesium bromide and titanium is formed on the surface of the discharge electrode part 18. <P>COPYRIGHT: (C)2006,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 FIG. 4, the discharge tube 60 is hermetically sealed with a pair of lid members 64, 64 that also serve as discharge electrodes, at both ends of a cylindrical case member 62 made of an insulating material that opens at both ends. Thus, an airtight envelope 66 is formed, and a predetermined discharge gas is sealed in the airtight 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.
A plurality of 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. 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 this alkali iodide, the simple substance or mixture of alkali iodides, such as potassium iodide (KI), sodium iodide (NaI), cesium iodide (CsI), and rubidium iodide (RbI), corresponds.
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. Also, a single or mixed gas of a rare gas or an inert gas, a mixed gas of negative polarity gas such as H ₂ corresponds.

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 electrode, and as a result, the initial discharge start voltage is increased and an initial discharge delay may occur. This initial discharge delay is particularly noticeable when the discharge tube 60 is used in the dark. This is because, when the discharge tube 60 is left in the dark for a long time, electrons and ions as a seed of discharge in the hermetic envelope 66 are reduced.

  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.

As a result of various investigations on the constituent material of the coating film formed on the surface of the discharge electrode, the present inventors have found that when the coating film is composed of a mixture of cesium bromide (CsBr) and titanium (Ti), the initial discharge start voltage As a result, the present invention has been completed.
That is, the discharge type surge absorbing element according to the present invention is 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 a mixture of cesium bromide and titanium is formed on the surface.
The mixing ratio of the cesium bromide and titanium is preferably 20 to 80% by weight for cesium bromide and 80 to 20% by weight for titanium.

  In the discharge tube according to the present invention, by forming a film containing a mixture of cesium bromide and titanium on the surface of the discharge electrode, it is possible to prevent an increase in the initial discharge start voltage and to cause an initial discharge delay. A long-life discharge tube can be realized.

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

A film 30 containing a mixture of cesium bromide (CsBr) and titanium (Ti) is formed on the surface of the discharge electrode portion 18.
The coating 30 can be formed by applying a mixture of a cesium bromide powder and a titanium powder to a binder composed of a sodium silicate solution and pure water on the surface of the discharge electrode portion 18. Alternatively, the binder to which cesium bromide is added and titanium powder added and mixed can be applied to the surface of the discharge electrode portion 18 to form.
The particle size of the titanium powder is, for example, 10 to 45 μm.
In this case, the mixing ratio of cesium bromide and titanium is preferably 20 to 80% by weight for cesium bromide and 80 to 20% by weight for titanium in order to effectively prevent an increase in initial discharge start voltage. .
The mixture ratio of the cesium bromide and titanium and the binder is such that the mixture of cesium bromide and titanium is 0.01 to 25% by weight and the binder is 99.99 to 75% by weight.
The mixing ratio of the sodium silicate solution and pure water in the binder is such that the sodium silicate solution is 0.01 to 70% by weight and the pure water is 99.99 to 30% by weight.

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. Also, a single or mixed gas of a rare gas or an inert gas, a mixed gas of negative polarity gas such as H ₂ corresponds.

  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 coating 30 containing a mixture of cesium bromide and titanium is formed on the surface of the discharge electrode portion 18, thereby preventing an increase in the initial discharge start voltage. Thus, it is possible to realize a long-life discharge tube 10 that does not cause an initial discharge delay.
Titanium contained in the coating 30 of the discharge tube 10 of the present invention has a very large ionization tendency, so that the titanium ionizes discharge gas molecules. Can be supplied in large quantities.
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.

FIG. 3 shows a discharge tube 10 of the present invention in which a coating 30 containing a mixture of cesium bromide and titanium is formed on the surface of the discharge electrode portion 18, and potassium iodide (KI) as a comparative example. In a conventional discharge tube 60 in which a coating 80 is formed on the surface of the discharge electrode portion 68, and in a discharge tube in which a coating containing only cesium bromide is formed on the surface of the discharge electrode portion as a comparative example, It is a graph which shows the relationship with a discharge start voltage. Any of these discharge tubes is used in which the discharge start voltage is set to 800 V. In this case, if the initial discharge start voltage exceeds 1000 V, it becomes unsuitable for use.
The discharge tube 10 of the present invention is obtained by adding a mixture of 2 g of cesium bromide powder and 2 g of titanium powder (particle size: 10 μm) to 20 g of binder (12 g of sodium silicate solution + 8 g of pure water). Coating 30 was formed on the surface. Therefore, the mixing ratio of cesium bromide and titanium in this case is 50% by weight for cesium bromide and 50% by weight for titanium.
Moreover, the mixture ratio of the mixture of cesium bromide and titanium and the binder is such that the mixture of cesium bromide and titanium is about 16.7% by weight and the binder is about 83.3% by weight.
As shown in the graph of FIG. 3, in the case of the conventional discharge tube 60 (graph B of FIG. 3), the number of discharges is about 100,000 times and the initial discharge start voltage exceeds 1000 V, making it unsuitable for use. . Further, in the case of a discharge tube in which a coating containing only cesium bromide is formed on the surface of the discharge electrode portion (graph C in FIG. 3), although an increase in the initial discharge start voltage can be suppressed as compared with the conventional discharge tube 60, The initial discharge start voltage gradually increases, the number of discharges is about 450,000 times, and the initial discharge start voltage exceeds 1000 V, making it unsuitable for use.
On the other hand, in the case of the discharge tube 10 of the present invention (graph A in FIG. 3), the initial discharge start voltage is almost constant even when the number of discharges reaches 500,000, and therefore a discharge delay occurs even in the dark. Long life has been achieved without any problems.

It is a schematic sectional drawing which shows the discharge tube which concerns on this invention. It is an AA schematic sectional drawing of FIG. It is a graph which shows the relationship between the frequency | count of discharge and the initial stage discharge start voltage in the discharge tube which concerns on this invention, and the discharge tube of a comparative example. It is sectional drawing which shows the conventional discharge tube.

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 mixture of cesium bromide and titanium is contained on the surface of the discharge electrode. A discharge tube characterized by forming a coated film. A discharge tube characterized in that the mixing ratio of cesium bromide and titanium is 20 to 80% by weight of cesium bromide and 80 to 20% by weight of titanium.

Images