JPS61208803A - Molding for current limiting element structural body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a method for molding a current-limiting element structure, and more specifically, a method for forming a current-limiting element structure, which strengthens the bond between a current-limiting element and a terminal member, and reduces the number of man-hours and parts for molding. The present invention relates to a method for molding a high-quality current limiting element structure that improves watertightness while reducing costs.

[Conventional technology and its problems]

A current limiting device in which an arcing horn is attached to the equipment to prevent the subsequent current that continues to flow after a flashover caused by a lightning surge overvoltage, and the electrode of the arcing horn is made of a material with nonlinear voltage-current characteristics. It is known that the current limiting element is connected to an element, and the current limiting element needs to be watertight because its properties change rapidly when it comes into contact with moisture.

For this reason, conventionally, an insulating rod with screws at both ends is passed through the inner hole of a current-limiting element formed into a cylindrical shape, and a terminal member is screwed into the screws at both ends of the insulating rod. A current limiting element structure has been devised in which the terminal members are integrated and their joints are brazed, and then this is placed in a molding die and a jacket is formed around it.

However, although this device has the advantage that the state of bonding between the current limiting element and the terminal member does not change due to the pressure applied during outer molding, it is necessary to mold the current limiting element into a cylindrical shape. An insulating rod with threads on both ends is required. It is necessary to provide the terminal member with a female screw for screwing the insulating rod,
There are problems such as the need to take measures to fill in the gap created between the hole of the cylindrical current limiting element and the insulating rod and the gap created after the screw of the insulating rod is screwed into the female thread of the terminal member with an insulating material.

In addition, the outer shape of the current limiting element and the terminal member when they are joined is extremely uneven, which causes the thickness of the outer molding to be uneven, causing uneven shrinkage after molding, and causing so-called sink marks. be.

On the other hand, a conventional method for forming a current limiting element structure involves screwing together a cylindrical case provided with a hole through which a terminal rod passes and a cylindrical lid to maintain the connection between the current limiting element and the terminal member. Some are integrated and a mantle is molded around them.

This method requires a cylindrical case and a cylindrical lid, and also requires work to assemble them, leaving a gap between the current limiting element and the cylindrical case/cylindrical lid, which impedes high voltage withstand characteristics. There are problems such as it being undesirable from a maintenance perspective.

[Purpose of the invention]

The invention was made in view of the above problems, and provides a current limiting element structure that strengthens the connection between the current limiting element and the terminal member, reduces the number of parts and man-hours required for molding, and improves watertightness. The purpose is to provide a molding method.

[Means to achieve the purpose]

In order to achieve the above object, in the uninvention, when joining the current limiting element and the terminal member, a pbb
A solder alloy containing Zn and Sn as essential components and at least one component of Zn and rare earth metals is melt-coated in a non-oxidizing gas atmosphere and under ultrasonic vibration, and the melt-coated surface is After solidification, the current limiting element and the terminal member are bonded using a conductive adhesive, and then a mantle is molded around the current limiting element and the bonded portion.

The above solder alloy has, for example, 2% as an essential component in terms of weight%.
Contains ~98.5% PB and 1~97.5% Sn,
Further, it contains a small amount of Zn (0.05 to 30%) and a rare earth metal (0.1 to 15%).

A non-oxidizing gas atmosphere means an atmosphere that does not substantially contain oxygen, and specifically refers to an atmosphere consisting of an inert gas such as nitrogen, helium, or argon, a reducing gas such as hydrogen, or a mixture of these gases. .

The ultrasonic vibration serves to remove the air in the solder alloy and the soldering impediments present at the bonding interface to increase the adhesive force, and is preferably 10 to 100 KHz.

For example, melamine resin paint with copper fine powder added thereto, cyanoacrylate with silver powder added (Cyclone B: manufactured by Atsugi Central Research Institute Co., Ltd.), and the like.

By molding the jacket, the joint between the current limiting element and the terminal member is made watertight. Before this molding, if a first molding layer made of a heat-resistant, low-pressure moldable resin mixture is formed directly above and around the current limiting element and the joint part, the outer shape of the material before the mantle molding will be smooth, and the mantle molding will be smooth. It is possible to prevent abnormal shrinkage at the time of heating, reduce the molded thickness of the mantle, and shorten the pouring time.

〔effect〕

Since this invention is configured as described above, it exhibits the following effects.

■ The solder alloy is firmly and firmly bonded to the current-limiting element, and the terminal member is bonded to the current-limiting element using conductive adhesive through the solder, which increases the bonding strength between the current-limiting element and the terminal member. Since the mantle is molded, there are no voids inside the structure, and there is no need to worry about corona outbreaks.

■ It is possible to obtain a low-cost, high-quality current limiting element structure with a small number of parts and man-hours.

■ If a molding layer made of a heat-resistant and low-pressure moldable resin mixture is formed directly above the current limiting element and the joint portion before forming the outer mold, the outer shape of the material before forming the outer mantle will be smooth, making it easier to form the outer mantle. It is possible to prevent abnormal shrinkage during vulcanization, reduce the molded thickness of the mantle, and shorten the vulcanization time. Furthermore, by using a resin with good water-shielding properties for the molding layer and a resin with good tracking resistance for the jacket, a product having both properties can be obtained.

Hereinafter, embodiments of the invention will be described based on the accompanying drawings.

[Embodiment 1] Reference numeral 11 denotes a current limiting element, 15 a brass collar, and a female screw 13 into which the male screw 14 of the terminal bar 12 is screwed is provided at the center thereof. The current limiting element 11 and the flange 15 are preheated to approximately 350°C, and a ceramic solder alloy containing Pb-5n-Zn as a basic component and having a melting point of 297°C is applied to the surface where they are to be joined in a nitrogen gas atmosphere for 12 to 30 minutes. Melt coating while applying 3QKHz ultrasonic vibration.

After this melt-coated surface solidifies, the current-limiting element 11 and the collar 15 are
Both surfaces are bonded together using a conductive adhesive.

A male screw 14 provided at the end of the terminal bar 12 is screwed into the central female screw 13 of the joined collar 15 to form a terminal member 16.

The integrated current limiting element 11 and terminal member 16 are placed in a molding die, and a jacket 17 is molded with a resin mixture mainly composed of ethylene propylene rubber with good weather resistance and tracking resistance. A shade 18 is provided to lengthen the creepage.

[Embodiment 2] Reference numeral 21 denotes a current limiting element, 25 a brass collar, and a female screw 23 into which the male screw 24 of the terminal bar 22 is screwed is provided at the center thereof. The current limiting element 21 and the flange 25 are preheated to approximately 310°C, and the surface where they are joined is coated with a ceramic solder alloy whose basic component is Pb-5n-Zn and whose melting point is 260°C in a nitrogen gas atmosphere and at a frequency of 12 to 3 QKHz. Melt coating while applying ultrasonic vibration.

After this melt-coated surface solidifies, the current limiting element 21 and the collar 25 are
Both surfaces are bonded together using a conductive adhesive.

A male screw 24 provided at the end of the terminal bar 22 is screwed into the central female screw 23 of the joined collar 25 to form a terminal member 26.

The current-limiting element 21 and the terminal member 26 that have been bonded and integrated are mounted in an injection molding mold, and are molded with a thickness of 2 mm to 4 mm using, for example, Noryl (trade name) (manufactured by General Electric Company) or Zylon (manufactured by Asahi Dow Company). Then, a primary molding layer 27 is formed.

In addition, watertightness can be further improved by applying an adhesive that has adhesive properties to both the terminal bar and the injection molding resin to the surface of the terminal bar before loading it into the mold.

Note that when performing the work up to this point, the characteristics of the current limiting element 21 will change rapidly if it comes into contact with moisture or sweat, so be careful of moisture and avoid doing it with bare hands.

The current limiting element 21 on which the primary molding layer 27 has been formed is then placed in a mold for molding a mantle, and a mantle 28 is molded with a resin mixture mainly composed of ethylene-propylene rubber and having good weather resistance and tracking resistance. Note that a shade 24 is provided on the mantle to lengthen the creepage if necessary.

[Comparative example]

Next, in order to confirm the bonding strength between the current limiting element and the flange in Examples 1 and 2, the current limiting element and the flange were bonded using ceramic solder and conductive adhesive based on each example, and then the current limiting element was was gripped with a scroll chuck, and the bolt was forcibly screwed into the female thread provided in the collar until the joint broke. Observation of the broken surfaces revealed that in each of the examples of the present invention, the ceramic solder did not peel off at the bonding interface, but broke at the conductive adhesive layer.

On the other hand, in the conventional technique, after thermally spraying AL on the end face of the current limiting element, the flange is joined with a known brazing method or with a conductive adhesive, and then the joint is destroyed in the same manner as described above, and the fractured surface is Upon observation, it was found that in both cases, the current limiting element and the sprayed metal were peeled off at the interface.

From this, in the present invention, the bonding strength between the current limiting element and the collar is determined by the bonding strength of the four-conductor adhesive, whereas in the conventional device, the bonding strength of the sprayed metal bonding surface is determined not by the conductive adhesive layer. It can be seen that the bonding strength of the former is higher than that of the latter.

[Brief explanation of drawings]

FIGS. 1 and 2 are longitudinal sectional views of current limiting element structures according to embodiments of the present invention. 11.21 Current-limiting element, 16.26 Terminal member, 17°2 day Mantle, 27 Blow-molded layer. Patent applicant: TAC Electric Cable Co., Ltd. Otowa Electric Industry Co., Ltd. Agent: Kama 1) Text 2 Figure 1 Figure 2

Claims (4)

[Claims] (1) When joining the current-limiting element and the terminal member, a solder alloy containing PB and Sn as essential components and at least one component of Zn and rare earth metals is not applied to the joint surface of the current-limiting element. Hot-coating is carried out in an oxidizing gas atmosphere and under ultrasonic vibration, and after the coated surface has solidified, the current-limiting element and the terminal member are bonded with a conductive adhesive, and then the current-limiting element and A method for molding a current limiting element structure, comprising molding a jacket around a joint part. (2) A method for molding a current limiting element structure according to claim (1), characterized in that the solder alloy is also grooved on the joint surface of the terminal member. (3) In claim (1) or (2), when forming a groove with a solder alloy on the joint surface of the current limiting element and the terminal member, the joint portion is preheated. A method for forming a current limiting element structure. (4) Claims paragraph (1), (2) or (
In item 3), before molding the mantle, a molding layer made of a heat-resistant and low-pressure moldable resin mixture is formed directly above and around the current-limiting element and the joint portion. Molding method.