JPH09306634A - Microgap surge absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a surge absorber small and enhance its life characteristics. SOLUTION: An element 13 having a ceramic element body 14 on which a conductive film 16 is formed and a microgap 18 formed on the circumferential surface of the ceramic element body 14 is housed in a container 12 for keeping insulation. A pair of cap electrodes 17, 17 is formed at both ends of element 13, and gas not containing molecular state oxygen is sealed in the container 12. An optical shield 14b is arranged between a pair of cap electrodes 17, 17 and a microgap 18. The ceramic element body 14 is formed in an element with step having a smaller diameter part 14a than the outer diameter of a part coming in contact with the cap electrodes 17, 17 of the ceramic element body 14 in a part far from the cap electrodes 17, 17, and the microgap 18 is formed on the circumferential surface of the small diameter part 14a. The shield 14b is the step part of the ceramic element body 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surge absorber having a function of absorbing a surge voltage applied to electronic equipment for communication equipment such as telephones, facsimiles, telephone exchanges and modems. More specifically, a device having a microgap is sealed in a glass tube or the like together with an inert gas (herm
etic seal) is a discharge type surge absorber.

[0002]

2. Description of the Related Art Conventionally, as a microgap type surge absorber, as shown in FIG. 6, the surface of a cylindrical ceramic body 3a made of an insulating ceramic such as mullite is used to form a metal, a metal oxide, or a metal nitride on the surface. A device 3 is formed by being covered with a conductive film 3b such as a metal carbide, and a laser is provided on the circumferential surface of the device 3 with one or two or more linear microgaps 3c having a width of 10 to 1000 μm in the circumferential direction. The conductive film 3b is electrically divided into a plurality of parts by being formed by light or the like, and further, a pair of cap electrodes 9 and 9 having a pair of lead wires 4 and 4 are fitted to both ends of the element 3 to fit them. There is known a surge absorber 1 that is enclosed in a glass tube 2 in a state in which some of the lead wires 4 and 4 are included. In this surge absorber 1, N ₂ , Ar, H
A gas such as e, CO ₂ , CO, SF ₆ or the like is filled. on the other hand,
As a microgap type surge absorber, a state in which a microgap type element 3 having a pair of cap electrodes fitted at both ends as shown in FIG. 7 is sandwiched by a pair of lead wires 8 and a sealing electrode 7 having 8 A surge absorber 5 sealed in a glass tube 6 is also known.

These microgap type surge absorbers 1 or 5 are connected in parallel to an electronic device in a power supply circuit or as a ground circuit. Normally, no current flows through the surge absorber 1 or 5 due to the presence of the microgap 3c, but if a surge voltage enters the power supply circuit and a surge voltage above a certain value is applied to the surge absorber 1 or 5, the microgap 3c A glow discharge is generated between the electrodes, which then becomes a creeping discharge along the conductive film 3b, and when the surge continues, an arc discharge occurs between the pair of cap electrodes 9 and 9 accompanied by the generation of ions. As a result,
The current caused by the surge voltage is surge absorber 1 or 5
Only the current flows to the electronic device, so the electronic device is protected from surge.

However, in the above-mentioned microgap type surge absorber 1 or 5, when a surge voltage is applied to the surge absorber 1 or 5 to cause arc discharge between the pair of cap electrodes 9, 9, either one of the cap electrodes is discharged. 9
Then, metal ions of this electrode material are generated, and these ions contaminate the microgap 3c. When this surge voltage is repeatedly applied to the surge absorber 1 or 5, the micro gap 3c is filled with the metal by the above-mentioned metal ions, so that the divided conductive film 3b becomes conductive, and the surge absorber 1 or 5 performs its original function. I couldn't finish.

In order to solve this problem, the present applicant has provided a pair of annular arc discharge absorbing electrodes spaced apart from and surrounding the conductive coating in the radial direction of the ceramic body, A patent application has been filed for a surge absorber in which the pair of arc discharge absorbing electrodes face each other and are electrically connected to the pair of sealing electrodes, respectively (Japanese Patent Laid-Open No. 6-310).
251). The ring-shaped arc discharge absorbing electrode is incorporated separately from the cap electrode so as to accommodate the cap electrode, or is formed integrally with the cap electrode such that the peripheral edge of the cap electrode has a larger diameter than the cap electrode. In the surge absorber configured as described above, since arc discharge is performed between the pair of arc discharge absorbing electrodes that float from the conductive film, fatigue or deterioration of the microgap, the conductive film and the cap electrode is reduced, and the surge is reduced. The life characteristics can be improved.

[0006]

However, in the above-mentioned conventional improved surge absorber, the outer diameter of the arc discharge absorbing electrode must be made larger than the outer diameter of the ceramic body, and the surge absorber becomes large in size. There was a problem to do. Further, it is necessary to incorporate the arc discharge absorbing electrode as an independent component or process the cap electrode into a special shape. An object of the present invention is to provide a microgap type surge absorber that is small in size and can improve surge life characteristics. Another object of the present invention is to provide a microgap type surge absorber which has a small number of parts and does not require special processing of the cap electrode.

[0007]

The invention according to claim 1 is
As shown in FIG. 1, it is a microgap type surge absorber in which an optical shield 14 b is arranged between a pair of main discharge electrodes 17, 17 and a microgap 18. In the microgap type surge absorber according to claim 1, since the metal ions generated in the main discharge electrode 17 adhere to the optical shield 14b and do not adhere to the microgap 18 shielded by the shield 14b, The plurality of conductive films 16 divided by the micro gap 18 do not conduct.

In the present invention, the optical shield 14b provided between the main discharge electrode 17 and the microgap 18 exhibits the above-mentioned action due to the linearity of the metal ions. That is, the metal ions generated in either one of the pair of main discharge electrodes 17 progress toward the counter electrode, but if the shield 14b is not present at this time, the microgap 18 which is the counter electrode closest to the main discharge electrode 17 is present. It collides with the peripheral edge of and is discharged at this peripheral edge to be reduced to metal.
However, when the shield 14b is present, it collides with the shield 14b due to its inertia and is reduced to metal by the shield 14b, so that the microgap 18 is not contaminated.

[0009]

Next, a first embodiment of the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, the surge absorber 11 is a micro-gap type discharge surge absorber, and is configured by housing an element 13 inside a container 12 that maintains insulation. The element 13 has a ceramic body 14, a conductive film 16 formed on the surface of the ceramic body 14, and a microgap 18 circumferentially formed on the peripheral surface of the ceramic body 14. A pair of cap electrodes 17, 17 which are a pair of main discharge electrodes are fitted to both ends of the element 13. The ceramic body 14 is formed into a stepped body having a small-diameter portion 14a that is smaller than the outer diameter of the portion of the ceramic body 14 that is in contact with the cap electrodes 17 and 17 at a portion apart from the pair of cap electrodes 17 and 17. . The micro gap 18 is formed on the peripheral surface of the small diameter portion 14a. Ceramic body 14
The stepped portion 14b is formed in the ceramic body 14 by forming the small diameter portion 14a in the stepped portion 14b.
Is a pair of cap electrodes 17, 17 and a microgap 1
It becomes an optical shield between 8 and.

The container for maintaining the insulating property of the present invention is a container made of a glass tube or an insulating ceramic tube, a container using a metal tube as a part of the glass tube or the insulating ceramic tube,
Alternatively, it is a container using glass or an insulating ceramic material for a part of the metal tube. The glass tube is made of lead glass, barium glass, soda glass, borosilicate glass or the like. The ceramic body 14 is formed of alumina, mullite, corundum mullite, or the like, and the shape is a cylinder, an elliptic cylinder, a rectangular parallelepiped, a cube, a truncated cone, a triangular prism or other prisms, a truncated pyramid, for both the small diameter portion and the small diameter portion. It is possible to use other truncated pyramids or a modified version of these. The ratio of the outer diameter of the small-diameter portion 14a to the outer diameter of the portion of the ceramic body 14 to which the cap electrode 17 is fitted is preferably in the range of 0.2 to 0.9, and the ratio to the entire length of the ceramic body 14 is The length ratio of the small diameter portion 14a is preferably in the range of 0.2 to 0.9. The conductive film 16 is made of metal, alloy, conductive ceramics or the like, and is made of, for example, Ti, Ni, Ta,
It is formed of W, TiN, TiC, SnO ₂ , BaAl alloy or the like. The film 16 is formed by a thin film forming method such as a spray method, a sputtering method, a vapor deposition method, a printing method, an ion plating method, a plating method, a CVD method or the like.
4 is formed on the surface. The cap electrode 17 is made of SUS (stainless steel), Ni, Mo, Ta or the like.
1 to 14 micro gaps 18 are formed in the small-diameter portion 14a so as to divide the conductive film 16 of the small-diameter portion 14a by a fine processing method such as laser processing, etching, or a printing method. In the laser method, a width of 10 to 2000 μm is formed depending on the depth of focus of the laser beam and the thickness of the conductive film 16.

A pair of lead wires 19, 19 are welded to both ends of the element 13, that is, a pair of cap electrodes 17, 17 by a brazing material such as solder or an electric welding method.
A pair of cap electrodes 17, 17 and a pair of lead wires 19,
19 is electrically connected. A pair of lead wires 19, 1
9 is inserted into this sealing portion when sealing both ends of the container 12, and the element 13 sealed in the container 12 is held by a pair of lead wires 19 and 19 via a pair of cap electrodes 17 and 17. It is like this. Further, the container 12 is filled with gas. The gas is not particularly limited, but a gas containing no molecular oxygen, such as He, Ne, Ar, Xe,
N ₂ , CO ₂ , SF ₆ and C ₃ F ₈ can be preferably used.

In the micro-gap type surge absorber constructed as described above, the voltage due to the surge is transmitted through the pair of lead wires 19 and 19 to the pair of cap electrodes 17 and 17.
When applied to the cap gap 17, the glow discharge starts without delay in the microgap 18, the glow discharge extends to the pair of cap electrodes 17, 17 in the form of creeping discharge, and the arc discharge occurs between the pair of cap electrodes 17, 17. Is formed. At this time, since the micro gap 18 is blocked from the arc discharge path by the stepped portion 14b, even if the metal ions are scattered from the cap electrode 17 due to the arc discharge, the metal ions do not adhere to the micro gap 18, Stepped part 1
It adheres to 4b and is discharged to become a metal. As a result, it is possible to prevent the discharge voltage of the surge absorber 11 from being lowered and the insulation resistance from being deteriorated due to the metal filling the micro gap 18.

FIG. 2 shows a second embodiment of the present invention.
2, the same reference numerals as those in FIG. 1 indicate the same parts. In this embodiment, in addition to the elements configured in the same manner as the elements of the first embodiment, an electronic device or a printed circuit board on which the device is mounted when a continuous overvoltage or overcurrent enters the electronic device. The child 13 for preventing thermal damage or ignition of the container 3
2 and the both ends of the container 32 have a pair of sealing electrodes 3
Sealed by 9,39. A gas containing no molecular oxygen is enclosed in the container 32, and the element 13 is fixed by being sandwiched by the pair of sealing electrodes 39, 39. The pair of sealing electrodes 39, 39 are electrically connected to the conductive film 16 via the pair of cap electrodes 17, 17, and the pair of lead wires 41, 41 are provided on the outer surfaces of the sealing electrodes 39, 39. Are welded by a brazing material such as solder or by an electric welding method. The sealing electrode 39 is formed by a Dumet wire, a slag lead, or the like.

In the microgap type surge absorber constructed as described above, when a voltage due to a surge is applied to the pair of sealing electrodes 39, 39, the microgap 18
At this point, glow discharge is started without delay, and this glow discharge extends to the pair of cap electrodes 17 in the form of creeping discharge,
An arc discharge is formed between the pair of cap electrodes 17, 17. At this time, since the microgap 18 is blocked from the arc discharge path by the stepped portion 14b, even if the metal ions are scattered from the cap electrode 17 by the arc discharge, the metal ions do not adhere to the microgap 18.

FIG. 3 shows a third embodiment of the present invention.
3, the same reference numerals as those in FIG. 2 indicate the same parts. In this embodiment, the pair of cap electrodes are not fitted to both ends of the ceramic body 14 having the conductive coating 16 formed on the surface thereof, but a pair of cap electrodes are directly attached to the conductive coating 16 on both end surfaces of the ceramic body 14. The configuration is similar to that of the second embodiment except that the stop electrodes 39, 39 are pressed into contact with each other and the sealing electrodes 39, 39 are electrically connected to the conductive film 16.

In the microgap type surge absorber constructed as described above, when a voltage due to a surge is applied to the pair of sealing electrodes 39, 39, the microgap 18
At this point, glow discharge is started without delay, and this glow discharge extends to the pair of sealing electrodes 39, 39 in the form of creeping discharge, and arc discharge is formed between the pair of sealing electrodes 39, 39. At this time, since the micro gap 18 is shielded from the arc discharge path by the stepped portion 14b, even if the metal ions are scattered from the sealing electrode 39 by the arc discharge, the metal ions do not adhere to the micro gap 18.

FIG. 4 shows a fourth embodiment of the present invention.
4, the same reference numerals as those in FIG. 2 indicate the same parts. In this embodiment, the ceramic element body 74 is fitted with the pair of cap electrodes 17 and 17, respectively.
a and 74b and a small-diameter element body 74c smaller than the outer diameters of the first and second element bodies 74a and 74b. The outer diameters of the first and second element bodies 74a are formed to be the same. The first element body 74a and the small diameter element body 74c are integrally formed, and the second element body 74b is formed.
Are formed separately. First element body 74a and small-diameter element body 74c
The conductive film 16 is integrally formed on the surface of the second element body 74b, and the conductive film 16 is independently formed on the surface of the second element body 74b. The ratio of the outer diameter of the small-diameter element body 74c to the outer diameter of the first and second element bodies 74a and 74b is preferably in the range of 0.2 to 0.9.

The ratio of the length of the small diameter element body 74c to the total length of the first and second element bodies 74a and 74b and the small diameter element body 74c is preferably in the range of 0.2 to 0.9.
The first element body 74a, the small-diameter element body 74c, and the second element body 74b are formed of alumina, mullite, corundum mullite, or the like, and their surfaces have Ti, Ni, Ta, W, and Ti.
Conductive film 1 of N, TiC, SnO ₂ , BaAl alloy, etc.
6 are respectively formed. The container 32 has the first element 7
4a, the small-diameter element 74c, and the second element 74b are housed in this order, and the first element 74a, the small-element element 74c, and the second element 74 are housed.
The conductive film 16 of b is electrically connected in this order. Except for the above, the configuration is similar to that of the second embodiment. In addition,
The small-diameter element body may be formed integrally with the second element body instead of the first element body, or the first element body, the small-diameter element body, and the second element body may be formed separately.

In the microgap type surge absorber constructed as described above, the ceramic element body 74 is a relatively simple body of the first element body 74a and the small diameter element body 74c, and the second element body of a simple shape. 74b, the number of manufacturing steps of the ceramic body 74 can be slightly increased.

FIG. 5 shows a fifth embodiment of the present invention.
5, the same reference numerals as those in FIG. 3 indicate the same parts. This embodiment has the same configuration as that of the fourth embodiment except that a pair of cap electrodes is not fitted to the first and second element bodies 74a and 74b of the ceramic element body 74. The small-diameter element body may be formed integrally with the second element body instead of the first element body, or the first element body, the small-diameter element body, and the second element body may be formed separately. . In the microgap type surge absorber configured in this manner, since the pair of cap electrodes are not fitted to both ends of the ceramic body 74, the number of manufacturing steps of the surge absorber 91 can be reduced as compared with the surge absorber of the fourth embodiment. .

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described in detail with reference to the drawings. <Example 1> As shown in FIG. 1, a columnar ceramic body 14 made of corundum mullite and having a total length of 5.5 mm and a diameter of 1.7 mm has a columnar shape with a length of 1.5 mm and a diameter of 1 mm at the center in the longitudinal direction. The small-diameter portion 14a of is formed concentrically,
SnO ₂ conductive film 16 is formed on the entire surface by sputtering.
Is formed. Both ends of the ceramic body 14 have a thickness of 0.15 mm, an outer diameter of 1.3 mm, and a length of 0.8 m.
A pair of m cap electrodes 17, 17 is press-fitted. Further, one microgap 18 having a width of 50 μm is formed by laser light in the center of the peripheral surface of the small diameter portion 14a. As a result, the micro-gap type device 13 having the pair of cap electrodes 17, 17 fitted to both ends is produced.

A pair of lead wires 19, 19 are welded to the end faces of the pair of cap electrodes 17, 17, and in this state, the element 13 has an outer diameter of 2.6 mm, an inner diameter of 1.8 mm and a length of 7.
It is housed in a glass tube 12 made of 5 mm lead glass. In this state, the air in the glass tube 12 is replaced with SF ₆ gas to a predetermined pressure, and then heated to heat the glass tube 12
Both ends of the glass tube 12 are sealed by softening and deforming both ends of the glass tube 12. In this way, the surge absorber 11 was manufactured.

<Embodiment 2> As shown in FIG.
A microgap type device 13 is manufactured in the same manner as in. However, a cylindrical small-diameter portion 14 having a length of 1 mm and a diameter of 1 mm is formed at the center in the longitudinal direction of a cylindrical ceramic body 14 having a total length of 4 mm and a diameter of 1.7 mm made of corundum mullite.
a is formed concentrically. On the outer surfaces of the pair of sealing electrodes 39, 39 sealing both ends of the glass tube 32, a lead wire 41,
41 are welded together. The glass tube 32 is made of lead glass, and the sealing electrode 39 is made of slag lead. In a state where the element 13 having a pair of cap electrodes 17, 17 fitted at both ends is housed in the glass tube 12, the air in the glass tube 32 is replaced with SF ₆ gas to a predetermined pressure and then heated. The glass tube 32 is sealed by the pair of sealing electrodes 39, 39. The element 13 housed in the glass tube 32 is fixed by being sandwiched by the pair of sealing electrodes 39, 39 via the pair of cap electrodes 17, 17. The surge absorber 31 manufactured in this way
Was set as Example 2.

<Embodiment 3> As shown in FIG.
The device has the same configuration as that of the second embodiment, except that the pair of cap electrodes in the device is not used. However, the pair of sealing electrodes 39, 39 is directly pressed onto the conductive film 16 on both end surfaces of the ceramic body 14, and the sealing electrodes 39, 39
39 is electrically connected to the conductive film 16. The surge absorber 51 manufactured in this manner was used as Example 3.

<Embodiment 4> As shown in FIG. 4, a first element body 74a and a small-diameter element body 74 constituting a ceramic element body 74.
c is integrally manufactured, and the second element body 74b is separately manufactured. The first and second element bodies 74a and 74b are formed in the same shape, and each is formed in a cylindrical shape having an outer diameter of 1.7 mm and a length of 1.5 mm. The small-diameter element body 74c is formed in a cylindrical shape having an outer diameter of 1 mm and a length of 2 mm. The first element body 74a, the small diameter element body 74c, and the second element body 74b are formed by corundum mullite. First element body 74a and small-diameter element body 74c
The SnO ₂ conductive film 16 is integrally formed on the surface of, and the above-mentioned SnO ₂ conductive film 16 is independently formed on the surface of the second element body 74b. Further, in the glass tube 32 made of lead glass, the first element body 74a, the small diameter element body 74c and the second element body 74c
The body 74b is housed in this order, and the pair of sealing electrodes 39, 39
It is fixed by being sandwiched by. The first element body 7
4a, the small-diameter element body 74c, and the second element body 74b are electrically connected in series in this order. Except for the above, the configuration is similar to that of the second embodiment. The surge absorber 71 manufactured in this manner was used as Example 4.

<Embodiment 5> As shown in FIG. 5, Embodiment 4 except that the cap electrode 17 is not fitted to the first and second element bodies 74a and 74b of the ceramic element body 74.
The configuration is the same as The surge absorber 91 manufactured in this manner was used as Example 5.

<Comparative Example 1> As shown in FIG. 6, a ceramic body 3a is formed in a cylindrical shape having an outer diameter of 1.7 mm and a total length of 5.5 mm without a small diameter portion, and one ceramic body 3a is provided at the center in the longitudinal direction. The structure is similar to that of the first embodiment except that the micro gap 3c is formed. The surge absorber 1 manufactured in this manner was used as Comparative Example 1. <Comparative Example 2> As shown in FIG. 7, a ceramic body 3a is formed in a cylindrical shape having an outer diameter of 1 mm and a total length of 3 mm without a small diameter portion, and one microgap 3c is formed at the center in the longitudinal direction. Except for this, the configuration is similar to that of the second embodiment. The surge absorber 5 manufactured in this manner was used as Comparative Example 2.

<Comparative Test and Evaluation> The DC discharge inception voltage and surge life characteristics of the surge absorbers of Examples 1 to 5 and Comparative Examples 1 and 2 were examined, and the results are shown in Table 1. In addition, the surge life characteristic is such that the insulation resistance is deteriorated by repeatedly applying an impulse current of (8 × 20) μsec-100 A and checking whether or not the resistance value is reduced every 1000 times of the application of the impulse current. It was judged whether or not.

[0029]

[Table 1]

As is clear from Table 1, Examples 1-5,
Both surge absorbers of Comparative Examples 1 and 2 had the same DC discharge starting voltage. Regarding the surge life characteristics, although the surge absorbers of Examples 1 to 5 did not decrease in resistance value even after applying an impulse current of 5000 times,
When the resistance values of the surge absorbers of Comparative Examples 1 and 2 were measured 1000 times after the impulse current was applied, the resistance values were found to be low. Therefore, it was found that the surge absorbers of Examples 1 to 5 had significantly improved surge life characteristics than the surge absorbers of Comparative Examples 1 and 2.

[0031]

As described above, according to the present invention, the optical shield is disposed between the pair of main discharge electrodes and the microgap, so that the metal ions generated in the main discharge electrodes are optically shielded. It does not adhere to the micro-gap blocked by this shield, and does not adhere to the transparent gap. As a result, the plurality of conductive films divided by the micro gap do not conduct, so that the surge life characteristic of the surge absorber can be improved.

[Brief description of drawings]

FIG. 1 is a central longitudinal sectional view of a surge absorber according to a first embodiment of the present invention.

FIG. 2 is a central longitudinal sectional view of a surge absorber according to a second embodiment of the present invention.

FIG. 3 is a central longitudinal sectional view of a surge absorber according to a third embodiment of the present invention.

FIG. 4 is a central vertical sectional view of a surge absorber according to a fourth embodiment of the present invention.

FIG. 5 is a central longitudinal sectional view of a surge absorber according to a fifth embodiment of the present invention.

FIG. 6 is a central vertical cross-sectional view of a surge absorber of Comparative Example 1.

FIG. 7 is a central vertical cross-sectional view of a surge absorber of Comparative Example 1.

[Explanation of symbols]

 11, 31, 51, 71, 91 Surge absorber 14b, 74d Stepped portion (shield) 17 Cap electrode (main discharge electrode) 18 Micro gap 39 Sealing electrode (main discharge electrode)

Claims (1)

[Claims] 1. A micro characterized in that an optical shield (14b, 74d) is arranged between a pair of main discharge electrodes (17, 17, 39, 39) and a micro gap (18). Gap type surge absorber.