JP5513075B2 - Electric wire for automobile and manufacturing method thereof - Google Patents

Description

  The present invention relates to an automobile electric wire and a manufacturing method thereof, and more particularly to an automobile electric wire and a manufacturing method thereof for the purpose of weight reduction.

  While automobiles are becoming lighter for the purpose of reducing exhaust gas and improving fuel efficiency, there is a strong demand for reducing the weight of components mounted on automobiles. Among them, the wire harness is no exception, and the diameter of the electric wire for the purpose of reducing the weight has been reduced.

  Conventionally, soft copper (concentric stranded) has been mainly used as conductors for automobile wires, but as the wire diameter is naturally reduced, the wire diameter also becomes smaller, so there is concern about disconnection during wiring due to insufficient strength. Is done. Therefore, in order to maintain a high conductor tensile strength, measures such as adopting a hard material such as a copper alloy for the strand are being taken. However, it has been confirmed that by using a hard material, curled wrinkles are likely to occur in the stranded wire and the electric wire, and as a result, problems such as generation of kinks during harness assembly work have occurred. In addition, since the absolute cross-sectional area of the conductor (stranded wire) is small and the stranded wire itself becomes flexible due to the thinning of the strand, the entanglement of the element due to high flexibility occurs. It becomes easy and it may interfere with harness assembly work.

  In addition, the proposal (for example, patent document 1) which suppresses generation | occurrence | production of the kink of the electric wire at the time of a harness assembly operation on the equipment (electric wire feeding device) side is made. However, the actual situation is that no electric wire that can sufficiently solve the above-described problems associated with the reduction in the diameter of the electric wire has been found without special measures on the facility side.

JP 2009-004315 A

  The problem to be solved by the present invention is to provide an automobile electric wire and a method for manufacturing the same, which can smoothly carry out the work for making a harness even if the diameter is small.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have made the tensile strength and the twist pitch of the conductor wire constituting the stranded wire to be equal to or greater than a specific value, and the insulating layer covering the stranded wire and the stranded wire. By sufficiently increasing the adhesion strength, it was found that an electric wire that is less likely to cause disconnection and curling even with a small diameter can be obtained, and the present invention has been completed.

That is, the present invention is as follows.
(1) A stranded wire composed of a plurality of conductor strands has a configuration covered with an insulating layer;
The tensile strength of at least one conductor wire in the outer layer wire of the stranded wire is 350 MPa or more,
The pitch of the stranded wire is 30 times or more the layer core diameter,
The adhesion between the stranded wire and the insulating layer is 7 N / mm or more,
An electric wire for an automobile characterized by the above.
(2) The automotive electric wire according to (1), wherein the tensile strength of all the conductor wires constituting the outer layer wire of the stranded wire is 350 MPa or more.
(3) The automobile electric wire according to (1) or (2), wherein the plurality of conductor strands are seven conductor strands having a wire diameter in the range of 0.08 to 0.22 mm.
(4) The automotive electric wire according to any one of (1) to (3), wherein the pitch of the stranded wire is 60 times or less the layer core diameter.
(5) The automotive electric wire according to any one of the above (1) to (4), wherein the adhesion between the stranded wire and the insulating layer is 35 N / mm or less.
(6) A step of heating a twisted wire having a tensile strength of at least one conductor wire in the outer layer wire of 350 MPa or more and a twist pitch of 30 times or more the layer core diameter to 100 to 250 ° C .;
Extruding an insulating material mainly composed of a thermoplastic polymer on the heated stranded wire;
A step of cooling the insulating material to form an insulating layer, which includes at least cooling the insulating material with water, and the water cooling is performed within a range not lowering the temperature of the insulating material by 190 ° C. or more. And an insulating layer forming step. A method for manufacturing an automotive electric wire.
(7) The method for producing an automotive electric wire according to (6), wherein the plurality of conductor strands are seven strands having a wire diameter of 0.08 to 0.22 mm.
(8) The method for producing an automobile electric wire according to (6) or (7), wherein the pitch of the stranded wire is 60 times or less the layer core diameter.

As described above, in order to ensure that the strength of the conductor is insufficient due to the reduction in the diameter of the wire (maintaining high conductor tensile strength), it is necessary to increase the strength of the wire. As a result, the cross-sectional area of the absolute conductor is reduced, the stranded wire itself becomes flexible, and the harness assembly work is likely to be hindered.
In the present invention, in order to obtain a high conductor tensile strength, a conductor wire having a tensile strength of 350 MPa or more is applied to at least the outer layer wire of the twisted wire, and the flexibility of the twisted wire due to the thinning of the conductor wire is reduced. Is suppressed by setting the twist pitch to a certain value or more (30 times or more the layer core diameter). On the other hand, as the twist pitch increases, so-called “wara” is easily loosened in the twisted wire, and “wara” is likely to occur. It has been found that the occurrence of this “wara” can be suppressed by sufficiently increasing the adhesion strength between the stranded wire and the insulating layer covering the stranded wire.
Therefore, the electric wire of the present invention has a high conductor tensile strength even when the electric wire size is a small diameter of 0.13 SQ or less, and is less likely to cause curl wrinkles. In subsequent harness assembly, the work can be performed smoothly without causing entanglement or kinking of the elements. Further, the productivity of the electric wire is improved by sufficiently increasing the twist pitch of the stranded wire within a range that does not hinder the bending resistance of the electric wire.

FIG. 1 is a cross-sectional view of one embodiment of an automobile electric wire according to the present invention.

  FIG. 1 is a cross-sectional view of an embodiment of the electric wire for an automobile of the present invention (a cross-sectional view orthogonal to the axis of the electric wire). As shown in FIG. 1, the electric wire for an automobile of the present invention has a plurality of conductors. A stranded wire 2 made of the element wire 1 has a configuration covered with an insulating layer 3.

  For the material of the plurality of conductor wires 1 constituting the stranded wire 2, pure copper, copper alloy, etc. are usually used, but metals other than copper-based metals such as aluminum, aluminum alloy, and stainless steel can also be used. Among these, a copper alloy is preferable from the viewpoint of electrical characteristics and terminal crimping property, and a Cu—Sn alloy having a tin content of 0.1 to 2.0% by mass is particularly preferable. In the case of an alloy, inevitable impurities may be included.

  The plurality of conductor wires 1 are usually made of the same material from the viewpoint of productivity. However, if the object of the present invention can be achieved, they are made of different materials. It may be a thing.

  The size of the electric wire of the present invention is not particularly limited, but is preferably set to a size of 0.22 SQ or less, more preferably 0.13 SQ or less, in order to reduce the weight of the electric wire. The lower limit of the wire size is preferably 0.06 SQ or more from the viewpoint of conductor tensile strength and the like. Accordingly, as the plurality of conductor strands 1 constituting the stranded wire 2, those having a wire diameter of 0.22 mm or less are preferably used, and those having a wire diameter of 0.18 mm or less are more preferably used. However, if the wire diameter is too small, the conductor tensile strength tends to be insufficient (disconnection is likely to occur), so the lower limit of the wire diameter is preferably 0.08 mm or more, more preferably 0.12 mm or more. In addition, from the viewpoint of productivity and the like, the conductor wires 1 having the same wire diameter are usually used, but those having different wire diameters may be used in combination.

  The number of the plurality of conductor wires 1 is usually 37 or less, depending on the thickness of each wire, and typical examples include 37, 19, 7, and the like. In particular, since the number is seven, the length (L1) of the contact portion between the conductor (stranded wire 2) and the insulating layer 3 with respect to the area (A1) of the conductor (stranded wire 2) in the cross section of the electric wire. Since the ratio (L1 / A1) is increased, the ratio (L1 / A1) advantageously works to improve the adhesion between the conductor (stranded wire 2) and the insulating layer 3.

  In the electric wire of the present invention, in the plurality of conductor strands 1 constituting the stranded wire 2, at least one of the outer layer wires (that is, the conductor strand in contact with the insulating layer 3 in the stranded wire 2) has a tensile strength. Must be made of a conductor wire of 350 MPa or more. Thereby, the conductor tensile strength of an electric wire can be raised and the disconnection etc. at the time of wiring can be avoided. In order to sufficiently increase the conductor tensile strength of the electric wire, it is preferable that the tensile strength of more than half of the conductor wires in the outer layer wire is 350 MPa or more, and the tensile strength of all the conductor wires of the outer layer wire is 350 MPa or more. More preferably. In addition, when a conductor strand with a tensile strength smaller than 350 MPa is included in an outer layer wire, those tensile strengths are required to be at least 300 MPa or more. This is because, when the outer layer wire includes a conductor wire having a tensile strength of less than 300 MPa, the ease of manufacturing and productivity of the stranded wire are reduced.

  The high-strength conductor wire having a tensile strength of 350 MPa or more applied to the outer layer wire preferably has a tensile strength of 450 MPa or more. However, if the tensile strength is too large, the twisted wire tends to be soft and the flexibility tends to be inferior. Therefore, the tensile strength is preferably 850 MPa or less.

  The tensile strength of the conductor wires other than the outer layer wires in the stranded wire is not particularly limited, but in order to obtain a sufficiently high conductor tensile strength, the strands also need to have a certain high tensile strength. The strength is preferably 300 MPa or more, more preferably 350 MPa or more, and still more preferably 450 MPa or more. However, if the tensile strength is too large, the twisted wire tends to be soft and the flexibility tends to be inferior. Therefore, the tensile strength is preferably 850 MPa or less.

  The tensile strength of the conductor wire can be adjusted by a conventional method, that is, selection of the wire material, a combination of various processes such as casting, wire drawing, and heat treatment, processing conditions, a change in wire diameter, and the like. In addition, the tensile strength of a conductor strand is calculated | required based on JISC3002.

  When the specific example of the conductor strand used suitably in this invention is given, the tension | tensile_strength obtained by drawing and heat-processing a Cu-Sn alloy whose tin content rate is 0.1-2.0 mass%. A Cu-Sn alloy wire (wire diameter: 0.08 to 0.22 mm) having a strength of 300 to 850 MPa can be mentioned.

  The stranded wire 2 is obtained by twisting a plurality of conductor strands 1 according to an ordinary method using a known stranded wire machine. The twisting method of the twisted wire may be collective twisting or concentric twisting, but concentric twisting is preferable if possible depending on the number of strands. Collective twisting is simply a matter of collecting and twisting strands, and has the advantage of low manufacturing costs. In the concentric twisting, strands are arranged concentrically as in the example of FIG. 1 and twisted so that the cross-section becomes a shape that approximates a regular polygon or a circle.

  In particular, when twisting conductor wires having the same wire diameter, concentric twisting of another conductor wire around one conductor wire, which is the center line, rather than twisting a plurality of conductor wires mutually Twist is preferable in that it can be stably twisted with low tension. Further, even in concentric twisting, it is preferable to close-fill the conductor wires without gaps in order to reduce the diameter of the electric wire. In this case, when the strands are packed close to one layer around the center line, 7 (= 1 + 6) Concentric strands, 19 (= 1 + 6 + 12) strands are tightly packed around the center line, and 37 (= 1 + 6 + 12) strands are densely packed around the center line, 37 (= 1 + 6 + 12 + 18) This is a concentric twist. In addition, if the number of strands is large, the cross-sectional area of one strand is small and breaks easily, and the manufacturing process may be complicated in the case of multilayer twisting. Particularly preferred.

  In the example of FIG. 1, seven strands having a circular cross-sectional shape are concentrically twisted, and then compression processing is performed on the outer layer wire. In order to set the thickness of the insulating layer thin, it is desirable to make the unevenness of the outermost layer surface of the stranded wire (the surface of the outer layer wire) as small as possible. However, in the example of FIG. Processing is adopted to reduce the unevenness of the outermost layer of the stranded wire (the surface of the outer layer wire). The circular compression process is a process for reducing unevenness by passing a stranded wire through a round die or the like.

  In the electric wire of the present invention, the twist pitch of the stranded wire 2 needs to be 30 times or more the layer core diameter. The “twist pitch” is a distance traveled during one turn of the twist when the conductor wire is traced along the twist. The “layer core diameter” is the distance between the centers of two strands having the maximum distance between the centers of the strands constituting the outer layer wire in the cross section of the stranded wire indicated by the symbol D in FIG. Distance (dimension).

  When the twist pitch of the twisted wire is 30 times or more the layer core diameter, the twisted wire can be prevented from being softened due to the thinning of the conductor wire, and the workability for making the harness is improved. However, as the twisting pitch increases, so-called “soft” twisting of the twisted wire is likely to occur, and when “wara” occurs, the curl of the twisted wire becomes stronger in the harnessing operation, and the automatic cutting machine In terminal crimping (element manufacturing) and subsequent harness assembly, kinks and entanglement of elements are likely to occur.

  In the electric wire of the present invention, the occurrence of this “wara” is suppressed by increasing the adhesion strength between the stranded wire 2 and the insulating layer 3. That is, in the electric wire of the present invention, the adhesion between the stranded wire 2 and the insulating layer 3 is set to at least 7 N / mm or more, thereby reliably preventing the occurrence of “wara” accompanying the increase in the twist pitch, and the automatic cutting machine In terminal crimping (element manufacturing) and subsequent harness assembly, the work can be smoothly performed without generating kinks or entanglement of the elements. The adhesion between the stranded wire 2 and the insulating layer 3 is preferably 10 N / mm or more. The adhesion between the stranded wire and the insulating layer is determined in accordance with JASO D618.

  As the twist pitch of the stranded wire increases, the bending resistance of the electric wire tends to decrease. Accordingly, the twist pitch of the stranded wire is preferably 60 times or less the layer core diameter in order to maintain the practically required bending resistance of the electric wire. Note that the productivity of the stranded wire is improved by sufficiently increasing the twist pitch of the stranded wire within a range that does not hinder the bending resistance of the electric wire.

  Although the upper limit of the adhesive force between the stranded wire 2 and the insulating layer 3 is not particularly limited, it is preferably 35 N / mm or less, more preferably 20 N / mm or less in consideration of the peelability at the time of terminal crimping.

  The electric wire of the present invention is for automobiles, and the insulating layer 3 covering the stranded wire 2 needs high flame resistance. Therefore, an insulating material in which at least a flame retardant is blended with a thermoplastic polymer as a base component is usually applied to the insulating layer 3. As the thermoplastic polymer, as halogen-free (HF) material, for example, polypropylene, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, ethylene-α-olefin copolymer (as α-olefin, propylene Olefin resins such as 1-butene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, etc.); olefin thermoplastic elastomer, styrene thermoplastic elastomer, polyester thermoplastic elastomer, etc. And an aromatic polymer such as an aromatic polyester such as polybutylene terephthalate and polyethylene terephthalate. Moreover, polyvinyl chloride etc. are mentioned as a material which is not halogen free (HF). Among these, polypropylene, an aromatic polymer, and polyvinyl chloride are preferable in terms of excellent wear resistance. Moreover, when polypropylene is used for the insulating layer, the assembly workability of the harness is also improved. In addition, polypropylene has an MFR (melt flow rate) of 0.1 to 10 g / 10 min. From the viewpoint of increasing the adhesion between the stranded wire 2 and the insulating layer 3. Those within the range are preferred. In addition, MFR here is measured according to the measuring method of JISK7210 using the extrusion-type plastometer defined by JISK6760.

  As the flame retardant, inorganic flame retardants are preferable, metal hydroxides such as magnesium hydroxide and aluminum hydroxide; antimony oxide (antimony dioxide, antimony trioxide, etc.), titanium oxide, cerium oxide, molybdenum oxide, tungsten oxide, Boron oxide, zirconium oxide, bismuth oxide, iron oxide (such as ferric trioxide), manganese zinc, manganese nickel, etc. soft ferrite, neodymium oxide, samarium oxide, dysprosium oxide, magnesium oxide, zinc oxide, yttrium oxide, aluminum oxide , Tellurium oxide, lithium oxide, rubium oxide, cerium oxide, beryllium oxide, strontium oxide, barium oxide, scandium oxide, lanthanum oxide, praseodymium oxide, europium oxide, gadolinium oxide, terbium oxide, holmium oxide Erbium oxide, thulium oxide, ytterbium oxide, lutetium oxide, hafnium oxide, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, manganese oxide, rhenium oxide, ruthenium oxide, osmium oxide, cobalt oxide, rhodium oxide, iridium oxide, Examples thereof include nickel oxide, palladium oxide, platinum oxide, gallium oxide, indium oxide, thallium oxide, germanium oxide, and selenium oxide. Among these, metal hydroxides such as magnesium hydroxide and aluminum hydroxide are preferable from the viewpoint of high flame retardancy. These inorganic flame retardants are preferably contained in an amount of 10 to 300 parts by weight, more preferably 50 to 200 parts by weight with respect to 100 parts by weight of the thermoplastic polymer. If the content is too small, the flame retardant effect cannot be exhibited. Conversely, if the content is too large, the wear resistance tends to decrease.

  An appropriate amount of additives other than the flame retardant can be blended in the thermoplastic polymer. Examples thereof include fillers such as silica, talc, mica and clay, antioxidants, light stabilizers, antistatic agents, lubricants, dispersants, neutralizing agents and the like.

The thickness of the insulating layer 3 is not particularly limited, but is preferably 0.1 mm or more and more preferably 0.15 mm or more because it requires abrasion resistance and flame retardancy. However, if the thickness is too large, it will hinder weight reduction and production cost (material cost) reduction, so the upper limit is preferably 0.3 mm or less, and more preferably 0.25 mm or less. The thickness of the insulating layer 3 in the present invention is measured as follows.
In each of the arbitrary four cross sections of the electric wire, the thickness of the minimum thickness portion of the portion covering the individual conductor wire constituting the outer layer wire of the stranded wire 2 of the insulating layer 3 is measured, and the average value thereof is calculated. Then, the thickness of the insulating layer is calculated, and the average value of the thickness of the insulating layer at the four cross sections is calculated.

  The electric wire of the present invention is manufactured, for example, by the following method.

  First, a plurality of strands including at least one strand having a tensile strength of 350 MPa or more are prepared, twisted so that the twist pitch is 30 times or more of the layer core diameter, and the tensile strength is 350 MPa or more. A stranded wire is prepared so that at least one of the strands is included in the outer layer wire.

  Next, the stranded wire is heated to about 100 to 250 ° C. using an electric heater or the like, and an insulating material mainly composed of the above-mentioned thermoplastic polymer is put into a wire extruder, and the heated stranded wire is Insulating material is extruded. At this time, the extrusion temperature of the insulating material is a temperature equal to or higher than the melting point of the thermoplastic polymer, but is generally in a range not exceeding 100 ° C. higher than the melting point of the thermoplastic polymer.

  Next, the insulating material extruded onto the stranded wire is cooled to form an insulating layer. In the present invention, in the step of cooling the insulating material, it is important to include at least cooling the insulating material by water cooling. When the insulating material is rapidly cooled by water cooling, the insulating material contracts greatly. The adhesion between the stranded wire 2 and the insulating layer 3 is improved. However, in order to set the adhesion between the stranded wire 2 and the insulating layer 3 to 7 N / mm or more, the cooling of the insulating material by water cooling is within a range in which the temperature decrease amount of the insulating material is less than 190 ° C. ( That is, it is performed within a range in which the temperature of the insulating material is not lowered by 190 ° C. or more. If a long-term water cooling treatment is performed in which the temperature of the insulating material is lowered by 190 ° C. or more, the amount of shrinkage of the insulating material becomes too large, and a gap is generated between the stranded wire 2 and the insulating layer 3. This is because the adhesive strength of the insulating layer 3 is reduced instead. In addition, when the cooling period of the insulating material by water cooling is too short, the insulating material does not sufficiently contract, and the adhesion between the stranded wire 2 and the insulating layer 3 may not be sufficiently increased. It is preferable to carry out for a period in which the temperature of the insulating material is lowered by at least 40 ° C. A particularly preferred embodiment is an embodiment in which water cooling is performed for a period in which the temperature drop of the insulating material by water cooling is in the range of 40 to 180 ° C. In addition, "water cooling" as used in this invention is that an insulating material contacts and cools about 20-40 degreeC water.

  In addition, cooling by water cooling is preferably performed at least in the final cooling process of the insulating material until the insulating material reaches a solidified material (insulating layer) at room temperature. As a specific aspect of the cooling process of the insulating material, (A) A mode in which an insulating material extruded on a stranded wire is once cooled by air (natural cooling) and / or hot water, and then cooled to a solidified product (insulating layer) at room temperature by water cooling (B) ) Once the insulating material extruded on the stranded wire is water-cooled, it is air-cooled (natural cooling) and / or hot-water cooled, and then cooled to a solidified product (insulating layer) at room temperature by water cooling. It is done. In addition, although it varies depending on the extrusion temperature of the insulating material and the temperature of the water used for water cooling, when the insulating material extruded on the stranded wire is cooled only with water cooling until it becomes a solidified material (insulating layer) at room temperature, In many cases, the temperature drop amount of the insulating material is 190 ° C. or more, and it is difficult to make the adhesion between the stranded wire 2 and the insulating layer 3 7 N / mm or more. “Hot water cooling” means that the insulating material is cooled in contact with hot water having a temperature exceeding 40 ° C. and not exceeding 90 ° C.

  Insulating materials are usually cooled by using a stranded wire coated with an insulating material in a cooling device in which a water cooling zone (water tank), a hot water cooling zone (hot water tank), an air cooling zone (air tank), etc. are arranged in a predetermined order. This is done by passing at a predetermined speed. The temperature at which the insulating material is lowered by water cooling can be controlled by the temperature of the water in the water cooling tank and the speed (linear speed) of the stranded wire covered with the insulating material passing through the water cooling tank.

  An electric wire in which a stranded wire is covered with an insulating layer by passing through a cooling process of the insulating material is wound and stored on a bobbin or a reel according to a standard method.

  The electric wire of the present invention is used in a wire harness for transmitting electric power, a control signal, and the like between various electronic devices in an automobile, a power source and a computer. The wire harness includes a plurality of electric wires and connectors attached to ends of the electric wires, and is wired in an automobile to connect between an electronic device and a power source or a computer.

  When assembling the wire harness, the long wire wound on the handle or bobbin or reel is measured by an automatic cutting machine and cut to a predetermined length, and the insulating layer at the end of the cut wire is provided. After being removed (peeled) and the terminal fitting is attached by crimping, the terminal fitting is inserted into the connector housing, and the connector is attached to the end of the electric wire. And a wire harness is assembled with the electric wire with a connector by which element manufacture (terminal attachment) was made to this electric wire.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not limited to these Examples.

(Examples 1-10, Comparative Examples 1-6)
By using a Cu-Sn alloy (tin content 0.3 mass%), wire drawing and heat treatment, 7 types of strands with different tensile strength (strand 1: 350 MPa, strand 2: 380 MPa) Wire 3: 400 MPa, Wire 4: 450 MPa, Wire 5: 480 MPa, Wire 6: 520 MPa Wire 7: 300 MPa). In addition, the wire diameter of all the strands was 0.17 mm.

  Using these seven types of wires and a polypropylene composition in which 150 parts by mass of magnesium hydroxide (a flame retardant) is blended with 100 parts by mass of polypropylene (MFR: 5 g / 10 min.) As an insulating material, 1. Electric wires of Examples 1 to 10 and Comparative Examples 1 to 6 having physical properties shown in Table 1 (layer core diameter: 0.34 mm, insulating layer) having a structure in which a single seven-strand stranded wire is covered with an insulating layer Thickness: 0.2 mm, electric wire size: 0.13 SQ).

  In addition, in Examples 1-9 and Comparative Examples 1-6, strand wire No. After seven strands of the wire were concentrically twisted, circular compression was performed using a round die having an inner diameter (φ) of 0.45 mm. In Example 10, a total of 7 strands of 1 strand 1 and 6 strands 7 were used, and the strands 1 were concentrically twisted so as to be included in the outer layer wire. Circular compression was performed using a round die having a φ) of 0.45 mm.

  For extruding the insulating material onto the stranded wire, the flame-retardant polypropylene composition is put into an electric wire extruder (φ: 30 mm), and the stranded wire heated to 100 ° C. at an extrusion speed of 500 mm / min and an extrusion temperature of 230 ° C. Extruded.

  The insulating material is cooled by passing a stranded wire, the outer circumference of which is covered with a polypropylene composition, from a hot water cooling zone into a cooling bath in which a hot water cooling zone and a water cooling zone are partitioned, and the polypropylene composition is passed through the water cooling zone. It was performed by cooling to ° C. At that time, the running speed (linear speed) of the stranded wire was changed to control the lowering temperature of the polypropylene composition in the water cooling zone. Table 1 shows the temperature when the insulating material (polypropylene composition) enters the water-cooling zone and the temperature at which the insulating material (polypropylene composition) decreases in the water-cooling zone.

  The physical properties and evaluation in Table 1 are as follows.

1. Tensile strength of strands Measured according to JIS C 3002.

2. Adhesion (adhesion between stranded wire and insulating layer)
In accordance with JASO D 618, the following method was used.
(1) The electric wire is cut into 50 to 75 mm, and the insulating layer is peeled off by the length of 25 mm.
(2) A round hole equivalent to the outer diameter of the conductor is made in the metal plate, the conductor is passed through the hole, the conductor is pulled at a speed of 25 mm / sec, and the maximum tensile force until the insulating layer falls off is measured.

3. Harness assembling workability In case of terminal crimping with automatic cutting machine (element manufacturing) and subsequent harness assembling, if the work can be done smoothly without generating kinks and entanglement of elements (○), either However, when it occurred, it was determined as rejected (x).
The number of samples was 500.

  The present invention can be preferably used as an automobile electric wire, and is particularly suitable for applications requiring strength.

1 Conductor Wire 2 Stranded Wire 3 Insulating Layer

Claims (8)

The wire diameter is in the range of 0.08 to 0.22 mm, and the stranded wire composed of seven conductor strands has a configuration covered with an insulating layer,
The tensile strength of all the conductor wires constituting the outer layer wire of the stranded wire is 350 MPa or more,
The twisted wire pitch is 30 times or more and 60 times or less the layer core diameter,
The strands and the adhesion strength between the insulating layer is 7N / mm or more state, and are less 35N / mm,
The insulating layer has an MFR (melt flow rate) of 0.1 to 10 g / 10 min. Including polypropylene in the range of
The insulating layer has a thickness of 0.1 to 0.3 mm.
An electric wire for an automobile characterized by the above. The electric wire for automobiles according to claim 1, wherein the insulating layer contains a flame retardant. The electric wire for motor vehicles of Claim 1 or 2 whose tensile strength of all the conductor strands which comprise the outer layer wire of a strand wire is 850 Mpa or less. The electric wire for automobiles according to any one of claims 1 to 3, wherein the electric wire size is 0.13 SQ or less. A step of heating a twisted wire having a tensile strength of at least one conductor wire in the outer layer wire of 350 MPa or more and a twist pitch of 30 times or more the layer core diameter to 100 to 250 ° C .;
Extruding an insulating material mainly composed of a thermoplastic polymer on the heated stranded wire;
A step of cooling the insulating material to form an insulating layer, which includes at least cooling the insulating material with water, and the water cooling is performed within a range not lowering the temperature of the insulating material by 190 ° C. or more. And an insulating layer forming step. A method of manufacturing an automobile electric wire. 6. The method of manufacturing an automotive electric wire according to claim 5, wherein the stranded wire is obtained by concentrically twisting a plurality of conductor strands and then subjecting the wire to a circular compression process. The manufacturing method of the electric wire for motor vehicles of Claim 5 or 6 whose multiple conductor strands which comprise a strand are seven strands whose wire diameter is 0.08-0.22 mm. The manufacturing method of the electric wire for motor vehicles of any one of Claims 5-7 whose pitch of a strand wire is 60 times or less of a layer core diameter.

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