JPS6040250B2 - Cable insulation reinforcement part and its formation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in the insulation reinforcing portion of a cable, for example, at a connection portion, a terminal portion, or a direct connection portion of a cable, and a method for forming the same.

For example, it is already known that electric field concentration tends to occur at the connection portion, terminal portion, or direct connection portion of a cable, and that it is necessary to provide an appropriate insulation reinforcing portion to alleviate this electric field concentration. However, the most common form is the cable insulation coating layer exposed by successively peeling off the cable sheath and external conductive layer of the cable sheath and the cable external conductive layer of the connection section, terminal section, or direct connection section of the device where the insulation should be reinforced. Some are constructed by covering the surface of an insulating reinforcing material molded in a predetermined shape with iron. For more details,
An insulating reinforcing body is formed on the surface of the cable insulating sheathing layer, and an insulating reinforcing body is formed on the cable insulating sheathing layer and the cable outer conductive layer along with the insulating reinforcing body on the cable sheath side of the insulating reinforcing body, and substantially A conductive bell mouth portion is formed in close contact with the insulating reinforcing body. However, in this case, since the cable outer conductive layer has a certain thickness, a gap is likely to be formed between the conductive bell mouth part, the end of the cable outer conductive layer, and the cable insulation coating layer, and a portion There was a problem in that it was prone to electrical discharge.

Conventionally, in order to solve this problem, a method of applying a thin layer of conductive tape to the surface of the cable insulation coating layer near the end of the cable's external conductive layer, that is, the surface of the cable insulation coating layer inside the conductive bell mouth part, has been proposed. It had been taken. By doing this, the formation of gaps between the conductive bell mouth portion, the end of the cable outer conductive layer, and the cable insulating coating layer is substantially eliminated, and the above-mentioned problem has been solved to a certain extent. However, a problem still remained.

In other words, in this type of cable insulation reinforcement part, the conductivity is increased due to the expansion and contraction of the insulation reinforcement body and the conductive bell mouth part due to the heat cycle of the cable caused by energization of the cable and heating/cooling from the outside. There was a problem in that a thin layer of conductive tape adjacent to the conductive bell mouth area was likely to form a layer. Therefore, due to the beat cycle of the cable, the insulating reinforcing body and the conductive bell mouth expand and contract in the axial direction of the cable, and the conductive tape winding layer follows this expansion and contraction, and the surface of the conductive tape winding layer expands. As a result of repeated rubbing, wrinkles eventually appeared. When wrinkles occur, the conductive tape-wrapped thin layer forms gaps between the cable insulation coating layers, and as a result, partial discharge is likely to occur in the gaps, which significantly reduces the electrical breakdown strength. Needless to say.

The present invention has been made in view of the above-mentioned points, and aims to eliminate the above-mentioned drawbacks and provide an insulation reinforcing portion of a cable that can exhibit stable electrical characteristics over a long period of time, and a useful method for forming the same. , the gist of this is that the conductive layer formed on the surface of the cable insulation coating layer near the cable external conductive layer is chemically cross-linked to the cable insulation coating layer, and its formation method. . As the conductive thin layer, a material that can be crosslinked by heating is applied to the surface of the cable insulation coating layer, and when crosslinked by heating, crosslinking also occurs between the conductive thin layer and the cable insulation coating layer. The most realistic and practical is the one that consists of these things.

Note that materials that can be crosslinked by heating include certain conductive materials (for example, conductive paint made by dissolving ethylene-vinyl acetate copolymer, which has become conductive by mixing conductive carbon, with a solvent such as toluene). A compound containing any crosslinking agent (e.g., dioxide, ketone/gu oxide, diacyl/gu oxide, etc.) is used, but the workability when crosslinking by heating and the workability when cooling it are taken into consideration. If so, as a crosslinking agent,
It can be said that it is preferable to use a material with a decomposition temperature as low as possible. However, in order to increase the bonding strength of the conductive crosslinked thin layer to the cable insulation coating layer, the heat treatment of the crosslinkable conductive thin layer is preferably carried out at a temperature equal to or higher than the melting point of the insulation coating layer.

That is, for example, when forming an electrically conductive thin layer when the insulating coating layer is made of crosslinked polyethylene, a crosslinking agent whose decomposition temperature is also 10,000 (the melting point of polyethylene is 100qo) is blended. using the materials, and 1
It is preferable to carry out the heat treatment at a temperature exceeding 0,000°C. In summary, the key is to select a material that does not impair its workability and also does not impair its bonding strength. Next, embodiments of the cable insulation reinforcing portion of the present invention and a method for forming the same will be described with reference to the accompanying drawings, but it goes without saying that the present invention is not to be construed as being limited by these embodiments.

That is, there may be some embodiments other than this embodiment, but if they essentially fall within the technical scope of the present invention, they are all part of the present invention. Now, 1 in the diagram
is a cross-linked polyethylene insulated vinyl sheathed cable at the cable connection section, terminal section, or direct connection section to equipment (although not particularly shown, there is actually an object to be connected on the left side of the figure) and the end section ( That is, the cable sheath 2 and the cable outer conductive layer 3 in the portions to be insulated and reinforced are sequentially stripped in stages over a predetermined length. Reference numeral 4 denotes a cable insulation coating layer exposed by peeling off the cable sheath 2 and the cable outer conductive layer 3.

5 is a conductive crosslinked thin layer formed over the cable insulating coating layer 4 near the end of the cable external conductive layer 3 and the surface of the external conductive layer 3, which is a conductive crosslinked layer containing a predetermined crosslinking agent. Paint coating layer (details will be described later).

), and by heat-treating it, it is chemically cross-linked to the cable insulation coating layer 4 and the cable external conductive layer 3. - 6 is a conductive tape-wrapped protective layer provided on the conductive crosslinked thin layer 5; this may be omitted. 7 is an insulation reinforcing body formed on the circumference of the cable insulation coating layer 4, and 8 is an insulation reinforcement body formed on the cable sheath 2 side of the insulation reinforcement body 7, along with the insulation reinforcement body 7, on the circumference of the conductive tape-wrapped protective layer 6. This is an electrically conductive bell mouth portion which is formed in a manner such that it is substantially in close contact with the insulating reinforcing body 7.

According to the cable insulation reinforcing section of this embodiment configured in this manner, the conductive crosslinked thin layer located inside the conductive bell mouth section and formed on the cable insulation coating layer is itself Because it is chemically cross-linked to the cable insulation coating layer, wrinkles will occur even if the surface is rubbed due to the expansion and contraction of the conductive bell mouth part due to the heat cycle of the cable. Therefore, there is no need to worry about creating a gap with the cable insulation coating layer, and the initial excellent electrical characteristics can be maintained over a long period of time.

Furthermore, according to the cable insulation reinforcement section of this embodiment, since the conductive thin layer is crosslinked, it can exhibit extremely stable characteristics against heat, chemicals, etc.

Next, to explain the method of forming the cable insulation reinforcing portion of the present embodiment, first, the cable sheath 2 and the cable external conductive layer 3 of the portion of the cable 1 to be insulated and reinforced are sequentially peeled off, and the cable insulation covering layer 4 is removed. expose. Next, a predetermined cross-linkable conductive paint ( Toluene was added as a solvent to a composition consisting of 10 parts by weight of ethylene-vinyl acetate copolymer, 50 to 70 parts by weight of conductive carbon, and 5 parts by weight of dialkyl peroxide, and the viscosity was adjusted to make it coatable. What I did.
), and then heat-treated with a burner, hot gun, etc. at a cable surface temperature of 140° for 1 minute to cause crosslinking in the conductive paint coating layer itself, and to bond the coating layer and the cable insulation coating layer. 4 and cable outer conductive layer 3
Crosslinking is also caused between them, thereby chemically bonding them together. The conductive crosslinked thin layer 5 is virtually complete. In reality, it is then cooled and completed.

Furthermore, a conductive tape-wrapped protective layer 6 is provided if necessary.

Next, the part to become the insulating reinforcement body 7 and the part to become the conductive bell mouth part 8 are bonded and integrated with each other, and a cable core insertion hole is formed in the direction of the central axis of each part, and the parts are pre-molded. The molded body thus formed is inserted from the cable end, and the insulation reinforcing body 7 is placed on the cable insulation coating layer 4, and the conductive bell mouth portion 8 is placed on the conductive tape wrapping layer 6, and the work is completed.

Now, according to the present embodiment forming method carried out in this manner, no particularly advanced or troublesome techniques are required as a whole, and therefore no special training is required for the operator. This is a very practical method.

Incidentally, the present inventors conducted a peeling test and a melting test of the conductive crosslinked thin layer in order to confirm the effects of this example, and the results will be shown below.

The results were as shown in the table below. Notes: {1' The peeling test is performed by heating the sample at 80℃ for 1 hour, then applying the layer at room temperature (20℃) for 1 hour, repeated 30 times, and then observing the peeling condition. I did it.

Note that 19/20 in the table means that peeling was observed in 19 out of 20 cases. same as below. [2' Melting test is performed by performing the previous heat cycle in xylene in '1'.

I looked at the melting state at that time. From the above results, it can be seen that the conductive crosslinked thin layer in this example has extremely good adhesion to the cable insulation coating, and is also very stable in terms of heat resistance and chemical resistance. Note that, as can be seen from the results of Reference Examples, the amount of the crosslinking agent blended is preferably 5% by weight or more.

[Brief explanation of the drawing]

The figure is an explanatory diagram of an embodiment of the cable insulation reinforcing portion and the method for forming the same according to the present invention. DESCRIPTION OF SYMBOLS 1: Cable, 2: Cable sheath, 3: Cable external conductive layer, 4: Cable insulation coating layer, 5: Conductive crosslinked thin layer, 6: Conductive tape-wrapped protective layer, 7: Insulating reinforcement, 8:
Conductive bell mouth part.

Claims (1)

[Scope of Claims] 1. A cable in which a cable insulation coating layer is exposed by sequentially peeling off a cable sheath and an external conductive layer of the cable at a portion to be insulated and reinforced, and a cable formed on the circumference of the insulation coating layer of the cable. an electrically conductive bell mouth portion formed on the cable insulation covering layer on the cable sheath side of the insulation reinforcement body in line with the insulation reinforcement body and substantially in close contact with the insulation reinforcement body; and a conductive crosslinked thin layer formed on the surface of the cable insulation coating layer inside the conductive bellmouth portion and electrically connected to the cable external conductive layer, the conductive crosslinked thin layer A cable insulation reinforcing portion, characterized in that the cable insulation reinforcing portion is chemically crosslinked to the cable insulation coating layer by causing crosslinking between the cable insulation coating layer and the cable insulation coating layer. 2. The cable insulation reinforcement part according to claim 1, wherein the insulation reinforcement body is a molded body that is pre-molded with a cable core insertion hole formed in the direction of its own central axis. 3. Claim 1, which is a molded body in which the insulating reinforcing body and the conductive bell mouth part are integrally bonded to each other and are pre-molded with a cable core insertion hole formed in the direction of the respective central axes. Cable insulation reinforcement section as described in section. 4. The cable insulation reinforcement part according to claim 1, wherein the conductive thin layer is a conductive paint coating layer. 5. The cable insulation reinforcement part according to claim 4, wherein the conductive paint is a composition comprising an ethylene-vinyl acetate copolymer, conductive carbon, a solvent, and an organic peroxide. 6 Steps of sequentially peeling off the cable sheath and cable external conductive layer of the part of the cable to be insulation reinforced to expose the cable insulation coating layer, and the step of exposing the cable insulation coating layer near the end of the cable external conductive layer of the exposed cable insulation coating layer. and the surface of the external conductive layer by applying a conductive material that can be crosslinked by heating to form a predetermined conductive thin layer in the area, and heating the conductive thin layer to form a conductive thin layer. A step of cross-linking the conductive thin layer and the cable insulation coating layer, thereby chemically cross-linking them; forming an insulating reinforcement body located on the surface of the cable insulation coating layer, and further forming a conductive bell mouth part adjacent to the insulation reinforcement body and located on the surface of the conductive thin layer. A method for forming a cable insulation reinforcing portion, characterized by: 7 It is a molded body in which the insulating reinforcement body and the conductive bell mouth part are integrally bonded to each other and are pre-molded with a cable core insertion hole formed in the direction of the central axis of each. 7. The method of forming a cable insulation reinforcing portion according to claim 6, wherein the formation of the bellmouth portion is performed in one step of passing the molded body over the surface of the cable insulation coating layer and the conductive thin layer.