JPH0748928B2 - Surge absorber - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to a telephone, a facsimile,
The present invention relates to a surge absorber suitable for electronic components for communication equipment such as telephone exchanges and modems. More specifically, it relates to a surge absorber having a function of preventing abnormal heat generation of a surge absorbing element when an overvoltage or an overcurrent continuously enters, in addition to a function of absorbing a surge voltage applied to an electronic component. 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 A surge absorbing element of this type is connected in parallel to a pair of input lines of an electronic component and is configured to operate at a voltage higher than the voltage used by the electronic component. That is, the surge absorbing element 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. Therefore, in this type of surge absorbing element, when a large current such as a lightning surge instantaneously enters, the surge absorbing element discharges and absorbs the surge voltage to protect the electronic component. However, if an overvoltage or overcurrent is continuously applied to the surge absorbing element for several seconds due to an unexpected accident,
A current continues to flow in the surge absorbing element, and the surge absorbing element has a characteristic of generating excessive heat. In particular, if an AC power line having a voltage equal to or higher than the discharge start voltage touches the communication line for some reason, the surge absorbing element used in the telephone will generate heat and cause ignition. Normally, it is unlikely that such an overvoltage or overcurrent will continue to enter the circuit, but it is becoming more and more popular to take maximum safety measures in anticipation of an unexpected accident. For example, UL in the United States
(Underwriter's Laboratories Inc.) provides surge absorbers with specified safety measures so that the surge absorbers do not pose a fire or electric shock hazard to communications equipment during such continuous overvoltage or overcurrent intrusions. Has established standards.

Conventionally, a fuse or a low melting point metal member has been adhered to the surface of a surge absorbing element as a surge absorber which complies with such safety standards and can prevent ignition of electronic equipment due to continuous overvoltage or overcurrent. Japanese Patent Application Laid-Open No. 63-11022, 63-189 discloses a fuse or a low melting point metal member connected in series with a surge absorbing element.
23). Further, as shown in FIG.
It is known that the surge absorber 3 is connected in parallel to the electronic component 5 to the pair of input lines 1 and 2 and the low melting point metal member or the fuse 4 is connected to one of the input lines 1 in the preceding stage of the surge absorber 3. Has been. In these surge absorbers, when an overvoltage or an overcurrent enters, the fuse and the low melting point metal member are blown to prevent abnormal heat generation of the surge absorbing element.

[0004]

Therefore, fuses and low melting point metal members used in conventional surge absorbers have surge withstand capability that does not blow when a surge voltage is momentarily applied, and also has an overvoltage or overvoltage limit. Two functions are required to open the circuit by fusing when current flows continuously. However, it is not easy to select the material and dimensions of the fuse and the low melting point metal member so as to combine these functions. Further, the surge absorber including the fuse and the low-melting point metal member has a complicated structure and has a problem of increasing in size.

An object of the present invention is, in addition to the function of absorbing a momentary surge voltage such as a lightning surge, also prevents abnormal heat generation of a surge absorbing element when a continuous overvoltage or overcurrent is introduced. Another object of the present invention is to provide a surge absorber having a function of protecting peripheral electronic devices. Another object of the present invention is to provide a small surge absorber that combines the above two functions with a simple structure.

[0006]

In order to achieve the above object, the structure of the present invention will be described with reference to FIG. 1 corresponding to an embodiment. The surge absorber 25 of the present invention includes a gap type surge absorber 10 and a conductive material 24 such as a metal tube or a metal plate.
Composed of and. The gap type surge absorbing element 10 has electrodes 21 and 22 to which lead wires 18 and 19 are connected at both ends.
And a gap 12 is formed between the electrodes 21 and 22 and the electrodes 21 and 22 surround the gap 12.
A tube body 23 such as a glass tube having conductivity in a molten state and insulation in a non-molten state is sealed around the outer periphery of the. Tube 2
An inert gas is filled in the chamber 3. The conductive material 24 is provided in close contact with the outer periphery of the tube body 23 including the electrodes 21 and 22 at both ends. As the gap type surge absorbing element, a micro gap type discharge tube as shown in FIG. 1 or a gap type discharge tube as shown in FIG. 2 is exemplified. The conductive material is preferably a metal tube or metal plate made of copper, stainless steel, or the like because it has heat resistance and is easily adhered to the outer circumference of the tube body. A tube having conductivity in a molten state and insulation in a non-molten state is preferably a glass tube made of borosilicate glass, lead glass or the like because of excellent sealing property.

[0007]

When a lightning surge enters, a current flows through the gap type surge absorbing element 10 to protect communication equipment. When an overvoltage or an overcurrent is continuously applied, the surge absorbing element 10 causes abnormal heat generation due to arc discharge, and the heat generation melts the tube body 23. Since the molten tube 23 has conductivity,
The electrodes 21 and 22 at both ends are electrically connected to the conductive material 24 via the molten tube body 23, and an overcurrent is generated by melting the one electrode 21, the molten tube body 23, the conductive material 24, and the molten material. The tubular body 23 and the other electrode 22 flow in this order to short-circuit both electrodes 21, 22. As a result, the arc discharge between the electrodes is stopped and the abnormal heat generation is stopped.

Next, an embodiment of the present invention will be described in detail with reference to the drawings. The invention is not limited to these examples. <Example 1> As shown in FIG. 1, in this example, the gap type surge absorbing element 10 is a microgap type discharge tube having a discharge starting voltage of 300V. This surge absorbing element 10 is provided with a cylindrical ceramic body 13 whose surface is covered with a conductive film 11 and in which a microgap 12 of several tens of μm is formed in the circumferential direction of the central portion. Cap electrodes 16 and 17 are capped on both ends of the element body 13, and lead wires 18 and 19 are formed on the outer surfaces of the end surfaces of the cap electrodes 16 and 17, respectively.
The sealed electrodes 21 and 22 welded to each other are brought into contact with each other.
In this example, the sealing electrodes 21 and 22 are formed by cutting a Du-met wire having a diameter of about 1.5 mm into a length of about 2 mm. Ceramic body 13 with cap electrodes 16 and 17, and sealing electrode 2 with lead wires 18 and 19
1, 22 are inserted into the glass tube 23 as shown in the figure, and in this state, the glass tube 23 is filled with an inert gas, and the glass tube 23 is sealed to the electrodes 21 and 22 so that the surge absorber 10
Is made. In this example, the glass tube 23 has a glass thickness of about 0.
5 mm lead glass with an outer diameter of about 2.5 mm.

The electrodes 2 on both ends of the surge absorbing element 10
A metal tube 24 made of stainless steel is provided in close contact with the outer periphery of the glass tube 23 including the glass tubes 1 and 22. Specifically, the inner diameter of the metal tube 24 is about 2.5 mm, and the surge absorber 25 of this embodiment is made by press-fitting the surge absorbing element 10 described above into the metal tube 24. The surge absorber 25 configured in this manner is mounted on the printed board 26. That is, after bending the lead wires 18 and 19 into an L shape,
With the outer peripheral surface of the metal tube 24 in contact with the surface of the substrate 26, the lead wires 18 and 19 are connected to the through holes 27 of the substrate 26,
28 and fixed with solders 31 and 32.

<Embodiment 2> As shown in FIG. 2, in this example, the gap type surge absorbing element 40 has a discharge starting voltage of 30.
It is a 0 V gap type discharge tube. The same reference numerals as those in FIG. 1 indicate the same components. The surge absorbing element 40 is composed of stainless steel sealing electrodes 41, 42 to which a pair of lead wires 38, 39 are welded, and a glass tube 43 encapsulating these electrodes 41, 42. A gap 46 is formed between the electrodes 41 and 42, and the glass tube 43 is filled with an inert gas. In the surge absorber 35 of this embodiment, a metal plate 45 is previously fixed to the upper surface of the printed circuit board 26 with an adhesive, and the glass tube 43 of the surge absorbing element 40 is brought into contact with the upper surface of the metal plate 45 to solder 31. , 32.

The surge absorber 25 of the first and second embodiments
3 and 35 are connected in parallel to the electronic component 30 to the input lines 31 and 32 of the electronic component 30 as shown in FIG. As a comparative example, a surge absorber 3 including only the surge absorbing element 10 without the metal tube 24 is provided between the input line 1 provided with the 0.5 A fuse 4 and another input line 2 as shown in FIG. Connected <Overvoltage Overcurrent Test> A current of 2.2 A at 600 V AC was applied to the input lines of these test circuits for 30 minutes. In the test circuit of the comparative example, the fuse 4 was blown out within several seconds after applying 600 V, and no current flowed in the circuit. After 30 minutes, the surge absorber 3 and the electronic component 5 did not show heat damage or ignition. On the other hand, in the test circuits of Example 1 and Example 2, the glass tube 2 was applied within a few seconds after applying 600V.
3 and 43 were in a molten state, the electrode electrodes 21, 22 and 41, 42 were short-circuited to each other, and the arc discharge stopped between these electrodes. Although the surge absorbers 25 and 35 generate a little heat during and after application for 30 minutes, the surge absorbers 25 and 3 generate heat.
5 and the printed circuit board 26 on which it was mounted did not ignite, and the electronic component 30 was not damaged by heat.

<Pseudo-surge response test> Further, (8 × 20) μsec-50 is applied to the input line of the circuit shown in FIGS. 3 and 4.
A 0 A pseudo surge current was applied to each. In the comparative example,
When the first surge current was applied, the fuse melted and the circuit was cut off. On the other hand, in Example 1 and Example 2, the pseudo surge current was repeatedly flowed 5 times, but the surge absorbing element operated 5 times and the electronic components were also protected.

[0013]

As described above, according to the present invention, a glass tube including electrodes at both ends of a gap type surge absorbing element is conductive in a molten state and insulative in a non-molten state. Since a conductive material such as a metal tube or metal plate is closely attached to the outer periphery of such a tubular body, in addition to the function of absorbing instantaneous surge voltage such as lightning surge, continuous overvoltage or overvoltage In the event of a current intrusion, the surge absorbing element itself generates heat to short-circuit between the electrodes on both ends via a tube and a conductive material that protects the surrounding electronic devices from thermal damage and ignition. Can have Further, the surge absorber of the present invention has the features of having the above two functions in a simple structure and being compact. Further, unlike a conventional surge absorber using a fuse, it has a feature that it can be repeatedly used even when a surge of a large current enters.

[Brief description of drawings]

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

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

FIG. 3 is a configuration diagram of a surge absorbing circuit according to an embodiment of the present invention.

FIG. 4 is a configuration diagram of a surge absorbing circuit to which a surge absorber of a comparative example is connected.

[Explanation of symbols]

 10,40 Surge absorbing element 12,46 Gap 18,19,38,39 Lead wire 21,22,41,42 Electrode 23,43 Glass tube (tubular body) 24 Metal tube (conductive material) 25,35 Surge absorber 45 Metal plate (conductive material)

Claims (5)

[Claims] 1. An electrode (21, 22, 41, 42) having lead wires (18, 19, 38, 39) connected to both ends, and a gap between the electrodes.
(12, 46) is formed, and a tube (23, 43) having conductivity in a molten state and insulating in a non-molten state fills the gap with an inert gas to fill the outer circumference of the electrode. A sealed gap type surge absorbing element (10, 40) and a conductive material provided in close contact with the outer periphery of the tubular body (23, 43) including the electrodes (21, 22, 41, 42) at both ends. Surge absorber with material (24,45). 2. The surge absorber according to claim 1, wherein the gap type surge absorbing element (10) is a microgap type discharge tube. 3. The electrically conductive material (24) is a metal tube.
Surge absorber described. 4. The conductive material (45) is a metal plate.
Surge absorber described. 5. The tube body (23, 43) is a glass tube.
Surge absorber described.