JP4896324B2 - Lightning arrestor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention belongs to the technical field of lightning arresters for protecting communication devices from lightning surges.
[0002]
[Prior art]
Conventional lightning arresters having this type of air gap have a low inter-electrode voltage (hereinafter referred to as a sustain voltage) after discharge when the discharge start voltage is low. (Hereinafter referred to as continuation). Therefore, in order to cut off this continuity and prevent damage to the electrode due to electric discharge to improve the performance of the lightning arrester, molybdenum, dungsten, or the like, which is a refractory metal, is often used as an electrode material (Japanese Patent Laid-Open No. 2001) -6839).
[0003]
For example, a surface coating of molybdenum, which is one refractory metal, is a highly insulating semiconductor. When molybdenum is used as a discharge electrode of a lightning arrester, a large current lightning surge flows between the electrodes, but normal current such as commercial power does not flow. However, when the gap length between the electrodes is narrow and many discharges occur between the electrodes, the surface coating of molybdenum breaks through and the continuity from the commercial power source cannot be cut off.
[0004]
In addition, the brazing material was directly melted and joined to the joint surface between the metal electrode containing the refractory metal and the insulating envelope, but the metal electrode has a large coefficient of thermal expansion, and the joint surface should be firmly joined. Was difficult.
[0005]
For this reason, an organic or inorganic adhesive having a relatively higher bonding strength than the brazing material may be used for bonding the insulating envelope and the electrode. However, in this case, when a lightning surge with a large current flows between the electrodes, a force larger than the adhesive force of the adhesive acts between the electrodes, and thus the adhesive peels off. As a result, the insulation envelope and the electrode lose the bonding force, and the lightning arrester is defective or damaged.
[0006]
[Problems to be solved by the invention]
The present invention has been made in response to the above circumstances, and an object thereof is to provide a novel lightning arrester in which an insulation envelope and an electrode are firmly joined and air discharge is reliably performed.
[0007]
It is another object of the present invention to provide a lightning arrester capable of controlling the sustain voltage to be equal to or higher than the commercial power supply voltage and interrupting the continuity from the commercial power supply.
[0008]
[Means for Solving the Problems]
Considering the above-described problems, the lightning arrester of the present invention employs the following means.
[0009]
That is, according to claim 1, in the lightning arrester in which the electrodes are separated via the cylindrical insulating envelope, male and female screws are respectively provided on the electrode and the insulating envelope, and the male screw and the female screw are screwed together. An air gap is formed by assembly.
[0010]
In this means, the insulation envelope and the electrode are firmly joined, and the lightning arrester is prevented from being damaged. Moreover, the gap length of the discharge gap is controlled, and the discharge start voltage is adjusted. Furthermore, the continuity from the commercial power source is interrupted.
[0011]
According to a second aspect of the present invention, in the lightning arrester according to the first aspect, a male screw is provided on the outer peripheral edge of the electrode and a female screw is provided on the inner peripheral edge of the insulating envelope, and at least two threaded portions are provided. A lightning arrester characterized in that the number of screw threads is larger than that of male threads.
[0012]
By this means, the bonding strength between the insulating envelope and the electrode is enhanced. Further, the inner wall distance of the insulating envelope is set to be long by the thread of the female screw that is not screwed with the electrode on the inner periphery of the insulating envelope.
[0013]
According to a third aspect of the present invention, in the lightning arrester according to the first or second aspect, the electrode is provided with a flange portion joined to the opening end face of the insulating envelope.
[0014]
This means serves as a stopper for terminating the screwing. Further, the displacement of the screwing portion is prevented.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a lightning arrester of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view illustrating the structure of a lightning arrester according to the embodiment, and FIG. 2 is an enlarged longitudinal sectional view showing the lightning arrester according to the embodiment. In the embodiment, a case where a male screw is provided on the outer peripheral edge of the electrode and a female screw is provided on the inner peripheral edge of the insulating envelope will be described.
[0016]
As shown in FIG. 1, the lightning arrester 1 includes electrodes 2 and 4 that are spaced apart via a cylindrical insulating envelope 3 made of ceramic or the like.
[0017]
The electrodes 2 and 4 are metal electrodes having a button shape as a whole, and are composed of discharge portions 20 and 40, screw portions 21 and 41, and flange portions 22 and 42.
[0018]
The discharge parts 20 and 40 have a convex shape and are provided to face the insides of the electrodes 2 and 4. The discharge parts 20 and 40 are made of a refractory metal and are made of, for example, molybdenum, tungsten, or an alloy material thereof. The thermal conductivity of the discharge parts 20 and 40 is about 140 to 240 W / m · K. Moreover, the discharge parts 20 and 40 are provided with discharge surfaces 201 and 401 at the lower end and projecting parts 202 and 402 at the upper part.
[0019]
The discharge surfaces 201 and 401 are circular and are formed substantially flat to the extent that the opposing electrodes 2 and 4 can discharge.
[0020]
The protruding portions 202 and 402 are provided at the center of the discharge portions 20 and 40 and are fitted with the screw portions 21 and 41, and have, for example, a cylindrical shape.
[0021]
The screw parts 21 and 41 are, for example, cylindrical shapes having the same diameter as the discharge surfaces 201 and 401. The screw portions 21 and 41 are made of metal, and are made of, for example, iron, stainless steel, aluminum, or the like. The thermal conductivity of the metal electrode is about 80 to 240 W / m · K. The screw portions 21 and 41 are provided with male screws 210 and 410 and receiving portions 212 and 412.
[0022]
The male screws 210 and 410 are provided on the outer peripheral edges of the screw portions 21 and 41. Moreover, it is formed from at least two or more threads 211,411. The outer diameters of the threads 211 and 411 are set to such an extent that they can be smoothly screwed into the inner wall 33 of the insulating envelope 3.
[0023]
The receiving portions 212 and 412 are provided at the center of the screw portions 21 and 41 and are fitted with the protruding portions 202 and 402 of the screw portions 21 and 41, and have, for example, a cylindrical shape.
[0024]
The flange portions 22 and 42 are, for example, disk-shaped, have an outer diameter larger than the outer diameter of the screw portions 21 and 41 described above, and are integrally formed with the screw portions 21 and 41. The flange portions 22 and 42 are made of metal, and are made of the same metal as the screw portions 21 and 41. The flange portions 22 and 42 are provided with flange surfaces 221 and 421 on the screw portions 21 and 41 side and circular electrode surfaces 222 and 422 on the opposite side.
[0025]
The flange surfaces 221 and 421 have a flat collar shape facing the screw portions 21 and 41 side. The surfaces of the flange surfaces 221 and 421 are configured as smooth surfaces. Specifically, the average surface roughness is preferably about 0.1a to 0.5a. The flange surfaces 221 and 421 serve as stoppers for terminating the screwing.
[0026]
The insulating envelope 3 is made of, for example, a ceramic material having a cylindrical shape. A threaded portion 31 is formed along the inner wall 33 of the insulating envelope 3, and a female thread 310 is formed on the threaded portion 31. Ring-shaped opening end faces 32 are formed at the upper and lower ends of the insulating envelope 3. The surface of the opening end surface 32 is configured as a smooth surface that can be in close contact with the flange portions 221 and 421. Specifically, the average surface roughness is preferably about 0.1a to 0.5a. The circumferential width of the opening end surface 32 is a joining distance W when the flange surfaces 221 and 421 and the opening end surface 32 are joined, and serves as a stopper for terminating the screwing and the position of the screwing portion. Sufficient distance is secured to prevent deviation.
[0027]
The female screw 310 is formed with at least two or more threads 311 on the creeping surface of the inner wall 33 of the insulating envelope 3 and has at least one thread more than the threads 211 and 411 of the male threads 210 and 410. And an extra thread 314 is formed.
[0028]
Next, the manufacturing process of the lightning arrester 1 will be described.
[0029]
The electrodes 2 and 4 are formed by fitting the projecting portions 202 and 402 of the discharge portions 20 and 40 and the receiving portions 212 and 412 of the screw portions 21 and 41, for example, by press fitting. A metal having a small difference in thermal conductivity between the discharge parts 20 and 40 and the screw parts 21 and 41 is selected in order to cause a lightning surge of a large current to flow instantaneously.
[0030]
Since the insulating envelope 3 is formed by sintering, the insulating envelope 3 using the ceramic material is somewhat shrunk in the sintering heat at the time of formation compared to the electrodes 2 and 4 using the metal material. May occur. However, the provision of the extra thread 314 absorbs shrinkage errors that may occur during the formation of the internal thread 310 by sintering. In addition, the inner wall distance of the insulating envelope is set to be long.
[0031]
The electrodes 2 and 4 are assembled by screwing the screw portions 21 and 41 from the upper and lower opening ends of the insulating envelope 3. The male screws 210 and 410 that have started to be screwed are screwed into the female screw 310 formed on the inner wall 33 of the insulating envelope 3. When the male screws 210 and 410 are screwed into the insulating envelope 3, a tightening force is generated in the insulating envelope 3 by screwing of the male and female screws. Since this tightening force acts in the axial direction, contact portions are formed between the screw threads 211 and 411 of the male screws 210 and 410 and the screw thread 311 of the female screw 310 on the axial direction side. That is, as shown in FIG. 2, the screw surfaces 213, 413, and 313 come into contact with each other and are brought into close contact with each other by having at least two or more threaded portions. The flange surfaces 221 and 441 of the flange portions 22 and 42 and the open end surface 32 of the insulating envelope 3 are joined to form joint surfaces 5 and 6 having high adhesion.
[0032]
When the joining surfaces 5 and 6 are formed, the discharge gap 23 is formed between the discharge surfaces 201 and 401 screwed into the insulating envelope 3, and the gap length G is determined. Specifically, the gap length G preferably forms a gap of about 0.05 to 0.5 μm. The smaller the gap length G, the greater the discharge electric field strength. Therefore, even if it is air discharge, if it is in the said range, discharge will be easy to induce.
[0033]
Further, since the electrodes 2 and 4 and the insulating envelope 3 are easily threaded as described above, the gap length G can be set easily and freely to such an extent that discharge can be performed. That is, the gap length G can be easily controlled. Accordingly, the discharge start voltage is adjusted, and the sustain voltage after discharge is adjusted to be equal to or higher than the commercial power supply voltage. The lightning arrester 1 is completed by the above manufacturing process.
[0034]
【Example】
For the discharge parts 20 and 40, molybdenum having a thermal conductivity of about 140 W / m · K was used. The projecting portions 202 and 402 are projecting pieces having a diameter of about 3.2 mm. The screw parts 21 and 41 were made of aluminum having a thermal conductivity of about 240 W / m · K. The receiving portions 212 and 412 of the screw portions 21 and 41 are receiving pieces having a diameter of about 3.0 mm. As the male screws 210 and 410, first-class male screws having six threads are used, and for example, M6, a pitch of 1 mm, and an outer diameter of 6 mm can be formed. The flange portions 22 and 42 were made of aluminum having an outer diameter of about 10 mm. As the insulating envelope 3, an alumina (Al ₂ O ₃ ) envelope having a diameter of about 10 mm was used. The finished surfaces of the flange surfaces 221 and 421 and the open end surface 32 have an average roughness Ra = 0.2a. The width W of the joining surfaces 5 and 6 was set to about 1.0 mm.
[0035]
As a result of press-fitting the projecting portions 202 and 402 of the discharge portions 20 and 40 and the receiving portions 212 and 412 of the screw portions 21 and 41 by the above members, the electrodes 2 and 4 were formed. In addition, as a result of sintering the electrodes 2 and 4 and the alumina envelope 3, both male and female screws 211, 311 and 411 can be easily formed, and six threaded portions can be formed and firmly joined together. did it. Further, one extra thread was formed on the inner wall 33 of the insulating envelope 3.
[0036]
The gap length G could be easily formed as about 0.05 mm.
[0037]
Also, with the above configuration, the discharge start voltage can be adjusted to 1.5 kV, and the sustain voltage after discharge can be maintained at about 300 V, so that the continuity from the commercial power source can be cut off, and the alumina envelope It was possible to reliably discharge in the air.
[0038]
[Effect of the present invention]
As described above in detail, the lightning arrester of the present invention controls the gap length of the discharge gap by screwing the male and female screws to join the insulating envelope and the electrode, and starts discharge. It has an excellent effect that the voltage can be adjusted.
[0039]
Further, it is possible to cut off the continuity from the commercial power source and adjust the sustain voltage between the electrodes to be equal to or higher than the commercial power source voltage, thereby suppressing the lightning arrester from being defective or damaged.
[Brief description of the drawings]
FIG. 1 is a perspective view illustrating a structure of a lightning arrester according to an embodiment.
FIG. 2 is an enlarged longitudinal sectional view showing a lightning arrester according to the embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Lightning arrester 2, 4 Electrode 20, 40 Discharge part 201, 401 Discharge surface 202, 402 Protruding part 203, 403 Outer peripheral edge 21, 41 Screw part 210, 410 Male thread 211, 411 Male screw thread 212, 412 Reception part 213 413 Male screw thread surface 22, 42 Flange portion 221, 421 Flange surface 222, 422 Electrode surface 23 Discharge gap 3 Insulation envelope 31 Screw portion 310 Female screw 311 Female screw thread 313 Female screw thread surface 314 Extra thread 32 Open end face 33 Inner walls 5, 6 Joint surface W Joint distance G Gap length

Claims (2)

In a lightning arrester in which electrodes are separated via a cylindrical insulating envelope, male and female screws are provided on the electrode and the insulating envelope, respectively, and an air gap is formed by screwed assembly of the male and female screws. And
The electrode is composed of a discharge part, a screw part in which the male screw is formed, and a flange part joined to the opening end surface of the insulating envelope,
The discharge portion includes a circular and flat discharge surface, and a projecting portion that fits into a receiving portion provided in the center of the screw portion,
The lightning arrester characterized in that an average roughness Ra of an opening end face of the insulating envelope and a joint surface of the flange portion joined to the opening end face of the insulating envelope is 0.1a to 0.5a.   2. The lightning arrester according to claim 1, wherein a male screw is provided on the outer peripheral edge of the electrode and a female screw is provided on the inner peripheral edge of the insulating envelope, and has at least two threaded portions. A lightning arrester characterized in that it is provided more than the number of screw threads.

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