Electric wire conductor, insulated electric wire, and wire harness

Abstract

Provided are: an electric wire conductor in which a stranded wire obtained by twisting together element wires is formed into a flat shape, and which can suppress increase in resistance caused by reducing the twist pitch; and an insulated electric wire and a wire harness provided with such an electric wire conductor.　A wire conductor 1 is configured as a stranded wire including a lower twisted layer 10 in which a plurality of child stranded wires 2 obtained by twisting together a plurality of element wires 3 are bundled and twisted together, and an upper twisted layer 20 in which a plurality of child twisted wires 2 are twisted around the outer periphery of the lower twisted layer 10, wherein: a cross section orthogonal to the axial direction of the stranded wire has a flat portion having a flat shape of which a dimension w in a width direction is larger than a dimension h in a height direction; and the flat portion satisfies (0.2a+b+0.5) / c ≤ 1, wherein a (mm) is the twist pitch of the element wires 3 in the child stranded wires 2, b (mm) is the twist pitch of the child stranded wires 2 in the lower twisted layer 10, and c (mm) is the twist pitch of the child stranded wires 2 in the upper twisted layer 20.

Description

Wire conductors, insulated wires, and wiring harnesses

[0001] The present disclosure relates to an electrical wire conductor, an insulated wire, and a wiring harness.

[0002] A flat cable made of a flat conductor is known, and the use of the flat cable can reduce the space occupied when routing the cable compared to a typical electric wire having a conductor with a substantially circular cross section.

[0003] In conventional general flat cables, rectangular conductors are often used as the electric wire conductor, as disclosed in Patent Documents 1 and 2. A rectangular conductor is a metal solid wire formed into a rectangular cross section. In addition, Patent Documents 3 to 5 filed by the applicant disclose electric wire conductors in which a stranded wire made by twisting together multiple elemental wires is formed into a flat shape from the viewpoint of achieving both flexibility and space saving.

[0004] JP 2014-130739 A JP 2019-149242 A International Publication No. 2019 / 093309 International Publication No. 2019 / 177016 JP 2022-058941 A

[0005] As disclosed in Patent Documents 3 to 5, the use of electric wire conductors in which stranded wires are formed into a flat shape can achieve space savings while maintaining flexibility. However, as currents become larger, electric wire conductors with larger conductor cross-sectional areas are being used. Even in electric wire conductors made of stranded wires formed into a flat shape, the larger the conductor cross-sectional area, the more difficult it becomes to ensure sufficient flexibility for installation. One method for increasing the flexibility of electric wire conductors with large conductor cross-sectional areas is to reduce the twist pitch used to twist the element wires. However, reducing the twist pitch of the element wires in an electric wire conductor increases the actual length of the element wires constituting a given length of the electric wire conductor, resulting in increased conductor resistance. Furthermore, when an electric wire conductor with a reduced twist pitch is formed into a flat shape, the element wires are densely packed, which significantly deforms the element wires during forming. This easily leads to increased conductor resistance due to work hardening, a reduction in cross-sectional area, and the like. In this way, if the twist pitch of the wires is reduced to increase the flexibility of the flat conductor, the conductor resistance may increase due to two factors: an increase in the actual length of the wires and the progression of deformation of the wires. As a result, the cross-sectional area of ​​the conductor required to ensure the desired conductivity increases, which hinders efforts to reduce the space required for the conductor.

[0006] Therefore, an object of the present invention is to provide an electric wire conductor in which a stranded wire made by twisting element wires together is formed into a flat shape, and which can minimize the increase in resistance that occurs when the twist pitch is reduced, and also to provide an insulated electric wire and a wire harness that include such an electric wire conductor.

[0007] The electric conductor of the present disclosure is configured as a twisted wire having a first twisted layer in which child twisted wires, each formed by twisting together a plurality of strands of wire, are bundled together, and a top twisted layer in which a plurality of the child twisted wires are twisted around the outer periphery of the first twisted layer, and the cross section of the twisted wire perpendicular to the axial direction has a flat portion having a flat shape in which the width dimension is greater than the height dimension, and in the flat portion, where a (mm) is the twist pitch of the strands of wires in the child twisted wire, b (mm) is the twist pitch of the child twisted wires in the first twisted layer, and c (mm) is the twist pitch of the child twisted wires in the top twisted layer, the relationship (0.2a + b + 0.5) / c≦1 is satisfied.

[0008] The insulated wire of the present disclosure includes the conductor and an insulating coating that covers the outer periphery of the conductor. The wire harness of the present disclosure includes the insulated wire.

[0009] The electric wire conductor of the present disclosure is an electric wire conductor formed by twisting together element wires and shaping the twisted wire into a flat shape, and can minimize an increase in resistance caused by a small twist pitch. Furthermore, an insulated electric wire and a wire harness of the present disclosure include such an electric wire conductor.

[0010] FIG. 1 is a cross-sectional view schematically illustrating an electric wire conductor according to one embodiment of the present disclosure. The individual strands constituting the child strand are omitted from the main diagram, and the enlarged view enclosed by a rectangle illustrates a cross section of the child strand including the strands. FIG. 2A is a diagram showing the relationship between the child twist pitch a and the difference (c-b) between the primary twist pitch b and the final twist pitch c. Data points with a resistance increase rate of less than 10% are indicated by solid figures, and data points with a resistance increase rate of 10% or more are indicated by open figures. FIG. 2B shows the relationship between (0.2a + b + 0.5) / c and the resistance increase rate.

[0011] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be described below. [1] An electric conductor according to the present disclosure is configured as a stranded wire having a first twist layer in which child strands each formed by twisting together a plurality of strands of elemental wires are bundled together, and a final twist layer in which the plurality of child strands are twisted around the outer periphery of the first twist layer, wherein a cross section of the stranded wire perpendicular to the axial direction has a flat portion having a flat shape in which the width dimension is greater than the height dimension, and the flat portion satisfies (0.2a + b + 0.5) / c≦1, where a (mm) is the twist pitch of the elemental wires in the child strand, b (mm) is the twist pitch of the child strands in the first twist layer, and c (mm) is the twist pitch of the child strands in the final twist layer.

[0012] In the flattened portion of the conductor, the three twist pitches, i.e., the twist pitch a of the child strands in the child strand, the twist pitch b of the child strands in the lower twist layer, and the twist pitch c of the child strands in the upper twist layer, satisfy the relationship (0.2a + b + 0.5) / c ≦ 1. As shown in the examples below, this relationship is defined as a range in which the increase in resistance due to flattening of the conductor is sufficiently suppressed. This indicates that if the twist pitch c of the child strands in the upper twist layer (upper twist pitch) is sufficiently larger than the twist pitch b of the child strands in the lower twist layer (lower twist pitch) and the twist pitch a of the child strands in the child strand, particularly compared with the lower twist pitch b, the increase in conductor resistance due to deformation of the wires due to forming the conductor into a flat shape can be suppressed. Furthermore, by increasing the twist pitch c of the upper twist layer, through which the child strands pass at the outermost part of the conductor, the actual length of the wires constituting the conductor can be reduced, thereby suppressing conductor resistance. In other words, by setting the three twist pitches a, b, and c so as to satisfy the above-mentioned relational expressions, it is possible to suppress deformation of the element wires due to flattening of the conductor and to reduce the actual length of the element wires constituting the conductor, thereby reducing the conductor resistance of the flattened conductor. When the twist pitches a, b, and c are set as small as possible to increase the flexibility of the conductor, for example, when the conductor cross-sectional area of ​​the conductor is increased, it is possible to achieve both high flexibility and reduced conductor resistance in the conductor.

[0013] [2] In the above aspect [1], it is preferable that the shape of at least some of the strands constituting the conductor be deformed from a circular shape in the cross section. The deformation of the strands indicates that the flat conductor is formed by rolling a raw conductor having a substantially circular cross section. Even if the strands are deformed by rolling, an increase in the conductor resistance due to the deformation of the strands can be kept small by selecting the twist pitches a, b, and c so as to satisfy the above-mentioned relational expressions.

[0014] [3] In the above aspect [1] or [2], the conductor may be manufactured by rolling a raw conductor made of a stranded wire with a circular cross section, and the increase rate of the conductor resistance of the flat portion relative to the raw conductor may be suppressed to less than 10%. In the insulated wire according to the embodiment of the present disclosure, when the three twist pitches a, b, and c satisfy the relationship (0.2a + b + 0.5) / c ≦ 1, deformation of the strands due to rolling can be suppressed to a minimum when the raw conductor is rolled into a flat shape. As a result, the increase in conductor resistance due to work hardening of the strands and reduction in cross-sectional area can be suppressed to a minimum. In fact, as shown in the examples below, by satisfying the above relationship, the increase rate of conductor resistance due to rolling can be suppressed to less than 10%. As a result, a flat-shaped conductor can be obtained that has high space-saving properties and flexibility without an excessive increase in conductor resistance compared to the state before being flattened. The fact that the conductor is manufactured by rolling a raw conductor is indicated by the fact that the cross-sectional shape of at least a portion of each of the child strands and each of the strands constituting the conductor is deformed from a circular shape, and is further indicated by the fact that the deformation rate of the child strands and strands from a circular shape is smaller in the top twist layer than in the bottom twist layer.

[0015] [4] In any one of the above aspects [1] to [3], the flattening ratio, which indicates the ratio of the width dimension of the flattened portion to the height dimension, may be 3 or greater. As the flattening ratio increases, the conductor resistance of the wire conductor tends to increase due to deformation of the strands during flattening. However, in the insulated wire according to the embodiment of the present disclosure, by having the three twist pitches a, b, and c satisfy the relationship (0.2a + b + 0.5) / c≦1, deformation of the strands during flattening can be minimized even when the wire conductor is formed into a flat shape with a flattening ratio of 3 or greater. As a result, increases in conductor resistance due to work hardening of the strands, reduction in cross-sectional area, and the like can be minimized. Increasing the flattening ratio of the wire conductor improves the space-saving properties of the wire conductor.

[0016] [5] In any one of the above [1] to [4], the conductor cross-sectional area of ​​the electric wire conductor is 16 mm ２Preferably, the twist pitch a of the strands of the child strands is 10 mm or more, and the twist pitch c of the child strands of the upper twist layer is 70 mm or more. ２ In the above cases, by setting the child twist pitch a and the final twist pitch c to be sufficiently large as described above, it becomes easier to keep the increase in conductor resistance small.

[0017] [6] In any one of the above aspects [1] to [5], the wires may be made of aluminum or an aluminum alloy. Wires made of aluminum or an aluminum alloy are less likely to provide electrical continuity between the wires in the conductor due to the influence of an oxide film on their surfaces. Therefore, the conductor resistance of the entire conductor tends to increase when the actual length of the wires constituting the conductor increases. However, in the conductor according to the embodiment of the present disclosure, the twist pitches a, b, and c are set so as to satisfy the relationship (0.2a + b + 0.5) / c≦1, thereby effectively suppressing the increase in conductor resistance.

[0018] [7] An insulated wire according to the present disclosure includes the conductor according to any one of [1] to [6] above and an insulating coating covering the outer periphery of the conductor. The insulated wire includes the conductor in which the three twist pitches a, b, and c satisfy a predetermined relationship, thereby minimizing the increase in resistance. Therefore, the suppression of the increase in resistance in the conductor can be utilized as a characteristic of the insulated wire.

[0019] [8] A wire harness according to the present disclosure includes the insulated wire according to [7]. The wire harness as a whole can also enjoy the effect of suppressing an increase in resistance in the wire conductor.

[0020] [Details of Embodiments of the Present Disclosure] Hereinafter, electric conductors, insulated wires, and wire harnesses according to embodiments of the present disclosure will be described in detail with reference to the drawings. In this specification, with respect to the structure of each part of an electric conductor, concepts indicating the shape or arrangement of components, such as straight, parallel, perpendicular, circular, circumferential, etc., include errors from the geometric concepts within the range allowable for this type of electric conductor, such as deviations of approximately ±15% in length and approximately ±15° in angle. In this specification, unless otherwise specified, the cross section of an electric conductor refers to a cross section cut perpendicular to the axial direction (longitudinal direction).

[0021] <Configuration of Electric Conductor, Insulated Wire, and Wire Harness> Fig. 1 is a schematic cross-sectional view of an electric conductor 1 according to an embodiment of the present disclosure. The electric conductor 1 includes a plurality of elemental wires 3, and is configured as a stranded wire in which the plurality of elemental wires 3 are twisted together.

[0022] The electric wire conductor 1 has a flat outer shape in at least a partial region along the axial direction. That is, the electric wire conductor 1 has a flat portion in which a cross section perpendicular to the axial direction of the electric wire conductor 1 has a flat shape in at least a partial region along the axial direction. In this embodiment, a form in which the entire axial area of ​​the electric wire conductor 1 has such a flat portion is discussed. Here, the cross section of the electric wire conductor 1 having a flat shape refers to a state in which the width w, which is the dimension of the longest straight line among straight lines that cross the cross section parallel to the sides constituting the cross section and include the entire cross section, is larger than the height h, which is the dimension of the straight line that is perpendicular to the longest straight line and includes the entire cross section.

[0023] The cross section of the electric wire conductor 1 may have any specific shape as long as it has a flat shape. Examples of flat shapes include a rectangle, an ellipse, an oval, an oval (a shape of 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 electric wire conductor 1 can be considered to have each of these shapes. Of the listed shapes, it is preferable to adopt one of a rectangle, an ellipse, an oval, and an oval. In the embodiment shown in FIG. 1 , the electric wire conductor 1 has a cross section that can approximate an oval.

[0024] In the electric conductor 1, not all of the wires 3 are twisted together, but the wires 3 are divided into a plurality of child strands 2 to form the electric conductor 1. The plurality of child strands 2 also form two parent twist layers: a lower twist layer 10 and a final twist layer 20. In other words, the child strand 2 is formed by twisting a plurality of wires 3 together. The child strand 2 is then formed by twisting a plurality of child strands 2 together in a bundle to form the lower twist layer 10. Furthermore, the final twist layer 20 is formed around the outer periphery of the lower twist layer 10. The final twist layer 20 is formed by twisting a plurality of child strands 2 coaxially around the outer periphery of the lower twist layer 10. In the main diagram of Figure 1, the cross section of each child strand 2 is simplified and shown by a solid circle (child strand 2 constituting the upper twist layer 20) and a dashed circle (child strand 2 constituting the lower twist layer 10), and the enlarged view enclosed in a rectangle illustrates the structure of a child strand 2 including multiple wires 3.

[0025] In the electric wire conductor 1 according to this embodiment, as will be described in detail later, the twist pitch a of the wires 3 in the child strand 2, the twist pitch b of the child strands 2 in the lower twist layer 10, and the twist pitch c of the child strands 2 in the upper twist layer 20 are set to satisfy a predetermined relationship. By ensuring that the twist pitches a, b, and c satisfy the predetermined relationship, it is possible to suppress an increase in the conductor resistance in the electric wire conductor 1 due to an increase in the actual length of the wires 3 constituting the electric wire conductor 1 and an increase in resistance due to deformation of the wires 3 during flattening.

[0026] The electric wire conductor 1 can be formed by rolling a raw conductor made of a stranded wire having a substantially circular cross section. The raw conductor may be formed by twisting together a plurality of strands 3 each having a substantially circular cross section to form a child strand 2 having a substantially circular cross section, and then using the child strands 2 to form a lower twist layer 10 and a top twist layer 20, respectively, to form a conductor wire having a substantially circular cross section. As the raw conductor is formed into a flat shape, at least a portion of each child strand 2 and at least a portion of each strand 3 constituting the electric wire conductor 1 may be deformed from their circular cross section. The deformation rate of the child strands 2 and the strands 3 from circularity is often smaller in the outer periphery of the cross section of the electric wire conductor 1, i.e., the top twist layer 20, than in the inner portion, i.e., the bottom twist layer 10. The deformation rate of the child strands 2 and the strands 3 is particularly likely to be small at both widthwise ends of the outer periphery and in the vicinity thereof.

[0027] The electric wire including the electric wire conductor 1 according to this embodiment has a flat cross section, which allows it to reduce the space required for routing compared to an electric wire having a conductor wire with the same conductor cross section but a substantially circular cross section. In other words, the space around a certain electric wire where other electric wires or other components cannot be arranged can be reduced. In particular, the space occupied by the electric wire in the height direction can be reduced, making it easier to achieve space saving. Furthermore, since the electric wire conductor 1 is made of a stranded wire in which multiple element wires 3 are twisted together, it has high flexibility. The electric wire conductor 1 exhibits high flexibility, especially in the height direction. Thus, since the electric wire conductor 1 is made of a stranded wire and has a flat shape, the electric wire achieves both high space saving and flexibility. Because an insulated electric wire and a wire harness including the electric wire conductor 1 combine high space saving and flexibility, they are particularly suitable for applications requiring routing in narrow spaces or complex paths, such as inside an automobile.

[0028] From the viewpoint of particularly enhancing space-saving performance in the height direction and enhancing the effect of suppressing an increase in conductor resistance due to flattening by the relationship between the three twist pitches a, b, and c, as will be described later, it is preferable that the width w of the cross section of the conductor 1 is three times or more the height h. In other words, it is preferable that the flattening ratio (w / h) is 3 or more. It is more preferable that the flattening ratio is 5 or more. Although there is no particular upper limit set for the flattening ratio of the conductor 1, it is preferable to keep it at about 10 or less from the viewpoint of avoiding application of excessive load to the conductor 1 when it is formed into a flat shape.

[0029] The conductor cross-sectional area of ​​the electric wire conductor 1 is not particularly limited, but the larger the conductor cross-sectional area, the greater the effect of flattening the electric wire conductor 1 and improving space saving. Also, the larger the conductor cross-sectional area, the more likely it is that the twist pitch will be set small from the viewpoint of ensuring flexibility. However, as will be described later, by maintaining a predetermined relationship between the twist pitches a, b, and c, it is possible to suppress an increase in conductor resistance due to a small twist pitch. From these viewpoints, for example, when the conductor cross-sectional area is set to 2 mm ２Although there is no particular upper limit to the conductor cross-sectional area, it is preferable to set it to, for example, 200 mm ２ It is best to keep it below this.

[0030] The material constituting the wires 3 of the electric conductor 1 is not particularly limited, and various metal materials can be used. Typical metal materials constituting the wires 3 include copper and copper alloys (copper-based metals), and aluminum and aluminum alloys (aluminum-based metals). Aluminum-based metals, in particular, have lower electrical conductivity than copper-based metals, so the conductor cross-sectional area is often set larger to ensure the necessary electrical conductivity. As described above, the larger the conductor cross-sectional area, the greater the effect of flattening the electric conductor 1 and of setting the twist pitches a, b, and c to satisfy a predetermined relationship. Furthermore, since the wires 3 made of aluminum-based metals have an oxide film on their surfaces, electrical continuity between the wires in the electric conductor 1 is reduced. Therefore, if the path through which the wires 3 constituting the outermost strands 2 of the electric conductor 1 pass is long, the influence of the outermost wires 3 tends to increase the conductor resistance of the electric conductor 1 as a whole. Due to these factors, electric conductors using wires made of aluminum-based alloys are prone to increase in conductor resistance. However, by setting the twist pitches a, b, and c so as to satisfy a predetermined relationship, it is possible to effectively suppress the increase in conductor resistance due to these factors.

[0031] The outer diameter of the wires 3 constituting the conductor 1 is not particularly limited, but can be in the range of 0.18 mm or more and 2 mm or less. The number of wires 3 constituting one child strand 2 is also not particularly limited, but can be in the range of 2 or more and 230 or less. In this embodiment, the child strands 2 constituting the lower twist layer 10 and the upper twist layer 20 have the same configuration. That is, the material, outer diameter, number, and twist pitch (c) of the wires 3 constituting the child strands 2 are the same for all child strands 2 included in the conductor 1. The specific number of child strands 2 constituting the lower twist layer 10 and the upper twist layer 20 is not particularly limited, but can be in the range of 2 or more and 7 or less for the lower twist layer 10 and 6 or more and 12 or less for the upper twist layer 20.

[0032] An insulated wire according to one embodiment of the present disclosure includes a conductor 1 and an insulating coating (not shown). The insulating coating covers the entire outer periphery of the conductor 1. The material constituting the insulating coating is not particularly limited as long as it is an insulating material, but it is preferable that the insulating coating be based on an organic polymer. Examples of organic polymers include olefin-based polymers such as polyolefins and olefin-based copolymers, halogen-based polymers such as polyvinyl chloride, various elastomers, rubber, etc. The organic polymer may be crosslinked or foamed. Furthermore, the insulating coating may contain various additives such as a flame retardant in addition to the organic polymer. The insulating coating is preferably formed as an extrusion molded body.

[0033] The insulated electric wire according to the embodiment of the present disclosure 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 insulated electric wire according to the embodiment of the present disclosure. The wire harness may include a plurality of insulated electric wires according to the embodiment of the present disclosure, or may include other types of insulated electric wires in addition to the insulated electric wire according to the embodiment of the present disclosure. Preferably, a plurality of insulated electric wires according to the embodiment of the present disclosure are arranged in the width direction and / or the height direction. In this case, the specific arrangement structure of the plurality of insulated electric wires is not particularly limited, but a preferred embodiment is one in which the plurality of insulated electric wires 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 insulated electric wires are uniform. The insulated electric wires and wire harness according to the embodiment of the present disclosure are not particularly limited in their applications, but they can be particularly suitable for use as wiring materials in automobiles where electric wires must be routed in a limited space.

[0034] <Twist Pitch of Electrical Wire Conductor> The electrical wire conductor 1 according to the embodiment of the present disclosure has a structure in which a plurality of elemental wires 3 are twisted together to form a child strand 2, and a plurality of elemental wires 2 are further used to form a lower twist layer 10 and a upper twist layer 20, and therefore has the following three twist pitches: Child twist pitch: The twist pitch of the elemental wires 3 in the child strand 2 minus a (mm). Lower twist pitch: The twist pitch of the child strands 2 in the lower twist layer 10 minus b (mm). Upper twist pitch: The twist pitch of the child strands 2 in the upper twist layer 20 minus c (mm).

[0035] In the electric wire conductor 1 according to the embodiment of the present disclosure, the three pitches a, b, and c satisfy the following formula (1): (0.2a+b+0.5) / c≦1 (1) By setting the three twist pitches a, b, and c so as to satisfy formula (1), it is possible to minimize an increase in resistance in the electric wire conductor 1 having a flat shape. The reason for this is as follows.

[0036] As will be shown in the examples below, by setting three twist pitches so as to satisfy formula (1), it is possible to minimize the increase in conductor resistance associated with deformation of the strands 3 during flattening when the raw conductor is formed into a flat shape to obtain the electric wire conductor 1. Formula (1) indicates that if the top twist pitch c is sufficiently larger than the bottom twist pitch b and the child twist pitch a, especially the bottom twist pitch b, the increase in conductor resistance associated with flattening can be minimized in the electric wire conductor 1. In other words, it is possible to minimize the rate of increase in conductor resistance associated with flattening, based on the conductor resistance of the raw conductor.

[0037] Here, formula (1) can also be expressed as formula (1') below: c - b ≥ 0.2a + 0.5 (1') Formula (1') indicates that the final twist pitch c should be set large enough relative to the final twist pitch b. If the difference between the final twist pitch c and the final twist pitch b is small, when the raw conductor is flattened by rolling or other means to obtain the electric wire conductor 1, the strands 3 constituting the final twist layer 10 are constrained by the final twist layer 20, making them susceptible to large loads during forming. Furthermore, deformation in which the final twist layer 10 pushes up the final twist layer 20 occurs, making it difficult to stably form and maintain the flat shape of the electric wire conductor 1. In contrast, if there is a sufficient difference between the final twist pitch c and the final twist pitch b, the child strands 2 constituting the final twist layer 20 can move more easily during flattening, making it less likely that the final twist layer 10 will be subjected to excessive loads or deformation due to the constraints of the final twist layer 20. This minimizes deformation of the strands 3 associated with flattening. As a result, the flat shape of the conductor 1 can be stably formed and maintained, and an increase in resistance due to work hardening, a reduction in cross-sectional area, etc., associated with deformation of the wires 3 can be suppressed. In fact, in the examples, formula (1') is determined as a range in which an increase in resistance can be sufficiently suppressed.

[0038] In order to reduce the value of the left side of Equation (1) and make it easier to satisfy Equation (1), increasing the final twist pitch c is the most effective way. In other words, even if the child twist pitch a and the primary twist pitch b are relatively large, Equation (1) can be satisfied as long as the final twist pitch c is sufficiently large. Increasing the final twist pitch c means that the final twist layer 20 constituting the outer periphery of the conductor 1 can move with a high degree of freedom when the raw conductor is flattened to form the conductor 1. This makes it easier to minimize the load and deformation of the strands 3 associated with flattening, as well as the resulting increase in resistance, for the conductor 1 as a whole by utilizing the movement of the final twist layer 20. Furthermore, because the stranded structure of the final twist layer 20 is formed by the child strands 2 passing through the outermost periphery of the conductor 1, the length of the child strands 2 constituting the final twist layer 20 and the actual length of the strands 3 constituting those child strands 2 tend to be long. Therefore, by making the upper twist pitch c larger than the child twist pitch a and the lower twist pitch b and keeping the actual length of the wires 3 that make up the child twisted wire 2 of the upper twist layer 20 short, the effect of keeping the conductor resistance of the electric wire conductor 1 small can be achieved.

[0039] In this way, by determining the child twist pitch a, the first twist pitch b, and the top twist pitch c so as to satisfy the relationship of Equation (1), the conductor resistance of the flattened electric wire conductor 1 can be reduced by both suppressing the increase in resistance due to deformation of the wires 3 when formed into a flat shape and suppressing the actual length of the wires 3 that make up the electric wire conductor 1. In fact, as confirmed in the examples, by satisfying Equation (1), the rate of increase in conductor resistance due to flattening can be reduced to less than 10%. It is more preferable to suppress the rate of increase in conductor resistance to less than 8%, and even more preferably less than 7%. Here, the rate of increase in conductor resistance can be determined based on the conductor resistance of a raw conductor or a reference conductor. The reference conductor refers to a twisted wire whose wire materials and outer diameters, the number of wires constituting the child strands, and the number of child strands constituting the lower and upper twist layers are the same as those of the electric wire conductor 1, whose cross-sectional shape is circular, and whose centers of the child strands constituting the upper twist layer are located on the circumference in a cross section perpendicular to the axial direction (i.e., the cross-sectional shape of the reference conductor as a whole is approximately circular). The twist pitches a, b, and c in the reference conductor may be each 10 mm larger than those in the electric wire conductor 1. Although the reference conductor itself is a virtual conductor wire, it can be associated with the raw conductor used as a raw material when actually manufacturing the electric wire conductor 1 by flattening. The conductor resistances of the flat portion of the electric wire conductor 1, the raw conductor, and the reference conductor are measured in sections of the same length, and the rate of increase in the conductor resistance (R1) of the flat portion is evaluated using the conductor resistance (R0) of the raw conductor or reference conductor as a reference ((R1 - R0) / R0 × 100%). The reason why the twist pitches a, b, and c of the reference conductor are each 10 mm larger than those of the conductor 1 is that the twist pitch decreases as the raw conductor is rolled. The actual change in the twist pitches a, b, and c due to rolling is 10 mm or less.

[0040] As shown in formula (1), if the value of (0.2a+b+0.5) / c is 1 or less (1.0 or less), the increase in resistance of the electric conductor 1 can be kept sufficiently small, but if the value is 0.8 or less, or even 0.7 or less, it becomes easier to keep the increase in resistance of the electric conductor 1 small. On the other hand, there is no particular lower limit set for the value of (0.2a+b+0.5) / c, and it may be set small within a range not subject to constraints of manufacturing equipment and materials, but it is preferable to set it to about 0.1 or more.

[0041] As long as the relationship of formula (1) is satisfied, the ranges of the three twist pitches a, b, and c are not particularly specified, and may be appropriately selected within a range that is not restricted by manufacturing equipment or materials, depending on parameters such as the outer diameter of the wire 3 and the conductor cross-sectional area of ​​the electric wire conductor 1. For example, when the conductor cross-sectional area is 16 mm, ２ In this case, the three twist pitches a, b, and c can be determined so that formula (1) holds, with the child twist pitch a set to 10 mm or more and the final twist pitch c set to 70 mm or more. By setting the child twist pitch a and final twist pitch c to be sufficiently large as described above, it is easy to minimize increases in conductor resistance due to two factors: an increase in the actual length of the strands 3 constituting the electric wire conductor 1 and deformation of the strands 3 due to forming into a flat shape, even when the conductor cross-sectional area is increased. In particular, by setting the final twist pitch c to 70 mm or more, formula (1) can be satisfied and increases in conductor resistance can be minimized, even when the final twist pitch b is relatively large. Furthermore, the magnitude relationship between the three twist pitches a, b, and c should be a < b < c.

[0042] Examples are shown below. However, the present invention is not limited to these examples. Here, we investigated the influence of the relationship between three types of twist pitch on the increase in conductor resistance in a flat conductor. Samples were prepared and evaluated at room temperature in the atmosphere.

[0043] (Sample Preparation) First, a raw conductor was prepared. Specifically, multiple aluminum alloy wires with an outer diameter of 0.3 mm were twisted together to form a child strand. These child strands were bundled and twisted together to form a primary twist layer. A child strand was then placed around the outer periphery of the primary twist layer and twisted coaxially with the primary twist layer to form a top twist layer, resulting in a raw conductor with a substantially circular cross section. As shown in Table 2 below, multiple samples of the raw conductor were prepared with different conductor cross-sectional areas, child twist pitches a, b, and c. The conductor cross-sectional area was varied by changing the number of wires constituting the child strand and the number of child strands constituting the primary and top twist layers. Specifically, each parameter was determined as shown in Table 1 below. The conductor cross-sectional area is expressed as a nominal cross-sectional area. When the primary twist layer contained seven child strands, six child strands were twisted around one central child strand to form the primary twist layer.

[0044] The raw conductor samples obtained above were flattened by rolling with rollers to produce flat conductor wires. The flatness ratio of the conductor wires was controlled by the magnitude of the force applied to the raw conductor wires by the rollers. Note that, although the pitches a, b, and c were reduced by flattening, the change in each pitch was 10 mm or less.

[0045] (Evaluation of Conductor Resistance Increase Rate) For each sample of electric wire conductor, the conductor resistance was measured for the raw conductor before flattening and for the state after flattening. Then, the conductor resistance before flattening (R0) was used as a reference, and the increase rate of the conductor resistance after flattening (R1) was calculated ((R1-R0) / R0 x 100%). The conductor resistance was measured using a resistance meter by the four-terminal method for sections of the same length (1 m) of the raw conductor and the flattened electric wire conductor.

[0046] (Evaluation Results) For each sample, the conductor cross-sectional area, flattening ratio, ply twist pitch a, primary twist pitch b, and final twist pitch c are shown, along with the evaluation results of the rate of increase in conductor resistance due to flattening. The table also shows the calculated values ​​of c-b and (0.2a+b+0.5) / c.

[0047]

[0048] Figure 2A shows the relationship between the ply twist pitch a and the difference c-b between the top twist pitch and the primary twist pitch, based on the data in Table 2 above. In the figure, data points for which the conductor resistance increase rate was less than 10% are shown as solid black figures, and data points for which the conductor resistance increase rate was 10% or more are shown as open figures. Furthermore, as indicated in the legend, data points are displayed as different figures for each conductor cross-sectional area.

[0049] According to Figure 2A, data points with a conductor resistance increase rate of less than 10%, represented by solid black shapes, are distributed in the upper part of the figure, i.e., the region where c - b is large, and data points with a conductor resistance increase rate of less than 10%, represented by open shapes, are distributed in the lower part of the graph, i.e., the region where c - b is small. A boundary can be set to separate these two types of data points, as shown by the dashed line in the figure. This boundary line can be expressed by the formula c - b = 0.2a + 0.5. For data points above this line, i.e., in the region where c - b ≥ 0.2a + 0.5, the conductor resistance increase rate is suppressed to less than 10%.

[0050] In Figure 2A above, c-b≧0.2a+0.5 is obtained as the equation showing the region in which the rate of increase in conductor resistance is kept below 10%, but by rearranging this, we obtain (0.2a+b+0.5) / c≦1. The value of (0.2a+b+0.5) / c, which is the left-hand side of this equation, is shown in Table 2. The relationship between the value of (0.2a+b+0.5) / c and the measured value of the rate of increase in conductor resistance is shown in Figure 2B.

[0051] 2B, it can be seen that the rate of increase in conductor resistance generally tends to increase as (0.2a + b + 0.5) / c increases. It can also be seen that the rate of increase in conductor resistance is less than 10% in the region where (0.2a + b + 0.5) / c≦1.0. From these results, it can be said that the increase in conductor resistance due to flattening can be kept small by setting the ply twist pitch a, the primary twist pitch b, and the final twist pitch c so that (0.2a + b + 0.5) / c is a sufficiently small value, such as 1.0 or less.

[0052] 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.

[0053] 1 Electrical conductor 2 Child strand 3 Wire 10 Lower twist layer 20 Upper twist layer h Height of electrical conductor w Width of electrical conductor

Claims

1. An electric wire conductor in which a child strand formed by twisting together a plurality of strands is configured as a stranded wire having a lower twist layer in which a plurality of strands are twisted together in a bundle, and a top twist layer in which a plurality of the child strands are twisted around the outer periphery of the lower twist layer, wherein a cross section of the twisted wire perpendicular to the axial direction has a flat portion in which the width dimension is greater than the height dimension, and wherein, in the flat portion, the twist pitch of the wires in the child strand is a (mm), the twist pitch of the child strands in the lower twist layer is b (mm), and the twist pitch of the child strands in the top twist layer is c (mm), and the relationship (0.2a + b + 0.5) / c≦1 is satisfied.

2. The electric wire conductor according to claim 1, wherein the cross section of at least some of the wires constituting the electric wire conductor is deformed from a circular shape.

3. The electric wire conductor according to claim 1, wherein the electric wire conductor is manufactured by rolling a raw conductor consisting of a stranded wire with a circular cross section, and the rate of increase in conductor resistance of the flat portion based on the raw conductor is kept to less than 10%.

4. The electric wire conductor according to claim 1, wherein a flatness ratio, which indicates a ratio of the width dimension of the flat portion to the height dimension, is 3 or more.

5. The cross-sectional area of ​​the wire conductor is 16 mm ２ The electric wire conductor according to claim 1, wherein a twist pitch a of the wires in the child strand is 10 mm or more, and a twist pitch c of the child strands in the upper twist layer is 70 mm or more.

6. The electric wire conductor according to claim 1, wherein the wire is made of aluminum or an aluminum alloy.

7. An insulated wire comprising: the conductor according to any one of claims 1 to 6; and an insulating coating that covers the outer periphery of the conductor.

8. A wire harness comprising the insulated wire according to claim 7.

Images