Insulated wire and wiring harnesses

Abstract

Provided are: a covered cable having a conductor configured to have a flat cross-section, wherein both flame resistance and ease of removal of an insulation covering can be achieved; and a wire harness provided with such a covered cable.　A covered cable 1 having a conductor 10 in which a plurality of wires 15 are intertwined, and an insulation covering 20 for covering the outer periphery of the conductor 10, wherein: the covered cable 1 has a flat section; in a cross-section of the flat section, a conductor-external void V is provided as a void between the conductor 10 and the insulation covering 20; in each corner-portion divided region Rc positioned at one of four corners, among eight divided regions obtained by dividing the cross-section into four equal portions in a width direction and then into two equal portions in a height direction orthogonal to the width direction, the area of the conductor-external void V is less than 20% of the area of the conductor-external void V in the entire cross-section; and there is no location where the insulation covering 20 cuts into the conductor 10 at a depth equal to or greater than half the outside diameter of the wires 15.

Description

[Technical Field]

[0001] The present disclosure relates to a covered electric wire and a wire harness. [Background technology]

[0002] Flat cables made of flat conductors are well known, and the use of flat cables can reduce the space occupied when installed compared to general electric wires with conductors having a substantially circular cross section.

[0003] In conventional general flat cables, rectangular conductors are often used as the conductor, as disclosed in Patent Documents 1 and 2. A rectangular conductor is a metal wire formed into a rectangular cross section. In addition, Patent Documents 3 to 5 filed by the applicant disclose a conductor that is made of a stranded wire formed by twisting together multiple elemental wires, with the aim of achieving both flexibility and space saving, and that has a flat portion in which the cross section intersecting the axial direction of the stranded wire is flat. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-130739 [Patent Document 2] Japanese Patent Application Publication No. 2019-149242 [Patent Document 3] International Publication No. 2019 / 093309 [Patent Document 4] International Publication No. 2019 / 093310 [Patent Document 5] International Publication No. 2021 / 200937 Summary of the Invention [Problem to be solved by the invention]

[0005] When forming an insulating coating around a conductor to produce a coated electric wire, if the conductor has a flattened shape, the contact area between the conductor and the insulating coating is larger than that of a conventional circular conductor with the same cross-sectional area, which tends to increase the adhesive strength of the insulating coating to the conductor. This increased adhesive strength can make it difficult to remove all of the insulating coating from a predetermined area when removing the insulating coating from the terminal of the coated electric wire. If some of the insulating coating remains, problems such as an inability to properly form an electrical connection between the conductor and the terminal connected to the terminal can occur. While it is possible to reduce the adhesive strength between the insulating coating and the conductor by selecting the conditions for forming the insulating coating by extrusion molding, this would make it more difficult for heat to dissipate from the insulating coating to the conductor, thereby reducing the flame retardancy of the coated electric wire.

[0006] Therefore, an object of the present invention is to provide a coated electric wire having a conductor with a flat cross section, which can achieve both flame retardancy and ease of removal of the insulating coating, and a wire harness including such a coated electric wire. [Means for solving the problem]

[0007] The insulated electric wire of the present disclosure is an insulated electric wire having a conductor formed by twisting together a plurality of strands of wires and an insulating coating that covers the outer periphery of the conductor, wherein the insulated electric wire has a flat portion in a cross section perpendicular to the axial direction, where the conductor has a flat shape that is elongated in the width direction, and an outer conductor gap is provided in the cross section of the flat portion as a gap between the conductor and the insulating coating, and the cross section is divided into four equal parts in the width direction and into two equal parts in the height direction perpendicular to the width direction, and in each of the corner divided regions located at the four corners, the area of ​​the outer conductor gap is less than 20% of the area of ​​the conductor outer gap in the entire cross section, and there is no part where the insulating coating penetrates into the conductor to a depth of more than half the outer diameter of the strands of wires.

[0008] The wire harness of the present disclosure includes the coated electric wire. [Effects of the Invention]

[0009] The covered electric wire and wire harness according to the present disclosure are a covered electric wire having a conductor with a flat cross section, which can achieve both flame retardancy and ease of removal of the insulating coating, and a wire harness including such a covered electric wire. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view showing a coated electric wire according to one embodiment of the present disclosure. [Figure 2] FIG. 2A is a cross-sectional view showing a covered electric wire with an increased corner void ratio, and FIG. 2B is a cross-sectional view showing a covered electric wire in which an insulating coating has a conductor-biting portion. [Figure 3] 3A to 3E are photographs showing cross sections of coated electric wires of Samples 1 to 5, each having a different state of insulating coating. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described. The insulated electric wire according to the present disclosure is an insulated electric wire having a conductor formed by twisting together a plurality of strands of wires, and an insulating coating that covers the outer periphery of the conductor, wherein the insulated electric wire has a flat portion in a cross section perpendicular to the axial direction, where the conductor has a flat shape that is elongated in the width direction, and an outer conductor gap is provided in the cross section of the flat portion as a gap between the conductor and the insulating coating, and the cross section is divided into four equal parts in the width direction and into two equal parts in the height direction perpendicular to the width direction, and in each of the corner divided regions located at the four corners, the area of ​​the outer conductor gap is less than 20% of the area of ​​the outer conductor gap in the entire cross section, and there is no portion where the insulating coating penetrates into the conductor to a depth of more than half the outer diameter of the strands of wires.

[0012] In the above-described insulated electric wire, the area of ​​the conductor outer gap in each of the four corner division regions in the cross section of the flat portion is limited to less than 20% of the total area of ​​the conductor outer gap. This ensures the proximity of the insulating coating to the conductor at the corners of the insulated electric wire. When an insulating coating is formed around the periphery of a flat conductor by extrusion molding, the thickness of the insulating coating may be greater at the corners of the flat insulated electric wire than at other locations. In such cases, heat dissipation from the insulating coating to the conductor tends to be difficult. However, by ensuring the proximity of the insulating coating to the conductor at the corners, heat dissipation from the insulating coating to the conductor is improved, thereby improving flame retardancy. On the other hand, by preventing the insulating coating from penetrating the conductor to a depth of more than half the outer diameter of the strand, the adhesive strength of the insulating coating to the conductor is not excessively strong, and the insulating coating can be easily removed at the terminals of the insulated electric wire.

[0013] Here, in the cross section of the flattened portion, it is preferable that the flattening ratio evaluated as w / h, where w is the length of the conductor along the width direction and h is the length along the height direction, be equal to or less than 5. In this case, the proportion of the corners in the perimeter of the conductor's outer periphery in the cross section of the flattened portion increases, and the relative contribution of the corners to flame retardancy also increases, so the effect of improving flame retardancy by keeping the proportion of the extra-conductor voids in each corner-divided region to less than 20% of the total becomes particularly significant.

[0014] In the cross section of the flat portion, the area of ​​the extra-conductor void in each of the four corner divided regions may be 5% or more of the area of ​​the extra-conductor void in the entire cross section, thereby restricting the proximity of the insulating coating to the conductor at the corners to an appropriate range, effectively improving the ease of removing the insulating coating.

[0015] In the cross section of the flat portion, the conductor outer voids may be distributed throughout the entire area between the conductor and the insulating coating in four of the eight divided regions other than the corner divided regions, which makes it particularly easy to remove the insulating coating and makes it less likely that the insulating coating will remain when removing the insulating coating from a predetermined area, such as at the end of a coated electric wire.

[0016] A wire harness according to the present disclosure includes the insulated electric wire according to the present disclosure. As described above, in the cross section of the flat portion, the proportion of the voids outside the conductor in each corner division region is kept to less than 20% of the total, and the insulating coating does not have any portions where it penetrates into the conductor to a depth of more than half the outer diameter of the wire, thereby achieving both high flame retardancy and ease of removal of the insulating coating. By including the insulated electric wire in the wire harness, the insulated electric wire's high flame retardancy and ease of removal of the insulating coating can also be utilized in the wire harness.

[0017] [Details of the embodiments of the present disclosure] In the following, a covered electric wire and a wire harness according to an embodiment of the present disclosure will be described in detail with reference to the drawings. In this specification, concepts indicating the shape and arrangement of components, such as straight, parallel, and perpendicular, for each part of a covered electric wire include errors from the geometric concepts within the range allowable for this type of covered electric wire, such as deviations of approximately ±15% in length and approximately ±15° in angle. In this specification, unless otherwise specified, the cross section of a covered electric wire or a conductor refers to a cross section cut perpendicular to the axial direction (longitudinal direction).

[0018] <Insulation electric wire Overview of 1 shows a cross-sectional view of a coated electric wire 1 according to one embodiment of the present disclosure. The coated electric wire 1 according to this embodiment has a conductor 10 and an insulating coating 20. The insulating coating 20 covers the entire outer periphery of the conductor 10.

[0019] The conductor 10 is configured as a stranded wire in which a plurality of wires 15 are twisted together. The conductor 10 has a flat outer shape in at least a portion of its axial region. That is, the conductor 10 has a flat portion with a flat cross section. In this embodiment, the entire axial region of the conductor 10 has such a flat portion. A stranded wire having a flat shape can be formed, for example, by rolling a raw stranded wire in which a plurality of wires 15 are twisted together to have a substantially circular cross section.

[0020] Here, the term "the outer shape of the conductor 10 is flat" refers to a state in which the width w, which is the length of the longest straight line that crosses the cross section in a direction along the sides or diameters that constitute the cross section and encompasses the entire cross section, is greater than the height h, which is the length of the straight line that intersects the longest straight line and encompasses the entire cross section at right angles to the longest straight line. The cross section of the conductor 10 may have any specific shape as long as it is flat. Examples of flat shapes include a rectangle, an ellipse, an oval, an oval (a rectangle with semicircles at both ends), a parallelogram, and a trapezoid. If the circumscribed figure of the cross section can approximate each of these shapes, the cross section of the conductor 10 can be considered to have each of these shapes. Of the listed shapes, it is preferable to adopt either a rectangle or an oval. If the cross section of the conductor 10 can approximate a rectangle, it is preferable that the corners of the conductor 10, i.e., the joints between the width and height sides, have rounded shapes (rounded corners). This makes it easier to reduce the thickness of the insulating coating 20 at the corners and increase the proximity of the insulating coating 20 to the conductor 10, thereby significantly improving the flame retardancy of the coated electric wire 1, which will be described later.

[0021] The coated electric wire 1 according to this embodiment has a conductor 10 made of a stranded wire with a flat cross section, which allows it to achieve both high flexibility and space-saving. In particular, high flexibility and space-saving are achieved along the height direction of the conductor 10. The aspect ratio w / h of the conductor 10 is not particularly limited, but from the viewpoint of sufficiently enhancing the effects of the flattening, it is preferable that it be 2 or more. On the other hand, from the viewpoint of enhancing the effect of improving flame retardancy, which will be described later, it is preferable that the aspect ratio w / h be 5 or less, and further preferably 3 or less.

[0022] In the conductor 10 configured as a stranded wire, the cross-sectional shape of at least some of the wires 15 constituting the conductor 10 may be deformed from a circular shape as it is formed into a flat shape. However, from the viewpoint of ensuring high flexibility in the conductor 10, it is preferable that the deformation rate of the wires 15 from a circular shape is smaller at the outer periphery of the cross section of the conductor 10 than at the inner portion. Furthermore, it is preferable that, in the cross section of the conductor 10, gaps capable of accommodating one or more, or even two or more, wires 15 are left between the wires 15 constituting the conductor 10.

[0023] In the insulated electric wire 1, the conductor cross-sectional area is not particularly limited. However, in general, the larger the conductor cross-sectional area of ​​the insulated electric wire, the lower the flame retardancy of the insulated electric wire and the ease of removing the insulating coating. Therefore, as will be described later, in the insulated electric wire 1 according to this embodiment, the larger the conductor cross-sectional area, the greater the relative effect of improving the flame retardancy and the ease of removing the insulating coating 20 by defining the state of the insulating coating 20. Therefore, from the viewpoint of obtaining these effects to a high degree, it is preferable to use a conductor 10 with a relatively large conductor cross-sectional area. For example, when the conductor cross-sectional area is 15 mm in nominal value, 2 Above, even 50mm 2 It would be better if it was more than that.

[0024] The material constituting the conductor 10 is not particularly limited, and various metal materials can be used. Typical metal materials constituting the conductor 10 include copper and copper alloys, and aluminum and aluminum alloys. In particular, aluminum and aluminum alloys have lower electrical conductivity than copper and copper alloys, so the cross-sectional area of ​​the conductor tends to be larger to ensure the necessary electrical conductivity. As described above, the larger the cross-sectional area of ​​the conductor, the greater the effect of improving flame retardancy and ease of removal of the insulating coating 20 by defining the state of the insulating coating 20. From this perspective, it is preferable to construct the conductor 10 from aluminum or an aluminum alloy.

[0025] In the covered electric wire 1 according to this embodiment, the outer periphery of the conductor 10 is covered with an insulating coating 20, and corresponding to the flat shape of the conductor 10, the covered electric wire 1 as a whole, including the insulating coating 20, also has a flat shape. As will be described in detail later, in the covered electric wire 1, the insulating coating 20 is in a predetermined state in terms of the distribution of voids between the conductor 10 and the state of engagement with the conductor 10, and accordingly, the covered electric wire 1 exhibits high flame retardancy and ease of removal of the insulating coating 20.

[0026] The material constituting the insulating coating 20 is not particularly limited as long as it is an insulating material, but it is preferable that it be primarily composed of an organic polymer. From the perspective of enhancing the flame retardancy of the insulating coating 20, the material constituting the insulating coating 20 is preferably flame retardant. However, if the material constituting the insulating coating 20 itself has extremely high flame retardancy, it is more likely to achieve sufficient flame retardancy regardless of the state of the insulating coating 20. If the material constituting the insulating coating 20 itself does not have a particularly high flame retardancy, the effect of improving the flame retardancy by specifying the state of the insulating coating 20 is relatively greater. Specifically, it is preferable that the organic polymer constituting the insulating coating 20 is not made of a polymer with high flame retardancy such as polyvinyl chloride (PVC), but is made of an organic polymer that does not contain chlorine and has a relatively low flame retardancy, such as polyethylene or other polyolefin, and that the polymer is made flame retardant by adding a flame retardant to the polymer. Furthermore, as the flame retardant to be added, it is preferable to use a flame retardant containing a metal compound, such as a metal hydroxide including magnesium hydroxide, rather than a bromine-based flame retardant, which exhibits high flame retardancy in a small amount.

[0027] The method for forming the insulating coating 20 is not particularly limited, but it is preferable to extrude a composition containing necessary components to form a layer of the insulating coating 20 around the outer periphery of the conductor 10. For example, the shape of the mold used for extrusion molding can control the distribution of voids between the insulating coating 20 and the conductor 10 and the state of penetration of the insulating coating 20 into the conductor 10.

[0028] The covered electric wire 1 according to the present embodiment may be used alone or as a component of the wire harness according to the embodiment of the present disclosure. The wire harness according to the embodiment of the present disclosure includes the covered electric wire 1 according to the above embodiment. The wire harness may include a plurality of the covered electric wires 1, or may include other types of covered electric wires in addition to the covered electric wire 1. Preferably, a plurality of the covered electric wires 1 are arranged in the width direction and / or the height direction. In this case, the specific arrangement structure of the plurality of covered electric wires 1 is not particularly limited, but a preferred embodiment can be one in which the plurality of covered electric wires 1 are arranged in the width direction and fixed to a common sheet material by fusion or the like. In this case, it is particularly preferable that the heights of the arranged plurality of covered electric wires 1 are uniform.

[0029] <Insulation coating condition> In the coated electric wire 1 according to this embodiment, the distribution of voids between the insulating coating 20 and the conductor 10 and the state of the insulating coating 20 biting into the conductor 10 are controlled to a predetermined form. That is, an extra-conductor void V is provided as a void between the conductor 10 and the insulating coating 20, and the corner void ratio of the extra-conductor void V, which will be described below, is kept to less than 20%. In addition, the insulating coating 20 does not have a portion that bites into the conductor.

[0030] Here, the definition of the corner gap ratio will be explained. 15The term "extra-conductor void V" refers to voids that are not occupied by the outer periphery of the conductor 10 or the insulating coating 20, but are distributed between the outer periphery of the conductor 10 and the insulating coating 20, rather than inside the conductor 10. To define the distribution of this extra-conductor void V, divided regions are set as eight equal regions obtained by dividing the cross section of the insulated electric wire 1. That is, as shown by the dashed lines in FIG. 1, the cross section of the insulated electric wire 1 is divided into four equal parts in the width direction and two equal parts in the height direction to set eight divided regions. Of these eight divided regions, the divided regions located at the four corners are called corner divided regions Rc. The extra-conductor void V included in these corner divided regions Rc are called corner voids. Then, for each of the four corner divided regions Rc, the ratio of the area of ​​the corner void (Ac) to the area of ​​the extra-conductor void V (A) in the entire cross section of the insulated electric wire 1, that is, the ratio to the total area of ​​the extra-conductor void V in all eight divided regions, is called the corner void ratio (Ac / A × 100%). In the coated electric wire 1 according to this embodiment, the corner void ratio is less than 20% in each of the four corner divided regions Rc, that is, in all the individual corner divided regions Rc.

[0031] Generally, in the case of a covered electric wire, even if a flame comes into contact with the insulating coating or the insulating coating burns, if heat can be dissipated from the insulating coating to the conductor, the occurrence and progression of combustion of the insulating coating can be suppressed, and the covered electric wire can achieve high flame retardancy. When the insulating coating is in close proximity to the conductor, heat dissipation (heat transfer) from the insulating coating to the conductor occurs more easily, which is highly effective in improving flame retardancy. The smaller the extra-conductor gap between the insulating coating and the conductor is kept, the closer the insulating coating is to the conductor.

[0032] In a coated electric wire in which the conductor 10 has a flat cross-section, when the insulating coating 20 is formed around the conductor 10 by extrusion molding or the like, the insulating coating 20 tends to be thicker at the corners of the flat cross-section than at the flat sides (regions along the width and height sides). This makes it difficult for heat to dissipate from the insulating coating 20 to the conductor 10 at the corners. Furthermore, the amount of combustible insulating coating 20 at the corners is greater. As a result, the flat corners are more likely to have reduced flame retardancy than the sides. As described above, the closer the insulating coating 20 is to the conductor 10, the more effectively heat dissipates from the insulating coating 20 to the conductor 10. However, conversely, if a large extra-conductor gap V exists between the insulating coating 20 and the conductor 10, the closer the insulating coating 20 and the conductor 10 are, the more difficult heat dissipation becomes. 2A, if a large extra-conductor gap V exists at the corner of a flattened shape, heat dissipation from the insulating coating 20 to the conductor 10 at the corner is unlikely to occur. As a result, the corner, which is prone to reducing flame retardancy due to the thickness of the insulating coating 20 as described above, further reduces the flame retardancy of the insulated wire 9.

[0033] However, in the insulated electric wire 1 according to this embodiment, the corner void ratio is kept to less than 20% in each of the four corner divided regions Rc, and the extra-conductor gap V between the conductor 10 and the insulating coating 20 is kept small at the corners. This ensures the proximity of the insulating coating 20 to the conductor 10 at the corners. This makes it easier for heat to dissipate from the insulating coating 20 to the conductor 10 at the corners, and the corners are less likely to reduce the flame retardancy of the insulated electric wire 1. As a result, the flame retardancy of the insulated electric wire 1 as a whole can be improved compared to when large extra-conductor gaps V are distributed at the corners.

[0034] From the viewpoint of more effectively improving the flame retardancy of the coated electric wire 1, it is more preferable that the corner void ratio in each of the four corner divided regions Rc is less than 17%. Furthermore, it is preferable that the corner void ratio in at least one of the four corner divided regions Rc is less than 15%, or even less than 10%. From the viewpoint of improving flame retardancy, there is no particular lower limit for the corner void ratio. However, from the viewpoint of facilitating the removal of the insulating coating 20, which will be described next, it is preferable that the corner void ratio in each of the four corner divided regions Rc is 5% or more. Furthermore, it is preferable that the corner void ratio in at least one of the four corner divided regions Rc is 10% or more.

[0035] In the insulated electric wire 1, the smaller the aspect ratio w / h of the conductor 10, the greater the influence of the corners on flame retardancy, and the greater the effect of improving flame retardancy by keeping the corner void ratio low. As described above, when the aspect ratio w / h is 5 or less, or even 3 or less, the effect of improving flame retardancy can be greatly obtained by keeping the corner void ratio in each of the four corner divided regions Rc to less than 20%.

[0036] Furthermore, flame retardancy is improved when the conductor outer gap V is kept small throughout the entire coated electric wire 1. For example, in the cross section, the ratio of the area occupied by the conductor outer gap V to the area of ​​the region surrounded by the inner peripheral surface of the insulating coating 20 should be 25% or less. There is no particular lower limit to this area ratio, but from the viewpoint of making it easier to remove the insulating coating 20, which will be explained next, it is preferable to set it to 5% or more.

[0037] In the cross section of the covered electric wire 1 according to this embodiment, the corner void ratio at each of the four corners is kept to less than 20%, and the insulating coating 20 does not have a conductor-biting portion I. Here, the conductor-biting portion I refers to a portion where the penetration depth d of the insulating coating 20 reaches more than half the outer diameter of the wire 15, as shown in the covered electric wire 9′ in FIG. 2B . The penetration depth d of the insulating coating 20 refers to the amount of protrusion of the inner peripheral surface of the insulating coating 20 in a region where the inner peripheral surface of the insulating coating 20 is in contact with the conductor 10 continuously along the outer periphery of the conductor 10 in the cross section of the covered electric wire, where the inner peripheral surface of the insulating coating 20 protrudes inward compared to both sides.

[0038] Insulated wire in Figure 2B 9’ When the insulating coating 20 has the conductor biting portion I, the insulating coating 20 tightly adheres to the conductor 10 at the conductor biting portion I. Then, when a terminal is to be connected to the end of the conductor 10, for example, the insulating coating 20 is tightly attached to the conductor 10. 9’ When removing the insulating coating 20 from a portion of the axial direction of the conductor 10, the insulating coating 20 cannot be easily removed. Even if the insulating coating 20 can be easily removed from portions of the outer periphery of the conductor 10 other than where the conductor biting portion I is formed, there is a possibility that some of the insulating coating 20 will remain in the conductor biting portion I and its surroundings. This can easily cause problems such as an inability to form a good electrical connection between the terminal and the conductor 10. In particular, since the conductor 10 has a flat shape and a large surface area, the adhesive force between the conductor 10 and the insulating coating 20 is greater than in the case of a circular cross-sectional electric wire having the same conductor cross-sectional area, and the presence of the conductor biting portion I can make it difficult to remove the insulating coating 20.

[0039] However, in the coated electric wire 1 according to this embodiment, the insulating coating 20 does not have the conductor-biting portion I, which makes it easier to remove the insulating coating 20. In other words, the insulating coating 20 can be easily removed by performing an operation such as peeling with little force. Furthermore, when removing the insulating coating 20 over a predetermined length at a portion such as the terminal portion of the coated electric wire 1, the insulating coating 20 can be removed over the entire predetermined region so that it does not remain on the outer periphery of the conductor 10, which makes it less likely that problems such as poor connection will occur due to the insulating coating 20 remaining locally.

[0040] Furthermore, from the viewpoint of enhancing the ease of removing the insulating coating 20, it is preferable that the conductor extra-void V is distributed throughout the entire area of ​​the outer periphery of the conductor 10 in the cross section of the insulated electric wire 1 except for the corner divided regions Rc (in this case, the conductor extra-void V may or may not be present in the corner divided regions Rc). In other words, it is preferable that the conductor extra-void V is present throughout the entire area between the conductor 10 and the insulating coating 20 in four divided regions out of the eight divided regions excluding the corner divided region Rc. Furthermore, it is preferable that the conductor extra-void V is distributed throughout the entire outer periphery of the conductor 10, including the four corner divided regions Rc, except for the locations where the conductor 10 and the insulating coating 20 inevitably come into contact with each other.

[0041] As described above, in the cross section of the flat portion of the insulated electric wire 1 according to this embodiment, the corner void ratio is suppressed to less than 20%, and the insulating coating 20 does not have a conductor-biting portion I. Therefore, the insulated electric wire 1 has both high flame retardancy and easy removal of the insulating coating 20. The insulated electric wire 1 according to this embodiment is suitable for use in vehicles such as automobiles. This is because the insulated electric wire 1 has high flexibility and space-saving features, allowing it to be routed even in narrow spaces inside a vehicle. Furthermore, even if the insulated electric wire 1 comes into contact with flames due to a vehicle fire or the like, the insulated electric wire 1 has high flame retardancy, making it possible to suppress combustion of the insulating coating 20 and the spread of the fire via the insulated electric wire 1. [Example]

[0042] Examples are shown below. However, the present invention is not limited to these examples. In these examples, the relationship between the state of the insulating coating of a coated electric wire and the flame retardancy and ease of removing the insulating coating was investigated.

[0043] [Test method] (Sample preparation) First, the conductor that constitutes the insulated wire was prepared. First, a stranded wire with a circular cross section was prepared by twisting together aluminum alloy wires, and the twisted wire was rolled into a flat shape using a roller to produce the conductor. In this case, wires with a wire diameter of 0.26 mm were used, and the conductor cross section was set to 130 mm. 2 The aspect ratio w / h was set to 3.

[0044] An insulating coating was formed around the outer periphery of the fabricated conductor by extrusion molding. Samples 1 to 5 were fabricated by changing the shape of the mold used to vary the distribution of voids outside the conductor and the presence or absence of conductor bite-in portions. Cross-linked polyethylene was used as the constituent material of the insulating coating. The thickness of the insulating coating was 1.6 mm on average for all samples.

[0045] (Changes in the state of the insulating coating) Cross-sectional photographs were taken of the prepared insulated electric wires of Samples 1 to 5, and the state of the insulating coating was evaluated. The cross-sectional samples were prepared by cutting the insulated electric wires perpendicular to the axial direction while they were embedded in acrylic resin. To evaluate the state of the insulating coating, the corner void ratio was determined for each of the four corners in the cross-sectional photograph, and the presence of a conductor penetration area where the insulating coating penetrated into the conductor to a depth of more than half the outer diameter of the wire was confirmed. To evaluate the corner void ratio, the total area (A) of the void outside the conductor was determined as the area of ​​the region sandwiched between the outer periphery of the conductor and the inner periphery of the insulating coating on the cross-sectional photograph. In addition, the insulated electric wire was divided into eight divided regions (quarters in the width direction and halves in the height direction), and the area (Ac) of the void outside the conductor was similarly determined for each of the four corner divided regions. The corner void ratio was then calculated for each of the four corners as Ac / A × 100%.

[0046] (Flame retardancy evaluation) The insulated electric wires of Samples 1 to 5 were subjected to a combustion test to evaluate their flame retardancy. Specifically, each insulated electric wire was cut into a length of 30 cm, held horizontally, and a 35 mm-long reducing flame was applied to the center of the insulated electric wire. Ignition of the insulating coating was confirmed within 30 seconds of application of the flame, and after ignition, the flame was removed from the insulated electric wire. The time until the flame spontaneously extinguished after removal of the flame (flame extinction time) was measured. The test was performed in two ways: one where the flame was applied to the flat surface (surface along the width direction) of the insulated electric wire, and the other where the flame was applied to the edge surface (surface along the height direction). If the flame extinction time was less than 70 seconds in both cases, the insulated electric wire was evaluated as having high flame retardancy (A). On the other hand, if the flame extinction time was 70 seconds or longer in at least one of the two cases, the insulated electric wire was evaluated as having low flame retardancy (B).

[0047] (Evaluation of the ease of removing the insulating coating) The insulated wires of Samples 1 to 5 were evaluated for ease of removal of the insulating coating. Specifically, a stripping machine equipped with four blades on the top, bottom, left, and right sides was used to make a 1.0 mm deep incision 20 mm from the end of the insulated wire, and the insulating coating was then pulled out in the direction of the end. If no insulating coating remained after removal and no fraying occurred on the wire, the ease of removal of the insulating coating was evaluated as high (A). On the other hand, if at least one of the remaining insulating coating and fraying of the wire occurred, the ease of removal of the insulating coating was evaluated as low (B).

[0048] [Test Results] Figures 3A to 3E show cross-sectional photographs of samples 1 to 5. Table 1 below shows the corner void ratio and the presence or absence of conductor penetration for the four corner division regions, as well as the evaluation results for flame retardancy and ease of insulating coating removal. The corner void ratio is shown for corners 1, 2, 3, and 4, respectively, in the upper left, upper right, lower right, and lower left corner division regions of the cross-sectional photographs.

[0049] [Table 1]

[0050] 3A to 3E, in sample 5 in Fig. 3E, the insulating coating is in close contact with the conductor over almost the entire inner circumference, whereas in samples 1 to 4 in Fig. 3A to 3D, a clear extra-conductor void is formed between the conductor and the insulating coating. Furthermore, in comparing samples 1 to 4, the extra-conductor void is distributed uniformly in various parts along the outer circumference of the conductor in samples 1 to 3, with no noticeable uneven distribution in the corners, whereas in sample 4, the extra-conductor void is unevenly distributed in the corners, particularly in the upper right and lower left corners.

[0051] The trends seen in these cross-sectional photographs are made even clearer by the evaluation results of the state of the insulating coating shown in Table 1. First, looking at the evaluation results for the presence or absence of conductor penetration into the insulating coating, no penetration was observed in samples 1 to 4, whereas penetration was observed in sample 5. Furthermore, while the corner void ratios at all four corners of samples 1 to 3 were less than 20%, the corner void ratios at corner 2 corresponding to the upper right and corner 4 corresponding to the lower left of sample 4 exceeded 20%.

[0052] The evaluation results for the ease of insulating coating removal in Table 1 show that sample 5 exhibited low removability, while samples 1 to 4 exhibited high removability. This suggests that the ease of insulating coating removal can be improved by preventing the conductor from biting into the insulating coating. Next, the evaluation results for flame retardancy show that sample 4 exhibited low flame retardancy, while samples 1 to 3 exhibited high flame retardancy. This suggests that high flame retardancy can be achieved by keeping the corner void ratio at all four corners below 20%. The above study results show that for an insulated electric wire having a conductor with a flat cross section, high flame retardancy and easy insulating coating removal can be achieved by keeping the corner void ratio at each of the four corners below 20% and preventing the conductor from biting into the insulating coating.

[0053] Although the embodiments of the present disclosure have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0054] 1,9,9' insulated wire 10 Conductors 15 wire 20 Insulation coating I Conductor bite area Rc corner division area V Outer conductor gap d Penetration depth h conductor height w conductor width

Claims

1. a conductor in which a plurality of strands are twisted together; An insulating coating that covers the outer periphery of the conductor, The coated electric wire has a flat portion in which the conductor has a flat shape that is elongated in a width direction in a cross section perpendicular to the axial direction, In the cross section of the flat portion, an outer conductor gap is provided as a gap between the conductor and the insulating coating; In the cross section, the conductor has side portions that are flat portions along the width direction and a height direction perpendicular to the width direction, and corner portions that correspond to joints between the side portions in the width direction and the side portions in the height direction, the cross section is divided into four equal parts in the width direction and into two equal parts in the height direction, and in each of four corner divided parts including one of the four corner parts, the area of ​​the extra-conductor void is less than 20% of the area of ​​the extra-conductor void in the entire cross section, In at least one of the four corner divided regions, the area of ​​the conductor outer gap is less than 10% of the area of ​​the conductor outer gap in the entire cross section, The insulated electric wire has no portion where the insulating coating bites into the conductor to a depth of half or more of the outer diameter of the wire.

2. 2. The coated electric wire according to claim 1, wherein in the cross section of the flattened portion, a flattening ratio evaluated as w / h, where w is a length along the width direction of the conductor and h is a length along the height direction, is 5 or less.

3. 2. The coated electric wire according to claim 1, wherein in the cross section of the flat portion, the area of ​​the conductor outer gap in each of the four corner divided regions is 5% or more of the area of ​​the conductor outer gap in the entire cross section.

4. 2. The coated electric wire according to claim 1, wherein in the cross section of the flat portion, the conductor outer voids are distributed throughout the entire area between the conductor and the insulating coating in four of the eight divided regions other than the corner divided region.

5. 2. The coated electric wire according to claim 1, wherein the area of ​​the outer conductor gap in at least one of the four corner divided regions is 10% or more of the area of ​​the outer conductor gap in the entire cross section.

6. The coated electric wire according to claim 1 , wherein the insulating coating is formed thicker at the corners than at the sides.

7. A wire harness comprising the coated electric wire according to any one of claims 1 to 6.

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