Patent Application
20240274315
The present disclosure relates to a wire conductor, an insulated wire, and a wire harness.
As disclosed in Patent Documents 1 and 2, wires including a conductor (aluminum conductor) made of aluminum or an aluminum alloy are increasingly used as wires to be routed in a vehicle. Lightweight and high-current wires are being developed as wires for use in vehicles, and aluminum conductors can be used to reduce the weight of wires, compared to the case where conductors made of copper or a copper alloy are used. Also, when large diameter conductors are used to handle high currents, using aluminum conductors can suppress an increase in mass of the wires.
In Patent Document 2, a coated wire having an aluminum-containing conductor is crimped and connected to a connection terminal, but it is also often the case that an aluminum conductor is ultrasonically welded to a connection terminal. For example, Patent Document 3 discloses a configuration in which a male terminal and a twisted wire conductor are connected to each other by ultrasonic welding. According to the disclosure of Patent Document 3, the connection is made during ultrasonic welding with bare wires (strands) of the twisted wire conductor twisted as a whole so that they do not dissociate.
When an aluminum conductor is ultrasonically welded to a connection terminal, there may be cases where bare wires constituting the conductor are deflected in the welded portion as indicated by the arrow A2 in
Accordingly, it is an object 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 the welded portion, and to provide an insulated wire and a wire harness that are provided with such a wire conductor.
According to the present disclosure, a wire conductor includes: a lower strand layer in which a plurality of strands formed by twisting together a plurality of bare wires made of aluminum or an aluminum alloy are bundled and twisted together; and an upper strand layer formed by twisting a plurality of strands around an outer circumference of the lower strand layer, wherein in a cross section of the wire conductor that is orthogonal to its axial direction, a proportion of an area occupied by gaps formed between the lower strand layer and the upper strand layer to an area of gaps that are not occupied by the bare wires is 63% or less.
According to the present disclosure, an insulated wire includes: the above-described wire conductor; and an insulating coating that coats an outer circumference of the wire conductor.
According to the present disclosure, a wire harness includes: the above-described insulated wire; and a connection terminal, wherein, at a terminal of the insulated wire, the wire conductor exposed from the insulation coating is ultrasonically welded to the connection terminal.
The wire conductor according to the present disclosure is 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 the welded portion. Also, the insulated wire and the wire harness according to the present disclosure are provided with the above-described wire conductor.
First, embodiments of the present disclosure will be listed and described.
The above-described wire conductor has a structure in which the proportion of gaps formed between the lower strand layer and the upper strand layer to the gaps that are not occupied by the bare wires is suppressed to 63% or less, and the gaps are not concentrated between the lower strand layer and the upper strand layer. Accordingly, when performing ultrasonic welding, the bare wires constituting the strands are likely to dissociate. When ultrasonic welding is performed in a state in which the dissociated bare wires are put together closely, the welded portion is not likely to undergo a deflection. Also, a large fixation force can be obtained at the welded portion. With this, welding defects are not likely to occur between the wire conductor and a connection terminal.
The following will describe a wire conductor, an insulated wire, and a wire harness in detail, according to an embodiment of the present disclosure with reference to the drawings.
A lower strand layer 11 is configured as a structure obtained by twisting a plurality of strands 10 into a bundle. The number of strands 10 constituting the lower strand layer is not particularly limited, but is preferably 7. Furthermore, an upper strand layer 12 is formed around the outer circumference of the lower strand layer 11. The upper strand layer 12 is configured as a layer obtained by twisting a plurality of strands 10 around the outer circumference of the lower strand layer 11 coaxially with the lower strand layer 11. Also, the number of strands 10 constituting the upper strand layer 12 is not particularly limited, but is preferably 12.
In a cross-section of the wire conductor 1 according to the present embodiment that is orthogonal to its axial direction thereof (hereinafter, also referred to simply as “cross section”), the proportion (inter-layer gap proportion) of the area occupied by inter-layer gaps G1, that is, gaps G1 formed between the lower strand layer 11 and the upper strand layer 12, to the area of gaps that are not occupied by any bare wire 1a is suppressed to be low. As shown in
In the wire conductor 1 according to the present embodiment, a specific range of the inter-layer gap proportion may preferably be not greater than 63% by way of example. More preferably, the inter-layer gap proportion may be not greater than 62%. An example of a method for quantitatively evaluating the inter-layer gap proportion is such that, using a photo of a cross-section, as described with reference to
As will be described in detail later, if the wire conductor 1 has a low inter-layer gap proportion, when the wire conductor 1 is ultrasonically welded to a surface of a connection terminal 30 or the like, the bare wires 1a are likely to dissociate (disperse), suppressing a welding defect from occurring. There is no particular lower limit for the inter-layer gap proportion, but the inter-layer gap proportion of the actual wire conductor 1 of a two-layer structure including a lower strand layer and an upper strand layer is at least about 50%.
The inter-layer gap G1 may encompass an inter-layer gap G1 that is annular and is continuous over the entire outer circumference of the lower strand layer 11, or inter-layer gaps G1 including a plurality of gaps divided at positions at which a strand 10 of the lower strand layer 11 and a strand 10 of the upper strand layer 12 are in contact with each other. However, such inter-layer gaps G1 including a plurality of divided gaps are preferable in view of suppressing an occurrence of a welding defect. In this case, it is more preferable that the area of a single continuous inter-layer gap G1 in a cross section is, for example, not greater than three times as large as the cross-sectional area of the bare wire 1a. Furthermore, it is preferable that there is no continuous gap between the lower strand layer 11 and the upper strand layer 12. The phrase “there is no continuous gap” means that in a cross section of the wire conductor 1, there is no gap of a dimension such that, e.g., three bundles of bare wires (la) included in the upper strand layer 12 are accommodated in the gap directly, i.e., without deformation. This may mean that there is no gap of a dimension such that more preferably two bundles or most preferably one bundle of bare wires (la) are accommodated in the gap directly i.e. without deformation.
The area (dimension) itself of the inter-layer gaps G1 is not particularly limited as long as the inter-layer gap proportion in a cross section of the wire conductor 1 is sufficiently low. However, if the area of the inter-layer gaps G1 is kept small, the bare wires 1a dissociate more easily, resulting in the highly advantageous effect of suppressing welding defects. Therefore, a gap ratio of the entire wire conductor 1 is suppressed to preferably 25% or less, and more preferably 20% or less, for example. As a result of the gap ratio of the entire wire conductor 1 being suppressed so as not to be too high, the area of the inter-layer gaps G1, which is obtained based on the product of the inter-layer gap proportion and the gap ratio, with respect to the area of the entire wire conductor 1 is suppressed to be low. On the other hand, if the gaps between the bare wires 1a inside the strands 10 are too small, it will be difficult to dissociate the bare wires 1a efficiently, and thus the gap ratio of the entire wire conductor 1 is preferably at least 15%. The gap ratio of the entire wire conductor 1 can be estimated as a proportion of the entire gap area (A) to the area of the entire wire conductor 1 (total area AO of the region inside the outer boundary of the entire wire conductor 1) (A/A0×100%).
The twist pitch (strand twist pitch) of the bare wires 1a of each strand 10, the twist pitch (lower twist pitch) of the strands 10 of the lower strand layer 11, and the twist pitch (upper twist pitch) of the strands 10 of the upper strand layer 12 are not particularly limited. However, it is preferable that the upper twist pitch be greater than the lower twist pitch in view of reducing the inter-layer gap proportion. For example, the upper twist pitch is preferably at least 1.1 times as large as the lower twist pitch, and is more preferably at least 1.2 times as large as the lower twist pitch. This ratio is not particularly limited, but the upper twist pitch is preferably suppressed to at most 2 times as large as the lower twist pitch, in view of suppressing an occurrence of disorderly twisting or a reduction in bendability.
Furthermore, the bare wires 1a can be more easily dissociated during ultrasonic welding the larger the strand twist pitch, the lower twist pitch, and the upper twist pitch are, at least to some extent, and thus the effect of suppressing welding defects is enhanced. Particularly, by increasing the strand twist pitch, it is possible to achieve a greater effect. As a preferable example of a specific twist pitch, the strand twist pitch is preferably at least 90 times, more preferably at least 150 times, and most preferably at least 200 times as large as the outer diameter of the bare wires 1a. Alternatively, the strand twist pitch is preferably at least 30 mm, more preferably at least 50 mm, and most preferably at least 65 mm. Although there is no upper limit for the strand twist pitch, the strand twist pitch is preferably at most 250 times as large as the outer diameter of the bare wires 1a, or is at most 75 mm, for example.
The lower twist pitch is preferably at least 200 times, and more preferably at least 250 times as large as the outer diameter of the bare wires 1a. Alternatively, the lower twist pitch is preferably at least 68 mm, and more preferably at least 80 mm. Although there is no upper limit for the lower twist pitch, the lower twist pitch is preferably at most 300 times as large as the outer diameter of the bare wires 1a, or is at most 93 mm, for example. The upper twist pitch is preferably at least 250 times, and more preferably at least 300 times as large as the outer diameter of the bare wires 1a. Alternatively, the upper twist pitch is preferably at least 85 mm, and more preferably at least 100 mm. Although there is no upper limit for the upper twist pitch, the upper twist pitch is preferably at most 400 times as large as the outer diameter of the bare wires 1a, or is at most 130 mm, for example. The dimensions of the twist pitches are parameters that affect the inter-layer gap proportion, but other parameters that affect the inter-layer gap proportion may include, for example, the strength of tensile force or the like to be applied to the bare wires 1a or the strands 10, when a plurality of bare wires 1a are twisted into a strand 10 or when a plurality of strands 10 are twisted into the lower strand layer 10 or the upper strand layer 11.
In the wire conductor 1 according to the present embodiment, the conductor cross-sectional area as a whole is not particularly limited. However, if the conductor cross-sectional area is too small, welding defects are relatively less likely to occur regardless of the specific configuration of the wire conductor 1, and thus the conductor cross-sectional area is preferably large to some extent in view of enhancing the effect of suppressing a welding defect due to a reduction in the inter-layer gap proportion. For example, the conductor cross-sectional area is preferably at least 16 mm2. On the other hand, even if the conductor cross-sectional area is too large, there may be cases where it is difficult to suppress a welding defect, and thus the conductor cross-sectional area is preferably at most 50 mm2, for example.
When the wire conductor 1 is manufactured, a plurality of bare wires 1a are twisted into the strand 10, and then a plurality of such strands 10 are twisted into the lower strand layer 11. Furthermore, a plurality of strands 10 of the same type are arranged around the outer circumference of the lower strand layer 11, and are twisted coaxially thereto, thereby forming the upper strand layer 12. During or after the formation of the wire conductor 1, a softening process using heating may be performed as appropriate. Examples of a timing at which the heating is performed can include a timing after the lower strand layer 11 is formed, and a timing after the upper strand layer 12 is formed.
The insulated wire 2 includes the above-described wire conductor 1 according to the embodiment of the present disclosure, and an insulation coating 20 that coats the outer circumference of the wire conductor 1. Also, the wire harness 3 according to the embodiment of the present disclosure includes the insulated wire 2 and the connection terminal 30. At a terminal of the insulated wire 2, the insulation coating 20 is removed, and the wire conductor 1 exposed from the insulation coating 20 is ultrasonically welded to the connection terminal 30. The connection terminal 30 is made of, for example, copper or a copper alloy serving as a base material, and the wire conductor 1 is fixed to a wire fixation portion 31 in a flat plate shape by ultrasonic welding.
In the above-described wire conductor 1 according to the embodiment of the present disclosure, the inter-layer gap proportion is kept low. With this, when the wire conductor 1 of the insulated wire 2 is ultrasonically welded to the wire fixation portion 31 of the connection terminal 30 in order to manufacture the wire harness 3, it is possible to suppress the occurrence of any welding defect.
When the wire conductor 1 is ultrasonically welded to the wire fixation portion 31 of the connection terminal 30, the wire conductor 1 exposed from the insulation coating 20 is inserted, together with the wire fixation portion 31 of the connection terminal 30, between a horn and an anvil of an ultrasonic welding machine. If, as the wire conductor 1′ shown in
In contrast, in the wire conductor 1 with small inter-layer gaps G1 as shown in
As a result, as indicated by the arrow A1 in
Also, in view of not only the area of gaps between the lower strand layer 11 and the upper strand layer 12 but also the mode as to whether or not they are continuous, the gaps may be involved in suppression of welding defects. As described above, as shown in
As also described above, if the upper twist pitch is larger than the lower twist pitch, the inter-layer gap proportion will be reduced and the bare wires 1a will be more easily dissociated during the ultrasonic welding, resulting in particularly advantageous effects of suppressing the occurrence of any welding defect. Also, by increasing the strand twist pitch, the lower twist pitch, and the upper twist pitch, the effect of suppressing welding defects is enhanced due to the bare wires 1a being more easily dissociated.
The following will describe working examples. Note that the present invention is not limited to the working examples. Here, the correlation between the inter-layer gap proportion of the wire conductor and the occurrence of a welding defect was examined.
Thirteen bare wires with an outer diameter of 0.32 mm that are made of an aluminum alloy were twisted together into a strand. A lower strand layer was formed by disposing such six strands around the outer circumference of one strand, and bundling and twisting together the seven strands. Furthermore, an upper strand layer was formed by disposing twelve strands around the outer circumference of the lower strand layer, and twisting them coaxially with the lower strand layer.
Here, three types of samples 1 to 3 of wire conductors were formed. The twist pitches of the samples were set as given in Table 1 below.
Furthermore, insulated wires were manufactured by forming insulation coatings around the outer circumference of the wire conductors. Here, as the insulation coatings, cross-linked polyethylene were extruded with a thickness of 1.1 mm.
The insulation coatings were removed over a region of a length of 15.5 mm at terminal portions of the respective insulated wires manufactured in the above-described manner, and the wire conductors were exposed. At this time, the insulation coatings were maintained in a semi-stripped state. The exposed conductor portions of the insulated wires were respectively fixed to wire fixation portions of connection terminals using ultrasonic welding. The connection terminals are made of a copper alloy and the wire fixation portions thereof have a width of 10 mm, a length of 10.5 mm, and a thickness of 2.6 mm.
The insulated wires manufactured in the above-described manner were embedded into an acrylate resin, and were cut orthogonally to the axial direction, so that cross-sections of the samples were obtained. The cross-sections of the samples were shot using a digital camera and photos were acquired.
The inter-layer gap proportions in the photos acquired in the above-described manner were evaluated. First, as indicated by the guide lines in
For the wire harnesses manufactured in the above-described manner, the states of the welded portions between the wire conductor and the wire fixation portion of the connection terminal were observed. The welded portion was determined as “having no welding defect” when the corresponding bare wires were not deflected or the extent (distance d in
With reference to the photos in
The difference in dimension of the inter-layer gaps recognizable from the photos of the cross-sections is also clear from the evaluation results of the inter-layer gap proportions shown in Table 2. The inter-layer gap proportions of samples 2 and 3 have large values that exceed 63%. Particularly, the inter-layer gap proportion of sample 2 exceeds 70%. In contrast, the inter-layer gap proportion of sample 1 has a smaller value of 63% or less. Sample 1 has a smaller gap ratio of the entire wire conductor than in samples 2 and 3.
Then, referring to the determination results as to whether or not there are any welding defects in Table 2, only in sample 1 there was no welding defect, but there were welding defects in samples 2 and 3. These results can be attributed to the inter-layer gap proportions. That is to say, in sample 1 that had a small inter-layer gap proportion of 63% or less, no welding defects occurred, while in samples 2 and 3 that had an inter-layer gap proportion exceeding 63%, and welding defects occurred. It can be said that the lower the inter-layer gap proportion is, the less welding defects are likely to occur.
The embodiments of the present disclosure have been described in detail, but the present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-082668 | May 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/020146 | 5/13/2022 | WO |
