JP2016213007A - Electric cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric cable having no breakage of a metal braid even by a thermal cycle test.SOLUTION: An electric cable 1 has a central conductor 11 having cross section area of 20 mmor more, an insulation layer 12 extruded coated on a circumference of the central conductor 11, a resin tape 13 wound around the insulation layer 12, a braid 14 of a thin metallic wire covering a circumference of the resin tape 13 and an outer cover 15 coated around the braid 14 of the thin metallic wire. In the electric cable 1, electric cable diameter/central conductor diameter is 1.40 or more and 1.77 or less and 2% secant modulus of the insulation layer 12 is 10 MPa or more and 50 MPa or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electric cable used for wiring in an electric device or a vehicle.

  For example, in Patent Document 1, an outer periphery of a conductor is covered with an insulator made of an insulating resin containing a flame retardant, a shield conductor made of a metal braid is arranged on the outer periphery of the insulator, and the outer periphery of the shield conductor is further insulated. An electric cable covered with a resin jacket is disclosed.

JP 2014-139932 A

  In the electric cable disclosed in Patent Document 1, the metal braid constituting the shield conductor may be broken by being subjected to a thermal cycle. This is presumably because the insulator expands and contracts due to temperature fluctuation, and the metal braid covering the periphery of the insulator buckles due to the expansion and contraction of the insulator.

  An object of the present invention is to provide an electric cable in which a metal braid does not break even when subjected to a thermal cycle.

The electrical cable according to the present invention comprises:
A central conductor having a cross-sectional area of 20 mm ² or more;
An insulating resin layer extrusion coated on the outer periphery of the central conductor;
A resin tape wound around the insulating resin layer;
A braid of fine metal wires covering the periphery of the resin tape;
A jacket coated around the braid of the fine metal wire,
Electric cable diameter / center conductor diameter is 1.40 or more and 1.77 or less,
The insulating resin layer has a 2% secant modulus of 10 MPa to 50 MPa.

  According to the present invention, it is possible to provide an electric cable in which a braid of fine metal wires does not break even when subjected to a thermal cycle.

It is a figure explaining the outline of the electric cable which concerns on this embodiment.

[Description of Embodiment of Present Invention]
First, the contents of the embodiments of the present invention will be listed and described.
An electric cable according to an embodiment of the present invention is
(1) a central conductor having a cross-sectional area of 20 mm ² or more;
An insulating resin layer extrusion coated on the outer periphery of the central conductor;
A resin tape wound around the insulating resin layer;
A braid of fine metal wires covering the periphery of the resin tape;
A jacket coated around the braid of the fine metal wire,
Electric cable diameter / center conductor diameter is 1.40 or more and 1.77 or less,
The insulating resin layer has a 2% secant modulus of 10 MPa to 50 MPa.
According to this configuration, it is possible to provide an electric cable in which a braid of thin metal wires (hereinafter, metal braid) is not broken even when subjected to a heat cycle.

(2) It is preferable that the linear expansion coefficient of the resin tape is smaller than the linear expansion coefficient of the insulating resin layer.
According to this configuration, the metal braid is less susceptible to the expansion and contraction of the insulating resin layer by using the resin tape that is less likely to heat shrink than the insulating resin layer.

(3) It is preferable that the overlap width of the resin tape is ¼ or more and ½ or less of the tape width of the resin tape.
According to this configuration, it is possible to sufficiently prevent the insulating layer from biting into the metal braid.

(4) It is preferable that the said metal fine wire is comprised from an annealed copper wire.
According to this configuration, breakage of the metal braid can be prevented more reliably.

[Details of the embodiment of the present invention]
Hereinafter, the outline of the electric cable according to the present embodiment will be described with reference to the drawings. FIG. 1 shows an example of an electric cable 1 according to this embodiment.

The electric cable 1 which concerns on this embodiment is used for wiring of power supply systems, such as a motor and an inverter in a hybrid vehicle or an electric vehicle, for example.
As shown in FIG. 1, the electric cable 1 includes a center conductor 11, an insulating layer 12, a resin tape 13, a metal braid 14, and a jacket 15.

The center conductor 11 has a conductor cross-sectional area of 20 SQ (20 mm ² ) or more, for example, about 50 mm ² . The center conductor 11 is formed of a single wire or a stranded wire obtained by twisting a plurality of strands. The central conductor 11 is made of a generally used conductor material such as copper, annealed copper, silver, nickel-plated annealed copper, or tin-plated annealed copper. In addition, when forming with a stranded wire, the thing with a strand diameter of about 0.18 mm-0.5 mm is used.

  Around the center conductor 11, an insulating layer 12 using a polyolefin resin as a base resin is coated. Examples of the polyolefin resin that is the base resin of the insulating layer 12 include, for example, low density polyethylene (LDPE), linear low density polyethylene (L-LDPE), and the like other than α-olefin in order to impart flexibility to the resin. Copolymers such as ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl acrylate copolymer (EMA), and ethylene-vinyl acetate copolymer (EVA) into which other polar monomers are introduced are also used. be able to. Then, additives such as a flame retardant, an antioxidant, and a crosslinking agent are added to the above base resin, and the outer periphery of the center conductor 11 is extruded (extruded) as an insulating layer 12.

  The insulating layer 12 is coated on the outer surface of the center conductor 11 with a substantially uniform thickness by extrusion molding. The thickness of the insulating layer 12 is preferably 1.0 mm or more. In addition, the insulating layer 12 as an insulating coating is to improve its heat distortion resistance in order to prevent it from being deformed when the external force is applied in a relatively high temperature environment and lowering the electrical insulation. In addition, after the periphery of the central conductor 11 is coated, it is subjected to crosslinking treatment by irradiation with ionizing radiation (γ rays, electron beams, etc.), peroxide crosslinking, and chemical crosslinking such as silane crosslinking. The electric cable 1 of this embodiment may or may not be cross-linked, but it is preferable because cross-linking improves tensile strength and heat resistance. Further, by cross-linking the insulating layer 12, the secant modulus (2% secant modulus) described later increases by several% to several tens of%.

  Among the polyolefin-based resins used for the base resin of the insulating layer 12, it is particularly preferable to use EEA. EEA has a low degree of crystallinity due to ethyl acrylate (EA) contained therein, and high flexibility preferable for this application is obtained. EEA has a high thermal decomposition start temperature of 300 ° C. Then, long-term aging heat resistance is high, and it is preferable for long-term use as an electric cable that generates heat when energized. Further, it is easy to form a carbonized layer at the time of combustion, and oxygen is shielded by the carbonized layer and combustion is hindered. Therefore, it is easy to realize high flame retardancy with low specific gravity by reducing the amount of flame retardant added. The content of the copolymer is preferably 23% by weight or more. If it is smaller than this, the crystallinity is large and the flexibility is lowered. Further, the insulating layer 12 may be a copolymer of an olefin and a comonomer having a polarity, or a mixture of this copolymer and an olefin and an α-olefin copolymer.

A resin tape 13 is wound around the insulating layer 12. The resin tape 13 is preferably wound spirally so that the resin tapes 13 overlap each other. The overlapping width of the resin tapes 13 is from 1/4 to 1/2 of the tape width of the resin tape 13, preferably about 1/3. As the resin tape 13, it is particularly preferable to use a PET tape made of a polyethylene terephthalate (PET) resin. The linear expansion coefficient (for example, 2 × 10 ⁻⁵ / ° C.) of PET is smaller than the linear expansion coefficient (for example, 16 to 20 × 10 ⁻⁵ / ° C.) of a resin material such as EVA constituting the insulating layer 12. Therefore, the resin tape 13 made of PET tape is less likely to be deformed than the insulating layer 12 even when subjected to a thermal cycle. Moreover, since the 2% secant modulus (for example, 200 MPa) of PET is larger than the 2% secant modulus (for example, 20 MPa) of EVA, it is less susceptible to the expansion and contraction of the insulating layer 12. In this embodiment, the resin tape 13 mainly functions as a buffer material by interposing the resin tape 13 made of such a PET tape between the insulating layer 12 and the metal braid 14.

  Around the resin tape 13, a metal braid 14 formed by braiding metal fine wires is disposed. As the thin metal wire constituting the metal braid 14, it is preferable to use an annealed copper wire having excellent flexibility. By using an annealed copper wire excellent in flexibility, damage when the metal braid 14 is produced can be prevented. Alternatively, the metal braid 14 may be produced by plating the metal thin wire so that the soldering is easy and the copper damage is small.

  The periphery of the metal braid 14 is covered with a jacket 15. The outer cover 15 only needs to be made of the same resin material as that of the insulating layer 12. The outer jacket 15 is coated with a substantially uniform thickness on the outer surface of the metal braid 14 by extrusion molding (extrusion coating). The thickness of the outer jacket 15 is preferably at least 0.8 mm. The jacket 15 may be subjected to crosslinking treatment after being extruded.

  As shown in FIG. 1, the electric cable 1 according to the present embodiment has a conductor when the outer diameter of the central conductor 11 is D1, the outer diameter of the insulating layer 12 is D2, and the outer diameter of the jacket 15 is D3. A cable having a ratio (D3 / D1) of a jacket outer diameter D3 to an outer diameter D1 in a range of 1.40 to 1.77 is targeted. Further, the ratio (D2 / D1) of the insulating layer outer diameter D2 to the conductor outer diameter D1 is preferably in the range of 1.15 or more and 1.40 or less.

Further, in the electric cable 1 according to the present embodiment, it is preferable that the 2% secant modulus of at least one insulator portion of the insulating layer 12 and the jacket 15 is 10 MPa or more and 50 MPa or less. By setting the 2% secant modulus to 50 MPa or less, the electric cable 1 has flexibility and handling properties. The reason why the 2% secant modulus is set to 10 MPa or more is that when the value is smaller than this value, the electric cable 1 is deformed when wound after being extruded, and the outer diameter becomes unstable without becoming a predetermined outer diameter. The 2% secant modulus is measured by the following method. A test piece having a length of 100 mm is prepared by peeling the insulating layer from the electric cable. And the tensile strength at the time of 2% elongation when this test piece was pulled in the length direction at a speed of 50 mm / min using an Instron tensile tester was measured and multiplied by 50 to 2% secant. Modulus (kg / mm ² (1 kg / mm ² = 9.8 MPa)).

In this embodiment, paying attention to the value of the cable outer diameter / conductor outer diameter, the insulating layer 12, the resin tape 13, the metal braid 14 and the jacket 15 are disposed around the center conductor 11 having a cross-sectional area of 20 mm ² or more. For the electric cable 1 coated in this order and having an electric cable diameter / conductor diameter of 1.15 or more and 1.40 or less, if the 2% secant modulus of the insulating layer 12 is 10 MPa or more and 50 MPa or less, the flexibility is good. An electric cable 1 is obtained.

<Evaluation>
Here, a thermal cycle test was performed on the following Examples 1 to 3. Example 1 shows an example of the electric cable 1 according to the present embodiment, and Examples 2 and 3 show electric cables according to comparative examples. Table 1 shows specific configurations of the electric cables of Examples 1 to 3.

  As shown in Table 1, in Example 1, the resin tape was interposed between the insulating layer and the metal braid by winding a resin tape made of PET tape around the insulating layer. On the other hand, in Examples 2 and 3, the metal braid was directly disposed around the insulating layer without interposing a resin tape between the insulating layer and the metal braid. In Example 3, a metal braid braided at a braid density (95%) higher than that of Example 1 and Example 2 (90%) was used.

The electric cable according to Examples 1 to 3 configured as described above was subjected to a thermal cycle test in which the temperature change was switched in a short time, thereby evaluating whether or not the metal braid was broken. In the thermal cycle test, the temperature change from −40 ° C. to 150 ° C. was performed in 5 minutes, and this cycle was repeated 1000 times.
As a result of this thermal cycle test, no breakage or damage of the metal braid was confirmed in the electric cable according to Example 1. On the other hand, in the electric cable according to Example 2 and Example 3 in which the braid density was increased, it was confirmed that the metal braid was broken.
Further, even if the cross-sectional area of the center conductor was 20 mm ^2, the breaking and damage of the metal braid in the example is interposed resin tape between the insulating layer and the metal braid is not confirmed, the insulating layer and the metal braid In an example in which no resin tape was interposed, the metal braid broke.

From the above, when the resin tape 13 made of, for example, PET tape is interposed between the insulating layer 12 and the metal braid 14 as in the electric cable 1 according to the present embodiment, the insulating layer 12 expands and contracts due to temperature fluctuations. Even in such a case, the resin tape 13 becomes a so-called cushioning material, and the metal braid 14 is hardly affected by the expansion and contraction of the insulating layer 12. Therefore, it is possible to provide the electric cable 1 in which the metal braid 14 does not break even when it is subjected to a thermal cycle without buckling of the fine metal wires constituting the metal braid 14.
In the electric cable 1 according to the present embodiment, the cross-sectional area of the center conductor 11 is 20 mm ² or more, the electric cable diameter / center conductor diameter is 1.40 or more and 1.77 or less. The one whose% secant modulus is 10 MPa or more and 50 MPa or less is used. Since the cross-sectional area of the center conductor 11 is 20 mm ² or more, the outer diameter of the electric cable 1 having the metal braid 14 exceeds 10 mm, and the expansion and contraction of the insulating layer 12 due to heat is large, and the metal braid 14 is easily cut. Depending on the configuration, the metal braid 14 is difficult to cut. Furthermore, the flexibility of the electric cable 1 can be sufficiently ensured, wiring work (managing) in a narrow space is facilitated, and space saving can be achieved by reducing the bending radius.

  In the present embodiment, it is preferable to select materials for the insulating layer 12 and the resin tape 13 so that the linear expansion coefficient of the resin tape 13 is smaller than the linear expansion coefficient of the insulating layer 12. By using the resin tape 13 that is less likely to heat shrink than the insulating layer 12, the metal braid 14 is less susceptible to the expansion and contraction of the insulating layer 12, and the metal braid 14 can be reliably prevented from breaking.

  The overlapping width of the resin tape 13 is preferably not less than ¼ and not more than ½ of the tape width of the resin tape 13. Since the resin tape 13 opens when the electric cable 1 is bent, the overlapping width of the resin tape 13 is not less than ¼ in order to prevent the expansion and contraction of the insulating layer 12 from affecting the metal braid 14 even in that case. It is preferable that Even if the overlap width of the resin tape 13 exceeds 1/2, the effect of not exerting the influence of expansion and contraction of the insulating layer 12 on the metal braid 14 is saturated, and the production of the electric cable 1 is performed in order to increase the overlap width of the resin tape 13. Therefore, it is preferable that the overlapping width of the resin tape 13 is ½ or less, because disadvantages such as deterioration of the properties and the hardening of the electric cable 1 occur.

  Moreover, it is preferable that the metal fine wire which comprises the metal braid 14 is comprised from an annealed copper wire. By using an annealed copper wire having a high elongation rate and excellent flexibility, the metal braid 14 can be more reliably prevented from breaking.

  While the invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. In addition, the number, position, shape, and the like of the constituent members described above are not limited to the above-described embodiments, and can be changed to a number, position, shape, and the like that are suitable for carrying out the present invention.

1: Electric cable 11: Central conductor 12: Insulating layer 13: Resin tape 14: Metal braid (braid)
15: Jacket

Claims (4)

A central conductor having a cross-sectional area of 20 mm ² or more;
An insulating layer extrusion coated on the outer periphery of the central conductor;
A resin tape wound around the insulating layer;
A braid of fine metal wires covering the periphery of the resin tape;
A jacket coated around the braid of the fine metal wire,
Electric cable diameter / center conductor diameter is 1.40 or more and 1.77 or less,
The electric cable having a 2% secant modulus of the insulating layer of 10 MPa to 50 MPa.   The electric cable according to claim 1, wherein a linear expansion coefficient of the resin tape is smaller than a linear expansion coefficient of the insulating layer.   The electric cable according to claim 1 or 2, wherein an overlapping width of the resin tape is ¼ or more and ½ or less of a tape width of the resin tape.   The electric metal cable according to any one of claims 1 to 3, wherein the thin metal wire is composed of an annealed copper wire.

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