JPH0765930A - Discharge type surge absorber - Google Patents

Abstract

PURPOSE:To provide a surge absober which can simply be assembled in a small size with a less number of component parts, excels in the mass-productivity, can absorb a next W surge voltage, and which can prevent overheat or firing of electronic component etc., automatically stopping electric discharge when an overcurrent or overvoltage is applied. CONSTITUTION:A surge absorber 10 of electric discharge type is so structured that a pair of electrodes 12, 13 are installed and sealed at the two ends of an insulated tube 11 in such a positioning as opposing each other, wherein a surge absorber 20 is interposed according to necessity. An inert gas 14 is encapsulated in the space bounded by the electrodes 12, 13 and the insulated tube 11. Hole's) 15 is formed in at least either of the mating electrodes 12, 13 and is sealed with a low melting point metal 16. This metal 16 melts with the heat emitted by an electric discharge of the surge absorber 10, and the hole 15 is opened to allow the air to flow via hole 15 into the insulated tube 11 filled with the inert gas 14, and the discharge hold voltage becomes higher than the overvoltage so that the discharge is stopped which is achieved by a simple and small-sized configuration.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a telephone, a facsimile,
In addition to the function of absorbing surge voltage applied to electronic components for communication equipment such as telephone exchanges and modems, the electronic components and the printed circuit boards on which these components are mounted when continuous overvoltage or overcurrent enters the electronic components. The present invention relates to a discharge type surge absorber that prevents thermal damage or ignition. More specifically, the present invention relates to a discharge type surge absorber in which both ends of an insulating tube having a gap or a microgap inside the tube are hermetically sealed with a pair of opposing electrodes. In the present specification, the overvoltage or the overcurrent refers to an abnormal voltage exceeding the discharge start voltage of the surge absorbing element and an abnormal current associated therewith.

[0002]

2. Description of the Related Art This type of surge absorber is connected to a pair of input lines of an electronic component in parallel with the electronic component, and is configured to operate at a voltage higher than the working voltage of the electronic component. That is, the surge absorber is a resistor having a high resistance value at a voltage lower than the discharge starting voltage, but becomes a resistor having a low resistance value of several tens Ω or less when the applied voltage is equal to or higher than the discharge starting voltage. When a surge voltage such as a lightning surge of several kV to several tens of kV is momentarily applied to an electronic component, the surge absorber is discharged, and the surge voltage is absorbed to protect the electronic component. Therefore, if an overvoltage or an overcurrent is continuously applied to a circuit including electronic components due to an accident or the like, current continues to flow in the surge absorber. As a result, the surge absorber generates heat, which causes ignition of electronic devices in the vicinity.

Normally, it is unlikely that such an overvoltage or overcurrent will continuously enter the circuit, but it is becoming more and more popular to take the maximum possible safety measures in anticipation of an accident. For example, UL (Underwriter's Labo) in the United States
ratories Inc.) has established a prescribed safety standard for surge absorbers so that the surge absorbers do not pose a risk of fire or electric shock to communication equipment when such continuous overvoltage or overcurrent enters. ing.

Conventionally, a fuse or a low melting point metal member has been adhered to the surface of a surge absorber as a surge absorber which complies with such safety standards and can prevent ignition of electronic equipment due to continuous overvoltage or overcurrent. A fuse and a low melting point metal member connected in series to a surge absorber are disclosed (Japanese Patent Laid-Open Nos. 63-11022 and 63-18923).

[0005]

However, a surge absorber in which a fuse or a low melting point metal member is connected in series to a surge absorber has a surge absorbing circuit which is not activated when the fuse or the low melting point metal member is blown out by the intrusion of overvoltage or overcurrent. Since it is in the open state, there is the trouble of having to replace the surge absorber with a new one in preparation for the next surge voltage. The object of the present invention is to absorb not only an instantaneous surge voltage such as a lightning surge but also not only abnormal heat generation of the surge absorber when there is a continuous overvoltage or overcurrent intrusion, but also electronic parts. Another object of the present invention is to provide a discharge type surge absorber capable of preventing thermal damage, ignition, etc. of a printed circuit board on which this component is mounted, and capable of absorbing a surge voltage that comes next. Another object of the present invention is to provide a discharge type surge absorber which has a small number of parts, is small in size, is easy to assemble, and is excellent in mass productivity.

[0006]

DISCLOSURE OF THE INVENTION The inventors have found that the discharge start voltage of an air-filled discharge surge absorber is higher than the discharge start voltage of an inert gas-filled discharge surge absorber, and the latter discharge start The present invention has been accomplished by paying attention to the point that the voltage is higher than the overvoltage generated by, for example, the contact between the telephone line and the distribution line.

That is, as shown in FIG. 1, the discharge type surge absorber 10 of the present invention includes an insulating pipe 11 and the insulating pipe 1.
A pair of opposed electrodes 12 which are sealed to face each other at both ends of
13 and an inert gas 14 sealed in a space formed by the counter electrodes 12 and 13 and the insulating tube 11. The characteristic configuration is that the pair of counter electrodes 12 and 13 are
Holes 15 are formed in either or both of
5 is sealed with the low melting point metal 16.

The present invention will be described in detail below. The discharge type surge absorber of the present invention includes a counter electrode type surge absorber and a microgap type surge absorber having a microgap inside the insulating tube. In the counter electrode type surge absorber, a pair of electrodes 12 and 13 facing each other are provided at both ends of an insulating tube 11 as shown in FIG. 3 at intervals of several mm, and an inert gas 14 is filled between these electrodes. There is a surge absorber 30 that is enclosed, or a surge absorber (not shown) in which a pair of metal cylindrical electrodes are opposed to each other at intervals of several millimeters and filled with an inert gas by an insulating tube and enclosed.

As shown in FIG. 1, the surge absorber 10 of the microgap type has a surge absorbing element 20 housed inside an insulating tube 11. In the surge absorbing element 20, a pair of cap electrodes 24 and 25 are attached to both ends of a cylindrical ceramic body 22 covered with a conductive film 21, and then a microgap 23 is circumferentially formed in the center of the ceramic body 22. Made by forming. The conductive film 21 is formed by the sputtering method,
The ceramic body 22 is formed on the surface of the ceramic body 22 by a thin film forming method such as a vapor deposition method, an ion plating method, a plating method, and a CVD method. It is formed to be divided. The micro gap is formed in a width of 10 to 200 μm depending on the depth of focus of the laser beam and the thickness of the conductive film. The surge absorber 10 accommodates the surge absorbing element 20 in an insulating tube 11 and arranges a pair of counter electrodes 12 and 13 at both ends of a ceramic body 22. The counter electrodes 12 and 13 are cap electrodes 24 and 25, respectively. It is made by electrically connecting and at the same time enclosing the inert gas 14 inside the insulating tube 11. The accommodated surge absorbing element 20 is fixed by the counter electrodes 12 and 13 when the pair of counter electrodes 12 and 13 is sealed at both ends of the insulating tube 11.

The insulating tube of the present invention is a glass tube, a ceramic tube or the like. The glass tube is made of hard glass such as borosilicate glass, or soft glass such as lead glass, soda lime glass. The ceramic tube is not limited to one made of a ceramic sintered body that transmits visible light, such as PLZT or transparent alumina, but may be another ceramic tube having an insulating property.

The counter electrode is made of a metal whose coefficient of thermal expansion is substantially the same as that of the insulating tube in order to prevent the occurrence of cracks due to thermal contraction of the insulating tube during sealing. Therefore, the material of the counter electrode is selected according to the type of insulating tube. When the insulating tube is a soft glass tube, iron 52 wt% -nickel 42 wt% is applied to the counter electrode.
-Chromium 6wt% alloy is used, and when the insulating tube is a hard glass tube, iron 58wt% -nickel 42wt%
% Alloy (hereinafter referred to as 42 alloy) or the like is used. When the insulating tube is a ceramic tube, a clad material of 42 alloy and copper, Kovar, or the like is used for the counter electrode. The clad material of 42 alloy and copper is made by a clad method in which a copper thin film is adhered to one or both sides of a plate material of 42 alloy and mechanically rolled at high temperature. It is preferable to oxidize the copper thin film of the clad material to form cuprous oxide on the copper surface, because the compatibility with glass becomes good at the time of sealing. After punching this clad material into a disk, it is drawn to form a counter electrode.

Both the counter electrode type surge absorber and the micro gap type surge absorber are filled with an inert gas such as argon gas, neon gas or nitrogen gas when the counter electrode is sealed. Further, the number of holes formed in the counter electrode of the present invention is not limited to one, and a plurality of holes may be formed. Further, not only one counter electrode but also both counter electrodes may be formed. Further, the low melting point metal of the present invention is aluminum,
Either lead, tin or zinc or alloys thereof are used.

[0013]

When an overvoltage or an overcurrent continuously enters the line to which the surge absorber 10 of the present invention is connected, the surge absorbing element 20 is a resistor and generates heat, and the counter electrodes 12 and 13 also generate heat accordingly. To do. This heat melts the low melting point metal 16 that has sealed the hole 15 formed in the counter electrode. The holes 15 are opened by this melting, and the inert gas 1
Air flows through the hole 15 into the insulating tube 11 which is filled with 4. When air enters the insulating tube 11, the discharge sustaining voltage becomes higher than the normal overvoltage and the discharge is stopped.

[0014]

Embodiments of the present invention will now be described in detail with reference to the drawings. <Example> As shown in FIG. 1, a microgap type surge absorber 10 was manufactured by the following method. First, the surge absorbing element 20 housed in the insulating tube 11 was prepared. The cylindrical ceramic body 22 of the surge absorbing element 20 is made of a mullite sintered body, and its surface is covered with a conductive film 21 made of TiN by sputtering. Cap electrodes 24 and 25 made of stainless steel are attached to both ends of the ceramic body 22. Ceramic body 2
By irradiating the central portion of 2 with a laser beam and trimming the conductive film 21 in the circumferential direction, a microgap 23 having a width of about 30 μm is formed, and the surge absorbing element 20 is manufactured.

A low melting point lead glass tube was prepared as the insulating tube 11, and the glass tube 11 was placed in a sealing chamber (not shown) provided with a carbon heater. The hat-shaped counter electrode 13 in which the hole 15 is not formed is inserted into the glass tube 11, and then the surge absorbing element 20 is inserted into the glass tube 11.
The cap electrode 25 was inserted into the recess 13 a of the counter electrode 13. As a result, the surge absorbing element 20 is arranged in the center of the glass tube 11, and subsequently, the recess 12a of the hat-shaped counter electrode 12 in which the hole 15 is formed is covered with the cap electrode 24 of the surge absorbing element 20, and the counter electrode 12 is made of glass. It was inserted into the tube 11. The counter electrodes 12 and 13 are iron 52 wt% -nickel 4
2 wt% -chromium 6 wt% alloy.

After the air inside the glass tube was evacuated by setting the negative pressure in the sealing chamber, argon gas was supplied to the sealing chamber instead, and the argon gas 14 was introduced into the glass tube at a pressure of 240 Torr. In this state, the glass tube 11 and the counter electrodes 12, 13 are heated to 740 ° C. by a carbon heater.
Heated for 1 minute. After the counter electrodes 12 and 13 are sealed to the glass tube 11, the low melting point metal 16 of Pb /
Arranging Sn alloy, Argon gas 14 in the glass tube 11
The carbon heater was heated to a temperature at which the low-melting point metal 16 melts in a state of satisfying the above condition, and the hole 15 was sealed with the low-melting point metal 16 to obtain the surge absorber 10. This surge absorber 10 had a length of 8.0 mm and an outer diameter of 6.0 mm.

<Comparative Example 1> The same surge absorber as that of the embodiment was prepared except that the counter electrode 12 having neither the hole 15 nor the low melting point metal 16 was used. As shown in FIG. 4, the surge absorber 1 was connected in series with the fuse 2 which is blown for the first time at (8 × 20) μsec-600 A, and the height was 1.0 cm.
It was placed in a case 3 having dimensions of width 2.0 cm and height 0.5 cm.

<Comparative Example 2> The same surge absorber as that of the embodiment was prepared except that the counter electrode 12 having neither the hole 15 nor the low melting point metal 16 was used.

<Comparison Test and Evaluation> (a) Overvoltage Application Test An overvoltage of 600 V at 1 A was applied to each of the surge absorber 10 of the example, the surge absorber with a fuse of comparative example 1 and the surge absorber of comparative example 2. as a result,
In the surge absorber 10 of the embodiment, the counter electrodes 12, 1
3 overheated, and the low melting point metal 16 melted. The hole 15 was opened, air entered the glass tube 11, and the discharge stopped in about 3 seconds. In the surge absorber with a fuse of Comparative Example 1, the fuse 2 was blown out in about 3 seconds due to overheating.
The surge absorber 1 has stopped discharging. With the surge absorber of Comparative Example 2, the discharge did not stop, the counter electrode overheated, and the connected printed circuit board ignited.

(B) Impulse Response Test The discharge start voltage Vs (V) and the surge response voltage Vimp (V) were measured. The discharge start voltage was measured for each of 20 samples, and the surge response voltage was measured in the surge absorber 10 of the example and the surge absorbers of the comparative examples 1 and 2 (1.
2 x 50) μsec-10kV pseudo surge for each 5
The voltage was applied repeatedly and the operating voltage was measured. Table 1 shows these average values.

[0021]

[Table 1]

As is clear from Table 1, it was found that the surge absorber 10 of the example has the same excellent surge response as compared with the surge absorbers of the comparative examples 1 and 2.

[0023]

As described above, according to the present invention, in addition to absorbing a momentary surge voltage such as a lightning surge, when there is a continuous overvoltage or overcurrent intrusion, Since the low melting point metal melts and air flows into the insulating tube, the discharge sustaining voltage rises, causing not only abnormal heat generation of the surge absorber, but also thermal damage and ignition of electronic components and the printed circuit board on which these components are mounted. Can be prevented. Further, since the discharge type surge absorber of the present invention does not use a fuse as in the prior art, the number of parts can be reduced and the cost can be reduced, the occupying space is small, the assembly is easy and the mass productivity is excellent. In particular, even after air has flowed into the insulating tube, the response to the surge is reduced, but it still has the original function of the surge absorber that absorbs the next surge voltage.

[Brief description of drawings]

FIG. 1 is a central longitudinal sectional view of a micro-gap type surge absorber of the present invention.

FIG. 2A is a front view of one counter electrode in which the hole is formed. (B) The front view of the other counter electrode in which the hole is not formed.

FIG. 3 is a central longitudinal sectional view of a counter electrode type surge absorber of the present invention.

FIG. 4 is a circuit configuration diagram of a conventional surge absorber with a fuse.

[Explanation of symbols]

 10,30 Surge absorber 11 Insulation tube (glass tube) 12,13 Counter electrode 14 Inert gas 15 Hole 16 Low melting point metal 20 Surge absorbing element 21 Conductive film 22 Ceramic element body 23 Microgap 24,25 Cap electrode

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[Procedure amendment]

[Submission date] August 24, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 2

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1] ─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] September 27, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

The counter electrode is made of a metal whose coefficient of thermal expansion is substantially the same as that of the insulating tube in order to prevent the occurrence of cracks due to thermal contraction of the insulating tube during sealing. Therefore, the material of the counter electrode is selected according to the type of insulating tube. When the insulating tube is a soft glass tube, iron 52 wt% -nickel 42 wt% is applied to the counter electrode.
-Chromium 6wt% alloy, Iron 58wt% -Nickel 42w
If t% alloy (hereinafter referred to as 42 alloy) and copper clad material are used and the insulating tube is a hard glass tube, 4
2 alloy or the like is used. When the insulating tube is a ceramic tube, a clad material of 42 alloy and copper, Kovar, or the like is used for the counter electrode. The clad material of 42 alloy and copper is made by a clad method in which a copper thin film is adhered to one or both sides of a plate material of 42 alloy and mechanically rolled at high temperature. It is preferable to oxidize the copper thin film of the clad material to form cuprous oxide on the copper surface, because the compatibility with glass becomes good at the time of sealing. After punching this clad material into a disk, it is drawn to form a counter electrode.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

A low melting point lead glass tube was prepared as the insulating tube 11, and the glass tube 11 was placed in a sealing chamber (not shown) provided in a carbon heater. The hat-shaped counter electrode 13 in which the hole 15 is not formed is inserted into the glass tube 11, and then the surge absorbing element 20 is inserted into the glass tube 11.
The cap electrode 25 was inserted into the recess 13 a of the counter electrode 13. As a result, the surge absorbing element 20 is arranged in the center of the glass tube 11, and subsequently, the recess 12a of the hat-shaped counter electrode 12 in which the hole 15 is formed is covered with the cap electrode 24 of the surge absorbing element 20, and the counter electrode 12 is made of glass. It was inserted into the tube 11. The counter electrodes 12 and 13 are iron 52 wt% -nickel 4
2 wt% -chromium 6 wt% alloy.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masatoshi Abe 2270 Yokoze, Yokose-cho, Chichibu-gun, Saitama Sanryo Materials Co., Ltd. Ceramics Laboratory (72) Mikio Harada 2270 Yokose, Yokose-cho, Chichibu-gun, Saitama Sanryo Materials Co., Ltd. Ceramics Laboratory

Claims (3)

[Claims] 1. An insulating tube (11), a pair of counter electrodes (12, 13) sealed at opposite ends of the insulating tube (11) so as to face each other, the counter electrode (12, 13) and the In a discharge type surge absorber (10) provided with an inert gas (14) sealed in a space formed by an insulating tube (11), one or both of the pair of counter electrodes (12, 13) A discharge type surge absorber, characterized in that a hole (15) is formed in the hole, and the hole (15) is sealed with a low melting point metal (16). 2. A microgap (23) is formed on a peripheral surface of a cylindrical ceramic body (22) covered with a conductive film (21), and a pair of caps is provided at both ends of the ceramic body (22). The surge absorbing element (20) having the electrodes (24, 25) is housed in the insulating tube (11), and the pair of opposing electrodes (12, 13) are fixed to fix the surge absorbing element (20). And the pair of cap electrodes (24, 25)
The discharge type surge absorber according to claim 1, which is electrically connected to the. 3. The low melting point metal (16) is aluminum, lead, tin or zinc, or an alloy thereof.
Alternatively, the discharge type surge absorber described in 2.