JPH054794B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cylindrical surge absorbing element, and particularly to a cylindrical surge absorbing element that is easy to assemble and can be downsized.

[Prior Art] Voltage nonlinear resistors such as gap type surge absorbers or zinc oxide varistors are currently widely used as surge absorption elements that absorb surge voltage.
However, gap-type surge absorbers have a large discharge delay and lack of stability in characteristics due to light and shade effects, and zinc oxide varistors have low insulation resistance, making it difficult to obtain sufficient surge voltage absorption effects. It has its drawbacks.

The present applicant discovered a micro-gap type surge absorbing element as a solution to the poor characteristics of conventional surge absorbing elements, and filed a patent application earlier (Japanese Patent Laid-Open No. 55-128283. Hereinafter referred to as the "prior application"). ) The surge absorption element of the earlier application is as shown in Figure 2.
Electrodes 16 with lead wires 15 are provided at both ends of a ceramic element 14 in which a conductive film 13 having micro-gap insulating grooves 12 is formed on the surface of a ceramic insulator 11, and the electrodes 16 are placed inside an insulating exterior body 17. Both ends are sealed by heat fusion or the like.

The micro-gap type surge absorbing element as shown in FIG. 2 has excellent characteristics such as no discharge delay, no difference in characteristics due to brightness, and high insulation resistance value.

[Problems to be Solved by the Invention] Although the micro-gap type surge absorbing element shown in Fig. 2 has extremely excellent surge voltage absorption characteristics, its structure is , had the following problems.

When fixing the ceramic element 14 in the exterior body 17, it is difficult to position the element 14 and the exterior body 17, so when assembling it, it is arranged on the central axis of the exterior body 17, and the space 18 is evenly spaced around the element 14.
It is not easy to set up

Both ends of the exterior body 17 are sealed by heat fusion or the like, but in order to prevent the transmission of heat effects during the heat fusion, the size of the exterior body 17 is made to be somewhat larger than the ceramic element 14. bird,
Since it is necessary to provide the space 18, there is a limit to miniaturization of the surge absorbing element.

[Means for Solving the Problems] The present invention solves the above-mentioned conventional problems and provides a surge absorption element that is easy to assemble and can be downsized. , consisting of a conductive film that covers the outer peripheral surface and both end faces of the insulator, and a linear exposed portion that goes around the outer peripheral surface of the insulator and exposes the insulator in a circular line shape, and a plurality of conductive films are formed. A ceramic element consisting of an insulating groove as a discharge gap divided into individual parts;
A cylindrical exterior body in which the ceramic element is coaxially disposed, and an insulating exterior body in which the inner peripheral surface of the exterior body and the outer surface of the ceramic element are separated; A disc-shaped electrode is fitted inside each end in the axial direction of the cylinder; and a recess formed in the inner surface of the exterior body of the electrode; both ends of the ceramic element are fitted into the recess of the electrode, respectively. The gist is a cylindrical surge absorbing element formed by combining the two.

[Function] In the surge absorbing element of the present invention, a disk-shaped electrode having a recess on one surface is disposed so that both ends of the ceramic element fit into the respective recesses, so the ceramic element can be easily inserted into the outer casing. Positioning can be set. Moreover, an effective space for discharge can also be secured.

Moreover, since the disc-shaped electrodes are arranged on both ends of the cylindrical exterior body and are fitted into the ceramic element, there is no need to provide extra space inside the exterior body, making the device more compact. This makes it possible to achieve

[Example] Hereinafter, an example of the cylindrical surge absorbing element of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the cylindrical surge absorbing element of the present invention.

The cylindrical surge absorbing element 1 of the present invention has a ceramic element 5 formed by forming a conductive film 4 having an insulating groove 3 on the surface of a columnar ceramic insulator 2.
is housed in a cylindrical insulator exterior body 6, and a recess 7 is formed on one surface of the exterior body 6 at both ends in the cylindrical axis direction.
A disk-shaped electrode 7 having a diameter a is arranged such that both ends of the ceramic element 5 fit into the respective recesses 7a. The conductive film 4 is formed to cover the outer peripheral surface and both end surfaces of the ceramic insulator 2, and the insulating groove 3 goes around the outer peripheral surface of the ceramic insulator 2 and exposes the insulator 2 in the form of a circuit line. This is a linear exposed portion and is a discharge gap that divides the conductive film 4 into a plurality of parts (two in the figure). The ceramic element 5 is coaxially arranged inside the exterior body 6, and the inner peripheral surface of the exterior body 6 and the outer surface of the ceramic element 5 are separated from each other.

The details of each component of the surge absorbing element of the present invention will be explained below.

The ceramic insulator 2 concentrates the electric field in the insulating groove 3 of the conductive film 4 when a surge voltage is applied between the electrodes. Suitable ceramic materials for the insulator include, for example, mullite porcelain, forsterite porcelain, alumina porcelain, and steatite porcelain.

The conductive film 4 formed on the surface of such a ceramic insulator 2 may be a metal film such as silver,
Other conductive ceramic films are used.
Examples of conductive ceramics include conductive ceramics containing conductive metal oxides and interstitial nitrides, and examples of conductive metal oxides include SnO ₂ ,
Nb ₂ O ₃ , MoO ₃ , WO ₂ and the like are suitable. On the other hand, interstitial nitrides mainly correspond to nitrides of transition elements, which have a structure in which nitrogen atoms penetrate into the gaps between metal atoms, so they have conductivity even without the addition of trace amounts of impurities. Yes, TiN, TaN, etc. are suitable. Both of these conductive metal oxides and interstitial nitrides have high melting points and are excellent in oxidation resistance and corrosion resistance.

In order to form these conductive films 4 on the surface of the insulator 2, a vapor phase deposition method such as plating, sputtering or ion plating is advantageous.

The insulating groove 3 provided in such a conductive film 4 is
In order to reduce the discharge delay, it is preferable that it be thin, but if it is too narrow, there is a risk of a short circuit due to fusion during discharge.

Although FIG. 1 shows an example in which one groove 3 is provided, the number of grooves 3 may be two or more depending on the purpose of the surge absorbing element.

The insulation groove 3 is usually formed by laser processing,
As the laser, a solid laser such as a YAG laser or a gas laser such as an argon gas laser is used. In particular, YAG laser is highly stable and suitable.

The electrode 7 has a disc shape with a recess 7a formed at the center of one surface. The size of this recess 7a,
The shape is set so that the concavity and convexity match the edge of the ceramic element 5, but generally the concave part and the edge of the ceramic element are enlarged to increase the contact area, but this is advantageous in terms of conductivity. .

Note that the surge absorbing element 1 of the present invention has an exterior body 6
Since the ceramic element 5 is inserted into the electrode 7 and both ends of the ceramic element are supported and sealed in the recess 7a formed in the center of the electrode 7, materials with a small difference in thermal expansion are selected for the exterior body 6 and the electrode 7. It is preferable to do so.

The exterior body 6 is usually made of an insulating material such as glass. As the electrode 7, diamond, Kovar, etc. are used.

In the surge absorbing element 1 of the present invention, a ceramic element 5 is inserted into a cylindrical exterior body 6, and a recess 7a is formed at both ends of the exterior body 6 with a disc-shaped electrode 7 at its center.
By fitting and enclosing the ceramic element so that it fits with both ends of the ceramic element, the ceramic element can be easily assembled without requiring complicated operations when positioning the ceramic element within the exterior body.

In this case, at least one gas selected from the group consisting of rare gas and nitrogen gas is used as the filler gas. The pressure of the sealed gas is not particularly limited, but it is preferably reduced pressure.

Note that what is shown in FIG. 1 is one embodiment of the present invention, and the present invention is not limited to what is shown in FIG. 1 in any way.

For example, the shape of the ceramic element 5 is not limited to the shape shown in FIG.
A substantially cylindrical shape as shown in FIG. 3 may be used. However, when the cross-sectional area of both ends is made large and the cross-sectional area of the center part is made small as shown in Fig. 1, conductivity is increased by maintaining a large contact area between the ceramic element and the electrode. This is extremely advantageous since it is possible to secure a sufficient space 10 necessary for discharge and improve electrical characteristics such as surge resistance.

Although FIG. 1 shows a surge absorbing element in which the electrode 7 is not provided with a lead wire, the surge absorbing element of the present invention may be of a type in which the electrode 7 is connected to a lead wire. However, when lead wires are connected, high-frequency signal distortion occurs due to the stray capacitance of the lead wires.

The lead wires limit the spatial arrangement with other electronic components. Furthermore, it is difficult to attach it to a substrate, etc., and the attachment mechanism is also complicated.

The lead wire portion is long, which limits miniaturization, making it difficult to reduce costs such as material costs.

Since such problems may occur, it is advantageous to use a type without lead wires.

[Effects of the Invention] As detailed above, the cylindrical surge absorption element of the present invention includes a columnar ceramic insulator, a conductive film covering the outer peripheral surface and both end surfaces of the insulator, and an outer periphery of the insulator. A ceramic element consisting of a linear exposed part that goes around the surface and exposes the insulator in a circular line shape, and an insulating groove as a discharge gap that divides the conductive film into a plurality of parts; A cylindrical exterior body in which elements are arranged coaxially, and an insulating exterior body in which the inner peripheral surface of the exterior body and the outer surface of the ceramic element are separated; both ends of the exterior body in the axial direction of the cylinder a disc-shaped electrode fitted inside each side; and a recess formed on the inner surface of the exterior body of the electrode; both ends of the ceramic element are fitted into the recess of the electrode, respectively. In addition to having the extremely superior surge absorption characteristics of the micro-gap type surge absorption element, it is also characterized in that the components can be easily assembled and miniaturized.

Therefore, the cylindrical surge absorbing element of the present invention is industrially extremely useful as a surge voltage absorbing element for various electrical and electronic circuits.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing one embodiment of the cylindrical surge absorbing element of the present invention, Fig. 2 is a cross-sectional view of a conventional surge absorbing element, and Fig. 3 is a cross-sectional view showing another embodiment of the surge absorbing element of the present invention. FIG. 1... Surge absorption element, 2... Insulator, 3...
Insulating groove, 4... Conductive film, 5... Ceramic element, 6... Exterior body, 7... Electrode.

Claims (1)

[Scope of Claims] 1. A columnar ceramic insulator, a conductive film that covers the outer peripheral surface and both end surfaces of the insulator, and a conductive film that goes around the outer peripheral surface of the insulator and exposes the insulator in the form of a circuit line. a ceramic element consisting of an insulating groove as a discharge gap, which is made up of a linear exposed part and divides the conductive film into a plurality of parts; a cylindrical exterior body in which the ceramic element is coaxially arranged; an insulating exterior body in which the inner circumferential surface of the exterior body and the outer surface of the ceramic element are separated from each other; disc-shaped electrodes fitted inside each end of the exterior body in the cylinder axis direction; and A recess formed on the inner surface of the electrode's exterior body;
A cylindrical surge absorbing element comprising: a cylindrical surge absorbing element, wherein both ends of the ceramic element are respectively fitted into recesses of the electrode. 2. The cylindrical surge absorbing element according to claim 1, wherein the ceramic element has a shape in which the cross-sectional area at the center is smaller than the cross-sectional area at both ends.