JPH03230488A - Discharge type surge absorbing element - Google Patents

Abstract

PURPOSE:To improve the life characteristic of an element by providing a fine gap generating the initial creeping discharge of the discharge type surge absorbing element between discharge electrodes and a conducting thin film. CONSTITUTION:A discharge type surge absorbing element 1 is fitted with a pair of discharge electrodes 4, 4' formed into a cap shape with a metal having good discharge characteristic such as Ni, Fe or their alloy connected with external terminals 3, 3' made of a Dumet wire on both ends of a nearly columnar insulator 2 made of ceramic such as alumina to form a discharge gap between the opposite end sections 4a, 4a' of the discharge electrodes 4, 4'. A conducting thin film 6 is coated around the insulator 2, a fine gap 7 is formed between the thin film 6 and the opposite end face 4a of one electrode 4, the other discharge electrode 4' is connected to the thin film 6, it is sealed in an airtight container 8 made of glass together with rare gas such as He, and external terminals 3, 3' are guided to the outside. Since the fine gap 5 generating the initial creeping discharge is provided between the discharge electrodes 4 and the conducting thin film 6, the occurrence of insulation deterioration due to spattering is prevented, and the life of the element 1 is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a discharge type surge absorbing element that utilizes a discharge phenomenon in a discharge gap housed in an airtight container, and in particular to a discharge type surge absorbing element with improved life characteristics. Related to surge absorption elements.

[Prior Art] Conventionally, varistors made of high-resistance elements with non-linear voltage characteristics have been used as surge absorbing elements to protect electronic circuits from surges caused by induced lightning, etc. Arresters, etc., are widely used.

However, although the above-mentioned varistor has excellent surge absorption response, the current withstand capacity per unit cross-sectional area tooth is relatively small.
Therefore, it has been difficult to efficiently absorb large surge currents. In addition, the above arrester can increase the current withstand capacity by generating an arc discharge in the discharge gap, but the time required from the application of a surge to the arc discharge is slower than that of the above varistor, and its response is He had sexual problems.

Therefore, in order to improve the response of surge absorption in the arrester, as shown in FIG.
A minute gap 7 with a width of about O.lam is formed in a circumferential manner to divide the conductive thin film 6, and discharge electrodes 4, 4' are fitted on both ends of the insulator 2 with a discharge gap 5 between them. The conductive thin film 6゜6 and the discharge electrodes 4, 4' are connected, and this is sealed together with the discharge gas in an airtight container 8, and the external terminal 3゜3 is connected.
A surge absorbing element 10 has been proposed that derives the value .

When a surge is applied to the surge absorbing element 1o having this minute gap 7, first the conductive thin film 6 is applied through the minute gap 7.
, 6, which causes electrons to be emitted into the minute gap 7, causing creeping discharge. Next, a creeping discharge occurs between the discharge electrodes 4 and 4' due to the priming effect of electrons generated with this creeping discharge. Then, as the surge current increases, this creeping discharge shifts to arc discharge in the discharge gap 5, and the surge is absorbed by this arc discharge. As described above, since the surge absorbing element 10 having the minute gap 7 utilizes creeping discharge which has a fast response speed, it has superior responsiveness such as alignment compared to the above-mentioned varistor, and also has a higher current response. It also has excellent durability.

[Problems to be Solved by the Invention] However, in the conventional surge absorbing element 10 having the minute gap 7 as described above, the conductive thin films 6, 6 are thinly deposited and have poor physical strength. As the surge absorption is repeated, the conductive thin film 6.6 is sputtered due to the creeping discharge formed in the micro gap 7, which deteriorates the electrical insulation of the micro gap 7, resulting in poor insulation and the micro gap. There was a drawback that the function as 7 could no longer be exerted.

SUMMARY OF THE INVENTION Therefore, the present invention aims to solve the above-mentioned problems and to realize a discharge type surge absorbing element that can have a long life without deteriorating its insulation properties even after repeated surge absorption.

[Means for Solving the Problems] In order to achieve the above object, the discharge type surge absorbing element of the present invention has a conductive thin film coated on the surface of an insulator, and a discharge gap is formed at both ends of the insulator. Discharge electrodes are attached facing each other with a gap between them, a minute gap is formed between the one discharge electrode and the conductive thin film, and the other discharge electrode and the conductive thin film are connected to cause a discharge. It is stored in an airtight container along with the gas.

[Function] Since the discharge type surge absorbing element of the present invention has the above-described configuration, when a surge is applied to the surge absorbing element,
A potential difference is generated between the discharge electrode and the conductive thin film across the microgap, and when this exceeds a predetermined value, electrons are immediately emitted into the microgap and a creeping discharge is generated. This creeping discharge further generates electrons as it discharges, and transforms into a creeping discharge between the discharge electrodes due to the priming effect of the electrons and an increase in voltage drop due to the resistance of the conductive thin film and the surge current. Furthermore, this creeping discharge between the discharge electrodes shifts to arc discharge in the discharge gap due to an increase in surge current, and this arc discharge can absorb large current surges.

In the discharge type surge absorbing element of the present invention, a minute gap is provided between the discharge electrode and the conductive thin film, and since this discharge electrode is physically difficult to sputter, the gap is provided between the conductive thin film. Compared to conventional microgaps, there is less risk of causing insulation deterioration due to sputtering, and it is possible to extend the life of the discharge type surge absorbing element.

[Example] Hereinafter, an example of the present invention will be described based on the drawings.

FIG. 1 shows a discharge type surge absorbing element according to an embodiment of the present invention, FIG. 1(a) is a schematic perspective view, and FIG. 1(b) is a sectional view of a main part. In fig.

The discharge type surge absorbing element 1 has an approximately cylindrical insulator 2 made of ceramics such as alumina, forsterite, steatite, etc., and external terminals 3 made of dumet wires at both ends thereof.
Nickel, iron or alloys of these, etc. with 3' connected,
A pair of discharge electrodes 4 and 4' made of a cap-shaped metal with good discharge characteristics are attached by means such as fitting or adhesion, and a discharge is generated between the opposite ends 4a and 4a' of the discharge electrodes 4 and 4'. A gap 5 is formed. Further, a conductive thin film 6 is deposited on the circumferential surface of the insulator 2, a minute gap 7 is formed between the conductive thin film 6 and the opposite end 4a of the one discharge electrode 4, and the other The discharge electrode 4' and the conductive thin film 6 were connected and then heated with He.

It has a structure in which it is sealed in an airtight container 8 made of glass or the like together with a discharge gas made of a rare gas such as N ey Ar, and the external terminals 3 and 3' are led out.

The microgap 7 is created by spraying, vapor deposition, coating, etc. with carbon, conductive ceramics, etc. after masking in advance the part of the peripheral surface of the insulator 2 where one of the discharge electrodes 4 is attached and the part where the microgap 7 is formed. After the masking is removed and one of the discharge electrodes 4 is attached and formed, or the conductive thin film 6 is deposited on the entire circumferential surface of the insulator 2, machining means such as polishing and cutting are applied. By removing unnecessary conductive thin film portions, one discharge electrode 4 can be attached and formed.

Furthermore, as shown in FIG. 2, the minute gap 7 is
After applying a conductive thin film 6 to the entire circumferential surface of the.

In this conductive thin film 6, grooves wider than the required width of the minute gap 7 are formed using a cutting machine, a laser processing machine, etc. at the position where the minute gap 7 is to be formed and at a position with a uniform width. The conductive thin film in this portion may be removed and one discharge electrode 4 may be attached to the end of the insulator 2 on the side where the groove is formed. Note that electrical connection between the conductive thin film 6a on the side to which one discharge electrode 4 is attached and one discharge electrode 4 is not necessary, but when these are electrically connected, the above-mentioned conductive The end of the thin film 6a on the microgap 7 side needs to be located deeper than the opposing end 4a of the one discharge electrode 4. This is because the first creeping discharge in surge absorption is generated between the opposing end 4a of one discharge electrode 4 and the end of the conductive thin film 6 connected to the other discharge electrode 4'. be.

The width of the minute gap 7 is set to an appropriate value in consideration of the discharge starting voltage during surge absorption, as well as the type of discharge gas to be filled, the gas pressure, the discharge gap width, etc.

This width is preferably approximately 200 μm or less, and if this value is exceeded, the degree of electric field concentration in the minute gap 7 may decrease depending on the conditions, resulting in an increase in discharge delay.

[Effects of the Invention] As described in detail above, according to the present invention, by providing a minute gap between the discharge electrode and the conductive thin film in which the first creeping discharge is generated in the discharge type surge absorbing element, the physical Since discharge electrodes are less prone to sputtering than conductive thin films, which have lower physical strength, there is less risk of causing insulation deterioration due to sputtering than with conventional micro-gaps between conductive thin films. This makes it possible to improve the life characteristics of the surge absorbing element.

[Brief explanation of drawings]

FIG. 1 shows a discharge type surge absorbing element according to an embodiment of the present invention, FIG. 1(a) is a schematic perspective view, FIG. 1(b) is a sectional view of a main part, and FIG. 2 is a diagram of the present invention. FIG. 3 is a sectional view of a main part showing another embodiment, FIG. 3 shows a conventional discharge type surge absorption element, FIG. 3(a) is a schematic perspective view, and FIG. 3(b) is a sectional view of a main part. It is. 1... Discharge type surge absorption element 2... Insulator 4.
4'...Discharge electrode 5...Discharge gap 6...
Conductive thin film 7...Minute gap 8...Airtight container cylinder diagram (a) - Figure (b) Figure 2 Figure 3 (a) 3' Figure (b)

Claims (1)

[Claims] A conductive thin film is deposited on the surface of the insulator, and discharge electrodes are attached to both ends of the insulator so as to face each other with a discharge gap in between, and a minute gap is formed between one of the discharge electrodes and the conductive thin film. a discharge type surge absorbing element, in which the other discharge electrode and a conductive thin film are connected, and this is housed in an airtight container together with a discharge gas.