JP7794651B2 - electric wire - Google Patents

Description

The present invention relates to an electric wire comprising a conductor core, an insulating coating arranged to surround the outer periphery of the conductor core, and an outer sheath layer arranged to surround the outer periphery of the insulating coating.

Conventionally, electric wires have been proposed for power supply, etc., with a structure in which a conductor core is covered with multiple layers, such as an insulating coating and an outer layer (so-called sheath) (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2019-176617

When an electric wire is actually used, the temperature of the conductor core generally rises due to Joule heat generated in the conductor core when current is applied. In the conventional electric wires described above, the conductor core is covered with multiple layers of insulating coatings, etc., making it difficult for the heat generated in the conductor core to be dissipated to the outside of the wire. As a result, as the temperature of the conductor core rises, the temperature of the entire wire also rises, and there is a possibility that the insulating coating and outer layer will deteriorate due to the heat. From the perspective of maintaining the quality and safety of the electric wire, it is desirable to suppress such deterioration.

One of the objectives of the present invention is to provide an electric wire with excellent heat dissipation properties for heat generated in the conductor core to the outside.

To achieve the above-mentioned objectives, the electric wire of the present invention has the following features:

A conductor core wire,
an insulating coating disposed so as to surround the outer periphery of the conductor core;
an outer skin layer disposed so as to surround the outer periphery of the insulating coating,
The skin layer is
The material is composed of a base material and a mixture having a higher thermal conductivity than the base material and being mixed into the base material.
It is an electric wire.

According to the present invention, the outer skin layer surrounding the insulating coating that covers the conductor core wire is composed of a material that includes a substrate and a mixture that has better thermal conductivity than the substrate and is mixed into the substrate. Therefore, compared to when the outer skin layer is composed of only the substrate, heat can be transferred from the insulating coating to the outer skin layer and dissipated from the outer skin layer to the outside of the wire more efficiently. In other words, the overall heat dissipation performance of the multilayer structure including the insulating coating and outer skin layer can be improved. Therefore, an electric wire with this configuration has excellent heat dissipation characteristics for heat generated in the conductor core wire to the outside.

Furthermore, as another effect, the electric wire configured as described above has superior workability when routing the electric wire and freedom of routing path compared to cases where a heat-absorbing material (such as a metal case) is provided on the outside of the outer skin layer.

In addition to the above configuration, the overall heat dissipation of the multilayer structure can be further improved by mixing a mixture with excellent thermal conductivity into the material that makes up the insulating coating. However, mixing such a mixture into the material that makes up the insulating coating may result in a decrease in the insulating properties of the insulating coating, or in deterioration of the insulating coating due to localized discharges that may occur in tiny gaps around the mixture when the mixture is exposed on the inner surface of the insulating coating. Therefore, if maintaining the functionality of the insulating coating is more important than further improving heat dissipation, it is preferable to construct the outer layer from a material that contains a mixture with excellent thermal conductivity and the insulating coating from a material that does not contain such a mixture.

The present invention has been briefly described above. Furthermore, details of the present invention will become clearer by reading the detailed description of the invention (hereinafter referred to as "embodiments") described below with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view of an electric wire according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view of an electric wire according to a second embodiment. FIG. 3 is an enlarged view of part A in FIG. FIG. 4 is a cross-sectional view of the electric wire according to the third embodiment.

First Embodiment
Hereinafter, an electric wire 1 according to a first embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the electric wire 1 comprises a linear conductor core wire 10, a cylindrical insulating coating 20 arranged to surround the outer periphery of the conductor core wire 10, and a cylindrical outer jacket layer 30 arranged to surround the outer periphery of the insulating coating 20. The outer jacket layer 30 constitutes the outermost layer of the electric wire 1 and is also referred to as a sheath.

The conductor core wire 10 may be a single conductor wire, a conductor bundle consisting of multiple conductor wires (element wires), or a twisted wire consisting of multiple conductor wires twisted together. Here, the conductor wire is made of a conductive metal material, typically copper, copper alloy, aluminum, aluminum alloy, etc.

In this example, the insulating coating 20 surrounds the outer periphery of the conductor core wire 10 so as to adhere closely to the entire outer periphery of the conductor core wire 10. The insulating coating 20 is made of an insulating resin material, typically cross-linked polyethylene. The insulating coating 20 is formed, for example, by extrusion molding the resin material that makes up the insulating coating 20 so that it surrounds the conductor core wire 10.

In this example, the outer layer 30 (sheath) surrounds the outer periphery of the insulating coating 20 so as to adhere closely to the entire outer periphery of the insulating coating 20. The outer layer 30 is composed of a material (i.e., a composite material) including an insulating base material 31 and a mixture 32 mixed into the base material 31. The effect of mixing the mixture 32 into the base material 31 will be described later.

The substrate 31 of the outer skin layer 30 is made of an insulating resin material, typically polyvinyl chloride or polyethylene. The mixture 32 is made of a material with better thermal conductivity than the substrate 31. For example, alumina particles or boron nitride filler may be used as the mixture 32. It is preferable that the thermal conductivity of the material (composite material) containing such substrate 31 and mixture 32 be greater than 0.29 W/m·K.

The outer sheath layer 30 can be formed, for example, by extruding the insulating coating 20 so that it surrounds the conductor core wire 10, and then extruding the material that makes up the outer sheath layer 30 so that it surrounds the insulating coating 20 that covers the conductor core wire 10. Alternatively, it can be formed by extruding the resin material that makes up the insulating coating 20 and the material that makes up the outer sheath layer 30 all at once so that they surround the conductor core wire 10.

The effect of mixing the mixture 32 into the substrate 31 in the outer sheath layer 30 will be described below. When the electric wire 1 is actually used, the temperature of the conductor core 10 rises due to Joule heat generated in the conductor core 10 when current is applied. In the electric wire 1, the conductor core 10 is covered in multiple layers with the insulating coating 20 and the outer sheath layer 30, making it difficult for the heat generated in the conductor core 10 to dissipate to the outside of the electric wire 1. Therefore, as the temperature of the conductor core 10 rises, the temperature of the entire electric wire 1 also rises, which may cause thermal deterioration of the insulating coating 20 and the outer sheath layer 30.

In this regard, in the electric wire 1 according to the first embodiment, the outer cover layer 30 surrounding the insulating cover 20 covering the conductor core wire 10 is composed of a material including a substrate 31 and a mixture 32 that has better heat conductivity than the substrate 31 and is mixed into the substrate 31. Therefore, compared to when the outer cover layer 30 is composed of only the substrate 31, heat transfer from the insulating cover 20 to the outer cover layer 30 and heat dissipation from the outer cover layer 30 to the outside of the electric wire 1 can be more efficient. In other words, the overall heat dissipation performance of the electric wire 1, which is a multilayer structure including the insulating cover 20 and the outer cover layer 30, can be improved. Furthermore, the electric wire 1 according to the first embodiment offers greater ease of installation and greater flexibility in routing the electric wire 1 compared to when a heat-absorbing material (e.g., a metal case) is provided outside the outer cover layer 30.

Second Embodiment
In the first embodiment described above, as shown in Fig. 1 , the outer peripheral surface of the insulating coating 20 is configured as a smooth cylindrical outer peripheral surface, and the inner peripheral surface of the outer cover layer 30 is configured as a smooth cylindrical inner peripheral surface. In contrast, as in the second embodiment shown in Fig. 2 , the outer peripheral surface of the insulating coating 20 may be provided with convex portions 20A that protrude radially outward from the electric wire 1 and extend in the extending direction of the electric wire 1 at a plurality of positions in the circumferential direction, and the inner peripheral surface of the outer cover layer 30 may be provided with concave portions 30A that are recessed radially outward from the electric wire 1 and extend in the extending direction of the electric wire 1 corresponding to the convex portions 20A of the insulating coating 20 at a plurality of positions in the circumferential direction, so that the outer peripheral surface of the insulating coating 20 and the inner peripheral surface of the outer cover layer 30 may have a concave-convex fitting structure in which the convex portions 20A and the concave portions 30A are fitted together.

In the second embodiment shown in Figure 2, the recessed/protruding fitting structure formed by the outer peripheral surface of the insulating coating 20 and the inner peripheral surface of the outer skin layer 30 allows the size of the area contributing to heat transfer between the insulating coating 20 and the outer skin layer 30 (i.e., the surface area of the outer peripheral surface of the insulating coating 20 and the surface area of the inner peripheral surface of the outer skin layer 30) to be larger than in the case where there is no recessed/protruding fitting structure (first embodiment shown in Figure 1). This allows for more efficient heat transfer from the insulating coating 20 to the outer skin layer 30, further improving the heat dissipation characteristics of the electric wire 1.

In the second embodiment shown in Figure 2, as in the first embodiment, the insulating coating 20 may be extruded to surround the conductor core wire 10, and then the material that constitutes the outer sheath layer 30 may be extruded to surround the insulating coating 20 that covers the conductor core wire 10. Alternatively, the resin material that constitutes the insulating coating 20 and the material that constitutes the outer sheath layer 30 may be extruded together to surround the conductor core wire 10.

In the second embodiment shown in Figure 2, when the outer cover layer 30 is formed, the material constituting the outer cover layer 30 penetrates between the multiple protrusions 20A formed on the outer surface of the insulating coating 20 and solidifies, forming a concave-convex interlocking structure. However, if the outer surface of the insulating coating 20 and the inner surface of the outer cover layer 30 that form the concave-convex interlocking structure are not in complete contact, a minute gap S may be formed between the outer surface of the insulating coating 20 and the inner surface of the outer cover layer 30 (see Figure 3). If air, which has poor thermal conductivity, is present in this minute gap S, heat transfer from the insulating coating 20 to the outer cover layer 30 may be hindered, potentially reducing the heat dissipation characteristics of the electric wire 1.

To address this issue, in the second embodiment shown in Figure 2, a soft heat transfer material 40 with better thermal conductivity than air is disposed to fill part or all of the minute gap S (including the gap between the convex portion 20A and the concave portion 30A) between the outer surface of the insulating coating 20 and the inner surface of the outer skin layer 30, which constitute the concave-convex fitting structure (see Figure 3). Grease, for example, is used as the soft heat transfer material 40. This prevents the presence of air in the minute gap S (including the gap between the convex portion 20A and the concave portion 30A) from interfering with heat transfer from the insulating coating 20 to the outer skin layer 30.

When placing a soft heat conductor 40, for example, the soft heat conductor 40 can be placed in the minute gap S by simultaneously supplying the soft heat conductor 40 between the insulating coating 20 and the outer sheath layer 30 when extruding the insulating coating 20 and the outer sheath layer 30 as described above. Alternatively, the insulating coating 20 can be extruded to surround the conductor core wire 10, and then the soft heat conductor 40 can be applied to the outer surface of the insulating coating 20 by a method such as spraying, and then the material that makes up the outer sheath layer 30 can be extruded to surround the insulating coating 20 that covers the conductor core wire 10.

Third Embodiment
1 and 2, the outer cover layer 30 is disposed so as to surround (so as to be in close contact with) the outer periphery of a single insulating coating 20 that covers a single conductor core wire 10. In contrast, as in a third embodiment shown in Fig. 4, the outer cover layer 30 may be disposed so as to surround (so as to be in close contact with) the outer periphery of a plurality of (two) insulating coatings 20 that individually cover a plurality of (two in this example) conductor core wires 10.

<Other forms>
It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be adopted within the scope of the present invention. For example, the present invention is not limited to the above-described embodiments, and modifications, improvements, etc. are possible as appropriate. In addition, the material, shape, dimensions, number, location, etc. of each component in the above-described embodiments are arbitrary and not limited as long as the present invention can be achieved.

For example, in the electric wire 1 according to the first embodiment, the insulating coating 20 does not contain a heat-conductive mixture like the mixture 32 in the outer cover layer 30. However, like the outer cover layer 30, the material constituting the insulating coating 20 may also contain a heat-conductive mixture. This allows for more efficient heat transfer from the conductor core wire 10 to the insulating coating 20, thereby further improving the overall heat dissipation of the electric wire 1, which has a multilayer structure. However, mixing a mixture into the material constituting the insulating coating 20 may result in a decrease in the insulating properties of the insulating coating 20 or in deterioration of the insulating coating 20 due to localized discharges occurring in minute gaps around the mixture that may occur when the mixture is exposed on the inner surface of the insulating coating 20. Therefore, when prioritizing the maintenance of the functionality of the insulating coating 20 over further improvement of heat dissipation, it is preferable to construct the outer cover layer 30 from a resin material containing the mixture 32 with excellent heat conductivity and the insulating coating 20 from a resin material that does not contain such a mixture, as in the electric wire 1 according to the first embodiment.

Furthermore, in the second embodiment described above, the outer peripheral surface of the insulating coating 20 and the inner peripheral surface of the outer skin layer 30 have a concave-convex fit structure, and a soft heat transfer material 40 is disposed in the minute gap S between the outer peripheral surface of the insulating coating 20 and the inner peripheral surface of the outer skin layer 30. In contrast, if the adhesion between the outer peripheral surface of the insulating coating 20 and the inner peripheral surface of the outer skin layer 30 is sufficient from the perspective of heat dissipation, it is not necessary to dispose the soft heat transfer material 40 in the gap.

Furthermore, in the second embodiment, the convex portion 20A extending in the extension direction of the electric wire 1 and the concave portion 30A extending in the extension direction of the electric wire 1 are adapted to fit together. However, a convex-convex fitting structure may be formed by fitting together convex portions and concave portions having other shapes. For example, a convex-convex fitting structure may be formed using convex portions and concave portions extending in the circumferential direction of the electric wire 1, convex portions and concave portions extending spirally around the axis of the electric wire 1, or convex portions that are mountain-shaped or columnar protrusions and concave portions that receive them.

Furthermore, in the third embodiment, the outer surface of the insulating coating 20 that covers each of the multiple conductor core wires 10 is a smooth cylindrical outer surface. Alternatively, protrusions as shown in FIG. 2 may be provided on some or all of the outer surfaces of these insulating coatings 20, and recesses to accommodate the protrusions may be provided in the outer layer 30. In other words, the features of the second embodiment and the third embodiment may be combined.

Here, the features of the electric wire 1 according to the present invention described above are briefly summarized and listed below in [1] to [3].

[1]
A conductor core wire (10),
an insulating coating (20) arranged to surround the outer periphery of the conductor core wire (10);
an outer skin layer (30) arranged to surround the outer periphery of the insulating coating (20),
The skin layer (30) is
The heat exchanger is composed of a material including a substrate (31) and a mixture (32) that has better heat conductivity than the substrate (31) and is mixed into the substrate (31).
Electric wire (1).

In the electric wire having the configuration [1] above, the outer skin layer surrounding the insulating coating that covers the conductor core wire is composed of a material including a substrate and a mixture that has better heat conductivity than the substrate and is mixed into the substrate. Therefore, compared to when the outer skin layer is composed only of the substrate, heat transfer from the insulating coating to the outer skin layer and heat dissipation from the outer skin layer to the outside of the electric wire can be performed more efficiently. In other words, the overall heat dissipation performance of the multilayer structure including the insulating coating and outer skin layer can be improved. Therefore, the electric wire having this configuration has excellent heat dissipation characteristics for heat generated in the conductor core wire to the outside. Furthermore, as another effect, the electric wire having the above configuration has excellent workability when routing the electric wire and flexibility in routing the wire compared to when a heat-absorbing material (e.g., a metal case) is provided outside the outer skin layer.

[2]
In the electric wire (1) described in [1] above,
The outer peripheral surface of the insulating coating (20) and the inner peripheral surface of the outer skin layer (30) are
The electric wire (1) has a projection (20A) projecting toward the other end in the radial direction thereof, and a recess (30A) recessed toward the other end in the radial direction thereof, and the electric wire (1) has a recess-projection fitting structure.
Electric wire (1).

In the electric wire having the configuration [2] above, the concave-convex fitting structure formed by the outer surface of the insulating coating and the inner surface of the outer sheath layer allows the size of the area contributing to heat transfer between the insulating coating and the outer sheath layer (i.e., the surface area of the outer surface of the insulating coating and the surface area of the inner surface of the outer sheath layer) to be larger than when there is no concave-convex fitting structure. This allows for more efficient heat transfer from the insulating coating to the outer sheath layer, further improving the heat dissipation characteristics of the electric wire. Note that such a concave-convex fitting structure can be formed, for example, by extruding the insulating coating and outer sheath layer together so that they surround the conductor core wire.

[3]
The electric wire (1) according to the above [2],
The heating element further includes a soft heat transfer body (40) arranged so as to fill at least a part of the gap (S) between the convex portion (20A) and the concave portion (30A).
Electric wire (1).

In the electric wire having the configuration [3] above, a soft heat conductor is disposed so as to fill at least a portion of the gap between the convex and concave portions that constitute the concave-convex fitting structure. This prevents air from being trapped between the convex and concave portions, which would hinder heat transfer from the insulating coating to the outer skin layer. This allows for more efficient heat transfer from the insulating coating to the outer skin layer, further improving the heat dissipation characteristics of the electric wire. For example, the heat conductor can be disposed in the gap by supplying a soft heat conductor between the insulating coating and the outer skin layer during the extrusion molding of the insulating coating and the outer skin layer.

REFERENCE SIGNS LIST 1 Electric wire 10 Conductor core 20 Insulating coating 30 Outer layer 31 Substrate 32 Mixture 40 Heat transfer body S Gap

Claims (2)

A conductor core wire,
an insulating coating disposed so as to surround the outer periphery of the conductor core;
an outer skin layer disposed so as to surround the outer periphery of the insulating coating,
The skin layer is
a material including a base material and a mixture having higher thermal conductivity than the base material and mixed into the base material , the material constituting the outermost layer of the electric wire;
The outer peripheral surface of the insulating coating and the inner peripheral surface of the outer skin layer are
The wire has a protrusion on one side that protrudes toward the other side in the radial direction of the wire, and a recess on the other side that is recessed toward the one side.
Electric wire. The electric wire according to claim 1 ,
Further provided is a soft heat transfer material arranged to fill at least a part of the gap between the protrusion and the recess.
Electric wire.