Surge Protection Device

Abstract

To provide a surge protective element that improves surge resistance without enlarging the inner diameter of an insulating tube.SOLUTION: A surge protective element includes an insulating member 2, a pair of protruding electrode members 3 disposed oppositely with their tips touching both ends of the insulating member, and an insulating tube 4 having base ends 3b of the pair of protruding electrode members or sealing electrodes in contact with the base ends joined to both ends thereof and sealing the insulating member therein together with a discharge control gas. The tip side of the protruding electrode member protrudes into the insulating tube, and a space is formed between the outer circumferential surface of the protruding portion and the inner circumferential surface of the insulating tube, and the protruding portion protrudes longer than the distance between the tips facing each other.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a surge protection element that protects various devices from surges generated by lightning strikes and the like, and is used to prevent breakdowns and accidents. [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 electrical shock from abnormal voltages (surge voltages) such as lightning surges and static electricity, such as where they connect to communication lines, power lines, antennas, or CRT drive circuits, in order to prevent destruction by thermal damage or fire of the electronic equipment or the printed circuit boards on which it is mounted due to abnormal voltages.

[0003] 2. Description of the Related Art Conventionally, as a surge protection element, a surge absorber is known in which both ends of an insulating tube are sealed with sealing electrodes and an insulator made of an insulating material is enclosed within the insulating tube, as shown in Patent Document 1, for example. Glass tubes are often used as such insulating tubes. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3265874 Summary of the Invention [Problem to be solved by the invention]

[0005] The above conventional techniques still have the following problems. In conventional surge protection devices, a method of increasing the inner diameter of the insulating tube has been known to ensure surge resistance, but this method has the disadvantage of reducing productivity and increasing costs. In particular, when a glass tube is used as the insulating tube, ensuring a surge resistance of 5 kA or more requires the glass tube to have an inner diameter of 10 mm or more, which significantly reduces productivity. That is, when a glass tube is used, breakdown due to the application of a large current occurs at the contact point between the end of the glass tube and the electrode or lead wire, and is largely due to Joule heat caused by the concentration of heat from the discharge and current.

[0006] The present invention has been made in view of the above-mentioned problems, and has as its object to provide a surge protection element that improves surge resistance without increasing the inner diameter of the insulating tube. [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 member, a pair of protruding electrode members arranged opposite each other with their tip ends in contact with both ends of the insulating member, and an insulating tube having base ends of the pair of protruding electrode members or sealing electrodes in contact with the base ends joined to both ends and sealing the insulating member together with a discharge control gas therein, wherein the tip ends of the protruding electrode members protrude into the insulating tube, a space is formed between the outer peripheral surface of the protruding portion and the inner peripheral surface of the insulating tube, and the protruding portion protrudes longer than the distance between the opposing tip ends.

[0008] In this surge protection element, the protruding portions of the protruding electrode members protrude longer than the distance between the opposing tip ends, so that the space around the outer periphery of the protruding portions of the protruding electrode members is longer in the axial direction than the space between the opposing tip ends, thereby improving surge resistance without increasing the inner diameter of the insulating tube. In other words, by expanding the internal space of the insulating tube in the axial direction rather than in the inner diameter direction, it is possible to ensure a large surge resistance. Furthermore, by lengthening the pair of protruding electrode members, Joule heat and surge current are less likely to be transmitted to the base end side, which makes it possible to avoid destruction of both ends of the insulating tube and reduce damage.

[0009] The surge protection element of the second invention is characterized in that, in the first invention, the insulating tube is a glass tube, and includes a pair of joining glass members interposed between the base ends of the pair of protruding electrode members and both ends of the insulating tube and joined to them, and at least one of the pair of protruding electrode members has an enlarged diameter portion that engages with the inner end surface of the joining glass member. In other words, in this surge protection element, at least one of the pair of protruding electrode members has an enlarged diameter portion that engages with the inner end surface of the joining glass member, so that the enlarged diameter portion can prevent the joining glass member from slipping axially inward from the end of the insulating tube during manufacturing.

[0010] The surge protection element of the third invention is characterized in that, in the first or second invention, the pair of protruding electrode members have a pair of recesses formed at the tip ends facing each other, and the insulating member has a pair of protrusions at both ends that fit into the pair of recesses. In other words, in this surge protection element, a pair of protruding electrode members have a pair of recesses formed at their opposing tip ends, and the insulating member has a pair of protrusions at both ends that fit into the pair of recesses, so that the insulating member is stably held between the pair of protruding electrode members by the protrusions fitting into the recesses.

[0011] The surge protection element according to the fourth invention is characterized in that, in any of the first to third inventions, when the distance between the opposing tip ends of the pair of protruding electrode members is a and the axial length of the internal space of the insulating tube is b, the relationship between a and b is b / a≧4. In other words, in this surge protection element, the relationship between a, which is the discharge gap width, and b, which is the length of the internal space of the insulating tube, is b / a≧4, so even with a glass insulating tube, a high breakdown resistance of 5kA or more can be obtained. [Effects of the Invention]

[0012] According to the present invention, the following effects are achieved. In other words, according to the surge protection element of the present invention, the protruding portions of the protruding electrode members protrude longer than the distance between the opposing tip ends, so that the surge resistance can be improved without increasing the inner diameter of the insulating tube. [Brief explanation of the drawings]

[0013] [Figure 1] 1A and 1B are a front view and a side view, respectively, of a surge protection element according to a first embodiment of the present invention. [Figure 2] 5A and 5B are a front view and a side view of a surge protection element according to a second embodiment of the present invention. [Figure 3] FIG. 10 is a cross-sectional view of a surge protection element according to a third embodiment of the present invention. [Figure 4] 4 is a graph showing the relationship between breakdown resistance and b / a in an example of a surge protection element according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] A first embodiment of a surge protection device according to the present invention will be described below with reference to Fig. 1. Note that the scale of each drawing used in the following description has been changed appropriately so that each component can be recognized or easily recognized.

[0015] As shown in FIG. 1, the surge protection element 1 of this embodiment comprises an insulating member 2, a pair of protruding electrode members 3 arranged opposite each other with their tip ends 3a in contact with both ends of the insulating member 2, and an insulating tube 4 to which the base ends 3b of the pair of protruding electrode members 3 are joined at both ends and which seals the insulating member 2 together with a discharge control gas inside. The tip end 3a of the protruding electrode member 3 protrudes into the insulating tube 4, and a space S1 is formed between the outer peripheral surface of the protruding portion c and the inner peripheral surface of the insulating tube 4. In other words, the outer diameter of the protruding portion c is set to be smaller than at least the inner diameter of the insulating tube 4. The protruding portion c of the protruding electrode member 3 protrudes longer than the distance a between the opposing tip portions 3a.

[0016] The insulating tube 4 is a glass tube, and is made of soft glass such as lead glass or soda-lime glass, and has a cylindrical shape. In addition, the surge protection element 1 of this embodiment is provided with a pair of joining glass members 5 that are interposed between the base ends 3b of the pair of protruding electrode members 3 and both ends of the insulating tube 4 and joined to them.

[0017] The joining glass member 5 is a so-called bead glass formed into an annular shape, and constitutes a glass layer for fusing the base end portion 3 b and the insulating tube 4 together. At least one (upper side) of the pair of protruding electrode members 3 is provided with an expanded diameter portion 3c that engages with the inner end surface of the bonding glass member 5.

[0018] When the distance between the opposing tip ends 3a of a pair of protruding electrode members 3 is a and the axial length of the internal space of the insulating tube 4 is b, the relationship between a and b is set to b / a≧4. The insulating member 2 is a plate member made of a ceramic material such as alumina, and has an elliptical shape when viewed from the front.

[0019] The protruding electrode member 3 is a cylindrical electrode made of a metal, for example, an Fe (iron)-Ni (nickel) alloy whose surface is coated with copper oxide. The protruding electrode member 3 is a so-called slug lead, with a lead wire (not shown) welded to the base end portion 3b. The enlarged diameter portion 3c is a portion of the protruding electrode member 3 on the base end portion 3b side that is crimped and crushed to enlarge the diameter.

[0020] The discharge control gas is a sealing gas whose composition is adjusted so that electrical properties such as discharge start voltage are at desired values, and is an inert gas such as He, Ar, Ne, Xe, SF, CO, C, F, C, F, CF, H, or a mixture thereof. In this embodiment, Ar, N2 and a mixture thereof are used as the discharge control gas.

[0021] Next, a method for manufacturing the surge protection element of this embodiment will be described. First, one of the pair of protruding electrode members 3 and the bonding glass member 5 are inserted from the top opening into the upright insulating tube 4. At this time, the protruding electrode member 3 is inserted from the insulating tube 4 from the base end portion 3b side. Next, the insulating member 2 is inserted, and then the other of the pair of protruding electrode members 3 is inserted from the top opening of the insulating tube 4, starting from the tip end 3a side.

[0022] Then, the bonding glass member 5 is inserted from the upper opening of the insulating tube 4. At this time, the bonding glass member 5 is locked by the enlarged diameter portion 3c, so that the bonding glass member 5 remains at the top of the insulating tube 4 and does not fall downward. In addition, the pair of joining glass members 5 position the pair of protruding electrode members 3 so that their axes coincide with the central axis of the insulating tube 4, while maintaining a space S1 between the protruding portions c of the pair of protruding electrode members 3 and the inner surface of the insulating tube 4. In this state, the air inside the insulating tube 4 is replaced with a predetermined discharge control gas, and then both ends of the insulating tube 4 are heated and melted in an atmosphere of discharge control gas, thereby tightly welding and sealing the pair of protruding electrode members 3 and the insulating tube 4, thereby producing the surge protection element 1.

[0023] As described above, in the surge protection element 1 of this embodiment, the protruding portions c of the protruding electrode members 3 protrude longer than the distance between the opposing tip ends 3a, so that the space S1 around the outer periphery of the protruding portions of the protruding electrode members 3 can be secured to be longer in the axial direction than the space between the opposing tip ends 3a, thereby improving the surge resistance without enlarging the inner diameter of the insulating tube 4. In other words, by expanding the internal space of the insulating tube 4 in the axial direction rather than in the inner diameter direction, it is possible to secure a large surge resistance. Furthermore, by lengthening the pair of protruding electrode members 3, Joule heat and surge current are less likely to be transmitted to the base end portion 3b side, which makes it possible to avoid destruction of both ends of the insulating tube 4 and reduce damage.

[0024] In particular, since the relationship between a, which is the discharge gap width, and b, which is the length of the internal space of the insulating tube 4, is b / a≧4, even a glass insulating tube 4 can achieve a high breakdown resistance of 5kA or more. Furthermore, at least one of the pair of protruding electrode members 3 has an expanded diameter portion 3c that engages with the inner end surface of the joining glass member 5, so that the expanded diameter portion 3c can prevent the joining glass member 5 from slipping axially inward from the end of the insulating tube 4 during manufacturing.

[0025] Next, second and third embodiments of the surge protection device according to the present invention will be described below with reference to Figures 2 and 3. In the following description of each embodiment, the same components as those described in the above embodiments will be denoted by the same reference numerals, and their description will be omitted.

[0026] The difference between the second embodiment and the first embodiment is that in the first embodiment, the base ends 3b of a pair of protruding electrode members 3 are joined to both ends of the insulating tube 4 by joining glass members 5 to form a seal, whereas in the surge protection element 21 of the second embodiment, as shown in Figure 2, the sealing electrodes 26 in contact with the base ends 3b of a pair of protruding electrode members 23 are joined to both ends of the insulating tube 4 by joining glass members 5 to form a seal.

[0027] That is, in the second embodiment, the pair of protruding electrode members 23 have sealed electrodes 26 disposed at both ends (base end portions 3b) thereof in contact with each other. Furthermore, the protruding electrode member 23 is not a slug lead, but a slug lead to which the sealed electrode 26 is welded to a lead wire (not shown). The protruding electrode member 23 is a rivet-like member having an enlarged diameter portion 23c at the base end portion 3b, and is made of a metal such as stainless steel or Cu (copper). Further, the expanded diameter portion 23c is not a portion expanded in diameter by crimping, but is a portion expanded in diameter by molding the base end portion 3b into a circular cross section. Furthermore, in the second embodiment, the insulating member 22 is a plate member that is rectangular in plan view.

[0028] A method for manufacturing the surge protection device 21 of the second embodiment will be described. First, one of the pair of sealing electrodes 26 and the bonding glass member 5 are inserted from the top opening into the upright insulating tube 4. Furthermore, one of the pair of protruding electrode members 23 is inserted into the insulating tube 4 from the base end portion 3b side. Next, the insulating member 22 is inserted, and then the other of the pair of protruding electrode members 23 is inserted from the top opening of the insulating tube 4 from the tip end 3a side.

[0029] Then, the bonding glass member 5 is inserted from the upper opening of the insulating tube 4. At this time, the bonding glass member 5 is locked by the expanded diameter portion 23c, so that the bonding glass member 5 remains at the top of the insulating tube 4 and does not fall downward. Furthermore, the sealing electrode 26 is inserted into the bonding glass member 5. In this state, the air inside the insulating tube 4 is replaced with a predetermined discharge control gas, and then both ends of the insulating tube 4 are heated and melted in the discharge control gas atmosphere, thereby tightly welding and sealing the pair of sealing electrodes 26 and the insulating tube 4, thereby producing the surge protection element 21.

[0030] As described above, in the surge protection element 21 of the second embodiment, as in the first embodiment, the protruding portion c of the protruding electrode member 23 protrudes longer than the distance between the opposing tip ends 3a, so that the surge resistance can be improved without enlarging the inner diameter of the insulating tube 4.

[0031] Next, the difference between the third embodiment and the second embodiment is that in the second embodiment, the insulating member 22 is rectangular when viewed from the front, whereas in the surge protection element 31 of the third embodiment, as shown in Figure 3, the insulating member 32 has a central portion 32a that is rectangular when viewed from the front, and a pair of protrusions 32b that protrude axially outward from the central portion 32a. That is, in the third embodiment, a pair of protruding electrode members 33 have a pair of recesses 33d formed on the mutually opposing tip portions 33a, and the insulating member 32 has a pair of protrusions 32b at both ends that fit into the pair of recesses 33d.

[0032] The recess 33d of the tip 33a corresponds to the shape of the protrusion 32b to be fitted in. That is, since the protrusion 32b has a rectangular protruding shape when viewed from the front, the recess 33d is also a slit-shaped hole that is rectangular when viewed from above. In this way, in the surge protection element 31 of the third embodiment, the pair of protruding electrode members 33 have a pair of recesses 33d formed on the mutually facing tip portions 33a, and the insulating member 32 has a pair of protrusions 32b at both ends that fit into the pair of recesses 33d, so that the insulating member 32 is stably held between the pair of protruding electrode members 33 by the protrusions 32b fitting into the recesses 33d. [Example]

[0033] In the first embodiment, when the distance between the opposing tip ends 3a of a pair of protruding electrode members 3 is defined as a and the axial length of the internal space of the insulating tube 4 is defined as b, the breakdown resistance was investigated when the value of b / a was changed. The results are shown in Figure 4. As can be seen from this result, when b / a≧4, a high breakdown resistance of 5 kA or more can be obtained even with the insulating tube 4 made of a glass tube.

[0034] The technical scope of the present invention is not limited to the above-described embodiments and examples, and various modifications can be made without departing from the spirit of the present invention. [Explanation of symbols]

[0035] 1, 21, 31... surge protection element, 2, 22, 32... insulating member, 3, 23, 33... protruding electrode member, 3a... tip portion of protruding electrode member, 3b... base end portion of protruding electrode member, 3c, 23c... enlarged diameter portion, 4... insulating tube, 5... joining glass member, 26... sealing electrode, 32b... convex portion, 33d... concave portion, a... spacing between opposing tip portions of a pair of protruding electrode members, b... axial length of internal space of insulating tube, c... protruding portion

Claims

1. an insulating member; a pair of protruding electrode members disposed opposite each other with their tips in contact with both ends of the insulating member; an insulating tube to which base ends of the pair of protruding electrode members or sealing electrodes in contact with the base ends are joined, and which seals the insulating member together with a discharge control gas therein; a tip end side of the protruding electrode member protrudes into the insulating tube, and a space is formed between an outer peripheral surface of the protruding portion and an inner peripheral surface of the insulating tube; the protruding portions protrude longer than the distance between the opposing tip portions, the insulating tube is a glass tube, a pair of joining glass members interposed between the base ends of the pair of protruding electrode members and both ends of the insulating tube and joined thereto; A surge protection element characterized in that at least one of the pair of protruding electrode members has an enlarged diameter portion that engages with the inner end surface of the bonding glass member.

2. 2. The surge protection device according to claim 1, the pair of protruding electrode members each have a pair of recesses formed at the tip end portions facing each other, The surge protection element is characterized in that the insulating member has a pair of protrusions at both ends thereof that fit into the pair of recesses.

3. The surge protection device according to claim 1 or 2, a distance between the opposing tip ends of the pair of protruding electrode members is defined as a, When the length of the inner space of the insulating tube in the axial direction is defined as b, A surge protection element, characterized in that the relationship between the a and the b satisfies b / a≧4.

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