JP7494402B2 - Insulated electric wire and its manufacturing method, and insulated electric wire with terminal and its manufacturing method - Google Patents

Description

The present invention relates to an insulated electric wire and a method for manufacturing the same, and an insulated electric wire with a terminal and a method for manufacturing the same.

Insulated electric wires having a conductor and a coating layer that covers the conductor have been used as power lines, signal lines, etc. for vehicles and industrial use. Recently, with the complex control and automation of vehicles and industrial machines, there is a demand for thinner and stronger electric wires. Insulated electric wires for vehicles are often used with a cross-sectional area of ^0.35 mm2, but the development of insulated electric wires with smaller diameters is also progressing.

For example, Patent Document 1 describes adjusting the composition of the copper alloy used in the conductor so that the cross-sectional area of the conductor is approximately 0.22 ^mm2 .
Patent Document 2 describes reducing the amount of oil adhering to the surface of the central strand of the conductor in order to suppress buckling when the insulated wire is thinned.

Patent No. 6134103 Patent No. 6864856

Generally, insulated wires are rarely used alone, but terminals are connected to both ends of the insulated wire, and the wire is connected to various devices through these. When assembling automobiles or industrial machinery, or when using these, the device may fall while the wire is connected to the device. This may cause instantaneous stress in the direction of free fall on the insulated wire, which may cause the wire to break. If such a break occurs, the device may be damaged or sufficient conductivity may not be achieved between the devices. The insulated wires described in Patent Documents 1 and 2 do not mention resistance to such instantaneous stress.

The main object of the present invention is to provide an insulated electric wire that can withstand momentary stress and is less likely to break.

In order to solve the above problems, according to the present invention,
An insulated wire having a conductor in which a plurality of strands are twisted together and a coating layer that covers the conductor,
The wire is made of a copper alloy, and the copper alloy contains one or more additive elements selected from the group consisting of Fe, Ti, Mg, Sn, Ag, Ni, In, Zn, Cr, Al, P, Be, Co, and Si, with the balance being Cu and unavoidable elements;
The amount of the additive element in the copper alloy is 0.2 to 0.4 mass %,
The conductor is composed of a central strand and a plurality of concentric strands arranged concentrically around the central strand,
The amount of oil adhering to the central strand is 6 μg/g or less relative to the mass of the central strand, the twist pitch of the conductor is 5 to 10 mm, and the cross-sectional area is 0.15 mm2 or ^less ,
The coating layer is made of polyvinyl chloride resin,
The insulated wire has a coating layer having a thickness of 0.15 to 0.25 mm.

According to the present invention, it is possible to provide an insulated electric wire that is less likely to break and can withstand momentary stress.

FIG. 1A is a schematic cross-sectional view showing an example of an insulated wire. FIG. 1B is a schematic cross-sectional view showing another example of an insulated wire. FIG. 2 is a flow chart that generally illustrates a method for producing an insulated wire. FIG. 3 is a side view showing an example of an insulated electric wire with a terminal.

Preferred embodiments of the present invention will now be described.
In this specification, the term "to" indicating a range of values means that the upper and lower limits of the range are included.

(Insulated wire)
INDUSTRIAL APPLICABILITY The insulated wire according to the preferred embodiment of the present invention is extremely useful as a power line or a signal line for automobiles or industrial machines.

1A and 1B , an insulated wire 1 of the present embodiment includes a conductor 2 formed by twisting together a plurality of wires, and a coating layer 3 for covering the conductor 2. The conductor 2 is made of a copper alloy, which will be described later, and the coating layer 3 is made of a resin, which will be described later.
1A, the conductor 2 is composed of one central strand 2a and six concentric strands 2b surrounding it in a concentric manner, although the number of these strands may be appropriately selected depending on the application of the insulated wire 1, etc.

Conductor 2 may be a non-compressed conductor made by simply twisting together multiple strands as shown in FIG. 1A, or it may be a compressed conductor made by twisting together multiple strands and then compressing them into a desired shape as shown in FIG. 1B.

Although the cross-sectional area and diameter of each wire are not particularly limited, the total cross-sectional area of each wire, i.e., the cross-sectional area of the conductor 2, is ^0.15 mm2 or less. The cross-sectional area of the conductor 2 is preferably 0.120 ^mm2 or more and 0.140 ^mm2 or less, and more preferably 0.125 ^mm2 or more and 0.134 ^mm2 or less. According to the insulated wire 1 having the configuration of this embodiment, even if the cross-sectional area of the conductor 2 is reduced to 0.15 ^mm2 or less, sufficient strength and conductivity to withstand use can be obtained.

The cross-sectional shape of the conductor 2 may be approximately circular or elliptical, or may be polygonal, etc. The thickness of each of the wires constituting the conductor 2 may be the same or different, but is usually the same.

In the conductor 2, a central strand 2a and concentric strands 2b arranged around the central strand 2a are twisted in a fixed direction with the central strand 2a as the axis. The twist pitch may be 5 to 10 mm, and more preferably 6 to 8 mm. The "twist pitch" refers to the length of the conductor 2 required for the conductor 2 to rotate 360° around the central wire as the axis.
If the twist pitch of the conductor 2 is 10 mm or less, when the coating layer 3 is formed around the conductor 2, the coating layer 3 is likely to bite into the conductor 2. As a result, not only the conductor 2 but also the coating layer 3 can function as a tension member. In other words, when a stress (tensile stress) is momentarily applied to the insulated wire 1, not only the conductor 2 but also the coating layer 3 can relieve the stress, thereby suppressing breakage of the insulated wire 1. On the other hand, if the twist pitch of the conductor 2 is 5 mm or more, the adhesive force between the conductor 2 and the coating layer 3 is not excessively high, and the coating layer 3 can be peeled off without leaving any trace when, for example, connecting the conductor 2 to a terminal.

Here, it is preferable that each of the strands of the conductor 2 is tempered. If each strand is tempered, it is possible to achieve both strength and elongation of the conductor 2.

Furthermore, the amount of oil adhering to the central strand 2a of the conductor 2 is 10 μg/g or less, more preferably 6 μg/g or less, relative to the mass of the central strand 2a.
The smaller the amount of oil adhering to the central strand 2a, the greater the affinity between the conductor 2 and the coating layer 3. As a result, the coating layer 3 is more likely to penetrate into the gaps between the strands and to adhere to the surface of the conductor 2. Therefore, when a stress is momentarily applied to the insulated wire 1, breakage of the insulated wire 1 is more likely to be suppressed.
The reason why the oil content of the concentric wires 2b of the conductor 2 was excluded from the measurement target is that (i) when the coating layer 3 is formed on the conductor 2, additives such as plasticizers contained in the resin composition of the coating layer 3 adhere to the concentric wires 2b during the manufacturing process, making it impossible to measure the oil content accurately, or conversely, (ii) when the coating layer 3 is removed from the conductor 2, the oil adhered to the concentric wires 2b is also removed at the same time, making it impossible to measure the oil content accurately. That is, if the oil content of the central wire 2a is measured and controlled, it is reflected in the number of concentric wires 2b, which ultimately leads to controlling the oil content of the entire conductor 2, making it possible to quantify the penetration of the coating layer 3 into the gaps between the wires and the adhesion of the coating layer 3 to the surface of the conductor 2.

The amount of oil adhering to the central strand 2a of the conductor 2 can be determined, for example, by the following method.
The insulated wire 1 is cut to a predetermined length, and the coating layer 3 is removed with a dedicated tool such as a stripper. The conductor 2 is then pulled out. The central strand 2a is then taken out of the conductor 2, and the oil is extracted with an extraction solvent (e.g., a trimer of chlorotrifluoroethylene). This process is repeated multiple times, and the oil content in the extract is determined with an oil concentration meter. The amount of oil thus obtained is then divided by the mass of the central strand 2a used for measurement to calculate the amount of oil. The amount of oil adhering to the central strand 2a can be adjusted by the type and time of treatment performed in the degreasing step of the conductor 2 in the manufacturing method of the insulated wire 1 described below.

Here, the copper alloy constituting each wire of the conductor 2 contains one or more additive elements selected from the group consisting of Fe, Ti, Mg, Sn, Ag, Ni, In, Zn, Cr, Al, P, Be, Co and Si, with the remainder being composed of Cu and unavoidable elements.
The additive element may be one kind or two or more kinds. Usually, the number of kinds is three or less. Among the above-mentioned additive elements, Mg and Sn are particularly preferable.

The amount of the additive element in the copper alloy is 0.2 to 0.4 mass%, preferably 0.25 to 0.35 mass%, and more preferably 0.28 to 0.32 mass%. When the amount of the additive element in the copper alloy is 0.2 mass% or more, the strength of the conductor 2 is increased, for example, the tensile strength is increased. On the other hand, when the amount of the additive element in the copper alloy is 0.4 mass% or less, the conductivity of the conductor 2 is likely to be increased.

Here, the conductivity of the conductor 2 is preferably 75% IACS or more, and more preferably 80% IACS or more. When the conductivity of the conductor 2 is 75% IACS or more, the insulated wire 1 can be used for various applications. The conductivity of the conductor 2 is a value calculated from the electrical resistance value based on JIS H 0505. The electrical resistance value is measured by the double bridge method using a conductor with a length of 500 mm. The conductivity of the conductor 2 can be adjusted, for example, by the type and amount of the above-mentioned added elements.

The strength of the conductor 2 is preferably 350 MPa or more and 450 MPa or less, more preferably 390 MPa or more and 430 MPa or less, and even more preferably 400 MPa or more and 420 MPa or less. When the strength of the conductor 2 is within this range, the insulated electric wire 1 can be used for various applications. The strength of the conductor 2 is a value measured using a universal testing machine (autograph) manufactured by Shimadzu Corporation. The strength of the conductor 2 is adjusted by the type and amount of the added elements, the degree of tempering, etc.

The elongation of the conductor 2 is preferably 5 to 10%, more preferably 8 to 10%, and even more preferably 9 to 10%. When the elongation of the conductor 2 is within this range, the insulated wire 1 can be used for a variety of applications. The elongation of the conductor 2 is also a value measured using a universal testing machine (autograph) manufactured by Shimadzu Corporation. The elongation of the conductor 2 is adjusted according to the type and amount of the added elements, the degree of tempering, etc.

On the other hand, the coating layer 3 is a layer that insulates the conductor 2 and contains polyvinyl chloride resin. Usually, the coating layer 3 is formed by extrusion using an extruder or the like. The coating layer 3 only needs to contain polyvinyl chloride resin as a main component, and may contain components other than polyvinyl chloride resin as long as the purpose and effect of this embodiment are not impaired. The coating layer 3 containing polyvinyl chloride resin may have lower adhesion to the conductor 2 compared to, for example, a coating layer containing polypropylene resin. However, according to this embodiment in which the twist pitch of the conductor 2 is controlled, the adhesion to the conductor 2 can be sufficiently increased, and an insulated wire 1 that can withstand momentary stress can be obtained.

The thickness of the coating layer 3 is not particularly limited, but is usually preferably 0.15 mm to 0.25 mm, and more preferably 0.15 mm to 0.20 mm. If the thickness of the coating layer 3 is 0.15 mm or more, sufficient insulation is easily obtained, and further, as described above, the coating layer 3 can also function as a tension member when instantaneous tensile stress is applied to the insulated wire 1. On the other hand, if the thickness of the coating layer 3 is 0.25 mm or less, the insulated wire 1 can be made thinner.

Here, the adhesion strength between the conductor 2 and the coating layer 3 is preferably 19 to 23 N (i) when the conductor 2 is a non-compressed conductor, and preferably 20 to 21 N (ii) when the conductor 2 is a compressed conductor with a degree of compression of 3 to 4%. When the adhesion strength is equal to or greater than each lower limit, the adhesion is sufficient, and the insulated wire 1 can be used for various applications. On the other hand, when the adhesion strength is equal to or less than each upper limit, the coating layer 3 can be easily removed when connecting the insulated wire 1 to a terminal or the like. The adhesion strength is measured based on JASO D618.
When the conductor 2 is a compressed conductor, the compression ratio is preferably 3 to 4%. The compression ratio of the conductor 2 is calculated by the following formula.
Compression ratio = (conductor cross-sectional area before compression - conductor cross-sectional area after compression) / conductor cross-sectional area before compression x 100%

(Method of manufacturing insulated wire)
As shown in FIG. 2 , the method for manufacturing the insulated wire 1 basically includes a step S1 of twisting a plurality of wires together to prepare the conductor 2, a step S2 of degreasing the conductor 2, a step S3 of conditioning the conductor 2, and a step S4 of covering the conductor 2 with polyvinyl chloride resin to form a covering layer 3.

In the preparation step S1 of the conductor 2, each wire is obtained, for example, by casting the copper alloy to form a casting material and processing the casting material into a wire shape, but the manufacturing method is not limited to this.
In the preparation step S1 of the conductor 2, a plurality of wires are twisted together at a twist pitch of 5 to 10 mm, and the cross-sectional area is controlled to ^0.15 mm2 or less. At this time, one wire is arranged as a central wire 2a, and six concentric wires 2b are arranged concentrically around it, and these are twisted together at the twist pitch mentioned above.
The resulting conductor 2 may be subjected to compression processing.
An example of the compression method includes, but is not limited to, a method in which the conductor 2 is fed into a die and then pulled out from the die.

In the degreasing process S2 of the conductor 2, degreasing is performed until the total amount of oil adhering to the central strand 2a is 10 μg/g or less, preferably 6 μg/g or less, relative to the total mass of the central strand 2a. Degreasing until the total amount of oil is 6 μg/g or less increases the affinity between each strand and the coating layer 3 that covers it. Furthermore, degreasing in this manner makes it easier for heat to be transferred uniformly to each strand, making it easier for the coating layer 3 to penetrate uniformly into the gaps between the strands and for the coating layer 3 to adhere to the surface of each strand.

The method of the degreasing step S2 of the conductor 2 is not particularly limited, and for example, the conductor 2 may be degreased with an organic solvent or may be degreased by heat treatment.
When degreasing is performed with an organic solvent, the type of organic solvent is appropriately selected depending on the type of oil adhering to the wire. For example, alcohol or the like can be used. The method of treating with an organic solvent is not particularly limited, and may be, for example, a method of immersing the wire in an organic solvent or a method of wiping it off with a cloth or the like soaked in an organic solvent.
On the other hand, when degreasing is performed by heat treatment, it is preferable to perform heating in the presence of an inert gas. The heating temperature and heating time are appropriately selected depending on the type of oil adhering to the wire. For example, a method of heating at 250 to 350°C for 2 to 10 hours may be used.

In the conductor 2 tempering step S3, the temperature and time for tempering the conductor 2 are not particularly limited, but it is preferable to perform the tempering at a temperature in the range of 250 to 350°C for 2 to 10 hours, for example. At this time, it is preferable to perform the heating in the presence of an inert gas, such as a nitrogen gas flow. By tempering, the conductor 2 is able to achieve both elongation and strength. Furthermore, tempering gives the wires a suitable degree of flexibility, which makes it easier for the resin to penetrate into the gaps between the wires when forming the coating layer 3.

In the degreasing step S2 of the conductor 2, a plurality of wires are degreased together, but they may be degreased one by one. From the viewpoint of the production efficiency of the insulated electric wire 1, it is preferable to degrease a plurality of wires together.
The degreasing step S2 and the tempering step S3 of the conductor 2 may be performed before twisting the wires in the preparation step S1 of the conductor 2, or the order of the steps may be reversed, or the steps may be performed simultaneously. For example, the degreasing step S2 and the tempering step S3 of the conductor 2 can be performed simultaneously by heating the conductor 2 at 250 to 350° C. for 2 to 10 hours.
Basically, the degreasing step S2 and the thermal refining step S3 of the conductor 2 may be carried out at any time after the wire is manufactured and before the insulating layer 3 is formed.

In the coating layer 3 formation step S4, the coating layer 3 can be formed by extrusion processing of polyvinyl chloride resin or the like. This makes it possible to obtain the above-mentioned insulated wire 1 in which the coating layer 3 is disposed around the conductor 2.

(insulated wire with terminal)
The insulated electric wire with terminal of the present embodiment can be used for various wiring applications. For example, it can be used for wiring various electric devices such as devices for automobiles and airplanes, and control devices for industrial robots. More specifically, it can be used for automobile wire harnesses, etc.

3, the insulated electric wire with terminal has an insulated electric wire 1 and a terminal 10 connected to an end of the insulated electric wire 1. In the insulated electric wire with terminal, the terminal 10 may be connected to one end of the insulated electric wire 1 or to both ends.
Terminal 10 has, arranged from one end, a female or male fitting portion 11 for connecting to various devices, a wire barrel portion 12 for fixing conductor 2 of insulated wire 1, and an insulation barrel portion 13 for supporting coating layer 3 of insulated wire 1, in that order.
The fitting portion 11 may have any structure that allows connection to various devices, and is appropriately selected depending on the type of device. The wire barrel portion 12 has a structure for compressing and fixing the conductor 2 to reliably connect the conductor 2 and the terminal 10 electrically and mechanically. The insulation barrel portion 13 has a structure for adequately supporting and fixing the coating layer 3. These structures are similar to those of a general terminal.

(Manufacturing method of insulated electric wire with terminal)
The method for manufacturing an insulated electric wire with a terminal basically includes a step of peeling off the coating layer 3 from the end of the insulated electric wire 1 to expose the conductor 2 , and a step of connecting the terminal 10 to the exposed portion of the conductor 2 .

The method for peeling off the coating layer 3 from the end of the insulated wire 1 to expose the conductor 2 is similar to a general method, and for example, the conductor 2 may be exposed using a dedicated tool such as a stripper.

The method of connecting the terminal 10 to the conductor 2 of the insulated wire 1 is similar to the general method, and can involve, for example, fixing the coating layer 3 of the insulated wire 1 to the insulation barrel portion 13 of the terminal 10, and crimping the wire barrel portion 12 to press the conductor 2 exposed to the wire barrel portion 12.

In addition, this embodiment will also contribute to Goal 9 of the Sustainable Development Goals (SDGs), which are international targets aimed at a sustainable and better world by 2030 as set out in the 2030 Agenda for Sustainable Development adopted at the United Nations Summit in September 2015, and which states, "Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation."

(1) Preparation of samples (1.1) Sample 1
A copper alloy containing 0.3 mass% Sn and the balance being Cu and unavoidable elements was continuously cast by a horizontal continuous casting machine having a graphite mold with a water-cooled jacket on the outer periphery to produce a cast rod having a diameter of 12 mm. The cast rod was subjected to cold working to obtain a plurality of strands having a diameter of about 0.16 mm.

Then, seven strands were prepared, one of which was a central strand and the remaining six were concentric strands arranged concentrically around the central strand. These strands were then twisted together at a twist pitch of 12 mm to form a conductor. The cross-sectional area of the conductor was ^0.13 mm2.
The conductor was then heat treated at 300° C. for 2 hours in a nitrogen stream (to degrease and condition the conductor).

After that, polyvinyl chloride resin was extruded from the die of the extruder to cover the conductor, forming a coating layer around the conductor. The coating layer was 0.2 mm thick.

(1.2) Samples 2 to 5
The twist pitch of the conductor was changed as shown in Table 1.
Other than that, Samples 2 to 5 were prepared in the same manner as Sample 1.

(1.3) Sample 11
A wire was produced in the same manner as in the production of Sample 1, and a conductor with a twist pitch of 15 mm was prepared.
The conductor was then passed through a die hole and subjected to a circular compression process with a compression ratio of 3%.
The conductor was then heat treated at 300° C. for 2 hours in a nitrogen stream (to degrease and condition the conductor).
Other than that, Sample 11 was prepared in the same manner as Sample 1.

(1.4) Samples 12 to 16
The twist pitch of the conductor was changed as shown in Table 1.
Other than that, Samples 12 to 16 were prepared in the same manner as Sample 11.

(2) Evaluation The following measurements and tests were carried out on Samples 1 to 5 and Samples 11 to 16. The results are shown in Table 1.

(2.1) Measurement of the amount of oil adhering to the central strand 80 m of insulated wire was cut into a predetermined length, and the coating layer was removed with a special tool to extract the conductor. The concentric strands were twisted in the opposite direction to the twisting direction to remove them, and the central strand was extracted. This operation was performed inside a thermostatic chamber at 25°C and 20% humidity. The mass of the extracted central strand was then measured. After that, the central strand and the extraction solvent (chlorotrifluoroethylene trimer) were placed in an oil-cleaned glass Erlenmeyer flask with a stopper, and the flask was stopped with a glass stopper and stirred well. The solution in which the oil adhering to the central strand had been extracted was transferred to a measuring flask, and the extraction solvent was further added to the Erlenmeyer flask with a stopper, stirred again, and the solution in which the oil had been extracted was transferred to the measuring flask. These operations were repeated three times to measure up the volume. The mass of the oil dissolved in the extraction solvent was measured using an oil concentration meter (OCMA-555H manufactured by Horiba, Ltd.). The mass was then divided by the mass of the central strand to determine the residual oil.

(2.2) Measurement of elongation and conductor strength The elongation and conductor strength of each insulated wire were measured using a universal testing machine (autograph) manufactured by Shimadzu Corporation. As a result of the measurement, the elongation was 10% and the conductor strength was 402 MPa in all samples (not shown in the table).

(2.3) Measurement of Electrical Conductivity The electrical conductivity of each insulated wire was calculated from the electrical resistance value based on JIS H 0505. The electrical resistance value was measured by a double bridge method using a conductor with a length of 500 mm. As a result of the measurement and calculation, the electrical conductivity was 81% IACS in all samples (not shown in the table).

(2.4) Measurement of Adhesion Strength of Coating Layer The adhesion strength of the coating layer was measured based on JASO D618. Specifically, an insulated electric wire with a length of 100 mm was prepared, and the coating layer at one end of the wire was removed to expose a conductor with a length of 25 mm, and the other end was cut and discarded with a length of 25 mm. The insulated electric wire with a total length of 75 mm was used as the measurement object, and the exposed conductor was inserted into a through hole of a holding plate (a hole whose diameter is larger than the outer diameter of the conductor and smaller than the outer diameter of the insulated electric wire). The holding plate was fixed, and one end of the conductor protruding from the holding plate was pulled. The minimum load at which the coating layer peeled off from the conductor and the conductor was pulled out was determined as the adhesion strength.

(2.5) Free-fall test A terminal was attached to one end of each 300 mm insulated electric wire, and a 400 g weight was attached to the tip of the terminal so that a load was applied to the wire barrel part and the insulation barrel part of the terminal. The end on the side not attached to the terminal was fixed at a height of 1000 mm. The weight was then allowed to freely fall from the height of 1000 mm, and visual inspection was performed to see whether or not the insulated electric wire had broken. Evaluation was performed according to the following criteria.
Pass: No break occurred in the insulated wire. Fail: Break occurred in the insulated wire.

(2.6) Coating Removal Test The coating layer at one end of each insulated electric wire was removed with a dedicated tool (a fully automatic wire cutting and stripping machine manufactured by Kodera Electronics Manufacturing Co., Ltd.) to check whether the coating layer could be removed. Evaluation was performed according to the following criteria.
Pass: When the coating layer was removed with a specified pull-out force, no residual resin of the coating layer was observed. Fail: When the coating layer was removed with a specified pull-out force, part of the coating layer (resin) remained attached.

As shown in Table 1, samples 2 to 4 and samples 13 to 15 gave excellent results in both the free drop test and the coating removal test.
Specifically, when the conductor twist pitch was 5 to 10 mm, the free drop test results were good (Samples 2 to 4 and Samples 13 to 15). In contrast, when the conductor twist pitch exceeded 10 mm, the free drop test results were unsuccessful (Samples 1, 11, and 12). When the twist pitch was less than 5 mm, the coating layer could not be completely removed.
From these findings, it was inferred that in order to provide an insulated electric wire that can withstand momentary stress and is less likely to break, it would be useful to comprehensively consider and control the conductor twist pitch, the amount of oil in the central wire, the material of the coating layer, the thickness of the coating layer, etc., to keep them constant.

The present invention relates to an insulated electric wire having a conductor made of multiple strands twisted together and a coating layer covering the conductor, which is useful as a power line or signal line for automobiles and industrial machinery.

Reference Signs List 1 Insulated wire 2 Conductor 2a Central strand 2b Concentric strand 3 Covering layer 10 Terminal 11 Fitting portion 12 Wire barrel portion 13 Insulation barrel portion

Claims (5)

An insulated wire having a conductor in which a plurality of strands are twisted together and a coating layer that covers the conductor,
The wire is made of a copper alloy, and the copper alloy contains one or more additive elements selected from the group consisting of Fe, Ti, Mg, Sn, Ag, Ni, In, Zn, Cr, Al, P, Be, Co, and Si, with the balance being Cu and unavoidable elements;
The amount of the additive element in the copper alloy is 0.2 to 0.4 mass %,
The conductor is composed of a central strand and a plurality of concentric strands arranged concentrically around the central strand,
The amount of oil adhering to the central strand is 6 μg/g or less relative to the mass of the central strand, the twist pitch of the conductor is 5 to 10 mm, and the cross-sectional area is 0.15 mm2 or ^less ,
The coating layer is made of polyvinyl chloride resin,
The coating layer has a thickness of 0.15 to 0.25 mm. The insulated wire according to claim 1,
When the conductor is a non-compressed conductor, the adhesion strength between the conductor and the coating layer is 19 to 23 N;
An insulated wire, characterized in that when the conductor is a compressed conductor having a compression rate of 3 to 4%, the adhesion strength between the conductor and the coating layer is 20 to 21 N. The insulated wire according to claim 1 or 2,
A terminal connected to an end of the insulated wire;
A terminal-attached insulated wire having the following features. preparing a conductor by twisting together a plurality of wires;
degreasing the conductor;
a step of tempering the conductor;
and a step of coating the conductor with a resin to form a coating layer,
In the step of preparing the conductor, a copper alloy containing one or more additive elements selected from the group consisting of Fe, Ti, Mg, Sn, Ag, Ni, In, Zn, Cr, Al, P, Be, Co, and Si, with the balance being Cu and unavoidable elements, is produced from the copper alloy in which the amount of the additive element is 0.2 to 0.4 mass%, and among the plurality of strands, one is used as a central strand, and a plurality of concentric strands are concentrically arranged around the central strand with a stranding pitch of 5 to 10 mm to produce the conductor having a cross-sectional area of ^0.15 mm2 or less;
In the step of degreasing the conductor, an amount of oil adhering to the central strand is controlled to 6 μg/g or less relative to a mass of the central strand;
In the step of tempering the conductor, the conductor is heated at 250 to 350° C. for 2 to 10 hours;
In the step of forming the coating layer, the conductor is coated with polyvinyl chloride resin to form the coating layer having a thickness of 0.15 to 0.25 mm. a step of peeling off the coating layer from an end of the insulated wire manufactured by the method for manufacturing an insulated wire according to claim 4 to expose the conductor;
connecting a terminal to the exposed portion of the conductor;
The method for producing an electric wire with a terminal comprising the steps of: