JP7443766B2 - electrical insulated cable - Google Patents

Description

TECHNICAL FIELD This disclosure relates to electrically insulated cables.

Patent Document 1 discloses an insulated wire characterized by having an insulating layer made of a polyvinyl chloride resin composition containing predetermined components on the outer periphery of a conductor.

Japanese Patent Application Publication No. 2014-133856

In various electrical devices, for example, the international standard IEC62368-1 stipulates that a predetermined spatial distance from a conductive part be maintained depending on the voltage applied to the conductive part. Clearance distance means the shortest distance between two conductive parts, or between a conductive part and an accessible surface of a device, measured through the air.

For this reason, in order to ensure the spatial distance, in electrically insulated cables, the thickness of the insulating layer covering the conductor may be required to be greater than the spatial distance specified by the standard. However, when the thickness of the insulating layer is increased, the electrically insulated cable becomes heavy, resulting in problems such as reduced handling properties and limited installation locations.

Therefore, an object of the present disclosure is to provide an electrically insulated cable that is lightweight while ensuring a spatial distance.

The electrically insulated cable of the present disclosure includes a conductor;
an insulating layer covering the conductor and having an exposed outer surface;
the insulating layer includes voids,
In a cross section perpendicular to the longitudinal direction of the conductor, an average value of the thickness of a first solid portion that is a region between the innermost void located closest to the conductor among the voids and the outer periphery of the conductor. is 0.02 mm or more and 0.15 mm or less.

According to the present disclosure, it is possible to provide an electrically insulated cable that is lightweight while ensuring a spatial distance.

FIG. 1 is a cross-sectional view of an electrically insulated cable according to one embodiment of the present disclosure, taken in a plane perpendicular to the longitudinal direction of the conductor. FIG. 2 is a cross-sectional view of another configuration example of the electrically insulated cable according to one aspect of the present disclosure, taken in a plane perpendicular to the longitudinal direction of the conductor. FIG. 3 is a cross-sectional view of another configuration example of the electrically insulated cable according to one aspect of the present disclosure, taken in a plane perpendicular to the longitudinal direction of the conductor. FIG. 4 is a partial perspective view of an extruder that can be used in manufacturing electrically insulated cables according to one aspect of the present disclosure. FIG. 5 is an explanatory diagram of a flexibility evaluation method in an experimental example.

The embodiment will be described below.

[Description of embodiments of the present disclosure]
First, embodiments of the present disclosure will be listed and described. In the following description, the same or corresponding elements are given the same reference numerals, and the same description will not be repeated.

(1) An electrically insulated cable according to one aspect of the present disclosure includes a conductor;
an insulating layer covering the conductor and having an exposed outer surface;
the insulating layer includes voids,
In a cross section perpendicular to the longitudinal direction of the conductor, an average value of the thickness of a first solid portion that is a region between the innermost void located closest to the conductor among the voids and the outer periphery of the conductor. is 0.02 mm or more and 0.15 mm or less.

The inventor of the present invention conducted extensive research on electrically insulated cables that are lightweight while ensuring spatial distance. As a result, they discovered that by using an insulating layer containing voids, even when the insulating layer is made thicker to ensure spatial distance, the weight of the entire cable can be suppressed, making it possible to create an electrically insulated cable with excellent lightness.

However, when voids are distributed throughout the insulating layer, the withstand voltage characteristics of the electrically insulated cable may deteriorate. Therefore, after further investigation, it was discovered that the withstand voltage characteristics could be improved by providing a region of the insulating layer that does not contain voids near the conductor. Here, in a cross section of the electrically insulated cable perpendicular to the longitudinal direction of the conductor, the region between the innermost void located closest to the conductor among the voids and the outer periphery of the conductor is defined as the first solid portion. According to the study by the inventor of the present invention, by setting the average thickness of the first solid portion to 0.02 mm or more and 0.1 mm or less, an electrically insulated cable with light weight and withstand voltage characteristics can be obtained. can do.

(2) In a cross section perpendicular to the longitudinal direction of the conductor, a region between the outermost gap located closest to the outer surface of the insulating layer among the gaps and the outer surface of the insulating layer. The average value of the thickness of a certain second solid portion may be 0.05 mm or more and 0.15 mm or less.

(3) The outer diameter may be 1 mm or more and 4 mm or less.

(4) The insulating layer may have an average porosity of 10% or more and 50% or less.

(5) The insulating layer may have an average porosity of 38% or more and 45% or less.

(6) The void may have a columnar shape with a central axis extending along the longitudinal direction of the conductor.

(7) The insulating layer may contain crosslinked fluororubber.

(8) The dielectric strength of the insulating layer may be 25 kV/mm or more.

(9) The insulating layer may include a plurality of layers made of different materials.

(10) The dielectric strength of the insulating material in contact with the conductor in the insulating layer may be 25 kV/mm or more, and the tensile strength of the insulating material on the outer surface of the insulating layer may be 8 MPa or more.

[Details of embodiments of the present disclosure]
A specific example of an electrically insulated cable according to an embodiment of the present disclosure (hereinafter referred to as "this embodiment") will be described below with reference to the drawings. Note that the present invention is not limited to these examples, but is indicated by the scope of the claims, and is intended to include all changes within the meaning and scope equivalent to the scope of the claims.
(electrical insulated cable)
FIG. 1 shows a configuration example of a cross section perpendicular to the longitudinal direction of the electrically insulated cable of this embodiment.

As shown in FIG. 1, the electrically insulated cable 10 of this embodiment can include a conductor 11 and an insulating layer 12 that covers the conductor 11 and has an exposed outer surface 12A.

Insulating layer 12 may include voids 13 . In a cross section perpendicular to the longitudinal direction of the conductor 11, the thickness of the first solid portion 121, which is a region between the innermost position gap 131 located closest to the conductor 11 among the gaps 13 and the outer periphery 11A of the conductor 11. The average value of the length L1 can be 0.02 mm or more and 0.15 mm or less.

Each member and configuration of the electrically insulated cable of this embodiment will be described below with reference to the drawings.
(1) Conductor The conductor 11 is a conducting wire, and can be composed of a single metal wire or a plurality of metal wires. When the conductor 11 has a plurality of metal wires, the plurality of metal wires may be twisted together. That is, when the conductor 11 has a plurality of metal wires, the conductor 11 can also be a twisted wire of the plurality of metal wires.

As shown in FIG. 1, the conductor 11 can also have a circular outer shape in a cross section perpendicular to the longitudinal direction. When the conductor 11 is made by twisting a plurality of metal wires, the conductor having a circular outer shape can be formed by circularly compressing the conductor in the radial direction. Further, the conductor 11 can also have surface irregularities that follow the contours of the plurality of metal wires.

The material of the conductor 11 is not particularly limited, but for example, one or more commonly used conductor materials selected from copper, annealed copper, silver-plated annealed copper, nickel-plated annealed copper, tin-plated annealed copper, etc. can be used.

The diameter of the conductor 11 is not particularly limited, but is preferably, for example, 0.35 mm or more and 2.0 mm or less.
(2) Insulating layer, void The electrically insulated cable of this embodiment can have an insulating layer 12 that covers the conductor 11 and has an exposed outer surface 12A. The insulating layer 12 can have voids 13 .

The inventor of the present invention conducted extensive research on electrically insulated cables that are lightweight while ensuring spatial distance. As a result, we found that by using the insulating layer 12 that includes voids 13, even when the insulating layer 12 is made thicker to ensure spatial distance, the weight of the entire cable can be suppressed and an electrically insulated cable with excellent lightness can be obtained. I found it.

However, when the voids 13 are distributed throughout the insulating layer 12, the withstand voltage characteristics of the electrically insulated cable may deteriorate. Therefore, after further investigation, it was discovered that the withstand voltage characteristics could be improved by providing a region of the insulating layer 12 near the conductor 11 that does not include the void 13. Here, in a cross section perpendicular to the longitudinal direction of the conductor 11 of the electrically insulated cable, a region between the innermost position gap 131 located closest to the conductor 11 among the gaps 13 and the outer periphery 11A of the conductor 11 is first filled. Section 121. According to the study by the inventor of the present invention, by setting the average value of the thickness L1 of the first solid portion 121 within a predetermined range, an electrically insulated cable with light weight and withstand voltage characteristics can be obtained. I can do it.

Hereinafter, the insulating layer 12 and the voids 13 that the insulating layer 12 has will be described in detail.

As described above, the insulating layer 12 is arranged to cover the outer periphery 11A of the conductor 11, and the outer shape of the insulating layer 12 can have a circular shape in a cross section perpendicular to the longitudinal direction of the conductor 11. The circular shape here does not mean only a circle in the strict sense, that is, a perfect circle, but also includes distorted circles such as ellipses.
(2-1) Shape of voids The shape of the voids 13 in the insulating layer 12 is not particularly limited. For example, as shown in FIG. 1, spherical voids may be arranged randomly within the insulating layer 12. . Note that the spherical shape in this case does not mean only a sphere in the strict sense, that is, a true sphere, but also includes distorted spheres such as ellipsoids.

Moreover, the void 13 can also have a columnar shape, for example like the void 13 of the electrically insulated cables 20, 30 shown in FIGS. 2 and 3. Specifically, the void 13 can have, for example, a columnar shape in which the central axis of the void is formed along the longitudinal direction of the conductor 11. In this case, the void 13 has a continuous shape along the longitudinal direction of the conductor 11. Although FIGS. 2 and 3 show an example of a void having a circular cross section, that is, a cylindrical shape, the shape is not limited to this, and the shape of the cross section perpendicular to the central axis may be a polygonal columnar shape such as a quadrangle or a triangle. It may be a shape. When the voids 13 have a columnar shape as described above, it is preferable because the porosity of the insulating layer 12 and the arrangement of the voids 13 within the insulating layer 12 can be controlled more accurately.

The insulating layer 12 having spherical voids 13 and randomly arranged as shown in FIG. 1 can be manufactured, for example, by molding a resin to which a foaming agent is added.

The insulating layer 12 including the voids 13 having a columnar shape as shown in FIGS. 2 and 3 can be manufactured using, for example, an extruder 40 shown in FIG. 4 that combines a die 41 and a point jig 42. A method of manufacturing an electrically insulated cable including an insulating layer 12 including voids 13 having a columnar shape as shown in FIGS. 2 and 3 will be described with reference to FIG. 4.

The point jig 42 can have as many columnar members 43 as the number of columnar gaps to be provided. FIG. 4 shows an example in which a member having a cylindrical shape is provided as the columnar member 43, and in this case, the insulating layer 12 having a cylindrical void 13 can be formed.

The die 41 has a circular outlet 411 and extrudes the resin from channels 44 and 45 between the point jig 42 and the die 41. At this time, the conductor is also pulled out from the center hole 422 of the cylindrical portion 421 of the point jig 42. By performing the above operations, the extruded resin is coated on the conductor. The resin may be coated by a drawing method in which the resin exiting the exit of the die 41 is stretched to reduce its diameter and coated. The resin does not flow into the columnar member 43, and by providing ventilation holes 431 in the columnar member 43, a gap is secured in the resin extruded from the die 41 where the resin does not flow. For example, when the columnar member 43 has a cylindrical shape, the cross section becomes circular or elliptical.

In the extruder 40 described above, the porosity of the insulating layer can be easily adjusted by adjusting the diameter and number of columnar members 43 provided on the point jig 42.
(2-2) First solid portion As described above, in the cross section perpendicular to the longitudinal direction of the conductor 11 of the electrically insulated cable, the innermost position gap 131 located closest to the conductor 11 among the gaps 13 and the conductor 11 and the outer periphery 11A is defined as a first solid portion 121. Specifically, as shown in FIGS. 1 to 3, for example, the first solid portion 121 can be formed between the circle in contact with the conductor 11 side of the innermost position gap 131 and the outer periphery 11A of the conductor 11. .

The average value of the thickness L1 of the first solid portion 121 is preferably 0.02 mm or more and 0.15 mm or less, and more preferably 0.04 mm or more and 0.10 mm or less.

According to studies by the inventor of the present invention, by setting the average value of the thickness L1 of the first solid portion 121 to 0.02 mm or more, the withstand voltage characteristics of the electrically insulated cable can be improved. Further, by setting the average value of the thickness L1 of the first solid portion 121 to 0.15 mm or less, a sufficient amount of voids can be provided within the insulating layer 12, and the weight of the electrically insulated cable can be increased.

The average value of the thickness L1 of the first solid portion 121 means the average value of the thickness L1 of the first solid portion 121 measured on arbitrary four cross sections perpendicular to the longitudinal direction of the conductor 11.
(2-3) Second solid part Although the void 13 can be arranged up to the vicinity of the outer surface 12A of the insulating layer 12, the appearance of the electrically insulated cable is improved by having the outer surface 12A of the insulating layer 12 smooth. It is preferable from the viewpoint of improvement. In the cross section perpendicular to the longitudinal direction of the conductor 11 of the electrically insulated cable, the gap between the outermost gap 132 located closest to the outer surface 12A of the insulating layer 12 among the gaps 13 and the outer surface 12A of the insulating layer 12. The area is defined as the second solid portion 122. Specifically, as shown in FIGS. 1 and 2, for example, the second solid portion 122 is defined as the space between the circle in contact with the outer surface 12A of the outermost gap 132 and the outer surface 12A of the insulating layer 12. be able to.

When the second solid portion 122 is provided, the average value of the thickness L2 of the second solid portion 122 is preferably 0.05 mm or more and 0.15 mm or less, more preferably 0.05 mm or more and 0.12 mm or less. preferable.

By setting the average value of the thickness L2 of the second solid portion 122 to 0.05 mm or more, the outer surface 12A of the insulating layer 12 can be made smooth and the appearance can be improved. Further, by setting the average value of the thickness L2 of the second solid portion 122 to 0.15 mm or less, a sufficient amount of voids can be provided within the insulating layer 12, and the weight of the electrically insulated cable can be particularly improved.

The average value of the thickness L2 of the second solid portion 122 means the average value of the thickness L2 of the second solid portion 122 measured on arbitrary four cross sections perpendicular to the longitudinal direction of the conductor 11.

Note that, like the electrically insulated cable 30 shown in FIG. 3, the second solid portion 122 may not be provided and the void-containing portion 123 may constitute the outer surface 12A of the insulating layer 12.
(2-4) Gap Containing Portion In a cross section of the electrically insulated cable perpendicular to the longitudinal direction of the conductor 11, a region including the void 13 is defined as a void containing portion 123.

In the electrically insulated cable 10 shown in FIG. 1, the gap 13 has a spherical shape as described above. In the electrically insulated cable 10, the voids 13 are randomly distributed in the void-containing portion 123 between the first solid portion 121 and the second solid portion 122.

The electrically insulated cable 10 shown in FIG. 1 may not have the second solid portion 122 and may be arranged so that the void-containing portion 123 is exposed, that is, so as to constitute the outer surface 12A.

In the electrically insulated cable 20 shown in FIG. 2, the gap 13 has a cylindrical shape with a central axis extending along the longitudinal direction of the conductor 11. Then, in the void-containing portion 123 between the first solid portion 121 and the second solid portion 122, the voids 13 are arranged in one layer along the circumferential direction of a circle centered on the conductor 11. An example is shown. In this case, one arbitrarily selected void 13 is the innermost void 131 and the outermost void 132.

However, when the void 13 has a columnar shape, the arrangement of the void 13 is not limited to the form shown in FIG. They may be arranged along the circumferential direction of a circle centered on the conductor 11 so that there are two or more layers within the conductor 11, or they may be arranged randomly.

In the electrically insulated cable 30 shown in FIG. 3, similarly to the electrically insulated cable 20, the void 13 has a cylindrical shape with the central axis extending along the longitudinal direction of the conductor 11. Then, in the void-containing portion 123, the voids 13 are arranged in one layer along the circumferential direction of a circle centered on the conductor 11, and the voids are arranged up to the vicinity of the outer surface 12A of the insulating layer 12. An example is shown below. In this case, one arbitrarily selected void 13 is the innermost void 131 and the outermost void 132. Further, the electrically insulated cable 30 has the void 13 disposed up to the vicinity of the outer surface 12A of the insulating layer 12, and does not include the second solid portion 122.

Also in the electrically insulated cable 30 shown in FIG. 3, the voids 13 may be arranged along the circumferential direction of a circle centered on the conductor 11 so that there are two or more layers in the void-containing portion 123. They may be placed randomly.
(2-5) Porosity of insulating layer The degree of voids provided in the insulating layer 12 is not particularly limited, and can be arbitrarily selected depending on the degree of weight reduction required for the electrically insulated cable, withstand voltage characteristics, etc. can. For example, the average porosity of the insulating layer 12 is preferably 10% or more and 50% or less, more preferably 15% or more and 50% or less, even more preferably 20% or more and 50% or less, and 38 % or more and 45% or less is particularly preferable.

It is preferable that the average porosity of the insulating layer 12 is 10% or more because the electrically insulated cable can be particularly lightweight. Further, it is preferable to set the average porosity of the insulating layer 12 to 50% or less, since this prevents the voids 13 from being disposed near the outer surface 12A of the insulating layer 12 and improves the appearance of the electrically insulated cable.

The average porosity of the insulating layer 12 means the average value of the area ratio of voids in the insulating layer 12 determined in four arbitrary cross sections perpendicular to the longitudinal direction of the conductor 11.

The average porosity of the insulating layer 12 can also be calculated as the volume ratio of voids in the insulating layer 12, and can be calculated from, for example, the mass and volume of the insulating layer 12, and the density of the material used for the insulating layer 12. .

According to the studies of the inventor of the present invention, no matter which method is used, the values are approximately the same.
(2-6) Material of Insulating Layer The material of the insulating layer 12 is not particularly limited, and various insulating materials commonly used for electrically insulated cables can be used. The insulating layer 12 may contain an insulating material in a portion other than the void 13, or may be composed only of an insulating material.

As the material for the insulating layer 12, one or more materials selected from, for example, polyvinyl chloride (PVC), polyethylene, fluororesin, fluororubber, etc. can be used.

Specific examples of the fluororesin include ethylene-tetrafluoroethylene copolymer (E-TFE copolymer), polytetrafluoroethylene (PTFE), and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA). , tetrafluoroethylene-hexafluoropropylene copolymer (FEP), vinylidene fluoride resin (PVDF), and the like.

Specific examples of fluororubber include vinylidene fluoride rubber (FKM), tetrafluoroethylene-propylene rubber (FEPM), tetrafluoroethylene-perfluoromethyl vinyl ether rubber (FFKM), and tetrafluoroethylene/propylene copolymer. (TFE-P copolymer), a mixture of TFE-P copolymer and ethylene-tetrafluoroethylene copolymer (E-TFE copolymer), and a mixture of FKM and vinylidene fluoride resin (PVDF) One or more types selected from the following can be used.

The insulating layer 12 can be electrically insulated by covering the outer surface of the conductor 11 by extrusion molding or the like. The insulating layer 12 is formed on the outer surface of the conductor 11 in order to improve its thermal deformation resistance in order to prevent deformation and deterioration of electrical insulation properties when subjected to external force in a relatively high-temperature environment. After the coating is coated, it is preferable to perform a crosslinking treatment by irradiation with ionizing radiation (gamma rays, electron beams, etc.) or chemical crosslinking such as peroxide crosslinking or silane crosslinking. That is, the material used for the insulating layer 12 is preferably crosslinked. Note that the insulating layer 12 may or may not be crosslinked, but crosslinking is preferable because it improves tensile strength and heat resistance.

In particular, it is preferable that the insulating layer 12 contains crosslinked fluororubber. When the insulating layer 12 contains crosslinked fluororubber, the flexibility and durability of the electrically insulated cable can be particularly improved.

The insulating layer 12 can be formed of a single material, but can also have multiple layers of different materials. By forming the insulating layer 12 with a plurality of layers made of different materials, it is possible to use materials depending on the location of the insulating layer 12, and particularly improve properties such as flexibility, durability, and voltage resistance characteristics. For example, in the case of the electrically insulated cable 10 shown in FIG. 1, the first solid portion 121, the second solid portion 122, and the void-containing portion 123 may be made of different materials, or may all be made of the same material.

When the insulating layer 12 has a plurality of layers made of different materials, there is no need to change the materials of the first solid portion 121, second solid portion 122, and void-containing portion 123 described above.

Here, as shown in FIG. 2, for example, a region surrounded by a dotted line A placed closer to the conductor 11 than the inner peripheral surface 123A of the void-containing portion 123 and the outer periphery 11A of the conductor 11 is covered with the first insulating layer. 141. A region surrounded by a dotted line B disposed on the outer peripheral side of the outer peripheral surface 123B of the void-containing portion 123 and the outer surface 12A of the insulating layer 12 is defined as a second insulating layer 142. A region surrounded by dotted line A and dotted line B is defined as a third insulating layer 143.

Further, some or all of the first insulating layer 141, the second insulating layer 142, and the third insulating layer 143 may be made of different materials. That is, for example, the three insulating layers, the first insulating layer 141, the second insulating layer 142, and the third insulating layer 143, can be made of different materials. The first insulating layer 141 and the third insulating layer 143 may be made of the same material, and the second insulating layer 142 may be made of a different material from the other insulating layers, or the second insulating layer 142 and the third insulating layer 143 may be made of a different material from the other insulating layers. The first insulating layer 141 may be made of a different material from the other insulating layers. Alternatively, the first insulating layer 141 and the second insulating layer 142 may be made of the same material, and the third insulating layer 143 may be made of a different material.

Here, explanation has been given using FIG. 2 and showing dotted lines A and dotted line B only in FIG. 2, but the same applies to the electrically insulated cable 10 shown in FIG. 1 and the electrically insulated cable 30 shown in FIG. 3. , it is also possible to have a plurality of insulating layers made of different materials.

As described above, when the electrically insulated cable of this embodiment has a plurality of insulating layers made of different materials, it is preferable to arrange crosslinked fluororubber at least on the conductor 11 side of the insulating layer 12 of the electrically insulated cable, for example. That is, for example, it is preferable that the first insulating layer 141 is made of crosslinked fluororubber. By arranging crosslinked fluororubber on the conductor 11 side of the insulating layer 12 of the electrically insulated cable, the flexibility and withstand voltage characteristics of the electrically insulated cable can be particularly improved.

Further, the dielectric strength of the insulating layer 12 is preferably 25 kV/mm or more, more preferably 30 kV/mm or more. Dielectric strength means the voltage that can be applied without causing dielectric breakdown, and the higher the dielectric strength, the higher the voltage that the insulating layer 12 can withstand. Further, it is preferable that the dielectric strength of the insulating layer 12 is 25 kV/mm or more, since it is possible to obtain an electrically insulated cable with particularly excellent withstand voltage characteristics.

The dielectric strength can be evaluated according to, for example, JIS C 2110-1 (2016).

In particular, in the insulating layer 12, the dielectric strength of the insulating material in contact with the conductor 11 is 25 kV/mm or more, and the tensile strength of the insulating material on the outer surface 12A of the insulating layer 12 is 8 MPa or more. preferable. Tensile strength can be evaluated according to JIS C 3005 (2014).

By setting the dielectric strength of, for example, the first insulating layer 141 in contact with the conductor 11 to 25 kV/mm or more, an electrically insulated cable with particularly excellent withstand voltage characteristics can be obtained. Furthermore, by setting the tensile strength of the second insulating layer 142, which constitutes the outer surface 12A, to 8 MPa or more, for example, the insulating layer 12 can be prevented from being deformed or destroyed when an external force is applied to the electrically insulated cable. The tensile strength of the insulating material on the outer surface 12A of the insulating layer 12 is more preferably 30 MPa or more, and even more preferably 40 MPa or more. The upper limit of the tensile strength of the insulating material that can be suitably used for the outer surface 12A is not particularly limited, but is preferably 50 MPa or less, for example.

As described above, the insulating layer 12 can be made of a single material, so the entire insulating layer 12 is made of a material having a dielectric strength of 25 kV/mm or more and a tensile strength of 8 MPa or more, for example. You can also do that.

The insulating layer 12 may further contain additives such as a flame retardant, an antioxidant, and a crosslinking agent, if necessary.
(3) Electrically insulated cable The outer diameter D of the electrically insulated cable of this embodiment is not particularly limited, but is preferably, for example, 1 mm or more and 4 mm or less.

By setting the outer diameter of the electrically insulated cable to 1 mm or more, a sufficient spatial distance from the conductor 11 can be ensured. Further, by setting the outer diameter of the electrically insulated cable to 4 mm or less, the lightness of the electrically insulated cable can be particularly improved.

The outer diameter D of the electrically insulated cable can be, for example, the diameter of a circle passing through the outer surface 12A of the insulating layer 12 in a cross section perpendicular to the longitudinal direction of the conductor 11. Note that in a cross section perpendicular to the longitudinal direction of the conductor 11, the outer surface 12A of the insulating layer 12 may not be a perfect circle. In that case, draw the smallest circle circumscribing the outer surface 12A of the insulating layer 12. In this case, the diameter of the circle can be taken as the outer diameter of the electrically insulated cable.

Although one electrically insulated cable of this embodiment can be used alone, a plurality of electrically insulated cables can also be used in combination.

Although the embodiments have been described in detail above, they are not limited to specific embodiments, and various modifications and changes are possible within the scope of the claims.

The present invention will be described below with reference to specific examples, but the present invention is not limited to these examples.
(Evaluation method)
First, a method for evaluating electrically insulated cables produced in the following experimental examples will be described.
(1) Thickness of the first solid part, the void-containing part, and the second solid part For the electrically insulated cable produced in the following experimental example, the first solid part and the void are found in any four cross sections perpendicular to the longitudinal direction of the conductor 11. The thicknesses of the containing part and the second solid part were measured, and the average value was taken as the average thickness of each part.
(2) Average porosity For the electrically insulated cables produced in the following experimental examples, the porosity, which is the ratio of the area of voids in the insulating layer in four arbitrary cross sections perpendicular to the longitudinal direction of the conductor 11, is determined, and the average The value was taken as the average porosity.
(3) Flexibility The flexibility test method will be explained using FIG. 5.

The electrically insulated cable to be evaluated was bent at the bending point P so that the radius of curvature R51 at the bending point P was 80 mm, and a pre-bending cable 51 was obtained.

The electrically insulated cable was bent at the bending point P from the pre-bending cable 51 set at the starting position until the radius of curvature R52 at the bending point P became 40 mm, resulting in a post-bending cable 52.

Then, the maximum repulsive force was measured when the degree of bending was changed from the cable 51 before bending to the cable 52 after bending.

The results of Experimental Example 12 were set as 1 and expressed as an index.

An index of 0.96 or more and 1 or less was evaluated as D, 0.9 or more and less than 0.96 as C, 0.83 or more and less than 0.9 as B, and less than 0.83 as A. A is the highest evaluation, and B, C, and D are the lowest evaluations. In the case of A to C, the test is passed, and in the case of D, the test is failed.
(4) Lightweight A 10 cm piece of the electrically insulated cable produced in the following experimental example was cut out along the longitudinal direction, and its mass was measured. The mass in Experimental Example 12 was taken as 1 and expressed as an index.

An index of 0.9 or more and 1 or less was evaluated as D, an index of 0.7 or more and less than 0.9 was evaluated as C, an index of 0.6 or more and less than 0.7 was evaluated as B, and an index of less than 0.6 was evaluated as A. A is the highest evaluation, and B, C, and D are the lowest evaluations. In the case of A, B, and C, the test is passed, and in the case of D, the test is failed.
(5) Appearance evaluation The outer surface 12A of the insulating layer 12 of the 10 cm electrically insulated cable produced in the following experimental example was visually observed to confirm the presence or absence of surface irregularities. An electrical insulated cable with no irregularities was evaluated as A, a rating of B if the number of recesses was 1 or more and 10 or less, and a C if the number of recesses was 11 or more. did. A is the highest evaluation, and B and C are the lowest evaluations.
(6) Dimensional evaluation Regarding the electrically insulated cable produced in the following experimental example, if the evaluation result of the outer diameter explained below is within ±5% of the standard value, it is A, and if it exceeds the standard value ±5%, it is ±5% of the standard value. If it was within 7%, it was evaluated as B, and if it exceeded the standard value ±7%, it was evaluated as C.
(7) Outer diameter In any cross section perpendicular to the longitudinal direction of the conductor 11 of the electrically insulated cable obtained in each of the following experimental examples, draw the smallest circumscribed circle that is in contact with the outer surface 12A of the insulating layer 12, and The diameter was taken as the outer diameter of the electrically insulated cable.
(8) Withstand voltage evaluation For evaluation of withstand voltage characteristics, an evaluation test was conducted according to the standard JIS C 3005 (2014), and those with 3000 ACV/1 min or more were evaluated as A, and those with less than 3000 ACV/1 min were evaluated as B.

The electrically insulated cables in each experimental example will be explained below. Experimental Examples 1 to 11 are examples, and Experimental Example 12 is a comparative example.
(Experiment example 1)
An electrically insulated cable 20 having a cross section perpendicular to the longitudinal direction having the structure shown in FIG. 2 was manufactured by the following procedure.

Specifically, it was manufactured using an extruder 40 shown in FIG. 4, which is a combination of a die 41 and a point jig 42.

A plurality of columnar members 43 were provided in the point jig 42 in accordance with the target porosity of the insulating layer 12. In this experimental example, a member having a cylindrical shape and provided with ventilation holes 431 was used as the columnar member 43.

The die 41 had a circular outlet 411, and extruded fluororubber from channels 44 and 45 between the point jig 42 and the die 41. At this time, the conductor was also drawn out from the center hole 422 of the cylindrical portion 421 of the point jig 42. Then, the outer periphery of the conductor was coated with resin by a draw-down method in which the resin exiting the exit of the die 41 was stretched to reduce its diameter and then coated. After covering the outer periphery of the conductor with a resin, the resin was crosslinked by irradiation with an electron beam.

Note that a single tinned annealed copper wire with a diameter of 0.81 mm was used as the conductor. Further, as the fluororubber, tetrafluoroethylene-propylene rubber (FEPM) was used. The crosslinked fluororubber had a tensile strength of 10 MPa and a dielectric strength of 32 kV/mm.

The obtained electrically insulated cable was evaluated as described above. The evaluation results are shown in Table 1.
(Experiment example 2 to experiment example 6)
An electrically insulated cable was produced and evaluated in the same manner as in Experimental Example 1, except that the number of columnar members 43 provided in the extruder 40 was changed in accordance with the targeted porosity of the insulating layer 12.

The evaluation results are shown in Table 1.
(Experiment example 7 to experiment example 9)
A columnar member 43 provided in the extruder 40 was arranged near the outer periphery of the circular outlet 411 of the die 41 so that a void was located near the outer surface 12A of the insulating layer 12. Furthermore, the thickness of the void-containing portion was adjusted by using members having different diameters in cross sections perpendicular to the longitudinal direction for the columnar members 43.

An electrically insulated cable was produced and evaluated in the same manner as in Experimental Example 1 except for the above points.

Note that in Experimental Examples 7 to 9, the void 13 is arranged near the outer surface 12A of the insulating layer 12 and does not have the second solid portion 122. Therefore, a cross section perpendicular to the longitudinal direction of the conductor 11 becomes the electrically insulated cable 30 shown in FIG.

The evaluation results are shown in Table 1.
(Experiment Example 10, Experiment Example 11)
Regarding the columnar member 43 provided in the extruder 40, the thickness of the void-containing portion was adjusted by using members having different diameters in the cross section perpendicular to the longitudinal direction.

An electrically insulated cable was produced and evaluated in the same manner as in Experimental Example 1 except for the above points.

The evaluation results are shown in Table 1.
(Experiment example 12)
An electrically insulated cable was produced and evaluated in the same manner as in Experimental Example 1, except that the extruder 40 was not provided with the columnar member 43.

The evaluation results are shown in Table 1.

表１に示した結果によると、絶縁層１２に空隙を設け、第１充実部の平均厚さが０．０２ｍｍ以上０．１５ｍｍ以下である実験例１～実験例１１の電気絶縁ケーブルでは、柔軟性、軽量性の評価がＡ～Ｃのいずれかとなることを確認できた。すなわち、実験例１～１１の電気絶縁ケーブルは、絶縁層の厚さを０．５ｍｍと厚くすることで、電気機器等に設置した場合でも十分に空間距離を確保しつつも、軽量性や、柔軟性に優れることを確認できた。

According to the results shown in Table 1, the electrically insulated cables of Experimental Examples 1 to 11, in which voids are provided in the insulating layer 12 and the average thickness of the first solid portion is 0.02 mm or more and 0.15 mm or less, are flexible. It was confirmed that the evaluation of durability and lightness was one of A to C. In other words, in the electrically insulated cables of Experimental Examples 1 to 11, the thickness of the insulating layer is increased to 0.5 mm, so that even when installed in electrical equipment, a sufficient spatial distance is secured, and the cables are lightweight and It was confirmed that it has excellent flexibility.

In particular, the electrically insulated cables of Experimental Examples 1 and 4 to 11, which have an average porosity of 20% or more, were evaluated as A or B for both flexibility and lightness. We were able to confirm that it was excellent.

On the other hand, the electrically insulated cable of Experimental Example 12, in which the insulating layer 12 does not contain any voids, is lightweight and flexible, even though the average thickness of the insulating layer 12 is the same as the other experimental examples. It was confirmed that the evaluation was D, which was inferior.

10, 20, 30 Electrical insulated cable 11 Conductor 11A Outer periphery 12 Insulating layer 12A Outer surface 121 First solid portion 122 Second solid portion 123 Gap-containing portion 123A Inner circumferential surface 123B Outer circumferential surface 13 Gap 131 Innermost position gap 132 Outermost position Gap 40 Extruder 41 Dice 411 Outlet 42 Point jig 421 Cylindrical portion 422 Center hole 43 Member 431 Vent holes 44, 45 Channel 51 Cable before bending 52 Cable after bending 141 First insulating layer 142 Second insulating layer 143 Third insulating Layer A, B Dotted line D Outer diameter P Bend point

Claims (7)

a conductor;
an insulating layer covering the conductor and having an exposed outer surface;
The insulating layer is made of one or more selected from fluororesin and fluororubber,
the insulating layer includes voids,
The void has a columnar shape with a central axis extending along the longitudinal direction of the conductor,
In a cross section perpendicular to the longitudinal direction of the conductor, an average value of the thickness of a first solid portion that is a region between the innermost void located closest to the conductor among the voids and the outer periphery of the conductor. is 0.02 mm or more and 0.15 mm or less,
In a cross section perpendicular to the longitudinal direction of the conductor, a second solid area is a region between the outermost gap located closest to the outer surface of the insulating layer among the gaps and the outer surface of the insulating layer. The average value of the thickness of the part is 0.05 mm or more and 0.15 mm or less,
The dielectric strength of the insulating layer is 25 kV/mm or more,
An electrically insulated cable that can secure the spatial distance specified by the international standard IEC62368-1 . The electrically insulated cable according to claim 1, having an outer diameter of 1 mm or more and 4 mm or less. The electrically insulated cable according to claim 1 or 2, wherein the insulating layer has an average porosity of 10% or more and 45 % or less. The electrically insulated cable according to claim 1 or 2, wherein the insulating layer has an average porosity of 38% or more and 45% or less. The electrically insulated cable according to any one of claims 1 to 4 , wherein the insulating layer contains crosslinked fluororubber. The electrically insulated cable according to any one of claims 1 to 5 , wherein the insulating layer has a plurality of layers made of different materials. Among the insulating layers, an insulating material in contact with the conductor has a dielectric strength of 25 kV/mm or more,
The electrically insulated cable according to any one of claims 1 to 6 , wherein the insulating material on the outer surface of the insulating layer has a tensile strength of 8 MPa or more.

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