JP2010113835A - Cable coated with foamed sheath and method of manufacturing the same - Google Patents

Abstract

An object of the present invention is to provide a foamed sheath-covered cable that solves the problem that the contact area between an electric wire and a sheath is reduced by the amount the foamed sheath is used for the cable, and is displaced in the longitudinal direction. .
A cable in which a foamed sheath is coated on an insulated wire, and the foaming rate of the sheath is reduced from the central portion of the surface thickness of the foamed sheath toward the insulated wire. As the means, by cooling the insulating layer 1b of the insulated wire and then covering the foamed sheath, the foamed sheath of the insulated wire side is foamed from the insulated wire toward the thickness of the foamed sheath. It is good to suppress growth.
[Selection] Figure 1

Description

  The present invention relates to a cable with little deviation between an insulating layer and a sheath of an electric wire, and a manufacturing method thereof.

Normally, as shown in FIG. 4, a cable is provided with an insulator 1 b around a conductor 1 a and further covered with a sheath 2. This is shown in a sectional view as shown in FIG. 4 and 5 are three-core flat type, but the number of wires and the shape covered with a sheath vary depending on the application.
In order to obtain effects such as lightening the sheath, imparting flexibility, reducing the amount of raw material used, and facilitating separation from the electric wire, a technique using a foamed sheath has been proposed.
For example, as shown in FIG. 3, a cable described in Patent Document 1 is covered with a foamed sheath around a coating layer of an electric wire. In the case of this cable, it is described that the deep layer portion 2c has a higher foaming rate than the skin portion 2a, and this is excellent in external damage resistance, has a surface gloss, and has a good appearance.
Japanese Patent No. 3963633

  However, the cable described in Patent Document 1 has a problem that the contact area between the electric wire and the sheath is reduced because the sheath is greatly foamed at the contact portion with the electric wire, and the adhesion strength is low.

As a result of diligent study in view of the above problems, the present inventors have improved the adhesion with the electric wire by controlling the foaming rate in the thickness direction of the foamed sheath with respect to the insulating layer of the electric wire, and further improved the flexibility of the cable. The inventors have found that the reduction of the materials used can be maintained, and have made the present invention.
The above problems have been solved by the following invention.
(1) A cable in which a foamed sheath is coated on an insulated wire, wherein the foaming rate of the foamed sheath is reduced from the intermediate portion of the surface thickness of the foamed sheath toward the insulated wire in the thickness direction. .
(2) The foaming rate of the foamed sheath is 8% or less between 0.1 to 0.2 mm in the thickness direction of the sheath from the insulated wire side. Cable.
(3) Growth of foaming of the foamed sheath on the insulated wire side from the insulated wire toward the thickness direction of the foamed sheath by cooling the insulating layer of the insulated wire and then covering the foamed sheath (1) or the manufacturing method of the cable as described in (2) characterized by the above-mentioned.

  According to the present invention, the adhesion between the insulating layer and the sheath of the electric wire is improved, and the effects such as flexibility and weight reduction of the sheath are maintained as before.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is an explanatory view showing a part of an example of the cable of the present invention in a sectional view. An electric wire composed of the conductor 1a and the insulating layer 1b is covered with a foamed sheath 2. The sheath portion 2a of the sheath has a low foaming rate. On the other hand, the intermediate part 2b has a high foaming rate, and the deep layer part 2c has a low foaming rate. Thereby, the area where the sheath 2 contacts the insulated wire 1 was increased, and the problem that the wire 1 and the sheath 2 were shifted in the longitudinal direction was solved.

FIG. 2 is a schematic graph showing an example of the foaming rate of the sheath at each part of the cable of the present invention. Foaming peaks are provided in the central part (intermediate part) in the thickness direction of the sheath instead of uniform foaming, and the skin layer and the contact part (deep part) with the insulated wire are less foamed. With this configuration, the sheath and the insulated wire can be more closely attached while maintaining characteristics such as flexibility and lightness in the entire sheath.
Here, “thickness” refers to the length indicated by arrow A in FIG.

In the present invention, as the material for the insulating layer and the sheath, a commonly used material such as a vinyl compound can be used, and there is no particular limitation. Specifically, for example, a vinyl chloride resin can be used. The thickness of the sheath may be a thickness that is usually performed, but is preferably 1.4 to 1.5 mm. There is no restriction | limiting in particular also about the conductor of an electric wire, The copper wire, aluminum, etc. which are generally used can be used.
In the present invention, it can be confirmed from the cross section and specific gravity of the cable that the foaming rate of the foamed sheath is reduced from the middle part of the surface thickness of the foamed sheath toward the insulated wire in the thickness direction.
In the present invention, the foaming rate from the insulating layer contact portion in the thickness direction to 0.1 to 0.2 mm is preferably 8% or less, and more preferably 1.0 to 6.0%.
The foaming ratio in the present invention is the ratio (%) of the volume of bubbles in the entire volume of each layer when the sheath is divided into a surface layer portion, an intermediate portion, and a deep layer portion in the thickness direction. . The surface layer portion preferably occupies 10 to 30% of the entire sheath thickness from the sheath surface, and more preferably 15 to 25%. Moreover, it is preferable that a deep layer part occupies 10-30% of the whole sheath thickness from an electric wire contact part, and 15-25% is further more preferable. An intermediate layer exists between the two layers.
The foaming rate peak in the graph shown in FIG. 2 is preferably 15 to 30%.

In the present invention, the foaming rate can be controlled as described above, for example, by sufficiently cooling the insulating layer covering the conductor and then covering the foamed sheath. Since the contact portion with the insulating layer is cooled compared to the center of the sheath, the foaming rate of the sheath is not uniform. The cooling temperature at this time is preferably 15 to 25 ° C.
The number of insulated wires of the present invention is not particularly limited, and may be one or more.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

Example 1
A three-core insulated wire was extruded into a hopper of a 70 mm single-screw extruder (manufactured by Mitsuba Seisakusho) and extruded as an insulating layer when the core was manufactured. At this time, the temperature (cylinder (supply part-compression part-metering part)) temperature was set to 150 to 180 ° C. and the die was set to 160 ° C. After coating from the die, it was water cooled in a cooling water bath. At this time, the cooling temperature of the water tank was set to 18 ° C., and the cooling was performed so that the surface temperature of the insulating layer after cooling was about 20 to 25 ° C. In the next step, foamed sheath extrusion was performed on the insulating layer, and the foaming rate in the vicinity of the insulating layer was adjusted to be about 3%.

Example 2
The cooling temperature of the water bath was adjusted to about 25 ° C., and the foaming rate close to the insulating layer was adjusted to 5%. The other conditions were the same as in Example 1.

Comparative Example 1
The cooling temperature of the water tank was set to 35 ° C., and the foaming rate in the vicinity of the insulating layer was adjusted to 9.0%. The other conditions were the same as in Example 1.

1) Test method a) Foaming ratio A sample was thinly sliced with a slicer, a sample was taken, and the specific gravity was measured by an underwater substitution method in accordance with JIS K 7112-5.1. The foaming rate was calculated from the specific gravity difference between the non-foamed (solid) material and the target foamed material.
B) Adhesive strength Adjust the sheath insulator length to 200 mm and measure the adhesive strength at 200 mm / min with an Instron type tensile tester.

It is explanatory drawing which showed an example of the cable of this invention with the partial cross section figure. It is the graph which showed typically an example of the foaming rate of the sheath in this invention. It is explanatory drawing which showed an example of the conventional cable with the partial cross section figure. It is a perspective view which shows the shape of a 3 core flat type cable. It is sectional drawing which shows the shape of a 3 core flat type cable.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a Conductor 1b Insulation layer 1 Electric wire 2a Skin part 2b Middle part 2c Deep layer part 2 Foam sheath

Claims (3)

  A cable in which a foamed sheath is coated on an insulated wire, wherein the foaming rate of the foamed sheath is reduced from the intermediate portion of the surface thickness of the foamed sheath toward the insulated wire in the thickness direction.   2. The cable according to claim 1, wherein the foaming rate of the foamed sheath is 8% or less between 0.1 to 0.2 mm in the thickness direction of the sheath from the insulated wire side.   By covering the foamed sheath after cooling the insulating layer of the insulated wire, the foamed sheath on the insulated wire side is restrained from growing in the thickness direction of the foamed sheath from the insulated wire. The cable manufacturing method according to claim 1 or 2, wherein

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