JPH05207649A - Discharge type surge absorbing element - Google Patents

Abstract

PURPOSE:To realize a discharge type surge absorbing element which can be protected against overvoltage without requiring any special interrupting means or current limiting means and in which the generation of following current can be prevented. CONSTITUTION:The discharge type surge absorbing element comprises an enclosure 4 and a pair of sealing members 6, 6 equipped with discharge parts 8, 8 wherein the sealing members 6, 6 seal the opening of the enclosure 4 hermetically and the discharge parts 8, 8 are opposed each other through a discharge gap 16 in the enclosure 4. Furthermore, discharge gas is encapsulated in the enclosure 4 and positive characteristic resistors 18, 18 are applied onto the surfaces of the discharge parts 8, 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 by utilizing a discharge phenomenon in a discharge gap enclosed with a discharge gas in an airtight container, and more particularly,
A discharge type surge that can effectively prevent a follow-up current after extinguishing a surge and can prevent element burnout by avoiding a continuous state of heat generation due to arc discharge when an overvoltage exceeding the rated voltage is continuously applied. Regarding the absorption element.

[0002]

2. Description of the Related Art Conventionally, various surge absorbing elements have been 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. 3 shows a discharge type surge absorbing element 52 which is a kind of such a surge absorbing element. This discharge type surge absorbing element 52 is a pair of substantially cup-shaped discharges that also serve as a cylindrical envelope 54 with both ends opened and a sealing member that seals the openings at both ends of the envelope 54. The electrodes 56, 56 and the bottom surfaces 58 of the recesses of the discharge electrodes 56, 56,
Lead wires 60 and 60 led out from 58 are provided, and the convex top surfaces 62 and 62 of the respective discharge electrodes 56 and 56 are opposed to each other with a predetermined discharge gap 64 therebetween. The discharge space formed in the envelope 54 is filled with a predetermined discharge gas.

As shown in FIG. 4, the discharge type surge absorbing element 52 is connected in parallel with the protected circuit 66 between the lines A and A '. A fuse 68 as an overcurrent interrupting means is connected to the input side of the line A.

However, when a surge exceeding the rated voltage of the discharge type surge absorbing element 52 is instantaneously applied to the lines A and A'from the input side, a glow discharge is generated in the discharge gap 64. An arc discharge is generated, and the surge is absorbed through the large current of the arc discharge.

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 ' Between the above-mentioned discharge type surge absorber
When an overvoltage more than the rated voltage of 52 is continuously applied, the fuse 68 is blown to open the line A, thereby interrupting the overcurrent conduction due to the application of the overvoltage, and thus the discharge type surge. The melting short circuit and the burnout of the absorbing element 52 are prevented.

[0006]

As described above, since the discharge type surge absorbing element 52 has a simple structure, it absorbs a surge through the air discharge, so that a large current withstand capability can be realized. There is. However, as described above, connecting the fuse 68 for protecting the discharge type surge absorbing element 52 to the line A in addition to the discharge type surge absorbing element 52 causes a complicated structure and a complicated connecting work.

Further, in order to protect the discharge type surge absorbing element 52 from continuous overvoltage, once the fuse 68 is blown and the line A is opened, the line A remains open even after the overvoltage application state is released. However, there is a problem in that it is necessary to reconnect a new fuse in order to restart the use of the electronic device, and it takes time to restore the fuse.

Further, when the discharge type surge absorbing element 52 is connected to the power source line, the voltage between both ends of the discharge type surge absorbing element 52 is drastically lowered to the peak voltage of the power source line or less by the arc discharge. Therefore, a continuous discharge occurs due to the power supply voltage even after the surge disappears. In order to prevent this so-called continuous current, it is necessary to separately connect an element having a current limiting function, such as a varistor or a resistor, which is a cause of complication of the configuration.

The present invention has been made in view of the above-mentioned problems of the 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, a recovery operation thereof. It is an object of the present invention to realize a discharge type surge absorbing element that can effectively prevent the occurrence of a follow current without the need for the above and without separately connecting the element having the current limiting function.

[0010]

In order to achieve the above object, a discharge type surge absorbing element according to the present invention has an envelope having both ends opened and a pair of sealing members having a discharge part. The opening of the envelope is hermetically sealed by the sealing member, and the discharge parts of the sealing member are opposed to each other with a predetermined discharge gap in the envelope. A discharge type surge absorbing element in which a discharge gas is sealed in the envelope, and a positive temperature coefficient resistor whose resistance value increases with temperature rise is attached to at least one of the discharge parts. Configured as The positive-characteristic resistor is a heat-sensitive resistor having a positive temperature-resistance characteristic, and has a property that when it is heated to a certain temperature or higher due to the passing of a current, its resistance value rapidly increases due to its own heat generation. .. The temperature at which the resistance value of the positive-characteristic resistor starts to increase is preferably 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.

[0011]

The above-mentioned discharge type surge absorbing element is connected in parallel to the electronic circuit between the lines forming the power supply line or the communication line leading to the electronic circuit of the electronic device. And
When a surge exceeding the rated voltage of the discharge type surge absorbing element is applied to the line, an arc discharge is generated through the glow discharge in the discharge gap to absorb the surge. Only supplied.

At this time, the positive characteristic resistor generates heat due to the supply of the surge current, and its resistance value rapidly increases to limit the current. Therefore, the voltage across the discharge type surge absorbing element is equal to the power supply voltage. It does not fall below the peak value. Therefore, it is possible to prevent a follow current from occurring after the end of the application of the surge.

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 assuming these situations, the above line is discharged. Even when an overvoltage that is equal to or higher than the rated voltage of the surge absorber is continuously applied, the positive characteristic resistor generates heat due to continuous energization of the overcurrent due to the overvoltage. Then, when the positive temperature coefficient resistor heats up to a predetermined temperature or higher, the resistance value increases and the current is limited, so that the arc discharge in the discharge gap disappears. Therefore, it is possible to prevent melting short circuit and burnout of the element due to continuous heat generation due to arc discharge. When the applied state of the overvoltage is released, the temperature of the positive temperature coefficient resistor gradually decreases and its resistance value also decreases, so that the original state is automatically restored.

The "rated voltage" in the above "when an overvoltage more than the rated voltage of the discharge type surge absorbing element is continuously applied" is the operating voltage of the discharge type surge absorbing element. Specifically, it means "DC discharge starting voltage". Similarly, the expression "continuously applied" means "applied for a certain period of time", which is an alternative concept of "instantaneously applied". Therefore, the “overvoltage” continuously applied naturally includes an AC voltage whose voltage value changes with the passage of time. The same applies to the following.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the illustrated embodiments. FIG. 1 is a schematic sectional view showing an embodiment of the discharge type surge absorber according to the present invention. The discharge-type surge absorbing element 2 includes a cylindrical envelope 4 having upper and lower ends opened, and a pair of sealing members 6 and 6 having a substantially cup shape for sealing the openings at both ends of the envelope 4. And the discharge parts 8 and 8 formed on the sealing members 6 and 6. Lead wires 12, 12 are led out from the bottom surfaces 10, 10 of the recesses of the sealing members 6, 6. In the envelope 4, the discharge parts 8 of the sealing members 6 and 6,
8 are opposed to each other with a predetermined discharge gap 16 therebetween. Positive characteristic resistors 18 and 18 are attached to the surfaces of the discharge units 8 and 8. In addition, emitter materials 20 and 20 are applied to the surfaces of the positive-characteristic resistors 18 and 18 in order to lower the discharge starting voltage and improve the sputtering resistance. The emitter materials 20, 20 are, for example, LaB ₆ , BaO, BaO · A.
1 ₂ O ₃ etc.

The sealing members 6 and 6 are made of a conductive material such as Ni or Fe, and the envelope 4 is made of an insulating material such as a ceramic tube. The discharge space in the envelope 4 is filled with a discharge gas mainly containing an inert gas such as a rare gas such as He, Ne, Xe, Ar or a nitrogen gas.
The sealing members 6 and 6 and the envelope 4 are airtightly bonded by the sealing materials 22 and 22.

The positive characteristic resistors 18 and 18 are heat-sensitive resistors having a positive temperature-resistance characteristic, and when heat is generated at a certain temperature or more due to the application of a current, the resistance value sharply rises due to their own heat generation. It has the property. Specifically, the positive temperature coefficient resistors 18, 18 are made of barium titanate (BaT).
It is made of a material in which a rare earth element is mixed with iO ₃ ) and is deposited on the surfaces of the discharge parts 8 and 8 by plasma spraying. Alternatively, a paste-like positive-characteristic resistor may be applied to the surface of the discharge parts 8 and 8 to apply it.

As shown in the circuit diagram of FIG. 2, the discharge type surge absorbing element 2 is constructed by connecting the lead wires 10, 10 to the lines A and A'which communicate with the electronic circuit 24 in the electronic equipment. It is connected in parallel to the electronic circuit 24 between A and A '.

However, when a surge exceeding the rated voltage of the discharge type surge absorbing element 2 is applied to the lines A and A ', an arc discharge which is a main discharge is generated in the discharge gap 16 through a glow discharge, which is a large amount. Surge is absorbed.

In this case, when the surge current is applied, the positive characteristic resistors 18 and 18 generate heat, and the resistance value sharply increases to limit the current. Therefore, the voltage across the discharge type surge absorbing element 2 is increased. Does not drop below the peak value of the power supply voltage. Therefore, it is possible to prevent a follow current from occurring after the end of the application of the surge.

Further, even when an overvoltage equal to or higher than the rated voltage of the discharge type surge absorbing element 2 is continuously applied to the lines A and A ', the positive current is continuously applied by the overcurrent due to the overvoltage. The characteristic resistors 18, 18 generate heat. And
When the positive temperature coefficient resistors 18, 18 generate heat above a predetermined temperature, the resistance value 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 positive characteristic resistors 18, 18
Since the temperature of the device gradually decreases and its resistance value also decreases,
Automatically returns to the original state.

As the positive characteristic resistors 18 and 18,
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 18 and 18 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 18 and 18 start to increase can be set to a desired value by appropriately adjusting the type and ratio of the rare earth element mixed with the barium titanate.

The initial resistance values before the resistance values of the positive-characteristic resistors 18 and 18 start to rise as the temperature rises are preferably set to 100 Ω or less, and suppressed to several Ω or less. Ideal. That is, the positive temperature coefficient resistor 1
When the initial resistance value of 8 and 18 is high, the voltage drop of the positive temperature coefficient resistors 18 and 18 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 24 side.

In the above description, the positive characteristic resistors 18 and 18 are attached to the discharge parts 8 and 8 of both sealing members 6 and 6, but the present invention is not limited to this, and the sealing members 6 and 6 are not limited thereto. It suffices if the positive characteristic resistor 18 is attached to at least one of the discharge portions 8 of the six. This is because if any one of the discharge parts 8 is in a high resistance state, it is possible to effectively avoid continuation of arc discharge and generation of a follow current. Further, the positive temperature coefficient resistor 18 is adhered only to the front surface of the discharge parts 8 and 8 used for electric discharge, but it goes without saying that it may be adhered to the entire rear surface of the sealing members 6 and 6. Nor.

[0025]

The discharge type surge absorbing element according to the present invention,
At least one of the discharge parts facing each other across the discharge gap,
Since the positive-characteristic resistor is attached, when a surge is applied, the positive-characteristic resistor generates heat due to the supply of the surge current, and its resistance value increases to limit the current. Therefore, the voltage across the discharge type surge absorbing element does not drop below the peak value of the power supply voltage,
It is possible to prevent the occurrence of a follow current after the surge disappears.

Further, even when an overvoltage higher than the rated voltage of the discharge type surge absorbing element is continuously applied, the resistance value of the positive temperature coefficient resistor rises due to heat generation, and the current flow is limited to discharge. Since the arc discharge generated in the gap is extinguished, it is possible to effectively prevent the melting short circuit and burnout of the element due to the continued heat generation due to the arc discharge. Moreover, 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 sectional view showing a discharge type surge absorber according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing an example of use of the discharge type surge absorber.

FIG. 3 is a schematic cross-sectional view showing a conventional discharge type surge absorber.

FIG. 4 is a circuit diagram showing a usage example of a conventional discharge type surge absorbing element.

[Explanation of symbols]

 2 Discharge type surge absorber 4 Envelope 6 Encapsulation member 8 Discharge part 16 Discharge gap 18 Positive resistor

Claims (3)

[Claims] 1. An envelope having an opening at both ends, and a pair of sealing members having a discharge part, wherein the opening of the envelope is hermetically sealed by the sealing members. A discharge-type surge absorption element in which the respective discharge parts of the sealing member are opposed to each other with a predetermined discharge gap in the envelope, and a discharge gas is enclosed in the envelope. A discharge type surge absorbing element, characterized in that at least one of the discharge parts is covered with a positive temperature coefficient resistor whose resistance value increases as 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.