Coated wires and wiring harnesses

Abstract

Provided are a covered electric wire (1) having a structure in which an insulating coating is provided on the outer periphery of a conductor having a flat cross-section, and capable of obtaining high flame retardancy, and a wire harness having such a covered electric wire. Provided are a covered electric wire (1) having a conductor (10) and an insulating coating (20) covering the outer periphery of the conductor (10), wherein the covered electric wire (1) has a flat portion in a cross section intersecting the axial direction, wherein the conductor (10) is a flat portion having a long width direction, and in the cross section of the flat portion, the insulating coating (10) has a width direction portion (21) along the width direction and a height direction portion (22) along the height direction intersecting the width direction as a flat portion on the outer periphery, wherein a circular shape having a radius R is formed at a joint portion (23) between the width direction portion (21) and the height direction portion (22), wherein the radius R and a thickness t of the insulating coating (20) at the flat portion (21, 22) satisfy a relationship of R>t. Also provided is a wire harness including the covered electric wire (1).

Description

Technical Field

[0001] The present invention relates to a coated electric wire and a wire harness. Background Art

[0002] A flat cable formed using a flat conductor is known. By using a flat cable, the space occupied during wiring can be reduced compared to the case of using a general electric wire having a conductor with a substantially circular cross section.

[0003] In conventional general flat cables, as disclosed in Patent Documents 1 and 2, rectangular conductors are often used as conductors. A rectangular conductor is formed by shaping a metal single wire into a quadrilateral cross section. In addition, Patent Documents 3 and 4 obtained through applications by the applicants disclose an electric wire conductor, which is composed of a stranded wire formed by twisting a plurality of wires, and has a flat portion having a flat shape in a cross section intersecting the axial direction, from the viewpoint of both flexibility and space saving.

[0004] Prior art literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2014-130739

[0006] Patent Document 2: Japanese Patent Application Publication No. 2019-149242

[0007] Patent Document 3: International Publication No. 2019 / 093309

[0008] Patent Document 4: International Publication No. 2019 / 093310

[0009] Patent Document 5: Japanese Patent Application Publication No. 2018-129195

[0010] Patent Document 6: Japanese Patent Application Publication No. 2018-6174 Summary of the invention

[0011] Problems to be solved by the invention

[0012] When forming an insulating coating on the outer periphery of a wire conductor, if the cross section of the wire conductor is circular, the insulating coating layer can be formed with a relatively uniform thickness at each portion of the outer periphery of the wire conductor. However, when the cross section of the wire conductor is flat, it is difficult to form an insulating coating with a uniform thickness at each portion of the flat shape. For example, Figure 4As shown in the insulated wire 100, the insulating coating 120 formed on the outer periphery of the flat conductor 10 tends to be thicker (t'>t) at the portion corresponding to the flat corner 123 than at the portion corresponding to the flat portion 121, 122. If the insulating coating is thicker at a portion, sufficient flame retardancy may not be obtained at that portion. This is because the volume of the insulating coating that can burn increases, and the distance from the surface of the insulating coating to the surface of the conductor increases, making it difficult for heat to be fully dissipated from the insulating coating to the conductor. In particular, when the insulated wire is mounted on a vehicle such as an automobile, if the flame retardancy of the insulated wire is low, combustion is likely to spread through the insulated wire in the event of a fire.

[0013] Therefore, a covered electric wire having a structure in which an insulating coating is provided on the outer periphery of a conductor having a flat cross-section and which can obtain high flame retardancy, and a wire harness including such a covered electric wire are provided.

[0014] Technical solutions to solve problems

[0015] The covered electric wire disclosed in the present invention comprises: a conductor; and an insulating coating covering the outer periphery of the above-mentioned conductor, the above-mentioned covered electric wire has a flat portion in which the above-mentioned conductor is a flat shape long in the width direction in the cross section intersecting the axial direction, in the above-mentioned cross section of the above-mentioned flat portion, the above-mentioned insulating coating has a width direction portion along the above-mentioned width direction and a height direction portion along the height direction intersecting the above-mentioned width direction as a flat portion on the outer peripheral surface, and a circular shape with a radius R is formed at the junction of the above-mentioned width direction portion and the above-mentioned height direction portion, and the above-mentioned radius R and the thickness t of the above-mentioned insulating coating at the above-mentioned flat portion satisfy the relationship of R>t.

[0016] The wire harness of the present disclosure includes the above-mentioned covered electric wire.

[0017] Effects of the Invention

[0018] The insulated electric wire and the wire harness according to the present disclosure are insulated electric wires and wire harnesses having a structure in which an insulating coating is provided on the outer periphery of a conductor having a flat cross-section, and can obtain high flame retardancy. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a cross-sectional view showing a covered electric wire according to one embodiment of the present disclosure.

[0020] Figure 2 This is an enlarged view showing the vicinity of a corner of a covered electric wire according to one embodiment of the present disclosure, showing a case where the radius R of the corner R shape of the insulating coating is small. The conductor is shown as a circumscribed figure.

[0021] Figure 3This is an enlarged view showing the vicinity of a corner of a covered electric wire according to one embodiment of the present disclosure, showing a case where the radius R of the corner R shape of the insulating coating is large. The conductor is shown as a circumscribed figure.

[0022] Figure 4 1 is a cross-sectional view showing a case where the corner R is not provided in the insulating coating covering the flat conductor.

[0023] Figures 5A to 5D These are photographs of cross sections of covered electric wires having angles R of different sizes. DETAILED DESCRIPTION

[0024] [Description of Embodiments of the Present Disclosure]

[0025] First, embodiments of the present disclosure will be described.

[0026] The covered electric wire involved in the present disclosure comprises: a conductor; and an insulating coating covering the outer periphery of the above-mentioned conductor, the above-mentioned covered electric wire has a flat portion in which the above-mentioned conductor is a flat shape long in the width direction in the cross section intersecting the axial direction, in the above-mentioned cross section of the above-mentioned flat portion, the above-mentioned insulating coating has a width direction portion along the above-mentioned width direction and a height direction portion along the height direction intersecting the above-mentioned width direction as a flat portion on the outer peripheral surface, and a circular shape with a radius R is formed at the junction of the above-mentioned width direction portion and the above-mentioned height direction portion, and the above-mentioned radius R and the thickness t of the above-mentioned insulating coating at the above-mentioned flat portion satisfy the relationship of R>t.

[0027] In the above-mentioned covered electric wire, in the insulating coating provided on the flat portion of the conductor having a flat shape, a rounded shape is provided at the corner formed as the junction of the flat portion, i.e., the width direction portion and the height direction portion. In addition, the radius R of the rounded shape R is R>t relative to the thickness t of the insulating coating at the flat portion, and the corner has a gently curved surface shape. Therefore, the thickness of the insulating coating does not become excessively thicker at the corner compared with the width direction portion and the height direction portion. As a result, the volume of the insulating coating can be suppressed to be smaller at the corner, and the distance from the surface of the insulating coating to the conductor becomes closer. Even when the insulating coating is exposed to flames or burns, the heat of the insulating coating can be efficiently dissipated to the conductor in various regions including the corner, thereby reducing the temperature of the insulating coating. That is, by forming a rounded shape at the corner, the burning of the insulating coating is suppressed, and a covered electric wire with high flame retardancy is obtained.

[0028] Here, the insulating coating preferably contains polyolefin and a flame retardant containing a metal compound. In this case, the resin component constituting the insulating coating itself does not have high flame retardancy as in the case of a chlorine-containing polymer, so if the corners of the insulating coating are not rounded, sufficient flame retardancy may not be obtained at the corners. However, as described above, by forming a rounded shape with R>t, high flame retardancy can be obtained at the corners.

[0029] The conductor cross-sectional area is s, and it is best to satisfy the following relationship with the thickness t of the insulating coating at the flat portion: In this case, the insulating coating is thick relative to the conductor cross-sectional area, but a rounded shape of R>t is formed at the corner, so that the insulating coating does not become excessively thick at the corner, and sufficient flame retardancy is easily ensured at the corner.

[0030] The thickness of the insulating coating at the circular portion is set to t', and preferably satisfies the relationship of t'>0.8t with the thickness t of the insulating coating at the flat portion. Therefore, the thickness t' of the insulating coating at the corner portion is not extremely smaller than the thickness t of the insulating coating at the flat portion, so that the influence caused by the insulating coating becoming too thin, such as the decrease in insulation or wear resistance, can be suppressed at the corner portion.

[0031] The length of the conductor along the width direction is w, and the length along the height direction is h, and the aspect ratio evaluated as w / h is preferably not more than 4. Thus, the conductor does not become excessively flat, and thus it is possible to suppress the situation in which the flame retardancy of the insulating coating as a whole decreases due to an increase in the volume of the insulating coating caused by the flattening of the conductor.

[0032] The conductor is preferably a stranded wire formed by twisting a plurality of wires. Thus, it is easy to achieve both flexibility and space saving in the conductor. In addition, by using a stranded wire, it is easy to form a conductor having a flat portion even when the conductor cross-sectional area is large. However, when the conductor cross-sectional area is larger, the insulating coating is often formed thicker. Therefore, the effect of improving flame retardancy by forming a rounded shape at the corner becomes relatively large.

[0033] The wire harness of the present disclosure includes the above-mentioned covered wire of the present disclosure. As described above, the covered wire of the present disclosure has a rounded shape at the corner of the insulating coating at the flat portion, and the radius R of the rounded shape is sufficiently large relative to the thickness t of the insulating coating at the flat portion, R>t, so that the corner exhibits high flame retardancy. This high flame retardancy can also be utilized in the wire harness.

[0034] [Details of the embodiments of the present disclosure]

[0035] Hereinafter, the covered electric wire and the wire harness involved in the embodiment of the present disclosure will be described in detail using the drawings. In this specification, the shape of each part of the insulating coating is assumed to be within the concept of the shape or configuration of the component, such as straight line, arc, flat, parallel, vertical, etc., and the deviation of the length is about ±15%, and the deviation of the angle is about ±15°, etc., which are within the allowable range in such a covered electric wire, and include errors relative to the geometric concept. In this specification, unless otherwise specified, the cross section of the covered electric wire or conductor refers to the cross section cut perpendicular to the axial direction (long side direction).

[0036] <Overview of covered electric wire>

[0037] exist Figure 1 A cross-sectional view of a covered electric wire 1 according to an embodiment of the present disclosure is shown in FIG. Figure 2 FIG. 2 shows an enlarged view of the corner of the covered electric wire 1. The covered electric wire 1 according to the present embodiment includes a conductor 10 and an insulating coating 20. The insulating coating 20 covers the entire periphery of the conductor 10. Figure 2 In FIG. 1 , the conductor 10 is shown as a circumscribed diagram.

[0038] The conductor 10 has a flat outer shape in at least a part of the region along the axial direction. That is, it has a flat portion with a flat cross section. In the present embodiment, the entire region of the conductor 10 in the axial direction is such a flat portion.

[0039] Here, the cross section of the conductor 10 has a flat shape, which means that the length of the longest straight line among the straight lines included in the entire cross section when the cross section is cut parallel to the side constituting the cross section, that is, the width w, is greater than the length of the straight line included in the entire cross section orthogonal to the straight line, that is, the height h. The cross section of the conductor 10 can be any specific shape as long as it is a flat shape, but in the present embodiment, the cross section of the conductor 10 preferably has a cross section that can be approximated to a rectangle except for the circular shape of the four corners 13. This is because it is easy to improve the space saving of the coated wire 1, and it is easy to form the insulating coating 20 described later to a uniform thickness at the flat parts 21 and 22. Here, the cross section of the conductor 10 is a rectangle, which means that the circumscribed figure of the conductor 10 can be approximated to a rectangle within an error range of about ±15° in the relationship between the sides.

[0040] In addition, as described later, in the present covered electric wire 1, the insulating coating 20 is provided with a rounded shape at the corner 23 from the viewpoint of reducing the thickness of the insulating coating 20 at the corner 23, but from the viewpoint of improving the effect thereof, it is also preferred that the corner 13, i.e., the junction between the side 11 in the width direction and the side 12 in the height direction, has a rounded shape (R chamfered shape; corner R shape) on the conductor 10. The radius r of the corner R shape of the conductor 10 is preferably set to be not less than 33% and not more than 66% with respect to the length of the side (short side) in the height direction of the conductor 10. In addition, the radius r of the corner R shape of the corner 13 of the conductor 10 is as shown in Figure 2 As shown in FIG. 1 , the evaluation can be performed in the circumscribed pattern of the conductor 10, but Figure 1 In order to facilitate understanding, the number of wires 15 constituting the conductor 10 is reduced for display, so it is not necessarily obvious whether the circumscribed figure has an angle R shape. When the number of wires 15 constituting the conductor 10 is larger (for example, more than 150), the angle R shape in the circumscribed figure can be clearly identified.

[0041] The conductor 10 may have a flat portion, and the specific structure is not particularly limited. For example, the conductor 10 may have a single wire structure composed of a metal material such as a metal foil or a metal plate that is integrally continuous, but in the present embodiment, it is composed of a stranded wire in which a plurality of wires 15 are twisted together. By configuring the conductor 10 as a stranded wire, the space saving due to the flat shape of the conductor 10 and the flexibility due to the twisted structure can be taken into account in the covered electric wire 1. The stranded wire having a flat shape can be formed by rolling a raw stranded wire obtained by twisting a plurality of wires 15 into a substantially circular cross section.

[0042] In the conductor 10 configured as a stranded wire, the cross-sectional shape of at least a portion of each wire 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 wire 15 from a circular shape is smaller at the outer peripheral portion of the cross section of the conductor 10 than at the inner portion. In addition, in the cross section of the conductor 10, it is preferable that a gap that can accommodate one or more, and further two or more wires 15 is left between each wire 15.

[0043] In the covered electric wire 1, there is no particular limitation on the conductor cross-sectional area. However, in general, in the covered electric wire, there is a tendency that the thickness of the insulating coating provided on the outer periphery of the conductor becomes thicker when the conductor cross-sectional area becomes larger. In the covered electric wire 1 involved in the present embodiment, the thicker the insulating coating 20 is, the better the effect of suppressing the thickness of the insulating coating 20 at the corner 23 by providing an angle R shape at the corner 23 of the insulating coating 20 as described later. Therefore, from the viewpoint of enjoying the effect of forming the angle R shape at the corner 23 to a greater extent, it is preferred to use a conductor 10 with a larger conductor cross-sectional area. For example, the conductor cross-sectional area is preferably 15mm according to the nominal value. 2 Above, further 50mm 2 above.

[0044] The material constituting the conductor 10 is not particularly limited, and various metal materials can be applied. As representative metal materials constituting the conductor 10, copper and copper alloys, and aluminum and aluminum alloys can be cited. In particular, aluminum and aluminum alloys have lower electrical conductivity than copper and copper alloys, so in order to ensure the required electrical conductivity, the conductor cross-sectional area is easily increased. From the viewpoint that the larger the conductor cross-sectional area, the greater the effect of providing the corner R shape at the corner 23 of the insulating coating 20, it is preferable to constitute the conductor 10 with aluminum or an aluminum alloy.

[0045] In the covered electric wire 1 according to the present embodiment, the insulating coating 20 covers the outer periphery of the conductor 10. In the cross section, the conductor 10 has a flat shape, and accordingly, the covered electric wire 1 as a whole including the insulating coating 20 also has a flat shape. In addition, the cross-sectional shape of the covered electric wire 1 as a whole including the insulating coating 20 can be made to be approximately rectangular except for the corner R shape of the corner 23. Here, the cross-sectional shape of the covered electric wire 1 is a rectangle, which means that the circumscribed figure can be approximately rectangular in the mutual relationship of each side within the error range of about ±15°. In addition, in the cross section, the width direction portion 21, which is the side extending in the width direction, and the height direction portion 22, which is the side extending in the height direction, of the outer peripheral surface of the insulating coating 20 are both flat portions that can be approximately straight lines. In addition, the thickness t of the insulating coating 20 is uniform in each portion on the width direction portion 21 and the height direction portion 22 except for the corner 23 and its vicinity, within the error range of about ±15%.

[0046] In the cross section of the covered electric wire 1, a rounded shape (R chamfered shape; corner R shape; cornerroundness: rounded corner) is provided at the four corners 23 of the insulating coating 20, that is, the joint between the width direction portion 21 and the height direction portion 22 which are formed as flat portions. The corner R shape can improve the flame retardancy of the insulating coating 20 at the corner 23. The shape of the insulating coating 20 at the corner 23 and the effect brought about by the shape will be described in detail later.

[0047] In addition, in this specification, the description is centered on the form in which the insulating coating 20 is closely attached to the outer peripheral surface of the conductor 10. Although it is preferred that the insulating coating 20 is closely attached to the conductor 10 in order to improve the flame retardancy of the insulating coating 20, it is also possible to adopt a form in which there is a gap between the conductor 10 and the insulating coating 20. In the case where such a gap exists, the structure of the insulating coating 20, such as the shape of the insulating coating 20 at the corner 23, can also be appropriately applied to the form described below in addition to such a gap. In addition, in this specification, as described above, the case in which the cross-sectional shape of the conductor 10 can be approximated to a rectangle is mainly handled, but the cross section of the conductor 10 can also take a shape other than the shape that can be approximated to a rectangle. In this case, it is also preferred that an angle R shape is formed at the corner 13 (one of the intersection of two straight lines, the intersection of a straight line and a curve, and the intersection of two curves) of the approximate figure of the cross section of the conductor 10, and the corner 13 of the conductor 10 and the corresponding corner 23 of the insulating coating 20 take the structure described below. In addition to the rectangle, polygons such as an ellipse (a shape formed by joining arcs on both sides of a rectangle; a small gold coin shape; an athletic track shape), a hexagon, and an octagon can be exemplified as an approximate figure of a flat conductor shape having a corner portion 13. In the case of an ellipse, the corner portion 13 is formed as the intersection of a straight line and a curve, and in the case of a polygon, the corner portion 13 is formed as the intersection of two straight lines.

[0048] The material constituting the insulating coating 20 is not particularly limited as long as it is an insulating material, but preferably a material having an organic polymer as a main component. From the viewpoint of improving the flame retardancy of the insulating coating 20, the constituent material of the insulating coating 20 is preferably a flame retardant material, but if the constituent material of the insulating coating 20 itself has extremely high flame retardancy, then regardless of the presence of the corner R shape of the corner 23 or the shape of the insulating coating 20, it is highly likely that sufficient flame retardancy can be achieved. In the case where the constituent material of the insulating coating 20 itself has low flame retardancy, the effect of improving flame retardancy by providing the corner R shape to the corner 23 of the insulating coating 20 is relatively high. Specifically, the organic polymer constituting the insulating coating 20 is preferably not composed of a polymer having high flame retardancy such as polyvinyl chloride (PVC), but is composed of an organic polymer that does not contain chlorine and has low flame retardancy such as polyolefins headed by polyethylene, and flame retardancy is imparted to the polymer by adding a flame retardant. 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 flame retardant such as a bromine-based flame retardant that exhibits high flame retardancy in a small amount.

[0049] The material obtained by adding a flame retardant containing a metal compound to a polyolefin such as polyethylene is excellent as a halogen-free wire covering material because of its high heat resistance, and can also be appropriately used in the present embodiment. From the viewpoint of improving heat resistance, it is particularly preferred if the polyolefin is cross-linked. Regarding the content of the flame retardant, from the viewpoint of exerting sufficient flame retardancy, it is preferably set to 50 parts by mass or more relative to 100 parts by mass of polyolefin. On the other hand, from the viewpoint of maintaining good mechanical properties of the insulating coating 20 such as wear resistance, its content is preferably less than 200 parts by mass. In addition, the insulating coating 20 may contain polymers other than polyolefin in addition to the polyolefin and the flame retardant, and may also contain additives other than the flame retardant.

[0050] The method for forming the insulating coating 20 is not particularly limited, but it is preferable to use a composition obtained by mixing various components and perform extrusion molding to form a layer of the insulating coating 20 on the outer periphery of the conductor 10. The insulating coating 20 having a predetermined angle R shape can be formed at the corner 23 of the cross section by the shape of the die during the extrusion molding.

[0051] The insulated electric wire 1 involved in the present embodiment can be used in a separate state or as a component of the wire harness involved in the embodiment of the present disclosure. The wire harness involved in the embodiment of the present disclosure includes the insulated electric wire 1 involved in the above-mentioned embodiment. The wire harness can include a plurality of the above-mentioned insulated electric wires 1, and can also include other types of insulated electric wires in addition to the above-mentioned insulated electric wires 1. Preferably, it is best to arrange a plurality of the above-mentioned insulated electric wires 1 in the width direction and / or the height direction. At this time, there is no particular limitation on the specific arrangement structure of the plurality of insulated electric wires 1, but as an appropriate form, it is possible to exemplify a form in which the plurality of insulated electric wires 1 are arranged side by side in the width direction and fixed to a common sheet by welding or the like. In this case, it is particularly preferred if the heights of the plurality of insulated electric wires 1 arranged side by side are consistent.

[0052] <Insulation coating details>

[0053] In the covered electric wire 1 according to the present embodiment, as described above, in the cross section of the flat portion, the insulating coating 20 covering the outer periphery of the conductor 10 has an R-shaped corner portion 23 at the junction between the width direction portion 21 and the height direction portion 22 constituting the flat portion. Figure 2 , 3 As shown, the radius of the corner R shape of the corner portion 23 of the insulating coating 20, that is, the radius of the arc when the corner R shape is close to an arc, is set to R. In addition, Figure 2 The case where the radius R is small and the center O2 of the corner R shape is located outside the conductor 10 is shown. Figure 3 The case where the radius R is large and the center O2 of the corner R shape is located in the conductor 10 is shown.

[0054] Assuming that the thickness of the insulating coating 20 at the flat portion, that is, the width direction portion 21 and the height direction portion 22 is t, in the covered electric wire 1 according to the present embodiment, the relationship between the radius R of the corner R shape of the insulating coating 20 and the thickness t at the flat portions 21 and 22 is R>t. That is, the radius R of the corner R shape of the corner 23 of the insulating coating 20 is larger than the thickness t of the insulating coating 20 at the flat portions 21 and 22. The larger the radius R of the corner R shape, the greater the degree of rounding of the corner R shape, and the more gently curved the corner 23 takes.

[0055] In the covered electric wire 1, the thickness direction of the corner 23 corresponds to the diagonal direction of the flat shape. Therefore, when the corner 23 of the insulating coating 20 does not have an R-shaped corner, or even if it has an R-shaped corner, but the radius R is small, the thickness t' of the insulating coating 20 at the corner 23 becomes larger, and the volume occupied by the insulating coating 20 at the corner 23 becomes larger. In addition, the distance from the surface of the insulating coating 20 to the surface of the conductor 10 becomes longer. As a result, in the case where there is a situation where flames come into contact with the insulating coating 20 or the insulating coating 20 burns, the amount of the insulating coating that can burn becomes larger, and the heat generated at the insulating coating 20 is not easily dissipated to the conductor 10. Therefore, the insulating coating 20 is easy to burn. In addition, when the insulating coating 20 burns, the burning is likely to continue for a long time.

[0056] However, if the corner 23 of the insulating coating 20 is formed with a corner R shape having a sufficiently large radius R, the thickness t' of the insulating coating 20 at the corner 23 becomes smaller, and the volume of the insulating coating 20 at the corner 23 becomes smaller. In addition, at the corner 23, the distance from the surface of the insulating coating 20 to the surface of the conductor 10 becomes shorter. Therefore, even if there is a situation where flames come into contact with the insulating coating 20 or the insulating coating 20 burns, since the volume of the insulating coating 20 that can burn is small, and since the distance required for heat conduction when the heat is dissipated from the insulating coating 20 to the conductor 10 is shortened, the heat generated at the insulating coating 20 is easily dissipated from the insulating coating 20 to the conductor 10, and the temperature rise of the insulating coating 20 and the progress of the burning can be suppressed. As a result, the insulating coating 20 is not easy to burn. In addition, even if it is assumed that the insulating coating 20 burns, it is self-extinguished and the burning stops in a short time. By forming the corner R shape having a sufficiently large radius R at the corner 23 of the insulating coating 20 in this manner, the flame retardancy at the corner 23 can be improved.

[0057] In particular, if the radius R of the corner R shape provided at the corner 23 of the insulating coating 20 is R>t relative to the thickness t of the insulating coating 20 at the flat portions 21 and 22, the effect of improving the flame retardancy due to the reduction in the thickness of the insulating coating 20 at the corner 23 becomes sufficiently high. For example, when the thickness t of the insulating coating at the flat portions 21 and 22 is made equal to the coating thickness adopted as a standard in conventional general covered electric wires with a circular cross section, in comparison with these covered electric wires with a circular cross section, sufficiently high flame retardancy can be obtained at each portion of the insulating coating 20 including the corner 23. In particular, when the covered electric wire 1 is mounted on a vehicle such as an automobile, even if the insulating coating 20 is ignited due to a fire or the like, the insulating coating 20 has a high flame retardancy and can be extinguished at an early stage, thereby suppressing the spread of the combustion through the covered electric wire 1. If R>1.5t or R>2t, the flame retardancy becomes further high, which is preferable. In addition, R>r+0.5t is more preferable. In addition, when R=r+t, the thickness t of the insulating coating 20 at the flat portions 21 and 22 is equal to the thickness t′ of the insulating coating 20 at the corner portion 23 .

[0058] Providing the corner R shape to the corner portion 23 of the insulating coating 20 has the effect of improving the adhesion between the external components and the covered wire 1 in addition to improving the flame retardancy. For example, when a rubber plug is wrapped around the outer periphery of the insulating coating 20 for the purpose of waterproofing, the rubber plug is well adhered to the outer peripheral surface of the insulating coating 20. Therefore, high waterproofness can be achieved at the end of the insulating coating 20 and the like.

[0059] From the viewpoint of improving the flame retardancy of the insulating coating 20 at the corner 23, there is no particular upper limit on the radius R of the corner R shape provided at the corner 23. However, it is preferable to suppress the radius R of the corner R shape within a relatively small range and to sufficiently ensure the thickness t' of the insulating coating 20 at the corner 23, in order to make it easy for the insulating coating 20 to fully exhibit its characteristics such as insulation and wear resistance at the corner 23. Specifically, the thickness t' of the insulating coating 20 at the corner 23 preferably maintains a relationship of t'>0.8t with respect to the thickness t at the flat portions 21 and 22. Furthermore, it is preferable that t'≥t.

[0060] Here, the relationship between the thickness t' at the corner 23 of the insulating coating 20 and the radius R of the corner R shape is described. Figure 3As shown, it is assumed that the center O2 of the corner R shape (radius R) of the corner 23 of the insulating coating 20 is located at a distance a inward in the width direction and the height direction compared to the center O1 of the corner R shape (radius r) of the corner 13 of the conductor 10. At this time, if a straight line (straight line L1) connecting the center O2 and the center O1 and extending to the surface of the insulating coating 20 is assumed, the radius R of the corner R shape of the insulating coating 20 can be expressed by the following formula 1.

[0061]

[0062] On the other hand, assuming a straight line (straight line L2) connecting the center O2 to the junction point P between the flat portion 21 and the corner R shape of the corner portion 23 of the insulating coating 20, the radius R of the corner R shape of the insulating coating 20 can be expressed by the following formula 2.

[0063] R=t+r+a (2)

[0064] Since the right sides of Formula 1 and Formula 2 are equal, the distance a can be expressed as follows.

[0065]

[0066] If Expression 3 is substituted into Expression 1 or Expression 2 and rearranged, the radius R of the corner R shape of the insulating coating 20 can be expressed as follows.

[0067]

[0068] Here, if t'>0.8t as described above, the range of the thickness R of the insulating coating 20 is R<r+1.48t according to Formula 4. If the requirement of R>t defining the lower limit of the radius R described above is met, the range of the radius R of the corner R shape of the corner 23 is preferably t<R<r+1.48t.

[0069] In the covered electric wire 1 according to the present embodiment, as described above, the corner 23 of the insulating coating 20 is provided with an R-shaped corner, and the radius R of the R-shaped corner is R>t, so that even when the insulating coating 20 is formed thickly at the flat portions 21 and 22, it is possible to suppress the decrease in flame retardancy due to the thickening of the insulating coating 20 at the corner 23. In the case where the thickness t of the insulating coating 20 at the flat portions 21 and 22 is large, the effect of improving the flame retardancy by forming the R-shaped corner at the corner 23 can be relatively improved. From this viewpoint, regarding the thickness t of the insulating coating 20 at the flat portions 21 and 22, it is preferable to set the conductor cross-sectional area to s, and satisfy The thickness is equivalent to or thicker than the thickness of the insulating coating generally used in a standard circular cross-section covered electric wire. Further, it is preferred that or If the thickness of the insulating coating 20 is too large, not only the corners 23 but also the entire insulating coating 20 may not have sufficient flame retardancy.

[0070] In the covered electric wire 1, regardless of the degree of flatness of the flat shape of the conductor 10, the effect of improving the flame retardancy can be obtained by setting the corner R shape on the corner 23 of the insulating coating 20, so there is no particular limitation on the flatness ratio w / h of the conductor 10. However, the flatness ratio w / h of the conductor 10 is preferably 2 or more. Therefore, the space saving effect brought about by setting the conductor 10 to a flat shape becomes higher, and the circumference of the conductor 10 becomes longer, and heat is easily dissipated from the insulating coating 20 to the conductor 10 through the interface, so it is effective to improve the flame retardancy. On the other hand, the flatness ratio w / h is preferably 6 or less, and further 4 or less. This is because it is not easy to occur that the volume of the insulating coating 20 covering the conductor 10 becomes larger due to the increase in the flatness ratio, and the flame retardancy of the insulating coating 20 becomes lower.

[0071] Example

[0072] Examples are shown below. However, the present invention is not limited to these examples. Here, the relationship between the radius R of the corner R shape of the corner portion of the insulating coating and the flame retardancy was investigated.

[0073] (Sample production)

[0074] First, the conductor constituting the covered wire is produced. First, a stranded wire with a circular cross section is prepared by twisting aluminum alloy wires, and the stranded wire is compressed into a flat shape with a roller to produce a conductor. As the stranded wire, a conductor with a cross-sectional area (nominal value) of 130 mm 2 The stranded wire (wire diameter is 0.42mm, wire number is 931) and the conductor cross-sectional area (nominal value) is 60mm 2 The stranded wire (wire diameter is 0.32mm, number of wires is 741). In addition, by changing the compression rate, the flatness ratio w / h varies between 2.5 and 4, and various conductors are produced for each conductor cross-sectional area. The radius r of the corner R shape of the conductor is 130mm when the conductor cross-sectional area is 2 In the case of 4.0mm, the conductor cross-sectional area is 60mm 2 The case is 2.6mm.

[0075] An insulating coating is formed on the outer periphery of the produced conductor by extrusion molding. At this time, the thickness of the insulating coating and the radius R of the corner R shape of the corner are changed by changing the shape and size of the mold used. As the constituent material of the insulating coating, a material obtained by adding 70 parts by mass of magnesium hydroxide to 100 parts by mass of cross-linked polyethylene as a flame retardant is used.

[0076] In the above manner, covered electric wires of samples 1 to 12 were produced. For each of the produced samples, a cross-sectional photograph was taken to confirm that the dimensions of each part of the conductor and the insulating coating were the same as set. The cross-sectional sample was produced by cutting the covered electric wire perpendicularly to the axial direction while it was embedded in the acrylic resin.

[0077] (Evaluation of flame retardancy)

[0078] The coated wire obtained by the above is subjected to a combustion test and flame retardancy is evaluated. Specifically, a length of 30 cm is cut out of each coated wire, and the wire is kept horizontally so that a flame having a length of 35 mm of the reducing flame is in contact with the center thereof. Within 30 seconds from contact with the flame, the ignition of the insulating coating is confirmed, and after ignition, the flame is separated from the coated wire. Furthermore, after the flame is separated, the time (fire extinguishing time) until it extinguishes naturally is measured. If the fire extinguishing time is within 30 seconds, it can be evaluated as having sufficient flame retardancy. In addition, if the fire extinguishing time evaluated by the same combustion test in a general coated wire with a circular cross section is within 30 seconds, it can be regarded as having sufficiently high flame retardancy to prevent the spread of combustion to other components.

[0079] (result)

[0080] Table 1 summarizes the dimensions of each part of the covered wire and the fire extinguishing time obtained through the combustion test. Figures 5A to 5D In the drawings, as representatives, photographs of cross sections of Samples 1 and 3 to 5 before the combustion test are shown.

[0081] [Table 1]

[0082]

[0083] First, if we observe Figures 5A to 5D From the cross-sectional photographs of the conductor, it was confirmed that the insulating coating formed on the outer periphery of the flat conductor had a flat portion with a relatively uniform thickness and a corner portion with an R-shaped corner. In addition, the larger the radius R of the R-shaped corner, the more gently curved the corner portion becomes.

[0084] According to the results in Table 1, in samples 1, 2, 6, 10 to 12 where R≤t, i.e., R / t≤1.0, the extinguishing time exceeds 30 seconds, and sufficient flame retardancy cannot be obtained. On the other hand, in samples 3 to 5, 7 to 9 where R>t, i.e., R / t>1.0, although the structure of the conductor and the thickness t of the insulating coating at the flat portion are different, the extinguishing time is within 30 seconds in any one of them. It can be seen from this that the ratio of the radius R of the corner R shape of the corner of the insulating coating to the thickness t of the flat portion is an excellent indicator of flame retardancy, and by setting R>t, higher flame retardancy can be obtained.

[0085] In the groups of samples 3 to 5 and the groups of samples 8 and 9, the relationship R>t is satisfied and only the radius R of the corner R shape changes among the parameters. If the test results of these samples are compared, the larger the radius R, the shorter the fire extinguishing time. Based on this, it can be said that the larger the radius R of the corner R at the corner of the insulating coating, the better the flame retardancy.

[0086] As mentioned above, although embodiment of this disclosure was demonstrated in detail, this invention is not limited at all to the said embodiment, Various changes are possible within the range which does not deviate from the summary of this invention.

[0087] Description of Reference Numerals

[0088] 1. 100 coated wire

[0089] 10 Conductor

[0090] 11 The width of the conductor

[0091] 12 The edge of the conductor in the height direction

[0092] 13 Corner of conductor

[0093] 15 Wire

[0094] 20, 120 insulation coating

[0095] 21, 121 Width direction part (flat part)

[0096] 22, 122 Height direction part (flat part)

[0097] 23, 123 Corner (joint)

[0098] a The distance between center O1 and center O2 along the width and height directions

[0099] L1, L2 straight lines for analysis

[0100] H Height of the conductor

[0101] O1 Center of the angular R shape of the conductor

[0102] O2 Center of the R-shaped corner of the insulating coating

[0103] P The junction between the R shape and the flat part

[0104] r The radius of the conductor's corner R shape

[0105] R Radius of the corner R shape of the insulating coating

[0106] t Thickness of the insulating coating at the flat portion

[0107] t' Thickness of the insulating coating at the corner

[0108] w Width of the conductor.

Claims

1. A coated electric wire having: conductors; and an insulating coating covering the outer circumference of the conductor, The covered electric wire has a flat portion in which the conductor is a flat shape that is long in the width direction in a cross section intersecting the axial direction. In the cross section of the flat portion, the insulating coating has a width direction portion along the width direction and a height direction portion along a height direction intersecting the width direction as a flat portion on an outer peripheral surface. A circular shape with a radius R is formed at the junction of the width direction portion and the height direction portion, The radius R and the thickness t of the insulating coating at the flat portion satisfy the relationship R>t, The conductor cross-sectional area is s, and the conductor cross-sectional area and the thickness t of the insulating coating at the flat portion satisfy the relationship t>0.10√s.

2. The covered electric wire according to claim 1, wherein The insulating coating contains polyolefin and a flame retardant including a metal compound.

3. The covered electric wire according to claim 1 or 2, wherein: The thickness of the insulating coating at the circular portion is t', and the thickness t of the insulating coating at the flat portion satisfies the relationship t'>0.8t.

4. The covered electric wire according to claim 1 or 2, wherein: The length of the conductor along the width direction is represented by w, and the length along the height direction is represented by h, and the aspect ratio evaluated as w / h is 4 or less.

5. The covered electric wire according to claim 1 or 2, wherein: The conductor is configured as a stranded wire formed by twisting a plurality of wires. 6 . A wire harness comprising the covered electric wire according to claim 1 .

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