JPH05144541A - Discharge type surge absorbing element - Google Patents

Abstract

PURPOSE:To realize a discharge type surge absorbing element, which is able to effectively protect the discharge type surge absorbing element from overvoltage without using a shutoff means such as a fuse, and accordingly requires no release work. CONSTITUTION:First discharge electrode 6 and second discharge electrode 8 are arranged opposingly with a discharge gap, and are enclosed in an airtight enclosure 4 with discharge gas so as to form a discharge type, surge absorbing element 2. Positive characteristic resistance bodies 14, whose resistance values increase as their temperatures rise, are coated on the surfaces of respective core members 12, 12, which compose the first discharge electrode 6 and the second discharge electrode 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge type surge absorbing element which absorbs a surge due to a discharge phenomenon in a discharge gap enclosed in an airtight container, and particularly when an overvoltage higher than a rated voltage is continuously applied. In addition, the present invention relates to a discharge type surge absorbing element provided with a safety mechanism for preventing the element from burning and the like by avoiding a continuous state of heat generation due to arc discharge.

[0002]

2. Description of the Related Art Conventionally, a discharge type surge absorbing element is connected between lines constituting a power supply line or a communication line leading to an electronic circuit of an electronic device to protect the electronic circuit from an overvoltage such as a surge. There is. FIG. 5 shows an example thereof, and a discharge type surge absorbing element a is connected between the lines A and A ′, and a fuse b as an overcurrent interrupting means is connected to the input side of the line A.

However, when an overvoltage such as a surge is momentarily applied to the lines A and A'from the input side, the discharge type surge absorbing element a operates and absorbs the overvoltage, so that A voltage in a certain range is supplied to the circuit c side.

In addition, when the electronic equipment is erroneously connected to a power source exceeding its rated voltage, the communication line is erroneously connected to the power source, or an overvoltage test is performed assuming these situations, the lines A, A ' When an overvoltage equal to or higher than the rated voltage of the discharge type surge absorbing element a is continuously applied in the meantime, the fuse b is blown and the line A is opened to apply an overcurrent by applying the overvoltage. To prevent melting short circuit and burnout of the discharge type surge absorbing element a.

[0005]

However, as described above, connecting the fuse b for protecting the discharge type surge absorbing element a to the line A in addition to the discharge type surge absorbing element a complicates the configuration and the connecting work. Will be complicated. Also,
In order to protect the discharge type surge absorbing element a from continuous overvoltage, once the fuse b is blown to open the line A, the line A remains open even after the overvoltage application state is released, and the electronic device To restart the use of
This is a problem in that it is necessary to reconnect a new fuse b, and it takes time to restore the fuse.

The present invention has been made in view of the problems of the above-mentioned conventional example, and the discharge type surge absorbing element can be effectively protected from an overvoltage without using a breaking means such as a fuse, and therefore, the restoration thereof. It is an object of the present invention to realize a discharge type surge absorbing element that requires no work.

[0007]

In order to achieve the above object, in a discharge type surge absorbing element according to the present invention, a plurality of discharge electrodes are arranged facing each other with a discharge gap, and these are arranged together with a discharge gas in an airtight container. A discharge type surge absorbing element enclosed inside, wherein at least one of the plurality of discharge electrodes is provided on the surface of the core member with a positive temperature coefficient resistor whose resistance value increases as temperature rises. It was configured to be coated and formed.

It is desirable that the temperature at which the resistance value of the positive resistance element starts to rise is 70 ° C. or higher and 200 ° C. or lower. Further, the positive resistance element preferably has an initial resistance value of 100Ω or less before the resistance value starts to increase.

[0009]

The discharge type surge absorbing element is connected between lines forming a power supply line or a communication line communicating with an electronic circuit of an electronic device. Then, when a surge of the rated voltage of the discharge type surge absorbing element or more is applied to the line, an arc discharge is generated in the discharge gap to absorb the surge,
Only a certain range of voltage is supplied to the electronic circuit.

Further, when an electronic device is erroneously connected to a power source exceeding its rated voltage, a communication line is erroneously connected to a power source, or an overvoltage test is performed in consideration of these situations, the discharge line is discharged to the line. When an overvoltage that is equal to or higher than the rated voltage of the surge absorbing element is continuously applied, the positive characteristic resistor generates heat due to the overcurrent conduction due to the overvoltage, and the temperature of the positive characteristic resistor becomes equal to or higher than a predetermined value. , Its resistance value rises sharply. As a result, the current is limited and the arc discharge in the discharge gap disappears, so that it is possible to prevent melting short circuit and burnout of the element due to continuous heat generation due to the arc discharge.

The "rated voltage" is an operating voltage of the discharge type surge absorbing element, and specifically means "DC discharge starting voltage". Further, the expression “continuously applied” means “applied for a certain period of time”, which is an opposite concept of “instantaneously applied”. Therefore, the "overvoltage" applied continuously is
Naturally, an AC voltage whose voltage value changes with the passage of time is also included. The same applies to the following.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the illustrated embodiments. FIG. 1 shows a discharge type surge absorber according to the present invention.
FIG. 2 is a schematic cross-sectional view showing the whole of the embodiment, and a discharge type surge absorbing element 2 according to the present embodiment includes an airtight container 4 made of glass or the like, and a first discharge electrode housed in the airtight container 4. 6 and the second discharge electrode 8. The first
The discharge electrode 6 and the second discharge electrode 8 are arranged so as to face each other in a substantially parallel manner with a discharge gap therebetween, and one ends of lead wires 10, 10 made of dumet wire are connected to each other. The other ends of the lead wires 10, 10 penetrate the airtight container 4 and are led out to the outside. Ne, Ar, He are contained in the airtight container 4.
A discharge gas mainly containing an inert gas such as a noble gas such as nitrogen gas or nitrogen gas is filled.

Both the first discharge electrode 6 and the second discharge electrode 8 have the sectional structure shown in FIG. That is, the surface of the core member 12 made of a metal having a good discharge characteristic such as Ni is coated with the positive temperature coefficient resistor 14, and the base end portion 16 of the core member 12 is welded to one end of the lead wire 10. It will be connected by.

The positive-characteristic resistor 14 is a heat-sensitive resistor having a positive temperature-resistance characteristic, and has a characteristic that, when it is heated to a certain temperature or higher by the application of a current, its resistance value rapidly increases due to its own heat generation. Have This PTC resistor
Specifically, 14 is barium titanate (BaTiO ₃ ).
It is composed of a material in which a rare earth element is mixed.

FIG. 3 is an equivalent circuit diagram of the discharge type surge absorbing element 2, wherein r ₁ and r ₂ are positive electrodes covering the surface of each core member 12 of the first discharge electrode 6 and the second discharge electrode 8. Characteristic resistor
14, 14, R represents the insulation resistance of the glass surface of the airtight container 4, and C represents the capacitance between the first discharge electrode 6 and the second discharge electrode 8.

As shown in the circuit diagram of FIG. 4, the discharge type surge absorbing element 2 is constructed by connecting the lead wires 10 and 10 to the lines A and A'which communicate with the electronic circuit 18 in the electronic equipment. It is connected in parallel to the electronic circuit 18 between A and A '. Then, when an overvoltage such as a surge is momentarily applied to the line A or the line A ′, an arc discharge which is a main discharge is generated in a discharge gap between the first discharge electrode 6 and the second discharge electrode 8. To absorb the overvoltage.

When an overvoltage is continuously applied to the line A or A ', the positive characteristic resistors 14 and 14 generate heat due to the application of an overcurrent due to the overvoltage. Then, when the positive temperature coefficient resistors 14 and 14 generate heat up to a predetermined temperature or higher, the resistance value sharply increases and the current is limited, so that the arc discharge disappears. As a result, it is possible to avoid melting short circuit and burnout of the element due to continuous arc discharge.

On the other hand, when the applied state of the overvoltage is released, the temperatures of the positive characteristic resistors 14 and 14 are gradually lowered,
Since the resistance value also decreases, the original state is automatically restored.

The positive characteristic resistors 14 and 14 are as follows.
The temperature at which the resistance value starts to rise is 70 ° C or more and 200
Use the one that is below ° C. This is because if the resistance value is set to start increasing at a temperature below 70 ° C,
The positive temperature coefficient resistors 14 and 14 may malfunction due to changes in the environmental temperature around the protected equipment.
If the arc discharge continues even if the temperature exceeds
This is because the high heat may adversely affect the circuit board or the like in which the discharge type surge absorbing element 2 is incorporated.
The temperature at which the resistance values of the positive temperature coefficient resistors 14 and 14 start to increase can be set to a desired value by appropriately setting the type and ratio of the rare earth element mixed with barium titanate.

The initial resistance values before the resistance values of the positive-characteristic resistors 14 and 14 start to rise with temperature rise are preferably set to 100 Ω or less, and are suppressed to several Ω or less. Ideal. That is, the positive temperature coefficient resistor 1
When the initial resistance value of 4 and 14 is high, the voltage drop of the positive temperature coefficient resistors 14 and 14 becomes large when a current flows due to the application of surge, and the higher voltage is the electronic circuit of the electronic device.
This is because it will be applied to the 18th side.

In the above description, the discharge type surge absorbing element 2 of the bipolar type having the first discharge electrode 6 and the second discharge electrode 8 as the discharge electrodes has been exemplified, but the discharge electrode is not limited to this. The present invention can also be applied to a three-pole discharge type surge absorbing element in which three discharge electrodes are opposed to each other with a discharge gap therebetween.

Although both the first discharge electrode 6 and the second discharge electrode 8 are coated with the positive temperature coefficient resistors 14 and 14, the invention is not limited to this, and at least one of the discharge electrodes is provided. It suffices that the positive electrode is coated with a positive characteristic resistor 14, and the remaining discharge electrode is a normal discharge electrode in which the surface of a core member made of Ni or the like is coated with an emitter material such as BaO or BaO.Al ₂ O _3. You may substitute with. That is, if any of the discharge electrodes is in a high resistance state, the continuous state of arc discharge can be effectively avoided.

[0023]

The discharge type surge absorbing element according to the present invention,
Since at least one of the discharge electrodes is formed by coating the surface of the core member with the positive temperature coefficient resistor, when a continuous overvoltage is applied, the resistance of the positive temperature coefficient resistor is increased by heat generation. The value sharply rises, the current flow is limited, and the arc discharge generated in the discharge gap is extinguished. Therefore, it is possible to effectively prevent the melting short circuit and the burnout of the element due to the continued heat generation due to the arc discharge.

Further, since the line is not cut, when the continuous application of the overvoltage is released, the line is automatically returned to the normal state, so that the recovery work is unnecessary. Further, since replacement of parts is not necessary, it can be used repeatedly.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a discharge type surge absorber according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view showing a discharge electrode of the discharge type surge absorber.

FIG. 3 is an equivalent circuit diagram of the discharge type surge absorber.

FIG. 4 is a circuit diagram showing an example of use of the discharge type surge absorber.

FIG. 5 is a circuit diagram showing a conventional example.

[Explanation of symbols]

 2 Discharge type surge absorber 4 Airtight container 6 First discharge electrode 8 Second discharge electrode 12 Core member 14 Positive temperature coefficient resistor

Claims (3)

[Claims] 1. A discharge-type surge absorption element comprising a plurality of discharge electrodes, which are arranged to face each other with a discharge gap therebetween, and which are enclosed together with a discharge gas in an airtight container, wherein at least one of the plurality of discharge electrodes is provided. One on the surface of the core member,
A discharge type surge absorbing element, characterized by being formed by coating a positive temperature coefficient resistor whose resistance value rises as the temperature rises. 2. The discharge type surge absorbing element according to claim 1, wherein the positive temperature coefficient resistor has a temperature at which the resistance value starts to rise from 70 ° C. to 200 ° C. inclusive. 3. The discharge type surge absorbing element according to claim 1, wherein the positive characteristic resistor has an initial resistance value of 100Ω or less before the resistance value starts to increase.