Flat curled cord

Abstract

Provided is a curled cord that achieves a reduction in diameter while ensuring springiness and a wire harness including such a curled cord.　A flat curled cord 1 comprises an insulated wire 2 wound in a spiral shape, the insulated wire 2 including a conductor 12 and an insulating cover 13 covering the outer circumference of the conductor 12. The insulated wire 2 is a flat wire in which the conductor 12 as well as the insulated wire 2 has a flat cross-sectional shape along the axial direction. Flat surfaces of the flat wire 2, which are outer surfaces along the width direction of the flat shape, face outward and inward in the spiral shape.

Description

[Technical Field]

[0001] The present disclosure relates to a flat curled cord. [Background technology]

[0002] Curl cords, which are made by processing an insulated electric wire into a spiral shape and making it flexible, are known. This type of curl cord is used for purposes such as forming an electrical connection between movable parts, and is placed in locations inside an automobile where the electric wire is required to be flexible, such as a sliding door or rear window. Patent Document 1 is an example of a document that describes curl cords. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-243399 Summary of the Invention [Problem to be solved by the invention]

[0004] Because a curl cord is an insulated electric wire formed into a spiral, it requires more space for routing than a linear insulated electric wire. In other words, when comparing a curl cord having a certain natural length with a linear insulated electric wire of the same length, the curl cord occupies a larger radial space. As described above, curl cords are suitable for use in moving parts of devices such as automobiles. In various devices, such as automobiles, it is advantageous for various electric wires to have high space-saving properties so that electric wires can be routed in narrow spaces. It is also desirable to improve space-saving properties of curl cords by reducing their diameter. While it may be possible to reduce the diameter by reducing the conductor cross-sectional area of ​​the insulated electric wire that constitutes the curl cord or by reducing the spiral diameter of the curl cord, this may result in a decrease in the springiness of the curl cord (a decrease in spring constant), making it difficult to ensure sufficient restoring force during expansion and contraction. It is desirable to achieve a smaller diameter while maintaining the high springiness of the curl cord.

[0005] In view of the above, an object of the present invention is to provide a curl cord that has a small diameter while maintaining spring properties, and a wire harness including such a curl cord. [Means for solving the problem]

[0006] The flat curl cord according to the present disclosure comprises an insulated electric wire, which includes a conductor and an insulating coating that covers the outer periphery of the conductor, wound in a spiral shape, and the insulated electric wire is a flat electric wire in which the cross-sectional shape of the conductor and the insulated electric wire along the axial direction is flat, and the flat plane, which is the outer surface of the flat electric wire along the width direction of the flat shape, faces outward and inward from the spiral shape.

[0007] The wire harness of the present disclosure includes the flat curl cord. [Effects of the Invention]

[0008] The flat curl cord according to the present disclosure is a curl cord that has a small diameter while maintaining spring properties. The wire harness according to the present disclosure includes such a curl cord. [Brief explanation of the drawings]

[0009] [Figure 1] Fig. 1A is a side view showing a flat curl cord according to an embodiment of the present disclosure, Fig. 1B is a cross-sectional view showing a cross section of a flat electric wire constituting the flat curl cord, cut perpendicular to the axial direction, and Fig. 1C is a front view of the flat curl cord. [Figure 2] FIG. 2 is a perspective view showing a conductor of a flat electric wire constituting a flat curl cord according to an embodiment of the present disclosure. [Figure 3] Fig. 3A is a side view showing a round curl cord in which a round electric wire having a circular cross section intersecting the axial direction is used as a curl cord, and Fig. 3B is a cross section intersecting the axial direction of the round electric wire. [Figure 4] Fig. 4A is a cross-sectional view of the flat curl cord according to one embodiment of the present disclosure, taken along the central axis of the spiral shape. Fig. 4B is a cross-sectional view of the round curl cord having a substantially circular conductor, taken along the central axis of the spiral shape. Fig. 4C is a diagram comparing the flat curl cord and the round curl cord. The internal structure of the electric wire is omitted in the cross section. [Figure 5] Figures 5A and 5B are graphs showing the relationship between the flattening ratio and the outer diameter of a flat curl cord and a round curl cord. Figure 5A is a graph for the curl cord in Figure 1C, which has an inner diameter I of 3 mm and an equivalent circular wire diameter of 1.6 mm, and Figure 5B is a graph for the curl cord, which has an inner diameter I of 3 mm and an equivalent circular wire diameter of 3 mm. Figure 5C is a graph showing the relationship between the flattening ratio and the number of turns required to produce a flat curl cord and a round curl cord with a total length of 150 mm. [Figure 6] FIG. 6 is a graph showing the relationship between tension and displacement for a flat curl cord and a round curl cord. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Description of the embodiments of the present disclosure] First, an embodiment of the present disclosure will be described. A flat curl cord according to an embodiment of the present disclosure includes an insulated electric wire including a conductor and an insulating coating that covers the outer periphery of the conductor, wound in a spiral shape, and the insulated electric wire is a flat electric wire in which the cross-sectional shape of the conductor and the insulated electric wire along the axial direction is flat, and flat surfaces, which are the outer surfaces of the flat electric wire along the width direction of the flat shape, face outward and inward of the spiral shape.

[0011] In the flat electric wire, the curl cord is made of a flat electric wire, and the flat electric wire is wound so that the flat surfaces of the flat electric wire, i.e., the surfaces parallel to the width direction of the flat shape, face inward and outward of the spiral structure. In this spiral structure, the flat surfaces of the flat electric wire are aligned in the width direction along the central axis of the curl cord. In the flat electric wire, the height dimension, which intersects with the width direction, is smaller than the diameter of a substantially circular cross-section (round electric wire) having the same conductor cross-sectional area, so the thickness of the spiral shape in the radial direction is smaller. Therefore, when comparing curl cords in which a flat electric wire and a round electric wire are wound in a spiral shape with the same inner diameter, the flat electric wire can make the outer diameter of the curl cord smaller, thereby achieving a thinner flat curl cord. As described above, the flat curl cord has a smaller outer diameter than a curl cord using a round electric wire with the same conductor cross-sectional area. However, as shown in the following examples, if the natural lengths are the same, the same spring constants are ensured.

[0012] The overall shape of the flat electric wire preferably has a flattening ratio, which represents the ratio of the height to the width of the flat shape, where the height is the direction intersecting the width of the flat shape. A flattening ratio of 0.79 or less can improve the effect of reducing the diameter of the curled cord. Furthermore, a flattening ratio of 0.79 or less makes the width of the flat electric wire longer than the diameter of a substantially circular electric wire (round electric wire) having the same conductor cross-sectional area, increasing the length of the flat electric wire along the central axis of the spiral. Therefore, when a curled cord of the same natural length is formed using a flat electric wire and a round electric wire, the use of the flat electric wire allows for a reduction in the actual length of the electric wire used, and therefore reduces the amount of conductor used, by the amount of wire that occupies each turn along the axis of the spiral shape. This means that the weight of the curled cord can be reduced.

[0013] The conductor may be made of a twisted wire formed by twisting a plurality of element wires together. By using a twisted wire formed by twisting a plurality of element wires together as the conductor, it becomes easier to form the flat electric wire into a spiral shape and furthermore, it is possible to increase the flexibility of the curl cord when it is stretched and contracted. Therefore, it is preferable that the conductor be made of a twisted wire.

[0014] A round electric wire having the same conductor cross-sectional area and insulating coating thickness as the flat electric wire and a circular cross section intersecting the axial direction is wound in a spiral shape with the same spacing between spiral turns and the same inner diameter as the flat curl cord to form a round curl cord, and the outer diameter of the spiral shape of the flat curl cord is preferably 90% or less of the outer diameter of the spiral shape of the round curl cord, thereby achieving a sufficiently smaller diameter of the flat curl cord compared to the round curl cord.

[0015] The spring constant of the flat curl cord is preferably 90% or more of the spring constant of the round curl cord. Since there is no significant difference in the spring constant between the flat curl cord and the round curl cord, the flat curl cord can have the same level of restoring force as the round curl cord, and the flat curl cord can be suitably routed in areas where elasticity is required.

[0016] The wire harness according to the present embodiment includes the flat curl cord. The wire harness to which the flat curl cord is applied can be suitably used for wiring of moving parts of various devices, such as a sliding door or a rear window in an automobile.

[0017] [Details of the embodiments of the present disclosure] Hereinafter, a flat curl cord according to an embodiment of the present disclosure will be described in detail with reference to the drawings.

[0018] (Overall structure of flat curled cord) FIG. 1A shows a side view of a flat curl cord 1 according to one embodiment of the present disclosure. FIG. 1B shows a cross-sectional view of a flat electric wire 2 constituting the flat curl cord 1, cut along a plane intersecting the axial direction. FIG. 1C shows a front view of the flat curl cord 1. FIG. 4A shows a cross-sectional view of the flat curl cord 1, cut along the central axis of the spiral shape. In the present disclosure, the axial direction of the flat electric wire 2 refers to the direction in which the electric wire extends in the flat electric wire 2, and the central axis of the flat curl cord 1 refers to the axis passing through the center of the spiral of the flat curl cord.

[0019] The flat curl cord 1 is configured by spirally winding a flat electric wire 2. As will be described in detail below, the flat electric wire 2 is an electric wire whose cross section intersecting the axial direction has a flat shape. In the flat curl cord 1, the flat surfaces, which are the outer surfaces of the flat electric wire 2 along the width b direction of the flat shape (width direction x), face outward and inward of the spiral shape. As long as the flat electric wire 2 constituting the curl cord 1 has a flat shape, the shape of the entire spiral structure is not particularly limited, but it is preferably a substantially cylindrical shape. As described above, in the flat curl cord 1, the flat surfaces of the flat electric wire 2 facing outward and inward of the spiral shape means that in each turn of the spiral, the flat surfaces of the flat electric wire 2 are aligned in the width direction (x direction) approximately along the direction of the central axis of the spiral shape (stretching direction). In other words, the flat curl cord 1 is configured by adjacent turns forming a spiral shape adjacent to each other along the width direction x of the flat shape.

[0020] As shown in FIG. 1B , the flat electric wire 2 constituting the flat curl cord 1 has a conductor 12 and an insulating coating 13. The outer periphery of the conductor 12 is coated with the insulating coating 13. The flat electric wire 2 has a flat shape in a cross section perpendicular to the axial direction. Preferably, the cross section of the flat electric wire 2 has a shape that can be approximated to a rectangle. In the cross section perpendicular to the axial direction of the flat electric wire 2, not only is the overall shape of the flat electric wire 2, that is, the shape of the entire flat electric wire 2 including the conductor 12 and the insulating coating 13, flat, but the conductor 12 itself also has a flat shape. In this embodiment, the overall shape of the flat electric wire 2 and the shape of the conductor 12 are flat as described above throughout the entire region constituting the spiral shape of the flat curl cord 1.

[0021] In the flat wire 2, the conductor 12 The conductor 12 is made of a metal such as copper or a copper alloy, aluminum or an aluminum alloy, and the insulating coating 13 is made of an insulating polymer material or a material containing an additive such as a filler. The conductor 12 may be made of a single wire, but from the viewpoint of improving the formability into a spiral shape and the stretchability of the curl cord, it is preferable to use a conductor 12 made of a twisted wire of multiple wires 11. An example of a flat conductor 12 made of a twisted wire is shown in a perspective view in Figure 2. Note that in each figure, for ease of understanding, the number of wires 11 making up the electric wire conductor 12 is shown to be fewer than that of an actual typical flat electric wire.

[0022] When manufacturing the flat electric wire 2, a plurality of wires 11 are twisted together to have a substantially circular cross section, and then rolled to have a flat cross section, thereby forming the conductor 12. Then, a polymer composition that will become the insulating coating 13 is extruded or the like to form the conductor 12. 12 The flat electric wire 2 can be provided by covering the entire circumference of the flat electric wire 2. The flat electric wire 2 thus obtained can be wound around the outer periphery of a round bar, for example, to form a spiral, thereby producing a curled cord 1. At this time, the flat electric wire 2 is wound around the outer periphery of the round bar so that the flat surface along the width direction x faces the inside and outside of the spiral. 2 The direction is set and the wire is wound into a spiral shape.

[0023] In this embodiment, a multi-core cable including a plurality of insulated wires may be used as the flat wire 2 formed into a spiral shape, and a multi-core curled cord may be formed. However, even in this case, the multi-core cable formed as an assembly including a plurality of insulated wires not only has a flat shape, but also each insulated wire and each conductor body itself The body of the flattened wire 1 has a flat shape, and the width direction x of the flat shape is oriented along the central axis of the spiral. Preferably, from the viewpoint of simplicity of configuration, the flattened wire 1 is formed by winding a single flat electric wire 2, which is formed by covering the outer periphery of a single flat conductor 12 with an insulating coating 13, into a spiral shape by itself, as shown in the figure.

[0024] Furthermore, in the flat curl cord 1, in addition to the above-described components, i.e., the conductor 12 and the insulating coating 13, other components may be provided between or around the components as appropriate. For example, Patent Document 1 describes a steel wire that is plastically deformed into a spiral shape and is integrated with the sheath of an insulated wire processed into a spiral shape. An example of such other components is a configuration in which another wire is disposed around the spirally formed flat electric wire 12. However, from the viewpoint of increasing the diameter and weight of the flat curl cord 1, it is preferable that no components other than the above-described conductor 12 and insulating coating 13 are provided.

[0025] (Details of the flat curl cord shape) Here, we will explain the details of the shape of the flat curl cord 1 and the resulting flat curl cord characteristics, while comparing it with a round curl cord 1'. The round curl cord 1' used for comparison is shown in Figures 3A and 3B. Figure 3A shows a side view of the round curl cord 1', and Figure 3B shows a cross-sectional view of a round electric wire 2' constituting the round curl cord, cut perpendicular to the axial direction. The round curl cord 1' is obtained by winding the round electric wire 2', which has the same conductor cross-sectional area and insulating coating thickness as the flat electric wire 2 and has a substantially circular cross section intersecting the axial direction, in a spiral shape with the same spacing between spiral turns (zero in the illustrated form) and inner diameter (I) as the flat curl cord 1.

[0026] In the flat curl cord 1 according to this embodiment, the flat electric wire 2 is wound in a manner that the flat surface faces the inside and outside of the spiral. Therefore, the length a in the height direction y of the flat electric wire 2 accounts for the radial thickness of the spiral (dimension L in FIG. 1C ). When comparing a round curl cord 1' and a flat curl cord 1 having the same conductor cross-sectional area, the height a of the flat electric wire 2 is smaller than the diameter of the round electric wire 2', so the radial thickness L of the spiral of the flat curl cord 1 is smaller than that of the round curl cord 1'. In this case, if the inner diameter I of the curl cord is the same, the outer diameter P of the flat curl cord 1 can be kept small. FIG. 4C shows a comparison of the outer diameters of the flat curl cord 1 (A) and the round curl cord 1' (B). The outer diameter of the flat curl cord 1 is smaller than that of the round curl cord 1' by a length 2d, where d is the length corresponding to the difference in the widthwise length b between the flat electric wire 2 and the round electric wire 2'. Therefore, when forming a curled cord with the same inner diameter, using the flat electric wire 2 is superior in terms of reducing the diameter of the electric wire.

[0027] In the flat curl cord 1 according to the embodiment of the present disclosure, the flat electric wire 2 is wound in such a way that the flat surfaces face the inside and outside of the spiral. As a result, the width direction x of the flat electric wire 2 faces substantially along the central axis of the spiral, and therefore, in each turn of the spiral, the length of the flat electric wire 2 in the axial direction of the spiral becomes a large dimension corresponding to the width b of the flat shape. Here, if the ratio of the height direction length (a) to the width direction length (b) of the flat surface of the conductor 12 of the flat electric wire 2 is defined as the flattening ratio (a / b), as shown in the examples below, when the flattening ratio is 0.79 or less, the width direction dimension b of the flat electric wire 2 becomes longer than the outer diameter of a round electric wire 2' having the same conductor cross-sectional area and insulating coating thickness, and the length of the flat electric wire 2 in the direction along the central axis of the spiral becomes large. In other words, in a flat curl cord 1 using a flat electric wire 2 with a flattening ratio of 0.79 or less, the length of each turn in the axial direction of the spiral is greater than in the case of a round curl cord 1' using a round electric wire 2' with the same conductor cross-sectional area. Therefore, when forming a curl cord of the same length (natural length), the number of turns can be reduced by using a flat electric wire 2 with a flattening ratio of 0.79 or less compared to when using a round electric wire 2', so the actual length of the electric wire can be shorter and the amount of conductor used can be reduced. The total volume of the insulating coating 13 can also be reduced. As a result, the weight of the curl cord can be reduced.

[0028] In order to further shorten the actual length of the flat electric wire 2 used in the flat curl cord 1 from the viewpoint of enhancing the effect of reducing the amount of conductor used, it is advisable to increase the length of the flat electric wire 2 in the axial direction of the spiral. That is, the length (b) in the width direction x of the flat shape of the flat electric wire 2 should be increased. Also, from the viewpoint of reducing the diameter of the flat curl cord 1, the outer diameter P of the flat curl cord 1 can be further reduced by decreasing the thickness of the spiral in the radial direction. That is, the length (a) in the height direction y of the flat electric wire 2 should be reduced. Here, as described above, when the flattening ratio of the flat electric wire 2 is 0.79 or less, the actual length of the electric wire can be shorter than when a round electric wire 2' is used, and the amount of conductor used can be reduced. However, to further enhance the effect of reducing the amount of conductor used and reducing the diameter, it is advisable to further reduce the flattening ratio from 0.79. For example, it is advisable to set the flattening ratio to 0.5 or less. On the other hand, if the flattening ratio is too small, it becomes difficult to maintain the overall shape of the conductor 12 and the flat electric wire 2. Therefore, from the viewpoint of ensuring durability sufficient for use as a curled cord, it is preferable that the flattening ratio be 0.1 or more.

[0029] When the insulating coating 13 is formed by extrusion, the fact that the cross section of the conductor 12 has a flat shape also has the effect of improving the uniformity of the thickness of the insulating coating 13. 12 The outer periphery of the conductor has a flat surface in the vertical direction. 12 The insulating coating 13 that covers the outer periphery of the wire can be easily formed with a uniform thickness at each part. Covering By increasing the uniformity of the thickness of the insulating coating 13, it is possible to ensure properties such as abrasion resistance even if the entire insulating coating 13 of the flat electric wire 2 is made thin. Therefore, the amount of conductor used can be reduced and the thickness of the insulating coating 13 can be made thinner, which is effective in reducing the weight of the flat curled cord 1.

[0030] As described above, the flat curl cord 1 according to this embodiment has a smaller outer diameter than the round curl cord 1' having the same conductor cross-sectional area and natural length. Furthermore, when the flattening ratio of the flat electric wire 2 of the flat curl cord 1 is 0.79 or less, the amount of conductor used is smaller than that of the round curl cord 1'. Generally, the elasticity of a spring depends on the amount of metal material used and the spiral diameter. However, as confirmed in the examples below, the flat curl cord 1 according to this embodiment can ensure a spring constant that is comparable to or close to that of the round curl cord 1' (e.g., 90% or more). This ensures high spring properties for the flat curl cord 1. Therefore, sufficient restoring force can be obtained during the expansion and contraction of the flat curl cord 1.

[0031] In the flat curl cord 1, the diameter of each wire 11, the overall conductor dimensions of the conductor 12, and the specific shape of the spiral in the flat curl cord 1 may be determined appropriately taking into consideration the required elasticity (springiness) and conductivity, and the following ranges can be given as suitable examples. Diameter of wire 11: 50~250μm Conductor dimensions: 0.80 to 1.13 mm (height direction y length), 2.25 to 3.19 mm (width direction x length) Spiral pitch: 1.12~16.85mm Spiral turn spacing: 0~15mm

[0032] (Wire harness) A wire harness according to an embodiment of the present disclosure will also be briefly described. The wire harness according to this embodiment is configured by appropriately attaching connecting members such as terminals to the flat curled cord 1 according to the embodiment of the present disclosure described above, and / or combining it with other electric wires. Such a wire harness can be suitably routed to moving parts of various devices. Use of the flat curled cord, which achieves a reduced diameter and a reduced amount of conductor used while maintaining spring properties, can also contribute to reducing the weight and diameter of the wire harness. In the automotive field, reducing the weight of components is an important issue, and the wire harness according to this embodiment can be suitably used in automobile sliding doors, rear windows, etc. [Example]

[0033] Examples are shown below, but the present invention is not limited to these examples.

[0034] (1) Evaluation of the thinness of the curled cord <Evaluation method> The outer diameter P shown in Figure 1C was calculated when the flattening ratio of the flat curl cord was changed from 0.1 to 1.0. The outer diameter P of a round curl cord, which has the same conductor cross-sectional area as the flat curl cord, was also calculated using the same method as for the flat curl cord. The flat curl cord samples were designated F1 and F2, and the round curl cord samples were designated R1 and R2. The inner diameter I of samples F1 and F2, and samples R1 and R2, was the same at 3 mm, but the equivalent circular wire diameters of samples F1 and R1 were 1.6 mm, and those of samples F2 and R2 were 3 mm. Here, the equivalent circular diameter refers to the diameter of a circle having the same cross-sectional area as the electric wire of interest; in the case of a round curl cord, it corresponds to the diameter of the cross section itself.

[0035] When calculating the outer diameter P, the widthwise dimension b of the flat electric wire that constitutes the flat curl cord was calculated from the circular equivalent electric wire diameter and the flattening ratio. In the case of a round curl cord, the circular equivalent electric wire diameter itself was used as the widthwise dimension b. Then, the outer diameter P was estimated assuming that a coating with a thickness b was formed on the outer periphery of a cylinder with a given inner diameter I. In other words, P = I + 2b, Curl cord outer diameter P We estimated the following.

[0036] <Result> 5A and 5B are graphs in which the horizontal axis represents the flattening ratio of each sample and the vertical axis represents the calculated outer diameter P. The outer diameter P of the flattened curled cord at each flattening ratio is indicated by a triangle. The outer diameter P of the round curled cord is also indicated by a circle in the figures.

[0037] In both Figures 5A and 5B, the plot points for the flat electric wire are below the outer diameter values ​​for the round electric wire, confirming that the outer diameter P can be reduced by using a flat electric wire instead of a round electric wire in a curl cord. Furthermore, the smaller the flattening ratio (the greater the degree of flattening), the greater the effect of reducing the diameter. For example, in Figure 5A, when comparing the outer diameter P of flat curl cord sample F1 and round curl cord sample R1, when the flattening ratio is 0.1, the outer diameter P of sample F1 is approximately 37% smaller than the outer diameter P of sample R1 (outer diameter reduction rate). Note that in the graph, a flat electric wire with a flattening ratio of 1 indicates a case where the width direction length (b) and height direction length (a) are equal, i.e., a case where the cross section is square. The flattening ratio of the round wire is also 1, but the cross-sectional area of ​​the round wire and the flat wire are the same, and the diameter of a circle with the same area is greater than the length of the side of a square. Therefore, the round wire has a larger diameter than the flat wire with a flattening ratio of 1. diameter P is getting larger.

[0038] Next, let's compare the results in Figures 5A and 5B. The inner diameter I of the curl cords is the same for both, but the cross-sectional area (circular equivalent wire diameter) of the wire used in Figure 5B is larger. When comparing the outer diameter reduction rate from the round curl cords R1 and R2 for the flat curl cord F1 in Figure 5A and the flat curl cord F2 in Figure 5B, with the same flattening ratio, the flat curl cord F2 clearly has a larger outer diameter reduction rate at each flattening ratio. In other words, the larger the cross-sectional area of ​​the wire, the greater the diameter reduction effect when converting a round curl cord into a flat curl cord. For example, when comparing the outer diameter reduction rate for both samples at a flattening ratio of 0.1, sample F1 is 37% and sample F2 is 48%, meaning that sample F2 has a greater outer diameter reduction effect by 11 percentage points.

[0039] (2) Evaluation of conductor usage in curl cords <Evaluation method> To compare the amount of conductor used in flat and round curl cords, we estimated the number of spiral turns for each curl cord formed to the same length. The number of spiral turns is roughly proportional to the conductor length of the flat and round wires used. For samples F1, F2, R1, and R2 used in evaluation (1), we calculated and compared the number of turns for each sample in a curl cord with a total length of 150 mm. If the cross-sectional area of ​​the insulated wire and the inner diameter of the curl cord are the same, the number of spiral turns in the curl cord is roughly proportional to the actual length of the insulated wire that makes up the curl cord and the amount of conductor used. If the turn spacing (the width of the gap between the insulated wires that make up adjacent turns) is set to zero, the number of turns T can be estimated as T = 150 / b, where b is the widthwise dimension of the flat and round wires.

[0040] <Result> Figure 5C is a graph with the flattening ratio of each sample plotted on the horizontal axis and the calculated number of turns plotted on the vertical axis. The number of turns for the flat curl cord F1 at each flattening ratio is indicated by an open triangle, and the number of turns for sample F2 is indicated by a filled triangle. The number of turns for the round curl cord R1 is indicated by an open circle, and the number of turns for sample R2 is indicated by a filled circle.

[0041] In Figure 5C, comparing the number of turns T between flat curl cord F1 and round curl cord R1, and between flat curl cord F2 and round curl cord R2, the plot points for flat electric wires with a flatness ratio of 0.1 to 0.8 are below the number of turns T for round electric wires. This confirms that using a flat electric wire instead of a round electric wire for the curl cord reduces the number of turns. In other words, using a flat electric wire with a flatness ratio of 0.79 or less can reduce the amount of electric wire used. This is because when the flatness ratio is between 0.1 and 0.79 or less, the flat electric wire is longer in the width direction than the round electric wire, and therefore the length along the central axis of the spiral is larger, resulting in a larger length of electric wire occupying each turn. As mentioned above, reducing the number of turns means that the actual length of the electric wire used can be reduced. The results in Figure 5C demonstrate that using a flat curl cord made from a flat electric wire with a flatness ratio of 0.79 or less can reduce the amount of conductor used. When the aspect ratio is 0.79 or less, the smaller the aspect ratio (the greater the degree of flattening) for curl cords F1 and F2, the greater the effect of reducing the number of turns, and therefore the effect of reducing the amount of conductor used. Note that in the area where the aspect ratio is 0.8 or greater but less than 1, the cross-sectional shape of the flattened electric wire, while still long, approaches a square, and the width dimension b is larger than that of the round electric wire, resulting in a greater number of turns than when using a round electric wire. Here, the point at which the number of turns in the flattened curl cord, treated as a flattening ratio of 0.8, reverses that of the round curl cord corresponds to the aspect ratio of a rectangle with the width dimension b equal to the diameter of a circle of the same area; more precisely, it corresponds to the point where the aspect ratio is π / 4 ≒ 0.79.

[0042] Next, samples F1 and F2 are compared. While the inner diameters I of samples F1 and F2 are the same, sample F2 has a larger cross-sectional area (circular equivalent wire diameter) of the wire. Comparing the reduction in the number of turns from round curl cords R1 and R2 for the flat curl cord F1 and flat curl cord F2 in Figure 5C, the reduction in the number of turns remains the same for each flattening ratio. In other words, the reduction in conductor usage when converting a round curl cord into a flat curl cord does not depend on the cross-sectional area of ​​the wire. For example, when comparing the reduction in the number of turns for both samples at a flattening ratio of 0.1, the reduction is 36% for both. The reduction in the number of turns corresponds to the reduction in conductor usage, and it can be said that the reduction in conductor usage when converting a round curl cord into a flat curl cord is achieved regardless of the cross-sectional area of ​​the wire.

[0043] (3) Spring constant <Curled cord production> A round curl cord and a flat curl cord having a conductor with a substantially circular cross section as shown below were prepared, and designated as a round curl cord R3 and a flat curl cord F3, respectively.

[0044] <Round Curl Cord R3> 37 copper alloy wires twisted together, conductor cross section 2mm 2 A conductor wire of this type was prepared. A polyvinyl chloride resin was then extruded around the outer periphery of the obtained conductor to produce a round insulated wire with an insulating coating 0.4 mm thick. Next, the insulated wire was spirally wound around a straight rod with an outer diameter of 7.8 mm, with a turn spacing of 2.6 mm, to produce Sample R3, a round curled cord with a total length of 150 mm.

[0045] <Flat Curl Cord F3> A conductor wire was prepared in the same manner as for the round curl cord, and then rolled using a roller to produce a conductor wire with a flat conductor cross section and a flattening ratio of 0.28. A flat insulated electric wire (flat electric wire) with a 0.4 mm thick insulating coating was produced by extrusion molding around the outer circumference of the obtained conductor in the same manner as for the round curl cord. The flat electric wire was wound around a straight rod with an outer diameter of 7.8 mm, with a turn spacing of 2.6 mm, so that the flat surfaces of the flat electric wire aligned in the width direction of the flat shape faced both the outside and inside of the spiral shape, to produce Sample F3, a flat curl cord with a total length of 150 mm. As shown above, the natural lengths of Samples R3 and F3 were the same.

[0046] <Evaluation method> The flat curl cord F3 and the round curl cord R3 prepared above were fixed at one end and stretched at the other end with a predetermined tension, and the amount of displacement was measured and the relationship between the amount of displacement (mm) and the tension (N) was recorded. The spring constant of the curl cord was evaluated by determining the slope of the recorded graph.

[0047] <Result> Figure 6 shows the tension required to stretch (displace) the curled cords of sample F3 and sample R3 by a given length. The plots for sample F3 and sample R3 can be linearly approximated and are very similar. If the amount of displacement is x (mm), the tension is F (N), and the spring constant is k, Hooke's law gives F = kx, and the spring constant k is calculated as F (N) / x (mm). Then, by linearly approximating each sample and finding the slope, the spring constant k is calculated as 0.029 N / mm for sample F3 and 0.031 N / mm for sample R3. In other words, sample F3 has a spring constant approximately 95% of that of sample R3, indicating that the spring constants of both samples are comparable. Sample F3 has a flattened conductor, and while its total conductor volume is smaller than that of sample R3, which is made up of round wires with the same conductor cross-sectional area, the conductor cross-sectional area and natural length are consistent. Therefore, even if the total amount of conductor is small, it can be said that equivalent spring properties can be obtained as long as the conductor cross-sectional area and natural length are consistent.

[0048] As shown by the above results, a flat curl cord in which a flat electric wire is used as a curl cord has the same spring properties as a round curl cord with the same conductor cross-sectional area, while being able to achieve a thinner diameter by reducing the outer diameter. In particular, by reducing the flattening ratio of the conductor and increasing the degree of flattening, the effect of reducing the diameter becomes greater, and this effect becomes more pronounced as the conductor cross-sectional area becomes larger.

[0049] 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]

[0050] 1 Flat curled cord 1' round curl cord 2. Insulated wire (flat wire) 2' insulated wire (round wire) 11 Wire 12 Conductors 13 Insulation coating a Height b Width P outer diameter I Inner diameter L Radial thickness of the spiral

Claims

1. an insulated wire including a conductor and an insulating coating covering the outer periphery of the conductor, the insulated wire being wound in a spiral shape; The insulated wire is a flat wire in which the cross-sectional shapes of the conductor and the insulated wire along the axial direction are flat, a flat curled cord in which a flat surface, which is an outer surface of the flat electric wire along the width direction of the flat shape, faces outward and inward of the spiral shape, A round electric wire having the same conductor cross-sectional area and insulating coating thickness as the flat electric wire and a circular cross section intersecting the axial direction is wound in a spiral shape with the same spacing between spiral turns, inner diameter, and natural length as the flat curl cord, to form a round curl cord. the spring constant of the flat curl cord is 90% or more of the spring constant of the round curl cord; A flat curled cord in which the turn spacing, defined as the width of the gap between the insulated wires constituting adjacent turns in the spiral shape, is zero.

2. 2. The flat curl cord according to claim 1, wherein a flattening ratio, which represents a ratio of a length in a height direction to a length in a width direction of the flat shape, is 0.79 or less, for an entire shape of the flat electric wire, where a direction intersecting the width direction of the flat shape is a height direction.

3. The flattened curled cord according to claim 2, wherein the flattening ratio is 0.5 or less.

4. 2. The flat curl cord according to claim 1, wherein the conductor is made of a stranded wire formed by twisting together a plurality of wires.

5. 2. The flat curl cord according to claim 1, wherein the outer diameter of the spiral shape of the flat curl cord is 90% or less of the outer diameter of the spiral shape of the round curl cord.

6. 2. The flat curled cord according to claim 1, wherein the cross section of the flat electric wire is approximately rectangular.

7. 7. The flat curl cord according to claim 6, wherein the flat electric wire is formed by twisting a plurality of wires together into a circular cross section, rolling the twisted wire into a flat cross section, and providing the insulating coating on the entire circumference.

8. A wire harness comprising the flat curled cord according to any one of claims 1 to 7.

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