JPH077699B2 - Method of manufacturing surge absorber - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a surge absorbing element utilizing a spark discharge phenomenon.

[Background technology]

Conventionally, the surge absorbing element 50, a pair of carbon electrodes 51,
As shown in FIG. 6, the electrodes 51 and 51 are opposed to each other with a space of a predetermined distance therebetween. Electrode 51,
An electrically insulating spacer 52 is provided between the 51 to provide a space of a predetermined distance. The electrodes 51, 51 and the spacer 52 are housed in an insulating cylindrical body 53.
On the other hand, the metal plate 5 is formed by closing the openings at both ends of the cylindrical body 53.
4, 54 are attached to the end of the cylindrical body 53. These metal plates 5
4, 54 and the cylindrical body 53 form a container. There is a slight negative pressure inside the container and the metal plates 54, 54 warp inward and both electrodes 51,
It is in contact with 51 and is electrically connected. That is, a metal plate
54 and 54 also serve as extraction electrodes.

The surge absorbing element 50 is connected in parallel to the load L as shown by the alternate long and short dash line in FIG. 6, and when an abnormal surge voltage is applied, a spark discharge is generated between the electrodes 51, 51 to generate a surge. It absorbs and protects the load L.

By the way, the spacer 52 of the surge absorbing element 50 is
It is made of a ceramic that is as thin as 0.2 mm. Therefore, there is a problem in that cracks and the like are likely to occur at the manufacturing stage and in use, resulting in a reduction in manufacturing yield and deterioration of the protective function.

[Object of the Invention]

The present invention has been made in view of the above circumstances, and an object thereof is to provide a surge absorbing element that essentially solves the problems associated with breakage of conventional spacers.

[Disclosure of Invention]

In order to achieve the above-mentioned object, the present invention comprises a pair of electrodes facing each other with a space of a predetermined distance therebetween, an electrically insulating cylinder, and a container having a metal plate closing both end openings of the cylinder, The electrode is housed in a container, the metal plate serves as an extraction electrode in contact with both electrodes,
In a surge absorbing element that absorbs surge by spark discharge generated between both electrodes, each of the both electrodes is fixed to a metal plate fixed to the cylindrical body, and the predetermined distance is maintained. A method of manufacturing a surge absorbing element characterized in that the thickness between the outer surfaces of a pair of electrodes facing each other with a space of the predetermined distance is made thinner than the thickness of the tubular body, A concave recess that fits into the opening of the cylinder is provided in the center of the metal plate to be fixed, and the coefficient of thermal expansion in the thickness direction of the metal plate is larger than the coefficient of thermal expansion in the thickness direction of the cylinder. When the surge absorbing element is manufactured by setting the pair of electrodes in the center of the opening of the tubular body and fixing the metal plate to the tubular body and the electrodes, the entire body is heated and heated to thermally expand. The metal plate in contact with the tube and electrode. As electrodes are upon contacts, thereby fixing the cylindrical body and the electrode to the metal plate, then
A gist of a method for manufacturing a surge absorbing element is characterized in that the electrodes are confronted with each other with a space of a predetermined distance therebetween by cooling the entire body to cause thermal contraction.

Hereinafter, the surge absorbing element according to the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the configuration of an embodiment of a surge absorbing element according to the present invention. FIG. 3 shows the surge absorber disassembled.

The surge absorbing element 1 includes a pair of carbon discharge electrodes 2, 2 '. The electrodes 2 and 2'include a cylindrical body 3 made of an electrically insulating material, and a metal plate 4 attached to the ends of the cylindrical body 3 so as to close the openings at both ends of the cylindrical body 3.
It is housed in a container having 4 '. As shown in FIG. 1, the electrodes 2, 2'can be formed even if spacers are not provided.
Face each other across a space of a predetermined distance. Even if there is no spacer, the electrodes 2 and 2'are respectively provided with the metal plate 4 and
The predetermined distance is maintained by the rigidity of the metal plates 4, 4'fixed to the metal plate 4 '. The metal plates 4, 4 '
The electrodes 2, 2'and the metal plates 4, 4'and the cylindrical body 3 are fixed to each other by brazing.

The surge absorbing element 1 is connected in parallel to the load L,
When an abnormal surge voltage is applied, a spark discharge is generated between the electrodes 2 and 2 ', and a surge current does not pass through the load L,
It is made to flow to the ground side through 2 ', and a high voltage higher than the spark discharge starting voltage is prevented from being applied to the load L.

As described above, since the surge absorbing element 1 does not have a spacer that is easily damaged, the yield and the protection function are not deteriorated due to the damage of the spacer. Further, conventionally, as shown in FIG. 6, a gap G is generated between the electrode 51 and the metal plate 54, the contact resistance between the electrode and the metal plate increases, and the discharge current is limited. Although the spark discharge start voltage fluctuates due to fluctuations, in this surge absorbing element 1, since the electrodes 2 and 2'are fixed to the metal plates 4 and 4'which are extraction electrodes, electrical conduction is reliable. Yes, a stable discharge operation is performed.

Next, the manner of manufacturing the surge absorber 1 will be described.

FIG. 2 shows the metal plate 4 in the manufacture of the surge absorbing element 1,
The 4'attachment step is schematically shown.

In manufacturing the surge absorbing element 1, parts as shown in FIG. 3 are prepared. Disc-shaped electrode 2 made of carbon,
2'is an electrode for spark discharge. The cylindrical body 3 is made of an electrically insulating material such as ceramic (for example, amylna) or glass. The metal plates 4 and 4'are made of a metal material such as copper or nickel. The metal plates 4, 4'are respectively formed with concave depressions 4a, 4'a.

An example of specific dimensions of each of the above components will be given below.

The cylindrical body 3 is selected to have an outer diameter of 4 to 5 mm and an inner diameter of 2 to 4 mm, for example. The height (length in the axial direction) of the cylindrical body 3 is selected to be, for example, about 2 to 4 mm. Disc-shaped electrodes 2, 2 '
Has an outer diameter substantially equal to the inner diameter of the cylindrical body 3 and a thickness of, for example, about 0.02 to 1.0 mm. The outer diameters of the metal plates 4, 4'are substantially equal to the outer diameter of the cylindrical body 3, and the thickness is, for example,
It is selected to be about 0.1 to 0.35 mm. The recesses 4a and 4'a have an outer diameter substantially equal to the inner diameter of the cylindrical body 3 and a height of 1 mm or less.

Next, the assembly of the surge absorber 1 will be described.

The electrodes 2, 2 ', the cylindrical body 3, and the metal plates 4, 4'are combined as shown in FIG. And the metal plate 4,
4'and the ends of the electrodes 2, 2'and the cylindrical body 3 are brazed B ... B to hermetically seal. At this time, brazing is performed in the inert gas atmosphere S. The gas atmosphere S is, for example, He or Ar gas of 20 to 760 Torr and has a temperature of about 900 ° C. That is, in the warm atmosphere, the electrodes 2 and 2 '
Are in contact with each other, and the depressions 4a, 4'a of the metal plates 4, 4 '
The outer surfaces of the bottoms 4b and 4'b of the electrodes are combined so as to contact the surfaces of the electrodes 2 and 2 ', respectively. After the brazing, the metal plates 4 and 4 ′ are accompanied by the electrodes 2 and 2 ′, respectively, and the cylindrical body 3 contracts in the axial direction (height direction) as the temperature is returned from the warm atmosphere to room temperature. Also greatly contracts, as shown in FIG. 1, the electrodes 2, 2'are separated from each other,
The space of a predetermined distance is separated.

In this case, each component is selected as follows. Under heating during brazing, the axial dimensions (thickness) l1 of the two electrodes 2, 2'are recesses 4a, 4'on the assumption that the cylindrical body 3 is combined only with the metal plates 4, 4 '. bottom 4a of a,
4'b is equal to the outer surface dimension l2, for example 0.0 to 100 μm
It is getting longer. On the contrary, at room temperature, the electrode 2,
The axial dimension (thickness) 11 of 2'is shorter than the dimension 12 between the outer surfaces of the bottoms 4b and 4'b by a range not exceeding 100 .mu.m, for example. This dimensional difference between the warmed state and the room temperature state creates a space of a predetermined distance, and each part, particularly the cylindrical body 3 and the metal plate 4, has such a dimensional relationship between the warmed state and the room temperature state. The size and the coefficient of thermal expansion of 4'are selected.

When brazing in an inert gas, the inert gas is sealed in the cylindrical body 3. When sealed under reduced pressure, the inside of the cylindrical body 3 of the surge absorbing element 1 is in a negative pressure state.

For the above brazing, a brazing material having an active metal that combines with carbon is used. For example, Ag: 70-80%, Copper: 20-
30%, brazing filler metal composed of Ti: 2-10%, or BAg-8
There is a brazing material in which Ti foil is layered on silver brazing material such as. Such a brazing material is particularly useful for fixing the carbon used in the electrodes 2, 2'to a metal material. The above brazing material is, of course, also suitable for fixing the alumina used in the cylindrical body 3 and the metal material.

The present invention is not limited to the above embodiment. For example, as shown in FIG. 4, the metal plate is not a cylindrical shape but a truncated cone-shaped metal plate 1
It may be 4, 14 '. When the metal plates 14 and 14 'are frustoconical, when the metal plates 14 and 14' are manufactured by the above manufacturing method,
The amount of 14 'axial shrinkage is large. It is because the radial reduction of the bottom surface of the recess of the metal plate affects the axial displacement of the metal plate, but the degree of the effect is greater in the truncated cone metal plate than in the cylindrical metal plate. Is. Metal plate 14
The diameter of the bottom 14b is slightly shorter than the diameter of the metal plate 4, but the shortened length is extremely small when viewed from the entire length of the diameter. Therefore, it can be considered that the reduction amount Δ in the radial direction is equal to that of the metal plates 4 and 14. When the radial length is reduced, the side faces 4c and 14c are pulled inward and the bent bottoms 4b and 14b are lifted, as shown in FIG. The metal plates 4 and 14 contract axially as much as they are lifted. As shown in FIG. 5, when the radial reduction amounts Δ are equal, the axial reduction amount δ of the metal plate 14 becomes larger than the axial reduction amount δ ′ of the metal plate 4.

The inside of the cylinder may be atmospheric pressure instead of negative pressure, or the inert gas may not be sealed. The electrodes may be made of a material other than carbon.

〔The invention's effect〕

As described above, the surge absorbing element according to the present invention is a container having a pair of electrodes facing each other with a space of a predetermined distance, an electrically insulating tubular body, and a metal plate closing both end openings of the tubular body. A configuration in which the electrode is housed in the container, the metal plate is in contact with the electrodes to serve as an extraction electrode, and surge absorption is caused by spark discharge generated between the electrodes. In the above, each of the both electrodes is fixed to the metal plate fixed to the cylindrical body,
The predetermined distance is maintained. Therefore, an electrically insulating spacer, which is easily damaged, is not required, and there is no reduction in yield or deterioration of protective function due to damage to the spacer, which improves productivity and reliability.

In particular, the thickness between the outer surfaces of a pair of electrodes facing each other across the space of the predetermined distance as a means for fixing the metal plate to the cylindrical body and the electrodes in the state where the electrodes are held at the predetermined distance without the spacers. Is made thinner than the thickness of the tubular body, and a concave recess that fits into the opening of the tubular body is provided in the center of the metal plate that is fixed to both end surfaces of the tubular body. The coefficient of thermal expansion in the thickness direction of the metal plate is set to be larger than the coefficient of thermal expansion, and the pair of electrodes are arranged in the center of the opening of the cylinder to fix the metal plate to the cylinder and the electrode. When manufacturing a surge absorption element, the whole is heated and heated to thermally expand, so that when the metal plate contacts the cylinder and the electrode, the electrodes contact each other, and the metal plate is fixed to the cylinder and the electrode. Then, the whole is cooled to heat shrink And the causes the electrodes to each other are disposed oppositely across a space of a predetermined distance.

Since the work of fixing the metal plate to the cylindrical body and the electrodes can be performed in a state where the electrodes are in contact with each other and are stably fixed, the fixing work such as brazing can be easily and reliably performed. As a result, the adhesion between the metal plate and the electrode is good, and the electrical connection performance is also excellent.

Moreover, if the temperature is lowered from the heating temperature rising state during the fixing operation to the working temperature state, a predetermined interval is automatically set between the electrodes, so that the electrodes can be arranged easily and reliably. . During this period, since the metal plate remains fixed to the cylindrical body and the electrodes, there is no concern that foreign matter will enter the space between the electrodes and the opposing surface of the electrodes will be soiled.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the configuration of an embodiment of a surge absorbing element according to the present invention, and FIG. 2 is a cross-sectional view schematically showing a metal plate attaching step when manufacturing this surge absorbing element. FIG. 3 is an exploded perspective view of the surge absorbing element, FIG. 4 is a sectional view showing a structure of another embodiment of the surge absorbing element according to the present invention, and FIG. 5 is a metal plate in both the surge absorbing elements. FIG. 6 is an explanatory view of axial reduction that accompanies the radial reduction, and FIG. 6 is a cross-sectional view showing the configuration of a conventional surge absorbing element. 1, 1 '... Surge absorbing element 2, 2' ... Electrode 3 ... Cylindrical body (cylindrical body) 4, 4 '... Metal plate

Claims (1)

[Claims] 1. A pair of electrodes facing each other across a space of a predetermined distance, a container having an electrically insulating cylindrical body and a metal plate closing both end openings of the cylindrical body, and the electrode is provided in the container. It is a surge absorbing element that is housed in the metal plate and serves as an extraction electrode by making contact with the electrodes, and is a surge absorbing element that absorbs surge by spark discharge generated between the electrodes, and is fixed to the cylindrical body. A method of manufacturing a surge absorbing element in which each of the electrodes is fixed to a metal plate, and the predetermined distance is held, wherein an outer surface of a pair of electrodes facing each other across a space of the predetermined distance is provided. The thickness of the cylinder is made thinner than the thickness of the cylinder, and a concave recess that fits into the opening of the cylinder is provided in the center of the metal plate fixed to both end surfaces of the cylinder. In the thickness direction of the metal plate rather than the coefficient of thermal expansion in the direction When the surge absorbing element is manufactured by setting a larger thermal expansion coefficient, the pair of electrodes is arranged in the center of the opening of the cylindrical body and the metal plate is fixed to the cylindrical body and the electrodes. Is heated and thermally expanded to cause the electrodes to come into contact with each other when the metal plate comes into contact with the tubular body and the electrodes, and the metal plate is fixed to the tubular body and the electrodes, and thereafter,
A method for manufacturing a surge absorbing element, characterized in that the electrodes are opposed to each other with a space of a predetermined distance therebetween by lowering the temperature of the entire body and causing thermal contraction.