JP3199088B2 - Discharge type surge absorber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a telephone, a facsimile,
In addition to the function of absorbing surge voltage applied to electronic components for telecommunications equipment such as telephone exchanges and modems, in the event of continuous overvoltage or overcurrent intrusion into electronic components, the electronic components and the printed circuit board on which these components are mounted 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 counter electrodes. In this specification, an overvoltage or an overcurrent refers to an abnormal voltage exceeding the discharge starting voltage of the surge absorbing element and an abnormal current accompanying the abnormal voltage.

[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 start voltage, but has a low resistance value of several tens Ω or less when the applied voltage is higher than the discharge start voltage. When a surge voltage of several kV to several tens of kV, such as a lightning surge, is momentarily applied to an electronic component, a surge absorber is discharged, and the surge voltage is absorbed to protect the electronic component. For this reason, when an overvoltage or an overcurrent is continuously applied to a circuit including an electronic component due to an accident or the like, a current continues to flow through the surge absorber. As a result, the surge absorber generates heat, which causes ignition of surrounding electronic devices.

Normally, it is unlikely that such an overvoltage or overcurrent will continuously enter the circuit, but the idea of taking maximum safety measures in anticipation of an accident has become widespread. For example, the UL (Underwriter's Labo
ratories Inc.) has established certain safety standards for surge absorbers so that surge absorbers should not pose a risk of fire or electric shock to communication equipment when such continuous overvoltage or overcurrent enters. ing.

Heretofore, as a surge absorber which conforms to such safety standards and can prevent ignition of electronic equipment due to continuous overvoltage or overcurrent, a fuse or a low melting point metal member is brought into close contact with the surface of the surge absorber. A fuse and a low melting point metal member connected in series to a surge absorber are disclosed (JP-A-63-11022 and JP-A-63-18923).

[0005]

However, a surge absorber in which a fuse or a low-melting metal member is connected in series to a surge absorber has a surge absorbing circuit when a fuse or a low-melting metal member blows due to intrusion of overvoltage or overcurrent. Because of the open state, the surge absorber has to be replaced with a new surge absorber in preparation for the next surge voltage. An object of the present invention is to not only absorb an instantaneous surge voltage such as a lightning surge, but also to not only generate abnormal surge of a surge absorber when continuous intrusion of an overvoltage or an overcurrent occurs, but also to produce electronic components. Another object of the present invention is to provide a discharge-type surge absorber that can prevent thermal damage, ignition, and the like of a printed circuit board on which this component is mounted, and that can absorb the next incoming surge voltage. Another object of the present invention is to provide a discharge type surge absorber which requires a small number of parts, is small in size, easy to assemble, and is excellent in mass productivity.

[0006]

Means for Solving the Problems The present inventors have found that the discharge start voltage of a pneumatic discharge type surge absorber is higher than the discharge start voltage of a discharge type surge absorber containing an inert gas. The present inventors arrived at the present invention by paying attention to a point that the voltage is higher than an overvoltage caused by, for example, contact between a telephone line and a distribution line.

[0007] That is, as shown in FIG. 1, the present invention is conductive
Around a cylindrical ceramic body 22 covered with a conductive film 21
Micro gap 23 is formed on the surface,
The body 22 has a pair of cap electrodes 24 and 25 at both ends.
The surge absorbing element 20 is accommodated in the insulating tube 11 and
A pair of opposing electrodes 12, 13 oppose each other at both ends of the insulating tube 11.
And the counter electrodes 12 and 13 are sealed.
To fix the surge absorbing element 20 and a pair of cap electrodes.
Are electrically connected to the poles 24 and 25,
Inert gas 14 in the space defined by
Is an improvement of the discharge type surge absorber 10 in which
You. Its characteristic configuration is a pair of opposing electrodes 12 and 13.
A hole 15 is formed in one or both of the holes, and this hole 15
Sealed with metal 16 having a melting point lower than that of aluminum
Then, the heat generated by the counter electrodes 12 and 13 causes the metal 1
6 is configured such that air flows into the space inside the insulating tube 11 when the hole 6 is melted and the hole 15 is opened.

Hereinafter, the present invention will be described in detail. Discharge type surge absorber of the present invention is a surge absorber of the micro-gap having a microgap inside insulation tube.

As shown in FIG. 1, a surge absorber 10 of a microgap type has a surge absorbing element 20 housed inside an insulating tube 11. The surge absorbing element 20 has a pair of cap electrodes 24 and 25 mounted on both ends of a cylindrical ceramic body 22 covered with a conductive film 21, and then a micro gap 23 is provided at the center of the ceramic body 22 in the circumferential direction. Formed. The conductive film 21 is formed by a sputtering method,
The ceramic gap 22 is formed on the surface of the ceramic body 22 so as to cover 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 so as to be divided. The micro gap is formed to have a width of 10 to 200 μm based 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 the insulating tube 11 and arranges a pair of opposing electrodes 12 and 13 at both ends of a ceramic body 22. These opposing electrodes 12 and 13 are used as cap electrodes 24 and 25. It is made by electrically connecting and simultaneously filling an inert gas 14 inside the insulating tube 11. The housed surge absorbing element 20 is fixed by the opposing electrodes 12, 13 when the pair of opposing electrodes 12, 13 is sealed to 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 any other insulating ceramic tube.

The counter electrode is made of a metal having substantially the same thermal expansion coefficient 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 based on the type of the insulating tube. When the insulating tube is a soft glass tube, the opposite electrode has 52 wt% of iron and 42 wt% of nickel.
-6 wt% chromium alloy, 58 wt% iron-42 w nickel
When a t% alloy (hereinafter, referred to as 42 alloy) and a copper clad material are used, and the insulating tube is a hard glass tube, 4% alloy is used.
Two alloys or the like are used. When the insulating tube is a ceramic tube, a cladding material of 42 alloy and copper, Kovar, or the like is used for the counter electrode. The 42 alloy and copper clad material is produced by a cladding method in which a copper thin film is adhered to one or both surfaces of a 42 alloy plate and mechanically rolled at a high temperature. It is preferable to oxidize the copper thin film of the clad material to convert the copper surface to cuprous oxide, because the affinity with glass at the time of sealing is improved. After punching this clad material into a disk, drawing is performed to form a counter electrode.

When sealing the counter electrode of the micro-gap type surge absorber, the inside of the insulating tube is filled with an inert gas such as an argon gas, a neon gas or a nitrogen gas. The number of holes formed in the counter electrode of the present invention is not limited to one, but may be plural. Also, not only one counter electrode,
It may be formed on both counter electrodes. Furthermore, the hole of the present invention is sealed.
The stopping metal has a melting point below the melting point of aluminum
A metal, for example, aluminum,
Lead, either or these alloys thereof et tin or zinc
It is.

[0013]

When overvoltage or overcurrent continuously enters the line to which the surge absorber 10 of the present invention is connected, heat is generated because the surge absorbing element 20 is a resistor . Surge absorber
The child 20 is connected to the opposing electrode 1 via the cap electrodes 24 and 25.
Since the electrodes 2 and 13 are in contact with each other, the counter electrodes 12 and 13 also generate heat. Metals 16 which has sealed the hole 15 formed on the counter electrode by the hot melts. The hole 15 is opened by this melting, and the inert gas 14 is opened.
Air flows through the hole 15 into the insulating tube 11 filled with the air. When air enters the inside of the insulating tube 11, the discharge maintaining voltage becomes higher than the normal overvoltage, and the discharge stops.

[0014]

Next, an embodiment of the present invention will be described in detail with reference to the drawings. <Example> As shown in FIG. 1, a micro-gap 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 the surface thereof is formed by sputtering.
It is covered with a conductive film 21 made of iN. A stainless steel cap electrode 24 is provided on both ends of the ceramic body 22.
And 25 are crowned. The conductive film 21 is circumferentially trimmed by irradiating a laser beam to the center of the ceramic body 22 to form a micro gap 23 having a width of about 30 μm, and the surge absorbing element 20 is manufactured.

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

After the inside of the glass tube was evacuated by reducing the 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 and 13 are heated to 740 ° C. by a carbon heater.
Heat for 1 minute. After the counter electrodes 12 and 13 is sealed to the glass tube 11, metal composed of P b / Sn alloy on the hole 15
16 are arranged, in the glass tube 11 by heating the carbon heater to the temperature metals 16 melts in a state filled with argon gas 14, sealing the hole 15 in the metallic 16, to obtain a surge absorber 10. This surge absorber 10 has a length of 8.0
mm and an outer diameter of 6.0 mm.

[0017] except for using <Comparative Example 1> hole 15 counter electrode 12 without及beauty Metals 16 was prepared by the same surge absorber and examples. As shown in FIG. 3 , (8 × 20) μs
Fuse 2 which is blown for the first time at c-600A is connected in series, and the height is 1.0 cm, the width is 2.0 cm, and the height is 0.5 cm.
In case 3 having the following dimensions.

[0018] except for using <Comparative Example 2> hole 15 counter electrode 12 without及beauty Metals 16 was prepared by the same surge absorber and examples.

<Comparative 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 embodiment, 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 to overheat, metallic 16 is melted. Hole 15 is opened,
Air entered the glass tube 11 and the discharge stopped in about 3 seconds. In the surge absorber with fuse of Comparative Example 1,
The fuse 2 was also blown in about 3 seconds due to overheating, and the discharge of the surge absorber 1 was stopped. In the surge absorber of Comparative Example 2, discharge did not stop, the counter electrode was overheated, and the connected printed circuit board was ignited.

(B) Impulse Response Test The discharge starting voltage Vs (V) and the surge response voltage Vimp (V) were measured. The measurement of the discharge starting voltage was performed on 20 samples each, and the surge response voltage was measured by the surge absorber 10 of the embodiment and the surge absorbers of Comparative Examples 1 and 2 (1.
2 × 50) μsec-10kV pseudo surge of 5
The operation voltage was measured repeatedly. Table 1 shows these average values.

[0021]

[Table 1]

As is evident from Table 1, the surge absorber 10 of the embodiment has the same excellent surge response as the surge absorbers of Comparative Examples 1 and 2.

[0023]

As described above, according to the present invention, in addition to absorbing an instantaneous surge voltage such as a lightning surge, when an overvoltage or overcurrent is continuously introduced, Since the metal that sealed the holes 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 heat of the electronic components and the printed circuit board on which the components are mounted. Damage, ignition, etc. can be prevented. Further, since the discharge type surge absorber according to the present invention does not use a fuse as in the related art, the number of parts can be reduced, the cost can be reduced, the occupied space is small, the assembly is simple, and the mass productivity is excellent. In particular, even after the air flows into the insulating tube, the response to the surge is reduced, but the surge absorber still has the original function of absorbing the next incoming surge voltage.

[Brief description of the 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) Front view of the other counter electrode where the hole is not formed.

FIG. 3 is a circuit configuration diagram of a conventional surge absorber with a fuse.

[Reference Numerals] 10 surge absorber 11 insulating tube (glass tube) 12, 13 counter electrode 14 inert gas 15 hole 16 Metal 20 surge absorbing element 21 conductive film 22 ceramic body 23 microgap 24,25 cap electrodes

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masatoshi Abe 2270 Yokoze, Yokoze-machi, Chichibu-gun, Saitama Mitsubishi Materials Corporation Ceramics Research Laboratory (72) Mikio Harada 2270 Yokoze, Yokoze-cho, Yokoze-cho, Chichibu-gun, Saitama Mitsubishi Materials (56) References JP-A-3-214580 (JP, A) JP-A-1-176689 (JP, A) JP-A-1-235179 (JP, A) Jpn. JP, U) JP-A 55-20123 (JP, U) JP-A 3-39292 (JP, U) JP-A 3-39291 (JP, U) JP 2-26150 (JP, Y2) JP Hei 4-39673 (JP, Y2) Real public Hei 4-39674 (JP, Y2) (58) Fields surveyed (Int. Cl. ⁷ , DB name) H01T 1/00-4/20

Claims (2)

(57) [Claims] 1. A micro gap (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). A surge absorbing element (20) having electrodes (24, 25) is housed in an insulating tube (11)), and a pair of counter electrodes (1) is provided at both ends of the insulating tube (11).
2, 13) are opposed to each other and sealed, and the pair of counter electrodes (12, 1
3) fixes the surge absorbing element (20) in a sealed state, and is electrically connected to the pair of cap electrodes (24, 25) ,
It is formed by the counter electrodes (12, 13) and the insulating tube (11).
Discharge type surgers with inert gas (14)
In the absorber, one or both of the pair of counter electrodes (12, 13)
A hole (15) is formed, and the hole (15) is at or below the melting point of aluminum.
Sealed with a metal (16) having a lower melting point, the counter electrode (1
(13) The metal (16) melts due to the heat generated by the holes (15).
When air is released, air flows into the space inside the insulating tube (11).
A discharge type surge absorber characterized in that it is configured to be inserted . 2. The method according to claim 1, wherein the metal for sealing the hole is aluminum.
Lead, tin or any or claims 1 Symbol placement of discharge surge absorber is these alloys of zinc.