Wire conductor, insulated wire, and wire harness

Abstract

To provide a wire conductor that is made of aluminum or an aluminum alloy, and is not likely to, when it is ultrasonically welded to a connection terminal, cause a welding defect in a welded portion, and also to provide an insulated wire and a wire harness including the wire conductor.SOLUTION: A wire conductor 1 includes: a lower strand layer 11 in which a plurality of sub-strands 10, each formed by twisting together a plurality of bare wires 1a made of aluminum or an aluminum alloy, are bundled and twisted together; and an upper strand layer 12 in which a plurality of the sub-strands 10 are twisted around an outer circumference of the lower strand layer 11; wherein, in a cross section orthogonal to the axial direction, a proportion of an area occupied by a gap G1 formed between the lower strand layer 11 and the upper strand layer 12 to an area of gaps not occupied by the bare wires 1a is 63% or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] As described in Patent Documents 1 and 2, electric wires equipped with conductors made of aluminum or aluminum alloys (aluminum conductors) are increasingly being used as electric wires arranged inside automobiles. In electric wires for automobiles, weight reduction and large current capacity are being promoted, and by using aluminum conductors, the weight of the electric wires can be reduced compared to the case where a conductor made of copper or copper alloy is used. Furthermore, even when the diameter of the conductor is increased to accommodate large current capacity, the use of aluminum conductors can suppress an increase in the mass of the electric wire.

[0003] In Patent Document 2, a coated electric wire having a conductor containing aluminum is crimped to a connection terminal, but ultrasonic welding is often used to connect an aluminum conductor to a connection terminal. For example, Patent Document 3 discloses a form in which a male terminal and a stranded conductor are connected by ultrasonic welding. Patent Document 3 describes that when ultrasonic welding is performed, the joining is performed while the entire conductor is in a twisted state so that the stranded conductor's elemental wires (child strands) do not come apart. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 079048 [Patent Document 2] JP 2020-87523 A [Patent Document 3] JP 2019-200997 A Summary of the Invention [Problem to be solved by the invention]

[0005] When ultrasonically welding an aluminum conductor to a connection terminal, the wires that make up the conductor may bend at the welded portion, as shown by arrow A2 in Figure 5. Such bending can cause poor appearance and is an indicator of low adhesion of the conductor to the connection terminal, so it is considered to be a weld defect. It is preferable to prevent the occurrence of such structures that are considered to be weld defects as much as possible.

[0006] Therefore, an object of the present invention is to provide an electric wire conductor made of aluminum or an aluminum alloy, which is less likely to cause welding defects at the welded portion when ultrasonically welded to a connection terminal, and to provide an insulated wire and a wire harness including such an electric wire conductor. [Means for solving the problem]

[0007] The electric wire conductor of the present disclosure has a lower twisted layer in which a plurality of child twisted wires, each of which is made of aluminum or an aluminum alloy, are twisted together into a bundle, and a top twisted layer in which a plurality of the child twisted wires are twisted around the outer periphery of the lower twisted layer, and in a cross section perpendicular to the axial direction, the area of ​​the gaps not occupied by the strands that are formed between the lower twisted layer and the top twisted layer is 63% or less.

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

[0009] The wire harness of the present disclosure includes the insulated wire and a connection terminal, and at an end of the insulated wire, the wire conductor exposed from the insulating coating is ultrasonically welded to the connection terminal. Effect of the Invention

[0010] The electric wire conductor according to the present disclosure is made of aluminum or an aluminum alloy, and is unlikely to cause welding defects at the welded portion when ultrasonically welded to a connection terminal. Furthermore, the insulated wire and the wire harness according to the present disclosure include such an electric wire conductor. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view illustrating a schematic diagram of an electric wire conductor having a small interlayer void ratio according to one embodiment of the present disclosure. [Diagram 2] FIG. 2 is a cross-sectional view that typically shows a conductor having a large interlayer void ratio. [Diagram 3] Fig. 3 is a simplified cross-sectional view of an electric wire conductor, in which the wires that make up the child strands are omitted, except for one child strand. [Figure 4] FIG. 4 is a side view that typically illustrates a state in which an insulated electric wire including the electric conductor shown in FIG. 1 is ultrasonically welded to a connection terminal. [Diagram 5] FIG. 5 is a side view that typically illustrates a state in which an insulated electric wire including the electric conductor shown in FIG. 2 is ultrasonically welded to a connection terminal. [Figure 6] 6A to 6C are photographed images of the cross sections of the produced electric wire conductors, and correspond to Samples 1 to 3, respectively. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described.

[0013] (1) An electric wire conductor according to the present disclosure comprises a lower twisted layer in which a plurality of child twisted wires, each of which is made of aluminum or an aluminum alloy, are twisted together into a bundle, and a top twisted layer in which a plurality of the child twisted wires are twisted around the outer periphery of the lower twisted layer, and in a cross section perpendicular to the axial direction, the area of ​​the gaps not occupied by the strands that are formed between the lower twisted layer and the top twisted layer is 63% or less.

[0014] In the above electric wire conductor, the proportion of voids formed between the lower twisted layer and the upper twisted layer among voids not occupied by the strands is suppressed to 63% or less, and the voids are not concentrated in the area between the lower twisted layer and the upper twisted layer. Correspondingly, the strands constituting each child strand are easily separated when ultrasonic welding is performed. By performing ultrasonic welding with the separated strands of strands tightly packed together, bending of the welded portion is less likely to occur. Furthermore, a large fixing force is obtained at the welded portion. In this way, poor welding is less likely to occur between the electric wire conductor and the connection terminal.

[0015] (2) In the above embodiment (1), the twist pitch of the upper twist layer may be greater than the twist pitch of the lower twist layer. This makes it easier to keep the gap between the lower twist layer and the upper twist layer small. As a result, it is easier to prevent welding defects during ultrasonic welding.

[0016] (3) In the above-mentioned (1) or (2) aspect, the ratio of the area of ​​the cross section occupied by the gaps formed between the lower twisted layer and the upper twisted layer may be 15% or more and 25% or less. In this way, by having gaps of a suitable range in the entire electric wire conductor, the wires are easily separated during ultrasonic welding, and welding defects are less likely to occur.

[0017] (4) In any of the above aspects (1) to (3), the twist pitch of the wires in the child strand may be 90 times or more the outer diameter of the wires. If the twist pitch of the wires constituting the child strand is large, the wires are more likely to come apart during ultrasonic welding, making it less likely that welding defects will occur.

[0018] (5) In any of the above embodiments (1) to (4), the twist pitch of the child strands in the first twisted layer is preferably 200 times or more the outer diameter of the strands, and the twist pitch of the child strands in the second twisted layer is preferably 250 times or more the outer diameter of the strands. When the twist pitches of the first twisted layer and the second twisted layer are large, it is easy to keep the gap between the first twisted layer and the second twisted layer small. In addition, the strands constituting the child strands are easy to separate. These effects make it easy to prevent welding defects during ultrasonic welding.

[0019] (6) In any one of the above (1) to (5), the overall conductor cross-sectional area is 16 mm 2 More than 50mm 2 When the electric wire conductor has a conductor cross-sectional area in this range, the proportion of the area of ​​the gap between the lower twisted layer and the upper twisted layer in the total gap area is reduced, and thereby the effect of reducing welding defects during ultrasonic welding can be significantly obtained.

[0020] (7) An insulated wire according to the present disclosure includes a conductor according to any one of the above aspects (1) to (5) and an insulating coating that covers the outer periphery of the conductor. This insulated wire has a conductor in which the ratio of the area of ​​the voids between the lower twisted layer and the upper twisted layer to the total voids is controlled within a predetermined range, and therefore, when the conductor is exposed at the terminal and ultrasonically welded to a connection terminal, bending of the wire or poor welding caused by a decrease in fastening strength can be suppressed.

[0021] (8) A wire harness according to the present disclosure includes the insulated wire according to the aspect (7) and a connection terminal, and the wire conductor exposed from the insulating coating at the end of the insulated wire is ultrasonically welded to the connection terminal. In this wire harness, the wire conductor, in which the ratio of the gap between the lower twist layer and the upper twist layer to the total gap is kept within a predetermined range, is exposed at the end of the insulated wire and ultrasonically welded to the connection terminal, so that welding defects such as bending of the wires and a decrease in the adhesive strength between the wire conductor and the connection terminal are unlikely to occur at the welded portion. Therefore, this wire harness has a good welding structure between the insulated wire and the connection terminal.

[0022] [Details of the embodiment of the present disclosure] Hereinafter, a conductor, an insulated wire, and a wire harness according to embodiments of the present disclosure will be described in detail with reference to the drawings.

[0023] (Structure of Electric Wire Conductor) FIG. 1 shows a schematic cross-sectional view of a structure of an electric wire conductor 1 according to an embodiment of the present disclosure. The electric wire conductor 1 includes a plurality of elemental wires 1a made of aluminum or an aluminum alloy. A plurality of elemental wires 1a are twisted together to form a child strand 10. The outer diameter of the elemental wires 1a is not particularly limited, but can be in the range of 0.1 mm or more and 0.7 mm or less. The number of elemental wires 1a constituting one child strand 10 is also not particularly limited, but can be in the range of 7 or more and 80 or less.

[0024] A plurality of child strands 10 are bundled and twisted together to form the primary twist layer 11. The number of child strands 10 that form the primary twist layer is not particularly limited, but seven is preferred. A top twist layer 12 is formed on the outer periphery of the primary twist layer 11. The top twist layer 12 is formed as a layer in which a plurality of child strands 10 are twisted coaxially with the primary twist layer 11 and twisted around the outer periphery of the primary twist layer 11. The number of child strands 10 that form the top twist layer 12 is also not particularly limited, but twelve is preferred.

[0025] In the electric wire conductor 1 according to the present embodiment, in a cross section perpendicular to the axial direction (hereinafter sometimes simply referred to as a cross section), the ratio of the area occupied by the interlayer gaps G1, i.e., the gaps G1 formed between the lower twisted layer 11 and the upper twisted layer 12, to the gaps not occupied by the strands 1a (interlayer gap ratio) is kept small. As shown in FIG. 2, in an electric wire conductor 1' in which the upper twisted layer 12 is formed on the outer periphery of the lower twisted layer 11, a large interlayer gap G1 may be formed between the lower twisted layer 11 and the upper twisted layer 12. In this case, the interlayer gap ratio becomes large. However, in the electric wire conductor 1 according to the present embodiment, as shown in FIG. 1, the interlayer gap G1 between the lower twisted layer 11 and the upper twisted layer 12 is not significantly larger than the gaps between the child strands 10 inside the lower twisted layer 11 and the gaps between the child strands 10 within the upper twisted layer 12, and the interlayer gap ratio is small.

[0026] In the electric wire conductor 1 according to the present embodiment, a specific preferred range of the interlayer void ratio is 63% or less. More preferably, the interlayer void ratio is 62% or less. As a method for quantitatively evaluating the interlayer void ratio, for example, as illustrated in FIG. 3, an image of a cross section is used to subtract an area of ​​a void existing inside a circle (a circle having a core diameter R1 of the primary twist layer) that passes through the center of each child stranded wire 10 that constitutes the upper twist layer 12 from an area of ​​a void existing inside a circle (a circle having a core diameter R2 of the primary twist layer) that passes through the center of each child stranded wire 10 that faces the outer periphery of the primary twist layer 11, and the result is defined as an area (a) of an interlayer void G1. In addition, an area of ​​a void (a void existing inside the outer periphery of the electric wire conductor 1 as a whole) in the entire electric wire conductor 1 is estimated as a total void area (A). Then, a ratio of an area of ​​an interlayer void G1 to a total void area may be defined as an interlayer void ratio (a / A×100%).

[0027] As will be described in detail later, if the interlayer void ratio in the electric wire conductor 1 is kept small, the wires 1a tend to come apart (become dispersed) when the electric wire conductor 1 is ultrasonically welded to the surface of the connection terminal 30 or the like, thereby suppressing the occurrence of welding defects. Although there is no particular lower limit for the interlayer void ratio, in a practical electric wire conductor 1 having a two-layer structure of a lower twisted layer / top twisted layer, the interlayer void ratio is generally 50% or more.

[0028] The interlayer gap G1 may be continuous in an annular shape around the entire outer circumference of the primary twisted layer 11, or may be divided into a plurality of gaps at the contact points between the child strands 10 constituting the primary twisted layer 11 and the child strands 10 constituting the upper twisted layer 12. However, it is preferable that the interlayer gap G1 is divided into a plurality of gaps from the viewpoint of suppressing the occurrence of poor welding. In this case, for example, it is more preferable that the area of ​​one continuous interlayer gap G1 in the cross section is three times or less the cross-sectional area of ​​the strands 1a. Furthermore, it is preferable that there is no continuous gap between the primary twisted layer 11 and the upper twisted layer 12. The absence of a continuous gap means, for example, that there is no gap in the cross section of the electric wire conductor 1 that is large enough to accommodate a bundle of three strands (1a) included in the upper twisted layer 12 as it is, that is, without deformation. More preferably, there should be no gap large enough to accommodate two strands of wire (1a), and most preferably, one strand of wire (1a).

[0029] In the cross section of the electric wire conductor 1, the area (size) of the interlayer gap G1 itself is not particularly limited as long as the interlayer gap ratio is sufficiently small. However, the smaller the area of ​​the interlayer gap G1, the more effective it is in suppressing poor welding caused by the promotion of the separation of the wires 1a. Therefore, it is preferable that the void ratio of the electric wire conductor 1 as a whole is suppressed to, for example, 25% or less, and further 20% or less. By suppressing the void ratio of the electric wire conductor 1 as a whole so as not to be too large, the area of ​​the interlayer gap G1 based on the entire area of ​​the electric wire conductor 1, which is obtained by multiplying the void ratio by the interlayer gap ratio, is suppressed to be small. On the other hand, if the gap between the wires 1a inside each child strand 10 is too small, it becomes difficult to effectively promote the separation of the wires 1a, so that the void ratio of the electric wire conductor 1 as a whole is preferably 15% or more. The void ratio of the entire wire conductor 1 can be estimated as the ratio of the total void area (A) to the area of ​​the entire wire conductor 1 (the total area of ​​the area inside the outer casing of the entire wire conductor 1; A0) (A / A0 × 100%).

[0030] The twist pitch of the strands 1a in the stranded wires 10 (stranded wire pitch), the twist pitch of the stranded wires 10 in the stranded layer 11 (ply twist pitch), and the twist pitch of the stranded wires 10 in the ply twist layer 12 (ply twist pitch) are not particularly limited. However, from the viewpoint of easily reducing the interlayer void ratio, it is preferable that the ply twist pitch is larger than the ply twist pitch. For example, the ply twist pitch is preferably 1.1 times or more, and even more preferably 1.2 times or more, of the ply twist pitch. There is no particular upper limit to this ratio, but from the viewpoint of suppressing the occurrence of twist disorder and deterioration of flexibility, it is preferable to keep the ply twist pitch, for example, no more than twice the ply twist pitch.

[0031] Furthermore, the child twist pitch, lower twist pitch, and upper twist pitch can be increased to a certain extent to promote the separation of the wires 1a during ultrasonic welding, thereby enhancing the effect of suppressing welding defects. In particular, a high effect can be obtained by increasing the child twist pitch. As a specific example of a suitable twist pitch, the child twist pitch is preferably 90 times or more, more preferably 150 times or more, or 200 times or more, the outer diameter of the wires 1a. Alternatively, it is preferably 30 mm or more, more preferably 50 mm or more, or 65 mm or more. There is no particular upper limit to the child twist pitch, but it is preferably, for example, 250 times or less, or 75 mm or less, the outer diameter of the wires 1a.

[0032] The first twist pitch is preferably 200 times or more, or even 250 times or more, the outer diameter of the wire 1a. Alternatively, it is preferably 68 mm or more, or even 80 mm or more. There is no particular upper limit to the first twist pitch, but it may be, for example, 300 times or less, or 93 mm or less, the outer diameter of the wire 1a. The second twist pitch is preferably 250 times or more, or even 300 times or more, the outer diameter of the wire 1a. Alternatively, it is preferably 85 mm or more, or even 100 mm or more. There is no particular upper limit to the second twist pitch, but it may be, for example, 400 times or less, or 130 mm or less, the outer diameter of the wire 1a. The magnitude of each twist pitch is a parameter that affects the interlayer void ratio, but other parameters that affect the interlayer void ratio include the magnitude of tension applied to the strands 1a and the strands 10 when multiple strands 1a are twisted together to form the child strand 10, and when multiple child strands 10 are twisted together to form the lower twist layer 11 and the upper twist layer 12.

[0033] In the electric wire conductor 1 according to the present embodiment, the overall conductor cross-sectional area is not particularly limited. However, if the conductor cross-sectional area is too small, welding defects are relatively unlikely to occur regardless of the specific configuration of the electric wire conductor 1. Therefore, from the viewpoint of enhancing the effect of suppressing welding defects by reducing the ratio of interlayer voids, it is preferable that the conductor cross-sectional area is somewhat large. For example, when the conductor cross-sectional area is 16 mm 2 On the other hand, if the conductor cross-sectional area is too large, it may be difficult to suppress welding defects. 2 It would be better to keep it as follows.

[0034] When manufacturing the electric wire conductor 1, a plurality of wires 1a are twisted together to form a child twisted wire 10, and then a plurality of the child twisted wires 10 are twisted together to form the first twisted layer 11. Furthermore, a plurality of the same child twisted wires 10 are arranged around the outer periphery of the first twisted layer 11 and twisted coaxially to form the top twisted layer 12. During or after the formation of the electric wire conductor 1, a softening treatment by heating may be appropriately performed. Examples of the timing for heating include after the formation of the first twisted layer 11 and after the formation of the top twisted layer 12.

[0035] (Insulated wire and wiring harness structure) FIG. 4 shows a wire harness 3 according to an embodiment of the present disclosure, including an insulated wire 2 according to an embodiment of the present disclosure.

[0036] The insulated wire 2 includes the wire conductor 1 according to the embodiment of the present disclosure described above and an insulating coating 20 that covers the outer periphery of the wire conductor 1. The wire harness 3 according to the embodiment of the present disclosure includes the insulated wire 2 and a connection terminal 30. At an end of the insulated wire 2, the insulating coating 20 is removed, and the wire conductor 1 exposed from the insulating coating 20 is ultrasonically welded to the connection terminal 30. The connection terminal 30 is configured using, for example, copper or a copper alloy as a base material, and the wire conductor 1 is fixed to a flat wire fixing portion 31 by ultrasonic welding.

[0037] (Structure of Electric Wire Conductor and Ultrasonic Welding) In the electric wire conductor 1 according to the embodiment of the present disclosure described above, the interlayer void ratio is suppressed to be small, which can suppress the occurrence of welding defects when ultrasonically welding the electric wire conductor 1 of the insulated wire 2 to the electric wire fastening portion 31 of the connection terminal 30 in order to manufacture the wire harness 3.

[0038] When ultrasonically welding the electric wire conductor 1 to the electric wire fixing portion 31 of the connection terminal 30, the electric wire conductor 1 exposed from the insulating coating 20 is sandwiched between the horn and anvil of an ultrasonic welding machine together with the electric wire fixing portion 31 of the connection terminal 30. When a large interlayer gap G1 is formed between the lower twisted layer 11 and the upper twisted layer 12 as in the electric wire conductor 1' shown in FIG. 2 and has a large interlayer gap ratio, the strands 1a are unlikely to come apart when the electric wire conductor 1' is sandwiched from above and below and ultrasonically welded. This is thought to be because when the electric wire conductor 1' is sandwiched, slippage is likely to occur between the child strands 10 in the region between the lower twisted layer 11 and the upper twisted layer 12, and the force applied by the sandwiching is consumed in the slippage between the child strands and does not effectively work to separate the strands 1a. If misalignment occurs between the child strands 10 before the wires 1a constituting the child strands 10 unravel during welding, the wires 1a cannot be welded in a sufficiently unraveled state. Because the wires 1a are not easily unraveled, the wires 1a pushed out by the horn before welding are bent at the welded portion 40, as shown by arrow A2 in the wire harness 3' in FIG. 5. The bending of the wires 1a at the welded portion 40 deteriorates the appearance of the wire harness 3'. In addition, because the wires 1a are not easily unraveled, ultrasonic energy is not efficiently transmitted to the welded portion 40, and the fixing strength between the electric wire conductor 1' and the connection terminal 30 is also reduced.

[0039] In contrast, in the electric wire conductor 1 with a small interlayer gap G1 as shown in FIG. 1, since there are no gaps concentrated between the lower twisted layer 11 and the upper twisted layer 12, when the electric wire conductor 1 is sandwiched between the horn and the anvil of the ultrasonic welding machine, the child strands 10 are unlikely to slide between the lower twisted layer 11 and the upper twisted layer 12. Therefore, at least a part of the twist of the child strands 10 is untwisted by the force applied by the sandwiching, and the strands 1a constituting the child strands 10 are loosened (dispersed). Since the electric wire conductor 1 is welded in such a state that the strands 1a are loosened, the welded portion 40 is formed with the strands 1a densely and flatly stacked. Since the loose strands 1a are densely stacked, the ultrasonic energy is efficiently transmitted to the welded portion 40, and the strands 1a are firmly fixed to the electric wire fixing portion 31 of the connection terminal 30 in a state where they are stretched and stacked without bending.

[0040] As a result, as shown by the arrow A1 in FIG. 4, the wire 1a is not bent or the bend of the wire 1a is small, and the welded part 40 with excellent appearance is easily formed. In addition, a large fixing strength is easily obtained at the welded part 40. In other words, the occurrence of welding defects accompanied by bending of the wire 1a or a decrease in fixing strength is reduced. It is preferable that the length of bending of the wire 1a measured from the lower end face of the wire fixing part 31 of the connection terminal 30 (distance d in FIG. 5) is equal to or less than the thickness of the plate surface of the wire fixing part 31, and further, is equal to or less than 60% of the thickness of the plate surface of the wire fixing part 31. Alternatively, it is preferable that the wire 1a is not bent to reach a position lower than the lower end of the insulating coating 20 of the ultrasonically welded insulated wire 2.

[0041] In addition, the gap between the lower twist layer 11 and the upper twist layer 12 can contribute to suppression of welding defects not only in terms of its area but also in terms of the presence or absence of continuity. As described above, it is preferable that there is no continuous gap between the lower twist layer 11 and the upper twist layer 12 as shown in FIG. 1. Then, when deformation (change in the relative position of the strands 1a) occurs in the upper twist layer 12 due to welding, the strands 1a of the upper twist layer 12 and the strands 1a of the lower twist layer 11 easily come into contact with each other. This allows the force applied during welding to be transmitted to the lower twist layer 11 with high efficiency. Therefore, not only the upper twist layer 12 but also the lower twist layer 11 is easily deformed, making welding defects less likely to occur. In other words, it can be said that the absence of a continuous gap between the lower twist layer 11 and the upper twist layer 12 makes welding defects less likely to occur. 2, if there are continuous gaps between the primary twist layer 11 and the final twist layer 12, deformation of the final twist layer 12 during welding is absorbed by the continuous gaps, making it difficult for force to be transmitted to the primary twist layer 11. As a result, the primary twist layer 11 does not deform sufficiently, making welding defects more likely to occur.

[0042] As explained above, when the top twist pitch is larger than the bottom twist pitch, the interlayer void ratio is reduced, which promotes the separation of the wires 1a during ultrasonic welding and is particularly effective in suppressing the occurrence of welding defects. Also, by increasing the child twist pitch, bottom twist pitch, and top twist pitch, the effect of suppressing welding defects by promoting the separation of the wires 1a is increased. EXAMPLES

[0043] Examples are shown below. However, the present invention is not limited to these examples. Here, the correlation between the interlayer void ratio in the electric wire conductor and the occurrence of welding defects was studied.

[0044] [Sample preparation] (Manufacture of electric conductors and insulated wires) Thirteen aluminum alloy wires with an outer diameter of 0.32 mm were twisted together to form a child strand. Six child strands were arranged around one of these child strands, resulting in a total of seven child strands that were twisted together to form a primary twist layer. Twelve more child strands were then arranged around the primary twist layer and twisted coaxially with it to form a top twist layer.

[0045] Here, three types of electric wire conductors were formed, Samples 1 to 3. In each sample, the twist pitch was as shown in Table 1 below. [Table 1]

[0046] Further, an insulating coating was formed around the outer periphery of each conductor to prepare an insulated wire. The insulating coating was made of cross-linked polyethylene extruded to a thickness of 1.1 mm.

[0047] (Making wire harnesses) At the end of each of the insulated wires prepared above, the insulating coating was removed over a region of 15.5 mm in length to expose the wire conductor. At this time, the insulating coating was left in a semi-striped state. The exposed conductor portion of the insulated wire was fixed to the wire fixing portion of the connection terminal by ultrasonic welding. The connection terminal was made of a copper alloy, and the wire fixing portion had dimensions of 10 mm in width, 10.5 mm in length, and 2.6 mm in thickness.

[0048] [Test Method] (Evaluation of interlayer void ratio) Each of the insulated wires prepared above was embedded in acrylic resin and cut perpendicularly to the axial direction to obtain a cross-sectional sample, which was then photographed with a digital camera to obtain a photographed image.

[0049] The interlayer void ratio was evaluated for the photographed images obtained above. First, as shown by the guide lines in FIG. 3, the area of ​​the interlayer voids (a) was estimated as the difference between the total area of ​​voids present inside the circle corresponding to the upper twisted layer core diameter (R2) and the total area of ​​voids present inside the circle corresponding to the lower twisted layer core diameter (R1). Furthermore, the area of ​​the voids inside the outer casing of the entire conductor was estimated as the total void area (A). Then, the ratio of the interlayer void area (a) to the total void area (A) was taken as the interlayer void ratio (a / A×100%). In addition, the void ratio was also calculated as the ratio of the total void area (A) to the area inside the outer casing of the entire conductor (A0) (A / A0×100%). The evaluation was performed on three specimens for each of samples 1 to 3, and the average value of the three specimens was recorded.

[0050] (Determining poor welding) For each of the wire harnesses produced above, the condition of the welded portion between the electric conductor and the electric wire fixing portion of the connection terminal was observed. If there was no bending of the wire in the welded portion, or if the magnitude of the bending of the wire based on the lower end face of the electric wire fixing portion (distance d in Fig. 5) was within 1.5 mm, it was judged as "no welding defect." On the other hand, if the magnitude of the bending of the wire exceeded 1.5 mm, it was judged as "welding defect."

[0051] [Test Results] 6A to 6C show cross-sectional images of the insulated wires of Samples 1 to 3, respectively. Table 2 below shows the interlayer void ratio and the void ratio of the entire wire conductor obtained in the above test for each of Samples 1 to 3, as well as the judgment results on the presence or absence of welding defects. The same evaluation results were obtained for the presence or absence of welding defects for all three samples evaluated for each of Samples 1 to 3.

[0052] [Table 2]

[0053] From the photographed images of Figs. 6A to 6C, it can be seen that in Samples 2 and 3, a gap is formed between the upper twisted layer located at the outer periphery of the entire electric wire conductor and the lower twisted layer located further inside, which is more clearly recognizable than in other places. This is an interlayer gap. In particular, in Sample 2, a clear separation is seen between the upper twisted layer and the lower twisted layer, and a clear interlayer gap that is close to a ring is formed between these layers. In contrast, in Sample 1, it is difficult to clearly see the boundary between the upper twisted layer and the lower twisted layer. This indicates that a gap that is significantly larger than other places is not formed as an interlayer gap between the upper twisted layer and the lower twisted layer. Also, when focusing on the continuity of the gap between the upper twisted layer and the lower twisted layer in the photographed images, the continuity of the gap is lower in Sample 1 than in Samples 2 and 3, especially Sample 2. In other words, the size of the continuous gap is smaller. In Sample 1, a gap that can directly accommodate one strand is not found between the upper twisted layer and the lower twisted layer.

[0054] The difference in the size of the interlayer voids, which can be seen from the cross-sectional images, is also clearly reflected in the evaluation results of the interlayer void ratio shown in Table 2. Samples 2 and 3 have large interlayer void ratios exceeding 63%. In particular, the interlayer void ratio of sample 2 exceeds 70%. In contrast, the interlayer void ratio of sample 1 is kept to a small value of 63% or less. The void ratio of the entire wire conductor is also smaller in sample 1 than in samples 2 and 3.

[0055] Next, looking at the results of the judgment of the presence or absence of welding defects in Table 2, only sample 1 did not experience welding defects, while samples 2 and 3 did. This result can be correlated with the magnitude of the interlayer void ratio. That is, sample 1, in which the interlayer void ratio is kept to a small value of 63% or less, did not experience welding defects, whereas samples 2 and 3, in which the interlayer void ratio exceeds 63%, experienced welding defects. It can be said that the smaller the interlayer void ratio, the less likely welding defects are to occur.

[0056] 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 without departing from the gist of the present invention. [Explanation of symbols]

[0057] 1,1' Wire conductor 1a bare wire 10 stranded wire 11 Primary twist layer 12 Top twist layer 2. Insulated wire 20 Insulation coating 3,3' Wire Harness 30 Connection terminal 31 Wire fixing part 40 Welded area A1 No bending of wires at welded part A2 Structure in which the wire is bent at the welded part d The magnitude of deflection of the wire G1 interlayer void R1 Circle of the core diameter of the first twist layer R2: Circle of the core diameter of the upper twisted layer

Claims

1. A primary twist layer is formed by twisting together a plurality of child twisted wires, each of which is made of aluminum or an aluminum alloy, into a bundle; An electric wire conductor having an upper twisted layer in which the child strands are twisted around the outer periphery of the lower twisted layer, an electric wire conductor, in which, in a cross section perpendicular to the axial direction, the ratio of an area of ​​gaps formed between the lower twisted layer and the upper twisted layer to the total area of ​​gaps not occupied by the wires is 63% or less, and a void ratio of the entire electric wire conductor, estimated as a ratio of the total void area to the entire area of ​​the electric wire conductor, is 25% or less.

2. The conductor wire of claim 1 , wherein a twist pitch of the upper twist layer is greater than a twist pitch of the lower twist layer.

3. 2. The electric wire conductor according to claim 1, wherein a ratio of an area of ​​the cross section occupied by gaps formed between the first twist layer and the second twist layer is 15% or more and 25% or less.

4. 2. The electric wire conductor according to claim 1, wherein a twist pitch of the strands of the child strands is 90 to 250 times an outer diameter of the strands.

5. The twist pitch of the child strands in the first twist layer is 200 to 300 times the outer diameter of the wire, 2. The electric wire conductor according to claim 1, wherein a twist pitch of the child strands in the upper twist layer is 250 to 400 times an outer diameter of the wire.

6. The overall conductor cross-sectional area is 16 mm ２ More than 50 mm ２ 2. The electric wire conductor according to claim 1, wherein:

7. The conductor according to any one of claims 1 to 6, and an insulating coating covering the outer periphery of the electric conductor.

8. The insulated wire according to claim 7 , A connection terminal; the wire conductor exposed from the insulating coating at an end of the insulated wire is ultrasonically welded to the connection terminal.

Images