Surge Protection Device

Abstract

To provide a surge protection element capable of reducing damage caused by a surge and suppressing fluctuations in discharge start voltage. [Solution] The device comprises an insulating tube 2, a pair of sealing electrodes 3 that close the openings at both ends of the insulating tube to seal a discharge control gas inside, a pair of discharge electrodes 4 whose base ends contact the inner surface of the sealing electrodes and whose tips protrude into the insulating tube and face each other, and an insulating member 5 that is sandwiched between the tip faces of the pair of discharge electrodes and stored inside the insulating tube, the insulating member being columnar with an axis perpendicular to the axis of the insulating tube, and a groove portion 5a extending along its own axis is formed on the outer peripheral surface exposed between the pair of discharge electrodes.

Description

[Technical field]

[0001] The present invention relates to a surge protection element used to protect various devices from surges generated by lightning strikes and the like, and to prevent accidents before they occur. [Background technology]

[0002] Surge protection elements are connected to parts of electronic equipment for communication devices such as telephones, facsimiles, and modems that are susceptible to electric shock from abnormal voltages (surge voltages) such as lightning surges and static electricity, in order to prevent destruction by heat damage or fire of the electronic equipment or the printed circuit board on which this equipment is mounted, caused by abnormal voltages, such as connections to communication lines, power lines, antennas, and CRT drive circuits.

[0003] Conventionally, a surge absorber has been known as a surge protection element, in which a discharge element consisting of a ceramic insulator with a conductive film formed on its surface divided in the middle to provide one or more discharge gaps (microgaps), and a pair of cap electrodes (discharge electrodes) provided on both ends of the insulator, is sealed in a glass tube by a pair of sealing electrodes (see, for example, Patent Document 1). In such surge protection elements, a conductive film is formed as an electrode film, and the thin conductive film locally enhances the surrounding electric field, thereby working in favor of the response voltage to a surge. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 8-153565 Summary of the Invention [Problem to be solved by the invention]

[0005] The above conventional techniques still have the following problems. In the conventional surge protection elements described above, the electrode film is made of a conductive film several to several tens of microns formed using film-forming techniques such as thick-film printing and sputtering. However, because the film is thin, there is a risk that the conductive film will melt and shatter, making it impossible to maintain its functionality, when a high-intensity surge is applied or when this surge is applied repeatedly. In addition, conductive debris such as metal that is scattered from the discharge electrode and adheres to the outer circumferential surface of the insulator significantly disrupts the electric field distribution, causing the discharge start voltage Vs to fluctuate, making it impossible to maintain a stable discharge start voltage Vs.

[0006] The present invention has been made in view of the above-mentioned problems, and has an object to provide a surge protection element capable of reducing damage caused by a surge and suppressing fluctuations in discharge start voltage. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention employs the following configuration. That is, a surge protection element of a first invention includes an insulating tube, a pair of sealing electrodes that close both end openings of the insulating tube to seal a discharge control gas inside, a pair of discharge electrodes whose base ends contact the inner surface of the sealing electrodes and whose tips protrude into the insulating tube and face each other, and an insulating member sandwiched between the tip surfaces of the pair of discharge electrodes and housed in the insulating tube, the insulating member being columnar with an axis perpendicular to the axis of the insulating tube, and a groove extending along the axis of the insulating member is formed on the outer circumferential surface exposed between the pair of discharge electrodes.

[0008] In this surge protection element, the insulating member is columnar with an axis perpendicular to the axis of the insulating tube, and a groove extending along its axis is formed on the outer peripheral surface exposed between the pair of discharge electrodes. Therefore, even if conductive debris from the discharge electrodes generated by surge discharge adheres to the outer peripheral surface of the insulating member, it is difficult to adhere to the groove, and is divided and split by the groove. Therefore, the scattering area where the conductive debris adheres is divided and divided, and each becomes smaller, so that the disturbance of the electric field distribution is small, and the fluctuation of the discharge start voltage Vs after the surge life test can be suppressed. In addition, by adopting a discharge electrode that is a conductive member, the heat capacity is increased and the thermal resistance is reduced compared to a thin conductive film, and the durability against surges is improved, and the fluctuation of the discharge start voltage can be suppressed.

[0009] The surge protection element according to a second aspect of the present invention is the surge protection element according to the first aspect of the present invention, characterized in that the insulating member has a plurality of the grooves. In other words, in this surge protection element, the insulating member has multiple grooves, so that even if conductive debris adheres to the outer peripheral surface of the insulating member, the multiple grooves separate and divide the scattering area into multiple areas, making each scattering area even smaller.

[0010] The surge protection element according to a third invention is the second invention, characterized in that the insulating member is formed in a gear-like cross section having a plurality of the grooves equally spaced in the circumferential direction. That is, in this surge protection element, the insulating member is formed in a gear-shaped cross section with multiple grooves equally spaced circumferentially, so that when the insulating member is inserted between a pair of discharge electrodes inside the insulating tube, the multiple grooves can be easily exposed between the pair of discharge electrodes, eliminating the need for positioning during assembly.

[0011] The surge protection element according to a fourth invention is characterized in that, in the third invention, the insulating member is formed in a gear-like cross section having eight of the groove portions equally spaced circumferentially. That is, in this surge protection element, the insulating member is formed in a gear-like cross section with eight grooves equally spaced in the circumferential direction, and has eight teeth on the outer circumferential surface, and two adjacent teeth of the eight teeth abut against the opposing discharge electrodes, thereby stably disposing the insulating member between the pair of discharge electrodes. Also, three grooves are exposed on each of the outer circumferential surface portions on both sides exposed between the pair of discharge electrodes, which makes it possible to divide and separate the scattering region into three.

[0012] The surge protection element of the fifth invention is characterized in that, in the first or second invention, the outer diameter of the insulating member is made smaller than the outer diameter of the discharge electrodes, and areas are formed on both sides of the insulating member where the tip faces of the pair of discharge electrodes directly face each other. That is, in this surge protection element, the outer diameter of the insulating member is made smaller than the outer diameter of the discharge electrodes, and an area is formed on both sides of the insulating member where the tip faces of a pair of discharge electrodes directly face each other, so that a discharge path is formed on both sides of the insulating member, making it easier for arc discharge to travel between the pair of discharge electrodes. Effect of the Invention

[0013] According to the present invention, the following effects are obtained. That is, in the surge protection element of the present invention, the insulating member is columnar with an axis perpendicular to the axis of the insulating tube, and a groove extending along its own axis is formed on the outer peripheral surface exposed between the pair of discharge electrodes, so that disturbance of the electric field distribution is small, fluctuations in the discharge start voltage Vs after a surge life test can be suppressed, and durability against surges is improved. Therefore, the surge protection element of the present invention can improve the surge breakdown resistance and surge characteristic resistance. [Brief description of the drawings]

[0014] [Figure 1] 1 is a front view showing a surge protection element with a portion cut away in one embodiment of the surge protection element according to the present invention. [Diagram 2]4 is an explanatory diagram showing a scattering region of conductive scattered matter on an insulating member disposed between a pair of discharge electrodes in the present embodiment. FIG. [Diagram 3] 2 is a side view showing a partially broken away surge protection element in the present embodiment. FIG. [Figure 4] FIG. 2 is a perspective view showing an insulating member disposed between a pair of discharge electrodes in the present embodiment. [Diagram 5] 4 is a graph showing the change in discharge start voltage Vs versus the number of life tests in an embodiment of the surge protection element according to the present invention. [Figure 6] 4 is a graph showing the change in discharge start voltage Vs versus the number of life tests in a comparative example of a surge protection element according to the present invention. [Figure 7] 4A and 4B are images showing the outer circumferential surfaces of insulating members after a life test in an example (a) and a comparative example (b) of a surge protection element according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, one embodiment of a surge protection element according to the present invention will be described with reference to Figures 1 to 4. In addition, in each of the drawings used in the following description, the scale is appropriately changed so that each component is sized to be recognizable or easily recognizable.

[0016] As shown in Figures 1 to 4, the surge protection element 1 of this embodiment comprises an insulating tube 2, a pair of sealed electrodes 3 that close the openings at both ends of the insulating tube 2 to seal a discharge control gas inside, a pair of discharge electrodes 4 whose base ends contact the inner surface of the sealed electrodes 3 and whose tips protrude into the insulating tube 2 and face each other, and an insulating member 5 that is sandwiched between the tip surfaces 4a of the pair of discharge electrodes 4 and stored in the insulating tube 2.

[0017] As shown in FIG. 3, the insulating member 5 is columnar with an axis AX2 perpendicular to the axis AX1 of the insulating tube 2, and has a groove portion 5a extending along the axis AX2 of the insulating member 5 on the outer peripheral surface exposed between the pair of discharge electrodes 4. Moreover, the insulating member 5 has a plurality of grooves 5a. Furthermore, as shown in Figs. 1 and 2, the insulating member 5 is formed in a gear-like cross section having a plurality of grooves 5a at equal intervals in the circumferential direction.

[0018] That is, the insulating member 5 is formed in a gear-like cross section having eight grooves 5a and eight teeth 5b equally spaced in the circumferential direction. The groove depth of the grooves 5a is preferably set, for example, within a range of 10 to 20% of the radius of the insulating member 5. In this embodiment, the grooves 5a have a depth of 150 μm for an insulating member 5 with a radius of 1 mm.

[0019] The outer diameter of the insulating member 5 is smaller than the outer diameter of the discharge electrodes 4, and regions A1 are formed on both sides of the insulating member 5 where the tip faces 4a of the pair of discharge electrodes 4 directly face each other. The pair of discharge electrodes 4 are formed at their tips with annular protrusions 4b that protrude in the axial direction along the outer periphery. The discharge electrode 4 is formed in a cylindrical shape with a circular hole 4c at the tip end thereof centered on the axis AX1. That is, at the tip of the discharge electrode 4, an annular protrusion 4b is formed on the outer periphery of a hole 4c. The discharge electrode 4 in this embodiment is made of, for example, copper.

[0020] In this embodiment, one end of a lead wire 7 is connected to the outside of the sealed electrode 3 by welding, soldering, embedding, or the like. The sealing electrode 3 is formed of a metal, for example, an Fe (iron)-Ni (nickel) alloy whose surface is coated with copper oxide, and has a disk or columnar shape. For example, the encapsulation electrode 3 is made from dumet wire.

[0021] The insulating tube 2 is, for example, a glass tube made of lead glass or the like and formed into a substantially cylindrical shape. The pair of sealed electrodes 3 are fitted into the openings at both ends of the insulating glass tube 2 and fused by heat treatment, so that the insulating tube 2 is fixed in a tight contact state.

[0022] The discharge control gas sealed in the insulating tube 2 is an inert gas, such as He, Ar, Ne, Xe, Kr, SF 6 ,CO 2 ,C 3 F 8 ,C 2 F 6 ,CF 4 ,H 2 , air, etc. and mixtures of these gases are used. The insulating member 5 is made of a ceramic material such as alumina, mullite, corundum-mullite, etc. The insulating member 5 in this embodiment is made of alumina.

[0023] Thus, in the surge protection element 1 of this embodiment, the insulating member 5 is columnar with an axis AX2 perpendicular to the axis AX1 of the insulating tube 2, and a groove portion 5a extending along its own axis AX2 is formed on the outer peripheral surface exposed between the pair of discharge electrodes 4. Therefore, as shown in the right part of Figure 2, even if conductive debris generated from the discharge electrode 4 by the surge discharge TB scatters in the direction of arrow M1 and adheres to the outer peripheral surface of the insulating member 5, it is unlikely to adhere within the groove portion 5a, but is cut off and divided by the groove portion 5a.

[0024] Therefore, the scattering area M with the conductive debris attached is divided and split, and each of them becomes smaller, which reduces the disturbance of the electric field distribution and suppresses the fluctuation of the discharge start voltage Vs after the surge life test. Also, by adopting the discharge electrode 4 which is a conductive material, the heat capacity increases and the thermal resistance decreases compared to a thin conductive film, improving durability against surges and suppressing the fluctuation of the discharge start voltage Vs.

[0025] In the case of a surge protection element using, for example, a cylindrical insulating member 15 (hereinafter also referred to as a round insulator) without a groove portion 5a, as shown in the left part of Figure 2, conductive debris from the discharge electrode 4 scatters in the direction of arrow M2 and adheres widely to the outer peripheral surface of the insulating member 15, so that the scattering area M becomes large without being divided, which makes it easy for the electric field distribution to become disturbed.

[0026] In addition, since the insulating member 5 has a plurality of groove portions 5a, even if conductive debris adheres to the outer peripheral surface of the insulating member 5, the plurality of groove portions 5a divide and separate the scattering area M into a plurality of areas, making each scattering area M even smaller. Furthermore, since the insulating member 5 is formed in a gear-shaped cross section having a plurality of grooves 5a equally spaced circumferentially, when the insulating member 5 is inserted between a pair of discharge electrodes 4 inside the insulating tube 2, the plurality of grooves 5a can be easily exposed between the pair of discharge electrodes 4, eliminating the need for positioning during assembly.

[0027] In particular, the insulating member 5 is formed in a gear-like cross section having eight grooves 5a equally spaced in the circumferential direction, and therefore has eight teeth 5b on its outer circumferential surface, and two adjacent teeth 5b of the eight teeth 5b come into contact with the opposing discharge electrodes 4, thereby stably disposing the insulating member 5 between the pair of discharge electrodes 4. In addition, three grooves 5a are exposed on each of the outer circumferential surface portions on both sides exposed between the pair of discharge electrodes 4, making it possible to divide and separate the scattering region M into three.

[0028] Furthermore, the outer diameter of the insulating member 5 is made smaller than the outer diameter of the discharge electrodes 4, and an area A1 is formed on both sides of the insulating member 5 where the tip surfaces 4a of the pair of discharge electrodes 4 directly face each other. As a result, a discharge path is formed on both sides of the insulating member 5, and the arc discharge TB becomes easily transmitted between the pair of discharge electrodes 4. EXAMPLES

[0029] FIG. 5 shows the results of investigating the change in discharge start voltage Vs when a life test was conducted by repeatedly applying surges to a surge protection element using an insulating member (gear insulator) having a groove formed therein according to the above embodiment as an example of the present invention (referred to as gear insulator in the figure). As a comparative example, the change in discharge start voltage Vs after a life test was also examined for a surge protection element using an insulating material (round insulator) without a groove, and the results are shown in Figure 6 (referred to as round insulator in the figure).

[0030] These results show that in the comparative example using a round insulator without grooves, the discharge inception voltage Vs drops significantly after 100 life tests, whereas in the embodiment of the present invention using a gear insulator with grooves, the drop in discharge inception voltage Vs is suppressed even after 300 life tests.

[0031] Fig. 7(a) shows an image of the outer circumferential surface of the insulating member of the example of the present invention taken out after 300 cycles of the life test, and Fig. 7(b) shows an image of the outer circumferential surface of the insulating member of the comparative example taken out in the same manner. It can be seen that in the round insulator of the above-mentioned comparative example, the scattering area with the conductive debris attached is distributed widely and overall over the outer peripheral surface, whereas in the gear insulator of the embodiment of the present invention, the scattering area with the conductive debris attached is divided by grooves on the outer peripheral surface and becomes smaller.

[0032] The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. [Explanation of symbols]

[0033] 1...surge protection element, 2...insulating tube, 3...sealed electrode, 4...discharge electrode, 4a...tip surface of discharge electrode, 5...insulating member, 5a...groove portion, AX1...axis line of insulating tube, AX2...axis line of insulating member, A1...area directly opposed to tip surface of discharge electrode

Claims

1. An insulating tube; a pair of sealing electrodes for sealing the discharge control gas inside the insulating tube by closing the openings at both ends of the insulating tube; a pair of discharge electrodes, the base ends of which contact the inner surface of the sealed electrode and the tips of which protrude into the insulating tube and face each other; an insulating member sandwiched between the tip surfaces of the pair of discharge electrodes and housed within the insulating tube, the insulating member is columnar having an axis perpendicular to the axis of the insulating tube, and a plurality of grooves and a plurality of protrusions are formed on an outer peripheral surface exposed between the pair of discharge electrodes, the grooves and protrusions extending along the axis of the insulating member; at least one of the plurality of protrusions and at least one of the plurality of grooves in both of two regions exposed in a direction perpendicular to both the axis of the insulating tube and the axis of the insulating member on the outer circumferential surface of the insulating member are spaced apart from the pair of discharge electrodes over their entire lengths; A surge protection element, characterized in that the at least one groove portion is provided adjacent to the at least one protrusion portion.

2. 2. The surge protection device according to claim 1, A surge protection element, characterized in that the insulating member is formed in a gear-shaped cross section having a plurality of the grooves at equal intervals in the circumferential direction.

3. 3. The surge protection device according to claim 2, A surge protection element, characterized in that the insulating member is formed in a gear-like cross section having eight of the grooves equally spaced in the circumferential direction.

4. 3. The surge protection device according to claim 1, A surge protection element characterized in that the outer diameter of the insulating member is smaller than the outer diameter of the discharge electrodes, and areas are formed on both sides of the insulating member where the tip faces of the pair of discharge electrodes directly face each other.

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