JPH07192535A - Electric wire for automobile and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain an electric wire for an automobile in which shock resistance is improved with lightweight and reduction of a wiring space being achieved by twisting plural copper-alloy element wires formed by adding a specific amount of tin to pure copper to make a predetermined cross-sectional area of conductor. CONSTITUTION:An copper alloy in which tin of 0.3 to 2.0% by weight is added to pure copper, is made into a roughtly drawn wire. The roughly drawn wire is drawn so as to obtain a predetermined wire diameter, and at the same time a copper alloy wire which is being drawn in the process of wire drawing, is anealed by a anealing method at least once by means of electric conduction annealing, and successively after the wire is drawn up to the final diameter, it is anealed again. Thereby, an element wire of copper alloy having elongation percentage of not less than 30% is obtained. After that, plural copper alloy element wires are twisted so as to obtain a predetermined conductor cross-sectional area, for instance, 0.15 to 0.50mm<2>.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automobile electric wire used in an automobile wire harness and a method of manufacturing the same, and more particularly to an automobile electric wire having improved impact resistance while reducing weight and wiring space. The manufacturing method is related.

[0002]

2. Description of the Related Art Automotive wire harnesses are, for example,
It is widely used in vehicles as an electric wire for electrically connecting each device, control device, and the like inside an engine room. In particular, in recent years, the number of wiring parts has increased due to the increase in various control devices as the performance of automobiles has increased, and the amount of wire harness used has also increased.

On the other hand, regarding automobiles, it is required to reduce the weight of the vehicle body from the viewpoint of improving fuel efficiency, and to reduce the size of parts from the perspective of expanding the effective space of the vehicle. In addition, a wiring space occupying space is required to be low.

[0004] As an electric wire for an automobile used for a wire harness, conventionally, an electric conductor formed by covering an outer periphery of a copper conductor formed by twisting several soft copper wires made of tough pitch copper with an insulator is used. The cross-sectional area is 0.30 to 0.
The one with 50 mm ² was the mainstream.

Therefore, in order to reduce the weight of the electric wire, the above-mentioned demand has been initially addressed by reducing the thickness of the insulator to such an extent that the heat resistance is not impaired. Then, as a second step, the weight reduction of the conductor itself was examined. Reducing the weight of a conductor means thinning the conductor. Here, what is important is that even if the wire is thinned, it must have impact resistance equal to or higher than that of the electric wire before that. That is, a wire harness is connected to each instrument of a car through a connector and then routed to each part of the vehicle body by an operator. If it is made thin, wire breakage is likely to occur during the work, and especially at the connection part with the connector, it becomes noticeable, so even if the wire is thinned, the wire before that, that is, the wire when it is not thinned It must have the same or higher impact resistance.

On the other hand, as one of the methods for making the impact resistance equal or higher even if the wire is thinned, it is conceivable to improve the strength and proof strength of the conductor. As an example thereof, it is conceivable to use a hard copper wire as the tough pitch copper, but when actually used as an electric wire for a harness, it is easy to break at the connecting portion between the connector and the electric wire during the drawing operation of the wire harness. This is because the elongation property of the hard copper wire is only about 1 to 2%. Further, since the wire harness is a hard copper wire, the rigidity of the wire harness itself is increased, which causes a problem that the handleability is extremely deteriorated.

As described above, the impact resistance depends on the strength and the elongation, and by combining these in a well-balanced manner,
Even if the wire is thinned, impact resistance is obtained so that the wire is not broken under the above-mentioned circumstances.

That is, when an impact force is applied to the conductor, the impact force serves to plastically deform the conductor, but on the contrary, the conductor deforms to absorb the impact force. If this is defined as impact absorption energy, its magnitude can be expressed by load (tensile strength) and strain (elongation).

FIG. 2 shows load-strain curves of Samples 1 to 3, and the impact absorption energy can be evaluated by the area surrounded by these curves. Here, the area is sample 1
<Sample 2 <Sample 3, and Sample 3 has the largest impact absorption energy. From this, it is understood that in order to obtain a conductor having impact resistance equivalent to that of the electric wire before thinning even if the wire is thinned, it is necessary to have impact absorption energy equal to or higher than that.

In the presence of such a background, a conventional electric wire for an automobile, for example, one having an improved strength is
JP-A-1-306534 and JP-A-1-31204
And Japanese Patent Publication No. 60-30043.

Japanese Unexamined Patent Publication Nos. 1-306534 and 1
The electric wire for an automobile disclosed in Japanese Patent No. 31204 uses a precipitation alloy such as a copper-chromium-based or copper-zirconium-based conductor as a conductor, and has a tensile strength (40 to 50 kg / about twice that of conventional tough pitch copper). mm ² ).

On the other hand, the electric wire for an automobile disclosed in Japanese Patent Publication No. 60-30043 uses Cu-Sn or Cu-Cr copper alloy as a conductor, and is 0.2% of the element conductor.
The% yield strength is 30 to 40 kg / mm ² .

[0013]

However, according to the conventional electric wire for automobiles, although the tensile strength is twice as high as that of the tough pitch copper, the elongation rate is only about 10%, which is about half, and the impact strength is high. The absorbed energy is equivalent to that of the conductor before thinning with tough pitch copper. Therefore, when the above conductor is thinned, sufficient impact resistance cannot be obtained, and the rigidity of the conductor is increased, so that the handleability is deteriorated.

Therefore, it is an object of the present invention to provide an electric wire for an automobile and a method of manufacturing the same, which can improve the impact resistance while reducing the weight and the wiring space.

[0015]

In view of the above problems, the present invention adds 0.3 to 2.0 wt% tin to pure copper in order to improve impact resistance while reducing weight and reducing wiring space. The present invention provides an electric wire for an automobile having a predetermined conductor cross-sectional area by twisting a plurality of the copper alloy wires.

The copper alloy wire is preferably annealed at least once in the wire drawing step by an electric current annealing method and then annealed again at the final wire diameter to have an elongation of 30% or more. As a predetermined conductor cross-sectional area, 0.
It is preferable to have 15 to 0.50 mm ² .

The method for producing an electric wire for an automobile according to the present invention which achieves the above object, produces a rough drawn wire of a copper alloy in which tin is added to pure copper in an amount of 0.3 to 2.0 wt. While drawing the wire to the wire diameter, the copper alloy wire being drawn is annealed at least once in the middle of the wire drawing by the current annealing method to produce a copper alloy element wire, and the copper wire drawn to a predetermined wire diameter is drawn. The alloy element wire is annealed again, and a plurality of annealed copper alloy element wires are twisted together to form a predetermined conductor cross-sectional area.

The reason why the tin concentration is set to 0.3 to 2.0 wt% is that if it is less than 0.3 wt%, the tensile strength of the tough pitch copper with respect to the wire is not improved so much and the impact absorption energy is sufficiently increased. This is because the improvement in tensile strength becomes almost saturated when the content is 2 wt% or more, while the conductivity is unnecessarily reduced to 40% IACS or less.

The reason why the elongation rate is 30% or more is that if it is smaller than that, the impact absorption energy of the conductor is not sufficiently improved, and when the wire is thinned, it has the same resistance as the non-thinned tough pitch copper wire. This is because impact resistance cannot be obtained.

Further, the conductor cross section is 0.15 to 0.50 m.
The reason why m ^{2 is set} is that if it is less than 0.15 mm ² , the impact absorption energy of the conductor is considerably smaller than the impact absorption energy of the non-thinned tough pitch copper wire, and the impact resistance is deteriorated. , Again, 0.5
This is because if the diameter is 0 mm ² or more, it is not possible to reduce the diameter.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An electric wire for an automobile and a method for manufacturing the same according to the present invention will be described below in detail with reference to the accompanying drawings.

Using a large-scale continuous casting machine (SCR), Cu-0.7 wt% Sn and Cu-1.0 wt% Sn alloys having tough pitch copper (TPC) as copper were manufactured as a rough wire having an outer diameter of 8 mm. Then, these rough drawn wires have an outer diameter of 2.6 mm.
After cold drawing, it was annealed with an electric annealing. After that, these outer diameters are 0.32 mm and 0.26 m, respectively.
m, 0.23 mm, 0.21 mm, 0.18 mm, and finally drawn by running annealing in argon gas to obtain annealed copper wire (element wire).

Then, a total of 10 strands of wire thus obtained were twisted together to form a conductor, and a conductor was formed. The outer periphery of the conductor was covered with an insulator having a thickness of 0.20 mm. Automotive wires of the present invention up to Sample 10 were manufactured.

On the other hand, as a comparative example, Cu was prepared by the same method as above.
-0.7 wt% Sn and Cu-1.0 wt% Sn alloys were drawn to an outer diameter of 0.16 mm, respectively, and these were twisted and coated with an insulator to obtain Sample 11 and Sample 12.

Further, the following automobile electric wires were manufactured as comparative examples without annealing the current-carrying annealing during wire drawing.

Outer diameter of 0.32 mm using tough pitch copper,
Manufacture 0.26mm strands, twist these,
Samples 13 and 14 were coated with an insulator. Sample 15 was drawn to a diameter of 0.23 mm using tough pitch copper.

Further, Cu-0.7 wt% Sn and Cu-
1.0 wt% Sn alloy, outer diameter 0.26 mm,
Samples of 0.23 mm and 0.21 mm strands, which were twisted in the same manner as above and covered with an insulator
6 to Sample 21.

Further, samples 22 to 24 were obtained using an intermediate wave melting furnace. That is, Cu-0.7 wt% Sn
And a Cu-0.8 wt% Cr alloy were cast into a billet having an outer diameter of 100 mm and a length of 2000 mm. Then, this was hot-rolled to an outer diameter of 10.5 mm, then, this was solution-treated in argon gas at 800 ° C. for 1 hour, and then quenched in water. And for Cu-0.7 wt% Sn alloy, up to 0.26 mm outer diameter, Cu-0.8 wt%
For Cr alloys, after cold drawing to wire diameters of 0.26 mm and 0.23 mm, 450 ° C in argon gas
Aged for 3 hours.

Next, with respect to these electric wires (Samples 1 to 2 and Sample 4), impact resistance was evaluated by an experimental apparatus as shown in FIG.

Here, the experimental apparatus is one in which the tray 3 is attached to the lower end of the suspended sample (electric wire) 2 and the weight 1 is dropped onto the tray 3. In addition, the experiment method is 1 m, 0.75 m, 0.50 m, with the weight 1 as the height h.
Drop from 0.25m, 0.01m, sample (electric wire) 2
The impact resistance was evaluated by the presence or absence of wire breakage. This is an evaluation simulating an impact force applied by an operator during the connection between the wire harness and each instrument or the like in the vehicle body, or during the retracting work, and at this time, the tray 3 corresponds to a connector. The height h is changed in order to evaluate the impact resistance when the speed (strain speed) of the impact force applied to the sample is changed. The experiment was performed 5 times, and the experimental results are shown in Table 1. In Table 1, a conductor made of tough pitch copper having an outer diameter of 0.26 mm, that is, one having impact resistance superior to that of Sample 14, is indicated by ⊚, and one having equivalent impact resistance is indicated by ○. Those having a lower impact resistance are indicated by x.

Table 1 also shows the structure of the conductor portion of each sample, conductor cross-sectional area, conductivity, 0.2% proof stress, tensile strength, elongation ratio,
And the impact absorption energy (ratio to the impact absorption energy of tough pitch copper) are also shown.

[Table 1]

As is clear from Table 1, Sample 1 of the present invention
From sample 10 of Cu-0.7 wt% Sn alloy and Cu-
The electric wire of 1.0 wt% Sn alloy has improved impact resistance compared to the electric wire of Tough pitch copper of Sample 14, and even if it is made thin, the electric shock resistance does not deteriorate as compared with the electric wire of Tough pitch copper. .

On the other hand, when the electric current heating is not performed during the wire drawing, the elongation characteristics are poor and the impact resistance is not sufficient as shown in the samples 13 to 24 of the comparative example. Therefore, if this is thinned, there is a risk of disconnection, and this cannot be applied.

[0034]

As described above, according to the automobile electric wire and the method for manufacturing the same of the present invention, pure copper is 0.3 to 2.0.
wt% tin added, at least 1 in the wire drawing process
Since a plurality of copper alloy wires annealed by the re-current annealing method are twisted together to form a predetermined conductor cross-sectional area, it is possible to improve impact resistance while reducing weight and wiring space.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an experimental device for evaluating impact resistance.

FIG. 2 is a graph showing shock absorption energy.

[Explanation of symbols]

 1 weight 2 sample 3 saucer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Michiaki Shimizu 5-1-1 Hidakacho, Hitachi City, Ibaraki Prefecture Hidaka Plant, Hitachi Cable, Ltd. (72) Inventor Yasuo Tachibana Hidakacho, Hitachi City, Ibaraki Prefecture 5-1-1, Hitachi Cable Co., Ltd. Hidaka Factory

Claims (4)

[Claims] 1. An electric wire for an automobile, characterized in that a plurality of copper alloy wires obtained by adding 0.3 to 2.0 wt% of tin to pure copper are twisted together to form a predetermined conductor cross-sectional area. 2. The copper alloy element wire is annealed at least once by an energizing annealing method in a wire drawing step and is annealed again at a final wire diameter to have an elongation of 30% or more. Electric wire for automobiles. 3. The predetermined conductor cross-sectional area is 0.15 to
The electric wire for an automobile according to claim 1, which has a size of 0.50 mm ² . 4. A rough drawn wire of a copper alloy in which tin is added to pure copper in an amount of 0.3 to 2.0 wt% is drawn, and the drawn wire is drawn to a predetermined wire diameter. The copper alloy wire in the wire is annealed at least once by an energization annealing method to produce a copper alloy wire, and the copper alloy wire drawn to the predetermined wire diameter is annealed again, and the annealed copper alloy A method for manufacturing an electric wire for an automobile, comprising twisting a plurality of strands into a predetermined conductor cross-sectional area.